ELECTRICALLY ACTIVATED RECORDING MATERIAL CONTAINING A DYE-FORMING COUPLER AND AN OXIDATION-REDUCTION COMBINATION

PRODUIT D'ENREGISTREMENT ACTIVE A L'ELECTRICITE, RENFERMANT UN AGENT DE COPULATION POUR LA COULEUR ET UNE COMBINAISON D'OXYDO-REDUCTION

English Abstract

-1-
DYE FORMING ELECTRICALLY ACTIVATED
RECORDING MATERIAL AND PROCESS
Abstract of the Disclosure
A dye-forming electrically activated recording
element comprises an electrically conductive support having
thereon (a) an electrically activated recording layer com-
prising in an electrically conductive polymeric binder, an
organic silver salt and a reducing agent, (b) a photo-
conductive layer separated from (a) by an air gap of
up to 20 microns and (c) an electrically conductive layer
on (b), wherein the recording layer (a) comprises in reactive
association, (A) a dye-forming coupler, and (B) an oxidation-
reduction combination comprising (i) an organic silver salt
oxidizing agent, with (ii) a reducing agent which in its
oxidized form forms a dye with the dye-forming coupler.
The recording element can be room light handleable and can
provide a dye image and silver image by dry development
processing.

Claims

-42-
WHAT IS CLAIMED IS:
1. In an electrically activated recording
element comprising an electrically conductive support
having thereon, in sequence:
(a) an electrically activated recording layer
comprising an organic silver salt and a reducing
agent,
(b) a photoconductive layer separated from (a)
by an air gap of up to 20 microns, and
(c) an electrically conductive layer on (b),
the improvement comprising, as said recording layer,
the following, in reactive association:
(I)
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent,
with
(ii) a reducing agent which, in its oxidized
form, forms a dye with said dye-forming
coupler; and
(II)
an electrically active conductive subbing layer
as said electrically conductive support.
2. An electrically activated recording
element as in Claim 1 wherein said dye-forming
coupler is a resorcinol, dye-forming coupler.
3. An electrically activated recording
element as in Claim 1 wherein said dye-forming
coupler is a resorcinol, dye-forming coupler
represented by the formula:
<IMG>

-43-
wherein R is hydroxy, phenyl, alkyl containing 1 to
20 carbon atoms, or haloalkyl.
4. An electrically activated recording
element as in Claim 1 wherein said dye-forming
coupler is a compound selected from the group
consisting of 2',6'-dihydroxyacetanilide and
2',6'-dihydroxytrifluoroacetanilide and combinations
thereof.
5. An electrically activated recording
element as in Claim 1 wherein said organic silver
salt oxidizing agent is a silver salt of a 1,2,4-
mercaptotriazole derivative represented by the
formula
<IMG>
wherein Y is aryl containing 6 to 12 carbon atoms, m
is 0 to 2; and Z is hydrogen, hydroxyl, or amine.
6. An electrically activated recording
element as in Claim 1 wherein said organic silver
salt oxidizing agent consists essentially of a silver
salt of 3-amino-5-benzylthio-1,2,4-triazole.
7. An electrically activated recording
element as in Claim 1 also comprising an electrically
conductive binder in said electrically activated
recording layer.
8. An electrically activated recording
element as in Claim 1 also comprising an electrically
conductive binder consisting essentially of a
copolymer of acrylamide and vinyl imidazole.
9. An electrically activated recording
element comprising, in sequence:
(a) a first support having thereon
(b) a first electrical conducting layer, and
(c) a photoconductive layer, having thereover
(d) an electrically activated recording layer
separated from (c) by an air gap of up to 20 microns,

-44-
and comprising, in an electrically conductive poly-
acrylamide binder, in reactive association:
(A) a dye-forming coupler consisting essentially
of 2',6'-dihydroxytrifluoroacetanilide,
(B) an oxidation-reduction combination consist-
ing essentially of
(i) an organic silver salt oxidizing agent
consisting essentially of a silver salt
of 3-amino-5-benzylthio-1,2,4-triazole,
with
(ii) a reducing agent consisting essentially
of 4-amino-2-methozy-N,N,5-trimethyl-
aniline sulfate,
(e) an electrically conductive subbing layer
comprising a poly(alkyl acrylate-co-vinylidene
chloride), and
(f) a second electrically conductive layer, on
(g) a second support.
10. A dry, electrically activated recording
process for producing a dye enhanced silver image in
an electrically activated charge-sensitive recording
element comprising at least one electrically acti-
vated recording, image-forming combination compris-
ing, in an electrically conductive binder, in
reactive association:
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent,
with
(ii) a reducing agent which, in its oxidized
form, forms a dye with said dye-forming
coupler,
said processing comprising the steps:
(I)
applying an electric potential imagewise to said
recording element of a magnitude and for a sufficient
time to produce in the image areas a charge density

-45-
within the range of about 10-3 coulomb per cm2 to
about 10-9 coulomb per cm2, said charge density
forming a developable latent image in the image-
forming combination; and,
(II)
heating said recording element substantially
uniformly at a temperature within the range of 80° to
200°C and for a time sufficient to develop a dye
enhanced silver image.
11. A dry, electrically activated recording
process for producing a dye enhanced silver image in
an electrically activated charge-sensitive recording
element comprising, in sequence:
(a) a first electrically conductive layer,
(b) a photoconductive layer,
(c) an electrically activated recording layer
separated from (b) by an air gap of up to 20 microns
and comprising, in an electrically conductive binder,
in reactive association:
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent,
with
(ii) a reducing agent which, in its oxidized
form, forms a dye with said dye-forming
coupler, and
(d) an electrically active conductive subbing
layer on
(e) an electrically conductive support;
said process comprising
(I)
imagewise altering the conductivity of said
photoconductive layer in accord with an image to be
recorded while simultaneously
(II)
applying an electrical potential across said
photoconductive layer and said recording layer of a

-46-
magnitude and for a sufficient time to produce in the
image areas a charge density within the range of
about 10-3 coulomb per cm2 to about 10-9
coulomb per cm2, said charge density forming a
developable latent image in said recording layer
corresponding to the image to be recorded; and,
(III)
heating said recording layer substantially
uniformly at a temperature within the range of 80° to
200°C and for a time sufficient to produce a dye
enhanced silver image in said recording layer.
12. A process as in Claim 11 wherein said
recording layer is heated in (III) to a temperature
within the range of about 100°C to about 180°C until
a dye enhanced silver image is produced in said
recording layer.
13. A dry, electrically activated recording
process for producing a dye enhanced silver image in
a charge-sensitive recording element comprising, in
sequence:
(a) a first support having thereon
(b) a first electrically conductive layer, and
(c) a photoconductive layer, having thereover
(d) an electrically activated recording layer
separated from (c) by an air gap of about up to 20
microns, and comprising, in an electrically conduc-
tive polyacrylamide binder,
(A) a dye-forming coupler consisting essentially
of a compound selected from the group consisting of
2',6'-dihydroxyacetanilide and 2',6'-dihydroxytri-
fluoroacetanilide and combinations thereof,
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent
consisting essentially of a silver salt
of 3-amino-5-benzylthio-1,2,4-triazole,
with

-47-
(ii) a reducing agent consisting essentially
of 4-amino-2-methoxy-N,N,5-trimethyl-
aniline sulfate,
(e) an electrically active conductive subbing
layer, and
(f) a second electrically conductive layer on
(g) a second support,
said process comprising
(I)
imagewise altering the conductivity of said
photoconductive layer in accord with an image to be
recorded while simultaneously
(II)
applying an electrical potential across said
photoconductor layer and recording layer of a magni-
tude and for a sufficient time to produce in the
image areas a charge density within the range of
about 10-3 coulomb per cm2 to about 10-9
coulomb per cm2, said charge density forming a
developable latent image in said recording layer
corresponding to said image to be recorded; and,
(III)
heating said recording layer substantially
uniformly at a temperature within the range of 80° to
200°C and for a time sufficient to produce a dye
enhanced silver image in said recording layer.
14. A process as in Claim 13 wherein said
recording layer is heated in (III) to a temperature
within the range of about 100°C to about 180°C until
a dye enhanced silver image is produced in said
recording layer.
15. A dry, electrically activated record-
ing process for producing a dye enhanced silver image
in an electrically activated charge-sensitive record-
i ing element comprising an electrically conductive
support having thereon, in sequence, an electrically
active conductive subbing layer, and, contiguous to

-48-
said electrically active conductive subbing layer, an
electrically activatable recording layer; said
process comprising the steps:
(I) imagewise altering the conductivity of a
photoconductive layer (Z) in accord with an image
that is to be recorded;
(II) positioning the imagewise altered photo-
conductive layer (Z) from (I) within 20 microns
adjacent an electrically activated recording layer of
said recording element comprising, in an electrically
conductive binder, in reactive association:
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination
comprising
(i) an organic silver salt oxidizing
agent, with
(ii) a reducing agent which, in its
oxidizing form, forms a dye with
said dye-forming coupler;
(III) applying an electrical potential across
said photoconductive layer and recording layer of a
magnitude and for a sufficient time to produce in the
areas of said recording layer corresponding to the
imagewise altered portions of said photoconductive
layer a charge density within the range of about
10-3 coulomb/cm2 to about 10-9 coulomb/cm2,
said charge density forming in said areas a develop-
able latent image; and,
(IV) uniformly heating the recording element at
a temperature within the range of 80° to 200°C and
for a time sufficient to produce a dye enhanced
silver image in said recording element.
16. A dry, electrically activated recording
process as in Claim 15 also comprising the steps:
(V) positioning said imagewise altered photo-
conductive layer within 20 microns adjacent a second
electrically activated recording layer;

