JP4520284B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that forms a high-definition and high-definition image. Specifically, in an image forming apparatus in which writing is performed with a beam diameter of 50 μm or less, the electrophotographic photosensitive member used in the image forming apparatus contains at least a titanyl phthalocyanine crystal having a specific crystal type and a specific particle size. The present invention relates to an image forming apparatus which is an electrophotographic photosensitive member obtained by sequentially laminating a charge transport layer.

  In recent years, there has been a remarkable development of information processing system machines using electrophotography. In particular, an optical printer that converts information into a digital signal and records information by light is markedly improved in print quality and reliability. This digital recording technique is applied not only to printers but also to ordinary copying machines, and so-called digital copying machines have been developed. In addition, since a variety of information processing functions are added to a conventional copying machine equipped with this digital recording technology for analog copying, the demand is expected to increase further in the future. In addition, with the spread of personal computers and the improvement in performance, the progress of digital color printers for performing color output of images and documents is rapidly progressing.

  In recent years, the above-mentioned printers and copiers are required to improve the image quality of devices including colorization. There are two problems in improving the image quality in a digital machine. One is how to uniformly form an electrostatic latent image with minute dots, and the other is how to reduce various abnormal images.

  Regarding the former, it is necessary to develop a peripheral technique for making the write beam system for forming the electrostatic latent image smaller and making the most of it. Regarding the latter, the generation of abnormal images due to deterioration of the photoconductor is the main cause, and the photoconductor that has acquired the high durability and high stabilization technology of the photoconductor and understands the characteristics of the process to be used. Development is required.

  As the former technique, two directions are presented. One is a technique using short-wavelength laser light, and a writing light source having an oscillation wavelength of 450 nm or less, called a blue laser that oscillates in purple to blue, has been developed. Since this has high energy and the beam diameter can be easily reduced, high-density writing is possible. As a result, writing with a smaller beam diameter can be realized as compared with writing using a conventional light source.

  However, since this writing light source is shorter than the light wavelength of an exposure member that has been used in the past, it creates several problems. First, most of the charge transport materials used in the charge transport layer that have been used so far have a structure in which the π-conjugated system is expanded to improve transport properties, and the material itself is yellow. It has an absorptivity to the wavelength of writing light by the short wavelength light source. For this reason, the charge transport material blocks the writing light, and the photosensitivity of the photoreceptor is lowered. Further, the charge transport material itself absorbs light, so that the charge transport material promotes deterioration through an excited state, thereby deteriorating the function of the photoreceptor itself. The second is the problem of charge generation materials. Conventionally, conventional electrophotographic photoreceptors have been used in a functionally separated type photosensitive layer structure in which a charge transport layer containing a charge transport material is laminated on a charge generation layer containing a charge generation material. As described above, since most of the charge transport materials that have been used so far are yellow, light having a wavelength shorter than about 450 nm (for example, ultraviolet light emitted from a charging member, ultraviolet light emitted from a fluorescent lamp, etc.). Is absorbed by the charge transport layer and does not pass through the charge generation layer, and in fact, the charge generation layer (charge generation material) has been protected. Light on the shorter wavelength side than 450 nm has high energy, and also has surplus energy that is higher than the energy necessary for generating optical carriers.

FIG. 1 shows a schematic diagram of a photocarrier generation mechanism using an organic charge generating material. As shown in FIG. 1, the generation of photocarriers in the organic charge generating substance is performed through the lowest excited singlet state (S ₁ ). The charge generation material existing in the ground state (S ₀ ) is excited to an excited state by light absorption. At this time, the height (potential) to be launched energetically differs depending on the light energy (that is, wavelength). The charge generating material that has obtained an energy higher than the energy difference between S ₀ and S ₁ is once launched to a higher excited state (S ^* ), and is normally thermally relaxed to the S ₁ state. Is generated. At this time, higher energy than the energy level of the S ₁ (the energy difference between the S ₁ and S ^*) is excess energy, may also be all used for other reactions without being relaxed thermally. The excited state of the organic substance is a very active state, and in addition to being thermally relaxed internally and settled in the S ₁ state, it reacts with other substances using its surplus energy (oxidation, decomposition, etc.) It also binds between the same molecules and changes the molecular structure (isomerization, etc.). Thus, considering only the reaction process of photocarrier generation, surplus energy is actually harmful and requires high chemical stability for the charge generating material.

  From the above, when writing with a short wavelength laser beam is used, it is necessary to develop main materials (charge generating substance, charge transporting substance) constituting the photosensitive member.

  Another technique related to writing light is a technique that uses an existing light source (semiconductor laser (LD or the like)) and optically narrows the beam diameter of light emitted from the light source. This technology requires the development of an optical system (lens, mirror, etc.), but recently it can be narrowed to a beam diameter of 50 μm or less using an LD light source generally used in digital image forming apparatuses so far. (For example, Patent Document 2).

  The development of such a writing technique makes it possible to develop an existing material technique in developing a photoreceptor, which is very advantageous in terms of cost.

  With the development of the optical system in the image forming apparatus as described above, the writing diameter can be made much smaller than the conventional one (approximately 60 to 70 μm or more). This has led to the possibility of reducing the dot diameter of the electrostatic latent image formed on the photoreceptor. However, the electrostatic latent image is formed by canceling the charge applied to the photosensitive member by the reverse charge generated by writing, and a small-diameter dot is simply formed by using a small-diameter beam. However, it is also necessary to devise to make use of the small-diameter beam forming technology.

  That is, although the beam diameter irradiated on the charge generation layer by writing with a small-diameter beam is certainly small, optical carriers are generated at a high density in a narrow area because of the high-density writing. These photocarriers are generated as a pair of holes and electrons, but move to the surface of the photoreceptor and the electrode (conductive support) by the electric field applied to the photoreceptor. At this time, the moving direction is determined by the polarity applied to the surface of the photoconductor. However, in the case of the function-separated organic laminated photoconductor, a negative polarity is generally applied to the surface. Will proceed in the electrode direction.

  It is known that when charges of the same polarity are close to each other, Coulomb repulsion is caused by the mutual charges, and the case of a photoconductor is no exception. In particular, when high-density writing is performed as described above, photocarrier generation is performed at high density. Therefore, if charges are not moved smoothly, recombination by holes and electrons (results in a decrease in carrier generation efficiency) In addition to this, a problem arises in that the dots spread when moving through the charge transport layer. As a result, the dot diameter of the electrostatic latent image formed on the surface of the photosensitive member is increased even if it is intended to write with a small diameter beam (see FIG. 2).

  FIG. 3 shows the relationship between the electric field strength applied to the photoreceptor and the dots developed from the electrostatic latent image. FIG. 3 shows a toner image when developed using a toner having a sufficiently small particle diameter. However, when the electric field strength is small, the dots are large and blurred. This shows that the carriers generated in the charge generation layer spread due to Coulomb repulsion when crossing the charge transport layer, and the potential contrast corresponding to the writing portion and the non-writing portion on the surface of the photoreceptor was not sufficiently obtained. Results are shown. Therefore, when forming minute dots by writing such a small-diameter beam, the electric field strength applied to the photoreceptor must be set high. According to the study by the present inventors, application of an electric field strength of 30 V / μm or more is necessary for a normal electrophotographic photosensitive member having a charge transport layer thickness of about 30 μm or less.

  This electric field strength of 30 V / μm or higher is set higher than the normal applied electric field strength, and increases the stress on the photoreceptor. FIG. 4 shows the relationship between the electric field strength applied to the photoreceptor and the background stain. The scumming rank in the figure indicates the level of scumming, and the greater the number, the better the level of scumming. As can be seen from the figure, an increase in the electric field strength promotes the occurrence of background staining, and the background contamination and dot reproducibility (formation of minute dots) have a trade-off relationship with respect to the field strength. Therefore, in order to improve the reproducibility of the fine dots as described above, a photoconductor having a strong anti-smudge property is required.

  In addition, in order for the beam written in the charge generation layer to generate a homogeneous charge, the charge generation layer itself needs to be a fairly homogeneous body. The charge generation layer is usually constituted by a form in which an organic pigment as a charge generation material is dispersed in a binder resin. Therefore, it is essentially a heterogeneous body. However, in such a dispersion film, if the dispersion is sufficiently carried out to some extent or if the pigment particles themselves are present in a sufficiently small state, the behavior of a homogeneous body is optically observed. For this reason, the pigment particles constituting the charge generation layer of the photoreceptor must have a sufficiently small particle size with respect to the writing wavelength.

  Therefore, the following items are necessary in an image forming apparatus that forms fine dots using a writing light source having a beam diameter of 50 μm or less.

  (1) Since high-density writing is performed per unit area, the photoconductor (charge generating material) used has a high photocarrier generating ability.

  (2) The electric field intensity applied to the photosensitive member is sufficiently increased so that the charge is not diffused due to the influence of Coulomb repulsion when the charge is transferred (30 V / μm or more is required).

  (3) Since application of high electric field strength tends to cause scumming, a photoconductor with high scumming resistance is required.

  (4) It has sufficient homogeneity for writing of a small-diameter beam. For this reason, the charge generation material contained in the charge generation layer should be sufficiently small.

  The above problems are all related to the photosensitive layer (charge generation layer) except for the transparency of the charge transport material, and the development of photoconductors for image forming devices intended for the formation of fine dots by high-density writing is a charge generation. Indicates whether it depends on substance development.

  In the present application, the field strength defined by the following formula is used.

Electric field strength (V / μm) = surface potential of unexposed portion of photoreceptor at development position (V) / {photosensitive layer thickness (μm) + protective layer thickness (μm)} Expression (A)
As a charge generating material for photoreceptors having high sensitivity and high speed response, a diffraction peak (± 0.2 °) with a Bragg angle 2θ for CuKα rays (wavelength 1.542 mm) has a maximum diffraction peak at least 27.2 °. It is known to use a titanyl phthalocyanine crystal having (see Patent Document 1).

  This specific crystal type has a very high carrier generation function and can be effectively used as a charge generation material for a photoreceptor for a high-speed image forming apparatus. However, this crystal type has a problem that it is low in stability as a crystal and easily undergoes a crystal transition due to mechanical stress such as dispersion and thermal stress. The sensitivity is very low compared to the previous crystal type, and when a part of the crystal undergoes crystal transition, sufficient photocarriers cannot be generated. Further, when the photoreceptor is used repeatedly, there is a problem that the chargeability is likely to be lowered and the negative residue is likely to be caused. In addition, there is a problem that an abnormal image called a smudge image, which is a problem inherent to negative / positive development, is likely to occur.

  In addition, writing with a small-diameter beam is intended to write at high density. However, as will be described later, there may be a problem of reciprocity failure of the sensitivity of the photosensitive member at high density, or the writing (electrostatic latent image) dot outline on a small-diameter beam may be blurred.

  Furthermore, when forming a small-diameter dot using a small-diameter beam as described above, if the charge generation layer does not have a sufficiently homogeneous structure, the outline of the fine dot will not be clear, and the advantages of the small-diameter beam are not necessarily obtained. Therefore, the homogenization of the charge generation layer (that is, miniaturization of the charge generation material particles) has not been considered.

In this way, the development of a photoreceptor is sufficient for the process restrictions (requests) that arise in order to design an image forming apparatus that forms a small-diameter beam by optical system innovation and realizes high-density writing. However, the situation is that the development of a photoreceptor for realizing stable and repetitive image formation is not sufficient.
JP 2001-19871 A JP 2002-277801 A JP-A-6-293769 JP-A-8-110649 JP 52-36016 A Japanese Patent Laid-Open No. 3-109460 JP 2000-206723 A JP 2001-340001 A JP-A-5-94049 JP-A-5-113688 JP-A-1-299874 Japanese Patent Laid-Open No. 3-269064 Japanese Patent Laid-Open No. 2-8256 JP-A 64-17066 Japanese Patent Laid-Open No. 11-5919 JP-A-3-255456 Japanese Patent Laid-Open No. 61-239248 Japan Hardcopy '89 Proceedings p. 103 1989 Moser et al. “Phthalogicane Compounds” (1963), “The Phthalogicanes” (1983)

  Accordingly, an object of the present invention is to provide an image forming apparatus that performs high-density writing using a small-diameter beam and outputs an image in a stable state without generating an abnormal image when repeatedly used.

  Specifically, an image forming apparatus that uses a light source having a beam diameter of 50 μm or less as a writing light source to form a high-definition image, by using a photoreceptor containing a specific crystal type titanyl phthalocyanine crystal. Another object of the present invention is to provide an image forming apparatus that maintains the high sensitivity inherent to titanyl phthalocyanine, is highly durable, and can output a high-speed image.

  In the image forming apparatus using a light source having a beam diameter of 50 μm or less, the present inventors have made a number of studies in order to form an image with few abnormal images even during repeated use. Is an electrophotographic photosensitive member in which at least a charge generation layer and a charge transport layer are sequentially laminated on a conductive support, and a diffraction peak of a Bragg angle 2θ with respect to CuKα rays (wavelength 1.542 mm) in the charge generation layer ( ± 0.2 °) having a maximum diffraction peak at least 27.2 °, and further having major peaks at 9.4 °, 9.6 °, and 24.0 °, and the lowest angle As a diffraction peak, there is a peak at 7.3 °, and there is no peak between the peak at 7.3 ° and the peak at 9.4 °, and there is no peak at 26.3 °. And the average particle size of the primary particles is 0.2 μm by including the following titanyl phthalocyanine crystals were found to be able to solve the above problems.

  It is understood that the above-mentioned background contamination problem in image formation is due to a charge leak phenomenon in the photoreceptor. Although the detailed reason for the effect of the present invention is not clear, as for soil contamination, the titanyl used in the present invention is compared with the other known titanyl phthalocyanine crystals having a maximum diffraction peak at 27.2 °. It is presumed that it originates from the high chemical stability of phthalocyanine crystals and is due to the reduction in the occurrence of soiling.

  In addition, the unclearness of the fine dot outline is based on the non-uniformity in the charge generation layer. If the charge generation material particles in the charge generation layer are sufficiently fined as in the present invention, optical charge generation is performed. The layer has a homogeneous structure and the contours in the latent image dots are very sharp. This is a problem that comes from the writing beam size in which the particle size must be further reduced by the amount that the beam diameter has become smaller than the beam diameter as the light source that has been used so far. The charge generation layer corresponding to the writing beam size is considered to be a problem that cannot be handled.

  FIGS. 5 and 6 are schematic views of electrostatic latent images when writing is performed with the same size beam when the size of the charge generation material particles contained in the charge generation layer is small and large, respectively. . As shown in FIG. 5, when the particle size of the charge generation material is fine and the particle size distribution is narrow, the outline of the dots is sharp, while the particle size is large and the particle size distribution is wide (or coarse particles are In the case of (including) (FIG. 6), the outline of the dot collapses and lacks clarity. Therefore, by using a charge generation layer having a fine particle size and a narrow particle size distribution, a high-definition dot formation technique can be more effectively implemented using a small particle size toner.

  Furthermore, when a small-diameter beam is formed by devising an optical system, the number of incident photons per unit area increases, and the number of photons per unit time irradiated to the charge generation material increases. As a result, the carrier generation efficiency is reduced when the electric field is low, and the surface charge cannot be sufficiently reduced. This is due to the fact that reciprocity failure occurs in the generation of carriers.

  There are several reasons for reciprocity failure. For example, (i) excitons generated in the charge generation particles reach the particle surface and are deactivated before free carriers, and (ii) before the generated free carriers pass carriers to the charge transport material. Recombination (geminate / recombination). It is thought that these causes originate from the fact that the size of the charge generation material particles is too large and the surface area is not sufficient for the number of photons received in proportion to the volume (cross-sectional area with respect to the writing direction). .

  FIG. 7 shows the light attenuation characteristics of two types of photoconductors when the particle size of the charge generating material used in the photoconductor is changed. When the particle size is large (A in FIG. 7), the attenuation of light attenuation occurs in the low electric field region (region where the photoreceptor surface potential is low), in addition to the slow light attenuation rate. . As a result, the saturation decay potential is high and saturated. On the other hand, when the particle size is controlled to be sufficiently small (B in FIG. 7), the tail of light attenuation is good, the light is sufficiently attenuated even at a low electric field, and the saturation potential is also low.

  As for the reason why the above-mentioned problems do not occur in the present invention, the titanyl phthalocyanine crystal used in the present invention has a high carrier generation ability, including high chemical stability as described above, and further sufficient It is considered that the reciprocity failure phenomenon is suppressed because the fine particles are applied.

