JPH06342215A - Organic electrophotoreceptor - Google Patents

Abstract

PURPOSE:To provide an org. electrophotoreceptor usable at both positive and negative electrification polarities. CONSTITUTION:This org. electrophotoreceptor contains a compd. represented by the general formula (where each of R<1>-R<8> is H, cyano, halogen, amino or alkyl, cycloalkyl, aryl or alkoxy which may have a substituent).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic photoconductor for electrophotography used in PPCs, laser printers, PPFs and the like. More specifically, the present invention relates to an organic photoconductor for electrophotography, which can be positively charged or both charged, and in which the sensitivity and the residual potential are remarkably improved when a single layer is formed.

[0002]

2. Description of the Related Art An electrophotographic copying machine using a digital optical system usually uses a light source having a wavelength of 700 nm or more. As a photoreceptor having sensitivity in this wavelength range,
Conventionally, amorphous chalcogenite materials containing amorphous selenium (a-Se) and its alloys, amorphous silicon (α-Si) -based materials, and II-VI group inorganic compound-based materials such as zinc oxide or cadmium sulfide (CdS) have been used. An inorganic photoconductor to be used, or an organic photoconductor (OPC) using a high-molecular or low-molecular organic compound is known. Of these, organic photoreceptors are often used from the viewpoints of sensitivity, cost, and the like.

At present, the organic photoconductors mainly used for practical use are of the function-separated type. This type of photoconductor
By separating the functions of charge generation and transfer into separate substances, it is possible to appropriately combine substances having high charge generation efficiency and transfer efficiency, which has the advantage of broadening the range of material selection. Most of the above function-separated type organic photoreceptors have a laminated structure composed of a charge generation layer (CGL) and a charge transport layer (CTL), but a single layer in which all materials are dispersed in a binder resin in the same layer. Those having a structure are also known. Most of the laminated organic photoconductors were negatively charged organic photoconductors. This is because a substance having a high charge mobility is required as the charge transporting agent, but most of the charge transporting agents having a high charge mobility exhibit a hole transporting property.

However, the negatively charged organic photoconductor uses a negative corona discharge to generate a large amount of ozone, which not only pollutes the environment but also deteriorates the photoconductor. there were. Therefore, in order to prevent this, a special charging system that does not generate ozone, a system that decomposes generated ozone, a system that exhausts ozone in the apparatus, and the like are required, and there is a drawback that the entire process and system become complicated. .

Further, in the case of a laminated type photoreceptor, it is generally necessary to coat the photosensitive layer twice, so that a film defect is likely to occur, and the interface between the charge generation layer and the charge transport layer is formed in the photoreceptor layer. Since it exists, there is a problem that interference fringes are likely to occur.

In order to solve these drawbacks, it has been studied to obtain a positively charged photoreceptor by using an electron transfer material as a charge transfer material. Japanese Patent Laid-Open No. 1-206349
In the publication, a compound having a diphenoquinone structure is proposed as an electron transfer agent for an organic photoconductor for electrophotography.

Further, in Japanese Patent Application Laid-Open No. 4-295853, the sensitivity of an organic photoconductor can be improved by using diphenoquinones as an electron transfer agent in combination with a hole transfer agent having a specific ionization potential. Is described.

[0008]

The charge transfer in the photoconductor by the electron transfer agent such as the above diphenoquinones is carried out by repeating the intramolecular charge transfer and the intermolecular charge transfer, that is, hopping. Be seen. In general, hopping transfer has poor transportability as compared with intramolecular transfer. This is because, during the hopping process, a phenomenon occurs in which charges are trapped by impurities in the photoconductor and remain as space charges. The low charge transport efficiency results in the drawback that electron transfer is unlikely to occur in a low electric field condition and the residual potential is high. Therefore,
From such a point of view, there has been a demand for the development of an electron transfer material having further improved electron transfer characteristics.

Further, by using an electron transfer material having an excellent electron transfer property in combination with a hole transfer material, the organic photoreceptor can be used for both positive charging and negative charging, and particularly as a single layer dispersion type. Needless to say, the application range of the photoconductor can be further expanded and the above-mentioned various problems can be solved.

