US3617268A - Electrophotographic materials - Google Patents

Electrophotographic materials Download PDF

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Publication number
US3617268A
US3617268A US4200A US3617268DA US3617268A US 3617268 A US3617268 A US 3617268A US 4200 A US4200 A US 4200A US 3617268D A US3617268D A US 3617268DA US 3617268 A US3617268 A US 3617268A
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Prior art keywords
solution
sensitizer
compound
vinylcarbazole
methoxystyryl
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US4200A
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Yoshinobu Murakami
Kazuhisa Morimoto
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Panasonic Holdings Corp
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Matsushita Electric Industrial Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D311/00—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only hetero atom, condensed with other rings
    • C07D311/02—Heterocyclic compounds containing six-membered rings having one oxygen atom as the only hetero atom, condensed with other rings ortho- or peri-condensed with carbocyclic rings or ring systems
    • C07D311/04—Benzo[b]pyrans, not hydrogenated in the carbocyclic ring
    • C07D311/22—Benzo[b]pyrans, not hydrogenated in the carbocyclic ring with oxygen or sulfur atoms directly attached in position 4
    • 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
    • G03G5/06—Photoconductive layers; Charge-generation layers or charge-transporting layers; Additives therefor; Binders therefor characterised by the photoconductive material being organic
    • G03G5/0622—Heterocyclic compounds
    • G03G5/0624—Heterocyclic compounds containing one hetero ring
    • G03G5/0635—Heterocyclic compounds containing one hetero ring being six-membered
    • G03G5/0637—Heterocyclic compounds containing one hetero ring being six-membered containing one hetero atom

