JP2000122315A - Electrophotographic photoreceptor and electrophotographic image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make recordable image information at a high density and to make outputtable it as an image having high image quality. SOLUTION: A photosensitive layer 13 comprising successively laminated an electric charge generating layer 13a and an electric charge transport layer 13b is laminated on an electrically conductive substrate 1 by way of an intermediate layer 12. The electric capacity of the photosensitive layer 13 is >=160 pF/cm2. When an image is formed, the photosensitive layer 13 is electrified to >=8×10-8 C/cm2 surface charge density and a latent image is formed at a high density of >=1,200 dpi. This latent image is made visible by a reversal developing method using a toner of <=6 μm average particle diameter.

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 electrophotographic image forming apparatus such as a printer, a digital copying machine, a facsimile, etc., and an electrophotographic image forming method using the electrophotographic photosensitive member. .

[0002]

2. Description of the Related Art An electrophotographic image forming method represented by the Carlson method is capable of forming a high-quality image at a high speed (high-speed recording) and has no impact (non-impact). To have advantages,
It is widely used in image forming apparatuses such as copying machines, printers, and facsimile machines. In this electrophotographic image forming method,
A photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated is used to form an image using an electrophotographic photosensitive member laminated on a conductive support.

In the electrophotographic image forming method, first, a photosensitive layer of an electrophotographic photosensitive member is uniformly charged, an image is formed by exposing the charged photosensitive layer to an image, and image information is recorded. The latent image formed on the photosensitive layer is visualized by developing with a toner. The toner image formed on the photosensitive layer is fixed after being transferred to plain paper.

In recent years, with the digitization of image information, etc.,
Instead of conventional white light, semiconductor laser or LE
Image information is recorded by exposing a photosensitive layer with a semiconductor laser beam or an LED array beam using a D array as a recording light source. At present, a near-infrared light of 780 nm or a red light source of 650 nm is most often used as an exposure light source for the photosensitive layer.

When information such as characters is directly used as computer output, digitized image information is recorded on a photoreceptor by output information of a computer converted into an optical signal. When the image information of the original is input, the image information of the original is read as optical information, converted into a digital electric signal, then converted again into an optical signal, and the optical signal is used to convert the image information on the photoconductor. Is recorded.

[0006] In any case, image information is recorded on the photosensitive layer by a minute light spot irradiated on the photosensitive layer from an optical recording head, a recording optical system, or the like.
The portion irradiated with the light spot is developed by the toner. An image is represented by a set and arrangement of small dots called pixels developed by toner. For this reason, the resolution of optical recording heads, recording optical systems, and the like has been increased so that spots as small as possible can be formed so that image information can be recorded at high density.

As for the optical system for recording image information on the photosensitive layer, a variable spot laser recording method (O plus E 1996)
May), multi-laser beam recording method, 1200dpi L
ED print heads, ultra-precision and ultra-high-speed polygon mirrors (Japan Hardcopy '96, etc.) have been developed.
As a result, at present, 1200 dpi (dot / dot)
inch: the number of dots per inch)
Image information can be recorded on the photosensitive layer.

However, even if the image information is recorded on the photosensitive layer at a high density, it is not always easy to develop the recorded image information with toner with good reproducibility. It is required to be obtained.

In order to improve the quality of the formed toner image, it is important to reduce the particle size of the toner particles and to minimize scattering of the toner during development or transfer. It is also important to perform image processing so as to conform to image reproduction characteristics in electrophotography.

Japanese Patent No. 2696400 describes a method of exposing a digital image to a photoreceptor at a recording density of 600 dpi or more to form an image with a toner having a particle diameter of 8 μm or less. However, in digital image recording with a high resolution of 1200 dpi or more, simply specifying the weight average particle diameter of the toner to be used can faithfully reproduce an electrostatic latent image formed at a high recording density on a photoconductor. It is difficult. In particular, when a toner having a particle diameter larger than a predetermined weight average particle diameter is present, the resolution is significantly deteriorated. In addition, since the toner having a small particle diameter has a large charge amount distribution, the resolution may be reduced. Further, it is necessary that the recording density of the electrophotographic photoreceptor used does not deteriorate over time.

The image quality of an image viewed by the human eye is determined by the synergistic effect of the image resolution and the gradation. Printed materials such as art books have a resolution of only about 200 dpi, but 256
Since the image is expressed by gradation, a high quality image is obtained. It is said that the human eye has a resolution of 300 dpi and the ability to detect 64 levels of density.The expression method using area gradation requires a high resolution to obtain a high-quality image. With the gradation expression method, a high-quality image can be obtained even at a low resolution. Therefore, it is important in the electrophotographic image forming method to consider the balance between the two. Considering the temporal stability of image quality, environmental stability, etc., and the instability of halftone density in the electrophotographic image forming method, stable resolution is achieved by increasing the resolution in the former area gradation by area gradation. High image quality can be realized.

In a paper entitled "Enhancing the Quality of Electrophotography ... Digital Recording Technology" published in the Journal of the Institute of Electrophotography, Vol. 26, No. 1 (1987), a pulse width modulation method was used as a multilevel output method of a laser. When used, the peak value of the light energy distribution decreases, and the distribution takes on the intensity modulation characteristic. Therefore, the latent image potential distribution in the electrophotographic photoreceptor is defined as the difference between the dark charging potential and the light surface potential. It is described that it shows an intermediate value. Therefore, the higher the resolution and multi-value recording, the higher the sensitivity and the higher the resolution of the electrophotographic photosensitive member.

However, 400 dpi-
At a recording density of 600 dpi, sufficient resolution can be obtained even with the thickness of the photosensitive layer in the used electrophotographic photoreceptor, and resolution degradation due to charge diffusion depending on the thickness of the photosensitive layer does not matter. In addition, the resolution of the electrophotographic photosensitive member itself, particularly the resolution of the electrophotographic photosensitive member related to the recording method, is hardly considered. For example, JP-A-3-11353, JP-A-3-63653, JP-A-3-
87749, JP-A-3-56966, JP-A-6-301224
JP-A-7-244388, JP-A-7-261415, and the like, in order to increase the sensitivity and long life of the electrophotographic photoreceptor, by increasing the thickness of the photosensitive layer, the electrophotographic photosensitive Consideration has been given to reducing the electrical capacity of the body. Therefore, in such an electrophotographic photosensitive member, when information is recorded at a high density, a high-quality image cannot be obtained.

For an electrophotographic photosensitive member for digital images, 78
It is required to have high sensitivity to near-infrared light of 0 nm and red light source of 650 nm, and crystalline phthalocyanine-based compounds have been put to practical use. For example, patent registration 20736
No. 96 discloses a photoreceptor using titanyl phthalocyanine, and Japanese Patent Publication No. 59-155851 discloses a photoreceptor using β-type indium phthalocyanine.

