Image forming device and process cartridge

Abstract

An image forming device and a process cartridge. The image forming device includes: an image holding member having a photosensitive layer and a surface protective layer on a conductive substrate; a latent image forming unit for forming an electrostatic latent image on the image holding member; a developing unit containing an electrostatic image developer containing an electrostatic image developing toner, and developing the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image using the electrostatic image developer; a transfer unit for transferring the toner image to a recording medium; and a cleaning unit having a cleaning blade for cleaning the toner off the surface of the image holding member. The electrostatic image developing toner contains toner particles and silica particles, wherein the silica particles have a number average particle size of 110 nm to 130 nm, a large diameter side number particle size distribution index (upper GSDp) of less than 1.080, an average circularity of 0.94 to 0.98, and a proportion of particles having a circularity of 0.92 or greater of 80% by number or greater.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus and a process cartridge. Background Art

[0002] Methods such as electrophotography that visualize image information via electrostatic images are currently used in various fields.

[0003] Conventionally, electrophotography typically uses a method for visualization that involves multiple steps: forming an electrostatic latent image on a photoreceptor or electrostatic recording medium using various means, attaching electrostatic particles called toner to the latent image, developing the latent image (toner image), transferring it to the surface of the transfer medium, and fixing it by heating or the like.

[0004] Furthermore, as a conventional toner, a toner described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2013-137508) is known.

[0005] Japanese Patent Application Laid-Open No. 2013-137508 discloses an electrostatic image developing toner, characterized in that the electrostatic image developing toner contains an external additive, wherein the external additive comprises silica fine particles whose surfaces are covered with a plurality of protrusions, and the number average particle size of the silica fine particles is 80 to 200 nm.

[0006] Furthermore, as a conventional toner, the toner described in Patent Document 2 (Japanese Patent Application Laid-Open No. 2007-322919) is known.

[0007] Japanese Patent Application Laid-Open No. 2007-322919 discloses an image forming apparatus comprising: an image holding member; a charging roller disposed in non-contact with a surface of the image holding member and applying a voltage obtained by superimposing an AC voltage on a DC voltage when charging the surface of the image holding member; an electrostatic latent image forming unit for forming an electrostatic latent image on the surface of the image holding member charged by the charging roller; and a developing unit for developing the electrostatic latent image using a developer for developing electrostatic charge. A toner image is formed on the surface of the image holding member, wherein the developer for electrostatic charge development uses a toner to which at least silica is added, wherein the silica has a number average particle size within a range of 100 to 150 nm, a standard deviation in a number particle size distribution of not more than 0.22 times the number average particle size, and a true specific gravity of not less than 1.95; a transfer unit that transfers the toner image from the surface of the image holding member to a recording medium; and a cleaning blade that cleans the surface of the image holding member after the toner image is transferred.

[0008] Furthermore, as a conventional external additive for toner, an external additive for toner described in Patent Document 3 (Japanese Patent Application Laid-Open No. 2007-264142) is known.

[0009] Japanese Patent Application Laid-Open No. 2007-264142 discloses an external additive for a toner, characterized in that it contains silica, wherein the silica has a number average particle size within a range of 100 to 150 nm, a standard deviation in the number particle size distribution greater than 0.77 times the number average particle size, and a true specific gravity of 1.9 or less. Summary of the Invention

[0010] The problem to be solved by the present invention is to provide an image forming apparatus comprising a cleaning unit for cleaning toner from the surface of an image holding member having a photosensitive layer and a surface protective layer on a conductive substrate, wherein the image forming apparatus has excellent wear suppression properties of a cleaning blade and suppression properties of film formation of the external additive on the image holding member, compared to a case where the external additive in the toner for electrostatic image development is silica particles having a number average particle size of less than 110 nm or greater than 130 nm, or a large diameter side number particle size distribution index (upper side GSDp) of 1.080 or greater, or an average circularity of less than 0.94 or greater than 0.98, or a proportion of less than 80% by number of particles having a circularity of 0.92 or greater.

[0011] According to a first aspect of the present invention, there is provided an image forming apparatus comprising:

[0012] An image holding member comprising a photosensitive layer and a surface protective layer on a conductive substrate;

[0013] a latent image forming unit for forming an electrostatic latent image on the image holding member;

[0014] a developing unit that accommodates an electrostatic image developer including an electrostatic image developing toner and develops the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image using the electrostatic image developer;

[0015] a transfer unit configured to transfer the toner image onto a recording medium; and

[0016] a cleaning unit having a cleaning blade for cleaning the toner on the surface of the image holding member;

[0017] The above-mentioned toner for electrostatic image development contains toner particles and silica particles, the number average particle size of the above-mentioned silica particles is greater than 110 nm and less than 130 nm, the large diameter side number particle size distribution index (upper side GSDp) is less than 1.080, the average circularity is greater than 0.94 and less than 0.98, and the proportion of particles with a circularity of greater than 0.92 is greater than 80% by number.

[0018] According to the second aspect of the present invention, the large-diameter side number size distribution index (upper GSDp) of the silica particles is less than 1.075.

[0019] According to the third aspect of the present invention, the silica particles have a smaller diameter side number size distribution index (lower GSDp) of less than 1.080.

[0020] According to a fourth aspect of the present invention, the average circularity of the silica particles is 0.95 or more and 0.97 or less.

[0021] According to a fifth aspect of the present invention, the surface protective layer contains an acrylic resin.

[0022] According to a sixth aspect of the present invention, the acrylic resin has a charge-transporting skeleton.

[0023] According to a seventh aspect of the present invention, the charge-transporting skeleton is a triarylamine skeleton.

[0024] According to the eighth aspect of the present invention, among the silica particles, the proportion of particles having a circularity of 0.92 or greater is 85% by number or greater.

[0025] According to a ninth aspect of the present invention, the electrostatic image developing toner further includes inorganic oxide particles having a number average particle size of 5 nm to 50 nm.

[0026] According to a tenth aspect of the present invention, the toner particles contain a styrene acrylic resin as a binder resin.

[0027] According to an eleventh aspect of the present invention, the toner particles contain an amorphous polyester resin as a binder resin.

[0028] According to a twelfth aspect of the present invention, there is provided a process cartridge which is detachably mounted in an image forming apparatus.

[0029] It has:

[0030] An image holding member comprising a photosensitive layer and a surface protective layer on a conductive substrate;

[0031] a developing unit that accommodates an electrostatic image developer including an electrostatic image developing toner and develops the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image using the electrostatic image developer; and

[0032] a cleaning unit including a cleaning blade for cleaning the toner on the surface of the image holding member;

[0033] The above-mentioned toner for electrostatic image development contains toner particles and silica particles, the average particle size of the above-mentioned silica particles is greater than 110 nm and less than 130 nm, the large diameter side number particle size distribution index (upper side GSDp) is less than 1.080, the average roundness is greater than 0.94 and less than 0.98, and the proportion of particles with a roundness of greater than 0.92 is greater than 80% by number.

[0034] Effect

[0035] According to the above-mentioned scheme 1, 10 or 11, an image forming device is provided, which has a cleaning unit for cleaning the toner on the surface of an image holding member having a photosensitive layer and a surface protective layer on a conductive substrate. Compared with the case where the external additive in the toner for electrostatic image development is silica particles having a number average particle size of less than 110 nm or greater than 130 nm, or a large diameter side number particle size distribution index (upper side GSDp) of 1.080 or greater, or an average circularity of less than 0.94 or greater than 0.98, or a proportion of circularity of 0.92 or greater than less than 80% by number, the image forming device has excellent wear suppression properties of the cleaning blade and suppression properties of external additive filming on the image holding member.

[0036] According to the above-mentioned solution 2, an image forming apparatus is provided, which has better resistance to wear of a cleaning blade and resistance to film formation of an external additive on an image holding member than when the above-mentioned large-diameter side number particle size distribution index (upper side GSDp) of the above-mentioned silica particles is 1.075 or more.

[0037] According to the above-mentioned solution 3, an image forming apparatus is provided, which has better resistance to abrasion of a cleaning blade and resistance to film formation of external additives on an image holding member than when the smaller diameter side number size distribution index (lower side GSDp) of the silica particles is 1.080 or more.

[0038] According to the fourth aspect, there is provided an image forming apparatus having a cleaning blade that is more excellent in suppressing wear and suppressing filming of an external additive on an image holding member, compared to a case where the average circularity of the silica particles is less than 0.95 or greater than 0.97.

[0039] According to the above aspect 5 or 6, there is provided an image forming apparatus which is more excellent in suppressing abrasion of a cleaning blade and suppressing film formation of an external additive on an image holding member than when the surface protective layer contains only a styrene resin.

[0040] According to the seventh aspect, there is provided an image forming apparatus having a cleaning blade that is more effectively prevented from abrasion and an external additive from filming on an image holding member than when the charge-transporting skeleton in the acrylic resin is a benzidine skeleton.

[0041] According to the above-mentioned embodiment 8, an image forming apparatus is provided, which has better resistance to abrasion of a cleaning blade and resistance to film formation of external additives on an image holding member than a case where the proportion of the particles having a circularity of 0.92 or greater in the silica particles is less than 85% by number.

[0042] According to the above-mentioned embodiment 9, an image forming apparatus is provided, which is more excellent in suppressing abrasion of a cleaning blade and suppressing film formation of the external additive on an image holding member than in a case where the external additive in the electrostatic image developing toner is only the above-mentioned silica particles.

[0043] According to the above-mentioned scheme 12, a processing box is provided, which has a cleaning unit for cleaning the toner on the surface of an image holding member having a photosensitive layer and a surface protective layer on a conductive substrate. Compared with the case where the external additive in the toner for electrostatic image development is silica particles with a number average particle size of less than 110 nm or greater than 130 nm, or a large diameter side number particle size distribution index (upper side GSDp) of 1.080 or greater, or an average circularity of less than 0.94 or greater than 0.98, or a proportion of less than 80% with a circularity of 0.92 or greater, the processing box has excellent wear inhibition of the cleaning scraper and inhibition of external additive film formation on the image holding member. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic structural diagram showing an example of the image forming apparatus according to the present embodiment.

[0045] Figure 2 This is a schematic cross-sectional view showing an example of the layer structure of the image holding member in the image forming apparatus according to the present embodiment.

[0046] Figure 3 This is a schematic cross-sectional view showing another example of the layer structure of the image holding member in the image forming apparatus according to the present embodiment.

[0047] Figure 4 It will Figure 1An enlarged view showing an enlarged view of a position where a cleaning blade contacts an image holding member in an image forming apparatus. DETAILED DESCRIPTION

[0048] In the numerical ranges described in this specification, the upper limit or lower limit of one numerical range may be replaced by the upper limit or lower limit of another numerical range described in this specification. In addition, in the numerical ranges described in this specification, the upper limit or lower limit of the numerical range may be replaced by the value shown in the Examples.

[0049] In this specification, when referring to the amount of each component in a composition, if there are plural or more substances corresponding to each component in the composition, unless otherwise specified, the amount refers to the total amount of the plural or more substances present in the composition.

[0050] In this specification, “toner for developing electrostatic images” is also simply referred to as “toner”, and “developer for developing electrostatic images” is also simply referred to as “developer”.

[0051] Hereinafter, an embodiment as an example of the present invention will be described.

[0052] <Image Forming Apparatus>

[0053] The image forming apparatus of this embodiment includes: an image holding member, the image holding member including a photosensitive layer and a surface protective layer on a conductive substrate; a latent image forming unit, the latent image forming unit forming an electrostatic latent image on the image holding member; a developing unit, the developing unit developing the electrostatic latent image using an electrostatic image developing toner to form a toner image; a transfer unit, the transfer unit transferring the toner image to a recording medium; and a cleaning unit, the cleaning unit cleaning the toner on the surface of the image holding member, the electrostatic image developing toner containing toner particles and silica particles, the silica particles having a number average particle size of not less than 110 nm and not more than 130 nm, a large diameter side number particle size distribution index (upper side GSDp) of less than 1.080, an average circularity of not less than 0.94 and not more than 0.98, and a proportion of particles with a circularity of not less than 0.92 being not less than 80% by number.

[0054] In recent years, in image forming apparatuses using electrophotographic technology, a structure has been adopted to extend the life of image-retaining members (also referred to as "photoreceptors" or "electrophotographic photoreceptors"). This structure improves the abrasion resistance of the photoreceptor layer and the damage resistance of the photoreceptor by using an organic photoreceptor (hereinafter referred to as "OC photoreceptor") provided with a resin layer (hereinafter referred to as "surface protection layer") to protect the photoreceptor layer. This structure enhances the strength of the photoreceptor surface, making it less susceptible to wear and scratches caused by friction with the cleaning unit that cleans the toner from the photoreceptor surface.

[0055] On the other hand, OC photoreceptors have high surface hardness and are not easily scratched, so they have excellent surface smoothness and a high surface friction coefficient, which makes them susceptible to wear of the cleaning blade and results in low cleaning performance.

[0056] When using existing toners in OC photoreceptors, the rolling action of the external additives is strong, and the amount of toner released from the surface of the toner particles increases. This causes the cleaning unit to engage with the tip, making it impossible to maintain the effective nip width required for cleaning on the image retaining member. As a result, a large amount of external additives slips through. When used with OC photoreceptors with low surface cleanability, this often causes external additive filming (a phenomenon in which the external additive itself and the resulting fragments of the external additive adhere to the surface of the image retaining member).

[0057] It is speculated that the image forming device of this embodiment uses the above-mentioned silica particles with specific physical property values ​​as an external additive for the electrostatic image developing colorant. The rolling action of the above-mentioned silica particles is moderate, the free amount of the above-mentioned silica particles is sufficient, and the slippage amount of the external additive is reduced. When combined with the OC photoreceptor, the wear of the cleaning scraper and the formation of the external additive film on the image holding component can be suppressed.

[0058] Next, the configuration of the image forming apparatus according to this embodiment will be described in detail.

[0059] The image forming device of this embodiment includes: an image holding member, the image holding member includes a photosensitive layer and a surface protective layer on a conductive substrate; a latent image forming unit, the latent image forming unit forms an electrostatic latent image on the image holding member; a developing unit, the developing unit contains an electrostatic image developer containing an electrostatic image developing toner, and uses the electrostatic image developer to develop the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image; a transfer unit, the transfer unit transfers the toner image to a recording medium; and a cleaning unit, the cleaning unit having a cleaning scraper for cleaning the toner on the surface of the image holding member.

[0060] The image forming device of this embodiment is applied to the following well-known image forming devices: a direct transfer device, which directly transfers the electrostatic image developing toner image formed on the surface of the image holding member to the recording medium; an intermediate transfer device, which transfers the electrostatic image developing toner image formed on the surface of the image holding member to the surface of the intermediate transfer body for the first time, and transfers the electrostatic image developing toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium for the second time; a device equipped with a static elimination unit, which irradiates the surface of the image holding member with static elimination light to eliminate static after the transfer of the electrostatic image developing toner image and before charging; etc.

[0061] In the case of an intermediate transfer method device, the transfer unit application has, for example, a structure having the following components: an intermediate transfer body, the surface of which is transferred the electrostatic image developing toner image; a primary transfer unit, which primarily transfers the electrostatic image developing toner image formed on the surface of the image holding member to the surface of the intermediate transfer body; and a secondary transfer unit, which secondarily transfers the electrostatic image developing toner image transferred to the surface of the intermediate transfer body to the surface of the recording medium.

[0062] The image forming apparatus of the present embodiment may have, for example, a cartridge structure (process cartridge) in which a portion including at least the image holding member is attachable to and detachable from the image forming apparatus.

[0063] Hereinafter, an example of the image forming apparatus according to the present embodiment is shown, but the present invention is not limited thereto. It should be noted that the main parts shown in the drawings will be described, and description of other parts will be omitted.

[0064] Figure 1 This is a schematic structural diagram showing an example of the image forming apparatus according to the present embodiment.

[0065] like Figure 1 As shown, the image forming apparatus 10 of this embodiment is provided with, for example, an image holding member (electrophotographic photoreceptor) 12. The image holding member 12 is cylindrical and is connected to a drive unit 27 such as a motor via a driving force transmission member (not shown) such as a gear. The drive unit 27 is driven to rotate around a rotation axis indicated by a black dot. Figure 1 In the example shown, the motor is driven to rotate in the direction of arrow A.

[0066] Around the image holding member 12, for example, a charging unit 15, a latent image forming unit 16, a developing unit 18, a transfer unit 31, a cleaning unit 22, and a neutralizing unit 24 are arranged in order along the rotational direction of the image holding member 12. Furthermore, the image forming apparatus 10 is also provided with a fixing unit 26 having a fixing member 26A and a pressure member 26B arranged in contact with the fixing member 26A. Furthermore, the image forming apparatus 10 includes a control unit 36 ​​that controls the operation of each unit (or each part). It should be noted that the unit including the image holding member 12, the charging unit 15, the latent image forming unit 16, the developing unit 18, the transfer unit 31, and the cleaning unit 22 corresponds to the image forming unit.

[0067] In the image forming apparatus 10 , at least the image holding member 12 may be provided as a process cartridge integrated with other devices.

[0068] Hereinafter, each unit (each part) of the image forming apparatus 10 will be described in detail.

[0069] [Image holding member]

[0070] The image holding member in the image forming apparatus of this embodiment includes a photosensitive layer and a surface protective layer on a conductive substrate.

[0071] The photosensitive layer may be a single-layer photosensitive layer containing a charge generating material and a charge transporting material in the same photosensitive layer, integrating their functions, or a laminated photosensitive layer having separate functions of a charge generating layer and a charge transporting layer. In the case of a laminated photosensitive layer, the order of the charge generating layer and the charge transporting layer is not particularly limited, but the image holding member preferably has a configuration comprising a charge generating layer, a charge transporting layer, and a surface protective layer in this order on a conductive substrate. Furthermore, the image holding member may include layers other than these.

[0072] Figure 2 This is a schematic cross-sectional view illustrating an example of the layer configuration of an image holding member in the image forming apparatus of this embodiment. Image holding member 107A has the following structure: an undercoat layer 101 is provided on a conductive substrate 104, and a charge generating layer 102, a charge transport layer 103, and a surface protective layer 106 are formed thereon in this order. Image holding member 107A includes a photosensitive layer 105 whose functions are separated into the charge generating layer 102 and the charge transport layer 103.

[0073] in addition, Figure 3 This is a schematic cross-sectional view showing another example of the layer structure of the image holding member in the image forming apparatus according to the present embodiment. Figure 3The image holding member 107B shown has a structure in which an undercoat layer 101 is provided on a conductive substrate 104, and a photosensitive layer 105 and a surface protective layer 106 are sequentially formed. In the image holding member 107B, a single-layer photosensitive layer is formed in which a charge generating material and a charge transporting material are contained in the same photosensitive layer 105, thereby integrating their functions.

[0074] It should be noted that the image holding member in this embodiment may or may not be provided with the primer layer 101 .

[0075] Hereinafter, the image holding member in this embodiment will be described in detail, with reference numerals omitted for explanation.

[0076] (Conductive substrate)

[0077] Examples of the conductive substrate include metal plates, metal drums, and metal belts made of metals (aluminum, copper, zinc, chromium, nickel, molybdenum, vanadium, indium, gold, platinum, etc.) or alloys (stainless steel, etc.). Examples of the conductive substrate also include paper, resin films, and belts coated, vapor-deposited, or laminated with conductive compounds (e.g., conductive polymers, indium oxide, etc.), metals (e.g., aluminum, palladium, gold, etc.), or alloys. Here, "conductive" means a volume resistivity of less than 10 13 Ωcm.

[0078] When using an image holding member in a laser printer, the surface of the conductive substrate is preferably roughened to a centerline average roughness Ra of 0.04 μm or more and 0.5 μm or less to suppress interference fringes generated during laser irradiation. While roughening to prevent interference fringes is not particularly necessary when using non-interference light as a light source, it is beneficial for extending the lifespan by suppressing defects caused by surface irregularities on the conductive substrate.

[0079] Examples of surface roughening methods include wet honing in which an abrasive is suspended in water and sprayed onto a support; centerless grinding in which a conductive substrate is pressed against a rotating grindstone and continuously ground; and anodizing.

[0080] As a method for roughening the surface, the following method can also be cited: instead of roughening the surface of the conductive substrate, conductive or semiconductive powder is dispersed in a resin to form a layer on the surface of the conductive substrate, and the surface is roughened using the particles dispersed in the layer.

[0081] The roughening treatment based on anodic oxidation is to form an oxide film on the surface of the conductive substrate by using a conductive substrate of a metal system (such as aluminum) as an anode, performing anodic oxidation in an electrolyte solution. As an electrolyte solution, for example, sulfuric acid solution, oxalic acid solution, etc. can be enumerated. However, the porous anodic oxide film formed by anodic oxidation is chemically active under the state of being kept as it is, is easily contaminated, and the resistance change caused by the environment is also large. Therefore, for the porous anodic oxide film, it is preferably carried out following sealing treatment: the micropores of the oxide film are sealed by the volume expansion caused by the hydration reaction in pressurized steam or boiling water (metal salts such as nickel can be added), and become a more stable hydrated oxide.

[0082] The thickness of the anodic oxide film is preferably 0.3 μm to 15 μm, for example. When the film thickness is within the above range, it tends to exhibit a barrier property against injection and to suppress an increase in residual potential due to repeated use.

[0083] The conductive substrate may be subjected to treatment with an acidic treatment liquid or boehmite treatment.

[0084] The treatment using an acidic treatment solution is carried out, for example, as follows. First, an acidic treatment solution containing phosphoric acid, chromic acid, and hydrofluoric acid is prepared. Regarding the mixing ratio of phosphoric acid, chromic acid, and hydrofluoric acid in the acidic treatment solution, for example, phosphoric acid is in the range of 10% by mass to 11% by mass, chromic acid is in the range of 3% by mass to 5% by mass, and hydrofluoric acid is in the range of 0.5% by mass to 2% by mass, and the overall concentration of these acids is in the range of 13.5% by mass to 18% by mass. The treatment temperature is preferably, for example, 42°C to 48°C. The film thickness of the coating is preferably 0.3μm to 15μm.

[0085] The boehmite treatment is preferably performed by immersing the film in pure water at 90°C to 100°C for 5 to 60 minutes, or by contacting the film with heated steam at 90°C to 120°C for 5 to 60 minutes. The film thickness is preferably 0.1 μm to 5 μm. The film can be further anodized using an electrolyte solution with low film solubility, such as adipic acid, boric acid, a borate, a phosphate, a phthalate, a maleate, a benzoate, a tartrate, or a citrate.

[0086] (Base coating)

[0087] The undercoat layer is, for example, a layer containing inorganic particles and a binder resin.

[0088] Examples of inorganic particles include particles with a powder resistance (volume resistivity) of 10 2 Ωcm or more 10 11Among these, suitable inorganic particles having the above resistance value include metal oxide particles such as tin oxide particles, titanium oxide particles, zinc oxide particles, and zirconium oxide particles, and zinc oxide particles are particularly preferred.

[0089] The specific surface area of ​​the inorganic particles obtained by the BET method is, for example, 10 m 2 / g or above is appropriate.

[0090] The volume average particle size of the inorganic particles is suitably, for example, from 50 nm to 2000 nm (preferably from 60 nm to 1000 nm).

[0091] The content of the inorganic particles is preferably from 10% by mass to 80% by mass, and more preferably from 40% by mass to 80% by mass, based on the binder resin.

[0092] The inorganic particles may be surface-treated. Two or more inorganic particles having different surface treatments or different particle sizes may be mixed and used.

[0093] Examples of the surface treatment agent include silane coupling agents, titanate coupling agents, aluminum coupling agents, surfactants, etc. Silane coupling agents are particularly preferred, and silane coupling agents having an amino group are more preferred.

[0094] Examples of the silane coupling agent having an amino group include, but are not limited to, 3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane.

[0095] Silane coupling agents can be used in combination of two or more. For example, a silane coupling agent having an amino group can be used in combination with other silane coupling agents. As such other silane coupling agents, for example, vinyl trimethoxysilane, 3-methylacyloxypropyl tris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyl triacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, 3-chloropropyltrimethoxysilane, etc. can be cited, but are not limited to these.

[0096] The surface treatment method using the surface treatment agent may be any method as long as it is a known method, and may be either a dry method or a wet method.

[0097] The treatment amount of the surface treatment agent is preferably, for example, 0.5% by mass or more and 10% by mass or less relative to the inorganic particles.

[0098] Here, from the viewpoint of long-term stability of electrical characteristics and improvement of carrier-blocking properties, it is appropriate for the undercoat layer to contain an electron-accepting compound (acceptor compound) together with the inorganic particles.

[0099] Examples of electron-accepting compounds include quinone compounds such as tetrachlorobenzoquinone and tetrabromobenzoquinone; tetracyanobenzoquinone dimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone and 2,4,5,7-tetranitro-9-fluorenone; oxadiazole compounds such as 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole, 2,5-bis(4-naphthyl)-1,3,4-oxadiazole and 2,5-bis(4-diethylaminophenyl)-1,3,4-oxadiazole; xanthone compounds; thiophene compounds; dibenzoquinone compounds such as 3,3',5,5'-tetra-tert-butyldibenzoquinone; and other electron-transporting substances.

[0100] As the electron-accepting compound, a compound having an anthraquinone structure is particularly preferred.

[0101] Examples of the compound having an anthraquinone structure include hydroxyanthraquinone compounds, aminoanthraquinone compounds, and aminohydroxyanthraquinone compounds. Specific examples include anthraquinone, alizarin, quinizarin, anthrarutin, and pyrline.

[0102] The electron-accepting compound may be contained in the undercoat layer in a dispersed state together with the inorganic particles, or may be contained in a state of being attached to the surface of the inorganic particles.

[0103] Examples of a method for attaching the electron-accepting compound to the surface of the inorganic particles include a dry method and a wet method.

[0104] The dry method, for example, involves directly adding an electron-accepting compound or an electron-accepting compound dissolved in an organic solvent while stirring the inorganic particles using a mixer with high shear force. The electron-accepting compound is then sprayed with dry air or nitrogen to adhere to the surface of the inorganic particles. The electron-accepting compound is preferably added or sprayed at a temperature below the boiling point of the solvent. After the addition or spraying of the electron-accepting compound, the mixture may be baked at a temperature above 100°C. There are no particular restrictions on the baking temperature and duration, as long as the temperature and duration achieve electrophotographic properties.

[0105] The wet method is, for example, the following method: while dispersing the inorganic particles in a solvent using stirring, ultrasonic waves, a sand mill, a grinder, a ball mill, etc., an electron-accepting compound is added, and after stirring or dispersing, the solvent is removed to allow the electron-accepting compound to adhere to the surface of the inorganic particles. The method of removing the solvent can be, for example, by filtering or distilling. After the solvent is removed, baking can be further performed at a temperature of 100°C or above. There are no particular restrictions on baking as long as the temperature and time are such that electronic photographic characteristics can be obtained. In the wet method, the water contained in the inorganic particles can be removed before adding the electron-accepting compound. As examples thereof, a method of removing the water while stirring and heating in a solvent and a method of removing the water by azeotropic co-existence with the solvent can be cited.

[0106] The electron-accepting compound may be attached before or after the inorganic particles are surface-treated with a surface treatment agent, or the electron-accepting compound may be attached and the surface treatment with a surface treatment agent may be performed simultaneously.

[0107] The content of the electron-accepting compound is preferably from 0.01% by mass to 20% by mass, and more preferably from 0.01% by mass to 10% by mass, relative to the total mass of the inorganic particles.

[0108] Examples of the binder resin used in the primer layer include acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, unsaturated polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, urea-formaldehyde resins, phenol-formaldehyde resins, melamine resins, urethane resins, alkyd resins, epoxy resins, and other well-known polymer compounds; zirconium chelate compounds; titanium chelate compounds; aluminum chelate compounds; titanium alkoxide compounds; organic titanium compounds; and silane coupling agents.

[0109] As the binder resin used in the primer layer, for example, a charge transport resin having a charge transport group, a conductive resin (such as polyaniline, etc.) and the like can also be cited. Among these, the binder resin used in the primer layer is preferably a resin that is insoluble in the coating solvent of the upper layer, and is particularly preferably a resin obtained by reacting at least one resin selected from the group consisting of a urea-formaldehyde resin, a phenol-formaldehyde resin, a phenol-formaldehyde resin, a melamine resin, a urethane resin, an unsaturated polyester resin, an alkyd resin, an epoxy resin, and a thermosetting resin such as a polyamide resin, a polyester resin, a polyether resin, a methacrylic resin, an acrylic resin, a polyvinyl alcohol resin, and a polyvinyl acetal resin with a curing agent.

[0110] When two or more of these binder resins are used in combination, the mixing ratio thereof is set as needed.

[0111] The undercoat layer may contain various additives for the purpose of improving electrical characteristics, enhancing environmental stability, and improving image quality.

[0112] Examples of additives include known materials such as polycyclic condensed and azo-based electron transport pigments, zirconium chelate compounds, titanium chelate compounds, aluminum chelate compounds, titanium alkoxide compounds, organic titanium compounds, and silane coupling agents. Silane coupling agents can be used for surface treatment of inorganic particles as described above, but can also be added to the primer layer as an additive.

[0113] Examples of the silane coupling agent as an additive include vinyltrimethoxysilane, 3-methacryloxypropyltris(2-methoxyethoxy)silane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltriacetoxysilane, 3-mercaptopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, N,N-bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane, and 3-chloropropyltrimethoxysilane.

[0114] Examples of the zirconium chelate compound include butoxy zirconium, ethyl acetoacetate zirconium, triethanolamine zirconium, butyloxy zirconium acetylacetonate, butyloxy zirconium ethyl acetoacetate, zirconium acetate, zirconium oxalate, zirconium lactate, zirconium phosphonate, zirconium octylate, zirconium naphthenate, zirconium laurate, zirconium stearate, zirconium isostearate, butyloxy zirconium methacrylate, butyloxy zirconium stearate, and butyloxy zirconium isostearate.

[0115] Examples of the titanium chelate compound include tetraisopropyl titanate, tetra-n-butyl titanate, butyl titanate dimer, tetra(2-ethylhexyl) titanate, titanium acetylacetonate, titanium polyacetylacetonate, titanium octanediate, titanium ammonium lactate, titanium lactate, titanium ethyl lactate, titanium triethanolamide, and titanium polyhydroxystearate.

[0116] Examples of the aluminum chelate compound include aluminum isopropoxide, monobutoxyaluminum diisopropoxide, aluminum butoxide, bis(ethyl acetoacetate)aluminum diisopropoxide, and tris(ethyl acetoacetate)aluminum.

[0117] These additives may be used alone or as a mixture or polycondensate of two or more compounds.

[0118] The Vickers hardness of the primer layer is suitably 35 or higher.

[0119] In order to suppress moiré images, it is appropriate to adjust the surface roughness (ten-point average roughness) of the undercoat layer to 1 / (4n) (n is the refractive index of the upper layer) to 1 / 2 of the wavelength λ of the exposure laser used.

[0120] To adjust the surface roughness, resin particles or the like may be added to the undercoat layer. Examples of the resin particles include silicone resin particles and cross-linked polymethyl methacrylate resin particles. Furthermore, to adjust the surface roughness, the surface of the undercoat layer may be ground. Examples of the grinding method include polishing, sandblasting, wet honing, and grinding.

[0121] The undercoat layer can be formed by a known formation method without particular limitation. For example, a coating film of an undercoat layer-forming coating liquid prepared by adding the above-mentioned components to a solvent is formed, and the coating film is dried and optionally heated.

[0122] Examples of the solvent used for preparing the coating liquid for forming the undercoat layer include known organic solvents such as alcohol solvents, aromatic hydrocarbon solvents, halogenated hydrocarbon solvents, ketone solvents, ketone alcohol solvents, ether solvents, and ester solvents.

[0123] Specific examples of these solvents include common organic solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, benzyl alcohol, methyl cellosol, ethyl cellosol, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene.

[0124] Examples of a method for dispersing the inorganic particles when preparing the coating liquid for forming an undercoat layer include known methods such as a roll mill, a ball mill, a vibration ball mill, an attritor, a sand mill, a colloid mill, and a paint shaker.

[0125] Examples of a method for applying the undercoat layer-forming coating liquid to the conductive substrate include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0126] The film thickness of the coating layer is set, for example, preferably within the range of 15 μm or more, and more preferably within the range of 20 μm or more and 50 μm or less.

[0127] (Middle layer)

[0128] Although illustration is omitted, an intermediate layer may be further provided between the undercoat layer and the photosensitive layer.

[0129] The intermediate layer is, for example, a layer containing a resin. Examples of the resin used in the intermediate layer include polymer compounds such as acetal resins (e.g., polyvinyl butyral), polyvinyl alcohol resins, polyvinyl acetal resins, casein resins, polyamide resins, cellulose resins, gelatin, polyurethane resins, polyester resins, methacrylic resins, acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, vinyl chloride-vinyl acetate-maleic anhydride resins, silicone resins, silicone-alkyd resins, phenol-formaldehyde resins, and melamine resins.

[0130] The intermediate layer may be a layer containing an organometallic compound. Examples of the organometallic compound used in the intermediate layer include organometallic compounds containing metal atoms such as zirconium, titanium, aluminum, manganese, and silicon.

[0131] The compounds used in the intermediate layer may be used alone or as a mixture or polycondensate of two or more compounds.

[0132] Among these, the intermediate layer is preferably a layer containing an organometallic compound containing a zirconium atom or a silicon atom.

[0133] The intermediate layer can be formed by any known method without particular limitation. For example, a coating film of an intermediate layer-forming coating liquid prepared by adding the above-mentioned components to a solvent is formed, and the coating film is dried and optionally heated.

[0134] As a coating method for forming the intermediate layer, a common method such as a dip coating method, a push-up coating method, a wire bar coating method, a spray coating method, a blade coating method, a knife coating method, or a curtain coating method is used.

[0135] The thickness of the intermediate layer is preferably set to be within a range of, for example, 0.1 μm to 3 μm. The intermediate layer may also be used as a primer layer.

[0136] (Charge Generation Layer)

[0137] The charge generating layer is, for example, a layer comprising a charge generating material and a binder resin. Alternatively, the charge generating layer may be a vapor-deposited layer of the charge generating material. This vapor-deposited layer of the charge generating material is preferably used when a non-interference light source such as an LED (Light Emitting Diode) or an organic EL (Electro-Luminescence) image array is used.

[0138] Examples of the charge generating material include azo pigments such as disazo and trisazo; condensed-ring aromatic pigments such as dibromoanthraquinone; perylene pigments; pyrrolopyrrole pigments; phthalocyanine pigments; zinc oxide; and trigonal selenium.

[0139] Among these, metal phthalocyanine pigments or metal-free phthalocyanine pigments are preferably used as charge-generating materials to cope with near-infrared laser exposure. Specifically, more preferred are hydroxygallium phthalocyanines disclosed in Japanese Patent Application Laid-Open Nos. 5-263007 and 5-279591; chlorogallium phthalocyanines disclosed in Japanese Patent Application Laid-Open No. 5-98181; dichlorotin phthalocyanines disclosed in Japanese Patent Application Laid-Open Nos. 5-140472 and 5-140473; and titanium phthalocyanines disclosed in Japanese Patent Application Laid-Open No. 4-189873.

[0140] On the other hand, in order to cope with laser exposure in the near-ultraviolet region, preferred charge-generating materials include fused-ring aromatic pigments such as dibromoanthraquinone; thioindigo pigments; tetraazaporphyrin compounds; zinc oxide; trigonal selenium; and disazo pigments disclosed in Japanese Patent Application Publication Nos. 2004-78147 and 2005-181992.

[0141] These charge-generating materials can also be used when using non-interference light sources such as LEDs and organic EL image arrays with a central emission wavelength between 450 nm and 780 nm. However, from a resolution perspective, using a photosensitive layer with a thickness of 20 μm or less increases the electric field intensity within the photosensitive layer, making it prone to charge injection from the substrate, resulting in image defects known as black spots. This problem becomes more pronounced when using charge-generating materials such as trigonal selenium and phthalocyanine pigments, which are prone to generating dark current in p-type semiconductors.

[0142] In contrast, when using n-type semiconductors such as fused-ring aromatic pigments, perylene pigments, and azo pigments as charge-generating materials, dark current is less likely to occur, and image defects known as black spots can be suppressed even when formed into thin films. Examples of n-type charge-generating materials include, but are not limited to, compounds (CG-1) to (CG-27) described in paragraphs 0288 to 0291 of JP-A-2012-155282.

[0143] Note that n-type is determined by the polarity of the flowing photocurrent using the commonly used time-of-flight method, and a charge-generating material in which electrons flow more easily as carriers than holes is defined as n-type.

[0144] The binder resin used in the charge generating layer can be selected from a wide range of insulating resins. Alternatively, the binder resin can be selected from organic photoconductive polymers such as poly-N-vinylcarbazole, polyvinylanthracene, polyvinylpyrene, and polysilane.

[0145] Examples of the binder resin include polyvinyl butyral resin, polyarylate resin (polycondensate of bisphenols and aromatic dicarboxylic acids), polycarbonate resin, polyester resin, phenoxy resin, vinyl chloride-vinyl acetate copolymer, polyamide resin, acrylic resin, polyacrylamide resin, polyvinyl pyridine resin, cellulose resin, urethane resin, epoxy resin, casein, polyvinyl alcohol resin, and polyvinyl pyrrolidone resin. Here, "insulating property" refers to a volume resistivity of 10 13 Ωcm or more.

[0146] These binder resins may be used alone or in combination of two or more.

[0147] The mixing ratio of the charge generating material to the binder resin is preferably within a range of 10:1 to 1:10 in terms of mass ratio.

[0148] The charge generating layer may contain other known additives.

[0149] The charge generating layer can be formed using any known method without particular limitation. For example, a coating film of a charge generating layer-forming coating solution prepared by adding the above-mentioned components to a solvent is formed, the coating film is dried, and optionally heated. The charge generating layer can be formed by vapor deposition of the charge generating material. Formation of the charge generating layer by vapor deposition is particularly suitable when using condensed-ring aromatic pigments or perylene pigments as the charge generating material.

[0150] Examples of the solvent used to prepare the charge generating layer-forming coating solution include methanol, ethanol, n-propanol, n-butanol, benzyl alcohol, methyl cellosolve, ethyl cellosolve, acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, n-butyl acetate, dioxane, tetrahydrofuran, dichloromethane, chloroform, chlorobenzene, and toluene. These solvents may be used alone or in combination of two or more.

[0151] As a method for dispersing particles (e.g., charge generating material) in the charge generating layer-forming coating liquid, a medium disperser such as a ball mill, a vibrating ball mill, an attritor, a sand mill, a horizontal sand mill, or a medium-free disperser such as a stirring machine, an ultrasonic disperser, a roller mill, or a high-pressure homogenizer can be used. Examples of high-pressure homogenizers include an impact method in which the dispersion is dispersed by liquid-liquid collision or liquid-wall collision under high pressure, and a penetration method in which the dispersion is dispersed by penetrating fine flow channels under high pressure.

[0152] During the dispersion, it is effective to adjust the average particle size of the charge generating material in the charge generating layer-forming coating liquid to preferably 0.5 μm or less, more preferably 0.3 μm or less, and even more preferably 0.15 μm or less.

[0153] Examples of methods for applying the charge generating layer-forming coating liquid onto the base coat (or intermediate layer) include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0154] The film thickness of the charge generating layer is set, for example, preferably within the range of 0.1 μm to 5.0 μm, more preferably within the range of 0.2 μm to 2.0 μm.

[0155] (Charge Transport Layer)

[0156] The charge transport layer is, for example, a layer containing a charge transport material and a binder resin. The charge transport layer may be a layer containing a polymer charge transport material.

[0157] Examples of charge transport materials include electron transport compounds such as quinone compounds such as p-benzoquinone, chloranil, tetrachlorobenzoquinone, and tetrabromobenzoquinone; tetracyanoquinodimethane compounds; fluorenone compounds such as 2,4,7-trinitrofluorenone; xanthone compounds; benzophenone compounds; cyanovinyl compounds; and vinyl compounds. Other examples of charge transport materials include hole transport compounds such as triarylamine compounds, benzidine compounds, arylalkane compounds, aryl-substituted vinyl compounds, stilbene compounds, anthracene compounds, and hydrazone compounds. These charge transport materials may be used alone or in combination of two or more, but are not limited to these.

[0158] As the charge transport material, from the viewpoint of charge mobility, a triarylamine derivative represented by the following structural formula (a-1) or a benzidine derivative represented by the following structural formula (a-2) is preferred.

[0159] [Chemistry 1]

[0160]

[0161] In the structural formula (a-1), Ar T1 、Ar T2 and Ar T3 Each independently represents a substituted or unsubstituted aryl group, -C6H4-C(R T4 )=C(R T5 )(R T6 ), or -C6H4-CH=CH-CH=C(R T7 )(R T8 ), R T4 、R T5 、R T6 、R T7 and R T8Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group.

[0162] Examples of substituents for the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Examples of substituents for the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0163] [Chemistry 2]

[0164]

[0165] In the structural formula (a-2), R T91 and R T92 Each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms, or an alkoxy group having 1 to 5 carbon atoms, and R T101 、R T102 、R T111 and R T112 Each independently represents a halogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, an amino group substituted by an alkyl group having 1 to 2 carbon atoms, a substituted or unsubstituted aryl group, -C(R T12 )=C(R T13 )(R T14 ), or -CH=CH-CH=C(R T15 )(R T16 ), R T12 、R T13 、R T14 、R T15 and R T16 Each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted aryl group, and Tm1, Tm2, ​​Tn1, and Tn2 each independently represent an integer of 0 or more and 2 or less.

[0166] Examples of substituents for the above groups include halogen atoms, alkyl groups having 1 to 5 carbon atoms, and alkoxy groups having 1 to 5 carbon atoms. Examples of substituents for the above groups include substituted amino groups substituted with alkyl groups having 1 to 3 carbon atoms.

[0167] Here, among the triarylamine derivatives represented by the structural formula (a-1) and the benzidine derivatives represented by the structural formula (a-2), the one having "-C6H4-CH=CH-CH=C(R T7 )(R T8 )" or a triarylamine derivative having "-CH=CH-CH=C(RT15 )(R T16 )"" benzidine derivatives.

[0168] As polymeric charge transport materials, known materials having charge transport properties, such as poly-N-vinylcarbazole and polysilane, are used. Polyester-based polymeric charge transport materials disclosed in Japanese Patent Application Laid-Open Nos. 8-176293 and 8-208820 are particularly preferred. It should be noted that polymeric charge transport materials can be used alone or in combination with a binder resin.

[0169] The binder resin used in the charge transport layer can include polycarbonate resin, polyester resin, polyarylate resin, methacrylic resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl acetate resin, styrene-butadiene copolymer, vinylidene chloride-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic anhydride copolymer, silicone resin, silicone alkyd resin, phenol-formaldehyde resin, styrene-alkyd resin, poly-N-vinyl carbazole, polysilane, etc. Among these, as the binder resin, preferably polycarbonate resin or polyarylate resin. These binder resins can be used alone or in combination.

[0170] It should be noted that the mixing ratio of the charge transport material to the binder resin is preferably 10:1 to 1:5 in terms of mass ratio.

[0171] The charge transport layer may contain other known additives.

[0172] The charge transport layer can be formed by any known method without particular limitation. For example, a coating film of a charge transport layer-forming coating liquid prepared by adding the above-mentioned components to a solvent is formed, the coating film is dried, and optionally heated.

[0173] Examples of solvents used to prepare the charge transport layer coating solution include common organic solvents such as aromatic hydrocarbons such as benzene, toluene, xylene, and chlorobenzene; ketones such as acetone and 2-butanone; halogenated aliphatic hydrocarbons such as dichloromethane, chloroform, and vinyl chloride; and cyclic or linear ethers such as tetrahydrofuran and diethyl ether. These solvents may be used alone or in combination of two or more.

[0174] Examples of the coating method for applying the charge transport layer-forming coating liquid onto the charge generating layer include common methods such as blade coating, wire bar coating, spray coating, dip coating, bead coating, air knife coating, and curtain coating.

[0175] The film thickness of the charge transport layer is set, for example, preferably within the range of 5 μm to 50 μm, more preferably within the range of 10 μm to 30 μm.

[0176] (Surface protection layer)

[0177] A surface protective layer (hereinafter simply referred to as a "protective layer") is provided on the photosensitive layer. The protective layer is provided, for example, to prevent chemical changes in the photosensitive layer during charging or to further improve the mechanical strength of the photosensitive layer. Therefore, a layer composed of a cured film (crosslinked film) is preferably used as the protective layer. Examples of such layers include the layers described in 1) or 2) below.

[0178] 1) A layer composed of a cured film of a composition containing a reactive group-containing charge transport material having a reactive group and a charge-transporting skeleton in the same molecule (ie, a layer containing a polymer or a crosslinked product of the reactive group-containing charge transport material).

[0179] 2) A layer consisting of a cured film of a composition comprising a non-reactive charge transport material and a reactive group-containing non-charge transport material having no charge transport skeleton but having a reactive group (i.e., a layer comprising a non-reactive charge transport material and a polymer or crosslinked body of the reactive group-containing non-charge transport material).

[0180] Examples of the reactive group include chain polymerizable groups, epoxy groups, -OH, -OR (wherein R represents an alkyl group), -NH2, -SH, -COOH, -SiR Q1 3-Qn (OR Q2 ) Qn (Among them, R Q1 represents a hydrogen atom, an alkyl group, or a substituted or unsubstituted aryl group, R Q2 represents a hydrogen atom, an alkyl group or a trialkylsilyl group, and Qn represents an integer from 1 to 3. As the reactive group in the non-charge transport material containing a reactive group, the above-mentioned reactive groups can be mentioned.

[0181] As a chain polymerizable group, as long as it is a functional group that can undergo free radical polymerization, there is no particular limitation. As a chain polymerizable group, for example, a functional group containing a group having an ethylenically unsaturated bond can be cited. Specifically, as a functional group having an ethylenically unsaturated bond, a group having at least one selected from the group consisting of vinyl, vinyl ether, vinyl sulfide, styryl (vinylphenyl), acryloyl, methacryloyl and their derivatives can be cited. Among the above, for the reason of its excellent reactivity, as a chain polymerizable group, it is preferably a group having at least one selected from the group consisting of vinyl, styryl (vinylphenyl), acryloyl, methacryloyl and their derivatives, more preferably a group having at least one selected from the group consisting of acryloyl, methacryloyl and their derivatives, further preferably a group having at least one of acryloyl and methacryloyl.

[0182] The charge transport skeleton is not particularly limited as long as it is a known structure in image holding members. Examples include structures derived from the skeleton of a nitrogen-containing hole transporting compound such as a triarylamine compound (a compound having a triarylamine skeleton), a benzidine compound (a compound having a benzidine skeleton), or a hydrazone compound (a compound having a hydrazone skeleton), and conjugated with a nitrogen atom. Among these, the charge transport skeleton preferably contains a triarylamine skeleton.

[0183] The reactive group-containing charge transport material, the non-reactive charge transport material, and the reactive group-containing non-charge transport material can be selected from publicly known materials.

[0184] Furthermore, from the viewpoint of suppressing film formation of the external additive and suppressing abrasion of the cleaning blade, the surface protection layer preferably contains an acrylic resin.

[0185] In the present embodiment, the acrylic resin refers to a resin having a structural unit derived from a (meth)acrylic compound, and the content of the structural unit is preferably 30% by mass or more, more preferably 50% by mass or more, relative to the total mass of the resin.

[0186] Examples of the (meth)acrylic compound include (meth)acrylate compounds, (meth)acrylic acid, (meth)acrylamide compounds, and (meth)acrylonitrile.

[0187] In addition, from the viewpoint of suppressing film formation of external additives and suppressing wear of the cleaning blade, the acrylic resin contained in the surface protection layer preferably has a charge-transporting skeleton, and the charge-transporting skeleton more preferably includes a triarylamine skeleton, and the charge-transporting skeleton is particularly preferably a triarylamine skeleton.

[0188] Of the above 1) and 2), from the perspective of suppressing film formation of the external additive and suppressing wear of the cleaning blade, the surface protective layer preferably comprises a cured product of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule as in 1) above. When the surface protective layer comprises a cured product of a composition containing a reactive group-containing charge transport material having a reactive group and a charge transport skeleton in the same molecule as in 1) above, the surface protective layer tends to have a higher hardness than a surface protective layer comprising a cured product as in 2) above.

[0189] From the viewpoint of suppressing film formation of external additives and suppressing wear of the cleaning blade, the above-mentioned reactive group-containing charge transport material preferably includes a reactive group-containing charge transport material having at least one of an acryloyl group and a methacryloyl group as a reactive group (hereinafter also referred to as "specific reactive group-containing charge transport material (a)").

[0190] ·Specific charge transport material containing reactive groups (a)

[0191] The specific reactive group-containing charge transport material (a) used in the surface protective layer is a compound having a charge transport skeleton and an acryloyl group or a methacryloyl group in the same molecule and is not particularly limited as long as the structural requirements are met.

[0192] The specific reactive group-containing charge transport material (a) is preferably a compound having a methacryloyl group. The reason for this is not clear, but it is speculated as follows. Typically, compounds having highly reactive acryloyl groups are used in the curing reaction. In the case where a highly reactive acryloyl group is used as a substituent on a bulky charge transport skeleton, the curing reaction is prone to unevenness, and therefore unevenness and wrinkles in the surface protective layer are easily generated on the cured film. On the other hand, it is speculated that by using a specific reactive group-containing charge transport material (a) having a methacryloyl group having a lower reactivity than an acryloyl group, the generation of unevenness and wrinkles in the surface protective layer in the cured film is easily suppressed.

[0193] In the specific reactive group-containing charge transport material (a), a structure having one or more carbon atoms sandwiched between the charge transport backbone and the acryloyl group or methacryloyl group is preferred. Specifically, a preferred embodiment of the specific reactive group-containing charge transport material (a) is one in which a carbon chain containing one or more carbon atoms is provided as a linking group between the charge transport backbone and the acryloyl group or methacryloyl group. In particular, an alkylene group is the most preferred embodiment of the linking group.

[0194] The reasons for preferring the above embodiment are not necessarily clear, but the following are considered: Regarding the mechanical strength of the surface protective layer, it is believed that when the bulky charge transport skeleton is close to the polymerization site (acryloyl or methacryloyl group) and is rigid, the polymerization sites are difficult to move relative to each other, and the probability of reaction is sometimes reduced.

[0195] In addition, a preferred embodiment is a compound (a') in which the specific reactive group-containing charge transport material (a) is a structure having a triphenylamine skeleton and three or more, more preferably four or more, methacryloyl groups in the same molecule. In this embodiment, the stability of the compound during synthesis is easily ensured. In addition, this embodiment can form a surface protective layer with a high crosslinking density and sufficient mechanical strength, thereby easily achieving a thick film of the surface protective layer.

[0196] In the present embodiment, the specific reactive group-containing charge transport material (a) is preferably a compound represented by the following general formula (A) because of its excellent charge transport properties.

[0197] [Chemistry 3]

[0198]

[0199] In the above general formula (A), Ar 1 to Ar 4 Each independently represents a substituted or unsubstituted aryl group, Ar 5 represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted arylene group, and D represents -(CH2) d -(O-CH2-CH2) e -O-CO-C(CH3)=CH2, c1 to c5 each independently represent an integer of 0 or more and 2 or less, k represents 0 or 1, d represents an integer of 0 or more and 5 or less, e represents 0 or 1, and the total number of D is 4 or more.

[0200] In the general formula (A), Ar 1 to Ar 4 Each independently represents a substituted or unsubstituted aryl group. 1 to Ar 4 They can be the same or different.

[0201] Here, as the substituent in the substituted aryl group, an alkyl group or alkoxy group having 1 to 4 carbon atoms, a substituted or unsubstituted aryl group having 6 or more and 10 or less carbon atoms, etc. can be cited as D: -(CH2) d -(O-CH2-CH2) e -O-CO-C(CH3)=CH2.

[0202] As Ar1 to Ar 4 , preferably any one of the following formulas (1) to (7). It should be noted that in the following formulas (1) to (7), Ar 1 to Ar 4 Each of the above can be connected to "-(D) C " together with the "-(D) C "Merge expression" - (D) C1 ” to “-(D) C4 ”.

[0203] [Chemistry 4]

[0204]

[0205] In the above formulas (1) to (7), R 1 represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group substituted with an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, and an aralkyl group having 7 to 10 carbon atoms, and R 2 to R 4 Each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted by an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom, Ar represents a substituted or unsubstituted arylene group, and D represents -(CH2) d -(O-CH2-CH2) e -O-CO-C(CH3)=CH2, c represents 1 or 2, s represents 0 or 1, and t represents an integer of 0 or more and 3 or less.

[0206] Here, as Ar in formula (7), a group represented by the following structural formula (8) or (9) is preferred.

[0207] [Chemistry 5]

[0208]

[0209] In the above formulas (8) and (9), R 5 and R 6 Each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a phenyl group substituted by an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom, and t' each represents an integer of 0 to 3.

[0210] In the above formula (7), Z' represents a divalent organic linking group, preferably a group represented by any one of the following formulas (10) to (17). In the above formula (7), s represents 0 or 1.

[0211] [Chemistry 6]

[0212]

[0213] In the above formulas (10) to (17), R 7 and R 8 Each independently represents one selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a phenyl group substituted with an alkoxy group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms, an unsubstituted phenyl group, an aralkyl group having 7 to 10 carbon atoms, and a halogen atom, W represents a divalent group, q and r each independently represent an integer of 1 to 10, and t" each independently represents an integer of 0 to 3.

[0214] W in the above formulae (16) to (17) is preferably any of the divalent groups represented by the following (18) to (26). In formula (25), u represents an integer of 0 or more and 3 or less.

[0215] [Chemistry 7]

[0216]

[0217] In the general formula (A), Ar 5 When k is 0, it is a substituted or unsubstituted aryl group. Examples of the aryl group include 1 to Ar 4 The same aryl groups as those exemplified in the description of . 5 When k is 1, it is a substituted or unsubstituted arylene group. Examples of the arylene group include Ar 1 to Ar 4 The aryl group exemplified in the description is removed from one -N(Ar 3 -(D) C3 )(Ar 4 -(D) C4 ) is replaced by a hydrogen atom in the position of arylene group.

[0218] Specific examples of the compound represented by general formula (A) include the compounds described in paragraphs 0236 to 0240 of JP-A-2018-4968.

[0219] Examples of methods for producing the compound represented by general formula (A) include the methods described in paragraphs 0241 to 0244 of JP-A-2018-4968.

[0220] The reactive charge transport material may contain a compound other than the specific reactive group-containing charge transport material (a) (hereinafter also referred to as "other reactive charge transport material (a")"). As the other reactive charge transport material, a compound obtained by introducing an acryloyl group or a methacryloyl group into a known charge transport material is used.

[0221] The ratio of the specific reactive group-containing charge transport material (a) to the reactive group-containing charge transport material is preferably 90% by mass or more and 100% by mass or less, and more preferably 98% by mass or more and 100% by mass or less.

[0222] The content of the reactive group-containing charge transport material relative to the composition (solid content) used to form the surface protective layer is preferably 30% by mass or more and 100% by mass or less, more preferably 40% by mass or more and 100% by mass or less, and even more preferably 50% by mass or more and 100% by mass or less. Within this range, the electrical properties of the cured film are excellent, and the cured film can be thickened.

[0223] From the viewpoint of suppressing film formation of the external additive and suppressing abrasion of the cleaning blade, the hardness (universal hardness) of the surface protection layer is preferably 140 N / mm 2 Above 300N / mm 2 Below, more preferably 160mN / mm 2 Above 280N / mm 2 Below, more preferably 180mN / mm 2 Above 260mN / mm 2 the following.

[0224] The universal hardness of the surface protection layer is measured by the following method.

[0225] The universal hardness of the surface protection layer is the universal hardness measured when a Vickers square pyramid diamond indenter is used in a hardness test at 25° C. and a relative humidity of 50% and the indentation is performed with a maximum load of 20 mN.

[0226] (Details of measurement)

[0227] As a measuring device, FISCHERSCOPE H100V (microhardness measuring device) manufactured by Fischer Instruments KK was used. The indenter used in the measurement was a Vickers square pyramid diamond indenter with an opposite angle of 136°.

[0228] (Measurement conditions)

[0229] Loading conditions: The Vickers indenter was pressed into the surface of the surface protection layer of the image holding member at a rate of 4 mN / sec.

[0230] Loading time: 5 seconds.

[0231] Hold time: 5 seconds.

[0232] Unloading condition: Remove the load at the same speed as the load.

[0233] The sample was fixed to an H100V tester and a Vickers indenter was inserted perpendicularly to the surface of the surface protective layer. The measurement was performed in the following order: indenter load (5 seconds), load retention (5 seconds), and then unloading.

[0234] The surface protective layer may contain other known additives.

[0235] The surface protective layer can be formed by any known method without particular limitation. For example, a coating film of a surface protective layer-forming coating liquid prepared by adding the above-mentioned components to a solvent is formed, the coating film is dried, and then cured by heating or the like as needed.

[0236] Examples of solvents used to prepare the coating solution for forming the surface protective layer include aromatic solvents such as toluene and xylene; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester solvents such as ethyl acetate and butyl acetate; ether solvents such as tetrahydrofuran and dioxane; cellosolve solvents such as ethylene glycol monomethyl ether; and alcohol solvents such as isopropyl alcohol and butanol. These solvents can be used alone or in mixtures of two or more. It should be noted that the coating solution for forming the protective layer may also be solvent-free.

[0237] Examples of a method for applying the coating liquid for forming a surface protective layer onto a photosensitive layer (e.g., a charge transport layer) include common methods such as dip coating, push-up coating, wire bar coating, spray coating, blade coating, knife coating, and curtain coating.

[0238] The film thickness of the surface protection layer is set, for example, preferably within the range of 1 μm to 20 μm, more preferably within the range of 2 μm to 10 μm.

[0239] (Single-layer photosensitive layer)

[0240] The single-layer photosensitive layer (charge generation / charge transport layer) is, for example, a layer containing a charge generation material and a charge transport material, and optionally a binder resin and other known additives. It should be noted that these materials are the same as those described for the charge generation layer and charge transport layer.

[0241] Furthermore, in the single-layer photosensitive layer, the content of the charge generating material is preferably from 0.1% by mass to 10% by mass, more preferably from 0.8% by mass to 5% by mass, relative to the total solids content of the single-layer photosensitive layer. Furthermore, in the single-layer photosensitive layer, the content of the charge transport material is preferably from 5% by mass to 50% by mass, relative to the total solids content.

[0242] The method for forming the single-layer photosensitive layer is the same as the method for forming the charge generating layer and the charge transporting layer.

[0243] The film thickness of the single-layer photosensitive layer is preferably, for example, 5 μm to 50 μm, and more preferably 10 μm to 40 μm.

[0244] [Charging unit]

[0245] The image forming apparatus of the present embodiment preferably includes a charging unit for charging the surface of the image holding member.

[0246] The charging unit 15 charges the surface of the image holding member 12. The charging unit 15 includes, for example, a charging member 14 disposed on the surface of the image holding member 12 in a contact or non-contact manner to charge the surface of the image holding member 12; and a power source 28 (an example of a voltage application unit for the charging member) that applies a charging voltage to the charging member 14. The power source 28 is electrically connected to the charging member 14.

[0247] Examples of the charging member 14 of the charging unit 15 include contact chargers using a conductive charging roller, a charging brush, a charging film, a charging rubber blade, a charging tube, and the like. Furthermore, examples of the charging member 14 include non-contact roller chargers, scorotron chargers or corotron chargers utilizing corona discharge, and other known chargers.

[0248] [Latent image forming unit]

[0249] The latent image forming unit 16 forms an electrostatic latent image on the surface of the charged image holding member 12. Specifically, for example, the latent image forming unit 16 irradiates the surface of the image holding member 12 charged by the charging unit 14 with light L modulated based on image information of the target image to be formed, thereby forming an electrostatic latent image corresponding to the image information on the image holding member 12.

[0250] As the latent image forming unit 16 , for example, an optical device including a light source for performing exposure using light such as semiconductor laser light, LED light, or liquid crystal light valve light according to an image pattern may be mentioned.

[0251] [Developer unit]

[0252] The developing unit 18 is disposed, for example, downstream of the position where the latent image forming unit 16 irradiates the image holding member 12 in the rotational direction. A container for storing a developer is provided within the developing unit 18. This container contains an electrostatic image developer comprising a specific electrostatic image developing toner. The electrostatic image developing toner is stored within the developing unit 18 in a charged state, for example.

[0253] The developing unit 18 includes, for example, a developing member 18A for developing the electrostatic image formed on the surface of the image holding member 12 using a developer containing electrostatic image developing toner, and a power source 32 for applying a development voltage to the developing member 18A. The developing member 18A is electrically connected to the power source 32, for example.

[0254] The developing member 18A of the developing unit 18 is selected according to the type of developer, and an example thereof is a developing roller having a developing sleeve with a built-in magnet.

[0255] The developing unit 18 (including the power supply 32) is electrically connected to, for example, a control unit 36 ​​provided in the image forming apparatus 10. The control unit 36 ​​controls the development of the developing unit 18A, applying a development voltage. Upon application of the development voltage, the developing unit 18A is charged to a development potential corresponding to the development voltage. Furthermore, the developing unit 18A, charged to the development potential, for example, retains the developer contained in the developing unit 18 on its surface and supplies the electrostatic image developing toner contained in the developer from the developing unit 18 to the surface of the image holding member 12. On the surface of the image holding member 12, to which the electrostatic image developing toner has been supplied, the electrostatic image formed is developed as an electrostatic image developing toner image.

[0256] [Transfer unit]

[0257] The transfer unit 31 is provided, for example, downstream of the position of the developing unit 18A in the rotational direction of the image holding member 12. The transfer unit 31 includes, for example, a transfer unit 20 for transferring an electrostatic developing toner image formed on the surface of the image holding member 12 onto a recording medium 30A, and a power supply 30 for applying a transfer voltage to the transfer unit 20. The transfer unit 20 is, for example, cylindrical, and the recording medium 30A is conveyed while being sandwiched between the transfer unit 20 and the image holding member 12. The transfer unit 20 is, for example, electrically connected to the power supply 30.

[0258] Examples of the transfer member 20 include contact transfer chargers using belts, rollers, films, rubber cleaning blades, and non-contact transfer chargers known per se, such as scorotron transfer chargers or corotron transfer chargers utilizing corona discharge.

[0259] The transfer unit 31 (including the power supply 30) is electrically connected to, for example, a control unit 36 ​​provided in the image forming apparatus 10, and is driven and controlled by the control unit 36 ​​to apply a transfer voltage to the transfer member 20. The transfer member 20, to which the transfer voltage is applied, is charged to a transfer potential corresponding to the transfer voltage.

[0260] When a transfer voltage having a polarity opposite to that of the electrostatic image developing toner constituting the electrostatic image developing toner image formed on the image holding member 12 is applied to the transfer member 20 from the power supply 30 of the transfer member 20, for example, in the area where the image holding member 12 and the transfer member 20 face each other (see Figure 1 A transfer electric field having an electric field strength that causes each electrostatic image developing toner constituting the electrostatic image developing toner image on the image holding member 12 to be transferred from the image holding member 12 to the transfer component 20 side by electrostatic force is formed.

[0261] The recording medium 30A is housed in a housing (not shown), for example, and is transported from the housing along a transport path 34 by a plurality of transport members (not shown) to a transfer area 32A where the image holding member 12 and the transfer member 20 face each other. Figure 1 In the illustrated example, the recording medium 30A is conveyed in the direction of arrow B. Upon reaching the transfer area 32A, the electrostatic image-developing toner image on the image holding member 12 is transferred by the transfer electric field formed in that area by, for example, applying a transfer voltage to the transfer member 20. Specifically, the electrostatic image-developing toner image is transferred to the recording medium 30A, for example, by transfer of the electrostatic image-developing toner from the surface of the image holding member 12 to the recording medium 30A. Furthermore, the electrostatic image-developing toner image on the image holding member 12 is transferred to the recording medium 30A by the transfer electric field.

[0262] [Cleaning unit (cleaning unit)]

[0263] The cleaning unit 22 is provided downstream of the transfer area 32A in the rotational direction of the image holding member 12. The cleaning unit 22 cleans (sweeps) residual toner adhering to the image holding member 12 after the toner image for electrostatic image development is transferred to the recording medium 30A. The cleaning unit 22 also cleans away adhering matter such as paper dust in addition to residual toner.

[0264] The cleaning unit 22 includes a cleaning blade 220 , and removes adhering matter on the surface of the image holding member 12 by directing the front end of the cleaning blade 220 in a direction opposite to the rotation direction of the image holding member 12 .

[0265] Here, refer to Figure 4 The cleaning unit 22 will be described.

[0266] Figure 4 It shows Figure 1 FIG. 2 is a schematic structural diagram showing the arrangement of the cleaning blade 220 in the cleaning unit 22 .

[0267] like Figure 4 As shown, the front end of the cleaning blade 220 faces a direction opposite to the rotation direction (arrow direction) of the image holding member 12 , and in this state, contacts the surface of the image holding member 12 .

[0268] The angle θ between the cleaning blade 220 and the image holding member 12 is preferably set to 5° or more and 35° or less, and more preferably set to 10° or more and 25° or less.

[0269] In addition, the pressing pressure N of the cleaning blade 220 on the image holding member 12 is preferably set to 0.6 gf / mm 2 Above 6.0gf / mm 2 the following.

[0270] Here, if Figure 4 As shown, the angle θ specifically refers to the tangent line of the contact portion between the front end of the cleaning blade 220 and the image holding member 12 ( Figure 4 The angle formed by the single-dot chain line in FIG. 1 and the non-deformed portion of the cleaning blade 220.

[0271] In addition, if Figure 4 As shown, the pressing pressure N is the pressure (gf / mm2) applied toward the center of the image holding member 12 at the position where the cleaning blade 220 contacts the image holding member 12. 2 ).

[0272] The cleaning blade 220 is joined to a support member (at the side opposite to the surface in contact with the image holding member 12). Figure 4 (not shown) and supported by the support member. The cleaning blade 220 is pressed against the image retaining member 12 by the support member with the aforementioned pressing pressure. Examples of the support member include metal materials such as aluminum and stainless steel. It should be noted that an adhesive layer formed of an adhesive or the like may be provided between the support member and the cleaning blade 220 to bond the two together.

[0273] The cleaning unit may include known components in addition to the cleaning blade 220 and a supporting member that supports the cleaning blade 220 .

[0274] The cleaning blade is preferably constructed such that at least the portion of the cleaning blade that contacts the image retaining member comprises a plate-shaped rubber substrate. The cleaning blade may have a single-layer structure of the rubber substrate, or a laminated structure in which a back layer is laminated on the back side of the rubber substrate (the side not facing the image retaining member). The back layer may be a plurality of layers.

[0275] The rubber substrate comprises rubber as a whole. Here, rubber refers to a polymer compound having rubber elasticity at room temperature (25°C). Examples of rubber include polyurethane, silicone rubber, fluororubber, chloroprene rubber, butadiene rubber, and the like. Among the above, polyurethane is preferred as the rubber substrate, and highly crystalline polyurethane is more preferred.

[0276] Polyurethane is usually synthesized by polymerizing polyisocyanates and polyols. In addition, in addition to polyols, resins having functional groups that can react with isocyanate groups can also be used. It should be noted that the polyurethane preferably has a hard segment and a soft segment.

[0277] Here, the "hard segments" and "soft segments" refer to segments in which the material constituting the former is made of a relatively harder material than the material constituting the latter, and the material constituting the latter is made of a relatively softer material than the material constituting the former.

[0278] The combination of the material constituting the hard segment (hard segment material) and the material constituting the soft segment (soft segment material) is not particularly limited and can be selected from known materials so as to form a combination in which one is relatively harder than the other and the other is relatively softer than the one. The following combination is preferred.

[0279] Soft segment materials

[0280] First, as soft segment materials, polyester polyols obtained by dehydration condensation of diols and dibasic acids, polycarbonate polyols obtained by reaction of diols and alkyl carbonates, polycaprolactone polyols, polyether polyols, etc. It should be noted that commercially available products of the above-mentioned polyols used as soft segment materials include, for example, PLACCEL 205 and PLACCEL 240 manufactured by Daicel.

[0281] Hard segment materials

[0282] In addition, as the hard segment material, a resin having a functional group reactive with an isocyanate group is preferably used. Furthermore, a flexible resin is preferred, and from the perspective of flexibility, an aliphatic resin having a linear structure is more preferred. As specific examples, acrylic resins containing two or more hydroxyl groups, polybutadiene resins containing two or more hydroxyl groups, and epoxy resins having two or more epoxy groups are preferably used.

[0283] Examples of commercially available products of acrylic resins containing two or more hydroxyl groups include Actflow (grades: UMB-2005B, UMB-2005P, UMB-2005, UME-2005, etc.) manufactured by Soken Chemical Co., Ltd.

[0284] Examples of commercially available products of the polybutadiene resin containing two or more hydroxyl groups include R-45HT manufactured by Idemitsu Kosan Co., Ltd.

[0285] As the epoxy resin having two or more epoxy groups, an epoxy resin that is more flexible and tough than existing epoxy resins is preferably used, rather than an epoxy resin that is hard and brittle like existing general epoxy resins. As the epoxy resin, for example, from the perspective of molecular structure, an epoxy resin having a structure (flexible backbone) in its main chain structure that can improve the mobility of the main chain is preferably used. Examples of the flexible backbone include alkylene backbones, cycloalkane backbones, and polyoxyalkylene backbones, with polyoxyalkylene backbones being particularly preferred.

[0286] Furthermore, from a physical property perspective, epoxy resins with a lower viscosity relative to their molecular weight are preferred compared to existing epoxy resins. Specifically, a weight-average molecular weight within the range of 900 ± 100 and a viscosity at 25°C within the range of 15,000 ± 5,000 mPa·s are preferred, with a viscosity at 25°C within the range of 15,000 ± 3,000 mPa·s being more preferred. Commercially available epoxy resins with these properties include, for example, EPLICON EXA-4850-150 manufactured by DIC Corporation.

[0287] When using hard segment materials and soft segment materials, the mass ratio of the material constituting the hard segment relative to the total amount of the hard segment material and the soft segment material (hereinafter referred to as the "hard segment material ratio") is preferably in the range of 10 mass% to 30 mass%, more preferably in the range of 13 mass% to 23 mass%, and further preferably in the range of 15 mass% to 20 mass%.

[0288] By setting the hard segment material ratio to 10% by mass or more, wear resistance can be achieved. On the other hand, by setting the hard segment material ratio to 30% by mass or less, flexibility and elongation can be achieved without becoming too hard, and the occurrence of chipping can be suppressed.

[0289] Polyisocyanate

[0290] Examples of polyisocyanates used in the synthesis of polyurethane include 4,4′-diphenylmethane diisocyanate (MDI), 2,6-toluene diisocyanate (TDI), 1,6-hexamethylene diisocyanate (HDI), 1,5-naphthalene diisocyanate (NDI), and 3,3-dimethylphenyl-4,4-diisocyanate (TODI).

[0291] From the viewpoint of easily forming hard segment aggregates of a desired size (particle diameter), the polyisocyanate is more preferably 4,4′-diphenylmethane diisocyanate (MDI), 1,5-naphthalene diisocyanate (NDI), or hexamethylene diisocyanate (HDI).

[0292] The amount of the polyisocyanate compounded is preferably from 20 to 40 parts by mass, more preferably from 20 to 35 parts by mass, and even more preferably from 20 to 30 parts by mass, relative to 100 parts by mass of the resin having a functional group reactive with an isocyanate group.

[0293] By having a content of 20 parts by mass or more, a larger amount of urethane bonds can be secured, the hard segments can be grown, and the required hardness can be obtained. On the other hand, by having a content of 40 parts by mass or less, the hard segments will not become too large, elongation can be obtained, and cracking of the sliding member can be suppressed.

[0294] Cross-linking agent

[0295] Examples of crosslinking agents include diols (2-functional), triols (3-functional), and tetraols (4-functional), and these may be used in combination. Furthermore, amine compounds may be used as crosslinking agents. It should be noted that it is preferred to use a crosslinking agent with three or more functional groups for crosslinking. Examples of trifunctional crosslinking agents include trimethylolpropane, glycerol, and triisopropanolamine.

[0296] The amount of the crosslinking agent added is preferably 2 parts by mass or less per 100 parts by mass of the resin having a functional group reactive with an isocyanate group. By setting the amount to 2 parts by mass or less, molecular motion is not restricted by chemical crosslinking, and the hard segments derived from urethane bonds generated by aging grow significantly, making it easier to achieve the desired hardness.

[0297] ·Molding method of rubber substrate

[0298] The rubber substrate comprising polyurethane as an example of rubber is produced using a general polyurethane production method such as a prepolymer method or a one-shot method. The prepolymer method is suitable for obtaining polyurethane with excellent strength and wear resistance, but the method is not limited thereto.

[0299] Polyurethane is formed by mixing a polyisocyanate compound and a crosslinking agent with the above-mentioned polyol. It should be noted that the rubber substrate is formed by forming the rubber substrate-forming composition prepared by the above-mentioned method into a sheet by, for example, centrifugal molding or extrusion molding, and then cutting the sheet.

[0300] ·Physical properties

[0301] When the rubber contained in the rubber base is polyurethane, the weight average molecular weight of the polyurethane is preferably in the range of 1,000 to 4,000, and more preferably in the range of 1,500 to 3,500.

[0302] From the viewpoint of suppressing film formation of the external additive and suppressing wear of the cleaning blade, the JIS-A hardness (H) of at least the portion of the cleaning blade in contact with the image holding member is BLD ) is preferably 60° or more and 95° or less, more preferably 65° or more and 90° or less, and further preferably 70° or more and 85° or less.

[0303] The JIS-A hardness is a value measured using a type A durometer specified in JIS K 7215 (1986) in accordance with the hardness testing method shown in JIS K 7311 (1995).

[0304] The contact portion with the image holding member refers to both a portion where the cleaning blade contacts the image holding member when the rotation of the image holding member stops and a portion where the cleaning blade contacts the image holding member when the image holding member rotates.

[0305] In order to make the JIS-A hardness of at least the contact portion of the cleaning blade with the image holding member not less than 60 and not more than 75, for example, the following methods can be mentioned: a method of adjusting the combination of the hard segment material and the soft segment material; a method of adjusting the material ratio (mixing ratio) of the hard segment material and the soft segment material; a method of adjusting the curing conditions (e.g., aging time, aging temperature) of the composition for forming the rubber substrate (cleaning blade molding composition).

[0306] From the viewpoint of suppressing film formation of external additives and suppressing wear of the cleaning blade, the hardness (H BLD ) and the hardness of the surface protective layer (H OCL ) ratio (H BLD / H OCL ) is preferably 0.8 or less, more preferably 0.7 or less, and further preferably 0.6 or less.

[0307] [Static elimination unit]

[0308] The image forming apparatus of the present embodiment preferably includes a static eliminating unit that exposes the surface of the image holding member to eliminate static electricity after the electrostatic image developing toner image is transferred.

[0309] The static elimination unit 24 is provided, for example, on the downstream side of the image holding member 12 in the rotational direction relative to the cleaning unit 22. The static elimination unit 24 removes static electricity by exposing the surface of the image holding member 12 after the electrostatic image developing toner image is transferred. Specifically, for example, the static elimination unit 24 is electrically connected to a control unit 36 ​​provided in the image forming apparatus 10 and is driven and controlled by the control unit 36 ​​to remove static electricity by exposing the entire surface of the image holding member 12 (specifically, the entire image forming area, for example).

[0310] Examples of the static eliminating unit 24 include a device having a light source such as a tungsten lamp that emits white light or a light emitting diode (LED) that emits red light.

[0311] [Fusing unit]

[0312] The image forming apparatus according to the present embodiment preferably includes a fixing unit that fixes the toner image transferred onto the recording medium.

[0313] The fixing unit 26 is disposed, for example, downstream of the transfer area 32A in the conveyance direction of the recording medium 30A along the conveyance path 34. The fixing unit 26 includes a fixing member 26A and a pressure member 26B disposed in contact with the fixing member 26A. The fixing unit 26 fixes the electrostatic developing toner image transferred onto the recording medium 30A at the contact portion between the fixing member 26A and the pressure member 26B. Specifically, for example, the fixing unit 26 is electrically connected to a control unit 36 ​​provided in the image forming apparatus 10. The control unit 36 ​​controls the driving of the fixing unit 26, and the fixing unit 26 uses heat and pressure to fix the electrostatic developing toner image transferred onto the recording medium 30A onto the recording medium 30A.

[0314] As the fixing unit 26 , a known fixing device per se, for example, a heat roller fixing device, an oven fixing device, etc. can be cited.

[0315] Specifically, for example, a known fixing unit including a fixing roller or a fixing belt as the fixing member 26A and a pressure roller or a pressure belt as the pressure member 26B is applied as the fixing unit 26 .

[0316] Here, the recording medium 30A to which the electrostatic image developing toner image has been transferred by passing through the opposing area (transfer area 32A) between the image retaining member 12 and the transfer member 20 transported along the transport path 34 further reaches the setting position of the fixing unit 26 along the transport path 34 under the action of, for example, a transport member not shown in the figure, and the electrostatic image developing toner image on the recording medium 30A is fixed.

[0317] The recording medium 30A, on which the image is formed by fixing the electrostatic image developing toner image, is discharged to the outside of the image forming apparatus 10 by a plurality of transport members (not shown). It should be noted that after being de-electrified by the de-electrification unit 24, the image holding member 12 is recharged to the charging potential by the charging unit 15.

[0318] [Operation of Image Forming Apparatus]

[0319] An example of the operation of the image forming apparatus 10 according to this embodiment will be described. It should be noted that various operations of the image forming apparatus 10 are performed by a control program executed by the control unit 36 ​​.

[0320] The image forming operation of the image forming apparatus 10 will be described.

[0321] First, the surface of the image holding member 12 is charged by the charging unit 15. The latent image forming unit 16 exposes the charged surface of the image holding member 12 based on image information. This forms an electrostatic image corresponding to the image information on the image holding member 12. The developing unit 18 develops the electrostatic image formed on the surface of the image holding member 12 using a developer containing a specific electrostatic image developing toner. This forms an electrostatic image developing toner image on the surface of the image holding member 12.

[0322] The electrostatic image developing toner image formed on the surface of the image holding member 12 is transferred to the recording medium 30A in the transfer unit 31 . The electrostatic image developing toner image transferred to the recording medium 30A is fixed by the fixing unit 26 .

[0323] On the other hand, the surface of the image holding member 12 to which the electrostatic image developing toner image has been transferred is cleaned (cleaned) by the cleaning blade 220 in the cleaning unit 22 and then de-electrified by the de-electrification unit 24 .

[0324] [Electrostatic image developer]

[0325] The image forming apparatus of the present embodiment preferably includes an electrostatic image developer containing an electrostatic image developing toner.

[0326] The electrostatic image developer used in the present embodiment may be a single-component developer containing only a toner, or a two-component developer containing a toner and a carrier.

[0327] [Toner for electrostatic image development]

[0328] The electrostatic image developing toner used in this embodiment contains toner particles and silica particles, wherein the silica particles have a number average particle size of not less than 110 nm and not more than 130 nm, a large diameter side number particle size distribution index (upper side GSDp) of less than 1.080, an average circularity of not less than 0.94 and not more than 0.98, and a proportion of particles with a circularity of not less than 0.92 of not less than 80% by number.

[0329] Furthermore, the electrostatic image developing toner used in the present embodiment may further contain inorganic oxide particles, lubricant particles, and external additives other than the inorganic oxide particles and lubricant particles, as needed.

[0330] (Toner particles)

[0331] The toner particles are composed of, for example, a binder resin and, if necessary, a colorant, a release agent, and other additives.

[0332] -Binding resin-

[0333] Examples of the binder resin include vinyl resins composed of homopolymers of monomers such as styrenes (e.g., styrene, p-chlorostyrene, α-methylstyrene, etc.), (meth)acrylates (e.g., methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, etc.), ethylenically unsaturated nitriles (e.g., acrylonitrile, methacrylonitrile, etc.), vinyl ethers (e.g., vinyl methyl ether, vinyl isobutyl ether, etc.), vinyl ketones (vinyl methyl ketone, vinyl ethyl ketone, vinyl isopropenyl ketone, etc.), and olefins (e.g., ethylene, propylene, butadiene, etc.), or copolymers obtained by combining two or more of these monomers.

[0334] Examples of the binder resin include non-vinyl resins such as epoxy resins, polyester resins, polyurethane resins, polyamide resins, cellulose resins, polyether resins, and modified rosin, mixtures of these non-vinyl resins with the above-mentioned vinyl resins, and graft polymers obtained by polymerizing vinyl monomers in the presence of these non-vinyl resins.

[0335] These binder resins may be used alone or in combination of two or more.

[0336] (1) Styrene acrylic resin

[0337] As the binder resin, styrene acrylic resin is preferred.

[0338] Styrene acrylic resin is a copolymer obtained by copolymerizing at least a styrene monomer (a monomer having a styrene skeleton) and a (meth)acrylic monomer (a monomer having a (meth)acryloyl group, preferably a monomer having a (meth)acryloyloxy group). Styrene acrylic resin includes, for example, a copolymer of a styrene monomer and the aforementioned (meth)acrylate monomer. It should be noted that the acrylic resin portion of the styrene acrylic resin is a partial structure formed by polymerizing either an acrylic monomer or a methacrylic monomer. In addition, "(meth)acrylic acid / acyl" is an expression that includes both "acrylic acid / acyl" and "methacrylic acid / acyl."

[0339] Specific examples of the styrene-based monomers include styrene, alkyl-substituted styrenes (e.g., α-methylstyrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, etc.), halogen-substituted styrenes (e.g., 2-chlorostyrene, 3-chlorostyrene, 4-chlorostyrene, etc.), and vinylnaphthalene. The styrene-based monomers may be used alone or in combination of two or more.

[0340] Among these, styrene is preferred as the styrene-based monomer from the viewpoints of easiness of reaction, easiness of reaction control, and availability.

[0341] Specific examples of the (meth)acrylic acid monomer include (meth)acrylic acid and (meth)acrylic acid esters. Examples of the (meth)acrylic acid esters include (meth)acrylic acid alkyl esters (e.g., methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, n-pentyl (meth)acrylate, n-hexyl acrylate, n-heptyl (meth)acrylate, n-octyl (meth)acrylate, n-decyl (meth)acrylate, n-dodecyl (meth)acrylate, n-lauryl (meth)acrylate, n-tetradecyl (meth)acrylate, n-hexadecyl (meth)acrylate, n-octadecyl (meth)acrylate, isopropyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, isoamyl (meth)acrylate, pentyl (meth)acrylate), and tert-butyl (meth)acrylate. The (meth)acrylate monomers include esters such as neopentyl (meth)acrylate, isohexyl (meth)acrylate, isoheptyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, and tert-butylcyclohexyl (meth)acrylate, etc.), aryl (meth)acrylates (for example, phenyl (meth)acrylate, biphenyl (meth)acrylate, diphenylethyl (meth)acrylate, tert-butylphenyl (meth)acrylate, and terphenyl (meth)acrylate, etc.), dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, β-carboxyethyl (meth)acrylate, and (meth)acrylamide. The (meth)acrylic acid-based monomers may be used alone or in combination of two or more.

[0342] Among (meth)acrylic acid monomers, (meth)acrylic acid esters are preferably (meth)acrylic acid esters having an alkyl group with 2 to 14 carbon atoms (preferably 2 to 10 carbon atoms, more preferably 3 to 8 carbon atoms) from the viewpoint of improving the fixing properties of the toner. Among them, n-butyl (meth)acrylate is preferred, and n-butyl acrylate is particularly preferred.

[0343] The copolymerization ratio of the styrene-based monomer to the (meth)acrylic-based monomer (based on mass, styrene-based monomer / (meth)acrylic-based monomer) is not particularly limited, but is preferably 85 / 15 to 60 / 40.

[0344] The styrene acrylic resin preferably has a cross-linked structure. Preferred examples of the styrene acrylic resin having a cross-linked structure include styrene acrylic resins obtained by copolymerizing at least a styrene monomer, a (meth)acrylic monomer, and a cross-linking monomer.

[0345] Examples of the crosslinkable monomer include bifunctional or higher-functional crosslinking agents.

[0346] Examples of bifunctional crosslinking agents include divinylbenzene, divinylnaphthalene, di(meth)acrylate compounds (e.g., diethylene glycol di(meth)acrylate, methylenebis(meth)acrylamide, decanediol diacrylate, glycidyl(meth)acrylate, etc.), polyester di(meth)acrylates, and 2-([1'-methylpropylideneamino]carboxyamino)ethyl methacrylate.

[0347] Examples of trifunctional or higher-functional crosslinking agents include tri(meth)acrylate compounds (e.g., pentaerythritol tri(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.), tetra(meth)acrylate compounds (e.g., pentaerythritol tetra(meth)acrylate, oligoesters (meth)acrylate, etc.), 2,2-bis(4-methacryloyloxypolyethoxyphenyl)propane, diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, triallyl trimellitate, and diaryl chlorendic acid.

[0348] Among them, as the crosslinking monomer, from the viewpoint of improving the fixing property of the toner, a (meth)acrylate compound having two or more functional groups is preferred, a difunctional (meth)acrylate compound is more preferred, a difunctional (meth)acrylate compound having an alkylene group having 6 to 20 carbon atoms is further preferred, and a difunctional (meth)acrylate compound having a linear alkylene group having 6 to 20 carbon atoms is particularly preferred.

[0349] The copolymerization ratio of the cross-linking monomer to all monomers (weight basis, cross-linking monomer / all monomers) is not particularly limited, but is preferably 2 / 1,000 to 20 / 1,000.

[0350] From the viewpoint of improving the fixing property of the toner, the glass transition temperature (Tg) of the styrene acrylic resin is preferably 40° C. or higher and 75° C. or lower, and more preferably 50° C. or higher and 65° C. or lower.

[0351] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, according to the "extrapolated glass transition onset temperature" method described in JIS K 7121-1987 "Plastics - Determination of Transition Temperatures".

[0352] From the viewpoint of storage stability of the toner, the weight average molecular weight of the styrene acrylic resin is preferably 5,000 to 200,000, more preferably 10,000 to 100,000, and particularly preferably 20,000 to 80,000.

[0353] The method for producing the styrene acrylic resin is not particularly limited, and various polymerization methods (e.g., solution polymerization, precipitation polymerization, suspension polymerization, bulk polymerization, emulsion polymerization, etc.) can be applied. In addition, the polymerization reaction can be applied to a known operation (e.g., batch, semi-continuous, continuous, etc.).

[0354] (2) Polyester resin

[0355] As the binder resin, polyester resin is preferred.

[0356] Examples of the polyester resin include known amorphous (non-crystalline) polyester resins. A crystalline polyester resin may also be used in combination with the amorphous polyester resin. However, the crystalline polyester resin is preferably used in an amount of 2% by mass to 40% by mass (preferably 2% by mass to 20% by mass) relative to the total binder resin.

[0357] The "crystallinity" of a resin means that the resin exhibits a clear endothermic peak rather than a step-like change in endothermic value in differential scanning calorimetry (DSC). Specifically, the half-value width of the endothermic peak is within 10°C when measured at a heating rate of 10°C / min.

[0358] On the other hand, the "amorphous nature" of a resin means that the half-value width exceeds 10° C., the endothermic value shows a step-like change, or a clear endothermic peak is not confirmed.

[0359] Amorphous polyester resin

[0360] Examples of the amorphous polyester resin include polycondensates of polycarboxylic acids and polyols. A commercially available amorphous polyester resin may be used, as may a synthetic product.

[0361] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid, succinic acid, alkenylsuccinic acid, adipic acid, and sebacic acid), alicyclic dicarboxylic acids (e.g., cyclohexanedicarboxylic acid), aromatic dicarboxylic acids (e.g., terephthalic acid, isophthalic acid, phthalic acid, and naphthalene dicarboxylic acid), anhydrides thereof, and lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof. Among these, aromatic dicarboxylic acids are preferred as the polycarboxylic acid.

[0362] Regarding polycarboxylic acids, trivalent or higher carboxylic acids that have a cross-linked structure or a branched structure may also be used in combination with dicarboxylic acids. Examples of trivalent or higher carboxylic acids include trimellitic acid, pyromellitic acid, their anhydrides, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters of their anhydrides.

