JPH07301931A - Photoconductive material, electrophotographic photoreceptor using the same, and methods for producing the same - Google Patents

Abstract

(57) [Summary] [Purpose] A photosensitive liquid containing a photoconductive material with good stability and a uniform electron distribution over the entire photoreceptor without degrading electrophotographic characteristics such as photoresponsiveness (sensitivity) and dark decay. Provided are an electrophotographic photoreceptor having photographic characteristics, and a photoconductive material and a method for producing an electrophotographic photoreceptor. In a photoconductor for electrophotography comprising a substrate and a photosensitive layer in which particles of a phthalocyanine compound are dispersed in a binder resin, a photoconductive material obtained by treating the particle surface of the phthalocyanine compound with a polymer compound containing a hydroxyl group. Materials, electrophotographic photoreceptors using the same, and methods for producing them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductive material used in electrophotographic copying machines, printers, etc., an electrophotographic photoreceptor using the same and a method for producing them.

[0002]

2. Description of the Related Art In electrophotographic recording conventionally used in copying machines, printers, etc., the surface of a photosensitive layer of a photoconductor is charged and then exposed to form an electrostatic latent image. This is a method of visualizing (developing), transferring a visible image to paper or the like, and fixing it to obtain an image. Further, the toner adhering to the photoconductor is removed, and the surface is cleaned by removing the charge (cleaning) and is repeatedly used many times.

Therefore, in addition to the electrophotographic characteristics of the electrophotographic photosensitive member, which are excellent in charging characteristics and photosensitivity and have a small dark decay, the electrophotographic characteristics show little change over time when repeatedly used, and It is required to have excellent physical properties such as printability, abrasion resistance, and moisture resistance, and excellent chemical resistance to ozone, NO _x, etc. generated during charging.

Inorganic materials such as selenium, cadmium sulfide, and zinc oxide have been used as electrophotographic photoconductors. However, they have been used as an exposure source due to problems of material toxicity and speeding up of copying machines and printers. Higher brightness, that is, semiconductor laser and L
Organic materials such as azo, perylene, phthalocyanine, and quinacridone have been widely used in order to increase the photosensitive wavelength by using ED.
However, organic materials are inferior to inorganic materials in durability and stability due to environmental changes. Various researches and developments have been carried out to solve these problems. For example, JP-A-53-64040 and JP-A-53-837.
JP-A-44 and JP-A-60-256146 propose a photoreceptor using a phthalocyanine photoconductive material. These photoconductors use a photoconductive photosensitive material in which phthalocyanine is dispersed in a binder resin, are excellent in processability and sensitivity, have no hygiene problems, and can withstand long-wavelength light such as a semiconductor laser. However, it is known to exhibit high sensitivity. It is also known that in these photoconductors, the electrical characteristics, moisture resistance and durability characteristics greatly change depending on the types of phthalocyanine and binder resin and their compounding ratios.

In addition, due to the problem of health maintenance of equipment users,
A great deal of attention has been paid to positively charged organic photoconductors that can minimize the amount of ozone generated during corona charging. The advantage of using a phthalocyanine-based photoconductive compound as the positively chargeable organic photosensitive material is described in, for example, US Pat.
It is well known as shown in the specification of 6,118 and Japanese Patent Publication No. 49-4338. In other words, the phthalocyanine-based compound not only has large absorbance characteristics, excellent heat resistance, chemical resistance, and light resistance, but also has large photoconductivity by light irradiation, that is, excellent generation efficiency of electron-hole pairs. .

A positive charging type photoreceptor using a phthalocyanine compound is usually provided with an undercoat layer on an aluminum drum, and then a layer in which phthalocyanine photoconductive compound particles are dispersed in a binder resin is provided. It is configured. Here, as the binder resin which is preferably used, there is a polyester-melamine system as disclosed in JP-A-1-169454. This is a resin selected to satisfy the electrical characteristics, moisture resistance and durability of the photoreceptor.

However, as a method for solving the problem of non-uniformity of electrophotographic characteristics of the photoconductor caused by the instability of the photosensitive solution composed of phthalocyanine compound particles, the method that can be easily considered is first used in the field of paints. It is considered that the dispersion stabilizer is used to stabilize the photosensitive solution. Then, as a result of using zinc stearate as a generally known dispersion stabilizer, the dispersion stability of the phthalocyanine-based photoconductive compound particles in the photosensitive solution was confirmed. However, the electrophotographic characteristics of the photoconductor manufactured using this photosensitizing solution were deteriorated, such as the increase of dark decay.

