US3881925A - Bi-chargeable electrophotographic materials including zinc oxide and a binder resin - Google Patents

Bi-chargeable electrophotographic materials including zinc oxide and a binder resin Download PDF

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US3881925A
US3881925A US380027A US38002773A US3881925A US 3881925 A US3881925 A US 3881925A US 380027 A US380027 A US 380027A US 38002773 A US38002773 A US 38002773A US 3881925 A US3881925 A US 3881925A
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weight
electrophotographic
image
chargeable
electrophotographic photosensitive
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Koji Uchida
Shigeyoshi Suzuki
Sadao Kuriu
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Mitsubishi Paper Mills Ltd
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Mitsubishi Paper Mills 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
    • G03G5/0546—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

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  • ABSTRACT An electrophotographic material chargeable both positively and negatively comprising a zinc oxide type electrophotographic layer containing as the binder for zinc oxide a copolymerized acrylic resin comprising 50-95% by weight acrylic ester and 1-5% by weight organic acid having vinyl group copolyrnerizable with the acrylic ester.
  • the electrophotographic layer may contain further low-molecular weight polystyrene.
  • the present invention relates to electrophotography and more particularly, it relates to a bi-chargeable electrophotographic material which can be charged to any of positive charge or negative charge by an electrostatic charging step in electrophotographic process.
  • the process of obtaining visible images by electrophotographic method is mainly composed of l electrostatic charging of a photosensitive or photoconductive layer, (2) image exposure (the formation of electrostatic latent images), and (3) development by charged colored particles or toners.
  • the photosensitive or photoconductive layer is charged for forming latent images as the patterns of electrostatic charge on the surface thereon in the subsequent image exposure step. That is, because an electrophotographic material has high insulative property in the dark, the electrophotographic layer can be charged by proper means.
  • electrostatic latent image When the photosensitive or photoconductive layer of the electrophotographic material is, after uniformly charging the whole surface of the layer, imagewise exposed to light, the portions of the electrophotographic layer exposed to light become conductive to lose the electrostatic charge on the surfaces of those portions, while the portions of the layer which have not been exposed to light bear thereon the electrostatic charge, whereby a pattern of electrostatic charge is formed in conformity with the exposed image. This process is called formation of electrostatic latent image.”
  • Such an electrostatic latent image can generally be developed by colored fine particles or toners having an electrostatic charge opposite to the electrostatic charge on the photosensitive or photoconductive layer, said fine particles or toners being used as a state of powder or a dispersion in highly insulative liquid.
  • a photosensitive or photoconductive layer is exposed imagewise to light in uncharged state, a conductive pattern is formed in conformity of the image on the photosensitive layer during the exposure or within a quite short period of time after exposure but such a pattern does not have a life as the aforesaid electrostatic pattern and further cannot be developed by charged colored tine particles.
  • the step of charging photosensitive or photoconductive layers is important and an indispensable step.
  • an electrophotographic photosensitive layer is charged by conducting corona discharging by means of a high-voltage direct current electric source of 6000-8000 volts to ionizing surrounding air and attaching the ionized air onto the surface of the photosensitive layer.
  • the charging system of utilizing such a dc. corona discharging can generate a positive charge or a negative charge by changing the poles of the dc. electric source.
  • a conventional electrophotographic photosensitive layer is charged to definite one of a positive charge and a negative charge, duplication can be conducted well, but when the same electrophotographic photosensitive layer is charged to the opposite charge, duplication cannot be conducted well. Consequently, the charging device is set for giving the definite polarity of electrostatic charge fitted for the characteristics of the electrophotographic layer to be used.
  • the charging device is set for providing a positive charge, while for a photosensitive or photoconductive layer composed of a zinc oxide-resin dispersion system as in Electrofax (resistered trade name), the charging device is set for provid ing a negative charge.
  • the charge on a photoconductor to be provided is selected according to whether the photoconducter is a P-type or a N-type. That is, a P-type photoconductor in which the current carrier is a positive hole is readily charged to a positive charge and further the positive charge vanishes smoothly when the photoconductor is exposed to light.
  • a N-type photoconductor in which the current carrier is electron is fit for negative charging. According to the view, when a photosensitive layer prepared by using zinc oxide which is a N-type photoconductor is used, the electrophotographic process can be performed well in case of charging negatively the photosensitive layer.
