JPS6136225B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a photoreceptor for electrophotography, and more specifically, a layer containing a substance (hereinafter referred to as a charge-generating substance) that generates charge carriers when irradiated with light (hereinafter referred to as a charge-generating substance).
This is called the charge generation layer. ) and the charge generation layer accepts the generated charge carriers and transports them (hereinafter referred to as
It is called a charge transport material. ) (hereinafter referred to as a charge transport layer). Conventionally, there have been inorganic photoreceptors for electrophotography, such as those using selenium and its alloys, or photoreceptors with dye-sensitized zinc oxide dispersed in a binder resin, and organic photoreceptors. So,
A typical example is one using a charge transfer complex of 2,4,7-trinitro-9-fluorenone (hereinafter referred to as TNF) and poly-N-vinylcarbazole (hereinafter referred to as PVK). be. but,
Although these photoreceptors have many advantages, it is also true that they also have various disadvantages. For example, the currently widely used selenium photoreceptor has difficult manufacturing conditions and high manufacturing costs, is difficult to process into a belt shape due to its lack of flexibility, and is sensitive to heat and mechanical shock. Therefore, care must be taken when handling it. Zinc oxide photoreceptors are low in cost because they can be manufactured by applying inexpensive zinc oxide to a support, but they generally have low sensitivity, poor surface smoothness, hardness, tensile strength, and durability. It has mechanical drawbacks such as friction,
As a photoreceptor for a plain paper copying machine, which is normally used repeatedly, there are many problems such as durability. Also, TNF and
Photoreceptors using PVK charge transfer complexes have low sensitivity and are unsuitable as photoreceptors for high-speed copying machines. In recent years, extensive research has been carried out to eliminate the drawbacks of these photoreceptors, and in particular, various organic photoreceptors have been proposed. Among them, a laminated photoreceptor in which a thin film of organic pigment is formed on a conductive support (charge generation layer), and a layer mainly composed of a charge transport substance (charge transport layer) is formed on top of this, is different from conventional organic-based photoreceptors. Compared to photoconductors, photoconductors are attracting attention as photoconductors for plain paper copying machines because they generally have higher sensitivity and stable charging properties, and some of them are in practical use. Conventional laminated photoreceptors of this type include (1) those using perylene derivatives in the charge generation layer and oxadiazole derivatives in the charge transport layer (U.S. Patent No.
3871882), (2) a charge generation layer coated with chlordiane blue using an organic amine as a solvent, and a charge transport layer using a pyrazoline derivative (Japanese Patent Laid-Open No. 52-55643) (3) As a charge generation layer, a triphenylamine trisazo pigment (see Japanese Patent Application Laid-Open No. 53-132347) is dispersed in a dispersion medium such as tetrahydrofuran. Known methods include those coated with a dispersion liquid and using 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole or TNF in the charge transport layer. However, although conventional photoreceptors of this type have many advantages, they also have various drawbacks. For example, although the photoreceptor using the perylene derivative and oxadiazole derivative shown in (1) above may have no practical problems, it has low sensitivity for use in higher-speed copying machines and the like. Additionally, the perylene derivative, which is the charge-generating material that controls the spectral sensitivity of this photoreceptor, has the disadvantage of not being absorbent over the entire visible range, making it unsuitable as a photoreceptor for color copying machines. . Furthermore, although the photoreceptor using chlordiane blue and pyrazoline derivatives shown in (2) has relatively good sensitivity in our experiments, it is generally not used as a coating solvent for forming a charge generation layer. It is necessary to use a difficult organic amine (for example, ethylenediamine), which has many disadvantages in producing a photoreceptor. The photoreceptor shown in (3) was proposed by the present inventors, and these photoreceptors use a pigment dispersion (if necessary) in which fine pigment particles are dispersed in an organic solvent as a method of forming a charge generation layer. Although it has the advantage of being easily formed by coating a support with a binder resin (a binder resin may be added thereto), the sensitivity is somewhat low, making it unsatisfactory as a photoreceptor for high-speed copying machines. On the other hand, the demand for photoreceptors for laser printers has increased in recent years, and the development of highly sensitive photoreceptors in the wavelength range of semiconductor lasers is particularly desired.
The photoreceptor described above has extremely low sensitivity to these semiconductor lasers and cannot be put to practical use. The mechanism of electrostatic latent image formation in this type of laminated photoreceptor is that when the photoreceptor is charged and then irradiated with light, the light passes through a transparent charge transport layer and is absorbed by the charge generation substance in the charge generation layer. , the charge-generating substance that absorbs light generates charge carriers, and these charge carriers are injected into the charge transport layer and move in the charge transport layer according to the electric field generated by charging, increasing the charge on the surface of the photoreceptor. It is thought that an electrostatic latent image is formed by neutralizing the electrostatic latent image. Therefore, the charge generating material used in this type of photoreceptor is required to generate charge carriers efficiently when irradiated with light for image formation. On the other hand, the charge transport material is required to be transparent to the light used, to be able to maintain a desired charging potential, and to have the ability to promptly transport the charge carriers generated by the charge generation material when irradiated with light. be done. In view of the above points, the present inventors aimed to develop a laminated photoconductor that is highly sensitive, exhibits almost flat sensitivity over the entire visible spectrum and semiconductor laser wavelength range, and is easy to manufacture. As a result of extensive research into numerous charge-generating and charge-transporting materials, we have discovered that photoreceptor properties vary greatly depending on the combination of charge-generating and charge-transporting materials, and we have found that specific combinations of these materials As a result, a photoreceptor with excellent photosensitive properties was obtained, and the above objectives were achieved. The object of the present invention is to laminate a charge generation layer containing a charge generation substance with extremely excellent charge carrier generation ability and a charge transport layer containing a charge transfer substance that exhibits excellent performance when used together with the charge generation substance. By applying a sufficient charging potential in a dark place and quickly dissipating the surface charge during exposure, there will be no damage even if these steps are repeated in the copying process that repeats charging, exposure, development, transfer, and cleaning. An object of the present invention is to provide a laminated electrophotographic photoreceptor whose characteristics do not change. That is, the present invention is a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, and the charge generation layer has the formula (1). The charge transport layer is composed of a layer containing a specific trisazo pigment represented by the general formula (2). [In the formula, R ₁ represents a methyl group, an ethyl group, a 2-hydroxyethyl group, or a 2-chloroethyl group,
R ₂ represents a methyl group, ethyl group, benzyl group, or phenyl group, and R ₃ represents hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a dialkylamino group, or a nitro group. represents. ] This is a laminated photoreceptor with a specific combination of layers containing a specific hydrazone compound. Table 1 shows examples of the hydrazone compounds represented by the general formula (2) used in the present invention.