[0008]

The conventional positively charged organic photoconductor using a phthalocyanine compound having photoconductivity has the above-mentioned constitution. However, the particles of the phthalocyanine compound are formed by polyester-melamine. Dispersion stability of the photosensitive liquid dispersed in a binder resin such as that of the phthalocyanine-based photoconductive compound is extremely poor, and the photosensitive liquid is dispersed to produce a photoconductor having uniform characteristics. It was necessary to apply it immediately after. When coating is performed using the secondary aggregation photosensitive liquid, a portion (minute area) in which the concentration of phthalocyanine-based photoconductive compound particles is high is formed, and the charge retention ability of that portion decreases, and finally When printed, it appears as black dots or white spots. Further, a binder resin system in which phthalocyanine-based photoconductive compound particles do not cause secondary aggregation, such as butyral resin or cellulose, does not satisfy the moisture resistance and durability as a photoreceptor.

The present invention has a charging property, a photosensitivity (photoresponsiveness),
It is an object of the present invention to improve the dispersion stability of particles of a phthalocyanine compound in a photosensitive solution without deteriorating the electrophotographic characteristics such as dark decay.

[0010]

The present invention has been made to solve the above-mentioned problems, and the photoconductive material of the present invention means that the phthalocyanine compound on the surface of the particle is a polymer compound containing a hydroxyl group. The particles are treated so as to interact with each other or to form a structure in which a part or all of the surface of the particle is covered with a hydroxyl group-containing polymer compound, so that secondary aggregation or crystal growth of the particle can be suppressed. The electrophotographic photoreceptor of the present invention has a structure comprising a substrate and a layer formed on the substrate by a photosensitive material in which the photoconductive material is dispersed in a binder resin. It shows uniform electrophotographic characteristics over the entire body.

That is, the present invention relates to a photoconductive material obtained by treating the particle surface of a phthalocyanine compound having photoconductivity with a hydroxyl group-containing polymer compound.

The phthalocyanine compound is preferably an X-type metal-free phthalocyanine.

The hydroxyl group-containing polymer compound is preferably at least one selected from the group consisting of polyvinyl butyral, polyvinyl alcohol and polyvinyl formal.

The present invention also relates to a method for producing a photoconductive material in which the solution in which the hydroxyl group-containing polymer compound is dissolved and the phthalocyanine compound are mixed and dispersed.

The present invention further relates to an electrophotographic photoreceptor comprising a substrate and a photosensitive layer obtained by forming a dispersion of the photoconductive material in a binder resin on the substrate.

Further, the present invention is for electrophotography in which a solution in which a polymer compound containing a hydroxyl group is dissolved and a phthalocyanine compound having photoconductivity are mixed and dispersed in a binder resin to form a layer on a substrate. A method of manufacturing a photoreceptor is provided.

[0017]

Examples Examples of the phthalocyanine compound having photoconductivity in the present invention include those described in Japanese Patent Publication No. 49-43.
No. 38, JP-A-1-169454, and other publicly known documents are used. Particles of a phthalocyanine compound are preferably used in the organic photoreceptor of the present invention for the above reasons. As the phthalocyanine compound, α type, β type, which are called metal-free phthalocyanine,
ε-type or X-type crystals are preferable, and X-type crystals are more preferable in terms of sensitivity to semiconductor lasers. As the metal phthalocyanine, α-copper phthalocyanine and titanyl phthalocyanine are preferable.

The particle size of the phthalocyanine compound particles in the present invention is 0.05 to 1 μm, preferably 0.1.
Is about 0.2 μm. If the particle size is less than 0.1 μm, it tends to be difficult to pulverize and the crystal form may not be retained.
If it exceeds 2 μm, the electrophotographic properties tend to deteriorate.

As the hydroxyl group-containing polymer compound used in the present invention, for example, polyvinyl butyral, polyvinyl acetal, polyvinyl formal and the like are preferable, and these may be used alone or in combination of two or more kinds. However, it is not limited to these.

The solvent used when the photosensitive compound is prepared by dissolving the hydroxyl group-containing polymer compound used in the present invention and treating the phthalocyanine compound, an aromatic solvent such as toluene or xylene, or methyl ethyl ketone (ME) is used.
K), ketone solvents such as dibutyl ketone, acetone and 3-hexanone, ester solvents such as ethyl acetate and isobutyl acetate, ether solvents such as tetrahydrofuran (THF), alcohol solvents such as methanol, ethanol and butanol are preferable. Can be used for, among these, aromatic solvents, ketone solvents are soluble,
It is preferable in terms of coatability, and toluene is more preferable in terms of coatability.
MEK is preferred.

