JP2013011644A - Toner for electrostatic charge developer and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide toner for electrostatic charge developer that uses a polyester resin component, prevents the occurrence of electrostatic aggregation after continuous use for a long period, and thereby preventing failure including spots in an image, as well as a manufacturing method of the toner.SOLUTION: Toner for electrostatic charge developer is configured in a core-shell structure. A core layer contains at least a styrene-acrylic modified polyester resin, is covered with a spherical particle for shell covered at least with a styrene-acrylic resin component, and has the surface coverage with the spherical particle of 10% or more and 50% or less.

Description

  The present invention relates to a toner for an electrostatic charge developer used for electrophotographic image formation and a method for producing a toner for an electrostatic charge developer.

  In recent years, in the field of toner for electrostatic charge developer (hereinafter, also simply referred to as “toner”), development of an electrophotographic apparatus suitable for it and a toner that can be used in accordance with the demand from the market has advanced at a rapid pace. It has been.

  For example, as a toner corresponding to high image quality, since the reproducibility of minute dots is remarkably improved by developing behavior for each individual toner particle, a toner having a sharp particle size distribution is required. . However, it is not easy to obtain a toner having a sharp particle size distribution by a conventional pulverization method. On the other hand, an emulsion polymerization 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 dispersion of colorant fine particles or, if necessary, a dispersion of wax fine particles is mixed with an emulsified dispersion of binder resin fine particles. The toner particles are obtained by aggregating the fine particles and further fusing the agglomerated particles by heating.

  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 (Tg) 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 the heat resistant storage property of the toner being lowered.

  In order to satisfy both the low-temperature fixing property and the heat-resistant storage property, a technique for forming toner particles with a core-shell structure has been reported (for example, see Patent Document 1). That is, by forming a shell layer having a high softening point and excellent heat resistance on the surface of the core particles excellent in low temperature fixability, a toner satisfying both low temperature fixability and heat resistant storage stability can be produced. . In particular, in the production of toner by the emulsion polymerization aggregation method, there is an advantage that such shape control can be easily performed.

  However, in recent years, especially in the production printing area, while the speed of copying machines and printers and the expansion of compatible paper types are progressing, both the low-temperature fixing property and the heat-resistant storage property can be satisfied only by the toner technology of the core shell structure. It has become difficult.

  In order to solve such a problem, a toner using a polyester resin as a material for the 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, and by using polyester resin for the shell layer, it can be stored in heat resistant with low-temperature fixability. Toner with good properties can be obtained.

  However, the styrene acrylic resin and the polyester resin have poor affinity. When the styrene acrylic resin is used as the binder resin constituting the core particle and the polyester resin is used as the resin constituting the shell layer, the thin layer is uniform. Since the formation of the shell layer is difficult, there is a problem that the heat storage stability cannot be obtained sufficiently stably. In addition, since it is difficult for the core particles and the resin fine particles to form the shell layer to be fused, it is difficult to control the shape of the toner particles. Therefore, it is difficult to produce toner particles having a smooth surface. As a result, high chargeability cannot be obtained, and the shell layer is peeled off when the toner is stirred in the developing device during continuous printing. As a result, there is a problem that image noise is generated when an image is formed, and good image quality is not ensured.

  In order to solve these problems, from the viewpoint of improving the affinity between the styrene acrylic resin and the polyester resin, a toner having a core-shell structure in which a urethane-modified polyester resin and / or an acrylic-modified polyester resin is introduced into the shell layer has been proposed. (For example, Patent Document 3).

  However, if a highly charged resin such as a polyester resin is present on the surface of the toner particles, electrostatic aggregation is likely to occur due to the influence of frictional charging between the toners. For this reason, in toner that has been used for a long period of time, image spots are generated when the surface of the mother body is exposed due to embedding / releasing external additives. As a countermeasure, an effect is to suppress electrostatic aggregation by attaching resin fine particles to toner particles and bringing the toners into point contact. Various inventions for attaching resin fine particles to the toner surface have been disclosed as follows.

  For example, an invention in which organic resin fine particles are mixed and adhered to toner particles is disclosed (Patent Document 4). This includes a method in which organic resin fine particles are prepared by soap-free emulsion polymerization and dry-mixed as an external additive. However, in this method, the toner particles are not easily fixed on the surface of the toner particles, but simply adhere to the surface, so that they are easily released, and the organic resin fine particles are easily transferred to the carrier as the continuous use proceeds. As a result, when the toner particle surface is exposed, electrostatic aggregation is caused, causing image spots.

  Further, there is an invention in which organic resin fine particles having a resin composition different from that of toner particles are embedded in toner particles (Patent Document 5). However, in this method, since the composition of the toner particles and the organic resin fine particles is different, the adhesion of the organic resin fine particles to the toner surface is difficult to proceed. Therefore, when the external additive is buried and the toner particle surface is exposed as the continuous use proceeds, the organic resin fine particles are liberated, electrostatic aggregation due to frictional charging of the toner surface is likely to occur, and image spots are likely to occur. This is particularly noticeable when the toner particles have a highly chargeable resin structure such as polyester.

JP 2005-221933 A JP 2005-338548 A JP 2005-173202 A JP 2009-2551092 A JP 2008-268872 A

  The present invention has been made to solve the above problems.

  That is, when a highly chargeable resin composition such as a polyester resin is present on the surface layer of the toner particles, electrostatic aggregation easily occurs due to friction between the toners because of the high charging performance. When the toner particle surface is exposed by continuous use over a long period of time, electrostatic aggregation is likely to occur, causing a spot failure in the image.

