JPH08328277A - Electrophotographic photoreceptor - Google Patents

Abstract

PURPOSE: To obtain an electrophotographic photoreceptor with an org. photosensitive layer having residual potential controlled to a low level and superior sensitivity and excellent in repetitive characteristics. CONSTITUTION: This electrophotographic photoreceptor is obtd. by forming an org. photosensitive layer on an electrically conductive substrate and a bonding resin in the org. photosensitive layer contains at least an electric charge generating agent, an electron transferring agent made of a nitrated tryptoanthrineimine deriv. represented by formula I and a positive hole transferring agent made of a phenan-threnediamine deriv. represented by formula II. In the formula I, each of R<1> -R<5> is H, alkyl, aryl, aralkyl or halogen and (n) is an integer of 1-4. In the formula II, each of R<6> -R<9> is H, alkyl, alkoxy or halogen and each of (b)-(e) is an integer of 1-3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member used in an image forming apparatus such as a copying machine or a laser printer, and more specifically, it is suitable for a positive charging type and has improved sensitivity and residual potential. And an electrophotographic photoreceptor having improved repeating characteristics.

[0002]

2. Description of the Related Art Electrophotographic photoreceptors made of various materials are used in image forming apparatuses such as copying machines using the Carlson process. One is an inorganic photoreceptor using an inorganic material such as selenium as a photosensitive layer, and the other is an organic photoreceptor using an organic material as a photosensitive layer. Among them, the organic photoconductor has many advantages such as being cheaper and higher in productivity than the inorganic photoconductor and being non-polluting. Therefore, extensive research has been conducted.

The organic photoconductor is often a laminated type organic photoconductor in which a charge generation layer and a charge transport layer are laminated, that is, a so-called function-separated type photoconductor. A single-layer type organic photoconductor dispersed therein is also known. Although charge transport agents used in these photoconductors are required to have high carrier mobility, most charge transport agents having high carrier mobility have hole transporting properties. For this reason, the organic photoconductors that have been put to practical use are limited to the negative charging type photoconductors in which the charge transport layer is provided as the outermost layer in terms of mechanical strength. However, since the negatively charged organic photoconductor uses negative corona discharge, a large amount of ozone is generated, and there are problems such as polluting the environment and degrading the photoconductor.

In order to eliminate such drawbacks, it has been studied to use an electron transfer agent as the charge transfer agent. For example, Japanese Patent Laid-Open No. 1-206349 discloses a diphenoquinone structure as such electron transfer agent. A compound having is proposed. However, in general, a conventional electron transfer agent containing a diphenoquinone derivative has poor compatibility with a binder resin and a hopping distance becomes long, so that electron transfer in a low electric field hardly occurs. Therefore, the electrophotographic photoreceptor containing the conventional electron transfer material has a drawback that the residual potential is considerably high and the sensitivity is low.

Further, if the organic photoreceptor can be used in a single layer type, the production of the photoreceptor is facilitated, and although there are many advantages in preventing the occurrence of coating defects and improving the optical characteristics, the single layer is used. In the organic photosensitive layer of the type, there is a problem that the electron transport is hindered by the interaction between the diphenoquinone and the hole transport material.

A main object of the present invention is to provide an electrophotographic photosensitive member which has a low residual potential suppressed to a low level, exhibits excellent sensitivity, and has excellent repetitive characteristics.

[0007]

MEANS FOR SOLVING THE PROBLEMS AND ACTIONS The present inventors first conducted an examination focusing on the electron transfer material in the electrophotographic photosensitive member. As a result, the nitrated tryptantholinimine derivative is excellent in solubility in a solvent, compatibility with a binder resin, and matching with a charge generating agent (pigment),
It has been found that the injection of electrons is smooth, and that the electron transporting property is excellent particularly in a low electric field, and that the compound has an excellent function as an electron transferring agent as compared with a conventional diphenoquinone compound.

Therefore, as a result of further research to solve the above problems by using this derivative as an electron transfer agent, a phenanthrene diamine derivative having a specific structure was used as a hole transfer agent, which was used as the electron transfer agent. The present invention has been completed by discovering the new fact that an electrophotographic photoreceptor having excellent initial sensitivity characteristics and repetition characteristics can be obtained by using them in combination.

