Note: Descriptions are shown in the official language in which they were submitted.
BACKGROUND OF THE INVENTION
r'his Invention relates in general to xerography and, more specifi-
cally, to a novel photoconductive device and method of use.
In the art of xerography, a xerographic plate containing a photo-
5 conductive insulating layer is imaged by first uniformly electrostaticallycharging its surface. The plate is then exposed to Q pattern of activating
electromagnetic radiation such as light, which selectively dissipates the
charge in the illuminated areas of the photoconductive insulator while leaving
behind a latent electrostatic image in the non-illuminated areas. This latent
10 electrostatic image may then be developed to form a visible image by
depositing finely divided electroscopic marking particles on the surface of the
photoconductive insulating layer.
A photoconductive layer for use in xerography may be a homo-
geneous layer OI a single material such as vitreous selenium or it may be a
15 composite layer containing a photoconductor and another material. One type
of composite photoconductive layer used in xerography is illustrated by U.S.
- Patent 3,121,û06 to Middleton and Reynolds which describes a number of layers
comprising inely divided particles of a photoconductive inorganic compound
dispersed in an electrically insulating organic resin binder. In its present
20 commercial form, the bînder layer contains particles of zinc oxide uniformly
dispersed in a resin binder and coated on a paper backing.
~; In the particular examples described in Middleton et al, the binder
comprises a material which is incapable of transporting injected charge
carriers generated by the photoconductor particles for any significant
25 distance. As a result, witll the particular material disclosed in Middleton et al
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the photoconductor par-ticles must be, in substantlally continuous
particle-to-particle contact throughou-t the layer in order to
permit the charge dissipation required for cyclic operation.
Therefore, with the uniform dispersion of photoconductor particles
described in Middleton et al, a relatively high volume concen-
tration of photoconductor, about 50 percent by volume, is
usually necessary in order to obtain sufficient photoconductor
particle-to-particle contact for rapid discharge. However, it
has been found that high photoconductor loadings in -the binder
results in the physical continuity of the resin being destroyed,
-thereby significan-tly reducing the mechanical properties of the
binder layer. Systems with high photoconductor loadings are often
characterized as having little or no flexibility. On the other
hand, when the photoconductor concentration is reduced
appreciably below about 50 percent by volume, the photo~induced
discharge rate is reduced, making high speed cyclic or repeated
imaging difficult or impossible.
U.S. Patent 3,121,007 to Middleton et al teaches another
type of photoreceptor which includes a two-phase photoconductive
layer comprising photoconductive insulating particles dispersed in
a homogeneous photoconductive insulating matrix. The photoreceptor
is in the form of a particulate photoconductive inorganic pigment
broadly disclosed as being present in an amount from about 5 to 80
percent by weight. Photodischarge is said to be caused by the
combination of charge carriers generated in the photoconductive
insulating matrix material and charge carriers injected from the
photoconductive pigment into the photoconductive insulating matrix.
U.S, Patent 3,037,861 to Hoegl et al teaches that
poly(N-vinylcarbazole) exhibits some long-wave length U.V. sensi-
tivity and suggests that i-ts spectral sensitivity can be extended
.
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into the visible spec-trum by the addition of dye sensitizers. The
Iloegl et ~1 pa-tent further suggests that other additives such as
zinc oxide or titanium dio~ide may also be used in conjunction wi-th
poly(N-vinylcarbazole). In the Hoegl et al patent, the poly(N-
vinylcarbazole) is intended to be used as a photoconductor, with
or without additive materials which extend its spectral sensitivlty.
In addition to the above, certain specialized layered
structures particularly designed for xeflex imaging have been
proposed. For example, U.S. Patent 3,165,405 to Hoesterey
utilizes a two-layered zinc oxide bincler structure for reflex
imaging. The Hoesterey patent utilizes two separate contiguous
photoconductive layers having different spectral sensitivies in
order to carry out a particular reflex imaging sequence. The
Hoesterey device utilizes the properties of multiple photocon-
ductive layers in order to obtain the combined advantages of the
separate photoresponse of the respective photoconductive layers.
It can be seen from a review of the conventional com-
posite photoconductive layers cited above, that upon exposure to
light, photoconductivity in the layered structure is accomplished
by charge transport through the bulk of the photoconductive layer,
as in the case of vitreous selenium (and other homogeneous layered
modifications). In devices employing photoconductive binder
structures which include inactive eléctrically insulating resins
such as those described in the Middleton et al, U.S. Paten-t
3,121,006, conductivity or charge transport is accomplished through
high loadings of the photoconductive pigment and allowing particle-
to-particle contact of the photoconductive particles. In the case
of photoconductive particles dispersed in a photoconductive matrix,
such as illustrated by the Middleton et al 3,121,007 patent,
photoconductlvity occurs through the generation and transport of
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char~e carriers in both the photoconductive matrix and the
photoconductor pigment particles.
Although the above patents rely upon distinct
mechanisms o~ discharge throughout the photoconductive layer, they
generally suffer from com~on deficiencies in that the photocon-
ductive surface during operation is exposed to the surrounding
environment, and particularly i:n the case of repetitive xero-
graphic cycling where these photoconducti,ve layers are susceptible
to abrasion, chemical attack, heat and multiple exposure to light.
These effects are characterized by a gradual deterioration in the
electrical characteristics of the photoconductive layer resulting
in the printing out of surface defects and scratches, localized
areas of persistent conductivity which fa.il to retain an electro-
~ static charge, and high dark discharge.
:' 15 In addition to the problems noted above, these photo-receptors require that the photoconductor comprise either a
hundred percent of the layer, as in the case of the vitreous
selenium layer, or that they preferably contain a high proportion
of photoconductive material in the binder configuration. rrhe
requirements of a photoconductive layer containing all or a ma~or
proportion of a photoconductive material further restricts the
' physical characteristics of the final plate, drum or belt in that
the physical characteristics such as fle~ibility and adhesion of
the photoconductor to a supporting substrate are primarily dictated
by the physical properties of the photoconductor, and not by the
':' :
,. resin or matri~ material which is preferably present in a minor
amount.
Another form of a composite photosensitive layer which
; has also been considered by the prior art includes a layer of
; ~30 photoconductive material which is covered with a realtive,ly thick
. :
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.
.
plastic layer and coated on a supporting substrate.
U.S. Patent 3,041,166 to Bardeen describes such a
configuration in which a transparer-t plastic material overlies
a layer of vitreous selenium which is contained on a supporting
substrate. In operation, the free surface of the transparent
plastic is electrostatically charged to a given polarity. The
device is then exposed to activating radiation which generates
a hole-electron pair in the photoconductive layer. ~he electrons
move through the plastic layer ancl neutralize positive charges
on the free surface of the plastic layer thereby creating an
electrostatic image. Bardeen, however, does not teach any
specific plastic materials which will function in this manner,
and confines his examples to structures which use a photoconductor
material for the top layer.
French Patent 1, 577r 855 to Herrick et al describes a
special purpose composite photosensitive device adapted for reflex
exposure by polari2ed light. One embodiment which employs a layer
of dichroic organic photoconductive particles arrayed in oriented
fashion on a supporting substrate and a layer of poly(N-vinylcar-
bazole) formed over the oriented layer of dichroic material. When
charged and exposed to light polarized perpendicular to the
orientation of the dichroic layer, the oriented dichroic layer and
poly(N-vinylcarbazole) layer are both substantially transparent to
the initial exposure light. When the polarized light hits the
white background of the document being copied, the light is
depolarized, reflected back through the device and absorbed by
the dichroic photoconductive material. In another embodiment, the
dichroic photoconductor is dispersed in oriented fashion through-
out the layer of poly(N-vinylcarbazole).
The Shattuck et al, U.S. Patent 3~837~851~ discloses a
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particular electrophotographic member having a charge generation
layer and a separate charge transport layer. The charge transport layer
comprises at least one tri-aryl pyrazoline compound. These pyrazoline
compounds may be dispersed in binder material such as resins Icnown in the art.
Cherry et al, U.S. Patent 3,791,826 discloses an electrophoto-
graphic member comprising a conductive substrate, a barrier layer, an
inorganic charge generation layer and an organic charge transport layer
comprising at least 2û percent by wei~ht trinitrofluorenone.
