JPH04336540A - Manufacture of photosensitive body for electronic photograph - Google Patents

Abstract

PURPOSE:To manufacture the photosensitive body for electronic photograph with which the uniform film thickness and the uniform electric characteristic are secured, in the continuous production of the photosensitive body for electronic photograph, by adjusting the coating quantity by controlling the film thickness in the production of a substrate layer or an electric charge transport layer. CONSTITUTION:When a transparent film 3 such as substrate layer or electric charge transport layer is coated in the manufacture of a photosensitive body for electronic photograph, the film thickness is successively measured by the light interference method, and the result of the measurement is feedback- controlled, and the coating speed is automatically controlled by a personal computer 20, and the variation of the film thickness is suppressed, and the film thickness is made uniform.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electrophotographic photoreceptor.

0002

BACKGROUND OF THE INVENTION In recent years, organic photoconductive materials have been developed in electrophotographic photoreceptors and are now being used more frequently than inorganic photoconductive materials that have been used in the past. Although photoreceptors using organic materials have some problems in sensitivity, durability, stability against the environment, etc., they have many advantages over inorganic materials in terms of toxicity, cost, freedom of material design, etc.

Organic electrophotographic photoreceptors are generally classified into single-layer type and functionally separated (laminated) type. The laminated type layer structure consists of two or three layers. In the case of a two-layer structure, there is a charge generation layer on top of a conductive substrate, and on top of that a charge transport layer, and in the case of three layers, there is a charge generation layer on top of a conductive substrate. The structure includes an undercoat layer on the substrate, and a charge generation layer and a charge transport layer on the undercoat layer in this order. These photosensitive layers are prepared by dissolving or dispersing organic photoconductive materials for forming each layer in an organic solvent together with a binder resin, and then preparing a photoconductor coating liquid by applying this photoconductor coating liquid onto a conductive substrate. It is manufactured by sequentially coating and drying. Examples of the coating method include a spray method, a bar coating method, a roll coating method, a blade method, a ring method, and a dipping method. In particular, the dip coating method is a relatively simple method in which a conductive substrate is immersed in a coating tank filled with the above-mentioned photoreceptor coating liquid and then pulled up at a constant speed or at a rate that changes sequentially to form a photosensitive layer. Since it is excellent in terms of productivity and cost, it is often used in manufacturing photoreceptors.

However, since this dip coating method forms a coating film by lifting the substrate from a coating tank, sag tends to occur in the vertical direction. As a result, there are disadvantages in that coating unevenness and streaks occur in the photosensitive layer formed on the substrate, and film thickness unevenness increases in the vertical direction, which adversely affects images such as uneven density. In addition, since the coating liquid uses an organic solvent that evaporates relatively easily to form a coating film, the solvent easily evaporates from the coating liquid in the coating tank, resulting in changes in the viscosity and concentration of the coating liquid. It is difficult to maintain a constant coating amount on the substrate and obtain a uniform coating film. That is, since the thickness of the photosensitive layer gradually changes, it becomes difficult to provide a photoreceptor with constant characteristics.

[0005] For this reason, variations in film thickness are managed, and if the variations exceed a permissible range, the amount of coating is adjusted to stabilize the characteristics.

Conventionally, in order to manage (measure) this film thickness, contact methods such as a level difference meter, surface roughness meter, and eddy current type film thickness meter, a method of measuring coating weight, or a gamma ray method using radiation, have been used. There are measurement methods and photographic methods in which the cross section of the sample is observed using a light microscope, an electron microscope, etc.

[0007] Furthermore, JP-A-59-7957 discloses a method of measuring and controlling the thickness of the charge generation layer using a color difference meter.

[0008]

[Problems to be Solved by the Invention] However, the contact method and the photographic method require processing of the sample to measure the film thickness, which takes time and is not easy to use.Also, the photoreceptor itself is damaged, so it is difficult to produce a product after measurement. There is a drawback that it cannot be used as The coating weight measurement method is difficult to use because the photoreceptor film is very thin (in the charge transport layer,
10 μm to 100 μm; 0.1 to 100 μm for undercoat layer
(about 5 μm) There is a problem with measurement accuracy in capturing such minute changes in weight. Gamma ray measurement methods require permission to use radioactive isotopes, and there are issues with special qualifications, facilities, and safety.

The method using a color difference meter is very useful for measuring the film thickness of relatively dark-colored films such as a charge generation layer, but it is very useful for measuring the film thickness of a colorless transparent or relatively light-colored film such as a charge transport layer or an undercoat layer. There are problems with accuracy in measuring changes in
It is insufficient.

