JPH0357471B2 - - Google Patents

Description

[Detailed description of the invention]

B. Field of Industrial Application The present invention relates to a photoreceptor, particularly an electrophotographic photoreceptor. B. Prior art In general, it is difficult for substances that absorb visible light to generate carriers to form a film on their own, with the exception of a few substances such as amorphous selenium. It has the disadvantage of poor retention of a given charge. On the contrary, materials that have excellent film-forming ability and can retain a charge of 500 V or more for a long time with a thickness of about 10 μm generally have the disadvantage of not having sufficient photoconductivity due to absorption of visible light. have. For this reason, as shown in Figure 4A,
A carrier generation layer 2 containing a substance that absorbs visible light and generates charge carriers is provided on a conductive substrate 1 such as Al, with a subbing layer 5 interposed therebetween. It has been proposed to provide a carrier transport layer 3 for transporting one or both of them to form a laminate 4, and to configure the photosensitive layer with this laminate. In this way, by assigning charge carrier generation and transport to separate materials, the range of material selection is widened and the properties required in the electrophotographic process, such as charge retention, surface strength, and visible It has become possible to improve sensitivity to light and stability during repeated use. In such photoreceptors, it is known to use a brominated anthrone pigment as a high grade organic pigment in the photosensitive layer, particularly in the carrier generation layer. This pigment has higher sensitivity than conventional inorganic particles or perylene pigments, and can provide a uniform photosensitive layer with good scratchability. However, in order to use this pigment as an electrophotographic photoreceptor, it is not enough to select the above-mentioned brominated anthurone as a carrier generating substance, and it is necessary to select an effective carrier transporting substance. No effective carrier transport material has yet been proposed. C. Purpose of the Invention It is an object of the present invention to improve the characteristics of a photoreceptor, especially its sensitivity, its environmental stability, residual potential characteristics, and durability by selecting specific carrier generating substances and carrier transporting substances. It is about improving sexuality. D. Structure of the invention and its effects That is, the present invention provides a photoreceptor in which a carrier generation layer and a carrier transport layer are sequentially laminated on a support, which is represented by the following structural formula and has an average particle size of 2 μm.
and a brominated anthanthrone pigment purified by a chemical purification method is contained in the carrier generation layer, and half of the diffraction intensity at 2θ=18.4° and 26.7° of the X-ray diffraction spectrum of the brominated anthanthrone pigment. When the price range is Δθ (18.4°) and Δθ (26.7°), respectively, {Δθ (18.4°) ≦0.8°} and/or {Δθ (26.7°) ≦1°} and is expressed by the general formula below. The invention relates to a photoreceptor in which the carrier transport layer contains an amine compound. Structural formula: General formula: (However, in this general formula, R ₁ represents a divalent aromatic group or a heterocyclic group. R ₁ represents an arylene group,
Examples of arylene groups include arylene groups, carbazole residues, etc.

