JP2002049167A - Electrophotographic device and process cartridge - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device and a process cartridge such that deterioration in images due to influences by continuous use or environmental changes is not caused but images of high picture quality can be always obtained in an electrophotographic device using a method for electrification to apply only DC voltage on an electrifying member disposed in contact with an electrophotographic photoreceptor to electrify. SOLUTION: The electrophotographic device has an electrophotographic photoreceptor and an electrifying means disposed in contact with the photoreceptor and has an electrifying means to electrify the surface of the photoreceptor by applying only DC voltage on the electrifying member. Further, the electrophotographic device has a discharging means so that the electrification potential of the part of the photoreceptor not exposed to light for an image is controlled to >=1/5 and <=1/3 of the electrification potential before the exposure by the discharging means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus and a process cartridge using a charging method in which only a direct current voltage is applied to a charging member arranged in contact with an electrophotographic photosensitive member.

[0002]

2. Description of the Related Art In an electrophotographic method, selenium,
When an image is obtained by performing basic processes such as charging, exposing, developing, transferring and cleaning an electrophotographic photosensitive member such as cadmium sulfide, zinc oxide, amorphous silicon and organic photoconductor, a corona charging method is used for a charging process. Is conventionally used. However, the corona charging method has a problem that a corona product such as ozone or NOx generated at the time of corona generation alters the surface of the photoreceptor and causes deterioration of image quality such as image blur.
In particular, electrophotographic photoreceptors in which the photosensitive layer is mainly composed of an organic photoconductor have lower chemical stability than amorphous silicon photoreceptors and the like, and when exposed to a corona product, undergo a chemical reaction (particularly an oxidation reaction). And the surface of the photosensitive layer tends to deteriorate. Therefore, when repeatedly used under corona charging, image blurring due to the above-described deterioration and a decrease in copy density due to a decrease in sensitivity tend to shorten the life of printing (copying resistance). Also, the generation of corona products is undesirable from an ecological point of view.

As a method of improving the problem of the corona charging method, for example, Japanese Patent Application Laid-Open Nos. 57-178267 and
6-104351, JP-A-58-40566, JP-A-58-139156 and JP-A-58-139156.
A so-called direct charging method (hereinafter referred to as a DC direct charging method) in which a voltage is applied to a charging member disposed in direct contact with the surface of a photoreceptor to charge the photoreceptor has been proposed in, for example, Japanese Patent Publication No. 150975. In this method, the surface of the photoconductor is charged to a predetermined potential by bringing a charging member such as a conductive elastic roller to which a DC voltage of about 1 to 2 KV is externally applied into contact with the surface of the photoconductor. In the DC direct charging method, since the amount of corona products generated is much smaller than in the corona charging method, deterioration of the photosensitive layer surface due to a chemical change is suppressed, and deterioration of image quality due to image blurring and the like is less likely to occur.

However, the direct DC charging method has a problem that it is difficult to uniformly charge the surface of the photosensitive member. This has a length of 2 to 2 in the direction perpendicular to the direction of movement of the surface to be charged.
It causes a streak-like charge unevenness of about 200 mm and a width of about 0.5 mm or less. The white streak (a phenomenon in which white streaks appear in a solid black or halftone image) which occurs in the case of the normal development method, or the reverse development method. This may cause image defects such as black streaks that occur in some cases.

As one of the methods for solving such problems and improving the uniformity of charging, a method of superposing an AC voltage on a DC voltage and applying the AC voltage to a charging member (hereinafter referred to as an AC / DC direct charging method). Has been proposed (JP-A-63-1496).
No. 68). In this charging system, a pulsating voltage is applied by superimposing an _AC voltage (VAC) on a DC voltage ( _VDC ) to uniformly charge the surface of the photoreceptor. In this case, in order to maintain the uniformity of charging, the superimposed AC voltage is set to a discharge starting voltage Vth (V) according to Paschen's law.
It is necessary to have a peak-to-peak potential difference (V _pp ) that is twice or more of the following.

[0006] However, when the superimposed AC voltage is increased, discharge breakdown easily occurs even at a small defective portion inside the photoconductor due to the maximum applied voltage of the pulsating voltage. In particular, when the photosensitive member is an organic electrophotographic photosensitive member having a low withstand voltage, this dielectric breakdown is remarkable. In this case, in the regular development method, the image is blank in the longitudinal direction of the contact portion, and in the reversal development method, black obscuration occurs. Further, when there is a pinhole, there is a problem that the portion becomes a conduction path, current leaks, and the voltage applied to the charging member drops. Further, since the amount of current flowing through the photoconductor is large, there is a problem that the damage to the photoconductor is large, the shaving amount of the photoconductor is increased, and the durability is reduced.

