JP2007058050A - Electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic apparatus which suppresses the occurrence of a secondary color ghost in color images and is high in durability and low in cost. <P>SOLUTION: The electrophotographic apparatus comprises: a plurality of image forming sections each consisting of an electrophotographic photoreceptors; a charging means for charging the surface of the electrophotographic photoreceptor; an exposing means for forming an electrostatic latent image by exposure light on the surface of the electrophotographic photoreceptor charged by the charging means; a developing means for forming a toner image by developing the electrostatic latent image, which is formed by the exposing means on the surface of the electrophotographic photoreceptor, by development with a toner; and a transfer means for transferring the toner image to a transfer material or an intermediate transfer member, in which the charge mobility in field intensity of 2x205V/cm of the photoreceptor disposed in the image forming section for forming the color images is ≥1.2 times the charge mobility of the photoreceptor disposed in the image forming section for forming the black toner image. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a color electrophotographic apparatus having a plurality of electrophotographic photosensitive members.

  In recent years, various electrophotographic color image forming apparatuses have been proposed. The image forming apparatus includes a plurality of image forming units, and each image forming unit forms a visible image (toner image) having a different color. 2. Description of the Related Art Color image forming apparatuses that transfer an image in sequence on the same recording material are frequently used. In such an electrophotographic color image forming apparatus, a plurality of image forming units, generally four image forming units, are juxtaposed, and a dedicated photoconductor is used as an image carrier for these image forming units.

  A visible image of yellow (Y), magenta (M), cyan (C), and black (Bk), that is, a toner image is separately formed on each photoreceptor, and each color is sequentially formed on the intermediate transfer member or the recording material. When the toner image is transferred onto the intermediate transfer member, the toner image is further transferred to the recording material, and further transferred onto the recording material, and the multiple toner images on the recording material are heated and fixed together by a fixing device, thereby obtaining a desired full-color image. And trying to get multicolor images. Many attempts have been made for this method because a color image can be output at high speed.

  Such an image forming apparatus can perform high-speed image formation, but has a disadvantage that the apparatus is large because of having a plurality of image forming units, and the cost is high. For this reason, a photoreceptor having a small diameter and an organic photoreceptor having a high productivity and a low production cost are often used.

  However, in the image forming apparatus configured as described above, even when a single color (usually black) image is formed, the other photoconductors rotate in contact with the transfer material or the intermediate transfer body in the same manner as the photoconductors for image formation. Therefore, there is a drawback that the photoconductor is worn and the life is shortened. Therefore, there is a strong demand for improvement in mechanical durability, mainly wear resistance, on the photoreceptor. One possible solution is to increase the photosensitive layer thickness of the photoreceptor.

  In the case of a color electrophotographic apparatus, in order to prevent a phenomenon in which toner of a previously transferred color returns to the photoreceptor when transferring the subsequent color, that is, so-called retransfer, the transfer current is increased each time the colors are overlapped. I often go. Increasing the transfer current causes a high-voltage transfer bias to be applied to the photosensitive member, intermediate transfer member or recording material conveying member, which may cause pinhole leakage, impair the durability of the photosensitive member, The material that makes up the body may be destroyed.

Although it is required for all electrophotographic apparatuses to sufficiently increase transfer efficiency without increasing the transfer current, among these, color electrophotographic apparatuses as described above are required to have higher dimensions. That is. As means for increasing the transfer efficiency, the surface layer of the photoconductor is made to contain a silicone resin, or fluorine atom-containing resin particles (fluorine resin powder) are dispersed to improve the releasability of the photoconductor surface. It is known (see Patent Documents 1 and 2).
JP 2000-081715 A Japanese Patent Laid-Open No. 2001-249481

  However, when the photosensitive layer thickness is increased or the photosensitive layer contains silicone resin or fluorine atom-containing resin particles, it is called a ghost in which a non-original pattern appears on the image in the full-color image of the image forming apparatus having the above configuration. A phenomenon sometimes occurred. In particular, since a color image is formed by superimposing a plurality of toner images, it may appear more noticeably as a secondary color ghost than a single color image.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a highly durable and low-cost electrophotographic apparatus that suppresses the occurrence of secondary color ghosts in a color image.

