JPH0331254B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a photoreceptor, and more particularly to a novel electrophotographic photoreceptor having a photosensitive layer containing a carrier-generating substance and a carrier-transporting substance. [Prior Art] Conventionally, photoreceptors having a photosensitive layer containing as a main component an inorganic photoconductor such as selenium, zinc oxide, cadmium sulfide, silicon, etc. have been widely known. However, these are not necessarily satisfactory in terms of properties such as thermal stability and durability, and furthermore, there are problems in manufacturing and handling. On the other hand, photoreceptors having a photosensitive layer containing an organic photoconductive compound as a main component are relatively easy to manufacture, inexpensive, easy to handle, and are generally more heat sensitive than selenium photoreceptors. It has many advantages such as excellent stability, and has attracted a lot of attention in recent years. Poly-N-vinylcarbazole is the most well-known such organic photoconductive compound, and a charge transfer complex formed from poly-N-vinylcarbazole and a Lewis acid such as 2,4,7-trinitro-9-fluorenone is Photoreceptors having a photosensitive layer as a main component have already been put into practical use. On the other hand, photoconductors are known that have a functionally separated photoconductor layer of a laminated type or a dispersion type in which the carrier generation function and the carrier transport function of the photoconductor are assigned to separate substances. A photoreceptor having a photosensitive layer consisting of a carrier generation layer consisting of a thin selenium layer and a carrier transport layer containing poly-N-vinylcarbazole as a main component has already been put into practical use. However, since poly-N-vinylcarbazole lacks flexibility, its coating is hard and brittle, and is prone to cracking and peeling. Therefore, photoreceptors using it have poor durability. If a plasticizer is added to improve this drawback, the residual potential will increase when subjected to the electrophotographic process, and as it is repeatedly used, the residual potential will accumulate and gradually cause fog in the copied image. It has the disadvantage of becoming. In addition, since low-molecular organic photoconductive compounds generally do not have film-forming ability, they are used in combination with any binder, and therefore the film can be formed by selecting the type and composition ratio of the binder used. Although it is preferable in that the physical properties or photosensitive characteristics can be controlled to a certain extent, the types of organic photoconductive compounds that have high compatibility with binders are limited, and in reality, photoreceptors, especially The reality is that there are not many materials that can be used in the construction of the photosensitive layer of an electrophotographic photoreceptor. For example, 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole described in U.S. Pat. No. 3,189,447 is usually preferred as a material for the photosensitive layer of an electrophotographic photoreceptor. Since it has low compatibility with the binder used, if it is mixed with a binder such as polyester or polycarbonate in the proportion required to obtain favorable electrophotographic properties to form a photosensitive layer, At temperatures above 50°C, oxadiazole crystals begin to precipitate, resulting in a disadvantage that electrophotographic properties such as charge retention and sensitivity deteriorate. On the other hand, the diarylalkane derivative described in U.S. Patent No. 3,820,989 does not usually have a problem with its compatibility with binders, but its stability against light is low, so it cannot be charged or exposed to light. When used in the construction of a photosensitive layer of a photoreceptor for repetitive transfer type electrophotography in which transfer is repeatedly performed, it has the disadvantage that the sensitivity of the photosensitive layer gradually decreases. Also, US Patent No. 3,274,000, Japanese Patent Publication No. 47-
36428 describes different types of phenothiazine derivatives, but all of them have the drawbacks of low photosensitivity and low stability during repeated use. The reality is that no carrier transport material has yet been found that has practically satisfactory characteristics for producing electrophotographic photoreceptors. [Object of the Invention] An object of the present invention is to provide a highly sensitive photoreceptor. Another object of the present invention is to provide an electrophotographic photoreceptor with high sensitivity and low residual potential. Another object of the present invention is that when used as a photoreceptor for electrophotography of a repetitive transfer type in which charging, exposure, development, and transfer steps are repeated, fatigue deterioration due to repeated use is small and stable characteristics can be maintained for a long time. An object of the present invention is to provide an electrophotographic photoreceptor that has excellent durability over a long period of time. [Structure of the Invention] As a result of intensive research to achieve the above object, the present inventors have discovered that the object can be achieved by using a specific phenothiazine derivative as a carrier transport material for a functionally separated photoreceptor. Heading: This completes the invention. The above object has been achieved by a photoreceptor characterized in that it has a photoreceptor layer containing a phenothiazine derivative represented by the following general formula on a conductive support. general formula In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are each a hydrogen atom,
