JP2010271636A - Electrophotographic photoreceptor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly sensitive electrophotographic photoreceptor where charge generation and movement of a hole and an electron are performed efficiently, the charge polarity is used at both positive/negative polarities, and a stable sensitivity characteristic is acquired for environmental variation. <P>SOLUTION: This electrophotographic photoreceptor is provided with: a conductive support body; and a photosensitive layer disposed on the conductive support body. The photosensitive layer contains: a charge generator; diphenoquinone compound expressed by a general formula (1); and a hole transport agent of a specific distyryl structure. In general the formula (1), R<SB>1</SB>, R<SB>2</SB>and R<SB>3</SB>are saturated hydrocarbon, and may be the same mutually and different from each other. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic photoreceptor used for a copying machine, a laser printer, and the like, and more particularly to an electrophotographic photoreceptor using an organic thin film.

Conventionally, a thin film made of a material such as selenium, selenium-tellurium, selenium-arsenic, amorphous silicon or the like has been used as a photosensitive layer in an electrophotographic photosensitive member used in a copying machine, a laser printer, or the like.
However, in recent years, those using organic photoreceptors that are low in cost and have little environmental pollution are becoming mainstream. Such organic photoreceptors can be classified into a single-layer dispersion type photosensitive layer and a function-separated type photosensitive layer when classified by the structure of the photosensitive layer.

  Single layer dispersion type photoreceptors are those in which a charge generation agent is dispersed in a charge transfer agent medium and both functions are achieved by a single layer film. Function separation type photoreceptors generate charges that generate charges. A layer (CGL) and a charge transfer layer (CTL) for moving generated charges are separately formed. At present, both types of electrophotographic photoreceptors are in practical use. In particular, for a single-layer type photoreceptor, development of an electron transfer agent with high mobility is desired in order to improve sensitivity.

Organic photoconductors can be classified into two types: positively charged and negatively charged. Among the currently known charge transfer agents, most of those with high mobility are those with hole mobility. Since there is much room for selection of materials and the characteristics of the photoconductor can be easily controlled, a layered negative belt photoconductor is mainly used as a practical organic photoconductor.
On the other hand, the single-layer type photoreceptor not only has a small coating process but is advantageous in terms of cost, and has an advantage that interference fringes in monochromatic light such as laser light hardly occur. Furthermore, since incident light is almost absorbed near the surface of the photosensitive layer and charges are generated, there is almost no diffusion of irradiated light in the photosensitive layer, and the distance of charge movement until neutralization of the surface charge after charging is laminated. There are few points compared to the type of photoreceptor. For this reason, image blur due to diffusion of light and charge carriers hardly occurs, and high resolution can be expected.

  Single-layer electrophotographic photoreceptors containing an electron transfer agent and a hole transfer agent in the photosensitive layer can be used with both positive and negative polarities, expanding the application range of the photoreceptor and increasing sensitivity. This is also advantageous in reducing costs and speeding up by reducing the number of body types. In addition, the effect of ozone can be reduced when used with positive charging.

Although it is a single layer type photoconductor having such advantages, a photoconductor having both durability and electrostatic characteristics comparable to those of a negatively charged laminated photoconductor has not been obtained.
This is because the single-layer photoconductor needs to have the function of moving electrons and holes in the same film, and furthermore, since it has a charge generation function in the same film, it is difficult to develop and combine materials that fulfill each function. . Electron transfer is carried out by an electron transfer agent, but it has not yet been developed as a material that performs high carrier transfer like a hole transfer agent. Furthermore, the compatibility of the hole transfer agent used for the single layer photoreceptor with the electron transfer agent is important, and the guideline for selecting the electron transfer agent and the hole transfer agent was not clear.

  At present, the electron transfer agents that can be used for the single-layer photoconductor include trinitrofluorenone (TNF), tetracyanoethylene, tetracyanoquinodimethane (TCNQ), quinone, diphenoquinone, naphthoquinone, anthraquinone, and the like. Only a substance with insufficient properties, such as a derivative thereof, has been found. Specifically, these electron transfer agents have the following drawbacks (i) to (iv).

(I) Most of these electron transfer agents have poor compatibility with the binder resin and cannot be uniformly dispersed at a high concentration in the photosensitive layer, so that the electrical properties cannot be satisfied due to insufficient content. .
(Ii) TNF has a high electron-accepting property and therefore has a high mobility, but is not suitable for practical use because of its high toxicity.
(Iii) Although TCNQ exhibits a very high electron accepting property, it is strongly colored. Therefore, when a photosensitive layer is formed, light that should originally reach the charge generating agent is absorbed and sensitivity is lowered.
(Iv) In the diphenoquinone skeleton, an asymmetrically substituted compound has been proposed in order to improve the compatibility, but a compound having sufficient performance to produce a highly sensitive positively charged electrophotographic photoreceptor has not been obtained. Absent.

