JPH01112252A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To enhance sensitivity in the shorter wavelength region and to prevent accumulation of residual potential and deterioration of chargeability by incorporating a polyurethane resin in an interlayer. CONSTITUTION:The electrophotographic sensitive body is formed by successively laminating on a conductive substrate an electric charge transfer layer, a charge generating layer, the interlayer containing the polyurethane resin, and a protective layer. The interlayer is formed on the charge generating layer as a layer for preventing injection of charge due to corona charging and trapping charge carriers at the time of repeated uses. It is preferred to use the polyurethane resin of a solvent-soluble type from the view point of coating performance, thus permitting the obtained photosensitive body to be superior in sensitivity also in the shorter wavelength region, to prevent accumulation of residual potential and deterioration of chargeability and superior in durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to improvements in electrophotographic photoreceptors, particularly positively charged electrophotographic photoreceptors.

[Prior art]

2. Description of the Related Art Electrophotographic photoreceptors have been known that are provided with a charge generation layer containing a charge generation substance and various resins.

Examples of this include polyvinyl butyral (Japanese Patent Application Laid-open No. 58-105154), fatty acid cellulose ester (
JP-A-58-166353), acrylic resin with Tg of 70°C or less and an acid value of 10 to 40 (JP-A-58-192)
No. 040), resin with Tg of 70°C or less, and resin with Tg of 75°C
A mixture of the above resins (JP-A-58-193549
No.), which is redispersed by adding a less compatible resin-solvent system to the charge-generating substance-resin-solvent system (JP-A-56-
No. 12646), polyvinylpyrrolidone (Japanese Patent Application Laid-open No. 12646-
113140) and polyvinyl formal resin (Japanese Patent Application Laid-open No. 61-235844).

However, conventionally known photoreceptors have a problem in that sensitivity and chargeability against pre-exposure fatigue vary depending on the mixing ratio of the charge generating substance and the binder resin.

In other words, in conventional photoreceptors, sensitivity can be increased by reducing the amount of binder resin used for the charge-generating substance, but the chargeability deteriorates significantly due to pre-exposure fatigue, and conversely, the use of binder resin for the charge-generating substance If the amount is increased, it is possible to suppress a decrease in chargeability due to pre-exposure fatigue, but this includes the problem of a significant decrease in sensitivity.

Furthermore, in recent years, organic photoreceptors, particularly negatively charged photoreceptors in which a charge generation layer and a charge transfer layer are successively laminated on a support, have been widely used. This photoreceptor generates more ozone than the positively charged type, and therefore the surface of the photoreceptor is susceptible to chemical changes, resulting in blurred images and increased residual potential.

In addition, light yellow to light yellow compounds such as hydrazone compounds, pyrazoline compounds, oxazole compounds, and styryl compounds are used in the charge transfer layer.
Since a yellow hole transfer material is used, short wavelength light, such as blue light of 500 Ωm or less, is absorbed by this charge transfer layer, and such a photoreceptor has the disadvantage of extremely weak sensitivity in the short wavelength range. . This decrease in sensitivity is significant for blue light, and therefore the light attenuation effect cannot be achieved unless the amount of light is increased. However, increasing the amount of light in this manner causes a problem in that fatigue accumulates on the photoreceptor and its durability decreases.

On the other hand, in a positively charged photoreceptor in which a charge transfer layer and a charge generation layer are laminated in that order, the charge generation layer becomes the surface layer, and the surface layer wears out due to repeated processes of charging, exposure, development, transfer, and cleaning. and its durability decreases.

As a method to eliminate these drawbacks, a method of increasing the thickness of the charge generation layer has been proposed (Japanese Patent Laid-Open No. 59-22
4846, JP-A-59-174849), this method has the disadvantage that residual potential accumulates due to carrier traps in the charge generation layer and charging properties deteriorate.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor that exhibits excellent sensitivity even in the short wavelength range, does not accumulate residual potential or deteriorate charging performance, and has excellent durability.

〔composition〕

According to the present invention, there is provided an electrophotographic photoreceptor in which a charge transfer layer, a charge generation layer, an intermediate layer, and a protective layer are sequentially provided on a conductive support, characterized in that the intermediate layer contains a polyurethane resin. An electrophotographic photoreceptor is provided.

Next, each constituent material used in the present invention will be explained.

The conductive support is intended to supply charges of opposite polarity to the charged charges to the substrate side, and has an electrical resistance of 1.
08 Ωcm or less and can withstand the film forming conditions of the undercoat layer for the charge generation layer and the charge transfer material. Examples of these are AQ, Ni, Cr
The surfaces of electrically conductive metals and alloys such as Zn and stainless steel, inorganic insulating substances such as glass and ceramics, and organic insulating substances such as polyester, polyimide, phenolic resin, nylon resin, and paper are coated by vacuum evaporation, sputtering, and spraying. AQ, N depending on the method of painting etc.
j, Cr, Zn, stainless steel, carbon, 5n02, In2
Examples include those coated with an electrically conductive substance such as O3 and subjected to conductive treatment.