In order to achieve the above object, the invention described in claim 1 includes an electrophotographic photosensitive member, a charging unit for charging the surface of the electrophotographic photosensitive member, exposure light on the surface of the electrophotographic photosensitive member charged by the charging unit. An exposure means for forming an electrostatic latent image by the developing means, a developing means and a transfer material for forming a toner image by developing the electrostatic latent image on the surface of the electrophotographic photosensitive member formed by the exposure means with toner, or In an electrophotographic apparatus having a plurality of image forming units composed of transfer means for transferring to an intermediate transfer member, 2 × 10 5 of the photoconductor provided in the image forming unit for forming a color toner image.
The charge mobility at an electric field intensity of V / cm is 1.2 times or more the charge mobility of the photoconductor provided in the image forming unit for forming a black toner image.

  The invention according to claim 2 is the structure according to claim 1, wherein each of the electrophotographic photoreceptors has a structure in which a charge generation layer and a charge transport layer are laminated on a conductive support, and the film thickness of the charge transport layer. Is 28 μm or more.

  According to the present invention, it is possible to provide an electrophotographic apparatus that suppresses the occurrence of a secondary color ghost in a color image, and has high durability and low cost.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic configuration diagram showing an example of a color electrophotographic apparatus of the present invention. In the following description, examples of four colors (yellow, magenta, cyan, and black) are given. However, the “color” in the present invention is not limited to four colors, and black and two or more kinds It is a combination of colors.

  This apparatus can form, for example, yellow (Y), magenta (M), cyan (C), and black (K) visible images (toner images) in the apparatus main body. Each image forming unit includes dedicated photoconductors 1Y, 1M, 1C, and 1K as image carriers. Each of the photoreceptors 1Y, 1M, 1C, and 1K is driven to rotate in the direction indicated by the arrow about the axes 2Y, 2M, 2C, and 2K, and is surrounded by primary charging means 3Y, 3M that are dedicated image forming process means, respectively. , 3C, 3K, image exposure (exposure means not shown) 4Y, 4M, 4C, 4K, developing means 5Y, 5M, 5C, 5K storing toner of each color, cleaning means 6Y, 6M, 6C, 6K, etc. It is arranged. The cleaning unit is not necessarily required when a toner or a photoconductor with high transfer efficiency is used, and the developing unit may collect residual toner on the photoconductor. Although it is possible to have a discharging means before the primary charging means, it is not always necessary.

  An intermediate transfer member 8 is stretched between a plurality of rollers and is rotated in the direction of the arrow below the photoreceptors 1Y, 1M, 1C, and 1K of each image forming unit. 7M, 7C, and 7K are provided. Further, a secondary transfer unit 9 and a fixing device 11 are arranged on the downstream side of the intermediate transfer member 8.

  In the present invention, as shown in FIG. 2, the above-described electrophotographic photoreceptors 1Y, 1M, 1C, 1K, primary charging means 3Y, 3M, 3C, 3K, developing means 5Y, 5M, 5C, 5K and cleaning means 6Y, A plurality of components such as 6M, 6C, 6K, etc. are integrally combined as a process cartridge, and the process cartridge is configured to be detachable from an electrophotographic apparatus main body such as a copying machine or a laser beam printer. You may do it.

  The image exposures 4Y, 4M, 4C, and 4K, when the electrophotographic apparatus is a copying machine or a printer, read reflected light or transmitted light from the original, or read the original with a sensor and convert it to a signal. The light is emitted by scanning the laser beam, driving the LED array, driving the liquid crystal shutter array, and the like.

