CA1172893A

CA1172893A - Polymeric electrically active conductive layer for electrically activatable recording element and process

Info

Publication number: CA1172893A
Application number: CA000367980A
Authority: CA
Inventors: Richard C. Sutton; Mark Lelental
Original assignee: Eastman Kodak Co
Current assignee: Eastman Kodak Co
Priority date: 1980-02-25
Filing date: 1981-01-06
Publication date: 1984-08-21
Also published as: EP0034952A2; EP0034952A3

Abstract

Abstract of the Disclosure In an electrically activatable recording element, such as one comprising an electrically conductive support having thereon, in sequence: (a) a polymeric electrically active conductive (EAC) layer, (b) an electrically activatable recording layer comprising (A) a dye-forming coupler, and (B) an oxidation-reduction combin-ation comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercap-totriazole derivative, with (ii) a reducing agent which, in its oxidized form, forms a dye with the dye-forming coupler, (c) a photoconductive layer separated from (b) by an air gap of up to 20 microns, and (d) an electrically conductive layer; improvements are provided by means of a polymeric EAC layer (a) consisting essentially of a vinyl addition polymer, such as poly(methyl acrylate-co-vinylidene chloride). The recording element is room light handleable and provides a dye image and silver image by dry development processing.

Description

` ~728~3 POLYMERIC ELECTRIGALLY ACTIVE CONDUCTIVE
LAYER FOR ELECTRICALLY ACTIVATABL~
RECORDING ELEMENT AND PROCESS

BACKGROUND OF THE INVENTION

Field of the Invention Thi~ invention relate~ to a dye-forming charge-~en6itive recordlng element and process. One agpect o~
the invention relate~ to the u6e of a vinyl addition poly-mer in the electric~lly ~ctive conductive layer, refexred to herein ~ a polymeric EAC layer, in a charge-~ens~tive recording element wh~ch i8 capable of producing a dye image ~nd cilver image by dry development processes.

De~cript10n of the 5tate of the Art Production of ~ dye image and 8~ lver image in an electrically activ~tsble recording materi~l by dry devel-opment techniqwe6 i~ de~cribed ~n Re~earch Disclosure, October 1979, Item 18627. In accordance with that invention, production of a dye image und sllver image ls accompli~hed by mean~ of an electrically ac~i~ated r~cording element eomprising ~n electrically conductive support, such as a poly(ethyl~ne terephthalate~ fil~ h~v-ing a cermet co~ting on the film, havlng ther~on, ~nsequen~e~ (A) an electrically act1va~ed recording layer compri~ing ~n orgAn~c ~ilver ~alt And a redllcing agen'c, and (b) ~ photoconductive l~yer ~eparated from (a~ by an air gap of up to 20 microns and (c) an electrically con-ductive layer on Sb) 9 wherein the reco~ding laye~ com-priges, in zeactive a~60ciation, ~A) a dye-forming coup-ler, and (B) an oxida'cion~reduction combinatlon comprising ~) an organio silver aalt oxidizing agen~c, with (i~) 8 "

JL 1~2~93 reducing agent which, in its oxidized forin, forms a dye with the dye-forming coupler. Such an electrically acti-vated recording element ena~les formation of a dye image and silver image by heat processing after imagewise expo-sure. It has been desirable to increase tne charge sensi-tivity of such elements. Increased charge sensitivity would lower the levels of charge required to form a latent image in the electrically activated recording layer.
In our attempt to increase charge sensitivity, we found that a polymeric layer between the electrically con-ductive support and the electrically activated recording layer could provide some increased charge sensitivity.
However, as indicated in the following comparative exam-ples, many polymeric materials do not provide a suitable increase in charge sensitivity. No answer to the problem of producing the desirea degree of increased charge sensi-tivity by means of some type of interlayer or some type of polymer in a subbing layer was clear rrom the art.

~UIY~KY ~F T~E INVENTION
It has been found according to the invention that increased charge ~ensi~ivity can be o~tained ln an elec-trically activatable recording element, such as one com-prising an electrically conductive support having thereon, in sequence:
~5 (a) a polymeric electrically act-lve conductive (EAC) layer, (b) an electrically activatable recording layer comprising (A) a dye-forming coupler, and (B) an oxidation-reduction combination com-prising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercapto-triazole derivative, especially such a derivative represen~ed by the structure:

.

N - NH
Il ~
- Z~ S (CH23mY

w~erein Y i8 aryl conta~ning 6 to 12 carbon atoms D m is O to 2; and9 Z i8 hydrogefl, hydroxyl, or amine, wi th (ii) a reducing agent whlch, irl It B
oxidi~ed fortn, formQ a dye with the dye-forming coupler, tc) a photoconductive l~yer separated from (b) by an air gap of up to 20 micron~3 and (d) an electricAlly ronduct~ve layer.
The increased charge sensitivity i8 provided by means of a polymeric EAC layer (a~ that comprise6 a vinyl addltion polymer comprlBing recurring u~its repre~ented by ~he Btructure:
R I X
~CH2 C~n ~CH~ - ~p whereln Rl iB hydrogen or methyl; R2 iB ~ryl contain-25 in8 6 to :L0 carbon atoms, ~uch 115 phenyl and naphthyl, o~
o CoR3 whereln R3 i8 ~lkyl containing 1 to 2Q carbon atoms, 30 such ~B methyl, ethyl, propyl and butyl, or aryl oontain-lng 6 ~o 10 carbon atom~ 7 such ~ phenyl and n~phthyl;
each X i8 br~mine or chlor~ne; n represer1ts 15 to 50 weight percent, and ~ repre~en~cæ 50 to 85 weight pereent of ~aid vinyl addition polymer. The ~erm "alkyl" lnclud~
35 ~traight chain alkyl and branched ch~in elkyl~ The ~lkyl groups can be ~ub~tituted by ~Rean~ of groups th~t do not advexsely affect the desired properties of ~he ~ectri-, ~

cally activated recording element, such as an oxo group.The term "alkyl" includes such groups.
It has also been found according to the invention tnat a dye i~age and silver image, especially a dye enhanced silver image, can be produced by a dry, electri-cally activated recording process comprising the steps of (I) imagewise applying an electric potential, of a magni-tude and for a time sufficient to produce in the image areas a charge density within the range of about lO- 5 coulomb/cm2 to about lO-~ coulomb/cm2 to an electri-cally activatable recording layer of a charge-sensitive recording element, having a vinyl addition polymer EAC
layer according to the invention, the charge density form-ing a developable latent image in the charge-sensitive recording layer; and, then (II) heating the element sub-stantially uniformly at a temperature and for a time sufficient to produce a dye image and silver image in the recording layer. In this process embodiment, other means than a photoconductor are useful to produce the desired charge density in the recording layer, such as a contact or non-contact electrode.
A further process according to the invention which produces a dye image and silver image comprises (I) imagewise altering the conductivity of the photoconductive layer of tne electrically activatable recording elemen~
according to the invention in accord with an image to be recorded; (II) applying across tne photoconductive layer and recording layer an electrical potential of a magnitude and for a time sufficient to produce a developable latent image in the recording layer corresponding to the image to be recorded; and then (III) heating the recording layer substantially uniformly at a temperature and for a time sufficient to produce a dye image and a silver image1 preferably a dye enhanced silver image, in the recording layer. The step (I) of imagewise altering t~e conduc-tivity of the photoconductive layer is preferably carried out ~hile simultaneous1y (II) applyin~ ~he described elec-~ 1~28~3 trical potential across the photoconductive layer andrecording layer.
A further process according to the invention is a dry, electrically activated recording process for produc-ing a dye image and silver image, preferably a dyeenhanced silver image, in an electrically activatable recording element, having a vinyl addition polymer ~AC
layer according to tne invention, comprising the ~teps:
(I) imagewise altering the conductivity of a photoconduc-tive layer in accord with an ima~e to ~e recorded; ~II)positioning the imagewise altered photoconductive layer from (I) in face-to-face relationship with an electrically activatable recording layer of the recording element;
(III) applying across the photoconductive layer and recording layer an electrical potential of a magnitude and for a time sufficient to produce in the areas of tne recording layer corresponding to the imagewise altered portions of the photoconductive layer a charge density within the rang~ of about 10-5 coulomb/cm2 to about lO-~ coulomb/cm2, the charge density forming in the areas a developable latent image; and then (IV) uniformly heating the recording element at a temperature and for a time sufficient to produce a dye image arld silver image, especially a dye enhanced silver image, in the recording element, Another process according to the invention is a dry electrically activated recording process for producing a dye image and silver image, preferably a dye enhanced silver image, in a charge-sensitive recording element having a vinyl addition polymer EAC layer according to the invention, preferably having ohmic resistivity within the range of about 104 ~o about 1 x 1012 ohm-cm, contain~
ing at least one electrically activatable recording mater-ial comprising in an electrically conductive binder, (A) a dye--forming coupler, and (B) an image-forming combination comprising (i) an organic silver salt oxidizing agent con-sisting essentially of a silver salt of a 1,2,4-mercapto-l ~J2~9 3 triazole derivative, with (ii) a reducing agent which, inits oxidized form, forms a dye with the dye-forming coup-ler; comprising the steps: (I) positioning the recording material on an electrically conductive backing member;
(II) modulating a corona ion current flow to tbe recording element by an electrostatic field established imagewise between an image grid comprising an electroconductive core sequentially connectable to sources of different potential relative to the backing member and covered with a coating of a photoconductive insulating material and a control grid that is electrically conductive and sequentially connectable to sources of different potential relative to tne backing memDer, sai~ current flow being of a magnitude sufficient to produce a charge density within tbe range o~
about 10-5 to about 10-C coulomblcm2 imagewise in said recording element, which char~e density forms a developable latent image in the electrically activated recording material; and, (III) substantially uniformly heating the recording element at a tempera~ure and for a time sufficient to produce a dye enhanced silver image in the recording element, The heating step in each of the described process embodiments is carried out at a temperature within the range of about 80C to about 200C, typically at a temper-a~ure within the range oE aDout 10~C to a~out 1~0C,until the desired silver image and dye image are formed.

~RIEF UESC~IPrION OF THE DRA~INGS
Figures 1 and 2 illustrate schematically an image recording material and process according to one illustra-tive embodiment of the invention; and Figures 3 and 4 illustrate schematically an electrically activated record-ing process embodying the described invention.
Figure 5 illustrates schematically an image recording material that is especially useful according to the invention.

