JP2008076808A - Electrophotographic photoreceptor and image forming apparatus using the same, and process cartridge - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor which has high electrostatic charging performance, further stable characteristics even in a high temperature and high humidity environment and low temperature and low humidity environment, hardly gives rise to troubles, such as color dots, and is excellent in the adhesiveness between the electrophotographic photoreceptor and the photosensitive layer, and an image forming apparatus using the same, and a process cartridge. <P>SOLUTION: In the electrophotographic photoreceptor having an under coating layer on a conductive support and further having a photosensitive layer thereon, the under coating layer contains at least n type semiconductor particles and a binder resin and the n type semiconductor particles are subjected to a plurality of times of surface treatment. The surface treatment includes the treatment by a compound selected from at least alumina, silica and zirconia and further treatment by dimethyl polysiloxane thereon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic photosensitive member used in the field of copying machines and printers, an image forming apparatus using the same, and a process cartridge.

  In recent years, organic photoconductors using various materials have been developed as electrophotographic photoconductors.

  The structure is mainly function-separated type photoconductors, in which charge generation and charge transport functions are assigned to different materials. Among them, stacked type photoconductors with stacked charge generation layers and charge transport layers are widely used. It has been.

  Turning to the electrophotographic process, latent image formation has recently been implemented as a digital hard disk printer as a printer for personal computers, and also in ordinary copying machines due to the ease of image processing and deployment to multifunction devices. Latent image formation has become mainstream.

  In digital latent image formation, a laser, particularly a semiconductor laser or an LED, is used as a light source for writing image information converted into a digital electric signal as an electrostatic latent image on a photoconductor. If the exposure beam diameter is reduced in digital writing, the writing speed is slowed down. The reversal development method is mainly used as a development method for the improvement and also for the necessity of extending the life of the photoreceptor. As a problem of the image forming method using the reversal development, there is a phenomenon (described in the case of black development) in which toner adheres to a place where an image should be originally formed as a white background portion to generate a black spot. This is due to a local defect in the photoreceptor, which is known as a so-called color spot failure.

  In order to solve this color defect, a technique for installing an undercoat layer in the photoreceptor has been developed. For example, an electrophotographic photoreceptor having a configuration in which an undercoat layer is provided between a conductive support and a photosensitive layer, and titanium oxide particles are dispersed in a resin in the undercoat layer is known. In addition, a technique of an undercoat layer containing titanium oxide subjected to surface treatment is also known. For example, titanium oxide surface-treated with iron oxide or tungsten oxide disclosed in JP-A-4-304646, titanium oxide surface-treated with an amino group-containing coupling agent disclosed in JP-A-9-96916, JP-A-9-258469 And titanium oxide surface-treated with an organosilicon compound disclosed in JP-A-8-328283, and titanium oxide surface-treated with methylhydrogenpolysiloxane disclosed in JP-A-8-328283.

  However, even if these technologies are used, the effect of preventing the occurrence of color spots is not sufficient in a severe environment of high temperature and high humidity or low temperature and low humidity, or the residual potential increases due to repeated use, exposure There is a problem that the partial potential increases and the image density cannot be sufficiently obtained. Further, JP-A-11-344826 proposes an electrophotographic photosensitive member having an undercoat layer using dendritic titanium oxide surface-treated with a metal oxide or an organic compound. Some are described in 1 and 2. In addition, a technique for performing surface treatment multiple times with different materials has been developed (see Patent Documents 3 and 4).

However, as a result of conducting an additional test of the embodiment disclosed in this patent, the effect of preventing the occurrence of color spots in a high-temperature and high-humidity environment or a low-temperature and low-humidity environment is still insufficient, and the conductive support or photosensitive layer is not sufficiently effective. It has been found that there is also a problem with adhesion.
Japanese Patent Laid-Open No. 11-15183 JP 2000-112164 A Japanese Patent Application Laid-Open No. 2002-236381 JP 2003-66639 A

  The present invention has been made to solve the above problems.

  That is, the object of the present invention is that the charging performance is high, the characteristics are stable even in a high-temperature and high-humidity environment and a low-temperature and low-humidity environment, and troubles such as color spots do not easily occur. It is an object to provide an electrophotographic photosensitive member having good adhesiveness, an image forming apparatus using the same, and a process cartridge.

  Conventionally, an undercoat layer (also referred to as an intermediate layer) using N-type semiconductor particles such as titanium oxide particles has problems in charge potential stability, environmental fluctuation, image defect prevention performance such as color spots, adhesion, and the like. However, it has been put to practical use by adjusting the image forming process conditions to obtain appropriate performance.

