JP2008242240A - Yellow toner and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a yellow toner and a method for manufacturing the toner allowing formation of an image with excellent image quality, suppressing degradation in the image quality even when the number of prints increases, and having excellent printing durability. <P>SOLUTION: The yellow toner contains at least a binder resin and a yellow pigment, wherein the yellow pigment contains a combination of a yellow pigment showing a hydrophobicity degree of 2% or more in terms of the start point of settling and a yellow pigment showing a hydrophobicity degree of less than 2% in terms of the start point of settling. The method for manufacturing the above yellow toner is carried out by a suspension polymerization method. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a yellow toner used for developing an electrostatic latent image formed on a photoreceptor in an image forming apparatus using an electrophotographic system or an electrostatic printing system.

  In image forming apparatuses such as electrophotographic (including electrostatic printing) copiers and printers that use toner for developing electrostatic images, printing (printing) speeds up, fixing temperature is lowered, full color, etc. The demand is growing.

  When full-color printing is performed using an electrophotographic image forming apparatus, the color spectrum visible to the human eye is reproduced using the principle of subtractive color mixing of three basic colors of yellow, cyan, and magenta. Specifically, in full color printing, a full color image is formed using yellow toner, cyan toner, and magenta toner. In addition to these three full-color toners, black toner is often used.

  Each color full-color toner is composed of colored resin particles containing a binder resin and a colorant. The colored resin particles contain various additive components such as a charge control agent, a release agent, and a dispersant as required. As the colorant, a yellow colorant, a magenta colorant, a cyan colorant, or the like is used.

  The level of demand for each color is increasing for full color toners so that accurate color reproduction is possible. If the image quality of a full-color toner of a certain color is insufficient, the color reproduction is insufficient and a clear full-color image cannot be formed. If the toner charge amount and the toner adhesion amount become insufficient during development, the image density and the print hue are deteriorated, and toner fog on the photosensitive member is likely to occur. Among full-color toners, the yellow toner has been difficult to sufficiently meet the high level of demand.

  Conventionally, JP-A-11-202558 (Patent Document 1) discloses C.I. I. An electrophotographic toner mainly composed of Pigment Yellow is disclosed. In the example of Patent Document 1, C.I. I. A pulverized toner obtained by kneading, pulverizing, and classifying Pigment Yellow is disclosed.

  JP 2001-166540 A (Patent Document 2) discloses C.I. I. A yellow toner using any yellow pigment selected from the group consisting of CI Pigment Yellow 74, 155, 180, and 185 has been proposed. In Examples 1 to 4 of Patent Document 2, a polyester resin is used as a binder resin. I. A pulverized toner containing Pigment Yellow 74, 155, 180, and 185, respectively, is shown.

  Japanese Patent Application Laid-Open No. 2004-184562 (Patent Document 3) discloses a two-component developer composed of a toner and a carrier in which a binder resin and C.I. I. It has been proposed to use a toner containing Pigment Yellow. In Example 1 of Patent Document 3, polyester resin and C.I. I. A masterbatch containing Pigment Yellow 155 and water is prepared, and then a polyester resin (binder resin), a release agent, and the masterbatch are dissolved in an organic solvent to prepare a toner material liquid. It is described that the toner material liquid thus obtained was poured into ion-exchanged water in which hydroxyapatite and sodium dodecylbenzenesulfonate were dissolved and stirred to form toner particles.

  In JP-A-2005-31163 (Patent Document 4), a yellow toner containing at least a binder resin, a colorant, and a wax, C.I. I. A yellow toner containing Pigment Yellow 74 and 155 is disclosed. The example of Patent Document 4 shows a two-component developer in which a yellow toner using a hybrid resin, a polyester resin, or a vinyl copolymer as a binder resin is mixed with a carrier.

  Japanese Patent Application Laid-Open No. 2006-313302 (Patent Document 5) contains at least a binder resin, a colorant, and a wax component. I. Pigment yellow 155 and C.I. I. A yellow toner using Solvent Yellow 162 (dye) in combination is disclosed.

JP-A-11-202558 JP 2001-166540 A JP 2004-184562 A JP 2005-31163 A JP 2006-313302 A

  As shown in the prior art, many yellow toners using various yellow pigments as colorants have been proposed. However, according to the examination results of the present inventors, when yellow toner is produced by suspension polymerization using a yellow pigment having a low degree of hydrophobicity, colored polymer particles (yellow toner) having a broad particle size distribution are obtained. Colored polymer particles that are easy to produce and have an enlarged particle size may also be produced.

  Generally, according to the suspension polymerization method, colored polymer particles (polymerized toner) having a spherical shape and a small particle size with a sharp particle size distribution can be obtained. When such a polymerized toner is used, a high-definition image can be formed. However, yellow pigments with a low degree of hydrophobicity are difficult to uniformly disperse in a polymerizable monomer and it is difficult to form droplets having a sharp particle size distribution in an aqueous dispersion medium. The particle size distribution of the yellow toner obtained later tends to be broad, and the colorant tends to exist near the toner particle surface. If such a yellow toner is used, the image quality becomes insufficient and the printing durability also decreases.

  On the other hand, when yellow pigments with a high degree of hydrophobicity are used, yellow toner with a sharp particle size distribution can be obtained by suspension polymerization, but the image quality tends to decrease as the number of printed sheets increases, and printing durability Is significantly worse. Further, when a yellow pigment having a high degree of hydrophobicity is used, the viscosity when dispersed in the polymerizable monomer is increased, and the operational stability (handling property, particle size stability, etc.) is deteriorated.