17~93 DETAIL~D DE~CRIPTI~N OF THE INVENTION
The term "electrically active conductive" herein has been abbreviated as "EAC". This term describes a layer according to the invention which is located between the electrically activatable recording layer (the layer in which a latent image is formed~ and the electrically con-ductive support of an element accor~ing to the invention.
This EAC layer is define~ as electrically active because the desired degree of increased sensitivity to tne image recording layer is produced when electrical charge is passed through the layers during imagewise exposure.
Many vinyl sddition polymers having the described recurring units are useful as tne EAC layer in an electri-caLly activate~ element according to the invention. The exact mechanisms by wnich the latent ima~e is formed and by which the EAC layer enables increased charge sensi-tivity in an elem~nt according to the invention are not fully understood. It is postulated that the injection of a charge carrier due to the electric field into the com-bination of components results in the formation of adevelopable latent image in the electrically activated recording layer. Some form of interaction which is not fully understood occurs between the electrically activated recording layer and the EA~ layer. For reasons not fully understood, the image apparently forms in tne exposcd areas in the recording layer closest to the interface between the electrically activated recording layer and tne EAC layer in an element according to the invention, rather than uniformly through the exposed areas of tne el~ctri-cally activated recording layer. It is believed that thedevelopment of the latent image is accomplished Dy a reac-tion in which the latent image cataly7es the reaction of the described image-forming combination. In such a reac-tion, the organic silver salt oxidizing agent reacts with tne reducing agent. Then, the oxidized form of the reduc-ing agent resulting from this reaction in turn reacts with the dye-forming coupler to produce a dye in tne image ~ 172~93 areas. It is not entirely clear, however, what part, if any, the dye-forming coupler and the other described com-ponents play in latent i~age formation.
While many image recording combinations contain-ing the described components are useful, the optimum imagerecording combination and image recording element will depend upon such factors as the desired image, the partic-ular dye-forming coupler, the particular organic silver salt oxidizing agent and reducing agent, the source of exposing energy, processing condition ranges and the like.
The term 'lcharge-sensitive~recording element" as used herein means an element which when subjected to an electrical current undergoes a chemical and/or electrical change which provides a developable latent image.
The term "latent image" as used herein is intended to mean an image that is not visible to the unaided eye or is faintly visible to tne unaided eye and that is capable of~amplification in a subsequent proces-sin~ step, especially in a subsequent heat development step.
The term "resistive recording material" as used herein is intended to mean a material that has an ohmic resistivity of at least about 104 ohm-cm.
The term "electrically conductive" such as in "electrically conductive support" or "polymeric electri-cally active conductive (EAC) layer" is intended herein to mean a support and EAC layer that have a resistivity less than about 101 2 ohm-cm.
The vinyl addition polymers useful in an electri-cally activated recording element according to tne inven-tion are prepared by methods known in the polymer art.
Tne following preparation of poly(methyl acrylate-co-vinylidene chloride) (20:80 weight ratio) is illustrative of methods that are used for preparing such polymers: To a 7.57 liter stainless steel reactor equipped with a stirrer, condenser, baffle and heated jacket is added 4.0 Kg of distilled water and 4.5 g K2S208. The ` ~ ;172~93 solution is deoxygenated such as by evacuation four times to boiling with release of pressure using nitrogen gas.
The reactor mixture is cooled to 15C; and 150 grams of surfactant, such as a sodium salt of an alkylarylpolyether sulfate available under the trade name TRITON 770 from the Rohm and Haas Co., U.~.A., vinylidene chloride (1440 grams) and methyl acrylate (360 grams) are added. Stir-ring of the reactor contents is maintained throughout the procedure. An additional 200 grams of distilled water containing 2.26 grams of dissolved Na2S2O5 is added and the reactor sealed and heated to 3SC. The tempera-ture is maintained at 35C for 17 hours at a pressure of 170 KPa. The reactor contents are cooled to produce a latex solution of 27.8 percent solids. The polymer is isolated by means of a freeze-thaw technique, wasned with dis~illed water three times using 60 liters of water per wash, centrifuged, and dried at 40C in vacuum for 17 hours. The resulting desired polymer has an inherent vis-cosity in cyclohexane of 0.93 with a rg of 31C.
~any photoconductors are useful in an element according to the invention. ~election of an optimum photoconductor will depend upon such factors as the par-ticular electrically activatable recording layer, the chsrge sensitivity of the element, the desired image, the ohmic resis~ivity desired, exposure means, processing con-ditions and the like. It is advantageous to select a photoconductor which has the property of being the most useful with the operative voltages to be used for imag-ing. The photoconductor is either an organic photoconduc-tor or an inorganic photoconductor. Combinations ofphotoconductors may be used. Tne resistivity of the photoconductor can change rapidly in the operating voltage ranges that may be used. In some cases, it is desirable that the pnotoconductive layer have what is known in the art as persistent conductivity. Examples of useful ~hoto-conductors include lead oxide, caamium sulfide, cadmium selenide, cadmium telluride an~ selenium. Useful organic photoconductors include, for instance, polyvinyl carDa-zole/trinitrofluorenone photoconductors and aggregate type organic photoconductors described int f~r example, U.S.
3,615,414. These photoconductors are known in the image recording art and are described in, for example, U.S.
Patent 3,577,272; Research Disclosure, August 1973, Item 1121~ of Reithel, published Dy Industrial Opportunities Ltd., Homewell, Havant, Hampshire, PO9 lEF, UK;
"Electrography" by R. M. Schaffert (1975) and "Xerography and Related Processes" by Dessauer and Clark (1965) both published by Focal Press ~imited, and U.S. 3,615,414.
An especially useful photoconductive layer com-prises a dispersion of a lead oxide photoconductor in an insulating binder, such as a binder comprising a polycar-bonate (for example, LEXAN, a trademark of GeneralElectric Company, U.S.A., consisting of a ~isphenol A
polycarbonate), polystyrene or poly(vinyl Dutyr~l).
A recording element according to the invention is especiaLly useful wherein tne photoconauctive layer is X-ray sensitive and the conductivity of the photoconduc-tive layer can be imagewise altered ~y imagewise exposing the photoconductive layer to X-ray radiation.
~ any dye-forming couplers are useful in the ele-ment and process according to the invention. The exact mechanism by which tne dye image and sllver image are pro-duced is not Eully understood. However, it is beLieved that the dye-forming coupler reacts with the oxidized form of the reducing agent to form a dye. The term dye-forming coupler herein means a compound or combination of com-pounds which with other of the components produces adesired dye image upon heating the recording layer after exposure. These are designated as dye-forming couplers because it is believed that tne compounds couple with ~he oxidized developer to produce the dye. The dye-forming couplers described nerein are also known in the pno~o-grapnic art as color-forming couplers. Selection of a suitable dye-forming coupler will be influenced ~y such factors as the desired dye image, other co~ponents o~ tne recording layer, processing conditions, particular reduc-ing agent in the recording layer and the like. An example of a useful magenta dye-forming coupler is l-(2,4,6-tri-chlorophenol)-3-[~ -(3 pentadecylphenoxy)-t~utyramido Lbenzamido]-5-pyrazolone. A useful cyan dye-forming coup-ler is 2,4-dichloro-1-naphthol. A useful yellow dye-forming coupler is ~-[3-{~-(2,4-di-tertiary-amyl-phenoxy) acetamido}-benzoy]]-2-fluoroacetanilide. Use-ful cyan, magenta and yellow dye-forming couplers can be selected from those described in, for example, "Neblette's ~andbook of Photography and Reprography", edited by John ~. Sturge, 7th Edition, 1977, pages 120-121 and Kesearch Disclosure, December 1978, Item 17643, Paragraphs 15 VII C-G. ;
An especially useful dye-forming coupler is a resorcinol dye-forming coupler. Tne resorcinol dye-forming coupler is preferably one that produces a neutral (black) or nearly neutral appearing dye with tne oxi~ized form of the described reducing agent. MonosuDstituted resorcinol dye-forming couplers containing a substituent in the two position are especially useful. The resorcinol dye-forming coupler and other components in the recording layer should be sufficiently stable to avoid any si~nifi-cant adverse interaction in the recording layer prior toimagewise exposure and processing. Many resorcinol dye-forming couplers are useful. A useful resorcinol dye-forming coupler is one represented by the formula:

i I
R7/ \t/ \Rs wherein ~4 is hydrogen, %93 o , o Il' 11 11 COH , NHCR8 , CR9 , or NHS02~1 ;

.
R~ is hydrogen, () O O
Il 11 11 COH > CNHCH2CH20H , or CNH-~C6Hs-~Oc5~1ln ;

R6 is hydrogen, O O
Il 11 NHCRa , or CR9 ~7 iS hydrogen, O O O
Il 11 11 COH , CNHCH2CH20H , or CNH-4C6Hs-~C5Hlln ~8 iS haloalkyL containing 1 to 3 carbon atoms, 6UCh as CCl~, CF3 and C3H4Br3, CH20C
CH2SR , NHR , C2H4COOH, CH=CH2, NHC~H4Cl, alkyl containing 1 to 20 carbon atoms, such as 1 to 10 carbon atoms, including methyl, ethyl, propyl and decyl, or phenyl;
R9 is l~H, NH2, NHCH2CH20H and NH(C6Hs)Oc5Hlln;
Rl is alkyl containing 1 to 5 carbon atoms, such as methyl, ethyl, propyl or pentyl, or phenyl; and Rll is hydrogen, haloalkyl containing 1 to 3 carbon atoms, such as CC13, CF3 and C3H4Br, CH20CH3, or C2H4COOH.
The letter n, such as in:

' - ~ 1728~3 CNH~c6H5~oc5Hlln means normal. Alkyl and phenyl, as described, include alkyl and phenyl that are unsubstituted alkyl and phenyl, as well as alkyl and phenyl that contain substituent groups that do not adversely effect the desired image. An example of a suitable substituent group is alkyl contain-ing l to 3 CarDon atoms, sucn as methyl or ethyl.
Examples of useful resorcinol dye-forming coup-lers are described in, for example, Research Disclosure, September 1978, Item 17326. Especially useful resorcinol dye-forming couplers include 2',6'-dihydroxyacetanilide and 2',6'-dihydroxytrifluoroacetanilide. Anottler useful resorcinol dye-forming coupler is 2',6'-dihydroxy-2,5-dimethylbenzanilide (2',6'-dihydroxyacetanilide has also been known as 2,6-dihydroxyacetanilide and 2',6'-di-hydroxy2,S-dimethylbenzanilide has also been known as

2,6-dihydroxy-2',5'-dimethylbenzanilide).
Resorcinol dye-forming couplers as described are prepared by procedures known in the chemical art. For example, resorcinol couplers as described are prepared from amino resorcinols or dihydroxybenzoic acids.
The dye-forming coupler is useful in a range of concentrations in the described recording layer. Typi-cally, the recording layer contains a conCentratiOn of dye-forming coupler tnat is within the range of about 0.1 to about 1.0 mole of tne dye-forming coupler per mole of total silver in the recording layer. An especially useful concentration of dye-forming coupler is within the range of about 0.25 to about 0.75 mole of dye-forming coupler per mole of total silver in the recording layer.
Selection of an optimum concentration of dye-forming coupler will depend upon such factors as the par-ticular coupler, the desired image, processing conditions, other components in the recording layer and the like.