As another method, this is not limited to the DC direct charging method, but it is widely practiced to perform a pre-exposure before charging to achieve uniform charging. That is,
Pre-exposure uniformly reduces the potential of the photoreceptor surface to the residual potential, and then performs the next charging to eliminate charging unevenness. On the other hand, this method has the effect of simultaneously suppressing ghost, which is one of the image defects,
In some cases, pre-exposure is performed for that purpose. However, in general, pre-exposure irradiates the photoreceptor with a strong exposure of 5 to 10 times the image exposure amount, so that long-term use of the electrophotographic apparatus causes deterioration of the photoreceptor, reduction in sensitivity, and low image density. In some cases, this could be harmful.

As another method, a method of improving the uniformity of charging without superimposing an AC voltage has been proposed.
Japanese Patent Application Laid-Open No. 7-64302 proposes a method using an electrophotographic photosensitive member having a capacitance C per cm ² of 95 pF or more. When this method is used, even if only a DC voltage is used, the surface of the photosensitive member is uniformly charged, and a good image free from image defects such as streaks can be obtained.

[0009]

However, in the study of the present inventors, it has been found that a bright potential is greatly reduced when an electrophotographic apparatus of a DC direct charging system is continuously used. This phenomenon is observed before and after a relatively short durability test of several hours, and is characterized by the fact that the recovery starts immediately after the durability test is stopped. The degree of the decrease in the potential depends on the thickness of the photosensitive layer, the setting of the charging potential during the endurance, the print density during the endurance, the temperature and humidity during the endurance, the length of the endurance time, and the like. With respect to the thickness of the photosensitive layer, the amount of decrease in the bright potential is greater as the film thickness is reduced, but the feature is that the amount of decrease in the bright potential after the endurance becomes extremely large when the photosensitive layer is thinner than about 16 to 18 μm. Was also seen. The recovery of the bright potential was also examined, and it was found that the recovery of the bright potential started immediately after the end of the endurance, and when left for about 24 hours, the potential increased to near the potential before the start of the endurance. In addition, the potential (dark potential) of the non-exposed portion hardly changed before and after the durability.

As described above, if the bright potential greatly changes according to the state of use of the electrophotographic apparatus, the output image is adversely affected, such as a change in halftone density.

On the other hand, when an endurance test was performed using an AC / DC direct charging type electrophotographic apparatus under the same conditions except for the charging type, almost all changes were observed before and after the durability test in both the light potential and the dark potential. Did not. Therefore, it is considered that this phenomenon of the decrease in the light potential is a phenomenon peculiar to the DC direct charging type electrophotographic apparatus.

Although the cause of this phenomenon has not yet been elucidated, it is a phenomenon that is observed when the charging voltage is DC only, that it exhibits rapid recovery, and that the electric field (V / μm), the potential tends to decrease greatly as the intensity increases, and the dark potential hardly changes in response to a large change in the light potential. Therefore, the carrier injected from the conductive support by the electric field always applied in the same direction is used. Is gradually accumulated between the underlayer and the photosensitive layer, and the local electric field created by the inventor promotes the generation of photocarriers at the time of image exposure, and as a result, the present inventors have found that the light potential has decreased. Speculate.

Further, according to the study of the present inventors, it has been found that the decrease in the bright potential tends to decrease as the printing density during durability increases. From this, the portion of the photoreceptor surface that is less likely to receive image exposure is exposed to a high electric field for a longer time,
Therefore, it is considered that the accumulation of the above-mentioned carriers proceeds, and a larger decrease in the bright potential is caused.

An object of the present invention is to provide an electrophotographic apparatus using a charging method in which only a direct current voltage is applied to a charging member arranged in contact with an electrophotographic photosensitive member to perform charging, due to the effects of continuous use and environmental changes. An object of the present invention is to provide an electrophotographic apparatus and a process cartridge which can always obtain a high-quality image without image deterioration.

[0015]

(1) The present invention comprises an electrophotographic photosensitive member and a charging member arranged in contact with the electrophotographic photosensitive member, and the electrophotographic photosensitive member is applied by applying only a DC voltage to the charging member. In an electrophotographic apparatus having a charging unit for charging a surface of a photoconductor, the electrophotographic apparatus further includes a static elimination unit, and the static elimination unit sets a charging potential of a portion of the electrophotographic photoconductor that has not been subjected to image exposure. An electrophotographic apparatus characterized in that the charge potential is set to 1/5 or more and 1/3 or less of the charged potential before image exposure.

