Classifications

• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/14—Inert intermediate or cover layers for charge-receiving layers
  • G03G5/142—Inert intermediate layers
• • G—PHYSICS
  • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
  • G03G—ELECTROGRAPHY; ELECTROPHOTOGRAPHY; MAGNETOGRAPHY
  • G03G5/00—Recording members for original recording by exposure, e.g. to light, to heat, to electrons; Manufacture thereof; Selection of materials therefor
  • G03G5/02—Charge-receiving layers
  • G03G5/04—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor
  • G03G5/05—Organic bonding materials; Methods for coating a substrate with a photoconductive layer; Inert supplements for use in photoconductive layers
  • G03G5/0503—Inert supplements
  • G03G5/0507—Inorganic compounds

Definitions

• ABSTRACT A photoelectrostatic copy sheet is prepared by using a paper base sheet having a roughness in the range of from 100 to 250 Sheffield units. Bonded to the rough surfaced paper is a photoconductivelayer comprising zinc oxide and in another embodiment sub-millimicron sized particles of hydrophobic silica dispersed in a resin binder. The layer conforms to the rough fiber textured surface of the base sheet to provide a finished recording surface having a roughness in the range of from 70 to 250 Sheffield units and a gloss (75, Gardner) not in excess of 20 percent. This sheet has the appearance, feel and handle of an uncoated piece of paper.
• This invention relates generally to an improved photoelectrostatic recording member and, more particularly, to a novel copy sheet which, despite being coated, has the general appearance, feel and handle of ordinary, uncoated bond paper.
• Known photoelectrostatic recording members comprise a conductive base or substrate, ordinarily paper, and a photoconductive layer bonded to and supported by the substrate.
• the layer is a resinous substance having dispersed therein finely divided particles of photoconductive material, such as zinc oxide.
• Such members are imaged in accordance with the well known photoelectrostatic copying process, and developed using a pigmented thermoplastic powder that is attracted to the image areas and fixed to the recording surface of the sheet.
• the resin material is dissolved in an organic solvent medium, principally toluene, with photoconductive particles of zinc oxide being mixed with this liquid medium until a paint-like consistency is achieved.
• This mixture is applied as a coating to a paper base, and the solvent medium is then evaporated leaving a thin, homogeneous, photoconductive layer bonded to the support surface of the paper base.
• known photoelectrostatic copy papers have a smooth recording surface which does not readily receive pencil markings or the like and tends to be glossy, reflecting illumination in a mirror-like fashion to produce glare.
• care is taken to insure against producing a rough recording surface, since it has heretofore been considered important to have maximum recording surface smoothness in order to avoid mechanical entrapment of the developer powder in the background or non-imaged areas of the sheet.
• known recording members although having a surface which does not tend to entrap developer powder, provide a surface that is somewhat difficult to read and is a poor medium on which to write with pen or pencil.
• a recording surface can have a limited degree of roughness and need not be as smooth as heretofore considered necessary for high quality copy.
• a recording surface having a roughness in the range of from about 70 to 250 Sheffield units and a gloss (75, Gardner) of less than 20 percent provides a finish which does not entrap developer material and has an uncoated and substantially glare-free appearance.
• a sheet of this type can readily be converted into a lithographic master that produces excellent prints. Sheets having rough surfaces ordinarily do not function well as lithographic masters. Recording surfaces which have a roughness in the range of to Shefiield units provide even better results.
• the first technique calls for applying a zinc oxide resin binder coating to a paper base having a critical support surface roughness in the range of from 100 to 250 Sheffield Units.
• the resinous coating upon distributing itself over the rough support surface in conformity with the contours of the fibrous structure of the base provides a recording surface which has the same or substantially the same degree of roughness as the support surface.
• a recording surface is formed which is sufficiently smooth to avoid mechanical entrapment of the developer powder, but has numerous irregularities acting to scatter or diffuse incident light rather than reflect the light in an orientated or mirror-like fashion. Resins which enhance or re-enforce the surface effect of light scattering are preferred.
