JP6269653B2 - Method for producing yellow toner - Google Patents

Description

  The present invention relates to a method for producing yellow toner that can be used for development of an image forming apparatus using electrophotography such as a copying machine, a facsimile machine, and a printer.

  In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed on a photoreceptor is first developed with toner. Next, the formed toner image is transferred onto a transfer material such as paper as necessary, and then fixed by various methods such as heating, pressurization, or solvent vapor.

In such image forming apparatuses, digital full-color copiers and digital full-color printers have been put into practical use. The digital full-color copying machine separates a color image original with blue, green and red filters, and then converts an electrostatic latent image having a dot diameter of 20 to 70 μm corresponding to the original color original into yellow, magenta, Development is performed using cyan and black toners, and a full-color image is formed using a subtractive color mixing effect.
The full-color toners for each color are required to have the same level of coloring power so that accurate color reproduction can be achieved. However, among the full-color toners, the yellow toner has a problem that the coloring power is low. .

  In order to improve coloring power, for example, Patent Document 1 discloses a yellow toner containing a combination of two yellow pigments having different precipitation initiation hydrophobicity. In Patent Document 2, a mixture containing a polymerizable monomer and a yellow pigment is dispersed by a disperser, and a primary amine is added to the polymerizable monomer mixture in which the yellow pigment is dispersed in the polymerizable monomer. A method for producing a yellow toner is disclosed in which a compound is added and a dispersion treatment is performed in the presence of the primary amine compound. In Patent Document 3, a yellow toner using a pigment dispersion obtained by adding a basic alkali metal salt aqueous solution to a mixture containing at least a yellow pigment and a polymerizable monomer and performing a dispersion treatment, and a method for producing the same Is disclosed.

  On the other hand, C.I. I. Pigment Yellow 93 is generally used in toner applications because it is generally said to be excellent in heat resistance and weather resistance, and also excellent in coloring power. However, this C.I. I. Even in Pigment Yellow 93, the coloring power may be insufficient, so that the coloring power is increased.

  Patent Documents 4 and 5 disclose C.I. as a yellow colorant in a yellow toner containing at least a binder resin and a yellow colorant. I. A yellow toner containing a dye having a specific structure in a yellow pigment including CI Pigment Yellow 93 is disclosed.

JP 2008-242240 A JP 2009-157017 A JP 2012-111873 A JP 2000-162824 A JP 2011-257706 A

On the other hand, C.I. I. Since most pigments including CI Pigment Yellow 93 are chemically synthesized by a batch reaction, the amount of impurities contained in the pigment may differ between production lots, and the toner obtained by the difference in the amount of impurities There was a difference.
As a result of intensive studies on the above problems, the present inventors have found that C.I. I. It was found that when Pigment Yellow 93 was used, there was a problem that the coloring power greatly fluctuated depending on the production lot.
An object of the present invention is to provide a method for producing a yellow toner that solves the above-described problems and obtains a certain coloring power.

  In order to solve the above problems, the present inventors have determined that C.I. I. Focusing on the difference in calcium content in Pigment Yellow 93, by using a yellow pigment with this calcium content in a specific range, the above problems can be solved, and the image density (coloring power) is high and stable. It has been found that yellow toner can be produced.

  That is, according to the present invention, as a yellow pigment, C.I. I. There is provided a method for producing yellow toner, characterized by using CI Pigment Yellow 93.

  In the present invention, it is preferable to include at least a step of forming an organic phase in which the raw material for toner containing the yellow pigment is dispersed, and emulsifying or dispersing the organic phase in an aqueous medium.

  In the present invention, the organic phase in which the toner raw material containing the yellow pigment is dispersed preferably has a viscosity at 25 ° C. of 500 to 3,500 mPa · s.

  In the present invention, a polymerizable monomer composition in which a raw material for toner containing at least a polymerizable monomer and the yellow pigment is dispersed is prepared, and the polymerizable monomer composition is added to an aqueous medium containing a dispersion stabilizer. It is more preferable to include a step of dispersing the monomer composition and polymerizing in the presence of a polymerization initiator to form colored resin particles.

  In the present invention, the polymerizable monomer composition preferably has a viscosity at 25 ° C. of 500 to 3,500 mPa · s.

  According to the method for producing a yellow toner of the present invention as described above, C.I. I. By using CI Pigment Yellow 93, a yellow toner having a high image density, in particular, less likely to cause fogging in a high-temperature and high-humidity (H / H) environment, and having a more uniform particle diameter than before.

  The method for producing a yellow toner of the present invention is a C.I. having a Ca content of 400 to 2,000 ppm as a yellow pigment. I. Pigment Yellow 93 is used.

A method for producing the yellow toner of the present invention (hereinafter sometimes simply referred to as “toner”) will be described below.
The yellow toner produced according to the present invention preferably contains colored resin particles containing a binder resin and a yellow pigment.
Hereinafter, the method for producing colored resin particles used in the present invention, the colored resin particles obtained by the production method, the method for producing the yellow toner of the invention using the colored resin particles, and the yellow toner obtained by the production method Will be described in order.

1. Production method of colored resin particles Generally, the production method of colored resin particles is roughly classified into dry methods such as a pulverization method, and wet methods such as an emulsion polymerization aggregation method, a suspension polymerization method, and a dissolution suspension method. The wet method is preferable because it is easy to obtain a toner excellent in printing characteristics such as the property. Among wet methods, a polymerization method such as an emulsion polymerization aggregation method and a suspension polymerization method is preferable because a toner having a relatively small particle size distribution on the order of microns is preferable. A suspension polymerization method is more preferable among polymerization methods. preferable.

