JPH0772660A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To provide an electrophotographic toner having both releasability and low temperature fixation properties to prevent the winding around the fixing roller and the hot off-set of the toner from occurring. CONSTITUTION:In this toner, the crosslinked structure of the binder in the surface layer of the toner is different from that in the inner layer of the toner and the crosslink density in the surface layer of the toner is higher than that in the inner layer of the toner. This toner preferably consists of polymer particles obtained by subjecting a vinyl monomer to dispersion polymerization and thereafter dyeing the resulting polymer. The polymeric materials in the surface layer and inner layer of the toner are desirably crosslinked by the diacrylate compound represented by the formula: CH2=CR<2>COO-(R<1>)-OOCCR<2>= CH2, wherein R<1> is a specified group and R<2> is hydrogen or an alkyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

[0002]

2. Description of the Related Art The developing method of an electrostatic latent image formed on an electrophotographic photosensitive member or electrostatic recording material is a coloring agent such as a dye or a pigment in a binder resin or a charge control agent. A one-component type or two-component type dry developing method in which a toner in which is dispersed alone or mixed with a solid carrier is widely used. Although there are various fixing methods of toner used for developing these electrostatic latent images, the heat roller method is widely adopted because of its high thermal efficiency and high-speed fixing. When high-speed fixing is carried out by this method, the toner is required to have good low-temperature fixing property (low fixing lower limit temperature). However, if a low softening point resin is added to the binder resin in order to satisfy such requirements,
At the time of fixing, a part of the toner image adheres to the surface of the heat roller, which transfers to the copy paper and causes scumming, a so-called hot offset phenomenon, or a phenomenon in which the copy paper adheres to the surface of the heat roller and winds up ( When the temperature of the heat roller is low, it frequently occurs). In particular, with a binder resin using a vinyl-based monomer such as styrene-acrylic resin, it is extremely difficult to achieve both releasability and low-temperature fixability to prevent winding around a fixing roller and hot offset.

As a means for preventing these phenomena from the viewpoint of toner design, JP-A-51-143333 discloses.
No. 57-148752, No. 58-97056, No. 6
In each publication such as 0-247250, it is proposed to add solid silicone varnish for a release agent, higher fatty acid, higher alcohol, various waxes, etc. to the toner. However, there is no known one showing sufficient hot offset resistance and wrapping resistance while maintaining good low temperature fixability. For example, polyolefin waxes such as low-molecular-weight polyethylene and low-molecular-weight polypropylene have good hot offset resistance but insufficient low-temperature fixability, and plant waxes such as carnauba wax and candelilla wax are
Good hot offset resistance and low temperature fixability, but insufficient winding resistance. Also, solid silicone varnish,
Solid silicone oil, amide wax, higher fatty acid,
Higher alcohols, montan wax, etc. exhibit good low-temperature fixability, but their hot offset resistance and winding resistance are not sufficient.

In addition to the above, conventional release materials often have a so-called filming or a phenomenon in which the release agent is released from the toner during development and adheres to the photoreceptor or carrier, and is stable and of good quality for a long time. It was difficult to form an image. Therefore, recently, a method of kneading / dispersing a resin having excellent releasability such as polyester or polypropylene has been studied to solve the above problem, but it is still not sufficient. Further, Japanese Patent Application Laid-Open No. 4-50859 proposes a method of fixing and embedding silicone resin fine particles to achieve both low temperature fixing and releasability. In this method, the silicone resin fine particles are fixed to the surface of the toner particles. There is a drawback that it requires a work for burying and a device therefor, which takes time and cost. Therefore, investigations are being made from the aspect of the fixing device, and a method of applying silicone oil to the fixing roller as a release agent has been proposed. However, this method has a problem that an oil tank is required, which is contrary to the recent trend of space saving, and also has a problem that an odor peculiar to silicone oil is generated.

Recent toners aiming at high image quality are required to have a small particle size, a narrow particle size distribution, and an even dispersion of a charge control agent. Therefore, it has been proposed to manufacture by suspension polymerization that does not require a pulverization step, and by this method polymer particles containing a color pigment and a charge control agent can be directly obtained, but a small particle size product having a narrow particle size distribution can be stably prepared. A classification step is required because it is difficult to manufacture. In addition, a dispersion polymerization method has been proposed in which the monomer is dissolved but the obtained polymer is not soluble in the solvent to polymerize the monomer to form particles. In this method, a classification step is unnecessary and the particle size distribution is narrow. A product with a small particle size can be stably obtained. In the toner by dispersion polymerization method,
It is difficult to incorporate the resin added by the pulverization and kneading method in the polymerization step, but it is possible to attach it to the particle surface.
As described above, since a method for producing toner particles having good releasability only by the polymerization step has not been well established, it is difficult to obtain toner particles having both releasability and low temperature fixability only by the polymerization step. . That is, when the thermal characteristics of the toner for low-temperature fixing are lowered, hot offset tends to occur, while when a resin composition that eliminates hot offset is used, low-temperature fixing becomes difficult. Therefore, there is a trade-off between hot offset prevention and low temperature fixability, and it is quite difficult to solve this problem.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a toner which has both low releasability and releasability for preventing winding around a fixing roller or hot offset.

[0007]

In order to solve the above problems, the inventors of the present invention have earnestly studied, and as a result, individual toner particles have a multi-layered structure to impart low temperature fixability to the inside of the toner particles. It has been found that in the toner surface layer, the internal cohesive force of the binder resin is enhanced to improve the releasability, and hot offset and winding around the fixing roller can be suppressed. That is, according to the present invention, in the electrophotographic toner comprising at least a binder and a colorant, there is a difference in the cross-linking structure of the binder between the toner surface layer and the inner layer, and the cross-linking density of the toner surface layer is An electrophotographic toner is provided that is higher than that of the toner inner layer. Further, according to the present invention, the electrophotographic toner is a polymer particle toner obtained by dispersing and granulating one or more vinyl monomers for dispersion and granulating, and then dyeing the polymer particle toner. Toner is provided.

Further, according to the present invention, there is provided an electrophotographic toner in which the surface layer of the electrophotographic toner is crosslinked using a vinyl monomer represented by the following general formula (I). To be done. ^{_{CH 2 = CR 2 COO- (R}} 1) -OOCCR 2 = CH 2 ............ (I) wherein, - (R ¹⁾ -, the groups shown in the following (a) (d) R ² represents a hydrogen atom or an alkyl group.

