Toner particles for electrostatic charge image development and toner composition for electrostatic charge image development

Abstract

Provided are toner particles for electrostatic charge image development, which are hardly affected by the particle size of resin fine particles and have more excellent fixability and heat-resistant storage properties. The toner particles for electrostatic charge image development of the present invention are characterized in that they contain a toner masterbatch and a resin film covering the toner masterbatch, the surface of the toner masterbatch has recesses, the recesses include recesses with a depth of 50 to 500 nm, the resin film has a film (A) part with a thickness of 10 nm or more and less than 50 nm and a film (B) part with a thickness of 50 nm or more and 500 nm or less, and the film (B) part is present on the recesses.

Description

Technical Field

[0001] The present invention relates to toner particles for developing an electrostatic charge image and a toner composition for developing an electrostatic charge image. Background Art

[0002] Electrophotography is widely used as one of the image forming methods in copiers, printers, facsimiles, etc. In general, image formation using electrophotography has: a charging step of using a charging blade, a charging brush, etc. to irradiate laser light, LED light, etc. on a photoconductive insulator (photosensitive member) that is equally charged to form an electrostatic latent image, and using static electricity to attach toner for developing an electrostatic charge image (the same meaning even when simply referred to as toner hereinafter) to the electrostatic latent image to form a toner image; a transfer step of transferring the toner image to a recording medium such as a recording medium to be recorded; and a fixing step of melting the transferred toner image on the recording medium by contacting with a heat medium, irradiating infrared rays, etc. and then releasing heat for fixing.

[0003] Regarding such toner, from the viewpoint of power saving, in order to obtain good fixability in a low temperature range, improve high temperature storage stability, and improve anti-blocking properties, toner having a core-shell structure is used in which a toner masterbatch using a low melting point binder resin is covered with a resin film composed of a resin having a glass transition temperature (Tg) higher than that of the binder resin of the toner masterbatch.

[0004] In addition, when the resin film forms a homogeneous film, there is a case where even if pressure is applied to the toner in the above fixing step, the resin film is not easily broken, and there is a problem that it is difficult to fix the toner well on the recording medium. Therefore, Patent Document 1 points out that toner for developing an electrostatic charge image in which cracks are observed in the resin film in a direction substantially perpendicular to the surface of the toner masterbatch from the interface between the resin particles is easily broken, thereby improving fixability to a recording medium, etc., and further showing excellent heat-resistant storage properties.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-026126 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The toner for developing an electrostatic charge image disclosed in Patent Document 1 can obtain a toner with excellent fixability and heat-resistant storage property for a recording medium or the like by forming cracks in a direction substantially perpendicular to the surface of the toner core particles inside the shell layer. Therefore, it is necessary to arrange the resin fine particles in a state where cracks are generated on the surface of the toner core particles. If there are irregularities on the surface of the toner core particles, cracks in a direction substantially perpendicular to the surface of the toner core particles cannot be formed, and thus there is a concern that a toner with excellent fixability and heat-resistant storage property for a recording medium or the like cannot be obtained. In addition, the cracks are related to the exudation of the toner core particles, and there is a possibility of a decrease in heat-resistant storage property. To prevent this drawback, it is considered necessary to increase the particle size of the resin fine particles (particle size: 100 nm) to prevent exudation. Therefore, there are drawbacks such as a small degree of freedom in toner design and limited applicable image forming apparatuses. Further, in the manufacturing process, spheroidization treatment is indispensable, and there is a concern about an increase in manufacturing cost.

[0010] Therefore, an object of the present invention is to provide toner particles for developing an electrostatic charge image, which use a toner master particle containing recesses, are hardly affected by the particle size of the resin fine particles, and have more excellent fixability and heat-resistant storage property.

[0011] Method for solving the problem

[0012] To solve the above problems, the toner particles for developing an electrostatic charge image of the present invention are characterized by having a toner master particle containing specific recesses and a resin film having a specific structure. That is, the present invention is as follows.

[0013] The present invention (1) is a toner particle for developing an electrostatic charge image, which is characterized by containing a toner master particle and a resin film covering the toner master particle, the surface of the toner master particle has recesses, the recesses include recesses with a depth of 50 to 500 nm, the resin film has a film (A) portion with a thickness of 10 nm or more and less than 50 nm and a film (B) portion with a thickness of 50 nm or more and 500 nm or less, and the film (B) portion exists on the recesses.

[0014] The present invention (2) is the toner particle for developing an electrostatic charge image of the above invention (1), which is characterized in that the film (B) portion is a resin layer in which a plurality of resin layers are laminated.

[0015] The present invention (3) is the toner particle for developing an electrostatic charge image of the above invention (2), which is characterized in that in the film (B) portion, the lamination direction of the plurality of resin layers is a direction away from the surface of the toner master particle.

[0016] The present invention (4) is toner particles for developing an electrostatic latent image in any one of the above-mentioned inventions (1) to (3), characterized in that, with respect to the resin film contained in the toner particles for developing an electrostatic latent image, the proportion of the total of the film (B) portions contained in the resin film is 30 to 60%.

[0017] The present invention (5) is toner particles for developing an electrostatic latent image in any one of the above-mentioned inventions (1) to (4), characterized in that the average particle diameter of the toner particles for developing an electrostatic latent image is 3 to 15 μm.

[0018] The present invention (6) is a toner composition for developing an electrostatic latent image, which contains toner particles for developing an electrostatic latent image in any one of the above-mentioned inventions (1) to (5).

[0019] Advantages of the Invention

[0020] According to the present invention, it is possible to provide toner particles for developing an electrostatic latent image, which use a toner masterbatch having specific irregularities, are hardly affected by the particle diameter of resin fine particles, and have more excellent fixability and heat-resistant storage properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is an explanatory view of cross-sections of a plurality of toner particles for developing an electrostatic latent image. DETAILED DESCRIPTION OF THE INVENTION

[0022] In the present invention, when a compound name is simply given, it is assumed to include all its isomers.

[0023] In the present invention, when simply referred to as "toner", it means a toner composition containing toner particles for developing an electrostatic latent image.

[0024] <<<Toner Particles for Developing an Electrostatic Latent Image>>>

[0025] In the present invention, toner particles for developing an electrostatic latent image are sometimes simply referred to as toner particles.

[0026] The toner particles for developing an electrostatic latent image of the present invention contain a toner masterbatch and a resin film covering the toner masterbatch.

[0027] The average particle diameter of the toner particles for developing an electrostatic latent image of the present invention is not particularly limited as long as the effects of the present invention are not impaired. For example, it can be set to 3 to 15 μm, preferably 3 to 12 μm, and more preferably 3 to 10 μm. By setting the average particle diameter of the toner particles for developing an electrostatic latent image within this range, it is possible to obtain effects such as being relatively easy to manufacture, being able to control the usage amount of toner particles during printing, and obtaining clear printing.

[0028] It should be noted that the average particle diameter of the toner particles is the volume average particle diameter, which can be measured using a commercially available device such as a Coulter counter.

[0029] The surface of the toner masterbatch according to the present invention has recesses, and the depth of the recesses is 50 to 500 nm.

[0030] The resin film according to the present invention has a film (A) portion with a thickness of 10 nm or more and less than 50 nm and a film (B) portion with a thickness of 50 nm or more and 500 nm or less.

[0031] The film (B) portion is present on the recesses of the toner masterbatch.

[0032] The composition of the toner particles for developing a static charge image according to the present invention will be described in detail below.

[0033] <<Composition of Toner Particles for Developing a Static Charge Image>>

[0034] Figure 1 An explanatory diagram of the cross-section of the toner particles for developing a static charge image is illustrated. Based on the following Figure 1 Details will be described. Figure 1 is a magnified photograph of a single toner particle 10 for developing a static charge image. For the toner particle 10 for developing a static charge image, the toner masterbatch 11 is covered with a resin film 12, and recesses 13, protrusions 14, and flat portions 15 (only one example is shown) are present on the surface of the toner masterbatch 11. It is shown that a film (B) portion 16 is formed in the recesses 13. In addition, a film (A) portion 17 is formed near the protrusions 14 and the flat portions 15.

[0035] <Toner Masterbatch>

[0036] The toner masterbatch according to the present invention constitutes the core material of the toner particles for developing a static charge image and is covered with a resin film.

