Note: Descriptions are shown in the official language in which they were submitted.
3937
- ,
This invention relates to x-ray sensitive elements and a
process for producing visible lmages from an x-ray exposed image.
The process of forming a visible image by exposure
to x-radiation is quite valuable for medical and industrial ;
applications. Although the primary use is in diagnosis of human
- disease, x-radiation can also be used as a means of detection of
mechanical flaws in machinery and equipment for
industrial purposes. The major requirements for elements `~
to-be treated by x-radiation for these purposes are that ~ ;~
the intensity and length of time of exposure be as low as
possible and the resulting image be of high contrast and
high Dmax. For industrial applications the speed is of less
importance than the contrast and Dmax.
. The process of xeroradiography such as described
.~! in U.S. Patents 3,577,272 and 3,453,:L41, empLoys a xero-
radiographic element comprising a support material bearing a
coating of a normally insulating material whose electrical
resistance varies with the amount of incident x-radiation ;~
it receives during an imagewise exposure. The element, ~
20 commonly termed a photoconductive element, is first given -~ ;
a uniform surface charge. It is then exposed to a pattern
of x-radiation which has-the effect of differentially.reducing
the potential of this surface charge in accordance with the
. .
relative energy contained in various parts of the radiation
pattern. The differential surface charge or electrostatic
latent image remaining on the xeroradiographic element is ~
then made visible by contacting the surface with a suitable ~ ~-
;,~.
electroscopic marking material. Such marking material or
toner, whether contained in an insulating liquid or on a dry
; 30 carrier, can be deposited on the exposed surface in accordance ~
" . . ..
'-'' ' ~ '
! ~ . .
~ ~^~
~ 5~3~37
with ei-ther the charge pattern or in the absence of charge
pattern as desired. Deposited marking material can then be
either permanently fixed to the surface of -the sensitive
. element by known means such as heat, pressure, solvent vapor,
or the like, or transferred to a second element to ~hich it
can similarly be fixed. Likewise, the electrostatic.latent
~ image can be transferred to a second element and 'dev'eloped
';' there.
The above process is, however, not always useful
for medical applications or industrial applications requiring
extremely high contrast and Dmax The xeroradiography process
~` produces images having only acceptable contrast and D~ax so
that the detail required may not be sufficient to be useful.
~ Furtherg the xeroradiography method generally results in a
'~' problem known as "fringe toning". Fringe toning is the
-~ phenomenon of differential Dmax in image areas. Thus, the
~j Dmax may be high at the edges or fringes of the image and
;;~ low around the center of the image.
l A further problem involved with the use of x- ' -
: . .
'' 20 radiation in ~eroradiography is xeroradiographic undercukting -
-~ caused by the ionization of air in the dark space between the
'i - .
dark slide and the surface of the radiographic plate. The
x-rays create positive and negative air ions in the dark ~
spaces with the negative ions being attracted preferentially ~ '
to the image discontinuities of the surface. This results
in a neutralization of surface charges and a narrowing of
. ~ - .
the unexposed areas of the electrostatic image. Substantial
;. !
' damage to the resulting image occurs. The problem is further '
described in Schaffert R.M.~ Elect ophotography, New York,
Focal, 1965 (pages 105-106) and Dessauer and Clark, '~'~
,:; " .
i Xeroradiography and Related Processes, New York, Focal, ' ''
'' 1965, (pages 500-501). ' ~
'~'' : ,"
:: ' , ' , , . ~ ,
8 C3 5~3'7
A still further problem :involving the use of electrical
radiographic processes is the dark decay inherent in such
a process. The photoconductor cannot hold the charge for
as long as is necessary for the x-ray exposure and this results ~
" : in a substantial loss of contrast ~nd Dmax. Therefore~ ~ -
if prolonged exposure t~mes are required a substantia~l loss , -
of image results.
It is, therefore, an object of this inventiQn to
provide an element capable of being exposed to x-radiation
at high speed and being developed to an image of high Dmax
: ..................................................................... . . .
~ and contrast with no loss of image due to dark decay and ~
,:,
fringe toning. ~ ~
~; It is another object of this invention to provide ~; --
novel x-ray sensitive elements which can result in negative
or positive images. `~
It is a further object of this invention to `
i provide a novel process for produci~g ima~es of high contrast
and Dmax using the elements of this invention.
It is a still further object of this invention to
20 provide a novel process for producing negative or positive;~
.
images at high speed using the elements of this i~vention. `~
In the drawing, the figure is a horizontal section ~;
through an element and shows the process of exposing and
applying potential to said element to create sites for
physical development. ~
These and other objects of the lnvention are
accomplished with an x-ray sensitive element for physical
development comprising a support (1) coated with an image- -
; receiving layer (2) which comprises pigments which form
active sites for reduction of metal ions when subjected to
'':'1 an electric field and in a binder, wherein the pigment
.... .
" ..
'; ' .
" ~
" , , . :. .. . . - , .. ... . .. . ..
~OS8~ 7
to binder weight ratio i9 from 2:1 to 10:1, and a layer
(3) thereover comprising an inorganic photoconductor having
~ a metallic atom having an atomic nu~ber of 48 or higher
'~: with a conductive topcoat (4), wherein an air gap of up to
:'
': 20 microns separates th.e.layers (2) and (3).
