JPS5825264B2 - Electrophotographic photoreceptor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrophotographic photoreceptor having a photoconductive layer on a substrate.

Conventionally, various types of electrophotographic photoreceptors have been known depending on the electrophotographic method used, and typical ones include a photoreceptor with a photoconductive layer formed on a substrate, or a photoreceptor with a photoconductive layer formed on the photoconductive layer. Examples include photoreceptors provided with an insulating layer.

During image formation, these photoreceptors are constantly subjected to adverse electrical, mechanical, and physical conditions due to charging by high voltage application, dry or wet development, transfer, screening, and other means.

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 the application of high voltage, deterioration of the photoconductive layer caused by the developer, and scratches and defects caused by mechanical pressure will sensitively appear in the formed image, and will also shorten the life of the photoreceptor itself. This is something that leads to

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, so it is used only for the purpose of protecting the photoconductive layer. It is effective in some cases.

The insulating layer in this case is selected as being required to have the ability to hold a uniform electrostatic charge, and also to not cause dielectric breakdown when voltage is applied.

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

The protective layer has (1) a surface hardness of I in terms of pencil hardness;
H or more, (2) dielectric breakdown is 1. Conditions such as strength of OKV/mi1 or more, (3) volume resistivity of 103 Ω·α or more, and (4) good translucency must be satisfied.

In addition, the protective layer has excellent adhesion to the photoconductive layer.
This is the other important requirement.

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, CdSe, TiO2
, ZnS1ZnSa1 Se, 5e-Te, 5e-Te
-As, an organic photoconductor such as polyvinyl carboxy resin, etc., alone or together with a binder resin, are formed by bonding, 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 the photoconductive layer was to laminate a resin film that has this function, but the adhesive used in laminating it may soak into the photoconductive layer. This is not always the best method as it may cause the photoconductive layer to be coated with a thermoplastic resin or thermosetting resin and heated to form the photoconductive layer. It was also used.

According to this method, it is necessary to reduce the temperature to a high level 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.

The present invention provides a material and a manufacturing method for an insulating layer or a protective layer (hereinafter referred to as a coating layer) provided on a photoconductive layer of a photoreceptor for electrophotography, which can eliminate the above-mentioned drawbacks.

That is, when forming the coating layer, electron beam irradiation is sufficient without raising the temperature, and the photoconductive layer itself has excellent workability without any adverse effects on its properties.

Furthermore, it has excellent adhesion to the photoconductive layer, and furthermore, can satisfy the above-mentioned conditions as a coating layer.

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

The resin used in the present invention has a degree of unsaturation (number of moles of unsaturated group in 1 kg of resin) of 15 to 3.3 mol/kg, and a bone density of 15 to 3.3 mol/kg, into which polymerizable unsaturated groups are introduced by various methods. II Urethane bond in case (-N CC)-) Number 2.0
~6.6 mol/kg of unsaturated resin.

That is, the total weight of atoms forming 1 mole of urethane bonds is 597 because N: 1, C: 1, 0: 2, and H: 1.

Therefore, there are 354 urethane bonds in 1 kg of resin. In some cases, the urethane bond will be included at 6 mol/ky.

For example, the synthesis reaction model for the unsaturated resin varnish synthesized in Example 1 is expressed as follows.

1 mole of the unsaturated resin varnish synthesized in this way is 15
69g (C-nia 5.0:28, N:10H:81), and it contains 100 moles of urethane bonds, so it is about 6.3 moles per kg of unsaturated resin. It will be.

That is, the unsaturated resin is obtained by reacting a diisocyanate with a polyol and adding a monomer having a hydroxyl group and a polymerizable unsaturated group to an excess of NGO to the resulting urethane compound having a urethane bond. However, it is also possible to use a resin obtained by linking mono- and jepoxy acrylic acid or methacrylic acid adducts with diisocyanate to form a urethane.

Diisocyanates that can be used include ethylene diisocyanate, propylene diisocyanate, butylene diisocyanate, hexamethylene diisocyanate, cyclopentylene diisocyanate, cyclohexylene diisocyanate, 2,4-tolylene diisocyanate,
2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,cudiphenylpropane-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4' diisocyanate, P- or m-phenylene diisocyanate, etc. Examples of polyols include ethylene glycol, diethylene glycol, triethylene glycol, ■・3-butylene glycol, ■・6-hexanediol, pentyl glycol, polyethylene glycol, polypropylene glycol, trimethylolpropane, and trimethylol. Examples include ethane and polyester having OH as a terminal group.