  In the emulsion polymerization aggregation method, an emulsified polymerizable monomer is polymerized to obtain a resin fine particle emulsion, which is aggregated with a colorant dispersion or the like to produce colored resin particles. The dissolution suspension method produces droplets of a solution in which toner components such as a binder resin and a colorant are dissolved or dispersed in an organic solvent in an aqueous medium, and the organic solvent is removed to produce colored resin particles. Each of which is a known method.

The method for producing a yellow toner of the present invention includes at least a step of forming an organic phase in which a raw material for toner containing a yellow pigment described later is dispersed, and granulating the organic phase by emulsifying or dispersing in an aqueous medium. It is preferable. Examples of the production method including such steps include a suspension polymerization method and a dissolution suspension method. The toner raw material referred to here is a mixture containing a yellow resin, a binder resin, and other additives such as a charge control agent added as necessary, as described later.
In these suspension polymerization methods and dissolution suspension methods, the viscosity at 25 ° C. of the organic phase in which the toner raw material containing the yellow pigment described later is dispersed is preferably 500 to 3,500 mPa · s. When the viscosity is less than 500 mPa · s, the dispersion stability of the yellow pigment in the organic phase is lowered, and the image density may be lowered. On the other hand, when the viscosity exceeds 3,500 mPa · s, the circularity of the obtained toner may be lowered.
About the said organic phase, it is more preferable that the viscosity in 25 degreeC is 1,000-3,000 mPa * s, and it is further more preferable that it is 1,500-2,700 mPa * s.

  The colored resin particles of the present invention can be produced by employing a wet method or a dry method. Among the wet methods, a preferred suspension polymerization method is adopted, and the following process is performed.

(A) Suspension polymerization method (A-1) Preparation step of polymerizable monomer composition First, other additives such as a polymerizable monomer and a yellow pigment, and a charge control agent added as necessary. To prepare a polymerizable monomer composition. The mixing at the time of preparing the polymerizable monomer composition is performed using, for example, a media type dispersing machine.

  In the present invention, the polymerizable monomer means a monomer having a polymerizable functional group, and the polymerizable monomer is polymerized to become a binder resin. It is preferable to use a monovinyl monomer as the main component of the polymerizable monomer. Examples of the monovinyl monomer include styrene; styrene derivatives such as vinyl toluene and α-methylstyrene; acrylic acid and methacrylic acid; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, acrylic acid 2 Acrylic esters such as ethylhexyl and dimethylaminoethyl acrylate; methacrylic esters such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate and dimethylaminoethyl methacrylate; acrylonitrile And nitrile compounds such as methacrylonitrile; amide compounds such as acrylamide and methacrylamide; and olefins such as ethylene, propylene, and butylene. These monovinyl monomers can be used alone or in combination of two or more. Of these, styrene, styrene derivatives, and acrylic esters or methacrylic esters are preferably used as monovinyl monomers.

In order to improve hot offset and storage stability, it is preferable to use any crosslinkable polymerizable monomer together with the monovinyl monomer. A crosslinkable polymerizable monomer means a monomer having two or more polymerizable functional groups. Examples of the crosslinkable polymerizable monomer include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; alcohols having two or more hydroxyl groups such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; Ester compounds in which two or more carboxylic acids having a carbon-carbon double bond are ester-bonded; other divinyl compounds such as N, N-divinylaniline and divinyl ether; compounds having three or more vinyl groups; Can be mentioned. These crosslinkable polymerizable monomers can be used alone or in combination of two or more.
In the present invention, the crosslinkable polymerizable monomer is usually used at a ratio of 0.1 to 5 parts by mass, preferably 0.3 to 2 parts by mass with respect to 100 parts by mass of the monovinyl monomer. desirable.

Furthermore, it is preferable to use a macromonomer as a part of the polymerizable monomer because the balance between the storage stability of the obtained toner and the fixing property at low temperature is improved. The macromonomer has a polymerizable carbon-carbon unsaturated double bond at the end of the molecular chain, and is a reactive oligomer or polymer having a number average molecular weight of usually 1,000 to 30,000. The macromonomer is preferably one that gives a polymer having a higher Tg than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer (hereinafter sometimes referred to as “Tg”).
The macromonomer is preferably used in an amount of 0.03 to 5 parts by mass, more preferably 0.05 to 1 part by mass, with respect to 100 parts by mass of the monovinyl monomer.

In the present invention, C.I. having a Ca content of 400 to 2,000 ppm as a yellow pigment. I. The use of pigment yellow 93 is one of the main features.
In the present invention, “Ca content” means the content of calcium element.
In the present invention, “CI Pigment Yellow 93 having a Ca content of 400 to 2,000 ppm” refers to C.I. I. This means that 400 to 2,000 ppm of calcium element is present as an impurity in CI Pigment Yellow 93.

When the Ca content in the yellow pigment is less than 400 ppm, as shown in Comparative Example 1 described later, the image density of the obtained toner is low. This is because when the Ca content is too low, the dispersion stability of the yellow pigment in the organic phase is lowered, or the dispersibility in the binder resin is lowered, and the yellow pigment in the toner tends to aggregate. This is thought to be due to falling into On the other hand, when the Ca content in the yellow pigment exceeds 2,000 ppm, as shown in Comparative Examples 2 and 3 to be described later, the image density of the obtained toner is low and fog is likely to occur. This is considered to be due to the fact that when the Ca content is too high, the obtained toner easily absorbs moisture.
The Ca content in the yellow pigment is preferably 600 to 1,600 ppm, and more preferably 800 to 1,200 ppm.