  Furthermore, C.I. used as a yellow pigment in the above-mentioned prior art. I. Pigment Yellow 155 was found to have grades with different degrees of hydrophobicity. Thus, the same C.I. I. Yellow pigments classified as pigment yellow product numbers may have grades with different degrees of hydrophobicity, and when these are used alone, it is difficult to obtain yellow toner that exhibits satisfactory characteristics. is there. Even when two or more yellow pigments are used in combination, they are satisfactory when yellow pigments with low hydrophobicity are used in combination or yellow pigments with high hydrophobicity are used in combination. It is difficult to obtain a yellow toner exhibiting excellent characteristics.

  Accordingly, an object of the present invention is to provide a yellow toner that can form an image with excellent image quality, suppresses a decrease in image quality even when the number of printed sheets increases, and has excellent printing durability. is there.

  Another object of the present invention is to provide a method for producing a yellow toner, which can produce a yellow toner having good operational stability and a sharp molecular weight distribution even when a suspension polymerization method is employed. It is in.

  As a result of diligent research to solve the above-mentioned problems, the present inventors can accurately classify the hydrophobicity of yellow pigments by using the degree of precipitation initiation hydrophobicity as an indicator of the hydrophobicity of yellow pigments. And, it was found that the above-mentioned problem can be achieved by using a yellow pigment having a precipitation initiation hydrophobicity of 2% or more and a yellow pigment having a precipitation initiation hydrophobicity of less than 2%, preferably 0%, The present invention has been completed.

  According to the present invention, in a yellow toner containing at least a binder resin and a yellow pigment, the yellow pigment has a precipitation initiation hydrophobicity of 2% or more and a precipitation initiation hydrophobicity of 2%. A yellow toner comprising a combination of less than yellow pigment (b) is provided.

  Further, according to the present invention, in an aqueous dispersion medium containing a dispersion stabilizer, a polymerizable monomer composition containing at least a polymerizable monomer and a yellow pigment is added in the presence of a polymerization initiator. In the method for producing a yellow toner including a step of polymerizing to form colored polymer particles, the yellow pigment (a) having a precipitation initiation hydrophobicity of 2% or more and a precipitation initiation hydrophobicity of 2% as the yellow pigment There is provided a method for producing a yellow toner characterized by using a combination of less than yellow pigment (b).

  According to the present invention, it is possible to form an image with excellent image quality, and it is possible to provide a yellow toner excellent in printing durability, in addition, the deterioration in image quality is suppressed even when the number of printed sheets increases. In addition, according to the present invention, there is provided a method for producing a yellow toner capable of producing a yellow toner having good operational stability and a sharp molecular weight distribution even when a suspension polymerization method is employed. Can do.

  In the present invention, a yellow pigment (a) having a precipitation initiation hydrophobicity of 2% or more and a yellow pigment (b) having a precipitation initiation hydrophobicity of less than 2% are used in combination as the yellow pigment. The degree of hydrophobicity of starting precipitation of the yellow pigment can be measured on the basis of a methanol titration amount at which the yellow pigment starts to precipitate after the yellow pigment sample is floated on water and methanol is added dropwise with stirring. Details of the measurement method will be described in the following examples.

  When the precipitation initiation hydrophobicity is used as an index of hydrophobicity, the difference in hydrophobicity of the yellow pigment becomes clearer than when the hydrophobicity is used. The yellowish pigment (a) used in the present invention has a precipitation initiation hydrophobicity of 2% or more, preferably 3% or more, more preferably 5% or more. The upper limit of the precipitation-initiating hydrophobicity of the yellow pigment (a) is preferably 10%, and in many cases 8%. On the other hand, the yellowing degree hydrophobization degree of the yellow pigment (b) used in the present invention is less than 2%, preferably 1% or less, more preferably 0%.

  The yellow pigments (a) and (b) are generally 1 to 20 parts by weight, preferably 2 to 100 parts by weight of the binder resin or the polymerizable monomer forming the binder resin. It is used in a proportion of 15 parts by weight, more preferably 3 to 10 parts by weight. If the total amount of yellow pigments is too small, it will be difficult to obtain a yellow toner capable of expressing a sufficient yellow hue, and if it is too large, the polymerizable monomer composition will have too high a viscosity or an excessive tone. .

  The weight ratio (a: b) of the yellow pigments (a) and (b) is usually 10:90 to 90:10, preferably 20:80 to 80:20, more preferably 30:70 to 80:20. . When the proportion of the yellow pigment (a) is too small, the particle size distribution of the yellow toner tends to be broad, the image quality is lowered, and the printing durability tends to be lowered. When the ratio of the yellow pigment (a) is too large, the image quality is lowered as the number of printed sheets is increased, and the tendency of the printing durability to be lowered is also increased. When each of the yellow pigments (a) and (b) is used alone, a yellow toner having satisfactory toner characteristics cannot be obtained in either case. An image with high image quality can be formed, and even when the number of printed sheets is increased, deterioration in image quality is suppressed, and in addition, yellow toner having excellent printing durability can be obtained. A plurality of yellow pigments (a) and (b) may be used. For example, as the yellow pigment (b), a yellow pigment having a small precipitation initiation hydrophobicity may be used alone, or two or more kinds may be used.

  The yellow pigment (a) is based on the premise that the precipitation initiation hydrophobicity is 2% or more, and from the viewpoint of light resistance, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 151, and C.I. I. C.I. is preferably at least one selected from the group consisting of yellow pigments classified as pigment yellow 155; I. Pigment Yellow 155 is more preferable.

  The yellow pigment (b) is based on the premise that the precipitation initiation hydrophobicity is less than 2%, and from the viewpoint of light resistance, C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 151, and C.I. I. C.I. is preferably at least one selected from the group consisting of yellow pigments classified as pigment yellow 155; I. Pigment Yellow 155 is more preferable.

  The yellow toner of the present invention may be colored resin particles containing at least a binder resin and the two types of yellow pigments, and is not particularly limited by the production method. The colored resin particles are also called toner particles, and in the case of a polymerized toner, they are often called colored polymer particles.