-49-
(VI) applying an electrical potential across
said photoconductive layer and said second recording
layer of a magnitude and for a sufficient time to
produce in the areas of said image of said photo-
conductive layer a charge density within the range of
about 10-3 coulomb/cm2 to about 10-9 coulomb/-
cm2, said charge density forming a developable
latent image; and,
(VII) uniformly heating said second recording
layer at a temperature within the range of 80° to
200°C and for a time sufficient to produce a
developed image in said second recording layer.
17. A dry, electrically activated recording
process for producing a dye enhanced silver image in
an electrically activated charge-sensitive recording
element comprising an electrically conductive support
having thereon, in sequence, an electrically active
conductive subbing layer, and, contiguous to said
electrically active conductive subbing layer an
electrically activatable recording layer comprising,
in an electrically conductive binder, in reactive
association:
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent,
with
(ii) a reducing agent which, in its oxidized
form, forms a dye with said dye-forming
coupler,
said process comprising the steps:
(I) positioning said recording element in
face-to-face relationship with a photoconductive
element wherein said recording element is separated
from said photoconductive element by an air gap of up
to 20 microns;
(II) exposing said photoconductive element to an
imagewise pattern of actinic radiation while

-50-
simultaneously applying an electrical potential
having a field strength of at least about 1 X 104
volts/cm across said photoconductive element and said
recording element for a time sufficient to provide a
developable latent image in the areas of said record-
ing element corresponding to the exposed areas of
said photoconductive element; and
(III) substantially uniformly heating the
recording element at a temperature within the range
of 80° to 200°C and for a time sufficient to produce
a dye enhanced silver image in said recording element.
18. A process as in Claim 17 wherein the
impedance of said recording element differs from the
impedance of said photoconductive element by no more
than about 105 ohm-cm when said electrical
potential is applied across said photoconductive
element and said recording element.
19. A process as in Claim 17 wherein said
electrical potential produces a charge flow within
the range of about 10-3 coulomb/cm2 to about
10-9 coulomb/cm2 in the areas of said recording
element corresponding to the exposed areas of said
photoconductive element.
20. A process as in Claim 17 wherein said
recording element in (III) is substantially uniformly
heated to a temperature within the range of about
100°C to about 180°C until a dye enhanced silver
image is produced.
21. A process as in Claim 17 wherein said
photoconductive element is X-ray sensitive and the
conductivity of said element is imagewise altered by
exposing said photoconductive element to X-ray
radiation in accord with an image to be recorded.
22. A process as in Claim 17 wherein said
dye-forming coupler is a compound selected from the
group consisting of 2,6'-dihydroxyacetanilide and
2',6'-dihydroxytrifluoroacetanilide and combinations

-51-
thereof; said organic silver salt oxidizing agent
consists essentially of a silver salt of 3-amino-5-
benzylthio-1,2,4-triazole; and said reducing agent
consists essentially of 4-amino-2-methoxy-N,N,5-tri-
methylaniline sulfate.
23. A dry, electrically activated record-
ing process for producing a dye enhanced silver image
in an electrically activated recording element
comprising an electrically active conductive layer,
and contiguous to said electrically active conduc-
tive layer, an electrically activatable recording
layer comprising, in an electrically conductive
binder, in reactive association:
(A) a dye-forming coupler, and
(B) an oxidation-reduction combination comprising
(i) an organic silver salt oxidizing agent,
with
(ii) a reducing agent which, in its oxidized
form, forms a dye with said dye-forming
coupler;
said process comprising the steps:
(I) positioning said recording element on an
electrically conductive backing member;
(II) modulating a corona ion current flow to the
recording element by an electrostatic field estab-
lished imagewise between an image grid comprising an
electroconductive core sequentially connectable to
sources of different potential relative to said
backing member and covered with a coating of a
photoconductive insulating material and a control
grid that is electrically conductive and sequentially
connectable to sources of different potential rela-
tive to said backing member, said current flow being
of a magnitude sufficient to produce a charge density
within the range of about 10-3 to about 10-9
coulomb/cm2 imagewise in said recording element,
which charge density forms a developable latent image

-52-
in said electreically activated recording material;
and
(III) substantially uniformly heating said
recording element at a temperature within the range
of 80° to 200°C and for a time sufficient to produce
a dye enhanced silver image in said recording element.

Description

1151461
--1--
DYE FORMING ELECTRICALLY ACTIVATED
RECORDING MATERIAL AND PROCESS
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
This invention relates to dye-forming charge-
sensitive recording materials. One aspect of the invention
relates to the use of (A) a dye-forming coupler and (B) an
image-forming combination in a charge-sensitive
recording material which is capable of producing a dye
10 image and silver image by dry development processes.
DESCRIPTION OF THE STATE OF THE ART
A variety of recording materials and processes
have been proposed to provide image recording. The better
known and commercially more successful of these recording
15 materials and processes can be classified as photographic,
thermographic or electrographic or as a combination of two
or more of these processes. For example, one known recording
material is a photothermographic material which is a heat
developable photosensitive material. Each of the known image
20 recording materials and processes have certain advantages
for particular uses. However, the materials and processes
also suffer from disadvantages which limit the usefulness
in particular applications. For example, conventional
photographic materials have the disadvantage that they
25 are not room light handleable prior to imagewise exposure
and processing. Thermographic materials require imagewise
heating to provide a visible image and are not capable of
the degree of light sensitivity provided by conventional
photographic materials. Electrographic materials including,
30 for example, xerographic materials require mechanical dust
pattern transfer procedures to provide a desired image.
It has been desirable to provide an image recording
material and process which enable the formation of a dye
image and a silver image under daylight conditions, yet
35 avoid the need for conventional processing baths and
solutions.
~,i
,
,, ' :
:... :
~ - :
:- ,' . ~ ~
. .

115~1
--2--
Heat developable photographic materials which after
imagewise exposure can be heated to produce a developed image
in the absence of processing solutions or baths are known.
These photosensitive materials have the disadvantage that
5 they are not room light handleable prior to imagewise
exposure for recording purposes.
Another means proposed for imaging involves a
recording material which produces an image by passing an
electric current through the recording materlal. Such
10 recording materials involve electrographic image recording
techniques. One such recording material comprises a
conventional light sensitive photographic material that is
positioned contiguous to a photoconductive layer for image
recording purposes. Upon applying a uniform electric field
15 across the photoconductive and photographic layers and
simultaneously imagewise exposing the photoconductive layer
to a light pattern, an imagewise current flow is produced in
the photographic layer. This imagewise current flow in turn
produces a developable latent image in the photographic
20 layer. The recording material, however, has the disadvantages
associated with light sensitive photographic materials which
require processing with conventional solutions and baths.
Moreover, the material requires a substantial current flow
in the recording layer and therefore provides a relatively
25 lengthy exposure time with low current flow or a high
current flow with a short exposure time.
Dry electrographic recording materials and
processes which involve production of a visible image in a
charge-sensitive recording element have been described in,
30 for example, French Patent 2,280,517 published February 27,
1976 and U.S. Patent 4,113,484. Such dry electrographic
recording materials can be processed by dry development
techniques. However, no suggestion is given of producing
a dye image and silver image in such a recording material
35 and process.

~51461
--3--
Accordingly, a continuing need has existed to
provide an electrically activated recording element that
(a) avoids the need for conventional processing solutions
and baths, (b) enables room light handling of the recording
5 material prior to imagewise exposure and processing, and
(c) enables the formation of a dye image and silver image,
preferably a dye image that enhances the silver image.
SUMMARY OF THE INVENTION
It has been found according to the invention that
10 the described advantages are provided in an electrically
activated recording element comprising an electrically
conductive support having thereon, in sequence, (a) an
electrically activated recording layer comprising an organic
silver salt and a reducing agent, and (b) a photoconductive
15 layer separated from (a) by an air gap of up to 20 microns
and (c) an electrically conductive layer on (b), wherein
the recording layer comprises, in reactive association, (A)
a dye-forming coupler, and (B) an oxidation-reduction com-
bination comprising (i) an organic silver salt oxidizing
20 agent, with (ii) a reducing agent which, in its oxidized
form, forms a dye with the dye-forming coupler. Such an
electrically activated recording element enables formation
of a dye image and silver image by heat processing after
imagewise exposure. The electrically activated recording
25 element according to the invention preferably also comprises
an electrically conductive subbing layer on the electrically
conductive support.
It has also been found according to the invention
that a dye image and silver image, especially a dye enhanced
30 silver image, can be produced by a dry, electrically
activated recording process comprlsing the steps o~ (I)
applying an electric potential lmagewise to an electrically
activated recording layer of a charge-sensitive recording
element of a magnitude and for a sufficient time to produce
35 in the image areas a charge density within the range of
about 10 3 coulomb/cm to about 10 9 coulomb/cm2, said

115146
charge density forming a developable latent image in the
charge-sensitive recording layer; and, then (II~ heating the
element substantially uniformly at a temperature and for a
time sufficient to produce a dye image and silver image,
preferably a dye enhanced silver image, in the recording
layer. In this process embodiment the electrically activated
recording layer comprises the described components; however,
other means than a photoconductor can be useful to produce
the desired charge density in the recording layer, such as a
contact or non-contact electrode.
A further process which has been found according
to the invention which produces a dye image and silver image
comprises ~I) imagewise altering the conductivity of the
photoconductive layer of the described element in accord with
an image to be recorded; (II) applying across the photo-
conductive layer and recording layer an electrical potential
of a magnitude and for a sufficient time to produce a
developable latent image in the recording layer corresponding
to the image to be recorded; and then (III) heating the
recording layer substantially uniformly at a temperature and
for a time sufficient to produce a dye image and a silver
image, preferably a dye enhanced silver image, in the
recording layer. The step (I) of imagewise altering the
conductivity of the photoconductive layer is preferably
carried out while simultaneously (II) applying the
described electrical potential across the photoconductive
layer and recording layer.
A further process which has been found according
to the invention is a dry, electrically activated recording
3 process for producing a dye image and silver image, preferably
a dye enhanced silver image, in an electrically activated
recording element comprising the steps: (I? imagewise
altering the conductivity of a photoconductive layer CZ)
in accord with an image to be recorded; CII~ positioning the
imagewise altered photoconductive layer CZ~ from ~I~ in
face-to-face relationship with an electrically activated
recording layer CY~ of the recording element, which element
comprises (A) a dye-forming coupler and (B) an image-forming
combination comprising (i) an organic silver salt oxidizing