Thus, in the present invention, the Ca content in the yellow pigment is an index of the viscosity of the polymerizable monomer composition.
According to the study by the present inventors, when the Ca content in the yellow pigment is in the range of 0 to 1,200 ppm, the viscosity of the organic phase in which the yellow pigment is dispersed decreases as the Ca content increases. There is a tendency.

According to the study by the present inventors, the same C.I. I. The pigment content of Pigment Yellow 93 and the same product are widely distributed in Ca content. This is because C.I. I. The pigment yellow 93 shows that the performance varies depending on the manufacturer, the product type, or the lot of the same product.
The present invention provides such a C.I. I. The objective is to select the optimum lot for yellow toner production by determining whether the performance of Pigment Yellow 93 is good or bad by using an index of Ca content.

The Ca content in the yellow pigment can be appropriately adjusted according to the conditions at the time of yellow pigment synthesis.
For example, as a method for refining a yellow pigment, a so-called salt milling method is known in which a yellow pigment and an inorganic salt are mixed while applying a shearing force. When a calcium salt is used in the salt milling method, it is considered that the Ca content in the yellow pigment can be improved.
Further, the Ca content in the yellow pigment can also be adjusted in the step of washing the yellow pigment. For example, it is considered that the Ca content in the yellow pigment can be improved by washing the yellow pigment with hard water containing calcium ions. Moreover, it is thought that Ca content in a yellow pigment can be reduced by washing the yellow pigment with soft water from which calcium ions have been removed by ion exchange.

  In the present invention, C.I. I. Pigment Yellow 93 may be used in combination with one or more other yellow colorants. Examples of other yellow colorants include monoazo pigments, azo pigments such as disazo pigments, and compounds such as condensed polycyclic pigments. I. Pigment yellow 3, 12, 13, 14, 15, 17, 62, 65, 73, 74, 83, 97, 120, 138, 155, 180, 181, 185, 186, and 213.

  From the viewpoint of improving the releasability of the toner from the fixing roll during fixing, it is preferable to add a release agent to the polymerizable monomer composition. Any releasing agent can be used without particular limitation as long as it is generally used as a releasing agent for toner.

The release agent preferably contains at least one of ester wax and hydrocarbon wax. By using these waxes as a release agent, the balance between low-temperature fixability and storage stability can be made suitable.
The ester wax suitably used as the release agent in the present invention is more preferably a polyfunctional ester wax, such as pentaerythritol ester such as pentaerythritol tetrapalinate, pentaerythritol tetrabehenate, pentaerythritol tetrastearate, etc. Compound: hexaglycerin tetrabehenate tetrapalinate, hexaglycerin octabehenate, pentaglycerin heptabehenate, tetraglycerin hexabehenate, triglycerin pentabehenate, diglycerin tetrabehenate, glycerin tribe Glycerin ester compounds such as henate; Dipentaerythritol ester compounds such as dipentaerythritol hexamyristate and dipentaerythritol hexapalmitate; It is.

Examples of the hydrocarbon wax suitably used as a release agent in the present invention include polyethylene wax, polypropylene wax, Fischer-Tropsch wax, paraffin wax, microstarin wax, petroleum-based wax, etc., among which Fischer-Tropsch wax, petroleum-based wax Waxes are preferred and petroleum waxes are more preferred.
The number average molecular weight of the hydrocarbon wax is preferably 300 to 800, more preferably 400 to 600. Moreover, the penetration of the hydrocarbon wax measured by JIS K2235 5.4 is preferably 1 to 10, and more preferably 2 to 7.

In addition to the mold release agent, for example, natural wax such as jojoba; mineral wax such as ozokerite;
The release agent is preferably a combination of one or more waxes as described above.
The release agent is preferably used in an amount of 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass with respect to 100 parts by mass of the monovinyl monomer.

As other additives, a positively or negatively chargeable charge control agent can be used to improve the chargeability of the toner.
The charge control agent is not particularly limited as long as it is generally used as a charge control agent for toner, but among charge control agents, the compatibility with the polymerizable monomer is high, and stable chargeability. (Charge stability) can be imparted to the toner particles, and therefore a positively or negatively chargeable charge control resin is preferred. Further, from the viewpoint of obtaining a positively chargeable toner, a positively chargeable charge control resin is preferred. More preferably used.
Examples of positively chargeable charge control agents include nigrosine dyes, quaternary ammonium salts, triaminotriphenylmethane compounds and imidazole compounds, polyamine resins as charge control resins that are preferably used, and quaternary ammonium group-containing copolymers. , And quaternary ammonium base-containing copolymers.
Negatively chargeable charge control agents include azo dyes containing metals such as Cr, Co, Al, and Fe, salicylic acid metal compounds and alkylsalicylic acid metal compounds, and sulfonic acid group containing charge control resins that are preferably used Examples thereof include a copolymer, a sulfonate group-containing copolymer, a carboxylic acid group-containing copolymer, and a carboxylic acid group-containing copolymer.
In the present invention, the charge control agent is usually used in a proportion of 0.01 to 10 parts by mass, preferably 0.03 to 8 parts by mass, with respect to 100 parts by mass of the monovinyl monomer. If the addition amount of the charge control agent is less than 0.01 parts by mass, fog may occur. On the other hand, when the addition amount of the charge control agent exceeds 10 parts by mass, printing stains may occur.

