JP2002023398A - Electrophotographic photoreceptor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor having high electrification potential and high sensitivity and showing stable performance without causing changes in the characteristics even for repeated use. SOLUTION: The electrophotographic photoreceptor having a photosensitive layer containing a charge generating substance and a charge transfer substance as the structural components on a conductive supporting body contains at least one kind of phthalocyanine composition having a specified crystalline structure as the charge generating substance and contains at least one kind of triaryl amine compound having a specified structure as the charge transfer substance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member containing a specific phthalocyanine compound and a specific triarylamine compound.

[0002]

2. Description of the Related Art Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, zinc oxide, and silicon have been known for electrophotographic photoreceptors, and have been widely studied and put to practical use. . While these inorganic materials have many advantages, they also have various disadvantages. For example, selenium has drawbacks in that the production conditions are difficult and it is easy to crystallize due to heat and mechanical shock, and cadmium sulfide and zinc oxide have poor moisture resistance and durability. It has been pointed out that silicon is insufficient in chargeability and difficult to manufacture. Furthermore,
Selenium and cadmium sulfide also have toxicity problems.

On the other hand, organic photoconductive materials have good film-forming properties, excellent flexibility, are lightweight, have good transparency, and are sensitive to a wide wavelength range by an appropriate sensitization method. Due to its advantages such as easy design of the body, its practical use has been gradually attracting attention.

Incidentally, the photoreceptor used in the electrophotographic technology is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in a dark place, (2) little leakage (dark decay) of the obtained charge in a dark place, and (3) charge charge by light irradiation. (4) The residual charge after light irradiation is small.

However, many studies have been made on photoconductive polymers such as polyvinyl carbazole as organic photoconductive substances to date, but these have not always had sufficient film-forming properties, flexibility and adhesiveness. Also, it is difficult to say that the above-mentioned basic properties of the photoreceptor are sufficiently provided.

On the other hand, as for the organic low-molecular-weight photoconductive compound, by selecting a binder or the like used for forming the photoreceptor, the photoreceptor having excellent mechanical strength such as film property, adhesiveness and flexibility can be obtained. Can be obtained, but it is difficult to find a compound suitable for maintaining high sensitivity characteristics.

In order to improve such a point, an organic photoreceptor having a higher sensitivity characteristic has been developed in which the charge generation function and the charge transport function are shared by different substances. The feature of such a photoreceptor, which is called a function-separated type, is that a material suitable for each function can be selected from a wide range, and a photoreceptor having an arbitrary performance can be easily manufactured. Has been advanced.

Among them, various substances such as phthalocyanine, squarium dye, azo pigment, and perylene pigment have been studied as substances in charge of the charge generation function. Among them, azo pigments can have various molecular structures. It has been widely studied because high charge generation efficiency can be expected, and its practical use is also progressing. However, in this azo pigment,
The relationship between molecular structure and charge generation efficiency has not yet been clarified. The fact is that we are pursuing an enormous amount of synthetic research and searching for the optimal structure.

In recent years, laser beam printers, which use laser light as a light source instead of the conventional white light and have advantages of high speed, high image quality and non-impact, have become widespread in conjunction with advances in information processing systems. There is a demand for the development of materials that can withstand the demands. Particularly, in recent years, semiconductor lasers, which have been increasingly applied to compact discs, optical discs, and the like and are undergoing remarkable technological advances, have been actively applied in the field of printers as compact and highly reliable light source materials. In this case, since the wavelength of the light source is about 780 nm, a photoreceptor having high sensitivity to long wavelength light of about 780 nm is suitable, and its development is strongly desired. Among them, the development of a photoreceptor using phthalocyanine, which has light absorption in the near infrared region in particular, has been actively conducted, but no satisfactory photoconductor has yet been obtained.

