JP5790342B2 - Electrophotographic photoreceptor and image forming method - Google Patents

Description

  The present invention relates to an electrophotographic photosensitive member that can be used in the field of light printing and the like and capable of forming an extremely high-quality halftone image, and an image forming method using the electrophotographic photosensitive member.

In recent years, with respect to an image forming apparatus based on electrophotography, it has become possible to obtain a relatively high-quality image as its performance is improved. The image forming apparatus according to has been widely used.
As a result, an image forming apparatus based on electrophotography is required to have a higher level of image quality. Also, it is rarely used in conventional electrophotographic image forming apparatuses, such as printing on coated paper, printing of high-coverage images, printing of extremely high-definition images and images with subtle tones (color tone), and the same An electrophotographic image forming apparatus is used for mass continuous printing of images. Along with these problems, there have been problems that have been hardly or not pointed out in the past.

One of the problems is the occurrence of oblique streak-like density unevenness in images, which has frequently occurred in recent years in the combination of outputting a halftone image with improved uniformity of intermediate colors to coated paper, etc., using a high-quality image forming apparatus. There is.
This oblique stripe-shaped density unevenness is so-called interference streak, and is the surface of a cylindrical substrate of an electrophotographic photosensitive member (hereinafter also simply referred to as “photosensitive member”) used in an electrophotographic image forming apparatus. In order to bring the dimensional accuracy of the outer diameter, etc. to a desired level, and to make it fresh except for the oxide film on the surface, cutting irregularities are periodically formed on the outer peripheral surface in the direction of the central axis. It is presumed that it is caused by interference between the period of the cutting irregularities formed on the surface of the cylindrical substrate of the photoconductor and the period (pitch) of the screen pattern (exposure pattern) used for the screen processing. .

As a technique for suppressing the occurrence of interference stripes, there is a technique for devising the shape of the cutting irregularities on the surface of a cylindrical substrate constituting a photoreceptor (for example, Patent Documents 1 to 3). That is, the cutting shape on the surface of the cylindrical substrate is often formed by cutting with a bite, but cutting irregularities with a relatively less harmful cycle such as a cycle that is not an integral multiple of the cycle of the exposure pattern are obtained by constant-speed cutting. It has been practiced to eliminate the uneven shape of the cut by performing additional processing which is costly and harmful, such as anodizing and blasting. Specifically, the difference ΔL between the maximum value and the minimum value of the periodic width of the cutting irregularities in the central axis direction of the cylindrical base body disclosed in Patent Documents 1 to 3 is about 4 μm at the maximum.
In an image forming apparatus using a cylindrical substrate photoconductor having such cut irregularities, a general halftone image output on plain paper in an office or the like is satisfactory as having a sufficient image quality level. It had been.

  However, the density unevenness visibility is marked for the output of a halftone image in which the uniformity of the intermediate color is improved to the coated paper by the high-quality image forming apparatus used in the light printing field as described above. Therefore, the above-described technique is not sufficient in suppressing the occurrence of interference streaks.

  On the other hand, attempts have been made to improve the wear resistance of photoconductors. For example, a protective layer is provided on the uppermost layer of the photoreceptor, and specifically, a protective layer is formed by polymerizing a compound having a curable functional group by a heat or light energy by a curing reaction. Technology is being considered. In the technique of forming a protective layer by a curing reaction, a crosslinking reaction using light energy is particularly preferably used from the viewpoint of controllability of the crosslinking reaction (for example, see Patent Document 4).

  However, in such a photoreceptor, a photosensitive layer having charge transport characteristics is formed on a cylindrical substrate, but it is difficult to impart charge transport characteristics to the protective layer formed by the curing reaction as described above. Therefore, there is a problem that the sensitivity is lowered, which is not preferable for practical use.

  Further, conventionally, there is a problem that minor image unevenness rarely occurs in a halftone image in the first image formed after leaving the copier for a long time.

JP 2003-91085 A Japanese Patent No. 3894023 JP 2001-289630 A JP 2001-125297 A

  The present invention has been made based on the above circumstances, and an object of the present invention is to obtain a high-quality halftone image having excellent wear resistance and suppressing occurrence of interference streaks and image unevenness. It is an object of the present invention to provide an electrophotographic photosensitive member that can be used and an image forming method using the electrophotographic photosensitive member.

The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor in which at least a charge generation layer and at least two charge transport layers are laminated in this order on a cylindrical substrate,
The cylindrical substrate has a cutting shape that satisfies the following formula (1), in which cutting irregularities are periodically formed in the central axis direction on the outer peripheral surface thereof,
The uppermost charge transport layer contains inorganic particles having a number average primary particle size (Dp) of 3 to 100 nm.
Formula (1): ΔL ≧ 10 μm
[In Expression (1), ΔL is the difference between the maximum value and the minimum value of the periodic width of the cutting irregularities in the central axis direction in the image region on the outer peripheral surface of the cylindrical base. ]

  In the electrophotographic photoreceptor of the present invention, the inorganic particles are preferably silica particles.

  The electrophotographic photosensitive member of the present invention is characterized in that an image is formed using the above-described electrophotographic photosensitive member.

According to the electrophotographic photosensitive member of the present invention, since the cylindrical substrate has a reduced periodicity of cutting irregularities, the period of the exposure pattern and the cutting formed on the surface of the cylindrical substrate of the electrophotographic photosensitive member. Interference with the period of unevenness is reduced, and therefore, the occurrence of interference streaks in the obtained high-quality halftone image is suppressed.
In addition, according to the electrophotographic photoreceptor of the present invention, the cylindrical substrate has a charge transport layer containing inorganic particles having a particle size in a specific range as well as having a reduced periodicity of cutting irregularities, Since a scattering effect is obtained in the photoreceptor, the occurrence of image unevenness in the obtained image is suppressed.
Furthermore, according to the electrophotographic photosensitive member of the present invention, excellent wear resistance can be obtained by containing a specific range of inorganic particles in the uppermost charge transport layer.

2 is a partial cross-sectional view showing an example of the configuration of the electrophotographic photosensitive member of the present invention. FIG. It is an image figure of the interference stripe which appears in the formed halftone image. It is the elements on larger scale in the cross section of a photoreceptor. It is a figure explaining the measuring method of (DELTA) L concerning this invention. 1 is a cross-sectional view for explaining an example of a configuration of an image forming apparatus on which an electrophotographic photosensitive member of the present invention is mounted.

  Hereinafter, the present invention will be specifically described.

[Photoconductor]
The electrophotographic photoreceptor of the present invention comprises at least a charge generation layer and at least two charge transport layers laminated in this order, and a cylindrical substrate is periodically cut in the central axis direction on the outer peripheral surface thereof. A number-average primary particle size (having a cutting shape satisfying the condition of the above formula (1) (hereinafter also referred to as “specific cutting shape”) in which irregularities are formed, It is characterized by comprising a specific photoconductor containing Dp) 3 to 100 nm inorganic particles (hereinafter also referred to as “specific inorganic particles”).

As a specific example, for example, as shown in FIG. 1, an intermediate layer 1b, a charge generation layer 1c, and a charge transport layer not containing specific inorganic particles are formed on a cylindrical substrate 1a having a specific cutting shape. (Hereinafter also referred to as “lower charge transport layer”) 1d, a charge transport layer containing specific inorganic particles (hereinafter also referred to as “uppermost charge transport layer”) 1e is laminated in this order, The charge generation layer 1c, the lower charge transport layer 1d, and the uppermost charge transport layer 1e constitute a photosensitive layer 1α that is indispensable for the construction of the electrophotographic photosensitive member. Such a photoreceptor 1 is a so-called organic photoreceptor in which the charge generation layer 1c and the charge transport layers 1d and 1e are organic photosensitive layers made of a known organic charge generation material and organic charge transport material, respectively. preferable.
In the following description, it is assumed that the specific photoreceptor is an organic photoreceptor.

(Cylindrical substrate)
The cylindrical substrate constituting the specific photoconductor is conductive and has a cylindrical shape in which a specific cutting shape is formed on the outer peripheral surface thereof.
In the condition of the above formula (1) indicating a specific cutting shape, ΔL indicates the width of the fluctuation of the cutting unevenness, specifically, the cutting unevenness in the image area of the outer peripheral surface of the cylindrical substrate. It is the difference between the maximum value and the minimum value of the period width (indicated by W in FIG. 3).