il51gt6
--5--
agent, with ~ii) a reducing agent which, in its oxidized
form, forms a dye with the dye-forming coupler; ~III)
applying across the photoconductive layer and recording
layer an electrical potential of a magnitude and for a
sufficient time to produce in the areas of the recording
layer corresponding to the imagewise altered portions of the
photoconductive layer a charge density within the range of
about 10 3 coulomb/cm2 to about 10 9 coulomb/c~2, the charge
density forming in the areas a developable latent image, and
then ~IV) unifor~ly heating the recording element at a
temperature and for a time sufficient to produce a dye image
and silver image, especially a dye enhanced silver image, in
the recording element.
Another process according to the invention is
a dry electrically activated recording process for
producing a dye image and silver image, preferably a dye
enhanced silver image, in a charge-sensitive recording
element, preferably having ohmic resistivity within the
range of about 104 to about 1 x 1012 ohm-cm, containing
at least one electrically activated recording material
comprising in an electrically conductive binder, (A)
a dye-forming coupler, and (B) an image-forming combination
comprising (i) an organic silver salt oxi.dizing agent,
with (ii) a reducing agent which, in its oxidized form,
forms a dye with the dye-forming coupler; comprising the
steps: (I) positioning the recording material on an
electrically conductive backing member; (II) modulating
a corona ion current flow to the recording element by an
electrostatic field established imagewise between an
3 image grid comprising an electroconductive core sequentially
connectable to sources of different potential relative to
the backing member and covered with a coating of a photo-
conductive insulating material and a control grid that
is electrically conductive and sequentially connectable to
sources of different potential relative to the backing

115~
member, said current flow being of a magnitude sufficient
to produce a charge density within the range of about 10 3
to about 10 9 coulomb/cm2 imagewise in said recording-
element, which charge density forms a developable latent
image in the electrically activated recording material; and,
(III) substantially uniformly heating the recording element
at a temperature and for a time sufficient to produce a
dye enhanced silver image in the recording element.
The heating step in each of the described process
embodiments can be carried out at a temperature within the
range of about 80C to about 200~C, typically at a
temperature within the range of about 100C to about 180C,
until the desired silver image and dye image are formed.
BRIEF DESCRIPTION OF THE DRAWINGS
~igures 1 and 2 illustrate schematically an
image recording material and process according to one
illustrative embodiment of the invention; and Figures 3
and 4 illustrate schematically an electrically activated
recording process embodying the described invention.
Figure 5 illustrates schematically an image
recording material that is especially useful according
to the invention.
DETAILED DESCRIPTION OF THE INVENTION
. _ _ .. . . .. _ _
Many dye-forming couplers, organic silver salt
oxidizing agents and reducing agents which in their oxidized
form form a dye with the dye-forming coupler may be used in
the described electrically activated recording materials
according to the invention. The exact mechanism by which
the latent image is formed in the recording material is not
fully understood. It is postulated that the in~ection of an
electron due to the electric field into the comblnation of
components results in the formation of a developable latent
image. It is believed that the development of the latent
image is accomplished by a reaction in which the latent
image catalyzes the reaction of the described image-forming
combination. In such a reaction the organic silver salt

1~51~161
--7--
oxidizing agent reacts with the described reducing agent.
Then, the oxidized form of the reducing agent resulting
from this reaction in turn reacts with the dye-forming
coupler to produce a dye in the image areas. It is not
entirely clear, however, what part, if any, the dye-forming
coupler and the other described components play in latent
image formation.
While a variety of image recording combinations
containing the described components can be useful, the
optimum image recording combination and image recording
element will depend upon such factors as the desired image,
the particular image-forming combination, the source of
exposing energy, processing condition ranges and the like.
The term "charge-sensitive recording material"
as used herein is intended to mean a material which when
subjected to an electrical current undergoes a chemical
and/or electrical change which provides a developable latent
image.
The term "latent image" as used herein is intended
to mean an image that is not visible to the unaided eye
or is faintly visible to the unaided eye and that is capable
of amplification in a subsequent processing step, especially
in a subsequent heat development step.
The term "resistive recording material" as used
herein is intended to mean a material that has an ohmic
resistivity of at least about 104 ohm-cm.
The term "electrically conductive" such as in
"electrically conductive support" or "electrically conductive
subbing layer" is intended herein to mean a support and
subbing layer that have a resistivity less than about 1012
ohm-cm.
Many photoconductors may be used in an element
according to the invention. Selection of an optimum photo-
conductor will depend upon such factors as the particular
electrically activated recording layer, the charge sensitivity
of the element, the desired image, the ohmic resistivity

~5
--8--
desired, exposure means, processing conditions and the like.
It is advantageous to select a photoconductor which has the
property of being the most useful with the operative voltages
to be used for imaging. The photoconductor can be either an
organic photoconductor or an inorganic photoconductor.
Combinations of photoconductors can be useful. The
resistivity of the photoconductor can change rapidly in the
operating voltage ranges which can be useful according to
the invention. In some cases, it is desirable that the
photoconductive layer have what is known in the art as
persistent conductivity. Examples of useful photoconductors
include lead oxide, cadmium sulfide, cadmium selenide,
cadmium telluride, selenium and lanthanum oxide. Useful
organic photoconductors include, for instance, polyvinyl
carbazole/trinitrofluorenone photoconductors and aggregate
type organic photoconductors described in, for example, U.S.
3,615,414. These photoconductors are known in the image
recording art and are described in, for example, U.S. Patent
3,577,272; Research Disclosure, August 1973, Item 1120 of
Reithel, published by Industrial Opportunities Ltd., Homewell,
Havant, Hampshire, PO9 lEF, UK; "Electrography" by R. M.
Schaffert (1975) and "Xerography and Related Processes" by
Dessauer and Clark (1965) both published by Focal Press
Limited, and U.S. 3,615,414.
An especially useful photoconductive layer comprises
a dispersion of lead oxide in an insulating binder, such as
a binder comprising a polycarbonate (for example, LEXAN, a
trademark of General Electric Company, U.S.A., consisting of
a Bisphenol A polycarbonate~, polystyrene or polytvinyl
butyral~.
A recording element according to the invention is
especially useful wherein the photoconductive layer is
X-ray sensitive and the conductivity of the photoconductor
layer can be imagewise altered by imagewise exposing the
35 photoconductive layer to X-ray radiation.
, . . .

1:~5~
Many dye-forming couplers may be used in the
element and process as described. The exact mechanism by
which the dye image and silver image are produced is
not fully understood. However, it is believed that the
dye-forming coupler reacts with the described oxidized
form of the reducing agent to form a desired dye. The
dye-forming coupler herein is accordingly intended to
mean a compound or combination of compounds which with
other of the described components produces a desired
dye image upon heating the recording layer after exposure.
These are designated as dye-forming couplers because it is
believed that the compounds couple with the oxidized
developer to produce the desired dye. The dye-forming
couplers described herein are also known in the
photographic art as color-forming couplers. Selection
of a suitable dye-forming coupler will be influenced by
such factors as the desired dye image, other components
of the recording layer, processing conditions, particular
reducing agent in the recording layer and the like. An
example of a useful magenta dye-forming coupler is 1-(2,4,6-
trichlorophenol)-3-[3-]-(3-pentadecylphenoxy)butyramido
[benzamido]-5-pyrazolone. A useful cyan dye-forming coupler
is the described 2,4-dichloro-1-naphthol. A useful yellow
dye-forming coupler is ~-[3-]-(2,4-di-tertiary-amylphenoxy~
acetamido]-benzoyl]-2-fluoroacetanilide. Useful cyan,
magenta and yellow dye-forming couplers can be selected
from those described in, for example, "Neblette's Handbook
of Photography and Reprography", edited by John M. Sturge,
7th Edition, 1977, pages 120-121 and Research Disclosure,
December 1978, Item 17643, Paragraphs VII C-G.
An especially useful dye-forming coupler is
a resorcinol dye-forming coupler. The resorcinol
dye-forming coupler is preferably one that produces a
neutral (black~ or nearly neutral appearing dye with the
oxidized form of the described reducing agent. Mono-
substituted resorcinol dye-forming couplers containing a
substituent in the two position are especially useful.

1~5~61
--10--
The resorcinol dye-forming coupler and other components in
the recording layer should be sufficiently stable to avoid
any significant adverse interaction in the recording layer
prior to imagewise exposure and processing. A variety of
resorcinol dye-forming couplers can be useful. A useful
resorcinol dye-forming coupler is typically one
represented by the formula:
R1
H O~ ~O H
IoI
R4/ \t/ \R2
R3
wherein
O O O
Rl is hydrogen, COH, NHCR5, CR6, or NHSo2R7;
O O
2 ~ "
R is hydrogen, COH, CNHCH2CH20H, or
o
CNH~C6H5~0C5Hlln;
O O
R3 is hydrogen, NHCR5, or CR6;
O O
Jl ,. ..
R' is hydrogen, COH, CNHCH2CH20H or
o
CNH~C6H5~C5Hlln;
R5 is haloalkyl containing 1 to 3 carbon atoms, such as
CC13, CF3, and C3H~IBr3, CH20CH3, CH2SR ,
C2H4COOH, CH=CH2, NHC2H4Cl, alkyl containing
1 to 20 carbon atoms, such as 1 to 10 carbon atoms,
including methyl, ethyl, propyl~ and decyl, or
phenyl;

-` ~i51~61
R6 is OH, NH2, NHCH2CH20H, and NH~C6H5~0C5Hlln;
R7 is alkyl containing 1 to 5 carbon atoms, such as
methyl, ethyl, propyl or pentyl, or phenyl; and
R8 is hydrogen, haloalkyl containing 1 to 3 carbon atoms,
such as CC13, CF3 and C3H4Br, CH20CH3, or
C2H4COOH .
o
The letter n, such as in CNH~C6H5~0C5Hlln, means normal-
Alkyl and phenyl, as described, are intended to include alkyl
and phenyl that are unsubstituted alkyl and phenyl as
well as alkyl and phenyl that contain substituent groups
that do not adversely effect the desired image. An example
of a suitable substituent group is alkyl containing 1 to 3
carbon atoms, such as methyl or ethyl.
Examples of useful resorcinol dye-forming
couplers are described ln, for example, Research Disclosure,
September 1978, Item 17326. Especially useful resorcinol
dye-forming couplers include 2l,6'-dihydroxyacetanilide and
2',6'-dihydroxytrifluoroacetanilide. Another useful
resorçinol dye-forming coupler is 2',6'-dihydroxy-2,5-
dimethylbenzanilide (2',6'-dihydroxyacetanilide has also
been known as 2,6-dihydroxyacetanilide and 2',6'-dihydroxy-
2,5-dimethylbenzanilide has also been known as 2,6-dihydroxy-
2',5'-dimethylbenzanilide).
Resorcinol dye-forming couplers as described can
be prepared by procedures known in the chemical art. For
example, resorcinol couplers as described can be prepared
from amino resorcinols or dihydroxybenzoic acids.
The dye-forming coupler can be used in a range of
concentrations in the descrlbed recording layer.
Typically, the recording layer contains a concentration
of dye-forming coupler that is within the range of about
0.1 to about 1.0 mole of the dye-forming coupler per mole
of total silver in the recording layer. An especially
useful concentration of dye-forming coupler is within the
.