[Chemical 1]

The present invention provides a classification type toner in which colored particles obtained by kneading and pulverizing or suspension polymerization are classified, or polymer particles granulated by dispersion polymerization are not classified after dyeing The present invention is applied to a dispersion polymerization type toner that can obtain a toner having a narrow distribution. The latter is particularly preferable for the electrophotographic toner of the present invention, and the toner dyes the polymer particles obtained from the seed particle production step by dispersion polymerization, the growth particle production step, the particle surface cross-linking structure imparting step and the above step. It is manufactured by a method comprising the steps of: The toner according to the present invention has a narrow particle size distribution, and uses a Coulter Multisizer (manufactured by Coulter Electronics Co., Ltd.) with an aperture tube of 100 μm, and has a volume at a count value of 30,000 or more when the aperture current and the like are automatically measured. Average particle size (dv) and number average particle size (d
The ratio n) has a particle size distribution in the range of 1.00 ≦ dv / dn ≦ 1.15, and this ratio is preferably 1.10 or less. This ratio serves as an index of the particle size distribution. If the ratio is large, the particle size distribution will be broad and the particles will not be colored uniformly. In addition, the particle diameter is such that the dv is 1 to 20 μm.
The toner having a particle size of 10 μm or less is most suitable for high-resolution image reproduction.

The dispersion polymerization step is carried out in a hydrophilic organic liquid in which a polymer dispersant is dissolved, and the resulting polymer is a substance which may be swollen in the solution but hardly dissolved, and is soluble in the solution. This is a step of forming resin particles using one or more vinyl monomers as raw materials. The step also includes a reaction of growing polymer seed particles having a particle size smaller than the intended particle size and a narrow particle size distribution. The monomer used for the growth reaction may be the same as or different from the one used in the production of seed particles. Examples of the hydrophilic organic liquid include methanol, ethanol, modified ethanol, isopropanol, n-butanol, isobutanol, t-butanol, s-butanol, t-amyl alcohol, 3-pentanol, octanol, benzyl alcohol, cyclohexanol. ,
Alcohols such as furfuryl alcohol, tetrahydrofurfuryl alcohol, ethylene glycol, glycerin, and diethylene glycol; methyl cellosolve, cellosolve, isopropyl cellosolve, butyl cellosolve, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, dieethylene. Examples thereof include ether alcohols such as glycol monoethyl ether.

These organic liquids may be used alone or as a mixture of two or more kinds. In addition, the solubility coefficient (SP value) is changed by adding an organic liquid other than the above to the organic liquid within a range in which the produced polymer particles are not dissolved even when used in combination with the alcohols or ether alcohols, and thereby polymerization is performed. It is possible to control the size of particles generated by changing the conditions, and to suppress the bonding between particles and the generation of new particles. Examples of the organic liquid used in combination therewith include hydrocarbons such as hexane, octane, petroleum ether, cyclohexane, benzene, toluene and xylene; halogenated hydrocarbons such as carbon tetrachloride, trichloroethylene and tetrabromoethane; ethyl ether, Ethers such as dimethyl glycol, trioxane and tetrahydrofuran; methylal,
Acetals such as diethyl acetal; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as butyl formate, butyl acetate, ethyl propionate, and cellosolve acetate;
Acids such as formic acid, acetic acid and propionic acid; nitropropene,
Organic compounds containing sulfur and nitrogen such as nitrobenzene, dimethylamine, monoethanolamine, pyridine, dimethylsulfoxide, and dimethylformamide; others are included.

In the solvent mainly composed of the hydrophilic organic liquid described above in detail, the polymerization reaction may be carried out in the presence of inorganic ions such as the following ions and a small amount of water.

[Chemical 2] Further, the average particle size and particle size distribution of the produced polymer particles can be controlled by changing the type and composition of the polymerization solvent at the start of polymerization, during the polymerization, and at the end of polymerization. The polymer dispersant added during the production of seed particles or grown particles has a molecular weight of 10,000 or more and a relatively long molecular chain in order to increase the steric repulsion between particles and prevent the formation of bonds between particles. What can be adsorbed on the surface of resin particles produced by being dissolved in a hydrophilic organic liquid is used. Examples of such a polymer dispersant include homopolymers or copolymers of the hydrophilic monomers shown in (A) below, polymers shown in (B) and monomers shown in (C). Examples thereof include a copolymer of a monomer and the hydrophilic monomer.

(A) Monomers used as raw materials for polymer dispersant Acrylic acid, methacrylic acid, α-cyanoacrylic acid, α
-Unsaturated fatty acids such as cyanomethacrylic acid, itaconic acid, crotonic acid, fumaric acid, maleic acid, maleic anhydride; acrylic acid-β-hydroxyethyl, methacrylic acid-β-hydroxyethyl, acrylic acid-β-hydroxypropyl , Methacrylic acid-β-hydroxypropyl, acrylic acid-γ-hydroxypropyl, methacrylic acid-γ
-Hydroxypropyl, acrylic acid-3-chloro-2-
Hydroxypropyl, methacrylic acid-3-chloro-2-
Hydroxypropyl, diethylene glycol monoacrylic acid ester, diethylene glycol monomethacrylic acid ester, glycerin monomethacrylic acid ester, glycerin monomethacrylic acid ester, N-methylol acrylamide, N-methylol methacrylamide, and other hydroxyl group-containing acrylic monomers; vinyl methyl ether Vinyl ethers such as vinyl acetate, vinyl ethyl ether and vinyl propyl ether; vinyl esters such as vinyl acetate, vinyl propionate and vinyl butyrate; unsaturated acid amides such as acrylamide, methacrylamide, diacetone acrylamide and their methylol compounds; acrylic Unsaturated acid chlorides such as acid chloride and methacrylic acid chloride; vinylpyridine, vinylpyrrolidone, vinylimidazole, ethyleneimid Nitrogen-containing polymerizable compounds such as; Other.

(B) Polymer Used as Polymer Dispersant Polyoxyethylene, polyoxypropylene, polyoxyethylene alkylamine, polyoxypropylene alkylamine, polyoxyethylene alkylamide, polyoxypropylene alkylamide, polyoxy Polyoxyethylenes such as ethylene nonyl phenyl ether, polyoxyethylene lauryl phenyl ether and polyoxyethylene stearyl phenyl ether; celluloses such as methyl cellulose, hydroxyethyl cellulose and hydroxypropyl cellulose; and others. (C) A monomer which becomes a polymer dispersant by copolymerizing with the compound described in (A). Aromatic hydrocarbons having vinyl groups such as styrene, α-methylstyrene and vinyltoluene or derivatives thereof; acrylic monomers such as acrylonitrile, methacrylonitrile and acrylamide; ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, allyl methacrylate , Crosslinkable monomers such as divinylbenzene; others.

