US3748128A - Process in which heterocyclic n alkoxides and acyloxides exhibit an imagewise change in triboelectric charging properties - Google Patents

Abstract

VISIBLE IMAGES CORRESPONDING TO LATENT ELECTROSTATIC CHARGE IMAGES ARE PRODUCED ON ENERORESPONSIVE LAYER, I.E, RESPONSIVE TO VARIOUS FORMS OF ENERGY SUCH AS ELECTROMAGNETIC RADIATION, HEAT, PRESSURE, VIBRATION (E.G. FROM EXPOSURE TO SOUND WAVES), HAVING INCORPORATED THEREIN AN ENERGY-SENSITIVE HETEROCYCLIC ALKOXIDE OR HETEROCYCLIC ACYLOXIDE MATERIAL WHICH EXHIBITS A CHANGE IN TRIBOELECTRIC SERIES POSITION UPON IMPINGEMENT BY ACTIVATING ENERGY, BY MEANS OF AN ENEROGRAPHIC PROCESS WHICH COMPRISES (A) IMAGEWISE EXPOSING THE ENERORESPONSIVE LAYER TO ENERGY CAPABLE OF PROVIDING AN IMAGEWISE CHANGE IN TRIBOELECTRIC SERIES POSITION, (B) DIFFERENTIALLY TRIBOELECTRICALLY CHARGING THE SURFACE OF THE EXPOSED ENERORESPONSIVE LAYER IMAGEWISE TO FORM AN ELECTROSTATIC CHARGE PATTERN THEREON AND (C) DEVELOPING THE ELECTROSTATIC CHARGE PATTERN BY CONTACTING THE CHARGED SURFACE WITH A DEVELOPER COMPOSITION CONTAINING ELECTROSTATICALLY ATTRACTABLE TONER PARTICLES, TO FORM A PATTERN OF THE TONER PARTICLES ON THE CHARGED SURFACE CORRESPONDING TO THE NON-EXPOSED OR THE EXPOSED REGIONS.

Description

United States Patent Office 3,748,128 Patented July 24, 1973 US. Cl. 961.4 34 Claims ABSTRACT OF THE DISCLOSURE Visible images corresponding to latent electrostatic charge images are produced on eneroresponsive layer, i.e., responsive to various forms of energy such as electromagnetic radiation, heat, pressure, vibration (e.g. from exposure to sound waves), having incorporated therein an energy-sensitive heterocyclic alkoxide or heterocyclic acyloxide material which exhibits a change in triboelectric series position upon impingement by activating energy, by means of an enerographic process which comprises (a) imagewise exposing the eneroresponsive layer to energy capable of providing an imagewise change in triboelectric series position, (b) difierentially triboelectrically charging the surface of the exposed eneroresponsive layer imagewise to form an electrostatic charge pattern thereon and developing the electrostatic charge pattern by contacting the charged surface with a developer composition containing electrostatically attractable toner particles, to form a pattern of the toner particles on the charged surface corresponding to the non-exposed or the exposed regions.

This application is a continuation-in-part of copending application Ser. No. 51,349, filed June 30, 1970, now abandoned.

This invention relates to the electroenerographic production of images and particularly to the triboelectric production of electrostatic charge images and visible images corresponding to the electrostatic charge images.

The production of electrostatic charge images is well known. Typically, such images are produced by methods of electrophotography on elements utilizing a photoconductive, electrically-insulating layer superposed on and contiguous to an electrically-conducting support member. The photoconductive layer is first uniformly electrically charged, conventionally by a corona discharge apparatus, then imagewise exposed to light or other activating electromagnetic radiation which selectively dissipates the charge in illuminated areas through the conducting support or layer, leaving an unexposed imagewise electrostatic charge pattern on the photoconductive layer. This electrostatic charge pattern, also conventionally termed an electrostatic latent image, can be developed or intensified according to well-known techniques of dry powder or I liquid electrophotographic development by depositing charge electrostatically attracta'ble toner particles having a polarity opposite to that of the electrostatic charge pattern to be intensified.

With known electrostatic image-forming processes and using conventional photoconductive species and corona charging methods, there are certain disadvantages inherent in the image-forming operation. Generally, a high voltage power supply is required to charge the corona apparatus to the point wherein an adequate voltage potential can be impressed on the photoconductive layer. Due to the significant voltages involved, such apparatus olfers a potentially dangerous electrical shock hazard. Additionally, the corona discharge and power supply apparatus can be expensive. Conventional apparatus utilized in the mechanized, imagewise exposure of photoconductive species often requires an intricate traveling optical system to secure the sharp formation of an exposure pattern either from a traveling original to be copied or onto a traveling or rotating photoconductive element. Upon development, the image usually produced in electrophotographic image-forming processes is a boundary image (fringe development) wherein toner is deposited only at the edges of the charged portion of the photoconductvie element. The efifect of this phenomenon is to render the uniform development of solid areas exceedingly difficult or even impossible without additional specialized apparatus. Moreover, the latent electrostatic image formed on a photoconductive sheet is not generally a persistent charge image, and if the subsequent formation of identical copies is desired, each copy typically requires a recharging of the photoconductive element and a re-exposure of the charged surface to produce a latent electrostatic image prior to the toning step to prepare a visible image. Conventional electrophotographic systems are also positive working and form toner images corresponding to unexposed regions of the photoconductive surface. Negativeworking systems are known, but these typically require additional specialized apparatus such as development electrodes and the like, and can involve delicate electrical calibration and adjustment to ensure negative image forming operation.

Accordingly, it is an object of the present invention to provide a novel electrophotographic image-forming process wherein high voltage corona discharge apparatus is not required to provide an electrostatic latent image.

Another object of this invention is to provide a new electroenerographic image-forming process utilizing ttiboelectric charging means.

Still another object of the present invention is to pro vide a new electroenerographic image-forming process wherein the electrostatic latent image or charge pattern which is formed is a persistent image from which subsequent identical copies can be prepared without the necessity for re-exposure or re-charging.

Still another object of the present invention is to provide a novel electroenerographic image-forming process wherein, from an original to be copied, a uniformly solid area developed positive or negative image can be prepared without additional, specialized apparatus.

Still an additional object of the present invention is to provide a new image-forming process wherein graphic images are prepared by electroenerographic means on an enerographic layer or element which includes an electrica-lly insulating surface upon which the graphic images are formed.

'Still another object of this invention is to provide a new photographic image-forming process wherein photographic images are prepared by electrophotographic means on a photographic layer or element having a high photographic speed.

These and other objects of the present invention will become increasingly apparent from a reading of the following specification and appended claims.

The objects of this invention are accomplished with an enerographic image-forming process for the preparation of images by electroenerographic means on the surface of an eneroresponsive layer comprising an energysensitive, enerotriboelectrically alterable material selected from either a heterocyclic alkoxide or a heterocyclic acyloxide material which exhibits a change in triboelectric series position upon exposure to activating energy, which process comprises:

(a) Imagewise exposing the eneroresponsive layer to energy capable of effecting an imagewise change in triboelectric series position within the exposed regions of the energy-sensitive material;

(b) Ditferentially triboelectrically charging the surface of the exposed layer imagewise to form an electrostatic charge pattern (latent electrostatic image) thereon; and

Developing the electrostatic charge pattern by contacting the charged surface with a developer composition containing electrostatically attractable toner particles to form a pattern of the toner particles on the charged surface corresponding to either the non-exposed or the exposed regions.

The terms, energy-sensitive, eneroresponsive and others employing the prefix enero-, as used herein, refer broadly to a sensitivity of a responsiveness to a wide range of energy forms such as (l) electromagnetic radiation including ultraviolet, visible and infrared light, X-rays, gamma rays, electron beams, laser beams, etc., including other wavelengths of electromagnetic radiation suitable to initiate triboelectrical alteration of those sensitive materials, (2) heat derived from various sources such as infrared radiation, (3) energy produced by mechanical means such as that produced by the local application of pressure, (4) other energy forms like sound waves, etc.

When the energy-sensitive compounds of this invention are exposed to any of the various forms of energy enumerated above, the pursuant alteration is thought to be a fragmentation of the compound molecule. It is theorized that the resultant disparity in triboelectrical properties between the compound molecule and one or more components of the fragmentation promotes the formation of images according to the process described herein. The particular route of the fragmentation reaction is somewhat dependent upon the structure of the original compound. However, based upon observations, it is believed that the route followed when a dye useful in the process of this invention (such as the one given below) is exposed to a form of energy (such as light) is the following:

1 I /s N OH=CHCH=C (ii-CH1 N additional fragments In this example, a chemical alteration is apparently effected by a heterolytic cleavage of the nitrogen-oxygen (N-O) bond to produce an RO+ ion and a dye base which may fragment even further. Eneroresponsive compounds useful herein are described in detail in a United States patent application Ser. No. 766,307, filed Oct. 9, 1968, and entitled, Energy-Sensitive Systems, now Pat. No. 3,615,432, issued Oct. 26, 1971.

Of particular relevance to the process of this invention is the previously undiscovered enerotriboelectrical alterability of these compounds. In discussing the enerographic process of this invention, it is noted that the various forms of activating energy are interchangeable and additive and that one form of energy can be combined with or substituted for another without changing the basic process.

more extensive than photoenergy is useful in effecting tri-' boelectrical alteration of the energy-sensitive compounds disclosed herein.

After exposing the eneroresponsive layer to activating energy, the exposed layer is diiferentially triboelectrically charged in an imagewise fashion by rubbing the surface of the layer with a material capable of inducing an electrostatic charge pattern onto either the exposed regions exclusively, the unexposed regions exclusively, or the exposed and non-exposed regions, simultaneously, but differentiated in either polarity, magnitude of electrical potential (volts) or both between exposed and non-exposed regions. The designation electrostatic charge pattern, or latent electrostatic image as it is also conventionally designated, defines an imagewise electrostatic charge pattern which is typically invisible to detection by the human eye, but which can be intensified or developed to provide a corresponding visible image by suitable development techniques. The electrostatic charge pattern is conveniently developed to yield a visible image by contact with a developer composition including electrostatically-attractable toner particles having a polarity opposite to that of the electrostatic charge pattern intended for development. The toner particles adhere to the oppositely charged electrostatic charge pattern to define a corresponding visible im age. Either the electrostatic latent image or the visible image can be transferred, if desired, according to techniques such as those which are described herein, and the ultimate visible image is typically stabilized or fixed by such means as heat or solvent action to provide a durable reproduction of the exposed or unexposed image areas. The visible images produced according to the process of this invention are advantageously solid area developed, providing substantially uniform visual image density over expansive, solid image areas, as contradistinguished from line copy.

