JPS59157651A - Electrophotographic sensitive agent composition - Google Patents

Abstract

PURPOSE:To obtain a satisfactory sensitization effect by incorporating nitrophthalic anhydride in a combination of polyvinylcarbazole (PVK)-perylene type pigment. CONSTITUTION:A perylene type electrostatic charge generating pigment is dispersed into a charge transfer medium composed essentially of a PVK type resin, and this medium incorporates nitrophthalic anhydride represented by the formula shown here (n being 1 or 2) as a sensitizer, in an amt. of 0.1-10, preferably, 1-4pts.wt. per 100pts.wt. PVK type resin.

Description

DETAILED DESCRIPTION OF THE INVENTION In more detail, there is a method for significantly increasing the sensitivity of an electrophotographic photosensitive composition comprising a polyvinyllupasol charge transport medium and a perylene charge generating pigment dispersed in this medium. Regarding improvements.

Conventionally, a single-layer photosensitive composition comprising a charge-generating pigment dispersed in a charge transport medium has been prepared by dispersing a phthalocyanine pigment or a disazo pigment in a medium mainly composed of polyvinylcarbazole (hereinafter sometimes simply referred to as PVK). Although pigments in which pigments are dispersed are known, those in which perylene pigments are dispersed in polyvinylcarnosol exhibit a sensitivity that is hardly practical.

Conventionally, trinitroanthracene, 2+4+. 7) 'J=Various electron acceptor substances such as polycyclic or heterocyclic nitro compounds such as trofluorenone, acid anhydrides such as fucuric anhydride and trimellidic anhydride, and talolanil and bromanil are known. However, most of these known sensitizers are still unsatisfactory in terms of sensitivity, charging characteristics, etc. when used in combination with PvK-perylene pigments.

In addition, the present inventors previously found that a very satisfactory sensitizing effect can be obtained when a lonaphthoquinone is added to the above-mentioned combination of PVK-perylene pigments, but nitrophthalic anhydride It has been found that even better sensitivity can be obtained by adding PVK-perylene pigments to the combination of PVK and perylene pigments.

That is, an object of the present invention is to provide a PVK-perylene thread pigment-dispersed photosensitizer composition that exhibits extremely superior sensitivity compared to known photosensitizers.

According to the present invention, in an electrophotographic photosensitive composition comprising a perylene pigment as a charge generating pigment dispersed in a charge transporting medium mainly composed of a polyvinylcarbazole resin, in the following formula, n is a number from 1 to 2. There is provided an electrophotographic photosensitizer composition characterized by containing nitrophthalic anhydride represented by the following as a sensitizer.

The nitro-phthalic anhydride used in the present invention is a compound represented by the following general formula: where n is a number of 1 or 2. The most preferably used in the present invention are 4-nitro-7thalic anhydride, 3-nitro-phthalic anhydride, and 3,5-dinitro-phthalic anhydride.

Of course, the above-mentioned nitrophthalic anhydride may be used alone or in combination.
It can also be used in combinations of more than one species. Furthermore, this nitro-phthalic anhydride can be used in combination with sensitizers consisting of other electron acceptors known per se.

The present invention is based on the knowledge that nitro-phthalic anhydride specifically exhibits a sensitizing effect on PVK-perylene pigment dispersions. As is clear from the structure of Ni(1+), nitro-7curic anhydride has a chemical structural feature in which a nitro group (-NO2) with strong electron absorption is bonded to the benzene nucleus of phthalic anhydride. Known sensitizers most similar to nitro-phthalic anhydride, such as phthalic anhydride, have little effect on PvK-perylene-based photosensitizer compositions. However, when the above-mentioned nitro-phthalic anhydride was used, an extremely excellent increase in sensitivity was observed.This indicates that the nitro group is bonded to the benzene ring. It is understood that this has a significant influence on the sensitizing effect of this system.

However, even when this nitrophthalic anhydride is contained in a photosensitive brain containing a resin other than PVK, that is, a non-photoconductive resin-perylene pigment dispersion system, it shows almost no sensitizing effect. It appears that the sensitizing effect according to the present invention is based on the interaction between nitrophthalic anhydride and PVK.

In the present invention, this nitrophthalic anhydride is used in PVK~1
0.1 to 10 parts by weight per 00 parts by weight, more preferably 1
It is also important to use amounts of from 4 parts by weight. PVK-
As nitrophthalic anhydride is gradually added to perylene pigments, the sensitivity tends to gradually increase, but beyond the above range, the amount of charge decreases rapidly and 1 becomes almost unusable. A trend can be seen. Also, nitro anhydrous 7
If the amount of tarric acid is less than the above range, both the sensitivity and the amount of charge will be low, making it unsuitable for the purpose of the present invention.

Polyvinylcarbazole, which serves as a charge transport medium, is a polymer consisting of the following repeating unit -6H2-CH-, and is itself a film-forming resin and an electron-donating resin. Nuclear substitution products, such as halogen-spanning nitro substitution products, etc. can be used similarly.

As the perylene pigment, there may be used a pigment known per se represented by the following formula, in which each of R1 and R2 represents a hydrogen atom, a substituted or unsubstituted alkyl group, or an aryl group.

