US3488189A - Electrophotographic recording member having solid crystalline plasticizer available at the imaging surface - Google Patents

Description

United States Patent Int. Cl. G03g 5/00 U.S. Cl. 96-1.5 20 Claims ABSTRACT OF THE DISCLOSURE Fused toner images on an imaging surface corresponding to an electrostatic field are formed by depositing on the imaging surface in image configuration toner particles containing a thermoplastic resin, the imaging surface carrying a solid crystalline plasticizer having a lower melting point than the melting range of the thermoplastic resin and heat fusing the resulting toner image.

This invention relates in general to imaging systems and, more particularly to improved electrophotographic recording members, their manufacture and use.

In the xerographic process as described in U.S. Patent 2,297,691 to C. F. Carlson, a base plate of relatively low electrical resistance such as metal having a photoconductive insulating surface coated thereon is electrostatically charged in the dark. When the charged coating is exposed to a light image, the charges in the radiated areas leak off rapidly to the base plate in proportion to the intensity of the light; the charges being retained in non-exposed areas. After such exposure, the coating is contacted with an electroscopic marking material referred to in the art as toner. The toner will normally be attracted to those areas of the photoconductive insulating surface which retain a charge, thereby forming a toner image corresponding to a latent electrostatic image. This powder may then be transferred to a receiving surface such as paper. The transferred image may subsequently be permanently affixed to the receiving surface as by heat. Alternatively, where the base plate is relatively inexpensive or where base plate expense is not a controlling factor, it may be desirable to fix the powder image directly to the photoconductive insulating surface. Several methods are known for applying electroscopic particles to the latent electrostatic image to be developed. These methods include cascade development, magnetic brush development, powder cloud development and liquid development as described in U.S. Patents 2,618,552; 2,874,063; 2,221,776; and 2,891,911 respectively. The processes mentioned above together with numerous variations are well known to the art through various patents and publications and through the wide-spread availability and utilization of electrostatic imaging equipment.

When the type of process described by Carlson above is employed, sharp reproductions can be obtained of line drawings, typewritten or printed matter, and the like. The process also has the further advantages of simplicity of apparatus required and treatment and ease of handling of the developing materials. However, the process has some inherent disadvantages which it would be desirable to eliminate. For example, in order to make a single final copy on paper it is necessary to first make a transferable copy on the photosensitiv plate. This is somewhat tedious and time-consuming where a large number of separate items are to be copied. Moreover, the photosensitive plate must be subjected to a special cleaning process to remove the intermediate print each Patented Jan. 6, 1970 ICC time, before the plate may be used again. Further, the photosensitive surface is also subject to fatigue and wear and must be repaired or replaced from time to time. It will therefore, be apparent that, where th electrophotographic plate is relatively inexpensive and only single copies of items are to be made, it may be desirable to fuse the toner image directly on an electrophotographic surface thereby eliminating the need for forming a preliminary image on an intermediate photosensitive plate, transferring this image to a final receiving surface, and then cleaning the intermediate photosensitive plate.

Several types of finely divided toner particles are disclosed in the Carlson patent. However, as the art of electrostatic copying has progressed, a variety of pigmented thermoplastic resins have evolved as the preferred toner materials when heat is employed to fuse the thermoplastic toner image to a support surface. While ordinarily capable of producing excellent quality images, these toner materials possess serious deficiencies in certain areas. When the toner is to be fused onto an inflammable surface such as paper, the toner resin should have a fusing temperature below the thermal degradation temperature of the paper. Upon heating to the discoloration temperature or flame point of some papers, resinous toners having high fusing temperatures often do not become sufficiently fluid to penetrate and adhere to the paper. The resulting powdery incompletely fused images are easily removed by rubbing. On the other hand, toner resins having low fusing temperatures are usually tacky at ordinarily encountered ambient temperatures and form undesirable agglomerates during storage and handling. Additionally, images on copies manufactured from tacky toners have a tendancy to offset onto adjacent surfaces. Thermoplastic resins having consistently uniform molecular weights are diflicult to manufacture. The molecular weight of the thermoplastic resin determines the melting point of the resin. Since thermoplastic resins are usually a mixture of polymers having different molecular weights and normally possess a non-uniform melting range rather than a sharp melting point, it is difiicult to accurately predict the temperature at which any given polymeric thermoplastic resin will fuse and adhere to a receiving sheet. Toners having erratic fusing temperatures and wide fusing temperature ranges require that the machines have a built in fusing safety factor. Since the temperature in the fuser cannot be raised above the char point of the paper, this often imposes an undesirably 10w upper limit on the speed of the paper through the fuser. Further, the fusing units currently employed to fuse conventional thermoplastic tones often cause the temperature of poorly ventilated rooms to reach levels which shorten machine component life and contribute to operator discomfort. It is known, as disclosed in U.S. Patent 3,130,064 to improve toner fusing at lower temperatures by employing business machine record cards treated with thermoplastic resins dissolved in organic solvents. Unlike a plasticizer, the thermoplastic resin apparently functions as a wetting agent with like wetting like. Although the disclosed plastic resin films may reduce toner fixing temperatures, the thermoplastic resin melting range problems described above have not been obviated. Also, more complex equipment and specially designed paper making processes are required when the thermoplastic resin films are applied with inflammable expensive toxic organic solvents. Since most thermoplastic toner particles, recording sheets, and developing processes are deficient in one or more of the above areas, there is a continuing need for better systems for fusing toner images.