The enerograp'hic layers which are used in carrying out the photographic image-forming process of this invention include those layers utilizing an enerotriboelectrically alterable heterocyclic alkoxide material as the sensitive component. The designation enerotriboelectrically alterable, as that term is utilized herein, designates the capability of a material, upon exposure to activating energy of a type such as those described herein, to undergo a change in triboelectric series position. Upon energy impingement, the exposed regions of a layer including an enerotriboelectrically alterable material exhibit a triboelectric series position which is different from that of the remain ing, unexposed regions. The mechanism of alteration in triboelectric series position is not completely understood. It has been theorized, however, that a materials molecular orientation, as well as the electronic energy levels and ionization potentials associated with a particular physical or chemical state may afiect its triboelectrification potential or level relative to other materials or other physical or chemical states of the same material.

An attribute of electrochemical potential is expressed in the phenomenon that electrically neutral materials of unlike electrochemical potentials will assume mutual elec-I trostatic charges of opposite polarity on each other when brought into intimate contact, advantageously 'by rubbing. The magnitude of these charges is directly related to the disparity of electrochemical potential existing between the materials. This charging phenomenon is typically designated triboelectric charging or triboelectrification. Additionally, the relative electrochemical potential separation existing between a grouping of materials and the relative triboelectric charging characteristics associated with each relative to one or more additional members of the grouping can be conveniently ascertained by establishing a triboelectric series of the component materials.

A triboelectric series is an artificial reference framework that conveniently positions materials in a relative fashion according to their respective electrochemical potentials. The term triboelectric series, well established in the literature, is often interposed with the designation electrostatic series, and they are frequently used as equivalent expressions, as a Hacks Chemical Dictionary, 4th ed., McGraw- Hill Inc. (1969), page 689. Determining a triboelectric series position of any material relative to another is conveniently accomplished merely by contacting two materials, separating them and detecting the charge polarity of each with an electrometer or other suitable charge recording instrument. The series is then conventionally compiled in descending order from positive to negative such that a material higher in the series charges positively with respect to those lower in the series. Although each member of a triboelectric series is itself electrically neutral, when two members (their surfaces differing in electrochemical potential) are placed in intimate contact, such as by rubbing, an imbalance in surface potential is created at their contact interface, and it is thought that electrons tend to flow from the member having a higher energy level to the member having a lower energy level. This flow produces a net charge transfer as a compensation for the noted surface potential imbalance. When the members are separated or removed from intimate contact, the change transfer that has occurred between such members to equalize their varying surface potentials cannot undergo a reversal which is sufficiently rapid to reattain the original electrical neutrality of each member. The net effect is an electrostatic surface charge being present on each member, the charges being of equal magnitude but of opposite polarity. The member that is higher in the triboelectric series will have a positive polarity charge. Additionally, the magnitude of electrostatic charge potential is directly related to the degree of separation in triboelectric series position, with lower voltages being produced by mutual rubbing or contact of closely positioned members than by like interaction of members having a greater separation of position in the series.

The energy-sensitive, enerotriboelectrically alterable heterocyclic alkoxide materials advantageous herein include those which, after imagewise exposure to activating energy, can be differentially triboelectrically charged, imagewise, to provide an electrostatic latent image capable of intensification to a visible image. For desirable visible image density, enerotriboelectric alteration produced in the radiation-sensitive materials described herein is advantageously suflicient to produce a potential difference of at least about 50 volts between exposed and non-exposed regions of an energy-sensitive layer after triboelectric charging. In calculating a voltage differential, if exposed and non-exposed regions are charged to voltages of posi tive polarity and negative polarity respectively, the potential difference is equal to their sum total, without regard to sign. As such, a polarity of 100 volts positive in exposed regions and of 100 volts negative in non-exposed regions provides a potential difference of 200 volts. Preferably, the electrostatic charge in regions intended for visible image development is at least about 50 electrostatic units (ESU)/ cm.

It is to be emphasized that the electroenerographic process of this invention is not one which relies on either eneroconductivity including photoconductivity, eneroconductive media including photoconductive media or any of the imaging techniques specific to conductography. Rather, the process described herein must operate under electrically insulating conditions or image formation is not obtained. That imagewise conductivity is not obtained is illustrated elsewhere herein by examples wherein either a negative or a positive imagewise reproduction of an imagewise energy exposure is developed merely by altering the polarity of electrostatically attractable toner particles in a developer composition. In effect, a single triboelectric charging step on the surface of an imagewise exposed photographic or other enerographic layer containing an energy-sensitive enerotriboelectrically (e.g., phototriboelectrically) alterable material, as described herein can effect a latent electrostatic image (electrostatic charge pattern) having dual polarity between exposed and non-exposed areas. Accordingly, positively charged toner particles can adhere to the negative polarity latent electrostatic image, and negatively charged toner particles can adhere to the positively charged latent electrostatic image. This same effect can be produced between areas of similar polarity but differing in charge potential. Were electrical conductivity to exist through the enerographic layer, then visible image development would not occur.

Advantageous energy-sensitive, enerotriboelectrically alterable materials which exhibit a change in triboelectric series position upon exposure to an activating energy form include a wide range of heterocyclic alkoxide compounds.

Energy-sensitive heterocyclic alkoxide compounds which are useful in the present process include heterocyclic alkoxide compounds which are energy fragmentable and have one of the following general formulae:

wherein R can be either:

(a) An alkyl radical preferably having 1 to 8 carbon atoms such as methyl, propyl, ethyl, butyl, etc., including a substituted alkyl radical such as sulfoalkyl, e.g., (CH SO and aralkyl, e.g., Ibenzyl or pyridinatooxyalkyl salt, e.g., (CH OY wherein Y is a substituted or unsubstituted pyridinium salt; or

(b) An acyl radical, e.g.,

wherein R is an alkyl radical preferably having 1 to 8 carbon atoms or aryl radical, e.g., methyl, ethyl, propyl, butyl, phenyl, naphthyl, etc.;

Z represents the atoms necessary to complete a 5- to 6-membered heterocyclic nucleus including a substituted heterocyclic nucleus which nucleus can contain at least one additional hetero atom such as oxygen, sulfur, selenium or nitrogen, e.g., a pyridine nucleus, an indole nucleus, a quinoline nucleus, etc.; and X- represents an anion, e.g., chloride, bromide, iodide, perchlorate, sulfamate, thiocyanate, p-toluenesulfonate, methyl sulfate, tetrafluoroborate, etc.

R can be any of the following:

(a) A methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes, e.g., those set forth in Mees and James, The Theory of the Photographic Process, MacMillan, 3rd ed., pp. 198-232; the methine linkage can be substituted or unsubstituted, e.g., CH=, C(CH C(C H CH=CH, CH=CHCH=, etc.;

(b) An alkyl radical preferably containing 1 to 22 carbon atoms and including substituted alkyl radicals;

(0) An aryl radical including a substituted aryl radical such as a phenyl radical, a naphthyl radical, a tolyl radical, etc.;

(d) A hydrogen atom;

(e) An acyl radical having the formula wherein R is hydrogen or an alkyl group preferably having 1 to 22 carbon atoms;

(f) An anilinovinyl radical such as a radical having the formula wherein R is hydrogen or an alkyl radical having from 1 to 22 carbon atoms; or

(g) a styryl radical including substituted styryl radicals e.g.,

Ra CH=CH wherein Q Q Q and Q and Q each represent the non-metallic atoms necessary to complete a sensitizing or desensitizing nucleus containing 5 or 6 atoms in the heterocyclic ring, which nucleus can contain at least one additional hetero atom such as oxygen, sulfur, selenium or nitrogen, i.e., a nucleus of the type used in the production of cyanine dyes, such as the following representative nuclei: a thiazole nucleus, e.g., thiazole, 4-methylthiazole, B-ethylthiazole, 4-phenylthiazole, S-methylthiazole, 5- phenylthiazole, 4,5-dimethylthiazole, 4,5-diphenylthiazole, 4-(2-thienyl)thiazole, 4-chlorobenzothiazole, 4- or S-nitrobenzothiazole, S-chlorobenzothiazole, fi-chlorobenzothiazole, 7-chl0robenz0thiazole, 4-methylbenzothiazo1e,

S-methylbenzothiazole, 6-methylbenzothiazole, 6-nitrobenzothiazole, S-bromobenzothiazole, 6-bromobenzothiazole, S-chloro 6 nitrobenzothiazole, 4-phenylbenzothiazole, 4-methoxybenzothiazole, S-methoxybenzothiazole, 6- methoxybenzothiazole, 5-iodobenzothiazole, 6-iodobenzothiazole, 4ethoxybenzothiazole, S-ethoxybenzothiazole, a tetrahydrobenzothiazole nucleus, 5,6-dimethoxybenzothiazole, 5,6 methylenedioxybenzothiazole, S-hydroxybenzothiazole, 6-hydroxybenzothiazole, a-naphthothiazole, finaphthothiazole, ;8,/3naphthothiazole, 5 methoxy-fi,finaphthothiazole, S-ethoxy-B-naphthothiazole, S-methoxya-naphthothiazole, 7 methoxy 0c naphthothiazole, 4'- methoxythianaphtheno-7',6,4,5-thiazole, nitro group substituted naphthothiazoles, etc.; an oXazole nucleus, e.g., 4-methyloxazole, 4-nitro-oxazole, S-methyloxazole, 4- phenyloxazole, 4,5-diphenyloxazole, 4-ethyloxazole, 4,5- dimethyloxazole, S-phenyloxazole, benzoxazole, S-chlorobenzoxazole, S-rnethylbenzoxazole, 5-phenylbenzoxazole, 5- or 6-nitrobenzoxazole, 5-chloro-6-nitrobenzoxazole, 6- methylbenzoxazole, 5,6-dimethylbenzoxazole, 4,6-dimethylbenzoxazole, S-methoxybenzoxazole, S-ethoxybenzoxazole, S-chlorobenzoxazole, 6-methoxybenzoxazole, S-hydroxybenzoxazole, 6-hydroxybenzoxazole, ot-naphthoxazole, ,B-naphthoxazole, nitro group substituted naphthoxazoles, etc.; a selenazole nucleus, e.g., 4-methylselenazole, 4-nitroselenazole, 4-phenylselenazole, benzoselenazole, 5- chlorobenzoselenazole, 5-methoxybenzoselenazole, 5-hydroxybenzoselenazole, 5- or 6-nitrobenzoselenazole, tetrahydrobenzoselenazole, a-naphthoselenazole, B-naphthoselenazole, nitro group substituted naphthoselenazoles, etc.; a thiazoline nucleus, e.g., thiazoline, 4-rnethylthiazoline, etc.; a pyridine nucleus, e.g., 2-pyridine, S-methyl- Z-pyridine, 4-pyridine, 3-methyl-4-pyridine, nitro group substituted pyridines, etc.; a quinoline nucleus, e.g., 2- quinoline, 3-methyl-2-quinoline, S-ethyl-Z-quinoline, 6- chloro-Z-quinoline, 6-nitro-2-quinoline, 8-chloro-2-quinoline, 6-methoxy-2-quinoline, 8-ethoXy-2-quinoline, 8-hydroxy-Z-quinoline, 4-quinoline, 6-methoxy-4-quinoline, 6- nitro-4-quinoline, 7-methyl-4-quinoline, 8-chloro-4-quinoline, l-isoquinoline, 6-nitro-1-isoquinoline, 3,4-dihydrol-isoquinoline, 3-isoquinoline, etc.; a 3,3-dialkylindolenine nucleus, preferably having a nitro or cyano substituent, e.g., 3,3-dimethyl-5 or 6-nitroindolenine, 3,3-dimethyl-5- or 6-cyanoindolenine, etc.; and, an imidazole nucleus, e.g., imidazole, l-alkylimidazole, 1-alkyl-4-phenylimidazole, 1-a1kyl-4,S-dimethylimidazole, benzimidazole, 1 alkylbenzimidazole, 1-alkyl-5-nitrobenzimidazole, 1-aryl-5,6- dichlorobenzimidazole, 1-alkyl-a-naphthimidazole, l-arylfi-naphthimidazole, 1 alkyl-5-methoxy-fl-naphimidazole, or, an imidazo[4,5-b]quinoxaline nucleus, e.g., l-alkylimidazo[4,5-b1quinoxaline such as 1-ethylimidazo [4,5-b]- quinoxaline, 6 chloro-l-ethylimidazo[4,5-b1quinoxaline, etc., 1-alkenylirnidazo[4,5-b]quinoxaline such as l-allylimidazol [4,5-b] quinoxaline, 6-chlorol-allylimidazo [4, 5- b]quinoxaline, etc., l-arylimidazo[4,5-b]quinoxaline such as 1-phenylimidazo[4,5-b]quinoxaline, 6-chloro1-phenylimidazo[4,5-b]quinoxaline, etc.; a 3,3-dialkyl-3H-pyrrolo- [2,3-b]pyridine nucleus, e.g., 3,3-dimethyl-3H-pyrrolo- [2,3-b1pyridine, 3,3 diethyl-3H-pyrrolo[2,3-b]pyridine, etc.; a thiazo1o[4,5-b]quinoline nucleus; R represents an alkyl group, including substituted alkyl (preferably a lower alkyl containing from 1 to 4 carbon atoms), e.g., methyl, ethyl, propyl, isopropyl, butyl, hexyl, cyclohexyl, decyl, dodecyl, etc., and substituted alkyl groups (preferably a substituted lower alkyl containing from 1 to 4 carbon atoms), such as a hydroxyalkyl group, e.g., 9- hydroxyethyl, w-hydroxybutyl, etc., an alkoxyalkyl group, e.g., B-methoxyethyl, w-butoxybutyl, etc., a carboxyalkyl group, e.g., B-carboxyethyl, w-carboxybutyl, etc., an alkoxy group, e.g., methoxy, ethoxy, etc., a sulfoalkyl group, e.g., 18-sulfoethyl, w-sulfobutyl, etc., a sulfatoalkyl group, e.g., fl-sulfatoethyl, w-sulfatobutyl, etc., an acyloxyalkyl group, e.g., B-acetoxyethyl, -acetoxypropyl, wbutyryloxybuytl, etc., an alkoxycarbonylalkyl group, e.g., fi-methoxycarbonylethyl, w-ethoxycarbonylbutyl, etc., or an aralkyl 18) 1-methoxy-3'-methyl-2-pyridothiazolinocarbocyanine perchlorate 19) 3-ethyl-1-methoxy-4-pyridothiacyanine perchlorate (20) 3 '-ethyl-1-methoxy-4-pyridothiacarbocyanine perchlorate (21 1'-ethoxy-3-ethyl-4,5-benzothia-2'-carbocyanine tetrafluoroborate (22) Z-fi-anilinovinyll-methoxypyridinium p-toluenesulfonate (23 l-ethyl- 1 '-methoxy-4,5-benzothia-4-carbocyanine perchlorate (24) l-methoxy-2-methylpyridinium-p-toluenesulfonate (25 l-methoxy-4-methylpyridinium p-toluenesulfonate 26) anhydro-2-methyl-1-(3-sulfopropoxy)pyridinium hydroxide (27) l-ethoxy-Z-methylpyridinium tetrafiuoroborate 28) 1-benzyloxy-Z-methylpyridinium bromide (29) l-ethoxy-2-methylquinolinium tetrafluoroborate (3 1,1'-ethylenedioxybispyridinium dibromide (3 l l,1'-trimethylenedioxybispyridinium dibromide (32) l, l '-tetramethylenedioxybis(2-methylpyridinium) dibromide (3 3) 1,1-tetramethylenedioxybis (4-methylpyridinium) dibromide 34) 1,1-tetramethylenedioxybispyridinium dibromide (35) 1, l -tetramethylenedioxybispyridinium dibromide (3 6) 1-acetoxy-2- (4-dimethylaminostyryl) pyridinium perchlorate (37 1-benzoyloxy-2- (4-dimethylaminostyryl) pyridinium (3 8) 1,3-diethyl--[ (1-methoxy-2(1H)-PYridylidene) ethylidene]-2-thiobarbituric acid 39) 3-ethyl-5-[ (1-methoxy-2( 1H) -pyridylidene ethylidene1-rhodanine (40) 1,3-diethyl-5- 1-methoxy-2(1H)-PYridylidene) ethylidene1-barbituric acid (41 2-(3,3-dicyanoalkylidpne)-1-methoxy-1,2-dihydro pyridine (42) 2- 1-methoxy-2(1H)-py1idylidene)-ethylidene] benzo [b] thiophen-3 (2H) -one-1,1-dioxide (43 3-cyano-5- 1-methoxy-2( 1H) -pyridylidene) ethylidene] -4-phenyl-2 5 H) -furanone Enerographic layers useful in the subject process are advantageously self-supporting layers where the energysensitive material is itself a film-forming material. In this case, the aid of an underlying support material to maintain the dimensional integrity of the photographic layer is not required. In the event that the sensitive, enerotriboelectrically alterable material is not sufficiently film-forming to maintain a self-supporting layer, it can be advantageously dissolved or dispersed in a film-forming resinous matrix vehicle to provide a composite sensitive material which is capable of forming a self-supporting, energy-sensitive layer. Suitable resinous matrices include, for example, materials such as hydrophilic colloids like gelatin or polyvinyl alcohol. Especially advantageous are electrically insulating, substantially hydrophobic and film-forming resinous vehicles such as those including styrenebutadiene copolymers; silicone resins; styrene-alkyd resins; siliconealkyd resins; soya-alkyd resins; poly(vfinyl chloride); poly(vinylidene chloride); vinylidene chloride-acrylonitrile copolymers; poly(vinyl acetate); vinyl acetate-vinyl chloride copolymers; poly(vinyl acetals), such as poly- (vinyl butyral); polyacrylic and methacrylic esters, such as poly(methylemethacrylate), poly(n-butylmethacrylate), poly-(isobutyl methacrylate), etc.; polystyrene; nitrated polystyrene; polymethylstyrene; isobutylene polymers; polyesters, such as poly(ethylenealkaryloxyalkylene terephthalate); phenolformaldehyde resins; ketone resins; polyamide; poly-carbonates; polythiocarbonates; poly(ethyleneglycolcobishydroxyethoxyphenyl propane terephthalate); etc.

Methods of making resins of this type have been described in the prior art, for example, styrene-alkyl resins can be prepared according to the method described in US. Pats. 2,361,019 and 2,258,423. Suitable resins of the type contemplated for use in the photographic layers described herein are sold under such tradenames as Vitel PE-l Ol, Cymac, Piccopale 100, Saran F-220 and Lexan 105. Other types of binders which can be used in these layers include such materials as paraffin, mineral waxes, etc. When a resinous matrix vehicle is employed, the radiation-sensitive material is typically present, in the composite coating composition, in an amount of from about 1 to about 50 parts by weight per parts by weight of resin binder. More widely varying ratios can be utilized for particular formulations or coating operations according to conventional practice.

