JP6569484B2 - Method for producing coating film of electrophotographic photosensitive member - Google Patents

Description

  The present invention relates to a method for producing a coating film on an electrophotographic photoreceptor.

The electrophotographic system is widely used as a printer or a copying machine in an office because printing with high speed and high image quality is obtained compared to other printer systems such as an ink jet system and printing productivity is high. In the electrophotographic system, printing such as charging / exposure / development / transfer is performed on the electrophotographic photosensitive member.
As a method for producing an electrophotographic photoreceptor (a coating film thereof), a dip coating method is one common method. The dip coating method is a method in which a member to be coated is (i) dipped in a coating solution and (ii) pulled up from the coating solution at a specific speed to form a coating film on the member to be coated. The dip coating method is used for sequentially laminating an undercoat layer and a photosensitive layer on a cylindrical support.

An example of the dip coating method is disclosed in Patent Documents 1 and 2.
In the technique of Patent Document 1, a member to be coated is submerged in a coating solution and applied while being rotated relatively in the circumferential direction to obtain a smooth surface state (the second column, left column 12). Line to the right column of the same page, line 12, see FIG.
In the technique of Patent Document 2, first, the first member to be coated is lifted and applied while being immersed and rotated in the coating solution, and the thickness of the coating film is measured. Thereafter, the measured film thickness is compared with a predetermined film thickness, and the rotation condition at the time of applying the member to be coated is acquired from the information obtained there. Finally, using the obtained rotation conditions, the second member to be coated is pulled up and applied while being immersed in a coating solution and rotated (see paragraphs 0011 to 0016). As a result, liquid dripping at the time of pull-up coating is prevented, and attempts are made to suppress thinning of the coating film.

By the way, in the dip coating method, another problem has emerged as follows.
As described above, the dip coating method requires a two-step operation in which the member to be coated is (i) rushed once and then (ii) pulled up and coated. In order to maintain the quality at the time of application by pulling up, it is necessary to consider the influence of the rush immersion operation that is the previous stage. That is, when air bubbles are involved during rush immersion, they grow in volume in the coating solution, and are released (detached) from the member to be coated when they are lifted and applied to swim. In such a case, the coating film thickness may partially fluctuate and a coating film defect may occur. This can be a cause of greatly damaging image quality in the electrophotographic system.

JP-A 63-259669 JP 2011-045863 A

The present inventor has studied the problem caused by such bubble entrainment and newly found out that the following technical matters are inherent.
In the electrophotographic photoreceptor, in order to suppress interference fringes due to interference between the wavelength of light at the time of exposure and the layer thickness of the undercoat layer, the photosensitive layer, etc., as shown in FIG. In many cases, the surface is roughened. In such a case, it is assumed that the rough surface shape (Rt is around ± 1 μm) is a trigger and bubbles are involved. In the case of forming a photosensitive layer (such as a charge generation layer) after forming an undercoat layer on the support, fine unevenness of the entire coating film already applied and formed in the previous process, or unevenness (scratches) on the lower end portion 102 of the coating film Even if a small lump or the like is formed, it is assumed that bubbles are involved during rush immersion.

  On the other hand, in order to obtain film formation uniformity of the entire coating film, the temperature of the member to be coated and the coating liquid are controlled. However, depending on the conditions, bubbles may grow in volume, and the entrained fine bubbles may grow in volume. It is conceivable to swim at the time of lifting application. There is a limit to the temperature management of the member to be coated and the coating liquid, and there is a limit to the suppression of bubble growth. Of course, as in Patent Documents 1 and 2, it is also one method that the member to be coated is pulled up and rotated at the time of coating, and bubbles entrained in the member to be coated are detached by centrifugal force. However, it is not sufficient to detach only by centrifugal force, so it is necessary to rotate the member to be coated at high speed. In such a case, the coating film already formed can be damaged and the coating film can be peeled off as an extreme example. There is also sex. It is difficult to suppress coating film defects caused by bubbles only by pulling up and rotating the member to be coated during coating.

  Accordingly, a main object of the present invention is to provide a method for producing a coating film for an electrophotographic photosensitive member that can suppress coating film defects caused by bubbles.

In order to solve the above problems, according to the present invention,
A step of preparing a cylindrical coated member;
E Bei and a step of immersing is plunged into the coating solution while rotating the object to be coated member,
In the step of preparing the member to be coated,
Preparing a support or a support on which an undercoat layer is formed as the coated member,
In the step of immersing the member to be coated into the coating liquid,
An undercoat layer is formed on the support, or an electrode is formed on the undercoat layer already formed on the support.
When forming the load generating layer, the rotational speed of the coated surface is 100 to 400 mm / sec, the rush speed is 25 to 100 mm / sec, and
In the temperature of the coating solution is 20 to 50 ° C., the manufacturing method of the coating film of the electrophotographic photosensitive member at which the viscosity of the coating solution is characterized to Rukoto and 1~800mPa · sec is provided.

  According to the present invention, coating film defects caused by bubbles can be suppressed.

It is a figure which shows schematic structure of a photoreceptor, Comprising: Especially the upper stage part is a partial expanded sectional view. It is a partial expanded sectional view which shows the other aspect of a photoreceptor. It is a figure which shows schematic structure of a dip coating apparatus. It is a schematic flowchart explaining the manufacturing method of the coating film of a photoreceptor over time. It is a figure for demonstrating the problem in the coating film manufacture of the conventional photoconductor.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
In the present application, “to” is used in the sense of including the numerical values described before and after the lower limit value and the upper limit value.