  As described above, although a basic design for achieving high speed has been performed, an effective photoconductor that takes advantage of its features has not been developed, so stable image formation cannot be realized, and various image formation However, the present invention solves this problem.

That is, the said subject is solved by following this invention (1)-( 17 ).
(1) An electrophotographic photosensitive member having a charge transport layer and a charge generation layer containing a titanyl phthalocyanine crystal as a charge generation material on a conductive support; and writing means using a light source having a beam diameter of 50 μm or less ;
In an image forming apparatus comprising:
The titanyl phthalocyanine crystal has a Bragg angle 2θ diffraction peak (± 0.2 °) with respect to CuKα rays (wavelength 1.542Å):
Has a maximum diffraction peak at 27.2 °;
Has major peaks at 9.4 °, 9.6 ° and 24.0 °;
Has a peak at 7.3 ° as the lowest diffraction peak;
And no peaks between the 7.3 ° peak and the 9.4 ° peak and at 26.3 °;
The titanyl phthalocyanine crystal has an average primary particle size of 0.25 μm or less,
The titanyl phthalocyanine crystal has a maximum diffraction peak at 7.0 to 7.5 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-ray (wavelength 1.542 mm), Crystalline conversion of amorphous titanyl phthalocyanine or low crystalline titanyl phthalocyanine having a half-width of diffraction peak of 1 ° or more and an average primary particle size of 0.1 μm or less with an organic solvent in the presence of water In the state of crystal conversion so that the average particle size of the subsequent primary particles is 0.25 μm or less , it is fractionally filtered from the organic solvent,
The electrophotographic photosensitive member is applied with an electric field intensity represented by the following formula (A) in a range of 30 to 50 V / μm.
Electric field strength (V / μm) = surface potential of unexposed portion of photoreceptor at development position (V) / {photosensitive layer thickness (μm) + protective layer thickness (μm)} Expression (A)
As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having an excellent electrophotographic characteristic and a beam diameter of 50 μm or less.
(2) The titanyl phthalocyanine crystal is stirred using an organic solvent having an amount of 30 times or more the weight of amorphous titanyl phthalocyanine and / or low crystalline titanyl phthalocyanine during the crystal conversion. The image forming apparatus described in 1. As a result, an image forming apparatus having a stable photoreceptor potential and stable image quality can be obtained.
(3) The image forming apparatus according to claim 1 or 2, wherein the charge transport layer contains a polycarbonate having at least a triarylamine structure in a main chain and / or a side chain. As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less while maintaining wear resistance and having excellent electrophotographic characteristics.
(4) The image forming apparatus according to any one of claims 1 to 3, wherein the electrophotographic photosensitive member has a protective layer on the charge transport layer. As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less while maintaining wear resistance and having excellent electrophotographic characteristics.
(5) The image forming apparatus according to claim 4, wherein the protective layer contains an inorganic pigment or metal oxide having a specific resistance of 10 ¹⁰ Ω · cm or more. As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less, which is resistant to electrophotographic characteristics, particularly image blurring, while maintaining wear resistance.
(6) The image forming apparatus according to (4) or (5), wherein the protective layer contains a polymer charge transport material. As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less while maintaining wear resistance and having excellent electrophotographic characteristics.
(7) The image forming apparatus according to any one of claims 4 to 6, wherein the binder resin of the protective layer has a crosslinked structure. As a result, a photoconductor having high wear resistance can be obtained, and as a result, an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less with excellent durability can be obtained.
(8) The image forming apparatus according to (7), wherein the binder resin having a crosslinked structure has a charge transporting portion. As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less, which greatly contributes to the wear resistance of the photosensitive member and is excellent in durability.
(9) The image forming apparatus according to any one of claims 1 to 8, wherein the surface of the conductive support is anodized. As a result, the barrier property of the photocarrier generated in the photoconductor is improved, and as a result, it is possible to obtain an image forming apparatus having writing means using a light source having a beam diameter of 50 μm or less having good electrophotographic characteristics. Become.
(10) The image forming apparatus according to any one of (1) to (9), wherein the image is formed by a direct transfer method. As a result, it is possible to apply a good transfer bias, and thus it is possible to obtain an image forming apparatus provided with writing means using a light source having a good electrophotographic characteristic and a beam diameter of 50 μm or less.
(11) The surface potential of the photosensitive member after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photosensitive member by the writing means is the absolute value of the polarity charged by the main charger. The image forming apparatus according to claim 10, wherein the voltage is 100 V or less. As a result, the amount of charge passing through the photoreceptor in repeated use can be reduced, and as a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less having good electrophotographic characteristics. .
(12) The surface potential of the photoconductor after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photoconductor by the writing means is opposite to the polarity charged by the main charger. The image forming apparatus according to claim 10, wherein the image forming apparatus is an image forming apparatus. As a result, the amount of charge passing through the photoreceptor in repeated use can be reduced, and as a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less having good electrophotographic characteristics. .
(13) The surface potential of the photoconductor after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photoconductor by the writing means is opposite to the polarity charged by the main charger. The image forming apparatus according to claim 12, wherein the absolute value of the voltage is 100 V or less. As a result, the amount of charge passing through the photoreceptor in repeated use can be reduced, and as a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less having good electrophotographic characteristics. .
(14) The image forming apparatus according to any one of (1) to (13), wherein an optical static elimination mechanism is not used. As a result, the amount of charge passing through the photoreceptor in repeated use can be reduced, and as a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less having good electrophotographic characteristics. .
(15) The image forming apparatus according to any one of (1) to (14), wherein a plurality of image forming elements including at least a charging unit, an exposure unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member are arranged. . As a result, it is possible to obtain an image forming apparatus provided with writing means using a light source having a beam diameter of 50 μm or less corresponding to full color printing.
(16) The image forming apparatus according to any one of (1) to (15), wherein an AC superimposed voltage is applied to a charging unit of the electrophotographic apparatus. As a result, it is possible to stabilize the charging of the photosensitive member and to obtain a high-quality image.
(17) An apparatus main body and a detachable cartridge are mounted, in which the photosensitive member and at least one means selected from the group consisting of a charging means, an exposure means, a developing means, and a cleaning means are integrated. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. Accordingly, the image forming apparatus with improved handling performance can be obtained by the user, and a writing unit using a light source having a beam diameter of 50 μm or less can be selected according to the purpose. An image forming apparatus can be obtained.

  As described above, as is clear from the detailed and specific invention, according to the present invention, it is an image forming apparatus that outputs an extremely high-speed image. An image forming apparatus that outputs an image with high resolution is provided.

(Image forming apparatus in the present invention)
First, the image forming apparatus of the present invention will be described in detail with reference to the drawings.

  FIG. 8 is a schematic diagram for explaining the image forming apparatus of the present invention, and modifications as described later also belong to the category of the present invention.

  In FIG. 8, the photosensitive member 1 is provided with a photosensitive layer including at least a charge generation layer and a charge transport layer on a conductive support, and the charge generation layer has a Bragg angle 2θ with respect to CuKα rays (wavelength 1.542 mm). As a diffraction peak (± 0.2 °), it has a maximum diffraction peak at least 27.2 °, and further has main peaks at 9.4 °, 9.6 °, 24.0 °, and the lowest As a diffraction peak on the corner side, it has a peak at 7.3 °, has no peak between the peak at 7.3 ° and the peak at 9.4 °, and has a peak at 26.3 °. It contains no titanyl phthalocyanine crystal having an average primary particle size of 0.25 μm or less. The photosensitive member 1 has a drum shape, but may be a sheet shape or an endless belt shape.

  Any known member can be used as the charging charger 3 as long as it can sufficiently charge the photosensitive member. Among them, a scorotron charging member, a contact charging member (roller shape), or a charging member in which the surface of the photosensitive member and the charging member surface are arranged close to 100 μm or less is preferably used. When the dot reproducibility is prioritized for high-definition image formation, an electric field strength of 30 V / μm or more is applied to the photoreceptor by this charging member. The higher the electric field strength applied to the photoconductor, the better the dot reproducibility. However, there is a possibility of causing problems of dielectric breakdown of the photoconductor and carrier adhesion at the time of development, and the upper limit is about 60 V / μm or less. Preferably, it is 50 V / μm or less.

  Further, the image exposure unit 5 has a light source in which a high luminance such as a light emitting diode (LED), a semiconductor laser (LD), and electroluminescence (EL) can be secured and an optical system capable of writing at 50 μm or less can be written. used.

  The idea of the optical system described above is a technique for reducing the writing beam diameter by, for example, a method described in Patent Document 2, and in the present invention, if the writing beam can be formed to 50 μm or less, Any method can be used.

  Here, the beam diameter of 50 μm or less will be described. Usually, writing light emitted from an optical element is applied to the surface of the photoreceptor through an optical system (mirror or lens). The writing beam does not become a perfect circle, but has a slightly flattened shape like an ellipse. The writing size is determined in the major axis direction of the ellipse, and the beam diameter in the present invention refers to the length of the major axis.

Further, such a beam has a Gaussian distribution from the center of light emission, and has a shape as described in Patent Document 2 (FIG. 6). Therefore, the above-mentioned major axis cannot be determined without defining the light intensity, but the definition generally used in the present invention is used. That is, the major axis of the area light intensity is greater than 1 / e ² of maximum intensity of the exposure beam and the beam diameter of the present invention.

  Depending on the resolution of the light source (writing light), the resolution of the formed electrostatic latent image, and thus the toner image, is determined. The higher the resolution, the clearer the image. However, if writing is performed at a higher resolution, writing takes longer, so writing with one writing light source is limited by the drum linear speed (process speed). Therefore, when there is one writing light source, a resolution of about 2400 dpi is the upper limit. If there are a plurality of writing light sources, each of them only has to bear the writing area, and the upper limit is substantially “2400 dpi × number of writing light sources”. The writing light source here refers to one LD element or one LED element. For example, LEDs arranged in an array are handled as a plurality of light sources.

  Among these light sources, light emitting diodes and semiconductor lasers have high irradiation energy and long wavelength light of 600 to 800 nm. Therefore, the specific crystal type phthalocyanine pigment which is a charge generation material used in the present invention has high sensitivity. Used well from showing.

  The developing unit 6 can handle both normal development and reversal development depending on the charging polarity of the toner used. When toner having a polarity opposite to the charged polarity of the photoreceptor is used, normal development is used. When toner having the same polarity is used, the electrostatic latent image is developed by reversal development. Depending on the light source used in the previous image exposure unit, in the case of a digital light source used in recent years, considering the life of the light source, etc. A reversal development system in which development is performed is advantageous. There are two methods, a one-component method in which development is performed using only toner and a two-component method in which a two-component developer composed of toner and carrier is used.

  The transfer charger 10 may be a transfer belt or a transfer roller, but it is desirable to use a contact type such as a transfer belt or a transfer roller that generates less ozone. In particular, a direct transfer method in which a toner image formed on the surface of a photoreceptor is directly transferred to a transfer target is favorably used. As a voltage / current application method at the time of transfer, either a constant voltage method or a constant current method can be used, but the transfer charge amount can be kept constant, and a constant voltage with excellent stability can be used. The current method is more desirable.

  In addition, the toner image formed on the photosensitive member is transferred onto the transfer paper to become an image on the transfer paper. At this time, there are two methods. One is a method of directly transferring a toner image developed on the surface of the photoreceptor as shown in FIG. 8 to the transfer paper, and the other is that the toner image is once transferred from the photoreceptor to the intermediate transfer body, and this is transferred to the transfer paper. It is the method of transferring to. Either case can be used in the present invention. In particular, a direct transfer system that directly transfers a toner image formed on the surface of the photoreceptor to a transfer target (such as paper to be output) is preferably used.

  As such a transfer member, a known member can be used as long as the structure of the present invention can be satisfied.

  At this time, the surface potential of the photoreceptor after transfer has a great influence on the electrostatic fatigue of the photoreceptor in repeated use. That is, the electrostatic fatigue of the photoreceptor is greatly influenced by the amount of charge passing through the photoreceptor. This passing charge amount corresponds to the amount of charge flowing in the film thickness direction of the photoreceptor. As an operation in the image forming apparatus of the photoconductor, the main charger is charged to a desired charging potential (in most cases, negatively charged), and optical writing is performed based on an input signal corresponding to the original. At this time, photocarriers are generated in the portion where writing is performed, and the surface charge is neutralized (potential decay). At this time, the amount of charge depending on the amount of generated photocarriers flows in the direction of the photoreceptor film thickness.

  On the other hand, the area where the optical writing is not performed (non-writing portion) proceeds to the charge removal process through the development process and the transfer process (a cleaning process is performed before that if necessary). Here, when the surface potential of the photoconductor is close to the potential applied by main charging (excluding dark decay), the amount of charge is almost the same as that in the area where optical writing is performed. Will flow into. In general, since the current document has a low writing rate, in this method, most of the passing charge amount of the photoreceptor in repeated use is a current that flows in the static elimination process (if the writing rate is 10%, The current that flows in the static elimination process occupies 90% of the total).

  This passing charge greatly affects the electrostatic characteristics of the photoconductor, for example, causing deterioration of the material constituting the photoconductor. As a result, the residual potential of the photosensitive member is raised, depending on the amount of passing charge. When the residual potential of the photosensitive member is increased, the image density is lowered in the negative / positive development used in the present invention, which is a serious problem. Therefore, there is a problem of how to reduce the passing charge amount of the photoconductor in order to increase the lifetime (high durability) of the photoconductor in the image forming apparatus.

  On the other hand, there is a way of thinking that the photostatic discharge is not performed, but if the main charger is not sufficiently charged, the charging cannot be stabilized and a problem such as an afterimage may occur.

  The passing charge of the photoconductor is generated by the movement of the generated optical carrier by light irradiation by the electric potential (the electric field generated thereby) charged on the surface of the photoconductor. Therefore, if the photoreceptor surface potential can be attenuated by means other than light, the amount of charge passing per rotation of the photoreceptor (one cycle of image formation) can be reduced.

  For this purpose, it is effective to adjust the charge passing through the photosensitive member by adjusting the transfer bias in the transfer process. That is, a non-writing portion that is charged by main charging and does not perform writing enters the transfer process in a state close to the charged potential except for the dark attenuation amount. At this time, the absolute value on the polarity side charged by the main charger is reduced to 100 V or less, so that almost no photocarrier is generated even if the subsequent charge removal process is entered, and no passing charge is generated. This value is preferably closer to 0V.

  Furthermore, by adjusting the transfer bias, by applying a transfer bias so that the surface potential of the photosensitive member is charged to a polarity opposite to the charging polarity applied by the main charging, it is more preferable because no optical carrier is generated. . However, under transfer conditions that charge to a reverse polarity, there may be cases where a large amount of transfer dust occurs or the main charge of the next image forming process (cycle) cannot catch up. In that case, since a problem such as an afterimage may occur, the absolute value of the reverse polarity is preferably 100 V or less.

  As a light source such as the static elimination lamp 2, general light emitting materials such as a fluorescent lamp, a tungsten lamp, a halogen lamp, a mercury lamp, a sodium lamp, a light emitting diode (LED), a semiconductor laser (LD), and an electroluminescence (EL) can be used. . Various types of filters such as a sharp cut filter, a band pass filter, a near infrared cut filter, a dichroic filter, an interference filter, and a color temperature conversion filter can be used to irradiate only light in a desired wavelength range.

  Such a light source or the like irradiates the photosensitive member with light by providing a process such as a transfer process, a charge eliminating process, a cleaning process, or a pre-exposure using light irradiation in addition to the process shown in FIG.

  When the AC (alternating current) component is used in a superposed manner in the previous charging method, or when the residual potential of the photosensitive member is small, this static elimination mechanism can be omitted. Further, instead of optical static elimination, an electrostatic static elimination mechanism (for example, a static elimination brush with a reverse bias applied or grounded) can be used. As described above, a document having a small writing rate has a large effect of light neutralization, and it is preferable not to use light neutralization as long as there is no influence of afterimage or the like in the next image forming cycle.

  In the figure, 8 is a registration roller, 11 is a separation charger, and 12 is a separation claw.

  Further, the toner developed on the photosensitive member 1 by the developing unit 6 is transferred to the transfer paper 9. When toner remaining on the photosensitive member 1 is generated, the fur brush 14 and the cleaning blade 15 cause the photosensitive member to move. More removed. Cleaning may be performed only with a cleaning brush, and a known brush such as a fur brush or a mag fur brush is used as the cleaning brush.