Examples of monomers having a hydroxyl group and a polymerizable unsaturated group include 2-hydroxyethyl, 2-hydroxypropyl,
These include acrylic acid and hismethacrylic acid esters of 3-hydroxypropyl and 3-chloro-2-hydroxypropyl.

In these cases, when introducing the unsaturated group, the number of moles of the unsaturated group per kg of resin should be controlled to 1.5 to 3.3, and the number of urethane bonds should be controlled to 2.2 to 6.6 moles. is required.

In other words, if the degree of unsaturation is 1.5 or less, curing is slow and electrical deterioration is likely to occur, dielectric breakdown is likely to occur when high voltage is applied, and it is also easily affected by humidity, making it difficult to maintain a constant resistance value. It becomes difficult.

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

On the other hand, if the degree of unsaturation is 3.3 or more, the resulting coating film will have weak mechanical strength.

Further, if the urethane bond is 2.2 or less, the electrical resistance value is low and it is difficult to apply it to an electrophotographic device on a photoconductive layer.

On the other hand, if it is 6.6 or more, the resin may aggregate due to hydrogen bonding due to urethane groups, or structural viscosity may occur, resulting in poor coating workability, making it impossible to obtain a uniform coating film, or yellowing due to irradiation.

The resin obtained above has an extremely high viscosity and is extremely difficult to work with when coating it on a photoconductive layer.

Therefore, it is necessary to adjust the viscosity so that it can be easily coated onto the photoconductive layer, and in this case it is preferable to use unsaturated monomers and/or common solvents.

At the time of polymerization and curing, the unsaturated monomer is
Since the polymer itself contributes to polymerization, it is particularly effective without the need for solvent removal. Examples include acrylic acid and methacrylic acid esters such as hydroxypropyl, and known vinyl monomers such as styrene and vinyltoluene.

The organic solvent is not particularly limited and may be used within the range possible, but for example, ketone, ester, or alcohol organic solvents, trol, kijirol, and the like are particularly preferred.

These unsaturated monomers and organic solvents have an effect in the range of about 5 to 300 parts by weight, either alone or in a mixed state, based on 100 parts by weight of the urethanized unsaturated resin.

If it is less than 5, the viscosity is too high to be coated, and if it is more than 300, the curability is poor and the electrical properties are poor, making it unusable.

The urethanized unsaturated resin whose viscosity has been appropriately adjusted in this manner is cured by electron beams.

In the present invention, the polymerizable composition obtained as described above is applied onto a photoconductive layer, and then polymerized and cured with an electron beam to form a coating layer.

This coated resin exhibits electrical properties such as a volume resistivity value of 108 Ω or more, does not cause dielectric breakdown due to high voltage application, has a remarkable effect on withstand voltage, and has a mechanical resistance. It is extremely resistant to mechanical pressure, and there are almost no scratches on the surface as long as it is adapted to electrophotographic equipment. Also, it exhibits excellent translucency, so it is suitable for image exposure from the surface of the photoreceptor. This is convenient.

Therefore, it can work effectively either when the photoconductive layer is simply provided with the function of a protective film or when the photoconductive layer is provided with the function of an insulating layer having charge retention ability.

In order to meet both of these objectives, it can be determined simply by specifying the thickness of the coating layer.

That is, a thickness of 10μ or less is sufficient for the protective function of the photoconductive layer, and a thickness of 10μ to 50μ for the function as an insulating layer.
A sufficient effect can be achieved by providing the layer with a thickness of about μ.

Further, the resin according to the present invention also has an adhesive effect due to its characteristics.

This also shows an excellent effect on the adhesion to the photoconductive layer, but if the degree of unsaturation is increased in order to increase the curability of the resin itself, the hardness may become extremely high, resulting in adhesion. In such cases, it is effective to apply a thin layer of the resin in advance for the purpose of imparting adhesive properties.

In this case, a base compound having an epoxy group as a functional group or another functional group of an unsaturated monomer is effective, and an unsaturated compound obtained by an epoxy acid addition reaction or an epoxy amine addition reaction is used.

The present invention will be explained below using examples.

Example 1 After reacting 2 mol of trimethylolethane and 1 mol of 2,4-tolylene diisocyanate at 60°C for 2 hours,
・Add 4 mol of 4-tolylene diisocyanate and make 60
React at ℃ for 2 hours.

