JP2010102166A - Electrophotographic photoreceptor, image forming method, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which has high sensitivity and high potential stability to write light and with which a clear electrophotographic image with high resolution is stably obtained, and an image forming method and an image forming apparatus using the electrophotographic photoreceptor. <P>SOLUTION: The electrophotographic photoreceptor includes a charge generating layer and a charge transport layer in this order on a conductive support, wherein the charge generating layer contains a condensed polycyclic pigment and a resin including a repeating structure represented by general formula (1), the resin having a molecular weight component in each of a range of 5,000-50,000 and a range of 100,000-200,000 and having a molecular weight distribution index (weight average molecular weight Mw/number average molecular weight Mn) of 7-25. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

  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, a high-definition digital image forming apparatus and a corresponding electrophotographic photoreceptor sensitive to short waves have been proposed by using a short wavelength laser as an exposure light source ( For example, see Patent Document 1 and Patent Document 2).

  Condensed polycyclic pigments are known as charge generating substances having sensitivity in the short wave region. However, condensed polycyclic compounds have a problem of low affinity with binders and difficulty in uniform dispersion.

  Further, in order to improve the dispersibility, when the ratio of the binder to the pigment is increased, the electric characteristics tend to be extremely deteriorated, so that it is difficult to achieve both the electric characteristics and the dispersibility. Further, the coating film in a state where the dispersion liquid is low has a problem that the image quality is deteriorated due to insufficient sharpness at the time of latent image formation upon exposure.

As described above, high definition by short wave exposure does not provide performance that is sufficiently satisfactory in both sensitivity and image quality.
JP 2000-250239 A JP 2006-126246 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrophotographic photosensitive member that has high sensitivity, high potential stability against writing light, and can stably obtain a clear electrophotographic image with high resolution. Is to provide. Another object of the present invention is to provide an image forming method and an image forming apparatus using the electrophotographic photosensitive member.

The above object of the present invention can be achieved by the following configuration.
(1)
An electrophotographic photosensitive member having at least a charge generation layer and a charge transport layer on a conductive support, wherein the charge generation layer and the charge transport layer are arranged on the conductive support in the order of a charge generation layer and a charge transport layer. The charge generation layer contains a condensed polycyclic pigment and a resin having a repeating structure represented by the following general formula (1);

[Wherein R represents an alkyl group having 1 to 6 carbon atoms. l, m, and n represent the molar ratio of each unit structure. If 1 + m + n = 100, then 15 ≦ l ≦ 40 and m ≦ 12. ]
When the resin having the repeating structure represented by the general formula (1) is subjected to molecular weight measurement by gel permeation chromatography, the molecular weight is in each of the region of 5,000 to 50,000 and the region of 100,000 to 200,000. An electrophotographic photosensitive member having a component, wherein the resin has a molecular weight distribution index (weight average molecular weight Mw / number average molecular weight Mn) of 7 or more and 25 or less.
(2)
The molecular weight distribution measured by gel permeation chromatography of the resin represented by the general formula (1) has at least one peak in each of the region of 10,000 to 30,000 and 80,000 to 150,000. The electrophotographic photosensitive member according to item (1), wherein
(3)
The electrophotographic photosensitive member according to any one of (1) and (2), wherein the condensed polycyclic pigment is a compound of the following general formula (2).

(In the formula, X represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, a nitro group, a cyano group, an acyl group, or a carboxyl group, and n represents an integer of 0 to 6. Here, n is 2 to 6. And each X may be the same or different, provided that X is substituted at any substitutable position of the compound.)
(4)
At least a step of forming a latent image on the surface of the electrophotographic photosensitive member according to the item (1) using exposure light having a wavelength of 390 nm or more and 500 nm or less and a dot diameter in the principal direction of 10 μm or more and 50 μm or less; A developing step of developing the latent image formed on the surface of the body using toner, a transfer step of transferring the toner image formed on the surface of the electrophotographic photosensitive member onto a transfer material or a transfer medium, A fixing step of fixing the toner image transferred onto the transfer material;
An image forming method characterized in that image formation is performed through the process.
(5)
At least the electrophotographic photoreceptor according to item (1) and exposure light having a wavelength of 390 nm to 500 nm and a dot diameter in the principal direction of 10 μm to 50 μm are formed, and the exposure light is applied to the surface of the electrophotographic photoreceptor An exposure unit that exposes the toner, a developing unit that supplies toner to the surface of the electrophotographic photosensitive member on which a latent image has been formed by the exposing unit, and a toner image that is formed on the surface of the electrophotographic photosensitive member by the developing unit. Transfer means for transferring the toner image formed,
An image forming apparatus comprising: a fixing unit configured to fix a toner image transferred onto a transfer material after being transferred by the transfer unit.

