JPH08278650A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE: To provide an electrophotographic photoreceptor having high sensitivity and high durability. CONSTITUTION: At least one of azo compds. represented by formulae I, II is incorporated as a photoconductive material into a layer on conductive substrate. In the formulae I, II, each of R1 -R3 is H, halogen, alkyl which may have a substituent, alkoxy, aryl or a heterocyclic group and Cp is a residue of a coupler.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an electrophotographic photoreceptor containing a novel azo compound.

[0002]

2. Description of the Related Art Inorganic photoconductive substances such as selenium, cadmium sulfide, zinc oxide, and silicon have been heretofore 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 drawbacks. For example, selenium has drawbacks that it is difficult to produce under conditions and is easily crystallized by heat or mechanical shock, and cadmium sulfide and zinc oxide have poor moisture resistance and durability. It has been pointed out that silicon has insufficient chargeability and is difficult to manufacture. Furthermore, selenium and cadmium sulfide have toxicity problems.

On the other hand, organic photoconductive materials have good film-forming properties, excellent flexibility, light weight, good transparency, and are sensitized to a wide range of wavelengths by a suitable sensitizing method. Because of its advantages such as easy body design, its practical application is gradually gaining attention.

By the way, the photosensitive member used in the electrophotographic technique is generally required to have the following basic properties. That is, (1) high chargeability against corona discharge in the dark, (2) little leakage (dark decay) of the obtained charged charge in the dark, and (3) charge charging by light irradiation. The light is rapidly dissipated (4), and (4) there is little residual charge after light irradiation.

However, much research has been conducted on photoconductive polymers such as polyvinylcarbazole as an organic photoconductive substance to date, but these are not always sufficient in film formability, flexibility and adhesiveness. Also, it cannot be said that the photoconductor has the basic properties sufficiently.

On the other hand, regarding the organic low-molecular-weight photoconductive compound, by selecting a binder or the like used for forming the photoconductor, the photoconductor having excellent mechanical strength such as film-forming property, adhesive property and flexibility. However, it is difficult to find a compound suitable for retaining the highly sensitive property.

In order to improve such a point, the carrier generation function and the carrier transport function are shared by different substances,
Organic photoreceptors having higher sensitivity have been developed. The characteristic of such a photoconductor, which is called a function-separated type, is that materials suitable for each function can be selected from a wide range, and many studies have been carried out because a photoconductor having arbitrary performance can be easily prepared. Has been promoted.

Among these, various substances such as phthalocyanine, squarium dye, azo pigment, and perylene pigment have been investigated as substances in charge of the function of generating carriers. Among them, azo pigments can have various molecular structures, and Since it can be expected to have high charge generation efficiency, it has been widely studied and put into practical use. However, in this azo pigment, the relationship between the molecular structure and the charge generation efficiency has not yet been clarified. The reality is that we are conducting an enormous amount of synthetic research to search for the optimal structure, and many improvements have been made, but the basic properties and high durability required for the photoreceptors listed above have been made. Those satisfying such requirements have not yet been sufficiently obtained.

As described above, various improvements have been made in the preparation of the electrophotographic photosensitive member, but the basic properties and high durability required for the photosensitive member described above are satisfied. The current situation is that the products have not been obtained sufficiently.

[0010]

The object of the present invention is to have high sensitivity and high durability, a high charging potential, and a decrease in the sensitivity even after repeated use, and a stable charging potential. Another object of the present invention is to provide an electrophotographic photosensitive member.

[0011]

DISCLOSURE OF THE INVENTION The present inventors have conducted research on photoconductive substances having high sensitivity and high durability, and as a result, the novel azo compounds represented by the general formulas 1 and 2 are effective. Therefore, the object of the present invention was achieved by using at least one of these compounds.

In the chemical formulas 1 and 2, R _{1 to} R _{3 each} represent a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group, an aryl group or a heterocyclic group. Cp represents a coupler residue.

Specific examples of R _{1 to} R ₃ include hydrogen atom, halogen atom such as chlorine atom and bromine atom, alkyl group such as methyl group, ethyl group, ethoxyethyl group, n-propyl group and isopropyl group. , Alkoxy groups such as methoxy group, ethoxy group, propoxy group, butoxy group, phenyl group, methoxyphenyl group, methylphenyl group, chlorophenyl group, naphthyl group, anthryl group, aryl groups such as pyrenyl group, pyridyl group, furyl group, Heterocyclic groups such as thienyl groups can be mentioned.

In the chemical formulas 1 and 2, the coupler residue C
Specific examples of p include those shown in Tables 1 to 14, for example.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

[0018]

[Table 4]

[0019]

[Table 5]

[0020]

[Table 6]

[0021]

[Table 7]

[0022]

[Table 8]

[0023]

[Table 9]

[0024]

[Table 10]

[0025]

[Table 11]

[0026]

[Table 12]

[0027]

[Table 13]

[0028]

[Table 14]

Specific examples of the azo pigment represented by Chemical Formula 1 of the present invention include those shown in Tables 15 to 18. In the formula, Cp represents a coupler residue. In the table, Py represents a pyridyl group.