Belgium Patent 7fi3,540, issued August 26, 1971 discloses an
electrophotographic member having at least two electrically operative layers.
The first layer comprises a photoconductive layer which is capable of
photogenerating charge carriers and injecting the photogenerated holes into a
contiguous active layer. The active layer comprises a transparent organic
material which is substantially non-absorbing in the spectral region of
intended use, but which is "active" in that it allows injection of photo-
generated holes from the photoconductive layer, and allows these holes to be
transported to the active layer. The active polymers may be mixed with
interactive polymers or non-polymeric material.
Gilman, Defensive Publication of Serial Number 93,~49, filed
November 27, 1970, published in 888 O.G. 707 on July 20, 1970, I~efensive
Publication No. P888~013, U.S. Cl. 96/1.5, discloses that the speed of an
inorganic photoconductor such as amorphous selenium can be improved by
including an organic photoconductor in the electrophotographic element. For
exarnple, an insulating resin binder may have TiO2 dispersed therein or it
may
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be a layer oE amorphous selenium. This la~er is overcoated with
a layer of electrically insulating binder resin hav:ing an organic
photoconductor such as 4,4'-diethylamino-2,2' dimethyltriphenyl-
methane dispersed therein.
"~ulti-Active Photoconductive Element", Martin A. Berwick,
Charles J. Fox and William A. Light, Research Disclosure, Vol. 133;
pages 38-43, May 1975, was published by Industrial Opportunities
Ltd., Homewell, Havant, Hampshire, England. This disclosure
relates to a photoconductive element having at least two layers
comprising an organic photoconductor containing a charge-
transport layer in electrical contact with an aggregate charge-
generation layer. Both the charge-generation layer and the charge-
transport layer are essentially organic compositions. The charge~
generation layer contains a continuous, electrically insulating
polymer phase and a discontinuous phase comprising a finely-
divided, particulate co-crystalline complex of (1) at least one
polymer having an alkylidene diarylene group in a recurring unit
and (2) at least one pyrylium-type dye salt. The charge-transport
layer is an organic material which is capable of accepting and
transporting injected charge carriers from the charge-generation
layer. This layer may comprise an insulating resinous material
having 4,4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane
dispersed therein.
Fox, U.S. Patent 3,265,496, discloses that N,N,N'N'-
; 25 tetraphenylbenzidine may be used as photoconductive material in
electrophotographic elements. This compound is not sufficiently
soluble in the resin binders of the instant invention to permit a
sufficlent rate of photo-induced discharge.
Straughan, U.S. Patent 3,312,548, in pertin~nt part,
discloses a xe:rographic plate having a photoconductive insulating
layer comprising a composition of selenium, arsenic and a halogen.
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.
The halogen may be present in amounts from abou~ 10 to 10,000 parts per
million. This patent further discloses a xerographic plate having a support, a
layer of selenium and an overlayer of a photoconductive material comprising a
mixture of vitreous selenium9 arsenic and a halogen.
S The compound OI the instant invention is represented by the
formula:
\N--~N
X~ ~X
wherein X is selected from the group consisting of (ortho) CH3, (meta) CH3,
(para) CH3, (ortho) Cl, (meta) Cl and (para) Cl, is dispersed in a polyearbonateresin in order to form a charge transport layer for a multi-layered device
15 comprising a charge generation layer and a charge transport layer. The ehargetransport layer must be substantially non-absorbing in the spectral region of
intended use, but must be "active" in that it allows injection of photo-excited
~ holes from the photoconductive layer~ i.e., the charge generation layer, and
- allows these holes to be transported through the charge transport layer.
Most organic charge transporting layers using active materials
dispersed in organic binder materials have been found to trap charge carriers
causing an unacceptable build-up of residual potential when used in a cyclic
mode in electrophotographyO Also, most organic charge transporting materials
known when used in a layered configuration contiguous to an amorphous
25 selenium eharge generating layer have been found to trap charge at the
interface between the two layers. This results in lowering the potential
differences between ths illuminated and non-illuminated regions when these
structures are exposed to an image.
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This, i.n turn, lowers the print density of the end product,
i.e., the electrophotographic copy.
In addition/ most of the organic transport materials
known to date are found to undergo deterioration when exposed
to ultraviolet radiation, e. g. U. V. emitted from corotrons,
lamps, etc.
Another consideration which is necessary in the
system is the glass transition temperature (Tg~. The (Tg) of the
transpor~n~ L~yer has to be subs~antially higher than the normal operat,-
ing temperatures. Many organic charge transporting
layers using active materials dispersed in organic binder
material have unacceptable low (Tg) at loadings of the active
material in the organic binder material which is required for
efficient charge transport. This result in the softening
of the matrix of the layer andr in turn, becomes susceptible
to impac~ion of dry developers and toners. Another unaccept-
able feature of a low (T~) is the case of leaching or exudation
of the active materials from the organic binder material result~
ing in degradation of charge transport properties from the
~ charge transport layer.
:: 20 Another consideration for the use of organic trans-
port Iayers in electrophotography is the value of the charge
carriers mobilities. Most of th,e organicsknown to date are
deficient in this respect in that they set a limit to the
cyclic speed of the system employing the same. ..
: 25 'It was found that one or a combination of compounds
within the general formula:
~: ' ` ' ,
: N ~ N~ ~
X ~ ~ ~ X
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.:. ...... : . ~ . : . .
wherein X is selec-ted from the group consisting of (ort~o)
CH3, (meta) CH3, (para) CH3, (ortho) Cl, (meta) Cl and (para)
Cl dispersed in a polycarbonate resin transports charge very
efficiently without any trapping when this layer is used con-
tiguous with a generation laye:r and subjected to charge/lîghtdischarge cycles in an electrophotographic mode. There is no
buildup of the residual potent:ial over many thousands of
cycles.
The above described small molecules due to the
presence of solubilizing groups, such as, methyl (CE13) or
chlorine (Cl) are substantially more soluble in resin
binders described herein whereas unsubstituted tetra phenyl
benzidine, is not sufficiently soluble in the resin binders
described herein for the intended purpose.
Furthermore, when the diamines of the instant
invention dispers-ed in a polycarbonate binder are used as
-transport layers contiguous a charge generation layer, there
-~ is no interfacial trapping of the charge photogenerated in
and injected from the generating layer. When subjected to
ultraviolet radiation, no deterioration in charge transport
was observed in these transport layers containing the sub-
stituted N,N, N ' ,N' ,- tetraphenyl~ bipheny ~-4,4'-diamines
of the instant invention.
Furthermore, diamines of t e instant lnvention
dispersed in a polycarbonate binder were found to have
sufficiently high ~g) even at hi~h loadings, thereby elimi-
nating the pr~blems associated with low (Tg) as discussed
above.
; None of the above-mentioned art overcomes the above-
mentioned~pro]blems. Furthermore, none of the above-mentioned
art discloses~specific d~u~e generating material in a separate
layer which is overcoated with a charge-transport layer
comprising a polycarbonate resin matrix material having
dispersed therein the diamines of the instant invention.
The charge
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transport material is substantially non-absorbing in the spectral region of
intended use, but is "active" in that it allows injection of photogenerated holes
from the charge generation layer and allows these holes to be transported
therethrough. The charge-generating layer is a photoconductive layer which is
5 capable of photogenerating and injecting photogenerated holes into the
contiguous charge-transport layer.
- It has also been found that when an alloy of selenium and arsenic
containing a halogen is used as a charge carrier generation layer in a
multilayered device which contains a contiguous charge carrier transport
10 layer, the member, as a result of using this particular charge generation layer,
has unexpectedly high contrflst potentials as compared to similar multilayered
members employing other generating layers. Contrast potentials are impor-
tant characteristics which determine print density.
OBJ~CTS OF TlIE INVENTION
It is an object of an aspect of this invention to provide a novel
imaging system.
It is an object of an aspect of this invention to provide a novel
photoconductive device adapted for cyclic imaging which overcomes the
above-noted disadvantages.