  Examples of the method for producing the yellow toner include a pulverization method and a polymerization method. Examples of the polymerization method include an emulsion polymerization method, an aggregation method, a dispersion polymerization method, and a suspension polymerization method. According to the polymerization method, micron-order toner particles can be obtained directly with a relatively small particle size distribution. The yellow toner of the present invention may be a core-shell type toner (sometimes referred to as “capsule toner”) in which a resin (polymer) coating layer is formed on the surface of colored resin particles (colored polymer particles). The yellow toner of the present invention is particularly preferably colored polymer particles (polymerized toner) obtained by suspension polymerization from the viewpoint of toner characteristics. Since the polymer toner has a core-shell structure in which a shell composed of a polymer layer is formed on the surface of the colored polymer particles, low-temperature fixability and storage stability (blocking resistance) can be balanced. More preferable.

  Polymerized toner by suspension polymerization is a suspension polymerization of a polymerizable monomer composition containing at least a polymerizable monomer and a yellow pigment in an aqueous dispersion medium containing a dispersion stabilizer in the presence of a polymerization initiator. Can be obtained. A polymer formed by polymerization of the polymerizable monomer serves as a binder resin. The polymerized toner having a core-shell structure can be produced by a method such as a spray dry method, an interfacial reaction method, an in situ polymerization method, or a phase separation method. In particular, the in situ polymerization method and the phase separation method are preferable because of high production efficiency. Specifically, colored polymer particles obtained by suspension polymerization of a polymerizable monomer composition containing at least a polymerizable monomer and a yellow pigment in an aqueous dispersion medium containing a dispersion stabilizer. Can be obtained by suspension polymerization of the polymerizable monomer for shell in the presence of the core. A polymer layer formed by polymerization of the shell monomer is a coating layer. The polymerizable monomer composition may contain various additives such as a charge control agent, a release agent, a crosslinkable monomer, a macromonomer, a molecular weight modifier, a lubricant, and a dispersion aid as necessary. Can do.

  As the polymerizable monomer, a monovinyl monomer is preferable. Specifically, styrene monomers such as styrene, vinyl toluene, α-methyl styrene; acrylic acid, methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, Acrylic acid or methacrylic such as dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide Derivatives of acids; Ethylenically unsaturated monoolefins such as ethylene, propylene and butylene; Vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride; Vinyls such as vinyl acetate and vinyl propionate Esters; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl ketones such as vinyl methyl ketone and methyl isopropenyl ketone; nitrogen-containing vinyl compounds such as 2-vinyl pyridine, 4-vinyl pyridine and N-vinyl pyrrolidone; . Monovinyl monomers can be used alone or in combination of a plurality of monomers. Of the monovinyl monomers, it is preferable to use a styrene monomer and a (meth) acrylic acid derivative in combination.

  Use of a crosslinkable monomer and / or a crosslinkable polymer together with the polymerizable monomer is effective in improving hot offset resistance. The crosslinkable monomer is a monomer having two or more polymerizable carbon-carbon unsaturated double bonds, and examples thereof include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; Diethylenically unsaturated carboxylic acid esters such as methacrylate and diethylene glycol dimethacrylate; (meth) acrylates derived from aliphatic both-end alcohols such as 1,4-butanediol and 1,9-nonanediol; N, N-divinylaniline; Divinyl compounds such as divinyl ether; compounds having 3 or more vinyl groups;

  Examples of the crosslinkable polymer include polyethylene, polypropylene, polyester and polysiloxane-derived (meth) acrylate having two or more hydroxyl groups in the molecule. These crosslinkable monomers and crosslinkable polymers can be used alone or in combination of two or more. The crosslinkable monomer and / or crosslinkable polymer is usually 10 parts by weight or less, preferably 0.01 to 5 parts by weight, more preferably 0.1 to 2 parts per 100 parts by weight of the polymerizable monomer. Used in parts by weight.

  When a macromonomer is used together with a polymerizable monomer, the balance between storage stability, offset prevention property and low-temperature fixability can be improved. A macromonomer is a relatively long linear molecule having a polymerizable functional group (for example, an unsaturated group such as a carbon-carbon double bond) at the end of a molecular chain. As the macromonomer, an oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000 is preferable. When a macromonomer having a small number average molecular weight is used, the surface portion of the toner particles becomes soft and the storage stability is lowered. On the other hand, if a macromonomer having a large number average molecular weight is used, the meltability of the macromonomer is poor, and the toner fixability is lowered.

  Specific examples of the macromonomer include styrene, a styrene derivative, a methacrylic acid ester, an acrylic acid ester, acrylonitrile, a methacrylonitrile, a polymer obtained by polymerizing two or more kinds alone, and a macromonomer having a polysiloxane skeleton. Etc. Among the macromonomers, a polymer having a glass transition temperature higher than the glass transition temperature of the binder resin is preferable, and a copolymer macromonomer or polymethacrylic acid ester macromonomer of styrene and methacrylic acid ester and / or acrylic acid ester is particularly preferable. Is preferred. When using a macromonomer, the blending ratio is usually 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight, more preferably 0.05 to 100 parts by weight with respect to 100 parts by weight of the polymerizable monomer. 1 part by weight. When the proportion of the macromonomer used is too large, the fixability tends to decrease.

  Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan and n-octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide; These molecular weight modifiers can be added before the start of polymerization or during the polymerization. The molecular weight modifier is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, with respect to 100 parts by weight of the polymerizable monomer.