, An advantage of these elements is that the
contrast and Dmax obtained a:re exceptionally good for ~,
~' exposures in the x-ray region. An additional advantage of
1, these elements is that the contrast and Dmax are not' 10 deleteriously affected by dark decay and the images obtained . . :.
from these elements have uniform Dmax properties.
.. . ~ . -: .
,, Further, the undercu~ting problem encountered in the xero- .
~:~ radiographic method is not encountered using the elements
of this invention. Actually the ions formed by the x-rays ;~
,'~' ...... aid in`the i.onization of the air gap and produce better :~:
~$
. image resolution. . . . ~'
I Also in accordance with this invention a process
,', is provided wherein an x-ray patterh is projected onto an ~t~
, element comprising a support ~)coated with a layer~2)which '.
forms active sites for reduction of metal ions when subjected
. . . . . .
,.: to an electric field and a layer (3)thereover comprising an ~.
~ inorganic photoconductor having a meta1iic atom having an atomic ~,
'., number of, 48 or higher and pre~erably a binder therefor ,
,.~, w1~h a conductive topcoat (4), wherein an air gap of .01 to
~ 20 microns separates the layer forming actinic sites for . .''~
'' the reduction of metal ions (2) and the layer comprising
.. ' the inorganic photoconductor (3), and applying an electric .'
., . - .
,:,, f1eld across said element to form metal nuclei and separating - ~:
,', . the layers (1) and (2) from ~ayers (3) and (4? and physically ,;
developing the met'al nuclei on layer (2) to form an image. .
,'', The image obtained can'be either negative or positive i;'
, . . . .
~' depending upon the parti~l~r-process used
. : ~
; ',: '.
"`' , _5
`,' :
:, . . . .. . . . . .
~ 58~37
. In accordance with this :inventlon, the fi~ure of the
; drawing represents an element comprising layer (1) which is a
.~ support, preferably baryta coated paper, and a pigmented layer (2)
preferably a TiO2 containing layer which is sandwiched with a
` photoconductive layer (3) and conductive topcoat (4). The air gap
depicted between layers (2) and (3) is grea.tly enlarg~ed since the .
photoconductive layer (3) generally rests on layer (~). The process
comprises exposing x-rays to a test object 5 while either simul- ~
taneously or later applying a potential be-tween the conductive ~: :
topcoat (4) and a grounded platen 6 adjacent to the support layer (1). . .
j The conductive topcoat is carried on a conductive . .
support 7. The conductive support 7 may be formed from any
.~ of the materials for support (1).
.~ ............. .The support (1), on which the layer forming actîve .
siteS for reduction of metal ions when subjected to an electrical
~! field is coated, may be any electrically conducting or semi~
l~ ~ conducting support material, such as paper or conventional ::~
`j`. film supports, e.g., cellulose acetate, cellulose nitrate, .
.~ poly~styrene), poly(ethylene.terephthalate), poly(vinyl acetal), ~
... 1 20 polycarbonates and related films containing an evaporated - ~ .
or chemically deposited metal layer such as nickel-coated .
supports. Further examples of supports to which conductive :~
coatings can be added which are.useful herein are described
in Product Licensing Index, Vol. 92, December 1971, Publication -~
.. , ~ . . . ... .-:
~` 9232, page 108. The layer (1) should have an electrical ..
~ resistivity of less than about lolO ohm per square.
,. . 1ayer(~ comprises a material which forms active. -
sites for reduc.tion of metal ions when subjected to an `.
~ .
electric fleld. This electrically activatable 1ayer : ~
30 forms activatable sites which may be physically developed ~ ~-
: to an image. The preferred materials are pigments having the
above properties are TiO2~ W03, MoO3 and lead iodide with `.
rutile TiO2 being especially preferred. .
'' ~ ~,
: 6
.,.~ ' . : . , , :
58~
The p.igments generally have particle sizes in the
range of from about 0.25~Xm to about 3.0 ~ m. As the
reaction involves surface effects, the surface-to-volume _ ... . ~.
: ratio increases as the particle size decreases. Therefore,.
it is preferable to use pigments having lower particle sizes.
; Binders ror use in preparing layer 2 :i.nclude
~ . any hydrophobic binders such as styrene.butadiene copolymers;
- polyolefins; soya-alkyd resins; poly(vinyl chloride),;~
. poly(vinylidenechloride); vinylidene chlo.ride-acrylonitrile
:j 10 copolymers; poly(vinyl acetate); vinyl acetate - vinyl ~ .
chloride copolymers; poly(vinyl acetals), such as poly(vinyl
butyral); polyacrylic and methacrylic esters, such as poly~
(methylmethacrylate); poly.(n-bu.tylmethacrylate), poly(isobutyl
~ methacrylate), etc; polystyrene;; nitrated polystyrene,
~ poly d .-methylstyrene; isobutylene polymers; polyesters, such as ~.
. , . _ . _ ....................... . _ . _ _ .. _ . .
.~ . poly(ethylenealkaryloxyalkylene terephthaiate); phenol- ~ :~
formaldehyde resins; polyamides; polycarbonates; polythio- ..
