JPH03167560A - Electrophotographic sensitive body using laser beams - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body practicably sufficient in sensitivity to semiconductor laser beams and small in dark decay and change of dark decay due to environmental conditions by using a specified polymethine cyanine dye as a sensitizing dye and a specified cyclic anhydride as a sensitizing aid. CONSTITUTION:The electrophotographic sensitive body is formed by laminating on a conductive waterproof substrate an electrophotographic photosensitive layer containing a photoconductive zinc oxide, a binder resin, at least one least one of the sensitizing dyes reresented by formula I, and at least one of the cyclic acid anhydrides as the sensitizing aid, represented by formula II, and in formulae I and II, each of R1 and R2 is methyl, ethyl, or the like; X is halo gen; Y1 is H or halogen; and Y2 is halogen, thus permitting the obtained electrophotographic sensitive body to be practicably sufficient in sensitivity to semiconductor laser beams and small in dark decay and its change due to environmental conditions.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor for laser light. More specifically, the present invention relates to an electrophotographic photoreceptor spectrally sensitized to semiconductor laser light.

[Conventional technology]

Generally, an electrophotographic photoreceptor with a zinc oxide/resin dispersion system has photoconductive zinc oxide as a main component on the surface of a conductive support.
A photosensitive layer is formed by blending a binder and a sensitizer with this.

Since the sensitive wavelength range of zinc oxide itself contained in the photosensitive layer exists only in the ultraviolet range, it is generally necessary to add a sensitizing dye to widen the sensitive wavelength range in order to match the wavelength range of the exposure light source. It is.

Conventionally, visible light such as a halogen lamp has been used as the exposure light source for these electrophotographic photoreceptors, but in recent years, with the development of recording equipment and the trend toward digitalization of data,
Laser light, especially semiconductor laser light, which is compact and can be directly modulated, is increasingly being used. The photoreceptor used for such light rays is 700-1
It is required to have sensitivity to long wavelength light of 000 nm.

Examples of electrophotographic photoreceptors sensitive to the wavelength range of semiconductor laser light include JP-A-57-46245 and JP-A-57-46245;
No. 8-58554, No. 58-59453, No. 59-2
No. 2053, No. 59-78358, etc. Such a zinc oxide-based electrophotographic photoreceptor is one in which a sensitizing dye such as a vorimethine-based cyanine dye is blended into the photosensitive layer to perform spectral sensitization to a long wavelength range. however,
When the Z-sensitizing dye was simply added as in these examples, the sensitivity was not sufficient for practical use.

As an example of obtaining high sensitivity by using a sensitizing dye and a sensitizing aid in combination, for example, in JP-A-1-16253, there is a type that has an alkylsulfonic acid group in the N-substituent of the dimethylindole ring at both ends. A formulation in which a polymethine cyanine dye and maleic anhydride as a sensitizing agent are used in combination is described.

An electrophotographic photoreceptor with such a formulation has sufficient sensitivity for use in a laser printer or a laser plate making machine that utilizes semiconductor laser light, and the photoreceptor also has good thermal stability. However, the problem is that the dark decay is large, and the dark decay becomes even larger in a high temperature and high humidity environment.

(Problems to be Solved by the Invention) The present invention has high sensitivity to long wavelength light with a wavelength of 700 to 1000 nm, and therefore has high sensitivity that is practical for semiconductor laser light, and has low dark decay. The object of the present invention is to provide an electrophotographic photoreceptor whose dark decay changes little due to environment.

[Means for Solving the Problems] As a result of intensive research to improve the above-mentioned problems and obtain a good electrophotographic photoreceptor for semiconductor laser light, the present inventor has found that
By using a specific polymethine cyanine dye as a sensitizing dye and a specific cyclic acid anhydride as a sensitizing auxiliary agent, it has practically sufficient sensitivity to semiconductor laser light and dark decay. The inventors have discovered that it is possible to obtain a photoreceptor that has a small dark decay and a small change in dark decay due to the environment, and has brought the present invention to its full potential. That is, the electrophotographic photoreceptor for laser light of the present invention includes a support having conductivity and water resistance, and a photoconductive zinc oxide formed on the support, a resin binder, and a sensitizing dye. , and a sensitizing auxiliary, wherein (a) the sensitizing dye is represented by the following general formula (I): [However, in the above formula, R. ,R. are each independently of the other -CL, -CJs and -CH. -CH=CH. X represents a halogen atom]; Y1 represents a hydrogen atom or a halogen atom, and Y2 represents a halogen atom =] At least 1
It is characterized by containing a species of cyclic acid anhydride.

