JPH0736202A - Electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] [Structure] An electrophotographic photoconductor having a photoconductive layer containing, on a conductive support, a charge-transporting substance exhibiting a "reversible" or "quasi-reversible" electrochemical redox electrode reaction. body. When the oxidation potential of the charge generating substance is α (V), the limit oxidation potential β (V) of the compatible charge transporting substance is α−0.5 ≦ β <α−
An electrophotographic photoreceptor in the range of 0.2. [Effect] It is possible to repeatedly provide stable high-quality printed images from a copying machine, a printer, etc. in all environments of low temperature and low humidity to high temperature and high humidity.

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 copying machines, LD printers, LED printers, LCD printers and the like.

[0002]

2. Description of the Related Art An electrophotographic photosensitive member mounted in a copying machine, a printer or the like using an electrophotographic process is required to satisfy the following general characteristics. (1) It has sufficient charging ability to be charged to an appropriate potential in a dark place. (2) The ability to retain electric charges in the dark is large. (3) The photosensitivity is such that the light can be rapidly and sufficiently deviated from the electric charge by light irradiation. (4) An electrophotographic photoreceptor having an appropriate area can be easily manufactured. (5) Excellent in repeated stability. (6) Excellent durability. (7) It is inexpensive. (8) It is non-toxic.

These characteristics are largely controlled by the materials used for the photoreceptor, that is, the charge generating substance and the charge transporting substance, and the binder resin for binding them.
Therefore, many researchers are currently focusing on the new development of these materials, and the molecular design by introducing quantum chemistry theory for these materials and the photoconductor to be finally obtained, for example, charge As represented by the SPH theory regarding the charge transport process in the transport layer, an increasing number of researchers are conducting basic physics analyzes of the photoconductivity phenomenon from the viewpoint of physical properties. Body design is becoming possible.

At present, as an electrophotographic photoreceptor, an organic compound photoreceptor is more preferable than an inorganic compound photoreceptor due to reasons such as easiness of film formation, toxicity, merit in productivity and cost, and ease of use. Usage is the mainstream. Furthermore, for the purpose of improving electrophotographic characteristics such as photosensitivity and repetitive stability, a function-separated type laminated organic photoreceptor in which a charge generating function and a charge transporting function are individually shared is widely used.

For example, taking the photosensitivity of the function-separated type organic photoconductor as an example, the governing factors of the photosensitivity will be briefly described. The photosensitivity of the photoconductor depends on the charge generation ability in the charge generation layer and the charge generation layer. The efficiency of charge injection into the charge transport layer and the charge transport ability in the charge transport layer are roughly governed by the product of these three factors. In addition, a method for independently and quantitatively evaluating each physical quantity has been established, and is a useful information source for the photoconductor design.

However, it is difficult to easily describe the governing factor of the repeating stability of the function-separated type organic photoconductor as in the photosensitivity described above. Only by evaluating the repeated stability of the photoconductor using a measuring machine or an actual machine, it was possible to determine whether the repeated stability was good or bad.

[0007]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention The purpose of the present invention is to provide an electrophotographic photoconductor having a photoconductive layer containing a charge generating substance and a charge transporting substance on a conductive support, including the function-separated type organic photoconductor. It is a problem to be solved by the present invention to establish a method for determining repetitive stability without making a photoreceptor and evaluate it so as to provide an electrophotographic photoreceptor having excellent repetitive stability.

[0008]

The inventors of the present invention have conducted extensive studies to solve the above-mentioned problems, and as a result, among the materials used for the photoconductor, charge, which is a substance directly involved in photoconduction, Form of electrochemical redox reaction of transport material,
By examining the oxidation potential value measured by this reaction of the charge generating substance and the charge transporting substance, we succeeded in determining the repeated stability of the photoconductor.

The present invention will be described in detail below. The electrochemical redox reaction in the present invention specifically means an electrode reaction obtained by cyclic voltammetry. This cyclic voltammetry is comparatively easy to carry out, much information can be obtained, and theoretical studies have been conducted, and it is now widely used as one of the major electrochemical measurement methods.

First, the measuring method of cyclic voltammetry used in the present invention will be described.