[Photosensitive member (10)]
A photoreceptor 10 shown in FIG. 1 is an example of a so-called electrophotographic photoreceptor (photoreceptor drum) that is subjected to various processes such as charging / exposure / development / transfer in an electrophotographic system.
As shown in the enlarged portion of FIG. 1, the photoconductor 10 has a conductive support 1 having a cylindrical shape as a substrate, and an undercoat layer 2, a photosensitive layer 3, and a surface protective layer 6 are formed on the support 1. It has a stacked configuration. The surface protective layer 6 contains metal oxide fine particles 7.
The photosensitive layer 3 is a layer having both a function of generating charges by absorbing light and a function of transporting charges. The layer structure of the photosensitive layer 3 may be a structure in which a charge generation layer 4 containing a charge generation material and a charge transport layer 5 containing a charge transport material are laminated, or a charge generation material and a charge transport material It may be a single layer structure containing
The layer structure of the photosensitive layer 3 is not particularly limited, and examples of a specific layer structure including the surface protective layer 6 include the following.
(I) Layer configuration in which an undercoat layer 2, a charge generation layer 4, a charge transport layer 5 and a surface protective layer 6 are sequentially laminated on the support 1. (ii) On the support 1, the undercoat layer 2, the charge transport. Layer structure in which a single layer containing a substance and a charge generating substance and a surface protective layer 6 are sequentially laminated. The photoconductor 10 may have any one of the above-described layer structures (i) or (ii). The substrate 1 preferably has a layer structure (i) prepared by sequentially providing the undercoat layer 2, the charge generation layer 4, the charge transport layer 5 and the surface protective layer 6 on the support 1.
As shown in FIG. 2, the photoreceptor 10 may not have the surface protective layer 6.

[Support (1)]
Any support may be used as long as it has conductivity. For example, a support formed by forming a metal such as aluminum, copper, chromium, nickel, zinc, or stainless steel into a cylindrical shape (drum shape) is used.
The diameter of the support is preferably 20 to 150 mm.
The length of the support is preferably 220 to 500 mm.
The surface roughness Rt of the support is preferably 0.6 μm or more, more preferably 0.9 to 1.1 μm. “Surface roughness Rt” is a parameter based on JIS B 0601: 2001, and is the maximum cross-sectional height of a roughness curve according to JIS standards.

[Undercoat layer (2)]
The undercoat layer is formed between the conductive support 1 and the photosensitive layer 3 and has a barrier function and an adhesive function.
The undercoat layer is formed by a dip coating method by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane and gelatin in a known solvent. It is preferable to use an alcohol-soluble polyamide resin as the binder resin.

The undercoat layer contains at least a metal oxide for the purpose of adjusting resistance. Similarly, the undercoat layer may contain inorganic fine particles such as various conductive fine particles for the purpose of adjusting the resistance. Examples thereof include various metal oxides such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide and bismuth oxide. Ultrafine particles such as indium oxide doped with tin, tin oxide doped with antimony, and zirconium oxide can also be used.
These metal oxides may be used alone or in combination of two or more. When two or more types are mixed and used, it may take the form of a solid solution or fusion. Such a metal oxide is preferably contained in the undercoat layer in the form of fine particles. In this case, the number average primary particle size is preferably 0.3 μm or less, more preferably 0.1 μm or less. .
The method for measuring the number average primary particle size of the metal oxide is the same as that of the metal oxide fine particles contained in the surface protective layer (see below).

As the solvent that can be used for forming the undercoat layer, a solvent that can satisfactorily disperse the above-described inorganic fine particles such as conductive fine particles and metal oxides and dissolve a binder resin such as a polyamide resin is preferable.
Specific examples include alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol and sec-butanol. These alcohols are preferable because they exhibit good solubility and coating performance with respect to an official polyamide resin as a binder resin.
In order to improve storage stability and dispersibility of inorganic fine particles, the following cosolvents can be used in combination with such a solvent. Examples of the co-solvent that can provide a preferable effect include methanol, benzyl alcohol, toluene, cyclohexanone, and tetrahydrofuran.

The binder resin concentration at the time of forming the coating liquid can be appropriately selected according to the thickness of the undercoat layer.
When the inorganic fine particles are dispersed, the mixing ratio of the inorganic fine particles to the binder resin is preferably 20 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin. preferable.
Examples of the means for dispersing the inorganic fine particles include, but are not limited to, an ultrasonic disperser, a ball mill, a sand grinder, and a homomixer.
As a method for drying the undercoat layer, a known drying method can be appropriately selected according to the type of solvent and the layer thickness to be formed, and thermal drying is particularly preferable.
The thickness of the undercoat layer is preferably in the range of 1 to 30 μm, more preferably 0.1 to 15 μm, and still more preferably 0.3 to 10 μm.

[Photosensitive layer (3)]
As described above, the photosensitive layer preferably has a layer structure in which the functions (charge generation function and charge transport function) of the photosensitive layer are separated into the charge generation layer and the charge transport layer. According to the function-separated layer structure, the increase in the residual potential due to repeated use can be controlled to be small, and various electrophotographic characteristics can be easily controlled according to the purpose.
The negatively chargeable photoreceptor has a structure in which a charge generation layer is provided on an undercoat layer and a charge transport layer is provided thereon. The positively chargeable photoreceptor has a structure in which a charge transport layer is provided on the undercoat layer and a charge generation layer is provided thereon.
A preferred embodiment of the photosensitive layer is a negatively chargeable photoreceptor having a function separation structure.
Here, as a specific example of the photosensitive layer, each layer of the photosensitive layer of the function-separated negatively chargeable photoreceptor will be described.

[Charge generation layer (4)]
The charge generation layer contains a charge generation material (CGM) and a binder resin, and is formed by a dip coating method using a coating liquid in which the charge generation material is dispersed in a binder resin solution.

