JPS6341052B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a photoreceptor drum for electrophotography, particularly when a photoreceptor coating is formed on the surface of a drum (for example, made of aluminum) together with a protective film or an adhesive film made of a material soluble in an organic solvent. The present invention relates to a method of manufacturing a photoreceptor drum for electrophotography which is suitably applied. In recent years, various new materials, both organic and inorganic, have been announced as electrophotographic photoreceptor materials. The method for manufacturing electrophotographic photoreceptors from these materials, especially organic materials, is generally a solution in which a photoconductor, plasticizer, binder, and sensitizing dye are dissolved or dispersed in an organic solvent (hereinafter referred to as photoreceptor). A solution (referred to as a solution) is applied onto a conductive support by a coating method such as a doctor blade method, a bar coater method, a spray method, a spin coater method, and a dipping method,
Drying methods are known. However, when forming a photoreceptor coating film with a thickness of 2 to 100 μm with extremely high smoothness and uniformity of film thickness on a drum, a photoreceptor coating film whose chemical composition or composition ratio changes in the film thickness direction is required. When forming such coatings, the conventional methods have the disadvantage that it is difficult to produce a coating film that is sufficiently practical. That is, spraying methods, dipping methods, and the like have been conventionally adopted as methods for applying a thick coating of several μm or more to the drum surface, but in this case, for example, the spraying method has the following drawbacks. Photoconductive polymers such as poly-N-vinylcarbazole, polyvinylpyrene, and polyvinylanthracene, polymer charge transfer consisting of this photoconductive polymer and an electron acceptor such as 2,4,7-trinitro-9-fluorenone. Tetrahydrofuran, benzene, toluene, methyl ethyl ketone, 1,2-dichloroethane, and the like are generally used as solvents for complexes and recent organic photoreceptor materials in which a sensitizing dye is added to a photoconductive polymer. These organic solvents have relatively low boiling points, so when coating a photoconductor solution using these solvents by spraying, the photoconductor solution evaporates the solvent before reaching the drum surface from the spray gun. It is lost and adheres to the drum surface in a state similar to powder. It is clear that a photoreceptor solution deposited in such a state cannot form a coating film with a smooth surface. Therefore, if the solvent content of the photoreceptor solution is increased to prevent the solvent from disappearing, the excess solvent will flow on the drum surface or accumulate locally, making it difficult to obtain a coating film with a smooth surface. Can not. Furthermore, if a photoreceptor with an uneven surface is used as a latent image forming medium for electrophotography, the film thickness will be non-uniform, so if pre-charging is performed, the charge density will be non-uniform and the photosensitivity will vary depending on the film thickness. It not only causes uneven printing during development, but also has various drawbacks such as being susceptible to abrasion due to the development brush and the like and not being able to be cleaned properly. In addition, for example, an adhesive layer made of resin may be provided between the drum base material and the photoreceptor coating film in order to increase the adhesive force between the two, or in order to protect the surface of the photoreceptor coating film, the surface may be When applying resin coating,
Conventional coating methods have the following problems. In such a case, the resin is preferably a resin that is soluble in organic solvents, such as butyral resin, chlorsulfonated polyethylene, or polyester HES 49000 (DuPont), and this resin is applied onto the drum base material and dried. At the very least, if an adhesive layer made of the resin is provided, the adhesiveness to the drum base material will certainly be strong. However, when a photoreceptor solution containing an organic solvent is applied over this, the solvent permeates into the already dried adhesive layer, causing the adhesive layer to swell.
Furthermore, if this is heated and dried, the surface of the paint film dries first, gasifies from the solvent in the lower layer, and bubbles that are delayed in escaping are trapped by the dry film on the surface, causing bumps on the surface of the paint film. Scatter the bubbles. Therefore, conventionally, the resin has been limited to polyacrylamide resin, polyacrylate, polyvinyl acetal, polyvinyl acetate, etc., which are water-soluble or alcohol-soluble and difficult to dissolve in organic solvents, so as not to be dissolved in the solvent of the photoreceptor solution. For this reason, even if cheaper materials and materials with better mechanical and electrical properties were provided, they had disadvantages such as being unable to be used if they were soluble in organic solvents. Furthermore, since it is more difficult to find a high-quality photoconductor that is water-soluble, it is practically impossible to use a resin that is soluble in organic solvents. Recently, a coating method has been proposed in which a drum is placed in a vapor atmosphere of an organic solvent for paint, and the drum is coated with a container having a slit-shaped paint outlet, that is, a blade. In this coating method, the vapor pressure atmosphere around the drum is gradually removed from the end of coating, the coating film is dried slowly to avoid cracks in the coating film, and the excess paint is sucked into the blade. It has been proposed that it is possible to recover the paint film to avoid uneven coating ``sagging'' at the end of coating, and to avoid uneven coating ``seams'' at the beginning of coating. That is, in the coating method using this blade, a highly smooth coating film can be obtained. Thus, the present invention has been proposed in consideration of the above, and is aimed at solving the above-mentioned drawbacks. In the present invention, this purpose is achieved by forming multiple layers of photoreceptor coatings each having a different photosensitivity on the drum, or by forming