JPH04346354A - Dip coating method for electrophotographic photoconductor - Google Patents

Abstract

PURPOSE:To prevent latent nonuniformity of coating and image defect by providing a buffer disk for relieving liquid flow at the bottom of a coating reservoir. CONSTITUTION:A coating liquid with a viscosity of below 30cp at a temperature of 25 deg.C is used, and a flow ordering plate 2 for rectifying the coating liquid flow and/or a buffer disk 3 for relieving the direct collision of the coating liquid against the end of a cylindrical base body 4 is provided between a coating liquid flow-in opening portion at the bottom of a coating reservoir 1 and the end of the cylindrical base body 4. In this case, the coating liquid flows from the flow-in opening portion, controlled by the flow ordering plate 2 and/or the buffer disk 3, flows through a clearance between the cylindrical base body 4 and the wall of the coating reservoir 1, and comes over from an overflow edge 5. Then the cylindrical body 4 is pulled up in the arrow direction at a constant speed. The opening rate of the flow ordering plate 2 must be 10 to 80% in both cases that the plate is used independently and used in combination with the buffer disk 3. Also the buffer disk 3 is provided coaxially with the base body cylinder 4.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrophotographic photoreceptor, and more particularly to a method for coating a photoconductive layer.

0002

[Prior Art] In order to manufacture a thin film such as a photosensitive layer on a cylindrical substrate such as an electrophotographic photoreceptor, a method is widely used in which the necessary chemical composition is made into a solution, coated on the substrate and dried. ing.

In this case, it is important to form a layer of uniform thickness over the entire surface of the cylindrical portion of the base.

[0004] As a coating method that can form such a layer,
JP-A-59-139967 discloses a method of disposing a disk or a cone above the coating liquid inflow opening to make the flow of the coating liquid uniform; however, in recent years photosensitive drums for laser beam printers have However, the uniformity is still insufficient, and image defects due to uneven coating are detected.

[0005] Also, JP-A-60-146240 and JP-A-63
No. 104059 and Japanese Unexamined Patent Publication No. 3-20747 disclose that a stirring member is provided in the dip coating tank to prevent uneven coating. However, both methods have a serious weakness in terms of contamination of the coating liquid by dust, etc., compared to methods in which the coating liquid in the coating tank overflows or is applied while keeping the liquid level constant.

[0006]

OBJECTS OF THE INVENTION The first object of the present invention is to suppress image defects caused by uneven coating. In particular, when reversal development is performed as a photoreceptor for a laser beam printer, even slight coating unevenness can be detected, so the purpose is to suppress these defects.

[0007] The second purpose is to prevent image defects when used repeatedly. This is because coating unevenness that was not found in the initial stage appears after many copies have been made.

A third object is to provide a photoreceptor that does not cause image defects even when used under high temperature, high humidity or low temperature conditions.

A fourth object is to provide a highly sensitive photoreceptor, such as a photoreceptor coated with a pigment dispersion such as titanyl phthalocyanine, which is free from image defects.

0010

[Structure of the Invention] The object of the present invention is to use a cylindrical substrate in the production of an electrophotographic photoreceptor, replenish overflow or coating loss and keep the level of the coating liquid in the coating tank constant. In dip coating in which the substrate is pulled up and coated, a coating liquid with a viscosity of 30 cp or less at 25° C. is used, and a rectifying plate and/or rectifying plate is provided between the coating liquid inflow opening at the bottom of the coating tank and the end of the cylindrical substrate to rectify the coating liquid flow. Alternatively, this can be achieved by a dip coating method for an electrophotographic photoreceptor, which is characterized by providing a buffer disk to reduce the direct impact of the coating liquid flow on the end surface of the cylindrical substrate.

In the aspect of the present invention, the aperture ratio of the current plate is preferably 10 to 80%, whether the current plate is used alone or in combination with a buffer disk. Furthermore, when a current plate and a buffer disk are used together, when the diameters of the cylindrical base, the current plate, and the buffer disk are respectively D, d1, and d2, d1≧D.
, and preferably 1.2D≧d2≧0.8D.

Furthermore, in the present invention, when the coating liquid used is a pigment dispersion, the viscosity is 30 cp (25° C.) or less and the difference in specific gravity between the solvent (dispersion medium) and the pigment is 0.4 g.
/cc or more.

The use of a current plate or a combination of a current plate and a buffer disk significantly improves coating properties because the flow of the coating liquid near the surface of the cylindrical substrate (drum) is made uniform.

[0014] Further, a remarkable effect is obtained when the viscosity of the coating liquid is 30 cp (25°C) or less, particularly 20 cp (25°C) or less. Furthermore, in the case of a dispersion system such as a charge generating layer (CGL) liquid, the difference in specific gravity between the dispersion medium and the pigment is 0.4 g/cc, preferably 0.
．． If it is 5 g/cc or more, the effect is significant.

[0015] If the viscosity of the coating solution is increased or the difference in specific gravity between the pigment and the dispersion medium is reduced, the coating properties are relatively good even without a current plate, but the coating speed must be slowed down and the coating properties are unstable. Therefore, a state that is satisfactory in terms of electrophotographic performance or production technology cannot be reached.

FIG. 1 shows an example of the shape of the current plate used in the present invention (
A) to (H), and the aperture ratio (opening area/total area) is shown below each symbol.

Further, FIG. 2 shows side views of embodiments (a) to (f) of the dip coating method using overflow according to the present invention.

In the figure, 1 is a coating tank, 2 is a rectifying plate, 3 is a buffer disk, 4 is a cylindrical base, 5 is an overflow edge, and 6 is a coating liquid inflow opening.

The coating liquid flows in from the inflow opening, is controlled by a rectifying plate and/or a buffer disk, flows between the cylindrical substrate 4 and the inner wall of the coating tank, and overflows from the overflow edge 5. The cylindrical base body is pulled up in the direction of the arrow at a constant speed.

The current plate and buffer disk used in the present invention may be made of any material as long as it is inert to ordinary ketones, alcohols, halogenated hydrocarbons, and aromatic solvents. Examples include plastics such as Teflon, thermosetting resins, aluminum, stainless steel, iron, nickel, brass, and the like.

[0021] The buffer disk is preferably provided coaxially with the base cylinder, and it is sufficient that the flow line of the coating liquid does not substantially penetrate through the disk.

When the cylindrical substrate (drum) is immersed in the coating tank, the flow rate of the liquid between the two walls depends on the diameter of the drum, the size of the coating tank,
Although it varies depending on the amount of liquid supplied, 0.1 to 15 cm/
It is within the range of sec. Preferably 0.2-10cm/
sec.

In the present invention, the viscosity of the coating liquid and the difference in specific gravity between the pigment and the dispersion medium are adjusted by the mixing ratio of the solvent and the binder.

[0024] Examples of the solvent for the coating solution for forming the organic photoconductive material include butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine,
Triethylenediamine, N,N-dimethylformamide, acetone, methyl ethyl ketone, cyclohexanone,
Benzene, toluene, xylene, chloroform, 1,2
- Dichloroethane, dichloromethane, tetrahydrofuran, dioxane, methanol, ethanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, methyl cellosolve, ethyl cellosolve, methyl cellosolve, acetate, and the like.

[0025] Further, as the photoconductive substance, an azo compound,
Quinone compounds, phthalocyanine compounds, triazole compounds, oxadiazole compounds, imidazole compounds,
Examples include materials having charge generation ability and charge transport ability, such as pyrazoline compounds, triarylalkane compounds, phenylenediamine compounds, hydrazone compounds, amino-substituted chalcone compounds, triarylamine compounds, carbazole compounds, and stilbene compounds.

As binders, commonly used resins such as polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polyvinyl butyral, styrene copolymer, vinyl chloride-acetic acid can be used. Examples include vinyl copolymers.

Furthermore, various commonly used additives can be usefully utilized.

The base body of the present invention can be made of a freely selected material such as aluminum, and its molding method can be arbitrary, such as impact processing, drawing processing, or drawing processing, such as closing one side of the circular tube with another member. You can choose the method.

The components and layer structure of the electrophotographic photoconductive layer applied to the substrate of the present invention are not particularly limited, and may be a dispersion or solution of various photoconductive substances and a binder, or a photoconductive layer. Various coating liquids such as a subbing liquid that strengthen the adhesion of the conductive layer to the substrate can be optionally applied. Examples include a subbing liquid and a charge generation layer for forming an organic photoconductor photosensitive layer. Examples include a coating liquid, a charge transport layer coating liquid, and the like.

[0030]

[Examples] Next, the present invention will be specifically explained with reference to Examples.

Example 1 As a charge generation layer (CGL), the main peaks of the Bragg angle 2θ with respect to Cu-Kα characteristic X-rays (wavelength 1.54 Å) are at least 9.6±0.2° and 27.2±0. 3 parts of oxytitanyl phthalocyanine pigment at 2°, 10 parts of silicone resin "KR-5240; 15% xylene/butanol solution" (manufactured by Shin-Etsu Chemical Co., Ltd.) as a binder resin,
Add t-butyl acetate as a dispersion medium, and the total solid content is 3%.
The mixture was mixed in a W/V ratio and dispersed in a sand mill for 4 hours to prepare a CGL solution. The viscosity at this time is 1 at 25°C.
It was 5 cp. Also, the difference in specific gravity between the pigment and the solvent is 0.5g/
It was cc.

[0032] This CGL liquid was placed in a 200 mm diameter coating tank in which the shape of the rectifier plate, the size and position of the buffer disk were changed as shown in Table 1, and a 100 mmφ aluminum cylinder was immersed in it, and the applied amount was 2.7 mg/ It was applied so that it was dm2. The comparative example is drum No. 1 and 2. The coated drum was observed under bright light to evaluate the coatability.

(Evaluation display) Significant uneven coating: XX Somewhat: × Slightly recognized: △ Passing level (no problem in practical use):○ Not at all: ◎

[0034]

[Table 1]

As can be read from Table 1, it can be seen that coating unevenness can be eliminated by using a buffer disk size of 90 to 110 mmφ and a rectifying plate.

[0036] Without the rectifying plate, uneven coating will occur. Furthermore, it can be seen that the use of a buffer disk improves the applicability by one level. Also, the size of the buffer disk is 80 to 120 mm.
It is sufficient if it is φ.

Example 2 3 parts of copolymerized polyamide "Laccamide 5003" (manufactured by Dainippon Ink Co., Ltd.) was mixed with methanol/butanol = 90/10.
(Volume ratio, dissolved in 100 parts of mixed solvent, undercoat layer (UC)
L) Solution was prepared. The viscosity at this time was 20 cp at 25°C. This UCL liquid was placed in a coating tank with a diameter of 200 mmφ, in which the shape of the rectifying plate, the size and position of the buffer disk were changed as shown in Table 2, a 100 mmφ aluminum cylinder was immersed, and the coating was applied so that the adhesion was 5 mg/dm2. did. Further, as a comparative example, 70 parts of the above mixed solvent was used instead of 100 parts to prepare a liquid having a viscosity of 60 cp at 25°C, and applied in the same manner. 21 to 23 were created. The comparative example is drum No. 1, 2 and 21-23. Furthermore, drum No. of Example 1 is added on top of this. 7 and the same coating solution and coating conditions were used to form layers up to CGL.

The coated drum was observed under bright light to evaluate the coatability. The results are shown in Table 2.

[0039]

[Table 2]

Example 3 Drum No. 2 of Example 2. In exactly the same way as 7, UC
Liquid L was applied to 13 drums to the same thickness, and No. 1 of Example 1 was applied on top of this to the same thickness. 1~No. CGL coating liquid was applied up to No. 13 at the same film thickness.

Further, on top of this, a charge transport substance C having the following structural formula is added.
A charge transport layer made by dissolving 120 g of TM and 165 g of polycarbonate resin (Iupilon Z-200 manufactured by Mitsubishi Gas Chemical Industries, Ltd.) in 1000 ml of 1,2-dichloroethane (
CTL) The drums coated up to the above CGL were immersed in the coating solution and coated to a film thickness of 20 μm to prepare the samples listed in Table 3.

After coating, it was dried at 90° C. for about 1 hour and then used for actual copying.

Characteristic evaluation was carried out as follows.

[0044]

[Chemical formula 1]

[0045]

[Table 3]

[Characteristics Evaluation] Each of the photoreceptors of Examples and Comparative Examples was mounted on a modified "LP-3010" (manufactured by Konica) machine (equipped with a semiconductor laser light source), and the VH was -600±.
Adjust the grid voltage so that it becomes 10 [V], and 0.7
The potential of the exposed surface upon irradiation with mW was set to VL, and reversal development was performed at a developing bias of -500 [V], and image unevenness was visually evaluated.

[0047] Also, after printing 5000 times, 500
VH and VL after 0 prints are VH5000 and VL5
It was set as 000.

[0048] The displacement amounts of VH and VL from the initial stage were set as △VH5000 and △VL5000, respectively.

Therefore, △VH5000=(VH5000
+600), △VL5000=(VL5000-VL)
It is.

Furthermore, image unevenness after 5000 times was evaluated. The results are shown in Table 3.

According to the present invention, there is no image unevenness after 5000 times, and there is little variation in VH and VL.

[0052] Next, photoreceptors similar to those in the above-mentioned example were prepared with a drum size for DC-8010 (manufactured by Konica). When images were produced on each of these photoreceptors using DC-8010 under each development condition shown in Table 4, no image unevenness was observed under each development condition when any of the photoreceptors was used except for the comparative example. A good image with no blemishes was obtained.

Development was carried out by so-called two-component non-contact jumping development.

[0054]

[Table 4]

Development conditions: 70 wt% magnetite powder with an average particle size of 0.1 μm, 30 wt% polyester resin as a binder resin,
The mixture was kneaded, crushed and granulated, and then classified to a particle size of 20 to 30 μm to obtain a carrier. The specific gravity of this carrier was about 3.5 or less. A toner for a copying machine (a toner made of polyester resin containing carbon) of U-Bix 1800 (manufactured by Konica) was blended into this carrier so that the toner concentration was 20 wt %, and copying was performed under the following conditions.

The circumferential speed of the image carrier is 60 mm/sec, the gap between the image carrier and the developing sleeve is 0.3 mm, the thickness of the developer layer is 0.05 mm, the diameter of the developing sleeve is 24 mm, and the rotation speed is 200 rpm. did.

[0057]

[Effects of the Invention] By applying the present invention, coating unevenness of electrophotographic photoreceptors manufactured by dip coating method, especially fine coating unevenness, latent coating unevenness that peels off due to repeated use, and use under harsh conditions can be prevented. Image defects that occur can be prevented.

[Brief explanation of drawings]

FIG. 1 is a plan view of an example of the shape of a current plate used in the present invention.

FIG. 2 is a side view of an example of the operation of the overflow dip coating method of the present invention.

Claims (7)

[Claims] Claim 1: Dip coating in which a cylindrical substrate is used in the manufacture of electrophotographic photoreceptors, and the cylindrical substrate is pulled up and coated while keeping the level of the coating liquid in the coating tank constant by replenishing overflow or coating loss. A dip coating method for an electrophotographic photoreceptor, characterized in that a coating solution having a viscosity of 30 cp or less at 25° C. is used and a current plate is provided between the coating solution inflow opening at the bottom of the coating tank and the end of the cylindrical substrate. . 2. The dip coating method for an electrophotographic photoreceptor according to claim 1, wherein the aperture ratio of the rectifying plate is 10 to 80%. 3. Dip coating in which a cylindrical substrate is used for manufacturing an electrophotographic photoreceptor, and the cylindrical substrate is pulled up and coated while keeping the level of the coating liquid in the coating tank constant by replenishing overflow or coating loss. , a coating solution with a viscosity of 30 cp or less at 25° C. is used, and a coating solution is placed between the coating solution inflow opening at the bottom of the coating tank and the end of the cylindrical substrate to soften the direct contact of the coating solution flow with the end surface of the cylindrical substrate. 1. A dip coating method for an electrophotographic photoreceptor, which comprises providing a buffer disk. 4. Dip coating in which a cylindrical substrate is used in the production of electrophotographic photoreceptors, and the cylindrical substrate is pulled up and coated while keeping the level of the coating liquid in the coating tank constant by replenishing overflow or coating loss. In this method, a coating liquid with a viscosity of 30 cp or less at 25°C is used, and a current plate is provided between the coating liquid inflow opening at the bottom of the coating tank and the end of the cylindrical substrate, and the flow of the coating liquid is directly directed to the end surface of the cylindrical substrate. A dip coating method for an electrophotographic photoreceptor, characterized in that a buffer disk for softening the abutment is provided above or below a rectifying plate. 5. The dip coating method for an electrophotographic photoreceptor according to claim 4, wherein the current plate has an aperture ratio of 10 to 80% in the dip coating method in which the current plate and the buffer disk are provided together. 6. In the dip coating method in which the current plate and the buffer disk are provided together, when the diameters of the cylindrical substrate, the current plate, and the buffer disk are respectively D, d1, and d2, d1≧
D, and 1.2D≧d2≧0.8D, the dip coating method for an electrophotographic photoreceptor according to claim 4 or 5. 7. Dip coating in which a cylindrical substrate is used in the manufacture of an electrophotographic photoreceptor, and the cylindrical substrate is pulled up and coated while keeping the level of the coating liquid in the coating tank constant by replenishing overflow or coating loss. The coating liquid used has a viscosity of 30 cp or less at 25° C., is a pigment dispersion, and the difference in specific gravity between the solvent (dispersion medium) and pigment of the dispersion is 0.4 g/c.
A dip coating method for an electrophotographic photoreceptor, characterized in that the coating temperature is at least c.