(2) The present invention is the electrophotographic apparatus according to (1), wherein the charge removing means is a charge removing means for exposing the electrophotographic photosensitive member.

(3) In the present invention, the electrophotographic photoreceptor has at least a photosensitive layer on a conductive support, and the thickness of the photosensitive layer is 18 μm or less (1) or (2).
Is an electrophotographic apparatus.

(4) The present invention is the electrophotographic apparatus according to (3), wherein the photosensitive layer of the electrophotographic photosensitive member contains at least a phthalocyanine compound.

(5) Further, according to the present invention, the photosensitive layer of the electrophotographic photosensitive member has a charge generation layer and a charge transport layer, and the charge generation layer contains at least a phthalocyanine compound. It is a photographic device.

(6) The present invention is the electrophotographic apparatus according to (4) or (5), wherein the phthalocyanine compound is a gallium phthalocyanine compound or an oxytitanium phthalocyanine compound.

(7) The present invention also relates to a hydroxygallium phthalocyanine crystal in which the gallium phthalocyanine compound has strong peaks at 7.4 ° and 28.2 ° at Bragg angles 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction. (6) The electrophotographic apparatus according to (6).

(8) Further, according to the present invention, the oxytitanium phthalocyanine compound can be used at 24.0 ° and 27.2 ° at Bragg angles 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction.
The electrophotographic apparatus according to (6), which is an oxytitanium phthalocyanine crystal having a peak at °.

(9) The present invention further provides an electrophotographic photosensitive member used in the electrophotographic apparatus of (1) to (8), a charging means having a charging member arranged in contact with the electrophotographic photosensitive member, a developing means,
A process cartridge which integrally supports at least one means selected from the group consisting of a cleaning means and a static elimination means and is detachable from an electrophotographic apparatus main body.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The contact charging method in which a charging member is brought into contact with an electrophotographic photosensitive member to perform charging is performed by a gap breaking discharge according to Paschen's rule in a minute space near a contact portion between the photosensitive member and the charging member. . In general, in an electrophotographic apparatus, a drum-shaped or belt-shaped photosensitive member is used, and any of the photosensitive members is charged while rotating or moving with respect to a charging member. That is, the boundary between the contact position of the photosensitive member and the charging member is divided into an upstream side and a downstream side, and a gap breaking discharge according to the Paschen rule occurs in each of the upstream and downstream small spaces, and the charging is performed. Done.

FIG. 1 shows a specific example of the electrophotographic apparatus of the present invention. In this apparatus, a roller-shaped charging member 1, an image exposure unit 4, a developing unit 5, a transfer charger 6, a cleaner 7, and a pre-exposure unit 8 are arranged on a peripheral surface of an electrophotographic photosensitive member 2.
G1 and G2 are discharge parts, and N is a contact part.

The charging member 1 is arranged in contact with the electrophotographic photosensitive member 2 and charges the photosensitive member 2 by a voltage applied from an external power supply 3 connected thereto.

The shape of the charging member 1 used in the present invention may be any shape such as a roller or a blade or a belt as shown in FIG. 1, and can be selected according to the specifications and form of the electrophotographic apparatus. It is. Examples of the material of the charging member include metals such as aluminum, iron and copper, conductive polymers such as polyacetylene, polypyrrole and polythiophene, rubber and artificial fibers in which carbon and metal are dispersed and conductively treated, Alternatively, an insulating material such as polycarbonate, polyvinyl chloride, and polyester whose surface is coated with a metal or another conductive material can be used. The volume resistivity of the charging ^{member, 10 0 ~10 12 Ω · cm} , especially 10 ² -
A range of 10 ¹² Ω · cm is preferable.

As the charge removing means used in the present invention, in addition to the pre-exposure means as shown in FIG. 1, for example, a contact charger using a conductive or semiconductive roller, brush, film, rubber blade or the like, corona Scorotron chargers and corotron chargers using discharge are conceivable,
In general, pre-exposure means is used in view of the load applied to the photoreceptor.

The light source used for the pre-exposure means is an LED
Known light sources such as light, tungsten lamp light, and halogen lamp light can be used. The light used for the pre-exposure may be white or red as long as it is included in a spectral region where the electrophotographic photosensitive member has photosensitivity, and can be appropriately selected depending on the purpose. Examples of the pre-exposure unit include an optical device that can expose the surface of the electrophotographic photosensitive member using a light source such as LED light, tungsten lamp light, and halogen lamp light.

The amount of exposure in the pre-exposure is such that the potential of a portion of the electrophotographic photosensitive member after the pre-exposure that has not been subjected to image exposure after charging is 1/5 or more of the dark potential in the image exposed portion and 1 / 3 or less. Specifically, the exposure amount of the pre-exposure by the pre-exposure means is adjusted so as to achieve such an exposure amount.

The exposure amount in the pre-exposure is insufficient, and the surface potential of the photoreceptor after the pre-exposure is 1/3 of the dark potential at the image exposure position.
If it becomes larger, it is not possible to effectively suppress a decrease in bright potential during continuous use. On the other hand, when the photoreceptor surface potential after the pre-exposure is smaller than 1/5 of the dark potential at the image exposure position due to the excessive pre-exposure light amount, the photoreceptor becomes fatigued by long-time continuous strong exposure. Since the sensitivity is lowered, the light potential after continuous use is higher than before use. In any case, a change in halftone density or the like is caused after continuous use, and a high-quality image cannot be obtained.

Although the reason why the reduction of the light potential during continuous use can be suppressed by performing appropriate charge elimination is still unknown, the time during which a high voltage is applied to the photoconductor by the charge elimination is relatively shortened. Therefore, the present inventors speculate that injection and accumulation of carriers from the conductive support may be suppressed.

The conductive support used in the electrophotographic photoreceptor of the present invention may be any as long as it has conductivity, for example, aluminum, an aluminum alloy,
Copper, zinc, stainless steel, vanadium, molybdenum, chromium, titanium, nickel, indium, gold and platinum can be used. In addition, plastics (for example, polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, and polyolefin) having a layer in which aluminum, an aluminum alloy, indium oxide, tin oxide, and indium oxide-tin oxide alloy are formed by a vacuum deposition method. Ethylene oxide), conductive particles (for example, aluminum powder, titanium oxide, tin oxide,
A support in which zinc oxide, carbon black, silver particles and the like are coated on a plastic or the support with a suitable binder resin (for example, phenol resin); a support in which conductive particles are impregnated in plastic or paper; Plastic having a polymer or the like can be used.

In the present invention, an undercoat layer having a barrier function and an adhesive function may be provided between the support and the photosensitive layer. Examples of the material of the undercoat layer include polyvinyl alcohol, polyethylene oxide, ethyl cellulose, methyl cellulose, casein, polyamide (eg, nylon 6, nylon 66, nylon 610, copolymerized nylon and N-alkoxymethylated nylon), polyurethane, glue, aluminum oxide, and the like. Gelatin or the like is used.
The film thickness is preferably 0.1 to 10 μm,
More preferably, it is 0.5 to 5 μm.

The charge generating layer of the electrophotographic photoreceptor used in the present invention comprises a homogenizer, an ultrasonic wave, a ball mill, a vibration ball mill, and a charge generating substance together with a binder resin and a solvent in an amount of 0.2 to 4 times by mass. It is well dispersed by a method such as a sand mill, an attritor, a roll mill, or the like, coated, and dried. The thickness is preferably 5 μm or less, more preferably 0.01 to 1 μm.

As the charge generating substance, pyrylium,
Examples include thiopyrylium dyes, phthalocyanine pigments, anthantrone pigments, dibenzopyrene quinone pigments, pyratron pigments, azo pigments, indigo pigments, quinacridone pigments, asymmetric quinocyanines and quinocyanines. Among them, phthalocyanine pigments exhibiting high sensitivity to red laser light are preferable, and among them, gallium phthalocyanine and oxytitanium phthalocyanine exhibit preferable characteristics.

As the binder resin used for the charge generation layer, for example, polyester, acrylic resin, polyvinyl carbazole, phenoxy resin, polycarbonate,
Resins such as polyvinyl butyral, polystyrene, polyvinyl acetate, polysulfone, polyarylate, polyvinylidene chloride, acrylonitrile copolymer and polyvinyl benzal are included.

The charge transport layer of the electrophotographic photoreceptor of the present invention comprises:
A coating material in which a charge transport material and a binder resin are mainly dissolved in a solvent is applied and dried to form a coating. The thickness is preferably 5 to 18 μm, more preferably 10 to 18 μm.

Examples of the charge transport material include various triarylamine compounds, hydrazone compounds, stilbene compounds, pyrazoline compounds, oxazole compounds,
And thiazole compounds and triallylmethane compounds.

Examples of the binder resin used for the charge transport layer include polyester, acrylic resin, polyvinyl carbazole, phenoxy resin, polycarbonate,
Resins such as polyvinyl butyral, polystyrene, polyvinyl acetate, polysulfone, polyarylate, polyvinylidene chloride, acrylonitrile copolymer and polyvinyl benzal are included.

