JP4525505B2 - Electrophotographic toner, electrophotographic developer containing the toner, and image forming method using the same - Google Patents

Description

  The present invention relates to an electrophotographic toner that can be used in an electrophotographic apparatus using an electrophotographic process such as a copying machine, a printer, and a facsimile machine, an electrophotographic developer, and an image forming method using the same.

Many methods are known as electrophotographic methods (see, for example, Patent Document 1). In general, a latent image is electrically formed by various means on the surface of a photoreceptor (latent image holding body) using a photoconductive substance, and the formed latent image is developed with toner. After the image is formed, the toner image may be transferred to the surface of a transfer medium such as paper, optionally via an intermediate transfer body, and fixed by heating, pressurization, heat pressurization, solvent vapor, or the like. An image is formed through the process. Further, the toner remaining on the surface of the photoreceptor is cleaned by various methods as necessary, and is used again for developing the toner image.
As a fixing technique for fixing the toner image transferred to the surface of the transfer target, a hot roll fixing is performed in which the transfer target having the toner image transferred is inserted between a pair of rolls including a heating roll and a pressure roll and fixed. The law is common. As a similar technique, a fixing method in which one or both of the rolls is replaced with a belt is also known. These techniques have the advantage that a fast and robust image is obtained, energy efficiency is high, and environmental damage due to volatilization of solvents and the like is small compared to other fixing methods.

In recent years, from the viewpoint of energy saving, there is a tendency to save power in a fixing process that occupies most of the power used in the image forming process. For high-speed image formation, the toner image is fixed in a short time, and the maximum power is inevitably increased. Therefore, power saving in the fixing step is particularly important.
In order to achieve this requirement, lowering the fixing temperature of the toner itself leads to lowering the setting temperature of the fixing process, leading to a reduction in the maximum power consumption of the fixing process and a reduction in warm-up time from standby. It is also very important for energy saving because it leads to reduction of power consumption during standby.
However, with conventional amorphous styrene acrylic resins and non-crystalline polyester resins, when the fixing temperature of the toner itself is lowered, its glass transition temperature is also lowered, causing toner blocking during storage or development. There is a problem that toner aggregates are generated due to stress in the container.

In order to solve this problem, it has been proposed to use a crystalline resin having sharp melt properties. When a crystalline resin is used as a binder for toner, it is necessary to appropriately control the viscoelasticity in the fixing temperature region in order to achieve both fixing to paper and offset to a fixing member such as a heating roll. Crystalline polyester resins and the like can be raised as crystalline resins that satisfy this required characteristic. However, these resins have a portion that is easily polarized such as an ester bond in the resin, and the resistivity of the resin itself is low. There is a problem that the charging performance is low and the charging performance essential for the electrophotographic toner is low.
Specifically, a method has been proposed in which a crystalline polyester resin and an amorphous polyester resin are mixed and a layer separation structure is used (see, for example, Patent Document 2). Exists on the surface and adversely affects the charging performance of the toner. In addition, when the resins are incompatible with each other, the adhesion at the domain interface is poor, and the toner particles are liable to break down due to stress in the developer. In other words, the fogging of the background portion or the lowering of the density accompanied by a decrease in developability is caused.
Japanese Patent Publication No.49-23910 JP 2004-151535 A

An object of the present invention made in consideration of the above-mentioned problems is an electrophotographic toner used in an image forming method such as an electrophotographic method, which has excellent low-temperature fixability, blocking resistance during storage, and stress in the image forming apparatus. It is an object of the present invention to provide an electrophotographic toner that is excellent in blocking resistance and can stably form a high-quality image.
Another object of the present invention is to provide an electrophotographic developer containing such a toner and an image forming method using the same.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using a toner having a specific core-shell structure, and have completed the present invention.
That is, the electrophotographic toner of the present invention is contained in the range of 10 to 35% by mass in the colorant and the binder resin constituting the electrophotographic toner, and at the time of dynamic viscoelasticity measurement, the angular velocity is 1 Hz, 2 ° C. per minute. The storage elastic modulus G ′ at 30 ° C. is 10 ⁷ [Pa] or more and 10 ⁹ [Pa] when the storage elastic modulus G ′ in the temperature rising process from 30 ° C. to 130 ° C. is measured under the temperature change condition of The ratio tan δ between the loss elastic modulus G ″ and the storage elastic modulus G ′ at 30 ° C. is 0.2 or more and 0.7 or less, and the temperature at which tan δ = 1 is 50 ° C. or more and 80 ° C. or less, And a core containing a crystalline polyester resin having a solubility parameter of 9.00 to 9.57, an amorphous polyester resin having a glass transition temperature of 50 ° C. to 80 ° C., and an amorphous resin covering the surface of the core. An electron with a shell A toner, amorphous resin for covering the core surface, the glass transition temperature of 60 ° C. or higher, and, you, wherein the solubility parameter is a polyester resin is 10.1 or more.

The electrophotographic developer according to claim 2 of the present invention is an electrophotographic developer containing a carrier and a toner, and the electrophotographic toner of the present invention is used as the toner. .
According to a third aspect of the present invention, there is provided an image forming method comprising: forming an electrostatic latent image on an image latent image holding member; and developing the electrostatic latent image with a sleeve peripheral speed of a developing device of 250 mm / sec to 500 mm / A process for forming and developing a toner image by supporting the developer for electrophotography according to claim 2 on a sec sleeve, and transferring the toner image formed on the image latent image holding member onto the transfer target. And a step of thermally fixing the toner image on the transfer target.

According to the present invention, there is provided an electrophotographic toner that is excellent in low-temperature fixability, excellent in blocking resistance during storage and blocking resistance against stress in the image forming apparatus, and can stably form a high-quality image. be able to.
In addition, according to the present invention, it is possible to provide an electrophotographic developer containing such a toner and an image forming method that can stably form a high-quality image using the developer.

The electrophotographic toner of the present invention is an electrophotographic toner having a core containing at least a colorant and a crystalline polyester resin, and a shell made of an amorphous resin that coats the core surface. The resin is a polyester resin having a glass transition temperature of 60 ° C. or higher and a solubility parameter of 10.1 or higher.
In the present invention, it is necessary to use an amorphous resin for the shell portion. The glass transition temperature (Tg) of the amorphous resin used here is 60 ° C. or higher, and preferably in the range of 63 to 80 ° C.
When the glass transition temperature of the amorphous resin covering the core surface is less than 60 ° C., the storage stability of the toner is deteriorated, and the toner is fixed in the cartridge during high temperature storage or blocking in the developing device occurs. Problems arise.
Further, the solubility parameter of the amorphous resin is 10.1 or more, and preferably in the range of 10.15 to 10.7.
If the solubility parameter is less than 10.1, compatibilization with the core resin is likely to occur, the heat resistance of the toner surface substantially decreases, the storage stability of the toner deteriorates, and the toner is fixed in the cartridge during high temperature storage. Or blocking in the developing device occurs. Moreover, there is a concern that the crystalline resin of the core is likely to appear on the surface, the charging characteristics are deteriorated, and background fogging or density reduction occurs.

  Since the toner of the present invention contains a crystalline polyester resin in the core, a resin capable of appropriately controlling the compatibility with the core is selected as the amorphous resin used for coating the core. In other words, if the compatibility between the resin used for the core and the resin used for the shell part is too high, the physical properties of the shell part may be affected by the resin of the core part and the heat resistance may be reduced. When the resin that does not have a toner is used, sufficient adhesion between the core part and the shell part is not obtained, and the shell part peels off when subjected to stress in the image forming apparatus, and the heat resistance of the toner surface There is a concern of adversely affecting storage stability. Therefore, from the viewpoint of having appropriate compatibility with the core, the resin used for the shell portion is preferably an amorphous polyester.

  The core portion of the toner particles contains crystalline polyester and a colorant as essential components, but the hardness of the toner can be increased by further using an amorphous polyester resin. By improving the hardness of the core portion, it becomes possible to suppress undesired adhesion of the toner to a member that comes into contact with the toner in the apparatus, that is, the photosensitive member, the charging roll, the transfer belt, etc. By being performed effectively, there is an advantage that a higher quality image can be provided.

The ratio of the amorphous polyester resin to be blended in the core is preferably 10 to 35% by mass of the whole binder resin, and the glass transition temperature of this amorphous polyester resin is preferably 50 ° C to 80 ° C. In this temperature range, low-temperature fixability can be realized while maintaining the blocking resistance of the toner.
The toner secures low-temperature fixability by using the sharp melt property at the melting point of the crystalline resin, but the effect is sufficiently obtained when the amount of the crystalline polyester resin contained in the toner particles is 10% by mass or less. On the other hand, when the content is 35% by mass or more, the soft crystalline resin is dominant in the hardness of the toner binder resin compared to the amorphous resin, and the image strength is not sufficiently obtained, and the toner is crushed during the transfer process. Since problems such as occurrence occur, the amount of the crystalline resin is preferably in the range of 10 to 35% by mass, and more preferably in the range of 10 to 25% by mass. The content of the crystalline resin is the content ratio of the entire toner, that is, the total resin amount of the core portion and the shell portion.

First, the core part in the electrophotographic toner of the present invention will be described.
The core portion contains a colorant and a crystalline polyester resin as essential components.
In the present invention, the crystalline polyester used for the core portion of the toner contains a polyester resin containing an acid-derived constituent component and an alcohol-derived constituent component, and optionally contains other components.
The polyester resin is synthesized from an acid (dicarboxylic acid) component and an alcohol (diol) component. In the present invention, the “acid-derived component” refers to an acid component before synthesis of the polyester resin. The “alcohol-derived constituent component” refers to a constituent portion that was an alcohol component before the synthesis of the polyester resin.
In the present invention, “crystalline polyester resin” refers to a resin having a clear endothermic peak, not a stepwise endothermic change in differential scanning calorimetry (DSC), and does not have such characteristics. This is called “amorphous polyester resin”. In the case of a polymer obtained by copolymerizing another component with the crystalline polyester main chain, when the other component is 50% by weight or less, this copolymer is also called crystalline polyester.

-Acid-derived components-
The acid-derived constituent component is preferably an aliphatic dicarboxylic acid, and particularly preferably a linear carboxylic acid. For example, succinic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelic acid, sebacic acid, 1,9-nonanedicarboxylic acid, 1,10-decanedicarboxylic acid, 1,11-undecanedicarboxylic acid Acid, 1,12-dodecanedicarboxylic acid, 1,13-tridecanedicarboxylic acid, 1,14-tetradecanedicarboxylic acid, 1,16-hexadecanedicarboxylic acid, 1,18-octadecanedicarboxylic acid, etc., or lower alkyl esters thereof And acid anhydrides, but are not limited thereto.

As the acid-derived constituent component, in addition to the above-mentioned aliphatic dicarboxylic acid-derived constituent components, constituent components such as a dicarboxylic acid-derived constituent component having a double bond and a dicarboxylic acid-derived constituent component having a sulfonic acid group are included. Also good.
The component derived from a dicarboxylic acid having a double bond is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a double bond in addition to a component derived from a dicarboxylic acid having a double bond. Components are also included. The dicarboxylic acid-derived constituent component having a sulfonic acid group is derived from a lower alkyl ester or acid anhydride of a dicarboxylic acid having a sulfonic acid group, in addition to a constituent component derived from a dicarboxylic acid having a sulfonic acid group. Components are also included.

  The dicarboxylic acid having a double bond can be suitably used to prevent hot offset at the time of fixing since the entire resin can be crosslinked using the double bond. Examples of such dicarboxylic acids include, but are not limited to, fumaric acid, maleic acid, 3-hexenedioic acid, and 3-octenedioic acid. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, fumaric acid, maleic acid and the like are preferable in terms of cost.

  The dicarboxylic acid having a sulfonic acid group is effective in that it can favorably disperse a coloring material such as a pigment. Further, when the entire resin is emulsified or suspended in water to produce fine particles, if a sulfonic acid group is present, it can be emulsified or suspended without using a surfactant as described later. Examples of such a dicarboxylic acid having a sulfone group include, but are not limited to, 2-sulfoterephthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, and sulfosuccinic acid sodium salt. Moreover, these lower alkyl esters, acid anhydrides, etc. are also mentioned. Among these, 5-sulfoisophthalic acid sodium salt is preferable in terms of cost.

As content in acid-derived components of acid-derived components other than these aliphatic dicarboxylic acid-derived components (dicarboxylic acid-derived components having a double bond and / or dicarboxylic acid-derived components having a sulfonic acid group) Is preferably 1 to 20 mol%, more preferably 2 to 10 mol%.
In the present invention, “constituent mol%” refers to the percentage when each constituent component (acid-derived constituent component, alcohol-derived constituent component) in the polyester resin is 1 unit (mol).

<Constituents derived from alcohol>
As alcohol constituents, aliphatic diols are desirable, for example, ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol. 1,8-octanediol, 1,9-nonanediol, 1,10-decanediol, 1,11-dodecanediol, 1,12-undecanediol, 1,13-tridecanediol, 1,14-tetradecanediol 1,18-octadecanediol, 1,20-eicosanediol, and the like, but are not limited thereto.

The alcohol-derived constituent component has an aliphatic diol-derived constituent component content of 80 constituent mol% or more, and includes other components as necessary. As the alcohol-derived constituent component, the content of the aliphatic diol-derived constituent component is preferably 90 constituent mol% or more.
When the content is less than 80 mol%, the crystallinity of the polyester resin is lowered and the melting point is lowered, so that toner blocking resistance, image storage stability, and low-temperature fixability are deteriorated.

Other components included as necessary include diol-derived components having double bonds and diol-derived components having sulfonic acid groups.
Examples of the diol having a double bond include 2-butene-1,4-diol, 3-butene-1,6-diol, 4-butene-1,8-diol, and the like.
Examples of the diol having a sulfonic acid group include 1,4-dihydroxy-2-sulfonic acid benzene sodium salt, 1,3-dihydroxymethyl-5-sulfonic acid benzene sodium salt, and 2-sulfo-1,4-butanediol sodium. Examples include salts.
When adding an alcohol-derived component other than these linear aliphatic diol-derived components, that is, when adding a diol-derived component having a double bond and / or a diol-derived component having a sulfonic acid group, the alcohol is derived. As content in a structural component, 1-20 structural mol% is preferable and 2-10 structural mol% is more preferable.

Next, the amorphous polyester resin constituting the shell portion will be described. The amorphous polyester resin may be contained not only in the shell portion but also in the core portion of the toner of the present invention.
As the monomer component of the amorphous polyester resin used in the invention, for example, a conventionally known 2 which is a monomer component described in “Polymer Data Handbook: Basics” (Science of Polymer Science: Bafukan) There are carboxylic acids having a valence of 3 or more and alcohols having a valence of 2 or more. Specific examples of these monomer components include divalent carboxylic acids such as succinic acid, glutaric acid, adipic acid, peric acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and naphthalene-2. , 6-dicarboxylic acid, naphthalene-2,7-dicarboxylic acid, cyclohexanedicarboxylic acid, malonic acid, mesaconic acid, and other dibasic acids, and their anhydrides and their lower alkyl esters, maleic acid, fumaric acid, itaconic acid And aliphatic unsaturated dicarboxylic acids such as citraconic acid. Examples of the trivalent or higher carboxylic acid include 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, and the like, and anhydrides thereof. And lower alkyl esters. These may be used individually by 1 type and may use 2 or more types together.

  Examples of the divalent alcohol include bisphenol A, hydrogenated bisphenol A, ethylene oxide or (and) propylene oxide adduct of bisphenol A, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, ethylene glycol, diethylene glycol, Examples include propylene glycol, dipropylene glycol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, and neopentyl glycol. Examples of the trivalent or higher alcohol include glycerin, trimethylolethane, trimethylolpropane, pentaerythritol and the like. These may be used individually by 1 type and may use 2 or more types together. If necessary, monovalent acids such as acetic acid and benzoic acid, and monovalent alcohols such as cyclohexanol and benzyl alcohol can be used for the purpose of adjusting the acid value and the hydroxyl value.

  These polyester resins can be used in any combination of the above monomer components, for example, polycondensation (chemical doujin), polymer experimental studies (polycondensation and polyaddition: Kyoritsu Publishing) and polyester resin handbook (Nikkan Kogyo Shimbun) Etc.) can be synthesized by using a conventionally known method described in the above, etc., and a transesterification method, a direct polycondensation method or the like can be used alone or in combination. Moreover, when using the said polyester resin as binder resin, it is preferable to use the thing of the range whose weight average molecular weight Mw is 5,000-40,000 and whose number average molecular weight Mn is 2,000-10,000.

  The production method of the polyester resin is not particularly limited, and can be produced by a general polyester polymerization method in which an acid component and an alcohol component are reacted. For example, direct polycondensation, transesterification method, etc. Depending on the type of production. The molar ratio (acid component / alcohol component) when the acid component reacts with the alcohol component varies depending on the reaction conditions and the like, and cannot be generally stated, but is usually about 1/1.

The production of the polyester resin can be carried out at a polymerization temperature of 180 to 230 ° C., and the reaction is carried out while reducing the pressure in the reaction system as necessary and removing water and alcohol generated during the condensation.
When the raw material monomer is not dissolved or compatible at the reaction temperature, a high boiling point solvent is added as a solubilizing agent and dissolved. In the polycondensation reaction, the dissolution auxiliary solvent is distilled off. If there is a monomer with poor compatibility in the copolymerization reaction, it is advisable to condense the monomer with poor compatibility with the monomer and the acid or alcohol to be polycondensed in advance before polycondensing with the main component. .

  Catalysts that can be used in the production of the polyester resin include alkali metal compounds such as sodium and lithium, alkaline earth metal compounds such as magnesium and calcium, metal compounds such as zinc, manganese, antimony, titanium, tin, zirconium, and germanium, A phosphorous acid compound, a phosphoric acid compound, an amine compound, etc. are mentioned, Specifically, the following compounds are mentioned.

  For example, sodium acetate, sodium carbonate, lithium acetate, lithium carbonate, calcium acetate, calcium stearate, magnesium acetate, zinc acetate, zinc stearate, zinc naphthenate, zinc chloride, manganese acetate, manganese naphthenate, titanium tetraethoxide, titanium Tetrapropoxide, titanium tetraisopropoxide, titanium tetrabutoxide, antimony trioxide, triphenylantimony, tributylantimony, tin formate, tin oxalate, tetraphenyltin, dibutyltin dichloride, dibutyltin oxide, diphenyltin oxide, zirconium tetrabutoxide, naphthene Zirconate, zirconyl carbonate, zirconyl acetate, zirconyl stearate, zirconyl octylate, germanium oxide, triphenyl Phosphite, tris (2,4-di -t- butyl-phenyl) phosphite, ethyltriphenylphosphonium bromide, triethylamine, compounds such as triphenyl amine.

The solubility parameter of the polyester resin can be calculated from the skeleton of the resin using Fedors Parameter. Here, the solubility parameter is a square root (ΔEv / V) ^2/1 of a value obtained by dividing the molar evaporation energy ΔEv of the liquid by the molar volume V (cohesive energy density), and is a value indicating the solubility of the polymer. Widely used. The method for calculating the solubility parameter from the resin skeleton using Fedors Parameter is described in detail in the Polymer Handbook (4th edition, A Willy-interscience Publication) and the like, and the same method is applied to the present invention. can do.

There is no restriction | limiting in particular as a coloring agent used for this invention, A well-known coloring agent is mentioned, It can select suitably according to the objective. One type of pigment may be used alone, or two or more types of pigments of the same type may be mixed and used. Two or more different types of pigments may be mixed and used.
Specific examples of the colorant include carbon black such as furnace black, channel black, acetylene black, and thermal black, inorganic pigments such as bengara, aniline black, bitumen, titanium oxide, and magnetic powder, fast yellow, and monoazo. Yellow, disazo yellow, pyrazolone red, chelate red, brilliant carmine (3B, 6B, etc.), azo pigments such as para brown, phthalocyanine pigments such as copper phthalocyanine, metal-free phthalocyanine, flavantron yellow, dibromoanthrone orange, perylene red, quinacridone Examples thereof include condensed polycyclic pigments such as red and dioxazine violet.

  Chrome Yellow, Hansa Yellow, Benzidine Yellow, Slen Yellow, Quinoline Yellow, Permanent Orange GTR, Pyrazolone Orange, Vulcan Orange, Watch Young Red, Permanent Red, Dupont Oil Red, Resol Red, Rhodamine B Lake, Lake Red C, Rose Various pigments such as Bengal, Aniline Blue, Ultramarine Blue, Calco Oil Blue, Methylene Blue Chloride, Phthalocyanine Blue, Phthalocyanine Green, Malachite Green Oxalate, Para Brown; Acridine, Xanthene, Azo, Benzoquinone, Azine, Anthraquinone, dioxazine, thiazine, azomethine, indigo, thioindigo, phthalocyanine, aniline black , Polymethine dyes, triphenylmethane dyes, diphenylmethane dyes, thiazole type, various dyes such as xanthene; and the like. You may mix black pigments, such as carbon black, and dye to such an extent that transparency is not reduced to these colorants. Moreover, a disperse dye, an oil-soluble dye, etc. are mentioned.

The content of the colorant in the toner is preferably 1 to 20 parts by mass with respect to 100 parts by mass of the binder resin, but as long as the smoothness of the image surface after fixing is not impaired, as much as possible in such a numerical range. More is preferable. Increasing the content of the colorant is advantageous in that the thickness of the image can be reduced when an image having the same density is obtained, which is effective in preventing offset.
In addition, each color toner such as yellow toner, magenta toner, cyan toner, and black toner can be obtained by appropriately selecting the type of colorant, hue, and the like.

  The other components used in the toner of the present invention are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include various known additives such as inorganic fine particles, organic fine particles, charge control agents, and release agents. Can be mentioned. The other components may be used not only as added to the core particles but also as an external additive for toner particles.

Inorganic fine particles are generally used for the purpose of improving the fluidity of toner particles. Examples of the inorganic fine particles include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite, diatomaceous earth, cerium chloride, Examples thereof include fine particles of bengara, chromium oxide, cerium oxide, antimony trioxide, magnesium oxide, zirconium oxide, silicon carbide, and silicon nitride. Among these, silica fine particles are preferable, and silica fine particles that have been hydrophobized are particularly preferable.
The average primary particle diameter (number average particle diameter) of the inorganic fine particles is preferably 1 to 1000 nm, and the addition amount (external addition) is 0.01 to 20 parts by mass with respect to 100 parts by mass of the toner particles. preferable.

Organic fine particles are generally used for the purpose of improving cleaning properties and transferability. Examples of the organic fine particles include fine particles such as polystyrene, polymethyl methacrylate, and polyvinylidene fluoride.
The charge control agent is generally used for the purpose of improving the chargeability. Examples of the charge control agent include salicylic acid metal salts, metal-containing azo compounds, nigrosine and quaternary ammonium salts.
A mold release agent is generally used for the purpose of improving mold release properties. Specific examples of the release agent include low molecular weight polyolefins such as polyethylene, polypropylene and polybutene; silicones having a softening point by heating; fatty acid amides such as oleic acid amide, erucic acid amide, ricinoleic acid amide and stearic acid amide Plant waxes such as carnauba wax, rice wax, candelilla wax, tree wax, jojoba oil; animal waxes such as beeswax; minerals such as montan wax, ozokerite, ceresin, paraffin wax, microcrystalline wax, and Fischer-Tropsch wax -Petroleum waxes; ester waxes such as fatty acid esters, montanic acid esters, and carboxylic acid esters. In this invention, these mold release agents may be used individually by 1 type, and may use 2 or more types together.
The addition amount of these release agents is preferably 0.5 to 50% by mass, more preferably 1 to 30% by mass, and further preferably 5 to 15% by mass with respect to the total amount of toner particles. is there. If it is less than 0.5% by mass, there is no effect of adding a release agent, and if it is 50% by mass or more, the chargeability is likely to be affected, or toner particles are likely to be destroyed inside the developing machine. In addition to the effect that the agent is spent on the carrier and the charge is likely to decrease, for example, when color toner is used, the image surface tends to be insufficiently oozed out at the time of fixing. Since the release agent tends to stay in the film, the transparency is deteriorated, which is not preferable.

Means for forming the core-shell structure of the toner of the present invention will be described below. The method for producing the core particles is preferably a wet granulation method.
Suitable examples of the wet granulation method include known melt suspension methods, emulsion aggregation methods, and dissolution suspension methods. Hereinafter, the emulsion aggregation method will be described as an example.
The emulsion aggregation method includes an emulsification step of emulsifying the specific polyester resin and, if necessary, other binder resin to form emulsion particles (droplets), and forming an aggregate of the emulsion particles (droplets). An aggregating step and a fusing step of fusing and aggregating the aggregate.

-Emulsification process-
The emulsification process will be described using a specific polyester resin as an example.
In the emulsification step, emulsified particles (droplets) of a specific polyester resin give a shearing force to a solution obtained by mixing an aqueous medium and a mixed liquid (polymer liquid) containing a polyester resin and, if necessary, a colorant. Is formed.
At that time, the viscosity of the polymer liquid can be lowered to form emulsified particles by heating or dissolving the polyester resin in an organic solvent. Moreover, a dispersing agent can also be used for stabilization of emulsified particles and thickening of the aqueous medium. Hereinafter, such a dispersion of emulsified particles may be referred to as a “resin particle dispersion”.

  Examples of the dispersant include water-soluble polymers such as polyvinyl alcohol, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, sodium polyacrylate, and sodium polymethacrylate, sodium dodecylbenzenesulfonate, sodium octadecylsulfate, and sodium oleate. , Anionic surfactants such as sodium laurate and potassium stearate, cationic surfactants such as laurylamine acetate, stearylamine acetate and lauryltrimethylammonium chloride, zwitterionic surfactants such as lauryldimethylamine oxide, poly Nonoxy such as oxyethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, etc. Surfactants such as emissions surfactant, tricalcium phosphate, aluminum hydroxide, calcium sulfate, calcium carbonate, and inorganic compounds such as barium carbonate.

When an inorganic compound is used as the dispersant, a commercially available product may be used as it is, but for the purpose of obtaining fine particles, a method of producing fine particles of an inorganic compound in the dispersant may be employed.
As a usage-amount of a dispersing agent, 0.01-20 mass parts is preferable with respect to 100 mass parts of said polyester resins (binder resin).
In the emulsification step, the polyester resin is copolymerized with a dicarboxylic acid having a sulfonic acid group (that is, a suitable amount of a dicarboxylic acid-derived component having a sulfonic acid group is included in the acid-derived component). And dispersion stabilizers, such as surfactant, can be reduced, or an emulsified particle can be formed even if it does not use it.

Examples of the organic solvent that can be used here include ethyl acetate and toluene, which are appropriately selected according to the polyester resin.
The organic solvent is used in an amount of 50 to 5000 parts by mass with respect to 100 parts by mass of the total amount of the polyester resin and other monomers used as necessary (hereinafter sometimes simply referred to as “polymer”). Is preferable, and 120-1000 mass parts is more preferable. In addition, a colorant can be mixed before forming the emulsified particles. The colorant used is the same as already described in the section “Colorant” of the electrophotographic toner of the present invention.

  Examples of the emulsifier used when forming the emulsified particles include a homogenizer, a homomixer, a pressure kneader, an extruder, and a media disperser. The size of the emulsified particles (droplets) of the polyester resin is preferably 0.01 to 1 μm, more preferably 0.03 to 0.3 μm, more preferably 0.03 to 0.03 in terms of the center particle size (volume center particle size). 0.4 μm is more preferable.

As a method for dispersing the colorant, any method such as a general shearing method such as a rotary shearing homogenizer, a ball mill having a medium, a sand mill, or a dyno mill can be used, and is not limited at all.
If necessary, an aqueous dispersion of these colorants can be prepared using a surfactant, or an organic solvent dispersion of these colorants can be prepared using a dispersant. Hereinafter, such a colorant dispersion may be referred to as a “colored particle dispersion”. As the surfactant and the dispersing agent used for dispersion, the same dispersing agents that can be used when dispersing the polyester resin can be used.
The addition amount of the colorant is preferably 1 to 20% by mass, more preferably 1 to 10% by mass, still more preferably 2 to 10% by mass, based on the total amount of the polymer. It is especially preferable to set it as 2-7 mass%.
When the colorant is mixed in the emulsification step, the polymer and the colorant can be mixed by mixing the colorant or the organic solvent dispersion of the colorant with the organic solvent solution of the polymer.

-Aggregation process-
In the aggregation step, the obtained emulsified particles are aggregated by heating at a constant temperature to form an aggregate.
Formation of the aggregate of the emulsified particles is performed by acidifying the pH of the emulsion under stirring. The pH is preferably 2 to 6, more preferably 2.5 to 5, and still more preferably 3 to 4.5. At this time, it is also effective to use a flocculant.
As the flocculant to be used, a surfactant having a reverse polarity to the surfactant used for the dispersant, an inorganic metal salt, and a metal complex having a valence of 2 or more can be preferably used. In particular, the use of a metal complex is particularly preferable because the amount of the surfactant used can be reduced and the charging characteristics are improved.

  Examples of inorganic metal salts include metal salts such as calcium chloride, calcium nitrate, barium chloride, magnesium chloride, zinc chloride, aluminum chloride, and aluminum sulfate, and inorganic substances such as polyaluminum chloride, polyaluminum hydroxide, and calcium polysulfide. Examples thereof include metal salt polymers. Of these, aluminum salts and polymers thereof are particularly preferred. In order to obtain a sharper particle size distribution, the valence of the inorganic metal salt is bivalent than monovalent, trivalent than bivalent, trivalent than trivalent, and tetravalent than trivalent. The inorganic metal salt polymer is more suitable.

-Fusion process-
In the fusion step, under the same stirring as in the aggregation step, the aggregation suspension is stopped by setting the pH of the suspension of the aggregate to a range of 5 to 10, and the melting point or glass transition temperature of the polyester resin or higher is stopped. The aggregates are fused and fused by heating at a temperature of.
The heating time may be performed so that the fusion is sufficiently performed, and may be performed for about 0.5 to 10 hours.
The fused particles obtained by fusing can be made into toner particles through a solid-liquid separation process such as filtration and, if necessary, a washing process and a drying process. In this case, in order to ensure sufficient charging characteristics and reliability as a toner, it is preferable to sufficiently wash in the washing step.
In the drying process, an arbitrary method such as a normal vibration type fluidized drying method, a spray drying method, a freeze drying method, or a flash jet method can be adopted. It is desirable that the toner particles have a moisture content after drying of 1.0% or less, preferably 0.5% or less.

  When core-shell structured particles are produced by attaching an amorphous polyester resin to the core particles prepared by the above-described method, the solid content concentration is preferably 15 to 50%, more preferably 30 to 40%. . If the solid content concentration is less than 15%, the amorphous polyester resin hardly adheres to the core particles, and if the solid content concentration is higher than 50%, the viscosity of the dispersion liquid of the amorphous polyester resin is excessively increased. A great deal of energy is required. The emulsion particle diameter of the amorphous polyester resin is preferably 0.02 μm to 0.2 μm. Preferably, it is 0.04 μm to 0.12 μm. It is preferable that the pH of the liquid at the production of the non-crystalline polyester resin adhered particles is a stable pH of the non-crystalline polyester resin to be used. It is preferable to adjust the pH around emulsification around plus or minus 2.

In order to assist the formation of core-shell structured particles containing an amorphous polyester resin in the shell portion, a coagulant can be used in combination. Specific examples of the flocculant that can be used here are the same as those listed as flocculants that can be used when forming the core particles.
Since the amount of the flocculant used varies depending on the type of flocculant, it is determined in accordance with the flocculant cohesive force. If too much is added, the toner particles will aggregate, and if less, the shell layer tends to peel off. When a metal salt is used as the flocculant, generally, when the valence of the metal salt is large, the cohesive force is strong and the amount of the flocculant is small.
For example, in the case of polyaluminum chloride, the use of about 0.01 to 0.15% with respect to the shell material is appropriate.

The amount of the amorphous polyester resin forming the shell portion varies depending on the core particle diameter, and the amount is adjusted so as to obtain a desired film thickness. When the volume center particle diameter of the core particles is in the range of 3 to 13 μm, 5 to 60% by mass of latex is used. Of course, the particle size of the resin latex is also taken into consideration.
When the amount of the amorphous polyester resin is too small or too large when forming the core-shell structured particles, the core-shell structured particles are difficult to be uniform, or are not partially coated with the amorphous polyester resin. There is a place. On the other hand, if the amount is too large, the thickness of the entire shell layer increases, so that the fixing temperature increases, so that low temperature fixing cannot be achieved.If the diameter of the non-crystalline polyester resin is too small, the aggregation of particles proceeds first. , The uniformity becomes low.
The core-shell structured particles thus obtained are heated at around 50 ° C., and a shell layer is formed by semi-adhering the interface with the core particles and the amorphous polyester resins. Thereafter, the toner particles with the shell layer semi-fused are taken out of the reactor, washed and dried. When drying, it is effective to form the shell layer by slowly dehydrating at a temperature not higher than Tg of the resin forming the shell layer. An oven dryer or a flash jet dryer is effective. If a part of the resin latex is not yet melted even after this drying step, it is also effective to further smooth the uneven surface using mechanical force.
The core-shell structure of the obtained toner particles can be confirmed by observing with a TEM, for example.

  As described above, the electrophotographic toner of the present invention can be produced by an agglomeration process in which an amorphous polyester resin is adhered to core particles to form amorphous polyester resin adhered particles, and an amorphous polyester resin adhered. A melting step of heating the particles to form a shell layer. The toner for electrophotography of the present invention obtained by such a production method has the core-shell structure, that is, the structure whose surface is coated with an amorphous resin layer, so that the storage stability, toner blocking resistance, When it is subjected to stress, the blocking resistance, the image storage stability, and the low-temperature fixing property are excellent.

In the present invention, a chargeable substance may be chemically or physically attached to the surface of the toner particles. Further, fine particles such as metal, metal oxide, metal salt, ceramic, resin, and carbon black may be externally added for the purpose of improving charging property, conductivity, powder fluidity, lubricity and the like.
The volume center particle diameter of the toner particles according to the electrophotographic toner of the present invention is preferably 1 to 20 μm, and more preferably 2 to 8 μm.

  The volume center particle diameter of the toner particles can be determined by measuring with a 50 μm aperture diameter using, for example, a Coulter counter [TA-II] type (manufactured by Coulter). At this time, the measurement is performed after the toner is dispersed in an electrolyte aqueous solution (Isoton aqueous solution) and dispersed by ultrasonic waves for 30 seconds or more.

Here, in order to examine preferable physical property values of the electrophotographic toner of the present invention, this toner was measured from 30 ° C. under a temperature change condition of 1 Hz angular velocity and 2 ° C. per minute at the time of dynamic viscoelasticity measurement. When measuring the storage elastic modulus G ′ during the heating process up to 130 ° C.,
The storage elastic modulus G ′ at 30 ° C. is 10 ⁷ [Pa] or more and 10 ⁹ [Pa] or less,
The ratio tan δ of the loss elastic modulus G ″ and storage elastic modulus G ′ at 30 ° C. is 0.2 or more and 0.7 or less,
(sometimes referred to hereinafter crosspoint.) tanδ = 1 and becomes temperatures it is desirable satisfies for all those less 80 ° C. or higher 50 ° C..
Each condition will be briefly described below.

In order to ensure the image strength at room temperature, the storage elastic modulus of the toner at 30 ° C. is desirably 10 ⁷ [Pa] or more. When the pressure is less than 10 ⁷ [Pa], the image is easily damaged by stress.

The tan δ at room temperature is considered to represent the ratio of the amount of domains in the crystalline state to the domain in the amorphous state in the crystalline resin. When a crystalline resin having a glass transition point of room temperature or less is used, the domain in the amorphous state is viscous-dominant, and thus contributes to the loss elastic modulus G ″, whereas the domain in the crystalline state is crystalline elastic. Therefore, it is considered that it contributes to the storage elastic modulus G ′.
At this time, when tan δ is less than 0.2, since the ratio of the crystalline domain is too large, when the image is stressed, the crystal plane slips easily in the domain, and the image strength becomes weak. This occurs, or there is a problem that the low temperature fixability cannot be ensured because the amount of the crystalline resin itself is small.
On the other hand, when tan δ exceeds 0.7, the amount of the domain in the amorphous state is too large, so that the viscosity of the whole toner becomes high, causing a problem in storage at room temperature. Further, since the sharp melt property of the crystalline resin is lost, the low temperature fixability cannot be ensured.

Above the temperature at which tan δ = 1, the toner becomes dominant in viscosity, causing a problem in storage. Since the maximum temperature during toner conveyance may be about 50 ° C. depending on the season, the temperature at which tan δ = 1 is preferably 50 ° C. or higher in order to ensure storage stability during conveyance. In order to fix the toner, it is desirable that the viscosity is dominated by the fixing temperature. Therefore, the temperature at which tan δ = 1 is preferably 80 ° C. or less. If the temperature is higher than that, low-temperature fixing becomes difficult.
Here, the rheometer was used for the viscoelasticity measurement, and the temperature was raised from 30 ° C. to 130 ° C. at a temperature raising rate of 2 ° C./min under the condition of a frequency of 1 Hz.

[Electrophotographic developer]
The electrophotographic developer of the present invention contains at least the electrophotographic toner of the present invention. The electrophotographic toner of the present invention can be used as it is as a one-component developer. Further, it can be used as a toner in a two-component developer comprising a carrier and a toner. Hereinafter, the two-component developer will be described.
The carrier that can be used in the two-component developer is not particularly limited, and a known carrier can be used. For example, a resin-coated carrier having a resin coating layer on the surface of the core material can be exemplified. Further, a resin dispersion type carrier in which a conductive material or the like is dispersed in a matrix resin may be used.

  Coating resins and matrix resins used for carriers include polyethylene, polypropylene, polystyrene, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl ether, polyvinyl ketone, vinyl chloride-vinyl acetate copolymer, styrene-acrylic. Examples thereof include, but are not limited to, acid copolymers, straight silicone resins composed of organosiloxane bonds or modified products thereof, fluororesins, polyesters, polycarbonates, phenol resins, epoxy resins and the like.

Examples of the conductive material include metals such as gold, silver and copper, carbon black, titanium oxide, zinc oxide, barium sulfate, aluminum borate, potassium titanate, tin oxide, and carbon black. It is not limited.
Examples of the core material of the carrier include magnetic metals such as iron, nickel, and cobalt, magnetic oxides such as ferrite and magnetite, and glass beads. It is preferable.
The volume center particle diameter of the carrier core material is generally 10 to 500 μm, preferably 30 to 100 μm.

In order to coat the surface of the core material of the carrier with a resin, there may be mentioned a method of coating with a coating layer forming solution in which the coating resin and, if necessary, various additives are dissolved in an appropriate solvent. The solvent is not particularly limited and may be appropriately selected in consideration of the coating resin to be used, coating suitability, and the like.
Specific resin coating methods include an immersion method in which the carrier core material is immersed in the coating layer forming solution, a spray method in which the coating layer forming solution is sprayed onto the surface of the carrier core material, and the carrier core material is fluidized air. And a kneader coater method in which the carrier core material and the coating layer forming solution are mixed in a kneader coater and the solvent is removed in a kneader coater.

  The mixing ratio (mass ratio) of the electrophotographic toner of the present invention and the carrier in the two-component developer is preferably in the range of toner: carrier = 1: 100-30: 100, 3: 100-20: 100. A range of the degree is more preferable.

The image forming method of the present invention includes a step of forming an electrostatic latent image on an image latent image holding member, and the electrostatic latent image on the sleeve having a sleeve peripheral speed of 250 mm / sec to 500 mm / sec. A step of forming and developing a toner image by carrying the developer for electrophotography of the invention, a step of transferring the toner image formed on the image latent image holding member onto the transfer member, and a toner on the transfer member And a step of heat-fixing the image.
The electrophotographic developer of the present invention used in the image forming method of the present invention is preferably a two-component system.

For each of the above steps, any known step can be used in the image forming method except that the sleeve peripheral speed of the developing device is maintained within this range. When the sleeve peripheral speed of the developing device is 250 mm / sec to 500 mm / sec, more preferably when the peripheral speed is 350 to 500 mm / sec, compared to the case where a known electrophotographic developer is used, Generation of image defects and fog due to toner blocking is effectively suppressed, and a high-quality image can be formed.
As described in detail above, the toner for electrophotography of the present invention has a core-shell structure and uses an amorphous polyester resin for the shell portion, so that it has thermal stability and anti-blocking during storage. Because it has excellent anti-blocking properties and resistance to stress in the image forming device, the sleeve peripheral speed of the fixing device is high, and even in an environment where blocking due to stress and frictional heat is likely to occur, blocking is effectively generated. It can be said that the effect of the present invention is remarkable when used in such a severe environment because of being suppressed.

A well-known image forming apparatus can be applied as it is. However, as described above, the sleeve peripheral speed of the developing device can be suitably applied to a peripheral speed higher than that of a general apparatus.
As the latent image holding member, for example, an electrophotographic photosensitive member and a dielectric recording member can be used.
In the case of an electrophotographic photosensitive member, the surface of the electrophotographic photosensitive member is uniformly charged by a corotron charger, a contact charger or the like and then exposed to form an electrostatic latent image (latent image forming step). Next, the toner particles are adhered to the electrostatic latent image in contact with or in proximity to a developing roll having a developer layer formed on the surface, thereby forming a toner image on the electrophotographic photosensitive member (developing step). The formed toner image is transferred onto the surface of a transfer medium such as paper using a corotron charger or the like (transfer process). Further, the toner image transferred to the surface of the transfer target is heat-fixed by a fixing device, and a final toner image is formed.
In order to prevent offset or the like during heat fixing by the fixing machine, a release agent is usually supplied to a fixing member in the fixing machine, but when a release agent is contained in the toner, It is not necessary to supply a release agent in the fixing machine.
In the image forming method of the present invention, since the electrophotographic toner of the present invention is used, even when a developing device having a high sleeve peripheral speed that is likely to cause image defects or fogging due to toner blocking is used, it is possible to obtain high quality. An image can be formed stably.

EXAMPLES Hereinafter, although an Example demonstrates this invention, this invention is not limited to these Examples.
(Production of resin latex)
40 parts of each of the polyester resins (A1 to A3, B1 to B6) shown in Table 1 and Table 2 are added to 360 parts of ion exchange water, heated to 96 ° C., adjusted to pH = 9 with 5% ammonia water, 10 A polyester resin latex (A1Ltx to A3Ltx, B1Ltx to B6Ltx) was prepared using Ultra Turrax T-50 (manufactured by IKA) while adding 0.8 part of a% dodecylbenzenesulfonic acid aqueous solution and stirring at 8000 rpm.

(Preparation of release agent dispersion C-1)
The following composition was mixed, heated to 97 ° C., and then dispersed with IKA Ultra Turrax T50. Then, it was dispersed with a gorin homogenizer (manufactured by Matsuzaka Trading Co., Ltd.) and treated 20 times under the conditions of 105 ° C. and 550 kg / cm ² to obtain a release agent dispersion C-1 having a center diameter of 190 nm.
・ Polywax (trade name: WEP-2 (manufactured by NOF Corporation)) 100 parts ・ Anionic surfactant Neogen SC 5 parts ・ Ion-exchanged water 230 parts

(Preparation of blue pigment dispersion D-1)
The following composition was mixed and dissolved, and dispersed by homogenizer (IKA Ultra Tarrax) and ultrasonic irradiation to obtain a blue pigment dispersion B-1 having a central particle size of 150 nm.
・ Cyan pigment PB15: 3 (Copper phthalocyanine manufactured by Dainippon Ink) 50 parts ・ Anionic surfactant Neogen SC 5 parts ・ Ion-exchanged water 200 parts

[Production of core particles]
(Preparation of core particle (1))
The following composition was mixed and dispersed with Ultra Turrax T50 in a round stainless steel flask, and then the contents in the flask were heated to 55 ° C. with stirring in an oil bath for heating and held at 55 ° C. for 1 hour.
-Crystalline polyester resin latex (A1Ltx) 1000 parts-Anionic surfactant 8 parts-Pigment dispersion B-1 25 parts-Release agent dispersion C-1 40 parts-Calcium chloride 10 mass% aqueous solution 10 parts

  Then, when the obtained content was observed with an optical microscope, it was confirmed that about 4.5 μm aggregated particles were generated. Further, the temperature of the heating oil bath was raised and held at 60 ° C. for 20 minutes. When the obtained contents were observed with an optical microscope, it was confirmed that aggregated particles of about 6.5 μm were formed. Adjust the pH to 8.0 with an aqueous sodium hydroxide solution, then raise the temperature of the heating oil bath to 75 ° C., cool, filter, wash thoroughly with ion-exchanged water, concentrate, and concentrate to a solid content of 40 % Core particle suspension (1) was obtained. When the particle size of the core particles was measured with a Coulter counter, the volume center particle size was 6.8 μm.

(Preparation of core particle (2))
The following composition was mixed and dispersed in a round stainless steel flask using Ultra Turrax T50, and then the contents in the flask were heated to 55 ° C. with stirring in an oil bath for heating and held at 55 ° C. for 1 hour.
-Crystalline polyester resin latex (A2Ltx) 500 parts-Amorphous polyester resin latex (B5Ltx) 500 parts-Anionic surfactant 8 parts-Pigment dispersion B-1 25 parts-Release agent dispersion C-1 40 parts・ 10 parts by weight of calcium chloride 10 parts

  Then, when the obtained content was observed with an optical microscope, it was confirmed that about 4.5 μm aggregated particles were generated. Further, the temperature of the heating oil bath was raised and held at 60 ° C. for 20 minutes. When the obtained contents were observed with an optical microscope, it was confirmed that aggregated particles of about 6.5 μm were formed. Adjust the pH to 8.0 with an aqueous sodium hydroxide solution, then raise the temperature of the heating oil bath to 75 ° C., cool, filter, wash thoroughly with ion-exchanged water, concentrate, and concentrate to a solid content of 40 % Core particle suspension (1) was obtained. When the particle size of the core particles was measured with a Coulter counter, the volume center particle size was 7.0 μm.

(Preparation of core particle (3))
The following composition was mixed and dispersed in a round stainless steel flask with Ultra Turrax T50, and then the contents in the flask were heated to 55 ° C. with stirring in an oil bath for heating and held at 55 ° C. for 1 hour.
-Crystalline polyester resin latex (A3Ltx) 500 parts-Non-crystalline polyester resin latex (B6Ltx) 500 parts-Anionic surfactant 8 parts-Pigment dispersion B-1 25 parts-Release agent dispersion C-1 40 parts・ 10 parts by weight of calcium chloride 10 parts

  Then, when the obtained content was observed with an optical microscope, it was confirmed that about 4.5 μm aggregated particles were generated. Further, the temperature of the heating oil bath was raised and held at 60 ° C. for 20 minutes. When the obtained contents were observed with an optical microscope, it was confirmed that aggregated particles of about 6.5 μm were formed. Adjust the pH to 8.0 with an aqueous sodium hydroxide solution, then raise the temperature of the heating oil bath to 75 ° C., cool, filter, wash thoroughly with ion-exchanged water, concentrate, and concentrate to a solid content of 40 % Core particle suspension (1) was obtained. When the particle size of the core particles was measured with a Coulter counter, the volume center particle size was 7.2 μm.

(Preparation of core particle (4))
The following composition was mixed and dispersed with Ultra Turrax T50 in a round stainless steel flask, and then the contents in the flask were heated to 55 ° C. with stirring in an oil bath for heating and held at 55 ° C. for 1 hour.
-Crystalline polyester resin latex (A3Ltx) 500 parts-Amorphous polyester resin latex (B1Ltx) 500 parts-Anionic surfactant 8 parts-Pigment dispersion B-1 25 parts-Release agent dispersion C-1 40 parts・ 10 parts by weight of calcium chloride 10 parts

  Then, when the obtained content was observed with an optical microscope, it was confirmed that about 4.5 μm aggregated particles were generated. Further, the temperature of the heating oil bath was raised and held at 60 ° C. for 20 minutes. When the obtained contents were observed with an optical microscope, it was confirmed that aggregated particles of about 6.5 μm were formed. Adjust the pH to 8.0 with an aqueous sodium hydroxide solution, then raise the temperature of the heating oil bath to 75 ° C., cool, filter, wash thoroughly with ion-exchanged water, concentrate, and concentrate to a solid content of 40 % Core particle suspension (1) was obtained. When the particle size of the core particles was measured with a Coulter counter, the volume center particle size was 7.2 μm.

(Preparation of core particle (5))
The following composition was mixed and dispersed with Ultra Turrax T50 in a round stainless steel flask, and then the contents in the flask were heated to 55 ° C. with stirring in an oil bath for heating and held at 55 ° C. for 1 hour.
-Crystalline polyester resin latex (A3Ltx) 1000 parts-Anionic surfactant 8 parts-Pigment dispersion B-1 25 parts-Release agent dispersion C-1 40 parts-10% by weight calcium chloride aqueous solution 10 parts

  Then, when the obtained content was observed with an optical microscope, it was confirmed that about 4.5 μm aggregated particles were generated. Further, the temperature of the heating oil bath was raised and held at 60 ° C. for 20 minutes. When the obtained contents were observed with an optical microscope, it was confirmed that aggregated particles of about 6.5 μm were formed. Adjust the pH to 8.0 with an aqueous sodium hydroxide solution, then raise the temperature of the heating oil bath to 75 ° C., cool, filter, wash thoroughly with ion-exchanged water, concentrate, and concentrate to a solid content of 40 % Core particle suspension (1) was obtained. When the particle size of the core particles was measured with a Coulter counter, the volume center particle size was 6.9 μm.

[Preparation of toner for electrophotography]
(Preparation of toner for electrophotography (1))
To 125 parts of the core particle suspension (1), 100 parts of an amorphous polyester resin latex (B1Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. And stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (1). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.0 μm.
After 100 parts of the above toner particles (1) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (1).

(Preparation of toner for electrophotography (2))
To 125 parts of the core particle suspension (2), 100 parts of an amorphous polyester resin latex (B1Ltx) is added under stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (2). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.2 μm.
After 100 parts of the toner particles (2) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive for 30 minutes at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, The coarse particles were removed using a toner to obtain an electrophotographic toner (2).

(Preparation of toner for electrophotography (3))
To 125 parts of the core particle suspension (3), 100 parts of an amorphous polyester resin latex (B1Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (3). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.5 μm.
After 100 parts of the toner particles (3) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (3).

(Preparation of toner for electrophotography (4))
To 125 parts of the core particle suspension (1), 100 parts of an amorphous polyester resin latex (B2Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (4). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 6.9 μm.
After 100 parts of the above toner particles (4) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (4).

(Preparation of toner for electrophotography (5))
To 125 parts of the core particle suspension (2), 100 parts of an amorphous polyester resin latex (B2Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (5). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.5 μm.
After 100 parts of the above toner particles (5) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (5).

(Preparation of toner for electrophotography (6))
To 125 parts of the core particle suspension (3), 100 parts of an amorphous polyester resin latex (B2Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (6). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.4 μm.
After 100 parts of the toner particles (6) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having a 45 μm aperture was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (6).

(Preparation of toner for electrophotography (7))
To 125 parts of the core particle suspension (1), 100 parts of an amorphous polyester resin latex (B3Ltx) is added with stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (7). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.2 μm.
After 100 parts of the toner particles (7) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having a 45 μm aperture was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (7).

(Preparation of toner for electrophotography (8))
To 125 parts of the core particle suspension (2), 100 parts of an amorphous polyester resin latex (B3Ltx) is added under stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (7). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.2 μm.
After 100 parts of the above toner particles (8) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive at a peripheral speed of 30 m / s × 15 minutes using a Henschel mixer, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (8).

(Preparation of toner for electrophotography (9))
To 125 parts of the core particle suspension (3), 100 parts of an amorphous polyester resin latex (B3Ltx) is added under stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (9). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.6 μm.
After 100 parts of the toner particles (9) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (9).

(Preparation of toner for electrophotography (10))
To 125 parts of the core particle suspension (1), 100 parts of an amorphous polyester resin latex (B6Ltx) is added under stirring, the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (10). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.2 μm.
After 100 parts of the toner particles (10) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having a 45 μm aperture was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (10).

(Preparation of electrophotographic toner (11))
While stirring, 125 parts of a non-crystalline polyester resin latex (B6Ltx) is added to 125 parts of the core particle suspension (4), the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (11). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.3 μm.
After 100 parts of the above toner particles (11) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having an opening of 45 μm was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (11).

(Preparation of toner for electrophotography (12))
While stirring, 125 parts of amorphous polyester resin latex (B4Ltx) is added to 125 parts of the core particle suspension (4), the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (7). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.3 μm.
After 100 parts of the toner particles (7) and 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) were blended with an external additive using a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having a 45 μm aperture was obtained. The coarse particles were removed using a toner to obtain an electrophotographic toner (7).

(Preparation of toner for electrophotography (13))
While stirring, 125 parts of a non-crystalline polyester resin latex (B5Ltx) is added to 125 parts of the core particle suspension (5), the pH is adjusted to 2.5, and 0.75 part of a 10% polyaluminum chloride aqueous solution is added dropwise. The stirring was continued for 30 minutes. The suspension was then warmed to 55 ° C. and stirred for an additional 3 hours. The obtained toner particles were filtered, and the wet cake was dried using a freeze dryer to obtain toner particles (13). When the particle size of the toner was measured with a Coulter counter, the volume center particle size was 7.2 μm.
After blending 100 parts of the above toner particles (13) with 1 part of silica fine particles (RX-200: manufactured by Nippon Aerosil Co., Ltd.) with a Henschel mixer at a peripheral speed of 30 m / s × 15 minutes, a sieve having an opening of 45 μm The coarse particles were removed using a toner to obtain an electrophotographic toner (13).

[Production of carrier]
(Production of carrier (1))
Trifunctional isocyanate 80 wt% ethyl acetate in a carbon dispersion obtained by mixing 1.25 parts by weight of toluene with 0.12 part by weight of carbon black (trade name; VXC-72, manufactured by Cabot) and stirring and dispersing in a sand mill for 20 minutes. A coating agent resin solution obtained by mixing and stirring 1.25 parts by weight of a solution (Takenate D110N: manufactured by Takeda Pharmaceutical Co., Ltd.) and Mn—Mg—Sr ferrite particles (average particle size: 35 μm) were put into a kneader, and at room temperature for 5 minutes. After mixing and stirring, the temperature was raised to 150 ° C. at normal pressure, and the solvent was distilled off. After further 30 minutes of mixing and stirring, the heater was turned off and the temperature was lowered to 50 ° C. The obtained coated carrier was sieved with a 75 μm mesh to prepare a carrier.

[Preparation of developer for electrophotography]
(Preparation of electrophotographic developers (1) to (13))
After 5 parts by weight of each of the electrophotographic toners (1) to (13) and 95 parts by weight of the carrier (1) obtained as described above were placed in a V blender and stirred for 20 minutes, they were sieved with a 105 μm mesh, Photographic developers (1) to (13) were prepared.

[Evaluation of toner for electrophotography and developer]
(Evaluation of minimum fixing temperature)
The obtained electrophotographic toners (1) to (13) were formed on a copy paper (J paper) manufactured by Fuji Xerox so as to have a toner amount of 1.3 mg / cm ^2. An image was fixed using a fixing device modified from Xerox Co., Ltd. so that the temperature can be freely controlled, and the low-temperature fixing property was evaluated. In the evaluation, the fixing device temperature was changed from 80 ° C. to 150 ° C. at every 10 ° C., and a fixed image was prepared at each fixing temperature. The degree of peeling of the image was observed, and the width of the paper that appeared at the crease as a result of peeling the image was measured. The fixing temperature at which the width was 0.5 mm or less was defined as MFT (minimum fixing temperature, ° C.).

(Measurement of viscoelasticity of toner)
Using a rheometer (Rheometric Scientific Co., Ltd .: ARES rheometer), a temperature rise measurement was performed under the condition of a frequency of 1 Hz using a parallel plate. The sample set was performed at a temperature 10 to 20 ° C. higher than the melting point of the crystalline resin contained in the binder resin, cooled to 30 ° C., and then allowed to stand at 30 ° C. for 30 minutes for a cooling period. Heat at a rate of temperature increase of 2 ° C / min, measure the dynamic complex modulus at 30 ° C to 130 ° C every 1 ° C and increase the dynamic complex modulus at strain of 0.1% at 30 ° C. Obtained.

(Evaluation of storage stability)
400 g of the obtained electrophotographic toners (1) to (13) are filled in a toner cartridge of the dough center color 500, stored in an environment of 55 ° C. for 72 hours, and then loaded into the dough center color 500, continuously 500 sheets. The image was evaluated and image defects (streaks on the image) were evaluated.

(Evaluation of density maintenance and background fog)
Using the obtained electrophotographic developers (1) to (13), a dough center collar 500 was used to print out 100,000 sheets at a sleeve peripheral speed of 450 mm / sec. The difference between the average density up to 9991 and the average density of the 99999th sheet to the 100,000th sheet) and the fogging of the background portion were evaluated. The density measurement was performed using a Macbeth densitometer, and the background fog was visually evaluated from the following viewpoints.
○: No visual problem △: There is some fogging on the background, but acceptable for practical use ×: The background is stained blue, practically unacceptable

[Examples 1 to 6 and Reference Examples 1 to 3 ]
Using the electrophotographic toners (1) to (9) and the electrophotographic developers (1) to (9), evaluation of the minimum fixing temperature, evaluation of toner viscoelasticity, evaluation of storage stability, in the developing device The stability evaluation, density maintenance, and background fogging were evaluated.
[Comparative Examples 1-4]
Using electrophotographic toners (10) to (13) and electrophotographic developers (10) to (13), evaluation of minimum fixing temperature, evaluation of toner viscoelasticity, evaluation of storage stability, in developing unit The stability evaluation, density maintenance, and background fogging were evaluated.
Table 3 shows the evaluation results of Examples , Reference Examples and Comparative Examples.

  From these results, when the toner of the present invention is used, it has excellent low-temperature fixability, excellent blocking resistance during storage, excellent blocking resistance against stress in the image forming apparatus, maintains image density, and covers the background area. An electrophotographic toner capable of stably providing a uniform image can be provided.

Claims (3)

Colorant ,
Contained in the binder resin constituting the electrophotographic toner in the range of 10 to 35% by mass, from 30 ° C. to 130 ° C. under the temperature change condition of 1 ° C. and 2 ° C./min during dynamic viscoelasticity measurement. The storage elastic modulus G ′ at 30 ° C. is 10 ⁷ [Pa] or more and 10 ⁹ [Pa] or less when the storage elastic modulus G ′ in the temperature rising process is measured , and the loss elastic modulus G ″ at 30 ° C. The ratio tan δ of the storage elastic modulus G ′ is 0.2 or more and 0.7 or less, the temperature at which tan δ = 1 is 50 ° C. or more and 80 ° C. or less, and the solubility parameter is 9.00 to 9.57. A crystalline polyester resin , and
A core containing an amorphous polyester resin having a glass transition temperature of 50 ° C. to 80 ° C . ;
An electrophotographic toner having a shell made of an amorphous resin covering the surface of the core,
An electrophotographic toner, wherein the amorphous resin covering the core surface is a polyester resin having a glass transition temperature of 60 ° C. or higher and a solubility parameter of 10.1 or higher. An electrostatic image developer containing a carrier and a toner, wherein the electrophotographic toner according to claim 1 is used as the toner. Forming an electrostatic latent image on the image latent image holding member;
A step of carrying the electrophotographic developer according to claim 2 on a sleeve having a sleeve peripheral speed of 250 mm / sec to 500 mm / sec and developing the electrostatic latent image to form a toner image;
Transferring the toner image formed on the image latent image holding member onto the transfer target;
And a step of thermally fixing the toner image on the transfer target.