JP2009198566A - Electrophotographic photoreceptor, image forming device, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor capable of forming clear electrophotographic image having high resolution with high sensitivity without causing rupture, damage or the like including crack. <P>SOLUTION: The electrophotographic photoreceptor uses a write light source having wavelength of 390-500 nm and has: a charge generation layer containing a condensed polycyclic compound on at least an electrical conductive support; and a charge transport layer containing a charge transport substance expressed by formula (1), a plasticizer of benzotriazole compound or triazine compound, and a binder. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member used for forming an electrophotographic image used in a copying machine, a printer, and the like, an image forming apparatus equipped with the electrophotographic photosensitive member, and a process cartridge.

  With the progress of digital image forming technology, in recent years it has become possible to produce high-quality monochrome images and color images using electrophotographic copying machines and printers, and these devices can be used in the printing field including color printing. Print production has become popular. In forming an image at such a print image level, it has been proposed to form a high-definition digital image by using a short wavelength laser beam as an exposure light source (see, for example, Patent Document 1).

  At present, an electrophotographic apparatus using a laser beam as an exposure light source has appeared, as represented by a laser printer or the like. As the laser light source, a semiconductor laser that outputs light having a wavelength of 780 to 800 nm or 680 nm is mainly used. However, in recent years, there has been an increasing demand for higher image quality and higher resolution of output images, and various attempts have been made to meet this demand.

  One technique is to reduce the spot diameter of the writing light. The reduction of the spot diameter can theoretically be considerably reduced by shortening the wavelength of the writing light source, which is very advantageous for increasing the writing density of the latent image, that is, the resolution. Therefore, development of a highly sensitive and highly stable electrophotographic photosensitive member has been studied by using a semiconductor laser or light emitting diode in the 390 to 500 nm region as a writing light source.

  When the wavelength of the writing light source is shortened, the organic photoreceptor is required to have a light-transmitting layer light transmittance with respect to the writing light, and the same potential stability and sensitivity as those of the conventional organic photoreceptor corresponding to the near infrared region are required. It is done. So far, organic photoreceptors having sensitivity in the short wavelength region have been proposed, but the above-mentioned problems have not necessarily been satisfied.

  One of the development requirements for an electrophotographic photosensitive member corresponding to this short wavelength light source is the development of a charge transport material that absorbs less light in the 390 to 500 nm region of the writing light source. Currently, many of the charge transport materials used in electrophotographic photoreceptors have absorption on the short wavelength side. Therefore, when such a charge transport material is used for an electrophotographic photoreceptor exposed with a short wavelength light source. , Sensitivity decreases.

  In response to this problem, a triarylamine compound has been proposed as a charge transport material suitable for an electrophotographic photosensitive member that is exposed to a light source having a short wavelength (see, for example, Patent Document 2). However, since this compound has low solubility in ordinary solvents and poor compatibility with binders, the coating solution for forming a photosensitive layer of an electrophotographic photoreceptor has poor storage stability, and crystals are precipitated during storage. As a result, it is not possible to fill the electrophotographic photosensitive member with a sufficient concentration of this compound, resulting in poor sensitivity, or high crystallinity, so that cracks are likely to occur. There was a problem that occurred.

  For such a problem, a polyarylalkane compound having a phenyl group methyl-substituted at the para position as a charge transport material has been proposed, but the compound has a solubility in ordinary solvents and binders due to structural characteristics. Insufficient filling concentration due to the lack of sensitivity, resulting in poor sensitivity due to the lack of sufficient filling concentration, and leading to poor image quality and reduced light fatigue resistance due to the occurrence of film defects in durability tests, aiming for high image quality and high durability It was not suitable for photoconductor formulations. Some measures have been taken as a measure for increasing the solubility of triarylamine, but the performance in terms of electrophotographic characteristics has been drastically reduced, and none has been put to practical use.

As a countermeasure against this, a method of mixing several kinds of charge transport materials having different chemical structures has been proposed (for example, see Patent Document 3). However, this method has a problem that sensitivity and high-speed response are lowered although solubility is improved. Since the chemical structures are different, the charge transfer between the compounds is not smooth, and the electrical characteristics are considered to be deteriorated.
JP 2000-250239 A JP 2000-105475 A JP 2001-350282 A

  The present invention has been made in view of the above problems, and the object thereof is to obtain a high-resolution and clear electrophotographic image with high sensitivity without causing breakage such as cracks. An electrophotographic photoreceptor is provided. Another object of the present invention is to provide an image forming apparatus and a process cartridge using the electrophotographic photosensitive member. In particular,

  In order to develop an electrophotographic photosensitive member that can smoothly form an image using a semiconductor laser or a light emitting diode of 390 to 500 nm as a writing light source, the present inventor has focused on the charge transport layer constituting the electrophotographic photosensitive member. . The inventors have found that the problem of the present invention can be solved by finding a charge transport layer using a specific amine compound as a charge transport material and a benzotriazole compound or a triazine compound as a plasticizer.

  That is, it has been found that the problems of the present invention can be solved by any of the configurations described below.

The invention described in claim 1
“An electrophotographic photosensitive member using a semiconductor laser having an oscillation wavelength of 390 to 500 nm or a light emitting diode having a peak wavelength of 390 to 500 nm as a writing light source, wherein the electrophotographic photosensitive member is condensed on at least a conductive support. A charge generation layer containing a polycyclic compound and a charge transport layer containing a charge transport material, a binder and a plasticizer, wherein the charge transport material is a compound represented by the following general formula (1): An electrophotographic photoreceptor, wherein the plasticizer is a benzotriazole compound or a triazine compound.