  For uniform dispersion of yellow pigments, lubricants such as fatty acids such as oleic acid and stearic acid, fatty acid metal salts composed of fatty acids and metals such as Na, K, Ca, Mg and Zn; silane-based or titanium-based coupling agents Dispersion aids such as: can be used. The lubricant and the dispersant are usually used at a ratio of about 1/1000 to 1/1 based on the weight of the yellow pigment.

  In order to improve the chargeability of the toner, various positively chargeable or negatively chargeable charge control agents are used. Examples of the charge control agent include Bontron N01 (manufactured by Orient Chemical), Nigrosine Base EX (manufactured by Orient Chemical), Spiro Black TRH (manufactured by Hodogaya Chemical), T-77 (manufactured by Hodogaya Chemical), and Bontron S-. 34 (manufactured by Orient Chemical), Bontron E-81 (manufactured by Orient Chemical), Bontron E-84 (manufactured by Orient Chemical), Bontron E-89 (manufactured by Orient Chemical), Bontron F-21 (manufactured by Orient Chemical) ), COPY CHRGE NX VP434 (Clariant), COPY CHRGE NEG VP2036 (Clariant), TNS-4-1 (Hodogaya Chemical), TNS-4-2 (Hodogaya Chemical), LR-147 Charge control agents such as Nippon Carlit Co., Ltd .; JP-A-11-15192 Quaternary ammonium (salt) group-containing copolymers described in JP-A-3-175456, JP-A-3-243594, etc., JP-A-3-243594, JP-A-1-217464, JP-A-3-243 Charge control resins such as sulfonic acid (salt) group-containing copolymers described in Japanese Patent No. 15858 can be used. The charge control agent is usually used in a proportion of 0.01 to 10 parts by weight, preferably 0.1 to 7 parts by weight, with respect to 100 parts by weight of the binder resin or the polymerizable monomer forming the binder resin. .

  The release agent is used for the purpose of preventing toner offset. Examples of the release agent include low molecular weight polyolefin waxes such as low molecular weight polyethylene, low molecular weight polypropylene, and low molecular weight polybutylene; molecular end oxidized low molecular weight polypropylene, low molecular weight end-modified polypropylene having molecular ends substituted with epoxy groups, and these And low molecular weight polyethylene block polymers, low molecular weight oxidized low molecular weight polyethylene, low molecular weight polyethylene with molecular ends substituted with epoxy groups, and terminal modified polyolefin waxes such as these and low molecular weight polypropylene block polymers; Candelilla, Carnauba, Rice, Plant-based natural waxes such as tree wax and jojoba; petroleum-based waxes such as paraffin, microcrystalline and petrolactam and their modified waxes; mineral waxes such as montan, ceresin and ozokerite Camphor; multi valence alcohol fatty acid ester compounds; synthetic waxes such as Fischer-Tropsch wax and a mixture thereof.

  Among the releasing agents, fatty acid ester compounds of polyhydric alcohols are preferable because they improve the low-temperature fixability of the toner and do not deteriorate the printing durability. Examples of the fatty acid ester compound of polyhydric alcohol include pentaerythritol esters such as pentaerythritol tetramyristate, pentaerythritol tetrapalmitate, pentaerythritol tetrastearate, pentaerythritol tetralaurate; dipentaerythritol hexamyristate, dipentalyst And dipentaerythritol esters such as erythritol hexapalmitate and dipentaerythritol hexalaurate; and fatty acid ester compounds of polyglycerin.

  When these mold release agents are used, the amount is usually 0.1 to 20 parts by weight, preferably 1 to 15 parts by weight, based on 100 parts by weight of the binder resin or the polymerizable monomer forming the binder resin. Used in proportions.

  As the polymerization initiator, a radical polymerization initiator is preferably used. Specifically, persulfates such as potassium persulfate and ammonium persulfate; 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2 '-Azobis-2-methyl-N-1,1-bis (hydroxymethyl) -2-hydroxyethylpropioamide, 2,2'-azobis (2,4-dimethylvaleronitrile), 2,2'-azo Azo compounds such as bisisobutyronitrile and 1,1'-azobis (1-cyclohexanecarbonitrile); isobutyryl peroxide, 2,4-dichlorobenzoyl peroxide, 3,5,5'-trimethylhexanoyl Diacyl peroxides such as peroxides; bis (4-t-butylcyclohexyl) peroxydicarbonate, di-n-propylperoxydi- -Bonate, di-isopropyl peroxy di-carbonate, di-2-ethoxyethyl peroxy di-carbonate, di (2-ethyl ethyl peroxy) di-carbonate, di-methoxybutyl peroxy di-carbonate, di (3- Peroxydicarbonates such as methyl-3-methoxybutylperoxy) dicarbonate; (α, α-bis-neodecanoylperoxy) diisopropylbenzene, cumylperoxyneodecanoate, 1,1 ′, 3, 3'-tetramethylbutylperoxyneodecanoate, 1-cyclohexyl-1-methylethylperoxyneodecanoate, t-hexylperoxyneodecanoate, t-butylperoxyneodecanoate, t- Hexyl peroxypivalate, t-butyl peroxypivalate Methyl peroxide, di-t-butyl peroxide, acetyl peroxide, dicumyl peroxide, lauroyl peroxide, benzoyl peroxide, t-butyl peroxy-2-ethylhexanoate, di-isopropyl peroxide Other peroxides such as dicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyisobutyrate are exemplified. A redox initiator in which these polymerization initiators and a reducing agent are combined can also be used.