That is, the electrophotographic photoreceptor of the present invention comprises an electroconductive support and an organic photosensitive layer provided on the electroconductive support.

[0010]

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(Wherein R ^{1 to} R ⁵ are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group or a halogen atom, and a is an integer of 1 to 4). Of an electron transfer agent comprising a modified tryptoanthrine imine derivative, and a general formula (2):

[0012]

[Chemical 4]

(Wherein R ^{6 to} R ⁹ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and b to e are the same or different and each represents an integer of 1 to 3). And a hole transporting agent composed of a phenanthrene diamine derivative.

The electrophotographic photoreceptor of the present invention will be described in detail below. As the electron transfer agent in the electrophotographic photosensitive member of the present invention, the nitrated tryptoanthrine imine derivative represented by the general formula (1) is used. The general formula
Examples of the alkyl group corresponding to the substituents R ^{1 to} R ⁵ in (1) include methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, n-pentyl, n-hexyl. Examples of the aryl group include a group having 1 to 6 carbon atoms such as phenyl, naphthyl, anthryl,
Examples of groups such as phenanthryl and aralkyl groups include groups such as benzyl, benzhydryl, trityl and phenethyl. Halogen atoms include fluorine, chlorine, bromine and iodine. Further, in the general formula (1), the number of nitro groups defined by the symbol a is arbitrarily selected within the range of 1 to 4.

Specific examples of the nitrated tryptoanthrin imine derivative (1) include, for example, the following formulas (1-1) to (1-1)
Examples thereof include compounds represented by 1).

[0016]

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[0017]

[Chemical 6]

[0018]

[Chemical 7]

[0019]

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[0020]

[Chemical 9]

[0021]

[Chemical 10]

[0022]

[Chemical 11]

[0023]

[Chemical 12]

[0024]

[Chemical 13]

[0025]

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[0026]

[Chemical 15]

Nitrated tryptoanthrin imine derivative
First, as shown in the following reaction process formula (I), the synthesis of (1) is usually carried out in a solvent such as a mixed solvent (mixed acid) of nitric acid and sulfuric acid of tryptoanthrin (A) at −20 to 80 ° C. The nitrated tryptoanthrine (B) is synthesized by reacting (nitrating) at the temperature of about 30 minutes to 6 hours, and then, as shown in the reaction process formula (II), the above compound (B) and the aniline derivative are synthesized.
It can be obtained by reacting (C) with a solvent such as acetic acid, propionic acid, butanoic acid, chloroform, tetrahydrofuran, dimethylformamide and dimethylsulfoxide at a temperature of 30 to 170 ° C. for about 20 minutes to 4 hours. Reaction process formula (I)

[0028]

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(In the formula, a is the same as above.) Reaction process formula (II)

[0030]

[Chemical 17]

(In the formula, R ^{1 to} R ⁵ and a are the same as above.) The nitrated tryptanthrin imine derivative of the above-mentioned examples.
(1) has a π-electron conjugated system having a wider spread than that of the diphenoquinone derivative conventionally used as an electron transfer agent, and exhibits a high electron transfer ability. In addition, it has good solubility in a solvent and compatibility with a binder resin, and is also excellent in matching with a charge generating agent. This matching with the charge generating agent is performed by the substituent R ¹ of the derivative (1).
It becomes more excellent by introducing the above-mentioned groups to R ⁵ .

Therefore, when the nitrated tryptoanthrin imine derivative (1) is used as an electron transfer agent in an electrophotographic photosensitive member, electrons are smoothly injected from the charge generating agent, and the electron transfer is performed in a low electric field. As well as
The ratio of electrons and holes that recombine decreases, and the apparent charge generation efficiency approaches the actual value, resulting in improvement in the sensitivity of the photoconductor. In addition, the residual potential of the photoconductor also becomes low, and the stability and durability upon repeated exposure are improved.