[In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ each independently represent an aryl group which may have a substituent, and Ar ₁ and Ar ₂ , and Ar ₃ and Ar ₄ are bonded to each other. To form a ring. R ₁ and R ₂ each independently represents an alkyl group or an aryl group, and R ₁ and R ₂ may combine to form a ring. R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group or an aryl group. N and m each independently represents an integer of 1 to 4. ]].

  According to a second aspect of the present invention, the spectral transmittance of the charge transporting layer is 70% or more and less than 100% at any wavelength of 390 to 500 nm. Photoconductor. ].

  According to a third aspect of the present invention, there is provided, on the electrophotographic photosensitive member according to the first or second aspect, using a writing light source of at least a semiconductor laser having an oscillation wavelength of 390 to 500 nm or a light emitting diode having a peak wavelength of 390 to 500 nm. An image forming apparatus having an exposure means for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member of the writing light source, wherein the exposure spot diameter is 10 to 50 μm. ].

  According to a fourth aspect of the present invention, “the electrophotographic photosensitive member according to the first or second aspect, a charging unit that charges the electrophotographic photosensitive member, and an electrostatic latent image is formed on the electrophotographic photosensitive member. An exposure unit, a developing unit that visualizes the electrostatic latent image formed on the electrophotographic photosensitive member to form a toner image, and a transfer unit that transfers the toner image visualized by the developing unit onto a transfer material At least one cleaning means for removing toner remaining on the electrophotographic photosensitive member after the transfer is performed by the transfer means is integrally mounted, and is detachably attached to the image forming apparatus main body. A process cartridge characterized by that. ].

  According to the present invention, the coating state of the electrophotographic photosensitive member is improved, the film has sufficient crack resistance, and image defects (such as spots) are less likely to occur when writing with a short-wavelength semiconductor laser or light-emitting diode, resulting in sharpness. Thus, an electrophotographic photoreceptor can be provided which can form an excellent electrophotographic image and exhibits stable potential characteristics upon repeated use. In addition, it is possible to provide an image forming apparatus and a process cartridge capable of forming an electrophotographic image with good sharpness.

  The present inventor considered to realize a high-sensitivity electrophotographic photosensitive member that has a high light-transmitting property of the charge transport layer and efficiently generates charges in the charge generation layer with respect to the exposure light source. Therefore, the present inventor preferably does not absorb the exposure light source with respect to the charge transport material and has high hole mobility, and can maintain high charge generation efficiency with respect to the charge generation material regardless of environmental changes. I thought it was preferable.

  However, even if a charge transporting material or a charge generating material satisfying the above performance is used, satisfactory results cannot be obtained when it is made to function as an electrophotographic photosensitive member. The present inventor considered to solve the problem by controlling the compatibility between the charge transporting substance and the binder used together with the charge transporting substance and the blending of the solvent for dissolving the binder. Alone could not satisfy all required properties.

  As a result of extensive studies, the present inventors have used a charge generation layer containing a condensed polycyclic compound and an amine compound represented by the following general formula (1) as a charge transport material, or a benzotriazole compound or A photoconductor combined with a charge transport layer containing a triazine compound was considered. The inventors have found that the problems of the present invention can be solved by the electrophotographic photosensitive member comprising the charge generation layer and the charge transport layer, and have reached the present invention.

  The reason why the problem was solved by the electrophotographic photoreceptor having the above-described configuration was considered as follows. That is, by adding a benzotriazole-based compound or a triazine-based compound to the charge transporting layer, a decrease in light fatigue resistance is suppressed, and crack resistance can be improved by imparting plasticity. And even if such a compound is added, it is considered that the amine compound of the general formula (1), which is a charge transporting substance, can be added at a sufficient concentration, so that good charge transporting performance is expressed. In addition, the condensed polycyclic compound added to the charge generation layer makes some contribution to the charge generation material, so that the charge generation layer can efficiently generate charges without being affected by environmental fluctuations. it is conceivable that.

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

  The amine compound of the present invention is represented by the following general formula (1).

[In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ each independently represent an aryl group which may have a substituent, and Ar ₁ and Ar ₂ , and Ar ₃ and Ar ₄ are bonded to each other. To form a ring. R ₁ and R ₂ each independently represents an alkyl group or an aryl group, and R ₁ and R ₂ may combine to form a ring. R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group or an aryl group. N and m each independently represents an integer of 1 to 4. ]
The amine compound has a small absorption with respect to an exposure light source having a wavelength of 390 to 500 nm, a large potential decay value with respect to a unit exposure amount, improved repetition characteristics, and can form a small dot latent image sharply. . In addition, when used in combination with a benzotriazole or triazine compound, solvent solubility and compatibility with a binder such as polycarbonate are improved. The charge transport layer has improved crack resistance.

  Although the specific example of the amine compound used for this invention is illustrated below, the amine compound which can be used for this invention is not limited to these specific examples.

  Below, the synthesis example of the amine compound which can be used as a charge transport material by this invention is shown below.

(Synthesis Example 1): Compound (CTM-16)
In a 200 ml three-headed flask, weigh 10 parts by weight of N, N-bis (p-dimethylphenyl) aniline, 6.2 parts by weight of 4-methylcyclohexanone, 20 ml of acetic acid and 0.35 parts by weight of methanesulfonic acid. Stir at 70 ° C. After 6 hours, the reaction was stopped, 300 ml of toluene and 200 ml of water were added, and the mixture was washed with a separatory funnel until the aqueous layer became neutral. The toluene layer was taken, dried over anhydrous magnesium sulfate and concentrated. CTM-16, which was the target product, was taken out by column chromatography. Recrystallized and purified with ethyl acetate. The yield of CTM-16 obtained was 4.7 parts by mass.