(Tandem image forming device)
FIG. 9 is a schematic diagram for explaining the tandem-type full-color image forming apparatus of the present invention, and the following modifications also belong to the category of the present invention.

  Also in the image forming apparatus shown in FIG. 9, a light source designed to have a beam diameter of 50 μm or less is used.

  In FIG. 9, reference numerals 16Y, 16M, 16C, and 16K denote drum-shaped photoconductors. The photoconductors are formed by providing a photosensitive layer including at least a charge generation layer and a charge transport layer on a conductive support. The layer has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα rays (wavelength 1.542 mm), and further 9.4 ° and 9.6 °. , Having a main peak at 24.0 °, and having a peak at 7.3 ° as the lowest diffraction peak, and between the 7.3 ° peak and the 9.4 ° peak Does not have a peak, and further contains a titanyl phthalocyanine crystal having no peak at 26.3 ° and an average primary particle size of 0.25 μm or less.

  The photoreceptors 16Y, 16M, 16C, and 16K rotate in the direction of the arrow in the drawing, and at least around them, the charging members 17Y, 17M, 17C, and 17K, the developing members 19Y, 19M, 19C, and 19K, the cleaning member 20Y, 20M, 20C, and 20K are arranged. The charging members 17Y, 17M, 17C, and 17K are members that constitute a charging device for uniformly charging the surface of the photoreceptor. Laser light 18Y, 18M, 18C, 18K from an exposure member (not shown) is irradiated from the surface of the photoreceptor between the charging members 17Y, 17M, 17C, 17K and the developing members 19Y, 19M, 19C, 19K. The electrostatic latent images are formed on the photoconductors 16Y, 16M, 16C, and 16K. Then, four image forming elements 25Y, 25M, 25C, and 25K centering on such photoconductors 16Y, 16M, 16C, and 16K are juxtaposed along a transfer conveyance belt 22 that is a transfer material conveyance unit. The transfer conveyance belt 22 contacts the photosensitive members 16Y, 16M, 16C, and 16K between the developing members 19Y, 19M, 19C, and 19K of the image forming elements 25Y, 25M, 25C, and 25K and the cleaning members 20Y, 20M, 20C, and 20K. Transfer brushes 21Y, 21M, 21C, and 21K for applying a transfer bias are disposed on a surface (back surface) that is in contact with and contacts the back side of the transfer conveyor belt 22 on the photosensitive member side. Each of the image forming elements 25Y, 25M, 25C, and 25K has a different toner color inside the developing device, and the others have the same configuration.

  In the full-color image forming apparatus having the configuration shown in FIG. 9, the image forming operation is performed as follows. First, in each of the image forming elements 25Y, 25M, 25C, and 25K, electrostatic latent images are formed on the photoreceptors 16Y, 16M, 16C, and 16K. Then, each of the photoconductors 16Y, 16M, 16C, and 16K rotates, and the photoconductors are charged by the charging members 17Y, 17M, 17C, and 17K. At this time, in order to form a high-definition latent image, the photosensitive member is charged so that the electric field strength is 30 V / μm or more (60 V μm or less, preferably 50 V / μm or less).

  Next, writing is performed at a resolution of 1200 dpi or more (preferably 2400 dpi or more) with laser beams 18Y, 18M, 18C, and 18K having a beam diameter of 50 μm or less at an exposure unit (not shown) arranged outside the photoreceptor. The electrostatic latent image corresponding to each color image to be created is formed. In this case as well, 2400 dpi writing is generally the upper limit for one writing light source.

  Next, the latent image is developed by the developing members 19Y, 19M, 19C, and 19K to form a toner image. The developing members 19Y, 19M, 19C, and 19K are developing members that perform development with toners of Y (yellow), M (magenta), C (cyan), and K (black), respectively, and the four photosensitive members 16Y and 16M. , 16C, and 16K, the toner images of the respective colors are superimposed on the transfer paper. The transfer paper 26 is fed out of the tray by a paper feed roller (not shown), temporarily stopped by a pair of registration rollers 23, and sent to the transfer conveyance belt 22 in synchronization with the image formation on the photosensitive member. The transfer paper 26 held on the transfer conveyance belt 22 is conveyed, and the toner images of the respective colors are transferred at the contact positions (transfer portions) with the photoconductors 16Y, 16M, 16C, and 16K.

  The toner image on the photoconductor is transferred onto the transfer paper 26 by an electric field formed by a potential difference between the transfer bias applied to the transfer brushes 21Y, 21M, 21C, and 21K and the photoconductors 16Y, 16M, 16C, and 16K. The Then, the transfer paper 26 on which the four color toner images are passed through the four transfer portions is conveyed to the fixing device 24, where the toner is fixed, and is discharged to a paper discharge portion (not shown).

  Further, the residual toner remaining on the photoreceptors 16Y, 16M, 16C, and 16K without being transferred by the transfer unit is collected by the cleaning members 20Y, 20M, 20C, and 20K.

  Subsequently, excess residual charges on the photosensitive member are removed by a charge eliminating member (not shown) as necessary. Thereafter, the charging member is uniformly charged again, and the next image formation is performed.

  In the example of FIG. 9, the image forming elements are arranged in the order of Y (yellow), M (magenta), C (cyan), and K (black) from the upstream side to the downstream side in the transfer sheet conveyance direction. However, the order is not limited to this order, and the color order may be arbitrarily set. In addition, when creating a black-only document, it is particularly effective to use the present invention to provide a mechanism that stops the image forming elements (25Y, 25M, 25C) other than black.

  Also in this case, as described above, the surface potential of the photoconductor after transfer is controlled to 100 V or less, preferably reverse polarity, more preferably 100 V or less, on the main charging polarity side. The increase in residual potential during use can be reduced, which is effective.

(Image forming means)
The image forming means as described above may be fixedly incorporated in a copying apparatus, a facsimile, or a printer, but may be incorporated in these apparatuses in the form of a process cartridge. A process cartridge is a single device (part) that contains a photoconductor and further includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a neutralizing unit, and the like. There are many shapes and the like of the process cartridge, but a general example is shown in FIG. The photoreceptor 101 is provided with a photosensitive layer including at least a charge generation layer and a charge transport layer on a conductive support, and the charge generation layer has a diffraction peak (±±) with a Bragg angle 2θ with respect to CuKα rays (wavelength 1.542 mm). 0.2 °) and has a maximum diffraction peak at least 27.2 °, and further has major peaks at 9.4 °, 9.6 °, and 24.0 °, and the diffraction at the lowest angle. There is a peak at 7.3 ° as a peak, and there is no peak between the peak at 7.3 ° and the peak at 9.4 °, and no peak at 26.3 °. And it contains a titanyl phthalocyanine crystal having an average primary particle size of 0.25 μm or less.

  As described above, a known charging member is used for the charging member 102. When high-definition image formation is performed, the charging member is 30 V / μm or more (60 V / μm or less, preferably 50 V / μm or less) with respect to the photoreceptor. The electric field strength of is applied.

  As described above, the image exposure unit 103 uses a light source having a beam diameter of 50 μm or less that can be written at a resolution of 1200 dpi or more (preferably 2400 dpi or more). In FIG. A transfer body, 106 is a transfer means, 107 is a cleaning means, and 108 is a charge eliminating means.

  Hereinafter, the electrophotographic photosensitive member used in the image forming apparatus of the present invention will be described in detail.

  The electrophotographic photosensitive member used in the present invention is an electrophotographic photosensitive member in which at least a charge generation layer and a charge transport layer are formed on a conductive support, and CuKα rays (wavelength of 1. nm) are formed in the charge generation layer. As a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to 542 Å), it has a maximum diffraction peak at least 27.2 °, and further main peaks at 9.4 °, 9.6 °, and 24.0 ° And has a peak at 7.3 ° as the lowest angle diffraction peak, and no peak between the 7.3 ° peak and the 9.4 ° peak, and It contains a titanyl phthalocyanine crystal having no peak at 26.3 ° and an average primary particle size of 0.25 μm or less.

  Although this crystal type is described in Patent Document 1, by using this titanyl phthalocyanine crystal, it is possible to obtain a stable electrophotographic photosensitive member that does not cause deterioration in chargeability even after repeated use without losing high sensitivity. Can do.

  Patent Document 1 discloses a charge generating material used in the present invention, a photoconductor using the same, an electrophotographic apparatus, and the like. However, in the case of using a writing light source having a beam diameter of 50 μm or less for the purpose of high resolution, there are cases where the problem of unclearness of the small-diameter dot outline and the problem of carrier generation efficiency in a low electric field have occurred. Further, under the situation where the resolution is 1200 dpi or higher or 2400 dpi or higher, it is necessary to increase the electric field strength applied to the photosensitive member in order to make use of the writing resolution. However, when the electric field strength is high, there is a problem that soiling occurs. Such a phenomenon remarkably appears when used in an image forming apparatus that performs writing with higher resolution than the image forming apparatus described in the publication. Thus, in the past process (apparatus), not only the ability of the material described in the same publication is not sufficiently drawn out, but if the process conditions are not optimized, a side effect is produced.

  Further, Patent Document 1 does not describe the particle size and the technology for controlling the particle size, and the particle size is not optimized. In the present invention, a more optimal image forming apparatus is constructed by using a photoconductor containing a specific crystal type titanyl phthalocyanine having a controlled particle size and optimizing the process conditions of the image forming apparatus.

  As a method for synthesizing a titanyl phthalocyanine crystal, as described in Patent Document 3, a method in which titanium halide is not used as a raw material is favorably used. The biggest merit of this method is that the synthesized titanyl phthalocyanine crystal is free of halogenation. If the titanyl phthalocyanine crystal contains a halogenated titanyl phthalocyanine crystal as an impurity, there are many adverse effects such as a decrease in photosensitivity and a decrease in chargeability in the electrostatic characteristics of a photoreceptor using the crystal (Non-patent Document 1). . Also in the present invention, the halogenated free titanyl phthalocyanine crystal as described in Patent Document 1 is mainly used, and these materials are effectively used.

  In order to synthesize a halogenated free titanyl phthalocyanine, it is necessary not to use a halogenated material as a raw material in the synthesis of titanyl phthalocyanine. Specifically, the method described later is used.

(Synthesis method of titanyl phthalocyanine crystal in the present invention)
First, a method for synthesizing a titanyl phthalocyanine crystal having a specific crystal type used in the present invention will be described.

  First, a method for synthesizing a crude product of titanyl phthalocyanine crystal will be described. Methods for synthesizing phthalocyanines have been known for a long time, and are described in Non-Patent Document 2, Patent Document 3, and the like.

  For example, as a first method, a mixture of phthalic anhydrides, metal or metal halide and urea is heated in the presence or absence of a high boiling point solvent. In this case, a catalyst such as ammonium molybdate is used in combination as necessary. As a second method, phthalonitriles and metal halides are heated in the presence or absence of a high boiling point solvent. This method is used for phthalocyanines that cannot be produced by the first method, such as aluminum phthalocyanines, indium phthalocyanines, oxovanadium phthalocyanines, oxotitanium phthalocyanines, zirconium phthalocyanines, and the like. The third method is to first react phthalic anhydride or phthalonitrile with ammonia to produce an intermediate such as 1,3-diiminoisoindoline, and then react with a metal halide in a high boiling solvent. It is a method to make it. The fourth method is a method in which phthalonitriles and a metal alkoxide are reacted in the presence of urea or the like. In particular, the fourth method does not cause chlorination (halogenation) to the benzene ring, and is a very useful method as a method for synthesizing an electrophotographic material, and is used extremely effectively in the present invention.

  Next, a method for synthesizing amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) will be described. This method is a method in which phthalocyanines are dissolved in sulfuric acid, diluted with water, and reprecipitated, and a method called an acid paste method or an acid slurry method can be used.

  As a specific method, the above synthetic crude product is dissolved in 10 to 50 times the amount of concentrated sulfuric acid, and if necessary, insoluble matters are removed by filtration, etc., and this is sufficiently cooled relative to the amount of sulfuric acid. The resulting solution is slowly poured into 10 to 50 times the amount of water or ice water to reprecipitate titanyl phthalocyanine. The precipitated titanyl phthalocyanine is filtered, washed with ion-exchanged water and filtered, and this operation is sufficiently repeated until the filtrate becomes neutral. Finally, after washing with ion-exchanged water, filtration is performed to obtain a water paste having a solid concentration of about 5 to 15 wt%.

  At this time, it is important to thoroughly wash with ion-exchanged water so as not to leave concentrated sulfuric acid as much as possible. Specifically, it is preferable that the ion-exchanged water after washing exhibits the following physical property values. That is, if the residual amount of sulfuric acid is expressed quantitatively, it can be expressed by the pH and specific conductivity of ion-exchanged water after washing. When expressed in terms of pH, the pH is preferably in the range of 6-8. Within this range, it can be determined that the remaining amount of sulfuric acid does not affect the photoreceptor characteristics. This pH value can be easily measured with a commercially available pH meter. In terms of specific conductivity, it is desirably 8 μS / cm or less (preferably 5 μS / cm or less, more preferably 3 μS / cm or less). Within this range, it can be determined that the remaining amount of sulfuric acid does not affect the photoreceptor characteristics. This specific conductivity can be measured with a commercially available electric conductivity meter. The lower limit of the specific conductivity is the specific conductivity of the ion exchange water used for cleaning. In any measurement, in the range deviating from the above range, the remaining amount of sulfuric acid is large, and the chargeability of the photoreceptor is lowered or the photosensitivity is deteriorated.

  In this way, the amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) used in the present invention is produced. In this case, the amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) is at least 7.0 to 7 as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542Å) of CuKα. It preferably has a maximum diffraction peak at 5 °. In particular, the half width of the diffraction peak is more preferably 1 ° or more. Further, the average particle size of the primary particles is preferably 0.1 μm or less.

(Crystal conversion method)
Next, a crystal conversion method will be described.

  Crystal transformation is performed by using the amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) as a diffraction peak (± 0.2 °) at a Bragg angle 2θ with respect to the characteristic X-ray of CuKα (wavelength 1.542Å) at least 27.2 °. And has a major peak at 9.4 °, 9.6 °, and 24.0 °, and a peak at 7.3 ° as the lowest diffraction peak, And, it is a step of converting to a titanyl phthalocyanine crystal having no peak between the peak at 7.3 ° and the peak at 9.4 ° and not having a peak at 26.3 °.

  As a specific method, the crystalline form can be obtained by mixing and stirring the amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) with an organic solvent in the presence of water without drying.

  At this time, any organic solvent can be used as long as the desired crystal form can be obtained. In particular, tetrahydrofuran, toluene, methylene chloride, carbon disulfide, orthodichlorobenzene, 1,1, Good results are obtained when one selected from 2-trichloroethane is selected. These organic solvents are preferably used alone, but two or more of these organic solvents may be mixed or used in combination with other solvents. The amount of the organic solvent used for crystal conversion is desirably 10 times or more, preferably 30 times or more, relative to the weight of amorphous titanyl phthalocyanine. This is because crystal transformation can be caused quickly and sufficiently, and impurities contained in the amorphous titanyl phthalocyanine can be sufficiently removed. The amorphous titanyl phthalocyanine used here is prepared by the acid paste method, but it is desirable to use one obtained by thoroughly washing sulfuric acid as described above. If crystal conversion is performed under conditions where sulfuric acid remains, it remains, and even if an operation such as washing with water is performed, sulfate ions cannot be completely removed from the resulting crystals. When sulfate ions remain, preferable results cannot be obtained, such as a decrease in sensitivity and a decrease in chargeability of the photoreceptor. For example, Patent Document 4 (Comparative Example) describes a method in which titanyl phthalocyanine dissolved in sulfuric acid is added to an organic solvent together with ion-exchanged water to perform crystal conversion. At this time, a crystal similar to the X-ray diffraction spectrum of the titanyl phthalocyanine crystal obtained in the present invention can be obtained. However, since the sulfate ion concentration in titanyl phthalocyanine is high and the light attenuation characteristic (photosensitivity) is poor, It is not suitable for the production method of titanyl phthalocyanine of the invention. The reason for this is as described above.

  The above crystal conversion method is a crystal conversion method according to Patent Document 1. On the other hand, in the charge generating material contained in the photoreceptor used in the electrophotographic apparatus of the present invention, the effect is achieved by making the particle size of the titanyl phthalocyanine crystal finer (0.25 μm or less). The following describes a synthetic approach for titanyl phthalocyanine having a small particle size.

