JPH01171674A - Coating method - Google Patents

Abstract

PURPOSE:To form a uniform thin layer on a body to be coated by coating by gradually increasing the amt. of a coating soln. fed for at least a prescribed time from the time when the pulling of the body is started. CONSTITUTION:The amt. Q of a coating soln. fed is gradually increased from the time when the pulling of a substrate drum 12 is started. The useless length hA of a coating film is made smaller than hS and hC and a uniform coating film can be formed on the entire surface of the drum 12. The ratio of QA:QO is regulated to 1:10, preferably 3:10. If the time when the pulling of the drum 12 finishes is represented by t2, the ratio of t1/t2 is 1/6, preferably 1/40-1/10. The material cost of the coating soln. can be reduced.

Description

[Detailed description of the invention] It is something to do.

Prior art In recent years, attempts have been made to develop organic window photoreceptors with high sensitivity and durability by assigning carrier generation and carrier transport functions to different substances in the photosensitive layer of electrophotographic photoreceptors. is being done. In such so-called function-separated type electrophotographic photoreceptors, substances that exhibit each function can be selected from a wide range of materials, so it is relatively easy to produce electrophotographic photoreceptors with arbitrary characteristics. Is possible.

When coating and forming the photosensitive layer of such an electrophotographic photoreceptor, it is necessary to form a thin, uniform layer with high precision in order to maintain good sensitivity characteristics and prevent image defects such as density unevenness, thereby exhibiting good performance as a photoreceptor. It is necessary to apply a layer.

Conventionally, various coating methods such as dip coating, spray coating, spinner coating, wire bar coating, blade coating, and roller coating have been known as coating methods for the photosensitive layer of electrophotographic photoreceptors. Spray application is used.

Among them, uniform coating on cylindrical objects (conductive substrates, etc.)
Dip coating is often used to form a coating film.

Among such dip coating methods, a so-called overflow one-type method is known in order to prevent foreign matter defects (coating defects) due to the formation of dry solids on the side walls of the coating tank.

FIG. 1 is a schematic sectional view showing a dip coating device using this method.

A predetermined coating liquid 3 is contained in the coating tank 2, and a tray 5 is provided around the side wall 2b of the coating tank 2. The coating liquid 3 is sent out from the tank 8 by the pump (P) 9, is supplied from the supply lower into the coating tank 2 as shown by the arrow via the filter (F) 10, and is further supplied to the upper edge of the side wall 2b. The liquid overflows in the circumferential direction of the coating tank 2 beyond the portion 2a, is collected by the tray 5, and is discharged from the discharge port 6 into the tank 8. The cylindrical conductive substrate 12 is immersed in the coating liquid 3, and then the conductive substrate (hereinafter sometimes referred to as a substrate drum).

) 12 is pulled up at a predetermined speed as shown by arrow A, and dip coating is applied.

During this dip application, the coating liquid 3 is applied to the side wall 2 as described above.
Since the coating liquid 3 continues to overflow beyond the upper edge 2a of the coating liquid 3, the height of the interface 3a of the coating liquid 3 is kept constant.

However, the above-mentioned overflow type coating apparatus has the following drawbacks.

That is, as shown in FIG. 3, the base drum 12 is pulled up, a coating layer is formed on the surface of the base drum, and the coating layer 11 is dried.
When forming No. 8, the thickness of the coating film on day 11 was thinner at the upper part of the base drum. Therefore, if we try to use only the part with a uniform thickness for the image area, the coating film in the part of length hB will be wasted, and in order to obtain the desired image area, the base drum will have to be made longer. Problems such as not being able to do so may arise.

As a method for solving problems beyond the process leading to the invention, JP-A-59-176
No. 746 discloses an electrophotographic photoreceptor coating method in which the supply flow rate of the coating liquid is gradually decreased from the start of coating, as shown by graph C in FIG. However, Q is the coating liquid supply amount (circulation amount), t is the elapsed time from the start of coating (application), and Qc>Q.

However, as a result of repeated studies by the wood inventor, the surprising fact was that even with this method, thinning of the upper part of the base drum could not be prevented, and on the contrary, the film became even stronger and thinner, as shown in the coating film 11C shown in Figure 3. There was found. That is, the coated WJI IC is wasted by the length hc (>ha).

The present invention has been made based on the above-mentioned new findings.

26. OBJECTS OF THE INVENTION It is an object of the present invention to provide a coating device that can prevent the formation of three layers on the upper part of an object to be coated and can form a uniform coating over the entire surface.

