JP4458080B2 - Electrophotographic photoreceptor - Google Patents

Description

  The present invention relates to a method for producing an electrophotographic photoreceptor. Specifically, the present invention relates to a method for producing an electrophotographic photosensitive member using a coating solution for an electrophotographic photosensitive member that has the effect of significantly extending the life of the coating solution without impairing sensitivity and durability.

  In recent years, electrophotographic technology has been widely used and applied not only in the field of copying machines but also in the field of various printers because of its immediacy and high quality images. Photoconductors, the core of electrophotographic technology, have been used as conventional photoconductive materials for inorganic photoconductors such as selenium, arsenic-selenium alloys, cadmium sulfide, and zinc oxide. A photoreceptor using an organic photoconductive material having advantages such as easy and easy manufacture has been developed. As the organic photoreceptor, a so-called dispersion type photoreceptor in which a photoconductive fine powder is dispersed in a binder resin, and a laminate type photoreceptor in which a charge generation layer and a charge transfer layer are laminated are known.

  Multilayered photoreceptors can be obtained by combining highly efficient charge generating materials and charge transfer materials to obtain highly sensitive photoreceptors, and having a wide range of materials and a highly safe photoreceptor. In addition, since the productivity of coating is high and relatively advantageous in terms of cost, the possibility of becoming the mainstream of photoconductors is high, and they have been developed and put into practical use. However, the multi-layer photoreceptor that is currently in practical use is inferior to the inorganic photoreceptor in terms of durability. One of the factors that determine the durability is physical characteristics. In other words, the load varies depending on the development with toner, the friction with paper, and the method, but there is a defect that wear and surface scratches are likely to occur due to a practical load such as friction with a cleaning member. At present, the printing performance is limited. In general, a charge transfer layer is subjected to such a load in the case of a laminated type photoreceptor. The charge transfer layer is usually composed of a binder resin and a charge transfer agent, and it is the binder polymer that substantially determines the strength. However, the amount of the charge transfer agent doped is so large that it does not have sufficient mechanical strength. . In addition, when used in a higher-speed electrophotographic process, in addition to high sensitivity and long life, it is also necessary to have good responsiveness because the time from exposure to development is shortened. . It is known that the responsiveness of the photoreceptor is governed by the charge transfer layer, particularly the charge transfer agent, but is greatly changed by the binder polymer.

  Conventional binder polymers for charge transfer layers include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, thermoplastic resins such as polycarbonate, polyester, polysulfone, phenoxy, epoxy, and silicone resins, and various types. These thermosetting resins have been used. Among the various binder polymers, the polycarbonate resin has a relatively excellent performance, and various polycarbonate resins have been developed and put into practical use. For example, a bisphenol P type polycarbonate (see Patent Document 1), a bisphenol Z type polycarbonate (Patent Document 2), a copolymer type polycarbonate of bisphenol P and bisphenol A (Patent Document 3) may be used as a binder polymer. Each is disclosed.

  On the other hand, the technology of an electrophotographic photosensitive member using a polyarylate resin having the following structure marketed under the trade name “U-polymer” as a binder has been started, and it is disclosed that sensitivity is particularly excellent compared to polycarbonate. (Patent Document 4)

Further, there is disclosed an electrophotographic carrier and a charge imparting member characterized by containing polyarylate (aromatic polyester) having a specific structure using only terephthalic acid as a dicarboxylic acid component (Patent Document 5).
JP 50-98332 A JP 59-71057 A JP 59-184251 JP-A-56-135844 JP 7-333911 A

  However, when the currently used polycarbonate resin is used in the electrophotographic process, it is still often insufficient in terms of abrasion resistance, scratch resistance, responsiveness, adhesion to the substrate, and the like. In addition, although the commercially available polyarylate resin “U-polymer” shows some improvement in wear resistance and sensitivity, the stability of the coating solution is extremely poor and solidifies in about one week and becomes unapplicable. . Further, when a polyarylate having a specific structure using only terephthalic acid is used for the dicarboxylic acid component disclosed in Patent Document 5, although it dissolves easily in halogenated hydrocarbons, tetrahydrofuran, 1,4-dioxane Such an environmentally friendly non-halogen solvent has low solubility and the stability of the liquid is also poor. Therefore, the present situation is that a binder polymer that is more excellent in abrasion resistance, is readily soluble in a non-halogen solvent, and has excellent liquid stability is desired.