It is therefore, an object of this invention to provide an electrophotographic recording member overcoming the above-noted deficiencies.

It is another object of this invention to provide an electrophotographic recording member which reduces the quantity of heat energy necessary to fuse toner images.

It is another object of this invention to provide an electrophotographic recording member which effectuates uniform and sharp toner fusion temperatures.

It is another object of this invention to provide an electrophotographic recording member which allows employment of cooler, more compact toner fusing units.

It is another object of this invention to provide an electrophotographic recording member which permits the use of higher electrophotographic imaging machine speeds.

It is another object of this invention to provide a recording member which allows the employment of high melting non-tacky toners.

It is another object of this invention to provide an electrophotographic recording member having physical and chemical properties superior to those of known recording members.

The above objects and others are accomplished, generally speaking, by providing an electrophotographic recording member treated with a solid crystalline plasticizer which effectuates complete thermoplastic toner fusion under heating conditions at which untreated electrophotographic members afford only marginal or no fusion. Crystalline plasticizers which separate rapidly from thermoplastic resins when the plasticized resin is cooled to room temperature are used because tacky images and attendant offset problems are then avoided. It is believed that separation occurs in the form of tiny islands of crystalline plasticizer particles in a matrix of toner material. Although it is not clear, it is believed that when solid crystalline plasticizers are heated above their melting point they weaken the Van der Waal forces existing in the thermoplastic toner polymers and allow slippage of the long linear polymer chains thereby promoting fluidity at lower temperatures. Experiments have revealed that some liquid plasticizers provide virtually complete toner fusion under heating conditions at which untreated electrophotographic receiving surfaces give only marginal fusion, but the resulting image is either permanently tacky or tacky for extended periods of time. Electrophotographic recording surfaces carrying tacky images plasticized with liquid plasticizers will offset toner material to adjacent toner surfaces and cause feathering of the images. Additionally, the non-imaged areas of recording surfaces treated with liquid plasticizers will at room temperature actively soften and render tacky any thermoplastic image on adjacent surfaces. A solid crystalline plasticizer having a melting point greater than about 45 C. is preferred, because premature melting and activation during storage is avoided and rapid plasticizer crystallization in toner images is promoted. To be eflective, the solid plasticizer should have a melting point below the melting range of the thermoplastic toner resin. The uniform sharp melting point characteristics of crystalline plasticizers permit the employment of cooler and more efiicient fusing units in precision electrostatic imaging machines.

Outstanding results have been obtained with ethylene glycol dibenzoate (EGDB) and blends of EGDB and diphenyl phthalate (DPP). When electrophotographic receiving members treated with EGDB are employed, the speed of existing electrophotographic copying machines have been substantially increased. Additionally, EGDB recrystallizes in seconds when cooled to room temperature. These are accordingly the preferred materials for use in the invention. Other suitable solid plasticizers may, however, be substituted for EGDB. Typical solid crystalline plasticizers include: ethylene glycol dibenzoate, dimethyl isophthalate, glycerol tribenzoate, dicyclohexyl phthalate and blends thereof.