1 1'72~9 Useful silver salts of 1,2,4-mercaptotriazole derivatives according to the invention include those represented by the formula:

N N~
(I'~ I! !
Z/ \N~ S-(C~2-)mY
.

wherein Y is aryl containing 6 to 12 carbon atoms, SUCh as phenyl, naphthyl and para-chlorophenyl; m is O to 2, and Z
is hydrogen, hydroxyl or amine (-NH2). Especially use-ful organic silver salt oxidizing agents witnin tnis class are those silver salts of the described 1,2~4-mercapto-triazole derivatives wnerein Y is phenyl, naphthyl orpara-chlorophenyl and Z is amine (-NH2). An example of such a compound is the silver salt of 3-amino-5-benzyl-thio-1,2,4-triazole (referred to herein as ABT). Such organic silver salt oxidizing agents are described in, for instance, ~.S. Patent 4,123,274 aod U.S. Patent 4,128,557.
Com~inations of organic silver salt oxidizing agents are useful. An example of a combination of organic silver salt oxidizing agents is tne combination of the silver salts of ABT with the silver salt of l-methyl-4-imidazoline-2-thione. Other combinations incLude the combination of the silver salt of ABT with silver salts o ni~rogen acids described in Kesearch ~isclosure, Volu.ne l50, ~ctober 1976, Item 15026.
Selection of an optimum organic silver salt oxid-izing agent or combination of organic silver salt oxid-izing agents will depend upon the descriDed ~actors, such as ~he desired image, the particular reducing agent, the particular dye-forming coupler, processing conditions, the particular binder and the like. An especially useful organic silver salt oxidizing agent is the silver salt of ABT.

.~.

1 ~7~3 The organic silver salt oxidizing agent or com-bination of organic silver salt oxidizing agents are use-ful in a range of concentrations in the described record-ing layer. Selection of an optimum concentration of organic silver salt oxidizing agent or combination of organic silver salt oxidizing agents will depend upon the described factors, such as tne desired image, the partic-ular reducing agent, the particular dye-forming coupler, processing conditions and tne like. A typically use~ul concentration of organic silver salt oxidizing agent or combination of organic silver salt oxidizing agents is within the range of aDout ~.l mole to about 2.0 moles of silver salt oxidizing agent per mole of reaucing agent in the recording layer. For example, when the organic silver salt oxidizing agent is the silver salt o~ ABT, a ty~i-cally useful concentration of the organic silver salt oxidizing agent is within tne range of about 0.1 to about 2.0 moles of organic silver salt oxidizing agent per mole of reducing agent in the recording layer.
Preparation of ~he described organic silver salt oxidizing agent is typicalLy not carried out in situ, that is, not in combination with other co~ponents of the recording layer as described. ~ather, the preparation of the oxidizing agent is typically carried out ex situ, that is separate from otner components of the recording layer.
In most instances, the preparation of the organic silver salt oxidizing agent will be separate from the other co~-ponents based on the ease of control of preparation and storage capability.
The term "salt" as used herein, such as in organic silver salt, is intended to include any type of bonding or complexing mechanism which enables the result-ing material to produce desired imaging properties in the described recording layer. In some instances, the exact bonding of the described silver salt with the organic com-pound is not fully understood. Accordingly, the term "salt" is intended to include what are known in the chemi-2g93 cal art as "complexes". Tne term "salt" is intended to include, for example, neutral complexes and non-neutral complexes. The term is also intended to include compounds which contain any form of bonding which enables the desired image-forming combination to provide tne desired image.
Many reducing agents which, i~ their oxidized form, form a dye with tne described dye-forming coupler are useful in the recording element according to the invention. The reducing agent is typically an organic silver halide color developing agent. Combinations of reducing agents are useful. It is important that tne reducing agent produces sn oxidized ~orm upon reaction with tne organic silver salt oxidizing agent which reacts at processing temperature with the described dye-forming coupler to produce a desired dye. ~:specially useful reducing agents are primary aromatic amines including, for example, paraphenylenediamines. ~xamples of useful reduc-ing agents which are primary aroma~ic amines inclule 4-amino-N,N-dimethylaniline; 4-amino-N,N-diethylaniline;
4-amino-3-methyl-N,N-diethylaniline (also known as N,N-diethyl-3-methyl-paraphenylenediamine); 4-amino-N-ethyl-N-~-hydroxyethylaniline; 4-amino-3-methyl-N-ethyl-N-~-hydroxyethylaniline; 4-amino-3-methoxy-N-ethyl-N-~-hydroxyethylaniline; 4-amino-N-butyl-N-gamma-sulfobutylaniline; 4-amino-3-methyl-N-ethyl-N-~-sulfo-ethylaniline; 4-amino-3-~-(methanesulEonamido)ethyl-N,N-diethylaniline; 4-amino-3-methyl-N-ethyl-N-~-(methanesulfonamido)ethylaniline; and 4-amino-3-methyl-N-ethyl-N-~-methoxyethylaniline.
The term "reducing agent" as used hereln inclu~es compounds which are reducing agent precursors in the des-cribed recording layer. That is, those compounas are included which are not reducing agents in the recording layer until a condition occurs such as heating of the recording layer.

~ 172~93 _ ~7 -An especially useful reducing agent is one that consists essentially of a paraphenylenediamine silver halide developing agent that exhibits an E 1/2 value in aqueous solution at pH 10 ~ithin the range of -25 to ~17S
5 millivolts versus SCE. The term 'IE 1/2 value" herein means half wave potential. The term "SCE" herein means saturated calomel electrode. These values are determined by analytical procedures known in the photographic art and described in, for example, the text "The Theory of the 10 Photographic Process", 4th ~dition, ~ees and James, 1977, pages 318-314.
The described reducing agent is useful in a range of concentrations in the described element accor~ing to tne invention. Selection of an optimum concentration of 15 reducing agent or combination of reducing agents will depen~ upon the described ractors including the desired image, tne particular or~anic siiver salt oxidizing agent, the particular dye-forming coupler, processing conditions and tne like. A typically useful concentration of reduc-20 ing agent or combination of reducing agents is within therange of a~out 0.1 to about 5.0 moles of reducing agent per mole of organic silver salt in the recording layer as described. An especially useful concentration of reducing agent is within the range o about 0.2 to about 2 moles of 25 reducing agent per mole of organic silver salt in the recording layer.
The tone of the combined silver image and dye image produced according to tne invention will vary~
depending upon such factors as the silver morphology of 30 the developed silver image, tne covering power of the silver materials, the particular dye-forming coupler, the particular developing agent, processing conditions and ~he like. In recording layers that produce a Drown silver image, the hue of the dye image produced is preferably 35 complimen~ary to the hue of tne silver image. An image hue of the combined dye image and silver image is prefer-ably "neutral"~

I ;l '~2~g3 Tne term "neutral" herein includes hues which occasionally are described in the photographic art as blue-black, gray, purple-black, black and the like.
Whether or not a given image is "neutral" can be readily 5 determined by visual inspection with tne unaided eye.
Procedures for determining whether or not an i~age is ''neutral" are known in tne photographic art, such as described in Research Disclosure, September 1978, Item .
17326.
Silica is generally useful in an image recording layer of a recording element according to the invention.
Silica in the recording layer helps produce increased den-sity in a developed image upon imagewise e~posure and heating the recording layer. A variety of forms of silica 15 are useful. However, colloidal silica is especially use-ful because it has a large surface area. The optimum con-centration of silica in the recording layer will depena upon such tactors as the aesired image, other components in the recoraing layer, processing conditions, layer 20 thickness and the like. The concentration of silica i5 within the range of aDout 1 to about l,000 milligrams per 500 square centimeters of support. The silica is a dis-advantage in preparation of a high resolution trans-parency, because the silica may reduce resolution of the 25 developed image and cause undesired light scattering.
The average particle size and particle slze range of silica in the recording layer will vary. The optimum average particle size and particle size range of silica will depend upon the described factors regarding silica 30 concentration. Typically, ~he average particle size and particle size range of colloidal silica are most useful.
Colloidal silica that is useful includes such commercially available colloidal silica products as "Cab-0-Sil", a trademark of and available from the Cabot Corporation, 35 U.S.A. and "Aerosil", a traaemark of and available from l)FGUSSA, West Germany. It is important that the average particle size and particle size range of the silica or any ~17X893 other equivalent particles not adversely af~ect tne desirea properties of the electrically activated recording element of the invention or the desired image produced upon imagewise exposure and heating of the recording 5 layer. For instance, the silica selected should not decrease sensitivity of the recording layer or produce undesired fogging of the developed image.
The mechanism and properties which cause col-loidal silica to produce increased density in a recording 10 layer according to the invention is not fully understood.
It is believed that the large surface area of colloidal silica contributes to the desired results. In any case, an especially useful embodiment of t~e invention, as des-cribed, is one containing colloidal silica in the record-15 ing layer of a charge-sensitive recording paper according to the invention.
The described element according to the invention comprises various colloids and polymers alone or in com-Dination as vehicles and binding agents. These vehicles 20 and binding agents can be in various layers of the ele-ment, especially in the recording layer. Suitable mater-ials are hydrophobic or hydrophilic~ It is necessary, however, that the vehicle or binder in the element not adversely affect the ch~rge sensitivity or ohmic resistiv-25 ity of the element of the invention. It is also necessarythat the vehicle or binder be compatible with the ~AC
layer according to the invention. Accordingly, the selec-tion of an optimum colloid or polymer, or combination of colloids or polymers, will depend upon such factors as the 30 desired charge sensitivity, desired ohmic resistivity, particular polymer, desired image, particular processing conditions, particular EAC layer and the like. Useful colloids and polymers are transparent or translucent and include both naturally occurring substances such as pro-35 teins, for example, gelatin, gelatin derivatives, cellu-lose derivatives, polysacchariaes, such as de~tran, gum arabic and the like. Synthetic polymers, however, are ~ 17~3 ~o -preferre~ due to their desired charge sensitivity proper-ties and Ohmic resistivity properties. Use~ul polymeric materials for this purpose include polyvinyl compounds, such as poly(vinyl pyrroliaone), acrylamide polymers and 5 dispersed vinyl compounds such as in latex form. Effect-ive polymers include water insoluble polymers of alkyl-acrylates and methacrylates containing minor amounts of acrylic acid, sulfoalkylacrylates or methacrylates and those which have crosslinking sites which facilitate hard-10 ening or curing. Especially useful polymers are nighmolecular weight materials and resins which are compatible with the described components of the element according to the invention. These include, for example, poly(vinyl butyral), cellulose acetate butyrate, poly(methyl methac-15 rylate), poly(vinyl pyrrolidone), ethyl cellulose, poly-styrene, poly~vinyl chloriae), poly(isobutylene), buta-diene-styrene copolymers, vinyl chloride-vinyl acetate copolymers, copolymers of vinyl acetate, vinyl chloride and maleic acid and poly(vinyl alcohol). Combinations of 20 colloids and polymers are also useful depending upon the described factors. Highly preferred binaers include poly-acrylamiae, as well as co~olymers of acrylamiae and other vinyl addition monomers such as copolymers of acrylamide and vinyl imidazole or copolymers oE acrylamide alld 25 ~-methyl acrylamide.
An overcoat layer is useful on the recordin~
layer according to the invention. It is important that the o~ercoat layer not adversely affect the desired charge sensitivity and ohmic resistivity properties of the ele-30 ment according to the invention. Such an overcoat layerreduces fingerprinting and abrasion marks before and after exposure and processing~ The overcoat layer is one or more of the described polymers which are use~ul as binders. These materials must be compatible with other 35 components of the described element according to the invention and must be able to tolerate the processing temperatures which are useful for developing the ~escribed images.