The electrophotographic photosensitive member used in the present invention may be used by providing a protective layer on the above-mentioned photosensitive layer, if necessary.

As a method for applying each of the above-mentioned layers, an application method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a blade coating method and a beam coating method can be used.

The above-described charge generating substance, charge transporting substance, and binder resin used for each layer may be used alone or in combination of two or more.

Each layer may contain various additives such as a dispersant, an antioxidant, an ultraviolet ray inhibitor and a lubricant, if necessary.

In the method of forming an image in an electrophotographic apparatus according to the present invention, taking the electrophotographic apparatus shown in FIG. 1 as an example, first, a voltage is applied to the charging member 1 which is arranged in contact with the electrophotographic photosensitive member 2. And the surface of the photoconductor 2 is charged, and an image corresponding to the original is image-exposed on the photoconductor 2 by the image exposure unit 4.
An electrostatic latent image is formed. Next, the electrostatic latent image on the photoconductor 2 is developed (visualized) by attaching the toner in the developing device 5 to the photoconductor 2. Further, the transfer charger 6 transfers the toner image formed on the photoconductor 2 onto a transfer material P such as paper supplied.
The remaining toner remaining on the photoreceptor 2 without being transferred to the transfer material by the cleaner 7 is collected. Thereafter, the pre-exposure unit 8 irradiates the photoreceptor 2 with light to remove electricity. On the other hand, the transfer material on which the toner image has been formed is sent to the fixing device 9 by a transport unit (not shown), and the toner image is fixed.

In this image forming apparatus, the image exposing means 4
, A halogen light, a fluorescent lamp, a laser light, or the like can be used. Other auxiliary processes may be added as needed.

In the present invention, a plurality of components such as the above-described electrophotographic photosensitive member 2, charging member 1, developing unit 5, cleaner 7, and pre-exposure means 8 are integrally connected as a process cartridge. The process cartridge may be configured to be detachable from an electrophotographic apparatus body such as a copying machine or a laser beam printer. For example, at least one of the charging member 1, the developing device 5, and the cleaner is integrally supported together with the photoreceptor 2 to form a cartridge, which can be attached to and detached from the apparatus main body by using a guide means such as a rail (not shown) of the apparatus main body. It can be a process cartridge.

The electrophotographic apparatus of the present invention can be applied not only to an electrophotographic copying machine but also to a wide range of electrophotographic applications such as laser beam printers, CRT printers, LED printers, liquid crystal printers, and laser plate making.

[0050]

The present invention will be described below with reference to examples.

"%" And "parts" shown below mean "% by mass" and "parts by mass", respectively.

Example 1 50 parts of titanium oxide powder coated with tin oxide containing 10% of antimony oxide, 25 parts of resole type phenol resin, methyl cellosolve 20
Parts, 5 parts of methanol and 0.002 parts of silicone oil (polydimethylsiloxane / polyoxyalkylene copolymer, average molecular weight 3,000) were dispersed in a sand mill using 1 mmφ glass beads for 2 hours to prepare a coating for the conductive layer. Prepared. A conductive layer paint is applied on an aluminum cylinder (φ30 mm, length 260.5 mm) by a dip coating method, and dried at 140 ° C. for 30 minutes.
A conductive layer of 0 μm was formed.

A solution obtained by dissolving 5 parts of a 6-66-610-12 quaternary polyamide copolymer in a mixed solvent of 70 parts of methanol and 25 parts of butanol was applied on the conductive layer by dip coating, and dried. An undercoat layer having a thickness of 0.7 μm was formed.

Next, 3.5 parts of hydroxygallium phthalocyanine crystal having strong peaks at 7.4 ° and 28.2 ° of Bragg angle 2θ ± 0.2 ° in CuKα characteristic X-ray diffraction were added to a polyvinyl butyral resin (commercially available). Name: Esrec BX-1, manufactured by Sekisui Chemical Co., Ltd.) 1 part was mixed with a resin solution dissolved in 19 parts of cyclohexanone and dispersed in a sand mill using 1 mmφ glass beads for 3 hours to prepare a dispersion. 69 parts and 132 parts of ethyl acetate were added and diluted to prepare a charge generation layer coating. A paint for a charge generation layer is applied on the undercoating layer by a dip coating method, and dried at 100 ° C. for 10 minutes.
A 15 μm charge generation layer was formed.

FIG. 2 shows an X-ray powder diffraction pattern of the hydroxygallium phthalocyanine crystal. The powder X-ray diffraction was measured using CuKα radiation under the following conditions.