(Particle size and crystal form of titanyl phthalocyanine crystal in the present invention)
According to the observation by the present inventors, according to the observation by the present inventors, the above-mentioned amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) has a primary particle size of 0.1 μm or less (most of them). (Refer to FIG. 11), it was found that the crystal type was converted with crystal growth. Usually, in this type of crystal conversion, a sufficient crystal conversion time is ensured due to fear of remaining of the raw material, and after the crystal conversion is sufficiently performed, filtration is performed to obtain a titanyl phthalocyanine crystal having a desired crystal type. Have gained. For this reason, even though a raw material having sufficiently small primary particles is used as the raw material, a crystal having a large primary particle (approximately 0.3 to 0.5 μm) is obtained in the crystal after crystal conversion (see FIG. 12).

  The scale bars in the figure are all 0.2 μm.

  In order to disperse the titanyl phthalocyanine crystal produced as shown in FIG. 12, in order to reduce the particle size after dispersion (0.25 μm or less), dispersion is performed by giving a strong share, and further necessary. In response to this, dispersion is performed by giving strong energy to pulverize the primary particles. As a result, as described above, there is a possibility that a part of the particles may be transferred to a crystal type which is not a desired crystal type.

  In this regard, by controlling the primary particle size of the titanyl phthalocyanine crystal from the synthesis stage, it is possible to obtain a crystal having a small size and solve this problem, and it is effectively used in the present invention. Specifically, the range in which crystal growth hardly occurs during crystal conversion (the range in which the size of the amorphous titanyl phthalocyanine particles observed in FIG. 11 is inferior after the crystal conversion, approximately 0.25 μm or less. ), It is possible to obtain a titanyl phthalocyanine crystal having a primary particle size as small as possible by determining when the crystal conversion is completed. The particle size after crystal conversion increases in proportion to the crystal conversion time. For this reason, as described above, it is important to increase the efficiency of crystal conversion and complete it in a short time. There are several important points for this.

  The first point is to select an appropriate crystal conversion solvent as described above and increase the crystal conversion efficiency, and another point is that the solvent and titanyl phthalocyanine are used in order to complete the crystal conversion in a short time. Stir vigorously to bring the water paste (raw material prepared as described above: amorphous titanyl phthalocyanine) into sufficient contact. Specifically, crystal conversion in a short time is realized by a method such as stirring using a propeller having a very strong stirring force, or using a strong stirring (dispersing) means such as a homogenizer (homomixer). Under these conditions, it is possible to obtain a titanyl phthalocyanine crystal in a state in which crystal conversion is sufficiently performed and crystal growth does not occur without remaining raw materials. Also in this case, optimization of the amount of organic solvent used for crystal conversion is an effective means. Specifically, it is desirable to use 10 times or more, preferably 30 times or more of the organic solvent with respect to the solid content of the amorphous titanyl phthalocyanine. As a result, crystal conversion in a short time can be ensured and impurities contained in the amorphous titanyl phthalocyanine can be surely removed.

  FIG. 13 is a TEM image of a titanyl phthalocyanine crystal subjected to crystal conversion in a short time in consideration of the above two points. The scale bar in the figure is 0.2 μm.

  In addition, since the crystal grain size and the crystal conversion time are in a proportional relationship as described above, a method of immediately stopping the reaction when a predetermined reaction (crystal conversion) is completed is also an effective means. One example of this means is to immediately add a large amount of a solvent in which crystal conversion hardly occurs after crystal conversion as described above. Examples of the solvent that hardly causes crystal transformation include alcohol-based and ester-based solvents. Crystal conversion can be stopped by adding about 10 times these solvents to the crystal conversion solvent.

  The smaller the primary particle size produced in this way, the better the results for the problem of the photoreceptor, but the next step for pigment preparation (pigment filtration step), the dispersion stability in the dispersion liquid When considered, other problems can occur if it is too small. That is, if the primary particles are very fine, the filtration time becomes very long in the step of filtering the primary particles. In addition, when the primary particles are too fine, the surface area of the pigment particles in the dispersion increases, so that the possibility of reaggregation of the particles increases. Therefore, the suitable particle size of the pigment particles is in the range of about 0.05 μm to 0.2 μm.

  FIG. 13 shows a TEM image of a titanyl phthalocyanine crystal when crystal conversion is performed in a short time. Unlike the case of FIG. 12, the particle size is small and almost uniform, and the coarse particles observed in FIG. 12 are not recognized at all.

  As shown in FIG. 13, when dispersing titanyl phthalocyanine crystals prepared in a state where the primary particles are small, the particle size after dispersion is made small (0.25 μm or less, more preferably 0.2 μm or less). For this purpose, it is possible to disperse by giving a share sufficient to loosen the secondary particles formed by aggregation of the primary particles. As a result, since the energy more than necessary is not given, as described above, it is possible to easily produce a dispersion having a fine particle size distribution without transferring a part of the particles to a desired crystal type. is there.

  The average particle size referred to here is a volume average particle size, measured by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba), and a particle size (Median diameter) corresponding to 50% of the cumulative distribution. ). However, this method may not be able to detect a very small amount of coarse particles. Therefore, in order to obtain more details, it is important to observe the titanyl phthalocyanine crystal powder or dispersion directly with an electron microscope and determine its size. It is.

  As a result of further examination of the microscopic defects by further observation of the dispersion, the above phenomenon is understood as follows. Normally, in the method of measuring the average particle size, it can be detected when extremely large particles are present in a few percent or more, but when the amount becomes as small as 1% or less of the whole, it is below the detection limit. turn into. As a result, the presence of coarse particles cannot be detected only by measuring the average particle size, and it is difficult to interpret the above-described minute defects. Hereinafter, the results of experimental verification on minute defects will be shown.

  FIGS. 14 and 15 show photographs observing the state of two types of dispersions in which only the dispersion time is changed while fixing the dispersion conditions. The dispersion time in FIGS. 14 and 15 is shorter in FIG. 14, and in FIG. 14, it is observed that coarse particles remain. The black particles in FIG. 14 are coarse particles.

  The average particle size and particle size distribution of these two types of dispersions were measured by a commercially available particle size distribution measuring device (manufactured by Horiba: ultracentrifugal automatic particle size distribution measuring device, CAPA 700). The result is shown in FIG. “A” in FIG. 16 corresponds to the dispersion shown in FIG. 14, and “B” corresponds to the dispersion shown in FIG. When both are compared, there is almost no difference in the particle size distribution. In addition, the average particle diameter values of the two are “A” of 0.29 μm and “B” of 0.28 μm, and taking into account measurement errors, there is no difference between the two.

  Therefore, it is understood that the remaining of a very small amount of coarse particles cannot be detected only by the definition of the known average particle size (particle size), and it is not possible to cope with the recent high-resolution negative / positive development. The presence of such a minute amount of coarse particles can be recognized for the first time by observing the coating solution at the microscope level.

  In response to such a fact, it is an effective means to make the primary particles produced at the time of crystal conversion as small as possible. For this reason, an effective method is to select an appropriate crystal conversion solvent as described above to increase the crystal conversion efficiency, and in order to complete the crystal conversion in a short time, a solvent and a titanyl phthalocyanine water paste (as described above). It is to stir vigorously in order to bring the prepared raw material) into sufficient contact.

  By adopting such a crystal conversion method, a titanyl phthalocyanine crystal having a small primary particle size (0.25 μm or less, more preferably 0.2 μm or less) can be obtained. In addition to the technique described in Patent Document 1, it is an important means in the present invention to use the above-described technique (crystal conversion method for obtaining fine titanyl phthalocyanine crystals) as necessary.

  Subsequently, the crystallized titanyl phthalocyanine crystal is immediately filtered to be separated from the crystal conversion solvent. This filtration is performed by using a filter of an appropriate size. In this case, it is most appropriate to use vacuum filtration.

  Thereafter, the separated titanyl phthalocyanine crystal is heat-dried as necessary. Any known dryer can be used for heat drying, but a blower dryer is preferred when the drying is performed under atmospheric pressure. Furthermore, drying at a reduced pressure is a very effective means in order to increase the drying speed and to exhibit the effects of the present invention more remarkably. In particular, this is an effective means for a material that decomposes at a high temperature or changes its crystal form. In particular, it is effective to dry in a state where the degree of vacuum is higher than 10 mmHg.

  The thus obtained titanyl phthalocyanine crystal having a specific crystal type is extremely useful as a charge generating material for an electrophotographic photoreceptor. However, as described above, the crystal form is unstable, and there is a drawback that the crystal form is easily transferred when a dispersion is prepared. However, by synthesizing primary particles as small as possible in the present invention, a dispersion with a small average particle size can be prepared without giving an excessive share during the preparation of the dispersion, and the crystal type is also extremely stable. (Without changing the synthesized crystal form).

(Method for creating dispersion)
Next, a method for preparing the dispersion will be described.

  A general method is used for the preparation of the dispersion, and the titanyl phthalocyanine crystal is dispersed in a suitable solvent together with a binder resin as necessary by using a ball mill, an attritor, a sand mill, a bead mill, an ultrasonic wave, or the like. can get. At this time, the binder resin may be selected depending on the electrostatic characteristics of the photoreceptor, and the solvent may be selected depending on the wettability to the pigment, the dispersibility of the pigment, and the like.

  As already mentioned, the titanyl phthalocyanine crystal having a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα rays (wavelength 1.542 mm) is It is known that a crystal transition easily occurs to another crystal type due to a stress such as a dynamic share. This tendency does not change in the titanyl phthalocyanine crystal used in the present invention. In other words, in order to produce a dispersion containing fine particles, it is necessary to devise a dispersion method, but the stability of the crystal form and the micronization tend to be in a trade-off relationship. Although there are methods for avoiding this by optimizing the dispersion conditions, all of them make the manufacturing conditions extremely narrow, and a simpler method is desired. In order to solve this problem, the following method is also an effective means.

  That is, it is a method in which a dispersion liquid in which the particles are made as fine as possible is prepared as long as crystal transition does not occur, and then filtered through an appropriate filter. This method is a very effective means in that it can remove even a trace amount of coarse particles that cannot be visually observed (or cannot be detected by particle size measurement) and that the particle size distribution is uniform. Specifically, the dispersion prepared as described above is filtered through a filter having an effective pore size of 3 μm or less, more preferably 1 μm or less to prepare a dispersion. Also by this method, a dispersion containing only titanyl phthalocyanine crystals having a small particle size (0.25 μm or less, more preferably 0.2 μm or less) can be produced, and a photoconductor using the dispersion is mounted on an image forming apparatus. By using it, the effect of the present application becomes even more remarkable.

  The filter for filtering the dispersion varies depending on the size of coarse particles to be removed, but according to the study by the present inventors, a photosensitive member used in an electrophotographic apparatus requiring a resolution of about 600 dpi is at least 3 μm. The presence of the above coarse particles affects the image. Therefore, a filter with an effective pore size of less than 3 μm should be used. More preferably, a filter having an effective pore size of 1 μm or less is used. By performing such a filtering process, unnecessary coarse particles can be removed, and a dispersion having a narrow particle size distribution and no coarse particles can be produced.

  As for the effective pore size, finer particles are effective in removing coarse particles. However, if they are too fine, necessary pigment particles themselves are also filtered, so an appropriate size is selected. Also, if the effective diameter is too small, (1) it takes time to filter, (2) the filter is clogged, (3) too much load is applied when using a pump, etc. Cause problems. As a matter of course, the material of the filter used here is one that is resistant to the solvent used in the dispersion to be filtered.

  During filtration, if the amount of coarse particles in the dispersion to be filtered is too large, the amount of pigment to be removed increases, and the solid content concentration of the dispersion after filtration changes, which is not preferable. Therefore, an appropriate particle size distribution (particle size, standard deviation) exists when performing filtration. As in the present invention, there is no loss of pigment due to filtration, filter clogging, etc., and in order to perform filtration efficiently, the volume average particle size of the dispersion before filtration is 0.3 μm or less, and its standard deviation is It is desirable to disperse to 0.2 μm or less.

  By adding such an operation of filtering the dispersion, coarse particles can be removed, and as a result, background contamination generated on the photoconductor using the dispersion can be reduced. As described above, the finer the filter, the greater the effect, but the pigment particles themselves may be filtered. In such a case, a very large effect can be obtained by using in combination with the above-described technology for refining and synthesizing the primary titanyl phthalocyanine particles.

  That is, (i) by synthesizing and using refined titanyl phthalocyanine, the dispersion time can be shortened and the dispersion stress can be reduced, and the possibility of crystal transition in dispersion is reduced. (Ii) Since the size of coarse particles remaining by dispersion is smaller than that in the case where the particles are not refined, a smaller filter can be used, and the effect of removing coarse particles becomes more reliable. In addition, the amount of titanyl phthalocyanine particles to be removed is reduced, and there is little change in the composition of the dispersion before and after filtration, which enables stable production. (Iii) As a result, the manufactured photoreceptor is stably produced with a high resistance to soiling.

(Electrophotographic photoreceptor)
Next, the electrophotographic photosensitive member used in the present invention will be described in detail with reference to the drawings.

  FIG. 17 is a cross-sectional view showing a structural example of the electrophotographic photosensitive member used in the present invention. A titanyl phthalocyanine crystal (charge generating material) having a specific crystal size and a specific particle size is formed on a conductive support 31. A charge generation layer 35 having a main component and a charge transport layer 37 having a charge transport material as a main component are stacked.

  FIG. 18 is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the present invention. On the conductive support 31, a titanyl phthalocyanine crystal (charge) having the specific particle size and the specific particle size is provided. The charge generation layer 35 mainly composed of a generation material) and the charge transport layer 37 mainly composed of a charge transport material are laminated, and a protective layer 39 is further provided on the charge transport layer.

Examples of the conductive support 31 include those having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, metals such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, indium oxide, etc. The metal oxide of the above is coated with film or cylindrical plastic or paper by vapor deposition or sputtering, or a plate made of aluminum, aluminum alloy, nickel, stainless steel or the like and extruded by drawing or drawing. After pipe formation, surface treatment pipes such as cutting, superfinishing, and polishing can be used. Further, an endless nickel belt and an endless stainless steel belt disclosed in Patent Document 5 can also be used as the conductive support 31.

  Of these, a cylindrical support made of aluminum, which can be easily subjected to the anodic oxide film treatment, can be most preferably used. As used herein, aluminum includes either pure aluminum or aluminum alloy. Specifically, JIS 1000, 3000, and 6000 series aluminum or aluminum alloy is most suitable. Anodized films can be obtained by anodizing various metals and various alloys in an electrolyte solution, but the most suitable for the photoreceptor used in the present invention is aluminum or an aluminum alloy in an electrolyte solution. It is a film called anodized. In particular, it is excellent in that it can prevent point defects (black spots, background stains) that occur when used in reversal development (negative / positive development).

The anodizing treatment is performed in an acidic bath such as chromic acid, sulfuric acid, oxalic acid, phosphoric acid, boric acid, sulfamic acid. Of these, treatment with a sulfuric acid bath is most suitable. For example, sulfuric acid concentration: 10 to 20%, bath temperature: 5 to 25 ° C., current density: 1 to 4 A / dm ² , electrolytic voltage: 5 to 30 V, treatment time: treatment in the range of about 5 to 60 minutes However, the present invention is not limited to this. Since the anodic oxide film produced in this way is porous and has high insulating properties, the surface is very unstable. For this reason, it changes with time after fabrication, and the physical property value of the anodized film is likely to change. In order to avoid this, it is desirable to further seal the anodized film. Examples of the sealing treatment include a method of immersing the anodized film in an aqueous solution containing nickel fluoride and nickel acetate, a method of immersing the anodized film in boiling water, and a method of treating with pressurized steam. Among these, the method of immersing in the aqueous solution containing nickel acetate is the most preferable. Subsequent to the sealing treatment, the anodic oxide film is washed. The main purpose of this is to remove excess metal salts and the like attached by the sealing treatment. If the metal salt remains excessively on the surface of the support (anodized film), not only will it adversely affect the quality of the coating film formed on the surface, but generally low resistance components will remain. It will also cause the occurrence of. Washing may be performed only once with pure water, but usually multi-stage cleaning is performed. At this time, it is preferable that the final cleaning liquid is as clean (deionized) as possible. Further, in one of the multi-stage cleaning processes, it is desirable to perform physical rubbing cleaning with a contact member. The film thickness of the anodized film formed as described above is preferably about 5 to 15 μm. If it is too thin, the barrier effect as an anodic oxide film is not sufficient, and if it is too thick, the time constant as an electrode becomes too large, resulting in the generation of residual potential and the response of the photoreceptor. There is a case.