~ 28g3 While it is in most cases unnecessary and unde-sirable, a photosensitive component can be present in the electrically activated recording layer, as aescribe~, if desired. The photosensitive component is any photosensi-5 tive ~letal salt or complex which prodUces developaDlenuclei upon charge exposure according to the invention.
If a photosensitive component is present in the recording layer, an especially useful photosensitive metal salt is photosensitive silver halide due to its desired properties 10 in forming developable nuclei upon cha~r~e exposure, A
typical concentration of photosensitive metal salt is within the range of about 0.0001 to about 10.0 moles of photosensitive metal salt per mole of organic silver salt in the described element according to the invention. For 15 example, a typical concentration range of photosensitive silver halide is within the range of about 0.001 to about 2.0 moles of silver hali~e per mole of organic silver salt in the recording element. A preferred photosensitive silver halide is silver chloride, silver bromide, silver 20 bromoiodide or mixtures thereof. ~or purposes of the invention, silver iodide is also considered to ~e a photo-sensitive silver halide. Very fine grain photographic silver halide is useful, although a range of grain size from ~ine grain to coarse grain photographic silver halide 25 can be included in the recor~ing layer, if desired. The photographic silver halide can be prepared by any of tne procedures known in the photographic art. Such procedures and forms of photographic silver halide are described in, for example, Research Disclosure, December 1978, Item No.
30 17643. The photographic silver halide can be washed or unwashed, can be chemically sensitized by means of chemi-cal sensitization procedures known in the art, can be pro-tected against the production of fog and stabilized against loss of sensitivity during keeping, as described 35 in the above Kesearch Disclosure publication.
If a photosensitive component is present in the described electrically activated recording layer, the des-~ ~2~93 criDed image-forming combination enables the concentration of the photosensitive component to be lower than normally would be expected in a photosensitive' element~ This lower concentration is enabled by the amplification affect of 5 the image-forming combination, as described, ~s well as the formation of developable nuclei according to the invention in addition to tne dye enhancement of tne silver image formed. In some instances the concentration of photosensitive metal salt can ~e sufficiently low that 10 after i~agewise exposure and development of the photo-sensitive metal salt alone, in the absence of other of t~e described component, the developed image is not visible to the unaided eye.
The elements according to the invention contain, 15 if desired, addenda which aid in producing a desired image. These addenda include, for example, development modifiers that function as speed-increasing compounds, hardeners, plasticizers and lubricants, coating aids, brighteners, spectral sensitizing dyes, absor~ing and 20 filter dyes. These addenda are described in, for example, Res_arch Disclosure, December 197~, Item 17643.
While it is in many cases unnecessary and unde-sirable, a post-processing stabilizer or stabilizer yre-cursor to increase post processing stability of the devel-25 oped ima~e is included, if ~esired, ln tne descriDedrecording layer. In ~any cases the recording layer following processing is sufficiently stable to avoid the need for incorporation of a stabilizer or stabilizer pre-cursor in t~e recording layer. However, in the case of

3 recording ~aterials' which contain photosensitive silver halide, it is desirable to include such a stabilizer or post-processing stabilizer precur'sor to provide increased post-processing stability. Many stabilizer or stabilizer precursors are useful in the elements according to the 35 invention. 'rhese stabilizers Or stabilizer precursors are useful alone or in com'bination, if desired. Typically useful stabilizers or stabilizer precursors include, for ~ ~7~3 instance, photolytically active polybrominated organic compounds. Thioethers or blocked azolinethione stabilizer precursors or other organic thione stabilizer precursors known to be useful in photothermographic materials are 5 useful, if desired.
~ nen a stabilizer or stabilizer precursor is present in the recording layer of an element according to the invention, a range of concentrations of stabilizer or sta~ilizer precursor is useful. The optimum concencration 10 of stabilizer or sta~ilizer precursor will depend upon such factors as the particular element, processing condi-tions, particular stabilizer or stabilizer precursor, desired stability of the developed image and the like. A
useful concentration of stabilizer or stabilizer precursor 15 is within the range of a~out 1 to about 10 moles of stab-ilizer or stabilizer precursor per mole of photosensitive component in the element according to the invention.
It is often advantageous to include a heat sensi-tive base-release agent or base precursor in the recording 20 element according to the invention to produce improved and more effective image development. A base-release agent or base precursor herein includes compounds, which upon heat-ing in ths recording layer, pro~uce a more effective reac-tion between the described components of the image-forming ~5 combination and in ad~ition produce improvea reaccion between the oxidized form of the described reducing agent and the dye-forming coupler. Examples of useful ~eat sensitive Dase-release agents or base precursors are aminimi~e base-release a~ents, sucn as described in 30 Research Disclosure, Volume 157, May 1977, Items 15733, 15732, 15776 and 15734; guanidinium compounds, such as guanidinium trichloroacetate; and other compounds which are known in the photothermographic art to release a base moiety upon heating, but do not adversely affect the 35 desired properties of the recording element. Combinations of heat sensitive base-release agents are useful, if desired.

A heat sensitive base-release agent or base pre cursor, or combinations of such compounds, is use~ul in a range of concentrations in the described elements accord-ing to the invention. The optimum concentration of heat 5 sensitive base-release agent or base precursor will depend upon such factors as the desired image, particular dye-forming coupler, particular reducing agent, other compon-ents of the imaging element, processing conditions and the like. A useful concentration of described ~ase-rale~se 10 agent is typically within the range of about 0.25 to 2.5 moles of base-release agent or Dase precursor per mole of reducing agent in the recording layer according to the invention.
The electrically activatable recording element 15 according to the invention advantageously comprises a variety of supports. The term "electrically conductive support" herein includes (a) supports that are electri-cally conductive without the need for separate addenda in the support or on the support to produce the desired 20 degree of electrical conductivity and (b) supports that comprise addenda or separate electrically conductive layers that enable the desired degree o~ electrical con-ductivity. Typical supports include cellulose ester, poly(vinyl acetal), poly(ethylene terephthalate), polycar-25 bonate and polyester film supports an~ related films andresinous materials. Other supports are useful, such as glass, paper, metal and the like which can withstand the processing temperatures described and do not adversely affect the charge-sensitive properties and ohmic resistiv-30 ity WhiCh iS desired. A flexible support is most useful.It is necessary that the various layers according to the invention adhere to the support. A subbing layer to aide adhesion is preferred on the support. Such a subbing layer is, for e%ample, a poly(methyl acrylate-co-vinyli-35 dene chloride-co-itaconic acid) subbing layer.
The recording element according to the invention generally includes an electrically conductive layer posi-tioned between the support and the described polymeric EAC
layer. Tnis is illustrated by electrically conductive layer 55 in Figure 5. The electrically conductive layers, as described, such as layers 62 and 55 in Figure 5, com-5 prise a variety of electrically conducting compounds whichdo not adversely effect the charge sensitivity and ohmic resistivity properties of an element according to the invention. Examples of useful electrically conductive layers include layers comprising an electrically conduc-10 tive chromium composition, such as cermet, and nickel.
In some embodiments, tne photoconauctive lay~r isa self-supporting layer, such as a photoconductor in a suitable binder. In such embodiments an electrically con-ductive layer, such as an electrically conductive nickel 15 or chro~ium composition layer, is coated on tne photoCOn-ductive layer. This is illustrated in, for instance, Figure 3 in the drawings in which electrically conductive layer 28 is on photoconductive layer 30 which is self-supporting. Alternatively, tne photoconductive layer is 20 coated on an electrically conductive support, such as illustrated in Figure 5 of the drawings.
The described layers according to the invention are coated by coating procedures known in the photographic art, including vacuum deposition, sintering, dip coating, 25 airknife coating, curtain coating or extrusion coatîn~, using hoppers known in the photographic art. If desired, two or more layers are coated simultaneously.
The various components of the charge-sensitive materials according to the invention are prepared for 3o coatin~ by mixin~ ~he components with suitable solutions or mixtures including suitable organic solvents ~epenaing on the particular charge-sensitive material and the com-ponents. The components are added ~y means of procedures known in the photographic art.
Useful charge-sensitive elements according to the invention comprise an electrically conductive support having thereon an electrically activatable recording layer ;~ 17~393 which has a thickness within the range of about 1 to about 30 microns, typically within the range of about 2 to about 15 ~icrons. The optimum layer thickness of each of the layers of an element according to the invention will 5 depend upon such factors as the particular ohmic resistiv-ity desired, charge sensitivity, particular components of the layers, desired lmage and the like.
The EAC layer, such as layer 56 illustrated in Figure 5, has a thickness within the range of about 0.02 10 to about 10 microns, such as within the range of about 0.05 to about 5 microns. Tne optimum layer thickness of tne polymeric electrically conductive EAC layer of an ele-ment according to the invention will depend upon such factors as the particular ohmic resistivity desired, 15 charge sensitivity, desired image, the electrically acti-vated r~cording layer and the like.
A "melt-forming compound" is useful in tne recording layer according to the invention to produce an improved developed image. A "melt-forming compound" is 20 especially useful with recording materials containing silver salts of nitrogen acids. The term "melt-forming compound" herein is intended to mean a compound which upon heating to the described processing temperature produces an improved reaction medium, typically a molten medium, 25 wherein the described image-forming combination produces a desired image upon developrnent, The exact nature of the reaction medlum at processing temperature described is not fully understood. It is believed that at the reaction temperature, a meLt occurs which permits the reaction com-30 ponents to better interact. If desired, a melt-forming compound is included with other components of tne recor~-ing layer prior to coating on the support. Examples of useful melt-forming compounds inclu~e succinimide~
dimethyl urea, sulfamide and acetamide.
The optimum concentra~ion of the described com-ponents of the element according to the invention will aepend upon a variety of factors. An especially useful ~ 172~CJ3 recording eleme~t accordin~ to the invention comprises about 1 to about 5 moles of the dye-forming coupler for each 1 to 5 moles of the reducing agent and about 3 to about 20 moles of the organic silver salt oxidizing agent.
The described organic silver salt oxidizing a~ent contains a range of ratios of the organic moiety to the silver ion. The optimum ratio of the organic moiety to silver ion in the organic silver salt oxidizing agent will depend upon such factors as the particular organic moiety, 10 the particular concentration of silver ion desired, processing conditions, the particular dye-forming coupler and the like. The molar ratio of organic moiety to silver as silver ion in the salt is typically within the range of abou~ 0.5:1 to about 3:1.
The image recording layer of the invention has a range of pA~. The pAg is measured ~y means of conven-tional calomel and silver-silver chloride electrodes, con-nected to a commercial digital 2H meter. Tne pAg in a dispersion containing the described components for the 20 recording layer is advantageously within tne ran~e of about 2.5 to about 7.5. The optimum pAg will depend upon the described factors, such as the desired image, proces-sing conditions and the like.
A recording material containing the described 25 organic silver salt oxidizing agent typically has a pH
that is within the range of about 1.5 to about 7Ø An especially useful pH for the described recording layer is within the range of about 2.0 to about 6Ø
The desired resistivity characteristics of a 30 recording material according to tne invention is obtained by separately measuring the current-voltage characteristic of each sample coating at room temperature by means of a mercury contact sample holder to make a mercury contact to the surface of tne costing. To eliminate tne possibility 35 tnat a micro thickness surface air gap might affect the measured resistivity, exposures are made with evaporated metal (typically, bismuth or aluminum) electrode on the surface of a charge sensitive coating to be tested. The resistivity is measured at various ambient temperatures.
The data are measured at a voltage of, for example, 20 volts or 4 x 10~ volts per centimeter, which is within the ohmic response range of the layer to be tested. The resistivity of the charge-sensitive layer will vary widely with temperature. The dielectric strength of the layer will also vary with temperature.
An especially useful embodiment of the inven~ion having the desired characteristics comprises a charge-sensitive recording element, preferably having an ohmic resistivity of at least about 104 ohm-cm, comprising, in sequence: (a) a first electrical conducting layer, (~) a photoconductive layer, (c) an electrically activatable recording layer separated from (b) by an air gap of up to about 20 microns and comprising, in reactive association:
(A) a dye-forming coupler consisting essentially of 2',6'-dihydroxytrifluoroacetanilide, (B) an image-forming com-bination consisting essentially of (i) an organic silver salt oxidizing agent consisting essentialLy of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) a reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethylanillne sulfate, and (C) a poly-acrylamide binder, (d) an EAC layer consisting essentially of a poly(alkyl acryLate-co-vinylidene chloride) on (e) a second electrical conducting layer, such as a cermet layer, on (f) a support, such as a suppor~ containing a subbing layer comprising poly(methyl acrylate-co-vinyli-dene chloride-co-itaconic acid).
3 A variety of energy sources are useful for image-wise exposure of a recording element according to the invention. Selection of an optimum energy source for imagewise exposure will depend upon the described factors, such as the sensitivity of the photoconductor layer, the particular image recording combination in the electrically activatable recording layer, desired i~nage and the like.
Useful energy sources for imagewise exposure include, for example, visible light, X-rays, lasers, electron beams, ultraviolet radiation, infrared radiation and gamma rays.

