JPS62226156A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To form a photosensitive layer high in sensitivity to light in the near infrared region by using an alpha type metal-free phthalocyanine and a specified bisazo compound. CONSTITUTION:The bisazo compound to be used is represented by the formula shown on the right in which each of Ar1, Ar2 is optionally substituted phenyl or naphthyl. An electrostatic charge generating layer is formed by coating an aluminum plate in a film thickness of 0.5mum with a coating solution prepared by pulverizing this bisazo compound powder in a ball mill by a mechanical stress into a uniform fine powder of <=0.01mum particle diameter, mixing 1pts.wt. of a mixture of this fine powder with the alpha type metal-free phthalocyanine in a prescribed weight ratio with 30pts.wt. of N,N-dimethylformamide, and kneading them in an ultrasonic wave homogenizer.

Description

[Detailed description of the invention] [Technical field to which the invention pertains]

The present invention relates to an electrophotographic photoreceptor having a photosensitive layer made of an organic photoconductive material and used in laser beam printers and the like.

[Prior art and its problems]

Photoreceptors for electrophotography (hereinafter also simply referred to as photoreceptors) can be charged to the required potential by corona discharge in a dark place, and have little charge leakage (they have the ability to rapidly discharge charges by irradiation with light). Conventionally, inorganic materials such as amorphous selenium, amorphous silicon, selenium-tellurium alloy, cadmium sulfide, and zinc monoxide have been used as photoconductive materials for photoreceptors with such performance. However, it has the disadvantage of being somewhat inferior in mechanical properties such as flexibility and impact resistance.In recent years, organic photoconductive materials that have excellent ductility and impact resistance and are easy to form into films, such as indigo pigments and phthalocyanine pigments, have been developed. In addition to pigments, photoreceptors using azo compounds are attracting attention (for example, JP-A-44-16474, JP-A-47-37543, and JP-A-52-4241). For example, the Carlson method is commonly used to form images using electrophotographic methods. Image formation in this method involves charging the photoreceptor in a dark place by corona discharge, and static image formation by exposing the surface of the charged photoreceptor to light. formation of electrolatent image,
This is done by developing the formed electrostatic latent image with toner, transferring the developed toner image to a support such as paper, and fixing the toner image to the support. After the toner image is transferred, the photoreceptor is neutralized. After residual toner is removed and static electricity is removed, it is reused. When copying an original using a copying machine, it is desirable to be able to obtain a copy that faithfully reproduces the image density of the original, but in order to do so, the photosensitivity of the photoreceptor used must exceed the human eye's sensitivity over the entire visible light range. It was necessary to overcome the visual sensitivity with respect to color density. However, in electrophotographic printers used as output terminals for information processing devices, the demand for which has increased rapidly in recent years with the development of an information society, semiconductor lasers and light emitting diodes (LEDs) are used as light sources, and therefore this Photoreceptors used in such printers must be highly sensitive to light of specific wavelengths from these light sources. The wavelength of light emitted from a semiconductor laser beam or an LED is in the near-infrared region. However, conventional photoconductors for copying machines have a sensitivity peak at a wavelength of 550 to approximately match the visibility of the human eye.
Since it is around ns, it does not have high sensitivity to light sources for printers. Phthalocyanine compounds such as selenium-tellurium alloys containing a high concentration of tellurium and the τ-type metal-free phthalocyanine found in JP-A-58-182639 have photoconductive properties that are highly sensitive to wavelength light in the near-infrared region. Are known. Also, JP-A No. 57-203061. JP-A-58-76841 discloses that a photoreceptor using a trisazo compound is sensitive not only to visible wavelength light but also to near-infrared wavelength light. However, τ-type metal-free phthalocyanine must be produced by converting the crystal form of α-type phthalocyanine, which is produced industrially, and trisazo compounds are also special materials and are more expensive than bisazo compounds, which are commonly used as pigments. be. However, neither the α-type metal-free phthalocyanine nor the bisazo compound is highly sensitive to wavelength light in the near-infrared region.

[Purpose of the invention]

The present invention solves the above-mentioned problems and uses α-type metal-free phthalocyanine and bisazo compound, which are common materials but are not highly sensitive to wavelength light in the near-infrared region, and are highly sensitive in the near-infrared region. An object of the present invention is to provide a photoreceptor on which a photoreceptor layer is formed.

[Key points of the invention]

The present invention provides a charge generation layer of an electrophotographic photoreceptor consisting of a bisazo compound represented by the following structural formula, where ++Arz is a substituted or unsubstituted phenyl group or naphthyl group, and an α-type metal-free By forming the photoreceptor from a mixture of phthalocyanines, a photoreceptor having excellent photoconductive properties in the near-infrared region is obtained, and the above object is achieved.

[Embodiments of the invention]

The present invention will be explained below based on examples. A compound having the structural formula shown below was used as a bisazo compound, and the powder of this bisazo compound was ground into a fine powder with a uniform particle size of 0.0 IJllI or less by mechanical strain using a ball mill. Take 1 part by weight of this fine powder and α-type metal-free phthalocyanine at the weight ratio shown in Table 1, and add 30 parts by weight of N,N dimethylformamide (DMF).
Parts by weight were mixed and kneaded using an ultrasonic homogenizer to form a coating film with a thickness of 0.5 mm on an aluminum plate. Table 1 This coating film is used as a charge generation layer, and 1-phenyl-3
-(p-diethylaminostyryl)-5-(p-diethylaminophenyl)-2-pyrazoline 60 parts by weight, polymethyl methacrylic acid polymer 40 parts by weight, toluene 30 parts by weight
A photoreceptor was prepared on which a charge transfer layer was deposited with a thickness of 20 μm using a mixed solution containing 0 parts by weight. Example 1.2.3.4 was prepared according to the above method except for the mixing ratio shown in Table 1. Comparative Example 1.2. The photoreceptor was charged to -6 kV using an electrostatic recording paper tester rsP-428J manufactured by Kawaguchi Electric Manufacturing Co., Ltd.
The half-reduction exposure amount using light with a wavelength of 0n- was measured. The results are shown in Table 2. It can be seen that, compared to the comparative example in Table 2, the half-decrease exposure amount of the example is significantly reduced, that is, the sensitivity is high. The details of the reason are unknown. Next, Example 1 was followed except that a bisazo compound having a different structural formula was used in place of the bisazo compound used in Examples 1 to 4 and Comparative Example 1.2. Example 5 in the same manner as Comparative Example 1. A photoreceptor of Comparative Example 3 was prepared, and the half-decreased exposure amount was determined. Table 3 shows the results. Table 3 Again, the example has higher sensitivity to light with a wavelength of 800 ns+ than the comparative example.

【Effect of the invention】

Claims (1)

[Scope of Claims] 1) A bisazo compound represented by the structural formula ▲There are mathematical formulas, chemical formulas, tables, etc.▼, where Ar_1 and Ar_2 are each substituted or unsubstituted phenyl group or naphthyl group. An electrophotographic photoreceptor having a charge generation layer made of a mixture of α-type metal-free phthalocyanine and α-type metal-free phthalocyanine.