(A) Measuring instrument and equipment In this measurement, a three-electrode type electrolytic cell having the structure shown in FIG. 1 was used, and a platinum rod was embedded in a resin (Teflon) as a working electrode, and a constant surface area (S = 0) A platinum electrode (manufactured by BAS Co., Ltd.) in which a circle of 0.021 cm ² ) was exposed was used. Platinum has a narrower potential window than ITO, etc., but even if the sweeping potential width is wide, the electrode will not break, and Teflon coated products like this shape are commercially available, and the electrode is always constant. This platinum electrode was used in this measurement because of the advantage of being able to react in an area.

A spirally wound platinum wire electrode was used as the counter electrode, and a calomel electrode (usually abbreviated as saturated calomel electrode, SCE) immersed in a saturated potassium chloride aqueous solution was used as the reference electrode.

A potentio / galvanostat (HAB-151 manufactured by Hokuto Denko Co., Ltd.) with a built-in function generator was used as the electrode reaction power supply device, and a triangular wave function was used in potentiostat mode.

(B) Electrolyte Preparation Tetra-n-butylammonium perchlorate (hereinafter, T) as a supporting electrolyte using a charge generating substance or a charge transporting substance.
Abbreviated as BA / ClO ₄ . ), And dissolved in N, N-dimethylformamide (hereinafter abbreviated as DMF) with the following composition to obtain an electrolytic solution.

2 mM charge generating substance / 0.1 MTBA · C
DMF solution of lO ₄ or 2mM charge transport material /
DMF solution of 0.1 MTBA / ClO _{4 Since} the pigment-based charge generating substance such as titanyl phthalocyanine was difficult to dissolve in DMF, an ultrasonic disperser [Model-23 manufactured by KAIJO DENKI CO., LTD.] Was used.
80] at an output of 45 W for 1 to 3 hours.

C) Measurement procedure After the prepared electrolytic solution was placed in a three-electrode type electrolytic cell, the electrodes were connected to a measuring instrument. With the electrolytic solution stationary, the sweep start potential was set to 0 V, the sweep lower end potential was set to 0 V, the sweep upper end potential was set to 0.8 to 1.5 V, and the sweep speed was set to 50 to 500 mV / sec.
(° C). Here, the sweep upper end potential is shaken because the sweep turnaround point is changed, and the sweep speed is shaken because the decomposition rate of the reactant is investigated. In this measurement, the sweeping potential is positive because it is intended to measure the oxidation potential of the charge generating substance and the hole transporting substance.However, when measuring the reduction potential of the charge generating substance and the electron transporting substance, the sweeping potential is set to be positive. The potential becomes negative. Also,
Since the sweep on the minus side is easily affected by the dissolved oxygen in the electrolytic solution, it is desirable to perform sufficient bubbling and flow of the electrolytic solution with nitrogen gas to remove the dissolved oxygen, and then perform the measurement.

Next, the results obtained by this cyclic voltammetry will be briefly described.

A) Cyclic voltammograms of charge-generating substance and charge-transporting substance As examples of the charge-generating substance, cyclic voltammograms of α-type titanyl phthalocyanine, β-type titanyl phthalocyanine and X-type metal-free phthalocyanine are respectively given. This is shown in FIGS. 2, 3 and 4.

As examples of the charge transport material, three types of charge transport materials having the following chemical structural formulas No. 1 to No.
Cyclic voltammgrams of No. 3 are shown in FIGS. 5 to 7, respectively.

[0020]

[Chemical 1]

[0021]

[Chemical 2]

[0022]

[Chemical 3]

Regarding the cyclic voltamgram of the charge generating substance, all show the "irreversible" electrode reaction in which no peak current appears when the potential is swept toward the cathode. The charge-generating pigment used in Example 1 was difficult to dissolve in a solvent having a large polarity, such as DMF, which is usually used in an electrolytic solution. Therefore, the measurement was performed in a dispersed solution state, and the reaction morphology could not be evaluated.

Next, regarding the charge-transporting substance, since all of this material was well dissolved in DMF, it was possible to evaluate the electrode reaction form from the shape of the cyclic voltamgram.