As other additives, it is preferable to use a molecular weight modifier when polymerizing a polymerizable monomer that is polymerized to become a binder resin.
The molecular weight modifier is not particularly limited as long as it is generally used as a molecular weight modifier for toner. For example, t-dodecyl mercaptan, n-dodecyl mercaptan, n-octyl mercaptan, and 2,2, Mercaptans such as 4,6,6-pentamethylheptane-4-thiol; tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, N, N′-dimethyl-N, N′-diphenylthiuram disulfide, N, And thiuram disulfides such as N′-dioctadecyl-N, N′-diisopropylthiuram disulfide; These molecular weight modifiers may be used alone or in combination of two or more.
In this invention, it is desirable to use a molecular weight modifier in the ratio of 0.01-10 mass parts normally with respect to 100 mass parts of monovinyl monomers, Preferably it is 0.1-5 mass parts.

(A-2) Suspension step for obtaining a suspension (droplet formation step)
In the present invention, a polymerizable monomer composition containing at least a polymerizable monomer and a yellow pigment is dispersed in an aqueous medium containing a dispersion stabilizer, a polymerization initiator is added, and then the polymerizable monomer is added. It is preferable to perform droplet formation of the composition. The method of forming the droplet is not particularly limited, but, for example, an (in-line type) emulsifying disperser (trade name: Milder, manufactured by Taiheiyo Kiko Co., Ltd.), a high-speed emulsifying disperser (manufactured by PRIMIX Corporation, trade name: TK Homomixer (MARK II type) and the like capable of strong stirring.

  As a polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate: 4,4′-azobis (4-cyanovaleric acid), 2,2′-azobis (2-methyl-N- (2- Hydroxyethyl) propionamide), 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis (2,4-dimethylvaleronitrile), and 2,2′-azobisisobutyronitrile Azo compounds such as: di-t-butyl peroxide, benzoyl peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxydiethyl acetate, t-hexylperoxy-2-ethylbutanoate Diisopropyl peroxydicarbonate, di-t-butylperoxyisophthalate, and t-butylperoxyiso Organic peroxides such as Chireto like. These can be used alone or in combination of two or more. Among these, it is preferable to use an organic peroxide because residual polymerizable monomers can be reduced and printing durability is excellent.

  Among organic peroxides, peroxyesters are preferable because non-aromatic peroxyesters, that is, peroxyesters having no aromatic ring, are preferable because initiator efficiency is good and the amount of remaining polymerizable monomers can be reduced. More preferred.

  As described above, the polymerization initiator may be added before the droplet formation after the polymerizable monomer composition is dispersed in the aqueous medium. However, the polymerization initiator is not dispersed in the aqueous medium. It may be added to the monomer composition.

  The addition amount of the polymerization initiator used for the polymerization of the polymerizable monomer composition is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 100 parts by mass of the monovinyl monomer. It is -15 mass parts, Most preferably, it is 1-10 mass parts.

  In the present invention, the aqueous medium refers to a medium containing water as a main component.

  In the present invention, the aqueous medium preferably contains a dispersion stabilizer. Examples of the dispersion stabilizer include sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metals such as aluminum oxide and titanium oxide. Oxides; metal hydroxides such as aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; inorganic compounds such as; water-soluble polymers such as polyvinyl alcohol, methylcellulose, and gelatin; anionic surfactants; Organic compounds such as nonionic surfactants; amphoteric surfactants; The said dispersion stabilizer can be used 1 type or in combination of 2 or more types.

  Among the above dispersion stabilizers, inorganic compounds, particularly colloids of poorly water-soluble metal hydroxides are preferred. By using a colloid of an inorganic compound, particularly a poorly water-soluble metal hydroxide, the particle size distribution of the colored resin particles can be narrowed, and the residual amount of the dispersion stabilizer after washing can be reduced. The toner thus produced can reproduce the image clearly and has excellent environmental stability.

(A-3) Polymerization step As in (A-2) above, droplet formation is performed, the resulting aqueous dispersion medium is heated to initiate polymerization, and an aqueous dispersion of colored resin particles is formed.
The polymerization temperature of the polymerizable monomer composition 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.

About a polymerizable monomer composition, it is preferable that the viscosity in 25 degreeC is 500-3,500 mPa * s. When the viscosity is less than 500 mPa · s, the dispersion stability of the yellow pigment in the organic phase is lowered, and the image density may be lowered. On the other hand, when the viscosity exceeds 3,500 mPa · s, the circularity of the obtained toner may be lowered.
As for the polymerizable monomer composition, the viscosity at 25 ° C. is more preferably 1,000 to 3,000 mPa · s, and further preferably 1,500 to 2,700 mPa · s.

  The colored resin particles may be used as a polymerized toner by adding an external additive as it is, but the so-called core-shell type obtained by using the colored resin particles as a core layer and forming a shell layer different from the core layer on the outside thereof. It is preferable to use colored resin particles (also referred to as “capsule type”). The core-shell type colored resin particles balance the reduction of the fixing temperature and the prevention of aggregation during storage by coating the core layer made of a material having a low softening point with a material having a higher softening point. be able to.

