JPH0114576B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor in which a photoconductive substance is bound onto a conductive substrate using a binder resin having excellent charging characteristics, sensitivity, dark decay, and repeatability.

Generally, in electrophotography, like the xerography method, a photoreceptor made of a thin film of photoconductive material such as selenium or cadmium sulfide formed on a metal drum is charged in a dark place, and then a light image is irradiated (exposed). After forming an electrostatic latent image, a visible image is created with toner (development), and this is transferred and fixed onto paper, etc., or a photoconductive layer is provided on paper as in the electrofax method, and this photosensitive There are methods of obtaining a permanent visible image on the photoconductive layer by charging, exposing, developing and fixing on the body.

The photoconductive layer in a typical electrophotographic photoreceptor is prepared by mixing a photoconductive substance with a binder resin and a sensitizer using an appropriate method, and then applying and drying the mixture onto a conductive substrate using a roll coater or the like. has been done. This binder resin not only has the ability to bind the photoconductive substance to the substrate, but also has good film-forming ability and appropriate electrical resistance, and has electrophotographic properties and charging properties of the photoconductive substance. It is required that sensitivity, dark decay, repetition characteristics, etc. be not impaired.

Conventionally, many binder resins are known, such as silicone resins, epoxy resins, alkyd resins, vinyl resins, acrylic resins, and urethane resins. However, although these binder resins are used in appropriate combinations, there is no one that satisfies all of the above-mentioned properties and is by no means sufficient as a binder resin for electrophotographic photoreceptors. For example, urethane resins have good charging characteristics, dark decay, film strength, etc., but cannot be said to be binder resins that have sufficient performance in terms of printing durability in terms of electrophotographic characteristics in repeated use of sensitivity.

The present invention relates to an electrophotographic photoreceptor using a binder resin that is highly sensitive and has improved printing durability in terms of electrophotographic properties in repeated use. In other words, the present invention uses a photoconductive substance (A).
and an epoxy resin and a (meth)acrylic ester polymer obtained by polymerizing a monomer composition containing an acrylic ester and/or methacrylic ester containing a hydroxyl group and another polymerizable monomer having an ethylenically unsaturated bond. This is an electrophotographic photoreceptor in which a photoconductive layer containing a binder resin (B) is formed on a conductive substrate.

The photoconductive substance (A) according to the present invention can be applied to both inorganic and organic photoconductive substances, such as cadmium sulfide, zinc oxide, polyvinylcarbazole, and phthalocyanine. Phthalocyanines are particularly desirable in combination with the binder resins of the present invention for their processing, non-toxicity, flexibility of the photoconductive layer, and electrophotographic properties. Various crystal forms of phthalocyanine are known, and any crystal form may be used as long as the phthalocyanine has photoconductivity. Preferably, JP-A-Sho, which has good electrophotographic properties such as sensitivity,
X-ray diffraction angle 2θ± of CuKα shown in 51−109841
0.2 degrees is a copper phthalocyanine that shows three strong lines at 7.0, 7.7 and 9.2 degrees. Or Tokukai Sho
Copper phthalocyanine in the ε-type crystalline form as shown in No. 50-38543 also gives good results.

One of the methods for producing these copper phthalocyanines
For example, there is a method in which copper phthalocyanine having an ε-type crystal form is milled at 50 to 120° C. under mechanical strain. ε-type copper phthalocyanine is produced by the production method described in Japanese Patent Publication No. 1972-2780, that is, between phthalic anhydride-copper or copper salt-urea or between phthalodinitrile-copper or copper salt-urea in the presence or absence of a catalyst. In production by condensation, the total amount of urea used is 3 to 15 times the weight of phthalic anhydride or phthalodinitrile, and phthalic anhydride or phthalodinitrile is added little by little into the molten system containing excess urea. A manufacturing method in which salt milling is performed after the addition of copper phthalocyanine and a condensation reaction, or (1) copper phthalocyanine and (2) phthalocyanine derivatives with substituents introduced into the benzene nucleus, phthalocyanine nitrogen isomer, metal-free phthalocyanine, and metals other than copper. 80 with one or more selected from the group of phthalocyanines.
It is a copper phthalocyanine obtained by a manufacturing method of milling with strong mechanical strain at ~200°C (Japanese Patent Application Laid-Open Nos. 48-76925 and 49-59136).