Any suitable electrophotographic recording member may be treated with the plisticizer material of this invention. The physical shape or configuration of the photo- .4 conductive recording element may be in any form whatsoever as desired by the formulator such as flat, spherical or cylindrical. The recording element may be flexible or rigid. The treated recording elements of this invention may comprise a self-supporting photoconductive insulating layer or a base coated or impregnated with the photoconductive insulating material. The function of the base is to provide a physical support for the photoconductive insulating material and to act as a ground thereby permitting the photoconductive insulating layer to receive an electrostatic charge in the dark and permitting the charges to migrate when exposed to light. It is evident that a wide variety of materials may be employed in the base, for example, metal surfaces such as aluminum, brass, stainless steel, copper, nickel, and zinc; conductively coated glass such as tinor indium-oxide coated glass and aluminum coated glass; similar coatings on plastic substrates; or paper rendered conductive by the inclusion of a suitable chemical therein or through conditioning in a humid atmosphere to insure the presence therein of sufiicient water content to render the material conductive. To act as a ground plane as described herein, a backing material may have a surprisingly high resistivity such as 10 or 10 ohms-cm. Where the photoconductive material has suificient strength to form a self-supporting layer (pellicle), it is possible to eliminate a physical base or support member and substitute therefor any of the various arrangements well known in the art in place of the ground plane previously supplied by the base layer. A ground plane, in effect, provides a source of mobile charges of both polarities. Thus, it is obvious that if the physical ground plane is omitted, a substance therefor may be provided by simultaneously depositing on opposite sides of the photoconductive insulating ellicle electrostatic charges of opposite polarity.

The photoconductive insulating material may be employed alone or dispersed in a high electrical resistance binder. Typical photoconductive insulating material which may be used without a binder include: vitreous selenium, sulfur, anthracene, and mixtures thereof. Typical photoconductive materials which may be employed in an insulating binder include: sulfur, vitreous selenium, amorphous alpha monoclinic selenium, zinc sulfide, zinc oxide, zinc cadmium sulfide, zinc magnesium oxide, cadmium selenide, zinc silicate, calcium-strontium sulfide, cadmium sulfide, mercuric iodide, mercuric oxide, mercuric sulfide, indium trisulfide, gallium triselenide, arsenic disulfide, arsenic trisulfide, arsenic triselenide, antimony trisulfide, cadmium sulfo-selenide, doped calcogenides of zinc and cadmium (O, S, Se, Te), aluminum oxide, bismuth oxide, molybdenum oxide, lead oxide, molybdenum iodide, molybdenum selenide, molybdenum sulfide, molybdenum telluride, aluminum iodide, aluminum selenide, aluminum sulfide, aluminum telluride, bismuth iodide, bismuth selenide, bismuth sulfide, bismuth telluride, cadmium telluride, mercuric selenide, mercuric telluride, lead iodide, lead selenide, lead sulfide, lead telluride, cadmium arsenide, lead chromate, gallium sulfide, gallium telluride, indium sulfide, indium selenide, indium telluride, red lead (Pb O triphenyl amine,

2,4-bis (4,4-diethyl-aminophenyl) -1 ,3,4-oxadiazol,

N-isopropylcarb azol triphenylpyrrol,

4,5 -dip'henylimidazolidine,

4,5 -diphenylimidazolidinethione,

4,5-bis 4-amino-phenyl) -imidazolidinone,

1 ,5 -cyanonaphthalene,

1,4-dicyanonaphthalene,

amino phthalodiuitrile,

nitrophthalidinitrile,

1,2,5 ,6-tetraazacyclooctatetraene- (2,4,6,8

3,4-di-(4'-methoxy-phenyl -7,8-dipheny1- l,2,5,6-

tetraazocyclooctatetraene- (2,4,6,8

3,4-di- 4'-phenoxy-phenyl -7,8-diphenyl-1,2,5 ,6-

tetraaza-cyclo-octatetraene- (2,4,6,8

3,4,7,8-tetramethoxy-1,2,5,-6-tetraaza-cyclooctatetraene- 2-mercapto-benzthiazole,

2-phenyl-4-alpha-naphthylidene-oxazolone,

2-phenyl-4-diphenylidene-oxazol0ne,

2-phenyl-4-p-methoxybenzylidene-oxazolone,

6-hydroxy-2-phenyl-3- (p-dimethylamino phenyl) benzofurane,

6-hydroxy-2,3-di(p-methoxyphenyl) benzofurane,

2,3,5 ,6-tetra-(p-methoxyphenyl) -furo- 3,2

benzofurane,

4-dimethylamino-benzylidene-benzhydrazide,

4-dimethylaminobenzylideneisonicotinic acid hydrazide.