  However, in recent years, improvement in image quality, stability of image forming conditions, and durability have been demanded at a high level at the same time.

  The present invention has been made in consideration of measures for obtaining sufficiently satisfactory performance even under recent circumstances.

  As a result of intensive studies by the inventors of the present invention, it has been found that the object of the present invention can be achieved by adopting the following configuration.

(1)
In an electrophotographic photosensitive member having an undercoat layer on a conductive support and a photosensitive layer thereon, the undercoat layer contains at least N-type semiconductor particles and a binder resin, and a plurality of the N-type semiconductor particles are provided. An electrophotographic photosensitive member, wherein the surface treatment is performed at least once, and the surface treatment is performed with a compound selected from at least alumina, silica and zirconia, and further treated with dimethylpolysiloxane. .

(2)
2. The electrophotographic photosensitive member according to 1, wherein the N-type semiconductor particles are titanium oxide particles.

(3)
3. The electrophotographic photoreceptor according to 1 or 2, wherein the N-type semiconductor particles have a number average primary particle size of 10 nm to 200 nm.

(4)
In an image forming apparatus that has at least a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit around the electrophotographic photosensitive member and repeatedly forms an image, the electrophotographic photosensitive member is any one of the above-described one to three. 2. An image forming apparatus, which is the electrophotographic photosensitive member according to item 1.

(5)
A process cartridge used in an image forming apparatus that has at least a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit around the electrophotographic photosensitive member and that repeatedly forms an image is at least one of the above-described items 1 to 3. 1. The electrophotographic photosensitive member according to item 1 and at least one of the charging unit, the exposure unit, the developing unit, the transfer unit, and the cleaning unit are integrated and designed to be able to be taken in and out of the image forming apparatus. Process cartridge characterized by.

  According to the present invention, the charging performance is high, the characteristics are stable even in high-temperature and high-humidity environments and low-temperature and low-humidity environments, and troubles such as color spots are unlikely to occur, and adhesion to a conductive support or photosensitive layer is also good. An electrophotographic photosensitive member, an image forming apparatus using the same, and a process cartridge can be provided.

  Hereinafter, the present invention will be described in detail.

  The electrophotographic photoreceptor of the present invention (hereinafter also simply referred to as a photoreceptor) comprises an N-type semiconductor particle and a binder resin, which have at least a specific surface treatment applied to an undercoat layer provided between a conductive support and a photosensitive layer. Contain. The surface treatment of the N-type semiconductor particles is performed with a plurality of surface treatments, and the surface treatment is performed with any compound selected from at least alumina, silica and zirconia (zirconium oxide), It is a feature of the present invention that it is a treatment with dimethylpolysiloxane.

  The reason why the object of the present invention is achieved by the configuration of the present invention is not necessarily clear. However, the present inventors think that the reason is that the conventional treatment with a reaction point does not improve the potential performance, but in the treatment of the present invention, the treatment without the reaction point can be achieved. ing.

  In any case, although many developments related to the undercoat layer have been made before the present invention, it cannot be predicted that the combined structure of the present invention has a remarkable effect, and has been actually studied. I never had it.

  First, the surface treatment will be described in detail for the N-type semiconductor particles used in the present invention.

[N-type semiconductor particles]
The N-type semiconductor particles used in the present invention are fine particles having the property that the conductive carrier is an electron. The property that the conductive carrier is an electron is that the N-type semiconductor particles are contained in an insulating binder to efficiently block the hole injection from the conductive support, while the electron from the photosensitive layer is blocked. Refers to those having the property of not exhibiting blocking properties.

Specific examples of the N-type semiconductor particles include fine particles such as titanium oxide (TiO ₂ ), zinc oxide (ZnO), and tin oxide (SnO ₂ ). In the present invention, titanium oxide is particularly preferably used.

  The average particle diameter of the N-type semiconductor particles used in the present invention is preferably in the range of 10 nm to 200 nm in terms of the number average primary particle diameter, more preferably 10 nm to 100 nm, and particularly preferably 15 nm to 50 nm.

  The undercoat layer using N-type semiconductor particles having a number average primary particle size within the above range can be finely dispersed in the layer, has sufficient potential stability, and prevents color spot generation. It has been found that it has a function, and surprisingly has the effect of improving the adhesion between the photosensitive layer and the conductive support.