[0030]

[Table 15]

[0031]

[Table 16]

[0032]

[Table 17]

[0033]

[Table 18]

Specific examples of the azo pigment represented by Chemical Formula 2 of the present invention include those shown in Tables 19 to 22. In the formula, Cp represents a coupler residue. In the table, Py represents a pyridyl group.

[0035]

[Table 19]

[0036]

[Table 20]

[0037]

[Table 21]

[0038]

[Table 22]

The azo pigments represented by the above chemical formulas 1 and 2 used in the present invention are represented by the following chemical formulas 3 and 4 (in the formula, R _{1 to} R ₃
Can be easily obtained by converting a diamino compound represented by Chemical formula 1 and Chemical formula 2) into a tetrazonium salt by a conventional method and reacting it with a corresponding coupler in the presence of an alkali.

[0040]

Embedded image

[0041]

[Chemical 4]

Next, a synthesis example will be specifically described. Synthesis Example 1 (Synthesis of Raw Material Diamine Corresponding to B-45 in Table 17) 3,8-dinitro-5,6,11,12-tetrahydrodibenz [b, f] azocin-6-one , 4-dioxane, suspended in 600 ml, and previously activated with 6.0 ml of acetic acid, 60.0 g of iron powder, 1,4
-Add to a suspension of 60 ml of dioxane, 60 ml of water under reflux over about 5 minutes. After 30 minutes, the insoluble material is filtered off and the residue is concentrated under reduced pressure. 35.8 g of the obtained brown powder
Is subjected to silica gel chromatography using ethyl acetate as a solvent to obtain 14.8 g (yield 61.0%) of a brown powder. Melting point 254.0-256.3 ° C

Synthesis Example 2 (Exemplified Compound: B-45 in Table 17)
(Synthesis of Cp = A-45) 0.51 g of the diamine obtained in Synthesis Example 1 was mixed with N, N-dimethylformamide (DMF) (40 ml) and 1N hydrochloric acid (1
2 ml), and sodium nitrite (0.
An aqueous solution (2 ml) of 30 g) was added. 42% after 30 minutes
Boron hydrofluoric acid (10 ml) was added, and the precipitated tetrazonium salt was collected by filtration. This and 2-hydroxy-3
-(M-Trifluoromethyl) phenylcarbamoylbenzo [a] carbazole (1.68 g) was added to DMF (20
0 ml) and an aqueous solution (10 ml) of sodium acetate (1.48 g) was added dropwise at 5 to 10 ° C over 5 minutes. After stirring at the same temperature for 2 hours and then at room temperature for 2 hours,
The precipitate was collected by filtration and washed with 100 ml each of DMF, acetone and water. Yield 1.78g (Yield 79.7%) Melting point 250 ° C or higher

The electrophotographic photosensitive member of the present invention can be obtained by containing one kind or two or more kinds of the azo compounds shown in Chemical formula 1 or Chemical formula 2. Various types of photoreceptors are known, and any of them can be used. For example, there is one in which a photosensitive layer made of an azo compound, a charge transport material, and a film-forming binder resin is provided on a conductive support. Further, there is also known a laminated type photoreceptor in which a charge generation layer composed of an azo compound 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. Either the charge generation layer or the charge transport layer may be the upper layer. If necessary, an undercoat layer may be provided between the conductive support and the photosensitive layer, an overcoat layer may be provided on the surface of the photoreceptor, and an intermediate layer may be provided between the charge generation layer and the charge transport layer in the case of a laminated type photoreceptor. Can be provided. As a support for forming a photoreceptor using the compound of the present invention, a metal drum, a metal plate, a conductive processed paper, a sheet of plastic film, a drum-shaped or belt-shaped support, etc. are used. .

As the film-forming binder resin used for forming the photosensitive layer on these supports, various resins can be mentioned depending on the field of use. For example, in the application of photoconductor for copying, polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyester resin, polyphenylene oxide resin, polyarylate resin, acrylic resin, methacrylic resin, phenoxy resin and the like can be mentioned. Among these, polystyrene resin, polyvinyl acetal resin, polycarbonate resin, polyester resin, polyarylate resin and the like are excellent in potential characteristics as a photoreceptor. Further, these resins can be used alone or as a copolymer by mixing two or more kinds.

The content of these resins contained in the photosensitive layer is preferably 10 to 500% by weight with respect to the azo pigment, and 50 to 15% by weight.
0% by weight is more preferred. 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, the film formability becomes a problem.

Some of these resins include pulling, bending,
Some have weak mechanical strength such as compression. To improve this property, plasticizing agents can be added. Specifically, phthalate ester (for example, DOP, D
BP, etc., phosphoric acid ester (eg TCP, TOP
Etc.), sebacic acid ester, adipic acid ester, nitrile rubber, chlorinated hydrocarbon and the like. If these substances are added more than necessary, the electrophotographic characteristics are adversely affected, so the proportion thereof is preferably 20% or less relative to the binder resin.

In addition, an antioxidant, an anti-curl agent or the like can be added as an additive to the photosensitive member, if necessary.

