JP2013257404A - Toner for electrostatic charge image development, and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner for electrostatic charge image development that has low glossiness and prevents the occurrence of glossiness unevenness, while maintaining low-temperature fixability and the manufacturing method of the same.SOLUTION: A toner for electrostatic charge image development contains toner particles of a core-shell structure each having a shell layer containing a binder resin on the surface of a core particle containing at least a binder resin and colorant. The toner particle has an inorganic layer on the surface of the core particle, and a shell layer on the surface of the inorganic layer.

Description

  The present invention relates to a toner for developing an electrostatic image and a method for producing the same, and more particularly to a toner for developing an electrostatic image used in an electrophotographic image forming apparatus and a method for producing the same.

  In recent years, in the field of electrostatic charge image developing toner (hereinafter also simply referred to as “toner”), there is a demand for a toner that can cope with high image quality in response to a demand from the market. As a toner corresponding to high image quality, there is a demand for a toner having a smaller particle size and a sharper particle size distribution than conventional toners. When the toner has a small particle size and a sharp particle size distribution, the development behavior of the individual toner particles is aligned, so that the reproducibility of the minute dots is remarkably improved. However, in the conventional toner manufacturing method by the pulverization method, there is a limit to the atomization of the toner, and it is not easy to sharpen the particle size distribution of the toner.

  On the other hand, an emulsion aggregation method has been proposed as a production method capable of arbitrarily controlling the shape and particle size distribution of toner particles. In this method, a colorant particle dispersion or, if necessary, a wax dispersion is mixed in an emulsified dispersion of resin fine particles, and while stirring, each particle is aggregated by adding a flocculant, controlling pH, etc., and further heating. By doing so, the particles are aggregated and fused to obtain toner particles.

  Further, from the viewpoint of energy saving, development of a low-temperature fixing toner that can be fixed with less energy is in progress. In order to lower the fixing temperature of the toner, it is necessary to lower the melting temperature and melt viscosity of the binder resin. However, if the glass transition point or molecular weight of the binder resin is lowered in order to lower the melting temperature or melt viscosity of the binder resin, new problems arise, such as poor heat storage stability of the toner or occurrence of hot offset.

  In order to achieve both low-temperature fixability and heat-resistant storage stability, a technique for controlling the toner to a core / shell structure has been proposed (see, for example, Patent Document 1). In other words, a technology to achieve both low-temperature fixability and heat-resistant storage stability by forming a shell layer made of resin particles with high glass transition point and softening point and excellent heat resistance on the core particle surface with excellent low-temperature fixability is proposed. Has been. Particularly in the production of toner by the emulsion aggregation method, there is an advantage that such shape control and function improvement can be easily performed. On the other hand, in recent years, in the production print area, copying machines and printers have been increased in speed and the number of compatible paper types has been increasing, and the application of such core / shell toners with excellent low-temperature fixability and heat-resistant storage stability has progressed. It is out.

  Toner that can be fixed at a low temperature can be melted at a low fixing temperature and has a low melt viscosity at the fixing temperature, so that the toner image surface of the fixed image becomes smooth when pressed against a fixing roller or a fixing belt. The toner image tends to be glossy. Such glossy images are preferred for photographic images, but are not particularly preferred for office documents, and low gloss images are desired.

  In addition, since the fixing roller and the fixing belt are deprived of heat when a transfer material such as copy paper passes, the second rotation of the fixing roller and the fixing belt in the same transfer material, that is, in one copy sheet. In the portion corresponding to the above, the fixing temperature is lowered, so that the toner is not sufficiently melted, the glossiness of the toner image surface is lowered, and gloss unevenness occurs in the same transfer material.

  On the other hand, for the purpose of making the toner image low gloss, a technique for incorporating inorganic fine particles in the toner particles has been proposed (see, for example, Patent Document 2).

  According to this technique, by including inorganic fine particles in the toner particles, the elasticity of the toner is improved, and the surface of the fixed image is hardly smoothed. As a result, the peelability of the image is improved, and the low A glossy image can be obtained. However, when inorganic fine particles are contained in the toner particles, there is a problem that the elasticity increases and the low-temperature fixability is impaired.

  Thus, it has not been sufficient in terms of suppressing low gloss and uneven gloss while maintaining low temperature fixability.

JP 2002-116574 A JP 2011-39382 A

  SUMMARY OF THE INVENTION The present invention has been made in view of the above problems and circumstances, and a solution to the problem is to provide a toner for developing an electrostatic image with low gloss and no gloss unevenness while maintaining low-temperature fixability, and a method for producing the same. It is to be.

  In order to solve the above-mentioned problems, the present inventor, in the process of examining the cause of the above-mentioned problems, in the toner particles having a core-shell structure, to make toner particles having an inorganic layer composed of inorganic fine particles on the core particle surface. Thus, the inventors have found that the above problems can be solved and have reached the present invention.

  That is, the said subject which concerns on this invention is solved by the following means.

  1. In an electrostatic charge image developing toner containing core-shell toner particles having a shell layer containing a binder resin on the surface of core particles containing at least a binder resin and a colorant, the surface of the core particles An electrostatic charge image developing toner comprising an inorganic layer and toner particles having a shell layer on the surface of the inorganic layer.

  2. 2. The electrostatic charge image developing toner according to item 1, wherein the resin constituting the shell layer contains at least a styrene-acryl-modified polyester resin.

  3. 3. The electrostatic image developing toner according to item 1 or 2, wherein the inorganic layer comprises inorganic fine particles containing at least silica.

  4). Item 4. The electrostatic image developing toner according to any one of Items 1 to 3, wherein the inorganic layer has a thickness in the range of 0.1 to 1.2 µm.

5. An electrostatic charge image developing toner manufacturing method for manufacturing the electrostatic charge image developing toner according to any one of Items 1 to 4,
Preparing an aqueous dispersion of core particles;
Forming an inorganic layer on the surface of the core particles;
A shelling step of mixing an aqueous dispersion of fine particles for forming a shell layer with an aqueous dispersion of core particles formed with the inorganic layer to form a shell layer on the surface of the inorganic layer on the surface of the core particles. A method for producing a toner for developing an electrostatic charge image.

  6). 6. The method for producing a toner for developing an electrostatic charge image according to claim 5, wherein the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on a surface of the core particle by a sol-gel method. .

  7). 6. The method for producing a toner for developing an electrostatic charge image according to claim 5, wherein the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on a surface of the core particle by a dry method. .

  By the above means of the present invention, it is possible to provide a toner for developing an electrostatic image with low gloss and no gloss unevenness while maintaining low temperature fixability, and a method for producing the same.

  The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

  In the present invention, in the electrostatic image developing toner containing core-shell toner particles having a shell layer containing the binder resin on the surface of the core particles containing at least the binder resin and the colorant, By having the inorganic layer on the surface of the core particle, the elasticity of the toner is increased and the surface of the fixed image is not easily smoothed, so that the fixed image can be made low gloss. In addition, it is considered that fixing unevenness can be reduced by making the fixed image low gloss. That is, by reducing the glossiness of the fixed image, it is considered that uneven glossiness becomes inconspicuous in the same sheet even when the surface temperature of the fixing belt or the fixing roller is lowered.

  Furthermore, in the present invention, for example, when a styrene-acryl-modified polyester resin is used as a resin constituting the shell layer, the shell layer has a low-temperature fixing effect due to the high glass transition point and low softening point characteristics of the polyester resin. With the high elasticity effect of the core particles having an inorganic layer, a fixed image having low gloss and no gloss unevenness can be more reliably realized while maintaining low-temperature fixability. As a result, it is considered that a low gloss and non-uniform gloss image can be realized while maintaining the low temperature fixability.

Schematic diagram illustrating the structure of the toner of the present invention

  The electrostatic charge image developing toner of the present invention comprises an electrostatic charge image containing toner particles having a core-shell structure having a shell layer containing a binder resin on the surface of core particles containing at least a binder resin and a colorant. The developing toner is characterized by containing toner particles having an inorganic layer on the surface of the core particle and a shell layer on the surface of the inorganic layer. This feature is a technical feature common to the inventions according to claims 1 to 7.

  As an embodiment of the present invention, the resin constituting the shell layer contains a styrene-acryl-modified polyester resin, and the toner for developing an electrostatic charge image that does not cause uneven glossiness while maintaining low-temperature fixability. And a method for producing the same can be provided.

  Furthermore, in the present invention, it is preferable that the inorganic layer is inorganic fine particles containing at least silica because the elasticity of the core resin can be increased and uneven gloss can be reduced.

  Moreover, in this invention, since the thickness of the said inorganic layer exists in the range of 0.1-1.2 micrometers, since the effect of an inorganic layer can be expressed, it is preferable.

  Further, the electrostatic image developing toner of the present invention is a production method by an emulsion aggregation method, the step of preparing an aqueous dispersion of core particles, the step of forming an inorganic layer on the surface of the core particles, A shell forming step of mixing an aqueous dispersion of fine particles for forming a shell layer with an aqueous dispersion of core particles on which an inorganic layer is formed, and forming a shell layer on the surface of the inorganic layer on the surface of the core particles. The production method is preferable in terms of obtaining a toner having a core-shell structure with easy shape control and a small particle size.

  Furthermore, since the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on the surface of the core particles by a sol-gel method, the inorganic layer can uniformly cover the core, so the low temperature fixing effect of the shell layer Is preferable.

  Further, if the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on the surface of the core particles by a dry method, the inorganic layer can uniformly cover the core, so that the shell layer can be fixed at low temperature. Since an effect can be exhibited, it is preferable.

  Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used in the sense of including the numerical values before and after the lower limit value and the upper limit value.

<Toner>
The electrostatic image developing toner of the present invention comprises toner particles having a core / shell structure, and has a core layer having a shell layer containing a binder resin on the surface of core particles containing at least a binder resin and a colorant. The toner for developing an electrostatic charge image containing toner particles having a shell structure is characterized by having an inorganic layer on the surface of the core particle and a shell layer on the surface of the inorganic layer. FIG. 1 is a schematic diagram for explaining the toner particles having the core / shell structure, and has a structure in which an inorganic layer B is provided on the surface of the core particle C and a shell layer A is provided on the surface of the inorganic layer B.

The average particle diameter of the core-shell toner particles constituting the toner of the present invention is preferably 3 to 10 μm by volume-based median diameter (D ₅₀ ), and 0.1 to 1.2 μm thick on the surface of the core particle. It has an inorganic layer on which a shell layer having a thickness of 100 to 300 nm is formed.