On the other hand, the substances in charge of the charge transport function include a hole transport substance and an electron transport substance. Examples of the hole transport substance are hydrazone compounds and styryl compounds, and examples of the electron transport substance are 2,4,7-trinitro-9-fluorenone.
Many kinds of substances such as diphenoquinone derivatives have been studied and put into practical use, but the fact is that they are also conducting extensive synthetic research and searching for the optimal structure. There are a wide variety of combinations of these charge generation materials and charge transport materials, and even more enormous exploration research is required to achieve the optimal combination. In fact, many improvements have been made so far, but those that satisfy the requirements for the basic properties and high durability required for the photoconductors listed above,
Not yet obtained.

As described above, various improvements have been made in the production of an electrophotographic photosensitive member, but it satisfies the above-mentioned requirements for the basic characteristics and high durability required for the photosensitive member. At the moment, things have not been obtained enough.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high sensitivity and high durability, a high charging potential, and the sensitivity is hardly lowered even after repeated use, and the charging potential is stable. To provide an electrophotographic photosensitive member.

[0013]

The present inventors have conducted research on a photoconductive substance having high sensitivity and high durability. -48800 and the like have found that a combination of triarylamine compounds is effective, and have led to the present invention. That is, the present invention includes the following (I) and (II).

(I) In an electrophotographic photosensitive member having a photosensitive layer containing a charge generating substance and a charge transporting substance as constituents on a conductive support, a phthalocyanine composition containing titanyloxyphthalocyanine and a metal-free phthalocyanine as charge generating substances And the phthalocyanine composition has a CuKα 1.541 Å X-ray Bragg angle (2θ ± 0.2 °) of 7.0.
°, 9.0 °, 14.1 °, 18.0 °, 23.7 °,
An electrophotographic photosensitive member having a peak at 27.3 °.

(II) The electrophotographic photoreceptor according to the above (I), which contains at least one triarylamine compound represented by the general formula (1) as a charge transporting substance.

[0016]

Embedded image

In the general formula (1), R ¹ is a hydrogen atom,
It represents an alkyl group, an alkoxy group, or a halogen atom. Ar ¹ and Ar ² each represent an optionally substituted alkyl group, alkenyl group, aryl group, or aralkyl group, and Ar ¹ and Ar ² may be bonded to each other to form a ring.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the general formula (1), specific examples of R ¹ include, for example, a hydrogen atom, a methyl group, an ethyl group,
Examples include alkyl groups such as propyl group, isopropyl group, n-butyl group and t-butyl group, alkoxy groups such as methoxy group, ethoxy group, propoxy group and n-butoxy group, and halogen atoms such as fluorine, chlorine and bromine. Can be. Ar
Specific examples of ¹ and Ar ² include, for example, alkenyl groups such as vinyl group, allyl group and methallyl group, aryl groups such as phenyl group, naphthyl group and anthryl group, benzyl group, 2-
Examples include an aralkyl group such as a phenylethyl group and a 1-naphthylmethyl group, and the above-described alkyl group. Ar
¹ and Ar ² may have a substituent, for example, dimethylamino group, amino group such as diphenylamino group, methylthio group, alkylthio group such as ethylthio group, arylthio group such as phenylthio group, Examples include a heterocyclic group such as a pyridyl group, a furyl group, and a thienyl group, a hydroxyl group, a carboxyl group which may be esterified, a cyano group, the above-described alkyl group, alkenyl group, aryl group, alkoxy group, and halogen atom. it can.

Specific examples of the triarylamine compound represented by the general formula (1) used in the present invention include, for example, the triarylamine compounds described in Japanese Patent Application No. 11-48800 already proposed. .

The phthalocyanine composition used in the present invention can be produced by the method described in Japanese Patent Application No. 11-122309 already proposed.

The electrophotographic photoreceptor of the present invention is obtained by containing at least one specific phthalocyanine composition as a charge generating substance and at least one compound represented by the general formula (1) as a charge transporting substance. The specific phthalocyanine composition referred to herein includes titanyloxyphthalocyanine and metal-free phthalocyanine,
Bragg angles (2θ ± 0.2 °) with respect to X-ray of uKα1.541 Å are 7.0 °, 9.0 °, 1
It is a phthalocyanine composition having peaks at 4.1 °, 18.0 °, 23.7 °, and 27.3 °.

