JP2008241995A - Toner for electrostatic charge image development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a toner for electrostatic charge image development, the toner of a core-shell structure ensuring low temperature fixing property and having enough strength to prevent fracture in a fixed image even when the sheet is folded, and having excellent document offset resistance. <P>SOLUTION: The toner for electrostatic charge image development has a core-shell structure and contains at least a resin and a colorant, wherein the resin contains a polymerizable monomer expressed by general formula (1):H<SB>2</SB>C=CR<SB>1</SB>-COOR<SB>2</SB>, by 0.5 to 20 mass% as a copolymerization ratio, and the glass transition temperature of the toner for electrostatic charge image development is 20 to 45°C. In formula (1), R<SB>1</SB>represents H or CH<SB>3</SB>; and R<SB>2</SB>represents a long-chain alkyl group or a cyclic alkyl group having 14 to 22 carbon atoms. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrostatic image developing toner, and more particularly to an electrostatic image developing toner having a core-shell structure.

  In recent years, in the field of image forming technology using electrophotography such as copying machines and printers, as digital technology has been introduced and image quality has been improved, 1200 dpi (dpi is the number of dots per 2.54 cm) level is very small. A technique for accurately reproducing a simple dot image has become necessary.

  As a powerful means for accurately reproducing such a minute dot image, a reduction in toner particle diameter has been studied, and so-called polymerized toner capable of controlling physical properties in a manufacturing process has been attracting attention.

  Also, from the viewpoint of consideration for the global environment in recent years, a technique for reducing the power consumption of the image forming apparatus has been studied, and polymerized toner has attracted attention as a means for solving this problem.

  As an example, a technique has been developed that can form a fixed image at a lower temperature than conventional ones using a polymerized toner containing a wax having a low melting point (see, for example, Patent Document 1).

  On the other hand, toner that can be fixed at a low temperature tends to have a difficulty in thermal stability, and may cause a phenomenon such as blocking that the toners adhere to each other during storage or transportation.

  Further, in order to perform stable image formation, it is necessary to design the toner so that components such as a colorant and wax are not exposed on the toner surface.

  In view of such needs, a toner having a so-called core-shell structure in which the surface of core particles containing a colorant and wax in a resin having a low softening point is coated with a shell resin has been proposed (see, for example, Patent Document 2).

Furthermore, various techniques have been developed as techniques for producing a core-shell toner. For example, resin particles are fused on the surface of core particles produced by associatively fusing resin particles and a colorant to form a shell. A technique for forming a core-shell structure with a controlled film thickness is disclosed (for example, see Patent Document 3).
JP 2000-275908 A JP 2002-116574 A JP 2004-191618 A

  However, a fixed image fixed at a low temperature using the toner for developing an electrostatic charge image has a problem that when the paper is folded, the fixed image is broken or a document offset occurs.

  The present invention has been made in view of the above problems, and has an electrostatic charge image with a core-shell structure that ensures low-temperature fixability, has a strength that does not break a fixed image even when paper is folded, and has excellent document offset properties. The object is to provide a developing toner.

The above object of the present invention is achieved by adopting the following configuration.
1. In the electrostatic image developing toner having a core-shell structure containing at least a resin and a colorant,
The resin contains a polymerizable monomer represented by the following general formula (1) in a copolymerization ratio of 0.5 to 20% by mass, and an electrostatic charge image developing toner has a glass transition temperature of 20 to 45. A toner for developing an electrostatic charge image, wherein the toner has a temperature of ° C.

Formula _{(1) H 2 C = CR} 1 -COOR 2
(In the formula, R ₁ represents H or CH ₃ , and R ₂ represents a long-chain alkyl group having 14 to 22 carbon atoms or a cyclic alkyl group.)
2. 2. The electrostatic image developing device according to 1 above, wherein a resin obtained by polymerizing the polymerizable monomer represented by the general formula (1) is contained in core particles having a core-shell structure. toner.

  3. The resin constituting the electrostatic image developing toner has a weight average molecular weight (Mw) of 10,000 to 100,000, a number average molecular weight (Mn) of 5,000 to 50,000, and Mw / Mn of 2 to 4. 3. The toner for developing an electrostatic charge image according to 1 or 2 above, wherein:

  The toner for developing an electrostatic charge image of the present invention has a low-temperature fixability and has a strength that prevents a fixed image from being broken even when the paper is folded, and has an excellent document offset property.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have developed the following general formula (1) in a toner for developing an electrostatic image having a core-shell structure containing at least a resin and a colorant (hereinafter also simply referred to as a toner). ) (Hereinafter also simply referred to as a polymerizable monomer of the general formula (1)) is contained in the resin constituting the toner in an amount of 0.5 to 20% by mass as a copolymerization ratio. In addition, the toner having a core-shell structure with a glass transition temperature of 20 to 45 ° C. ensures low-temperature fixability and has a strength that does not break the fixed image even when paper is folded, and has excellent document offset property. I found out.

Formula _{(1) H 2 C = CR} 1 -COOR 2
(In the formula, R ₁ represents H or CH ₃ , and R ₂ represents a long-chain alkyl group having 14 to 22 carbon atoms or a cyclic alkyl group.)
In order to obtain a toner having low temperature fixability, it is necessary to improve the heat melting property of the resin constituting the toner (lower the softening point of the resin).

  A toner produced using a resin having a lowered softening point improves the adhesion to paper even if it is fixed at a low temperature. However, the strength of the obtained fixed image is not sufficient only by lowering the softening point of the resin, and there is a problem that the toner at the crease part is peeled off when the paper is folded. Or, when the paper is stacked in a high temperature environment, the toner is transferred to the paper in contact with the toner image and the toner image is peeled off.

  This is presumably because the softening point of the resin forming the toner is lowered and the glass transition temperature is lowered at the same time, so that the fixed image is weak against heat or external impact.

  In the present invention, by using an acrylate ester into which a polymerizable monomer having a long-chain alkyl group or a cyclic alkyl group having a carbon number of 14 to 22 represented by the general formula (1) is used, the low-temperature fixability is used. And the strength of the fixed image could be secured.

  Although the mechanism that could secure the strength of the fixed image is not clear, the presence of a long-chain alkyl group or a cyclic alkyl group in the molecular structure derived from the acrylic resin ester according to the present invention in the resin constituting the toner, It is speculated that that part may absorb and mitigate external impacts.

  The polymerizable monomer represented by the general formula (1) can improve the resin strength while maintaining the low-temperature fixability unlike the effect of the so-called resin crosslinking agent. It should be noted that deterioration of the low-temperature fixability is inevitable with the crosslinking agent.

  Hereinafter, the present invention will be described in detail.

[Polymerizable monomer of general formula (1)]
The present invention is characterized by containing a polymerizable monomer of the general formula (1) as a copolymer component of a resin.

  As the polymerizable monomer of the general formula (1), for example, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, behenyl (meth) acrylate, cyclohexyl (meth) ) Acrylate and isobornyl (meth) acrylate.

