JP5375304B2 - Image forming method and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method and an image forming apparatus, forming an electrostatic latent image with high sensitivity and high density to a short-wavelength laser beam, and obtaining a toner image of high image quality. <P>SOLUTION: An organic photoreceptor includes a layer structure in which an intermediate layer, a charge generating layer and a charge transport layer are sequentially stacked on a conductive support. The spectral absorption strength (Ae&lambda;) of the charge generating layer at a wavelength (E&lambda;) of the laser beam is 0.20-0.65 times as large as the maximum spectral absorption strength (Amax) of spectral absorption spectrum at 350-600 nm of the charge generating layer. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an image forming method and an image forming apparatus capable of obtaining an electrophotographic image with high image quality by performing image exposure using a short wavelength light source.

  In recent years, there are increasing opportunities to use electrophotographic copying machines and printers in the fields of printing and color printing. In the fields of printing and color printing, there is a strong tendency to demand high-quality digital monochrome images or color images. In response to such a demand, it has been proposed to form a high-definition digital image using a short wavelength laser beam as an exposure light source (Patent Document 1). However, even if the short-wavelength laser light is used to narrow the exposure dot diameter and a fine electrostatic latent image is formed on the electrophotographic photosensitive member, the finally obtained electrophotographic image has sufficient high image quality. The current situation has not been achieved. One of the causes is that, when a conventional electrophotographic photosensitive member developed for a long wavelength is used, the electrophotographic characteristics such as sensitivity are not sufficiently satisfied with the short wavelength laser light.

  On the other hand, from this point of view, development technology for electrophotographic photosensitive members corresponding to short-wavelength laser light has been proposed. In such technology, an undercoat layer, a charge generation layer, and charge transport are formed on a conductive support. An organic photoreceptor using a condensed polycyclic pigment as a charge generation material as a charge generation material of a charge generation layer in an organic photoreceptor in which layers are sequentially laminated has been proposed (Patent Document 2).

  However, the actual condition is that the conditions for obtaining a high-quality digital image are not satisfied just by satisfying desired sensitivity and potential characteristics using a short wavelength laser.

  One of the causes is that when image exposure is performed at a wavelength at which the maximum sensitivity of the organic photoconductor is obtained with respect to exposure to the organic photoconductor containing titanium oxide or the like in the intermediate layer, the support of the organic photoconductor and Scattering of the exposure wavelength of the intermediate layer existing between the photosensitive layers is increased, and there is a problem that a digital electrostatic latent image is hardly formed clearly due to the influence of the scattered light.

JP 2000-250239 A JP 2000-47408 A

  The present invention has been made to solve the above problems. That is, it is an object to provide an image forming method and an image forming apparatus capable of forming a high-sensitivity and high-density electrostatic latent image with respect to a short wavelength laser beam and obtaining a high-quality toner image.

  As a result of intensive studies, the inventors of the present invention have achieved that the wavelength of the image exposure light source for forming a latent image on the organic photoreceptor is the same as that of the charge generation layer of the organic photoreceptor. By having a specific relationship with the spectral absorption spectrum, an electrostatic latent image can be clearly formed even on an organic photoreceptor containing scattering fine particles such as titanium oxide, and as a result, a high-quality toner image can be obtained. As a result, the present invention was achieved.

  That is, the present invention is achieved by using an image forming method having the following configuration.

1. A charged potential is applied to the organic photoreceptor, and the organic photoreceptor to which the charged potential is applied is subjected to image exposure using a laser beam having a wavelength in the range of 350 to 500 nm to form an electrostatic latent image, In the image forming method of developing the electrostatic latent image to form a toner image, the organic photoreceptor has a layer structure in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support, The spectral absorption intensity (Aeλ) of the charge generation layer at the wavelength (Eλ) of the laser beam is 0.20 times the maximum spectral absorption intensity (Amax) of the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer. ~ 0.65 times ,
The charge generation material of the charge generation layer is any of CGM-1, CGM-2, or CGM-4 shown below,
When the charge generation material is the CGM-1, the wavelength of the laser light is either 405 nm or 420 nm,
When the charge generation material is CGM-2, the wavelength of the laser light is either 405 nm, 420 nm, or 500 nm,
The image forming method according to claim 1 , wherein when the charge generation material is CGM-4, the wavelength of the laser beam is 405 nm .

  2. 2. The image forming method as described in 1 above, wherein the intermediate layer contains titanium oxide.

  3. 3. The image forming method according to 1 or 2, wherein the maximum spectral absorption intensity (Amax) is a maximum spectral absorption intensity.

  4). 4. An image forming apparatus using the image forming method according to any one of items 1 to 3.

  By using the image forming method of the present invention, it is possible to provide a high-quality electrophotographic image with high reproducibility of dot images and fine lines for image exposure with short wavelength laser light.

