US3732096A - Electrophotographic photosensitive layer - Google Patents

Electrophotographic photosensitive layer Download PDF

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Publication number
US3732096A
US3732096A US00105051A US3732096DA US3732096A US 3732096 A US3732096 A US 3732096A US 00105051 A US00105051 A US 00105051A US 3732096D A US3732096D A US 3732096DA US 3732096 A US3732096 A US 3732096A
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United States
Prior art keywords
copolymer
layer
photosensitive layer
alkyd resin
binder
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Expired - Lifetime
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US00105051A
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English (en)
Inventor
S Honjo
M Takimoto
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Fujifilm Holdings Corp
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Fuji Photo Film Co Ltd
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    • 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
    • G03G5/0528—Macromolecular bonding materials
    • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
    • G03G5/0553—Polymers derived from conjugated double bonds containing monomers, e.g. polybutadiene; Rubbers
    • 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
    • G03G5/0528—Macromolecular bonding materials
    • G03G5/0532—Macromolecular bonding materials obtained by reactions only involving carbon-to-carbon unsatured bonds
    • G03G5/0546—Polymers comprising at least one carboxyl radical, e.g. polyacrylic acid, polycrotonic acid, polymaleic acid; Derivatives thereof, e.g. their esters, salts, anhydrides, nitriles, amides
    • 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
    • G03G5/0528—Macromolecular bonding materials
    • G03G5/0592—Macromolecular compounds characterised by their structure or by their chemical properties, e.g. block polymers, reticulated polymers, molecular weight, acidity