0010

[Means for Solving the Problems] In order to solve the above-mentioned drawbacks, as a result of intensive research by the present inventors, when coating a transparent film for an undercoat layer or a charge transport layer in an organic electrophotographic photoreceptor, the film In order to suppress variations in thickness and achieve uniformity, we measure the film thickness sequentially using optical interferometry and feed back the measurement results to automatically control the coating speed to the appropriate speed.
It is possible to adjust the coating amount of the colorless transparent or very light colored subbing layer and charge transport layer, allowing the production of photoreceptors with appropriate film thickness and eliminating coating film unevenness (streaks, pinholes, etc.) The present invention has been completed based on this finding.

[0011]

[Operation] The principle of film thickness measurement using the optical interference method used in the present invention is as follows.

When light 1 is incident on a transparent film sample 3 with a film thickness d and a refractive index N, the light causes multiple reflections within the sample film (Fig. 1
(A)). The light measured as reflected light 2 passes through the sample film 2.
It is a composite of light that has been reflected back and forth three times. Furthermore, since light is a wave, it is necessary to take the phase of each ray into consideration when combining them (interference effect). That is, if the adjacent phase differences are an integer multiple of 2π, they will strengthen each other, and if they are an odd multiple of π, they will cancel each other out, causing optical interference.

The reflectance when light is incident on a transparent thin film as shown in FIG. 1(B) is expressed by the following equation (1).

Reflectance R=[R1 2 +R2 2 −2R1 R
2 cos(X)]/[1+R1 2 +R2 2
-2R1 R2 cos(X)]
(1) [X=4πN1 d/λ where N2 >
N1, λ: wavelength, d: thickness, R1: reflectance on the surface, R2: reflectance on the substrate, N1: refractive index of the thin film, N
2: Refractive index of substrate, R1 = (1-N1)/(1+
N1 ), R2 = (N1 - N2 )/(N1 + N
2)] Due to light interference, the reflectance takes a maximum value (or minimum value) at wavelengths that are constructive (or destructive). Therefore, by differentiating the reflectance R with respect to the wavelength λ, we obtain (d/dλ)R(λ )=0, (1/λn)−(1/λn+1)=1/2N1
d (2) (n: wavelength having the n-th maximum value (minimum value)). Using this equation (2), if the constructive (or destructive) wavelength and the refractive index of the thin film are known, the thickness of the transparent thin film can be calculated. The reflectance and wavelength of the thin film can be measured with a spectrophotometer. If the refractive index of a thin film is unknown, it can be actually determined from equation (2) by optical interferometry using a sample with a known film thickness.

Generally, in the case of dip coating, the relationship between the coating film thickness (wet film thickness), the physical properties of the coating liquid, and the coating speed is expressed by equation (3).

h=K(ηv/ρgsinα)n
(3) [h: coating film thickness (wet film thickness), v: coating speed,
ρ: specific gravity of coating liquid, η: viscosity of coating liquid, α: contact angle, K: constant (
0.9 to 1.9), n=constant (0.5 to 0.7)] From equation (3), it can be seen that the coating film thickness can be controlled by the coating speed and the specific gravity and viscosity of the coating liquid. The specific gravity and viscosity of the coating liquid are adjusted by diluting the coating liquid with a solvent or by evaporating it, but adjustment by dilution and evaporation is very difficult, and dilution is mainly done in a stirring tank attached to the coating tank, so it is difficult to adjust the specific gravity and viscosity of the coating liquid immediately during production. It is difficult to respond to changes in film thickness. Adjustment by coating speed can be made by simply changing the rotation speed of the elevator motor to change the lifting speed (coating speed). For example, to increase the film thickness, the coating speed may be increased, and to make the film thinner, the coating speed may be decreased. Therefore, the production equipment is simple and can be immediately adjusted to changes in film thickness.

[0017] The present invention will be explained in detail below.
The conductive substrate of the electrophotographic photoreceptor used in the present invention includes:
Examples include cylindrical substrates or thin film sheets of metals such as aluminum, copper, nickel, stainless steel, and brass, and cylindrical substrates of polyester films, paper, and metal films on which aluminum, tin, gold, and indium oxide are deposited. Next, an undercoat layer may be provided to improve the adhesion of the photoreceptor layer, to improve the coating properties, to cover defects on the substrate, to improve charge injection from the substrate to the charge generation layer, and the like. Known materials for the undercoat layer include resins such as polyamide, copolymerized nylon, casein, polyvinyl alcohol, cellulose, and gelatin. These are dissolved in various organic solvents and coated onto a conductive substrate to a film thickness of approximately 0.1 to 5 μm.

