JPH02173754A - Dip coating method - Google Patents

Abstract

PURPOSE:To perform dip coating processing by the same device regardless of the size of a photosensitive base body and to suppress the production of the condensate of a photosensitive material by supplying coating liquid to a coating layer when the photosensitive base body is lifted from the coating layer and putting the coating liquid in a state right before the coating liquid overflows. CONSTITUTION:In the dipping processing of the photosensitive base body 1, the coating liquid enters at least the state right before the overflow when lifted from a coating tank 3 and the liquid level of the coating liquid reaches the upper end of the coating tank 3 at all times without reference to the size of the photosensitive base body 1. Consequently, a photosensitive layer never varies in thickness unless the size of the coating tank 3 and the lifting speed of the photosensitive base body 1 are varied. Further, the liquid level is in the state right before the liquid overflows, so the wall surface of the coating tank is never exposed and no condensate sticks on the wall surface.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to an improvement in a dip coating method in which a photoreceptor substrate is immersed in a coating liquid to form a photosensitive layer.

(b) Prior Art Organic photoreceptors used in electrophotographic copying machines and the like are formed by coating a photosensitive material such as PVK or TNF on the surface of a conductive substrate such as A1. Coating of a photosensitive material is generally carried out by immersing a photoreceptor substrate in a coating bath filled with a coating solution, and a photosensitive layer of a predetermined thickness is formed on the surface of the photoreceptor substrate lifted from the dipping bath. Ru.

By the way, if a coating film or dust from the coating liquid adheres to the surface of the photosensitive layer during such immersion treatment, it becomes a defect and causes image omission when used as a photosensitive member. Therefore, conventionally, as shown in Japanese Patent Publication No. 63-50693, the film, dust, etc. floating on the surface of the coating solution are removed from the coating tank by overflowing the coating solution when the photoreceptor substrate is immersed, thereby preventing the occurrence of film formation defects. Was.

On the other hand, the size of the photoreceptor varies depending on the type of copying machine used, and there are various sizes such as large ones and small ones. Conventionally, when manufacturing photoreceptors of different sizes,
The solution was to change the size of the coating tank or change the dipping speed. When the photoreceptor substrate is lifted from the coating tank, the liquid level will drop by the volume of the photoreceptor substrate, but if photoreceptor substrates of different sizes are immersed in the same equipment, the speed of this liquid level drop will differ depending on the size. This is because there is a difference in the thickness of the photosensitive layer formed.

(C1 Problem to be Solved by the Invention As mentioned above, in the past, the size of the coating tank or the dipping speed had to be changed depending on the size of the photoreceptor substrate, and a coating tank depending on the size was required. There was a problem that the speed control became complicated due to the speed control depending on the size.

In addition, in conventional dip coating equipment, when the photoreceptor substrate is lifted from the coating tank, the liquid level drops, and the solvent evaporates on the exposed wall of the coating tank, causing condensation of photosensitive material and other materials to adhere to the wall. Ta. For example, Fig. 3 (A) to CC) shows coating tank 1.
2 is a diagram showing the liquid level of the coating liquid 13 when the photoreceptor base 1 is pulled up from the photoreceptor base 1). The F1 plane is lowered and condensate 14 is generated on the exposed wall surface of the coating tank 12. This condensate 14 was mixed into the coating solution 13 during the next dipping treatment, causing defects in the photosensitive layer 15.An object of the present invention is to perform dip coating treatment using the same device regardless of the size of the photoreceptor substrate. It is an object of the present invention to provide a dip coating method that can prevent the formation of condensate from photosensitive materials.

(d) Means for Solving the Problems This invention provides a dip coating method in which a coating layer is formed on the surface of a photoconductor substrate by dipping the photoconductor substrate into a coating layer filled with a coating solution. The method is characterized in that the coating liquid is supplied to the coating layer when the substrate is pulled up from the coating layer, so that the coating liquid is at least in a state immediately before overflow.

(e) Effect When a photoreceptor substrate is subjected to immersion treatment by the dip coating method of the present invention, the coating liquid is at least in a state immediately before overflowing when the photoreceptor substrate is pulled up from the coating tank;
The surface of the coating liquid is always at the top of the coating tank, regardless of the size of the photoreceptor substrate. Therefore, the thickness of the photosensitive layer does not change even if the size of the coating tank, the speed of pulling up the photoreceptor substrate, etc. are not changed. In addition, since the liquid level is just before overflow, the walls of the coating tank are not exposed, and no condensate adheres to the walls.

(FIG. 2 is a diagram showing the configuration of a dip coating apparatus for carrying out the dip coating method of the present invention.