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~ t is an object of an aspect of this invention to provide a
photoconductive member comprising a generating layer and a charge transport
layer comprising a polycarbonate resin material having dispersed therein
$~N ~X
10 wherein X is selected from the group consisting of (ortho) CEI3, (meta) CH3,
(para) CH3, (ortho) Cl, (meta) Cl and (para) Cl. The chemical name of the
above formula is N,N'-diphenyl-N,N'-bis-(alkylphenyl)-[l,l'-biphenyl]- 4,4'-di-
amine wherein the alkyl is selected from the group consisting of ~ methyl, 3
methyl and 4 methyl or the compound may be N,N'-diphenyl-N,N' -bis(halo
15 phenyl)-[1,1'-biphenyl]-4,4'-diamino wherein the halo is selected from the
group consisting of 2 chloro, 3-chloro and 4-chloro.
It is an object of an aspect of this invention to provide a novel
imaging member capable of remaining flexible while still retaining its electri-
cal properties after extensive cycling and exposure to the ambient, i.e.,
20 oxygen, ultraviolet radiation, elevated temperatures, etc.
n is an object of an aspect of this invention to provide a novel
imaging member which has no bulk trapping of charge upon extensive cycling.
SUMMARY OF THE INVENTIVN
The foregoing objects and others are accomplished in accordance
25 with this invention by providing a photoconductive member having at least two
operative layers. The first layer comprises a layer of photoconductive
material which is capable of photogenerating and injecting photogenerated
holes in~o Q
,
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,
contiguous or adjacent electrically active layer. The electrically active
material comprises a polycarbonate resin material having dispersed therein
from about 25 to about 75 percent by weight of one or more compounds having
the gener~l formula:
~ <~
/ N ~ ~ N ~
X X
wherein X is selected from the group s~onsisting of (ortho) CH3, (meta) CH3,
(para) CH3, (ortho) Cl, (meta) Cl and (para) Cl. The compound may be named
N,N'-diphenyl~N,N'-bis(alkylphenyl)-[l,l'-biphenyl]-4,4'-diamine wherein the
alkyl is selected from the group consisting of 2 methyl, 3 methyl and 4 methyl
15 or the compound may be N,N'-bis(halo phenyl)[l,l'-biphenyl]-4,4'-diamirle
wherein the halo is selected from the group consisting of 2-chloro, 3-chloro
and 4-chloro. The active overcoating layer, i.e., the charge transport layer, issubstantially non-absorbing to visible light or radiation in the region of
intended use but is "active" in that it allows the injection of photogenerated
20 holes from the photoconductive layer, i.e., charge generation layer, and allows
these holes to be transported through the active charge trnnsport layer to
selectively discharge a surface charge on the surfaee of the active layer.
It was found that, unlike the prior art, when the diamines of the
instant invention were dispersed in a polycarbonate binder this layer transports25 charge very efficiently without any trapping of charges when this layer is used
contiguous a generator layer and sub~ected to charge/light discharge cycles in
an electrophotographic mode. There is no buildup of the residual potential
over
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many thousands of cycles.
Furthermore, the transport layers comprising the
diamines the instant invention dispersed in a polycarbonate
binder were found to have sufficiently high (Tg) even at
high loadings thereby eliminating the problems associated
with low (Tg). The prior art suffers from this deficiency.
Furthermore, no deterioration in charge transport
was observed when these transport layers containing the
diamines of the instant invention dispersed in a polycarbonate
binder were subjected to ultraviolet radiation encountered
in its normal usage in a xerographic machine environment.
The prior art also suffers from this deficiency.
Therefore, when members containing charge trans-
port layers comprising a polycarbonate resin material having
the diamines of the instant invention are exposed to ambient
conditions, i. e., oxygen, U.V. radiation~ etc., these layers
remain stable and do not lose their electrical properties.
Furthermore, diamines of the instant invention do not
crystallize and become insoluble in the electrically in-
active resinous material into ~hich these materials wereoriginally dispersed. Therefore, since the diamines of the
instant invention do not appreciably react with oxygen or
are not affected by U.V. radiation, normally encountered
in their normal usage in a xerographic machine environment,
the charge transport layer comprising a polycarbonate resin
material having diamines of the instant invention allow
acceptable injection of photo-
., . -.
'
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genera-ted holes from the photoconductor layer, i.e., charge
genera-tion layer, and allow these holes to be transported repeatedly
through the active layer sufficiently to acceptably discharge a
surface charge on the free surface of the active layer in order to
form an acceptable electrostat:ic latent image.
As mentioned, the foregoing objects and others may be
accomplished in accordance with this invention by providing a
speci~ically preferred photoconductive member having at least
two operative layers. The first layer being a most preferred
specie which consists essentially of a mixture of amorphous
selenium, arsenic and a halogen. Arsenic i5 present in amounts
from about 0.5 percent to about 50 percent by weight and the
halogen is present in amounts from about 10 to about 10,000 parts
per million with the balance being amorphous selenium. This layer
is capable of photogenerating and injecting photogenerated holes
I-~ into a contiguous or adjacent charge transport layer. The charge
~-J' ~ p ~ ar b of ~ afe
transport layer consists essentially of
resinous material having dispersed therein from about 10 to about
75 percent by weight of the substituted N,N,N',N'-tetraphenyl-
[1,1'-biphenyl]-4,4'-diamines of the instant invention.
"Electrically active" when used to define active layer 15
means that the material is capable of supporting the injection of
photogenerated holes from the generating material and capable of
allowing the transport of these holes thr~ugh the active layer in
order to discharge a surface charge on the active layer~
"Electrically inactive" when used to describe the
organic material which does not contain any substituted N,N,N',N'-
tetraphenyl-[l,l'-biphenyl]-4,4'-diamines of the instant
invention means that the material is not capable of supporting the
~; 30 injection of photogenerated holes from the generating material
and is not capable of allowing the transport o~ these holes
j:
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through the material.
It should be understood that the polycarbonate resinous material
which becomes electrically active when it contains from about 25 to about 75
percent by weight of the diamine does not function as a photoconductor in the
5 wavelength region of intended use. As stated above, hole-electron pairs are
photogenerated in the photoconductive layer and the holes are then injected
into the active layer and hole transport occurs through this active layer.
A typical application of the instant invention involves the use of a
layered configuration member which in one embodiment consists of a
10 supporting substrate such as a conductor containing a photoconduetive layer
thereon. For e~ample, the photoconductive layer may be in the form of
amorphous, vitreous or trigonal selenium or alloys of selenium such as
selenium-arsenic, selenium-tellurium-arsenic and selenium-tellurium. A
charge transport layer of electrically inactive polycarbonate resinous material
1~ having dispersed therein from about 25 percent to about 75 percent by weight
of the diamine is coated over the selenium photoconduetive layer. Generally,
a thin interfacial barrier or blocking layer is sandwiched between the
photoconductive layer and the substrate. The barrier layer may comprise any
suitable electrically insulating material such as metallic oxide or organic
20 resin. The use of the polycarbonate containing the diamine allows one to take
advantage of placing a photoconductive layer adjacent to a supporting
substrate and protecting the photoconductive layer with a top surface which
will allow for the transport of photogenerated holes from
.
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the photoconductor, and at the same time f-lnction to physically proteet the
photoconductive layer from environrslental conditions. This structure can then
be imaged in the conventional xerographic manner which usually includes
charging, optîcal projection exposure and development.
~s mentioned, when an alloy of selenium and arsenic containing a
halogen of the instant invention is used as a charge carrier generation layer ina multilayered device which contains a contiguous charge currier transport
layer, the member, as a result of using this particular charge generation layer
has unexpectedly high contrast potentials as compared to similar multilayered
members using different generator layer materials.
--18--
~;
A comparison is made between a 60 micron thick single layer
photoreceptor member containing 64.5 percent by weight amorphous selenium,
35.5 percent by weight arsenic and 850 parts per million iodine and a
multilayer member of the instant invention. The instant invention member
5 used in the comparison is a multilayered device with a 0.2 micron thick charge
generation layer of 35.5 percent by weight arsenic, 64.5 percent by weight
amorphous selenium and 850 parts per million iodine. This charge generation
layer is overcoated with a 30 micron thick charge transport layer of
MakrolonR, a polycarbonate resin, which has dispersed therein 40 percent by
10 weight N,NI-diphenyl-N,N'-bis(3-methylphenyl)-[2,2'-dimethyl-l,l'-biphenyl]-
4,4'-diamine.