Therefore, as a result of detailed studies on the binder polymer used in the photosensitive layer, the present inventors have obtained sufficient mechanical characteristics by using a polyarylate resin having a specific structure as the binder resin, and are suitable for non-halogen solvents. The present invention was found to show high solubility and the stability of the coating solution was remarkably improved.
Specifically, the subject matter of the present invention Oite the electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer has a charge transport layer and the charge generation layer, 50 [mu] m charge transport layer has a thickness of 10μm or more And a resin having a polyarylate structure represented by the following general formula (1) (excluding a resin having a terminal structure terminated with a fluorinated alkyl group), and a non-halogen solvent as a solvent by applying and drying a coating liquid using, in the electrophotographic photosensitive member and forming the charge transfer layer.

(In the formula, R ¹ represents an alkyl group having 1 to 4 carbon atoms, and R ² , R ³ and R ⁴ each independently represents a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. (The value of m / (m + n) is 0.3 or more and 1.0 or less)

The polyarylate resin of the present invention is excellent in solubility in organic solvents, and exhibits high solubility in non-halogen solvents such as 1,4-dioxane and tetrahydrofuran. Preparation of a coating solution using these solvents Therefore, there are few environmental and safety issues.
Further, when the coating solution prepared with a non-halogen solvent is stored at normal temperature, it can be stored for 1 month or more without solidification, so that the photoreceptor can be stably produced without cost.

  In addition, the photoconductor using the polyarylate resin of the present invention is inferior in mechanical characteristics and electrical characteristics, particularly sensitivity, as compared with a photoconductor using a conventional polycarbonate resin or “U-polymer”.

The present invention will be described in detail below.
The resin of the present invention is used for an electrophotographic photoreceptor and is provided on a conductive support of the photoreceptor. As a conductive support, a metal material such as aluminum, stainless steel, copper, nickel, etc., a polyester film provided with a conductive layer such as aluminum, copper, palladium, tin oxide, indium oxide on the surface, phenol resin pipe, paper An insulating support such as a tube is used.

A photosensitive layer is provided on such a conductive support, and a known barrier layer which is usually used may be provided therebetween. As the barrier layer, for example, polyamide, polyurethane, cellulose, nitrocellulose, sodium caseinate, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylamide, aluminum anodized film, or the like is used. Usually, the film thickness of the barrier layer is 0.1 μm to 20 μm. The photosensitive layer in which the resin of the present invention is used may be either a dispersion type or a lamination type. As the photoconductive material in the case of the dispersion type, selenium and its alloys, cadmium sulfide, other inorganic photoconductors, phthalocyanine pigments, azo pigments, quinacridone pigments, indigo pigments, perylene pigments, polycyclic quinone pigments, anthanthrone pigments, Organic pigments such as benzimidazole pigments can be used, and these fine particles and charge transfer materials described later are used in a form bound with the polyarylate resin of the present invention. In this case, the photoconductive particles are preferably used in an amount of 1 to 50 parts by weight and the charge transfer material in an amount of 30 to 150 parts by weight with respect to 100 parts by weight of the polyarylate resin. The film thickness is usually 5 to 50 μm, preferably 10 to 30 μm. In the case of a multilayer photoreceptor, the above-mentioned various photoconductive materials can be used as the charge generation material used in the charge generation layer, and these fine particles are used as the polyarylate resin, polyvinyl acetate, polyacrylate, polymethacrylate of the present invention. It is used in a form bound with various binder resins such as acid ester, polycarbonate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester, and cellulose ether. The use ratio in this case is used in the range of 30 to 500 parts by weight with respect to 100 parts by weight of the binder resin, and the film thickness is usually 0.1 μm to 1 μm, preferably 0.15 μm to 0.6 μm.