E9 Structure of the Invention The present invention provides a method for applying the coating liquid to the object by immersing the object to be coated in a coating liquid stored in a coating tank and then pulling up the object. In the coating method in which the coating liquid is supplied from the supply port into the coating tank so that the coating liquid overflows beyond the upper edge of the side wall of the tank, at least The present invention relates to a coating method characterized in that the supply amount of the coating liquid is gradually increased until a predetermined time elapses.

To, Example The present invention will be explained in detail below.

First, explanation will be given using the coating apparatus shown in FIG.

In this example, as shown in graph A in FIG. 2, t=
0 (1 from the time of starting to pull up the base drum I2)
=1. The present invention is characterized in that the supply amount (Wi ring amount) Q of the coating liquid supplied from the supply lower is gradually increased until (predetermined time) elapses.

That is, conventionally, the supply amount of the coating liquid was kept constant as shown in the graph, or the amount of the coating liquid supplied was gradually decreased as shown in the graph C. However, as mentioned above, not only in the case of Graph 1, but also in the case of Graph C, the coating film became even stronger and thinner, like the coating film 11C shown in FIG. 3.

On the other hand, as a result of further study, the inventor of the present invention gradually increased the supply IQ of the coating liquid from the point at which the base drum began to be lifted, as shown in graph A in FIG. As shown in the coating film +1A, the base drum 1
It is possible to prevent the paint film from becoming thinner in the upper part of the paint film, and the wasted length of the paint film, hA, is significantly smaller than both hA and h. Therefore, it is possible to form a uniform coating film over the entire base drum 12, prevent the wastage of the coating liquid, and use the coating solution over the entire base drum. This makes it possible to reduce the cost of materials, improve the productivity of the coating film, and also shorten the base drum and make the copying machine smaller accordingly. .

The causes of the effects described above can be considered as follows. In other words, in a normal coating liquid, the viscosity does not necessarily increase due to an increase in the flow rate considering its concentration, viscosity range, etc., and as the flow rate decreases, destruction of the weak structure formed by the pigment can be avoided. This seems to be due to reasons such as maintaining the viscosity of the coating liquid.

When the coating method of this example is applied to the constituent layers of an electrophotographic photoreceptor, the effect is even more remarkable because uniform thin layer formation is required. Historically, when applied to a carrier transport layer or the like of a functionally separated photoreceptor, a particularly remarkable effect can be obtained because the film thickness is larger and liquid blurring is more likely to occur.

In Figure 2, Q and Q. The ratio is preferably within the range of 1:10, more preferably within the range of 3:10. Further, when t is the time point when the lifting of the base drum is completed, the ratio t+/jz of tl and t2 is preferably within the range of 1/6 or less, and 1/40 to 1/40.
More preferably, it is within the range of 1/10.

4 to 6 each show an example of an electrophotographic photoreceptor in which layers are formed by the coating method of the present invention.

In the photoreceptor shown in FIG.
A carrier generation layer 22 is provided as a layer, and a carrier transport layer 23 is provided as a second layer on the carrier generation layer 22. The photoreceptor shown in FIG. 5 has a carrier transport layer 2j as a first layer and a carrier generation layer 2j as a second layer stacked in this order when viewed from the conductive substrate 21 side. The photoreceptor shown in FIG. 6 has a photosensitive layer 24 having a single-layer structure containing both a carrier-generating substance and a carrier-transporting substance as a first layer.

Of course, the number and types of coating layers coated and formed by the coating apparatus of the present invention are not limited to the examples shown in FIGS. 4 to 6, nor are their compositions, functions, etc. can be set freely according to the design intention.

For example, when viewed from the conductive substrate side, the first layer and the second layer are an undercoat layer and a photosensitive layer with a single layer structure, the photosensitive layer with a single layer structure, and a protective layer. The second layer and the third layer are respectively an undercoat layer, a carrier transport layer, and a carrier generation layer, a carrier generation layer, a gear transport layer, and a protective layer, the first layer, the second layer, the third N, and the fourth layer. The layers are respectively an undercoat layer, a carrier generation layer, a carrier transport layer, and a protective layer, or an undercoat layer, a carrier transport layer, a carrier generation layer,
Examples include those that are protective layers.

The undercoat layer is acrylic, methacrylic, vinyl chloride, vinyl acetate, epoxy, polyurethane, phenol, polyester, alkyd, polycarbonate, silicone, melamine, vinyl chloride/vinyl acetate copolymer. It can be formed by combining various resins such as vinyl chloride, vinyl acetate, and maleic anhydride copolymers.