As the hole transporting agent in the present invention, the phenanthrene diamine derivative represented by the above general formula (2) is used. In the general formula (2), examples of the alkyl group and halogen atom corresponding to the substituents R ^{6 to} R ⁹ include the same groups as described above. Examples of the alkoxy group include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, s-butoxy, t-butoxy, n-butoxy.
Examples include groups such as pentyloxy and n-hexyloxy.

Specific examples of the phenanthrene diamine derivative (2) include compounds represented by the following formulas (2-1) to (2-5).

[0035]

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[0036]

[Chemical 19]

[0037]

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[0038]

[Chemical 21]

[0039]

[Chemical formula 22]

Further, in the present invention, it is preferable to use one having an ionization potential (Ip) of 4.8 to 5.8 eV among the above hole transfer agents, and further, an electric field strength of 3 × 10 ⁵ V.
Those having a charge mobility of 1 × 10 ⁻⁶ cm ² / V · sec or more / cm ² are particularly preferable. By using the hole transfer material having the ionization potential and the charge mobility within the above ranges, the residual potential of the photoconductor can be further lowered and the sensitivity can be improved. The reason is not clear, but it is considered as follows.

That is, the easiness of injecting charges from the charge generating agent into the hole transporting agent is closely related to the ionization potential of the hole transporting agent, and the ionization potential of the hole transporting agent is higher than the above range. When the value is large, the degree of charge injection from the charge generating agent to the hole transport material is low, or the degree of hole transfer between the hole transport agents is low. Therefore, it is recognized that the sensitivity is lowered.

In a system in which a hole-transporting material and an electron-transporting material coexist, when the ionization potential of the hole-transporting material is smaller than the above range, the interaction between the two, more specifically, the charge-transfer complex. Attention must be paid to the formation of When such a complex is formed between the two, recombination occurs between the holes and the electrons, and the mobility of the charge is lowered as a whole. As described above, when the ionization potential of the hole transfer material is smaller than the above range, there is a large tendency to form a complex with the electron transfer material, and electron-hole recombination occurs. It is considered that the yield is lowered and the sensitivity is lowered.

The hole transfer agent used in the present invention [general formula
When the compound of (2) and an electron transfer agent [the compound of general formula (1)] are combined, the complex is extremely unlikely to be formed, but the general formula (1) and / or the general formula (2) The risk of forming a complex can be sufficiently eliminated by introducing a bulky substituent into the compound (1).

The electrophotographic photoreceptor of the present invention is most effectively used as a single layer type. Such a single-layer type electrophotographic photosensitive member is one in which an organic photosensitive layer is provided on a conductive support, and the binder resin in this organic photosensitive layer is at least a charge generating agent and a nitrated tryptoanthrine imine derivative.
It contains an electron transfer material consisting of (1) and a hole transfer material consisting of a phenanthrene diamine derivative (2). Therefore, the single-layer type electrophotographic photoreceptor of the present invention has excellent sensitivity and excellent repeatability.

The single-layer type photoconductor is applicable to both positive charging and negative charging, but it is particularly preferable to use the positive charging type. According to the single-layer type electrophotographic photosensitive member, the electrons released from the charge generating agent in the exposure step can be smoothly injected into the electron transfer agent represented by the general formula (1). Such electrons move to and from the surface of the photosensitive layer by transfer between the electron transfer agents, and cancel the positive charge (+) charged in advance on the surface of the photosensitive layer. On the other hand, the holes (+) are smoothly injected into the hole transfer agent represented by the general formula (2), move to the surface of the conductive support without being trapped, and The negative charge (-) on the surface is canceled. Thus, it is considered that the sensitivity of the photoconductor is improved because the series of movement of electrons and holes is performed smoothly and efficiently as described above. When the single-layer type photoreceptor is used with negative charging, the sensitivity is similarly improved only by reversing the direction of charge transfer.

The electrophotographic photosensitive member of the present invention can also be used as a laminated type. In this case, the laminated photoreceptor is applicable to both positive charging and negative charging.

[0047]

As the charge generating agent used in the present invention, for example, selenium, selenium-tellurium, amorphous silicon, pyrylium salt, azo pigment, ansanthuron pigment, phthalocyanine pigment, perylene pigment, naphthalocyanine pigment, Examples thereof include indigo pigments, triphenylmethane pigments, slene pigments, toluidine pigments, pyrazoline pigments, quinacridone pigments and dithioketopyrrolopyrrole pigments.