a protective film, an adhesive film, etc. on the drum in addition to one or more layers of the photoreceptor coating. A method for producing an electrophotographic photoreceptor drum that forms a non-photosensitive coating includes: a substantially sealed container housing the drum; and an atmosphere substantially saturated with solvent vapor and a dry atmosphere, or a dry atmosphere provided therein. vapor pressure regulating means for supplying a mixed atmosphere; means for rotating the drum; a blade proximate to the circumferential surface of the drum; and a plurality of solutions being selectively and continuously switched to the blade for each solution. By means of these means, the chemical composition or composition ratio of the applied solution can be successively changed, and the application of subsequent solutions can be performed without drying the applied solution. After coating is completed, the chemical composition or composition is changed in the thickness direction by drying the coating film on the drum while gradually lowering the solvent vapor pressure in the container using the vapor pressure regulating means. This is accomplished by forming coatings with different ratios on the drum. Embodiments of the present invention will be described in detail below with reference to the drawings. In FIG. 1, reference numeral 1 denotes a drum, and the drum 1 is driven by a suitable drive source (not shown) via a belt 2 to rotate at a constant speed in the direction of the arrow. On the drum 1, there is a roller 6 on which the coating blade 4 can move up and down, and a vertical movement adjustment screw 7.
It is provided integrally with a position adjustment mechanism including a position adjustment mechanism, so that the gap length between the drum 1 and the drum 1 can be adjusted. The coating blade 4 is connected to a switching valve 5 via a pipe 8, and the switching valve 5 is connected to a pipe 8a,
It is connected to a plurality of cylinders 3, 3a via 8a. The plurality of cylinders 3, 3a house photoreceptor solutions, coating solutions, etc. with different solute compositions, and a piston (not shown) that is driven linearly inside the cylinder by a drive source (not shown) is connected to the switching valve 5. The photoreceptor solution is pushed out or sucked into the cylinder selected by the cylinder. Note that A is a coating film formed by applying a photoreceptor solution. By the way, each of the above-mentioned members is housed in a closed container, which will be explained in detail below with reference to FIG. In FIG. 2, reference numeral 100 denotes a high-pressure cylinder filled with nitrogen gas, and the pressure of the nitrogen gas taken out from the cylinder is lowered to a predetermined pressure by a pressure regulating valve 110. Next, this nitrogen gas is divided into two directions, connecting pipes P and Q, by a flow dividing valve 120. One of them is introduced into a tank 130 containing a container containing the same solvent as the photoreceptor solution, where it is preferably saturated with solvent vapor obtained by evaporating the solvent, and then the other is saturated with solvent vapor obtained by evaporating the solvent. is introduced into the coating container 140 together with the nitrogen gas. The coating container 140 is a sealed container in which each of the components shown in FIG.
A uniform atmosphere is created by this, and the remaining gas is exhausted to the outside air through the exhaust hole 160. The coating apparatus for carrying out the present invention is constructed as described above, and the operation thereof will now be explained. First, the inside of the coating container 140 is saturated with vapor of the same solvent as that used for the photoreceptor solution. Next, the cylinders 3 and 3a are selected, and a resin that will be the composition of the adhesive layer, a photoreceptor with high photosensitivity to a specific wavelength,
One solution is selected from a plurality of solutions in which a charge transfer resin, a protective coating resin, etc. are dissolved, and is sent to the coating blade 4. At this time, the drum 1 is rotated in advance,
The amount of solution supplied is kept low to avoid non-uniform coating thickness in the circumferential direction, and the coating is repeated several times. Since this operation is carried out in an atmosphere of high solvent vapor pressure, the non-uniformity in film thickness that conventionally occurs at the starting point of coating due to drying of the coated surface is eliminated. After a predetermined amount of solution is supplied to the coating blade 4, the switching valve 5 is operated to supply the next solution to the coating blade 4 from another cylinder 3 or 3a. Thereafter, unless necessary, a predetermined amount of a plurality of solutions having compositions different from these two solutions are supplied to the coating blade 4 from cylinders (not shown) other than the cylinders 3 and 3a. When the thickness is reached, the supply of solution to the coating blade 4 is stopped. Next, the coating blade 4 is pulled away from the coating surface, but at this time, the remaining solution remains between the coating blade 4 and the coating surface due to its surface tension. The piston (not shown) in 3 or 3a is moved back. As a result, the non-uniformity in film thickness that conventionally occurs at the coating end point can be completely eliminated. Finally, the rotation of the drum 1 is stopped, and the vapor pressure inside the coating container 140 is gradually lowered to slowly dry the coating film. Note that this adjustment of the steam pressure is performed by operating the flow dividing valve 120 and the pressure regulating valve 110. In the present invention, since the coating is performed as described above, each layer of the coating film made of each of the plurality of solutions is uniformly applied and dried, so that only the surface of the coating film dries first. The generation of bumpy bubbles that conventionally occur in the paint film is avoided,
Therefore, a multilayer coating film with high smoothness can be obtained. Examples will be described below, consisting of experiments to confirm the effects of the present invention. Example 1 Photoreceptor solutions A and B having different composition ratios were applied in this order onto an aluminum drum. Γ Composition of each solution

