JP2005165153A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact image forming apparatus which outputs a stable image having high resolution without producing an abnormal image when the apparatus is repeatedly used at a high speed. <P>SOLUTION: The image forming apparatus is equipped with a non-contact type electrifying means in proximity disposition so that the gap between the photoreceptor surface and the surface of an electrifying member is ≤100 μm, and with an exposure means having ≥600 dpi resolution. The apparatus has ≥30 (V/μm) electric field intensity defined by (surface potential V in an unexposed part of the photoreceptor in a developing position/film thickness μm of the photosensitive layer). The charge generating layer of the apparatus contains a titanyl phthalocyanine crystal having the maximum diffraction peak at least at 27.2° as a diffraction peak of the Bragg angle 2θ for CuKα line (at 1.542Å wavelength), and further main peaks at 9.4°, 9.6°, 24.0°, a peak at 7.3° as a diffraction peak in the smallest angle side, and no peak between the peaks at 7.3° and 9.4°, and having ≤0.25 μm average size of primary particles. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In the present invention, an electric field strength of 30 V / μm or more is applied to the photosensitive member by a non-contact charging means arranged so that the gap between the surface of the photosensitive member and the surface of the charging member is 100 μm or less, and the resolution is 600 dpi or more. The present invention relates to an image forming apparatus using an electrophotographic photosensitive member in which a charge generation layer containing a titanyl phthalocyanine crystal having at least a specific crystal type and a specific particle size and a charge transport layer are sequentially stacked.

  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 has a remarkable improvement 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, there has been a demand for downsizing, high speed, and high image quality of the printers and copiers.
For the problem of downsizing, as a compact charging method, a contact-type charging member that is in the form of a roller and is in contact with the photoreceptor is used. Compared to the wire method (Corotron, Scorotron), this method can keep the bias applied to the charging member low, so the capacity of the power pack used for the charging member can be small, which is very effective in reducing power consumption. This is an advantageous method. In addition, since the electric field strength between the charging member and the photoconductor is small during charging, the generation amount of oxidizing gas such as ozone and NOx is reduced, and the influence on the environment and the electrophotographic photoconductor are also reduced. Is reduced. For this reason, it is possible to prevent occurrence of abnormal images and deterioration of the photoreceptor.

  For example, Japanese Patent Application Laid-Open No. 4-336556 (Patent Document 1) discloses a contact charging device in which a charging roller is used as a charging member and the charging roller is brought into contact with a photosensitive member. The surface of the charging roller is a dielectric, and the rotation direction of the charging roller is the same as the rotation direction of the photosensitive member (the moving direction at the closest portion between the charging roller and the photosensitive member is opposite). Since the surface of the charging roller is a dielectric, even if there is a pinhole on the photoconductor, the surface around the pinhole of the opposing charging member does not lose its charge, and this causes an uncharged portion on the photoconductor Does not occur. Further, by rotating the charging roller in the above-mentioned direction, even if each of the photosensitive member and the dielectric member is charged, the photosensitive member comes into contact with the dielectric member having a lower charging potential in order, so that the photosensitive member can be exposed with a low applied voltage. The body can be charged to a desired potential. Thus, the charging roller is used in a state where it is in contact with the photosensitive member.

However, the contact charging device has the following problems:
1. Charging roller trace,
2. Electrified sound,
3. Deterioration of charging performance due to adhesion of toner on the photosensitive member to the charging member,
4). Adhesion of the material constituting the charging member to the photoreceptor,
5). Permanent deformation of the charging member that occurs when the photoreceptor is stopped for a long time.

  Charging roller traces occur because substances constituting the charging member ooze out from the charging member and adhere to and transfer to the surface of the charged body during the stop period of the charged body. Further, the charging sound is generated because the charging member in contact with the member to be charged vibrates when an AC voltage is applied to the charging member. As a method for solving such a problem, a proximity charging device has been devised in which a charging member is brought close to a photoconductor in a non-contact manner.

  In the proximity charging device, the charging device is opposed so that the distance at the closest part to the photosensitive member is 0.005 to 0.3 [mm], and a voltage is applied to the charging member, whereby the photosensitive member A charging device that performs charging. In the proximity charging device, since the charging device and the photoconductor are not in contact with each other, there is a problem with the contact charging device such as “adhesion of the substance constituting the charging member to the photoconductor”, “the photoconductor has been stopped for a long time. “Permanent deformation sometimes occurs” is not a problem. Further, with respect to “decrease in charging performance due to adhesion of toner or the like on the photosensitive member to the charging member”, the proximity charging device is superior because less toner adheres to the charging member.

  Examples of such proximity charging include JP-A-2-148059 (Patent Document 2), JP-A-5-127296 (Patent Document 3), JP-A-5-273737 (Patent Document 4), Japanese Laid-Open Patent Publication No. 5-307279 (Patent Document 5), Japanese Laid-Open Patent Publication No. 6-308807 (Patent Document 6), Japanese Laid-Open Patent Publication No. 8-202126 (Patent Document 7), Japanese Laid-Open Patent Publication No. 9-171282 (Patent Document 8). JP-A-10-288888 (Patent Document 9), JP-A 2002-148904 (Patent Document 10), JP-A 2002-148905 (Patent Document 11), and the like.

  However, although charging is performed in a state where the photosensitive member and the charging member are not in contact with each other, the charging is based on a discharge phenomenon in a minute gap between the photosensitive member and the charging member. If a portion having a low resistance exists locally or if conductive foreign matter or the like is mixed in the charging nip, there may occur a problem that the photoconductor is liable to cause dielectric breakdown. In this regard, it is no exaggeration to say that the problem with the contact charging member remains as it is.

  For the problem of speeding up, a photoconductor having high sensitivity and high speed response has been used. Usually, an LED of 780 nm LD or near 760 nm is used as a light source, and a corresponding photoconductor (charge generation material) has a diffraction peak (± 0. 0) with respect to a characteristic X-ray (wavelength 1.542Å) of CuKα. 2 °), it is known to use a titanyl phthalocyanine crystal having a maximum diffraction peak at least 27.2 ° (see Patent Document 12). 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 its stability as a crystal is low, and it is easy to undergo a crystal transition against mechanical stress such as dispersion, and thermal stress. Compared to the above, the sensitivity is very low, and when a part of the crystal undergoes crystal transition, a sufficient photocarrier generation function cannot be exhibited. In addition, there is also a problem that abnormal images called “dirt images” that are problems inherent to negative / positive development are likely to occur during repeated use of the photoreceptor.

  In addition, since the frequency of outputting images has increased significantly, it has become an important issue to improve the image quality of the apparatus. In order to achieve high image quality, (i) an electrostatic latent image on the photosensitive member formed by the charging unit and exposure unit is formed as a high-density image, and (ii) a subsequent developing unit There are three problems: to form a toner image faithfully to the electrostatic latent image, and (iii) to accurately transfer the toner image on the photoconductor to the transfer paper.

  As means for solving these problems, (i) a method of forming an electrostatic latent image by high-density writing using a small-diameter beam as an exposure means can be cited. Optical carriers generated in the layer spread due to Coulomb repulsion, and dots having a size corresponding to the beam diameter cannot be formed. (Ii) There is a method of forming a toner image faithful to the electrostatic latent image on the photosensitive member by reducing the toner particle size in the developing means. However, if the surface potential of the photosensitive member is low, the developing efficiency decreases. In other words, the dots are scattered and dots scattered with respect to the dots of the electrostatic latent image are formed. (Iii) Increasing the gap electric field strength in the transfer means can increase the transfer efficiency and faithfully transfer the toner image on the photoconductor to the transfer paper. However, if the transfer electric field strength is increased, a discharge occurs. In some cases, transfer dust may occur and fatigue of the electrical characteristics of the photoreceptor may be promoted.

  Among these, the increase in the photoreceptor surface potential (electric field strength) particularly in (i) and (ii) is caused by the diffraction peak (± 0.2 °) of the Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542１．５) of the CuKα. ), When a photoreceptor using a titanyl phthalocyanine crystal having a maximum diffraction peak of at least 27.2 ° is repeatedly used, it causes an abnormal image called “dirt”.

  FIG. 1 shows how dots are formed with respect to the electric field strength (photoconductor surface potential / photosensitive layer film thickness) applied to the photoconductor (writing is performed at 1200 dpi). As shown in FIG. 1, in order to faithfully reproduce small-diameter dots, the electric field strength needs to be set higher. FIG. 2 shows the change in the soiling rank with respect to the electric field intensity. The background dirt rank referred to here indicates the degree of background dirt, and the greater the numerical value, the better the degree of background dirt (the less frequently the background dirt is generated). As can be seen from FIGS. 1 and 2, there is a trade-off relationship between the two in terms of electric field strength. In order to avoid scumming, a system is generally used in which the electric field strength of the photosensitive member is used at 30 V / μm or less and the reproduction of small-diameter dots is somewhat sacrificed. For example, Japanese Patent Application Laid-Open No. 2001-154379 (Patent Document 13) describes that the electric field strength of the photosensitive member is used at 12 to 40 V / μm in order to achieve both reproducibility of background stains and fine lines.

