JPS5898738A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic receptor which has high moisture resistance and always sharp image are obtained by providing a photoconductive layer consisting of photoconductive material particles subjected to hardened coating of a modified silicone resin on the surfaces and a binder resin. CONSTITUTION:A coating soln. prepd. by dispersing the photoconductive material particles wherein inorg. photoconductive materials such as CdS and org. photoconductive materials such as phthalocyanine are applied with hardened coatings of such epoxy modified silicone resins, etc. expressed by the formula in a soln. of satd. polyester resins, vinyl chloride-vinyl acetate copolymers, etc. is coated on a conductive substrate such as Al drum and is dried, whereby a photoconductive layer is formed. A coating soln. prepd. by adding block isocyanate to a modified silicone resin soln. is used as a hardener for the modified silicone resin. Thus sharp images are obtained with less degradation in sensitivity, electrical properties and optical properties even in high moisture environment.

Description

[Detailed description of the invention] The present invention relates to an electrophotographic photoreceptor.

Electrophotographic photoreceptors have various configurations in order to obtain predetermined characteristics or depending on the type of electrophotographic process to which they are applied. As representative electrophotographic photoreceptors, there are photoreceptors having a photoconductive layer formed on a support and photoreceptors having an insulating layer on the surface, which are widely used. The photoreceptor is composed of a support and a photoconductive layer.
It is used for image formation by the most common electrophotographic processes, ie, charging, image exposure and development, and optionally transfer. For photoreceptors with an insulating layer, this insulating layer can be used to protect the photoconductive layer, improve the mechanical strength of the photoreceptor, improve dark decay properties, or be applied to certain electrophotographic processes (and It is established for the purpose of eliminating pollution). A typical example of an electrophotographic process using a photoreceptor having an insulating layer is disclosed in US Pat. No. 28600, for example.
48 Publication, Special Publication No. 41-16429, Special Publication No. 3
Publication No. 8-15446, Japanese Patent Publication No. 46-3713,
Special Publication No. 42-23910, Special Publication No. 43-24'7
48 Publication, Special Publication No. 42-19747, Special Publication No. 3
It is described in Publication No. 6-4121 and the like.

As a matter of course, an electrophotographic photoreceptor is required to have predetermined sensitivity, electrical properties, and optical properties depending on the electrophotographic process to which it is applied. However, not only that, but also the moisture resistance of the photoreceptor is an important property. Even if a photoreceptor has excellent electrophotographic properties at low humidity, the surface potential of the photoreceptor decreases significantly under high humidity.
It is difficult to obtain stable and clear images. Further, in an electrophotographic process in which transfer is performed, a photoreceptor is usually used repeatedly, so that the moisture resistance of the photoreceptor often deteriorates further due to charging deterioration of the photoreceptor. This can be improved to some extent by heating the photoconductor with a heater and dehumidifying it, but it is still not enough to always obtain stable and clear images, and the heater must be constantly activated. This causes an increase in costs.

The main factors determining the moisture resistance of a photoreceptor are the moisture resistance of the binder in the photoconductive layer and the compatibility of the binder with the photoconductive material. Therefore, the selection of binder has a very large influence on the moisture resistance of the photoreceptor.
3 However, as a binder, coatability and solvent resistance (in the case of coating an insulating layer) are also required, and including these, it is necessary to bind a photoconductive layer that has sufficient characteristics as an electrophotographic photoreceptor. This is very difficult to achieve with agents alone.

The main object of the present invention is to provide an electrophotographic photoreceptor having excellent moisture resistance.

The electrophotographic photoreceptor according to the present invention is characterized in that it has a photoconductive layer comprising photoconductive material particles having a hardened coating of modified silicone resin on the surface and a binder resin.

A typical modified silicone resin used in the present invention is an epoxy modified silicone resin represented by the following formula.

R=H,C! H,,0,H,,0,H.

A typical commercially available product represented by is TSR194 (product name: Toshiba Silicon) F81001.
N (product name: Shin-Etsu Chemical Exhibition), etc.

A curing agent is added to apply the modified resin/resin to the surface of the photoconductive material particles and then cure to form a cured resin coating.

Blocked isocyanates are particularly preferred as curing agents. As the block isocyanate, incyanate prepolymer can be used as aromatic secondary amine, tertiary alcohol,
Use one masked with amide, lactam, phenol oxime, etc. When a typical incyanate prebolimisocyanate prepolymer is masked, the NOO groups are regenerated by heating, and the regenerated product reacts with an active hydrogen compound. That is, the NOO groups of the blocked isocyanate are regenerated by heating, and the regenerated NOO groups react with the hydroxyl groups at the terminals of the silicone resin to form a coating film with excellent solvent resistance and durability. Further, during heat curing, the curing temperature can be particularly lowered by adding an amine compound or carboxylic acid amine salt as a catalyst. The addition ratio of the block isocyanate to the silicone resin is set in the range of 10 to 200X, that is, in the range of 10:1 to 1:2, and the addition ratio of the catalyst to the block isocyanate is set to about 1 to 5.

This resin can also be used as a binder and has good moisture resistance. Further, solvent resistance appears by crosslinking and curing with blocked isocyanate.

Naturally, when a powdered photoconductive material is used, its dispersibility is poor and it is difficult to form a uniform coating surface. However, in the present invention, by encapsulating the photoconductive material particles with a modified silicone resin, By taking advantage of its excellent coating properties, it is possible to form a photoconductive layer with good coating properties due to ``adhesion.''

The encapsulation method is as follows: (1) Photoconductive material particles and modified silicone resin are mixed in advance, hardened, and then pulverized and dispersed in a binder. (2) A method of mixing photoconductive material particles and modified silicone resin and dispersing them in a binder resin in an uncured state can also be adopted, but in method (1), the photoconductive material is crushed by pulverization after curing. The electrophotographic properties may be destroyed and the electrophotographic properties may be deteriorated, and (2) may not result in sufficient encapsulation. A suitable method is one in which particles of a photoconductive material having a surface coated with a modified silicone resin are dispersed in a medium in which the coating is not dissolved, and then subjected to a curing treatment.

In this case, the ratio of photoconductive material, modified silicone resin, and blocked isocyanate (solid content 9 weight ratio) is 100:10 to
100:30, viscosity when mixed is 30-100c
PS is preferred, and water or an aliphatic hydrocarbon solvent is used as the dispersion medium.

The mixing ratio and viscosity of the photoconductive material and modified silicone resin are as follows:
It affects the degree of coverage of the photoconductive material particles, and if the degree of coverage is too high (specific weight of silicone resin, high viscosity), the contact between the photoconductive material particles will be poor and the movement of carriers (1! charge) will be insufficient. .

On the other hand, if the degree of coverage is low (low W fat percentage, low viscosity), moisture resistance will be insufficient.

The photoconductive materials used in the present invention include ZnO, Od
8, Tiet, 0dSe, Se, 8eT
e, 8eAs, etc.

Inorganic materials, phthalocyanine, polyvinylcarbazole,
Examples include anthracene, polyvinylpyrene, and polyvinylanthracene.

Resins used as binders for the photoconductive layer include solvent-soluble S-type vinyl chloride-vinyl acetate copolymers, saturated polyester resins, polycarbonate resins, polysulfono resins, polyacetal resins, polyacrylate resins, epoxy resins, and butyral resins. , alkyd resin, acrylic resin, etc.

The thickness of the photoconductive layer depends on the type and characteristics of the photoconductive material used, but is generally 5 to 100 μm, particularly 10 to 50 μm.
degree is suitable.

The thickness of the insulating layer is set appropriately, but is usually 5~
It is set to 70μ, particularly 10 to 50μ.

Example 1 100 parts (by weight, the same applies hereinafter) of OdS powder was added to an epoxy modified silicone resin solution (trade name: TSR194, J[
Made of Shiba Silicone) and Block Incyanate (Product name: D
20mK mixture with O2971 (manufactured by Nippon Boliureta)
Add and stir. The ratio of silicone resin (hereinafter abbreviated as S) to blocked isocyanate (hereinafter abbreviated as BI) is 5:
Set it to 2. The viscosity of this was adjusted to 50 cps K, dispersed in water, stirred vigorously, and heated at 140°C in an autoclave.
Heat and cure for 30 minutes. After heat-treating the obtained encapsulated OdS powder at 100°C for 60 minutes, 10 parts of a toluene solution of a beaten polyester resin (trade name: Vylon 200° manufactured by Toyobo Co., Ltd.) as a binder was added to 100 parts of the powder. Mix and disperse through three passes through a roll mill with an 80μ gap.

The above coating material was applied by dipping onto an M drum support having a length of 40 mm, and dried at 100 DEG C. for 20 minutes to form a photoconductive layer having a thickness of 35 .mu.m. Next, a cylindrical heat-shrinkable polyethylene terephthalate film with a thickness of 20μ (product name: Ho5taphanshrink Film KAL
LE) 90+m≠ covered with the above cylinder K, 12
Heat shrinkage was performed at 0° C. for 30 minutes to form an insulating layer.

This will be referred to as photoreceptor I.

Example 2 10 parts of a mixture of S and BI was added to 100 parts of 0d8 powder to make the viscosity 80 cps, and chlorine vinegar and copolymer resin (trade name: VMOH, UO) were used as a binder.
A photoreceptor manufactured in the same manner as in Example 1 except that a photoreceptor manufactured by O.

Comparative Example 1 20 parts of a mixture of S and BI were added to 100 parts of 0dS powder, mixed well, and dried at 100° C. for 30 molecules. For 100 parts of the crushed powder, binder Vyron 20
Mix 10 parts of 0 and dry the material and set the curing temperature to 140
A photoreceptor prepared in the same manner as in Example 1 except that the temperature was changed to 20 minutes was used as photoreceptor ①.

Comparative Example 2 100 parts of 0dS powder, 10 parts of S and BI mixture, and 200.10 parts of Vylon were added and mixed, and the paint was passed through a roll mill device with an 80μ gap three times, and then prepared in the same manner as in Example 1. The resulting photoreceptor is referred to as photoreceptor (■).

Various evaluations were performed on the photoreceptors I to (2) obtained in this way using a process consisting of -2 charging, secondary AO static elimination simultaneous exposure, full surface irradiation, dry development with e-toner, transfer, and blade cleaning.

The results are shown in Table 1.

As shown in Table 1, Table IK, the photoreceptor (2) produced by the method of Comparative Example 1 had problems in image quality and was unsuitable as an encapsulation method.

How much the surface potential of the photoreceptor in the dark area of the next VcwJJ image was reduced by a durability test under high humidity was investigated. 1 showed a good potential retention rate, and the image density did not decrease.

However, it is considered that the OdS surface of the photoreceptor (1) was partially destroyed during the crushing of the heated mixture of silicone resin and Od8, making it susceptible to moisture attack.

In addition, since the photoreceptor ■ contains silicone resin and another binder (Vylon 200) mixed with Od8 at the same time, Od8
It is thought that the surface is not sufficiently coated with silicone resin.・Example 3 0d8 powder 100 gK to S to B I fi 41
A photoreceptor was prepared in the same manner as in Example 1, except that 140 parts were added and the viscosity was adjusted to 200 cps Kail.

Example 4 10 parts of S and BI mixture were added to 100 parts of 0d8 powder to give a viscosity of 80 cps, and a vinyl chloride-vinyl acetate copolymer resin (trade name: VMOH, manufactured by Union Carbide) was used as a binder. , a photoreceptor was prepared in the same manner as in Example 1. On the other hand, the image properties and moisture resistance of photoreceptors I and II were also good.

In order of appearance: Canon Co., Ltd.

Claims (2)

[Claims] (1) An electrophotographic photoreceptor characterized by having a photoconductive layer consisting of photoconductive material particles having a hardened powder of modified silicone resin on the surface and a binder resin. (2) The cured coating is formed by curing the photoconductive material particles having a modified silicone resin coating on the surface while being dispersed in a medium in which the coating does not dissolve. The electrophotographic photoreceptor described above.