  SUMMARY OF THE INVENTION An object of the present invention is a toner for an electrostatic charge developer that does not cause electrostatic agglomeration and does not cause image spot failure even when the toner uses a polyester resin component, and is used continuously for a long period of time. It is to provide a manufacturing method.

  In the present invention, at least core particles having a styrene acrylic modified polyester as the outermost layer are formed into a shell by agglomerating and fusing at least a glass particle having a styrene acrylic resin as a main component. The styrene acrylic part of the core part and the styrene acrylic part of the shell particle are partially compatible, and the shell particle is fixed to the surface layer of the core. As a result, the shell particles are not released from the surface of the toner particles even if they are continuously used for a long time and receive great stress, so that electrostatic aggregation of the toner particles does not occur and a good image can be obtained for a long time. Is possible.

  That is, the object of the present invention is achieved by obtaining the following configuration.

(1)
A core-shell type toner for electrostatic charge developer, wherein the core layer contains at least a styrene-acrylic modified polyester resin, and the core layer is coated with spherical particles for a shell covered with at least a styrene-acrylic resin component. A toner for an electrostatic charge developer, having a rate of 10% to 50%.

(2)
The toner for electrostatic charge developer according to (1), wherein the core layer has a structure in which a styrene acrylic resin is used as a core and a styrene acrylic modified polyester resin is coated.

(3)
In a core shell type electrostatic charge developer manufacturing method, a core layer containing at least a styrene acrylic modified polyester resin is prepared, and the core layer is coated with spherical particles for a shell containing at least a styrene acrylic resin component. A method for producing a toner for an electrostatic charge developer, wherein the rate is 10 to 50%.

(4)
In the core shell type electrostatic charge developer manufacturing method, a core layer containing at least a styrene acrylic resin is prepared, and the core layer is coated with spherical particles for a first stage shell containing at least a styrene acrylic modified polyester resin component, Next, a method for producing a toner for an electrostatic charge developer, which is coated with spherical particles for the second stage shell, and the surface coverage of the second stage shell is 10% or more and 50% or less.

  According to the present invention, a toner for an electrostatic charge developer that is a toner using a polyester resin component, does not cause electrostatic aggregation even when continuously used for a long time, and does not cause image spot failure, and a method for producing the same Can be provided.

  The present invention will be further described.

  According to the present invention, the styrene acrylic part on the surface of the toner particle core and the shell particles made of at least styrene acrylic resin are partially compatible with each other to form protrusions on the surface of the toner particle. % Or less. Therefore, since the toner particles are in point contact with each other, charging due to friction between the toner particle core portions hardly occurs, and it is possible to obtain a toner for an electrostatic charge developer that hardly causes electrostatic aggregation. That is, a good image can be obtained without causing an image white spot failure even after continuous use over a long period of time.

  The “surface coverage” in the present invention is determined by the following calculation method.

  Observation is performed 5000 times with a scanning electrophotographic microscope (SEM). Image processing is performed from the SEM image data, and the surface area of the core particles on the image is calculated. The diameter is measured from SEM image data of surface protrusions (shell particles) on the surface of one toner core particle, the number of particles existing on the surface of one core particle is counted, and the total area of the shell particles is calculated. From the above, the surface coverage of the toner core particles is calculated by the following formula.

Surface coverage = (total area of shell particles / surface area of core particles) × 100 (%)
The above operation is performed for 10 particles, and the average value is defined as the surface coverage.

  The toner for an electrostatic charge developer of the present invention has a shell particle layer containing at least a binder resin containing a styrene acrylic resin formed on core particles containing a styrene acrylic modified polyester resin on the surface. Have.

  The styrene-acrylic modified polyester resin is obtained by bonding a styrene-acrylic polymer segment to an end of a polyester segment, and the content ratio of the styrene-acrylic polymer segment in the styrene-acrylic modified polyester resin is 5% by mass or more and 30%. It is desirable that it is less than mass%. The weight average molecular weight is preferably 2000 to 20000.

  When the modification rate is less than the above, the shell layer particles are difficult to be fixed, and when the modification rate is large, the compatibility proceeds and is buried, so that image white spots tend to occur.

  Moreover, it is preferable that the aliphatic unsaturated dicarboxylic acid which forms polyester is what is 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)
The content of the styrene acrylic modified polyester resin is 5 to 40% by mass, more preferably 10 to 20% by mass of the toner particles. If it is less than this, the fixability tends to deteriorate, and if it is more, the fixability tends to deteriorate.

  The shell particle layer containing the binder resin including the styrene acrylic resin is 5% by mass to 40% by mass, more preferably 15% by mass to 25% by mass of the toner particles. When the amount is less than this, image spots are likely to occur, and when the amount is more, the fixing property is impaired.

  The polymerization latex of the shell particle containing the binder resin including the styrene acrylic resin is obtained by seed-polymerizing the St / Ac resin on the core of the resin particles different from styrene acrylic (St / Ac). Is preferred. The content of the resin encapsulated in the shell particles is 3 to 20% by mass, more preferably 5 to 10% by mass, based on the entire shell particle. If the content of the resin encapsulated in the shell particles is small, the St / Ac part is buried in the core particles, and if it is large, the St / Ac part is reduced and is not easily fixed.