【table】

【table】

【table】

[Table] Next, the present invention will be explained in more detail. FIG. 1 is an enlarged sectional view of an electrophotographic photoreceptor showing an embodiment of the present invention. This photoreceptor is constructed such that a charge generation layer 22 and a charge transport layer 33 are provided on a conductive support 11 to form a photosensitive layer 44 . The conductive support used in the present invention includes a metal plate, metal drum, or metal foil made of aluminum, nickel, chromium, etc.;
Plastic films provided with a thin layer of tin oxide, indium oxide, chromium, palladium, etc., and paper or plastic films coated with or impregnated with a conductive substance are used. The charge generation layer is made by making fine particles of the specific trisazo pigment represented by the formula (1) shown above by means such as a ball mill, and dispersing them in a suitable solvent, or dissolving a binder resin therein as necessary. The resulting dispersion is coated onto a conductive support, and if necessary, the surface may be finished by buffing or the like, and the film thickness may be adjusted. The thickness of this charge generation layer is 0.01 to 5 μm, preferably 0.05 to 2 μm, and the proportion of trisazo pigment in the charge generation layer is 10 to 100% by weight, preferably 30% by weight.
~95% by weight. Charge generation layer thickness is 0.01μm
If the diameter is less than 5 μm, the sensitivity is poor, and if the diameter is 5 μm or more, the potential cannot be maintained. Furthermore, if the proportion of the trisazo pigment in the charge generation layer is less than 10% by weight, the sensitivity is poor. The charge transport layer is formed by coating a solution of the hydrazone compound represented by the general formula (2) and a binder resin in a suitable solvent such as tetrahydrofuran on the charge generation layer. The proportion of the hydrazone compound contained in the charge transport layer is 10 to 80% by weight, preferably 25 to 75% by weight, and the film thickness is 2 to 100 μm, preferably 5 to 40 μm. If the proportion of the hydrazone compound contained in the charge transport layer is less than 10% by weight, the sensitivity will be poor, and if it is more than 80% by weight, the film will become brittle or crystals will precipitate and the charge transport layer will become cloudy, which is not preferable. Further, if the thickness of the charge transport layer is 5 μm or less, the potential is not maintained well, and if the thickness is 40 μm or more, the residual potential becomes high. Examples of binder resins for the charge generation layer used here include polyester resins, butyral resins, ethyl cellulose resins, epoxy resins, acrylic resins, vinylidene chloride resins, polystyrene resins, polybutadiene resins, and copolymers thereof. They can be used alone or in a mixture of two or more. Examples of binder resins for the charge transport layer include polycarbonate resins, polyester resins, polystyrene resins, polyurethane resins, epoxy resins, acrylic resins, silicone resins, and copolymers thereof, and these may be one or two types. It is used in a mixed state. Furthermore, various additives can be added to the charge transport layer for the purpose of improving flexibility or durability. Additives used for this purpose include halogenated paraffins, dialkyl phthalates, silicone oils, and the like. In addition, in the photoreceptor of the present invention, a barrier layer may be provided between the conductive layer and the charge generation layer, an intermediate layer between the charge generation layer and the charge transport layer, and an overcoat layer on the charge transport layer, if necessary. can. The structure of the present invention is as described above, and as is clear from the Examples and Comparative Examples described later, the present invention is easier to manufacture than an electrophotographic photoreceptor having a photosensitive layer with a conventional laminated structure. It is an electrophotographic photoreceptor that has excellent properties such as stable characteristics even after repeated use and high sensitivity even in the semiconductor laser wavelength range (approximately 800 nm). EXAMPLES Next, the present invention will be specifically explained using Examples, but the embodiments of the present invention are not limited thereby. Example 1 1 part by weight of trisazo pigment (1), 19 parts by weight of tetrahydrofuran, and 6 parts by weight of a 5% by weight tetrahydrofuran solution of polyvinyl butyral resin (XYHL; manufactured by Union Carbide Plastics Company) were thoroughly ground in a ball mill. Next, this pulverized mixture was taken out and diluted with 104 parts by weight of tetrahydrofuran while stirring gently. This solution was applied onto a polyester film on which aluminum had been vapor-deposited using a doctor blade with a wet gap of 35 μm and dried at 80° C. for 5 minutes to form a charge generation layer with a thickness of 0.8 μm. In the charge generation layer, 10 parts by weight of a hydrazone compound represented by structural formula (2-5) and 10 parts by weight of polycarbonate resin (Panlite K-1300; manufactured by Teijin Kasei Ltd.) were added.
A solution containing 0.002 parts by weight of silicone oil (KF-50; manufactured by Shin-Etsu Chemical Co., Ltd.) and 80 parts by weight of tetrahydrofuran was applied using a doctor blade with a wet gap of 200 μm, heated at 80°C for 2 minutes, and then heated at 100°C for 5 minutes. It was dried for a minute to form a charge transport layer with a thickness of 20 μm, and photoreceptor No. 1 was prepared. Example 2 Example 1 except that hydrazone compound (2-5) in Example 1 was changed to hydrazone compound (2-8)