furfurylidene- (2) -4-dimethylamino-benzhydrazide,

S-benzilidene-amino-acenaphthene,

3-benzylidene-amino-carb azole,

(4-N,N-dimethyl aminobenzylidene) -p-N,N-

dimethylaminoaniline,

(2-nitro benzylidene) -p-bromo-aniline,

N,N-dimethyl-N'- Z-nitro-4-cyano-benzylidene) -pphenylene-diamine,

2,4-diphenyl-quinazo1ine,

2- 4-amino-phenyl -4-phenyl-quinazoline,

2-phenyl-4- 4'-dimethyl-amino-phenyl -7-methoxyquinazoline,

1,3-diphenyl-tetrahydroirnidazole,

1,3-di- (4-chlorophenyl) -tetrahydroimidazole,

1,3-diphenyl-2-4'-dimethyl amino pbenyl) -tetrahydroimidazole,

1,3-di- (p-tolyl) -2- [quinolyl- (2-) ]-tetrahydroimidazole,

3- (4-dimethylamino-phenyl) -5- (4"-methoxy-phenyl) 6-phenyl-1,2,4-triazine,

S-pyridyl- (4' -5- (4"-dimethylamino-phenyl) -6-phenyl- 1,2,4-triazine,

3-(4-amino-phenyl)-5,6-diphenyl-1,2,4-triazine,

2, S-bis- [4-amino-phenyl- 1) ]-3,4-triazole,

2,5 -bis- [4'-N-ethyl-N-acetylamino-phenyl- 1) 1,3,4-triazole,

1,5-dipheny1-3-methy1pyrazoline,

1,3 ,4,5-tetraphenyl-pyrazoline,

1-p'henyl-3- (p-methoxy styryl -5- (p-methoxy-phenyl pyrazoline,

1-methy1-2-(3,4'-dihydroxy-methylene-phenyl)- benzimidazole,

2- (4-dirnethylamino phenyl -benzoxazole,

2-(4'-methoxyphenyl -benzthiazole,

2,5-bis-[p-aminophenyl-(1) -1,3,4-oxadiazole,

4,5 -diphenyl-imidazolone,

3-aminocarbazole,

and mixtures thereof.

Any suitable high resistance binder may be employed to suspend the photoconductive material. A film-forming binder material having a relatively high dielectric constant and high dielectric strain is preferred. Typical film-forming materials include: polyolefins such as polyethylene, polypropylene and chlorinated polyethylene; vinyl and vinylidene resins such as polystyrene, polyvinyl pyrrolidone, acrylic polymers, polyvinyl acetate, polyvinyl butyral, and polyvinyl chloride; fluorocarbons such as polytetrafluoroethylene and polychlorotrifluoroethylene; styrene-butadiene, heterochain thermoplastics such as polyamides, polyesters, and polycarbonates; phenolic resins such as phenol-formaldehyde and resorcinol-formaldehyde; melamineformaldehyde resins such as metholyl melamine resins, dimethyl trimethylol melamine resins, and trimethylol melamine resins; silicone resins; epoxy resins; and mixtures thereof. Any suitable additives such as emulsifiers, wetting agents, pH regulators, brightening agents and stabilizers may be admixed with the film-forming binder.