  As the charge transfer material of the charge transfer layer, electron withdrawing substances such as 2,4,7-trinitrofluorenone and tetracyanoquinodimethane, carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, And electron donating substances such as heterocyclic compounds such as aniline derivatives, hydrazone compounds, aromatic amine derivatives, stilbene derivatives, or polymers having groups composed of these compounds in the main chain or side chain. The charge transfer layer is formed in such a form that these charge transfer materials are bound to the polyarylate resin of the present invention. In this case, the charge transfer material is used in an amount of 20 to 150 parts by weight, preferably 50 to 110 parts by weight, based on 100 parts by weight of the binder resin. The film thickness is 10 to 50 μm, preferably 15 to 45 μm. The charge transfer layer may contain additives such as known plasticizers, antioxidants, ultraviolet absorbers, and leveling agents in order to improve film formability, flexibility, and coatability.

Next, although the specific example is shown about the structure of the polyarylate resin in Claim 1, this invention is not limited to these specific examples. In the general formula (1), R ¹ represents an alkyl group having 1 to 4 carbon atoms, and R ² , R ³ , and R ⁴ each independently represent a hydrogen atom and an alkyl group having 1 to 4 carbon atoms. Specific examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, and tert-butyl group.

  In addition, for m and n, the value of m / (m + n) is 0.3 or more and 1.0 or less because the solubility in non-halogen solvents when the proportion of terephthalic acid is much larger than the proportion of isophthalic acid. This is because of a drastic decrease.

Hereinafter, the present invention will be described in more detail with reference to production examples, examples and comparative examples. In addition, this invention is not limited to the manufacturing method by the manufacturing example shown here.
Production Example 1 (Production Method of Polyarylate Resin A of Example 1)
To a 1 L Erlenmeyer flask was added sodium hydroxide (8.0 g), H ₂ O (800 ml), 2,2-bis (3-methyl-4-hydroxyphenyl) propane (25.66 g), benzyltriethylammonium chloride (1.37 g). ) Was weighed and dissolved by stirring. This alkaline aqueous solution was transferred to a 2 L reaction vessel and stirred vigorously, and dichloromethane (200 ml) was added. Separately, a solution of isophthalic acid chloride (10.15 g) and terephthalic acid chloride (10.15 g) dissolved in dichloromethane (100 ml) was immediately added. After stirring vigorously for 1 hour, the stirring was stopped and the organic layer was separated by standing. The organic layer was washed successively with 0.1N hydrochloric acid (800 ml), H ₂ O (800 ml), and H ₂ O (800 ml). . A white fibrous solid obtained by pouring the washed organic layer into methanol (4 L) was filtered off and dried to obtain the desired polyarylate resin A. The structure was confirmed by ¹ H-NMR. Moreover, the number average molecular weight of obtained polyarylate resin A; Mn was 22500, the weight average molecular weight; Mw was 67200 (Mn and Mw are polystyrene conversion values.). The structural formula is shown below.

Production Example 2 (Production Method of Polyarylate Resin B of Example 2)
Manufacture except that bisphenol in Production Example 1 was replaced with 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane (28.04 g) and the amount of benzyltriethylammonium chloride was replaced with (13.75 g). Performed as in Example 1. Mn of the obtained polyarylate resin B was 22500 and Mw was 64600 (Mn and Mw are both polystyrene equivalent values). The structural formula is shown below.

Production Example 3 (Production Method of Polyarylate Resin E of Comparative Example 3)
The same procedure as in Production Example 1 was conducted, except that bisphenol in Production Example 1 was replaced with 1,1-bis (4-hydroxyphenyl) cyclohexane (26.84 g). Mn of the obtained polyarylate resin E was 24400, Mw was 72100 (Mn and Mw are both polystyrene conversion values). The structural formula is shown below.

Example-1
10 parts by weight of a bisazo compound having the following structural formula was added to 150 parts by weight of 4-methoxy-4-methyl-2-pentanone, and pulverized and dispersed in a sand grind mill. The pigment dispersion obtained here was made of 100 parts of a 5% dimethoxyethane solution of polyvinyl butyral (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name # 6000-C) and phenoxy resin (trade name PKHH, manufactured by Union Carbide). In addition to 100 parts of a 5% dimethoxyethane solution, a dispersion having a solid content concentration of 4.0% was finally produced.