For purposes of convenient, or where the enerographic layer is insufficiently dimensionally stable to form its own self-supporting layer, such layers can be coated onto an electrically insulating support material to prepare a composite enerographic element. The designation electrically insulating refers to supporet materials having an electrically insulating surface on which the photographic layers described herein can be coated. It is desirable that the electrically insulating support members have a surface resistivity in excess of about 10 ohms per square as measured by Van der Pauw technique, described in Philips Research Report, 13, l-9 (1958). Preferred insulating supports exhibit a surface resistivity of at least about 10 ohms per square. Advantageous support materials include, generally in the form of a flexible film, a wide variety of compositions such as cellulosic materials like cellulose nitrate, cellulose acetate, cellulose acetate butyrate, cellulose butyrate, etc., as well as a variety of additional resinous materials including polystyrene resins, polycarbonate resins and polyester resins, such as poly(ethylene terephthalate). Other advantageous supports include either rigid or flexible materials such as glass and paper including paper coated with alpha-olefin polymers such as those containing 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylenebutene copolymers and the like. Additional desirable electrically insulating support members include electrically conducting materials having an electrically insulating layer coated or otherwise laminated contiguous to an electrically conducting surface of the material. Exemplary electrically conducting materials include metallic foils and plates of such metals as iron, copper, aluminum and other metallic conductors as well as electrically insulating materials (e.g., glass and a wide variety of resinous films such as polyesters, polystyrene polycarbonates, etc.) on which is present an electrically conducting layer such as a metal salt layer or an evaporated metal layer. Suitable electrically insulat ing layers include those exhibiting surface resistivities described herein as desirable, and they can be conveniently formed from a resinous matrix coated over and contiguous to an electrically conducting surface. Prefereably, the vehicle is a substantially hydrophobic, film-forming resin such as those described hereinabove as useful in the preparation of self-supporting layers. Exemplary electrically insulating supports including an electrically conducting material are, for example, aluminum overcoated with a poly(vinylbutyraldehyde) layer, poly(ethylene terephthalate) having on a surface an evaporated nickel layer itself overcoated with a polystyrene resin layer, aluminum overcoated with a polyethylene layer, etc.

Preparing an enerographic layer or element of the sort mentioned herein is conveniently accomplished by coating an enerotriboelectrically alterable material, e.g., one of the heterocyclic alkoxides described herein, from a solvent medium onto a receptive surface or electrically insulating support material. As noted previously, the coating formulation can contain a resinous matrix if desired. Coating can be effected by a variety of techniques, with such means as doctor blade coating, brushing, whirl coating, flow coating and extrusion hopper coating being desirable. Where a self-supporting layer is prepared, the receptive surface is typically one which exhibits low adhesion for the enerographic material, for example, a highly polished metal surface such as chromium or an organic surface having high natural lubricity like a polyhalogenated alkane, e.g., poly(tetrafluoroethylene). After the layer has obtained suflicient dimensional stability, e.g., after chilling or solvent extraction, it is usually physically stripped from the underlying receptive coating surface. With enerographic elements incorporating an electrically insulating support material, the coated layer is merely allowed to dry in situ on the support, providing a composite energysensitive element.

The thickness of the coated layers is widely variable in accordance with conventional practice. When present on an underlying electrically insulating support material, the thickness of the layer, as coated, need only be suflicient to form a continuous film that covers any surface irregularities in the support. Typical thicknesses range from about .0001 mil to about 1.0 mil, although more widely varying thicknesses can be utilized if desired for any reason since enerotriboelectric alterability of the energy-sensitive materials described herein is substantially independent of coating thickness variations. When the layers are coated Without a support and exist as self-supporting layers, then coating thickness is advantageously sufiicient to maintain a dimensionally stable layer. Such a thickness is variable and depends in a large part on the stability characteristics associated with the matrix vehicle, which is typically present. Generally, thicknesses of from about 1 mil toabout 5 mils are employed, although more extensive thickness variations can be utilized for particular coating formulations if desired.

Prior to image formation, the enerographic layers and elements of the types described herein, which are useful in preparing images according to the process of this invention, are advantageously maintained under conditions of darkness or in other environments which are free from energies of the sort which produce enerotriboelectric alteration in the sensitive component. Typically, yellow light is acceptable as being free from activating energy, since many of the useful alkoxide compounds are inherently sensitive to the ultraviolet and other actinic rays which are substantially excluded from light transmitted by a yellow filter.

The preparation of latent electrostatic images and of subsequent visible images corresponding to the latent electrostatic images is accomplished by sequentially (a) exposing (b) differentially triboelectrically charging image-wise and (c) contacting the charged surface with a developer composition. Additionally, transfer of either electrostatic or visible toner image and stabilization of the visible toner image can be effected by convenient techniques.

Exposing an enerographic layer such as those described herein can be carried out by imagewise irradiating or otherwise energizing the sensitive material with a source of electromagnetic radiation including light, heat, X-rays, ultraviolet rays, gamma rays, etc. Additional energizing or activating means, such as those energy forms described hereinabove, can also be used. Using electromagnetic radiation as an example, the radiation is desirably of a wavelength, e.g., ultraviolet or actinic rays, such that triboelectric alteration, i.e., a change in triboelectric series position, is produced in exposed areas. The exposing step can be a direct transmission exposure e.g., contact exposure, wherein the photographic layer or element is exposed to activating radiation, conventionally through a photographic transparency or other material permitting an imagewise pattern of the exposing rays to impinge upon the sensitive-material.

Alternatively, the exposure can be accomplished by reflex exposing techniques wherein the image bearing surface of an original to be copied is first contacted against the radiation-sensitive surface of the photographic layer or element, after which exposing rays are then sequentially directed through the element and the original, and there- 14 after in the reverse direction as a reflection, to elfect an exposed imagewise change in triboelectric series position in the photographic layer. In this fashion, offset (laterally reversed) copies of an original can be prepared. With either a transfer step or using the offset image as a printing master, right-reading copies are obtained. Where the radiation-sensitive materials are carried in a self-supporting layer, either a right-reading image or an offset image can be obtained merely by triboelectrically charging and developing a visible image on the proper surface of the layer which is imagewise struck by exposing rays. This is possible since either surface of the imagewise exposed photographic layer, in the absence of a contiguous support material, can be charged and developed to prepare a visible image. Reflex exposing techniques can be used advantageously, but either offset or direct, right-reading images are thus obtainable with direct transmission exposures of an element existing as a self-supporting layer.

Where an energy for-m other than electromagnetic rays is used, the exposing or activiting means is varied accordingly, and alternative techniques like imagewise pressure, as with a typewriter, imagewise h'eating, as with infra-red exposure a selective contact with a heated member, imagewise sonification, etc., can be used. Alternatively, combinations of these energy forms can be used.

As described elsewhere herein, imagewise exposure of the above-described enerographic layers and elements to activating energy including electromagnetic radiation causes triboelectric alteration, a shifting in triboelectric series position, in areas of the sensitive material exposed or otherwise impinged upon by activating energy. Exposed and unexposed regions remain electrically insulating, but each exhibits distinct triboelectric charging characteristics which can be used to advantage in the formation of latent electrostatic images and corresponding visible images.

A variety of charging technique can be used to form a latent, electrostatic image, including various corona charging methods. Especially advantageous, however, are charging operations which utilize either the frictional charging or contact charging phenomena conventionally designated triboelectrification. These triboelectric charging methods advantageously provide an imagewise differential charging which significantly heightens the imageforming flexibility of the enerographic elements and layers useful herein.

A detailed summary of the mechanisms of triboelectric contact electrifications is presented in US. patent application Ser. No. 730,624, filed May 20, 1968, and presently copending herewith, now US. Pat. 3,579,330. Contact electrification utilizes the charge transfer which occurs when two materials, differing in triboelectric series position, are intimately contacted and separated to form a latent electrostatic image corresponding to the areas in which the contacting surfaces exhibit a relative dissimilarity electrochemical potential. This disparity in electrochemical potential is conveniently expressed as a difference in triboelectric series position.

Frictional triboelectric charging is conveniently accomplished by frictionally contacting the imagewise exposed enerographic layer or element with a material which has a triboelectric series position, i.e., an electrochemical potential, which is different from that of at least one of either the exposed or the non-exposed regions of the enerographic material. In this fashion, since electrical charge transfer occurs between materials differing in triboelectric series position, a latent electrostatic charge image is formed on the eneroresponsive layer or element in those areas which possess a triboelectric series position different from that of the frictionally contacted rubbing material. The magnitude of charge buildup is generally directly related to the amount of triboelectric series separation existing between a rubbing material and the rubbed enerographic material. Additionally, where the rubbing material is separated in the triboelectric series, i.e., exhibits a different triboelectric series position, from both the exposed and non-exposed regions of the rubber enerotriboelectrically alterable material, then a distinct electrostatic charge pattern is established in each of the exposed and non-exposed regions. If the triboelectric series position of the rubbing material is either above or below both exposed and non-exposed regions, then the electrostatic charge image in each region will be of a similar polarity but of a lower potential (voltage) in the region which is triboelectrically closer to the rubbing material. If, however, the triboelectric series position on the rubbing material intervenes those of the exposed and non-exposed regions, then the polarity of electrostatic charge image in each area of the enerographic material will be of opposite sign, and the magnitude of potential in each will be related to the amount of its separation in the triboelectric series from the triboelectric series position of the rubbing material. With this charging phenomenon, it is possible to form two distinct electrostatic charge images either simultaneously or at different times, by differentially triboelectrically charging the enerographic layer or element imagewise.

The triboelectric charging operation is conveniently accomplished by frictionally contacting the enerographic surface with a rubbing material. Advantageous rubbing materials include generally any material that has a triboelectric series position different from that of at least one of the exposed or non-exposed regions of the enerographic material. Especially advantageous rubbing materials include flexible materials which contain multiple filimentary projections that facilitate contact between the rubbing material and rubbed surface, such as animal fur, cotton cloth or additional natural fibers such as wool, etc., as well as linen, cellulosic materials and other synthetic fibers in woven or other physical form, such as numerous resinous fibers including polyamides, polyesters and additional polymeric species like polyvinyl compounds, poly-alphaolefins, etc. The chemical composition of the ultimate rubbing material is secondary. Of primary significance is its triboelectric series position relative to either the exposed regions of the enerographic material, the unexposed regions or both. Triboelectrical charging of the enerographic surface by frictional contact with a rubbing material can be accomplished by a variety of techniques. As an example, the rubbing material can be hand held and drawn across the enerographic surface. Alternatively, it can be maintained in a holding apparatus adapted to produce the desired frictional contact. In another aspect, it can be formed into a cylinder, for example by being wrapped about a cylindrical support, and then rotated to provide a smooth, continuous triboelectric charging operation.

