Image formation method

Abstract

To provide an image forming method with which, when using an ink having high thixotropy and discharging the ink circulating it in the vicinity of a nozzle, it is possible to suppress a change in ink viscosity at discharge time and uniformize discharge rates among nozzles to improve picture quality.SOLUTION: An image forming method pertaining to the present invention is characterized in that: contact type electrification means, development means, transfer means and a cleaning blade are arranged around an electrophotographic photoreceptor; inorganic particles are contained in a surface protective layer of the electrophotographic photoreceptor; an elastic deformation rate of the electrophotographic photoreceptor is 50% or less; an impact resilience of the cleaning blade is 30% or less; toner particles constituting a toner contains a lubricant, a positively charged inorganic external additive and a negatively charged inorganic external additive; and mass of the positively charged inorganic external additive and mass of the negatively charged inorganic external additive satisfy a relation in formula (1). Formula (1): 0.28≤mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an image forming method, and more particularly to an image forming method capable of preventing the occurrence of raindrops and improving the wear resistance of a photoconductor in an electrophotographic process using a charging roller. [Background technology]

[0002] In recent years, the proximity charging method, which uses a charging roller, has been adopted as a photoconductor charging method, as it is advantageous for improving image quality and making the device more compact, and can reduce the amount of oxidizing gases such as ozone and NOx generated compared to the scorotron / corotron charging method. The charging process using the proximity charging method requires a large amount of discharge energy on the photoconductor, which leads to a large deterioration in the film strength of the photoconductor, resulting in a large amount of film wear and a shorter lifespan of the photoconductor. Conventionally, the technology of using a charging roller and adopting thermoplastic resin such as polycarbonate resin for the surface protection layer of the photoconductor has been widely used, but there was a problem that the photoconductor's lifespan was shortened due to a large amount of film wear on the photoconductor. To solve this problem, we worked on product development to extend the photoconductor's lifespan by adding inorganic fine particles to the surface protection layer of the photoconductor, but this has caused a problem of dripping, where toner external additive components adhere to the surface protection layer of the photoconductor due to poor cleaning.

[0003] Another conventional technique is disclosed in, for example, Patent Document 1, which uses scorotron charging as the charging mechanism and a photoconductor having inorganic fine particles dispersed in a surface protective layer made of thermoplastic resin to suppress the occurrence of raindrops, and this technique has also been commercialized. It is known that one of the factors that suppresses the occurrence of raindrops is that when a lubricant is applied to the surface protective layer of the photoconductor, it prevents external additives in the toner from adhering to the surface protective layer of the photoconductor, thereby suppressing raindrops. However, compared to scorotron charging, roller charging has a larger discharge energy, which breaks down the lubricant adhering to the photoconductor surface and promotes the adhesion of external additives to the toner, making raindrops more likely to occur. In particular, in a process in which a charging roller is used to develop the lubricant contained in the developer in the developing machine onto the photoconductor, the amount of lubricant supplied to the photoconductor is small, and the amount of lubricant remaining on the photoconductor surface is very small, making it easy for dripping to occur. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2006-301497 A Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above problems and circumstances, and the problem to be solved by the present invention is to provide an image forming method that can prevent the occurrence of raindrops and improve the wear resistance of a photoconductor in an electrophotographic process using a charging roller system. [Means for solving the problem]

[0006] In the course of investigating the causes of the above problems in order to solve the above problems, the present inventors discovered that raindrops can be prevented and the wear resistance of the photoreceptor can be improved by incorporating inorganic fine particles in the surface protective layer of the photoreceptor, making the elastic deformation rate of the photoreceptor 50% or less and the rebound elasticity of the cleaning blade 30% or less, and further by incorporating a lubricant, a positively charged inorganic external additive and a negatively charged inorganic external additive as external additives in the toner, with the masses of the positively charged inorganic external additive and the negatively charged inorganic external additive satisfying a specific relationship, thereby arriving at the present invention. That is, the above-mentioned problems of the present invention are solved by the following means.

[0007] 1. An image forming method by an electrophotographic process using a toner for developing an electrostatic image, comprising: A contact charging means, a developing means, a transfer means and a cleaning blade are disposed around the electrophotographic photoreceptor, The surface protective layer of the electrophotographic photoreceptor contains inorganic fine particles, The elastic deformation rate of the electrophotographic photoreceptor is 50% or less, The cleaning blade has a rebound elasticity of 30% or less, the toner particles constituting the electrostatic image developing toner contain a lubricant, a positively charged inorganic external additive, and a negatively charged inorganic external additive; the lubricant is zinc stearate, the negatively charged inorganic external additive is silica and titanium oxide, The image forming method according to claim 1, wherein a mass of the positively chargeable inorganic external additive and a mass of the negatively chargeable inorganic external additive satisfy the relationship of the following formula (1): Formula (1): 0.28≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive ≦0.47

[0008] 2. The image forming method described in item 1, wherein the inorganic fine particles contained in the surface protective layer of the electrophotographic photoreceptor are silica (SiO2) particles.

[0009] 3. The image forming method according to item 1 or 2, wherein the surface protective layer of the electrophotographic photoreceptor contains a thermoplastic resin.

[0010] 4. The image forming method described in any one of items 1 to 3, wherein the edge angle of the cleaning blade that comes into contact with the electrophotographic photosensitive member is formed to be an obtuse angle.

[0011] 5. The image forming method described in any one of items 1 to 4, wherein the positively charged inorganic external additive is calcium titanate particles.

[0012] 6. The image forming method described in any one of items 1 to 4, wherein the positively charged inorganic external additive is strontium titanate particles.

[0013] 7. The image forming method described in any one of items 1 to 4, wherein the positively charged inorganic external additive is silica particles whose surfaces are modified with cyclic silazane and alkylalkoxysilane.

[0014] 8. The image forming method according to any one of items 1 to 7, wherein the toner particles contain a crystalline polyester resin and a styrene-acrylic resin.

[0015] 9. The image forming method according to item 8, wherein the crystalline polyester resin is a hybrid crystalline polyester resin. Effect of the Invention

[0016] According to the above-mentioned means of the present invention, it is possible to provide an image forming method capable of preventing dripping caused by poor cleaning due to toner adhering to the surface of the photoreceptor and improving the wear resistance of the photoreceptor. Although the mechanism by which the effects of the present invention are expressed or the mechanism by which the effects of the present invention are acted upon has not been clarified, it is speculated as follows. In the charging roller method, there is little lubricant functioning on the surface of the photoconductor, so toner components (toner particles and external additives) tend to adhere to the surface of the photoconductor, which tends to cause dripping. Therefore, in order to prevent the occurrence of raindrops, it is necessary to form a stationary layer of inorganic external additives that has a sufficient length in the nip portion of the cleaning blade and is uniform in the longitudinal direction of the cleaning blade, and to efficiently scrape off the toner particles adhering to the photoreceptor surface. That is, it was found that in order to form a stationary layer having sufficient length and uniformity in the longitudinal direction of the cleaning blade, it is necessary to add a certain amount or more of a positively charged inorganic external additive as an external additive to the toner used. This is presumably because, when silica particles, which are the majority of the external additive constituting the stationary layer, aggregate, the formation of the stationary layer is deteriorated, but when negatively charged silica particles and positively charged inorganic external additive are adsorbed, the aggregation of silica particles is suppressed, and the formation of the stationary layer is improved.

[0017] Specifically, as shown in Fig. 1, in the nip portion N of the cleaning blade 119Y, a mass of the external additive particles 300 is formed as a stationary layer L so that the particle diameter of the external additive particles 300 increases with distance from the nip portion N, and the toner particles T are stationary and cleaned, while the external additive particles 300 polish the surface of the photoreceptor 111Y. In the nip portion N, external additive particles with small particle diameters (for example, small-diameter silica particles 301) ultimately form the stationary layer L, but the presence of the positively charged inorganic external additive particles 303 in the nip portion N makes it easier for particle size selection to occur in a state in which the negatively charged large-diameter silica particles 302 and small-diameter silica particles 301 are mixed, and the aggregation of the small-diameter silica particles 301 is suppressed, so that the well-disintegrated small-diameter silica particles 301 gather in the nip portion N, and a stationary layer L that is uniform in the longitudinal direction of the cleaning blade 119Y can be formed. Furthermore, the large-diameter silica particles 302 are also prevented from agglomerating by the positively charged inorganic external additive particles 303, so that a stationary layer L can be formed uniformly in the longitudinal direction of the cleaning blade 119Y. In this manner, a stationary layer L consisting of external additive particles 300 (small-diameter silica particles 301, large-diameter silica particles 302, and positively charged inorganic external additive particles 303) having a sufficient length in the nip portion N and uniform in the longitudinal direction of the cleaning blade 119Y is formed, so that the toner particles T adhering to the surface of the photoreceptor 111Y can be efficiently scraped off, and as a result, it is presumed that raindrops can be reliably prevented even in the charging roller method.

[0018] In the present invention, the reason why the resilience modulus of the cleaning blade is set to 30% or less is that the blade vibration is small, resulting in blade conditions that are less susceptible to raindrops. The reason for setting the elastic deformation rate of the photoconductor at 50% or less is that, in reality, the higher the elastic deformation rate of the photoconductor, the less likely it is to be scratched by external additives that slip through the blade, making it less likely for external additives to adhere to it and less likely for raindrops to occur. However, in the present invention, when using a photoconductor with a relatively small elastic deformation rate that is unfavorable to raindrops (elastic deformation rate of 50% or less), the occurrence of raindrops can be suppressed by devising the blade conditions (specifying the resilience modulus) and the developer components (addition of a positively charged external additive) as described above. Furthermore, the surface protective layer of the electrophotographic photoreceptor contains inorganic fine particles, and since the inorganic fine particles generally have high surface hardness, the abrasion resistance of the photoreceptor can also be improved. [Brief description of the drawings]

[0019] [Figure 1] Schematic diagram showing the state of toner particles and external additives in the nip area of ​​a cleaning blade [Diagram 2] FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus used in the present invention. [Diagram 3] FIG. 1 is a schematic diagram showing an example of a configuration of a main part of an image forming apparatus used in the present invention. [Figure 4] FIG. 1 is a schematic diagram showing an example of the configuration of a charging unit of an image forming apparatus used in the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The image forming method of the present invention is an image forming method by an electrophotographic process using a toner for developing an electrostatic image, characterized in that a contact charging means, a developing means, a transfer means and a cleaning blade are arranged around an electrophotographic photosensitive member, inorganic fine particles are contained in a surface protective layer of the electrophotographic photosensitive member, the elastic deformation rate of the electrophotographic photosensitive member is 50% or less, and the rebound elasticity of the cleaning blade is 30% or less, the toner particles constituting the toner for developing an electrostatic image contain a lubricant, a positively charged inorganic external additive and a negatively charged inorganic external additive, and the mass of the positively charged inorganic external additive and the mass of the negatively charged inorganic external additive satisfy the relationship of the following formula (1). Formula (1): 0.28≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive This feature is a technical feature common to or corresponding to each of the following embodiments.

[0021] In an embodiment of the present invention, it is preferable that the inorganic fine particles contained in the surface protective layer of the electrophotographic photoreceptor are silica (SiO2) particles, since dispersing silica particles having high hardness increases the surface hardness of the photoreceptor and provides superior abrasion resistance.

[0022] Even in the case of a photoreceptor that does not contain the silica particles in the surface protective layer, the elastic deformation rate is small, and the photoreceptor is easily scratched by external additives, making it easy for raindrops to occur instantaneously. However, since the surface hardness of the photoreceptor is small and the amount of wear of the photoreceptor is large, any raindrops that do occur instantaneously are scraped off, and as a result, raindrops are less likely to occur.

[0023] It is preferable that the surface protective layer of the electrophotographic photoreceptor contains a thermoplastic resin, since this makes it possible to set the elastic deformation rate of the photoreceptor within the above range.

[0024] The edge angle of the cleaning blade that comes into contact with the electrophotographic photosensitive member is formed to be an obtuse angle, which is preferable in terms of excellent cleaning properties.

[0025] The positively charged inorganic external additive is preferably calcium titanate particles, strontium titanate particles, or silica particles surface-modified with cyclic silazane and alkylalkoxysilane, since aggregation of the negatively charged inorganic external additive is suppressed and a uniform stationary layer is easily formed in the longitudinal direction of the cleaning blade.

[0026] The toner particles preferably contain a crystalline polyester resin and a styrene-acrylic resin, and in particular, it is preferable from the viewpoint of manufacturability that the crystalline polyester resin is a hybrid crystalline polyester resin.

[0027] The present invention, its components, and embodiments for carrying out the present invention will be described below. In this application, the symbol "to" is used to mean that the numerical values ​​before and after the symbol "to" are included as lower and upper limits.

[0028] [Outline of the image forming method of the present invention] The image forming method of the present invention is an image forming method by an electrophotographic process using a toner for developing an electrostatic image, characterized in that a contact charging means, a developing means, a transfer means and a cleaning blade are arranged around an electrophotographic photosensitive member, inorganic fine particles are contained in a surface protective layer of the electrophotographic photosensitive member, the elastic deformation rate of the electrophotographic photosensitive member is 50% or less, and the rebound elasticity of the cleaning blade is 30% or less, the toner particles constituting the toner for developing an electrostatic image contain a lubricant, a positively charged inorganic external additive and a negatively charged inorganic external additive, and the mass of the positively charged inorganic external additive and the mass of the negatively charged inorganic external additive satisfy the relationship of the following formula (1). Formula (1): 0.28≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive

[0029] The electrophotographic photoreceptor according to the present invention has an elastic deformation rate of 50% or less. The elastic deformation rate in the present invention is a value calculated by the following formula (I). Formula (I): Elastic deformation rate (%) = We / Wtot In the above formula (I), "We" represents elastic energy, and "Wtot" represents the sum of elastic energy and plastic energy. Incidentally, "We" and "Wtot" are measured using a microhardness tester "H100V" (manufactured by Fscher) according to the following measurement conditions. (Measurement conditions) Indenter used: Vickers square pyramid diamond indenter with facing angle of 136° Loading conditions: Vickers indenter is pressed into the surface of the organic photoconductor at a speed of 6mN / sec. Loading time: 5sec (maximum load 30mN) ·Holding time: 5sec Unloading conditions: Unload at the same speed as the load

[0030] The elastic deformation rate is 50% or less, and preferably within the range of 40 to 50%. The elastic deformation rate is affected by whether the surface protective layer of the electrophotographic photoreceptor is a curing type (using a curing reaction of a monomer) or a thermoplastic type (not using a curing reaction of a monomer, but applying a resin, drying and molding it). Therefore, as a means for making the elastic deformation rate 50% or less, for example, the type and content of the monomer and thermoplastic resin constituting the surface protective layer of the photoreceptor can be adjusted.

[0031] Specifically, it is preferable to use an acrylic monomer as the monomer. The thermoplastic resin is preferably, for example, a polycarbonate resin, etc. The content of the monomer or thermoplastic resin in the entire surface protective layer is preferably within a range of 40 to 80% by mass.

[0032] The cleaning blade according to the present invention has a rebound resilience of 30% or less. The rebound resilience in the present invention is a rebound resilience measured at a temperature of 23° C. in accordance with the Lupke rebound resilience test of JIS K6255.

[0033] The rebound resilience is 30% or less, and preferably in the range of 10 to 25%. As a means for making the resilience modulus 30% or less, for example, the composition ratio or crosslinking state of the resin constituting the blade member of the cleaning blade may be adjusted.

[0034] Furthermore, the toner particles constituting the electrostatic image developing toner according to the present invention contain a lubricant, a positively charged inorganic external additive, and a negatively charged inorganic external additive, and the mass of the positively charged inorganic external additive and the mass of the negatively charged inorganic external additive satisfy the relationship of formula (1) above. It is more preferable that the relationship of the above formula (1) satisfies the relationship of the following formula (1-1). Formula (1-1): 0.42≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive≦0.7 Here, the mass of the positively charged inorganic external additive refers to the total mass of the positively charged inorganic external additives when multiple types of positively charged inorganic external additives are used. The same applies to the mass of the negatively charged inorganic external additives.

[0035] Table I below shows the types of negatively and positively chargeable inorganic external additives, their chargeability, average particle size, and surface treatment. [Table 1]

[0036] The strength of the negative chargeability and positive chargeability shown in Table I was determined by measuring the triboelectric chargeability of the ferrite carrier and judging according to the following criteria. <Method for measuring triboelectric charging> The ferrite carrier in the developer used in bizhub PRO 1050e (manufactured by Konica Minolta) was mixed with 1% by mass of an external additive in terms of total mass ratio, and the charge amount was measured using a blow-off charge measuring device to measure triboelectric chargeability. Weakly negative charge: Charge amount range is -10μC / g or less Medium negative charge: Charge amount range is greater than -10μC / g and less than 30μC / g Strongly negatively charged: Charge amount range is greater than -30μC / g Weakly positive charge: Charge amount range is 10μC / g or less Neutral positive charge: Charge amount range is greater than 10μC / g and less than 30μC / g Strong positive charge: Charge range is greater than 30μC / g

[0037] Therefore, in the present invention, the positively charged inorganic external additives and the negatively charged inorganic external additives shown in Table I are used, and are added so as to satisfy the relationship of formula (1).

[0038] [Image forming device] The image forming apparatus used in the image forming method of the present invention is a general electrophotographic image forming apparatus, in which at least a contact charging means, a developing means, a transfer means and a cleaning blade are installed around an electrophotographic photoreceptor (hereinafter also simply referred to as "photoreceptor"). It is preferable that the image forming apparatus further includes an exposure means and a fixing means. In particular, since the image forming method of the present invention is preferably an image forming method by a tandem process, it is preferable that the image forming apparatus used is a tandem type image forming apparatus.

[0039] FIG. 2 is an explanatory cross-sectional view showing an example of the configuration of an image forming apparatus of the present invention, and FIG. 3 is an explanatory cross-sectional view showing an example of the configuration of a main part of the image forming apparatus. This image forming apparatus 100 is called a tandem type color image forming apparatus, and has four image forming units 110Y, 110M, 110C, and 110Bk, a paper feeding and conveying means 150, and a fixing means 170. An original image reading device SC is disposed on the upper part of the main body of the image forming apparatus 100.

[0040] The image forming units 110Y, 110M, 110C, and 110Bk are arranged in a vertical line. The image forming units 110Y, 110M, 110C, and 110Bk each include a rotating drum-shaped photoconductor 111Y, 111M, 111C, and 111Bk, lubricant supplying means 116Y, 116M, 116C, and 116Bk, and contact-type charging means 113Y, 113M, 113C, and 113Bk, which are arranged in sequence along the rotation direction of the photoconductor in the outer peripheral surface area of ​​the drum-shaped photoconductor 111Y, 111M, 111C, and 111Bk, The device includes exposure means 115Y, 115M, 115C, and 115Bk, development means 117Y, 117M, 117C, and 117Bk, primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk, cleaning blades 119Y, 119M, 119C, and 119Bk, and lubricant removal means 114Y, 114M, 114C, and 114Bk. Yellow (Y), magenta (M), cyan (C), and black (Bk) toner images are formed on the photoconductors 111Y, 111M, 111C, and 111Bk, respectively. Image forming units 110Y, 110M, 110C, and 110Bk have the same configuration except that the colors of the toner images formed on photoconductors 111Y, 111M, 111C, and 111Bk are different, so the following description will be given using image forming unit 110Y as an example. The electrophotographic photosensitive member, the contact charging means, the exposure means, the developing means, the transfer means, the fixing means and the cleaning blade will be described in this order.

[0041] <Electrophotographic photoreceptor> As described above, the electrophotographic photoreceptor according to the present invention has an elastic deformation rate of 50% or less. The photoreceptor according to the present invention preferably has at least a surface protective layer (hereinafter also referred to as a "protective layer" or "hardened surface layer") and a photosensitive layer on a conductive support. Specifically, a photosensitive layer is formed by laminating a charge generating layer containing a charge generating material and a charge transporting layer containing a charge transporting material in this order on a conductive support, and a protective layer is formed as the outermost layer on the photosensitive layer (charge transporting layer). It is also preferable to provide an intermediate layer between the conductive support and the photosensitive layer. The photosensitive layer may have a single layer structure containing a charge generating material and a charge transporting material. A photoreceptor having such a structure will be described in detail below.

[0042] (Conductive support) The conductive support is a member that supports the photosensitive layer and has electrical conductivity. Preferred examples of the conductive support include a metal drum or sheet, a plastic film having a laminated metal foil, a plastic film having a layer of a vapor-deposited conductive material, a metal member or plastic film having a conductive layer formed by applying a conductive material or a paint consisting of a conductive material and a binder resin, and paper. Preferred examples of the metal include aluminum, copper, chromium, nickel, zinc, and stainless steel, and preferred examples of the conductive material include the metals, indium oxide, and tin oxide.

[0043] (Photosensitive layer) The photosensitive layer is a layer for forming an electrostatic latent image of a desired image on the surface of a photoreceptor by an exposure means described later. The photosensitive layer may be a single layer or may be composed of multiple laminated layers. Preferred examples of the photosensitive layer include a single layer containing a charge transport material and a charge generation material, and a laminate of a charge transport layer containing a charge transport material and a charge generation layer containing a charge generation material.

[0044] (protective layer) The protective layer is a layer for improving the mechanical strength of the surface of the photoreceptor and improving scratch resistance and abrasion resistance. In the image forming apparatus of the present invention, the protective layer is the outermost layer. In the present invention, the outermost layer of the photoreceptor refers to a layer disposed on the outermost side that comes into contact with the toner, and the protective layer is the outermost layer. The protective layer according to the present invention preferably contains a compound having a charge transport structure (hereinafter, also referred to as a "charge transport material") in terms of charge transport properties. The protective layer preferably contains inorganic fine particles. Furthermore, the protective layer preferably contains a binder resin and inorganic fine particles whose surfaces have been modified with a surface modifier, and the binder resin preferably contains a thermoplastic resin.

[0045] 《Charge transport material》 The charge transport material is not particularly limited, and known materials can be used. Examples thereof include carbazole derivatives, oxazole derivatives, oxadiazole derivatives, thiazole derivatives, thiadiazole derivatives, triazole derivatives, imidazole derivatives, imidazolone derivatives, imidazolidine derivatives, bisimidazolidine derivatives, styryl compounds, hydrazone compounds, pyrazoline compounds, oxazolone derivatives, benzimidazole derivatives, quinazoline derivatives, benzofuran derivatives, acridine derivatives, phenazine derivatives, aminostilbene derivatives, triarylamine derivatives, phenylenediamine derivatives, stilbene derivatives, and benzidine derivatives. Among these, triarylamine derivatives are preferred. As the triarylamine derivative, those represented by the following chemical formula (1) are preferred.

[0046] [ka]

[0047] In the above chemical formula (1), R1, R2, R3, and R4 each independently represent an alkyl group having 1 to 7 carbon atoms, or an alkoxy group having 1 to 7 carbon atoms. k, l, and n each independently represent an integer of 0 to 5, and m represents an integer of 0 to 4. However, when k, l, n, or m is 2 or more, the multiple R1s, R2s, R3s, and R4s may be the same or different from each other. Among these, it is preferable that R1, R2, R3, and R4 each independently represent an alkyl group having 1 to 3 carbon atoms. It is also preferable that k, l, n, and m each independently represent an integer of 0 to 1.

[0048] As the compound represented by the above chemical formula (1), for example, the compound described in JP 2015-114454 A can be used, and the compound can also be synthesized by a known synthesis method, for example, the method disclosed in JP 2006-143720 A.

[0049] From the viewpoint of achieving both memory performance and cleaning performance, the content of the charge transport material in the protective layer is preferably within a range of 20 to 80 parts by weight, more preferably within a range of 30 to 70 parts by weight, and even more preferably within a range of 40 to 60 parts by weight, relative to 100 parts by weight of the binder resin.

[0050] (Inorganic fine particles) The inorganic fine particles contained in the protective layer according to the present invention are contained in the protective layer for the purpose of improving the strength and electrical properties of the protective layer, and are preferably surface-modified (surface-treated) with a surface modifier (surface treatment agent). The inorganic fine particles surface-modified with a surface modifier are considered to be coated particles containing inorganic fine particles and chemical species (coating layer) derived from the surface modifier. Note that the surface-modified inorganic fine particles may have the chemical species (coating layer) derived from the surface modifier on at least a part of the surface.

[0051] In the present application, inorganic fine particles refer to fine particles containing metal elements, and are preferably metal oxide particles whose surface is at least composed of metal oxide.The examples of metal oxides constituting inorganic fine particles are not particularly limited, but include alumina, silica, magnesium oxide, zinc oxide, lead oxide, tin oxide, tantalum oxide, indium oxide, bismuth oxide, yttrium oxide, cobalt oxide, copper oxide, manganese oxide, selenium oxide, iron oxide, zirconium oxide, germanium oxide, tin oxide, titanium oxide, niobium oxide, molybdenum oxide, vanadium oxide, copper aluminum oxide, and tin oxide doped with antimony ions. These inorganic fine particles may be used alone or in combination of two or more kinds. The metal oxide particles may be synthetic products or commercially available products.

[0052] Among these inorganic fine particles, any one of alumina particles, tin oxide particles, titanium oxide particles, and silicon dioxide (silica) particles is preferred in terms of improving the strength of the protective layer, and silica particles are particularly preferred.

[0053] In addition, the inorganic fine particles are preferably particles (composite particles) having a core-shell structure, which has a core made of a metal oxide and an outer shell made of a surface modifier. By making the inorganic fine particles into composite particles having a core-shell structure, it is possible to increase the particle size of the inorganic fine particles. The core-shell structure is used when the inorganic fine particle size is to be increased, and it is not necessary to use the core-shell structure when the inorganic fine particle size is to be reduced.

[0054] The material constituting the core of the composite particle is not particularly limited, but examples thereof include barium sulfate (BaSO4), alumina, silicon oxide, etc. Among these, particles having barium sulfate as the core are preferred from the viewpoint of ensuring the light transmittance of the protective layer. The material constituting the outer shell of the composite particle is the same as the examples of metal oxides constituting the inorganic fine particles described above. A preferred example of a core-shell composite particle is a composite particle having a core material made of barium sulfate and an outer shell made of any one of tin oxide, alumina, and titanium oxide. The ratio of the number average primary particle size of the core material to the thickness of the outer shell may be appropriately set depending on the type of the core material and the outer shell used, and the combination thereof.

[0055] The number average primary particle diameter of the inorganic fine particles before surface modification (unmodified) with a surface modifier is preferably within the range of 50 to 500 nm, more preferably within the range of 65 to 400 nm, and even more preferably within the range of 80 to 300 nm. When the number average primary particle diameter of the inorganic fine particles is 50 nm or more, the inorganic fine particles provide appropriate unevenness, so that the posture of the cleaning blade during cleaning is stable and cleaning performance is improved. In addition, when the number average primary particle diameter of the inorganic fine particles is 500 nm or less, the convex parts are too large to be caught by the cleaning blade, so that deterioration of cleaning performance due to the occurrence of stick-slip of the blade can be prevented.

[0056] In this specification, the number average primary particle size of inorganic fine particles is defined as the number average primary particle size measured by the following method.

[0057] First, a 10,000x magnified photograph taken by a scanning electron microscope (manufactured by JEOL Ltd.) is imported into a scanner. Next, 300 particle images, excluding aggregated particles, are randomly binarized from the obtained photographic image using an automatic image processing and analysis system, Luzex (registered trademark) AP Software Ver. 1.32 (manufactured by Nireco Corporation), to calculate the horizontal Feret diameter of each of the particle images. Then, the average value of the horizontal Feret diameters of each of the particle images is calculated to obtain the number average primary particle size. Here, the horizontal Feret diameter refers to the length of the side parallel to the x-axis of the circumscribing rectangle when the particle image is binarized. In addition, the measurement of the number average primary particle size of inorganic fine particles is performed on inorganic fine particles that do not contain chemical species (coating layer) derived from a surface modifier.

[0058] (Surface Modifier) The inorganic fine particles according to the present invention are surface-modified with a surface modifier. The surface modifier is not particularly limited, but examples thereof include a silicone surface modifier having a silicone structure (silicone chain) and a surface modifier having a polymerizable functional group, and a surface modifier having a silicone chain (hereinafter also referred to as a silicone surface modifier) ​​is preferred.

[0059] The silicone surface modifier is not particularly limited, but may have a silicone chain in the main chain of the polymer main chain, may have a silicone chain in a side chain, or may have a silicone chain in both the main chain and the side chain. By having silicone chains in both the main chain and the side chain, the inorganic fine particles surface-modified with a surface modifier having silicone chains in both the main chain and the side chain have more silicone chains, which improves dispersibility in the protective layer and further improves the abrasion resistance of the protective layer.

[0060] In addition to the silicone chain, it is preferable that the silicone further has a reactive functional group. Examples of reactive functional groups include groups capable of bonding with metal oxide particles, such as carboxylic acid groups, hydroxy groups, -Rd-COOH (Rd is a divalent hydrocarbon group), alkylsilyl groups, halogenated silyl groups, and alkoxysilyl groups. Among these, carboxylic acid groups, hydroxy groups, and alkoxysilyl groups are preferred.

[0061] The polymer main chain of the silicone surface modifier is preferably a poly(meth)acrylate main chain or a silicone main chain, and more preferably a silicone main chain.

[0062] The side chains and main chain silicone chains preferably have a dimethylsiloxane structure as a repeating unit, and the number of repeating units is preferably 3 to 100, more preferably 3 to 50, and even more preferably 3 to 30.

[0063] The weight average molecular weight of the silicone surface modifier is not particularly limited, but is preferably within the range of 1000 to 50000. The weight average molecular weight of the silicone surface modifier can be measured by gel permeation chromatography (GPC).

[0064] The silicone surface modifier may be used alone or in combination of two or more kinds. The silicone surface modifier may be a synthetic product or a commercially available product. Specific examples of commercially available surface modifiers having silicone chains in side chains of a poly(meth)acrylate main chain include SIMAC (registered trademark) US-350 (all manufactured by Toagosei Co., Ltd.), KP-541, KP-574, and KP-578 (all manufactured by Shin-Etsu Chemical Co., Ltd.). Specific examples of commercially available surface modifiers having a silicone main chain and a silicone chain in its side chain (surface modifiers having a silicone chain in its main chain and a silicone chain in its side chain) include KF-9908 and KF-9909 (both manufactured by Shin-Etsu Chemical Co., Ltd.). Furthermore, a specific example of a commercially available surface modifier having a silicone chain only in the main chain is KF-9901 (manufactured by Shin-Etsu Chemical Co., Ltd.).

[0065] Surface modification method using surface modifiers (silicone surface modifiers) The method of surface modification using a surface modifier is not particularly limited, and any method capable of attaching (or bonding) the surface modifier to the surface of the inorganic fine particles may be used. Generally, such methods are roughly divided into two types, a wet treatment method and a dry treatment method, and either method may be used.