〔toner〕
The toner of the present invention is obtained by forming a shell particle layer containing at least a styrene acrylic resin on the surface of a core particle using a binder resin containing a styrene acrylic modified polyester resin. The styrene acrylic may be bonded to the terminal with respect to the polyester main chain, or may be grafted as a side chain. In the styrene acrylic modified polyester resin, a styrene acrylic polymer segment is bonded to the end of the polyester segment.

[Core layer]
The core layer constituting the toner of the present invention is made of a resin containing a styrene acrylic modified polyester resin. Examples of the resin that can be contained together with the styrene acrylic modified polyester resin in the core resin include styrene acrylic resin, Examples thereof include urethane resin.

  The core resin preferably has a glass transition point of 50 to 70 ° C. from the viewpoint of reliably obtaining heat resistance such as low temperature fixability and fixing separability, and heat resistant storage stability 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 core 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 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. 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, offset method temperature _{T offset} measured by setting the offset value 5mm at a melt temperature measurement method of temperature ramps are It is the softening point of the A resin.

[Production method of styrene acrylic modified polyester resin]
As a method for producing the styrene acrylic modified polyester resin contained in the core 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 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 and A method of forming a polyester segment by reacting a polyhydric alcohol monomer.

  (B): A method in which a polyester segment and a styrene acrylic polymer segment are 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 polycarboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene acrylic-modified polyester resin, a polymerizable unsaturated group, It is a monomer having

The method (A-1) will be specifically 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 (1), it is preferable to heat. The heating temperature may be within a range where 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 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. It is desirable that the ratio is 5% by mass or more and 30% by mass or less.

  The ratio of the total amount of aromatic vinyl monomer and (meth) acrylic acid ester monomer to the total mass of the resin material used is within the above range. Therefore, it is possible to form a smooth shell layer having a more uniform film thickness while being thin. On the other hand, when the ratio is too small, the resulting styrene acrylic-modified polyester resin is not capable of forming a shell layer with a uniform film thickness, resulting in partial exposure of the core particles, Sufficient heat storage stability and chargeability cannot be obtained for the obtained toner. On the other hand, when the ratio is excessive, the obtained polyester resin has a high softening point, so that the obtained toner cannot obtain sufficient low-temperature fixability as a whole.

  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 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, 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. Specifically, the amount of styrene or its derivative used is all monomers used to form a styrene acrylic polymer segment (aromatic vinyl monomer and (meth) acrylic ester monomer). ) Is preferably 50% by mass or more.

[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. Specific examples include acrylic acid, methacrylic acid, fumaric acid, maleic acid, and maleic anhydride.

[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 surface 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 to be used is in the above range, the obtained styrene acrylic modified polyester resin is more surely a thin layer with a more uniform film thickness and a smooth shell layer. It 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 in 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, 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 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), 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. 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, poly (tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds.

[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 both It is preferable to add in the range of 0.1 to 5% by mass with respect to the total amount of reactive monomers.

  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.

[Shell layer particles]
The shell layer particles constituting the toner of the present invention contain a binder resin containing at least a styrene acrylic resin.

  The binder resin constituting the shell layer particles may include, in addition to the styrene acrylic resin, a resin conventionally used as a binder resin for an electrophotographic toner. Examples of such other resins include various known resins. These resins can be used.

  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 vinyl chloride, N-vinylpyrrolidone, butadiene and 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 the polyfunctional vinyl monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol; dimethacrylates of tertiary or higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane; Examples include trimethacrylate.

  The copolymerization ratio of the polyfunctional vinyl monomer to the entire polymerizable monomer related to the binder resin is usually 0.001 to 5% by mass, preferably 0.003 to 2% by mass, more preferably 0. 0.01 to 1% by mass.

  By using a polyfunctional vinyl monomer, a gel component insoluble in tetrahydrofuran is generated. The gel component is preferably 40% by mass or less, more preferably 20% by mass or less, based on the entire binder resin. It is.

[Colorant]
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, and the like can be arbitrarily used.

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

  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 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, 95, etc. can be used, and mixtures 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 200 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.

  The above binder resin preferably has a glass transition point of 30 to 60 ° C, more preferably 30 to 50 ° C. Moreover, it is preferable that a softening point is 80-110 degreeC, More preferably, it is 90-100 degreeC.

  The glass transition point and softening point of the binder resin are measured in the same manner as described above using the binder resin as a measurement sample.

[Toner Production Method]
The toner of the present invention can be produced by various known methods. The core particles are formed by aggregating and fusing the binder resin fine particles and the colorant fine particles dispersed in the aqueous medium. It is preferable to produce the toner particles by an emulsion polymerization aggregation method in which toner particles are obtained by agglomerating and fusing the shell resin fine particles on the surface.

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.
(1-1) In a water-based medium, a shell resin fine particle dispersion preparing step for forming a shell resin fine particle by a shell resin and preparing a dispersion in which the shell resin fine particles are dispersed (the shell resin is 2 types are acceptable),
(1-2) Binder resin in which a core binder resin fine particle is formed by polymerization or dispersion in an aqueous medium to prepare a dispersion in which the binder resin fine particles are dispersed. Microparticle formation process,
(1-3) Colorant fine particle dispersion preparation step for preparing a dispersion in which colorant fine particles are dispersed in an aqueous medium.
(2) a core particle forming step of aggregating binder resin fine particles and colorant fine particles in an aqueous medium to form core particles;
(3) A step of forming toner base particles having a core-shell structure by adding shell resin fine particles to an aqueous medium in which core particles are dispersed to aggregate and fuse the shell resin fine particles on the surface of the core particles. ,
(4) An aging step of adjusting the shape of the toner base particles by aging with thermal energy;
(5) A cleaning step of filtering the toner base particles from the dispersion system (aqueous medium) of the toner base particles, and removing the surfactant and the like from the toner base particles. (6) Drying for drying the toner base particles that have been cleaned. Process,
Consisting of, if necessary,
(7) an external additive addition step of adding an external additive to the dried toner base particles;
Can be added.