  • a toner having a positive charge must be used for obtaining positive to positive duplications, while a toner having a negative charge must be used for obtaining negative to positive duplications.
  • a negatively charged toner must be used for obtaining positive to negative duplications, while a positively charged toner must be used for obtaining a negative to negative duplications.
  • the toner to be used must be changed or two specific equipments each containing a positive toner and a negative toner must be prepared.
  • the various kinds of duplications as stated above can be obtained in case of using the aforesaid electrophotographic layer which can be charged to any of a positive charge and a negative charge by simply changing the switch of a high dc voltage electric source for changing the poles.
  • FIG. 1 is a view showing the step of making a duplication of a positive by exposing to the light image of a positive original a negatively charged electrophotographic photosensitive layer
  • FIG. 2 is a view showing the step of making a duplication of a positive by exposing to the light image of a negative original a negatively charged electrophotographic photosensitive layer
  • FIG. 3 is a view showing the step of making a duplication of a positive by exposing to the light image of a negative original a positively charged electrophotographic photosensitive layer.
  • FIG. 1 shows the step of obtaining duplications of positive from a positive original.
  • the surface of an electrophotographic photosensitive layer 3 is first uniformly charged negatively by means of a corona discharging device 2 connected to a high voltage d.c. electric source 1 in the first step.
  • the electrophotographic photosensitive layer 6 thus charged negatively is exposed to the light image of positive original 4 through, if necessary a lense in the second step, whereby the portions of the layer exposed to light lose the electrostatic charge and the portions unexposed retain charge thereon, whereby an electrostatic latent image of a negative charge is formed on the layer.
  • the electrophotographic paper 7 is developed by a positively charged toner in the third step, whereby the toner is attached to the latent image by electrostatic attractive force, whereby the developed positive image as shown in the final step of FIG. 1 is obtained.
  • FIG. 2 and FIG. 3 show the step of obtaining a positive duplicate from a negative original.
  • FIG. 2 shows an example of using a conventional electrophotographic photosensitive layer which can provide the positive duplicate by a single pole charge, e.g., a negative electrostatic charge in the illustrated case.
  • a single pole charge e.g., a negative electrostatic charge in the illustrated case.
  • the portions corresponding the negative image lose the electrostatic charge, while the non-image portions of the layer retain negative charge as shown in the figure according to the characteristics of the photoconductor, whereby an electrostatic latent image of the type where no electrostatic charge is present on the image portion is formed.
  • the latent image is developed by toner in the third step but since for attaching the toner to the portion bearing no electrostatic charge, such a toner that will be repulsed by the electrostatic charge at the nonimaged portions must be used, a negatively charged toner is used for the development.
  • the latent image is developed by a negatively charged toner, the toner attaches to the imaged portions as shown in the final step of FIG. 2 to provide the positive image.
  • FIG. 3 shows an example of using the novel bi-chargeable electrophotographic photosensitive layer.
  • the layer 3 is positively charged as shown in the figure.
  • the positively charged photosensitive layer 6' is exposed to the light image of a negative original 4' through, if necessary, a lense 5
  • the portions corresponding to the negative image or exposed to light lose the charge, while the non-image portions retain the charge thereon to form a latent image.
  • the charge on the non-imaged portions is a positive charge. That is, in the case of FIG. 2, a negatively charged toner is used for developing the latent image to provide a positive image, while in the case of FIG. 3, a positively charged toner is used for developing the latent image.
  • the same toner as used in the process of FIG. 1 is used in this case.
  • the above-mentioned embodiment is only one example of using the electrophotographic photosensitive layer which can be charged to any of a positive charge and a negative charge but from the example only, it will be understood that the usefulness of the bi-chargeable electrophotographic photosensitive layer be large.
  • An object of this invention is, therefore, to provide the aforesaid both-chargeable electrophotographic photosensitive materials which are expected to be used wide purposes.
  • the binders for electrophotographic photosensitive layers were developed based on the resins for paints and thus the resins to be used as the binders for electrophotographic layers are in the range of the resins for paints.
  • Typical examples of such resins are silicone resins, various polyester resins including alkyd resins, and various vinylic resins such as vinyl acetate, polyacrylate, and polystyrene.
  • the binder resins for the bi-chargeable electrophotographic materials of this invention belong also to acrylic resins.
  • Acrylic resins include generally the resins prepared by polymerizing acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, the derivatives of the esters, styrene, styrene derivatives, and other monomer having polymerizable vinyl group.
