JP2012247659A - Toner for electrostatic image development and manufacturing method for electrostatic image development toner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a toner having a low-temperature fixability while satisfying heat resistance during storage, even when printing multiple paper sheets, causing no faulty cleaning leaving cleaning residual toner on a photoreceptor, and continuously providing a high-quality print image without any dirt on the image, and to provide a manufacturing method for the electrostatic image development toner.SOLUTION: In the toner for electrostatic image development with a core/shell structure including a shell layer provided on a surface of core particle, the core particle includes at least a styrene acrylic resin and a mold release agent, and the shell layer includes at least a styrene acrylic modified polyester resin. The styrene acrylic resin has a glass transition point of not less than 35°C and not more than 55°C and a weight-average molecular weight of not less than 20,000 and not more than 40,000. The styrene acrylic modified polyester resin has a glass transition point of not less than 50°C and not more than 70°C and a weight-average molecular weight of not less than 7,000 and not more than 19,000.

Description

  The present invention relates to an electrostatic image developing toner and a method for producing an electrostatic image developing toner.

  In order to achieve both low-temperature fixability and heat-resistant storage stability, a technique for controlling the toner into a core / shell structure has been reported (for example, see Patent Document 1). That is, by forming a shell layer composed of particles having a high softening point and excellent heat resistance on the surface of the core particles excellent in low temperature fixability, it becomes possible to achieve both low temperature fixability and heat resistant storage stability. Particularly in toner production by the emulsion aggregation method, there is an advantage that shape control can be easily performed.

  However, as the speed of copiers and printers and the expansion of compatible paper types are increasing in the production printing area in recent years, it has become difficult to achieve both low-temperature fixing and heat-resistant storage stability with the core-shell type toner. .

  In order to solve this problem, a toner using a polyester resin for a shell layer has been developed (for example, see Patent Document 2). Polyester resin has the advantage of being able to easily design a low softening point while maintaining a high glass transition point compared to styrene acrylic resin. By using polyester resin for the shell layer, low-temperature fixability and heat-resistant storage stability are achieved. A good toner can be obtained.

  However, when forming a shell layer made of a polyester resin on the surface of the core particles having a styrene acrylic resin, if the weight average molecular weight of the polyester resin is small, the cohesiveness of the polyester resin itself increases, and homoaggregated particles are formed only with the polyester resin. There has been a problem of causing poor cleaning due to homoaggregated particles. On the other hand, when the weight average molecular weight of the polyester resin is large, a high molecular weight substance is contained, and there is a problem that the low-temperature fixability is deteriorated.

JP 2005-221933 A Japanese Patent No. 4305155

  An object of the present invention is to provide a high-quality print that has low-temperature fixability, satisfies heat-resistant storage stability, and does not cause a cleaning failure in which residual toner remains on the photosensitive member and does not cause image contamination. It is an object of the present invention to provide an electrostatic image developing toner capable of obtaining an image and a method for producing the electrostatic image developing toner.

  The object of the present invention is achieved by the following configurations.

  1. In an electrostatic charge image developing toner having a core / shell structure in which a shell layer is provided on the surface of a core particle, the core particle has at least a styrene acrylic resin and a release agent, and the shell layer has at least a styrene acrylic modified polyester resin. The glass transition point of the styrene acrylic resin is 35 ° C. or more and 55 ° C. or less, the weight average molecular weight is 20,000 or more and 40,000 or less, and the glass transition point of the styrene acrylic modified polyester resin is 50 ° C. or more and 70 ° C. or less. A toner for developing electrostatic images, having a weight average molecular weight of 7,000 to 19,000.

  2. The styrene acrylic modified polyester resin is formed of a polyester segment and a styrene acrylic polymer segment, and the constituent ratio of the styrene acrylic polymer segment in the styrene acrylic modified polyester resin is 5% by mass or more and 30% by mass or less. An electrostatic charge image developing toner.

  3. The styrene acrylic modified polyester resin is characterized in that a styrene acrylic polymer segment is bonded to the end of a polyester segment, or a styrene acrylic polymer segment is grafted in the middle of a polyester segment. 3. The electrostatic image developing toner according to 1 or 2 above.

  4). In a method for producing a toner for developing an electrostatic charge image having a core-shell structure in which a shell layer is provided on the surface of a core particle, the core particle has at least a styrene acrylic resin and a release agent, and the shell layer is at least modified with styrene acrylic Having a polyester resin, the glass transition point of the styrene acrylic resin is from 35 ° C. to 55 ° C., the weight average molecular weight is from 20,000 to 40,000, and the glass transition point of the styrene acrylic modified polyester resin is from 50 ° C. to 70 ° C. The shell layer is formed by agglomerating and fusing the styrene-acrylic modified polyester resin particles in an aqueous medium on the surface of the core particles having a weight average molecular weight of 7,000 to 19,000 and having at least the styrene acrylic resin. A process for producing a toner for developing an electrostatic charge image, comprising the step of:

  The toner for developing an electrostatic charge image and the method for producing the toner for developing an electrostatic charge image according to the present invention have a low temperature fixability and satisfy a heat-resistant storage property, and also have a cleaning failure in which a residual toner remains on the photoreceptor. It has an excellent effect that a high-quality print image without image smearing is continuously obtained.

It is sectional drawing which shows an example of the image forming apparatus used by this invention.

  The inventors of the present invention have a low-temperature fixability while satisfying heat-resistant storage properties, are free from defective cleaning and toner filming, and can continuously obtain a high-quality printed image free from image contamination. A toner for developing a charge image (hereinafter also simply referred to as toner) and a method for producing the toner were studied.

  As a result of various investigations, in the core-shell structure toner, the core particles having a specific glass transition point (hereinafter also referred to as Tg) and a styrene acrylic resin exhibiting a weight average molecular weight (hereinafter also referred to as Mw) and a release agent. When a shell layer having a modified polyester resin exhibiting specific Tg and Mw is provided on the surface, homoaggregation composed only of the modified polyester resin does not occur in the step of forming the shell layer, and generation of fine particles composed of homoaggregation can be prevented. I found.