The reason why the above formula (1) is derived is as follows.
FIG. 2 shows interference streaks appearing in the formed image, which is a problem in the present invention. Thus, the interference streaks appear on the screen r as oblique stripe-shaped density unevenness extending in the circumferential direction of the photosensitive member, that is, in the direction along the conveying direction s of the image support P, and a uniform image. In particular, it is clearly visible in a high-quality halftone image of a large screen such as a light print on a smooth surface image.

  According to the inventor's investigation, the cause of the occurrence of the interference streak which is regarded as a problem in the present invention is as follows.

FIG. 3 is a partially enlarged view of the cross section of the photoconductor.
The interference streaks are not caused by the cutting irregularities of the cylindrical substrate itself, but are caused by the sensitivity of the photoreceptor 1 having a period reflecting the cutting irregularities.
That is, as shown in FIG. 3, the shape of the cutting irregularities on the surface of the cylindrical substrate 1a is reflected in the film thickness of the charge generation layer (CGL) 1c through the intermediate layer 1b, and specifically, the cylindrical substrate 1a. A portion β having a large film thickness, a portion α having a small film thickness, or the like is generated corresponding to the depth of the cutting unevenness of the film. As a result, the photosensitive member 1 has a film thickness of the charge generation layer 1c in accordance with a regular cycle. It will fluctuate.
Since the sensitivity of the photoreceptor 1 varies according to the film thickness of the charge generation layer 1c, the sensitivity pattern of the photoreceptor 1 and the screen pattern related to the exposure when exposure is performed by a laser beam, an LED light source, or the like. In the image obtained by developing, transferring, and fixing the electrostatic latent image, the image has a high image quality. In some cases, it is visualized as periodic density unevenness, that is, interference stripes.

  In the present invention, it has been found that changing the periodic width of the cutting irregularities generated by cutting on the surface of the cylindrical base body to some extent is extremely effective in suppressing the occurrence of interference streaks, and further, the lower limit of the width of the fluctuation The value is found.

  When ΔL is less than 10 μm, the periodicity of the cutting irregularities is not sufficiently reduced in the cylindrical substrate, and the period of the exposure pattern and the period of the cutting irregularities formed on the surface of the cylindrical substrate of the photosensitive member. When a high-quality halftone image is formed due to interference between the two, an interference streak may occur in the image.

  The upper limit value of ΔL is currently limited by the performance of the processing machine for forming the cutting shape, but there seems to be no limit due to the effect of the invention. However, depending on the characteristics of the processing machine, if the speed program of the processing machine is set to increase ΔL, the speed fluctuation will suddenly occur and a step will be generated on the processed surface. May occur. Therefore, ΔL is preferably 300 μm ≧ ΔL ≧ 10 μm, and more preferably 150 μm ≧ ΔL ≧ 10 μm.

(Method for producing cylindrical substrate)
The cylindrical base body can be manufactured by forming a specific cutting shape on the surface of a raw pipe made of, for example, a cylindrical pipe by a cutting tool.
The raw tube is not particularly limited, and examples thereof include a tube formed from a metal such as aluminum, copper, chromium, nickel, zinc, and stainless steel.

Specifically, when shaping the surface of the tube by cutting with a cutting tool, the specific cutting shape abuts while rotating the tube around the cylindrical axis and moving the cutting tool at a non-constant speed. Can be formed.
Hereinafter, the cutting tool for forming the specific cutting shape according to the present invention will be further described.

  The cutting of the cylindrical substrate is carried out by bringing the cylindrical substrate surface to a desired shape, making the dimensional accuracy such as the outer diameter of the cylindrical substrate a desired level, and excluding the oxide film on the surface of the cylindrical substrate. This is done for the purpose. The cylindrical substrate finished by the conventional cutting tool has a shape in which cutting irregularities are formed regularly in the central axis direction, and the film thickness distribution of the photosensitive layer formed on the cylindrical substrate is as follows: It has a periodicity reflecting the shape, and the reflection does not disappear easily even if the layers are stacked, such as through an intermediate layer.

  In the case where an intermediate layer (UCL) is provided on a cylindrical substrate and a charge generation layer is formed on the intermediate layer as in the example shown in the figure, the shape that forms the foundation of the charge generation layer is the intermediate layer. Although it becomes a surface shape, the surface shape of the intermediate layer is mainly determined by the shape of the surface of the cylindrical substrate and the composition of the intermediate layer.

  In order to set ΔL, which is an index of irregularity of the cutting irregularities, to 10 μm or more, when the surface of the blank tube is shaped by cutting tooling, the moving speed of the cutting bit with respect to the surface of the blank tube is changed during the machining. Add instructions to change frequently.

For example, when using a CNC lathe that indicates the moving speed X _n (mm / rotation) of the cutting tool and its indicated position Y _n (mm), (X ₁ , Y ₁ ), (X ₂ , Y ₂ ) ,... (X _n , Y _n ), n blocks are programmed. For example, in the m-th block, when (Y _{m + 1} −Y _m ) / X _m does not reach a specific number, the cutting tool moving speed is reduced to enable switching at the end of the block, and In the m + 1 block, the speed is increased to the designated speed _{Xm + 1} . In this case, for example, even if X _m and X _{m + 1} are instructions of the same speed, if (Y _{m + 1} −Y _m ) / X _m is not a specific number, deceleration and acceleration occur. Using this, it is possible to change the moving speed of the cutting tool. Moreover, even if the same program is used, ΔL may change if the spindle speed (the number of revolutions of the tube) is changed. This is considered to be because the program speed switching judgment performed based on the result of observing the movement of the cutting tool is intermittently performed by the digital circuit, and the interval is not sufficiently short with respect to the machining speed. It is thought that the specific number is not necessarily a natural number for the same reason.

  In other words, the specific number depends on the design and setting of the lathe and the spindle speed.

  When an analog lathe is used instead of a CNC lathe, the moving speed of the cutting tool is changed by outputting a motor voltage that controls the moving speed of the cutting tool, for example, through a circuit that switches a plurality of resistors. Is possible. Further, for example, the moving speed can be changed by moving the cutting tool using a power source capable of outputting a voltage having a specified waveform.

In order to further reduce the periodicity of the cutting irregularities, it is desirable that the instruction interval for changing the moving speed of the cutting tool is not constant. This is because, for example, when using the above CNC lathe, Y _n −Y _n−1 is not constant, and when using the above analog lathe, a plurality of switching timers are used, or the output waveform has a different waveform. This can be achieved by using a power source that can be complicated by superposition or the like.

  In addition, setting ΔL to 10 μm or more can also be realized by appropriately varying the number of rotations of the raw tube (the number of rotations of the main shaft) during cutting with a cutting tool. This can be achieved, for example, by means similar to those of the analog lathe described above.

  ΔL tends to be larger than the indicated value difference in the moving speed of the cutting tool because the above-mentioned deceleration is introduced in the case of the CNC lathe, and the overshoot when the voltage is changed in the case of the analog lathe. It is thought because of.

  Further, ΔL tends to increase as the number of rotations of the tube (the number of rotations of the main shaft) increases, and this is considered to be due to the influence of wobbling or wah of the rotating body.

  As described above, ΔL can be set to 10 or more by bringing the cutting bite into contact with the surface of the blank tube while irregularly moving the surface of the blank tube by biting cutting.

(Measurement method of ΔL)
The difference ΔL between the maximum value and the minimum value of the periodic width of the cutting irregularities in the image region on the outer peripheral surface of the cylindrical substrate in the present invention is, for example, a cross-sectional curve of the image region on the outer peripheral surface as illustrated in FIG. Is read from. Specifically, from the cross-sectional curve of FIG. 4A, the repetitive shape and period are focused, and the period width is read by increasing to an appropriate magnification as shown in the cross-sectional curve of FIG. 4B. Is. In addition, the cross-sectional curve of FIG.4 (b) makes lateral magnification 4 times the cross-sectional curve of Fig.4 (a).

  The number of periods of the cutting unevenness measured for reading the maximum value and the minimum value of the periodic width of the cutting unevenness may be 5 or more.

  The measurement location of the cross-sectional curve may be an arbitrary location in the image area on the outer peripheral surface of the cylindrical substrate, and may be one location or a plurality of locations. When the measurement location is one location, it is only necessary to read the maximum value and the minimum value from the periodic width of the cutting irregularities of 5 cycles or more that are continuous or intermittent from the measurement location, and when the measurement location is a plurality of locations, It is only necessary to select a periodic width of the cutting irregularities of 5 cycles or more from the plurality of measurement points and read the maximum value and the minimum value from these.