In general, the advantages of the improved structure and method of
imaging will become apparent upon consideration of the following disclosure of
invention, especially when taken in conjunction with the accompanying
15 drawings wherein:
:
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Fig. 1 is a schematic illustration of one embodiment
of a device of the instant invention.
Fig. 2 illustrates a second embodiment of the device
for the instant invention.
Fig. 3 illustrates a third embodiment of the device of
the instant invention.
Fig. 4 illus-trates a fourth embodiment of the device of
the instant invention.
DETAILED DESCRIPTION OF THE DRAWINGS
Fig. 1 designates imaging member 10 in the form of a
plate which comprises a supporting substrate 11 having a binder
layer 12 thereon, and a charge transport layer 15 positioned over
binder layer 12. Substrate 11 is preferably made up of any
suitable conductive ma~erial. Typical conductors include
;
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aluminum, steel, brass, graphite, dispersed conductive salts,
conductive polymers or the like. The substrate may be rigid or
flexible and of any conventional thickness. Typical substrates
include flexible belts or sleeves, sheets, webs, plates,
cylinders and drums. The substrate or support may also comprise
a composite structure such as a thin conductive layer such as
aluminum or copper iodide, or g;Lass coated with a thin conductive
coating of chromium or tin oxide. Particularly preferred are
substrates of metalized polyesters, such as Mylar.
In addition, if desired, an electrically insulating
substrate may be used. In this instance, the charge may be
placed upon the insulating member by double corona charging
techniques well known and disclosed in the art. Other modifi-
cations using an insulating substrate or no substrate at all
include placing the imaging member on a conductive backing member
or plate and charging the surface while in contact with said
backing member. Subsequent to imaging, the imaging member may
then be stripped from the conductive backing.
Binder layer 12 contains photoconductive particles 13
; 20 dispersed randomly without orientation in binder 14. The
photoconductive particles may consist of any suitable inorganic
or organic photoconductor and mixtures thereof. Inorganic
materials include inorganlc crystalline photoconductive compounds
and inorganic photoconductive glasses. Typical inorganic
crystalline compounds include cadmium sulfoselenide, cadmium
selenide, cadmium sulfide and mixtures thereof. Typical inorganic
photoconductive glasses include amorphous selenium and selenium
~ alloys such as selenium-tellurium, selenium-tellurium-arsenic
i~ and selenium-arsenic and mixtures thereof. Selenium may also be
~ 30 used in a crystalline form known as trigonal selenium. A method of
,
making a photosensitive imaging device utilizing trigonal selenium
tn~ nu~r~
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;
comprises vacuum evaporating a thin layer o~ vitreous selenium
onto a substrate, forming a relatively thicker layer of electrically
active organic material over said selenium layer, followed by
heating the device to an elevated temperature, e.g., 125C. to
210C., for a sufficient time, e.g., 1 to 24 hours, sufficient
to convert the vitreous selenium to the crystalline trigonal form.
Another method of making a photosensitive member which u-tilizes
trigonal selenium comprises forming a dispersion of finely divided
vitreous selenium particles in a liquid organic resin solution
and then coating the solution onto a supporting substrate and
drying to form a binder layer comprising vitreous selenium
particles contained in an organic resin matrix. Then the member
is heated to an elevated temperature, e.g., 100C. to 140C. for
a sufficient time, e.g., 8 to 24 hours, which converts the
vitreous selenium to the crystalline trigonal form.
Typical organic photoconductive material which may be
used as charge generators include phthalocyanine pigment such as
the X-form of metal-free phthalocyanine described in U.S. Patent
` 3,357,989 to Byrne et al; metal phthalocyanines such as copper
phthalocyanine; quinacridones available from DuPont under the
tradename Monastral Red, Monastral Violet and Monastral Red Y;
substituted 2,4-diamino-triazines dlsclosed by Weinberger in U.S.
; Patent 3,445,227; triphenodioxazines disclosed by Weinberger in
U.S. Patent 3,442,781; polynuclear aromatic quinones available
from Allied Chemical Corporation under the tradename Indofast
Double Scarletv Indofast Violet Lake B, Indofast Brilliant Scarlet
and Indofast Orange.
Intermolecular charge transfer complexes such as a
mixture of poly(N-vinylcarbazole~ (PVK) and trinitrofluorenone
(TNF) may be used as charge generating materials. These materials
`~ are capable of~injecting photogenerated holes into the transport
materlal.
~22-
One of the most preferred ernbodiments is a 0.2 micron thick
charge generation layer of 35.5 percent by weight arsenic, 64.5 percent by
weight amorphous selenium and 850 parts per rnillion iodine. This charge
generation layer may be overcoated with a 30 micron thick charge transport
5 layer Oe MakrolonR, a polycarbonate resin, which has dispersed therein 40
percent by weight of a substituted N,N,N',N'-tetraphenyl~ biphenyl]-4,4'-
diamine of the instant invention.
The above list of photoconductors should in no WQ~ be taken as
limiting, but merely illustrative as suitable materials. The size of the
10 photocondllctive particles is not particularly critical; but particles in a size
range of about 0.01 to 5.0 microns yield particularly satis~actory results.
Binder rnaterial 14 may comprise any electrically insulating resin
such as those described in the above-mentioned Middleton et al, IJ.S. Patent
3,121,006. When using an electrically inactive or insulating resin, it is essential
15 that there be particle-to-particle contact between the photoconductive
particles. This necessitates that the photoconductive material be present in
an amount of at least about 10 parcent by volume o~ the binder layer with no
limitation on the maximum amount of
.
.
:
-~3-
- . ... . .
.. . . . . .
photoeonductor in the binder layer. If the matrix or binder comprises an
flctive material, the photoconductive material need only to comprise about 1
percent or less by volume of the binder layer with no limitation on the
maximum amount of the photoconductor in the binder layer. The thickness of
5 the photoconductive layer is not critieal. Layer thicknesses from about 0.05
to 20.0 microns have been found satisfactory, with a preferred thickness of
about 0.2 to 5.0 microns yielding good results.
Another embodiment is where the photoconductive material may
be particles of amorphous selenium-arsenic-halogen as shown as particles 13
10 which may comprise from about 0.5 percent to about 50 percent by weight
arsenic and the halogen may be present in amounts from about 10 to 10,000
parts per million with the balance being amorphous selenium. The arsenic
preferred may be present from about 20 percent to about 40 percent by weight
with 35.5 percent by weight being the most preferred. The halogen preferably
15 may be iodine, chlorine or bromine. The most preferred halogen is iodine. The
remainder of the alloy or mixture is preferably selenium.
Active layer 15 comprises a transparent electrically inactive poly-
carbonate resinous material having dispersed therein from about 25 to 75
percent bV weight of the dinmines detined above.
'~
'
.
-24-
,- . : :
.J~ 6
In general, the t~ickness of active layer 15
should be from about 5 to 100 microns, but thicknesses out-
side this range can also be used.
The preferred polycarbonate resins for the trans-
port layer have a molecule weight (Mw) from about 20,000
to about 120,000, more preferably from about 50,000 to
about 120,000.
The materials most preferred as ~he electrical-
ly inactive resinous material is poly(4,4l isopropylidene-
diphenylene carbonate) with a molecular weight (~w) of
from about 35,000 to about 40,000, available'as Lexan~ ,
145 from General Electric Company; poly(4,4'-isopro-
pylidene-diphenylene carbonate) with a molecular weight
(Mw) of from about 40,000 to about 45,000, available as
Lexan~ 141 from the General Electric Company; a poly-
carbonate resin having a.molecular weigh.t.(Mw.) o~ from
about 50,000 to about 120,000 available as Makrolon~
from Farbenfabricken Bayer A.G. and a pol.ycarbonate resin
having a molecular weight (Mw) of from about 20lO00 to
about 50,000 available as Merlon~ from Mobay Chemical
Company.
In another embodiment of the instant invention,
::
~ the ~. . .
. .
'
I
`~: `:
:
~,
,
:
: ~ -25/26~
:::: : : :
..
structure of Fig. 1 is modified -to insure that the photoconductive
particles are in the Eorm of continuous chains through the
thickness of binder layer 12. This embodiment is illustrated by
Fig. 2 in which the basic struct:ure and materials are the same as
those in Fig. 1, except the phot:oconductive particles are in the
form of continuous chains. Layer 14 of Fig. 2 more specifically
may comprise photoconductive materials in a multiplicity of
interlocking photoconductive continuous paths through the
thickness of layer 1~, the photoconductive paths being present in
a volume concentration based on the volume of said layer, of
from about 1 to 25 percent.