Development of an electron transfer agent has been advanced to remedy these drawbacks. In particular, a diphenoquinone compound as disclosed in Patent Document 1 is excellent in compatibility and electron mobility, and even in a single layer photoreceptor. Body characteristics can be improved.
However, until now, no satisfactory one has been obtained in terms of photoreceptor sensitivity and environmental stability.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a single-layer type electrophotographic photosensitive member having high sensitivity and high stability for the purpose of solving the above-mentioned drawbacks of the prior art.

In order to solve the above problems, the electrophotographic photosensitive member according to the present invention specifically has the technical features described in (1) to (11) below.
(1): a conductive support and a photosensitive layer provided on the conductive support, the photosensitive layer comprising a charge generator and a diphenoquinone compound represented by the following general formula (1): And a hole transfer agent represented by the following general formula (2).

(In the above formula (1), R ₁ , R ₂ and R ₃ are saturated hydrocarbons and may be the same or different from each other.)

(In said formula (2), R < ₄ > -R < ₁₁ > is hydrogen, a halogen atom, the C1-C6 alkyl group which may have a substituent, or a C1-C6 alkoxy group each independently. Represents.)

(2) The diphenoquinone compound represented by the general formula (1) is represented by the following chemical formula (1a), and is the electrophotographic photosensitive member according to the above (1).

(In the above formula (1a), t-Bu represents a tert-butyl group.)

(3): The electrophotographic photosensitive member according to (1) or (2), wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2a): is there.

(4): The hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2b), and is the electrophotographic photoreceptor according to the above (1) or (2), is there.

(5): The hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2c), and is the electrophotographic photoreceptor according to the above (1) or (2), is there.

(6): In the electrophotographic photosensitive member according to (1) or (2), the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2d): is there.

(7): In the electrophotographic photosensitive member according to (1) or (2), the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2e): is there.

(8): The electrophotographic photosensitive member according to (1) or (2), wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2f): is there.

(9): The charge generator is an oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-rays (wavelength 1.542 mm). The electrophotographic photosensitive member according to any one of (1) to (8) above, wherein

(10): The charge generator is an oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-rays (wavelength 1.542 mm). And oxytitanyl phthalocyanine having a maximum diffraction peak at 26.3 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-rays (wavelength 1.542Å), The electrophotographic photosensitive member according to any one of (1) to (8) above.

(11): The charge generator is an oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-rays (wavelength 1.542 mm). And the chloroindium phthalocyanine. The electrophotographic photosensitive member according to any one of (1) to (8) above, wherein

  According to the present invention, charge generation and movement of holes and electrons are efficiently performed, and the sensitivity characteristic that is highly sensitive and can be used with both positive and negative polarities is stable against environmental fluctuations.

1 is an X-ray diffraction pattern of oxytitanyl phthalocyanine used in Examples. 1 is an X-ray diffraction pattern of oxytitanyl phthalocyanine used in Examples. 1 is an X-ray diffraction pattern of oxytitanyl phthalocyanine used in Examples. Chloroindium phthalocyanine and oxytitanyl phthalose used in the examples It is sectional drawing which shows the example of the layer structure of the electrophotographic photoreceptor which concerns on this invention. It is an X-ray diffraction pattern of anine.

  The electrophotographic photosensitive member according to the present invention includes a conductive support 2 and a photosensitive layer 3 provided on the conductive support 2, and the photosensitive layer 3 includes a charge generating agent and the following general formula. It contains a diphenoquinone compound represented by (1) and a hole transfer agent represented by the following general formula (2).

(In the above formula (1), R ₁ , R ₂ and R ₃ are saturated hydrocarbons and may be the same or different from each other.)

(In the above formula _{(2), R} 4 ~R ₁₁ are each independently hydrogen, a halogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, Represents.)

Next, the electrophotographic photoreceptor according to the present invention (hereinafter sometimes simply referred to as a photoreceptor) will be described in more detail.
Although the embodiments described below are preferred embodiments of the present invention, various technically preferable limitations are attached thereto, but the scope of the present invention is intended to limit the present invention in the following description. Unless otherwise described, the present invention is not limited to these embodiments.

In a single-layer photoreceptor, it is necessary to transport both electrons and holes in the same layer. Therefore, both the electron transfer agent and the hole transfer agent to be used must have excellent characteristics.
Conventionally, the electron transfer function of the electron transfer agent was not sufficient, but the electron transfer agent represented by the general formula (1) used in the present invention has an excellent electron transfer function and is excellent in compatibility. It can be dispersed at a high concentration in the photosensitive layer, and a sufficient electron transport ability as the photosensitive layer can be obtained.

However, since electron transfer agents and hole transfer agents generally form charge transfer complexes, the performance of each of the electron transfer agent and hole transfer agent as a single layer photoreceptor is reflected as the function of the photoreceptor. Not necessarily. That is, even when an electron transfer agent represented by the general formula (1) having an excellent electron transport function and a hole transfer agent having a sufficient hole transport function are used, a sufficient charge transport function as a photoreceptor is provided. It is not exhibited, and the sensitivity is lowered or the stability is problematic.
Although the detailed mechanism about the effect by the combination of the electron transfer agent and the hole transfer agent has not been clarified, in order to make a photoreceptor with good characteristics, the characteristics of the electron transfer agent and the hole transfer agent alone are excellent. Of course, the combination of an electron transfer agent and a hole transfer agent is also very important.