These polymer dispersants are appropriately selected according to the kind of hydrophilic organic liquid used, the kind of intended polymer particles and the purpose of production (production of seeds or grown particles). In order to prevent the binding of the above, it is desirable that the polymer particles have high affinity and adsorption property to the surface of the polymer particles and high affinity and solubility property to the hydrophilic organic liquid. Further, as described above, the molecular weight of the dispersant is preferably 10,000 or more, but when the molecular weight is too large, the liquid viscosity increases and the operability and agitability deteriorate, and therefore the dispersant on the surface of the polymer particles is generated. Care must be taken as it will be difficult to achieve uniform adsorption. Incidentally, a part of the monomers constituting the dispersant is added together with the polymer dispersant, or the stability of the polymer particles is often improved by using an inorganic fine powder or a surfactant together, and the particle size distribution is It is further improved.
The amount of the polymeric dispersant added during the production of the fine particles varies depending on the kind of the intended polymer particle-forming monomer, but is generally 0.1 to 10% by weight of the hydrophilic organic liquid, preferably 1 to It is 5% by weight. When the polymer dispersant concentration is low, relatively large particles are obtained, and when the polymer dispersant concentration is high, small particles are obtained.
If it exceeds the weight%, the effect of reducing the diameter is small.

The polymer particles produced by the dispersion polymerization are
It is composed of a homopolymer or copolymer containing the following vinyl monomer as a main component, and the monomer is soluble in the hydrophilic organic liquid. Styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, p- n-hexyl styrene, pn-octyl styrene, pn-
Styrenes such as nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene; methyl acrylate, acrylic acid Ethyl, acrylate-n-butyl, isobutyl acrylate, propyl acrylate, acrylate-n-octyl,
Dodecyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, methyl α-chloroacrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, methacrylic acid Acid-n
-Butyl, isobutyl methacrylate, methacrylic acid-n
-Acrylic unit amounts of octyl, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, etc. Body; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide, vinyl fluoride; etc.

In the dispersion polymerization using the above monomer, hydrophilic organic liquid and polymer dispersant, the polymer particles produced in the initial stage of the reaction are stabilized by the polymer dispersant, but the vinyl monomer is hydrophilic. When present in a fairly large amount in a volatile organic liquid,
The surface of the produced polymer particles is swelled to some extent with the monomer and becomes tacky, and therefore often aggregates even in the presence of the polymer dispersant. Then, when the amount of vinyl monomer in the reaction system becomes excessively large, the generated polymer particles are dissolved in the monomer, so that the polymer does not precipitate unless the amount of monomer decreases in the progress of the polymerization reaction. , The precipitate becomes a highly sticky lump. Therefore, the concentration of the monomer in the hydrophilic organic liquid during dispersion polymerization is limited and varies depending on the kind of the liquid, but is generally 100% by weight or less, preferably 50% by weight or less. In the present invention, a crosslinking agent may be present when producing grown particles by dispersion polymerization. In this case, the crosslink density is preferably smaller than that on the particle surface.

As the crosslinking agent, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, N, N-divinylaniline; ethylene glycol dimethacrylate,
Diethylenic carboxylic acid esters such as diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, 1,2-propylene glycol dimethacrylate, trimethylolpropane triacrylate, allyl methacrylate, tetraethylene glycol dimethacrylate, l, 3-butanediol dimethacrylate A divinyl compound such as divinyl ether, divinyl sulfide or divinyl sulfone; a bisphenol derivative such as hydrogenated bisphenol A or polyoxyethylenated bisphenol A having two or more vinyl groups; ethylenediamine having two or more vinyl groups; Polyvalent amine derivatives such as tetramethylenediamine and piperazine; all carboxyl groups are unsaturated alcohols such as vinyl alcohol and allyl alcohol. Examples thereof include esters of polyvalent carboxylic acids such as tellurized maleic acid, fumaric acid, mesaconic acid, citraconic acid, adipic acid, and malonic acid with unsaturated alcohols, which may be used alone or in admixture of two or more. Be seen.

In the present invention, in order to adjust the average molecular weight during dispersion polymerization, the compound may be polymerized in the presence of a compound having a large chain transfer constant. For this purpose, a low molecular weight compound having a mercapto group, carbon tetrachloride and Carbon tetrabromide is used. In the dispersion polymerization, a normal radical initiator soluble in the solvent used may be used, and 2,2'-azobisisobutyronitrile or 2,2'-azobis (2,4-dimethylvaleronitrile) may be used. ) Etc .; azo polymerization initiators; lauryl peroxide, benzoyl peroxide, tert-butyl peroctoate, etc. peroxide polymerization initiators; potassium persulfate, etc. persulfide polymerization initiators; A system in which sodium sulfate, amine or the like is used in combination is used. The polymerization initiator may be used alone or in combination of two or more,
It may be appropriately used in consideration of the type of the polymerization initiator, the polymerization conditions and the like.

As described above, the dispersion polymerization process is divided into two steps, that is, the production of seed particles and the growth of seed particles. In the former method, after the polymer dispersant is completely dissolved in the hydrophilic organic liquid, monomers such as styrene and acrylate and a polymerization initiator are added to make the flow in the reaction tank uniform. It may be carried out by heating to a temperature corresponding to the decomposition temperature of the used polymerization initiator while stirring at a speed. Since the temperature at the initial stage of polymerization has a great influence on the obtained particle size, it is desirable to add a polymerization initiator dissolved in a small amount of a solvent after adding a monomer and raising the temperature to the polymerization temperature. Further, in the initial stage of the polymerization, the concentration of the polymerization initiator in the reaction solution is 0.1% by weight or less, preferably 0.
The amount is preferably not more than 05% by weight, which allows the polymer particles (seed particles) to be stably and reproducibly synthesized. On the other hand, in the step of growing seed particles, it is preferable to add a polymerization initiator corresponding to 0.1 to 10% by weight of the monomers present in the reaction system, which accelerates the growth rate and increases the polymerization rate. It becomes possible to obtain desired polymer particles. The polymerization initiator in the growth step may be the same as or different from that used in the production of seed particles.

In the dispersion polymerization step for producing the toner of the present invention, it is necessary to remove oxygen in the reaction vessel with an inert gas such as nitrogen or argon, and if the oxygen removal is insufficient, fine particles are easily generated. Moreover, in order to obtain a high polymer, it is 5-40.
Although time is required, the polymerization time can be shortened by stopping the polymerization in the state of the desired particle size and particle size distribution, sequentially adding the polymerization initiator, and performing the reaction under high pressure. In the case of the dispersion polymerization type toner of the present invention, in the latter half of the growing particle production process following the seed particle production process by dispersion polymerization, in order to enhance the hot offset resistance by providing the particle surface layer with a crosslinking component, a polymerizable double A cross-linking structure imparting step of adding a cross-linking agent having two or more bonds is provided. As the cross-linking agent, the above-mentioned cross-linking agent may be used in the growing particle production process, but the effect can be further enhanced by using the vinyl monomer of the general formula (I). The reason will be described below.