The binder resin (B) according to the present invention is an acrylic ester containing a hydroxyl group (hereinafter, acrylic ester and methacrylic ester are collectively referred to as (meth)
These are a (meth)acrylic ester polymer and an epoxy resin obtained by polymerizing a monomer composition containing acrylic ester).

The (meth)acrylic ester polymer is obtained by polymerizing a monomer composition containing at least a hydroxyl group-containing (meth)acrylic ester. Examples of hydroxyl group-containing (meth)acrylic esters include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate,
It is at least one selected from 3-hydroxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, triethylene glycol mono(meth)acrylate, dipropylene glycol mono(meth)acrylate, and the like. Preferably it is 2-hydroxyethyl (meth)acrylate. Other polymerizable monomers having ethylenically unsaturated bonds include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate. , lauryl (meth)acrylate, styrene,
At least one selected from α-methylstyrene, β-chlorostyrene, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, acrylamide, methacrylamide, and the like. Note that it is desirable that acids such as (meth)acrylic acid, crotonic acid, and maleic acid are not included as a monomer component of the (meth)acrylic acid ester polymer of the present invention, or even if they are included, the amount is small. There are disadvantages of poor repeatability and increased dark sensitivity decay due to acid.

In the monomer composition of the (meth)acrylic ester copolymer according to the present invention, the specific gravity ratio of the hydroxyl group-containing (meth) acrylic ester to other monomers is suitably 5/95 to 30/70. or,
The obtained (meth)acrylic acid ester polymer has a hydroxyl value of about 10 to 60. The polymerization method is conventional solution polymerization. However, as a polymerization initiator, an initiator such as azobisisobutyronitrile is preferable to a peroxide such as benzoyl peroxide.

Almost all commonly used resins can be used as the epoxy resin. Bisphenol A
An epoxy resin obtained by the reaction of 4,4'-sec butylidene diphenol with epichlorohydrin, an epoxy resin obtained by the reaction of 4,4'-sec butylidene diphenol and epichlorohydrin, and an epoxy resin obtained by using β-methylepichlorohydrin in place of epichlorohydrin in the above epoxy resins. , phenol volak type epoxy resin, cresol novolak type epoxy resin, alicyclic epoxy resin, etc. The trade names of commercially available epoxy resins include solid resins Epicote #1001, #1004,
#1007, #1009, liquid resin Epicote #815, #827, #828, #834 (the above are epoxy resins manufactured by Ciel Chemical), etc. Epicote #1007 is preferred in the present invention.

The binder resin (B) according to the present invention is (meth)
It consists of an acrylic ester polymer and an epoxy resin, and the epoxy resin is used in a ratio of about 1 equivalent or less to the (meth)acrylic ester polymer (hydroxyl group). The solid content weight ratio varies depending on the type of (meth)acrylic acid ester polymer and epoxy resin used, but is 98/2~
70/30, preferably 95/5 to 85/15.

(Meth)acrylic acid ester polymer, epoxy resin, and photoconductive substance are uniformly dispersed together with a solvent and additives used as necessary using a kneading and dispersing machine such as a ball mill, sand mill, roll mill, attritor, or vibration mill. A photoconductive composition is prepared by performing the following steps. This photoconductive composition is applied onto a conductive substrate, such as an aluminum plate, electrically conductively treated paper, or plastic film, which is commonly used in electrophotographic photoreceptors, to form a photoconductive layer. As for the coating method, if necessary, add a solvent to the photoconductive composition to adjust the viscosity, and form a film using an air doctor coater, blade coater, rod coater, reverse roll coater, spray coater, hopper coater, squeeze coater, etc. Let's do it. After coating, the photoconductive layer is dried using a suitable drying device until a sufficient charging potential is applied to the photoconductive layer. In this drying process, the (meth)acrylic acid ester polymer and the epoxy resin are generally reacted, but the drying may be carried out under conditions where only a portion of the polymer reacts with the epoxy resin. An optical sensitizer or a chemical sensitizer may be added to the photoconductive composition of the present invention.

The electrophotographic photoreceptor according to the present invention exhibits the following effects.

That is, (1) high sensitivity; (2) The film has physical strength and is highly flexible. (3) Strong adhesion to conductive substrates. (4) High potential recovery rate during continuous repeated use. (5) There is no change in electrophotographic properties over time. (6) Good moisture resistance. (7) Lack of optical memory. (8) If phthalocyanine or the like is used as a photoconductive substance, there is no problem of toxicity. (9) The price of the electrophotographic photoreceptor is low. As described above, it can be seen that the electrophotographic photoreceptor of the present invention has extremely high practicality.

Next, the present invention will be explained by reference examples and examples. In examples, "parts" and "%" refer to parts by weight, weight %.
shows.

Reference Example 1 Charge 30 parts of cellosolve acetate, 30 parts of methyl ethyl ketone, and 0.4 parts of azobisisobutyronitrile into a four-necked flask equipped with a stirrer, nitrogen gas inlet tube, dropping funnel, and reflux condenser. Heat and stir to reflux temperature (approximately 90°C) while passing nitrogen gas. Next, a mixture of 23.6 parts of isobutyl methacrylate, 10 parts of methyl methacrylate, and 6.4 parts of 2-hydroxyethyl methacrylate was added dropwise from the dropping funnel over 2 hours. After the dropwise addition is complete, 0.2 part of azbisisobutyronitrile is added, and the mixture is heated and stirred at reflux temperature for an additional 3 hours, and then cooled to room temperature.

Colorless and transparent (meth) with a solid content of 40% and a viscosity of 150 cps.
An acrylic acid ester resin liquid was obtained.

Reference Example 2 Using the same equipment and polymerization method as in Reference Example 1, using 2 parts of isobutyl methacrylate, 26.8 parts of methyl methacrylate, and 11.2 parts of 2-hydroxyethyl methacrylate as monomers, the solid content was 40% and the viscosity was 250 cps.
A colorless and transparent (meth)acrylate resin liquid was obtained.

Reference Example 4 Using the same equipment and polymerization method as in Reference Example 1, using 4 parts of isobutyl methacrylate, 25.2 parts of methyl methacrylate, and 10.8 parts of 2-hydroxyethyl methacrylate as monomers, the solid content was 40% and the viscosity was
A colorless and transparent (meth)acrylate resin liquid of 220 cps was obtained.

Reference Example 4 Using the same equipment and polymerization method as in Reference Example 1, using 5 parts of 2-ethylhexyl acrylate, 15 parts of methyl methacrylate, 3 parts of styrene, and 7 parts of 2-hydroxypropyl methacrylate as monomers, the solid content was 40%. % and a viscosity of 210 cps, a colorless and transparent (meth)acrylate resin liquid was obtained.

Example 1 ε-type crystal copper phthalocyanine 15.0 parts (meth)acrylic acid ester resin solution obtained in Reference Example 1 151.9 parts Epicocoat #1007 (Ciel Chemical) 40% methyl ethyl ketone solution 16.9 parts 2, 4, 5, 7 -tetranitro-9-fluorene
0.4 parts Methyl ethyl ketone 35.0 parts Cellosolve acetate 35.0 parts The above composition was milled in a porcelain ball mill for 48 hours to form a photoconductive composition. This photoconductive composition was roll coated onto a laminate film of 5μ aluminum and 75μ polyester film to a film thickness of 8μ, and after the film was formed, it was placed in an oven uniformly heated to 130°C for 10 minutes, and then It was used as a photographic photoreceptor. The obtained electrophotographic photoreceptor was tested using an electrostatic copying paper tester (Electro Paper Analyzer SP-428).
corona applied voltage +5.5KV,
Continuously repeated 2000 times under the following conditions: charging speed 10 m/min, dark decay time 3 seconds, light decay time 1 second, light intensity 40 Lux.
When measurements were taken twice, the ratio of the 2000th charging potential to the initial charging potential (potential recovery rate) was
95%, and both dark decay change rate and sensitivity change rate are 5.
%, with extremely high sensitivity (2.5 Lux
second) It was a highly practical electrophotographic photoreceptor.
Furthermore, when this electrophotographic photoreceptor was subjected to a printing durability test using a commercially available electrophotographic copying machine, the image quality of the 2000th copy was the same as the initial image quality.