-` " 1151~
-12~
range of about 0.25 to about 0.75 mole of dye-forming
coupler per mole of total silver in the recording layer.
Selection of an optimum concentration of
dye-forming coupler will depend upon such factors as
the particular coupler, the desired image; processing
conditions, other components in the recording layer and
the like.
Many organic silver salt oxidizing agents may be
used in the described image-forming combination
in the recording layer. The organic silver salt oxidizing
agent is typically resistant to darkening upon illumination
which helps reduce undesired deterioration of the developed
image. One class of useful silver salt oxidlzing agents
is represented by the silver salts of long-chain fatty
acids which are stable to light. The term "long-chain"
as used herein is intended to mean a chain of carbon atoms
containing 10 to 30 carbon atoms. Compounds within this
class which are useful include silver behenate, silver
stearate, silver oleate, silver laurate, silver hydroxy-
stearate, silver caprate, silver myristate and silverpalmitate.
Another useful class of organic silver salt
oxidizing agents include silver salts of certain heterocyclic
thione compounds. Useful silver salts of heterocyclic thione
compounds include, for example, those represented by the
formula:
-R-~
~N - C=S
(Z'~COOH
wherein Z' is alkylene containing 1 to 10 carbon atoms,
such as methylene, ethylene and propylene; R represents
the atoms necessary to complete a heterocyclic nucleus
selected from carbon, oxygen, sulfur and nitrogen atoms,
such as a thiazoline or imidazoline nucleus. Useful silver
salts of the described thione compounds include, for example,
the silver salts of the following compounds:
;

iiS~9~61
-13-
3-(2-carboxyethyl)-4-methyl-4-thiazoline-2-thione;
3-(2-carboxyethyl~benzothiazoline-2-thione;
3-(2-carboxyethyl)-5-phenyl-1,3,4-oxadiazoline-2-
thione;
3-(2-carboxyethyl)-5-phenyl-1,3,4-thiadiazoline-
2-thione;
3-carboxymethyl-4-methyl-4-thiazoline-2-thione;
3-(2-carboxyethyl~ phenyl-1,3,4-triazoline-2-
thione;
1,3-bis~2-carboxyethyl~imidazoline-2-thione;
1,3-bis(2-carboxyethyl~benzimidazoline-2-thione;
3-~2-carboxyethyl)-1-methylimidazoline-2-thione;
3-~2-carboxyethyl~benzoxazoline-2-thione; and
3-(1-carboxyethyl~-4-methyl-4-thiazoline-2-thione.
Another useful class of organic silver salt
oxidizing agents is represented by the complexes of silver
with nitrogen acids, such as nitrogen acids selected from
the group consisting of imidazole, pyrazole, urazole,
1,2,4-triazole and lH-tetrazole nitrogen acids or combinations
of these acids. These silver salts of nitrogen acids are
described in, for example, Research Disclosure, Volume 150,
October 1976, Item 15026. Examples of useful silver salts
of nitrogen acids are the silver salts of the following
compounds: lH-tetrazole; 5-dodecyltetrazole; 5-n-butyl-
lH-tetrazole; 1,2,4-triazole; urazole; pyrazole; imidazole
and benzimidazole.
Another useful class of silver salt oxidizing
agent is represented by the silver salts of 1,2,4-mercapto-
triazole derivatives represented by the formula:
N NH
3 (I~
Z N S (CH2 )mY
wherein Y is aryl containing 6 to 12 carbon atoms, such as
phenyl, naphthyl and para-chlorophenyl; m is O to 2; and
.
.

-14-
Z is hydrogen, hydroxyl or amine (-NH2~. Especially useful
organic silver salt oxidizing agents within this class are
those silver salts of the described 1,2,4-mercaptotriazole
derivatives wherein Y is phenyl, naphthyl or para-chloro-
5 phenyl and Z is amine (-NH2) in the above formula (I').
An example of such a compound is the silver salt of 3-
amino-5-benzylthio-1,2,4-triazole (referred to herein as
ABT). Such organic silver salt oxidizing agents are described
in, for instance, U.S. Patent 4,123,274 and U.S. Patent
10 4,128,557.
Combinations of silver salt oxidizing agents can
also be useful. An example of a combination of silver salt
oxidizing agents is the combination of the silver salts
of ABT with the silver salt of l-methyl-4-imidazoline-
15 2-thione.
Selection of an optimum silver salt oxidizing agent
or combination of silver salt oxidizing agents will depend
upon the described factors, such as the desired image, the
particular reducing agent, the particular dye-forming
20 coupler, processing conditions, the particular binder and
the like. An especially useful silver salt oxidizing agent
is the silver salt of ABT, as described.
The silver salt oxidizing agent or combination of
silver salt oxidizing agents can be useful in a range of
25 concentrations in the described recording layer. Selection
of an optimum concentration of silver salt oxidizing agent
or combination of silver salt oxidizing agents will depend
upon the described factors, such as the desired image,
the particular reducing agent, the particular dye-~orming
30 coupler, processing condltions and the llke. A typically
useful concentration of silver salt oxidizing agent or
combination of silver salt oxidizing agents is within the
range of about 0.1 mole to about 2.0 moles of silver salt
oxidizing agent per mole of reducing agent in the recording
35 layer. For example, when the silver salt oxidizing agent
is the silver salt of ABT, a typically useful concentration
of the silver salt oxidizing agent is within the range of
about 0.1 to about 2.0 moles of silver salt oxidizing agent
per mole of reducing agent in the recording layer.
~ ,

5~
Preparation of the described organic silver salt
oxidizing agent is typically not carried out in situ~ that
is not in combination with other components of the recording
layer as described. Rather, the preparation of the
oxidiæing agent is typically carried out ex situ, that is
separate from other components of the recording layer.
In most instances, the preparation of the silver salt
oxidizing agent will be separate from the other components
based on the ease of control of preparation and storage
capability.
The term "salt" as used herein, such as in organic
silver salt, is intended to include any type of bonding or
complexing mechanism which enables the resulting material
to produce desired imaging properties in the described
recording layer. In some instances the exact bonding of
the described silver salt with the organic compound is not
fully understood. Accordingly, the term "salt" is intended
to include what are known in the chemical art as "complexes".
The term "salt" is intended to include, for example, neutral
complexes and non-neutral complexes. The term is also
intended to include compounds which contain any form of
bonding which enables the desired image-forming combination
to provide the desired image.
Many reducing agents which, in their oxidized
form, form a dye with the described dye-forming coupler
may be used in the recording element according to the
invention. The reducing agent is typically an organic
silver halide color developing agent. Combinations of
reducing agents can be useful. It is important that the
reducing agent produces an oxidized form upon reaction with
the organic silver salt oxidizing agent which can react at
processing temperature with the described dye-forming coupler
to produce a desired dye. Especially useful reducing agents
are primary aromatic amines including, for example~ para-
phenylenediamines. Examples of useful reducing agents whichare primary aromatic amines include 4-amino-N,N-dimethylaniline;

~51~
-16-
4-amino-N,N-diethylaniline; 4-amino-3-methyl-N,N-diethylaniline
(also krown as N,N-diethyl-3-methyl-paraphenylenediamine~;
4-amino-N-ethyl-N-~-hydroxyethylaniline; 4-amino-3-methyl-N-
ethyl-N-~-hydroxyethylaniline; 4-amino-3-methoxy-N-ethyl-N-
~-hydroxyethylaniline; 4-amino-N-butyl-N-gamma-sulfobutyl-
aniline; 4-amino-3-methyl-N-ethyl-N-~-sulfoethylaniline; 4-
amino-3~ methanesulfonamido~ethyl-N,N-diethylaniline; 4-
amino-3-methyl-N-ethyl-N-~-~methanesulfonamido)ethylaniline;
4-amino-3-methyl-N-ethyl-N-~-methoxyethylaniline and the like.
The term "reducing agent" as used herein is
intended to include compounds which are reducing agent
precursors in the described recording layer. That is,
those compounds are intended to be included which are
not reducing agents in the recording layer until a condition
occurs such as heating of the recording layer.
An especially useful reducing agent is one that
consists essentially of a paraphenylenediamine silver halide
developing agent that exhibits an E 1/2 value in aqueous
solution at pH 10 within the range of -25 to +175 millivolts
versus SCE. The term "E 1/2 value" herein means half wave
potential. The term "SCE" herein means saturated calomel
electrode. These values are determined by analytical
procedures known in the photographic art and described in,
for example, the text "The Theory of the Photographic
Process", 4th Edition, Mees and James, 1977, pages 318-319.
The described reducing agent can be useful in
a range of concentrations in the described element according
to the invention. Selection of an optimum concentration
of reducing agent or combination of reducing agents will
3 depend upon the described factors including the desired
image, the particular silver salt oxidizing agent, the
particular dye-forming coupler, processing conditions
and the like. A typically useful concentration of reducing
agent or combination of reducing agents is within the
range of about 0.1 to about 5.0 moles of reducing agent per
mole of organic silver salt in the recording layer as