The present invention has been achieved on the basis of the above points, and the object thereof is to use both positive and negative charging polarities.
An object is to provide a highly sensitive organic photoreceptor for electrophotography.

Another object of the present invention is to provide a monolayer-dispersed electrophotographic organic photoconductor capable of charging both sides.

Still another object of the present invention is to provide an organic photoconductor for electrophotography, which has stable characteristics upon repeated use.

[0013]

Means for Solving the Problems The present inventors can use both a positive electron transfer agent and a positive hole transfer agent in combination with a positive and negative charge, and can be used as a monolayer dispersion type. The present invention has been completed by finding that an organic photoconductor for electrophotography having high sensitivity and excellent stability in repeated use can be prepared.

In the organic photoreceptor for electrophotography of the present invention, a compound represented by the following general formula (1),

[0015]

[Chemical 3]

(In the formula, R ^{1 to} R ⁸ are each independently
It represents a hydrogen atom, a cyano group, a halogen atom, an amino group, or an optionally substituted alkyl group, cycloalkyl group, aryl group, or alkoxy group. )
An organic photosensitive layer containing is provided on a conductive substrate, whereby the above object is achieved.

In the organic photoconductor for electrophotography according to the present invention, the organic photosensitive layer comprises the above-mentioned general formula (1) in a binder resin.
It may be a single layer type in which a compound represented by, a hole transporting agent and a charge generating agent are dispersed.

Preferred examples of the hole transfer material include at least one compound represented by the following general formulas (2) to (4):

[0019]

[Chemical 4]

(Here, R ^{21 to} R ²⁵ , R ^{31 to} R ³⁷ , and R ^{41 to} R ⁴⁶ each independently represents a hydrogen atom, or an alkyl group or an alkoxy group, and a plurality of R ^{21 to} R ²⁵ are present on each benzene ring. It may be).

[0021]

In the compound (1) of the present invention which can be used as an electron transfer agent for an organic photoreceptor, a quinone-based oxygen atom having an excellent electron accepting property is bonded to the terminal portion of the anthracene-type condensed aromatic ring, Further, since the conjugated system of π electrons spreads throughout the molecule, the intramolecular migration distance becomes long. As a result, it is considered that the number of times of transfer of electrons by hopping is relatively reduced during electron transport in the photoconductor, so that the efficiency of electron transport is improved. This electron-transporting material and a suitable hole-transporting material, for example, the general formulas (2) to (4)
A single-layer organic photoreceptor is obtained by mixing and dispersing at least one of the above compounds and a charge generating agent in a binder resin. This single-layer type photoconductor, when charged positively or negatively, results in that electrons and holes generated in the photosensitive layer by light irradiation are efficiently transported by the electron transfer agent and the hole transfer agent, respectively. High sensitivity can be obtained, and a clear charge image can be formed.

[0022]

Preferred Embodiment The quinone derivative used as the electron transfer agent in the organic photoreceptor of the present invention is represented by the following general formula (1).

[0023]

[Chemical 5]

R ^{1 to} R ⁸ in the formula (1) each independently represent a hydrogen atom, a cyano group, a halogen atom, an amino group, an alkyl group, a cycloalkyl group, an aryl group or an alkoxy group. Here, the alkyl group, cycloalkyl group, aryl group and alkoxy group may have a substituent, and each may have an appropriate substituent, for example, a chlorine atom, a fluorine atom, a nitro group or a cyano group.

Suitable examples of the above quinone derivative include, but are not limited to, the compounds represented by the following formulas (11) and (12). The above quinone derivatives may be used alone or in combination of two or more.

[0026]

[Chemical 6]

In the organic photoreceptor of the present invention, a conventionally known compound is used as the hole transfer agent. Examples thereof include amine derivatives such as oxadiazole compounds, styryl compounds, carbazole compounds, pyrazoline compounds, hydrazone compounds, triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds. , Thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, triazole-based compounds and the like. Particularly, amine derivatives, for example, compounds represented by the following general formulas (2) to (4) are preferable.

[0028]

[Chemical 7]

R ^{21 to} R ²⁵ in the formula (2) and R in the formula (3)
Each of ^{31 to} R ³⁷ and R ^{41 to} R ⁴⁶ in the formula (4) independently represents a hydrogen atom, an alkyl group or an alkoxy group, and there may be a plurality on each benzene ring.