  Among these polymerization initiators, an oil-soluble radical initiator that is soluble in the polymerizable monomer is preferable, and a water-soluble initiator can be used in combination with the initiator if necessary. The use ratio of the polymerization initiator is usually 0.1 to 20 parts by weight, preferably 0.3 to 15 parts by weight, more preferably 0.5 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer. is there. If the use ratio is too small, the polymerization rate is slow, and if it is too large, the molecular weight is low, which is not preferable. The polymerization initiator can be added to the monomer composition in advance, but it is added to the suspension after completion of the granulation process of the monomer composition in the aqueous dispersion medium in order to avoid premature polymerization. You can also

  Examples of the dispersion stabilizer used in the present invention include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metal oxides such as aluminum oxide and titanium oxide. Products; metal hydroxides such as aluminum hydroxide, magnesium hydroxide and ferric hydroxide; water-soluble polymers such as polyvinyl alcohol, methylcellulose and gelatin; anionic surfactants, nonionic surfactants, amphoteric surfactants Surfactants such as agents; and the like. Among these, metal compounds such as sulfates, carbonates, metal oxides and metal hydroxides are preferable, and colloids of slightly water-soluble metal compounds are more preferable. In particular, colloids of poorly water-soluble metal hydroxides are suitable because the particle size distribution of toner particles can be narrowed and the sharpness of images is improved.

The colloid of the hardly water-soluble metal compound is not limited by its production method, but the colloid of the hardly water-soluble metal hydroxide obtained by adjusting the pH of the aqueous solution of the water-soluble polyvalent metal compound to 7 or more, particularly water-soluble A colloid of a poorly water-soluble metal hydroxide produced by a reaction in a water phase of a functional polyvalent metal compound and an alkali metal hydroxide is preferred. The colloid of a hardly water-soluble metal compound has a number particle size distribution D ₅₀ (50% cumulative value of the number particle size distribution) of 0.5 μm or less and a D ₉₀ (90% cumulative value of the number particle size distribution) of 1 μm or less. Preferably there is. When the particle size of the colloid becomes too large, the stability of polymerization is lost, and the storage stability of the toner is lowered.

  The dispersion stabilizer is preferably used in a proportion of 0.1 to 20 parts by weight, more preferably 0.3 to 10 parts by weight with respect to 100 parts by weight of the polymerizable monomer. When this use ratio is too small, it becomes difficult to obtain sufficient polymerization stability, and polymerized aggregates are easily generated. On the other hand, if the use ratio is too large, the particle size distribution of the toner particles is broadened due to an increase in fine particles, or the viscosity of the aqueous solution is increased and the polymerization stability is lowered.

  In order to produce colored resin particles (colored polymer particles) by suspension polymerization, first, a polymerizable monomer, a colorant, and other additive components are mixed to prepare a polymerizable monomer composition. . Next, the polymerizable monomer composition is put into an aqueous medium containing a dispersion stabilizer and stirred with a high shearing force using a high-speed stirrer or the like, and the polymerizable monomer composition is added to the aqueous medium. A minute droplet is formed.

  In forming droplets of the polymerizable monomer composition, first, primary droplets having a volume average particle size of about 50 to 1000 μm are formed. In order to avoid premature polymerization, the polymerization initiator is preferably added to the aqueous dispersion medium after the primary droplet size in the aqueous medium becomes uniform. A polymerization initiator is added to and mixed with the suspension in which the primary droplets of the polymerizable monomer composition are dispersed in an aqueous dispersion medium, and the particle size of the droplets is adjusted using a high-speed rotary shearing stirrer. Stir until a small particle size close to the colored polymer particles. In this way, secondary droplets having a minute particle diameter of about 2 to 15 μm in volume average particle diameter are formed.

  The method of forming droplets is not particularly limited. For example, (in-line type) emulsifying disperser (trade name “Milder” manufactured by Ebara Manufacturing Co., Ltd.), high-speed emulsifier / disperser (made by Tokushu Kika Kogyo Co., Ltd., trade name “ TK homomixer MARK type II)).

  The polymerizable monomer composition dispersed as droplets in an aqueous medium is polymerized in the presence of a polymerization initiator to produce colored polymer particles. The polymerization temperature is usually 50 ° C. or higher, preferably 60 to 95 ° C. The reaction time of the polymerization is usually 1 to 20 hours, preferably 2 to 15 hours. The aqueous dispersion containing the produced colored polymer particles is filtered, and then the colored polymer particles are recovered through the steps of washing, dehydration, and drying.

  The polymerizable monomer used to form the colored polymer particles has a glass transition temperature Tg of a polymer obtained by polymerizing it of usually 80 ° C. or lower, preferably 40 to 80 ° C., more preferably 50 to 70. It is desirable to select so that it becomes ° C. By using the polymerizable monomer alone or in combination of two or more, the glass transition temperature of the polymer to be produced can be adjusted to a desired range.

  In the case of core-shell type colored polymer particles, the glass transition temperature of the polymer constituting the shell is preferably higher than the glass transition temperature of the polymer constituting the core colored polymer particle, more preferably 5 ° C or higher. It is particularly preferable that the temperature is 10 ° C. or higher. As the polymerizable monomer for the shell, styrene, methyl methacrylate, acrylonitrile, a mixture thereof and the like capable of forming a polymer having a high glass transition temperature exceeding 80 ° C. are preferable. The upper limit of the glass transition temperature is 110 ° C, often 105 ° C.

  Polymerization initiators used for the polymerization of the polymerizable monomer for shell include persulfate metal salts such as potassium persulfate and ammonium persulfate; 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) propion Amido], 2,2′-azobis- [2-methyl-N- [1,1-bis (hydroxymethyl) 2-hydroxyethyl] propionamide] and other azo-based initiators; Can be mentioned. The addition amount of the polymerization initiator is preferably 0.1 to 30 parts by weight, more preferably 1 to 20 parts by weight with respect to 100 parts by weight of the polymerizable monomer for shell. The polymerization temperature of the shell layer is preferably 50 ° C. or higher, more preferably 60 to 95 ° C. The polymerization reaction time is preferably 1 to 20 hours, more preferably 2 to 15 hours.