  When the electron transfer agent (diphenoquinone compound) represented by the general formula (1) and the hole transfer agent represented by the general formula (2) are combined as in the electrophotographic photoreceptor of the present invention, The electron transport function and the hole transport function are sufficiently exhibited, the mobility of each of electrons and holes is excellent, and the photoconductor is highly sensitive in both positive and negative polarities. Further, even if it is repeatedly used, a stable photoconductor with little change in electrostatic characteristics such as sensitivity and chargeability is obtained.

  In addition, the characteristics of the charge generating agent are improved by using a specific material. An effective charge transfer agent (electron transfer agent, hole transfer agent) for a specific charge generation agent is not always effective for other charge generation agents. It is known that a charge generating agent effective against an agent is not necessarily effective against other charge transfer agents and has compatibility.

  When the diphenoquinone compound represented by the general formula (1) and the hole transfer agent represented by the general formula (2) are combined, the compatibility is particularly good when oxytitanyl phthalocyanine is used as a charge generator, In particular, it is best to use oxytitanium phthalocyanine having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) in Cukα characteristic X-ray diffraction of 27.2 ° (see FIG. 1). Further, oxytitanium phthalocyanine (see FIG. 2) having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 26.3 ° in Cukα characteristic X-ray diffraction has a maximum diffraction peak at 27.2 °. It can be used by mixing with oxytitanium phthalocyanine (see FIG. 3). Alternatively, chloroindium phthalocyanine and oxytitanium phthalocyanine having the maximum diffraction peak at 27.2 ° may be mixed (see FIG. 4). The peak may become a broad (wide), split (split), or shift (change in angle) depending on the crystal state and measurement conditions.

Hereinafter, the electrophotographic photosensitive member of the present invention will be described in detail with reference to the drawings.
FIG. 5 is a cross-sectional view schematically showing an example of the layer structure of the electrophotographic photosensitive member according to the present invention, in which the photosensitive layer 3 is provided on the conductive support 2.
[Conductive support 2]
The conductive support 2 that can be used in the present invention is made of a simple metal such as aluminum, brass, stainless steel, nickel, chromium, titanium, gold, silver, copper, tin, platinum, molybdenum, indium, or an alloy thereof. And conductive glass coated with tin oxide, indium oxide, and aluminum iodide, and a conductive plate such as metal or carbon treated with a method such as vapor deposition or plating to provide conductivity. Various materials having conductivity can be used without being limited by the type and shape of the conductive substrate. In general, a single cylindrical aluminum tube, a surface anodized on its surface, or a material coated with a conductive resin is often used.

[Photosensitive layer 3]
The photosensitive layer in the present invention contains at least a charge generator, a diphenoquinone compound represented by the general formula (1), and a hole transfer agent represented by the general formula (2).
(Charge generator)
First, the charge generating agent in the present invention will be described.
The charge generator that can be used in the electrophotographic photoreceptor of the present invention is preferably the oxytitanyl phthalocyanine described above, but is not limited thereto. For example, selenium, selenium-tellurium, selenium-arsenic, amorphous silicon, Other phthalocyanine pigments, monoazo pigments, disazo pigments, trisazo pigments, polyazo pigments, indigo pigments, selenium pigments, toluidine pigments, pyrazoline pigments, perylene pigments, quinacridone pigments, pyrylium salts, and the like can be used.
These charge generating agents may be used alone or in combination of two or more in order to obtain an appropriate photosensitivity wavelength and sensitizing action.

  The concentration of the charge generating agent in the photosensitive layer 3 is generally from 0.005% by weight to 10% by weight, and preferably from 0.5% by weight to 5% by weight. When the concentration of the charge generating agent is low, the photoreceptor sensitivity tends to decrease, and when the concentration is high, the chargeability and film strength tend to decrease.

(Charge transfer agent)
<Diphenoquinone compound>
Next, the charge transfer agent will be described.
The diphenoquinone compound represented by the general formula (1) used in the present invention has the structural skeleton shown below.

In said formula (1), R < ₁ >, R < ₂ >, R < ₃ > is saturated hydrocarbon, Comprising: You may mutually be same or different.

  In order to increase the electron acceptability and improve the electron mobility, it has been conventionally performed to use an electron withdrawing group as a substituent of the electron transfer agent. Since the force is increased, the compatibility of the known electron transfer agent with the binder resin is deteriorated, so that it cannot be dispersed at a high concentration in the photosensitive layer 3 and has not been put into practical use.

  In order to improve this compatibility, it is generally said that the electron transfer agent should have an asymmetric structure. In the prior art, for example, an electron transfer agent having an asymmetric structure such as the following chemical formula (3) has been proposed. Yes.

