JPH04213461A - Production of electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To form a satisfactory electric charge generating layer nearly free from unevenness in the thickness and defects in the appearance by preparing a coating liq. for an electric charge generating layer having viscosity regulated properly without deteriorating the dispersibility of an org. pigment by mixing with a high viscosity solvent. CONSTITUTION:An org. pigment as an electric charge generating material and polyvinyl butyral resin as a resin binder are dispersed in a mixture of a low viscosity solvent with a high viscosity solvent to prepare a coating liq. for an electric charge generating layer. The viscosity of the coating liq. can be regulated according to the amt. of the high viscosity solvent mixed and the deterioration of the dispersibility of the org. pigment by the high viscosity solvent can be compensated with the superior dispersibility of the polyvinyl butyral resin. The pref. weight ratio between the pigment and the polyvinyl butyral resin is (1:0.5)-(1:1.5) and the pref. amt. of the high viscosity solvent used is 10-30wt.% of the amt. of the low viscosity solvent.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a method for manufacturing an organic functionally separated laminated type electrophotographic photoreceptor comprising at least a charge generation layer and a charge transport layer on a conductive support, and more specifically to a method for producing a charge generation layer and a charge transport layer. It relates to the constituent materials of the layers and their formation methods.

0002

2. Description of the Related Art In organic functionally separated layered electrophotographic photoreceptors, organic pigments such as phthalocyanine pigments are often used as charge generating substances contained in charge generating layers. In that case, the charge generation layer contains an organic pigment and a binder resin such as vinyl chloride resin, polycarbonate resin, polyester resin, etc.
F), is formed by coating a coating liquid dispersed in a solvent such as cyclohexane or dichloroethane on a conductive support by a dipping method or the like.

However, when coating and forming the charge generation layer as described above, unevenness occurs in the film thickness, ring-shaped striped patterns,
Appearance defects such as dripping may occur. Many of the causes of this are related to the viscosity of the coating solution and the evaporation rate of the solvent, and as a countermeasure, it is possible to mix other types of resins into the binder resin of the coating solution, or Low viscosity solvents such as THF (viscosity 0.4
cP) and a high viscosity solvent such as butyl carbitol (viscosity of about 2.5 cP to 3.5 cP) is used.

0004

[Problems to be Solved by the Invention] However, if a solvent mixed with a high viscosity solvent is used in the coating solution for the charge generation layer, the dispersibility of the organic pigment deteriorates, and the organic pigment tends to aggregate after the coating solution is prepared. The problem arises that the lifespan of the film is shortened and the film formability is deteriorated.

An object of the present invention is to solve the above-mentioned problems and provide a method for manufacturing an electrophotographic photoreceptor having a charge generation layer with reduced film thickness unevenness and poor appearance. do.

[0006]

[Means for Solving the Problems] According to the present invention, in a method for manufacturing an electrophotographic photoreceptor comprising at least a charge generation layer and a charge transport layer on a conductive support, This problem can be solved by forming the generation layer by applying a coating liquid in which a material mainly consisting of an organic pigment and a polyvinyl butyral resin is dispersed in a mixed solvent of a low-viscosity solvent and a high-viscosity solvent.

Phthalocyanine pigments are preferred as the organic pigments, and the weight mixing ratio of the phthalocyanine pigments and polyvinyl butyral resin in the coating solution is preferably in the range of 1:0.5 to 1:1.5. . In addition, the weight mixing ratio of high viscosity solvent to low viscosity solvent is 10% or more3.
It is preferably 0% or less. In addition, THF is used as a low viscosity solvent.
As the high viscosity solvent, it is preferable to use one of isophorone, carbitol acetate and butyl carbitol.

[0008]

[Operation] Polyvinyl butyral resin dissolves well in a wide range of organic solvents and has excellent dispersibility of organic pigments. Furthermore, it has good adhesion to metals and plastics. By using a binder resin in the coating liquid of the charge generation layer as a material mainly consisting of polyvinyl butyral resin, it is possible to prevent deterioration of the dispersibility of the organic pigment due to mixing of a high viscosity solvent into the solvent of the coating liquid. Therefore, it is possible to prepare a coating liquid that contains organic pigments in a stable and uniformly dispersed manner over a long period of time and has an appropriate viscosity. This makes it possible to form a charge generation layer with less adhesiveness and good adhesion.