(Synthesis Example 2): Compound (CTM-17)
Compound (CTM-17) was synthesized in the same manner as in Synthesis Example 1, except that instead of the raw material 4-methylcyclohexanone, 6.92 parts by mass of 4-ethylcyclohexanone was used in Synthesis Example 1. The yield of CTM-17 obtained was 6.6 parts by mass.

(Synthesis Example 3): Compound (CTM-18)
Compound (CTM-18) was synthesized in the same manner as in Synthesis Example 1 except that 7.69 parts by mass of 3,3,5-trimethylcyclohexanone was used instead of the raw material 4-methylcyclohexanone in Synthesis Example 1. The yield of CTM-18 obtained was 4.3 parts by mass.

(Synthesis Example 4): Compound (CTM-6)
A compound (CTM-6) was synthesized in the same manner as in Synthesis Example 1 except that 5.37 parts by mass of cyclohexanone was used instead of the raw material 4-methylcyclohexanone in Synthesis Example 1. The yield of CTM-6 obtained was 6.9 parts by mass.

(Synthesis Example 5): Compound (CTM-4)
Compound (CTM-4) was synthesized in the same manner as in Synthesis Example 1 except that instead of the raw material 4-methylcyclohexanone, 5.44 parts by mass of methyl isobutyl ketone was used in Synthesis Example 1. The yield of CTM-4 obtained was 5.3 parts by mass.

  Furthermore, image defects (such as spots) are generated by using the amine compound represented by the general formula (1) in combination with a benzotriazole compound or a triazine compound (hereinafter also referred to as a plasticizer that can be used in the present invention). An image with less sharpness and good sharpness can be obtained.

  Specific examples of the plasticizer that can be used in the present invention are illustrated below, but the plasticizer that can be used in the present invention is not limited thereto.

  In addition, the benzotriazole type compound used as a plasticizer in the present invention can be synthesized, for example, by the method described in Japanese Examined Patent Publication No. 44-29620 or a method analogous thereto.

  The amount of the plasticizer that can be used in the present invention is preferably 1% by mass to 100% by mass, and more preferably 3% by mass to 50% by mass with respect to the total mass of the binder.

  When the amount of the compound is less than 1% by mass, the light fatigue resistance is lowered, and when the amount is more than 100% by mass, the viscosity of the charge transport layer coating solution is excessively lowered to make it difficult to form a coating film or to lower the film strength.

  The electrophotographic photosensitive member according to the present invention uses the amine compound of the general formula (1) as a charge transport material and contains a benzotriazole-based or triazine-based compound. What is used as an organic photoreceptor containing bismuth is preferred. Hereinafter, the constitution of the organic photoreceptor will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor formed by giving an organic compound at least one of a charge generation function and a charge transport function indispensable for the configuration of the electrophotographic photoconductor. All known organic photoconductors such as a photoconductor composed of an organic charge generating material or an organic charge transport material, a photoconductor composed of a polymer complex with a charge generating function and a charge transport function are contained.

The constitution of the organophotoreceptor of the present invention is not particularly limited as long as it contains the amine compound (charge transport material) of the general formula (1) and the benzotriazole compound or triazine compound. A configuration as shown in FIG.
1) A structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support;
2) A structure in which a charge generation layer, a first charge transport layer, and a second charge transport layer are sequentially laminated as a photosensitive layer on a conductive support;
3) A structure in which a surface protective layer is further formed on the photosensitive layer of the photoconductors 1) and 2) above.

  The photoconductor may have any of the above configurations. The electrophotographic photosensitive member according to the present invention may have any structure, or may be an undercoat layer (intermediate layer) formed before forming a photosensitive layer on a conductive support. Good.

  The charge transport layer in the present invention means a layer having a function of transporting charge carriers generated in the charge generation layer by photoexposure to the surface of the organic photoreceptor, and the charge transport function is the charge generation layer and the charge transport layer. This can be confirmed by laminating the layer on a conductive support and detecting optical conductivity.

  Next, the layer structure of the organic photoreceptor will be described focusing on the structure of 1) above.

Conductive Support The conductive support used for the photoreceptor may be either a sheet or a cylinder, but a cylindrical conductive support is preferred for designing an image forming apparatus compactly. .

  Cylindrical conductive support means a cylindrical support necessary for forming an endless image by rotating. Conductivity is within a range of 0.1 mm or less in straightness and 0.1 mm or less in deflection. A support is preferred. Exceeding the straightness and shake range makes it difficult to form a good image.

As the conductive material, a metal drum such as aluminum or nickel, a plastic drum deposited with aluminum, tin oxide, indium oxide or the like, or a paper / plastic drum coated with a conductive substance can be used. The conductive support preferably has a specific resistance of 10 ³ Ω · cm or less at room temperature. The conductive support of the present invention is most preferably an aluminum support. As the aluminum support, one in which components such as manganese, zinc, magnesium and the like are mixed in addition to the main component aluminum is also used.

Intermediate layer In the present invention, an intermediate layer is preferably provided between the conductive support and the photosensitive layer.

  The intermediate layer used in the present invention preferably contains N-type semiconductor particles. The N-type semiconductive particle means a particle whose main charge carrier is an electron. That is, since the main charge carriers are electrons, the intermediate layer containing the N-type semiconductor particles in the insulating binder effectively blocks hole injection from the substrate, and the electrons from the photosensitive layer. In contrast, it has a property of low blocking.

