JPH03213867A - Electrophotographic photoreceptor, electrophotographic device using the same, device unit, and image forming method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an electrophotographic photoreceptor, an electrophotographic device using the same, and an image forming method, and more specifically, the present invention relates to an electrophotographic photoreceptor, an electrophotographic device using the same, and an image forming method. The present invention relates to an electrophotographic photoreceptor capable of obtaining high-quality images without image defects such as (black spots), an electrophotographic apparatus using the same, and an image forming method.

[Conventional technology]

In recent years, laser beam printers, LED printers,
Demand for electrophotographic printers such as LCD printers is rapidly increasing.

Currently, the electrophotographic photoreceptors mainly used in these printers use organic photoconductors, and the basic composition of the photosensitive layer depends on the tolerance for material selection, durability, potential stability, For various reasons such as sensitivity and responsiveness, there are many so-called functionally separated types having a charge generation layer containing a charge generation substance and a charge transport layer containing a charge transport substance.

In such electrophotographic printers, especially digital printers, image input is often performed in reverse, and in this case, the developing means for the electrostatic latent image is also developed in reverse. In reversal development, the dark part of the electrostatic latent image becomes the white part of the image, so minute spot potential drops due to carrier injection from the photoreceptor substrate cause defects such as fogging on the white background and black spots, which are noticeable in the image. The problem is that it is easy to appear.

Conventionally, the following methods have been attempted as typical means for preventing image defects such as fog and black spots.

(2) A subbing layer having a carrier injection preventing effect is provided between the support and the charge generation layer.

■Use a material with low carrier mobility for the charge transport material.

■Heat the photoreceptor with a heater (in high-temperature environments, the resistance of the charge generation layer and undercoat layer decreases due to moisture, making carrier injection more likely to occur).

However, none of these methods exhibited sufficient effects or were associated with adverse effects.

On the other hand, semiconductor lasers are often used as light sources for electrophotographic printers and digital copying machines (oxytitanium phthalocyanine is attracting attention as a charge-generating material that has high sensitivity near its oscillation wavelength of 780 to 800 nm). Oxytitanium phthalocyanine is not only highly sensitive but also has excellent electrophotographic properties, making it suitable as a material for photoreceptors in electrophotographic printers and digital copying machines. It has been very difficult to avoid this problem.Since this significantly impairs the quality of images, improvements are desired.

[Problem that the invention seeks to solve]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photoreceptor, an electrophotographic apparatus equipped with the photoreceptor, and an image forming method that can eliminate the above-mentioned drawbacks and provide high-quality images without fogging even in a reversal development process. .

[Means to solve the problem]

That is, the present invention provides an electrophotographic photoreceptor used in an electrophotographic apparatus having a charging means and a reversal developing means, wherein the electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, The charge generation layer contains oxytitanium phthalocyanine, and the charge transport layer has a thickness of 22 μm.
This is an electrophotographic photoreceptor characterized by the above.

The present invention also provides an electrophotographic apparatus having an electrophotographic photoreceptor, a charging means, and a reversal developing means, wherein the charging means is a charging means capable of forming a dark area potential of 600 V or less in absolute value on the surface of the electrophotographic photoreceptor. The electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, the charge generation layer contains oxytitanium phthalocyanine, and the charge transport layer has a thickness of 22 μm or more. This is an electrophotographic device characterized by the following.

Furthermore, the present invention provides an electrophotographic photoreceptor that is charged so that its dark potential is 600 V or less in absolute value, and that the electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, The charge generation layer contains oxytitanium phthalocyanine, the charge transport layer has a thickness of 22 μm or more, forms an electrostatic latent image on the surface of the electrophotographic photoreceptor, and reversely develops the formed electrostatic latent image. This is an image forming method characterized by:

In the present invention, it is necessary to make the thickness of the charge transport layer thicker than conventional ones. The reason for this is not clear, but a thicker charge transport layer can reduce the electric field strength when a certain level of surface potential is applied to the photoreceptor than a thinner charge transport layer. This is thought to be due to the fact that carrier injection from the substrate as described above does not occur. Another reason is that if the thickness of the charge transport layer is thick, that is, the distance the carriers travel is long, It is also conceivable that it would be possible to terminate the development process before the carrier reaches the photoreceptor surface.

