JPS61149272A - Method for immersion coating of cylindrical substrate - Google Patents

Abstract

PURPOSE:To eliminate coating irregularity by preventing the generation of air bubbles at the time of immersion, by adjusting the relation between the temp. of a coating solution and that of gas in a cylindrical substrate prior to immersion. CONSTITUTION:In forming a thin film of a chemical substance to the surface of a cylindrical substrate such as an electrophotographic photosensitive drum, the penetration of a coating solution 2 into the cylindrical substrate 1 is obstructed in immersion coating by utilizing the pressure of air confined in the cylindrical substrate 1 and only the coating solution 2 is adhered to the surface of the substrate 1. In this case, in order to prevent the generation of air bubbles resulting in the disturbance of the uniformity of a coating layer, the temp. difference between the temp. of the gas in the cylindrical substrate 1 and the temp. of the coating solution 2 is adjusted to a range of -3-15 deg.C. As an adjustment means, a heating means such as heater or a cooling means such as a cooling pipe cooling through a cooling medium can be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION (r) Industrial Application Field The present invention relates to a dip coating method, and more particularly to a method for applying a chemical substance, such as a photosensitive layer, on the surface of a cylindrical substrate such as an electrophotographic photosensitive drum. The present invention relates to a dip coating method for a cylindrical substrate to be coated.

[Prior art]

BACKGROUND OF THE INVENTION In order to manufacture an electrophotographic photoreceptor having a thin layer such as a photosensitive layer on a cylindrical substrate, a widely used method is to prepare a solution of a necessary chemical composition and apply it onto the substrate and dry it.

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

As a coating method capable of forming such a layer, JP-A-59-
Japanese Patent No. 71058 discloses a cylindrical substrate having one end closed and the other open, immersed in a coating liquid with the opening facing down, and then pulled up.

[Problems to be Solved by the Invention] The above method utilizes the pressure of the air confined in the cylinder as shown in Figure 1A to stop the coating liquid 2 from entering the inside of the substrate 1 and to coat the surface of the substrate. Although this attempt was made to prevent unnecessary adhesion of the coating liquid to the inside of the cylinder by only allowing the coating liquid to adhere to the inside of the cylinder, it was found that a stable and good electrophotographic photoreceptor could not be obtained. That is, it was found that the cause was that gas often overflowed from the open end of the substrate during immersion in the coating liquid and rose as bubbles 4 as shown in FIG. 1B. This has the disadvantage of disturbing the uniformity of the coating layer. Particularly in electrophotographic photoreceptors, this is undesirable because it affects the image formation characteristics. This is thought to be caused by the thermal expansion of the air sealed in the immersion cylinder due to the temperature of the coating solution, and the increase in internal pressure due to evaporation of the solvent in the coating solution. Also, if the air temperature inside the cylinder is higher than the coating liquid temperature, the air contracts and
As shown in the figure, the coating liquid is drawn into the cylinder, causing unnecessary coating liquid to adhere to the inner surface of the cylinder, and dust etc. adhering to the inside of the cylinder are drawn out into the coating liquid, causing subsequent coating failures, and causing damage to the substrate. After dipping, the level of the coating liquid decreases, causing problems such as uneven coating on the upper end of the substrate.

[Means for solving the problem] As a result of various studies, the present inventors found that the temperature of the coating liquid (
Hereinafter, it may be referred to as TL. ) and the temperature of the gas inside the cylindrical substrate before immersion (hereinafter sometimes referred to as TA).
It has been found that the above problem can be solved by adjusting the relationship. Particularly preferably, the relationship between - and TA is -3(
0)≦TA−Tt,≦15 ('O)I! : It has been found that malfunctions such as uneven coating can be prevented by adjusting the gll.

The difference between the gas temperature TA in the cylindrical substrate and the temperature of the coating solution TA-
If Tt is within the range of -3°C to 15°C, proper coating can be performed without the generation of bubbles due to overflow of air and without excessive drawing of the coating liquid into the substrate. Changes in internal pressure due to thermal expansion and contraction of the gas in the substrate and evaporation of the solvent in the coating solution vary depending on the thermal conductivity of the substrate material and its thickness. In this case, it is more preferable that if the thickness is 1° or more, 2°C≦TA-TL≦10°C, and if it is 11i1 or less, 1°0≦TA-Tt+≦3°C.

The time during which the cylindrical substrate is immersed is the period from the time when the substrate comes into contact with the coating liquid until the coating starts. The time period during which the cylindrical substrate is in contact with the coating solution is determined by the speed at which the substrate is immersed and the speed at which the substrate is pulled up and coated. The dipping speed and coating speed are preferably 0.1 to 10 α/see. Further, when applying a coating liquid using a solvent with a high vapor pressure, it is preferable to shift the liquid temperature to a slightly lower level.

The temperature of the gas inside the cylindrical substrate may be adjusted by forcibly blowing gas adjusted to a predetermined temperature into the substrate before immersion. Further, it is preferable to perform the coating operation by adjusting the temperature of the atmosphere in the coating process and the temperature of the coating liquid in advance so that the difference between them falls within the range of the present invention. In order to adjust the gas temperature and the coating liquid temperature, it is desirable to provide a heating means such as a heater, and a cooling means such as a cooling pipe that cools through a cooling medium.