These charge generating agents may be used alone or in combination of two or more so as to have an absorption wavelength in a desired region. Further, in connection with the use of the hole transfer agent having an ionization potential of 4.8 to 5.8 eV, the charge generation agent has a well-balanced ionization potential with the hole transfer agent, that is, the ionization potential is 4.8-6.
It is desirable to use 0 eV, particularly 5.0 to 5.8 eV in order to reduce the residual potential and improve the sensitivity.

Suitable examples of an image forming apparatus of an analog optical system using a light source having a wavelength in the visible region include azo pigments represented by the following formulas (3-1) to (3-7). Can be mentioned.

[0051]

[Chemical formula 23]

[0052]

[Chemical formula 24]

[0053]

[Chemical 25]

[0054]

[Chemical formula 26]

[0055]

[Chemical 27]

[0056]

[Chemical 28]

[0057]

[Chemical 29]

As the binder resin for dispersing each of the above components, various resins conventionally used in organic photosensitive layers can be used, for example, a styrene polymer, a styrene-butadiene copolymer, In addition to styrene-acrylonitrile copolymer, styrene-maleic acid copolymer, styrene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, vinyl chloride-vinyl acetate copolymer, acrylic polymer and the like, polyethylene (PE), chlorinated polyethylene, polypropylene (PP), polystyrene (P
S), polystyrene copolymer (AS resin, ABS resin), vinyl chloride (PVC), vinylidene chloride (PVD)
C), (meth) acrylic resin, polyvinyl acetate resin (P
VAc), polyamide resin (PA), acetal resin,
Thermoplastic resins such as polycarbonate (PC), polyphenylene oxide (PPO), polyesters (PET, PBT, polyarylate, etc.), polysulfone resins, diallyl phthalate resins, ketone resins, polyvinyl butyral resins, polyether resins, and phenolic resins, Urea resin, melamine resin, alkyd resin, epoxy resin, silicone resin, polyurethane resin, other crosslinkable thermosetting resin, epoxy acrylate, urethane-
A photocurable resin such as acrylate can be used, and one kind or a mixture of two or more kinds can be used.

Of the above-exemplified resins, preferred ones are styrene-based polymers, acrylic-based polymers and styrene-based polymers.
Acrylic acid copolymers, polyesters, alkyd resins, polycarbonates, polyarylates and the like. To obtain a single-layer type electrophotographic photoreceptor, a predetermined electron transfer agent and hole transfer agent are dissolved or dispersed in a suitable solvent together with a charge generating agent, a binder resin and the like, and the coating solution thus obtained is used. It may be applied on a conductive support and dried. The coating solution is prepared by a known method (for example, roll mill, ball mill,
Disper mill, attritor, paint shaker or ultrasonic disperser) is used.

In the case of a single-layer type photoreceptor, the binder resin 10
The charge generating agent is 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight, and the hole transferring material is 5 parts by weight with respect to 0 parts by weight.
To 500 parts by weight, preferably 25 to 200 parts by weight, and 5 to 100 parts by weight, preferably 10 to 100 parts by weight of the electron transfer agent.
80 parts by weight are added respectively. Further, the total amount of the hole transfer material and the electron transfer material is appropriately 20 to 500 parts by weight, preferably 30 to 200 parts by weight with respect to 100 parts by weight of the binder resin. When an electron-accepting compound is contained, it is added in an amount of 0.1 with respect to 100 parts by weight of the binder resin.
It is suitable to blend in an amount of -40 parts by weight, preferably 0.5-20 parts by weight.

The film thickness of the single-layer type photosensitive layer is usually 5 to 100 μm.
m, preferably 10 to 50 μm. In order to obtain a laminated type electrophotographic photoreceptor, first, a charge generating layer containing a charge generating agent is formed on a conductive support by means such as vapor deposition or coating, and then an electron transporting agent is formed on the charge generating layer. Alternatively, a charge-transporting layer may be formed by applying a coating solution containing a hole-transporting agent and a binder resin and drying it.

In the multi-layer type photoreceptor, the charge generating agent and the binder resin constituting the charge generating layer can be used in various ratios, but the charge generating agent is added to 100 parts by weight of the binder resin. 5 to 1000 parts by weight, preferably 30 to 500
It is suitable to mix in a ratio of parts by weight. The electron transfer agent or hole transfer agent and the binder resin that form the charge transfer layer,
It can be used in various proportions within a range that does not inhibit charge transport and a range that does not crystallize.

The film thickness of the laminated photosensitive layer is usually about 0.01 to 5 μm, preferably about 0.1 to 3 μm for the charge generation layer, and 2 to 100 μm for the charge transport layer, preferably 5 to 5.
It is about 50 μm. In the case of a single-layer type photoreceptor, between the conductive support and the photosensitive layer, and in the case of the laminated type photoreceptor, between the conductive support and the charge generation layer, the conductive support and the charge transport layer. A barrier layer may be formed between the charge generation layer and the charge generation layer or between the charge generation layer and the charge transport layer as long as the characteristics of the photoreceptor are not impaired. Further, a protective layer may be formed on the surface of the photoconductor.

Various additives known per se, such as an antioxidant, a radical scavenger, and a singlet quencher, are added to each of the single-layer type and laminated type photosensitive layers as long as they do not adversely affect the electrophotographic characteristics. A deterioration inhibitor such as an ultraviolet absorber, a softening agent, a plasticizer, a surface modifier, a bulking agent, a thickener, a dispersion stabilizer, a wax, an acceptor, a donor and the like can be added.

In order to improve the sensitivity of the photosensitive layer,
For example, known sensitizers such as terphenyl, halonaphthoquinones and acenaphthylene may be used in combination with the charge generating agent.
In addition to the compound represented by the general formula (1), other conventionally known electron transfer agents may be contained in the photosensitive layer.
Examples of such electron transfer agents include benzoquinone-based, naphthoquinone-based, anthraquinone-based such as nitroanthraquinone and dinitroanthraquinone, diphenoquinone-based, thiopyran-based, fluorenone-based such as 3,4,5,7-tetranitro-9-fluorenone, and 2 In addition to xanthene-based compounds such as 4,4,8-trinitrothioxanthene, dinitroanthracene, dinitroacridine, malononitrile and the like. Further, tetracyanoethylene, dinitrobenzene, succinic anhydride, maleic anhydride, dibromomaleic anhydride and the like can also be used.

As the conductive support used in the photoconductor of the present invention, various conductive materials can be used. Examples thereof include aluminum, iron, copper, tin, platinum, silver,
Metal element such as vanadium, molybdenum, chromium, cadmium, titanium, nickel, palladium, indium, stainless steel, brass, etc., or a plastic material in which the above metal is vapor deposited or laminated, aluminum iodide, tin oxide, indium oxide, etc. The glass and the like are exemplified.

The conductive support may be in the form of a sheet, a drum or the like, as long as the support itself has conductivity or the surface of the support has conductivity. In addition, the conductive support preferably has sufficient mechanical strength. As a solvent for making coating liquid,
Various organic solvents can be used, such as methanol,
Alcohols such as ethanol, isopropanol, butanol, aliphatic hydrocarbons such as n-hexane, octane and cyclohexane, aromatic hydrocarbons such as benzene, toluene and xylene, halogenation such as dichloromethane, dichloroethane, carbon tetrachloride and chlorobenzene. Hydrocarbons, dimethyl ether, diethyl ether, tetrahydrofuran, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether and other ethers, acetone, methyl ethyl ketone, cyclohexanone and other ketones, ethyl acetate, methyl acetate and other esters, dimethylformaldehyde, dimethylformamide, dimethyl sulfoxide, etc. These solvents may be used alone or in admixture of two or more.

Further, in order to improve the dispersibility of the charge transport material or the charge generating material and the smoothness of the surface of the photosensitive layer, a surface active agent, a leveling agent, etc. may be used.