In exactly the same manner as above, photoreceptor No. 2 consisting of a charge generation layer with a thickness of 0.8 μm and a charge transport layer with a thickness of 17 μm was prepared. Example 3 A charge generation layer with a thickness of 0.8 μm and a charge generation layer with a thickness of 19 μm were prepared in the same manner as in Example 1 except that the hydrazone compound (2-5) was changed to the hydrazone compound (2-7). Photoreceptor No. 3 consisting of charge transport layer
It was created. Example 4 The same procedure as in Example 1 was carried out except that the polyvinyl butyral resin in Example 1 was changed to polyester resin (Vylon 200; manufactured by Toyobo Co., Ltd.).
Photoreceptor No. 4 was prepared, consisting of a charge generation layer with a thickness of 0.8 μm and a charge transport layer with a thickness of 20 μm. Comparative Example 1 N・N'-dimethylperylene-3,4,9,10-tetracarboxylic acid diimide was deposited as a charge generating substance on an aluminum plate at a vacuum level of 10 ^-5 mmHg, a deposition source temperature of 350°C, and a deposition time of 3 minutes. A charge generation layer was formed by vacuum evaporation under the following conditions. Next, on this charge generation layer, 5 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-osadiazole, 5 parts by weight of polyester resin (manufactured by DuPont, Polyester Adhesive 49000), and Apply a solution consisting of 90 parts by weight of tetrahydrofuran,
It was dried at .degree. C. for 10 minutes to form a charge transport layer with a thickness of about 10 .mu.m, thereby producing comparative photoreceptor No. 1. Comparative Example 2 1.08 parts by weight of Chlordiane Blue, a benzidine-based pigment, as a charge generating substance was dissolved in 24.46 parts by weight of ethylenediamine, and 20.08 parts by weight of n-butylamine was added to this solution with stirring, followed by 54.36 parts by weight of tetrahydrofuran. A charge generation layer coating solution was prepared. Next, this coating solution was applied onto a polyester film coated with aluminum using a doctor blade, dried at 80℃ for 5 minutes, and the thickness was approx.
A charge generation layer of 0.5 μm was formed. 1-phenyl-3-(4-diethylaminostyryl)-5-(4-diethylaminophenyl) on the charge generation layer.
- 1 part by weight of pyrazoline, 1 part of polycarbonate resin (Panlite K-1300; manufactured by Teijin Kasei Ltd.)
A solution consisting of 1 part by weight and 8 parts by weight of tetrahydrofuran was applied with a doctor blade and heated at 80℃ for 2 hours.
minutes, then dried at 100℃ for 5 minutes to a thickness of approximately 20μm.
A charge transporting layer was formed on the photoreceptor No. 2 for comparison. Comparative Example 3 A triphenylamine pigment, 4,4',4''-tris[2-hydroxy-3
2 parts by weight of -(2-methoxyphenylcarbamoyl)-1-naphthylazo]triphenylamine and 98 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto an aluminum-deposited polyester film using a doctor blade. , and air-dried to form a charge generation layer with a thickness of 1 μm. On the other hand, 2 parts by weight of 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole, 2 parts by weight of polycarbonate resin (Panlite L; manufactured by Teijin Kasei Ltd.) and 46 parts by weight of tetrahydrofuran were added. Mix to form a solution, apply this onto the charge generation layer with a doctor blade,
A charge transport layer having a thickness of 10 .mu.m was formed by drying at .degree. C. for 10 minutes to prepare comparative photoreceptor No. 3. Comparative Example 4 1 part by weight of polyester resin (manufactured by DuPont, Polyester Adhesive 49000), 4,4',4''-tris [2-hydroxy-3-(2,5-dimethoxyphene)], which is a triphenylamine pigment, 1 part by weight of (Nylcarbamoyl)-1-naphthylazo]triphenylamine and 26 parts by weight of tetrahydrofuran were pulverized and mixed in a ball mill, and the resulting dispersion was applied onto an aluminum-deposited polyester film using a doctor blade and heated at 100°C. Comparative photoreceptor No. 4 having a photosensitive layer with a thickness of 7 μm was obtained by drying for 10 minutes. Photoreceptor No. 1 to No. 4 prepared as described above
And for comparison photoreceptors No. 1 to No. 4, an electrostatic copying paper tester (manufactured by Kawaguchi Electric Seisakusho Co., Ltd., SP428 type)
After applying corona discharge of - or +6KV for 20 seconds to charge it negatively or positively using
Then, the surface is irradiated with light using a tungsten lamp at an illuminance of 20 lux, and the time (seconds) until the surface potential becomes 1/2 of Vpo is determined, and the exposure amount E1/2 is determined. (lux・sec) was calculated. In addition, the following measurements were performed to examine the sensitivity of each photoreceptor to long wavelength light. First, each photoreceptor was charged by corona discharge in a dark place, and then a monochromator was used to charge the photoreceptor.
Monochromatic light of 1 μw/cm ² with a wavelength of 800 nm was irradiated. Next, calculate the time (sec) until the surface potential attenuates to 1/2 (at this time, the attenuation of the surface potential due to dark decay was corrected), and then calculate the exposure amount (μw・sce/
cm ² ) and the light attenuation rate (volt・cm ²・μ ^-1・
sec ^-1 ) was calculated. These results are shown in Table-2.