Definitions

  • a photosensitive material for electrophotography comprising an organic photoconductive compound and a sensitizer consisting of reaction products of a benzopyrylium salt and a benzopyrane.
  • This invention relates to an electrophotographic material and more particularly to a photoconductive insulating material comprising an organic photoconductive compound and a sensitizer.
  • photoconductive insulating layers are well known in the electrophotographic art for making copies of documents, drawings, transparencies, etc. These layers contain on organic photoconductive compound, such as poly-N-vinylcarbazole, poly-3,6-dibromo-N-vinylcarbazole, brominated poly- N-vinylcarbazole, nitrated poly-N-vinylcarbazole, polyacenaphthylene, etc. These layers are nonconductors of electricity before exposure and become electrical conductors upon exposure.
  • the photoconductive insulating material has a high photoconductivity in the region of the visible spectrum.
  • Such a photoconductive insulating material makes it possible for the electrophotographic art to employ inexpensive and convenient light sources such as incandescent lamps in a reduced exposure time and to reproduce colored pictures.
  • the photoconductive compounds mentioned above however, have usually a low photoconductivity and spectrum characteristics sensitive to the short wavelength region of the exposure light and do not satisfy entirely the above requirement.
  • sensitizer can improve photoconductivity and spectrum response of the above photoconductive compounds.
  • Conventional sensitizers are dyestuffs, such as triarylmethane dyes, xanthene dyes, triazine dyes or acridine dyes, but the conventional sensitizers are-not entirely satisfactory for improvement of the photoconductivity and the spectrum response of the available organic photoconductive compounds.
  • the electrophotographic art requires a high electric resistance of photoconductive materials in the dark.
  • Conventional sensitizers promote the photoconductivity but increase the dark conductivity.
  • a high dark conductivity of photoconductive materials is not desirable because it results in a loss of the applied electrostatic charge in the dark.
  • Another object of the invention is to provide electrophotographic materials having a high electric resistance in the dark.
  • FIG. 1 represents the absorption spectra, in 1,2- dichloroethane, of one example (Sample Number 27) of sensitizers according to the present invention under comparison with those of 2-(p-methoxystyryl)-3-phenylbenzopyrylium perchlorate (Compound Number 2), in 1,2-dichloroethane, and Z-(p-methoxystyryl)-3-phenyl-4-methoxypyrane (Compound Number ll) in methanol.
  • FIG. 2 represents the infrared absorption spectra in KBr method ofCompound Number 2, 11 and Sample Number 27.
  • FIG. 3 represents the wedge spectrogram for an electrophotographic material coated with a solution containing weight percent of brominated poly-n-vinylcarbazole and 0.02 weight percent of sensitizer (Sample Number 27), the brominated poIy-N-vinylcarbazole being dissolved in a solvent consisting of4 parts by weight of chlorobenzene and 1 part by weight of 1,2-dichloroethane under comparison with those of brominated poly-N-vinylcarbazole.
  • FIG. 4 represents the wedge spectrogram of an electrophotographic material coated with a 10 weight percent solution of brominated poly-N-Vinylcarbazole sensitized with 0.02 weight of Sample Number 50, the brominated poly-N- vinylcarbazole being dissolved in a solvent consisting of 4 parts by weight of chlorobenzene and 1 part by weight of 1,2- dichloroethane, under comparison with the wedge spectrogram of an electrophotographic material coated with a 10 weight percent solution of brominated poly-N-vinylcarbazole sensitized with 0.06 weight percent of Compound Number 9, which is the raw material of Sample Number 50, the brominated poly-N-vinylcarbazole being dissolved in a solvent consisting of 4 parts by weight of chlorobenzene and 1 part by weight of 1,2-dichloroethane.
  • FIG. 5 represents the wedge spectrogram of an electrophotographic material coated with a 10 weight percent solution of poly-N-vinylcarbazole sensitized with 0.03 weight percent of Sample Number 39, the poly-N-vinylcarbazole being dissolvedin a solvent consisting of 4 parts by weight of toluene and 1 part by weight of l,2-dichloroethane.
  • FIG. 6 represents the wedge spectrogram of an electrophotographic material coated with l0 weight percent solution of poly-N-vinylcarbazole sensitized with 0.03 weight percent of Sample Number 28, the poly-N-vinylcarbazole being dissolved in a solvent consisting of 4 parts by weight of toluene and 1 part by weight of l,2-dichloroethane.
  • R is an aliphatic group such as styryl, p-methoxystyryl, w-phenylbutadienyl; aromatic group such as phenyl, pmethoxyphenyl;
  • R is selected from the group consisting of hydrogen and phenyl radical
  • R is selected from the group consisting of hydrogen and methoxy radical
  • Anion is fluoborate chloroferrate, perchlorate anion.
  • the chemical formula B is chlorozincate or /O -RI l L...
  • R is an aliphatic group such as styryl, p-methoxystyryl,
  • R is selected from the group consisting of hydrogen and phenyl radical
  • R is selected from the group consisting of hydrogen and methoxy radical.
  • Said reaction products can be formed by employing the following steps which comprise (1) providing a solution of said benzopyrylium salt in a suitable solvent such as 1,2- dichloroethane, (2) providing a solution of said benzopyrane in a suitable solvent such as l,2-dichloroethane, (3) mixing both solutions and heating the mixed solution (4) pouring the heated solution into a suitable precipitant such as ether to form a precipitate separating the precipitate from the precipitant and (6) purifying the separated precipitate.
  • the first method is a modification of a method disclosed in J. Chem. Soc.. i935, page 941 and is based on the reaction of a phenol or phenol derivative with a B-dicarbonyl compound or an a,B-unsaturated ketone in the presence of hydrogen chloride, sulfuric acid, ferric chloride, acetic or formic acid.
  • the second method comprises using an intermediate product prepared from a phenol and a coumarin derivative in the presence of phosphorus oxychloride or zinc chloride in a similar way to that disclosed in Helv. chim. acta, 34, page 1761 (1951).
  • the third method is based on a method disclosed in J. Chem. Soc., 74, page 3,445 (1952).
  • a ring closure process of an o-hydroxybenzaldehyde and a carbonyl compound in the presence of an alkali forms a benzopyrylium ring.
  • An ethenyl group of an active a-methylene radical in the 2-position of 2- alkylbenzopyrylium has an important role on the benzopyrylium ring closure process.
  • the fourth method is based on a method disclosed in J. Chem. Soc., 1929, page 936 and is effected in one step by both ring closure and ethenylation of an o-hydroxybenzaldehyde with a carbonyl compound in the presence of an alkali.
  • BENZOPYRANE The benzopyranes are easily prepared by one of the following two methods.
  • a first method is that benzopyrane is prepared by heating, under a reflux, a methanol solution of said benzopyrylium salt with sodium bicarbonate.
  • a second method is that benzopyrane is prepared by heating an alcohol solution of said benzopyrylium salt with sodium hydroxide or potassium hydroxide.
  • the crude compound filtered off is dissolved in 500 milliliters of methanol under heating in order to obtain a solution, then, the solution is cooled, added 500 milliliters of water and allowed to stand overnight. The resulting precipitate having a melting point of 84 to 86 C. is then collected by filtration.
  • the benzopyrane thus obtained is unstable and tends to change to a benzopyrylium salt by adding organic acid or inorganic acid. Furthermore, the benzopyrane is colored by air. Therefore, an improved preparation procedure is developed as follows: in the preparation procedure such as procedure (3) or (4), the crude benzopyrane is not recrystallized from a methanol-water solution, but the crude compound is shaken in SENSITIZER
  • the sensitizer according to the present invention is produced by the reaction of a benzopyrylium salt and a benzopyrane. Examples of the reaction products are shown in table 3 with their physical properties.