~LS14t~J
-17-
described. An especially useful concentratlon Or reduclng
agent is wi*hln the range or about 0.2 to about 2 moles Or
reduclng agent per mole Or organlc silver salt ln the
recordlng layer.
The tone Or the combined sllver lmage and dye ~mage
produced accordlng to the inventlon wlll vary dependlng
upon such factors as the sllver morphology Or the developed
silver image, the coverlng power Or the sllver materlals,
the particular dye-formlng coupler, the partlcular developlng
lO agent, processlng condltlons and the llke. In recordlng
layers that produce a brown sllver lmage, the hue Or the
dye lmage produced is preferably compllmentary to the hue
Or the silver image. An lmage hue of the comblned dye
image and sllver lmage ls preferably "neutral".
The term "neutral" as employed hereln ls lntended
to include hues whlch occaslonally are descrlbed ln the
photographic art as blue-black, grayj purple-black, black
and the llke. Whether or not a glven lmage ls "neutral" can
be readily determlned by vlsual lnspectlon wlth the unalded
20 eye.
Procedures for determlning whether or not an image
is "neutral" are known ln the photographlc art, such as
described ln Research Dlsclosure, September 1978, Item
17326.
Silica can be userul in an lmage recording layer
Or a recording element according to the lnventlon. Slllca
ln the recording layer can help produce lncreased denslty
ln a developed lmage upon lmagewlse exposure and heatlng
the recordlng layer. A varlety Or rOrms Or slllca can
30 be useful. However, colloldal slllca can be especlally
userul because lt has a large surrace area. The optlmum
concentratlon Or slllca ln the recordlng layer wlll depend
upon such factors as the deslred lmage, other components
ln the recordlng layer, processlng condltlons, layer

1~51 3L~;1
--18--
thickness and the like. Typically, the concentration
of silica is within the range of about 1 to about 1,000
milligrams per 500 square centimeters of support. The
silica can be a disadvantage in some cases, such as in
5 preparation of a high resolution transparency, because
the silica may reduce resolution of the developed image and
cause undesired light scattering.
The average particle size and particle size
range of silica in the recording layer can vary. The
10 optimum average particle size and particle size range
of silica will depend upon the described factors regarding
silica concentration. Typically, the average particle size
and particle size range of colloidal silica are most useful.
Colloidal silica that is useful includes such commercially
15 available colloidal silica products as "Cab-0-Sil", a
trademark of and available from the Cabot Corporation,
U.S.A. and "Aerosil", a trademark of and available from
DEGUSSA, West Germany. It is important that the average
particle size and particle size range of the silica or
20 any other equivalent particles not adversely affect the
desired properties of the electrically activated recording
element of the invention or the desired image produced
upon imagewise exposure and heating of the recording layer.
For instance, the silica selected should not decrease
25 sensitivity of the recording layer or produce undesired
fogging of the developed image.
The mechanism and properties which cause colloidal
silica to produce increased density in a recording layer
according to the invention is not fully understood. It is
30 believed that the large surface area of colloidal sillca
contributes to the desired results. In any case, an
especially useful embodiment of the invention, as described,
is one containing colloidal silica in the recording layer
of a charge-sensitive recording paper according to the
35 invention.

l:lS~46~
- ` "V.
The described element according to the invention
can comprise a variety of colloids and polymers alone or
in combination as vehicles and binding agents. These
vehicles and binding agents can be in various layers of the
5 element, especially in the recording layer. Suitable
materials can be hydrophobic or hydrophilic. It is necessary,
however, that the vehicle or binder in the element not
adversely affect the charge sensitivity or ohmic resistivity
of the element of the invention. Accordingly, the selection
10 of an optimum colloid or polymer, or combination of colloids
or polymers, will depend upon such factors as the desired
charge sensitivity, desired ohmic resistivity, particular
polymer, desired image, particular processing conditions
and the like. Useful colloids and polymers can be transparent
15 or translucent and include both naturally occurring
substances such as proteins, for example, gelatin, gelatin
derivatives, cellulose derivatives, polysaccharides, such
as dextran, gum arabic and the like. Synthetic polymers,
however, are preferred due to their desired charge
20 sensitivity properties and ohmic resistivity properties.
Useful polymeric materials for this purpose include polyvinyl
compounds, such as poly~vinyl pyrrolidone), acrylamide
polymers and dispersed vinyl compounds such as in latex
form. Effective polymers include water insoluble polymers
25 of alkylacrylates and methacrylates, acrylic acid, sulfo-
alkylacrylates, methacrylates and those which have
crosslinking sites which facilitate hardening or curing.
Especially useful polymers are high molecular weight
materials and resins which are compatible with the described
3 components of the element according to the invention. These
include, for example, poly(vinyl butyral), cellulose acetate
butyrate, poly(methyl methacrylate), poly(vinyl pyrrolidone),
ethyl cellulose, polystyrene, poly(vinyl chloride),
poly(isobutylene), butadiene-styrene copolymers, vinyl
35 chloride-vinyl acetate copolymers, copolymers of vinyl
acetate, vinyl chloride and maleic acid and poly(vinyl
,

~5~46~
-, ;1''
-20-
alcohol~. Combinations of colloids and polymers can also
be useful depending upon the described factors. Highly
preferred binders include polyacrylamide, as well as
copolymers of acrylamide and other vinyl addition monomers
such as copolymers of acrylamide and vinyl imidazole or
copolymers of acrylamide and N-methyl acrylamide.
An overcoat layer can be useful on the recording
layer according to the invention. It is important that
the overcoat layer not adversely affect the desired charge
sensitivity and ohmic resistivity properties of the element
according to the invention. Such an overcoat layer can
reduce fingerprinting and abrasion marks before and after
exposure and processing. The overcoat layer can be one or
more of the described polymers which are useful as binders.
These materials must be compatible with other components of
the described element according to the invention and must be
able to tolerate the processing temperatures which are
useful for developing the described images.
While it is in most cases unnecessary and
undesirable, a photosensitive component can be present in
the electrically activated recording layer, as described,
if desired. The photosensitive component can be any photo-
sensitive metal salt or complex which produces developable
nuclei upon charge exposure according to the invention. If a
photosensitive component is present in the recording layer,
an especially useful photosensitive metal salt is photo-
sensitive silver halide due to its desired properties in
forming developable nuclei upon charge exposure. A typical
concentration of photosensitive metal salt is within the
range of about 0.0001 to about 10.0 moles of photosensitive
metal salt per mole of organic silver salt in the described
element according to the invention. For example, a typical
concentration range of photosensitive silver halide is
within the range of about 0.001 to about 2.0 moles of
silver halide per mole of organic silver salt in the
recording element. A preferred photosensitive silver halide
'' '' ~ ' ~

: 1~514~1
-21-
is silver chloride, silver bromide, silver bromoiodide or
mixtures thereof. For purposes of the invention, silver
iodide is also considered to be a photosensitive silver
halide. Very fine grain photographic silver halide can be
5 useful, although a range of grain size from fine grain to
coarse grain photographic silver halide can be included in
the recording layer if desired. The photographic silver
halide can be prepared by any of the procedures known in the
photographic art. Such procedures and forms of photographic
silver halide are described in, for example, the Product
Licensing Index, Volume 92, December 1971, Publication 9232.
The photographic silver halide can be washed or unwashed,
can be chemically sensitized by means of chemical sensitiza-
tion procedures known in the art, can be protected against
15 the production of fog and stabilized against loss of
sensitivity during keeping as described in the above Product
Licensing Index publication.
If a photosensitive component is present in the
described electrically activated recording layer, the
20 described image-forming combination enables the concentration
of the photosensitive component to be lower than normally
would be expected in a photosensitive element. This lower
concentration is enabled by the amplification affect of the
image-forming combination, as described, as well as the
25 formation of developable nuclei according to the invention
in addition to the dye enhancement of the silver image
formed. In some instances the concentration of photosensitive
metal salt can be sufficiently low that after imagewise
exposure and development of the photosensitive metal salt
30 alone, in the absence of other of the described component,
the developed image is not visible to the unaided eye.
The elements according to the invention can contain
addenda which aid in producing a desired image. These addenda
can include, for example, development modifiers that function
:

~Sl ~
\
-22-
as speed-increasing compounds, hardeners, plasticizers and
lubricants, coating aids, brighteners, spectral sensitizing
dyes, absorbing and filter dyes. These addenda are described
in, for example, the Product Licensing Index, Volume 92,
December 1971, Publication 9232, and Research Disclosure,
December 1978, Item 17643.
While it is in many cases unnecessary and
undesirable, a post-processing stabilizer or stabilizer
precursor to increase post-processing stability of the
developed image can be included in the described recording
layer. In many cases the recording layer following
processing is sufficiently stable to avoid the need for
incorporation of a stabilizer or stabilizer precursor in the
recording layer. However, in the case of recording materials
which contain photosensitive silver halide, it can be
desirable to include such a stabilizer or post-processing
stabilizer precursor to provide increased post-processing
stability. A variety of stabilizer or stabilizer precursors
can be useful in the elements according to the invention.
These stabilizers or stabilizer precursors can be useful
alone or in combination if desired. Typically useful
stabilizers or stabilizer precursors include, for instance,
photolytically active polybrominated organic compounds.
Thioethers or blocked azolinethione stabilizer precursors
or other organic thione stabilizer precursors known to be
useful in photothermographic materials can be useful if
desired.
When a stabilizer or stabilizer precursor is
present in the recording layer of an element accordlng to
the invention, a range of concentrations of stabillzer or
stabilizer precursor can be useful. The optimum concen-
tration of stabilizer or stabilizer precursor will depend
upon such factors as the particular element, processing
conditions, particular stabilizer or stabilizer precursor,
desired stability of the developed image and the like.