  As the measurement location of the cross-sectional curve, for example, the vicinity of the center of the cylindrical base in the central axis direction is preferably selected.

The measurement length of the cross-sectional curve may be any length as long as the period width of the cutting irregularities can be read. However, when the number of measurement points is one, the period width of the cutting irregularities is a length that can be read by at least five cycles. It is preferable that the length is readable for 10 cycles or more.
The measurement length of the cross-sectional curve is specifically 4 mm, for example.

  The cross-sectional curve of the image region on the outer peripheral surface of the cylindrical substrate is obtained under the following measurement conditions using a stylus type surface roughness measuring instrument “Surfcom 1400D” (manufactured by Tokyo Seimitsu Co., Ltd.).

-Measurement conditions-
・ Measurement mode: Roughness measurement (JIS'01 standard)
・ Measurement length: 4.0mm
・ Cutoff: 0.8mm (Gaussian)
・ Measurement speed: 0.3mm / sec

(Middle layer)
The intermediate layer provides a barrier function and an adhesive function between the cylindrical substrate and the organic photosensitive layer. From the viewpoint of preventing various failures, it is preferable to provide such an intermediate layer.

For the intermediate layer, a coating solution is prepared by dissolving a binder resin such as casein, polyvinyl alcohol, nitrocellulose, ethylene-acrylic acid copolymer, polyamide, polyurethane, alkyd-melamine, epoxy and gelatin in a known solvent. Can be formed by coating the outer peripheral surface of the cylindrical substrate by dip coating or the like to form a coating film and drying the coating film.
As the binder resin for forming the intermediate layer, it is preferable to use an alcohol-soluble polyamide resin.

Further, the intermediate layer may contain various fine particles such as metal oxide particles for the purpose of adjusting resistance and imparting roughness.
According to a specific photoconductor in which various fine particles are contained in the intermediate layer, the surface shape of the intermediate layer reflects a random convex shape derived from the shape of the fine particles in addition to the cutting irregularities on the surface of the cylindrical substrate. Therefore, the periodicity of the sensitivity derived from the shape of the surface of the cylindrical substrate can be reduced, and the generation of interference streaks can be extremely effectively suppressed.

  Examples of the metal oxide particles include fine particles such as alumina, zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony-doped tin oxide, and zirconium oxide. It is done.

  These metal oxide particles may be used in combination of two or more. When two or more types are mixed, it may take the form of a solid solution or fusion. The average particle size of such metal oxide particles is preferably 0.3 μm or less, more preferably 0.1 μm or less. These metal oxide particles may be surface-treated with an inorganic compound or an organic compound in a single or multiple manner.

  Examples of the solvent that dissolves the binder resin that forms the intermediate layer include known ones. For example, when alcohol-soluble polyamide is used as the binder resin, methanol, ethanol, n-propyl alcohol, isopropyl alcohol, and n-butanol are used. C1-C4 alcohols such as t-butanol and sec-butanol are preferred because of excellent solubility and coating performance of polyamide. Further, in order to improve coating properties, storage stability, fine particle dispersibility, etc., it is preferable to use a co-solvent together with a solvent. Examples of co-solvents that can obtain a preferable effect include benzyl alcohol, toluene, methylene chloride, cyclohexanone, tetrahydrofuran. Etc.

  The concentration of the binder resin in the coating solution for forming the intermediate layer is appropriately selected according to the film thickness and production rate of the intermediate layer.

  When the intermediate layer contains fine particles, the mixing ratio of the fine particles with respect to the binder resin is preferably 20 to 400 parts by volume, more preferably 40 to 200 parts by volume with respect to 100 parts by volume of the binder resin.

  As a means for dispersing fine particles, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto. A preferred example is a bead mill using beads having an average particle diameter of 0.1 to 0.5 mm.

  The intermediate layer coating solution can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating.

  Although the drying method of an intermediate | middle layer can be suitably selected according to the kind of binder resin and a solvent, and a film thickness, heat drying is preferable.

  The film thickness of the intermediate layer is preferably 0.1 to 30 μm, and more preferably 0.3 to 15 μm.

(Charge generation layer)
The charge generation layer constituting a specific photoconductor is a binder resin containing a charge generation material.

  Examples of charge generation materials include azo pigments such as Sudan Red and Diane Blue, quinone pigments such as pyrenequinone and anthanthrone, quinocyanine pigments, perylene pigments, indigo pigments such as indigo and thioindigo, and phthalocyanine pigments. It is not something. These charge generating substances can be used alone or in a form dispersed in a known resin.

  As the binder resin for forming the charge generation layer, known resins can be used. For example, polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy Resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin, melamine resin, and copolymer resin containing two or more of these resins (for example, vinyl chloride-vinyl acetate copolymer resin) , Vinyl chloride-vinyl acetate-maleic anhydride copolymer resin) and polyvinyl carbazole resin, but are not limited thereto.

  The charge generation layer is prepared by dispersing a charge generation material in a solution in which a binder resin is dissolved in a solvent using a disperser to prepare a coating solution, and the coating solution is fixed on the outer peripheral surface of the intermediate layer by a coating device. It is preferable to apply to a film thickness and dry to produce a coating film.

  Solvents for dissolving and coating the binder resin used in the charge generation layer include, for example, toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, 4-methoxy-4-methyl-2-pentanone, cyclohexane, Examples include, but are not limited to, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

  As a means for dispersing the charge generating substance, an ultrasonic disperser, a ball mill, a sand grinder, a homomixer, or the like can be used, but is not limited thereto.

The mixing ratio of the charge generating material to the binder resin is preferably 10 to 600 parts by mass, more preferably 50 to 500 parts by mass with respect to 100 parts by mass of the binder resin.
The thickness of the charge generation layer varies depending on the characteristics of the charge generation material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 0.01 to 5 μm, more preferably 0.05 to 3 μm. It should be noted that the coating solution for the charge generation layer can prevent the occurrence of image defects by filtering foreign matter and aggregates before coating. It can also be formed by vacuum deposition of the pigment.

(Lower charge transport layer)
The lower charge transport layer constituting the specific photoconductor is a binder resin containing a charge transport material (CTM).

  Examples of charge transport materials include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazolines. Compound, oxazolone derivative, benzimidazole derivative, quinazoline derivative, benzofuran derivative, acridine derivative, phenazine derivative, aminostilbene derivative, triarylamine derivative, phenylenediamine derivative, stilbene derivative, benzidine derivative, poly-N-vinylcarbazole, poly-1 -Vinylpyrene, poly-9-vinylanthracene, triphenylamine derivatives, etc. Mixed and may also be used.

  As the binder resin, known resins can be used, such as polycarbonate resin, polyarylate resin, polyester resin, polystyrene resin, styrene-acrylonitrile copolymer resin, polymethacrylic ester resin, and styrene-methacrylic ester copolymer. Examples of the resin include polycarbonate resin. In addition, it is preferable to use BPA, BPZ, dimethyl BPA, BPA-dimethyl BPA copolymer and the like in terms of crack resistance, wear resistance, and charging characteristics.

  The lower charge transport layer is prepared by dissolving a binder resin and a charge transport material in a solvent to prepare a coating solution, and coating the coating solution on the outer peripheral surface of the charge generation layer with a coating film to a certain thickness. It is preferable to prepare by drying.

  Examples of the solvent for dissolving the binder resin and the charge transport material include toluene, xylene, methylene chloride, 1,2-dichloroethane, methyl ethyl ketone, cyclohexanone, ethyl acetate, butyl acetate, methanol, ethanol, propanol, butanol, tetrahydrofuran, Examples include, but are not limited to, 1,4-dioxane, 1,3-dioxolane, pyridine, and diethylamine.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin.

  The film thickness of the lower charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the mixing ratio, and the like, but is preferably 5 to 40 μm, and more preferably 10 to 30 μm.

  An antioxidant, an electronic conductive agent, a stabilizer and the like may be added to the lower charge transport layer. Examples of the antioxidant include those described in JP-A No. 2000-305291, and examples of the electronic conductive agent include those described in JP-A Nos. 50-137543 and 58-76483.

(Top charge transport layer)
The uppermost charge transport layer constituting the specific photoreceptor is a binder resin containing a charge transport material (CTM) and specific inorganic particles.
The reason for having two charge transport layers in a specific photoreceptor is to obtain both potential characteristics and wear resistance.