  • sensitizer is accomplished by heating a solution of the benzopyrylium salt and benzopyrane in a suitable solvent such as dichloroethane at 40 to 70 C. for several hours to dozens of hours.
  • a suitable solvent such as dichloroethane at 40 to 70 C.
  • the amount of benzopyrane to be used is oneto three times by molar weight of benzopyrylium salt to be used.
  • the color of the solution changes to dark color with a progress of the reaction. For example, FIG.
  • sensitizers Some examples of methods of preparing the sensitizer are set forth below in accordance with table 3. It will be apparent to those skilled in the art that other sensitizers according to the present invention may be prepared by methods similar to those described in general hereinabove and specifically herein below.
  • Sample Number 39 3.4 grams of Compound Number 13 and 2 grams of Compound Number 6 are dissolved in 75 milliliters of 1,2- dichloroethane which is purified to eliminate an acidic material. A so-obtained solution is stirred at 50 C. for 8 hours. After the same procedure as stated in (l), 3 grams of crystal is the yield. The crystal has a melting point of l70 to 174 C. and a solution of the crystal in 1,2-dichloroethane is green.
  • An improved photoconductive insulating material adapted for aforesaid photoconductive insulating layer can be obtained by a combination of aforesaid sensitizer and aforesaid organic photoconductive compound selected from the group consisting of poly-N-vinylcarbazole, poly-3,6-dibromo-N- vinylcarb'azole, brominated poly-N-vinylcarbazole, nitrated poly-N-vinylcarbazole and polyacenaphthylene.
  • the sensitizer according to the present invention is usually added to a solution of the'phot'oconductive compound in the form of a solution in a suitable solvent, such as dichloroethane, methylene chloride, chloroform, or a combination thereof.
  • a suitable solvent such as dichloroethane, methylene chloride, chloroform, or a combination thereof.
  • An added amount of said sensitizer is from 0.005 gram to 0.02 gram, preferably from 0.00l5 gram to 0.015 gram with respect to 1 gram ofsaid organic photoconductive compound.
  • Poly-3,6 dibromo-N-vinylcarbazole and brominated poly- Nvinylcarbazole'are prepared by the methods described in U.S. Pat. No: 3,421 .891.
  • Nitrated poly-N-vinylcarbazole is prepared by the method described in U.S. Pat. No. 3,418,116.
  • Other polymers are prepared by well-known methods.
  • a solution of the photoconductive polymer and the sensitizer in a suitable solvent is applied to the supports in the usual manner, for example, spraying, blade coating, wire-rod" coating or whirler coating, and then dried so as to produce a homogeneous photoconductive insulating layer on the electroconductive support.
  • suitable solvents are benzene, toluene, chlorobenzene, dioxane, methylene chloride, dichloroethane and combinations thereof.
  • the solution may include suitable plasticizers and/or organic colloids for improving the flexibility and strength of the photoconductive compound layer.
  • Suitable plasticizers include chlorinated diphenyl, dimethyl phthalate, diethyl phthalate and octyl phthalate.
  • Suitable organic colloids include natural and synthetic resins, e.g. phenol resin, phenol resin modified wit h rosin polyvinyl acetal, polyvinyl butyral, polyvinyl cinnamate and polycarbonate resin.
  • Suitable materials for a conductive support layer are those materials which satisfy the requirement of the electrophotographic art and include metal plates, glass plates having NESA coating and plates or foils made of electrically conductive resins or coated with a vacuum-deposited thin metal layer.
  • Transparent supports can be used to form transparent .electrophotographic plates, foils or films.
  • the reproduction of images by electrophotographic ,methods is carried out as follows: when the photoconductive insulating layer has been charged by means of a corona discharge apparatus, the electrophotographic material with the photoconductive insulating layer is exposed to light under a master and is then dusted over in a known manner with a resin powder colored with carbon black. The image that now becomes visible can easily be wiped off. It can also be fixed by heating at about 120 C. From positive masters, positive images exhibiting good contrast are produced.
  • EXAMPLE 1 One gram of poly-N-vinylcarbazole, 0.004 gram of a sensitizer listed in table 3 and 0.5 gram of chlorinated diphenyl (commercially available as Kanechlor") are dissolved in 10 milliliters of l,2-dichloroethane. The solution is applied to an aluminum plate and is dried to form a layer [p in thickness. After the aluminum plate provided with the layer is charged positively by means of corona discharge with a charging device maintained at approximately 6,000 volts in the dark, it is placed under a positive master and is exposed to a l00 W tungsten lamp at an illumination of 50 luxes. Subsequently, the plate is powdered over with a developer in a per se known manner.
  • the toner consists of a low melting-point polystyrene, colophony and carbon-black and is mixed with a carrier substance having a nature such that the toner becomes triboelectrically charged with a charge opposite to that produced on the plate.
  • a positive image is produced and is fixed by slight heating.
  • Table 4 shows the optimum amounts of exposure in lux-second units.
  • EXAMPLE 2 One gram of polyacenaphthylene. 0.6 gram of chlorinated diphenyl (commercially available as Kanechlor) and 0.004 gram of a sensitizer listed in table 3 are dissolved in 10 milliliters of l,2-dichloroethane The solution is applied to an aluminum plate and is dried to form a layer 6;; in thickness. An
  • electrophotographic image is produced in the same way as that described in example 1.
  • Table 5 shows the optimum amounts of exposure in lux-second units to produce exactly the original images.
  • Applicants preferred sensitizing compounds are those selected from the reaction products of a benzopyrylium salt having the chemical formula T Anionwherein R is a'radical selected from thejgroup consisting of a- -isopropyl-w-phenylbutadienyl, methoxystyryl, methoxyphenyl, styryl, a-isopropyl methoxystyryl a-isopropylstyryl and .phenyl,
  • R is hydrogen or phenyl
  • R is hydrogen or methoxy
  • R is aradical selected from the group consisting of styryl, methoxystyrl, a-isopropyl-m-phenylbutadienyl. aisopropyl-methoxystyryl, phenyl, a-isopropyl styryl and methoxyphenyl,
  • R is hydrogen or phenyl
  • R is hydrogen or methoxy.
  • An electrophotographic material comprising a conductive support layer and a 'photoconductive in'sulating'layer, the latter comprising a combination of an organic photoconductive compound :and a sensitizer, said organic photoconductive compound consisting essentially of at least one compound selected from the group consisting of poly-N-vinylcarbazole, poly-3,6-dibromo-N-vinylcarbazole, brominated poly-N-vinylcarbazole, nitrated poly-N-vinylcarbazole and polyacenaphthylene, said sensitizer comprising a compound selected from the group consisting of reaction products of a l)enzopyryliunisalt ha ving the chemical formula I I Anionwherein R is a radical selected from the group consisting of aisopropyl-wphenylbutadienyl, methoxystyryl, methoxyphenyl, styryl, a-isopropyl methoxys
  • R is a radical selected from the group consisting of styryl. methoxystryl a-isopropyl-w-phenylbutadienyl. aisopropyl-methoxystyryl, phenyl, a-isopropyl styryl and methoxyphenyl,
  • R is hydrogen or phenyl
  • R is hydrogen or methoxy.
  • the electrophotographic material of claim 1 wherein the sensitizer is the reaction product of Z-(a-isopropyl-w-phenylbutadienyl)-benzopyrylium perchlorate and Z-(p-methoxystyryl)-3-phenyl-4-methoxypyranev 3.
  • the electrophotographic material of claim 1 wherein the sensitizer is the reaction product of 2- p-methoxystyryl)-3 phenyl-benzopyrylium perchlorate and -(p-methoxystyryl)- 3-phenyl-4-methoxypyrane.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Photoreceptors In Electrophotography (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
US4200A 1969-01-30 1970-01-20 Electrophotographic materials Expired - Lifetime US3617268A (en)