~9 An especially useful process embodiment of the invention is a dry electrically activated recording . process for producing a dye en~anced silver image in a Charge-sensitive recordin~ element, preferabLy having an 5 ohmic resistivity of at least about 104 ohm-cm, compris-ing, in sequence, a support having thereon (a) a first electrically conductive layer, (b) an organic photoconduc-tive layer, ~c) an electrically activatable recording layer separated from (b) by an air gap of up to 20 microns 10 and comprising (A) a dye-forming coupler consisting essen-tially of a compound selected from the group consisting of 2,6-dihydroxyacetanilide and 2',6'-dihydroxytrifluoro-acetanilide and combinations thereof, (B) an image-forming combination comprising (i) an organic silver salt oxid-15 izing agent consisting essentially of a silver salt of3-amino-5-benzylthio-1,2,4-triazole, with (ii) a reducing agent consisting essentially of 4-amino-2-methoxy-N,N~5-trimethylanilinesulfate, and (iii) a polyacrylamide binder, (d) a polymeric EAC layer according to the inven-20 tion and (e) a second ~lectrically conductive layer; saidprocess comprising che steps: (I) imagewise altering the conductivity of the photoconductive layer in accord with an image (X') to be recorded while simultaneously (I~) applying across the photoconductive layer and recording 25 layer an electrical potential of a magnitude and for a sufficient time to produce a developable latent image in the recording layer corr0spondi.ng to the image (X'); and then (III) heating the recording layer substantially uni-formly at a temperature and for a time sufficient to pro-3O duce a dye enhanced silver image corresponding to image(X') in the recording layer.
An imagewise current flow is produced through the described electrically activated recording layer.
Although a particular technique to produce an imagewise 35 current flow has been described for use in a variety of recording apparatus, the especially useful techniques are those which include use of a photoconductive layer as an 8 9 ::~

