JP3287530B2 - Electrophotographic photoreceptor, process cartridge and electrophotographic apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photoreceptor,
More specifically, the present invention relates to an electrophotographic photosensitive member having a photosensitive layer containing a specific resin, a process cartridge having the electrophotographic photosensitive member, and an electrophotographic apparatus.

[0002]

2. Description of the Related Art An electrophotographic method is disclosed in U.S. Pat.
As shown in No. 1, a photoconductive material whose electrical resistance changes according to the amount of irradiation received during image exposure and which is made of a support coated with an insulating substance in a dark place is used. The basic characteristics required of an electrophotographic photoreceptor using this photoconductive material include (1) being able to be charged to an appropriate potential in a dark place, (2) being small in potential dissipation in a dark place, (3) Quickly dissipating the charge by light irradiation.

Hitherto, as an electrophotographic photoreceptor, an inorganic photoreceptor having a photosensitive layer mainly composed of an inorganic photoconductive compound such as selenium, zinc oxide, and cadmium sulfide has been widely used. However, they satisfy the conditions (1) to (3), but are not always satisfactory in heat stability, moisture resistance, durability, and productivity.

In order to overcome the disadvantages of inorganic photoconductors, electrophotographic photoconductors containing various organic photoconductive compounds as main components have been actively developed in recent years. For example, US Pat.
No. 851 discloses a photoreceptor having a charge transport layer containing triallylpyrazoline, and US Pat. No. 3,871,880 discloses a charge transport layer comprising a derivative of perylene pigment and a charge transport layer comprising a condensate of 3-propylene and formaldehyde. Are known.

Further, the photosensitive wavelength range of the electrophotographic photosensitive member can be freely selected depending on the organic photoconductive compound.
No. 2,754, JP-A-56-167759, which show high sensitivity in the visible region, are disclosed.
It is shown that the compound disclosed in JP-A-228453 has sensitivity up to the infrared region.

[0006] Of these materials, those exhibiting sensitivity in the infrared region are used in laser beam printers (hereinafter abbreviated as LBPs) and LED printers, which have been making remarkable progress in recent years.
The demand frequency is increasing.

Electrophotographic photoreceptors using these organic photoconductive compounds are function-separated type photoreceptors in which a charge transport layer and a charge generation layer are laminated in order to satisfy both electrical and mechanical properties. Often used. On the other hand, as a matter of course, the electrophotographic photoreceptor is required to have sensitivity, electrical characteristics, and optical characteristics according to the applied electrophotographic process.

In particular, in the case of an electrophotographic photosensitive member that is repeatedly used, an external electrical or mechanical force such as corona or direct charging, image exposure, toner development, a transfer process, and surface cleaning is directly applied to the surface of the electrophotographic photosensitive member. Therefore, durability for them is also required.

More specifically, electrical deterioration due to ozone and nitrogen oxides during charging, discharge during charging, mechanical deterioration in which the surface is worn or scratched due to rubbing of a cleaning member, Durability against mechanical deterioration is required.

[0010] The electrical degradation is particularly problematic in that a carrier stays in a portion irradiated with light and a potential difference is generated from a portion not irradiated with light, and this phenomenon occurs as a photo memory.

The mechanical deterioration is particularly different from the inorganic photoreceptor, and the organic photoreceptor having many soft materials is inferior in durability against the mechanical deterioration, and the improvement of the durability is particularly desired.

Various attempts have been made to satisfy the durability characteristics required for the photosensitive member as described above.

As a resin having good abrasion and electrical properties often used for the surface layer, attention has been paid to a polycarbonate resin having bisphenol A as a skeleton. However, not all of the above-mentioned problems can be solved. Has the following problems.

(1) Poor solubility, showing good solubility only in a part of halogenated aliphatic hydrocarbons such as dichloromethane and 1,2-dichloroethane, and since these solvents have a low boiling point, When a photoreceptor is manufactured using a coating solution prepared with these solvents, the coated surface tends to be whitened. It takes time to control the solid content of the coating liquid.

(2) Solvents other than halogenated aliphatic hydrocarbons are partially soluble in tetrahydrafuran, dioxane, cyclohexanenone or a mixed solvent thereof, but the solution gels in a few days. It is not suitable for photoreceptor manufacture because of poor aging properties.