[0066] When the inorganic fine particles are subjected to surface modification after the reactive surface modification described below, the surface modifier adheres (or bonds) to the surface of the inorganic fine particles or to the reactive surface modifier.

[0067] The wet treatment method is a method in which inorganic fine particles and a surface modifier are dispersed in a solvent, so that the surface modifier is attached (or bonded) to the surfaces of the inorganic fine particles. A preferred method for this purpose is to disperse inorganic fine particles and a surface modifier in a solvent, dry the resulting dispersion, and remove the solvent. Thereafter, a heat treatment is further performed to react the surface modifier with the inorganic fine particles, thereby adhering (or bonding) the surface modifier to the surface of the inorganic fine particles. Alternatively, the surface modification may be promoted at the same time by dispersing the surface modifier and the inorganic fine particles in a solvent and then wet-pulverizing the obtained dispersion.

[0068] The means for dispersing the inorganic fine particles and the surface modifier in the solvent is not particularly limited and any known means can be used, and examples of such means include general dispersing means such as a homogenizer, a ball mill, and a sand mill.

[0069] The solvent is not particularly limited and may be a known solvent, and preferred examples thereof include alcohol-based solvents such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol (2-butanol), tert-butanol, and benzyl alcohol, and aromatic hydrocarbon-based solvents such as toluene and xylene. These may be used alone or in combination of two or more. Among these, methanol, 2-butanol, toluene, and a mixed solvent of 2-butanol and toluene are more preferred.

[0070] The dispersion time is not particularly limited, but is, for example, preferably within the range of 1 to 600 minutes, more preferably within the range of 10 to 360 minutes, and even more preferably within the range of 30 to 120 minutes.

[0071] The method for removing the solvent is not particularly limited and any known method can be used. Examples of such a method include a method using an evaporator and a method of volatilizing the solvent at room temperature.

[0072] The heating temperature is not particularly limited, but is preferably within the range of 50 to 250° C., more preferably within the range of 70 to 200° C., and even more preferably within the range of 90 to 150° C. The heating time is not particularly limited, but is preferably within the range of 1 to 600 minutes, more preferably within the range of 10 to 300 minutes, and even more preferably within the range of 30 to 90 minutes. The heating method is not particularly limited, and a known method can be used.

[0073] The dry treatment method is a method in which a surface modifier is mixed with inorganic fine particles and kneaded without using a solvent, thereby adhering (or bonding) the surface modifier to the surface of the conductive metal oxide. The method may be a method in which the surface modifier is mixed with inorganic fine particles, kneaded, and then heat-treated to react with the inorganic fine particles, thereby adhering (or bonding) the surface modifier to the surface of the inorganic fine particles. In addition, when the inorganic fine particles and the surface modifier are mixed and kneaded, they may be dry-pulverized to reduce the size of the inorganic fine particles and simultaneously advance the surface modification.

[0074] The amount of the surface modifier used is preferably 0.1 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 2 parts by mass or more, based on 100 parts by mass of inorganic fine particles before treatment (in the case of surface-modifying inorganic fine particles after reactive surface modification described later, inorganic fine particles after reactive surface modification). Within this range, the abrasion resistance and fogging suppression effect of the protective layer are further improved.

[0075] The amount of the surface modifier used is preferably 100 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, relative to 100 parts by mass of inorganic fine particles before surface modification (in the case of surface-modifying inorganic fine particles after reactive surface modification described below, inorganic fine particles after reactive surface modification). Within this range, a decrease in the film strength of the protective layer due to unreacted surface modifier is suppressed, and the abrasion resistance of the protective layer is improved.

[0076] The surface modification of unmodified inorganic particles or inorganic particles after reactive surface modification can be confirmed by thermogravimetry / differential thermal analysis (TG / DTA) measurements, observation with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), analysis with energy dispersive X-ray spectroscopy (EDX), etc.

[0077] The surface-modified inorganic fine particles preferably have a group derived from a polymerizable group. The surface-modified inorganic fine particles have a group derived from a polymerizable group, and thus the abrasion resistance of the protective layer is improved. The type of polymerizable group is not particularly limited, but a radical polymerizable group is preferred. The method of introducing the polymerizable group is not particularly limited, but a method of surface-modifying the inorganic fine particles with a surface modifier having a polymerizable group is preferred.

[0078] The presence of polymerizable groups in the surface-modified inorganic fine particles and the presence of groups derived from polymerizable groups in the surface-modified inorganic fine particles in the protective layer can be confirmed by thermogravimetry / differential thermal analysis (TG / DTA) measurement, observation with a scanning electron microscope (SEM) or a transmission electron microscope (TEM), analysis with energy dispersive X-ray spectroscopy (EDX), mass spectrometry, and the like.

[0079] Surface modification method using a surface modifier having a polymerizable group (reactive surface modifier) The inorganic fine particles that have been surface-modified (silicone surface-modified) as described above are preferably further surface-modified with a reactive surface modifier. Polymerizable groups are supported on the surfaces of the inorganic fine particles by the reactive surface modification, and as a result, the surface-modified inorganic fine particles further have polymerizable groups. The surface-modified inorganic fine particles are then polymerized with the polymerizable monomer via the polymerizable group in the protective layer, forming a protective layer with higher film strength and further improving the abrasion resistance of the protective layer. At this time, the silicone surface-modified particles are present in the protective layer as a structure having a group derived from the polymerizable group.

[0080] The reactive surface modifier has a polymerizable group and a reactive functional group. The type of the polymerizable group is not particularly limited, but a radically polymerizable group is preferred. Here, the radically polymerizable group refers to a radically polymerizable group having a carbon-carbon double bond. Examples of the radically polymerizable group include a vinyl group and a (meth)acryloyl group, and among these, a methacryloyl group is preferred. In addition, the reactive functional group refers to a group that has reactivity with a polar group such as a hydroxyl group present on the surface of the inorganic fine particles. Examples of the reactive functional group include a carboxylic acid group, a hydroxyl group, -R'-COOH (R' is a divalent hydrocarbon group), an alkylsilyl group, a halogenated silyl group, an alkoxysilyl group, and among these, an alkylsilyl group, a halogenated silyl group, and an alkoxysilyl group are preferred.

[0081] The reactive surface modifier is preferably a silane coupling agent having a radical polymerizable group, and examples thereof include compounds represented by the following formulas S-1 to S-32. S-1: CH2=CHSi(CH3)(OCH3)2 S-2: CH2=CHSi(OCH3)3 S-3: CH2=CHSiCl3 S-4: CH2=CHCOO(CH2)2Si(CH3)(OCH3)2 S-5: CH2=CHCOO(CH2)2Si(OCH3)3 S-6: CH2=CHCOO(CH2)2Si(OC2H5)(OCH3)2 S-7: CH2=CHCOO(CH2)3Si(OCH3)3 S-8: CH2=CHCOO(CH2)2Si(CH3)Cl2 S-9: CH2=CHCOO(CH2)2SiCl3 S-10: CH2=CHCOO(CH2)3Si(CH3)Cl2 S-11: CH2=CHCOO(CH2)3SiCl3 S-12: CH2=C(CH3)COO(CH2)2Si(CH3)(OCH3 )2 S-13: CH2=C(CH3)COO(CH2)2Si(OCH3)3 S-14: CH2=C(CH3)COO(CH2)3Si(CH3)(OCH3)2 S-15: CH2=C(CH3)COO(CH2)3Si(OCH3)3 S-16: CH2=C(CH3)COO(CH2)2Si(CH3)Cl2 S-17: CH2=C(CH3)COO(CH2)2SiCl3 S-18: CH2=C(CH3)COO(CH2)3Si(CH3)Cl2 S-19: CH2=C(CH3)COO(CH2)3SiCl3 S-20: CH2=CHSi(C2H5)(OCH3)2 S-21: CH2=C(CH3)Si(OCH3)3 S-22: CH2=C(CH3)Si(OC2H5)3 S-23: CH2=CHSi(OCH3)3 S-24: CH2=C(CH3)Si(CH3)(OCH3)2 S-25: CH2=CHSi(CH3)Cl2 S-26: CH2=CHCOOSi(OCH3)3 S-27: CH2=CHCOOSi(OC2H5)3 S-28: CH2=C(CH3)COOSi(OCH3)3 S-29: CH2=C(CH3)COOSi(OC2H5)3 S-30: CH2=C(CH3)COO(CH2)3Si(OC2H5)3 S-31: CH2=CHCOO(CH2)2Si(CH3)2(OCH3) S-32: CH2=C(CH3)COO(CH2)8Si(OCH3)3

[0082] The reactive surface modifier may be used alone or in combination of two or more kinds. The reactive surface modifier may be a synthetic product or a commercially available product. Specific examples of commercially available products include KBM-502, KBM-503, KBE-502, KBE-503, and KBM-5103 (all manufactured by Shin-Etsu Chemical Co., Ltd.).

[0083] When both silicone surface modification and reactive surface modification are performed, it is preferable to perform the silicone surface modification after the reactive surface modification. By performing the surface modifications in this order, the abrasion resistance of the protective layer is further improved. The reason for this is that the silicone chains having an oil repellent effect do not prevent the reactive surface modifier from contacting the inorganic fine particle surface, so that the introduction of polymerizable groups into the inorganic fine particles is more efficiently performed.

[0084] The method of reactive surface modification is not particularly limited, and the same method as that described for silicone surface modification can be adopted, except for using a reactive surface modifier. Also, known surface modification techniques for inorganic fine particles may be used.

[0085] When reactive surface modification is carried out by a wet treatment method, the solvent is preferably methanol, ethanol or toluene, and more preferably methanol or toluene.

[0086] The amount of reactive surface modifier used is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and even more preferably 1.5 parts by mass or more, relative to 100 parts by mass of inorganic fine particles before reactive surface modification. In this range, the abrasion resistance and fogging suppression effect of the protective layer are further improved. In addition, the amount of reactive surface modifier used is preferably 15 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, relative to 100 parts by mass of inorganic fine particles before modification. In this range, the amount of reactive surface modifier is not excessive relative to the number of hydroxyl groups on the particle surface, and is a more appropriate range, so that the decrease in the film strength of the protective layer due to unreacted reactive surface modifier is suppressed, and the abrasion resistance of the protective layer is further improved.

[0087] The content of inorganic fine particles in the protective layer is preferably in the range of 5 to 40 parts by mass, more preferably 10 to 30 parts by mass, per 100 parts by mass of the binder resin, from the viewpoint of imparting durability such as abrasion resistance to the protective layer without impairing the effects of the present invention.

[0088] (binder resin) As the binder resin contained in the protective layer, general thermoplastic resins, thermosetting resins and photocurable resins can be used. Specific examples of the binder resin include polystyrene resin, polyethylene resin, polypropylene resin, acrylic resin, methacrylic resin, epoxy resin, polyurethane resin, polyester resin, alkyd resin, polycarbonate resin, polyarylate resin, polysulfone resin, polyamide resin, etc. In particular, thermoplastic resins such as polycarbonate resin, polyarylate resin, and polyester resin are preferred. Among these, polycarbonate resin is preferred in terms of electrical properties and film strength.

[0089] The binder resin contained in the protective layer is preferably a cured product of a polymerizable compound. Examples of the cured product of the polymerizable compound include polystyrene resin, acrylic resin, methacrylic resin, epoxy resin, polyurethane resin, etc. The protective layer is preferably a layer obtained by curing a composition containing a polymerizable compound and a charge transport material.

[0090] The polymerizable compound is preferably a monomer that is polymerized (cured) by exposure to actinic rays such as ultraviolet rays or electron beams to become a resin generally used as a binder resin for a photoreceptor, such as polystyrene resin, acrylic resin, methacrylic resin, etc. In particular, styrene-based monomers, acrylic monomers, methacrylic monomers, vinyl toluene-based monomers, vinyl acetate-based monomers, and N-vinylpyrrolidone-based monomers are preferred.

[0091] Among these, radical polymerizable monomers having an acryloyl group (CH2=CHCO-) ​​or a methacryloyl group (CH2=CCH3CO-) or oligomers thereof are particularly preferred because they can be cured with a small amount of light or in a short time.

[0092] From the viewpoint of forming a protective layer having high crosslink density and high hardness, the radical polymerizable monomer is preferably a polyfunctional radical polymerizable monomer having three or more radical polymerizable groups. Specific examples of the polyfunctional radical polymerizable monomer having three or more acryloyl groups or methacryloyl groups include compounds having structures represented by the following formulae M1 to M11. In the following compounds, R represents an acryloyl group, and R' represents a methacryloyl group.

[0093] [ka]

[0094] These radical polymerizable monomers are known and commercially available. As the radical polymerizable monomer, one of these may be used alone, or two or more of them may be used in combination.

[0095] As the radical polymerizable monomer for obtaining the binder resin, in addition to the polyfunctional radical polymerizable monomer having three or more functional groups, a bifunctional radical polymerizable monomer and a monofunctional radical polymerizable monomer may be used in combination.

[0096] The polymerization (curing) of the radical polymerizable monomer is carried out using a photopolymerization initiator. As the photopolymerization initiator, an alkylphenone compound or a phosphine oxide compound is preferable. In particular, a compound having an α-hydroxyacetophenone structure or an acylphosphine oxide structure is preferable.

[0097] Examples of compounds having an acylphosphine oxide structure include 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, etc. Commercially available products may be used, and Irgacure TPO (trade name, manufactured by BASF) can be used as 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and Irgacure 819 (trade name, manufactured by BASF) can be used as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0098] The photopolymerization initiator is preferably used in a proportion of 3 to 15 parts by mass, more preferably 5 to 10 parts by mass, per 100 parts by mass of the radical polymerizable monomer. When a cured product of a polymerizable compound is used as the binder resin, the amount of the photopolymerization initiator is the total amount of the polymerizable compound and the polymerization initiator.

[0099] (Other ingredients) The resin composition of the binder resin for forming the protective layer may further contain other components other than the above-mentioned components. Examples of other components include, but are not limited to, lubricants. The lubricant is not limited to, and can be a known one, and examples thereof include polymerizable silicone compounds and polymerizable perfluoropolyether compounds.

[0100] [Method of Manufacturing Electrophotographic Photoreceptor] The electrophotographic photoreceptor according to the present invention can be produced by a known method for producing an electrophotographic photoreceptor without any particular limitation. In particular, it is preferable to manufacture the photosensitive layer by a method including a step of applying a coating liquid containing a resin composition for forming a protective layer to the surface of a photosensitive layer formed on a conductive support, and a step of drying the applied resin composition for forming a protective layer.

[0101] The resin composition for forming the protective layer preferably contains at least a charge transport material, a thermoplastic resin, and inorganic fine particles surface-modified with a surface modifier. The resin composition for forming the protective layer may contain other components such as an antioxidant, and may further contain a dispersion medium.

[0102] As the dispersion medium, any medium can be used as long as it can dissolve or disperse the charge transport material, the thermoplastic resin, the surface-modified inorganic fine particles, and further the antioxidant added as required. Specific examples include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol (sec-butanol), tert-butanol, benzyl alcohol, toluene, xylene, methyl ethyl ketone, cyclohexane, ethyl acetate, butyl acetate, methyl cellosolve, ethyl cellosolve, tetrahydrofuran, 1,3-dioxane, 1,3-dioxolane, pyridine, and diethylamine. The dispersion medium can be used alone or in combination of two or more kinds.

[0103] The content of the dispersion medium relative to the total mass of the resin composition for forming the protective layer is not particularly limited, but is preferably in the range of 1 to 99 mass%, more preferably in the range of 40 to 90 mass%, and even more preferably in the range of 50 to 80 mass%.

[0104] The content of inorganic fine particles in the resin composition for forming the protective layer is not particularly limited, but is preferably 20% by mass or more, more preferably 30% by mass or more, and even more preferably 40% by mass or more. Within this range, the crosslink density of the protective layer increases, the mechanical strength is further improved, and the abrasion resistance of the protective layer is further improved.

[0105] The method for preparing the resin composition for forming the protective layer is not particularly limited. A charge transport material, a thermoplastic resin, surface-modified inorganic fine particles, and various additives such as an antioxidant, which are added as necessary, may be added to a dispersion medium, and the mixture may be stirred and mixed until dissolved or dispersed.

[0106] The protective layer according to the present invention can be formed by applying the resin composition for forming the protective layer prepared by the above-mentioned method onto a photosensitive layer, followed by drying and curing.

[0107] During the above coating, drying and curing process, the thermoplastic resin and the surface-modified inorganic fine particles are bonded to each other. and reactions between the surface-modified inorganic fine particles proceed, forming a protective layer containing a cured product of the resin composition for forming the protective layer.

[0108] The method for applying the resin composition for forming the protective layer is not particularly limited, and known methods such as dip coating, spray coating, spinner coating, bead coating, blade coating, beam coating, slide hopper coating, and circular slide hopper coating can be used.

[0109] After the coating liquid is applied, natural drying or heat drying is carried out to form a coating film.

[0110] Drying conditions can be appropriately selected depending on the type of solvent, film thickness, etc. The drying temperature is preferably 20 to 180° C., more preferably 80 to 140° C., and the drying time is preferably 1 to 200 minutes, more preferably 5 to 100 minutes.

[0111] The thickness of the protective layer is preferably within the range of 1 to 10 μm, and more preferably within the range of 1.5 to 5 μm.

[0112] Whether the protective layer contains the above composition can be confirmed by known analytical methods such as pyrolysis GC-MS, nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FT-IR), and elemental analysis.

[0113] <Contact charging means> The contact-type charging unit 113Y is a unit that charges the surface of the photoconductor 111Y using a charging roller. The charging unit 113Y in this example is composed of a charging roller arranged in contact with the surface of the photoconductor 111Y and a power source that applies a voltage to the charging roller.

[0114] In the present invention, the contact charging means employs a contact charging method in which a charging roller is brought into contact with the surface of the photoreceptor and charges the surface.

[0115] As shown in FIG. 4, the charging roller 113Y is configured such that an elastic layer 113b is laminated on the surface of a core metal 113a to reduce the amount of charge and provide elasticity to obtain uniform adhesion to the photoconductor 111Y, and a resistance control layer 113c is laminated on the surface of the elastic layer 113b as needed to obtain a highly uniform electrical resistance for the charging roller 113Y as a whole, and a surface layer 113d is laminated on the resistance control layer 113c, which is urged toward the photoconductor 111Y by a compression spring 113e and pressed against the surface of the photoconductor 111Y with a predetermined pressing force to form a charging nip portion, and the charging roller 113Y rotates in response to the rotation of the photoconductor 111Y.

[0116] The core 113a is made of a metal such as iron, copper, stainless steel, aluminum or nickel, or the surface of such a metal is plated to provide rust resistance and scratch resistance without impairing conductivity, and its outer diameter is, for example, within the range of 3 to 20 mm.

[0117] The elastic layer 11b is made of an elastic material such as rubber to which conductive fine particles such as carbon black or carbon graphite, or conductive fine salt particles such as alkali metal salt or ammonium salt are added. Specific examples of elastic materials include synthetic rubbers such as natural rubber, ethylene propylene diene methylene rubber (EPDM), styrene-butadiene rubber (SBR), silicone rubber, urethane rubber, epichlorohydrin rubber, isoprene rubber (IR), butadiene rubber (BR), nitrile-butadiene rubber (NBR), and chloroprene rubber (CR), resins such as polyamide resin, polyurethane resin, silicone resin, and fluororesin, and foams such as foamed sponge, etc. The degree of elasticity can be adjusted by adding process oil, plasticizer, etc. to the elastic material.

[0118] The elastic layer 11b has a volume resistivity of 1×10 1 ~1×10 10 The resistivity is preferably in the range of Ω·cm, and the layer thickness is preferably in the range of 500 to 5000 μm, and more preferably in the range of 500 to 3000 μm. The volume resistivity of the elastic layer 11b is a value measured in accordance with JIS K6911.

[0119] The resistance control layer 113c is provided for the purpose of providing uniform electrical resistance throughout the charging roller 113Y, but may not be necessary. The resistance control layer 113c can be provided by coating a material having appropriate electrical conductivity or by covering the charging roller 113Y with a tube having appropriate electrical conductivity.

[0120] Specific materials constituting this resistance control layer 113c include resins such as polyamide resin, polyurethane resin, fluororesin, and silicone resin; and rubbers such as epichlorohydrin rubber, urethane rubber, chloroprene rubber, and acrylonitrile-based rubber, to which conductive agents such as conductive fine particles made of carbon black, carbon graphite, etc.; conductive metal oxide fine particles made of conductive titanium oxide, conductive zinc oxide, conductive tin oxide, etc.; and conductive salt fine particles made of alkali metal salts, ammonium salts, etc. have been added.

[0121] The resistance control layer 113c has a volume resistivity of 1×10-2 ~1×10 14 It is preferably in the range of Ω·cm, and more preferably 1×10 1 ~1×10 10 The layer thickness is preferably in the range of 0.5 to 100 μm, more preferably 1 to 50 μm, and further preferably 1 to 20 μm. The volume resistivity of the resistance control layer 113c is a value measured in accordance with JIS K6911.

[0122] The surface layer 113d is provided for the purposes of preventing the plasticizer in the elastic layer 11b from bleeding out onto the surface of the resulting charging roller, of obtaining slipperiness and smoothness on the surface of the charging roller, and of preventing the occurrence of leaks even if there are defects such as pinholes on the photoconductor 11Y, and is provided by coating the surface with a material having appropriate electrical conductivity or by covering it with a tube having appropriate electrical conductivity.

[0123] When the surface layer 113d is provided by coating a material, specific examples of the material include resins such as polyamide resin, polyurethane resin, acrylic resin, fluororesin, and silicone resin, epichlorohydrin rubber, urethane rubber, chloroprene rubber, and acrylonitrile rubber, to which a conductive agent such as conductive fine particles made of carbon black, carbon graphite, or the like; or conductive metal oxide fine particles made of conductive titanium oxide, conductive zinc oxide, conductive tin oxide, or the like has been added. Examples of the coating method include a dip coating method, a roll coating method, and a spray coating method.

[0124] In addition, when the surface layer 113d is provided by covering with a tube, specific examples of the tube include nylon 12, tetrafluoroethylene-perfluoroalkylvinylether copolymer resin (PFA), polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer resin (FEP), and thermoplastic elastomers such as polystyrene, polyolefin, polyvinyl chloride, polyurethane, polyester, and polyamide, to which the above-mentioned conductive agent is added, molded into a tube shape. This tube may be either heat-shrinkable or non-heat-shrinkable.

[0125] The surface layer 113d has a volume resistivity of 1×10 1 ~1×10 8 It is preferably in the range of Ω·cm, and more preferably 1×10 1 ~1×10 5 The layer thickness is preferably 0.5 to 100 μm, more preferably 1 to 50 μm, and further preferably 1 to 20 μm. The volume resistivity of the surface layer 113d is a value measured in accordance with JIS K6911.

[0126] Moreover, the surface layer 113d preferably has a surface roughness Rz of 1 to 30 μm, more preferably 2 to 20 μm, and further preferably 5 to 10 μm.

[0127] In the charging roller 113Y as described above, a charging bias voltage is applied from a power source S1 to the core metal 113a of the charging roller 113Y, whereby the surface of the photoconductor 111Y is charged to a predetermined potential of a predetermined polarity. Here, the charging bias voltage may be, for example, only a DC voltage, but it is preferable to use an oscillating voltage in which an AC voltage is superimposed on a DC voltage, as this provides excellent charging uniformity. The charging bias voltage can be, for example, about −2.5 to −1.5 kV.

[0128] An example of the charging conditions using the charging roller shown in FIG. 4 is a charging bias voltage formed by a DC voltage of -500 V and an AC voltage that is a sine wave with a frequency of 1000 Hz and a peak-to-peak voltage of 1300 V. When this charging bias voltage is applied, the surface of the photoconductor is uniformly charged to -500 V.

[0129] <Exposure means> The exposure unit 115Y is a unit that exposes the surface of the photoconductor 111Y, to which a uniform potential has been applied by the charging unit 113Y, based on an image signal (yellow image signal) to form an electrostatic latent image corresponding to the yellow image. The exposure unit 115Y is composed of LEDs in which light emitting elements are arranged in an array in the axial direction of the photoconductor 111Y and an imaging element, or a laser optical system or the like is used.

[0130] <Developing method> The developing means (developing machine) 117Y is a means for supplying toner to the surface of the photoconductor 111Y, developing the electrostatic latent image formed on the surface of the photoconductor 111Y, and forming a toner image. Specifically, the developing means 117Y in this example is composed of a developing roller 118Y that has a built-in magnet and rotates while holding a developer, and a voltage application device (not shown) that applies a DC and / or AC bias voltage between the photoconductor 111Y and the developing roller 118Y. The developing unit 117Y is preferably disposed at the most downstream position in the rotation direction of the photoconductor, since raindrops are likely to occur at the most downstream position.

[0131] The toner is transported to the photoconductor 111Y by the rotation of the developing roller 118Y. Then, a thin layer of toner on the developing roller 118Y comes into contact with the photoconductor 111Y to develop the electrostatic latent image on the photoconductor 111Y. The developing roller 118Y is connected to a voltage application device. This voltage application device applies a DC and / or AC bias voltage to the developing roller 118Y. The developing potential (also called developing bias) (Vdc) can be adjusted to a desired value by controlling the voltage applied to the developing roller 1118Y. An electric field is formed in a developing section where the developing roller 118Y and the photoconductor 111Y face each other due to a potential difference (development potential difference) between the developing roller 118Y and the potential of the electrostatic latent image carried by the photoconductor 111Y.

[0132] The toner in the developer transported to the developing section by the rotation of the developing roller 118Y moves due to the force of the electric field and is attracted to the electrostatic latent image on the photoreceptor 111Y. The electrostatic latent image carried on the photoreceptor 111Y is visualized, and a toner image corresponding to the shape of the electrostatic latent image is formed on the surface of the photoreceptor 111Y.

[0133] <Transfer Method> The primary transfer roller 133Y constituting the transfer means is a means for transferring the toner image formed on the photoconductor 111Y to the endless belt-like intermediate transfer body 131. The primary transfer roller 133Y is disposed in contact with the intermediate transfer body 131.

[0134] In this image forming apparatus 100, an intermediate transfer method is adopted in which toner images formed on photoconductors 111Y, 111M, 111C, and 111Bk are transferred to intermediate transfer body 131 by primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk, and each toner image transferred to intermediate transfer body 131 is transferred to transfer material P by secondary transfer roller (secondary transfer means) 217, but a direct transfer method may also be adopted in which the toner images formed on the photoconductors are transferred directly to the transfer material by transfer means.

[0135] <Cleaning blade> The cleaning blade 119Y is a means for removing toner remaining on the surface of the photoreceptor 111Y. As described above, the cleaning blade 119Y according to the present invention has a resilience of 30% or less. When the blade member 119b of the cleaning blade 119Y has a multi-layer structure as described below, the resilience refers to the resilience of the cleaning blade 119Y in the multi-layer structure, and when the blade member 119b has a single-layer structure, the resilience refers to the resilience of the cleaning blade 119Y in the single-layer structure.

[0136] 3, the cleaning blade 119Y is composed of a support member 119a and a blade member 119b supported on the support member 119a via an adhesive layer (not shown). The blade member 119b is arranged such that its tip faces in the opposite direction (counter direction) to the rotation direction of the photoreceptor 111Y at the contact portion with the surface of the photoreceptor 11Y.

[0137] The supporting member 110a is not particularly limited, and may be any known material, such as a material made of a rigid metal, an elastic metal, plastic, ceramic, etc. Of these, a rigid metal is preferable.

[0138] The blade member 119b may have a multi-layer structure in which, for example, a base layer and an edge layer are laminated. The base layer and the edge layer are preferably made of polyurethane. Examples of polyurethane include those obtained by reacting polyol, polyisocyanate, and a crosslinking agent as necessary. The blade member 119b is not limited to the multi-layer structure, and may have a single-layer structure.

[0139] Moreover, the blade member 119b is formed such that the blade edge angle θ at one end thereof that abuts against the photoconductor 111Y is an obtuse angle. Here, the edge angle is the angle of the tip edge portion of the rubber material that is the abutment portion C with the photoconductor surface, as shown in FIG. 3, which is the angle θ. This provides an advantage in terms of cleaning performance. The edge angle θ is preferably, for example, greater than 90° and equal to or less than 130°.

[0140] The intermediate transfer body 131 is wound around a plurality of rollers 137A, 137B, 137C, and 137D and is supported rotatably. A cleaning means 135 is disposed above the intermediate transfer body 131 to remove any toner remaining on the intermediate transfer body.

[0141] In this image forming apparatus 100, the photoconductor 111Y, the developing means 117Y, the cleaning blade 119Y, etc. may be integrally combined to form a process cartridge (image forming unit) that is detachably attached to the main body of the apparatus, or the process cartridge (image forming unit) may be integrally formed with the photoconductor 111Y and one or more members selected from the group consisting of the contact charging means 113Y, the exposure means 115Y, the developing means 117Y, the primary transfer roller 133Y, and the cleaning blade 119Y.

[0142] The process cartridge 200 has a housing 201, and a photoconductor 111Y, a contact-type charging means 113Y, a developing means 117Y, a cleaning blade 119Y, and a primary transfer roller 133Y housed therein. In addition, the apparatus main body is provided with support rails 203L and 203R as means for guiding the process cartridge 200 into the apparatus main body. This allows the process cartridge 200 to be detachably attached to the apparatus main body. These process cartridges 200 can serve as a single image forming unit that is detachably attached to the apparatus main body.

[0143] The paper feed conveying means 150 is provided so as to be able to convey the transfer material P in the paper feed cassette 211 to a secondary transfer roller 217 via a plurality of intermediate rollers 213 A, 213 B, 213 C, and 213 D and a registration roller 215 .

[0144] The fixing means 170 fixes the color image transferred by the secondary transfer roller 217. The paper discharge rollers 219 are provided so as to be able to place the transfer material P on a paper discharge tray 221 while nipping the transfer material P that has been subjected to the fixing process.

[0145] In the image forming apparatus 100 configured as above, the image forming units 110Y, 110M, 110C, and 110Bk form toner images. Specifically, the contact charging means 113Y, 113M, 113C, and 113Bk discharge the surfaces of the photoconductors 111Y, 111M, 111C, and 111Bk to negatively charge them. Next, the exposure means 115Y, 115M, 115C, and 115Bk expose the surfaces of the photoconductors 111Y, 111M, 111C, and 111Bk based on an image signal to form an electrostatic latent image. Next, the developing means 117Y, 117M, 117C, and 117Bk apply toner to the surfaces of the photoconductors 111Y, 111M, 111C, and 111Bk to develop them, forming a toner image.