  The operation of the image forming apparatus configured as described above will be described using the image forming unit Y as an example. The photoreceptor 1Y has a photosensitive layer on the surface of the conductive support and rotates in the direction of the arrow in the figure. Then, after the surface is negatively charged uniformly by the charging roller 3Y, an electrostatic latent image corresponding to the original is formed by the laser exposure light 4Y. The developing unit 5Y performs development using negatively charged toner, and forms a toner image corresponding to the electrostatic latent image on the photoreceptor surface 1Y. This toner image is transferred onto the intermediate transfer belt 8 by the primary transfer roller 7Y, and the remaining toner adhering to the surface of the photoreceptor 1Y after the transfer is removed by the cleaner 6Y and used for the next image formation.

  Similarly, the M, C, and K images are sequentially transferred onto the intermediate transfer member to form a full color image. Thereafter, the image on the intermediate transfer belt is collectively transferred by the secondary transfer roller 9 to the recording material P supplied at a predetermined timing by the paper feed roller. Residual toner on the intermediate transfer member is removed by the intermediate transfer member cleaner 10 and used for the next image formation. The recording material P is sent to the fixing device 11 where it is fixed together and a desired full color image is obtained.

  Next, the photoreceptor in the present invention will be described.

The photoreceptor is a laminated photoreceptor in which a charge generation layer and a charge transport layer are formed in this order on a conductive support. The configuration of the photoconductor provided in the image forming unit for forming the color toner image is different from that of the photoconductor provided in the image forming unit for forming the black toner image, and is provided in the image forming unit for forming the color toner image. The charge mobility of the photoconductor at an electric field strength of 2 × 10 ⁵ V / cm is 1.2 times or more the charge mobility of the photoconductor provided in the image forming unit for forming a black toner image. The charge mobility can be changed by the configuration of the charge transport layer.

Also, the charge transport layer is more effective when it is an electrophotographic photosensitive member having a film thickness of 28 μm or more and a thicker film than usual. Further, the preferred value of the charge mobility at the electric field strength of 2 × 10 ⁵ V / cm of all the photoreceptors provided in the image forming unit depends on the process speed of the electrophotographic apparatus, but can cope with the recent increase in speed. The charge mobility is preferably 1 × 10 ⁻⁶ cm / V · sec or more.

  The conductive support used in the present invention may be any conductive support as long as it has conductivity, for example, a metal such as aluminum, copper, chromium, nickel, zinc, and stainless steel formed into a drum or sheet, aluminum Metal foil such as copper or copper laminated on plastic film, aluminum, indium oxide, tin oxide etc. deposited on plastic film, metal or plastic with conductive layer applied alone or with binder resin A film, paper, etc. are mentioned.

  In addition, when the image input of a laser beam printer or the like is laser light, a conductive layer may be provided on the support for the purpose of preventing interference fringes due to scattering or covering scratches on the substrate. This can be formed by dispersing conductive powder such as carbon black and metal particles in a binder resin. Further, it is also effective to add an appropriate amount of silica fine particles in order to suppress interference fringes. The film thickness of the conductive layer is preferably 0.5 to 25 μm. In addition, the support surface can be cut, roughened, anodized, or the like to suppress interference fringes.

  Furthermore, an undercoat layer can be provided on the conductive support or on the conductive layer. The undercoat layer can be formed of polyamide, polyvinyl alcohol, polyethylene oxide, casein, ethyl cellulose, polyurethane, polyether urethane, or the like. The thickness of the undercoat layer is 0.05 to 3 μm, preferably 0.3 to 1 μm.

  The charge generation layer is composed of at least a charge generation material and a binder resin. Examples of the charge generating material include azo pigments, quinone pigments, quinocyanine pigments, perylene pigments, indigo pigments, and phthalocyanine pigments. These materials may be used alone or in combination of two or more. Examples of the binder resin include polyamide resin, polyvinyl butyral resin, polyester resin, acrylic resin, polycarbonate resin, polyvinyl acetal resin, polystyrene resin, polyarylate resin, polyvinyl benzal resin, polyurethane, epoxy resin, and phenol resin. . The ratio of pigment to binder resin is in the range of 10: 1 to 1: 5, preferably 5: 1 to 1: 4, by weight. Furthermore, you may add a dispersing agent, silicone oil, a leveling agent, antioxidant, an electric charge (electron) conveyance agent etc. as an additive. The thickness of the charge generation layer is preferably in the range of 0.05 to 2 μm. The charge generation layer configuration and film thickness of the photoconductor provided in the image forming unit for forming the color toner image and the photoconductor provided in the image forming unit for forming the black toner image differ depending on the developability of the toner. Also good.