  However, when the resolution of the writing light is increased, the writing dots cannot be developed with good reproducibility unless this lower limit is set higher. In addition, the upper limit value of the electric field strength varies depending on the material (mainly charge generation material) constituting the photoconductor as to the soiling of the photoconductor. A 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 the characteristic X-ray (wavelength 1.542 mm) of the CuKα is very sensitive. However, it has a disadvantage that it is weak against soiling and is actually used only at an electric field strength of about 30 V / μm or less as described above.

The photocarrier generation efficiency (capability) of the titanyl phthalocyanine crystal depends on the electric field strength, and the carrier generation efficiency is extremely lowered as the electric field is lowered. For this reason, in an actual system, the advantage of the specific high sensitivity in the said titanyl phthalocyanine crystal cannot be fully utilized.
Such a problem is a phenomenon that does not cause much problem with low-resolution (400 dpi or less) writing light, but it appears prominently in recent high-resolution writing (600 dpi or more, finer writing is 1200 dpi or more). is there.

JP-A-4-336556 Japanese Patent Laid-Open No. 2-148059 Japanese Patent Application Laid-Open No. 5-127296 JP-A-5-273737 JP-A-5-307279 JP-A-6-308807 JP-A-8-202126 JP-A-9-171282 JP-A-10-288888 JP 2002-148904 A JP 2002-148905 A JP 2001-19871 A JP 2001-154379 A

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that is a compact image forming apparatus and outputs a stable and high-resolution image without occurrence of abnormal images when repeatedly used at high speed.
Specifically, in order to form a high-quality image, an electric field strength of 30 V / μm or more can be obtained by a non-contact charging means that is installed in close proximity so that the gap between the surface of the photoreceptor and the surface of the charging member is 100 μm or less. In an image forming apparatus for forming an electrostatic latent image by charging a photoconductor so that it is formed and writing with a writing light source of 600 dpi or more, a photoconductor containing a titanyl phthalocyanine crystal of a specific crystal type is used. Thus, an 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 addition, an image forming apparatus that can stably output images over a long period of time by solving the problem of dielectric breakdown of the photosensitive member, which is peculiar when using a non-contact charging member arranged in close proximity, and extending the life of the photosensitive member. Is to provide.

  The inventors of the present invention have made various studies to output a high-definition image even in repeated use in a small high-speed digital electrophotographic apparatus. As a result, the gap between the photoreceptor surface and the charging member surface becomes 100 μm or less. In this way, charging is performed so that the electric field strength applied to the photosensitive member is 30 V / μm or more by the non-contact charging means arranged close to each other, writing with a resolution of 600 dpi or more is performed, and the electrophotographic photosensitive member 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 diffraction of Bragg angle 2θ with respect to a characteristic X-ray (wavelength: 1.542 mm) of CuKα in the charge generation layer As a peak (± 0.2 °), it has a maximum diffraction peak at least 27.2 °, and further has major peaks at 9.4 °, 9.6 °, 24.0 °, and the lowest As a side diffraction peak, 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 °. In addition, it has been found that the above problems can be solved by including a titanyl phthalocyanine crystal having an average primary particle size of less than 0.25 μm.

  Such a charge intensity of 30 V / μm or more applied to the photoconductor is larger than a general electric field intensity in electrophotography, and can be more effective in a high-speed digital electrophotographic apparatus that performs high-resolution writing. It is. Although the detailed reason for the effect of the present invention is not clear, the results of our study show that the titanyl used in the present invention has a maximum diffraction peak at 27.2 ° known so far compared to other titanyl phthalocyanine crystals. 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.

  By the way, it is already known that the resolution is improved by reducing the beam of writing light and reducing the formed dots. Also, by increasing the voltage applied to the photoconductor to increase the electric field strength applied to the photoconductor, the linearity of the movement of the photocarrier generated inside the photoconductor is increased, and the diffusion of dots in the electrostatic latent image is increased. It is already known to hold down. If these can be combined, a small-diameter dot (a group of photocarriers) is formed inside the photoconductor, and the electric lines of force between the electrode (support) and the photoconductor surface are strengthened, thereby holding the photocarrier. By suppressing the Coulomb repulsion and moving the optical carrier along the lines of electric force, the shape of the dot written by the small-diameter beam itself can be formed as a photoconductor surface potential profile (dot of electrostatic latent image).

However, an increase in the electric field strength applied to the photosensitive member promotes charge injection from the support to the photosensitive layer and promotion of generation of heat carriers in the photosensitive layer, and as a result promotes the occurrence of soiling.
In addition, the increase in electric field strength not only causes the above-described problem, but also has a problem of causing dielectric breakdown of the photoreceptor. This breakdown is particularly a problem when using a contact charging member. However, a local defect in the photosensitive member or charging roller is caused by a discharge phenomenon in a minute space between the charging member and the photosensitive member. This is a phenomenon in which an electric field concentrates on (particularly a low resistance portion), a lightning phenomenon occurs, and a hole is formed in the photoreceptor itself.

  These phenomena are generally remarkable when a charge generation material having high photocarrier generation efficiency is used, and the diffraction peak (±±) of the Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542Å) of CuKα described above. 0.2 °), when a titanyl phthalocyanine crystal having a maximum diffraction peak at 27.2 ° is used, it is actually used in an area where the electric field strength is less than about 30 V / μm at most. .

  As described above, an effective means for controlling the process has been developed, but an effective photoconductor that takes advantage of the feature has not been developed. Therefore, a high electric field strength cannot be applied to improve the image quality. The current problem is that the electrostatic latent image that is faithful to the writing dots on the photoconductor and the toner development that is faithful to the electrostatic latent image remain, but the present invention solves this problem. ing.

  That is, the said subject is solved by following this invention (1)-(13).

(1) Non-contact charging means arranged so that at least the gap between the photoreceptor surface and the charging member surface is 100 μm or less, exposure means having a resolution of 600 dpi or more, developing means, transfer means, and electrophotography In an image forming apparatus comprising a photoconductor, the absolute value of the electric field strength applied to the photoconductor from the charging means defined as follows is 30 (V / μm) or more, and the electrophotographic photoconductor 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 diffraction of Bragg angle 2θ with respect to a characteristic X-ray (wavelength: 1.542 mm) of CuKα in the charge generation layer As a 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 angle. Side diffraction peak An average size of the primary particles having a peak at 7.3 °, no peak between the 7.3 ° peak and the 9.4 ° peak, and no further peak at 26.3 ° An image forming apparatus comprising a titanyl phthalocyanine crystal having a thickness of 0.25 μm or less.
Electric field strength (V / μm) = surface potential of unexposed photoconductor (V) / photosensitive layer thickness (μm)

(2) Dispersion liquid in which the average particle size of the titanyl phthalocyanine crystal particles is 0.3 μm or less and the standard deviation is 0.2 μm or less, followed by filtration with a filter having an effective pore size of 3 μm or less. The image forming apparatus according to item (1), wherein a charge generation layer is applied using

(3) 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 the characteristic X-ray (wavelength 1.542１．５) of CuKα. Amorphous titanyl phthalocyanine or low crystalline titanyl phthalocyanine having an average primary particle size of 0.1 μm or less having a half-width of the diffraction peak of 1 ° or more is crystallized with an organic solvent in the presence of water. The titanyl phthalocyanine after crystal conversion is fractionated and filtered from an organic solvent before the average particle size of primary particles after crystal conversion grows to 0.3 μm or more. (1) The image forming apparatus described in the item.

(4) The charge transporting layer according to any one of (1) to (3), wherein the charge transport layer contains a polycarbonate having at least a triarylamine structure in the main chain and / or side chain. Image forming apparatus.

(5) The image forming apparatus according to any one of (1) to (4), wherein a protective layer is provided on the charge transport layer.

(6) The image forming apparatus as described in (5) above, wherein the protective layer contains an inorganic pigment or metal oxide having a specific resistance of 10 ¹⁰ Ω · cm or more.

(7) The image forming apparatus according to any one of (5) or (6), wherein the protective layer contains a polymer charge transport material.

(8) The image forming apparatus according to any one of (5) to (7), wherein the binder resin of the protective layer has a crosslinked structure.