  Charge generation materials include azo raw materials such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, hydroxygallium phthalocyanine, chlorogallium phthalocyanine, and titanyl phthalocyanine And phthalocyanine pigments. Of these, phthalocyanine pigments having a sensitivity of 700 nm or more are preferable, and titanyl phthalocyanine pigments, particularly Y-titanyl phthalocyanine (a maximum diffraction peak at a position of at least 27.3 ° in Cu-Kα characteristic X-ray diffraction spectrum measurement). It is preferable that the titanyl phthalocyanine pigment has a very large absorption at 780 nm, which is described as Y-TiPh, but the charge generation material is not limited thereto.

  These charge generation materials can be used alone or in a form dispersed in a known binder resin.

  As the binder resin for forming the charge generation layer, known resins can be used. For example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy Resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin) , Vinyl chloride-vinyl acetate-maleic anhydride copolymer resin) and poly-vinyl carbazole resin, but are not limited thereto.

  When forming the charge generation layer, use a disperser to disperse the charge generation material in a solution in which the binder resin is dissolved in a solvent to prepare a coating solution, and apply the coating solution to a constant layer thickness by dip coating. It is preferable to dry the coating film.

  Solvents for dissolving and coating the binder resin used for the charge generation layer include, for example, toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran 1,4-dioxane, 1,3-dioxolane, pyridine, diethylamine and the like, but are not limited thereto.

  As a means for dispersing the charge generating material, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but the charge generating substance is not limited to these.

The mixing ratio of the charge generating material to the binder resin is preferably 1 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin.
The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, and more preferably 0.05 to 3 μm.
It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating.

[Charge transport layer (5)]
The charge transport layer contains a charge transport material (CTM) and a binder resin, and is formed by a dip coating method using a coating solution in which the charge transport material is dissolved in a binder resin solution.

  As the charge transport material, known compounds can be used, for example, carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidines. Derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, benzidine derivatives, poly -N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene and the like. These compounds can be used alone or in admixture of two or more.

  As the binder resin for the charge transport layer, a known resin can be used. For example, polycarbonate resin, polyacrylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylate resin, styrene- Examples thereof include methacrylic acid ester copolymer resins. Of these, polycarbonate resins are preferred, and polycarbonate resins of the types such as bisphenol A (BPA), bisphenol Z (BPZ), dimethyl BPA type, and BPA-dimethyl BPA copolymer are crack resistant and wear resistant. From the viewpoint of the property and charging characteristics, it is preferable.

  When forming the charge transport layer, the binder resin and the charge transport material are dissolved in a solvent to prepare a coating solution, the coating solution is applied to a constant layer thickness by a dip coating method, and the coating film is dried. preferable.

Examples of the solvent that dissolves the binder resin and the charge transport material include toluene, xylene, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, 1,4-dioxane, 1,3- And dioxolane.
The solvent used for preparing the coating solution for the charge transport layer is not limited to the above.

  The mixing ratio of the binder resin and the charge transport material is preferably 10 to 500 parts by weight, and more preferably 20 to 100 parts by weight with respect to 100 parts by weight of the binder resin.

  The layer thickness of the charge transport layer varies depending on the characteristics of the charge transport material and the binder resin and the mixing ratio thereof, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  In the charge transport layer, a known antioxidant can be added. For example, an antioxidant described in JP-A-2000-305291 can be used.

[Surface protective layer (6)]
The surface protective layer comprises at least a resin obtained by polymerizing a crosslinkable polymerizable compound and metal oxide fine particles.

  The surface protective layer contains a resin obtained by polymerizing a crosslinkable polymerizable compound as a binder resin. In the surface protective layer, in addition to a resin obtained by polymerizing a crosslinkable polymerizable compound, a known resin such as a polyester resin, a polycarbonate resin, a polyurethane resin, or a silicone resin can be used in combination.

(1) Crosslinkable polymerizable compound Examples of the crosslinkable polymerizable compound that can be used in the surface protective layer include a radical polymerizable compound having two or more radical polymerizable reactive groups. The radical polymerizable monomer having at least one of acryloyl group or methacryloyl group as the radical polymerizable reactive group is preferable.

  Examples of these radical polymerizable monomers include the following compounds, but the radical polymerizable monomers are not limited thereto.

The above radical polymerizable monomers are known and can be obtained as commercial products.
Here, R represents the following acryloyl group, and R ′ represents the following methacryloyl group.

(2) Metal oxide fine particles The surface protective layer contains metal oxide fine particles 7 (see FIG. 1).
As the metal oxide fine particles, tin oxide fine particles, zinc oxide fine particles, titanium oxide fine particles and aluminum oxide fine particles are preferable.
The number average primary particle size of the metal oxide fine particles is preferably in the range of 1 to 300 nm, more preferably in the range of 3 to 100 nm.

(2.1) Method for Measuring Number Average Primary Particle Size of Metal Oxide Fine Particles The number average primary particle size of metal oxide fine particles is 10,000 times using a scanning electron microscope “JSM-7401F” (manufactured by JEOL Ltd.). An automatic image processing analyzer "Luzex AP (LUZEX (registered trademark) AP)" (manufactured by Nireco Co., Ltd.) ) Software Ver. Using 1.32, binarization is performed, the horizontal ferret diameter is calculated, and the average value is calculated as the number average primary particle diameter.
The horizontal ferret diameter refers to the length of a side parallel to the x axis of a circumscribed rectangle when the image of metal oxide fine particles is binarized.

(2.2) Surface modification of metal oxide fine particles The metal oxide fine particles contained in the surface protective layer are preferably those modified with a coupling agent, and further a coupling agent having a reactive organic group. A surface-modified one is more preferable.