  Since the aqueous dispersion containing colored polymer particles (including core-shell type) produced by polymerization contains a dispersion stabilizer, a large number of fine particles of the dispersion stabilizer adhere to the surface of the colored polymer particles. ing. When an inorganic compound such as an inorganic hydroxide that is soluble in acid is used as the dispersion stabilizer, acid is added to the aqueous dispersion containing the produced colored polymer particles, and the dispersion stabilizer is washed with water. Dissolve in and remove. When the dispersion stabilizer is an alkali-soluble inorganic compound, the alkali is added to the aqueous dispersion containing the colored polymer particles, and the dispersion stabilizer is dissolved in water and removed.

  For example, when a colloid of a poorly water-soluble metal hydroxide such as magnesium hydroxide colloid is used as a dispersion stabilizer, an acid such as sulfuric acid is added to the aqueous dispersion to solubilize the dispersion stabilizer in water (this Is called "acid cleaning"). The pH of the aqueous dispersion is usually adjusted to 6.5 or less, preferably 2 to 6.5, more preferably 3 to 6.0 by acid washing. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid and nitric acid; organic acids such as formic acid and acetic acid can be used.

  The aqueous dispersion obtained in the acid washing or alkali washing step is filtered to separate the colored polymer particles. Next, the colored polymer particles separated by filtration are washed with water, and the washing water is filtered. In the water washing step, washing with water until the electric conductivity of the filtrate (filtered washing water) is 500 μS / cm or less, preferably 300 μS / cm or less, more preferably 100 μS / cm or less, and the washing water is filtered. preferable. The water washing step may be repeated batchwise or continuously using a belt filter or the like. As a cleaning apparatus used for water cleaning, for example, it is preferable to use any one of a belt filter, a rotary filter, and a filter press, or a combination thereof. After the washing step, the wet colored polymer particles are dehydrated and dried by the dehydration step.

  The toner particles (including the core-shell type) of the present invention have a volume average particle diameter (Dv) of usually 2 to 12 μm, preferably 3 to 11 μm, more preferably 6 to 10 μm. The particle size distribution represented by the ratio (Dv / Dp) of the volume average particle size (Dv) to the number average particle size (Dp) of the toner particles of the present invention is usually 1.0 to 1.4, preferably 1. 0.0-1.3, more preferably 1.0-1.2. If the volume average particle size of the toner particles is too large, the resolution is lowered and it becomes difficult to form a high-quality image.

  The volume specific resistance of the toner particles (including the core-shell type) of the present invention is preferably 11.2 (log Ω / cm) or more, and more preferably 11.3 (log Ω / cm) or more. When the volume resistivity is in the above range, the colorant and the electric resistance control agent are uniformly dispersed in the binder resin, so that the initial and post-durability printing characteristics are improved.

  The average thickness of the shell in the core-shell type toner particles is usually 0.001 to 1 μm, preferably 0.003 to 0.5 μm, more preferably 0.005 to 0.2 μm, and particularly preferably 0.02 to 0.05 μm ( 20-50 nm). If the shell thickness is too large, the fixing property is lowered, and if it is too small, the storage property is lowered. When the core particle diameter and the shell thickness of the polymerized toner can be observed with an electron microscope, they can be obtained by directly measuring the size and shell thickness of particles randomly selected from the observation photograph. If it is difficult to distinguish and observe the core particle and the shell with an electron microscope, calculate the thickness of the shell from the volume average particle diameter of the core particle and the amount of polymerizable monomer used to form the shell. Can do.

  In the case of a polymerized toner, the core-shell structure is formed by using the colored polymer particles as core particles, polymerizing a shell polymerizable monomer in the presence of the core particles, and polymer on the surface of the core particles. A method for forming a layer (shell) (in situ polymerization method) is preferred.

  When the yellow toner of the present invention is used as a nonmagnetic one-component developer, it is preferable to mix an external additive with the toner particles. Examples of the external additive include inorganic particles and organic resin particles that act as a fluidizing agent and an abrasive. Examples of the inorganic particles include silicon dioxide (silica), aluminum oxide, titanium oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. As organic resin particles, methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, a core is a methacrylic acid ester copolymer, and a shell And core-shell type particles formed of a styrene polymer.

  Among these, inorganic oxide particles are preferable, and silicon dioxide is particularly preferable. The surface of the inorganic fine particles can be hydrophobized, and silicon dioxide particles that have been hydrophobized are particularly suitable. Two or more types of external additives may be used in combination. In the case of using a combination of external additives, a method of combining inorganic particles having different average particle sizes or a combination of inorganic particles and organic resin particles is preferable. . The amount of the external additive is not particularly limited, but is usually 0.1 to 6 parts by weight with respect to 100 parts by weight of the toner particles. In order to attach the external additive to the toner particles, the toner particles and the external additive are usually placed in a mixer such as a Henschel mixer and stirred.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further in detail, this invention is not limited only to these Examples. Parts and% are based on weight unless otherwise specified. Various physical properties and characteristics were measured and evaluated by the following methods.

(1) Measurement of the hydrophobicity of the pigment:
A stir bar was placed in a 100 ml beaker, 50 ml of distilled water was added thereto, and the mixture was slowly stirred. A pigment sample of 0.2 g was placed on the water surface, methanol was added dropwise with stirring, and the methanol titer (ml) at which the pigment began to settle and the methanol titer (ml) at the end of sedimentation were confirmed. The sedimentation initiation hydrophobization degree (%) and hydrophobization degree were calculated by the following formulas (1) and (2), respectively. The measurement was performed three times, and the average value was defined as the degree of hydrophobicity.