  In the chemical formula (3), Me represents a methyl group, and tBu represents a tert-butyl group.

  However, the electron transfer agent represented by the chemical formula (3) has two identical substituents, does not have a completely asymmetric structure, and has a low electron mobility.

  When an electron withdrawing group is introduced into such an incompletely asymmetric structure of the electron transfer agent to improve the electron mobility, the compatibility obtained by the asymmetric structure is canceled by the cohesive force of the introduced electron withdrawing group. End up. For example, a known electron transfer agent represented by the following chemical formula (4) is only practically soluble in a binder resin and is not practical.

  The diphenoquinone compound of the general formula (1) has a completely asymmetric structure that does not have any symmetry axis, and has good compatibility with the binder resin even when an electron withdrawing group is introduced.

Specifically, when R ₁ , R ₂ , and R ₃ are saturated hydrocarbons and are the same or different from each other, the diphenoquinone compound represented by the general formula (1) has an electron mobility. Since it is high and compatible with the binder resin, when used as an electron transfer agent, a highly sensitive electrophotographic photosensitive member can be obtained by uniformly dispersing it in the photosensitive layer 3 at a high concentration. is there.

Specific examples of the saturated hydrocarbon group represented by such substituents R ₁ , R ₂ , and R ₃ include linear saturated hydrocarbon groups such as a methyl group, an ethyl group, and a propyl group, an isopropyl group, Branched saturated hydrocarbon groups such as isobutyl group, sec-butyl group, tert-butyl group, tert-pentyl group, cyclic saturated hydrocarbon groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, etc. It can be used without being limited by the number of carbon atoms or its structure, such as a chain, a branched chain, or a composite substituent between cyclic saturated hydrocarbon groups. Among these substituents, a linear saturated hydrocarbon group and a branched saturated hydrocarbon group are preferable. In particular, any of R _{1 to} R ₃ is a tert-butyl group, an ethyl group, or a methyl group, and is preferably the same as each other.

  Further, if all the substituents are tert-butyl groups, the compound represented by the following chemical formula (1a) can be easily obtained by bringing HCl gas into contact with a liquid in which the compound represented by the following chemical formula (5) is uniformly dissolved. Synthesis of a fully asymmetric diphenoquinone compound.

Further, R ₁ to R ₃ in the general formula (1), tert- not limited to butyl, for example, if a methyl group, compound an electron transfer agent represented by the following formula (1b) As obtained.

  Moreover, the diphenoquinone compound shown by the said Chemical formula (1) may be used individually by 1 type, and may be used in mixture of 2 or more types. Furthermore, the diphenoquinone compound represented by the general formula (1) is preferably contained in the photosensitive layer 3 at a concentration of 0.1 wt% to 80 wt%.

《Hole transport material》
The hole transport material represented by the general formula (2) used in the present invention has a structural skeleton shown below.

In the above formula (2), R _{4 to} R ₁₁ each independently represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group having 1 to 6 carbon atoms, or an alkoxyl group having 1 to 6 carbon atoms. . ]

  Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxy group include a methoxy group, an ethoxy group, and a propoxy group. These include a halogen atom, a nitro group, a cyano group, Substituted by alkyl groups such as methyl group, ethyl group, alkoxy groups such as methoxy group and ethoxy group, aryloxy groups such as phenoxy group, aryl groups such as phenyl group and naphthyl group, aralkyl groups such as benzyl group and phenethyl group May have been. Of these substituents, a methyl group and a methoxy group are preferable.

  Specific examples of the compounds represented by the following chemical formulas (2a) to (2f) are shown below as hole transfer agents used in the photoreceptor of the present invention, but are not limited thereto.

One kind of the compounds represented by the above chemical formulas (2a) to (2f) may be contained in the photosensitive layer 3, or two or more kinds thereof may be used.
The concentration of the hole transfer agent in the photosensitive layer 3 is not particularly limited because it varies depending on the required photoreceptor performance and charging polarity, but is preferably 0.1 wt% or more and 70 wt% or less. If the concentration is low, hole transfer may be insufficient and affect the characteristics of the photoconductor. If the concentration is high, compatibility with the resin will deteriorate, resulting in a non-uniform film or low resin concentration. There is also a possibility that the film strength is lowered.

  Furthermore, other charge transfer agents can be added to the electron transfer agent (diphenoquinone compound) represented by the general formula (1) and the hole transfer agent represented by the general formula (2). Can increase the sensitivity and decrease the residual potential, and can improve the characteristics of the electrophotographic photosensitive member of the present invention.

  Electron transfer agents and hole transfer agents that can be added to improve properties include polymer compounds such as polyvinyl carbazole, halogenated polyvinyl carbazole, polyvinyl pyrene, polyvinyl indoloquinoxaline, polyvinyl benzothiophene, polyvinyl anthracene, polyvinyl acridine, polyvinyl. Pyrazoline, polyacetylene, polythiophene, polypyrrole, polyphenylene, polyphenylene vinylene, polyisothianaphthene, polyaniline, polydiacetylene, polyheptadiene, polypyridinediyl, polyquinoline, polyphenylene sulfide, polyferrocenylene, polyperinaphthylene, polyphthalocyanine, etc. The conductive polymer compound can be used.