image to current converter. If desired, the imagewise current flow is provided by contacting the recording ele-ment with a suitable electrostatically charged means such as an electrostatically charged stencil or scanning the 5 recording element with a be~m of electrons.
Heating the recording element after latent image rormation is carried out by techniques and by m~ans known in the photothermographic art. For example, the heating is csrried out by passing the imagewise exposed recording 10 element over a heated platen or ~hrough heated rolls, by heating the element by means of microwaves, by means of dielectric heating or by means of heated air. A visible image is produced in the described exposed material within a short time, that is within about 1 to about 90 seconds, 15 by the described uniform heating step. An image having a maximum transmission density of at least 1.0 and typically at least 2.2 can be produced according to the invention.
For example, the recording element is uniformly heated to a temperature within tne range of about 100C to about 20 2~0C until a desired image is developed, typically within about 1 to about 90 seconds. Tne imagewise exposed m~cer-ial according to the invention is preferably heatea to a temperature within the ran~e of about 1~0C to about 1~0C. The optimum temperature and time for processing 25 will depend upon such ~actors as the aesired image, the particular recording element, heating means and the like.
The describe~ electrically activated recording process is useEul for producing multiple copies. Accord-ing to this embodiment of tne invention, multiple copies 30 are prepared by a dry electrically activated recording process for producing a dye image and silver image, preferably a dye enhanced silver image, in an electrically activatable recording element comprising the steps of (I) imagewise altering the conductivity of a photoconduc-35 tive layer in accord with an image that is to be recorded;(II) positioning the imagewise altered photoconductive layer from (I) adjacent an electrically activatable recording layer of the recording element, tIII) applying an electrical potential across the photoconductor layer and recording layer of a magnituae and for a time surfi-cient to produce in tne areas of the recording layer 5 corresponding to the imagewise altered portions of tn~
photoconductor layer a charge density within the range of about 10- 5 coulomb/cm2 to about 10- 8 coulomb/cm2, the cnarge density forming in tne areas a developable latent image; then (IV) uniformly heating the recording 10 element a~ a temperature and for a time sufficient to pro-duce a dye image snd silver image, preferably a dye enhanced silver image, in the recording element; followed by (V) positioning the imagewise altered photoconductor layer adjacent a second electrically activatable recording 15 layer, preferably having an ohmic resistivity of at least about 10~ ohm-cm, wherein said photoconductor layer is separated from said second recording layer by an air gap of up to 20 microns; ~VI) applying an electrical potential across the photoconductor layer and the second recording 20 layer of a magnitude and for a sufficient time to produce in tne areas of the image of said photoconductive layer a charge density within the range of about 10- 5 coulomb/cm2 to about 10-~ coulomb/cm2, the charge density forming a developable latent image; and then (VII) 25 uniformly heating tne second recording layer at a tempera-ture and for a time sufficient to pro~uce a developed i~age in the second recording layer.
Wnile the exact mechanism of image formation upon heating is not fully understood, it is believed that the 30 imagewise exposure to charge provides nuclei in the image areas. Such nuclei apparently increase the reaction rate and act as catalysts for the reaction between ~he organic i silver salt oxidizing agent and the reducing agent. It is believed that the nuclei enable a form of amplification 35 which would not otherwise be possible. The organic silver salt oxidizing agent and reducing agent must be in a loca-tion with respect to each other which enables the nuclei ~ l~Z~93 formed to provide the desired cataly~ic efect. Theorganic silver salt oxidizing agent and reducing agent as well as the dye-forming coupler are in reactive associa-tion in the electrically activated recording layer. The 5 term "in reactive association" is intended to mean that t~e nuclei resulting from the imagewise exposure are in a location with respect to the described components wnieh enables desired catalytic activity, desired processing temperature and capa~ility for a more useful dye i~age and 10 silver image.
~ eferring to the drawings, embodiments of the invention are depicted schematically in Figures 1 and 2.
According to the embodiment illustrated in Figures 1 and 2, a charge-sensitive recording layer lO naving a poly-15 meric EAC layer 11 according to the invention is placedupon a grounded electrically conductive backing or support 12. A current is selectively applied to the recording layer 10 by the point of a metal stylus 14 which is raised to a sufficiently high voltage relative to the support 12 20 by a voltage source 16, and brougnt into moving contact with the exposed surface of the recording layer 10 con-taining the described image-forming combination and dye-forming coupler. Upon contacting the recording layer 10 with the stylus 14, a current fLow is produced in the 25 areas, such as area 18, of the recording layer contacted by tne stylus and a developable latent image forms, i.e. a pattern of nuclei sites, in the pattern desired. The Charge density produced Dy the stylus in tne contacted areas of the recording layer need noL De sufficient to 30 produce a visible image in the recording layer 10; how-ever, the charge density must be sufficient to produce a latent image in the recording layer in those areas con-tacted by the stylus. Although a particular technique to produce an imagewise current flow through the recording 35 layer 10 has been described, techniques for producing imagewise current flow generally known in the art of recording may be used and are intended to be encompassed - ~17~3 by the description. The area of the recording layer 10 designated as 13 is intended to be illustrative of an area of nuclei sites formed upon contact of the stylus 14 ~1ith the recording layer 10. Other techniques for pro~ucing a 5 nuclei pattern include, for example, contacting the recording layer lO with an electrostatically charged stencil or scanning the layer 10 with a beam of electrons in an image pattern.
Figure 2 illustrates development of the latent lO ima~e formed in the recording element in Figure 1 by, for example, moving the element from Figure 1 into contact with a neated metal platen ~4. The heat ~rom platen ~4 passes through the support 22 and polymeric ~AC layer 21 accoraing to the invention to tne layer 20 containing tne 15 latent image to 'cause the desired reaction in the latent image area. Tne reaction in the latent image area causes development to produce a visible image 26 consisting essentially of a dye image and silver image, preferably a dye enhanced silver image, in the recording layer 20.
20 Upon development the recording element is removed from the platen 24. No processing solutions or baths are required in this heat development step.
Another illustrative embodiment of the invention is schematically shown in Figures 3 and 4. In this 25 embodiment~ in ~igure 3, the developable sites 40 and 42, that is tne latent image sites, are formed by sandwicl7ing a charge-sensitive recording layer 32 and an image-to-current converter layer 30, preferably a photocot~ductive layer, between a pair o electrically conductive layers ~8 30 and 34. A polymeric EAC layer 33 according to tne inven tion is present between electrically conductive layer 34 and charge-sensitive recording layer 32. Layers 2~ and 34 comprise, if desired, suitable supports for layers 30, 32 and 33 or layers 28 and 34 are on separate suitable sup-35 ports, not shown, such as film supports. A high potentialelectric field, such as at a voltage within the range of about 0.01 to about 6.0 KV, is established across the 28~
- 3~ -photoconductive layer 30 and recording layer 32 by con-necting the conductive layers 28 and 34 by connecting means 35 containing power source 36. The electric field across the layers is controlled by switch 38. The latent 5 image formation at latent image sites 40 and 42 is caused by imagewise exposing the photoconductive layer 30 through the conductor 28 to exposure means 44, typically actinic radiation, preferably X-ray. Tne layer 28 and any support for layer 28 must be sufficiently transparent to the 10 energy 44 to enable the ener~y to pass to a desired degree to photoconductive layer 30. The exposure selectively increases the con~uctivity of tne conductive layer in those regions exposed to actinic radiation. When switcn ~8 is in a closed conaltion, thereby establishing an elec-15 tric field across the layers, an imagewise current flow isproduced through the recording layer 32. The current flow occurs in those regions of the recording layer 32 only in position with the exposed portions of the photoconductive layer 30. An air gap 46 of up to 20 microns is provided 20 between layers 30 and 32. The air gap 46 is, for example, 1 to 1~ microns. ~fter a sufficient chargè density, typi-cally less than 1 millicoulomb per square centimeter, preferably about 1.0 microcoulomb/cm2, has been produced in the current exposed portions of the recording layer 32, 25 switch 38 is opened, thereby disrupting the current flow.
The described ~echnique ~or application of volt--age across the photoconductive and recording layers is illustrative. A variety of techniques known in the recording ar~ are useful and are intended to ~e inc.luded 30 in this descriptioL~. ~or exampLe, a grid control corona discharge means, not shown, such as aescribed in U.S.
Patent 3,370,212, can be substituted for the voltage source and conducting layer 28.
To develop the dye image and silver image in 35 latent image sites 40 and 42, tne recording element con-taining layers 32, 33 and 34 is moved away from the photo-conductive layer. Connecting means 35 is also disconnec-2~93 ted. The recording element illustrated in Figure 4 is then contacted with a heating means, such as a heated platen 52 illustrated in Figure 4. The ~eat from the platen 52 passes through the support 50 and polymeric EAC
5 layer 47 to the layer 48 containing a latent image to pro-duce a visible dye image and silver image 49. The heating is preferably carried out substantially uniformly by merely positioning the recording element in heat transfer relationship with the heated platen 52. After the devel-lO opment of the silver image and the dye image, the record-ing element is removed from tne platen.
An especially useful embodiment of the invention is illustrated in ~igure 5 in t~e drawings. In Figure 5 the charge-sensitive recording arrangement consists of a 15 support 53 having thereon a polymeric subDing layer 54, such as a poly~alkyl acrylate-co-vinylidene chloride-co-itaconic acid) subbing layer, having thereon an electri-cally conductive layer 55, typically consistin~ of a cermet com~3Osition, having thereon a polymeric EAC layer 20 56- The subbing layer 54 helps the conductive layer 55 adhere to the support 53. On the polymeric EAC layer 56 is coated a recording layer 57 containing the image-forming combination and dye-forming coupler. An air gap 59, such as up to 20 microns, is present between overcoat 25 layer 58 on recording layer S7 and a lead monoxi~e photo-conductive layer 60. The layer 60 has a nickel electri-cally conductive layer 62 which is on a transparent film support 64. Developable nuclei are formed in recording layer 57 by imagewise exposure with a suitable radiation 3O source, such as a tungsten light source or X-ray source3 not shown, through step tablet 66. At t~e time of image-wise exposure with the energy source, a high potential electric field, such as at a voltage withln the ran~e of about 0.0l to 6.0 KV, is established across the photocon-35 ductive and image-recording layers by connecting the con-ductive layer 62 and the electrically conductive layer 55 by connecting means 69 through a power source 68. The ~ ~7Z~93 electric field across tne layers is controlled by switch 7~. After the necessary charge density is established, switch 70 is opened, thereby disrupting the current flow.
Imagewise exposure for about 1 second at about 50 foot-candles produces a developable image in recording layer 57. A 0.3 density step wedge is used for imagewise expo-sure purposes if desired. To develop the resulting latent image, layer 57 is disconnected from connecting means 69 and power source 68 and moved away from the photoconduc-tive layer 60. The recording layer 57 is then heated uni-formly by contacting it with a heated metal platen, not shown, until the desired dye image and silver image ~re produced.
The photoconductive layer, such as the layer 60 in Figure 5, can incluae a variety of binders and/~r sen-sitizers ~nown in the electrophotographic art. Useful binders are described in, for example, U.~. Patent 2,3~1,019 of Gerhart and U.S. Patent ~,258,423 of Rust.
~ensitizing compounds useiul in tne photoconductive layer are described in, for example, U.S. Patent 3,978,335 of Gibbons.
In the embodiments illustrated which use an air gap between the photoconductor and image recording layers, the air gap distances are controlled by methods known in the art, such as by the roughness of the surface of the photoconductor layer, as well as the roughness of the sur-face of the image recording layer. The air gap need not be uniform. However, best results are often observed with a uniform air gap. The air gap is for example, up to about 20 microns thick. For example, the distance shown in Figure 3 between photoconauctor layer 30 and recording layer 32 is up to 20 microns, as illustrated by air gap 46.
The resistivity of a useful recording layer according to the invention can be effected by air gap effects. Tne number of variables affecting tne resistance of the recording layer can affect the choice of an optimum recor~ing material and imaging means. The resistivity 2 8 ~3 3 values as describe~ herein ~or particular recordin~ ula~er-ials are values measured under optimum temperature condi-tions during exposure.
If desired, the recording element and ima~ing means according to the invention are readily modified to provide a continuous image recording operation. This is carried out by means of desired control circuitry and con-tinuous transport apparatus, not shown.
Tne following examples are included for a further understanding of the invention.

Example 1 This is a comparative example.
This illustrates a negative-working electrically activatable recording element and process for producing a dye image and silver image.
The element and layers for this example are simi-lar to those described in Figure 5, with the exception that the layer 56 did not consist of a polymeric EAC layer accordin~ to tne invention. Layer 56 in this example con-sisted of poly(methyl acrylate-co-vinylidene chloride-co-i~aconic acid).
The following composition (A) was coated on an electrically conductive support. This support consisted of a poly(ethylene terephthalate) film support containing a poly(methyl acrylate-co-vinylidene chloride-co-itaconic acid) subbing (layer S4) layer having thereon a cermet conducting layer.

Composition (A):
silver 3-amino-5-benzylthio-1,2,4- 16.0 ml triazole (1.5:1 ligand to silver ion ratio) (dispersed in 1 percent gelatin)(or~anic silver salt oxidizing agent) 1~2~3 ~38-me~hyl me~captotrtazole ~1% solution 0.~ ml in ethanol) Santifogg~nt~

4-phenyl-3-imino-5-th~ourazole 0.6 ml (1% ~olution in ethanol) (development accelerator) ~urf~ctant (Surf~ct~nt lOG wh~ch 0.2 ml iB a tr~dem~rk of and ~
polyglycidol ether available from the Olin Corporatlon~
U.S.A.) (10% solution in water) 4-amino-methoxy-N,N,5-trimethyl 75 mg ~dl B-aniline ~ulate treduc~ng solved ~gent~ in 1 ml of watex) 2~,6~-dihydroxytri~luoroacet- 128 mg (di~
anil~de (dye-forming ~olved coupler~ in 1 ml of w~er poly(acrylamide-l-vi~yllmidazole) 1~0 ml (90:10 ratio) ~5.6 percent by weight solution in water) (blnder) The composition sft~r mixing wa~ coated at a 12 mil we~ coa~ing thickness to produce ~ recording lAyex (57 ln Figure 53 contalning 100 ~o 120 milligrams of s~lver per g29 cm2 of support~
The layer 60 consi6ted of a 17 micron ~hick coat~
ing of a compos~te type organic photoconductor consi~lng es~entially of a~ ~ggreg~te organic photoconductor a3 des~
cr~bed in U.S. 3,615j414 as the photoconduc~lve compound.
The photoconductor was coated on conductlng lAye~ 62 con-~ 17Z8~3 sisting of copper iodide on a poly(ethylene terephthalate) film support 64 shown in Figure 5. An air gap o up to 20 microns separated the photoconductive layer 60 from recording layer 57. Visible light exposure imagewise was made with simultaneous application of a voltage of posi-tive 4,000 volts to the resulting sandwich shown in Figure 5. The intensity and duration of light exposure were suf~icient to produce a developable latent image in the recording layer 57. A charge exposure of 2.4 micro-coulombs/cm2 was used for forming a latent image in the recording layer 57. This level of charge exposure was necessary to provide a developed image density of 1Ø
The photoconductive layer and the recording layer were separated after imagewise exposure and the recording layer was uniformly heated for 10 seconds at 180C. This produced a silver image and dye image in the exposed areas of the recording layer. A l.0 transmission density image was observed in the area exposed to charge.