The solid crystalline plasticizers of this invention may be added to the electrophotographic recording element in any suitable manner, e.g., as a component in the electrophotographic insulating layer or as a component in a coating over the photoconductive insulating layer. If the recording element contains a thermoplastic resin, it may be desirable to select a plasticizer which does not plasticize and distort the receiving surface. Conversely, distortion of the electrophotographic recording surface may be deliberately induced to achieve a desired decorative or other effect. The plasticizer composition may be applied to the electrophotographic recording material by any conventional method such as spraying, dipping, fluidized bed coating, brushing, roll coating, or mixing. Further, the plasticizer may be added to the recording material in any suitable manner prior to, during, or subsequent to the manufacture of the recording member. For example, the plasticizer may be applied alone or in combination with other materials as a powder, dispersion, solution, vapor, emulsion or melt to the electrophotographic material during or after the electrophotographic member manufacturing process. Although the plasticizer may be applied to the recording element as a loose powder, optimum results have been obtained when the plasticizer is immovably attached to the recording member by means of a binder. The employment of a binder and plasticizer combination eliminates the problem of dust contamination. The recording member may comprise a binder in the electrophotographic insulating layer, a binder in a coating overlying the photoconductive insulating layer or a binder in both the insulating layer and overcoating. Any suitable binder may be employed to immovably attach the solid plasticizer to the electrophotographic recording member. The binders employed to suspend photoconductive material may also be used with the plasticizer of this invention in a coating overlying the photoconductive insulating layer. Other binders which may be employed to attach the plasticizer to the recording member include carbohydrate derivatives, e.g., acetylated starch and carboxymethyl cellulose, natural resins and mixtures thereof. Surprisingly, toner images formed on electrophotographic recording surfaces treated with a binder and plasticizer mixture are more dense than toner images formed on untreated electrophotographic recording surfaces. Surface coatings containing at least about 0.4 pound of plasticizer per 1300 square feet will markedly reduce toner fusion power requirements although smaller or larger amounts may also have some effect. It is preferred that the binder content remain below about 40 percent, based on the weight of the plasticizer, as this provides much more eflicient fusing apparently because more plasticizer is available at the surface where the toner is to be fused to the receiving member. When the plasticizer is incorporated into the photoconductive insulating layer, proportionately more plasticizer is necessary in order to maintain a sutficient quantity of plasticizer at the surface of the paper sheet. Obviously, where the recording element carries a photoconductive layer on each side for two-sided development, both layers may be treated with the plasticizers of this invention.

Electroscopic toner compositions are well known to those skilled in the art. Among the patents describing such compositions are US. 2,618,551 to Walkup, US. 2,618,- 552 to Wise, US. 2,638,415 to Walkup and Wise, and US. 2,788,288 to Rheinfrank and Jones. Clearly, the plasticizer treated recording members should be used with those thermoplastic resin toners which will be plasticized by the specific plasticizer employed in the recording member. Selection of compatible combinations of solid crystalline plastcizer and thermoplastic resin toner will be obvious to those skilled in the art. Blends of two or more plasticizers may be used to broaden the toner spectrum of the recording member. Typical thermoplastic resins include: acrylic resins, methacrylic resins, cellulose acetate, cellulose nitrate, polystyrene, polyethylene, polypropylene, polycarbonate, modified phenolformaldehyde resins or mixtures thereof. When the thermoplastic toner mixtures are intended for use in cascade or magnetic brush development processes, it is preferred that the toner have a particle diameter less than about 30 microns. For employment in powder cloud development process particle diameters of slightly less than 1 micron are preferred.

The following examples further define, describe and compare methods of preparing the recording member of the present invention and of utilizing them as substrates for electrostatic latent images. Parts and percentages are by weight unless otherwise indicated. In the following, Examples I through XII are carried out with a toner comprising a styrene and n-butyl-methacrylate copolymer, polyvinyl butyral, and carbon black prepared by the method disclosed by M. A. Insalaco in Example I of US. Patent 3,079,342 and substantially identical electrophotographic recording members comprising paper sheets coated with a zinc oxide-melamine formaldehyde photoconductive insulating layer. The treated recording members in Examples VI through XI carry on the photoconductive insulating layer side a surface coating of a plasticizer mixture applied as an aqueous dispersion by means of a smooth metal reverse roll in a Dietzco Dixon Pilot Coater followed by doctoring with a reverse rotating No. 4 wire-wound rod and finally dried by heated air. After development, the electrophotographically imaged recording members in Example I are passed at selected speeds under a tungsten filament heating unit with a variable power input.

EXAMPLES I-III Three zinc oxide electrophotographic recording sheets are treated as described above with the following composition:

Ethylene glycol dibenzoate 648.0 Polyvinyl pyrrolidone (Type K-30, a filmformer) 8.6 Sodium salt of processed rosin (Dresinate X, an

emulisifier 4.3 Butadiene-styrene latex (Dow 636, a filmformer) 204.0 Distilled water 1,652.0

and air-dried. The treated recording members are then charged, exposed to a light image, developed with toner, and fixed with heat. The fusing power in watts seconds/in. required to obtain equivalent fusion with untreated recording sheets is determined by comparing toner rub off from a treated recording sheet with a standardized rub off series obtained with untreated recording sheets. The images on untreated and treated recording sheets are deemed equivalent when the quantity of rub off from each is identical. The toner material is rubbed off b drawing a two-inch square cloth (Crockmeter Square, T tFabrics, Inc.) weighted with a 500 gram balance weight across and along an 11 inch length of the imaged sheet. For comparative evaluations a power index value is assigned to the fusing conditions employed. The power index value is computed as follows:

Watt-sec. in.