Definitions

  • FIG.2 a s A L 3 3 -2ooi w 2 E a2 53 i i 0 I 2 3 (MIN)
  • FIG.2
  • FIG. 1 and FIG. 2 are time-potential curves showing the characteristics of electrophotographic photosensitive layer according to this invention.
  • This invention relates to a novel composition of electrophotographic photosensitive layer, and particularly to an electrophotographic photosensitive layer containing a resin composition hardened so as to be hardly soluble in most organic solvents.
  • an insulative photoconductive layer provided on a support material is subjected to uniform electrostatic charging, and then subjected to imagewise exposure to dissipate the charge in the areas exposed to light thereby forming an electrostatic latent image which is successively rendered visible by means of powder provided with an appropriate electrostatic charge.
  • the process of obtaining a visible image is called development, and at present an image of highest image quality can be obtained by liquid developing method.
  • This method consists of electrophoretic adhesion of electrostatically charged fine powder to said latent image from a developer consisting of said powder dispersed in a highly insulative carrier liquid not destroying said latent image.
  • dry developing methods such as cascade, magnetic, aerosol developing, etc.
  • the electrophotographic photosensitive material known in the prior art is composed of photoconductive insulating layer which consists of inorganic photoconductive material such as zinc oxide, cadmium sulfide, titanium dioxide, zinc sulfide, etc. dispersed in an insulating film forming material and which is provided on a flexible support material such as paper.
  • photoconductive insulating layer which consists of inorganic photoconductive material such as zinc oxide, cadmium sulfide, titanium dioxide, zinc sulfide, etc. dispersed in an insulating film forming material and which is provided on a flexible support material such as paper.
  • the fixing by lacquering is all the more desirable when more than two mono-chromatic images are superposed on a single photosensitive sheet to obtain a multi-color print, since the complete mixing of colors of toner images can only be achieved by effectively filling the minute pores present in the toner images by means of lacquering.
  • the toner of each primary color exhibits a lower optical density compared with black toner employed in document copying etc. and therefore is required to be used in a larger quantity, which cannot be fixed stably even if the binder in the photosensitive layer is slightly swelled during the liquid development.
  • lacquering can be most easily realized by a solution of film forming resin dissolved in an organic solvent selected in consideration of various factors such as drying speed, adhesion to the photosensitive layer or the affinity thereto, it is still difficult to find an appropriate solvent composition since thermoplastic resins are soluble in most solvents.
  • non-thermoplastic binder composition for electrophotography which is crosslinked with suitable crosslinking agent to have three dimensional network structure.
  • suitable crosslinking agent include various kinds of alkyd resins, epoxyesters containing unsaturated fatty acids cross linked in the presence of catalyst such as cobalt naphthenate, manganese naphthenate or organic peroxides.
  • the object of this invention is to provide a novel binder composition for electrophotographic layer free of the drawbacks mentioned above.
  • this invention is to provide an electrophotographic photosensitive layer comprising inorganic photoconductive powdered material and binder material which comprises containing, as said binder composition, a copolymer of vinyl monomer or butadiene and a component expressed by the following general formula:
  • R represents H or CH Z represents COO(CH CONHCH or OCH m represents an integer of from 1 to 5, and n represents or 1, an alkyd resin compatible with said copolymer and a poly-isocyanate compound capable of cross-linking at least a part of said copolymer.
  • Examples of the component expressed by the above general formula are hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, allyl alcohol, hydroxyethyl methacrylamide, hydroxyethyl acrylamide, hydroxyethyl vinylether etc.
  • the hydroxyl content in the copolymer is required to be within a range between 0.5 and 5.0 wt. percent, preferably between 0.5 and 3 wt. percent.
  • the vinyl monomer to be copolymerized with the hydroxyl group containing monomer expressed by the above general formula can be, for example, styrene, methylstyrene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylate esters, methacrylate esters, acrylonitrile, ethylene, propylene, etc. Also butadiene can be satisfactorily employed for this purpose.
  • the copolymer in this invention may further contain, as a minor component, compounds containing polar groups such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid etc., at an amount of not exceeding ca. of the total weight of said copolymer, preferably less than 3%.
  • compounds containing polar groups such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid etc.
  • the dispersibility of said inorganic photoconductive material in said binder is a factor more important than the electric resistance of binder itself.
  • the vinyl copolymers mentioned above are generally highly insulative themselves, they cannot Wet satisfactorily said inorganic powdered material and therefore provide a layer of poor charge retainability when used alone, and such problems cannot be resolved completely even by crosslinking with polyisocyanate.
  • alkyd resin is used as the auxiliary dispersing agent in this invention
  • the vinyl copolymer is required to be compatible with alkyd resin.
  • Empirically desired are those with long aliphatic side chain such as butyl methacrylate, ethylhexylmethacrylate, butylacrylate, or ethylhexylacrylate, and a wide compatibility can be realized by the superposed effect of containing the OH group contained in said monomer.
  • Acid radicals present in acrylic acids etc. are indispensable for realizing satisfactory afiinity with inorgainc powdered material when vinyl copolymer is exclusively employed, but in this invention they only perform secondary significance and therefore may be omitted completely.
  • Polyisocyanate compound can be, for example, toluene dissocyanate, hexarnethylene diisocyanate, 4,4',4-triphenylmethane, triisocyanate, diphenylmethane-4,4-diisocyanate etc., but is represented by a condensation product between 1 mol of trimethylolpropane and 3 mols of toluene diisocyanate which is scarcely volatile at room temperature, and which is commercially available from Bayer under the trade name of Desmodule L or from Japan Polyurethane Industries under the trade name of Coronate L. Also preferred is the condensation product of xylylene diisocyanate and trimethylolpropane due to its low tendency to yellowing.
  • alkyd resin employable is almost any commercially available product. This may be because the OH group in the vinyl copolymer contributes to the improvement of compatibilty.
  • Aikyd resin suitable for the present invention can be, for example, those modified .with styrene, acryl esters, drying oils, non-drying oils, phenol-formaldehyde resin, rosin etc.
  • the alkyd resin generally contains OH groups in the molecular structure thereof except for the case of extremely long chain-length therefore crosslinked by isocyanate, but such crosslinking is not important in certain purposes.
  • alkyd resin can stand practical purposes without hardening with isocyanate in case of dry development methods or of development with liquid developer using isoparaffinic solvent as the carrier.
  • alkyd resin particularly preferred are those modified with styrene, acrylics, phenolformaldehyde or rosin.
  • the alkyd resin is desired to be present within a range of 2-70 wt. percent, preferably 2-40 wt. percent of the total resin components, vinyl copolymer containing OH radical is desired to be present within a range of 30-85 wt. percent thereof and polyisocyanate compound is desired to be present within a range of 25-70 wt. percent, preferably 5-60 Wt. percent.