The sensitizing dye used in the present invention is characterized by very good dark decay and thermal stability.
When combined with commonly used sensitizing aids, sufficient sensitivity cannot be achieved. However, it has been discovered that when this is combined with the sensitizing aid of the present invention, sensitivity is specifically expressed favorably.

Generally, the content of the sensitizing dye contained in the electrophotographic layer is preferably within the range of 0.001 to 0.5%, and 0.01 to 0.2% based on the weight of zinc oxide. More preferably, it is within the range.

In the present invention, formula (II) used as a sensitizing agent
Specific examples of the cyclic acid anhydride include cyclic acid anhydrides such as monochloromaleic anhydride, dichloromaleic anhydride, and dibromaleic anhydride.

The content of the sensitizing agent is generally preferably in the range of 0.01 to 1% based on the weight of zinc oxide, and 0.0
It is more preferably within the range of 2 to 0.5%.

Zinc oxide used in the electrophotographic photosensitive layer has photoconductivity, and generally has a photoconductivity of 0. 1~0. It is a fine powder with a particle size of 510.

The insulating binder resin used in the electrophotographic photosensitive layer may be a single type of resin, or two or more types of resin may be mixed. Although various resins can be used as such binder resin, oil-soluble acrylic resin is generally used.

The solid content of the binder resin contained in the electrophotographic photosensitive layer is preferably 10 to 30% based on the weight of zinc oxide.
It is more preferably within the range of 15 to 25%.

The conductive support for the electrophotographic photoreceptor of the present invention may be a known support, such as a metal sheet, a plastic film laminated with a metal foil, a paper or plastic film having a vapor-deposited metal layer, or a support that has been subjected to conductive treatment. The material can be selected from the following: one made of paper or a plastic film treated with electrical conductivity, and one made of a laminated combination of two or more of the above materials.

To produce the electrophotographic photoreceptor of the present invention, first, a predetermined amount of zinc oxide, the sensitizing dye of the general formula (I), the sensitizing aid of the general formula (U), and the binder resin are added to A mixing and dispersing machine together with an organic solvent such as toluene, 2-butanone, etc.
For example, a coating liquid is prepared by mixing and dispersing using a ball, sand grinder, paint shaker, or the like. In this mixing step, all the components may be mixed at the same time, but preferably, the sensitizing agent is adsorbed on the zinc oxide particles in advance, and then the remaining components are mixed therein. In this case, zinc oxide is added and dispersed in a solution containing a sensitizing aid, and then the solvent is evaporated, or the sensitizing dye and binder resin are sequentially added to this dispersion without evaporation. Just prepare the liquid.

Next, the obtained coating solution is applied onto one surface of the support and dried to form an electrophotographic photosensitive layer. The thickness of the photosensitive layer in this case affects chargeability, sensitivity, and resolution, and
It is usually in the range of 5 to 25μ, more preferably 10 to 20μ.

Scanning exposure with semiconductor laser light is performed to form an electrostatic latent image on the electrophotographic photosensitive layer, which is developed with toner and fixed by heating to obtain an image.

The obtained image can also be used as a record as it is. Furthermore, if the surface is treated with a so-called etching solution containing sodium ferrocyanide or the like to make the non-image area hydrophilic, it can be used as a printing plate for offset printing.

〔Example〕

Next, the present invention will be explained in more detail with reference to examples, but these are not intended to limit the content of the present invention.

In addition, "parts" and "%" in the examples represent "parts by weight" and "% by weight", respectively, unless otherwise specified.

Some of the coating solutions listed below were added in this order to a rotary stirrer and mixed.

Toluene 120 Dichloromaleic anhydride 0.2 Zinc oxide Sakai Chemical SAZEXll2000 9
0 To this mixed solution was added the compound of general formula (I) as a sensitizing dye [wherein R, . R. A solution prepared by dissolving 0.02 parts of CH, X represents a ■ atom) in 3 parts of methanol was added, and this mixed solution was dispersed with a sand grinder to obtain a coating liquid.

As a support, conductive treatment with a basis weight of 80 g / rd
A composite sheet obtained by laminating aluminum foil with a thickness of 10 mm to paper was used.

Applying the coating liquid on the aluminum foil surface of the support,
It was dried with hot air at 100° C. to form a photosensitive layer with a thickness of 20 mm to obtain an electrophotographic photoreceptor.