A cross-linking agent having two or more polymerizable double bonds may aggregate when added in a large amount in order to increase the cross-linking component, and addition of a large amount also causes a rise in fixing temperature. Therefore, in order to improve the hot offset resistance without raising the fixing temperature, it is necessary to add a large amount of a crosslinking component to the surface layer of the particles. For this reason, a crosslinking agent is added in the process of growing the particles, but if the addition time of the crosslinking agent is early, the layer having the crosslinking component becomes thick and the low temperature fixing property may be impaired, so the polymerization rate is 60%. It is good to add it above. In this case, depending on the type of the cross-linking agent, it may be aggregated immediately after the addition, but the compound of the general formula (I) is a cross-linking agent capable of preventing the occurrence of hot offset even if added in a small amount. Then there is a margin to the amount of aggregation.

Winding or hot offset that occurs during thermal fixing of toner occurs when the cohesive force between toners is weaker than the adhesive force between the fixing roller (heat roller) and the toner. Therefore, this phenomenon can be prevented by increasing the cohesive force between the toner particles, so that it is preferable to enhance the elasticity of the toner particles. In the crosslinking agent represented by the general formula (I), the number of repeating units contained in (R ¹ ) is
As shown in the formulas (a), (b) and (d), the elasticity of the toner is increased to 2 or more. However, if the molecular weight is too large, the reactivity decreases, so the repeating number is preferably 2-20. Further, (R ¹ ) may be a heterocycle as shown by the formula (c), and since the heterocycle has a steric hindrance structure, it is capable of incorporating a linear polymer to form an apparent crosslinked structure. is there. Therefore, by having the structure, the crosslinking agent of the general formula (I) can be crosslinked not only by the double bond but also by the structure, so that a large amount of the crosslinking component can be present by adding a small amount.

The crosslinking agent of the general formula (I) may have an ionic functional group as shown in the formula (d). When a cross-linking agent having the functional group is used, it becomes difficult for the cross-linked polymer and the non-cross-linked polymer to be compatible with each other, so that the cross-linking component formed on the particle surface does not escape to the inside of the particle. Since the surface concentration of the crosslinking component is kept high, the hot offset resistance effect is enhanced. Examples of the ionic functional group that plays such a role include a carboxyl group, a phosphon group, a phosphine group, a sulfone group, and a hydroxyl group as the anionic functional group, and an amino group as the cationic functional group. In the cross-linking structure imparting step described above, the weight of the cross-linking agent added to give the cross-linking component to the surface layer of the polymer particles is the total amount of the monomer for forming particles (monomers that have already formed polymer particles. (Including a cross-linking agent) 1-10
Weight percent is preferred. If the addition amount is less than 1% by weight, the crosslinking component may not be formed on the surface, and if it is more than 10% by weight, the fixing energy amount may increase and the crosslinking agent may aggregate.

The produced polymer particles may be dyed by adding a dye to the liquid after the step of imparting the crosslinked structure. In this method, a polymer dispersant is present in the system, so that dyeing may be performed at a relatively high temperature. In addition to the low aggregation of polymer particles, the ratio of the dye in the system incorporated into the polymer particles (dyeing efficiency) is high. Further, the polymer particles may be easily purified by sedimentation separation, centrifugation, decantation, etc., and dyeing may be performed after removing most of the remaining polymerization solvent, monomer and polymer dispersant. It can be dyed with a solvent. The dyeing temperature is
The glass transition temperature of the polymer particles to 20 ° C. lower than the temperature is preferable, and the dyeing time is preferably 0.5 to 1 hour. The amount of dye used varies depending on the degree of coloring of the intended toner, but is generally about 1 to 50% by weight of the polymer particles. When dyeing the polymer particles after purification, it is preferable to disperse and dissolve the dye in a dyeing solvent and then disperse the polymer particles in the solvent. Further, it is preferable that the dyeing is carried out with stirring using a homomixer, a magnetic stirrer or the like.

The solvent used in the dyeing step is a solvent in which the polymer particles may swell to some extent, but is a solvent insoluble in the particles. Specifically, the solubility coefficient (SP value) of the solvent and the solvent constitute the particles. The solvent has a difference of 1.0 or more, preferably 2.0 or more from that of the polymer. For example, when the polymer is a styrene-acrylic resin having an SP value of about 9, an aliphatic lower ketone such as acetone or methylethylketone having an SP value of about 9 or an aromatic hydrocarbon solvent such as toluene or benzene has a heavy weight. It is not preferable because the coalesce dissolves well, SP
Higher value of lower aliphatic alcohol solvents such as methanol, ethanol and n-propanol, or lower SP value of n-
Lower aliphatic hydrocarbon solvents such as hexane and n-heptane are used. If the difference in SP value is too large, it becomes difficult for the polymer particles to be wetted by the solvent, so that the dispersibility of the particles is lowered and the dyeing efficiency is lowered.
~ 5 is good.

The dye used in the dyeing step has a solubility [D1] of the dye in a solvent used for dyeing is less than half of the solubility [D2] of the dye in a solvent which dissolves the polymer particles to be dyed well. The dye is preferably 1/5 or less. Solubility in solvent that dissolves polymer particles well [D2]
Means that the polymer has a high affinity with the dye. Therefore, when [D1] / [D2] is 0.5 or less, it indicates that the dye is more easily dissolved in the polymer particles to be dyed than the solvent used in the dyeing step. Further, since [D1] and [D2] are defined as above, when [D1] / [D2] is 0.5 or more, it is difficult to dye the polymer particles, and even if dyed, It is difficult to stay in the surface layer and dye the inside of the particles. [D2] is actually measured by using a solvent that most dissolves the polymer particles as the toner raw material, but it may be obtained by estimating an approximate value from the SP value.

The dye for toner of the present invention has the above-mentioned solubility, and water-insoluble dyes such as vat dyes and disperse dyes or oil-soluble dyes are used, and the latter is particularly preferable. When a water-soluble dye such as a cationic dye or an anionic dye is used, the electric resistance of the obtained toner may change significantly depending on the environment, and the transfer rate is low when a toner having a low electric resistance is used. The toner dye of the present invention may be appropriately selected depending on the hue, the type of polymer particles and the dyeing solvent, and the usable dyes are shown below by color index. CI Solv
ent Yellow (6,9,17,31,35,1
00, 102, 103, 105), CI Solven
t Orange (2, 7, 13, 14, 66), C.I.
I. Solvent Red (5, 16, 17, 18,
19, 22, 23, 143, 145, 146, 149,
150, 151, 157, 158), CI Solve
nt Violet (31, 32, 33, 37), C.
I. Solvent Blue (22, 63, 78, 8
3 to 86, 91, 94, 95, 104), CI Sol
Vent Green (24, 25), CI Solv
ent Brown (3, 9) and the like.