E _ ple 2 This is a comparative example.
The element and layers for this example are simi-lar to those described in ~igure 5, with the exception that the layer 56 did not consist of a polymeric E~C layer according to the invention.
A subbed poly(ethylene terephthalate) film sup-port was coated with a layer of cermet. The layer of cermet was then coated with a layer consisting of poly-(methyl acrylate-co-vinylidene chloride-co-itaconic acid) (15:83:02 ratio). This polymer was coated on the cermet layer by means of a solution of the polymer in methyl ethyl ketone (also known as MEK). The resulting layer was permitted to dry and then coated with the following com-position:

~ 1~2~3 silver 3~amino-5-benzylthio- 16 ml 1,2,4-triazole (1.5:1 ligand to silver ion ratio) (dispersed in a solvent consisting of water and ethanol) (organic silver salt oxidizing agent) methylmercaptotriazole (0.5% by weight 0.6 ml by weight solution in ethanol) poly(acrylamide-co-l-vinylimidazole) 0.8 ml (90:10 ratio) (5.6~ by weight solution in water) (binder) 4-amino-me~hoxy-N,N,5-trimethyl 1.0 ml aniline sulfate (75 mg dis-solved in 1 ml of water) ~developing agent) surfactant (Surfactant lOG which is a 0.2 ml paraisononylphenoxypoly-glycidol and a trademark of the O]in Corporation, U.S.A.) (10 percent by weight in water) 2,6--dihydroxytrifluoroacetanilide 1.0 ml (128 mg dissolved in 1 ml of water) (coupler) 4-phenyl-3-imino-5-thiourazole 0.6 ml (0.5~ by weight solution in ethanol) The composition was coated at a 12 mil wet coating thickness. The resulting coating contained 11 to 13 mg of silver per 100 square centimeters of support.

~ :17X~3 The resuLting element was imagewise exposed by means of a grid controlled corona exposing means, such as described in U.S. Patent 3,370,212. The grid potential of the exposing means was at +10~0 vol~s and the cnarge expo-sure was varied between 100 microcoulombs/cm2 and 1,0microcoulombs/cm2. After the element was imagewise exposed as described to pro~uce a latent image, the exposed element was removed from the exposing means and uniformly heated for lO secon~s at 1~0C. A dye ima~e and silver image were developed to produce a l.0 maximum ~ransmission density and a minimum uensicy of U.~0 at a charge exposure of 2.4 microcoulombs/cm2.

Example 3 This is a comparative example.
An electrically activated recording element was prepared as described in Example 2 with the exception that the layer 56 was omitted. The element was imagewise exposed and processed as described in Example 2.
A charge exposure of 100 microcoulombs/cm2 20 was necessary to obtain a maximum transmission image den-sity of 0.1~.

Example 4 This is a comparative example.
An electrically activated recording element was 25 prepared as described in Example 2 with the exception that tne layer 56 descriDed in Example 2 was replaced wi~h a polycarbonate layer (LE~AN 145, which is a trademark of General Electric Co., U.S.A.). The element was image~ise exposed and processed as described in Example 2.
A charge exposure of 10 microcoulombs/cm2 was necessary to produce a maximum transmission image density of 0.15.

` ~ 17~893 Example 5 Thi 8 i 8 a comp~ratlve example .
- An electrically ac~ivated recording elem~nt wa3 prep~red ~s descxibed in Example Z with the exceptlon that the layer 56 described in Example 2 wa6 replaced with a poly(vinyl butyral) layer (BUTVAR B-76, a tradem~rk of ~he Monsahto Co., U.S.A.). The element was lmagewise exposed and processed a8 described in Example 2.
A charge exposure of 10 microcoulombs/cm2 was necessary to obt~in a maximum tran~mlssion fmage density o~ 0.15.

Example 6 This is a comparat~ve example.
An electrically actiYated recording element wa~
prepared a6 descrlbed in Example 2 with the exception hat the layer 56 described in Example 2 was replaced with a poly(methyl methacrylate~ layer. The element w~ im~ge-wi~e expo~ed and processed a8 described in Example 2.
A charge expoæure of 10 microcoulombs/cm2 wa~
nece~sery to obtain a maximum tranemisæion image density of 0~15.

Example 7 Th~s is a compar~ti~e example.
An electrlc~lly Activated recording element wa~
prepared aG described in Example 2 with the exception that the layer 56 described in Example 2 was xeplaced with a poly(styrene) layex (STYRON, whlch i~ a trademark of Dow Chem~cal Co., U.S.A.~. The element Wa8 imag2wise expo~ed and processed as described in Example 2.
A charge expo~ure of 10 microcoulomb~/cm2 wa~
necessary to obtain a visible im~ge, th~ arl image h~ving a maximum transmisslon densit~ of 0.05.

3. ~ 3 ~xample 8 This is a comparative example.
An electrically activated recording element was prepared as described in Example 2 with the exception that the layer 56 described in Examp~e 2 was replaced with a poly(chloromethyl styrene) layer. The element was image-wise exposed and processed as described in Example 2.
A charge exposure of 10 microcoulombs/cm2 was necessary to obtain a visible image, ~hat is an image 10 having a maximum transmission density of 0.05.

F!X ample 9 This is a comparative example.
An electrically activated recording element was prepared as described in Example 2 with the exception that the layer 56 described in Fxamp~e 2 was replaced with a poly(vinyl chloride) layer. The element was imagewise exposed and processed as described in Example 2.
A charge exposure of 10 microcoulombs/cm2 was necessary to obtain a visible image, that is an image 20 having a maximum transmission density of 0.05.

Example 10 This is a comparative example.
Tnis illustrates use of a copolymer of N-Lso-propylacrylamide and vinylidene chlocide as an EAC layer.
An electricalLy activa~ed recording element was prepared as described in Example 1 with the exception that the layer 56 (EAC layer) consisted of a poly(N,-isopropyl-acrylamide-co-vinylidene chloride~. The element was imagewise exposed and thermally processed as described in 30 Example 1 to produce an image having a 0.1 density for a charge exposure of 1.5 microcoulombs/cm2.

~ 172~3 Exam~le 11 This is a comparative example.
This illustrates use of a copolymer of N-[2-(2-methyl-4-oxopentyl)]-acrylamide and vinylidene chloride as an EAC layer.
An electrically activated recording element was prepared as described in Example 1 with tne exception that layer S6 (EAC layer) consisted of poly(N-~2-(2-methyl-4-oxopentyl)]-acrylamide-co-vinylidene chloride). Tne ele-ment was imagewlse exposed and thermally processed as des-cribed in Example 1 to produce an image having 0.1 density at an exposure of 0.3 microcoulombs/cm2.

Example 12 This example illustrates the invention.
An electrically activated recording element was prepared as described in Example 2 with the exception that the layer 56 described in Example 2 was a poly(methyl acrylate-co-vinylidene chloride) (20:80 weight ratio) EAC
layer. This layer was coated on the cermet layer at 1.33 ml per 929 cm2 of support from a l.S percent by weight solution of the polymer in methyl ethyl ketone.
A charge exposure of 1.0 microcoulomb/cm2 was necessary to produce a developed image having a maximum transmission density of 1Ø
This illustrates that an element according to the invention requires significantly less charge exposure to obtain a developed image having a desired maximum den-sity than the elements described in Examples 1 through 9.
The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the inven-tion.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In an electrically activatable recording element comprising an electrically conductive support having thereon, in sequence:
(a) a polymeric electrically active conductive layer, (b) an electrically activatable recording layer com-prising:
(A) a dye-forming coupler, and (B) an oxidation-reduction combination com-prising:
(i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, (c) a photoconductive layer separated from (b) by an air gap of up to 20 microns, and d) an electrically conductive layer, the improvement wherein the polymeric electrically active conductive layer comprises a vinyl addition polymer com-prising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl contain-ing 6 to 10 carbon atoms, or:

wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, each X is bromine or chlorine; n represents 15 to 50 weight percent, and p represents 50 to 85 weight percent of said vinyl addition polymer.

2. An electrically activatable recording ele-ment as in Claim 1 wherein said vinyl addition polymer comprises recurring units represented by the structure:

wherein R6 is hydrogen or methyl; R7 is:

X is bromine or chlorine; n represents 15 to 50 weight percent of said vinyl addition polymer and p represents 50 to 85 weight percent of said vinyl addition polymer.

3. An electrically activatable recording ele-ment as in Claim 1 wherein said vinyl addition polymer consists essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units to about 80 weight percent vinyli-dene chloride units.

4. An electrically activatable recording ele-ment as in Claim 1 wherein said polymeric electrically active conductive layer is about 0.02 to about 10 microns thick.

5. An electrically activatable recording ele-ment as in Claim 1 wherein said 1,2,4-mercaptotriazole derivative is represented by the structure:

wherein Y is aryl containing 6 to 12 carbon atoms; m is 0 to 2; and Z is hydrogen, hydroxyl, or amine.

6. An electrically activatable recording ele-ment as in Claim 1 wherein said electrically conductive support comprises a poly(ethylene terephthalate) film having thereon, in sequence, a subbing layer and an elec-trically conductive cermet layer.

7. An electrically activatable recording ele-ment as in Claim 1 wherein said electrically activatable recording layer also comprises an electrically conductive polymeric binder.

8. An electrically activatable recording ele-ment as in Claim 1 wherein said electrically activatable recording layer also comprises an electrically conductive binder consisting essientially of a poly(acrylamide).

9, In an electrically activatable recording ele-ment comprising a poly(ethylene terephthalate) film sup-port having thereon a subbing layer comprising poly(methyl acrylate-co-vinylidene chloride-co-itaconic acid) and having on the subbing layer an electrically conductive cermet layer and having on said cermet layer, in sequence:
(a) a polymeric electrically active conductive layer, (b) an electrically activatable recording layer com-prising, in an electrically conductive polyacryl-amide binder, (A) a dye-forming coupler consisting essentially of a compound selected from the group con-sisting of 2,6-dihydroxyacetanilide and 2',6'-dihydroxytrifluoroacetanillde and com-binations thereof, and (B) an oxidation-reduction combination consist-ing essentially of (1) an organic silver salt oxidizing agent consisting essentially of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) a reducing agent consisting essentislly of 4-amino-2-methoxy-N,N,5-trimethyl aniline sulfate, (c) a photoconductive layer separated from (b) by an sir gap of up to 20 microns, and (d) an electrically conductive layers the improvement wherein the polymeric electrically activated con-ductive layer consists essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units to about 80 weight percent vinylidene chloride units.

10. In an electrically activatable recording element comprising an electrically conductive support having thereon, in sequence:
(a) a polymeric electrically active conductive layer, (b) an electrically activated recording layer com-prising (A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriszole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, the improvement wherein the polymeric electrically active conductive layer consists essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl contain-ing 6 to 10 carbon atoms, or:
wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, X is bromine or chlorine; n represents 15 to 50 weight percents and p represents 50 to 85 weight percent of said vinyl addition polymer.

