JPS6211771A - Production of highly crystalline brominated anthanthrone pigment for photosensitive substance - Google Patents

Abstract

PURPOSE:To obtain the titled pigment giving both high electrification potential and sensitivity, capable of affording photosensitive substance of good repeated stability, having electrophotographic photosensitive effect, by treating a brominated anthanthrone with nonionic solvent to effect crystallization. CONSTITUTION:A raw material consisting mainly of a brominated anthanthrone of formula is treated with a nonionic solvent (e.g., plenetole) to effect crystallization. The resulting crystal is subjected to washing followed by separation through filtration, thus obtaining the objective brominated anthanthrone. This anthanthrone gives half-widths of diffraction intensity at 2theta=18.4 deg. and 26.7 deg. in X-ray diffraction spectra: DELTAtheta(18.4 deg.)<=0.8 deg. and/or DELTAtheta(26.7 deg.)<=1 deg., respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for producing a highly crystalline brominated anth-anthrone pigment for use in photoreceptors, particularly electrophotographic photoreceptors.

Conventional technology Generally, substances that absorb visible light and generate carriers are
It is difficult to form a film by itself with the exception of a very small number of materials such as amorphous selenium, and the problem is that they have a poor ability to retain electric charges applied to their surfaces. 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 FIG. 5A, a carrier generating layer N2 containing a substance that absorbs visible light and generates charge carriers is provided on a conductive substrate l such as A1 via an underlayer 5. Furthermore, it has been proposed to provide a carrier transport layer 3 for transporting one or both of the positive and negative charge carriers generated in the carrier generation layer to form a laminate 4, and to construct a photosensitive layer using this laminate tank. In this way, by assigning charge carrier generation and transport to separate materials, a wide range of materials can be selected and the material properties required in the electrophotographic process, such as charge retention, surface strength, and resistance to visible light, can be improved. It has become possible to improve or improve sensitivity, stability during repeated use, etc.

Note that the carrier generation layer 2 may be provided on the carrier transport layer 3 as shown in FIG. 5B.

In such photoreceptors, it is known to use a brominated anthanthrone pigment as a high-grade organic pigment in the photosensitive layer, particularly in the carrier generation layer. This pigment has higher sensitivity compared to conventional inorganic particles or periresi pigments,
A photosensitive layer that is uniform and has good scratch and scratch properties can be obtained.

However, in order to use this pigment as an electrophotographic photoreceptor, it is necessary to improve both its crystallinity and purity, and the sublimation purification method is effective in achieving this.

However, upon investigation by the present inventor, it has been found that in the case of conventional methods, the shear stress (shαre) applied to the pigment is
5tress) is large (when the substrate temperature is high and the pigment particles are large and highly crystalline), the crystal lattice is likely to be distorted or impurities may easily enter from the dispersion container. For this reason, charging ability and sensitivity tend to decrease, and the amount of repeated potential decrease tends to increase.

Conversely, if the shear stress applied to the pigment is small (in this case, the substrate temperature is low and the pigment particles are small and have low crystallinity),
The electrophotographic characteristics deteriorate and are unsuitable.

OBJECT OF THE INVENTION An object of the present invention is to provide a method for producing a highly crystalline brominated anth-anthrone pigment suitable for obtaining a photoreceptor that exhibits high charging potential and sensitivity and has good cyclic stability. .

28 Structure of the invention and its effects, that is, the present invention is a method for crystallizing a raw material containing brominated anthurone represented by the following structural formula as a main component by treating it with a nonionic solvent (particularly an aromatic organic solvent). After washing and filtering the crystals, the X-ray diffraction spectrum shows 2θ=18.46 and 26.
The half width of the diffraction intensity at 7° is expressed as Δθ(18,
4°) and Δθ(26,7°), then (Δθ(1
8,4°)≦0.8°) and/or (Δθ(26,7°
)≦1′) The present invention relates to a method for producing a highly crystalline brominated anthanthrone pigment for photoreceptors, which obtains the brominated anthanthrone pigment satisfying the following conditions: )≦1′).

In the process of arriving at the present invention, the present inventor discovered that pulverization of the pigment as described increases its crystal defect density and deteriorates its properties, and that this crystal defect density Diffraction angle 2θ of spectrum = 18.
It has been found that the half width of the diffraction intensity at 4° and 26.7° (that is, the spectral width at half the intensity of the peak of the diffraction intensity spectrum) is closely related to Δθ. Figure 6 shows the spectrum of the brominated anthurone pigment obtained by the conventional sublimation purification method, but when it is ground in a ball mill, the peak at 2θ = 18.4° is blunted and Δθ is reduced as shown in Figure 7. (1B,4′) and Δθ(26,7”)
becomes larger. These Δθ become larger depending on the grinding time as described later.

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 anthanthrone having the same structural formula as that produced in the present invention.
This was washed and dried.

However, in this case, as shown in Figure 8, Δθ becomes too thick (too much) and only amorphous, non-crystalline particles are obtained.Also, when the degree of bromination is increased, the 2θ- 18,
The peak at 4° disappears and Δθ (26,7°) becomes large.

However, the sample brominated by the above method, that is, the above-mentioned brominated anthurone, is separated by filtration, and the crude raw material containing this as a main component is mixed with monochlorobenzene, nitrobenzene, β-naphthol, 1-chloronaphthalene, etc. It has been found that a highly crystalline brominated anthanthrone pigment can be obtained by treatment with a selected nonionic organic solvent, crystallization, washing, and separation by filtration. This pigment was found to be highly crystalline and highly pure, exhibiting high charging potential, high sensitivity, and good repeat stability, making it very suitable for use in photoreceptors.

FIG. 1 shows spectra obtained when the above nonionic organic solvent was used, and it can be seen that the half width Δθ is small and the peak is large, that is, the crystallinity and purity are good.

Furthermore, it has been found that by such a so-called chemical refining method, a purified product with clean crystallinity shown in FIG. 3 can be obtained from the amorphous raw material shown in FIG. 2. In addition, when this chemical refining method is used, the pigment does not decompose and the Br is removed.
The target product can be obtained in good yield without corrosion. That is,
According to the manufacturing method of the present invention explained above, there are the following advantages.

(1) Since it is a chemical refining method, it is easy to manage operating conditions even if the raw material is easily thermally decomposed.

(2) High yield and yield.

(3) No acid is generated during the debromination reaction and corrodes the equipment.

(4) Refining cost is low.

(5) A pigment with significantly improved crystallinity and purity that can be fully used as a raw material for organic semiconductors can be obtained.

(6) It is possible to realize an electrophotographic photoreceptor with low manufacturing cost, high sensitivity, and repeat stability.

In the method of the present invention, the dipole moment of the nonionic solvent (especially aromatic organic solvent) used is 1.0 to 5.
It is desirable that it be 0 (in Debye units).

Thus polar (i.e. OH,, C1, No.

It is preferable to use an aromatic solvent which has a high boiling point in addition to having a polar substituent such as

In other words, these solvents not only withstand high-temperature treatment, but also have an affinity for anthinthrone and have the effect of loosening its crystal lattice.

The nonionic solvent used in the present invention is preferably a polar solvent containing an oxygen atom, a nitrogen atom, a halogen atom, etc.; , phenoxy group, carboxyl group, hydroxy group, ester group,
Examples include aromatic hydrocarbons and heterocyclic compounds with substituents such as an amide group, a nitrile group, a formyl group, an amino group, a mercapto group, a sulfo group, and a sulfonamide group.

Organic solvents with a dipole moment of 1.0 to 5.0 (Debye units) are used, for example, in Techniques of Organic Chemistry 7.
! , l-IJ (TECHNIQUE OF O[
1GANICCHEMISTRY) vol■, 195
Published in the 5th edition of Interscience Publications, New York.

Specific examples of solvents that are effective in the present invention include the following. Phenethol, anisole, 0-cresol, m-)luidine, fluorobenzene, m-dichlorobenzene, aniline, p-1-luidine, m-cresol, p-cresol, monochlorobenzene, 1-chloronaphthalene, β-naphthol, 0 -) luidine, benzyl alcohol, phenol, bromobenzene, benzyl acetate, 0-chloroaniline, m-fluorotoluene, methyl benzoate, benzyl benzoate, ethyl benzoate, p-fluorotoluene, pyridine,
O-dichlorobenzene, dibutyl phthalate, methyl salicylate, benzaldehyde, phenylacetonitrile, nitrobenzene, benzonitrile, O-nitroanisole.

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, as shown in Figure 4 (data for samples chemically purified with nitrobenzene), Δθ changes depending on the grinding time (using a ball mill of 40 revolutions/minute), and in particular, depending on the selection of the grinding time, (Δθ (18,4°)≦0.
8°) and/or (Δθ(26,7°)≦1°). 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, if its short axis length is a and its long axis length is b, then b
It is desirable that /a≧1.1. That is, it was found that excellent characteristics could be obtained with this ratio. However, as the particles become finer, not only Δθ increases, but also the strength (absolute value) decreases, so even if Δθ≦1” is satisfied, sufficient crystallinity may not be obtained. In other words, Even if Δθ≦1′, the crystallinity of particles tends to decrease when b/a<1.1, so b/a≧1.1, and even 1.1≦b/
It is effective to set a≦20. Here, the major axis length b
indicates the length of the axis with the longest distance (major axis) in an arbitrarily selected crystal in an electron micrograph. Further, 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.

As a method for arbitrarily selecting crystals in an electron micrograph, for example, in the present invention, 5 crystals are selected vertically and horizontally at 1 cm intervals.
For each book, I drew a line on the photo and selected the crystal at the intersection. Measure the long axis length b and short axis length a of these crystals,
The b/a of each crystal was calculated. In the present invention, b/a refers to the average value of b/a of each of the crystals.

And the average particle size of the brominated anth-anthrone pigment particles (
Here, it means the average value of the long axis length. ) is 2μ
It is desirable that it be less than m. 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 form on the surface, but when the average particle size is 2 μm or less, such convex portions can be virtually eliminated and a flat surface can be achieved, and the sedimentation of particles in the dispersion can be reduced, making it easier to form liquids. can be stabilized. As a result, it is possible to obtain a photoreceptor that does not suffer from discharge breakdown or toner filming. The average particle size of the pigment is preferably 2 μm or less, more preferably 1 μm or less,
More preferably, the thickness is 0.5 μm or less. However, if the average grain size is too small, crystal defects will increase and sensitivity and 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, phenol resin, polyester resin, alkyd resin, Addition polymer resins, polyaddition resins, polycondensation resins such as polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more repeating units of these resins, such as vinyl chloride-vinyl acetate. Copolymer resin, vinyl chloride
Examples include vinyl acetate-maleic anhydride copolymer resin. However, the binder resin is not limited to these, and all resins commonly used for such purposes can be used.

Carrier transport substances used in the carrier transport layer in the present invention include oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidasilone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, and pyrazoline. derivatives, oxacilone derivatives, benzothiazole derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives,
Phenazine derivative, aminostilbene SA 28, hydrazone derivative, biphenylamine derivative, triphenylamine derivative, poly-N-vinylcarbazole, poly-1-vinylpyrene, poly-9-vinylanthracene,
2.4.7- N-linitrofluorenone, 2.4.5.
Examples include 7-tetranitrofluorenone and 2,7-sinitrofluorenone.

Further, examples of organic solvents used for forming the photosensitive layer of the present invention include methylene chloride, methylene bromide,
■, 2-dichloroethane, sym-tetrachloroethane, cis-1,2-dichloroethylene, 1,1.2-trichloroethane, chloroform, bromoform, dioxane, tetrahydrofuran, pyridine, etc. alone or containing these as main components Examples include various mixed solvents.

Example Embodiments of the present invention will be described in detail below with reference to the drawings.

After bromination of anthanthrone in sulfuric acid, 50 g of brominated anthurone fine powder obtained by draining the mixture was added to 100 ml of nitrobenzene, slowly stirred at 150° C. for 8 hours, and then allowed to cool. Next 1. ) and washing to obtain 49.0 g of highly crystalline brominated anth-anthrone pigment.

X-ray diffraction spectrum of purified pigment (JDXIO manufactured by JEOL)
RA CuKcrl, 541 individuals) are shown in FIG.

40 g of the obtained purified pigment was filled into a porcelain ball mill and pulverized for 1 hour at 40 revolutions per minute (the critical number of revolutions giving maximum pulverization energy was 70 revolutions).

Next, polycarbonate resin “Panlite L-1250J”
(manufactured by Kijin Kasei Co., Ltd.) 20g 1,2-dichloroethane 13
A solution dissolved in 00m It was added and subjected to dispersion treatment for 24 hours to obtain a coating solution for forming a carrier generation layer.

The pigment was separated by filtration using a part of the obtained Fufu liquid, and the half width of the X-ray diffraction spectrum was measured. The results are shown in Table 1.

Furthermore, as a result of observation using an electron microscope, it was confirmed that the crystals were needle-shaped crystals with b/a = 2.4 and b = 0.6/J.

The X-ray diffraction spectrum of the raw material used in Example 1 without crystallization is shown in FIG. In Example 1, a coating liquid for forming a carrier generation layer was prepared in the same manner as in Example 1 except that the ball mill grinding time was changed to 10 hours.

Table 1 shows the measured half width of the X-ray diffraction spectrum.

Furthermore, as a result of electron microscopy observation, b/a=2.0, b=0.4μ.

