JP2011227177A - Image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming method capable of preventing an image defect like a black spot which is caused by deformed toner or by a fragment of toner that adheres to a photoreceptor, and preventing an image defect which is caused by a scratch or bending of a toner image.SOLUTION: The image forming method has a peak count value Pc of a surface of the photoreceptor having specified ranges, and uses the toner having a domain-matrix structure which is consist of two kinds of resins with different mass average molecular weights.

Description

  The present invention relates to an image forming method, and more particularly to an electrophotographic image forming method.

  Lowering the molecular weight of the binder resin that makes up the toner to lower the softening point of the toner and fixing it at a lower temperature leads to a lower temperature in the fixing process, which can greatly save energy in the electrophotographic process. Become. In addition, if fixing can be performed at a lower temperature, that is, lower thermal energy, it becomes possible to cope with a high-speed process, which is useful for improving the productivity of document creation using a copying machine and a printer.

  In order to enable low-temperature fixing, it is effective to lower the softening point of the binder resin constituting the toner. In general, as a technical means for lowering the softening point of the binder resin, it is effective to lower the molecular weight of the binder resin. However, simply lowering the softening point using a low molecular weight binder resin results in poor heat-resistant storage stability and causes thermal aggregation in a high temperature environment. Or, for example, in the case of heat fixing, when the toner image transferred onto the copy paper is heated and melted by the fixing roller, the melted toner partially adheres to the fixing roller and is transferred to the next copy paper, The so-called offset phenomenon causes image smearing. Alternatively, there arises a problem of fixing wrapping in which the copy sheet cannot be separated from the fixing roller and the copy sheet is wound around the fixing roller.

  In order to prevent them, a release agent such as silicone oil is applied to the fixing roller to prevent the melted toner from adhering to the fixing roller, or a high-molecular weight component having a high softening point is added to the toner binder resin. There is known a technique that mixes and maintains fixing performance with a low viscosity, and moderately increases elasticity with a high molecular weight component to improve offset performance and wrapping prevention. For example, Patent Document 1 (Japanese Patent Laid-Open No. 10-198870) discloses a technique for optimally controlling thermal characteristics by using a low molecular weight latex and a high molecular weight latex in combination.

  On the other hand, Patent Document 2 (Japanese Patent Laid-Open No. 2008-26645) discloses a sea-island structure (hereinafter referred to as a domain matrix) in which a toner binder resin is composed of a resin having a high glass transition point (Tg) and a resin having a low glass transition point. In other words, the technology of toner resin is disclosed that has high heat melting property and has excellent smoothness of a fixed image and does not cause fixing wrapping.

  Further, in Patent Document 3 (Japanese Patent Application Laid-Open No. 2008-281777), a resin having a high glass transition point and a resin having a low glass transition point are combined, and the toner structure is a core-shell structure. A technique for improving the property and the offset property is disclosed.

  In order to satisfy the various characteristics required for the toner as described above, it is necessary to design the physical properties of the binder resin so as to be optimized in accordance with the purpose. For example, in order to enable fixing at a low temperature, resin characteristics with low viscosity are required. However, reducing the molecular weight to obtain a low-viscosity resin results in poor storage stability, separation performance during fixing, offset performance, and the like. In order to satisfy all these characteristics without contradiction, viewpoints such as toner binder resin molecular weight and molecular weight distribution, resin physical properties such as glass transition point, adoption of cross-linked resin, monomer composition, additives such as wax or toner structure, etc. Various studies have been added.

  As described above, various techniques have been studied for expressing mutually contradictory resin physical properties necessary for a toner without impairing both advantages.

JP-A-10-198070 JP 2008-26645 A JP 2008-281777 A

  As described above, there are various technical problems in order to enable low-temperature fixing, but another problem is that thermal properties such as the softening point of the toner are simply required to enable fixing at low temperatures. In the process using a conventional electrophotographic photosensitive member, the toner that is easily deformed by heat is fixed on the photosensitive member, so that the toner deformed by filming of the toner on the photosensitive member by so-called toner filming. In addition, there is a problem that a black spot-like image defect (also referred to as a black spot) occurs when a broken toner piece adheres to the photoreceptor, and there is a problem in long-term use.

  Also, in the fixed toner image, if the molecular weight of the binder resin constituting the toner is lowered and the thermal properties such as the softening point of the toner are lowered, the fixed toner image becomes a recording support (paper, OHP film, etc.). ) Has been rubbed off by slight rubbing or bending.

  The present invention has been made in order to solve the above-described problems, and enables low-temperature fixing. Black toner generated by toner particles deformed by filming of toner on the photosensitive member or broken toner pieces adhering to the photosensitive member. An object of the present invention is to provide an image forming method capable of preventing spot-like image defects (also referred to as black spots). Another object of the present invention is to provide an image forming method capable of preventing image defects caused by rubbing or bending a toner image formed on a recording support such as paper.

The above object of the present invention is achieved by the following configurations.
1. In an image forming method in which an electrostatic latent image formed on an electrophotographic photosensitive member is visualized using toner, the electrophotographic photosensitive member is formed by sequentially laminating at least a photosensitive layer and a surface layer on a conductive support. The electrophotographic photosensitive member is characterized in that the surface layer contains inorganic fine particles, and the peak count value Pc of the surface layer is 200 or more and 350 or less, and the toner is at least bound. A toner for developing an electrostatic charge image containing a resin and a colorant, wherein the binder resin is composed of at least two types of resins having a domain matrix structure composed of a domain resin and a matrix resin, and the mass average molecular weight of the domain resin is 150. From 5,000 to 600,000, and the weight average molecular weight of the matrix resin is from 15,000 to 60,000. Image forming method, wherein the amount is less than 25 wt% 5 wt% or more based on the entire binder resin.
2. 2. The image forming method according to 1 above, wherein the maximum height roughness Rz of the surface layer of the electrophotographic photosensitive member is 0.05 μm or more and 0.20 μm or less.
3. 3. The image forming method as described in 1 or 2 above, wherein the particle diameter of the domain resin is 70 nm or more and 300 nm or less.

  By adopting the above configuration, the present invention can be fixed at a low temperature, does not generate black spot-like image defects (black spots) caused by deformation or cracking of the toner, and is generated by rubbing or bending the toner image. Image formation that can prevent defects is possible.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the embodiments of the present invention are not limited to these.

  The present invention enables fixing at a low temperature by combining a photoreceptor having a specific surface shape as described above and a toner having a domain matrix structure composed of at least two types of resins having specific thermal characteristics. And an image forming method having excellent image characteristics.

  In the present invention, by dispersing fine particles of a high molecular weight resin as a domain in a low molecular weight matrix resin, the high molecular weight resin component having high elasticity exhibits high strength against deformation of the toner, and the mechanical strength of the toner is increased. By increasing the thickness, deformation and cracking are less likely to occur when the photosensitive member is pressed with a cleaning blade. Further, since the surface of the photoreceptor is smooth and minute peaks are present appropriately, the adhesion force of slightly deformed toner or broken toner pieces to the photoreceptor can be reduced.

That is,
(1) The toner is less likely to be deformed or cracked while maintaining low-temperature fixability.
(2) The adhesion of the photosensitive member to the toner is also reduced and the cleaning property is improved.
From the above, it is possible to prevent the toner from adhering to the photoreceptor.

  Further, the high elasticity of the high molecular weight component has a favorable influence on the strength of the toner image of the fixed image, and it is considered that the resistance to abrasion and bending is increased.

As a result,
(1) Prevention of black spot-like image defects (black spots) caused by adhesion of deformed toner or cracked toner pieces to the photoconductor by filming (2) Low-temperature fixability (3) Friction or bending of the fixed toner image It is presumed that the effect of preventing image defects by the above was obtained.