【table】

[Table] As is clear from the results in Table 2, the laminated photoreceptor of the present invention has higher sensitivity in the visible range than comparative photoreceptors No. 1 to No. 4, and has a higher sensitivity in the semiconductor laser wavelength range (800 nm). It can be seen that it has extremely excellent sensitivity. Further, in its production, it is not necessary to use the organic amine used in producing Comparative Photoreceptor No. 2, which is advantageous in terms of production. Furthermore, photoreceptors No. 1 to No. 4 of the present invention were used in an electrophotographic copying machine (FT- manufactured by Ricoh Co., Ltd.).
4700), and image output was repeated 10,000 times. As a result, clear images were obtained from all photoreceptors. From this, it can be understood that the photoreceptor of the present invention has extremely excellent durability.

[Brief explanation of the drawing]

FIG. 1 is an enlarged sectional view of an electrophotographic photoreceptor showing an embodiment of the present invention. 11... Conductive support, 22... Charge generation layer,
33... Charge transport layer, 44... Photosensitive layer.

Claims (1)

[Claims] 1. In a laminated electrophotographic photoreceptor in which a charge generation layer and a charge transport layer are provided on a conductive support, the charge generation layer has the formula (1). contains a trisazo pigment represented by the formula (2), and the charge transport layer has the general formula (2). [In the formula, R ₁ represents a methyl group, an ethyl group, a 2-hydroxyethyl group, or a 2-chloroethyl group,
R ₂ represents a methyl group, ethyl group, benzyl group, or phenyl group, and R ₃ represents hydrogen, chlorine, bromine, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a dialkylamino group, or a nitro group. represents. ] An electrophotographic photoreceptor comprising a hydrazone compound represented by the following.