1151461
-23-
A typically useful concentration of stabilizer or stabilizer
precursor is within the range of about 1 to about 10 moles
of stabilizer or stabilizer precursor per mole of photo-
sensitive component in the element according to the
invention.
It is often advantageous to include a heat
sensitive base-release agent or base precursor in the
recording element according to the invention to produce
improved and more effective image development. A base-release
agent or base precursor herein is intended to include
compounds which upon heating in the recording layer produce
a more effective reaction between the described components
of the image-forming combination and in addition produce
improved reaction between the oxidized form of the described
reducing agent and the dye-forming coupler. Examples of
useful heat sensitive base-release agents or base precursors
are aminimide base-release agents, such as described in
Research Disclosure, ~olume 157, May 1977, Items 15733,
15732, 15776 and 15734; guanidinium compounds, such as
guanidinium trichloroacetate; and other compounds which are
known in the photothermographic art to release a base moiety
upon heating, but do not adversely affect the desired
properties of the recording element. Combinations of
heat sensitive base-release agents can be useful if desired.
A heat sensitive base-release agent or base
precursor, or combinations of such compounds, can be useful
in a range of concentrations in the described elements
according to the invention. The optimum concentration of
heat sensitive base-release agent or base precursor will
3 depend upon such factors as the desired lmage, particular
dye-forming coupler, particular reducing agent, other
components of the imaging element, processing conditions and
the like. A useful concentration of described base-release -
agent is typically within the range of about 0.25 to 2.5
'` ' , ': ~ ~,
,~ . ~. - .. ,.:
.
- . .
'

llS~
--24-
moles of base-release agent or base precursor per mole of
reducing agent in the recording layer according to the
invention.
The charge-sensitive element according to the
invention can comprise a variety of supports. The term
"electrically conductive support" is intended herein to
include (a) supports that are electrically conductive without
the need for separate addenda in the support or on the
support to produce the desired degree of electrical
conductivity and (b) supports that comprise addenda or
separate electrically conductive layers that enable the
desired degree of electrical conductivity. Typical supports
include cellulose ester, polytvinyl acetal), poly(ethylene
terephthalate), polycarbonate and polyester film supports
and related films and resinous materials. Other supports
are useful, such as glass, paper, metal and the like which
can withstand the processing temperatures described and do
not adversely affect the charge-sensitive properties and
ohmic resistivity which is desired. Typically, a flexible
support is most useful.
The recording element according to the invention
can include an electrically conductive layer positioned
between the support and the described electrically conductive
subbing layer. This is illustrated by subbing layer 55 in
Figure 5 for example. The electrically conductive layers,
as described, such as layers 62 and 55 in Figure 5, can
comprise a variety of electrically conducting compounds
which do not adversely effect the charge sensitivity and
ohmic resistivity properties of an element according to the
invention. Examples of useful electrically conductive
layers include layers comprising electrically conductive
chromium compositions and nickel.
An especially useful embodiment of the invention
is an electrically activated recording element, as described,
,
.
: ~ .

11S ~L~
-25-
wherein the electrlcally conductlve support has an
electrlcally conductlve subblng layer between the electrlcally
conductlve support and the electrlcally actlvated recording
layer. The electrlcally conductive subbing layer can comprlse
a sultable electrlcally conductive polymer. ExampleS Or
suitable subbing layers lnclude poly(alkyl acrylate-co-
vlnylldene chlorlde-co-ltaconlc acld) layers. Sultable
polymers for the subbing layer are descrlbed in, for
example, U.S. Patent 3,271,345.
In some embodlments the photoconductlve layer
can be a self-supportlng layer, such as a photoconductor
ln a sultable blnder. In such embodlments an electrlcally
conductlve layer, such as an electrlcally conductlve nlckel
or chromium composition layer, can be coated on the photo-
conductive layer. This is lllustrated ln, ror instance,
Flgure 3 ln the drawings ln which electrlcally conductlve
layer 2B ls on photoconductlve layer 30 whlch ls
selr supportlng. Alternatlvely, the photoconductlve layer
can be coated on an electrlcally conductlve support, such
as lllustrated ln Figure 5 of the drawlngs.
The descrlbed layers accordlng to the lnvention
can be coated by coatlng procedures known ln the photo-
graphic art lncludlng dlp coatlng, alrknlfe coatlng, curtaln
coatlng or extruslon coatlng uslng hoppers known ln the
photographic art. I~ deslred, two or more layers can be
coated slmultaneously.
The various components of the charge-sensitlve
materlals accordlng to the inventlon can be prepared ror
coatlng by mlxlng the components wlth sultable solutlons
or mlxtures lncludlng sultable organlc solvents dependlng
on the partlcular charge-sensltlve materlal and the
components. The components can be added by means of
procedures known ln the photographlc art.
~ ~ t
~i

-26-
Useful charge-sensitive elements according to
the invention can comprise an electrically conductive
support having thereon an electrically activated recording
layer which has a thickness within the range of about l to
about 30 microns, typically within the range of about 2 to
about 15 microns. The optimum layer thickness of each of
the layers of an element according to the invention will
depend upon such factors as the particular ohmic resistivity
desired, charge sensitivity, particular components of the
layers, desired image and the like.
A "melt-forming compound" can be useful in the
recording layer according to the invention to produce an
improved developed image. A "melt-forming compound" can
be especially useful with recording materials containing
silver salts of nitrogen acids. The term "melt-forming
compound" herein is intended to mean a compound which upon
heating to the described processing temperature produces an
improved reaction medium, typically a molten medium, wherein
the described image-forming combination can produce a
desired image upon development. The exact nature of the
reaction medium at processing temperature described is not
fully understood. It is believed that at the reaction
temperature, as described, a melt occurs which permits the
reaction components to better interact. If desired, a
melt-forming compound can be included with other components
of the recording layer prior to coating on the described
support. Examples of useful melt-forming compounds include
succinimide, dimethyl urea, sulfamide and acetamide.
The optimum concentration of the described
components of the element according to the invention will
depend upon a variety of factors as described. An especially
useful recording element according to the invention comprises
about l to about 5 moles of the described dye-forming coupler
for each l to 5 moles o~ the described reducing agent and

` ~1514~1 ~
-27-
about 3 to about 20 moles of the described organic silver
salt oxidizing agent.
The described organic silver salt oxidizing agent
can contain a range of ratios of the organic moiety to the
silver ion. The optimum ratio of the organic moiety to
silver ion in the organic silver salt oxidizing agent will
depend upon such factors as the particular organic moiety,
the particular concentration of silver ion desired,
processing conditions, the particular dye-forming coupler
and the like. The molar ratio of organic moiety to silver
as silver ion in the salt is typically within the range of
about 0.5:1 to about 3:1.
The image recording layer of the invention can
have a range of pAg. The pAg can be measured using
conventional calomel and silver-silver chloride electrodes,
connected to a commercial digital pH meter. Typically,
the pAg in a dispersion containing the described components
for the recording layer is within the range of about 2.5
to about 7.5. The optimum pAg will depend upon the
described factors~ such as the desired image, processing
conditions and the like.
A recording material containing the described
organic silver salt oxidizing agent typically has a pH
that is within the range of about 1.5 to about 7Ø An
especially useful pH for the described recording layer
is within the range of about 2.0 to about 6.o.
The desired resistivity characteristics of
a recording material according to the invention can be
obtained by separately measuring the current-voltage
characteristic of each sample coating at room temperature
by means of a mercury contact sample holder to make a
mercury contact to the surface of the coating. To eliminate
the possibility that a micro thickness surface air gap
might affect the measured resistivity, exposures can be
made with evaporated metal (typically gold or aluminum~
~, , . , . j, , ~ , .

1~1461
-28-
electrode on the surface of a charge sensitive and
photoconductor coating to be tested. The resistivity can
be measured at various ambient temperatures. The data
can be measured at a voltage of, for example, 20 volts
5 or 4 x 10 volts per centimeter, which is within the ohmic
response range of the layer to be tested. It can be
expected that the resistivity of the charge-sensitive layer
will vary widely with temperature. It can also be expected
that the dielectric strength of the layer will vary with
10 temperature. The selection of an optimum temperature for
exposure can be determined based on the dielectric strength
of the layer.
An especially useful embodiment of the invention
having the desired characteristics comprises a charge-
sensitive recording element, preferably having an ohmicresistivity of at least about 104 ohm-cm, comprising, in
sequence: (a~ a first electrical conducting layer, (b) a
photoconductive layer, (c~ an electrically activated recording
layer separated from (b~ by an air gap of up to about 10
20 microns and comprising, in reactive association: (A) a
dye-forming coupler consisting essentially of 2',6'-dihydroxy-
trifluoroacetanilide, (B) an image-forming combination
consisting essentially of (i) an organic silver salt
oxidizing agent consisting essentially of a silver salt of
25 3-amino-5-benzylthio-1,2,4-triazole, with (ii~ a reducing
agent consisting essentially of 4-amino-2-methoxy-N,N,5-
trimethylaniline sulfate, and (C) a polyacrylamide binder,
(d) an electrically conductive subbing layer comprising a
poly(alkyl acrylate-co-vinylidene chloride~ on (e) a
3 second electrical conducting layer, on (f~ a support.
A variety of energy sources can be useful for
imagewise exposure of a recording element accordlng to the
invention. Selection of an optimum energy source for
imagewise exposure will depend upon the described factors,
35 such as the sensitivity of the photoconductor layer, the
particular image recording combination in the electrically
activated recording layer, desired image and the llke.
!
. ' .
.

l~S~
-2~-
Useful energy sources for imagewise exposure include, for
example, visible light, X-rays, lasers, electron beams,
ultraviolet radiation, infrared radiation and gamma rays.
A variety of processing steps and means can be
useful for producing a dye image and silver image in the
described recording layer after imagewise exposure. In
one embodiment of the invention a dry electrically
activated recording process for producing a dye image and
silver image, preferably a dye enhanced silver image, in a
charge-sensitive recording element, preferably having an
ohmic resistivity of at least about 104 ohm-cm, containing
at least one electrically activated recording image-forming
combination consisting essentially of ~A~ a dye-forming
coupler, and (B) an image-forming combination as described,
which process can comprise the steps: ~I) applying an electric
potential imagewise to the recording element of a magnitude
and for a sufficient time to produce in the image areas a
charge density within the range of about 10 3 coulomb/cm2 to
about 10 9 coulomb/cm , the charge density forming a
developable latent image in the image-forming combination;
and then (II) heating the recording element substantially
uniformly at a temperature and for a time sufficient to
produce a dye image and silver image, preferably a dye
enhanced silver image.
An especially useful process embodiment of the
invention is a dry electrically activated recording process
for producing a dye enhanced silver image in a charge-sensitive
recording element, preferably having an ohmic resistivity of
at least about 104 ohm-cm, comprising, in sequence, a
3 support having thereon (a~ a first electrically conductive
layer, (b~ an organic photoconductive layer, (c~ an
electrically activated recording layer separated from ~b~
by an air gap of up to 20 microns and comprising ~A~ a
dye-forming coupler consisting essentially of a compound
selected from the group consisting of 2,6-dihydroxy-
acetanilide and 2',6'-dihydroxytrifluoroacetanilide and