[0363] The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0364] Examples of the polyol include aliphatic diols (e.g., ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, butanediol, hexanediol, neopentyl glycol, etc.), alicyclic diols (e.g., cyclohexanediol, cyclohexanedimethanol, hydrogenated bisphenol A, etc.), and aromatic diols (e.g., ethylene oxide adducts of bisphenol A, propylene oxide adducts of bisphenol A, etc.). Among these, aromatic diols and alicyclic diols are preferred, and aromatic diols are more preferred.

[0365] As the polyol, a trivalent or higher polyol having a cross-linked structure or a branched structure may be used in combination with the diol. Examples of the trivalent or higher polyol include glycerin, trimethylolpropane, and pentaerythritol.

[0366] The polyols may be used alone or in combination of two or more.

[0367] The glass transition temperature (Tg) of the amorphous polyester resin is preferably 50°C or higher and 80°C or lower, and more preferably 50°C or higher and 65°C or lower.

[0368] The glass transition temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC), more specifically, according to the "extrapolated glass transition onset temperature" method described in JIS K 7121-1987 "Plastics - Determination of Transition Temperatures".

[0369] The weight average molecular weight (Mw) of the amorphous polyester resin is preferably 5,000 to 1,000,000, and more preferably 7,000 to 500,000.

[0370] The number average molecular weight (Mn) of the amorphous polyester resin is preferably 2,000 to 100,000.

[0371] The molecular weight distribution Mw / Mn of the amorphous polyester resin is preferably 1.5 or more and 100 or less, and more preferably 2 or more and 60 or less.

[0372] It should be noted that the weight average molecular weight and number average molecular weight are measured by gel permeation chromatography (GPC). Molecular weight determination based on GPC uses GPC HLC-8120GPC manufactured by Tosoh Corporation as a measuring apparatus and a column TSKgel SuperHM-M (15 cm) manufactured by Tosoh Corporation in tetrahydrofuran (THF) solvent. The weight average molecular weight and number average molecular weight are calculated from the molecular weight calibration curve prepared using a monodisperse polystyrene standard sample from the measurement results.

[0373] The amorphous polyester resin is obtained by a known production method. Specifically, for example, the polymerization temperature is set at 180°C to 230°C, and the reaction system is depressurized as needed to remove water and alcohol generated during condensation while the reaction is carried out.

[0374] It should be noted that if the raw monomers are insoluble or incompatible at the reaction temperature, a high-boiling-point solvent may be added as a cosolvent to dissolve them. In this case, the polycondensation reaction is carried out while distilling off the cosolvent. If a monomer with poor compatibility is present, the monomer with poor compatibility may be condensed with an acid or alcohol intended to be polycondensed with the monomer before being polycondensed with the main component.

[0375] Crystalline polyester resin

[0376] Examples of the crystalline polyester resin include polycondensates of polycarboxylic acids and polyols. As the crystalline polyester resin, a commercially available product may be used, or a synthetic product may be used.

[0377] Here, regarding the crystalline polyester resin, a polycondensate obtained using a polymerizable monomer having a linear aliphatic group is more preferable than a polycondensate obtained using a polymerizable monomer having an aromatic group in order to facilitate formation of a crystal structure.

[0378] Examples of the polycarboxylic acid include aliphatic dicarboxylic acids (e.g., oxalic acid, succinic acid, glutaric acid, adipic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc.), aromatic dicarboxylic acids (e.g., dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, and 2,6-naphthalene dicarboxylic acid), anhydrides thereof, or lower (e.g., having 1 to 5 carbon atoms) alkyl esters thereof.

[0379] Regarding polycarboxylic acids, trivalent or higher carboxylic acids that have a cross-linked or branched structure may be used in combination with dicarboxylic acids. Examples of trivalent carboxylic acids include aromatic carboxylic acids (e.g., 1,2,3-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, etc.), their anhydrides, or their lower (e.g., having 1 to 5 carbon atoms) alkyl esters.

[0380] As the polycarboxylic acid, a dicarboxylic acid having a sulfonic acid group or a dicarboxylic acid having an ethylenic double bond can be used in combination with these dicarboxylic acids.

[0381] The polyvalent carboxylic acid may be used alone or in combination of two or more.

[0382] Examples of the polyol include aliphatic diols (e.g., linear aliphatic diols having a main chain portion with 7 to 20 carbon atoms). Examples of the aliphatic diol include ethylene glycol, 1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,14-eicosanediol. Among these, preferred aliphatic diols are 1,8-octanediol, 1,9-nonanediol, and 1,10-decanediol.

[0383] Regarding the polyol, a trivalent or higher valent alcohol having a cross-linked structure or a branched structure may be used in combination with the diol. Examples of the trivalent or higher valent alcohol include glycerin, trimethylolethane, trimethylolpropane, and pentaerythritol.

[0384] The polyols may be used alone or in combination of two or more.

[0385] Here, the content of the aliphatic diol in the polyol is preferably 80 mol% or more, and preferably 90 mol% or more.

[0386] The melting temperature of the crystalline polyester resin is preferably 50°C to 100°C, more preferably 55°C to 90°C, and even more preferably 60°C to 85°C.

[0387] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) according to the “melting peak temperature” described in the method for determining the melting temperature in JIS K7121-1987 “Methods for determining transition temperatures of plastics”.

[0388] The weight average molecular weight (Mw) of the crystalline polyester resin is preferably 6,000 or more and 35,000 or less.

[0389] The crystalline polyester resin can be obtained, for example, by a known production method similar to the amorphous polyester.

[0390] The content of the binder resin is, for example, preferably 40% by mass to 95% by mass, more preferably 50% by mass to 90% by mass, and still more preferably 60% by mass to 85% by mass, based on the entire toner particles.

[0391] -Colorant-

[0392] Examples of the colorant include carbon black, chrome yellow, fast yellow, benzidine yellow, vat yellow (Threne Yellow), quinoline yellow, pigment yellow, permanent orange GTR, pyrazolone orange, sulfur fast orange, lake red, permanent red, brilliant carmine 3B, brilliant carmine 6B, Dupont Oil Red, pyrazolone red, lithol red, rhodamine B lake, golden red C, pigment red, rose bengal, aniline blue, ultramarine blue, calco oil blue, methylene blue chloride, phthalocyanine blue, pigment blue, phthalocyanine green, malachite green oxalate and various dyes such as acridine-based, xanthene-based, azo-based, benzoquinone-based, azine-based, anthraquinone-based, thioindigo-based, dioxazine-based, thiazine-based, azomethine-based, indigo-based, phthalocyanine-based, nigrosine-based, polymethine-based, triphenylmethane-based, diphenylmethane-based, and thiazole-based dyes.

[0393] The coloring agent may be used alone or in combination of two or more.

[0394] The colorant may be a colorant that has been subjected to surface treatment as needed, or may be used in combination with a dispersant. Furthermore, two or more colorants may be used in combination.

[0395] The content of the colorant is, for example, preferably from 1 mass % to 30 mass % inclusive, and more preferably from 3 mass % to 15 mass % inclusive, based on the total mass of the toner particles.

[0396] - Anti-sticking agent -

[0397] Examples of the release agent include hydrocarbon waxes, natural waxes such as carnauba wax, rice wax, and candelilla wax, synthetic or mineral / petroleum waxes such as montan wax, and ester waxes such as fatty acid esters and montanic acid esters. The release agent is not limited thereto.

[0398] The melting temperature of the release agent is preferably 50°C to 110°C, more preferably 60°C to 100°C.

[0399] The melting temperature is determined from a DSC curve obtained by differential scanning calorimetry (DSC) measurement according to the “melting peak temperature” described in the method for determining the melting temperature in JIS K 7121-1987 “Methods for determining transition temperatures of plastics”.

[0400] The content of the release agent is, for example, preferably from 1 mass % to 20 mass % both inclusive, and more preferably from 5 mass % to 15 mass % both inclusive, based on the entire toner particles.

[0401] -Other additives-

[0402] Examples of other additives include known additives such as magnetic materials, charge control agents, and inorganic powders. These additives are contained in the toner particles as internal additives.

[0403] - Characteristics of toner particles, etc. -

[0404] The toner particles may be toner particles of a single-layer structure or toner particles of a so-called core-shell structure composed of a core (core particle) and a coating layer (shell layer) that covers the core.

[0405] Here, the toner particles having a core-shell structure may be composed of, for example, a core portion containing a binder resin and, if necessary, other additives such as a colorant and a release agent, and a coating layer containing a binder resin.

[0406] The volume average particle diameter (D50v) of the toner particles is preferably 2 μm or more and 10 μm or less, and more preferably 4 μm or more and 8 μm or less.

[0407] Incidentally, various average particle diameters and various particle size distribution indices of the toner particles are measured using a Coulter Multisizer II (manufactured by Beckman Coulter) and an ISOTON-II (manufactured by Beckman Coulter) for the electrolyte.

[0408] During measurement, 0.5 mg to 50 mg of the sample is added to 2 ml of a 5% aqueous solution of a surfactant (preferably sodium alkylbenzenesulfonate) as a dispersant, and the solution is added to 100 ml to 150 ml of the electrolyte.

[0409] The electrolyte solution containing the sample was dispersed using an ultrasonic disperser for 1 minute. The particle size distribution of particles with a diameter of 2 to 60 μm was measured using a Coulter Multisizer II with a 100 μm aperture. A total of 50,000 particles were sampled.

[0410] For the particle size range (channel) divided based on the measured particle size distribution, the cumulative distribution of volume and number is drawn from the small diameter side, and the particle size at which the cumulative amount reaches 16% is defined as the volume particle size D16v and the number particle size D16p, the particle size at which the cumulative amount reaches 50% is defined as the volume average particle size D50v and the number average particle size D50p, and the particle size at which the cumulative amount reaches 84% ​​is defined as the volume particle size D84v and the number particle size D84p.

[0411] Using these particle sizes, (D84v / D16v) 1 / 2 Calculate the volume particle size distribution index (GSDv) as (D84p / D16p) 1 / 2 Calculate the particle size distribution index (GSDp).

[0412] The average circularity of the toner particles is preferably from 0.94 to 1.00, and more preferably from 0.95 to 0.98.

[0413] The average circularity of the toner particles is calculated by (equivalent circular circumference) / (circumference) [(circumference of a circle having the same projected area as the particle image) / (circumference of the particle projected image)]. Specifically, it is a value measured by the following method.

[0414] First, the toner particles to be measured were collected by suction, formed into a flat stream, and momentarily strobed to obtain a still image of the particles. This image was then analyzed using a flow-type particle image analyzer (FPIA-3000, manufactured by Sysmex) to determine circularity. The number of samples used to determine the average circularity was set to 3,500.

[0415] In the case where the toner contains an external additive, the toner (developer) to be measured is dispersed in water containing a surfactant and then subjected to ultrasonic treatment to obtain toner particles from which the external additive has been removed.

[0416] (First Silica Particles)

[0417] The toner used in this embodiment contains silica particles (hereinafter also referred to as "first silica particles") having a number average particle size of not less than 110 nm and not more than 130 nm, a large diameter side number particle size distribution index (upper side GSDp) of less than 1.080, an average circularity of not less than 0.94 and not more than 0.98, and a proportion of not less than 80% by number of circularities.

[0418] The image forming apparatus of this embodiment accommodates the toner containing the first silica particles as an external additive, and thus has excellent ability to suppress filming of the external additive on the image holding member.

[0419] The number average particle size of the first silica particles is 110 nm to 130 nm, preferably 113 nm to 127 nm, and more preferably 115 nm to 125 nm, from the viewpoint of suppressing film formation of the external additive and suppressing wear of the cleaning blade.

[0420] The method for making the number average particle size of the first silica particles fall within the above range is not particularly limited, and examples thereof include: preparing the first silica particles into sol-gel silica particles, and adjusting the temperature or reaction time when mixing the alkali catalyst and tetraalkoxysilane during the production of the sol-gel silica particles; adjusting the concentrations of the alkali catalyst and tetraalkoxysilane; etc.

[0421] The large diameter side number size distribution index (upper GSDp) of the first silica particles is less than 1.080. From the viewpoint of suppressing film formation of external additives and suppressing abrasion of the cleaning blade, it is preferably 1.077 or less, and more preferably less than 1.075.

[0422] From the viewpoint of suppressing film formation of external additives and suppressing abrasion of the cleaning blade, the first silica particles preferably have a smaller diameter side number size distribution index (lower GSDp) of less than 1.080, more preferably 1.075 or less.

[0423] The method for making the upper side GSDp and the lower side GSDp of the first silica particles within the above range is not particularly limited, and examples thereof include: preparing the first silica particles into sol-gel silica particles, and in the manufacture of the sol-gel silica particles, adjusting the temperature or reaction time when the base catalyst and tetraalkoxysilane are mixed; adjusting the concentrations of the above-mentioned base catalyst and tetraalkoxysilane; etc.

[0424] The number average particle size, upper GSDp, and lower GSDp of the first silica particles are determined as follows.

[0425] (1) The toner is dispersed in methanol, stirred at room temperature (23°C), and then treated in an ultrasonic bath to separate the external additive from the toner. The toner particles are then centrifuged to settle, and the dispersion containing the external additive is recovered. The methanol is then distilled off to remove the external additive.

[0426] (2) The external additives are dispersed in resin particles (polyester, weight-average molecular weight Mw=50,000) having a volume average particle size of 100 μm.

[0427] (3) An energy dispersive X-ray analyzer (EDX device) (manufactured by Horiba, Ltd., EMAX Evolution X-Max 80mm) was used. 2 The resin particles containing the external additives were observed using a scanning electron microscope (SEM) (S-4800, manufactured by Hitachi High-Technologies Corporation) at a magnification of 40,000x. EDX analysis confirmed the presence of Si, confirming the presence of at least 300 primary silica particles within a single field of view. SEM observations were performed at an accelerating voltage of 15 kV, an emission current of 20 μA, and a working distance (WD) of 15 mm. EDX analysis was performed under the same conditions for a 60-minute detection time.

[0428] (4) The obtained image was acquired by an image analyzer (LUZEXIII, manufactured by NIRECO Co., Ltd.), and the area of ​​each particle was determined by image analysis.

[0429] (5) The particle size of silica is calculated as the equivalent circle diameter from the measured area value.

[0430] (6) Select 100 silica particles with an equivalent circle diameter of 80 nm or more.

[0431] For the selected silica particles, a cumulative distribution of equivalent circle diameters was plotted starting from the smaller diameter side, and the particle size at which the cumulative distribution reached 50% was defined as the number average particle size of the first silica particles.

[0432] For the selected silica particles, the cumulative distribution of equivalent circle diameters was plotted starting from the smaller diameter side. The particle size at which the cumulative distribution reached 16% was defined as the number average particle size D16p, the particle size at which the cumulative distribution reached 50% was defined as the number average particle size D50p, and the particle size at which the cumulative distribution reached 84% was defined as the number average particle size D84p. Furthermore, (D84p / D50p) 1 / 2 Calculate the particle size distribution index of the large diameter side (upper side GSDp) as (D50p / D16p) 1 / 2 Calculate the number particle size distribution index on the smaller diameter side (lower side GSDp).

[0433] The average circularity of the first silica particles is 0.94 to 0.98, and is preferably 0.945 to 0.975, and more preferably 0.950 to 0.970, from the viewpoint of suppressing film formation of the external additive and suppressing wear of the cleaning blade.

[0434] The method for making the average circularity of the first silica particles fall within the above range is not particularly limited, and examples thereof include: preparing the first silica particles into sol-gel silica particles, and adjusting the temperature or reaction time when mixing the alkali catalyst and tetraalkoxysilane during the production of the sol-gel silica particles; adjusting the concentration of the above-mentioned alkali catalyst; etc.

[0435] The proportion of silica particles having a circularity of 0.92 or greater in the first silica particles is 80% by number or greater, preferably 85% by number or greater, and more preferably 87% by number or greater from the viewpoint of suppressing film formation of external additives and suppressing abrasion of the cleaning blade.

[0436] The method for making the proportion of silica particles having a roundness of 0.92 or greater in the first silica particles fall within the above range is not particularly limited, and examples thereof include: preparing the first silica particles into sol-gel silica particles, and adjusting the temperature or reaction time when mixing the alkali catalyst and tetraalkoxysilane during the production of the sol-gel silica particles; adjusting the concentration of the alkali catalyst; etc.

[0437] The average circularity of the first silica particles and the ratio of silica particles having a circularity of 0.92 or greater in the first silica particles were determined as follows.

[0438] The circularity of the 100 first silica particles selected in the above method for determining the number average particle size of the first silica particles was calculated using the following formula (1). The 50% circularity obtained by accumulating the circularity from the smaller diameter side was taken as the average circularity of the first silica particles.

[0439] Formula (1): roundness = 4π × (A / I 2 )

[0440] In formula (1), I represents the perimeter of the primary particle on the image, and A represents the projected area of ​​the primary particle.

[0441] When the average circularity is determined, the number ratio of first silica particles having a circularity of 0.92 or greater among 100 first silica particles of various circularities is defined as the number ratio of silica particles having a circularity of 0.92 or greater in the first silica particles.

[0442] From the viewpoint of suppressing film formation of external additives and suppressing abrasion of the cleaning blade, the hydrophobicity of the first silica particles is preferably 50% to 80%, more preferably 50% to 75%, and even more preferably 50% to 70%.

[0443] The method for making the hydrophobicity of the first silica particles within the above range is not particularly limited, and examples thereof include: preparing the first silica particles into sol-gel silica particles, and during the production of the sol-gel silica particles, subjecting the surfaces of the silica particles to a hydrophobic treatment using a hydrophobicizing agent in the presence of supercritical carbon dioxide, etc.

[0444] The hydrophobicity of the first silica particles is determined as follows.

[0445] 0.2% by mass of silica particles as a sample was added to 50 ml of ion-exchanged water. Methanol was then added dropwise from a burette while stirring with a magnetic stirrer. The methanol mass fraction (%) in the methanol-ion-exchanged water mixture, at the endpoint where the entire sample had sunk into the solution (= amount of methanol added / (amount of methanol added + amount of ion-exchanged water)), was calculated as the hydrophobicity (%).