【table】

[Table] Γ Coating conditions Drum rotation speed 170 rpm Solution discharge rate A 15 ml/min B 10 ml/min Solution discharge amount A 50 ml B 20 ml Specific vapor pressure in the container (vapor pressure in the three containers/saturated vapor pressure) 80% Γ Painting result Film thickness: 25 μm Variation in film thickness: Circumferential direction: ±0.7 μm Axial direction: ±0.5 μm Example 2 Solutions C and D were applied in this order onto an aluminum drum on which selenium was deposited (film thickness: 0.2 μm). Γ Composition of each solution

[Table] Γ Coating conditions Drum rotation speed 210 rpm Solution discharge speed C 20 ml/min D 12 ml/min Solution discharge amount C 60 ml D 25 ml Γ Coating result film thickness 16 μm Film thickness variation Circumferential direction 0 ± 0.8 μm Axial direction ±0.5 μm The photosensitivity and other properties of the coating film produced in this example were measured. Charging voltage of the coating film (maximum) -1100 (volts) Exposure amount to reduce the charging voltage by half 8 (lux seconds) In this way, a sufficiently uniform coating film can be formed even on the selenium surface, and the coating film It was found that the photosensitive properties were also good. Example 3 Solutions E, F, and G containing different sensitizing dyes were applied onto each drum, and coating solutions H, H, and I were applied thereon, respectively. Γ Composition of each solution

