JPH0547109B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to an electrophotographic photoreceptor used in an electrophotographic process. More specifically, the present invention relates to an electrophotographic photoreceptor containing a squarerium pigment in a photoconductive layer. [Prior Art] Conventionally, inorganic photosensitive materials such as amorphous selenium, selenium alloys, cadmium sulfide, and zinc oxide, and organic photosensitive materials such as polyvinyl carbazole and polyvinyl carbazole derivatives have been widely known as electrophotographic photoreceptors. It is being It is well known that amorphous selenium or selenium alloys have extremely excellent properties as electrophotographic photoreceptors and are used in practical applications. However, its production requires a complicated step of vapor deposition, and the produced vapor-deposited film has the drawback of not being flexible. When zinc oxide is used, it is used as a dispersed photosensitive material in which zinc oxide is dispersed in a resin, but such a photosensitive material has a drawback in mechanical strength and cannot withstand repeated use as it is. Polyvinylcarbazole, which is widely known as an organic photoconductive material, has excellent advantages in terms of transparency, film-forming properties, and flexibility, but polyvinylcarbazole itself has no sensitivity in the visible light range, so it cannot be used as is. Therefore, various sensitization methods have been devised.
However, when polyvinylcarbazole is spectrally sensitized using a dye sensitizer, the spectral sensitivity range is extended to the visible light range, but it still cannot achieve sufficient sensitivity as a photoreceptor for electrophotography and suffers from severe photofatigue. It has the disadvantage of being In addition, when chemically sensitized using an electron-accepting compound, a photoreceptor with sufficient sensitivity as an electrophotographic photoreceptor can be obtained, and some of them have been put into practical use. , there are many problems with life span, etc. Although active research has been conducted on organic dispersion photosensitive materials and there have been numerous reports, a photoreceptor with excellent electrical properties and sufficient sensitivity for use as an electrophotographic photoreceptor has not yet been obtained. At present, there are reports that phthalocyanine exhibits excellent electrophotographic properties as a dispersed light-sensitive material, but it has the disadvantage that its spectral sensitivity is biased towards the long wavelength range, and therefore its red color reproducibility is poor. [Problems to be Solved by the Invention] The object of the present invention is to provide extremely sensitive electrophotography that can be used in any existing electrophotographic process and has spectral sensitivity from the visible region to the near-infrared region. The purpose of the present invention is to provide a photoreceptor for Another object of the present invention is to have flexibility that inorganic photosensitive materials do not have, to improve low abrasion resistance and insufficient mechanical strength, which are defects of polyvinylcarbazole-trinitrofluorenone organic photosensitive materials, and to improve visible It is an object of the present invention to provide an electrophotographic photoreceptor which has extremely high sensitivity, has substantially flat spectral sensitivity over a wide range from the near-infrared region to the near-infrared region, and has excellent mechanical strength such as abrasion resistance. [Means and effects for solving the problems] The present inventors have improved various drawbacks of conventional inorganic photosensitive materials, organic photosensitive materials, and organic dispersion photosensitive materials,
As a result of intensive research to obtain a photoconductive material that has both excellent electrophotographic properties and flexibility, and also has high sensitivity over a wide range from the visible region to the near-infrared region,
The inventors discovered that a specific squarerium pigment has extremely excellent properties and completed the present invention. The squarium pigment used in the present invention is represented by the following general formula (). In the general formula (), R ₁ and R ₂ are independent of each other and each represents a hydrogen atom, a hydroxyl group, a methyl group, a carboxyl group, a halogen atom, or a trifluoromethyl group, and R ₁ and R ₂ are The bonded benzene ring may be further substituted with another substituent, and Ar ₁ and Ar ₂ are not the same,
Each is unsubstituted or has 1 or more carbon atoms.
6 is substituted with a linear alkyl group, hydroxyl group, alkoxy group having 1 to 4 carbon atoms, halogen atom, nitro group, cyano group, carboxyl group, methoxycarbonyl group having 1 to 4 carbon atoms, or trifluoromethyl group It represents a phenyl group, and Ar ₁ and Ar ₂ may be further substituted with other substituents. The squarerium pigment represented by the general formula () is the formula () 3,4-dichloro-3-cyclobutene-1,2-dione represented by the general formula () or () (Each symbol in the formula has the same meaning as above.) By reacting with an aniline derivative represented by the general formula () or () (Each symbol in the formula has the same meaning as above.) A compound represented by is obtained, and then this compound is hydrolyzed to form the general formula () or (). (Each symbol in the formula has the same meaning as above.) After converting the compound of the general formula () (or ()) into the compound represented by the general formula () (or ()), It can be obtained by reacting with Specific examples of the squarylium compound represented by the general formula () are shown below using the structural formula. Me during the ceremony
represents a methyl group. The squarerium pigment represented by the general formula () can be used in an electrophotographic photoreceptor having a multilayer structure. That is, in an electrophotographic photoreceptor including a photosensitive layer with a two-layer structure consisting of a charge generation layer and a charge transport layer, the chargeability of the photoreceptor can be improved by providing a charge generation layer containing a squareryllium pigment and a known charge transport layer. improvement, reduction in residual potential, further improvement in mechanical strength, etc. can be achieved. As the charge transport layer, N-methyl-N-
hydrazones such as phenylhydrazone-3-methylidene-9-ethylcarbazole, p-diethylaminobenzaldehyde-N,N-diphenylhydrazone, p-diethylaminobenzaldehyde-N-α-naphthyl-N-phenylhydrazone;
1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)pyrazoline, 1-[quinolyl(2)]-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl) ) Pyrazolines such as pyrazoline, oxazole compounds such as 2-(p-diethylaminostyryl)-6-diethylaminobenzoxazole, bis(4-diethylamino-2-methylphenyl)
-Triarylmethane compounds such as phenylmethane, N,N'-diphenyl-N,N'-bis-3-
methylphenyl)-[1,1'-biphenyl]-4,
There are binder resins containing diamine compounds such as 4'-diamine, and photoconductive polymers such as poly-N-vinylcarbazole and polyvinylanthracene. The structure of the electrophotographic photoreceptor having a two-layer structure of the present invention will be described. As shown in FIGS. 1 and 2, a charge generation layer 2 containing a squarium pigment and a charge transport material are formed on a conductive support 1. A photosensitive layer 4 made of a laminate with a charge transport layer 3 containing .
The stacking order of the charge generation layer 2 and the charge transport layer 3 is arbitrary. The charge generation layer may be formed by using the squarerium pigment alone, but it can also be formed by using it in combination with a binder resin. The ratio of pigment to binder wood is 10% to 90% by weight, preferably 10% to
50% by weight. Methods for forming a charge generation layer using squareylium 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 1μ.
It is. 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. As the known insulating resin, polystyrene, polyester, polyvinyltoluene, polyvinylanisole, 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, and when added by weight of 0 to 10% to the binder, it reduces the sensitivity and electrical properties of the photoreceptor. It is possible to further improve its mechanical strength without A protective layer may be provided on the photosensitive layer 4 or an intermediate layer may be provided between the photosensitive layer 4 and the conductive support 1. 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.
Examples of the intermediate layer include metal oxides such as aluminum oxide, acrylic resins, phenolic resins, polyester resins, and polyurethanes. A binder in which squarerium pigments are dispersed is applied onto a conductive support. Coating methods include a dipping method, a spray method, a bar coater method, and an applicator method, and a good photosensitive layer can be formed by any of these methods. Further, as the conductive support, metal, paper treated with conductivity, a polymer film having a conductive layer, glass, etc. can be used. The electrophotographic photoreceptor of the present invention can be widely used not only in copying machines but also in semiconductor laser printers and the like. Next, the present invention will be explained by examples. [Example] Example 1 Polyester resin (manufactured by DuPont, Adhesive 49000) was added to 1 part by weight of the compound of structural formula No. 1 of the specific example.
Add 1 part by weight and 10 parts by weight of tetrahydrofuran,
The dispersion was ground and mixed in a ball mill for 4 hours and then applied using a bar coater onto a polyester film coated with aluminum (Metal Me (registered trademark) manufactured by Toray), dried at 70°C for 5 hours, and the film thickness was determined.
A charge generation layer of 1μ was created. On this charge generation layer, N,N'-diphenyl-
N,N'-bis-(3-methylphenyl)-[1,
1 part by weight of 1'-biphenyl]-4,4'-diamine,
A homogeneous solution consisting of 1 part by weight of polycarbonate resin [manufactured by Teijin, Panlite (registered trademark)] and 10 parts by weight of tetrahydrofuran was applied using an applicator and dried at 70°C for 16 hours to form a charge transport layer with a thickness of 22μ. Then, a photoreceptor was created. Next, an electrostatic copying paper testing device (manufactured by Kawaguchi Electric, Electrostatic Paper Analyzer SP)
-428) to negatively charge the photosensitive layer with -6KV corona discharge, leave it in the dark for 2 seconds, and then use a tungsten lamp to irradiate the photosensitive layer with light so that the surface illuminance is 10 lux. The exposure amount E1/2 was determined so that the surface potential was 1/2 of the surface potential V _DDP after being left in the dark. The result is that the initial charging potential V ₀
=-1040V, potential after being left in the dark for 2 seconds V _DDP =-
980V, E1/2=2.3 Lux・sec, residual potential R _P =
It was 0V. In addition, the following measurements were performed to demonstrate that the material has extremely high sensitivity to long wavelength light. After charging the above photoconductor by corona discharge in a dark place, use a monochromator to
The photoreceptor was irradiated with monochromatic light of 1 μW/cm ² which was divided into 1 μW/cm 2 . The amount of exposure was determined by measuring the time it took for the surface potential to decrease to 1/2. The result was 11.5erg/cm ²
It was hot. Examples 2 to 6 Except for using the squarerium pigments of No. 2, 4, 17, 18, and 20 [Examples 2 to 6, respectively] in Table 1 instead of the squarerium pigment of No. 1 in Example 1. Photoreceptors were prepared and evaluated in the same manner as in Example 1, and the results are shown in Table 1.