  The number-average primary particle size of the N-type semiconductor particles is magnified 10,000 times by transmission electron microscope observation, 100 particles are randomly observed as primary particles, and are measured values as the average diameter in the ferret direction by image analysis. is there.

  The shape of the N-type semiconductor particles used in the present invention includes a dendritic shape, a needle shape, and a granular shape. The N-type semiconductor fine particles having such a shape are, for example, titanium oxide particles, There are anatase type, rutile type and amorphous type, but any crystal type may be used, or two or more crystal types may be used in combination. In general, the rutile type is the best.

[Surface treatment performed on N-type semiconductor particles]
The surface treatment performed on the N-type semiconductor particles of the present invention is a surface treatment performed using at least one compound selected from alumina, silica, and zirconia.

  The alumina treatment, silica treatment, and zirconia treatment are treatments for depositing alumina, silica, or zirconia on the surface of the N-type semiconductive fine particles. Alumina, silica and zirconia hydrates are also included in the alumina, silica and zirconia deposited on these surfaces. Further, the surface treatment of dimethylpolysiloxane means that the treatment liquid is treated with dimethylpolysiloxane.

  In addition, as another method of the surface treatment performed on the N-type semiconductor particles as in the present invention, for example, a plurality of surface treatments are performed, and the surface treatment is reactive to the last surface treatment among the plurality of surface treatments. Surface treatment is performed using an organic titanium compound or a reactive organic zirconium compound. In addition, among the plurality of surface treatments, at least one surface treatment is performed using at least one compound selected from alumina, silica, and zirconia in the same manner as described above, and finally a reactive organic titanium compound or The surface treatment is performed with a reactive organozirconium compound, but none of them is characteristically equivalent to the treatment of the present invention.

  In this way, the surface treatment of N-type semiconductor particles such as titanium oxide particles is performed at least twice, so that the surface of the N-type semiconductor particles is uniformly coated (treated), and the surface-treated N-type semiconductor particles Is used for the undercoat layer, it is possible to obtain a good photoconductor having good dispersibility of N-type semiconductor particles such as titanium oxide particles in the undercoat layer and causing no image defects such as color spots. .

  In addition, among the above-mentioned alumina, silica, and zirconia, the treatment in the case of using a plurality of compounds may be performed at the same time, but it is particularly preferable to perform the alumina treatment first and then the silica treatment. Further, the amount of treatment of alumina and silica when treating alumina and silica is preferably higher than that of alumina.

  The surface treatment of the N-type semiconductor particles such as titanium oxide with a metal oxide such as alumina, silica, and zirconia can be performed by a wet method. For example, N-type semiconducting fine particles subjected to silica or alumina surface treatment can be prepared as follows.

  When titanium oxide particles are used as the N-type semiconductor particles, titanium oxide particles (number average primary particle diameter: 50 nm) are dispersed in water at a concentration of 50 to 350 g / L to form an aqueous slurry, and a water-soluble silicate is added thereto. Alternatively, a water-soluble aluminum compound is added. Thereafter, alkali or acid is added for neutralization, and silica or alumina is precipitated on the surface of the titanium oxide particles. Subsequently, filtration, washing, and drying are performed to obtain the target surface-treated titanium oxide. When sodium silicate is used as the water-soluble silicate, it can be neutralized with an acid such as sulfuric acid, nitric acid or hydrochloric acid. On the other hand, when aluminum sulfate is used as the water-soluble aluminum compound, it can be neutralized with an alkali such as sodium hydroxide or potassium hydroxide.

  In addition, the amount of the metal oxide used for the surface treatment is 0.1 to 50 parts by mass with respect to 100 parts by mass of the N-type semiconductive fine particles such as titanium oxide particles in the charged amount during the surface treatment. More preferably, 1 to 10 parts by mass of a metal oxide is used. In the case of using alumina and silica as described above, for example, in the case of titanium oxide particles, it is preferable to use 1 to 10 parts by mass with respect to 100 parts by mass of titanium oxide particles, and it is preferable that the amount of silica is larger than that of alumina. .

  The surface treatment with dimethylpolysiloxane performed after the surface treatment with the metal oxide is preferably performed by the following wet method.

  Titanium oxide treated with the metal oxide is added to a solution in which the dimethylpolysiloxane is dissolved or suspended in an organic solvent or water, and the solution is stirred for several minutes to about 1 hour. And depending on the case, after heat-processing this liquid, it passes through processes, such as filtration, It dries, The titanium oxide particle which coat | covered the surface with dimethylpolysiloxane is obtained. Other reactive organosilicon compounds may be added to a suspension in which dimethylpolysiloxane is dispersed in an organic solvent or water.

  In the present invention, the surface of the titanium oxide particles is coated with dimethylpolysiloxane because photoelectron spectroscopy (ESCA), Auger electron spectroscopy (Auger), secondary ion mass spectrometry (SIMS), diffuse reflection FI-IR, etc. This can be confirmed in a composite manner using a surface analyzer.

  The amount of dimethylpolysiloxane used for the surface treatment is 0.1 to 50 parts by mass of dimethylpolysiloxane with respect to 100 parts by mass of titanium oxide treated with dimethylpolysiloxane in the charged amount during the surface treatment. Preferably 1-10 mass parts is preferable. When the surface treatment amount is in the above range, the surface treatment effect is more sufficiently imparted, the dispersibility of the titanium oxide particles in the undercoat layer is good, and as a result, the residual potential rise and the charge potential drop are less.

  Examples of silane compounds other than dimethylpolysiloxane include the following compounds, but their performance is lower than that of dimethylpolysiloxane.

  Tetrachlorosilane, diethoxydichlorosilane, tetramethoxysilane, phenoxytrichlorosilane, tetraisopropoxysilane, tetrakis (2-methoxyethoxy) silane, etc., or trichlorosilane, methyltrichlorosilane, vinyltrichlorosilane, ethyltrichlorosilane, allyl And trichlorosilane.

  Alternatively, dimethyldichlorosilane, dimethoxymethylsilane, dimethoxydimethylsilane, methyl-3,3,3-trifluoropropyldichlorosilane, diethoxysilane, diethoxymethylsilane, dimethoxymethyl-3,3,3-trifluoropropylsilane 3-chloropropyldimethoxymethylsilane, diethoxymethylsilane, diethoxymethylphenylsilane, diethoxy-3-glycidoxypropylmethylsilane, 3- (3-acetoxypropylthio) propyldimethoxymethylsilane, dimethoxymethyl-3- Examples include piperidinopropyl silane and diethoxymethyl octadecyl silane.

[Configuration of undercoat layer]
Next, N-type semiconductor particles such as titanium oxide particles subjected to the surface treatment (hereinafter also referred to as surface-treated N-type semiconductor particles. In particular, the surface-treated titanium oxide particles are also referred to as surface-treated titanium oxide. The structure of the undercoat layer using the above will be described.

  The undercoat layer of the present invention comprises a liquid obtained by dispersing surface-treated N-type semiconductor particles such as surface-treated titanium oxide obtained by performing the surface treatment a plurality of times in a solvent together with a binder resin on a conductive support. It is produced by coating.

  The undercoat layer of the present invention is provided between a conductive support and a photosensitive layer, and has a barrier function to improve adhesion between the conductive support and the photosensitive layer and to prevent charge injection from the support. . As the binder resin for the undercoat layer, thermosetting resins such as polyamide resin, vinyl chloride resin, vinyl acetate resin, polyvinyl acetal resin, polyvinyl butyral resin, polyvinyl alcohol resin, melamine resin, epoxy resin, alkyd resin, and the like Examples include copolymer resins containing two or more of the repeating units of the resin. Among these binder resins, polyamide resins are particularly preferable, and alcohol-soluble polyamides such as copolymerized and methoxymethylol are particularly preferable.

The amount of the surface-treated N-type semiconductor particles of the present invention dispersed in the binder resin is, for example, 10 to 10,000 parts by mass, preferably 50 to 1,000 parts by mass with respect to 100 parts by mass of the binder resin. . By using the amount of the surface-treated N-type semiconductor particles within this range, the dispersibility of the surface-treated N-type semiconductor particles can be kept good, and a good undercoat layer with good adhesion that does not generate color spots is formed. The thickness of the undercoat layer of the present invention is preferably 0.5 to 15 μm. By using the film thickness within the above range, it is possible to form an undercoat layer that is more particularly free from color spots and has better adhesion and electrophotographic characteristics.

  The undercoat layer coating solution prepared for forming the undercoat layer of the present invention is composed of surface-treated N-type semiconductor particles such as titanium oxide, a binder resin, a dispersion solvent, and the like. A solvent similar to the solvent used in the production of is used as appropriate.