1 is a schematic view in which functions of an image forming apparatus of the present invention are incorporated. 1 is a cross-sectional configuration diagram of a color image forming apparatus showing an embodiment of the present invention. 1 is a cross-sectional view of a color image forming apparatus using an organic photoreceptor of the present invention. 2 is a diagram of a spectral absorption spectrum of a charge generation layer of the photoreceptor 1. FIG. 3 is a diagram of a spectral absorption spectrum of a charge generation layer of the photoreceptor 2. FIG. 3 is a diagram of a spectral absorption spectrum of a charge generation layer of the photoreceptor 3. FIG. 3 is a diagram of a spectral absorption spectrum of a charge generation layer of the photoreceptor 4. FIG.

  In the image forming method of the present invention, a charged potential is applied to an organic photoconductor, and image exposure is performed on the organic photoconductor provided with the charged potential using a laser beam having a wavelength in the range of 350 to 500 nm. In the image forming method of forming an electrostatic latent image and developing the electrostatic latent image to form a toner image, the organic photoreceptor is formed by sequentially laminating an intermediate layer, a charge generation layer, and a charge transport layer on a conductive support. The spectral absorption intensity (Aeλ) of the charge generation layer at the wavelength (Eλ) of the laser beam is the maximum spectral absorption intensity (Amax) of the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer. On the other hand, it is 0.20 times to 0.65 times.

  By using the image forming method, it is possible to provide a high-quality electrophotographic image with high reproducibility of dot images and fine lines with respect to image exposure with a short wavelength laser beam.

  The present invention uses laser light having an oscillation wavelength in the range of 350 to 500 nm as exposure light, forms a high-density electrostatic latent image on an organic photoreceptor, and visualizes the electrostatic latent image as a toner image. The present invention relates to an image forming method for obtaining an electrophotographic image.

  The wavelength of the laser beam of the present invention has an oscillation wavelength in the range of 350 to 500 nm. Since such a laser beam having a shorter wavelength than the conventional one can narrow the irradiation spot smaller, High density dots can be written by image exposure on an organic photoreceptor using laser light in the wavelength range of the invention.

  However, even if high-density dots are written, if the latent image formed on the surface of the organophotoreceptor does not faithfully reproduce the shape and size of the irradiation spot, the desired high-quality image can be obtained. Absent. Naturally, image quality degradation also occurs in the subsequent development process, transfer process, and fixing process, but latent image formation, which is an initial stage, is an important factor for achieving high image quality.

  Therefore, as a result of intensive studies by the inventors, in order to obtain a high-quality image with high reproducibility of dot images and fine lines, the structure of the photoreceptor is an organic layer in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated. The spectral absorption intensity (Aeλ) of the charge generation layer at the wavelength (Eλ) of the laser beam is 0 with respect to the maximum spectral absorption intensity (Amax) of the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer. It has been found that this can be achieved by increasing the magnification 20 times to 0.65 times.

  The reason why the above configuration is effective for obtaining high image quality is presumed to be as follows.

  When the wavelength with the maximum spectral sensitivity of the photoconductor is matched with the wavelength of the laser beam, a dot latent image is easily formed by laser exposure, but the laser scattered light that is scattered and reflected from the intermediate layer of the photoconductor The dot latent image is easily blurred by the scattered light. As a result, the clearness of the dot image as the toner image deteriorates. In order to prevent such a phenomenon, in order to reduce the influence of the scattered light while sufficiently maintaining the sensitivity of the photosensitive member with respect to the laser beam, the spectral absorption intensity of the photosensitive member corresponding to the wavelength of the laser beam is set according to the present invention. It is presumed that it became necessary to configure.

  By taking the maximum spectral absorption intensity (Amax) in the wavelength range of 350 to 600 nm as a reference in the spectral absorption spectrum distribution of the charge generation layer, it is possible to sufficiently ensure the sensitivity of the photoreceptor when using the exposure wavelength of the present invention. it can.

  Further, the spectral absorption intensity (Aeλ) of the charge generation layer at the wavelength (Eλ) of the laser light is 0.20 times the maximum spectral absorption intensity (Amax) of the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer. By setting it to ˜0.65 times, it is possible to ensure sufficient sensitivity, prevent the dot latent image from being enlarged by scattered light, and form a latent image faithful to the exposure pattern. Most preferably, it is 0.35-0.65. If it is less than 0.20, the sensitivity may be insufficient and the image density and contrast may be low, which may be a problem. If it is larger than 0.65, the dot latent image tends to be blurred, and the target image quality may not be obtained.

  Here, a measurement method and the like of the spectral absorption spectrum of 350 to 600 nm of the charge generation layer will be described.

  A sample for measuring the spectral absorption spectrum of the charge generation layer is prepared by coating and drying a charge generation layer, which will be described later, on a quartz plate with the same film thickness as the charge generation layer of each photoconductor.