Various types of photosensitive members are known, and any of them can be used. For example, there is one in which a photosensitive layer comprising a charge generating substance, a charge transporting substance, and a film-forming binder resin is provided on a conductive support. Further, a laminated photoreceptor in which a charge generation layer composed of a charge generation substance and a binder resin and a charge transport layer composed of a charge transport substance and a binder resin are provided on a conductive support is also known. . Either of the charge generation layer and the charge transport layer may be an upper layer. In addition, if necessary, an undercoat layer is provided between the conductive support and the photosensitive layer, an overcoat layer is provided on the surface of the photosensitive member, and in the case of a laminated photosensitive member, an intermediate layer is provided between the charge generation layer and the charge transport layer. Can also be provided. As a support for producing a photoreceptor using the compound of the present invention, a metal drum, a metal plate, a paper subjected to conductive processing, a sheet of a plastic film, a drum or a belt, and the like are used. You.

As the film-forming binder resin used for forming the photosensitive layer on the support, there are various resins depending on the field of use. For example, in photoconductors for copying machines, polyvinyl chloride resin, polystyrene resin,
Examples thereof include polyvinyl acetal resin, polysulfone resin, polycarbonate resin, vinyl acetate / crotonic acid copolymer resin, polyester resin, polyphenylene oxide resin, polyarylate resin, alkyd resin, acrylic resin, methacrylic resin, and phenoxy resin. Among these, polystyrene resin, polyvinyl acetal resin,
Polycarbonate resin, polyester resin, polyarylate resin and the like have excellent potential characteristics as a photoconductor.
These resins can be used alone or as a mixture of one or more of them as a copolymer. The amount of the binder resin added to the photoconductive compound is 20 to 20.
It is preferably 1000% by weight, more preferably 50-500% by weight.

In the case of a laminated photoreceptor, these resins contained in the charge generation layer are 10 to 50 with respect to the charge generation substance.
0% by weight is preferable, and 50 to 150% by weight is more preferable. If the ratio of the resin is too high, the charge generation efficiency is lowered, and if the ratio of the resin is too low, there is a problem in film formability. Further, the content of these resins contained in the charge transport layer is preferably from 20 to 1,000% by weight, more preferably from 50 to 500% by weight, based on the charge transport material. If the ratio of the resin is too high, the sensitivity is lowered, and if the ratio of the resin is too low, the repetition characteristics may be deteriorated or the coating film may be damaged.

Some of these resins include tension, bending,
Some have weak mechanical strength such as compression. To improve this property, substances which impart plasticity can be added. Specifically, phthalic acid esters (eg, DOP, DOP
BP), phosphoric acid esters (eg, TCP and TOP), sebacic acid esters, adipic acid esters, nitrile rubber, chlorinated hydrocarbons, and the like. These substances are
If added more than necessary, the electrophotographic properties are adversely affected, so the ratio is preferably 20% or less based on the binder resin.

Other additives such as an antioxidant and an anti-curl agent may be added to the photoreceptor as needed to improve coating properties.

The compound represented by the general formula (1) can be used in combination with another charge transporting substance. The charge transport materials include a hole transport material and an electron transport material. Examples of the former include oxadiazoles disclosed in JP-B-34-5466 and JP-B-45-55.
5 and the like, pyrazolines described in JP-B-52-4188 and the like, hydrazones described in JP-B-55-42380 and the like; Oxadiazoles disclosed in JP-A-123544 and the like can be exemplified.
On the other hand, examples of the electron transporting substance include chloranil, tetracyanoethylene, tetracyanoquinodimethane,
4,7-trinitro-9-fluorenone, 2,4,5
7-tetranitro-9-fluorenone, 2,4,5,7
-Tetranitroxanthone, 2,4,8-trinitrothioxanthone, 1,3,7-trinitrodibenzothiophene, 1,3,7-trinitrodibenzothiophene-
5,5-dioxide and the like. These charge transport materials can be used alone or in combination of two or more.