  EFFECT OF THE INVENTION According to the present invention, an electrophotographic photosensitive member capable of stably obtaining a clear electrophotographic image having high sensitivity, high potential stability to writing light, and high resolution, and an image forming method and an image using the electrophotographic photosensitive member A forming device could be provided.

  As a result of extensive studies, the present inventors have used a condensed polycyclic pigment as a charge generation material, and a resin having a repeating structure of the above general formula (1) and having a specific molecular weight distribution as a binder. It has been found that the problem of the present invention is solved by an electrophotographic photosensitive member having a charge generating layer.

  The reason why the problem of the present invention has been solved by the electrophotographic photosensitive member having the charge generation layer as described above is considered as follows. That is, the resin having the repeating unit represented by the general formula (1) has a plurality of molecular weight distributions, so that the low molecular weight component is coated with the charge generation material, so that the dispersibility is increased and a uniform charge generation layer can be formed Therefore, an image with high sharpness can be formed.

  Furthermore, since the high molecular weight component imparts film strength, the physical stability of the charge generation layer during repeated use can be improved while maintaining good dispersibility even at a high PB ratio. it is conceivable that.

  These effects are particularly preferable when a condensed polycyclic pigment is used, and further, when used for dispersing a pyranthrone pigment, the dispersibility is remarkably high and more preferable.

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

Charge Generation Layer The electrophotographic photoreceptor of the present invention is characterized by containing a condensed polycyclic pigment. As such a charge generating substance, perylene pigments represented by the following general formulas (2) to (8), polycyclic quinone pigments, and the like are preferably used. Furthermore, preferred are the compounds of the following general formulas (6) to (8), and more preferred are the compounds of the general formula (2).

  Specific examples are illustrated below, but the condensed polycyclic pigment used in the present invention is not limited thereto.

  These pigments can be used in combination.

  The resin used for the charge generation layer of the present invention is a resin having a repeating structure of the general formula (1), and the molecular weight distribution measured by gel permeation chromatography (GPC) of the resin is from 5,000 to 50,000. Each having a molecular weight component and a molecular weight distribution index (weight average molecular weight Mw / number average molecular weight Mn) of the resin is 7 or more and 25 or less, preferably 7 or more 12 or less.

  The polyvinyl butyral which is a kind of alkyl acetalized polyvinyl alcohol will be described as the resin having the repeating structure of the general formula (1) according to the present invention. Polyvinyl butyral is obtained by hydrolysis of polyvinyl acetate to obtain polyvinyl alcohol, which is further converted into butyral. Since the yield of these reactions is not 100%, three types of hydroxyl groups, acetoxyl groups, and carboxyl groups are considered as the terminal group structure.

The molecular weight distribution, the number average molecular weight Mn, the weight average molecular weight Mw, and the molecular weight distribution index of the resin of the present invention were measured under the following conditions to obtain standard polystyrene converted values.
-Measuring device: Gel permeation chromatography (GPC) device HLC-8220GPC (manufactured by Tosoh Corporation)
Column: TSKgel SuperH2500 (manufactured by Tosoh Corporation)
-Mobile phase: Tetrahydrofuran-Temperature: 40 ° C
・ Flow rate: 0.35 ml / min
・ Injection volume: 10 μl
・ Concentration: 0.1% by mass
The molecular weight distribution index is defined as follows.

Molecular weight distribution index = weight average molecular weight Mw / number average molecular weight Mn
That is, the ratio of the weight average molecular weight Mw to the number average molecular weight Mn is called a molecular weight distribution index, and serves as an index of the width of the molecular weight distribution. Here, the number average molecular weight Mn and the weight average molecular weight Mw are defined as follows.