(3) Even if the above (1) and (2) are further improved, solvent cracks are liable to occur in the polycarbonate resin having bisphenol A as a skeleton.

(4) In addition, in the case of a conventional polycarbonate resin, since a film formed of the resin does not have lubricity, the photosensitive member is easily damaged, and the image is not formed in a cleaning setting in which the abrasion amount of the electrophotographic photosensitive member is reduced. In some cases, the cleaning blade may be defective, defective cleaning may occur due to early deterioration of the cleaning blade, and toner fusion may occur.

Regarding the solution stability described in the above (1) and (2), a polycarbonate Z resin having a bulky cyclohexylene group as a polymer structural unit is used, or copolymerized with bisphenol Z, bisphenol C or the like. It has been solved by

Solvent cracks can also be solved by using a silicon-modified polycarbonate or an ether-modified polycarbonate as disclosed in JP-A-6-51544 and JP-A-6-75415. . However, these modified polycarbonates have a structure that has flexibility against internal stress in the polymer in order to prevent solvent cracks compared to conventional polycarbonate resins,
As a result, there is a disadvantage that the mechanical strength of the polymer body is reduced.

In recent years, a direct charging system in which a voltage is applied directly to a charging member and a charge is applied to an electrophotographic photosensitive member as disclosed in JP-A-57-17826 and JP-A-58-40566. Is becoming mainstream.

This is a method in which a roller-shaped charging member made of a conductive rubber or the like is brought into direct contact with an electrophotographic photosensitive member to apply a charge, and the amount of ozone generated is significantly smaller than that of a scorotron or the like. While the scorotron is wasted because about 80% of the current flowing through the charger flows through the shield, direct charging has the advantage that it is very economical without this waste.

However, direct charging has a drawback that charging stability is very poor because of charging by discharge according to Paschen's rule. As a countermeasure, a so-called AC / DC charging method in which an AC voltage is superimposed on a DC voltage has been devised (Japanese Patent Application Laid-Open No. 63-149668).

Although the charging method improved the stability during charging, the amount of discharge on the surface of the electrophotographic photosensitive member was greatly increased due to the superposition of AC, and the amount of scraping of the electrophotographic photosensitive member was increased. A new drawback arises that not only mechanical strength but also electrical strength is required.

[0024]

SUMMARY OF THE INVENTION The object of the present invention is to
An electrophotographic photoreceptor that solves the problem of having a conventional polycarbonate resin as the surface layer, has high mechanical strength with solvent crack resistance, and has good electrical resistance due to direct charging, and is easy to manufacture. It is to provide.

[0025]

That is, the present invention SUMMARY OF THE INVENTION The conductive support, an electrophotographic photosensitive member having a photosensitive layer, the electron
Photographic photoreceptor, direct charging means, image exposure means, developing means and
An electrophotographic photoreceptor for an electrophotographic apparatus having a transfer means, wherein the surface layer of the electrophotographic photoreceptor comprises one or more dihydric phenols represented by the following formula (1): And an electrophotographic photoreceptor comprising a branched polyester resin obtained by reacting a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group with an ester-forming compound.

[0026]

Embedded image (X is —CR ₄ R ₅ — (wherein R ₄ and R ₅ are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms);
An optionally substituted 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, a single bond, -O-, -S-, -SO-, or -SO ₂₋
There also, R _1, R ₂ each independently represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an aryl group, an alkylene group, a, b are each independently an integer of 0-4. )

Tables 1 and 2 show examples of the constitutional unit produced from the dihydric phenol represented by the formula (1) and the ester-forming compound, but are not limited thereto.

[0028]

[Table 1]

[0029]

[Table 2] Preferred examples include Structural Unit Examples 1, 2, 7, and 10, and Structural Units 1 and 7 are particularly preferred.

Further, Table 3 shows specific examples of the structural units of the polyfunctional organic compounds represented by the formulas (3) to (5).

[0031]

[Table 3] In the present invention, the branched polyester resin used is a dihydric phenol represented by the formula (1) and a compound represented by the formulas (3) to (3).
By stirring a branching agent represented by (5) with a mixture of terephthalic acid chloride and isophthalic acid chloride capable of having a structural unit represented by the formula (2) in a solvent / water system under alkali. Interfacial polymerization can be performed.