The charge transfer layer can be formed by dissolving or dispersing a charge transfer substance and a resin binder in a suitable solvent, coating the solution on a conductive substrate, and drying the solution. Moreover, a plasticizer, a leveling agent, etc. can also be added if necessary.

Charge transfer substances include poly-N-vinylcarbazole and its derivatives, poly-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, oxadiazole derivatives. , imidazole derivatives, triphenylamine derivatives, 9-(p-diethylaminostyryl)anthracene, 1,1-bis-(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, α-phenylstilbene Examples include electron-donating substances such as derivatives.

Examples of the resin binder used in the charge generation layer include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate-1, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, poly-N-vinylcarbazole, acrylic resin, silicone resin, Examples include thermoplastic or thermosetting resins such as epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

The solvent at this time is tetrahydrofuran.

Dioxane, toluene, monochlorobenzene, dichloroethane, methylene chloride, etc. can be used.

The thickness of the charge transport layer is 5 to 40 μm, preferably 10 to 40 μm.
Approximately 25 μm is appropriate.

Specific examples of azo pigments are shown below.

The charge generation layer is composed of a charge generation substance or a charge generation substance and a resin binder.

Examples of such resin binders include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, and polyvinyl chloride.

Vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyvinylidene chloride, polyacrylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyltoluene, poly-N-vinylcarbazole resin, Examples include thermoplastic or thermosetting resins such as silicone resins, epoxy resins, melamine resins, urethane resins, phenolic resins, and alkyd resins.

The total amount of the binder resin is 100% of the charge generating substance.
It is appropriate to use 0.01 to 200 parts by weight, preferably 1 to 50 parts by weight. The polymer and/or copolymer must be contained in an amount of at least 0.01 part by weight, preferably 1 part by weight or more, per 100 parts by weight of the charge generating substance.

Examples of the charge generating substance include CI Pigment Blue 25 [Color Index (CI) 21180],
CI Pigment Red 41 (CI 21200),
C.I. Acid Red 52 (CI 45100), C.I. Basic Red 3 (C. 45210), phthalocyanine pigments having a porphyrin skeleton, azulenium salt pigments, squalic salt pigments, azo pigments having a carbazole skeleton (JP-A-53-95033) Azo pigments having a stilstilbene skeleton (described in JP-A-53-138229), azo pigments having a triphenylamine skeleton (described in JP-A-53-13254)
7), an azo pigment having a dibenzothiophene skeleton (described in JP-A No. 54-21728), an azo pigment having an oxadiazole skeleton (described in JP-A-54-12)
742), an azo pigment having a fluorenone skeleton (described in JP-A No. 54-22834), an azo pigment having a bisstilbene skeleton (described in JP-A-54-1773)
3), an azo pigment having a distyryloxadiazole skeleton (described in JP-A-54-2129)
, azo pigments having a distyrylcarbazole skeleton (described in JP-A-54-1.7734), triazo pigments having a carbazole skeleton (described in JP-A-57-195767 and JP-A-57-195768), etc. , furthermore, CI Pigment Blue 16 (CI 74100)
Phthalocyanine pigments such as Sea Eye Butt Brown 5
(CI 73410), Sea Eye Bat Die (CI 7
3030), etc., Argo Scarlet B
(manufactured by Violet), Indus Thread Scarlet R (
Organic pigments such as perylene pigments (manufactured by Bayer) can be used.

Among these charge-generating substances, azo pigments are particularly preferred, and among azo pigments, disazo pigments and trisazo pigments shown below are most preferred.

Specific examples of azo pigments are shown below.

υ 1 hill length - per person 1 O 1 (, C0 Q!- = 15- = 16- = 19- The thickness of the charge generation layer is approximately 0.1 to 10 μm, preferably 2 to 8 μm. be.

The charge generation layer can be formed by dissolving or dispersing a resin binder and a charge generation substance in a suitable solvent, applying the solution, and drying the solution. As a solvent, benzene, toluene, xylene, methylene chloride, dichloroethane, monochlorobenzene, dichlorobenzene, ethyl acetate, butyl acetate, methyl ethyl ketone, dioxane, tetrahydrofuran, cyclohexanone, methyl cellosolve, ethyl cellosolve, etc. can be used alone or in combination. can.

In the present invention, an intermediate layer made of polyurethane resin is provided on the charge generation layer as a layer for preventing charge injection due to corona charging and trapping of charge carriers during repeated use.