  Low molecular weight compounds include polycyclic aromatic compounds such as anthracene, pyrene and phenanthrene, nitrogen-containing heterocyclic compounds such as indole, carbazole and imidazole, fluorenone, fluorene, oxadiazole, oxazole, pyrazoline, hydrazone and triphenyl. Methane, triphenylamine, enamine, stilbene compounds and the like can be used.

  Furthermore, a polymer solid electrolyte in which a polymer compound such as polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethacrylic acid or the like is doped with a metal ion such as Li ion can also be used.

  Furthermore, an organic charge transfer complex formed of an electron donating compound represented by tetrathiafulvalene-tetracyanoquinodimethane and an electron accepting compound can also be used. Even if the above compounds are mixed and added, desired photoreceptor characteristics can be obtained.

(Binder resin)
Binder resins that can be used to form the photosensitive layer 3 include polycarbonate resin, styrene resin, acrylic resin, styrene-acrylic resin, ethylene-vinyl acetate resin, polypropylene resin, vinyl chloride resin, chlorinated polyether, vinyl chloride. -Vinyl acetate resin, polyester resin, furan resin, nitrile resin, alkyd resin, polyacetal resin, polymethylpentene resin, polyamide resin, polyurethane resin, epoxy resin, polyarylate resin, diarylate resin, polysulfone resin, polyethersulfone resin, poly Photocurable resins such as allyl sulfone resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, EVA resin, ACS resin, ABS resin, and epoxy arylate That. These may be used alone or as a copolymer, or they may be used in combination of two or more. Further, it is preferable to use a mixture of resins having different molecular weights because the hardness and wear resistance can be improved.

(solvent)
Solvents used in the coating solution include alcohols such as methanol, ethanol, n-propanol, i-propanol, and butanol, saturated aliphatic hydrocarbons such as pentane, hexane, heptane, octane, cyclohexane, cycloheptane, toluene, Aromatic hydrocarbons such as xylene, chlorinated hydrocarbons such as dichloromethane, dichloroethane, chloroform and chlorobenzene, ethers such as dimethyl ether, diethyl ether, tetrahydrofuran and methoxyethanol, and ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone , Esters such as ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, methyl propionate, N, N-dimethylformamide, dimethyl sulfoxide, etc. That. These may be used alone or as a mixture of two or more solvents.

(Other additives)
Addition of antioxidants, ultraviolet absorbers, radical scavengers, softeners, curing agents, crosslinking agents, etc. to the coating solution for producing the photoreceptor of the present invention within the range not impairing the electrophotographic photoreceptor characteristics It is possible to improve the characteristics, durability, and mechanical characteristics of the photoreceptor.
Furthermore, the addition of dispersion stabilizers, anti-settling agents, anti-color separation agents, leveling agents, antifoaming agents, thickeners, matting agents, etc. can improve the finished appearance of the photoreceptor and the life of the coating solution. It is preferable.

(Underlayer)
In the electrophotographic photoreceptor of the present invention, an undercoat layer having an adhesion function, a barrier function, a defect covering function on the surface of the conductive support 2 and the like may be provided between the conductive support 2 and the photosensitive layer 3. . As the undercoat layer, aluminum oxide, polyethylene resin, acrylic resin, epoxy resin, polycarbonate resin, polyurethane resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, polyamide resin, nylon resin, or the like can be used. These undercoat layers may be composed of a single resin or a mixture of two or more resins. Further, an undercoat layer in which a metal oxide or carbon is dispersed in a resin can be used.

(Surface protective layer)
On the photosensitive layer 3, a thin film made of an organic thin film such as polyvinyl formal resin, polycarbonate resin, fluororesin, polyurethane resin, or silicone resin or a siloxane structure formed from a hydrolyzate of a silane coupling agent is formed. Then, a surface protective layer may be provided. In that case, the durability of the electrophotographic photoreceptor is improved, which is preferable. This surface protective layer may be provided in order to improve functions other than the durability improvement.

Hereinafter, the present invention will be described more specifically with reference to examples.
<Example of production of diphenoquinone>
An example of a method for producing the diphenoquinone compound represented by the general formula (1) used in the present invention will be described.
First, 91.8 g of potassium permanganate was added to a solution of 30.0 g of 2,6-di-tert-butylphenol in 300 ml of chloroform, and the mixture was stirred for 25 hours while maintaining the temperature at 55-60 ° C. Next, the inorganic substance was filtered off, concentrated and filtered. The obtained residue was dissolved in 100 ml of chloroform and recrystallized by adding a small amount of methanol to obtain diphenoquinone having a melting point of 242 to 243 ° C. as reddish brown crystals. . When the weight was measured, it was 21.5g, and it was 72% when converted into a yield.