[Formula] Arylene The arylene group includes a biphenyl group. Among these, an arylene arylene group, particularly a biphenyl group, is preferred.
R ₂ , R ₃ , R ₄ and R ₅ are mutually different or the same groups, and are hydrogen atoms, halogen atoms, alkyl groups having 1 to 4 carbon atoms, or 1 to 4 carbon atoms.
represents an alkoxy group. ) According to the present invention, the brominated anthurone of the above structural formula has high sensitivity and good scratch resistance, and the carrier transport material of the above general formula used has excellent solubility in the binder resin,
It exhibits high sensitivity, low photofatigue resistance, and low residual potential. Therefore, the combination of carrier-generating substance and carrier-transporting substance according to the present invention can improve various properties as a photoreceptor. The brominated anthurone used in the present invention undergoes a pulverization process during its manufacturing process, but such pulverization (shear stress) increases its crystal defect density and deteriorates its properties. The half-width of the diffraction intensity at diffraction angles 2θ = 18.4° and 26.7° of the pigment's specific X-ray diffraction spectrum (i.e., the spectral width at half the intensity of the peak of the diffraction intensity spectrum) is closely related to Δθ. I know something. When the brominated anth-anthrone pigment obtained by the conventional sublimation purification method is ground in a ball mill, the peak at the diffraction angle of 2θ = 18.4° in the spectrum is blunted, and the peaks at Δθ (18.4°) and Δθ (26.7°) are
becomes larger. On the other hand, an attempt was made to produce a brominated anthanthrone pigment by the following method. That is, anthanthrone shown by the following structural formula is brominated in sulfuric acid, drained, and separated by filtration to obtain brominated anthurone having the same structural formula as that used in the present invention, which is then washed and dried. did. However, in this case, Δθ becomes too large and only amorphous, non-crystalline particles are obtained (see FIG. 5). Furthermore, when the degree of bromination is increased, the peak at 2θ=18.4° disappears and Δθ (26.7°) increases (see Figure 6). However, the crude raw material containing the brominated sample as a main component by the above method is treated with a nonionic organic solvent selected from monochlorobenzene, nitrobenzene, β-naphthol, 1-chloronaphthalene, etc. (preferably, this After treatment with a borderline solvent (a mixture of an organic solvent and an ionic solvent consisting of an acid such as H ₂ SO ₄ or an alkali such as NaOH) to ripen the crystals, washing and separation by filtration, highly crystalline bromine is produced. It has been found that a chemical anthurone pigment can be obtained. This pigment was found to be highly crystalline and highly pure, exhibiting high charging potential, high sensitivity, and good repeat stability, and is very suitable for use in photoreceptors. Figure 1 shows the case where a mixed solvent of the above nonionic organic solvent and an acid is used, Figure 2 shows the case when a mixed solvent of the above nonionic organic solvent and an alkali is used, and Figure 3 shows the case where the above nonionic organic solvent and an alkali are used. The spectra obtained when using organic solvents are shown, and it can be seen that the half-width Δθ is small and the peaks are large, that is, the crystallinity and purity are good (particularly in Figures 1 and 2). (Example is a good example.) In addition, it was found that by this so-called chemical refining method, a purified product with clean crystallinity can be obtained from amorphous raw materials.In addition, when using this chemical refining method, the pigment decomposes. Without a problem, get rid of it
There is no corrosion due to Br, and the desired product can be obtained in good yield. The brominated anthanthrone pigment obtained by the chemical purification method described above is actually pulverized and dispersed to obtain a desired particle size. At this time, Δθ changes depending on the grinding time, and especially depending on the grinding time and selection,
{Δθ(18.4°)≦0.8°} and/or {Δθ(26.7°)≦1°}
I found out what I can do. As is clear from the data described below, this half-width range reduces the crystal defect density of the pigment particles and greatly improves the electrophotographic properties. Regarding the particle shape of the brominated anth-anthrone pigment, the short axis length is a, and the long axis length is b.
Therefore, it is desirable that b/a≧1.1. That is,
It has been found that this ratio provides excellent properties. However, as the particles become finer, other strengths (absolute values) that improve Δθ also decrease, so even if Δθ≦1° is satisfied, sufficient crystallinity may not be obtained. In other words, even if Δθ≦1°, b/a
When <1.1, the crystallinity of the particles tends to decrease, so
It is effective to set b/a≧1.1, more preferably 1.1≦b/a≦20. Further, 1.5≦b/a≦15 is even better. Here, the long axis length b indicates the length of the axis (long axis) having the longest distance in an arbitrarily selected crystal in an electron micrograph. The short axis length a indicates the length of the axis (short axis) that passes through the bisecting point of the long axis and has the shortest distance. In an electron microscope, one way to arbitrarily select crystals is, for example, to select 5 crystals vertically and horizontally at 1 cm intervals.
For each book, I drew a line on the photo and selected the crystal at the intersection. The major axis length b and minor axis length a of these crystals were measured, and b/a of each crystal was calculated. The b/a mentioned above indicates the average value of b/a of each of the crystals. The average particle diameter (here, means the average value of the long axis length b) of the brominated anth-anthrone pigment particles is 2 μm or less. That is, by making the particles finer to 2 μm or less, the influence of the particle size on the surface of the photoreceptor can be prevented, the surface of the photoreceptor can be made smooth, and the pigment dispersion can be stabilized. When the average particle size exceeds 2 μm, convex portions are likely to appear on the surface, but
When the diameter is 2 μm or less, such protrusions can be substantially eliminated and a flat surface can be realized, and the sedimentation of particles in the dispersion liquid can be reduced to stabilize the liquid. As a result,
It becomes possible to obtain a photoreceptor that does not suffer from discharge breakdown or toner filming. The average particle size of the pigment is 2μ
m or less, more preferably 1 μm or less, and even more preferably 0.5 μm or less. However, if the average grain size is too small, crystal defects will increase and the repeatability will deteriorate, and there will be a limit to miniaturization, so it is desirable to set the lower limit of the average grain size to 0.01 μm. Examples of binder resins that can be used in the photoreceptor of the present invention include polyethylene, polypropylene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, epoxy resin, polyurethane resin, phenolic resin, polyester resin, alkyd resin, Addition polymerization resins such as polycarbonate resin, silicone resin, melamine resin,
