JPS5812579B2 - Electrophotographic photoreceptor - Google Patents

Description

Detailed Description of the Invention The present invention is characterized in that a resin layer that is polymerized and cured by electron beam irradiation is provided on the surface of the photoconductive layer of an electrophotographic photoreceptor, which improves the mechanical durability of the photoreceptor. The purpose of this is to improve the photoreceptor's lifespan and extend the life of the photoreceptor.

Conventionally, various electrophotographic photoreceptors are known, each having a different configuration depending on the electrophotographic method used.

For example, a photoreceptor having a photoconductive layer on a substrate used in the Carlson system, or, for example,
No. 910 or Japanese Patent Publication No. 43-24748, etc., and other electrophotographic methods including similar deformation processes. It is representative.

What these photoreceptors have in common is that they are exposed to physical, mechanical, or chemical pressure during image formation.

In other words, in the image forming process of electrophotography, an electrostatic latent image is formed by appropriately charging and exposing a photoreceptor, and a dry or wet developer is applied to this electrostatic latent image to make it visible. The steps of forming an image, transferring the visible image to the transfer material by contacting it with the transfer material, and further scrubbing the photoreceptor with a cleaning means to remove residual developer are repeatedly performed. .

Therefore, durability against high voltage application during charging, durability against developer during development, and durability against mechanical pressure during transfer and cleaning are essential elements for electrophotographic photoreceptors.

For example, electrical deterioration such as dielectric breakdown due to high voltage application,
Deterioration of the photoconductive layer caused by the developer and scratches and defects caused by mechanical pressure are sensitive to the formed images, and directly lead to a shortening of the life of the photoreceptor itself.

In order to solve these problems, it is possible to form a protective film on the surface of the photoconductive layer.

As mentioned above, in a photoreceptor having an insulating layer on the photoconductive layer, the insulating layer itself can function as a protective film, and therefore, it is not necessary to use it for the sole purpose of protecting the photoconductive layer. It is effective.

The insulating layer in this case is selected based on Shinsu's requirements that it has the ability to hold a uniform static charge and that dielectric breakdown does not occur when voltage is applied.

Therefore, priority has been given to superior electrical strength, and mechanical or other durability points as mentioned above have tended to be treated as secondary.

The protective layer has (1) a surface hardness of IH or higher (2
) Dielectric breakdown strength of 1.5 kV/mil or more, (3) Volume resistivity of 108 Ω or more, (4) Good translucency,
The following conditions must be satisfied.

Another important requirement is that the protective layer has excellent adhesion to the photoconductive layer.

That is, in electrophotography, an electrostatic latent image is formed by the action of charges on or near the surface of the photoconductive layer, and depending on the adhesive action of the protective layer, the surface of the photoconductive layer is This may cause the electrostatic latent image to become rough, non-uniform, or change its electrical characteristics, thereby adversely affecting the image quality of the electrostatic latent image itself.

Therefore, it is important that the protective layer be bonded homogeneously and smoothly without affecting the surface characteristics of the photoconductive layer.

For example, the photoconductive layer is ZnO, CdS, Cd8e, Ti02
ZnS t ZnSe , Se , Se-Te t
Lamination of organic photoconductors such as Se-Te-As and polyvinylcarbazole alone or together with a binder resin,
It is formed by vapor deposition, coating, etc.

In these various embodiments, the protective layer is required to have good adhesive properties.

Conventionally, the method of providing a protective film or an insulating layer on a photoconductive layer was to attach a resin film that had this function, but the adhesive used in laminating it could seep into the photoconductive layer. However, this method is not always the best as it may cause air bubbles to be trapped during lamination, so it is better to apply a thermoplastic resin or thermosetting resin to the photoconductive layer and heat-form it. It was used.

According to this method, it is necessary to apply high temperature when forming the protective film.

However, applying high temperature may also change the characteristics of the photoconductive layer itself, and is therefore not necessarily the best solution.

1) Method for introducing unsaturated groups The present invention provides a material and a manufacturing method for use as an insulating layer or protective layer on a photoconductive layer of a photoreceptor for electrophotography, which can eliminate the above-mentioned drawbacks.

That is, when forming a protective layer or an insulating layer, electron beam irradiation is sufficient without applying high temperatures, and the photoconductive layer itself has excellent workability without any adverse effects on the properties thereof.

Furthermore, it has excellent adhesion to the photoconductive layer, and can also be used as a protective layer or an insulating layer to satisfy the above-mentioned conditions.

That is, the resin used in the present invention and the method of forming the photoconductive layer using the resin are as follows.