Further, JP-A-61-28557 discloses a photoreceptor using vanadium phthalocyanine.
In particular, it has been reported that various crystalline systems exist in crystalline titanyl phthalocyanine, and there are large differences in chargeability, dark decay, sensitivity, and the like depending on the crystal systems. For example, Japanese Patent No. 2007449 discloses an α-type crystal,
Japanese Patent No. 1917796 discloses an A-type crystal, Japanese Patent No. 1876697 and Japanese Patent No. 1997269 describe a C-type crystal, Japanese Patent No. 1950255 and Japanese Patent No. 2128593 a Y-type crystal, and Japanese Patent Publication No. 7-15067. The publication discloses a Ma type crystal,
Patent registration 2502404 discloses an I-type crystal and a patent registration 1978469.
In the publication, M-type crystals are disclosed. Further, Japanese Patent No. 2700859 and Japanese Patent Application Laid-Open No. Hei 8-209023 disclose crystals which are basically classified into Y type.

[0016]

In order to further improve the quality of a digital image, a high-sensitivity photoreceptor capable of faithfully reproducing image information recorded at a high density of 1500 to 2400 dpi is required. . At the current recording density of 600 dpi or less, the surface charge density of a photoreceptor that has been put into practical use depends on factors such as the sensitivity required for the photoreceptor and printing durability (life). 4 × at surface potential of 500 to 800 V
The density is set to about 10 ⁻⁸ to 8 × 10 ⁻⁸ C / cm ² , and the latent image formed on the photosensitive layer does not pose any particular problem with respect to the reproducibility of the recording density. However, for example, 1500
When a latent image having a resolution of dpi or more is formed,
With a photoreceptor having a surface charge density of 8 × 10 ⁻⁸ C / cm ² or less, it is not easy to reproduce a latent image at that resolution. In such a photosensitive member having a small surface charge density, charge diffusion occurs due to charge traveling in the photosensitive layer, and the resolution of a latent image may be degraded. The diffusion of the charge is simulated to be about 30 μm when the thickness of the photosensitive layer is 35 μm and the surface charge density is 4 × 10 ⁻⁸ C / cm ² , which deteriorates the latent image.

In a photoreceptor requiring high resolution, in order to prevent the resolution from being deteriorated when forming a latent image, the surface charge density is increased, and the deterioration of the latent image due to the diffusion of the charge does not pose a problem. Thus, the thickness of the photosensitive layer may be reduced. However, when the surface charge density increases, the electric field applied to the photosensitive layer increases, so that the pressure resistance decreases, and a new problem arises in that the effective sensitivity decreases with an increase in the surface charge amount. When the pressure resistance of the photosensitive layer decreases, minute image defects occur in reversal development. Further, when the sensitivity of the photosensitive layer is reduced, the potential contrast is reduced. Therefore, it is necessary to increase the surface potential and the output of the recording light source to secure a predetermined image density.

An example of a high-resolution electrophotographic photosensitive member is an a-Si photosensitive member having an absolute sensitivity of 0.1 μJ / cm ² , and an organic photosensitive member has such a high sensitivity characteristic. Not obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances. In an electrophotographic image forming method, the surface charge density of a photoreceptor, the thickness of a photosensitive layer, the gradation expression method, the recording dot diameter, and the like are determined. The present inventors have made intensive studies and learned the relationship between the optimum recording dot diameter and the photoreceptor for improving the image quality, and completed the present invention.

An object of the present invention is to provide a semiconductor laser and an LED.
In an electrophotographic image forming method using an array or the like as a recording light source, a high-sensitivity electrophotographic photosensitive member capable of obtaining a high-quality image without fear of deteriorating the recording density, and using the electrophotographic photosensitive member To provide an electrophotographic image forming method.

[0021]

In the electrophotographic photoreceptor of the present invention, a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated is laminated on a conductive support, and the photosensitive layer is charged. Forming an electrostatic latent image by exposing the image to a latent image, and visualizing the latent image by a reversal developing method. Is 160 pF / cm ² or more, and the photosensitive layer is charged to a surface charge density of 8 × 10 ⁻⁸ C / cm ² or more, so that a latent image is formed at a high density of 1200 dpi or more. It is characterized by becoming.

The charge generation layer contains oxotitanyl phthalocyanine. The oxotitanyl phthalocyanine has a Bragg angle 2θ of at least 9.4 ± 0 in the X-ray diffraction spectrum of CuKα characteristic X-ray.
At 2 °, 9.6 ± 0.2 ° and 27.2 ± 0.2 °, they show major intense diffraction lines, respectively, and 7.3 ± 0.2 °, 1
In the case of 1.6 ± 0.2 ° and 24.1 ± 0.2 °, the crystal structures show relatively strong diffraction lines, respectively.

[0023] The oxotitanyl phthalocyanine is Cu
In the X-ray diffraction spectrum for the K α characteristic X-ray, the Bragg angle 2θ is at least 9.1 ± 0.2 °, 9.4 ± 0.
The crystal structure shows major intense diffraction lines at 2 °, 9.6 ± 0.2 °, and 27.2 ± 0.2 °, respectively.

An intermediate layer for preventing charge injection is provided between the conductive support and the photosensitive layer.

The intermediate layer comprises a resin layer obtained by dispersing 30 to 50% by weight of rutile type titanium oxide crystals in a polyamide resin.

The charge transport layer contains a charge material having an enamine structure represented by the following structural formula (1).

[0027]

Embedded image

However, Ar represents an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, And n is 2,
Either 3 or 4.

The charge transport layer has a viscosity average molecular weight of 3
5,000 to 85,000, which contains a binder resin mainly composed of a polycarbonate resin having the following structural formula (2).

[0030]

Embedded image

Wherein R _{1 to} R ₄ represent any of hydrogen, halogen, and an alkyl group having 1 to 4 carbon atoms;
Represents a group of atoms necessary to form a substituted or unsubstituted carbon ring or a substituted or unsubstituted heterocyclic ring.

The charge transport layer has the following structural formula (3):
The antioxidant having any of (4) and (5) is contained in the charge transporting material in a weight ratio of 5/1000 to 50/1000.

[0033]

Embedded image

[0034]

Embedded image

[0035]

Embedded image

The photosensitive layer has an absolute sensitivity to a recording wavelength of 780 nm of 0.15 .mu.J / a half-exposure energy value required to attenuate the surface potential from -500 V to -250 V.
cm ² or less.