Measuring machine used: Mac Science Co., Ltd., fully automatic X-ray diffractometer MXP18 X-ray tube: Cu Tube voltage: 50 kV Tube current: 300 mA Scanning method: 2θ / θ scan Scanning speed: 2 deg. / Min Sampling interval: 0.020 deg. Start angle (2θ): 5 deg. Stop angle (2θ): 40 deg. Divergence slit: 0.5 deg. Scattering slit: 0.5 deg. Receiving slit: 0.3 deg. Using a curved monochromator Next, 10 parts of the charge transport material of the following structural formula

[0057]

Embedded image And 10 parts of a polyarylate resin represented by the following structural formula (viscosity average molecular weight: about 100,000)

[0058]

Embedded image Was dissolved in 60 parts of chlorobenzene to prepare a charge transport layer coating. A charge transport layer paint was applied on the charge generation layer by a dip coating method, and dried at 120 ° C. for 60 minutes to form a charge transport layer having a thickness of 15 μm. Thus, an electrophotographic photosensitive member was prepared.

The evaluation method will be described below. An LBP "Laser Jet 4000" manufactured by Hewlett-Packard Company was modified and used as an evaluation machine.

The modification was performed as follows. The high-voltage power supply board was modified, and only the DC power supply was used as the high-voltage power supply, and charging was performed by constant voltage control. At this time, the charging member was also replaced with a DC charging member. The image exposure device is provided with a variable resistor,
The amount of laser light can be changed by adjusting the applied voltage. Further, a fuse lamp was provided immediately before the charger as a pre-exposure device, and the light amount could be changed by adjusting the applied voltage using a variable resistor.
The measurement was performed by placing the apparatus in an environment of 23 ° C. and 50% RH.

The measurement, sampling and image evaluation were performed as follows. First, the initial charging potential (Vd) of the photoconductor
Was adjusted to −720 (V). Next, the image exposure amount was adjusted so that the light potential (Vl) became -100 (V). Note that Vd and V
The value of 1 is a measurement at the position of the developing device. Further, the charging potential of the photoconductor immediately after the pre-exposure is -180 (V) (1 / V of Vd).
The pre-exposure amount was adjusted so as to satisfy 4). Under these conditions, a halftone image of one dot and one space was output, and the image was visually observed and observed with a microscope, and the change in halftone density and the collapse of the black line portion were evaluated. Next, after performing an endurance test of outputting 2,000 images printed with a line of about 2 mm width every 7 mm in length and width, measurement of bright potential, image output and evaluation were performed again in the same manner as before the endurance test, Comparisons were made before and after the durability test. Table 1 shows the results.

Example 2 Evaluation was performed in the same manner as in Example 1 except that the following compound was used as a charge transporting substance. Table 1 shows the results.

[0063]

Embedded image

Example 3 Evaluation was performed in the same manner as in Example 1 except that the following compound was used as a charge transporting substance. Table 1 shows the results.

[0065]

Embedded image

Example 4 Evaluation was carried out in the same manner as in Example 1 except that the following compound was used as a charge transporting substance. Table 1 shows the results.

[0067]

Embedded image

Example 5 CuKα was used as a charge generation material.
8. Bragg angle 2θ ± 0.2 ° in characteristic X-ray diffraction
An electrophotographic photoreceptor was prepared and evaluated in exactly the same manner as in Example 1, except that oxytitanium phthalocyanine pigments having strong peaks at 5 °, 11.7 °, 24.1 ° and 27.3 ° were used. . Table 1 shows the results.

Example 6 CuKα was used as the charge generating material.
8. Bragg angle 2θ ± 0.2 ° in characteristic X-ray diffraction
An electrophotographic photosensitive member was prepared and evaluated in exactly the same manner as in Example 1 except that an oxytitanium phthalocyanine pigment having strong peaks at 0 °, 14.2 °, 23.9 ° and 27.1 ° was used. . Table 1 shows the results.

Example 7 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that a polycarbonate resin (trade name: Iupilon Z-200, manufactured by Mitsubishi Gas Chemical Company) was used as a binder resin for the charge transport layer. Created and evaluated. Table 1 shows the results.

[Embodiment 8] In Embodiment 1, the pre-exposure amount is changed to change the charged potential of the photosensitive member after pre-exposure to -240.
(V) Evaluation was carried out in exactly the same manner as in Example 1 except that (１ ／) of (Vd). Table 1 shows the results.

Ninth Embodiment In the first embodiment, the pre-exposure amount is changed to change the charged potential of the photosensitive member after the pre-exposure to -144.
(V) Evaluation was carried out in the same manner as in Example 1 except that (1/5 of Vd) was used. Table 1 shows the results.