Usually, it is a characteristic of the "irreversible system" electrode reaction that the peak current does not appear in the potential sweep in the cathode direction, or the current value is small even if it appears. In the case of a completely "reversible" electrode reaction, the absolute values of the peak currents in the anode direction and the cathode direction are equal, and the absolute value of the potential difference giving each peak current is about 60 mV in the case of a one-electron reaction. Is characterized by
The “quasi-reversible” electrode reaction corresponds to an intermediate region between “reversible” and “irreversible”.

In consideration of these characteristics, Table 1 shows the results of evaluation of reaction forms of three types of charge transport materials.

[0027]

[Table 1]

In Table 1, the electrophotographic photosensitive member using the charge transporting substance exhibiting a "quasi-reversible system" as the reaction form is excellent in repeated stability, but is electrophotographic using the charge transporting substance exhibiting the "irreversible system". It has been found that the photoreceptor is unstable with repeated use.

This is because when the charge transport material directly involved in the conduction of holes or electrons shows an electrode reaction of "reversible system" or "quasi-reversible system", the cation radical or anion radical and the neutral molecule are Since the exchange of electrons is rapidly carried out in, the repetition of the exchange of electrons is stable, and in the case of the charge transport substance showing the electrode reaction of "irreversible system", "reversible system" or "quasi-reversible system" It is presumed that it is due to having a characteristic opposite to that of

Therefore, it has been clarified that the charge transfer in the photoconductive layer involves the radicals and neutral molecules of the charge transport material from the viewpoint of the molecular level, and the charge transport material 1
When focusing on a molecule, if the molecule is stable in repetition of radical state and neutral molecular state associated with electron transfer, that is, in repetition of redox reaction, repetition of photoconductive layer by use of the charge transport material. It was found that the characteristics were improved.

Further, from this fact, the cyclic stability of the photoconductor can be determined by measuring the cyclic voltammetry of the charge transport substance, which is a substance directly involved in photoconduction, without making the photoconductor to evaluate it. I found that I could do it.

B) Oxidation potential of charge generating substance and charge transporting substance When the oxidation potential is determined from cyclic voltamgram, the potential at which half the current change occurs, that is, the half-wave potential (E _1/2 ) is usually oxidized. The value of the electric potential is generally used, and this E _1/2 (V) and the ionization potential I of the solid
The relationship of c (eV) is R. O. It has been theoretically investigated by Loutfy and others. This E _1/2 is obtained as the average value of the peak values of the first redox wave of the cyclic voltamgram.

However, as shown in FIGS. 2 to 4 of the charge generating substance cyclic voltammgram and FIGS. 9 and 10 of the charge transporting substance, the peak current is generated by the potential sweep toward the cathode. If the current does not appear, or if it appears, but the current value is extremely small,
Since the peak potential of the reduction wave cannot be obtained, the peak potential (E _OX ) of the first oxidation wave in the cyclic voltamgram of the charge generating substance and the charge transporting substance was used as the oxidation potential value this time.

Therefore, the charge generation product obtained by this method
Quality, value of oxidation potential of charge transport material (E _OX) To Table 2
I showed it.

[0035]

[Table 2]

From this table, in the case of the charge generating substance, the difference in the oxidation potential due to the difference in the crystal type and the central metal of the phthalocyanine was observed. Particularly, regarding the difference in the oxidation potential depending on the crystal type, the phthalocyanine pigment was completely dissolved. No, it is the result reflecting the state of the dispersion solution. Various other information can be obtained from this measurement.

Also, regarding the charge transport substance, a difference in oxidation potential due to the difference in the molecular skeleton and the substituent is recognized, and various information can be obtained in the same manner as the charge generating substance.

Further, based on the data of Table 2 and the like, the relationship between the oxidation potential E _OX of the charge generating substance and the charge transporting substance showing the electrode reaction of the "reversible system" or the "quasi-reversible system" and the light composed of the combination thereof. As a result of examining the repeated stability of the conductive layer, when the oxidation potential of the charge generating substance is α (Vvs.SCE), the limit oxidation potential β (Vv
s. SCE)

[0039]

(2) α-0.5 ≦ β <α-0.2

It was found that the repeating stability of the photosensitive member was remarkably improved when the content was within the range.