As the substrate in the present invention, a conductor or an insulator that has been subjected to a conductive treatment is used. For example, a simple metal or alloy substrate of Al, Ni, Fe, Cu, Au or the like, polyester, polycarbonate, Examples include a material in which a thin film of a metal such as Al, Ag, or Au or a conductive material such as In ₂ O ₂ or SnO ₂ is formed on an insulator such as polyimide or glass, or paper subjected to a conductive treatment. From the viewpoint of low cost, Al or the like is preferable.

The shape of the substrate is not particularly limited and may be drum-shaped, plate-shaped, belt-shaped or the like, if necessary, but is not limited thereto.

In the electrophotographic photoreceptor of the present invention, the photoconductive material in a state of being dispersed in a resin binder is used, but the binder resin used in the present invention is one having a good charge retention rate. For example, acrylic resin, polyester resin, urethane resin, urea resin,
An amino resin such as a melamine resin and a heat or light curable resin such as an isocyanate resin are used.

The mixing ratio of the hydroxyl group-containing polymer compound and the phthalocyanine compound is 0.1 to 50% of the hydroxyl group-containing polymer compound with respect to the phthalocyanine compound.
(% By weight, the same applies hereinafter), preferably 0.5 to 10%. If the amount of the polymer compound is less than 0.1%, the dispersibility tends to be unstable, and if it exceeds 50%, the moisture resistance and the durability tend to decrease. Within this range, the phthalocyanine compound Since it is possible to suppress the secondary aggregation and crystal growth of the particles of the, the stability of the dispersion of the phthalocyanine-based compound is increased, the chargeability, photosensitivity (photoresponsiveness) of the electrophotographic photoreceptor of the present invention, Electrophotographic characteristics such as dark decay will not deteriorate.

The method for obtaining the photoconductive material of the present invention by treating the phthalocyanine compound with the hydroxyl group-containing polymer compound is 0.1 to 5 with respect to the phthalocyanine compound.
0% hydroxyl group-containing polymer is dissolved in the solvent,
It can be obtained by adding the phthalocyanine-based compound particles therein and pulverizing and stirring with a paint shaker or a planetary ball mill.

When the polymer compound is dissolved in a solvent, if the temperature is low, it takes a long time to dissolve it, and if the temperature is high, it is limited by the boiling point of the solvent.

In the dispersion liquid containing the phthalocyanine compound in the solvent, particles of the phthalocyanine compound cause crystal growth or secondary aggregation with time. Dispersion liquid of the phthalocyanine compound of the present invention, by treating the particle surface of the phthalocyanine compound with a hydroxyl group-containing polymer compound, to suppress the crystal growth and secondary aggregation of the particles of the phthalocyanine compound in the dispersion liquid, the primary The particles can be dispersed in the state of particles to make uniform the electrophotographic characteristics of the photoreceptor described below.

The resin binder was added to the dispersion and stirred to obtain the photosensitive liquid of the present invention.

The electrophotographic photoreceptor of the present invention can be manufactured as follows. That is, the substrate is dipped in the photosensitive solution for coating, dried at 22 ° C. for 8 hours, and then 120 to 22.
The photosensitive layer is formed by drying at 0 ° C., preferably 140 to 150 ° C. for 0.5 to 5 hours, preferably 3 to 4 hours and curing. If the temperature at this time is lower than 120 ° C., there is a tendency that it will not cure, and if the temperature exceeds 220 ° C., the photoreceptor will decompose. If the time is less than 0.5 hours, it tends not to cure, and
If the time is exceeded, the effect of taking extra time tends to be difficult to obtain.

The thickness of the photosensitive layer is 10 to 30 μm, preferably 15 to 25 μm. When it is less than 10 μm, the charge retention ability is lowered, pinholes are apt to occur, and printing durability tends to be remarkably lowered. However, if it exceeds 30 μm, the photoresponse speed tends to be insufficient, and the amount of expensive photoconductive material used tends to increase. Considering the charge retention ability and the photoresponse speed, the more preferable range of the film thickness is 15 to
It is 25 μm.

In order to obtain a photosensitive layer having the above-mentioned film thickness, a phthalocyanine compound, a resin binder and a solvent are mixed to prepare, for example, a paint shaker, a ball mill, a disper,
It is formed by dispersing using a planetary crusher or the like and applying it by a surface dipping method (dipping method) such as an aluminum drum provided with an undercoat layer, or a spraying method, but the dipping method is preferable.

In providing the photosensitive layer, an undercoat layer can be provided on the substrate, if necessary, and its function is to function as a barrier for stabilizing electrical characteristics and to improve mechanical characteristics. The adhesiveness between the substrate and the photosensitive layer can be improved.

The undercoat layer is obtained by applying the substrate by immersing it in a solution in which a polyamide resin or the like is dissolved in a solvent such as methanol and drying it, and the film thickness after drying is 0.1. ˜2 μm, preferably 0.5 to 1 μm.

If the film thickness is less than 0.1 μm, pinholes may occur, and if it exceeds 2 μm, the residual potential tends to increase.

Further, in order to protect the photosensitive layer, the substrate having the photosensitive layer formed thereon is dipped in a 20 to 40% solution of a binder resin in a solvent for coating. As the solvent at this time, those used when the above-mentioned hydroxyl group-containing polymer compound is dissolved can be preferably used.

The content of the phthalocyanine compound in the photosensitive layer of the present invention is 15 to 40%, preferably 20 to 35%.
Is. This is a condition necessary for the photoconductor to function as a positive charging type photoconductor, and if the ratio is less than 15%, the photosensitivity tends to be remarkably lowered, and if it exceeds 40%, the bulk resistance of the photoconductor is increased. And the charge retention ability tends to decrease. 25 to 3 in terms of the balance between photosensitivity and charge retention ability
The range of 5% is more preferable.

In the photoconductor, various additives such as a silane coupling agent, a titanate coupling agent, and 2,5-dichloro-p- are used in order to improve sensitivity, ozone resistance, durability and the like. Benzoquinone (DCB
Q) and a sensitizer such as tetracyanoethylene (TCNE) can be used in combination.

Next, the present invention will be described more specifically based on examples, but the present invention is not limited to these.

[Example 1] A polished aluminum substrate was replaced with a polyamide resin (trade name CM-8, manufactured by Toray Industries, Inc.).
000) was immersed in a 5% dissolved methanol solution for coating, and dried at 100 ° C. for 30 minutes to form an undercoat layer. The average film thickness of the layer was 0.5 μm.

X-type metal-free phthalocyanine particles (manufactured by Dainippon Ink and Chemicals, Inc., trade name Fastogen Bl)
ue 8120 BS) 150 g and 0.1 against this
% Of a hydroxyl group-containing polymer compound, polyvinyl butyral (Sekisui Chemical Co., Ltd., trade name S-REC BM)
-S) was added to 1300 g of toluene and mixed with a paint shaker for 2 hours for treatment to obtain a photoconductive material of the present invention. Next, polyester resin (Mitsui Toatsu Chemicals, Inc.)
279 g of Almatex P-645, trade name, and 70 g of butylated melamine resin (Uban 20-HS, trade name, manufactured by Mitsui Toatsu Chemicals, Inc.) and 1300 g of MEK, and further mixed and dispersed for 2 hours to obtain a photosensitive solution. Was produced.

The substrate having the undercoat layer formed thereon was dipped in the photosensitive solution for coating, dried at 25 ° C. for 60 minutes and then dried at 150 ° C. for 4 hours to be cured to form a photosensitive layer. Furthermore, polyester resin (Mitsui Toatsu Chemical Co., Ltd.,
Product name Almatex P-645) 24%, Butylated melamine resin (Mitsui Toatsu Chemicals, Inc., product name U-Van 2
It was dipped in a toluene solution in which 0-HS) 6% was dissolved and applied, dried at 150 ° C. for 4 hours and cured to obtain the electrophotographic photoreceptor of the present invention. The film thickness of the photosensitive layer was 18 to 22 μm. Further, a photoconductor drum was manufactured by the same method.

The following tests were conducted using the above-mentioned photoreceptor. The results are shown in Table 1.

Precipitation in Photosensitive Solution: The photosensitive solution was left in a dark room,
The number of days after which precipitation occurred was visually observed.

Secondary agglomeration of particles: Whether or not there are secondary agglomerated particles in the photosensitive solution immediately after preparation is determined by a scanning electron microscope (manufactured by JEOL Ltd., trade name JSM-T330A,
It was observed at 35,000 times using a resolution of 4.5 nm).

Dark decay: Using an electrostatic charging tester (Kawaguchi Electric Co., Ltd., trade name EPA-8100),
The photoreceptor was charged to +600 V, the charging was stopped, and the charging potential was measured after 1 second.

White spots in image quality: A solid black test was conducted using a prototype printer, and it was visually observed whether or not there were white spots.

Black dots in image quality: White printing was performed on the entire surface using a prototype printer, and it was visually observed whether or not there were black dots.

High temperature and high humidity test: Various tests were conducted at 35 ° C. and 80% RH.

Responsiveness: Using an electrostatic charging tester (Kawaguchi Electric Co., Ltd., trade name EPA-8100),
Light having a wavelength of 780 nm is exposed to the photoconductor at an exposure amount of 2.5 μJ / cm.
^The amount of change in charging potential when irradiated with ² was measured.

Example 2 An electrophotographic photoreceptor of the present invention was obtained in the same manner as in Example 1 except that the amount of the hydroxyl group-containing polymer compound used was 1%, and the same test as in Example 1 was conducted. I did. The results are shown in Table 1.

Example 3 An electrophotographic photoreceptor of the present invention was obtained in the same manner as in Example 1 except that the amount of the hydroxyl group-containing polymer compound used was 10%, and the same test as in Example 1 was conducted. I did. The results are shown in Table 1.

Example 4 An electrophotographic photosensitive member of the present invention was obtained in the same manner as in Example 1 except that the amount of the hydroxyl group-containing polymer compound used was 50%, and the same test as in Example 1 was conducted. I did. The results are shown in Table 1.

[Example 5] The same procedure as in Example 1 except that polyvinyl acetal (manufactured by Sekisui Chemical Co., Ltd., trade name S-REC KS-1) was used as the hydroxyl group-containing polymer, and 2% was used. Then, the electrophotographic photoreceptor of the present invention was obtained and the same test as in Example 1 was conducted. The results are shown in Table 1.

Example 6 An electrophotographic photoreceptor of the present invention was obtained in the same manner as in Example 1 except that polyvinyl formal (commercially available product) was used as the hydroxyl group-containing polymer, and the same test as in Example 1 was carried out. Was done. The results are shown in Table 1.

Example 7 When the X-type metal-free phthalocyanine and the hydroxyl group-containing polymer compound were added to toluene in Example 1, a silane coupling agent (trade name KBM-603, manufactured by Shin-Etsu Chemical Co., Ltd.) was used. ) The electrophotographic photoreceptor of the present invention was obtained in the same manner except that 0.045 g was added, and the same test as in Example 1 was conducted. The results are shown in Table 1.

The test was conducted as follows.

[0057]

[Table 1] Comparative Example 1 An electrophotographic photosensitive member was obtained in the same manner as in Example 1 except that the hydroxyl group-containing polymer compound was not used, and the same test as in Example 1 was conducted. The results are shown in Table 1.

[0058]

EFFECT OF THE INVENTION The stability of the photosensitive solution containing the photoconductive material in which the particle surface of the phthalocyanine compound is treated with the hydroxyl group-containing polymer is drastically improved. No white spots or black spots in image quality, good electrophotographic characteristics at high temperature and high humidity, and uniform electrophotographic characteristics over the entire photoreceptor can be obtained.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshimi Sugimoto 1-8 Midoricho, Fukuyama City Mitsubishi Electric Corporation Fukuyama Factory (72) Inventor Makoto Tsunoda 8-1-1 Tsukaguchihonmachi, Amagasaki Mitsubishi Electric Corporation Materials Device Laboratory

Claims (6)

[Claims] 1. A photoconductive material obtained by treating the particle surface of a phthalocyanine compound having photoconductivity with a hydroxyl group-containing polymer compound. 2. The photoconductive material according to claim 1, wherein the phthalocyanine compound is an X-type metal-free phthalocyanine. 3. The photoconductive material according to claim 1, wherein the hydroxyl group-containing polymer compound is at least one selected from the group consisting of polyvinyl butyral, polyvinyl acetal and polyvinyl formal. 4. The method for producing a photoconductive material according to claim 1, 2 or 3, wherein a solution in which the hydroxyl group-containing polymer compound is dissolved and the phthalocyanine compound are mixed and dispersed. 5. An electrophotographic photoreceptor comprising a substrate and a photosensitive layer obtained by forming a dispersion of the photoconductive material according to claim 1, 2 or 3 in a binder resin on the substrate. 6. A method for producing an electrophotographic photoreceptor, which comprises mixing a solution containing a hydroxyl group-containing polymer compound with a phthalocyanine compound having photoconductivity and dispersing the mixture in a binder resin to form a layer on a substrate. .