[0446] The first silica particles may be particles containing silica, i.e., SiO₂, as their main component, and may be either crystalline or amorphous. The first silica particles may be particles made from silicon compounds such as water glass and alkoxysilane, or particles obtained by crushing quartz. Examples of the first silica particles include sol-gel silica particles; aqueous colloidal silica particles; alcoholic silica particles; fumed silica particles obtained by a vapor phase method; and fused silica particles. Among the above, the first silica particles preferably include sol-gel silica particles.

[0447] Sol-gel silica particles can be obtained, for example, as follows. Tetraalkoxysilane (TMOS, etc.) is dropwise added to an alkaline catalyst solution containing an alcohol compound and aqueous ammonia to hydrolyze and condense the tetraalkoxysilane, thereby obtaining a suspension containing sol-gel silica particles. The solvent is then removed from the suspension to obtain granules. The granules are then dried to obtain sol-gel silica particles.

[0448] The first silica particles may be silica particles that have been hydrophobized using a hydrophobizing agent.

[0449] As hydrophobizing treatment agent, for example, known organosilicon compounds with alkyl (such as methyl, ethyl, propyl, butyl etc.) can be enumerated, and specific example can enumerate alkoxysilane compound, siloxane compound, silazane compound etc.. Among the above, hydrophobizing treatment agent preferably comprises at least one of siloxane compound and silazane compound. Hydrophobizing treatment agent can be used alone 1 kind, also can share 2 or more kinds.

[0450] Examples of the siloxane compound include silicone oil and silicone resin. Silicone oil preferably includes dimethyl silicone oil. The siloxane compound may be used alone or in combination of two or more.

[0451] Examples of the silazane compound include hexamethyldisilazane and tetramethyldisilazane. Of the above, the silazane compound preferably includes hexamethyldisilazane (HMDS). The silazane compound may be used alone or in combination of two or more.

[0452] From the viewpoint of increasing the degree of hydrophobization of the first silica particles, the surface adhesion amount of the hydrophobizing agent such as the silazane compound attached to the surface of the first silica particles is preferably from 0.01% by mass to 5% by mass, more preferably from 0.05% by mass to 3% by mass, and even more preferably from 0.10% by mass to 2% by mass, relative to the first silica particles.

[0453] As a method for hydrophobizing the first silica particles using a hydrophobizing agent, for example, there can be mentioned: a method of using supercritical carbon dioxide to dissolve the hydrophobizing agent in the supercritical carbon dioxide, so that the hydrophobizing agent adheres to the surface of the silica particles; a method of imparting (for example, spraying or coating) a solution containing a hydrophobizing agent and a solvent for dissolving the hydrophobizing agent to the surface of the silica particles in the atmosphere, so that the hydrophobizing agent adheres to the surface of the silica particles; a method of adding a solution containing a hydrophobizing agent and a solvent for dissolving the hydrophobizing agent to a silica particle dispersion in the atmosphere and maintaining the solution, and then drying the mixed solution of the silica particle dispersion and the above solution.

[0454] <Other additives>

[0455] The toner used in this embodiment may further contain other external additives (hereinafter referred to as "other external additives") in addition to the first silica particles. Examples of other external additives include inorganic oxide particles. Examples of inorganic oxide particles include SiO2, TiO2, Al2O3, CuO, ZnO, SnO2, CeO2, Fe2O3, MgO, BaO, CaO, K2O, Na2O, ZrO2, CaO·SiO2, K2O·(TiO2)n, Al2O3·2SiO2, CaCO3, MgCO3, BaSO4, and MgSO4. Among the above, the inorganic oxide particles preferably include TiO2, SiO2, that is, titanium dioxide particles, or silica particles (hereinafter referred to as "second silica particles").

[0456] From the viewpoint of improving the fluidity of the toner, the number average particle size of the inorganic oxide particles is preferably from 5 nm to 50 nm, and more preferably from 10 nm to 40 nm.

[0457] As the surface of the inorganic oxide particles of external additive, hydrophobization treatment can be implemented.Hydrophobic treatment is for example carried out by impregnating the inorganic oxide particles in a hydrophobization treatment agent.Hydrophobic treatment agent is not particularly limited, and for example silane coupling agent, silicone oil, titanate coupling agent, aluminum coupling agent etc. can be enumerated.These hydrophobization treatment agents can be used alone 1 kind, and can also be used in combination with more than 2 kinds.

[0458] The amount of the hydrophobizing agent is usually 1 part by mass or more and 10 parts by mass or less relative to 100 parts by mass of the inorganic oxide particles.

[0459] Examples of the external additives include resin particles (polystyrene, polymethyl methacrylate (PMMA), melamine resin, and other resin particles), detergent active agents (for example, particles of a fluorine-based high molecular weight substance), and the like.

[0460] The amount of other external additives added is, for example, preferably from 0.01% by mass to 5% by mass, and more preferably from 0.01% by mass to 2.0% by mass, based on the toner particles.

[0461] (Toner Manufacturing Method)

[0462] Next, a method for producing the toner used in this embodiment will be described.

[0463] The toner used in this embodiment is obtained by adding an external additive to the toner particles after producing the toner particles.

[0464] Toner particles can be produced by any of dry methods (such as kneading and pulverization) or wet methods (such as aggregation, suspension polymerization, and dissolution suspension). The method for producing toner particles is not particularly limited to these methods, and a known method can be used.

[0465] The toner in this embodiment is produced, for example, by adding an external additive to the obtained dry toner particles and mixing them. Mixing can be performed using, for example, a V-blender, Henschel mixer, or Lödige mixer. If necessary, a vibrating screen or pneumatic screen can be used to remove coarse toner particles.

[0466] [Carrier]

[0467] The carrier is not particularly limited, and known carriers may be used. Examples of the carrier include coated carriers in which a core material composed of magnetic powder is coated with a coating resin; magnetic powder-dispersed carriers in which magnetic powder is dispersed or mixed in a matrix resin; and resin-impregnated carriers in which porous magnetic powder is impregnated with a resin.

[0468] Note that the magnetic powder dispersed carrier and the resin impregnated carrier may be formed by coating the core material with the constituent particles of the carrier and the coating resin.

[0469] Examples of the magnetic powder include magnetic metals such as iron, nickel, and cobalt, and magnetic oxides such as ferrite and magnetite.

[0470] Examples of the coating resin and matrix resin include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymers, styrene-acrylate copolymers, linear silicone resins containing organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenolic resins, epoxy resins, etc. The coating resin and matrix resin may contain other additives such as conductive particles.

[0471] Examples of the conductive particles include particles of metals such as gold, silver, and copper, carbon black, titanium oxide, zinc oxide, tin oxide, barium sulfate, aluminum borate, and potassium titanate.

[0472] In order to coat the surface of the core material with the coating resin, the method of coating the coating layer formed by dissolving the coating resin and various additives as needed in a suitable solvent with a coating solution etc. can be cited. As the solvent, there is no particular limitation, and it is selectable by considering the coating resin used, coating suitability, etc. As specific resin coating methods, the dipping method in which the core material is immersed in the coating layer forming solution, the spraying method in which the coating layer forming solution is sprayed onto the core material surface, the fluidized bed method in which the coating layer is sprayed under the state in which the core material is floated by flowing air, the kneading coater method in which the core material of the carrier is mixed with the coating layer forming solution and the solvent is removed etc. can be cited.

[0473] The mixing ratio (mass ratio) of the toner and the carrier in the two-component developer is preferably toner:carrier=1:100 to 30:100, more preferably 3:100 to 20:100.

[0474] <Processing cartridge>

[0475] The process cartridge according to this embodiment will be described.

[0476] The processing box of this embodiment is a processing box that can be loaded and unloaded on an image forming device, which includes: an image holding member, which has a photosensitive layer and a surface protective layer on a conductive substrate; a developing unit, which accommodates an electrostatic image developer containing an electrostatic image developing toner, and uses the above-mentioned electrostatic image developer to develop the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image; and a cleaning unit, which has a cleaning blade for cleaning the toner on the surface of the above-mentioned image holding member, the above-mentioned electrostatic image developing toner contains toner particles and silica particles, the average particle size of the silica particles is greater than or equal to 110 nm and less than or equal to 130 nm, the large diameter side number particle size distribution index (upper side GSDp) is less than 1.080, the average roundness is greater than or equal to 0.94 and less than or equal to 0.98, and the proportion of roundness greater than or equal to 0.92 is greater than or equal to 80% by number.

[0477] The preferred embodiments of the electrostatic image developing toner, electrostatic image developer, image holding member, developing unit and cleaning unit in the process cartridge of this embodiment are respectively the same as the preferred embodiments of the electrostatic image developing toner, electrostatic image developer, image holding member, developing unit and cleaning unit in the image forming apparatus of this embodiment.

[0478] The process cartridge of the present embodiment may be configured to further include at least one selected from a charging unit, a latent image forming unit, a transfer unit, and the like, as necessary.

[0479] Preferred embodiments of the charging unit, latent image forming unit, transfer unit, etc. are respectively the same as those of the image forming apparatus of the present embodiment.

[0480] Example

[0481] Hereinafter, examples of the present invention will be described, but the present invention is not limited to the following examples. It should be noted that in the following description, "parts" and "%" are based on mass unless otherwise specified.

[0482] -Preparation of the First Silica Particles-

[0483] (Preparation of Silica Particle Dispersion (1))

[0484] 300 parts of methanol and 70 parts of 10% ammonia water were added to a glass reaction vessel equipped with a stirrer, a dropping nozzle, and a thermometer and mixed to obtain an alkali catalyst solution. After adjusting the alkali catalyst solution to 30°C (dropping start temperature), 185 parts of tetramethoxysilane and 50 parts of 8% ammonia water were added dropwise while stirring to obtain a hydrophilic silica particle dispersion (solid content 12%). The dropping time was set to 30 minutes. The obtained silica particle dispersion was then concentrated to a solid content of 40% using a rotary filter R-FINE (manufactured by Kotobuki Industry Co., Ltd.). The concentrated dispersion was designated as silica particle dispersion (1).

[0485] (Preparation of Silica Particle Dispersions (2) to (8) and (c1) to (c6))

[0486] In the preparation of the silica particle dispersion (1), silica particle dispersions (2) to (8) and (c1) to (c6) were prepared in the same manner as the silica particle dispersion (1), except that the conditions of the alkali catalyst solution (amount of methanol, concentration and amount of ammonia water) and the conditions for generating silica particles (amount of tetramethoxysilane (TMOS) in the alkali catalyst solution, concentration and total amount of ammonia water added, and time for adding TMOS and ammonia water and temperature at the start of addition) were changed according to Table 1.

[0487] (Preparation of Surface-treated Silica Particles (S1))

[0488] The silica particles were surface-treated with a siloxane compound using the silica particle dispersion (1) in a supercritical carbon dioxide atmosphere as follows. The surface treatment was performed using an apparatus equipped with a carbon dioxide gas cylinder, a carbon dioxide pump, an entrainer pump, an autoclave (500 ml capacity) equipped with a stirrer, and a pressure valve.

[0489] First, 300 parts of the silica particle dispersion (1) were added to an autoclave (500 ml capacity) equipped with a stirrer, and the stirrer was rotated at 100 rpm. Liquid carbon dioxide was then injected into the autoclave, and the temperature was raised using a heater while the pressure was increased using a carbon dioxide pump, so that the autoclave reached a supercritical state of 150° C. and 15 MPa. The pressure in the autoclave was maintained at 15 MPa using a pressure valve, while supercritical carbon dioxide was circulated using a carbon dioxide pump to remove methanol and water from the silica particle dispersion (1) (solvent removal step), thereby obtaining silica particles (untreated silica particles).

[0490] Next, when the amount of supercritical carbon dioxide flowing (cumulative amount: measured as the amount of carbon dioxide flowing in a standard state) reached 900 parts, the flow of supercritical carbon dioxide was stopped.

[0491] Then, the temperature was maintained at 150°C using a heater and the pressure was maintained at 15 MPa using a carbon dioxide pump. While maintaining the supercritical state of carbon dioxide in the autoclave, a treatment solution prepared by dissolving 0.3 parts of dimethyl silicone oil (DSO: trade name "KF-96 (Shin-Etsu Chemical Co., Ltd.)" with a viscosity of 10,000 cSt as a siloxane compound in 20 parts of hexamethyldisilazane (HMDS: manufactured by Organic Synthetic Chemicals Co., Ltd.) as a hydrophobizing agent was injected into the autoclave using an entrainer pump. The mixture was then stirred and reacted at 180°C for 20 minutes. Supercritical carbon dioxide was then recirculated to remove the remaining treatment solution. Stirring was then stopped, the pressure valve was opened, the pressure in the autoclave was released to atmospheric pressure, and the temperature was lowered to room temperature (25°C).

[0492] In this manner, the solvent removal step and the surface treatment with HMDS and DSO were sequentially performed to obtain surface-treated silica particles (S1).

[0493] (Preparation of Surface-treated Silica Particles (S2) to (S8) and (cS1) to (cS6))

[0494] Surface-treated silica particles (S2) to (S8) and (cS1) to (cS6) were obtained in the same manner as in the preparation of the surface-treated silica particles (S1).

[0495] (Preparation of surface-treated silica particles (cS7))

[0496] Surface-treated silica particles (cS7) were obtained in the same manner as in paragraphs 0051 to 0053 of JP-A-2008-174430.

[0497] (Preparation of surface-treated silica particles (cS8))

[0498] Surface-treated silica particles (cS8) were obtained in the same manner as in paragraph 0019 of JP-A-2001-194824.

[0499] [Table 1]

[0500]

[0501] -Preparation of Polyester Resin Particle Dispersion-

[0502] (Preparation of Amorphous Polyester Resin Particle Dispersion (A1))

[0503] Terephthalic acid: 70 parts

[0504] Fumaric acid: 30 parts

[0505] Ethylene glycol: 45 parts

[0506] 1,5-Pentanediol: 46 parts

[0507] The above materials were placed in a flask equipped with a stirrer, a nitrogen inlet tube, a temperature sensor, and a distillation column. The temperature was raised to 220°C over 1 hour under a nitrogen flow. One part of tetraethoxytitanium was added to 100 parts of the above materials. While distilling off the generated water, the temperature was raised to 240°C over 0.5 hours. After the dehydration condensation reaction was continued at this temperature for 1 hour, the reaction mixture was cooled. This produced a polyester resin with a weight-average molecular weight of 9,500 and a glass transition temperature of 62°C.

[0508] In a container equipped with a temperature control unit and a nitrogen displacement unit, 40 parts of ethyl acetate and 25 parts of 2-butanol were added to form a mixed solvent. 100 parts of a polyester resin was then slowly added to dissolve the mixture. A 10% aqueous ammonia solution (equivalent to three times the acid value of the resin in terms of molar ratio) was then added and stirred for 30 minutes. The container was then purged with dry nitrogen, and while the temperature was maintained at 40°C, 400 parts of ion-exchanged water was added dropwise at a rate of 2 parts / minute to emulsify the mixture. After the addition was complete, the emulsion was returned to 25°C to obtain a resin particle dispersion containing resin particles with a volume average particle size of 200 nm. Ion-exchanged water was added to this resin particle dispersion to adjust the solids content to 20%, thereby producing an amorphous polyester resin particle dispersion (A1).

[0509] (Preparation of Crystalline Polyester Resin Particle Dispersion (C1))

[0510] 1,10-Decanedicarboxylic acid: 98 parts

[0511] ·Sodium dimethyl 5-sulfonate isophthalate: 24 parts

[0512] 1,9-nonanediol: 100 parts

[0513] Dibutyltin oxide (catalyst): 0.3 parts

[0514] After adding the above ingredients to a heat-dried three-necked flask, the atmosphere inside the container was inertized with nitrogen gas by decompression. The mixture was stirred and refluxed at 180°C for 5 hours under mechanical stirring. The temperature was then slowly raised to 230°C under reduced pressure and stirred for 2 hours. When the mixture reached a viscous state, it was air-cooled to terminate the reaction and produce a crystalline polyester resin. Molecular weight measurement (polystyrene equivalent) revealed a weight-average molecular weight (Mw) of 9700 and a melting point of 78°C.

[0515] 90 parts of the obtained crystalline polyester resin, 1.8 parts of anionic surfactant NEOGEN RK (Daiichi Kogyo Seiyaku), and 210 parts of ion-exchanged water were heated to 100°C and dispersed using an ULTRA-TURRAX T50 manufactured by IKA. The mixture was then dispersed using a pressure-discharge Gaulin homogenizer for 1 hour to prepare a crystalline polyester resin particle dispersion (C1) having a volume average particle size of 200 nm and a solid content of 20%.

[0516] -Preparation of Styrene Acrylic Resin Particle Dispersion-

[0517] (Preparation of Styrene Acrylic Resin Particle Dispersion (B1))

[0518] Styrene: 200 parts

[0519] n-Butyl acrylate: 50 parts

[0520] Acrylic acid: 1 part

[0521] β-Carboxyethyl acrylate: 3 parts

[0522] Propylene glycol diacrylate: 1 part

[0523] 2-Hydroxyethyl acrylate: 0.5 parts

[0524] Dodecyl mercaptan: 1 part

[0525] A solution of 4 parts of anionic surfactant (DOWFAX manufactured by The Dow Chemical Company) dissolved in 550 parts of ion-exchanged water was added to a flask, and the mixture of the above raw materials was added to emulsify the mixture. The emulsion was gently stirred for 10 minutes, and 50 parts of ion-exchanged water containing 6 parts of ammonium persulfate was added. The system was then thoroughly purged with nitrogen, heated in an oil bath until the system reached 75°C, and polymerization was carried out for 30 minutes.

