JPH0254940B2 - - 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. A photoreceptor using an organic material, a so-called organic photoreceptor, has a structure in which different materials are used in combination, such as a material with a superior charge generation ability and a material with an excellent charge transport ability, compared to a configuration using a single material, that is, Functionally separated 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,
They must be selected taking into account 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 so far do not have sufficient properties, and their performance is particularly poor when compared to selenium-based photoreceptors, so they have had to be used mainly as photoreceptors for low-speed machines. . Furthermore, although it has sensitivity in the visible light region, it has no 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 was 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. An 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, A represents a methyl group or Cl.) The present invention was completed based on the discovery that the present invention can be achieved by a photoreceptor using a combination of charge transport materials shown in the following formula. 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 structure of the photoreceptor according to the present invention may be one 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 material is provided on a conductive support; The layer and the charge transport layer may be stacked 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 a layer of metal oxide such as aluminum oxide, or acrylic resin, phenolic resin, polyester resin, polyurethane, etc.
It 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, etc. 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.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 of the charge transport layer is selected from the same materials as those exemplified as the binder used in the charge generation layer described above. Furthermore, additives such as plasticizers and leveling agents may be included in the charge transport layer. 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 precipitated pale green crystals were filtered and washed with methanol to obtain 0.85 g (yield 26.8%) of the desired squarium compound (compound of formula (1-1) above). Example 1 To 1 part by weight of the compound of formula (1-1) obtained in the above synthesis example, 1 part by weight of polyester resin (Polyester 49000 manufactured by DuPont) and 10 parts by weight of methylene chloride were added, and the mixture was ground in a ball mill for 4 hours. The dispersion obtained by mixing was coated using a bar coater on a polyester film (Metal Me (registered trademark) manufactured by Toray) on which aluminum was deposited, and the mixture was heated at 70°C for 50 minutes.
It was dried for an hour to form a charge generation layer with a thickness of 1 μm. On this charge generation layer, N,N'-diphenyl-
N,N'-bis(3-methylphenyl)-[1,1'-
A homogeneous solution consisting of 1 part by weight of [biphenyl]-4,4-diamine, 1 part by weight of polycarbonate resin [manufactured by Teijin, Panlite (registered trademark)], and 10 parts by weight of methylene chloride was applied using an applicator at 70°C.
A photoreceptor was prepared by drying the photoreceptor for 16 hours to form a charge transport layer with a thickness of 22 μm. Next, an electrostatic copying paper testing device (Kawaguchi Electric, Electrostatic Paper Analyzer)
SP428), the photosensitive layer was charged negatively by applying -6KV corona discharge, left in a dark place for 2 seconds, and then the photosensitive layer was irradiated with light using a tungsten lamp so that the surface illuminance was 10 lux. , the exposure amount E at which the surface potential becomes 1/2 of the surface potential V _D after being left in the dark.
1/2 was calculated, and the result is the initial charging potential V ₀ =
-1150V, potential after being left in the dark for 2 seconds V _DDP = -
1140V, E 1/2 = 2.1 Lux sec, residual potential R _P
=O _V. In addition, the following measurements were performed to demonstrate that the material has extremely high sensitivity to long wavelength light. After the photoreceptor was charged by corona discharge in a dark place, the photoreceptor was irradiated with monochromatic light of 1 μW/cm ² at 800 nm using a monochromator. Then, the amount of exposure was determined by measuring the time it took for the surface potential to decrease to 1/2. The result was 11.3erg/ ^cm2 . Examples 2 to 9 In Example 1, the above formula No. (1-3) and (1-
5), (1-6), (1-9), (1-11), (1-14
),
Photoreceptors were prepared in the same manner as in Example 1, except that the squareium pigments (1-25) and (1-29) were used, and the evaluation results are shown in Table 1.

[Table] Effects of the 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. flat sensitivity not only in the visible light region but also in the near-infrared light region. Showing spectral sensitivity; 3. High initial charging potential and low dark decay;
It also has various excellent effects such as 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, but the photoreceptor of the present invention can form a latent image at high speed, and For example, 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 with high image quality. It has various 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, A represents a methyl group or Cl.) An electrophotographic photoreceptor comprising a charge transport layer containing a compound represented by the following formula.