JPH0430173A - Electrophotographic photoreceptor for laser light - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 that is spectrally sensitized with respect 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 spread of data digitization, laser light, especially laser light generators, has been used. Semiconductor laser light, which is small and can be directly modulated, is increasingly being used. A photoreceptor used for such laser light is required to have sensitivity to long wavelength light of 700 to 11,000 nm.

Various electrophotographic photoreceptors sensitive to the wavelength range of semiconductor laser light are described, for example, in Japanese Patent Application Laid-open Nos. 57-46245 and 5B.
-58554, 5B-59453, 59-22
No. 053 and No. 59-78358. The zinc oxide-based electrophotographic photoreceptor disclosed in the above-mentioned publication is one in which a sensitizing dye such as a polymethine-based cyanine dye is blended into the photosensitive layer to perform spectral sensitization over a long wavelength region. However, as in these examples, when a sensitizing dye was only added, 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, Japanese Patent Application Laid-Open No. 1-161253 discloses a type having an alkylsulfonic acid group on the N-substituent of the dimethylindole ring at both ends. A photosensitive layer formulation using a polymethine cyanine dye and maleic anhydride as a sensitizing auxiliary agent is described.

An electrophotographic photoreceptor having a photosensitive layer with such a formulation has sufficient sensitivity for use in laser printers that use semiconductor laser light and laser engraving machines, and the photoreceptor also has good thermal stability. It is. However, such photoreceptors have the disadvantage that dark decay is large, and the dark decay becomes even greater in high temperature and high humidity environments.

(Problems to be Solved by the Invention) The present invention has high sensitivity to long-wavelength light with a wavelength of 700 to 1000 ns+, 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 to solve the problem]

As a result of intensive research in order to improve the above-mentioned problems and obtain a good semiconductor laser-equipped electrophotographic photoreceptor, the present inventor 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 present invention was completed based on the discovery that it is possible to obtain a photoreceptor with a small dark decay and a small change in dark decay due to the environment.

The electrophotographic photoreceptor for laser light of the present invention includes a support having conductivity and water resistance, and a photoconductive zinc oxide, a resin binder, and a sensitizing dye formed on one surface of the support. and an electrophotographic photosensitive layer for laser light containing a sensitizing aid, and the sensitizing dye has the following general formula (■): [However, in the above formula (1), m and m2 are , each independently represents an integer of 1 or more, and R5 and R2 are
Each independently represents a -C00- or -5O1- group, and R1 is a metal atom 1. or a quaternary ammonium group, and the sensitizing auxiliary agent is derived from an aromatic acid having three or more -COOH groups substituted on a benzene ring. It is characterized by containing at least one kind of cyclic acid anhydride.

The sensitizing dye used in the present invention is characterized by very good thermal stability, but when it is combined with conventionally used sensitizing auxiliaries, it exhibits unsatisfactory performance such as large dark decay. However, the present inventors discovered the surprising phenomenon that when this sensitizing dye is combined with the sensitizing aid of the present invention, a practically sufficient sensitivity can be obtained and the dark decay is reduced. .

In the formula (1), m and m2 are each independently preferably from 1 to 5, and R3 is a metal atom such as Na and K, and HN(CtHs)s,
It is preferably selected from one group of -IN(CH3) and the like.

The content of the sensitizing dye of the present invention contained in the electrophotographic layer is generally preferably in the range of 0.001 to 0.5%, and 0.01 to 0.2% based on the weight of zinc oxide. It is more preferable that it is within the range of .

In the present invention, specific examples of the cyclic acid anhydride used as a sensitizing agent include trimellitic anhydride, pyromellitic anhydride, and the like.

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 is generally a fine powder having a particle size of 0.1 to 0.5-0.

The insulating binder resin used in the electrophotographic photosensitive layer may be composed of a single type of resin, or may be composed of two types of resin.
It may be a mixture of more than one type of resin. There is no particular limitation on the type of binder resin as long as it can sufficiently bind the zinc oxide fine powder, sensitizing dye, and sensitizing aid and has film-forming properties, but in general, it is an oil-based binder resin. It is preferable to use a soluble acrylic resin. As such an oil-soluble acrylic resin, for example, L manufactured by Mitsubishi Rayon
Examples include R-188 (trade name) and Acridic^405 (trade name) manufactured by Dainippon Ink and Chemicals.

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

Examples of the conductive water-resistant support for the electrophotographic photoreceptor of the present invention include known supports, such as metal sheets, paper laminated with metal foil, plastic films laminated with metal foil, paper with a vapor-deposited metal layer, and metal-deposited metal. You can choose from a plastic film with a layer, paper treated to make it conductive, a plastic film treated to make it conductive, or a lamination of two or more of the above materials. can.