. carbonates; poly(ethyleneglycol-co-bishydroxyethoxyphenyl
: . propane terephthalate) copolymers of vinyl haloarylates and ~. .
20 vinyl acetate such as poly(vinyl-m-bromobenzoate-co-vinyl~
.~ : acetate) and the like. Use~ul binders are insulating film-
-1 - forming resins having an electrical resistivity greater than
101 ohm per square. : .
! ~ Solvents of choice for preparing coating compositions
of layer.(?) can include a number of solvents such as .
~ benzene, toluene, acetone~ methyl iso-butyl ketone, methylene ~ ~
chloride, and the like, or mixtures of the above. ~.
,., . ~:~ ~.
'( . ' .: ~ ::,
:'' ' . ' ~' ':,
~;
:. . .
~51~C337
In preparing layer(~, useful results are obtained
when the pigment and binder are present in an amount from
`` about 30 to about 60 ~ by weight of the solvent solution.
- The pigment to binder ratio is dependent on particle size
; and the particular pigment or binder used, but may range from ~;
. .,. ~ .
about 2:1 to 10:1. In the preferred embodiment herein,the
pigment to binder ratio is from about 3:1 to about 5
The pigmented layer(~ can be applied to the support(~
: i~ .
. by any conventional coating process such as dip coating,
; 10 curtain coating, etc. A description of various methods of
coating can be found in Product Licensing Index, Vol. 923 ;
December 1971, Publication 9232, page 109. The coating
thickness of layer (2) may vary widely, but the preferred
dry thickness is from about 4 ~m to about 15 ~m. The
thickness should be enough so as to give covering power
to the support without being excessively thick. As the
process takes place in the surface of the layer and the
phyeical developer does not penetrate deeply into layer (2), ~ -
a heavy thickness is not needed. - ~
If deslred, an overcoat may be used over layer ~;
(2) in order to protect Iayer (2) from smearing or oxidation.
, Any overcoat layer which does not affect the electrical ~
transmission from layer (3) to layer (2) may be used. ;-
' Generally a thin layer of a water-penetratable colloid
, such as gelatin, polyvinyl alcohol, ethyl cellulose and the
like can be used. Gelatin is most effective, e.g., 2 to 5 ~m
thickness.
'.~ ::' :'~
:,:. . l .
i~51~393~ .
The element is preferably prepared by applying a
coating of layer(~ onto a conductive topcoat(~ and sandwiching ..
these layers with support(l) coated with layer(~. :
Suitable conductive topcoat materials(~ on which
the photoconductive layers(~ can be coated include any of a :~
wide variety of electrically conducting supports~ for example,
paper (at a relative humid.ity above 20 percent), alwninum~
paper laminatesj metal foil such as aluminum foil, zinc
foil, etc.; metal plates, such as aluminum, copper, zinc,
brass, and galvanized plates; vapor deposited metal layers,
such as silver, nickel or aluminum and the like on paper and .
-:. . ; .
:........ resin film supports. Such conducting layers both with and
3 . ~.
I without insulating barrier layers are described in U.S. Patent
: No. 3,245,833. Likewise, a suitable conducting coating can be
, . . ..
j prepared from the sodium salt of a carboxyester lactone maleic ; ~:
.~ anhydride and a vinyl acetate polymer. Such kinds of ccnduc~
~ ting layers and method for their optimum preparation and use .
::.' . . .
-.i are disclosed in U.S Patent Nos. 3,007,901 and 3,267,807
. : Preferably, layer (4) is more electrically conductive ~-
. i
~ 20 than is layer (3). Preferred layer (4) materials have an
; electrical resistivity of less than about 104 ohm p~r s~uare.
~ The layer containing the inorganic photoconductor (3)
:~ is generally prepared by milling a dispérsion o~ the photo- -
. conductive material with a binder and coating the layer (3) `
onto the layer (4). ~ . .
'', ' ' ' ' 'i''' '
.. . . . . .
""' ' ' ' ' '
, " , .
'' ' ' '",` ~ : ': .
, . - , . . :. .
',' " ~9~ .: ~.
' . . . .
., . _ ._ __,_.__ _ . . , .. _=____ . . . __.. ~,.= .=,=,~. . . _ . ....
~ 5~937
;
Preferred binders for use in preparing the present .
', photoconductive layers are film-forming hydrophobic polymeric ;;.
blnders having fairly high dielectric strength which are good .:. .
electrically insulating fi'lm-fo'rming vehicles. Materials ' '.''' ~:
: of this type cornprise styrene-butadiene copolymers" poly~
olefins; soya-alkyd resins; poly(vinyl chloride); poly.(vinyl-
idenechloride); vinylidene chloride-acrylonitrile copolymers; .:
~ poly(vinyl acetate); vi.nyl acetate-vinyl chloride copolymers; ~'
~'~ poly(vinyl acetals), such as poly(vinyl butyral), polyacrylic .
10 ~nd methacrylic esters, such as poly(methylmethacrylate), ~' -.
'' poly(n-butylmethacrylate), poly(isobutyI methacrylate), etc.;
' polystyrene; nitrated polystyrene; polyme~hylstyrene, iso- . .~;
.;~ . butylene polymers; polyesters, such as poly(ethylenealkaryloxy-
`' alkylene terephthalate); phenolformaldehyde resins; ketone `.