Among commercially available dyes, Aizen S from Hodogaya Chemical Co., Ltd.
OT dye Yellow-1,3,4, Orange-
1, 2, 3, Scarlet-1, Red-1, 2,
3, Brown-2, Blue-1, 2, Violet
-1, Green-1, 2, 3, Black-1, 4,
6,8; Sudan dye from BASF, Yellow-
146,150, Orange-220, Red-29
0,380,460, Blue-670; Mitsubishi Kasei's dial resin Yellow-3G, F, H2G, HG,
HC, HL, Orange-HS, G, Red-GG,
S, HS, A, K, H5B, Violet-D, Blu
e-J, G, N, K, P, H3G, 4G, Green-
C, Brown-A; oil color Yellow-3G, GG-S, # 105, Orange of Orient Chemical Company
e-PS, PR, # 201, Scarlet- # 30
8, Red-5B, Brown-GR, # 416, Gr
een-BG, # 502, Blue-BOS, IIN,
Black-HBB, # 803, EB, EX; Sumiplast Bull-GP, OR, Red FB, 3 from Sumitomo Chemical Co., Ltd.
B, yellow FL7G, GC; Kayaron polyester black EX-SF300, Kayaset Re from Nippon Kayaku Co., Ltd.
d-B, blue A-2R, etc. are used.

The liquid after the dyeing step contains some polymer dispersant and unreacted monomer even when the polymer particles are separated from the liquid for dispersion polymerization and used for dyeing. Further, since this liquid also contains undyed dye and ultrafine particles unsuitable for toner, it is necessary to remove these in order to obtain a purified toner. The removal is carried out by a method such as filtration using a filter having a desired size, centrifugal sedimentation, and liquid cyclone to obtain toner particles having a desired size. When the toner particles are obtained in the form of a cake, they may be dried with a rotary kiln or a vibration fluidized dryer, and when they are obtained in the form of a slurry, they may be dried with a spray dryer, a fluidized bed drier, etc. Is obtained. The method of increasing the crosslink density of the toner surface layer in the dispersion polymerization type toner described above higher than that in the inside of the toner is also applicable to the classification type toner obtained by the kneading pulverization method or the suspension polymerization method as shown below. As described above, it is possible to achieve both hot offset prevention and low temperature fixability by increasing the crosslinking density of the surface layer higher than that of the inside.

When the present invention is applied to a classification type toner, the monomer constituting the binder resin is styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene,
α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-
Butyl styrene, pn-hexyl styrene, pn-
Octyl styrene, pn-nonyl styrene, pn-
Styrenes such as decyl styrene, pn-dodecyl styrene, p-methoxy styrene, p-phenyl styrene, p-chloro styrene, 3,4-dichloro styrene; ethylene unsaturated such as ethylene, propylene, butene, isobutene Mono-olefins; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride; α-methylene such as methyl acrylate, ethyl acrylate, n-butyl acrylate, methyl methacrylate and ethyl methacrylate. Examples include aliphatic monocarboxylic acids; vinyl ethers such as vinyl methyl ether; vinyl ketones such as vinyl methyl ketone; N-vinyl compounds such as N-vinylpyrrole, N-vinylcarbazole, N-vinylindole, and N-vinylpyrrolidone. To be done. These monomers may be used alone or in combination of two or more. That is, it may be a copolymer.

In the binder resin for the classification type toner, the monomers for forming the polycondensation type resin include ethylene glycol, triethylene glycol, 1,2-propylene glycol, bisphenol, hydrogenated bisphenol A and polyoxy. Polyhydric alcohols such as ethylenic bisphenol A; polyhydric amines such as ethylenediamine, tetramethylenediamine, piperazine; polyhydric carboxylic acids such as maleic acid, fumaric acid, mesaconic acid, citraconic acid, adipic acid and malonic acid; or these Examples thereof include acid anhydrides and esters with lower alcohols. In the toner, as a colorant or a charge control agent, a carbon chelate dye such as carbon black, oil black, nigrosine dye, metal-containing dye, aniline dye, chalco oil blue, chrome yellow, ultramarine blue, methylene blue chloride, phthalocyanine blue is used. , Rose Bengal, etc. may be added. In addition, the surface of which is made hydrophobic, SiO ₂ or TiO ₂
Inorganic oxides such as, inorganic fine particles such as SiC, metal soaps such as zinc stearate and the like may be added to the toner as a fluidity improver.

In order to improve the offset resistance of the toner,
As in the case of the dispersion polymerization type toner, the binder resin inside the toner may have a crosslinked structure, but the crosslink density at this time is lower than that of the crosslinked resin layer forming the surface layer of the toner. Is desirable. The crosslinked resin layer is prepared by completely dissolving a polymeric dispersant such as polyvinylpyrrolidone in a hydrophilic organic solvent such as methanol, and then adding a coloring agent produced by a kneading / pulverizing method or a suspension polymerization method to the solution. It can be obtained by dispersing the particles obtained by classifying the coalesced particles, adding a cross-linking agent and an ionic vinyl monomer, and polymerizing the particles on the surface of the particles. The ionic vinyl monomer used here is acrylic acid, styrene sulfonic acid, or the like, and these ionic vinyl monomers act as a surfactant for the dispersion of the classified particles, and also the crosslinking reaction of the particle surface. It seems that it has also contributed strongly to. The cross-linking agent may be a cross-linkable vinyl monomer used in both the particle growth step and the cross-linking structure imparting step of the dispersion polymerization type toner.

[0034]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The following parts and% are based on weight. The evaluation of the toners produced in the examples and comparative examples was carried out as follows. 1. Fixing energy evaluation method Using a copying machine that can change the fixing temperature within the standard set temperature ± 30 ° C, fixed images with different fixing temperatures are obtained, and the black solid part of the image is erased with a sand eraser attached to a clock meter. 5
After rubbing, the reflection density was measured. Then, the fixing energy was calculated with the temperature at which the fixed image having the density of 0.8 or more was obtained as the fixing temperature.