Comparative Example 1 In Example 1, the (meth)acrylate ester resin solution was not used as the photoconductive composition, but instead a 40% solution of Epikote #1007 methyl ethyl ketone was used.
Using 1,600 copies, an electrophotographic photoreceptor was made in the same manner as in Example 1, and when tested, the sensitivity was 17 Lux second, and the potential recovery rate at the 2,000th time was 65%. The sensitivity was low and the potential recovery rate was also poor.

Comparative Example 2 An electrophotographic photoreceptor was prepared and tested in the same manner as in Example 1 except that 160.0 parts of (meth)acrylic acid ester resin liquid was used instead of using Epicoat #1007 as the photoconductive composition. However, the sensitivity is
6Lux・second, and the potential recovery rate for the 2000th time is
It was 30%. Although the sensitivity was almost good, the potential recovery rate was poor.

Example 2 Photoconductive zinc oxide 80 parts (meth)acrylate resin solution obtained in Reference Example 2 35 parts Epikote #1007 40% methyl ethyl ketone solution
5 parts bromophenol blue solution (1g/100c.c.)
0.5 parts Rose Bengal solution (500 mg/50 c.c.) 1.0 parts Methyl ethyl ketone 25.0 parts An electrophotographic photoreceptor was prepared using the above composition according to Example 1, and the corona applied voltage was set to -5.5 KV, and the other conditions were as in Example 1. Similarly, when measurements were performed 1000 times, the rate of change in sensitivity decreased by 20%.

Example 3 Metal-free phthalocyanine 15.0 parts (meth)acrylic acid ester resin solution obtained in Reference Example 3 143.5 parts Epikote #1001 (manufactured by Ciel Chemical) 40% methyl ethyl ketone solution 25.3 parts 2,4,7-trinitro-9- Fluorenone
1.2 parts Cellosolve acetate 80.0 parts The above composition was made into a photoconductive composition in the same manner as in Example 1, and a film thickness of about 80μ hard aluminum plate was prepared.
Roll coated to 6μ, after film formation, 150μ
The electrophotographic photoreceptor was placed in an oven uniformly heated to .degree. C. for 15 minutes. When this photoreceptor was tested in the same manner as in Example 1, the potential recovery at the 2000th time was 92
%, and a highly practical photoreceptor with dark decay change rate and sensitivity change rate within 10% was obtained. Moreover, the printing durability on a practical machine was also good.

Example 4 β-type crystalline copper phthalocyanine 200 parts (meth)acrylic acid ester resin liquid obtained in Reference Example 4 157.5 parts Epicote #828 (manufactured by Ciel Chemical) 40% methyl ethyl ketone solution 22.5 parts Tetracyanoethylene 0.5 part Methyl ethyl ketone 40.0 part cellosolve acetate 35.0 parts The above composition was milled as prescribed in a porcelain ball mill at room temperature for 24 hours to obtain a photoconductive composition. The resulting photoconductive composition was deposited on a 75μ polyester film by vacuum evaporation of 99.99% pure Al powder to a thickness of approximately 1μ at a vacuum level of 10 ^-5 torr to a film thickness of 7μ.
Roll coat to 120℃ after film formation.
The sample was placed in an oven heated uniformly for 30 minutes to obtain an electrophotographic photoreceptor.

When the thus obtained electrophotographic photoreceptor was measured in the same manner as in Example 1, the potential recovery rate at the 2000th time with respect to the initial potential was 85%, the dark decay rate of change, the sensitivity change rate. showed a change of 15%, indicating that the photoreceptor was slightly less cyclically stable than Example 1. Furthermore, when a printing durability test was conducted in the same manner as in Example 1, the quality of the 2000th copy showed that the density and contrast were slightly lower than the initial image quality, but the copies were generally good. Ta.

Claims (1)

[Scope of Claims] 1. A photoconductive substance (A) and a monomer composition containing a hydroxyl group-containing acrylic ester and/or methacrylic ester and another polymerizable monomer having an ethylenically unsaturated bond are bonded together. An electrophotographic photoreceptor comprising a photoconductive layer containing a binder resin (B) made of a (meth)acrylic acid ester polymer and an epoxy resin, formed on a conductive substrate. 2. The electrophotographic photoreceptor according to claim 1, wherein the photoconductive substance is phthalocyanine.