Preferable examples of the above amine derivative include the following formulas (21), (22), (31), (32) and (4).
1), (42) and (43) may be mentioned, but the present invention is not limited thereto. The amine derivative may be used alone or in combination of two or more.

[0031]

[Chemical 8]

[0032]

[Chemical 9]

[0033]

[Chemical 10]

In the organophotoreceptor of the present invention, the quinone derivative and the hole transfer agent are in a weight ratio of 1: 9 to 9 :.
1, preferably 1: 2 to 2: 1, more preferably 1: 1
To be mixed. The total weight of the quinone derivative and the hole transfer agent is 150 parts by weight or less, preferably 100 to 60 parts by weight, based on 100 parts by weight of the binder resin.
It is mixed with the binder resin in an amount of, preferably 80 parts by weight.

Generally, when an organic photoconductor containing an electron transfer material and a hole transfer material is used as a single-layer organic photoconductor, the interaction between the two does not adversely affect the resulting organic photoconductor layer. As such, it is necessary to select a combination of electron and hole transport materials. For example, it is known that, depending on the combination of the electron transfer agent and the hole transfer agent, they both associate with each other to form a kind of charge transfer complex. Such a charge transfer complex recombines electrons and holes, resulting in a decrease in apparent quantum yield and a decrease in sensitivity of the organophotoreceptor layer.

In the combination of the electron transfer agent and the hole transfer agent in the organic photoreceptor of the present invention, the above charge transfer complex is not substantially formed.

As the charge generating agent that can be used in the organic photoreceptor of the present invention, a compound having an absorption wavelength range within the wavelength range of the light source used when exposing the organic photoreceptor is selected. Examples thereof include selenium, selenium-tellurium, amorphous silicon, pyrylium salts, azo pigments, disazo pigments, anthanthrone pigments, phthalocyanine pigments, indico pigments, slene pigments, toluidine pigments, pyrazoline pigments, Perylene pigments, quinacridone pigments and the like can be mentioned. In particular, phthalocyanine pigments,
For example, X-type metal-free phthalocyanine is preferable.

The above charge generating agents may be used alone or in combination of two or more. The charge generating agent is 0.1 to 1 with respect to 100 parts by weight of the binder resin.
0 parts by weight, preferably 0.5 to 5 parts by weight,
It is added to the binder resin.

In the organophotoreceptor of the present invention, as the binder resin which can be used to disperse the above-mentioned electron transporting agent, hole transporting agent and charge generating agent, various binder resins used in conventional organophotoreceptors can be used. A resin is selected. For example,
Styrene polymer, acrylic polymer, styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, polypropylene, olefin polymers such as ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, Photocurable resins such as polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, and epoxy acrylate. , And various polymers. In particular, styrene polymers, acrylic polymers, styrene-acrylic copolymers, polyesters, alkyd resins, polycarbonates, and polyarylates are preferable.
Only one kind of these binder resins may be used, or two or more kinds thereof may be mixed and used.

The organic photoconductor of the present invention may further contain various known compounding agents within a range that does not adversely affect the electrophotographic characteristics. Examples of compounding agents are antioxidants, radical scavengers, singlet quenchers, UV absorbers, softeners, surface modifiers, defoamers, extenders, thickeners, dispersion stabilizers, waxes, acceptors. , Donors, etc.

In the organophotoreceptor of the present invention, typically, the above electron transporting agent, hole transporting agent and charge generating agent are uniformly dispersed in the above binder resin on a conductive substrate. It is used in a structure in which a single-layer organic photosensitive layer is formed. Such a single-layer type organic photoreceptor layer usually has a thickness of about 5 to about 100 μm.
m, preferably about 10 to about 40 μm. The organophotoreceptor of the present invention can also be used in a structure in which a charge generating layer and a charge transporting layer are laminated on a conductive substrate to form a laminated organic photoreceptor. In this case, the above-mentioned charge generating agent is dispersed in the binder resin in the charge generating layer, while the above-mentioned electron transporting agent and hole transporting agent are used alone or in the charge transporting layer. Dispersed in the resin. Such a laminated type organic photoreceptor layer is usually formed such that the charge generation layer and the electron transport layer have a layer thickness of 0.1 to 2 μm and 10 to 50 μm, respectively. In addition, as another example of the laminated organic photoreceptor, a charge generation layer containing a charge generation agent, a first charge transport layer containing an electron transport material and a second charge transport layer containing a hole transport material are used. It is also conceivable to form an organic photosensitive layer having a three-layer structure sandwiched between them on a conductive substrate.