The dispersion thus obtained was applied on a polyethylene terephthalate film having aluminum deposited on the surface, and a charge generation layer was provided so that the dry film thickness was 0.21 g / mm ² .
Next, on this film, 95 parts by weight of the following hydrazone compound and

  1.5 parts by weight of a cyano compound having the following structure:

  As an antioxidant, 3 parts by weight of hindered phenol having the following structure:

After applying 0.03 parts by weight of silicone oil as a leveling agent and 100 parts by weight of polyarylate resin A polymerized in Preparation Example 1 in a mixed solvent of dioxane and tetrahydrofuran (referred to as coating liquid A), The film was dried at 125 ° C. for 25 minutes, and the charge transfer layer was provided so that the film thickness after drying was 21 μm. The photoreceptor thus obtained is referred to as a photoreceptor A.

Example-2
A coating solution B and a photoreceptor B were prepared in the same manner as in Example 1 except that the polyarylate resin B polymerized in Production Example 2 was used as a binder for the charge transfer layer.
Comparative Example-1
A coating solution C and a photoreceptor C were prepared in the same manner as in Example 1 except that the following polycarbonate resin C ("Iupilon E-2000" manufactured by Mitsubishi Gas Chemical Co., Ltd.) was used as a binder for the charge transfer layer.

Comparative Example-2
Except that polyarylate resin D shown below ("U-polymer" U-100 manufactured by Unitika) was used as a binder for the charge transfer layer, the same procedure as in Example 1 was carried out to prepare a coating solution D and a photoreceptor D. .

Comparative Example-3
In order to use 100 parts by weight of the polyarylate resin E polymerized in Production Example 3 as a binder for the charge transfer layer, an attempt was made to dissolve it in a mixed solvent of 466 parts by weight of tetrahydrofuran and 252 parts by weight of 1,4-dioxane. On the way, when the resin E was added up to 73 parts by weight, the entire solution was solidified in white, and the coating solution was not prepared.

The charge transfer layer coating solutions A to D prepared in Examples 1 and 2 and Comparative Examples 1 and 2 were sealed in a glass bottle and allowed to stand at room temperature to observe the liquid stability. The results are shown in Table 1.
Next, in order to examine the abrasion resistance of these photoconductors A to D, the photoconductor film was cut into a circle having a diameter of 10 cm and subjected to wear evaluation by a Taber abrasion test. The test conditions were 23 ° C., 50% RH atmosphere, using a wear wheel CS-10F, and the average value of weight loss after 250 g load and 100 rotations was compared. The results are shown in Table 2. The abrasion test was performed four times per sample, and the average value of three points excluding the initial value was used as the amount of abrasion of the sample. The smaller the wear amount, the better the wear resistance.

Further, in order to investigate the electric characteristics, the photoconductors A to D are mounted on a photoconductor characteristic measuring machine (model EPA-8100, manufactured by Kawaguchi Electric Co., Ltd.), and the aluminum surface is set so that the potential at the time of charging is 750 ± 20V. Then, after charging and charging, exposure and static elimination were performed, and half-exposure sensitivity E _1/2 at that time was measured. The results are shown in Table 2. The smaller the value of E1 _{/ 2,} the better the sensitivity.

  From the above, it can be seen that the coating solution for an electrophotographic photosensitive member using the polyarylate resin of the present invention is less likely to change with time and has performance comparable to conventional binders in terms of wear resistance and sensitivity. .

Claims (2)

In an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer has a charge generation layer and a charge transfer layer, and the charge transfer layer has a thickness of 10 μm or more and 50 μm or less, and a general formula (1 By applying and drying a coating solution containing a resin having a polyarylate structure shown in (1) except for a resin having a terminal structure terminated with a fluorinated alkyl group, and using a non-halogen solvent as a solvent. An electrophotographic photosensitive member, wherein the charge transfer layer is formed.

(In the formula, R ¹ represents a methyl group , and R ² , R ³ , and R ⁴ each independently represents a hydrogen atom or a methyl group . For m and n, the value of m / (m + n) is 0. .3 or more and 1.0 or less.)   An electrophotographic photoreceptor, wherein the charge transfer layer is formed by coating and drying the coating solution according to claim 1 containing a leveling agent.