Although it is not clear why the intermediate layer containing a polyurethane resin has a charge injection prevention function in the present invention, since polyurethane resin has a functional group whose basic skeleton is a urethane bond of -NHCOO- in its molecule, this This seems to be due to the fact that the functional group and the azo pigment come into contact to form a good charge injection prevention layer and to suppress the accumulation of residual potential.

Although there are no particular limitations on the polyurethane resin used in the present invention, solvent-soluble polyurethane resins are preferably used from the viewpoint of coatability and the like.

Such polyurethane resins include polyol isocyanate resin, acrylic copolymer and isocyanate,
Examples include polyester isocyanate resin and epoxy isocyanate resin.

The thickness of this intermediate layer is 0.05 to 3 μm, preferably 0.0
It is 5 to 1 μm.

Further, in the present invention, it is necessary to provide a protective layer on the intermediate layer in order to improve wear resistance, damage resistance, etc.

Protective layer resins include ABS resin, AC5JaJ resin, olefin vinyl copolymer resin, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyarylate, polyallylsulfone, polybutylene, polybutylene terephthalate,
Polycarbonate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, methacrylic resin, polymethylpentene, polypropylene, polyphenylene oxide, polysulfone, polystyrene, A
Examples include S resin, butadiene-styrene resin, polyurethane, polyvinyl chloride, polyvinylidene chloride, and epoxy resin.

In addition, from the viewpoint of wear resistance, polytetrafluoroethylene resin, fluorine resin, and silicone resin can be added as additives to lower the friction coefficient and improve wear resistance and scratch resistance. Dispersing inorganic compounds such as tin oxide and potassium titanate in the resin also improves wear resistance. The thickness of this surface protective layer is 0.5 to 10 μm
, preferably 1 to 5 μm.

Further, in the present invention, a subbing layer having a barrier function and an adhesive function can be provided between the conductive layer and the charge transfer layer.

The subbing layer is made of casein, polyvinyl alcohol, cellulose, ethylene-acrylic acid copolymer, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin aluminum oxide, etc. It can be formed by

The thickness of the subbing layer is 0.1 to 5μ, preferably 0.5 to 3μ.
μ is appropriate.

In order to apply each of the above layers in the present invention, a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, a curtain coaching method, a screen printing method, etc. are used. This can be done using a coating method. For drying, it is preferable to dry to the touch at room temperature and then heat dry. Heat drying can be carried out at a temperature of 30 to 200° C. for a period of from 5 minutes to 2 hours, either stationary or under ventilation.

〔effect〕

Since the electrophotographic photoreceptor of the present invention has the above configuration,
It exhibits excellent sensitivity even in the short wavelength range, and has excellent durability without accumulation of residual potential or deterioration of charging performance.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples. Note that both parts and 2 are based on weight.

Example] The following charge transfer layer liquid was coated on an 80φ340 mm aluminum cylinder by a dipping method so that the dry film thickness was 20 μm. Drying was performed at 120°C for 20 minutes.

[Charge transfer layer coating liquid]

Polycarbonate (C-1400 manufactured by Ontaisha) 20
0 parts Silicone oil (KF-50 manufactured by Shin-Etsu Chemical Co., Ltd.) 0
．． 05 parts dichloromethane 15
00 parts [Charge generation layer coating liquid] 22 parts of azo pigment (Nα1) and 242 parts of cyclohexanone were dispersed in a ball mill for 72 hours, and 660 parts of cyclohexanone was added and dispersed for 2 hours to adjust the mill base. 1
．． Let down to 2%.

Next, the charge generation layer coating liquid was applied onto the charge transfer layer to a thickness of 0.4 μm by a spray method, and the coating solution was applied at 1'20°C to a thickness of 0.4 μm.
After drying for 0 minutes, a charge generation layer was provided.

Next, an intermediate layer forming solution consisting of 40 parts of tetrahydrofuran and 50 parts of cyclohexanone was prepared, and a film thickness of 0.3 after drying was prepared using a spray method.
It was coated to a thickness of μm. Drying was performed at 120°C for 10 minutes.

Next, 100 parts of conductive titanium (manufactured by Mitsubishi Metals) I-luene
240 parts butanol
A mixture consisting of 60 parts was dispersed in a ball mill for 72 hours, 240 parts of toluene and 60 parts of butanol were added, and dispersed again for 12 hours to prepare a mill base. Its mill base is 1 to luene/butanol-4
/J (weight ratio) of solvent to reduce the solid content to 1 da,
This was used as a protective layer forming liquid.

This liquid was coated on the intermediate layer so that the thickness after drying was 4 μm to prepare an electrophotographic photoreceptor of the present invention. Note that drying was performed at 120° C. for 20 minutes.

