JPH0342660B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor used in an electrophotographic process. To be more specific,
The present invention relates to an electrophotographic photoreceptor containing a squarium 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 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 process called vapor deposition.
Another disadvantage is that the produced vapor-deposited film is not 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 is extended to the visible light range, but it still does not have sufficient sensitivity as a photoreceptor for electrophotography and suffers from severe optical fatigue. 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, but mechanical strength still remains. However, there are still problems in terms of lifespan, 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.

Purpose of the Invention The purpose of the present invention is to provide an extremely sensitive photoconductive material that can be used in any existing electrophotographic process and has spectral sensitivity from the visible region to the near-infrared region. be.

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 that is highly sensitive and 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.

Composition of the Invention The present inventors have improved various drawbacks of conventional inorganic photosensitive materials, organic photosensitive materials, and organic dispersion photosensitive materials, and have created a material that has excellent electrophotographic properties and flexibility, and furthermore has As a result of intensive research to obtain a photoconductive material with high sensitivity over a wide range of near-infrared regions, the inventors discovered that a specific squarium 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 ().

■■■ Turtle shell [0041] ■■■ [In the formula, R represents a chain alkyl group having 2 to 6 carbon atoms. ] This squarium pigment is composed of 3,4-dihydroxy-3-cyclobutene-1,2-dione represented by the formula () ■■■ Tortoise Shell [0042] ■■■ and the formula () ■■■ Tortoise Shell [0043] ■ ■■ [In the formula, R represents the same meaning as above. ] It can be obtained by reacting with the aniline derivative shown below.

The squarium 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, a charge generation layer containing a squarium pigment and a known charge transport layer such as polyvinylbenzothiophene, polyvinylpyrene, photoconductive polymers such as polyvinylanthracene, polyvinylcarbazole, or triallylpyrazoline, triphenylmethane, oxadiazole,
By forming a layer containing tetraphenylbenzidine, trinitrofluorenone, etc. in the binder resin, it is possible to improve the charging properties of the photoreceptor, reduce the residual potential, and further improve the mechanical strength. .

To explain the structure of the two-layered electrophotographic photoreceptor of the present invention, as shown in FIGS. 1 and 2, a conductive support 1, a charge generation layer 2 containing a squarium pigment, and a charge transport A photosensitive layer 4 made of a laminate with a charge transport layer 3 containing a substance is provided.

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, but the grinding method is APEX MILL (trade name,
A publicly known method can be used, such as a ball mill or RED DEVIL (trade name, commercially available from Tokyo Kohden Co., Ltd.).

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.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.

A binder with squarium pigment dispersed therein 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 ordinary copying machines but also in semiconductor laser printers, intelligent copying machines, and the like.

Next, the present invention will be explained by examples.

Example 1 Squarium pigment 1, represented by the formula () where R=C ₂ H _{5 ,} is ground together with methylene chloride and a steel ball for 12 hours. Polyester resin after crushing (product name, Vylon)
200, commercial source: Toyobo Co., Ltd.) and mix with 30% by weight. The mixture was applied onto an aluminum plate using an applicator so that the film thickness after drying was approximately 0.5 μm to form a charge generation layer. On top of this, 1-phenyl-3-[p-diethylaminostyryl]-5-[p-diethylaminophenyl]-
A charge transport layer containing 50% by weight of pyrazoline mixed in a polycarbonate resin (trade name: Panlite, commercially available from Teijin Kasei Ltd.) was applied using an applicator to a thickness of about 15 μm.

Next, the surface of the photosensitive layer of this photoreceptor was negatively charged by applying -6KV corona discharge for 2 seconds using an electrostatic copying paper tester manufactured by Kawaguchi Electric, and then left in a dark place for 2 seconds, and the surface potential at that time was V _p and then the illuminance
The photosensitive layer was irradiated with a 10 lux tungsten halogen lamp, and the time (seconds) until the surface potential became 1/2 of V _p was determined to determine the half-reduction exposure amount E1/2.

As a result, V _p = 850V, E1/2 = 1.5 Lux・
It was hot in seconds.

Examples 2 to 4 In the formula (), R = n-C ₃ H ₇ (2), R = n-C ₄ H ₉
(3), R=i-C ₄ H ₉ (4) A photoreceptor was prepared in the same manner as in Example 1, except that the squarium pigment of (4) was used, and its electrical properties were measured. The results are shown in Table 1.

■■■ Turtle Shell [0011] ■■■ Examples 5 to 8 In the photoreceptor of this example, the order of the charge generation layer and the charge transport layer is reversed. That is, Example 1~
Photoreceptors were prepared under the same conditions as in Squarium Pigments 1 to 4 used in Example 4, except that the order of the charge generation layer and the charge transport layer was reversed, and the electrical properties were measured. Table 2 shows the results.

■■■ Turtle Shell [0012] ■■■ Effects of the Invention The present invention has the general formula () ■■■ Tortoise Shell [0044] ■■■ (In the formula, R represents a chain alkyl group having 2 to 6 carbon atoms.) The present invention provides an electrophotographic photoreceptor having a photosensitive layer containing a squarium pigment represented by It has improved flexibility and mechanical strength, has excellent electrophotographic properties and flexibility, and has high sensitivity over a wide range from the visible region to the near-infrared region.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of an example of the structure 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. A photosensitive layer containing a squarium pigment represented by the general formula ■■■ Turtle shell [0040] ■■■ (wherein R represents a chain alkyl group having 2 to 6 carbon atoms) An electrophotographic photoreceptor characterized by having the following.