Low viscosity solvent (viscosity 0.4c) for coating solution
High viscosity solvent (viscosity 2.5 cP to 3.0 cP)
(about 5 cP) is preferably in the range of 10% or more and 30% or less. When the mixing ratio of the high viscosity solvent is less than 10%, the effect of mixing is small, and when it exceeds 30%, the high boiling point of the high viscosity solvent causes problems due to the slow evaporation rate, which is not preferable.

As the organic pigment, a phthalocyanine pigment is preferable, and the weight mixing ratio of the phthalocyanine pigment and polyvinyl butyral resin is 1:0.5 to 1:1.
．． It is suitable that it is within the range of 5. If the amount of the phthalocyanine pigment is too small, the sensitivity of the resulting electrophotographic photoreceptor will be low, and if it is too large, the film formability will be reduced.

[0011]

[Examples] Examples of the present invention will be described in detail below.

Example 1

10 parts by weight of metal-free phthalocyanine and 10 parts by weight of polyvinyl butyral resin (manufactured by Sekisui Chemical Co., Ltd.: Elex B.BM-2) were mixed with 1000 parts by weight of THF and 100 parts by weight of carbitol acetate in a paint shaker.
A coating solution for a charge generation layer was prepared by dissolving and dispersing the sample in a mixed solvent with parts by weight. This coating liquid was applied to the outer surface of a cylindrical aluminum support to form a charge generation layer having a thickness of about 0.5 μm. To apply the coating, hold a ring whose diameter is slightly larger than the outer diameter of the cylindrical support so that the ring surface is horizontal, and insert the cylindrical support vertically into the ring so that its center axis coincides with the center axis of the ring. inserting the ring, and supplying a coating liquid between the outer surface of the cylindrical support and the ring while moving the two relative to each other in the vertical direction to form a coating film on the outer surface of the cylindrical support.
Although the so-called ring coating method was used, it is of course not limited to this method.

On this charge generation layer, 1-phenyl-3-(p-diethylaminostyryl) is added as a charge transport substance.
-5-(p-diethylaminophenyl)-2-pyrazoline (ASPP) 100 parts by weight and polycarbonate resin as a binder resin (manufactured by Mitsubishi Gas Chemical Co., Ltd.: C-1)
A coating solution prepared by dissolving 100 parts by weight of 400) in 2800 parts by weight of dichloromethane was applied using a dip method to obtain a film thickness of 18 μm.
A photoreceptor was prepared by forming a charge transport layer of m.

Example 2

A photoreceptor was prepared in the same manner as in Example 1, except that the amount of polyvinyl butyral resin in the charge generation layer coating liquid was halved to 5 parts by weight.

Example 3

A photoreceptor was prepared in the same manner as in Example 1, except that the amount of polyvinyl butyral resin in the coating solution for the charge generation layer was 15 parts by weight.

Comparative example 1

In Example 1, except that the polyvinyl butyral resin in the coating solution for the charge generation layer was changed to a vinyl chloride copolymer resin (manufactured by Nippon Zeon Co., Ltd.: MR110),
A photoreceptor was produced in the same manner as in Example 1.

Comparative example 2

A photoreceptor was prepared in the same manner as in Example 1, except that the polyvinyl butyral resin in the coating solution for the charge generation layer was changed to polycarbonate resin (PCZ-200, manufactured by Mitsubishi Gas Chemical Co., Ltd.). was created.