  That is, the solvent or dispersion medium used for forming the undercoat layer, photosensitive layer, and other resin layers of the present invention includes n-butylamine, diethylamine, ethylenediamine, isopropanolamine, triethanolamine, triethylenediamine, N, N-dimethyl. Formamide, 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 , Trichlorethylene, tetrachloroethane, tetrahydrofuran, dioxolane, dioxane, methanol, ethanol, butanol, isopropanol, ethyl acetate, butyl acetate, dimethyl sulfoxide, Chiruserosorubu, and the like.

  In particular, the undercoat layer coating solution solvent is not limited to these, but methanol, ethanol, butanol, 1-propanol, isopropanol, and the like are preferably used. These solvents may be used alone or as a mixed solvent of two or more.

  In addition, as the undercoat layer coating solvent, it is preferable to use a mixed solvent of methanol and linear alcohol having high resin solubility in order to prevent the occurrence of drying unevenness during the undercoat layer coating, and the preferred solvent ratio Is preferably a mixture of linear alcohol and methanol 1 at a volume ratio of 0.05 to 0.6. Thus, by using a coating solvent as a mixed solvent, the evaporation rate of the solvent can be maintained appropriately, and the occurrence of image defects due to drying unevenness during coating can be suppressed.

  Further, any dispersing means such as a sand mill, a ball mill, or an ultrasonic dispersion may be used as the dispersing means for the surface-treated titanium oxide particles used for preparing the undercoat layer coating solution.

  As the coating method for producing the electrophotographic photosensitive member of the present invention including the undercoat layer, coating processing methods such as dip coating, spray coating, and circular amount regulation type coating are used. The side coating process does not dissolve the lower layer film as much as possible, and in order to achieve a uniform coating process, it is preferable to use a coating process method such as spray coating or circular amount regulation type (circular slide hopper type is a typical example). preferable. The spray coating is described in detail in, for example, JP-A-3-90250 and JP-A-3-269238, and the circular amount-regulating coating is described in detail in, for example, JP-A-58-189061. Yes.

[Configuration as photoconductor]
The structure of the photoreceptor preferably used in the present invention will be described below.

Conductive Support The conductive support used in the photoreceptor of the present invention may be either a sheet or a cylinder, but in order to design an image forming apparatus in a compact manner, a cylindrical conductive support is used. Is preferred.

  The cylindrical conductive support of the present invention means a cylindrical support that needs to be able to form an endless image by rotating, and has a straightness of 0.1 mm or less and a deflection of 0.1 mm or less. A conductive 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 Ω · cm or less at room temperature.

  Hereinafter, a preferable photosensitive layer structure of the electrophotographic photosensitive member of the present invention will be described.

Photosensitive layer The photosensitive layer configuration of the photoreceptor of the present invention may be a single-layer photosensitive layer configuration in which the charge generation function and the charge transport function are provided on one layer on the undercoat layer. It is preferable that the function is separated into a charge generation layer (CGL) and a charge transport layer (CTL). By adopting a configuration in which the functions are separated, it is possible to control the increase in residual potential due to repeated use, and to easily control other electrophotographic characteristics according to the purpose. In the negatively charged photoconductor, it is preferable to employ a charge generation layer (CGL) on the undercoat layer and a charge transport layer (CTL) thereon. In the positively charged photoconductor, the order of the layer configuration is the reverse of that in the negatively charged photoconductor. The most preferred photosensitive layer structure of the present invention is a negatively charged photoreceptor structure having the function separation structure.

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

Charge generation layer Charge generation layer: The charge generation layer contains one or more charge generation materials (CGM). Other substances may contain a binder resin and other additives as necessary.

  A known charge generation material (CGM) can be used as the charge generation material (CGM). For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the CGM that can minimize the increase in residual potential due to repeated use has a three-dimensional and potential structure that can form a stable aggregate structure among a plurality of molecules. Specifically, a phthalocyanine having a specific crystal structure. CGM of pigments and perylene pigments. For example, CGMs such as titanyl phthalocyanine having a maximum peak at a Bragg angle 2θ of 27.2 ° with respect to Cu—Kα rays and benzimidazole perylene having a maximum peak at 2θ of 12.4 have little deterioration due to repeated use. Potential increase can be reduced.

  When a binder is used as the CGM dispersion medium in the charge generation layer, a known resin can be used as the binder, but the most preferred resins include formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Can be mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential associated with repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2.0 μm.

Charge Transport Layer 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 antioxidants as necessary.

A known charge transport material (CTM) can be used as the charge transport material (CTM). For example, a triphenylamine derivative, a hydrazone compound, a styryl compound, a benzidine compound, a butadiene compound, or the like can be used. These charge transport materials are usually dissolved in a suitable binder resin to form a layer. Among these, the CTM that can minimize the increase in the residual potential due to repeated use has a high mobility of 10 ⁻⁵ cm ² / V · sec or more, and the ionization potential difference from the combined CGM is 0. What has the characteristic of 5 (eV) or less is preferable, More preferably, it is 0.25 (eV) or less.

  The ionization potential of CGM and CTM is measured with a surface analyzer AC-1 (manufactured by Riken Keiki Co., Ltd.).

  Examples of the resin used for the charge transport layer (CTL) include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, and polycarbonate. Resin, silicone resin, melamine resin, and copolymer resin containing two or more of repeating units of these resins. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be used.

  Most preferred as a binder for these CTLs is a polycarbonate resin. The polycarbonate resin is most preferable in improving the dispersibility and electrophotographic characteristics of CTM. The ratio of the binder resin to the charge transport material is preferably 10 to 200 parts by mass with respect to 100 parts by mass of the binder resin. The thickness of the charge transport layer is preferably 10 to 40 μm.

[Image Forming Method and Image Forming Apparatus]
FIG. 1 is a cross-sectional view of a color image forming apparatus as an example of the image forming method of the present invention.

  An embodiment of an electrophotographic printer (hereinafter simply referred to as a printer) will be described as a full-color image forming apparatus to which the present invention is applied.

  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.

  An image forming unit 10Y that forms a yellow image has a charging unit 2Y, an exposing unit 3Y, a developing unit 4Y, and a primary transfer unit disposed around a drum-shaped photoconductor 1Y as a first image carrier. A primary transfer roller 5Y and a cleaning means 6Y are provided. 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 the present embodiment, a corona discharge type charger 2Y is used for the photosensitive drum 1Y.

  The image exposure means 3Y performs exposure based on the image signal (yellow) on the photosensitive drum 1Y given a uniform potential by the charger 2Y, and forms an electrostatic latent image corresponding to the yellow image. As the exposure means 3Y, the exposure means 3Y includes 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.

In the image forming method of the present invention, when an electrostatic latent image is formed on a photoreceptor, it is preferable to perform image exposure using an exposure beam having a spot area of 2000 μm ² or less. Even when such small-diameter beam exposure is performed, the organic photoreceptor of the present invention can faithfully form an image corresponding to the spot area. A more preferable spot area is 100 to 1000 μm ² . As a result, an electrophotographic image having a gradation of not less than 800 dpi (dpi is the number of dots per 2.54 cm) can be achieved.

The spot area of the exposure beam is a light intensity distribution plane appearing on the cut surface when the exposure beam is cut along a plane perpendicular to the beam, and in a region where the light intensity is 1 / e ² or more of the maximum peak intensity. It means the corresponding area.

Examples of the light beam used include a scanning optical system using a semiconductor laser, and a solid state scanner such as an LED or a liquid crystal shutter. The light intensity distribution includes a Gaussian distribution and a Lorentz distribution, but 1 / e of each peak intensity. ^The area up to ² is the spot area.

  The endless belt-shaped intermediate transfer body unit 7 is an endless belt-shaped intermediate transfer body 70 (transfer medium) as a semiconductive endless belt-shaped second image carrier that is wound around a plurality of rollers and 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 (transfer medium) P as a transfer material (support for supporting the final fixed image: for example, plain paper, transparent sheet, etc.) housed in the paper feed cassette 20 is fed by the paper feeding means 21. Then, it passes through a plurality of intermediate rollers 22A, 22B, 22C, 22D and a registration roller 23, and is conveyed to a secondary transfer roller 5b as a secondary transfer means, and is secondarily transferred onto a transfer material P, and color images are collectively transferred. The 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, the transfer medium refers to a transfer medium for a toner image on a photosensitive member such as an intermediate transfer member or a transfer material.

  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 pressure contact with the photoreceptor 1Bk. The other primary transfer rollers 5Y, 5M, and 5C are in pressure contact with the corresponding photoreceptors 1Y, 1M, and 1C, respectively, only during color image formation.

  The secondary transfer roller 5b is brought into pressure contact with 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.

  The developer includes, for example, a carrier in which the above ferrite is used as a core and an insulating resin is coated around the carrier, a colorant such as carbon black, a charge control agent, and the low molecular weight polyolefin of the present invention, which is mainly composed of the above styrene acrylic resin. And a toner obtained by externally adding silica, titanium oxide or the like to the colored particles.

