JPH06266126A - Production of electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To suppress the sag of coating liquid by increasing viscosity of the coating liquid and to uniformalize the film thickness over the entire part by adding a thickener to the charge transfer layer-forming liquid. CONSTITUTION:The production of the photosensitive body by a dip coating method is executed by adding the thickener to the charge transfer layer forming liquid. The thickener is preferably added to an under coating layer-forming liquid and is not added to a charge generating layer-forming liquid. The examples of the thickener include an org. amide material, modified castor oil deriv., modified polyolefin wax material and org. clay deriv. The org. amide material is strong to a high-temp. treatment and the example thereof includes a fatty acid amide wax. The org. clay deriv. is formed by a composite cation compd. to smectite clay and the examples thereof include two kinds; amine- modified bentonite and amine-modified hectolite. The ratio at which the thickener occupies in the coating liquid is 2 to 20wt.%, more preferably 5 to 15wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an electrophotographic photosensitive member, and more specifically, an undercoat layer, a charge generation layer and a charge transport layer are sequentially laminated on a cylindrical substrate (undercoat layer, charge transport layer). Layer, the charge generation layer may be laminated in this order),
The present invention relates to a method for producing an organic electrophotographic photosensitive member in which each layer is formed to have a uniform film thickness by a dip coating method.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors are roughly classified into inorganic ones and organic ones according to what is used as a photosensitive layer forming material. At present, organic electrophotographic photoconductors are often used because they are easy to manufacture, the manufacturing cost is low, and practical sensitivity increases. Such an organic electrophotographic photosensitive member is generally used in either an endless belt shape or a cylindrical shape.

By the way, in a cylindrical organic electrophotographic photoreceptor, a cylindrical substrate is dipped in a coating liquid (layer forming liquid) in a dipping tank and pulled up at a constant speed to form a coating film on the outer peripheral surface of the cylindrical substrate. It is manufactured by the so-called "dip coating method" of forming. At that time, it is desirable that the undercoat layer, the charge generation layer, and the charge transport layer, which are coated and laminated on the outer peripheral surface of the cylindrical substrate, have uniform layer thicknesses. In particular, the film thickness must be uniform within the effective image area where an image is formed. This is because the nonuniformity of the coating film is directly related to the image quality.

[0004]

However, in the dip coating method, the rising portion of the film thickness at the coating start portion is liable to sag, which causes a gradient in the film thickness and makes it impossible to form an effective image area well. However, it may be possible to increase the size of the cylindrical substrate and cut out only the portion having a uniform film thickness, but the high cost cannot be avoided. Therefore, it is necessary to make the rise of the coating start portion as short as possible and make the portion outside the effective image area shortest.

Further, due to environmental problems, the halogen-based solvents which have been used up to now and which have a high evaporation rate are not preferable, and the search for a non-halogen-based solvent has been promoted. However, the use of such a solvent causes the coating start portion to sag more than before. Further, electrophotographic photoreceptors are evolving toward higher durability, and in particular, charge transport layers are progressing toward thicker films. However, the problem of sagging at the coating start portion still remains due to this thickening of the film, and its solution is desired. An object of the present invention is to solve the above problems and provide an economical and high-quality method for producing an organic electrophotographic photosensitive member.

[0006]

The method for producing an electrophotographic photosensitive member according to the present invention is a photosensitive material comprising a charge generation layer and a charge transport layer formed on a cylindrical substrate by an undercoat layer by a dip pull-up coating method. At the time of providing the layer, at least the thickening agent is contained in the charge transport layer forming liquid.

To solve the problem of the uniformity of the coating film of the electrophotographic photosensitive member or the sagging of the coating starting portion, an approach using a coating apparatus and coating conditions is generally used. Is that the viscosity of the coating liquid increases at least by adding a thickening agent to the charge transport layer forming liquid, and the sagging of the coating liquid is suppressed so that the entire film thickness can be made uniform.
The reason why the thickening agent is added to at least the coating liquid for the charge transport layer is that the thickness of the charge transport layer is extremely thicker than the others. There are many examples of adding some kind of additive to the coating solution in order to improve the characteristics of the electrophotographic photoreceptor, but the additive is added to control the film thickness of the coating film of the electrophotographic photoreceptor. The reality is that few examples have been proposed.

The present invention will be described in more detail below.
In the present invention, a thickener is added to at least a charge transport layer forming liquid to produce an organic electrophotographic photoreceptor by a dip coating method. The thickener is used as a charge generating layer forming liquid or an undercoat layer forming liquid. It is optional whether or not it is contained. However, it is desirable that the thickener is added to the undercoat layer forming liquid and not added to the charge generating layer forming liquid. This is because the thinner the charge generation layer, the higher the charge generation efficiency.