[0037] The shape of the toner masterbatch is not particularly limited within the range that does not impair the effects of the present invention, and is not limited to a spherical shape or a shape generally regarded as spherical. The roundness of the toner masterbatch is 0.90 to 0.96, preferably 0.92 to 0.96. When the roundness of the toner masterbatch is within this range, the fluidity of the toner masterbatch during manufacturing is excellent, so that the resin fine particles can be uniformly attached to the toner masterbatch. At the same time, since it has many recesses, it is preferred as the raw material of the toner particles for developing a static charge image according to the present invention.

[0038] It should be noted that the roundness is represented by roundness = π · (diameter of a circle having the same area as the particle image) / (perimeter of the particle image), and can be obtained using a flow-type particle image analyzer (for example, manufactured by Sysmex Corporation, trade name: FPIA-2000).

[0039] The toner masterbatch involved in the present invention has recesses on its surface. The depth of the recesses is 50 nm to 500 nm, preferably 100 nm to 400 nm. When the depth of the recesses is within this range, a film (B) portion of a resin film described later can be formed on the recesses with a thickness of 50 to 500 nm. Due to the presence of this film (B) portion, the heat-resistant storage property of the toner particles is excellent.

[0040] In addition, the surface of the toner masterbatch has protrusions and flat portions. The protrusions are configured such that the radius of curvature of the vertex of the protrusion (or the radius of the inscribed sphere in the plane forming the angle when there is an angle at the vertex) is shorter than the radius of a sphere having a diameter equal to the length of the longest straight line contained in the toner masterbatch including the protrusion. In addition, the flat portions are configured such that not only the plane, but the radius of curvature of the flat portion is the same as or larger than the radius of a sphere having a diameter equal to the length of the longest straight line contained in the toner masterbatch including the flat portion.

[0041] Here, the depth of the recesses is defined as the shortest distance between the reference plane, which is the tangent plane of the vertex of the protrusion adjacent to the recess or the surface of the flat portion near the intersection of the inner wall of the recess and the flat portion of the flat portion adjacent to the recess, and the bottommost part of the recess. That is, it is defined as the perpendicular linear distance from the bottommost part of the recess to the lowest (the shortest distance from the bottommost part of the recess) reference plane adjacent to the recess. It is calculated from the TEM image of a sample obtained by slicing the toner masterbatch or toner based on the above reference.

[0042] In addition, when one recess approaches another recess via a protrusion or a flat portion, it is assumed that the tangent plane of the vertex of the protrusion or the surface of the flat portion is not included in the reference plane of the depth of the recess. For example, when two recesses form a "W" shape, it is assumed that the protrusion in the middle of the "W" is not included in the protrusions forming the reference plane. That is, when the protrusion in the middle of the "W" is lower than the ends, the "W"-shaped recess is regarded as a large recess formed by combining two recesses.

[0043] Here, the opening shape of the recesses is not particularly limited. That is, it is not limited to geometric shapes such as circular and elliptical shapes, and can be set to a circumferential shape including irregular straight portions and curved portions. In addition, the shape in the depth direction is not particularly limited, and is not limited to geometric shapes such as conical and spherical shapes, and can be set to a three-dimensional shape including irregular straight portions and curved portions.

[0044] The size of the opening of the concave portion (the diameter or the minimum length of the opening portion) is not particularly limited, as long as it is a size that allows the resin particles for forming the resin film described later to penetrate inside. For example, as the lower limit value, it can be set to 10 nm or more, 20 nm or more, 30 nm or more, 50 nm or more. The upper limit value is not particularly limited and can be set to 1000 nm or less, 800 nm or less, 600 nm or less, 500 nm or less. By the collision of the resin particles against the inner wall (including the bottom) of the concave portion, the resin particles are crushed to form a layer. Thereafter, other resin particles further collide and melt on the layered resin particles to form a single layer or are stacked to form a stacked structure. By repeating this process, a film (B) portion is formed on the concave portion. Here, the film (B) portion being on the concave portion does not necessarily mean that it completely exists within the concave portion, but also means that part or all of the film (B) portion exists on the concave portion.

[0045] The number of concave portions contained in the toner masterbatch according to the present invention is not particularly limited, as long as it is at least 1 or more. The total opening area of all the concave portions contained in the toner masterbatch is preferably 20% or more, more preferably 30% or more, and further preferably 40% or more of the surface area of the toner masterbatch. When the total opening area of all the concave portions contained in the toner masterbatch is within this range, toner particles for electrostatic charge image development with excellent fixability to the recording medium and excellent heat-resistant storage properties can be obtained.

[0046] The toner masterbatch according to the present invention contains a binder resin. The binder resin contained in the toner masterbatch is not particularly limited as long as it is a resin that has been conventionally used as a binder resin for toner. Examples of the binder resin include thermoplastic resins such as styrene resins, acrylic resins, styrene-acrylic resins, polyethylene resins, polypropylene resins, vinyl chloride resins, polyester resins, polyamide resins, polyurethane resins, polyvinyl alcohol resins, vinyl ether resins, N-vinyl resins, and styrene-butadiene resins. They can be used alone or in combination of multiple types. Among them, from the viewpoints of the dispersibility of the colorant in the binder resin, the chargeability of the toner, and the fixability to the recording medium, it is preferable to contain a polystyrene resin and a polyester resin. The polystyrene resin and the polyester resin will be described below.

[0047] The polystyrene resin may be a homopolymer of styrene or a copolymer with other comonomers copolymerizable with styrene. Specific examples of other comonomers copolymerizable with styrene include: p-chlorostyrene, vinylnaphthalene, ethylenically unsaturated monoolefins such as ethylene, propylene, butene, and isobutene, vinyl halides such as vinyl chloride, vinyl bromide, and vinyl fluoride, vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate, and vinyl butyrate, (meth)acrylate esters such as methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, dodecyl acrylate, n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate, other acrylic derivatives such as acrylonitrile, methacrylonitrile, and acrylamide, vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether, vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone, N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone. These comonomers can be combined in two or more to copolymerize with styrene monomers.

[0048] The polyester resin may be a substance obtained by polycondensation or co-polycondensation of a diol or higher alcohol component and a diacid or higher carboxylic acid component. As the components used in synthesizing the polyester resin, the following alcohol components and carboxylic acid components can be cited.

[0049] Specific examples of the diol or higher alcohol component include: diols such as ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,4-butenediol, 1,5-pentanediol, 1,6-hexanediol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol; bisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, and polyoxypropylenated bisphenol A; and triols or higher alcohols such as sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, diglycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, and 1,3,5-tris(hydroxymethyl)benzene.

[0050] Specific examples of the carboxylic acid component having 2 or more carboxyl groups include: maleic acid, fumaric acid, citraconic acid, itaconic acid, pentenedioic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, malonic acid or n-butyl succinic acid, n-butene succinic acid, isobutyl succinic acid, isobutene succinic acid, n-octyl succinic acid, n-octene succinic acid, n-dodecyl succinic acid, n-dodecene succinic acid, isododecyl succinic acid, isododecene succinic acid and other dibasic carboxylic acids such as alkyl or alkenyl succinic acids, 1,2,4-benzenetricarboxylic acid (trimellitic acid), 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylenecarboxypropane, 1,2,4-cyclohexanetricarboxylic acid, tetra(methylenecarboxy)methane, 1,2,7,8-octanetetracarboxylic acid, mellitic acid, EMPOL trimellitic acid and other carboxylic acids having 3 or more carboxyl groups. These carboxylic acid components having 2 or more carboxyl groups may be ester-forming derivatives such as acid halides, acid anhydrides, and lower alkyl esters. Here, the meaning of "lower alkyl" is an alkyl group having 1 to 6 carbon atoms.

[0051] When the toner of the present invention is used as a magnetic one-component toner, as the binder resin, a resin having one or more functional groups selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and an epoxy group (such as a glycidyl group) in the molecule can be used. By using a binder resin having these functional groups in the molecule, the dispersibility of magnetic powder, charge control agent, etc. in the binder resin can be improved. It should be noted that the presence or absence of these functional groups can be confirmed by a Fourier transform infrared spectrophotometer (FT-IR). In addition, the amount of these functional groups in the resin can be measured by a known method such as titration.

[0052] As the binder resin, a thermoplastic resin is preferably used because of its good fixability to the recording medium. It is also possible to not use a thermoplastic resin alone, but to add a crosslinking agent and a thermosetting resin to the thermoplastic resin. By introducing a partial crosslinked structure into the binder resin by adding a crosslinking agent and a thermosetting resin, the heat resistance storage property, durability, etc. of the toner can be improved without reducing the fixability of the toner. It should be noted that when a thermosetting resin is used, the amount of the crosslinked portion (gel amount) of the binder resin extracted by a Soxhlet extractor is preferably 10% by mass or less, more preferably 0.1% by mass or more and 10% by mass or less, relative to the mass of the binder resin.

[0053] As thermosetting resins that can be used together with thermoplastic resins, epoxy resins and cyanate ester resins are preferred. Specific examples of preferred thermosetting resins include bisphenol A epoxy resins, hydrogenated bisphenol A epoxy resins, novolac epoxy resins, polyalkylene ether epoxy resins, cycloaliphatic epoxy resins, and cyanate ester resins. These can be used alone or in combination of two or more.

[0054] The glass transition temperature (Tg) of the binder resin is preferably 40° C. to 70° C. If the glass transition temperature is too high, the low-temperature fixability of the carbon powder tends to decrease. If the glass transition temperature is too low, the heat-resistant storage stability of the carbon powder tends to decrease.

[0055] The glass transition temperature of the adhesive resin can be determined from the specific heat transition point of the adhesive resin using a differential scanning calorimeter (DSC). More specifically, a differential scanning calorimeter DSC-6200 manufactured by Seiko Corporation can be used as a measuring device to measure the endothermic curve of the adhesive resin and determine the glass transition temperature of the adhesive resin. Place 10 mg of the test sample in an aluminum pot, and use an empty aluminum pot as a control. The measurement is performed within a measurement temperature range of 25°C to 200°C, a heating rate of 10°C / min, and normal temperature and humidity. The glass transition temperature of the adhesive resin can be determined from the endothermic curve of the obtained adhesive resin.

[0056] The softening point of the binder resin is preferably 70° C. to 130° C., more preferably 80° C. to 120° C. The softening point of the polyester can be measured by a method based on JIS K7196:1991 "Test method for softening temperature of thermoplastic films and sheets by thermomechanical analysis" (Test method for softening temperature of thermoplastic films and sheets by thermomechanical analysis of thermoplastic films and sheets)".

[0057] The mass average molecular weight (Mw) of the binder resin is not particularly limited within the range not impairing the purpose of the present invention. Typically, the mass average molecular weight (Mw) of the binder resin is preferably 20,000 to 300,000, and more preferably 30,000 to 2,000,000. It should be noted that the mass average molecular weight of the binder resin can be determined by gel permeation chromatography (GPC) using a calibration curve prepared in advance using a standard polystyrene resin.

[0058] In addition, when the adhesive resin is a polystyrene-based resin, it is preferable that the adhesive resin has peaks in the low molecular weight region and the high molecular weight region in the molecular weight distribution measured by gel permeation chromatography or the like. Specifically, it is preferable to have a peak in the low molecular weight region in the range of a molecular weight of 3,000 or more and 20,000 or less, and it is preferable to have a peak in the high molecular weight region in the range of a molecular weight of 300,000 or more and 1,500,000 or less. In addition, for the polystyrene-based resin having such a molecular weight distribution, it is preferable that the ratio (Mw / Mn) of the number average molecular weight (Mn) to the mass average molecular weight (Mw) is 10 or more. By having a peak in the low molecular weight region and a peak in the high molecular weight region in the molecular weight distribution of the adhesive resin, toner with excellent low-temperature fixability and suppressed high-temperature migration can be obtained.

[0059] The toner masterbatch according to the present invention may contain other additives such as silica, titanium oxide, alumina, carbon, and magnetic powder (iron powder).

[0060] <Resin film>

[0061] The resin film according to the present invention is formed by aggregation of resin fine particles. The resin film is formed by deforming and adhering the resin fine particles by colliding with the toner masterbatch.

[0062] The resin film according to the present invention covers the entire surface or a part of the surface of the toner masterbatch. The coverage rate of the resin film covering the surface of the toner masterbatch is not particularly limited within the range that does not impair the effects of the present invention. For example, it can be set to 80% or more, preferably 85% or more, and more preferably 90% or more. By having the coverage rate of the resin film within this range, toner particles for electrostatic charge image development with excellent fixability to the recording medium and excellent heat-resistant storage properties can be obtained.

[0063] Regarding the coverage rate of the toner particles for electrostatic charge image development, using a transmission electron microscope, the cross-section of randomly selected toner particles for electrostatic charge image development is photographed in such a way that the entire cross-section of one particle is included in one image (for example, the magnification is set to 10,000 times), and the length of the outer peripheral part of the cross-section of the toner particles for electrostatic charge image development in the obtained image is measured, and then divided by the entire length of the outer peripheral part of the cross-section of the toner particles for electrostatic charge image development in the obtained image, thereby calculating the coverage rate of one toner particle for electrostatic charge image development. The same measurement is performed on 10 toner particles for electrostatic charge image development, and the average value thereof is used as the coverage rate.

[0064] The resin film according to the present invention includes a film (A) part having a thickness of 10 nm or more and less than 50 nm and a film (B) part having a thickness of 50 nm or more and 500 nm or less. The film (B) part exists on the concave parts contained in the toner masterbatch.

[0065] The film (A) portion is mainly formed in the portions (convex portions or flat portions) other than the concave portions of the toner masterbatch. When the resin fine particles collide with the portions (convex portions or flat portions) other than the concave portions of the toner masterbatch, the resin fine particles form a film and grow in the thickness direction, and will be directly exposed. When the resin fine particles collide continuously, a film with a thickness of more than a certain value is shaved off by the collision, and a film (A) portion with a thickness of more than 10 nm and less than 50 nm is formed.

[0066] In the film (A) portion, the resin fine particles can be softened and melted to form a single-layer film, or multiple resin layers can be stacked.

[0067] The film (B) portion is formed on the upper part of the concave portion of the toner masterbatch. When the resin fine particles collide with the inner wall portion (including the bottom) of the concave portion of the toner masterbatch, the resin fine particles form a film, and the film grows in the thickness direction. In the concave portion, the formed film is protected by the inner wall of the concave portion, so the continuous collision of the resin fine particles is restricted. Therefore, the thickness of the film continues to grow until the film reaches a thickness above the depth of the concave portion, and a film (B) portion is formed. If the thickness of the film (B) portion reaches above the depth of the concave portion, it is exposed to the collision of the resin fine particles, and the film significantly exceeding from the inside of the concave portion is shaved off by the collision, and a film (B) portion with a thickness of 50 or more and 500 nm or less equal to the depth of the concave portion is formed.

[0068] The thickness of the film (B) portion only needs to be 50 to 500 nm, and as long as at least a part of it exists inside the concave portion of the toner masterbatch.

[0069] The film (B) portion can be a single-layer film formed by softening and melting the resin fine particles, or multiple resin layers can be stacked. When multiple resin layers are stacked in the film (B) portion, the stacking direction can be set to the direction away from the surface of the toner masterbatch.

[0070] In one electrostatic charge image developing toner particle, the total of the film (B) portion can be set to 10 to 80% of the entire resin film, preferably 30 to 60%. When the ratio (occupancy rate) of the total of the film (B) portion to the entire resin film is in this range, electrostatic charge image developing toner particles with excellent fixability to the recording medium and excellent heat-resistant storage properties can be obtained.

[0071] The coverage rate of the total of the film (B) part in the toner particles for developing an electrostatic charge image relative to the entire resin film (occupancy rate) can be obtained by the following method: Using a transmission electron microscope, photograph the cross-section of randomly selected toner particles for developing an electrostatic charge image in such a way that the entire cross-section of one particle is included in one image (for example, set the magnification to 10,000 times), measure the length of the film (B) part contained in the outer peripheral part of the cross-section of the toner particles for developing an electrostatic charge image in the obtained image, and divide it by the length of the outer peripheral part covering the whole in the cross-section of the toner particles for developing an electrostatic charge image in the obtained image. Perform the same measurement on 10 toner particles for developing an electrostatic charge image, and use the average value as the coverage rate of the total of the film (B) part relative to the entire resin film (occupancy rate).

[0072] The shape of the resin fine particles is not particularly limited, and spherical shape is preferred. Here, "spherical shape" is not limited to a true spherical shape, and includes a near-spherical shape as long as it is generally regarded as a spherical shape. For example, it is also included that the aspect ratio (L / S) is 1 to 2 in an ellipsoid when the major axis is L and the minor axis is S. When the resin fine particles are spherical, the symmetry is high when the resin fine particles collide with the inner wall in the concave part of the toner masterbatch, so that a uniform resin layer can be formed. If a uniform resin layer is formed, the lamination state becomes good, and in the toner masterbatch, the film (B) part can have a sufficient thickness, and the heat-resistant storage property of the toner particles for developing an electrostatic charge image is excellent.

[0073] The resin fine particles forming the resin film according to the present invention are not particularly limited as long as they do not hinder the effects of the present invention. From the viewpoint of easily forming a resin film having a specified structure, the resin fine particles forming the resin film are preferably a polymer of a monomer having an unsaturated bond. In addition, the resin fine particles are preferably resins that can be synthesized by soap-free emulsion polymerization. Because if resin fine particles are manufactured by soap-free emulsion polymerization, the particle diameters are uniform, and resin fine particles containing no or almost no surfactant can be prepared. The standard deviation (fluctuation) of the resin fine particle diameters is as described below.

[0074] Regarding the type of the monomer having an unsaturated bond, as long as a resin having sufficient physical properties as a resin film can be synthesized, there is no particular limitation. As the monomer having an unsaturated bond, a vinyl-based monomer is preferred. The α-position of the vinyl group contained in the vinyl-based monomer may be substituted with an alkyl group. In addition, the vinyl group contained in the vinyl-based monomer may be substituted with a halogen atom. The alkyl group that the vinyl group may have is preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. In addition, the halogen atom that the vinyl group may have is preferably a chlorine atom or a bromine atom, and more preferably a chlorine atom.

[0075] The vinyl-based monomer may have a nitrogen-containing polar functional group or a hydrocarbon group substituted with fluorine. When a vinyl-based monomer having a nitrogen-containing polar functional group is used in the production of a resin, the resulting resin can be given a positive charge. In addition, when a vinyl-based monomer having a hydrocarbon group substituted with fluorine is used in the production of a resin, the resulting resin can be given a negative charge. As the material of the resin film, when the above-mentioned positively charged resin or negatively charged resin is used, even if a charge control agent is not added to the toner masterbatch or the amount of the charge control agent added to the toner masterbatch is reduced, a toner that can be charged with a desired charge amount can be obtained.

[0076] Specific examples of monomers that do not have a nitrogen-containing polar functional group and a hydrocarbon group substituted with fluorine in the vinyl-based monomer include: styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-n-butylstyrene, p-tert-butylstyrene, p-n-hexylstyrene, p-n-octylstyrene, p-n-nonylstyrene, p-n-decylstyrene, p-n-dodecylstyrene, p-methoxystyrene, p-ethoxystyrene, p-phenylstyrene, p-chlorostyrene, 3,4-dichlorostyrene and other styrenes, ethylene, propylene, butene, isobutene and other ethylenically unsaturated monoolefins, vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride and other vinyl halides, vinyl acetate, vinyl propionate, vinyl benzoate, vinyl butyrate and other vinyl esters, (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid n-butyl ester, (meth)acrylic acid isobutyl ester, (meth)acrylic acid propyl ester, (meth)acrylic acid n-octyl ester, (meth)acrylic acid dodecyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid stearyl ester, (meth)acrylic acid 2-chloroethyl ester, (meth)acrylic acid phenyl ester, methyl α-chloroacrylate and other (meth)acrylic acid esters, acrylonitrile and other (meth)acrylic acid derivatives, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and other vinyl ethers, vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone and other vinyl ketones, vinyl naphthalenes. Among them, styrenes are preferred, and styrene is more preferred. These monomers can be used in combination of two or more.

[0077] Examples of vinyl-based monomers having a nitrogen-containing polar functional group include N-vinyl compounds, amino (meth)acrylic acid-based monomers, and methacrylonitrile (meth)acrylamide. Specific examples of N-vinyl compounds include N-vinyl compounds such as N-vinyl pyrrole, N-vinyl carbazole, N-vinyl indole, and N-vinyl pyrrolidone. In addition, preferred examples of amino (meth)acrylic acid-based monomers include compounds represented by the following formula.

[0078] CH2=C(R1)-(CO)-X-N(R2)(R3)

[0079] In the formula, R1 represents hydrogen or methyl. R2 and R3 each represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X represents -O-, -O-Q-, or -NH. Q represents an alkylene group having 1 to 10 carbon atoms, a phenylene group, or a combination of these groups.

[0080] Specific examples of R2 and R3 in the above formula include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethylhexyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl (lauryl), n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl (stearyl), n-nonadecyl, and n-eicosyl.

[0081] Specific examples of Q in the above formula include methylene, 1,2-ethane-diyl, 1,1-ethenyl, propane-1,3-diyl, propane-2,2-diyl, propane-1,1-diyl, propane-1,2-diyl, butane-1,4-diyl, pentane-1,5-diyl, hexane-1,6-diyl, heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl, p-phenylene, m-phenylene, o-phenylene, and the divalent group obtained by removing hydrogen from the 4-position of the phenyl group contained in benzyl.

[0082] Specific examples of the amino(meth)acrylate monomer represented by the above formula include, for example, N,N-dimethylamino(meth)acrylate, N,N-dimethylaminomethyl(meth)acrylate, N,N-diethylaminomethyl(meth)acrylate, 2-(N,N-methylamino)ethyl(meth)acrylate, 2-(N,N-diethylamino)ethyl(meth)acrylate, 3-(N,N-dimethylamino)propyl(meth)acrylate, 4-(N,N-dimethylamino)butyl(meth)acrylate, p-N,N-dimethylaminophenyl(meth)acrylate, p-N,N-diethylaminophenyl(meth)acrylate, p-N,N-dipropylaminophenyl(meth)acrylate, p-N,N-di-n-butylaminophenyl(meth)acrylate, p-N-laurylaminophenyl(meth)acrylate, p-N-stearylaminophenyl(meth)acrylate, (p-N,N-dimethylaminophenyl)methyl(meth)acrylate, (p-N,N-diethylaminophenyl)methyl(meth)acrylate, (p-N,N-di-n-propylaminophenyl)methyl(meth)acrylate, (p-N,N-di-n-butylaminophenyl)methylbenzyl(meth)acrylate, (p-N-laurylaminophenyl)methyl(meth)acrylate, (p-N-stearylaminophenyl)methyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylamide, N,N-diethylaminoethyl(meth)acrylamide, 3-(N,N-dimethylamino)propyl(meth)acrylamide, 3-(N,N-diethylamino)propyl(meth)acrylamide, p-N,N-dimethylaminophenyl(meth)acrylamide, p-N,N-diethylaminophenyl(meth)acrylamide, p-N,N-dipropylaminophenyl(meth)acrylamide, p-N,N-di-n-butylaminophenyl(meth)acrylamide, p-N-laurylaminophenyl(meth)acrylamide, p-N-stearylaminophenyl(meth)acrylamide, (p-N,N-dimethylaminophenyl)methyl(meth)acrylamide, (p-N,N-diethylaminophenyl)methyl(meth)acrylamide, (p-N,N-di-n-propylaminophenyl)methyl(meth)acrylamide, (p-N,N-di-n-butylaminophenyl)methyl(meth)acrylamide, (p-N-laurylaminophenyl)methyl(meth)acrylamide, (p-N-stearylaminophenyl)methyl(meth)acrylamide, etc.

[0083] The vinyl monomer having a fluorine-substituted hydrocarbon group is not particularly limited as long as it is a substance used in the production of fluororesin. Specific examples of the vinyl monomer having a fluorine-substituted hydrocarbon group include fluoroalkyl (meth)acrylates such as 2,2,2-trifluoroethyl acrylate, 2,2,3,3-tetrafluoropropyl acrylate, 2,2,3,3,4,4,5,5-octafluoropentyl acrylate, 1H,1H,2H,2H-heptadecafluorodecyl acrylate, vinylidene chloride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, trifluoropropene, hexafluoropropene, and hexafluoropropylene. Among them, fluoroalkyl (meth)acrylates are preferred.

[0084] The addition polymerization method of the monomer having an unsaturated bond is not limited within the scope not impairing the object of the present invention, and an optional method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization can be selected. Among these production methods, emulsion polymerization is preferred in view of easily obtaining resin particles with uniform particle sizes.

[0085] As the polymerization initiator that can be used in the polymerization of the above-described vinyl monomer, known polymerization initiators such as potassium persulfate, acetyl peroxide, decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, and 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile can be used. The amount of these polymerization initiators used is preferably 0.1% by mass or more and 15% by mass or less based on the total mass of the monomer.

[0086] The polymerization method of the above-described vinyl monomer is not limited within the scope not impairing the object of the present invention, and an optional method such as solution polymerization, bulk polymerization, emulsion polymerization, or suspension polymerization can be selected. Among these production methods, emulsion polymerization is preferred in view of easily obtaining resin particles with uniform particle sizes.

[0087] As a method for producing resin particles by emulsion polymerization, a soap-free emulsion polymerization method that does not use an emulsifier (surfactant) is preferred. In the soap-free emulsion polymerization method, the radicals of the initiator generated in the aqueous phase combine with the monomer slightly dissolved in the aqueous phase, and as the polymerization proceeds, particle nuclei of insoluble resin particles are formed. By using the soap-free emulsion polymerization method, resin particles with a narrow particle size distribution width can be easily obtained, and in addition, the average particle size of the resin particles can be easily controlled within the range of 10 to 100 nm. Therefore, resin particles with uniform particle sizes can be obtained by using the soap-free emulsion polymerization method.

[0088] By using resin fine particles with uniform particle size obtained by the soap-free emulsion polymerization method, fluctuations in the adhesion of the resin fine particles to the toner masterbatch can be reduced, thereby forming a homogeneous resin film with uniform thickness. In addition, since no emulsifier (surfactant) is used in the formation of the resin fine particles manufactured by the soap-free emulsion polymerization method, a resin film that is hardly affected by moisture can be formed by using the resin fine particles obtained by the soap-free emulsion polymerization method.

[0089] The resin fine particles can be prepared in such a manner that they contain, as required, the above-mentioned colorant, charge control resin, etc. When a sufficient amount of charge control agent is contained in the resin fine particles, the toner masterbatch may not contain a charge control agent.

[0090] The glass transition temperature of the resin fine particles (the glass transition temperature of the resin constituting the resin fine particles) is not particularly limited. For example, it can be set to 50 to 100 °C, preferably 50 to 80 °C. When the glass transition temperature is within this range, it is easy to fix the toner on the recording medium in the low-temperature region, and toner aggregation hardly occurs during high-temperature storage (high heat-resistant storage property).

[0091] The glass transition temperature of the resin constituting the resin fine particles can be determined from the transition point of the specific heat of the resin constituting the resin fine particles using a differential scanning calorimeter (DSC).

[0092] The softening point of the resin constituting the resin fine particles is not particularly limited within the range that does not impair the object of the present invention. Typically, the softening point of the resin constituting the resin fine particles is preferably 100 °C or higher and 250 °C or lower, more preferably 110 °C or higher and 240 °C or lower. In addition, it is preferable that the softening point of the resin constituting the resin fine particles is higher than the softening point of the binder resin contained in the toner masterbatch, and more preferably 10 to 140 °C higher. By setting the temperature characteristics of the resin constituting the resin fine particles within such a range, when the resin fine particles are embedded in the toner masterbatch, the portion where the resin fine particles come into contact with the toner masterbatch is difficult to deform, so it is easy to form convex portions from the shape of the resin fine particles before the resin film changes on the inner surface of the resin film.

[0093] The softening point of the resin constituting the resin fine particles can be measured using a flow tester. The method for measuring the softening point of the resin constituting the resin fine particles using a flow tester will be described below.

[0094] The average particle size of the resin fine particles is not particularly limited within the range that does not impair the effects of the present invention. For example, it can be set to 10 to 100 nm, preferably 20 to 80 nm, more preferably 20 to 50 nm. When the average particle size of the resin fine particles is within this range, it is easy to form the film (B) portion by colliding with the inner wall portion through the concave portion of the toner masterbatch, and aggregation is difficult.

[0095] The average particle diameter of the resin particles can be calculated by measuring the particle diameters of 50 or more resin particles from an electron micrograph taken using a scanning microscope and determining the number-average particle diameter.

[0096] As described above, it is important to make the particle diameters of the respective resin particles uniform, that is, to reduce the standard deviation (fluctuation) of the resin particle diameters. The standard deviation of the resin particle diameters is not particularly limited as long as the effects of the present invention are not impaired. For example, it is preferably 0.15 or less, more preferably 0.14 or less. The lower limit value of the standard deviation of the resin particle diameters is 0.0. When the standard deviation of the resin particle diameters is within this range, even for resin particles having the same average particle diameter, since the fluctuation of the respective particle diameters of the resin particles is small and the degree of aggregation of the resin particles with each other is small, the resin particles easily enter the concave portions of the toner masterbatch and easily form the film (B) portion. The standard deviation of the resin particle diameters can be measured using a publicly known particle measuring instrument.

[0097] The standard deviation of the resin particle diameters can be adjusted not only by using a polymerization method that easily makes the particle diameters of the resin particles uniform, but also by methods such as (1) sieving the resin particles to remove particles larger and smaller than a specified particle diameter, and (2) applying ultrasonic waves to disperse the aggregated resin particle aggregates.

[0098] The weight-average molecular weight (Mw) of the resin constituting the resin particles is not particularly limited as long as the object of the present invention is not impaired. Typically, the weight-average molecular weight is preferably 20,000 or more and 1,500,000 or less. The weight-average molecular weight (Mw) of the resin constituting the resin particles can be measured by gel permeation chromatography by a conventionally known method.

[0099] <Others>

[0100] The toner particles for developing a static charge image of the present invention can be treated with a desired additive after forming a resin film on the surface of the toner masterbatch.

[0101] The type of the additive is not particularly limited as long as the object of the present invention is not impaired, and can be selected from the additives used in conventional toners. Specific examples of the additive include metal oxides such as silica, alumina, titanium oxide, magnesium oxide, zinc oxide, strontium titanate, and barium titanate. These additives can be used alone or in combination of two or more. The particle diameter of the additive is not particularly limited as long as the object of the present invention is not impaired. Typically, it is preferably 0.01 μm or more and 1.0 μm or less.

[0102] The amount of the additive used is not particularly limited as long as the object of the present invention is not impaired. Typically, the amount of the additive used is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.2% by mass or more and 5% by mass or less, based on the total mass of the toner particles produced by forming a resin film on the surface of the toner masterbatch. If the amount of the additive used is too small, the hydrophobicity of the toner tends to decrease. As a result, it is likely to be affected by water molecules in the air in a high-temperature and high-humidity environment, and problems such as a decrease in the image density of the formed image and a decrease in the fluidity of the toner due to an extreme decrease in the charge amount of the toner are likely to occur. In addition, if the amount of the additive used is too large, there is a concern that the image density may decrease due to overcharging of the toner.

[0103] The toner particles for electrostatic charge image development of the present invention can also be mixed with a desired carrier and used as a toner composition for electrostatic charge image development (hereinafter sometimes simply referred to as a two-component developer) constituting a two-component developer. When preparing the two-component developer, it is preferable to use a magnetic carrier as the carrier.

[0104] As a preferable carrier when the toner particles for electrostatic charge image development of the present invention are made into a two-component developer, a material in which a carrier core material is covered with a resin can be cited.

[0105] As the carrier core material, for example, particles such as iron, iron oxide-treated iron, reduced iron, magnetite, copper, silicon steel, ferrite, nickel, cobalt, particles of alloys of these materials with manganese, zinc, aluminum, etc., particles such as iron-nickel alloy and iron-cobalt alloy, ceramic particles such as titanium oxide, aluminum oxide, copper oxide, magnesium oxide, lead oxide, zirconium oxide, silicon carbide, magnesium titanate, barium titanate, lithium titanate, lead titanate, lead zirconate, lithium niobate, particles of high dielectric constant substances such as ammonium dihydrogen phosphate, potassium dihydrogen phosphate, and Rochelle salt, and resin carriers in which the above magnetic particles are dispersed in a resin can be cited.

[0106] As the resin covering the carrier, for example, (meth)acrylic polymers, styrene polymers, styrene-(meth)acrylic copolymers, olefin polymers (such as polyethylene, chlorinated polyethylene, polypropylene), polyvinyl chloride, polyvinyl acetate, polycarbonate, cellulose resins, polyester resins, unsaturated polyester resins, polyamide resins, polyurethane resins, epoxy resins, silicone resins, fluororesins (such as polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride), phenolic resins, xylene resins, diallyl phthalate resins, polyacetal resins, and amino resins can be cited. These resins can be used alone or in combination of two or more.

[0107] The particle size of the carrier is not particularly limited as long as the object of the present invention is not impaired. In terms of the particle size measured by an electron microscope, it is preferably 20 μm or more and 200 μm or less, more preferably 30 μm or more and 150 μm or less.

[0108] The apparent density of the carrier is not particularly limited within the range that does not impair the object of the present invention. The apparent density varies depending on the carrier composition and surface structure. Typically, it is preferably 2400 kg / m 3 or more and 3000 kg / m 3 or less.

[0109] When the toner for developing a static charge image of the present invention is used as a two-component developer, the content of the toner is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, based on the mass of the two-component developer. By setting the content of the toner in the two-component developer within this range, the image density of the formed image can be maintained at a desired density, and contamination caused by the toner inside the image forming apparatus and adhesion of the toner to the transfer recording medium or the like can be suppressed by suppressing toner scattering.

[0110] <<Method for manufacturing toner particles for developing a static charge image>>

[0111] The method for manufacturing the toner for developing a static charge image described above is not particularly limited as long as it forms a specified structure with the toner masterbatch and the resin film respectively. In addition, if necessary, an additive can be added to the surface of the toner masterbatch covered with the resin film. Hereinafter, the method for manufacturing the toner masterbatch, the method for forming the resin film, and the addition treatment method, which are preferred methods for manufacturing the toner for developing a static charge image, will be described in detail.

[0112] <<Method for manufacturing toner masterbatch>>

[0113] The method for manufacturing the toner masterbatch is not particularly limited as long as it can disperse optional components such as a colorant, a release agent, a charge control agent, and magnetic powder well in the binder resin. As specific examples of preferred methods for manufacturing the toner masterbatch, the following methods can be cited: after mixing the binder resin and other additives with a mixer or the like, the binder resin and the components incorporated in the binder resin are melt-kneaded using a kneader such as a single-screw or twin-screw extruder, and the cooled kneaded product is pulverized and classified. The average particle diameter of the toner masterbatch is not particularly limited within the range that does not impair the object of the present invention, and is generally preferably 2 μm or more and 15 μm or less. In addition, after pulverizing the kneaded product of the toner masterbatch, a spheroidization treatment can be performed within the range that does not impair the effects of the present invention.

[0114] <<Method for forming resin film>>

[0115] The resin film is formed using resin fine particles. More specifically, it is formed through the following steps: causing the resin fine particles to collide with the surface of the toner masterbatch, adhering to the surface of the toner masterbatch, and forming a resin fine particle layer covering the surface of the resin fine particles.

[0116] As a method for forming a resin film with resin fine particles, a known method can be used, and it can be set as a method using a mixing device capable of mixing a toner masterbatch and resin fine particles under dry or wet conditions. In a specific example, a method of forming a resin film on the surface of a toner masterbatch can be cited by using a mixing device capable of attaching resin fine particles to the surface of the toner masterbatch and simultaneously applying mechanical external force to the toner masterbatch with resin fine particles attached to its surface. As the mechanical external force, shear force applied to the toner masterbatch due to sliding between toner masterbatches, sliding between the toner masterbatch and the inner wall of the device, rotor, stator, etc. when the toner masterbatch moves at high speed in a narrow space in the mixing device, and impact force applied to the toner masterbatch due to collision between toner masterbatches or collision between the toner masterbatch and the inner wall of the device, etc. can be cited.

[0117] More specifically, by mixing the toner masterbatch and resin fine particles in a mixing device, the resin fine particles collide with and adhere to the surface of the toner masterbatch. The resin fine particles attached to the concave part of the toner masterbatch (there are also cases on the film) further collide with the subsequent resin fine particles on the concave part, do not discharge from the concave part, but are integrated or laminated due to melting caused by the energy of the collision, increasing the film thickness, and forming a film with a thickness of 50 nm or more and 500 nm or less (film (B) part). On the other hand, regarding the resin fine particles attached to parts other than the concave part of the toner masterbatch, the subsequent resin fine particles repeatedly adhere to and grind the previously attached film, forming a film with a thickness of 10 nm or more and less than 50 nm (film (A) part).

[0118] In the above method, if the mechanical external force is too strong, the deformation of the resin fine particles becomes too large, so sometimes the surface of the resin film cannot be formed. Depending on the device and material used in the formation of the resin film, the conditions for forming a resin film with a specified unevenness are different. By gradually changing the operating conditions in such a way that the mechanical external force generated on the toner masterbatch covered with resin fine particles is not too strong and confirming the structure of the resin film of the toner under each condition, the preferred conditions for forming a specified resin film for various devices can be determined.

[0119] The usage amount of the resin fine particles is not particularly limited as long as it does not hinder the effects of the present invention. Typically, the usage amount of the resin fine particles is preferably 1 part by mass or more and 20 parts by mass or less, more preferably 3 parts by mass or more and 15 parts by mass or less, relative to 100 parts by mass of the toner masterbatch. When the usage amount of the resin fine particles is within this range, the surface of the toner masterbatch can be completely covered, and it is difficult to agglomerate during high-temperature storage, improving the heat-resistant storage property.

[0120] As a device capable of covering toner master particles with resin fine particles and simultaneously applying mechanical external force to the toner master particles covered with resin fine particles, for example, Hybridizer NHS-1 (manufactured by Nara Machinery Co., Ltd.), Cosmossystem (manufactured by Kawasaki Heavy Industries, Ltd.), Henschel mixer (manufactured by NIPPON COKE&ENGINEERING CO., LTD), Multifunctional mixer (manufactured by NIPPON COKE&ENGINEERING CO., LTD), COMPOSI (manufactured by NIPPON COKE&ENGINEERING CO., LTD), Mechanofusion device (manufactured by Hosokawa Micron Corporation), Mechanomill (manufactured by Okada Seiko Co., Ltd.), Nobilta (manufactured by Hosokawa Micron Corporation), etc. can be cited.

[0121] <Addition treatment method>

[0122] The method of treating toner particles for electrostatic charge image development with an additive is not particularly limited, and the toner particles for electrostatic charge image development can be treated according to a conventionally known method. Specifically, the treatment conditions can be adjusted so that the particles of the additive do not bury in the toner particles for electrostatic charge image development, and a mixer such as a Henschel mixer or a Nauta mixer can be used to treat the toner particles for electrostatic charge image development with the additive.

[0123] <<Use of toner particles for electrostatic charge image development>>

[0124] The fixing property and heat-resistant storage property of the toner particles for electrostatic charge image development of the present invention described above are excellent, and thus can be suitably used for various image forming apparatuses.

[0125] Examples

[0126] <<<Manufacture of toner particles for electrostatic charge image development>>>

[0127] The toner particles for electrostatic charge image development in each example and comparative example were adjusted by the following method. The particle diameters and standard deviations of the particle diameters of the resin fine particles used in each example and comparative example are shown in Table 2. In addition, the coverage rates of the film (A) part, the coverage rate of the film (B) part, and the overall coverage rate of the resin film covering the toner particles for electrostatic charge image development (the coverage rate of the resin film covering the toner master particles in the toner particles for electrostatic charge image development) in the toner particles for electrostatic charge image development of each example and comparative example produced are shown in Table 2. It should be noted that these values were measured using the above method.

[0128] <<Example 1>>

[0129] Mix the toner masterbatch raw materials (polyester resin, wax, carbon black, charge control agent) according to the parts by weight described in Table 1, and perform hot melt mixing treatment using a commercially available extruder. After coarsely pulverizing the treated mixture with a hammer mill, perform fine pulverization with a jet mill, and classify the average particle size into 8 μm using a jet classifier to obtain the toner masterbatch. The obtained toner masterbatch has recesses of 50 nm or more and 500 nm or less.

[0130] After stirring the obtained toner masterbatch and resin fine particles (styrene acrylic resin: average particle size 40 nm, standard deviation of particle size 0.11), in a mixing device, collide the toner masterbatch with the styrene acrylic resin, and add silica to the obtained particles to obtain the toner particles of the present invention. It was confirmed that on the recesses of 50 nm or more and 500 nm or less in depth of the obtained toner masterbatch, there are portions where the film (B) part is formed. In the toner particles of Example 1, the proportion of the film (B) part (coverage rate of the film (B) part) is 35% with respect to the entire resin film. The coverage rate of the film (B) part in each example and comparative example was measured by the above method. In addition, in the resin film, except for the above-mentioned film (B) part, the whole is the film (A) part. Further, the film (B) part is a resin film in which resins are laminated in layers, and as the lamination method, it is laminated in a direction away from the surface of the toner masterbatch.

[0131] <<Example 2>>

[0132] Change the resin fine particles (acrylic resin) to 8 parts by weight, and perform the same operations as in Example 1 except for this to obtain the toner particles of Example 2. In the toner particles of Example 2, the proportion of the film (B) part with respect to the entire resin film is 56%. In addition, in the resin film, except for the above-mentioned film (B) part, the whole is the film (A) part. Further, the film (B) part is a resin film in which resins are laminated in layers, and as the lamination method, it is laminated in a direction away from the surface of the toner masterbatch.

[0133] <<Example 3>>

[0134] Change the toner masterbatch raw material (polyester resin) to styrene acrylic resin, and change the parts by weight of each raw material to the values described in Table 1, and perform the same operations as in Example 1 except for this to obtain the toner particles of Example 3. In the toner particles of Example 3, the proportion of the film (B) part with respect to the entire resin film is 35%. In addition, in the resin film, except for the above-mentioned film (B) part, the whole is the film (A) part. Further, the film (B) part is a resin film in which resins are laminated in layers, and as the lamination method, it is laminated in a direction away from the surface of the toner masterbatch.

[0135] <<Example 4>>

[0136] The resin fine particles (styrene-acrylic resin) were changed to acrylic resin (average particle size 40 nm, standard deviation of particle size 0.12). Except for this, the same operations as in Example 1 were carried out to obtain the toner particles of Example 4. In the toner particles of Example 4, the proportion of the film (B) part was 35% relative to the entire resin film. In addition, in the resin film, all except the above-mentioned film (B) part were the film (A) part. Further, the film (B) part is a resin film in which resins are laminated in layers, and as the lamination method, it is laminated in a direction away from the surface of the toner masterbatch.

[0137] <<Example 5>>

[0138] The weight part of the resin fine particles (styrene-acrylic resin) was changed to the value described in Table 1. Except for this, the same operations as in Example 1 were carried out to obtain the toner particles of Example 5. In the toner particles of Example 5, the proportion of the film (B) part was 70% relative to the entire resin film. In addition, in the resin film, all except the above-mentioned film (B) part were the film (A) part. Further, the film (B) part is a resin film in which resins are laminated in layers, and as the lamination method, it is laminated in a direction away from the surface of the toner masterbatch.

[0139] <<Example 6>>

[0140] Resin fine particles (styrene-acrylic resin: average particle size 40 nm, standard deviation of particle size 0.06) with a reduced standard deviation of particle size by sieving were used. Except for this, the same operations as in Example 1 were carried out to obtain the toner particles of the present invention. In the toner particles of Example 1, the proportions of the film (A) part and the film (B) part were both 50%.

[0141] <<Example 7>>

[0142] Resin fine particles (styrene-acrylic resin: average particle size 40 nm, standard deviation of particle size 0.147) with a reduced standard deviation of particle size by sieving were used. Except for this, the same operations as in Example 1 were carried out to obtain the toner particles of the present invention. In the toner particles of Example 1, the proportions of the film (A) part and the film (B) part relative to the entire resin film were 67% and 33%, respectively.

[0143] <<Example 8>>

[0144] Resin fine particles (styrene-acrylic resin: average particle size 40 nm, standard deviation of particle size 0.135) with a reduced standard deviation of particle size by sieving were used. Except for this, the same operations as in Example 1 were carried out to obtain the toner particles of the present invention. In the toner particles of Example 1, the proportions of the film (A) part and the film (B) part relative to the entire resin film were 66% and 34%, respectively.

[0145] <<Comparative Example 1>>

[0146] The weight part of the resin fine particles (styrene-acrylic resin) was changed to the value described in Table 1, and other than that, the same operations as in Example 1 were carried out to obtain toner particles. In the toner particles of Comparative Example 1, since there were few resin fine particles, the film (B) part was not formed (that is, a resin film of 50 nm or more was not formed).

[0147] <<Comparative Example 2>>

[0148] The same operations as in Example 1 were carried out. For 100 weight parts of the obtained toner masterbatch, 1 weight part of hydroxymethylmelamine and 4 weight parts of styrene-butyl acrylate copolymer were used. Ion-exchanged water was added to a 1-L three-necked flask equipped with a stirring blade, and the internal temperature of the flask was maintained at 30 °C using a water bath, followed by stirring. Dilute hydrochloric acid was added to the flask, and the pH of the aqueous solution in the flask was adjusted to 4. After adjusting the pH, an aqueous solution of hydroxymethylmelamine (solid content concentration: 80 mass%) and a fine particle dispersion of styrene-butyl acrylate copolymer (hydrophobic thermoplastic resin) were added to prepare a mixed solution.

[0149] 100 weight parts of the toner masterbatch obtained by the method of Example 1 were added to the above mixed solution. After stirring the mixture, the temperature was raised to 70 °C, and stirring was continued for 2 hours. Thereafter, sodium hydroxide was added to stop the reaction in order to adjust the pH of the aqueous solution in the flask to 7. The flask was cooled to room temperature to obtain a toner dispersion having a resin coating layer.

[0150] The obtained toner dispersion was filtered to obtain a toner cake. The obtained toner cake was washed with water and then subjected to a drying treatment to dry the washed toner cake. After an addition treatment of attaching an additive to the surface of the dried toner, toner using a resin film forming step by a polymerization method was manufactured.

[0151] The cross-section of the toner particles of Comparative Example 2 was observed. As a result, toner having a substantially uniform resin coating layer and a resin film thickness of 100 nm was obtained (that is, the film (A) part was not formed). Further, the resin film was a single resin layer.

[0152] <<Comparative Example 3>>

[0153] The amounts were changed to 2 weight parts of an aqueous solution of hydroxymethylmelamine and 8 weight parts of styrene-butyl acrylate copolymer, and other than that, the same operations as in Comparative Example 2 were carried out to obtain the toner particles of Comparative Example 3. On the cross-section of the toner particles obtained in Comparative Example 3, a substantially uniform resin film was formed, and toner having a resin layer thickness of 250 nm was obtained (that is, the film (A) part was not formed). Further, the resin film was a single resin layer.

[0154] <<Comparative Example 4>>

[0155] Without using a resin film material, silica was added to the obtained toner masterbatch, and otherwise, the same operations as in Example 1 were performed to obtain the toner particles of Comparative Example 4.

[0156] <<Comparative Example 5>>

[0157] The resin fine particles of Example 1 were changed to resin fine particles with a large standard deviation of particle size (styrene acrylic resin: average particle size 38 nm, standard deviation of particle size 0.19), and otherwise, the same operations as in Example 1 were performed to obtain toner particles. In the obtained toner particles, the film (B) part was not formed, and only the film (A) part was formed.

[0158] <<Comparative Example 6>>

[0159] The resin fine particles of Example 1 were changed to resin fine particles with a large standard deviation of particle size (styrene acrylic resin: average particle size 41 nm, standard deviation of particle size 0.23), and otherwise, the same operations as in Example 1 were performed to obtain toner particles. Similarly to the comparative example, in the obtained toner particles, the film (B) part was not formed, and only the film (A) part was formed.

[0160] <<Physical Property Value Measurement>>

[0161] For the raw materials of each example and comparative example, each physical property value was measured by the following measurement methods. The results are shown in Table 1.

[0162] <<Measurement Method of Glass Transition Temperature Tg>>

[0163] Weigh about 10 mg of the toner masterbatch and resin fine particles as raw materials, put them into an aluminum cell, and place them in a differential scanning calorimeter (SSC-5200 manufactured by Seiko Denshi Kogyo Co., Ltd.), and blow in 50 ml of N 2 gas per minute. Then, between 20 and 150 °C, the temperature was raised at a rate of 10 °C per minute, and then rapidly cooled from 150 °C to 20 °C, and this process was repeated twice. The heat absorption of the second time was measured, and its peak temperature was taken as the glass transition temperature. The same measurement was also performed for the raw materials of each example and comparative example.

[0164] <<Softening Point Measurement>>

[0165] The softening point was set as the flow softening point and measured using the following measuring device and measurement conditions. The flow softening point was measured as the temperature in the middle of the moving distance of the plunger of the measuring device from the start of descent to the stop. Weigh 2.0 g of each obtained sample and put it into a mold for measurement.

[0166] Measuring instrument: High-temperature flow tester CF-500 manufactured by Shimadzu Corporation

[0167] Measurement conditions:

[0168] Plunger: 1 cm 2

[0169] Mold diameter: 1 mm

[0170] Mold length: 1 mm

[0171] Load: 20 KgF

[0172] Preheating temperature: 50 - 80 °C

[0173] Preheating time: 300 sec

[0174] Heating rate: 6 °C / min

[0175] <Standard deviation of particle size>

[0176] The standard deviation of the resin particle diameter is measured using a laser diffraction particle size distribution analyzer SALD - 2300 after ultrasonically dispersing a sample obtained by diluting the resin particles to 2.5 wt% with EP water for 10 minutes.

[0177] <<<Evaluation>>>

[0178] The evaluation of each example and comparative example is carried out by the following method. The results are shown in Table 1.

[0179] <<Heat resistance and storage stability>>

[0180] 10 g of the toner particles of each example and comparative example are respectively put into a plastic container with a volume of 200 mL, and left standing in a thermo - hygrostat (PH - 3KT manufactured by ESPEC CORPORATION) set at 50 °C for 50 hours, and then taken out. Next, three kinds of sieves with mesh sizes of 150 μm, 75 μm, and 45 μm are successively installed on a Powder Tester (PT - S manufactured by Hosokawa Micron Corporation), and 2 g of toner particles are put on the sieve with a mesh size of 150 μm. The toner particles are sieved under the conditions of a variable resistor (Rheostat) scale of 2 and a time of 10 seconds, and the weight of the toner remaining on the sieve is measured. a, b, c, and the degree of aggregation are calculated by the following formula.

[0181] In addition, the standing temperature in the above - mentioned method is changed from 50 °C to room temperature (25 °C), and the degree of aggregation of the toner particles is calculated. The difference between the two degrees of aggregation obtained is taken as the heat resistance and storage stability.

[0182] Degree of aggregation (mass %) = a + b + c

[0183] a = (Residual toner weight on the 150 - μm mesh sieve / 2) × 100

[0184] b = (Residual toner weight on the 75 - μm mesh sieve / 2) × 100 × (3 / 5)

[0185] c = (the weight of the residual toner on a 45-μm mesh screen / 2) × 100 × (1 / 5)

[0186] The evaluation criteria are as follows.

[0187] ◎: The difference between the two degrees of aggregation is 5% or less

[0188] ○: The difference between the two degrees of aggregation exceeds 5% and is 10% or less

[0189] ×: The difference between the two degrees of aggregation exceeds 10%

[0190] <<Fixing property>>

[0191] For a fixing machine in which a heat fixing roller with a surface made of Teflon (registered trademark) and a pressure fixing roller with a surface made of silicone rubber rotate in pairs, adjust it so that the roller pressure is 1 Kg / cm 2 and the roller speed is 50 mm / sec. Gradually change the surface temperature of the heat fixing roller, and fix the toner image of the transfer paper with the unfixed image described above at each surface temperature.

[0192] Set the surface temperature of the heat fixing roller of the above fixing machine to 120°C, and fix the toner image of the transfer paper with the unfixed image described above. Then, after measuring the image density of the formed fixed image using a reflection densitometer (manufactured by Macbeth, product name: RD-914), rub the fixed image with a cotton pad (product name PPC pad manufactured by Dineke), and then perform the same operation and measure the image density. From the measured values obtained, calculate the fixing strength using the following formula and evaluate the fixing property.

[0193] Fixing strength (%) = (image density of the fixed image after rubbing / image density of the fixed image before rubbing) × 100

[0194] The evaluation criteria are as follows.

[0195] ◎: The fixing strength is 80% or more

[0196] ○: The fixing strength is 70% or more and less than 80%

[0197] △: The fixing strength is 60% or more and less than 70%

[0198] ×: The fixing strength is less than 60%

[0199] [Table 1]

[0200]

[0201] [Table 2]

[0202]

[0203] Symbol Explanation

[0204] 10: Toner particles for developing static charge images,

[0205] 11: Toner masterbatch,

[0206] 12: Resin film,

[0207] 13: Concave portion,

[0208] 14: Convex portion,

[0209] 15: Flat portion,

[0210] 16: Film (B) portion,

[0211] 17: Film (A) portion.

Claims

1. A toner particle for developing an electrostatic charge image, characterized in that, it contains a toner masterbatch and a resin film covering the toner masterbatch, the resin film covers a part of the surface of the toner masterbatch, the surface of the toner masterbatch has recesses, the recesses include a first recess with a depth of 50 nm to 500 nm, the resin film is composed of a film A part with a thickness of 10 nm or more and less than 50 nm and a film B part with a thickness of 50 nm or more and 500 nm or less, when the length of the part covered by the resin film in the outer peripheral part of the cross-section of the toner particle for developing an electrostatic charge image is set to 100%, the total of the film A part is 40 to 70% of the resin film, and the total of the film B part is 30 to 60% of the resin film, the film B part exists on the first recess, the coverage rate of the resin film is 80% or more and 96% or less, the toner masterbatch contains a binder resin, the glass transition temperature of the binder resin is 40°C or more and 70°C or less, and the softening point is 70°C or more and 130°C or less, the resin film is formed of resin fine particles, the glass transition temperature of the resin fine particles is 50 to 100°C, and the softening point is 100°C or more and 250°C or less, wherein, the length of the part covered by the resin film in the outer peripheral part of the cross-section of the toner particle for developing an electrostatic charge image and the coverage rate of the resin film are measured according to the following steps: (1) Using a transmission electron microscope, randomly select 10 toner particles for developing an electrostatic charge image and photograph them in such a way that the cross-section of one toner particle for developing an electrostatic charge image is entirely included in one image, and measure the overall length of the outer peripheral part of the cross-section of the toner particle for developing an electrostatic charge image in the obtained image and the length of the part covered by the resin film in the outer peripheral part; (2) Calculate the coverage rate of one toner particle for developing an electrostatic charge image obtained by dividing the length of the part covered by the resin film in the outer peripheral part by the overall length of the outer peripheral part of the cross-section of the toner particle for developing an electrostatic charge image; (3) Take the average value of the coverage rates obtained for the 10 toner particles for developing an electrostatic charge image as the coverage rate of the resin film.

2. The toner particle for developing an electrostatic charge image according to claim 1, characterized in that, the film B part is a resin layer in which a plurality of resin layers are laminated.

3. The toner particle for developing an electrostatic charge image according to claim 2, characterized in that, in the film B part, the lamination direction of the plurality of resin layers is the direction away from the surface of the toner masterbatch.

4. The toner particle for developing an electrostatic charge image according to any one of claims 1 to 3, characterized in that, the average particle diameter of the toner particle for developing an electrostatic charge image is 3 to 15 μm.

5. The toner particle for developing an electrostatic charge image according to any one of claims 1 to 3, characterized in that, the standard deviation of the particle diameter of the resin fine particles is 0.15 or less.

6. An electrostatic charge image developing toner composition containing the toner particle for developing an electrostatic charge image according to any one of claims 1 to 5.

Images