  On the other hand, the binder resin in which these particles are dispersed to form the layer structure of the intermediate layer is preferably a polyamide resin in order to obtain good dispersibility of the particles, but the polyamide resin shown below is particularly preferable.

  As the polyamide resin used for the binder resin of the intermediate layer, a polyamide resin soluble in alcohol is preferable.

Photosensitive layer The photosensitive layer configuration of the photoreceptor of the present invention is a configuration in which the function of the photosensitive layer is separated into a charge generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which the functions are separated, an increase in the residual potential due to repeated use can be controlled to be small, and other electrophotographic characteristics can be easily controlled according to the purpose. In the negatively charged photoconductor, it is preferable that a charge generation layer (CGL) is formed on the intermediate layer, and a charge transport layer (CTL) is formed thereon.

  The structure of the photosensitive layer of the function-separated negatively charged photoreceptor will be described below.

Charge generation layer The organophotoreceptor of the present invention is characterized by containing a condensed polycyclic compound. As the charge generation material, a charge generation material having high sensitivity characteristics in a wavelength region of 390 nm to 500 nm may be used. preferable. As such a charge generating substance, an azo pigment, a perylene pigment, a multisensitive quinone pigment, or the like is preferably used.

  In particular, polycyclic quinone pigments such as dibromoanthanthrone, which have high sensitivity to commercially available short wavelength lasers having an oscillation wavelength around 405 mm, or azo pigments represented by the compounds exemplified below Etc. are preferably used.

  These pigments can be used in combination.

  When a binder is used as a CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 800 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.3 μm to 2 μm.

Charge Transport Layer The charge transport layer of the present invention contains a charge transport material (CTM), a binder and a plasticizer. Other substances may contain additives such as inorganic fine particles such as silica and alumina, organic fine particles such as fluororesin fine particles, or an antioxidant as necessary.

  As the charge transport material (CTM), the charge transport material of the general formula (1) is used, but in addition to this, a known hole transport property (P type) charge transport material (CTM) may be used in combination. Good. For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer.

  The binder resin used for the charge transport layer (CTL) may be either a thermoplastic resin or a thermosetting resin. For example, polystyrene, 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 these resins A copolymer resin containing two or more of the repeating unit structures. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used. Of these, polycarbonate resins are most preferred because of their low water absorption and good CTM dispersibility and electrophotographic characteristics.

  The ratio of the binder resin to the charge transport material is preferably 50 to 200 parts by mass with respect to 100 parts by mass of the binder resin.

  The total film thickness of the charge transport layer is preferably 10 to 30 μm. If the total film thickness is less than 10 μm, it is difficult to sufficiently obtain the latent image potential during development, and the image density is likely to decrease. If it exceeds 30 μm, charge carrier diffusion (charge generated in the charge generation layer) Carrier diffusion) increases and dot reproducibility tends to deteriorate.

  Moreover, it is preferable to contain an antioxidant in the surface layer of the photoreceptor according to the present invention. The surface layer is easily oxidized by an active gas such as NOx or ozone when the photoreceptor is charged, and image blur is likely to occur. However, the presence of an antioxidant can prevent image blur.

  Specific examples of the antioxidant include, for example, known acid value inhibitors shown below. That is, phenolic antioxidants (hindered phenols), amine antioxidants (hindered amines, diallyldiamines, diallylamines), hydroquinone antioxidants, sulfur antioxidants (thioethers), phosphoric acid oxidations Examples include inhibitors (phosphorous esters).

  Among the antioxidants, hindered phenol-based and hindered amine-based antioxidants are particularly effective in preventing fogging and image blurring at high temperatures and high humidity.

  Moreover, as a solvent or dispersion medium used for layer formation, such as an intermediate | middle layer, a charge generation layer, and a charge transport layer, the following are mentioned, for example. That is, n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone, methyl ethyl ketone, methyl isopropyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1, 2 -Dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1-trichloroethane, trichloroethylene, tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate , Dimethyl sulfoxide, methyl cellosolve and the like. Although this invention is not limited to these, Dichloromethane, 1, 2- dichloroethane, methyl ethyl ketone, etc. are used preferably. These solvents can be used alone or as a mixed solvent of two or more.

  Examples of the coating method used for producing the electrophotographic photosensitive member according to the present invention include known coating methods. Specifically, in addition to coating with a circular slide hopper type coating device, dip coating and Examples include spray coating.

  Next, an image forming apparatus using the electrophotographic photosensitive member according to the present invention will be described.

  An image forming apparatus 1 shown in FIG. 1 is a digital image forming apparatus, and includes an image reading unit A, an image processing unit B, an image forming unit C, and a transfer paper transport unit D as a transfer paper transport unit. Yes.

  An automatic document feeder that automatically conveys the document is provided above the image reading unit A. The document placed on the document table 11 is separated and conveyed by the document conveyance roller 12 to the reading position 13a. The image is read. The document after the document reading is completed is discharged onto the document discharge tray 14 by the document transport roller 12.

  On the other hand, the image of the original when placed on the platen glass 13 is read at a speed v of the first mirror unit 15 comprising the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by moving the second mirror unit 16 composed of the two mirrors and the third mirror in the same direction at the speed v / 2.

  The read image is formed on the light receiving surface of the image sensor CCD, which is a line sensor, through the projection lens 17. The line-shaped optical image formed on the image sensor CCD is sequentially photoelectrically converted into an electric signal (luminance signal) and then A / D converted, and the image processing unit B performs processing such as density conversion and filter processing. Then, the image data is temporarily stored in the memory.