[Embodiment 10] In Embodiment 5, the pre-exposure amount is changed to change the charged potential of the photosensitive member after pre-exposure to -240.
(V) Evaluation was performed in exactly the same manner as in Example 5 except that (（) of (Vd) was used. Table 1 shows the results.

[Embodiment 11] In Embodiment 5, the pre-exposure amount is changed to change the charged potential of the photosensitive member after the pre-exposure to -144.
(V) Evaluation was carried out in exactly the same manner as in Example 5 except that (1/5 of Vd) was used. Table 1 shows the results.

[Embodiment 12] In Embodiment 6, the pre-exposure amount is changed to change the charged potential of the photosensitive member after pre-exposure to -240.
(V) Evaluation was performed in exactly the same manner as in Example 6 except that (に) of (Vd) was used. Table 1 shows the results.

[Embodiment 13] In Embodiment 6, the pre-exposure amount is changed to change the charging potential of the photosensitive member after the pre-exposure to -144.
(V) Evaluation was carried out in exactly the same manner as in Example 6, except that (1/5 of Vd) was used. Table 1 shows the results.

Example 14 Evaluation was carried out in exactly the same manner as in Example 1 except that 9 parts of the compound [1] and 1 part of the compound [3] were mixed and used as the charge transporting substance.
Table 1 shows the results.

Comparative Example 1 Evaluation was performed in the same manner as in Example 1 except that no pre-exposure was used.
Table 1 shows the results.

Comparative Example 2 In Example 1, the pre-exposure amount was changed to change the charging potential of the photoreceptor after pre-exposure to -360.
(V) Evaluation was performed in exactly the same manner as in Example 1 except that (（of Vd) was used. Table 1 shows the results.

[Comparative Example 3] In Example 1, the pre-exposure amount was changed to change the charged potential of the photosensitive member after the pre-exposure to -72 (V).
The evaluation was performed in exactly the same manner as in Example 1 except that (1/10 of Vd) was used. Table 1 shows the results.

Comparative Example 4 Evaluation was made in the same manner as in Example 5, except that no pre-exposure was used.
Table 1 shows the results.

Comparative Example 5 In Example 5, the pre-exposure amount was changed to change the charging potential of the photoreceptor after pre-exposure to -360.
(V) Evaluation was carried out in exactly the same manner as in Example 5, except that (１ ／ of Vd) was used. Table 1 shows the results.

[Comparative Example 6] In Example 5, the pre-exposure amount was changed to change the charged potential of the photosensitive member after the pre-exposure to -72 (V).
The evaluation was performed in exactly the same manner as in Example 5 except that (1/10 of Vd) was used. Table 1 shows the results.

Comparative Example 7 Evaluation was made in the same manner as in Example 6, except that no pre-exposure was used.
Table 1 shows the results.

[Comparative Example 8] In Example 6, the pre-exposure amount was changed to change the charging potential of the photosensitive member after the pre-exposure to -360.
(V) Evaluation was performed in exactly the same manner as in Example 6, except that (１ ／ of Vd) was used. Table 1 shows the results.

Comparative Example 9 In Example 6, the pre-exposure amount was changed to change the charged potential of the photoreceptor after pre-exposure to -72 (V).
The evaluation was performed in exactly the same manner as in Example 6, except that (1/10 of Vd) was used. Table 1 shows the results.

[0087]

[Table 1]

[Embodiment 15] In Embodiment 1, the aluminum cylinder of the photosensitive member was φ30 mm, and the length was 357 mm.
An electrophotographic photosensitive member was prepared in exactly the same manner as in Example 1 except that the thickness was changed to 5 mm and the thickness of the charge transport layer was changed to 18 μm.

The photoreceptor thus produced was manufactured by Canon G
The evaluation was carried out by mounting on a modified P211 copier (21 sheets per minute). Modification of the equipment is a high-voltage power supply board, image exposure equipment,
This was performed on the pre-exposure device. The high-voltage power supply substrate was modified so as to output a DC-only primary charge controlled at a constant voltage while the electrophotographic photosensitive member was rotating. In addition, the charging member was replaced with a DC charging member. The image exposure apparatus and the pre-exposure apparatus were modified so that the light amount could be adjusted. The measurement was performed by placing the apparatus in an environment of 23 ° C. and 50% RH.