The thickness of the charge transport layer in the present invention is preferably 22 μm or more, particularly preferably 25 μm or more.

In addition, in the present invention, the dark area potential (hereinafter referred to as "vd") of the photoreceptor at the time of forming an electrostatic latent image is set lower than that in the prior art. That is, it is preferable to set the dark potential to 600 V or less in absolute value, and particularly preferably to 550 V or less.

Conventionally, Vd was generally set at around 700V as an absolute value. One of the reasons for this is that by setting Vd as high as possible and the bright area potential (hereinafter referred to as rVfJ) as low as possible, and ensuring a sufficient potential difference between the two, there is a margin for potential fluctuations due to repeated use of the photoreceptor or environmental changes. One example of this is to obtain stable, high-contrast images.

However, the present inventor found that sulfur titanium phthalocyanine as a charge-generating substance has sufficiently high sensitivity, so that sufficient contrast can be obtained even when Vd is set low, and at the same time it is resistant to repeated use and environmental changes. They have discovered that it is possible to stably obtain good images with very little potential fluctuation.

As described above, the present invention has been developed for the first time in an electrophotographic photoreceptor having a charge transport layer containing oxytitanium phthalocyanine, which has a synergistic effect of increasing the thickness of the charge transport layer and keeping the dark area potential low. This made it possible to virtually eliminate image defects such as spots.

Next, specific aspects of the electrophotographic photoreceptor will be explained.

As the conductive support, the support itself is conductive, such as aluminum, aluminum alloy, copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold, platinum, etc. In addition, plastics with a layer formed by vacuum evaporation of aluminum, aluminum alloy, indium oxide, tin oxide, indium oxide-tin oxide alloy, etc., supports and conductive materials in which plastic or paper is impregnated with conductive particles Plastics containing polymers, etc. can be used.

In the present invention, between the conductive support and the charge generation layer,
A subbing layer having both barrier and adhesive functions can also be provided.

The undercoat layer consists of casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer polyvinyl butyral, phenolic resin, polyamides (nylon 6
, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, gelatin, aluminum oxide, etc.

The thickness of the undercoat layer is preferably 0.1 to 10 μm, particularly preferably 0.1 to 3 μm.

Furthermore, a coating is applied between the support and the undercoat layer to compensate for surface defects on the support, and a conductive layer is applied to prevent interference fringes due to scattering when the image input is a laser beam. can be provided.

This conductive layer can be formed by dispersing conductive powder such as carbon black, metal particles or metal oxide in a suitable binder resin. The thickness of the conductive layer is preferably 5 to 40 μm, particularly preferably 10 to 30 μm.

Further, the electrophotographic photoreceptor of the present invention may be provided with a surface protective layer such as a resin layer or a conductive resin layer on the surface of the photoreceptor. The thickness of the surface protective layer is preferably 0.001 μm to 5 μm, particularly preferably 0.2 μm to 3 μm.

Next, oxytitanium phthalocyanine, which is a charge generating substance used in the present invention, will be explained.

Oxytitanium phthalocyanine is a compound generally represented by the following structural formula.

(In the formula, x', x'', X3 and X4 are each independently CI
or Br, where n, m, l and k are each independently 0
Represents the number ~4. ) Literature regarding the synthesis method and electrophotographic properties of oxytitanium phthalocyanine includes, for example, Japanese Patent Application Laid-Open No. 1487-1987.
Publication No. 45, Publication No. 59-36254, Publication No. 59-44
No. 054, No. 59-31965, No. 61-2
There are No. 39248 and No. 62-67094. In the present invention, oxytitanium phthalocyanine obtained according to these disclosures can be used as a charge generating substance.

Among them, the Bragg angle 2θ± in X-ray diffraction of CuKα
0.2° is 9.0°, 14.2°, 23°9° and 27
．． Oxytitanium phthalocyanine having a strong peak at 1° is particularly preferred as the oxytitanium phthalocyanine used in the present invention because it has very high sensitivity and has a relatively low resistance so that carriers can be easily injected.

In order to form a film of oxytitanium phthalocyanine as a charge generation layer, it may be deposited on a support, or a phenol resin, urea urea resin, melamine resin, epoxy resin, silicon resin, vinyl chloride-vinyl acetate copolymer, butyral resin, This is done by applying a liquid binder resin such as xylene resin, urethane resin, acrylic resin, polycarbonate resin, polyacrylate resin, saturated polyester resin, or phenoxy resin, for example, a coating liquid in which oxytitanium phthalocyanine is dispersed in the solution. be able to. The film thickness is preferably 0.05 μm to 10 μm, particularly preferably 0.1 μm to 3 μm.

As the charge transport substance, common ones such as pyrazoline compounds, hydrazone compounds, stilbene compounds, triphenylamine compounds, benzidine compounds, or oxazole compounds can be used.

A charge transport layer can be formed by dissolving these in a solvent and applying them together with a binder resin as described in the section regarding the charge generation layer.

As described above, the thickness of the charge transport layer is set to 22 μm or more, particularly preferably 25 μm or more.

If it is less than 22 μm, the electric field strength applied to the photoreceptor becomes too large, making it difficult to obtain the effects of the present invention.

The weight ratio of charge transport material and binder resin is 1:3 to 3.1
1, preferably 1:2 to 2:1.

When the amount of the charge transport substance is less than 1=3, the charge transport ability is reduced, causing a decrease in sensitivity and an increase in residual potential. Particularly, when the thickness of the charge transport layer is set to be large as in the present invention, it is not preferable to increase the distance over which carriers must travel, since this leads to a decrease in mobility. On the other hand, if the amount of the charge transport material exceeds 3=1, this is not preferable because the mechanical strength of the charge transport layer decreases, leading to a decrease in the durability of the photoreceptor against repeated use.

In order to form each of these layers, a known coating method such as a dip coating method, a spray coating method, a beam coating method, a blade coating method, or a spinner coating method can be used.

Next, an electrostatic latent image forming process in an electrophotographic apparatus will be explained.

The process of uniformly charging the photoreceptor is usually carried out by corona discharge or direct charging in which a charging member in the form of a roller or blade is brought into contact with the photoreceptor. At this time, carriers are injected from the charge generation layer to the charge transport layer, or from the support through the charge generation layer and into the charge transport layer, and by lowering the surface potential of that part, a black spot image on a white background is formed through a reversal development process. becomes. In the present invention,
The charging step is set so that the dark potential on the photoreceptor is 600V or less, particularly preferably 550V or less.

Next, a synthesis example of oxytitanium phthalocyanine used in the present invention will be shown.

Synthesis Example 1 A mixture of 50 g of phthalodinitrile, 22.5 g of titanium tetrachloride, and 630 ml of α-chloronaphthalene was heated and stirred at 240° C. to 250° C. for 4 hours in a N2 gas stream to carry out a reaction. The product was filtered, and the resulting mixture of dichlorotitanium phthalocyanine and 380 ml of concentrated aqueous ammonia was heated under reflux for 1 hour. The product was washed with acetone using a Soxhlet extractor to obtain 22 g of B-type oxytitanium phthalocyanine.

Synthesis Example 2 In 100 g of α-chloronaphthalene, 5.0 g of 0-phthalodinitrile and 2.0 g of titanium tetrachloride were heated and stirred at 200°C for 3 hours, then cooled to 50°C and the precipitated crystals were filtered off. A paste of dichlorotitanium phthalocyanine was obtained. Next, this was washed with 100 ml of N,N'-dimethylformamide heated to 100°C, and then washed with 60 ml of N,N'-dimethylformamide while stirring.
Washing was repeated twice with 100 ml of methanol at °C, followed by filtration. Further, the obtained paste was soaked in 100 m of deionized water.
j! The mixture was stirred at 80° C. for 1 hour and filtered to obtain blue oxytitanium phthalocyanine crystals. Yield: 4.3g.

Next, the crystals were dissolved in 150 g of concentrated sulfuric acid and dropped into 1500 ml of deionized water at 20° C. under stirring to cause reprecipitation, filtration, and thorough washing with water to obtain amorphous oxytitanium phthalocyanine. .

The amorphous oxytitanium phthalocyanine 4, Og thus obtained was dissolved in 100 ml of methanol at room temperature (2
The mixture was suspended and stirred for 8 hours at 2° C.), filtered, and dried under reduced pressure to obtain low-crystalline oxytitanium phthalocyanine.

Next, 40 ml of n-butyl ether was added to 2.0 g of this oxytitanium phthalocyanine, and a milling process was performed at room temperature (22° C.) for 20 hours with glass beads of 1 mm diameter.

The solid content was taken out from this dispersion, thoroughly washed with methanol and then water, and dried to obtain the novel crystalline oxytitanium phthalocyanine of the present invention.

Yield: 1.8 g The X-ray diffraction pattern of this oxytitanium phthalocyanine is shown in FIG. As can be seen from the figure, this oxytitanium phthalocyanine has a Bragg angle 2θ±0.2° of 9.0° in X-ray diffraction of CuKα, and 14.
It has strong peaks at 2°, 23.9° and 27.1°.

FIG. 2 shows a schematic configuration example of a general transfer type electrophotographic apparatus using the electrophotographic photoreceptor of the present invention.

In the figure, reference numeral 1 denotes a drum-type photoreceptor as an image carrier, which is rotated at a predetermined circumferential speed in the direction of the arrow around an axis 1a. During the rotation process, the photoreceptor 1 is uniformly charged by the charging means 2 so that a predetermined positive or negative potential is formed on its surface, and then exposed to a light image by an image exposure means (not shown) in the exposure section 3. Receive L (slit exposure, laser beam scanning exposure, etc.). As a result, electrostatic latent images corresponding to the exposed images are sequentially formed on the circumferential surface of the photoreceptor.

The electrostatic latent image is then developed with toner by a reversal developing means 4, and the toner image is transferred by a transfer means 5 from a paper feed section (not shown) between the photoreceptor 1 and the transfer means 5 in synchronization with the rotation of the photoreceptor l. The images are sequentially transferred onto the surface of the transfer material P that is fed.

The transfer material P that has undergone the image transfer is separated from the photoreceptor surface and introduced into the image fixing means 8, where the image is fixed and a copy is produced.
will be printed out on the outside of the aircraft.

After the image has been transferred, the surface of the photoreceptor 1 is cleaned by a cleaning means 6 to remove residual toner, and is further subjected to a charge removal process by a pre-exposure means 7, and is used repeatedly for image formation.

As the uniform charging means 2 for the photoreceptor 1, a corona charging device is generally widely used. Also, as the transfer device 5, a corona transfer means is generally widely used.

An electrophotographic apparatus is constructed by combining a plurality of components such as the above-mentioned photoreceptor, developing means, and cleaning means into an apparatus unit, and this unit is configured to be detachable from the apparatus main body. It's okay. For example, at least one of a charging means, a developing means, and a cleaning means.
It is also possible to form a unit by integrally supporting one with the photoreceptor, and form a single unit that can be attached and detached from the main body of the apparatus, so that it can be freely attached and detached using a guide means such as a rail of the main body of the apparatus. At this time, the above-mentioned device unit may include a charging means and/or a developing means.

When an electrophotographic device is used as a copying machine or a printer, light image exposure uses reflected light or transmitted light from a document, or reads the document and converts it into a signal, and this signal is used to scan a laser beam and drive an LED array. , or by driving a liquid crystal shutter array.

When used as a facsimile printer, the optical image exposure is exposure for printing received data.

FIG. 3 is a block diagram showing an example of this case.

The controller 11 controls the image reading section IO and the printer 19. The entire controller 11 is controlled by a CPU 17. The read data from the image reading section is transmitted to the partner station through the transmitting circuit 13.

Data received from the partner station is sent to the printer 19 through the receiving circuit 12. Predetermined image data is stored in the image memory. The printer controller 18 is the printer 19
is controlled. 14 is a telephone.

After the image received from the line 15 (image information from a remote terminal connected via the line) is demodulated by the receiving circuit 12, the CPU 17 decodes the image information and sequentially stores it in the image memory 16. . and at least 1
When the image of the page is stored in the memory 16, the image of the page is recorded. The CPU 17 uses l from the memory 16.
Reads the image information of the vane and prints it to the printer controller 18
One page of decoded image information is sent.

When the printer controller 18 receives one page of image information from the CPU 1.7, it controls the printer 19 to record the image information of that page.

Note that the CPU 17 is receiving the next page while the printer 19 is recording.

As described above, images are received and recorded.