A further alternative for layer 14 of Fig. 2 comprises
photoconductive material in substantial particle-to-particle
contact in the layer in a multiplicity of interlocking photocon-
ductive paths through the thickness of said member, the photocon-
ductive paths being present in a volume concentration, based on
the volume of the layer, of from about 1 to 25 percent.
Alternatively, the photoconductive layer may consist
entirely of a substantially homogeneous photoconductive material
such as a layer of amorphous selenium, a selenium alloy or a
powder or sintered photoconductive layer such as cadmium sulfo-
selenide or phthalocyanine. This modification is illustrated by
Fig. 3 in which the photosensitive member 30 comprises a sub-
strate 11, having a homogeneous photoconductive layer 16 with an
overlylng active organic transport layer 15 which comprises an
electrically inactive organic resinous material having dispersed
therein from ahout ~ttto about 75 percent by weight of the suh-
.
stituted N,N,N',N'-tetraphenyl-[l,l'-biphenyl~-4,4'-diamines of
the instant invention.
~ ` 30 Another modification of the layered configuration
`~ ~ descrlbed in Pigs. 1, 2 and 3 include the use of a blocking layer
.. .
'
~ -27-
,: :
17 at the substrate-photoconductor interface. This configuration is illustrated
by photosensitive member 40 in ~ig. 4 in which the substrate 11 and photo-
sensitive layer 16 are separated by a blocking layer 17. The blocking layer
functions to prevent the injection of charge carriers from the substrate into
5 the photoconductive layer. Any suitable blocking material may be used.
Typical materials include nylon, epoxy and aluminum oxide.
It should be understood that in the layered configurations described
in Figs. 1, 2, 3 and 4, the photoconductive material preferably is selected from
the group consisting of amorphous selenium, trigonal selenium, selenium alloys
10 selected from the group consisting essentially of selenium-tellurium,
selenium-tellurium-arsenic, and selenium-arsenic and mixtures thereof. One
of the preferred photoconductive materials is trigonal selenium.
:
':
:
~ -28-
`:
- , .. .
Active layer 15, as described above, is non-absorbin~ to light in the
wavelength region of use to generate carriers in the photoconductive layer.
This preferred range for xerographic utility is f'rom about 4,000 to about 8,000angstrom UIlitS. In addition, the photoconductor should be responsive to all
wavelengths from ~,000 to 8,000 angstrom units if panchromatic responses are
required. All photoconductor-active material combination of the instant
invention results in the injection and subsequent transport of holes across the
physical interface between the photoconductor and the active material.
The reason for the requirement that active layer 15, i.e., charge
10 transport layer, should be transparent is that most of the incident radiation is
utilized by the charge carrier generator layer f'or ef'ficient photogeneration.
:
`: :
~. -29-
The active transport layer which is employed in conjunction with
the photoconductive layer in the instant invention is a material which is an
insulator to the extent that the electrostatic charge placed on said active
transport layer is not eonducted in the absence oE illumination, i.e., with a
5 rate sufficient to prevent the formation and retention of an electrostatic
latent image thereon.
In general, the -thickness of the active layer preferably is from
about 5 to lO0 microns, but thicknesses outside this range can also be used.
The ratio of the thickness of the active layer, i.e., charge transport layer, to
lO the photoconductive layer, i.e., charge generator layer, preferably should be
maintained from about 2:1 to 200:1 and in some instances as great as 400:1.
The following examples further specifieally define the present
invention with respect to a method of making a photosensitive member.
:
~ .
' ~
~:
--30--
',:
The percentages are by weight unless otherwise
indicated. The examples below are intended to illustrate
various preferred embodiments of the instant invention.
EX~MPLE I
Preparation of N,N'-diphenyl-N,N'-bis(3-methyl
phenyl)-~l,l'-biphenyl~-4,4'-diamine: In a 5000 milliliter,
round bottom, 3 necked flask fitted with a mechanical stir-
rer and blanketed with argon, is placed 336 grams (1 mole)
of N,N'-diphenylbenzidine, 550 grams (2.5 moles) of m-iodoto
luene, 550 grams (4 moles) potassium carbonate (anhydrous)
and 50 grams of copper bronze catalyst and 1500 ml dimethyl-
sul~oxide (anhydrous). The heterogeneous mixture is reflux-
ed for 6 days. The mixture is allowed to cool. 2000 ml of
benzene is added. The dark slurry is then filtered. The
filtrate is extracted 4 times with water~ Then the filtrate
is dried with magnesium sulfate and filtered. The benzene
is taken off under reduced pressure. m e black product is
column-chromatographed using Woelm neutral alumina. Color-
less crystals of the product are obtained by recrystallizat-
ing the product fron n-octane. The melting point is 167 -
169C. The yield is 360 grams (65%). ~
~ - Analytical ~alculation for C38H3~N2: C,88.34;H,
`~ 6.24;N,5.37. Found: C,88.58;H,6.21;N,5.37.
;~ NMR (CDC13) B 2.23(s,6,methyl),6.60-7.47 ppm (m,
26, aromatics).
EXAMPLE II
A photosensitive layer structure similar to that
~` illustrated in Fig. 3 comprises an aluminized Mylar~ sub-
~: :
strate, having a 1 micron layer of amorphous selenium over
the substrate, and a 22 micron thick layer of a charge
transport materiaI comprising 25 percent by weight of N,N' ; -
-diphenyl-N,N'-bis(3-methylphenyl)~ biphenyl7-4,4'-
31-
~".g ~ :
. . . . . . ...
f~6
d.iamine and 75 percent by weight bisphenol-A-polycarbonate
(Lexan~ 145, obtained from General Electric Company) over
the amorphous selenium layer. The member is prepared by
the following technique:
A 1 micron layer of vitreous selenium is formed
over an
, : ,
'.
.
`
~: :
-31a-
:,. . . .
: ~; ' ' . ' . .
~ ~f~
aluminized Myla ~ substra-te by conventional vacuum deposition
-technique such as -those disclosed by Bixby in U.S. Patent
2,753,278 and U.S. Patent 2,970,906.
A charge transport layer is prepared by dissolving in
135 grams of methylene chloride, 3.34 grams of ~ diphenyl-
N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4' diamine as pre-
pared in Example I and 10 grams of bisphenol-A-polycarbonate
(Lexar~ 145, obtained from General Electric Company). A layer of
the above mixture is formed on the vitreous selenium layer using
a Bird Film Applicator. The coating is then vacuum dried a-t
40C. for 18 hours to form a 22 micron thin dry layer of charge
transport material.
; The above member is then heated to about 125C. for
16 hours which is sufficient to convert the vitreous selenium to
lS the crystalline trigonal form.
The plate is tested electrically by negatively charging
the plate to a field of 60 volts/micron and discharging it at a
wavelength of 4,200 angstrom units at 2 x 1012 photons/cm2 seconds.
The plate exhibits satisfactory discharge at the above fields and
is capable of use in forming visible images.
EXAMPLE III
A photosensitive layer structure similar to that
illustrated in Example I comprising an aluminized MyIar sub-
strate, having a 1 micron layer of trigonal selenium over the
substrate, and a 22 micron thick layer of charge transport layer
comprising 50 percent by weight of N,N' diphenyl-N,N'-bis(3-
methylphenyl)-[l,l'-biphenyl]-4,4'-diamine and 50 percent by
weight bisphenol-A-polycarbonate (Lexan~ 141, obtained from
i General Electr:ic Company) is overcoated onto the trigonal
selenium layer The member is prepared by the following techni~ue:
A 1 micron layer of amorphous selenium is vacuum
-32-
- : .
. .
~f~
evaporated on a 3 mil aluminum substrate by conventional vacuurn
deposition technique such as those disclosed by Bixby in U.S.
Patents 2,753,278 and 2,970,906. Prior to evaporating the
amorphous selenium onto the substrate, a 0.5 micron layer of an
epoxy-phenolic barrier layer is formed over the aluminum by dip
coating. Vacuum deposition is carried out at a vacuum of 10 6
Torr while the substrate is maintained at a temperature of about
50C. during the vacuum deposition. A 22 micron thick layer of
charge transport material comprising 50 percent by weight of
N,N'-diphenyl-N,NI-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-
diamine and 50 percent by weight of poly(4,4l-isopropylidene-
diphenylene carbonate) having a (Mw) of about 40,000 (available as
Lexan~ 141 from General Electric Company) is coated over the
amorphous selenium layer.