'~ . resins; polyamides, polycarbonates; polythiocarbonates, .. ~ .
poly(ethyleneglycol-co-bishydroxyethoxyphenyl propane
terephthalate) copolymers of vinyl haloarylates and vinyl
'~ acetate, such as poly(vinyl-m-bromobenzoate-co-vinylacetate)', ' .`.''
etc. Sui.table resins of the type contemplated for use in the ~'
20 : Fhotoconductive layers of the invention are sold under such
: tradémarks as Vitél PE-101*, Cymac*, Pliolite S-5*, Piccopale
" ~
~ 100*, Saran F-220*, Lexan 105* and Lexan 145*. Other types of .~
., ~ : , .
binders which can be used in the phot~conductive layers of
' the invention include such materials as paraffin, mineral'~
:, waxes, etc._ ~
Solvents of choice for preparing coating compositions ~: :
~' of ~he present invention can include a number of solvents ~ ~"
'': such as .benzene, toluene, acetone, 2-butanone, chlorinated
~' hydrocarbons, e.g., methylene chloride, ethylene chloridej .`
: 30 etc., ethers, e.g., tetrahydrofuran, or mixtures of these
solvents, etc. ' .
*Trademark -10
:, ' .
:
,;,,, . , " .' ~ ~ `' . ~ ,` ' '` . I '
1~5~ 7
The inorganic photoconductor used must contain
metallic atoms having an atomic number of 48 or higher .
such as PbOg CdS, Bi203, CdSe, Se, Sb2S3 and the like
such as described in U.S. Patent No. 2,825,814. The
' preferred inorganic photoconductor is tetragonal lead . : .'
- monoxide as described in U.S. Patent No. 3,5'l7,272. '
: ~ ' ' ' ' ' , ' ' ::. 'In preparing the coating compositio~ useful results
- are obtained where the photoconductor substance is present in :
an amount equal'to at least about 30 weigh-t percent of the
coating-composition. The.upper limit in'the amount of photo-
'.' conductor substance present can be widely varied in accordance
' with usual practiceO More generally, from 1.5 to 12~5 parts by
'~ weight of photoconductor for each part by weight of binder in
the final composition is used. A preferred weight range in
the'final coated and dry composition is 1.5 to about 7.5 parts ' .
:. . . . , ~
''' ' by weight of photo~onductor for each part by weight'of b.inder.
`' If desired, the layer.(3) can be prepared without
': a binder by hot-pressing such as by a process described in i~ .
Research Disclose~ Volume 124, August 1974, item 12,427.............. ~:
' 20 : ~ .
. . . ..
' Coating thicknesses of the photoconductive compo- '~ . .;
. . ~:
sition on a suppor~ can vary widely. More generally, a
'........ coating in the range of about 0.005 inch to about 0.. ~0 inch
,: ,
~ before drying is useful for the practice of this invention.
.' The preferred range of coating thickness is in the range . .~
:` from about 15 ~m to about 200 A~m after drying although . ' ~: :
.': ueeful results can be obtained outside of this range. ` ''-~
, ' . . .'.' ~ . ~:
"'. ' - ~ '
... : . . . . .
11 ' ' ~ .~ '
.
'
:
;~ ~
~L05~9~7 i .
~:
The layer(~ can be applied to the layer(~ in a ~ -
variety of ways as long as an air gap exists between the two
layers. Thus, a solvent cast coating of layer(~ onto layer(2)
is not an acceptable method of application. Generally, the
~. layer(~ is merely sandwiched with layer(~ in a cont:Lguous ~`
,.~< - , :
face-to-face relationship. Although layer(~ and layer;(3)
are in face-to-face relationship an air gap exists between
the two layers owing to the roughness of the surfaces~ In
some cases it may be desirable to fasten layer(~ to layer(3)
at the edges at a specified distance if a more substantial
.~, , ,
.
gap is preferred. Spaces of defined thickness can be built s
into the surface of either layer (2) or layer (3~ such as by ;
.`3 adding glass beads or polymeric beads to either or both of ~;
; said layers. Other methods of forming the air gap between
the layers are well known in the art. --
The thickness of the air gap is generally
determined by the roughness of the layers (2) and (3). Generally,
an air gap of up to about 20 microns is satisfactory. The
preferred air gap is from about O.I micron to about lO
. I, ..
., 20 microns.
The element is exposed imagewise to x-radiation ~
and preferably simultaneously a potential is applied between - -
the layer (l) and the Iayer (4). Alternatively,~the exposure can ~ ;
take place prior to the application of the electric field. ~ ;
: : : , :-:
,
The x-ray pattern is projected onto the element by
irradiating through an object to be photographed and the ~ .
.~ . . . .
electric charge is applled to form an electric field pattern
' corresponding to the x-ray pattern. Typical sources of x-
-~ radiation emit a wavelength from about 0.1 angstrom to about
lOO angstroms. The period of exposure to x-radiation can vary
from seconds to minutes dependant upon the particular use in
either medical or industrial radiography.