~5
-30-
combinations thereof, (B? an image-forming combination
comprising (i) an organic silver salt oxidizing agent
consisting essentially of a silver salt of 3-amino-5-benzyl-
thio-1,2,4-triazole, with tii~ a reducing agent consisting
essentially of 4-amino-2-methoxy-N,N,5-trimethylanilinesulfate,
and (iii) a polyacrylamide binder, (d~ an electrically
conductive polymer subbing layer and te) a second electrically
conductive layer; said process comprising the steps: (I)
imagewise altering the conductivity of the photoconductor
layer in accord with an image (X') to be recorded while
simultaneously (II~ applying across the photoconductor layer
and recording layer an electrical potential of a magnitude
and for a sufficient time to produce a developable latent
image in the recording layer corresponding to the image
~X'); and then (III~ heating the recording layer substantially
uniformly at a temperature and for a time sufficient to
produce a dye enhanced silver image corresponding to image
(X') in the recording layer.
An imagewise current flow is produced through the
described electrically activated recording layer. Although
a particular technique to produce an imagewise current flow
has been described for use in a variety of recording
apparatus, the especially useful techniques are those
which include use of a photoconductive layer as an image to
current converter. The imagewise current flow can be
provided, however, by contacting the recording element with
a suitable electrostatically charged means such as an
electrostatically charged stencil or scanning the recording
element with a beam of electrons.
Heating the recording element after latent image
formation can be carrled out by technlques and by means
known in the photothermographic art. For example, the
heating can be carried out by passing the imagewise exposed
recording element over a heated platen or through heated
rolls, by heating the element by means of microwaves, by

-31-
means of dielectric heating or by means of heated air and
the like. A visible image can be produced in the described
exposed material within a short time, that is within about
l to about 90 seconds, by the described uniform heating
step. An image having a maximum transmission density of at
least 1.8 and typically at least 2.2 can be produced
according to the invention. For example, the recording
element can be uniformly heated to a temperature within the
range of about 100C to about 200C until a desired image is
developed, typically within about l to about gO seconds.
The imagewise exposed material according to the invention is
preferably heated to a temperature within the range of about
120C to about 180C. The optimum temperature and time for
processing will depend upon such factors as the desired
image, the particular recording element, heating means and
the like.
The described electrically activated recording
process can be useful for producing multiple copies.
According to this embodiment of the invention, multiple
copies can be prepared by a dry electrically activated
recording process for producing a dye image and silver
image, preferably a dye enhanced silver image, in an
electrically activated recording element comprising the
steps: (I) imagewise altering the conductivity of a
photoconductive layer (Z) in accord with an image that
is to be recorded; (II) positioning the imagewise altered
photoconductive layer (Z) from (I) adjacent an electrically
activated recording layer of the recording element
comprising (A) a dye-forming coupler, and (B) an image-
3 forming combination comprising ~i~ an organic silver saltoxidizing agent, with ~ii) a reducing agent which, in its
oxidized form, forms a dye with the dye-forming coupler,
wherein the photoconductive layer ls separated from the
recording layer by an air gap of up to 20 microns, (III)
, !
.~

-32-
applying an electrical potential across the photoconductor
layer and recording layer of a magnltude and for a sufficient
time to produce in the areas of the recording layer
corresponding to the imagewise altered portions of the
photoconductor layer a charge density within the range of
about lO 3 coulomb/cm2 to about lQ 9 coulomb/cm2, the charge
density forming in the areas a developable latent image;
then (IV~ uniformly heating the recording element at a
temperature and for a time sufficient to produce a dye image
and silver image, preferably a dye enhanced silver image, in
the recording element; followed by (V) positioning the
imagewise altered photoconductor layer ad~acent a second
electrically activated recording layer, preferably having an
ohmic resistivity of at least about 104 ohm-cm, wherein
said photoconductor layer is separated from said second
recording layer by an air gap of up to 20 microns; (VI)
applying an electrical potential across the photoconductor
layer and the second recording layer of a magnitude and for
a sufficient time to produce in the areas of the image of
said photoconductive layer a charge density within the range
of about lO 3 coulomb/cm2 to about lO 9 coulomb/cm2, the
charge density forming a developable latent image; and then
(VII? uniformly heating the second recording layer at a
temperature and for a time sufficient to produce a developed
image in the second recording layer.
While the exact mechanism of image formation
upon heating is not fully understood, it is believed that
the imagewise exposure to charge provides nuclei in the
image areas. It is believed that the nuclei formed in the
image areas increase the reaction rate and act as catalysts
for the reaction between the organic silver salt oxidizing
agent and the reducing agent. It is believed that the nuclei
enable a form of amplification which would not otherwise
be possible. -The described organic silver salt oxidizing
agent and reducing agent must be in a location with respect
,,,
` .
- .
- `~ . .,' - ' `:
`

llS1461
--33-
to each other which enables the nuclei formed to provide thedesired catalytic effect. The described organlc silver salt
oxidizing agent and reducing agent as well as the dye-forming
coupler are in reactive association in the electrically
activated recording layer. The term "in reactive association"
is intended to mean that the nuclei resulting from the imagewise
exposure are in a location with respect to the described
components which enables desired catalytic activity, desired
processing temperature and capability for a more useful dye
image and silver image.
Referring to the drawings, embodiments of the
invention are depicted schematically in Figures 1 and 2.
According to the embodiment illustrated in Figures 1 and 2,
a charge-sensitive recording layer 10 is placed upon a
grounded electrically conductive backing or support 12.
A current is selectively applied to the recording layer 10
by the point of a metal stylus 14 which is raised to a
sufficiently high voltage relative to the support 12 by a
voltage source 16, and brought into moving contact with the
exposed surface of the recording layer 10 containing the
described image-forming combination and dye-forming coupler.
Upon contacting the recording layer 10 with the stylus 14,
a current flow is produced in the areas of the recording
layer contacted by the stylus and a developable latent
image forms, i.e. a pattern of nuclei sites, in the
pattern desired. The charge density produced by the stylus
in the contacted areas of the recording layer need not be
sufficient to produce a visible image in the recording layer
10, however, the charge density must be sufficient to produce
a latent image in the recording layer in those areas
contacted by the stylus. Although a particular technlque
to produce an imagewise current flow through the recording
layer 10 has been described, techniques for producing
imagewise current flow generally known in the art of
recording can be useful and are intended to be encompassed
.. A~
I .:~

5~4~1
-34-
by the description. The area of the recording layer 10
designated as 18 is intended to be illustrative of an area
of nuclei sites formed upon contact of the stylus 14 with
the recording layer 10. Other techniques for producing a
nuclei pattern include, for example, contacting the recording
layer 10 with an electrostatically charged stencil or
scanning the layer 10 with a beam of electrons in an image
pattern.
Figure 2 illustrates development of the latent
image formed in the recording element in Figure 1 by, for
example, moving the element from Figure 1 into contact
with a heated metal platen 24. The heat from platen 24 passes
through the support 22 to the layer 20 containing the latent
image to cause the desired reaction in the latent image area.
The reaction in the latent image area causes development
to produce a visible image 26 consisting essentially of a
dye image and silver image, preferably a dye enhanced silver
image, in the recording layer 20. Upon development the
recording element is~removed from the platen 24. No
processing solutions or baths are required in this heat
development step.
Another illustrative embodiment of the invention
is schematically shown in Figures 3 and 4. In this
embodiment, in Figure 3, the developable sites 40 and 42,
that is the latent image sites, are formed by sandwiching a
charge-sensitive recording layer 32 and an image-to-current
converter layer 30, preferably a photoconductive layer,
between a pair of electrically conductive layers 28 and 34.
Layers 28 and 34 can comprise suitable supports for layers
30 and 32 or layers 28 and 34 can be on separate suitable
supports, not shown, such as film supports. A high potential
electric field is established across the photoconductive
layer 30 and recording layer 32 by connecting the conductive
layers 28 and-34 by connecting means 35 containing power