〔Effect of the invention〕

The present invention provides an electrophotographic photoreceptor having a photosensitive layer containing a squareryllium compound that has spectral sensitivity from the visible region to the near-infrared region and has high sensitivity and excellent electrical properties. sex,
It has excellent electrical properties such as dark decay, and can be widely used not only in ordinary copying machines but also in semiconductor laser printers.

[Brief explanation of the drawing]

1 and 2 are cross-sectional views of examples of the electrophotographic photoreceptor of the present invention. Symbols in the figure: 1... Conductive support; 2... Charge generation layer; 3... Charge transport layer; 4... Photosensitive layer.

Claims (1)

[Claims] 1. General formula (In the formula, R ₁ and R ₂ are independent of each other and each represents a hydrogen atom, a hydroxyl group, a methyl group, a carboxyl group, a halogen atom, or a trifluoromethyl group, and Ar1 and Ar2 are not the same as each other. each unsubstituted or linear alkyl group having 1 to 6 carbon atoms, hydroxyl group, 1 carbon number
~4 alkoxy group, halogen atom, nitro group,
Represents a phenyl group substituted with a cyano group, carboxyl group, methoxycarbonyl group or trifluoromethyl group. ) An electrophotographic photoreceptor comprising a photosensitive layer containing a squarium pigment.