,
-12-
~058~37
The electric charge is generally applied with
the applica-tion of a potentia] difference between th~s con-
ductive layer(4) and a plate contiguous to layer(~ so that an
electric field image is placed on layer(~ due to selective
potential across the air gap between layers(~ and(~ in the
x-ray exposed areas. The charge may be applied ln anyi ;~
conventional manner3 such as described in U.S. Patent Nos.
2,825,814 and 3,598,579. A potential of from about 600
volts to 4,000 volts applied for from about 5 to about
10 60 seconds is generally sufficient to achieve the -
desired results. f . .
` After exposure and charging,the portion of the
element comprising layers(~ and(~ can be removed from the
portion of the element comprising layers(~ and(~ and the
I image deueloped on layer (2~. The portion of the element
comprising layers(3~ and (~) is reusable in this process. ~ .
In some instances such as when the activatable
~ layer(~ comprises W03 or MoO3 pigments, nucleating sites are
`l formed directly which upon the application of a physical de-
veloper form a visible image, In othe~ cases, such as when the
activatable layer(2)comprises TiO2 or BaTiO3, treatment
with a nucleating agent (a material which is an oxidizing
agent containing a reducible metal ion) may be necessary
prior to the use of the physical developer Examples of
nucleating agents useful herein include metal ions such '~
as Ag , Hg , Pb+~, Au~3, Pt+4, Ni+2 Sn+2 pb+2 Cu-~1 d
Cu+2. The preferred nucleating agent is silver nitrate.
.. . . .
,j, ' ' ~'
,.
13
. ' '
~, . . , . - . . :
.- , . . . . , : .
~ ?
: 1~5~3~37
-' The nucleating agent generally comprises from about ' -'
a .05 to about a 5% by weight solution in a solvent such as ~ '
.
water or alcohol and waterl or the like. In a preferred embodi- -
'' ment, the nucleating agent is in a concentration of 2% by weight
in water. The layer (2) can be treated with the nucleating
~ agent by merely immersing the layer (2) in a bath of the nucleat-
`~ ing agent for a period of from about 10 to about 60 seconds.
The image on layer (2) is physically developed in any
~'~ conventional physical development bath. The physical develop~
'j 10 ment bath generally contains metal ions in salt form and a re-
l ducing agent for the metal ions. Typical physical developer '~
, ~
'~ solutions are well-known (see Hornsby, Basic Photograph'ic
3 Chemistry, (1956) 66, and Mees and James, ed., The Theory o'f'the
'~ Photographic Process, 3rd edition (1966), 329-331, and U.S. '' '-
.. ~ . ~-
~3 Patent 3,650,748 by Yudelson et al issued March 21, 1972) and '-~
"1 ~ contain the metallic ions such as s:ilver, copper, iron, nickel ~'`'- '
or cobalt necessary to form a visib:Le image at and in the vicinity ~'~
of the nucleating centers.
i~ The preferred metal salts employed as the source of '
;`~ 20 metal for physical development are water-soluble salts such as
; silver nitrate, silver acetate, cupric salts such as copper
chloride, copper nitrate, copper sulfate, copper formate, copper '`
acetate and the like, and nickel salts such as nickel chloride,
'~ nickel bromide, nickel sulfate, nickel nitrate, nickel formate
~' and the like.
~; . ,~ i
; -14- ~
' ' ' ` :.
~: .
' ' ~;
. ~ ,`
, . .
:,., - , .: .. . :
937
Typical reducing agents used in the physical developer
include, for example, polyhydroxy-substituted aryl compounds
such as hydroquinones, catechols, and pyrogallols; ascorbic acid
derivatives; aminophenols; _-phenylenediamines; and the like
; developing agents used in the photographic art. Particular
;l examples of reducing agents for physical developer solutions are
2-methyl-3-chlorohydroquinone, bromohydroquinone, catechol, 5-
; phenylcatechol, pyrogallol monomethyl ether (1-methoxy-2,3-dihy-
- droxybenzene), 5-methylpyrogallol monomethyl ether, isoascorbic
acid, _-methyl-_-aminophenol, dimethyl-_-phenylenediamine, 4-
amino-N,N-di(n-propyl)aniline and 6-amino-1-ethyl-1,2,3~4-tetra-
~` hydroquinoline. Particularly useful reducing agents are ferrous- ` ;
'' J ferric salts containing silver nitrate. Borane reducing agents -~
~i such as amineboranes, borohydride and the like may also be -
used. ~
The preferred physical development baths include the ~ ;
Copper Enthone~ developer baths (a trademark of Enthonics Corp.)
containing copper sulfate, formaldehyde, Rochelle salt and ~ ~
-~ nickel sulfate and physical developers prepared from ferrous -~ `
: ^ , ~ .. .
ammonium sulfate, ferrous nitrate, citric acid, and silver
, nitrate. `-
~ The physical developer solutions, in addition to the
.'tmetal salt and reducing agent, can comprise a complexing agent
for the metal salt such as Rochelle salt or other ligands such ;~
as ethylene diamine tetraacetic acid for the metal salt, and can -
include a variety of other materials to facilitate maintenance
and operation of the developer and to improve the quality of the
'' ''i, '. ~ " ,' ~
. ....................................................................... .
~: :, :
~15- ~
~'' `.
?
,'; '.
. :,., . . , ~ ~ .