  In addition, the conductive support 31 of the present invention can be used in which conductive powder is dispersed in a suitable binder resin and coated on the support. Examples of the conductive powder include carbon black, acetylene black, metal powder such as aluminum, nickel, iron, nichrome, copper, zinc and silver, or metal oxide such as conductive tin oxide and indium tin oxide (ITO). Examples include powder. The binder resin used at the same time is polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer. , Polyvinyl acetate, polyvinylidene chloride, polyarylate resin, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, Examples thereof include thermoplastic, thermosetting resins, and photocurable resins such as melamine resin, urethane resin, phenol resin, and alkyd resin. Such a conductive layer can be provided by dispersing and coating these conductive powder and binder resin in a suitable solvent such as tetrahydrofuran, dichloromethane, methyl ethyl ketone, and toluene.

  Furthermore, a heat-shrinkable tube in which the conductive powder is contained in a material such as polyvinyl chloride, polypropylene, polyester, polystyrene, polyvinylidene chloride, polyethylene, chlorinated rubber, polytetrafluoroethylene fluororesin on a suitable cylindrical substrate. Those provided with a conductive layer can be favorably used as the conductive support 31 of the present invention.

  Next, the photosensitive layer will be described. As described above, the laminated type composed of the charge generation layer 35 and the charge transport layer 37 exhibits excellent characteristics in sensitivity and durability, and is used favorably.

  The charge generation layer 35 has, as a charge generation material, a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to a characteristic X-ray (wavelength 1.542 mm) of CuKα. Further, it has major peaks at 9.4 °, 9.6 °, and 24.0 °, and has a peak at 7.3 ° as the diffraction peak at the lowest angle side, and the above-mentioned 7.3 ° There is no peak between the peak at 9.4 ° and the peak at 9.4 °, and there is no further peak at 26.3 °. The average particle size of the primary particles is 0.25 μm during crystal synthesis or by dispersion filtration. This is a layer mainly composed of titanyl phthalocyanine crystal of the following (preferably 0.2 μm or less).

  The charge generation layer 35 is dispersed in a suitable solvent together with a binder resin as necessary using a ball mill, attritor, sand mill, ultrasonic wave, etc., and this is applied onto a conductive support and dried. Is formed.

  As the binder resin used for the charge generation layer 35 as necessary, polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicon resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly-N -Vinylcarbazole, polyacrylamide, polyvinyl benzal, polyester, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, polyphenylene oxide, polyamide, polyvinyl pyridine, cellulosic resin, casein, polyvinyl alcohol, polyvinyl pyrrolidone, etc. Can be mentioned. The amount of the binder resin is suitably 0 to 500 parts by weight, preferably 10 to 300 parts by weight with respect to 100 parts by weight of the charge generating material.

  Examples of the solvent used here include isopropanol, acetone, methyl ethyl ketone, cyclohexanone, tetrahydrofuran, dioxane, ethyl cellosolve, ethyl acetate, methyl acetate, dichloromethane, dichloroethane, monochlorobenzene, cyclohexane, toluene, xylene, ligroin and the like. As a coating method for the coating solution, a dip coating method, spray coating, beat coating, nozzle coating, spinner coating, ring coating, or the like can be used. The thickness of the charge generation layer 35 is suitably about 0.01 to 5 μm, preferably 0.1 to 2 μm.

  The charge transport layer 37 can be formed by dissolving or dispersing a charge transport material and a binder resin in a suitable solvent, and applying and drying the solution on the charge generation layer. Moreover, a plasticizer, a leveling agent, antioxidant, etc. can also be added as needed.

  Charge transport materials include hole transport materials and electron transport materials.

  Examples of the electron transporting material include chloroanil, bromoanil, tetracyanoethylene, tetracyanoquinodimethane, 2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone, 2,4 , 5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone, 2,6,8-trinitro-4H-indeno [1,2-b] thiophen-4-one, 1,3,7-tri Examples thereof include electron-accepting substances such as nitrodibenzothiophene-5,5-dioxide and benzoquinone derivatives.

  Examples of hole transport materials include poly-N-vinylcarbazole and derivatives thereof, poly-γ-carbazolylethyl glutamate and derivatives thereof, pyrene-formaldehyde condensates and derivatives thereof, polyvinylpyrene, polyvinylphenanthrene, polysilane, oxazole derivatives, Oxadiazole derivatives, imidazole derivatives, monoarylamine derivatives, diarylamine derivatives, triarylamine derivatives, stilbene derivatives, α-phenylstilbene derivatives, benzidine derivatives, diarylmethane derivatives, triarylmethane derivatives, 9-styrylanthracene derivatives, pyrazolines Derivatives, divinylbenzene derivatives, hydrazone derivatives, indene derivatives, butadiene derivatives, pyrene derivatives, etc., bisstilbene derivatives, enamine derivatives, etc. Other known materials may be mentioned. These charge transport materials may be used alone or in combination of two or more.

  Binder resins include polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene copolymer, styrene-maleic anhydride copolymer, polyester, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polyvinyl acetate, poly Vinylidene chloride, polyarate, phenoxy resin, polycarbonate, cellulose acetate resin, ethyl cellulose resin, polyvinyl butyral, polyvinyl formal, polyvinyl toluene, poly-N-vinyl carbazole, acrylic resin, silicone resin, epoxy resin, melamine resin, urethane resin, phenol resin And thermoplastic or thermosetting resins such as alkyd resins.

  The amount of the charge transport material is appropriately 20 to 300 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder resin. The thickness of the charge transport layer is preferably about 5 to 100 μm.

  As the solvent used here, tetrahydrofuran, dioxane, toluene, dichloromethane, monochlorobenzene, dichloroethane, cyclohexanone, methyl ethyl ketone, acetone and the like are used. Among these, it is desirable to use a non-halogen solvent for the purpose of reducing the environmental load. Specifically, cyclic ethers such as tetrahydrofuran, dioxolane and dioxane, aromatic hydrocarbons such as toluene and xylene, and derivatives thereof are preferably used.

  In addition, a polymer charge transport material having a function as a charge transport material and a function of a binder resin is also preferably used for the charge transport layer. The charge transport layer composed of these polymer charge transport materials is excellent in wear resistance. As the polymer charge transport material, known materials can be used, and in particular, a polycarbonate containing a triarylamine structure in the main chain and / or side chain is preferably used. Among these, polymer charge transport materials represented by the formulas (I) to (X) are preferably used, and these are exemplified below and specific examples are shown.

... (I) Formula (I) In the formula, R ₁ , R ₂ and R ₃ are each independently a substituted or unsubstituted alkyl group or a halogen atom, and R ₄ is a hydrogen atom or a substituted or unsubstituted alkyl group. , R ₅ and R ₆ are substituted or unsubstituted aryl groups, o, p and q are each independently an integer of 0 to 4, k and j are compositions, and 0.1 ≦ k ≦ 1, 0 ≦ j ≦ 0.9, n represents the number of repeating units and is an integer of 5 to 5000. X represents an aliphatic divalent group, a cycloaliphatic divalent group, or a divalent group represented by the following general formula. In the formula (I), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

R ₁₀₁ and R ₁₀₂ each independently represents a substituted or unsubstituted alkyl group, aryl group or halogen atom. l and m are integers of 0 to 4, Y is a single bond, a linear, branched or cyclic alkylene group having 1 to 12 carbon atoms, —O—, —S—, —SO—, —SO ₂ —. , -CO-, -CO-O-Z-O-CO- (wherein Z represents an aliphatic divalent group) or

(A represents an integer of 1 to 20, b represents an integer of 1 to 2000, R ₁₀₃ and R ₁₀₄ represent a substituted or unsubstituted alkyl group or aryl group). Here, R ₁₀₁ and R ₁₀₂ , and R ₁₀₃ and R ₁₀₄ may be the same or different.

· · · (II) Formula (II) _wherein, R 7, _{R 8} represents a substituted or unsubstituted aryl _group, Ar 1, Ar ₂ and Ar ₃ independently represent an arylene group. X, k, j and n are the same as in the case of formula (I). In the formula (II), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

· · · (III) formula (III) _{wherein, R 9,} R ₁₀ is a substituted or unsubstituted aryl _group, Ar 4, Ar ₅ and Ar ₆ independently represent an arylene group. X, k, j and n are the same as in the case of formula (I). In the formula (III), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

(IV) Formula (IV) In the formula, R ₁₁ and R ₁₂ are substituted or unsubstituted aryl groups, Ar ₇ , Ar ₈ and Ar ₉ are the same or different arylene groups, and p is an integer of 1 to 5. To express. X, k, j and n are the same as in the case of formula (I). In the formula (IV), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

(V) Formula (V) In the formula, R ₁₃ and R ₁₄ are substituted or unsubstituted aryl groups, Ar ₁₀ , Ar ₁₁ and Ar ₁₂ are the same or different arylene groups, and X ₁ and X ₂ are substituted or It represents an unsubstituted ethylene group or a substituted or unsubstituted vinylene group. X, k, j and n are the same as in the case of formula (I). In the formula (V), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

· · · (VI) formula (VI) _{wherein, R 15, R 16, R} 17 and _{R 18} are a substituted or unsubstituted aryl _{group, Ar 13, Ar 14, Ar} 15 and _{Ar 16} are identical or different arylene group , Y ₁ , Y ₂ and Y ₃ represent a single bond, a substituted or unsubstituted alkylene group, a substituted or unsubstituted cycloalkylene group, a substituted or unsubstituted alkylene ether group, an oxygen atom, a sulfur atom and a vinylene group, and are the same Or different. X, k, j and n are the same as in the case of the equation (V). still,
In the formula (I), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

· · · (VII) wherein (VII) _formula, R _{19, R 20} represents a hydrogen atom, a substituted or unsubstituted aryl group, R19 and R20 may form a ring. Ar ₁₇ , Ar ₁₈ and Ar ₁₉ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (VII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

... (VIII) Formula (VIII) In the formula, R ₂₁ represents a substituted or unsubstituted aryl group, and Ar ₂₀ , Ar ₂₁ , Ar ₂₂ and Ar ₂₃ represent the same or different arylene groups. X, k, j and n are the same as in the case of formula (I). In the formula (VIII), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

... (IX) Formula (IX) In the formula, R ₂₂ , R ₂₃ , R ₂₄ and R 25 are substituted or unsubstituted aryl groups, and Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ and Ar ₂₈ are the same or different. Represents an arylene group. X, k, j and n are the same as those in the formula (I). In the formula (IX), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

· · · (X) formula (X) _{wherein, R 26,} R ₂₇ is a substituted or unsubstituted aryl _{group, Ar 29,} Ar ₃₀ and _{Ar 31} independently represent an arylene group. X, k, j and n are the same as those in the formula (I). In the formula (X), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

  Further, as the polymer charge transport material used in the charge transport layer, in addition to the polymer charge transport material described above, in the state of the monomer or oligomer having an electron donating group at the time of film formation of the charge transport layer, Polymers finally having a two-dimensional or three-dimensional crosslinked structure are also included by carrying out a curing reaction or a crosslinking reaction.

  A charge transport layer composed of a polymer having these electron donating groups or a polymer having a crosslinked structure is excellent in wear resistance. Usually, in the electrophotographic process, since the charging potential (unexposed portion potential) is constant, if the surface layer of the photoreceptor is worn by repeated use, the electric field strength applied to the photoreceptor increases accordingly. As the electric field strength increases, the occurrence frequency of scumming increases. Therefore, the high wear resistance of the photosensitive member is advantageous for scumming. The charge transport layer composed of a polymer having these electron donating groups is excellent in film-forming properties because the charge transport layer itself is a polymer compound, and has a charge transporting property as compared with a charge transport layer composed of a low molecular dispersion type polymer. It is possible to construct the transport site with high density and excellent charge transport ability. For this reason, a photoreceptor having a charge transport layer using a polymer charge transport material can be expected to have a high response speed.

  Examples of other polymers having an electron donating group include known monomer copolymers, block polymers, graft polymers, star polymers, and, for example, Patent Document 6, Patent Document 7, Patent Document 8, and the like. It is also possible to use a cross-linked polymer having an electron donating group disclosed in the above.

  In the present invention, a plasticizer or a leveling agent may be added to the charge transport layer 37. As the plasticizer, those used as general plasticizers such as dibutyl phthalate and dioctyl phthalate can be used as they are, and the amount used is suitably about 0 to 30% by weight based on the binder resin. As the leveling agent, silicone oils such as dimethyl silicone oil and methylphenyl silicone oil, polymers or oligomers having a perfluoroalkyl group in the side chain are used, and the amount used is 0 to 0 with respect to the binder resin. 1% by weight is suitable.

  In the electrophotographic photosensitive member of the present invention, an intermediate layer can be provided between the conductive support 31 and the photosensitive layer. In general, the intermediate layer is mainly composed of a resin. However, considering that the photosensitive layer is coated with a solvent on the resin, it is desirable that the resin be a resin having a high solvent resistance with respect to a general organic solvent. . Examples of such resins include water-soluble resins such as polyvinyl alcohol, casein, and sodium polyacrylate, alcohol-soluble resins such as copolymer nylon and methoxymethylated nylon, polyurethane, melamine resin, phenol resin, alkyd-melamine resin, and epoxy. Examples thereof include a curable resin that forms a three-dimensional network structure, such as a resin. Further, in order to prevent moiré, reduce the residual potential, etc., for example, fine powder pigments of metal oxides such as titanium oxide, silica, alumina, zirconium oxide, tin oxide, and indium oxide may be added to the intermediate layer.

These intermediate layers can be formed by using an appropriate solvent and coating method like the above-mentioned photosensitive layer. Furthermore, a silane coupling agent, a titanium coupling agent, a chromium coupling agent, or the like can be used as the intermediate layer of the present invention. In addition, the intermediate layer of the present invention is provided with Al ₂ O ₃ by anodic oxidation, organic matter such as polyparaxylylene (parylene), SiO ₂ , SnO ₂ , TiO ₂ , ITO, CeO _2, etc. Those provided with an inorganic material by a vacuum thin film forming method can also be used satisfactorily. In addition, known ones can be used. The thickness of the intermediate layer is suitably from 0 to 5 μm.

  In the electrophotographic photoreceptor of the present invention, a protective layer may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. In recent years, computers have been used on a daily basis, and there has been a demand for downsizing of the apparatus as well as high-speed output by a printer. Therefore, by providing a protective layer and improving the durability, it is possible to use the photosensitive member of the present invention with high sensitivity and no abnormal defects.

  In the photoreceptor of the present invention, a protective layer 39 may be provided on the photosensitive layer for the purpose of protecting the photosensitive layer. Materials used for the protective layer 39 are ABS resin, ACS resin, olefin-vinyl monomer copolymer, chlorinated polyether, allyl resin, phenol resin, polyacetal, polyamide, polyamideimide, polyacrylate, polyallylsulfone, polybutylene. , Polybutylene terephthalate, polycarbonate, polyarylate, polyethersulfone, polyethylene, polyethylene terephthalate, polyimide, acrylic resin, polymethylbenten, polypropylene, polyphenylene oxide, polysulfone, polystyrene, AS resin, butadiene-styrene copolymer, polyurethane, poly Examples thereof include resins such as vinyl chloride, polyvinylidene chloride, and epoxy resin. Of these, polycarbonate or polyarylate can be most preferably used.

  In addition to the protective layer, fluorine resins such as polytetrafluoroethylene and silicone resins for the purpose of improving wear resistance, and inorganic fillers (inorganic pigments such as titanium oxide, tin oxide, potassium titanate, and silica) ) Or a composition in which an organic filler (organic pigment) is dispersed can be added.

  Among the filler materials used for the protective layer of the photoreceptor, examples of the organic filler material include fluororesin powder such as polytetrafluoroethylene, silicone resin powder, a-carbon powder, and the like. Metals such as copper, tin, aluminum, indium, etc., metals such as silica, tin oxide, zinc oxide, titanium oxide, indium oxide, antimony oxide, bismuth oxide, antimony-doped tin oxide, tin-doped indium oxide Inorganic materials such as oxide and potassium titanate can be mentioned. In particular, it is advantageous to use an inorganic material among them from the viewpoint of the hardness of the filler. In particular, silica, titanium oxide, and alumina can be used effectively.