(2.2.1) Coupling agent The coupling agent for modifying the surface of the metal oxide fine particles is preferably a coupling agent that reacts with a hydroxy group or the like present on the surface of the metal oxide fine particles. Examples thereof include silane coupling agents and titanium coupling agents.
As the coupling agent, a coupling agent having a reactive organic group is preferable for the purpose of further increasing the hardness of the surface protective layer, and the coupling agent having a reactive organic group is a cup having a radical polymerizable reactive group. A ring agent is preferred. These radical polymerizable reactive groups can react with a crosslinkable polymerizable compound to form a strong protective film.
As the coupling agent having a radical polymerizable reactive group, a silane coupling agent having a radical polymerizable reactive group such as a vinyl group, an acryloyl group or a methacryloyl group is preferable, and a silane coupling agent having such a radical polymerizable reactive group. Examples of the agent include the following known compounds.

_{S-1: CH 2 = CHSi} (CH 3) (OCH 3) 2
_{S-2: CH 2 = CHSi} (OCH 3) 3
S-3: CH ₂ = CHSiCl _{3
S-4: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-5: CH 2 = CHCOO} (CH 2) 2 Si (OCH 3) 3
_{S-6: CH 2 = CHCOO} (CH 2) 2 Si (OC 2 H 5) (OCH 3) 2
_{S-7: CH 2 = CHCOO} (CH 2) 3 Si (OCH 3) 3
_{S-8: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) Cl 2
_{S-9: CH 2 = CHCOO} (CH 2) 2 SiCl 3
_{S-10: CH 2 = CHCOO} (CH 2) 3 Si (CH 3) Cl 2
S-11: CH ₂ = CHCOO (CH ₂ ) ₃ SiCl _{3
S-12: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) (OCH 3) 2
_{S-13: CH 2 = C} (CH 3) COO (CH 2) 2 Si (OCH 3) 3
_{S-14: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) (OCH 3) 2
_{S-15: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OCH 3) 3
_{S-16: CH 2 = C} (CH 3) COO (CH 2) 2 Si (CH 3) Cl 2
_{S-17: CH 2 = C} (CH 3) COO (CH 2) 2 SiCl 3
_{S-18: CH 2 = C} (CH 3) COO (CH 2) 3 Si (CH 3) Cl 2
_{S-19: CH 2 = C} (CH 3) COO (CH 2) 3 SiCl 3
_{S-20: CH 2 = CHSi} (C 2 H 5) (OCH 3) 2
_{S-21: CH 2 = C} (CH 3) Si (OCH 3) 3
_{S-22: CH 2 = C} (CH 3) Si (OC 2 H 5) 3
_{S-23: CH 2 = CHSi} (OCH 3) 3
_{S-24: CH 2 = C} (CH 3) Si (CH 3) (OCH 3) 2
_{S-25: CH 2 = CHSi} (CH 3) Cl 2
_{S-26: CH 2 = CHCOOSi} (OCH 3) 3
_{S-27: CH 2 = CHCOOSi} (OC 2 H 5) 3
_{S-28: CH 2 = C} (CH 3) COOSi (OCH 3) 3
_{S-29: CH 2 = C} (CH 3) COOSi (OC 2 H 5) 3
_{S-30: CH 2 = C} (CH 3) COO (CH 2) 3 Si (OC 2 H 5) 3
_{S-31: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) 2 (OCH 3)
_{S-32: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OCOCH 3) 2
_{S-33: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (ONHCH 3) 2
_{S-34: CH 2 = CHCOO} (CH 2) 2 Si (CH 3) (OC 6 H 5) 2
_{S-35: CH 2 = CHCOO} (CH 2) 2 Si (C 10 H 21) (OCH 3) 2
_{S-36: CH 2 = CHCOO} (CH 2) 2 Si (CH 2 C 6 H 5) (OCH 3) 2

  As the silane coupling agent, other than the above S-1 to S-36, a silane compound having a reactive organic group capable of radical polymerization may be used. These silane coupling agents can be used alone or in admixture of two or more.

(2.2.2) Surface Modification Method for Metal Oxide Fine Particles When surface modification is performed, 0.1 to 100 parts by mass of coupling agent and 50 to 5000 parts by mass of solvent are used with respect to 100 parts by mass of metal oxide fine particles. Surface modification is preferably performed using a wet media dispersion type apparatus. The surface can be modified even in a dry process.

  Hereinafter, a surface modification method for producing metal oxide fine particles whose surface is uniformly modified with a coupling agent will be described.

  By wet pulverizing the slurry (suspension of solid particles) containing the metal oxide fine particles and the coupling agent, the metal oxide fine particles are refined and at the same time the surface modification of the fine particles proceeds. Thereafter, by removing the solvent and pulverizing, metal oxide fine particles whose surface is uniformly modified with a coupling agent can be obtained.

Wet media dispersion type device, which is a surface modification device, crushes agglomerated particles of metal oxide fine particles by filling beads in a container as media and rotating a stirring disk mounted perpendicular to the rotation axis at high speed. It is an apparatus having a process of pulverizing and dispersing.
The configuration of the dispersion type apparatus is not a problem as long as the metal oxide fine particles are sufficiently dispersed and surface-modified when performing surface modification on the metal oxide fine particles. For example, the vertical type / horizontal type, continuous type / batch type can be used. Various forms such as a formula can be adopted. Specifically, a sand mill, ultra visco mill, pearl mill, glen mill, dyno mill, agitator mill, dynamic mill and the like can be used. In these dispersion-type apparatuses, pulverization and dispersion are performed by impact crushing, friction, shearing, shear stress, and the like using a pulverizing medium (media) such as balls or beads.