• the thickness of the photoconductive layer lies within the range of from 0.1 to 0.5 mil, and is preferably within the range of from 0.2 to 0.4 mil. Microscopic examination of the recording surface reveals that a layer of this thickness conforms substantially to the fiber texture of the base.
• the second technique calls for dispersing in the resin binder, in addition to the zinc oxide, particles of hydrophobic silica.
• a coating containing this type of silica forms a recording surface which has a roughness of about 100 Sheffield units.
• silica/zinc oxide/binder coatings are applied to a base sheet having a roughness in the range of from 100 to 250 Sheffield units.
• silica to a photoconductive coating interferes with the photoconductive properties of the sheet.
• hydrophobic silica is added to the photoconductive coating in small amounts, usually not more than 5 percent by weight of the zinc oxide, the photoconductive properties of the copy sheet are not impaired, and, surprisingly, print density is generally improved.
• the preferred amount of silica is from 0.2 percent to 1.5 percent by weight of the zinc oxide. If the resin binder comprises from about 0.1 percent to 10 percent by weight of a silicone resin, and silica is incorporated into the coating, the surface roughness of the copy sheet is further enhanced.
• the addition of a small amount of a silicone resin to the binder also improves the performance of the sheet at high humidity conditions.
• a preferred hydrophobic silica is sold by the Pigments Division of the Degussa Corporation of New Jersey under the trade name Aerosil R972.
• This silica has a very fine particle size of approximately 0.20 millimicrons.
• Treatment of raw silica with an oil or the like in accordance with standard processing techniques imparts to the R972 silica a hydrophobic character.
• This type of silica does not interfere with the photoconductive properties of the copy sheet is not clearly understood. However, it is believed that because water is not absorbed by this type of silica, the coating will remain free of this aqueous contamination which interferes with the electrical properties of the sheet.
• the silica must have a hydrophobic character. This is critical. It is believed that the small particle size may be important, however, particle size does not seem to be per se critical.
• an uncalender paper base having a relatively low basis weight and high degree of stiffness is employed. Using such a base having the proper support surface roughness, a
• copy sheet is provided which handles like ordinary paper.
• a solvent holdout precoat Before the base sheet is coated the support surface is usually treated'with a solvent holdout precoat, care being taken to insure that the critical roughness of the support surface is kept intact.
• suitable precoat materials are: polyvinyl alcohol, starch, casein, animal glue, carboxymethyl cellulose, methyl cellulose, styrenebutadiene latex, acrylic latex, polytetratluoroethylene and algin.
• the polyvinyl alcohol has been found to be especially well suited for this purpose.
• the effectiveness of the barrier coating holdout may be tested in accordance with conventional techniques using an I.G.T. printability tester which is manufactured by the Institute of Graphic Techniques, Amsterdam Holland.
• the I.G.T. tester consists of a pendulum having a sector to which a test specimen is clamped, and a printing disc.
• a test dye solution applied to the test specimen by means of the printing disc, is used to stain the specimen.
• the solution comprises a blend of the binder resin, toluene, and lrisol dye (General Aniline and Film Corporation).
• the viscosity of this solution is about 14.5 seconds when measuredat 74 F. using a No. 2 Zahn Cup.
• a drop (0.005 cc.) of the solution is applied to the disc and the pendulum is permitted to swing freely.
• the dye solution is spread over the test specimen staining it. The longer the stain on the specimen, the better the holdout. Test results indicate that the length of the stain must exceed 60 mm. and preferably should exceed 100 mm.
• the photoconductive coating which is applied to the substrate is prepared in accordance with standard techniques.
• the resin, silica and zinc oxide are blended together in an organic solvent medium and applied to the support surface using conventional coating equipment. As the solvent is evaporated, the resinous coating conforms to the fibrous support surface to form a rough, irregular layer.
• the coating weight and weight of the base are controlled in order to keep the weight of the copy sheet in the preferred range of to 25 lbs. per ream 17 inches X 22 inches 500 sheets).