As an alternative to the use of a distinct rubbing material the imagewise exposed or activated enerographic layers described herein can be conveniently triboelectrically charged by cascade means. With such a technique, imagewise differential triboelectric charging is accomplished simultaneously with visible image development. A developer composition, such as those described in detail hereinbelow and containing carrier particles, is cascaded (i.e., poured or otherwise permitted to fiow) across the enerographic surface such that there ismutual frictional contact between the enerographic surface and the surfaces of numerous carrier particles. These carrier particles, as the rubbing materials described hereinabove, exhibit a triboelectric series position different from at least one of the exposed or non-exposed regions of the enerographic layer and cause a latent electrostatic charge image to be formed in at least one of the noted regions of the enerogrphic layer. The cascade charging phenomenon is analogous to the previously described triboelectrification by rubbing; it differs only in the particular technique used to effect frictional contact and is likewise a triboelectric charging means.

Subsequent to the production of an imagewise latent electrostatic image or images on the surface of the enerographic material, this electrostatic charge pattern can either be developed to form a visible image in situ, or it can be transferred to a receiver sheet and developed thereon. Transfer of an electrostatic image is accomplished merely by contacting the electrostatic-image-bearing surface of the enerographic layer or element with an electricallyinsulating surface of a receiver sheet. Such contact is advantageously effected while maintaining each contacting surface stationary with respect to each other in order to prevent blurring, spreading or other distortion of the latent electrostatic image. Suitable receiver sheets for accepting a latent electrostatic image include those having an electrically insulating surface, i.e., having a surface resistivity of at least about 10 ohms per square. Certain paper materials, either coated with a hydrophobic resin layer or having a low moisture content, are extremely useful and readily available. Additionally, the receiver sheet is preferably possessed of a smooth surface to facilitate complete, uniform contact with the charged enerographic surface, thereby promoting effective transfer of the latent electrostatic image.

After an electrostatic charge pattern has been formed, either in situ on an enerographic surface or on a receiver sheet subsequent to transfer, it can be intensified or developed to provide a visible image corresponding to the latent electrostatic image. Developing the electrostatic charge pattern is conveniently accomplished by contacting the electrostatic image-bearing surface with a developer composition containing electrostatically attractable toner particles. Upon contact, toner particles are drawn to the charged surface to form a visible pattern corresponding to the latent electrostatic image. This pattern of toner particles can then be stabilized or fixed to render the visible image substantially permanent Developer compositions useful in the image-forming process of this invention include both dry developers and liquid developers. Dry developer compositions conventionally incorporate a particulate carrier vehicle and toner particles. The range of carrier vehicles which are desirable is extensive and includes various non-magnetic particles such as glass beads, crystals or inorganic salts such as sodium or potassium chloride, hard resin particles, metal particles, etc. Additionally, magnetic carrier particles can be used. Suitable magnetic carrier materials are particles of ferromagnetic materials such as iron, cobalt, nickel and alloys thereof. Other magnetic carriers that can be used are resin particles coated with a thin, continuous layer of a ferromagnetic material as disclosed in Miller, US. application Ser. No. 699,030, filed Jan. 19, 1968, now abandoned, and entitled, Metal Shell Carrier Particles. Still other useful magnetic carriers are ferromagnetic particles overcoated with a thin, continuous layer of a film-forming, alkali-soluble carboxylated polymer as disclosed in Miller, US. application Ser. No. 702,201, filed Feb. 1, 1968, now US. Patent 3,547,822, and entitled, Scum Retardant Carrier Particles and Compositions Thereof.

Toners useful with a carrier vehicle such as those described herein, to produce a composite, dry powder electrostatic developer composition, can be selected from a wide variety of materials to give desired physical properties to the developed image and proper triboelectric relationship to match the carrier particles used. Generally, any of the toner powders known in the art are suitable for mixing with the carrier particles to form a developer composition. Toners are generally prepared by finely grinding a resinous material and mixing the resultant, finely ground resin with a coloring material such as a pigment or a dye. The resin, or mixture in the event that a colorant is added, is then typically ground additionally, for example in a ball mill, and then heated so that the resin flows and encases the coloring material. The mass is cooled, broken into small chunks and finely ground again. After this procedure, the toner powder particles usually range in diameter from about 0.5 to about 25 microns with an average nominal size of about 2 to about 15 microns. Optionally, where initial particle sizes are desirable, additional grinding is not performed. Other methods of toner preparation are also useful, and these methods are well known to those skilled in that art.

The resin material used in preparing the toner can be selected from a wide variety of materials, including natural resins, modified natural resins and synthetic resins. Exemplary useful natural resins are balsam resins, colophony and shellac. Examplary suitable modified natural resins are colophony-tmodified phenol resins and other resins listed below with a large proportion of colophony. Suitable synthetic resins include the extensive variety of synthetic resins known to be useful for toner purposes, for example, polymers, such as vinyl polymers including polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl acetals, polyvinyl ether and polyacrylic and polymethacrylic esters; polystyrene and substituted polystyrenes or polycondensates, e.g., polyesters, such as phthalate resin, terephthalic and isophthalic polyesters, maleinate resin and colophony-mixed esters of higher alcohols; phenol-formaldehyde resins, including colophony-modified phenolformaldehyde condensates, aldehyde resins, ketone resins, polyamides and polyadducts,

e.g., polyurethanes. Moreover, polyolefins, such as vari-,

ous polyethylenes, polypropylenes, polyisobutylenes and chlorinated rubber are suitable. Additional resinous toner materials which are useful are disclosed in the following US. Patents: 2,917,460; Re. 25,136; 2,788,288; 2,638,416; 2,618,552 and 2,659,670.

As noted above, color material can be incorporated into toners to render electrostatic images toned therewith more distinct or visible. The coloring material additives useful in suitable toners are preferably dyestuffs and colored pigments. These materials serve to color the toner and thus render it more visible. In addition, they sometimes affect, in known manner, the polarity of the toner. In principle, virtually all of the compounds mentioned in the Color Index, Vols. I and H, second ed., 1956, can be used as colorants. Included among the vast number of suitable colorants would be such materials as Nigrosin Spirit soluble (0.1. 50415), Hausa Yellow G (C. I. 11680), Chromogen Black BT (C.I. 14645), Rhodamine B (CI. 45170), Solvent Black 3 (CI. 26150), Fuchsine N (CI. 42510), C.I. Basic Blue 9 (01. 52015) etc. Another useful classof colorants are nigrosine salts such as nigrosine salts of mono and difunctional organic acids having from 2 to about 26 carbon atoms such as chloroacetic acid, stearic acid, sebacic acid, lauric acid, azelaic acid, adipic acid, abietic acid, docosanoic acid and the like. Nigrosine salts of this type are disclosed in copending application Ser. No. 770,122, filed Oct. 23, 1968, in the name of James R. Olson and entitled, Uniform Polarity Resin Electrostatic Toners, now US. Pat. 3,647,696. In addition to the resin and colorant, dry toners can also contain such additional desirable components as are known in the art. In toners for dry developers, colorant materials are typically included in an amount of from about 1 part to about 10 parts by weight per 100 parts by weight of the resin binder. Composite dry developers generally include from about 1 part to about 10 parts by weight of toner particles and other addenda per 100 parts by weight of the entire developer, i.e., from about 90 to about 99 parts by weight of carrier vehicle.

Latent electrostatic images can also be developed using liquid developer compositions, these typically including a dyed or pigmented resin dispersed in an electrically insulating carrier liquid. Typical liquid developers are prepared by grinding or ball milling at least one pigment with a suitable polymer solution and diluting this concentrate with an insulating carrier liquid. Alternatively, a dye.

can be dispersed or dissolved in the polymer solution in lieu of or in addition to the pigment. The resultant developer is in the form of a carrier liquid having dispersed 18 therein toner particles comprised of the pigments or dyes or both as a colorant and a suitable resinous material.

Advantageous pigments include inorganicmaterials such as structural forms of carbon like graphite, carbon black,

lamp black, bone black, charcoal, etc, as well as additional materials including cadmium sulphide, titanium dioxide, zinc oxide, iron oxide, magnetic or non-magnetic iron oxide, aluminum powder and bronze powder. Suitable dyestuff colorants include organic dyes such as In addition to the pigment or dyestuif colorants which are dispersed in the carrier liquid, a resinous material can be used ifdesired to facilitate binding of the colorant to the surface to be developed. Suitable resinous materials used in the present developers appear to form a coating around each colorant particle and thusalso facilitate dis: persion of the colorants in the carrier liquid; Useful resins can be selected from a wide variety of substances. The following are illustrative of suitable materials: rosins, in-

cluding hydrogenated rosins and esters of hydrogenated rosins, alkyl methacrylate copolymers havingfrom 2 to 5 carbon atoms in each alkyl moiety, such as isobutyl methacrylate and normal butyl methacrylate copolymers, etc.; phenolic resins including modified phenolic resins such as phenol formaldehyde resins; pentaerythritol phthalate; cournaroneindene resins; ester gum resins; vegetable oil polyamides; alkyd resins, including modified alkyds such as soya oil-modified and linseed oil modified alkyds, phthalic, maleic and styrenated alkyds, etc.; and the like...

In addition, the electrostatic charge polarity of the toner particles present in liquid developers can be enhanced or altered by the addition of suitable charge control agents if so desired. A variety of materials can be used as charge control agents. Illustrative of suitable charge agents are the polyoxyethylated alkyl surfactants such as polyoxyethylated alkylamine, polyoxyethylene palmitate, polyoxyethylenestearate, etc. Other useful materials are magnesium and heavier metal soaps of fatty and aromatic acids as described in Beyer U.S. Pat. No. 3,417,019. Useful metal soaps include cobalt naphthenate, magnesium naph thenate and maganese naphthenate, zinc resinate, calcium naphthenate, zinc linoleate, aluminum resinate, isopropyltitanium stearate, aluminum stearate, and others many of which are also described in US. Pat. No. 3,259,581. Typically, the amount of such materials used is less than about 2% byweight based on the weight of toner. In certain instances, the resinous binder per se can function as the charge control agent as can the colorant.

