JPH03144573A - Organic photosensitive body - Google Patents

Abstract

PURPOSE:To enhance stability of a photosensitive body at the time of repeating electric charging-exposure operations and to suppress rises of surface potential and residual potential by incorporating a diphenoquinone derivative in a positive hole transfer material, such as organic silane. CONSTITUTION:For example, a charge generating layer 2 is formed on a conductive substrate 1, and on this layer 2 is formed a charge transfer layer 3 made of an organic polysilane composition as a charge transfer material, i.e. the positive hole transfer material composition containing the diphenoquinone derivative. When such a photosensitive material undergoes repeated charging-exposure operations, it rises in both surface potential and residual potential considerably, thus permitting the positive hole transfer material in an excited state to be deactivated by the electron receptivity of the diphenoquinone derivative, and the rises of surface potential and residual potential to be suppressed at the time of repeating charging-exposure processes, and electrophotographic characteristics to be stabilized for a long period.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrophotographic organic photoreceptor used in copying machines, laser printers, etc., and more specifically, it has improved stability during repeated use. The present invention relates to an organic photoreceptor for electrophotography.

(Prior Art) In the field of electrophotographic photoreceptors, so-called functionally separated organic photoreceptors in which a charge generation layer (CGLI) and a charge transport layer (CTLI) are laminated are increasingly being used.

In addition to this laminated type photoreceptor, a single-layer dispersed type organic photoreceptor in which a charge generating substance is dispersed in a medium of a charge transporting substance is already known.

Charge transport materials for this type of photoreceptor are required to have high Canoyer mobility, and the transition from early polymer materials such as polyvinylcarbazole (PVKI) to low-molecular compound materials used in resin dispersion systems. However, from the point of view of moldability, it is desirable that the charge transport material be a film-forming material that can be used alone. There is a problem in that the formed dimersite acts as a structural hole carrier trap, causing a decline in the electrophotographic properties of the photoreceptor.

Recently, Japanese Unexamined Patent Application Publication No. 170747/1983 states that
Photoreceptors containing organic polysilane as a hole transport material have been proposed. This organic polysilane can be formed into a film from a solution, and is known to exhibit a high hold lift mobility (~10-'Cm2/V·sec) among amorphous polymer materials.

(Problem to be solved by the invention) Photoconductors installed in copying machines, etc. are required to have not only initial characteristics but also stability when used repeatedly, but photoconductors using organic polysilane have not yet been developed. It seems that this stability has not been sufficiently investigated.

The present inventors investigated the application of organic polysilane to commercial electrophotographic photoreceptors, and found that when this photoreceptor was repeatedly charged and exposed, the surface potential and residual potential of the photoreceptor increased. It has been found that this causes density changes and fog in the copied images. Such increases in surface potential and residual potential during repeated charging and exposure are particularly remarkable in organic polysilanes, but are also observed when other hole transporting materials are used.

Therefore, an object of the present invention is to suppress the upper limit of the surface potential and residual potential during repeated charging and exposure in a photoreceptor using a hole transport material, especially an organic polysilane, and to obtain stable electrophotographic characteristics over a long period of time. An object of the present invention is to provide an electrophotographic photoreceptor.

(F E'l 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 form or a monolayer dispersed form, the charge transporting substance is diphenoquinone. An organic photoreceptor for electrophotography is provided, which is characterized by comprising a hole transport material composition containing a derivative.

The diphenoquinone derivative is preferably contained in an amount of 0.1 to 30 parts by weight, particularly 1 to 15 parts by weight, per 100 parts by weight of the hole transport substance. The effects of the present invention are particularly significant when the hole transport material is an organic polysilane.

(Function) The present invention provides a hole-transporting material such as an organic polysilane.
This is based on the knowledge that when a diphenoquinone derivative is blended, the stability of the photoreceptor is improved when charging and exposure operations are repeated, and increases in surface potential and residual potential can be significantly suppressed.