Alkyl groups such as methyl group, ethyl group, t-butyl group, benzyl group, etc., alkoxy groups such as ethoxy group, 2-methoxyethoxy group, methoxy group, etc.
It represents a halogen atom, such as a bromine atom, a chlorine atom, a fluorine atom, etc., or an amino group, such as a dimethylamino group, a diethylamino group, an N-ethyl-N-benzylamino group, etc. m represents an integer of 0 or 1, n represents an integer of 1 or 2, and when n is 2
R ₂ may be a different group. If no substituent is specified, all hydrogen atoms are assumed to be bonded. That is, in the present invention, the carrier transport ability of the phenothiazine derivative represented by the above general formula is used to transport carriers in the photosensitive layer of a so-called functionally separated photoreceptor in which carrier generation and transport are performed using separate substances. By using it as a substance, it has excellent film properties, excellent electrophotographic properties such as charge retention, sensitivity, and residual potential, and has little fatigue deterioration even after repeated use, and the above properties do not change. It is possible to create an electrophotographic photoreceptor that can exhibit stable characteristics. Specific examples of the phenothiazine derivatives represented by the above general formula that are effective in the present invention include those having the following structural formula, but are not limited thereto. These compounds can be synthesized, for example, by the method described below or by a known method. Synthesis Example 1 Synthesis of Exemplified Compound A-(1) Mix 10 g of phenothiazine, 17 g of 4(p-methoxystyryl)iodobenzene, and 30 ml of nitrobenzene, and add 10 g of potassium carbonate and 0.2 g of copper powder.
The mixture was heated under reflux at 200°C for 15 hours. After the reaction, the solvent was removed by steam distillation, and the resulting precipitate was collected by filtration and separated and purified using a column (silica gel 200 mesh, developed with toluene). The obtained solid was recrystallized from ethyl acetate to obtain white crystals. Fixed by elemental analysis. Calculated value C79.56 H5.20 N3.44 S7.87 Actual value C79.62 H5.29 N3.50 S7.99 Yield 10.5g Yield 52% The above phenothiazine derivative can be used as a carrier transport substance and any carrier generating substance. In combination, an electrophotographic photoreceptor can be effectively constructed. Carrier generating substances used in the present invention include inorganic photoconductors such as selenium, selenium alloys and amorphous silicon, as well as organic dyes and pigments having carrier generating ability. Particularly preferred organic dyes/pigments here include polycyclic quinone pigments and monoazo dyes,
Examples include azo dyes such as bisazo dyes and trisazo dyes. The photoreceptor of the present invention can also be constructed by containing the phenothiazine derivative according to the present invention in the same layer as the carrier generating substance as described above; however, a carrier generating substance containing the carrier generating substance, It is particularly preferable to form a laminate with a carrier transport layer containing the above-mentioned phenothiazine derivative as a carrier transport substance. Since the phenothiazine derivative according to the present invention does not have film-forming ability, when it is used to form a photosensitive layer, it is preferably used together with a binder.
The preferred binder used in the present invention is a hydrophobic, high dielectric constant, electrically insulating film-forming polymer. Examples of such polymers include the following. B-(1) Polystyrene B-(2) Polyvinyl chloride B-(3) Polyvinylidene chloride B-(4) Polyvinyl acetate B-(5) Acrylic resin B-(6) Methacrylic resin B-(7) Polyester B -(8) Polycarbonate B-(9) Phenol formaldehyde resin These binders may be used alone or in combination of two or more types, or copolymers containing at least one type of monomer constituting the above-mentioned polymer. Although used as a binder, the binder used in the present invention is not limited to these. As shown in FIG. 1, FIG. 2, FIG. 3, and FIG. When the carrier transport layer 3 is provided adjacent to the layer and the photosensitive layer has a two-layer structure, a photoreceptor having the most excellent electrophotographic properties can be obtained.