(9) The image forming apparatus as described in (8) above, wherein the structure of the binder resin having a crosslinked structure has a charge transporting site.

(10) The image forming apparatus as described in any one of (1) to (9) above, wherein a surface of a conductive support of the electrophotographic photosensitive member is anodized. .

(11) Any one of (1) to (10) above, wherein a plurality of image forming elements comprising at least charging means, exposure means, developing means, transfer means, and electrophotographic photosensitive member are arranged. The image forming apparatus described in 1.

(12) The image forming apparatus according to any one of (1) to (11), wherein an AC superimposed voltage is applied to a charging unit of the electrophotographic apparatus.

(13) The apparatus main body in which the photosensitive member and at least one means selected from charging means, exposure means, developing means, and cleaning means are integrated and a detachable cartridge are mounted. The image forming apparatus according to any one of items 1) to (12).

According to the present invention, there is provided an image forming apparatus that is a compact image forming apparatus and outputs a stable and high-resolution image without occurrence of abnormal images when repeatedly used at high speed.
Specifically, in order to form a high-quality image, an electric field strength of 30 V / μm or more is obtained by a non-contact charging member that is arranged so that the gap between the surface of the photoreceptor and the charging member surface is 100 μm or less. In an image forming apparatus for forming an electrostatic latent image by charging a photoconductor so that it is formed and writing with a writing light source of 600 dpi or more, it contains a titanyl phthalocyanine crystal of a specific crystal type and a specific particle size. By using the photoreceptor, an image forming apparatus that maintains the high sensitivity inherent to titanyl phthalocyanine, is highly durable, and can output a high-speed image is provided.

First, the image forming apparatus of the present invention will be described in detail with reference to the drawings.
FIG. 3 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. 3, 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 characteristic X-ray of CuKα (wavelength 1.542Å). As a diffraction peak (± 0.2 °) with a Bragg angle of 2θ, the maximum diffraction peak is at least 27.2 °, and the main peaks are at 9.4 °, 9.6 °, and 24.0 °. In addition, the diffraction peak at the lowest angle side has a peak at 7.3 °, and there is no peak between the peak at 7.3 ° and the peak at 9.4 °. It contains titanyl phthalocyanine crystals having no peak at 3 ° and an average primary particle size of 0.25 μm or less. The photosensitive member (1) has a drum shape, but may be a sheet or an endless belt.

  As the charging roller (3), a non-contact type charging member is preferably used that is disposed in close proximity so that the gap between the surface of the photoreceptor and the surface of the charging member is 100 μm or less. In particular, a roller-shaped charging member is effectively used because of its operating mechanism and simple apparatus. By this charging member, an electric field strength of 30 V / μm or more is applied to the photoreceptor. 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.

  The transfer / conveying belt (10) may be a transfer charger or a transfer roller, but it is desirable to use a contact type such as a transfer belt or transfer roller that generates less ozone. 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.

  Of the charging methods, at least a charging member (denoted as a charging roller (3) in FIG. 1) used for main charging to the photosensitive member is preferably a non-contact charging method arranged in close proximity. The non-contact charging type charging member has advantages such as high charging efficiency, a small amount of ozone generation, and downsizing of the apparatus.

  The charging member arranged close here is a type in which the charging member is arranged in a non-contact state so as to have a gap of 100 μm or less between the photosensitive member surface and the charging member surface. If this gap is too large, the charging tends to become unstable, and if it is too small, the surface of the charging member may be contaminated when toner remaining on the photoreceptor exists. . Therefore, the gap is suitably 5 to 100 μm, preferably 10 to 50 μm. From the distance of the air gap, it is distinguished from known charging wire type chargers such as corotrons and scorotrons, contact charging members such as contact type charging rollers, charging brushes and charging blades.

  The adjacently arranged charging member used in the present invention may have any shape as long as it has a mechanism capable of appropriately controlling the gap with the surface of the photoreceptor. For example, the rotation shaft of the photosensitive member and the rotation shaft of the charging member may be mechanically fixed so as to have an appropriate gap. Among them, using a charging member in the shape of a charging roller, a gap forming member is disposed at both ends of the non-image forming portion of the charging member, and only this portion is brought into contact with the surface of the photoreceptor, and the image forming region is disposed in a non-contact manner. Alternatively, the gap forming member at both ends of the non-photosensitive portion of the photoconductor is disposed, and only this portion is brought into contact with the surface of the charging member, and the image forming region is disposed in a non-contact manner, so that the gap can be stably stabilized. It is a method that can be maintained. In particular, the methods described in JP-A Nos. 2002-148904 and 2002-148905 can be used satisfactorily. An example of the proximity charging mechanism in which the gap forming member is disposed on the charging member side is shown in FIG.

  Furthermore, as an application method, there is an advantage that uneven charging is less likely to occur by using AC superposition, and it can be used satisfactorily. In particular, in the tandem type full-color image forming apparatus described later, in addition to the problem of uneven density of a halftone image due to uneven charging that occurs in the case of a monochrome image forming apparatus, there is a serious problem of deterioration in color balance (color reproducibility). Connected. The above problem is greatly improved by superimposing the AC component on the DC component, but if the AC component conditions (frequency, peak-to-peak voltage) are too large, the hazard to the photoconductor increases. In some cases, deterioration of the photoconductor may be accelerated. For this reason, superposition of alternating current components should be kept to the minimum necessary.

  The frequency of the AC component varies depending on the linear velocity of the photosensitive member, but 3 kHz or less, preferably 2 kHz or less is appropriate. Regarding the peak-to-peak voltage, when the relationship between the voltage applied to the charging member and the charging potential to the photoconductor is plotted, there is a region where the photoconductor is not charged despite the voltage being applied, and the charging rises from a certain point. Potential is observed. About twice this rising potential is the optimum potential (usually about 1200 to 1500 V) as the peak-to-peak voltage. However, when the charging ability of the photosensitive member is low or the linear velocity is very high, the peak-to-peak voltage twice the rising potential as described above may be insufficient. On the other hand, when the chargeability is good, the potential stability may be sufficiently exhibited even when it is twice or less. Therefore, the peak-to-peak voltage is preferably 3 times or less, more preferably 2 times or less of the rising potential. If the peak-to-peak voltage is rewritten as an absolute value, it is desirably used at 3 kV or less, preferably 2 kV or less, more preferably 1.5 kV or less.

  The image exposure unit (5) uses a light source capable of ensuring high brightness and capable of writing at a resolution of 600 dpi or more, such as a light emitting diode (LED), a semiconductor laser (LD), and electroluminescence (EL). . 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 1200 dpi is the upper limit. When there are a plurality of writing light sources, each of them only has to bear the writing area, and the upper limit is substantially “1200 dpi × number of writing 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, there is generally a reversal development method in which toner development is performed on the writing portion in response to a low image area ratio. This is advantageous in view of the life of the light source. 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.

Further, the toner image formed on the photosensitive member is transferred to the transfer paper and becomes 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 photosensitive member as shown in FIG. 3 to the transfer paper, and the other is that the toner image is once transferred from the photosensitive member to the intermediate transfer member, and this is transferred to the transfer paper. It is the method of transferring to. Either case can be used in the present invention.
As such a transfer member, a known member can be used as long as the structure of the present invention can be satisfied.

  Use light sources such as fluorescent lamps, tungsten lamps, halogen lamps, mercury lamps, sodium lamps, light-emitting diodes (LEDs), semiconductor lasers (LDs), and electroluminescence (ELs) as light sources such as static elimination lamps (2). Can do. 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.
This neutralization mechanism can be omitted when the AC component is used in a superposed manner in the previous charging method, or when the residual potential of the photoreceptor is small. 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. In the figure, 7 is a pre-transfer charger, 8 is a registration roller, 11 is a separation charger, 12 is a separation claw, and 13 is a pre-cleaning charger.

  In addition, the toner developed on the photoreceptor (1) by the developing unit (6) is transferred to the transfer paper (9), but when toner remaining on the photoreceptor (1) is generated, a fur brush ( 14) and the blade (15) to remove from the photoreceptor. 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.

FIG. 5 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.
In FIG. 5, reference numerals (16Y), (16M), (16C), and (16K) denote drum-shaped photoconductors, and the photoconductors include at least a charge generation layer and a charge transport layer on a conductive support. The charge generation layer has a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray (wavelength 1.542 mm) of CuKα. Furthermore, it has major peaks at 9.4 °, 9.6 °, and 24.0 °, and has a peak at 7.3 ° as the lowest diffraction peak, and the above-mentioned 7.3 ° And a titanyl phthalocyanine crystal having no peak at 26.3 ° and an average primary particle size of 0.25 μm or less. It becomes.