  There is no restriction | limiting in particular as a method of manufacturing a core shell type colored resin particle using the said colored resin particle mentioned above, It can manufacture by a conventionally well-known method. An in situ polymerization method and a phase separation method are preferable from the viewpoint of production efficiency.

A method for producing core-shell type colored resin particles by in situ polymerization will be described below.
Addition of a polymerizable monomer (polymerizable monomer for shell) and a polymerization initiator to form a shell layer into an aqueous medium in which colored resin particles are dispersed, and then polymerize to form a core-shell type color. Resin particles can be obtained.

  As the polymerizable monomer for the shell, the same monomers as the aforementioned polymerizable monomers can be used. Among them, it is preferable to use monomers such as styrene, acrylonitrile, and methyl methacrylate, which can obtain a polymer having a Tg exceeding 80 ° C., alone or in combination of two or more.

  As a polymerization initiator used for polymerization of the polymerizable monomer for shell, persulfate metal salts such as potassium persulfate and ammonium persulfate; 2,2′-azobis (2-methyl-N- (2-hydroxyethyl) Water-soluble such as azo initiators such as) propionamide) and 2,2′-azobis- (2-methyl-N- (1,1-bis (hydroxymethyl) 2-hydroxyethyl) propionamide); A polymerization initiator can be mentioned. These can be used alone or in combination of two or more. The amount of the polymerization initiator is preferably 0.1 to 30 parts by mass, and more preferably 1 to 20 parts by mass with respect to 100 parts by mass 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.

(A-4) Washing, filtration, dehydration, and drying steps The aqueous dispersion of colored resin particles obtained by polymerization is washed, dehydrated, and filtered to remove the dispersion stabilizer according to a conventional method after completion of the polymerization. The drying operation is preferably repeated several times as necessary.

  As the above washing method, when an inorganic compound is used as the dispersion stabilizer, the dispersion stabilizer can be dissolved in water and removed by adding an acid or alkali to the aqueous dispersion of colored resin particles. preferable. When a colloid of a poorly water-soluble inorganic hydroxide is used as the dispersion stabilizer, it is preferable to adjust the pH of the colored resin particle aqueous dispersion to 6.5 or less by adding an acid. As the acid to be added, inorganic acids such as sulfuric acid, hydrochloric acid, and nitric acid, and organic acids such as formic acid and acetic acid can be used. Particularly, since the removal efficiency is large and the burden on the manufacturing equipment is small, Sulfuric acid is preferred.

  Various known methods and the like can be used as the method of dehydration and filtration, and there is no particular limitation. Examples thereof include a centrifugal filtration method, a vacuum filtration method, and a pressure filtration method. Also, the drying method is not particularly limited, and various methods can be used.

(B) Pulverization method When the pulverization method is used to produce colored resin particles, the following process is performed.
First, a binder resin, a yellow pigment, and other additives such as a charge control agent added as necessary are mixed in a mixer, such as a ball mill, a V-type mixer, an FM mixer (trade name), a high-speed dissolver, Mix using an internal mixer. Next, the mixture obtained as described above is kneaded while being heated using a pressure kneader, a twin-screw extrusion kneader, a roller or the like. The obtained kneaded material is coarsely pulverized using a pulverizer such as a hammer mill, a cutter mill, or a roller mill. Furthermore, after finely pulverizing using a pulverizer such as a jet mill or a high-speed rotary pulverizer, it is classified into a desired particle size by a classifier such as an air classifier or an airflow classifier, and colored resin particles obtained by a pulverization method Get.

  In addition, as the binder resin and yellow pigment used in the pulverization method, and other additives such as a charge control agent added as necessary, those mentioned in the above (A) suspension polymerization method can be used. . Further, the colored resin particles obtained by the pulverization method can be made into core-shell type colored resin particles by a method such as an in situ polymerization method in the same manner as the colored resin particles obtained by the suspension polymerization method (A) described above.

  As the binder resin, other resins that have been widely used for toners can be used. Specific examples of the binder resin used in the pulverization method include polystyrene, styrene-butyl acrylate copolymer, polyester resin, and epoxy resin.

2. Colored resin particles Colored resin particles are obtained by a production method such as the above-described (A) suspension polymerization method or (B) pulverization method.
Hereinafter, the colored resin particles constituting the toner will be described. The colored resin particles described below include both core-shell type and non-core type.

  The volume average particle diameter (Dv) of the colored resin particles is preferably 4 to 12 μm, and more preferably 5 to 10 μm. When Dv is less than 4 μm, the fluidity of the toner is lowered, the transferability may be deteriorated, and the image density may be lowered. When Dv exceeds 12 μm, the resolution of the image may decrease.

  The colored resin particles preferably have a ratio (Dv / Dn) of the volume average particle diameter (Dv) to the number average particle diameter (Dn) of 1.0 to 1.30, more preferably 1. 0-1.25. When Dv / Dn exceeds 1.30, transferability, image density, and resolution may decrease. The volume average particle diameter and the number average particle diameter of the colored resin particles can be measured using, for example, a particle size analyzer (trade name: Multisizer, manufactured by Beckman Coulter).

From the viewpoint of image reproducibility, the average circularity of the colored resin particles of the present invention is preferably 0.96 to 1.00, more preferably 0.97 to 1.00, and 0.98 to More preferably, it is 1.00.
When the average circularity of the colored resin particles is less than 0.96, the fine line reproducibility of printing may be deteriorated.