According to the electrophotographic image forming method of the present invention, a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated is laminated on a conductive support, and the capacitance of the photosensitive layer is 160 pF /
an electrophotographic image forming method using the electrophotographic photoreceptor becomes cm ² or more, and charged so as the photosensitive layer becomes 8 × 10 ^-8 C / cm ² or more surface charge density, 1200 dpi After the latent image is formed at the above high density, the latent image is visualized by a reversal developing method using a toner having an average particle diameter of 6 μm or less.

In the toner, the standard deviation with respect to the average particle diameter is 30% or less of the average value, and the ratio of the toner having a particle diameter outside the standard deviation is less than 10%.

[0039]

Embodiments of the present invention will be described below in detail.

FIG. 1 is a perspective view showing an example of an embodiment of the electrophotographic photoreceptor of the present invention, and FIG. 2 is a sectional view of a main part thereof. The electrophotographic photoreceptor 10 has a photosensitive layer 1 on an outer peripheral surface of a cylindrical conductive support 11 via an intermediate layer 12.
3 are stacked. The photosensitive layer 13a includes a charge generation layer 13a stacked on the intermediate layer 12, and a charge transport layer 13b stacked on the charge generation layer 13a.

As the conductive support 11, for example, aluminum, aluminum alloy, stainless steel, iron, gold,
Metallic materials such as silver, copper, zinc, nickel, and titanium, aluminum, gold, silver, copper, nickel, indium oxide, tin oxide, and other plastic substrates, polyester films, paper, or plastics containing conductive particles Paper, plastic containing a conductive polymer, or the like can be used.

The intermediate layer 12 provided between the conductive support 11 and the charge generation layer 13a is constituted by a resin layer in which a rutile type titanium oxide crystal is dispersed in a polyamide resin.

The rutile-type titanium oxide crystal may be either a surface-treated one or an untreated one.
The shape may be spherical, acicular, or irregular. As the polyamide resin, alcohol-soluble nylon is preferable. For example, so-called copolymerized nylon obtained by copolymerizing 6-nylon, 66-nylon, 610-nylon, 11-nylon, 12-nylon, etc., and N-alkoxyethyl modified nylon A material obtained by chemically modifying nylon can be used. The intermediate layer 12 is formed by mixing a polyamide resin and rutile-type titanium oxide crystal particles in an organic solvent using a ball mill,
The coating liquid obtained by dispersing with a device such as a sand grinder or a paint shaker is applied to the conductive support 1.
1 is formed by coating. The method of applying the coating liquid to the conductive support 11 is such that the raw material of the conductive support 11 is in the form of a sheet, the coating liquid is applied to the sheet-like member to form the intermediate layer 12, and then the sheet-like member is formed. When the conductive support 11 is formed by winding, the sheet-like member is coated with a baker applicator, a bar coater, or the like. When the conductive support 11 is formed in a drum shape in advance, a coating liquid is applied by a spray method, a vertical ring method, a dip coating method, or the like. In general,
Since the apparatus is simple, an immersion coating method in which the conductive support 11 formed in a drum shape in advance is immersed in an application liquid and applied is adopted. The thickness of the intermediate layer 12 is 0.01 μm
To 20 μm, more preferably 0.05 μm to 10 μm.

Charge generation layer 13 laminated on intermediate layer 12
As a, crystalline oxotitanyl phthalocyanine is preferable. In particular, as shown in FIG. 3, in the X-ray diffraction spectrum of CuKα characteristic X-ray (wavelength: 1.5418 angstroms), its Bragg angle (2θ) is at least 9.4. In the case of ± 0.2 °, 9.6 ± 0.2 °, and 27.2 ± 0.2 °, each shows a strong diffraction line, and the Bragg angle (2θ) is at least 24.1 ± 0.2 °, 11.6 ±
In the case of 0.2 ° and 7.3 ± 0.2 °, those having a crystal structure showing diffraction lines, respectively, or as shown in FIG. 4, the Bragg angles (2θ) are at least 9.1 ± 0.2 °, 9.4
Particularly preferred are those having a crystal structure that shows comparable strong diffraction lines at ± 0.2 °, 9.6 ± 0.2 °, and 27.2 ± 0.2 °.

As described above, the difference in the characteristics of the photosensitive layer due to the difference in the crystal structure measured as the relative intensity ratio of the diffraction lines is as follows.
It is thought to be based on the difference in molecular arrangement in the crystal lattice. In order to obtain a photosensitive layer having excellent characteristics, the order of molecular arrangement over a long distance region is good, and the lamination mode of molecules in a short distance region (between the nearest neighbor molecules) is limited. Is preferably a crystalline material that has little or no effect due to the dimerization mode of the molecules.

The charge generation layer 13a is generally produced by applying a coating solution obtained by adding an organic solvent to fine particles of a phthalocyanine compound and dispersing the same using the same apparatus as used for the intermediate layer 12.

In order to increase the binding property, for example, a polyester resin, a polyester resin,
Polyvinyl acetate, polyacrylate, polycarbonate, polyarylate, polyvinyl acetoacetal, polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin,
Various binder resins such as melamine resin, silicone resin, acrylic resin, cellulose ester, cellulose ether, and vinyl chloride-vinyl acetate copolymer resin may be added. The thickness of the charge generation layer 13a is generally 0.05 μm to
5 μm, preferably 0.1 to 1 μm is suitable. Also,
If necessary, the charge generating layer 13a may contain various additives such as a leveling agent, an antioxidant, and a sensitizer for improving applicability.

The charge transport layer 13b laminated on the charge generation layer 13a is mainly composed of a charge transport material and a binder resin. As the charge transport substance, a compound having an enamine structure represented by the following structural formula (1) is particularly suitable because of its excellent charge injection efficiency.

[0049]

Embedded image

However, Ar may be an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, or an aryl group which may have a substituent. And n is any one of 2, 3 or 4. Further, not limited to compounds having such an enamine structure, 2,4,7-trinitrofluorenone,
Electron withdrawing substances such as tetracyanoquinodimethane, carbazole, indoleimidazole oxazole, pyrazole, oxadiazole, pyrazoline, heterocyclic compounds such as thiazole, aniline derivatives, hydrazone compounds,
Aromatic amine derivatives, styryl compounds and the like can also be used. These charge transporting materials may be used alone, or a plurality of materials may be mixed and used. Charge transport layer 1
3b is formed with the charge transport material bound to the binder resin. As the binder resin used for the charge transport layer 13b, a polycarbonate resin represented by the following structural formula (2) and having a viscosity average molecular weight of 35,000 to 85,000 is particularly preferable.

[0051]

Embedded image

Wherein R _{1 to} R ₄ represent hydrogen, halogen, or an alkyl group having 1 to 4 carbon atoms, and Z forms a substituted or unsubstituted carbon ring or a substituted or unsubstituted heterocyclic ring. Represents the group of atoms required for

The binder resin is not limited to this, and examples thereof include vinyl polymers or vinyl copolymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, polyester, polyester carbonate, polyarylate, polysulfone, polyimide, and the like. Phenoxy, epoxy, silicone resins and the like can also be used. Further, these partially crosslinked cured products can also be used. These resins may be used alone or in combination of two or more.

The ratio between the binder resin and the charge transport material is as follows:
Usually, the charge transporting material is used in an amount of 30 to 200 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The charge transport layer 13b is formed by being applied on the charge generation layer 13a by the same device as that used when forming the intermediate layer 12.

Charge transport layer 13b and charge generation layer 13a
Is preferably at least 160 pF / cm ² or more.

It is preferable that the charge transport layer 13b contains, in particular, vitamin E, hydroquinone, a hydroxytoluene compound, etc., because the potential characteristics are remarkably stabilized. In order to improve film formability, flexibility, applicability, and the like, for example, the following structural formulas (3), (4), and (5)
It is preferable to contain the antioxidants represented by the formulas in a ratio of 5/1000 to 50/1000 by weight with respect to the charge transporting material.

[0057]

Embedded image

[0058]

Embedded image

[0059]

Embedded image

Further, additives such as well-known plasticizers, ultraviolet absorbers and leveling agents may be contained.

The electrophotographic photoreceptor of the present invention is incorporated in an image forming apparatus for forming an image by a usual electrophotographic image forming method, and forms an image. When an image is formed by an electrophotographic image forming method, first, the photosensitive layer 13 of the electrophotographic photosensitive member 10 is uniformly charged, and image information is exposed on the charged photosensitive layer 13. As a result, the image information is recorded on the photosensitive layer 13 as a latent image. Next, the latent image formed on the photosensitive layer 13 is developed with toner, and the developed toner image is transferred and fixed on plain paper. Thus, a toner image is formed on plain paper.

Electrophotographic photoreceptor 10 onto which toner image has been transferred
Usually, after the toner on the surface of the photosensitive layer is removed by a cleaning process, the surface of the photosensitive layer is neutralized by a neutralization process.

The photosensitive layer may be charged by any method such as corotron charging using corona discharge, scorotron charging, and contact charging using a conductive roller or brush. In the charging method using corona discharge,
In order to keep the dark portion potential in the photosensitive layer constant, it is generally employed, and in particular, scorotron charging is frequently used.

The recording of image information on the photosensitive layer is usually performed by
The exposure is performed by adjusting the beam diameter of an exposure light source such as a semiconductor laser having a main energy peak at 600 to 850 nm to a predetermined beam diameter by an optical system and exposing the photosensitive layer.

The latent image formed on the photosensitive layer is brought into contact with a magnetic or non-magnetic one-component developer or a two-component developer having a small particle diameter of 6 μm or less, or in a non-contact manner. Developed. In either case, a reversal developing method of developing a light-area potential irradiated with light is adopted. In order to obtain a high-resolution and high-gradation image, even a small-particle toner having a particle diameter of 6 μm or less preferably has a narrow particle size distribution width, and the standard deviation of the average particle diameter is It is particularly preferred that the proportion of toner having a particle diameter of 30% or less and deviating from its standard deviation is less than 10%.

The method of transferring the toner image on the photosensitive layer to plain paper includes a method using corona discharge, a method using a transfer roller, and the like, and any method may be used. For fixing the toner image to plain paper, generally used heat fixing, pressure fixing and the like are employed.

[0067]

Embodiments of the present invention will be described below.

<Example 1> 72.6 parts by weight of titanium oxide (trade name "STR-60NN" manufactured by Sakai Chemical Co., Ltd.) and 107.4 parts by weight of copolymerized nylon (trade name "Amilan CM8000" manufactured by Toray Industries, Inc.) 287 parts by weight methyl alcohol and 533 parts by weight
In addition to a mixed solvent with 1,2-dichloroethane, the mixture was mixed with a paint shaker for 8 hours to prepare a coating solution for forming an intermediate layer. The tank was filled with the obtained coating solution for forming an intermediate layer, and a cylindrical aluminum conductive support having a diameter of 65 mm and a length of 322 mm was immersed in the coating solution for forming an intermediate layer in the tank and then pulled up. Then, a coating solution for forming an intermediate layer was applied to the outer peripheral surface of the cylindrical conductive support. afterwards,
The coating liquid for forming an intermediate layer was dried at a temperature of 110 ° C. for 10 minutes to form an intermediate layer having a thickness of 1.5 μm on the conductive support.

Next, CuKα characteristic X
In the X-ray diffraction spectrum for the X-ray (wavelength: 1.5418 Å), the Bragg angle (2θ) was 9.4 ± 0.2.
°, 9.6 ± 0.2 °, 27.2 ± 0.2 ° shows the main strong diffraction line respectively, and 24.1 ± 0.2 °, 11.6 ± 0.
Diffraction lines are shown at 2 ° and 7.3 ± 0.2 °, respectively (see FIG. 3).
Parts by weight, 1 part by weight of polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., trade name: "S-LEC BL-1") and 97 parts by weight of methyl ethyl ketone were mixed for 1 hour with a paint shaker, and a coating solution for forming a charge generation layer was mixed. Was prepared. This coating solution was filled in a tank, and a cylindrical aluminum conductive support having an intermediate layer formed thereon was immersed in the tank and then pulled up to apply a charge generating layer forming coating solution on the intermediate layer. Then, the coating liquid for forming a charge generation layer applied at a temperature of 80 ° C. for 1 hour is dried to a thickness of 0.5 μm.
m of the charge generation layer was formed.

Further, 1 part by weight of an enamine compound represented by the following structural formula (6) as a charge transporting material and 1 part by weight of polycarbonate (trade name “PCZ-400” manufactured by Mitsubishi Gas Chemical Company) as a binder. And dichloromethane 8
It was dissolved in parts by weight to prepare a charge transport layer coating solution.

[0071]

Embedded image

This coating solution was dip-coated on the charge generating layer of the conductive support having the intermediate layer and the charge generating layer formed thereon in the same manner as the intermediate layer and the charge generating layer. For 1 hour to form a charge transport layer having a thickness of 16 μm. Thus, an electrophotographic photosensitive member as shown in FIG. 1 was obtained. The electric capacity of the obtained electrophotographic photosensitive member was 200 pF / cm ² .

The electrophotographic photosensitive member produced was evaluated for electrophotographic characteristics by an electrostatic recording paper tester (trade name “EPA-8200” manufactured by Kawaguchi Electric). The measurement conditions are as follows: applied voltage is -6 kV,
Static was N0.3, and monochromatic light of 780 nm (irradiation light: ² μW / cm ² ), which was separated by an interference filter, was used as exposure light. The surface charge density (C / cm ² ) when the surface potential of the photoreceptor is -500 V, the exposure amount E _1/2 (μJ / cm ² ) required to attenuate the surface potential to -250 V, and The initial potential V ₀ (−volt) was measured.

The surface charge density of the obtained electrophotographic photosensitive member was 10 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy value was 0.06 μJ / cm ² , which was extremely high sensitivity. Table 1 shows the results.

Further, a commercially available digital copying machine (manufactured by Sharp Corp., trade name "AR5130") was modified to incorporate the manufactured electrophotographic photosensitive member, and a continuous blank copy (Non Copy Agin) was performed.
g) is performed 40,000 times, before and after the initial potential V ₀ is measured, and the electrostatic recording paper test device is used to measure
The amount of exposure E _1/2 required for optically attenuating the surface potential to -250 V was measured, and the light intensity in a low-temperature and low-humidity environment of 5 ° C./20% RH and a high-temperature and high-humidity environment of 35 ° C./85% RH were measured. The change of the potential level (ΔV _L : V) was measured. Further, the charge reduction amount FV at the first rotation of the drum after dark adaptation in a low temperature and low humidity environment.
₀ ↓ (V) was measured. The results are also shown in Table 1.

Further, the developing tank of the copying machine was modified to enable development with a toner having a predetermined small particle size. Image information was recorded by the copying machine at a recording density of 1500 dpi, and the average particle size was 5.5 ± 1.4. μm polymerized toner (particle size 4-7 μm
(The ratio of the toner outside the range is less than 6%), and a toner image obtained by reversal development at -800 V under a high-temperature and high-humidity environment was also evaluated.

The formed image could be resolved at 16 lines / mm, and was a clear image with no fog on a white background and no minute black spots. The results are also shown in Table 1.

<Example 2> CuK α was used as a charge generation material.
X for characteristic X-rays (wavelength: 1.5418 angstroms)
In the X-ray diffraction spectrum, its Bragg angle (2θ)
But 9.1 ± 0.2 °, 9.4 ± 0.2 °, 9.6 ± 0.2 °, 27.2
In the case of ± 0.2 °, titanyl phthalocyanine which is a crystal type (see FIG. 4) showing a major strong diffraction line was used. Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 1. The electric capacity of the manufactured electrophotographic photoreceptor was measured in Example 1.
Similarly, it was 200 pF / cm ² . Then, when the manufactured electrophotographic photosensitive member was evaluated in the same manner as in Example 1,
The surface charge density was 10 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was 0.04 μJ / cm ² , showing extremely high sensitivity.

Further, an image was formed in the same manner as in Example 1 using a polymerized toner having an average particle diameter of 5.1 ± 1.1 μm (the ratio of the toner having a particle diameter outside the range of 4-6.5 μm was less than 8%). When the formed image was evaluated, 16 lines /
mm could be clearly resolved. The results are also shown in Table 1.

Example 3 As a binder resin for the charge transport layer, a polycarbonate resin (manufactured by Mitsubishi Gas Chemical Company, trade name "PCZ-800") and a polyester resin (manufactured by Toyobo Co., trade name "Vylon V-290") were used. Were mixed at a weight ratio of 8: 2 to prepare a coating solution for the charge transport layer, and the film thickness was 14 μm.
An electrophotographic photoreceptor was manufactured in the same manner as in Example 1 except that the charge transport layer was formed. The electric capacity of this electrophotographic photosensitive member was 240 pF / cm ² . When the produced electrophotographic photoreceptor was evaluated in the same manner as in Example 1, the surface charge density was 12 × 10 ⁻⁸ C / cm ² , the half-life exposure energy was 0.07 μJ / cm ² , and the sensitivity was extremely high. showed that.

Further, an image was formed in the same manner as in Example 1 by using a polymerized toner having an average particle diameter of 5.0 ± 0.8 μm (the ratio of toner having a particle diameter outside the range of 4 to 6 μm was less than 5%). When the formed image was evaluated, 20 lines / mm
Could be clearly resolved. The results are also shown in Table 1.

Example 4 As a charge transporting material, 1 part by weight of a butadiene compound represented by the following structural formula (7):
As a binder, 1 part by weight of polycarbonate (trade name “PCZ-400” manufactured by Mitsubishi Gas Chemical Company) was dissolved in 8 parts by weight of dichloromethane to prepare a coating solution for coating the charge transport layer. Thus, a 15 μm charge transport layer was formed.

[0083]

Embedded image

Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 1. The electric capacity of this electrophotographic photoreceptor is
220 pF / cm ² . The manufactured electrophotographic photoreceptor
When evaluated in the same manner as in Example 1, the surface charge density was 12
× 10 ^-8 C / cm ² and half-exposure energy is 0.11μ
J / cm ² , indicating extremely high sensitivity.

Further, an image was formed in the same manner as in Example 1 by using a polymerized toner having an average particle size of 5.5 ± 1.4 μm (the ratio of toner outside the particle size range of 4 to 7 μm was less than 6%). When the formed image was evaluated, 16 lines / mm
Could be resolved. The results are also shown in Table 1.

Example 5 1 part by weight of a triphenylamine dimer compound represented by the following structural formula (8) was used as a charge transporting material, and polycarbonate (trade name “PCZ-” manufactured by Mitsubishi Gas Chemical Company, Ltd.) was used as a binder. 400 ") was dissolved in 8 parts by weight of dichloromethane to prepare a coating solution for coating the charge transport layer, and a 18 μm charge transport layer was formed in the same manner as in Example 1.

[0087]

Embedded image

Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 1. The electrical capacity of this photoconductor is 180 pF / cm
^{Was 2} . When the produced electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 9 × 10 ⁻⁸ C / cm.
^{2. The} half-life exposure energy was 0.08 μJ / cm ² , showing extremely high sensitivity.

Further, a polymerized toner having an average particle diameter of 5.5 ± 1.4 μm (toner having a particle diameter outside the range of 4 to 7 μm is 6%
), An image was formed in the same manner as in Example 1, and the formed image was evaluated. As a result, 16 lines / mm could be resolved. The results are also shown in Table 1.

<Example 6> Instead of surface-untreated acicular titanium oxide (trade name "STR-60N" manufactured by Sakai Chemical Co., Ltd.), surface-untreated granular titanium oxide (trade name "Ishihara Sangyo Co., Ltd.") TTO
-55N ") and an intermediate layer composed of 90 parts by weight of copolymer Nylon (trade name" Amilan CM8000 "manufactured by Toray Industries, Inc.), and a CuKα characteristic X-ray (wavelength: 1.
5418 angstroms), the Bragg angles (2θ) were 9.1 ± 0.2 °, 9.4 ± 0.2
In the cases of °, 9.6 ± 0.2 °, and 27.2 ± 0.2 °, titanyl phthalocyanine, which is a crystal type showing major intense diffraction lines, was used. Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 1. The capacitance of this photoconductor is 200 pF /
It was cm ^2. The manufactured electrophotographic photoreceptor was used in Example 1.
When evaluated in the same manner as above, the surface charge density was 10 × 10 ⁻⁸ C /
cm ² , the half-life exposure energy is 0.06 μJ / cm ² ,
It showed very high sensitivity.

Further, a polymerization toner having an average particle diameter of 5.1 ± 1.1 μm (toner having a particle diameter outside the range of 4-6.5 μm is 8
%), An image was formed in the same manner as in Example 1, and the formed image was evaluated. As a result, 16 lines / mm could be resolved. The results are also shown in Table 1.

<Example 7> Al ₂ O 3 was used instead of untreated surface-shaped acicular titanium oxide (trade name “STR-60N” manufactured by Sakai Chemical Co., Ltd.).
Acicular titanium oxide surface-treated with O ₃ (trade name “STR-60”, manufactured by Sakai Chemical Co., Ltd.) was used. Otherwise, in the same manner as in Example 6, an electrophotographic photosensitive member was manufactured. The electric capacity of this electrophotographic photosensitive member was 200 pF / cm ² . The produced electrophotographic photosensitive member was evaluated in the same manner as in Example 1. As a result, the half-life exposure energy was 0.06 μJ / cm ² , showing extremely high sensitivity.

Further, an image was formed in the same manner as in Example 1 using a polymerized toner having an average particle diameter of 5.1 ± 1.1 μm (the ratio of the toner having a particle diameter outside the range of 4-6.5 μm was less than 8%). Then, when the formed image was evaluated, 16 lines / mm could be resolved. The results are also shown in Table 1.

Example 8 To the charge transporting layer of Example 3, α-tocopherol was added as an antioxidant in an amount of 2/100 parts by weight of the charge transporting material. Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 3. The electric capacity of this electrophotographic photosensitive member was 240 pF / cm ² . When the manufactured electrophotographic photoreceptor was evaluated in the same manner as in Example 1, the surface charge density was 12 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was 0.09 μJ / cm ^2. Indicated. .

Further, an image was formed in the same manner as in Example 1 by using a polymerized toner having an average particle size of 5.0 ± 0.8 μm (the ratio of toner having a particle size outside the range of 4 to 6 μm was less than 5%). When the formed image was evaluated,
mm could be clearly resolved.

When an image corresponding to 40,000 sheets was formed by a copying machine incorporating the electrophotographic photosensitive member of this embodiment, the reduction in the thickness of the photosensitive layer was as small as 2.7 μm.
Deterioration of the charging ability was not a problem in practical use.
The results are also shown in Table 1. <Example 9> 1/100 parts by weight of t-butylhydroquinone as an antioxidant was added to the charge transporting layer of Example 3 with respect to the charge transporting material. Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 3. The electric capacity of this electrophotographic photosensitive member was 240 pF / cm ² . When the produced electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 12 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was:
0.12 μJ / cm ² , indicating extremely high sensitivity.

Further, an image was formed in the same manner as in Example 1 by using a polymerized toner having an average particle diameter of 5.0 ± 0.8 μm (the ratio of the toner having a particle diameter outside the range of 4 to 6 μm was less than 5%). When the formed image was evaluated,
mm could be clearly resolved.

Further, when the electrophotographic photosensitive member of this embodiment formed an image corresponding to 40,000 sheets by the copying machine used in Example 1, the reduction in the thickness of the photosensitive layer was as small as 2.5 μm, and Also, the deterioration of the charging ability was not a problem in practical use. The results are also shown in Table 1.

Example 10 To the charge transporting layer of Example 3 was added 5/1000 parts by weight of t-butylhydroxytoluene as an antioxidant to the charge transporting material. Otherwise, an electrophotographic photosensitive member was manufactured in the same manner as in Example 3.
The electric capacity of this electrophotographic photosensitive member was 240 pF / cm ² . When the manufactured electrophotographic photoreceptor was evaluated in the same manner as in Example 1, the surface charge density was 12 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was 0.09 μJ / cm ^2. Indicated.

Further, an image was formed in the same manner as in Example 1 by using a polymerized toner having an average particle diameter of 5.0 ± 0.8 μm (the ratio of the toner having a particle diameter outside the range of 4 to 6 μm was less than 5%). When the formed image was evaluated,
mm could be clearly resolved.

When an image corresponding to 40,000 sheets was formed by a copying machine incorporating the electrophotographic photosensitive member of this embodiment, the reduction in the film thickness of the photosensitive layer was as small as 2.1 μm, and the deterioration of the charging ability was also reduced. However, there was no particular problem in practical use. The results are also shown in Table 1.

<Example 11> An electrophotographic photosensitive member was manufactured in the same manner as in Example 1 except that no intermediate layer was provided.
The electric capacity of this electrophotographic photosensitive member was 190 pF / cm ² . When the manufactured electrophotographic photoreceptor was evaluated in the same manner as in Example 1, the surface charge density was 9.5 × 10 ⁻⁸ C / cm ² , the half-life exposure energy was 0.04 μJ / cm ² , and the potential holding property was low. It was getting a little worse.

Further, an image was formed in the same manner as in the example using the same toner as in the example 1.
mm could be resolved, and no image defects were observed. The results are also shown in Table 1.

<Example 12> An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that a polycarbonate resin (trade name “C1400” manufactured by Teijin Chemicals Ltd.) was used as a binder resin for the charge transport layer. Manufactured. The electric capacity of this electrophotographic photosensitive member was 200 pF / cm ² . When the manufactured electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 10 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was:
0.07 μJ / cm ² , indicating high sensitivity.

Further, an image was formed in the same manner as in the example using the same toner as in the example 1.
mm could be resolved, and no image defects were observed. Further, when an image equivalent to 50,000 sheets was formed by a copying machine, the film thickness of the photosensitive layer was reduced to 4.4 μm, and although the charging ability was slightly deteriorated, there was no particular problem in practical use. . The results are also shown in Table 1. Comparative Example 1 An electrophotographic photosensitive member was manufactured in the same manner as in Example 1 except that the thickness of the charge transport layer was 35 μm and the capacity of the photosensitive member was 90 pF / cm ² . The produced electrophotographic photoreceptor was evaluated in the same manner as in Example 1. As a result, the surface charge density was 4.5 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was 0.5.
It was 04 μJ / cm ² .

