JPH0254942B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to an electrophotographic photoreceptor, and particularly to an electrophotographic organic photoreceptor. Prior Art An electrophotographic photoreceptor forms an electrostatic latent image by charging and image exposure, and after this electrostatic latent image is visualized with toner, it is transferred and fixed onto paper or the like for copying. . Various materials have been used and proposed for photoreceptors. One is an inorganic material such as selenium, zinc oxide or cadmium sulfide, and the other is an organic material. Photoreceptors using organic materials, so-called organic photoreceptors, are constructed using a combination of different materials, such as a material with excellent charge generation ability and a material with excellent charge transport ability, rather than using a single material. Separate photoreceptors are the mainstream. Charge-generating materials include bisazo pigments, phthalocyanine pigments, benzopyrylium dyes, perylene pigments, etc., and charge-transporting materials include pyrazoline, hydrazone, polyvinylcarbazole, etc., but these charge-generating materials and charge-transporting materials are simply defined as They are not used in combination and must be selected in consideration of various electrophotographic properties, such as injection properties. Many proposals have been made for this functionally separated type organic photoreceptor, such as the one described in Japanese Patent Application Laid-Open No. 105536/1983. This JP-A-49-105536
The organic photoreceptor proposed in this issue uses a combination of squarium pigment as a charge-generating material and triallylpyrazoline as a charge-transporting material. However, this photoreceptor has several drawbacks that should be improved. One of these is charging properties such as charge retention ability, dark decay, or residual potential, and the other is photosensitive properties such as sensitivity (particularly flat sensitivity from the visible light region to the near-infrared region). The various organic photoreceptors that have been proposed heretofore do not have sufficient properties, and their performance is particularly poor when compared with selenium-based photoreceptors, so they have had to be used primarily as photoreceptors for low-speed machines. Furthermore, although it has sensitivity in the visible light region, it does not have sensitivity in the near-infrared light region, making it particularly difficult to use semiconductor laser light for exposure. Purpose of the Invention The present invention has been made in view of the above circumstances, and has excellent charging characteristics, high photosensitive characteristics, especially high absolute sensitivity, and flat sensitivity to light from visible light to near-infrared light. The object of the present invention is to provide an organic photoreceptor having the following properties. Structure of the Invention As a result of extensive studies, the inventors have found that the above purpose has been achieved by the following general formula () (In the formula, X is a halogen atom such as F, Cl, Br,
It represents a methyl group, a methoxy group, a nitro group, a cyano group, a carboxyl group or an ethoxycarbonyl group, n is 0 or an integer of 1 to 5, and Y represents hydrogen, a hydroxyl group or a methyl group. ) is used as a charge-generating material, and the following general formula () is applied to it. (In the formula, R ₁ represents a methyl group, phenyl group, or benzyl group, and R ₂ and R ₃ each represent a methyl group or an ethyl group.) What can be achieved by a photoreceptor using a combination of charge transport materials shown in They discovered this and completed the present invention. The photoreceptor according to the present invention is formed by laminating a photosensitive layer comprising a charge generation layer containing the above-mentioned charge generation material and a charge transport layer containing a charge transport material on a conductive substrate. The photoreceptor of the present invention may have a structure in which a photosensitive layer consisting of a laminate of a charge generation layer containing a squarium pigment and a charge transport layer containing a charge transport substance is provided on a conductive support; and a charge transport layer may be laminated in the reverse order. A protective layer may be provided on the photosensitive layer, or an intermediate layer may be provided between the photosensitive layer and the conductive support. The protective layer may be one in which a metal oxide is dispersed in a resin, or one in which an electron-accepting compound is added to a resin. The intermediate layer is made of metal oxide such as aluminum oxide,
Alternatively, it is a layer of acrylic resin, phenolic resin, polyester resin, polyurethane, etc., which acts as a barrier layer or an adhesive layer. Specific examples of the charge generation material represented by the above general formula () used in the charge generation layer include the following compounds. The charge generation layer may be formed by using the squarium pigment alone, but it can also be formed by using it in combination with a binder resin. The ratio of pigment to binder resin is 10% to 90% by weight, preferably 10% to 50% by weight
Weight%. Methods for forming a charge generation layer using a squarium pigment alone without using a binder resin include solvent coating and vacuum evaporation. The thickness of the charge generation layer is 0.1 to 3μ, preferably 0.2 to 3μ.
It is 1μ. When dispersing the pigment in the binder, the pigment is ground and used, and known methods such as SPEX MILL, ball mill, RED DEVIL (trade name), etc. can be used for the grinding method. The binder of the charge generation layer may or may not itself have photoconductivity. Examples of the photoconductive binder include photoconductive polymers such as polyvinylcarbazole, polyvinylcarbazole derivatives, polyvinylnaphthalene, polyvinylanthracene, and polyvinylpyrene, and other organic matrix materials having charge transport ability. Furthermore, known insulating resins that do not have photoconductivity can also be used as the binder. Known insulating resins include polystyrene, polyester,
Polyvinyl toluene, polyvinyl anisole, polychlorostyrene, polyvinyl butyral, polyvinyl acetate, polyvinyl butyl methacrylate, copolystyrene-butadiene, polysulfone, copolystyrene-methyl methacrylate, polycarbonate, and the like can be used. At this time, in order to further improve the mechanical strength of the resulting photoreceptor, a plasticizer can be used in the same manner as in general polymeric materials. As the plasticizer, for example, chlorinated paraffin, chlorinated biphenyl, phosphate plasticizer, phthalate plasticizer, etc. can be used, and they are added in an amount of 0 to 10% by weight to the binder, and are used to control the sensitivity and electrical properties of the photoreceptor. It is possible to further improve its mechanical strength without deterioration. The charge transport layer is a layer in which a compound represented by the above general formula () is dispersed in a binder resin,
The charge transport material is present in the transport layer in an amount of 10 to 90% by weight, preferably 30 to 70% by weight. The thickness of the charge transport layer is greater than that of the charge generation layer, and is used in the range of 10 to 100 μm, preferably 15 to 60 μm. The binder for the charge transport layer is selected from the same materials as those exemplified as the binder used for the charge generation layer described above. Furthermore, additives such as plasticizers and leveling agents may be included in the charge transport layer. Specific examples of charge transport materials include compounds having the following substituents in the general formula ().