The ratio of terephthalic acid chloride and isophthalic acid chloride is determined in consideration of the solubility of the polymer and is not defined. However, any chloride is 30 mol%
Attention must be paid to the following, since the solubility of the synthesized polymer is extremely reduced. Usually, it is preferable to synthesize at a ratio of 1/1.

The branching agent is used in an amount of 0.01 to 3 mol% based on the dihydric phenol, particularly 0.05 to 2 mol%.
It is preferably used.

In the electrophotographic photoreceptor of the present invention, even if a polymer composed of the same structural unit formed from the dihydric phenol represented by the formula (1) and the ester-forming compound is used, two or more types of the formula It may be a copolymer comprising another kind of constituent unit produced from the dihydric phenol represented by (1) and an ester-forming compound.

Further, a copolymer with other general bisphenols such as bisphenol Z, bisphenol A, bisphenol C and bisphenol AF may be prepared in consideration of solubility during polymerization. However, in this case, equation (1)
The structural unit produced from the dihydric phenol and the ester-forming compound represented by the formula is 20 to 99 mol of the entire polymer.
%, More preferably 50 to 99 m
ol%.

The electrophotographic photoreceptor according to the present invention has particularly excellent solvent crack resistance, mechanical strength and electric resistance in AC charging, and has good electrophotographic characteristics.

The polymer according to the present invention is obtained by branching a polyester resin with a polyfunctional organic compound.
It has a dimensional mesh and durability.

It is presumed that the three-dimensional structure maintains the internal stress and does not cause cracks even if a chemical causing a solvent crack enters.

The mechanical strength is enhanced by taking a three-dimensional structure, and the same is applied to a polycarbonate resin.

Regarding the electric resistance, even if molecular breakage due to electrical degradation occurs due to the three-dimensional structure, it is difficult for a sharp decrease in film strength to occur, and the ester bond of the aryl group is more resistant to current due to AC charging than the carbonate bond. In particular, the electric resistance has been improved. The reason for this has not been confirmed, but it is presumed that the carbonate bond has a large dipole moment due to oxygen atoms on both sides of the carboxy group and is weak against electric energy.

It has also been found that the use of the aryl ester structure improves the matching with the charge transporting material and improves the memory characteristics.

The structure of the electrophotographic photosensitive member used in the present invention will be described below.

The electrophotographic photoreceptor of the present invention may be a single layer type in which the photosensitive layer contains a charge transporting material and a charge generating material in the same layer, or a laminated type in which the charge transporting layer and the charge generating layer are separated. Although good, the laminated type is preferable in terms of electrophotographic characteristics.

The conductive substrate to be used only needs to have conductivity, such as metals such as aluminum and stainless steel.
Alternatively, metal, paper, plastic, or the like provided with a conductive layer may be used, and the shape may be a sheet, a cylinder, or the like.

When the image input is a laser beam such as LBP, a conductive layer may be provided for the purpose of preventing interference fringes due to scattering or covering a scratch on the substrate. This can be formed by dispersing conductive powder such as carbon black and metal particles in a binder resin. The thickness of the conductive layer is 5
40 μm, preferably 10 to 30 μm is suitable. Then, an intermediate layer having an adhesive function is provided. Examples of the material of the intermediate layer include polyamide, polyvinyl alcohol, polyethylene oxide, ethyl cellulose, casein, polyurethane, and polyether urethane.
These are applied by dissolving in an appropriate solvent. The thickness of the intermediate layer is suitably 0.05 to 5 μm, preferably 0.3 to 1 μm.

The charge generation layer is formed on the intermediate layer.
Examples of the charge generating material used in the present invention include selenium-tellurium, pyrylium, thiapyrylium dyes, phthalocyanine, anthantrone, dibenzopyrene quinone, trisazo, cyanine, disazo, monoazo, indigo, quinacridone, and asymmetric quinocyanine pigments. Can be In the case of the function-separated type, the charge generation layer comprises a homogenizer, an ultrasonic dispersion, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, and a liquid collision with the charge generation material together with a binder resin and a solvent in an amount of 0.3 to 4 times. It is well dispersed by means such as a mold high-speed disperser, coated with a dispersion, and dried to form a dispersion. The thickness of the charge generation layer is 5 μm
Hereinafter, preferably, 0.1 to 2 μm is appropriate.