Examples of the material of the conductive support used in the present invention include aluminum, copper, manganese, silicon, magnesium, zinc, stainless steel, chromium, titanium, nickel, molybdenum, vanadium, indium,
Gold, metal cylinders of metals such as platinum or alloys thereof, or conductive polymers, conductive compounds such as indium oxide, aluminum, palladium, metals such as gold or alloys thereof, electrolytic polymerization, chemical polymerization, gas phase polymerization, Examples include, but are not limited to, those coated with paint, vapor-deposited, laminated paper, plastic film and the like, and those subjected to surface oxidation treatment.

Further, in the present invention, an electrophotographic photoreceptor having a photosensitive layer on a conductive support is used. At present, a laminated electrophotographic photosensitive member in which the photosensitive layer contains an organic photoconductive substance is generally the mainstream, but the present invention is not limited to this. .

Examples of the charge generating material used in the photosensitive layer of the present invention include phthalocyanine pigments, azo pigments, quinone pigments, perylene pigments, indigo pigments,
Thioindigo pigment, bisbenzimidazole pigment,
Quinacridone pigment, quinoline pigment, lake pigment, azo lake pigment, anthraquinone pigment, oxazine pigment, dioxazine pigment, triphenylmethane pigment,
Various organic pigments and dyes such as azurenium dyes, squarerium dyes, pyrylium dyes, triallylmethane dyes, xanthene dyes, thiazine dyes, cyanine dyes, and further amorphous silicon, amorphous selenium,
Inorganic materials such as tellurium, selenium-tellurium alloy, cadmium sulfide, antimony sulfide, zinc oxide and zinc sulfide can be mentioned.

These materials are used by being dispersed in a binder resin and coated on a conductive support, or by being formed into a film by means of vacuum deposition, sputtering, CVD method or the like.

The charge generating substance is not limited to those listed here, and may be used alone or in the case of using it.
A mixture of more than one type can be used.

The charge generating substance and the binder resin are preferably used in a weight ratio of 2: 1 to 1: 1.

The thickness of the charge generation layer is preferably in the range of 0.01 to 1 μm.

The charge-transporting substance used in the photosensitive layer is generally classified into two types, a substance that transports an electron and a substance that transports a hole, and both can be used in the photoconductor of the present invention. .

Examples of the electron transport material include 2, 4,
7-trinitro-9-fluorenone, 3-nitro-9,
Materials such as 9-bis (n-butylthio) fluorenone that exhibit a quasi-reversible system electrode reaction may be mentioned. In addition to this, the electrochemical redox electrode reaction may be a "reversible system" due to the shape of the Cyclec voltamgram. Electron transport materials that are recognized as "quasi-reversible" electrode reactions are preferred.

Examples of the hole-transporting substance include the above-exemplified compound No. 3 and the like. In addition to this, the electrochemical redox electrode reaction is a "reversible system" due to the shape of the Cyclek voltamgram. Alternatively, a hole transport material recognized as a “quasi-reversible” electrode reaction is preferable.

These materials can be used for the photosensitive layer by being dispersed in a binder resin and applied, or formed into a film by a means such as vacuum deposition, sputtering or CVD.

The charge-transporting substance is not limited to those listed here, and may be used alone or in combination with the above.
A mixture of more than one type can be used.

The weight ratio of the charge transport material to the binder resin is preferably in the range of 2: 1 to 1: 2.

The thickness of the charge transport layer is preferably in the range of 5 to 50 μm.

As the binder, it is preferable to use a high molecular polymer which is hydrophobic and can form an electrically insulating film. Examples of such high molecular weight polymers include polycarbonate, polyester, methacrylic resin, acrylic resin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyvinyl acetate, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile polymer,
Vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone-alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinylcarbazole, polyvinyl butyral, Examples thereof include, but are not limited to, polyvinyl formal and polysulfone. These binders can be used alone or 2
Used by mixing more than one kind.

It is also possible to use additives such as a plasticizer, a sensitizer and a surface modifier together with these binders.

Examples of the plasticizer include biphenyl, biphenyl chloride, o-terphenyl, dibutyl phthalate, diethylene glycol phthalate, dioctyl phthalate, triphenyl phosphoric acid, methylnaphthalene, benzophenone, chlorinated paraffin, polypropylene, polystyrene and various fluorohydrocarbons. Etc.