<< Photosensitive member used in the present invention >>
The electrophotographic photoreceptor according to the present invention (hereinafter simply referred to as “photoreceptor”) has at least a photosensitive layer and a surface layer on a conductive support, and contains inorganic fine particles in the surface layer. The peak count value Pc of the surface layer has a value within a specific range. In addition, a photoconductor having a maximum height roughness Rz within a specific range is more preferable.

  Here, the peak count value Pc is defined by the American Society of Mechanical Engineers ASME B46.1 (1995), and is counted by a method of setting one peak when exceeding the positive reference level + H after exceeding the negative reference level −H. It means the number of peaks in the evaluation length. In the present invention, the number of peaks per 8.0 mm is counted, and here, a value measured as H = ± 0.02 mm is used. The measurement was performed using a surface roughness measuring machine “Surfcom 1400D” manufactured by Tokyo Seimitsu Co., Ltd.

  The maximum height roughness Rz is defined in JIS B0601 (2001) and means the sum of the maximum peak height and the maximum valley depth of the roughness curve at the reference length (λc). That is, it is the sum (Rz = Rp + Rv) of the maximum value Rp of the peak height Zp of the contour curve and the maximum value Rv of the valley depth Zv at the reference length. In the present invention, the measurement was performed under the conditions of the reference length λc = 0.08 mm, the evaluation length L = 8 mm, and the measurement speed = 0.15 mm / sec, and the average value of the maximum height roughness of 100 points. Is used. The measurement was performed using a surface roughness measuring machine “Surfcom 1400D” manufactured by Tokyo Seimitsu Co., Ltd.

  The shape of the surface layer is optimally managed by the peak count value Pc. In order to control the Pc within the optimal range, the average particle diameter, dispersibility, and addition amount of the inorganic fine particles are managed, and the circular amount is regulated. The drying rate is controlled by adopting a mold coating method and using a solvent having a high vapor pressure. Specifically, Pc is controlled by the amount of inorganic fine particles added and the coating film drying conditions. In the present invention, in order to cue inorganic fine particles on the outermost surface of the coating film, a volatile solvent having a high vapor pressure is used to promote convection inside the coating film, and Obtained by controlling the drying speed using a solvent vapor concentration control means such as a drying hood so that only the outermost surface does not dry first and is dried as uniformly as possible in the thickness direction of the coating film. Can do. In order to obtain a more preferable surface shape, the maximum height roughness Rz is controlled to be within a preferable range, but the preferable range of Rz can be controlled by the average particle diameter and dispersion level of the inorganic fine particles.

<Layer structure of photoconductor>
The photoreceptor used in the present invention may contain inorganic fine particles having a number average primary particle size of 0.01 μm or more and 1.00 μm or less in the surface layer, and the layer structure is not particularly limited, Specifically, the following configurations can be exemplified.
(1) A structure in which a charge generation layer and a charge transport layer are sequentially laminated as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
(2) A structure in which a single layer containing a charge transport material and a charge generation material is formed as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
(3) A structure in which a charge transport layer and a charge generation layer are sequentially laminated as a photosensitive layer on a conductive support, and a surface layer is formed thereon;
The photoconductor of the present invention may have any of the above structures, but among these, a photoconductor in which a charge generation layer, a charge transport layer, and a surface layer are provided on a conductive support is preferable.

  In the present invention, an intermediate layer can be provided between the conductive support and the photosensitive layer for the purpose of improving electrical characteristics and adhesion.

<Production of photoconductor>
The photoreceptor can be prepared by dip coating, circular amount regulation type coating, or a combination of dip coating and round amount regulation type coating, but is not limited thereto. The circular amount regulation type application is described in detail in JP-A No. 58-189061.

  Next, the members constituting the conductive support, the intermediate layer, the photosensitive layer, and the surface layer and the method for forming each layer will be described.

<Conductive support>
Examples of the conductive support used in the present invention include a sheet-like or cylindrical conductive support.

  Examples of the material for the conductive support include metal drums such as aluminum and nickel, plastic materials on which aluminum, tin oxide, indium oxide, and the like are vapor-deposited, paper coated with a conductive material, plastic, and the like.

The conductive support used in the present invention means a cylindrical support necessary for forming an endless image by rotating. Here, the conductive support preferably has a specific resistance of 10 ³ Ω · cm or less, and specifically includes cylindrical aluminum whose surface has been cleaned after cutting.

<Intermediate layer>
The intermediate layer is formed by applying and drying an intermediate layer coating liquid composed of a binder resin and a dispersion solvent on a conductive support.

  Examples of the binder resin for the intermediate layer include polyamide resins, vinyl chloride resins, vinyl acetate resins, and copolymer resins containing two or more of the repeating units of these resins. Among these resins, a polyamide resin is preferable because a residual potential due to repeated use can be reduced.

  As the solvent for preparing the intermediate layer coating solution, a solvent that satisfactorily dissolves the intermediate layer binder resin such as polyamide resin is preferable. Specifically, alcohols having 2 to 4 carbon atoms such as ethanol, n-propyl alcohol, isopropyl alcohol, n-butanol, t-butanol, sec-butanol and the like are preferable because of excellent binder resin solubility and coating performance. . The thickness of the intermediate layer is preferably 0.2 μm to 40 μm, and more preferably 0.3 μm to 20 μm.

<Photosensitive layer>
The photosensitive layer may have a single layer structure in which the charge generation function and the charge transport function are assigned to one layer, but more preferably, the function of the photosensitive layer is separated into the charge generation layer (CGL) and the charge transport layer (CTL). It is more preferable to adopt the layer structure. By adopting a layer structure with separated functions, it is possible to control the increase in residual potential with repeated use and to easily control other electrophotographic characteristics according to the purpose. In the negatively charged photoreceptor, a charge generation layer is formed on the intermediate layer, and a charge transport layer is formed thereon. In the positively charged photoreceptor, the order of the layer configuration is opposite to that of the negatively charged photoreceptor. A preferred photosensitive layer structure is a function-separated negatively charged photoreceptor in which an intermediate layer, a charge generation layer, and a charge transport layer are sequentially laminated on a conductive support.

  Each layer of the function-separated negatively charged photoreceptor will be described below.

(Charge generation layer)
The charge generation layer contains a charge generation material (CGM). Other materials may contain a binder resin and other additives as necessary.

  As the charge generation material, a known charge generation material can be used. For example, a phthalocyanine pigment, an azo pigment, a perylene pigment, an azulenium pigment, or the like can be used. Among these, the charge generating material that can minimize the increase in residual potential due to repeated use has a three-dimensional structure that can take a stable aggregate structure among a plurality of molecules, and specifically has a specific crystal structure. Examples include phthalocyanine pigments and perylene pigments. For example, charge generation materials such as titanyl phthalocyanine having a maximum peak when the Bragg angle θ is 27.2 ° with respect to the Cu—Kα line and benzimidazole perylene having the maximum peak when 2θ is 12.4 ° are deteriorated by repeated use. Almost no residual potential can be achieved.

  When a binder resin is used as a dispersion medium in the charge generation layer, a known resin can be used as the binder resin, but the most preferable resins are formal resin, butyral resin, silicone resin, silicone-modified butyral resin, phenoxy resin, and the like. Is mentioned. The ratio of the binder resin to the charge generating material is preferably 20 to 600 parts by mass with respect to 100 parts by mass of the binder resin. By using these resins, the increase in residual potential due to repeated use can be minimized. The thickness of the charge generation layer is preferably 0.01 μm to 2 μm.

(Charge transport layer)
The charge transport layer contains a charge transport material (CTM) and a binder resin. As other substances, an antioxidant, a dispersant and the like may be contained as necessary. Examples of the binder resin include polystyrene, acrylic resin, methacrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl butyral resin, epoxy resin, polyurethane resin, phenol resin, polyester resin, alkyd resin, polycarbonate resin, silicone resin melamine resin, and Examples thereof include a copolymer resin containing two or more of the repeating units of these resins. In addition to these insulating resins, high molecular organic semiconductors such as poly-N-vinylcarbazole can be given.

  The most preferred binder resin for these charge transport layers is a polycarbonate resin. The polycarbonate resin is most preferable in terms of good compatibility with the charge transport material and good electrophotographic characteristics.

  Further, by adding an antioxidant to the photoreceptor of the present invention, it is possible to effectively prevent fogging and image blur at high temperature and high humidity.

Here, examples of the antioxidant include known compounds. A typical example is a substance that has the property of preventing or inhibiting the action of oxygen under conditions of light, heat, discharge, etc., against an auto-oxidizing substance present in the electrophotographic photoreceptor or on the surface of the photoreceptor. is there. Specifically, the following compounds may be mentioned.
(1) Radical chain inhibitor, phenolic antioxidant (hindered phenol), amine antioxidant (hindered amine, diallyldiamine, diallylamine), hydroquinone antioxidant (2) peroxide decomposer , Sulfur antioxidants (thioethers), phosphoric acid antioxidants (phosphites)
Among the above antioxidants, the radical chain inhibitor (1) is good, and a hindered phenol-based or hindered amine-based antioxidant is particularly preferable. Two or more types may be used in combination, for example, a combination of (1) a hindered phenol antioxidant and (2) a thiophenol antioxidant. Furthermore, the above-mentioned structural unit, for example, a hindered phenol structural unit and a hindered amine structural unit may be contained in the molecule.

  Among the antioxidants, hindered phenol-based and hindered amine-based antioxidants are particularly effective in preventing fogging and image blurring at high temperatures and high humidity. Examples of the antioxidant effective in the present invention include pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (Irganox 1010 (manufactured by Ciba Japan)), 3, And 5-di-tert-butyl-4-hydroxytoluene.

  The content of the hindered phenol-based or hindered amine-based antioxidant in the resin is preferably 0.01 to 20 parts by mass. If it is less than 0.01 parts by mass, there is no effect on fogging and image blur at high temperature and high humidity, and if the content is more than 20 parts by mass, the charge transport ability in the resin is lowered, and the residual potential tends to increase. A decrease in film strength occurs.

  The thickness of the charge transport layer is preferably 10 μm to 40 μm, more preferably 15 μm to 30 μm.

(Surface layer)
The surface layer contains inorganic fine particles and a binder resin according to the present invention. If necessary, other materials may contain a charge transport material, an antioxidant, a dispersant and the like.

  As the binder resin for the surface layer, a resin having abrasion resistance is preferable, and specifically, a resin containing a silicon atom or a resin containing a fluorine atom which is excellent in dispersibility of inorganic fine particles and stability after dispersion. , Polycarbonate resin, acrylic resin, phenol resin, epoxy resin, urethane resin and siloxane resin.

(Inorganic fine particles)
The inorganic fine particles added to the surface layer are not particularly limited, and examples thereof include silica particles, alumina particles, and titanium dioxide particles. Of these, silica particles are preferred.

  The number average primary particle size of the inorganic particles is preferably 0.01 μm or more and 1.00 μm or less. Particularly preferably, it is 0.03 μm or more and 0.3 μm or less.

  Here, the number average primary particle size of the inorganic fine particles is calculated from a photograph image obtained by observing and photographing the inorganic fine particles with a transmission electron microscope, and taking a picture by setting the magnification of the microscope to 10,000 times, 100 inorganic fine particles are extracted at random from the photographic image and calculated. Specifically, the average diameter in the ferret direction of 100 inorganic fine particles is measured by image analysis processing, and this is used as the number average primary particle diameter. Note that the image analysis processing can be automatically performed by driving a program built in the transmission electron microscope measurement apparatus, for example. In the present invention, a transmission electron microscope JEM-2000FX (JEOL Ltd.) was used to measure the particle size of the inorganic fine particles.

  As the inorganic fine particles, those described above can be used, but these inorganic fine particles are preferably hydrophobized with a silane coupling agent, a titanium coupling agent, or the like in order to improve dispersibility and stability of electrophotographic characteristics.

  Specific examples of the surface treatment include silicone varnish, various modified silicone varnishes, silicone oil, silane coupling agent, silane coupling agent having a functional group, and other organosilicon compounds. These treatment agents may be used alone or in combination.

  Examples of such organosilicon compounds include hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, trimethylethoxysilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, β-chloroethyltrichlorosilane, chloromethyldimethylchlorosilane, triorganosilylmercaptan, trimethylsilylmercaptan, triorganosilylacrylate, vinyldimethylacetoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, Hexamethyldisiloxane, 1,3-divinyltetramethyldisiloxane 1,3-diphenyltetramethyldisiloxane, dimethylpolysiloxane having 2 to 12 siloxane units per molecule, each having a hydroxyl group bonded to one Si at each terminal unit is there. These are used alone or in a mixture of two or more.

  The proportion of the inorganic fine particles in the surface layer is preferably 1.0 part by mass or more and 50 parts by mass or less of the entire surface layer. Particularly preferably, it is 5.0 parts by mass or more and 30 parts by mass or less.

(Surface shape)
In the present invention, the shape of the surface layer is controlled by the particle size and the added amount of the inorganic fine particles, but it is not possible to exert the optimum effect only by managing these, and the inorganic fine particles protruding from the surface This is achieved for the first time by optimally controlling the size, height and density. That is, when the maximum surface roughness Rz and the peak count value Pc are in appropriate ranges, a uniform thin film of lubricant can be formed on the surface of the photosensitive layer, and good cleaning performance can be exhibited. The peak count value Pc of the present invention is 200 or more and 350 or less, and the maximum height roughness Rz of the surface layer is preferably 0.05 μm or more and 0.2 μm or less.

(Method for forming surface layer)
As a method for forming the surface layer of the present invention, a means for controlling the evaporation rate of the solvent on the surface layer is provided on the upper part of the coating head of the circular amount regulating type coating device, and the drying rate of the surface layer coating film is optimally controlled. It is preferable to control the maximum height roughness Rz and the peak count value Pc. In the present invention, as an example of the embodiment, a cylindrical dry hood provided so as to cover the photoreceptor on the upper part of the coating head is used. The drying hood may be provided with a solvent vapor amount adjusting means having an opening such as a slit or a circle to control the drying speed of the solvent. In the present invention, it is preferable that a long hood having a high hermeticity is installed on the upper part of the circular slide hopper so as to cover the photoconductor, and then applied and dried. Further, the drying speed control means of the present invention is not limited to this drying hood.

  The length of the dry hood is preferably 150 mm or more and 400 mm or less, and particularly preferably 200 mm or more and 350 mm or less.

  In order to obtain the surface layer of the present invention, a dip coating method (dip coating method) or a spray coating method is not suitable. That is, in the dip coating method, it is difficult to find the fine particles uniformly, and in the spray coating method, it is difficult to use a highly volatile solvent, and the amount of the fine particles found on the surface is reduced.

(Surface layer coating solvent)
As a highly volatile solvent having a high vapor pressure, a solvent having a vapor pressure (13.3 kPa) or higher is preferable, and as an organic solvent meeting this condition, dichloromethane (46.7 kPa) and tetrahydrofuran (18.9 kPa) are applicable. . In the present invention, these solvents having a high vapor pressure are used, but in order to control the drying rate, it is also possible to use a solvent having a low vapor pressure mixed in an arbitrary ratio. For example, low-volatile solvents with low vapor pressure such as toluene (4.9 kPa), methyl ethyl ketone (4.0 kPa), isopropyl alcohol (4.3 kPa), methanol (12.3 kPa), cyclohexanone (0.53 kPa) are also highly volatile. It can be used by mixing with an ionic solvent.

<< Toner used in the present invention >>
The toner of the present invention is an electrostatic charge image developing toner containing at least a binder resin and a colorant, and the binder resin comprises at least two types of resins having a domain matrix structure, and the mass of the resin in the domain The average molecular weight (Mw) is 150,000 to 600,000, the mass average molecular weight (Mw) of the binder resin to be the matrix is 15,000 to 60,000, and the resin forming the domain Content is 5 mass%-25 mass% with respect to the whole binder resin, It is characterized by the above-mentioned.

<Matrix resin>
In the present invention, examples of the monomer component constituting the matrix resin include vinyl aromatic monomers, vinyl ester monomers, vinyl ether monomers, olefin monomers, and the like. Use of a vinyl copolymer (hereinafter referred to as vinyl copolymer A) containing a radical polymerizable monovalent carboxylic acid (hereinafter also referred to as “radical polymerizable monovalent carboxylic acid”) component as a monomer component. Is preferred. This is because the presence of a carboxyl group, which is a polar group, allows the polymerization for obtaining the vinyl copolymer A to proceed stably in the aqueous medium and the resin fine particles by the vinyl copolymer A in the aqueous medium. While ensuring high dispersion stability, the degree of polarity is significantly different from that of the vinyl copolymer (hereinafter referred to as vinyl copolymer B) constituting the domain resin described later, and the domain matrix structure It is because it can be obtained.

  Examples of the radical polymerizable monovalent carboxylic acid include methacrylic acid and acrylic acid. Further, the content ratio of the radically polymerizable monovalent carboxylic acid in the whole monomer to form the vinyl copolymer A is preferably 3% by mass to 20% by mass, and more preferably 5% by mass to 5% by mass. 10% by mass.

  Examples of vinyl aromatic monomers include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-ethyl styrene, pn-butyl styrene, p. -Tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2,4-dimethyl styrene, and the like Derivatives can be mentioned.

  Examples of vinyl ester monomers include vinyl acetate, vinyl butyrate, vinyl propionate, vinyl benzoate, and examples of vinyl ether monomers include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether, vinyl phenyl ether. And so on.

  Other radical polymerizable monomers other than the above include acrylic ester monomers such as ethyl acrylate, butyl acrylate, and 2-ethylhexyl acrylate; methyl methacrylate, ethyl methacrylate, butyl methacrylate, and the like. Methacrylic acid ester monomers; N-alkyl-substituted acrylamides such as N-methylacrylamide and N-ethylacrylamide; Nitrile monomers such as acrylonitrile and methacrylonitrile; Divinylbenzene, ethylene glycol (meth) acrylate, trimethylolpropane A (meth) acrylate etc. can be mentioned.

  Further, for example, as a monomer component to form the vinyl copolymer A, a crosslinkable having two or more unsaturated bonds such as divinylbenzene, divinylnaphthalene, divinyl ether, ethylene glycol dimethacrylate, and polyethylene glycol dimethacrylate. A vinyl monomer may further be contained.

  The vinyl-based copolymer A constituting the matrix resin preferably has a mass average molecular weight of 15,000 to 60,000, more preferably 25,000 to 35,000.

  When the vinyl-based copolymer A has a mass average molecular weight of 15,000 to 60,000, the vinyl-based copolymer A has a low content of oligomer components, so there is little adverse effect on heat resistance. In addition, it is possible to ensure high glossiness and smoothness in the obtained image without causing a significant increase in elasticity without entanglement of polymer chains and without eventually reducing heat resistance. .

  The mass average molecular weight of the vinyl monomer A constituting the matrix resin can be measured by gel permeation chromatography (GPC). Specifically, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent. The sample was flowed at a flow rate of 0.2 ml / min, and dissolved in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition in which the measurement sample was treated for 5 minutes using an ultrasonic disperser at room temperature, and then the pore size was 0.2 μm. A sample solution is obtained by processing with a membrane filter, 10 μl of this sample solution is injected into the apparatus together with the above carrier solvent, and detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample is determined. Calculate using a calibration curve measured using monodisperse polystyrene standard particles .

  A calibration curve was prepared using measured values of 10 standard polystyrene particles each having a different mass average molecular weight.

  The glass transition temperature TgA of the vinyl copolymer A constituting the matrix resin is preferably 25 ° C to 45 ° C, more preferably 25 ° C to 35 ° C.

<Domain resin>
In the present invention, the domain resin is, for example, a vinyl copolymer obtained by polymerization from a radical polymerizable monomer containing a radical polymerizable polycarboxylic acid (hereinafter also referred to as “radical polymerizable polycarboxylic acid”) component. The radical polymerizable monomer comprising the polymer B includes, in addition to the radical polymerizable polycarboxylic acid component, vinyl aromatic monomers and vinyl esters mentioned as monomers used in the matrix resin. Examples thereof include a monomer, a vinyl ether monomer, and an olefin monomer.

<Radically polymerizable polyvalent carboxylic acid>
Examples of the radical polymerizable polycarboxylic acid that forms the vinyl copolymer B constituting the domain resin include dicarboxylic acids such as itaconic acid and maleic acid, and itaconic acid is particularly preferable. The carboxyl group is a very polar functional group, and since there are two or more carboxyl groups in one molecule of the radical polymerizable polycarboxylic acid, the vinyl copolymer can be efficiently used with a small amount of the radical polymerizable polycarboxylic acid. The surface of the fine particles of the domain resin formed by the coalescence B can be brought into a state of high polarity. Thereby, the vinyl copolymer A and the vinyl copolymer B can be made into a phase-separated state (incompatible state) independent from each other, without impairing the high meltability by the vinyl copolymer A. Good elastic force due to the vinyl copolymer B can be expressed.

  The content ratio of the radical polymerizable polycarboxylic acid in the polymerizable monomer composition forming the vinyl copolymer B constituting the domain resin is preferably 3% by mass to 20% by mass, and more preferably 5% by mass to 10% by mass.

  When the content ratio of the radically polymerizable polyvalent carboxylic acid in the polymerizable monomer composition is within the above range, the resin-based fine particles due to the vinyl copolymer B are not aggregated in the toner production process. Resin particles by copolymer A and a highly uniform mixed state can be obtained, and the degree of polarity with vinyl copolymer A can be made very different, so that it is compatible with vinyl copolymer A. Thus, the domain matrix structure can be obtained without any significant effect.

  In the toner of the present invention, the diameter of the domain resin dispersed in the matrix resin constituting the toner particles (hereinafter also simply referred to as domain diameter) is preferably in the range of 70 nm to 300 nm.

  Since the domain diameter is in the range of 70 nm to 300 nm, the vinyl copolymer B and the vinyl copolymer A are aggregated with higher uniformity when toner particles are formed in the salting out and aggregation processes described later. It is necessary to disperse the domain resin of the vinyl-based monomer B in the toner particles without being localized, and the effect can be exhibited more remarkably.

  The domain matrix structure in the toner particles is measured as follows.

(Sample preparation)
0.6 g of toner particles conditioned at 20 ° C. and 50% RH are pellet-molded with a load of 3 tons and held at 80 ° C. for 30 minutes. The toner pellets are embedded in a UV curable resin, cured for 24 hours, and then cut with an ultramicrotome (MT-7 manufactured by RMC) to cut out the observation surface. The heating and holding after the pellet forming is for suppressing the measurement error due to the unevenness by fusing the toner particles to eliminate the voids between the particles.

(Domain observation)
For observation, an atomic force microscope (SPI3800N manufactured by SPM Seiko Instruments Inc., cantilever is SN-AF01) is used at room temperature, and an area of 2 μm square is scanned in a micro viscoelastic mode and observed. In order to confirm the detailed dispersion state of the domain / matrix resin, three or more 2 μm square regions where wax and pigment were not dispersed were searched and measured.

  The domain diameter was measured as the domain diameter by the longest diameter of the domain, that is, the distance at which the two parallel lines contacting the domain took the maximum distance.

  The vinyl copolymer B constituting the domain resin has a mass average molecular weight of 150,000 to 600,000, more preferably 180,000 to 220,000.

  The mass average molecular weight of the vinyl copolymer B constituting the domain resin can be measured by the same method as the method for measuring the mass average molecular weight of the vinyl copolymer A constituting the matrix resin.

  The toner production method of the present invention is produced, for example, by a process of aggregating the vinyl copolymer A to form the matrix resin and the resin fine particles B by the vinyl copolymer B to form the domain resin. Is done.

  The glass transition temperature TgB of the vinyl copolymer B constituting the domain resin is preferably 40 ° C to 100 ° C, and more preferably 60 ° C to 80 ° C, for example. When the glass transition temperature TgB of the domain resin is in the above range, the effect of maintaining the elastic force of the high molecular weight domain resin can be reliably obtained.

  In the toner of the present invention, the content ratio of the domain resin is preferably 5% by mass to 25% by mass with respect to the entire binder resin. When the content ratio of the domain resin is 5% by mass to 25% by mass with respect to the total mass of the binder resin, the obtained toner ensures both excellent filming resistance and sufficient low-temperature fixability. It becomes what you have.

  The content ratio of the domain resin is also reflected in the domain diameter in the matrix resin. If the content ratio of the domain resin is small, there is no coalescence of the domain particles in the aggregation process, and the domain diameter becomes small. Conversely, when the content ratio of the domain resin is large, the particle size becomes large due to coalescence of the resin particles constituting the domain in the aggregation process.

<Method for producing toner>
Next, a method for producing the toner of the present invention will be described.

  As a method for producing the toner of the present invention, for example, a method of obtaining toner particles having a matrix resin made of vinyl copolymer A and a domain resin made of vinyl copolymer B dispersed in the matrix resin in the form of fine particles. Is mentioned. Specific toner production methods include emulsion polymerization aggregation method, miniemulsion polymerization aggregation method, suspension polymerization method, dispersion polymerization method, dissolution suspension method, melting method, kneading and pulverization method, etc. Among these, domain particles Can be easily introduced into the matrix resin, and a toner production method by a miniemulsion polymerization aggregation method or an emulsion polymerization aggregation method is preferable.

As a specific example of a toner production method by the miniemulsion polymerization aggregation method,
(1) a step of adjusting a radical polymerizable monomer solution containing a release agent as required,
(2) a polymerization step in which the radical polymerizable monomer solution is converted into oil droplets in an aqueous medium, and a dispersion of binder resin particles is prepared by performing a miniemulsion polymerization treatment;
(3) Toner particles can be obtained by aggregating binder resin particles together with fine particles of other toner particle constituents such as colorant fine particles in an aqueous medium and, if necessary, fusing the particles in parallel by thermal fusion or the like. An assembly process for the formation of intermediates,
(4) An aging step for adjusting the shape of the toner particles by aging with thermal energy following the association step,
(5) a cooling step for cooling the toner dispersion;
(6) a step of solid-liquid separating the toner base particles from the cooled dispersion of toner particles to remove the surfactant from the toner particles;
(7) a drying step of drying the washed toner particles;
(8) an external additive addition step of adding toner to the dried toner particles to obtain toner particles;
Consists of

  In the toner production method by the miniemulsion polymerization aggregation method, the domain resin can be introduced in the aggregation / fusion step (3).

  One is that in the above-mentioned (3) aggregation / fusion process, the domain resin should be formed simultaneously with the addition of the binder resin fine particles (vinyl copolymer particles A) that should form the matrix resin in the aqueous medium. A method in which the resin fine particles (vinyl copolymer particles B) are added and then aggregated.

  The other is (3) in the aggregation / fusion process, after the aggregation of the binder resin fine particles (vinyl copolymer particles A) to form the matrix resin in the aqueous medium is started, the aggregation is completed. A method in which the binder resin particles (vinyl copolymer particles B) to form the domain resin are added in the middle of the aggregation step before the addition, and these are introduced by agglomeration.

  The method of adding and aggregating the domain resin particles simultaneously with the addition of the matrix resin particles can disperse the domain resin most uniformly and without localization, and the domain diameter in the matrix resin can be reduced.

  As the addition of the domain resin particles is delayed during the aggregation process, coalescence of the domain particles occurs and the domain diameter in the matrix resin increases.

  Here, the “aqueous medium” refers to a medium composed of 50 to 100% by mass of water and 0 to 50% by mass of a water-soluble organic solvent. Examples of the water-soluble organic solvent include methanol, ethanol, isopropyl alcohol, butanol, methyl ethyl ketone, and tetrahydrofuran. An alcohol-based organic solvent that does not dissolve the obtained resin is preferable.

<Colorant>
As the colorant constituting the toner of the present invention, a known inorganic or organic colorant can be used, for example, carbon black such as furnace black, channel black, acetylene black, thermal black, lamp black, magnetite, ferrite, etc. And magnetic powder. These colorants can be used alone or in combination of two or more.

  Further, as the colorant, a surface-modified one can be used. As the surface modifier, conventionally known ones can be used, and specifically, silane coupling, titanium coupling agent, aluminum coupling agent and the like can be preferably used.

  The amount of the colorant added is in the range of 1 to 30% by mass, preferably 2 to 20% by mass, based on the total amount of toner.

<Chain transfer agent>
In the polymerization step, a chain transfer agent generally used for the purpose of adjusting the molecular weight of the matrix resin and the domain resin can be used. The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as 2-chloroethanol, octyl mercaptan, dodecyl mercaptan, and t-dodecyl mercaptan, and styrene dimers.

<Polymerization initiator>
In the polymerization step, any polymerization initiator for obtaining a matrix resin and a domain resin can be used as long as it is a water-soluble polymerization initiator. Specific examples of the polymerization initiator include, for example, persulfates (potassium persulfate, ammonium persulfate, etc.), azo type compounds (4,4′-azobis-4-cyanovaleric acid and its salts, 2,2′-azobiz). (2-aminodipropane) salt), peroxide compounds and the like.

<Surfactant>
In the binder resin polymerization step, as the surfactant to be used, conventionally known various ionic surfactants, nonionic surfactants and the like can be used.

<Flocculant>
In the coagulation / fusion process, a coagulant is used in the coagulation / fusion process, and examples of the coagulant include alkali metal salts and alkaline earth metal salts. Examples of the alkali metal constituting the flocculant include lithium, potassium and sodium, and examples of the alkaline earth metal constituting the flocculant include magnesium, calcium, strontium and barium. Of these, potassium, sodium, magnesium, calcium and barium are preferred. Examples of the counter ion (anion constituting the salt) of the alkali metal or alkaline earth metal include chlorine ion, bromine ion, iodine ion, carbonate ion, and sulfate ion.

<Release agent>
The toner particles constituting the toner of the present invention may contain a release agent. As the mold release agent, for example, polypropylene and polyethylene are preferable as the polyolefin wax, and paraffin wax, Fischer-Tropsch wax, microcrystalline wax, and metallocene wax are preferably used as conventional names after the production method. Other examples include fatty acid wax having 12 to 24 carbon atoms and ester compounds thereof, higher alcohol wax, lanolin wax, carnauba wax, rice wax, beeswax, scale insect wax, montan wax, and the like.

  As a method for incorporating a wax in the toner particles, a vinyl resin and a release agent constituting the matrix resin are added by adding a dispersion liquid (wax emulsion) of release agent fine particles in the aggregation / fusion process for forming the toner particles. Examples include a method of salting out, agglomerating, and fusing fine particles, and a method of previously containing a release agent in the monomer solution to form the vinyl copolymer A to be a matrix resin in the monomer solution adjustment step. These methods may be combined.

  The content ratio of the release agent in the toner particles is usually 5 to 30% by mass, preferably 10 to 20% by mass with respect to the binder resin.

<Charge control agent>
The toner particles constituting the toner of the present invention may contain a charge control agent as necessary. Various known compounds can be used as the charge control agent.

  As a method for incorporating the charge control agent into the toner particles, a method similar to the method for incorporating the above-mentioned release agent can be employed.

<Toner particle size>
The particle diameter of the toner of the present invention is preferably 4 to 8 μm, and more preferably 6 to 8 μm, for example, as a volume-based median diameter. When the toner production method is, for example, an emulsion polymerization aggregation method, the particle size should be controlled by the concentration of the coagulant (salting out agent) used, the amount of organic solvent added, the fusing time, and the polymer composition. Can do. When the particle size of the toner is in the above range, the transfer efficiency is increased, the image quality of halftone is improved, and the image quality of fine lines and dots is improved.

  The volume-based median diameter of the toner is measured and calculated using a device in which a computer system for data processing (manufactured by Beckman Coulter) is connected to “Coulter Multisizer 3” (manufactured by Beckman Coulter).

  Specifically, 0.02 g of toner is added to 20 ml of a surfactant (for example, a surfactant solution in which a neutral detergent containing a surfactant component is diluted 10-fold with pure water for the purpose of dispersing the toner). Then, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion, and this toner dispersion is displayed in a beaker containing the electrolytic solution “ISOTONII” (manufactured by Beckman Coulter) in the sample stand. Pipette until 5-10%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measurement device, the measurement particle count is 25,000, the aperture diameter is 50 μm, the frequency range is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integrated fraction is 50% from the largest. The particle diameter (volume D50% diameter) is defined as the volume-based median diameter.

<Average circularity of toner particles>
The average circularity of the toner particles is preferably 0.910 to 0.960 from the viewpoint of achieving both cleaning properties and transferability on the photoreceptor.

  The average circularity of the toner is a value measured using “FPIA-2100” (manufactured by Sysmex). Specifically, the toner is acclimated to an aqueous solution containing a surfactant, subjected to ultrasonic dispersion treatment for 1 minute to disperse, and then subjected to measurement conditions HPF (high magnification photography) mode by “FPIA-2100” (manufactured by Sysmex). Then, photographing is performed at an appropriate density of 3,000 to 10,000 HPF detected, the circularity is calculated for each toner particle according to the following formula (3), the circularity of each toner particle is added, and all toners are added. It is a value calculated by dividing by the number of particles. If the number of HPF detections is in the above range, reproducibility can be obtained.

Formula (3): Average circularity = peripheral length of circle having the same projected area as the particle image / perimeter length of the projected particle image <Glass transition temperature of toner>
Further, the glass transition temperature of the toner is preferably 20 to 45 ° C. This is because, by setting the glass transition point temperature of the toner as a whole in this range, good meltability of the toner can be obtained at the time of fixing, and therefore sufficient low-temperature fixability can be obtained.

<External additive>
The above toner particles can constitute the toner of the present invention as they are, but in order to improve fluidity, chargeability, cleaning properties, etc., a solubilizing agent, a cleaning agent, which is a so-called external additive, is added to the toner particles. An external additive such as an auxiliary agent may be added to constitute the toner of the present invention.

  As the post-treatment agent, for example, inorganic oxide fine particles composed of silica fine particles, alumina fine particles, titanium oxide fine particles, etc., inorganic stearate compound fine particles such as aluminum stearate fine particles, zinc stearate fine particles, or strontium titanate, titanium Inorganic titanic acid compound fine particles such as zinc acid are listed. These can be used individually by 1 type or in combination of 2 or more types.

  These inorganic fine particles are preferably subjected to surface treatment with a silane coupling agent, a titanium coupling agent, a higher fatty acid, silicone oil or the like in order to improve heat-resistant storage stability and environmental stability.

  The total amount of these various external additives added is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner. In addition, various external additives may be used in combination.

<Developer>
The toner of the present invention can be used as a magnetic or non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer. When the toner of the present invention is used as a two-component developer, the carrier is made of a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. Magnetic particles can be used, and ferrite particles are particularly preferable. Further, as the carrier, a coat carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a binder type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.

  The coating resin constituting the coat carrier is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene-acrylic resins, silicone resins, ester resins, and fluorine resins. Moreover, it does not specifically limit as binder resin which comprises a binder type carrier, A well-known thing can be used, For example, a styrene-acrylic resin, a polyester resin, a fluororesin, a phenol resin etc. can be used.

  The carrier preferably has a volume-based median diameter of 20 to 100 μm, more preferably 20 to 60 μm, since a high-quality image is obtained and carrier fogging is suppressed. The volume-based median diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  Preferred carriers include a coated carrier using a silicone resin, a copolymer resin (graft resin) of an organopolysiloxane and a vinyl monomer or a polyester resin as a coating resin from the viewpoint of spent resistance. Coat carrier coated with resin obtained by reacting isocyanate with copolymer resin (graft resin) of organopolysiloxane and vinyl monomer from the viewpoint of durability, environmental stability and spent resistance Is preferred. The vinyl-based monomer forming the above coat carrier is a monomer having a substituent such as a hydroxyl group reactive with isocyanate.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

(Production of photoconductor)
<Creation of photoconductor 1>
(Conductive support)
As the conductive support, a cylindrical aluminum substrate whose surface was washed after cutting was used.

(Formation of intermediate layer)
On the washed cylindrical aluminum support (diameter 100 mm, length 360 mm), the following intermediate layer coating solution was applied by a dip coating method and dried at 120 ° C. for 30 minutes to form an intermediate layer having a dry film thickness of 5 μm. .

  The following intermediate layer dispersion was diluted twice with the same mixed solvent, and allowed to stand overnight, then filtered (filter; rigesh mesh filter made by Nihon Pall Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) to prepare an intermediate layer coating solution did.

(Preparation of intermediate layer dispersion)
Binder resin: (Structural formula: N-9 below) 1 part by mass Rutile-type titanium oxide (primary particle size 35 nm; surface-treated with dimethylpolysiloxane having a hydroxyl group at the terminal to prepare a hydrophobized degree of 33 titanium oxide pigment 5.6 parts by mass Ethanol / n-propyl alcohol / THF (= 45/20/30 mass ratio)
10 parts by mass The above components were mixed and dispersed in a batch system for 10 hours using a sand mill disperser to prepare an intermediate layer dispersion.

(Formation of charge generation layer)
A liquid in which the following components were mixed was dispersed using a sand mill disperser to prepare a charge generation layer coating liquid.

Charge generation layer coating liquid Y-type oxytitanyl phthalocyanine (X-ray diffraction spectrum by Cu-Kα characteristic X-ray, titanyl phthalocyanine pigment having a maximum diffraction peak at a Bragg angle (2θ ± 0.2 °) of 27.3 °) 20 Part by mass Silicone-modified polyvinyl butyral 10 parts by mass 4-methoxy-4-methyl-2-pentanone 700 parts by mass t-butyl acetate 300 parts by mass This coating solution was applied onto the intermediate layer by dip coating, and the dry film thickness was 0.3 μm. The charge generation layer was formed.

(Formation of charge transport layer)
A solution in which the following components were dissolved and mixed was filtered (filter: rigesh mesh filter manufactured by Nippon Pole Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) to prepare a charge transport layer coating solution.

Charge transport layer coating solution 4-methoxy-4 ′-(4-phenyl-α-phenylstyryl) triphenylamine
70 parts by mass Bisphenol Z-type polycarbonate "Iupilon Z300" (Mitsubishi Gas Chemical Co., Ltd.)
100 parts by mass Antioxidant “Irganox 1010” (manufactured by Ciba Japan) 8 parts by mass Solvent (tetrahydrofuran / toluene (mass ratio 8/2)) 750 parts by mass After applying this coating solution on the charge generation layer by dip coating And dried at 110 ° C. for 60 minutes to form a charge transport layer having a dry film thickness of 20 μm.

(Formation of surface layer)
A liquid in which the following components are mixed is dispersed for 10 hours using a batch-type sand mill disperser, and then filtered (filter: rigesh mesh filter manufactured by Nihon Pall Co., Ltd., nominal filtration accuracy: 5 μm, pressure: 50 kPa) and applied to the surface layer. A liquid was created.

Surface layer coating solution 4-methoxy-4 ′-(4-methyl-α-phenylstyryl) triphenylamine
70 parts by mass Bisphenol Z-type polycarbonate "Iupilon Z300" (Mitsubishi Gas Chemical Co., Ltd.)
100 parts by mass 3,5-di-t-butyl-4-hydroxytoluene 8 parts by mass Tetrahydrofuran 1000 parts by mass Inorganic fine particles “silica” (number average primary particle size 0.033 μm) 22 parts by mass The above surface on the charge transport layer The layer coating solution was applied using a circular slide hopper coating apparatus, and then dried at 110 ° C. for 60 minutes to form a surface layer having a dry film thickness of 6 μm, thereby preparing “Photoreceptor 1”. Here, a dry hood (length 200 mm, no solvent vapor amount adjusting hole) was used.

  The maximum height roughness Rz of this photoconductor was 0.18 μm, and the peak count value Pc was 342.

<Preparation of photoconductors 2 to 6 and comparative photoconductors 1 and 2>
Photoconductors 2 to 6 and a comparative photoconductor, except that the amount of inorganic fine particles added and the dry hood conditions used in the preparation of the surface layer of the “photoconductor 1” were changed as shown in Table 1. 1 and 2 were created. Table 1 shows the peak count values Pc of these photoreceptors.

(Production of toner)
<Preparation example A1 of matrix resin fine particle dispersion>
(1) First-stage polymerization 2.0 g of an anionic surfactant (sodium dodecylbenzenesulfonate: SDS) was previously added to 2900 g of ion-exchanged water in a 5 L reaction vessel equipped with a stirrer, temperature sensor, cooling pipe, and nitrogen introducing device. The surfactant solution dissolved in was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

After adding 9.0 g of a polymerization initiator (potassium persulfate: KPS) to this surfactant solution and adjusting the internal temperature to 78 ° C., 540 g of styrene, 270 g of n-butyl acrylate, 65 g of methacrylic acid, n-octyl mercaptan (Chain transfer agent) A monomer solution [1] consisting of 17 g was dropped over 3 hours, and after completion of the dropping, polymerization (first stage polymerization) was performed by heating and stirring at 78 ° C. for 1 hour to obtain a resin. A dispersion of fine particles [a1] (resin fine particle dispersion [a1]) was prepared.
(2) Second-stage polymerization: formation of intermediate layer In a flask equipped with a stirrer, a single amount consisting of 103 g of styrene, 26 g of n-butyl acrylate, 8.5 g of methacrylic acid, and 2 g of n-octyl mercaptan (chain transfer agent) To the body composition, 51 g of paraffin wax “HNP-57” (manufactured by Nippon Seiwa Co., Ltd.) was added as a release agent, and the mixture was heated to 85 ° C. and dissolved to prepare a monomer solution [2].

On the other hand, a surfactant solution in which 2 g of an anionic surfactant (polyoxy (2) dodecyl ether sulfate sodium salt) was dissolved in 1100 g of ion-exchanged water was heated to 90 ° C., and resin fine particles were dispersed in this surfactant solution. After adding 28 g of the liquid [a1] in terms of solid content of the resin fine particles [a1], the monomer solution [2] is obtained by a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. Was mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm, and an initiator aqueous solution in which 2.5 g of a polymerization initiator (KPS) was dissolved in 110 g of ion-exchanged water in this dispersion. Then, this system is heated and stirred at 90 ° C. for 2 hours to perform polymerization (second stage polymerization) to obtain a dispersion of resin fine particles [a11] (resin fine particle dispersion) a11]) was prepared.
(3) Third-stage polymerization: formation of outer layer An initiator aqueous solution in which 2.5 g of a polymerization initiator (KPS) was dissolved in 110 g of ion-exchanged water was added to the above resin fine particle dispersion [a11], Under temperature conditions, a monomer solution [3] consisting of 230 g of styrene, 100 g of n-butyl acrylate, and 6.2 g of n-octyl mercaptan (chain transfer agent) was added dropwise over 1 hour. After completion of the dropping, polymerization (third stage polymerization) was carried out by heating and stirring for 3 hours, and then the mixture was cooled to 28 ° C. to obtain a resin fine particle dispersion [A1] composed of composite resin fine particles having a multilayer structure.

<Preparation examples A2 to A4 of matrix resin fine particle dispersion>
Resin fine particle dispersions [A2] to [A4] were obtained in the same manner as in Preparation Example A1 of the fine resin particle dispersion except that the amounts of the monomer and chain transfer agent were changed as shown in Table 2. Table 2 shows the mass average molecular weight of the resin fine particles constituting the matrix resin fine particle dispersion.

<Preparation Example B1 of Domain Resin Fine Particle Dispersion>
A surfactant solution in which 2.7 g of an anionic surfactant (SDS) was previously dissolved in 2800 g of ion-exchanged water was put into a 5 L reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen introducing device, and a nitrogen stream The internal temperature was raised to 80 ° C. while stirring at a lower stirring speed of 230 rpm.

  On the other hand, 630 g of methyl methacrylate, 130 g of n-butyl acrylate, 40 g of itaconic acid, and 1.2 g of n-octyl mercaptan (chain transfer agent) were mixed and dissolved by heating to 78 ° C. to prepare a monomer solution. Here, the monomer solution and the warmed surfactant solution were mixed and dispersed by a mechanical disperser having a circulation path to prepare emulsified particles having a uniform dispersed particle size. Next, a solution in which 11.0 g of a polymerization initiator (KPS) was dissolved in 400 g of ion exchange water was added, and the mixture was heated and stirred at 78 ° C. for 2 hours to obtain a resin fine particle dispersion [B1].

<Preparation Examples B2 to B4 of Domain Resin Fine Particle Dispersion>
Resin fine particle dispersions [B2] to [B4] in the same manner as in Preparation Example B1 of the resin fine particle dispersion, except that the amount of monomer, chain transfer agent and polymerization initiator were changed as shown in Table 3. Got. Table 3 shows the mass average molecular weight of the resin fine particles constituting the domain resin fine particle dispersion.

<Preparation Example 1 of Colorant Dispersion>
To a solution in which 90 g of sodium dodecyl sulfate was stirred and dissolved in 1600 g of ion-exchanged water, 420 g of carbon black “Regal 330R” (manufactured by Cabot) was gradually added with stirring, and then a stirring device “Cleamix” (M Technique) A colorant dispersion liquid [1] was obtained by carrying out a dispersion treatment using As a result of measuring the particle diameter of the colorant in the colorant dispersion [1] using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.), the mass average diameter was 110 nm.

<Production Example 1 of Toner Particles>
In a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device, the resin fine particle dispersion [A1] is 368 g in terms of solid content, and the resin fine particle dispersion [B1] is 32 g in terms of solid content. Then, 1100 g of ion-exchanged water and 200 g of the colorant dispersion [1] were charged and the liquid temperature was adjusted to 30 ° C., and then 5N sodium hydroxide aqueous solution was added to adjust the pH to 10.0. Next, an aqueous solution in which 60 g of magnesium chloride was dissolved in 60 g of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. Thereafter, the temperature was raised after being allowed to stand for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman). When the volume-based median diameter reached 6 μm, 190 g of sodium chloride was dissolved in 760 g of ion-exchanged water. Is added to stop the particle growth, and further, as a ripening process, the mixture is heated and stirred at a liquid temperature of 80 ° C., and cooled to 30 ° C. when the circularity is in the range of 0.950 to 0.975, and the stirring is stopped. did. The circularity was 0.962.

  The produced fused particles are filtered, washed with ion-exchanged water, and then dried with a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.), and dried until the water content becomes 1.0 mass% or less. Thus, toner particles [1] were obtained.

<Production Examples 2 to 8 of Toner Particles>
Table 4 shows combinations and composition ratios of the matrix resin fine particle dispersion (resin fine particle dispersion [A1] to [A4]) and the domain resin fine particle dispersion (resin fine particle dispersion [B1] to [B4]). Toner particles [2] to [4] and toner particles for comparison [5] to [8] were obtained in the same manner as in Toner Particle Preparation Example 1 except that the toner particles were changed to.

  The domain diameter in the toner produced as described above was measured as follows.

(Sample preparation)
0.6 g of toner particles conditioned at 20 ° C. and 50% RH were formed into pellets under a load of 3 tons and held at 80 ° C. for 30 minutes. The toner pellets were embedded in a UV curable resin, cured for 24 hours, and then cut with an ultramicrotome (RMC MT-7) to cut out the observation surface. The heating and holding after the pellet forming is for suppressing the measurement error due to the unevenness by fusing the toner particles to eliminate the voids between the particles.

(Domain observation)
For observation, an atomic force microscope (SPI3800N manufactured by SPM Seiko Instruments Inc., cantilever is SN-AF01) was used at room temperature, and a 2 μm square region was scanned in a micro viscoelastic mode and observed. In order to confirm the detailed dispersion state of the domain / matrix resin, three or more 2 μm square regions where wax and pigment were not dispersed were searched and measured. The domain diameter was measured as the domain diameter by the longest diameter of the domain, that is, the distance at which the two parallel lines contacting the domain took the maximum distance.

<External additive treatment of toner particles>
Each of the toner particles [1] to [4] and the comparative toner particles [5] to [8] are 1% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68), hydrophobic Titanium oxide (number average primary particle size = 20 nm, hydrophobization degree = 63) is added in a proportion of 1% by mass and zinc stearate is added in an amount of 0.2% by mass, and “Henschel mixer” (Mitsui Miike Chemical Industries, Ltd.) is added. Then, coarse particles were removed using a sieve having an opening of 45 μm, and toners [1] to [4] and comparative toners [5] to [8] were obtained.

<Preparation of developer>
For toners [1] to [4] and comparative toners [5] to [8], a ferrite carrier having a volume average particle diameter of 60 μm coated with a silicone resin is mixed so that the toner concentration becomes 6% by mass. Then, developers [1] to [4] as two-component developers and comparative developers [5] to [8] were prepared.

(Evaluation)
The combination as shown in Table 5 using the photoconductor and developer (toner) produced as described above is incorporated into a “bizhubPRO1050” remodeling machine to evaluate low-temperature fixability and black spot (BS). went.

(1) Low temperature fixability (Evaluation method)
Evaluation of low-temperature fixability was performed by changing the fixing temperature in the range of 140 to 190 ° C. in increments of 5 ° C. with a modified “bizhubPRO1050” machine, and a solid image of 1.5 cm × 1.5 cm (attachment amount 10.0 mg / cm ² ), each image is folded in half from the middle, and the peel resistance of the image is visually evaluated. Between the fixing temperature when the image is slightly peeled and the lower limit fixing temperature at which no peeling occurs. The temperature was defined as the minimum fixing temperature.

  The following evaluation criteria of good (◯) or higher were considered acceptable.

(Evaluation criteria)
Excellent (A): The minimum fixing temperature is 155 ° C. or lower.

  Good (O): The minimum fixing temperature is higher than 155 ° C. and not higher than 165 ° C.

  Practical use (Δ): The minimum fixing temperature is higher than 165 ° C. and 170 ° C. or lower.

  Defect (x): The minimum fixing temperature is 175 ° C. or higher.

(2) Black spot (BS) evaluation (Evaluation method)
Plaque spot-like image defects are printed on an A3 half-tone image (image density 0.4) after copying 30000 sheets, and the periodicity coincides with the period of the photoconductor. The number of image defects was determined per rotation of the photoreceptor.

(Evaluation criteria)
Excellent (◎): Number of black spot-like image defects is less than 4 Pass (○): Number of black spot-like image defects is less than 9 Fail (×): Number of black spot-like image defects However, 9 or more evaluation results are shown in Table 5.

  The combination of the comparative photoreceptors 1 (Pc and Rz are large) and the comparative photoreceptor 2 (Pc and Rz are small) of Comparative Examples 1 and 2 and the developer of the present invention has good fixability. However, image staining due to black spots occurred, and the photoreceptors of the present invention of Comparative Examples 3 and 5, the comparative developer 5 (the mass average molecular weight of the matrix resin A4 was large), and the comparative developer 7 (the domain resin was In many combinations, the fixing performance is inferior. Further, the combination of the photoreceptor of the present invention of Comparative Examples 4 and 6 and the comparative developer 6 (domain resin has a low molecular weight) outside the present invention and the comparative developer 8 (low domain resin) causes black spots. Image smudges occur frequently.

  Further, in the examples 10 and 11 in which the photosensitive member 4 and the photosensitive member 5 of the present invention were used and the developer 2 was used, the range result of the fixing minimum temperature black spot was “下限” level. 12 using the photoconductor 3 and the photoconductor 6 of the present invention and using the developer 2, the determination level of the minimum fixing temperature was “「 ”and the result of the black spot was“ ◯ ”level.

  As is apparent from the above results, the image forming method of the present invention has excellent characteristics at the minimum fixing temperature and the black spot.

Claims (3)

  In an image forming method in which an electrostatic latent image formed on an electrophotographic photosensitive member is visualized using toner, the electrophotographic photosensitive member is formed by sequentially laminating at least a photosensitive layer and a surface layer on a conductive support. The electrophotographic photosensitive member is characterized in that the surface layer contains inorganic fine particles, and the peak count value Pc of the surface layer is 200 or more and 350 or less, and the toner is at least bound. A toner for developing an electrostatic charge image containing a resin and a colorant, wherein the binder resin is composed of at least two types of resins having a domain matrix structure composed of a domain resin and a matrix resin, and the mass average molecular weight of the domain resin is 150. From 5,000 to 600,000, and the weight average molecular weight of the matrix resin is from 15,000 to 60,000. Image forming method, wherein the amount is less than 25 wt% 5 wt% or more based on the entire binder resin.   2. The image forming method according to claim 1, wherein the maximum height roughness Rz of the surface layer of the electrophotographic photosensitive member is 0.05 μm or more and 0.20 μm or less.   The image forming method according to claim 1, wherein the particle diameter of the domain resin is 70 nm or more and 300 nm or less.