【table】

【table】

【table】

[Table] The coating conditions were the same as in Examples 1 and 2, and as a result, the photosensitivity was measured for each coating film made of solutions E and H, solutions F and H, and solutions G and I. The results shown in FIGS. 3, 4, and 5 were obtained. On the other hand, separately, the solutions E, F, G, and H were applied on a drum in this order and dried, and the photosensitivity of the resulting coating film was measured.
The results shown in FIG. 6 were obtained. With this example, the wavelength of the exposure light source is 4000 Å ~
In order to obtain a photoreceptor with a wide range of photosensitivity characteristics of around 6200 Å, we added a solution, such as a sensitizing dye, that improved the sensitivity to light in a narrow range of wavelengths without using a special photoconductor. It has been found that it is sufficient to apply several types of photoreceptor solutions in layers.
Furthermore, when the coating film created by this layered coating was charged with -900 volts by corona discharge in a dark place and then irradiated with white light (3 microjoules/cm ² ), the surface potential was - Attenuated to 250 volts. This revealed that the coating film had good performance as a latent image recording medium for electrophotography. Example 4 Solutions A and B of Example 1 on an aluminum drum
were applied in this order, and solution D of Example 2 was further applied thereon, and the hardness of the surface of the resulting coating film was measured. Pencils with a hardness of up to 2H will not cause scratches.
It was found that the photoreceptor layer was sufficiently protected by forming a protective coating layer by coating Solution D. Example 5 A case (1) in which the solution J consisting only of the photoreceptor was directly applied on an aluminum drum, and a case in which the solution J of Example 2 containing a thermoplastic resin was applied on the aluminum drum and then the solution J was applied. The dark resistance of the paint film created was compared with case (2). Composition of Γ solution

[Table] Thickness of the coating film (1) 16 μm (2) 15 μm The surface of the coating film is negatively charged according to the film thickness so that the potential gradient in the film thickness direction is 7×10 ⁵ volts/cm at the initial stage. The average decay rate of the surface potential (dark decay rate) was measured for 10 seconds in the dark. (1) 48.2 volts/sec (2) 5.5 volts/sec From these results, we can see that the surface of the aluminum drum is not subjected to oxidation treatment as in the past, and in the latter case, as in (2), the photoreceptor layer and aluminum drum are separated. It has been found that an electrophotographic photoreceptor can be obtained by simply providing a resin layer between the two. A similar experiment was also conducted when solution K containing a charge transport agent in addition to a thermoplastic resin was used instead of solution D, and solutions L and M containing photoreceptors were applied thereon. . As a result, it was found that the resin layer between the photoreceptor layer and the aluminum drum does not have to be made only of thermoplastic resin. Composition of Γ solution

【table】

[Table] Film thickness: 20 μm Dark decay rate: 6 volts/second Example 5 Two types of coatings, X and Y, were prepared with the protective coating of Example 3 and also had the resin layer of Example 4, and their photosensitivity was measured. etc. were measured. Γ Solutions used and application order Coating film Application Γ Drying conditions Both coating films X and Y were dried at 30℃ in a nitrogen gas stream.
time, then dried for 8 hours at 75℃ in the same airflow Γ Coating film properties, etc. Film thickness X: 16 μm Y: 18 μm Initial surface potential and dark decay rate Coating film -800 volts Volt/sec Surface potential reached by light irradiation with intensity of 3 microjoules/cm ² when attenuated by 50 volts from the initial surface potential Coating film X: -300 volts Coating film Y: -280 volts From these results, the above Both coatings X and Y were found to be suitable for electrophotographic photoreceptors. Furthermore, the coating film Y was actually developed and transferred using toner as follows. First, the coating film Y was charged with a surface potential of −800 volts by corona discharge in a dark place, and then
Light was irradiated with an intensity of 5000 Å and an intensity of 3 microjoules/second. After depositing positively charged black toner on top of this in a dark place, paper is stacked and a -6000 volt charge is applied from the back of the paper, and the toner transferred to the paper is fixed with a heating plate. I forced it. When the toner image fixed on the paper surface, that is, the printed sample, was observed, no toner was observed in the non-exposed areas, and the S/N ratio was good. When we further measured the printing density, we found that
The printing density was 1.1 (OD), and it became increasingly clear that this coating film Y was suitable as an electrophotographic photoreceptor. Various examples have been described above, and FIG. 7 shows the cross-sectional structure of the coating film created in each of these examples. That is, in FIG. 7, AL is an aluminum drum, SE is a selenium vapor deposited film, A' to M' are coating layers formed by the solutions A to M, respectively, and the coating layers A', B',
C′E′, F′, G′, J′, L′, M′ are photoreceptor layers; coating layers D′, H′, I′ are protective coating layers shown by hatched points (〓〓): The dot and diagonal hatching area (〓
The coating layers D' and K' shown in 〓) are layers for increasing dark resistance, etc. And each figure a to l and Examples 1 to 6
(a) corresponds to Example 1, (b) corresponds to Example 2, and (c) corresponds to Example 1.
~(f) corresponds to Example 3, (g) corresponds to Example 4, (h) to (j) correspond to Example 5, and (k) and (l) correspond to Example 6, respectively. As described above, according to the present invention, it is possible to form various multilayer photoreceptor coating films on a drum,
The effect is great.

[Brief explanation of the drawing]

FIG. 1 is a perspective view partially showing an embodiment of a coating station for an electrophotographic photosensitive drum according to the present invention;
The figure is a block diagram for explaining the operation of the coating container in which each member shown in FIG. FIG. 7 is a diagram showing a cross section of this photoreceptor coating film. 1: drum, 2: belt, 3, 3a: cylinder, 4: coating blade, 5: switching valve,
6: Roller, 7: Vertical adjustment screw, 8, 8a: Pipe, A: Paint film, 100: High pressure cylinder, 110:
Pressure regulating valve, 120: Diversion valve, P, Q: Connection pipe,
130: Tank, 140: Paint container, 150: Stirring means.

Claims (1)

[Scope of Claims] 1. A plurality of layers of photoreceptor coatings having different photosensitivity for each layer are formed on the drum, or a non-photosensitive film such as a protective film or an adhesive film is formed on the drum in addition to one or more layers of the photoreceptor coating. A method for manufacturing an electrophotographic photoreceptor drum that forms a coating includes a substantially sealed container that houses the drum, and an atmosphere substantially saturated with solvent vapor, a dry atmosphere, or a mixture thereof. A vapor pressure regulating means for supplying, a means for rotating the drum, a blade close to the circumferential surface of the drum, and a means for selecting and continuously switching and supplying a plurality of solutions to the blade for each solution. and by these means, the chemical composition or composition ratio of the solution to be applied is successively changed, and successive solutions are applied successively without drying the previously applied solution. After completion, the coating film on the drum is dried while the vapor pressure of the solvent in the container is gradually lowered by the vapor pressure adjusting means, thereby forming a coating film having a different chemical composition or composition ratio in the thickness direction. 1. A method of manufacturing an electrophotographic photoreceptor drum, comprising: forming on the drum. 2. A patent characterized in that the coating film is multilayered, an adhesive layer located at the bottom layer is formed by applying a solution containing a thermoplastic resin, and a photosensitive layer is formed on top of the adhesive layer by applying a photoreceptor solution. Claim 1
A method for manufacturing a photosensitive drum for electrophotography as described in 2. 3. The coating film is multilayered, a photosensitive layer is formed by applying a photoreceptor solution on the drum or the adhesive layer, and a solution containing a thermoplastic resin is applied as the uppermost layer on the photosensitive layer. 3. The method for manufacturing an electrophotographic photosensitive drum according to claim 1 or 2, wherein the protective layer is formed by: 4. The method for manufacturing an electrophotographic photoreceptor drum according to claim 2 or 3, wherein the photoreceptor solution contains a photoconductor, a plasticizer, and a binder. 5. The method according to claim 2 or 3, wherein there is a plurality of photoreceptor solutions, each of which contains a photoconductor of a different composition, a plasticizer, and a binder. A method of manufacturing a photoreceptor drum for electrophotography.