It is also possible to form a charge transfer complex with the organic photoconductive material according to the present invention and to add a certain electron-withdrawing compound as a sensitizer for further enhancing the sensitizing effect. Examples of the electron-withdrawing compound include 2,3-
Dichloro-1,4-naphthoquinone, 1-nitroanthraquinone, 1-chloro-5-nitroanthraquinone, 2-
Chloroanthraquinone, quinones such as phenanthrenequinone, aldehydes such as 4-nitrobenzaldehyde,
9-benzoylanthracene, indandione, 3,5
Ketones such as dinitrobenzophenone, 3,3 ', 5,5'-tetranitrobenzophenone, phthalic anhydride,
Acid anhydrides such as 4-chloronaphthalic anhydride, terephthalalmalononitrile, 9-anthrylmethylidenemalononitrile, 4-nitrobenzalmalononitrile, 4- (p
-Nitrobenzoyloxy) cyano compounds such as benzalmalononitrile, 3-benzalphthalide, 3- (α-cyano-p-nitrobenzal) phthalide, 3- (α-cyano-p-nitrobenzal) -4,5,6,7 -Phthalides such as tetrachlorophthalide and the like.

The organic photoconductive material according to the present invention is dissolved or dispersed in a suitable solvent together with the above-mentioned various additives depending on the form of the photoreceptor, and the coating solution is applied to the above-mentioned conductive support. It can be applied on top and dried to produce a photoreceptor.

Examples of the coating solvent include halogenated hydrocarbons such as chloroform, dichloroethane, dichloromethane, trichloroethane, trichloroethylene, chlorobenzene and dichlorobenzene, aromatic hydrocarbons such as benzene, toluene and xylene, dioxane, tetrahydrofuran, methylcellosolve, ethylcellosolve, and the like. Ether solvents such as ethylene glycol dimethyl ether, ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, methyl isopropyl ketone and cyclohexanone, ester solvents such as ethyl acetate, methyl formate, methyl cellosolve acetate, N, N-dimethylformamide, acetonitrile, Non-protonic polar solvents such as N-methylpyrrolidone and dimethyl sulfoxide and alcohol solvents can be exemplified. These solvents can be used alone or as a mixed solvent of two or more kinds.

[0031]

EXAMPLES Next, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

The structural formulas of the triarylamine compounds used in the following examples are shown in (2) to (11).

[0033]

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[0034]

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[0035]

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Example 1 The phthalocyanine composition used in the following examples was produced according to the method described in Japanese Patent Application No. 11-122309 already proposed. The obtained phthalocyanine composition 1
Parts by weight and 1 part by weight of a polyarylate resin (U-polymer manufactured by Unitika) were mixed with 100 parts by weight of tetrahydrofuran, and dispersed together with glass beads by a paint conditioner for 2 hours. The dispersion thus obtained was applied on an aluminum vapor-deposited polyester using an applicator to form a charge generation layer having a thickness of about 0.2 μm. Next, the triarylamine compound (2) was mixed with a polyarylate resin (U-Polymer manufactured by Unitika) at a weight ratio of 1: 1 to prepare a 10% solution using dichloroethane as a solvent. To the film thickness of about 20
A μm charge transport layer was formed.

The laminated photoreceptor thus produced is
Electrophotographic characteristics were evaluated using an electrostatic recording tester (SP-428, manufactured by Kawaguchi Electric Co., Ltd.). Measurement conditions: applied voltage -6 kV, static No. 3 (turntable rotation speed mode: 10 m / min)
). As a result, the charged potential V0 was -730 V, and the half-life exposure amount E1 / 2 was 0.7 lux / sec, which was a high sensitivity value.

Further, the same apparatus was used to evaluate characteristics for repeated use in which charge-discharge (discharge light: irradiation with white light at 400 lux for 1 second) was performed in one cycle. 5000
The change in the charged potential due to the repetition of
The initial potential at the 5000th time was −695 V compared to the initial potential at the −700 V time, and it was found that the potential was not reduced by repetition and was stable. It was also found that the 5000th half-exposure dose was 0.8 lux / sec, which was the same as the first half-exposure dose of 0.8 lux-sec.