  The polymerizable monomer represented by the general formula (1) needs to be contained in the resin constituting the toner in an amount of 0.5 to 20% by mass, preferably 1 to 10% by mass.

  The resin obtained by polymerizing the polymerizable monomer of the general formula (1) contains the above-mentioned range, so that it is effective to improve heat resistance and strength against external pressure from the outside while ensuring low temperature fixability. Can demonstrate.

[Polymerizable monomer other than polymerizable monomer of general formula (1)]
Examples of the polymerizable monomer other than the polymerizable monomer represented by the general formula (1) as the copolymer component of the resin according to the present invention include styrene, o-methylstyrene, m-methylstyrene, and p-methyl. Styrene, α-methylstyrene, p-chlorostyrene, 3,4-dichlorostyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butylstyrene, pn-hexylstyrene, Styrene or styrene derivatives such as pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methacrylic acid Isopropyl, isobutyl methacrylate, t-butyl methacrylate, n-octyl methacrylate, methacryl 2-ethylhexyl, lauryl methacrylate, diethylaminoethyl methacrylate, acrylic acid ester derivatives such as methacrylic acid ester derivatives such as dimethylaminoethyl methacrylate, olefins such as ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, vinyl bromide , Vinyl halides such as vinyl fluoride and vinylidene fluoride, vinyl esters such as vinyl propionate, vinyl acetate and vinyl benzoate, vinyl ethers such as vinyl methyl ether and vinyl ethyl ether, vinyl methyl ketone and vinyl ethyl ketone , Vinyl ketones such as vinyl hexyl ketone, N-vinyl compounds such as N-vinyl carbazole, N-vinyl indole and N-vinyl pyrrolidone, vinyl compounds such as vinyl naphthalene and vinyl pyridine And acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These vinyl monomers can be used alone or in combination.

  Further, it is more preferable to use a combination of monomers having an ionic dissociation group as the polymerizable monomer constituting the resin. For example, it has a substituent such as a carboxyl group, a sulfonic acid group, a phosphoric acid group as a constituent group of the monomer, specifically, acrylic acid, methacrylic acid, maleic acid, itaconic acid, cinnamic acid, fumar Acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate, 3-chloro-2-acid phosphooxy And propyl methacrylate.

[Materials other than the above polymerizable monomers]
In addition to the polymerizable monomer, the toner of the present invention has colored particles produced using a colorant, a wax (release agent), a polymerization initiator, a chain transfer agent, a surfactant (dispersion stabilizer), and the like. Those prepared by mixing external additives are preferred.

(Coloring agent)
As the colorant used in the toner of the present invention, carbon black, a magnetic material, a dye, a pigment, and the like can be arbitrarily used. Examples of the carbon black include channel black, furnace black, acetylene black, thermal black, and lamp black. used. Magnetic materials include ferromagnetic metals such as iron, nickel and cobalt, alloys containing these metals, compounds of ferromagnetic metals such as ferrite and magnetite, alloys that do not contain ferromagnetic metals but exhibit ferromagnetism by heat treatment, For example, a kind of alloy called Heusler alloy such as manganese-copper-aluminum, manganese-copper-tin, chromium dioxide, or the like can be used.

  As the dye, C.I. I. Solvent Red 1, 49, 52, 58, 63, 111, 122, C.I. I. Solvent Yellow 19, 44, 77, 79, 81, 82, 93, 98, 103, 104, 112, 162, C.I. I. Solvent Blue 25, 36, 60, 70, 93, 95, etc. can be used, and mixtures thereof can also be used. Examples of the pigment include C.I. I. Pigment Red 5, 48: 1, 53: 1, 57: 1, 122, 139, 144, 149, 166, 177, 178, 222, C.I. I. Pigment Orange 31 and 43, C.I. I. Pigment Yellow 14, 17, 74, 93, 94, 138, 156, 158, 180, 185, C.I. I. Pigment green 7, C.I. I. Pigment Blue 15: 3, 60, etc. can be used, and a mixture thereof can also be used. The number average primary particle diameter varies depending on the type, but is preferably about 10 to 200 nm.

  As a method for adding a colorant, the polymer particles are colored by adding resin particles at the stage of agglomeration by addition of an aggregating agent. The colorant can be used by treating the surface with a coupling agent or the like.

(Wax (release agent))
Examples of the wax that can be used in the toner of the present invention include conventionally known waxes. Specifically, polyolefin waxes such as polyethylene wax and polypropylene wax, long chain hydrocarbon waxes such as paraffin wax and sazol wax, dialkyl ketone waxes such as distearyl ketone, carnauba wax, montan wax, trimethylolpropane. Tribehenate, pentaerythritol tetramyristate, pentaerythritol tetrastearate, pentaerythritol tetrabehenate, pentaerythritol diacetate dibehenate, glycerin tribehenate, 1,18-octadecanediol distearate, trimellit Ester waxes such as acid tristearyl and distearyl maleate, amides such as ethylenediamine dibehenyl amide and trimellitic acid tristearyl amide Box, and the like.

  The melting point of the wax is usually 40 to 160 ° C, preferably 50 to 120 ° C, more preferably 60 to 90 ° C. By setting the melting point within the above range, the heat-resistant storage stability of the toner is ensured, and stable toner image formation can be performed without causing cold offset or the like even when fixing at a low temperature. Further, the wax content in the toner is preferably 1 to 30% by mass, more preferably 5 to 20% by mass.

  Next, a polymerization initiator, a chain transfer agent, and a surfactant used for producing the toner will be described.

(Polymerization initiator)
The resin constituting the toner of the present invention is produced by polymerizing the aforementioned polymerizable monomer, and the following polymerization initiators can be used in the present invention.

  Specifically, oil-soluble polymerization initiators include 2,2′-azobis- (2,4-dimethylvaleronitrile), 2,2′-azobisisobutyronitrile, 1,1′-azobis ( Cyclohexane-1-carbonitrile), 2,2'-azobis-4-methoxy-2,4-dimethylvaleronitrile, azo- or diazo-based polymerization initiators such as azobisisobutyronitrile, benzoyl peroxide, methyl ethyl ketone peroxide Oxide, diisopropylperoxycarbonate, cumene hydroperoxide, t-butyl hydroperoxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, lauroyl peroxide, 2,2-bis- (4,4-t-butylperoxycyclohexyl) propane Tris - like polymer initiators having a (t-butylperoxy) peroxide polymerization initiator or a peroxide such as triazine in a side chain.

  In the case of forming resin particles by the emulsion polymerization method, a water-soluble polymerization initiator can be used. Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, azobisaminodipropane acetate, azobiscyanovaleric acid and its salts, hydrogen peroxide and the like.

(Chain transfer agent)
A chain transfer agent can be used for the purpose of adjusting the molecular weight of the resin.

  The chain transfer agent is not particularly limited, and examples thereof include mercaptans such as octyl mercaptan, dodecyl mercaptan, tert-dodecyl mercaptan, n-octyl-3-mercaptopropionate, terpinolene, carbon tetrabromide and α-methyl. Styrene dimer or the like is used.

(Surfactant)
In addition, a dispersion stabilizer can be used in order to appropriately disperse the polymerizable monomer and the like in the reaction system. Dispersion stabilizers include tricalcium phosphate, magnesium phosphate, zinc phosphate, aluminum phosphate, calcium carbonate, magnesium carbonate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, calcium metasilicate, calcium sulfate, barium sulfate , Bentonite, silica, alumina and the like. Furthermore, those generally used as surfactants such as polyvinyl alcohol, gelatin, methylcellulose, sodium dodecylbenzenesulfonate, ethylene oxide adduct, and higher alcohol sodium sulfate can be used as the dispersion stabilizer.

  The surfactant used in the present invention will be described.

  In order to perform polymerization using the above-described polymerizable monomer, it is necessary to disperse oil droplets in an aqueous medium using a surfactant. Although it does not specifically limit as surfactant which can be used in this case, The following ionic surfactant can be mentioned as an example of a suitable thing.

  Examples of ionic surfactants include sulfonates (sodium dodecylbenzenesulfonate, sodium arylalkylpolyethersulfonate, 3,3-disulfonediphenylurea-4,4-diazo-bis-amino-8-naphthol-6 Sodium sulfonate, ortho-carboxybenzene-azo-dimethylaniline, 2,2,5,5-tetramethyl-triphenylmethane-4,4-diazo-bis-β-naphthol-6-sodium sulfonate, etc.), sulfuric acid Ester salts (sodium dodecyl sulfate, sodium tetradecyl sulfate, sodium pentadecyl sulfate, sodium octyl sulfate, etc.), fatty acid salts (sodium oleate, sodium laurate, sodium caprate, sodium caprylate, sodium caproate, potassium stearate) Beam, calcium oleate and the like).

  Nonionic surfactants can also be used. Specifically, polyethylene oxide, polypropylene oxide, combination of polypropylene oxide and polyethylene oxide, ester of polyethylene glycol and higher fatty acid, alkylphenol polyethylene oxide, ester of higher fatty acid and polyethylene glycol, ester of higher fatty acid and polypropylene oxide, sorbitan ester Etc. can be mentioned.

(External additive)
The toner of the present invention may be used by mixing so-called external additives with colored particles for the purpose of improving fluidity, chargeability and cleaning properties. These external additives are not particularly limited, and various inorganic fine particles, organic fine particles and lubricants can be used.

  A conventionally well-known thing can be used as an inorganic fine particle. Specifically, silica, titania, alumina, strontium titanate fine particles and the like can be preferably used. These inorganic fine particles may be hydrophobized if necessary. Specific examples of the silica fine particles include commercially available products R-805, R-976, R-974, R-972, R-812, R-809 manufactured by Nippon Aerosil Co., Ltd., HVK-2150, H- manufactured by Hoechst. 200, commercial products TS-720, TS-530, TS-610, H-5, MS-5 and the like manufactured by Cabot Corporation.

  As titania fine particles, for example, commercially available products T-805 and T-604 manufactured by Nippon Aerosil Co., Ltd., commercially available products MT-100S, MT-100B, MT-500BS, MT-600, MT-600SS, JA- 1. Commercial products TA-300SI, TA-500, TAF-130, TAF-510, TAF-510T manufactured by Fuji Titanium Co., Ltd. Commercial products IT-S, IT-OA, IT-OB, IT- manufactured by Idemitsu Kosan Co., Ltd. OC etc. are mentioned.

  Examples of the alumina fine particles include commercial products RFY-C and C-604 manufactured by Nippon Aerosil Co., Ltd. and commercial products TTO-55 manufactured by Ishihara Sangyo Co., Ltd.

  As the organic fine particles, spherical organic fine particles having a number average primary particle diameter of about 10 to 2000 nm can be used. Specifically, homopolymers such as styrene and methyl methacrylate and copolymers thereof can be used.

  The addition amount of these external additives is preferably 0.1 to 10.0% by mass with respect to the whole toner.

[Toner Production Method]
Next, a method for producing the toner of the present invention will be described.

  The toner production method is not particularly limited as long as a toner satisfying the claims can be obtained. For example, the suspension polymerization method, the emulsion association method, the dispersion polymerization method, the dissolution suspension method, the kneading and pulverization method, etc. An example is a method in which after the colored particles are produced, an external additive is mixed into the colored particles. Among these, the emulsion polymerization method is preferred from the viewpoint of the selectivity of the composition of the shell of the toner having a core-shell structure and the controllability of the film thickness.

The toner of the present invention is produced, for example, through the following steps.
(1) Dissolution / dispersion step for dissolving or dispersing the release agent in the polymerizable monomer (2) Polymerization step for preparing a dispersion of resin fine particles (3) Resin fine particles and colorant particles in an aqueous medium Aggregation and fusion step for agglomeration and fusion to obtain core particles (association particles) (4) First aging step for aging core particles with thermal energy to adjust the shape (5) In the core particle dispersion, Shell forming step of adding resin particles for shell and aggregating and fusing the resin particles for shell on the surface of the core particles to form core-shell structure colored particles (6) Aging the core-shell structure colored particles with thermal energy Second ripening step for adjusting the shape of the core-shell structured colored particles (7) Solid-liquid separation of the colored particles from the cooled colored particle dispersion, and a washing step for removing the surfactant from the colored particles ( 8) Washed clothes Drying process of drying the particles also after the drying step if necessary,
(9) There may be a step of adding an external additive to the dried colored particles.

  When the toner of the present invention is produced, first, core particles serving as a core are produced by associatively fusing resin fine particles and colorant particles. Next, the resin particles for the shell are added to the dispersion of the core particles, and the core resin surface is coated with the shell resin particles by agglomerating and fusing the resin particles for the shell to the core particle surface. Colored particles having

  As described above, the toner of the present invention is prepared, for example, by adding resin particles for a shell to the core particle dispersion prepared by the above-described manufacturing method and fusing the core resin particles to the core particles. Is.

  The core particles constituting the toner of the present invention may be prepared by, for example, dissolving or dispersing a release agent component in a polymerizable monomer that forms a resin, and then mechanically dispersing fine particles in an aqueous medium. A method of salting out and fusing the composite resin fine particles and the colorant particles formed through the step of polymerizing the polymerizable monomer by the following method is preferably used. When the release agent component is dissolved in the polymerizable monomer, the release agent component may be dissolved or melted or dissolved.

  Hereinafter, each manufacturing process of the toner of the present invention will be described.

(1) Dissolution / dispersion step This step is a step of preparing a polymerizable monomer solution in which a release agent compound is dissolved in a polymerizable monomer and a release agent compound is mixed.

(2) Polymerization step In a preferred example of this polymerization step, a polymerizable monomer solution in which a wax is dissolved or dispersed in an aqueous medium containing a surfactant having a critical micelle concentration (CMC) or less is added. Then, mechanical energy is applied to form droplets, and then a water-soluble polymerization initiator is added to allow the polymerization reaction to proceed in the droplets. An oil-soluble polymerization initiator may be contained in the droplet. In such a 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.

  By this polymerization step, resin fine particles containing a wax and a binder resin are obtained. Such resin fine particles may be colored fine particles or non-colored fine particles. The colored resin fine particles can be obtained by polymerizing a monomer composition containing a colorant. In the case of using uncolored resin fine particles, a dispersion of colorant particles is added to the dispersion of resin fine particles in the agglomeration / fusion process described later to melt the resin fine particles and the colorant particles. Color particles can be obtained by attaching.

(3) Aggregation / fusion process As a method of aggregation and fusion in the fusion process, a salting out / fusion method using resin fine particles (colored or non-colored resin fine particles) obtained in the polymerization process is preferable. In the agglomeration / fusion step, fine particles of internal additives such as release agent fine particles and charge control agents can be agglomerated and fused together with resin fine particles and colorant particles.

  In this case, “salting out / fusion” means that aggregation and fusion are performed in parallel, and when the particles have grown to a desired particle size, an aggregation terminator is added to stop the particle growth. The heating for controlling the particle shape according to the above is performed continuously.

  The “aqueous medium” in the agglomeration / fusion step is one in which the main component (50% by mass or more) is made of water. Examples of components other than water include organic solvents that dissolve in water, such as methanol, ethanol, isopropanol, butanol, acetone, methyl ethyl ketone, and tetrahydrofuran.

  The colorant particles can be prepared by dispersing the colorant in an aqueous medium. The dispersion treatment of the colorant is performed in a state where the surfactant concentration is set to a critical micelle concentration (CMC) or more in water. The disperser used for the dispersion treatment of the colorant is not particularly limited, but preferably an ultrasonic disperser, a mechanical homogenizer, a pressure disperser such as a manton gorin or a pressure homogenizer, a sand grinder, a Getzmann mill, a diamond fine mill, or the like. Examples thereof include a medium type disperser. Examples of the surfactant used include the same surfactants as those described above. The colorant (fine particles) may be surface-modified. In the surface modification method of the colorant, the colorant is dispersed in a solvent, the surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is separated by filtration, washed and filtered with the same solvent, and dried to obtain a colorant (pigment) treated with the surface modifier.

  The salting-out / fusion method, which is a preferred agglomeration and fusion method, is a salting-out method comprising an alkali metal salt, an alkaline earth metal salt, a trivalent salt, or the like in water in which resin fine particles and colorant particles are present. An agent is added as an aggregating agent having a critical agglomeration concentration or higher, and then salting-out proceeds by heating to a temperature not lower than the glass transition temperature of the resin fine particles and not lower than the melting peak temperature (° C.) of the mixture. At the same time, it is a process of fusing. Here, the alkali metal salt and the alkaline earth metal salt which are salting-out agents include lithium, potassium, sodium and the like as the alkali metal, and examples of the alkaline earth metal include magnesium, calcium, strontium and barium. Preferably, potassium, sodium, magnesium, calcium, and barium are used.

  When agglomeration and fusion are performed by salting out / fusion, it is preferable to make the time allowed to stand after adding the salting-out agent as short as possible. The reason for this is not clear, but there are problems that the aggregation state of the particles fluctuates depending on the standing time after salting out, the particle size distribution becomes unstable, and the surface property of the fused toner fluctuates. appear. The temperature for adding the salting-out agent needs to be at least the glass transition temperature of the resin fine particles. The reason for this is that if the temperature at which the salting-out agent is added is equal to or higher than the glass transition temperature of the resin fine particles, the salting out / fusion of the resin fine particles proceeds rapidly, but the particle size cannot be controlled. There arises a problem that particles having a particle size are generated. Although the range of this addition temperature should just be below the glass transition temperature of resin, generally it is 5-55 degreeC, Preferably it is 10-45 degreeC.

  Further, the salting-out agent is added at a temperature not higher than the glass transition temperature of the resin fine particles, and then the temperature is raised as quickly as possible to a temperature not lower than the glass transition temperature of the resin fine particles and not lower than the melting peak temperature (° C.) of the mixture. Heat to. The time until this temperature rise is preferably less than 1 hour. Further, although it is necessary to quickly raise the temperature, the rate of temperature rise is preferably 0.25 ° C./min or more. The upper limit is not particularly clear, but if the temperature is increased instantaneously, salting out proceeds rapidly, so there is a problem that particle size control is difficult, and 5 ° C./min or less is preferable. By this fusion step, a dispersion of core particles (association particles) obtained by salting out / fusion of resin fine particles and arbitrary fine particles is obtained.

(4) First aging step And, in the present invention, by controlling the heating temperature of the coagulation / fusion step and particularly the heating temperature and time of the first aging step, the particle size is constant and the distribution is narrow. The core particle surface is controlled so as to have a smooth but uniform shape. Specifically, the heating temperature is lowered in the aggregation / fusion process to suppress the progress of fusion between the resin particles to promote homogenization, the heating temperature is lowered in the first aging process, and the time The surface of the core particles is controlled to have a uniform shape by increasing the length.

(5) Shelling step In the shelling step, the resin particle dispersion for the shell is added to the core particle dispersion to agglomerate and fuse the resin particles for the shell onto the surface of the core particles. The resin particles are coated to form colored particles.

  Specifically, the core particle dispersion is added with a dispersion of the resin particles for shells while maintaining the temperature in the above-described aggregation / fusion step and the first aging step, and it takes several hours while continuing the heating and stirring. Then, the resin particles for shell are slowly coated on the surface of the core particles to form colored particles. The heating and stirring time is preferably 1 hour to 7 hours, and more preferably 3 hours to 5 hours.

(6) Second ripening step Resin for shell which is added to a core particle after adding a terminator such as sodium chloride to stop the particle growth at the stage when colored particles become a predetermined particle size by shelling. Heating and stirring are continued for several hours in order to fuse the particles. In the shelling step, a shell having a thickness of 100 to 300 nm is formed on the surface of the core particle. In this way, the shell resin particles are fixed to the surface of the core particles to form a shell, and rounded colored particles having a uniform shape are formed.

  In the present invention, it is possible to control the shape of the colored particles in the true sphere direction by setting the time of the second aging step longer or by setting the aging temperature higher.

(7) Cooling Step / Solid-Liquid Separation / Washing Step This step is a step of cooling (rapid cooling) the dispersion of the colored particles. As a cooling treatment condition, cooling is performed at a cooling rate of 1 to 20 ° C./min. The cooling treatment method is not particularly limited, and examples thereof include a method of cooling by introducing a refrigerant from the outside of the reaction vessel, and a method of cooling by directly introducing cold water into the reaction system.

  In this solid-liquid separation / washing step, a solid-liquid separation process for solid-liquid separation of the colored particles from the dispersion of colored particles cooled to a predetermined temperature in the above-described step, and a solid-liquid separated toner cake (in a wet state) A cleaning treatment for removing deposits such as a surfactant and a salting-out agent from an aggregate obtained by agglomerating certain colored particles into a cake is performed. Here, the filtration method is not particularly limited, such as a centrifugal separation method, a vacuum filtration method using Nutsche or the like, a filtration method using a filter press or the like.

(8) Drying step This step is a step of drying the washed cake to obtain dried colored particles. Examples of dryers used in this process include spray dryers, vacuum freeze dryers, vacuum dryers, etc., stationary shelf dryers, mobile shelf dryers, fluidized bed dryers, rotary dryers It is preferable to use a stirring dryer or the like. The water content of the dried colored particles is preferably 5% by mass or less, and more preferably 2% by mass or less. In addition, when the dried colored particles are aggregated by weak interparticle attractive force, the aggregate may be crushed. Here, as the crushing treatment device, a mechanical crushing device such as a jet mill, a Henschel mixer, a coffee mill, a food processor, or the like can be used.

(9) External Addition Processing Step This step is a step of preparing a toner by mixing the dried colored particles with an external additive as necessary.

  As an external additive mixing device, a mechanical mixing device such as a Henschel mixer or a coffee mill can be used.

In the above process, as a method for introducing the polymerizable monomer of the general formula (1), for example, it can be introduced in the following process.
1. In the polymerization step (2), copolymer resin particles containing a polymerizable monomer of the general formula (1) in the composition are previously added to an aqueous medium, and mini-emulsion polymerization is started. The method of taking in the resin particle | grains of the copolymer which contains the polymerizable monomer of General formula (1) in a composition in a miniemulsion polymer particle by this.
2. (3) In the aggregation / fusion process for obtaining the core particles, in the middle of the aggregation process before the completion of the aggregation of the core particles in the aqueous medium, the copolymer containing the polymerizable monomer of the general formula (1) is included in the composition. A method in which polymer resin particles are added and introduced into core particles.

[Glass transition temperature (Tg) of toner]
The toner of the present invention has a glass transition temperature (Tg) of 20 to 45 ° C. When Tg is less than 20 ° C, heat-resistant storage stability is not preferable, and when it exceeds 45 ° C, low-temperature fixability becomes difficult.

  In order to make Tg into the range of 20-45 degreeC, the kind and quantity of the polymerizable monomer which form copolymer resin are adjusted. Propyl acrylate, propyl methacrylate, butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, and the like are polymerizable monomers that lower Tg, and styrene, methyl methacrylate, methacrylic acid, and the like are polymerizable monomers that increase Tg.

  Tg can be measured by a differential scanning calorimetry method, for example, using a DSC-7 differential scanning calorimeter (Perkin Elmer) or a TAC7 / DX thermal analyzer controller (Perkin Elmer).

  As a measurement procedure, 4.5 to 5.0 mg of toner is precisely weighed to 0.01 mg, sealed in an aluminum pan (KITNO.0219-0041), and set in a DSC-7 sample holder. The reference used an empty aluminum pan. As measurement conditions, the measurement temperature is 0 to 200 ° C., the temperature increase rate is 10 ° C./min, the temperature decrease rate is 10 ° C./min, and the heat-cool-heat control is performed. went.

  Tg draws an extension line of the baseline before the rise of the first endothermic peak and a tangent line indicating the maximum inclination between the rising portion of the first endothermic peak and the peak apex, and the intersection is defined as Tg.

[Molecular weight of resin]
The resin constituting the toner of the present invention has a weight average molecular weight (Mw) of 10,000 to 100,000, a number average molecular weight (Mn) of 5,000 to 50,000, and Mw / Mn of 2 to 4. preferable.

  By adjusting the kind and amount of the polymerizable monomer, and adjusting the molecular weight of the resin obtained by polymerizing the polymerizable monomer within these ranges, a toner having Tg as defined in the present invention is obtained. be able to. In addition, when a material having a wide molecular weight distribution is used, it becomes difficult to melt partially, which may cause poor fixing.

  The molecular weight of the resin can be measured by GPC by the following method.

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

  The measurement conditions for GPC are shown below.

Apparatus: HLC-8220 (manufactured by Tosoh Corporation)
Column: TSKguardcolum + TSKgelSuperHZM-M 3 series (manufactured by Tosoh Corporation)
Column temperature: 40 ° C
Solvent: Tetrahydrofuran Flow rate: 0.2 ml / min Detector: Refractive index detector (RI detector)
In the measurement of the molecular weight of a sample, the molecular weight distribution of the sample is calculated using a calibration curve measured using monodisperse polystyrene standard particles. Ten polystyrenes for calibration curve measurement were used.

(Toner particle size)
The toner of the present invention preferably has a particle diameter of 3 to 8 μm in terms of volume-based median diameter (D ₅₀ ). When toner having this particle size range is used, a high-quality image corresponding to high image quality can be reproduced.

The median diameter (D ₅₀ ) on the volume basis of the toner is obtained by measuring with the following measuring method.

  Specifically, measurement and calculation are performed using a device in which a computer system (manufactured by Coulter) equipped with data processing software “Software V3.51” is connected to Coulter Multisizer 3 (manufactured by Coulter).

  As a measurement procedure, 0.02 g of toner is blended with 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 the toner). After that, ultrasonic dispersion is performed for 1 minute to prepare a toner dispersion. This toner dispersion is injected into a beaker containing ISOTON II (manufactured by Coulter) in a sample stand with a pipette until the display density of the measuring instrument becomes 5% to 10%. By setting this concentration range, a reproducible measurement value can be obtained. In the measuring machine, the measurement particle count is 25000, the aperture diameter is 50 μm, and the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256 parts. The particle diameter of 50% from the larger volume integrated fraction is defined as the volume-based median diameter.

(Toner circularity)
The toner shape factor (SF-1) according to the present invention is preferably 110 to 150. This is because, within the above range, it is easy to achieve both toner transportability and cleanability.

(Developer)
The toner of the present invention can be used as a one-component developer, a non-magnetic one-component developer, or a two-component developer.

  When used as a one-component developer, examples include a non-magnetic one-component developer or a magnetic one-component developer containing about 0.1 to 0.5 μm magnetic particles in a toner. be able to. Further, it can be mixed with a carrier and used as a two-component developer. In this case, conventionally known materials typified by iron-containing magnetic particles such as iron, ferrite, and magnetite can be used as the magnetic particles of the carrier, but ferrite particles or magnetite particles are particularly preferable. The volume average particle diameter of the carrier is preferably 15 to 100 μm, more preferably 20 to 80 μm.

The median diameter (D ₅₀ ) of the volume-based distribution of the carrier can be measured using a laser diffraction particle size distribution measuring device “HELOS” (manufactured by Sympathec).

  The carrier is preferably a coating carrier in which magnetic particles are further coated with a resin, or a so-called resin dispersion type carrier in which magnetic particles are dispersed in a resin. The resin composition for coating is not particularly limited, and for example, olefin resin, styrene resin, styrene-acrylic resin, silicone resin, ester resin, fluorine-containing polymer resin, or the like is used. Moreover, it does not specifically limit as resin for comprising a resin dispersion type carrier, A well-known thing can be used, For example, a styrene-acrylic-type resin, a polyester resin, a fluorine resin, a phenol resin etc. are used. be able to.

  Further, the mixing ratio of the carrier and the toner is preferably in the range of carrier: toner = 1: 1 to 50: 1 by mass ratio.

[Image Forming Method and Image Forming Apparatus Using Toner of Present Invention]
Next, an image forming method in which the toner of the present invention can be used will be described. The toner of the present invention is preferably used in, for example, a high-speed full-color image forming apparatus having a printing speed of 300 mm / sec or higher (65 sheets / min output performance in terms of A4 paper) level or higher. Specifically, a printer or the like that can create a large amount of documents on demand in a short time can be mentioned. Further, the present invention can be applied to an image forming method in which the temperature of the fixing roller is 150 ° C. or lower, preferably 130 ° C. or lower.

  FIG. 1 is an example of an image forming apparatus capable of using the toner of the present invention, and shows a cross-sectional view thereof.

  Each color image formed by the image forming units 9Y, 9M, 9C, and 9K is sequentially primary-transferred onto the rotating intermediate transfer body 6 by the transfer means 7Y, 7M, 7C, and 7K, and the combined color image. Is formed.

  The paper P stored in the paper feed cassette 20 as the paper feed means is fed one by one by the paper feed roller 21, is conveyed to the transfer means 7 A through the registration roller 22, and the color image is transferred onto the paper P. Is secondarily transferred.

  The paper P on which the color image has been transferred is fixed by the fixing device 17, passes through the transport rollers 23 and 24, which are transport means, and is sandwiched by the paper discharge rollers 25 and placed on the paper discharge tray 26 outside the apparatus. Is done.

  FIG. 2 is a cross-sectional view showing an example of the fixing device 17 that can be used in the image forming apparatus of FIG.

  The fixing device 17 in FIG. 2 includes a heating roller 17a and a pressure roller 17b in contact with the heating roller 17a. In FIG. 2, T is a toner image formed on a transfer paper (image forming support) P.

  In the heating roller 17a, a coating layer 171 made of a fluororesin or an elastic body is formed on the surface of the cored bar 172, and includes a heating member 173 made of a linear heater.

  The cored bar 172 is made of metal and has an inner diameter of 10 to 70 mm. Although it does not specifically limit as a metal which comprises the metal core 172, For example, metals, such as iron, aluminum, copper, or these alloys can be mentioned.

  The thickness of the cored bar 172 is set to 0.1 to 15 mm, and is determined in consideration of the balance between the energy saving requirement (thinning) and the strength (depending on the constituent materials). For example, in order to maintain the same strength as that of a cored bar made of iron of 0.57 mm with a cored bar made of aluminum, the wall thickness needs to be 0.8 mm.

  Examples of the fluororesin constituting the coating layer 171 include PTFE (polytetrafluoroethylene) and PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer).

  The thickness of the coating layer 171 made of a fluororesin is 10 to 500 μm, preferably 20 to 400 μm. Examples of the elastic body constituting the coating layer 171 include silicone rubber and silicone sponge rubber having good heat resistance such as LTV, RTV, and HTV. The Asker C hardness of the elastic body constituting the coating layer 171 is less than 80 °, preferably less than 60 °. Moreover, the thickness of the coating layer 171 made of an elastic body is 0.1 to 30 mm, preferably 0.1 to 20 mm.

  As the heating member 173, a halogen heater can be preferably used.

  The pressure roller 17 b is formed by forming a coating layer 174 made of an elastic body on the surface of the cored bar 175. The elastic body constituting the covering layer 174 is not particularly limited, and examples thereof include various soft rubbers such as urethane rubber and silicone rubber, and sponge rubber, and the silicone rubber and the silicone sponge rubber exemplified as those constituting the covering layer 174. Is preferably used. The Asker C hardness of the elastic body constituting the coating layer 174 is less than 80 °, preferably less than 70 °, and more preferably less than 60 °. The thickness of the covering layer 220 is 0.1 to 30 mm, preferably 0.1 to 20 mm.

  Although it does not specifically limit as a material which comprises the metal core 175, Metals, such as aluminum, iron, copper, or those alloys can be mentioned.

  The contact load (total load) between the heating roller 17a and the pressure roller 17b is usually 40 to 350N, preferably 50 to 300N, and more preferably 50 to 250N. This contact load is defined in consideration of the strength of the heating roller 17a (the thickness of the cored bar 110). For example, a heating roller having a cored bar made of iron of 0.3 mm should be 250 N or less. Is preferred.

From the viewpoint of offset resistance and fixability, the nip width is preferably 4 to 10 mm, and the surface pressure of the nip is preferably 0.6 × 10 ^{5 to} 1.5 × 10 ⁵ Pa. .

  The image forming apparatus according to the present invention may use an induction heating type fixing device instead of the heating roll type fixing device.

  The transfer material P used in the present invention is a support for holding a toner image, and is usually called an image support, a recording material, or transfer paper. Specifically, various transfer materials such as plain paper and fine paper from thin paper to thick paper, coated printing paper such as art paper and coated paper, commercially available Japanese paper and postcard paper, plastic film for OHP, cloth, etc. However, it is not limited to these.

  EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these embodiments.

<< Preparation of polymerizable monomer of general formula (1) >>
Seven kinds of polymerizable monomers of the general formula (1) used for preparing resin particles for core particles were prepared.

Table 1 shows the polymerizable monomers prepared, R ₁ and R ₂ in the general formula (1), and compound names.

<Production of resin particles for core particles>
Resin fine particles for core particles were produced as follows.

<Preparation of resin particles 1 for core particles>
Preparation of Resin Fine Particle Dispersion (A1) (1) First Stage Polymerization An anionic surfactant (sodium dodecylbenzene sulfonate: SDS) was previously placed in a reaction vessel equipped with a stirrer, temperature sensor, condenser, and nitrogen inlet. A surfactant solution in which 2.0 parts by mass was dissolved in 2900 parts by mass of ion-exchanged water was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

After adding 9.0 parts by mass of a polymerization initiator (potassium persulfate: KPS) to this surfactant solution and adjusting the internal temperature to 78 ° C.,
Styrene 551 parts by weight Myristyl acrylate 280 parts by weight Methacrylic acid 44 parts by weight n-Octyl mercaptan 19 parts by weight of a monomer solution (1) was added dropwise over 3 hours. By stirring, polymerization (first stage polymerization) was performed to prepare a dispersion of resin fine particles (resin fine particle dispersion (a1)).

(2) Second stage polymerization: formation of an intermediate layer In a vessel equipped with a stirrer,
Styrene 107 parts by weight n-butyl acrylate 50 parts by weight Methacrylic acid 8 parts by weight n-octyl mercaptan 4 parts by weight Paraffin wax “HNP-57” (manufactured by Nippon Seiwa Co., Ltd.) as a release agent 51 parts by mass was added, and the mixture was heated to 85 ° C. and dissolved to prepare a monomer solution (2).

  On the other hand, a surfactant solution in which 2 parts by mass of an anionic surfactant (polyoxy (2) dodecyl ether sulfate sodium salt) was dissolved in 1100 parts by mass of ion-exchanged water was heated to 90 ° C., and this surfactant solution After adding 245 parts by mass of the resin fine particle dispersion (a1) to the solid content of the resin fine particles, the monomer solution is obtained by a mechanical disperser “CLEARMIX” (M Technique Co., Ltd.) having a circulation path. (2) was mixed and dispersed for 4 hours to prepare a dispersion containing emulsified particles having a dispersed particle diameter of 350 nm. An initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator (KPS) was dissolved in 110 parts by mass of ion-exchanged water was added to this dispersion, and this system was heated and stirred at 90 ° C. for 2 hours. Polymerization (second stage polymerization) was performed to prepare a dispersion of resin fine particles (resin fine particle dispersion (a11)).

(3) Third-stage polymerization: Formation of outer layer An initiator aqueous solution in which 2.5 parts by mass of a polymerization initiator (KPS) is dissolved in 110 parts by mass of ion-exchanged water is added to the resin fine particle dispersion (a11). Under the temperature condition of 80 ° C.
Styrene 238 parts by mass n-butyl acrylate 92 parts by mass n-octyl mercaptan 4.2 parts by mass A monomer solution (3) was added dropwise over 1 hour. After completion of the dropping, polymerization (third stage polymerization) was performed by heating and stirring for 3 hours, and then cooled to 28 ° C., and “resin fine particles for core particles (1)” with composite resin fine particles having a multilayer structure. A dispersion was prepared. The resin particle for core particles had a glass transition temperature (Tg) of 38.0 ° C., Mw: 50,000, Mn: 25,000, and Mw / Mn: 2.00.

<Preparation of resin fine particles (2) to (11) for core particles>
First-stage polymerized myristyl acrylate (polymerizable monomer of general formula (1)) used in the preparation of the resin fine particles for core particles (1) and the polymerizable monomer of general formula (1) in the resin for core particles “Resin fine particles for core particles (2) to (11)” were produced in the same manner except that the composition ratio of the monomer was changed as shown in Table 2.

<Preparation of resin fine particles (12) for core particles>
First-stage polymerized myristyl acrylate (polymerizable monomer of general formula (1)) used in the preparation of the resin fine particles for core particles (1) and the polymerizable monomer of general formula (1) in the resin for core particles The composition ratio of the monomer was changed as shown in Table 2,
Second-stage polymerization styrene from 108 parts by weight to 89 parts by weight, n-butyl acrylate from 50 parts by weight to 68 parts by weight,
“Core particle resin fine particles (12)” were prepared in the same manner except that the styrene in the third stage polymerization was changed from 238 parts by mass to 198 parts by mass and n-butyl acrylate was changed from 92 parts by mass to 132 parts by mass.

<Preparation of resin fine particles (13) for core particles>
First-stage polymerized myristyl acrylate (polymerizable monomer of general formula (1)) used in the preparation of the resin fine particles for core particles (1) and the polymerizable monomer of general formula (1) in the resin for core particles Change the composition ratio of the monomer as shown in Table 2,
Second-stage polymerization styrene from 108 parts by weight to 122 parts by weight, n-butyl acrylate from 50 parts by weight to 35 parts by weight,
“Core particle resin fine particles (12)” were prepared in the same manner except that the styrene in the third stage polymerization was changed from 238 parts by mass to 267 parts by mass and n-butyl acrylate was changed from 92 parts by mass to 63 parts by mass.

  Table 2 shows the polymerizable monomer of the general formula (1) used for the production of the resin fine particles for core particles (1) to (13), and the polymerizable monomer of the general formula (1) in the resin fine particles for core particles. The copolymerization ratio (composition ratio) and glass transition temperature (Tg) of the body are shown.

  Tg is a value obtained by the method described above.

<< Preparation of Resin Fine Particles for Shell Layer (1) >>
In a reaction vessel equipped with a stirrer, a temperature sensor, a cooling tube, and a nitrogen introducing device, 2.0 parts by mass of an anionic surfactant (sodium dodecylbenzenesulfonate: SDS) was dissolved in 2900 parts by mass of ion-exchanged water in advance. The surfactant solution was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.

After adding 9.0 parts by mass of a polymerization initiator (potassium persulfate: KPS) to this surfactant solution and adjusting the internal temperature to 78 ° C.,
Styrene 576 parts by weight Butyl acrylate 168 parts by weight Methacrylic acid 56 parts by weight n-Octyl mercaptan 16.4 parts by weight of a monomer solution was added dropwise over 3 hours. By stirring, polymerization was performed to prepare a dispersion of “resin fine particles for shell layer (1)”. The resin particles for shell layer (1) had a glass transition temperature (Tg) of 53.0 ° C.

<< Preparation of Colorant Particle Dispersion (1) >>
To a solution obtained by stirring and dissolving 90 parts by weight of sodium dodecyl sulfate in 1600 parts by weight of ion-exchanged water, 420 parts by weight of carbon black “Regal 330R” (manufactured by Cabot) is gradually added. "(Color Technique Particle Dispersion (1)") was prepared by dispersion treatment using "M-Technique". As a result of measuring the particle diameter of the colorant in the colorant particle dispersion (1) using an electrophoretic light scattering photometer “ELS-800” (manufactured by Otsuka Electronics Co., Ltd.), the mass average diameter was 110 nm.

<< Production of Toner 1 >>
(Formation of core particles (aggregation / fusion process))
420.7 parts by mass (in terms of solid content) of “resin fine particles for core particles (1)”, 900 parts by mass of ion-exchanged water, and 200 parts by mass of “colorant particle dispersion (1)” The mixture was stirred in a reaction vessel equipped with a sensor, a condenser, a nitrogen introducing device, and a stirring device. After adjusting the temperature in a container to 30 degreeC, 5 mol / liter sodium hydroxide aqueous solution was added to this solution, and pH was adjusted to 8-11.

Next, an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the core particles was measured with “Coulter Multisizer 3” (manufactured by Coulter), and when the volume-based median system (D ₅₀ ) became 5.5 μm, 40.2 mass of sodium chloride. An aqueous solution in which 1000 parts by mass of ion-exchanged water is dissolved is added to stop the particle size growth, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment. Particle 1 "was formed.

  The circularity of the “core particle 1” was measured by “FPIA2000” (manufactured by Systex) and found to be 0.912.

(Formation of shell layer (shelling process))
Subsequently, 96 parts by mass (solid content conversion) of “resin fine particles for shell layer (1)” at 65 ° C. was added, and further 2 parts by mass of magnesium chloride hexahydrate was dissolved in 1000 parts by mass of ion-exchanged water. Was added over 10 minutes, and then the temperature was raised to 70 ° C. (shelling temperature), and stirring was continued for 1 hour. On the surface of “core particles 1”, “resin fine particles for shell layer (1)” After fusing the particles, aging treatment was performed at 75 ° C. for 20 minutes to form a shell layer.

  Here, 40.2 parts by mass of sodium chloride was added, the mixture was cooled to 30 ° C. at 8 ° C./min, the produced fused particles were filtered, washed repeatedly with ion-exchanged water at 45 ° C., and then 40 ° C. By drying with warm air, “colored particles 1” having a shell layer on the surface of the core particles were produced.

(External additive treatment)
1% by mass of hydrophobic silica (number average primary particle size = 12 nm, degree of hydrophobicity = 68) and hydrophobic titanium oxide (number average primary particle size = 20 nm, degree of hydrophobicity = 63) ) Was added in an amount of 1.2% by mass and mixed with a Henschel mixer to prepare “Toner 1”.

<< Production of Toners 2-13 >>
“Toners 2 to 13” were prepared in the same manner except that the resin particles for core particles (1) used in preparation of toner 1 were changed to resin particles for core particles (2) to (13) shown in Table 3. did.

  Table 3 shows copolymerization ratios of the polymerizable monomer of the general formula (1) in the resin fine particles for the core particles, the resin fine particles for the shell layer, and the resin constituting the toner used in the production of “Toners 1 to 13” ( Composition ratio), toner glass transition temperature (Tg), weight average molecular weight (Mw), number average molecular weight (Mn), and Mw / Mn.

  Tg is a value obtained by the method described above. Mw and Mn are values measured after removing the colorant with a membrane filter by the GPC (gel permeation chromatograph) described above.

<< Preparation of developer >>
Next, a ferrite carrier coated with a silicone resin and having a volume average particle size of 50 μm was mixed with each of the toners prepared above to prepare “Developers 1 to 13” having a toner concentration of 6% by mass.

<Evaluation>
The produced toner was evaluated as follows.

Print images for evaluation are created by loading the above-prepared toner and developer into a digital color multifunction peripheral bizhub PRO C500 (manufactured by Konica Minolta Business Technologies) in order, and printing in an environment of 20 ° C. and 55% RH. did. The print uses an image with a pixel rate of 10% (an original image in which a character image is 7%, a human face photo, a solid white image, and a solid black image are each divided into quarters), and is A4 size fine paper ( 64 g / m ² ).

<Low temperature fixability> (cold offset)
The surface temperature of the heating roller of the image evaluation apparatus was changed in increments of 5 ° C. within the range of 90 to 130 ° C., and the occurrence of image contamination due to fixing offset was evaluated at each surface temperature. Specifically, an A4 size toner image that outputs a belt-like solid image having a width of 5 mm and a halftone image having a width of 20 mm in a direction perpendicular to the transfer paper with respect to the conveyance direction is laterally fed and conveyed, and a temperature region in which image contamination does not occur ( (Non-offset region) was detected and evaluated.

A: The lower limit temperature of the non-offset region is 110 ° C. or lower, and the non-offset region is 15 ° C. or higher. ○: The lower limit temperature of the non-offset region is 120 ° C. or lower, and the non-offset region is lower than 15 ° C. ×: The lower limit temperature of the non-offset region is 125 ° C or higher.

<Fold crease strength>
The fixing strength of the folds was evaluated by measuring the fixing rate of the folds as follows. Here, the crease fixing rate is the fixing rate indicating the degree of toner peeling at the bent portion when the print image surface is folded.

  The solid image part (image density is 0.8) is folded inside and rubbed with a finger three times, then the image is opened and wiped three times with “JK Wiper” (manufactured by Crecia Co., Ltd.). This is a value calculated from the image density before and after the folding of the crease portion by the following formula.

Fold fixing rate (%) = (image density after folding) / (image density before folding) × 100
The crease strength was ranked from the obtained crease fixing rate as follows.

  In addition, ○ or more is a level with no problem.

Evaluation criteria A: 90 to 100%, excellent crease fixing strength B: 80 to less than 90%, good crease fixing strength ×: Less than 80%, fold fixing strength is poor.

<Document offset>
The document offset property is evaluated by setting the temperature of the heating belt to 130 ° C., and printing two sheets of the same test image as described above, and superimposing the image surface (print surface) and the non-image surface (back surface) on a glass plate. And a weight equivalent to 7.8 kPa was placed on the overlapped portion and left standing in an environment of 60 ° C. and 50% RH for one week. After standing, the two overlapped sheets were peeled off, and the degree of image loss of the printed images peeled off visually was ranked and evaluated in the following four stages “R1” to “R4”. The ranks “R3” and “R4” are acceptable.

“R1”: Level where two sheets stick together and difficult to peel off “R2”: Level where image transfer is seen on the back side when two sheets are peeled off “R3”: Although gloss reduction in the image area is seen, Acceptable level with almost no image defects (image transfer on the back side) “R4”: a good level where no image defects or image transfer are seen in both the image area and the non-image area.

  Table 4 shows the evaluation results.

  From the results of Table 4, “Toners 1 to 7” of “Examples 1 to 7” of the present invention are excellent in all evaluation items of low-temperature fixability (cold offset), crease fixing strength, and document offset properties. I understand that. However, it was found that the toners 8 to 13 of “Comparative Examples 1 to 6” outside the present invention have a problem in at least one of the evaluation items.

1 is a cross-sectional view of an example of an image forming apparatus that can use the toner of the present invention. FIG. 2 is a cross-sectional view illustrating an example of a fixing device 17 that can be used in the image forming apparatus of FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 9Y, 9M, 9C, 9K Image forming unit 6 Intermediate transfer body 17 Fixing apparatus T Toner

Claims (3)

In the electrostatic image developing toner having a core-shell structure containing at least a resin and a colorant,
The resin contains a polymerizable monomer represented by the following general formula (1) in a copolymerization ratio of 0.5 to 20% by mass, and an electrostatic charge image developing toner has a glass transition temperature of 20 to 45. A toner for developing an electrostatic charge image, wherein the toner has a temperature of ° C.
Formula _{(1) H 2 C = CR} 1 -COOR 2
(In the formula, R ₁ represents H or CH ₃ , and R ₂ represents a long-chain alkyl group having 14 to 22 carbon atoms or a cyclic alkyl group.) 2. The electrostatic charge image development according to claim 1, wherein the resin obtained by polymerizing the polymerizable monomer represented by the general formula (1) is contained in core particles having a core-shell structure. Toner. The resin constituting the electrostatic image developing toner has a weight average molecular weight (Mw) of 10,000 to 100,000, a number average molecular weight (Mn) of 5,000 to 50,000, and Mw / Mn of 2 to 4. The electrostatic image developing toner according to claim 1, wherein the toner is for developing an electrostatic image.

Images