The carrier generation layer is made of, for example, a monoazo dye, a disazo dye,
Abu dyes such as trisazo dyes, perylenic anhydride,
Perylene dyes such as perylenic acid imide, indigo dyes such as indigo and thioindigo, polycyclic quinones such as anthraquinone, pyrenequinone, and furapanthrones, quinacridone dyes, bisbenzimidazole dyes, indathrone dyes, and squarelillium dyes. Various known carrier-generating substances such as thalocyanine pigments (such as dyes, metal phthalocyanines, and metal-free phthalocyanines), pyrylium salt dyes, and eutectic complexes formed from thiapyrylium salt dyes and polycarbonate are combined with a suitable binder resin and, if necessary, a carrier transport substance. It can be formed by dissolving or dispersing it in a solvent and applying it.

The carrier transport layer can be made of electron-accepting substances that easily transport electrons, such as trinitrofluorenone or tetranitrofluorenone, as well as polymers with side chains of heterocyclic compounds such as poly-N-vinylcarbazole, and triazoles. Various known derivatives such as oxadiazole derivatives, imidazole derivatives, pyrazoline derivatives, polyarylalkane gR forms, phenylenediamine derivatives, hydrazone derivatives, amino-substituted chalcone derivatives, triarylamine derivatives, carbazole derivatives, stilbenes, phenothiazine derivatives, etc. It can be formed by dissolving a carrier transporting substance that easily transports holes in a solvent together with a suitable binder resin, applying the solution, and drying it.

Further, a photosensitive layer having a single layer structure can be formed by dissolving or dispersing the carrier generating substance as described above in a solvent together with a suitable carrier transporting substance and a binder resin, and coating the solution.

Examples of the binder resin include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, and styrenic copolymer resins (e.g., styrene-butadiene copolymer, styrene methacrylate). copolymer), acrylonitrile copolymer resin (e.g. vinylidene chloride-acrylonitrile copolymer, etc.), vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone
Alkyd resin, phenolic resin (e.g. phenol-
formaldehyde resin, m-tales formaldehyde resin, etc.), styrene-alkyd resin, poly-N-
Film-forming polymers such as vinyl carbazole, polyvinyl butyral, and polyvinyl formal are preferred.

The protective layer contains polyurethane, polyethylene, polypropylene, etc. as the carrier transporting substance and binder resin.
Acrylic resins, methacrylic resins, vinyl chloride resins, vinyl acetate resins, epoxy resins, polyester resins, phenolic resins, polycarbonate resins, silicone resins, melamine resins, etc. ;lfE and compounds containing two or more repeating units of these resins; It can be formed from polymer resin or the like.

Solvents used for coating and forming the carrier transport layer, carrier generation layer, etc. include acetone, methyl ethyl chloride, etc.
-, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,1.1-trichloroethane, L 1,2
．． 2-Tetrachloroethane, 1,1.11lichloropropane, ■.

1.2.2-tetrachloropropane, 1,2.3-trichloropropane, 1,1.2-1-dichlorobutane, 1
, 2,3.4-tetrachlorobutane-tetrahydrofurani/, monochlorobenzene, dichlorobenzene, dioxane, methanol, ethanol, isopropanol,
Ethyl acetate, butyl acetate, dimethyl sulfoxide, methylcellosolve acetate, n-butylamine, diethylamine, ethylenediamine, isopropanolamine,
Triethanolamine, triethylenediamine, N.

Examples include N-dimethylformamide.

Further, as a solvent for dissolving the carrier transport substance and the binder resin to form a coating liquid, a solvent is selected that can uniformly dissolve these, and a solvent with a boiling point (bp) of 80° is selected.
It is preferably 90°C to 120°C, and more preferably 90°C to 120°C. If the boiling point is less than 80°C, drying is too rapid, resulting in dew condensation, which tends to cause brushing. Exceeding the range tends to cause dripping and uneven coating.Specifically, dichloromethane, 1,2-dichloroethane (bp-83,5°C), 1.1.2-)dichloroethane (bp=113.5°C), 1.4-dioxa7 (bp=101.3°C), benzene (bp=
80.1°C), toluene (bp=110.6'C)
, o, m, p-xylene (bp=138-144°C),
Examples include tetrahydrofuran, dioxane, and monochlorobenzene. Further, even if the boiling point of a solvent is not in the range of 80°C to 150°C, the boiling point can be adjusted by mixing a high boiling point solvent and a low boiling point solvent.