As mentioned above, a photoreceptor using a hole-transporting substance is charged.
When the exposure operation is repeated, both the surface potential and the residual potential increase considerably. This increase in surface potential and residual potential is due to deterioration of the hole transport layer or the surface of the hole transport layer, and the carrier transport ability of the surface portion decreases, resulting in an increase in the surface potential and residual potential. The mechanism of this deterioration is still not fully understood, but an insulating film is formed on the surface due to ultraviolet light generated during charging, ozone, excited oxygen, etc., and the surface potential increases. It is thought that the repetition causes charge to accumulate in this insulating film, thereby increasing the residual potential. Organopolysilanes, which have these drawbacks particularly,
It is recognized that an insulating film like siloxane is formed due to the cutting of the St--St main chain on the surface.

On the other hand, according to the present invention, when a diphenoquinone derivative is blended into a hole transporting material, its electron accepting property causes
It is thought that the hole transport substance in the excited state is deactivated, thereby suppressing its deterioration and the generation of radical species. This can also be confirmed from the fact that diphenoquinone effectively deactivates the fluorescence of organic polysilane. Furthermore, since the diphenoquinone derivative itself is stable, it is thought to have a significant effect.

Among various electron-accepting substances, the diphenoquinone derivative used in the present invention is particularly effective in suppressing increases in surface potential and residual potential during repeated charging and exposure, and in addition, has a good etching effect. The light resistance of the photoreceptor to ultraviolet light can also be improved. This is recognized to be related to a specific chemical structure, ie, a conjugated bond structure, possessed by the diphenoquinone derivative.

The diphenoquinone derivative used in the present invention has excellent compatibility with various hole transport substances and has high electron transport ability itself, so it has the advantage of preventing charge accumulation in the hole transport substance layer. It brings about a positive effect.

(Preferred Embodiment) The diphenoquinone derivative used by the present invention is IJ, in the following formula, each of R+, R2, Rs and R4 is a hydrogen atom,
An alkyl group, a silyloalkyl group, an aryl group, an aralkyl group, etc. represented by the following are preferably used. Suitable examples include, but are not limited to, 2,5-dimethyl-2',6
'-di-t-butyldiphenoquinone, 2,2 dimethyl-6
, δ゛-di-t-butyldiphenoquinone 2,6゛-dimethyl-2゛, 6°-di-t-butyldiphenoquinone, 2,6
．． 2°, 6′-tetramethyldiphenoquinone, 2.6
．． 2',6'-tetra-t-butyldiphenoquinone,
2,6.2',6°-tetraphenyldiphenoquinone,
2,6.2'', 6°-tetracyclohexyldiphenoquinone, and the like.

As the hole transport substance, a low molecular weight hole transport substance or a high molecular weight hole transport substance is used, and the low molecular weight hole transport substance is used in combination with a binder described below. Examples of such hole transport substances include 2.5-di(4-
oxadiazole compounds such as methylaminophenyl), 1.3.4-oxadiazole, styryl compounds such as 9-(4-diethylaminostyrylphanthracene), carbazole compounds such as polyvinylcarbazole, organic polysilane compounds, Pyrazoline compounds such as 1-phenyl-3=(p-dimethylaminophenyl)pyrazoline, hydrazone compounds, triphenylamine compounds,
Examples include nitrogen-containing cyclic compounds and fused polycyclic compounds such as indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds, deadiazole compounds, imidazole compounds, pyrazole compounds, and triazole compounds.

The present invention is particularly useful when using organic polysilanes. This organic polysilane may be any known per se, but it is one whose main chain consists of a silicon chain and which has an organic group, especially a -valent hydrocarbon group, in the side chain, and in the following formula: Each of R and R2 is a monovalent hydrocarbon group, particularly an alkyl group having 4 or less carbon atoms, an aryl group having 6 or more carbon atoms,
It represents an aralkyl group and consists of repeating units shown as.