The charge transport material includes a hole transport material and an electron transport material. As an example of the former, for example, Japanese Patent Publication No. 34-5
Oxadiazoles shown in Japanese Patent Publication No. 466, triphenylmethanes shown in Japanese Patent Publication No. 45-555, pyrazolines shown in Japanese Patent Publication No. 52-18888, Japanese Patent Publication No. 55-42380. Hydrazones disclosed in JP-A-56-123544, oxadiazoles disclosed in JP-A-56-123544, and JP-B-58-3237.
Examples thereof include the triarylamines disclosed in JP-A No. 2 and the stilbenes disclosed in JP-A No. 58-198043. On the other hand, examples of the electron transport material include chloranil, tetracyanoethylene, 2,
4,7-trinitro-9-fluorenone, 2,4,5,
7-tetranitroxanthone, 1,3,7-trinitrodibenzothiophene and the like. These charge transport materials may be used alone or in combination of two or more.

[0050]

EXAMPLES The present invention will now be described in more detail by way of examples, which should not be construed as limiting the invention thereto.

Example 1 1 part by weight of Exemplified Compound B-45 (Cp = A-115) and 1 part by weight of a polyester resin (Vylon 200 manufactured by Toyobo) were mixed with 100 parts by weight of tetrahydrofuran, and the mixture was mixed with glass beads by a paint conditioner device. Dispersed for 2 hours. With the applicator, the dispersion thus obtained,
Coating on aluminum vapor-deposited polyester, film thickness of about 0.2μ
The charge generation layer of was formed. Next, p-dibenzylaminobenzaldehyde = diphenylhydrazone 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 prepare the above charge generation layer. Was applied with an applicator to form a charge transport layer having a thickness of about 20 μm.

The laminated type photoreceptor thus prepared is
Electrophotographic characteristic evaluation was performed using an electrostatic recording tester (SP-428 manufactured by Kawaguchi Denki). Measurement conditions: Applied voltage -6 kV, Static No. 3 (turntable rotation speed mode: 10 m / min
). As a result, the charging potential V0 was -530 V and the half-exposure amount E1 / 2 was 1.9 lux.sec, which was a high sensitivity value.

Further, using the same apparatus, characteristics evaluation was carried out for repeated use in which one cycle of charging-discharging (eliminating light: irradiation with white light of 400 lux × 1 second) was set as one cycle. 5000
When the change in charging potential due to repetition was calculated, 1
It was found that the initial potential at the 5000th time was -500V, whereas the initial potential at the 5000th time was -530V, and the decrease in the potential due to repetition was small and stable. It was also found that the half-time exposure amount at the 5000th time was 1.9 lux-seconds, which was 1.9 lux-seconds at the first time.

Examples 2 to 6 Photosensitive members were prepared in the same manner as in Example 1 except that the azo pigments shown in Table 23 were used, and their characteristics were evaluated. The results are shown in Table 23.

[0055]

[Table 23]

Example 7 1 part by weight of Exemplified Compound B-45 (Cp = A-115) and 40 parts by weight of tetrahydrofuran were dispersed together with zirconia beads in a ball mill for 48 hours. 2.5 parts by weight of N-ethylcarbazole-3-carbaldehyde = diphenylhydrazone, polycarbonate resin (PCZ-200; manufactured by Mitsubishi Gas Chemical Co., Inc.) were added to the dispersion liquid thus obtained.
After 10 parts by weight and 60 parts by weight of tetrahydrofuran were added and ultrasonic dispersion treatment was further performed for 2 minutes, it was applied on aluminum vapor-deposited polyester by an applicator to form a photoreceptor having a film 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, +380 V, half-exposure amount 1.8 lux · sec, initial potential after repeating 5000 times +360 V, half-exposure amount 1.8 lux · sec,
It showed excellent characteristics with high sensitivity and little change.

Examples 8 to 12 Photosensitive members were prepared in the same manner as in Example 7 except that the azo pigments shown in Table 24 were used, and their characteristics were evaluated. The results are shown in Table 24.

[0058]

[Table 24]

Comparative Example 1 A photoreceptor was prepared in the same manner as in Example 1 except that Azo Compound 5 was used, and its characteristics were evaluated. As a result, the initial potential at the first time was -630V, the half-exposure amount E1 / 2 was 2.9 lux.sec., And the initial potential at the 5000th time was -310V, the half-exposure amount was 3.5 lux.sec. Was also an inadequate level, and a large decrease in the electric potential was observed with repetition.

Comparative Example 2 A photoconductor was prepared in the same manner as in Example 7 except that Azo Compound 5 was used, and its characteristics were evaluated. As a result, the initial potential was 300 V, the half-exposure amount E1 / 2 was 4.2 lux.
Seconds and lack of sensitivity.

[0061]

Embedded image

[0062]

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 (1)

[Claims] 1. An electrophotographic photoreceptor having a photosensitive layer containing at least one azo compound represented by the following general formulas 1 and 2 on a conductive support. Embedded image Embedded image (In Chemical Formula 1 and Chemical Formula 2, R _{1 to} R ₃ represent a hydrogen atom, a halogen atom, an alkyl group which may have a substituent, an alkoxy group, an aryl group, or a heterocyclic group. (Indicates a coupler residue.)