  The photosensitive members (16Y), (16M), (16C), and (16K) rotate in the direction of the arrow in the figure, and charging members (17Y), (17M), (17C), (17K), developing members (19Y), (19M), (19C), (19K), and cleaning members (20Y), (20M), (20C), (20K) are arranged. The charging members (17Y), (17M), (17C), and (17K) are charging members that constitute a charging device for uniformly charging the surface of the photoreceptor.

From an exposure member (not shown) from the back side of the photoreceptor between the charging members (17Y), (17M), (17C), (17K) and the developing members (19Y), (19M), (19C), (19K). Laser beams (18Y), (18M), (18C), and (18K) are irradiated so that an electrostatic latent image is formed on the photoconductors (16Y), (16M), (16C), and (16K). It has become.
Then, the four image forming elements (25Y), (25M), (25C), and (25K) centering on such photoconductors (16Y), (16M), (16C), and (16K) serve as transfer materials. They are juxtaposed along the transfer conveyance belt (22) which is a conveyance means.

  The transfer / conveying belt (22) includes developing members (19Y), (19M), (19C), (19K) and cleaning members (20Y) of the image forming units (25Y), (25M), (25C), (25K). , (20M), (20C), and (20K) are in contact with the photosensitive member (16Y), (16M), (16C), and (16K), and contact the back side of the photosensitive member side of the transfer conveyance belt (22). Transfer brushes (21Y), (21M), (21C), and (21K) for applying a transfer bias are arranged on the surface (back surface). Each of the image forming elements (25Y), (25M), (25C), and (25K) is different in the color of the toner inside the developing device, and the others are the same in configuration.

  In the full-color image forming apparatus having the configuration shown in FIG. 5, the image forming operation is performed as follows. First, in each of the image forming elements (25Y), (25M), (25C), and (25K), the photoconductors (16Y), (16M), (16C), and (16K) are in the direction indicated by the arrow (the direction around the photoconductor). ) To rotate the charging member (17Y), (17M), (17C), (17K) so that the electric field strength of the photosensitive member is 30 V / μm or more (60 V / μm or less, preferably 50 V / μm or less). Charged.

  Next, writing is performed at a resolution of 600 dpi or more by laser light (18Y), (18M), (18C), and (18K) at an exposure unit (not shown) arranged inside the photoconductor, and each color to be created is written. An electrostatic latent image corresponding to the image is formed. Also in this case, 1200 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. Development members (19Y), (19M), (19C), and (19K) are development members that perform development with toners of Y (yellow), M (magenta), C (cyan), and K (black), respectively. The toner images of the respective colors formed on the two photoconductors (16Y), (16M), (16C), and (16K) are superimposed on the transfer paper.

  The transfer paper (26) is fed out from the tray by a paper feeding roller (not shown), temporarily stopped by a pair of registration rollers (23), and transferred and conveyed (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 each color is in contact with each photoconductor (16Y), (16M), (16C), (16K) (transfer section). The toner image is transferred. The toner image on the photoconductor includes transfer bias applied to the transfer brushes (21Y), (21M), (21C), and (21K) and the photoconductors (16Y), (16M), (16C), and (16K). The image is transferred onto the transfer paper (26) by an electric field formed from the potential difference.

  Then, the recording paper (26) on which the four color toner images are passed through the four transfer sections is conveyed to the fixing device (24), where the toner is fixed, and is discharged to a paper discharge section (not shown).

  Further, residual toner remaining on each of the photoconductors (16Y), (16M), (16C), and (16K) without being transferred by the transfer unit is removed from the cleaning devices (20Y), (20M), (20C), ( 20K).

  In the example of FIG. 5, 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 paper conveyance direction. However, it is not limited to this order, and the color order is arbitrarily set. Further, when creating a black-only document, it is particularly effective to use the present invention to provide a mechanism that stops image forming elements other than black ((25Y), (25M), (25C)). .

  The image forming means as described above may be fixedly incorporated in a copying apparatus, facsimile, or printer, but each electrophotographic element may be incorporated in the apparatus in the form of a process cartridge. The process cartridge is a single device (part) that contains a photosensitive member and includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a charge eliminating unit, and the like.

  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. The process cartridge is a single device (part) that contains a photosensitive member and includes a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, a charge eliminating 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. The charge generation layer has a Bragg angle 2θ with respect to a characteristic X-ray of CuKα (wavelength 1.542Å). Diffraction peak (± 0.2 °) having a maximum diffraction peak at least 27.2 °, and further having major peaks at 9.4 °, 9.6 °, 24.0 °, and most It has a peak at 7.3 ° as a diffraction peak on the low angle side, and there is no peak between the peak at 7.3 ° and the peak at 9.4 °, and a peak at 26.3 °. And a titanyl phthalocyanine crystal having an average primary particle size of 0.25 μm or less.

  As described above, a light source capable of writing with a resolution of 600 dpi or more is used for the image exposure unit (103), and a contact type charging member is used for the charging roller (102) as described above. An electric field strength of 30 V / μm or more (60 V / μm or less, preferably 50 V / μm or less) is applied to the photoreceptor. In FIG. 6, reference numeral 104 denotes a developing unit, 105 denotes a transfer body, 106 denotes a transfer unit, and 107 denotes a cleaning unit.

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 a characteristic X-ray of CuKα ( As a diffraction peak (± 0.2 °) with a Bragg angle 2θ for a wavelength of 1.542 mm, it has a maximum diffraction peak at least 27.2 °, and further at 9.4 °, 9.6 °, and 24.0 °. It has a main peak and has a peak at 7.3 ° as the lowest diffraction peak, and has a peak between the 7.3 ° peak and the 9.4 ° peak. Furthermore, it contains a titanyl phthalocyanine crystal having no peak at 26.3 ° and an average primary particle size of 0.25 μm or less.
This crystal type is described in Patent Document 1, but by using this titanyl phthalocyanine crystal, a stable electrophotographic photosensitive member that does not cause deterioration in chargeability even after repeated use without losing high sensitivity. Can be obtained.

  Japanese Patent Laid-Open No. 2001-19871 discloses a charge generating material used in the present invention, a photoreceptor using the same, an electrophotographic apparatus, and the like. However, in a situation where the resolution is 600 dpi or higher or 1200 dpi or higher, it is necessary to increase the intensity of the electric field 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.

  Japanese Patent Laid-Open No. 2001-19871 does not have a description of particle size and a technique for controlling the particle size, and the particle size has not been 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.

  Further, as a method for synthesizing titanyl phthalocyanine crystals, a method using no titanium halide as a raw material can be favorably used as described in JP-A-6-293769. The biggest merit of this method is that the synthesized titanyl phthalocyanine crystal is free of halogenation. When a titanyl phthalocyanine crystal contains a halogenated titanyl phthalocyanine crystal as an impurity, it often has adverse effects such as a decrease in photosensitivity and a decrease in chargeability in the electrostatic characteristics of a photoconductor using the crystal (Japan Hardcopy '89 paper). Collection 'p. 103 1989). Also in the present invention, halogenated free titanyl phthalocyanine crystals as described in JP-A-2001-19871 are mainly used, and these materials are effectively used.

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 “Phthacyanine Compounds” (1963), “The Phthalocyanines” (1983), JP-A-6-293769, etc. by Moser et al.

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 second 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. In this method, phthalocyanines are dissolved in sulfuric acid, diluted with water and reprecipitated, and an acid paste method or an acid slurry method can be used.

  As a specific method, the above synthetic crude product is dissolved in 10-50 times the amount of concentrated sulfuric acid, and if necessary, insoluble matter is removed by filtration or the like, and this is sufficiently cooled to 10-50 times the amount of sulfuric acid. Slowly throw it into 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 clean ion-exchanged water, filtration is performed to obtain a water paste having a solid content concentration of about 5 to 15 wt%. What was produced in this way was the amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) used in the present invention. 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 is preferable to have 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.

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 (wavelength 1.542Å) of CuKα of at least 27.2 °. And has a major peak at 9.4 °, 9.6 °, 24.0 °, and a peak at 7.3 ° as the lowest diffraction peak, And, it is a step of converting into 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 amorphous form of the titanyl phthalocyanine (low crystalline titanyl phthalocyanine) is mixed and stirred with an organic solvent in the presence of water without drying, thereby obtaining the crystal form.
In this case, any organic solvent can be used as long as the desired crystal form can be obtained, but 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. It is desirable that the amount of the organic solvent used for crystal conversion is 10 times or more, preferably 30 times or more the weight of amorphous titanyl phthalocyanine. This is because crystal conversion is caused quickly and sufficiently, and an effect of sufficiently removing impurities contained in amorphous titanyl phthalocyanine is exhibited.