  As the binder resin and the charge transport material constituting the uppermost charge transport layer, the same materials as those of the lower charge transport layer can be used.

  The uppermost charge transport layer is prepared by dissolving a binder resin and a charge transport material in a solvent, and dispersing specific inorganic particles in the solution to prepare a coating solution. It is preferable that the surface is coated with a coating film by a coating machine, and the coating film is dried.

  As the solvent for dissolving the binder resin and the charge transport material, the same solvents as those for forming the lower charge transport layer can be used.

  The mixing ratio of the charge transport material to the binder resin is preferably 10 to 500 parts by mass, more preferably 20 to 100 parts by mass with respect to 100 parts by mass of the binder resin.

  Moreover, it is preferable that the usage-amount of the specific inorganic particle with respect to binder resin is 2.5-40 mass parts with respect to 100 mass parts of binder resin, More preferably, it is 5-35 mass parts.

  The film thickness of the uppermost charge transport layer varies depending on the characteristics of the charge transport material, the characteristics of the binder resin, the characteristics of the specific inorganic particles, the mixing ratio, etc., but is preferably 2 to 12 μm, more preferably 5 to 9 μm. is there.

  In the uppermost charge transport layer, an antioxidant, an electronic conductive agent, a stabilizer and the like may be added in the same manner as the lower charge transport layer.

(Specific inorganic particles)
As the specific inorganic particles contained in the uppermost charge transport layer, metal oxide particles can be used.
As metal oxide particles, magnesium oxide, zinc oxide, lead oxide, aluminum oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, oxidation Examples thereof include germanium, tin oxide, titanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, and among these, particles such as titanium oxide, alumina, zinc oxide, and tin oxide are preferable.
Silica particles can also be used as the specific inorganic particles.
Among the above inorganic particles, it is particularly preferable to use silica particles.

  The metal oxide particles are preferably prepared by a known method such as a general method such as a gas phase method, a chlorine method, a sulfuric acid method, a plasma method, or an electrolytic method.

The specific inorganic particles contained in the uppermost charge transport layer of the photoreceptor of the present invention have a number average primary particle size (Dp) in the range of 3 to 100 nm.
When the number average primary particle size (Dp) of the inorganic particles contained in the uppermost charge transport layer is less than 3 nm, there is a possibility that a sufficient effect on the wear resistance may not be obtained. When the number average primary particle size (Dp) of the inorganic particles contained in the transport layer exceeds 100 nm, the inorganic particles are likely to precipitate in the coating liquid, and aggregates may be generated.

  The number average primary particle size (Dp) of the specific inorganic particles was taken at 10,000 times with a scanning electron microscope (manufactured by JEOL Ltd.), and 300 of these photographic images were randomly removed except for aggregated particles. Are selected by a scanner so that they are included, and an automatic image processing analyzer “LUZEX AP” (manufactured by Nireco) software version Ver. This is a value calculated as an average diameter in the ferret direction by performing image analysis using 1.32.

The specific inorganic particles contained in the uppermost charge transport layer of the photoreceptor of the present invention are preferably those subjected to a hydrophobic treatment.
When the specific inorganic particles have been subjected to a hydrophobic treatment, the specific inorganic particles can be dispersed in a uniform dispersed state in the uppermost charge transport layer.

(Method for producing hydrophobized inorganic particles)
Hydrophobized inorganic particles can be obtained by surface-treating inorganic particles as a material using a surface treatment agent such as a silane coupling agent or a titanium coupling agent.

  As a specific method for producing the hydrophobized inorganic particles, when a reactive organosilicon compound that is one of silane coupling agents is used as a surface treatment agent, a reactive organosilicon compound is used against an organic solvent or water. The inorganic particle dispersion obtained by adding inorganic particles as a material to the dissolved or suspended treatment agent solution is stirred for several minutes to 1 hour, and in some cases, the inorganic particle dispersion is subjected to heat treatment and then filtered. The specific inorganic particles whose surface is coated with the organosilicon compound can be produced by drying after passing through the above-described steps. In the inorganic particle dispersion liquid, a reactive organosilicon compound may be added after adding inorganic particles as a material to an organic solvent or water.

  The amount of the reactive organosilicon compound used for the hydrophobization treatment is 0.1 to 50 parts by mass, more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the inorganic particles used as the material in the charged amount. Is preferred.

  Examples of the reactive organosilicon compound include compounds represented by the following general formula (A), and the following compounds can be used as long as they are compounds that undergo a condensation reaction with a reactive group such as a hydroxyl group on the surface of the inorganic particles used as the material. It is not limited to.

Formula (A): (R) _n —Si— (X) _4-n
[In General Formula (A), R represents a monovalent organic group, X represents a hydrolyzable group, and n represents an integer of 0 to 3. ]

In the reactive organosilicon compound represented by the general formula (A), examples of the organic group represented by R include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, and a dodecyl group. Alkyl group; aryl group such as phenyl group, tolyl group, naphthyl group and biphenyl group; epoxy-containing group such as γ-glycidoxypropyl group and β- (3,4-epoxycyclohexyl) ethyl group; γ-acryloxypropyl Group, (meth) acryloyl group such as γ-methacryloxypropyl group; hydroxyl group such as γ-hydroxypropyl group and 2,3-dihydroxypropyloxypropyl group, vinyl group such as vinyl and propenyl, γ-mercapto Mercapto groups such as propyl; amino-containing groups such as γ-aminopropyl group, N-β (aminoethyl) -γ-aminopropyl group; Chloropropyl group, 1,1,1-trifluoropropyl group, nonafluorohexyl group, a halogen-containing group, such as perfluorooctyl ethyl group; and other nitro group and a cyano-substituted alkyl group.
Examples of the hydrolyzable group represented by X include alkoxy groups such as methoxy group and ethoxy group; halogen groups and acyloxy groups.

  In the reactive organosilicon compound represented by the general formula (A), when n is 2 or more, a plurality of R may be the same as or different from each other. Similarly, when n is 2 or less, the plurality of X may be the same or different from each other.

  Specific examples of reactive organosilicon compounds in which n is 0 include tetrachlorosilane, diethoxydichlorosilane, tetramethoxysilane, phenoxytrichlorosilane, tetraacetoxysilane, tetraethoxysilane, tetraallyloxysilane, tetrapropoxysilane, tetraiso Examples include propoxysilane, tetrakis (2-methoxyethoxy) silane, tetrabutoxysilane, tetraphenoxysilane, tetrakis (2-ethylbutoxy) silane, tetrakis (2-ethylhexyloxy) silane, and the like.

  Specific examples of the reactive organosilicon compound in which n is 1 include trichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, ethyltrichlorosilane, allyltrichlorosilane, n-propyltrichlorosilane, n-butyltrichlorosilane, chloromethyltriethoxy. Silane, methyltrimethoxysilane, mercaptomethyltrimethoxysilane, trimethoxyvinylsilane, ethyltrimethoxysilane, 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, phenyltrichlorosilane, 3,3,3-trifluoropropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, triethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 2-amino Tylaminomethyltrimethoxysilane, benzyltrichlorosilane, methyltriacetoxysilane, chloromethyltriethoxysilane, ethyltriacetoxysilane, phenyltrimethoxysilane, 3-allylthiopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane 3-bromopropyltriethoxysilane, 3-allylaminopropyltrimethoxysilane, propyltriethoxysilane, hexyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane, bis (ethylmethylketo Oxime) methoxymethylsilane, pentyltriethoxysilane, octyltriethoxysilane, dodecyltriethoxysilane and the like.

  Specific examples of the reactive organosilicon compound in which n is 2 include dimethyldichlorosilane, dimethoxymethylsilane, dimethoxydimethylsilane, methyl-3,3,3-trifluoropropyldichlorosilane, diethoxysilane, diethoxymethylsilane, Dimethoxymethyl-3,3,3-trifluoropropylsilane, 3-chloropropyldimethoxymethylsilane, chloromethyldiethoxysilane, diethoxydimethylsilane, dimethoxy-3-mercaptopropylmethylsilane, 3,3,4,4 5,5,6,6,6-nonafluorohexylmethyldichlorosilane, methylphenyldichlorosilane, diacetoxymethylvinylsilane, diethoxymethylvinylsilane, 3-methacryloxypropylmethyldichlorosilane, 3-aminopropyldiet Cymethylsilane, 3- (2-aminoethylaminopropyl) dimethoxymethylsilane, t-butylphenyldichlorosilane, 3-methacryloxypropyldimethoxymethylsilane, 3- (3-cyanopropylthiopropyl) dimethoxymethylsilane, 3- (2 -Acetoxyethylthiopropyl) dimethoxymethylsilane, dimethoxymethyl-2-piperidinoethylsilane, dibutoxydimethylsilane, 3-dimethylaminopropyldiethoxymethylsilane, diethoxymethylphenylsilane, diethoxy-3-glycidoxypropyl Examples include methylsilane, 3- (3-acetoxypropylthio) propyldimethoxymethylsilane, dimethoxymethyl-3-piperidinopropylsilane, and diethoxymethyloctadecylsilane.