As the beads used in the wet media dispersion type apparatus, balls made of glass, alumina, zircon, zirconia, steel, flint stone or the like can be used, but those made of zirconia or zircon are particularly preferable.
As the size of the beads, those having a diameter of about 1 to 2 mm can be usually used, but those having a diameter of about 0.1 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon, and ceramic can be used for the disk and container inner wall used in wet media dispersion type equipment, but especially ceramic disk or container inner wall such as zirconia or silicon carbide is used. It is preferable to do this.

By the wet treatment as described above, metal oxide fine particles whose surface is modified with a coupling agent can be obtained.
The surface-modified metal oxide fine particles described above are preferably contained in an amount of 30 to 250 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound from the viewpoint of improving the wear resistance of the surface protective layer.

(3) Formation of surface protective layer The surface protective layer comprises a crosslinkable polymerizable compound, surface-modified metal oxide fine particles, and, if necessary, other resins, polymerization initiators, lubricant particles, and antioxidants. The coating solution prepared by addition is applied by a dip coating method, and then the coating film is naturally dried or heat-dried and cured (polymerized) to form.
The layer thickness of the surface protective layer is preferably 0.2 to 10 μm, and more preferably 0.5 to 6 μm.

(3.1) Solvent As the solvent used for forming the surface protective layer, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, benzyl alcohol, Methyl isopropyl ketone, methyl isobutyl ketone, methyl ethyl ketone, cyclohexane, toluene, xylene, methylene chloride, ethyl acetate, butyl acetate, 2-methoxyethanol, 2-ethoxyethanol, tetrahydrofuran, 1,4-dioxane, 1,3-dioxolane, pyridine And diethylamine, but are not limited thereto.

(3.2) Polymerization initiator As a method for polymerizing a crosslinkable polymerizable compound that can be used for the surface protective layer, a method using an electron beam cleavage reaction or light or heat in the presence of a radical polymerization initiator is used. The polymerization reaction can be performed by the method used.
When performing a polymerization reaction using a radical polymerization initiator, both a photopolymerization initiator and a thermal polymerization initiator can be used as the polymerization initiator. Further, both light and heat initiators can be used in combination.

  Examples of thermal polymerization initiators include 2,2'-azobisisobutyronitrile, 2,2'-azobis (2,4-dimethylazobisvaleronyl), 2,2'-azobis (2-methylbutyro). Nitriles), benzoyl peroxide (BPO), di-tert-butyl hydroperoxide, tert-butyl hydroperoxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, and lauroyl peroxide Examples thereof include thermal polymerization initiators such as peroxides.

  Examples of the photopolymerization initiator include diethoxyacetophenone, 2,2-dimethoxy-1,2-diphenylethane-1-one, 1-hydroxy-cyclohexyl-phenyl-ketone, 4- (2-hydroxyethoxy) phenyl- (2 -Hydroxy-2-propyl) ketone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 (Irgacure 369: manufactured by BASF Japan Ltd.), 2-hydroxy-2-methyl-1-phenyl Acetophenones such as propan-1-one, 2-methyl-2-morpholino (4-methylthiophenyl) propan-1-one, and 1-phenyl-1,2-propanedione-2- (o-ethoxycarbonyl) oxime Or ketal photopolymerization initiator, benzoin, benzoin methyl ether, benzo Benzoin ether photopolymerization initiators such as ethyl ether, benzoin isobutyl ether, and benzoin isopropyl ether, benzophenone, 4-hydroxybenzophenone, methyl o-benzoylbenzoate, 2-benzoylnaphthalene, 4-benzoylbiphenyl, 4-benzoylphenyl Benzophenone-based photopolymerization initiators such as ether, acrylated benzophenone, and 1,4-benzoylbenzene, 2-isopropylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, and 2,4 -Thioxanthone photopolymerization initiators such as dichlorothioxanthone are included.

  Other photopolymerization initiators include ethyl anthraquinone, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, bis (2,4,6-trimethylbenzoyl) phenylphosphine Oxide (Irgacure 819: manufactured by BASF Japan), bis (2,4-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide, methylphenylglyoxyester, 9,10-phenanthrene, acridine compound, Examples include triazine compounds and imidazole compounds. Moreover, what has a photopolymerization acceleration effect can also be used individually or in combination with the said photoinitiator. Examples include triethanolamine, methyldiethanolamine, ethyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl (2-dimethylamino) benzoate, and 4,4′-dimethylaminobenzophenone.

  The polymerization initiator used for the surface protective layer is preferably a photopolymerization initiator, preferably an alkylphenone compound and a phosphine oxide compound, and more preferably an initiator having an α-hydroxyacetophenone structure or an acylphosphine oxide structure. preferable.

These polymerization initiators may be used alone or in combination of two or more.
The content of the polymerization initiator is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass with respect to 100 parts by mass of the crosslinkable polymerizable compound.

(3.3) Lubricant Particles, etc. In addition to these, the surface protective layer may contain lubricant particles, an antioxidant and the like as necessary.
As the lubricant particles, for example, fluorine atom-containing resin particles can be added.
Examples of the fluorine atom-containing resin particles include tetrafluoroethylene resin, trifluorinated ethylene chloride resin, hexafluoroethylene chloride propylene resin, vinyl fluoride resin, vinylidene fluoride resin, ethylene difluoride dichloride resin, and these It is preferable to select one or two or more types from among the copolymers, and tetrafluoroethylene resin and vinylidene fluoride resin are particularly preferable.

(3.4) Polymerization reaction of the surface protective layer In the polymerization reaction of the surface protective layer, the coating film is irradiated with actinic rays to generate radicals and polymerize, and the cross-linking by cross-linking reaction between molecules and within the molecule. It is preferable to form and cure to produce a cured resin.
The active ray is preferably light such as ultraviolet light or visible light, or an electron beam, and ultraviolet light is particularly preferred from the standpoint of ease of use.