Example 1 A coating solution for a conductive layer composed of the following materials was applied by dipping onto an Af cylinder with an outer diameter of 30 mm and a length of 260 mm, and then thermally cured at 140° C. for 30 minutes to form a conductive layer with a film thickness of 18 μm. formed.

Hereinafter, "part" means 1 part by weight unless otherwise specified.

・Conductive pigment tin oxide coating treatment Titanium oxide 10 parts [Product name: Kronos ECT-62 (manufactured by Titan Industries)] ・Resistance adjustment pigment titanium oxide 10 parts [Product name: Titone 5R-IT (Manufactured by Sakai Chemical Co., Ltd.) Co-binding Resin Phenol resin 10 parts [Product name: J-325 (manufactured by Dainippon Ink)]・Surface roughness imparting agent spherical silicone resin powder 1.5 parts [Product name Nidosparu 120 (manufactured by Toshiba Silicon)]・Solvent methanol/methyl cellosolve =1/1 20 copies Next,
A 5% methanol solution of polyamide resin [trade name: Amilan CM-8000 (manufactured by Toshi Co., Ltd.)] was coated on the conductive layer by a dip coating method to form a subbing layer having a thickness of 1 μm.

Furthermore, 10 parts of the titanyl phthalocyanine synthesized in Synthesis Example 1, 44 parts of polyvinyl butyral resin [trade name: Eslec BX-1 (manufactured by Tsukisui Kagaku)], and 200 parts of cyclohexanone were placed in glass beads with a diameter of 1 mm. The mixture was mixed and dispersed in a Santo Mill apparatus for 10 hours, and 500 parts of tetrahydrofuran was added thereto, and the mixture was coated on the undercoat layer by dip coating to form a charge generation layer with a thickness of 0.15 μm.

Finally, as a charge transport layer, 1O part of a stilbene compound of the following structural formula and 1O part of bisphenol Z type polycarbonate resin [trade name: Z-200 (manufactured by Mitsubishi Gas Chemical Co., Ltd.)] were dissolved in 45 parts of monochlorobenzene and 15 parts of dichloromethane. A coating solution was prepared. This coating solution was applied onto the charge generation layer by a dip coach ink method to form a charge transport layer having a thickness of 26 μm.

The photoreceptor thus created is equipped with a semiconductor laser light source,
Reversal development type racer beam printer [Product name: LB
P-3X (manufactured by Canon)], Vd is 1540
The charging conditions were set so that the voltage was V, and Vl was set to be -80V. Further, toner development was performed using a jumping method using a one-component negative toner, and the development bias was set at -400V.

Table 1 shows the results of evaluating the printed images under these conditions.

Example 2 A photoreceptor was produced in the same manner as in Example 1 except that the thickness of the charge transport layer was 23 μm. In addition, the charging settings of the racer beam printer were adjusted so that the Vd of the photoreceptor was 1600 V, and the images were evaluated in the same manner.

Incidentally, Vl at this time is -90v1 development bias is -16
It was set as 0~'.

As a result, in the case of Example 1, high-quality printing without fogging was stably obtained from a room temperature environment to a high temperature and high humidity environment. On the other hand, in the case of Example 2, in which the thickness of the charge transport layer was made thinner than in Example 1, and the charging setting was moved to the high voltage side, good images were obtained up to room temperature; Some black spots were seen in the environment.

Furthermore, a printing durability test of 10,000 sheets was conducted at room temperature, and the image remained as good as the initial state. In addition, the potential fluctuation of the photoreceptor after the 10,000-sheet test is as follows: In the case of Example 1, Vd=-530V and UV1=-85V.
In Example 2, tVd=-590V and Vl=-95V
This was an extremely small value.

The results are shown in Table 1.

Example 3 A conductive layer, an undercoat layer, and a charge generation layer were coated in the same manner as in Example 1, and a charge transport layer was prepared using 9 parts of a compound having the following structure and a styrene-acrylic copolymer resin [trade name: MS600,
A coating liquid was prepared by dissolving 10 parts of Co. (manufactured by Nippon Steel Chemical) in 40 parts of monochlorobenzene and 12 parts of dichloromethane. This was applied onto the charge generation layer by dip coating to form a charge transport layer with a thickness of 24 μm. The obtained photoreceptor was installed in the same laser beam printer as in Example 1, and image evaluation was performed at Vd=-500VSV/=-60V and developing bias of -350V. The results are shown in Table 1.