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

The composition, layer structure, etc. of the electrophotographic photosensitive layer applied to the substrate of the present invention are not particularly limited. Various coating liquids such as a subbing liquid can be optionally applied to strengthen the adhesion to the organic photoconductor, such as a subbing liquid, a charge generation layer coating liquid,
Examples include a charge transport layer coating liquid.

In the case of forming an organic photoconductor photosensitive layer, the coating liquid components include n-butylamine, diethylamine,
Ethylenediamine, isopropaturamine, 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. Coating film materials that can be dissolved in solvents include azo compounds, quinone compounds, phthalocyanine compounds, triazole compounds, oxadiazole compounds, imidazole compounds, pyrazoline compounds, triarylalkane compounds, phenylene diamine compounds, hydrazone compounds, and imino compounds. Materials such as substituted carhun compounds, triarylamine compounds, carbazole compounds, stilbene compounds, and binders such as polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, polyvinyl butyral, and styrene copolymer. In addition, various other additives such as vinyl chloride-vinyl acetate copolymer and the like can be mentioned.

〔Example〕

Prepare a coating solution with the following formulation, and prepare a coating solution with a diameter of 801111.mm with one end closed and the other end open. Length 300 Dragon Thickness 2
An electrophotographic photoreceptor was prepared by dip coating a cylindrical aluminum substrate of Ill.

(Coating liquid formulation) Liquid temperature during coating and room temperature, that is, room temperature T inside the cylindrical substrate
A was adjusted as shown in Table 1, and in immersion tests 1 and 2, the immersion and lifting processes were smooth and uniform as shown in Figure 1A, whereas in test 3, where the room temperature was lower. In this case, the air inside the substrate expanded and, as shown in FIG. 1B, overflowed from the lower end of the cylinder during the pulling process, forming bubbles and rising upward, causing large unevenness in the coating film. In addition, in the case of Test 4, where the room temperature was high, the air inside the cylindrical substrate contracted during immersion, and as shown in Figure 1C, the liquid level inside the substrate rose by L, and the liquid level outside fell by l accordingly. Paint film - Step unevenness occurred at the upper end, but
No other coating unevenness due to bubble generation occurred.

1st Table 1 20.020.50.5 2 25.824.0-1.0 3 25.020.0-5.0 4 10.028.018.0 Figure 1 A, R, and C are respectively , is a conceptual diagram showing the situation during application in the case of Test 1, 3° 4.2,
, I are conceptual diagrams showing the situations immediately after immersion, at the start of pulling up, and during pulling up, respectively. In the figure, 1 is a cylindrical base, 2
3 is a coating liquid, 3 is a coating container, and 4 is a bubble.

As shown in FIG. 2, the dip coating method involves pumping the coating liquid 2 from the liquid reservoir 5 into the coating liquid tank 3 via a gear pump 6, and placing the cylindrical substrate 1 fixed in the coating liquid tank 3 in advance.
Alternatively, the coating liquid may be immersed in the coating liquid, and then the coating liquid is returned to the liquid reservoir so that the liquid level falls at a predetermined speed.

〔Effect of the invention〕

By the method of the present invention, it was possible to easily form a uniform coating layer on the surface of a cylindrical substrate. In the above embodiment, an electrophotographic photoreceptor is formed as a coating layer, but dip coating is carried out by the method of the present invention, and the coating liquid can be freely selected without being limited thereto.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing the liquid level situation during dip coating.
FIG. 2 is a schematic diagram of a coating method using movement of the liquid level. 1...Cylindrical substrate 2...Coating liquid 3...Coating container 4...Bubble agent Patent attorney Field 1) Parent-in-law Figure 1 I I [Procedural amendment 1. Case description 1982 Patent M No. 275083 2 Name of the invention Dip coating method for cylindrical substrates 3 Person making the amendment Relationship to the case Patent applicant address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 191 Konishiroku Photo Industry Co., Ltd., 1 Sakuracho, Hino City, Tokyo (Tel: 0425-83-1.
521) Patent Part 4, Date of amendment order (1.3.22'! 5, "Detailed description of the invention" column of the specification to be amended. 6, Contents of amendment 1) Page 7 of the specification Line 16, "Polycarbonate" has been corrected to "Polycarbonate L-1,250J," 2] Page 7, Line 17, "1'-4,,10, dibrom" has been replaced with J4,10.-
Jibrom,” I am corrected.

Claims (1)

[Claims] A cylindrical substrate having one end substantially closed and the other end open is immersed in a coating liquid with the open end facing down, and the coating liquid is applied to the surface of the cylindrical substrate. In the dip coating method for a cylindrical substrate, generation of air bubbles can be prevented during dip coating of the cylindrical substrate by adjusting the relationship between the temperature of the coating solution and the temperature of the gas inside the cylindrical substrate before dipping. A dip coating method for a cylindrical substrate characterized by preventing