  The filler concentration in the protective layer varies depending on the type of filler used and also on the electrophotographic process conditions using the photoconductor, but the ratio of filler to the total solid content on the outermost layer side of the protective layer is preferably 5% by weight or more, preferably 10% by weight or more and 50% by weight or less, preferably about 30% by weight or less is good.

  Further, the volume average particle size of the filler used is preferably in the range of 0.1 μm to 2 μm, and preferably in the range of 0.3 μm to 1 μm. In this case, if the average particle size is too small, the wear resistance is not sufficiently exhibited, and if it is too large, the surface property of the coating film is deteriorated or the coating film itself cannot be formed.

  The average particle size of the filler in the present invention is a volume average particle size unless otherwise specified, and is measured by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba). It is calculated as a particle diameter (Median diameter) corresponding to 50%. In addition, it is important that the standard deviation of each particle measured simultaneously is 1 μm or less. When the standard deviation value is 1 μm or more, the particle size distribution is too wide, and the effects of the present invention may not be obtained remarkably.

  Further, the pH of the filler used in the present invention greatly affects the resolution and the dispersibility of the filler. One possible reason is that hydrochloric acid or the like used during production remains in the filler, particularly the metal oxide. When the residual amount of hydrochloric acid or the like is large, image blurring occurs, and the dispersibility of the filler may be affected depending on the residual amount.

  Another reason is due to the difference in chargeability on the surface of the filler, particularly the metal oxide. Usually, particles dispersed in a liquid are charged positively or negatively, and ions having opposite charges gather to try to keep it electrically neutral, and an electric double layer is formed there. The dispersed state of the particles is stabilized. The potential (zeta potential) gradually decreases with increasing distance from the particle, and the potential in a region that is sufficiently away from the particle and electrically neutral is zero. Therefore, the stability increases as the repulsive force of the particles increases due to an increase in the absolute value of the zeta potential, and the particles tend to aggregate and become unstable as they approach zero. On the other hand, the zeta potential varies greatly depending on the pH value of the system (vehicle), and at a certain pH value, the potential becomes zero and has an isoelectric point. Therefore, the dispersion system is stabilized by increasing the absolute value of the zeta potential away from the isoelectric point of the system (vehicle) as much as possible.

  In the configuration of the present invention, the filler having a pH at the isoelectric point of at least 5 is preferably from the viewpoint of image blur suppression, and the more basic the filler, the higher the effect. confirmed. A filler having a basic pH with a high pH at the isoelectric point has a higher zeta potential when the system (vehicle) is more acidic, thereby improving dispersibility and its stability.

  Here, the pH of the filler in the present invention is the pH value at the isoelectric point from the zeta potential. At this time, the zeta potential was measured with a laser zeta potentiometer manufactured by Otsuka Electronics Co., Ltd.

Further, as the filler that is less likely to cause image blur, a filler having high electrical insulation (specific resistance is 10 ¹⁰ Ω · cm or more) is preferable, and the filler having a pH of 5 or more or the filler having a dielectric constant of 5 or more. The ones shown can be used particularly effectively. In addition, a filler having a pH of 5 or more or a filler having a dielectric constant of 5 or more can be used alone, or two or more fillers having a pH of 5 or less and a filler having a pH of 5 or more can be mixed. It is also possible to use a mixture of two or more fillers having a dielectric constant of 5 or less and fillers having a dielectric constant of 5 or more. Among these fillers, α-type alumina, which has high insulation properties, high thermal stability, and high wear resistance, is a hexagonal close-packed structure, from the viewpoint of suppressing image blur and improving wear resistance. It is particularly useful.

The specific resistance of the filler used in the present invention is defined as follows. Since the specific resistance value of the powder such as the filler varies depending on the filling rate, it is necessary to measure under a certain condition. In the present invention, the specific resistance value of the filler was measured using an apparatus having the same configuration as the measurement apparatus shown in Patent Document 9 (FIG. 1) and Patent Document 10 (FIG. 1), and this value was used. . The electrode area of the measuring device is 4.0 cm ² . Prior to the measurement, a load of 4 kg is applied to the electrode on one side for 1 minute, and the sample amount is adjusted so that the distance between the electrodes is 4 mm. At the time of measurement, the measurement is performed with the upper electrode weight (1 kg) loaded, and the applied voltage is measured at 100V. The area of 10 ⁶ Ω · cm or higher was measured with a HIGH RESISTER METER (Yokogawa Hewlett Packard), and the area below it was measured with a digital multimeter (Fluk). In the present invention, the specific resistance value obtained by this measurement is defined as the specific resistance value.

  The dielectric constant of the filler was measured as follows. A cell similar to the measurement of the specific resistance described above was used, and after applying a load, the capacitance was measured, and the dielectric constant was determined therefrom. For the measurement of the capacitance, a dielectric loss measuring device (Ando Electric) was used.

Further, these fillers can be surface-treated with at least one kind of surface treatment agent, and it is preferable from the viewpoint of dispersibility of the fillers. Decreasing the dispersibility of the filler not only increases the residual potential, but also decreases the transparency of the coating film, causes defects in the coating film, and decreases the wear resistance. It can develop into a big problem to hinder. As the surface treatment agent, all conventionally used surface treatment agents can be used, but a surface treatment agent capable of maintaining the insulating properties of the filler is preferable. For example, titanate coupling agents, aluminum coupling agents, zircoaluminate coupling agents, higher fatty acids, etc., or a mixture thereof with a silane coupling agent from the viewpoint of improving filler dispersibility and preventing image blurring It is more preferable to perform the treatment, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , silicone, aluminum stearate or the like, or a combination thereof. The treatment with the silane coupling agent is strongly influenced by image blur, but the influence may be suppressed by performing a mixing treatment of the surface treatment agent and the silane coupling agent. The surface treatment amount varies depending on the average primary particle size of the filler used, but is preferably 3 to 30 wt%, more preferably 5 to 20 wt%, based on the total solid content constituting the protective layer. If the surface treatment amount is less than this, the filler dispersing effect cannot be obtained, and if the surface treatment amount is too much, the residual potential is significantly increased. These filler materials may be used alone or in combination of two or more. The surface treatment amount of the filler is defined by the weight ratio of the surface treatment agent to be used with respect to the filler amount as described above.

  These filler materials can be dispersed by using an appropriate disperser. Further, from the viewpoint of the transmittance of the protective layer, it is preferable that the filler used is dispersed to the primary particle level and has less aggregates.

  In order to reduce residual potential and improve responsiveness, the protective layer 39 may contain a charge transport material, and the materials described in the description of the charge transport layer can be used as the charge transport material. When a low molecular charge transport material is used as the charge transport material, a concentration gradient in the protective layer may be provided. In order to improve wear resistance, it is an effective means to reduce the concentration of the surface side. The concentration here means the ratio of the weight of the low-molecular charge transporting substance to the total weight of all the materials constituting the protective layer, and the concentration gradient means that the layer has a lower concentration on the surface side in the weight ratio. It shows that it is provided. The use of a polymer charge transport material is very advantageous in terms of enhancing the durability of the photoreceptor.

  As a method for forming the protective layer, a normal coating method is employed. In addition, about 0.1-10 micrometers is suitable for the thickness of a protective layer. In addition to the above, a known material such as a-C or a-SiC formed by a vacuum thin film forming method can be used as the protective layer.

  In addition, the polymer charge transport material described in the section of the charge transport layer can be used as the binder resin for the protective layer. As the effect when this is used, the effect of improving the wear resistance and the high-speed charge transport can be obtained as described in the section of the charge transport layer.

  Moreover, the protective layer which consists of a crosslinked structure is also used effectively as a binder structure of a protective layer. Regarding the formation of the cross-linked structure, a reactive monomer having a plurality of cross-linkable functional groups in one molecule is used to cause a cross-linking reaction using light or heat energy to form a three-dimensional network structure. This network structure functions as a binder resin and exhibits high wear resistance.

  Moreover, it is a very effective means to use a monomer having a charge transporting ability in whole or in part as the reactive monomer. By using such a monomer, a charge transporting site is formed in the network structure, and the function as a protective layer can be sufficiently expressed. A reactive monomer having a triarylamine structure is effectively used as the monomer having charge transporting ability. The charge transport layer having such a network structure has high wear resistance, but has a large volume shrinkage during the crosslinking reaction, and may be cracked if it is too thick. In such a case, the protective layer may be a laminated structure, a low molecular dispersion polymer protective layer may be used for the lower layer (photosensitive layer side), and a protective layer having a crosslinked structure may be formed on the upper layer (surface side). good.

  As described above, the use of a polymer charge transport material for the photosensitive layer (charge transport layer) or the provision of a protective layer on the surface of the photoreceptor increases the durability (wear resistance) of each photoreceptor. In addition, when used in a tandem type full-color image forming apparatus as described later, a new effect not found in a monochrome image forming apparatus is also produced.

  In the case of a full-color image, various types of images are input, but on the contrary, a typical image may also be input. For example, a check in a Japanese document or the like. The marking or the like is usually placed at the end of the image area, and the colors used are also limited. In a state in which a random image is always written, image writing, development, and transfer are performed on the photoconductor in the image forming element on average. When many image formations are repeated or only a specific image forming element is used, the durability balance is lost. When a photoreceptor having low surface durability (physical / chemical / mechanical) is used in such a state, this difference becomes significant, and an image problem is likely to occur. On the other hand, when the photoconductor is made highly durable, the amount of such local change is small, and as a result, it becomes difficult to appear as a defect on the image, so that high durability is achieved and the stability of the output image is improved. This is very effective.

  Hereinafter, although an example is given and the present invention is explained, the present invention is not restricted by an example. All parts are parts by weight.

  First, a synthesis example of a charge generation material (titanyl phthalocyanine crystal) will be described.

(Comparative Synthesis Example 1)
A pigment was prepared in accordance with the cited document 1. That is, 29.2 g of 1,3-diiminoisoindoline and 200 ml of sulfolane are mixed, and 20.4 g of titanium tetrabutoxide is added dropwise under a nitrogen stream. After completion of the dropwise addition, the temperature was gradually raised to 180 ° C., and the reaction was carried out by stirring for 5 hours while maintaining the reaction temperature between 170 ° C. and 180 ° C. After the completion of the reaction, the mixture was allowed to cool, and then the precipitate was filtered, washed with chloroform until the powder turned blue, then washed several times with methanol, further washed several times with hot water at 80 ° C., and dried. Crude titanyl phthalocyanine was obtained. Crude titanyl phthalocyanine is dissolved in 20 times the amount of concentrated sulfuric acid, added dropwise to 100 times the amount of ice water with stirring, the precipitated crystals are filtered, and then ion-exchanged water (pH: 7.0, until the washing solution becomes neutral). Repeated washing with specific conductivity (1.0 μS / cm) (pH value of ion-exchanged water after washing was 6.8, specific conductivity was 2.6 μS / cm), wet cake of titanyl phthalocyanine pigment ( Water paste) was obtained. 40 g of the obtained wet cake (water paste) was put into 200 g of tetrahydrofuran, stirred for 4 hours, filtered and dried to obtain titanyl phthalocyanine powder (referred to as pigment 1).

  The solid content concentration of the wet cake was 15 wt%. The weight ratio of the crystal conversion solvent to the wet cake is 33 times. Incidentally, the raw material of Comparative Synthesis Example 1 does not use a halide.

  The obtained titanyl phthalocyanine powder was subjected to X-ray diffraction spectrum measurement under the following conditions. As a result, the Bragg angle 2θ with respect to Cu-Kα ray (wavelength 1.542Å) was 27.2 ± 0.2 °, and the maximum peak and minimum angle 7 A titanyl phthalocyanine powder having a peak at .3 ± 0.2 °, no peak between the peak at 7.3 ° and the peak at 9.4 °, and no peak at 26.3 ° Was obtained. The result is shown in FIG.

  A part of the water paste obtained in Comparative Synthesis Example 1 was dried at 80 ° C. under reduced pressure (5 mmHg) for 2 days to obtain a low crystalline titanyl phthalocyanine powder. An X-ray diffraction spectrum of the dry powder of the water paste is shown in FIG.

(X-ray diffraction spectrum measurement conditions)
X-ray tube: Cu
Voltage: 50kV
Current: 30mA
Scanning speed: 2 ° / min Scanning range: 3 ° -40 °
Time constant: 2 seconds

(Comparative Synthesis Example 2)
A pigment was prepared according to the method described in Patent Document 11 and Example 1. That is, the wet cake produced in the previous Comparative Synthesis Example 1 was dried, 1 g of the dried product was added to 50 g of polyethylene glycol, and sand milling was performed with 100 g of glass beads. After the crystal transition, it was washed successively with dilute sulfuric acid and ammonium hydroxide aqueous solution and dried to obtain a pigment (referred to as pigment 2). The raw material of Comparative Synthesis Example 2 does not use a halide.

(Comparative Synthesis Example 3)
A pigment was prepared according to the method described in Patent Document 12 and Production Example 1. That is, the wet cake prepared in Comparative Synthesis Example 1 was dried, and 1 g of the dried product was stirred (50 ° C.) in a mixed solvent of 10 g of ion-exchanged water and 1 g of monochlorobenzene for 1 hour, and then methanol and ion-exchanged water. The pigment was obtained by washing and drying (referred to as pigment 3). The raw material of Comparative Synthesis Example 3 does not use a halide.

(Comparative Synthesis Example 4)
A pigment was prepared according to the method described in the production example of Patent Document 13. That is, 9.8 g of phthalodinitrile and 75 ml of 1-chloronaphthalene are stirred and mixed, and 2.2 ml of titanium tetrachloride is added dropwise under a nitrogen stream. After completion of the dropping, the temperature was gradually raised to 200 ° C., and the reaction was carried out by stirring for 3 hours while maintaining the reaction temperature between 200 ° C. and 220 ° C. After completion of the reaction, the mixture was allowed to cool to room temperature and heated to 130 ° C., filtered while hot, then washed with 1-chloronaphthalene until the powder turned blue, then washed several times with methanol, and further heated at 80 ° C. After washing several times with water, it was dried to obtain a pigment (referred to as pigment 4). As a raw material of Comparative Synthesis Example 4, a halide is used.

(Comparative Synthesis Example 5)
A pigment was prepared according to the method described in Patent Document 14 and Synthesis Example 1. That is, 5 parts of α-type titanyl phthalocyanine was subjected to crystal conversion treatment at 100 ° C. for 10 hours with a sand grinder together with 10 g of sodium chloride and 5 g of acetophenone. This was washed with ion-exchanged water and methanol, purified with dilute sulfuric acid aqueous solution, washed with ion-exchanged water until the washing solution became neutral, and dried to obtain a pigment (referred to as pigment 5). The raw material of Comparative Synthesis Example 5 uses a halide.

(Comparative Synthesis Example 6)
A pigment was prepared according to the method described in Patent Document 15 and Example 1. That is, 20.4 parts of O-phthalodinitrile and 7.6 parts of titanium tetrachloride were heated and reacted in 50 parts of quinoline at 200 ° C. for 2 hours, the solvent was removed by steam distillation, 2% hydrochloric acid, and then 2% The product was purified with an aqueous sodium hydroxide solution, washed with methanol and N, N-dimethylformamide, and then dried to obtain titanyl phthalocyanine. 2 parts of this titanyl phthalocyanine is dissolved little by little in 40 parts of 98% sulfuric acid at 5 ° C., and the mixture is stirred for about 1 hour while maintaining the temperature at 5 ° C. or less. Subsequently, this mixture is slowly poured into 400 parts of ice water stirred at high speed, and the precipitated crystals are filtered. Wash with distilled water until the crystals are neutral to obtain a wet cake. The cake was stirred in 100 parts of THF for about 5 hours, filtered, and the residue was washed with THF and dried to obtain a pigment (referred to as pigment 6). As a raw material of Comparative Synthesis Example 6, a halide is used.

(Comparative Synthesis Example 7)
A pigment was produced according to the method described in Patent Document 16 and Synthesis Example 2. That is, 10 parts of the wet cake prepared in the previous Comparative Synthesis Example 1 was mixed with 15 parts of sodium chloride and 7 parts of diethylene glycol, and milled for 60 hours with an automatic mortar under heating at 80 ° C. Next, sufficient washing with water was performed to completely remove sodium chloride and diethylene glycol contained in the treated product. After drying this under reduced pressure, 200 parts of cyclohexanone and glass beads having a diameter of 1 mm were added, and the mixture was treated with a sand mill for 30 minutes to obtain a pigment (referred to as pigment 7). The raw material of Comparative Synthesis Example 7 does not use a halide.