Example 2 In Example 1, the intermediate layer coating liquid was replaced with the following 5
An electrophotographic photoreceptor of the present invention was prepared in the same manner as in Example 1 except that the thickness of the intermediate layer was 0.3 μm.

[Intermediate layer forming liquid]

Hexamethylene diisocyanate 8.4 parts Propylene glycol 7.7 parts Coronate (manufactured by Nippon Polyurethane Co., Ltd.) 1 part Methyl ethyl ketone 100 parts Example 3 Same as Example 1 except that the intermediate layer forming liquid was replaced with the following. An electrophotographic photoreceptor of the present invention was produced in the same manner.

[Intermediate layer forming liquid]

Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) 5 parts Methyl ethyl ketone 100 parts Example 4 In Example 1, the charge transfer layer forming liquid and the charge generation layer forming liquid were replaced with the following, and the thickness of the charge generation layer was 0. An electrophotographic photoreceptor of the present invention was prepared in the same manner as in Example 1 except that the thickness of the intermediate layer was 0.6 μm.

[Charge transfer layer forming liquid]

Polycarbonate (C-1400 manufactured by Ontaisha) 20
0 parts silicone oil (F-50 manufactured by Shin-Etsu Chemical Co., Ltd.) 0
．． 05 parts dichloromethane 15
00 parts [Charge generation layer forming liquid] Azo pigment (Nα39) 50
After grinding and dispersing the above product in a ball mill for 42 hours,
Added 0 parts of methyl ethyl ketone, dispersed again for 24 hours, and let down to 1% solids with methyl ethyl ketone solution.

Comparative Example 1 An electrophotographic photoreceptor of a comparative example was prepared in the same manner as in Example 1 except that the intermediate layer was omitted in the practical side.

Comparative Example 2 Same as Example 1 except that the polyurethane resin in the intermediate layer was replaced with a 2:1:50 solution of zirconium acetoacetonate, 3-methacryloxypropyltritoxysilane and n-butanol. An electrophotographic photoreceptor was prepared as a comparative example.

Next, the various photoreceptors obtained above were
67, rotate it at 11000 rpm, discharge a voltage of +6 KV in the dark, apply it for 20 seconds, find the potential Vm, and then stop the discharge and let it decay in the dark for 20 seconds to find the potential Vo at that time. was measured. Furthermore, the tungsten light has a light intensity of 26 Lux and a slit width of 6 mm.
Sensitivity was determined by setting the amount E1/2.1/10, which is the amount reduced by half from vO by irradiation for seconds, as El/10.

Further, the potential after 20 seconds was defined as VR. Table 1 shows the results.
Shown below.

Furthermore, these photoreceptors were mounted on FT-5510 manufactured by Ricoh Co., Ltd., and a durability test was conducted. The amount of light and charge are the dark potential (V)8
00V, and the dark potential (V) was set to 80V.

As a result, the electrophotographic photoreceptors of Examples 1 to 5 were able to obtain clear images even at the initial stage of the continuous test of 10,000 sheets and after printing,
Further, the electrical characteristics were stable without any change. Also,
No wear on the surface of the photoreceptor could be confirmed. On the other hand, Comparative Example 1 had poor charging properties and poor image contrast. In addition, in Comparative Example 2, the residual potential increased significantly, causing background smudges and density unevenness in halftone image areas, and furthermore, the volume shrinkage after drying was large and a uniform film thickness could not be obtained.

=35- Procedural amendment band (shu) 1. Indication of the case Patent Application No. 270900 of 1988 2. Name of the invention Electrophotographic photoreceptor 3. Person making the amendment Relationship to the case Patent applicant address Ota, Tokyo 1-3-6 Nakamagome, Ward Name
(674) Rico Co., Ltd. - Representative Hama
1) Hiro 4, Agent 〒151 5, Date of amendment order Voluntary 6, Number of inventions increased by amendment 07, Subject of amendment ``Detailed explanation of the invention'' column 8 of the specification, Contents of the amendment Specification of the application The following amendments will be made in this document.

(1) ro, 01-200 parts by weight on page 8, line 7,
Correct it to "0-200 parts by weight".

(2) Change “1 to 50 parts by weight” on page 8, line 8 to “0 to 5 parts by weight”
Corrected to 0 parts by weight.

(3) Delete "Also, the above polymer is necessary" from lines 8 to 11 on page 8.

(4) “Preferably 2 to 8 pages from the bottom of page 25, line 12
Correct mJ to "preferably 0.2 to 2 μm".

Claims (1)

[Claims] (1) In an electrophotographic photoreceptor in which a charge transfer layer, a charge generation layer, an intermediate layer, and a protective layer are sequentially provided on a conductive support,
An electrophotographic photoreceptor characterized in that the intermediate layer contains a polyurethane resin.