  • the acrylic resins as the binder resins for zinc oxide of electrophotographic layers have hitherto been investigated about the composition of monomers and degrees of polymerization for obtaining the electrophotographic characteristics such as dispersibility of ZnO, adhesion to the substrates, mechanical strength or durability, charge acceptance, photosensitivity, moisture resistance and thermal resistance.
  • various kinds of acrylic resins for the purpose are disclosed in the specifications of Japanese Patent Publication Nos. 6395/69, 6392/69, 6393/69, 6394/69, l7,3l6/69. ll,636/7l and l8,l l6/7l.
  • acrylic resins there are no disclosures of showing or suggesting the binders for the bi-chargeable purpose.
  • the possibility of obtaining the bi-chargeable is determined by the amount of acrylic ester in acrylic resin compositions.
  • acrylic ester and methacrylic ester as components for acrylic resins, that is, almost all of acrylic resins are mainly composed of such components.
  • the component ratios of the monomers are so selected that the mechanical strength, resistance, chargeability of electrostatic charge, and sensitivity required for the purposes can be obtained.
  • the necessary content of acrylic ester is 5095% by weight, preferably 70-90% by weight.
  • 15% by weight is at least one organic acid monomer copolymerizable with the acrylic ester, such as acrylic acid, methacrylic acid, furnaric acid, maleic acid, itaconic acid, maleic anhydride, itaconic anhydride, and the monoesters of the above-mentioned dibasic acids.
  • ком ⁇ онент may be any monomers copolymerizable with the acrylic ester, such as a methacrylic ester (e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc.), a methacrylic ester derivative (e.g., hydrocyethyl methacrylate, glycidyl methacrylate, etc.), styrene, a styrene derivative (e.g., methyl styrene, chloromethylstyrene, etc.) and the like.
  • a methacrylic ester e.g., methyl methacrylate, ethyl methacrylate, butyl methacrylate, etc.
  • a methacrylic ester derivative e.g., hydrocyethyl methacrylate, glycidyl methacrylate, etc.
  • styrene e.g.
  • acrylic ester to be used there are illustrated ethyl acrylate, propyl acrylate, and butyl acrylate. They may be used individually or as a combination thereof. The selection of the acrylic ester or esters is determined by the mechanical properties required.
  • the acrylic ester for the copolymerized acrylic resin there are methyl methacrylate, ethyl methacrylate, propyl methacrylate, and butyl methacrylate each having different chain length of alkyl group as well as lauryl methacrylate having further longer chain length of alkyl group as in case of methacrylic esters.
  • the proportion of the methacrylic ester becomes higher than 50% by weight, the bi-chargeable property of the resin is, on the contrary, lowered.
  • both-chargeable property was used before frequently in this specification without giving any clear definition to the term and thus the term will be explained in detail a little for giving no misunderstanding.
  • the term both-chargeable property used in this spec ification is somewhat different from the meaning capable of being simply charged to positive and negative electrostatic charges. Of course, it is the necessary factor of the term to be able to charge positive and negative electrostatic charges but the term also means that when the material having the property of being charged to positive and negative electrostatic charges is charged to the positive or the negative charge and developed by toner after imagewise exposure, it can give sharp images without forming fog.
  • the electric potential characteristic curve of an electrophotographic photosensitive layer is cited as one of means of testing the characteristics of it.
  • the potential characteristic curve By the potential characteristic curve, the electric potential to be employed for charging the photosensitive layer and the decaying state of the electric potential of the layer when the layer is exposed to light can be obtained.
  • the results obtained from the potential characteristic curve not always coincide with the real properties of the electrophotographic image obtained by applying an electrophotographic process. In case of testing the bichargeable property of an electrophotographic photosensitive or photoconductive material, the above difference in properties becomes remakable.
  • an electrophotographic photosensitive layer is charged to 500 volts when charged negatively and to +500 volts when charged positively and also the decaying tendency by light exposure is completely the same in the both cases, that is, the potential characteristic curve completely symmetrical in the both areas of the zero potential base line is obtained, it frequently happens that the electrophotographic image obtained by processing the electrophotographic photosensitive layer in an electrophotographic process is sharp and has no fogs on blank areas in case of charging negatively the layer but becomes dim and has much fogs on blank areas.
  • the electrophotographic photosensitive layer is not said to have the both-chargeable property in this invention even if the layer may be charged negatively or positively in same charged amount.
  • the use of the methacrylic ester is not excluded in this invention. That is, as mentioned before, when 50-95% acrylic ester and l5% organic acid copolymerizable with the acrylic ester are used as the components for the acrylic copolymer to be used as the electrophotographic photosensitive or photoconductive layer in this invention, a methacrylic ester can be used as the rest component for the copolymer if any without deteriorating the both-chargeable property of the photosensitive layer. Furthermore, other components than the methacrylic ester, such as a derivative of the acrylic ester or the methacrylic ester, styrene, and a styrene derivative may be used as the other component for the acrylic copolymer.