Next, a mixed liquid of 300 ml of acetic acid and 120 ml of chloroform was prepared, and 3.0 g of the reddish brown crystals of diphenoquinone was dissolved as a reaction solvent, and kept at room temperature in a nitrogen atmosphere, and HCl gas was blown and reacted while stirring. .
After blowing the HCl gas for 7 hours, the mixture was stirred overnight at room temperature, and the precipitate was filtered off. After the filtrate was concentrated under reduced pressure, 300 ml of water was added and filtered to obtain 3.8 g of a yellow solid precipitate. When 3.8 g of the yellow solid precipitate was dissolved in 25 ml of methanol and recrystallized by adding a small amount of water, 2.4 g of diphenol having a melting point of 150 to 151 ° C. was obtained as pale yellow crystals. In terms of yield, it was 84%.

The 2.4 g of diphenol was dissolved in 180 ml of chloroform, 28.0 g of lead dioxide was added, and the mixture was stirred at room temperature for 3 hours, and then the residue was filtered off. The filtrate was concentrated and 20 ml of methanol was added. The precipitated crystals were filtered and washed with methanol to obtain 1.9 g of diphenoquinone represented by the above formula (1a) having a melting point of 155 to 156 ° C. as reddish purple crystals. In terms of yield, it was 81%.
The above reaction process is shown below.

  The diphenoquinone compound represented by the formula (1a) used in the following examples is synthesized by the production method of the production example.

<Production example of oxytitanyl phthalocyanine>
6.5 ml of titanium tetrachloride was dropped into a mixture of 64.4 g of phthalodinitrile and 150 ml of α-chloronaphthalene under a nitrogen stream for 5 minutes. After dropping, the reaction was completed by heating at 200 ° C. for 2 hours with a mantle heater. Thereafter, the precipitate was filtered, and the filtration residue was washed with α-chloronaphthalene, then washed with chloroform, and further washed with methanol. Thereafter, a hydrolysis reaction was performed at a boiling point for 10 hours with a mixed solution of 60 ml of concentrated ammonia water and 60 ml of ion-exchanged water, followed by suction filtration at room temperature and washing with ion-exchanged water until the washing became neutral. Then, after washing with methanol and drying with hot air at 90 ° C. for 10 hours, 64.6 g of blue-violet crystalline titanyl phthalocyanine powder was obtained. The titanyl phthalocyanine thus obtained has a maximum peak at 26.3 ° (maximum diffraction peak) as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα as shown in FIG. It was a thing having.

Next, it was dissolved in about 10 times the amount of concentrated sulfuric acid, poured into water and precipitated, and 30 g of the filtered crude wet cake was washed with pure water until neutral, and filtered to obtain 29 g of titanyl phthalocyanine wet cake. .
10 g of the wet cake was put into 500 ml of tetrahydrofuran cooled to −5 ° C., stirred for 30 minutes, filtered and dried to obtain 9.5 g of titanyl phthalocyanine. The resulting titanyl phthalocyanine has a maximum peak at 27.2 ° (maximum diffraction peak) as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα as shown in FIG. It was a thing having.

  Also, 1 g of titanyl phthalocyanine powder having the X-ray diffraction spectrum of FIG. 1 and 20 g of titanyl phthalocyanine having the X-ray diffraction spectrum of FIG. 2 were mixed. The obtained phthalocyanine has peaks at 26.3 ° and 27.3 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα as shown in FIG. It was a thing.

  Also, 9.5 g of titanyl phthalocyanine having the X-ray diffraction spectrum of FIG. 1 and 0.5 g of chloroindium phthalocyanine are dissolved in 100 ml of concentrated sulfuric acid and stirred at room temperature for 30 minutes, and then this is added to ion-exchanged water cooled with ice water. The crude wet cake was separated by filtration. Subsequently, the precipitate was washed with 1000 ml of ion exchange water to obtain a wet cake. To the wet cake, 400 ml of 0.2 mol / l hydrochloric acid was added and stirred at room temperature for 3 hours. The precipitate was again separated by filtration, washed with 4000 ml of ion-exchanged water and filtered to obtain a wet cake. Next, 500 ml of wet cake was added to tetrahydrofuran cooled to −5 ° C. for crystal conversion. Thereafter, the phthalocyanine was stirred under cooling, returned to room temperature, filtered and dried to obtain a phthalocyanine mixture. The results of measuring the X-ray diffraction spectrum of the crystals of the obtained phthalocyanine composition are shown in FIG.

<Example 1>
First, 0.5 g of oxytitanyl phthalocyanine having the X-ray diffraction spectrum shown in FIG. 1 obtained by the above-mentioned production example of oxytitanyl phthalocyanine, 30 ml of glass beads and 320 ml of tetrahydrofuran are dispersed for 5 hours with a paint shaker, and the glass beads are filtered off. 308 ml of liquid is obtained. To the obtained CGL solution, 25 g of the hole transfer agent represented by the chemical formula (2a), 25 g of diphenoquinone of the chemical formula (1a) obtained in the production example of diphenoquinone, and 42 g of Z-type polycarbonate as a binder resin are dissolved. Then, a coating solution for a single layer photoreceptor was prepared.
The obtained coating solution was applied to an aluminum drum, dried at 100 ° C. for 1 hour to form a photosensitive layer having a thickness of 20 μm, and an electrophotographic photosensitive member was produced.