• resins are available, the preferred resins being: multipolymers containing vinyl acetate as the major monomeric component, polyvinyl acetate resins, polyester resins, copolymers of vinyl chloride-vinyl acetate, phenoxy resins, acrylic resins styrenated acrylic copolymers and copolymers of styrene-butadiene. It has been found that resins containing a polyvinyl acetate component as the major polymeric constituent of the resin are particularly well suited for the purposes of this invention, since they tend to dry to a dull finish, more so than the other resins.
• the first type of member comprises a light weight, stifi, precoated paper base having a rough support surface, and bonded to the support surface a thin, solvent laid photoconductive layer which conforms to the rough support surface.
• the roughness of the fiber textured support surface is within the range of from about to 250 Sheffield units, preferably in the range of from to I75 Sheffield units.
• the photoconductive layer comprises. finely divided particles of zinc oxide dispersed in an insulating resin binder. This layer on confonning to the support surface provides a recording surface having a roughness in the range of from 70 to 250 Sheffield units.
• the second type of member comprises a light weight, stiff, precoated paper base having either a smooth or, preferably a rough support surface, and bonded to the support surface a thin, solvent laid zinc oxide/resin binder photoconductive layer containing submillimicron size particles of hydrophobic silica.
• the photoconductive layer formed on a relatively smooth base has a rough character and low gloss (75, Gardner), i.e., less than 10 percent.
• a copy sheet which greatly resembles ordinary uncoated paper in general appearance, the ability to accept pencil markings, and reading quality.
• an aqueous solution of polyvinyl alcohol is applied to the support surface of the base.
• a suitable polyvinyl alcohol is sold by the DuPont de Nemours & Co., Inc. under the tradename ELVANOL 5105.
• the base is then dried by slowly passing it through an oven maintained at a temperature of 200 F.
• the preferred barrier coating weight is in the range of from 0.3 to 0.6 lb. per 3,000 square feet, with the optimum barrier coat being 0.5 lb. per 3,000 square feet.
• Such a thin coating has sufficient solvent holdout strength to prevent the penetration of the solvent and resin into the base. Since the barrier layer is thin, the rough, fibrous character of the support surface remains intact and is not masked or otherwise materially altered.
• the resins, pigments and solvents are milled together for about 1 hour to thoroughly disperse the pigment particles in the resin, insuring a uniform consistency.
• the paint-like resinous blend is applied to the pretreated base support surface.
• the solvent is volatilized at a temperature of about 115 F. leaving on the support surface of the base a dried photoconductive layer about 0.3 mil thick which weighs about 15 lbs. per 3,000 square feet.
• the photoconductive layer has a paper-like finish and the copy sheet is light, weighing 19 lbs. per ream (17 inches X 22 inches 500). This sheet has excellent photoconductive properties and provides a very dense image on being developed.
• EXAMPLE III This example differs from Example I in the substitution of a different type of polyvinyl acetate copolymer, Resyn 26-1404, manufactured by National Starch, for resin 78-3306.
• the weights, mixing procedures and coating techniques are substantially the same as in Example II.
• EXAMPLE IV This example differs from Example II in the substitution of a polyvinyl acetate terpolymer, 5 912 A manufactured by Midland Industrial Finishing Company of Waukegan, Illinois,
• EXAMPLE V This example differs from Example I in the substitution of a polyvinyl acetate, Vinac B-l00, manufactured by Air Reduc tion Chemical and Carbide Company of New York for resin 78-3306. Pure methyl ethyl ketone is used in place of toluene as the solvent medium.
• EXAMPLE VI This example differs from Example II in the substitution of a polyvinyl acetate Daratak 9228, manufactured by Dewey and Almy Company of Cambridge, Massachusetts, for resin 78- 3306.
• the weights mixing procedures and coating techniques are substantially the same as in Example ll.
• Example II The resin, pigments and solvents are blended together as described in Example I and applied in the same manner to the pretreated paper substrate having a roughness in the range of from to 250 Sheffield units.
• the recording member of this example upon being developed, has very good image density.
• EXAMPLE VIII This example differs from Example VII in the of a different acrylic resin, Bakelite 150, manufactured by the Union Carbide Corporation for resin AT-56.
• Example I Materials were blended together as in Example I and applied to the rough support surface of the paper base described in Example I.
• EXAMPLE XI This example differs from Example I in the substitution of a, styrene-butadiene copolymer, Pliolite CPR 1141A, manufac-; tured by the Goodyear Company, for the polyvinyl acetate copolymer resin. 78-3306. i