  In the present invention, the circularity is defined as a value obtained by dividing the circumference of a circle having the same projected area as the particle image by the circumference of the projected image of the particle. The average circularity in the present invention is used as a simple method for quantitatively expressing the shape of the particles, and is an index indicating the degree of unevenness of the colored resin particles. The average circularity is determined by the colored resin particles. 1 is shown in the case of a perfect sphere, and the value becomes smaller as the surface shape of the colored resin particles becomes more complicated.

3. Method for Producing Yellow Toner In the present invention, the colored resin particles are mixed and stirred together with an external additive and subjected to an external addition treatment, whereby the external additive is attached to the surface of the colored resin particles, thereby producing a one-component toner ( Developer) is preferable. The one-component toner may be further mixed and stirred together with carrier particles to form a two-component developer.

  The stirrer that performs the external addition treatment is not particularly limited as long as the stirrer can attach the external additive to the surface of the colored resin particles. For example, an FM mixer (trade name, manufactured by Nippon Coke Kogyo Co., Ltd.), Super Mixer (: trade name, manufactured by Kawada Seisakusho Co., Ltd.), Q mixer (: trade name, manufactured by Nihon Coke Kogyo Co., Ltd.), mechano-fusion system (: trade name, manufactured by Hosokawa Micron), and mechano mill (: trade name, manufactured by Okada Seiko Co., Ltd.) The external addition treatment can be performed using a stirrer capable of mixing and stirring.

Examples of the external additive include inorganic fine particles composed of silica, titanium oxide, aluminum oxide, zinc oxide, tin oxide, calcium carbonate, calcium phosphate, and / or cerium oxide; polymethyl methacrylate resin, silicone resin, and / or melamine Organic fine particles made of a resin or the like; Among these, inorganic fine particles are preferable, and among inorganic fine particles, silica and / or titanium oxide are preferable, and fine particles made of silica are particularly preferable.
These external additives can be used alone or in combination of two or more. Among these, it is preferable to use two or more types of silica having different particle diameters in combination.

  In the present invention, the external additive is usually used in a proportion of 0.05 to 6 parts by mass, preferably 0.2 to 5 parts by mass with respect to 100 parts by mass of the colored resin particles. When the added amount of the external additive is less than 0.05 parts by mass, a transfer residue may occur. If the amount of the external additive exceeds 6 parts by mass, fog may occur.

4). Yellow toner The yellow toner obtained through the above process is a yellow toner having a high image density, being less likely to cause fogging particularly in a high-temperature and high-humidity (H / H) environment, and having a uniform particle diameter as compared with the conventional toner.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited only to these examples. Parts and% are based on mass unless otherwise specified.
The test methods performed in the examples and comparative examples are as follows.

1. Characteristics of Yellow Pigment (1) Method for Measuring Ca Content C. Measured in a platinum crucible. I. Pigment Yellow 93 was weighed and then heated by adding a small amount of sulfuric acid, followed by heating at 700 ° C. for several hours. I. Pigment Yellow 93 was dry ashed. A small amount of sulfuric acid was added to this ash, and the volume was made up to 10 mL with ultrapure water, and further diluted 10-fold and 100-fold from that sample, and an ICP emission analyzer (product name: manufactured by SII Nano Technology Co., Ltd.) Using SPS-5100), the Ca content in the yellow pigment was measured.

(2) Method for Measuring Viscosity of Organic Phase in which Yellow Pigment is Dispersed The viscosity of the organic phase in which the yellow pigment is dispersed is measured using a B-type viscometer (manufactured by Brookfield, device name: Digital Rheometer DV- I +). A sample of the organic phase in which the yellow pigment was dispersed was brought to 25 ° C. using a constant temperature water bath, and then the spindle was rotated at a spindle rotation speed of 6 rpm for 1 minute, and then the viscosity was measured.

2. Preparation of yellow toner [Example 1]
75 parts of styrene and 25 parts of n-butyl acrylate, polymethacrylate macromonomer (manufactured by Toa Gosei Chemical Co., Ltd., trade name: AA6, Tg = 94 ° C.) 0.3 part, 0.6 part of divinylbenzene, t-dodecyl 1.6 parts of mercaptan and C.I. I. 6.0 parts of lot A of Pigment Yellow 93 (manufactured by BASF, trade name: CROMOPHTAL YELLOW 3G) was wet-ground using a media type disperser. Here, C.I. I. Pigment Yellow 93 lot A had a Ca content of 400 ppm.
To the mixture obtained by wet pulverization, 1 part of a charge control resin (manufactured by Fujikura Kasei Co., Ltd., trade name: Acrybase FCA-207P) and 6 parts of fatty acid ester wax (manufactured by NOF Corporation, trade name: WEP7) are added, The polymerizable monomer composition was prepared by mixing and dissolving.

  On the other hand, in a stirring tank, an aqueous solution in which 10.6 parts of magnesium chloride was dissolved in 220 parts of ion-exchanged water and an aqueous solution in which 5.9 parts of sodium hydroxide were dissolved in 50 parts of ion-exchanged water were stirred at room temperature. By gradually adding, a magnesium hydroxide colloidal dispersion was prepared.

  Into the magnesium hydroxide colloid dispersion obtained above (magnesium hydroxide colloid amount 6.0 parts), the polymerizable monomer composition is charged at room temperature, and further stirred until the droplets are stabilized. Then, 5 parts of t-butylperoxy-2-ethylhexanoate was added as a polymerization initiator. The dispersion added with the polymerization initiator was subjected to high-shear stirring at a rotational speed of 15,000 rpm using an in-line type emulsion disperser (trade name: Milder MDN303V, manufactured by Taiheiyo Kiko Co., Ltd.). Droplets were formed.

  A suspension (polymerizable monomer composition dispersion) in which droplets of the polymerizable monomer composition obtained as described above are dispersed is charged into a reactor equipped with a stirring blade and heated to 90 ° C. Warm to initiate the polymerization reaction. When the polymerization conversion reached almost 100%, 2,2′-azobis (2-methyl) dissolved in 2 parts of methyl methacrylate (polymerizing monomer for shell) and 20 parts of ion-exchanged water in the reactor. 0.1 part of -N- (2-hydroxyethyl) -propionamide) (polymerization initiator for shell, manufactured by Wako Pure Chemical Industries, Ltd., trade name: VA-086, water-soluble) was added to the reactor. Thereafter, the temperature was raised to 95 ° C. and maintained at 95 ° C. for 4 hours to continue the polymerization, and then the reaction was stopped by cooling with water to obtain an aqueous dispersion of colored resin particles.

  Sulfuric acid was added dropwise to the aqueous dispersion of colored resin particles obtained as described above while stirring at room temperature, and acid washing was performed until the pH became 6.5 or lower. Subsequently, filtration separation was performed, 500 parts of ion-exchanged water was added to the obtained solid content to make a slurry again, and water washing treatment (washing, filtration, and dehydration) was repeated several times. Next, filtration separation was performed, and the obtained solid content was put in a container of a dryer and dried at 45 ° C. for 48 hours to obtain dried colored resin particles.

  To 100 parts of the colored resin particles, 0.6 part of silica fine particles having a number average primary particle diameter of 7 nm subjected to hydrophobic treatment and 1 part of silica fine particles having a number average primary particle diameter of 35 nm subjected to hydrophobic treatment are added, and a high speed stirrer (Nippon Coke Kogyo Co., Ltd., trade name: FM mixer) was used for mixing and external addition treatment to produce the yellow toner of Example 1.

[Examples 2 to 4, Comparative Examples 1 to 3]
In Example 1, C.I. I. Yellow toners of Examples 2 to 4 and Comparative Examples 1 to 3 were produced in the same manner as Example 1 except that Pigment Yellow 93 lot A was changed to lots B to G shown in Table 1.

3. Characteristic Evaluation of Colored Resin Particles The characteristics of the colored resin particles used in the toners of Examples 1 to 4 and Comparative Examples 1 to 3 were examined. Details are as follows.
(1) Particle size measurement of colored resin particles The volume average particle size Dv, number average particle size Dn, and particle size distribution Dv / Dn of the colored resin particles are determined by a particle size measuring machine (Beckman Coulter, trade name: Multisizer). ). The measurement with this multisizer was performed under the conditions of an aperture diameter: 100 μm, a dispersion medium: Isoton II (trade name), a concentration of 10%, and a measurement particle number: 100,000.
Specifically, 0.2 g of a colored resin particle sample was placed in a beaker, and an alkylbenzenesulfonic acid aqueous solution (manufactured by Fuji Film, trade name: Drywell) was added as a dispersant therein. Further, 2 mL of a dispersion medium was added to wet the colored resin particles, 10 mL of the dispersion medium was added, and the mixture was dispersed with an ultrasonic disperser for 1 minute, and then measured with the particle size measuring instrument.

4). Printing evaluation of toner Printing evaluation was performed on the toners of Examples 1 to 4 and Comparative Examples 1 to 3. Details are as follows.
(1) Toner Image Density Using a printer that has been modified so that the temperature of the fixing roll of a commercially available non-magnetic one-component developing type printer (printing speed: 20 sheets / min) can be changed, normal temperature and normal humidity (N / N ) A solid 50 mm × 50 mm square was printed on the copy paper under the environment (temperature: 23 ° C., humidity: 50%).
The unfixed image was taken out from the printer, the toner developed on the copy paper was blown off with air, and the transport amount (M / A) was calculated from the following equation using the mass of the copy paper before and after the toner was blown off.
^{M / A (mg / cm 2} ) = (W1-W2) / 25cm 2
W1 = Mass of copy paper before toner blowing (mg)
W2 = mass (mg) of copy paper after toner blowing
When the transport amount (M / A) is 0.40 mg / cm ² , the image density of a solid print-fixed image of 50 mm × 50 mm square is measured with a spectrophotometer (trade name: Spectroeye, manufactured by X-rite). It measured using. The image density is preferably 1.25 or more, and more preferably 1.30 or more.

(2) Fog test under high-temperature and high-humidity (H / H) environment Use the same printer and toner to be evaluated as those used in the evaluation of “(1) Toner Image Density” at a temperature of 35 ° C. and a humidity of 80%. After being left overnight in a high temperature and high humidity (H / H) environment, fog was measured.
The hue of paper that is not used for printing is measured with the spectrophotometer as a reference value, and then white solid is printed with the above-mentioned printer using the toner to be measured, and the hue at any six positions of the white solid is printed. Then, the value having the largest difference (ΔE) from the reference value was defined as the fog value.
Smaller fog values are better with less fog. The fog value is preferably less than 2.0, and more preferably less than 1.0.

  Table 1 shows the measurement and evaluation results of the yellow toners of Examples 1 to 4 and Comparative Examples 1 to 3. In Table 1 below, “H / H fog” means a fog value in a high temperature and high humidity (H / H) environment.

5). Summary of Toner Evaluation Hereinafter, the toner evaluation will be examined with reference to Table 1.
First, the toner of Comparative Example 1 is examined. From Table 1, the toner of Comparative Example 1 contains a yellow pigment (CI Pigment Yellow 93) having a Ca content of 300 ppm.
From Table 1, the toner of Comparative Example 1 has a volume average particle size (Dv) of 7.4 μm, a toner particle size distribution (Dv / Dn) of 1.22, and a fog value in a high temperature and high humidity (H / H) environment. Is 0.5. Therefore, with respect to the toner of Comparative Example 1, at least the toner particle size, the toner particle size distribution, and the fogging problem in a high temperature and high humidity (H / H) environment are not observed.
However, the toner of Comparative Example 1 has a low image density of 1.20. Therefore, it can be seen that the toner of Comparative Example 1 using a yellow pigment having a Ca content of less than 400 ppm is inferior in image density. This is because when the Ca content is too small, the yellow pigment is not highly dispersed in the polymerizable monomer, and further, the dispersion stability in the binder resin is lowered, and the yellow pigment in the toner tends to aggregate. This is thought to be due to falling into

Next, the toner of Comparative Example 2 will be examined. From Table 1, the toner of Comparative Example 2 contains a yellow pigment (CI Pigment Yellow 93) having a Ca content of 2,200 ppm.
From Table 1, the toner of Comparative Example 2 has a volume average particle size (Dv) of 7.8 μm and a toner particle size distribution (Dv / Dn) of 1.26. Therefore, for the toner of Comparative Example 2, there is no problem in at least the toner particle size and the toner particle size distribution.
From Table 1, the toner of Comparative Example 2 has a low image density of 1.22, and a high fog value of 2.5 in a high temperature and high humidity (H / H) environment. Therefore, it can be seen that the toner of Comparative Example 2 using a yellow pigment having a Ca content exceeding 2,000 ppm is inferior in image density and is likely to cause fogging. This is considered to be because it becomes easy to absorb moisture when the Ca content is too large.

Subsequently, the toner of Comparative Example 3 will be examined. From Table 1, the toner of Comparative Example 3 contains a yellow pigment (CI Pigment Yellow 93) having a Ca content of 2,500 ppm.
From Table 1, the toner of Comparative Example 3 has a wide toner particle size distribution (Dv / Dn) of 1.56, a low image density of 1.10, and a fog value in a high temperature and high humidity (H / H) environment. 3.1 High. Further, the volume average particle diameter (Dv) (8.6 μm) of the toner of Comparative Example 3 is about 1 μm larger than the volume average particle diameter (Dv) (7.4 to 7.8 μm) of other toners. . Therefore, the toner of Comparative Example 3 using a yellow pigment having a Ca content exceeding 2,000 ppm by more than 25% has a wider particle size distribution than that of Comparative Example 2, and the volume average particle size of the toner is the target particle size. It can be seen that the image density is further shifted, the image density is inferior, and fog is likely to occur. This is because, when the Ca content is higher than that of Comparative Example 2, calcium ions destabilize the droplets of the polymerizable monomer composition in the toner polymerization step, resulting in an adverse effect on toner particle formation. It is thought that it is to reach.

On the other hand, from Table 1, the toners of Examples 1 to 4 contain a yellow pigment (CI Pigment Yellow 93) having a Ca content of 400 to 1,800 ppm.
From Table 1, the toners of Examples 1 to 4 have a narrow toner particle size distribution (Dv / Dn) of 1.21 to 1.23, a high image density of 1.27 to 1.34, and a high temperature and high temperature. The fog value in a wet (H / H) environment is as small as 0.4 to 1.6. Further, the volume average particle diameter (Dv) of the toners of Examples 1 to 4 is 7.5 to 7.8 μm, which is smaller in deviation from the target toner particle diameter than Comparative Example 3.
Accordingly, C.I. having a Ca content of 400 to 2,000 ppm. I. It can be seen that the yellow toner of the present invention produced using Pigment Yellow 93 has a high image density, is less likely to cause fogging particularly in a high-temperature and high-humidity (H / H) environment, and has a more uniform particle size than the conventional one.

Claims (5)

As a yellow pigment, C.I. having a Ca content of 400 to 2,000 ppm. I. A method for producing yellow toner, wherein only Pigment Yellow 93 is used.   2. The method according to claim 1, further comprising a step of forming an organic phase in which a raw material for toner containing the yellow pigment is dispersed, and granulating the organic phase by emulsifying or dispersing in an aqueous medium. A method for producing yellow toner.   The method for producing a yellow toner according to claim 2, wherein the organic phase in which the raw material for toner containing the yellow pigment is dispersed has a viscosity at 25 ° C of 500 to 3,500 mPa · s.   A polymerizable monomer composition in which a raw material for toner containing at least a polymerizable monomer and the yellow pigment is dispersed is prepared, and the polymerizable monomer composition is placed in an aqueous medium containing a dispersion stabilizer. The method for producing a yellow toner according to claim 1, further comprising a step of dispersing and polymerizing in the presence of a polymerization initiator to form colored resin particles.   The method for producing a yellow toner according to claim 4, wherein the polymerizable monomer composition has a viscosity at 25 ° C. of 500 to 3,500 mPa · s.