  The charge transport layer is composed of at least a charge transport material and a binder resin.

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

  Examples of the binder resin include polyester resin, acrylic resin, polyvinyl carbazole resin, phenoxy resin, polycarbonate resin, polyvinyl butyral resin, polystyrene resin, polyvinyl acetate resin, polysulfone resin, polyarylate resin, vinylidene chloride and acrylonitrile copolymer resin. It is done. Among them, a polyarylate resin is exemplified as one having excellent wear resistance.

  The ratio (mass) between the charge transport material and the binder resin is about 5/1 to 1/5, preferably about 3/1 to 1/3.

  In charge transport layer, to improve transfer efficiency and improve durability, silicone modified resin and fluorine modified resin, inorganic filler as lubricant, polyethylene, fluorine atom-containing resin particles, silica, etc., dispersant, silicone oil, leveling It is more preferable to add an agent, an antioxidant or the like. In particular, as an additive for increasing the transfer efficiency, it is preferable to use a silicone-modified resin, a fluorine-modified resin, or fluorine atom-containing resin particles. These additives easily form trap sites in the charge transport layer and have the effect of slowing charge mobility. Therefore, the additive amount in the photoreceptor provided in the image forming portion for forming a color toner image is black toner image. It is preferable to make it smaller than the amount of addition in the photoconductor provided in the image forming part for forming the film.

  Further, when the charge transport layer is thickened, the electric field applied to the photoconductor is reduced, and the number of carriers remaining in the photoconductor is increased, so that a ghost is easily generated, and the present invention effectively operates. On the other hand, in order to increase the sensitivity of the organic photoreceptor, it is known that the thickness of the photosensitive layer should be increased. From the viewpoint of improving the durability of the photoreceptor, charge transport is carried out in the practice of the present invention. The thickness of the layer is desirably 28 μm or more, which is thicker than usual. Further, although there is no upper limit of the film thickness, generally, if it is 40 μm or more, there may be a problem in production, the thickness is more preferably less than 40 μm.

  Solvents used in the coating solution for the charge transport layer include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, ethers such as tetrahydrofuran, chlorobenzene, chloroform, and carbon tetrachloride. Hydrocarbons substituted with halogen atoms such as are used.

  Examples of the method for applying each layer include general methods such as dip coating, spray coating, blade coating, and roll coating.

Hereinafter, the present invention will be described in more detail with reference to specific examples. However, the present invention is not limited to these. In the examples, “part” means “part by mass”.
[Photosensitive member production example 1]
An aluminum cylinder having a diameter of 30 mm and a length of 260 mm was used as a support.

Next, a mixed solvent of SnO ₂ coated treated barium sulfate (conductive particles) 10 parts, titanium oxide (for resistance adjustment) 2 parts, phenol resin 6 parts, silicone oil 0.001 part and methanol 4 parts / methoxypropanol 16 parts Was dispersed in a sand mill apparatus using glass beads having a diameter of 1 mm for 2 hours to prepare a conductive layer coating solution.

  This conductive layer coating solution was dip-coated on a support and thermally cured at 140 ° C. for 30 minutes to form a conductive layer having a thickness of 15 μm.

  Next, 5 parts of N-methoxymethylated nylon and 1 part of copolymer nylon were dissolved in a mixed solvent of 65 parts of methanol / 30 parts of n-butanol to prepare an intermediate layer coating solution.

  This intermediate layer coating solution was dip coated on the conductive layer and dried at 100 ° C. for 10 minutes to form an intermediate layer having a thickness of 0.7 μm.