Suitable developer compositions can be prepared simply by grinding the pigments to the appropriate size and dispersing the pigment powder in a carrier liquid without the addition of a resinous binder and/or charge control agenuA developer which does not contain a binder material would produce developed images which were not fixed. Accordingly, it would be necessary to overcoat such images by spraying with a lacquer composition in order to hold the pigment particles in place. The pigment or pigment-binder particles generally have an average particle size of from about 0.05 to about 5 microns with preferred materials in the range of from about 0.1 to about 1 micron. Typical developer compositions contain the present pigments or other colorant in a concentration of from about 0.01 to about 1.0 gram per liter. When a resin binder is used, the pigment (colorant) to binder weight ratio can vary from about 1:30 to about 2:1.

Carrier liquids which can be used to form such developers can be selected from a wide variety of materials. Preferably, the liquid has a low dielectric constant and a very high electrical resistance such that it Wlll not disturb or destroy the electrostatic latent image. In general, useful carrier liquids should have a dielectric constant of less than about 3, should have a volume resistivity of greater than about ohm-cm. and should be stable under a variety of conditions. Suitable carrier liquids include halogenated hydrocarbon solvents, for example, fluorinated lower alkanes, such as trichloromonofluoromethane, trichlorotrifluoroethane, etc., having a typical boiling range of from about 2 C. to about 55 C. Other hydrocarbon solvents are useful such as isoparaffinic hydrocarbons having a boiling range of from about 145 C. to about 185 C. such as Isopar G (Humble Oil & Refining Co.) or cyclohydrocarbons having a major aromatic component and also having a boiling range of from about 145 C. to about 185 C., such as Solvesso 100 (Humble Oil & Refining Co.). Additional useful carrier liquids include polysiloxanes, odorless mineral spirits, octane, cyclohexane, etc. Conventionally, the amount of toner dispersed in a carrier vehicle to provide a composite developer varies from about .1 g. to about 10 g. of toner per liter of carrier liquid.

Contacting the charged surface with the developer composition can be accomplished with a variety of development techniques. With dry developers, it is convenient to cascade the developer over the charged surface by, for example, pouring or otherwise directing the developer composition onto the charged surface. As previously mentioned, where the triboelectric series position of the carrier particles is suitably separated from that of at least one of the exposed or non-exposed regions, the formation of an electrostatic charge pattern and visible image development can occur simultaneously, thus eliminating the need for a separate charging operation. Alternatively, when ferromagnetic carrier materials are utilized, dry developers can be applied to a previously electrostatically charged surface by magnetic brush techniques. An example of apparatus suited for magnetic brush development is that type which is described in US. Pat. No. 3,003,462, which apparatus often comprises a non-magnetic, rotatably mounted cylinder having fixed magnetic means mounted inside. The cylinder is arranged to rotate so that part of the surface is immersed in or otherwise contacted with a supply of developer mix. The granular mass comprising the developer mix is magnetically attracted to the surface of the cylinder. As the developer mix comes within the influence of the field generated by the magnetic means within the cylinder, the particles thereof arrange themselves in bristle-like formations resembling a brush. The bristle formations of developer mix tend to conform to the lines of magnetic flux, standing erect in the vicinity of the poles and lying substantially fiat when said mix is outside the environment of the magnetic poles. Within one revolution the continually rotating tube picks up developer mix from a supply source and returns part or all of this material to the supply. This mode of operation assures that fresh mix is always available to the copy sheet surface at its point of contact with the brush. In a typical rotational cycle, the roller performs the successive steps of developer-mix pickup, brush formation, brush contact with the electrostatically charged surface, brush collapse and finally mix release. Still additional advantageous development techniques, e.g., powder cloud development and other aerosol techniques, are well known by those skilled in this art.

When liquid developers are utilized, development is conveniently effected by a wide range of techniques including immersion of the charged surface into the developer, flowing the liquid developer across the charged surface, spraying the developer onto the charged surface, etc. When spray aerosol techniques are used, the toner particle charge can be intensified by passage of the aerosol by or through a charged point source of grid.

Conventionally, after visible image development, the resultant toner image is fixed or stabilized to render it resistant to smudging or other degradation caused by physical contact, chemical action or the like. Fixation can be accomplished by a number of techniques in accordance with usual practice. When binderless toners are used, a film-forming, adherent layer is typically applied over the toner image to bind it to the underlying substrate. Advantageous materials include film-forming, thermoplastic resins or lacquers such as described hereinabove. When a binder component is present in the toner, fixation can easily be accomplished by heating or solvent treatment means. Upon heating, a thermoplastic binder can be melted or suitably softened such that the toner particles fuse to form a continuous film which adheres tightly to the underlying surface. Alternatively, the toner image can be treated with a solvent or solvent vapors which produce a solvent effect upon the resinous binder. Upon resolidification, the resin binder forms a solid film which also tightly adheres to the supporting surface.

With the enerotriboelectrically alterable materials described herein, both exposed and non-exposed regions remain electrically insulating and can be simultaneously or sequentially electrostatically charged and developed, by techniques such as those described elsewhere herein, to provide separate images of, for example, varying colors. Also, when an imagewise exposed enerographic layer as described herein is triboelectrically charged to produce charge patterns in exposed and non-exposed regions simultaneously, either a negative or a positive copy of the original can be obtained from a single imagewise exposure, merely by developing the charged surface with a developer composition whose toner particles exhibit a polarity opposite to that of the image region intended for development. Additionally, if the imagewise exposed and developed photographic layers and element of the types herein described are not subsequently overall exposed to activating rays, then additional, add-on images can be prepared in previously undeveloped areas, whether previously exposed or unexposed, by a suitable combination of the exposing, charging and development techniques previously mentioned.

Enerographic layers and elements described herein as useful in the subject process provide not only a wide range of enerosensitivity, but also a high photographic speed when the activating energy is electromagnetic radiation, such as light. The photographic speeds exhibited by the heterocyclic alkoxide salts described herein are significantly greater than those obtainable from conventional non-silver halide photosensitive compounds like diazonium salts, diazo resins, etc. As such, the process of this invention can form visible images with less exposure to activating energy than can similar processes using less sensitive enerotriboelectrically alterable materials.

The following examples are included for a further understanding of the invention:

EXAMPLE '1 A coating composition containing the heterocyclic alkoxide, N-methoxy 2 anilinovinyl-pyridinium p-toluene sulfonate (0.066 gm.); cellulose acetate butyrate (0.33 gm.); acetone (10 ml.); and ethanol ml.) is dip coated on polyethylene coated paper support at a wet laydown of 1.2 ml./ft. to provide, after drying, a heteroaccomplished by cascading a dry powder developer, containing positively charged toner particles, across the charged surface. The developer composition is of the type described above and is composed of iron carrier particles admixed with toner particles of a polystyrene resin dyed with nigrosine base (the free base of CI50,415) as a colorant. Toner particles are attracted to exposed areas, thereby producing a negative copy of the original line transparency. Fixation is obtained by heat fusing the toner particles to the support.

EXAMPLE 2 A photographic (enerographic) element (Element B) is prepared, exposed (for 1.55 seconds) and charged as in Example 1, but development of the resultant electrostatic charge image is accomplished by cascading a dry powder developer composition containing negatively charged toner particles. The developer composition is of the type described above and is composed of iron carrier particles admixed with toner particles of a polystyrene resin pigmented with carbon black as a colorant. Toner adheres to the unexposed areas, and image stabilization is accomplished by treatment with trichloroethylene vapors which exert a solvent effect on the toner particles and permanently fuse them to the underlying support.

The negative-working and positive-working capabilities illustrated in Examples 1 and 2, using similar charging means, are obtained since the nylon plush rubbing material, in the triboelectric series lies between the triboelectric series positions of the exposed and the unexposed regions. Therefore, use of but one charging operaiton renders each area capable of development.

EXAMPLE 3 An element is prepared as in Example 1. Exposure is for 5 seconds and at 20x magnification through a line transparency using a projector whose light source is a 300- watt xenon arc lamp producing ultraviolet rich rays. The light source is approximately 6 feet from the exposure plane. After charging as in Example 1, visible image development of the electrostatic latent image is accomplished by flowing a liquid electrostatic developer containing positively charged toner particles which adhere to negatively charged exposed regions of the charged surface. The liquid developer composition is of the type described hereinabove and is composed of cyclohexane carrier liquid having dispersed therein toner particles of an alkyd resin dyed with phthalocyanine blue as a colorant. Fixation of the resultant visible image is obtained without further treament upon solvent evaporation of the carrier liquid. A second, similar element is exposed and charged in a like fashion, but development is accomplished by contacting the charged surface with a dry powder developer containing negatively charged toner particles. The dry developer is of the type described in Example 1. Deposition of toner occurs in the positively charged, unexposed regions of the charged surface. Image stabilization is accomplished by treatment with trichloroethylene vapors.

EXAMPLE 4 Using an element as in Example 1, a printed. document incorporating both ink and typewritten characters is copied by reflex exposure, the laminate of original and element being positioned on a reflecting surface during exposure. Exposure is by the source of Example 1, and for a duration of 10 seconds. Charging of the exposed element is accomplished by rubbing with nylon plush fabric. The charged surface, bearing an electrostatic charge pattern is then developed by contact with a dry powder developer having negatively charged toner particles. The developer is of the type described in Example 1. Toner deposition occurs in the positively charged, unexposed areas. Fixation is obtained by treatment of the toned image with trichloroethylene vapors.

22 EXAMPLE 5 A coating formulation containing the heterocyclic alkoxide of Example 1 (0.10 gm.); cellulose acetate butyrate (0.10 gm.); acetone (10 ml.); and methanol ml.), is dip coated onto polyethylene coated paper. The Wet laydown is 1.2 ml./ft. providing a dry alkoxide coverage of 0.75 mg./ift. After drying, the resultant enerographic (photographic) element is exposed for 10 seconds as in Example 1, but simultaneously through a line positive transparency and a 1.0 neutral density filter held in an overlay relationship. Charging is as in Example 1, and development is accomplished by contact with a dry powder developer containing negatively charged toner particles. The developer is of the type described in Example 1. Toner deposition occurs in unexposed regions to provide a positive copy of the original transparency. Fixation is effected by heat fusing the toner image. The visible toner image exhibits reduced toner deposition in background areas, presumably due to the smooth surface provided for development, thereby providing improved definition and increased apparent speed.