  The measurement sample prepared above was measured with an ultraviolet-visible spectrophotometer V-530 (manufactured by JASCO Corporation) (scanning speed 1000 nm / min), and the maximum spectroscopic spectrum was obtained from the spectral absorption spectrum distribution chart of the measurement result. The absorption intensity (Amax) (the value of the maximum absorption intensity), the spectral absorption intensity corresponding to the wavelength (Eλ) of the laser beam (the value of the absorption intensity corresponding to Eλ), and the like are read.

  In the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer, the maximum spectral absorption intensity (Amax) is the absorption value at the position of * in FIGS. 4 to 7.

  The maximum spectral absorption intensity means the intensity of a peak existing in the wavelength range.

  Next, the structure of the organic photoreceptor according to the present invention will be described.

  In the present invention, the organic photoconductor means an electrophotographic photoconductor constituted by providing an organic compound with at least one of a charge generation function and a charge transport function essential to 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 photosensitive layer of the organic photoreceptor of the present invention has a configuration in which at least an intermediate layer, a charge generation layer and a charge transport layer are sequentially laminated on a conductive support.

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 range of straightness and shake 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 Ωcm 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 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 semiconductive 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.

As the N-type semiconductor particles, titanium oxide (TiO ₂ ) and zinc oxide (ZnO) are preferable, and titanium oxide is particularly preferably used.

  As the N-type semiconductor particles, fine particles having a number average primary particle size in the range of 3.0 to 200 nm are used. Particularly, 5 nm to 100 nm is preferable. The number average primary particle diameter is a measured value as an average diameter in the ferret direction by observing 100 particles as primary particles at random by magnifying the fine particles 10,000 times by transmission electron microscope observation and image analysis. N-type semiconducting particles having a number average primary particle size of less than 3.0 nm are difficult to uniformly disperse in the intermediate layer binder, and easily form aggregated particles. Is likely to occur. On the other hand, N-type semiconducting particles having a number average primary particle size larger than 200 nm tend to make large irregularities on the surface of the intermediate layer, and the dot image tends to deteriorate through these large irregularities. In addition, the N-type semiconductive particles having a number average primary particle size larger than 200 nm are likely to precipitate in the dispersion and easily generate aggregates. As a result, the dot image tends to deteriorate.

  The titanium oxide particles include anatase type, rutile type, brookite type, and amorphous type as crystal types. Among them, the rutile type titanium oxide pigment or the anatase type titanium oxide pigment has a rectifying property of charge passing through the intermediate layer. In other words, the mobility of electrons is increased, the charging potential is stabilized, the residual potential is prevented from increasing, and the dot image is prevented from deteriorating, which is most preferable as the N-type semiconductor particles of the present invention. .

  N-type semiconductive particles are preferably surface-treated with a silane coupling agent or a reactive organosilicon compound represented by the following formula.

(R) _n -Si- (X) _4-n
(In the above formula, Si represents a silicon atom, R represents an organic group in which carbon is directly bonded to the silicon atom, X represents a hydrolyzable group, and n represents an integer of 0 to 3).
In the organosilicon compound represented by the above formula, the organic group in which carbon is directly bonded to the silicon represented by R includes alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl and dodecyl, phenyl , Aryl groups such as tolyl, naphthyl and biphenyl, epoxy-containing groups such as γ-glycidoxypropyl and β- (3,4-epoxycyclohexyl) ethyl, γ-acryloxypropyl and γ-methacryloxypropyl ( (Meth) acryloyl group, hydroxyl group such as γ-hydroxypropyl, 2,3-dihydroxypropyloxypropyl, vinyl group such as vinyl and propenyl, mercapto group such as γ-mercaptopropyl, γ-aminopropyl, N-β Amino-containing groups such as (aminoethyl) -γ-aminopropyl, γ-chloropropyl, 1,1, - trifluoropropyl, nonafluorohexyl, halogen-containing groups such as perfluorooctylethyl, other nitro, and cyano-substituted alkyl group. Examples of the hydrolyzable group for X include alkoxy groups such as methoxy and ethoxy, halogen groups, and acyloxy groups.

  Moreover, the organosilicon compound represented by the above formula may be used alone or in combination of two or more.

  Further, in the case of a specific compound of an organosilicon compound represented by the above formula and n is 2 or more, a plurality of R may be the same or different. Similarly, when n is 2 or less, the plurality of Xs may be the same or different. Moreover, when using 2 or more types of organosilicon compounds represented by the above formula, R and X may be the same or different between the respective compounds.

  The intermediate layer coating solution prepared for forming the intermediate layer used in the present invention is composed of a binder resin, a dispersion solvent and the like in addition to the N-type semiconductive particles such as the surface-treated titanium oxide.