The toner having an average particle diameter of 6.5 ± 2.5 μm (the ratio of toner having a particle diameter outside the range of 4 to 8 μm is 15%
Using the above, an image was formed in the same manner as in Example 1, and the formed image was evaluated. As a result, 12 lines / mm could be resolved, but 16 lines / mm could be resolved. I couldn't image it. The results are also shown in Table 1.

Comparative Example 2 An intermediate layer was not provided. As a charge generation material, the Bragg angle (2θ) of the X-ray diffraction spectrum of CuKα characteristic X-rays (wavelength: 1.5418 Å) as shown in FIG. The maximum diffraction line is shown at 27.3 ± 0.2 °, 7.4 ± 0.2 °, 9.7 ± 0.2 °, 24.
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that the crystal type titanyl phthalocyanine classified into the so-called Y-type, each showing a diffraction line even at 2 ± 0.2 °, was used. The electric capacity of this electrophotographic photosensitive member is 195 pF /
It was cm ^2. When this electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 9.75 × 10 ⁻⁸ C / cm.
² , half-exposure energy was 0.24 μJ / cm ² ,
The potential retention is extremely poor, and the electrical retention after 5 seconds when the surface charge density in the dark is 10 × 10 ⁻⁸ C / cm ² is as follows:
It was 81%. Further, when an image was formed in the same manner as in Example 1, the image was markedly soiled on a white background, and the image quality was extremely poor. The results are also shown in Table 1.

<Comparative Example 3> 120 parts by weight of titanium oxide (trade name "STR-60N" manufactured by Sakai Chemical Co., Ltd.) and 60 parts by weight of copolymerized nylon (trade name "Amilan CM8000" manufactured by Toray Industries, Inc.) An electrophotographic photosensitive member was manufactured in the same manner as in Example 1 except that the intermediate layer was provided. The electric capacity of this electrophotographic photosensitive member was 210 pF / cm ² . When this electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 10.5 × 10 ⁻⁸ C / cm ² , and the half-life exposure energy was 0.09 μJ.
/ Cm ² , an image was formed in the same manner as in Example 1. As a result, many fine black spots were generated on a white background in the image, and a high-quality image could not be obtained. The results are also shown in Table 1.

<Comparative Example 4> As a charge generating material, 2 parts by weight of a crystalline titanyl phthalocyanine classified as a so-called Y type of Comparative Example 2 and polyvinyl butyral (trade name “ESLEC BM-1” manufactured by Sekisui Chemical Co., Ltd.) An electrophotographic photoreceptor was manufactured in the same manner as in Example 1 except that a charge generation layer composed of 1 part by weight was formed. The electric capacity of this electrophotographic photosensitive member was 200 pF / cm ² . Further, when this electrophotographic photosensitive member was evaluated in the same manner as in Example 1,
The surface charge density was 10 × 10 ⁻⁸ C / cm ² , and the half-life energy was 0.24 μJ / cm ² .

Further, when halftone recording was performed by pulse width modulation using a copying machine, the amount of attenuation of the potential on the high duty side was small, and the formed image was poor in gradation expression. In addition, the charging potential in the first rotation after dark adaptation was low, and many fine black spots were observed on a white background in the image.
Furthermore, the change of the light potential level in the low temperature and low humidity environment and the high temperature and high humidity environment was the largest. The results are also shown in Table 1.

<Comparative Example 5> CuK α was used as a charge generation material.
X for characteristic X-rays (wavelength: 1.5418 angstroms)
In the line diffraction spectrum, as shown in FIG. 6, the maximum diffraction line is shown when the Bragg angle (2θ) is 27.3 ± 0.2 °, and 7.3 ± 0.2 °, 9.5 ± 0.2 °, 9.7 ± 0.2 °, and 11.
7 ± 0.2 °, 15.0 ± 0.2 °, 18.0 ± 0.2 °, 23.5 ± 0.2
In the cases of ° and 24.1 ± 0.2 °, an electrophotographic photoreceptor was manufactured in the same manner as in Example 1 except that a crystalline type titanyl phthalocyanine classified basically as a Y-type having diffraction lines was used. did. The electric capacity of this electrophotographic photosensitive member was 200 pF / cm ² . When the electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was
10 × 10 ⁻⁸ C / cm ² , half-exposure energy is 0.22 μJ /
It was cm ^2.

Further, when halftone recording was performed by pulse width modulation using a copying machine, the amount of potential attenuation on the high duty side was small, and the formed image was poor in gradation expression. In addition, the charging potential in the first rotation after dark adaptation was low, and many fine black spots were observed on a white background in the image.
Furthermore, in a high-temperature and high-humidity environment, the residual potential was -96 V, and was significantly deteriorated by aging. The results are also shown in Table 1.

<Comparative Example 6> CuK α was used as the charge generation material.
X for characteristic X-rays (wavelength: 1.5418 angstroms)
In the line diffraction spectrum, as shown in FIG. 7, the maximum diffraction line is shown when the Bragg angle (2θ) is 27.3 ± 0.2 °, and 9.1 ± 0.2 °, 14.3 ± 0.2 °, 18.0 ± 0.2 °, 2
An electrophotographic photoreceptor was produced in the same manner as in Example 1 except that a crystalline type titanyl phthalocyanine classified into the so-called I-type, which exhibited a diffraction line even at 4.0 ± 0.2 °, was used. The electric capacity of this electrophotographic photosensitive member is 205 pF / cm
^{Was 2} . When the electrophotographic photosensitive member was evaluated in the same manner as in Example 1, the surface charge density was 10.3 × 10 ⁻⁸ C
/ Cm ² , and the half-life exposure energy was 0.30 μJ / cm ² . Furthermore, when an image was formed by a copying machine in the same manner as in Example 1, the residual potential was as high as about -105 V, and when halftone recording was performed by pulse width modulation, the amount of attenuation of the potential on the high duty side was small. The formed image was inferior in gradation expression. In addition, the charging potential in the first rotation after dark adaptation was low, and many fine black spots were observed on a white background in the image. The results are also shown in Table 1.

[0114]

[Table 1]

[0115]

The electrophotographic photoreceptor of the present invention has a large electric capacity and a high surface charge density, so that the deterioration of the resolution of the electrostatic latent image due to the diffusion of the charges is suppressed, and the surface charge density is reduced. Is prevented from lowering due to the resolution. As a result, the image information can be recorded at a high density, and the recorded image information can be output as a high-quality image.

Further, by employing a highly sensitive crystalline oxotitanyl phthalocyanine which emits very little charge even under a high electric field in the dark, an effective charge injection prevention between the conductive support and the charge generation layer can be achieved. By inserting an intermediate layer to be a layer, furthermore, as a charge transport layer laminated on a charge generation layer composed of a highly sensitive crystalline oxotitanyl phthalocyanine, a charge injection efficiency having a small charge injection barrier enamine structure By adopting a good charge transport material, even if the surface charge density is increased by increasing the electric capacity of the photoreceptor, there is no possibility that problems such as generation of minute image defects and reduction in sensitivity will occur, High quality images can be formed.

Further, in the electrophotographic image forming method of the present invention, a high recording density image can be formed with high image quality by using such an electrophotographic photosensitive member and a toner having a specific average particle size or less. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of an embodiment of an electrophotographic photosensitive member of the present invention.

FIG. 2 is a sectional view of a main part of the electrophotographic photosensitive member.

FIG. 3 is a graph showing an X-ray diffraction pattern of a crystalline oxotitanyl phthalocyanine used in a charge generation layer of the electrophotographic photoreceptor.

FIG. 4 is a graph showing an X-ray diffraction pattern of another crystalline oxotitanyl phthalocyanine used in the charge generation layer of the electrophotographic photoreceptor.

FIG. 5 is a graph showing an X-ray diffraction pattern of another crystalline oxotitanyl phthalocyanine used for a charge generation layer of an electrophotographic photosensitive member for comparison.

FIG. 6 is a graph showing an X-ray diffraction pattern of another crystalline oxotitanyl phthalocyanine used for a charge generation layer of an electrophotographic photosensitive member for comparison.

FIG. 7 is a graph showing an X-ray diffraction pattern of another crystalline oxotitanyl phthalocyanine used for a charge generation layer of an electrophotographic photosensitive member for comparison.

[Explanation of symbols]

 Reference Signs List 10 electrophotographic photosensitive member 11 conductive support 12 intermediate layer 13 photosensitive layer 13a charge generation layer 13b charge transport layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 5/14 101 G03G 5/14 101D 9/08 9/08 F term (Reference) 2H005 EA05 FA00 2H068 AA16 AA19 AA20 AA34 AA35 AA37 AA44 BA05 BA12 BA39 BB26 BB52 FA11 FC05 FC08

Claims (12)

[Claims] 1. A photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated are laminated on a conductive support, and after the photosensitive layer is charged, an image is exposed to form a latent image. An electrophotographic photoreceptor used in an image forming apparatus adapted to visualize the latent image by a reversal development method, wherein the electric capacity of the photosensitive layer is 160 pF / cm ² or more; An electrophotographic photoreceptor, wherein the photosensitive layer is charged to a surface charge density of 8 × 10 ⁻⁸ C / cm ² or more, and a latent image is formed at a high density of 1200 dpi or more. . 2. The electrophotographic photoreceptor according to claim 1, wherein said charge generation layer contains oxotitanyl phthalocyanine. 3. The oxotitanyl phthalocyanine is
In the X-ray diffraction spectrum for CuK α characteristic X-ray,
Bragg angle 2θ is at least 9.4 ± 0.2 °, 9.6 ±
Crystal structure showing major strong diffraction lines at 0.2 ° and 27.2 ± 0.2 °, respectively, and relatively strong diffraction lines at 7.3 ± 0.2 °, 11.6 ± 0.2 °, and 24.1 ± 0.2 °, respectively The electrophotographic photosensitive member according to claim 2, wherein 4. The oxotitanyl phthalocyanine is
In the X-ray diffraction spectrum for CuK α characteristic X-ray,
Bragg angle 2θ is at least 9.1 ± 0.2 °, 9.4 ±
3. A crystal structure showing major intense diffraction lines at 0.2 °, 9.6 ± 0.2 °, and 27.2 ± 0.2 °, respectively.
2. The electrophotographic photoreceptor of claim 1. 5. The method according to claim 1, wherein the conductive support and the photosensitive layer are provided between:
The electrophotographic photoreceptor according to claim 1, further comprising an intermediate layer for preventing charge injection. 6. The electrophotographic photoreceptor according to claim 5, wherein the intermediate layer comprises a resin layer obtained by dispersing 30 to 50% by weight of rutile-type titanium oxide crystals in a polyamide resin. 7. The charge transport layer has the following structural formula (1)
The electrophotographic photoreceptor according to claim 2, further comprising a charge material having an enamine structure represented by the following formula: Embedded image However, Ar is an aryl group which may have a substituent, a heterocyclic group which may have a substituent, an aralkyl group which may have a substituent, and an aryl group which may have a substituent. Any of the good heterocyclic alkyl groups wherein n is 2, 3 or 4
Is one of 8. The charge transport layer has a viscosity average molecular weight.
The electrophotographic photoreceptor according to claim 2, wherein the electrophotographic photoreceptor contains 35,000 to 85,000 and a binder resin containing a polycarbonate resin having the following structural formula (2) as a main component. Embedded image However, R _{1 to} R ₄ are hydrogen, halogen, or C 1
And Z represents an atom group necessary to form a substituted or unsubstituted carbon ring or a substituted or unsubstituted heterocyclic ring. 9. An antioxidant having any one of the following structural formulas (3), (4) and (5) is contained in the charge transporting layer in an amount of 5/1000 to 50/1000 with respect to the charge transporting material. The electrophotographic photoreceptor according to claim 2, which is contained in a weight ratio of: Embedded image Embedded image Embedded image 10. The photosensitive layer has an absolute sensitivity with respect to a recording wavelength of 780 nm of 0.15 μm at a half-exposure energy value required to attenuate the surface potential from −500 V to −250 V.
^2. The electrophotographic photoreceptor according to claim 1, which has a J / cm ² or less. 11. An electrophotographic photoreceptor in which a photosensitive layer in which a charge generation layer and a charge transport layer are sequentially laminated is laminated on a conductive support, and the electric capacity of the photosensitive layer is 160 pF / cm ² or more. Wherein the photosensitive layer was charged so as to have a surface charge density of 8 × 10 ⁻⁸ C / cm ² or more, and a latent image was formed at a high density of 1200 dpi or more. An electrophotographic image forming method, wherein a latent image is visualized by a reversal developing method using a toner having an average particle diameter of 6 μm or less. 12. The toner according to claim 1, wherein the standard deviation with respect to the average particle diameter is 30% or less of the average value, and the ratio of toner having a particle diameter outside the standard deviation is less than 10%. 12. The method for forming an electrophotographic image according to item 11.