[0526] then,

[0527] Styrene: 110 parts

[0528] n-Butyl acrylate: 50 parts

[0529] β-Carboxyethyl acrylate: 5 parts

[0530] 1,10-Decanediol diacrylate: 2.5 parts

[0531] Dodecyl mercaptan: 2 parts

[0532] The mixed solution of the above raw materials was added and emulsified. The emulsion was added to the flask over 120 minutes, and emulsion polymerization was continued for 4 hours. This yielded a resin particle dispersion containing resin particles having a weight-average molecular weight of 32,000, a glass transition temperature of 53°C, and a volume-average particle size of 240 nm. Ion-exchanged water was added to the resin particle dispersion to adjust the solids content to 20%, thereby producing a styrene acrylic resin particle dispersion (B1).

[0533] (Preparation of Anti-adhesive Particle Dispersion)

[0534] Paraffin wax (HNP-9, manufactured by Nippon Seiro Co., Ltd.): 100 parts

[0535] Anionic surfactant (Neogen RK, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 1 part

[0536] Ion exchange water: 350 parts

[0537] The above materials were mixed and heated to 100°C, dispersed using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA), and then dispersed using a Manton Gaulin high-pressure homogenizer (manufactured by Gaulin) to obtain a release agent particle dispersion (solid content 20%) in which release agent particles having a volume average particle size of 200 nm were dispersed.

[0538] (Preparation of Black Particle Dispersion)

[0539] Carbon black (Regal 330 manufactured by Cabot Corporation): 50 parts

[0540] Anionic surfactant NEOGEN RK (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.): 5 parts

[0541] Ion exchange water: 192.9 parts

[0542] The above components were mixed and treated at 240 MPa for 10 minutes using an Altimizer (manufactured by SUGINO MACHINE LIMITED CO., LTD.) to prepare a black particle dispersion (solid content: 20%).

[0543] (Preparation of Toner Particles (A1))

[0544] Ion exchange water: 200 parts

[0545] Amorphous polyester resin particle dispersion (A1): 150 parts

[0546] Crystalline polyester resin particle dispersion (C1): 10 parts

[0547] Black particle dispersion: 15 parts

[0548] Anti-sticking agent particle dispersion: 10 parts

[0549] Anionic surfactant (TaycaPower): 2.8 parts

[0550] The above materials were placed in a round stainless steel flask, and after adjusting the pH to 3.5 with 0.1N nitric acid, an aqueous solution of polyaluminum chloride (PAC, manufactured by Oji Paper Co., Ltd.: 30% powder) (2.0 parts) dissolved in 30 parts of ion-exchanged water was added. Dispersed at 30°C using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA Co., Ltd.), the mixture was heated to 45°C in a heating oil bath and maintained until the volume average particle size reached 4.8 μm. Subsequently, 60 parts of the amorphous polyester resin particle dispersion (A1) was added and maintained for 30 minutes. When the volume average particle size reached 5.2 μm, another 60 parts of the amorphous polyester resin particle dispersion (A1) was added and maintained for 30 minutes. Subsequently, 20 parts of a 10% aqueous solution of NTA (nitrilotriacetic acid) metal salt (Chelest 70: manufactured by Chelest Co., Ltd.) was added, and the pH was adjusted to 9.0 using a 1N aqueous sodium hydroxide solution. Then, 1.0 part of an anionic active agent (Tayca Power) was added, and the mixture was heated to 85°C while continuing to stir and maintained for 5 hours. The mixture was then cooled to 20°C at a rate of 20°C / min, filtered, thoroughly washed with ion-exchanged water, and dried to obtain toner particles (A1) having a volume average particle size of 6.0 μm.

[0551] (Preparation of Toner Particles (B1))

[0552] Ion exchange water: 400 parts

[0553] Styrene acrylic resin particle dispersion (B1): 200 parts

[0554] Black particle dispersion: 40 parts

[0555] Anti-sticking agent particle dispersion: 12 parts

[0556] The above components were placed in a reaction vessel equipped with a thermometer, pH meter, and stirrer. The temperature was controlled externally with a mantle-type resistance heater, and the temperature was maintained at 30°C and a stirring speed of 150 rpm for 30 minutes. While being dispersed using a homogenizer (ULTRA-TURRAX T50 manufactured by IKA JAPAN Co., Ltd.), an aqueous solution of polyaluminum chloride (PAC, manufactured by Oji Paper Co., Ltd.: 30% powder) dissolved in 100 parts of ion-exchanged water was added. The temperature was then raised to 50°C, and the particle size was measured using a Coulter Multisizer II (pore diameter: 50 μm, manufactured by Coulter Co., Ltd.) to obtain a volume average particle size of 5.0 μm. 115 parts of the resin particle dispersion (1) were then added to adhere the resin particles (shell structure) to the surface of the aggregated particles. Next, 20 parts of a 10% aqueous solution of NTA (nitrilotriacetic acid) metal salt (Chelest 70, manufactured by Chelest Co., Ltd.) was added, and the pH was adjusted to 9.0 using a 1N aqueous sodium hydroxide solution. The temperature was then raised to 91°C at a rate of 0.05°C / min and held at 91°C for 3 hours. The resulting toner slurry was then cooled to 85°C and held for 1 hour. It was then cooled to 25°C to obtain a magenta toner. This was further repeatedly redispersed with ion-exchanged water and filtered. After washing until the filtrate had an electrical conductivity of 20 μS / cm or less, the filtrate was vacuum-dried in a 40°C oven for 5 hours to obtain toner particles (B1).

[0557] (Preparation of Toner (A1))

[0558] 100 parts of toner particles (A1), 1.5 parts of first silica particles (S1), and 0.5 parts of titanium dioxide particles having a number average particle size of 20 nm as inorganic oxide particles were mixed, and mixed for 30 seconds using a sample mill at a rotation speed of 13,000 rpm. The mixture was sieved using a vibrating sieve with a mesh size of 45 μm to obtain toner (A1).

[0559] (Preparation of Toners (A2) to (A12) and (cA1) to (cA8))

[0560] Each toner was obtained in the same manner as in the toner (A1) except that the kind of the first silica particles had the specifications shown in Table 2.

[0561] (Preparation of Developers (A1) to (A12) and (cA1) to (cA8))

[0562] 10 parts of each toner and 100 parts of the following resin-coated carrier were added to a V-type blender, stirred for 20 minutes, and then sieved with a vibrating sieve with a mesh size of 212 μm to obtain a developer.

[0563] Mn-Mg-Sr ferrite particles (average particle size 40 μm): 100 parts

[0564] Toluene: 14 parts

[0565] 2 parts of polymethyl methacrylate

[0566] Carbon black (VXC72, manufactured by Cabot Corporation): 0.12 parts

[0567] The above materials, excluding the ferrite particles, were mixed with glass beads (1 mm in diameter, equal in amount to toluene) and stirred at 1200 rpm for 30 minutes using a sand mill manufactured by Kansai Paint Co., Ltd. to obtain a dispersion. This dispersion and the ferrite particles were added to a vacuum degassing kneader and dried under reduced pressure while stirring to obtain a resin-coated carrier.

[0568] [Table 2]

[0569]

[0570] <Production of Image Holding Member A1>

[0571] (Formation of Primer Layer)

[0572] Zinc oxide (average particle size 70 nm: manufactured by TAYCA Co., Ltd.; specific surface area 15 m 2 100 parts by mass of zinc oxide (100 parts by mass of 1% dapoxetine / g) and 500 parts by mass of toluene were stirred and mixed, and 1.3 parts by mass of a silane coupling agent (KBM503: manufactured by Shin-Etsu Chemical Co., Ltd.) was added and stirred for 2 hours. The toluene was then removed by vacuum distillation, and the mixture was baked at 120°C for 3 hours to obtain zinc oxide surface-treated with the silane coupling agent. 110 parts by mass of the surface-treated zinc oxide was stirred and mixed with 500 parts by mass of tetrahydrofuran, and a solution of 0.6 parts by mass of alizarin dissolved in 50 parts by mass of tetrahydrofuran was added, followed by stirring at 50°C for 5 hours. The alizarin-coated zinc oxide was then filtered out by vacuum filtration and further dried under reduced pressure at 60°C to obtain alizarin-coated zinc oxide.

[0573] 60 parts by mass of the alizarin-coated zinc oxide, 13.5 parts by mass of a curing agent (blocked isocyanate, Sumidur 3175, manufactured by Sumitomo Bayer Urethane Co., Ltd.), and 15 parts by mass of a butyral resin (S-LEC BM-1, manufactured by Sekisui Chemical Co., Ltd.) were mixed with 85 parts by mass of methyl ethyl ketone, and 38 parts by mass of the resulting solution was mixed with 25 parts by mass of methyl ethyl ketone. Glass beads were dispersed in a sand mill for 2 hours to obtain a dispersion. To the resulting dispersion, 0.005 parts by mass of dioctyltin dilaurate and 40 parts by mass of silicone resin particles (Tospear 145, manufactured by Momentive Performance Materials Inc.) were added as a catalyst to obtain a coating solution for forming a primer layer. This primer layer coating solution was applied to an aluminum substrate using a dip coating method and dried and cured at 170°C for 40 minutes to obtain a 20 μm thick primer layer.

[0574] (Formation of Charge Generation Layer)

[0575] Use diameter A mixture of 15 parts by mass of hydroxygallium phthalocyanine (CGM-1), which has diffraction peaks at at least 7.3°, 16.0°, 24.9°, and 28.0° in the X-ray diffraction spectrum obtained using Cukα characteristic X-rays, 10 parts by mass of vinyl chloride-vinyl acetate copolymer resin (VMCH, manufactured by Unicar Co., Ltd. of Japan) as a binder resin, and 200 parts by mass of n-butyl acetate was dispersed for 4 hours using a sand mill. 175 parts by mass of n-butyl acetate and 180 parts by mass of methyl ethyl ketone were added to the obtained dispersion, and the mixture was stirred to obtain a coating solution for forming a charge generation layer. The coating solution for forming a charge generation layer was dip-coated on the undercoat layer and dried at room temperature (25°C) to form a charge generation layer with a thickness of 0.2 μm.

[0576] (Formation of Charge Transport Layer)

[0577] 30 parts by mass of a trimethylsilane compound (1,1,1,3,3,3-hexamethyldisilazane (manufactured by Tokyo Chemical Industry Co., Ltd.)) as a hydrophobizing agent was added to 100 parts by mass of untreated (hydrophilic) silica particles "trade name: OX50 (manufactured by AEROSIL Co., Ltd.), volume average particle size: 40 nm", and the mixture was reacted for 24 hours, and then filtered to obtain hydrophobized silica particles. These particles were referred to as silica particles (1). The condensation rate of the silica particles (1) was 93%.

[0578] 250 parts by mass of tetrahydrofuran were added to 50 parts by mass of silica particles (1), and 25 parts by mass of 4-(2,2-diphenylethyl)-4',4"-dimethyltriphenylamine as a charge transport material and 25 parts by mass of bisphenol Z polycarbonate resin (viscosity-average molecular weight: 30,000) as a binder resin were added while maintaining the liquid temperature at 20°C. The mixture was stirred and mixed for 12 hours to obtain a coating liquid for forming a charge transport layer.

[0579] This charge transport layer-forming coating liquid was applied onto the charge generating layer and dried at 135° C. for 40 minutes to form a charge transport layer having a film thickness of 30 μm, thereby obtaining an image holding member.

[0580] (Formation of Surface Protective Layer)

[0581] 30 parts by mass of the compound (A-4) shown below as a charge transport material, 0.2 parts by mass of colloidal silica (trade name: PL-1, manufactured by Fuso Chemical Industries, Ltd.), 30 parts by mass of toluene, 0.1 parts by mass of 3,5-di-tert-butyl-4-hydroxytoluene (BHT), 0.1 parts by mass of azobisisobutyronitrile (10-hour half-life temperature: 65°C) and V-30 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 10-hour half-life temperature: 104°C) were added to prepare a coating liquid for forming a surface protective layer. The coating liquid was applied to the charge transport layer by a spray coating method, air-dried at room temperature (25°C) for 30 minutes, and then heated from room temperature to 150°C for 30 minutes under a nitrogen flow at an oxygen concentration of 110 ppm, and then heat-treated at 150°C for 30 minutes to cure it, forming a surface protective layer with a film thickness of 10 μm. In addition, the universal hardness of the surface protective layer measured by the above-mentioned measurement method was 200 N / mm 2 As described above, the image holding member A1 was obtained.

[0582] [Chemistry 8]

[0583]

[0584] <Production of Cleaning Blade A1>

[0585] As the cleaning blade A1, a plate-shaped object made of polyurethane, having a hardness of 75 degrees and a size of 347 mm × 10 mm × 2 mm (thickness) was used. BLD ) and the hardness (H) of the surface protective layer as the surface of the image holding member OCL ) ratio (H BLD / H OCL ) is 0.38.

[0586] (Examples 1 to 8 and Comparative Examples 1 to 8)

[0587] As an image forming apparatus, a modified Color 1000 Press manufactured by Fuji Xerox Co., Ltd. was prepared. The developer shown in Table 3 was stored therein. The image holding member shown in Table 3 and the cleaning blade shown in Table 3 were attached. The angle (contact angle) θ between the cleaning blade and the image holding member was 11°, and the pressing pressure N of the cleaning blade against the image holding member was set to 2.5 gf / mm. 2 .

[0588] -evaluate-

[0589] <Image Defect Evaluation under High Temperature and High Humidity Environment (Evaluation of Abrasion Inhibitory Properties of Cleaning Blade)>

[0590] Using the above-mentioned evaluation machine, low-density images (average image density 2%) were printed on 50,000 sheets of A4 paper at 28°C and 85% RH. The presence of image defects and the condition of the cleaning blade were confirmed and evaluated according to the following evaluation criteria. The amount of image defects produced under the above conditions corresponds to the amount of wear on the cleaning blade.

[0591] A: There are no image quality defects. There are no problems with the cleaning blade.

[0592] B: No image quality defects. The cleaning blade is slightly contaminated.

[0593] C: Image quality defects (white streaks / colored streaks) occurred.

[0594] <Evaluation of Inhibitory Effect of External Additive Filming on Image Holding Member>

[0595] Using the above-mentioned evaluation machine, medium-density images (average image density 5%) were printed on 1,000 A4 sheets at 10°C and 15% RH, followed by high-density images (average image density 40%) on 10,000 A4 sheets. Film formation of the external additive on the printed image holding member was visually inspected and evaluated according to the following evaluation criteria.

[0596] A: In the observation image obtained by the laser microscope, the area ratio of the film formation within the 300 μm×250 μm field of view is less than 5%.

[0597] B: In the observation image obtained by the laser microscope, the area ratio of the formed film within the 300 μm×250 μm field of view is 5% or more and less than 25%.

[0598] C: In the observation image obtained by the laser microscope, the area ratio of the formed film within the 300 μm×250 μm field of view is 25% or more and less than 50%.

[0599] D: In the observation image obtained by the laser microscope, the area ratio of the formed film within the 300 μm×250 μm field of view is 50% or more and less than 75%.

[0600] E: In the observation image obtained by the laser microscope, the area ratio of the formed film within the 300 μm×250 μm field of view is 75% or more.

[0601] [Table 3]

[0602]

[0603] As shown in Table 3, the image forming apparatus of Example was superior in the ability to suppress abrasion of the cleaning blade and the ability to suppress filming of the external additive on the image holding member, compared with the image forming apparatus of Comparative Example.

Claims

1. An image forming apparatus comprising: An image holding member comprising a photosensitive layer and a surface protective layer on a conductive substrate; a latent image forming unit that forms an electrostatic latent image on the image holding member; a developing unit that accommodates an electrostatic image developer containing an electrostatic image developing toner and develops the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image using the electrostatic image developer; a transfer unit configured to transfer the toner image onto a recording medium; and a cleaning unit having a cleaning blade for cleaning toner from the surface of the image holding member, The electrostatic image developing toner comprises toner particles and silica particles, wherein the silica particles have a number average particle size of 110 nm to 130 nm, a large diameter side number particle size distribution index (GSDp) of less than 1.080, an average circularity of 0.94 to 0.98, and a proportion of particles with a circularity of 0.92 or greater of 80% by number or greater. The surface protection layer includes an acrylic resin having a charge-transporting skeleton.

2. The image forming apparatus according to claim 1, wherein The large-diameter side number size distribution index of the silica particles, that is, the upper side GSDp, is less than 1.

075.

3. The image forming apparatus according to claim 1 or claim 2, wherein: The silica particles have a smaller diameter number size distribution index, that is, a lower GSDp, which is less than 1.

080.

4. The image forming apparatus according to claim 1 or claim 2, wherein: The average circularity of the silica particles is 0.95 or more and 0.97 or less.

5. The image forming apparatus according to claim 1, wherein The charge transport skeleton is a triarylamine skeleton.

6. The image forming apparatus according to claim 1 or claim 2, wherein: Among the silica particles, the proportion of particles having a circularity of 0.92 or greater is 85% by number or greater.

7. The image forming apparatus according to claim 1 or claim 2, wherein: The electrostatic image developing toner further includes inorganic oxide particles having a number average particle diameter of 5 nm or more and 50 nm or less.

8. The image forming apparatus according to claim 1 or claim 2, wherein: The toner particles contain a styrene acrylic resin as a binder resin.

9. The image forming apparatus according to claim 1 or claim 2, wherein: The toner particles contain an amorphous polyester resin as a binder resin.

10. A process cartridge comprising: An image holding member comprising a photosensitive layer and a surface protective layer on a conductive substrate; a developing unit that accommodates an electrostatic image developer containing an electrostatic image developing toner and develops the electrostatic latent image formed on the surface of the image holding member into an electrostatic image developing toner image using the electrostatic image developer; and a cleaning unit including a cleaning blade for cleaning toner from the surface of the image holding member; The electrostatic image developing toner comprises toner particles and silica particles, wherein the silica particles have an average particle size of 110 nm to 130 nm, a large diameter side number size distribution index (GSDp) of less than 1.080, an average circularity of 0.94 to 0.98, and a proportion of particles having a circularity of 0.92 or greater of 80% by number or greater. The processing box is installed and removed from the image forming device. The surface protection layer includes an acrylic resin having a charge-transporting skeleton.

Images