  Specific examples of the reactive organosilicon compound in which n is 3 include trimethylchlorosilane, methoxytrimethylsilane, ethoxytrimethylsilane, methoxydimethyl-3,3,3-trifluoropropylsilane, 3-chloropropylmethoxydimethylsilane, methoxy- Examples include 3-mercaptopropylmethylmethylsilane.

The reactive organosilicon compound represented by the general formula (A) may be used alone or in combination of two or more.
When two or more reactive organosilicon compounds represented by the general formula (A) are used in combination, R and X may be the same or different between the respective compounds.

  As the reactive organosilicon compound represented by the general formula (A), it is preferable to use a compound represented by the following general formula (B).

Formula (B): R′—Si— (X ′) ₃
[In general formula (B), R ′ represents an alkyl group or an aryl group, and X ′ represents a methoxy group, an ethoxy group, or a halogen group. ]

  As the reactive organic silicon compound represented by the general formula (B), an organic silicon compound in which R ′ is an alkyl group having 4 to 8 carbon atoms is more preferable. Specifically, trimethoxy n-butylsilane, trimethoxy Examples include i-butylsilane, trimethoxyhexylsilane, trimethoxyoctylsilane, and the like.

  Moreover, a hydrogen polysiloxane compound can also be mentioned as a reactive organosilicon compound. It is preferable to use a hydrogen polysiloxane compound having a molecular weight of 1000 to 20000 because it is generally easily available and has a good function to prevent black spots. In particular, good effects can be obtained by using methylhydrogenpolysiloxane for the final hydrophobization treatment (surface treatment).

  In addition, examples of the reactive organosilicon compound include an organosilicon compound having a fluorine atom.

  Specific examples of the organosilicon compound having a fluorine atom include 3,3,4,4,5,5,6,6,6-nonafluorohexyltrichlorosilane, 3,3,3-trifluoropropyltrimethoxy. Silane, methyl-3,3,3-trifluoropropyldichlorosilane, dimethoxymethyl-3,3,3-trifluoropropylsilane, 3,3,4,4,5,5,6,6,6-nonafluoro Examples include hexylmethyldichlorosilane.

  Moreover, as the surface treatment agent, a reactive organic titanium compound which is a kind of titanium coupling agent can also be used. Examples of the reactive organic titanium compound include metal alkoxide compounds such as tetrapropoxy titanium and tetrabutoxy titanium, diisopropoxy titanium bis (acetyl acetate), diisopropoxy titanium bis (ethyl acetoacetate), diisopropoxy titanium bis ( Metal chelate compounds such as lactate), dibutoxytitanium bis (octylene glycolate), diisopropoxytitanium bis (triethanolaminate), and the like.

  Further, as the surface treating agent, a reactive organic zirconium compound can also be used. Examples of the reactive organic zirconium compound include metal alkoxide compounds such as tetrabutoxyzirconium and butoxyzirconium tri (acetylacetate), and metal chelate compounds.

In addition, as another method for producing the hydrophobized inorganic particles, a method using a wet media dispersion type apparatus may be employed.
Specifically, for example, when alumina particles are used as inorganic particles as a material, a slurry (a suspension of solid particles) containing alumina particles and a surface treatment agent is wet-pulverized to simultaneously refine the alumina particles. Hydrophobization of the surface of the alumina particles proceeds. Thereafter, by removing the solvent from the slurry, it is possible to obtain alumina particles that are made uniform and finer and whose surface is hydrophobized by a compound derived from a surface treatment agent such as a silane compound.

  The wet media dispersion type device has a function of crushing and pulverizing and dispersing alumina agglomerated particles by filling beads in the container as media and rotating the stirring disk mounted perpendicular to the rotation axis at a high speed. As its specific configuration, there is no problem as long as the alumina particles are sufficiently dispersed and can be hydrophobized, for example, various types such as a vertical type, a horizontal type, a continuous type, a batch type, etc. Styles can be adopted. Specifically, a sand grinder mill, an ultra visco mill, a pearl mill, a glen mill, a dyno mill, an agitator mill, a dynamic mill and the like can be used. In these wet media dispersion type apparatuses, pulverization and dispersion are performed by impact crushing, friction, cutting, shear stress, etc., using a grinding medium (media) such as balls and beads.

  As the beads used in the sand grinder mill, balls made of glass, alumina, zircon, zirconia, steel, flint stone and the like can be used, but those made of zirconia or zircon are particularly preferable. Further, as the size of the beads, those having a diameter of about 1 to 2 mm are usually used, but in the present invention, those having a diameter of about 0.1 to 1.0 mm are preferably used.

  Various materials such as stainless steel, nylon, and ceramic can be used as the disk and container inner wall in the wet media dispersion type apparatus, but it is particularly preferable to use a ceramic material such as zirconia or silicon carbide. .

The amount of the surface treatment agent used for the hydrophobization treatment is preferably 0.1 to 100 parts by mass with respect to 100 parts by mass of alumina particles as a material in the charged amount.
Moreover, it is preferable that the solvent of a slurry is 50-5000 mass parts with respect to 100 mass parts of alumina particles used as a material with preparation amount.

According to the photoreceptor as described above, the periodicity of the cutting unevenness is reduced by the cylindrical substrate, so that the period of the exposure pattern and the cutting unevenness formed on the surface of the cylindrical substrate of the electrophotographic photosensitive member. Interference with the period is reduced, and accordingly, the occurrence of interference streaks in the obtained high-quality halftone image is suppressed.
In addition, since the cylindrical substrate has a charge transport layer containing inorganic particles having a particle size in a specific range, with the periodicity of the cutting irregularities being reduced, a scattering effect is obtained in the photoreceptor. Occurrence of image unevenness in the obtained image is suppressed.
Furthermore, excellent wear resistance can be obtained by containing a specific range of inorganic particles in the uppermost charge transport layer.

[Image forming apparatus]
FIG. 5 is an explanatory sectional view showing an example of the configuration of an image forming apparatus on which the electrophotographic photosensitive member of the present invention is mounted.
This image forming apparatus is called a tandem type color image forming apparatus. Each of the image forming units 10Y, 10M, 10C, and 10Bk that forms yellow, magenta, cyan, or black toner images, and these image forming units. Image formation comprising an intermediate transfer unit 7 for transferring toner images of respective colors formed on 10Y, 10M, 10C, and 10Bk onto the image support P, and fixing means 24 for fixing the toner image to the image support P An apparatus main body A is provided, and an original image reading apparatus SC for optically scanning an original and reading image information as digital data (original image data) is disposed above the image forming apparatus main body A.

The image forming unit 10Y will be described in detail below.
Each of the image forming units 10M, 10C, and 10Bk forms a toner image with magenta toner, cyan toner, and black toner instead of yellow toner, and basically has the same configuration as the image forming unit 10Y. Is.

  The image forming unit 10Y is exposed around a drum-shaped photoreceptor 1Y that is an image forming body, a charging unit 2Y that applies a uniform potential to the surface of the photoreceptor 1Y, and a uniformly charged photoreceptor 1Y. Exposure unit 3Y that performs exposure based on the image data signal (yellow) for image formation and forms an electrostatic latent image corresponding to the yellow image, and conveys color toner onto the photoreceptor 1Y to visualize the electrostatic latent image The developing means 4Y for cleaning and the cleaning means 6Y for collecting the residual toner remaining on the photoreceptor 1Y after the primary transfer are arranged to form a yellow (Y) toner image on the photoreceptor 1Y.

  As the charging means 2Y, a corona discharge type charger is used.

  As the exposure unit 3Y, a light emitting device using a light emitting diode as an exposure light source, for example, an LED unit in which light emitting elements made of light emitting diodes are arranged in an array in the axial direction of the photoreceptor 1Y and an imaging element Alternatively, the image forming apparatus shown in FIG. 5 uses a laser irradiation device, such as a laser optical system laser irradiation device using a semiconductor laser as an exposure light source.

  The exposure means 3Y is preferably composed of an apparatus using a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 850 nm as an exposure light source. By using such an exposure light source with an exposure dot diameter of 10 to 100 μm narrowed down in the writing direction, and performing digital exposure on the photoreceptor 1Y, a high-resolution electrophotographic image of 600 to 2400 dpi or more is provided. Can be obtained.

The exposure method in the exposure means 3Y may be a scanning optical system using a semiconductor laser or a solid type using an LED. Regarding the light intensity distribution, there are a Gaussian distribution, a Lorentz distribution, etc., but an area of 1 / e ² or more of each peak intensity may be set as the exposure dot diameter.

  In the image forming apparatus of this example, the photosensitive member 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 6Y in the image forming unit 10Y are provided as an integrated process cartridge.

  The image forming apparatus as described above is configured by integrally coupling a photosensitive member in one image forming unit and components such as a developing unit and a cleaning unit as a process cartridge, and this process cartridge is attached to the main body of the image forming apparatus. On the other hand, it may be configured to be detachable. In addition, a process cartridge is formed by integrally supporting at least one of a charging unit, an exposure unit, a developing unit, a transfer unit or a separation unit (not shown), and a cleaning unit in one image forming unit together with a photosensitive member. It may be configured to be detachable from the main body of the image forming apparatus using a guide means.

  The intermediate transfer unit 7 is formed by an endless belt-like intermediate transfer body 70 that is stretched by a plurality of support rollers 71 to 74 and supported so as to be circulated, and image forming units 10Y, 10M, 10C, and 10Bk, respectively. The primary transfer rollers 5Y, 5M, 5C, and 5Bk for transferring the toner image to the intermediate transfer member 70, and the toner image transferred onto the intermediate transfer member 70 by the primary transfer rollers 5Y, 5M, 5C, and 5Bk are image supports. A secondary transfer roller 5b for transferring onto P and a cleaning means 6b for collecting residual toner remaining on the intermediate transfer member 70 are provided.

  The primary transfer roller 5Bk in the intermediate transfer unit 7 is always in contact with the photoconductor 1Bk during the image forming process, and the other primary transfer rollers 5Y, 5M, and 5C are each only when forming a color image. It contacts the corresponding photoreceptors 1Y, 1M, 1C.

  Further, the secondary transfer roller 5b is brought into contact with the intermediate transfer body 70 only when the image support P passes through the secondary transfer roller 5b and the secondary transfer is performed.

  In this image forming apparatus, each of the process cartridges in the image forming units 10Y, 10M, 10C, and 10Bk and other than the secondary transfer roller 5b of the intermediate transfer unit 7 are housed in a housing 8, and the housing 8 is configured to be drawable from the image forming apparatus main body A through the support rails 82L and 82R.

  In this image forming apparatus, among the photoconductors 1Y, 1M, 1C, and 1Bk of all the image forming units 10Y, 10M, 10C, and 10Bk, all the photoconductors 1Y, 1M, 1C, and 1Bk have the specific cutting process described above. It is preferable that the photosensitive member is made of a specific photosensitive member having a shape. However, if at least one of the photosensitive members 1Y, 1M, 1C, and 1Bk is made of the specific photosensitive member, generation of interference streaks is suppressed. The effect of forming a high-quality image can be obtained.

  The image forming apparatus on which the electrophotographic photosensitive member of the present invention is mounted is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers. It can be widely applied to apparatuses such as recording, light printing, plate making and facsimile.

(Image forming method)
In the above image forming apparatus equipped with the electrophotographic photoreceptor of the present invention, the surfaces of the photoreceptors 1Y, 1M, 1C, and 1Bk are charged by the charging means 2Y, 2M, 2C, and 2Bk, and the exposure means 3Y, 3M, 3C, and 3Bk are operated in accordance with the image data signals for exposure of each color obtained by performing various image processing on the document image data obtained by the document image reading device SC. Laser light modulated in accordance with the image data signal is output from the exposure light source, and the photoconductors 1Y, 1M, 1C, and 1Bk are scanned and exposed by the laser light, and are read by the document image reading device SC. An electrostatic latent image corresponding to each color of yellow, magenta, cyan, and black corresponding to the original is formed on each of the photoreceptors 1Y, 1M, 1C, and 1Bk.

Next, the electrostatic latent images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are developed with the toners of the respective colors in the developing units 4Y, 4M, 4C, and 4Bk, thereby forming toner images of the respective colors. The toner images of the respective colors are sequentially transferred onto the intermediate transfer body 70 by the transfer rollers 5Y, 5M, 5C, and 5Bk, and are superimposed and combined to form a color toner image.
Further, in synchronism with the formation of the color toner image, the image support P such as plain paper or transparent sheet accommodated in the paper feed cassette 20 is fed by the paper feed means 21 and a plurality of intermediate rollers 22A, 22B. , 22C, 22D and the registration roller 23, the color toner images conveyed to the secondary transfer roller 5b and transferred onto the intermediate transfer body 70 by the secondary transfer roller 5b on the image support P in a lump. Transcribed.
The color toner image transferred onto the image support P is fixed by, for example, heating and pressurization in the fixing unit 24 to form a visible image, and then the image support P on which the visible image has been formed is discharged to the discharge roller. 25 is discharged out of the apparatus and placed on the discharge tray 26.

The photoreceptors 1Y, 1M, 1C, and 1Bk after the toner images of the respective colors are transferred to the intermediate transfer member 70 remain on the photoreceptors 1Y, 1M, 1C, and 1Bk by the cleaning units 6Y, 6M, 6C, and 6Bk, respectively. After the toner is removed, it is used to form toner images of the following colors.
On the other hand, the intermediate transfer member 70 after the color toner image is transferred onto the image support P by the secondary transfer roller 5b and the curvature of the image support P is separated is left on the intermediate transfer member 70 by the cleaning means 6b. After the removed toner is removed, it is used for intermediate transfer of the next toner image.

[Toner and developer]
The toner used in the image forming method of the present invention may be a pulverized toner or a polymerized toner. However, the image forming method of the present invention is prepared by a polymerization method from the viewpoint of obtaining a stable particle size distribution. It is preferable to use the polymerized toner.

  A polymerized toner is obtained by generating a binder resin for forming a toner and forming a toner particle shape by performing polymerization of raw material monomers to obtain a binder resin and, if necessary, subsequent chemical treatment in parallel. Means toner.

  More specifically, it means a toner formed through a step of obtaining resin fine particles by a polymerization reaction such as suspension polymerization or emulsion polymerization, and a step of fusing the resin fine particles performed thereafter if necessary.

  The volume average particle diameter of the toner, that is, the 50% volume particle diameter (Dv50) is preferably 2 to 9 μm, more preferably 3 to 7 μm. By setting this range, the resolution can be increased. In addition, by combining with the above range, the amount of toner having a fine particle diameter can be reduced while being a small particle diameter toner, the dot image reproducibility is improved over a long period of time, and the sharpness is excellent. In addition, a stable image can be formed.

  The toner according to the present invention may be used alone as a one-component developer, or may be mixed with a carrier and used as a two-component developer.

  When used as a one-component developer, a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm of magnetic particles in the toner can be used. be able to.

  In addition, when used as a two-component developer by mixing with a carrier, conventionally known magnetic particles of the carrier, such as metals such as iron, ferrite and magnetite, alloys of these metals with metals such as aluminum and lead, etc. Material can be used. Ferrite particles are particularly preferable. The magnetic particles preferably have a volume average particle size of 15 to 100 μm, more preferably 25 to 80 μm.

  The volume average particle diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  The carrier is preferably a carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, fluorine-containing polymer resin, or the like is used. In addition, the resin for constituting the resin-dispersed carrier is not particularly limited, and a known resin can be used. For example, a styrene-acrylic resin, a polyester resin, a fluorine resin, a phenol resin, or the like is used. be able to.

According to the image forming method of the present invention, since the cylindrical substrate of the photosensitive member has a reduced periodicity of cutting irregularities, the exposure pattern cycle and the surface of the cylindrical substrate of the electrophotographic photosensitive member are formed. Interference with the period of the cut irregularities is reduced, and accordingly, the occurrence of interference streaks in the obtained high-quality halftone image is suppressed.
In addition, since the cylindrical substrate of the photoreceptor has a charge transport layer containing inorganic particles having a specific range of particle diameters and having a reduced periodicity of cutting irregularities, a scattering effect can be obtained in the photoreceptor. Therefore, occurrence of image unevenness in the obtained image is suppressed.

As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.
For example, the specific layer structure of the photoreceptor is not limited to the above structure.

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.
ΔL is a cross-sectional curve in the vicinity of the center of the outer peripheral surface of the cylindrical substrate using “Surfcom 1400D” (manufactured by Tokyo Seimitsu Co., Ltd.). It was obtained by roughness measurement performed under measurement conditions of 8 mm (Gaussian) and a measurement speed of 0.3 mm / sec, and was measured as described above using this cross-sectional curve.
Rz was calculated from the cross-sectional curve obtained in the same manner except that the cut-off was 0.25 mm in the measurement of the cross-sectional curve.

<Photosensitive substrate base production example 1>
A base tube made of aluminum alloy having a length of 362 mm is mounted on a CNC lathe, and is cut with a diamond sintered cutting tool under the following conditions so that the outer diameter is 59.95 mm and the surface Rz is 0.75 μm. Thus, a cylindrical substrate [1] was produced.
In the cutting of the cutting tool, the rotation speed of the main spindle of the lathe is set to 6000 rpm, and the moving speed of the cutting tool (the cutting tool feed speed) is set to 0.005 mm for every processing distance of 1.5 mm between 0.340 and 0.360 mm / rotation. / The speed was changed by a program that repeatedly increased and decreased the feed rate so as to change every rotation.
When ΔL on the outer peripheral surface of the cylindrical substrate [1] was measured, it was 50 μm.

<Photosensitive substrate base production example 2>
A cylindrical substrate [2] was obtained in the same manner as in Preparation Example 1 of the photoreceptor substrate, except that the spindle speed of the lathe for cutting by cutting was set to 2000 rpm. It was 30 micrometers when (DELTA) L of the outer peripheral surface of this cylindrical base | substrate [2] was measured.

<Photosensitive substrate base production example 3>
The same as in Example 2 for producing the photosensitive member substrate except that the cutting speed of the cutting tool is changed by a program that switches between 0.340 mm / rotation and 0.345 mm / rotation every processing distance of 1.5 mm. Thus, a cylindrical substrate [3] was obtained. It was 10 micrometers when (DELTA) L of the outer peripheral surface of this cylindrical base | substrate [3] was measured.

<Photosensitive substrate base production example 4>
A cylindrical base body is prepared by mounting a 362 mm long aluminum alloy tube on a CNC lathe and performing cutting with a diamond sintered cutting tool under the following conditions so that the surface Rz is 0.75 μm. [4] was prepared.
In the cutting of the cutting tool, the turning speed of the main spindle of the lathe is set to 4000 rpm, the cutting tool feed speed value is constant at 400 μm / rotation, and the processing distance is 1.43 mm, 2.28 mm, 1.64 mm, starting from the end of the tube. 2.49 mm, 1.85 mm, 2.71 mm, 2.06 mm, 2.92 mm, and the program set to repeat.
The ΔL of the outer peripheral surface of the cylindrical substrate [4] was measured and found to be 20 μm.

<Photosensitive substrate base production example 5>
A cylindrical base body is prepared by mounting a 362 mm long aluminum alloy tube on a CNC lathe and performing cutting with a diamond sintered cutting tool under the following conditions so that the surface Rz is 0.75 μm. [5] was prepared.
In the cutting of the cutting tool, the rotation speed of the main spindle of the lathe is set to 3160 rpm, the cutting tool feed speed value is kept constant at 400 μm / rotation, and the processing distance is 2.20 mm, 2.21 mm, 2.22 mm, starting from the end of the tube. , 2.23 mm, 2.24 mm, 2.23 mm, 2.22 mm, and 2.21 mm.
The ΔL of the outer peripheral surface of the cylindrical substrate [5] was measured and found to be 65 μm.

<Photosensitive substrate base production example 6>
A cylindrical base body is prepared by mounting a 362 mm long aluminum alloy tube on an analog lathe and cutting with a diamond sintered tool under the following conditions so that the surface Rz is 0.75 μm. [6] was produced.
In the tool cutting process, the spindle rotation speed of the lathe is set to 3160 rpm, and the tool feed speed instruction value (working distance-speed instruction value) relative to the processing distance
0.5 mm-380 μm / revolution, 1.6 mm-390 μm / revolution, 2.8 mm-380 μm / revolution, 1.1 mm-390 μm / revolution, 2.5 mm-380 μm / revolution, 3.2 mm-390 μm / revolution In order to achieve this, a voltage through a circuit in which a timer and a resistor were combined was input to the bite moving motor.
It was 25 micrometers when (DELTA) L of the outer peripheral surface of the cylindrical base | substrate [6] was measured.

<Photoconductor substrate production example 7>
In the photoconductor substrate manufacturing example 1, the cylindrical substrate [7 is similarly manufactured except that the rotation speed of the spindle of the cutting tool is set to 3000 rpm and the cutting speed is fixed to 0.350 mm / rotation. ] Was obtained. The ΔL of the outer peripheral surface of this cylindrical substrate [7] was measured and found to be 3 μm.

<Photosensitive substrate base production example 8>
A cylindrical base body is prepared by mounting a 362 mm long aluminum alloy tube on a CNC lathe and performing cutting with a diamond sintered cutting tool under the following conditions so that the surface Rz is 0.75 μm. [8] was prepared.
In the cutting of the cutting tool, the turning speed of the main spindle of the lathe is set to 4000 rpm, the cutting tool feed speed value is constant at 400 μm / rotation, the starting distance is 1.47 mm, 2.32 mm, 1.68 mm , 2.53 mm, 1.89 mm, 2.75 mm, 2.10 mm, 2.96 mm.
It was 8 micrometers when (DELTA) L of the outer peripheral surface of cylindrical base | substrate [8] was measured.

[Example 1: Photoconductor Production Example 1]
(1) Formation of intermediate layer 1 part by mass of a binder resin represented by the following formula (N-1) is mixed with 20 parts by mass of a mixed solvent of ethanol, n-propyl alcohol and tetrahydrofuran (volume ratio = 45: 20: 35). In addition, after stirring and dissolving, 4.2 parts by mass of rutile-type titanium oxide particles surface-treated with 5% by weight of methylhydrogenpolysiloxane were mixed, and this mixture was averaged using a bead mill. An intermediate layer coating solution [1] was prepared by using zirconia beads having a particle diameter of 0.5 mm and dispersing under conditions of a filling rate of 80%, a peripheral speed setting of 4 m / sec, and a mill residence time of 3 hours. This intermediate layer coating solution [1] is filtered through a filter using a polypropylene filter medium having a filtration accuracy of 5 μm, and this is applied to the outer peripheral surface after washing the cylindrical substrate [1] by dip coating. Then, an intermediate layer [1] having a dry film thickness of 2 μm was formed on the cylindrical substrate [1] by drying at 120 ° C. for 20 minutes.

(2) Formation of charge generation layer Next, the following components were mixed and dispersed using a sand mill disperser to prepare a charge generation layer coating solution.
This charge generation layer coating solution was applied onto the intermediate layer [1] by a dip coating method to form a charge generation layer [1] having a dry film thickness of 0.3 μm.
Y-titanyl phthalocyanine (a titanyl phthalosine pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 ° in an X-ray diffraction spectrum by Cu-Kα characteristic X-ray)
20 parts by mass-polyvinyl butyral ("BX-1" (manufactured by Sekisui Chemical Co., Ltd.)) 10 parts by mass-700 parts by mass of methyl ethyl ketone-300 parts by mass of cyclohexanone

(3) Formation of charge transport layer (lower layer) Next, the following components were mixed and dissolved to prepare a charge transport layer (lower layer) coating solution.
The charge transport layer (lower layer) coating solution is applied onto the charge generation layer [1] by dip coating and dried at 120 ° C. for 70 minutes to form a lower charge transport layer [1a] having a dry film thickness of 20 μm. did.
-50 parts by mass of a charge transport material represented by the following formula (CTM)-100 parts by mass of polycarbonate resin "Iupilon-Z300" (manufactured by Mitsubishi Gas Chemical Company)-Antioxidant (2,6-di-t-butyl-4 -Methylphenol) 8 parts by mass / tetrahydrofuran / toluene (volume ratio 8/2) 750 parts by mass

(4) Formation of charge transport layer (uppermost layer) Subsequently, the following components were mixed and stirred to prepare a charge transport layer (uppermost layer) coating solution.
The charge transport layer (uppermost layer) coating solution is applied onto the charge transport layer [1a] by a dip coating method and dried at 120 ° C. for 70 minutes, whereby the uppermost charge transport layer [1b] having a dry film thickness of 5 μm is obtained. As a result, a photoreceptor [1] was obtained.
-1.2 parts by mass of charge transport material represented by the above formula (CTM)-2.7 parts by mass of polycarbonate resin "Iupilon-Z300" (Mitsubishi Gas Chemical Co., Ltd.)-(methyl of 25% by mass of titanium oxide) Titanium oxide having a 50% particle size of 31 nm, surface-treated with hydrogen polysiloxane (surface treatment agent) 1.0 parts by mass, antioxidant (2,6-di-t-butyl-4-methylphenol ) 0.1 part by mass-tetrahydrofuran / toluene (volume ratio 8/2) mixed solution 30 parts by mass-silicone oil "KF-96" (manufactured by Shin-Etsu Silicone Co., Ltd.) 0.005 part by mass

[Examples 2-11: Comparative Examples 1-3: Photoconductor Production Examples 2-14]
In Production Example 1 of the photoreceptor, the type of cylindrical substrate, the type of inorganic particles contained in the uppermost charge transport layer, and the surface treatment agent of the inorganic particles were changed in the same manner as in Table 1, Photoconductors [2] to [14] were obtained.
In Table 1, the surface treatment agents “SH-1”, “SH-2”, “SH-3”, and “SH-4” represent the following.

“SH-1”: methyl hydrogen polysiloxane “SH-2”: octyltrimethoxysilane “SH-3”: methyltrimethoxysilane “SH-4”: diisopropoxytitanium bis (acetylacetate)

[Image quality evaluation A]
One of the above photoconductors [1] to [14] is mounted on an image forming apparatus “bizhub PRO C6501” (manufactured by Konica Minolta Business Technologies), and the following test images A to C are coated with “POD gloss coat”. (100 g / m ² ) ”(manufactured by Oji Paper Co., Ltd.), and the obtained test images A to C were subjected to image quality evaluation for interference streaks and photosensitive member circumferential direction streaks. The results are shown in Table 1.

  In the test image A, at the black (Bk) position, using the exposure pattern A below, the density instruction values are 17 gradations up to 255/255 every 0/255, 15/255, 31/255. This is a halftone image output by shaking.

  Exposure pattern A: “bizhub PRO C6501” internal mounting pattern no. 53 Dot1, a typical exposure pattern formed in a regular dot pattern.

  In the test image B, at the black (Bk) position, using the following exposure pattern B, the density instruction values are changed to 0/255, 15/255, 31/255... And 17 gradations up to 255/255 every 16th. This is a halftone image output by shaking.

  Exposure pattern B: “bizhub PRO C6501” internal mounting pattern no. 7 Contonne, a typical exposure pattern formed continuously in a direction perpendicular to the photosensitive body axis direction.

  In the test image C, at the black (Bk) position, the following exposure pattern C is used, and the density instruction values are changed to 0/255, 15/255, 31/255... This is a halftone image output by shaking.

  Exposure pattern C: “bizhub PRO C6501” internal mounting pattern no. 1 Line1, a typical exposure pattern formed continuously in a direction parallel to the axial direction of the photoreceptor.

(Image quality evaluation 1) Diagonal stripe density unevenness (interference lines)
The test image A based on the exposure pattern A and the test image B based on the exposure pattern B were evaluated according to the following evaluation criteria. The image quality evaluation was performed on the worst-level image portion among image portions having different density instruction values.
-Evaluation criteria-
○: No oblique stripe density unevenness is observed.
Δ: Slight stripe-like density unevenness is slightly observed, but there is no problem in actual use.
X: Oblique stripe-like density unevenness is observed, and there is a problem in actual use.

(Image quality evaluation 2) Photoconductor circumferential direction streak Image quality evaluation was performed on the test image C by the exposure pattern C. The image quality evaluation was performed on the worst-level image portion among image portions having different density instruction values.
-Evaluation criteria-
○: No stripes in the circumferential direction of the photoreceptor are observed.
Δ: Slight streaks in the circumferential direction of the photoconductor are seen, but there is no problem in actual use.
X: Photoreceptor circumferential direction streaks are observed, and there is a problem in actual use.

[Image quality evaluation B: Image unevenness]
One of the above photoconductors [1] to [14] is mounted on the image forming apparatus “bizhub PRO C6501” (manufactured by Konica Minolta Business Technologies), and the following test image D is applied to the coated paper “POD gloss coat (100 g). / M ² ) ”(manufactured by Oji Paper Co., Ltd.) 100 test prints were formed, and the resulting 100 test prints were evaluated for image unevenness according to the following evaluation criteria. The results are shown in Table 1.

  The test image D is a halftone image output at a black (Bk) position using the exposure pattern A as a density instruction value of 75/255.

-Evaluation criteria-
○: Image unevenness does not occur in all 100 test prints.
Δ: Some image unevenness is seen in 100 test prints, but there is no problem in actual use.
X: Some of the 100 test prints show image unevenness, and the level is problematic in practical use.

[Evaluation of wear resistance]
One of the above photoconductors [1] to [14] is mounted on the image forming apparatus “bizhub PRO C6501” (manufactured by Konica Minolta Business Technologies), and a printing durability test is performed for 500,000 sheets before and after the printing durability test. The abrasion resistance was evaluated using the difference in film thickness of the photosensitive layer as the amount of film thickness reduction. The results are shown in Table 1. In addition, it can be judged that it is a pass without a problem practically when the amount of film thickness wear is 4.0 micrometers or less.

  As is apparent from Table 1, an image is formed using a photoconductor (specific photoconductor) having a cylindrical substrate with ΔL ≧ 10 and a charge transport layer containing specific inorganic particles in the uppermost layer. In the case of forming an image, a good image in which the occurrence of interference streaks and image unevenness was suppressed was obtained, whereas an image was obtained using a photoconductor with a cylindrical substrate having a small ΔL as in Comparative Examples 1 to 3. Is formed, the interference streaks estimated to be caused by the interference between the period of the cutting irregularities of the cylindrical substrate and the period of the exposure pattern, and the image estimated to be caused by the small scattering effect on the photoconductor Unevenness occurred. In addition, it was confirmed that a photoconductor in which specific inorganic particles are not contained in the uppermost charge transport layer as in Comparative Example 3 has a large film thickness loss and low wear resistance.

1, 1Y, 1M, 1C, 1Bk Photoconductor 1a Cylindrical substrate 1b Intermediate layer 1c Charge generation layer 1d Lower charge transport layer 1e Uppermost charge transport layer 1α Photosensitive layer 2Y, 2M, 2C, 2Bk Charging means 3Y, 3M 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Development unit 5Y, 5M, 5C, 5Bk Primary transfer roller 5b Secondary transfer roller 6Y, 6M, 6C, 6Bk Cleaning unit 6b Cleaning unit 7 Intermediate transfer unit 8 Housing 10Y 10M, 10C, 10Bk Image forming unit 20 Paper feed cassette 21 Paper feed means 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper discharge roller 26 Paper discharge tray 70 Intermediate transfer body 71-74 Support roller 82L , 82R Support rail A Image forming apparatus main body P Image support SC Original image reading apparatus

Claims (3)

An electrophotographic photoreceptor in which at least a charge generation layer and at least two charge transport layers are laminated in this order on a cylindrical substrate,
The cylindrical substrate has a cutting shape that satisfies the following formula (1), in which cutting irregularities are periodically formed in the central axis direction on the outer peripheral surface thereof,
The electrophotographic photoreceptor, wherein the uppermost charge transport layer contains inorganic particles having a number average primary particle size (Dp) of 3 to 100 nm.
Formula (1): ΔL ≧ 10 μm
[In Expression (1), ΔL is the difference between the maximum value and the minimum value of the periodic width of the cutting irregularities in the central axis direction in the image region on the outer peripheral surface of the cylindrical base. ]   The electrophotographic photosensitive member according to claim 1, wherein the inorganic particles are silica particles. An image forming method comprising forming an image using the electrophotographic photosensitive member according to claim 1.

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