(Comparative Synthesis Example 8)
A pigment was produced according to the method for producing a titanyl phthalocyanine crystal of Patent Document 17. That is, 58 g of 1,3-diiminoisoindoline and 51 g of tetrabutoxytitanium were reacted in 210 mL of α-chloronaphthalene at 210 ° C. for 5 hours, and then washed with α-chloronaphthalene and dimethylformamide (DMF) in this order. Thereafter, it was washed with hot DMF, hot water and methanol and dried to obtain 50 g of titanyl phthalocyanine. 4 g of titanyl phthalocyanine was added to 400 g of concentrated sulfuric acid cooled to 0 ° C., followed by stirring at 0 ° C. for 1 hour. After confirming that phthalocyanine was completely dissolved, it was added to a 800 mL water / 800 mL toluene mixture cooled to 0 ° C. After stirring at room temperature for 2 hours, the precipitated phthalocyanine mixed crystal was filtered from the mixed solution and washed with methanol and water in this order. After confirming the neutrality of the washing water, the phthalocyanine mixed crystal was filtered from the washing water and dried to obtain 2.9 g of titanyl phthalocyanine mixed crystal. The raw material of Comparative Synthesis Example 8 does not use a halide.

(Synthesis Example 1)
In accordance with the method of Comparative Synthesis Example 1, a titanyl phthalocyanine pigment water paste was synthesized and subjected to crystal conversion as follows to obtain phthalocyanine crystals having smaller primary particles than Comparative Synthesis Example 1.

  400 parts of tetrahydrofuran was added to 60 parts of the water paste before crystal conversion obtained in Comparative Synthesis Example 1, and the mixture was stirred vigorously (2000 rpm) with a homomixer (Kennis, MARKIIf model) at room temperature. When the color changed to light blue (20 minutes after the start of stirring), stirring was stopped and filtration under reduced pressure was immediately performed. The crystals obtained on the filtration device were washed with tetrahydrofuran to obtain a wet cake of pigment. This was dried under reduced pressure (5 mmHg) at 70 ° C. for 2 days to obtain 8.5 parts of titanyl phthalocyanine crystals (referred to as pigment 9). The raw material of Synthesis Example 1 does not use a halide. The solid content concentration of the wet cake was 15 wt%. The weight ratio of the crystal conversion solvent to the wet cake is 44 times.

(Synthesis Example 2)
Under the same conditions as in Synthesis Example 1, except that the stirring time was changed to 30 minutes, crystal conversion was performed in the same manner as in Synthesis Example 1 to obtain a titanyl phthalocyanine crystal (referred to as Pigment 10).

(Synthesis Example 3)
Under the same conditions as in Synthesis Example 1, except that the stirring time was changed to 40 minutes, crystal conversion was performed in the same manner as in Synthesis Example 1 to obtain titanyl phthalocyanine crystals (referred to as Pigment 11).

  Part of the titanyl phthalocyanine (water paste) prepared in Comparative Synthesis Example 1 was diluted with ion-exchanged water to approximately 1% by weight, and the surface was scooped with a copper net that had been subjected to conductive treatment, to obtain titanyl phthalocyanine particles. The size was observed with a transmission electron microscope (TEM, Hitachi: H-9000NAR) at a magnification of 75000 times. The average particle size was determined as follows.

  The TEM image observed as described above is taken as a TEM photograph, and 30 titanyl phthalocyanine particles (a shape close to a needle shape) projected are arbitrarily selected, and the size of each major axis is measured. The arithmetic average of the major diameters of the 30 individuals measured was determined as the average particle size.

  The average particle size in the water paste in Synthesis Example 1 determined by the above method was 0.06 μm.

  Further, the titanyl phthalocyanine crystal of Comparative Synthesis Example 1 and the titanyl phthalocyanine crystal just before filtration in Synthesis Examples 1 to 3 were diluted with tetrahydrofuran to be about 1% by weight, and observed in the same manner as the above method. The average particle size obtained as described above is shown in Table 1. In addition, the titanyl phthalocyanine crystal produced in Comparative Synthesis Example 1 and Synthesis Example 1 did not necessarily have the same shape of all crystals (a shape close to a triangle, a shape close to a square, etc.). For this reason, the average particle size was calculated with the length of the largest diagonal of the crystal as the major axis.

  Table 1

The pigments 2 to 8 prepared in the above Comparative Synthesis Examples 2 to 8 were measured for X-ray diffraction spectra by the same method as described above, and confirmed to be the same as the spectra described in the respective publications. Further, the X-ray diffraction spectra of the pigments 9 to 11 prepared in Synthesis Examples 1 to 3 coincided with the spectrum of the pigment 1 prepared in Comparative Synthesis Example 1. Table 2 shows the characteristics of each X-ray diffraction spectrum and the peak position of the X-ray diffraction spectrum of the pigment obtained in Comparative Synthesis Example 1.

  Table 2

(Dispersion Preparation Example 1)
Pigment 1 prepared in Comparative Synthesis Example 1 was dispersed under the following composition under the following conditions to prepare a dispersion as a charge generation layer coating solution.

Titanyl phthalocyanine pigment (Pigment 1) 15 parts Polyvinyl butyral (manufactured by Sekisui Chemical: BX-1) 10 parts 2-butanone 280 parts A commercially available bead mill disperser was used to dissolve polyvinyl butyral using PSZ balls having a diameter of 0.5 mm. All butanone and pigment were added, and the rotor rotation speed was 1200 r. p. m. The dispersion was performed for 30 minutes to prepare a dispersion (referred to as dispersion 1).

(Dispersion Preparation Examples 2 to 11)
In place of Pigment 1 used in Dispersion Preparation Example 1, pigments 2 to 11 prepared in Comparative Synthesis Examples 2 to 8 and Synthesis Examples 1 to 3 were used, respectively, and dispersed under the same conditions as Dispersion Preparation Example 1. Liquids were produced (corresponding to the pigment numbers, dispersions 2 to 11, respectively).

(Dispersion Preparation Example 12)
The dispersion 1 prepared in Dispersion Preparation Example 1 was filtered using a cotton wind cartridge filter, TCW-1-CS (effective pore size 1 μm) manufactured by Advantech. In filtration, a pump was used to perform filtration in a pressurized state to obtain a filtrate (referred to as dispersion 12).

(Dispersion Preparation Example 13)
Dispersion is performed by pressure filtration in the same manner as in Dispersion Preparation Example 10, except that the filter used in Dispersion Preparation Example 10 is changed to an Advantech Co., Ltd. cotton wind cartridge filter, TCW-3-CS (effective pore diameter 3 μm). A liquid was prepared (referred to as dispersion 13).

(Dispersion Preparation Example 14)
Dispersion was performed by pressure filtration in the same manner as in Dispersion Preparation Example 12, except that the filter used in Dispersion Preparation Example 12 was changed to Advantech's Cotton Wind Cartridge Filter, TCW-5-CS (effective pore size 5 μm). A liquid was prepared (referred to as dispersion 14).

(Dispersion Preparation Example 15)
Dispersion was performed by changing the dispersion conditions in Dispersion Preparation Example 1 as follows (referred to as Dispersion 15). Rotor rotation speed: 1000 r. p. m. For 20 minutes.

(Dispersion Preparation Example 16)
The dispersion prepared in Dispersion Preparation Example 15 was filtered using a cotton wind cartridge filter, TCW-1-CS (effective pore size 1 μm) manufactured by Advantech. During filtration, a pump was used and filtration was performed in a pressurized state. During the filtration, the filter was clogged, and it was not possible to filter all the dispersions. Therefore, the following evaluation was not performed.

  The particle size distribution of the pigment particles in the dispersion prepared as described above was measured by HORIBA, Ltd .: CAPA-700. The results are shown in Table 3.

  Table 3

(Photoreceptor Preparation Example 1)
An undercoat layer coating solution, a charge generation layer coating solution, and a charge transport layer coating solution having the following composition were sequentially applied and dried on an aluminum cylinder (JIS1050) having a diameter of 60 mm, and an undercoat layer of 3.5 μm, A charge generation layer and a 28 μm charge transport layer were formed to produce a laminated photoreceptor (referred to as photoreceptor 1). The film thickness of the charge generation layer was adjusted so that the transmittance of the charge generation layer at 780 nm was 20%. The charge generation layer transmittance was measured by applying a charge generation layer coating solution having the following composition to an aluminum cylinder wrapped with a polyethylene terephthalate film under the same conditions as the preparation of the photoreceptor, and coating the charge generation layer as a comparative control. The transmittance was measured at 780 nm using a commercially available spectrophotometer (Shimadzu: UV-3100).

◎ Undercoat layer coating solution Titanium oxide (CR-EL: manufactured by Ishihara Sangyo Co., Ltd.) 70 parts Alkyd resin 15 parts (Beckolite M6401-50-S (solid content 50%),
Dainippon Ink & Chemicals)
Melamine resin 10 parts (Super Becamine L-121-60 (solid content 60%),
Dainippon Ink & Chemicals)
2-butanone 100 parts-Charge generation layer coating liquid The dispersion liquid 1 produced previously was used.

◎ Charge transport layer coating solution Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts Charge transport material of the following structural formula 7 parts

80 parts of methylene chloride (Photoconductor Preparation Examples 2 to 15)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 1 except that the charge generation layer coating solution (dispersion 1) used in Photoconductor Preparation Example 1 was changed to dispersions 2 to 15, respectively. Note that the thickness of the charge generation layer was adjusted so that the transmittance at 780 nm was 20% when all the coating solutions were used, as in Photoreceptor Preparation Example 1.

(Examples 1-5 and Comparative Examples 1-25)
The electrophotographic photoconductors of photoconductor production examples 1 to 15 produced as described above are mounted on the image forming apparatus shown in FIG. 8, charged with the following charging conditions using a scorotron charging member, and subjected to image exposure. A semiconductor laser having an oscillation wavelength of 655 nm was used as a light source, a beam having a major axis of 45 μm was formed by an image exposure apparatus comprising a coupling lens, an aperture, a cylindrical lens, a polygon mirror, and a scanning lens, and writing was performed on the photoconductor. For development, two-component development (toner with a volume average particle diameter of 6 μm) is performed, a transfer belt is used as a transfer member, a 780 nm LED is used for charge removal light, and the entire surface of the photoconductor is irradiated with light to perform charge removal. did. Using a chart with a writing rate of 6%, continuous printing of 50,000 sheets was performed (the test environment was 22 ° C.-55% RH).

Charging condition 1:
Discharge voltage: -6.0 kV
Grid voltage: -920V (surface potential of unexposed portion of photoconductor is -900V)
Development bias: -650V
Charging condition 2:
Discharge voltage: -5.8 kV
Grid voltage: -780V (surface potential of unexposed portion of photoconductor is -750V)
Development bias: -500V
The following three evaluations were performed after printing 50,000 sheets.

(I) Evaluation of soiling:
A white solid image was output, and rank evaluation was performed from the number and size of black spots generated on the background.

(Ii) Evaluation of dot formation state A halftone image (one dot image having a diameter of 50 μm) was formed, and the dot formation state was observed (dot scattering state and dot reproducibility).

  (Iii) The outline of the dot The sharpness of the peripheral (edge) portion of the dot was evaluated.

  In each case, the rank evaluation was performed in 4 stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by x. The results are shown in Table 4.

  Table 4

(Examples 6 to 10 and Comparative Examples 26 to 35)
The electrophotographic photoconductors of photoconductor production examples 1 to 15 produced as described above are mounted on the image forming apparatus shown in FIG. 8 and are charged under the following charging conditions using a contact type charging member (charging roller having a diameter of 18 mm). The surface of the photoconductor is charged to −880 V, a semiconductor laser having an oscillation wavelength of 655 nm is used as an image exposure light source, and the long diameter is measured by an image exposure apparatus including a coupling lens, an aperture, a cylindrical lens, a polygon mirror, and a scanning lens. A 45 μm beam was formed, and writing was performed on the photoreceptor. For development, two-component development (toner with a volume average particle diameter of 6 μm) is performed, a transfer belt is used as a transfer member, a 780 nm LED is used for charge removal light, and the entire surface of the photoconductor is irradiated with light to perform charge removal. did. Using a chart with a writing rate of 6%, continuous printing of 50,000 sheets was performed (the test environment was 22 ° C.-55% RH).

Charging conditions:
DC bias: -1580V
The following three evaluations were performed after printing 50,000 sheets.

(I) Evaluation of soiling:
A white solid image was output, and rank evaluation was performed from the number and size of black spots generated on the background.

(Ii) Evaluation of dot formation state A halftone image (one dot image having a diameter of 50 μm) was formed, and the dot formation state was observed (dot scattering state and dot reproducibility).

(Iii) Dot outline The sharpness of the periphery (edge) of the dot was evaluated.

  The soil stain rank was evaluated in four stages. Very good ones were indicated by 、, good ones by ○, slightly inferior by Δ, and very bad by x. The results are shown in Table 5.

  Table 5

(Example 11)
In Example 1, the chart used for the paper passing test was changed to a chart with a writing rate of 1%, and continuous printing of 50,000 sheets was performed. At this time, in order to measure the photosensitive member surface potential at the developing portion of the image forming apparatus shown in FIG. 3 and the photosensitive member surface potential immediately after the transfer, the surface potential meter was modified so that it could be set.

  Before and after the paper passing test, the potential of the exposed portion of the photoreceptor at the development site was measured. At this time, in order to measure the surface potential of the exposed portion, the optical writing was performed on the entire surface of the photoconductor.

  In the paper passing test in Example 4, the transfer bias was adjusted so that the potential of the non-written portion of the photoconductor after transfer was −150V. In this measurement, optical writing was not performed, and the potential after transfer of the photosensitive member was measured. The results are shown in Table 6.

(Example 12)
In Example 11, the test was performed in the same manner as in Example 11 except that the potential of the non-written portion of the photoconductor after transfer was adjusted to −80V. The results are shown in Table 6.

(Example 13)
In Example 11, the test was performed in the same manner as in Example 11 except that the potential of the non-written portion of the photoconductor after transfer was adjusted to 0V. The results are shown in Table 6.

(Example 14)
In Example 11, the test was performed in the same manner as in Example 11 except that the potential of the non-written portion of the photoconductor after transfer was adjusted to + 70V. The results are shown in Table 6.

(Example 15)
In Example 11, the test was performed in the same manner as in Example 11 except that the potential of the non-written portion of the photoconductor after transfer was adjusted to + 150V. The results are shown in Table 6.

(Example 16)
In Example 11, the test was performed in the same manner as in Example 11 except that the static elimination member was changed from the static elimination lamp to a conductive brush (connected to ground). The results are shown in Table 6.

  Table 6

(Photoreceptor Production Example 16)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 9 except that the charge transport layer coating solution in Photoconductor Preparation Example 9 was changed to one having the following composition.

◎ Charge transport layer coating solution 10 parts of polymer charge transport material having the following composition (weight average molecular weight: about 135,000)

0.5 parts of additive with the following structure

100 parts of methylene chloride (Photoconductor Preparation Example 17)
Similar to Photoreceptor Preparation Example 9 except that the thickness of the charge transport layer in Photoreceptor Preparation Example 9 was 22 μm, a protective layer coating solution having the following composition was applied and dried on the charge transport layer, and a protective layer of 5 μm was provided. A photoreceptor was prepared.

◎ Protective layer coating solution Polycarbonate (TS2050: manufactured by Teijin Chemicals Ltd.) 10 parts Charge transport material of the following structural formula: 7 parts

4 parts of alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Cyclohexanone 500 parts Tetrahydrofuran 150 parts (Photoconductor Preparation Example 18)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 17 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 17 were changed to the following.

4 parts of titanium oxide fine particles (specific resistance: 1.5 × 10 ¹⁰ Ω · cm, average primary particle size: 0.5 μm)
(Photoreceptor Preparation Example 19)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 17 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 17 were changed to the following.

4 parts of tin oxide-antimony oxide powder (specific resistance: 10 ⁶ Ω · cm, average primary particle size 0.4 μm)
(Photoreceptor Preparation Example 20)
An electrophotographic photoreceptor was produced in the same manner as in the photoreceptor preparation example 17 except that the protective layer coating solution in the photoreceptor preparation example 17 was changed to the one having the following composition.