  The ratio of the N-type semiconductive particles in the intermediate layer is preferably 0.5 to 2.0 times in terms of the volume ratio of the intermediate layer to the binder resin (when the volume of the binder resin is 1). By using the N-type semiconducting particles of the present invention at such a high density in the intermediate layer, the rectification of the intermediate layer is enhanced, and the increase in residual potential and dot image degradation are effective even when the film thickness is increased. Therefore, a good organic photoreceptor can be formed. Further, such an intermediate layer preferably uses 100 to 200 parts by volume of N-type semiconductive particles with respect to 100 parts by volume of the binder resin.

  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.

  The binder resin for the intermediate layer is preferably an alcohol-soluble polyamide resin. As the binder resin for the intermediate layer of the organic photoreceptor, a resin having excellent solvent solubility is required in order to form the intermediate layer with a uniform film thickness. As such alcohol-soluble polyamide resins, copolymerized polyamide resins and methoxymethylated polyamide resins composed of a chemical structure with few carbon chains between amide bonds such as 6-nylon described above are known. In addition, the following polyamides can also be preferably used.

  The molecular weight of the polyamide resin is preferably 5,000 to 80,000, more preferably 10,000 to 60,000 in terms of number average molecular weight. When the number average molecular weight is 5,000 or less, the uniformity of the film thickness of the intermediate layer is deteriorated, and the effects of the present invention are not sufficiently exhibited. On the other hand, if it is larger than 80,000, the solvent solubility of the resin is likely to be reduced, and an agglomerated resin is likely to be generated in the intermediate layer.

  A part of the polyamide resin is already commercially available. For example, the polyamide resin is sold under the trade name such as Vestamelt X1010, X4585 manufactured by Daicel Degussa Co., Ltd., and can be produced by a general synthesis method of polyamide.

  The thickness of the intermediate layer of the present invention is preferably 0.3 to 10 μm. If the thickness of the intermediate layer is less than 0.5 μm, black spots or the like are likely to occur, and the dot image is likely to deteriorate. If it exceeds 10 μm, the residual potential is likely to increase, and the dot image tends to deteriorate. As for the film thickness of an intermediate | middle layer, 0.5-5 micrometers is more preferable.

Photosensitive layer The photosensitive layer of the photoreceptor of the present invention preferably has a structure in which a charge generation layer (CGL) and a charge transport layer (CTL) are separated on the intermediate layer. 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 is described below.

Charge Generation Layer The charge generation layer used in the present invention preferably contains a charge generation material and a binder resin, and is formed by dispersing and coating the charge generation material in a binder resin solution.

  As the charge generation material used in the present invention, it is preferable to use a charge transport material having high spectral absorption intensity at any wavelength in the range of 340 to 600 nm, that is, high sensitivity. Examples of such a charge generating substance include condensed polycyclic compounds, among which pyranthrone pigments and condensed polycyclic quinone pigments can be selected.

  As the binder resin of the charge generation layer, a known resin 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 resins, phenol resins, polyester resins, alkyd resins, polycarbonate resins, silicone resins, melamine resins, and copolymer resins containing two or more of these resins (eg, vinyl chloride-vinyl acetate copolymer resins, chlorides) Vinyl-vinyl acetate-vinyl alcohol copolymer resin) and poly-vinyl carbazole resin, but are not limited thereto.

  The charge generation layer is formed 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 applying the coating solution to a certain film thickness using a coating device. It is preferable to prepare the film by drying.

  As a means for dispersing the charge generating material, 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 1 to 600 parts by weight, more preferably 50 to 500 parts by weight based on 100 parts by weight 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. The pigment can also be formed by vacuum deposition.

Charge Transport Layer The charge transport layer contains a charge transport material (CTM) and a binder resin that forms a film by dispersing CTM. Other substances may contain additives such as inorganic fine particles and antioxidants as necessary.

  As the charge transport material (CTM), a known charge generation material can be used. However, in the present invention, it is preferable to use a charge transport material having good permeability to a short wavelength laser beam or the like. A charge transport material having good permeability to a short wavelength laser beam or the like is preferable, and a charge transport material such as the following compound is preferably used. Since the charge transport material has no absorption in the wavelength region of 350 to 500 nm, the charge transport material reaches the charge generation layer without blocking the exposure light of image exposure in the wavelength region of 350 to 500 nm, and in the charge transport layer, There is no generation of charge traps due to light exposure, and hole carriers from the charge generation layer can be efficiently transported to the surface of the photoreceptor.

  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 thickness of the charge transport layer is preferably 10 to 35 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 and the dot reproducibility are liable to be deteriorated. Diffusion of charge carriers generated in the generation layer) increases, and dot reproducibility tends to deteriorate. Further, when the charge transport layer is formed of a plurality of layers, the thickness of the charge transport layer serving as the surface layer is preferably 1.0 to 8.0 μm.

  Solvents or dispersion media used to form layers such as intermediate layers, charge generation layers, and charge transport layers include n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethylformamide, acetone , Methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, cyclohexanone, benzene, toluene, xylene, chloroform, dichloromethane, 1,2-dichloroethane, 1,2-dichloropropane, 1,1,2-trichloroethane, 1,1,1- Trichloroethane, trichlorethylene, tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, t-butyl acetate, dimethyl Rusuruhokishido, and methyl cellosolve. Although this invention is not limited to these, Solvents friendly to global environment, such as tetrahydrofuran and methyl ethyl ketone, are used preferably. These solvents may be used alone or as a mixed solvent of two or more.

  Next, as a coating processing method for producing the organic photoreceptor, a coating processing method such as dip coating or spray coating is used in addition to the slide hopper type coating device.

  Among the above coating liquid supply type coating apparatuses, the coating method using a slide hopper type coating apparatus is most suitable when the above-described dispersion using a low boiling point solvent is used as the coating liquid, and is a cylindrical photoconductor. In this case, the coating is preferably performed using a circular slide hopper type coating apparatus described in detail in JP-A No. 58-189061 and the like.

  The surface layer of the photoreceptor according to the present invention preferably contains an antioxidant. The surface layer is easily oxidized by an active gas such as NOx or ozone during charging of the photoconductor, and image blur is likely to occur. However, the presence of an antioxidant can prevent image blur. Typical examples of the antioxidants are those that prevent the action of oxygen under conditions of light, heat, discharge, etc. on auto-oxidizing substances present in the organic photoreceptor or on the surface of the organic photoreceptor, It is a substance that has the property of inhibiting.

  Next, an image forming apparatus using the organic photoreceptor 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 material conveying unit D as a transfer material conveying 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 including the illumination lamp and the first mirror constituting the scanning optical system, and the V-shaped first image is located. Reading is performed by the movement of the second mirror unit 16 including 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 discharging means (light discharging process) PCL (precharge lamps) 27 are 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, an image based on an image signal called from the memory of the image processing unit B by an exposure optical system as an image exposure unit (image exposure step) 30 is used. Exposure is performed. The exposure optical system as the image exposure means 30 as the writing means uses a laser diode (not shown) as a light source, and the optical path is bent by the reflection mirror 32 via the rotating polygon mirror 31, the fθ lens 34, and the cylindrical lens 35, and main scanning is performed. Therefore, 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, when forming an electrostatic latent image on a photoreceptor, a semiconductor laser or light emitting diode having an oscillation wavelength of 350 to 500 nm is used as an image exposure light source. Using these image exposure light sources, the exposure dot diameter in the writing direction is narrowed down to 10 to 50 μm, and digital exposure is performed on the organic photoreceptor, so that it is 600 dpi (dpi: the number of dots per 2.54 cm) or more. A high-resolution electrophotographic image of 2500 dpi can be obtained.

The exposure dot diameter refers to the length of the exposure beam along the main scanning direction (Ld: measured at the maximum length) in a region where the intensity of the exposure beam is 1 / e ² or more of the peak intensity.

The light beams used have a scanning optical system and LED solid scanner such as a semiconductor laser, there is a Gaussian distribution and Lorentz distribution, etc. also the light intensity distribution is in each 1 / e ² or more regions of peak intensity The exposure dot 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.

<toner>
The electrostatic latent image formed on the organic photoreceptor of the present invention is visualized as a toner image by development. The toner used for development may be a pulverized toner or a polymerized toner, but the toner according to the present invention is preferably a polymerized toner that can be prepared by a polymerization method from the viewpoint of obtaining a stable particle size distribution.

  The term “polymerized toner” means a toner in which a toner binder resin is formed and the toner shape is formed by polymerization of a raw material monomer of the binder resin and, if necessary, subsequent chemical treatment. More specifically, it means a toner formed through a polymerization reaction such as suspension polymerization or emulsion polymerization, and if necessary, a step of fusing particles between them.

  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.

<Developer>
The toner according to the present invention may be used as a one-component developer or 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.

  Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials such as metals such as iron, ferrite and magnetite, and alloys of these metals with metals such as aluminum and lead can be used as the magnetic particles of the carrier. 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, or fluorine-containing polymer resin 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.

  In the transfer material transport unit D, paper feed units 41 (A), 41 (B), and 41 (C) are provided below the image forming unit as transfer material storage means in which transfer materials P of different sizes are stored. Further, a manual paper feeding unit 42 for manually feeding paper is provided on the side, and the transfer material P selected from any of them is fed along the transport path 40 by the guide roller 43 and fed. The transfer material P is temporarily stopped by a pair of paper feed registration rollers 44 that correct the inclination and bias of the transfer material P, and then re-feeded. The transport path 40, the pre-transfer roller 43a, and the paper feed path 46 are transferred. The toner image on the photosensitive member 21 is transferred onto the transfer material P by the transfer electrode 24, the separation electrode 25, the nail separation means 250, and the like at the transfer position Bo, and the transfer material P is also photosensitive. Separated from the body, After the transfer material P is placed conveyed to the transfer conveying belt 454 of the transfer conveyor belt device 45, 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 material P between the fixing roller 51 and the pressure roller 52, the toner is fixed by heating and pressing. After the toner image is fixed, the transfer material P is discharged onto the paper discharge tray 64.

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

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

  The transfer material P moves a conveyance guide 131 provided in the duplex copying paper supply unit 130 in the paper supply direction, refeeds the transfer material P by the paper supply roller 132, and guides the transfer material P to the conveyance path 40. .

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

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge, and this unit is configured to be detachable from the apparatus main body. Also good. In addition, a process cartridge is formed by integrally supporting at least one of a charger, an image exposure device, a developing device, a transfer or separation device, and a cleaning device together with a photosensitive member, and a single unit that is detachable from the apparatus main body. It is good also as a structure which can be attached or detached using guide means, such as a rail of an 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. It comprises a paper conveying means 21 and a fixing means 24. 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. A unit (developing step) 4Y, a primary transfer roller 5Y as a primary transfer unit (primary transfer step), and a cleaning unit 6Y. An image forming unit 10M that forms a magenta image includes a drum-shaped photosensitive member 1M as a first image carrier, a charging unit 2M, an exposure unit 3M, a developing unit 4M, a primary transfer roller 5M as a primary transfer unit, It has a cleaning means 6M. An image forming unit 10C for forming a cyan image includes a drum-shaped photoreceptor 1C as a first image carrier, a charging unit 2C, an exposure unit 3C, a developing unit 4C, and a primary transfer roller 5C as a primary transfer unit. It has cleaning means 6C. The 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, a primary transfer roller 5Bk as a primary transfer unit, and a cleaning unit. 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 and 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 this 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 an LED 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 laser optical system or the like is used.

  The image forming apparatus of the present invention is configured by integrally combining the above-described photosensitive member and components such as a developing device and a cleaning device as a process cartridge (image forming unit), and this image forming unit is connected to the apparatus main body. It may be configured to be detachable. In addition, at least one of a charging device, an image exposure device, a developing device, a transfer or separation device, and a cleaning device is integrally supported together with a photosensitive member to form a process cartridge (image forming unit), which is detachable from the apparatus main body. A single image forming unit may be detachable using guide means such as a rail of the apparatus main body.

  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 sequentially transferred onto a rotating endless belt-shaped intermediate transfer body 70 by primary transfer rollers 5Y, 5M, 5C, and 5Bk as primary transfer means. Thus, a synthesized color image is formed. 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 rollers 22A, 22B, 22C, 22D and registration roller 23, they are conveyed to a secondary transfer roller 5b as a secondary transfer means, and are secondarily transferred onto a transfer material P to transfer a color image all at once. 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, after the color image is transferred to the transfer material P by the secondary transfer roller 5b as the secondary transfer means, the residual toner is removed by the cleaning means 6b from the endless belt-shaped intermediate transfer body 70 in which the transfer material P is separated by curvature. 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, respectively, 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.

  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. Consists of.

  Next, FIG. 3 shows a color image forming apparatus using the organic photoreceptor of the present invention (a copying machine having at least a charging means, an exposure means, a plurality of developing means, a transfer means, a cleaning means, and an intermediate transfer body around the organic photoreceptor. 1 is a cross-sectional view of a configuration of a laser beam printer). The belt-shaped intermediate transfer body 70 uses an elastic body having a medium resistance.

  Reference numeral 1 denotes a rotary drum type photoconductor that is repeatedly used as an image forming body, and is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed.

  In the rotation process, the photoreceptor 1 is uniformly charged to a predetermined polarity and potential by a charging means (charging process) 2, and then time-series electric digital of image information by an image exposure means (image exposure process) 3 (not shown). An electrostatic latent image corresponding to a yellow (Y) color component image (color information) of a target color image is formed by receiving image exposure by scanning exposure light or the like by a laser beam modulated in accordance with a pixel signal. The

  Then, the electrostatic latent image is developed with yellow toner as the first color by yellow (Y) developing means: developing step (yellow color developing device) 4Y. At this time, the second to fourth developing means (magenta developer, cyan developer, black developer) 4M, 4C, and 4Bk are turned off and do not act on the photosensitive member 1. The first color yellow toner image is not affected by the second to fourth developing units.

  The intermediate transfer member 70 is stretched by rollers 79a, 79b, 79c, 79d, and 79e, and is driven to rotate in the clockwise direction at the same peripheral speed as the photosensitive member 1.

  The first color yellow toner image formed and supported on the photosensitive member 1 is applied to the intermediate transfer member 70 from the primary transfer roller 5a in the process of passing through the nip portion between the photosensitive member 1 and the intermediate transfer member 70. The intermediate transfer (primary transfer) is sequentially performed on the outer peripheral surface of the intermediate transfer body 70 by the electric field formed by the primary transfer bias.

  The surface of the photoreceptor 1 after the transfer of the first color yellow toner image corresponding to the intermediate transfer body 70 is cleaned by the cleaning device 6a.

  Similarly, the second color magenta toner image, the third color cyan toner image, and the fourth color black (black) toner image are sequentially superimposed and transferred onto the intermediate transfer body 70 to correspond to the target color image. A superimposed color toner image is formed.

  The secondary transfer roller 5b is supported in parallel with the secondary transfer counter roller 79b so as to be separated from the lower surface of the intermediate transfer body 70.

  The primary transfer bias for sequentially superimposing and transferring the first to fourth color toner images from the photosensitive member 1 to the intermediate transfer member 70 has a polarity opposite to that of the toner and is applied from a bias power source. The applied voltage is, for example, in the range of +100 V to +2 kV.

  In the primary transfer process of the first to third color toner images from the photosensitive member 1 to the intermediate transfer member 70, the secondary transfer roller 5b and the intermediate transfer member cleaning means 6b can be separated from the intermediate transfer member 70. is there.

  When the superimposed color toner image transferred onto the belt-shaped intermediate transfer member 70 is transferred to the transfer material P, which is the second image carrier, the secondary transfer roller 5b is brought into contact with the belt of the intermediate transfer member 70. At the same time, the transfer material P is fed from the pair of paper registration rollers 23 through the transfer material guide to the belt of the intermediate transfer body 70 to the contact nip with the secondary transfer roller 5b at a predetermined timing. A secondary transfer bias is applied to the secondary transfer roller 5b from a bias power source. By this secondary transfer bias, the superimposed color toner image is transferred (secondary transfer) from the intermediate transfer body 70 to the transfer material P as the second image carrier. The transfer material P that has received the transfer of the toner image is introduced into the fixing means 24 and heated and fixed.

  The image forming apparatus of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, and further displays, recordings, light printing, plate making, and facsimiles using electrophotographic technology. The present invention can be widely applied to such devices.

  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.

Production of Photoreceptor 1 Photoreceptor 1 was produced according to the following procedure.

  First, the surface of the cylindrical aluminum support was cut to prepare a conductive support having a ten-point average surface roughness Rz = 0.6 (μm).

(1) Preparation of intermediate layer Polyamide resin: CM8000 (manufactured by Toray Industries, Inc.) 10 parts Titanium oxide: SMT500SAS (manufactured by Teika) 30 parts Methanol 100 parts The above composition was dispersed using a sand mill for 12 hours to prepare a dispersion. . This dispersion was diluted with methanol, which is the same solvent as the dispersion having the above composition, and allowed to stand overnight, followed by filtration using a rigesh mesh 5 μm filter manufactured by Nippon Pole, 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.

(2) Preparation of charge generation layer Charge generation material (CGM): CGM-1 compound having the following structure 3 parts Binder resin: Vinyl chloride-vinyl acetate-vinyl alcohol copolymer resin (n1: n2: n3 (mol%)) 93: 2: 5) 1 part 2-butanone / cyclohexanone (volume ratio 4/1) mixed solution 70 parts The above composition is mixed, and a sand mill is used so that the average particle diameter of the charge generation material is 100 nm to 300 nm. A dispersion treatment was performed for 15 hours 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 0.5 μm to form a charge generation layer.

(3) Preparation of charge transport layer Charge transport material (exemplary compound (CTM-1)) 2 parts Binder: Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Company) 2.7 parts Ultraviolet absorber (TinvinP (manufactured by Ciba Japan)) 0.1 part Antioxidant (Irganox 1010 (Ciba Japan)) 0.1 part Tetrahydrofuran / toluene (volume ratio 4/1) mixed solution 30 parts Silicone oil (KF-96 (Shin-Etsu Silicone Co., Ltd.)) 0.005 part The above composition was mixed and stirred to prepare a charge transport layer coating solution. This coating solution was applied on the charge generation layer by a dip coating method so as to have a dry film thickness of 23 μm, followed by drying at 120 ° C. for 70 minutes to form a charge transport layer. In this manner, the photoreceptor 1 was produced.

Production of photoconductors 2 to 4 Photoconductors 2 to 4 were produced in the same manner as the photoconductor 1 except that the charge generation material (CGM) of the charge generation layer was changed to the following CGM-2, CGM-3, and CGM-4. Was made.

  As the oxo titanyl phthalocyanine of CGM-4, a pigment of a Y-type crystal (showing a maximum diffraction peak at 27.3 ° in an X-ray diffraction spectrum) was used.