Examples of effective thickeners include organic amide-based substances, modified castor oil derivatives, modified polyolefin wax-based substances, and organic clay derivatives. Organic amide-based substances are resistant to high temperature treatment, and fatty acid amide wax is an example of this. Specifically, "FLOWNON series" manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.
And part of the "TALEN series". Examples of modified castor oil derivatives include Baker
"THIXATROL series" manufactured by Castor Oil Co., Ltd. is available. As an example of the modified polyolefin wax-based substance, “FLOWNO” manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd.
Part of "N series" and "TALEN series"
There is a part of. The organoclay derivative is a smectite clay to which a complex cation compound is added, and there are two types of amine-modified bentonite and amine-modified hectorite.
Specifically, "TIXOGEL" manufactured by Sud Chemie of Germany
Series "or" BENTON "manufactured by RHEOX in the United States
E series ”and so on. However, some organic clay derivative substances require an activator (such as propylene carbonate) depending on the solvent.

The amount of the thickener in the coating liquid varies depending on the type of the thickener, the composition of the coating liquid, the pulling rate after immersion, etc., but roughly speaking, it is 2 to 20% by weight, preferably. It is 5 to 15% by weight. Further, the above-mentioned four kinds of thickeners can be used in combination of two or more kinds.

[0011]

EXAMPLES Next, the method of the present invention will be described more specifically with reference to Examples and Comparative Examples.

Comparative Example 1 (1) A sample for film thickness evaluation was prepared by coating a cylindrical Al substrate with a charge transport layer forming liquid as described below. 9 parts by weight of a charge transfer agent having the following structural formula and 10 parts by weight of a polycarbonate resin were dissolved in 81 parts by weight of tetrahydrofuran to prepare a coating solution, which was dried at 130 ° C. in an oven dryer at 25 ° C.
Done in minutes. A sample for film thickness evaluation was prepared by performing dip coating by adjusting the lifting speed so that the film thickness after drying was about 28 μm.

[Chemical Formula 1] (2) The sample for evaluating the characteristics of the photoconductor is cylindrical A
an undercoat layer, a charge generation layer, A charge transport layer was sequentially laminated to obtain an electrophotographic photoreceptor. (2-1) The undercoat layer is an alcohol-soluble polyamide resin (nylon 6/66/610/12, "CM-
8000 ") 8 parts by weight is dissolved in 130 parts by weight of methanol, and 60 parts by weight of butanol is further added to form a coating solution. The coating solution is dip-coated on a cylindrical Al substrate and dried by an oven drier. A film having a film thickness of about 0.3 μm formed at 10 ° C. for 10 minutes. (2-2) The charge generation layer is a bisazo pigment 2 having the following structural formula.
Parts by weight and 40 parts by weight of cyclohexanone are kneaded and dispersed in a ball mill for 48 hours to obtain a highly viscous cream dispersion liquid. To this dispersion liquid, a mixed liquid of 40 parts by weight of methyl isobutyl ketone and 20 parts by weight of cyclohexanone is added. ,
After kneading and dispersing again for 2 hours, it is further diluted with 100 parts by weight of methyl isobutyl ketone to obtain a coating solution, which is dip coated on the undercoat layer and dried by an oven drier.
The temperature was kept at 10 ° C. for 10 minutes to form a charge generation layer having a thickness of about 0.2 μm. The coating film is a glossy and uniform smooth film.

## STR00002 ## (2-3) The charge transport layer is subjected to dip coating in the same manner as the film formation of the charge transport layer in (1) above. Was formed.

Examples 1 to 16 Comparative Example 1 except that the charge transport layer forming liquid of Comparative Example 1 was further mixed with the following thickening agent and stirred vigorously to prepare the charge transport layer forming liquid of the present invention. A film thickness evaluation sample and a photoconductor characteristic evaluation sample were prepared in exactly the same manner. (Example 1) "FLOWNON SA-1000" (organic amide type substance, manufactured by Kyoeisha Oil & Fat Chemical Co., Ltd.) 1 part by weight (Example 2) "FLOWNON SA-1000" (organic amide type substance, Kyoeisha fat and oil) Chemical Industry Co., Ltd.) 2 parts by weight (Example 3) "FLOWNON SA-1000" (organic amide-based substance, Kyoeisha Oil and Fat Chemical Co., Ltd.) 3 parts by weight (Example 4) "FLOWNON SA-1000" (Organic amide-based substance, manufactured by Kyoeisha Oil & Fat Chemical Co., Ltd.) 5 parts by weight (Example 5) "THIXATROL ST" (modified castor oil derivative, manufactured by Baker Castor Oil Co., USA) 1 part by weight (implemented Example 6) 2 parts by weight of "THIXATROL ST" (modified castor oil derivative, manufactured by Baker Castor Oil Co., USA) (Example 7) "THIXATROL" ST "(modified castor oil derivative, manufactured by Baker Caster Oil Co., USA) 3 parts by weight (Example 8)" THIXATROL ST "(modified castor oil derivative, manufactured by Baker Caster Oil Co., US) 5 parts by weight ( Example 9) 1 part by weight of "FLOWNON SA-200" (modified polyolefin wax-based substance, manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd.) (Example 10) "FLOWNON SA-200" (modified polyolefin wax-based substance, Kyoeisha Oil and Fat Chemical) Industrial Co., Ltd.) 2 parts by weight (Example 11) "FLOWNON SA-200" (modified polyolefin wax-based substance, Kyoeisha Oil and Fat Chemical Co., Ltd.) 3 parts by weight (Example 12) "FLOWNON SA-200" (Modified polyolefin wax type substance, manufactured by Kyoeisha Yushi Kagaku Kogyo Co., Ltd.) 5 parts by weight (Example 13) "T 1 part by weight of "IXOGEL EZ-200" (organic clay derivative, manufactured by Sud Chemie, Germany) (Example 14) 2 parts by weight of "TIXOGEL EZ-200" (organic clay derivative, manufactured by Sud Chemie, Germany) Example 15) "TIXOGEL EZ-200" (organic clay derivative, manufactured by Sud Chemie, Germany) 3 parts by weight (Example 16) "TIXOGEL EZ-200" (organic clay derivative, manufactured by Sud Chemie, Germany) 5 Parts by weight

