JP2006010822A - Developing toner for electrostatic charge image - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing toner for electrostatic charge image having satisfactory low temperature fixing property and giving images with stable image density, resolution and without fogging, even after copying a large number of sheets. <P>SOLUTION: The electrostatic charge image developing toner comprises amorphous resin particles, containing at least colorant particles, wherein the surface of the resin particles is coated with a crystalline resin. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrophotographic electrostatic image developing toner.

  By using a toner for developing an electrostatic image having a core-shell structure (hereinafter, also referred to as toner), the toner particles are prevented from being exposed to the toner surface, thereby obtaining charge stability and environmental stability of the toner (for example, patent documents). 1). However, when the shell layer is formed on the surface of the core particle, the longer the heating time for forming the shell layer, the longer the pigment particle moves to the surface, resulting in insufficient effect of the shell layer. The charge stability and environmental stability of the toner cannot be obtained.

  In the field of electrophotography, from the viewpoint of energy saving, there is a demand for a toner that can provide sufficient fixing strength at a low fixing temperature. For this purpose, the binder resin used in the toner preferably has a low glass transition point, but the lower limit of the glass transition point is determined from the viewpoint of storage stability. In order to achieve both low-temperature fixability and storage stability, the sharp-melt property of the toner binder resin is required. Polyester resin is excellent in sharp melt property compared with styrene-acrylic resin. Even in a toner using styrene-acrylic resin as a binder resin, it is difficult to satisfy the level of polyester resin, although a certain degree of sharp melt property can be realized by narrowing the molecular weight distribution.

A number of methods of mixing an amorphous resin and a crystalline polyester resin and using it as a toner resin have been disclosed (for example, see Patent Documents 2 to 4). I can't say that.
JP-A-57-45558 (Claims) JP 2002-284866 A (paragraph numbers 0002 to 0006) JP 2003-176339 A (paragraph numbers 0002 to 0004) JP 2002-318471 A (paragraph numbers 0002 to 0006)

  An object of the present invention is to provide a toner that satisfies low-temperature fixability and has stable toner charge.

  The above object of the present invention can be achieved by the following configuration.

(Claim 1)
A toner for developing an electrostatic charge image, wherein at least surfaces of amorphous resin particles containing colorant particles are coated with a crystalline resin.

(Claim 2)
Ratio of softening point of crystalline resin to maximum peak temperature of heat of fusion (softening point / peak temperature) is 0.6 to 1.5, and ratio of softening point of amorphous resin to maximum peak temperature of heat of fusion (softening) The toner for developing an electrostatic charge image according to claim 1, wherein the point / peak temperature is 1.5 to 3.0.

(Claim 3)
The electrostatic image developing toner according to claim 1, wherein the amorphous resin is an amorphous polyester, and the crystalline resin is a crystalline polyester.

  According to the present invention, an electrostatic charge image developing toner is obtained which satisfies low-temperature fixability and can produce an image having stable image density, fog and resolution even after many copies.

  The present invention will be described in more detail. In the toner for developing an electrostatic charge image of the present invention, at least the surface of amorphous resin particles containing colorant particles is coated with a crystalline resin.

  As the resin used in the present invention, conventionally used condensation polymerization resins, addition polymerization resins, and mixtures thereof are used.

  In particular, a condensation polymerization resin having a hydrocarbon ring exhibits a high glass transition point even with a relatively low molecular weight due to crystallinity due to the hydrocarbon ring, and has a low melt viscosity because of its relatively low molecular weight. Specifically, it is a very preferable resin. Polyester resins having a hydrocarbon ring such as an aromatic ring such as a benzene ring or a naphthalene ring or an alicyclic ring such as a cyclohexane ring are preferred resins.

  A polyester resin having an aromatic ring or an alicyclic ring is a polyester resin obtained using a diol having these rings and / or a dicarboxylic acid having those rings as a main raw material.

  Examples of the diol having an aromatic ring or an alicyclic ring include alkylene (C2-C4) oxide adducts of bisphenols such as bisphenol A, bisphenol B, bisphenol C, bisphenol F, bisphenol Z, p-xylene glycol, Bis (hydroxyethoxy) benzene, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol and the like can be mentioned.