Power Input, (watts) VX Transport Speed, (in. /sec.)

paper width (in.)

Power Index,

Fusing power input Fusing power input Percent for plasticizer for untreated reduction treated electroeleetrophotoin fusing photographic paper graphic paper power Example (watt-sem/m?) (watt-seo/infi) input In Examples IV-VIII, the imaged recording members are passed at selected speeds under a flat plate heating unit operated with a fixed power input. For comparative evaluations a power index value is assigned to the 8 fusing conditions employed. The power index value is computed as follows:

Watt-see.

Power Input, (watts) VX Transport Speed, (in. leec.)

paper width (in.)

Power Index,

Tack and the degree of powder rub-off of the fused images onto cotton are also compared.

EXAMPLE IV A control group consisting of untreated zinc oxide electrophotographic paper sheets is impaged with styrene copolymer toner particles and subjected to a heat fusing treatment. A power index of 50 watt-sec./in. is employed. The resulting toner images are fused and non-tacky.

EXAMPLE V A control group consisting of untreated Zinc oxide electrophotographic paper sheets is imaged with styrene copolymer toner particles and subjected to a heat fusing treatment. A power index of 25 watt-sec./in. is employed. The resulting toner images are poorly fused and easily removed when rubbed with cotton wads.

EXAMPLE VI Zinc oxide electrophotographic paper identical with that of Examples IV and V is coated with a plasticizer composition comprising:

Ethylene glycol dibenzoate 27.90 Sodium salt of processed rosin (Dresinate X, an

emulsifier) .19 Polyvinyl pyrrolidone (Type K-30, a filmformer) 15.40 Distilled water 51.50

and air-dried. The coated and dried recording member is then imaged with styrene copolymer toner particles and subjected to a heat fusing treatment in which a power index of 13 watt-sec./in. is employed. The resulting toner image is fused, non-tacky and does not rub off onto cotton.

EXAMPLE VII Zinc oxide electrophotographic paper identical to that of Examples IV and V is coated with a plasticizer composition comprising:

and air-dried. The coated and dried recording sheet is then imaged with styrene copolymer toner particles and subjected to a heat fusing treatment at which a power index of 22.5 watt-sec./in. is employed. The resulting toner image is dense, fused, non-tacky and does not rub off onto cotton.

EXAMPLE VIII Zinc oxide electrophotographic paper identical to that of Examples IV and V is coated with a plasticizer composition comprising:

Ethylene glycol dibenzoate 27.90 Sodium salt of processed rosin (Dresinate X, an

emulsifier) .19 Polyvinyl pyrrolidone (Type K-30, a filmformer) .37 Styrene-butadiene latex (Dow 636, a filmformer) 6.50 Distilled water 51.50

and air-dried. The coated and dried recording member is then imaged with styrene copolymer toner particles and subjected to a heat fusing treatment in which a power 9 index of 12.5 watt-sec./in. is employed. The resulting toner image is fused, non-tacky and does not rub off onto cotton.

EXAMPLE IX Zinc oxide electrophotographic paper identical to that of Examples IV and V is coated with a plasticizer composition comprising:

Diphenyl phthalate 3.50 Ethylene glycol dibenzoate 25.40 Sodium salt of processed rosin (Dresinate X, an

emulsifier) .17 Polyvinyl pyrrolidone (PVP Type K30, a film former) .34 Distilled water 49.20

and air-dried. The coated and dried recording member is then imaged with styrene copolymer toner particles and subjected to a heat fusing treatment in which a power index of 11.5 watt-sec./in. is employed. The resulting toner image is fused non-tacky and does not rub off onto cotton.

EXAMPLE X Zinc oxide electrophotographic paper identical to that of Examples IV and V is coated with a plasticizer composition comprising:

Dimethyl isophthalate 40.20 Sodium salt of processed rosin (Dresinate X, an

emulsifier) .27 Polyvinyl pyrrolidone (Type K-30, a filmformer) .55 Styrene butadiene latex (Dow 636, a filmformer) 51.00 Distilled water 39.00

and air-dried. The coated and dried recording sheet is then imaged with styrene copolymer toner particles and subjected to a heat fusing temperature in which a power index of 27.6 watt-sec./in. is employed. The resulting toner is fused, non-tacky and does not rub off onto cotton.