  In the image forming unit C, as an image forming unit, a drum-shaped photoconductor 21 as an image carrier, a charging means (charging step) 22 for charging the photoconductor 21 on the outer periphery thereof, and a surface potential of the charged photoconductor. Potential detecting means 220 for detecting the toner, developing means (developing process) 23, transfer / conveying belt device 45 serving as a transferring means (transfer process), cleaning device (cleaning process) 26 for the photosensitive member 21, and light neutralizing means (light slow charge). PCL (precharge lamp) 27 as a process is arranged in the order of operation. Further, on the downstream side of the developing means 23, a reflection density detecting means 222 for measuring the reflection density of the patch image developed on the photosensitive member 21 is provided. As the photosensitive member 21, the organic photosensitive member according to the present invention is used, and the photosensitive member 21 is driven and rotated in the clockwise direction shown in the drawing.

  After the rotating photosensitive member 21 is uniformly charged by the charging unit 22, image exposure based on an image signal called from the memory of the image processing unit B is performed by an exposure optical system as an exposure unit (exposure process) 30. Done. The exposure optical system as the exposure means 30 serving as the writing means uses a semiconductor laser (not shown) as a writing light source, passes through a rotating polygon mirror 31, an fθ lens 34, and a cylindrical lens 35, and the optical path is bent by the reflecting mirror 32 to perform main scanning. Thus, image exposure is performed on the photoconductor 21 at the position Ao, and an electrostatic latent image is formed by rotation (sub-scanning) of the photoconductor 21. In one example of the present embodiment, the character portion is exposed to form an electrostatic latent image.

  In the image forming apparatus of the present invention, a semiconductor laser having an oscillation wavelength of 390 to 500 nm or a light emitting diode having a peak wavelength of 390 to 500 nm is used as a writing light source when an electrostatic latent image is formed on a photoreceptor. By using these writing light sources, the exposure spot diameter of the writing light source on the surface of the electrophotographic photosensitive member is narrowed to 10 to 50 μm, and digital exposure is performed on the organic photosensitive member, whereby 600 dpi (dpi: 2.54 cm per dot). A high resolution electrophotographic image of 2500 dpi can be obtained.

  The exposure spot diameter refers to the length of the exposure beam along the main scanning direction (Ld: the length is measured at the maximum position) in a region where the intensity of the exposure beam is 1 / e2 or more of the peak intensity.

  The light beam used includes a scanning optical system using a semiconductor laser and a solid-state scanner of a light emitting diode. The light intensity distribution also includes a Gaussian distribution and a Lorentz distribution, but a region of 1 / e2 or more of each peak intensity is used. The exposure spot diameter according to the present invention is used.

  The electrostatic latent image on the photoconductor 21 is reversely developed by the developing unit 23, and a visible toner image is formed on the surface of the photoconductor 21. In the image forming method of the present invention, it is preferable to use a polymerized toner as a developer used in the developing means. By using a polymer toner having a uniform shape and particle size distribution in combination with the organic photoreceptor according to the present invention, an electrophotographic image with better sharpness can be obtained.

  In the transfer paper transport section D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer paper storage means for storing transfer paper P of different sizes. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer paper P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer paper P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer paper P to be transferred, and then fed again. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 Then, the toner image on the photosensitive member 21 is guided to the transfer guide belt 47 and is transferred to the transfer paper P while being transferred to the transfer transport belt 454 of the transfer transport belt device 45 by the transfer pole 24 and the separation pole 25 at the transfer position Bo. Photographed, transfer sheet P is separated from the photosensitive member 21 surface, it is conveyed to the fixing unit 50 by the transfer conveyor belt device 45.

  The fixing unit 50 includes a fixing roller 51 and a pressure roller 52. By passing the transfer paper P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image has been fixed, the transfer paper P is discharged onto the paper discharge tray 64.

  The above describes the state in which image formation is performed on one side of the transfer paper. However, in the case of double-sided copying, the paper discharge switching member 170 is switched, the transfer paper guide 177 is opened, and the transfer paper P is indicated by a broken arrow. Conveyed in the direction.

  Further, the transfer paper P is transported downward by the transport mechanism 178 and switched back by the transfer paper reversing unit 179, and the rear end portion of the transfer paper P becomes the leading end portion and transported into the duplex copying paper supply unit 130. The

  The transfer paper P is moved in a paper feed direction by a conveyance guide 131 provided in the double-sided copy paper supply unit 130, the transfer paper P is re-fed by the paper supply roller 132, and the transfer paper P is guided to the conveyance path 40. .

  Again, as described above, the transfer paper P is conveyed in the direction of the photosensitive member 21, the toner image is transferred to the back surface of the transfer paper P, fixed by the fixing unit 50, and then discharged onto the paper discharge tray 64.

  The electrophotographic image forming apparatus of the present invention is constructed by integrally combining the above-described photosensitive member and components such as a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit as a process cartridge. You may comprise so that attachment or detachment with respect to an apparatus main body is possible. Further, at least one of charging means, exposure means, developing means, transfer means, and cleaning means is integrally supported together with the electrophotographic photosensitive member of the present invention to form a process cartridge, which is a single unit that is detachable from the apparatus main body. Further, it may be configured to be detachable using guide means such as a rail of the apparatus main body.

  FIG. 2 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention.

  This color image forming apparatus is called a tandem type color image forming apparatus, and includes four sets of image forming units (image forming units) 10Y, 10M, 10C, and 10Bk, an endless belt-shaped intermediate transfer body unit 7, and a feeding unit. The paper transport unit 21 and the fixing unit 24 are included. A document image reading device SC is disposed on the upper part of the main body A of the image forming apparatus.