  Next, a mixed solution obtained by dissolving 10 parts of polyvinyl butyral resin (trade name BX-1, manufactured by Sekisui Chemical Co., Ltd.) in 300 parts of special grade cyclohexanone, and a diffraction angle 2θ ± 0 in an X-ray diffraction spectrum of CuKα as a charge generating substance. 15 parts of a hydroxygallium phthalocyanine pigment having a strong peak at 7.3 ° and 28.1 ° at 2 ° (Chemical formula 1)

を、サンドミル装置にて４時間分散を行った。得られた分散液を特級酢酸エチル５００部及び特級シクロヘキサノン２００部で希釈して塗布液を調整した。この塗布液におけるフタロシアニン顔料の平均体積粒径を粒度分布計（ＣＡＰＡ−７００、堀場製作所製）で測定したところ、０．１２μｍであった。この塗布液を上記下引き層上に浸漬塗布法で塗布し、５０℃で１０分乾燥し、乾燥後塗布重量が０．１５μｍの電荷発生層を形成した。

Was dispersed in a sand mill apparatus for 4 hours. The obtained dispersion was diluted with 500 parts of special grade ethyl acetate and 200 parts of special grade cyclohexanone to prepare a coating solution. It was 0.12 micrometer when the average volume particle diameter of the phthalocyanine pigment in this coating liquid was measured with the particle size distribution analyzer (CAPA-700, Horiba, Ltd. make). This coating solution was applied onto the undercoat layer by a dip coating method and dried at 50 ° C. for 10 minutes. After drying, a charge generation layer having a coating weight of 0.15 μm was formed.

  Next, 9 parts of a compound represented by the following structural formula as a charge transport material,

下記構造式で示す化合物を１部、

1 part of a compound represented by the structural formula

バインダー樹脂として下記式で示される繰り返し構造単位を有するポリアリレート樹脂（化４、重量平均分子量１０００００）１２．５部、

12.5 parts of a polyarylate resin (chemical formula 4, weight average molecular weight 100000) having a repeating structural unit represented by the following formula as a binder resin:

下記式で示されるシリコーン変性樹脂（化５、重量平均分子量５０００）０．０２５部を、

0.025 part of a silicone-modified resin (chemical formula 5, weight average molecular weight 5000) represented by the following formula:

ジメトキシメタン４０部とモノクロロベンゼン６０部の混合溶液に溶解した。この液を上記電荷発生層上に浸漬コーティング法で塗布し、１２０℃で１時間乾燥し、膜厚が２８μｍの電荷輸送層を形成し、電子写真感光体を作製した。

Dissolved in a mixed solution of 40 parts of dimethoxymethane and 60 parts of monochlorobenzene. This solution was applied onto the charge generation layer by a dip coating method and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm, thereby producing an electrophotographic photoreceptor.

The charge mobility of the produced photoreceptor was determined by a method for measuring the carrier mobility of the photoreceptor, known as the so-called xerography-time of flight method (X-TOF method). Specifically, the surface of the photoreceptor is charged to −500 to −800 V using CYNTHIA-71 manufactured by GENTEC, and the surface potential is attenuated by irradiating laser light having a wavelength of 675 nm for 100 μsec. The mobility was calculated. The electric field strength was determined from the charged potential on the surface of the photoreceptor and the charge transport layer of the measurement sample. As a result, the charge mobility at an electric field strength of 2 × 10 ⁵ V / cm was 4.3 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 2]
An electrophotographic photoreceptor was produced in the same manner as in photoreceptor preparation example 1 except that the charge generation layer thickness was changed to 0.17 μm and the charge transport layer was changed as follows.

  As a charge transport layer coating solution, first, 10 parts of a polyarylate resin having a repeating structural unit represented by the above formula (Chemical Formula 4) is dissolved in 100 parts of chlorobenzene, and tetrafluoroethylene resin particles as fluorine atom-containing resin particles. (Product name: Lubron L-2, manufactured by Daikin Industries, Ltd., average particle size (primary particles) 0.3 μm, average particle size (secondary particles) 5 μm) 10 parts, diorganopolysiloxane (Chemical Formula 6) 0 .5 parts

を添加して良く振り混ぜた。この混合物を、液衝突型分散機を用い、２回分散することによって、フッ素原子含有樹脂粒子分散液を調製した。

Was added and shaken well. This mixture was dispersed twice using a liquid collision type disperser to prepare a fluorine atom-containing resin particle dispersion.

  Next, a polyarylate resin having a repeating structural unit represented by the above formula (Chemical Formula 4): the charge transport agent (Chemical Formula 2): the charge transport agent (Chemical Formula 3): the tetrafluoroethylene resin particles: the diorgano Polyarylate resin (Chemical Formula 4), charge transfer agent so that the final mass ratio of polysiloxane (Chemical Formula 6): chlorobenzene: dimethoxymethane is 12.5: 9: 1: 1: 0.05: 60: 40 (Chemical Formulas 2 and 3), chlorobenzene, and methylal were added to the fluorine atom-containing resin particle dispersion for adjustment. It was 0.18 micrometer when the average volume particle diameter of the fluorine atom containing resin particle in this dispersion liquid was measured with the particle size distribution analyzer (CAPA-700, Horiba, Ltd. make).

  This dispersion was dip coated on the charge generation layer and dried at 120 ° C. for 1 hour to form a charge transport layer having a thickness of 28 μm.

When the charge mobility at 2 × 10 ⁵ V / cm of the produced photoreceptor was measured, it was 3.9 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 3]
In Photoconductor Preparation Example 2, a polyarylate resin having a charge generation layer having a thickness of 0.18 μm and a charge transport layer having a repeating structural unit represented by the above formula (Formula 4): the charge transport agent (Formula 2): Charge transfer agent (chemical formula 3): tetrafluoroethylene resin particles: diorganopolysiloxane (chemical formula 6): chlorobenzene: dimethoxymethane in a final mass ratio of 12.5: 9: 1: 2.5: 0. An electrophotographic photoreceptor was produced in the same manner as in photoreceptor preparation example 2 except that the adjustment was made to be 125: 60: 40. The average volume particle size of the fluorine atom-containing resin particles in the charge transport layer coating solution was 0.19 μm.

The charge mobility at 2 × 10 ⁵ V / cm of the produced photoreceptor was measured and found to be 3.1 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 4]
In Photoconductor Preparation Example 1, a polyarylate resin having a repeating structural unit represented by the following formula as a binder resin for a charge transport layer (Chemical Formula 7, weight average molecular weight 100,000)

に変更した以外は、感光体作成例１と同様にして電子写真感光体を作製した。

An electrophotographic photosensitive member was produced in the same manner as in Photoreceptor Preparation Example 1 except that the above was changed.

The charge mobility of the produced photoreceptor at 2 × 10 ⁵ V / cm was 3.8 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 5]
In Photoconductor Preparation Example 2, the charge transport layer binder resin was changed to a polyarylate resin (Chemical Formula 7) having a repeating structural unit represented by the above formula, and an antioxidant having the following structure (Chemical Formula 8).

を樹脂に対して５質量％添加した以外は、感光体作成例２と同様にして電子写真感光体を作製した。電荷輸送層塗布液におけるフッ素原子含有樹脂粒子の平均体積粒径は０．１９μｍであった。

An electrophotographic photosensitive member was produced in the same manner as in Photoreceptor Preparation Example 2 except that 5% by mass of was added to the resin. The average volume particle size of the fluorine atom-containing resin particles in the charge transport layer coating solution was 0.19 μm.