◎ Protective layer coating solution 17 parts of polymer charge transport material having the following structural formula (weight average molecular weight: about 135,000)

4 parts of alumina fine particles (specific resistance: 2.5 × 10 ¹² Ω · cm, average primary particle size: 0.4 μm)
Cyclohexanone 500 parts Tetrahydrofuran 150 parts (Photoconductor Preparation Example 21)
An electrophotographic photoreceptor was produced in the same manner as in the photoreceptor preparation example 17 except that the protective layer coating solution in the photoreceptor preparation example 17 was changed to the one having the following composition.

◎ Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts Charge transporting compound with the following structure 35 parts

Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.) 1 part Curing agent (dibutyltin acetate) 1 part 2-propanol 200 parts (Photoconductor Preparation Example 22)
An electrophotographic photoreceptor was produced in the same manner as in the photoreceptor preparation example 17 except that the protective layer coating solution in the photoreceptor preparation example 17 was changed to the one having the following composition.

◎ Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts Charge transporting compound with the following structure 35 parts

α-alumina particles (Sumicorundum AA-03: manufactured by Sumitomo Chemical Co., Ltd.) 15 parts Antioxidant (Sanol LS2626: manufactured by Sankyo Chemical Co., Ltd.) 1 part Polycarboxylic acid compound BYK P104: 0.4 parts manufactured by BYK Chemie Co., Ltd. Tin acetate) 1 part 2-propanol 200 parts (Photoconductor Preparation Example 23)
The aluminum cylinder (JIS 1050) in photoreceptor preparation example 9 was subjected to the following anodic oxide film treatment, and then a charge generation layer and a charge transport layer were provided in the same manner as photoreceptor preparation example 9 without providing an undercoat layer. Was made.

◎ Anodic oxide film treatment Mirror surface finishing of the support surface, degreasing and water washing, immersion in an electrolytic bath with a liquid temperature of 20 ° C and sulfuric acid of 15 vol%, and an anodic oxide film treatment at an electrolytic voltage of 15 V for 30 minutes Was done. Further, after washing with water, sealing treatment was performed with a 7% nickel acetate aqueous solution (50 ° C.). Thereafter, the substrate was washed with pure water to obtain a support on which a 7 μm anodic oxide film was formed.

(Examples 17 to 24)
As described above, the electrophotographic photoreceptors produced in the photoreceptor preparation examples 16 to 23 are mounted on the image forming apparatus shown in FIG. 8 and charged using the scorotron charging member under the following charging conditions to perform image exposure. A semiconductor laser having an oscillation wavelength of 655 nm was used as a light source, a beam having a major axis of 45 μm was formed by an image exposure apparatus comprising a coupling lens, an aperture, a cylindrical lens, a polygon mirror, and a scanning lens, and writing was performed on the photoconductor. For development, two-component development (toner with a volume average particle diameter of 6 μm) is performed, a transfer belt is used as a transfer member, a 780 nm LED is used for charge removal light, and the entire surface of the photoconductor is irradiated with light to perform charge removal. did. Using a chart with a writing rate of 6%, continuous printing of 50,000 sheets was performed (the test environment was 22 ° C.-55% RH).

Charging conditions:
Discharge voltage: -6.0 kV
Grid voltage: -920V (surface potential of unexposed portion of photoconductor is -900V)
Development bias: -650V
The following three evaluations were performed after printing 50,000 sheets.

(I) Evaluation of soiling:
A white solid image was output, and rank evaluation was performed from the number and size of black spots generated on the background.

(Ii) Evaluation of dot formation state A halftone image (one dot image having a diameter of 50 μm) was formed, and the dot formation state was observed (dot scattering state and dot reproducibility).

(Iii) Dot outline The sharpness of the periphery (edge) of the dot was evaluated.

  In each case, the rank evaluation was performed in 4 stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by x. The results are shown in Table 7.

  In addition, the amount of abrasion of the photosensitive layer after printing 50,000 sheets (the amount of abrasion of the protective layer when a protective layer is provided) was measured. The results are shown in Table 7 together with the case of Example 1.

  Table 7

(Photoconductor Preparation Example 24)
The aluminum cylinder of the photoreceptor preparation example 1 was changed to one having a diameter of 30 mm, and a photoreceptor having the same composition as that of the photoreceptor preparation example 1 was prepared.

(Photoconductor Preparation Example 25)
The aluminum cylinder of the photoreceptor preparation example 4 was changed to one having a diameter of 30 mm, and a photoreceptor having the same composition as that of the photoreceptor preparation example 4 was prepared.

(Photoconductor Preparation Example 26)
A photoconductor having the same composition as that of photoconductor production example 5 was produced by changing the aluminum cylinder of photoconductor production example 5 to one having a diameter of 30 mm.

(Photoconductor Preparation Example 27)
The aluminum cylinder of the photoreceptor preparation example 8 was changed to one having a diameter of 30 mm, and a photoreceptor having the same composition as that of the photoreceptor preparation example 8 was prepared.

(Photoreceptor Preparation Example 28)
The aluminum cylinder of the photoreceptor preparation example 9 was changed to one having a diameter of 30 mm to prepare a photoreceptor having the same composition as the photoreceptor preparation example 9.

(Photoconductor Preparation Example 29)
The aluminum cylinder of the photoreceptor preparation example 12 was changed to one having a diameter of 30 mm, and a photoreceptor having the same composition as that of the photoreceptor preparation example 12 was prepared.

(Examples 25-26 and Comparative Examples 36-39)
The photoconductors of the photoconductor production examples 24-29 produced as described above are mounted on a single process cartridge for an image forming apparatus as shown in FIG. 10 together with a charging member (scorotron charging), and further, the full color shown in FIG. It was installed in an image forming apparatus. In the four image forming elements, a charging member is charged with a scorotron charging member so that the surface potential of the photosensitive member becomes −900 V, and a semiconductor laser having an oscillation wavelength of 655 nm is used as an image exposure light source. A beam having a major diameter of 40 μm was formed by an image exposure apparatus composed of an aperture, a cylindrical lens, a polygon mirror, and a scanning lens, and writing was performed on the photoconductor. For development, two-component development (toner with a volume average particle diameter of 6 μm) is performed, a transfer belt is used as a transfer member, a 780 nm LED is used for charge removal light, and the entire surface of the photoconductor is irradiated with light to perform charge removal. did. Using a chart with a writing rate of 6%, continuous 30,000 sheets were printed (the test environment was 22 ° C.-55% RH).

  The following four evaluations were performed after printing 30,000 sheets.

(I) Evaluation of soiling:
A white solid image was output, and rank evaluation was performed from the number and size of black spots generated on the background.

(Ii) Evaluation of dot formation state A halftone image (one dot image with a diameter of 45 μm) was formed, and the dot formation state was observed (dot scattering state and dot reproducibility).

  (Iii) The outline of the dot The sharpness of the peripheral (edge) portion of the dot was evaluated.

(Iv) Evaluation of color reproducibility The same full-color image was output after the initial state of the photoreceptor and 30,000 sheets of running, and evaluation of color reproducibility was attempted.

  In each case, the rank evaluation was performed in 4 stages, and very good ones were indicated by ◎, good ones by ○, slightly inferior by Δ, and very bad by x. The results are shown in Table 8.

  Table 8

Finally, 7.3 ° which is the lowest angle peak of Bragg 2θ, which is a feature of the titanyl phthalocyanine crystal used in the present invention, will be verified as to whether it is the same as the lowest angle 7.5 ° of known materials.

(Comparative Synthesis Example 9)
A titanyl phthalocyanine crystal was obtained in the same manner as in Comparative Synthesis Example 1 except that the crystal conversion solvent in Comparative Synthesis Example 1 was changed from methylene chloride to 2-butanone.

  As in Comparative Synthesis Example 1, the XD spectrum of the titanyl phthalocyanine crystal produced in Comparative Synthesis Example 9 was measured. This is shown in FIG. From FIG. 21, the lowest angle in the XD spectrum of the titanyl phthalocyanine crystal produced in Comparative Synthesis Example 9 is 7.5 ° different from the lowest angle (7.3 °) of the titanyl phthalocyanine produced in Comparative Synthesis Example 1. It can be seen that it exists.

(Measurement Example 1)
To the pigment obtained in Comparative Synthesis Example 1 (minimum angle 7.3 °), 3% by weight of the pigment prepared in the same manner as the pigment described in Patent Document 17 (having a maximum diffraction peak at 7.5 °) was added, The mixture was mixed in a mortar, and the X-ray diffraction spectrum was measured in the same manner as before. The X-ray diffraction spectrum of Measurement Example 1 is shown in FIG.

(Measurement example 2)
3% by weight of the pigment prepared in Comparative Synthesis Example 9 (minimum angle 7.5 °) prepared in the same manner as the pigment described in Patent Document 17 (having a maximum diffraction peak at 7.5 °) was added, The mixture was mixed in a mortar, and the X-ray diffraction spectrum was measured as before. The X-ray diffraction spectrum of Measurement Example 2 is shown in FIG.

  In the spectrum of FIG. 22, it can be seen that there are two independent peaks at 7.3 ° and 7.5 ° on the low angle side, and at least the peaks at 7.3 ° and 7.5 ° are different. . On the other hand, in the spectrum of FIG. 23, the low angle side peak exists only at 7.5 °, which is clearly different from the spectrum of FIG.

  From the above, it can be seen that the minimum angle peak of 7.3 ° in the titanyl phthalocyanine crystal of the present invention is different from the 7.5 ° peak in the known titanyl phthalocyanine crystal.

It is a schematic diagram of optical carrier generation. It is a figure showing that a dot diffuses in charge transportation. It is a figure showing the electric field strength and the state of dot (toner image) formation. It is a figure showing the relationship between electric field strength and background dirt. FIG. 4 is a schematic diagram of an electrostatic latent image (dot) of a photoreceptor using a charge generating material having a small particle size and a small particle size distribution. FIG. 3 is a schematic diagram of an electrostatic latent image (dot) of a photoreceptor using a charge generating material having a large particle size and a large particle size distribution (or including coarse particles). It is a figure for demonstrating the difference in the light attenuation characteristic of the photoreceptor at the time of using the charge generating substance from which particle sizes differ. A is a case where the particle size is large, and B is a case where the particle size is small. 1 is a schematic view for explaining an electrophotographic process and an image forming apparatus of the present invention. 1 is a schematic view for explaining a tandem-type full-color image forming apparatus of the present invention. FIG. FIG. 4 is a diagram for explaining a process cartridge for an image forming apparatus according to the present invention. It is a TEM image of amorphous titanyl phthalocyanine. The scale bar in the figure is 0.2 μm. It is a TEM image of titanyl phthalocyanine after crystal conversion. The scale bar in the figure is 0.2 μm. It is a TEM image of a titanyl phthalocyanine crystal that has undergone crystal conversion in a short time. The scale bar in the figure is 0.2 μm. It is a figure which shows the state of the dispersion liquid when dispersion time is short. It is a figure which shows the state of the dispersion liquid when dispersion time is long. It is a figure which shows an average particle diameter and a particle size distribution about the dispersion liquid of FIG. It is a figure showing the layer structure of the electrophotographic photosensitive member used for this invention. It is a figure showing the layer structure of another electrophotographic photosensitive member used for this invention. 4 is a diagram showing an XD spectrum of titanyl phthalocyanine synthesized in Comparative Synthesis Example 1. FIG. It is a figure showing the XD spectrum of the dry powder of the water paste. 14 is a diagram illustrating an XD spectrum of titanyl phthalocyanine synthesized in Comparative Synthesis Example 9. FIG. It is a figure showing the XD spectrum of the titanyl phthalocyanine used in the measurement example 1. It is a figure showing the XD spectrum of the titanyl phthalocyanine used in the measurement example 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Static elimination lamp 3 Charger charger 5 Image exposure part 6 Developing unit 8 Registration roller 9 Transfer paper 10 Transfer charger 11 Separation charger 12 Separation claw 14 Fur brush 15 Cleaning blade 16Y, 16M, 16C, 16K Photoconductor 17Y, 17M, 17C, 17K Charging member 18Y, 18M, 18C, 18K Laser light 19Y, 19M, 19C, 19K Developing member 20Y, 20M, 20C, 20K Cleaning member 21Y, 21M, 21C, 21K Transfer brush 22 Transfer conveyance belt 23 Registration roller 24 Fixing Apparatus 25Y, 25M, 25C, 25K Image forming element 26 Transfer paper 27Y, 27M, 27C, 27K Static elimination member 31 Conductive support 35 Charge generation layer 37 Charge transport layer 39 Protective layer 101 Photoconductor 102 Collecting member 103 image exposing unit 104 developing means 105 transfer member 106 transfer means 107 Chestnut - training means 108 discharging means

Claims (17)

An electrophotographic photosensitive member having a charge transport layer and a charge generation layer containing a titanyl phthalocyanine crystal as a charge generation material on a conductive support; and writing means using a light source having a beam diameter of 50 μm or less;
In an image forming apparatus comprising:
The titanyl phthalocyanine crystal has a Bragg angle 2θ diffraction peak (± 0.2 °) with respect to CuKα rays (wavelength 1.542Å):
Has a maximum diffraction peak at 27.2 °;
Has major peaks at 9.4 °, 9.6 ° and 24.0 °;
Has a peak at 7.3 ° as the lowest diffraction peak;
And no peaks between the 7.3 ° peak and the 9.4 ° peak and at 26.3 °;
The titanyl phthalocyanine crystal has an average primary particle size of 0.25 μm or less,
The titanyl phthalocyanine crystal has a maximum diffraction peak at 7.0 to 7.5 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to CuKα characteristic X-ray (wavelength 1.542 mm), Crystalline conversion of amorphous titanyl phthalocyanine or low crystalline titanyl phthalocyanine having a half-width of diffraction peak of 1 ° or more and an average primary particle size of 0.1 μm or less with an organic solvent in the presence of water In a state where the crystal is converted so that the average particle size of the subsequent primary particles is 0.25 μm or less , it is fractionally filtered from the organic solvent,
The electrophotographic photosensitive member is applied with an electric field strength represented by the following formula (A) in a range of 30 to 50 V / μm.
Electric field strength (V / μm) = surface potential of unexposed portion of photosensitive member at development position (V) / {photosensitive layer thickness (μm) + protective layer thickness (μm)} Expression (A)   The said titanyl phthalocyanine crystal | crystallization is stirred using the organic solvent 30 times or more of amorphous titanyl phthalocyanine and / or low crystalline titanyl phthalocyanine weight in the case of the said crystal transformation. Image forming apparatus.   The image forming apparatus according to claim 1, wherein the charge transport layer contains a polycarbonate having at least a triarylamine structure in a main chain and / or a side chain.   The image forming apparatus according to claim 1, wherein the electrophotographic photosensitive member has a protective layer on the charge transport layer. The image forming apparatus according to claim 4, wherein the protective layer contains an inorganic pigment or a metal oxide having a specific resistance of 10 ¹⁰ Ω · cm or more.   The image forming apparatus according to claim 4, wherein the protective layer contains a polymer charge transport material.   The image forming apparatus according to claim 4, wherein the binder resin of the protective layer has a crosslinked structure.   The image forming apparatus according to claim 7, wherein the binder resin having a crosslinked structure has a charge transporting portion.   The image forming apparatus according to claim 1, wherein the surface of the conductive support is anodized.   The image forming apparatus according to claim 1, wherein the image is formed by a direct transfer method.   The surface potential of the photoconductor after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photoconductor by the writing means is 100 V as the absolute value of the polarity charged by the main charger. The image forming apparatus according to claim 10, wherein:   The surface potential of the photoconductor after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photoconductor by the writing means is opposite to the polarity charged by the main charger. The image forming apparatus according to claim 10.   The surface potential of the photoconductor after transfer of the toner image in the non-writing portion where no electrostatic latent image is formed on the electrophotographic photoconductor by the writing means is the absolute value of the polarity opposite to the polarity charged by the main charger. The image forming apparatus according to claim 12, wherein the image forming apparatus is 100 V or less.   The image forming apparatus according to claim 1, wherein an optical static elimination mechanism is not used.   The image forming apparatus according to claim 1, wherein a plurality of image forming elements including at least a charging unit, an exposure unit, a developing unit, a transfer unit, and an electrophotographic photosensitive member are arranged.   The image forming apparatus according to claim 1, wherein an AC superimposed voltage is applied to a charging unit of the electrophotographic apparatus.   An apparatus main body and a detachable cartridge are mounted, in which a photosensitive member and at least one means selected from the group consisting of a charging means, an exposure means, a developing means, and a cleaning means are integrated. The image forming apparatus according to claim 1.