Suitable organopolysilanes include methylphenylpolysilane,
Examples include methyltolylpolysilane, methyl t-butylpolysilane, diphenylpolysilane, methyltolylpolysilane, and copolymers thereof.

The organic polysilane used should have a molecular weight sufficient to form a so-called film, and preferably has a weight average molecular weight i (Mw) of generally 50[)(l to 5oooo, particularly 5000 to 21)000.

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

The diphenoquinone derivative is preferably used in an amount of 0.1 to 30 parts by weight, particularly 1 to 15 parts by weight, per 100 parts by weight of the hole transport material. The effect of suppressing the increase in surface potential and residual potential tends to be inferior to that within the above range,
When the amount is greater than the range indicated in "--", the sensitivity tends to be lower than when it is within the range indicated in L.

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 fcGLl2 is formed on a conductive substrate 1''2, and on this charge generation layer,
is a charge transport layer (CT
I, )3 can be provided. Alternatively, as shown in FIG. 2, a charge transport layer 3 made of the polysilane composition described above may be provided on a conductive substrate 1, and a charge generation layer upper layer 2 may be provided on this charge transport layer. can. Furthermore, the third
As shown in the figure, a single layer of a photosensitive layer 4 containing a charge generating substance 2 dispersed in a charge transporting medium 3 made of an organic polysilane composition is provided on a conductive 47I: )% plate 112. You can also do it.

Examples of the charge generating material include selenium, selenium-
Tellurium, amorphous silicon, biryllium salts, azo pigments, disazo pigments, anthanthrone pigments, phthalocyanine pigments, indigo pigments, threne pigments, toluidine pigments, pyrazoline pigments, perylene pigments, quinacridone pigments, etc. For example, one type or a mixture of two or more types can be used so as to have an absorption wavelength range 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. Various resins can be used as such a binder resin, such as styrene-based electropolymer, acrylic polymer, styrene-acrylic copolymer, ethylene-
Vinyl acetate copolymer, polypropylene, olefin polymers such as ionomer, polyvinyl chloride, vinyl chloride 1-vinyl acetate copolymer, polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyaryl 1-, polysulfone, Examples include various polymers such as diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyl resin, polyether resin, phenol resin, and photocurable resin such as epoxy acrylate. These binder resins may be used alone or in combination of two or more.

In addition, various organic solvents can be used as the solvent used to form the coating solution, including alcohols such as methanol, ethanol, isopropanol, and butanol, and carbonized aliphatic solvents such as n-hexane, octane, and cyclohexane. Hydrogen, aromatic hydrocarbons such as benzene, toluene, and xylene, halogenated hydrocarbons such as dichloromethane, dichloroethane, carbon tetrachloride, and chlorobenzene, dimethyl ether, diethyl ether, detrahydrofuran, ethylene glycol dimethyl ether, and diethyl ether. Needle jaws such as glycicol dimethyl ether, a]2, ketones such as methyl ethyl ketone and cyclohexane, esters such as ethyl acetate and methyl acetate, dimethyl formamide, dimegol sulfoxide, etc., and fΦ horn solvents are exemplified. -fin or two types of dust" are used in combination.

Various conductive materials can be used as the conductive substrate, such as aluminum, copper, tin, platinum, gold, silver,
Single metals such as vanadium, molybdenum, chromium, cadmium, titanium, nira gel, indium, stainless steel, and brass, plastic materials on which the above metals are vapor-deposited or laminated, and coated with aluminum iodide, tin oxide, indium oxide, etc. Examples include glass.

In order to form the coating liquid, the charge generating material and the binder B resin are adjusted using a conventionally known method such as a roll mill, a ball mill, an attritor, a pane shaker, an ultrasonic disperser, etc. What is necessary is just to apply|coat and dry by the conventionally well-known coating means.