Polyaddition type resins, polycondensation type resins, and copolymer resins containing two or more repeating units of these resins, such as vinyl chloride-vinyl acetate copolymer resins, vinyl chloride-vinyl acetate-maleic anhydride copolymers Examples include coalescent resins. However, binder resins are not limited to these,
All resins commonly used for such applications can be used. The carrier transport material used in the present invention is composed of an amine compound having the above-mentioned general formula, and these are exemplified below. Note that the carrier transport substances described above are used to constitute the carrier transport layer, but may also contain a carrier generation layer. In addition, the thickness of the carrier generation layer is 0.1 to 10 μm, and the thickness of the carrier transport layer is 5 to 10 μm.
It may be 30 μm. Note that there is a preferable range for the ratio of the carrier-generating substance and the carrier-transporting substance described above. When configured for negative charging, the ratio of the carrier generating substance to the binder is 0 to 100% by weight (especially 0 to 100% by weight).
(10% by weight), and the carrier transport material is preferably 10 to 500 parts by weight. Outside the above range, if there are few carrier-generating substances, the photosensitivity will be poor and the residual potential will increase.
In addition, if the amount is too large, the acceptance potential tends to decrease more often. The content of the carrier transport substance is also important; carrier transport substance/binder resin = 20 to 200 parts by weight/100 parts by weight (preferably 30 to 100 parts by weight/100 parts by weight).
(parts by weight), within this range, the residual potential is small and the photosensitivity is good, and the solvent solubility of the carrier transport substance is also maintained well. Outside this range, if the carrier transport substance is small, the residual potential and photosensitivity tend to deteriorate, and if it is too large, the solvent solubility tends to deteriorate. The content range of this carrier transport substance may be the same for the carrier transport layer. In addition, when using the carrier generating substance and the carrier transporting substance together in the carrier generating layer, in order to effectively exhibit the respective functions of both substances, the weight ratio of the carrier generating substance:carrier transporting substance is (1:0.2). ) ~ (1:3) is best,
It is more desirable that the ratio be from (1:0.4) to (less than 1:2.0). Examples of organic solvents used for forming the photosensitive layer of the present invention include methylene chloride, methylene bromide, 1,2-dichloroethane, sym-
Tetrachloroethane, cis-1,2-dichloroethylene, 112-trichloroethane, chloroform,
Examples include single solvents such as bromoform, dioxane, tetrahydrofuran, and pyridine, and various mixed solvents containing these as main components. E. Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Examples 1 to 3, Comparative Examples 1 to 3 Carrier generation layer: 40 g of 4,10-dibromoanthrone purified by sublimation was placed in a porcelain ball mill and pulverized at 40 rpm for 20 hours. 20 g of "-1250" (manufactured by Teijin Chemicals) and 1,300 ml of 1,2-dichloroethane were added and subjected to dispersion treatment for 30 hours to obtain a coating solution for forming a carrier generation layer. Dibromoanthrone was separated by fractionation using a portion of the obtained coating liquid, and the half-width of the X-ray diffraction spectrum was measured, and the following results were obtained. Δθ (18.4°)≦0.57 Δθ (26.7°)≦0.66 =3.2 =0.4μ Using this coating liquid, a carrier generation layer was formed in the following manner. That is, a 0.1 μm thick intermediate layer made of vinyl chloride-vinyl acetate-maleic anhydride copolymer "Eslec MF-10" (manufactured by Sekisui Chemical Co., Ltd.) was provided on a polyester film on which aluminum was vapor-deposited. Next, the coating liquid for forming a carrier generation layer was applied onto the intermediate layer to form a carrier generation layer having a thickness of 1 μm. This was used as a carrier generation layer. Carrier generation layer: Amorphous 4,10-dibromoanthrone 50
Put 1,000 g of nitrobenzene into a magnetic ball mill.
ml and 10 ml of sulfuric acid were added and dispersed at 30 rpm for 300 hours. This was filtered, washed and dried to obtain highly crystalline dibromoanthrone. Put 40g of this dibromoanthrone into a magnetic ball mill and grind for 1 hour at 40rpm, then add 20g of polycarbonate "Panlite L-1250" (manufactured by Teijin Chemicals) and 1300ml of 1,2-dichloroethane and disperse for 24 hours. A coating solution for forming a carrier generation layer was obtained. Using a portion of the obtained coating liquid, dibromoanthrone was separately dispersed and the half-width of the X-ray diffraction spectrum was measured, and the following results were obtained. Δθ (18.4°)≦0.36 Δθ (26.7°)≦0.49 =2.8 =0.8μ Using this coating liquid, a carrier generation layer was formed in the following manner. That is, vinyl chloride-vinyl acetate-
Maleic anhydride copolymer “Eslec MF-10”
(manufactured by Sekisui Chemical Co., Ltd.) with a thickness of 0.1μ. Next, the coating liquid for forming a carrier generation layer was applied onto the intermediate layer to form a carrier generation layer having a thickness of 1 μm. This was used as a carrier generation layer. Carrier transport layer: 7.5g carrier transport material and 10g binder resin
A solution prepared by dissolving 1,2-dichloroethane in 80 ml of
A carrier transport layer was formed by coating 15 μm, and electrophotographic photoreceptors of Comparative Examples 1 to 3 and Examples 1 to 3 were prepared. These have the structure shown in FIG. 4A. Comparative Example 4 7.5 g of tetraethylbenzidine represented by the following structural formula as a carrier transport substance and 10 g of polycarbonate were dissolved in 80 ml of 1,2-dichloroethane. Carrier generation layer using the solution in Comparative Examples 1 to 3
A comparative electrophotographic photoreceptor was prepared by coating the film to a thickness of 15 μm. Comparative Example 5 The following diethyldibenzylbenzidine was used as a carrier transport material, and as a carrier generation layer. A comparative electrophotographic photoreceptor was prepared in the same manner as Comparative Example 4, except that the carrier generation layer used in Examples 1 to 3 was used. The electrophotographic photoreceptor obtained in the above example was attached to a photoreceptor testing machine (manufactured by Konishiroku Photo Industries), and a surface electrometer "Electrostatic Voltmeter 144D-1D" was used.
The amount of exposure required to reduce the surface potential from ₆₀₀ V to 100 V using a mold (manufactured by Monroe Electronics Inc.).
E ⁶⁰⁰ ₁₀₀ (lx·sec) and the surface potential were set to 600V, and the potential retention rate DD (%) after 5 seconds was investigated. In addition, a test was repeated 5,000 times to examine the stability of the electrostatic potential. In addition, for samples whose charging potential was less than 600 V, E ⁶⁰⁰ ₁₀₀ and DD were measured by increasing the charging current from the standard value. In addition, E ⁶⁰⁰ ₁₀₀ was measured in two environments: 25℃ and 10℃. The results are shown in the table below. The carrier transport materials used in each example are as follows.