[Inorganic layer]
(Inorganic fine particles)
The inorganic layer on the surface of the core particle according to the present invention is preferably composed of inorganic fine particles, and the inorganic fine particles constituting the inorganic layer are not particularly limited. preferable. Specific examples include fine particles such as silica, alumina, titania, and zirconia. The particle size of the inorganic fine particles is preferably 30 to 200 nm. In the present invention, silica is preferred, and the inorganic layer containing silica preferably contains fine silica particles formed on the surface of the core particles by a wet method.

(Formation of inorganic layer)
The method for covering the surface of the core particle with an inorganic layer made of silica fine particles in the present invention can be achieved, for example, by using a silica coating technique using a sol-gel method. By forming the inorganic layer by the sol-gel method, the surface of the core particles can be covered with a more uniform inorganic layer, so that the low-temperature fixing effect of the shell layer can be exhibited. It is also possible to form an inorganic layer on the surface of the core particles by a dry method.

(Formation of inorganic layer by sol-gel method)
Specifically, the silica coating by the sol-gel method is performed by the following method.

  Water in which silane alkoxide is dissolved or an aqueous medium is added to an aqueous dispersion of core particles as a base material. This dispersion solution is dropped into water to which an alkali has been added or an aqueous medium, or water or an aqueous medium to which an alkali has been added to the above dispersion is dropped. According to this method, the silane alkoxide dissolved in the dispersion containing the core particles undergoes hydrolysis and polycondensation in the presence of alkali and gradually insolubilizes. It will deposit on the surface of the core particle from the interaction. As a result, an inorganic layer of silica is formed on the surface of the core particles by fixing the granular masses containing silica to each other.

  Examples of the silane alkoxide used above include the following. Examples of the bifunctional or higher alkoxide include tetramethoxysilane, methyltriethoxysilane, hexyltriethoxysilane, triethoxychlorosilane, di-t-butoxydiacetoxysilane, hydroxymethyltriethoxysilane, tetraethoxysilane, and tetra-n. -Propoxysilane, tetrakis (2-methacryloxyethoxysilane) silane, allyltriethoxysilane, allyltrimethoxysilane, 3-aminopropyltriethoxysilane, bis (triethoxysilyl) ethylene, bis (triethoxysilyl) methane, bis (Triethoxysilyl) 1,7-octadiene, 2,2- (chloromethyl) allyltrimethoxysilane, ((chloromethyl) phenylethyl) trimethoxysilane, 1,3-divinyltetraethoxy Siloxane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, (3-glycidoxypropyl) methyldiethoxysilane, (3-glycidoxypropyl) methyldimethoxysilane (3-glycidoxypropyl) tri Methoxysilane, 3-mercaptopropyltriethoxysilane, methacrylamidopropyltriethoxysilane, methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane, 7-octenyltrimethoxysilane, vinylmethyldiethoxysilane, vinylmethyldimethoxysilane Vinyltriethoxysilane, vinyltriphenoxysilane, and the like.

  Examples of monofunctional silane alkoxides that can be used in combination with the above bifunctional or higher silane alkoxides include (3-acryloxypropyl) dimethylmethoxysilane, o-acryloxy (polyethyleneoxy) trimethylsilane, Loxytrimethylsilane, 1,3-bis (methacryloxy) -2-trimethylsiloxypropane 3-chloro-2-trimethylsiloxypropene, (cyclohexenyloxy) trimethylsilane, methacryloxyethoxytrimethylsilane, and (methacryloxymethyl) dimethylethoxy Silane etc. are mentioned. These silane alkoxides may be used alone or in combination of two or more.

  In the present invention, 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, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran, and alcohol-based organic solvents that do not dissolve the resulting resin are preferable. When the organic nature of these solvents increases, the solubility of the polycondensate of silane alkoxide increases, and the polycondensate of silane alkoxide is difficult to deposit on the toner particle surface. Therefore, it is preferable to use methanol or ethanol as the aqueous medium.

  Moreover, in order to give the core particle which has inorganic layers, such as a silica produced by said method, the stable effect also under high temperature and high humidity, the hydrophobization process of the core particle surface which has an inorganic layer can also be performed. As a method of hydrophobizing, it may be coupled with a hydrophobizing agent. A general silane compound can be used as the hydrophobizing agent. Specifically, tetramethoxysilane, methyltriethoxysilane, hexyltriethoxysilane, triethoxychlorosilane, di-t-butoxydiacetoxysilane, hydroxymethyltriethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetrakis (2-methacryloxyethoxysilane) silane, allyltriethoxysilane, allyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, bis (triethoxysilyl) ethylene, bis (triethoxysilyl) Methane, bis (triethoxysilyl) 1,7-octadiene, 2,2- (chloromethyl) allyltrimethoxysilane, ((chloromethyl) phenylethyl) trimethoxysilane, 1,3-divinyltetrae Xylodisiloxane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, (3-glycidoxypropyl) methyldiethoxysilane, (3-glycidoxypropyl) methyldimethoxysilane, (3-glycidoxy Propyl) trimethoxysilane, 3-mercaptopropyltriethoxysilane, methacrylamidopropyltriethoxysilane, methacryloxymethyltriethoxysilane, methacryloxymethyltrimethoxysilane, 1,7-octadienyltriethoxysilane, 7-octenyl Trimethoxysilane, tetrakis (ethoxyethoxy) silane, tetrakis (2-methacryloxyethoxy) silane, vinylmethyldiethoxysilane, vinylmethyldimethoxysilane, vinyltriethoxysilane, vinyltripheno In addition to bifunctional or more functional silane compounds such as silane and methacryloxypropylmethyldimethoxysilane, (3-acryloxypropyl) dimethylmethoxysilane, o-acryloxy (polyethyleneoxy) trimethylsilane, acryloxytrimethylsilane, 1, Monofunctional functions such as 3-bis (methacryloxy) -2-trimethylsiloxypropane, 3-chloro-2-trimethylsiloxypropene, (cyclohexenyloxy) trimethylsilane, methacryloxyethoxytrimethylsilane, and (methacryloxymethyl) dimethylethoxysilane These silane compounds are mentioned. Furthermore, so-called silylating agents such as allyloxytrimethylsilane, trimethylchlorosilane, hexamethyldisilazane, dimethylaminotrimethylsilane, bis (trimethylsilyl) acetamide, trimethylsilyldiphenylurea, bis (trimethylsilyl) urea, or trimethylsilylimidazole are also used in the present invention. It can be used as a hydrophobizing agent.

(Formation of inorganic layer by dry method)
For the formation of the inorganic layer by the dry method, a method similar to a general toner external additive mixing method can be used. That is, an inorganic layer composed of inorganic fine particles can be formed on the surface of the core particles by stirring and mixing the core particle matrix and the inorganic fine particles taken out by filtration and drying using, for example, a mechanical stirring mixer.

[Inorganic layer thickness]
The thickness in particular of an inorganic layer is not restrict | limited, Usually, it is preferable that it is 0.1-1.2 micrometers. When the thickness of the inorganic layer is in the range of 0.1 to 1.2 μm, the effect of reducing gloss can be reliably obtained, and when the thickness is 1.2 μm or less, good low-temperature fixability can be achieved. It is preferable because it is possible. Further, the content of the inorganic fine particles in the toner is preferably 0.2 to 2% by mass because an effect of preventing low gloss and uneven gloss can be obtained. That is, when the content of the inorganic fine particles is 0.2 to 2% by mass, the effect of reducing gloss and preventing occurrence of uneven glossiness is sufficiently exhibited, and the low-temperature fixability is also favorably exhibited.

  The thickness of the inorganic layer can be controlled by a known method. For example, when an inorganic layer containing silica is formed by a sol-gel method, it is a raw material as described in Examples described later. It is possible to control the thickness of the inorganic layer to be formed by changing the amount of silane alkoxide added. Moreover, when forming by a dry method, it is possible to control thickness by changing the addition amount of inorganic layer forming raw materials, such as hydrophobic silica.

(Measurement method of thickness of inorganic layer)
The thickness of the inorganic layer was measured using “Microtrack UPA-150” (manufactured by Nikkiso Co., Ltd.), and the particle size of the particles forming the core particles and the inorganic layer was measured, and the difference was defined as the thickness of the inorganic layer.

  Specifically, the following procedure is performed. First, several drops of measurement particles are dropped into a 50 ml graduated cylinder, 25 ml of pure water is added, and dispersed for 3 minutes using an ultrasonic cleaner “US-1 (manufactured by asone)” to prepare a measurement sample. Next, 3 ml of the measurement sample is put into the cell of “Microtrack UPA-150”, and it is confirmed that the value of Sample Loading is in the range of 0.1-100. And it measures on the following measurement conditions.

(Measurement condition)
Transparency (transparency): Yes
Refractive Index (refractive index): 1.59
Particle Density (particle specific gravity): 1.05 mg / cm ³
Spherical Particles (Spherical Particles): Yes
(Solvent conditions)
Refractive Index (refractive index): 1.33
Viscosity (Viscosity): High (temp) 0.797 × 10 ⁻³ Pa · s
Low (temp) 1.00 ² × 10 ^-3 Pa · s
[Shell layer]
As the resin constituting the shell layer constituting the toner of the present invention, a resin conventionally used as a binder resin for an electrophotographic toner can be used. Examples of such resins include styrene resins, (meth) acrylic resins, styrene- (meth) acrylic resins, vinyl resins such as olefin resins, polyester resins, styrene-acrylic modified polyester resins, polyamide resins. Polycarbonate resin, polyether resin, polyvinyl acetate resin, polysulfone resin, epoxy resin polyurethane resin, urea resin, or the like can be used. Two or more of these resins may be mixed.

  In the present invention, the resin constituting the shell layer (hereinafter also referred to as “shell resin”) is a styrene-acrylic modified polyester resin having a structure in which a styrene-acrylic copolymer molecular chain and a polyester molecular chain are molecularly bonded. It is preferable from the viewpoint of low-temperature fixability.

  Examples of the resin that can be contained in the shell resin together with the styrene-acrylic modified polyester resin include styrene-acrylic resin, polyester resin, and urethane resin.

  The content of the styrene-acrylic modified polyester resin in the shell resin is preferably 70 to 100% by mass and more preferably 90 to 100% by mass in 100% by mass of the shell resin.

  By setting the content ratio of the styrene-acrylic modified polyester resin in the shell resin within the above range, sufficient affinity can be easily obtained between the core particles and the shell layer, and a desired shell layer can be easily formed. As a result, it is possible to more reliably produce toner particles having a core / shell structure having sufficient heat-resistant storage property, charging property, or crushing resistance.

  Further, the thickness of the shell layer is preferably in the range of 100 to 300 nm from the viewpoints of heat resistant storage stability and crush resistance.

  Moreover, the following effects can be obtained by using a styrene-acryl-modified polyester resin as the resin of the shell layer constituting the toner.

  That is, in general, the advantage of using a polyester resin as a binder resin in designing toner particles is that the polyester resin maintains a high glass transition point (Tg) as compared with a styrene-acrylic resin and is designed to have a low softening point. Is easy to do. That is, the polyester resin is a suitable resin for satisfying both low-temperature fixability and heat-resistant storage stability. And by introducing a styrene-acrylic polymer segment into the polyester resin used in the shell layer, the affinity of the core particle with the styrene-acrylic resin of the core particle while maintaining the high glass transition point and low softening point of the polyester resin As a result, a shell layer having a more uniform film thickness and a smooth surface can be formed while being a thin layer. Therefore, according to the toner of the present invention, both low-temperature fixability and heat-resistant storage stability are satisfied, and excellent chargeability is obtained. Further, since the shell layer is hardly peeled off, the toner is stirred in the developing device. As a result, sufficient resistance to crushing that is not crushed even when subjected to stress is obtained, and as a result, a high-quality image such as a high-speed machine can be obtained without causing image noise.

  In the present invention, the content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin (hereinafter, also referred to as “styrene-acrylic modification amount”) is 5% by mass or more and 30% by mass or less. In particular, the content is preferably 5% by mass or more and 20% by mass or less.

  Specifically, the amount of styrene-acrylic modification is the total mass of the resin material used for synthesizing the styrene-acrylic modified polyester resin, that is, the unmodified polyester resin that becomes the polyester segment, and the styrene-acrylic polymer. The aromatic vinyl monomer and (meta) with respect to the total mass of the aromatic vinyl monomer and (meth) acrylic acid ester monomer to be combined with the both reactive monomers for bonding them. ) Refers to the mass ratio of the acrylate monomer.

  When the amount of styrene-acrylic modification is in the above range, the affinity between the styrene-acrylic modified polyester resin and the core particles is properly controlled, and a thin shell layer with a more uniform thickness and a smooth layer can be obtained. Can be formed. On the other hand, when the amount of styrene-acryl modification is too small, a shell layer with a uniform film thickness cannot be formed, and the core particles are partially exposed. As a result, sufficient heat storage stability and chargeability are obtained. I can't get it. If the amount of styrene-acrylic modification is excessive, the styrene-acrylic modified polyester resin has a high softening point, so that sufficient low-temperature fixability cannot be obtained for the entire toner particles.

  In the toner of the present invention, an aliphatic unsaturated dicarboxylic acid is used as a polyvalent carboxylic acid monomer to form a polyester segment of a styrene-acryl-modified polyester resin, and the aliphatic unsaturated dicarboxylic acid is added to the polyester segment. It is preferable that a structural unit derived from an acid is contained.

  The aliphatic unsaturated dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule.

  According to the styrene-acryl-modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid, it is possible to reliably form a smooth shell layer having a more uniform film thickness while being a thin layer.

  The proportion of structural units derived from aliphatic unsaturated dicarboxylic acids in the structural units derived from polyvalent carboxylic acid monomers constituting the polyester segment of the styrene-acrylic modified polyester resin (hereinafter referred to as “specific unsaturated dicarboxylic acid-containing” The ratio is also preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.

  When the content ratio of the specific unsaturated dicarboxylic acid is within the above range, a smooth shell layer having a more uniform film thickness can be more reliably formed while being a thin layer. On the other hand, if the specific unsaturated dicarboxylic acid content is too low, sufficient heat-resistant storage stability and chargeability may not be obtained, and if the specific unsaturated dicarboxylic acid content is excessive, Sufficient chargeability may not be obtained.

  The structural unit derived from the aliphatic unsaturated dicarboxylic acid is preferably a structural unit derived from one represented by the following general formula (A).

General formula (A): HOOC- (CR < ₁ > = CR _{< 2 >} ) _n- COOH
[In formula, R < ₁ >, R < ₂ > is a hydrogen atom, a methyl group, or an ethyl group, Comprising: You may mutually be same or different. n is an integer of 1 or 2. ]
By containing the structural unit derived from such an aliphatic unsaturated dicarboxylic acid, it is possible to more reliably form a smooth shell layer with a more uniform film thickness while being a thin layer.

  This was emulsified by using a styrene-acryl-modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid having a vinylene group, for example, when producing toner particles by an emulsion polymerization aggregation method described later. It is inferred that the aggregation of fine particles with the styrene-acryl-modified polyester resin at the time is improved, and the aggregation of the core particles to the surface proceeds uniformly. In addition, since the styrene-acryl-modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid having a vinylene group has a high polarity, the toner particles are used, for example, by an emulsion polymerization aggregation method described later. This is also presumed that the polyester segment portion of the fine particles of the styrene-acrylic modified polyester resin to form the shell layer is easily oriented to the surface side in the aggregated particles.

  The shell resin preferably has a glass transition point of 50 to 70 ° C. from the viewpoint of reliably obtaining fixing properties such as low temperature fixing property and fixing separation property, and heat resistance such as heat resistant storage property and blocking resistance, More preferably, it is 50-65 degreeC, and it is preferable that a softening point is 80-110 degreeC.

  The glass transition point of the shell resin is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82.

  The softening point of the shell resin is measured as follows.

First, in an environment of 20 ° C. ± 1 ° C. and 50% ± 5% RH, 1.1 g of shell resin is placed in a petri dish and left flat for 12 hours or more. Then, a molding machine “SSP-10A” (Shimadzu Corporation) Pressure) with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample having a diameter of 1 cm, and this molded sample is then subjected to an environment of 24 ° C. ± 5 ° C. and 50% ± 20% RH. Using a flow tester “CFT-500D” (manufactured by Shimadzu Corporation), a cylindrical die hole (1 mm diameter) under the conditions of a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min. from × 1 mm), extruded from the time of preheating ends with piston diameter 1 cm, the offset method temperature _{T offset} measured by setting the offset value 5mm at a melt temperature measurement method of temperature ramps It is the softening point of the shell resin.

  The content ratio of the shell resin in the binder resin constituting the toner is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass based on the total amount of the binder resin.

  It is preferable that the content ratio of the shell resin in the binder resin is within the above range since heat resistant storage stability and low temperature fixability are improved.

(Method for producing styrene-acrylic modified polyester resin)
As a method for producing the styrene-acrylic modified polyester resin contained in the shell resin as described above, an existing general scheme can be used. Typical methods include the following three methods.

  (A-1) A polyester segment is polymerized in advance, and both reactive monomers are reacted with the polyester segment, and an aromatic vinyl monomer and (meta) are formed to form a styrene-acrylic polymer segment. ) A method of forming a styrene-acrylic polymer segment by reacting an acrylate monomer.

  (A-2) A polyvalent carboxylic acid monomer for polymerizing a styrene-acrylic polymer segment in advance, reacting the styrene-acrylic polymer segment with both reactive monomers, and further forming a polyester segment And a method of forming a polyester segment by reacting a polyhydric alcohol monomer.

  (A-3) A method in which a polyester segment and a styrene-acrylic polymer segment are respectively polymerized in advance, and both are reacted by reacting them with both reactive monomers.

  In the present specification, the both reactive monomers are a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene-acryl-modified polyester resin, and a polymerizable unsaturated group. And a monomer having

The method (A-1) will be specifically described.
(1) A mixing step (1) of mixing an unmodified polyester resin, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and a reactive monomer.
(2) Polymerization step (2) for polymerizing an aromatic vinyl monomer and a (meth) acrylic acid ester monomer,
By passing through, a styrene-acrylic polymer segment can be formed at the end of the polyester segment.

  In the mixing step (1), it is preferable to heat. The heating temperature may be within a range in which an unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer, and both reactive monomers can be mixed. Since it is obtained and polymerization control becomes easy, it can be set to, for example, 80 to 120 ° C., more preferably 85 to 115 ° C., and further preferably 90 to 110 ° C.

  Among unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and both reactive monomers, aromatic vinyl monomer and (meth) acrylic acid ester monomer The ratio of use is the total mass of the resin material used, that is, the total of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer when the total mass of the above four members is 100 mass%. The ratio is 5% by mass or more and 30% by mass or less, and particularly preferably 5% by mass or more and 20% by mass or less.

  When the total ratio of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to the total mass of the resin material used is within the above range, the styrene-acrylic modified polyester resin and the core particle The affinity is appropriately controlled, and a smooth shell layer can be formed with a more uniform film thickness while being a thin layer.

  The relative proportion of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer is such that the glass transition point (Tg) calculated by the FOX formula represented by the following formula (A) is 35. It is preferable that the ratio is in the range of -80 ° C, preferably 40-60 ° C.

Formula (A): 1 / Tg = Σ (Wx / Tgx)
[In Formula (A), Wx is the weight fraction of monomer x, and Tgx is the glass transition point of the homopolymer of monomer x. ]
In the present specification, both reactive monomers are not used for calculation of the glass transition point.

  Among the unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer and amphoteric monomer, the proportion of both reactive monomers used is the total mass of the resin material used, that is, The ratio of the two reactive monomers when the total mass of the four components is 100% by mass is 0.1% by mass or more and 5.0% by mass or less, and particularly 0.5% by mass or more and 3.0% by mass. The following is preferable.

(Aromatic vinyl monomers and (meth) acrylic acid ester monomers)
The aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic polymer segment have an ethylenically unsaturated bond capable of radical polymerization.

  Examples of the aromatic vinyl monomer include styrene, o-methyl styrene, m-methyl styrene, p-methyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, p-ethyl styrene, p. -N-butyl styrene, p-tert-butyl styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, 2, Examples include 4-dimethylstyrene, 3,4-dichlorostyrene, and derivatives thereof.

  These aromatic vinyl monomers can be used alone or in combination of two or more.

  Examples of (meth) acrylic acid ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, and methacrylic acid. Examples include butyl, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate.

  These (meth) acrylic acid ester monomers can be used alone or in combination of two or more.

  As an aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming a styrene-acrylic polymer segment, styrene or a derivative thereof is used from the viewpoint of obtaining excellent chargeability and image quality characteristics. It is preferable to use a large amount. Specifically, the amount of styrene or its derivative used is the total amount of monomers (aromatic vinyl monomer and (meth) acrylic acid ester based monomer) used to form the styrene-acrylic polymer segment. It is preferable that it is 50 mass% or more in the body.

(Amotropic monomer)
Examples of the both reactive monomers for forming the styrene-acrylic polymer segment include a group capable of reacting with the polyvalent carboxylic acid monomer and / or the polyhydric alcohol monomer for forming the polyester segment, and a polymerizable unsaturated group. Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride and the like can be used.

(Polyester resin)
The polyester resin used for producing the styrene-acrylic modified polyester resin according to the present invention is obtained by polycondensation reaction in the presence of an appropriate catalyst using a polyvalent carboxylic acid monomer (derivative) and a polyhydric alcohol monomer (derivative) as raw materials. It is manufactured.

  As polyvalent carboxylic acid monomer derivatives, alkyl esters, acid anhydrides and acid chlorides of polyvalent carboxylic acid monomers can be used. As polyhydric alcohol monomer derivatives, ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acids are used. Can be used.

  Examples of the polyvalent carboxylic acid monomer include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid. Acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucoic acid, phthalic acid, Isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, Diphenylacetic acid, diphenyl-p, p'- Divalent carboxylic acids such as carboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid; trimellitic acid, pyromellitic Examples thereof include divalent or higher carboxylic acids such as acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  As the polyvalent carboxylic acid monomer, it is preferable to use an aliphatic unsaturated dicarboxylic acid such as fumaric acid, maleic acid, or mesaconic acid. In particular, the aliphatic unsaturated dicarboxylic acid represented by the above general formula (A) is used. It is preferable to use it.

  By using the aliphatic unsaturated dicarboxylic acid, the obtained styrene-acryl-modified polyester resin can surely form a smooth shell layer with a more uniform film thickness while being a thin layer. . In particular, by using the aliphatic unsaturated dicarboxylic acid represented by the general formula (A), the obtained styrene-acryl-modified polyester resin is more surely a thin layer with a more uniform film thickness and A smooth shell layer can be formed.

  The ratio of the aliphatic unsaturated dicarboxylic acid in the total polyvalent carboxylic acid monomer to be used is preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.

  When the ratio of the aliphatic unsaturated dicarboxylic acid used is in the above range, the obtained styrene-acryl-modified polyester resin is more surely a thin shell with a more uniform film thickness and a smooth shell layer. Can be formed. On the other hand, if the proportion of the aliphatic unsaturated dicarboxylic acid used is too small, sufficient heat-resistant storage stability and chargeability may not be obtained for the obtained toner, and the proportion of the aliphatic unsaturated dicarboxylic acid used is If it is excessive, sufficient chargeability may not be obtained for the obtained toner.

  Examples of the polyhydric alcohol monomer include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, and the like. And trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  The ratio of the polyhydric carboxylic acid monomer to the polyhydric alcohol monomer is such that the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the polyhydric alcohol monomer and the carboxy group [COOH] of the polyhydric carboxylic acid is Preferably it is 1.5 / 1-1 / 1.5, More preferably, it is 1.2 / 1-1 / 1.2.

  As the catalyst for synthesizing the polyester resin, various conventionally known catalysts can be used.

  The unmodified polyester resin for obtaining the styrene-acrylic modified polyester resin preferably has a glass transition point of 40 ° C. or higher and 70 ° C. or lower, more preferably 50 ° C. or higher and 65 ° C. or lower. When the glass transition point of the unmodified polyester resin is 40 ° C. or higher, the cohesive force in the high temperature region becomes appropriate for the polyester resin, and the occurrence of hot offset phenomenon during fixing is suppressed. Further, since the glass transition point of the unmodified polyester resin is 70 ° C. or less, sufficient melting can be obtained at the time of fixing, and a sufficient minimum fixing temperature can be ensured.

  The unmodified polyester resin preferably has a weight average molecular weight (Mw) of 1,500 to 60,000, more preferably 3,000 to 40,000.

  When the weight average molecular weight is 1,500 or more, a cohesive force suitable for the entire binder resin is obtained, and the occurrence of a hot offset phenomenon during fixing is suppressed. Further, when the weight average molecular weight is 60,000 or less, it is possible to obtain a sufficient melting and secure a minimum fixing temperature, while suppressing occurrence of a hot offset phenomenon during fixing. The

  The unmodified polyester resin has a partially branched structure or a crosslinked structure formed by selecting a carboxylic acid valence or an alcohol valence as a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer to be used. May be.

(Polymerization initiator)
In the polymerization step (2), the polymerization is preferably performed in the presence of a radical polymerization initiator, and the timing of addition of the radical polymerization initiator is not particularly limited, but it is easy to control radical polymerization. It is preferably added after the mixing step.

  Various known polymerization initiators are preferably used as the polymerization initiator. Specifically, for example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, Lauroyl oxide, ammonium persulfate, sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, performic acid-tert -Butyl, peracetic acid-tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl, etc. Peroxides; 2 2'-azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (1-methylbutyronitrile-3-sulfonic acid sodium salt) 4,4'-azobis-4-cyanovaleric acid, and azo compounds such as poly (tetraethylene glycol-2,2'-azobisisobutyrate).

(Chain transfer agent)
In the polymerization step (2), a generally used chain transfer agent can be used for the purpose of adjusting the molecular weight of the styrene-acrylic polymer segment. The chain transfer agent is not particularly limited, and examples thereof include alkyl mercaptans and mercapto fatty acid esters.

  The chain transfer agent is preferably mixed with the resin material in the mixing step.

  The addition amount of the chain transfer agent varies depending on the molecular weight and molecular weight distribution of the desired styrene-acrylic polymer segment. Specifically, the aromatic vinyl monomer and the (meth) acrylate monomer, and It is preferable to add in the range of 0.1-5 mass% with respect to the total amount of both reactive monomers.

  The polymerization temperature in the polymerization step (2) is not particularly limited, and is appropriately selected within the range in which the polymerization between the aromatic vinyl monomer and the (meth) acrylic acid ester monomer and the bonding to the polyester resin proceed. be able to. For example, the polymerization temperature is preferably 85 ° C. or higher and 125 ° C. or lower, more preferably 90 ° C. or higher and 120 ° C. or lower, and further preferably 95 ° C. or higher and 115 ° C. or lower.

  In the production of the styrene-acrylic modified polyester resin, it is practically preferable that volatile organic substances from the emulsion such as the amount of residual monomer after the polymerization step are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, Preferably it is 200 ppm or less.

[Core particles]
The core particles constituting the toner of the present invention may contain at least a binder resin and contain a colorant, or may contain no colorant.

  The binder resin constituting the core particle may include a resin conventionally used as a binder resin for an electrophotographic toner, and various known resins can be used as such a resin. For example, styrene resins, (meth) acrylic resins, styrene- (meth) acrylic resins, vinyl resins such as olefin resins, polyester resins, styrene-acrylic modified polyester resins, polyamide resins, polycarbonate resins, polyether resins Polyvinyl acetate resin, polysulfone resin, epoxy resin polyurethane resin, urea resin, or the like can be used. Two or more of these resins may be mixed.

  The core particles constituting the toner of the present invention can be prepared by a pulverization method or a suspension polymerization method. However, in order to obtain a core / shell structure, it is preferable to prepare the core particles by an emulsion aggregation method. As the polymerizable monomer for obtaining the binder resin constituting the core particle, various known polymerizable monomers can be used. As the polymerizable monomer, the above-mentioned monofunctional monomer can be used. A binder resin having a crosslinked structure can also be used by using a polyfunctional crosslinkable monomer as the polymerizable monomer.

  As the binder resin used for the core particles constituting the toner of the present invention, a styrene- (meth) acrylic resin, a polyester resin, and a styrene-acrylic modified polyester resin are preferable.

(Styrene-acrylic resin)
The styrene-acrylic resin constituting the core particles is preferably a low molecular weight styrene-acrylic resin, and preferably has a weight average molecular weight (Mw) in the range of 20,000 to 40,000. It is preferable that the weight average molecular weight is within the above range because excellent low-temperature fixability can be obtained.

  Examples of the polymerizable monomer used to form the styrene-acrylic resin include the aromatic vinyl monomers and (meth) acrylic acid ester monomers mentioned above. The above aromatic vinyl monomers and (meth) acrylic acid ester monomers can be used singly or in combination of two or more.

  As the polymerizable monomer, together with the above aromatic vinyl monomer and (meth) acrylic acid ester monomer, acrylic acid, methacrylic acid, maleic anhydride, vinyl acetate, acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene chloride Vinyl, N-vinyl pyrrolidone, butadiene, or the like can also be used.

  Moreover, a polyfunctional vinyl-type monomer can also be used as a polymerizable monomer with said aromatic vinyl monomer and (meth) acrylic acid ester monomer. Examples of polyfunctional vinyl monomers include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol; dimethacrylates and trimethacrylates of tertiary and higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. Etc.

(Polyester resin)
The polyester resin is produced by a polycondensation reaction using a polyvalent carboxylic acid monomer (derivative) and a polyhydric alcohol monomer (derivative) as raw materials in the presence of an appropriate catalyst.

  As polyvalent carboxylic acid monomer derivatives, alkyl esters, acid anhydrides and acid chlorides of polyvalent carboxylic acid monomers can be used. As polyhydric alcohol monomer derivatives, ester compounds of polyhydric alcohol monomers and hydroxycarboxylic acids are used. Can be used.

  Examples of the polyvalent carboxylic acid monomer include oxalic acid, succinic acid, maleic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, dodecanedicarboxylic acid, fumaric acid. Acid, citraconic acid, diglycolic acid, cyclohexane-3,5-diene-1,2-dicarboxylic acid, malic acid, citric acid, hexahydroterephthalic acid, malonic acid, pimelic acid, tartaric acid, mucoic acid, phthalic acid, Isophthalic acid, terephthalic acid, tetrachlorophthalic acid, chlorophthalic acid, nitrophthalic acid, p-carboxyphenylacetic acid, p-phenylenediacetic acid, m-phenylenediglycolic acid, p-phenylenediglycolic acid, o-phenylenediglycolic acid, Diphenylacetic acid, diphenyl-p, p'- Divalent carboxylic acids such as carboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid; trimellitic acid, pyromellitic Examples thereof include divalent or higher carboxylic acids such as acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

  Examples of the polyhydric alcohol monomer include ethylene glycol, propylene glycol, butanediol, diethylene glycol, hexanediol, cyclohexanediol, octanediol, decanediol, dodecanediol, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, and the like. And trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  The ratio of the polyhydric carboxylic acid monomer to the polyhydric alcohol monomer is such that the equivalent ratio [OH] / [COOH] of the hydroxy group [OH] of the polyhydric alcohol monomer and the carboxy group [COOH] of the polyhydric carboxylic acid is Preferably it is 1.5 / 1-1 / 1.5, More preferably, it is 1.2 / 1-1 / 1.2.

  As the catalyst for synthesizing the polyester resin, various conventionally known catalysts can be used.

(Styrene-acrylic modified polyester resin)
The styrene-acrylic modified polyester resin is a resin in which a styrene-acrylic resin segment and a polyester resin segment are copolymerized via both reactive monomers, and is used as a resin constituting the shell layer. Resin can be used.

(Glass transition point of core resin)
(Measurement method of glass transition point)
The glass transition point of the binder resin (core resin) constituting the core particles is preferably in the range of 35 ° C. to 55 ° C. from the viewpoint of low-temperature fixability. If the glass transition point is within this range, both low temperature fixability and high temperature offset resistance can be satisfied.

  The glass transition point of the core resin is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82.

(Softening point of core resin)
Similarly, from the viewpoint of low-temperature fixing, the softening point of the core resin is preferably in the range of 80 ° C to 110 ° C. When the softening point of the core resin is within this range, the low-temperature fixability and the high-temperature offset property are preferable.

  The softening point of the core resin is measured as follows.

First, in an environment of 20 ° C. ± 1 ° C. and 50% ± 5% RH, 1.1 g of the core resin is placed in a petri dish and left flat for 12 hours or more, and then a molding machine “SSP-10A” (Shimadzu Corporation) Pressure) with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample having a diameter of 1 cm, and this molded sample is then subjected to an environment of 24 ° C. ± 5 ° C. and 50% ± 20% RH. With a flow tester “CFT-500D” (manufactured by Shimadzu Corporation), a cylindrical die hole (1 mm diameter ×× 1 kg), with a load of 196 N (20 kgf), a starting temperature of 60 ° C., a preheating time of 300 seconds, and a heating rate of 6 ° C./min. than 1 mm), extruded from the time of preheating ends with piston diameter 1 cm, offset method temperature _{T offset} measured by setting the offset value 5mm at a melt temperature measurement method of temperature ramps are co It is the softening point of the resin.

(Weight average molecular weight of core resin)
The weight average molecular weight of the binder resin constituting the core particle is preferably in the range of 20,000 to 40,000. Within this range, a toner having good low-temperature fixability can be obtained, which is preferable.

(Measurement method of weight average molecular weight)
As a method for measuring the molecular weight of a resin by GPC (gel permeation chromatography), a measurement sample is dissolved in tetrahydrofuran so as to have a concentration of 1 mg / ml. As dissolution conditions, it is carried out at room temperature for 5 minutes using an ultrasonic disperser. Next, after processing with a membrane filter having a pore size of 0.2 μm, 10 μl of sample solution is injected into GPC. Specific examples of GPC measurement conditions are shown below.

Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKguardcolumn + TSKgelSuperHZM-M3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 0.2 ml / min
Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes are used for calibration curve measurement.

(Coloring agent)
As the colorant in the case where the core particles are configured to contain a colorant, carbon black, a magnetic material, a dye, a pigment, or the like can be arbitrarily used.

  As the carbon black, channel black, furnace black, acetylene black, thermal black, lamp black, or the like can be used.

  As the magnetic material, a ferromagnetic metal such as iron, nickel, or cobalt, an alloy containing these metals, a compound of a ferromagnetic metal such as ferrite or magnetite, or the like can be used.

  As the pigment, C.I. I. Pigment Red 2, 3, 5, 7, 15, 16, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 123, 139, 144, 149, 166, 177, 178, 208, 209, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 3, 9, 14, 17, 35, 36, 65, 74, 83, 93, 94, 98, 110, 111, 138, 139, 153, 155, 180, 181, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, and phthalocyanine pigments whose central metal is zinc, titanium, magnesium, or the like can be used, and a mixture thereof can also be used. As the dye, C.I. I. Solvent Red 1, 3, 14, 17, 17, 22, 22, 49, 51, 52, 58, 63, 87, 111, 122, 127, 128, 131, 145, 146, 149, 150, 151, 152, 153, 154, 155, 156, 157, 158, 176, 179, pyrazolotriazole Azo dyes, pyrazolotriazole azomethine dyes, pyrazolone azo dyes, pyrazolone azomethine dyes, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, or 95 can be used, and a mixture thereof can also be used.

  The number average primary particle size of the colorant varies depending on the type, but is preferably about 10 to 300 nm.

  In the case where the core particles are configured to contain a colorant, the content ratio of the colorant in the toner is preferably 1 to 30% by mass, more preferably 2 to 20% by mass with respect to the binder resin. is there.

(wax)
Examples of the wax include low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, hydrocarbon waxes such as paraffin wax, carnauba wax, pentaerythritol behenate, behenyl behenate, and And ester waxes such as behenyl citrate. These can be used alone or in combination of two or more.

  As the wax, it is preferable to use a wax having a melting point of 50 to 95 ° C. from the viewpoint of reliably obtaining low-temperature fixability and releasability of the toner.

  The content ratio of the wax is preferably 2 to 20% by mass, more preferably 3 to 18% by mass, and further preferably 4 to 15% by mass with respect to the total amount of the binder resin.

(Charge control agent)
In addition, when a charge control agent is contained in the toner particles according to the present invention, various known charge control agents can be used.

  As the charge control agent, various known compounds that can be dispersed in an aqueous medium can be used. Specifically, nigrosine dyes, metal salts of naphthenic acid or higher fatty acids, alkoxylated amines, fourth compounds. Examples include quaternary ammonium salt compounds, azo metal complexes, salicylic acid metal salts or metal complexes thereof.

  Examples of the method of incorporating the charge control agent in the toner particles include the same method as the method of incorporating the offset preventing agent described above.

  The content ratio of the charge control agent is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass with respect to the total amount of the binder resin.

<Toner production method>
In the toner production method of the present invention, an aqueous dispersion of resin fine particles forming a shell layer is mixed with an aqueous dispersion of core particles having an inorganic layer, and the shell layer is formed on the surface of the core particles having an inorganic layer. It is characterized by producing by.

  In the present invention, since the shell layer can be uniformly formed on the surface of the core particles, the binder resin fine particles and the colorant fine particles dispersed in the aqueous medium are aggregated and fused to form the core particles. It is preferable to produce by the emulsion polymerization aggregation method in which toner particles are obtained by polymerizing a crosslinkable monomer on the surface of the core particles to form shell resin fine particles and fusing them.

When the toner of the present invention is produced by an emulsion polymerization aggregation method, a production example of a toner containing a colorant is specifically shown.
(1) A binder resin polymerization process for core particles in which a binder resin fine particle for core particles is formed by polymerization in an aqueous medium to prepare a dispersion in which the binder resin fine particles are dispersed;
(2) A colorant fine particle dispersion preparation step for preparing a dispersion in which colorant fine particles are dispersed in an aqueous medium.
(3) a core particle forming step of forming core particles by aggregating binder resin fine particles for core particles and colorant fine particles in an aqueous medium;
(4) To the aqueous dispersion of core particles prepared as described above, water or an aqueous medium in which silane alkoxide is dissolved is added, and this dispersion is added dropwise to the water or aqueous medium to which alkali has been added. Or by dropping water or an aqueous medium in which alkali is added to the dispersion to form an inorganic layer of silica on the surface of the core particles,
(5) An aqueous dispersion of shell layer resin fine particles is added to an aqueous medium in which core particles coated with an inorganic layer are dispersed to form a shell layer on the surface of the inorganic layer formed on the surface of the core particles. Forming a toner base particle having a core-shell structure,
(6) An aging step of adjusting the shape of the toner base particles by aging with thermal energy;
(7) a washing step of filtering the toner base particles from the dispersion of the toner base particles (aqueous medium) and removing the surfactant from the toner base particles;
(8) A drying step of drying the washed toner base particles;
Consisting of, if necessary,
(9) An external additive addition step of adding an external additive to the dried toner particle matrix can be added.

(1) Binder resin polymerization process for core particles In this binder resin polymerization process for core particles, resin particles for cores are formed, and this is used for the core particle formation process.

  Specifically, the resin fine particles related to the binder resin include a wax as necessary in a polymerizable monomer for forming the binder resin in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less. A monomer solution in which toner constituents such as a charge control agent or the like are dissolved or dispersed is added, mechanical energy is applied to form droplets, and then a water-soluble radical polymerization initiator is added to form droplets. The polymerization reaction proceeds inside. Note that an oil-soluble polymerization initiator may be contained in the droplet. In such a binder resin polymerization process, mechanical energy is imparted and forcedly emulsified (formation of droplets) is essential. Examples of the mechanical energy applying means include strong stirring or ultrasonic vibration energy applying means such as homomixer, ultrasonic wave, and manton gorin.

  The binder resin fine particles formed in the binder resin polymerization step for the core particles can be composed of two or more layers made of resins having different compositions. In this case, an emulsion polymerization treatment ( It is possible to employ a method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of the first resin fine particles prepared by the first stage polymerization), and this system is polymerized (second stage polymerization). In the present invention, since the first-stage polymerization is a high-molecular weight polyester, a polyester resin is synthesized by a normal polycondensation reaction, which is finely divided into a fine particle dispersion in an aqueous medium. The second monomer is added to the second monomer and, if necessary, the third monomer is added. Examples of the method of making the polyester resin into the fine particle dispersion include a method of pulverizing by a mechanical method and dispersing in an aqueous medium using a surfactant, and a phase inversion emulsification method. May be used.

  In the case where a surfactant is used in the binder resin polymerization step, for example, the following surfactants can be used as the surfactant.

(Surfactant)
A dispersion stabilizer is preferably added to the aqueous medium in order to prevent aggregation of dispersed fine particles.

  As the dispersion stabilizer, various known surfactants such as a cationic surfactant, an anionic surfactant, and a nonionic surfactant can be used.

  Specific examples of the cationic surfactant include dodecyl ammonium bromide, dodecyl trimethyl ammonium bromide, dodecyl pyridinium chloride, dodecyl pyridinium bromide, hexadecyl trimethyl anonium bromide and the like.

  Specific examples of nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose.

  Specific examples of anionic surfactants include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, and polyoxyethylene (2) sodium lauryl ether sulfate. Can do.

  The above surfactants can be used singly or in combination of two or more as desired.

  In addition to the binder resin and the colorant, the toner particles of the present invention may contain an internal additive such as a wax, a charge control agent, or a magnetic powder as necessary. For example, in this binder resin polymerization step, it can be introduced into the toner particles by dissolving or dispersing in advance in a monomer solution for forming the binder resin.

  In addition, such an internal additive is prepared by separately preparing a dispersion of internal additive fine particles consisting of only the internal additive, and aggregating the internal additive fine particles together with the resin fine particles and the colorant fine particles in the core particle forming step. Although it can be introduced into the toner particles, it is preferable to adopt a method in which it is introduced in advance in the binder resin polymerization step.

(Polymerization initiator)
As the polymerization initiator used in the binder resin polymerization step, the same polymerization initiator as that described above can be used.

(Chain transfer agent)
In the binder resin polymerization step, a commonly used chain transfer agent can be used for the purpose of adjusting the molecular weight of the binder resin. As the chain transfer agent, those similar to the aforementioned polymerization initiators can be used.

  The average particle diameter of the binder resin fine particles obtained in this binder resin polymerization step is preferably in the range of, for example, 50 to 500 nm as a volume-based median diameter.

  The volume-based median diameter was measured using “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.).

(2) Colorant fine particle dispersion preparation step The colorant fine particle dispersion can be prepared by dispersing a colorant in an aqueous medium. The colorant dispersion treatment is preferably performed in a state where the surfactant concentration in the aqueous medium is not less than the critical micelle concentration (CMC) since the colorant is uniformly dispersed. Various known dispersers can be used as a disperser used for the dispersion treatment of the colorant.

  Examples of the surfactant used include the same surfactants as those described above.

  The dispersion diameter of the colorant fine particles in the colorant fine particle dispersion prepared in the colorant fine particle dispersion preparing step is preferably in the range of 10 to 300 nm in terms of volume-based median diameter.

  The volume-based median diameter of the colorant fine particles in the colorant fine particle dispersion is measured with an electrophoretic light scattering photometer “ELS-800 (manufactured by Otsuka Electronics Co., Ltd.)”.

  When a surfactant is used in this colorant fine particle dispersion preparation step, the same surfactant as the surfactant that can be used in the above-mentioned shell resin fine particle dispersion preparation step, for example, is used. Can be used.

(3) Core particle forming step In this core particle forming step, fine particles of other toner constituent components such as an offset preventive agent and a charge control agent are aggregated together with the binder resin fine particles and the colorant fine particles as necessary. You can also.

  As a specific method for aggregating and fusing the binder resin fine particles and the colorant fine particles, a flocculant is added to the aqueous medium so as to have a critical aggregation concentration or higher, and then at a glass transition point or higher of the binder resin fine particles. In addition, by heating to a temperature not higher than the melting peak temperature of these mixtures, the salting out of the fine particles such as the binder resin fine particles and the colorant fine particles proceeds, and at the same time, the fusion is advanced in parallel to obtain the desired particles. In this method, the particle growth is stopped by adding a coagulation terminator when it has grown to the diameter, and further, heating is continued to control the particle shape as necessary.

  In this method, the time allowed to stand after the addition of the flocculant is shortened as much as possible, and immediately heated to a temperature not lower than the glass transition point of the resin fine particles related to the binder resin and not higher than the melting peak temperature of these mixtures. It is preferable to do. The reason for this is not clear, but depending on the standing time after salting out, the aggregation state of the particles may fluctuate and the particle size distribution may become unstable, and the surface properties of the fused particles may vary. This is because there is concern about the occurrence. The time until this temperature rise is usually preferably within 30 minutes, and more preferably within 10 minutes. Moreover, it is preferable that it is 1 degree-C / min or more as a temperature increase rate. The upper limit of the heating rate is not particularly specified, but is preferably 15 ° C./min or less from the viewpoint of suppressing the generation of coarse particles due to rapid progress of fusion. Furthermore, after the reaction system reaches a temperature equal to or higher than the glass transition point, it is important to continue the fusion by maintaining the temperature of the reaction system for a certain time. Thereby, the growth and fusion of the core particles can be effectively advanced, and the durability of the toner particles finally obtained can be improved.

(Flocculant)
The flocculant used in the core particle forming step is not particularly limited, but a material selected from metal salts is preferably used. Examples of the metal salt include monovalent metal salts such as alkali metal salts such as sodium, potassium and lithium; divalent metal salts such as calcium, magnesium, manganese and copper; and trivalent metal salts such as iron and aluminum. Etc. Specific examples of the metal salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. It is particularly preferable to use a divalent metal salt because aggregation can be promoted. These can be used alone or in combination of two or more.

  When using a surfactant in the core particle forming step, it is possible to use, for example, the same surfactant as the surfactant that can be used in the above-mentioned shell resin fine particle dispersion preparation step. it can.

The particle size of the core particles obtained in the core particle forming step, for example, preferably the volume-based median diameter (D ₅₀₎ is 2～9Myuemu, more preferably 4～7Myuemu.

  The volume-based median diameter of the core particles is measured by “Coulter Multisizer 3” (manufactured by Coulter Beckman).

(4) Inorganic layer forming step Water or an aqueous medium in which silane alkoxide is dissolved is added to the aqueous dispersion of core particles prepared as described above. This dispersion solution is dropped into water or an aqueous medium to which alkali is added, or water or an aqueous medium to which alkali is added to the dispersion is dropped. According to this method, the silane alkoxide dissolved in the dispersion containing the core particles undergoes hydrolysis and polycondensation in the presence of alkali and gradually insolubilizes. It will deposit on the surface of the core particle from the interaction. As a result, an inorganic layer of silica is formed on the surface of the core particles by fixing the granular masses containing silica to each other.

  As another method, an inorganic layer of silica is formed by a sol-gel method on the surface of the core binder resin fine particles constituting the core particles, and then the aqueous dispersion of the core binder resin fine particles having the inorganic layer and the colorant fine particles An aqueous dispersion of core particles having an inorganic layer can also be prepared by mixing and aggregating and fusing the dispersion. In addition, an inorganic layer can also be formed on the surface of the core particle by the dry method described above.

(5) Shelling step In this shelling step, an aqueous dispersion of shell resin fine particles constituting the binder resin of the shell layer is added to the dispersion of core particles coated with the inorganic layer, and the surface of the core particles The shell resin fine particles are aggregated and fused on the surface of the inorganic layer, and the shell layer is coated on the surface of the core particles coated with the inorganic layer to form toner base particles.

  Specifically, the aqueous dispersion of the resin fine particles constituting the shell layer constituting the binder resin of the shell layer is added to the core particle dispersion while maintaining the temperature in the core particle formation step, and the heating and stirring are continued. Then, a shell layer having a thickness of 100 to 300 nm is formed on the surface of the core particle coated with the inorganic layer by slowly associating and fusing the shell resin fine particles on the surface of the core particle coated with the inorganic layer over several hours. The toner base particles are formed by coating. The heating and stirring time is preferably 1 to 7 hours, particularly preferably 3 to 5 hours.

(6) Aging step The toner particle shape in the toner can be made uniform to some extent by controlling the heating temperature in the core particle forming step and the shelling step, but in order to further make the shape uniform, the aging step Go through.

  This aging step is controlled by controlling the heating temperature and time so that the surface of the toner base particles formed with a uniform particle size and a narrow distribution has a smooth but uniform shape. Specifically, the heating temperature is lowered in the core particle forming step and the shelling step to suppress the progress of fusion between the resin fine particles to promote homogenization, and in this aging step, the heating temperature is lowered, and The toner base particles have a desired average circularity by extending the time. That is, the surface is controlled to have a uniform shape.

(7) Washing step and (8) Drying step The washing step and the drying step can be performed by employing various known methods.

(9) External additive addition step This external additive addition step is a step of preparing toner particles by adding and mixing external additives as necessary to the dried toner base particles.

  The toner base particles prepared through the steps up to the drying step can be used as toner particles as they are, but are known on the surface from the viewpoint of improving charging performance, fluidity, or cleaning properties as a toner. It is preferable to add particles such as inorganic fine particles and organic fine particles and a lubricant as external additives.

  Various external additives may be used in combination.

  Examples of the inorganic fine particles include inorganic oxide fine particles such as silica fine particles, alumina fine particles, and titanium oxide fine particles, inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, strontium titanate, and zinc titanate. And inorganic titanic acid compound fine particles.

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

  The amount of these 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 base particles.

  Examples of the method for adding the external additive include a dry method in which the external additive is added in powder form to the dried toner base particles. Examples of the mixing device include mechanical mixing devices such as a Henschel mixer and a coffee mill. Can be mentioned.

〔toner〕
The “toner” of the present invention comprises “toner base particles” in which an inorganic layer is formed on the surface of core particles and a shell layer is further formed thereon. The “toner base particles” can be used as “toners” as they are, but normally, the “toner base particles” added with an external additive are referred to as “toner particles”. “Toner” refers to an aggregate of “toner particles”.

(Average particle diameter of toner particles)
The average particle diameter of the toner particles of the present invention is preferably, for example, 3 to 10 μm in volume-based median diameter (D ₅₀ ). This particle size can be controlled by the concentration of the coagulant used, the amount of organic solvent added, the fusing time, or the composition of the polymer, for example, when the emulsion polymerization aggregation method described later is employed. .

  When the volume-based median diameter is in the above range, a very minute dot image of, for example, 1200 dpi (dpi; number of dots per inch (2.54 cm)) level can be faithfully reproduced.

  The volume-based median diameter of the toner particles is measured and calculated using a measuring device in which a computer system equipped with data processing software “Software V3.51” is connected to “Multisizer 3” (manufactured by Beckman Coulter). Is. Specifically, 0.02 g of toner is added to 20 ml of a surfactant solution (for example, a surfactant solution obtained by diluting a neutral detergent containing a surfactant component 10 times with pure water for the purpose of dispersing toner particles). Then, ultrasonic dispersion was performed for 1 minute to prepare a toner particle dispersion, and this toner particle dispersion was placed in a beaker containing “ISOTON II” (manufactured by Beckman Coulter) in a sample stand. Inject with a pipette until the displayed concentration of the measuring device is 8%. Here, a reproducible measurement value can be obtained by setting the concentration range. In the measuring apparatus, the frequency value is calculated by setting the number of measured particle counts to 25000 and the aperture diameter to 100 μm, and the particle diameter of 50% from the larger volume integrated fraction is set as the volume-based median diameter.

(Average circularity of toner particles)
The toner particles according to the present invention have an arithmetic average value of circularity represented by the following formula (T) of 0.850 to 0.990 from the viewpoint of improving the transfer efficiency of the individual toner particles constituting the toner. Preferably there is.

Formula (T): Circularity = perimeter of perfect circle having projection area equivalent to particle projection image / perimeter of particle projection image Here, the average circularity of toner particles is “FPIA-2100” (manufactured by Sysmex). Is a value measured using.

  Specifically, the toner particles are moistened with an aqueous surfactant solution, and ultrasonic dispersion is performed for 1 minute. After dispersion, HPFP detection is performed in the measurement condition HPF (high magnification imaging) mode using “FPIA-2100”. Measurement is performed at appropriate concentrations of several thousand to 10,000. Within this range, reproducible measurement values can be obtained.

(Developer)
The toner of the present invention can be used as a magnetic or nonmagnetic one-component developer, but may be mixed with a carrier and used as a two-component developer.

  As the carrier, for example, magnetic particles made of conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead can be used. It is preferable to use particles. As the carrier, a coated carrier in which the surface of magnetic particles is coated with a coating agent such as a resin, a resin-dispersed carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.

  The carrier preferably has a volume average particle diameter of 15 to 100 μm, more preferably 25 to 80 μm.

[Image forming apparatus]
The toner of the present invention can be used in a general electrophotographic image forming method. As an image forming apparatus in which such an image forming method is performed, for example, a photosensitive member that is an electrostatic latent image carrier, A charging means for applying a uniform potential to the surface of the photoconductor by corona discharge having the same polarity as that of the toner, and an electrostatic latent image by performing image exposure on the surface of the uniformly charged photoconductor based on image data. An exposure means for forming an image; a developing means for conveying the toner to the surface of the photoreceptor to visualize the electrostatic latent image to form a toner image; and passing the toner image through an intermediate transfer member as necessary. For example, a transfer unit that transfers to a transfer material and a fixing unit that fixes a toner image on the transfer material can be used. Among image forming apparatuses having such a configuration, a color image forming apparatus having a configuration in which image forming units related to a plurality of photoconductors are provided along the intermediate transfer body, in particular, the photoconductors are arranged in series on the intermediate transfer body. It can be suitably used for the tandem type color image forming apparatus.

  As mentioned above, although embodiment of this invention was described concretely, embodiment of this invention is not limited to said example, A various change can be added.

  Hereinafter, the present invention will be specifically described with reference to Examples.

<< Production of Toner [1] >>
The toner was prepared as follows.

<Preparation of dispersion of resin fine particles for core particles>
(1-1) First-stage polymerization Ion-exchange 2.0 parts by mass of the anionic surfactant “sodium lauryl sulfate” in advance in a reaction vessel equipped with a stirrer, temperature sensor, temperature controller, condenser, and nitrogen inlet. An anionic surfactant solution dissolved in 2900 parts by mass of water 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 parts by mass of a polymerization initiator “potassium persulfate: KPS” to this surfactant solution and adjusting the internal temperature to 78 ° C.,
Solution (1)
Styrene 540 parts by mass n-butyl acrylate 270 parts by mass Methacrylic acid 65 parts by mass n-octyl mercaptan 17 parts by mass The solution (1) is added dropwise over 3 hours, and after completion of the addition, the mixture is heated and stirred at 78 ° C for 1 hour. Thus, polymerization (first-stage polymerization) was performed to prepare a dispersion of “resin fine particles (a1)”.

(1-2) Second stage polymerization In a flask equipped with a stirrer,
Solution (2)
Styrene 94 parts by weight n-butyl acrylate 60 parts by weight Methacrylic acid 11 parts by weight n-octyl mercaptan 5 parts by weight Paraffin wax (melting point: 73 ° C.) 51 parts by weight is added to the solution (2), and 85 “Monomer solution (2)” was prepared by heating to 0 ° C. and dissolving. On the other hand, a surfactant solution in which 2 parts by mass of the anionic surfactant “sodium lauryl sulfate” was dissolved in 1100 parts by mass of ion-exchanged water was heated to 90 ° C., and “resin fine particles (a1)” was added to this surfactant solution. Is added to 28 parts by mass in terms of solid content of the resin fine particles (a1), and then mixed and dispersed for 4 hours by a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. Then, a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm is prepared, and an initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator “KPS” is dissolved in 110 parts by mass of ion-exchanged water is added to the dispersion, This system was heated and stirred at 90 ° C. for 2 hours to conduct polymerization (second stage polymerization) to prepare a dispersion of “resin fine particles (a11)”.

(1-3) Third-stage polymerization An initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator “KPS” is dissolved in 110 parts by mass of ion-exchanged water is added to the dispersion of “resin fine particles (a11)”. Then, under the temperature condition of 80 ° C., the following solution (3) was added dropwise over 1 hour.
Solution (3)
Styrene 230 parts by mass n-butyl acrylate 100 parts by mass n-octyl mercaptan 5.2 parts by mass Polymerization (third stage polymerization) was carried out by heating and stirring for 3 hours after completion of dropping. Then, it cooled to 28 degreeC and obtained the "dispersion liquid of the resin particle for core particles" in which the resin particle for core particles was disperse | distributed in the anionic surfactant solution.

<Preparation of colorant dispersion>
90 parts by mass of sodium dodecyl sulfate was dissolved in 1600 parts by mass of ion-exchanged water with stirring. While stirring this solution, 420 parts by mass of carbon black “Mogal L” (manufactured by Cabot) is gradually added, and then dispersed using a stirrer “Claremix” (manufactured by M Technique). A “colorant dispersion” having dispersed particles of the colorant was prepared. The particle diameter of this dispersion was measured using a particle size distribution measuring apparatus “Microtrac UPA-150” (manufactured by Nikkiso Co., Ltd.) and found to be 117 nm.

<Preparation of core particle dispersion>
To a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling pipe, 5 mol / liter of an aqueous sodium hydroxide solution of “dispersed resin particles for core particles” was added to adjust the pH to 10 (25 ° C.). Thereafter, 40 parts by mass of the above “colorant dispersion” was added in terms of solid content. Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. Thereafter, the temperature was raised after being left for 3 minutes, and the temperature of the system was raised to 90 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 90 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman), and when the median diameter (D50) on the volume basis reached 6.0 μm, 190 parts by mass of sodium chloride was added. An aqueous solution dissolved in 760 parts by mass of ion-exchanged water was added to stop particle growth to obtain a “core particle dispersion”.

<Preparation of dispersion of inorganic layer forming particles 1 (formation of inorganic layer)>
150 parts by mass of the “core particle dispersion” of 6.0 μm prepared as described above was dispersed in 1000 parts by mass of pure water, 10 parts by mass of ammonia water (28% by mass) was added, and the mixture was stirred for 5 minutes. Subsequently, 30 mass parts of tetraethoxysilane was dripped over 3 hours, and also it stirred at room temperature for 5 hours. The solvent in this dispersion was distilled off at 50 ° C. under reduced pressure to obtain “inorganic layer-forming particles 1” in which an inorganic layer (silica layer) was formed on the surface of the core particles. Thereafter, 90 parts by mass of sodium dodecyl sulfate was added to a solution obtained by dissolving 1600 parts by mass of ion-exchanged water to obtain “dispersion liquid of inorganic layer-forming particles 1” in which an inorganic layer was formed on the core particle surface.

  About the "inorganic layer forming particles 1" obtained as described above, the thickness of the inorganic layer was measured as follows.

[Measurement of inorganic layer thickness]
The thickness of the inorganic layer was measured using “Microtrack UPA-150” (manufactured by Nikkiso Co., Ltd.), and the particle diameters of the core particles and the inorganic layer forming particles 1 were measured, and the difference was defined as the thickness of the inorganic layer.

  First, a few drops of “dispersion liquid of inorganic layer forming particles 1” are dropped on a 50 ml graduated cylinder, 25 ml of pure water is added, and dispersed for 3 minutes using an ultrasonic cleaner “US-1 (manufactured by asone)” A measurement sample was prepared. Next, 3 ml of the measurement sample was put into the cell of “Microtrack UPA-150”, it was confirmed that the value of Sample Loading was in the range of 0.1 to 100, and measurement was performed under the following measurement conditions.

(Measurement condition)
Transparency (transparency): Yes
Refractive Index (refractive index): 1.59
Particle Density (particle specific gravity): 1.05 mg / cm ³
Spherical Particles (Spherical Particles): Yes
(Solvent conditions)
Refractive Index (refractive index): 1.33
Viscosity (Viscosity): High (temp) 0.797 × 10 ⁻³ Pa · s
Low (temp) 1.00 ² × 10 ^-3 Pa · s
The film thickness of the inorganic layer measured as described above was 0.60 μm.

<Preparation of dispersion of resin fine particles for shell layer>
(Synthesis of styrene acrylic modified polyester resin)
In a four-necked flask equipped with a nitrogen inlet tube, dehydration tube, stirrer and thermocouple,
Bisphenol A propylene oxide 2-mole adduct 500 parts by mass Terephthalic acid 117 parts by mass Fumaric acid 82 parts by mass Esterification catalyst (tin octylate) 2 parts by mass were added and subjected to a polycondensation reaction at 230 ° C. for 8 hours. After reacting for hours and cooling to 160 ° C,
Acrylic acid 10 parts by mass Styrene 30 parts by mass Butyl acrylate 7 parts by mass Polymerization initiator (di-t-butyl peroxide) 10 parts by mass of the mixture was added dropwise with a dropping funnel over 1 hour, and then maintained at 160 ° C. Then, after continuing the addition polymerization reaction for 1 hour, the temperature was raised to 200 ° C. and held at 10 kPa for 1 hour, and then unreacted acrylic acid, styrene, butyl acrylate, and generated water were removed to obtain “styrene”. An “acryl-modified polyester resin” was prepared.

  This “styrene acrylic modified polyester resin” had a glass transition point of 60 ° C. and a softening point of 105 ° C.

100 parts by mass of the “styrene acrylic modified polyester resin” produced above was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.) and 638 parts by mass of a 0.26% by mass sodium lauryl sulfate solution prepared in advance. The mixture is stirred and ultrasonically dispersed with an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) at V-LEVEL, 300 μA for 30 minutes, and the median diameter (D ₅₀ ) based on volume is 250 nm. A “dispersion of resin fine particles for shell layer” in which resin fine particles for shell layer were dispersed was prepared.

<Preparation of Toner [1]>
(Preparation of toner base particles 1)
To a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling tube, a 5 mol / liter sodium hydroxide aqueous solution of “dispersion of inorganic layer-forming particles 1” was added to adjust the pH to 10 (25 ° C.). Next, an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. Thereafter, the temperature was raised after standing for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes. In this state, 72 parts by mass of “dispersion of resin fine particles for shell layer” in terms of solid content was added. It was added over 30 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), and 190 parts by mass of sodium chloride was ionized when the median diameter (D50) on a volume basis reached 6.2 μm. An aqueous solution dissolved in 760 parts by mass of exchange water was added to stop the formation of the shell layer. Thereafter, the temperature is raised, and the particles are fused by heating and stirring at 85 ° C., and the average circularity measuring device “FPIA-2100” (manufactured by Sysmex) is used (HPF detection number is 4000). When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to prepare a “dispersion of toner base particle 1”.

  The “dispersion of toner base particles 1” prepared above was subjected to solid-liquid separation with a centrifugal separator to form a wet cake of toner base particles. The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). Drying to 0.5 mass% produced “toner base particle 1”.

(External additive treatment)
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to the dried “toner base particles 1”, and a Henschel mixer is added. The toner [1] was prepared by mixing.

<< Production of Toners [2] to [5] >>
In the preparation of the toner [1], toners [2] to [5] were prepared by adjusting the thickness of the inorganic layer to Table 1. That is, in the preparation of the toner [1], the thickness of the inorganic layer was reduced to 0 by performing the same procedure except that 5 parts by mass of tetraethoxysilane was dropped over 30 minutes in the preparation of the inorganic layer forming particle dispersion. A 1 μm toner [2] was prepared. Also, a toner [3] having an inorganic layer thickness of 1.2 μm was prepared by taking the same procedure except that 60 parts by mass of tetraethoxysilane was dropped over 6 hours in preparation of the inorganic layer forming particle dispersion. .

  Further, a toner [4] having an inorganic layer thickness of 1.4 μm was prepared by taking the same procedure except that 70 parts by mass of tetraethoxysilane was dropped over 7 hours in preparation of the inorganic layer forming particle dispersion. . Further, a toner [5 μm with an inorganic layer thickness of 0.05 μm was obtained by taking the same procedure except that 2.5 parts by mass of tetraethoxysilane was dropped over 15 minutes in the preparation of the inorganic layer forming particle dispersion. ] Was produced.

<< Production of Toner [6] >>
(Preparation of toner base particles 6)
The “core particle dispersion” used in the preparation of the toner [1] was subjected to solid-liquid separation with a centrifugal separator to form a wet cake of core particles (core particle 6). The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm in the centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). It dried until it became 0.5 mass%, and produced "core particle 6". Hydrophobic silica (number average primary particle size = 12 nm) 1% by mass and hydrophobic titania (number average primary particle size = 20 nm) 0.3% by mass are added to the “core particle 6”, and the mixture is added using a Henschel mixer. By mixing at 0 ° C., “inorganic layer forming particles 6” having an inorganic layer on the surface of the core particles formed by a dry process were produced. When the thickness of this inorganic layer was measured by the same method as described above, it was 0.60 μm.

  420 parts by mass of the “inorganic layer forming particles 6” were dispersed in 90 parts by mass of a surfactant sodium dodecyl sulfate in 1600 parts by mass of ion-exchanged water. Thereafter, the temperature was raised after standing for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes. In this state, 72 parts by mass of “dispersion of resin fine particles for shell layer” in terms of solid content was added. The mixture was added over 30 minutes, and the shell formation 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), and 190 parts by mass of sodium chloride was ionized when the median diameter (D50) on a volume basis reached 6.2 μm. An aqueous solution dissolved in 760 parts by mass of exchange water was added to stop shell formation. Thereafter, the temperature is raised, and the particles are fused by heating and stirring at 85 ° C., and the average circularity measuring device “FPIA-2100” (manufactured by Sysmex) is used (HPF detection number is 4000). When the average circularity reached 0.945, it was cooled to 30 ° C. to prepare “dispersion of toner base particle 6”.

  The “dispersed liquid of toner base particles 6” produced above was subjected to solid-liquid separation with a centrifugal separator to form a wet cake of toner base particles 6. The wet cake was washed with ion-exchanged water at 35 ° C. until the electric conductivity of the filtrate reached 5 μS / cm with the centrifuge, and then transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.). “Toner base particles 6” were prepared by drying to 0.5 mass%.

(External additive treatment)
1% by mass of hydrophobic silica (number average primary particle size = 12 nm) and 0.3% by mass of hydrophobic titania (number average primary particle size = 20 nm) are added to dried “toner base particles 6”, and a Henschel mixer is added. Was mixed to prepare toner [6].

<< Production of Toner [7] >>
Toner [7] was prepared in the same manner as in the preparation of toner [1] except that the inorganic layer was not formed. This was used as a comparative toner.

上記のようにして作製したトナー〔１〕〜トナー〔７〕について、以下の評価を行った。

The toner [1] to toner [7] produced as described above were evaluated as follows.

<Evaluation method>
For evaluation, a commercially available composite printer “bizhub PRO C550 (manufactured by Konica Minolta Business Technologies, Inc.)” corresponding to a two-component development type image forming apparatus was used. The heat source was adjusted so that the temperature on the surface of the fixing upper roller was 160 ° C.

  In addition, the evaluation procedure is that 500 sheets of A4 size are continuously printed, and at the start of continuous printing, a sample of uneven gloss evaluation sample having a step shape on the 10th sheet, the 100th sheet, and the 500th sheet. Was output. A step-like gloss unevenness evaluation sample was prepared by outputting a solid image on the entire surface of an A4 size image support, and evaluated according to the contents described later. The continuous printing by the image forming apparatus was performed in a so-called normal temperature and normal humidity environment at a temperature of 20 ° C. and a relative humidity of 55% RH.

[Glossiness measurement]
For the glossiness of the fixed image, a gloss meter “GMX-203” (manufactured by Murakami Color Research Laboratory Co., Ltd.) is used according to JIS Z8741 1983 Method 2, and an angle indicated by θ is selected as a 75 ° measuring square type. Measurements were made. The glossiness was an average value of a total of 5 points at the center and four corners of the measurement image.

(Glossiness criteria)
The glossiness of 40 or less obtained as described above was determined to be acceptable.
[Measurement of gloss unevenness]
Using the above-described evaluation sample that outputs an A4 size solid image, the glossiness at 10 points is measured at equal intervals from one end to the other in the longitudinal direction. The difference was determined. The glossiness was measured using the above-described measuring apparatus, and the evaluation was as follows. That is, when the maximum glossiness value was set to 100, the difference from the minimum glossiness value was evaluated.

Gloss difference (%) = (Maximum gloss value−Minimum gloss value) × 100 / Maximum gloss value (Gloss unevenness criterion)
A: The difference between the maximum and minimum gloss values (gloss difference) is 1% or less (no problem)
○: Gloss difference exceeds 1% and is less than 5% (no problem at a level that is hardly visible)
Δ: Gloss difference of 5% or more and less than 6% (difference is visually observed but practically acceptable)
X: Gloss difference is 6% or more (there is a problem at the level where the difference is visible even visually)
[Fixing temperature (low temperature fixing property evaluation)]
In a commercially available color multifunction peripheral “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies), the surface temperature of the upper fixing belt is in the range of 130 to 170 ° C., and the surface temperature of the lower fixing roller is 110 to 150 ° C. In this case, the toner is applied on an evaluation paper “NPi fine paper 128 g / m ² ” (manufactured by Nippon Paper Industries Co., Ltd.) at a fixing speed of 300 mm / sec and a toner adhesion amount of 11.3 g / m 2. ^{In the} fixing experiment to fix the solid image of ^2, the fixing temperature (surface temperature of the fixing upper belt) is decreased by 170 ° C, 165 ° C, etc. in increments of 5 ° C until fixing failure due to cold offset is observed. The test was repeated while changing. The lower fixing roller was always set to a surface temperature 20 ° C. lower than the surface temperature of the upper fixing belt. Then, the lowest fixing temperature in the fixing experiment in which fixing failure due to cold offset was not observed was evaluated as the lower limit fixing temperature. The lower the fixing minimum temperature, the better the low-temperature fixability. When the temperature was 155 ° C. or lower, it was judged acceptable and practically acceptable.

表２の結果ら明らかなように、本発明のトナー〔１〕〜〔６〕は低温定着性に優れ、光沢度、光沢ムラにおいても優れていることが分かる。それに対して、比較用のトナー〔７〕は、低温定着性は優れているが、光沢度が高く、光沢ムラが大きい結果であった。

As is apparent from the results of Table 2, it can be seen that the toners [1] to [6] of the present invention are excellent in low-temperature fixability and excellent in glossiness and gloss unevenness. On the other hand, the comparative toner [7] was excellent in low-temperature fixability, but had high gloss and large gloss unevenness.

A Shell layer B Inorganic layer C Core

Claims (7)

  In an electrostatic charge image developing toner containing core-shell toner particles having a shell layer containing a binder resin on the surface of core particles containing at least a binder resin and a colorant, the surface of the core particles An electrostatic charge image developing toner comprising an inorganic layer and toner particles having a shell layer on the surface of the inorganic layer.   2. The electrostatic image developing toner according to claim 1, wherein the resin constituting the shell layer contains at least a styrene-acryl-modified polyester resin.   The electrostatic image developing toner according to claim 1, wherein the inorganic layer comprises inorganic fine particles containing at least silica.   The electrostatic image developing toner according to claim 1, wherein the inorganic layer has a thickness in a range of 0.1 to 1.2 μm. A method for producing an electrostatic charge image developing toner for producing the electrostatic charge image development toner according to any one of claims 1 to 4,
Preparing an aqueous dispersion of core particles;
Forming an inorganic layer on the surface of the core particles;
A shelling step of mixing an aqueous dispersion of fine particles for forming a shell layer with an aqueous dispersion of core particles formed with the inorganic layer to form a shell layer on the surface of the inorganic layer on the surface of the core particles. A method for producing a toner for developing an electrostatic charge image.   6. The method for producing a toner for developing an electrostatic charge image according to claim 5, wherein the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on a surface of the core particle by a sol-gel method. .   6. The method for producing a toner for developing an electrostatic charge image according to claim 5, wherein the step of forming the inorganic layer is a step of forming an inorganic layer containing silica on a surface of the core particle by a dry method. .

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