Further, as a solvent for forming a carrier generation layer and a photosensitive layer having a single layer structure, it is necessary to dissolve the binder resin and the carrier transport substance contained if necessary, and to transfer the carrier generation substance to a particle size of preferably 2 μm or less, more preferably 1 μm or less. A material that can be dispersed in the form of fine particles and provide a stable dispersion, and that does not unduly melt or swell the underlying carrier transport layer, undercoat layer, etc., if present, is selected. In particular, among the above, toluene, chloroform, dichloromethane, 1,2-dichloroethane, 1゜1.2-trichloroethane, 1,1.2.2-tetrachloroethane, tetrahydrofuran, monochlorobenzene, and dioxane are used in the carrier generation layer. , is a preferred solvent for both carrier transport layers.

The coating liquid used in the present invention may contain other substances in addition to those mentioned above. For example, the inclusion of a siloxane compound has the effect of smoothing the coating surface. Examples of siloxane compounds include dimethylpolysiloxane and methylphenylpolysiloxane.

The amount added is preferably 1 to 110,000 pp, more preferably 10 to 11,000 pp with respect to the total amount of the coating liquid.

In addition, it is also possible to form a photoreceptor using the same binder resin and the same solvent, especially in the coating liquid for the carrier transport layer and the coating liquid for the carrier generation layer. In that case, the productivity and performance of the photoreceptor may be improved. This has the advantage of further improving the performance. That is,
If the same binder resin can be used, the barrier between the carrier generation layer and the carrier transport layer will be reduced, and the carriers generated during light irradiation will be smoothly injected and transported to the carrier transport layer, which will improve the photoreceptor's sensitivity characteristics, low residual potential, and memory characteristics. etc. will also be improved.

Furthermore, if the same binder resin, solvent, etc. can be used in common, there is an advantage that the coating process becomes easier, more accurate, and faster.

Although the shape and material of the conductive substrate are not particularly limited, a cylindrical shape is preferably used. In addition, the materials include metal plates, metal drums, conductive polymers,
Applying a conductive thin layer made of a conductive compound such as indium oxide or a metal such as aluminum, palladium, or gold,
The material used is one that is provided on a substrate such as a film or a plastic film by means such as vapor deposition or lamination.

More specifically, the following method is selected for forming the carrier generation layer and the photosensitive layer having a single layer structure.

(a) A method of applying a solution in which a carrier-generating substance is dissolved in a suitable solvent, or a solution in which a binder is added and mixed and dissolved.

(b) A method in which a carrier-generating substance is made into fine particles in a dispersion medium using a ball mill, a homomixer, etc., and a binder is added as necessary to mix and disperse the obtained dispersion, and the resulting dispersion is applied.

Dispersing the particles under the action of ultrasound in these methods allows for homogeneous dispersion.

The coating liquid for forming photoreceptor constituent layers such as the photosensitive layer, undercoat layer, and protective layer preferably has a viscosity within the range of 5 to 500 cp (centivoise) in order to better achieve the effects of the present invention. More preferably, it is within the range of 10 to 300 cp. If the viscosity is smaller than the above range, the coating film tends to sag, and the lower part of the drum tends to become an FX film than the upper part, and if it is larger than the above range, the viscosity of the coating liquid in the coating tank tends to become uneven. , there is a tendency for film thickness unevenness to occur in the two films.

The thickness of the carrier transport layer after coating and drying is preferably in the range of 5 to 50 μm. Further, the carrier generation layer after coating and drying usually has a thickness of 0.205 to 10 μm. In the case of a single-layer photosensitive layer, the layer thickness after coating and drying is 10~
Preferably, it is 50 μm.

The i! ! The layer thickness is 0.01
It is preferable to set it within the range of ~1 micrometer. Further, the thickness of the undercoat layer (or intermediate layer, barrier layer, adhesive layer, etc.) provided between the photosensitive layer and the tetraelectric substrate is preferably within the range of 0.01 to 2 μm.

In coating and forming each photoreceptor constituent layer, coating methods such as blade coating, spray coating, and spiral coating may be used in combination.

Examples of the present invention will be described in more detail below, but the present invention is not limited thereto.

<Preparation of coating liquid> First, 11 coating liquids were prepared as follows.

Career busy beautiful voice cold cloth 1,2-dichloroethane (manufactured by Kanto Kagaku Co., Ltd.) 4000m
1, 480 g of polycarbonate (Panlite L-1250, manufactured by Ondai Kasei Co., Ltd.) was dissolved as a binder resin, and 1,1-bis (,!
A coating solution for forming a carrier transport layer was prepared by dissolving 480 g of -N,N-dibenzylamino-2-methylphenyl) normal butane.