Suitable examples of substituents are a hydroxy group, an alkoxy group, an amine group, a nitro group, or a norogen atom.

Examples of suitable perylene pigments include, but are not limited to, the following:

N,N'-dimethylperylene-3,4,9,10-
Tetracarboxylic acid diimide, N,N'-di(3,5dimethylphenyl)perylene-3,4,9,10'tetracarboxylic acid diimide, N,N'-di(4-ethoxydiphenyl)perylene- 3
, 4,9,10-tetracarboxylic acid diimide, N , N/-di(4-tolyl)perylene-3,4°9.10-tetracarboxylic acid diimide.

It is also important to use the perylene pigment in an amount of 5 to 50 parts by weight, particularly 10 to 30 parts by weight, per 100 parts by weight of polyvinylcarbasol; if it is less than the above range, satisfactory sensitivity may not be obtained. Moreover, when the amount exceeds the above range, the initial saturation charging potential tends to decrease and the sensitivity also tends to decrease.

In this photoreceptor, binders that do not themselves have photoconductivity, such as polyester resins, epoxy resins, and polycarbonate resins, are used to increase the mechanical strength of the photosensitive layer and improve its adhesion to the conductive body. , polyurethane resin, xylene resin, acrylic resin, styrene-butadiene copolymer, etc. can be used, and these binders include the aforementioned polyvinylcarbazole 100.
It may be used in amounts of 0.1 to 50 parts by weight, especially 10 to 30 parts by weight.

Further, in order to improve the surface smoothness of the photosensitive layer surface, a leveling agent such as polydimethylsiloxane may be used in an amount of 0.005 to 5 parts by weight per 100 parts by weight of polyvinylcarbazole.

The photosensitive composition of the present invention is applied as a layer of a certain thickness onto a conductive substrate and used in the form of an electrophotographic photoreceptor.

As conductive substrates, metal foils or plates made of aluminum, copper, tin, tinplate, etc., are used in the form of sheets or drums, and these metals can be used as film substrates such as biaxially stretched polyester films, glass, etc. Those applied by means such as vacuum evaporation, sputtering, and electroless plating, and NESA glass are used.

In preparing the coating composition, first, polyvinylcarbazole is dispersed using a good solvent such as tetrahydrofuran, dichloroethane, or by intermittent stirring, and then polyvinylcarbazole and nitrophthalic anhydride are dissolved in this dispersion. Since the nitro-phthalic anhydride used in the present invention is easily soluble in a solvent, it is also a great advantage that a homogeneous coating solution can be prepared. Furthermore, compared to other resins, nitro-phthalic anhydride has particularly excellent dispersibility with respect to PVKI/II.
This seems to be a major factor in the inability to efficiently transfer charges.

The solid concentration of the coating solution formed is 5.5% in terms of coating workability.
It is desirable that the content is in the range of 1% to 12% by weight.

In the present invention, the layer of the photosensitive composition is applied as a dry coating.
It should be in the range of 3 to 30 μ, especially 8 to 15 μ.
Desirable for its electrophotographic properties.

The photosensitive composition of the present invention exhibits excellent sensitivity both when it is charged positively or negatively. However, if this photosensitive layer is positively charged and then imagewise exposed, even more excellent sensitivity can be obtained.The present invention will be explained below with reference to the following example.

Example 1 A homogeneous dispersion liquid was prepared by dispersing the mixture in a liquid filter at a rotation speed of 80 rpm for 24 hours.

Next, this dispersion was added, followed by dispersion at a rotational speed of 80 rpm for 24 hours to obtain a uniformly dispersed coating solution.

The above coating solution was applied onto an 80μ thick aluminum plate using a wire parser so that the thickness after drying was 14μ.
Drying was performed at ℃ for 1 hour to obtain a photoreceptor.

Examples 2 to 5 and Comparative Examples 1 to 3 Examples 2 to 5 were carried out in exactly the same manner as in Example 1 except that the amount of 4-nitrophthalic anhydride was changed to the formulation shown in Table 1 below.
, photoreceptors of Comparative Examples 1 to 3 were produced.

Example 6 A photoreceptor was prepared in exactly the same manner as in Example 1, except that 3.0 parts by weight of 3-diphthalic anhydride was added instead of 4-nitrophthalic anhydride.

Measurement of Sensitivity and Charge Amount The sensitivity and charge amount of the obtained photoreceptor were measured using an electrostatic bar analyzer manufactured by Kawaguchi Electric KK under the following conditions.

Measurement mode 5tat 2 Applied voltage +6DKvolt Irradiation light White tungsten lamp 3Q1ux
For sensitivity, half-decreased exposure (lux, 5ec) was used. The measurement results are shown in Table 2.

Table 2 column ×: Poor, ○: Good, ◎: Especially good to Pe Li

Claims (1)

[Scope of Claims] +11 An electrophotographic photosensitive composition comprising a perylene pigment as a charge generating pigment dispersed in a charge transporting medium mainly composed of a polyvinylcarbazole resin, wherein n fd l to 2 in the following formula: An electrophotographic photosensitizer composition containing nitrophthalic anhydride represented by the following formula as a sensitizer. (2) The composition according to claim 1, which contains nitrophthalic anhydride in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the polyvinylcarbazole resin.