EXAMPLE 6 A 4-mil sheet of aluminum is coated with a 15 (by weight) toluene solution of polystyrene using a 2 mil doctor blade apparatus. The coated layer is then dried for 30 minutes at 50 C. after which a .1% (by weight) methanol solution of the heterocyclic alkoxide compound of Example 1 is flow coated over the styrene layer. The enerosensitive layer is dried for 10 minutes at 50 C. while being held in a vertical position to permit drainoff of excess material. The resultant element is then exposed for 20 seconds through a line negative transparency to the ultraviolet rich mercury are light source of a Filmsort 086 Uniprinter, marketed by the 3M Corporation. After triboelectrification as in Example 1, the electrostatic charge pattern is developed by immersing the element in a liquid electrostatic developer having positively charged toner particles. The developer is of the type described in Example 3. Toner deposition occurs in the negatively charged, unexposed areas to provide a positive copy of the original transparency. Fixation is accomplished by heat fusing the toner image.

EXAMPLE 7 An element is prepared and exposed as in Example 6, after which it is divided into three portions. One portion of the element is immersed in a liquid developer composition having negatively charged toner particles. The developer composition is of the type described hereinabove and is composed of an n-pentane carrier liquid having dispersed therein droplets of linseed oil pigmented with carbon black as a colorant. No image discrimination occurs. The second portion is developed by magnetic brush contact with a dry powder electrostatic developer composition containing negatively charged toner particles. The dry developer composition is as described in Example 1. Image discrimination occurs, with toner deposition occurring in positively charged exposed areas. The third portion is developed with the dry powder type developer, but by cascade development. Image density is higher than when development is performed by magnetic brush means.

EXAMPLE 8 A coating formulation containing 3-ethyl-1'-methoxy- 4,5-benzothia-2'-pyrido carbocyanine perchlorate (0.030 gm.); cellulose acetate butyrate (0.050 gm.); triethanolamine (0.40 gm.); and acetone ml.) is dip coated onto polyethylene coated paper support to provide a wet laydown of 1.2 InL/ft. and a dry heterocyclic alkoxide coverage of 0.2 Ing./ft. After drying, four portions of the resultant element are exposed through a line negative and a 1.0 neutral density filter (overlaid) for 3, 4, 5 and 6 seconds, respectively. Imagewise dilferential triboelectric charging to produce a latent electrostatic image is accomplished as in Example 1, after which development is carried out by contact with a dry powder developer containing positively charged toner-particles. The developer is of the type described in Example 1. Toner deposition occurs in the negatively charged exposed regions of each portion. The portions having 4-, 5-, and 6-second exposures exhibit visible images of extremely high quality. Fixation is obtained by heat fusing the toner image to the support. The shorter exposure times necessary to provide a desirably dense image are apparently due to the increased absorption of incident radiation by this particular heterocyclic alkoxide.

TABLE I Relative photographic speed of representative enerographic image-forming elements Relative photographic speed of the above coatings of this invention is compared with a commercially available diazotype composition using a standard exposure setup as described in Example 1. The diazo film is arbitrarily assigned a speed value of 1.0. Photographic speed (P) of coatings of the examples is calculated from an exposure series using a line copy overlay. The minimum exposure, S, which affords a commerically desirable image density and background clarity on charging and toning is substituted in the expression to give relative photographic speed (using the speed assigned to the diazotype film as a standard). It is recognized that many factors affect speed besides exposure interval. Chief among these are charging potential dilferences, the toner and nature of the insulating support. As far as possible these variables are held substantially constant during speed measurements.

The speed values tabulated above provide a convenient illustration of comparative photographic activity exhibited by the heterocyclic materials, such as pyridinium alkoxides, useful in this invention and a diazotype composition of the type widely used for the copying of documents, drawings and the like.

EXAMPLE 9 Eight elements (A-H) are prepared according to the procedure of Example 1, with coating formulations in parts by weight as follows:

Parts Heterocyclic oxide material 1 Cellulose acetate 2 Triethanolamine i 4 Acetone 2 24 Element B s or[ $CH3 1? 02H? TS- Element 0 s /CH=OH)CH QN a dons c104 CgHs Element D 9 CH=CH N.CH.

N (BCH; C1049 Element E ocm P'rse I CH3 Element F CH=CHCH N domotrn C1049 Element G s eh CHaO-N 0 ,-cn=

Element H The designation PTS- is descriptive of a p-toluene sulfonate anion. After coating and drying, each element (A-H) is divided into four portions and each is exposed according to the procedure of Example 1 but with the following light sources:

( 1) Photoflood lamp of Example 1;

(2) BOO-watt high pressure mercury arc lamp;

(3) BOO-watt xenon arc lamp;

(4) Carbon arc lamp having a lamp intensity of 1720 foot candles.

After exposure, portions 1 and 2 of each element are charged, developed and fixed as in Example 1, and portions 3 and 4 of each element are charged, developed and fixed as in Example 2. Similar images of a like high quality are obtained.

EXAMPLE An enerographic element is prepared, exposed and charged as in Example 1, after which it is developed according to the procedure of Example 2. The charged surface bearing the unfixed toner image is rolled in contact with a sheet of receiver paper by means of pressure rollers. A toner image is transferred from the matrix to the receiver sheet. Without further charging, the matrix sheet is retoned and a second transfer is made in this fashion. A copy similar in density to the first results. Each transferred toner image is then fused by exposure to trichloroethylene vapors.

EXAMPLE 11 A photographic element is prepared, exposed and charged as in Example 1. To transfer the latent electrostatic image, the charged surface is then placed in contact with the polyethylene surface of a polyethylene coated paper support material. After separation, the polyethylene receiver surface is developed by contact with a dry powder developer as in Example 1. Toner deposition occurs in those areas corresponding to the unexposed areas of the element to prepare a corresponding visible image.

EXAMPLE 12 A self-supporting eneroresponsive layer is prepared as follows: a coating formulation as in Example 1 is flow coated onto a smooth glass plate and dried to form a selfsupporting film. This resultant layer is then physically stripped from the glass to prepare a fully self-supporting energy-sensitive layer. The sensitive material is divided into two-portions and they are mounted side-by-side in a frame with the upper surface of one portion and the lower (i.e., previously in contact with glass) surface of the second portion being positioned towards the exposing source. Exposure, charging and development are accomplished as in Example 1, with the exposure of each portion being simultaneous. A toner image as that of Example 1 is produced, and fixation is carried out by treatment with trichloroethylene vapors.

EXAMPLE 13 Four photographic elements (A-D) are prepared, exposed and triboelectrically charged as in Example 1, but with the following fabric rubbing materials:

Element A.P1ush fabric of Kodel Type II polyester (1,4-dimethylenecyclohexylene terephthalate) marketed by the Eastman Kodak Company.

Element B.Ny1on plush fabric (polyamide fabric).

Element C.Plush fabric including, by weight, 40% Kodel Type II and 60% acrylate polymer.

Element D.--Plush fabric of acetate rayon.

Electrometer measurements of electrostatic potentials ing the exposed areas disclose that each of the rubbing materials produces of potential in excess of 200 volts.

In addition to being responsive to electromagnetic radiation of the visible and near visible light spectrum, the enerosensitive materials described herein, i.e., those of Formulas A-H, are triboelectrically alterable by other forms of energy, such as heat and pressure. Regarding heat activation, radiant sources, emitting in the infrared band, e.g. infrared lamps are useful to promote triboelectric alteration of exposed regions. Heated metal plates and other members useful in transmitting heat to the sensitive material by conduction are also useful.

EXAMPLE 14 An eneroresponsive element is prepared as in Example l. A printed document as in Example 4 is then contacted to the element with the printed surface contiguous to the energy-sensitive material. This overlay is then exposed through the document and for a period of 2 seconds, to the rays of a 300-watt infrared lamp held 12" from the exposure plane. Triboelectric ch'arging and development are accomplished as in Example 1 and similar high quality images are obtained.

EXAMPLE 15 According to the procedure of Example 14, an element is prepared and processed to yield an image but With the exception that exposure is obtained by pressing the raised image bearing surface of a metal relief printing plate against the sensitive material. Uniform pressure is obtained by means of a hand press and the surface of the element is not physically deformed. Toner deposition occurs in regions corresponding to the imagewise pressure exerted by the raised portions of the plate.

The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. An enerographic image-forming process for the preparation of images by electroenerographic means on the surface of an eneroresponsive layer comprising an energysensitive enerotriboelectrically alterable material consisting essentially of a material selected from the group consisting of a heterocyclic-N-alkoxide and a heterocyclic-N- acyloxide that exhibits a change in triboelectric series position upon exposure to activating energy, which process comprises:

(a) initially imagewise exposing said eneroresponsive layer to energy capable of producing an image-wise change in triboelectric series position within the exposed regions of said energy-sensitive material,

(b) differentially triboelectrically charging the surface of said exposed layer imagewise to form an electrostatic charge pattern thereon, and

(0) developing said electrostatic charge pattern by contacting said charged surface with a developer composition containing electrostatically attractable toner particles to form a pattern of said toner particles thereon corresponding to the non-exposed or the exposed regions.

2. An enerographic image-forming process as described in claim 1 wherein the energy-sensitive material is subtantially uniformly dispersed in an electrically insulating resin binder, and wherein the charging step comprises frictionally contacting the imagewise exposed eneroresponsive layer with a material having a triboelectric series position different from that of at least one of either the exposed or non-exposed regions of said layer.

3. An enerographic image-forming process as described in claim 1 wherein the exposing step is accomplished by reflex exposure.

4. An enerographic image-forming process as described in claim 1 wherein said charging step and said developing step are accomplished simultaneously.

5. An enerographic image-forming process as described in claim 1 and additionally including the step of transferring said pattern of toner particles to a receiver sheet.