[0069]

【Example】

Examples 1 to 30 In a ball mill, 5 parts by weight of a charge generating agent, 70 parts by weight of a hole transferring material, 30 parts by weight of an electron transferring material, 100 parts by weight of a binder resin (bisphenol A type polycarbonate) and 800 parts by weight of a solvent (tetrahydrofuran). And mixed and dispersed for 50 hours to prepare a single-layer type photosensitive layer coating solution. Then, this coating solution is applied on an aluminum base tube as a conductive base material by a dip coating method and dried with hot air at 110 ° C. for 30 minutes to obtain a single layer type photosensitive layer having a single layer type photosensitive layer having a film thickness of 25 μm. Manufactured body.

Examples of the charge generating agent include those represented by the formulas (3-1), (3-2),
Any of (3-3), (3-5) and (3-7) was used. Any one of the phenanthrene diamine derivatives represented by the formulas (2-1) to (2-5) as the hole transfer agent and the formula (1-1) as the electron transfer agent.
Any of the nitrated tryptoanthrin imine derivatives represented by ~ (1-11) was used. Comparative Example 1 A single-layer type photoreceptor was prepared in the same manner as in the above-mentioned example except that the electron transfer material was not used. Comparative Example 2 A single-layer type photoreceptor was prepared in the same manner as in the above Example except that the following formula (4-1) was used as the electron transport material.

[0071]

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Initial electrical characteristic test An applied voltage was applied to the surface of the photoconductor obtained in each of the examples and comparative examples using a drum sensitivity tester manufactured by GENTEC, and the surface was set to + 700V ± 20V. After charging, the surface potential V ₀ (V) was measured. And
The surface of the photoconductor was irradiated with white light (light intensity 10 lux) of a halogen lamp as an exposure light source (irradiation time of 1.5 seconds), and the time required for the surface potential to become 1/2 was measured. The half-exposure amount E _1/2 (lux · sec) was calculated. Further, the surface potential at the time point 0.5 seconds after the start of exposure was measured as the residual potential V _r (V).

Electrical property test after repeated exposure After electrophotographic photoreceptors of Examples and Comparative Examples were used in an electrostatic copying machine (DC2556 manufactured by Mita Kogyo Co., Ltd.), image formation was performed 10,000 times. , The surface potential V ₀ (V) and the residual potential V _r (V) were measured in the same manner as above using the drum sensitivity tester of the previous term, and the difference ΔV from the respective initial values was measured.
_The test results for ₀ (V) and ΔV _r (V) are shown in Table 1
6 is shown.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

[Table 3]

[0077]

[Table 4]

[0078]

[Table 5]

[0079]

[Table 6]

As shown in the above table, the half-exposure amount E _1/2 (lux · sec) and the residual potential V _r (V) of the initial electric characteristics are lowered, and it can be understood that the initial performance of the electrophotographic photosensitive member is improved. In addition, the surface potential difference ΔV after 10,000 times of image formation
_{Since 0} (V) and the residual potential difference ΔV _r (V) are low, it can be understood that the repeating performance of the electrophotographic photosensitive member is improved.

[0081]

EFFECTS OF THE INVENTION According to the present invention, since it contains an electron transfer agent composed of a nitrated tryptoanthrin imine derivative (1) and a hole transfer agent composed of a phenanthrene diamine derivative (2), It is possible to obtain an electrophotographic photosensitive member having an organic photosensitive layer whose electric potential is suppressed to a low level and which has excellent repeating characteristics.

Therefore, by using the photoconductor of the present invention, it is possible to increase the speed of copying machines, printers and the like.

Claims (1)

[Claims] 1. An electrophotographic photoreceptor having an organic photosensitive layer provided on a conductive support, wherein at least the compound represented by the general formula (1): (In the formula, R ^{1 to} R ⁵ are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, an aralkyl group or a halogen atom, and a represents an integer of 1 to 4.). An electron transfer agent comprising a trilinimine derivative and a compound represented by the general formula (2): (In the formula, R ^{6 to} R ⁹ are the same or different and each represents a hydrogen atom, an alkyl group, an alkoxy group or a halogen atom, and b
To e are the same or different and each represents an integer of 1 to 3. And a hole-transporting agent composed of a phenanthrene diamine derivative represented by the formula (1).