  As a result, the core particles having excellent low-temperature fixability enable low-temperature fixability, and heat resistant storage stability can be secured by forming a shell layer having excellent heat resistance on the surface of the core particles. It has been found that by preventing the generation of the fine particles, it is possible to prevent the occurrence of poor cleaning due to the fine particles passing through the cleaning blade, and it is possible to continuously obtain a high-quality print image free from image smear.

  The toner of the present invention has a core / shell structure in which a shell layer is provided on the surface of the core particle, and the core particle has at least a styrene acrylic resin exhibiting specific Tg and Mw and a release agent, The layer has a styrene acrylic modified polyester resin exhibiting at least specific Tg and Mw.

  The styrene acrylic resin forming the core particles has a Tg of 35 ° C. or more and 55 ° C. or less and an Mw of 20,000 or more and 40,000 or less.

  When the Tg of the styrene acrylic resin is 35 ° C. or more, the heat-resistant storage property is good, and when the Tg is 55 ° C. or less, the low-temperature fixability can be satisfied.

  When the Mw of the styrene acrylic resin is 20,000 or more, the heat-resistant storage property is good, and when the Mw is 40,000 or less, the low-temperature fixability can be satisfied.

  The styrene acrylic modified polyester resin forming the shell layer has a Tg of 50 to 70 ° C. and a Mw of 7,000 to 19,000.

  When the Tg of the styrene acrylic modified polyester resin is 50 ° C. or higher, the heat-resistant storage stability is good, and when the Tg is 70 ° C. or lower, the low-temperature fixability can be satisfied.

  When the Mw of the styrene acrylic modified polyester resin is 7,000 or more, the heat-resistant storage property is good, and when the Mw is 19,000 or less, the low-temperature fixability can be satisfied.

  In particular, when a styrene acrylic modified polyester resin having an Mw of 7,000 or more is used, homoaggregation of the styrene acrylic modified polyester resin is less likely to occur, and when a styrene acrylic modified polyester resin having an Mw of 19,000 or less is used, the surface of the core particles is reduced. It becomes easy to collect the styrene acrylic modified polyester resin, and a shell layer is easily formed on the surface of the core particle.

  If homo-agglomerated fine particles of styrene acrylic modified polyester resin are present in the toner, the fine particles slip through the cleaning blade during image formation, resulting in image contamination due to poor cleaning.

  Hereinafter, the present invention will be described in detail.

"toner"
The toner of the present invention has a core / shell structure in which a shell layer is provided on the surface of core particles. The ratio of the core particles and the shell layer (mass% of core particles: mass% of shell layer) is preferably 90:10 to 60:40.

  If the proportion of the shell layer containing the styrene acrylic modified polyester resin is less than 10% by mass, sufficient heat-resistant storage stability may not be obtained, and if it exceeds 40% by mass, sufficient low-temperature fixability may not be obtained. There is.

The median diameter (D ₅₀ ) of the toner of the present invention on a volume basis is preferably from 3.0 μm to 8.0 μm. By setting the median diameter (D ₅₀ ) on the volume basis within the above range, for example, a very small dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)) can be faithfully reproduced. It becomes possible.

《Core particle》
The core particle according to the present invention is composed of particles obtained by aggregating at least a styrene acrylic resin, a release agent, and a colorant added as necessary.

  Specifically, it is composed of particles obtained by aggregating at least resin particles for core particles having a styrene acrylic resin, release agent particles, and colorant particles added as necessary.

<Resin particles for core particles>
Polymer particles for at least a styrene acrylic resin containing a release agent, a charge control agent and the like in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less as the core particle resin particles. It is possible to use a product prepared by adding a functional monomer, applying mechanical energy to form droplets, then adding a water-soluble polymerization initiator, and allowing the polymerization reaction to proceed in the droplets. it can. Note that an oil-soluble polymerization initiator may be contained in the droplet. In such a production method, a process of applying mechanical energy and forcibly emulsifying (forming droplets) is essential. Examples of the means for applying mechanical energy include means for applying strong stirring or ultrasonic vibration energy such as homomixer, ultrasonic wave, and manton gorin.

  The particle diameter of the core resin particles is usually preferably in the range of 50 nm to 500 nm in terms of volume average particle diameter.

(Polymerizable monomer)
Examples of the polymerizable monomer used to form the styrene acrylic resin include styrene monomers such as styrene, methyl styrene, methoxy styrene, ethyl styrene, propyl styrene, butyl styrene, phenyl styrene, and chloro styrene, methyl acrylate, Ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, dodecyl acrylate, stearyl acrylate, ethyl hexyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, methacrylic acid Acrylic acid ester monomers such as pentyl, dodecyl methacrylate, stearyl methacrylate, ethyl hexyl methacrylate, lauryl methacrylate, etc. It is. Among these, it is preferable to use a styrene monomer in combination with an acrylic acid monomer and a methacrylic acid monomer. A third vinyl monomer can also be used as the polymerizable monomer. Examples of the third vinyl monomer include acid monomers such as acrylic acid, methacrylic acid, maleic anhydride, and vinyl acetate, acrylamide, methacrylamide, acrylonitrile, ethylene, propylene, butylene vinyl chloride, N-vinyl pyrrolidone, and butadiene. It is done.

  A polyfunctional vinyl monomer may be further used as the polymerizable monomer. Examples of the polyfunctional vinyl monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol, and dimethacrylates and trimethacrylates of tertiary or higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. Etc. The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, and more preferably 0.01 to 1% by mass. It is. Although the gel component insoluble in tetrahydrofuran is generated by using the polyfunctional vinyl monomer, the proportion of the gel component in the whole polymer is usually 40% by mass or less, preferably 20% by mass or less.

  The ratio of styrene constituting the styrene acrylic resin is preferably 56 to 81% by mass of the styrene acrylic resin.

  The polymerizable monomers used for forming the styrene acrylic resin, their copolymerization ratio, and the polymerization conditions are selected so that Tg and Mw are the values defined in the present invention.

(Chain transfer agent)
In the present invention, when forming a styrene acrylic resin, a chain transfer agent may be added together with the polymerizable monomer. The molecular weight of the polymer can be controlled by adding a chain transfer agent. Known chain transfer agents can be used, and examples thereof include alkyl mercaptans and mercapto fatty acid esters. The addition amount of the chain transfer agent varies depending on the desired molecular weight and molecular weight distribution, but it is preferably added in the range of 0.1 to 5% by mass with respect to the polymerizable monomer.