<Example 2>
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the chemical formula (2b). did.

<Example 3>
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the chemical formula (2c). did.

<Example 4>
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the chemical formula (2d). did.

<Example 5>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) in Example 1 was replaced with the hole transfer agent represented by the chemical formula (2e). did.

<Example 6>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) in Example 1 was replaced with the hole transfer agent represented by the chemical formula (2f). did.

<Example 7>
In Example 1, the same procedure as in Example 1 was followed except that the electron transfer agent (diphenoquinone compound) represented by the chemical formula (1a) was replaced with the electron transfer agent (diphenoquinone compound) represented by the chemical formula (1b). An electrophotographic photosensitive member was produced.

<Example 8>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generating agent having the X-ray diffraction spectrum of FIG. 1 was replaced with the charge generating agent having the X-ray diffraction spectrum of FIG.

<Example 9>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generator having the X-ray diffraction spectrum of FIG. 1 was replaced with the charge generator having the X-ray diffraction spectrum of FIG.

<Example 10>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generator having the X-ray diffraction spectrum shown in FIG. 1 was replaced with the charge generator having the X-ray diffraction spectrum shown in FIG.

<Reference Example 1>
An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generator having the X-ray diffraction spectrum shown in FIG. 1 was replaced with a disazo pigment of the following chemical formula (10).

<Comparative Example 1>
In Example 1, an electrophotographic photoreceptor was produced using diphenoquinone represented by the following chemical formula (6) instead of diphenoquinone represented by the chemical formula (1a).

<Comparative example 2>
In Example 1, instead of the diphenoquinone represented by the chemical formula (1a), the diphenoquinone represented by the chemical formula (6) was used, and the charge generating agent having the X-ray diffraction spectrum of FIG. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generating agent having a spectrum was used.

<Comparative Example 3>
In Example 1, instead of the diphenoquinone represented by the chemical formula (1a), the diphenoquinone represented by the chemical formula (6) was used, and the charge generating agent having the X-ray diffraction spectrum of FIG. An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the charge generating agent having a spectrum was used.

<Comparative example 4>
In Example 1, instead of diphenoquinone represented by the chemical formula (1a), diphenoquinone represented by the chemical formula (6) was used, and the hole transfer agent represented by the chemical formula (2a) was represented by the following chemical formula (7). An electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent was changed.

<Comparative Example 5>
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the following chemical formula (8). did.

<Comparative Example 6>
In Example 1, an electrophotographic photosensitive member was produced in the same manner as in Example 1 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the following chemical formula (9). did.

<Comparative Example 7>
In Example 11, an electrophotographic photosensitive member was produced in the same manner as in Example 11 except that the hole transfer agent represented by the chemical formula (2a) was replaced with the hole transfer agent represented by the chemical formula (9). did.

<Electrical characteristics measurement conditions>
Positive Charging Characteristic Evaluation Method The corona discharger was set so that the corona discharge current was 20 μA, and the single-layer dispersion type photoconductor produced in Examples 1 to 10, Comparative Examples 1 to 7, and Reference Example 1 was used in a dark place. Measure the charge potential by positively charging with corona discharge. The discharge current was adjusted so that the surface potential at this time was 700 V, and exposure was performed with light of 780 nm, and the exposure amount that reduced the surface potential of each photoconductor from 700 V to 350 was measured. Let the exposure amount at this time be a half exposure amount (μJ / cm ² ). This half-exposure amount is a value indicating the sensitivity of the photoconductor. The smaller the value of the half-exposure amount, the higher the sensitivity of the photoconductor. The high-sensitivity photoconductor is 0.25 μJ / cm2, and the practical range is 0. 45 μJ / cm ² or less. The temperature and humidity at which the photoreceptor is evaluated are reduced to half the photoreceptor in three environments: a normal temperature environment (25 ° C.—humidity 50%), a low temperature environment (10 ° C.—humidity 10%), and a high temperature environment (35 ° C.—humidity 80%). The exposure amount (μJ / cm ² ) is measured, and the deviation of the half-exposure amount under three environments is calculated by the following formula.

Deviation = ((Σ (Half exposure amount) ² − (Average of half exposure amount in each environment) ² × 3) / 2) ^0.5

The smaller the half-exposure deviation, the smaller the photoreceptor sensitivity fluctuation with respect to temperature and humidity changes, and the range of a general photoreceptor is preferably 0.03 or less.
Further, the surface potential of each photoconductor when irradiated with 780 nm light (exposure amount 2 μJ / cm ² ) at 700 V was measured. The surface potential at this time is defined as a residual potential (VL). This residual potential is a charge that does not decay after charging and remains on the surface of the photoreceptor without being completely discharged. Practically, the smaller the potential is, the more preferable it is 100 V or less.