The charge transport layer is prepared by dissolving
; in 135 grams of methylene chloride, 10 grams of N,N'-diphenyl-
N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine and 10 grams
of poly(4,4'-isopropylidene-diphenylene carbonate) (Lexa ~ 141,
having a (Mw) of about 40,000 obtained from General Electric
Company). A layer of the above mixture as mentioned above is
; formed on the amorphou~ selenium layer by using a Bird Film
Applicator. The coating is then dried at 40C. for 18 hours to
form a 22 micron thick dry layer of charge transport material.
The amorphous selenium layer is then converted to the crystalline
trigonal form by heating the entire device to 125C. and main-
taining this temperature for about 16 hours. At the end of 16
hours, the device is cooled to room temperature. The plate is
tested electrically by negatively charging the plate to fields of
60 volts/micron and di5charging them at a wavelength of 4,200
angstroms at 2 x 1012 photons/cm2 seconds. The plate exhibits
satisfactory discharge at the above fields, and is capable of use
in forming excellent visible images.
33-
'' ,
EXAMPLE IV
. _
A photosensitive layer structure similar to that
illustrated in Fig. 3 comprises an aluminized Myla ~ substra-te,
having a 0.2 micron layer of amorphous selenium-arsenic con-
taining a halogen over the substrate, and a 30 micron thick
layer of a charge transport material comprising 25 percent by
weight of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'
biphenyl]-4,4'-diamine and 75 percent by weight bisphenol-A-
polycarbonate (Lexan~ 145, obtained from General Electric
Company) over the amorphous selenium-arsenic-halogen layer.
The member is prepared by the following technique:
A mixture of about 35.5 percent by weight of arsenic
and about 64.5 percent by weight of selenium and about 850
parts per million (ppm) of iodine are sealed in a Pyrex~ vial and
reacted at about 525C. for abou-t 3 hours in a rocking furnance.
The mixture is then cooled to abou-t room temperature, removed
from the Pyrex~ vial and placed in a quartz crucible within a
bell jar. An aluminum plate is supported about 12 inches above
the crucible and maintained at a temperature of about 70C.
The bell jar is then evacuated to a pressure of about 5 x 10 5
torr and the quartz crucible is heated to a temperature of about
380C. to evaporate the mixture onto the aluminum plate. The
crucible is kept at the evaporation temperature for approximately
30 minutes. At the end of this time the crucible is permitted
to cool and the finished plate is removed from the bell jar.
A charge transport layer is prepared by dissolving in
,~
135 grams of methylene chlorine, 3.34 grams of N,N'-diphenyl-
N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine as pre~
pared in Example I and 10 grams of bisphenol-A-polycarbonate
(Lexan~ 145, obtained from General Electric Company). A layer
of the above mixture is formed on the vitreous selenium-arsenic-
-3~-
:~- ~ . ` . - . ' .
. : .
~ ~? ~Pr~
iodine layer using a Bird Film Applicator. The coating is then
vacuum dried at 80C. for 18 hours to form a 30 micron thin dry
layer of charge transport mater:ial.
The plate is tested electrically by negatively charging
the plate to a field of 60 volts/micron and discharging it at a
wavelength of 4,200 angstrom un:its at 2 x 1012 photons/cm2 seconds.
The plate exhibits satisfactory discharge at the above fields
~a~bJe
and is e~ of use in forming vis.ible images.
, 1 5
:
,
;~ :
~ ~ .
-35-
.,
~' ', ';
.~ , . . .
SllPPLEMENTARY DL ~SCL~"SURE
In the prlncipal disclc~ure the "X" substituent
attached to two of the phenyl groups of the charge transport
compound was defined as being selected from the group consist-
ing of (ortho) CH3, (meta) CH3, tpara) CH3, ~ortho) Cl, (meta)
Cl and (para) Cl.
It has now been discovered that this "X" substituent
should be more broadly defined, so that the compound of the
instant invention is represented by the formula:
.~ @~ ' .~
/ N ~ N ~
' X/Ç~ ~ ~X'
wherein X is selected from the group consisting of an alkyl
group having from 1 to about 4 carbon atoms (e.g. methyl, ethyl,
~- propyl, isopropyl, isobutyl, tert-butyl, n-butyl, etc.) and
chlorine in the ortho, meta or para position, and it is dis-
persed in a polycarbonate resin in order to form a charge
transport layer for a multi-layered device comprising a
charge generation layer and a charge transport layer. The
charge transport layer must be substantially nonabsorbing in
the spectral region of intended use, but must be "active" in
that it allows injection of photoexcited holes from the photo~
conductive layer, i.e., the charge generation layer, and
allows these holes to be transported through the charge trans-
port layer.
Thus, in accordance with this supplementary dis-
closure, the principal disclosure of this application should
be construed with the compound of the instant invention
-3 6 -
,
bein~ represented by the formula indicated in the im~diately
preceeding paragraph.
Thus, in accordance with one aspect of the instant
invention, there is provided an imaging member comprising a
charge generation layer comprising a layer of photoconductive
material and a contiguous charge transport layer.of a poly-
carbonate resin material having a molecular weight of from
about 20,000 to about 120,000 having dispersed therein from
about 25 to about 75 percent by weight of one or more compounds .
having the general formula:
N ~ ~
X ~ . ~ X
; .
, ~ .
: wherein X is selected from the group consisting of an alkyl
group, having from 1 to about 4 carbon.:atoms and chloride, said
photoconductive layer exhibiting the capability of photogenera-
tion of holes and injection of said holes and said charge
transport layer being substantially nonabsorbing in the spectral
region at which the phstoconductive layer generates and injects
photogenerated holes but being capable of supporting the injec-
tion of photogenerated holes from said photoconductive layer
:~ 25 and transporting said holes through said charge transport layer.
: ~ : :
' ;~ ~; . ''
`~:
:
, ;~ ,
:~ -37-
The following examples further specifically define the present
invention with respect to a methocl of making a photosensitive mernber. The
precentages are by ~eight unless otherwise indicated. The examples below are
intended to illustrate various preferred lembodiments of the instant invention.
EXAMPLE V
Preparation of N,N' diphenyl-N,N'bis(4-methylphenyl)-[1,1'-bi-
phenyl~ -4~4'-diamine.
A 500 ml, three necked, round bottom flask, equipped with a
magnetic stirrer and purged with argon, was charged with 20 grams of
p,p'-diiodo-biphenyl (0.05 mole~, 18.3 grams of p--tolyphenyl-amine (0.1 mole),
20.7 grams potassium carbonate (anhydrous) (0.15 mole), 3.0 grams of copper
powder and 50 mls of sulfolane (tetrahydrothiophene-l,l-dioxide). The mixture
was heated to 220-225C for 24 hours, allowed to cool to approximately 150C
and 300 mls of deionized water was added. The heterogeneous mixture was
heated to reflux while vigorously stirring. A light tan oily precipitate was
formed in the flask. The water was decanted. Then 300 mls of water was
added and the water layer was again decanted. 300 mls of methanol was added
and the mixture was refluxed to dissolve any unreacted starting materials.
`, The solids were filtered off, added to 300 mls of n-octane and heated to a
reflux temperature of 125C. The solution was filtered through 100 grams of
neutral Woelm alumina to give a pale yellow filtrate. The solution was again
filtered through lOO grams of neutral Woelm alumina to yield a colorless
filtrate and was allowed to cool yielding colorless crystals of the intended
compound having a M.P. of lG3-164 C.
Analytical Calculatlon for C381132N2: C, 88.34; 11, 6.24; M, 5.37
Found: C! 88.49i H, 6.44; N, 5.28.
~ NMR (CDC13)~2.30 (s,6,methyl~; 6.93-7.56 ppm (m,26, aromatics).
~: :
-38-
:
:
: ~ :
EXAMPLE Vl
Preparation of photoreceptor device employing_the compound_of
Example_V.