The film thickness distribution of the charge transport layer in the axial direction of the cylindrical substrate of Comparative Example 1 was measured as shown in FIG. At this time, the film thickness portion of about 28 μm is the stable film thickness, and the distance from the coating start position to the portion thinner than the stable film thickness by about 1 μm is the sagging length (L1). The shorter the sagging length, the faster the rise of the film thickness and the less sagging. An eddy current type film thickness meter was used to measure the film thickness, and as shown in FIG. 2, a distance of 5 m was set in the range of 0 to 50 mm in the axial direction of the cylindrical substrate from the coating start portion.
m, the range of 50 to 100 mm is 10 mm, and the interval is 10 mm.
After 0 mm, the film thickness was measured at an interval of 25 mm.

The samples for evaluating the characteristics of the photoconductors of Examples 1 to 16 and Comparative Example 1 were evaluated for the characteristics of the photoconductors described below (E1 / 10, VR) with a device for evaluating the characteristics of photoconductors having the following structure and manufactured by Ricoh Co., Ltd. The image was evaluated by incorporating it in a copying machine FT4820. That is, a device provided with a means for rotating a cylindrical photoreceptor at a constant linear velocity, a means for charging, a means for exposing, and a surface potential measuring means (Japanese Patent Laid-Open No. 60-100167).
Device), rotate at 1000 rpm, apply a voltage of −6 kV in the dark to perform corona discharge, and charge the photoreceptor. The charging potential is controlled to be 800 V, and then the illuminance on the surface of the photoconductor is set to 2 by the light having the color temperature of 2854 ° K of the tungsten lamp.
The exposure amount E1 / 10 necessary to reduce the surface potential of the photoconductor to 80 V by irradiating with light having a slit width of 6 mm in the state of 6 lux / cm ² was obtained. Further, the surface potential VR of the photoconductor after irradiation with the same light for 30 seconds was used.

As a result of these measurements, L1 of Comparative Example 1 was about 6
0 mm, L1 of Example 1 is about 50 mm, L1 of Example 2 is about 30 mm, L1 of Example 3 is about 20 mm,
L1 of Example 4 is about 15 mm, and the amount of sag is gradually shortened. However, in Example 4, a slight variation in the film thickness began to become a concern. The results are shown in Table 1 together with Examples 5 to 16. Further, FIG. 3 shows the relationship between the content of the thickener in the charge transport layer coating liquid and the amount of sag (L1). The photoreceptor characteristics (E1 / 10, VR) and the results of image evaluation are also summarized in Table-1 and shown in Tables-1. E1 / 10 is Comparative Example 1 and Example 1
In Examples 3, 5, 7, 9, 11 and 13-15, there was no problem, but in Examples 4, 8, 12 and 16, the rate was slow and VR was large. Comparative Example 1 showed good values for both E1 / 10 and VR, but there was a large amount of sagging during the production of the photoconductor, which was disadvantageous in terms of cost.

[0017]

[Table 1]

[0018]

According to the first and second aspects of the present invention, the film thickness can be controlled by adding a thickener to at least the charge transport layer forming liquid during the production of the organic electrophotographic photosensitive member.
As a result, a good quality copy image can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a film thickness distribution of a charge transport layer in an axial direction of a cylindrical substrate in a photoreceptor of Comparative Example 1.

FIG. 2 is a diagram for explaining measurement points of film thickness.

FIG. 3 is a diagram showing the relationship between the content of a thickener in a charge transport layer forming liquid and the amount of sag of the forming liquid.

Claims (2)

[Claims] 1. A method of providing a photosensitive layer comprising a charge generation layer and a charge transport layer on a cylindrical substrate by an immersion pull-up coating method via an undercoat layer, wherein at least the charge transport layer forming solution is thickened. A method for producing an electrophotographic photosensitive member, which comprises containing an agent. 2. An organic amide-based substance as the thickener,
The method for producing an electrophotographic photosensitive member according to claim 1, wherein at least one selected from a modified castor oil derivative, a modified polyolefin wax-based substance and an organic clay derivative is used.