JPS62148961A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To obtain the titled body having good electrostatic characteristics and photosensitivity by incorporating a specific bisazo compd. composed of a fine particle having a prescribed particle size to the titled body as a carrier substance. CONSTITUTION:The bisazo compd. which has a structure shown by the formula, and a particle size smaller than one-fifth of the film thickness of the photosensitive layer and is composed of the fine particle of a brokened crystal is incorporated into a photosensitive layer of the titled body. In the formula, Ar1 and Ar2 are each a substd or unsatd. phenyl or napthyl group. The functional separating type photosensitive body is composed of the carrier generating layer and the carrier transfer layer formed on the conductive substrate. The carrier generating layer is formed by uniformly mixing the bisazo compd. which is finely pulverized by milling treatment with a suitable resinous binding agent and a solvent to form a coating solution and by coating the obtd. coating solution on a substrate followed by drying it.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having a photosensitive layer containing a bisazo compound.

[Prior art and its problems]

As a photoreceptor for electrophotography (hereinafter simply referred to as a photoreceptor), it can be charged to the required potential by corona discharge in a dark place, has little charge leakage, and has the ability to discharge more rapidly each time it is irradiated with light. That is required. Therefore, the photoconductive material used for the photosensitive layer of the photoreceptor must have a large charging ability in the dark, low leakage current, the ability to generate a large amount of carriers by light irradiation, and the ability to generate carriers. It is desired to have excellent transport ability to quickly connect.

Conventionally, as photoconductive materials with such performance, jQE photoconductive materials such as amorphous hydrogen, a7alpha selenium alloy, zinc oxide, and 1 mI of sulfurization have been used, but in recent years, Organic photoconductive materials have attracted attention because of their flexibility, impact resistance, thermal stability, and film-forming properties.

Recently, there has been active research into functionally separated photoreceptors in which the performance of the photoreceptor is improved by assigning the carrier generation function and the carrier transport function to different substances. For such functionally separated photoreceptors, many methods have been proposed that use organic dyes or organic pigments as carrier generating substances, and indigo pigments, phthalocyanine pigments, azo pigments, etc. are known, but they do not have sufficient robustness. It is difficult to find a compound that has good properties, light resistance, and excellent carrier generation ability.

Under these circumstances, bisazo compounds are known to be effective as photoconductive materials for photoreceptors (for example,
JP-A-47-37543).

Bisazo compounds are pigments and are insoluble in -S solvents. Therefore, when producing a photoreceptor using a bisazo compound as a photoconductive material, the bisazo compound is usually made into a fine powder, and the fine powder is added to a synthetic resin binder or used as a binder. A method is used in which the additives are uniformly dispersed into a coating solution, and this coating solution is uniformly applied to a conductive substrate. In this case, the electrophotographic properties of the resulting photoreceptor vary greatly depending on the crystalline state and agglomerated state of the fine powder of the bisazo compound. A bisazo compound can be easily obtained by using a corresponding amino compound as a raw material and coupling it with a diazonium salt obtained by diazotizing the same and a coupler in a solvent.
can be synthesized. However, the crystal form obtained differs depending on the reaction conditions during the coupling.

In addition, in order to form a uniform coating film of a bisazo compound during the production of a photoreceptor, it is necessary that the fine powder of the bisazo compound be uniformly fine and that there be no large Iff particles or agglomerated clumps of fine particles. A method has been proposed in which a fine powder is obtained by washing the reaction product of a bisazo compound synthesized as described above with an organic solvent, further washing with water, and then drying. However, this method also causes variations in particle size in mass production, and is still not a satisfactory method.

Furthermore, if a coating liquid is to be prepared by adding a resin binder or the like to the finely powdered bisazo compound and performing a dispersion treatment using a kneader or the like, the bisazo compound must be finely powdered. The more the powder is exposed, the more likely it is that the fine powders will coagulate with each other, and a new aggregation state will be formed during the dispersion treatment process, making it difficult to obtain a coating solution in which the bisazo compound is evenly dispersed, and forming a uniform coating film. The problem is that there is no.

Further, in order to obtain a uniform coating film in which the fine powder is not aggregated, there is a drawback that a special solvent must be used, as shown in JP-A-52-55643, for example, nM.

[Purpose of the invention]

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide an electrophotographic photoreceptor having excellent charging characteristics and photosensitivity and having a layer containing a bisazo compound as a carrier generating substance.

[Key points of the invention]

The above object of the present invention is to provide an electrophotographic photoreceptor having a layer containing a bisazo compound as a gear generation substance.
This is achieved by using a specific bisazo compound and forming it into fine particles with a certain particle size.

Accordingly, the present invention provides an electrophotographic photoreceptor having a layer containing a bisazo compound as a carrier generating substance, wherein the bisazo compound has the following structural formula, and the thickness of the layer containing the bisazo compound is 115%. An electrophotographic photoreceptor characterized by having fine particles with a particle size smaller than that of , and 7' (
The substituent represents a halogen radical r, a lower ano-1-bar U, a lower arycoquine group, etc.).

In order to form a thin layer such as a photosensitive layer of a photoconductor, especially a carrier generation layer of a functionally separated photoconductor, to a uniform thickness, it is necessary to disperse the material in the film 11. It is required that the particle size is sufficiently small compared to the film thickness.In the case of a photoreceptor having a photosensitive layer containing a bisazo compound dispersed, ali
As a result of the inspection, the particle size of the fine particles of the bisazo compound was found to be 1 part of the film thickness.
It was found that 151 degrees or less is practically effective in terms of IJll)F of the photoreceptor. (5) Of course, from the viewpoint of uniformity of film thickness, it is desirable that the particles be as fine as possible.

Thus, in the case of the bisazo compound of the present invention having the above structural formula, even if the bisazo compound is pulverized into a fine powder, a resin binder is added thereto, and /f? When dispersion treatment is performed using a molten machine or the like, it is possible to obtain a uniformly dispersed coating film without agglomeration or agglomeration.

The bisazo compound of the present invention has a thickness of 11
It is necessary that the particles have a particle size smaller than 5, but the crystals are broken to a predetermined degree. Such pulverization can be carried out using a suitable pulverizing means such as a whole mill. The degree of crystal destruction can be determined by X-ray diffraction of copper using alpha rays. The bisazo compound of the present invention preferably has broken crystals to such an extent that a crystal diffraction peak as shown in FIG. 1 is observed, for example.

That is, in the X-ray diffraction diagram using α rays for Cu-, 2
2θ- based on the diffraction intensity at θ-40°
It is preferable that the crystal be broken so that the maximum value of the diffraction intensity between 23″ and 28° is 4 times or less.

Therefore, materials that do not satisfy these conditions, such as those in which diffraction peaks as shown in FIG. 2 are observed, are not preferred.

Hereinafter, embodiments of the present invention will be described in detail in connection with the production of a photoreceptor, particularly a functionally separated photoreceptor, containing the above bisazo compound as a carrier generating substance.

Of course, the present invention is not limited to such photoreceptors.

[Embodiments of the invention]

In general, a functionally separated photoreceptor is produced by providing a carrier generation layer on a conductive substrate and then providing a carrier transport layer thereon, or first providing a carrier transport layer and then a carrier generation layer. It is constituted by providing.

As the conductive substrate, a metal plate made of aluminum, copper, zinc, etc., or a plastic sheet or film made of sealed polyester, on which the metal described above is vapor-deposited, is used.

The carrier-generating layer is formed by uniformly mixing the bisazo compound of the present invention as a carrier-generating substance with a suitable resin binder, solvent, etc. to prepare a coating solution, applying this onto a conductive substrate, and drying it. It is formed. As a binder,
It may be any of the known resins used for this type of purpose, such as polyesters, (ivy)acrylics, polyamides, polyurethanes, epoxies, polycarbo-mono-1 silicone resins, and the like. The solvent may be alcohol, ether, aromatic hydrocarbon, etc. As a coating method, an applicator method, a bar coater method, etc. can be used.

The carrier transport layer can be formed by uniformly mixing a carrier transport substance with the same binder and solvent as described in 1- above to form a coating solution, and applying the same in the same manner.

Examples of carrier transport substances include known ones, such as aromatic tertiary amino (and diamino and triamino) compounds, polyvinylcarobazole compounds, pyrazoline derivatives, triazine derivatives, quinazoline derivatives, and oxadiazole derivatives.

The thickness of the carrier generation layer is generally 0.005 to 10 μm,
The thickness of the carrier transport layer may generally be about 5 to 100 μm.

Dog 111'' - A bisazo compound represented by the following structural formula is ground into a fine powder with a uniform particle size of 0.01 μm or less using a ball mill, and 41 parts by weight of each particle of the ground bisazo compound is prepared. , 30 parts by weight of tetrahydrofuran was subjected to a dispersion treatment using a mixer to prepare a suspension in which fine particles of a bisazo compound were uniformly dispersed in a solvent. When the crystalline state of the fine particles of the bisazo compound dispersed at this time was examined using α X-rays using CIJ-, a pattern with a broken crystal system as shown in the X-ray diffraction diagram of FIG. 1 was obtained.