X = [A / (A + 50)] × 100 (1)
X: Precipitation onset hydrophobicity (%)
A: Methanol titration at the start of sedimentation (ml)
50: Amount of distilled water (ml)
Y = [B / (B + 50)] × 100 (2)
Y: Hydrophobization degree (%)
B: Methanol titration at the end of sedimentation (ml)
50: Amount of distilled water (ml)

  In the above formula (1), when the degree of hydrophobicity of the pigment is low and sedimentation is started without dropping methanol, since A = 0, X = 0. In the above formula (2), when the degree of hydrophobicity of the pigment is low, the precipitation starts without dropping methanol, and the precipitation is completed, B = 0, so Y = 0. Even if the methanol titration amount is very small, X = 0 or Y = 0 may be obtained.

(2) Volume average particle size and particle size distribution of the toner:
The volume average particle diameter Dv of the toner (colored polymer particles; including the core-shell type) and the particle size distribution represented by the ratio Dv / Dp of the volume average particle diameter Dv to the number average particle diameter Dp are determined by a particle size measuring machine. (Beckman Coulter, trade name “Multisizer II”). The measurement conditions were as follows: aperture diameter = 100 μm, medium = isoton II, concentration = 10%, number of measured particles = 100,000. Specifically, 5 to 20 mg of a sample was taken in a beaker, and 0.1 to 1 ml of a surfactant (alkylbenzenesulfonic acid) was added. Add 0.5-2 ml of Isoton II to the beaker, moisten the toner, add 10-30 ml of Isoton II, and then disperse with an ultrasonic disperser for 1-3 minutes, then measure the particle size. Measurements were made with the instrument.

(3) Volume resistivity of toner:
The volume specific resistance of the toner was measured using a dielectric loss measuring device (trade name “TRS-10 type” manufactured by Ando Electric Co., Ltd.) under the conditions of a temperature of 30 ° C. and a frequency of 1 kHz.

(4) Durability printing test:
Toner was put in a developing device of a commercially available non-magnetic one-component developing type printer (printing speed: A4 size 24 sheets / min). After being left for 24 hours in a normal temperature and normal humidity (N / N) environment at a temperature of 23 ° C. and a relative humidity (RH) of 50%, continuous printing was performed up to 10,000 sheets at a 1% printing density in the same environment.

  Solid printing (printing at a printing density of 100%) was performed every 500 sheets, and the printing density of the solid printing part was measured using a reflection type image densitometer (manufactured by Macbeth, trade name “RD918”). After that, white solid printing (printing at a printing density of 0%) is performed, the printer is stopped in the middle of white solid printing, and the toner in the non-image area on the photoconductor after development is adhesive tape (manufactured by Sumitomo 3M, Product name “Scotch Mending Tape 810-3-18”) was affixed to the printing paper. Next, the color tone was measured with a spectral color difference meter (manufactured by Nippon Denshoku Industries Co., Ltd., trade name “SE-2000”). As a reference (reference sample), an unused adhesive tape was affixed to printing paper, and the color tone was measured in the same manner.

Each color tone is expressed as coordinates in L ^* a ^* b ^* space, and a color difference ΔE is calculated from the color tone of the measurement sample and the reference sample to obtain a fog value. The smaller this value is, the smaller the fog is. If the fog value ΔE is 1.0 or less, the image quality is good.

  The number of continuously printed sheets capable of maintaining an image quality with a print density of 1.2 or more and a fog value of 1.0 or less was examined up to 10,000 sheets. In the table, “> 10000” indicates that the above numerical standard is satisfied even when 10,000 sheets are printed.

(5) Image quality check:
In the above durability printing test, the initial printing and the solid printing at the time of 5000 sheets were visually confirmed, and those having no blur or density spots were evaluated as “good”, and those having blur or density spots were evaluated as “bad”.

[Example 1]
78 parts of styrene and 22 parts of n-butyl acrylate as monovinyl monomers (Tg of copolymer obtained by copolymerizing these monomers = 50 ° C.), polymethacrylate macromonomer (Toa Made by Synthetic Chemical Industry Co., Ltd., trade name “AA6”, Tg = 94 ° C.) 0.3 parts, cross-linkable monomer 0.6 parts divinylbenzene, molecular weight regulator 1.6 parts t-dodecyl mercaptan, and coloring C. as an agent I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) 4.5 parts and C.I. I. 1.5 parts of Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) was wet-ground using a media type disperser. To the mixture obtained by wet pulverization, 1 part of a charge control resin (trade name “Acrybase FCA-207P”, manufactured by Fujikura Kasei Co., Ltd.) as a charge control agent and fatty acid ester wax (trade name “WEP6”, manufactured by Nippon Oil & Fats Co., Ltd.) 5 parts was added, mixed and dissolved to prepare a polymerizable monomer composition.

  On the other hand, an aqueous solution in which 5.9 parts of sodium hydroxide is dissolved in 50 parts of ion-exchanged water is gradually added with stirring to an aqueous solution in which 10.6 parts of magnesium chloride is dissolved in 220 parts of ion-exchanged water. A magnesium colloidal dispersion was prepared.

  On the other hand, 2 parts of methyl methacrylate (Tg of the resulting polymer = 105 ° C.) and 130 parts of water were finely dispersed in an ultrasonic emulsifier to prepare an aqueous dispersion of a polymerizable monomer for shell.

  A polymerizable monomer composition is put into the magnesium hydroxide colloid dispersion (magnesium hydroxide colloid amount 4.3 parts), and further stirred, and t-butylperoxy-isobutyrate (as a polymerization initiator) is added thereto. 6 parts of Nippon Oil & Fats, trade name “Perbutyl IB”) was added. The dispersion added with the polymerization initiator is dispersed at a rotational speed of 15000 rpm using an in-line type emulsifying disperser (trade name “Ebara Milder MDN303V” manufactured by Ebara Seisakusho Co., Ltd.) to obtain a polymerizable monomer composition liquid Drops formed.

