JPH03196045A - Manufacturing method of electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE:To prevent nonuniform coating due to thixotropy of a coating soln. by supplying a coating homogenized outside a coating bath to the both immediately before coating to carry out coating, discharging the coating from the bath after coating and again homogenizing the coating which is reused. CONSTITUTION:A coating is charged into a reservoir 5, an impeller 6 is rotated, an ultrasonic treating machine 7 is actuated to homogenize the coating, and then the coating is supplied to the coating bath 2 by a pump 8. When the bath 2 is filled with the coating, a pretreated conductive substrate 1 is dipped and then pulled up to form a charge generating layer by coating. The supply of the coating is stopped after coating, a valve 13 is opened, a pump 11 is driven, a valve 12 is closed, and the coating is discharged from the bath. The coating is again homogenized and reused. Consequently, the nonuniformity in the photosensitive layer caused by the change in the viscosity of the coating in the bath due to thixotropy of the coating soln.exhibiting non-Newtonian flow is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing an electrophotographic photoreceptor, and particularly to a method for manufacturing an electrophotographic photoreceptor in which a surface coating is formed by a dip coating method.

[Prior Art] Various organic photoconductive materials have been developed in recent years as photoconductive materials for electrophotographic photoreceptors, and various film forming methods have also been proposed.

Depending on the material used, vapor deposition methods, curtain coating methods, blade coating methods, spray coating methods, spinner coating methods, dip coating methods, etc. are known, but this is the most common method and is superior in terms of cost and film formation quality. Dip coating is effective when using organic photoconductive materials. However, the properties of coating liquids vary, and in particular, pigment-dispersed coating liquids that exhibit double-kneeton flow exhibit chickentropic properties that exhibit different viscosities depending on the nuclear force (e.g., liquid flow, stirring) applied to the coating liquid. have. The property of this liquid is that it produces a uniform film thickness and quality. !
This poses an obstacle in the production of electrophotographic photoreceptors, which require systematic coating.

That is, in locations where external force is relatively less likely to be applied to the paint, such as in a coating bath, the viscosity tends to increase due to chicken tropism.

Furthermore, in the manufacture of electrophotographic photoreceptors, a conductive support is immersed in order to apply a paint, and at this time, shearing force is generated between the support and the paint. A relatively large shearing force is applied, and the shearing force becomes very small in a portion away from the support, that is, near the inner surface of the coating bath or near the bottom of the coating bath. As a result, differences in viscosity occur in each part of the coating bath, and photoconductors coated using such a coating bath may have uneven coating within a single photoconductor, or may be coated on multiple photoconductors. Even when coating under the same coating conditions, differences in film thickness occur between photoreceptors.Furthermore, in the circulating dip coating method, in which the coating solution is continuously coated in a Wl ring, new paint is supplied by a pump. However, since the paint flows easily in areas with low viscosity, new coating liquid is supplied sequentially and selectively.
In areas with high viscosity, such as near the inner surface of the coating bath, it is difficult for paint to flow compared to near the conductive support, so the supplied paint flows selectively near the support. There is less flow near the inner surface of the coating bath, which promotes an increase in viscosity.

In addition, since the cross-sectional area of the coating bath is large compared to the cross-sectional area of the pipe supplied from the pump, the flow rate of the coating liquid changes drastically, and the amount of the coating liquid flowing outward changes, resulting in a change in the viscosity of the paint. is easy to change.

If there is a difference in the viscosity of the paint in the coating bath, the coating conditions for the dip coating method (coating liquid solid content lifting rate)
Even if they are the same, if the viscosity is different, the amount of adhesion to the conductive support will be different.

-Of course, it is inconvenient for a book photoconductor to have different film thicknesses in different parts, but when a large number of books are manufactured, differences in film thickness occur between each photoconductor. Storing them away is even more inconvenient for mass production.

As a method to improve the uniformity of the coating solution, including the viscosity inside the coating bath, there is an example of installing a stirring blade in the coating bath for stirring. This is not an adequate method as it reduces mass productivity due to problems such as contact with the object to be coated and fluctuations in the liquid level.

[Problems to be Solved by the Invention] An object of the present invention is to provide a method for uniformly applying a coating film in the production of an electrophotographic photoreceptor using a dip coating method, and in particular to a method for uniformly applying a coating film, and in particular to solving coating unevenness caused by the chicken tropism of the coating solution. An object of the present invention is to provide a coating method for producing a coating film in the production of an electrophotographic photoreceptor, which does not produce any of the following.