1~15~
\
-35-
source 36. The electric field across the layers is con-
trolled by switch 38. The latent image formation at latent
image sites 40 and 42 is caused by imagewise exposing the
photoconductive layer 30 through the conductor 28 to exposure
means 44, typically actinic radiation, preferably X-ray.
The layer 28 and any support for layer 28 must be ~ufficiently
transparent to the energy 44 to enable the energy to pass
to a desired degree to photoconductive layer 30. The
exposure selectively increases the conductivity Or the
conductive layer in those regions exposed to actinic
radiation. When switch 38 is closed thereby establishing
an electric field across the layers, an imagewise current
flow is produced through the recording layer 32. The
current flow occurs in those regions of the recording layer
32 only in position with the exposed portions of the
photoconductive layer 30. An air gap 46 of up to 20 microns
is provided between layers 30 and 32. The air gap 46
can be, for example, 1 to 10 microns. After a sufficient
charge density, typically less than 1 millicoulomb per
square centimeter, preferably about 1.0 microcoulomb/cm2,
has been produced in the current exposed portions of the
recording layer 32, switch 38 is opened, thereby disrupting
the current flow.
The described technique for application of voltage
across the photoconductive and recording layers is
illustrative. A variety of techniques known in the
recording art can be useful and are intended to be included
in this description. For example, a grid control corona
discharge means, not shown, can be substituted for the
voltage source and conducting layer 28.
To develop the dye image and silver image in
latent image sites 40 and 42, the recording element containing
layers 32 and 34 is moved away from the photoconductive
layer. Connecting means 35 is also disconnected. The
recording element illustrated in Figure 4 is then contacted
with a heated platen 52 illustrated in Figure 4. The heat
,
: '

liS1~6~
-36-
from the platen 52 passes through the support 50 to the
layer 48 containing a latent image to produce a visible dye
image and silver image 54. The heating is preferably
carried out substantially uniformly by merely positioning
the recording element in heat transfer relationship with
the heated platen 52. After the development of the silver
image and the dye image, the recording element is removed
from the platen.
An especially useful embodiment of the invention
is illustrated in Figure 5 in the drawings. In Figure 5
the charge-sensitive recording arrangement consists of a
support 54 having thereon an electrically conductive layer
55, typically consisting of a ~ermet composition, having
thereon an electrically conductive subbing layer 56, such
as an alkyl acrylate polymer layer. On the subbing layer
56 is coated a recording layer 57 containing the image-forming
combination and dye-forming coupler. An air gap 59,
typically about 1 micron thick, is present between overcoat
layer 58 on recording layer 57 and a lead monoxide photo-
conductive layer 60. The layer 60 has a nickel electricallyconductive layer 62 which is on a transparent film support
64. Developable nuclei are formed in recording layer 57
by imagewise exposure with a suitable radiation source, such
as a tungsten light source or X-ray source, not shown, through
step tablet 66. At the time of imagewise exposure with the
energy source, a high potential electric field is established
across the photoconductive and image-recording layers by
connecting the conductive layer 62 and the electrically
conductive layer 55 by connecting means 6~ through a power
source 68. The electric field across the layers is controlled
by switch 70. After the necessary charge density is
established, switch 70 can be opened, thereby disrupting the
current flow. Imagewise exposure for about 1 second at
about 50 footcandles produces a developable image in recording
layer 57. A 0.3 density step wedge can be used for imagewise
exposure purposes if desired. To develop the resulting
latent image, layer 57 is disconnected from connecting means
, ~

~15~
-37~
69 and power source 68 and moved away from the photoconductive
layer 60. The recording layer 57 can then be heated
uniformly by contacting it with a heated metal platen, not
shown, until the desired dye image and silver image are
produced.
Interlayers can be useful in certain instances
in the charge-sensitive recording element as desired,
to help avoid undesired transfer of components of the
described layers. Useful interlayers are described in, for
example, U.S. Patent 3,978,335 of Gibbons.
The photoconductive layer, such as the layer 60 in
Figure 5, can include a variety of binders and/or sensitizers
known in the electrophotographic art. Useful binders are
described in, for example, U.S. Patent 2,361,019 of Gerhart
1~ and U.S. Patent 2,258,423 of Rust. Sensitizing compounds
useful in the photoconductive layer are described in, for
example, U.S. Patent 3,978,335 of Gibbons.
In the embodiments illustrated which use an air
gap between the photoconductor and image recording layers,
the air gap distances can be controlled by methods known in
the art, such as by the roughness of the surface of the
photoconductor layer as well as the roughness of the surface
of the image recording layer. The air gap need not be
uniform. However, best results are often observed with a
uniform air gap. The air gap can be, for example, up to
about 2~ microns thick, preferably within the range of about
1 to about 10 microns thick. For example, the distances
shown in Figure 3 between photoconductor layers 30 and 32 can
be up to 20 microns, such as within the range of about 1 to
about 10 microns, as illustrated by air gap 46.
The resistivity of a useful recording layer
according to the invention can be effected by such factors
as exposure history, the direction of the applied field and,
when sandwiched with a photoconductor, by air gap affects
and photoconductor affects. The number of variables affecting
the resistance of the recording layer coupled with non-ohmic
behavior of the layer at higher applied fields, can affect
the choice of an optimum recording material and imaging

~A~
-38-
means. The reslstlvlty values as descrlbed hereln rOr
particular recordlng materlals are thereror values measured
under temperature and voltage condltlons whlch produce
deslred ohmic behavlor.
If deslred, the recordlng element and lmaglng
means accordlng to the lnventlon can be readlly modlrled to
provlde a contlnuous lmage recordlng operatlon. This can be
carrled out by means Or deslred control clrcultry and
contlnuous transport apparatus, not shown.
The ~ollowlng examples are lncluded ror a rurther
understanding of the lnventlon.
Example 1
This lllustrates a negatlve-worklng electrlcally
activated recordlng element and process accordlng to the
lnventlon for produclng a dye lmage and sllver lmage.
The element and layers for thls e~ample are
slmllar to those descrlbed ln Flgure 5.
The followlng composltlon was coated on a
poly(ethylene terephthalate) fllm support contalnlng a
poly(methyl acrylate-co-vlnylldene chlorlde-co-ltaconlc acld)
subbing layer on a Cermet conductlng layer:
sllver 3-amino-5-benzylthlo-1,2,4-8.0 ml
trlazole (1.5:1 llgand to sllver
lon ratlo) (dlspersed ln 1% gelatln)
methyl mercaptotrlazole (1~ solutlon 0.3 ml
ln ethanol) (antlroggant)
4-phenyl-3-lmino-5-thlourazole (1%0.3 ml
solutlon ln ethanol~ (development
accelerator~
surfactant (Surractant lOG whlch0.2 ml
ls a polyglycldol ether avallable
rrom the Olln Corporatlon, U.S.A.)
tlO% solutlon ln water~
4-amlno-methoxy-N,N,5-trlmethyl-75 mg ~dlssolved
3~ anlllne sulfate ~reduclng agent~ ln 1 ml
Or water~
2'~6'-dlhydroxytri~luoroacet-180 mg tdlssolved
anlllde tdye-rormlng coupler)ln 1 ml
Or water)
~, . .
'~ '
~.
, ... . . ~ ... . ..

~i5
- 39-
The composition after mixing was coated at a 5 mil wet
coating thickness to produce a recording layer (57 in Figure
5) containing 90 to 100 milligrams of sllver per 929 cm2 of
support.
The layer 60 consisted of a 17 micron thick
coating of a composite type organic photoconductor con-
sisting essentially of an aggregate organic photoconductor
as described in U.S. 3,615,414 as the photoconductive
compound. The photoconductor was coated on conducting layer
10 62 consisting of copper iodide on a poly(ethylene terephthalate)
film support 64 shown in Figure 5. An air gap of about 1 to
about 7 microns separated the photoconductive layer 60 from
recording layer 57. ~isible light exposure imagewise was
made with simultaneous application of a voltage Or positive
15 4, ooo volts to the resulting so-called sandwich shown in
Figure 5. The intensity and duration of light exposure were
sufficient to produce a developable latent image in the
recording layer 57. A charge exposure of 100 microcoulombs/cm2
was used for forming a latent image in the recording layer
20 57-
The photoconductive layer and the recording layerwere separated after imagewise exposure and the recording
layer was uniformly heated for 10 seconds at 160C. This
produced a silver image and dye image in the exposed
25 areas of the recording layer. A 1.0 transmission density
image was observed in the area exposed to charge.
Example 2
A recording element as described in Example 1
was prepared with the exception that the described accelerator
30 was not included in the recording layer. Visible light
exposure imagewise was made with several silver film
test obJects by means of the photoconductor described in
Example 1 with simultaneous application of 1,800 volts
to the described so-called sandwich. A positive polarity
35 was applied to the photoconductor. The 15 seconds exposure
to visible light was made by means of a 55 footcandle
yellow fluorescent illumination source ~about 500 to 700
nanometers).

1~519Lg~
-40-
The resulting exposed recording layer was separated
from the photoconductive layer. The recording layer was
then uniformly heated for 20 seconds at 180C. This produced
a developed silver image and dye image in the exposed
areas. The resulting negative image had a maximum
transmission density of about 1.0 and a minimum transmission
density of about 0.20.
Example 3
A charge recording element was prepared as described
in Example 1.
X-ray exposures were made imagewise of several
metallic test objects by means of a 90 micron thick coating
of a photoconductor containing tetragonal lead oxide photo-
conductor and photoconductive layer 60 as shown in Figure 5.
The photoconductive layer was coated on a conducting layer
consisting essentially of nickel which was coated on a
poly(ethylene terephthalate) film support. The photo-
conductive layer served as a current transducer for the
X-ray imaging. Exposures were made for 20 seconds using
110 kVp X-rays from a commercially available X-ray energy
source. A voltage of 3,200 volts was applied to the
so-called sandwich during the imagewise exposure with X-rays.
A positive polarity was applied to the photoconductor.
After imagewise exposure, the recording layer was
separated from the photoconductive layer. The exposed
recording layer was then heated for 10 seconds uniformly
at 180C. A developed silver image and dye image was
produced in the recording layer.
The resulting developed negative image had a
maximum transmission density of about 1.2 to 1.1 and a
minimum transmission density of 0.20. The tone o~ the
developed image was neutral ~black).
Example 4
A charge recording element was prepared as
described in Example 1 with the exception that the silver
salt oxidizIng agent contained no gelatin binder. The
sllver salt oxidizing agent consisted of a binderless 1.5:1

- liSl~
--41--
ligand to silver ion dispersion of a silver salt of 3-amino-
5-benzylthio-1,2,4-triazole. Charge exposures were made by
means of a grid controlled corona exposure device, not
shown in the drawings, applying a positive 1,000 volt grid
potential. The exposure device is described in, for example,
U.S. 3,370,212.
The exposed recording layer was subsequentially
processed by uniformly heating for 12 seconds at 160C.
A developed dye enhanced silver image was produced. The
developed image had a maximum transmission density of
1.9. It was found that such an image could be produced
with a charge of about 100 microcoulombs/cm2.
The procedure was repeated with the exception
that the charge exposure was 4 microcoulombs/cm2. This
produced a developed image having a maximum transmission
density of 1.0 and a minimum transmission density of 0.20.
The invention has been described in detail with
particular reference to preferred embodiments thereof, but
it will be understood that variations and modifications can
be effected within the spirit and scope of the invention.