Number average molecular weight Mn = (ΣN _i · M _i ) / (ΣN _i )
Weight average molecular weight Mw = (ΣN _i · M _i ² ) / (ΣN _i · M _i )
Here, N _i denotes the number of i-th molecular, M _i represents the molecular weight of the i th molecule. i is the number of column stages.

  Although the molecular weight distribution of the resin in the charge generation layer in the present invention may be achieved by one kind of resin, it is practically preferable to achieve it by mixing a plurality of kinds of organic binder resins because adjustment is easy. In the case of mixing, a low molecular weight alkyl acetalized polyvinyl alcohol having a polystyrene equivalent weight average molecular weight of about 5,000 to 50,000 is used for the purpose of enhancing the adhesion, and a polystyrene equivalent weight average molecular weight of about 100,000 to 200,000 is medium to high. It is preferable to add to the molecular weight alkyl acetalized polyvinyl alcohol. These mixed resins may have molecular weight regions that overlap each other in the molecular weight distribution before mixing, but when the molecular weight distribution was examined by gel permeation chromatography after mixing, the molecular weight distributions were clearly separated from each other without overlapping. Those having a molecular weight distribution are more preferred.

  20-800 mass parts is preferable with respect to 100 mass parts of resin, and, as for the ratio of resin of this invention, and a charge generation material, 200-600 mass parts is especially preferable. By using these resins, the increase in residual potential associated with repeated use can be minimized.

  The film thickness of the charge generation layer is preferably from 0.1 μm to 5 μm, particularly preferably from 0.3 μm to 3 μm.

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

  The electrophotographic photoreceptor of the present invention is an electrophotographic photoreceptor comprising at least a charge generation layer and a charge transport layer in this order on a conductive substrate, with an intermediate layer on the conductive substrate and the charge generation layer. Also good. In addition, the charge transport layer may be a plurality of layers, and a surface layer may be provided on the charge transport layer.

  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.

Conductive Substrate As the conductive substrate used for the photoreceptor, either a sheet or a cylindrical substrate may be used, but a cylindrical conductive substrate is preferable in order to design the image forming apparatus compactly. The cylindrical conductive substrate means a cylindrical substrate necessary to be able to form an endless image by rotating. A conductive substrate having a straightness of 0.1 mm or less and a deflection of 0.1 mm or less is used. preferable. 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. Preferably less resistivity 10 ³ Ω · cm at room temperature as a conductive substrate. The conductive substrate of the present invention is most preferably an aluminum substrate. As the aluminum substrate, 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 substrate and the charge generation 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.

  The charge generation layer is as described above.

In the present invention, in addition to the charge transport material and the binder, if necessary, inorganic fine particles such as silica and alumina, organic fine particles such as fluororesin fine particles or an antioxidant, and further additives such as a plasticizer. It can be contained.

  The charge transport material is not particularly limited, and a known hole transport property (P-type) charge transport material can be used. For example, triphenylamine derivatives, hydrazone compounds, styryl compounds, benzidine compounds, butadiene compounds and the like can be used. Can be mentioned.

  As the binder resin used for the charge transport layer, a known thermoplastic resin or thermosetting resin can be used. For example, the following are mentioned. That is, there are polystyrene, acrylic resin, methacrylic resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, silicone resin, melamine resin, and the like. Moreover, the copolymer resin which has 2 or more of the repeating units of these resin is also mentioned. Further, in addition to these insulating resins, a polymer organic semiconductor such as poly-N-vinylcarbazole can be used in combination.

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

  The film thickness of the charge transport layer is preferably 10 to 40 μm, particularly preferably 15 to 30 μm. When the film thickness is 10 to 40 μm, the influence of the film thickness does not hinder the acquisition of the latent image potential or the predetermined image density at the time of development, and the charge carrier diffusion (charge generation layer) (Diffusion of charge carriers generated in step 1) is not a concern, and dot reproducibility is not affected.

  Moreover, it is also possible to contain an antioxidant in the surface layer of the electrophotographic photoreceptor according to the present invention. The surface layer may be oxidized by the action of active gases such as nitrogen oxides and ozone generated during charging, and image blurring may occur due to oxidation, so the presence of an antioxidant prevents the surface layer from being oxidized. Thus, the occurrence of image blur is prevented.