As the ultraviolet light source, any light source that generates ultraviolet light can be used without limitation.
For example, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultrahigh-pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, a flash (pulse) xenon, or an ultraviolet LED can be used.
Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 1 to 20 mJ / cm ² , preferably 5 to 15 mJ / cm ² . The output voltage of the light source is preferably 0.1 to 5 kW, and particularly preferably 0.5 to 3 kW.

  As an electron beam source, there is no particular limitation on the electron beam irradiation apparatus, and generally, an electron beam accelerator for electron beam irradiation is a curtain beam type that is relatively inexpensive and can provide a large output. Used. The acceleration voltage during electron beam irradiation is preferably 100 to 300 kV. The absorbed dose is preferably 0.005 Gy to 100 kGy (0.5 rad to 10 Mrad).

  The irradiation time of the active ray is a time for obtaining the necessary irradiation amount of the active ray, specifically 0.1 seconds to 10 minutes is preferable, and 1 second to 5 minutes is more preferable from the viewpoint of polymerization efficiency or work efficiency. It is said.

In the formation of the surface protective layer, the surface protective layer can be subjected to drying treatment before and after irradiation with active rays and during irradiation with active rays, and the timing of drying can be appropriately selected in combination with the irradiation conditions of active rays. .
The drying conditions for the surface protective layer can be appropriately selected depending on the type of solvent used in the coating solution, the layer thickness of the surface protective layer, and the like.
The drying temperature is preferably room temperature to 180 ° C, particularly preferably 80 to 140 ° C. The drying time is preferably 1 to 200 minutes, particularly preferably 5 to 100 minutes. By drying the surface protective layer under the above drying conditions, the amount of solvent contained in the surface protective layer can be controlled in the range of 20 ppm to 75 ppm.

  By providing the surface protective layer on the photosensitive layer as described above, it is possible to increase the hardness of the surface of the photoreceptor, improve the wear resistance, and improve the durability.

[Dip coater (20)]
As shown in FIG. 3, the dip coating apparatus 20 is an apparatus that forms a coating film on the member to be coated 40 by a dip coating method, and mainly includes a coating tank 22, a temporary storage tank 24, a supply tank 26, and a pump 28. Yes.
A coating solution 30 for forming a coating film on the member to be coated 40 is stored in the coating tank 22. A member to be coated 40 is immersed in the coating tank 22. The temporary storage tank 24 is a layer that temporarily receives the coating liquid 30 overflowing from the coating tank 22. The supply tank 26 is a layer for supplying the coating liquid 30 to the coating tank 22. The pump 28 is provided between the coating tank 22 and the supply tank 26.
According to the dip coating apparatus 20, when the member 40 to be coated is immersed in the coating liquid 30 in the coating tank 22, the coating liquid 30 in the coating tank 22 overflows from the coating tank 22 to the temporary storage tank 24 and is supplied to the supply tank 26. And is supplied from the supply tank 26 to the coating tank 22 by the pump 28. That is, the coating liquid 30 in the coating tank 22 circulates through these layers in the order of the coating tank 22 → the temporary storage tank 24 → the supply tank 26 → the coating tank 22, and the coating target member 40 is immersed. Even so, the liquid level of the coating liquid 30 in the coating tank 22 is controlled so as not to fluctuate.

[Method for producing coated film of photoreceptor]
In the manufacturing method of the coating film of the photoreceptor, the dip coating apparatus 20 shown in FIG. 3 is basically used.
The manufacturing method of the coating film of the photoreceptor is mainly as shown in FIG.
(I) Step S1 of preparing the member to be coated 40;
(Ii) Step S2 for plunging into the coating liquid 30 in the coating tank 22 and immersing it while rotating the member to be coated 40;
(Iii) Step S3 for pulling up and applying the member to be coated 40 from the coating liquid 30 in the coating tank 22, and
It has.
Such a method for producing a coated film of a photoreceptor can be applied to the formation of any of the undercoat layer 2, the charge generation layer 4, the charge transport layer 5 and the surface protective layer 6, and preferably the undercoat layer. 2 or the charge generation layer 4 is formed, and more preferably, the charge generation layer 4 is formed. Each layer of the undercoat layer 2, the charge generation layer 4, the charge transport layer 5 or the surface protective layer 6 is an example of a coating film.

In the preparation step S1 of (i), the application target member 40 is prepared.
The “coating member 40” is an object on which a coating film is formed, and here, the object is a support 1 or an object in which either the undercoat layer 2 or the photosensitive layer 3 is formed. Become.
That is, when the undercoat layer 2 is formed, the support 1 becomes the member to be coated 40 and the undercoat layer 2 becomes the coating film.
When the charge generation layer 4 is formed, the support 1 on which the undercoat layer 2 is formed becomes the member to be coated 40, and the charge generation layer 4 becomes the coating film.
When the charge transport layer 5 is formed, the support 1 on which the undercoat layer 2 and the charge generation layer 4 are formed serves as a member to be coated 40, and the charge transport layer 5 serves as a coating film.
When the surface protective layer 6 is formed, the support 1 on which the undercoat layer 2, the charge generation layer 4, and the charge transport layer 5 are formed becomes the coated member 40, and the surface protective layer 6 becomes the coating film.

  In the dip dipping step S2 of (ii) to the pulling up coating step S3 of (iii), the undercoat layer 2 is formed on the support 1 or the charge generation layer 4 is formed on the undercoat layer 2 as a coating film. Alternatively, the charge transport layer 5 can be formed on the charge generation layer 4, or the surface protective layer 6 can be formed on the charge transport layer 5.