• EXAMPLE XII This example difiers from Example I in the substitution of vinyl chloride-vinyl acetate copolymer, VAGH resin, manufactured by the Union Carbide Company for the polyvinyl. acetate copolymer resin, 78-3306. 1
• an aqueous solution including polyvinyl alcohol is applied to the support surface of the base.
• the base is then dried by slowly passing it through an oven maintained at a temperature of about 200 F.
• the preferred barrier coating weight is in the range of from 3.0 to 5.0 lbs. per 3,000 square feet.
• Example II The resin, pigment, etc., are milled together as described in Example I and applied to the precoated paper base which has a roughness of 159 Sheffield units, resulting in a recording surface having a roughness of 79 Sheffield units.
• This sheet has excellent photoconductive properties and provides copies with excellent contrast and print density.
• the following table lists the physical properties of the novel copy paper prepared in accordance with Examples 1, I1 and X11! standard bond paper and a typical prior art copy paper.
• This table serving as a basis for comparison, illustrates the marked improvement in paper-like appearance and feel exhibited by the copy paper of this invention as compared to the like properties of the prior art material.
• the results of Exam-3 The values in Table II were obtained using well known standard test procedures with all samples being conditioned at 72 F. and 50 percent relative humidity. All roughness measurements were made using a Sheffield Smoothness Tester manufactured by the Sheffield Company of Dayton, Ohio, a division of the Bendix Corporation.
• the smoothness and gloss values set forth hereinabove impart to the copy paper of this invention properties, such as a bond-like appearance and feel, similar to those of the standard bond paper.
• the relatively low gloss value of lack of glare also indicates that the sheet is of a good reading quality.
• the basis weight, caliper, and pencil take of the copy paper of this invention correspond to like properties in the standard bond sheet.
• the ratio of caliper to basis weight gives an indication of the bulkness of the sheet. As seen from Table II the sheet of this invention having a bulk even greater than that of bond paper is far superior to the prior art material. And, although the sheet of this invention is relatively light weight, it still has the same or substantially the same degree of stiffness as that of the bond paper.
• a photoelectrostatic recording member having improved visual readability properties comprising:
• said resin binder is a mixture of at least two resins, one of said resins having vinyl acetate as the major monomeric component and the other resin being a silicone resin, said mixture comprising no more than 10 percent by weight of the silicone resin.
• a photoelectrostatic recording member having improved visual readability properties comprising:
• silica particles being present in an amount not exceeding about percent by weight of the zinc oxide, and having the following physical characteristics:
• said resin binder is selected from the group consisting of multipolymers containing vinyl acetate as the major monomeric component, polyvinyl acetate resin, polyester resin, copolymers of vinyl chloride-vinyl acetate, a phenoxy resin, acrylic resin, and copolymers of styrene-butadiene.
• a photoelectrostatic recording member having improved visual readability properties comprising:
• a photoconductive layer covering and bonded to said base support comprising an organic laid coating a finely divided photoconductive zinc oxide and sub-millimicron sized hydrophobic silica particles dispersed in an insulating resin binder containing from 0.1 percent to 10 percent by weight of a silicone resin, and having the following physical characteristics:
• a photoelectrostatic recording member having improved visual readability properties comprising:
• a barrier coating applied to said base support providing a solvent holdout in excess of 60 mm;
• a photoconductive layer covering and bonded to said said recording member having a basis weight in the range of from 15 to 25 lbs. per (17 inches X 22 inches 500) and caliper of 3.0 to 4.5 mils.

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• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Paper (AREA)
• Photoreceptors In Electrophotography (AREA)

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Cited By (10)

Citations (14)

• 1968
  • 1968-08-29 GB GB1232406D patent/GB1232406A/en not_active Expired
  • 1968-08-30 BE BE720253D patent/BE720253A/xx unknown
• 1970
  • 1970-04-20 US US30238A patent/US3652271A/en not_active Expired - Lifetime

Patent Citations (14)

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