2. Evaluation method of releasability It was carried out based on whether or not the image fixed at the standard set temperature is smoothly discharged without being wound around the fixing roller, and whether the obtained image has an offset background stain. . 3. Method for Measuring Crosslinking Component The vinyl polymer that constitutes the toner of the present invention contains a toluene-soluble component and a toluene-insoluble component. Therefore,
Put a predetermined amount (B) of the polymer in a certain amount (A) of toluene, stir well, dissolve the toluene-soluble component, and then sample a fixed amount (D) and dissolve it in D. When the amount of the polymer present, that is, the dry residue E is determined, the crosslinking component amount G is determined by the following formula. Theoretical solid content C (%) = 100B / (A + B) Solid content F (%) = 100E / D Crosslinking component G (%) = 100-100F / C In addition, when the internal layer is also crosslinked, a transmission electron microscope ( T
When a cross-section is observed by EM), a difference in dyeability occurs in a pretreatment process using a heavy metal, so that the degree of crosslinking can be discriminated by the shade of color. The shade of color varies depending on the type of the crosslinkable monomer, and the styrene-based crosslinkable monomer becomes darker and the acrylic crosslinkable monomer becomes lighter, but the higher the degree of crosslinking, the darker the color becomes. The degree of crosslinking can be determined from these phenomena and the like.

Example 1 A sealable reaction vessel equipped with a stirring blade, a cooling condenser and a nitrogen gas introducing tube was placed in a constant temperature water tank, and 108 parts of methanol and polyvinylpyrrolidone 6 were placed in this reaction vessel.
A part was charged and the stirring blade was rotated to completely dissolve polyvinylpyrrolidone in methanol. Next, the following composition was prepared in a container. Styrene 32 parts Methyl acrylate 6 parts Ethyl acrylate 2 parts Dodecyl mercaptan 0.6 parts While continuing stirring, blow nitrogen gas into the container to completely expel oxygen and then raise the temperature in the constant temperature water bath to 65 ± 0.1 ° C. , 0.6 parts of azobisisobutyronitrile (AIB
Polymerization was initiated by adding a solution of N) dissolved in 12 parts of methanol.

In the liquid 10 hours after the initiation of the polymerization, the polymerization rate determined by the gravimetric method reached 62.8%, but the following composition was added to this liquid. To obtain a dispersion was cooled to room temperature Le 3.0 parts Then 14 hours after Mitsuruke _{- CH 2 = CHCOO (CH 2} CH 2) 2 OOCCH = CH 2 1.2 parts methanol. An attempt was made to measure the particle size distribution of the particles in the dispersion using a Coulter Multisizer using an aperture tube of 100 μm, and the volume average particle size of the particles was 6.34 μm and the number average particle size was 5.90 μm. The polymer particles had a sharp particle size distribution, as can be seen from the fact that the ratio was 1.075. Take 80 parts of this dispersion in a flask, add 20 parts of distilled water, and stir with stirring.
Dye powder mixed with 5 parts of Oil Orange 201 is added little by little over 30 minutes, and after addition of dye, the mixture is kept at room temperature for 3 minutes.
After stirring for 0 minutes, the mixture was stirred at 50 ° C. for 5 hours. The dyed-particle-containing liquid thus obtained was filtered through a filter having an opening of 75 μm, and nothing remained on the filter.

As a result of measuring the particle size distribution of the dyed particles by the above-mentioned method, the volume average particle diameter is 6.40 μm and the number average particle diameter is 5.94 μm, and the ratio thereof is calculated to be 1.07.
7 was obtained, and the particles had a sharp particle size distribution which was the same as that before dyeing. Moreover, the presence of aggregated particles could not be confirmed by observation with an optical microscope. Next, the dyeing solution is spun down by centrifugation to remove the supernatant, and redispersed in a mixed solvent of 70 parts of methanol and 30 parts of distilled water twice, and finally to a mixed solvent of 50 parts of methanol and 50 parts of distilled water. After redispersion, filtration and drying were carried out to obtain black polymer particles. 100 parts of the colored particles and 0.3 part of titanium oxide (fluidity improver) were stirred with a ball mill for 10 minutes to obtain a toner. When the cross section of the toner is observed by TEM, it can be seen that the surface portion of the particles has scattered portions having a different density from the inside, and it can be seen that the structure of the portion is different. 3 parts of this toner and carrier 97
The parts are agitated and mixed to form a developer.
Image evaluation was carried out with -4820 (oilless machine), and the obtained image was excellent in both resolution and halftone reproducibility. Also, the fixing energy is 0.
It was as low as 22 ca1 / cm ^2, and there was no image stain or winding due to hot offset. The crosslinking component of this toner was 4.6%. A silicon resin-coated ferrite carrier was used as the carrier.

Examples 2 to 4 Toners were prepared in the same manner as in Example 1 except that the crosslinkable monomer added 10 hours after the initiation of polymerization was changed to the following (addition amount was the same as that in Example 1). Then, the particle size was measured and evaluated in the same manner as in Example 1. The polymerization rate obtained by sampling the polymerization liquid immediately before the addition of the crosslinkable monomer was 6
It was 2 to 64%.

[Chemical 3]

The toners of Examples 2 to 4 have a volume average particle size after polymerization of 6.00 to 6.40 μm, and the ratio of the volume average particle size to the number average particle size is 1.10 or less. It had a sharp particle size distribution. Further, since the particles do not aggregate during dyeing, the particle size distribution hardly changed before and after dyeing. As with the toner of Example 1, it was found by TEM observation that the toner surface layer part and the inside were clearly separated. An image excellent in both resolution and halftone reproducibility was obtained from these toners, the fixing energy was as low as 0.20 to 0.21 cal / cm ^2, and there was no image stain or winding due to offset. The cross-linking component of these toners was 4.8 for the toner of Example 2.
%, The toner of Example 3 was 9.3%, the toner of Example 4 was 7.2%, and the toner of Example 3 had more crosslinking components than others.

Comparative Example 1 A dispersion was obtained by carrying out the polymerization in the same manner as in Example 1 except that divinylbenzene was used as the crosslinkable monomer added 10 hours after the initiation of the polymerization (the addition of the above-mentioned monomer). The polymerization rate immediately before was 62.5%). With respect to the particles in the dispersion, the particle size distribution was measured by the same method as in Example 1. The volume average particle diameter was 6.34 μm and the number average particle diameter was 5.90 μm, and the ratio of both was 1.075. As can be seen, the particles were polymer particles having a sharp particle size distribution. After the polymer particles were dyed in the same manner as in Example 1, this dyeing solution was filtered through a filter having an opening of 75 μm, and small aggregates were considerably present on the filter. The dyed-particle-containing liquid was centrifuged to remove the supernatant, and this was added with methanol 70
The work of redispersing in a mixed solvent of 30 parts of distilled water and 30 parts of distilled water was performed twice, and finally, redispersed in a mixed solvent of 60 parts of methanol and 50 parts of distilled water, and then the mother liquor was separated by filtration. When the precipitate was dried, black colored polymer particles were obtained. The colored particles (100 parts) and titanium oxide (0.3 parts) were stirred with a ball mill for 10 minutes to obtain a toner. When the same image evaluation as in Example 1 was performed using this toner, the fixing energy was as low as 0.20 cal / cm ² , but there was scumming due to hot offset. The crosslinking component of this toner was only 1.3%.

Comparative Example 2 Polymerization was started in the same manner as in Example 1, and after 3 hours, 1.2 parts of the following monomers and 3 parts of methanol were added. The polymerization rate immediately before the addition of the monomer was 28.7%.

[Chemical 4] Then, the reaction was continued for 20 hours and then cooled to room temperature to obtain a dispersion liquid. The particle size distribution of the particles in the dispersion was measured by the same method as in Example 1, and the volume average particle size was 6.4.
2 μm, number average particle size 5.79 μm, ratio of both is 1.1
The particles had a sharp particle size distribution of 09. The dispersion was dyed by the same method as in Example 1, and the dyed particles were observed with an optical microscope, but the presence of aggregated particles could not be confirmed. The dyed particle-containing liquid was washed, filtered and dried in the same manner as in Example 1 to obtain a toner. When the cross section of the toner is observed by TEM, it is unclear whether the cross-linking component exists in the surface layer of the particle because it is uniform from the surface layer to the inside of the particle. It can be seen that the crosslinking component is present. However, since the fixing energy is as high as 0.27 cal / cm ² , a cross-linking component is present even inside the particles, and the toner does not satisfy both the releasability and the low temperature fixability.

Example 5 A polyvinylpyrrolidone solution having the same composition as in Example 1 was formed in the same container as that used in Example 1, and the following composition was charged therein. Styrene 20 parts Methyl acrylate 20 parts Thioglycerine 0.08 parts A mixed solution containing the above composition was treated exactly as in Example 1, and then 0.01 parts AIBN was dissolved in 0.5 parts methanol. Was added to initiate polymerization. Although the inside of the system became cloudy 15 minutes after the addition of the solution, the reaction was continued for 30 minutes, and then a solution prepared by dissolving 0.4 parts of AIBN in 6 parts of methanol was added. It was found that the cloudiness became strong and the reaction was accelerated after a while after the addition. Three hours later, a solution prepared by dissolving 0.4 parts of thioglycerin in 1.2 parts of methanol was added by a syringe.

The liquid 11 hours after the above addition was sampled and the polymerization rate was determined by the gravimetric method to be 79.5%. At this time, 0.8 part of the following monomer and 2 parts of methanol were added, and the reaction was further continued for 15 hours and then cooled to room temperature to obtain a dispersion liquid. CH ₂ = CHCOO (CH ₂ CH ₂ ) ₅ OOCCH = CH ₂ The particle size distribution of the particles in the dispersion was measured by the same method as in Example 1, and the volume average particle diameter was 5.47 μm and the number average particle diameter was 4. The particle size was 92 μm, and the ratio of the both was 1.112, showing a sharp particle size distribution. When the dispersion was dyed in the same manner as in Example 1, all the dyeed solution passed through a filter having an opening of 75 μm, and nothing remained on the filter. The particle size distribution of the dyed particles was measured by the same method as described above, and the volume average particle size was 5.
The number average particle size was 52 μm, the number average particle size was 4.96 μm, and the particles had a sharp particle size distribution which was the same as that before dyeing, as can be seen from the ratio of both, 1.1 l3. The particles did not show aggregated particles when observed with an optical microscope. Further, the crosslinking component of the toner was 18.7%. An image obtained using this toner in the same manner as in Example 1 was excellent in both resolution and halftone reproducibility. Further, the fixing energy was as low as 0.20 cal / cm ^2, and there was no image stain or winding due to offset.

Example 6 Polymerization was started in the same manner as in Example 5 and, 15 hours after the reaction was allowed to proceed until thioglycerin and methanol were added, 3.2 parts of the following monomer and 8 parts of methanol were added. Was added. The polymerization rate at this time was 90.3%. CH ₂ = CHCOO (CH ₂ CH ₂ O) ₁₈ OOCCH = C
H ₂ Subsequently, to obtain a dispersion was cooled to room temperature and continued for 10 hours. When the particle size distribution of the dispersion was measured by the same method as in Example 1, the volume average particle size was 5.46 μm,
The number average particle diameter was 4.94 μm, the ratio between the two was 1.105, and the particles in the dispersion had a sharp particle size distribution. The toner obtained by treating this dispersion with the same method as in Example 1 showed the same particle size distribution as before treatment, and the image obtained with the toner was evaluated by the same method as in Example 1, and It was good with no background stains due to offset. Furthermore, the fixing energy is 0.22 cal / c.
It was as low as m ² .

Comparative Example 3 In Example 5, when styrene, methyl methacrylate and thioglycerin were charged into the container, 0.6 part of divinylbenzene was charged together, and the polymerization reaction was carried out in the same manner as in Example 5 except that. After adding thioglycerin and methanol, polymerization was continued for 20 hours without addition, and then the mixture was cooled to room temperature to obtain a dispersion liquid. When the particle size in the dispersion is measured by the above method, the volume average particle size is 5.38 μm and the number average particle size is 4.8.
5 μm was obtained, and the ratio of the both was 1.109, and the particles had a sharp particle size distribution. This dispersion was dyed in the same manner as in Example 1, and the solution was passed through a filter having an opening of 75 μm. As a result, no aggregate remained on the filter, but when observed with an optical microscope, 2-3 particles were observed. There were many aggregates. The dyed particles were made into toner by the same method as in Example 1 and evaluated. As a result, the fixing energy was as low as 0.20 ca1 / cm ² and paper jamming did not occur, but there was image stain due to offset and the resolution was poor. there were. The crosslinking component of the toner is 20.2%
Therefore, the reason why offset does not occur in the toner of Example 5 in which the crosslinking component is 18.7% is that the crosslinking component in the toner of Example 5 is concentrated on the particle surface layer.

Comparative Example 4 Since an offset occurred in Comparative Example 3, in this Example, the same as Comparative Example 3 except that the amount of divinylbenzene was increased by 0.2 parts from the case of Comparative Example 3 to 0.8 parts. When the polymerization was started under the conditions, several particles were observed to agglomerate every 2 hours after the initiation of the polymerization, and after 6 hours, they became large aggregates.

Example 7 300 parts of methanol and 30 parts of ion-exchanged water were placed in the reactor described in Example 1, and 6.4 parts of a copolymer of maleic anhydride and methyl vinyl ether was added thereto with stirring little by little. -After being dissolved, the following composition was added and completely dissolved. Styrene 25.6 parts n-Butyl methacrylate 6.4 parts 2,2'-Azobisisobutyronitrile 0.2 parts Todecyl mercaptan 0.2 parts Butanediol dimethacrylate 0.2 parts Stir the contents of the reactor. While purging the inside of the reactor with nitrogen gas, leave it for 1 hour and then in a constant temperature water bath at 60 ± 0.1 ° C for 200
Polymerization was started under stirring at a stirring speed of rpm. After the start 1
The liquid became cloudy in 5 minutes, and remained stable after 20 hours, but when this was sampled and analyzed by gas chromatography using an internal standard, the polymerization rate was 85%.
Met. After cooling this particle dispersion to room temperature, 0.5 parts of butanediol dimethacrylate, 5.0 parts of acrylic acid and 0.1 part of AIBN were added to initiate polymerization again. The dispersion obtained after 24 hours from the start was cooled to 2000 rp
After centrifugation at m, the polymer particles were completely settled and the upper liquid was transparent.

The supernatant was removed, 200 parts of fresh methanol was added, and the mixture was washed by stirring and washing for 1 hour, followed by centrifugation.
After drying under reduced pressure for 24 hours, white powdery styrene / n-butyl methacrylate particles were obtained with a yield of 98%. The particles have a volume average particle diameter of 5.2 μm and a number average particle diameter of 4.
The particle size was 9 μm, and the crosslinked content was 24% [hereinafter, the particles are referred to as (A)]. Next, 1.0 part of Oil Black 803 (manufactured by Orient Chemical Co., Ltd.) was heated and dissolved in 200 parts of methanol, cooled, and then filtered through a filter having an opening of 1 μm to prepare a dye solution. Particles (A) in the dye solution
24 parts was added and dispersed, and it heated and stirred at 50 degreeC for 1 hour. Then, the dyed polymer particle dispersion was cooled to room temperature, and the mother liquor was filtered off to obtain colored particles. The cross section of the particle is T
When observed by EM, it was found that the crosslinked structure of the particle surface layer was denser than the inside. The colored particles were vacuum dried at room temperature for 24 hours, and 1.5 parts of silica was added and mixed to obtain a toner. Next, 3 parts of the toner was mixed with 97 parts of a commercially available silicon resin-coated ferrite carrier (the same product as used in Example 1) to prepare a developer, and the image was fixed on a copying machine FT8200 manufactured by Ricoh Co. after fixing the image. Temperature 170 ℃
A good image was obtained by fixing with, and the image was good even after 100,000 copies. Also, the relative temperature is 90 at 35 ° C.
% And relative temperature of 15% at 10 ° C., an image similar to that at room temperature and normal humidity can be obtained even in a high temperature and high humidity environment and a low temperature and low humidity environment, and filming on the photoconductor is not observed, and left at 50 ° C. for 3 days. But no blocking occurred.

Example 8 Example 7 except that the amount of dodecyl mercaptan was halved.
Colored particles were obtained in the same manner as. The particles had a volume average particle diameter of 4.6 μm and a number average particle diameter of 4.2 μm, and a crosslinked content was 33%. When the cross section of the particles was observed by TEM, a dense crosslinked structure was observed on the surface of the particles. This was vacuum dried at room temperature for 24 hours, and 1.5 parts of silica was added and mixed to obtain a toner. Using this toner as a raw material, a developer was prepared in the same manner as in Example 7 and an image was formed. A good image was obtained at a fixing temperature of 170 ° C., and the image was of good quality even after 100,000 copies. It was Further, under the same high temperature and high humidity and low temperature and low humidity environment as in the case of Example 7, the same image as in the normal temperature and normal humidity environment was obtained, and no filming on the photosensitive member was observed, and it was left for 3 days at 50 ° C. But no blocking occurred.

Example 9 Colored particles were obtained in the same manner as in Example 7 except that the amount of dodecyl mercaptan was doubled. The particles had a volume average particle diameter of 5.9 μm and a number average particle diameter of 5.7 μm, and the crosslinked content was 18%. Further, when the cross section of the particles was observed by TEM, a crosslinked structure was observed only in the particle surface layer. This was vacuum dried at room temperature for 24 hours, and 1.5 parts of silica was added and mixed to obtain a toner. Using this toner as a raw material, a developer was prepared in the same manner as in Example 1 and an image was formed. As a result, a good image was obtained at a fixing temperature of 170 ° C., and the image was good even after 100,000 copies. . In addition, Example 7
In the same high temperature and high humidity environment and low temperature and low humidity environment as in the above case, the same image as in the normal temperature and normal humidity environment is obtained, the filming on the photoreceptor is not observed, and the blocking occurs even if left at 50 ° C for 3 days. Didn't happen.

Comparative Example 5 Polymerization was carried out in the same manner as in Example 7, but 20 minutes after the initiation of the polymerization.
The reaction was terminated at the initial polymerization step for a period of time, and the precipitate obtained by post-treatment in the same manner as in Example 7 was dried under reduced pressure at 50 ° C. for 24 hours to give 93% yield of white powdery styrene / n-. Butyl methacrylate particles were obtained. The particles had a volume average particle diameter of 5.0 μm and a number average particle diameter of 4.7 μm, and had a crosslinked content of 0%. When these particles were dyed by the same method as in Example 1 and the cross section of the obtained colored particles was observed by TEM, no crosslinked structure was observed in both the particle surface layer and the inner layer. Next, a developer was prepared in the same manner as in Example 1 and an image having a solid portion at the tip was formed. As a result, wrapping occurred around the fixing roller at a fixing temperature of 170 ° C.

[0053]

EFFECT OF THE INVENTION By using an electrophotographic toner having a crosslink density of the toner surface layer higher than that of the toner inner layer (particularly, a toner dyed after dispersion polymerization of a vinyl monomer), hot offset at the time of fixing is achieved. It was possible to provide a toner exhibiting good transferability without causing a phenomenon or a phenomenon of winding around a heat roller, capable of low-temperature fixing, and having less filming during development. It was also possible to obtain a high quality image by forming a crosslinked structure of the toner surface layer with a diacrylate monomer having a specific structure.

Claims (3)

[Claims] 1. In an electrophotographic toner comprising at least a binder and a colorant, there is a difference in the cross-linking structure of the binder between the toner surface layer and the inner layer, and the cross-linking density of the toner surface layer is the toner inner layer. A toner for electrophotography, which is characterized by being higher than that. 2. The electron particle toner according to claim 1, wherein the toner for electrophotography is a resin particle toner obtained by dispersion polymerization of one or more vinyl monomers, granulation, and then dyeing. Photographic toner. 3. The electrophotographic toner according to claim 1, wherein the surface layer of the electrophotographic toner is crosslinked with a vinyl monomer represented by the following general formula (I). . ^{_{CH 2 = CR 2 COO- (R}} 1) -OOCCR 2 = CH 2 ............ (I) wherein, - (R ¹⁾ -, the groups shown in the following (a) (d) R ² represents a hydrogen atom or an alkyl group selected from the group represented by the following: