JP6089466B2 - Toner for developing electrostatic image and image forming method - Google Patents

Description

  The present invention relates to an electrostatic image developing toner used for electrophotographic image formation and an image forming method using the electrostatic image developing toner.

  Conventionally, from the viewpoint of energy saving, development of a low-temperature fixable electrostatic image developing toner (hereinafter also simply referred to as “toner”) that can be fixed with less energy has been underway. In order to lower the toner fixing temperature, it is necessary to lower the melting temperature and melt viscosity of the toner 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 solve this problem, a technique has been reported in which toner particles have a core-shell structure in order to satisfy both low-temperature fixability and heat-resistant storage stability (see, for example, Patent Document 1). That is, by forming a shell layer using fine particles with high softening point and high heat resistance on the surface of core particles excellent in low temperature fixability, a toner satisfying both low temperature fixability and heat storage stability is produced. can do.
However, in recent years, as the speed of copying machines and printers and the expansion of compatible paper types have progressed in the production printing area, depending on the toner of the core-shell structure as disclosed in Patent Document 1, further low-temperature fixability and heat-resistant storage stability And it has become difficult to satisfy both.

  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 as compared with styrene-acrylic copolymer resin. By using polyester resin for the shell layer, low temperature fixability -A toner having good heat storage stability can be obtained.

However, the styrene-acrylic copolymer resin and the polyester resin are poor in affinity, and the styrene-acrylic copolymer resin is used as the binder resin constituting the core particles, and the polyester resin is used as the shell resin constituting the shell layer. However, since it is difficult to form a thin and uniform shell layer, there is a problem that sufficient heat-resistant storage stability cannot be obtained. Further, since it is difficult for the core particles and the fine particles to form the shell layer to be fused, it is difficult to control the shape of the toner particles, and thus it is difficult to produce toner particles having a smooth surface. High chargeability cannot be obtained, and the toner is agitated in the developing device during continuous printing to cause peeling of the shell layer. As a result, image noise occurs in the formed image, and good image quality is not ensured. There is also a problem. In particular, when such a toner is used as a non-magnetic one-component developer in a high-performance machine such as a high-speed machine, the toner particles covered with a thin shell layer are on the sleeve in the developing device. There is also a problem that it is deformed and crushed by pressure stress due to the formation of a thin layer.
Applying a charged charge to a non-magnetic one-component toner requires a pressing stress at the thin layer forming portion, but for a toner having a core-shell structure, the shell layer is likely to peel off due to this stress. Therefore, it was necessary to obtain a sufficiently charged charge with as little pressing stress as possible.

JP 2005-221933 A JP 2005-338548 A

The present invention has been made in view of the above circumstances, and its first object is to satisfy both the low-temperature fixability and the excellent heat-resistant storage stability, as well as the excellent chargeability and crush resistance. Is to provide a toner for developing an electrostatic charge image.
In addition, the second object of the present invention is to ensure high charging stability and crush resistance even when used as a non-magnetic one-component developer. Another object of the present invention is to provide an electrostatic image developing toner capable of stably obtaining a high-quality image even in a machine, and an image forming method using the electrostatic image developing toner.

The electrostatic image developing toner of the present invention comprises an electrostatic image comprising toner particles in which a shell layer is formed on core particles made of a binder resin containing a styrene-acrylic copolymer resin, and an external additive. Developing toner,
The shell layer contains a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment, and the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin. The content ratio is 5% by mass or more and 30% by mass or less,
The external additive contains at least silica fine particles and composite inorganic fine particles made of an inorganic compound containing magnesium and aluminum.

In the electrostatic charge image developing toner of the present invention, the composite inorganic fine particles have a magnesium to aluminum content ratio [Mg (atm%) / Al (atm%)] of 1 to 4, and an electrostatic resistance of 1 × 10 ^10. ˜1 × 10 ¹³ Ω · cm and a number average primary particle size of 50 to 1000 nm are preferable.

  In the electrostatic image developing toner of the present invention, it is preferable that the external additive further contains titanium-containing oxide fine particles.

  In the electrostatic image developing toner of the present invention, the composite inorganic fine particles are preferably contained in a ratio of 0.02 to 1.0% by mass with respect to the total mass of the electrostatic image developing toner.

  The image forming method of the present invention is characterized in that the electrostatic image developing toner is used as a non-magnetic one-component developer.

According to the electrostatic image developing toner of the present invention, the shell layer is made of a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment. Since the shell layer is thin and uniform, sufficient low-temperature fixability and excellent heat storage stability can be obtained, and excellent chargeability and crush resistance can be obtained. .
In addition, according to the toner for developing an electrostatic charge image of the present invention, even when the toner for developing an electrostatic charge image is used as a non-magnetic one-component developer, composite inorganic fine particles, so-called hydrotalls, are used as external additives. By using a site compound, it is possible to further minimize the pressing stress at the thin layer forming part to obtain the charge amount of the toner necessary for development. As a result, high-performance machines such as high-speed machines In this case, a high-quality image can be stably formed.

It is the schematic for description which shows the structure of the apparatus used when measuring the static resistance which concerns on this invention. FIG. 3 is a cross-sectional view illustrating an example of the configuration of a full-color image forming apparatus that uses the toner of the present invention as a nonmagnetic one-component developer. FIG. 5 is an explanatory cross-sectional view illustrating an example of a configuration of a developing cartridge for a one-component developer.

  Hereinafter, the present invention will be described in detail.

[Toner for electrostatic image development]
The toner of the present invention comprises toner particles in which a shell layer is formed on core particles made of a binder resin containing a styrene-acrylic copolymer resin, and an external additive. A styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment, and the content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin is The external additive contains at least silica fine particles and composite inorganic fine particles made of an inorganic compound containing magnesium and aluminum.

[Shell layer]
The shell layer constituting the toner particles according to the present invention is constituted by a shell resin containing a styrene-acryl-modified polyester resin. The shell resin may contain other resins such as a styrene-acrylic copolymer resin, a polyester resin, and a urethane resin in addition to the styrene-acrylic modified polyester resin.
The content ratio of the styrene-acrylic modified polyester resin in the shell resin has sufficient affinity between the core particles and the shell layer, and from the viewpoint that the desired shell layer can be reliably formed, the shell resin is 100% by mass. The content is preferably 70 to 100% by mass, and more preferably 90 to 100% by mass.

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

In the present invention, the content ratio of the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin (hereinafter, also referred to as “styrene-acrylic modification amount”) is 5% by mass or more and 30% by mass or less. In particular, it is preferably 5% by mass or more and 20% by mass or less.
Specifically, the amount of styrene-acryl modification is the total mass of the resin material used to synthesize the styrene-acryl modification polyester resin, that is, the unmodified polyester resin that becomes the polyester segment, and the styrene-acrylic copolymer weight. Aromatic vinyl monomer and (meth) acrylic acid ester monomer serving as a coalesced segment, and the total mass of both reactive monomers for bonding these aromatic vinyl monomer and ( It refers to the mass ratio of the (meth) acrylic acid ester monomer.

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

In the toner of the present invention, an aliphatic unsaturated dicarboxylic acid is used as a polyvalent carboxylic acid monomer to form a polyester segment of a styrene-acryl-modified polyester resin, and the aliphatic unsaturated dicarboxylic acid is added to the polyester segment. It is preferable that a structural unit derived from an acid is contained.
The aliphatic unsaturated dicarboxylic acid refers to a chain dicarboxylic acid having a vinylene group in the molecule.
According to the styrene-acryl-modified polyester resin having a structural unit derived from an aliphatic unsaturated dicarboxylic acid, it is possible to reliably form a smooth shell layer having a more uniform film thickness while being a thin layer.

The proportion of structural units derived from aliphatic unsaturated dicarboxylic acids in the structural units derived from polyvalent carboxylic acid monomers constituting the polyester segment of the styrene-acrylic modified polyester resin (hereinafter referred to as “specific unsaturated dicarboxylic acid-containing” The ratio is also preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.
When the content ratio of the specific unsaturated dicarboxylic acid is within the above range, a smooth shell layer having a more uniform film thickness can be more reliably formed while being a thin layer. On the other hand, if the specific unsaturated dicarboxylic acid content is too small, sufficient heat-resistant storage stability and chargeability may not be obtained, and if the specific unsaturated dicarboxylic acid content is excessive, Sufficient chargeability may not be obtained.

The structural unit derived from the aliphatic unsaturated dicarboxylic acid is preferably a structural unit derived from one represented by the following general formula (A).
General formula (A): HOOC- (CR < ¹ > = CR _< ² _> ) _n- COOH
[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.

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

The glass transition point of the shell resin is a value measured by a method (DSC method) defined in ASTM (American Society for Testing and Materials) D3418-82.
The softening point of the shell resin is measured as follows.
First, in an environment of 20 ° C. ± 1 ° C. and 50% ± 5% RH, 1.1 g of shell resin is placed in a petri dish and left flat for 12 hours or more. Then, a molding machine “SSP-10A” (Shimadzu Corporation) Pressure) with a force of 3820 kg / cm ² for 30 seconds to produce a cylindrical molded sample having a diameter of 1 cm. Then, the molded sample is 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. The offset method temperature T _offset measured from the end of preheating using a piston with a diameter of 1 cm from the end of preheating and measured at a setting of an offset value of 5 mm by the melting temperature measurement method of the temperature rising method is the shell tree. The softening point of fat.

The content ratio of the shell resin is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass, based on the total amount of the resin constituting the toner.
When the content ratio of the shell resin is excessively low, sufficient heat storage stability may not be obtained. When the content ratio of the shell resin is excessively high, sufficient low-temperature fixability may not be obtained. is there.

[Production Method of Styrene-Acrylic Modified Polyester Resin]
As a method for producing the styrene-acrylic modified polyester resin constituting 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, the polyester segment is allowed to react with both reactive monomers, and an aromatic vinyl monomer for forming a styrene-acrylic copolymer segment and ( A method of forming a styrene-acrylic copolymer segment by reacting a (meth) acrylic acid ester monomer.
(A-2) A polyvalent carboxylic acid for polymerizing a styrene-acrylic copolymer segment in advance, reacting the styrene-acrylic copolymer segment with both reactive monomers, and further forming a polyester segment. A method of forming a polyester segment by reacting an acid monomer and a polyhydric alcohol monomer.
(B) A method in which a polyester segment and a styrene-acrylic copolymer segment are respectively polymerized in advance, and both are reacted with each other to react them.
In this specification, the both reactive monomers are a group capable of reacting with a polyvalent carboxylic acid monomer and / or a polyhydric alcohol monomer for forming a polyester segment of a styrene-acryl-modified polyester resin, and a polymerizable unsaturated group. And a monomer having

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

  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, and particularly preferably 5% by mass or more and 20% by mass or less.

  When the total ratio of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to the total mass of the resin material used is within the above range, the styrene-acrylic modified polyester resin and the core particle The affinity is appropriately controlled, and a smooth shell layer can be formed with a more uniform film thickness while being a thin layer. On the other hand, when the ratio is too small, the resulting styrene-acryl-modified polyester resin cannot form a shell layer with a uniform film thickness, resulting in partial exposure of the core particles. Therefore, sufficient heat storage stability and chargeability cannot be obtained for the obtained toner. If the ratio is excessive, the resulting styrene-acryl-modified polyester resin has a high softening point, so that the resulting 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 weight fraction of monomer x, and Tgx is the glass transition point of the homopolymer of monomer x. ]
In the present specification, both reactive monomers are not used for calculation of the glass transition point.

  Among 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 copolymer 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 the aromatic vinyl monomer and (meth) acrylic acid ester monomer for forming the styrene-acrylic copolymer segment, styrene or its monomer is used from the viewpoint of obtaining excellent chargeability and image quality characteristics. It is preferable to use many derivatives. Specifically, the amount of styrene or a derivative thereof used is such that all monomers (aromatic vinyl monomers and (meth) acrylic acid ester units) used to form a styrene-acrylic copolymer segment are used. It is preferable that it is 50 mass% or more in (mer).

[Amotropic monomer]
As the both reactive monomers for forming the styrene-acrylic copolymer 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 Specifically, for example, acrylic acid, methacrylic acid, fumaric acid, maleic acid, maleic anhydride and the like can be used.

[Polyester resin]
The unmodified polyester resin used for preparing the styrene-acrylic modified polyester resin according to the present invention is a heavy polymer in the presence of an appropriate catalyst using a polyvalent carboxylic acid monomer (derivative) and a polyhydric alcohol monomer (derivative) as raw materials. It is produced by a condensation reaction.

  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, mesaconic acid, adipic acid, β-methyladipic acid, azelaic acid, sebacic acid, nonanedicarboxylic acid, decanedicarboxylic acid, undecanedicarboxylic acid, and dodecanedicarboxylic acid. Acid, fumaric 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-phenylenediglycol Glycolic acid, diphenylacetic acid, diphenyl divalent carboxylic acids such as p, p'-dicarboxylic acid, naphthalene-1,4-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, naphthalene-2,6-dicarboxylic acid, anthracene dicarboxylic acid, dodecenyl succinic acid; Examples thereof include divalent or higher carboxylic acids such as merit acid, pyromellitic 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-acryl-modified polyester resin can surely form a smooth shell layer with a more uniform film thickness while being a thin layer. . In particular, by using the aliphatic unsaturated dicarboxylic acid represented by the general formula (A), the obtained styrene-acryl-modified polyester resin is more surely a thin layer with a more uniform film thickness and A smooth shell layer can be formed.

The ratio of the aliphatic unsaturated dicarboxylic acid in the total polyvalent carboxylic acid monomer to be used is preferably 25 mol% or more and 75 mol% or less, and more preferably 30 mol% or more and 60 mol% or less.
When the ratio of the aliphatic unsaturated dicarboxylic acid used is in the above range, the obtained styrene-acryl-modified polyester resin is more surely a thin shell with a more uniform film thickness and a smooth shell layer. Can be formed. On the other hand, if the proportion of the aliphatic unsaturated dicarboxylic acid used is too small, sufficient heat-resistant storage stability and chargeability may not be obtained 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, and the like. And trivalent or higher polyols such as glycerin, pentaerythritol, hexamethylol melamine, hexaethylol melamine, tetramethylol benzoguanamine, and tetraethylol benzoguanamine.

  The ratio of the polyhydric carboxylic acid monomer to the polyhydric alcohol monomer is 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.

  Various conventionally known catalysts can be used as a catalyst for synthesizing the unmodified polyester resin.

  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 toner resin is obtained, and the occurrence of 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 of the styrene-acrylic copolymer segment, the polymerization is preferably performed in the presence of a radical polymerization initiator, and the timing of addition of the radical polymerization initiator is not particularly limited, but the control of the radical polymerization is easy. Therefore, it is preferable to add after mixing the aromatic vinyl monomer and the (meth) acrylic acid ester monomer for forming the polymerization of the styrene-acrylic copolymer segment.

  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-butyl 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. Peroxide 2,2'-azobis (2-aminodipropane) hydrochloride, 2,2'-azobis- (2-aminodipropane) nitrate, 1,1'-azobis (1-methylbutyronitrile-3-sulfone) Acid salt), 4,4'-azobis-4-cyanovaleric acid, poly (tetraethylene glycol-2,2'-azobisisobutyrate) and other azo compounds.

[Chain transfer agent]
In the polymerization of the styrene-acrylic copolymer segment, a generally used chain transfer agent can be used for the purpose of adjusting the molecular weight of the styrene-acrylic copolymer 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 mixed with the resin material in the mixing step of the aromatic vinyl monomer and the (meth) acrylic acid ester monomer to form the polymerization of the styrene-acrylic copolymer segment. It is preferable.

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

  The polymerization temperature in the polymerization of the styrene-acrylic copolymer segment is not particularly limited, and the polymerization between the aromatic vinyl monomer and the (meth) acrylic acid ester monomer and the unmodified polyester resin is performed. It can select suitably in the range which a coupling | bonding advances. 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 a 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 polymerization are suppressed to 1,000 ppm or less, more preferably 500 ppm or less, and still more preferably. Is 200 ppm or less.

[Core particles]
The core particles constituting the toner particles according to the present invention contain a binder resin containing at least a styrene-acrylic copolymer resin and contain a colorant even if they contain a colorant. It may not be.

  The binder resin constituting the core particles may include a resin conventionally used as a binder resin for an electrophotographic toner in addition to a styrene-acrylic copolymer resin. As such other resins, Various known resins can be used.

Examples of the polymerizable monomer used to form the styrene-acrylic copolymer resin include the aromatic vinyl monomers and (meth) acrylic acid ester monomers listed 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-based monomer include diacrylates such as ethylene glycol, propylene glycol, butylene glycol, and hexylene glycol; dimethacrylates and tri- and higher alcohols such as divinylbenzene, pentaerythritol, and trimethylolpropane. And methacrylate.
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 other than carbon black, 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.

(External additive)
The external additive constituting the toner of the present invention contains at least silica fine particles and composite inorganic fine particles made of an inorganic compound containing magnesium (Mg) and aluminum (Al).

The silica fine particles constituting the external additive may be any of fumed silica produced by a dry gas phase method and sol-gel silica produced by a wet sol-gel method, and is not limited.
In the toner of the present invention, high fluidity can be imparted to the toner particles by using silica fine particles as an external additive.

The number average primary particle size of the silica fine particles is preferably 5 to 200 nm, more preferably 10 to 150 nm. Two or more types having different number average primary particle sizes may be used in combination.
The content of the silica fine particles is preferably 0.05 to 5% by mass, and more preferably 0.1 to 3% by mass with respect to the total mass of the toner.

The composite inorganic fine particles constituting the external additive are made of an inorganic compound containing magnesium (Mg) and aluminum (Al).
Even when the composite inorganic fine particles in the toner of the present invention are used as a non-magnetic one-component developer, the pressure stress at the thin layer forming portion for obtaining the charge amount of the toner necessary for development is further minimized. As a result, high-quality images such as high-speed devices can be stably formed as a result.
In particular, among these composite inorganic fine particles, a double hydroxide having a layered crystal structure, so-called hydrotalcite compound, has good charging characteristics and can obtain a higher quality image, and therefore is more preferably used. it can.

Specific examples of the composite inorganic fine particles constituting the external additive include the following.
Compound (FM-1): MgAl ₂ O ₄
Compound (FM-2): Mg ₂ (Ni) ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O
Compound (FM-3): Mg _3.5 Zn _0.5 Al ₂ (OH) ₁₂ CO ₃ .3H ₂ O
Compound (FM-4): Mg ₄ Al ₂ (OH) ₁₂ CO ₃ .3H ₂ O
Compound (FM-5): Mg _4.5 Al ₂ (OH) ₁₃ CO ₃ .3.5H ₂ O
Compound (FM-6): Mg ₆ Al ₂ (OH) ₁₆ CO ₃ .4H ₂ O
Compound (FM-7): Mg ₁₀ Al ₂ (OH) ₂₄ CO ₃

The content ratio of the composite inorganic fine particles is preferably 0.02 to 1.0% by mass, and more preferably 0.05 to 0.80% by mass with respect to the total mass of the toner.
When the content ratio of the composite inorganic fine particles is 0.02% by mass or more, the charging characteristics and the degree of aggregation of the toner can be adjusted. Stability can be ensured.

The content ratio [Mg (atm%) / Al (atm%)] of Mg and Al in the composite inorganic fine particles is preferably 1 to 4, more preferably 1.5 to 2.5.
When the content ratio [Mg (atm%) / Al (atm%)] is within the above range, the intended charging performance can be ensured.

In the present invention, the content ratio [Mg (atm%) / Al (atm%)] is measured using a fluorescent X-ray analyzer (XRF).
An X-ray fluorescence analyzer (XRF) irradiates a sample with continuous X-rays to generate characteristic X-rays (fluorescent X-rays) unique to the elements constituting the sample. Then, the generated fluorescent X-ray is spectrally separated (spectral dispersion type) by a spectral crystal to generate a spectrum, the obtained spectrum is measured, and the constituent elements are quantitatively analyzed from the intensity.

In the fluorescent X-ray analysis method, a calibration curve is prepared with a fluorescent X-ray analyzer using composite inorganic fine particles having a known content ratio of magnesium and aluminum, and using the calibration curve, The content ratio of aluminum is obtained.
Examples of the X-ray fluorescence analyzer (XRF) include XRF-1800 (manufactured by Shimadzu Corporation) and ZSX-100E (manufactured by RIGAKU Corporation).

The determination of magnesium and aluminum by an X-ray fluorescence analyzer (XRF) can be performed, for example, by the following procedure.
(1) First, a sample for preparing a calibration curve is prepared. A known amount of magnesium hydroxide is added to 100 parts by mass of styrene powder to produce a measurement pellet for magnesium hydroxide. Similarly, a known amount of aluminum oxide is added to 100 parts by mass of styrene powder to produce a measurement pellet for aluminum oxide.
(2) Each of the produced pellets is measured with a fluorescent X-ray analyzer, and a calibration curve for magnesium and aluminum is prepared from the peak intensity obtained from each sample for magnesium hydroxide or aluminum oxide in styrene powder.
(3) Next, the composite inorganic fine particles containing magnesium and aluminum used in the present invention are measured with a fluorescent X-ray analyzer, and the obtained peak intensity is collated with a calibration curve, thereby containing magnesium and aluminum. Quantify the percentage.

  In the fluorescent X-ray analysis, rhodium (Rh) Kα ray is used as X-ray, and, for example, quantification is performed under an output condition of a tube voltage of 20 kV and a tube current of 100 mA. As the spectral crystal, known spectral crystals for magnesium and titanium can be used.

  Furthermore, a known scintillation counter or a proportion counter can be used as a detector for detecting the spectrum.

The static resistance of the composite inorganic fine particles is preferably 1 × 10 ¹⁰ to 1 × 10 ¹³ Ω · cm, more preferably 5 × 10 ^{10 to} 5 × 10 ¹² Ω · cm.
By static resistance of the composite inorganic fine particles used more than 1 × ¹⁰ 10 Ω · cm, even under high temperature and high humidity environment can charge amount suppress leakage, the use of the following 1 × 10 ¹³ Ω · cm Thus, overcharging can be suppressed even in a low temperature and low humidity environment, and environmental stability can be maintained.

  In the present invention, the static resistance of the composite inorganic fine particles is a value measured by the following procedure.

FIG. 1 is an explanatory schematic diagram showing the configuration of an apparatus used when measuring static resistance.
In FIG. 1, 1 is a load unit, 2 is a sample, 3 is the height of the sample, 4 is a main body cell, 5 is a high-voltage power supply, and 6 is a resistance measuring instrument.
In the measurement, first, the sample 2 (1 g) is put into the main body cell 4, and then the load unit 1 of 1400 g is put thereon, and the height 3 of the sample is measured in this state. Thereafter, a DC voltage of 1000 V is applied to the upper and lower electrode surfaces of the sample 2 using the high voltage power source 5, and the resistance value displayed by the resistance measuring instrument 6 after 30 seconds is read.
The area of the electrode of this measuring device is 0.968 cm ² , and the static resistance is calculated from these values by the following formula (1).
Formula (1): Static resistance = {resistance (Ω) × electrode area (cm ² )} / sample height (cm)

The number average primary particle size of the composite inorganic fine particles is preferably 50 to 1000 nm, more preferably 200 to 800 nm.
By using composite inorganic fine particles having a number average primary particle size of 50 nm to 1000 nm, it is added in a preferable state to the toner particle surface, and charging characteristics can be secured.

In the present invention, the number average primary particle size of the composite inorganic fine particles is measured by the following method.
A 30,000 times photograph of the toner is taken with a scanning electron microscope, and the photograph image is captured by a scanner. In the image processing analyzer “LUZEX AP (manufactured by Nireco)”, the external additive present on the toner particle surface of the photographic image is binarized, and the horizontal ferret diameter for 100 composite inorganic fine particles is obtained. The average value is calculated as the number average particle diameter.

The specific surface area of the composite inorganic fine particles is preferably 1.0 m ² / g or more, more preferably 5.0 to ²⁰⁰ m ² / g.

  In the present invention, the specific surface area is determined by adsorbing nitrogen gas on the sample surface using a specific surface area measuring device “Auto Soap 1” (manufactured by Yuasa Ionics) according to the BET method, and using the BET multipoint method. This is a value obtained by calculation.

In the present invention, the silica fine particles and the composite inorganic fine particles are preferably subjected to a hydrophobizing treatment with a surface treatment agent in order to stabilize the environment.
Examples of the surface treatment agent include silane coupling agents, titanium coupling agents, higher fatty acids, and silicone oils.
Of these, silane coupling agents are preferably used, such as hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxy. Silane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltri Methoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriace Etc. may be used Kishishiran, silicone - as is N'oiru, such as dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenyl polysiloxane and the like.

In the toner of the present invention, it is preferable to use titanium-containing oxide fine particles together with silica fine particles and composite inorganic fine particles as an external additive from the viewpoint of stabilization of chargeability. Specific examples of the fine particles include titania fine particles and composite oxide fine particles containing silicon atoms and titanium atoms.
By adding such titanium-containing oxide fine particles, the charge amount is stabilized at an appropriate value, so that fog can be further suppressed at the end of durability.

As the titania fine particles, anatase titania, rutile titania, amorphous titania and the like can be used, and anatase titania is preferable.
The number average primary particle diameter of the titania fine particles is preferably 5 to 200 nm, more preferably 8 to 100 nm.

In the composite oxide fine particles containing silicon atoms and titanium atoms, the ratio of titanium atoms to the total amount of metal elements is preferably 80 atm% or more and 99.5 atm% or less, more preferably 90 atm% or more and 97 atm% or less. It is.
The number average primary particle size of the composite oxide fine particles is preferably 10 to 500 nm, more preferably 20 to 200 nm.

  The method for producing composite oxide fine particles containing silicon atoms and titanium atoms that can be used in the present invention is not particularly limited. For example, the gas phase method is one of typical production methods. The gas phase method is a method for producing an oxide containing silicon atoms and titanium atoms by heating and vaporizing a raw material compound containing silicon atoms and titanium atoms, and burning the obtained gas. As a method for producing composite oxide fine particles such as oxide particles containing titanium atoms and silicon atoms by a vapor phase method, for example, a method for producing a mixed oxide by high thermal decomposition disclosed in Japanese Patent No. 32025573 Etc. is one of them.

  In the case of titania fine particles or composite oxide fine particles containing silicon atoms and titanium atoms, two or more kinds of fine particles having different particle diameters and surface treatments may be added, and the addition amount is 0 with respect to the total mass of the toner. The content is preferably 0.05 to 5% by mass, more preferably 0.1 to 3% by mass.

In the present invention, as the external additive, in addition to these, other fine particles can be used in combination. Examples of the other fine particles include inorganic stearate compound fine particles such as aluminum stearate fine particles and zinc stearate fine particles, and inorganic titanate compound fine particles such as strontium titanate and zinc titanate. The other inorganic fine particles preferably have a number average primary particle size of 5 to 200 nm, more preferably 8 to 100 nm.
The content of other inorganic fine particles is preferably 0.01 to 5% by mass, and more preferably 0.05 to 3% by mass with respect to the total mass of the toner.

From the viewpoint of environmental stability, titania fine particles, composite oxide fine particles containing silicon atoms and titanium atoms, and other fine particles are surface treated with silane coupling agents, titanium coupling agents, higher fatty acids, silicone oils, etc. It is preferable that
Of these, silane coupling agents are preferably used, such as hexamethyldisilazane, trimethylsilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, allyldimethylchlorosilane, benzyldimethylchlorosilane, methyltrimethoxysilane, methyltriethoxy. Silane, isobutyltrimethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, trimethylmethoxysilane, hydroxypropyltrimethoxysilane, phenyltrimethoxysilane, n-butyltrimethoxysilane, n-hexadecyltrimethoxysilane, n-octadecyltri Methoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrimethoxysilane, vinyltriace Kishishiran like can be used, and silicone - as is N'oiru, such as dimethylpolysiloxane, methylhydrogenpolysiloxane, methylphenyl polysiloxane can be used.

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

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) A shell resin fine particle dispersion preparing step of forming a shell resin fine particle by a shell resin in an aqueous medium to prepare a dispersion in which the shell resin fine particle is dispersed;
(1-2) A binder resin polymerization step in which a binder resin fine particle is formed by polymerization in an aqueous medium to prepare a dispersion in which the binder resin fine particle is dispersed;
(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 shelling step in which shell resin fine particles are added to an aqueous medium in which the core particles are dispersed, and the shell resin fine particles are aggregated and fused on the surface of the core particles to form toner particles having a core-shell structure;
(4) An aging step of adjusting the shape of the toner particles by aging with heat energy;
(5) a cleaning step of separating the toner particles from the toner particle dispersion (aqueous medium) and removing the surfactant from the toner particles;
(6) a drying step of drying the washed toner particles;
(7) An external additive adding step of adding an external additive to the dried toner particles.

(1-1) Shell resin fine particle dispersion preparation step In this shell resin fine particle dispersion preparation step, the dispersion of shell resin fine particles 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 as a volume-based median diameter.
The volume-based median diameter is measured using “UPA-150” (manufactured by Microtrack).

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

  When using a surfactant in the 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.

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

〔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 resin constituting the toner.

[Charge control agent]
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 wax 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 resin constituting the toner.

(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 the 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.

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

[Flocculant]
The flocculant used in the core particle forming step is not particularly limited, but a material selected from metal salts is preferably used. Examples of the metal salt include monovalent metal salts such as alkali metal salts such as sodium, potassium and lithium; divalent metal salts such as calcium, magnesium, manganese and copper; and trivalent metal salts such as iron and aluminum. Etc. Specific 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.

As for the particle size of the core particles obtained in this core particle forming step, for example, the volume-based median diameter (D ₅₀ ) is preferably 2 to 9 μm, more preferably 4 to 7 μm.
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 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. The toner particles are formed by aggregating and fusing the surfaces of the core particles with a shell layer having a thickness of 100 to 300 nm on the surface of the core particles. 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 particles formed with a constant 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 leveling, and in this aging step, the heating temperature is lowered. In addition, the toner particles are controlled so as to have a desired average circularity, that is, a surface having a uniform shape by extending the time.

(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 a toner by adding and mixing the external additive to the dried toner particles.
As the external additive, silica fine particles and composite inorganic fine particles are used, and in addition, titanium-containing oxide fine particles are further preferably used.

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

[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 flocculant used, the amount of organic solvent added, the fusing time, and the polymer composition when the emulsion polymerization aggregation method 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.

In the present invention, the volume-based median diameter of the toner is measured using a measuring apparatus in which a computer system equipped with data processing software “Software V3.51” is connected to “Multisizer 3” (manufactured by Beckman Coulter).・ It is calculated.
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]
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

In the present invention, the average circularity of the toner is a value measured using “FPIA-2100” (manufactured by Sysmex).
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.

  According to the toner as described above, since the shell layer is made of the styrene-acrylic modified polyester resin in which the styrene-acrylic copolymer segment is bonded to the terminal of the polyester segment, the core particle and the shell layer have high affinity. Since the shell layer is thin and uniform, sufficient low-temperature fixability and excellent heat storage stability are obtained, and excellent chargeability and crush resistance are obtained. Even when the toner is used as a non-magnetic one-component developer, a composite inorganic fine particle, so-called hydrotalcite compound, is used as an external additive to obtain the toner charge amount necessary for development. Therefore, the pressing stress in the thin layer forming portion can be minimized, and as a result, a high-quality image such as a high-speed device can be stably formed.

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

[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.

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.

  FIG. 2 is an explanatory sectional view showing an example of the configuration of a full-color image forming apparatus using the toner of the present invention as a non-magnetic one-component developer.

  In the full-color image forming apparatus shown in FIG. 2, a charging brush 111 as charging means for uniformly charging the surface of the photosensitive drum 10 to a predetermined potential around the photosensitive drum 10 to be rotationally driven, and the photosensitive drum. A cleaner 112 that removes toner remaining on the drum 10 is provided.

  Further, there is provided a laser scanning optical system 20 which is an exposure means for scanning and exposing the photosensitive drum 10 charged by the charging brush 111 with a laser beam. The laser scanning optical system 20 includes a laser diode, a polygon mirror, and an fθ optical system. It is a well-known device having a built-in element, and print data for each of yellow, magenta, cyan, and black is transferred from the host computer to the control unit. The laser scanning optical system 20 sequentially outputs the laser beam as a laser beam based on the print data for each color, scans and exposes the surface of the photosensitive drum 10, and thereby the static image for each color on the photosensitive drum 10. Electro latent images are sequentially formed.

  Further, the full-color developing cartridge 30 that is a developing unit that supplies toner of each color to the photosensitive drum 10 on which the electrostatic latent image is formed in this way and performs full-color development, has yellow, magenta, Four developing cartridges 31Y, 31M, 31C, and 31Bk for each color containing cyan and black non-magnetic one-component toners are provided. The developing cartridges 31Y, 31M, 31M, and 31B are rotated about the support shaft 33. 31C and 31Bk are guided to positions facing the photosensitive drum 10.

  Further, in each of the developing cartridges 31Y, 31M, 31C, and 31Bk in the full-color developing cartridge 30, for example, as shown in FIG. 3, the toner is formed on the outer peripheral surface of a developer carrier (developing roller) 25 that rotates and conveys the toner. A regulating member is pressed (contacted), and the toner regulating member regulates the amount of toner conveyed by the developing roller 25 and charges the conveyed toner.

  As described above, each time an electrostatic latent image of each color is formed on the photosensitive drum 10 by the laser scanning optical system 20, the full-color developing cartridge 30 is rotated about the support shaft 33 as described above. The developing cartridges 31Y, 31M, 31C, and 31Bk containing the corresponding color toners are sequentially guided to positions facing the photosensitive drum 10, and the developing rollers 25 in the developing cartridges 31Y, 31M, 31C, and 31Bk are moved. The charged toner of each color is sequentially supplied onto the photosensitive drum 10 in which the electrostatic latent images of each color are sequentially formed as described above in contact with or without contact with the photosensitive drum 10. Development is to be performed.

  Further, an endless intermediate transfer belt 40 that is rotationally driven is provided as an intermediate transfer member at a position downstream of the full-color developing cartridge 30 in the rotation direction of the photosensitive drum 10. The photosensitive drum 10 is rotated in synchronization with the photosensitive drum 10. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 so as to come into contact with the photosensitive drum 10, and a portion of the support roller 42 that supports the intermediate transfer belt 40 includes A secondary transfer roller 43 is rotatably provided, and the transfer material S such as recording paper is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43.

  Further, a cleaner 50 that scrapes off the toner remaining on the intermediate transfer belt 40 is provided in a space between the full-color developing cartridge 30 and the intermediate transfer belt 40 so as to be able to contact and separate from the intermediate transfer belt 40. .

  The sheet feeding means 60 that guides the transfer material S to the intermediate transfer belt 40 also feeds the transfer material S stored in the sheet feed tray 61 one by one. It is composed of a paper roller 62 and a timing roller 63 that feeds the transfer material S fed in synchronization with the image formed on the intermediate transfer belt 40 between the intermediate transfer belt 40 and the secondary transfer roller 43. In this way, the transfer material S sent between the intermediate transfer belt 40 and the secondary transfer roller 43 is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43, and the toner image is transferred from the intermediate transfer belt 40. The transfer material S is pressed and transferred.

  On the other hand, the transfer material S on which the toner image is pressed and transferred as described above is guided to the fixing unit 70 by the conveying unit 66 constituted by an air suction belt or the like, and is transferred by the fixing unit 70. The toner image is fixed on the transfer material S, and then the transfer material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

  Next, the operation of forming a full color image using this full color image forming apparatus will be specifically described.

  First, the photosensitive drum 10 and the intermediate transfer belt 40 are rotationally driven in the respective directions at the same peripheral speed, and the photosensitive drum 10 is charged to a predetermined potential by the charging brush 111.

  The photosensitive drum 10 thus charged is exposed to a yellow image by the laser scanning optical system 20 to form an electrostatic latent image of the yellow image on the photosensitive drum 10. A yellow toner charged by a toner regulating member is supplied from a developing cartridge 31Y containing yellow toner in the photosensitive drum 10 to develop a yellow image, and the yellow toner image is thus formed on the photosensitive drum 10 formed with the yellow toner image. On the other hand, the intermediate transfer belt 40 is pressed by the primary transfer roller 41, and the yellow toner image formed on the photosensitive drum 10 is primarily transferred to the intermediate transfer belt 40.

  After the yellow toner image is transferred to the intermediate transfer belt 40 in this way, the full-color developing cartridge 30 is rotated about the support shaft 33, and the developing cartridge 31M containing magenta toner is moved to the photosensitive drum 10. As in the case of the yellow image, the magenta image is exposed to the photosensitive drum 10 charged by the laser scanning optical system 20 to form an electrostatic latent image. Is developed by a developing cartridge 31M containing magenta toner, and the developed magenta toner image is primarily transferred from the photosensitive drum 10 to the intermediate transfer belt 40, and in the same manner, exposure of a cyan image and a black image is performed. Development and primary transfer are sequentially performed, and yellow, magenta, cyan, and black toner images are formed on the intermediate transfer belt 40. Superimposed in sequence to form a full color toner image.

  When the final black toner image is primarily transferred onto the intermediate transfer belt 40, the transfer material S is fed between the secondary transfer roller 43 and the intermediate transfer belt 40 by the timing roller 63, and the secondary transfer roller. 43, the transfer material S is pressed against the intermediate transfer belt 40, and the full-color toner image formed on the intermediate transfer belt 40 is secondarily transferred onto the transfer material S.

  When the full-color toner image is secondarily transferred onto the transfer material S in this way, the transfer material S is guided to the fixing means 70 by the conveying means 66, and the full-color toner transferred by the fixing means 70 is transferred. The image is fixed on the recording material S, and then the transfer material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

    FIG. 3 is an explanatory cross-sectional view showing an example of the configuration of a developing cartridge for a one-component developer.

  The developing cartridge 31 has at least a developing roller 25 and a regulating blade 28, and is used as a developing device for non-magnetic one-component toner.

  The developing cartridge 31 has a buffer chamber 26 adjacent to the developing roller 25 and a hopper 27 adjacent to the buffer chamber 26.

  In the buffer chamber 26, a regulating blade 28, which is a toner regulating member, is arranged in a state of being pressed (contacted) with the developing roller 25. The regulating blade 28 regulates the charge amount and adhesion amount (conveyance amount) of the toner on the developing roller 25. Further, it is possible to further provide an auxiliary blade 29 for assisting regulation of the toner charge amount and adhesion amount on the developing roller 25 on the downstream side of the regulating blade 28 with respect to the rotation direction of the developing roller 25.

  A supply roller 34 is pressed against the developing roller 25. The supply roller 34 is driven to rotate in the same direction as the developing roller 25 (counterclockwise direction in the figure) by a motor (not shown). The supply roller 34 has a conductive cylindrical base and a foam layer formed of urethane foam or the like on the outer periphery of the base.

  The hopper 27 contains toner T which is a non-magnetic one-component developer. The hopper 27 is provided with a rotating body 35 for stirring the toner T. A film-like conveying blade is attached to the rotator 35, and the toner T is conveyed by the rotation of the rotator 35 in the direction of the arrow. The toner T conveyed by the conveying blades is supplied to the buffer chamber 26 via a passage 32 provided in a partition wall that separates the hopper 27 and the buffer chamber 26. The shape of the conveying blade is bent while conveying the toner T in front of the rotating direction of the blade as the rotating body 35 rotates, and returns to a straight state when reaching the left end of the passage 32. Thus, the blade T supplies the toner T to the passage 32 by making the shape return straight through the curved state.

  The passage 32 is provided with a valve 321 for closing the passage 32. The valve 321 is a film-like member, one end of which is fixed to the upper side of the right side of the passage 32 of the partition wall. When the toner T is supplied from the hopper 27 to the passage 32, the valve 321 is pushed rightward by the pressing force from the toner T. 32 can be opened. As a result, the toner T is supplied into the buffer chamber 26.

  In the developing cartridge 31, the developing roller 25 is rotationally driven in the arrow direction during image formation, and the toner in the buffer chamber 26 is supplied onto the developing roller 25 by the rotation of the supply roller 34. The toner T supplied onto the developing roller 25 is charged and thinned by the regulating blade 28 and the auxiliary blade 29, and then conveyed to a region facing the image carrier, where the electrostatic latent image on the image carrier is transferred. It is used for development. The toner that has not been used for development is neutralized by the neutralization blade 24 as the developing roller 25 rotates. After reducing the electrostatic adhesion force between the developing roller 25 and the toner, the toner is scraped and collected from the developing roller 25 by the supply roller 34.

In the present invention, the contact pressure average of the regulating blade 28 that contacts the developing roller 25 is preferably 10 to 50 N / m, and more preferably 15 to 45 N / m.
By setting the contact pressure within the above range, the non-magnetic one-component toner can be transported in a uniform thickness without damaging the resin layer of the developing roller, and a uniform charge amount is imparted to the non-magnetic one-component toner. be able to.

  The regulating blade 28 used in the present invention is installed in the developing cartridge 31 for the purpose of uniformly thinning the toner on the surface of the developing roller 25 and uniformly charging the toner.

As the regulating blade 28, phosphor bronze having a spring elasticity capable of uniformly thinning and charging the non-magnetic one-component toner and controlling the average contact pressure to the developing roller within a specified range is used.
Phosphor bronze can provide a stable charge to the non-magnetic one-component toner as compared with other metal elastic materials (for example, stainless steel).
This is presumed that since the phosphor bronze charging sequence is more positive than stainless steel, the non-magnetic one-component toner can be charged more stably than stainless steel.
The material of the phosphor bronze plate is preferably a JIS H3731 equivalent.
The thickness of phosphor bronze is not particularly limited, but if a thickness of 0.03 to 0.12 mm is used, the contact pressure average can be easily adjusted to the above range.

  The regulating blade 28 is fixed by a holder, and is used by being attached to the developing cartridge 20 while being fixed to the holder.

  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.

[Toner Production Example 1]
(1) Step of preparing binder resin fine particle dispersion (1-1) First stage polymerization An anionic surfactant “in advance” in a reaction vessel equipped with a stirrer, a temperature sensor, a temperature controller, a condenser, and a nitrogen introducing device. An anionic surfactant solution prepared by dissolving 2.0 parts by mass of sodium lauryl sulfate in 2900 parts by mass of ion-exchanged water was added, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream. It was.
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 mass n-butyl acrylate 27 parts by mass Methacrylic acid 6 parts by mass n-octyl mercaptan 1.7 parts by mass Paraffin wax (melting point: 73 ° C.) 51 parts by mass is added as an anti-offset agent, and 85 The monomer solution [2] was prepared by heating to ° 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 the above-mentioned “resin fine particles [ a1] ”in the amount of solids of the resin fine particles [a1] is added in an amount of 28 parts by mass, and then the monomer is dispersed by a mechanical disperser“ CLEAMIX ”(manufactured by M Technique Co., Ltd.) having a circulation path. The solution [2] is mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersion particle diameter of 350 nm, and 2.5 parts by mass of a polymerization initiator “KPS” is added to 110 parts by mass of ion-exchanged water. A dispersion of “resin fine particles [a11]” is prepared by performing polymerization (second stage polymerization) by adding an initiator aqueous solution dissolved in the solution and heating and stirring the system at 90 ° C. for 2 hours. Shi .

(1-3) Third-stage polymerization: formation of outer layer Start of dissolving 2.5 parts by mass of polymerization initiator “KPS” in 110 parts by mass of ion-exchanged water in the dispersion of “resin fine particles [a11]” Aqueous agent aqueous solution is added and under the temperature condition 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. Then, it cooled to 28 degreeC and produced the "dispersion liquid of binder resin fine particles [A]" in which binder resin fine particles [A] were disperse | distributed in the anionic surfactant solution.
The binder resin fine particles [A] had a glass transition point of 45 ° C. and a softening point of 100 ° C.

(2) Preparation Step of Shell Resin Fine Particle Dispersion (2-1) Synthesis of Shell Resin (Styrene-Acrylic Modified Polyester Resin) Into the 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 continuing the addition polymerization reaction for 1 hour, the temperature was raised to 200 ° C. and maintained at 10 kPa for 1 hour, and then the acrylic acid, styrene, and butyl acrylate were removed to remove the styrene-acryl modified polyester resin [1]. Got.
This styrene-acryl-modified polyester resin [1] had a glass transition point of 60 ° C. and a softening point of 105 ° C.

(2-2) Preparation of Shell Resin Fine Particle Dispersion The obtained styrene-acrylic modified polyester resin [1] 100 parts by mass was pulverized with “Landel mill type: RM” (manufactured by Tokuju Kogakusha Co., Ltd.), and 0 prepared in advance. Mixing with 638 parts by mass of sodium lauryl sulfate solution with a concentration of 26 mass%, and ultrasonically dispersing with stirring using an ultrasonic homogenizer “US-150T” (manufactured by Nippon Seiki Seisakusho) at V-LEVEL, 300 μA for 30 minutes, A “dispersed liquid of shell resin fine particles [S1]” in which shell resin fine particles [S1] having a volume-based median diameter (D ₅₀ ) of 250 nm were dispersed was produced.

(3) Preparation Step of Colorant Fine Particle Dispersion Solution 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” (Cabot Corporation) 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 with a Microtrac particle size distribution measuring device “UPA-150” (manufactured by Nikkiso Co., Ltd.), and was 117 nm.

(4) Aggregation, fusion-maturation-washing-drying-addition 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). When the volume-based median diameter (D ₅₀ ) reached 6.0 μm, “shell resin fine particles [Dispersion of [S1]] was added in 72 parts by mass in terms of solid content over 30 minutes, and when the supernatant of the reaction liquid became transparent, 190 parts by mass of sodium chloride was dissolved in 760 parts by mass of ion-exchanged water. Aqueous solution was added to stop particle growth. 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 by a centrifuge to form a wet cake of toner particles, and this is centrifuged at 35 ° C. until the electric conductivity of the filtrate reaches 5 μS / cm. After washing with ion-exchanged water, it was transferred to a “flash jet dryer” (manufactured by Seishin Enterprise Co., Ltd.) and dried until the water content became 0.5 mass%.
To the dried toner particles [1], 0.8% by mass of silica fine particles [SI-1] shown in Table 2 and 0.03% by mass of composite inorganic fine particles [FM-1] shown in Table 3 were added. By mixing with a Henschel mixer and passing through a sieve having an opening of 50 μm, coarse particles and aggregates were removed to prepare toner [1].

[Toner Preparation Examples 2 to 17]
In the synthesis of the shell resin (styrene-acrylic modified polyester resin) in the preparation process of the shell resin fine particle dispersion in Preparation Example 1 of the toner, the shell resin fine particle dispersions [S2] to [S9] are changed according to the formulation in Table 1. The toners [2] to [17] were obtained in the same manner except that the types of the shell resin fine particle dispersions and the types and addition amounts of the external additives shown in Tables 2 to 4 were changed according to Table 5. Was made.

  Using the toners [1] to [17] described above as a non-magnetic one-component developer, the low-temperature fixing property, heat-resistant storage property, crushing resistance and image quality were evaluated.

(1) Low-temperature fixability A commercially available digital color printer “magiccolor 5440DL” (manufactured by Konica Minolta Business Technologies) was used as an evaluation machine. The surface temperature of the fixing heating roller of the fixing device is remodeled so that it can be changed within a range of 130 to 170 ° C., and the toner adhesion amount 11 on the evaluation paper “NPi fine paper 128 g / m ² ” (made by Nippon Paper Industries). In fixing experiments for fixing a solid image of ³ g / m ^2, the fixing temperature (surface temperature of the fixing heating roller) is set to 170 ° C., 165 ° C., and so on until fixing failure due to cold offset is observed. The test was repeated while changing the temperature to decrease in steps of ° C. Then, the lowest fixing temperature in the fixing experiment in which fixing failure due to cold offset was not observed was evaluated as the lower limit fixing temperature. In addition, it means that it is excellent in low temperature fixability, so that this fixing minimum temperature is low, and if it is 155 degrees C or less, it will be judged that there is no problem practically and is a pass. The results are shown in Table 6.

(2) Heat-resistant storage stability Take 0.5 g of toner in a 10 mL glass bottle with an inner diameter of 21 mm, close the lid, shake it 600 times at room temperature using a tap denser “KYT-2000” (manufactured by Seishin Enterprise), and then remove the lid. In the removed state, it was left for 2 hours in an environment of temperature 55 ° C. and humidity 35% RH. Next, the toner is placed on a 48-mesh (mesh 350 μm) sieve while being careful not to disintegrate the toner aggregates, set in a powder tester (manufactured by Hosokawa Micron), and fixed with a press bar and knob nut. After adjusting the vibration strength to a feed width of 1 mm and applying vibration for 10 seconds, the amount of residual toner remaining on the sieve was measured, and the toner aggregation rate, which is the ratio of the residual toner amount, was calculated by the following formula (1). In addition, if it is 20% or less, it will be judged that there is no problem practically and it is a pass. The results are shown in Table 6.
Formula (1): toner aggregation rate (%) = {residual toner amount (g) /0.5 (g)} × 100

(3) Crush resistance As a machine for evaluation, a commercially available digital color printer “magiccolor 5440DL” (manufactured by Konica Minolta Business Technologies) was used. The above-mentioned toner is put into the developing device installed in this evaluation machine, and after a stirring test is performed for 3.5 hours at a speed of 600 rpm with a single driving device, the developer in the developing device is sampled. The particle size distribution of the toner was measured with “Multisizer 3” (Beckman Coulter, Inc.). In the particle size distribution after the stirring test, the ratio of the toner particles having a number average particle diameter of 2.5 μm or less was evaluated. In addition, if the said ratio is 2% or less, there is no problem practically and it is judged that it is a pass. The results are shown in Table 6.

(4) Image Quality A commercially available digital color printer “magiccolor 5440DL” (manufactured by Konica Minolta Business Technologies, Inc.) was used as an evaluation machine. The above toner was added, 200,000 sheets were printed in an environment of 20 ° C./50% RH, and the following evaluation was performed in an initial state and a state after enduring 200,000 sheets.
(Solid density)
The image density of the solid image area at the initial stage and after durability was measured using a reflection densitometer “RD-918” (manufactured by Macbeth). If the solid density is 1.20 or more, it is good, and if it is 0.80 or more, it is judged as acceptable without practical problems. The results are shown in Table 6.
(Fog density)
The fog density at the initial stage and after the endurance was measured using a reflection densitometer “RD-918” (manufactured by Macbeth). The fog density is a value calculated as follows. The density of printing paper (white paper) that has not been printed is measured at 20 locations, and the average value is defined as the white paper density. Next, the density of the white background portion of the printing paper on which the plain image is printed is similarly measured, and The value obtained by subtracting the white paper density from the average value was defined as the fog density. If the fog density is less than 0.005, it is good, and if it is less than 0.010, it is judged acceptable without any practical problem. The results are shown in Table 6.

  From the above results, in the toners of the present invention according to Examples 1 to 10, good results were obtained in all of the low-temperature fixability, the heat-resistant storage property, the crush-proof property, the solid density and the fog density after the initial and after 200,000 durability. was gotten.

DESCRIPTION OF SYMBOLS 1 Load unit 2 Sample 3 Sample height 4 Main body cell 5 High voltage power supply 6 Resistance measuring device 10 Photosensitive drum 111 Charging brush 112 Cleaner 20 Laser scanning optical system 24 Static elimination blade 25 Developing roller 26 Buffer chamber 27 Hopper 28 Regulation blade 29 Auxiliary Blade 30 Full-color developing cartridge 31, 31Y, 31M, 31C, 31Bk Developing cartridge 32 Passage 321 Valve 33 Support shaft 34 Feed roller 35 Rotating body 40 Intermediate transfer belt 41 Primary transfer roller 42 Support roller 43 Secondary transfer roller 50 Cleaner 60 Supply Paper means 61 Paper feed tray 62 Paper feed roller 63 Timing roller 66 Transport means 70 Fixing means 80 Vertical transport path 100 Apparatus body S Transfer material

Claims (5)

An electrostatic charge image developing toner comprising toner particles in which a shell layer is formed on core particles made of a binder resin containing a styrene-acrylic copolymer resin, and an external additive,
The shell layer contains a styrene-acrylic modified polyester resin in which a styrene-acrylic copolymer segment is bonded to the end of the polyester segment, and the styrene-acrylic copolymer segment in the styrene-acrylic modified polyester resin. The content ratio is 5% by mass or more and 30% by mass or less,
The toner for developing an electrostatic charge image, wherein the external additive contains at least silica fine particles and composite inorganic fine particles made of an inorganic compound containing magnesium and aluminum. The composite inorganic fine particles have a magnesium / aluminum content ratio [Mg (atm%) / Al (atm%)] of 1 to 4, static resistance of 1 × 10 ¹⁰ to 1 × 10 ¹³ Ω · cm, number average primary. 2. The toner for developing an electrostatic charge image according to claim 1, wherein the toner has a particle diameter of 50 to 1000 nm. It said external additive toner according to claim 1 or claim 2, characterized in that the titanium-containing oxide fine particles are further contained.   The composite inorganic fine particles are contained in a proportion of 0.02 to 1.0 mass% with respect to the total mass of the electrostatic charge image developing toner. The toner for developing an electrostatic image according to the description. 5. An image forming method comprising using the electrostatic image developing toner according to claim 1 as a non-magnetic one-component developer.