JPH08101520A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic photoreceptor having high sensitivity and high durability. CONSTITUTION: An azo compd. represented by the formula is incorporated as a photoconductive material into a layer on an electrically conductive substrate. In the formula, R1 is H, halogen, cyano, alkyl which may have a substituent or aryl, each of R2 -R4 is H, halogen, alkyl which may have a substituent, alkoxy, aryl or a heterocyclic group, Ar is arylene which may have a substituent, (n) is 0 or 1 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, 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, 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]

As a result of research on a photoconductive substance having high sensitivity and high durability, the present inventors have found that the novel azo compound represented by the chemical formula 1 is effective. The present invention has been reached.

In the chemical formula ₁ , R ₁ represents a hydrogen atom, a halogen atom, a cyano group, an optionally substituted alkyl group or an aryl group, and R _{2 to} R ₄ represent a hydrogen atom,
Halogen atom, an alkyl group which may have a substituent,
An alkoxy group, an aryl group, or a heterocyclic group is shown. A
r represents an arylene group which may have a substituent, and n
Is 0 or 1. Cp represents a coupler residue.

Specific examples of R ₁ include a hydrogen atom,
Halogen atom such as chlorine atom, bromine atom, cyano group, alkyl group such as methyl group, ethyl group, n-propyl group, isopropyl group, phenyl group, methoxyphenyl group, methylphenyl group, chlorophenyl group, naphthyl group, anthryl group Aryl groups such as
Specific examples of _{2 to} R ₄ include halogen atoms such as hydrogen atom, chlorine atom and bromine atom, alkyl groups such as methyl group, ethyl group, ethoxyethyl group, n-propyl group and isopropyl group, methoxy group and ethoxy group. , Propoxy group, butoxy group, and other alkoxy groups, phenyl group, methoxyphenyl group, methylphenyl group, chlorophenyl group, naphthyl group, anthryl group, pyrenyl group, and other aryl groups, pyridyl group, furyl group, thienyl group, and other heterocycles A group can be mentioned. Specific examples of Ar include a phenylene group, a methoxyphenylene group, a methylphenylene group, a chlorophenylene group, a naphthalenediyl group, an anthracenediyl group, and a pyrenediyl group.

Specific examples of the coupler residue Cp in the chemical formula 1 include those shown in Tables 1 to 14.

[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 the chemical formula 1 of the present invention include those shown in Tables 15 to 23. In the formula, Cp represents a coupler residue.

[0030]

[Table 15]

[0031]

[Table 16]

[0032]

[Table 17]

[0033]

[Table 18]

[0034]

[Table 19]

[0035]

[Table 20]

[0036]

[Table 21]

[0037]

[Table 22]

[0038]

[Table 23]

The azo pigment of the present invention is represented by the following chemical formula 2 (wherein R ₁ to
R ₄ , n and Ar are the same as those in Chemical formula 1), which can be easily obtained by converting the diamino compound represented by the formula 1 into a tetrazonium salt by a conventional method and reacting it with a corresponding coupler in the presence of an alkali.

[0040]

Embedded image

Next, a synthesis example will be specifically described. Synthesis Example 1 (Synthesis of Raw Material Diamine Corresponding to B-9 in Table 15) 3- (3) -formyl compound obtained by formylation of 2- (p-nitrophenyl) imidazo [1,2-a] pyridine and diethyl p- Nitrobenzylphosphonate Wittig
A dinitro compound is synthesized by the reaction. This one 4.48
g was suspended in 150 ml of dioxane, and 2 ml of acetic acid was previously prepared.
11 g of iron powder that had been activated with, 11 ml of dioxane,
Add to a suspension of 11 ml of water under reflux over about 5 minutes.
After 50 minutes, the insoluble material is filtered off and the residue is concentrated under reduced pressure.
The obtained yellow solid is recrystallized from acetonitrile to obtain 3.1 g of the desired diamine (yield 81%). Melting point 144.2-145.2 [deg.] C.