One gram of N, N'-diphenyl-N,N'-bis(4-methylphenyl)-[1,1'-bi-
5 phenyl]-4,4'-diamine was dissolved in 13.5 grams of methylene chloride
containing 1.0 gram of Makrolon(~), a polycarbonate, to form a 50 percent by
weight solution of the diamine in the polycarbonate.
A generation layer was fabricated by vacuum evaporating a 0.5
micron thick amorphous selenium layer on an aluminum substrate by the
10 technique referred to in Example ILI. The methylene chloride-polycarbonate
solution of the diamine was applied, using a Bird Film Applicator, to the
generation layer in an amount such that it provided a dried thickness of about
25 microns after being subjected to a vacuum at 40C for 48 hours.
This member was xerographically tested by negatively charging it
15 in the dark to about -1500 volts; the dark decay was about 250 volts in 1.5
seconds~ and the member was then exposed to a flash of activating radiation of
wavelength of 4330 angstrom units and energy of 15 ergs/cm2 for about 2
microseconds duration. The member completely discharged to zero volts
almost instantaneously, i.e. in about 20 milliseconds. This rapid xerographic
20 discharge characteristic and the physical quality of the transport layer
(smoothness, homogenity, transparency) make for ideal use in a fast, cyclic
xerographic print mode.
EXAMPLE VII
Preparation of N N N' N'-tetraphenyl-~l,l'-bi~henyl]-4,4'diamine.
? ~ ~
25 (This compound is disclosed in Fox U.S. 3,265,496.)
A 500 ml three necked round bottom flask equipped with a
magnetic stirrer and purged with argon was charged with 20 grams p,p'-diiodo
biphenyl (0.05 mole), 16.9 grams diphenylamine (0.1 mole), 20.7 grams potas-
sium carbonate (anhydrous) (0.15 mole), 3 grams copper and 50 mls sulfolane
30 (tetrahydrothiophene-l,l-dioxide). The mixture was then heated to 220-225C
-39-
'~.
. .
..
for 24 hours, allowed to cool to approxima~ely 151)C and 300 mls of deionized
water was aclded. The heterogeneous m ixture was heated to reflux while
vigorously stirring. A dark grey almost solid precipitate was formed. The
water was decanted. Then 300 mls of l,vater was added and the water layer
was again decanted. 300 mls of methanol was added and the mixture was
refluxed while stirrin~ to remove unreacted starting materials. The solids
were filtered off, dissolved in 300 mls of benzene and refluxed until the vapor
temperature reached 80C. The solution was filtered while hot through 75
grams neutral Woelm alumina to give an orange/yellow filtrate. 200 mls of
10 ethanol was added and the solution allowed to cool. ~n orange crystalline
solid material was filtered off and dissolved in 3D0 mls of ben~ene and column
chromatographed using neutral Woelm alumina (500 grams) with benzene as
the eluent. A colorless product was collected and extracted with 300 mls of
acetone to yield colorless fine crystals with a M.P. of 230-231 C
Analytical Calculation for C36H28N2: (~, 88.;,
Found: C, 88.79; H 5.89; N, 5.43.
NMR (CDC13)~6.91-7.49 (m, aromatics).
EXAM LE VIII
Preparation of photoreceptor devices employing the compound of
20 Example VII.
` Two separate combinations were made of this compound, i.e. N,
N3N',N'-tetraphenyl-[l,l'-biphenyl]-4,4'-diamine with a methylene chloride
solution of Makrolor~polycarbonate. The first combination produced a 15
percent by weight solution of this compound in the polycarbonate after
25 removal of the methylene chloride, i.e. 0.177 gram of the compound of
Example VII in 1.0 gram of the polycarbonate. This was the maximum amount
that could be dissolved in the polycarbonate.
The seeond combination produced a dispersion or incomplete solu-
tion o~ 20 percent by weight of the compound in the same polycarbonate after
30 removal of the methylene chloride, i.e. 0.25 gram of the compound in 1.0 ~ram
--40--
,~
. . ' ' - ' ' - . ': . . '
of the polycarbonate. Transport layers coated from this dispersion showed
numerous white areas greater than 1 micron in size. These ~Nhite areas
indicate that the compound of U.S. 3,265,~196 crystallized from the matri2~.
Using the 15 and 20 percenl; by weight material respectively, two
photoreceptor devices were prepared as in Example VI.
The member containing the 15 percent by weight of the Fox et al
compound was negatively charged to about -1700 volts. It had a dark decay of
about 125 volts in 1.5 seconds. The charged member was exposed to a flash of
activating radiation for about 2 microseconds duration using a light wave
10 length of 4330 angstrom units with an energy of 15 ergs/cm2.
This member discharged at the following rate:
after 0.25 seconds discharged to about 900 volts;
after 0.50 seconds discharged to about 600 volts;
after 0.75 seconds discharged to about 500 volts;
after 1.00 seconds discharged to about 400 volts;
after 1.25 seconds discharged to about 360 volts;
after 1.50 seconds discharged lo about 290 volts;
after 1.75 seconds discharged to about 280 volts;
after 2.00 seconds discharged to about 260 volts;
after 4.00 seconds discharged to about 160 volts.
The nature of this xerographic curve precludes use of this device in
a practical, high speed, cyclic xerographic device.
The member containing the 20 percent by weight of the compound
~- of U.S. 3,265,496 was negatively charged to about -1425 volts and the dark
25 decay was about 150 volts in about 1.0 seconds. This charged member was
exposed to a flash of activating radiation of wavelength of 4300 angstrom
units and energS7 of 15 ergs/cm2 for about 2 microseconds duration. This
member discharged at the following rate:
after 0.25 seconds discharged to about 270 volts;
after û.5~ seconds discharged to about 195 volts,
- ,
~; . . , :, .. , -
:,, - . . . : .
.
after 0.75 seconds dischargecl to about 180 volts;
after 1.00 seconds diseharged to about 150 volts;
after 1.25 seconds discharged to about 140 volts;
after 1.50 seconds dischargecl to about 130 volts;
after 1.75 seconds dischargecl to about 120 volts;
after 2.00 seconds discharged to about 120 volts;
after 4.00 seconds discharged to about 100 volts.
While the shape of this curve is improved over that of the 15
percent by weight member, it still indicates that the member is unacceptable
for use in a practical, fast, cyclic xerographic device. Moreover, the
heterogeneous nature of the transport layer, results in extremely poor
xerographic print quality because of surface and bulk defects causing substan-
tial loss of transpareney, excessive scattering of incident light, loss of
mechanical strength, loss of resolution and excessive print defects.
~ EXAMPLE IX
Preparation of N,N'-diphen~l-N,N'-bis(2 meth~lphenyl)-[l.l'-bi-
phen~4,4l-diamine.
Into a 250 milliliter, round bottom9 3 neck flask fitted with a
mechanical stirrer, thermometer with temperature controller and a source of
20 argon are placed 804 grams of N,N7-diphenyl-[l,l'-biphenyl]-4,4'-diamine
~- (0.025 moles), 16.3 grams of 2-iodotoluene (0.075 moles), 7.5 grams copper
bronze and 25 milliliters of a mixture of C13-C15 aliphatic hydrocabrons, i.e.
Soltrol6~170, from Phillips Chemical Company. The contents of the flask are
heated to 190 C with stirring for a period of 18 hours. Using a water aspirator,
25 the ex~ess~2-iodotoluene is removed by vacuum~ distillation. The product is
: ~ :
isolated by the addition of 200 milliliters of n-octane and hot filtration to
remove the inor~ganic solids. The deep orange filtrate is column chromato-
graphed using Woelm oeutral alumina with cyolohexane/benezene in a 3:2 ratio
- as the eluent. ~ The resulting oil is recrystallized from n-octane to yield
30 colorless crystals of the intended compound having a melting point of
148-150 C.
,
-42-
:
' ~ ~
,: :: . . . - . , . :
Analytical Calculation for C38H32 N2: C, 8
Found: C, 88.63; H, 6.25; N, 5.22.
NMR (CDC13) 2.04 (s, 6, methyl); 6.84-7.44 ppm (m, 26, aromatics).
EXAMPLE X
Preparation of N,N'-diphenyl-N,N'-bis(3~ethYlphenyl)-[l~l'-bi-
phe~yl] -4,4'-diamine.