~L~58937
developed image, such as acids and bases to adjust pH, buffers,
preservatives, thickening agents, brightening agents and the like.
The rate of development can be increased, and hence the time of
,.
development decreased, by adding to the developer solution a
surfactant such as an alkaline metal salt of a sulfonated fatty ;~
acid, e.g., dodecyl sodium sulfonate.
The proportions in which the various components of the
,, :
physical developer are present in the developer solution can
vary over a wide range. Suitable concentrations of reducible ~ -
10 heavy metal salt can range from about 0.01 mole to about 1.0 mole
of metal salt per liter of solution. The upper limit of con~
centration is dependent upon the solubility of the particular
metal salt employed. Preferably, the solution is about 0.1 molar
to about 0.4 molar with respect to the heavy metal salt. The
'7, relative proportions of metal salt and complexing agent are
dependent upon the particular heavy metal salt or salts and the
particular complexing agent or agents which are employed. As a
general rule, sufficient complexing agent should be incorporated -
to "tie up" the reducible heavy metal ions which are in solution
(~ ~20 and to lessen the tendency of these metal ions to be reduced ~i
prior to use of the developer solution. Depending upon the par~
ticular heavy metal salt and the particular complexing agent
~` which is employed, the amount of complexing agent present typi~
cally can vary from about 0.2 mole to about 10 moles of complex-
ing agent per mole of metal salt present. Typically, the reduc-
ing agent can be present in amounts from about 0.01 mole to
about 5 moles of reducing agent per mole of metal salt present
in the solution. In order to permit the developer solution to
- :
~ 30
,~;
.' " -16-
.'' ~''
:,
"::
", . . . . . . ...
.~ .. . .. : . . .. , . . . : . ,. ,. ,... .. :
58g37
be utilized for i-ts maximum life, at least one equivalent of
reducing agent should be present in the solution for each equi-
valent of reducible heavy metal salt.
` The physlcal developers are operative over a wide range
of pH. However, since the borane reducing agents undergo an
acid-catalyzed hydrolytic reaction which reduces their stability
^~ during storage, it is preferred that the physical developers be
maintained at a moderately alkaline pH of about 8 to 11, and
preferably of about 8.5 to 9.5. Nevertheless, the physical ;~
developers can be used under acidic conditions as low as pH 3
if such conditions are advantageous for the particular photo-
; graphic process in which they are used. The physical developer
solution can be brought to the desired pH by addition of an `- -~;
appropriate amount of a suitable base, for example, ammonium
hydroxide or sodium hydroxide, and can be maintained at the
desired pH by addition of a suitable buffering system, for exam-
ple, sodium carbonate and sodium bicarbonate. Other materials , `
~: ,. .: : , -
~ which can be used to adjust the pH to the desired range and
J buffers which will maintain the pH in that range can be readily
l 20 determined by those skilled in the art.
;I~ The process outlined above may yield a positive or
negative image depending on the nature of the photosensitive
complex used and the development process. ~
! ~ . :
.:, ` .
., `" :': . ~
.~ "' ,' .
'' ,". ~,-. -
," "~
~17- ;
' ' ,;~,:
'' :`~' :''i -
': ' : " . ' ' :' ' , ' ,, .:, , ` " ': . ", . ' ~ '
~5~37
~;
Development of an image according to the invention
can be carried out under ambient conditions of temperature
and pressure, such as at a temperature of about 20 to about
30C at atmospheric pressure.
As described above, a negative image is developed
when the layer(~ is made the negative terminal of the circuit. ~
If a direct positive ima~e is desired5 layer (2) can be fogged r' ''
.j ~
prior to exposure and charging by pre~flashing uniformly with
` _ . Tungsten or W light such as to a photoflood for 1 to 60 seconds at ~ .-
., :
~` - 10 a distance of 6 to about 18 inches and the layer (3) can be made the
, . ~ . ._ .
positive terminal. Thus, the x-ray exposure deactivates the ex-
'~`J posed sites and the sites in the unexposed areas can be developed.
Alternatively, a positive image can be obtained by
pre-activating the layer (2) prior to exposure and charging by
unifor~ly charging with negative electricity and then following
~- with imagewise x-ray exposure and applying a potential with
~i layer (3) being made the positive terminal to deactivate
'. "s
j the sites in the exposed areas. ~
`: ' :1
i ~ In a preferred embodiment of this invention, a
,~ 20 "gain'l mechanism can be used to produce increased speed.
~ This is accomplished by the use of specific inorganic
,
photoconductors such as PbO which are persistent photocon-
ductors. These photoconductors remain more conducting ~
for long periods of time in the areas struck by radiant ~ ~ ;
energy after the radiant energy is removed. Therefore,
less exposure to x radiation is required.
The invention is further illustrated by the
following examples which include preferred embodiments
thereof.
~, :, . :
-18-
, ............................................................. . . .
~s', , ~
,.