  Specific examples of the antioxidant include, for example, the following known ones. That is, phenolic antioxidants (hindered phenols), amine antioxidants (hindered amines, diallyldiamines, diallylamines), hydroquinone antioxidants, sulfur antioxidants (thioethers), phosphoric acids There are antioxidants (phosphites) and the like. Among the antioxidants, hindered phenol antioxidants and hindered amine antioxidants are particularly effective in preventing fogging and image blurring at high temperatures and high humidity.

  Examples of the solvent or dispersion medium used for forming the intermediate layer, charge generation layer, charge transport layer and the like include the following. 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 photoreceptor according to the present invention include known coating methods. Specifically, in addition to coating with a circular slide hopper type coating device, dip coating or spraying is used. Examples thereof include a coating method.

Next, an image forming apparatus capable of implementing the full color image forming method according to the present invention will be described. First, a full-color image forming method according to the present invention includes at least the following steps. That is,
(1) An electrostatic latent image forming step for forming an electrostatic latent image on the surface of the electrophotographic photosensitive member according to the present invention using exposure light called so-called short wavelength light having a wavelength of 350 nm to 500 nm (2) A developing step of developing (developing) the electrostatic latent image formed on the surface of the electrophotographic photosensitive member using a developer containing toner to form a toner image (3) Electrophotographic according to the present invention (4) A fixing step of fixing the toner image transferred onto the transfer material. The transfer step transfers the toner image formed on the surface of the photoreceptor onto the transfer material or transfer means.

  In addition, you may have other processes other than the said 4 processes. For example, it is preferable to have a cleaning step of removing toner remaining on the surface of the electrostatic latent image carrier after transferring the toner image. In the transfer step, the toner image may be transferred from the electrostatic latent image carrier onto the recording medium via an intermediate transfer member.

  In the present invention, it is preferable to develop the electrostatic latent image by applying a developing bias in which an AC bias is superimposed on a DC bias in the developing step.

  In the present invention, a latent image is formed on a photoreceptor by irradiating exposure light having a wavelength of 350 nm to 500 nm, generally called short wavelength exposure, and a semiconductor laser or a light emitting diode is used as a light source for exposure. From these exposure light sources, exposure light having an exposure dot diameter of 5 to 50 [mu] m, preferably 10 to 25 [mu] m, is irradiated onto the photosensitive member in the writing principal direction to perform digital exposure. By such exposure means, a dot latent image having an image writing density of 1200 to 6000 dpi (dpi: the number of dots per inch, 1 inch = 2.54 cm) is formed on the photosensitive member, so that high-resolution image formation can be performed. It has become. Incidentally, the exposure dot diameter when the image writing density is 600 dpi is 42.3 μm, the exposure dot diameter when the image writing density is 1200 dpi is 21.7 μm, and the exposure dot diameter when the image writing density is 2400 dpi is 10.4 μm. 5 μm.

Here, the exposure dot diameter is the size (length, width) of the exposure light, and specifically, in the main scanning direction of the region where the intensity of the exposure light is 1 / e ² or more of the peak intensity. It means the length along. If the exposure dot diameter is smaller than the thickness of the photosensitive layer, the resolution of the latent image is increased. However, if the exposure dot diameter is too small, the reproducibility of the toner development amount may become unstable.

  In the present invention, a dot latent image corresponding to exposure dot light of 21.7 μm or less can be formed on the electrophotographic photosensitive member even when exposure is performed so that the image writing density is 1200 dpi or more. As shown in Examples described later, a fine and high-resolution toner image represented by a photographic image can be stably formed.

  FIG. 2 is a schematic diagram illustrating an example of an image forming apparatus capable of forming a full-color image using a two-component developer.

  In FIG. 2, 15Y, 15M, 15C and 15K are photoreceptors, 20Y, 20M, 20C and 20K are developing devices (developing means), 41Y, 41M, 41C and 41K are primary transfer rolls as primary transfer means, Reference numeral 43 denotes a secondary transfer roll as a secondary transfer means, 50Y, 50M, 50C and 50K denote cleaning devices, 4 denotes an intermediate transfer body unit, 70 denotes a heat roll type fixing device, and 40 denotes an intermediate transfer body.

  This image forming apparatus is called a tandem color image forming apparatus, and includes a plurality of sets of image forming units 20Y, 20M, 20C, and 20K, an endless belt-shaped intermediate transfer body unit 4 as a transfer unit, and a recording member P. It has an endless belt-shaped paper feeding and conveying means 21 for conveyance and a heat roll type fixing device 70 as a fixing means. A document image reading device SC is disposed above the main body A of the image forming apparatus.

  An image forming unit Y that forms a yellow image as one of the different color toner images formed on each photoconductor is arranged around a drum-shaped photoconductor 15Y as the first photoconductor and the photoconductor 15Y. The charging unit 16Y, the exposure unit 18Y, the developing unit 20Y, the primary transfer roll 41Y as the primary transfer unit, and the cleaning unit 50Y are included. In addition, an image forming unit M that forms a magenta image as one of toner images of different colors is a drum-shaped photoconductor 15M as a first photoconductor, and a charge disposed around the photoconductor 15M. Means 16M, exposure means 18M, development means 20M, primary transfer roll 41M as primary transfer means, and cleaning means 50M. In addition, an image forming unit C that forms a cyan image as one of toner images of different colors is a drum-shaped photoconductor 15C as a first photoconductor, and a charge disposed around the photoconductor 15C. Means 16C, exposure means 18C, development means 20C, primary transfer roll 41C as primary transfer means, and cleaning means 50C.

  Further, an image forming portion K that forms a black image as one of other different color toner images is disposed around a drum-shaped photoconductor 15K as a first photoconductor, and the photoconductor 15K. It has a charging means 16K, an exposure means 18K, a developing means 20K, a primary transfer roll 41K as a primary transfer means, and a cleaning means 50K.

  The endless belt-shaped intermediate transfer body unit 4 has an endless belt-shaped intermediate transfer body 40 as an intermediate transfer endless belt-shaped second image carrier that is wound around a plurality of rolls and is rotatably supported.

  The respective color images formed by the image forming units Y, M, C, and K are sequentially transferred onto the rotating endless belt-shaped intermediate transfer body 40 by the primary transfer rolls 41Y, 41M, 41C, and 41K to be combined. A colored image is formed. A recording member S such as a sheet as a transfer material accommodated in the sheet feeding cassette 60 is fed by a sheet feeding / conveying means 61, passes through a plurality of intermediate rolls 62A, 62B, 62C, 62D, and a registration roll 63, and then is secondary. It is conveyed to secondary transfer rolls 43A and 43B as transfer means, and color images are transferred onto the recording member S at once. The recording member S to which the color image has been transferred is fixed by the heat roll type fixing device 70, is sandwiched between the paper discharge rolls 75, and is placed on the paper discharge tray 76 outside the apparatus.

  On the other hand, after the color image is transferred to the recording member P by the secondary transfer rolls 43A and 43B, the residual toner is removed by the cleaning unit 48 from the endless belt-shaped intermediate transfer body 40 in which the recording member S is separated by curvature.

  During the image forming process, the primary transfer roll 41K is always in pressure contact with the photoreceptor 15K. The other primary transfer rolls 41Y, 41M, and 41C are in pressure contact with the corresponding photoreceptors 15Y, 15M, and 15C, respectively, only during color image formation.

  The secondary transfer rolls 43A and 43B are in pressure contact with the endless belt-shaped intermediate transfer body 40 only when the recording member S passes through the secondary transfer rolls 43A and 43B.

  In this way, a toner image is formed on the photoreceptors 15Y, 15M, 15C, and 15K by charging, exposure, and development, and the toner images of the respective colors are superimposed on the endless belt-shaped intermediate transfer body 40, and are collectively applied to the recording member P. The image is transferred and fixed by the fixing device 70 by pressing and heating. The photoconductors 15Y, 15M, 15C, and 15K after the toner image is transferred to the recording member S are cleaned by the cleaning device 50 after the toner remaining on the photoconductor is transferred, and then the charging, exposure, and development cycle described above. The next image formation is performed.

  FIG. 3 shows an example of a monochrome image forming apparatus in which the image forming method according to the present invention can be carried out. Like the image forming apparatus in FIG. 2, a two-component developer is used for the digital method. Image formation is performed.

(Explanation of development bias with DC bias and AC bias superimposed)
In the present invention, when the electrostatic latent image formed on the photoreceptor 1 is developed by the developing device 20, it is preferable to develop the electrostatic latent image by applying a developing bias in which an AC bias is superimposed on the DC bias. Here, a method for developing an electrostatic latent image by applying a developing bias obtained by applying an AC bias to the DC bias to the tenth power will be described.

  The developing device 20 in FIG. 2 develops an electrostatic latent image formed on the photosensitive member 1 by supplying the developer to the photosensitive member 1 from a developer carrying member 21 that rotates opposite to the photosensitive member 1. Thus, a toner image is formed on the photoreceptor 1 through such development. The developer carrying member 21 has a structure in which an aluminum sleeve having a stainless steel sprayed surface is provided around the magnet roll. A developing bias formed by superimposing an AC bias having an arbitrary frequency (Fac) and a peak value (Vacp-p) on a DC bias (Vdc) having an arbitrary voltage value is applied to the developer carrier 21. Then, development is performed with the development bias applied.

  When developing the electrostatic latent image on the photoreceptor 1 with a developing bias in which a DC bias and an AC bias are superimposed, the image forming apparatus in FIG. 2 performs development as follows by a control device such as a microcomputer (not shown). Controlled. That is, when developing the electrostatic latent image on the photoreceptor 1, control is performed so as to form a developing bias in which the AC bias having the peak value Vacp-p and the frequency Fac is superimposed on the DC bias Vdc. Development is performed by the development bias. The development bias is preferably, for example, Vdc of −300 to −700 kV, Vacp-p of 0.8 to 1.2 kV, and Fac of 3 to 7 kHz. Specific conditions of the developing bias formed by superimposing the DC bias and the AC bias include, for example, those with Vdc = −500 V, Vacp-p = 1.0 kV, and Fac = 5 kHz.

  The recording material (transfer paper) that can be used in the image forming method according to the present invention is a support capable of holding a toner image. Specifically, various types of support such as coated paper such as plain paper, fine paper, art paper, or coated paper from thin paper to thick paper, commercially available Japanese paper or postcard paper, plastic film for OHP, cloth, etc. The body can be mentioned, but is not limited thereto.

  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 photosensitive drum A)
“Photosensitive drum A” was prepared according to the following procedure.

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

(1) Preparation of intermediate 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 is dispersed for 12 hours using a sand mill to prepare a dispersion. did. 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-1) 7 parts by mass Polyvinyl butyral resin (l: m: n = 22: 5: 73, molecular weight distribution (1) shown in FIG. 1) 1 part by mass 2- 70 parts by mass of butanone / cyclohexanone (volume ratio 4/1) mixed solution The above composition is mixed, and dispersion treatment is performed for 15 hours using a sand mill so that the average particle size of the charge generating material is from 100 nm to 300 nm. A layer coating solution was prepared. 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 by mass Binder resin (PC-1) 2.7 parts by mass Ultraviolet absorber (Tinuvin P (manufactured by Ciba Japan)) 1 mass Part Antioxidant (Irganox 1010 (manufactured by Ciba Japan)) 1 part by mass Tetrahydrofuran / toluene (volume ratio 4/1) mixed liquid 150 parts by mass Silicone oil (KF-96 (manufactured by Shin-Etsu Silicone)) 0.01 Part by mass 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, “photosensitive drum A” was produced.

(Preparation of photosensitive drum B)
“Photoreceptor drum B” was prepared in the same procedure except that the charge generation material used in the charge generation layer of “photoreceptor drum A” was changed to exemplary compound CGM-2.

(Preparation of photosensitive drum C)
“Photosensitive drum C” was prepared in the same procedure except that the molecular weight distribution of the butyral resin used in the charge generation layer of “photosensitive drum A” was changed as shown in molecular weight distribution (2) shown in FIG.

(Preparation of photosensitive drum D)
“Photoreceptor drum D” was prepared in the same procedure except that the charge generation material used in the charge generation layer of “photoreceptor drum C” was changed to the exemplary compound CGM-2.

(Preparation of photosensitive drum E)
“Photosensitive drum E” was prepared in the same procedure except that the composition of the butyral resin used in the charge generation layer of “photosensitive drum C” was changed to 1: m: n = 25: 3: 72.

(Production of photosensitive drum F (for comparison))
The comparative “photosensitive drum F” was prepared in the same procedure except that the molecular weight distribution of the butyral resin used in the charge generation layer of “photosensitive drum A” was changed as shown in the molecular weight distribution (3) shown in FIG. Produced.

(Production of photosensitive drum G (for comparison))
A comparative “photosensitive drum G” was prepared in the same procedure except that the composition of the butyral resin used in the charge generation layer of “photosensitive drum F” was changed to l: m: n = 45: 3: 52. .

(Preparation of photosensitive drum H (for comparison))
“Photosensitive drum H” for comparison was made in the same manner except that the resin used in the charge generation layer of “photosensitive drum F” was changed to polyvinyl acetate resin (* l: m: n = 0: 100: 0). Was made.

(Production of photosensitive drum I (for comparison))
The comparative “photosensitive drum I” was prepared in the same procedure except that the molecular weight distribution of the butyral resin used in the charge generation layer of “photosensitive drum A” was changed as shown in the molecular weight distribution (4) shown in FIG. Produced.

(Production of photosensitive drum J (for comparison))
The charge generation material used in the charge generation layer of “Photoreceptor Drum E” was changed to Exemplified Compound CGM-2, and the molecular weight distribution of the butyral resin was changed as shown in Molecular Weight Distribution (4). “Photosensitive drum J” was prepared.

Evaluation A commercially available printer “bizhub C350 (manufactured by Konica Minolta Business Technologies, Inc.)” was remodeled (a semiconductor laser having an oscillation wavelength of 405 nm was mounted as an image exposure light source).

"Evaluation 1" (Evaluation of post-exposure potential Vi of the photoreceptor)
The initial post-exposure potential was measured by leaving the evaluation machine provided with the photosensitive drum in an environment of 30 ° C. and 80% RH for 12 hours, and then measuring the initial post-exposure potential in the environment. Next, the evaluation of the post-exposure potential after deterioration was rotated by an amount equivalent to 50000 A4 horizontal sizes in an environment of 30 ° C. and 80% RH, and then the post-exposure potential was measured.

“Evaluation 2” (Evaluation of dispersibility)
For evaluation of dispersion stability, the degree of sedimentation of fine particles after the charge generation layer coating solution prepared above was allowed to stand for the following period was visually evaluated.

Evaluation criteria A: No sedimentation of fine particles is observed even after being left for 30 days (good)
○: Settling of fine particles is observed after standing for 14 days (practical)
×: Sedimentation of fine particles is observed after standing for 1 day (problems in practical use)
"Evaluation 3" (adhesion evaluation)
Adhesive evaluation was performed by a cross-cut tape method based on JISK 5400. Unless otherwise specified, comply with JIS regulations.

  The measurement procedure is as follows.

  1. The electrophotographic photosensitive member produced in the example is fixed, and a cut on the grid is made at one central portion of the photosensitive member with a cutter knife having a clearance interval defined in the product standard of the sample by a cutter knife.

  The interval between the cuts is 1 mm, and the number of squares is based on 100. The grids peeled off at the interface other than the interface between the resin layer and the photosensitive layer are not subject to measurement. However, if more than half of the grids are excluded, the gap between the cuts is sequentially incremented by 1 mm. Measure by increasing the distance between eyes.

  2. Always use a new cutter knife when making cuts, and keep it at a constant angle in the range of 35 to 45 degrees to the coating surface.

  3. The cut is drawn at a constant speed over about 0.5 seconds per cut so as to penetrate the coating film and reach the conductive support.

  4). A cellophane adhesive tape is affixed on the grid so that the length of the adhesive portion is about 50 mm, and the tape is completely adhered to the coating film by rubbing with an eraser.

  5. One to two minutes after attaching the tape, hold one end of the tape at a right angle to the coating surface and peel it off instantaneously.

  6). The coated surface and the tape are observed, the number of grids peeled off at the interface between the photosensitive layer and the resin layer is determined, and the ratio of the peeled area is calculated. In the adhesion test, the above photoreceptor was subjected to a cross cut test according to the method described in JIS, and the number of cross cuts remaining out of 100 was counted. The residual rate was calculated from the following formula and evaluated.