Into a 250 milliliter 3 necked round bottom flask equipped with a
mechanical stirrer, thermometer with temperature controller and a source oi~
argon are placed 8.4 grams of N,N'-diphenyl-[l,l'-biphenyl]-4,4'-diamine
10 (0.025 moles), 13.8 grams of powdered potassium carbonate (0.1 moles), 17.4
grams of 3-ethyl iodo-benzene (0.075 moles), 7.5 grams of copper bronze and
25 milliliters of a mixture of C13-C15 aliphatic hydrocarbons, i.e. Soltrol~3)170,
from Phillips Chemical Company. The contents of the flask are heated to
l90~C for 18 hours. Using a water aspirator, the excess 3-ethyl iodobenæene is
15 removed by vacuum distillation. The product is isolated by the addition o~ 20milliliters of n-octane and hot filtration to remove the inorganic solids. The
deep orange filtrate is eolumn chromatographed using Woelm neutral alumina
with cyclohexane/benzene in the ratio of 3:2 as eluent. The resulting oil is
recrystallized from methanol and dried to yield pale yellow crystals of the
20 intended product having a melting point of 62-69C.
Analytical Calculntion for C40H36N2: C, 88.20; H, 6.66; N, 5.14.
Found: C, 88.37; H, 6.71; N, 5.03.
; NMR (CDC13) 1.17 (t,6, methyl); 2.65 (q, 4, methylene); 6.92-7.53
ppm (m, 26, aromatics).
EXAMPLE XI
Preparation of N,N'-diphenyl-N,N'-bis(4-ethylphenyl)-[1,1'-bi-
phenyl~-4,4'-diamine.
Into a 250 milliliter 3 neclced round bottom flask equipped with a
mechanical stirrer, thermometer with temperature controller and a source of
; 30 argon are placed 8.4 grams of N,N'-diphenyl-[l?l~-biphenyl]-4,4'-diamine
::
43-
: : :
,. ~ . . .
~: . . . : : ,
(0.025 moles), 13.8 grams of powdered potassium carbonate (0.1 moles), 17.4
grams of 4-ethyl iodobenzene (0.075 moles), 7.5 grams of copper bronze and 25
milliliters of a mixture of C13-C15 aliphatie hydrocarbons, i.e. Soltrol~170
from Phillips Chemical Company. Thle contents of the flask are heated to
190 C for 18 hours. Using a water aspirator, the excess 4-ethyl iodobenzene is
removed by vacuum distillation. The product is isolated by ~he addition of 20U
milliliters of n-octane and hot filtration to remove the inorganic solicls. The
deep orange filtrate is column chromatographed using Woelm neutral alumina
with cyclohexane/benzene in a ratio of 3:2 as eluent. The resulting oil is
10 recrystallized from octane to yield pale yellow crystals of the intended
product having a melting point of 149-151 C.
Analytical Calculation for C40H36N2: C, 88.20; M, 6.66; M, 5.14.
Found: C, 88.27; H, 6.72; N, 4.98.
NMR (CDC13)~1.22 (t,6, methyl); 2.60 (q, 4, methylene); 6.86-7.64
15 ppm (m, 26, aromatics).
EXAMPLE XII
Preparation of N,N~-diphenyl-N,N'-bis(4-n-butylphenyl)-~1,1'-bi-
phenyl]-4,4'-diamine.
Into a 250 miIliliter 3 neck round bottom flask equipped with a
20 mechanical stirrer, thermometer with temperature controller and a source of
argon are placed 8.4 grams of N,N'-diphenyl-[l,l'-biphsnyl]-4,4'-diamine
(0.025 moles), 13.8 grams of powdered potassium carbonate (0.1 moles), 19.5
grams of 4-n-butyl iodobenzene (0.075 moles~ 7.5 grams copper bronze and 25
milliliters of C13-C15 aliphatic hydrocarbons, i.e. Soltro~) 170, from the
25 Phillips Chemical Company. The contents of the flask are heated to l90~C
with stirring for a period of 18 hours. The product is isolated by the addition
of 200 milliliters of n-octane and hot filtration to remove the inorganic solids.
The deep orangle filtrate is column chromatographed using Woelm neutral
alumina with cyclohexane/benzene in a ratio of 3:2 as eluent. The resulting
30 viscous oil is recrystallized frorn octane to yield pale yellow crystals of the
intended product having a melting poinl of 130-132 C.
_a~4_
~ ~,
'. ` ~.
Analytical Caleulalion for C4~H44N2: C, 87.96; fl, 7.38; N, 4.66.
Found: C, 88.34; H, 7.30; N, 4.41.
NMR (CDC13)J0.93 (t, 6, methyl); 1.15-1.78 (m, 8, methylene) 2.57
(t, 4, methylene)~ 6.50-7.58 ppm (m, 26, aromaties).
EXAMPLE XIII
Preparation of _ N,N'-dipllen~-bis(3-chlor~phenyl)-[1.1'-bi-
phenyl]-4,4'-_iamine.
Into a 250 millimeter of three necked round bottom elask equipped
with a mechanical stirrer, thermometer with temperature controller and a
10 source of argon gas are placed 3.4 grams of N,N'-diphenyl-[l,l'-bi-
phenyl]-4,4'-diamine (.01 moles), 5.6 grams of potassium carbonate (.04
moles), 9.6 grams of 3-chloroiodobenzene (.04 moles) and 0.5 grams of copper
powder. The contents of the flask are heated with stirring for a period of 24
hours. Using a water aspirator, the excess 3-chloroiodobenzene is removed by
15 vacuum distillation. The product is isolated by the addition of 200 milliliters
n-octane and hot filtration to remove the inorganic solids. The deep orange
filtrate is column chromatographed using Woelm neutral alumina with cycl~
hexane/benzene as eluent (3/2). The resulting oil is recrystallized from
n-octane to yield colorless crystals of the intended product having a melting
20 point of 130-132 C .
EXAMPLE XIV
Preparation of_ N,N'-diphenyl-N?N'-bis(4-chlorophenyl)-[1,1'-bi-
phenyl] ~4,4'-diamine.
Into a 250 mllliliter three necked round bottom ilask equipped with
25 a mechanical stirrer, thermometer with temperature controller and a source
of non-oxidizing gas are placed 3.4 grams of N,N'-diphenyl-[l,it-bi-
phenyl]-4,4'-diamine (.01 mole)~ 5.6 grams potassium carbonate (.û4 rnole), 9.6
grams of 4-chloroiodobenzene ~.04 mole) and 0.5 grams copper powder the
contents of the flask are heated with stirring for a period of 24` hours. Using a
~ ~ 30 water asplrator, the excess 4-chloroiodobenzene Is removed by vacuum
:: :
-45-
.
. ~. .
distillation. The prodllct is isolated by the addition of 200 milliliters n-octane
and hot eiltration to remove the inorganic solids. The deep orange filtrate is
column chromatographed using W oelm neutral alumina with cyclo-
hexane/benzene as eluent (3/2). The resulting oil is recrystallized from
n-octane to yield colorless crystals of the intended product having a melting
point of 147-149 C.
EXAMPLE XV
Six photoreceptor devices were prepared employing the compounds
prepared in Examples IX-XIV in the transport layers. Six solutions were
10 prepared, each containing 1 gram of Makrolon~;), a polycarbonate, dissolved in
13.5 grams of methylene chloride. Into each solution was dissolved 1 gram of
the compounds prepared in Examples IX-XIV to form a 50 percent by weight
solid solution of the compound in the polycarbonate after the methylene
chloride is removed.
On six, two-inch square aluminum substrates, a 0.5 micron thick
- layer of amorphous selenium was evaporated. The polycarbonate solutions of
the compound of Examples IX-XIV were deposited over the selenium by the
use of a Bird Film Applicator and vacuum dried at 40 C for 24 hours to yield a
25 micron layer.
Electrical testing of ~hese plates as illustrated in Example V~
showed that the charge transport in these structures was comparable to the
photosensitive structures of Examples II, III, IV nnd VI. Using a Xerox
Corporation D~odel D Processor, each plate produced excellent xerographic
copies.
The invention has been described in detail with particular refer-
ence to prefeirred embodiments thereof but it u7ill be understood that
variations and modifications can be effected within the spirit and scope of the
invention as described hereinabove and as defined in the appended claims.
.~
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