In the case of the substrate/CGL/CTL photoreceptor shown in Figure 1, (',
G1. is 0.0 for vapor deposition. The former 0.115 gm becomes 0.1 to 0.5 μm μm in the case of coating, but C
TL is preferably in the range from 5 to 4074 m, especially from 10 to 25 μm. Board/CT1 in Figure 2. /CG 1
．． , in the case of a photoreceptor, CT [- is 5 to 40 it m
, in particular has a thickness of 10 to 25 μm, while CG I-
It is preferable to have a thickness of 0.1 to 0.5 μm6°.In addition, in the CTL and CG L shown in Fig. 3, and the dispersion type photoreceptor,
The charge generating material is preferably present in the photosensitive layer in an amount of 1 to 15 parts by weight, particularly 5 to 1.0 parts by weight, per 1.00 parts by weight of the organic polysilane, and the photosensitive layer contains 10 to 4.0 parts by weight. Ou
It preferably has a thickness of between 15 and 3014 m, especially between 15 and 3014 m.

(Effects of the Invention) According to the present invention, by incorporating a diphenoquinone derivative into the hole transport material, the upper limit of the surface potential and residual potential during repeated charging and exposure can be suppressed, and deterioration due to ultraviolet rays can be prevented, resulting in a long-term use. It has become possible to obtain stable electrophotographic characteristics over a long period of time. Furthermore, since the high ball drift mobility inherent to organic polysilane is maintained, a photoreceptor for copying machines or laser printers with high sensitivity and stable electrophotographic properties is provided.

<Examples> The present invention will be described in more detail below based on Examples.

(Example 1) [Synthesis of phenylmethylborisilane] 100 g of methylphenyldichlorosilane and 26 g of metallic sodium were added to 400 ml of dry toluene at 130 g.
'C and stirred for 11 hours, then cooled. Ethanol was added to the resulting reaction solution (a solution containing a dark purple precipitate) to convert unreacted sodium into ethoxide, and the precipitate was filtered off and dried, then dissolved in toluene and reprecipitated dropwise into ethanol to form a white color. Phenylmethylbolysilane was obtained (yield: 22.0 g: yield: 34%).

[Preparation of electrophotographic photoreceptor] 100 parts by weight of a-type oxotitanyl phthalocyanine as a charge generating material, 4 parts by weight of detrahydrofuran as a solvent
000 = 1 was placed in a ball mill, and after stirring for 245 hours, polyvinyl butyral (
A coating solution for the charge generation layer was prepared by adding 100 parts by weight of Kosuretsuku BM-3 (trade name, manufactured by Tsukisui Kagaku Co., Ltd.) and stirring vigorously for 1 hour. ) and then dried and cured with hot air at 100° C. for 30 minutes to form a charge generation layer of 5 μm. , then 100 parts by weight of phenylmethylpolysilane as a charge transport material, and 2,6-dimethyl-2',6'-diter as a diphenoquinone derivative.
t.

A coating solution for a charge transport layer was prepared by stirring and mixing 10 parts by weight of dibdel diphenoquinone and 1000 parts by weight of tetrahydrofuran as a solvent using a homomixer. This coating solution was applied onto the charge generation layer using a wire bar (No. 60), and then dried with hot air at 00°C for 30 minutes to form a charge transport layer with a thickness of approximately 511 m. Created a body.

(Example 2) In the preparation of a coating solution for a charge transport layer, 2.2-diphenoquinone was used instead of 2.6-diphenoquinone as a diphenoquinone derivative. An electrophotographic photoreceptor was prepared in the same manner as in Example 1 except that dimedyl-6,6,'-di-terL-butyldiphenoquinone was used.

(Example 3) Phenylmethylpolysilane 100 as charge transport material
parts by weight, 4 parts by weight of α-type oxoditanyl phthalocyanine as a charge generating material, 2 parts by weight as a diphenoquinone derivative
．． 6-dimethyl-2°, 6 di-tert-butyldiphenoquinone, and tetrahydrofuran 1000 as solvent
Parts by weight were stirred and mixed in a ball mill for 244 hours to prepare a coating solution for a single-layer type photosensitive layer. Apply this coating liquid to aluminum foil.
After applying with a wire bar (No. 60), 10
Film thickness is approximately 10g by drying with hot air at 0℃ for 30 minutes.
A single-layer type photosensitive layer was formed to prepare an electrophotographic photoreceptor.