Examples of the sensitizer include chloranil, tetracyanoethylene, methyl violet, rhodamine B, cyanine dye, merocyanine dye, pyrylium dye and thiapyrylium dye.

Examples of the surface modifier include silicone oil and fluororesin.

Further, in the present invention, in order to improve the adhesiveness between the substrate and the photosensitive layer and prevent the injection of free charges from the substrate to the photosensitive layer, the substrate and the photosensitive layer may be adhered to each other as necessary. An agent layer or a barrier layer (undercoat layer) can also be provided. Examples of materials used for these layers include polymer compounds used for the binder, casein, gelatin, polyvinyl alcohol, ethyl cellulose, phenolic resin, polyamide, polyimide, carboxy-methyl cellulose, vinylidene chloride-based polymer latex, polyurethane, and oxidation. Aluminum, tin oxide, titanium oxide, etc. may be mentioned.

These materials are applied as a paint,
It is used after being formed into a film by means such as vacuum deposition, sputtering, and CVD method.

The substances imparting a function as an adhesive or a barrier are not limited to those listed here,
When used, they can be used alone or in combination of two or more.

When the adhesive layer or the barrier layer is provided, the film thickness is preferably in the range of 0.01 to 1 μm.

When the laminated type photoreceptor is formed by coating, a paint prepared by dissolving the above-mentioned charge generating agent or charge transporting substance in a binder or the like is dissolved in a solvent. Although it depends on the type, it is preferable to select from those that do not dissolve the lower layer. Also, when the adhesive layer or the barrier layer is formed by coating, a paint prepared by dissolving the above binder and the like in a solvent is used, but the solvent for dissolving the binder does not dissolve the lower layer, although it varies depending on the kind of the binder. It is preferable to select from the above. Specific organic solvents include, for example, methanol, ethanol, n
-Alcohols such as propanol; Ketones such as acetone, methyl ethyl ketone and cyclohexanone; N, N-
Amides such as dimethylformamide and N, N-dimethylacetamide; ethers such as tetrahydrofuran, dioxane and methyl cellosolve; esters such as methyl acetate and ethyl acetate; sulfoxides and sulfones such as dimethyl sulfoxide and sulfolane; methylene chloride and chloroform , Halogenated hydrocarbons such as carbon tetrachloride, 1,1,2-trichloroethane; benzene, toluene, o
Examples thereof include aromatics such as -xylene, p-xylene, m-xylene, monochlorobenzene, and dichlorobenzene, but are not limited thereto. These solvents may be used alone or in combination of two or more.

As the coating method, for example, dip coating method, spray coating method, spin coating method, bead coating method, wire bar coating method, blade coating method, roller coating method,
A coating method such as a curtain coating method can be used.

[0066]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the examples. In the examples, "part" means "part by weight".

Example 1 8 parts of α-type titanyl phthalocyanine pigment and a commercially available butyral resin (trade name "S-REC B
H-3 "Sekisui Chemical Co., Ltd.) 4 parts was added to a mixed solvent composed of 300 parts of 1,1,2-trichloroethane and 200 parts of dichloromethane, and the resulting dispersion was dispersed to obtain a paint.
The charge generation layer was formed by coating so that the film thickness after drying would be 3000 angstroms.

Further, 8 parts of the compound of No. 1 which is a hole transporting substance and the following formula (I)

[0069]

[Chemical 4]

(In the formula, the ratio of a and b was confirmed by ¹ H-NMR measurement to be a: b = 86: 14.) 12 parts of polycarbonate and 3,5-bis-t-butyl 0.4 parts of -4-hydroxytoluene (BHT),
The coating material obtained by dissolving in a mixed solvent consisting of 43.2 parts of 1,1,2-trichloroethane and 64.8 parts of dichloromethane was applied on the charge generation layer so that the film thickness after drying would be 15 μm. Then, a photoconductor was prepared by forming a charge transport layer. This photosensitive member was used as a practical sample 1.

A photosensitive member obtained in the same manner as in Working Sample 1 was used as Comparative Sample 1 except that the No. 2 hole transporting material was used in place of the No. 1 hole transporting material. A photoreceptor obtained in the same manner as in Working Sample 1 was used as Comparative Sample 2 except that the No. 3 hole transporting material was used in place of the No. 1 hole transporting material.