The charge transport layer is formed by coating and drying a coating material in which a charge transport material and a binder resin of the present invention are dissolved in a solvent. Examples of the charge transport material used include a triarylamine compound, a hydrazone compound,
Examples include a stilbene compound, a pyrazoline compound, an oxazole compound, a triallylmethane compound, and a thiazole compound.

These are combined with a binder resin in an amount of 0.5 to 2 times and applied and dried to form a charge transport layer. The thickness of the charge transport layer is 5 to 40 μm, preferably 15 to 30 μm.
μm is appropriate.

FIG. 1 shows a schematic configuration of an electrophotographic apparatus having a process cartridge having the electrophotographic photosensitive member of the present invention.

In FIG. 1, reference numeral 1 denotes a drum-shaped electrophotographic photosensitive member of the present invention, which is driven to rotate around a shaft 2 in a direction indicated by an arrow at a predetermined peripheral speed. The photoreceptor 1 rotates during the rotation process.
The peripheral surface is uniformly charged with a predetermined positive or negative voltage by the primary charging means 3 and then receives image exposure light 4 from image exposure means (not shown) such as slit exposure or laser beam scanning exposure. Thus, an electrostatic latent image is sequentially formed on the peripheral surface of the photoconductor 1.

The formed electrostatic latent image is then transferred to developing means 5
The toner-developed image developed by the above-described process is transferred to a transfer material 7 fed from a paper supply unit (not shown) between the photoconductor 1 and the transfer unit 6 in synchronization with the rotation of the photoconductor 1. The image is sequentially transferred by the transfer unit 6.

The transfer material 7 having undergone the image transfer is separated from the surface of the photoreceptor, introduced into the image fixing means 8 and subjected to image fixing, thereby being printed out of the apparatus as a copy.

After the transfer of the image, the surface of the photoreceptor 1 is cleaned by removing the untransferred toner by the cleaning means 9, and is further cleaned by a pre-exposure light 10 from a pre-exposure means (not shown).
Is used for image formation repeatedly after the charge removal processing. When the primary charging unit 3 is a contact charging unit using a charging roller or the like, the pre-exposure is not necessarily required.

In the present invention, a plurality of components such as the above-described electrophotographic photosensitive member 1, primary charging means 3, developing means 5, and cleaning means 9 are integrally connected as a process cartridge. The process cartridge, a copier, a laser beam printer, or another electrophotographic apparatus body may be configured to be detachable. For example, a process in which at least one of the primary charging unit 3, the developing unit 5, and the cleaning unit 9 is integrally supported together with the photoreceptor 1 to form a cartridge, and which can be attached to and detached from the apparatus main body by using guide means such as the rail 12 of the apparatus main body It can be a cartridge.

When the electrophotographic apparatus is a copying machine or a printer, the image exposure light 4 is reflected or transmitted from the original, or the original is read by a sensor and converted into a signal, and the exposure is performed according to the signal. Laser beam scanning,
Light emitted by driving the LED array, driving the liquid crystal shutter array, and the like.

On the other hand, when used as a facsimile printer, the image exposure light 4 becomes exposure light for printing received data. FIG. 2 is a block diagram showing an example of this case.

The controller 14 controls the image reading unit 13 and the printer 22. The entire controller 14 is controlled by the CPU 20. The read data from the image reading unit 13 is transmitted to the partner station through the transmission circuit 16. Data received from the partner station is sent to the printer 22 through the receiving circuit 15. Predetermined image data is stored in the image memory. The printer controller 21 controls the printer 22. 17 is a telephone.

The image received from the line 18 (image information from a remote terminal connected via the line) is demodulated by the receiving circuit 15 and then decoded by the CPU 20 to be sequentially stored in the image memory 19. Is done. When at least one page of the image is stored in the image memory 19, the image of the page is recorded. CPU 20
Reads out one page of image information from the image memory 19 and sends out the decoded one page of image information to the printer controller 21. When receiving the image information of one page from the CPU 20, the printer controller 21 controls the printer 22 to record the image information of the page. The CPU 20 is receiving the next page during recording by the printer 22.

Thus, the reception and recording of the image are performed.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following is a description of embodiments.

(Example 1) Diameter 30 mmφ, length 254
mm aluminum cylinder as a support,
A coating composed of the following materials was applied onto the support by dipping and thermally cured at 140 ° C. for 30 minutes to form a 15 μm conductive layer.