[Table] As is clear from the above results, the electrophotographic photoreceptor of the present invention has better sensitivity and potential retention than the comparative photoreceptor, has less fatigue deterioration even after repeated use, and has improved potential stability. It has very good characteristics, with little loss of sensitivity even under low-temperature conditions.

[Detailed description of the invention]

The drawings are for explaining the present invention, and
Figures 1, 2, 3, 5, and 6 are X-ray diffraction spectra of carrier-generating substances, and Figure 4A
The figure is a cross-sectional view of an electrophotographic photoreceptor. In addition, in the reference numerals shown in the drawings, 1... conductive substrate, 2... carrier generation layer, 3... carrier transport layer.

Claims (1)

[Scope of Claims] 1. A photoreceptor in which a carrier generation layer and a carrier transport layer are sequentially laminated on a support, which is represented by the following structural formula, has an average particle size of 2 μm or less, and is purified by a chemical refining method. The brominated anthanthrone pigment is contained in the carrier generation layer, and the half-value width of the diffraction intensity at 2θ=18.4° and 26.7° of the X-ray diffraction spectrum of the brominated anthancerone pigment is expressed as Δθ (18.4°) and Δθ (18.4°), respectively. When Δθ(26.7°), {Δθ(18.4°)≦0.8°} and/or {Δθ(2
6.7゜)
≦1°}, and the carrier transport layer contains an amine compound represented by the following general formula. Structural formula: General formula: (However, in this general formula, R ₁ represents a divalent aromatic group or a heterocyclic group. R ₂ , R ₃ , R ₄ and R ₅ are different from each other or the same group, and are hydrogen atoms, Indicates a halogen atom, an alkyl group having 1 to 4 carbon atoms, or an alkoxy group having 1 to 4 carbon atoms.)