The charge mobility of the produced photoreceptor at 2 × 10 ⁵ V / cm was 3.0 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 6]
In Photoconductor Preparation Example 1, the charge generating material has strong peaks at diffraction angles 2θ ± 0.2 ° of 9.0 °, 14.2 °, 23.9 °, and 27.1 ° in the X-ray diffraction spectrum of CuKα. Oxytitanium phthalocyanine pigment (Chemical formula 9)

に変えた以外は感光体作製例１と同様に感光体を作製した。電荷発生層塗布液におけるフタロシアニン顔料の平均体積粒径は、０．０５μｍであった。

A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that The average volume particle size of the phthalocyanine pigment in the charge generation layer coating solution was 0.05 μm.

The charge mobility of the produced photoreceptor at 2 × 10 ⁵ V / cm was 4.3 × 10 ⁻⁶ cm / V · sec.
[Photoconductor Preparation Example 7]
In Photoconductor Preparation Example 3, the charge generating material has strong peaks at diffraction angles 2θ ± 0.2 ° of 9.0 °, 14.2 °, 23.9 °, and 27.1 ° in the X-ray diffraction spectrum of CuKα. An electrophotographic photoreceptor was produced in the same manner as in photoreceptor preparation example 3 except that the oxytitanium phthalocyanine pigment (Chemical Formula 9) was changed. The average volume particle size of the phthalocyanine pigment in the charge generation layer coating solution was 0.05 μm.

The charge mobility of the produced photoreceptor at 2 × 10 ⁵ V / cm was 3.2 × 10 ⁻⁶ cm / V · sec.

In the electrophotographic apparatus of FIG. 1 (process speed 150 mm / sec), the photoconductor of Preparation Example 3 is formed on the image forming unit for forming a black toner image, and the photoconductor of Preparation Example 1 is formed on the image forming unit for forming a color toner image. It was charged and charged so that the dark part potential was −600 V (direct current + alternating current contact charge), and this was irradiated with a laser beam having a wavelength of 780 nm and 2.5 mJ / m ² to measure the bright part potential to obtain sensitivity. The surface potential of the photosensitive member is measured by removing the intermediate transfer member of the electrophotographic apparatus and placing a potential measuring probe at the transfer position. The distance was 3 mm.

  Moreover, ghost evaluation was performed as follows. In the first round (94.2 mm length) of the photoreceptor, first, the solid white part (no exposure, Vd) is 30 mm, then the solid black part (exposure part, V1) is 30 mm, and further, the solid white part is 34.2 mm, and the second round. Thereafter, an image composed of a halftone portion was produced and output. In addition to black single color output, a color image was output as a mixed image (secondary color) of magenta and cyan. In the output image, density unevenness in the halftone part was measured with a reflection densitometer (X-Rite), and a ghost trunk was given as follows according to the density difference.

Concentration difference 0.000 <rank 1 ≦ 0.015
0.015 <rank 2 ≦ 0.025
0.025 <Rank 3 ≦ 0.035
0.035 <rank 4 ≦ 0.05
0.05 <Rank 5
Rank 1 is a level at which ghosts cannot be visually identified, and ranks 2 and 3 are levels at which ghosts can be slightly confirmed, and there is no problem in image quality, but ranks 4 and 5 are levels at which ghosts can be clearly identified visually.

  Furthermore, 40,000 full-color paper feed durability was performed in an intermittent mode in which an image with a printing ratio of 6% was stopped once for each print in an atmosphere environment of 23 ° C./55% RH. Ghost evaluation after 1,000 sheets was also performed. The results are shown in Table 1.

  In Example 1, the photosensitive member of Preparation Example 3 was attached to the image forming part for forming the black toner image, and the photosensitive member of Preparation Example 2 was attached to the image forming part for forming the color toner image. The results are shown in Table 1.

  In Example 1, the photosensitive member of Preparation Example 5 was attached to the image forming portion for forming the black toner image, and the photosensitive member of Preparation Example 4 was attached to the image forming portion for forming the color toner image. The results are shown in Table 1.

  In Example 1, the photosensitive member of Preparation Example 7 was attached to the image forming unit for forming a black toner image, and the photosensitive member of Preparation Example 6 was attached to the image forming unit for forming a color toner image. The results are shown in Table 1.

