JPH0746229B2 - Electrophotographic photoconductor - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electrophotographic photoreceptor used in a copying machine, a laser printer, etc., and more specifically, improved stability during repeated use. The present invention relates to a photoconductor for electrophotography.

(Prior Art) In the field of electrophotographic photoreceptors, so-called function-separated type organic photoreceptors in which a charge generation layer (CGL) and a charge transport layer (CTL) are laminated are gradually being used. Along with this laminated type photoreceptor, a single layer dispersion type organic photoreceptor in which a charge generating substance is dispersed in a medium of a charge transport substance is already known.

As the charge transport material for this type of photoconductor, one having a high carrier mobility is required, and from a high molecular weight material such as polyvinylcarbazole (PVK) at an early stage to a low molecular weight compound material used in a resin dispersion system. It is migrating. However, from the viewpoint of moldability, it is desirable that the charge transport material is a film-forming material that can be used alone. Mentioned above
Although PVK can be formed into a film, it has a problem that the dimer site formed by the adjacent carbazole ring acts as a structural hole carrier trap and causes deterioration of electrophotographic characteristics of the photoconductor.

Recently, Japanese Unexamined Patent Publication (Kokai) No. 61-170747 proposes a photoreceptor containing organic polysilane as a hole transport material. It is also known that this organic polysilane can be formed into a film from a solution and has a high hole drift mobility (10 ⁻⁴ cm ² / V · sec) among amorphous polymer materials.

(Problems to be Solved by the Invention) As a photoreceptor to be mounted on a copying machine, not only initial characteristics but also stability upon repeated use are required, but a photoreceptor using an organic polysilane is not yet available. It seems that this stability has not been fully investigated.

The present inventors have made a study to apply the organic polysilane to a commercial electrophotographic photoreceptor, and when charging-exposure is repeated on this photoreceptor, the surface potential of the photoreceptor and the residual potential increase, It has been found that the density change and the fog of the copied image are accompanied with this.

Therefore, an object of the present invention is to suppress an increase in surface potential or residual potential during repeated charging-exposure in a photoreceptor using an organic polysilane as a charge transport material (hole transport material), and to provide stable electrophotographic characteristics for a long period of time. Another object of the present invention is to provide a photoconductor for electrophotography, which is obtained.

(Means for Solving Problems) According to the present invention, in an electrophotographic photoreceptor containing a charge generating substance and a charge transporting substance in a laminated type or a monolayer dispersion type, the charge transporting substance is 1,1, 3-tris (2-methyl-4
Provided is an electrophotographic photoreceptor comprising an organic polysilane composition containing -hydroxy-5-tert-butylphenyl) butane.

In the organic polysilane composition used in the present invention, 1,1,
The 3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane is preferably contained in an amount of 1 to 50 parts by weight, particularly 5 to 30 parts by weight, based on 100 parts by weight of the organic polysilane.

(Function) In the present invention, when the above-mentioned specific high molecular weight polycyclic hindered phenol is blended in the organic polysilane, the stability of the photoreceptor when the charging-exposure operation is repeated is improved, and the surface potential and the residual potential of the photoreceptor are improved. It is based on the finding that the increase can be significantly suppressed.

As described above, when the charging-exposure operation is repeated on the photoreceptor using the organic polysilane as the charge transport material, both the surface potential and the residual potential increase considerably. This increase in surface potential and residual potential is due to the deterioration of the surface of the organic polysilane layer, which reduces the carrier transport ability of the surface portion,
The residual potential rises. The mechanism of this deterioration has not been fully clarified yet, but the ultraviolet light generated during charging, ozone, or excitation-doublet oxygen causes an insulating film to be formed on the surface, which increases the surface potential, resulting in repeated charging-exposure. Therefore, it is considered that the residual potential rises due to the accumulation of charges in this insulating film.

In the present invention, 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane is selected among the high molecular weight polycyclic hindered phenols, and when this is blended in the organic polysilane. , The specific phenol itself preferentially reacts with the component that deteriorates the surface, thereby preventing the deterioration of the organic polysilane body and suppressing the increase of the surface potential and the residual potential, and the above-mentioned phenol added. Since the and its reaction products do not serve as a trap for the organic polysilane, the initial characteristics are not deteriorated.