The obtained electrophotographic photoreceptor was heated at 20°C. After conditioning the humidity for 24 hours in a dark place at 65% Rll, the surface of the photoreceptor was charged with negative corona at -6V, then irradiated with light with a wavelength of 780 nm, and the potential of the photoreceptor surface was measured. From the measurement results, sensitivity expressed in half-reduced exposure was determined. Further, after negative corona charging, the sample was left in a dark place for 60 seconds, the potential after 60 seconds was determined, and the value divided by the initial potential was defined as the dark decay retention rate.

These results are shown in Table 1.

Further, the obtained photoreceptor was negatively corona charged at -6V, and then a semiconductor laser beam (2, 3, 4,
Scanning exposure was performed at a power of 5.6 mW and a wavelength of 780 nm). Next, the exposed electrophotographic photoreceptor was developed with a positively charged liquid toner (manufactured by Itek). The developed photoreceptor was mounted on a printing machine (Ryobi 2800CD), and the exposure latitude was evaluated. The evaluation of exposure latitude is based on the above 5
The number of stages is determined by the number of stages from when the thin white line on the black background part disappears to when the fine black line on the white background part starts to fly out due to overexposure in the exposure of the laser intensity in stages. The larger the number of stages, the wider the tolerance of exposure as a printing plate.

The results are also shown in Table 1.

In addition, for the above electrophotographic photoreceptor, 20°C, 30%
Under low humidity conditions of RH and 30'C. After being left for 12 hours under 85% RHO high humidity conditions and 80°C heating conditions, the sensitivity and dark decay of the obtained photoreceptor were measured in the same manner as in Example 1, and the environmental characteristics and heat resistance were measured. Stability was evaluated. The results are shown in Table 2.

Akira Huarashi I The same operation as in Example I was performed. However, dibromaleic anhydride may be used as a sensitizing agent. Three parts were used. The test results are shown in Tables 1 and 2.

Fumasu Group 1 The same operations as in Example 1 were performed. However, monochloromaleic anhydride is used as a sensitizing agent! 0.16 parts of Ik was used.

The test results are shown in Tables 1 and 2.

The same operation as in Example 1 was performed. However, as a sensitizing dye, a compound of general formula (I) [wherein R. Both R2 are -C}lx-CB=CHz, and X is an I atom]
was used.

The test results are shown in Tables 1 and 2.

The same operation as in Example 1 was performed. However, a compound having the following structural formula was used as a sensitizing dye.

The test results are shown in Tables 1 and 2.

The same procedure as in Main Example 1 was carried out. However, maleic anhydride was used as a sensitizing agent.

The test results are shown in Tables 1 and 2.

Stop plate The same operation as in main example 1 was performed. However, phthalic anhydride was used as a sensitizing agent.

The test results are shown in Tables 1 and 2.

Table 1 Table 2 (Note) Processed for 12 hours under each condition *E'b = Half exposure! (Sensitivity) (erg/c4) **D
D R = Dark decay retention rate (%) As shown in Table I,
The electrophotographic photoreceptors of Examples 1 to 4 according to the present invention had high sensitivity to semiconductor laser light and small dark decay. In addition, the exposure latitude was wide enough for practical use.

On the other hand, the electrophotographic photoreceptors of Comparative Examples 1 to 3 had insufficient sensitivity, large dark decay, or impractically narrow exposure latitude. Further, as shown in Table 2, the electrophotographic photoreceptor according to the present invention has high humidity, low humidity,
It was also confirmed that there is little variation in sensitivity and attenuation under high temperature conditions.

[Effects of the Invention] The electrophotographic photoreceptor of the present invention exhibits high sensitivity to semiconductor laser light and provides a recording medium or printing plate that is stable even in high-humidity and high-temperature environments. Therefore, the electrophotographic photoreceptor of the present invention facilitates scanning exposure with semiconductor laser light, which has been difficult with conventional zinc oxide electrophotographic photoreceptors, and is extremely useful for digitalization of printing plate making.

Claims (1)

[Claims] 1. A support having conductivity and water resistance, photoconductive zinc oxide formed on the support, and a resin binder;
(a) The sensitizing dye has the following general formula (I) ▲The numerical formula, chemical formula, table, etc. ▼(I) [However, in the above formula, R_1 and R_2 each independently represent -CH_3, -C_2H_5 and -CH_2-
(b) the sensitizing auxiliary agent has the following general formula (II) ▲Math. , chemical formulas, tables, etc. ▼ (II) [However, in the above formula, Y_1 represents a hydrogen atom or a halogen atom, and Y_2 represents a halogen atom]. Features: Electrophotographic photoreceptor for laser light.