The resin used in the present invention has the following characteristics with respect to the base compound:
By introducing an appropriate unsaturated monomer, the degree of unsaturation is 0.5~
This is a resin with a rating of 3.0.

These resins are placed on the photoconductive layer by irradiating them with electron beams.

Examples of functional groups in the base compound include epoxy groups, carboxyl groups, amino groups, hydroxyl groups, acid anhydride groups, N-methylolamide derivatives, etc. Base compounds having these functional groups in their skeletons include, for example, acrylic resins, Vinyl acetate resin, polyvinyl ether resin, epoxy resin (bisphenol A-Ebiku tetrahydrin type, glycidyl methacrylate copolymer), polyester resin (including unsaturated polyester and branched polyester), alkyd resin, polybutadiene (1.2- 4 or 1.4-) Resins, polyamide resins, etc., or simple substances such as acrylic monomers, glycols, triols, polyols, dibasic acids, polybasic acids, and diamines having functional groups in addition to unsaturated groups are listed.

Examples of methods for introducing unsaturated groups into these base compounds are shown below.

That is, the unsaturated bonds of the compound having a forming group obtained as described above are opened by electron beam irradiation, and a highly curable resin is obtained.

However, in order to have a protective function or an insulating function on the photoconductive layer, the degree of unsaturation in the forming group (1 kg of resin
The number of moles of unsaturated groups in the

For example, if the degree of unsaturation is 0.5 or less, electrical deterioration is likely to occur, dielectric breakdown is likely to occur when high voltage is applied, and it is also susceptible to humidity, making it difficult to maintain a constant resistance value.

Furthermore, it becomes difficult to withstand mechanical wear and has poor durability.

On the other hand, if it is 3.0 or more, the mechanical strength will be weak and it will not be practical.

Therefore, the degree of unsaturation of the resulting group is most preferably 0.5 to 3.0.

Furthermore, for resins that are polymerized and cured by electron beams, a solvent may be used to adjust the coating viscosity, and further dilution may be achieved using a monomer.

In this case, the diluent monomer itself hardens together with the resin, so conventionally it is diluted with a solvent and the diluted solvent is diffused into the atmosphere during drying.This process eliminates the release of pollutants into the atmosphere, which is the case with paints. It is effective because it can be done.

In this case, it is most effective to use the solvent or diluent monomer in an amount of 100 to 30% based on the solid content of the resin.

The resin used in the present invention, which is cured by irradiation with electron beams, has a high crosslinking density because it undergoes chain polymerization through radical reactions due to the high energy of the electron beam. This increases the mechanical strength of the material for forming a protective film on the surface of the photoconductive layer of the photoreceptor, making it less likely to be scratched during handling, development, and transfer, as well as providing abrasion resistance. The photoreceptor can be used repeatedly, and is resistant to dielectric breakdown when high voltage is applied. Compared to conventional products, the photoreceptor has much greater durability and a longer lifespan.

For example, when the above resin is used to form a protective film on the surface of a photoconductive layer, there is no increase in heat, so there is no thermal deterioration of the photoreceptor caused by the conventional DO thermal method.

The present invention will be explained below using examples.

Example 1. Zn0100g, silicone resin (product name: KR-211
, manufactured by Shin-Etsu Chemical, 50% solid) 80g xylene solution 40g and rose bengal 1% ethanol solution 4ml were dispersed in a roll mill for 6 hours, and this was applied onto pre-undercoated paper to a dry coating thickness of 20μ. A photoconductive layer was formed by coating and drying.

On the other hand, an acrylic resin with a molecular weight of 10,000 containing 7.1% GMA (glycidyl methacrylate) by weight was prepared, and acrylic acid was added to it at a rate of 36% per kg of acrylic resin.
9 was added to prepare an unsaturated acrylic resin.

(Unsaturation degree 0.5) This was diluted to 50% with MMA (methacrylate) monomer, and this was placed on the photoconductive layer for 2 to 30 minutes.
It was applied to a thickness of 3μ and cured with a 3MR electron beam to obtain an electrophotographic photoreceptor.

This photoreceptor was corona charged at -6 kV, and then a light image was irradiated to form an electrostatic latent image, which was developed with a developer to obtain a good black image.

Furthermore, this image was transferred to another general paper, and after cleaning the stain caused by the developer on the surface of this photoreceptor, it was reused, but a good image could be obtained without any damage to the photoreceptor.

Furthermore, the photoreceptor with a protected surface according to the present invention does not suffer from scratches during handling, resulting in a significant reduction in the number of defective products.

