JPS624187B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of coating an object having one end open and the other end closed.

Coating by dipping has been widely practiced. The method basically involves immersing the object to be coated in a coating liquid and then drawing the object out of the liquid at an appropriate speed to coat the surface of the object. In the case of coating by dipping, uniform coating is possible by appropriately setting the coating conditions such as the viscosity of the coating liquid and the pulling speed depending on the shape of the object to be coated. When coating the surface of an object to be coated where one end is open and the other end is closed, it is often impossible to form a uniform coating film due to the generation of bubbles. . For example, a cylindrical workpiece 1 with one end open and the other end closed as shown in FIG. 1 is immersed in a coating liquid 3 contained in a liquid tank 2 as shown in FIG. When the object to be coated is then pulled up and coated as shown in FIG. 3, the air inside the object remains trapped while the object is being pulled up. However, in such a situation, due to a slight temperature difference between the coating liquid and the outside air temperature, the air inside the object to be coated may expand, or the solvent of the coating liquid may evaporate inside the object, increasing its volume. Bubbles 4 are often generated from below during lifting. When such bubbles are generated, the coating liquid is shaken considerably, causing unevenness on the coated surface and hindering the formation of a uniform coating film.

Therefore, the main object of the present invention is to provide a coating method that can effectively prevent the generation of such bubbles.

In the coating method according to the present invention, the object to be coated is immersed in the coating liquid with its opening facing down during coating, thereby coating the surface of the object while keeping air sealed inside the object. This method is characterized in that when the object to be coated is immersed in the coating liquid, part of the air trapped inside the object to be coated is removed.

That is, in the present invention, in order to prevent bubbles from forming,
This method is designed to remove a portion of the air inside the object to be coated, and can be done using very simple means. FIGS. 4 and 5 show one embodiment of an apparatus for carrying out the coating method according to the present invention.

In FIG. 4, a substrate 5, which is an object to be coated, is a substrate of a photoreceptor used in an electrophotographic copying machine.
It is a cylindrical piece of aluminum with one end open and the other end closed in the shape shown in the figure, with a protrusion on the top end provided to support the photoreceptor.

9 is a ventilation pipe for passing air, and a small-capacity rubber air chamber 10 is attached to the end of the ventilation pipe. Reference numeral 6 denotes a support portion to which the base body is attached, and when the drive unit 7 is rotated, an elevating screw 8 is rotated to move the base body up and down. The support portion 6 is restricted to move only in the vertical direction.

Next, as shown in FIG.
When the rubber air chamber 10 is immersed in the liquid, the air pressure inside the base inflates the rubber air chamber 10, but the expansion capacity is preferably such that a portion of the liquid enters, for example, 1 cm at the bottom of the base, in order to prevent the formation of bubbles. be. The deeper the liquid enters, the less bubbles will form, but the inside of the substrate will also be coated, so it should normally be avoided. Note that the coating liquid will not enter the ventilation pipe 9. When the substrate is pulled up from the state shown in FIG. 5 at a speed suitable for coating, the coating liquid is evenly applied to the surface of the substrate. Note that when the substrate is pulled up and removed from the coating liquid, the air pressure inside the substrate approaches atmospheric pressure, so the air that once escaped into the air chamber returns to the inside of the substrate and partially enters the lower part of the interior of the substrate. Since the coating liquid that was present also comes out, the substrate can be smoothly removed from the coating liquid.

In addition, in the figure, a rubber air chamber was used to keep the volume of air removed constant, but in addition to this,
A method of removing a small amount of air by attaching a solenoid valve, valve, etc. to the end of the ventilation pipe can also be adopted as appropriate.

As described above, the present invention is an effective coating method when coating an object having one end open and the other end closed using a dipping method, such as a substrate for a photoreceptor.

[Brief explanation of the drawing]

FIG. 1 is a side view of the object to be coated. 2 and 3 are schematic views of the conventional dip coating method, with FIG. 2 showing the immersed state and FIG. 3 showing the pulled up state. FIG. 4 is a schematic diagram of a coating device used in the present invention. FIG. 5 is a diagram of the coating device of FIG. 4 in an immersed state. 1...Object to be coated, 2...Liquid tank, 3...Coating liquid, 4...Bubble,
5... Base body, 6... Support part, 7... Drive part, 8... Elevating screw, 9... Ventilation pipe, 10... Air chamber.

Claims (1)

[Scope of Claims] 1. During application, the surface of the object to be coated is coated while air is sealed inside the object by immersing the object with the opening side facing down in the coating solution. A coating method characterized in that when the object to be coated is immersed in the coating liquid, part of the air trapped inside the object to be coated is removed. 2. The coating method according to claim 1, wherein the object to be coated is a substrate of a photoreceptor for an electrophotographic copying machine.