【table】

[Table] Hereinafter, the present invention will be explained in detail with reference to Examples. Synthesis example Compound () 3,4-dihydroxy-3-cyclobutene-
0.76 g of 1,2-dione and 2.48 g of N-benzyl-N-methylaniline were added to 26.8 ml of 1-butanol and heated at 110° C. for 4 hours with stirring. After cooling, the pale green crystals precipitated were filtered, washed with methanol, and the desired squarium compound (above (1)
0.85 g (yield 26.8%) of the compound of formula -1) was obtained. Example 1 Squarium pigment 1 represented by formula (1-1)
1 part by weight of polyester resin (manufactured by Dupont, polyester 49000), tetrahydrofuran
The dispersion obtained by adding 10 parts by weight and grinding and mixing in a ball mill for 4 hours was coated on a polyester film coated with aluminum (Metal Me (registered trademark) manufactured by Toray Industries) using a bar coater, and heated at 70°C.
The mixture was dried for 5 hours to form a charge generation layer with a thickness of 1 μm. A homogeneous solution consisting of 1 part by weight of a hydrazone compound represented by formula (2-2), 1 part by weight of polycarbonate resin (manufactured by Teijin, Panlite (registered trademark)), and 10 parts by weight of tetrahydrofuran was applied onto this charge generation layer using an applicator. The photoreceptor was coated and dried at 70°C for 16 hours to obtain a photoreceptor with a thickness of 22μ. Next, an electrostatic copying paper testing device (Kawaguchi Electric, Electrostatic Paper Analyzer)
SP428), conduct corona discharge of -6KV for 2 seconds to measure the surface potential _VO when negatively charged.
Then, leave it in the dark for 2 seconds, and measure the surface potential at that time.
Measure V _DDP , then irradiate the photosensitive layer with a tungsten halogen lamp with an illuminance of 10 lux, calculate the time (seconds) until the surface density becomes 1/2 of V _DDP , and calculate the half-reduction exposure amount E1/2. I asked for The residual potential V _R after 10 seconds of light irradiation was also determined. As a result, V _O =
−1180V, V _DDP =−1140V, E1/2 = 1.9 Lux·sec, V _R =OV. In addition, the following measurements were performed to demonstrate that the material has extremely high sensitivity to long wavelength light. The above photoreceptor was charged by corona discharge in a dark place, and then monochromatic light of 1 μW/cm ² at 800 nm was irradiated onto the photoreceptor using a monochromator.
Then, the time (seconds) until the surface potential attenuated to 1/2 was determined, and the exposure amount was determined. the result,
It was 10.7erg/ ^cm2 . Examples 2 to 8 Squarium pigment of formula (1-1) was converted into squarium pigment of formula (1-1).
2), (1-3), (1-5), (1-11), (1-14
),
Photoreceptors were prepared and evaluated in exactly the same manner as in Example 1, except that the squarium pigments (1-22) and (1-27) were used. The results are shown in Table 1.

[Table] Examples 9 to 16 Formulas (1-1), (1-2), (1-3), (1-5)
,
(1-11), (1-14), (1-22) and (1-27)
A photoreceptor was prepared and evaluated in exactly the same manner as in Example 1 except that the squarium pigment was used and the hydrazone compound of formula (2-4) was used as the hydrazone compound. The results are shown in Table 2.

[Table] Effects of the present invention The photoreceptor according to the present invention has 1) high absolute sensitivity in both the visible light region and the near-infrared light region, and 2. high absolute sensitivity not only in the visible light region but also in the near-infrared light region. It has various excellent effects such as flat spectral sensitivity, 3. high initial charging potential, low dark decay, and low residual potential. That is, because conventional organic photoreceptors have low sensitivity, they must be used at relatively slow latent image formation speeds, and although they are sensitive to visible light, they are not sensitive to near-infrared light, or On the contrary, the photoreceptor of the present invention does not satisfy high sensitivity in both the visible light region and the near-infrared region.However, according to the photoreceptor of the present invention, a latent image can be formed at high speed. When combining images to form a latent image, it is possible to use both visible light and semiconductor laser light during exposure, and the difference between bright and dark potentials is large, making it possible to copy high quality images. Has excellent advantages.

Claims (1)

[Claims] 1. In an electrophotographic photoreceptor formed by laminating an organic photosensitive layer on a conductive substrate, the photosensitive layer has the following general formula (). (In the formula, X represents a halogen atom, methyl group, methoxy group, nitro group, cyano group, carboxyl group or ethoxycarbonyl group, and n is 0 or 1
It is an integer of ~5, and Y represents hydrogen, a hydroxyl group, or a methyl group. ) A charge generation layer containing a squarium pigment represented by the following general formula () (In the formula, R ₁ represents a methyl group, phenyl group, or benzyl group, and R ₂ and R ₃ each represent a methyl group or an ethyl group.) An electrophotographic photoreceptor.