  The amorphous titanyl phthalocyanine used here is prepared by the acid paste method, but it is desirable to use one obtained by sufficiently washing sulfuric acid as described above. When crystal conversion is performed under conditions where sulfuric acid remains, sulfate ions remain in the crystal particles, and the completed crystals cannot be completely removed even by an operation such as washing with water. 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, but the sulfate ion concentration in titanyl phthalocyanine is high and the light attenuation characteristic (photosensitivity) is poor. However, the method for producing titanyl phthalocyanine of the present invention is not good.

  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 method for synthesizing titanyl phthalocyanine particle size smaller than the synthesis step.

In order to make the particle size of the titanyl phthalocyanine crystal finer, the present inventors have observed that the above-mentioned amorphous titanyl phthalocyanine (low crystalline titanyl phthalocyanine) has a primary particle size of 0.1 μm or less (its Although most of them are about 0.01 to 0.05 μm) (see FIG. 7), it has been found that during crystal conversion, crystals are 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. Is what you get. For this reason, even though a raw material having sufficiently small primary particles is used as a raw material, a crystal having a large primary particle (approximately 0.3 to 0.5 μm) is obtained as a crystal after crystal conversion. Yes (see FIG. 8).
The scale bars in the figure are all 0.2 μm.

  In dispersing the titanyl phthalocyanine crystal produced as shown in FIG. 8, 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. Accordingly, the dispersion is performed by applying strong energy for pulverizing 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 to obtain a crystal having a small size, a method for solving this problem is possible 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. 6 is insignificantly small after crystal conversion, approximately 0.25 μm or less. ) Is 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.

FIG. 9 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.
One is to select an appropriate crystal conversion solvent as described above to increase the crystal conversion efficiency. The other is to use strong agitation to bring the solvent into contact with the titanyl phthalocyanine aqueous paste (raw material prepared as described above) in order to complete the crystal conversion in a short time. Specifically, it is possible to achieve crystal conversion in a short time by using a propeller with a very strong stirring force or using a strong stirring (dispersing) means such as a homogenizer (homomixer). is there. 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.

  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. As the above-mentioned means, it is possible 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), dispersion in dispersion In consideration of stability, side effects may occur even if it is too small. That is, when the primary particles are very fine, there arises a problem that 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, and 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. 9 shows a TEM image of a titanyl phthalocyanine crystal when crystal conversion is performed in a short time. Unlike the case of FIG. 8, the particle size is small and almost uniform, and the coarse particles observed in FIG. 7 are not recognized at all.
As shown in FIG. 9, 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, a dispersion liquid with a fine particle size distribution can be easily produced without producing the result that a part of the particles are easily transferred to a crystal form other than the desired crystal form as described above. It is possible.

  The average particle size referred to here is a volume average particle size, and is determined by an ultracentrifugal automatic particle size distribution analyzer: CAPA-700 (manufactured by Horiba, Ltd.). At this time, the particle size (Median system) corresponding to 50% of the cumulative distribution was calculated. 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 observation of the dispersion and examination of micro defects, the above phenomenon was understood as follows. Usually, in the method of measuring the average particle size, when an extremely large particle is present in several% or more, the presence can be detected, but it is about 1% or less of the whole. When the amount is too small, the measurement is below the detection limit. As a result, the presence of coarse particles is not detected only by measuring the average particle size, making it difficult to interpret the above minute defects.

10 and 11 show photographs observing the state of two types of dispersions in which only the dispersion time is changed while fixing the dispersion conditions. A photograph of the dispersion liquid having a short dispersion time under the same conditions is shown in FIG. 10, and it is observed that coarse particles remain as compared with FIG. 11 having a long dispersion time. Black grains in FIG. 10 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. 12 corresponds to the dispersion shown in FIG. 10, 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 purpose, in order to complete the crystal conversion in a short time while selecting the appropriate crystal conversion solvent as described above and improving the crystal conversion efficiency, the solvent and titanyl phthalocyanine water paste (the raw material prepared as described above) are used. It can be seen that a technique using strong agitation is effective to sufficiently bring a contact of

  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 Japanese Patent Laid-Open No. 2001-19871, it is important in the present invention to use the above-described technique (crystal conversion method for obtaining fine titanyl phthalocyanine crystals) as necessary. Means.

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 heating and drying, but a blower-type dryer is preferable when the drying is performed in the atmosphere. Furthermore, drying under 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 the crystal form is easily transferred when a dispersion is prepared. However, by synthesizing primary particles into infinitely small particles as in the present invention, a dispersion with a small average particle diameter can be prepared without giving an excessive share during the preparation of the dispersion, and the crystal type is also extremely high. It can be produced stably (without changing the synthesized crystal form).

Next, a method for preparing the dispersion will be described.
For the preparation of the dispersion, a general method is used. By dispersing the titanyl phthalocyanine crystal in a suitable solvent together with a binder resin as necessary using a ball mill, an attritor, a sand mill, a bead mill, an ultrasonic wave, or the like. It is obtained. 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 and the dispersibility of the pigment.

  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 the characteristic X-ray (wavelength 1.542 波長) of CuKα is It is known that crystal transition to other crystal forms easily occurs due to stress such as energy and mechanical 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 produced within a range where crystal transition does not occur, and then filtered through an appropriate filter. This method is a very effective means in that it can remove a minute 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, thereby completing the 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 is made 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, as a photoreceptor used in an electrophotographic apparatus that requires a resolution of about 600 dpi. The presence of coarse particles of at least 3 μm 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, coarse particles finer than the effective pore size 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, the finer the particle, the more effective the removal of coarse particles. However, if the particle size is too fine, the necessary pigment particles themselves are also filtered, and therefore there is an appropriate size. In addition, if it is too fine, it takes time for filtration, clogging of the filter, and excessive load is applied when liquid is sent using a pump or the like. As a matter of course, a material having resistance to the solvent used in the dispersion to be filtered is used as the material of the filter used here.

  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 (reliable), but there are cases where the pigment particles themselves are filtered. In such a case, using the titanyl phthalocyanine primary particles described above in combination with the technique for refining and synthesizing the particles produces a very large effect.

  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 the coarse particles remaining after 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 the 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 manufactured with high resistance to soiling.

Next, the electrophotographic photosensitive member used in the present invention will be described in detail with reference to the drawings.
FIG. 13 is a cross-sectional view showing a structural example of the electrophotographic photosensitive member used in the present invention. On the conductive support (31), a titanyl phthalocyanine crystal (charge generating material) having a specific crystal type with the specific particle size. ) As a main component and a charge transport layer (37) whose main component is a charge transport material are stacked.
FIG. 14 is a cross-sectional view showing another structural example of the electrophotographic photosensitive member used in the present invention, and a titanyl phthalocyanine crystal having the specific particle size and the specific particle size on the conductive support (31). A charge generation layer (35) mainly composed of (charge generation material) and a charge transport layer (37) mainly composed of a charge transport material are laminated, and a protective layer (39) is further formed on the charge transport layer. It has a configuration that is provided.

As the conductive support (31), a material having a volume resistance of 10 ¹⁰ Ω · cm or less, for example, a metal such as aluminum, nickel, chromium, nichrome, copper, gold, silver, platinum, tin oxide, oxidation A method of extruding and drawing metal oxides such as indium by film deposition or sputtering, or coating a film or cylindrical plastic or paper, or a plate of aluminum, aluminum alloy, nickel, stainless steel, etc. After forming the tube, it is possible to use a tube that has been surface-treated by cutting, superfinishing, polishing, or the like. Moreover, the endless nickel belt and the 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 both pure aluminum and aluminum alloys. Specifically, JIS 1000, 3000, and 6000 series aluminum or aluminum alloy is most suitable. Anodized films are obtained by anodizing various metals and various alloys in an electrolyte solution. Among them, a film called anodized aluminum or an aluminum alloy that has been anodized in an electrolyte solution is used in the present invention. Is the most suitable. In particular, it is excellent in preventing 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 insulation, the surface is very unstable. For this reason, there is a change 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 this remains excessively on the surface of the support (anodized film), it not only adversely affects the quality of the coating film formed on this surface, but also generally low resistance components remain, resulting in the occurrence of soiling. It can also be a cause. Cleaning may be performed with pure water only once, but usually multi-stage cleaning is performed. At this time, it is preferable that the final cleaning liquid is as clean (deionized) as possible. Moreover, it is desirable to perform physical rubbing cleaning with a contact member in one of the multi-step cleaning processes. 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 to the above, a conductive powder dispersed in a suitable binder resin and coated on the support can be used as the conductive support (31) of the present invention. 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 powder such as conductive tin oxide and ITO. It is done. 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 used favorably as the conductive support (31) of the present invention.