(Preferred Embodiment) The organic polysilane used in the present invention may be any known per se, but the main chain is composed of a chain of silicon,
It has an organic group, particularly a monovalent hydrocarbon group, in its side chain and has the following formula In the formula, each of R ₁ and R ₂ is a monovalent hydrocarbon group, particularly an alkyl group having 4 or less carbon atoms, an aryl group having 6 or more carbon atoms, and an aralkyl group. Suitable organic polysilanes are methylphenyl polysilane, methylpropyl polysilane, methyl t-butyl polysilane, diphenyl polysilane, methyltolyl polysilane or copolymers thereof.

The organic polysilane used should have a molecular weight sufficient to form a so-called film, generally 5,000 to 50,000,
It is particularly preferable to have a weight average molecular weight ( _w ) of 5,000 to 20,000.

The terminal of the organic polysilane may be a silanol group, an alkoxy group, or the like.

In the present invention, in combination with the above-mentioned organic polysilane, 1,1,3-tris (2-methyl-4-hydroxy-
5-tertiary brylphenyl) butane (hereinafter may be simply referred to as "high molecular weight polycyclic hindered phenol").
To use.

The high molecular weight polycyclic hindered phenol is preferably used in an amount of 1 to 50 parts by weight, particularly 5 to 30 parts by weight, per 100 parts by weight of organic polysilane. The effect of suppressing the increase in surface potential and residual potential during repetition tends to be inferior as compared with the case of being in the above range, while when it is more than the above range, the sensitivity is higher than that in the case of being in the range. Tends to decline.

The high molecular weight polycyclic hindered phenol used in the present invention is
Since the organic polysilane is soluble in a solvent such as tetrahydrofuran (THF), both can be mixed uniformly.

INDUSTRIAL APPLICABILITY The present invention can be applied to a laminated type electrophotographic photoreceptor or a single-layer dispersion type electrophotographic photoreceptor. For example, as shown in FIG. 1, a charge generation layer (CGL) 2 is formed on a conductive substrate 1.
And a charge transport layer (CTL) 3 composed of the organic polysilane composition can be provided on the charge generation layer. Alternatively, conversely, as shown in FIG. 2, the charge transport layer 3 made of the organic polysilane composition may be provided on the conductive substrate 1, and the charge generation layer 2 may be provided on the charge transport layer. Further, as shown in FIG. 3, on the conductive substrate 1,
A single layer may be provided as a photosensitive layer in which the charge generating material 2'is dispersed in the charge transporting medium 3'made of an organic polysilane composition.

Examples of the charge generation material include selenium and selenium-
Tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, ansanthrone pigments, phthalocyanine pigments, indigo pigments, slene pigments, toluidine pigments, pyrazoline pigments, perylene pigments, quinacridone pigments, etc. For example, one kind or a mixture of two or more kinds is used so as to have an absorption wavelength region in a desired region.

This charge generating material can be applied in the form of a layer by means such as vapor deposition, or can be applied as a layer in the form of being dispersed in a binder resin. As such a binder resin, various resins can be used, and examples thereof include styrene-based polymers, acrylic polymers, styrene-acrylic copolymers, ethylene-
Vinyl acetate copolymer, polypropylene, olefin polymers such as ionomer, polyvinyl chloride, vinyl chloride-
Vinyl acetate copolymer, polyester, alkyd resin,
Various polymers such as polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, and photocurable resin such as epoxy acrylate are available. It can be illustrated. These binder resins may be used alone or in combination of two or more.

For the solvent used to form the coating liquid,
Various organic solvents can be used, alcohols such as meatanol, ethanol, isopropanol, butanol,
Aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene, dimethyl ether, diethyl ether, tetrahydrofuran, Ethylene glycol dimethyl ether, ethers such as diethylene glycol dimethyl ether, acetone, methyl ethyl ketone, ketones such as cyclohexane, ethyl acetate, esters such as methyl acetate, dimethylformamide, dimethyl sulfoxide and the like, various solvents are exemplified,
One kind or a mixture of two or more kinds is used.

As the conductive substrate, various materials having conductivity can be used, and examples thereof include aluminum, copper, tin, platinum, gold, silver,
Single metal of vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel, brass, plastic material in which the above metal is vapor-deposited or laminated, glass coated with aluminum iodide, tin oxide, indium oxide, etc. Is exemplified.

In order to form the coating liquid, the charge generating material and the binder resin are adjusted by a conventionally known method, for example, using a roll mill, a ball mill, an attritor, a paint shaker, an ultrasonic disperser, or the like. It may be applied and dried by the application means.

In the case of the substrate / CGL / CTL photoreceptor of FIG. 1, CGL varies from 0.01 to 0.05 μm in the case of vapor deposition to 0.1 to 0.5 μm in the case of coating, but CTL is in the range of 5 to 40 μm, especially 10 to 25 μm. It is good to be in For the substrate / CTL / CGL photoreceptor of FIG. 2, the CTL should have a thickness of 5 to 40 μm, especially 10 to 25 μm, while the CGL should have a thickness of 0.1 to 0.5 μm. Further, in the CTL and CGL dispersion type photoreceptor of FIG. 3, the charge generating material is present in the photosensitive layer in an amount of 1 to 15 parts by weight, particularly 5 to 10 parts by weight, based on 100 parts by weight of the organic polysilane. Well, the photosensitive layer preferably has a thickness of 10 to 40 μm, particularly 15 to 30 μm.

(Effect of the invention) According to the present invention, by charging 1,1,3-tris (2-methyl-hydroxy-5-tert-butylphenyl) butane into an organic polysilane as a hole transport material, charging by -It has become possible to obtain stable electrophotographic characteristics over a long period of time by suppressing an increase in surface potential and residual potential during repeated exposure. Further, since the high hole drift mobility originally possessed by the organic polysilane is maintained as it is, a photoconductor for a copying machine or a laser printer having high sensitivity and stable electrophotographic characteristics is provided.

(Example) Hereinafter, the present invention will be described in more detail based on examples.

Example 1. [Synthesis of phenylmethylpolysilane] 100 g of methylphenyldichlorosilane, 26 sodium metal
g was added to 400 ml of dry toluene, heated to 130 ° C., stirred for 11 hours, and then cooled. Ethanol was added to the obtained reaction solution (solution containing a dark purple precipitate) to convert unreacted sodium to ethoxide, and the precipitate was filtered off, dried, dissolved in toluene, and added dropwise into ethanol to reprecipitate a white solution. Phenylmethylpolysilane was obtained (22.0 g: 34% yield).

[Adjustment of electrophotographic photoreceptor]

100 parts by weight of α-type oxotitanyl phthalocyanine as a charge generating material and 4000 parts by weight of tetrahydrofuran as a solvent were charged into a ball mill and stirred for 24 hours, and then polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name Eslec BM-3 was used as a binder. ) 100 parts by weight is added, and the mixture is stirred and mixed for an additional 1 hour to prepare a coating solution for the charge generation layer, which is coated on the aluminum foil with a wire bar (No. 5).
A 5 μm-thick charge generation layer was formed by drying in hot air at 30 ° C. for 30 minutes to cure.

Next, phenylmethylpolysilane as a charge transport material
100 parts by weight, 10 parts by weight of 1,1,3-tris (2-methyl-hydroxy-5-tert-butylphenyl) butane (manufactured by ADEKA GAS, trade name MARK AO-30) as an antioxidant, and as a solvent 1000 parts by weight of tetrahydrofuran was mixed with stirring with a homochimer to prepare a charge transport layer coating solution.
Apply this coating solution to the wire bar (No. 6) on the charge generation layer.
After coating at 0), it was dried with hot air at 100 ° C. for 30 minutes to form a charge transport layer having a film thickness of about 5 μm, to prepare an electrophotographic photoreceptor.

Example 2 Example 1 was repeated except that metal-free phthalocyanine was used in place of α-type oxotitanyl phthalocyanine as the charge generating material in the preparation of the coating liquid for the charge generating layer.
An electrophotographic photoreceptor was prepared in the same manner as in.

Example 3. 100 parts by weight of phenylmethylpolysilane as a charge transport material, 5 parts by weight of α-type oxotitanyl phthalocyanine as a charge generation material, 1,1,3-tris (2-methyl-4-hydroxy) as an antioxidant. -5-tert-Butylphenyl) butane (manufactured by ADEKA ARGUS CORPORATION, trade name MARK AO-30)
10 parts by weight and 1000 parts by weight of tetrahydrofuran as a solvent were stirred and mixed in a ball mill for 24 hours to prepare a coating solution for a single layer type photosensitive layer. This coating solution is applied on an aluminum foil with a wire bar (No.60) and then dried with hot air at 100 ° C for 30 minutes to form a single-layer type photosensitive layer with a film thickness of about 10 μm. It was created.

Comparative Example 1. In adjusting the coating liquid for the charge transport layer, a high-molecular-weight polycyclic hindered phenol (Adeka Argus Co., trade name MARK AO-30) as an antioxidant was used instead of a low-level antioxidant. Molecular weight hindered phenol (Kawaguchi Chemical Co.,
Example 1 except that the product name Antage BHT) was used
An electrophotographic photoreceptor was prepared in the same manner as in.

Comparative Example 2. Instead of high molecular weight polycyclic hindered phenol (manufactured by ADEKA ARGUS CORPORATION, trade name MARK AO-30) as an antioxidant in the preparation of the coating liquid for the charge transport layer, ( An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that Adeka Argus Co., Ltd., trade name LA-36) was used.

Comparative Example 3 An electrophotographic image was prepared in the same manner as Comparative Example 2 except that 100 parts by weight of (Adeka Argus Co., trade name LA-36) was used as an ultraviolet absorber in the preparation of the charge transport layer coating liquid. A photoconductor was created.

Comparative Example 4. In the preparation of the coating liquid for the charge transport layer, except that high molecular weight polycyclic hindered phenol (Adeka Argus Co., trade name MARK AO-30) as an antioxidant was not added,
An electrophotographic photoreceptor was prepared in the same manner as in Example 1.

Comparative Example 5. In the preparation of the coating liquid for the charge transport layer, except that high molecular weight polycyclic hindered phenol (manufactured by ADEKA ARGUS, trade name MARK AO-30) as an antioxidant was not added,
An electrophotographic photosensitive member was prepared in the same manner as in Example 2.

Comparative Example 6. In the preparation of the coating liquid for the charge transport layer, except that a high molecular weight polycyclic hindered phenol (manufactured by ADEKA ARGUS CORPORATION, trade name MARK AO-30) as an antioxidant was not added.
An electrophotographic photoreceptor was prepared in the same manner as in Example 3.

[Evaluation of electrophotographic photoreceptor]

Using an electrostatic copying tester (Model 8100, manufactured by Kawaguchi Denki Co., Ltd.), positively or negatively charged at an applied voltage of ± 6.0 KV, electrophotographic characteristics were measured under the following conditions, and the results are shown in Tables 1 and 2. Indicated.

Exposure time: 10 seconds Irradiation light: Wavelength 780 nm Exposure intensity: 10 μW / cm ² Dark decay after charging: 2 seconds In addition, V ₁ (V) in the table applies voltage under the above conditions to charge the photoreceptor. Shows the initial surface potential V ₁ (V) of the photoconductor when E ₁ 1/2 (μJ / cm ² ) is the initial surface potential
The half-exposure amount calculated from the exposure time required to become 1/2 of V ₁ (V) is shown. Further, V _1rp (V) in the table is the surface potential measured 5 seconds after the start of exposure as the residual potential, and the attenuation rate% is calculated by the following formula.

Further, among the above conditions, the exposure time was changed to 3 seconds, the dark decay after charging was changed to 1 second, and charging-exposure was repeated 100 times, and the surface potential V _2sp (V) of the photosensitive member at that time and the half-exposure amount
E ₂ 1/2 (μJ / cm ² ), residual potential V _2rp (V) and decay rate (%) were measured.

From the results in the above table, the electrophotographic photoreceptor of Comparative Example 1 using a low molecular weight hindered phenol as an antioxidant, and the electrophotographic photoreceptors of Comparative Examples 2 and 3 using an ultraviolet absorber instead of the antioxidant. In each of the electrophotographic photoreceptors of Comparative Examples 4, 5 and 6 in which the antioxidant was not added, the surface potential and the residual potential greatly increased due to repeated charging and coating. On the other hand, the electrophotographic photoconductors of Examples 1 to 3 using 1,1,3-tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane as the antioxidant were not charged. It was found that the amount of change in the surface potential and the residual potential was small even after repeated exposure, and that it had good repeatability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a negative charging type laminated photoreceptor of the present invention. FIG. 2 is a cross-sectional view of the positive charging type laminated photoreceptor of the present invention. FIG. 3 is a cross-sectional view of the positive charging type single layer photoreceptor of the present invention. 1 ... Substrate, 2 ... Charge generation layer, 3 ... Charge transport layer, 4
...... Single layer type photosensitive layer

Claims (2)

[Claims] 1. An organic photoconductor for electrophotography, comprising a charge-generating substance and a charge-transporting substance in a laminated type or in a monolayer-dispersed type, wherein the charge-transporting substance is 1,1,3-tris (2-methyl-4).
An electrophotographic photosensitive member comprising an organic polysilane containing -hydroxy-5-tert-butylphenyl) butane. 2. 1,1,3-Tris (2-methyl-4-hydroxy-5-tert-butylphenyl) butane is contained in an amount of 1 to 50 parts by weight per 100 parts by weight of the organic polysilane. The described photoreceptor.