[Means for Solving the Problems, Effects] The present invention provides a method for manufacturing an electrophotographic photoreceptor in which a coating material is immersed in a coating bath and raised at a required speed to form a coating film. Just before applying the paint!
A: A method for manufacturing an electrophotographic photoreceptor characterized by supplying a cloth hot bath, performing coating, and after coating, discharging the paint from the coating bath, making the paint uniform again, and reusing it. .

The present invention is a method for homogenizing a coating liquid exhibiting non-Newtonian flow, as opposed to the conventional method of applying an external force to the coating liquid in a coating bath. In this method, the paint is discharged to the outside of the coating bath, homogenized using the most suitable method for each paint, and then re-supplied immediately before coating.

Even in conventional dip coating methods and paint circulation dip coating methods, paints exhibiting non-Newtonian flow in the coating bath
Regardless of the amount, there will be areas where the viscosity is not uniform.

Therefore, in the present invention, in addition to simply circulating mII, the paint whose viscosity has become non-uniform within the coating bath is once taken out of the coating bath and made uniform by a more effective method. Resupply.

Methods for homogenization include commonly known methods such as a method of rotating at high speed using stirring blades of various shapes, an ultrasonic processor, a homogenizer, and a continuous sand mill.

Furthermore, by setting the amount of paint to be twice or more than three times the volume of the coating bath, a different amount from the amount used for coating inside the coating bath can be used for coating outside the coating bath. Equalization processing can be performed regardless of the time spent on processing.

Immediately before coating, the homogenized paint is supplied after the paint in the coating bath has been discharged, and the next coating is carried out using the conventional continuous circulation dip coating method, i.e. It becomes more effective when combined with a method that allows the paint to overflow.

Methods for discharging the coating solution from the coating bath include draining it from the top of the coating bath using a pump, and for continuous circulation type, stopping the supply and draining it from the supply port. Longer machining intervals result in lower production efficiency. Therefore, by providing a dedicated outlet for discharging at the bottom of the coating bath, rapid discharging becomes possible. Increasing the number of discharge ports or providing a discharge pump also enables more effective discharge.

The present invention will be explained with reference to FIG.

FIG. 1 is a schematic sectional view of a coating device for carrying out the present invention.

1 is a conductive support (seamless cylinder) which is an object to be coated, and its upper part is connected to a lifting device (not shown). 2 is a coating bath for dip coating the conductive support. 3 is a saucer for collecting overflowing coating liquid. The collected coating liquid passes through a pipe 4 and is poured into a coating liquid reservoir 5. The coating '15 liquid in the liquid reservoir 5 is stirred by the stirring blade j.
The fi 6 and the ultrasonic treatment device 7 sufficiently homogenize the particles.

This coating liquid is supplied to the coating bath by a pump 8.

A filter 9 is provided to remove dust and the like.

In general, in the method of the present invention, a vibrator 10 and a pump 1lt were provided so that the coating liquid in the coating bath 2 could be discharged. Valves 12 and 13 are electromagnetic valves that switch between supplying and discharging the coating liquid to the coating bath.

The operation of the above device is as follows: open valve 12, open valve 13,
is closed, and the coating liquid is supplied to the coating bath 2 by the pump 8. The coating bath is filled and the excess overflows into the reservoir 5.

In this state, the conductive support I is immersed, then pulled up,
Form a coating film.

This conductive support is moved to the next step by a moving device (not shown), and the uncoated conductive support is moved onto this coating bath.

During this time, first open valve 13, close valve 12,
The coating liquid in the coating bath is discharged by the pump 11.

Further, the valve 13 is closed and the valve 12 is opened to supply the homogenized coating liquid into the coating bath to prepare for the next coating.

Although it varies depending on the volume of the coating bath, the tL amount of the pump, etc., this process is usually completed in 30 seconds to 2 minutes, so it does not interfere with continuous production.

[Examples] Example 1 An electrophotographic photoreceptor was manufactured in a primary manner using the apparatus shown in FIG.

As the object to be coated, an aluminum cylinder with an outer diameter of 30 mm and a length of 346 mm was prepared.

First, 50 parts of titanium oxide powder coated with tin oxide containing 10% antimony oxide, 25 parts of resol type phenolic resin, 20 parts of methyl cellosolve, 5 parts of methanol
Part and silicone oil (polydimethylsiloxane polyoxyalkylene copolymer, average molecular weight 3,000) 0.0
02 was dispersed for 2 hours in a sand mill device using φimm glass beads to prepare a coating material for a conductive layer.