Polymethyl methacrylate (1) was added to this suspension.
), add 1 part by weight and 6 parts by weight of toluene, and add magnetic
A uniform coating solution was prepared by mixing well with a stirrer. This coating 4I liquid was dried with a wire bar on an aluminum vapor-deposited polyester film substrate with a thickness of 75 μm until the film thickness was 0.
．． It was coated to a thickness of 2xjm and dried to form a carrier generation layer. On top of this, a solution prepared by thoroughly suspending 1 part by weight of NXN-diethylaminohenzaldehyl-1-1.1-diphenyltodo 9 fufu and 1 part by weight of polynisder resin in tetrahydrofuran was applied so that the film thickness after drying was 15t1m. , and dried to form a carrier transport layer.

The electrophotographic properties of the thus prepared photoreceptor were evaluated using a Kawaguchi Electric Seisakusho Model 5P-428 electrostatic paper tester. Corona discharge was performed for 10 seconds at a voltage of -6, OKV to negatively charge the photoreceptor, and the charging voltage VA on the surface of the photoreceptor at that time was measured.

After that, the charged potential ■p was determined when discharging for 2 seconds in a dark place, and then the surface of the photoreceptor was irradiated with white light of 2 lux.
Measure the time it takes for Vp to decrease by half, and calculate the half ml light intensity E.
I found 1/2. The result was VA--1200 volts El/□-2,0 lux-sec.

From this result, it was found that a carrier generation layer containing fine particles of a bisazo compound with a particle size of 0.01μm or less, which is smaller than 175 with a film thickness of 0.2μm, and with a broken crystal shape as shown in Figure 1, is used as a carrier generation material. It can be seen that the photoreceptor having the above-mentioned structure is a photoreceptor with excellent electrophotographic properties.

The bisazo compound of Example 1 was pulverized in a ball mill until the crystal form was broken and the X-ray diffraction pattern shown in FIG. 1 was obtained. These bisazo compound fine particles are mixed into 1 part of Tetra and 1 part of Lofuran.
A solution of r)-butylamine 1 was dispersed into a suspension. When the fine particles of the bisazo compound that had been dispersed at this time were examined for the crystalline state using α X-rays in Cu-, it was found that A pattern with a well-organized crystal shape was shown as shown in Figure 2.

Tetrahydrofuran fA of the bisazo compound of Example 1
? A photoreceptor was produced in accordance with Example 1 except that the above mixed suspension was used instead of &. The electrophotographic properties of the obtained photoreceptor were evaluated.

As a result, a value of VA--1200 volts El/2=20 lux·sec was obtained, and it was found that the photosensitivity deteriorated when a bisfuji compound with a well-formed crystal form was used.

A photoreceptor was prepared in the same manner as in Example 1, except that the following structural formula was used in place of the bisazo compound of Example 1. However, when this bisazo compound was used, fine particles of the bisazo compound aggregated during preparation of the coating solution, making it impossible to obtain a uniform coating film.

〔Effect of the invention〕

As mentioned above, a bisazo compound having the above-mentioned structural formula is used as a carrier generating substance for a functionally separated photoreceptor, and the particle size is smaller than the H thickness of 115 of the layer containing this compound, and the crystal is broken. The photoreceptor according to the present invention using a photoreceptor of the present invention is a practically excellent electrophotographic photoreceptor having good charging characteristics and photosensitivity.

In addition, the bisazo compound used in the present invention can be used as a coating solution to create a uniform coating film without using special solvents, and can produce excellent photoelectric properties without going through the complicated process of conventional methods. A photoreceptor can be obtained.

[Brief explanation of drawings]

FIG. 1 shows the broken bisazo compound of the present invention in X
It is a line diffraction diagram (α for Cu-). FIG. 2 is an X-ray diffraction diagram (α for Cu-) of a bisazo compound with a well-formed crystal structure.

Claims (1)

[Scope of Claims] 1) In an electrophotographic photoreceptor having a layer containing a bisazo compound as a carrier generating substance, the bisazo compound has the structural formula shown below, and the thickness is 1/1 of the thickness of the layer containing the bisazo compound. 1. A photoreceptor for electrophotography, characterized in that the particles have a particle size smaller than /5 and have broken crystals. Structural formula ▲ Numerical formula, chemical formula, table, etc. ▼ (In the formula, Ar_1 and Ar_2 represent substituted or unsubstituted phenyl or naphthyl groups, respectively). 2) In the electrophotographic photoreceptor according to claim 1, the bisazo compound fine particles have a 2θ value based on the diffraction intensity at 2θ=40° in an X-ray diffraction diagram using Kα rays of copper. 1. A photoreceptor for electrophotography, characterized in that it exhibits an X-ray diffraction pattern in which the maximum value of diffraction intensity between =23° and 28° is 4 times or less.