Example 4 In the same manner as in Example 3, the thickness of the charge transport layer was set to 22 pm, and V
d--580V, V1=-80V and development bias -4
Image evaluation was performed at 20V.

The results are shown in Table 1.

Example 5 A photoreceptor was prepared in the same manner as in Example 1 except that the oxytitanium phthalocyanine obtained in Synthesis Example 2 was used,
evaluated.

The results are shown in Table 1.

Comparative Example 1 A photoreceptor was prepared and evaluated in the same manner as in Example 1, except that the thickness of the charge transport layer was 18 μm and the dark potential was -700V.

The results are shown in Table 1.

Comparative Example 2 A photoreceptor was prepared and evaluated in the same manner as in Example 3, except that a trisazo pigment was used as the charge generating substance.

The results are shown in Table 1. Further, the potentials of the photoreceptor after the durability test were Vd=-410V and Vl=-70V.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an electrophotographic photoreceptor, an electrophotographic apparatus, and an image forming method that produce images free of image defects such as black spots.

[Brief explanation of drawings]

FIG. 1 shows an X-ray diffraction pattern of oxytitanium phthalocyanine obtained in Synthesis Example 2. FIG. 2 shows a schematic configuration example of an electrophotographic apparatus using the electrophotographic photoreceptor of the present invention. FIG. 3 shows a block diagram of a facsimile machine using an electrophotographic apparatus using the electrophotographic photoreceptor of the present invention as a printer. 72 mouth chamber 30

Claims (8)

[Claims] (1) In an electrophotographic photoreceptor used in an electrophotographic apparatus having a charging means and a reversal developing means, the electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, and the charge generation An electrophotographic photoreceptor characterized in that the layer contains oxytitanium phthalocyanine and the charge transport layer has a thickness of 22 μm or more. (2) CuKα of the oxytitanium phthalocyanine
Bragg angle 2θ±0.2° in X-ray diffraction is 9.0
The electrophotographic photoreceptor according to claim (1), which has strong peaks at 14.2°, 23.9° and 27.1°. (3) In an electrophotographic apparatus having an electrophotographic photoreceptor, a charging means, and a reversal developing means, the charging means is a charging means capable of forming a dark area potential of 600 V or less in absolute value on the surface of the electrophotographic photoreceptor; The electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, the charge generation layer contains oxytitanium phthalocyanine, and the charge transport layer has a thickness of 22 μm or more. Characteristic electrophotographic equipment. (4) CuKα of the oxytitanium phthalocyanine
Bragg angle 2θ±0.2° in X-ray diffraction is 9.0
The electrophotographic apparatus according to claim (3), which has strong peaks at 14.2°, 23.9°, and 27.1°. (5) In an apparatus unit including an electrophotographic photoreceptor, a charging means, a reversal developing means, and a cleaning means, the charging means is a charging means capable of forming a dark area potential of 600 V or less in absolute value on the surface of the electrophotographic photoreceptor. The electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, the charge generation layer contains oxytitanium phthalocyanine, and the charge transport layer has a thickness of 22 μm or more. , An apparatus unit characterized in that the apparatus unit integrally supports an electrophotographic photoreceptor, a charging means, a reversal developing means, and a cleaning means, and is detachable from the apparatus main body. (6) CuKα of the oxytitanium phthalocyanine
Bragg angle 2θ±0.2° in X-ray diffraction is 9.0
The device unit according to claim (5), which has strong peaks at angles of 14.2°, 23.9° and 27.1°. (7) The electrophotographic photoreceptor is charged so that the dark area potential is 600 V or less in absolute value, the electrophotographic photoreceptor has a conductive support, a charge generation layer, and a charge transport layer in this order, and the charge generation The layer contains oxytitanium phthalocyanine, the charge transport layer has a thickness of 22 μm or more, forms an electrostatic latent image on the surface of the electrophotographic photoreceptor, and reversely develops the formed electrostatic latent image. Characteristic image forming method. (8) CuKα of the oxytitanium phthalocyanine
Bragg angle 2θ±0.2° in X-ray diffraction is 9.0
The image forming method according to claim (7), which has strong peaks at 14.2°, 23.9° and 27.1°.