  The image forming unit 10Y that forms a yellow image includes a charging unit (charging step) 2Y, an exposure unit (exposure step) 3Y, and a developing unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. Means (development process) 4Y, primary transfer roller 5Y as primary transfer means (primary transfer process), and cleaning means 6Y. The image forming unit 10M that forms a magenta image includes a drum-shaped photoconductor 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, and a primary transfer roller as a primary transfer unit. 5M and cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoconductor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller as a primary transfer unit. 5C and cleaning means 6C. An image forming unit 10Bk that forms a black image includes a drum-shaped photoreceptor 1Bk as a first image carrier, a charging unit 2Bk, an exposure unit 3Bk, a developing unit 4Bk, and a primary transfer roller 5Bk as a primary transfer unit. It has a cleaning means 6Bk.

  The four sets of image forming units 10Y, 10M, 10C, and 10Bk include charging means 2Y, 2M, 2C, and 2Bk that rotate around the photosensitive drums 1Y, 1M, 1C, and 1Bk, and image exposure means 3Y, 3M, 3C, 3Bk, rotating developing means 4Y, 4M, 4C, and 4Bk, and cleaning means 5Y, 5M, 5C, and 5Bk for cleaning the photosensitive drums 1Y, 1M, 1C, and 1Bk.

  The image forming units 10Y, 10M, 10C, and 10Bk have the same configuration except that the colors of toner images formed on the photoreceptors 1Y, 1M, 1C, and 1Bk are different, and the image forming unit 10Y is taken as an example in detail. explain.

  The image forming unit 10Y has a charging unit 2Y (hereinafter simply referred to as a charging unit 2Y or a charger 2Y), an exposure unit 3Y, a developing unit 4Y, and a cleaning unit 5Y (around a photosensitive drum 1Y as an image forming body). Hereinafter, the cleaning means 5Y or the cleaning blade 5Y) is simply disposed, and a yellow (Y) toner image is formed on the photosensitive drum 1Y.

  In the present embodiment, in the image forming unit 10Y, at least the photosensitive drum 1Y, the charging unit 2Y, the developing unit 4Y, and the cleaning unit 5Y are provided so as to be integrated.

  The charging unit 2Y is a unit that applies a uniform potential to the photosensitive drum 1Y. In the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, the exposure means 3Y includes a light emitting diode in which light emitting elements are arranged in an array in the axial direction of the photosensitive drum 1Y and an imaging element (trade name; Selfoc lens), or A semiconductor laser optical system or the like is used.

  The endless belt-like intermediate transfer body unit 7 includes an endless belt-like intermediate transfer body 70 as a second image carrier having a semiconductive endless belt shape that is wound around a plurality of rollers and is rotatably supported.

  Each color image formed by the image forming units 10Y, 10M, 10C, and 10Bk is transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. The images are sequentially transferred to form a synthesized color image. A transfer material P as a transfer material (a support for carrying a fixed final image: for example, plain paper, a transparent sheet, etc.) housed in the paper feed cassette 20 is fed by a paper feed means 21 and a plurality of intermediates. After passing through the rollers 22A, 22B, 22C, 22D and the registration roller 23, it is conveyed to the secondary transfer roller 5b as the secondary transfer means, and is secondarily transferred onto the transfer material P, and the color images are collectively transferred. The transfer material P onto which the color image has been transferred is subjected to fixing processing by the fixing unit 24, is sandwiched between paper discharge rollers 25, and is placed on a paper discharge tray 26 outside the apparatus. Here, a transfer support for a toner image formed on a photosensitive member such as an intermediate transfer member or a transfer material is collectively referred to as a transfer medium.

  On the other hand, the endless belt-shaped intermediate transfer body 70 obtained by transferring the color image onto the transfer material P by the secondary transfer roller 5b as the secondary transfer means and then separating the curvature of the transfer material P has the residual toner removed by the cleaning means 6b. The

  During the image forming process, the primary transfer roller 5Bk is always in contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in contact with the corresponding photoreceptors 1Y, 1M, and 1C only during color image formation.

  The secondary transfer roller 5b contacts the endless belt-shaped intermediate transfer body 70 only when the transfer material P passes through the secondary transfer roller 5b and the secondary transfer is performed.

  Further, the housing 8 can be pulled out from the apparatus main body A through the support rails 82L and 82R.

  The housing 8 includes image forming units 10Y, 10M, 10C, and 10Bk and an endless belt-shaped intermediate transfer body unit 7.

  The image forming units 10Y, 10M, 10C, and 10Bk are arranged in tandem in the vertical direction. An endless belt-shaped intermediate transfer body unit 7 is disposed on the left side of the photoreceptors 1Y, 1M, 1C, and 1Bk in the drawing. The endless belt-shaped intermediate transfer body unit 7 includes an endless belt-shaped intermediate transfer body 70 that can be rotated by winding rollers 71, 72, 73, 74, primary transfer rollers 5Y, 5M, 5C, 5Bk, and cleaning means 6b. It consists of.

  The image forming apparatus according to the present invention is generally applicable to an electrophotographic apparatus such as an electrophotographic copying machine, a laser printer, an LED printer, and a liquid crystal shutter printer, and further, a display, a recording, a light printing, and a plate making using an electrophotographic technique. It can also be widely applied to devices such as facsimiles.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to the following description. In addition, "part" in a sentence represents a mass part.

(Preparation of photoreceptor 1)
Photoreceptor 1 was produced according to the following procedure.

  The surface of the cylindrical aluminum support was cut to prepare a conductive support having a 10-point surface roughness Rz = 1.5 (μm).