  Reference numeral 70 denotes a process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated, that is, at least a charging means, an exposure means, a developing means, A process cartridge used in an image forming apparatus that includes a transfer unit and a cleaning unit and repeatedly forms an image includes at least one of an electrophotographic photosensitive member and the charging unit, exposure unit, developing unit, transfer unit, and cleaning unit. One of the preferred embodiments of the present invention is one that is designed to be inserted into and removed from the image forming apparatus.

  The organic electrophotographic photosensitive member of the present invention is generally applicable to electrophotographic apparatuses such as electrophotographic copying machines, laser printers, LED printers, and liquid crystal shutter printers, but also displays, recordings, light printing, plate making using electrophotographic technology. It can also be widely applied to apparatuses such as facsimiles.

  The developer used in the image forming apparatus of the present invention is not particularly limited. In the case of a one-component developer, a non-magnetic one-component developer is also magnetic. A one-component developer can also be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this. In the text, “part” means “part by mass”.

Preparation of Undercoat Layer Coating Solution Undercoat layer coating solutions for each Example and Comparative Example were prepared as follows.

(Preparation of coating solution 1 for undercoat layer)
1 part by mass of polyamide resin CM8000 (manufactured by Toray Industries, Inc.), 3 parts by mass of titanium oxide SMT500SAM (first time: silica / alumina treatment, second time: dimethylpolysiloxane treatment: manufactured by Teika), and 10 parts by mass of methanol are added to the same container. The undercoat layer coating solution 1 was prepared by dispersing using an ultrasonic homogenizer.

(Preparation of undercoat layer coating solutions 2 to 12)
Undercoat layer coating solutions 2 to 12 were prepared in the same manner as undercoat layer coating solution 1 except that the titanium oxide, its surface treatment and particle size, and the type of binder resin were as shown in Table 1 below.

  In Table 1, the numerical values described in percentages in parentheses in the secondary treatment column indicate the mass% of the material used for the secondary treatment with respect to titanium oxide before the primary treatment.

  These confirmation methods are based on the above-described methods.

(Preparation of undercoat layer coating solutions 13 to 15)
Undercoat layer coating solutions 13 to 15 were prepared in the same manner as undercoat layer coating solution 1 except that titanium oxide, its surface treatment, and binder resin were as shown in Table 1 below.

Example 1
The undercoat layer coating solution 1 was dip-coated on a cylindrical aluminum substrate to provide an undercoat layer with a dry film thickness of 4 μm. On top of that, 2 parts of a titanyl phthalocyanine compound having an X-ray diffraction spectrum (Bragg angle 2θ ± 0.2 degrees) of CuKα ray having a maximum diffraction peak at 27.2 degrees, 1 part of butyral resin, 70 parts of t-butyl acetate, 4 parts A liquid in which 30 parts of -methoxy-4-methyl-2-pentanone was dispersed using a sand mill was applied by dip coating to form a charge generation layer having a dry film thickness of about 0.3 μm. Next, 0.65 parts of charge transport material (Compound A); 1 part of polycarbonate resin “Iupilon-Z200” (Mitsubishi Gas Chemical Co., Ltd.) dissolved in 7.5 parts of dichloroethane was dip coated on the charge generation layer. A charge transport layer having a dry film thickness of about 24 μm was formed and dried at 100 ° C. for 70 minutes to prepare Example Photoreceptor 1.

Examples 2-12
The undercoat layer coating solution shown in Table 3 was used instead of the undercoat layer coating solution used in Example 1, and an undercoat layer was provided. 12 was produced.

Comparative Examples 1-3
The undercoat layer coating solution shown in Table 3 was used instead of the undercoat layer coating solution used in Example 1, and the undercoat layer was provided. 3 was produced.

Comparative Example 4
A comparative photoreceptor 4 was produced in the same manner as in Example 1 except that no undercoat layer was provided.

Evaluation 1 (post-exposure potential and stability)
Using a color copying machine Bizhub PRO C500 (Scotron, laser exposure, LED charge removal light) manufactured by Konica Minolta, each photoconductor was subjected to general environment (19 ° C., 30% RH), high temperature and high humidity (30 ° C., 83% RH), In each environment of low temperature and low humidity (7 ° C., 21% RH), a continuous repeating cycle of charging, exposure, and charge removal was performed 6000 times, and the exposed portion potential VL at the start and immediately before the end was measured.

  The VL in Table 3 indicates the VL at the start of the general environment. Further, the difference between the minimum value and the maximum value of the exposure part potential of laser exposure measured through each environment is shown in Table 3 as a VL environment difference (ΔVL).

Evaluation 2 (color pot)
Confirm changes in image characteristics in the general environment (NN; 19 ° C, 30% RH), high temperature and high humidity (HH; 30 ° C, 83% RH), and low temperature and low humidity (LL; 7 ° C, 21% RH). Therefore, the following acceleration experiment was conducted. Each photoconductor is mounted on Konica Minolta's color copier Bizhub PRO C500 (having a process using a scorotron charger, laser exposure, reversal development, electrostatic transfer, nail separation, and cleaning blade), and grid charging of the scorotron charger. The voltage was set to -1000 V, the development bias for reversal development was set to -800 V, and continuous image copying of A4 paper 10,000 was performed in each environment, and the presence or absence of color spot image defects at the start and end was confirmed. The evaluation up to evaluation B shown below is assumed to be acceptable. Table 3 shows the results.

Evaluation Criteria A: No color spot image defect occurs in any of NN, HH, LL B: Color spot image defect occurs in any one of NN, HH, LL C: Color in two or more environments of NN, HH, LL Pochi image defect occurrence evaluation 3 (image unevenness)
In addition, the occurrence of image unevenness in the halftone portion was evaluated using a gray background chart. The evaluation criteria are as follows. The evaluations up to Δ are acceptable. The results are shown in Table 3.

Evaluation criteria ○: No unevenness occurred.

  Δ: Slight occurrence is observed, but there is no practical problem.

  X: Out of the practical range.

Evaluation 4 (film adhesion (adhesiveness))
The adhesion between the conductive support and the photosensitive layer was evaluated. Evaluation is made by making a grid pattern on the surface of the photosensitive layer at intervals of 2 mm, and then sticking the adhesive tape to the surface of the photosensitive layer and peeling it off, thereby removing the photosensitive layer remaining on the conductive support when the photosensitive layer is peeled off from the surface. The number of squares in the layer was expressed as a percentage.

A: The remaining number of photosensitive layers is 90 to 100% (good)
○: Remaining number of photosensitive layers is less than 80 to 90% (no problem in practical use)
X: The remaining number of photosensitive layers is less than 80% (there is a problem in practical use)
The results are shown in Table 3 below.

  As shown in Table 3, Examples 1 to 12 in the present invention all show good characteristics, but it is understood that Comparative Examples 1 to 4 have problems in at least any of the characteristics. .

1 is a cross-sectional view of a color image forming apparatus as an example of an image forming method of the present invention.

Explanation of symbols

1Y, 1M, 1C Photoconductor 5Y, 5M, 5C, 5Bk Primary transfer roller 5b Secondary transfer roller 6b Cleaning means 10Y, 10M, 10C, 10Bk Image forming unit 20 Paper feed cassette 21 Paper feed means 22A, 22B, 22C, 22D Intermediate roller 23 Registration roller 24 Fixing means 25 Paper discharge roller 26 Paper discharge tray 70 Endless belt-shaped intermediate transfer member P Transfer material

Claims (5)

In an electrophotographic photosensitive member having an undercoat layer on a conductive support and a photosensitive layer thereon, the undercoat layer contains at least N-type semiconductor particles and a binder resin, and a plurality of the N-type semiconductor particles are provided. An electrophotographic photosensitive member, wherein the surface treatment is performed at least once, and the surface treatment is performed with a compound selected from at least alumina, silica and zirconia, and further treated with dimethylpolysiloxane. . The electrophotographic photosensitive member according to claim 1, wherein the N-type semiconductor particles are titanium oxide particles. The electrophotographic photosensitive member according to claim 1, wherein the N-type semiconductor particles have a number average primary particle size of 10 nm to 200 nm. An image forming apparatus that has at least a charging unit, an exposing unit, a developing unit, a transferring unit, and a cleaning unit around the electrophotographic photosensitive member, and repeatedly forms an image. An image forming apparatus comprising the electrophotographic photosensitive member according to claim 1. A process cartridge used in an image forming apparatus that has at least a charging unit, an exposure unit, a developing unit, a transfer unit, and a cleaning unit around an electrophotographic photosensitive member and that repeatedly forms an image. The electrophotographic photosensitive member according to claim 1 and at least one of the charging unit, the exposure unit, the developing unit, the transfer unit, and the cleaning unit are integrated and designed to be able to be taken in and out of the image forming apparatus. A process cartridge characterized by that.

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