EXAMPLE XI Zinc oxide electrophotographic paper identical to that of Examples IV and V is coated with a plasticizer composition comprising:

Dicyclohexyl phthalate 40.00 Sodium salt of processed rosin (Dresinate X, an

emulsifier) .27 Polyvinyl pyrrolidone (Type K-30, a filmformer) .53 Distilled water 39.20

and air-dried. The coated and dried recording sheet is then imaged with styrene copolymer toner particles and subjected to a heat fusing treatment in which a power index of 13.3 watt-sec./in. is employed. The resulting image is fused, slightly tackey and does not rub oil? on cotton.

EXAMPLE XII Zinc oxide electrophotographic paper is coated with cresyl diphenyl phosphate, a liquid plasticizer, by spraying the side of the sheet carrying the photoconductive insulating layer with a methyl alcohol solution containing about 9% by weight of the plasticizer. Thereafter, the alcohol solvent is driven off and the resulting treated recording sheet is imaged with styrene copolymer toner particles. The imaged recording sheet is then heated on the backside with a bar type heater for 5 seconds at C. The toner image is completely fused under these heating conditions. With untreated paper, the same heating conditions provide only marginal fusion of the toner image. However, upon aging, the paper treated with the liquid plasticizer is found to offset toner to adjacent sheets and cause feathering of ink images.

EXAMPLE XIV Zinc oxide electrophotographic paper is coated with ethyl phthalyl ethyl glycolate, a liquid plasticizer, by spraying the side of the sheet carrying the photoconductive insulating coating with a methyl alcohol solution containing about 10% by weight of a plasticizer. Thereafter, the alcohol solvent is driven off and the resulting dry recording member is imaged with styrene copolymer toner particles. The imaged recording sheet is then heated on the backside with a bar type heater for 5 seconds at 125 C. The toner image is completely fused under these conditions. With untreated paper, the same heating conditions provide only marginal fusion of the toner image. However, upon aging, the paper treated with the liquid plasticizer is found to offset toner to adjacent sheets and cause feathering of ink images.

EXAMPLE XV A rosin-modified phenol-formaldehyde resin toner prepared in the manner disclosed in Example I of U.S. Patent 2,573,308 is imaged onto a zinc oxide recording member treated with the ethylene glycol dibenzoate composition of Example V above and onto untreated zinc oxide paper. Upon heating between two parallel heating plates spaced one inch apart, the toner fuses more rapidly on the treated recording sheet than on the untreated recording sheets under substantially identical heating conditions.

EXAMPLE XVI Five hundred and eighty parts of zinc oxide and 975 parts ethylene glycol dibenzoate are mixed with a solution of parts dimethyl trimethylol melamine dis solved in 960 parts water. The zinc oxide dispersion is then coated on a brass sheet to a thickness of 0.004 in. The coated brass is heated to a temperature of about 245 F. for about 5 minutes to cure the resin. A rosin-modified phenol formaldehyde resin toner prepared in the manner disclosed in Example I in U.S. Patent 2,753,308 is imaged onto the treated recording member. Upon heating between two parallel heating plates, spaced one inch apart, the toner fuses more rapidly on the treated than on untreated paper under substantially identical heating conditions.

Although specific materials and conditions are set forth in the foregoing examples, these are merely intended as illustrations of the present invention. Various other suitable thermoplastic resin toners, electrophotographic recording members, plasticizers, binders and coating processes such as those listed above may be substituted for those in the example with similar results. Other materials may also be added to the base, photoconductive insulating layer, plasticizer, hinder or toner to subsidize, synergize or otherwise improve the resistivity, photosensitivity, fusing or other desirable properties of the system.

Other modifications of the present invention will occur to those skilled in the art upon a reading of the present disclosure. These are intended to be included within the scope of this invention.

What is claimed is:

1. An electrophotographic recording member comprising a photoconductive insulating element and available on at least one external surface thereof a composition consisting essentially of a solid crystalline plasticizer and up to a maximum of about 40% by weight,

11 based on the Weight of said solid crystalline plasticizer, of a binder.

2. An electrophotographic recording member according to claim 1 wherein said composition contains at least about 0.4 pound of said solid crystalline plasticizer per 1300 square feet of said external surface.

3. An electrophotographic recording member according to claim 1 wherein said crystalline plasticizer possesses a melting point of at least about 45 C.

4. An electrophotographic recording member according to claim 1 wherein said photoconductive insulating element is supported by a paper Web. i

5. An electrophotographic recording member according to claim 1 wherein said crystalline plasticizer is im movably attached to at least said external surface of said photoconductive insulating element.