(Middle layer)
Polyamide resin CM8000 (manufactured by Toray Industries, Inc.) 10 parts by mass Titanium oxide SMT500SAS (manufactured by Teika) 30 parts by mass Methanol 100 parts by mass The above composition was dispersed for 10 hours using a sand mill. This dispersion was diluted twice with the same mixed solvent with the same composition, left standing overnight, and then filtered using a rigesh mesh 5 μm filter manufactured by Nippon Pole Co., to prepare an intermediate layer coating solution.

  The said coating liquid was apply | coated by the dip coating method so that it might become a dry film thickness of 2 micrometers on the said support body, and the intermediate | middle layer was formed.

(Charge generation layer)
Charge generation material (exemplary compound (CG5)) 5 parts by mass Polyvinyl butyral resin BH-S (manufactured by Sekisui Chemical Co., Ltd.) 1 part by mass t-butyl acetate 70 parts by mass 4-methoxy-4-methyl-2-pentanone 30 Mass parts were mixed and dispersed for 10 hours using a sand mill to prepare a charge generation layer coating solution. This coating solution was applied onto the intermediate layer by a dip coating method so as to have a dry film thickness of 0.3 μm to form a charge generation layer.

(Charge transport layer)
Charge transport material (Exemplary compound (CTM-19)) 2 parts by weight Binder (Polycarbonate (Z300 (manufactured by Mitsubishi Engineering)))
2.7 parts by mass Antioxidant (Irganox 1010 (manufactured by Ciba Geigy Japan)) 0.1 part by mass Plasticizer (Exemplary Compound (A1)) 0.3 part by mass Dichloromethane 20 parts by mass are mixed, dissolved, and charge transport layer A coating solution was prepared. This coating solution was applied onto the charge generation layer with a circular slide hopper coating machine so as to have a dry film thickness of 23 μm to form a charge transport layer. Photoreceptor 1 was produced by this procedure.

(Preparation of photoconductors 2 to 5)
Photoconductors 2 to 5 were prepared in the same manner as the photoconductor 1 except that the charge generation material, the charge transport material, and the plasticizer were changed to those shown in Table 1, respectively.

(Preparation of photoconductors 1 to 4 for comparison)
In preparation of the photoreceptor 1, the following compounds CTM-A and CTM-B were used as charge transport materials, and the charge generation materials, charge transport materials, and plasticizers shown in Table 1 were used, respectively. Comparative photoreceptors 1 to 4 were prepared by the procedure described above.

(Preparation of photoreceptor 6)
A second charge transport layer coating solution was prepared by the following procedure, and a photoreceptor 6 formed by forming a second charge transport layer using this was prepared.

  0.1 parts by mass of silica (average particle size 15 nm, surface-treated with hexamethyldisilazane) is dissolved in 15 parts by mass of a tetrahydrofuran / toluene (volume ratio 8/2) mixed solution and 1 part by mass of polycarbonate resin “Z300”. The mixture was added and dispersed with a US homogenizer. Subsequently, 0.7 parts by mass of the charge transport material (CTM-6), 0.035 parts by mass of the antioxidant (Irganox 1010), 0.1 parts by mass of the exemplified compound A7 as a plasticizer are dissolved, and the second charge is dissolved. A transport layer coating solution was prepared.

  As shown in Table 1, except that a charge generating substance, a charge transporting substance, and a plasticizer are used, the first charge transporting layer is fabricated in the same procedure as that of the photoreceptor 1, and the second charge transporting layer is used as the second charge transporting layer. The transport layer coating solution was applied by a circular slide hopper coating method. After the application, a photoconductor 6 formed by forming a second charge transport layer having a dry film thickness of 6.0 μm was subjected to a heat drying treatment at 120 ° C. for 60 minutes.

(Preparation of photoconductors 7 to 9)
As shown in Table 1, the second charge transport was carried out in the same procedure as the second charge transport layer coating solution used in the production of the photoreceptor 6 except that the plasticizer used for the preparation of the second charge transport layer coating solution was changed to A6. Layer coating solution 2 was prepared. As shown in Table 1, except that a charge generating material, a charge transport material, and a plasticizer were used, the first charge transport layer was prepared in the same procedure as that of the photoreceptor 1, and the second charge transport layer coating solution 2 was used. Otherwise, the second charge transport layer was formed in the same procedure as the photoconductor 6 to prepare the photoconductor 7.

  Also, instead of silica in the second charge transport layer coating solution 1, titanium oxide (anaters type, average particle size 6 nm, 5% primary surface treatment with alumina and 30% secondary surface treatment with isobutyltrimethoxysilane) The second charge transport layer coating solution 3 was prepared by changing the plasticizer to A2. As shown in Table 1, except that a charge generating material, a charge transport material, and a plasticizer were used, the first charge transport layer was prepared in the same procedure as that of the photoreceptor 1, and the second charge transport layer coating solution 3 was used. Otherwise, the photoconductor 8 was produced by forming the second charge transport layer in the same procedure as the photoconductor 6.

  Further, a second charge transport layer coating solution 4 was prepared in the same procedure as the second charge transport layer coating solution 3 except that the plasticizer of the second charge transport layer coating solution 3 was changed to A1. As shown in Table 1, except that a charge generating material, a charge transport material, and a plasticizer were used, the first charge transport layer was prepared in the same procedure as the photoreceptor 1, and the second charge transport layer coating solution 4 was used. Otherwise, the photoconductor 9 was produced by forming the second charge transport layer in the same procedure as the photoconductor 6.