11. An electrically activatable recording ele-ment as in Claim 10 wherein said vinyl addition polymer comprises recurring units represented by the structure:
wherein R6 is hydrogen or methyl; R7 is:

X is bromine or chlorine; n represents 15 to 50 weight percent of said vinyl addition polymer and p represents 50 to 85 weight percent of said vinyl addition polymer.

12. An electrically activatable recording ele-ment as in Claim 10 wherein said vinyl addition polymer consists essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units to about 80 weight percent vinyli-dene chloride units.

13. An electrically activatable recording ele-ment as in Claim 10 wherein said 1,2,4-mercaptotriazole derivative is represented by the structure:

wherein Y is aryl containing 6 to 12 carbon atoms; m is 0 to 2; and Z is hydrogen, hydroxyl, or amine.

14. In an electrically activatable recording element comprising a poly(ethylene terephthalate) film support having thereon a subbing layer comprising poly-(methyl acrylate-co-vinylidene chloride-co-itaconic acid) and having on the subbing layer an electrically conductive cermet layer and having on the cermet layer, in sequence:
(a) a polymeric electrically active conductive layer, (b) an electrically activated recording layer com-prising, in an electrically conductive polyacryl-amide binder, (A) a dye-forming coupler consisting essentially of a compound selected from the group con-sisting of 2,6-dihydroxyacetanilide and 2',6'-dihydroxytrifluoroacetanilide and com-binations thereof, and (B) an oxidation-reduction combination consist-ing essentially of (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) a reducing agent consisting essentially of 4-amino-2-methoxy-N,N,5-trimethyl aniline sulfate, the improvement wherein the polymeric electrically active conductive layer consists essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units and about 80 weight percent vinylidene chloride units.

15. A dry, electrically activatable recording process for producing a dye enhanced silver image in an electrically activatable recording element comprising an electrically conductive support having thereon, in sequence:
(a) a polymeric electrically active conductive layer consisting essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl containing 6 to 10 carbon atoms, or wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, R4 and R5 are individually selected from hydrogen and alkyl containing 1 to 4 carbon atoms; X is bromine or chlorine; n represents 15 to 50 weight percent and p represents 50 to 85 weight percent of said vinyl addition polymer;
(b) an electrically activatable recording layer com-prising (A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, said process comprising the steps of:
(I) applying an electrical potential imagewise to said recording element of a magnitude and for a time sufficient to produce a latent image in the image-forming combination; and (II) heating said recording element substantially uniformly at a temperature and for a time sufficient to develop a dye enhanced silver image in said recording layer.

16. A dry, electrically activatable recording process for producing a dye enhanced silver image in an electrically activatable recording element comprising, in sequence:

(a) an electrically conductive layer, (b) a photoconductive layer, (c) an electrically activatable recording layer sep-arated from (b) by an air gap of up to 20 microns and comprising, in an electrically conductive binder, in reactive association:
(A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye forming coupler, (d) a polymeric electrically active conductive layer consisting essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl containing 6 to 10 carbon atoms, or wherein R3 is alkyl containing 1 to 4 carbon atoms; X is bromine or chlorine; n represents 15 to 50 weight percent and p represents 50 to 85 weight percent of said vinyl addition polymer;
(e) an electrically conductive support;
said process comprising the steps of:

(I) imagewise altering the conductivity of said photoconductive layer in accord with an image to be recorded;
(II) applying an electrical potential across said photoconductive layer and said record-ing layer of a magnitude and for a time sufficient to produce a latent image in said recording layer corresponding to the image to be recorded; and, (III) heating said recording layer substantially uniformly at a temperature and for a time sufficient to produce a dye enhanced silver image in said recording layer.

17. A process as in Claim 16 wherein said recording layer is heated in (III) to a temperature within the range of about 100°C to about 180°C until a dye enhanced silver image is produced in said recording layer.

18. A dry, electrically activatable recording process for producing a dye enhanced silver image in an electrically activatable recording element comprising, in sequence:
(a) a first transparent support having thereon (b) a first electrically conductive layer, and (c) a photoconductive layer, having thereover (d) an electrically activatable recording layer sep-arated from (c) by an air gap of up to 20 microns, and comprising, in an electrically con-ductive polyacrylamide binder, (A) a dye-forming coupler consisting essen-tially of a compound selected from the group consisting of 2,6-dihydroxyacet-anilide and 2',6'-dihydroxytrifluoroacet-anilide and combinations thereof, (B) an oxidation-reduction combination compris-ing (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of 3-amino-5-benzylthio-1,2,4-triazole, with (ii) a reducing agent consisting essen-tially of 4-amino-2-methoxy-N,N,5-tri-methyl aniline sulfate, (e) a polymeric electrically active conductive layer consisting essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units to about 80 weight percent vinylidene chloride units, (f) an electrically conductive cermet layer, and (g) a second support, said process comprising the steps of:
(I) imagewise altering the conductivity of said photoconductive layer in accord with an image to be recorded;
(II) applying an electrical potential across said photoconductive layer and recording layer of a magnitude and for a time suffi-cient to produce a latent image in said recording layer corresponding to said image to be recorded; and, (III) heating said recording layer substantially uniformly at a temperature and for a time sufficient to produce a dye enhanced silver image in said recording layer.

19. A process as in Claim 18 wherein said recording layer is heated in (III) to a temperature within the range of about 100°C to about 180°C until a dye enhanced silver image is produced in said recording layer.

20. A dry, electrically activatable recording process for producing a dye enhanced silver image in an electrically activatable recording element comprising the steps of:

(I) imagewise altering the conductivity of a photo-conductive layer in accord with an image to be recorded;
(II) positioning the imagewise altered photoconductive layer from (I) within 20 microns adjacent an electrically activated recording layer of said electrically activated recording element, said element comprising an electrically conductive support having thereon, in sequence:
(a) a polymeric electrically active conductive layer consisting essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl containing 6 to 10 carbon atoms, or wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, X
is bromine or chlorine; n represents 15 to 50 weight percent, and p represents 50 to 85 weight percent of said vinyl addition polymer; and (b) said electrically activatable recording layer comprising (A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxid-izing agent consisting essen-tially of a silver salt of a 1,2,4-mercaptotriazole deriv-ative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, (III) applying an electrical potential across said photoconductive layer and recording layer of a magnitude and for a sufficient time to produce in the areas of said recording layer corres-ponding to the imagewise altered portions of said photoconductive layer a charge density within the range of about 10-5 coulomb/cm2 to about 10-8 coulomb/cm2, said charge den-sity forming in said areas a latent image; and, (IV) uniformly heating the recording element at a temperature and for a time sufficient to produce a dye enhanced silver image in said recording element.

21. A dry, electrically activatable recording process as in Claim 20 also comprising the steps:
(V) positioning said imagewise altered photo-conductive layer within 20 microns adjacent a second electrically activated recording layer;
(VI) applying an electrical potential across said photoconductive layer and said second recording layer of a magnitude and for a sufficient time to produce in the imagewise altered portions of said photoconductive layer a charge density within the range of about 10-5 coulomb/cm2 to about 10-8 coulomb/cm2, said charge density forming a latent image; and, (VII) uniformly heating said second recording layer at a temperature and for a time sufficient to produce a developed image in said second recording layer.

22. A dry, electrically activatable recording process for producing a dye enhanced silver image in an electrically activated recording element comprising on an electrically conductive support, in sequence:
(a) a polymeric electrically active conductive layer consisting essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl containing 6 to 10 carbon atoms, or wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, X
is bromine or chlorine; n represents 15 to 50 weight percent, and p represents 50 to 85 weight percent of said vinyl addition polymer; and (b) an electrically activatable recording layer com-prising (A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, said process comprising the steps of:
(I) positioning said recording element in face-to-face relationship with a photoconductive element wherein said recording element is separated from said photoconductive element by an air gap of up to 20 microns;
(II) exposing said photoconductive element to an imagewise pattern of actinic radiation while simultaneously applying an electrical potential having a field strength of at least about 1 x 103 volts/cm across said photoconductive ele-ment and said recording element for a sufficient time to provide a latent image in the areas of said recording element corresponding to the exposed areas of said photoconductive element;
and (III) substantially uniformly heating the recording element at a temperature and for a time suffi-cient to produce a dye enhanced silver image in said recording element.

23. A process as in Claim 22 wherein said recording element in (III) is heated to a temperature within the range of about 100°C to about 180°C until a dye enhanced silver image is produced.

24. A process as in Claim 22 wherein said photo-conductive element is X-ray sensitive and the conductivity of said element is imagewise altered by exposing said photoconductive element to x-ray radiation in accord with an image to be recorded.

25. A process as in Claim 22 wherein said vinyl addition polymer consists essentially of poly(methyl acrylate-co-vinylidene chloride) having a weight ratio of about 20 weight percent methyl acrylate units to about 80 weight percent vinylidene chloride units.

26. A dry, electrically artivatable recording process for producing a dye enhanced silver image in an electrically activatable recording element comprising an electrically conductive support having thereon, in sequence:
(a) a polymeric electrically active conductive layer consisting essentially of a vinyl addition polymer comprising recurring units represented by the structure:

wherein R1 is hydrogen or methyl; R2 is aryl containing 6 to 10 carbon atoms, or wherein R3 is alkyl containing 1 to 20 carbon atoms or aryl containing 6 to 10 carbon atoms, X
is bromine or chlorine; n represents 15 to 50 weight percent, and p represents 50 to 85 weight percent of said vinyl addition polymer; and (b) an electrically activatable recording layer com-prising (A) a dye-forming coupler, and (B) an oxidation-reduction combination comprising (i) an organic silver salt oxidizing agent consisting essentially of a silver salt of a 1,2,4-mercaptotriazole derivative with (ii) a reducing agent which, in its oxidized form, forms a dye with said dye-forming coupler, said process comprising the steps of:
(I) positioning said recording element on an elec-trically conductive backing member;
(II) modulating a corona ion current flow to the recording element by an electrostatic field established imagewise between an image grid com-prising an electroconductive core sequentially connectable to sources of different potential relative to said backing member and covered with a coating of a photoconductive insulating mater-ial and a control grid that is electrically con-ductive and sequentially connectable to sources of different potential relative to said backing member, said current flow being of a magnitude sufficient to produce a charge density within the range of about 10- 5 to about 10-8 coulomb/cm2 imagewise in said recording ele-ment, which charge density forms a latent image in said electrically activated recording layer;
and, (III) substantially uniformly heating said recording element at a temperature and for a sufficient time to produce a dye enhanced silver image in said recording element.