Examples 2 to 10 Photoconductors were prepared in the same manner as in Example 1 except that the compounds shown in Table 1 were used instead of the triarylamine compound (2) of Example 1, and the characteristics were evaluated. did. Table 1 shows the results.

[0040]

[Table 1]

Example 11 Phthalocyanine composition 1 produced in the same manner as in Example 1
Parts by weight and 40 parts by weight of tetrahydrofuran were dispersed for 48 hours together with zirconia beads by a ball mill. To the dispersion thus obtained, 2.5 parts by weight of the triarylamine compound (2), 10 parts by weight of a polycarbonate resin (Panlite C-1400 manufactured by Teijin Chemicals), and 60 parts by weight of tetrahydrofuran are added, and ultrasonic waves are further added for 2 minutes. After the dispersion treatment, it was applied on an aluminum-evaporated polyester with an applicator to form a photoreceptor having a thickness of about 10 μm. The electrophotographic characteristics of this photoreceptor were measured in the same manner as in Example 1. However, only the applied voltage was changed to +5 kV. As a result, +405 V, half-exposure amount of 1.2 lux.sec, initial potential after repeating 5000 times +395 V, half-exposure amount of 1.1 lux-sec, exhibiting excellent characteristics with high sensitivity and little change.

Examples 12 to 20 Photoconductors were prepared in the same manner as in Example 11 except that the compounds shown in Table 2 were used instead of the triarylamine compound (2) of Example 11, and the characteristics were evaluated. . Table 2 shows the results
Shown in

[0043]

[Table 2]

The structural formulas of the comparative compounds used in the following comparative examples are shown in (12) to (14).

[0045]

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Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that the comparative compound (12) was used instead of the triarylamine compound (2), and the characteristics were evaluated. As a result, the first initial potential was -700 V, and the half-life exposure amount E1 / 2 was 1.8 lux.
Although the results were relatively good in seconds, the initial potential at the 5000th time was −330 V, the half-life exposure amount was 1.1 lux · sec, and a significant decrease in potential due to repetition was observed.

Comparative Example 2 A photoconductor was prepared and its characteristics were evaluated in the same manner as in Example 1, except that the comparative compound (13) was used instead of the triarylamine compound (2). As a result, the initial potential at the first time was -730 V, and the half-life exposure amount E1 / 2 was relatively good at 1.7 lux-sec. The initial potential at the 5000th time was -625 V, which was a relatively good result. However, the half-life exposure amount was 3.9 lux / sec, and a significant deterioration in sensitivity due to repetition was observed.

Comparative Example 3 A photoconductor was prepared in the same manner as in Example 11, except that the comparative compound (14) was used instead of the triarylamine compound (2), and the characteristics of the photoconductor were evaluated. As a result, the initial potential was 400 V, and the half-life exposure amount E1 / 2 was 4.0 lux / sec, which was insufficient sensitivity.

[0049]

As is apparent from the above, according to the present invention, an electrophotographic photosensitive member having high sensitivity and high durability can be provided.

Claims (2)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing a charge-generating substance and a charge-transporting substance as constituents on a conductive support, wherein the phthalocyanine composition contains titanyloxyphthalocyanine and a metal-free phthalocyanine as charge-generating substances. The phthalocyanine composition has a CuKα 1.541 Å X-ray Bragg angle (2θ ± 0.2 °) of 7.0 °,
9.0 °, 14.1 °, 18.0 °, 23.7 °, 2
An electrophotographic photosensitive member having a peak at 7.3 °. 2. The electrophotographic photoreceptor according to claim 1, comprising at least one triarylamine compound represented by the general formula (1) as a charge transporting substance. Embedded image (In the general formula (1), R ¹ represents a hydrogen atom, an alkyl group, an alkoxy group, or a halogen atom. Ar ¹
And Ar ² each represent an optionally substituted alkyl group, alkenyl group, aryl group, or aralkyl group, and Ar ¹ and Ar ² may combine with each other to form a ring. )