As shown in the figure, a photoreceptor in which fine particles 7 of a carrier generating substance are dispersed in a photosensitive layer 6 containing a carrier transporting substance as a main component on a conductive support 1 via an intermediate layer 5 if necessary. can also be effectively used in the present invention. Here, when the photosensitive layer 4 has a two-layer structure, which of the carrier generation layer 2 and the carrier transport layer 3 is to be the upper layer is determined depending on whether the charging polarity is positive or negative. In other words, when used with negative charge,
It is advantageous for the carrier transport layer 3 to be the upper layer,
This is because the phenothiazine derivative of the present invention in the carrier transport layer is a substance that has a high ability to transport holes. Further, the carrier generation layer 2 constituting the photosensitive layer 4 having a two-layer structure is formed directly on the conductive support 1 or the carrier transport layer 3, or if necessary, an intermediate layer such as an adhesive layer or a barrier layer is provided. It can be formed on the top by the following method. (C-1) Vacuum deposition method (C-2) Method of dissolving the carrier-generating substance in a suitable solvent and applying it (C-3) Dispersing the carrier-generating substance using a ball mill, homomixer, sand mill, colloid mill, etc. A method of applying a dispersion obtained by forming fine particles in a medium and mixing and dispersing them with a binder if necessary.The thickness of the carrier generation layer 2 formed in this way is 0.01 to 5 microns. It is preferable that
More preferably, it is 0.05 to 3 microns. Further, the thickness of the carrier transport layer 3 can be changed as necessary, but it is usually preferably 5 to 30 microns. The composition ratio in this carrier transport layer 3 is 0.8 parts by weight of the carrier transport substance whose main component is the above-mentioned phenothiazine derivative.
The amount of the binder is preferably 10 parts by weight or less, but when forming the photosensitive layer 4 in which a fine powder carrier-generating substance is dispersed, the amount of the binder is 5 parts by weight or less per 1 part by weight of the carrier-generating substance. It is preferable to use Further, when the carrier generating layer 2 is configured as a dispersed type layer using a binder, it is preferable to use the binder in an amount of 5 parts by weight or less per 1 part by weight of the carrier generating substance. The conductive support 1 used in the construction of the photoreceptor of the present invention is a metal plate, or a conductive compound such as a conductive polymer or indium oxide, or a thin layer of a metal such as aluminum, palladium, or gold coated thereon. , paper, plastic laminate, etc. that have been made conductive by vapor deposition or lamination are used. Intermediate layer 5 such as adhesive layer or barrier layer
In addition to the high molecular weight polymer used as the binder, gelatin, casein, starch, polyvinyl alcohol, vinyl acetate, ethyl cellulose,
Organic polymeric substances such as carboxymethyl cellulose or aluminum oxide are used. The photoreceptor of the present invention has the above structure,
As is clear from the Examples described later, it has excellent charging characteristics, sensitivity characteristics, image characteristics, etc. Examples of the present invention will be specifically described below, but the embodiments of the present invention are not limited thereto. Example 1 Selenium was evaporated onto a conductive support consisting of a polyester film laminated with aluminum foil to form a carrier generating layer with a thickness of 0.5 microns. On top of that, 6 parts by weight of exemplified compound part A-(1) and polycarbonate "Panlite L-1250"
(manufactured by Teijin Chemicals) in 90 parts by weight of 1,2-dichloroethane, and this solution was applied to form a carrier transport layer so that the film thickness after drying was 11 microns. An electrophotographic photoreceptor of the present invention was then produced. The electrophotographic properties of this electrophotographic photoreceptor were measured by a dynamic method using an electrostatic copying paper tester "SP-428 model" (manufactured by Kawaguchi Denki Seisakusho Co., Ltd.). That is, the surface of the photosensitive layer of the photoreceptor is charged with a -
The surface potential V _A when charged at 6 KV for 5 seconds, then the amount of exposure required to attenuate the surface potential V _A by half by irradiating the photoreceptor with light from a tungsten lamp so that the illumination intensity on the photoreceptor surface is 35 lux. (Half exposure amount) E1/2 (lux・sec) and 30lux・
Surface potential (residual potential) after irradiation with an exposure dose of sec
V _R was calculated for each. The same measurement was repeated 100 times. The results are shown in Table 1.