The measurement was performed as follows. First, the voltage applied to the charging member was adjusted so that the initial charging potential (Vd) of the photoconductor became -750 (V). Next, the image exposure amount was adjusted so that the light potential (Vl) became -200 (V). The values of Vd and Vl are measured values at the position of the developing device. Further, the pre-exposure amount was adjusted so that the charging potential of the photoconductor immediately after the pre-exposure was -250 (V) (１ ／ of Vd). After outputting 5,000 sheets of a character pattern image with A4 and a printing rate of 5% under these conditions, the bright potential was measured again, and comparisons were made before and after durability. Table 2 shows the results.

[Embodiment 16] In Embodiment 5, the aluminum cylinder of the photosensitive member was φ30 mm and the length was 357 mm.
An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 5 except that the thickness was changed to 5 mm and the thickness of the charge transport layer was changed to 20 μm, and the same evaluation as in Example 15 was performed except that the photoreceptor was used. . Table 2 shows the results.

[Embodiment 17] In Embodiment 6, the aluminum cylinder of the photosensitive member was φ30 mm, and the length was 357 mm.
An electrophotographic photoreceptor was prepared in exactly the same manner as in Example 6 except that the thickness was changed to 5 mm and the thickness of the charge transport layer was set to 20 μm, and the same evaluation as in Example 15 was performed except that the photoreceptor was used. . Table 2 shows the results.

Comparative Example 10 Evaluation was made in the same manner as in Example 15 except that no pre-exposure was used. Table 2 shows the results.

Comparative Example 11 Evaluation was performed in the same manner as in Example 16 except that no pre-exposure was used. Table 2 shows the results.

Comparative Example 12 Evaluation was performed in the same manner as in Example 17 except that no pre-exposure was used. Table 2 shows the results.

[0096]

[Table 2]

[0097]

According to the present invention, it is possible to provide a DC direct charging type electrophotographic apparatus and a process cartridge which can suppress a decrease in the light potential of the electrophotographic photosensitive member due to continuous use and can always output a high quality image.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an electrophotographic apparatus of the present invention.

FIG. 2 shows a powder X-ray diffraction pattern of the hydroxygallium phthalocyanine crystal used in Example 1.

Continuation of the front page (72) Inventor Hirotoshi Uesugi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Takashi Higashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. F-term (reference) 2H003 BB11 CC05 EE11 2H035 AA08 AB02 AB03 AC02 AZ09 2H068 AA19 AA34 AA35 BA39 FA27

Claims (9)

[Claims] 1. An electrophotographic photoreceptor and a charging member disposed in contact with the electrophotographic photoreceptor, and a charging unit for charging the surface of the electrophotographic photoreceptor by applying only a DC voltage to the charging member. In the electrophotographic apparatus, the electrophotographic apparatus further includes a static eliminator, and the static eliminator causes the charged potential of a portion of the electrophotographic photosensitive member that has not been subjected to image exposure to be at least 1/5 of the charged potential before image exposure. And an electrophotographic apparatus characterized in that it is reduced to 1/3 or less. 2. The electrophotographic apparatus according to claim 1, wherein said charge removing means is a charge removing means for exposing said electrophotographic photosensitive member to light. 3. The electrophotographic photosensitive member has at least a photosensitive layer on a conductive support, and the photosensitive layer has a thickness of 18
The electrophotographic apparatus according to claim 1, wherein the size is not more than μm. 4. The electrophotographic apparatus according to claim 3, wherein the photosensitive layer of the electrophotographic photosensitive member contains at least a phthalocyanine compound. 5. The electrophotographic apparatus according to claim 4, wherein the photosensitive layer of the electrophotographic photosensitive member has a charge generation layer and a charge transport layer, and the charge generation layer contains at least a phthalocyanine compound. 6. The electrophotographic apparatus according to claim 4, wherein the phthalocyanine compound is a gallium phthalocyanine compound or an oxytitanium phthalocyanine compound. 7. The gallium phthalocyanine compound,
Bragg angle 2θ ± 0.2 in CuKα characteristic X-ray diffraction
The electrophotographic apparatus according to claim 6, which is a hydroxygallium phthalocyanine crystal having strong peaks at 7.4 ° and 28.2 °. 8. The method according to claim 1, wherein the oxytitanium phthalocyanine compound has a Bragg angle 2θ in CuKα characteristic X-ray diffraction.
7. An oxytitanium phthalocyanine crystal having peaks at 24.0 ° and 27.2 ° of ± 0.2 °.
An electrophotographic apparatus according to claim 1. 9. An electrophotographic photosensitive member used in the electrophotographic apparatus according to claim 1, and a charging unit, a developing unit, a cleaning unit, and a discharging unit having a charging member arranged in contact with the electrophotographic photosensitive member. A process cartridge which integrally supports at least one means selected from the group consisting of and is detachable from the main body of the electrophotographic apparatus.