To produce the electrophotographic photoreceptor of the present invention, first, a predetermined amount of zinc oxide, the sensitizing dye of the general formula (1), the sensitizing aid, and the binder resin are mixed with an organic solvent such as toluene,
A coating solution is prepared by mixing and dispersing it with 2-butanone and the like using a mixing and dispersing machine such as a ball mill, sand grinder, or paint shaker.

Next, the obtained coating liquid 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
Usually, it is preferably in the range of 5 to 25,11111, more preferably in the range of 10 to 20.

To form an image on the electrophotographic photoreceptor of the present invention, an electrostatic latent image is formed on the photosensitive layer by scanning exposure with semiconductor laser light, and this latent image is developed with toner.
It can be fixed by heating.

The obtained image can also be used as a record as it is. In addition, the surface of the developed photosensitive layer is treated with a so-called etching solution containing sodium ferrocyanide, etc.
By making the non-image area hydrophilic, the developed photoreceptor 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 scope of the present invention. Note that "parts" and "%°" in the examples represent "parts by weight" and "% by weight", respectively, unless otherwise specified.

The following coating liquid components were added to a rotary stirrer in the order listed and mixed.

Add to this mixed solution a compound of the general formula (1) as a sensitizing dye [wherein m, =m, =3. R.

=Rt =SO3-, R3=HN(CxHs)s. A solution prepared by dissolving 0.02 part of ) in 3 parts of methanol was added, and this mixed solution was dispersed with a sand grinder to obtain a photosensitive layer coating solution.

As the support, a composite sheet obtained by laminating aluminum foil with a thickness of 10 m to electrically conductive treated paper with a basis weight of 80 g/% was used.

The photosensitive layer coating solution was applied onto the surface of the aluminum foil layer of the support and dried with hot air at 100°C to a thickness of 20°C.
A #Il photosensitive layer was formed to obtain an electrophotographic photoreceptor.

The obtained electrophotographic photoreceptor was heated at 20°C and 65% J? ) After applying III humidity for 24 hours in a dark place, the surface of the photoreceptor was charged with negative corona at -6V, and then irradiated with light with a wavelength of 7B0 nm, and the potential of the photoreceptor surface was measured. From the results, the 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.

Furthermore, after the electrophotographic photoreceptor was left for 12 hours under high humidity conditions of 30° C. and 85% RH, the sensitivity and dark decay of the obtained photoreceptor were measured in the same manner as above. The test results are shown in Table 1.

Ura Chong Char I The same operation as in Example 1 was performed. However, 0.05 part of trimellitic anhydride was used as a sensitizing agent.

The test results are shown in Table 1.

Backyard ■The same operation as in Example 1 was performed. However, as a sensitizing dye, the compound of general formula (1) [where m+ = m
t=3. R+ = Rt = SQ3-. R:I
=Na. ] 0.2 part was added in mm.

The test results are shown in Table 1.

The same operation as in Example 1 was performed for the northern comparison. However, 1 part of anhydrous maleic MO was used as a sensitizing agent.

The test results are shown in Table 1.

5 m The same operation as in Example 1 was performed. However, phthalic anhydride was used as a sensitizing agent.

The test results are shown in Table 1.

Table 1 As is clear from Table 1, Examples 1 to 3 according to the present invention
The electrophotographic photoreceptor had high sensitivity to semiconductor laser light and low dark decay. In contrast, comparative example 1. The electrophotographic photoreceptors No. 2 and 2 had insufficient sensitivity or large dark decay. In particular, when high-temperature treatment was performed, the electrophotographic photoreceptors of Comparative Examples 1 and 2 exhibited significantly greater dark decay than those of Examples 1 to 3.

(Effects of the Invention) The electrophotographic photoreceptor of the present invention exhibits high sensitivity to semiconductor laser light, exhibits low dark decay, and provides a recording medium or printing plate that is stable in a humid environment. This facilitates scanning exposure using semiconductor laser light, which has been considered difficult in zinc oxide electrophotographic photoreceptors, and is useful for digitalization in printing plate making.

Claims (1)

[Scope of Claims] 1. A support having conductivity and water resistance, a photoconductive zinc oxide formed on one surface of the support, a resin binder, a sensitizing dye, and a sensitizing material. The sensitizing dye has the following general formula (I): ▲There are numerical formulas, chemical formulas, tables, etc.▼(I) [However, the above formula ( I), m_1 and m_2 each independently represent an integer of 1 or more, and R_1 and R_2 each independently represent -COO- or -
It represents a SO_3^- group, and R_3 represents a metal atom or a quaternary ammonium group. ] The sensitizing auxiliary agent contains at least one cyclic acid anhydride derived from an aromatic acid having three or more -COOH groups substituted on a benzene ring. 1. A laser-filled electrophotographic photoreceptor characterized by containing an object.