[Table] As is clear from this table, the electrophotographic photoreceptor of the present invention has sufficient charge retention ability, high sensitivity, low residual potential, and maintains good characteristics even after repeated use. It has excellent physical properties. Comparative Example 1 Same as Example 1 except that 2,7-bisdimethylaminophenothiazine having the following structural formula was used instead of Exemplified Compound A-(1) as a carrier transport substance. A comparative photoreceptor was prepared. When this photoreceptor was measured in the same manner as in Example 1, the results shown in Table 2 were obtained.

[Table] As is clear from the above results, the comparative photoreceptor was significantly inferior in stability during repeated use compared to the photoreceptor of the present invention of Example 1. Examples 2 to 4 Same as Example 1 except that Exemplified Compounds A-(4), A-(6), and A-(8) were used instead of Exemplified Compound A-(1) as carrier transport substances. An electrophotographic photoreceptor of the present invention was prepared. The initial characteristics of these photoreceptors were measured in the same manner as in Example 1, and the results shown in Table 3 were obtained.

[Table] Example 5 Vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" was placed on a conductive support made of polyester film with aluminum vapor-deposited.
(manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.05 microns, and on top of that is dibromoanthrone "Monolite Red 2Y" (CI No. 59300 manufactured by ICI) 1
1.5 parts by weight of polycarbonate "Panlite L-1250" (manufactured by Teijin Chemicals) was dissolved in a dispersion obtained by adding 30 parts by weight of 1,2-dichloroethane to 30 parts by weight of 1,2-dichloroethane and dispersing with a ball mill, and then thoroughly mixed. A carrier generation layer was formed by applying the liquid so that the film thickness after drying was 2 microns. A coating solution prepared by dissolving 6 parts by weight of Exemplified Compound A-(2) and 10 parts by weight of polyester "Vylon 200" (manufactured by Toyo Boseki Co., Ltd.) in 90 parts by weight of 1,2-dichloroethane was applied onto the film after drying. A carrier transport layer was formed by coating to a thickness of 11 microns, thereby forming an electrophotographic photoreceptor of the present invention. When this photoreceptor was measured in the same manner as in Example 1, the fourth
Obtained the results in the table.

[Table] Comparative Example 2 A comparative photoreceptor was prepared in the same manner as in Example 5, except that a phenothiazine derivative having the following structural formula was used in place of Exemplary Compound A-(2) as a carrier transport material. When this comparative photoreceptor was measured in the same manner as in Example 1, the results shown in Table 5 were obtained.

[Table] As is clear from the above results, the comparative photoreceptor was significantly inferior to the photoreceptor of the present invention in sensitivity and repeated stability. Comparative Example 3 A comparative photoreceptor was prepared in the same manner as in Example 1, except that a compound having the following structural formula was used as a carrier transport material.

[Table] Comparative Example 4 A comparative photoreceptor was prepared in the same manner as in Example 1, except that a compound having the following structural formula was used as a carrier transport material.

〔Effect of the invention〕

According to the present invention, it is possible to obtain an excellent photoreceptor that has high sensitivity, extremely stable characteristics during repeated use, and has no problems such as toxicity.

[Brief explanation of the drawing]

1 to 6 are cross-sectional views showing examples of the mechanical structure of the electrophotographic photoreceptor of the present invention, respectively. 1... Conductive support, 2... Carrier generation layer,
3... Carrier transport layer, 4... Photosensitive layer, 5... Intermediate layer, 6... Layer containing a carrier transport substance, 7
...Carrier generating substance.

Claims (1)

[Scope of Claims] 1. A photoreceptor comprising a photosensitive layer containing a phenothiazine derivative represented by the following general formula on a conductive support. general formula [In the formula, R ₁ , R ₂ , R ₃ , and R ₄ are each a hydrogen atom, an alkyl group, an alkoxy group, a halogen atom,
or represents an amino group, m represents an integer of 0 or 1, and n represents an integer of 1 or 2. 2. The photoreceptor according to claim 1, wherein the photosensitive layer is constituted by a laminate of a carrier generation layer containing a carrier generation substance and a carrier transport layer containing a carrier transport substance.