A barrier layer may be formed between the single-layer type or multi-layer type photoreceptor and the conductive substrate as long as the characteristics of the photoreceptor are not impaired. In the laminated-type photoreceptor, a similar barrier layer may be formed between the charge generation layer and the charge transport layer. Further, a protective layer may be formed on the surface of the single-layer type or laminated type photoreceptor.

Examples of conductive substrates used in the organophotoreceptors of the present invention are: aluminum, copper, tin, platinum, gold,
A simple substance of metal such as silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel, brass; a plastic material in which the above metal is vapor-deposited or laminated; and aluminum iodide, tin oxide,
Various conductive materials such as glass coated with indium oxide or the like can be given. Furthermore, in the case of a single-layer type photoreceptor,
Since there is no occurrence of interference patterns, etc., which can be seen in a laminated type photoreceptor, a normal aluminum tube, particularly a film thickness of 1 to 50 is used.
It is also possible to use, as a conductive substrate, a blank tube that has been subjected to an alumite treatment so as to have a thickness of μm.

In the case of a single layer type photoreceptor, for example, the organic photoreceptor of the present invention is applied by dissolving or dispersing an electron transfer agent, a hole transfer agent and a charge generating agent in a solvent together with a binder resin. It can be manufactured by preparing a liquid, applying the coating liquid on a conductive substrate, and then drying.

In order to prepare the above coating solution, a conventionally known mixing device such as a roll mill, a ball mill, an attritor, a paint shaker or an ultrasonic disperser can be used. In addition, in order to apply the coating liquid onto the conductive substrate,
Conventionally known coating means can be adopted.

Examples of solvents that can be used to prepare the above coating solution are: alcohols such as methanol, ethanol, isopropanol, butanol; n-hexane,
Aliphatic hydrocarbons such as 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, ketones such as acetone, methyl ethyl ketone, and cyclohexanone; esters such as ethyl acetate and methyl acetate; dimethylformamide; and various organic solvents such as dimethyl sulfoxide. These solvents are
You may use it in mixture of 2 or more types.

[0047]

EXAMPLES The present invention will be described in more detail based on the following examples.

(Preparation of Quinone Derivative) The quinone derivative used in the organic photoreceptor of the present invention can be obtained, for example, by utilizing the following known synthesis method.

Anthracene (9) was dissolved in dimethylsulfoxide, an excess amount of methyl chloride and a catalytic amount of aluminum chloride were added, and the mixture was reacted at 60 ° C. for 4 hours to obtain a dimethyl compound (10). This dimethyl compound (10) was dissolved in chloroform, and potassium permanganate and oxygen were used as oxidants and reacted at 70 ° C. for 2 hours. The reaction mixture was filtered and recrystallized from ethanol to prepare the desired quinone derivative (11).

[0050]

[Chemical 11]

(Production of Photoreceptor) Examples (1) to (1) of the present invention
The organic photoreceptor of (14) was manufactured as follows. X-type metal-free phthalocyanine as a charge generating agent
Parts by weight, the following amine derivatives (21), (22), (31), (32), (41) as hole transport agents,
40 parts by weight of (42) or (43),

[0052]

[Chemical 12]

[0053]

[Chemical 13]

[0054]

[Chemical 14]

The following quinone derivatives (1
40 parts by weight of 1) or (12),

[0056]

[Chemical 15]

Polycarbonate as a binder resin
A coating liquid was prepared by mixing and dispersing 0 part by weight and 800 parts by weight of dichloromethane as a solvent for 50 hours using a ball mill. This coating solution is applied on an aluminum foil as a conductive substrate, and then at 60 ° C. for 12 hours.
By drying with hot air for 0 minutes, a single-layer type organic photoreceptor having a layer thickness of 15 to 20 μm was obtained.

Next, instead of the above quinone derivative (11) or (12) as an electron transfer agent, the following quinone derivative (51) or (52) is used.

[0059]

[Chemical 16]

Organic photoconductors of Comparative Examples (1) to (6) were prepared in the same manner as above except that the above-mentioned procedure was used.

(Evaluation of Photoreceptor) The above Examples (1) to
The photosensitivity and repeatability of the organic photoreceptors of (14) and Comparative Examples (1) to (6) were evaluated as follows. The results are shown in Table 1.

[0062]

[Table 1]

1. Photosensitivity electrostatic copying tester (Kawaguchi Electric Co., EPA-8100)
Using, a voltage was applied to the photoconductor to charge it positively or negatively, and the photosensitivity of the photoconductor was measured by exposing it to white halogen light. In Table 1, V1 is an initial surface potential (unit: volt (V)), which is a potential when a voltage is applied to charge the photoconductor. V2 is the residual potential (unit: Volt (V)), which was measured as the surface potential after 5 seconds from the start of exposure. E1 / 2 is the half exposure amount (unit: μJ / c
m ² ), and was calculated from the following formula: E1 / 2 = I x
t1 / 2 Here, I is the illuminance of the drum surface, and t1 / 2 is the time required for the surface potential to reach 1/2 of the initial value (that is, V1 / 2).

Therefore, the higher the photosensitivity of the photoconductor, the smaller the ratio of the residual potential to the initial surface potential (V2 / V1) and the half-exposure amount (E1 / 2). As can be seen from Table 1, the photoreceptor of the present invention (Examples (1) to (1
4)) is a photoreceptor of Comparative Example (Comparative Example (1) to
The photosensitivity is remarkably improved as compared with (6).

2. Repetitive characteristics After the photoconductor is attached on an aluminum cylinder in a copying machine (DC-1656, manufactured by Mita Kogyo Co., Ltd.) using an adhesive tape, it consists of positive charging, exposure to white halogen light, and static elimination. The cycle characteristics were measured by repeating the cycle 1000 times.

In Table 1, ΔV1 and ΔV2 were calculated from the following formulas: ΔV1 = V1 (1000) −V1 (1) ΔV2 = V2 (1000) −V2 (1) where V1 (1000) and V1 (1) ) Is the 1000th and 1st initial surface potential (unit: Volt (V)), and
2 (1000) and V2 (1) are residual potentials (unit: volt (V)) at the 1000th time and the 1st time.

Therefore, the better the repeatability, the more ΔV1
And ΔV2 both have small absolute values. As can be seen from Table 1, the photoreceptor of the present invention (Examples (1) to (1
4)) is a photoreceptor of Comparative Example (Comparative Example (1) to
It can be seen that the charging characteristics at the time of repeated use are superior to those of (6).

[0068]

As is apparent from the above description, according to the present invention, by using the compound represented by the general formula (1) as an electron transfer agent, excellent photosensitivity and repetitive properties can be obtained, and both positive and negative values can be obtained. Provided is an organic photoconductor for electrophotography, which can be used as a charge-type single-layer photoconductor.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C09K 3/00 U (72) Inventor Hideo Nakamori 1-2-2 Tamatsukuri, Chuo-ku, Osaka Mita Kogyo Business

Claims (3)

[Claims] 1. An organic photoreceptor for electrophotography comprising an organic photosensitive layer provided on a conductive substrate, wherein the organic photosensitive layer is a compound represented by the following general formula (1); (In the formula, R ^{1 to} R ⁸ are each independently a hydrogen atom, a cyano group, a halogen atom, an amino group, or an optionally substituted alkyl group, a cycloalkyl group, an aryl group, or Which represents an alkoxy group), and an organic photoconductor for electrophotography, which comprises: 2. The organic photosensitive layer is a single layer type in which a compound represented by the general formula (1), a hole transfer agent and a charge generating agent are dispersed in a binder resin. Organic photoconductor for electrophotography. 3. The hole transport material is at least one compound selected from the compounds represented by the following general formulas (2) to (4); (Here, R ^{21 to} R ²⁵ , R ^{31 to} R ³⁷ , and R ^{41 to} R ^46.
Each independently represents a hydrogen atom, or an alkyl group or an alkoxy group, and there may be a plurality on each benzene ring), and the organic photoconductor for electrophotography according to claim 1 or 2.