(Polymerization initiator)
As the polymerization initiator used for the polymerization, a water-soluble polymerization initiator is preferably used. For example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, -tert-butyl peroxide, propionyl peroxide benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate, Sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, formic acid-tert-butyl, peracetic acid- peroxides such as tert-butyl, perbenzoic acid-tert-butyl, perphenylacetic acid-tert-butyl, permethoxyacetic acid-tert-butyl, per-N- (3-toluyl) palmitic acid-tert-butyl; , 2'-azobis 2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (sodium 1-methylbutyronitrile-3-sulfonate), 4,4 ' -Azo compounds such as azobis-4-cyanovaleric acid and poly (tetraethylene glycol-2,2'-azobisisobutyrate).

(Surfactant)
A dispersion stabilizer is usually added to the aqueous medium in order to prevent aggregation of dispersed droplets. As the dispersion stabilizer, a known surfactant can be used, and a dispersion stabilizer selected from a cationic surfactant, an anionic surfactant, a nonionic surfactant and the like can be used. Two or more of these surfactants may be used in combination. The dispersion stabilizer can also be used in a dispersion liquid such as a colorant and an offset preventing agent. 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.

  Nonionic surfactants include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, lauryl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl polyoxyethylene ether And monodecanoyl sucrose. Examples of the anionic surfactant include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzene sulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like.

  In the present invention, the aqueous medium means that the main component (50% by mass or more) is made of water. Examples of components other than water include water-soluble organic solvents such as methanol, ethanol, isopropanol, butanol, and acetone.

<Release agent>
Examples of the release agent include hydrocarbon waxes such as low molecular weight polyethylene wax, low molecular weight polypropylene wax, Fischer-Tropsch wax, microcrystalline wax, and paraffin wax, carnauba wax, pentaerythritol behenate, and behenyl behenate. And ester waxes such as behenyl citrate. These can be used alone or in combination of two or more. The content ratio of the release agent is 2 to 20% by mass, preferably 3 to 18% by mass, more preferably 4 to 15% by mass, based on the total mass of the resin particles. Further, the melting point of the release agent is preferably 50 to 95 ° C. from the viewpoint of low-temperature fixability and releasability of the toner in electrophotography.

<Preparation of core particles>
Examples of a method for producing the core particles include a method in which at least styrene acrylic resin particles, a release agent, and if necessary, a colorant are aggregated and associated.

  Specifically, a core resin particle having a styrene acrylic resin and an aqueous dispersion of release agent particles are mixed with a dispersion of colorant particles, charge control agent particles, and other toner constituent particles as necessary. A method for preparing a dispersion of core particles by preparing a dispersion for aggregation, adding an aggregating agent, and aggregating and fusing in an aqueous medium can be mentioned.

(Flocculant)
The flocculant used in the present invention is not particularly limited, but those selected from metal salts are preferably used. For example, salts of monovalent metals such as alkali metal salts such as sodium, potassium and lithium, salts of divalent metals such as calcium, magnesium, manganese and copper, salts of trivalent metals such as iron and aluminum Examples of the salt include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, and manganese sulfate. Is a metal salt of valence. When a divalent metal salt is used, agglomeration can be promoted with a smaller amount. These may be used alone or in combination of two or more. In the flocculation step, it is preferable that the standing time (time until heating is started) to be left after adding the flocculant is as short as possible. That is, after adding the flocculant, it is preferable to start heating the flocculating dispersion liquid as quickly as possible so as to be equal to or higher than the glass transition point of the resin composition. The reason for this is not clear, but the agglomeration state of the particles fluctuates with the passage of time, and there is a possibility that the particle size distribution of the obtained core particles becomes unstable or the surface property fluctuates. Because there is.

  The standing time is usually within 30 minutes, preferably within 10 minutes. In the aggregation step, it is preferable to quickly raise the temperature by heating, and the rate of temperature rise is preferably 1 ° C./min or more. The upper limit of the heating rate is not particularly limited, 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, it is important to continue the fusion by holding the temperature of the aggregation dispersion liquid for a certain period of time after the aggregation dispersion liquid reaches a temperature equal to or higher than the glass transition temperature. Thereby, the growth and fusion of the core particles can be effectively advanced, and the durability of the finally obtained toner can be improved.

(Coloring agent)
As the colorant to be used, carbon black, magnetic substance, dye, pigment, etc. can be arbitrarily used, and as channel black, furnace black, acetylene black, thermal black, lamp black, etc. are used as carbon black. .

  As the magnetic material, ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, and compounds of ferromagnetic metals such as ferrite and magnetite can be used. As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, 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, 95, etc. can be used, and mixtures thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 48: 3, 53: 1, 57: 1, 81: 4, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 155, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 15: 4, 60, and the like, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

  The dispersion of the colorant can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is preferably performed in a state where the surfactant concentration in the aqueous medium is equal to or higher than the critical micelle concentration because the colorant is uniformly dispersed. A known disperser can be used as the disperser used for the dispersion treatment of the colorant. Moreover, as a surfactant which can be used, a publicly known thing can be used.

《Shell layer》
The shell layer according to the present invention is a layer having at least a styrene acrylic modified polyester resin.

  As the styrene acrylic modified polyester resin, those in which a styrene acrylic polymer segment is bonded to the terminal of the polyester segment, or those in which a styrene acrylic polymer segment is grafted in the middle of the polyester segment are used.

  As the styrene acrylic modified polyester resin used in the present invention, those having a styrene acrylic modified structure at the end of the polyester segment are preferable because they do not easily exceed homoaggregation.

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

  The amount of styrene acrylic modification is the total mass of the resin material used to synthesize the styrene acrylic modified polyester resin, that is, the unmodified polyester resin that becomes the polyester segment and the aromatic vinyl unit that becomes the styrene acrylic polymer segment. Aromatic vinyl monomer and (meth) acrylic acid ester monomer with respect to the total mass of the monomer and the (meth) acrylic acid ester monomer and the total amount of both reactive monomers for bonding them The ratio of the mass of

  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 appropriately controlled, and a thin shell layer with a more uniform film thickness is formed while being a thin layer. It becomes easy. On the other hand, if the amount of styrene acrylic modification is too small, it becomes difficult to form a shell layer with a uniform film thickness, and the core particles are partially exposed, resulting in sufficient heat storage stability and chargeability. Hateful. Further, when 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 as a whole toner particle.

  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 acrylic modified polyester resin, and the aliphatic unsaturated dicarboxylic acid is added to the polyester segment. It is preferable that the structural unit derived from is contained.

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

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

  The structural ratio of the structural unit derived from the aliphatic unsaturated dicarboxylic acid in the structural unit derived from the polyvalent carboxylic acid monomer constituting the polyester segment of the styrene acrylic modified polyester resin (hereinafter referred to as “specific unsaturated dicarboxylic structural ratio”) 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 specific unsaturated dicarboxylic acid constituent ratio is in the above range, it is easier to form a smooth shell layer having a more uniform film thickness while being a thin layer. On the other hand, if the specific unsaturated dicarboxylic acid constituent ratio is too small, sufficient heat-resistant storage stability and chargeability may not be obtained, and if the specific unsaturated dicarboxylic acid constituent ratio 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
[Wherein, R ¹ and R ² are a hydrogen atom, a methyl group or an ethyl group, and may be the same or different from each other. 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 is because when a toner particle is produced by, for example, an emulsion polymerization aggregation method described later by using a styrene acrylic modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid having a vinylene group, In order to improve the emulsification stability of the fine particles by the styrene acrylic modified polyester resin, it is presumed that the aggregation of the core particles on the surface proceeds uniformly. In addition, since the styrene acrylic modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid having a vinylene group has a high polarity, toner particles can be used, for example, by an emulsion polymerization aggregation method described later. When manufacturing, it is guessed that the polyester segment part of the fine particle by the styrene acrylic modified polyester resin which should form a shell layer became easy to orient to the surface side in an aggregated particle.

<Production method of 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 further, an aromatic vinyl monomer for forming a styrene acrylic polymer segment, and (meth) A method of forming a styrene acrylic polymer segment by reacting an acrylic ester monomer.
(A-2) A styrene-acrylic polymer segment is polymerized in advance, the styrene-acrylic polymer segment is reacted with both reactive monomers, and a polyvalent carboxylic acid monomer for forming a polyester segment A method of forming a polyester segment by reacting a monohydric alcohol monomer.
(B) A method in which a polyester segment and a styrene acrylic polymer segment are respectively polymerized in advance, and both are reacted with each other to react them.

  In the present invention, the both reactive monomers include a group capable of reacting with a polycarboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene acrylic modified polyester resin, and a polymerizable unsaturated group. It is a monomer having.

The method (A-1) will be described.
(1) A mixing step of mixing an unmodified polyester resin, an aromatic vinyl monomer and a (meth) acrylic acid ester monomer, and both reactive monomers,
(2) A styrene-acrylic polymer segment can be formed at the end of the polyester segment by undergoing a polymerization step in which an aromatic vinyl monomer and a (meth) acrylic acid ester monomer are polymerized.

  In the mixing step, it is preferable to heat. The heating temperature may be within a range in which unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer, and amount-reactive monomer can be mixed, and good mixing is possible. 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 total proportion of the resin material used, that is, the total amount of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer when the total mass of the four members is 100% by mass. The ratio is 5% by mass or more and 30% by mass or less.

  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 mass 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 unmodified polyester resin, aromatic vinyl monomer, (meth) acrylic acid ester monomer, and both reactive monomers, the proportion of both reactive monomers used is the total mass of the resin material used, that is, The proportion of both reactive monomers when the total mass of the four components is 100% by mass is preferably 0.1% by mass or more and 5.0% by mass or less, and 0.5% by mass or more and 3.0% by mass or less. Is more 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, diethylaminoethyl methacrylate, and the like.

  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 many. The amount of styrene or a derivative thereof used is 50 mass in all monomers (aromatic vinyl monomer and (meth) acrylic acid ester monomer) used to form a styrene acrylic polymer segment. % Or more is preferable.

(Amotropic monomer)
As the both reactive monomers for forming the styrene acrylic polymer segment, 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 are included. For example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride can be used.

(Polyester resin)
The polyester resin used for producing the styrene acrylic modified polyester resin according to the present invention is produced 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 has been done.

  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 And divalent or higher carboxylic acids such as acid, naphthalenetricarboxylic acid, naphthalenetetracarboxylic acid, pyrenetricarboxylic acid, and pyrenetetracarboxylic acid.

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

  By using the aliphatic unsaturated dicarboxylic acid, the obtained styrene acrylic 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-acrylic modified polyester resin is more surely thin and has a more uniform film thickness and smoothness. A shell layer can be formed.

  The proportion 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.

  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, etc. 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 preferably an equivalent ratio [OH] / [COOH] of the hydroxyl group [OH] of the polyhydric alcohol monomer and the carboxyl group [COOH] of the polyhydric carboxylic acid. Is 1.5 / 1 to 1 / 1.5, more preferably 1.2 / 1 to 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 or more and 19,000 or less, more preferably 3,000 or more and 19,000 or less.

  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. In addition, when the weight average molecular weight is 19,000 or less, it is possible to obtain sufficient melting and secure a minimum fixing temperature, while suppressing occurrence of 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), it is preferable to carry out the polymerization in the presence of a radical polymerization initiator, and the timing of addition of the radical polymerization initiator is not particularly limited, but mixing is performed because radical polymerization can be easily controlled. It is preferably added after the step.

  Various known polymerization initiators are preferably used as the polymerization initiator. For example, hydrogen peroxide, acetyl peroxide, cumyl peroxide, tert-butyl peroxide, propionyl peroxide, benzoyl peroxide, chlorobenzoyl peroxide, dichlorobenzoyl peroxide, bromomethylbenzoyl peroxide, lauroyl peroxide, ammonium persulfate Sodium persulfate, potassium persulfate, diisopropyl peroxycarbonate, tetralin hydroperoxide, 1-phenyl-2-methylpropyl-1-hydroperoxide, pertriphenylacetic acid-tert-hydroperoxide, formic acid-tert-butyl, peracetic acid Peroxides such as tert-butyl, tert-butyl perbenzoate, tert-butyl perphenylacetate, tert-butyl permethoxyacetate, and tert-butyl perN- (3-toluyl) palmitate; 2,2'-azo (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (sodium 1-methylbutyronitrile-3-sulfonate), 4, Examples thereof include azo compounds such as 4'-azobis-4-cyanovaleric acid and 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, but the aromatic vinyl monomer and (meth) acrylic acid ester monomer, and both reactive monomers It is preferable to add in the range of 0.1 to 5% by mass with respect to the total amount.

  The polymerization temperature in the polymerization step (2) is not particularly limited, and is appropriately selected within a 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 the 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, and still more preferably. Is 200 ppm or less.

  The shell layer may be formed by adding other resins in addition to the styrene acrylic modified polyester resin. Examples of other resins include styrene acrylic resin, polyester resin, and urethane resin.

  The constituent ratio of the styrene acrylic modified polyester resin in the resin forming the shell layer is preferably 70 to 100% by mass, and more preferably 90 to 100% by mass in 100% by mass of the resin forming the shell layer. preferable.

  When the component ratio of the styrene acrylic modified polyester resin is less than 70% by mass, sufficient affinity between the core particles and the shell layer cannot be obtained, and a desired shell layer cannot be formed. In addition, there is a possibility that sufficient chargeability or crush resistance cannot be obtained.

<Method for producing toner>
An example of a method for producing a toner having a core / shell structure having a shell layer on the surface of the core particles is a method of producing the toner by an emulsion aggregation method. In the emulsion aggregation method, a dispersion of shell layer resin particles is added to an aqueous dispersion of core particles, and the toner particles are prepared by aggregating and fusing the shell layer resin particles on the surface of the core particles. Thereafter, if necessary, an external additive is attached to the toner base particles to prepare a toner.

  The “toner base particle” in the present invention is a particle having a core-shell structure in which a shell layer is provided on the surface of the core particle. The toner base particles can be used as a toner as they are, but it is usually preferable to add an external additive. The toner is an aggregate of toner particles.

<Preparation of toner base particles>
Examples of a method for producing the toner base particles include a method in which the resin particles for the shell layer are aggregated and fused on the surface of the core particles. In this method, the shell layer is formed by aggregating and fusing the resin particles for the shell layer after the core particles are produced. That is, a dispersion of resin particles for a shell layer is added to an aqueous dispersion of core particles. When the shell layer is formed on the surface of the core particle by the adhesion of the resin particles for the shell layer, the temperature may be set to a reaction temperature or higher when reaching the desired particle size in the core particle aggregation / fusion process. preferable. In order to promote the adhesion of the resin particles for the shell layer to the core particles, a flocculant used at the time of forming the core particles can be appropriately added.

  After agglomerating the resin particles for the shell layer into the core particles, the cohesive force of the system is usually lost to stop the particle growth, and it is fused by heating and the shell layer is coated and the particle shape is controlled. The fusion may be performed by heating to a temperature higher than the glass transition point of the shell particles. Further, fusion may be performed simultaneously with the progress of aggregation.

  The shape of the toner base particles having a core / shell structure obtained as described above can be easily controlled by adjusting the heating conditions in the aging treatment stage of the aggregation / fusion process. The obtained toner base particles are usually subjected to washing treatment, drying treatment and external addition treatment.

  In the washing treatment, acidic and possibly basic water is added several times to the toner base particles and stirred, followed by filtration to obtain a solid content. The pure water is added several times to the solid content and stirred, followed by filtration. This operation is repeated several times, and when the pH of filtration after filtration reaches about 7, the toner base particles are obtained.

  In the drying treatment, the toner base particles obtained by the washing treatment are dried at a temperature below the glass transition point. As a drying method, any method such as a normal vibration type fluidized drying method, a spray drying method, a freeze drying method, a flash jet method, or the like can be adopted.

<Production of toner>
In the present invention, toner base particles to which an external additive is added can be used for the purpose of improving the fluidity and charging characteristics of the toner. Examples of the method of adding and mixing 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 types such as a Henschel mixer and a coffee mill. A mixing device is mentioned.

  Examples of the external additive used in the present invention 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, or strontium titanate. And inorganic fine particles such as inorganic titanic acid compound fine particles such as zinc titanate. 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 viewpoint of heat-resistant storage stability and environmental stability. The addition amount of the external additive is preferably 0.05 to 5 parts by mass and more preferably 0.1 to 3 parts by mass with respect to 100 parts by mass of the toner base particles. Various external additives may be used in combination.

<Measurement of physical properties>
(Glass transition point)
In the present invention, the glass transition point (Tg) can be measured using “DSC-7 differential scanning calorimeter” (manufactured by PerkinElmer) and “TAC7 / DX thermal analyzer controller” (manufactured by PerkinElmer).

  As a measurement procedure, 5.0 mg of a measurement sample is precisely weighed to two decimal places, sealed in an aluminum pan (KIT No. 0219-0041), and set in a DSC-7 sample holder. The reference uses an empty aluminum pan. The measurement conditions were a measurement temperature of 0 ° C. to 200 ° C., a temperature increase rate of 10 ° C./min, a temperature decrease rate of 10 ° C./min, and heat-cool-heat temperature control. Analysis is performed based on the data in Heat.

  The glass transition point draws an extension of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum slope between the rise portion of the first peak and the peak apex, and the intersection is taken as the glass transition point. Show.

(Weight average molecular weight)
The weight average molecular weight can be measured using gel permeation chromatography (807-IT type: manufactured by JASCO Corporation).

  A procedure of a method for measuring the molecular weight of a resin by the GPC method (gel permeation chromatography), which is one of the representative methods of the weight average molecular weight, will be described.

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

(Median diameter based on toner volume (D ₅₀ ))
The median diameter (D ₅₀ ) on the volume basis of the toner can be measured and calculated using a device in which a computer system for data processing is connected to Multisizer 3 (manufactured by Beckman Coulter). As a measurement procedure, 0.02 g of toner particles are used in 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). After being blended, ultrasonic dispersion is performed for 1 minute to prepare a toner particle dispersion. This toner particle dispersion is poured into a beaker containing ISOTON II (manufactured by Beckman Coulter) in a sample stand with a pipette until the measured concentration reaches 5% by mass, and the measuring machine count is set to 25,000. taking measurement. The aperture size of the multisizer 3 is 100 μm.

<Developer>
The toner of the present invention can be used as a two-component developer composed of a carrier and a toner, or as a non-magnetic one-component developer composed only of a toner.

  Carriers that are magnetic particles used when used as a two-component developer are conventionally known materials such as metals such as iron, ferrite, and magnetite, and alloys of these metals with metals such as aluminum and lead. It is possible to use. Among these, ferrite particles are preferable. Further, as the carrier, a coated carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a resin dispersion type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used. The carrier has a volume average particle size of preferably 15 to 100 μm, more preferably 25 to 80 μm.

<Image forming apparatus>
As an image forming apparatus in which the toner of the present invention is used, a charging unit, an exposing unit, a developing unit using a developer containing toner, and a toner image formed by the developing unit are formed on a photosensitive drum as an electrostatic latent image carrier. Examples thereof include a transfer unit that directly transfers a transfer material to a transfer material or an intermediate transfer member, and a fixing unit that thermally fixes a toner image transferred to the transfer material.

  FIG. 1 is a cross-sectional view showing an example of an image forming apparatus used in the present invention.

  In FIG. 1, reference numeral 50 denotes a photosensitive drum (photosensitive member) which is an electrostatic image carrier, which is a photosensitive member in which an organic photosensitive layer is applied on a drum and a resin layer is applied thereon, and is grounded and clockwise. Is driven and rotated. Reference numeral 52 denotes a scorotron charger (charging means) for uniformly charging the circumferential surface of the photosensitive drum 50 by corona discharge. Prior to the charging by the charger 52, the peripheral surface of the photosensitive member may be discharged by performing exposure by the pre-charging exposure unit 51 using a light emitting diode or the like in order to eliminate the history of the photosensitive member in the previous image formation.

  After uniform charging of the photoreceptor, image exposure based on the image signal is performed by an image exposure unit 53 as an image exposure unit. The image exposure unit 53 in this figure uses a laser diode (not shown) as an exposure light source. Scanning on the photosensitive drum is performed by the light whose optical path is bent by the reflection mirror 532 through the rotating polygon mirror 531 and the fθ lens, and an electrostatic latent image is formed.

  In the reversal development process, the surface of the photoreceptor is uniformly charged by the charger 52, and the exposed area of the photoreceptor, that is, the exposed area potential (exposed area) of the photoreceptor is visualized by the developing process (means). This is an image forming method. On the other hand, the unexposed portion potential is not developed by the developing bias potential applied to the developing sleeve 541.

The electrostatic latent image is then developed by a developing device 54 as developing means. A developing device 54 containing a two-component developer composed of toner and a carrier is provided at the periphery of the photosensitive drum 50, and development is performed by a developing sleeve 541 that contains a magnet and rotates while holding the developer. The inside of the developing device 54 is composed of developer agitating / conveying members 544 and 543, a conveying amount regulating member 542 and the like, and the two-component developer is agitated and conveyed and supplied to the developing sleeve. Controlled by a quantity regulating member. The transport amount of the two-component developer varies depending on the linear velocity of the applied photoreceptor and the developer specific gravity, but is generally in the range of ^{20 to} 200 mg / cm ² .

  The two-component developer is transported to the development area with the layer thickness regulated by the transport amount regulating member, and development is performed. At this time, usually, development is performed by applying a DC bias between the photosensitive drum 50 and the developing sleeve 541 and, if necessary, an AC bias voltage. Further, the developer is developed in contact with or not in contact with the photoreceptor. The potential of the photoconductor is measured by providing a potential sensor 547 above the development position.

  The recording paper P is fed to the transfer area by the rotation operation of the paper feed roller 57 when the transfer timing is ready after image formation.

  In the transfer area, a transfer electrode (transfer means: transfer device) 58 on the peripheral surface of the photosensitive drum 50 is operated in synchronization with the transfer timing, and the fed recording paper P is sandwiched and transferred.

  Next, the recording paper P is neutralized by a separation electrode (separator) 59 that is activated almost simultaneously with the transfer electrode, separated by the peripheral surface of the photosensitive drum 50, and conveyed to the fixing device 60. After the toner is welded by heating and pressurizing the pressure roller 602, the toner is discharged to the outside of the apparatus via the paper discharge roller 61. The transfer electrode 58 and the separation electrode 59 are retracted away from the peripheral surface of the photosensitive drum 50 after the recording paper P has passed to prepare for the next toner image formation. In FIG. 1, a transfer band electrode of corotron is used as the transfer electrode 58. The transfer electrode setting conditions vary depending on the process speed (peripheral speed) of the photosensitive member and cannot be specified. For example, the transfer current is set to +100 to +400 μA, and the transfer voltage is set to +500 to +2000 V. can do.

  On the other hand, the photosensitive drum 50 from which the recording paper P has been separated removes and cleans residual toner by the pressure contact of the cleaning blade 621 of the cleaning device (cleaning means) 62, and again performs charge removal by the pre-charge exposure unit 51 and by the charger 52. Upon receiving the charge, the next image forming process is started.

  Reference numeral 70 denotes a detachable process cartridge in which a photoconductor, a charger, a transfer device, a separator, and a cleaning device are integrated.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, the aspect of this invention is not limited to this.

  The following will be described in order.

<< Preparation of dispersion of resin particles A for core particles >>
(Preparation of dispersion of resin particles A1 for core particles)
(1-1) First-stage polymerization Into a reaction vessel equipped with a stirrer, temperature sensor, temperature controller, cooling tube, and nitrogen introducing device, 2.0 parts by mass of the anionic surfactant “sodium lauryl sulfate” is ion-exchanged in advance. 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 weight n-butyl acrylate 270 parts by weight Methacrylic acid 65 parts by weight n-octyl mercaptan 17 parts by weight 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 above 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)”. Under the temperature condition of 80 ° C.
Solution (3)
Styrene 230 mass parts n-butyl acrylate 100 mass parts n-octyl mercaptan 5.2 mass parts The said solution (3) was dripped over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) was carried out by heating and stirring for 3 hours. Then, it cooled to 28 degreeC and obtained "the dispersion liquid of resin particle A1 for core particles" in which resin particle A1 for core particles was disperse | distributed in the anionic surfactant solution.

(Preparation of dispersion of resin particles A2 to A9 for core particles)
“Dispersions of core particle resin particles A2 to A9” were prepared in the same manner except that the monomers used in the preparation of “core particle resin particles A1” were changed as shown in Table 1.

  Table 1 shows the monomers, Tg, and Mw used at the time of preparing the prepared core particle resin particles A.

<< Preparation of dispersion of resin particles B for shell layer >>
(Preparation of dispersion of resin particle B1 for shell layer)
[Synthesis of styrene acrylic modified polyester resin B1]
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”. Acrylic modified polyester resin B1 "was prepared.

  This “styrene acrylic modified polyester resin B1” 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 B1” 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 was mixed with a part and ultrasonically dispersed with an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) for 30 minutes at 300 μA, and the median diameter (D ₅₀ ) on a volume basis was 250 nm. A “dispersion of shell resin fine particles B1” in which certain shell resin fine particles B1 were dispersed was prepared.

(Preparation of dispersion of resin particles B2 to B9 for shell layer)
“Dispersions of resin particles B2 to B9 for shell layer” were prepared in the same manner except that the monomers used in the preparation of “dispersion of resin particles B1 for shell layer” were changed as shown in Table 2.

  In Table 2, the monomer used at the time of preparation of the produced resin particles B for the shell layer, the constituent ratio of the styrene acrylic polymer segment, Tg and Mw are shown.

(Preparation of dispersion of resin particle B10 for shell layer)
In a reaction vessel equipped with a cooling pipe, a stirrer and a nitrogen introduction pipe, 316 parts by mass of a bisphenol A propylene oxide 2-mole adduct, 80 parts by mass of terephthalic acid, 34 parts by mass of maleic anhydride, and titanium tetraisoso 2 parts by mass of propoxide was divided into 10 portions and reacted at 200 ° C. for 10 hours while distilling off the water generated under a nitrogen stream. Next, the reaction was carried out under reduced pressure of 13.3 kPa (100 mmHg), and the mixture was taken out when the softening point reached 104 ° C. This is designated as “polyester resin (a)”.

  In an autoclave reaction vessel equipped with a thermometer and a stirrer, 430 parts by mass of xylene and 430 parts by mass of “polyester resin (a)” were placed and dissolved. After substitution with nitrogen, 18.1 parts by mass of styrene and 2-ethylhexyl acrylate A mixed solution of 4.5 parts by mass, 0.16 parts by mass of di-t-butyl peroxide, and 100 parts by mass of xylene was dropped and polymerized at 170 ° C. for 3 hours, and further maintained at this temperature for 30 minutes. Next, the solvent was removed to prepare “dispersion of resin particles B10 for shell layer” which is a styrene acrylic graft-modified polyester resin. In addition, the composition ratio of the styrene acrylic polymer segment was 23% by mass. Tg of the resin particles B10 for shell layer was 65 ° C., and Mw was 13500.

100 parts by mass of the “styrene acrylic modified polyester resin B10” produced above was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.), and 638 parts by mass of a 0.26 mass% sodium lauryl sulfate solution prepared in advance. The mixture was mixed with a part and ultrasonically dispersed with an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) for 30 minutes at 300 μA, and the median diameter (D ₅₀ ) on a volume basis was 250 nm. A “dispersion of shell resin fine particles B10” in which certain shell resin fine particles B1 were dispersed was produced.

<< Production of Toner 1 >>
<Preparation of Toner 1>
(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 colorant particles was prepared. The particle diameter of this dispersion was measured using a Microtrac particle size distribution analyzer UPA-150 (manufactured by Nikkiso Co., Ltd.) and found to be 117 nm.

(Preparation of toner base particles 1)
Into a reaction vessel equipped with a stirrer, a temperature sensor, and a cooling pipe, 288 parts by mass of “dispersion of resin particles A1 for core particles” and 2,000 parts by mass of ion-exchanged water are added in an amount of 5 mol / liter. The pH was adjusted to 10 by adding aqueous sodium hydroxide. Thereafter, 40 parts by mass of “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 allowed to stand for 3 minutes, and the temperature of the system was raised to 80 ° C. over 60 minutes, and the particle growth reaction was continued while maintaining 80 ° C. In this state, the particle size of the associated particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman). When the median diameter (D ₅₀ ) on a volume basis reached 6.0 μm, “resin for shell layer” 72 parts by mass of the “dispersion of particle B1” in terms of solid content is added over 30 minutes, and when the supernatant of the reaction solution becomes transparent, an aqueous solution in which 190 parts by mass of sodium chloride is dissolved in 760 parts by mass of ion-exchanged water Was added to stop grain growth. Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusion of the particles, and the average circularity measuring device “FPIA-2100” (manufactured by Sysmex) is used (the number of detected HPFs). 4000) When the average circularity reached 0.945, it was cooled to 30 ° C. to prepare “Dispersion of toner base particle 1”.

  The “dispersion of toner base particles 1” produced 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”.

  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 “toner base particle 1”, and a Henschel mixer is used. By mixing, “Toner 1” was produced.

<Preparation of Toners 2 to 20>
“Toners 2 to 20” were similarly used except that “resin particles A for core particles” and “resin particles B for shell layers” used in the production of toner 1 and the mass% thereof were changed as shown in Table 3. Produced.

<Production of developer>
100 parts by mass of ferrite core and 5 parts by mass of copolymer resin particles of cyclohexyl methacrylate / methyl methacrylate (copolymerization ratio 5/5) are put into a high-speed mixer equipped with stirring blades and stirred and mixed at 120 ° C. for 30 minutes. Then, a resin coat layer was formed on the surface of the ferrite core by the action of mechanical impact force to obtain a “carrier” having a median diameter (D ₅₀ ) of 50 μm on a volume basis. The median diameter (D ₅₀ ) based on the volume of the carrier is a value measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

  “Toners 1 to 20” prepared above are added to the above “carrier” so that the toner concentration becomes 6% by mass, and the mixture is put into a micro type V type mixer (Tsutsui Rikenki Co., Ltd.), with a rotation speed of 45 rpm. Were mixed for 30 minutes to prepare “Developers 1 to 20”.

<Evaluation>
<Mixed amount of fine particles mixed in toner base particles>
The amount of fine particles mixed in the toner base particles is determined by dispersing each of the toner base particles prepared above in ion-exchanged water containing a surfactant, and the dispersion is called “FPIA-2100” (manufactured by Sysmex). ”And measured.

  The amount of fine particles mixed in the toner base particles was determined by measuring the number of 0.6 to 2.0 μm that can be measured by “FPIA”. The amount of fine particles mixed was 1.00% by number or less.

<Heat resistant storage>
The heat-resistant storage property was evaluated by the residual toner mass (toner aggregation rate) remaining on the sieve when measured by the following measurement method.

  0.5 g of toner is taken up in a 10 ml glass bottle with an inner diameter of 21 mm, the lid is closed, and after shaking 600 times at room temperature with “Tap Denser KYT-2000” (manufactured by Seishin Enterprise), the lid is removed at 55 ° C., 35 It was left for 2 hours in an environment of% RH. Next, the toner is placed on a 48 mesh (aperture 350 μm) sieve, taking care not to break up the toner aggregates, and set in a “powder tester” (manufactured by Hosokawa Micron). After fixing and adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the ratio (mass%) of the amount of toner remaining on the sieve was measured. The toner aggregation rate is a value calculated by the following formula. The residual toner mass on the sieve was 20% by mass or less.

Toner aggregation rate = residual toner amount on sieve / 0.5 g × 100
<Print evaluation>
The print evaluation was performed by sequentially loading the toner and the developer prepared above into a developing device of a commercially available image forming apparatus “bizhub PRO 602” (manufactured by Konica Minolta Business Technologies, Inc.).

(Low temperature fixability)
Evaluation of low-temperature fixability was performed using an image forming apparatus in which “bizhub PRO 602” was modified so that the fixing temperature, the toner adhesion amount, and the system speed could be freely set. Using “NPi fine paper” (128 g / m ² (manufactured by Nippon Paper Industries Co., Ltd.)) as an evaluation paper, a solid image with a toner adhesion amount of 11.3 g / m ² is fixed at a fixing speed of 300 mm / sec, and a heat roller is 150 to 200 ° C. The temperature was changed every 5 ° C., the pressure roller was set 20 ° C. lower than the heat roller, and the temperature at which no cold offset occurred when fixing at the level of 5 ° C. was evaluated as the lower limit fixing temperature. The lower the fixing minimum temperature, the better the low-temperature fixability. The low temperature fixability was determined to be acceptable when the minimum fixing temperature was 165 ° C. or lower.

(Cleanability)
The cleaning performance is that after printing on 400,000 sheets, a character image and a patch image with a printing rate of 10% are formed in a printing environment of room temperature and humidity (20 ° C., 50% RH), and after cleaning with a cleaning blade, The surface was evaluated by image observation due to visual observation and defective cleaning of the printed image. In addition, (double-circle) and (circle) were set as the pass.

Evaluation Criteria A: There is no cleaning defect on the surface of the photoconductor, and the printed image is good with no image contamination due to the cleaning defect. No dirt and practical problem. X: A defective cleaning occurs on the surface of the photoconductor, and the printed image has image dirt due to poor cleaning, and there is a practical problem. Table 4 shows the evaluation results.

  As shown in Table 4, the “toners 1 to 11 and 16” of the examples corresponding to the present invention have no problems in the low-temperature fixing property, the cleaning property, and the heat-resistant storage property, and have the effects of the present invention. confirmed. On the other hand, it was confirmed that “Toners 12 to 15 and 17 to 20” of Comparative Examples had problems in any of the above evaluation items and did not exhibit the effects of the present invention.

50 Photosensitive drum (photosensitive member)
DESCRIPTION OF SYMBOLS 51 Pre-charge exposure part 52 Charging device 53 Image exposure device 54 Developing device 57 Paper feed roller 58 Transfer electrode 59 Separation electrode 60 Fixing device 70 Process cartridge 601 Heat roller 602 Pressure roller 621 Cleaning blade P Recording paper

Claims (4)

In an electrostatic charge image developing toner having a core / shell structure in which a shell layer is provided on the surface of a core particle, the core particle has at least a styrene acrylic resin and a release agent, and the shell layer has at least a styrene acrylic modified polyester resin. The glass transition point of the styrene acrylic resin is 35 ° C. or more and 55 ° C. or less, the weight average molecular weight is 20,000 or more and 40,000 or less, and the glass transition point of the styrene acrylic modified polyester resin is 50 ° C. or more and 70 ° C. or less. A toner for developing electrostatic images, having a weight average molecular weight of 7,000 to 19,000. The styrene acrylic modified polyester resin is formed of a polyester segment and a styrene acrylic polymer segment, and the constituent ratio of the styrene acrylic polymer segment in the styrene acrylic modified polyester resin is 5% by mass or more and 30% by mass or less. An electrostatic charge image developing toner. The styrene acrylic modified polyester resin is characterized in that a styrene acrylic polymer segment is bonded to the end of a polyester segment, or a styrene acrylic polymer segment is grafted in the middle of a polyester segment. The toner for developing an electrostatic image according to claim 1. In a method for producing a toner for developing an electrostatic charge image having a core-shell structure in which a shell layer is provided on the surface of a core particle, the core particle has at least a styrene acrylic resin and a release agent, and the shell layer is at least modified with styrene acrylic Having a polyester resin, the glass transition point of the styrene acrylic resin is from 35 ° C. to 55 ° C., the weight average molecular weight is from 20,000 to 40,000, and the glass transition point of the styrene acrylic modified polyester resin is from 50 ° C. to 70 ° C. The shell layer is formed by agglomerating and fusing the styrene-acrylic modified polyester resin particles in an aqueous medium on the surface of the core particles having a weight average molecular weight of 7,000 to 19,000 and having at least the styrene acrylic resin. A process for producing a toner for developing an electrostatic charge image, comprising the step of:

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