(Evaluation experiment)
The above-mentioned “photosensitive members 1 to 9” and “comparative photoconductors 1 to 4” are mounted on a commercially available printer “bizhub C350 (manufactured by Konica Minolta)” (with a semiconductor laser having an oscillation wavelength of 405 nm as an image exposure light source. Exposure by an aperture) The spot diameter can be adjusted). Evaluations were made on the following items, assuming that "Photoconductors 1 to 9" were mounted as "Examples 1 to 9" and "Comparative Photoconductors 1 to 4" were mounted as "Comparative Examples 1 to 4". It was.

  Further, on the transparent quartz glass, a first charge transport layer provided above the charge generation layers of the “photosensitive members 1 to 9” and “comparative examples 1 to 4”, and further a second charge transport layer are provided. One also applied a second charge transport layer to form a layer. The layer thus formed was measured for spectral transmittance (%) at a wavelength of 390 to 500 nm using a spectrophotometer “U-3500 (manufactured by Hitachi, Ltd.)”. Table 1 shows the measured values of spectral transmittance at 405 nm.

"Evaluation 1" (Evaluation of fine line reproducibility)
The exposure spot diameter was changed to 10, 25, and 50 μm to form a 1-dot linear electrostatic latent image, and the thickness of the output image line on the developed and transferred transfer material was changed to a digital high scope (Keyence). And the toner image change rate Te was calculated to evaluate fine line reproducibility. The toner image change rate Te, which is the ratio of the thickness of the toner line to the exposure spot diameter, was calculated from the following equation.

Toner image change rate Te (%) = toner line thickness (μm) / exposure spot diameter (μm)
In addition, evaluation was performed according to the following criteria, and ◎, ○, and Δ were regarded as acceptable. That is,
A: 80% <Te ≦ 120%
○: 20% <Te ≦ 167%
Δ: 167% <Te
×: Other than above “Evaluation 2” (Evaluation of post-exposure potential Vi)
In an environment of 23 ° C. and 50% RH, the post-exposure potential Vi was measured before and after making 10,000 sheets / A4 continuous print.

"Evaluation 3" (Evaluation of sensitivity)
In the above “Examples 1 to 9” and “Comparative Examples 1 to 4”, the support was prepared in the same manner except that the support was changed from an aluminum tube to an aluminum deposition sheet, and the light source 405 nm when the unexposed portion potential Vo was −600 V. Sensitivity E1 / 2 (μJ / cm ² ) was evaluated. The sensitivity was evaluated using “EPA8300A (manufactured by Kawaguchi Electric Co., Ltd.)”.

  The results are shown in Table 1.

  From the results in Table 1, “Examples 1 to 9” which are electrophotographic photoreceptors having the configuration of the present invention have a large potential decay value with respect to unit exposure, improved repetitive characteristics, and sharpened small-diameter dot latent images. It was confirmed that it could be formed. It was also confirmed that the electrophotographic photosensitive member having the configuration of the present invention has improved crack resistance of the charge transport layer.

1 is a schematic view of an image forming apparatus on which an electrophotographic photosensitive member according to the present invention can be mounted. 1 is a cross-sectional configuration diagram of a color image forming apparatus on which an electrophotographic photoreceptor according to the present invention can be mounted.

Explanation of symbols

10Y, 10M, 10C, 10Bk Image forming unit 1Y, 1M, 1C, 1Bk Photoconductor 2Y, 2M, 2C, 2Bk Charging unit 3Y, 3M, 3C, 3Bk Exposure unit 4Y, 4M, 4C, 4Bk Developing unit

Claims (4)

An electrophotographic photosensitive member using a semiconductor laser having an oscillation wavelength of 390 to 500 nm or a light emitting diode having a peak wavelength of 390 to 500 nm as a writing light source,
The electrophotographic photoreceptor has a charge generation layer containing a condensed polycyclic compound and a charge transport layer containing a charge transport material, a binder and a plasticizer on at least a conductive support,
An electrophotographic photoreceptor, wherein the charge transport material is a compound represented by the following general formula (1), and the plasticizer is a benzotriazole compound or a triazine compound.

[In the formula, Ar ₁ , Ar ₂ , Ar ₃ and Ar ₄ each independently represent an aryl group which may have a substituent, and Ar ₁ and Ar ₂ , and Ar ₃ and Ar ₄ are bonded to each other. To form a ring. R ₁ and R ₂ each independently represents an alkyl group or an aryl group, and R ₁ and R ₂ may combine to form a ring. R ₃ and R ₄ each independently represents a hydrogen atom, an alkyl group or an aryl group. N and m each independently represents an integer of 1 to 4. ] 2. The electrophotographic photosensitive member according to claim 1, wherein a spectral transmittance of the charge transport layer is 70% or more and less than 100% at any wavelength of 390 to 500 nm. 3. Exposure means for forming an electrostatic latent image on an electrophotographic photosensitive member according to claim 1 or 2, using at least a writing light source of a semiconductor laser having an oscillation wavelength of 390 to 500 nm or a light emitting diode having a peak wavelength of 390 to 500 nm. An image forming apparatus having
An image forming apparatus, wherein an exposure spot diameter on the surface of the electrophotographic photosensitive member of the writing light source is 10 to 50 μm. The electrophotographic photosensitive member according to claim 1 or 2,
Charging means for charging the electrophotographic photosensitive member,
Exposure means for forming an electrostatic latent image on the electrophotographic photosensitive member;
Developing means for visualizing the electrostatic latent image formed on the electrophotographic photosensitive member to form a toner image;
Transfer means for transferring the toner image visualized by the developing means onto a transfer material;
At least one cleaning unit that removes toner remaining on the electrophotographic photosensitive member after being transferred by the transfer unit is integrally mounted, and is detachably mounted to the image forming apparatus main body. Process cartridge characterized by.

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