Conductive pigment: SnO ₂ coated barium sulfate 10 parts Resistance adjusting pigment: titanium oxide 2 parts Binder resin: phenol resin 6 parts Leveling agent: silicone oil 0.001 parts Solvent: methanol, methoxypropanol 0.2 / 0.8 20 parts Next, 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon were added thereto with 65 parts of methanol and 3 parts of n-butanol.
The solution dissolved in 0 parts of the mixed solvent was applied by dipping.
An intermediate layer of 5 μm was formed.

Next, the diffraction angles 2θ ± 0.2 ° in the X-ray diffraction spectrum of CuKα are 9.0 °, 14.2 °, 2
TiOPc having strong peaks at 3.9 ° and 27.1 °
4 parts and polyvinyl butyral (trade name: Eslec BM
2, 2 parts of Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone were dispersed in a sand mill using φ1 mm gas beads for 4 hours, and then 100 parts of ethyl acetate was added to prepare a dispersion for a charge generation layer. This is applied by dipping method.
A 3 μm charge generation layer was formed.

Next, 9 parts of an amine compound having the following structural formula

[0065]

Embedded image 1 part of amine compound of the following structural formula

[0066]

Embedded image And 10 parts of the polymer described in Condition 1 of Table 3 were dissolved in a mixed solvent of 30 parts of monochlorobenzene and 70 parts of dichloromethane.
This paint is applied by dipping and dried at 120 ° C. for 2 hours.
A μm charge transport layer was formed.

Next, the evaluation will be described.

The device is a Hewlett-Packard LBP
"Laser jet 4plus" (process speed 7
1 mm / sec). In the remodeling, primary charging was controlled by constant current control and constant voltage control. The produced electrophotographic photosensitive member was subjected to paper passing durability at 30 ° C. and 90% RH with this apparatus. The sequence was an intermittent mode in which the printing was stopped once for each print.

When the toner ran out, the toner was replenished and the image was durable until a problem occurred in the image. Further, the material was abraded for 15 minutes using a Taber abrasion tester using a polishing tape, and the weight loss at that time was measured.

Further, 3000 l of a part of the electrophotographic photosensitive member was
After 10 minutes of exposure to the light of a white fluorescent lamp, the bright portion potential was measured, and how much the bright portion potential had decreased before the light was applied was measured to obtain a photo memory value.

Further, regarding the solvent cracking property, a resin was adhered to the surface and left for 48 hours, and the presence or absence of solvent cracking was observed under a microscope.

Table 5 shows the results.

[0073]

[Table 4] The mixing ratio between terephthalic acid chloride and isophthalic acid chloride was 1: 1 in molar ratio.

(Example 2-12) An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that the binder of the charge transport layer used was one of the conditions 2 to 12 shown in Table 4. Table 5 shows the results.

[0075]

[Table 5] (Comparative Example 1-5) An electrophotographic photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the binder of the charge transport layer used was one of the conditions 1 to 3 in Table 6. Table 7 shows the results.

[0076]

[Table 6]

[0077]

[Table 7]

[0078]

As described above, the electrophotographic photoreceptor of the present invention has excellent solvent crack resistance and memory characteristics without impairing the mechanical strength, and further has high mechanical strength and direct charging. This makes it possible to provide an electrophotographic photoreceptor that has good electric resistance against electric discharge due to discharge and is suitable for direct charging that is easy to manufacture.

[Brief description of the drawings]

FIG. 1 is a process car having an electrophotographic photosensitive member of the present invention .
FIG. 2 is a diagram illustrating a schematic configuration of an electrophotographic apparatus having a cartridge.
You.

FIG. 2 shows a case where the electrophotographic apparatus of the present invention is a printer.
FIG. 2 is a block diagram showing a flow of received data and a control method.
You.