6. An electrophotographic recording memberaccording to claim 1 wherein said binder comprises a styrenebutadiene resin copolymer. Y

7. An electro-photographic recording member according to claim 1 wherein said solid crystalline plasticizer comprises ethylene glycol dibenzoate. Y

8. An electrophotographic recording member according to claim 7 wherein said ethylene glycol dibenzoate is blended with diphenyl phthalate.

9. An electrophotographic recording member according to claim 1 wherein said solid crystalline plasticizer comprises dimethyl isophthalate.

10. An imaging process comprising the steps of forming an electrostatic latent image on an imaging surface of an electrophotographic recording member, forming a toner image by contacting said electrostatic latent image with fusible finely divided toner particles comprising a thermoplastic resin having a melting range whereby said particles are attracted to and held on said imaging surface in conformance to said electrostatic latent image, said imaging surface carrying a composition on sisting essentially of a solid crystalline plasticizer for said resin and up to a maximum of about 40 percent by weight, based on the weight of said solid crystalline plasticizer, of a binder, said crystalline plasticizer having a lower melting point than said melting range of said thermoplastic resin whereby the time and temperature necessary to fuse said toner image on said imaging surface carrying said solid crystalline plasticizer is less than the time and temperature necessary to fuse said toner image alone and heat fusing saidtoner image to form a fused toner image.

11. An imaging process according to claim 10 wherein at least about 0.4 pound per 1300 square feetof said solid crystalline plasticizer is available at said imaging surface.

12. An imaging process according to claim 10 wherein said plasticizer possesses a melting point of at least about 45 C.

13. An imaging process according to claim 10 wherein said electrophotographic recordingmember comprises a photoconductive insulating layer supported by a paper web. l

14. An imaging process according to claim 10 wherein said solid crystalline plasticizer is immovably attached to said imaging surface by means of said binder;

15. An imaging process according to claim 14 wherein said binder comprises a styrene-butadiene resin copolymer.

16. An imaging process according to claim 10 wherein said solid crystalline plasticizer is ethylene glycol dibenzoate.

17. An imaging process according toclaim 16 wherein said ethylene glycol dibenzoate is blended with diphenyl phthalate.

18. An imaging process according to claim 10 wherein said solid ,crystatlline plasticizerisdimethyl isophthalate.

19. An imaging process according to claim 10 further including cooling saidvtoner image after said heat fusing step below the recrystallization point of said plasticizer. 20. An imaging process comprising'the steps of forming an electrostatic latent image on an imaging surface of an electrophotographic recording member, forming a toner image by contacting said electrostatic latent image with fusible finely divided toner particles comprising a thermoplastic resin having a melting range whereby said particles are attracted to and held on said imaging surfacein conformance to said electrostatic latent image, said imaging surface carrying a composition consisting essentially of a solid crystalline plasticizer for said resin and up to a maximum of'about' 40 percent by weight, based on the weight of said solid crystallineplasticizer, of a bindner, said crystalline plasticizer having a lower melting point than said melting range of said thermoplastic resin whereby the time and temperature necessary to fuse said toner image on said imaging surface carrying said solid crystalline'plasticizer is less than the time and temperature necessary to fuse said toner image alone and heat fusing said toner image for a time and temperature insu'fiicient-to fuse said toner image alone but sufficient' to fuse said toner image on said imaging surface carrying said solid crystalline plasticizer.

References Cited UNITED STATES PATENTS 3,155,503 11/1964 Cassiers 96-1 OTHER REFERENCES Condensed Chemical Dictionary, Reinhold 1961, pp. 1174, triphenyl phosphate; 902, plasticizers; 396, dimethyl isophthalate; 408, diphenyl phthalate; 467, ethylene glycol derivative.

' US. 01. X.R.

2% UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 488 189 Dated January 6 1970 Inventor(s) Edward F. Mayer and Carlton J. Baxter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the specification; column 2, line 51, "tones" should read toners-. Column 3, line 74, "plisticizer" should read plasticizer- Column 9, line 61, after "loose" and before "comprising" insert --powder-. Column 12 line 14 "crystatlline" should read crystalline-. Column 12, line 30, bindner" should read binder-.

SIGNED AND SEALED JUL 2 -1970 SEAL Attest:

Edward M. Fletcher, Ir. WILLIAM E mm a. Au fi Qffi omissioner of mi.