[0023] The above Examples 1, 2, 3 and Comparative Example 1,
The charge generation layer coating liquid used in step 2 was measured using a viscosity distribution meter (
BROOKHAVEN INSTRUMENTS Co
rp. , BI-90 PARTICLE SIZER
) to evaluate the dispersibility. The results are shown in Figure 1. In FIG. 1, the horizontal axis indicates the number of days left after preparing the coating solution.
The vertical axis indicates the average particle size of the phthalocyanine pigment, the solid line indicates the value for each coating solution of Examples 1, 2, and 3, and the dotted line indicates the value for each coating solution of Comparative Example 1.
, 2 are the values for each coating liquid. The vertical solid line at each measurement point indicates the dispersion of the measured values. As seen in Figure 1, the average particle size of the pigment in each coating solution was 200 nm to 3.
00 nm, but after standing for 7 days, Examples 1 and 2
, 3, the average particle size of the pigment is 300 nm to 400 nm.
nm, but in Comparative Examples 1 and 2 it was 800 nm to 900 nm.
It is clear that in the latter case, aggregation occurred due to poor dispersibility of the pigment. Almost no difference was observed between Examples 1, 2, and 3 and Comparative Examples 1 and 2. It is clear that the polyvinyl butyral resin prevents deterioration in the dispersibility of the pigment due to mixing with a high viscosity solvent.

For this reason, in Examples 1, 2, and 3 and Comparative Examples 1 and 2, when the charge generation layer was formed using the coating solution immediately after preparation, there was less unevenness in film thickness and no appearance such as dripping. Although a charge generation layer with no defects was obtained, in Comparative Examples 1 and 2, coating unevenness was observed in the charge generation layer when the coating solution was used after being left for 7 days. Furthermore, in the evaluation of adhesion by peeling off the adhesive tape, better results were obtained in Examples 1, 2, and 3 than in Comparative Examples 1 and 2.

The mixing ratio of the phthalocyanine pigment and polyvinyl butyral resin in the charge generation layer coating solution is such that when the amount of the phthalocyanine pigment increases, the dispersibility and adhesion deteriorate, resulting in a decrease in film forming properties, and when the amount decreases, the photosensitivity of the photoreceptor decreases. It has been found that a weight mixing ratio within the range of 1:0.5 to 1:1.5 is preferable because the

[0026] Furthermore, when the mixing ratio of high viscosity solvent to low viscosity solvent was investigated, it was found that if the mixing ratio is too low, the effect of reducing unevenness in coating film thickness and poor appearance is small; If the evaporation rate of
It has been found that a mixing ratio within the range of 0% by weight or less is preferable.

In the above Examples and Comparative Examples, carbitol acetate was used as the high viscosity solvent, but the solvent is not limited to this, and for example, butyl carbitol, isophorone, etc. are preferably used.

Furthermore, the order in which the charge generation layer and the charge transport layer are stacked is not limited to the order in the Examples and Comparative Examples.

[0029]

According to the present invention, the charge generation layer is formed by applying a coating liquid in which a material mainly consisting of an organic pigment and a polyvinyl butyral resin is dispersed in a mixed solvent of a low viscosity solvent and a high viscosity solvent. By doing so, it is possible to form a charge generation layer with less unevenness in film thickness and poor appearance, and to obtain an excellent photoreceptor for electrophotography that has less unevenness in sensitivity and provides output images with good image quality and fewer image defects. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the relationship between the number of days after preparation of the coating solution and the pigment average particle diameter for the charge generation layer coating solutions of Examples and Comparative Examples.

Claims (5)

[Claims] 1. A method for producing an electrophotographic photoreceptor comprising at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer is made of a material mainly containing an organic pigment and a polyvinyl butyral resin. 1. A method for producing an electrophotographic photoreceptor, the method comprising: coating a coating liquid in which a mixed solvent of a low viscosity solvent and a high viscosity solvent is dispersed. 2. The method for producing an electrophotographic photoreceptor according to claim 1, wherein the organic pigment is a phthalocyanine pigment. Claim 3: Claim 2, characterized in that the weight mixing ratio of the phthalocyanine pigment and polyvinyl butyral resin in the coating solution is within the range of 1:0.5 to 1:1.5.
The method for manufacturing the electrophotographic photoreceptor described above. 4. The electrophotographic method according to claim 1, wherein the weight mixing ratio of the high viscosity solvent to the low viscosity solvent is within a range of 10% to 30%. Method of manufacturing a photoreceptor. Claim 5: The low viscosity solvent is tetrahydrofuran (THF).
), and the high viscosity solvent is any one of isophorone, carbitol acetate, and butyl carbitol. How the body is manufactured.