The charge generating layer of the present invention mainly contains a charge generating material that generates charges upon irradiation with light, and contains a known binder, plasticizer, and sensitizer as necessary.

Examples of charge-generating materials include perylene pigments, polycyclic quinone pigments, phthalocyanine pigments, metal phthalocyanine pigments, squarylium dyes, azuleninium dyes, thiapyrylium dyes, and carbazole skeletons, styrylstilbene skeletons, triphenylamine skeletons, and dibenzoyl stilbene skeletons. Examples include azo pigments having a thiophene skeleton, an oxadiazole skeleton, a fluorenone skeleton, a bisstilbene skeleton, a distyryl oxadiazole skeleton, or a distyryl carbazole skeleton.

The charge transport layer of the present invention contains as essential components a charge transport material having the ability to accept and transport charges generated by the charge generation material, a silicone leveling agent, and a binder, and if necessary, known known materials may be used. Contains plasticizers, sensitizers, etc.

As the charge transport material, poly-N-vinylcarbazole and its derivatives, poly-γ-carbazolylethyl glutamate and its derivatives, pyrene-formaldehyde condensate and its derivatives, polyvinylpyrene, polyvinylphenanthrene, oxazole derivatives, Electron donors such as oxodiazole derivatives, imidazole derivatives, 9-(p-diethylaminostyryl)anthracene, 1,1-bis(4-dibenzylaminophenyl)propane, styrylanthracene, styrylpyrazoline, phenylhydrazones, hydrazone derivatives, etc. or fluorenone derivatives, dibenzothiophene derivatives, indenothiophene derivatives, phenanthrenequinone derivatives, indenopyridine derivatives, thioxanthone derivatives, benzo[c]cinnoline derivatives, phenazine oxide derivatives, tetracyanoethylene, tetracyanoquinodimethane ,
Examples include electron-accepting substances such as promanil, chloranil, and benzoquinone.

The binder constituting the charge transport layer may be any binder as long as it is compatible with the charge transport material, such as polycarbonate, polyvinyl butyral, polyamide, polyester, polyketone, epoxy resin, polyurethane, polyvinyl ketone, Examples include polystyrene, polyacrylamide, phenol resin, phenoxy resin, and the like.

A known dip coating method can be applied to the method of manufacturing the electrophotographic photoreceptor of the present invention. An example is described below.

For example, a charge generating material such as an azo pigment is mixed with a binder, a plasticizer, a sensitizer, and a suitable solvent such as cyclohexanone, benzene, chloroform, dichloroethane, ethyl ether, acetone, ethanol, if necessary. A conductive substrate is immersed in a coating liquid dispersed in , chlorobenzene, methyl ethyl ketone, etc. by a known method, pulled up, and dried to form a charge generation layer on the conductive substrate.

Next, a charge transport material such as a vidrazone compound, a silicone leveling agent and a binder are mixed with a suitable solvent such as dichloroethane, benzene, chloroform, cyclohexanone together with a plasticizer and a sensitizer as necessary. A conductive substrate coated with a charge generation layer is immersed in a coating solution dissolved in ethyl ether, acetone, ethanol, chlorobenzene, methyl ethyl ketone, etc. by a known method, pulled up, and dried to form a charge transport layer.

The adjustment of the coating amount in forming the charge transport layer described above will be explained with reference to FIG. Conductive substrate 13 suspended from arm 17 attached to elevator 14
is lowered by driving the lifting device 15 and immersed in the coating liquid 12 in the coating tank 11. Next, the conductive substrate 13 is pulled up from the coating liquid 12 by driving the lifting device 15, and at the same time, the coated charge transport layer is irradiated with light of a specific wavelength, and the spectrophotometer light receiving section 21 receives the reflected light. The data of the received reflected light is analyzed by the spectrophotometer calculation section 22 and immediately sent to the calculation processing device (personal computer) 20. Based on this data, the rotation adjustment unit 16 of the lifting device is controlled by a personal computer, and the rotation of the lifting device (motor) 15 is adjusted to an appropriate pulling speed (coating speed), thereby adjusting the thickness of the coating film.

The light source used includes visible light, ultraviolet light, infrared light, etc., and an appropriate light source is used depending on the film thickness and absorption of the sample.