Coating Experiment> The coating solution for forming a carrier transport layer was placed in a coating tank having an inner diameter of 100 nm in the anti-circular direction and a depth of 350 H, and the coating apparatus shown in FIG. 1 was prepared.

An aluminum cylindrical conductive base drum (cylinder) with an outer diameter of 80 flφ and a length of 300 n was immersed in this coating tank, and then the base drum was pulled up at a coating speed of 300 m/min.

At the start of lifting the base drum, the coating liquid is supplied at a rate of 2000cc/min, and as shown in graph A in Figure 2, the coating liquid supply IQ is gradually increased, and after 5 seconds, the coating liquid supply rate is increased to 6QOOcc/min. I kept it at ^. That is, QA=2
000cc/mtn, Qo =6000cc/ll1
in, t+=5 seconds.

As a result, a uniform coating film like the coating film +IA shown in FIG. 3 was obtained. However, the film thickness was 15 μm and hA=15.

, Comparison 2 Comparison The carrier transport layer was coated and formed under the same conditions as in the low example. However, as shown by the graph date in FIG. 2, the coating liquid supply rate was kept at 6000 cc/min. That is, Qo=6
000cc/min.

As a result, a coating film was obtained in which the upper part of the base drum was thinned, as shown in the coating film 11 in FIG. However, the film thickness is 15μm,
ha = 30.

, Comparison, Comparison ~ The carrier transport layer was coated and formed under the same conditions as in the examples. However, when starting to pull up the base drum, the temperature is 9000c.
The coating liquid was supplied at a rate of c/min, and the coating liquid supply rate Q was gradually decreased as shown by graph C in FIG. 2, and after 5 seconds had elapsed, the coating liquid supply rate was maintained at 6000 cc/min. That is, Q c = 9000cc/min, Q o =
6000cc/win, tl = 5 seconds.

As a result, a coating film such as coating film 11C in FIG. 3 in which the upper portion of the base drum was thinned was obtained. However, the film thickness is 15μm,
ha = 40.

Although the present invention has been illustrated above, the embodiments of the present invention are not limited to those described above, and various modifications can be made based on the technical idea of the present invention.

For example, when the amount of coating liquid supplied is gradually increased from the time when the object to be coated is started to be pulled up, the degree of increase in the amount of coating liquid supplied may vary, and the degree of increase is as shown in the graph shown in Figure 2. It's not limited to things. That is, various monotonically increasing functions can be employed, and a stepwise graph may also be used. Furthermore, there is no particular limitation on what happens after a predetermined period of time has elapsed.

According to the coating method of the present invention, the supply amount of the coating liquid is gradually increased until at least a predetermined time has elapsed from the time when the object to be coated is started to be pulled up. As the amount increases, the flow rate of the coating liquid in the coating tank increases, and an increase in the thickness of the coating film formed on the object to be coated is suppressed. Therefore, thinning of the coating film on the upper part of the object to be coated can be prevented, resulting in a single film. ■The area of the area decreases significantly.

Therefore, it is possible to prevent waste of the coating film and the coating liquid, and it is possible to improve the productivity of the coating film and reduce the cost of coating liquid materials and the like.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining the present invention. Figure 1 is a schematic partial sectional view showing the coating device, and Figure 2 shows the elapsed time from the time when the base drum was started to be pulled up. , a graph showing the relationship with the supply amount of the coating liquid; FIG. 3 is a sectional view showing a state in which a coating film is applied and formed on the upper end of the base drum. FIG. 4, FIG. 5, and FIG. 6 are all sectional views showing an example of an electrophotographic photoreceptor. In addition, in the reference numerals shown in the drawings, 2---1 Coating tank 2 a--1-- Coating tank side wall upper part 2 b-=-1-- Coating tank side wall 3-1 - 1 Coating liquid 7----1 Supply port +1A, 11th, zc-・-1---Coating film+2--
---1 Base drums A, B, C --- Graphs showing the relationship between elapsed time and coating liquid supply amount hA, hB, hc - Length of thinned region. Agent Patent Attorney Hiroshi Aisaka

Claims (1)

[Claims] 1. Immerse the object to be coated in the coating liquid contained in the coating tank,
Next, when the object to be coated is pulled up and the coating liquid is applied to the object to be coated, the coating liquid is caused to overflow beyond the upper edge of the side wall of the coating tank so that the coating liquid is supplied from the supply port to the A coating method in which the coating liquid is supplied into a coating tank, characterized in that the supply amount of the coating liquid is gradually increased until at least a predetermined period of time has elapsed from the time when the object to be coated is started to be pulled up.