  The charts of the spectral absorption spectra of the charge generation layers using these CGM-1, CGM-2, CGM-3, and CGM-4 are shown in FIGS. 4 to 7 (in the figure, the mark * indicates the maximum spectral absorption intensity (Amax). )

  In addition, the charge generation layer coating solution used for the preparation of the photoreceptors 1 to 4 was applied on a quartz plate with a dry film thickness of 0.5 μm to prepare Samples 1 to 4 for spectral absorption spectrum measurement.

  4 to 7 show charts of spectral absorption spectra measured using the samples 1 to 4 for measuring the spectral absorption spectrum.

  Combinations of these photoreceptors 1 to 4 and short-wave laser light were prepared as shown in Table 1 below.

(Evaluation 1)
The photoreceptor obtained as described above is basically mounted on a commercially available full-color multifunction device bizhub PRO C6500 (manufactured by Konica Minolta Business Technologies, Inc.) having the configuration shown in FIG. A short wavelength laser light source of 405 nm was used as the exposure light source, the exposure diameter in the main direction of the writing light source was 30 μm and 1200 dpi, and the spot exposure with the exposure diameter was set to 0.5 mW on the surface of the photoreceptor. Since the full-color multifunction peripheral has four image forming units, the photosensitive members of each image forming unit are the same type of photosensitive member (for example, in the case of the photosensitive member 1, four photosensitive members 1 are provided. Prepared) and unified and evaluated. Each evaluation was performed under an environment of 20 ° C. and 60% RH after an image printing test of 50,000 sheets of A4 paper on an A4 paper under conditions of 30 ° C. and 80% RH.

Evaluation items and evaluation criteria Dot image reproducibility (evaluated with black and white image)
Evaluation criteria Evaluation of 1-dot line A 1-dot line and a solid black image were prepared on a white A4 paper sheet, and evaluated according to the following criteria.

◎: 1 dot line is reproduced continuously, and the image density of solid black is 1.2 or more (good)
○: 1 dot line is reproduced continuously, but the image density of solid black is less than 1.2
1.0 or more (no problem in practicality)
×: Even if one dot line is cut and reproduced, or one dot line is reproduced continuously, the image density of black solid is less than 1.0 (problem is problematic)
Evaluation of 2-dot line A 2-dot white line was produced in a solid black image and evaluated according to the following criteria.

A: A white line of 2 dot lines is reproduced continuously, and the image density of solid black is 1.2 or higher (good)
○: The white line of 2 dot lines is reproduced continuously, but the image density of black solid is 1.2.
Less than -1.0 or more (no problem in practical use)
X: The white line of the 2-dot line is cut and reproduced, or the white line of the 2-dot line is reproduced continuously, but the black solid image density is less than 1.0 (there is a problem in practical use)
The above-mentioned solid image density is measured using RD-918 manufactured by Macbeth. The relative reflection density was measured with the paper reflection density set to “0”.

<Evaluation of color image>
Four sets of image forming units of the full color multifunction machine bizhub PRO C6500 dot diameter variable remodeling machine were operated, halftone images including human face photographs were printed on A4 paper, and evaluated according to the following criteria.

A: Halftone color image is smoothly reproduced, and no noticeable disturbance such as image blur is found (good)
○: Image blurring occurs partially, but halftone color image is reproduced smoothly (no problem in practical use)
×: Image blurring occurs on the entire surface of a halftone color image (practically problematic)

  From Table 2, the combination No. of the image forming method in the present invention is shown. Nos. 1, 2, 4, 6, 9, and 10 show good evaluation results in any of the evaluation items. 3, 5, 7, and 8 are evaluation items, and indicate evaluations that are not sufficiently practical.

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)

A charged potential is applied to the organic photoreceptor, and the organic photoreceptor to which the charged potential is applied is subjected to image exposure using a laser beam having a wavelength in the range of 350 to 500 nm to form an electrostatic latent image, In the image forming method of developing the electrostatic latent image to form a toner image, the organic photoreceptor has a layer structure in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support, The spectral absorption intensity (Aeλ) of the charge generation layer at the wavelength (Eλ) of the laser beam is 0.20 times the maximum spectral absorption intensity (Amax) of the spectral absorption spectrum distribution of 350 to 600 nm of the charge generation layer. ~ 0.65 times ,
The charge generation material of the charge generation layer is any of CGM-1, CGM-2, or CGM-4 shown below,
When the charge generation material is the CGM-1, the wavelength of the laser light is either 405 nm or 420 nm,
When the charge generation material is CGM-2, the wavelength of the laser light is either 405 nm, 420 nm, or 500 nm,
The image forming method according to claim 1 , wherein when the charge generation material is CGM-4, the wavelength of the laser beam is 405 nm .

  The image forming method according to claim 1, wherein the intermediate layer contains titanium oxide.   The image forming method according to claim 1, wherein the maximum spectral absorption intensity (Amax) is a maximum spectral absorption intensity.   An image forming apparatus using the image forming method according to claim 1.

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