  • Said polyisocyanate is observed to be already effective when present in 0.2 equivalent with respect to l equivalent of said vinyl copolymer and of OH radical contained in said alkyd resin, and can be added as high as 6-7 equivalents with respect to said OH radicals.
  • Alkyd resin in wide sense may be free from aromatic polybasic acid such as phthalic acid, isophthalic acid, terephthalic acid etc. However, the presence of such aromatic polybasic acid is desired when employed in this invention.
  • Said alkyd resin may be a mixture composed of more than two species. Also it is possible to use more than two species of vinyl copolymers so long as each contains monomer unit containing OH radicals.
  • the mixing ratio of photoconductive material to said resin may vary within a range from ca. 1:1 to ca. 20:1.
  • the photosensitive layer is suitable for reproducing continuous tone image, since this is capable of retaining surface charge for a long time even in a liquid dcveloper containing solvent with relatively high solubility parameter. Furthermore, mechanical reinforcement of toner image can be realized by dissolving a resinous material in the liquid developer and rinsing, after developing, the photosensitive layer with a weak solvent incapable of dissolving said resinous material. This method is suitable for obtaining a multi-color print by overprinting technique. Such process is disclosed in Japanese patent application No. 10,684/ 68, corresponding to U.S. patent application Ser. No. 801,179 filed Feb. 20, 1969.
  • the photosensitive layer stands the treatment with bath for decoloring sensitizing dyes containing ketones, alcohols or esters due to its durability against various solvents. Examples of such process are disclosed in Japanese patent application No. 60,617/69, corresponding to US. patent application Ser. No. 60,117 filed July 31, 1970.
  • This photosensitive layer enables toner image fixation with lacquering and provides prints of high image quality.
  • This photosensitive layer withstands the atmosphere of high humidity exhibiting excellent electrophotographic characteristics in a wide range of humidity.
  • EXAMPLE 1 In this example employed were acryl ester modified alkyd resin varnish (non-volatiles 50%, hydroxyl value ca. 50) as alkyd resin component, vinyl copolymer containing 34% of styrene, 51% of n-butyl methacrylate, of 2-hydroxyethyl acrylate and 0.2% of acrylic acid, and Desmodule L of Bayer AG as polyisocyanate for crosslinking said binder.
  • Four different photoconductive coatings of the formulations shown in Table 1 were applied to obtain a thickness of ca. 7 microns after drying on polyethylene terephthalate film provided with evaporated aluminum layer.
  • the coating dispersions were prepared using a mixed solvent composed of butyl acetate, xylene and toluene.
  • the dispersions containing non-volatile components shown in the table were added, as sensitizing dye, with 1.5 mg. of bromochlorophenol blue, 1.0 mg. of rose bengale and 1.3 mg. of fluorescein with respect to 10 g. of photoconductive zinc oxide.
  • Said dyes were previously dissolved in methanol, of which amount was limited to as small amount as possible since large amount of methanol, it added, will interfere with the hardening of the resins with poly-isocyanate.
  • the amount of methanol should be maintained to 510% of total amount of solvent used in the coating dispersion.
  • the dark-adapted photosensitive material was negatively charged with corona discharge, and the potential 30 seconds after the completion of charging was defined as the initial potential (A). Measurements were all carried out at a condition of 25 C. and 50-60% RH. The dark decay for 1 minute in the air was measured to give the value B. Then the surface of said material was uniformly covered with purified Decalin or isoparatfin such as Isoper H (Esso Standard Oil Co.) and further subjected to the measurement of potential. The potentials at the coating of liquid, 30 seconds thereafter and 1 minute further thereafter were defined as C, D and E respectively. Thus the decay characteristics in air, potential lowering by liquid immersion and decay characteristics in the liquid were respectively defined by B/A, C/B, and E/D.
  • FIGS. 1 and 2 show the automatically recorded potentials respectively in case of immersion in Decalin and in Isoper H.
  • photosensitivity is defined by 8/E in which E represents exposure of light source 0. I. E.;
  • the dispersion was then added with sensitizing dyes in amounts as shown in Example 1, diluted with xylene, added with 0.6 part of Desmodule L (non-volatiles 75%) of Bayer AG and applied on paper previously subjected to electroconductive treatment to obtain a thickness of 7 microns after drying.
  • Zinc oxide was stably dispersed in the coating solution to show sufficient fluidity and coating was extremely easily carried out.
  • the coated sample was made to stand a day in a thermostat of 40 C., then thoroughly dark adapted and subjected to the measurements as described in Example 1. The results are shown as No. 5 in Table 2.
  • EXAMPLE 4 10 parts of a copolymer consisting of 51% of n-butyl methacrylate, 34% of styrene and 15 of hydroxyethyl methacrylate, 5 parts of acryl-modified alkyd resin (hydroxyl value ca. 30) and 5 parts of a condensation product composed of 1 mol of trimethylolpropane and 3 mols of xylylene diisocyanate as polyisocyanate compound were mixed with 150 parts of zinc oxide to obtain photosensitive layer. Thus prepared was an excellent photosensitive layer with an extremely slow dark decay.
  • EXAMPLE 5 7 parts of a copolymer consisting of 30% of methyl methacrylate, 55% of n-butyl methacrylate and 15% of hydroxyethyl acrylamide, 7 parts of acryl-modified alkyd resin (hydroxyl value ca. 30) and 6 parts of polyisocyanate shown in Example 4 were mixed with parts of zinc oxide to obtain photoconductive layer of extremely excellent characteristics.
  • An electrophotographic photosensitive layer comprising inorganic photoconductive powdered material and binder which comprises using a binder composition containing a copolymer of vinyl monomer and a component expressed by the following general formula:
  • R represents H or H Z represents COO(CH CONHCH or OC H m represents an integer from 1 to 5, and n represents 0 or 1, an alkyd resin containing a hydroxyl group and compatible with said copolymer and a polyisocyanate compound capable of crosslinking at least a part of said copolymer, the hydroxyl content in said copolymer being from 0.5- by Weight.
  • a layer claimed in claim 1 wherein said alkyd resin content is 270% by weight of the whole binder.
  • a layer claimed in claim 1 wherein said component represented by the formula is a hydroxyethylmethacrylate or a hydroxyethylacrylate.
  • a layer claimed in claim 1 wherein said polyisocyanate compound is a condensation product of trimethylolpropane and toluene diisocyanate or a condensation product of trimethylolpropane and xylene diisocyanate.
  • a layer claimed in claim 1 wherein the hydroxyl content in said copolymer is from 0.5-3% by weight.
  • alkyd resin is those modified with styrene, acryl esters, phenolformaldehyde resin or rosin.
  • alkyd resin is capable of crosslinking with polyisocyanate.
  • a layer claimed in claim 2 wherein said alkyd resin content is 2 to 40% by weight of the whole binder.
  • a layer claimed in claim 5 wherein the hydroxyl content in said copolymer is from 0.5 to 3% by weight.
  • a layer claimed in claim 1 wherein said copolymer is 30 to 85% by weight of the whole binder.
  • a layer claimed in claim 1 wherein said polyisocyanate compound is 2.5 to 70% by weight of the whole binder.
  • a layer claimed in claim 13 wherein said polyisocyanate compound is 5 to by weight of the whole binder.
  • a layer claimed in claim 1 wherein said vinyl monomer is butadiene.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Photoreceptors In Electrophotography (AREA)
US00105051A 1970-01-08 1971-01-08 Electrophotographic photosensitive layer Expired - Lifetime US3732096A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP45002589A JPS4843147B1 (OSRAM) 1970-01-08 1970-01-08