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Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3881924A (en) * 1971-08-25 1975-05-06 Matsushita Electric Ind Co Ltd Organic photoconductive layer sensitized with trimethine compound
US3896112A (en) * 1971-10-21 1975-07-22 Ricoh Kk Bisbenzopyran and bisbenzopyrylium adducts
US3912508A (en) * 1970-10-07 1975-10-14 Matsushita Electric Ind Co Ltd Electrophotographic element comprising an organic photoconductive layer sensitized locally at its surface
USRE28698E (en) * 1970-03-13 1976-01-27 Matsushita Electric Industrial Co., Ltd. Electrophotographic material containing sensitizers
US3938994A (en) * 1972-03-17 1976-02-17 Eastman Kodak Company Pyrylium dyes for electrophotographic composition and element
US3953433A (en) * 1971-06-22 1976-04-27 Ricoh Co., Ltd. Sensitizer for use in electrophotographic light-sensitive material
US4283475A (en) * 1979-08-21 1981-08-11 Fuji Photo Film Co., Ltd. Pentamethine thiopyrylium salts, process for production thereof, and photoconductive compositions containing said salts
DE3331592A1 (de) 1982-09-01 1984-03-01 Fuji Photo Film Co., Ltd., Minamiashigara, Kanagawa Disazoverbindungen und diese enthaltende photoleitfaehige zusammensetzungen und elektrophotographische lichtempfindliche aufzeichnungsmaterialien
US4476313A (en) * 1982-04-02 1984-10-09 Rensselaer Polytechnic Institute Pyrylium salts
US5405976A (en) * 1990-11-21 1995-04-11 Polaroid Corporation Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use
US5753695A (en) * 1992-09-21 1998-05-19 Biogal Gyogyszergyar Rt Flavilium compounds and method of using
US5977351A (en) * 1990-11-21 1999-11-02 Polaroid Corporation Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3250615A (en) * 1961-10-23 1966-05-10 Eastman Kodak Co Light-sensitive layers containing pyrylium and thiapyrylium salts
US3526502A (en) * 1966-07-18 1970-09-01 Matsushita Electric Ind Co Ltd Electrophotographic material