Next, the photosensitive layer will be described. As described above, as the photosensitive layer, a 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 a maximum diffraction peak at 27.2 ° as a diffraction peak (± 0.2 °) with a Bragg angle 2θ with respect to the characteristic X-ray of CuKα (wavelength 1.542Å) as a charge generation material. And the main peak at 9.4 °, 9.6 ° 24.0 °, and the peak at 7.3 ° as the lowest diffraction peak, and 7.3 There is no peak between the peak at ° 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. This is a layer mainly composed of titanyl phthalocyanine crystals of 25 μm or less (preferably 0.2 μm or less).

In the charge generation layer (35), the pigment is dispersed in a suitable solvent together with a binder resin as necessary using a ball mill, an attritor, a sand mill, an ultrasonic wave, etc., and this is applied onto a conductive support, It is formed by drying.
The binder resin used for the charge generation layer (35) as required may be polyamide, polyurethane, epoxy resin, polyketone, polycarbonate, silicon resin, acrylic resin, polyvinyl butyral, polyvinyl formal, polyvinyl ketone, polystyrene, polysulfone, poly -N-vinyl carbazole, 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. 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-α-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 them, the use of a non-halogen solvent is desirable 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.

In the formula, R ₁ , R ₂ and R ₃ are each independently an optionally substituted alkyl group or a halogen atom, R ₄ is a hydrogen atom or an optionally substituted alkyl group, R ₅ and R ₆ are aryl groups which may have a substituent, o, p and q are each independently an integer of 0 to 4, k and j represent a composition, 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 represent an optionally substituted 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, and 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.

In the formula, R ₇ and R ₈ each represent an aryl group which may have a substituent, and Ar ₁ , Ar ₂ and Ar ₃ represent the same or different arylene groups. X, k, j and n are the same as those in the 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.

_{Wherein, R 9,} R ₁₀ is an aryl group which may have a _{substituent, Ar 4, Ar 5, Ar} 6 independently represent an arylene group. X, k, j and n are the same as those in the 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.

_{Wherein, R 11,} R ₁₂ is an optionally substituted aryl _{group, Ar 7, Ar 8, Ar} 9 are identical or different arylene group, p is an integer of 1-5. X, k, j and n are the same as those in the 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.

In the formula, R ₁₃ and R ₁₄ may be an aryl group which may have a substituent, Ar ₁₀ , Ar ₁₁ and Ar ₁₂ may be the same or different arylene groups, and X ₁ and X ₂ may have a substituent. It represents a good ethylene group or a vinylene group which may have a substituent. X, k, j and n are the same as those in the 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.

In the formula, R ₁₅ , R ₁₆ , R ₁₇ and R ₁₈ are aryl groups which may have a substituent, Ar ₁₃ , Ar ₁₄ , Ar ₁₅ and Ar ₁₆ are the same or different arylene groups, Y ₁ and Y _2. Y ₃ is a single bond, an alkylene group which may have a substituent, a cycloalkylene group which may have a substituent, an alkylene ether group which may have a substituent, an oxygen atom, a sulfur atom Represents a vinylene group, which may be the same or different. X, k, j, and n are the same as in the case of equation (V). In the formula (VI), two copolymer species are described in the form of an alternating copolymer, but a random copolymer may be used.

In the formula, R ₁₉ and R ₂₀ represent a hydrogen atom and an aryl group which may have a substituent, and R ₁₉ and R ₂₀ 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 those in the 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.

In the formula, R ₂₁ represents an aryl group which may have a substituent, Ar ₂₀ , Ar ₂₁ , Ar ₂₂ , Ar ₂₃ represent the same or different arylene groups. X, k, j and n are the same as those in the 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.

In the formula, R ₂₂ , R ₂₃ , R ₂₄ and R ₂₅ each represents an aryl group which may have a substituent, and Ar ₂₄ , Ar ₂₅ , Ar ₂₆ , Ar ₂₇ and Ar ₂₈ represent the same or different arylene groups. 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.

In the formula, R ₂₆ and R ₂₇ represent an aryl group which may have a substituent, Ar ₂₉ , Ar ₃₀ and Ar ₃₁ represent the same or different arylene groups. 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, A polymer having a two-dimensional or three-dimensional crosslinked structure is finally 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 a polymer compound, so it has excellent film-forming properties and has a charge transport site compared to a charge transport layer composed of a low molecular weight dispersed polymer. It can be configured with high density and has excellent charge transport capability. 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 copolymers of known monomers, block polymers, graft polymers, star polymers, and, for example, JP-A-3-109460 and JP-A-2000- It is also possible to use a cross-linked polymer having an electron donating group as disclosed in JP-A-206723 and JP-A No. 2001-34001.

  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 photoreceptor 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 these resins, it is desirable that the resin be a resin having 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, fine powder pigments of metal oxides exemplified by titanium oxide, silica, alumina, zirconium oxide, tin oxide, indium oxide and the like may be added to the intermediate layer in order to prevent moire and reduce residual potential.

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 miniaturization of devices as well as high-speed output by printers. 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) include 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 , Resins such as polyvinyl 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, silicone resins, and inorganic fillers such as titanium oxide, tin oxide, potassium titanate, and silica for the purpose of improving wear resistance (inorganic pigments) ), Or an organic filler (organic pigment) dispersed therein 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 It is 10% by weight or more and 50% by weight or less, preferably about 30% by weight or less.
Moreover, the volume average particle diameter of the filler to be 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.

In addition, unless otherwise indicated, the average particle diameter of the filler in this invention is a volume average particle diameter, and is calculated | required with the ultracentrifugal automatic particle size distribution measuring apparatus: CAPA-700 (made by Horiba Seisakusho). At this time, the particle size (Median system) corresponding to 50% of the cumulative distribution was calculated. In addition, it is important that the standard deviation of each particle measured simultaneously is 1 μm or less. If the standard deviation is larger than this, the particle size distribution may be 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 remains in the filler, particularly the metal oxide, during production. When the remaining amount is large, the occurrence of image blur is unavoidable, and depending on the remaining amount, the dispersibility of the filler may be affected.

  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, 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 as far as possible from the isoelectric point of the system.

  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. It was confirmed that there was. A filler exhibiting basicity having a high pH at the isoelectric point has a higher zeta potential when the system is 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.
Furthermore, as the filler that is less likely to cause image blurring, 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 a filler 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 a powder such as a filler varies depending on the filling rate, it is necessary to measure under certain conditions. In the present invention, the specific resistance value of the filler is determined using an apparatus having the same configuration as the measuring apparatus shown in Japanese Patent Laid-Open Nos. 5-94049 (FIG. 1) and 5-113688 (FIG. 1). Measured and used this value. In the measuring device, the electrode area 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 REISTANCE METER (Yokogawa Hewlett Packard), and the area below it was measured with a digital multimeter (Fluke). The specific resistance value thus obtained is defined as the specific resistance value in the present invention.

The dielectric constant of the filler was measured as follows. Using a cell similar to the measurement of the specific resistance as described above, after applying a load, the capacitance was measured, and the dielectric constant was determined from this. 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, causes defects in the coating, and decreases the wear resistance. It can develop into a big problem.

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, a titanate coupling agent, an aluminum coupling agent, a zircoaluminate coupling agent, a higher fatty acid, etc., or a mixing treatment of these with a silane coupling agent, Al ₂ O ₃ , TiO ₂ , ZrO ₂ , Silicone, aluminum stearate, or the like, or a mixture thereof is more preferable from the viewpoint of filler dispersibility and image blur. 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%. If the surface treatment amount is less than this, the filler dispersion effect cannot be obtained, and if it 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.