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US (1) US3732096A (OSRAM)
JP (1) JPS4843147B1 (OSRAM)
BE (1) BE761226A (OSRAM)
CA (1) CA925742A (OSRAM)
DE (1) DE2100158B2 (OSRAM)
FR (1) FR2075271A5 (OSRAM)
GB (1) GB1333294A (OSRAM)
NL (1) NL7100014A (OSRAM)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3885961A (en) * 1972-08-01 1975-05-27 Mitsubishi Rayon Co Polymeric binder material for use in a photoconductive layer employed in electrophotography
US4434218A (en) 1979-01-24 1984-02-28 Konishiroku Photo Industry Co., Ltd. Photosensitive composition for electrophotography
US20040152575A1 (en) * 2003-01-30 2004-08-05 Tokai Rubber Industries, Ltd. Semi-conductive roll

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3885961A (en) * 1972-08-01 1975-05-27 Mitsubishi Rayon Co Polymeric binder material for use in a photoconductive layer employed in electrophotography
US4434218A (en) 1979-01-24 1984-02-28 Konishiroku Photo Industry Co., Ltd. Photosensitive composition for electrophotography
US20040152575A1 (en) * 2003-01-30 2004-08-05 Tokai Rubber Industries, Ltd. Semi-conductive roll
US7288058B2 (en) * 2003-01-30 2007-10-30 Tokai Rubber Industries, Ltd. Semi-conductive roll

Also Published As

Publication number Publication date
FR2075271A5 (OSRAM) 1971-10-08
NL7100014A (OSRAM) 1971-07-12
CA925742A (en) 1973-05-08
DE2100158A1 (de) 1971-07-22
JPS4843147B1 (OSRAM) 1973-12-17
GB1333294A (en) 1973-10-10
DE2100158B2 (de) 1974-04-18
BE761226A (fr) 1971-06-16

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