In Example 1, the ball mill grinding time was 20 hours. Table 1 shows the measured half width of the X-ray diffraction spectrum.

b/a = 1.5, b = 0.4 μ.

In Example 1, the ball mill grinding time was set to 2 hours. The half width is shown in Table 1.

In Example 1, the ball mill grinding time was 48 hours. The half width is shown in Table 1.

``7 guns = 1.3, 7 guns = 0.3μ.

In Example 1, the ball mill rotation speed was 55 rpm, and the grinding time was 10 hours. The half width is shown in Table 1.

In Example 1, the ball mill rotation speed was 7 Orpm and the grinding time was 5 hours. The half width is shown in Table 1.

“7τ=1.05, b=0.2μ.

In Example 1, the ball mill rotation speed was 70 rpm+,
The grinding time was 10 hours. The half width is shown in Table 1.

b/a=1.03, b=0.2. It was u.

The parameter values of the samples obtained above and the comparative samples are summarized in Table 1.

In the table, "actual" indicates an example, and "ratio" indicates a comparative example.

(The following is a blank space, continued on the next page) Table 1 An electrophotographic photoreceptor drum was prepared by the following method using the coating liquid for forming a carrier generation layer obtained in the above Examples and Comparative Examples.

On a 100φ aluminum drum, the dry weight is 0.1g/
After forming an intermediate layer consisting of rrf vinyl chloride-vinyl acetate-maleic anhydride copolymer resin [S-LEC MF-10J (manufactured by Tsukiki Kagaku Kogyo Co., Ltd.) by a dip coating method, the above-mentioned carrier generation layer forming coating solution was applied in the same manner. It is coated on the intermediate layer by a dip coating method, and the dry weight is 2.
A carrier generation layer of 1 g/m was obtained.

On the other hand, carrier transport substance 2.4. expressed by the following structural formula.
6-trinitro-1-chlorobenzene 0.225 g
.

A carrier transport layer forming coating solution obtained by dissolving 300 g of polycarbonate resin in 2000 ml of 1,2-dichloroethane was applied onto the carrier generation layer by dip coating to form a carrier transport layer with a dry weight of 19 g/m. The electrophotographic photoreceptor of the present invention and the comparative electrophotographic photoreceptor (
Figure 5A) was created.

Note that instead of the above, a carrier transport layer may be formed first, and a carrier generation layer may be formed thereon.

(Figure 5B) The samples and comparative samples obtained in the above examples and comparative examples were mounted on a photoreceptor tester (manufactured by Konishi Roku Photo Industries), and a surface electrometer "electrostatic voltmeter 144D-ID" was used.
Using a mold (manufactured by Monroe Electronics Inc.), the charging potential Vo (V) and the surface potential were set to -6.
Exposure amount Er required to reduce from 00■ to 1100■:
: (lux s 5eC) and the surface potential was set to -600 ■, and the potential retention rate DD (%) after 5 seconds was investigated.

Further, the stability of the charging potential was investigated by conducting a repeated test 5000 times.

For samples whose charging potential does not reach 600 V, the charging current value is increased from the standard value to E? ':: and DD were measured.

The results are shown in Table 2 (the sample numbers in Table 2 correspond to the examples and comparative examples in Table 1).

(The following is a blank space, continued on the next page) Table 2 From Tables 1 and 2, it can be seen that the samples according to the present invention have good sensitivity and potential holding performance.

[Brief explanation of drawings]

The drawings are for explaining the present invention, and include FIG.
Figures 6, 7, 8, and 9 are X-ray diffraction spectra of the carrier-generating substance, Figure 2 is a micrograph showing the particle structure of the raw material for the carrier-generating substance, and Figure 3 is the carrier-generating substance. FIG. 4 is a graph showing changes in half-width depending on grinding time; FIGS. 5A and 5B are cross-sectional views of the electrophotographic photoreceptor. In addition, in the reference numerals shown in the drawings, (1)... Conductive substrate 2... Carrier generation layer 3... Carrier transport layer. Agent Patent Attorney Hiroshi Aisaka Figure 1 Figure 2 'ゝ'' (xlopOO) Figure 3 Figure 5A Figure 58 Figure 4 #Still time (hr) Figure 6 Figure 7 Figure 8 Figure 9

Claims (1)

[Claims] 1. The following structural formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A raw material containing brominated anthurone as a main component is treated with a nonionic solvent to crystallize it. After the process of washing, filtering and separating the
7°), {Δθ(18.4°)≦0.8°}
and/or a method for producing a highly crystalline brominated anthanthrone pigment for a photoreceptor, which obtains the brominated anthurone that satisfies {Δθ(26.7°)≦1°}.