This conductive paint was placed in a conventional coating device, applied onto an aluminum cylinder by dip coating, and dried at 140° C. for 30 minutes to form a conductive layer with a thickness of 20 pm.

A solution prepared by dissolving 5 parts of 6-66-610-12 quaternary polyamide copolymer in a mixed solvent of 70 parts of methanol and 25 parts of butanol was coated on top of this using a conventional dipping method and dried to undercoat lILm. was formed.

Next, 10 parts of a disazo pigment with the following structural formula, polyvinyl butyral (number average molecule (in the formula, 1.m, n are positive integers) with the following structural formula), and 200 parts of cyclihexanone were mixed in a sand mill apparatus using φinm glass beads. This pigment dispersion was suitably diluted with 500 to 700 parts of methyl ethyl ketone and placed in the liquid reservoir 5 of the dip coating apparatus shown in FIG. 1 used in the method of the present invention.

First, the stirring blade 6 (with a rotation radius of 40% of the inner diameter length of the liquid reservoir 5) was rotated at 15 Orpm, and the ultrasonicator 7 (oscillation frequency 26 KHz, output 350
W) was activated.

After uniformity, the paint was supplied to the coating bath 2 using the pump 8. The supply amount of the pump 8 was adjusted to set the time for filling the coating bath 2 with the paint to 30 seconds.

After the coating bath was filled with the paint, the previously treated conductive support (aluminum cylinder) 1 was immersed and then pulled up to coat and form a charge generation layer. After applying the bond,
The supply of paint was stopped, valve 3 was opened, pump 11 was activated, and valve 12 was closed to discharge the paint in the coating bath. It took about 30 seconds to drain the entire amount.

Immediately after the paint was discharged, the supply of paint for the next application was started.

At this time, the discharge valve 13 was closed one second after the start of paint supply to wash away the paint used in the previous application.

Thereafter, the coating bath was filled with paint in preparation for the next coating. During this time, the coated cylinder was moved to the next step by a moving device (not shown), and the uncoated cylinder, which was the conductive support, was moved onto the coating bath.

There is no significant difference in paint discharge and supply and cylinder movement time, and production efficiency does not decrease.

Next, 10 parts of a styryl compound having the following structural formula and bisphenol Z type polycarbonate (number average molecular weight 20,022
1,000) was dissolved in 100 parts of chlorobenzene.

This solution was applied onto the charge generation layer by a conventional dip coating method, and dried with hot air at 100°C for 1 hour to obtain a film thickness of 19 lm.
A charge transport layer was formed.

Sample 1 is the first-grain electrophotographic photoreceptor manufactured in this manner.

Sample 2 is a second-grain electrophotographic photoreceptor coated with 30 continuous charge generation layers.

As sample 3, 30 layers were coated with 30 continuous charge generation layers.
0 wood grain electrophotographic photoreceptor.

The evaluation of the sample electrophotographic photoreceptor was conducted using Canon Copy Machine N.
P-, 1215 to copy the halftone image, measure the density at the top of the image (5 cm from the top edge), the center of the image, and the bottom of the image (5 cm from the bottom edge) using a reflection densitometer, and calculate the difference between the two areas of the charge generation layer. Evaluation was made in terms of coating unevenness. The results will be described later.

The halftone density varies depending on the aperture value of the copying machine, but to be fair, I fixed it at the center aperture value.

Comparative Example 1 An electrophotographic photoreceptor was produced in the same manner as in Example 1, except that the paint in the coating bath was not drained/resupplied, and the paint was coated while being circulated only by the pump 8.

Comparative Samples 1 to 3 are electrophotographic photoreceptors coated without draining/resupplying the paint, and correspond to Samples 1 to 3 of Example 1, respectively.

Image density sample 1 measured by reflection densitometer 0.60 0.61 0.
61 sample 2 0.59 0.60
0.60 Sample 3 0.59 0.60
0.60 Comparative sample 1 0.60 0.60 0
．． 61 comparative sample 2 0.57 0.58 0.61
Comparative sample 3 0.50 0.55 0.60 Reflection density: Gray black 1.1-1.2: Halftone 0.5
5-0.65: White 0-0, 05 Example 2 80 mmφ on conductive support (aluminum cylinder)
An electrophotographic photoreceptor was manufactured by coating in exactly the same manner as in Example 1, except that a diameter of 360 mm was used.

Halftone images of Samples 4 to 6 were copied using a Canon NP-3725 copying machine and evaluated. The evaluation method was the same as in Example 1 except that the copying machine was different. The results will be described later.