  Examples of the dicarboxylic acid having an aromatic ring or alicyclic ring include isophthalic acid, terephthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, sodium sulfoisophthalate, 1,4-cyclohexanedicarboxylic acid, and cyclohexene-1,2. -Dicarboxylic acid, methyl nadic acid, etc. and their lower alkyl esters, acid halides, acid anhydrides and the like.

  Examples of the aliphatic dicarboxylic acid that can be used together with the diol having an aromatic ring or alicyclic ring include maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and decanedicarboxylic acid. Examples of the aliphatic diol that can be used together with the dicarboxylic acid having an aromatic ring or an alicyclic ring include ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, nonanediol, neo Examples include pentyl glycol, 3-methylpentanediol, diethylene glycol, triethylene glycol, and polytetramethylene glycol.

  These polyester resins having an aromatic ring or alicyclic ring have a glass transition point of about 50 ° C. or higher, particularly preferably 50 to 65 ° C., a softening point of about 70 to 100 ° C., and a sharp melting temperature range. -Melt-type resin that is solid at room temperature. The preferred mass average molecular weight of the resin is about 1,000 to 50,000, preferably 1,000 to 10,000.

  The toner of the present invention is produced by agglomerating and heat-sealing resin fine particles obtained by the above method and at least colorant particles.

  “Agglomeration” is used in the concept that at least a plurality of resin particles are intended to simply adhere. The “aggregation” forms so-called hetero-aggregated particles (group) in which the constituent particles are in contact with each other, but the bonding due to melting of the resin particles or the like is not formed. A group of particles formed by such “aggregation” is referred to as “aggregated particles”.

  “Fusion” is used in a concept that is intended to form a bond as a unit of use and handling by forming a bond due to melting of resin particles or the like in at least a part of the interface of the individual constituent particles in the aggregated particles. Shall. The particle group that has undergone such “fusion” is referred to as “fused particles”.

  “Aggregation / fusion” refers to an action in which aggregation and fusion occur simultaneously or in stages, or an action in which aggregation and fusion occur simultaneously or in stages.

  In the agglomeration / fusion, a resin fine particle dispersion and at least a separately prepared colorant dispersion are mixed, and the particles are agglomerated to form agglomerated particles (hereinafter, agglomeration step); A first method including a step of forming toner particles by fusing by heating (hereinafter referred to as a fusing step) may be employed, or the toner may be formed by fusing at the same time as the formation of aggregated particles proceeds. You may employ | adopt the 2nd method of forming particle | grains.

  Specifically, in the aggregation method of the first method, the resin particle dispersion, the colorant particle dispersion, and, if necessary, the offset inhibitor dispersion are mixed with each other, the flocculant is added to a critical aggregation concentration or more, and resin fine particles and the like are added. Aggregates to form aggregated particles. In the fusing step, fusing is performed by heating to a temperature equal to or higher than the glass transition temperature of the resin in the aggregated particles.

  Specifically, in the second method, a flocculant is added to a dispersion liquid in which the resin particle dispersion liquid, the colorant particle dispersion liquid and, if necessary, the offset inhibitor dispersion liquid are mixed with each other, and then the resin fine particles are added. Fusion is performed at the same time as agglomeration is advanced by heating above the glass transition point.

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

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

  Specific examples of the anionic surfactant include fatty acid soaps such as sodium stearate and sodium dodecanoate, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate and the like.

  Specific examples of the nonionic surfactant include dodecyl polyoxyethylene ether, hexadecyl polyoxyethylene ether, norylphenyl polyoxyethylene ether, ralyl polyoxyethylene ether, sorbitan monooleate polyoxyethylene ether, styrylphenyl poly Examples thereof include oxyethylene ether and monodecanoyl sucrose. Of these, anionic surfactants and / or nonionic surfactants are preferred.