  In Example 1, the photosensitive member of Preparation Example 5 was attached to the image forming unit for forming a black toner image, and the photosensitive member of Preparation Example 2 was attached to the image forming unit for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

  In Example 1, evaluation was made in the same manner as in Example 1 except that the thickness of the charge transport layer of the photoreceptor was changed to 25 μm. The results are shown in Table 1.

In Example 1, evaluation was made in the same manner as in Example 1 except that the thickness of the charge transport layer of the photoreceptor was changed to 32 μm. The results are shown in Table 1.
<Comparative Example 1>
In Example 1, the photosensitive member of Preparation Example 3 was attached to an image forming unit for forming a black toner image and an image forming unit for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
<Comparative example 2>
In Example 1, the photosensitive member of Preparation Example 5 was attached to an image forming part for forming a black toner image and an image forming part for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
<Comparative Example 3>
In Example 1, the photosensitive member of Preparation Example 7 was attached to an image forming unit for forming a black toner image and an image forming unit for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
<Comparative example 4>
In Example 6, the photoreceptor of Preparation Example 3 was attached to the image forming unit for forming a black toner image and the image forming unit for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.
<Comparative Example 5>
In Example 7, the photoreceptor of Preparation Example 3 was attached to the image forming unit for forming a black toner image and the image forming unit for forming a color toner image, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

以上のように本発明では、カラートナー用感光体の電荷移動度を黒用トナー用感光体の電荷移動度の１．２倍より速くすることで、カラー画像の２次色ゴーストを抑制することができ、高耐久で低コストのカラー電子写真装置を提供できる。特に電荷輸送層の膜厚が２８μｍ以上の場合、高耐久な感光体が得られる一方、２次色ゴーストのレベルが悪くなり易いため本発明が有効に作用する。

As described above, in the present invention, the secondary color ghost of the color image is suppressed by making the charge mobility of the color toner photoconductor faster than 1.2 times the charge mobility of the black toner photoconductor. Therefore, it is possible to provide a color electrophotographic apparatus with high durability and low cost. In particular, when the thickness of the charge transport layer is 28 μm or more, a highly durable photoreceptor can be obtained, while the secondary color ghost level tends to deteriorate, and the present invention works effectively.

1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus having a photoconductor of the present invention. 1 is a diagram illustrating an example of a schematic configuration of an electrophotographic apparatus including a process cartridge having a photosensitive member of the present invention.

Explanation of symbols

1: 1Y, 1M, 1C, 1K Photoconductor 2: 2Y, 2M, 2C, 2K Photoconductor rotating shaft 3: 3Y, 3M, 3C, 3K Primary charger 4: 4Y, 4M, 4C, 4K Image exposure 5: 5Y , 5M, 5C, 5K Developing device 6: 6Y, 6M, 6C, 6K Photoconductor cleaning means 7: 7Y, 7M, 7C, 7K Primary transfer means 8 Intermediate transfer body 9 Secondary transfer means 10 Intermediate transfer body cleaning means 11 Fixing Means 12 Process cartridge 13 Guide means

Claims (2)

An electrophotographic photosensitive member, a charging unit for charging the surface of the electrophotographic photosensitive member, an exposure unit for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member charged by the charging unit by exposure light, the exposure An image forming unit comprising a developing unit for developing an electrostatic latent image formed on the surface of the electrophotographic photosensitive member with toner to form a toner image and a transfer unit for transferring to a transfer material or an intermediate transfer member In an electrophotographic apparatus having a plurality of
The charge mobility in the electric field strength of 2 × 10 ⁵ V / cm of the photoconductor provided in the image forming unit for forming the color toner image is the charge of the photoconductor provided in the image forming unit for forming the black toner image. An electrophotographic apparatus having a mobility of 1.2 times or more.   2. The electron according to claim 1, wherein each of the electrophotographic photoreceptors has a structure in which a charge generation layer and a charge transport layer are laminated on a conductive support, and the thickness of the charge transport layer is 28 μm or more. Photo equipment.

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