In particular, in the rush immersion step S2 of (ii), as shown in FIG. 3, the member to be coated 40 is rushed into the coating liquid 30 in the coating tank 22 while rotating.
In such a case, the rotation speed of the coated surface is set to 100 to 400 mm / sec (seconds), and the entry speed is set to 25 to 100 mm / sec (seconds).
The “rotation speed of the coated surface” is a speed at which the coated surface moves along the rotation direction.
If the rotational speed is less than 100 mm / sec, there is a possibility of entraining bubbles, although it is within a range where there is no problem in manufacturing. When the rotation speed exceeds 400 mm / sec, the rotation speed is high and the load applied to the dip coating apparatus 20 is large. When the rush speed is less than 25 mm / sec, the rush speed is slow and the production speed is delayed. When the rush speed exceeds 100 mm / sec, the rush speed is fast and the load applied to the dip coating apparatus 20 is large.
According to such conditions, a coating film can be formed on the member to be coated 40 while using existing facilities without investing in new facilities mainly due to the relationship between the apparatus load and the production speed.

  Such conditions can be applied to the case of forming any of the undercoat layer 2, the charge generation layer 4, the charge transport layer 5 and the surface protective layer 6. Of course, for each layer (coating liquid 30) to be formed, the rotation speed and the entry speed of the surface to be coated may be appropriately changed within the numerical range.

  About the conditions of the coating liquid 30, normally, the temperature of the coating liquid 30 is preferably set at 20 to 50 ° C., and the viscosity of the coating liquid 30 is set at 1 to 800 mPa · sec.

  In the (iii) pull-up coating step S3, unlike the inrush dipping step S2 in (ii), it is preferably not rotated to make the thickness of the coating film uniform during the pull-up coating.

According to the above-described embodiment, since the member to be coated 40 is caused to enter the coating liquid 30 in the coating tank 22 while rotating, the piercing direction (vertical direction) of the member to be coated 40 and the direction to be coated are applied to the member to be coated 40. Inhibiting force for preventing air bubbles from being entrained at the time of entry and immersion of the member to be coated 40 in two directions, ie, a rotation direction (circumferential direction) about the axis of the member 40, or a centrifugal force for removing the entrained air bubbles It takes.
Therefore, it is possible to prevent air bubbles from being involved in the stage before the member to be coated 40 is immersed in the coating liquid 30 in the coating tank 22, and the member 40 to be coated is immersed in the coating liquid 30 in the coating tank 22. Even at the stage of making it, the entrained bubbles can be removed afterwards, and as a result, coating film defects caused by the bubbles can be suppressed.

(1) Production of Photoreceptor Sample (1.1) Support A surface of a cylindrical aluminum support having a diameter of 60 mm was cut at Rt = 1.0 μm to prepare a conductive support.

(1.2) Undercoat layer A dispersion having the following composition was allowed to stand overnight, and then filtered (filter; using a lysh mesh 5 μm filter manufactured by Nippon Pole Co., Ltd.) to prepare an undercoat layer coating solution.
Using a sand mill as a disperser, dispersion was performed for 10 hours.
Using the coating solution, an undercoat layer was formed on the conductive support by a dip coating method so that the layer thickness after drying was 1.5 μm.

Binder: Polyamide resin DAIAMID X4685 (manufactured by Daicel-Evonik)
100 parts by mass Inorganic fine particles: Titanium oxide SMT500SAS (manufactured by Teika) 300 parts by mass Solvent: ethanol 1440 parts by mass
360 parts by weight of 1-propanol

(1.3) Charge Generation Layer The following raw materials were mixed and dispersed for 10 hours using a sand mill to prepare a charge generation layer coating solution.
Thereafter, the coated member is rushed into the coating solution under the rotational speed and rushing speed conditions shown in Table 1 and dip coated at a pulling rate of 8 mm / sec. Then, a charge generation layer having a dried layer thickness of 0.3 μm was formed.
In this step, the temperature of the charge generation layer coating solution was set to 33 ° C., the viscosity of the charge generation layer coating solution was set to 5 mPa · sec, and the temperature of the member to be coated was set to 35 ° C.

Charge generation material: Y-TiPh (Titanyl phthalocyanine pigment (it is a titanyl phthalocyanine pigment having a maximum diffraction peak at a position of at least 27.3 ° in Cu-Kα characteristic X-ray diffraction spectrum measurement and has a sufficiently large absorption at 780 nm)) Part by mass Binder: Polyvinyl butyral resin (# 6000-C: manufactured by Denki Kagaku Kogyo Co., Ltd.)
10 parts by mass Solvent: 700 parts by mass of t-butyl acetate
4-Methoxy-4-methyl-2-pentanone 300 parts by mass

(1.4) Charge Transport Layer The following raw materials were mixed and dissolved to prepare a charge transport layer coating solution.
This coating solution was applied onto the charge generation layer by a dip coating method to form a charge transport layer having a layer thickness of 28 μm after drying.

Charge transport material: 150 parts by mass of CTM-A Binder: Polycarbonate (FPC6535A: manufactured by Mitsubishi Gas Chemical Company)
300 parts by mass Antioxidant: Irganox 1010 (manufactured by BASF Japan) 6 parts by mass Solvent: 1500 parts by mass of tetrahydrofuran
375 parts by mass of toluene Additive: Silicone oil (KF-96: manufactured by Shin-Etsu Chemical Co., Ltd.) 0.25 parts by mass

  The structural formulas of the charge generation material (Y-TiPh) and the charge transport material (CTM-A) used above are shown below.

From the above process, a sample of the photoreceptor was manufactured.
In this example, nine samples 1 to 9 shown in Table 1 were prepared by changing the rotation speed and rush speed of the coated surface or setting the presence or absence of rotation when forming the charge generation layer. Manufactured.