  As the aggregating agent, a compound having a polarity different from that of the resin particles, for example, a compound having a monovalent or higher charge such as an ionic surfactant, a nonionic surfactant or a metal salt can be used. Specifically, water-soluble surfactants such as the above-mentioned cationic surfactants, anionic surfactants and nonionic surfactants; acids such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid and oxalic acid; magnesium chloride, Metal salts of inorganic acids such as calcium chloride, sodium chloride, aluminum chloride, aluminum sulfate, calcium sulfate, aluminum nitrate, silver nitrate, copper sulfate, sodium carbonate; sodium acetate, potassium formate, sodium oxalate, sodium phthalate, potassium salicylate, etc. Aliphatic acids and aromatic acid metal salts; metal salts of phenols such as sodium phenolate, metal salts of amino acids, triethanolamine hydrochloride, inorganic salts of aromatic amines such as aniline hydrochloride Is mentioned. When considering the stability of the aggregated particles, the stability of the aggregating agent with respect to heat and time, and the removal during washing, a metal salt of an inorganic acid is preferable in terms of performance and use.

  The amount of the flocculant to be added varies depending on the valence of the charge, but any of them may be small. In the case of monovalent to the added dispersion, it is 3% by mass or less, and in the case of divalent, 1% by mass or less. In the case of trivalent, it is about 0.5% by mass or less. A smaller amount of the flocculant is preferable, and a compound having a higher valence is preferable because the amount added can be reduced.

  As the colorant to be agglomerated / fused with resin particles or the like, various organic or inorganic pigments and dyes as shown below can be used.

  That is, examples of black pigments include carbon black, copper oxide, manganese dioxide, aniline black, activated carbon, nonmagnetic ferrite, magnetic ferrite, and magnetite.

  Yellow pigments include yellow lead, zinc yellow, yellow iron oxide, mineral fast yellow, nickel titanium yellow, navel yellow, naphthol yellow S, Hansa yellow G, Hansa yellow 10G, benzidine yellow G, benzidine yellow GR, quinoline yellow lake, Permanent Yellow NCG, Tartragin Lake and others.

  Examples of the orange pigment include red yellow lead, molybdenum orange, permanent orange GTR, pyrazolone orange, Vulcan orange, indanthrene brilliant orange RK, benzidine orange G, and indanthrene brilliant orange GK.

  Red pigments include Bengala, Pangdan, Permanent Red 4R, Resol Red, Pyrazolone Red, Watching Red, Calcium Salt, Lake Red C, Lake Red D, Brilliant Carmine 6B, Eosin Lake, Rhodamine Lake B, Alizarin Lake, Brilliant Carmine 3B etc.

  Examples of purple pigments include manganese purple, fast violet B, and methyl violet lake.

  Examples of blue pigments include bitumen, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, phthalocyanine blue derivatives, first sky blue, and induslen blue BC.

  Examples of the green pigment include chrome green, chromium oxide, pigment green B, malachite green lake, final yellow green G, and phthalocyanine green.

  Examples of white pigments include zinc oxide, titanium oxide, zirconium oxide, aluminum oxide, calcium oxide, calcium carbonate, and tin oxide.

  Examples of extender pigments include barite powder, barium carbonate, clay, silica, white carbon, talc, alumina white, and kaolin.

  Examples of the dye include rose bengal, triphenylmethane dye, monoazo dye, disazo dye, rhodamine dye, condensed azo dye, and phthalocyanine dye.

  The pigment is usually used in the form of a dispersion dispersed in water in the presence of the dispersion stabilizer. Preferably, the pigment is provided with a self-dispersibility by introducing a hydrophilic group such as a carboxylic acid group on the surface. Is used in the form of a dispersion in which water is self-dispersed in water. The pigment desirably has a dispersed particle diameter of 1 μm or less in the dispersion, and more preferably in the range of 30 to 300 nm.

  These colorants can be used alone or in combination. The colorant is used in an amount of 1 to 20 parts by weight, preferably 2 to 15 parts by weight, based on 100 parts by weight of the polymer contained in the toner. When the amount of the colorant is more than 20 parts by mass, the toner fixing property is lowered, and when the amount is less than 1 part by mass, a desired image density cannot be obtained.

  As the offset preventive agent, any of known waxes can be used. Specifically, olefinic waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and copolymerized polyethylene, paraffin wax; behenic acid ester , Ester waxes having a long chain aliphatic group such as montanic acid ester and stearic acid ester; plant waxes such as hydrogenated castor oil and carnauba wax; ketones having a long chain alkyl group such as distearyl ketone; having an alkyl group Silicone; higher fatty acids such as stearic acid; (partial) esters of long-chain fatty alcohols, pentaerythritol, trimethylolpropane and other polyhydric alcohols and long-chain fatty acids; oleic acid amide, stearic acid amide, palmitic acid amide, etc. Examples include higher fatty acid amides It is.

  The offset inhibitor is preferably used in the form of a dispersion dispersed in water in the presence of the dispersion stabilizer. The offset inhibitor preferably has a dispersed particle size of 2 μm or less in the dispersion, and more preferably in the range of 50 to 500 nm.

  The offset inhibitor is generally used in an amount of 1 to 25 parts by mass, preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the polymer.

  As the charge control agent, there are various types of substances that can give positive or negative charge by triboelectric charging. As the positive charge control agent, for example, a two-glossin dye such as Nigrosine Base ES (manufactured by Orient Chemical Industries). Quaternary ammonium salts such as P-51 (manufactured by Orient Chemical Co., Ltd.), copy charge PX VP435 (manufactured by Clariant), alkoxylated amine, alkylamide, molybdate chelate pigment, and PLZ1001 (manufactured by Shikoku Kasei Kogyo Co., Ltd.) And imidazole compounds.

  As the negative charge control agent, for example, Bontron S-22 (manufactured by Orient Chemical Industries), Bontron S-34 (manufactured by Orient Chemical Industries), Bontron E-81 (manufactured by Orient Chemical Industries), Bontron E-84 ( Orient Chemical Co., Ltd.), Spiron Black TRH (Hodogaya Chemical Co., Ltd.) and other metal complexes; Quaternary ammonium salts such as Clariant), and fluorine compounds such as magnesium fluoride and carbon fluoride. In addition to the above-mentioned metal complexes serving as negative charge control agents, oxycarboxylic acid metal complexes, dicarboxylic acid metal complexes, amino acid metal complexes, diketone acid metal complexes, diamine metal complexes, azo group-containing benzene- It may have various structures such as a benzene derivative skeleton metal complex and an azo group-containing benzene-naphthalene derivative skeleton metal complex.

  These charge control agents desirably have a particle size of about 10 to 100 nm from the viewpoint of obtaining uniform dispersion. When the particle diameter exceeds the upper limit of the above range in the form supplied as a commercial product, it is desirable to adjust to an appropriate particle diameter by a known method such as pulverization with a jet mill or the like.

  The toner particles obtained as described above preferably have an average circularity of 0.9 to 1. The shape of the toner particles can be easily controlled by adjusting the heating conditions in the aging process of the fusing process.

  The obtained toner particles are usually subjected to washing treatment, drying treatment and external addition treatment.

  In the washing treatment step, acidic and possibly basic water is added several times to the fine particles and stirred, followed by filtration to obtain a solid content. The pure water is added several times to the solid content and stirred, followed by filtration. This operation is repeated several times. When the pH of the filtrate after filtration reaches about 7, the operation is completed to obtain colored toner particles.

  In the drying process, the toner particles obtained in the cleaning process are dried at a temperature not higher than the glass transition temperature. At this time, it is preferable to circulate dry air according to the required temperature, or to heat under vacuum conditions. In the drying step, an arbitrary method such as a normal vibration type fluidized drying method, a spray drying method, a freeze drying method, a flash jet method, or the like can be adopted.

  In the external addition treatment step, single or plural kinds of external additives are added and mixed to the toner particles subjected to the drying treatment. External additives include fine powder silica, alumina, titania and other fluidity improvers, magnetite, ferrite, cerium oxide, strontium titanate, conductive titania and other inorganic fine particles, styrene resin, acrylic resin, etc. , Lubricants etc. are used. The amount of these external additives used may be appropriately selected depending on the desired performance, and is usually 0.05 to 10 parts by mass with respect to 100 parts by mass of the toner particles. These additives may be contained inside the toner particles.

Measuring method [Softening point]
Using a Koka type flow tester (manufactured by Shimadzu Corporation, CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C./min, a load of 1.96 MPa was applied by a plunger, a diameter of 1 mm, A nozzle with a length of 1 mm is pushed out, thereby drawing a plunger tester drop amount (flow value) -temperature curve of the flow tester. When the height of the S-curve is h, the temperature corresponding to h / 2 (resin The temperature at which half of the effluent flowed out) is taken as the softening point.

[Maximum peak temperature of melting heat and glass transition point]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C., and the sample cooled from that temperature to 0 ° C. at a temperature lowering rate of 10 ° C./min was measured at a temperature rising rate of 10 ° C./min. Determine the maximum peak temperature of heat of fusion. Further, the glass transition point is defined as the temperature at the intersection of the extended line of the base line below the glass transition point and the tangent line showing the maximum inclination from the peak rising portion to the peak apex.

[Volume average particle diameter of toner]
The volume average particle diameter of the toner was measured using “Coulter Multisizer II; Coulter Beckman”.

[Average circularity of toner]
The average circularity was measured using “FPIA-2000; Sysmex Corporation”. The average circularity is
Average circularity = defined by the circumference of a circle equal to the projected area of the particle / the circumference of the projected particle image.

Example 1
Preparation of polyester resin fine particle dispersion A 100 parts by mass of polyester resin a shown in Table 1 was dissolved in 400 parts by mass of toluene to obtain a resin solution. Distilled water, tricalcium phosphate 10% suspension and sodium dodecyl sulfate are placed in a reactor equipped with a stirrer, a cooling tube, a temperature sensor, and a nitrogen introduction tube, and the toluene solution of the above polyester resin is stirred at 60 ° C. Was added. Thereafter, the temperature was raised to 96 ° C. to remove the solvent, thereby obtaining a polyester resin dispersion A having a solid content concentration of 20% by mass. The average particle diameter measured using UPA (manufactured by Microtrac) was 160 nm.

Preparation of Polyester Resin Fine Particle Dispersion B Using polyester resin b shown in Table 1, a polyester resin dispersion B having a solid content concentration of 20% by mass was obtained in the same manner as the preparation of polyester resin fine particle dispersion A. The average particle diameter measured using UPA (manufactured by Microtrac) was 150 nm.

Preparation of wax dispersion liquid 680 g of distilled water, 180 g of carnauba wax (manufactured by Noda Wax), 17 g of sodium dodecylbenzenesulfonate (Neogen SC, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) are mixed and emulsified and dispersed by high-pressure shear to disperse the wax particles. A liquid was obtained. When the particle size of the wax fine particles was measured using a dynamic light scattering particle size distribution analyzer, ELS-800 (manufactured by Otsuka Electronics Co., Ltd.), the average particle size was 110 nm.

Preparation of Colorant Fine Particle Dispersion As a colorant fine particle, a self-dispersing pigment having a carboxylic acid group introduced on the surface of carbon black was dispersed in distilled water to obtain a colorant fine particle dispersion having a solid content of 17% by mass. When the particle size of the dispersed carbon black was measured using a dynamic light scattering particle size distribution analyzer, ELS-800 (manufactured by Otsuka Electronics Co., Ltd.), the average particle size was 103 nm.

Preparation of toner particles A reactor is charged with 500 g of a polyester resin fine particle dispersion A, 6.8 g of a wax dispersion, and 12 g of a colorant fine particle dispersion, and a 2 mol / l sodium hydroxide aqueous solution is added with stirring to adjust the pH of the mixed dispersion. Was adjusted to 4. Next, 10 g of a 50 mass% magnesium chloride aqueous solution was added thereto, and then the temperature was raised to 70 ° C. while stirring until the desired average particle diameter was grown. When the desired particle size was reached, 20 g of polyester resin fine particle dispersion B was added and held at 70 ° C. for an additional 1.5 hours. After adding 60 g of a 20% by mass sodium chloride aqueous solution, the temperature was raised to 80 ° C., and kept at 80 ° C. until the circularity reached about 0.96. When the desired circularity is reached, the contents are cooled to room temperature, and the toner particles are obtained by drying several times by washing the solution, filtering the solution, and resuspending the resulting solid in distilled water. It was. The volume average particle diameter was 5.3 μm, the ratio of the volume average particle diameter to the number average particle diameter was 1.12, and the average circularity was 0.96.

Toner particle external addition treatment To 100 parts of the dried toner particles, 0.5 part of silica (H-2000; manufactured by Wacker) is added, and post-treatment is performed at 1000 rpm for 1 minute using a Henschel mixer. The toner of Example 1 was obtained.

Example 2
Preparation of Polyester Resin Fine Particle Dispersion C Using polyester resin c shown in Table 1, a polyester resin dispersion C having a solid content concentration of 20% by mass was obtained in the same manner as the preparation of polyester resin fine particle dispersion A. The average particle diameter measured using UPA (manufactured by Microtrac) was 170 nm.

Preparation of Toner Particles Toner particles were obtained in the same manner as in the preparation of toner particles in Example 1, except that polyester resin fine particle dispersion C was used instead of polyester resin fine particle dispersion B. The volume average particle diameter was 5.4 μm, the ratio of the volume average particle diameter to the number average particle diameter was 1.12, and the average circularity was 0.96.

Toner particle external addition treatment To 100 parts of the dried toner particles, 0.5 part of silica (H-2000; manufactured by Wacker) is added, and post-treatment is performed at 1000 rpm for 1 minute using a Henschel mixer. A toner of Example 2 was obtained.

Example 3
Preparation of Polyester Resin Fine Particle Dispersion D Using polyester resin d shown in Table 1, a polyester resin dispersion D having a solid content concentration of 20% by mass was obtained in the same manner as the preparation of polyester resin fine particle dispersion A. The average particle diameter measured using UPA (manufactured by Microtrac) was 150 nm.

Preparation of toner particles Preparation of toner particles of Example 1 except that polyester resin fine particle dispersion D was used instead of polyester resin fine particle dispersion A, and polyester resin fine particle dispersion C was used instead of polyester resin fine particle dispersion B. Toner particles were obtained by the same method. The volume average particle diameter was 5.4 μm, the ratio of the volume average particle diameter to the number average particle diameter was 1.11 and the average circularity was 0.96.

Toner particle external addition treatment To 100 parts of the dried toner particles, 0.5 part of silica (H-2000; manufactured by Wacker) is added, and post-treatment is performed at 1000 rpm for 1 minute using a Henschel mixer. A toner of Example 3 was obtained.

Comparative Example 1
Preparation of toner particles A reactor is charged with 500 g of a polyester resin fine particle dispersion A, 6.8 g of a wax dispersion, and 12 g of a colorant fine particle dispersion, and a 2 mol / L aqueous sodium hydroxide solution is added with stirring to adjust the pH of the mixed dispersion. Was adjusted to 4. Next, 10 g of a 50 mass% magnesium chloride aqueous solution was added thereto, and then the temperature was raised to 70 ° C. while stirring until the desired average particle diameter was grown. When the desired particle size was reached, 60 g of a 20% by mass aqueous sodium chloride solution was added, the temperature was raised to 80 ° C., and the temperature was maintained at 80 ° C. until the circularity reached about 0.96. When the desired circularity is reached, the contents are cooled to room temperature, and the toner particles are obtained by drying several times by washing the solution, filtering the solution, and resuspending the resulting solid in distilled water. It was. The volume average particle diameter was 5.2 μm, the ratio of the volume average particle diameter to the number average particle diameter was 1.12, and the average circularity was 0.96.

Toner particle external addition treatment To 100 parts of the dried toner particles, 0.5 part of silica (H-2000; manufactured by Wacker) is added, and post-treatment is performed at 1000 rpm for 1 minute using a Henschel mixer. The toner of Example 1 was obtained.

Comparative Example 2
Preparation of Toner Particles Toner particles were obtained in the same manner as in the preparation of toner particles in Example 1 except that polyester resin fine particle dispersion D was used instead of polyester resin fine particle dispersion B. The volume average particle diameter was 5.6 μm, the ratio of the volume average particle diameter to the number average particle diameter was 1.11 and the average circularity was 0.96.

Toner particle external addition treatment To 100 parts of the dried toner particles, 0.5 part of silica (H-2000; manufactured by Wacker) is added, and post-treatment is performed at 1000 rpm for 1 minute using a Henschel mixer. A toner of Example 3 was obtained.

Preparation of Developer The toners of Examples 1, 2, 3, and Comparative Examples 1 and 2 were mixed with a silicon resin-coated carrier to prepare a two-component developer having a toner concentration of 6% by mass. The developers corresponding to the toners are the developers in Examples 1, 2, and 3, and the developers in Comparative Examples 1 and 2.

Evaluation As an evaluation machine, a digital printer “Sitios 7075” (manufactured by Konica Minolta) was used. The fixing temperature of this evaluation machine was set to 140 ° C.

  An image for evaluation was produced by printing an original image having a quarter of a character image having a pixel ratio of 7%, a human face photo, a solid white image, and a solid black image on A4 board recording paper.

  First, after printing in an environment of high temperature and high humidity (35 ° C., 85% RH), continuous 200,000 sheets are printed in an environment of normal temperature and normal humidity (25 ° C., 50% RH). The images were printed in a high-temperature and high-humidity environment and at normal temperature and humidity, and the image density, image quality, fog, and resolution were evaluated. However, before starting printing, the surface of the photoconductor was coated with setting powder, and the photoconductor and the cleaning blade were blended to perform printing.

<Image density>
The density of the solid black image portion at the initial printing and after printing 200,000 sheets was measured with a reflection densitometer “RD-918” (manufactured by Macbeth). The image density is the relative reflection density when the reflection density of the recording paper is “0”.

Evaluation Criteria A: Good at an image density of 1.2 or higher both at the initial printing and after printing 200,000 sheets ○: Level at which the image density is 1.0 or higher both at the initial printing and after printing 200,000 sheets x: At least one of the initial printing and after printing 200,000 sheets is a practically problematic level when the image density is less than 1.0.

<Fog>
The image density of the unprinted portion after the initial printing and after printing 200,000 sheets was measured with a reflection densitometer “RD-918” (manufactured by Macbeth). The reflection density of the recording paper (white paper) is measured at 20 locations at the absolute image density, and the average value is defined as the white paper density. Next, the white area of the recording paper on which the image was formed was similarly measured at 20 locations at the absolute image density, and the value obtained by subtracting the white paper density from the average density was evaluated as the fog density.

Evaluation criteria A: Good at a fog density of 0.005 or less both in the initial stage of printing and after printing 200,000 sheets. At least one of the initial printing and after printing 200,000 sheets is a fogging level of 0.01, which is a practical problem.

<Resolution>
The character images after the initial printing and after printing 200,000 sheets were visually evaluated.

Evaluation standard ◎: good with no difference in resolution after initial printing and after printing 200,000 sheets ○: halftone image has a slight decrease in resolution after printing 200,000 sheets, but no problem in practical use ×: after printing 200,000 sheets There is a noticeable decrease in the resolution of the level that is a problem in practice.

  Table 3 shows the evaluation results.

  As is apparent from Table 3, the images printed using the toners of Examples 1, 2, and 3 of the present invention were compared with the images printed using the toners of Comparative Examples 1 and 2, and the image density, fog, It can be seen that the resolution characteristics are excellent.

Claims (3)

A toner for developing an electrostatic charge image, wherein at least surfaces of amorphous resin particles containing colorant particles are coated with a crystalline resin. Ratio of softening point of crystalline resin to maximum peak temperature of heat of fusion (softening point / peak temperature) is 0.6 to 1.5, and ratio of softening point of amorphous resin to maximum peak temperature of heat of fusion (softening) The toner for developing an electrostatic charge image according to claim 1, wherein the point / peak temperature is 1.5 to 3.0. The electrostatic image developing toner according to claim 1, wherein the amorphous resin is an amorphous polyester, and the crystalline resin is a crystalline polyester.