  More preferably, there are the following methods for dividing the shell fine particles into two stages.

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.
(1-1-1) First to prepare a dispersion liquid in which first-stage shell resin fine particles are formed from a first-stage shell resin in an aqueous medium, and the first-stage shell resin fine particles are dispersed. Corrugated shell resin fine particle dispersion preparation process,
The first shell resin is preferably a styrene acrylic modified polyester resin.
(1-1-2) Secondly, in the aqueous medium, second-stage shell resin fine particles are formed from the second-stage shell resin, and a second dispersion is prepared by dispersing the second-stage shell resin fine particles. Corrugated shell resin fine particle dispersion preparation process,
The second shell resin is preferably a styrene acrylic resin.
(1-2) A binder resin polymerization step of preparing a dispersion in which the core binder resin fine particles are formed by polymerization in a water-based medium and the core binder resin fine particles are dispersed;
The core layer resin is preferably a styrene acrylic resin or a mixture of a styrene acrylic resin and a styrene acrylic modified polyester resin.
(1-3) Colorant fine particle dispersion preparation step for preparing a dispersion in which colorant fine particles are dispersed in an aqueous medium.
(2) a core particle forming step of aggregating binder resin fine particles and colorant fine particles in an aqueous medium to form core particles;
(3-1) In the aqueous medium in which the core particles are dispersed, the first-stage shell resin fine particles are added, and the first-stage shell resin fine particles are aggregated and fused on the surface of the core particles to form a core-shell structure. Forming particles having,
(3-2) In the aqueous medium in which the core particles are dispersed, the second-stage shell resin fine particles are added to agglomerate and fuse the second-stage shell resin fine particles on the surface of the core particles to obtain a core-shell structure. Forming toner base particles having,
(4) An aging step of adjusting the shape of the toner base particles by aging with thermal energy;
(5) A cleaning step of filtering the toner base particles from the dispersion system (aqueous medium) of the toner base particles, and removing the surfactant and the like from the toner base particles. (6) Drying for drying the toner base particles that have been cleaned. Process,
Consisting of, if necessary,
(7) an external additive addition step of adding an external additive to the dried toner base particles;
Can be added.

A specific example of producing a toner containing a colorant when the toner of the present invention is produced by an emulsion polymerization aggregation method is as follows.
(1-1) Shell Resin Fine Particle Dispersion Preparation Step In this shell resin fine particle dispersion adjustment step, the shell resin fine particle dispersion is an aqueous system to which a surfactant is added by, for example, an ultrasonic dispersion method or a bead mill dispersion method. It can be obtained by a direct dispersion method.

  The average particle diameter of the shell resin fine particles obtained in the shell resin fine particle dispersion preparing step is preferably in the range of, for example, 50 to 500 nm in terms of volume-based median diameter.

  The volume-based median diameter is measured using “UPA-150” (manufactured by Microtrack). Two types of shell resins are preferred.

  In the present invention, the “aqueous medium” refers to a medium comprising 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.

[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 the anionic surfactant include aliphatic soaps such as sodium stearate and sodium laurate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, polyoxyethylene (2) sodium lauryl ether sulfate and the like. it can.

The above surfactants can be used singly or in combination of two or more as desired.
(1-2) Core Binder Resin Polymerization Step In this core binder resin polymerization step, resin fine particles related to the core binder resin are formed, and this is used for the core particle formation step.

  Specifically, the resin fine particles related to the core binder resin are polymerizable monomers for forming the core binder resin in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less. If necessary, a monomer solution in which toner components such as wax and charge control agent are dissolved or dispersed is added, mechanical energy is applied to form droplets, and then a water-soluble radical polymerization initiator To advance the polymerization reaction in the droplets. Note that an oil-soluble polymerization initiator may be contained in the droplet. In such a core binder resin polymerization step, mechanical energy is imparted and forcedly emulsified (formation of 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 binder resin fine particles formed in the core binder resin polymerization step may be composed of two or more layers made of resins having different compositions. In this case, an emulsion polymerization process (first method) according to a conventional method is used. 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 particles prepared by (stage polymerization), and this system is polymerized (second stage polymerization).

  When using a surfactant in the core binder resin polymerization step, use the same surfactant as the surfactant that can be used in the above-mentioned shell resin fine particle dispersion preparation step, for example. can do.

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

  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 that is introduced in advance in the core binder resin polymerization step.

  The core layer resin is preferably a styrene acrylic resin or a mixture of a styrene acrylic resin and a styrene acrylic modified polyester resin.

〔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 ester waxes such as behenyl acid. These can be used individually by 1 type or in combination of 2 or more types.

  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.

(Polymerization initiator)
As the polymerization initiator used in the binder resin polymerization step, the same ones as 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, the same ones as described above 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 in terms of volume-based median diameter.

The volume-based median diameter is measured using “UPA-150” (manufactured by Microtrack).
(1-3) 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 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.
(2) 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 binder resin fine particles and colorant fine particles, if necessary. You can also.

  As a specific method for agglomerating 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. And by heating to a temperature equal to or higher than the melting peak temperature (° C.) 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. This is a method in which when the particles have grown to a desired particle size, an aggregation terminator is added to stop the particle growth, and heating is continued to control the particle shape as necessary.

  In this method, the time allowed to stand after adding the flocculant is shortened as much as possible, and it is not less than the glass transition point of the resin fine particles related to the binder resin, and not less than the melting peak temperature (° C.) of these mixtures. Heating to temperature is preferred. 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 metal salts can include sodium chloride, potassium chloride, lithium chloride, calcium chloride, magnesium chloride, zinc chloride, copper sulfate, magnesium sulfate, manganese sulfate, and the like. It is particularly preferable to use a divalent metal salt. These can be used individually by 1 type or in combination of 2 or more types.

  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 a median diameter on a volume basis (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).
(3) Shelling step In this shelling step, shell resin fine particles are added to the dispersion of core particles to aggregate and fuse the shell resin fine particles on the surface of the core particles, and a shell layer is formed on the surface of the core particles. The toner base particles are formed by coating.

Specifically, the dispersion of the core particles is added to the dispersion of the shell resin fine particles while maintaining the temperature in the core particle formation step, and the shell resin fine particles are slowly removed over several hours while continuing the heating and stirring. By agglomerating and fusing to the surface of the toner, toner particles are formed by covering the surface of the core particles with a shell layer having a thickness of 100 to 300 nm. The heating and stirring time is preferably 1 to 7 hours, particularly preferably 3 to 5 hours.
(4) Ripening step The shape of the toner particles 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 ripening 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 the heating temperature is lowered also in this aging step, and The toner base particles are controlled to have a desired average circularity by extending the time, that is, to have a uniform surface shape.
(5) Washing step to (6) Drying step The washing step and the drying step can be performed by employing various known methods.
(7) 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, or strontium titanate and zinc titanate. An inorganic titanic acid compound fine particle etc. are mentioned.

  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 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 of 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. It is done.

〔toner〕
The toner of the present invention is composed of toner particles in which a shell layer is formed on the surface of core particles, and can be used as it is as it is. However, it is possible to use a toner added with an external additive as the toner. preferable.

[Average toner particle size]
The average particle diameter of the toner 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, and 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, for example, a very minute dot image at a level of 1200 dpi (dpi; number of dots per inch (2.54 cm)) can be faithfully reproduced.

  The volume-based median diameter of the toner particles is measured and calculated using a measuring device in which “Multisizer 3” (manufactured by Beckman Coulter) is connected to a computer system equipped with data processing software “Software V3.51”. 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 the volume-based median diameter.

[Average circularity of toner particles]
In the toner of the present invention, the arithmetic average value of the circularity represented by the following formula (T) is 0.850 to 0.990 from the viewpoint of improving the transfer efficiency of the individual toner particles constituting the toner. Is preferred.

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 non-magnetic 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. Among these, ferrite particles Is preferably used. 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.

  The toner of the present invention can be suitably used at a relatively low temperature where the fixing temperature (the surface temperature of the fixing member) is 100 to 200 ° C.

  Furthermore, the toner of the present invention can be suitably used for a high-speed machine in which the linear velocity of the electrostatic latent image carrier is 100 to 500 mm / sec.

  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, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Production of Toner 1]
(1) Preparation of Binder Resin Fine Particle Dispersion 1-1 First Stage Polymerization An anionic surfactant “sodium lauryl sulfate” in a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a cooling pipe and a nitrogen introducing device in advance. An anionic surfactant solution in which 2.0 parts by mass was dissolved in 2900 parts by mass of ion-exchanged 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 anionic surfactant solution and adjusting the internal temperature to 78 ° C.,
Styrene 540 parts by mass n-butyl acrylate 154 parts by mass Methacrylic acid 77 parts by mass n-Octyl mercaptan 17 parts by mass A monomer solution [1] was added dropwise over 3 hours. After completion of the dropping, polymerization (first stage polymerization) was carried out by heating and stirring at 78 ° C. for 1 hour to prepare a dispersion of “resin fine particles [a1]”.

1-2 Second-stage polymerization: Formation of intermediate layer In a flask equipped with a stirrer,
Styrene 94 parts by weight n-butyl acrylate 27 parts by weight Methacrylic acid 6 parts by weight n-octyl mercaptan 1.7 parts by weight Paraffin wax (melting point: 73 ° C.) 51 parts by weight as an anti-offset agent (release agent) Was added and heated to 85 ° C. to dissolve to prepare a monomer solution [2].

  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 the above-mentioned “resin fine particles [ a1] ”is added to the resin fine particles [a1] in terms of solid content by 28 parts by mass, and then the above-mentioned single amount is obtained by a mechanical disperser“ CLEAMIX ”(manufactured by M Technique Co., Ltd.) having a circulation path. The body solution [2] was mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm. An initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator “KPS” was dissolved in 110 parts by mass of ion-exchanged water was added to this dispersion, and this system was polymerized by heating and stirring at 90 ° C. for 2 hours. By performing the second stage polymerization), a dispersion of “resin fine particles [a11]” was prepared.

1-3 Third-stage polymerization: Formation of outer layer Initiator aqueous solution in which 2.5 parts by mass of polymerization initiator “KPS” is dissolved in 110 parts by mass of ion-exchanged water in the dispersion of “resin fine particles [a11]”. And at a temperature of 80 ° C.
Styrene 230 mass parts n-butyl acrylate 78 mass parts Methacrylic acid 16 mass parts n-octyl mercaptan 4.2 mass parts monomer 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. Thereafter, the mixture was cooled to 28 ° C., and a “dispersion of binder resin fine particles [A]” in which the binder resin fine particles [A] were dispersed in an anionic surfactant solution was prepared.

  The binder resin fine particles [A] had a glass transition point of 45 ° C. and a softening point of 100 ° C.

(2) First Step Shell Resin Fine Particle Dispersion Preparation Step 2-1 Synthesis of First Step Shell Resin (Styrene Acrylic Modified Polyester Resin A) 10 liter capacity equipped with nitrogen introduction tube, dehydration tube, stirrer and thermocouple Into a four-necked flask
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. After the addition polymerization reaction was continued for 1 hour, the temperature was raised to 200 ° C. and held at 10 kPa for 1 hour, and then acrylic acid, styrene, and butyl acrylate were removed to remove styrene acrylic modified polyester resin [A: StAc Modified PES] was obtained.

  This styrene acrylic modified polyester resin [A] had a glass transition point of 60 ° C. and a softening point of 105 ° C.

2-2 Preparation of Shell Resin Fine Particle Dispersion 100 parts by mass of the obtained styrene acrylic modified polyester resin [A] was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.) and 0.26 mass prepared in advance. The mixture was mixed with 638 parts by mass of a sodium lauryl sulfate solution with a concentration of 1%, and ultrasonically dispersed with stirring using an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho Co., Ltd.) at 300 μA for 30 minutes. A “dispersed liquid of shell resin fine particles [A]” in which a styrene acrylic modified polyester resin [A] having a median diameter (D ₅₀ ) of 250 nm was dispersed was produced.

(3) Preparation Step of Second Stage Shell Resin Fine Particle Dispersion B1C1 3-1 Production of “Shell Resin Particle Dispersion B1: For StAc” Anion in a reaction vessel equipped with a stirrer, temperature sensor, cooling tube, and nitrogen introducing device An aqueous surfactant solution was prepared by dissolving 2 parts by mass of a surfactant (sodium dodecylbenzenesulfonate: SDS) in 2900 parts by mass of ion-exchanged water. While stirring the surfactant aqueous solution at a stirring speed of 230 rpm under a nitrogen stream, the temperature was raised to 80 ° C.

After 9.0 parts by weight of potassium persulfate (KPS) was added to the surfactant aqueous solution, a monomer solution composed of the following compounds was added dropwise over 3 hours. That is,
n-Butyl acrylate 198 parts by weight Methyl methacrylate 945 parts by weight Itaconic acid 60 parts by weight After completion of the dropwise addition of the monomer solution, the liquid temperature is maintained at 78 ° C. for 1 hour to advance the polymerization reaction. A “shell resin particle dispersion B1” containing a copolymer formed from the three polymerizable monomers was prepared. The ratio of methyl methacrylate to itaconic acid in the copolymer constituting “resin particle B1” was 83.5% by mass. The “resin particle B1” had a weight average molecular weight Mw of 280,000 and a glass transition temperature Tg of 68 ° C.

3-2 Production of “Shell Resin Fine Particle Dispersion B1C1” 2 parts by mass of an anionic surfactant (sodium dodecylbenzenesulfonate: SDS) in a reaction apparatus equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introduction apparatus, and A surfactant solution was prepared by dissolving 50 parts by mass (in terms of solid content) of the “shell resin particle dispersion B1” in 2900 parts by mass of ion-exchanged water. The liquid temperature was raised to 80 ° C. while stirring the surfactant solution at a rotational speed of 230 rpm under a nitrogen stream.

After adding 9.0 parts by mass of potassium persulfate (KPS) to the surfactant solution, a monomer solution composed of the following compounds was added dropwise over 3 hours. That is,
Styrene 570 parts by mass n-butyl acrylate 170 parts by mass n-octyl mercaptan 12 parts by mass After completion of the dropwise addition of the above monomer solution, the liquid temperature is maintained at 78 ° C. for 1 hour to advance the polymerization reaction. “Shell resin fine particle dispersion B1C1” containing resin particles having a structure in which “resin B1” was encapsulated in “resin C1” was produced. The “shell resin fine particle dispersion B1C1” had a weight average molecular weight of 60,000 and a glass transition temperature of 47 ° C. The content of “shell resin fine particle dispersion B1” in “shell resin fine particle dispersion B1C1 (StAc)” was 6.3 mass%.

  The above polymerization was performed to form “resin particles C1” in the absence of “shell resin fine particle dispersion B1”. The weight average molecular weight Mw was 17,000 and the glass transition temperature Tg was 47 ° C. It was.

(4) Preparation Step of Colorant Fine Particle Dispersion 90 parts by mass of sodium dodecyl sulfate is dissolved in 1600 parts by mass of ion-exchanged water, and 420 parts by mass of carbon black “Mogal L” (manufactured by Cabot) while stirring this solution. Is added, and then dispersed using a stirrer “CLEARMIX” (M Technique Co., Ltd.) to disperse the colorant fine particles [C]. Liquid "was prepared. The particle diameter of the colorant fine particles [C] in this dispersion was measured using a Microtrac particle size distribution measuring device “UPA-150” (manufactured by Nikkiso Co., Ltd.), and was 117 nm.

(5) Aggregation, fusion-maturation-washing-drying-addition process of external additives "Dispersion of binder resin fine particles [A]" is converted to solid content in a reaction vessel equipped with a stirrer, temperature sensor, and cooling pipe. Then, 288 parts by mass and 2,000 parts by mass of ion-exchanged water were added, and a 5 mol / liter sodium hydroxide aqueous solution was added to adjust the pH to 10.

Thereafter, 40 parts by mass of “dispersion of colorant fine particles [C]” was added in terms of solid content, and then an aqueous solution in which 60 parts by mass of magnesium chloride was dissolved in 60 parts by mass of ion-exchanged water was stirred at 30 ° C. Added over 10 minutes. 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 diameter of the core particles was measured with “Coulter Multisizer 3” (manufactured by Coulter Beckman), and when the volume-based median diameter (D ₅₀ ) reached 6.0 μm, “shell resin fine particles 72 parts by mass of the “dispersion liquid [B]” was added over 30 minutes in terms of solid content and reacted until the supernatant of the reaction liquid became transparent. Next, 19.8 parts by mass of resin fine particles C1B1 are added over 10 minutes, the reaction liquid is allowed to react until the supernatant becomes transparent, and an aqueous solution in which 190 parts by mass of sodium chloride is dissolved in 760 parts by mass of ion-exchanged water is added. The particle growth was stopped. Further, the temperature is raised and the mixture is heated and stirred in a state of 90 ° C. to advance the fusing of the particles, and the average circularity measurement apparatus “FPIA-2100” (manufactured by Sysmex) is used (HPF detection). When the average circularity reached 0.945, the mixture was cooled to 30 ° C. to obtain a “dispersion of toner particles [1]”.

  This “dispersion of toner particles [1]” is solid-liquid separated with a centrifuge to form a wet cake of toner particles, and this is used until the electric conductivity of the filtrate reaches 5 μS / cm using the centrifuge. After washing with ion exchange water at 35 ° C., it was transferred to “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content became 0.5 mass%.

  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 particles [1], and a Henschel mixer is used. By mixing, Toner 1 was produced. This toner was observed by SEM, and the surface coverage was calculated to be 25%.

[Production of Toner 2]
In the agglomeration, fusion-maturation-washing-drying-external additive addition process in the production of toner 1, the addition amount was changed according to the coverage shown in Table 1 to obtain a toner having a surface coverage of 10%. . This is referred to as Toner 2.

[Production of Toner 3]
In the agglomeration, fusion-maturation-cleaning-drying-external additive addition step in the production of toner 1, the addition amount was changed according to the coverage shown in Table 1 to obtain a toner having a surface coverage of 50%. . This is toner 3.

[Preparation of Toner 4]
In the agglomeration, fusion-maturation-washing-drying-external additive addition process of toner production example 1, the addition amount was changed according to the coverage shown in Table 1 and replaced with binder resin fine particles [A]. A toner 4 having a surface coverage of 25% was prepared in the same manner except that the resin fine particles [A] were used.

[Preparation of Toner 5]
Styrene acrylic-modified polyester resin (StAc-modified PES-2) was prepared by the following synthesis method, and toner 5 having a surface coverage of 25% was prepared in the same manner as toner 4.

Production of Resin for Shell <Production of Polyester Resin (Production of Polyester (a))>
In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 500 parts by mass of bisphenol A propylene oxide 2 mol adduct, 127 parts by mass of terephthalic acid, 54 parts by mass of fumaric acid, and titanium tetraisopropoxy as a polycondensation catalyst. 2 parts by mass of the dough 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 (a). Polyester (a) had a Tg of 65 ° C., a number average molecular weight of 4500, and a weight average molecular weight of 13500.

<Production of styrene-acrylic modified polyester resin (resin for shell)>
In an autoclave reaction vessel equipped with a thermometer and a stirrer, 430 parts by mass of xylene and the polyester resin (a) obtained above were placed and dissolved, and after substitution with nitrogen, 60.4 parts by mass of styrene, 2-ethylhexyl acrylate A mixed solution of 15.2 parts by mass, 0.98 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 obtain a shell resin having a styrene-acryl content of 10% by mass.

Preparation of Shell Resin Particle Dispersion 100 parts by mass of the obtained shell resin was dissolved in 400 parts by mass of ethyl acetate (manufactured by Kanto Chemical Co., Inc.), and a 0.26% by mass sodium lauryl sulfate solution 638 prepared in advance was prepared. After mixing with mass parts, ultrasonically dispersing with ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) for 30 minutes with V-LEVEL 300 μA, the diaphragm vacuum pump V is heated to 40 ° C. -700 using (BUCHI Corporation), ethyl acetate was completely removed with stirring for 3 hours under a reduced pressure, an average particle diameter (median diameter _{(D 50} in volume)) is 160 nm, solid content of 13. A 5% by mass resin particle dispersion for shell (StAc-modified PES-2)) was obtained.

[Preparation of Toner 6]
In the agglomeration, fusion-maturation-washing-drying-external additive addition step in the production of toner 1, the addition amount is changed according to the coverage shown in Table 1, and a toner having a surface coverage of 9.0% is obtained. Obtained. This is designated as Toner 6.

[Preparation of Toner 7]
In the agglomeration, fusion-maturation-washing-drying-external additive addition step in the production of toner 1, the addition amount was changed according to the coverage shown in Table 1 to obtain a toner having a surface coverage of 51%. . This is designated as Toner 7.

[Preparation of Toner 8]
In the toner agglomeration, fusion-maturation-washing-drying-external additive addition step, the addition amount was changed according to the coverage shown in Table 1 and replaced with binder resin fine particles [A]. A toner 8 having a surface coverage of 25% was prepared in the same manner except that the following polyester resin particle dispersion [A] was used.

Preparation of polyester resin particle dispersion A Preparation of polyester resin (A) In a reaction vessel equipped with a cooling tube, a stirrer and a nitrogen introduction tube, 343 parts of bisphenol A propylene oxide 2 mol adduct, 87 parts of terephthalic acid, and heavy As a condensation catalyst, 2 parts of titanium tetraisopropoxide was added in 10 portions and reacted at 200 ° C. for 10 hours while distilling off the water produced in a nitrogen stream. Subsequently, it was made to react under the reduced pressure of 100 mmHg (1 mmHg = 133 Pa), and it pick_out | removed when the softening point became 104 degreeC. This is designated as polyester resin (A). Polyester resin (A) had a Tg of 55 ° C., a number average molecular weight of 3500, and a weight average molecular weight of 12,000.

430 parts by mass of the polyester resin (A) was dissolved in 1720 parts by mass of ethyl acetate (manufactured by Kanto Chemical Co., Inc.) with stirring. Next, the mixture was mixed with 1724 parts by mass of a sodium lauryl sulfate solution having a concentration of 0.26% by mass prepared in advance, and ultrasonically dispersed with an ultrasonic homogenizer “US-150T” (manufactured by Nihon Seiki Seisakusho) at 300 μA for 30 minutes with an ultrasonic homogenizer. Then, using a diaphragm vacuum pump V-700 (manufactured by BUCHI) in a state heated to 50 ° C., ethyl acetate was completely removed while stirring for 5 hours under reduced pressure, and the median diameter (D ₅₀ ) "of 170 nm and a solid content of 20% by mass was obtained as" Polyester resin particle dispersion A ".

[Preparation of Toner 9]
In the agglomeration, fusion-maturation-washing-drying-external additive addition process of toner preparation example 1, the addition amount was changed according to the coverage shown in Table 1, and toner 9 having a surface coverage of 25% was obtained. Produced.

[Production of Toner 10]
In the production of toner 1, in the fusion-maturation-washing-drying-external additive addition step, the addition amount is changed according to the coverage shown in Table 1, and the polyester resin using the second-stage shell as toner 8 A toner 10 was prepared in the same manner except that the particle dispersion liquid [A] was used.

  The configurations and surface coverage of the toners 1 to 10 are summarized in Table 1.

[Production of developers 1 to 10]
(1) Production of carrier 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) were put into a high-speed mixer equipped with stirring blades at 120 ° C. A carrier having a volume-based median diameter of 50 μm was obtained by stirring and mixing for 30 minutes to form a resin coat layer on the surface of the ferrite core by the action of mechanical impact force.

  The volume-based median diameter of the carrier was measured with a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by Sympathic) equipped with a wet disperser.

(2) Mixing of toner and carrier To each of toners 1 to 10, the above carrier is added so that the toner concentration is 6% by mass, and rotated by a micro-type V-type mixer (Tsutsui Rikenki Co., Ltd.). Developers 1-9 were produced by mixing at a speed of 45 rpm for 30 minutes.

  Using the developers 1 to 10 described above, image evaluation was performed when 200,000 sheets were printed by durable live action.

[Image evaluation]
Using a commercially available color multifunction device “bizhub PRO C6500” (manufactured by Konica Minolta Business Technologies, Inc.), an actual paper endurance test for printing 200,000 sheets on an evaluation paper “POD128 (Oji Paper)” at a printing rate of 20% was performed. The image was output and the number of white spots on the image was counted. As for the white spot on the image, 0 to 2 was good, 3 to 5 was acceptable, and 6 or more was rejected.

  In Examples 1 to 5 (Toners 1 to 5) in the present invention, the image spot characteristics are all good, but the toners 6 to 8, and 10 in Comparative Examples 1 to 5 are all problematic. . Toner 9 did not achieve fixing performance at all.

Claims (4)

  A core-shell type toner for electrostatic charge developer, wherein the core layer contains at least a styrene-acrylic modified polyester resin, and the core layer is coated with spherical particles for a shell covered with at least a styrene-acrylic resin component. A toner for an electrostatic charge developer, having a rate of 10% to 50%.   2. The toner for electrostatic charge developer according to claim 1, wherein the core layer comprises a styrene acrylic resin as a core and is coated with a styrene acrylic modified polyester resin.   In a core shell type electrostatic charge developer manufacturing method, a core layer containing at least a styrene acrylic modified polyester resin is prepared, and the core layer is coated with spherical particles for a shell containing at least a styrene acrylic resin component. A method for producing a toner for an electrostatic charge developer, wherein the rate is 10 to 50%.   In the core shell type electrostatic charge developer manufacturing method, a core layer containing at least a styrene acrylic resin is prepared, and the core layer is coated with spherical particles for a first stage shell containing at least a styrene acrylic modified polyester resin component, Next, a method for producing a toner for an electrostatic charge developer, which is coated with spherical particles for the second stage shell, and the surface coverage of the second stage shell is 10% or more and 50% or less.