Comparative Example 2 An electrophotographic photoreceptor was produced in the same manner as in Example 2, except that the paint in the coating bath was not drained/resupplied, and the paint was coated while only being circulated by the pump 8.

Comparative samples 4 to 6 are electrophotographic photoreceptors coated without draining/resupplying the paint, and correspond to samples 4 to 6 of Example 2, respectively.

Image density sample 40 Sample 50 Sample 60 Comparative sample 40 Comparative sample 50 Comparative sample 60 1 1 2 1 6 0 2 1 2 1 7 6 2 2 3 2 2 3 Reflection density: Black 1. 1 to 1.2: Halftone 0.55 to 0.65: White 0 to 0, 05 Travel Example 3 Preparation of conductive support (30 mmφ x 346 mm), application of conductive undercoat, and application of intermediate layer The same procedure as in Example 1 was carried out.

Next, 10 parts of a disazo pigment with the following structural formula, 5 parts of polyvinyl benzal (number average molecular weight 35,000, degree of benzalization 80) with the following structural formula, and 200 parts of cyclohexanone were mixed in a sand mill apparatus using lφ glass beads. Dispersed for 4 hours.

This pigment dispersion was appropriately diluted with 500 to 700 parts of methyl ethyl ketone, and was applied onto the intermediate layer under the same conditions using the same apparatus as that used in Example 1 shown in Figure J@1 to form a charge generation layer. .

Next, 10 parts of a hydrazone compound with the following structural formula and bisphenol Z type polycarbonate (number average molecular weight 20,000
1,000) was dissolved in 100 parts of chlorobenzene. This solution was applied onto the charge generation layer and dried with hot air at 100° C. for 1 hour to form a charge transport layer of 19 parts m.

Samples 7 to 9 of electrophotographic photoreceptors were selected under the same conditions as in Example 1, in which 30 pieces were continuously coated.

Evaluation of samples 7 to 9 was made using Canon ■ copier NP-1215.
A halftone image was not copied using the same method, and was evaluated in the same manner. The results will be described later.

Comparative Example 3 An electrophotographic photoreceptor was produced in the same manner as in Example 3, except that the paint in the coating bath was not discharged/resupplied, and the paint was coated while only being circulated by the pump 8.

Comparative Samples 7 to 9 are electrophotographic photoreceptors coated without draining/resupplying the paint, and correspond to Samples 7 to 9 of Example 3, respectively.

Image density sample 7 measured by reflection densitometer 0.59 0.59 0.
60 samples 8 0.59 0.59
0.60 sample 9 0.60 0.59
0.60 Comparative sample 7 0.59 0.59 0
．． 60 comparative sample 8 0.57 0.58 0.60
Comparative sample 9 0.55 0.58 0.62 Reflection density: Gray black 1.1-1.2: Halftone 0.5
5 to 0.65: White 0 to 0, 05 In the above examples and comparative examples, a device using an ultrasonic oscillator 7 is used to make the paint uniform, but the invention is not limited to this. However, as described above, a homogenizing device such as a homogenizer can be used.

[Effects of the Invention] The method of the present invention reduces photosensitivity caused by changes in the viscosity of the coating solution in the coating bath due to the chicken-tropic property of the coating solution that exhibits non-Newtonian flow when electrophotographic photoreceptors are manufactured by the immersion coating method. This can prevent layer unevenness. That is,
Even when a large number of photoreceptors are produced, the uniformity among each product is excellent, and the remarkable effect of preventing local unevenness in a single product is achieved.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of an example of a coating device used in the method of the present invention. Symbol 1 is a conductive support, 2 is a coating bath, 3 is a saucer, 4 is a pipe, 5 is a liquid reservoir, 6 is an impeller, 7 is an ultrasonic oscillator, 8 is a pump, 9 is a filter 1O is a pipe, 11 is a pump, 12 is a supply side valve, and 13 is a discharge side valve.

Claims (1)

[Scope of Claims] 1. A method for manufacturing an electrophotographic photoreceptor in which an object to be coated is immersed in a coating bath and raised at a required speed to form a coating film, in which a uniform coating is applied outside the coating bath. A method for manufacturing an electrophotographic photoreceptor, characterized in that the paint is supplied to a coating bath immediately before coating, and after coating is completed, the coating is discharged from the coating bath, and the coating is homogenized again for reuse. 2. The method of manufacturing an electrophotographic photoreceptor according to claim 1, wherein an apparatus is used in which a discharge port is provided at the bottom of the coating bath in addition to a paint supply port.