6. An enerographic image-forming process as described in claim 5 and additionally including the steps of sequentially repeating the developing and transfer steps at least (b) differentially triboelectrically charging the surface of said exposed layer imagewise to form an electrostatic charge pattern thereon,

(c) contacting said charged surface bearing an electrostatic charge pattern against an electrically insulating receiver surface to transfer substantially the entire electrostatic charge pattern to said receiver surface, and

(d) developing said transferred electrostatic charge pattern by contacting said receiver surface with a developer composition containing electrostatically attractable toner particles to form an imagewise pattern of said toner particles thereon.

8. An enerographic image-forming process for the preparation of images by electroenerographic means on the energy-sensitive surface of an enerographic element comprising an electrically insulating support having coated on a surface thereof an eneroresponsive layer comprising an enerosensitive, enerotriboelectrically alterable material consisting essentially of a material selected from the group consisting of a heterocyclic-N-alkoxide and a heterocyclic-N-acyloxide that exhibits a change in triboelectric series position upon exposure to activating energy, which process comprises:

(a) initially imagewise exposing said eneroresponsive layer to energy capable of producing an exposed imagewise change in triboelectric series position within the exposed regions of said material,

(b) differentially, triboelectrically charging the surface of said exposed layer imagewise to form an electrostatic charge pattern thereon and (c) contacting said charged surface with a developer composition containing electrostatically attractable toner particles to form a pattern of said toner particles thereon corresponding to the nonexposed or the exposed regions.

9. An enerographic image-forming process as described in claim 8 wherein the energy-sensitive heterocyclic material is energy fragmentable and has a formula selected wherein:

R is selected from the group consisting of:

(a) a methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes,

(b) an alkyl radical,

(c) an anilinovinyl radical,

(d) a hydrogen atom,

(e) an aryl radical,

(f) an aldehyde group, and

(g) a styryl radical:

R is selected from the group consisting of:

(a) a methine linkage terminated by a heterocyclic nucleus of the type contained in merocyaine dyes and (b) an allylidene radical;

R is selected from the group consisting of (a) an alkyl radical and (b) an acyl radical;

X is an acid anion; and

Z represents the atoms necessary to complete a 5 to 6 membered heterocyclic nucleus.

10. An enerographic image-forming process as described in claim 9 wherein Z represents the atoms necessary to complete a member selected from the group consisting of a pyridine nucleus and a quinoline nucleus.

11. An enerographic image-forming process as described in claim 9 wherein R is a methine linkage terminated by a 5 to 6 membered heterocyclic nucleus.

12. An enerographic image-forming process as described in claim 9 wherein the energy-sensitive material has the formula:

Q and Q each represent the non-metallic atoms necessary to complete a 5 to 6 membered heterocyclic nucleus;

R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical; R is selected from the group consisting of:

(a) an aryl radical, (b) a hydrogen atom, and (c) an alkyl radical;

L is a methine linkage;

X is an acid anion;

g is a positive integer from 1 to 2;

n is a positive integer from 1 to 4; and

R is selected from the group consisting of an alkyl radical, an alkenyl radical, an aryl radical and an alkoxy radical.

13. An enerographic image-forming process as described in claim 12 wherein Q represents the atoms necessary to complete a member selected from the group consisting of a pyridine nucleus and a quinoline nucleus.

14. An enerographic image-forming process as described in claim 9 wherein the energy-sensitive material has the formula:

wherein:

Q represents the atoms necessary to complete a 5 to 6 membered heterocyclic nucleus;

R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical; R is selected from the group consisting of:

(a) an aryl radical, (b) a hydrogen atom, and (c) an alkyl radical;

L is a methine linkage;

X is an acid anion;

'G is selected from the group consisting of an anilinovinyl radical and an aryl radical;

m isa positive integer from 1 to 3; and,

g is a positive integer from 1 to 2.

15. An enerographic image-forming process as described in claim 14 wherein Q represents the atoms necessary to complete a member selected from the group consisting of a pyridine nucleus and a quinoline nucleus.

16. An enerographic image-forming process as described in claim 8 wherein the energy-sensitive material has the formula:

wherein:

Q represents the non-metallic atoms necessary to complete. a 5 to 6 membered heterocyclic nucleus; R is selected from thegroup consisting of an alkyl radical and an acyl radical; R and R are each selected from the group consisting of an aryl radical, a hydrogen atom and an alkyl radical; and X is an acid anion.

19. An enerographic image-forming process as described in claim 18 wherein Q and Q each represent the atoms necessaryto complete a member selected from the group consisting of a pyridine nucleus and a quinoline nucleus.

20. An enerographic image-forming process as described in claim 9 wherein the energy-sensitive material is selected from the group consisting of 3-ethy1-1-methoxy- 4,5-benzothia-2-pyridocarbocyanine p-toluene sulttonate, 3 ethyl 1' methoxythia 4 pyridocyanine perchlorate and 2 B anilinovinyl 1 methoxypyridinium p-toluene sulfonate.

21. An enerographic image-forming process as described in claim 8 wherein the energy-sensitive material is dispersed in anelectrically insulating resin.

22. An enerographic image-forming process as described -in claim 8 wherein the exposing step is accomplished by exposure to an imagewise pattern of electromagnetic radiation. 1

23. An enerographic image-forming process as described in claim 8- wherein the exposing step is accomplished by exposure to visible light.

24. An enerographic image-forming process as described in claim 22 wherein. the exposing step is accom plished by reflex exposure. I a v 25. An enerographic image-forming process as described in claim 8 wherein the exposing step is accomplished by exposure to an imagewise pressure pattern.

26. An enerographic image-forming process as described in claim 8 wherein the exposing step is accomplished by exposure to an imagewise heat pattern.

'27. An enerographic image-forming process as described in claim 8 wherein said charging step and said developing step are accomplished simultaneously.

28. An enerographic image-forming process as described in claim 8 and additionally including the step of transferring said pattern of toner particles to a receiver sheet.

29. An enerographic image-forming process as described in claim 28 and additionally including the steps of sequentially repeating the developing and transfer steps at least once.

30. An enerographic image-forming process as described in claim 8, but wherein, after said charging step, the process comprises the steps of:

(a) contacting said charged surface bearing an electrostatic charge pattern against an electrically insulating receiver surface to transfer substantially the 30 entire electrostatic image to receiver surface and (b) developing said transferred electrostatic charge pattern by contacting said receiver surface with a developer composition containing electrostatically attractable toner particles to form an imagewise pattern of said toner particles thereon.

31. An enerographic image-forming process as described in claim 8 wherein said electrically insulating support comprises an electrically conducting material having an electrically insulating layer coated thereon.

32. An enerographic image-forming process as described in claim 8 wherein the energy-sensitive heterocyclic material is energy fragmentable and has a formula selected from the group consisting of:

Z represents the atoms necessary to complete a pyridine nucleus;

Z represents the atoms necessary to complete a pyridinium nucleus;

R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical;

R is selected from the group consisting of (a) a methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes,

(b) an alkyl radical,

(c) an anilinovinyl radical,

(d) a hydrogen atom,

(e) an aryl radical,

(f) an aldehyde group, and

(g) a styryl radical;

selected from the group consisting of (a) a methine linkage terminated by a heterocyclic nucleus of the type contained in merocyanine dyes and (b) an allylidene radical; and X- is an acid anion.

33. An enerographic process as described in claim 32 in which R and R are 2 or 4 position nucleus substituents.

34. An enerographic image-forming process as described in claim 8 wherein the energy-sensitive heterocyclic material is energy fragmentable and has a formula selected from the group consisting of:

R5 is ,'Z2\ ,Zr. B end 1 Rs N I N l (JR X- bR wherein:

Z represents the atoms necessary to complete a quinoline nucleus; Z represents the atoms necessary to complete a quinolinium nucleus; R is selected from the group consisting of:

(a) an alkyl radical and (b) an acyl radical; R is selected from the group consisting of (a) a methine linkage terminated by a heterocyclic nucleus of the type contained in cyanine dyes,

(b) an alkyl radical,

(c) an anilinovinyl radical,

(d) a hydrogen atom,

(e) an aryl radical,

(f) an aldehyde group, and

p (g) a styryl radical; R is selected from the group consisting of:

(a) a methine linkage terminated by a hetero- 31 cyclic nucleus of the type contained in mero- 3,451,811 cyanine dyes and 3,206,599 (b) an allylidene radical; and 3,128,198 X- is an acid anion. 3,206,600 5 3,286,025

References Cited UNITED STATES PATENTS 6/1970 Bickmore 96-1 R 3,574,622 4/1971 Jenkins et a1 9688 X 32 Brynko 96-1 R Gold 25065.2 Dulmage 117--17.5 Gold 25065.2 Ingersoll 961 R X ROLAND E. MARTIN, 111., Primary Examiner US. Cl. X.R.

Je s et a1 I R R, 1.5,

UNITED STATES PATENT OFFICE CE TIFICATE 0F CORRECTION Patent No 3 7 4 8 l 2 8 Dated July 24 4 l 973 James C McNal ly lnventofls) It is certified thaterror appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, lines 38-45,

d I should read I a Q C OrCHS O-CYH Column 3, lines 45:60, in that part of the formula n n I M\ u should read t I Column 5, line 31, "change" should read --charge---;

Column 7, line 17, "Methin" should read --Methine--' Column 9, line 9, after "one" insert l-phenyl2 pyrazolin5one-;

Column 10, line 64, "pictrate" should read ---picrate-- PO-WJO UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent 3 748 ,lZ8 Dated July 24', 1973 James G. McNally Inventofls) PAGE 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

' Column ll, line 29, after "pyridinium" insert --perchlorate---; Column 12, line 19, "supporet" should read -support---; Column 15 line ll, "on" should read -0:E I Column 21,. line 31, '.'operaiton" should read ,-ope ration---; Column 27,' line 43, delete the from the second formula. Column 30, line 1, after "to" ins'ert"- -sa idQ-'---; Column 30, line 19, in the second formula "0" should read OR Signed and sealed this 18th day of December 1973.

(SEAL) Attest:

EDWARD M.-PLETCHER,JR. RENE D. TEGTMEYER o Attesting Officer Acting Commissioner of Patents