Similar effects were also obtained with other resins listed in the table above.

Example 2 A polyester having a molecular weight of 500 was synthesized by reacting hexahydrophthalic anhydride and 1,6-hexanediol.

Add 236g1 of N-MAMBE (N-n butoxymethylacrylamide) to 1kg of this polyester, and create an unsaturated polyester resin by ether exchange (degree of unsaturation: 2
．． 0)l,ta.

The resin was coated to a thickness of 30 μm on a photoconductive layer formed by vacuum-evaporating a Se-Te alloy to a thickness of 60 μm on a Ni-plated surface of a 160φ aluminum drum.1.
It was irradiated with a 5MR electron beam and completely cured to produce a photoreceptor.

Charges with a polarity opposite to the charged polarity are captured on the surface of the resin layer of the photoreceptor at the interface between the photoconductive layer and the insulating layer or inside the photoconductive layer by a corona discharge of 98 kV, and an alternating current corona discharge is generated on the surface to be charged. After attenuating the charge on the surface of the insulating layer, image irradiation was performed to form an electrostatic latent image.

Next, it was developed with developer powder to obtain a visible image, which was then transferred to paper to obtain a copy.

This image was good with high contrast and no fog.

Furthermore, this process was repeated to obtain 50,000 copies, which were in good condition with no deterioration in characteristics.

Example 3 On the surface of a 16 oz aluminum drum, a photoreceptor paint was prepared by adding 100 parts of CdS and 10 parts of vinyl chloride-vinyl acetate copolymer resin (manufactured by Morikawa Ink) (resin content 20%) and mixing the mixture in a roll mill with methyl ethyl ketone to a viscosity of 500 cps. It was prepared and dip coated to form a 50 micron thick photoconductive layer.

Meanwhile, 212 g of hydrogenated bisphenol and 200 g of succinic anhydride
284g of GMA to the compound added by half-esterification
Create a compound with an unsaturated group introduced by epoxy ring opening (degree of unsaturation: 3.0) and make it 30% solid with MMA.
I diluted it to make a varnish.

This was coated by dip coating on the photoconductive layer to a thickness of 35 μm, and after coating, it was irradiated with a 5MH electron beam to cure, thereby producing a photoreceptor.

Simultaneously with image irradiation on the surface insulating layer using this photoreceptor, 7 kV of corona discharge is performed to form an electrostatic image due to the difference in surface potential that occurs depending on the brightness of the image, and further uniform exposure of 100 Luxsec is applied to the entire surface of the insulating layer. By reversing the surface potential difference, a high-contrast electrostatic latent image was obtained.

After developing with a developer and obtaining a visible image as in the previous example,
I was able to obtain a copy by transferring it to paper.

The same process was repeated 30,000 times, but no deterioration in the characteristics of the photoreceptor was observed.

Although the embodiments of the present invention have been described above, the resin disclosed in the present invention is used in photoreceptors applied to various electrophotographic systems, and is not limited in any way to the above embodiments. It's nothing.

As a comparative example, a case will be described in which a resin outside the range disclosed in the present invention is applied to a photoreceptor.

Comparative example 1. An acrylic resin having a molecular weight of 10,000 and containing a GMA of 3.6 in terms of weight was prepared, and 18 g of acrylic acid was added thereto per 1 kg of the acrylic resin.

(Unsaturation degree: 0.25) This was diluted to 50% solid with MMA monomer and cured with an electron beam. Since it was not completely cured by 3MR, IOMR irradiation was performed.

As a result, it was electrically weak and dielectric breakdown occurred, and its humidity resistance and abrasion resistance were also weak, making it impossible to use it as a photoreceptor for electrophotography.

Comparative Example 2 In Example 3, 144 g of acrylic acid was added to 212 g of hydrogenated bisphenol, and an unsaturated group was introduced by esterification (using PTSA...para-toluenesulfonic acid...catalyst) (degree of unsaturation 5. 6) When the material was cured by irradiation with a 1MH electron beam, it was mechanically weak and had poor durability, making repeated use difficult.

Claims (1)

[Claims] 1. One or more of epoxy acid addition, epoxy amine addition, esterification, half-esterification, or ether exchange reaction on the photoconductive layer on the substrate.
It is characterized by providing a resin layer obtained by applying a resin composition whose main component is a resin obtained by introducing an unsaturated group depending on a species, or by applying a resin composition of different types or multiple layers of the same type and curing with an electron beam. A photoreceptor for electrophotography.