(2) Evaluation of photoconductor sample When fine bubbles are involved in the formation of the charge generation layer, the bubbles are present on the coating surface and then float free from the coating surface. In the charge generation layer, a white spot is formed in a thin irregular line. In such a case, in the image (biz-hub C6500 Konica Minolta MFP), the halftone image is blank. These coating defect portions were compared with an appearance inspection apparatus, and the occurrence of defects was detected.
Using a light irradiation line sensor image processing device (SCANTEC-7000, manufactured by Nagase Sangyo Co., Ltd.) as an appearance inspection device, a bubble generation frequency in 10,000 (bubbles were generated among 10,000 photoconductor samples. Number).
Table 1 shows the measurement results and the evaluation results. In Table 1, the evaluation criteria of ◎, ○, Δ, × are as follows, and “Cp” in the evaluation criteria is the process capability.
A: Less than 0.01% (Cp ≧ 1.30)
○: 0.01% or more and less than 0.27% (1.00 ≦ Cp <1.30)
Δ: 0.27% or more and less than 1.00% (0.86 ≦ Cp <1.00)
X: 1.00% or more (Cp <0.86)

(3) Summary As shown in Table 1, when Samples 1 to 7 and Samples 8 to 9 were compared, the former samples 1 to 7 had a significantly low bubble generation frequency and good results.
For this reason, in order to suppress coating film defects caused by bubbles, it is useful to immerse the member to be coated (here, the support on which the undercoat layer is formed) into the coating liquid while rotating. I understood.
From comparison results between Samples 1 to 5 and 7 and Sample 6, it was found that it is useful to set the rotation speed of the coated surface to 100 to 400 mm / sec.
In addition, although a good result was obtained with Sample 5, the rush speed exceeded 100 mm / sec and the load applied to the dip coating apparatus was considered to be large, so the rush speed should be 25 to 100 mm / sec. It was.

(1) Preparation of Photoreceptor Sample (1.1) Support A conductive support similar to that in Example 1 was prepared.

(1.2) Undercoat layer A dispersion of the following composition was diluted twice with the same solvent, and allowed to stand overnight and then filtered (filter; using a lymesh 5 μm filter manufactured by Nihon Pall) to prepare an undercoat layer coating solution. did. Dispersion was performed for 6 hours using a sand mill as a disperser.
Thereafter, the coated member is plunged into the coating solution while rotating the coated member under the rotational speed and rushing speed conditions described in Table 2, and dip coated at a pulling speed of 7 mm / sec. An undercoat layer having a thickness of 1.5 μm after drying was formed thereon.
In this step, the temperature of the undercoat layer coating solution was set to 26 ° C., the viscosity of the undercoat layer coating solution was set to 80 mPa · sec, and the temperature of the member to be coated was set to 30 ° C.

Binder: Polyamide resin CM8000 (manufactured by Toray Industries, Inc.) 80 parts by mass Inorganic fine particles: Titanium oxide SMT500SAS (manufactured by Teika) 300 parts by mass Solvent: 1000 parts by mass of methanol
200 parts by mass of 1-propanol

(1.3) Charge generation layer and charge transport layer The charge generation layer was formed by dip coating after rotating entry under the same conditions as Sample 2 of Example 1 (see Table 1). Thereafter, a charge transport layer was formed in the same manner as in Example 1 to produce a sample of the photoreceptor.
In this example, at the time of forming the undercoat layer, whether or not to rotate was set, and two types of samples 11 to 12 shown in Table 2 were manufactured.

(2) Evaluation of photoconductor sample When bubbles are involved during the formation of the undercoat layer, local thin film portions are generated in the undercoat layer due to the floating of the bubbles, and locally dark portions are generated in the upper charge generation layer. To do. In such a case, a black dot appears in the white image on the image (the same multifunction machine as above). This was compared with the same appearance inspection apparatus as in Example 1 to detect the occurrence of defects. Evaluation criteria are in accordance with Example 1.

(3) Summary As shown in Table 2, when sample 11 and sample 12 were compared, the former sample 11 had a remarkably low bubble generation frequency and good results.
For this reason, even when the undercoat layer is formed, in order to suppress coating film defects caused by bubbles, it is useful to immerse the member to be coated (here, the support) into the coating solution while rotating it. I found out.

DESCRIPTION OF SYMBOLS 1 Support body 2 Undercoat layer 3 Photosensitive layer 4 Charge generation layer 5 Charge transport layer 6 Surface protective layer 7 Metal oxide fine particle 10 Photoconductor 20 Immersion coating apparatus 22 Coating tank 24 Temporary storage tank 26 Supply tank 28 Pump 30 Coating liquid 40 To-be-coated member 100 Support surface 102 Lower end of coating film

Claims (3)

A step of preparing a cylindrical coated member;
E Bei and a step of immersing is plunged into the coating solution while rotating the object to be coated member,
In the step of preparing the member to be coated,
Preparing a support or a support on which an undercoat layer is formed as the coated member,
In the step of immersing the member to be coated into the coating liquid,
An undercoat layer is formed on the support, or an electrode is formed on the undercoat layer already formed on the support.
When forming the load generating layer, the rotational speed of the coated surface is 100 to 400 mm / sec, the rush speed is 25 to 100 mm / sec, and
The method for producing a coating film on an electrophotographic photosensitive member according to claim 1, wherein the coating liquid has a viscosity of 1 to 800 mPa · sec at a temperature of 20 to 50 ° C. 2. The method for producing a coating film for an electrophotographic photosensitive member according to claim 1, wherein the coating solution for the charge generation layer contains a titanyl phthalocyanine pigment. The method for producing a coating film for an electrophotographic photosensitive member according to claim 1, wherein the coating solution for the undercoat layer contains a polyamide resin.

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