A drum-shaped photoreceptor base 1 is supported at both ends by a holding device 2 so as to be movable in the vertical direction. The coating bath 3 has a larger diameter and depth than the photoreceptor substrate 1, and the photoreceptor substrate 1 is immersed therein.

In this embodiment, the photoreceptor substrate 1 is moved vertically by the holding device 2 to immerse the photoreceptor substrate, but the coating tank 3 may also be moved. The coating tank 4 is provided with a tray 4 to receive overflowing coating liquid. This overflowing coating liquid is sent to the auxiliary tank 5 after filtering out condensate and dirt. Note that the liquid level in the coating tank 3 is detected by a sensor Sl,
Coating liquid is injected from the auxiliary tank depending on the liquid level.

The auxiliary tank 5 is equipped with a viscometer 7, and if the viscosity of the coating liquid increases, solvent is added from the solvent tank 8.

Further, when the amount of liquid in the auxiliary tank 5 decreases or when too much solvent is added and the viscosity becomes low, filtrate of the coating liquid is added from the filtrate tank 6. In this way, the viscosity in the auxiliary tank 5 is always maintained at a constant state, and the coating liquid in the auxiliary tank 5 is supplied to the coating tank 3 to immerse the photoreceptor substrate.

FIGS. 1(A) to 1(C) are diagrams showing the state of the coating bath when the photoreceptor substrate is immersed, and the procedure of the immersion treatment will be explained with reference to the figures.

The coating tank 3 is filled with a coating liquid, and the photoreceptor substrate I is immersed in it (FIG. 2(A)). When the photoreceptor substrate 1 is immersed, its volume pushes it away and the coating liquid overflows and is sent to an auxiliary tank (not shown). After a predetermined time, the photoreceptor substrate 1 is pulled up from the coating tank 3 ((B) and (C) in the same figure). At this time, the sensor Sl is sent to the coating tank 3.
In response to the detection, the coating liquid is supplied from the auxiliary tank 5, and the coating tank 3 is brought into an overflow state.

Here, if the photoreceptor substrate is large, the volume reduction rate during pulling is high, and if the photoreceptor substrate is small, the reduction rate is low. Therefore, the amount of coating liquid supplied when pulling up the photoreceptor substrate must be set in accordance with the size of the photoreceptor substrate. In this embodiment, a sensor S1 for detecting the liquid level is provided to detect the liquid level in the coating tank 3, and the flow rate from the auxiliary tank 5 is adjusted accordingly. Therefore, there is no need for complicated control such as flow rate setting according to the size of the photoreceptor substrate, and the coating tank 3 can be maintained at or just before overflow with simple control. The upper limit of the flow rate from the auxiliary tank 5 is such that fluctuations in the liquid level in the coating tank do not affect the formation of the photosensitive layer. Further, the coating tank may be provided with a maze-shaped protective wall that suppresses the flow of the coating solution so that the flow of the supplied coating solution does not affect the formation of the photosensitive layer.

Although this embodiment shows an example of an apparatus for forming a photosensitive layer on a drum-shaped photoreceptor substrate, the photoreceptor substrate may have other shapes. In that case, the coating tank is also set to a shape that matches the shape of the photoreceptor substrate. Since the coating liquid is supplied to the bath and the liquid level is maintained at a nearly constant level (at least the state immediately before overflow), the coating liquid can be maintained at a constant level without changing the size of the coating bath or the lifting speed according to the size of the photoreceptor substrate. A thick photosensitive layer can be obtained. Therefore, there is no need to provide coating tanks according to the size or perform complicated speed control. Furthermore, since the wall surface of the coating tank is not exposed and the generation of condensates can be prevented, it is possible to suppress the generation of defects on the surface of the photosensitive layer.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the liquid level state of the coating tank when the photoreceptor substrate is immersed in the dip coating method of the present invention, and FIG.
(B) shows the state after being pulled up, and (C) shows the state after being pulled up. Further, FIG. 2 is a block diagram of the entire dip coating apparatus, and FIGS. 3(A) to 3(C) are diagrams showing liquid level conditions during conventional dip coating of a photoreceptor substrate. Figure 1 1- Photoreceptor base, 3- Coating tank, 4- Receiver is plate. (A) (B) (C) Figure (A) Figure (B) Figure (C)

Claims (1)

[Claims] (1) In a dip coating method in which a coating layer is formed on the surface of a photoreceptor substrate by immersing the photoreceptor substrate in a coating tank filled with a coating solution, when the photoreceptor substrate is pulled up from the coating tank. A dip coating method characterized by supplying a coating liquid to a coating tank so that the coating liquid is at least in a state immediately before overflowing.