Synthesis Example 2 (Exemplified compound: B-9 in Table 15)
(Synthesis of Cp = A-21) 0.66 g of the diamine obtained in Synthesis Example 1 was added to DMF (40 m).
1) and 1N hydrochloric acid (12 ml), and an aqueous solution (2 ml) of sodium nitrite (0.30 g) was added at about 5 ° C. After 30 minutes, 42% borofluoric acid (10 ml) was added, and the precipitated tetrazonium salt was collected by filtration. This product and 3-hydroxy-2-naphthoic acid 2-chloroanilide (1.11 g) were dissolved in DMF (200 ml), and an aqueous solution of sodium acetate (1.48 g) (10 ml) was added to 5 ml.
The solution was added dropwise at -10 ° C over 5 minutes. After stirring at the same temperature for 2 hours and further at room temperature for 2 hours, the precipitate was collected by filtration and DM
It was washed with 100 ml each of F, acetone and water. Yield 1.58g (84% yield) 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 compound represented by Chemical formula 1. 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, the use of a photoreceptor for copying includes polystyrene resin, polyvinyl acetal resin, polysulfone resin, polycarbonate resin, polyester resin, polyphenylene oxide resin, polyarylate resin, acrylic resin, methacrylic resin, and phenoxy resin. 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 photoreceptor, if necessary.

The charge transport material includes a hole transport material and an electron transport material. An example of the former is, 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.

[0049]

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-9 (Cp = A-6) 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. The dispersion thus obtained was coated on aluminum vapor-deposited polyester with an applicator to form a charge generation layer having a thickness of about 0.2 μm. Next, p-dibenzylaminobenzaldehyde = diphenylhydrazone was mixed with a polyarylate resin (U-polymer manufactured by Unitika) in a weight ratio of 1: 1 to prepare a 10% solution using dichloroethane as a solvent.
The charge generation layer was coated on the charge generation layer 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 is -690V, and the half exposure amount E1 / 2
Showed a high sensitivity value of 1.5 lux · sec.

Further, using the same apparatus, characteristic 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 5,000th cycle was -650V, whereas the initial potential at the 5,000th cycle was -650V, and there was little decrease in the potential due to repetition and the stability was stable. Further, it was found that the half-exposure amount at the 5000th time was 1.5 lux · sec, which was not changed at all, while the half-exposure amount at the first time was 1.5 lux · sec.

Examples 2 to 6 Photosensitive members were prepared in the same manner as in Example 1 except that the azo pigments shown in Table 24 were used, and their characteristics were evaluated. The results are shown in Table 24.

[0054]

[Table 24]

Example 7 1 part by weight of Exemplified Compound B-9 (Cp = A-6) and 40 parts by weight of tetrahydrofuran were dispersed together with zirconia beads in a ball mill for 48 hours. To the dispersion thus obtained, 2.5 parts by weight of N-ethylcarbazole-3-carbaldehyde = diphenylhydrazone, 10 parts by weight of a polycarbonate resin (PCZ-200; manufactured by Mitsubishi Gas Chemical Co., Inc.) and 60 parts by weight of tetrahydrofuran were added, and further 2
After performing ultrasonic dispersion treatment for 1 minute, apply it on aluminum vapor-deposited polyester with an applicator to obtain a film thickness of about 10
A μ photoreceptor was formed. The electrophotographic characteristics of this photoreceptor are
The measurement was performed in the same manner as in Example 1. However, only the applied voltage was changed to +5 kV. As a result, excellent characteristics of +360 V, half-exposure amount of 1.6 lux · sec, initial potential after repeating 5000 times +330 V, half-exposure amount of 1.6 lux · sec, high sensitivity and little change were shown.

Examples 8 to 12 Photosensitive members were prepared in the same manner as in Example 7 except that the azo pigments shown in Table 25 were used, and their characteristics were evaluated. The results are shown in Table 25.

[0057]

[Table 25]

Comparative Example 1 A photoconductor was prepared in the same manner as in Example 1 except that Azo Compound 3 was used, and its characteristics were evaluated. As a result, the initial potential at the first time was −640 V, the half-exposure amount E1 / 2 was 2.9 lux · second, and the initial potential at the 5,000th time was −310 V, the half-exposure amount was 3.6 lux · second, which showed sensitivity. 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 3 was used, and its characteristics were evaluated. As a result, the initial potential was 290 V and the half-exposure amount E1 / 2 was 4.1 lux.
Seconds and lack of sensitivity.

[0060]

Embedded image

[0061]

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 an azo compound represented by the following general formula 1 on a conductive support. Embedded image (In Chemical formula ₁ , R ₁ represents a hydrogen atom, a halogen atom, a cyano group, an alkyl group which may have a substituent, or an aryl group, and R _{2 to} R ₄ represent a hydrogen atom, a halogen atom, or a substituent. Represents an alkyl group, an alkoxy group, an aryl group, or a heterocyclic group which may have Ar, Ar represents an arylene group which may have a substituent, and n is 0 or 1. Cp Indicates a coupler residue.)