[Description of Signs] 1 Photoconductor 2 Shaft 3 Primary charging means 4 Image exposure light 5 Developing means 6 Transfer means 7 Transfer material 8 Image fixing means 9 Cleaning means 10 Pre-exposure light 11 Process cartridge 12 Rail

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-76619 (JP, A) JP-A-7-181706 (JP, A) JP-A-7-92703 (JP, A) 102055 (JP, A) JP-A-7-109349 (JP, A) JP-A-8-208815 (JP, A) JP-A-5-281772 (JP, A) JP-A-7-84376 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 5/00 CA (STN)

Claims (7)

(57) [Claims] 1. An electrophotographic photosensitive member having a conductive support and a photosensitive layer, comprising: an electrophotographic photosensitive member, a direct charging means,
For electrophotographic apparatus having optical means, developing means and transfer means
In the electrophotographic photoreceptor, the surface layer of the electrophotographic photosensitive member, and one or more dihydric phenols represented by the following formula (1), trifunctional or higher-functional organic having a phenolic hydroxyl group An electrophotographic photoreceptor comprising a branched polyester resin obtained by reacting a compound with an ester-forming compound. Embedded image (X is —CR ₄ R ₅ — (wherein R ₄ and R ₅ are each independently a hydrogen atom, a trifluoromethyl group, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms);
An optionally substituted 1,1-cycloalkylene group having 5 to 11 carbon atoms, an α, ω-alkylene group having 2 to 10 carbon atoms, a single bond, -O-, -S-, -SO-, or -SO ₂₋
There also, R _1, R ₂ each independently represent a hydrogen atom, a halogen atom, an optionally substituted alkyl group, an aryl group, an alkylene group, a, b are each independently an integer of 0-4. ) 2. The electrophotographic photosensitive member according to claim 1, wherein the surface layer of the electrophotographic photosensitive member contains a polymer having a structural unit represented by the following formula (2). Embedded image (R ₃ is a hydrogen atom, a halogen atom, an alkyl group which may be substituted, an aryl group, or an arylene group;
4 is an integer. ) 3. The electrophotographic photoreceptor, wherein the trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group contained in the surface layer has a structure represented by the following formula (3). 2. The electrophotographic photosensitive member according to claim 1. Embedded image 4. In the electrophotographic photoreceptor, the trifunctional or higher functional polyfunctional organic compound having a phenolic hydroxyl group contained in the surface layer has a structure represented by the following formula (4). 2. The electrophotographic photosensitive member according to claim 1. Embedded image 5. The electrophotographic photoreceptor, wherein the trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group contained in the surface layer has a structure represented by the following formula (5) . 2. The electrophotographic photosensitive member according to claim 1. Embedded image 6. A process cartridge which integrally supports an electrophotographic photosensitive member and a direct charging means and is detachable from an electrophotographic apparatus main body, wherein the electrophotographic photosensitive member has a surface layer represented by the following formula (1). Containing a branched polyester resin obtained by reacting one or more dihydric phenols and a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group with an ester-forming compound. A process cartridge characterized by being a body. Embedded image (X is —CR ₄ R ₅ — (where R ₄ and R ₅ are each independently
Hydrogen atom, trifluoromethyl group, alkyl having 1 to 6 carbon atoms
A kill group or an aryl group having 6 to 12 carbon atoms),
1,1-cycloal having 5 to 11 carbon atoms which may be substituted
A kylene group, an α, ω-alkylene group having 2 to 10 carbon atoms,
Bond, -O -, - S -, - SO-, or -SO ₂ - in
R ₁ and R ₂ each independently represent a hydrogen atom, a halogen
Atom, alkyl group which may be substituted, aryl group, al
A and b are each independently an integer of 0 to 4;
You. ) 7. An electrophotographic apparatus having an electrophotographic photoreceptor, a direct charging unit, an image exposing unit, a developing unit and a transfer unit, wherein the electrophotographic photoreceptor has a surface layer formed by the following formula (1). An electrophotographic photoreceptor containing a branched polyester resin obtained by reacting one or more polyhydric phenols with a trifunctional or higher polyfunctional organic compound having a phenolic hydroxyl group with an ester-forming compound. An electrophotographic apparatus, comprising: Embedded image (X is —CR ₄ R ₅ — (where R ₄ and R ₅ are each independently
Hydrogen atom, trifluoromethyl group, alkyl having 1 to 6 carbon atoms
A kill group or an aryl group having 6 to 12 carbon atoms),
1,1-cycloal having 5 to 11 carbon atoms which may be substituted
A kylene group, an α, ω-alkylene group having 2 to 10 carbon atoms,
Bond, -O -, - S -, - SO-, or -SO ₂ - in
R ₁ and R ₂ each independently represent a hydrogen atom, a halogen
Atom, alkyl group which may be substituted, aryl group, al
A and b are each independently an integer of 0 to 4;
You. )