[0146] Next, the primary transfer rollers (primary transfer means) 133Y, 133M, 133C, and 133Bk are brought into contact with the rotating intermediate transfer body 131. As a result, the toner images of each color formed on the photoconductors 111Y, 111M, 111C, and 111Bk are transferred successively onto the rotating intermediate transfer body 131, thereby transferring a color image (primary transfer). During the image forming process, the primary transfer roller 133Bk is always in contact with the photoconductor 111Bk. Meanwhile, the other primary transfer rollers 133Y, 133M, and 133C are brought into contact with the corresponding photoconductors 111Y, 111M, and 111C only during color image formation.

[0147] Then, after the primary transfer rollers 133Y, 133M, 133C, and 133Bk are separated from the intermediate transfer body 131, the toner remaining on the surfaces of the photoconductors 111Y, 111M, 111C, and 111Bk is removed by the cleaning blades 119Y, 119M, 119C, and 119Bk. Next, the surfaces of the photoconductors 111Y, 111M, 111C, and 111Bk are neutralized by a neutralizing means (not shown) as necessary, and then negatively charged by the contact-type charging means 113Y, 113M, 113C, and 113Bk.

[0148] Meanwhile, a transfer material P (e.g., a support carrying a final image, such as plain paper or a transparent sheet) contained in a paper feed cassette 211 is fed by a paper feed conveying means 150 and conveyed to a secondary transfer roller (secondary transfer means) 217 ​​via a plurality of intermediate rollers 213A, 213B, 213C, 213D and a registration roller 215. Then, the secondary transfer roller 217 is brought into contact with the rotating intermediate transfer body 131, and a color image is transferred (secondarily transferred) onto the transfer material P in a lump. The secondary transfer roller 217 comes into contact with the intermediate transfer body 131 only when performing the secondary transfer onto the transfer material P. Thereafter, the transfer material P to which the color image has been transferred in a lump is separated at a portion of the intermediate transfer body 131 with a high curvature.

[0149] The transfer material P onto which the color image has been transferred in this manner is fixed by fixing means 170, and then sandwiched by discharge rollers 219 and placed on a discharge tray 221 outside the apparatus. In addition, after the transfer material P onto which the color image has been transferred in a lump is separated from the intermediate transfer body 131, the remaining toner on the intermediate transfer body 131 is removed by cleaning means 135.

[0150] [Toner for developing electrostatic images] The toner for developing electrostatic images used in the image forming method of the present invention includes toner particles having toner base particles and external additives attached to the surfaces of the toner base particles. In particular, the external additives include a lubricant, a positively charged inorganic external additive, and a negatively charged inorganic external additive, and the mass of the positively charged inorganic external additive and the mass of the negatively charged inorganic external additive satisfy the relationship of the following formula (1). Formula (1): 0.28≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive

[0151] In this specification, "toner base particles" are those that constitute the base of "toner particles." "Toner base particles" contain at least a binder resin, and may contain other components such as a colorant, a release agent (wax), and a charge control agent, as necessary. "Toner base particles" are called "toner particles" when an external additive is added. "Toner" refers to an aggregate of "toner particles."

[0152] <Toner base particles> The toner base particles according to the present invention may be any known toner base particles. Specifically, such toner base particles are composed of toner base particles containing at least a binder resin and, if necessary, a colorant. Furthermore, the toner base particles may further contain other components such as a release agent and a charge control agent, if necessary.

[0153] <Binding resin> As the binder resin, known resins can be used, and for example, amorphous resins and crystalline resins can be suitably used. In particular, it is preferable to use a styrene-acrylic resin and a crystalline polyester resin, which will be described later.

[0154] (amorphous resin) The amorphous resin that can be used in the present invention is not particularly limited, but known amorphous resins such as vinyl resins and polyester resins as described below, as well as urethane resins and urea resins can be preferably used.

[0155] <Vinyl resin> When a vinyl resin is used as the amorphous resin, the vinyl resin is not particularly limited as long as it is a polymer of a vinyl compound. For example, an acrylic ester resin, a styrene-acrylate resin, etc. Examples of the resin include acrylic ester resins, ethylene-vinyl acetate resins, etc. These resins may be used alone or in combination of two or more. Among the above vinyl resins, styrene-acrylic ester resins (styrene-acrylic resins) are preferred in consideration of the plasticity during thermal fixing. Therefore, although detailed explanation is omitted, it is preferable to use, as the styrene monomer, styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, and p-ethylstyrene; as the (meth)acrylic acid ester monomer, acrylic acid ester monomers such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, and isobutyl acrylate; and methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isopropyl methacrylate, and isobutyl methacrylate. These styrene monomers and (meth)acrylic acid ester monomers can be used alone or in combination of two or more kinds.

[0156] Other monomers may also be polymerized, and examples thereof include acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl esters, itaconic acid monoalkyl esters, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and polyethylene glycol mono(meth)acrylate. The method for producing the styrene-acrylic resin is not particularly limited, and the resin can be produced by an emulsion polymerization method or the like.

[0157] Polyester resin When a polyester resin is used as the amorphous resin, it refers to a resin that does not show a clear endothermic peak in differential scanning calorimetry (DSC) among known polyester resins obtained by polycondensation reaction of a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyalcohol). Specifically, a clear endothermic peak means a peak whose half-width of the endothermic peak is within 15°C when measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC).

[0158] Examples of polycarboxylic acids include aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, and 1,18-octadecanedicarboxylic acid; aromatic dicarboxylic acids such as maleic acid, isophthalic acid, terephthalic acid, and naphthalenedicarboxylic acid; aliphatic unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, citraconic acid, glutaconic acid, isododecenylsuccinic acid, n-dodecenylsuccinic acid, and n-octenylsuccinic acid; and divalent or higher carboxylic acids such as trimellitic acid, pyromellitic acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

[0159] Examples of polyhydric alcohols include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, 1,20 -Aliphatic diols such as eicosanediol; bisphenols such as bisphenol A and bisphenol F, and alkylene oxide adducts of bisphenols such as ethylene oxide adducts and propylene oxide adducts of these bisphenols; and trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

[0160] (Crystalline Resin) The toner base particles according to the present invention may contain a crystalline resin, and for example, in addition to the following crystalline polyesters, the crystalline resins described in paragraphs 0043 to 0102 of JP-A-2015-011325 can be suitably used. In particular, it is preferable from the viewpoint of production that the toner base particles contain a hybrid crystalline polyester resin.

[0161] <Crystalline polyester resin> The crystalline polyester resin is a portion derived from a known polyester resin obtained by a polycondensation reaction between a divalent or higher carboxylic acid (polycarboxylic acid) and a divalent or higher alcohol (polyalcohol), and refers to a resin unit that has a clear endothermic peak, not a stepwise endothermic change, in differential scanning calorimetry (DSC) of the toner. Specifically, the clear endothermic peak means a peak whose half-width is within 15°C when measured at a heating rate of 10°C / min in differential scanning calorimetry (DSC) described in the examples.

[0162] The crystalline polyester resin is not particularly limited as long as it is as defined above. For example, the crystalline polyester resin itself may be contained. Alternatively, as a hybrid resin having a crystalline polyester resin unit, a resin having a structure in which other components are copolymerized in a main chain of a crystalline polyester resin unit, or a resin having a structure in which a crystalline polyester resin unit is copolymerized in a main chain made of other components, in which a toner containing this resin shows a clear endothermic peak as described above, may be contained.

[0163] The crystalline polyester resin is produced from a polybasic carboxylic acid component and a polyhydric alcohol component. In this case, the crystalline polyester resin unit is composed of the polybasic carboxylic acid component with a carbon number C (acid) and the polyhydric alcohol component with a carbon number C (alcohol), and the valences of the polybasic carboxylic acid component and the polyhydric alcohol component are each preferably 2 to 3, and particularly preferably 2, so that a particularly preferred embodiment in which the valences are each 2 (i.e., dicarboxylic acid component, diol component) will be described.

[0164] As the dicarboxylic acid component, it is preferable to use an aliphatic dicarboxylic acid, and an aromatic dicarboxylic acid may be used in combination. As the aliphatic dicarboxylic acid, it is preferable to use a straight-chain type. By using a straight-chain type, there is an advantage that crystallinity is improved. The dicarboxylic acid component is not limited to one type, and two or more types may be mixed and used.

[0165] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid, 1,12-dodecanedicarboxylic acid (dodecanedioic acid), 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, and cyclohexanedicarboxylic acid. Lower alkyl esters and acid anhydrides of these acids can also be used.

[0166] Examples of aromatic dicarboxylic acids that can be used together with aliphatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, t-butylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, etc. Among these, it is preferable to use terephthalic acid, isophthalic acid, and t-butylisophthalic acid from the viewpoints of availability and ease of emulsification.

[0167] In the dicarboxylic acid component for forming the crystalline polyester resin, the content of the aliphatic dicarboxylic acid is preferably 50 constituent mol% or more, more preferably 70 constituent mol% or more, even more preferably 80 constituent mol% or more, and particularly preferably 100 constituent mol%. By making the content of the aliphatic dicarboxylic acid in the dicarboxylic acid component 50 constituent mol% or more, the crystallinity of the crystalline polyester resin unit can be sufficiently ensured.

[0168] In addition, as the diol component, it is preferable to use an aliphatic diol, and if necessary, a diol other than an aliphatic diol may be contained. As the aliphatic diol, it is preferable to use a straight-chain type. By using a straight-chain type, there is an advantage that crystallinity is improved. The diol component may be used alone or in combination of two or more types.

[0169] Examples of the aliphatic diol include ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1,10-dodecanediol, 1,11-undecanediol, 1,12-dodecanediol, 1,13-tridecanediol, 1,14-tetradecanediol, 1,18-octadecanediol, and 1,20-eicosanediol.

[0170] Examples of the diol other than the aliphatic diol that is used as necessary include a diol having a double bond and a diol having a sulfonic acid group. Specific examples of the diol having a double bond include 2-butene-1,4-diol, 3-butene-1,6-diol, and 4-butene-1,8-diol.

[0171] The diol component for forming the crystalline polyester resin unit preferably contains an aliphatic diol at 50 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and particularly preferably 100 mol %. By containing an aliphatic diol at 50 mol % or more in the diol component, the crystallinity of the crystalline polyester resin unit can be ensured, and the toner produced can have excellent low-temperature fixability, and the finally formed image can have gloss.

[0172] The method for forming the crystalline polyester resin is not particularly limited, and the resin can be formed by polycondensing (esterifying) the above-mentioned polyvalent carboxylic acid and polyhydric alcohol using a known esterification catalyst.

[0173] The use ratio of the polyhydric alcohol component and the polyvalent carboxylic acid component is preferably such that the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the diol component to the carboxy group [COOH] of the dicarboxylic acid component is 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 1 / 1.2.

[0174] Examples of catalysts that can be used in the production of crystalline polyester resins include alkali metal compounds such as sodium and lithium; alkaline earth metal compounds such as magnesium and calcium; metal compounds such as aluminum, zinc, manganese, antimony, titanium, tin, zirconium, and germanium; phosphorous compounds; phosphoric acid compounds; and amine compounds. Specifically, examples of tin compounds include dibutyltin oxide, tin octoate, tin dioctoate, and salts thereof. Examples of titanium compounds include titanium alkoxides such as tetra-normal-butyl titanate, tetraisopropyl titanate, tetramethyl titanate, and tetrastearyl titanate; titanium acylates such as polyhydroxytitanium stearate; and titanium chelates such as titanium tetraacetylacetonate, titanium lactate, and titanium triethanolamine. Examples of germanium compounds include germanium dioxide. Examples of aluminum compounds include oxides such as polyaluminum hydroxide, aluminum alkoxides, and tributylaluminate. These may be used alone or in combination of two or more.

[0175] The polymerization temperature and polymerization time are not particularly limited, and the pressure in the reaction system may be reduced during the polymerization, if necessary.

[0176] Furthermore, in the case of a hybrid resin having a crystalline polyester resin unit, the content of the crystalline polyester resin unit is preferably 50% by mass or more and less than 98% by mass based on the total amount of the hybrid resin. By setting the content in the above range, sufficient crystallinity can be imparted to the hybrid resin. The components and content ratios of each unit in the hybrid resin can be determined, for example, by NMR measurement or methylation reaction P-GC / MS measurement.

[0177] Here, the hybrid resin contains, in addition to the crystalline polyester resin unit, an amorphous resin unit other than the polyester resin described below. The hybrid resin may be in any form, such as a block copolymer or a graft copolymer, as long as it contains the crystalline polyester resin unit and an amorphous resin unit other than the polyester resin, but is preferably a graft copolymer. By using a graft copolymer, it becomes easier to control the orientation of the crystalline polyester resin unit, and sufficient crystallinity can be imparted to the hybrid resin.

[0178] From the above viewpoint, it is preferable that the crystalline polyester resin unit is grafted to an amorphous resin unit other than the crystalline polyester resin as the main chain, i.e., the hybrid crystalline polyester resin is preferably a graft copolymer having an amorphous resin unit other than the polyester resin as the main chain and a crystalline polyester resin unit as a side chain.

[0179] By adopting the above-mentioned embodiment, the orientation of the crystalline polyester resin units can be further enhanced, and the crystallinity of the hybrid resin can be improved.

[0180] The hybrid resin may further have a substituent such as a sulfonic acid group, a carboxy group, a urethane group, etc. The substituent may be introduced into a crystalline polyester resin unit or into an amorphous resin unit other than the polyester resin described below.

[0181] <<Amorphous resin unit other than polyester resin>> The amorphous resin unit other than the polyester resin is a portion derived from an amorphous resin other than the crystalline polyester resin. The amorphous resin unit contained in the hybrid resin (and further in the toner) can be characterized in terms of its chemical structure by selecting an appropriate analytical method from NMR measurement, P-GC / MS measurement, methylation reaction P-GC / MS measurement, etc., depending on the structure.

[0182] In addition, the amorphous resin unit is a resin having the same chemical structure and molecular weight as the unit. When differential scanning calorimetry (DSC) was performed on the resin unit, it was found that the resin unit had no melting point and a relatively high first glass transition point (Tg).

[0183] The amorphous resin unit is not particularly limited as long as it is as defined above. For example, with respect to a resin having a structure in which other components are copolymerized in a main chain of an amorphous resin unit, or a resin having a structure in which an amorphous resin unit is copolymerized in a main chain made of other components, if a toner containing this resin has the above-mentioned amorphous resin unit, the resin corresponds to a hybrid resin having an amorphous resin unit.

[0184] The amorphous resin unit is preferably composed of the same type of resin as the amorphous resin contained in the binder resin (i.e., a resin other than the hybrid resin). By adopting such a form, the affinity between the hybrid resin and the amorphous resin is further improved, the hybrid resin is further easily incorporated into the amorphous resin, and the charging uniformity and the like are further improved.

[0185] Here, "same type of resin" means that the repeating units have characteristic chemical bonds in common. In addition, "characteristic chemical bonds" are in accordance with the "polymer classification" described in the National Institute for Materials Science (NIMS) Materials Database (http: / / polymer.nims.go.jp / PoLyInfo / guide / jp / term_polymer.html). In other words, the chemical bonds that make up polymers classified into a total of 22 types, including polyacrylic, polyamide, polyanhydride, polycarbonate, polydiene, polyester, polyhaloolefin, polyimide, polyimine, polyketone, polyolefin, polyether, polyphenylene, polyphosphazene, polysiloxane, polystyrene, polysulfide, polysulfone, polyurethane, polyurea, polyvinyl, and other polymers, are called "characteristic chemical bonds."

[0186] In addition, when the resin is a copolymer, "same type of resin" refers to resins that have a common characteristic chemical bond when the monomer species having the above-mentioned chemical bond is used as a constituent unit in the chemical structure of the multiple monomer species that constitute the copolymer. Therefore, even if the properties exhibited by the resins themselves are different from each other or the molar component ratios of the monomer species that constitute the copolymer are different from each other, they are considered to be the same type of resins as long as they have a common characteristic chemical bond.

[0187] For example, a resin (or resin unit) formed by styrene, butyl acrylate, and acrylic acid and a resin (or resin unit) formed by styrene, butyl acrylate, and methacrylic acid have at least a chemical bond that constitutes polyacrylic, so they are the same type of resin. For further example, a resin (or resin unit) formed by styrene, butyl acrylate, and acrylic acid and a resin (or resin unit) formed by styrene, butyl acrylate, acrylic acid, terephthalic acid, and fumaric acid have at least a chemical bond that constitutes polyacrylic as a common chemical bond. Therefore, they are the same type of resin.

[0188] The resin component constituting the amorphous resin unit is not particularly limited, and examples thereof include a vinyl resin unit, a urethane resin unit, a urea resin unit, etc. Among these, a vinyl resin unit is preferred because the thermoplasticity can be easily controlled. The vinyl resin unit is not particularly limited as long as it is a polymer of a vinyl compound, and examples thereof include an acrylic ester resin unit, a styrene-acrylic ester resin unit, an ethylene-vinyl acetate resin unit, etc. These may be used alone or in combination of two or more.

[0189] The method for forming the styrene-acrylic resin unit is not particularly limited, and examples thereof include a method of polymerizing monomers using a known oil-soluble or water-soluble polymerization initiator. Specific examples of such polymerization initiators include the azo-based or diazo-based polymerization initiators and peroxide-based polymerization initiators shown below.

[0190] Examples of the azo or diazo polymerization initiator include 2,2'-azobis-(2,4-dimethylvaleronitrile), 2,2'-azobisisobutyronitrile, 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, and azobisisobutyronitrile.

[0191] Examples of the peroxide polymerization initiator include benzoyl peroxide, methyl ethyl ketone peroxide, diisopropyl peroxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis-(4,4-t-butylperoxycyclohexyl)propane, and tris-(t-butylperoxy)triazine.

[0192] When resin particles are formed by emulsion polymerization, a water-soluble radical polymerization initiator can be used, such as persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, and hydrogen peroxide.

[0193] The content of the amorphous resin unit is preferably 3% by mass or more and 50% by mass or less based on the total amount of the hybrid resin.More preferably, the content is 5% by mass or more and 30% by mass or less.By setting the content in the above range, sufficient crystallinity can be imparted to the hybrid resin.

[0194] <Production method of hybrid crystalline polyester resin (hybrid resin)> The method for producing the hybrid resin contained in the binder resin according to the present invention is not particularly limited as long as it is a method capable of forming a polymer having a structure in which the crystalline polyester resin unit and the amorphous resin unit are molecularly bonded to each other. Specific examples of the method for producing the hybrid resin include the following methods.

[0195] (1) A method for producing a hybrid resin by polymerizing an amorphous resin unit in advance and then carrying out a polymerization reaction to form a crystalline polyester resin unit in the presence of the amorphous resin unit. In this method, first, the monomers constituting the above-mentioned amorphous resin unit (preferably a vinyl monomer such as a styrene monomer and a (meth)acrylic acid ester monomer) are subjected to an addition reaction to form the amorphous resin unit. Next, in the presence of the amorphous resin unit, a polycarboxylic acid and a polyhydric alcohol are polymerized to form a crystalline polyester resin unit. At this time, the polycarboxylic acid and the polyhydric alcohol are condensed, and the amorphous resin unit is subjected to an addition reaction of the polycarboxylic acid or the polyhydric alcohol to form a hybrid resin.

[0196] In the above method, it is preferable to incorporate a site in the crystalline polyester resin unit or the amorphous resin unit where these units can react with each other. Specifically, when forming the amorphous resin unit, in addition to the monomer constituting the amorphous resin unit, a compound having a site capable of reacting with a carboxy group [-COOH] or a hydroxy group [-OH] remaining in the crystalline polyester resin unit and a site capable of reacting with the amorphous resin unit is also used. That is, this compound reacts with the carboxy group [-COOH] or the hydroxy group [-OH] in the crystalline polyester resin unit to form the crystalline polyester resin unit. The carboxylate can be chemically bonded to the amorphous resin unit. Alternatively, a compound may be used which is capable of reacting with a polyhydric alcohol or a polyvalent carboxylic acid when the crystalline polyester resin unit is formed, and which has a site capable of reacting with the amorphous resin unit. By using the above method, a hybrid resin having a structure (graft structure) in which a crystalline polyester resin unit is molecularly bonded to an amorphous resin unit can be formed.

[0197] (2) A method in which a crystalline polyester resin unit and an amorphous resin unit are formed separately and then bonded to produce a hybrid resin. In this method, first, a crystalline polyester resin unit is formed by condensation reaction of a polyvalent carboxylic acid and a polyhydric alcohol. In addition, a monomer constituting the above-mentioned amorphous resin unit is addition polymerized to form an amorphous resin unit, separately from the reaction system for forming the crystalline polyester resin unit. At this time, it is preferable to incorporate a site where the crystalline polyester resin unit and the amorphous resin unit can react with each other. The method for incorporating such a reactive site is as described above, and therefore a detailed description thereof will be omitted. Next, the crystalline polyester unit formed above is reacted with an amorphous resin unit to form a hybrid resin having a structure in which the crystalline polyester resin unit and the amorphous resin unit are molecularly bonded. In addition, when the reactive site is not incorporated in the crystalline polyester resin unit and the amorphous resin unit, a method may be adopted in which a system in which the crystalline polyester resin unit and the amorphous resin unit coexist is formed, and a compound having a site capable of bonding with the crystalline polyester resin unit and the amorphous resin unit is added thereto, and a hybrid resin having a structure in which the crystalline polyester resin unit and the amorphous resin unit are molecularly bonded via the compound can be formed.

[0198] (3) A method of producing a hybrid resin by forming a crystalline polyester resin unit in advance and then carrying out a polymerization reaction to form an amorphous resin unit in the presence of the crystalline polyester resin unit. In this method, first, a polyvalent carboxylic acid and a polyhydric alcohol are polymerized by condensation reaction to form a crystalline polyester resin unit, and then, in the presence of the crystalline polyester resin unit, a monomer constituting the amorphous resin unit is polymerized to form the amorphous resin unit. In this case, similarly to the above (1), it is preferable to incorporate a site in the crystalline polyester resin unit or the amorphous resin unit that allows these units to react with each other. Note that the method for incorporating such a reactive site is as described above, and therefore a detailed description thereof will be omitted.

[0199] By using the above method, a hybrid resin having a structure (graft structure) in which an amorphous resin unit is molecularly bonded to a crystalline polyester resin unit can be formed. Among the above forming methods (1) to (3), method (1) is preferred because it is easy to form a hybrid resin having a structure in which a crystalline polyester resin chain is grafted to an amorphous resin chain and because it can simplify the production process. Method (1) is preferred because it is easy to form a uniform orientation of the crystalline polyester resin unit since the amorphous resin unit is formed in advance and then the crystalline polyester resin unit is bonded to the amorphous resin unit. Therefore, it is preferred because it is possible to reliably form a hybrid resin suitable for the toner defined in the present invention.

[0200] <Coloring agent> As colorants that can constitute the toner base particles, carbon black, magnetic materials, dyes, pigments, etc. can be arbitrarily used, and as carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, etc. can be used. As magnetic materials, ferromagnetic metals such as iron, nickel, cobalt, etc., alloys containing these metals, compounds of ferromagnetic metals such as ferrite, magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism when heat treated, for example, alloys of the type called Heusler alloys such as manganese-copper-aluminum and manganese-copper-tin, chromium dioxide, etc. can be used.

[0201] Examples of colorants for magenta or red include CI Pigment Red 2, 3, 5, 6, 7, 15, 16, 48:1, 48:3, 53:1, 57:1, 60, 63, 64, 68, 81, 81:4, 83, 87, 88, 89, 90, 112, 114, 122, 123, 139, 144, 149, 150, 163, 166, 170, 177, 178, 184, 202, 206, 207, 209, 222, 238, and 269.

[0202] Examples of colorants for orange or yellow include CI Pigment Orange 31, CI Pigment Yellow 43, CI Pigment Yellow 12, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 138, CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 83, CI Pigment Yellow 93, CI Pigment Yellow 138, CI Pigment Orange 39, CI Pigment Orange 155, CI Pigment Orange 162, CI Pigment Yellow 180,

[0203] Furthermore, examples of colorants for green or cyan include CI Pigment Blue 2, 3, 15, 15:2, 15:3, 15:4, 16, 17, 60, 62, 66, CI Pigment Green 7, and the like.

[0204] These colorants can be used alone or in combination of two or more, as required. The amount of the colorant added is preferably in the range of 1 to 30% by mass, more preferably 2 to 20% by mass, based on the total amount of the toner base particles, and a mixture thereof can also be used. When the amount is in this range, the color reproducibility of the image can be ensured. The colorant dispersion diameter in the toner is preferably from 10 to 1000 nm, more preferably from 50 to 500 nm, and even more preferably from 80 to 300 nm, in terms of volume average particle diameter.

[0205] <Release agent> The releasing agent constituting the toner base particles is not particularly limited, and known ones can be used.Specific examples thereof include polyolefin waxes such as polyethylene wax and polypropylene wax, branched chain hydrocarbon waxes such as microcrystalline wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, behenic acid behenate, trimethylolpropane tribehenate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellitic acid tristearyl, distearyl maleate, and other ester waxes, and amide waxes such as ethylenediamine behenylamide and trimellitic acid tristearylamide.

[0206] The melting point of the release agent is preferably 40 to 160° C., more preferably 50 to 120° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and even when fixing is performed at a low temperature, stable toner image formation can be performed without causing cold offset or the like. The content of the release agent in the toner base particles is preferably 1 to 30% by mass, more preferably 5 to 20% by mass.

[0207] <Charge control agent> If necessary, a charge control agent can be added to the toner base particles according to the present invention. As the charge control agent, various known ones can be used.

[0208] As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specific examples of the charge control agent include nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, quaternary ammonium salt compounds, azo metal complexes, metal salicylate salts or metal complexes thereof, and the like.

[0209] The content of the charge control agent is preferably within a range of 0.1 to 10% by mass, more preferably within a range of 0.5 to 5% by mass, based on the total amount of the binder resin.

[0210] <External additives> From the viewpoint of improving the charging performance, fluidity or cleaning property of the toner, a lubricant, a positively chargeable inorganic external additive and a negatively chargeable inorganic external additive are added as external additives to the surface of the toner base particles. The mass of the positively chargeable inorganic external additive and the mass of the negatively chargeable inorganic external additive satisfy the relationship of formula (1) above.

[0211] Examples of the positively charged inorganic external additive include those listed in Table I, and preferred examples include inorganic fine particles such as calcium titanate particles, strontium titanate particles, or silica particles surface-modified with cyclic silazane and alkylalkoxysilane. The silica particles surface-modified with the cyclic silazane and alkylalkoxysilane preferably have a number average primary particle size within the range of 50 to 150 nm. The number average primary particle size is measured in the same manner as the number average primary particle size of the inorganic fine particles contained in the protective layer of the photoreceptor.

[0212] As the cyclic silazane, a compound represented by the following general formula (1) is preferably used.

[0213] [ka]

[0214] In the formula, R1 and R2 each independently represent a hydrogen atom, a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom, etc.), an alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a octyl group, etc.), an alkoxy group (e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), or an allyloxy group (e.g., a phenyloxy group, a naphthyloxy group, etc.).

[0215] R3 represents a hydrogen atom, -(CH2)nCH3 (wherein n represents an integer from 0 to 3), -C(O)(CH2)nCH3 (wherein n represents an integer from 0 to 3), a carbamoyl group, an alkyl-substituted carbamoyl group (e.g., ethylcarbamoyl, propylcarbamoyl, etc.), or -C(O)N((CH2)nCH3)(CH2)mCH3 (wherein n and m each represent an integer from 0 to 3).

[0216] R4 is ((CH2) a (CHX) b (CYZ) c ) (wherein X, Y and Z each represent a hydrogen atom, a halogen atom (e.g., a chlorine atom, a bromine atom, a fluorine atom, an iodine atom, etc.), an alkyl group (e.g., a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, an octyl group, etc.), an alkoxyl group (e.g., a methoxy group, an ethoxy group, a propoxy group, a butoxy group, etc.), an aryl group (e.g., a phenyl group, a naphthyl group, etc.), an allyloxy group (e.g., a phenyloxy group, a naphthyloxy group, etc.). a, b and c each represent an integer of 0 to 6, with the proviso that a+b+c represents an integer of 2 to 6.

[0217] Among the compounds represented by the above general formula (1), the compound C-1 represented by the following structural formula is most preferably used.

[0218] [ka]

[0219] Examples of the alkylalkoxysilane include propyltrimethoxysilane, hexyltriethoxysilane, and hexyltrimethoxysilane, and among these, propyltrimethoxysilane is preferably used.

[0220] The method for surface-modifying the silica particles with the cyclic silazane and alkylalkoxysilane can be either a wet treatment method or a dry treatment method, similar to the method for surface-modifying the inorganic fine particles contained in the protective layer of the photoreceptor.

[0221] Examples of the negatively charged inorganic external additive include those listed in Table I, and preferred examples include inorganic fine particles such as silica particles, titania particles, and alumina particles, with silica particles being particularly preferred. In addition, it is preferable that the negatively charged inorganic external additive contains large particles having a number average particle size within the range of 80 to 500 nm and small particles having a number average particle size within the range of 10 to 50 nm in combination.

[0222] If necessary, these inorganic fine particles may be subjected to a hydrophobic treatment. In addition, organic fine particles may be further added, and as the organic fine particles, spherical organic fine particles having a number average primary particle size of about 10 to 2000 nm can be used. Specifically, organic fine particles made of homopolymers such as styrene and methyl methacrylate, or copolymers thereof can be used.

[0223] The lubricant further improves the cleaning property and transfer property, and examples of the lubricant include metal salts of higher fatty acids such as salts of stearic acid with zinc, aluminum, copper, magnesium, calcium, etc., salts of oleic acid with zinc, manganese, iron, copper, magnesium, etc., salts of palmitic acid with zinc, copper, magnesium, etc., salts of linoleic acid with zinc, calcium, etc., salts of ricinoleic acid with zinc, calcium, etc. Various types of these external additives may be used in combination. Moreover, it is preferable that the average particle size of the lubricant used in the present invention is within the range of 1 to 5 μm, in order to reliably prevent the occurrence of raindrops. The amount of the external additive added is preferably 0.1 to 10.0% by mass relative to 100% by mass of the toner base particles.

[0224] [Toner manufacturing method] The method for producing the toner used in the present invention is not particularly limited, and includes known methods such as a kneading and pulverizing method, a suspension polymerization method, an emulsion aggregation method, a dissolution suspension method, a polyester elongation method, a dispersion polymerization method, etc. The method for producing the toner preferably includes the following external additive treatment step.

[0225] (External additive processing process) This process is a process in which an external additive is added to the surface of the toner base particles as necessary and mixed to prepare a toner. Methods for adding an external additive include methods using various known mixing devices such as a Turbula mixer, a Henschel mixer, a Nauta mixer, and a V-type mixer. The addition of an external additive improves the fluidity and chargeability of the toner, and also improves cleaning properties.

[0226] [Manufacturing of developer] The above-mentioned toner may be used, for example, in a two-component developer by mixing with a so-called carrier, or in a non-magnetic toner alone, and either of these may be suitably used. The carrier constituting the two-component developer is not particularly limited, but examples thereof include the following. As the magnetic substance, magnetic particles made of conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used, and it is particularly preferable to use ferrite particles. The resin composition for coating the carrier surface is not particularly limited, but may be, for example, an olefin resin, a cyclohexyl methacrylate-methyl methacrylate copolymer, a styrene resin, a styrene-acrylic resin, a silicone resin, an ester resin, or a fluororesin. The resin for constituting the resin dispersion-type carrier is not particularly limited, and may be any known resin, such as an acrylic resin, a styrene-acrylic resin, a polyester resin, a fluororesin, or a phenolic resin. It is also possible to use a so-called resin dispersion type carrier in which the above magnetic particles are dispersed in a resin, and this resin dispersion type carrier can be provided with a coating layer. The volume average particle size of the carrier is preferably within a range of 15 to 100 μm, and more preferably within a range of 20 to 60 μm. EXAMPLES

[0227] The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. In the following examples, unless otherwise specified, the operations were performed at room temperature (25°C). Furthermore, unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0228] [Preparation of photoreceptor] <Preparation of surface-modified metal oxide particles P1> 5 g of silicon dioxide (SiO2, number average primary particle size 100 nm), which is unmodified metal oxide particles (unmodified inorganic fine particles), was added to 10 mL of methanol and dispersed at room temperature for 30 minutes using a US homogenizer. 5 g of the conductive metal oxide particles obtained above was added to 40 g of 2-butanol, and dispersed at room temperature for 60 minutes using a US homogenizer. Next, 0.15 g of a surface modifier having a silicone chain on the side chain of the silicone main chain (KF-9908: manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and dispersion was further performed at room temperature for 60 minutes using a US homogenizer. After dispersion, the solvent was evaporated at room temperature, and the mixture was dried at 120°C for 60 minutes to produce surface-modified metal oxide particles P1 that were surface-modified with a reactive surface modifier and a surface modifier having a silicone chain on the main chain and side chain.

[0229] <Preparation of surface-modified metal oxide particles P2> α-alumina, an unmodified metal oxide particle (number average primary particle size 300 nm, specific resistance 10 10 Ω·cm or more, pH 8-9, 5 g of Sumicorundum AA-03 (Sumitomo Chemical Co., Ltd.) was added and dispersed at room temperature for 30 minutes using a US homogenizer. 5 g of the conductive metal oxide particles obtained above was added to 40 g of 2-butanol, and dispersed at room temperature for 60 minutes using a US homogenizer. Next, 0.15 g of a surface modifier having a silicone chain on the side chain of the silicone main chain (KF-9908: manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and dispersion was further performed at room temperature for 60 minutes using a US homogenizer. After dispersion, the solvent was evaporated at room temperature, and the mixture was dried at 120°C for 60 minutes to produce surface-modified metal oxide particles P2 that were surface-modified with a reactive surface modifier and a surface modifier having a silicone chain on the main chain and side chain.

[0230] <Preparation of surface-modified metal oxide particles P3> 5 g of unmodified metal oxide particles, titanium oxide (TiO2, number average primary particle size 100 nm), was added to 10 mL of methanol and dispersed at room temperature for 30 minutes using a US homogenizer. 5 g of the conductive metal oxide particles obtained above was added to 40 g of 2-butanol, and dispersed at room temperature for 60 minutes using a US homogenizer. Next, 0.15 g of a surface modifier having a silicone chain on the side chain of the silicone main chain (KF-9908: manufactured by Shin-Etsu Chemical Co., Ltd.) was added, and dispersion was further performed at room temperature for 60 minutes using a US homogenizer. After dispersion, the solvent was evaporated at room temperature, and the mixture was dried at 120°C for 60 minutes to produce surface-modified metal oxide particles P3 that were surface-modified with a reactive surface modifier and a surface modifier having a silicone chain on the main chain and side chain.

[0231] <Preparation of metal oxide particles P4> As the metal oxide fine particles P4, unmodified metal oxide particles of tin oxide (number average primary particle size=20 nm) were used.

[0232] [Preparation of photoreceptor] <Preparation of photoreceptor 1> (Preparation of conductive support) The surface of a cylindrical aluminum support was machined to prepare a conductive support.

[0233] (Formation of the intermediate layer) The following components were mixed in the amounts shown below, and dispersed in a batch manner for 10 hours using a sand mill as a dispersing machine to prepare a coating solution for forming an intermediate layer. The coating solution was applied to the surface of a conductive support by dip coating, and dried at 110°C for 20 minutes to form an intermediate layer with a thickness of 2 μm on the conductive support. X1010 (manufactured by Daicel-Evonik Corporation) was used as the polyamide resin, and SMT-500SAS (manufactured by Teika Corporation, number average primary particle size: 0.035 μm) was used as the titanium oxide particles. Polyamide resin 10 parts by weight Titanium oxide particles: 11 parts by weight Ethanol 200 parts by weight

[0234] (Formation of Charge Generation Layer) The following components were mixed in the amounts shown below and dispersed for 0.5 hours at a circulation flow rate of 40 L / hour at 19.5 kHz and 600 W using a circulating ultrasonic homogenizer (RUS-600TCVP, manufactured by Nippon Seiki Co., Ltd.) to prepare a coating liquid for forming a charge generating layer. The resulting coating liquid was applied to the surface of the intermediate layer by a dip coating method and air-dried to form a charge generating layer with a thickness of 0.3 μm on the intermediate layer. The charge generating material used was titanyl phthalocyanine, which has clear peaks at 8.3°, 24.7°, 25.1°, and 26.5° in Cu-Kα characteristic X-ray diffraction spectrum measurement, and a mixed crystal of a 1:1 adduct of (2R,3R)-2,3-butanediol and unadducted titanyl phthalocyanine. In addition, S-LEC (registered trademark) BL-1 (manufactured by Sekisui Chemical Co., Ltd.) was used as the polyvinyl butyral resin. In addition, 3-methyl-2-butanone / cyclohexanone = 4 / 1 (volume ratio) was used as the mixed solvent. Charge generating material 24 parts by weight Polyvinyl butyral resin 12 parts by weight Mixed solvent 400 parts by weight

[0235] (Formation of charge transport layer) A coating solution for the charge transport layer, prepared by mixing the following components in the following amounts, was applied to the surface of the charge generation layer by dip coating and dried at 120°C for 70 minutes to form a charge transport layer with a thickness of 24 μm on the charge generation layer. Charge transport material (CTM-A below: 4,4'-dimethyl-4"-(α-phenylstyryl)triphenylamine) 60 parts by weight Polycarbonate resin (Iupilon (registered trademark) Z300 (manufactured by Mitsubishi Gas Chemical Company, Inc., bisphenol Z-type polycarbonate)) 100 parts by mass Antioxidant (IRGANOX® 1010 (BASF Japan Ltd.) 4 parts by mass

[0236] [ka]

[0237] (Formation of protective layer) The following components were mixed in the amounts shown below to prepare a coating solution for the protective layer, which was dispersed in the coating solution. The coating solution was applied to the surface of the charge transport layer by dip coating, and dried at 120°C for 70 minutes to form a protective layer with a thickness of 24 μm on the charge transport layer, thereby preparing photoreceptor 1. Surface-modified metal oxide particles P1 (silica particles surface-modified with KF-9908) 60 parts by mass Charge transport material (CTM-A) 150 parts by mass Polycarbonate (Z300: manufactured by Mitsubishi Gas Chemical Co., Ltd.) 300 parts by weight Antioxidant (Irganox 1010: manufactured by Ciba-Geigy Japan) 12 parts by weight THF (tetrahydrofuran) (boiling point 66°C) 2800 parts by mass Silicone oil (KF-54: Shin-Etsu Chemical Co., Ltd.) 4 parts by weight Acidic dispersant (BYK-P105: manufactured by BYK Chemie) 1 part by mass

[0238] <Preparation of Photoreceptors 2 and 3> Photoreceptors 2 and 3 were prepared in the same manner as in the preparation of photoreceptor 1, except that the acidic dispersant (BYK-P105) was not added to the coating solution for the protective layer, and the metal oxide particles P2 or P3 were used instead of the metal oxide particles P1.

[0239] <Preparation of Photoreceptor 4> Photoreceptor 4 was prepared in the same manner as in preparation of photoreceptor 1, except that the formation of the protective layer was changed as follows. (Formation of protective layer) 85 parts by mass of the metal oxide fine particles P4, 100 parts by mass of the following compound M2 as a polyfunctional radical polymerizable compound, 400 parts by mass of 2-butanol and 40 parts by mass of THF as a solvent were mixed under light shielding and dispersed for 5 hours using a sand mill as a dispersing machine. Then, 10 parts by mass of a compound represented by the following chemical structural formula (P) was added as a polymerization initiator and dissolved by stirring under light shielding to prepare a coating solution for a protective layer. The protective layer coating solution was applied onto the charge transport layer using a circular slide hopper coating device to form a coating film. The coating film was irradiated with ultraviolet light for 20 seconds using a metal halide lamp. This formed a protective layer with a thickness of 3.0 μm after drying, and photoreceptor 4 was produced.

[0240] [ka]

[0241] <Preparation of Photoreceptor 5> Photoreceptor 5 was prepared in the same manner as in preparation of photoreceptor 1, except that the surface-modified metal oxide particles P1 and the acidic dispersant (BYK-P105) were not added to the coating solution for the protective layer.

[0242] <Preparation of Photoreceptor 6> Photoreceptor 6 was prepared in the same manner as in the preparation of photoreceptor 4, except that the ultraviolet ray irradiation time was changed to 40 seconds.

[0243] The elastic deformation rate of the resulting photoreceptor was calculated by the following method and is shown in the following table. The elastic deformation rate was calculated by the following formula (I). Formula (I): Elastic deformation rate (%) = We / Wtot In the above formula (I), "We" represents elastic energy, and "Wtot" represents the sum of elastic energy and plastic energy. Incidentally, "We" and "Wtot" are measured using a microhardness tester "H100V" (manufactured by Fscher) according to the following measurement conditions. (Measurement conditions) Indenter used: Vickers square pyramid diamond indenter with facing angle of 136° Loading conditions: Vickers indenter is pressed into the surface of the organic photoconductor at a speed of 6mN / sec. Loading time: 5sec (maximum load 30mN) ·Holding time: 5sec Unloading conditions: Unload at the same speed as the load

[0244] [Toner manufacturing] <Synthesis of hybrid crystalline polyester resin (c1)> The raw material monomers for the following addition polymerization resin (styrene-acrylic resin: StAc) unit, including a bireactive monomer, and a radical polymerization initiator were placed in a dropping funnel. Styrene 34 parts by weight n-Butyl acrylate 12 parts by weight Acrylic acid 2 parts by mass Polymerization initiator (di-t-butyl peroxide) 7 parts by mass In addition, the raw material monomers of the polycondensation resin (crystalline polyester resin: CPEs) unit described below were placed in a four-neck flask equipped with a nitrogen inlet tube, a dehydration tube, a stirrer and a thermocouple, and were heated to 170° C. to dissolve them. Sebacic acid 369 parts by mass 1,10-Decanediol 318 parts by mass Next, the raw material monomer of the addition polymerization resin (StAc) was dropped over 90 minutes while stirring, and after aging for 60 minutes, the unreacted addition polymerization monomer was removed under reduced pressure (8 kPa). Note that the amount of the monomer removed at this time was very small compared to the raw material monomer ratio of the above resin. Thereafter, 0.8 parts by mass of Ti(OBu)4 was added as an esterification catalyst, the temperature was raised to 235°C, and the reaction was carried out at normal pressure (101.3 kPa) for 5 hours and further at reduced pressure (8 kPa) for 1 hour. Next, after cooling to 200°C, the mixture was reacted under reduced pressure (20kPa) for 1 hour to obtain a hybrid crystalline polyester resin (c1). The hybrid crystalline polyester resin (c1) contained 8% by mass of resin (StAc) units other than CPEs (crystalline polyester resin) relative to the total amount, and was a resin in which CPEs were grafted to StAc. The number average molecular weight (Mn) of the hybrid crystalline polyester resin (c1) was 9000 and the melting point (Tc) was 76°C.

[0245] <Preparation of Aqueous Dispersion of Hybrid Crystalline Polyester Resin Particles (C1)> 30 parts by mass of the crystalline polyester resin (c1) was melted and transferred in the molten state to an emulsifying and dispersing machine "Cavitron CD1010" (manufactured by Eurotech Co., Ltd.) at a transfer rate of 100 parts by mass per minute. Simultaneously with the transfer of the crystalline polyester resin in the molten state, dilute ammonia water with a concentration of 0.37% by mass, which was obtained by diluting 70 parts by mass of reagent ammonia water with ion-exchanged water in an aqueous solvent tank, was transferred to the emulsifying and dispersing machine "Cavitron CD1010" (manufactured by Eurotech Co., Ltd.) at a transfer rate of 0.1 liters per minute while being heated to 100°C by a heat exchanger. Then, this emulsifying and dispersing machine "Cavitron CD1010" (manufactured by Eurotech Co., Ltd.) was rotated at a rotor rotation speed of 60Hz and a pressure of 5kg / cm. 2 A crystalline polyester resin microparticle dispersion having a solid content of 30 parts by mass was prepared by operating under the above conditions. At this time, the particles contained in the crystalline polyester resin microparticle dispersion had a volume-based median diameter of 200 nm.

[0246] <Preparation of Aqueous Dispersion of Amorphous Resin Particles (X1)> (First stage polymerization) A 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device was charged with 8 parts by mass of sodium dodecyl sulfate and 3,000 parts by mass of ion-exchanged water, and the internal temperature was raised to 80° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. After the temperature was raised, a solution of 10 parts by mass of potassium persulfate in 200 parts by mass of ion-exchanged water was added, and the liquid temperature was again raised to 80° C. Styrene 480 parts by weight n-Butyl acrylate 250 parts by weight Methacrylic acid 68.0 parts by mass The monomer mixture consisting of the above was added dropwise over 1 hour, and then the mixture was heated and stirred at 80° C. for 2 hours to carry out polymerization, thereby preparing a dispersion liquid (x1) of resin fine particles.

[0247] (Second stage polymerization) A 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device was charged with a solution of 7 parts by mass of sodium polyoxyethylene (2) dodecyl ether sulfate dissolved in 3,000 parts by mass of ion-exchanged water, heated to 98°C, and then charged with 260 parts by mass of a dispersion liquid (x1) of resin fine particles, Styrene (St) 284 parts by mass n-Butyl acrylate (BA) 92 parts by weight Methacrylic acid (MAA) 13 parts by weight n-Octyl-3-mercaptopropionate 1.5 parts by mass Release agent: behenic acid behenate (melting point 73°C) 190 parts by weight A solution of the monomer and release agent dissolved at 90°C was added, and the mixture was mixed and dispersed for 1 hour using a mechanical disperser "CLEARMIX" (manufactured by M Technique Co., Ltd.) with a circulation path to prepare a dispersion containing emulsified particles (oil droplets). Next, an initiator solution in which 6 parts by mass of potassium persulfate was dissolved in 200 parts by mass of ion-exchanged water was added to this dispersion, and the system was heated and stirred at 84°C for 1 hour to carry out polymerization, thereby preparing a dispersion of resin microparticles (x2).

[0248] (Third stage polymerization) Further, 400 parts by mass of ion-exchanged water was added to the dispersion liquid (x2) of the resin fine particles and mixed thoroughly, and then a solution in which 11 parts by mass of potassium persulfate was dissolved in 400 parts by mass of ion-exchanged water was added, and the mixture was stirred at a temperature of 82° C. Styrene (St) 350 parts by mass n-Butyl acrylate (BA) 215 parts by mass Acrylic acid (AA) 30 parts by weight n-Octyl-3-mercaptopropionate 8 parts by mass After the dropwise addition, polymerization was carried out by heating and stirring for 2 hours, and then the mixture was cooled to 28°C to prepare an aqueous dispersion (X1) of amorphous resin particles made of vinyl resin. The resulting aqueous dispersion (X1) of amorphous resin fine particles had a volume-based median diameter of 220 nm, a glass transition temperature (Tg) of 55° C., and a weight average molecular weight (Mw) of 32,000.

[0249] <Preparation of Water-Based Dispersion of Colorant Particles (Cy1)> 90 parts by mass of sodium dodecyl sulfate was added to 1600 parts by mass of ion-exchanged water. While stirring this solution, 420 parts by mass of copper phthalocyanine (CI Pigment Blue 15:3) was gradually added. Next, a dispersion process was carried out using a stirring device "Clearmix" (manufactured by M Technique Co., Ltd.) to prepare an aqueous dispersion of colorant particles (Cy1). For the resulting water-based dispersion of colorant particles (Cy1), the volume-based median diameter of the colorant particles was 110 nm.

[0250] <Production of Polyester Toner Base Particles 1> A reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube was charged with 288 parts by mass (solid content equivalent) of the aqueous dispersion of amorphous resin microparticles (X1), 70 parts by mass (solid content equivalent) of the aqueous dispersion of hybrid crystalline polyester resin microparticles (C1), and 2,000 parts by mass of ion-exchanged water, and then a 5 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 10. Then, 30 parts by mass (solid content equivalent) of an aqueous dispersion of colorant particles (Cy1) was added, and then an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added at 30°C over 10 minutes while stirring. After leaving it for 3 minutes, the temperature was increased, and the system was heated to 80°C over 60 minutes, and the particle growth reaction was continued while maintaining the temperature at 80°C. In this state, the particle size of the associated particles was measured using a "Coulter Multisizer 3" (manufactured by Coulter Beckman, Inc.), and when the volume-based median diameter reached 6.0 μm, an aqueous solution in which 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water was added to stop the particle growth. The temperature was then increased and the particles were heated and stirred at 90°C to promote particle fusion. When the average circularity of the toner reached 0.945 (HPF detection number: 4,000 particles) using an "FPIA-2100" toner average circularity measuring device (Sysmex Corporation), the particles were cooled to 30°C at a cooling rate of 2.5°C / min. Next, the toner cake was subjected to solid-liquid separation, and the dehydrated toner cake was redispersed in ion-exchanged water and subjected to solid-liquid separation. This operation was repeated three times for washing, and then the toner cake was dried at 40° C. for 24 hours to obtain toner base particles 1.

[0251] <Production of styrene-acrylic toner base particles 2> A reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube was charged with 288 parts by mass (solid content equivalent) of the aqueous dispersion liquid (X1) of amorphous resin microparticles and 2,000 parts by mass of ion-exchanged water, and then a 5 mol / L aqueous sodium hydroxide solution was added to adjust the pH to 10. Then, 30 parts by mass (solid content equivalent) of an aqueous dispersion of colorant particles (Cy1) was added, and then an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added at 30°C over 10 minutes while stirring. After leaving it for 3 minutes, the temperature was increased, and the system was heated to 80°C over 60 minutes, and the particle growth reaction was continued while maintaining the temperature at 80°C. In this state, the particle size of the associated particles was measured using a "Coulter Multisizer 3" (manufactured by Coulter Beckman, Inc.), and when the volume-based median diameter reached 6.0 μm, an aqueous solution in which 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water was added to stop the particle growth. The temperature was then increased and the particles were heated and stirred at 90°C to promote particle fusion. When the average circularity of the toner reached 0.945 (HPF detection number: 4,000 particles) using an "FPIA-2100" toner average circularity measuring device (Sysmex Corporation), the particles were cooled to 30°C at a cooling rate of 2.5°C / min. Next, the toner cake was subjected to solid-liquid separation, and the dehydrated toner cake was washed by repeating the operation of redispersing the toner cake in ion-exchanged water and separating the solid from the liquid three times. The toner cake was then dried at 40° C. for 24 hours to obtain toner particles 2.

[0252] <Production of Toner 1> (Addition of external additives) 100 parts by weight of the toner base particles 1 obtained above, 0.6 parts by weight of hydrophobic silica (number average primary particle size=12 nm, hydrophobicity=68, (R805) in Table I) as negatively charged inorganic external additives, 0.94 parts by weight of hydrophobic silica (number average primary particle size=30 nm, hydrophobicity=64, (NAX50) in Table I) and 0.6 parts by weight of hydrophobic titanium oxide (titania) (number average primary particle size=100 nm, hydrophobicity=63, (TAF520K) in Table I) Then, 0.3 parts by mass of calcium titanate (number average primary particle size = 100 nm, (TC-110) described in Table I) was added as a positively charged inorganic external additive, and 0.3 parts by mass of zinc stearate was added as a lubricant. The mixture was mixed in a Henschel mixer (manufactured by Mitsui Miike Chemical Engineering Co., Ltd.) at a rotor peripheral speed of 35 mm / sec at 32°C for 20 minutes. After that, an external additive treatment was carried out to remove coarse particles using a sieve with 45 μm openings, thereby obtaining toner 1 having a volume average particle size of 6.1 μm.

[0253] <Production of toners 2 to 11> Toners 2 to 11 were obtained in the same manner as in the production of toner 1, except that the type of toner base particles and the type and amount of positively charged inorganic external additive were changed as shown in Table II below. In Table II below, "two types of hydrophobic silica" refers to the above-mentioned hydrophobic silica (number average primary particle size=12 nm, hydrophobicity=68, (R805) in Table I) and hydrophobic silica (number average primary particle size=30 nm, hydrophobicity=64, (NAX50) in Table I). In addition, in the following Table II, "strontium titanate" has a number average primary particle size of 80 μm (SW200 in Table I).

[0254] Moreover, the "positively charged silica particles" are silica particles having an average particle size of 100 nm and surface-modified with cyclic silazane C-1 and propyltrimethoxysilane shown below.

[0255] [ka]

[0256] Specifically, 100 parts by mass of fumed silica, Aerosil 130 (manufactured by Nippon Aerosil Co., Ltd.) was dried at 150°C for 5 hours, then returned to room temperature, and 15 parts by mass of cyclic silazane C-1 represented by the above structural formula and 15 parts by mass of propyltrimethoxysilane were added under a nitrogen atmosphere and mixed for 20 minutes. After that, stirring was continued under a nitrogen atmosphere at 85°C for 15 hours to obtain silica particles (positively charged silica particles) surface-modified with cyclic silazane and propyltrimethoxysilane.

[0257] Furthermore, toner 10 and toner 11 contain two types of positively charged inorganic external additives in a ratio of 50:50 (0.3 parts by mass:0.3 parts by mass).

[0258] [Manufacture of developers 1 to 11] To each of the toners produced above, a ferrite carrier coated with an acrylic resin and having a volume average particle size of 60 μm was added and mixed so that the toner concentration in the developer was 6.5 mass %, thereby producing developers 1 to 11, respectively.

[0259] [Preparation of cleaning blade 1] <Production of rubber sheets> Using 4,4'-diphenylmethane diisocyanate, polyester polyol, and short-chain polyol as raw materials, a urethane rubber sheet having a thickness of 2 mm was produced by a known centrifugal molding method. By changing the compounding ratio, a rubber sheet (blade member) made of a rubber material with a resilience modulus of 29.0% was produced.

[0260] <Edge formation> The rubber sheet produced above was cut with a blade at an angle of 10° to the vertical direction to form an edge portion with an edge angle of 90°.

[0261] <Cutting and gluing cleaning blades> Further, the blade was cut vertically to a size of 340 mm x 14.0 mm. The blade was heat-bonded to a metal plate with a bonding margin of 4 mm using a thermosetting adhesive to prepare a cleaning blade 1 with a free length of 10.0 mm. The resilience was measured by the method described above.

[0262] [Preparation of cleaning blades 2, 4 and 5] Cleaning blades 2, 4 and 5 were produced in the same manner as cleaning blade 1, except that the compounding ratio of the raw materials of the rubber sheet was changed so that the rebound elasticity was as shown in the table below.

[0263] [Preparation of cleaning blade 3] In the same manner as in the preparation of cleaning blade 1, 4,4'-diphenylmethane diisocyanate, polyester polyol, and short chain polyol were used as raw materials, and two types of prescription liquids with different compounding ratios were continuously charged by a known centrifugal molding method to prepare a two-layered rubber material sheet (blade member) with a thickness of 2 mm consisting of a base layer (1.5 mm) and an edge layer (0.5 mm). The compounding ratio of each raw material of the base layer and edge layer was appropriately adjusted to prepare the rubber material sheet with a resilience modulus of 26.5%.

[0264] [Preparation of cleaning blade 6] Cleaning blade 6 was produced in the same manner as cleaning blade 1, except that the edge portion was formed so that the edge angle was 100°.

[0265] In the table below, a "single layer" in the layer structure means that it consists only of an edge layer that contacts the photoreceptor, and a "two layer" means that it consists of an edge layer and a base layer.

[0266] [evaluation] <Raindrop resistance> The above-obtained photoreceptors, developers and cleaning blades were used in the combinations shown in Table II below to form images. Specifically, a bizhub C650i (Konica Minolta) was used as an evaluation machine, and each photoconductor prepared above was mounted at the Bk position in a low temperature and low humidity environment (10°C, 20% RH; LL environment). The cleaning blade and developer prepared above were also installed. Here, the cleaning blade was installed so that the edge angle at which it contacted the photoconductor was as shown in Table II below. After continuously printing 30kP (30,000 sheets) of a 5% character chart on A4 paper, the photoconductor was removed from the evaluation machine and the entire circumference of the photoconductor with a diameter of 30 mm and a length of 360 mm (area conversion: 33929 mm 2 The number of drips (adherents) formed on the surface of the glass was visually observed and evaluated according to the following criteria. (standard) ○: The number of raindrops is 0 to 9 (no practical problem) ×: The number of raindrops is 10 or more (problems in practical use)

[0267] <Photoreceptor wear resistance> In the raindrop resistance evaluation method, the amount of wear of the photoreceptor after 30 kP durability was confirmed by the following method. The initial thickness (μm) of the laminated film of the photoreceptor (laminated film consisting of intermediate layer, charge generating layer, charge transport layer and surface protective layer) before the image formation test was started was measured, and the thickness (μm) after the image formation test was also measured, and the difference in thickness of the laminated film of the photoreceptor before and after the image formation test, ΔT (μm), was calculated. The thickness of the laminated film of the photoreceptor was measured at 10 random locations in the uniform thickness area (excluding at least 3 cm from both ends of the photoreceptor, since the thickness is likely to be non-uniform at both ends), and the average value was taken as the thickness of the laminated film of the photoreceptor. The film thickness was measured using an eddy current film thickness gauge "EDDY560C" (manufactured by Helmut Fischer). The difference in film thickness ΔT (μm) of the laminated film of the photoreceptor before and after the image formation test was converted to α value (μm / 100,000 rotations) per 100 krot (100,000 rotations) of the photoreceptor, and this was taken as the amount of wear of the photoreceptor. Using the obtained α value, the abrasion resistance was evaluated according to the following criteria. In Table II below, the numbers in parentheses indicate the α value. (standard) ○: α value is less than 1 (no problem in practical use) ×: α value is 1 or more (problems in practical use)

[0268] [Table 2]

[0269] [Table 3]

[0270] As shown by the above results, it is apparent that in the examples using the image forming method of the present invention, raindrops can be prevented and the amount of wear of the photoconductor can be reduced, as compared with the comparative examples. [Explanation of symbols]

[0271] 100 Image forming device 110Y, 110M, 110C, 110Bk Image forming unit 111Y, 111M, 111C, 111Bk photoconductor 113Y, 113M, 113C, 113Bk Contact charging means 113a Core metal 113b Elastic layer 113c Resistance control layer 113d surface layer 113e Compression spring 115Y, 115M, 115C, 115Bk Exposure means 117Y, 117M, 117C, 117Bk developing means 118Y, 118M, 118C, 118Bk developing roller 119Y, 119M, 119C, 119Bk cleaning blade 119a Support member 119b Blade member 131 Intermediate transfer body 133Y, 133M, 133C, 133Bk Primary transfer roller (transfer means) 135 Cleaning means 137A, 137B, 137C, 137D Rollers 150 Paper feed conveying means 170 Fixing means 200 Process Cartridge 201 Case 203R, 203L Support Rail 211 Paper feed cassette 213A, 213B, 213C, 213D Intermediate roller 215 Resist Roller 217 Secondary transfer roller (transfer means) 219 Paper ejection roller 221 Paper output tray 300 External additive particles 301 Small silica particles 302 Large silica particles 303 Positively charged inorganic additive particles θ Edge angle N Nip section L Stationary layer T Toner particles

Claims

1. 1. A method for forming an image by an electrophotographic process using a toner for developing an electrostatic image, comprising: A contact charging means, a developing means, a transfer means and a cleaning blade are disposed around the electrophotographic photoreceptor, The surface protective layer of the electrophotographic photoreceptor contains inorganic fine particles, The elastic deformation rate of the electrophotographic photosensitive member is 50% or less, The cleaning blade has a rebound elasticity of 30% or less, the toner particles constituting the electrostatic image developing toner contain a lubricant, a positively charged inorganic external additive, and a negatively charged inorganic external additive; the lubricant is zinc stearate, the negatively charged inorganic external additive is silica and titanium oxide, a mass of the positively chargeable inorganic external additive and a mass of the negatively chargeable inorganic external additive satisfying the relationship of the following formula (1): Formula (1): 0.28≦mass of positively charged inorganic external additive / mass of negatively charged inorganic external additive≦0.47

2. The inorganic fine particles contained in the surface protective layer of the electrophotographic photoreceptor are silica (SiO ２ 2. The image forming method according to claim 1, wherein the toner particles are 20.degree.

3. 3. The image forming method according to claim 1, wherein the surface protective layer of the electrophotographic photoreceptor contains a thermoplastic resin.

4. 4. The image forming method according to claim 1, wherein an edge angle of the cleaning blade that comes into contact with the electrophotographic photosensitive member is formed to be an obtuse angle.

5. 5. The image forming method according to claim 1, wherein the positively charged inorganic external additive is calcium titanate particles.

6. 5. The image forming method according to claim 1, wherein the positively chargeable inorganic external additive is strontium titanate particles.

7. 5. The image forming method according to claim 1, wherein the positively chargeable inorganic external additive is silica particles whose surfaces are modified with cyclic silazane and alkylalkoxysilane.

8. 8. The image forming method according to claim 1, wherein the toner particles contain a crystalline polyester resin and a styrene-acrylic resin.

9. 9. The image forming method according to claim 8, wherein the crystalline polyester resin is a hybrid crystalline polyester resin.

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