  • the charge acceptance of negative or positive charge can be increased and the density of image can also be increased without substantially deteriorating the both-chargeable property of the layer.
  • the binder of electrophotographic layer the acrylic copolymer resin with low molecular weight polystyrene having a molecular weight of up to about 5,000 in an amount of l0-50% by weight based on the whole weight of the resin for increasing further the amount of charge to be charged thereon.
  • the low molecular weight polystyrene to be used in this invention includes, besides styrene homopolymer, a copolymer of styrene and a small amount of an acrylic monomer such as acrylic acid, methacrylic acid, acrylic ester, methacrylic ester, and derivatives of such monomers.
  • EXAMPLE 1 solution thus prepared 200 g. of electrophotographic zinc oxide (made by Sakai Kagaku K. K.), 200 g. of xylene, and mg. of Bromophenol Blue as a dye sensitizer was mixed sufficiently by ultrasonic waves and the mixture was applied to the surface of an electrophotographic base paper, the surface of which had been subjected to conductive treatment, by means of a drawdown rod (a rod-form doctor having coiled fine copper wire thereon) in a coated amount as solid of 25 g./m. and dried.
  • a drawdown rod a rod-form doctor having coiled fine copper wire thereon
  • the sample thus prepared was seasoned overnight in the dark at a temperature of 20C. and a humidity of RH and then the bi-chargeable property of the sample was tested by the following manner.
  • Negatively chargeable test After charging negatively the photosensitive layer of the sample by facing the layer to the negative pole side of a double corona discharging device connected to a high potential d.c. electric source, the photosensitive layer thus charged was exposed to light through a positive image original and then developed by means of positively charged liquid toner or a so-called positive toner, whereby a clear positive image having no fogs on blank area was obtained.
  • EXAMPLE 2 The copolymers containing various quantities of ethyl acrylate as shown in Table l were prepared by the same way as in Example I and after preparing samples using the copolymers by the same manner as in Example l, the samples were tested about the bi-chargeable property, the results of which are also shown in the same table.
  • the electrophotographic image formed could be read even if the proportion of ethyl acrylate increased but the image density tended to decrease gradually as the increase of the proportion of ethyl acrylate.
  • the electrophotographic image could be read when the proportion of ethyl acrylate was more than 50% by weight but when the proportion of ethyl acrylate was weight polystyrene, Picolastic 0100 (registered trade mark, made by Esso Research and Engineering Co.) in
  • EXAMPLE 3 Six kinds of copolymers were prepared by using methyl acrylate or butyl acrylate in place of the ethyl acrylate as the monomer component of the copolymers in Example 2 and the same test as in Example 2 was conducted about the samples prepared by using the copolymers as binder. The results showed that the samples showed almost the same tendency as the cases of using ethyl acrylate, that is, when the proportion of the acrylic ester component was higher than 50% by weight, the sample exhibited good positive chargeable property but when the proportion of the acrylic ester was lower than 50% by weight, the positive chargeable property of the samples was reduced.
  • EXAMPLE 4 A series of copolymers having the monomer compositions as shown in Table 2, that is, the copolymers containing various proportions of styrene were prepared and the same procedure as in Example I was followed by using the copolymers as the binder for electrophotographic photosensitive layers.
  • EXAMPLE 5 The resin having the same composition as the sample 10 of Example 4 was mixed with a low molecular The results showed that as the increase of the mixing ratio of the low molecular weight polystyrene, the image density increased but when the content of the low molecular weight polystyrene became higher than 50% by weight, fogs were formed on blak areas in the positively chargeable property test and the image became dim.
  • EXAMPLE 6 The same procedure as in Example 5 was followed using commercially available low molecular weight polystyrenes, Picolastic A-75, Picolastic D-lOO and Picolastic D-l 25 (registered trade marks, made by Esso Research and Engineering Co.) or Himer ST-75, Himer ST-95, Himer ST-IZO, and Himer SU-l 20 (trade names, made by Sanyo Kasei K. K.) in place of Picolastic C-lOO. The results-were almost same as those in Example 5.
  • a bi-chargeable electrophotographic photosensitive material containing photoconductive zinc oxide and a binder resin comprising a mixture of:
  • the bi-chargeable electrophotographic photosencopolymerizable vinyl monomer is methyl methacrylsitive material as claimed in claim I wherein said orate, ethyl methacrylate, butyl methacrylate, a derivaganic acid is acrylic acid, methacrylic acid, fumaric tive of acrylic ester or methacrylic acid, styrene or a acid, maleic acid, itaconic acid, maleic anhydride, itastyrene derivative. conic anhydride, or the monoester of each of said 5 5.
  • the bi-chargeable electrophotographic photosenacids. sitive material as claimed in claim 1 which consists es- 4.