, . ,, . , , : ,., . , .. : , : .: . .:,
. ': :, '' ;: , ~ ' : ' ' ~ ' ' ' " , ' ' ' ''
. ~ ', ,' ' ~' '.: " ' - ' ' : '
`
ILa~S8~3'7
.Yampl e
The ~ollowing materials were added to ~ ball mill
conta~ning 30 3/'~ inch o.d agate balls:
11.6 grams of a 34.5~ solution of 70/30 styrene-
butadiene copolymer in toluene (Pliolite~ S-7)
~; 20.0 grams of TiO2 (rutile)
: 35.2 grams of toluene -
The materials were milled for 24 hours and cpated
at 0.005 inch wet thickness on baryta-coated paper sùpport. The
coating was air dried at room temperature for 4 hours. A
o 003 inch wet thickness overcoat of 40~ gelatin in water
containing 0.2% formalin was coated on top of the TiO2 layer, ~ -
chill set and forced air dried in a dark cabinet for 24 hours.
The layer of TiO2 was sandwiched with a 100 fU m
thick layer of PbO in a styrene-butadiene binder coated on
~,~ a conducting support as described in Example 2 of U.S
Patent 3~577~272. `A potential of 3 KV was established across
the sandwich with the PbO layer being made the negative terminal
of the circuit and a platen being made the positive terminal,
0 simultaneously with the application of 1 mm aluminum filtered -~
60 INP (3mA) (60 kilovolt peak having a rating of 3 milliamps)
x-rays through a test object for 3~0 seconds.
` ~ The TiO2 layer on paper support was then removed ;
from the sandwich, bathed in 2% AgNO3 solution in water for
10 seconds~ and then immersed in a physical developer bath
containing 0.4 M ~errous ammonium sulfate, 0.16 M ferric
!',~', ' nltrate, 0.18 M citric acid and 0.1 M AgN03 ~or 30 seconds. ;~
A high contrast negative image of the test object havin~
reflective maximum density of 1.2 resulted.
The above element and process was compared to the
same process using the same element with the exception that
only the TiO2 layer on the support was exposed to x-rays
and treated. The photoconductive layer was not sandwiched wiJch the
:; - .
TiO~2 layer. No image resulted after treatment in the nucleating
agent and in the physical developer bath.
~ ':
,9_
,. . . . . . . .
- ., ,. : . .. . .
1~5893~
Example 2
- The TiO2 coated layer on paper support of Example 1 ~ -
;~ was pre-flashed uniformly under a photoflood for 5 seconds
. at a distance of 8 inches. The pre-flashed layer was
sandwiched with the photoconducto,r of Example 1. A potential
'~ of 3 KV was applied across the sandwich with the PbO,layer
being the positive terminal of the circuit3 simultarIeously
with exposure of 1 mm aluminum filtered, 60 KVP x-rays (3mA)
'' through the same test object o~ Example l'for 30 seconds. ~-
The TiO2 layer on paper suppor-t was removed from the sand-
wich and developed as described in Example 1. A direct
~, ' positive image of the test object resulted having a maximum
,~ reflective density of 1.05. ,
. :: .
.
;, Example 3
:-.i
~";s; , The following materials were added to a ball mill
~; jar containing 30, 3/8 inch o.d. agate balls:
.
", 23.3 grams of a 30~ solution in toluene of
an 85/15 s-tyrene-butadiene
, copo~ymer (Pliolite S-5)
,
21.0 grams of TiO2 (anatase) ;~ ~
, ' 18.2 grams of toluene ~, ,
:, .
The materials were ball milled for 24 hours and coated
' on a paper support as described in Example 1. A gelatin overcoat
was applied as described in Example 1 and the photoconductive
~; coated support of Example l was sandwiched to the TiO2 layer.
.:
~' Negative and positive x-ray images having high contrast maximum ,,' ,
'~, density w,ere obtained when the processes of Examples 1 and 2
were followed using th~ layers of Example 3.
..
. :
''' ~20- ~ ;
: ,.
.
. " ., ., : . , ,, , .
. .
~;8~37
~xample 4
The following materials were added to a ball mill
jar containing 30 3/8 inch o.d, agate balls:
: 12.0 gram of Pliolite~ S-7
20.0 grams of BaTiO3 ,
~ 36.o grams Or toluene
-, The materials were milled in a ball mill ~r 24
~ ,~
hours and coated on a paper support as described in Example 1.
The ~aTiO3 layer on paper support was sandwiched
with the PbO photoconductive layer on conductive support as
described in Example 1 and exposed to x-ray exposure through
a mask as in Example 1, simultaneously with the appli~cation
of a potential of -2.5 KV on the PbO layer for 30 seconds.
The BaTiO3 layer on paper support was removed from
the sandwich and immersed in a 2~ AgN03 solution in water -~
`~ for cO seconds and physically developed in the physical -~
developer bath of Example 1 for 40 seconds. A negative `~
reproduction of the test object resulted.
.. , . . - ,
-. : .:-: ~.
Example 5
The BaTiO3 coating on paper support of Example 4
was uniformly pre-exposed to a W -21 Mineralite lamp for 20
,~ seconds at a distance of 8 inches. The layer was sandwiched ~ ~`
; with the photoconductive layer coated on a conductive support
described in Example 1 and ~3KV was applied to the PbO and ~ -
' across the sandwich, fiimultaneously with lmm aluminum filtered ~
, , :, ~ .~. ,
~ 60 KVP x-ray exposure through a test object for 40 seconds. ~
',' "` - ~ i:
.