Further, the protective layer (39) may contain a charge transport material for reducing residual potential and improving responsiveness. As the charge transport material, the materials described in the description of the charge transport layer can be used. 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 refers to the ratio of the weight of the low molecular charge transporting material to the total weight of all the materials constituting the protective layer, and the concentration gradient is a gradient that lowers the concentration on the surface side in the above weight ratio. It shows that. 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, as the binder resin for the protective layer, the polymer charge transport material described in the section of the charge transport layer can also be used. 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 a 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 thermal energy to form a three-dimensional network structure. is there. 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 if it is too thick, cracks may occur. 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 the 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, the presence of a seal in a Japanese document or the like. Something like indicia is usually located towards the edge 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 photoconductor having a low surface durability (physical / chemical / mechanical) is used in such a state, this difference becomes prominent and easily causes an image problem. 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 according to Japanese Patent Application Laid-Open No. 2001-19871. 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 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. Dissolve the crude titanyl phthalocyanine in 20 times the amount of concentrated sulfuric acid, add dropwise to 100 times the amount of ice water while stirring, filter the precipitated crystals, and then repeat washing with water until the washing solution becomes neutral. (Water paste) was obtained. 2 g of the obtained wet cake (water paste) was put into 20 g of tetrahydrofuran, stirred for 4 hours, filtered and dried to obtain titanyl phthalocyanine powder (referred to as pigment 1).
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 the characteristic X-ray of Cu—Kα (wavelength: 1.542 mm) was 27.2 ± 0.2 ° with the maximum peak. It has a peak at the lowest angle of 7.3 ± 0.2 ° and no peak between the peak at 7.3 ° and the peak at 9.4 °, and no peak at 26.3 ° A titanyl phthalocyanine powder 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. The X-ray diffraction spectrum of the dry powder of 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 Example 1 of JP-A-1-299874 (Patent No. 2512081). 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, the resultant was washed successively with dilute sulfuric acid and an aqueous ammonium hydroxide solution and dried to obtain a pigment (referred to as pigment 2).

(Comparative Synthesis Example 3)
A pigment was produced according to the method described in Production Example 1 of JP-A-3-269064 (Patent No. 2854682). 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).

(Comparative Synthesis Example 4)
A pigment was prepared according to the method described in the production example of JP-A-2-8256 (Japanese Patent Publication No. 7-91486). 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 130 ° C. and filtered while hot, then washed with 1-chloronaphthalene until the powder turned blue, then washed several times with methanol, and further with hot water at 80 ° C. After washing twice, it was dried to obtain a pigment (referred to as pigment 4).

(Comparative Synthesis Example 5)
A pigment was produced according to the method described in Synthesis Example 1 of JP-A No. 64-17066 (Japanese Patent Publication No. 7-97221). That is, 5 parts of α-type TiOPc 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 acid content disappeared, and then dried to obtain a pigment (referred to as pigment 5).

(Comparative Synthesis Example 6)
A pigment was prepared according to the method described in Example 1 of JP-A-11-5919 (Japanese Patent No. 3003664). 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, and then the solvent was removed by steam distillation, followed by 2% aqueous chloride solution, followed by 2 Purified with an aqueous sodium hydroxide solution, washed with methanol and N, N-dimethylformamide and 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, the sulfuric acid solution is slowly poured into 400 parts of ice water stirred at a high speed, and the precipitated crystals are filtered. The crystals are washed with distilled water until no acid remains, and a wet cake is obtained. The cake was stirred in 100 parts of THF for about 5 hours, filtered, washed with THF and dried to obtain a pigment (referred to as pigment 6).

(Comparative Synthesis Example 7)
A pigment was produced according to the method described in Synthesis Example 2 of JP-A-3-255456 (Patent No. 3005052). 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 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).

(Comparative Synthesis Example 8)
A pigment was prepared according to the method for producing a titanyl phthalocyanine crystal of JP-A-8-110649. 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 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 separated 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.

(Synthesis Example 1)
In accordance with the method of Comparative Synthesis Example 1, a titanyl phthalocyanine pigment water paste was synthesized, and crystal conversion was performed as follows to obtain phthalocyanine crystals having smaller primary particles than Comparative Synthesis Example 1.
To 60 parts of the aqueous paste before crystal conversion obtained in Comparative Synthesis Example 1, 1500 parts of tetrahydrofuran was added and 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 58 parts of titanyl phthalocyanine crystals (referred to as pigment 9).

  A portion of titanyl phthalocyanine (water paste) before crystal transformation 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 having been subjected to conductive treatment. The particle size of phthalocyanine 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.

  In addition, the titanyl phthalocyanine crystal after crystal conversion just before filtration in Comparative Synthesis Example 1 and Synthesis Example 1 was diluted with tetrahydrofuran to 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 calculation was performed with the length of the largest diagonal line of the crystal as the major axis.

  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 spectrum of the pigment 9 produced in Synthesis Example 1 was identical to the spectrum of the pigment 1 produced 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.

(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. And dispersion was performed for 30 minutes to prepare a dispersion (referred to as dispersion 1).

(Dispersion preparation examples 2 to 9)
Instead of pigment 1 used in dispersion preparation example 1, using pigments 2 to 9 prepared in comparative synthesis examples 2 to 8 and synthesis example 1, respectively, the dispersion was prepared under the same conditions as dispersion preparation example 1. It produced (it is set as the dispersion liquids 2-9, respectively corresponding to a pigment number).

(Dispersion Preparation Example 10)
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. During filtration, filtration was performed using a pump in a pressurized state (referred to as dispersion 10).
(Dispersion Preparation Example 11)
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 11).

(Dispersion Preparation Example 12)
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 Advantech's Cotton Wind Cartridge Filter and TCW-5-CS (effective pore size 5 μm). A liquid was prepared (referred to as dispersion liquid 12).

(Dispersion Preparation Example 13)
Dispersion was performed by changing the dispersion conditions in Dispersion Preparation Example 1 as follows (referred to as Dispersion 13).
Rotor rotation speed: 1000 r. p. m. For 20 minutes.

(Dispersion Preparation Example 14)
The dispersion prepared in Dispersion Preparation Example 13 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 has not been conducted.

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.

(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 22 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: 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 solution Dispersion 1 prepared earlier 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

(Photosensitive member production examples 2 to 13)
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 2-13, respectively. In addition, the film thickness of the charge generation layer was adjusted so that the transmittance at 780 nm was 20% when all the coating liquids were used, as in Photoreceptor Preparation Example 1.

(Examples 1 to 3 and Comparative Examples 1 to 23)
The electrophotographic photoconductors of the photoconductor production examples 1 to 13 produced as described above are mounted on the image forming apparatus shown in FIG. 3, and a charging roller (non-contact type charging roller as shown in FIG. 4) is used as a charging member. The gap between the members is 50 μm) and is charged under the following charging conditions. The image exposure light source is written using a semiconductor laser of 780 nm (image writing by a polygon mirror, resolution 600 dpi) to form an electrostatic latent image. After the formation and development, a transfer belt was used as a transfer member, and continuous 50,000 sheets were printed using a chart with a writing rate of 6% (the test environment is 22 ° C.-55% RH).
Charging condition 1:
DC bias: -750V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz
Charging condition 2:
DC bias: -600V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz

The following two 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 one-dot image having a diameter of 60 μm was formed, and the dot formation state was observed with a 150 × microscope, and rank evaluation was performed.

In any 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.
In the calculation of the electric field strength in Table 4, the film thickness of the charge generation layer was about 0.1 μm, but the calculation was performed assuming that the film thickness of the photosensitive layer is equal to the film thickness of the charge transport layer.

(Photoreceptor Preparation Example 14)
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 methylene chloride

(Photoreceptor Preparation Example 15)
Similar to Photoreceptor Preparation Example 9, except that the thickness of the charge transport layer in Photoreceptor Preparation Example 9 was 16 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

(Photoreceptor Production Example 16)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 15 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 15 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 17)
A photoconductor was prepared in the same manner as in Photoconductor Preparation Example 15 except that the alumina fine particles in the protective layer coating solution in Photoconductor Preparation Example 15 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 18)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 15 except that the protective layer coating solution in the photosensitive member preparation example 15 was changed to the following composition.
Protective layer coating solution 17 parts of polymer charge transport material having the following structural formula "As a result of measurement by GPC, n was determined to be about 250"
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

(Photoreceptor Preparation Example 19)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 15 except that the protective layer coating solution in the photosensitive member preparation example 15 was changed to the following composition.
Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts 35 parts of charge transport compound with the following structure
Antioxidant (Sanol LS2626: Sankyo Chemical Co., Ltd.) 1 part Curing agent (dibutyltin acetate) 1 part 2-propanol 200 parts

(Photoreceptor Preparation Example 20)
An electrophotographic photosensitive member was prepared in the same manner as in the photosensitive member preparation example 15 except that the protective layer coating solution in the photosensitive member preparation example 15 was changed to the following composition.
Protective layer coating solution Methyltrimethoxysilane 100 parts 3% acetic acid 20 parts 35 parts of charge transport compound with the following structure
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. Curing agent (dibutyl Tin acetate) 1 part 2-propanol 200 parts

(Photoconductor Preparation Example 21)
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 1 without providing an undercoat layer. Was made.
Anodized film treatment After mirror polishing 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 anodizing film treatment for 30 minutes at an electrolysis voltage of 15V. I did it. 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 4 to 11 and Comparative Examples 22 to 29)
As described above, the electrophotographic photoreceptors produced in the photoreceptor preparation examples 13 to 20 are mounted on the image forming apparatus shown in FIG. 3, and a charging roller (non-contact type charging roller as shown in FIG. The gap between the members is charged under the following charging conditions, and an image exposure light source is written by a semiconductor laser of 780 nm (image writing by a polygon mirror, resolution 600 dpi) to form an electrostatic latent image. After development, a transfer belt was used as a transfer member, and continuous 50,000 sheets were printed using a chart with a writing rate of 6% (test environment is 22 ° C.-55% RH).
Charging condition 1:
DC bias: -750V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz
Charging condition 2:
DC bias: -600V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz
The following two 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 one-dot image having a diameter of 60 μm was formed, and the dot formation state was observed with a 150 × microscope, and rank evaluation was performed.
In any 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. 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 5 together with the case of Example 1.