After that, 4 mol of hydroxyethyl acrylate was added, and 80
C. for 5 hours and diluted with methyl methacrylate to 70% solid content to prepare a varnish.

In this case, the unsaturation equivalent is 2.5 and the number of urethane bonds is 6.3.
It is.

On the other hand, after mixing 5100 parts of Cd with 50 parts of MIBK diluted solution of vinyl chloride-vinyl acetate copolymer with a resin content of 20%,
Furthermore, after drying the coating solution to which 20 parts of MIBK was added, it was applied to an aluminum cylinder to a thickness of 40 μm and heated at 70°C.
Dry for 0 minutes.

Furthermore, for sealing, a photoconductive layer was formed by immersing it in a 5% polyvinyl alcohol aqueous solution and drying it at 70°C for 20 minutes.

The varnish was applied by dip coating to a thickness of 10μ on the photoconductive layer obtained, and irradiated with an IOMR electron beam from a distance of 30CrfL to completely cure, and this operation was repeated 3 times.
An insulating layer having a thickness of μ was formed to obtain a photoreceptor.

Using the photoreceptor, 7KV corona charging is performed, and then static electricity is removed by AC6KV corona at the same time as the optical image is irradiated.Furthermore, the entire surface is uniformly irradiated with 100 lux see light, and the surface of the insulating layer is statically charged. After forming an electrostatic latent image, it was developed using a developer and further transferred onto plain paper to obtain a copy.

This image had a high density, was sharp, and had no fog.

Furthermore, clean the photoconductor surface □ and repeat the above process in step 5.
Copies were made ten thousand times, but good results were obtained with no change in electrostatic contrast, no pinholes, no mechanical wear, no scratches, etc.

Example 2 The unsaturated urethane compound varnish in Example 1 was applied on the photoconductive layer in Example 1 to a thickness of 3μ,
It was cured with an electron beam and formed as a protective film on the photoconductive layer.

The photoreceptor thus obtained was corona charged to -6 KV, then irradiated with a light image to form an electrostatic latent image, which was developed with a developer to obtain a good black image.

Furthermore, this image was transferred to other general paper, and the photoreceptor was reused after cleaning, but a good image with no scratches could be obtained.

Although this process was repeated 50,000 times, no damage occurred to the protective film on the photoconductive layer.

Example 3 The photoreceptor obtained in Example 1 (in which a Se photoconductive layer was formed instead of Cd50) was charged with a corona discharge of 08 KV on the surface of the resin layer to separate the photoconductive layer and the insulating layer. A charge having a polarity opposite to the above charge polarity was captured at the interface or inside the photoconductive layer, and an AC corona discharge of 7 KV or 5' KV was applied to the m-charged surface to attenuate the charge on the surface of the insulating layer. After that, image irradiation was performed to form an electrostatic latent image.

Next, the image was developed with developer powder to obtain a visible image, which was then transferred to paper to obtain a copy. This image had a high contrast and was good with no fog.

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

Example 4 For the photoreceptor obtained in Example 1, at the same time as image irradiation was performed on the surface insulating layer, corona discharge was performed at 7 KV to form an electrostatic image due to the difference in surface potential that occurred according to the brightness of the image,
Further, the entire surface of the insulating layer was uniformly exposed to 100 lux see to reverse the surface potential difference to obtain a high-contrast electrostatic latent image.After developing with a developer to obtain 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 of the characteristics of the photoreceptor was observed, and good results were obtained.

Although one embodiment of the present invention has been described above, the resin disclosed in the present invention is used in photoreceptors applied to various electrophotographic systems, and is not restricted in any way to the above embodiments.

Claims (1)

[Claims] 1 (1) 1.5 to 3.3 moles of unsaturated groups in the resin lky and urethane bonds (-N-C-0) 2.2 to 6.
and (2) an unsaturated monomer having an ethylenically unsaturated group and/or an organic solvent in an amount of 5 parts by weight per 100 parts by weight of the urethanized unsaturated resin.
1. An electrophotographic photoreceptor comprising a resin layer obtained by applying an electron beam curable composition having 300 parts by weight to 300 parts by weight and curing the composition with an electron beam. 2. The electron beam curable composition according to claim 1 is applied onto the photoconductive layer via a resin obtained by polymerizing and curing an unsaturated compound obtained by an epoxy acid addition reaction or an epoxy amine addition reaction. 1. An electrophotographic photoreceptor comprising a resin layer obtained by curing the resin layer.