Residual rate (%) = number not peeled off (mass) / total number (100 squares)
In addition, evaluation was performed according to the following criteria, and ◎, ○, and Δ were regarded as acceptable. That is,
A: 90% <Te ≦ 100%
○: 75% <Te ≦ 90%
Δ: 60% <Te ≦ 75%
X: Other than the above The results are shown in Table 1.

  From the results of Table 1, in Examples 1 to 5, which are electrophotographic photoreceptors having the configuration of the present invention, the adhesiveness of the photosensitive layer is improved, and the charge generation layer has potential stability and sensitivity to writing light. It was confirmed that they were fully satisfied.

It is a schematic diagram of the molecular weight distribution curve obtained by GPC measurement. 1 is a schematic diagram illustrating an example of a two-component developing type image forming apparatus. 1 is a schematic diagram illustrating an example of a two-component developing type image forming apparatus.

Explanation of symbols

15 (15Y, 15M, 15C, 15K) Electrophotographic photosensitive member 20 (20Y, 20M, 20C, 20K) Developing device 21 Developing roller 24 Blade (toner layer regulating member, charging member)
4 Intermediate transfer body unit 40 Intermediate transfer belt 41Y, 41M, 41C, 41K Primary transfer roll 43A, 43B Secondary transfer roll 50 (50Y, 50M, 50C, 50K) Cleaner (cleaning device)
60 Paper feeder 70 Fixing device

Claims (5)

An electrophotographic photoreceptor having at least a charge generation layer and a charge transport layer on a conductive support,
The charge generation layer and the charge transport layer are formed on a conductive support in the order of a charge generation layer and a charge transport layer,
The charge generation layer contains a condensed polycyclic pigment and a resin having a repeating structure represented by the following general formula (1):

[Wherein R represents an alkyl group having 1 to 6 carbon atoms. l, m, and n represent the molar ratio of each unit structure. If 1 + m + n = 100, then 15 ≦ l ≦ 40 and m ≦ 12. ]
When the resin having the repeating structure represented by the general formula (1) is subjected to molecular weight measurement by gel permeation chromatography, the molecular weight is in each of the region of 5,000 to 50,000 and the region of 100,000 to 200,000. An electrophotographic photosensitive member having a component, wherein the resin has a molecular weight distribution index (weight average molecular weight Mw / number average molecular weight Mn) of 7 or more and 25 or less. The molecular weight distribution measured by gel permeation chromatography of the resin represented by the general formula (1) has at least one peak in each of the region of 10,000 to 30,000 and 80,000 to 150,000. The electrophotographic photosensitive member according to claim 1. The electrophotographic photoreceptor according to claim 1, wherein the condensed polycyclic pigment is a compound of the following general formula (2).

(In the formula, X represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, a nitro group, a cyano group, an acyl group, or a carboxyl group, and n represents an integer of 0 to 6. Here, n is 2 to 6. And each X may be the same or different, provided that X is substituted at any substitutable position of the compound.) The step of forming a latent image on the surface of the electrophotographic photosensitive member according to claim 1 using exposure light having a wavelength of at least 390 nm to 500 nm and a dot diameter in the principal direction of 10 μm to 50 μm, and the electrophotographic photosensitive member A developing step of developing the latent image formed on the surface with toner, a transfer step of transferring the toner image formed on the surface of the electrophotographic photosensitive member onto a transfer material or a transfer medium, and the transfer A fixing step of fixing the toner image transferred onto the material;
An image forming method characterized in that image formation is performed through the process. At least exposure light having a wavelength of 390 nm to 500 nm and a dot diameter in a principal direction of 10 μm to 50 μm is formed on the surface of the electrophotographic photosensitive member with the electrophotographic photoreceptor according to claim 1. An exposure means for exposing; a developing means for supplying a toner to the surface of the electrophotographic photosensitive member on which a latent image is formed by the exposing means; and a toner image formed on the surface of the electrophotographic photosensitive member by the developing means. Transfer means for transferring the toner image,
An image forming apparatus comprising: a fixing unit configured to fix a toner image transferred onto a transfer material after being transferred by the transfer unit.

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