In the calculation of the electric field strength in Table 5, the film thickness of the charge generation layer is about 0.1 μm, but the film thickness of the photosensitive layer is assumed to be equal to the film thickness of (charge transport layer + protective layer). Calculated.

(Example 12)
Evaluation was performed in the same manner as in Example 1 except that the gap between the photosensitive member of the non-contact charging member used in Example 1 and the charging member was changed to 80 μm. The results are shown in Table 6.

(Comparative Example 32)
Evaluation was performed in the same manner as in Example 1 except that the gap between the photosensitive member and the charging member of the non-contact charging member used in Example 1 was changed to 120 μm. The results are shown in Table 6.

The larger the gap between the photoconductor and the charging member, the lower the charging uniformity and the worse the dot formation state.
As seen in Comparative Example 32, when the gap exceeds 100 μm, it is determined that it cannot withstand actual use.

(Photoconductor Preparation Example 22)
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 23)
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 24)
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 25)
A photoconductor having the same composition as that of Photoconductor Preparation Example 8 was prepared by changing the aluminum cylinder of Photoconductor Preparation Example 8 to one having a diameter of 30 mm.

(Photoconductor Preparation Example 26)
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 27)
The aluminum cylinder of the photoreceptor preparation example 10 was changed to one having a diameter of 30 mm, and a photoreceptor having the same composition as that of the photoreceptor preparation example 10 was prepared.

(Examples 13 to 14 and Comparative Examples 33 to 42)
The photoconductors of Photoconductor Preparation Examples 22 to 27 manufactured as described above were used for a single image forming apparatus as shown in FIG. 6 together with a charging member (non-contact charging roller as shown in FIG. 4 and gap of 50 μm). It was mounted on a process cartridge and further mounted on a full-color image forming apparatus shown in FIG. In each of the four image forming elements, a non-contact proximity charging roller is used as a charging member, charging is performed under the following charging conditions, and an image exposure light source is a semiconductor laser of 780 nm (image writing by a polygon mirror, resolution 600 dpi). After writing to form an electrostatic latent image and developing, a transfer belt was used as a transfer member, and a continuous writing of 50,000 sheets was performed using a chart with a writing rate of 6% (the test environment was 22 ° C. -55% RH).
Charging condition 1:
DC bias: -750V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz
Charging condition 2:
DC bias: -600V
AC bias: 2.0 kV (peak to peak), frequency: 1.5 kHz
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 one-dot image having a diameter of 60 μm was formed, and the dot formation state was observed with a 150 × microscope, and rank evaluation was performed.
(Iii) Evaluation of color reproducibility The same full-color image was output after the initial state of the photoreceptor and 50,000 sheets running, and an attempt was made to evaluate the color reproducibility.
In any 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. In addition, the amount of abrasion of the photosensitive layer after printing 100,000 sheets (when the protective layer is provided, the amount of abrasion of the protective layer) was measured. The results are shown in Table 7.

  Finally, 7.3 ° which is the lowest angle peak of the Bragg angle 2θ, which is a characteristic 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. 16, the lowest angle in the XD spectrum of the titanyl phthalocyanine crystal produced in Comparative Synthesis Example 9 is 7.5 °, which is 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)
3 was prepared in the same manner as the pigment described in JP-A-61-239248 (having a maximum diffraction peak at 7.5 °) as the pigment obtained in Comparative Synthesis Example 1 (minimum angle 7.3 °). Weight% was added and 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 was prepared in the same manner as the pigment described in JP-A-61-239248 (having a maximum diffraction peak at 7.5 °) as the pigment obtained in Comparative Synthesis Example 9 (minimum angle 7.5 °). Weight% was added and 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 2 is shown in FIG.

In the spectrum of FIG. 17, 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. 18, 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 figure for demonstrating the electric field strength dependence in dot formation. It is a figure for demonstrating the electric field strength dependence of a dirt rank. 1 is a schematic view for explaining an electrophotographic process and an image forming apparatus of the present invention. It is the schematic for showing an example of a non-contact charging member. 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 Charging roller 5 Image exposure part 6 Development unit 7 Charger before transfer 8 Registration roller 9 Transfer paper 10 Transfer charger 11 Separation charger 12 Separation nail 13 Charger before cleaning 14 Fur brush 15 Cleaning brushes 16Y, 16M, 16C , 16K photoconductors 17Y, 17M, 17C, 17K charging members 18Y, 18M, 18C, 18K laser beams 19Y, 19M, 19C, 19K developing members 20Y, 20M, 20C, 20K cleaning members 21Y, 21M, 21C, 21K transfer brush 22 Transfer conveyor belt 23 Registration roller 24 Fixing device 25Y, 25M, 25C, 25K Image forming element 26 Transfer paper 31 Conductive support 35 Charge generation layer 37 Charge transport layer 39 Protective layer 101 Photoconductor 102 Charging means 10 3 Exposure 104 Developing means 105 Transfer body 106 Transfer means 107 Cleaning means 111 Photoconductor 112 Charging roller 113 Gap forming member 114 Metal shaft 115 Image forming area 116 Non-image forming area

Claims (13)

A non-contact charging unit, an exposure unit having a resolution of 600 dpi or more, a developing unit, a transfer unit, and an electrophotographic photosensitive member are arranged so that at least the gap between the surface of the photosensitive member and the surface of the charging member is 100 μm or less. In the image forming apparatus provided, the electric field strength applied to the photosensitive member from the charging means defined as follows is 30 (V / μm) or more, and the electrophotographic photosensitive member is placed on the conductive support. An electrophotographic photosensitive member in which at least a charge generation layer and a charge transport layer are sequentially laminated. A diffraction peak (± 0.2) with a Bragg angle 2θ with respect to a characteristic X-ray of CuKα (wavelength 1.542Å) in the charge generation layer. )) At least 27.2 ° with a maximum diffraction peak, 9.4 °, 9.6 °, 24.0 ° with major peaks, and 7 as the lowest angle diffraction peak. .3 ° And no peak between the peak at 7.3 ° and the peak at 9.4 °, no peak at 26.3 °, and the average primary particle size is 0.25 μm or less An image forming apparatus comprising a titanyl phthalocyanine crystal.
Electric field strength (V / μm) = surface potential of unexposed portion of photoreceptor at development position (V) / photosensitive layer thickness (μm)   Dispersion was performed until the average particle size of the titanyl phthalocyanine crystal particles was 0.3 μm or less and the standard deviation thereof was 0.2 μm or less, and then filtered using a filter having an effective pore size of 3 μm or less. The image forming apparatus according to claim 1, wherein a charge generation layer is applied.   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 the characteristic X-ray (wavelength 1.542Å) of CuKα, Crystal transformation of amorphous titanyl phthalocyanine or low crystalline titanyl phthalocyanine with an average primary particle size of 0.1 μm or less with a half-width of the diffraction peak of 1 ° or more is carried out with an organic solvent in the presence of water. 2. The image formation according to claim 1, wherein titanyl phthalocyanine after crystal conversion is fractionated and filtered from an organic solvent before the subsequent primary particles grow to an average particle size of 0.3 μm or more. apparatus.   The image forming apparatus according to claim 1, wherein the charge transporting 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, further comprising a protective layer on the charge transport layer. The image forming apparatus according to claim 5, 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 5, wherein the protective layer contains a polymer charge transport material.   The image forming apparatus according to claim 5, wherein the binder resin of the protective layer has a crosslinked structure.   The image forming apparatus according to claim 8, wherein a charge transporting portion is included in a structure of the binder resin having the crosslinked structure.   The image forming apparatus according to claim 1, wherein the surface of the electroconductive support of the electrophotographic photosensitive member is anodized.   11. 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.   13. The apparatus main body and a detachable cartridge are mounted, in which the photosensitive member and at least one means selected from charging means, exposure means, developing means, and cleaning means are integrated. The image forming apparatus according to any one of the above.