As described above, the method for manufacturing an electrophotographic photoreceptor of the present invention includes measuring the film thickness of the photoreceptor by optical interference method, and automatically adjusting the coating speed of the photoreceptor based on the data.
Since the film thickness can be measured without damaging the surface of the photoreceptor and it is easy to measure the film thickness, it is possible to immediately adjust the coating amount and always provide a photoreceptor with an appropriate film thickness. This makes it easy to detect paint film irregularities (streaks, pinholes, etc.). Furthermore, since it is possible to measure the thickness of a colorless transparent or very pale-colored film that cannot be measured with a color difference meter, it is easy to form an undercoat layer or a charge transport layer with an appropriate thickness.

[0029]

[Examples] The present invention will be specifically explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Copolymerized nylon resin (CM4000: manufactured by Toray Industries, Inc.) 6
Parts by weight were dissolved in 94 parts by weight of methanol to prepare a coating liquid for an undercoat layer.

[0031] This undercoat layer coating liquid was applied sequentially to the surface of 100 aluminum cylindrical supports (conductive substrates) by dip coating, and the film thickness was successively measured using the coating apparatus shown in Fig. 2. The thickness of the undercoat layer is 1.5μm ± 0.3μm
When the film thickness was exceeded, the pulling speed (coating speed) was automatically controlled by a computer according to the film thickness. The coating speed was 10 mm/sec for the first coat and 7.1 mm/sec for the 100th coat. The applied coating film was dried at 110°C for 10 minutes to form an undercoat layer. As a result of continuously applying 100 undercoat layers, there was almost no difference in the thickness of the undercoat layer between the 1st and 100th layers. The results are shown in Table 1.

For film thickness measurement, a spectrophotometer (MCPD-1
100, manufactured by Otsuka Electronics Co., Ltd.) was used. The refractive index is determined in advance using a sample whose film thickness is known, and each time the undercoat layer is dip-coated, the reflection spectrum of the coating film is measured, and the adjacent peaks (valleys) of the spectrum are measured. The wavelength was calculated, and the film thickness was calculated using the previously determined refractive index and equation (2).

Next, a charge generation layer is sequentially formed on the undercoat layer.
A charge transport layer was formed. As a coating liquid for forming the charge generation layer, 2 parts by weight of ε-type copper phthalocyanine (Liophoton EPPC, manufactured by Toyo Ink Co., Ltd.), 1 part by weight of butyral resin (S-LEC BL-1, manufactured by Sekisui Chemical Co., Ltd.), and 100 parts by weight of tetrahydrofuran. The mixture was prepared by dispersing it in a ball mill for 8 hours. This coating liquid was applied by dip coating method so that the dry film thickness was 0.4 μm.
C. for 30 minutes to obtain a charge generation layer.

Next, as a coating liquid for forming a charge transport layer, a butadiene charge transport material (1,1-bis(p-diethylaminophenyl)-4,4-diphenyl-1,3-butadiene, manufactured by Takasago Fragrance Co., Ltd.) was used. 1 part by weight of polycarbonate resin (Panlite L-1225, manufactured by Teijin Kasei Ltd.), 1 part by weight of silicone leveling agent (KF-96)
, manufactured by Shin-Etsu Chemical Co., Ltd., was dissolved in 10 parts by weight of dichloromethane to prepare a coating liquid for forming a charge transport layer. This coating liquid was applied onto the charge generation layer by dip coating method so that the dry film thickness was 17 μm.
A charge transport layer was formed by drying at °C for 1 hour to prepare an electrophotographic photoreceptor for LBP.

The first and 100th photoreceptors were mounted on a predetermined laser printer and their electrical characteristics were measured. Undercoat layer thickness, chargeability (Vo), residual potential (Vr
) and sensitivity (VL) are shown in Table 1.

[0036]

[Table 1]

Comparative Example 1 Instead of forming an undercoat layer by automatically controlling the coating speed using the coating apparatus shown in FIG. 2 of Example 1, the undercoat layer was formed at a coating speed of 10.0 mm/sec. Dry film thickness is 1.5
100 continuous dip coatings were carried out so that the coating thickness was 100 μm, the 1st, 50th and 100th coats were removed, and the film thickness of the undercoat layer was measured using a level difference meter (Talysurf 5, manufactured by Taylor & Bobson). An electrophotographic photoreceptor was produced in the same manner as in Example 1.

Table 2 shows the thickness, chargeability (Vo), residual potential (Vr) and sensitivity (VL) of the undercoat layer.

[0039]

[Table 2]

Example 3 As a coating liquid for forming a charge generation layer, 1 part by weight of dibrom anthron, butyral resin (S-LEC BM-2
, manufactured by Sekisui Chemical Co., Ltd.) 1 part by weight, cyclohexanone 12
0 parts by weight was prepared and dispersed in a ball mill for 12 hours. This coating solution was coated on the surface of 100 cylindrical aluminum conductive substrates by dip coating so that the dry film thickness was 0.5 μm, and dried at 80° C. for 30 minutes to form a charge generation layer.

Next, hydrazone-based charge transport material (ABPH,
1 part by weight of polycarbonate resin (manufactured by Nippon Kayaku Co., Ltd.)
Add 1 part by weight of Panlite L-1250 (manufactured by Teijin Kasei Ltd.) and 0.00013 parts by weight of a silicone leveling agent (KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) to 8 parts by weight of dichloroethane, and add 45 parts by weight to 8 parts by weight of dichloroethane. The mixture was heated and dissolved at ℃, and after being completely dissolved, it was naturally cooled to prepare a coating liquid for forming a charge transport layer. This coating liquid was applied onto the charge generation layer by dip coating, and the film thickness was successively measured using the coating device shown in Fig. 2. If the film thickness of the charge transport layer exceeded 20 μm ±0.5 μm, the film thickness The pulling speed (coating speed) was automatically controlled by a computer according to the thickness. The coating speed is 7.0mm/1.
The 100th one was 6.4 mm/sec. The applied coating film was dried at 70° C. for 1 hour to form a charge transport layer, and an electrophotographic photoreceptor was prepared. There was almost no difference in the thickness of the charge transport layer and the electrical properties of the resulting photoreceptor between the 1st and 100th photoreceptor, and a good electrophotographic photoreceptor could be obtained. Chargeability (Vo), residual potential (Vr),
Low-light sensitivity (VL ex=1) and high-light sensitivity (V
L ex = 5) is shown in Table 3.

The film thickness was measured using a spectrophotometer (MCPD-110).
0, manufactured by Otsuka Electronics Co., Ltd.) was used. The refractive index is also Example 1
Similarly to Example 1, the film thickness was determined in advance from the charge transport layer of the prescription of this example, whose thickness was known, and the film thickness was calculated using the previously determined refractive index and equation (2) in the same manner as in Example 1.

[0043]

[Table 3]

Comparative Example 2 Instead of forming a charge transport layer by automatically controlling the coating speed using the coating apparatus shown in FIG. 2 of Example 2, the charge transport layer was formed at a coating speed of 7.0 mm/sec. Dry film thickness is 20
The film thickness of the charge transport layer was measured using a level difference meter (Talysurf 5, manufactured by Taylor & Bobson). An electrophotographic photoreceptor was prepared in the same manner as in Example 2. Charge transport layer thickness, chargeability (Vo), residual potential (Vr), low illuminance sensitivity (
VL ex=1) and high-light side sensitivity (VL ex=5)
are shown in Table 4.

[0045]

[Table 4]

As is clear from Tables 1 and 3, the film thickness, chargeability, residual potential, and sensitivity of the electrophotographic photoreceptor produced by the method of the present invention are uniform with almost no difference observed between the first and 100th photoreceptors. In addition, a good electrophotographic photoreceptor could be obtained.

On the other hand, as shown in Tables 2 and 4,
Electrophotographic photoreceptors not using the method of the present invention did not have uniform characteristics.

[0048]

[Effects of the Invention] According to the method of the present invention, the film thickness can be easily measured and the coating amount can be adjusted immediately, making it possible to obtain an electrophotographic photoreceptor that always has appropriate film thickness and electrical properties. .

[Brief explanation of drawings]

FIG. 1 is a diagram showing the reflection of light on a coating film.

FIG. 2 is a schematic diagram of a coating apparatus that measures the thickness of a coating film using the optical interference method of the present invention and forms a coating film by controlling the coating speed.

[Explanation of symbols]

1 Incident light 2 Reflected light 3 Coating film 11 Coating tank 12 Coating liquid 15 Elevator motor 20 Arithmetic processing unit (PC) 21 Spectrophotometer light receiving part

Claims (1)

[Claims] Claim 1: Manufacture an electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are coated on the surface of a conductive substrate, or an electrophotographic photoreceptor in which a subbing layer, a charge generation layer, and a charge transport layer are sequentially coated. The method includes a step of sequentially measuring the film thickness of the undercoat layer or charge transport layer by optical interference method, a step of feeding back the measurement results to a processing device, and a step of controlling the lifting speed from the processing device to adjust the coating amount. A method for manufacturing an electrophotographic photoreceptor, comprising the steps of: