JP3192527B2 - Organic photoreceptor for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic photoreceptor 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-sidedly charged, and in particular, has a remarkably improved sensitivity and residual potential when a single layer is formed.

[0002]

2. Description of the Related Art In an electrophotographic copying machine using a digital optical system, a light source having a wavelength of 700 nm or more is usually used. As a photoconductor having sensitivity in this wavelength range,
Conventionally, amorphous chalcogenite materials including amorphous selenium (a-Se) and alloys thereof, 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 photoreceptor to be used or an organic photoreceptor (OPC) using a high molecular weight or low molecular weight organic compound is known. Among these, an organic photoreceptor is often used from a comprehensive viewpoint such as sensitivity and cost.

At present, organic photoconductors mainly used for practical use are of a function-separated type. This type of photoreceptor
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, and there is an advantage that the range of material selection can be widened. Many of the above-mentioned function-separated organic photoconductors 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 photoreceptors were negatively charged organic photoreceptors. As the charge transporting agent, a substance having a high charge mobility is required, but most of the charge transporting agents having a high charge mobility show a hole transporting property.

However, the negatively charged organic photoreceptor generates a large amount of ozone due to the use of the negative corona discharge, which causes problems such as not only contaminating the environment but also deteriorating the photoreceptor. there were. Therefore, in order to prevent this, a special charging system that does not generate ozone, a system that decomposes the generated ozone, a system that exhausts ozone in the apparatus, and the like are required, and there is a disadvantage that the entire process and the system are complicated. .

Further, in the case of a laminated type photoreceptor, coating defects are likely to occur because the photosensitive layer needs to be coated twice, and the interface between the charge generation layer and the charge transport layer is formed on the photoreceptor layer. There is a problem that interference fringes are likely to be generated due to the presence.

In order to solve these drawbacks, it has been studied to obtain a positively charged photosensitive member by using an electron transporting agent as a charge transporting agent. JP-A-1-206349
In the publication, a compound having a diphenoquinone structure is proposed as an electron transporting agent for an organic photoreceptor for electrophotography.

[0007] Japanese Patent Application Laid-Open No. 4-295585 discloses that the sensitivity of an organic photoreceptor can be improved by using a diphenoquinone as an electron transporting agent in combination with a hole transporting agent having a specific ionization potential. It is described.

[0008]

The charge transport in the photoreceptor by the electron transport agent such as diphenoquinones is carried out by repetition of charge transfer within molecules and charge transfer between molecules, that is, hopping. Will be In general, hopping has poor transportability as compared with intramolecular movement. This is because, in the hopping process, for example, 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 disadvantage that electron transfer is unlikely to occur under low electric field conditions and the residual potential is high. Therefore,
From such a viewpoint, development of an electron transporting agent having further improved electron transfer characteristics has been desired.

In addition, by using an electron transporting agent having excellent electron transfer characteristics in combination with a hole transporting agent, the organic photoreceptor can be used for both positively and negatively charged, and in particular, it can be used as a single layer dispersion type. Of course, the range of application of the photoreceptor 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-mentioned points, and has an object to be used with both positively and negatively charged polarities.
An object of the present invention is to provide a highly sensitive organic photoreceptor for electrophotography.

Another object of the present invention is to provide an organic photoconductor for electrophotography which is a single-layer dispersion type and can be charged both ways.

Still another object of the present invention is to provide an organic photoreceptor for electrophotography which has stable characteristics when used repeatedly.

[0013]

The present inventors have made it possible to use the specific electron transporting agent in combination with the hole transporting agent so that both positive and negative charging can be performed, and a single layer dispersion type can be used. It has been found that an organic photoreceptor for electrophotography having high sensitivity and excellent stability during repeated use can be prepared, and the present invention has been completed.

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

[0015]

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(Wherein, R ^{1 to} R ⁸ each independently represent
An organic photosensitive layer containing 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 an alkoxy group) on the conductive substrate. It is provided in,
Thereby, the above object is achieved.

In the organic photoreceptor for electrophotography according to the present invention, the organic photoconductive layer contains the above-mentioned general formula (1) in a binder resin.
, A hole transporting agent and a charge generating agent may be dispersed in a single layer type.

Preferred examples of the hole transport agent include at least one of the compounds represented by the following general formulas (2) to (4):

[0019]

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(Wherein, R ^{21 to} R ²⁵ , R ^{31 to} R ³⁷ , and R ^{41 to} R ⁴⁶ each independently represent a hydrogen atom, an alkyl group or an alkoxy group, May be present).

[0021]

In the compound (1) of the present invention, which can be used as an electron transporting agent for an organic photoreceptor, a quinone-based oxygen atom having excellent electron-accepting property is bonded to a terminal portion of a pyrene-type condensed aromatic ring, In addition, since the conjugated system of π electrons is spread over the entire molecule, the intramolecular movement distance is increased. As a result, it is considered that the number of times of electron transfer by hopping is relatively reduced during electron transport in the photoconductor, so that the efficiency of electron transport is increased. This electron transport agent,
When a suitable hole transporting agent, for example, at least one of the compounds of the general formulas (2) to (4) and a charge generating agent are mixed and dispersed in a binder resin, a single-layer organic photoreceptor is obtained. Regardless of whether the single-layer photoreceptor is charged positively or negatively, electrons and holes generated in the photosensitive layer by light irradiation are efficiently transported by the electron transporting agent and the hole transporting agent, respectively. , High sensitivity is obtained, and a clear charge image can be formed.

[0022]

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

[0023]

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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, the cycloalkyl group, the aryl group, and the alkoxy group may have a substituent, and each may have a suitable substituent, for example, a chlorine atom, a fluorine atom, a nitro group, and a cyano group.

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

[0026]

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As the hole transporting agent in the organic photoreceptor of the present invention, conventionally known compounds are used. Examples include oxadiazole compounds, styryl compounds, carbazole compounds, pyrazoline compounds, hydrazone compounds, amine derivatives such as triphenylamine compounds, indole compounds, oxazole compounds, isoxazole compounds, thiazole compounds. And thiadiazole-based compounds, imidazole-based compounds, pyrazole-based compounds, and triazole-based compounds. Particularly, amine derivatives, for example, compounds represented by the following general formulas (2) to (4) are preferable.

[0028]

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

Preferred examples of the amine derivative include the following formulas (21), (22), (31), (32) and (4)
Examples include, but are not limited to, the compounds shown in 1), (42) and (43). The amine derivative may be used alone or as a mixture of two or more.

[0031]

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[0032]

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[0033]

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In the organic photoreceptor of the present invention, the quinone derivative and the hole transporting agent are in a weight ratio of 1: 9 to 9:
1, preferably 1: 2 to 2: 1, more preferably 1: 1
Are mixed so that The total weight of the quinone derivative and the hole transporting 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 blended with the binder resin so as to be 80 parts by weight, more preferably 80 parts by weight.

In general, when an organic photoreceptor containing an electron transporting agent and a hole transporting agent is used as a single-layered organic photoreceptor, the interaction between the two does not adversely affect the resulting organic photoreceptor layer. Thus, it is necessary to select a combination of an electron transporting agent and a hole transporting agent. For example, it is known that, depending on the combination of an electron transporting agent and a hole transporting agent, they associate with each other to form a kind of charge transfer complex. Such a charge transfer complex recombines electrons and holes, resulting in a reduced apparent quantum yield and reduced sensitivity of the organic photoreceptor layer.

In the combination of an electron transporting agent and a hole transporting agent in the organic photoreceptor of the present invention, the above-mentioned 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, slen pigments, toluidine pigments, pyrazoline pigments, Examples include perylene pigments and quinacridone pigments. In particular, phthalocyanine pigments,
For example, X-type metal-free phthalocyanine is preferable.

The above-mentioned charge generating agents may be used alone or in a combination of two or more. The charge generating agent is used in an amount of 0.1 to 1 based on 100 parts by weight of the binder resin.
0 parts by weight, preferably 0.5 to 5 parts by weight,
It is blended with the binder resin.

In the organic photoreceptor of the present invention, the binder resin that can be used to disperse the above-mentioned electron transporting agent, hole transporting agent and charge generating agent includes various binder resins used in conventional organic photoreceptors. Resin is selected. For example,
Styrene polymer, acrylic polymer, styrene-acrylic copolymer, ethylene-vinyl acetate copolymer, polypropylene, olefin polymer such as ionomer, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, Polyester, alkyd resin, polyamide, polyurethane, epoxy resin, polycarbonate, polyarylate, polysulfone, diallyl phthalate resin, silicone resin, ketone resin, polyvinyl butyral resin, polyether resin, phenol resin, photocurable resin such as epoxy acrylate, etc. And various polymers. In particular, a styrene-based polymer, an acrylic-based polymer, a styrene-acryl-based copolymer, a polyester, an alkyd resin, a polycarbonate, and a polyarylate are preferred.
These binder resins may be used alone or in a combination of two or more.

The organic photoreceptor of the present invention may further contain various known additives as long as the electrophotographic properties are not adversely affected. Examples of compounding agents include antioxidants, radical scavengers, singlet quenchers, UV absorbers, softeners, surface modifiers, defoamers, extenders, thickeners, dispersion stabilizers, waxes, acceptors , Donors and the like.

In the organic photoreceptor of the present invention, typically, the above-described electron transporting agent, hole transporting agent and charge generating agent are all uniformly dispersed in the above-mentioned binder resin on a conductive substrate. It is used in a configuration in which a single 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 organic photoreceptor of the present invention can also be used to form a laminated organic photoreceptor in which a charge generation layer and a charge transport layer are laminated on a conductive substrate. In this case, the charge generating agent is dispersed in the binder resin in the charge generating layer, while the electron transporting agent and the hole transporting agent are used alone or in combination in the charge transporting layer. It is dispersed in the resin. Such a laminated 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. Further, as another example of a laminated organic photoreceptor, a charge generation layer containing a charge generation agent may be formed of a first charge transport layer containing an electron transport agent and a second charge transport layer containing a hole transport agent. It is also conceivable to form an organic photosensitive layer having a three-layer structure sandwiched between the conductive layers on a conductive substrate.

A barrier layer may be formed between the above-described single-layer or multilayer photoconductor and the conductive substrate as long as the characteristics of the photoconductor are not impaired. In the laminated photoconductor, 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 or multilayer photoconductor.

Examples of the conductive substrate used in the organic photoreceptor of the present invention include: aluminum, copper, tin, platinum, gold,
Metals such as silver, vanadium, molybdenum, chromium, cadmium, titanium, nickel, indium, stainless steel, brass, etc .; plastic materials on which the above metals are 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 prints and the like seen in the laminated photoreceptor, a normal aluminum pipe, particularly a film having a thickness of 1 to 50
An alumite-treated tube having a thickness of μm may be used as the conductive substrate.

For example, in the case of a single-layer type photoreceptor, the organic photoreceptor of the present invention is coated by dissolving or dispersing an electron transporting agent, a hole transporting agent and a charge generating agent in a solvent together with a binder resin. A liquid can be prepared by preparing a liquid, applying the coating liquid on a conductive substrate, and then drying.

In order to prepare the coating liquid, a conventionally known mixing apparatus, for example, a roll mill, a ball mill, an attritor, a paint shaker or an ultrasonic disperser can be used. Also, in order to apply the coating liquid on the conductive substrate,
Conventionally known coating means can be employed.

Examples of solvents that can be used to prepare the above coating solution include: alcohols such as methanol, ethanol, isopropanol and 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 and ethylene glycol dimethyl ether And 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
Two or more kinds may be used as a mixture.

[0047]

The present invention will be described in more detail with reference to 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 using the following known synthesis method.

Pyrene (9) was dissolved in chloroform, and potassium permanganate and oxygen were used as oxidizing agents.
The reaction was carried out at 50 ° C. for 3 hours to obtain a quinone compound (10). This quinone compound (10) is dissolved in dimethyl sulfoxide,
An excess amount of methyl chloride and a catalytic amount of aluminum chloride were added and reacted at 60 ° C. for 3 hours. The reaction mixture is filtered off,
The target quinone derivative (11) was prepared by washing with dimethyl sulfoxide.

[0050]

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(Preparation of Photoreceptor) Examples (1) to (1) of the present invention
The organic photoreceptor of (14) was produced 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 transporting agents:
40 parts by weight of (42) or (43),

[0052]

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[0053]

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[0054]

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As the electron transporting agent, the following quinone derivative (1)
40 parts by weight of 1) or (12),

[0056]

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Polycarbonate as a binder resin was 10
A coating liquid was prepared by mixing and dispersing 0 parts by weight and 800 parts by weight of dichloromethane as a solvent using a ball mill for 50 hours. This coating solution was applied on an aluminum foil as a conductive substrate,
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 transporting agent, the following quinone derivative (51)

[0059]

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Organic photoreceptors of Comparative Examples (1) to (3) were prepared in the same manner as described above except that the above was used.

(Evaluation of Photoconductor) Examples (1) to (4)
The photosensitivity and the repetition characteristics of the organic photoconductors of (14) and Comparative Examples (1) to (3) were evaluated as follows. Table 1 shows the results.

[0062]

[Table 1]

1. Photosensitivity Electrostatic copying tester (Kawaguchi Electric Co., Ltd., EPA-8100)
Was used to apply a voltage to the photoreceptor to charge it positively or negatively, and then exposed to white halogen light to measure the photosensitivity of the photoreceptor.

In Table 1, V1 is an initial surface potential (unit volt (V)), and indicates a potential when a photosensitive member is charged by applying a voltage. V2 is a residual potential (unit volt (V)), which was measured as a surface potential 5 seconds after the start of exposure. E1 / 2 is a half-life exposure amount (unit: μJ / cm ² ) and was calculated from the following equation: E1 / 2 = I × t1 / 2 where I is the illuminance on the drum surface and t1 / 2 is the initial surface potential. This is the time required to reach 1/2 of the value (that is, V1 / 2).

Accordingly, the higher the photosensitivity of the photoreceptor, the smaller the ratio of the residual potential to the initial surface potential (V2 / V1) and the half-exposure (E1 / 2). As can be seen from Table 1, the photoconductors of the present invention (Examples (1) to (1)
4)) are the photoconductors of Comparative Examples (Comparative Examples (1) to
Light sensitivity is remarkably improved as compared with (3)).

2. Repetition characteristics After the photoreceptor is adhered to an aluminum cylinder in a copying machine (DC-1656, manufactured by Mita Kogyo Co., Ltd.) using an adhesive tape, it is composed of positive charging, exposure to white halogen light, and static elimination. By repeating the cycle 1000 times, the repetition characteristics of the photoreceptor were measured.

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

Therefore, the better the repetition characteristics, the more ΔV1
Both ΔV2 and ΔV2 have small absolute values. As can be seen from Table 1, the photoconductors of the present invention (Examples (1) to (1)
4)) are the photoconductors of Comparative Examples (Comparative Examples (1) to
It can be seen that the charging characteristics during repeated use are superior to (3)).

[0069]

As is clear from the above description, according to the present invention, by using the compound represented by the general formula (1) as an electron transporting agent, excellent photosensitivity and repetition characteristics are obtained, Provided is an organic photoconductor for electrophotography, which can be used as a charged single-layer photoconductor.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hideo Nakamori 1-2-28 Tamazo, Chuo-ku, Osaka-shi Inside Mita Kogyo Co., Ltd. (56) References JP-A 3-1155 (JP, A) JP-A-5 JP-A-92936 (JP, A) JP-A-4-300970 (JP, A) JP-A-4-298570 (JP, A) JP-A-5-341545 (JP, A) JP-A-4-295858 (JP, A) JP-A-2-16569 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 5/06

Claims (3)

(57) [Claims] 1. An organic photoreceptor for electrophotography, wherein an organic photosensitive layer is provided on a conductive substrate, wherein the organic photosensitive layer is a compound represented by the following general formula (1): (Wherein, R ^{1 to} R ⁸ each independently represent a hydrogen atom, a cyano group, a halogen atom, an amino group, or an optionally substituted alkyl group, cycloalkyl group, aryl group, or Which represents an alkoxy group). 2. The organic photosensitive layer according to claim 1, wherein the compound represented by the general formula (1), a hole transporting agent and a charge generating agent are dispersed in a binder resin. Organic photoreceptor for electrophotography. 3. The compound according to claim 1, wherein the hole transporting agent is at least one compound selected from compounds represented by the following general formulas (2) to (4): (Where 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 may be plural on each benzene ring).