-21-
~ .
'', '1~'~ '` ";' '
1051!39~7
~ The BaTiO3 layer on paper support was removed
'~ from the sandw:ich and ba,thed in 2~ AgN03 solution in water
for 30 seconds and then immersed in the physical developer
, of Example 1 for 40 seconds. A direct positive reproduction
of the test object resulted.
This example was repeated except that the PbO
layer on a conductive support was not sandwiched with the
- BaTiO3 layer during x-ray exposure. No image resulted after
physical development without the PbO layer.
;~' ' ' , ~.
10 Example 6
The following materials were added to a ball mill
jar containing 30 3/8 inch agate balls:
i 5.7 grams of Pliolite S-7
0 10.0 grams of W03 '
.
11.0 grams of toluene
~, The mixture was ball-milled for 24 hours on a ball
, mill and coated on paper support as in Example 1. No gelatin
.
~, overcoat was used.
'~ The W03 layer on paper support was sandwiched with
;20 PbO on a conductive support as described in Example 1. A
''~ 3 KV potential was applied across the sandwich with the PbO
.,,, ~
~'' layer being the negative terminal,of the circuit, simultaneously
with the exposure from 1 mm aluminum filtered 60 KVP (3mA) ,;
,' x-rays through a test object for 30'seconds. ;
', The W03 layer on paper support was removed from
,, the sandwich at which tlme a visible printout image was
~, discernible. The layer was then developed directly,in the
.~ .; , .
,'' physical developer of Example 1 without pre-nucleation. A
high density (D~ = 1.15) negative image of the test pattern
;~ 30 resulted.
-22- ,
.
.
, : ,, . ;
. . . : ,
r~ j,
~ ~5~3~93~
:' ~L ' ' ~'
The following materials were added in a ball mill
~i jar containing 30 3/8 inch o.d. agate balls:
11.6.grams of Pliolite~ S-7 , .
20.0 grams of TiO2 (Titano ~ ~A-50) .
35.2 grams of tol~ene
The mixture was milled for 24 hours on a ball mill
and coated onto a paper support as in Example 1. No gelatin ; .~
overcoat was used. . . ~ . :
The TiO2 layer on paper support was sandwiched
.,. with a 100 ~ m thick layer of CdS powder dispersed~in a
70/30 styrene-butadiene binder at a pigment-to-binder ratio
r 4/1. The CdS powder had been doped with 15 parts per ~ ~
million copper and 100 parts per million antimony by a thermal ;.
activation process comprising firing the pre-doped powder at
~I 730C ~or one hour in a nitrogen and iodine a~mosphere. The
l ~ layer was coated on a conductive support of o.4D nickel~
eoated poly(ethylene terephthaiate) by knife coating.
, .: A potential of 2KV was established across the
.~ 20~ sandwich with the CdS layer being made the negat.~ve terminal .;
~o~ the circuit, simultaneously with the application o~ 1 mm ;~
- ~ aluminum filtered 80 KVP x-rays through a test objeet for .'
~i : 60 seconds. The TiO2 layer on paper support w~s then removed
from the sandwich, bathed in a 2% AgN03 solution ~or 15
-~ seconds and immersed in the physical developer bath of
.. Exarnple I ~or 20 seconds. A negatlve image of the test object .. -
resulted,
~ ' ~ L
,., .' ,~ , ' ;` ` ~ . "~ '
-23-
.,.,~,, , . ,' ~'. .
:', ;''': ':
',; 7 r';~; '~i,.,~ '
589~7
:
The air gaps between the image-reeeiver (2) and
layer (3) having the inorganie photoconductor was for the
respeetive examples, as follows:
Example 1 .01 to 12 microns
Example 2 .01 to 12 microns
. Example 3 .01 to 12 microns
Example 4 .01 to 10.5 mierons
Example 5 .01 to 10.5 mierons
:~ Example 6 .01 to 20 mierons
~ 10 EXample 7 .01 to 12 mierons
''. ',;~ ~ ',
":'' ,... ~
~ ~ :
'':`. ,i ,. '
,"" , , ~ .
.~ 20
''', ',.. ~.' ~"
~;; , :
:: :
:., .:,.
~ ,:
'.` ''~ ' '',
"; ." ~ ~ ' `
. 30
-23a-
' .
. ~",-, - - , . . -: , ~ .
,,, ,. ~, . ~ ' :
'~ ,:' ~ . : . ,' ' .
:
9~7
Although the invention has been described in
considerable detail with reference to certain preferred
' embodiments thereof, it wi.ll be understood that variations
and modifications can be ef~ected without departing from the
spirit and scope of the invention as described here:inabove.
: .
,
-'~: . . . : -
: ~.' ' ' ' ' . .
,, ,
, . . .
"~, ~
'':'.'. ; ~ ~',,
;:.' . .
. '. ' -
:, , .
:.:., '- .
.'~, '
. j . . . ..
~ ' . ' ' ' ." ~'' ~'
'"'' ~ '
... 1 , , ;. .
-: " . : ., -
: -24- . : ~
.
: .
,~ ,, ', . . ~ ., , , . . " . ,: , ,
, , .,, , . . , , , ~ .
.: .. ,, ,. , . : , ,