  A dispersion containing droplets of the polymerizable monomer composition was placed in a reactor, and the temperature was raised to 95 ° C. to conduct a polymerization reaction. After the polymerization conversion rate reached almost 100%, 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) as a polymerization initiator for the shell was added to the aqueous dispersion of the polymerizable monomer for the shell. -Propionamide] (trade name “VA-086”, manufactured by Wako Pure Chemical Industries, Ltd .; water-soluble initiator) in which 0.1 part was dissolved was added to the reactor. Subsequently, after maintaining at 95 degreeC for 4 hours and continuing superposition | polymerization, it cooled with water and reaction was stopped, and the aqueous dispersion of the core-shell type colored polymer particle was obtained.

  While stirring the aqueous dispersion of the colored polymer particles, sulfuric acid was added until the pH was 4.5 or lower and the acid washing was performed (25 ° C., 10 minutes). Wash with water and wash water was filtered. The electric conductivity of the filtrate at this time was 45 μS / cm. Further, the colored polymer particles after the washing / filtration step were dehydrated and dried to obtain dried colored polymer particles.

  To 100 parts of colored polymer particles, 0.6 part of silica fine particles hydrophobized with cyclic silazane (number primary average particle size = 7 nm) and silica fine particles hydrophobized with amino-modified silicone oil (number primary average particle size = 1 part of 35 nm) was added and mixed using a high-speed stirrer (trade name Henschel mixer, manufactured by Mitsui Mining Co., Ltd.) to prepare a non-magnetic one-component developer (electrophotographic toner). The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Example 2]
In Example 1, the amount of each pigment added was changed to C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) in 3 parts, C.I. I. An electrophotographic toner was prepared in the same manner as in Example 1 except that Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) was changed to 3 parts. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Example 3]
In Example 1, C.I. I. 1.5 parts of Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) I. An electrophotographic toner was prepared in the same manner as in Example 1 except that Pigment Yellow 120 (trade name “PV FAST Tellow H2G” manufactured by Clariant Co., Ltd.) was changed to 1.5 parts. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Example 4]
In Example 1, C.I. I. 1.5 parts of Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) I. An electrophotographic toner was prepared in the same manner as in Example 1 except that Pigment Yellow 151 (trade name “IRGAZINE Yellow 2088” manufactured by Ciba Specialty Chemicals, Inc.) was changed to 1.5 parts. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Example 5]
In Example 1, C.I. I. 1.5 parts of Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) I. An electrophotographic toner was prepared in the same manner as in Example 1 except that CI Pigment Yellow 139 (trade name “Paliotol Yellow D1819” manufactured by BASF Corporation) was changed to 1.5 parts. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Comparative Example 1]
In Example 1, C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) 4.5 parts and C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) 1.5 parts instead of C.I. I. An electrophotographic toner was prepared in the same manner as in Example 1 except that 6 parts of Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) was used. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Comparative Example 2]
In Example 1, C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) 4.5 parts and C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) 1.5 parts instead of C.I. I. An electrophotographic toner was prepared in the same manner as in Example 1 except that 6 parts of Pigment Yellow 155 (trade name “Novoperm Yellow 4G01”, manufactured by Clariant) was used. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Comparative Example 3]
In Example 1, C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) 4.5 parts and C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Novoperm Yellow 4G01”) 1.5 parts instead of C.I. I. An electrophotographic toner was prepared in the same manner as in Example 1 except that 6 parts of Pigment Yellow 120 (trade name “PV FAST Tellow H2G” manufactured by Clariant Co., Ltd.) was used. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

[Comparative Example 4]
In Example 2, C.I. I. Pigment Yellow 155 (manufactured by Clariant, trade name “Toner Yellow 3GP”) instead of 3.0 parts, C.I. I. An electrophotographic toner was prepared in the same manner as in Example 2 except that 3.0 parts of Pigment Yellow 120 (manufactured by Clariant, trade name “PV FAST Tellow H2G”) was used. The characteristics of the pigments used are shown in Table 1, and the test results of the toner characteristics are shown in Table 2.

  The yellow toner of the present invention can be used as a developer for developing an electrostatic latent image formed on a photoreceptor in an electrophotographic (including electrostatic printing) image forming apparatus. The yellow toner of the present invention can be used as a developer for forming a full color image in combination with a cyan toner or a magenta toner. As the developer, a non-magnetic one-component developer is preferable.

Claims (5)

  In a yellow toner containing at least a binder resin and a yellow pigment, the yellow pigment comprises a yellow pigment (a) having a precipitation initiation hydrophobicity of 2% or more and a yellow pigment (b) having a precipitation initiation hydrophobicity of less than 2%. ) In combination with a yellow toner.   The yellow pigment (a) is C.I. I. The yellow toner according to claim 1, wherein the yellow toner is selected from yellow pigments classified as CI Pigment Yellow 155.   The yellow toner according to claim 1, wherein the yellow pigment (b) is a yellow pigment having a precipitation initiation hydrophobicity of 0%.   The yellow pigment (b) is C.I. I. Pigment yellow 120, C.I. I. Pigment yellow 139, C.I. I. Pigment yellow 151, and C.I. I. The yellow toner according to claim 3, which is at least one selected from the group consisting of yellow pigments classified as pigment yellow 155. 5.   Colored polymer particles obtained by polymerizing a polymerizable monomer composition containing at least a polymerizable monomer and a yellow pigment in the presence of a polymerization initiator in an aqueous dispersion medium containing a dispersion stabilizer. In the method for producing a yellow toner including a step of forming a yellow pigment (a) having a precipitation initiation hydrophobicity of 2% or more and a yellow pigment (b) having a precipitation initiation hydrophobicity of less than 2%, as the yellow pigment A method for producing a yellow toner, wherein the toner is used in combination.