JPH0470629B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoconductor useful as a photoconductor for electrophotographic copying machines and the like, and more particularly, the present invention relates to a photoconductor that is useful as a photoconductor for electrophotographic copying machines, etc. The present invention relates to improvements in toner cleaning performance and service life of a two-layer photoreceptor having an electrically insulating resin layer formed thereon or a three-layer photoreceptor having an electrically insulating resin layer on its surface.

Removal of residual toner in conventional photoconductive photoreceptors is carried out by static elimination operation and mechanical operation such as a brush, but conventional photoreceptors have insufficient toner cleaning properties and also require mechanical operation. Since the surface of the photoreceptor is subject to changes due to this, there is a drawback that the copy quality rapidly deteriorates. In order to improve these drawbacks, methods have been proposed in which silica powder is added to the resin component constituting the photoreceptor, but these methods result in poor dispersion of silica, which impairs light transmittance. On the contrary, the sensitivity and surface characteristics of the photoreceptor deteriorate, making it impossible to obtain desirable results.

As a result of intensive research in order to solve the above-mentioned drawbacks of the prior art, the inventor of the present invention has discovered that by including a specific material in the resin component constituting the photoreceptor, the sensitivity and surface characteristics of the photoreceptor will not be harmed in any way. The present invention was completed based on the finding that a photoreceptor having excellent toner cleaning properties and a long service life can be obtained.

That is, the present invention provides a photoreceptor comprising a conductive substrate, a photoconductive layer consisting of a photoconductive material, and a binder resin, and which may further have an electrically insulating resin layer on the surface. The surface layer of the layer and the electrically insulating resin layer contains silica (mainly composed of SiO ₂ ) dispersed in a colloidal form in an organic medium and/or its resin modified product. It is a photoreceptor that

To explain the present invention in detail, the conductive substrate constituting the photoreceptor of the present invention is a conventionally known conductive substrate, such as aluminum, chromium, nickel,
Metal-deposited polyester film, etc. A photoconductive layer is formed on a conductive substrate, and is made of a photoconductive material powder such as photoconductive cadmium sulfide, zinc oxide, titanium oxide, etc., such as acrylic resin, urethane resin, or silicone resin. , powder/resin = 10/1 to 10/8 (solid content ratio) depending on the binding resin such as epoxy resin, styrene resin, fluorine resin, etc.
It is formed by forming a bonded layer at a ratio of 1, and as far as this is concerned, a conventionally known structure may be used.

The electrically insulating resin layer that may be formed on the photoconductive layer is, for example, a resin film formed of polyester resin, acrylic resin, silicone resin, fluorine resin, epoxy resin, styrene resin, etc. In this case, conventionally known ones may be used.

A feature of the present invention is that in the structure of the photoreceptor as described above, silica (mainly composed of SiO ₂ ) and/or a modified resin thereof.

The silica used in the present invention is silica (mainly composed of SiO ₂ ) dispersed in an organic medium in the form of a colloid (hereinafter simply referred to as colloidal silica) and its resin-modified product. Such colloidal silica can be obtained by various methods, including a method in which colloidal silica is formed by hydrolyzing an organic silicate such as ethyl silicate in alcohol, ketone, or other organic medium, and a method known in the art. It can be easily obtained by substituting water-based colloidal silica into an organic medium.
In addition, these modified products of colloidal silica utilize the silanol group that the silica has, and can be obtained, for example, by reacting an organic substance containing an isocyanate group or an organic substance containing an epoxy group. It is something.

Preferred examples of such organic materials for modification include urethane prepolymers containing isocyanate groups, epoxy resins containing epoxy groups, acrylic oligomers, and acrylic polymers that have functional groups that react with silanol groups. Moreover, the product is a stable organic substance.

In one embodiment of the present invention, colloidal silica and/or its resin modified product as described above is added to a photoconductive coating composition comprising a photoconductive material, a binder resin, and a solvent in an amount of 100 parts by weight of a binder resin. Hit, about 5
Add in a proportion such that the silica content is ~30 parts by weight,
Forming a photoconductive layer. Of course, the same effect can be obtained by adding colloidal silica to the binding resin solution in advance. In addition, in the above, when the binding resin itself has reactive groups such as isocyanate groups and epoxy groups, those reactive groups react with the surface silanol groups of the silica, and the binding resin itself becomes attached to the colloidal silica. It becomes a modified form of.

In another embodiment of the present invention, the colloidal silica and/or its resin modified product is included in an electrically insulating resin layer formed as necessary. For example, colloidal silica and/or its resin modified product as described above is added to a resin solution for forming an electrically insulating resin layer so that the silica content is about 5 to 60 parts by weight per 100 parts by weight of resin. Then, an electrically insulating resin layer is formed. Of course, if the resin has a group capable of reacting with the surface silanol group of silica, by mixing the two, the resin itself becomes a modified product of the colloidal silica.

In yet another embodiment of the invention, both the photoconductive layer and the electrically insulating resin layer described above may include colloidal silica and/or its resin modified product.

According to the present invention as described above, since the silica used is colloidal silica dispersed in colloidal form or a modified product thereof, it is uniformly and finely dispersed in the resin of the photoconductive layer and/or the electrically insulating resin layer. The silica does not impede light transmittance, and the surface hardness of these layers is significantly improved. Also, the silica significantly improves the cleaning properties of the toner, so it can be used for long periods of time. Gives excellent quality reproductions.

Next, the present invention will be explained in more detail with reference to Examples. Note that "%" or "%" in the text is based on weight.

Example 1 (Production of colloidal silica) Ethyl silicate (silica content 40%) 100 parts water 10
1 N HCl and 88 parts of ethyl alcohol were uniformly mixed, 2.0 parts of 1N HCl was added thereto, and the mixture was stirred for 2 hours. Then, water was removed, the concentration was adjusted with ethanol, and colloidal silica (20% silica content) ) was obtained.

Example 2 (Production of colloidal silica) 20 parts of ethyl alcohol was added to 100 parts of water-based colloidal silica (silica content 40%), water was removed,
Also, add the same amount of alcohol and repeat this operation to phase-shift the colloidal silica to the alcohol phase.
Colloidal silica () with a silica content of 20% was obtained.

Example 3 (Production of colloidal silica) Colloidal silica () obtained in Example 2
To this, a mixed solvent of toluene and methyl ethyl ketone (1:1) was added and distilled under reduced pressure, and toluene and methyl ethyl ketone were added and distilled under reduced pressure, and this operation was repeated to obtain 20% colloidal silica ().

Example 4 (Production of modified colloidal silica) 2 parts of terminal isocyanate urethane prepolymer (NCO2%) having a molecular weight of about 2000 was added to 100 parts of the colloidal silica obtained in Example 3, and the mixture was heated at 80°C for 7
After reacting for a period of time, resin-modified colloidal silica () was obtained.

Example 5 (Production of resin-modified colloidal silica) 5 parts of epichlorohydrin was added to 100 parts of the colloidal silica obtained in Example 3 and mixed well.
0.2 part of diethylenetriamine was added little by little to this mixture, and the mixture was reacted at 0° C. for 2 hours to obtain resin-modified colloidal silica ().

Reference Example 1 (Prior art photoreceptor) 100 g of photoconductive zinc oxide, 50 g of acrylic resin (50% solids), 20 mg of rose bengal, and 80 ml of isopropanol/toluene (80:20) mixed solvent were thoroughly dispersed in a ball mill. After treatment, it is applied to a cylindrical aluminum substrate to a dry film thickness of 40 μm.
It was dried by heating to produce a photoreceptor (2).

When we repeatedly performed image tests on the above photoreceptor using the Carlson process at a photoreceptor charging potential of -500V, we found that the photoreceptor had poor cleaning performance and toner remained on the photoreceptor, resulting in fogging and afterimage phenomena on copies. observed and no good quality copies were obtained.

Example 6 37.5 g of colloidal silica () (30% silica content based on resin) of Example 1 was added and mixed to the same dispersion as in Reference Example 1, and an image test was conducted in the same manner as in Reference Example 1. When repeated, although the sensitivity was the same, the toner cleaning performance of the photoreceptor was extremely good, and high-quality copies could be obtained for a long period of time.

Reference example 2 (Prior art photoreceptor) Photoconductive cadmium sulfide 100g, acrylic polyol (hydroxyl value 25) (solid content 50%) 80g, isocyanate (NCO 12.5g) 8g and butyl acetate/toluene (1:1) After dispersing 20ml with an ultrasonic dispersion machine, the dry film thickness is 40μm on a cylindrical aluminum substrate.
The photoreceptor was prepared by coating the photoreceptor so that the photoreceptor was coated and drying by heating. The resulting photoreceptor drum was soaked in an acrylic resin solution with a viscosity of 10 cps, and dried by heating.
A photoreceptor () was obtained by forming an insulating layer with a thickness of 0.7 μm.

On the other hand, add 30% of the resin content to the above acrylic resin solution.
% of white carbon was added and thoroughly dispersed in a ball mill, the viscosity was adjusted to 10 cps with a solvent, and a photoreceptor () was obtained in the same manner as above.

When repeated image tests were conducted on the photoreceptors () and () in the same manner as in Reference Example 1, it was found that the photoreceptor () had poor cleaning properties and could not produce good quality copies. Changes were observed on the surface of the photoreceptor. The photoconductor () has a poor surface, poor image quality, and a sensitivity of about 30.
% had decreased.

Example 7 To the acrylic resin solution of Reference Example 1 above, the colloidal silica () of Example 2 corresponding to 30% of the silica content of the resin solid content was added, and the rest was as in Reference Example 2.
A photoreceptor of the present invention was obtained in the same manner as described above. When the photoreceptor was subjected to repeated image tests in the same manner as in Reference Example 1, the cleaning quality was good, the sensitivity was the same as that of the photoreceptor (2), and good quality copies were obtained. The photosensitive characteristics after repeated copying about 50,000 times were almost the same as the initial characteristics, and no change was observed on the surface of the photoreceptor.

Example 8 The same results as in Example 6 were obtained even when the resin-modified colloidal silica of Example 4 or 5 containing the same amount of silica was used in place of the colloidal silica of Example 6.

As is clear from the above-mentioned Reference Examples and Examples, it is clear that the photoreceptor of the present invention has significantly improved cleaning properties and surface stability during repeated use.

Claims (1)

[Claims] 1. A photoreceptor consisting of a conductive substrate, a photoconductive layer consisting of a photoconductive material, and a binder resin, which may further have an electrically insulating resin layer on the surface, in which the photoconductive layer and electrically insulating A photoreceptor characterized in that a surface layer of the resin layer contains silica (mainly composed of SiO ₂ ) dispersed in an organic medium in a colloidal manner and/or a resin-modified product thereof.