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3250615A (en) * 1961-10-23 1966-05-10 Eastman Kodak Co Light-sensitive layers containing pyrylium and thiapyrylium salts
US3526502A (en) * 1966-07-18 1970-09-01 Matsushita Electric Ind Co Ltd Electrophotographic material

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE28698E (en) * 1970-03-13 1976-01-27 Matsushita Electric Industrial Co., Ltd. Electrophotographic material containing sensitizers
US3912508A (en) * 1970-10-07 1975-10-14 Matsushita Electric Ind Co Ltd Electrophotographic element comprising an organic photoconductive layer sensitized locally at its surface
US3953433A (en) * 1971-06-22 1976-04-27 Ricoh Co., Ltd. Sensitizer for use in electrophotographic light-sensitive material
US3881924A (en) * 1971-08-25 1975-05-06 Matsushita Electric Ind Co Ltd Organic photoconductive layer sensitized with trimethine compound
US3896112A (en) * 1971-10-21 1975-07-22 Ricoh Kk Bisbenzopyran and bisbenzopyrylium adducts
US3938994A (en) * 1972-03-17 1976-02-17 Eastman Kodak Company Pyrylium dyes for electrophotographic composition and element
US4283475A (en) * 1979-08-21 1981-08-11 Fuji Photo Film Co., Ltd. Pentamethine thiopyrylium salts, process for production thereof, and photoconductive compositions containing said salts
US4476313A (en) * 1982-04-02 1984-10-09 Rensselaer Polytechnic Institute Pyrylium salts
DE3331592A1 (de) 1982-09-01 1984-03-01 Fuji Photo Film Co., Ltd., Minamiashigara, Kanagawa Disazoverbindungen und diese enthaltende photoleitfaehige zusammensetzungen und elektrophotographische lichtempfindliche aufzeichnungsmaterialien
US5405976A (en) * 1990-11-21 1995-04-11 Polaroid Corporation Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use
US5627014A (en) * 1990-11-21 1997-05-06 Polaroid Corporation Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use
US5977351A (en) * 1990-11-21 1999-11-02 Polaroid Corporation Benzpyrylium squarylium and croconylium dyes, and processes for their preparation and use
US5753695A (en) * 1992-09-21 1998-05-19 Biogal Gyogyszergyar Rt Flavilium compounds and method of using

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NL142250B (nl) 1974-05-15
GB1244582A (en) 1971-09-02
JPS4825658B1 (ja) 1973-07-31
NL7001389A (ja) 1970-08-03
DE2004766C3 (ja) 1974-08-15
DE2004766A1 (de) 1970-07-30
FR2029686A1 (ja) 1970-10-23
DE2004766B2 (de) 1974-01-24

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