-Negative charge characteristic evaluation method The charge polarity was switched to negative charge, and evaluation was performed in the same manner as the above method.

<Measurement results>
Table 1 shows the measurement results of Examples 1 to 10, Comparative Examples 1 to 7, and Reference Example 1.

According to Table 1 above, the electrophotographic photoreceptors of Examples 1 to 10 are highly sensitive in evaluation of the bipolar photoreceptor, and the deviation in half-exposure energy under each environment is small, and the variation with respect to the environmental change is small. I understand.
In particular, oxytitanium phthalocyanine having a maximum peak (maximum diffraction peak) at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα is used as a charge generator. When used, it is very sensitive. As a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray of CuKα as a charge generator (± 0.2 °), oxytitanium phthalocyanine having peaks at 26.3 °, 27.2 °, or Mixture of oxytitanium phthalocyanine and chloroindium phthalocyanine having a maximum peak (maximum diffraction peak) at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα When is used, the sensitivity is high and the variation due to the environment is further reduced.

  On the other hand, since the photoconductors of Comparative Examples 1 to 3 have insufficient symmetry of the electron transfer agent, the charge transferability is poor, and the positive charge characteristics practically enter a half-exposure amount in the low sensitivity region. Sufficient sensitivity cannot be obtained with the negative charging characteristics in which electron transfer is important. Further, Comparative Examples 4 to 7 are combined with other hole transfer agents, but the sensitivity is not sufficient and the fluctuation due to the environment is also large. Although the sensitivity of the reference example is not sufficient, it can be seen that both the positive and negative polarities are more sensitive than the comparative example 7, and the fluctuation due to the environment is small.

As described above, the combination of the electron transfer agent (diphenoquinone compound), the hole transport agent and the charge generator used in the present invention has the following characteristics.
(A) The movement of electrons and holes is smooth, the positive and negative charges are excellent in photoreceptor sensitivity, and there are few fluctuations with respect to the environment.
(B) Further, the charge generator has a maximum peak (maximum diffraction peak) at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα. By combining titanium phthalocyanine, an unprecedented high-sensitivity bipolar single-layer photoconductor can be realized by high charge generation, high electron and hole transfer efficiency.
(C) Oxytitanium phthalocyanine having peaks at 26.3 ° and 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542Å) of CuKα as a charge generating agent Or oxytitanium phthalocyanine and chloroindium phthalocyanine having a maximum peak (maximum diffraction peak) at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα When these mixtures are combined, the sensitivity is high, and fluctuation due to the environment can be further suppressed.

  According to the electrophotographic photoreceptor of the present invention, the combination of an electron transfer agent, a hole transport agent, and a charge generation agent efficiently generates charges and transfers holes and electrons, and has high sensitivity and positive and negative charge polarity. It can be used in both polarities, and stable sensitivity characteristics can be obtained against environmental fluctuations. Further, the use of the electrophotographic photosensitive member can be applied to a stable image quality and a high-speed image forming apparatus.

1 electrophotographic photoreceptor 2 conductive support 3 photosensitive layer

Japanese Patent No. 3778595

Claims (11)

A conductive support;
A photosensitive layer provided on the conductive support,
The photosensitive layer contains a charge generating agent, a diphenoquinone compound represented by the following general formula (1), and a hole transfer agent represented by the following general formula (2). Photoconductor.

(In the above formula (1), R ₁ , R ₂ and R ₃ are saturated hydrocarbons and may be the same or different from each other.)

(In said formula (2), R < ₄ > -R < ₁₁ > is hydrogen, a halogen atom, the C1-C6 alkyl group which may have a substituent, or a C1-C6 alkoxy group each independently. Represents.) The electrophotographic photoreceptor according to claim 1, wherein the diphenoquinone compound represented by the general formula (1) is represented by the following chemical formula (1a).

(In the above formula (1a), t-Bu represents a tert-butyl group.) The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2a).

The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2b).

The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2c).

The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2d).

The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2e).

The electrophotographic photosensitive member according to claim 1, wherein the hole transfer agent represented by the general formula (2) is represented by the following chemical formula (2f).

  The charge generating agent is oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542１．５) of CuKα. The electrophotographic photosensitive member according to any one of claims 1 to 8, wherein   The charge generating agent includes oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542Å) of CuKα, and CuKα. 2. An oxytitanyl phthalocyanine having a maximum diffraction peak at 26.3 ° as a diffraction peak (± 0.2 °) at a Bragg angle 2θ with respect to characteristic X-rays (wavelength 1.542Å). The electrophotographic photosensitive member according to any one of items 1 to 8.   The charge generating agent includes oxytitanyl phthalocyanine having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to a characteristic X-ray (wavelength 1.542１．５) of CuKα, and chloroindium. The electrophotographic photosensitive member according to claim 1, comprising phthalocyanine.

Images