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US380027A 1972-07-17 1973-07-17 Bi-chargeable electrophotographic materials including zinc oxide and a binder resin Expired - Lifetime US3881925A (en)

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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097417A (en) * 1974-05-02 1978-06-27 National Starch And Chemical Corporation Photocurable electroconductive coating composition
US4820620A (en) * 1986-07-17 1989-04-11 Minnesota Mining And Manufacturing Company Supersensitization of and reduction of dark decay rate in photoconductive films
US4871638A (en) * 1987-03-09 1989-10-03 Fuji Photo Film Co., Ltd. Electrophotographic photosensitive material with binder combination
US5028502A (en) * 1990-01-29 1991-07-02 Xerox Corporation High speed electrophotographic imaging system
US5306586A (en) * 1992-08-06 1994-04-26 Xerox Corporation Dual layer switch photoreceptor structures for digital imaging
US20030191338A1 (en) * 2002-04-09 2003-10-09 Johnston Allen D. Methods for inhibiting the polymerization of methacrylate monomers

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8100163A (nl) * 1981-01-15 1982-08-02 Oce Nederland Bv Herhaaldelijk bruikbaar electrofotografisch element en werkwijze voor de vervaardiging van dat element.

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3578446A (en) * 1967-07-26 1971-05-11 Firestone Tire & Rubber Co Electrophotographic reproduction employing bi-charging and negative-charging zinc oxide
US3672889A (en) * 1969-07-14 1972-06-27 Addressograph Multigraph Acrylate terpolymer resin binders for photoelectrostatic members
US3681069A (en) * 1966-10-28 1972-08-01 Rohm & Haas Binder plate for use in xerography and process therefor

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3681069A (en) * 1966-10-28 1972-08-01 Rohm & Haas Binder plate for use in xerography and process therefor
US3578446A (en) * 1967-07-26 1971-05-11 Firestone Tire & Rubber Co Electrophotographic reproduction employing bi-charging and negative-charging zinc oxide
US3672889A (en) * 1969-07-14 1972-06-27 Addressograph Multigraph Acrylate terpolymer resin binders for photoelectrostatic members

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4097417A (en) * 1974-05-02 1978-06-27 National Starch And Chemical Corporation Photocurable electroconductive coating composition
US4820620A (en) * 1986-07-17 1989-04-11 Minnesota Mining And Manufacturing Company Supersensitization of and reduction of dark decay rate in photoconductive films
US4871638A (en) * 1987-03-09 1989-10-03 Fuji Photo Film Co., Ltd. Electrophotographic photosensitive material with binder combination
US5028502A (en) * 1990-01-29 1991-07-02 Xerox Corporation High speed electrophotographic imaging system
US5306586A (en) * 1992-08-06 1994-04-26 Xerox Corporation Dual layer switch photoreceptor structures for digital imaging
US20030191338A1 (en) * 2002-04-09 2003-10-09 Johnston Allen D. Methods for inhibiting the polymerization of methacrylate monomers

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DE2336338A1 (de) 1974-01-31
JPS5116148B2 (enrdf_load_stackoverflow) 1976-05-21
DE2336338B2 (de) 1975-11-27
JPS49109039A (enrdf_load_stackoverflow) 1974-10-17

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