(Comparative Example 1) In preparing a coating solution for a charge transport layer, 2,6-dimethyl-2°,6dit,ert as a diphenoquinone derivative was used.
, - except that dibutyldiphenoquinone is not added,
An electrophotographic photoreceptor was produced in the same manner as in Example 1.

(Comparative Example 2) In preparing a coating solution for a charge transport layer, 2,6-dimethyl-2゛,6゜-dite as a diphenoquinone derivative was used.
An electrophotographic photoreceptor was prepared in the same manner as in Example 3 except that r t,-dibutyldiphenoquinone was not added.

[Evaluation of electrophotographic photoreceptor 1 Electrostatic copying test device (manufactured by Kawaguchi Electric Co., Ltd., Model, -81)
The photoreceptors obtained in each example were positively or negatively charged using 0[1] at an applied voltage of ±6.0 kV, and the electrophotographic characteristics were measured under the following conditions. The results are shown in Table 1. 2 and Table 3.

Exposure for 14 seconds, 10 seconds Irradiation light: Wavelength 780 nm Exposure intensity: 10 ILW/cm2 Dark decay after charging: 2 seconds Note that V in the table, (V) is the voltage applied under the above conditions to charge the photoreceptor. The initial surface potential of the photoreceptor at time viv
l and E + 1/2 (μJ/am21
indicates the half-reduced exposure amount calculated from the exposure time required for the surface potential to become 1/2 of the initial surface potential V, H. In addition, V and rp (V) in the table are the surface potential measured 5 seconds after the start of exposure as the residual potential, and the attenuation rate %
is calculated using the following formula.

Furthermore, under the above conditions, the exposure time was changed to 3 seconds and the dark decay after charging was changed to 1 second, and charging and exposure were repeated 100 times.
At that time, the surface potential V2 (V) of the photoreceptor, the half-decreased exposure amount E2
1/2 (μJ/cm2), residual potential Vzrpm, and attenuation rate % were measured.

On the other hand, ultraviolet rays (300 to 4
00 nm, 60 mW/am-2) for 10 minutes, the surface potential of the photoreceptor v + om, the half-reduced exposure amount E + o
l/2 (u, J/cm2), residual potential V,
, , m , and attenuation rate % were measured.

9 Table 1 Table 2 Table 3 According to the results shown in Table 2, the electrophotographic photoreceptors of Comparative Examples 1 and 2, to which no diphenoquinone derivative was added, had a surface potential that was lowered by repeated charging and exposure or by irradiation with ultraviolet rays. In contrast, the electrophotographic photoreceptors of Examples 1 to 3 to which diphenoquinone derivatives were added showed changes in surface potential and residual potential even with repeated charging and exposure and irradiation with ultraviolet rays. It was found that the amount was small and that it had excellent repeatability and light resistance.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a negatively charged laminated photoreceptor of the present invention. Figure 2 is a diagram. Figure 3 is a diagram. DESCRIPTION OF SYMBOLS 1...Substrate, 2...Charge generation layer, 4...Single layer type photosensitive layer. Cross section of the positively charged laminated photoreceptor of the present invention Cross section of the positively charged single layer photoreceptor of the present invention 3...charge transport layer,

Claims (3)

[Claims] (1) In an electrophotographic organic photoreceptor containing a charge-generating substance and a charge-transporting substance in a layered form or a monolayer dispersed form,
1. An organic photoreceptor for electrophotography, characterized in that the charge transport material is composed of a hole transport material composition containing a diphenoquinone derivative. (2) Claim 1, wherein the diphenoquinone derivative is contained in an amount of 0.1 to 30 parts by weight per 100 parts by weight of the hole transport substance.
Photoreceptor as described. (3) The photoreceptor according to claim 1, wherein the hole transport material is an organic polysilane.