The electrophotographic characteristics of the sample obtained above were evaluated using an electrostatic copying paper tester MODEL SP-428 (manufactured by Kawaguchi Electric Co., Ltd.). The measurement method was as follows. The photoconductor was attached to the apparatus, charged in a dark place by corona discharge with an applied voltage of -6 kV, and the surface potential immediately after charging was set to V ₀ , and used to evaluate the chargeability of the photoconductor. Next, the potential after standing in the dark for 10 seconds was measured and set to V _10, and the charge retention ability was evaluated by the V ₁₀ / V ₀ ratio. Then, in in light intensity on the photosensitive member surface 1 .mu.W / cm ^2, the surface potential after 15 seconds attenuate the surface potential of the photosensitive member by irradiating a monochromatic light having a wavelength of 778nm was measured, and the residual potential V _R did. The energy E _1/2 (half decay exposure amount) required to decay to half of the photoreceptor surface potential V _10, and the energy E ₁ required for decay of the value of 1/5 of the V _{10 The} sensitivity was evaluated by _{/ 5} . The measurement was performed at a temperature of 23 ° C. and a relative humidity of 50% R.V.
H. I went under the environment.

Further, the evaluation of the repeating characteristics of the photosensitive member was carried out by leaving it in the dark for 1 second, exposing for 1 second, and removing static electricity for 0.
By continuously applying electrostatic fatigue 100 times under the condition of 1 second, and measuring the values of V ₀ , V ₁₀ / V ₀ , V _R , E _1/2 , and E _1/5 immediately after the same in the same manner as described above. went. The results are shown in Table 3.

[0074]

[Table 3]

From this table, it can be seen that the photosensitive member using the charge transporting substance showing the "quasi-reversible system" electrode reaction shows a decrease in sensitivity (E _1/2 , E _1/5 ) and a residual potential (V _R ) does not increase and shows good characteristics, whereas the photoconductor using a charge-transporting substance that exhibits an "irreversible" electrode reaction causes a decrease in sensitivity and an increase in residual potential due to repeated use. It can be seen that the repeated stability is poor. Further, it can be seen from this that a method of examining the reaction form of the electrochemical redox electrode reaction is effective as a means for easily determining whether the repeated stability of the photoconductor is good or bad.

(Example 2) Thickness of anodized film
Is 5 μm and φ30 × 262 mm (wall thickness: 0.5 mm)
Α-type titanyl phthalocyanine on the surface of the minium cylinder
Pigment (oxidation potential E _OX= 1.23 Vvs. SCE) 8 copies
Commercially available butyral resin (trade name "ESREC BH-3")
Sekisui Chemical Co., Ltd.) 4 parts, 1,1,2-trichloro
Mixture of 300 parts ethane and 200 parts dichloromethane
In addition to the solvent, the paint obtained by dispersing with a sand mill is dried.
Coating so that the film thickness after drying is 3000 angstroms
Cloth was formed to form a charge generation layer.

Further, the compound of No. 1 which is a hole-transporting substance (reaction form: "quasi-reversible"; oxidation potential E _OX = O.97 Vv
s. SCE) 8 parts and the following formula (I)

[0078]

[Chemical 5]

(In the formula, the ratio of a and b was confirmed by ¹ H-NMR measurement to be a: b = 86: 14.) 12 parts of polycarbonate and 3,5-bis-t-butyl 0.4 parts of -4-hydroxytoluene (BHT),
The coating material obtained by dissolving in a mixed solvent consisting of 43.2 parts of 1,1,2-trichloroethane and 64.8 parts of dichloromethane was applied on the charge generation layer so that the film thickness after drying was 22 μm. Then, a photoconductor was prepared by forming a charge transport layer. This photoconductor was used as a practical sample 2.

The following formula instead of No. 1

[0081]

[Chemical 6]

A comparative sample 3 was prepared as a photoconductor prepared under the same conditions as in the practical sample 2 except that the hole transporting material represented by No. 4 and the compound of No. 4 were used.

The compound of No. 4 exhibits a "quasi-reversible" electrochemical redox electrode reaction, and the peak potential of the first oxidation wave is E _OX = 1.03 (Vvs.SCE). It was

Therefore, the electrophotographic characteristics of these samples were evaluated using a laser beam page printer having a process speed of 3770 mm / min. However, the photoconductor surface potential (initial potential) immediately after corona discharge from the scorotron
At room temperature and normal humidity (23 ° C./50% RH), V ₀ = −460
V, the exposure for measuring the photosensitivity was 0.6 mW (0.5 m on the surface of the photoconductor) with a semiconductor laser having a wavelength of 780 nm.
W) was used.

Generally, under the environment of temperature 33 ° C. and relative humidity of 85% RH, which is the environment in which the variation of the repetitive potential characteristics of the electrophotographic photosensitive member is the largest, the cycle is 1,500 cycles, 3,000 cycles, and 4,500 cycles. The stability of the potential immediately after the cycle was evaluated. The results are shown in Table 5.
In Table 5, V ₀ represents an unexposed potential (charging ability), V _L represents a 100% exposure potential (sensitivity potential), and V _R represents a residual potential.

[0086]

[Table 4]

From this table, it can be seen that even in the case of a photoconductor using a charge transporting substance exhibiting a "quasi-reversible system" electrode reaction, the difference in the oxidation potential value of the charge generating substance in the photoconductive layer is 0.
A photoreceptor containing a charge-transporting substance having an oxidation potential value of 2 (V) or less shows a tendency that the sensitivity decreases with repeated use thereof, and the residual potential rises, resulting in a repetition failure. It turns out that it becomes a stable photoconductor.

Therefore, in order to improve the repeated stability, the charge transport material contained in the photoconductive layer exhibits a "reversible" or "quasi-reversible" electrode reaction, and the oxidation potential α (V ), The limit oxidation potential β (V) of the compatible charge transport material is

[0089]

(3) β <α-0.2

It can be seen that it is necessary to be

[0091]

According to the present invention, it is possible to repeatedly and stably provide a high-quality output print image from a copying machine, an LD printer, an LED printer, an LCD printer or the like in all environments of low temperature and low humidity to high temperature and high humidity.

[Brief description of drawings]

FIG. 1 is a schematic view of a three-electrode type electrolytic cell used for cyclic voltammetry.

[Explanation of symbols]

 1 Platinum Working Electrode 2 Platinum Counter Electrode 3 Calomel Reference Electrode 4 3 Electrode Electrolytic Cell 5 Electrolyte 6 G4 Sintered Glass 7 Agar Salt Bridge 8 Saturated Potassium Chloride Aqueous Solution

FIG. 2 is a cyclic voltammgram of α-type titanyl phthalocyanine.

FIG. 3 is a cyclic voltammgram of β-type titanyl phthalocyanine.

FIG. 4 is a cyclic voltammgram of X-type metal-free phthalocyanine.

FIG. 5 is a cyclic voltamgram of No. 1 charge transport material.

FIG. 6 is a cyclic voltammgram of charge transport material No. 2.

FIG. 7 is a cyclic voltammgram of charge transport substance No. 3.

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[Procedure amendment]

[Submission date] July 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0050

[Correction method] Change

[Correction content]

Examples of the hole-transporting substance include the above-mentioned Exemplified Compound No. 1 and the like. In addition to this, the electrochemical redox electrode reaction is “reversible” due to the shape of the Cyclec voltamgram. Hole transport materials that are recognized as "quasi-reversible" electrode reactions are preferred.

Claims (3)

[Claims] 1. An electrophotographic photosensitive member having a photoconductive layer containing a charge-generating substance and a charge-transporting substance on a conductive support, wherein the charge-transporting substance is a "reversible" or "quasi-reversible" electricity. An electrophotographic photoreceptor characterized by being a material exhibiting a chemical redox electrode reaction. 2. The electrophotographic photosensitive member according to claim 1, which has a photoconductive layer comprising at least a charge generation layer and a charge transport layer on a conductive support. 3. When the oxidation potential of the charge generating substance is α (V), the limit oxidation potential β (V) of the compatible charge transporting substance.
Is in the range of α-0.5 ≦ β <α-0.2, and the electrophotographic photosensitive member according to claim 1 or 2, wherein