JP2006267911A - Electrophotographic yellow toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a yellow toner having high electrostatic charge stability and satisfactory color reproducibility without being affected by a change in temperature and humidity. <P>SOLUTION: In the toner containing a binder resin, a colorant and a charge control agent, the binder resin is a polyester resin composed of an alcohol component of an aromatic system and the charge control agent includes organic bentonite. The toner contains, as the colorant, a monoazo yellow main pigment expressed by Formula (1), and a disazo yellow pigment expressed by Formula (2) and/or a monoazo yellow pigment expressed by Formula (3). In the formulas, R<SP>1</SP>and R<SP>2</SP>differently to each other denote a hydrogen atom, chlorine atom, nitro group, methyl group or methoxy group; R<SP>3</SP>, R<SP>4</SP>and R<SP>5</SP>each identically or differently denote a hydrogen atom, chlorine atom, methyl group or methoxy group; R<SP>6</SP>and R<SP>7</SP>denote a methyl group or methoxy group; Q<SP>1</SP>to Q<SP>4</SP>each independently denote hydrogen atom, 1C to 2C lower alkyl group or lower alkoxy group or hydroxyl group; W is a substituent selected from the group expressed in -CH<SP>2</SP>- , -O- , -S- , -SO<SB>2</SB>- , -CONH- ; (m) is an integer of 0 or 1; A and B each independently denote either of a group expressed by -NH-Y-SO<SB>3</SB>H or -OH group, where Y is a group selected from an ethylene group, phenylene group and naphthylene group and may contain a substituent. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrophotographic yellow toner. More specifically, the present invention relates to a full-color electrophotographic yellow toner used as a developer in a so-called electrophotographic image forming apparatus such as an electrostatic copying machine or a laser beam printer.

  Image formation in an electrophotographic image forming apparatus is performed according to each process of charging, exposure, development, transfer, and fixing. First, in the charging step, the surface of the photoreceptor is uniformly charged to form an electrostatic latent image. In the exposure step, an electrostatic latent image is formed on the surface of the photoconductor by irradiating the charged photoconductor surface with light according to image information. In the development process, for example, black toner is selectively attached to the formed electrostatic latent image, and a visible image (toner image) is formed on the surface of the photoreceptor. In the transfer step, the toner image is transferred onto transfer paper by an electric force. In the final fixing step, the toner image transferred onto the transfer paper is melted by heat to fix the toner image onto the transfer paper.

  In recent years, colorization technology in electrophotography has been rapidly developed, and full-color image forming apparatuses have been developed and provided to the market. The market for full-color image forming apparatuses is expanding with the spread of black-and-white image forming apparatuses. Generally, for color reproduction in a full-color image forming apparatus, three subtractive primary colors, yellow (Y), magenta (M), cyan (C), or black (K) are added to these three colors. Four color toners are used. As a color reproduction procedure, for each of C, M, Y, and K colors, the steps from charging, exposure, development, and transfer in the image forming process are repeated, and toner composed of a plurality of color toners on the transfer paper. A full color image is formed by overlapping the images. In the final fixing step, the superimposed toner images are melted and fixed on the transfer paper. In this procedure, the superimposed toner images are mixed by being melted, so that the color is reproduced according to the principle of subtractive color mixing.

  In such a full-color electrophotographic method, development is performed a plurality of times, and it is necessary to superimpose several kinds of toner images having different colors on the same support as a fixing process. Charging characteristics, flow characteristics, and fixing characteristics are extremely important factors.

  That is, in order to maintain a stable and good color reproducibility of a full-color image, it is necessary to first transfer a predetermined amount of toner onto the transfer paper during the transfer from the development process. The toner adhesion amount in the development and transfer processes is greatly influenced by the charging characteristics of the toner, the flow characteristics, such as the rising characteristics of the charge quantity of the toner, the environmental stability of the charge quantity, and the stability and durability over time. In such a color electrophotographic method in which development and transfer are performed a plurality of times and several toner images of different colors are required to be superimposed on the same support as a fixing process, the hue that the color toner should have And transparency is a very important factor. In other words, the fixed color toner must be a color toner with a wide color reproduction range that can provide transparency when the toner particles are melted so that the toner particles are not diffusely reflected by light and hinder color reproduction. Don't be.

  For this reason, an external additive is added to the toner in order to improve and adjust the charge amount, fluidity, etc., to the base particles containing a binder resin, a colorant, a charge control agent and the like.

  The colorant needs to be well dispersed in the toner of the pigment constituting the colorant in order to increase the transparency of the toner particles. For this purpose, first, a master batch in which a pigment is dispersed at a high concentration in a resin as a colorant is prepared, and then mixed with a binder resin and a charge control agent, which are other components of the toner material, and then melt-kneaded. A method for producing a toner is generally used. Therefore, the dispersion of the pigment in the masterbatch is particularly important. Since the pigment dispersion in the master batch becomes the dispersion state of the pigment in the toner as it is, the dispersion must be uniform without aggregates. If the dispersion is poor, the toner has low transparency and color reproduction becomes narrow. In addition, the charging characteristics are also deteriorated by the aggregate of the pigment on the toner surface.

  Therefore, in the production of a masterbatch, a processing method for increasing dispersion and a device for surface treatment of the pigment have been devised.

  Furthermore, it is known that it is important for the charge control agent to be uniformly finely dispersed in the toner particles or on the surface of the toner particles in order to improve the toner chargeability. Even if the charge control agent is agglomerated in a part of the toner or evenly dispersed, if it is not finely divided and exists as coarse particles, the initial charge amount cannot be obtained. In addition, if the charge control agent is not dispersed, the charge rise characteristic becomes poor, or the toner has a remarkable charge attenuation. For this reason, various ideas have been made to uniformly and finely disperse the charge control agent in the toner, and the selection of the type and chemical composition of the binder resin is an important factor. Therefore, in order to improve the charge characteristics of the toner, not only a charge control agent having excellent charge characteristics is used, but also the charge control agent can be uniformly finely dispersed according to the charge control agent used. It is important to select and use a resin.

  As the binder resin for full-color toner, a resin excellent in sharp melt property, color developability and fixing property is required, and a polyester resin is usually used. Polyester resins usually have strong negative charge characteristics. Toners using this resin are designed for negative charge. As negative charge control agents, oil-soluble dyes such as oil black and spiron black, metal-containing dyes are used. Azo dyes, naphthenic acid metal salts, metal salts of alkyl salicylic acid, fatty acid soaps, resin acid soaps, and the like are used.

  Examples of the external additive of the negatively chargeable toner using a polyester resin as the binder resin include inorganic fine powders such as silicon dioxide, titanium oxide, aluminum oxide, cerium oxide, zinc oxide, tin oxide, zirconium oxide, and the like. Surface treated with a hydrophobizing agent such as silicone oil, silane coupling agent, polystyrene, acrylic, styrene acrylic, polyester, polyolefin, cellulose, polyurethane, benzoguanamine, melamine, nylon, silicon, phenol, vinylidene fluoride, etc. Resin fine powder or the like is used.

  In order to solve the problems related to the charging characteristics of such full-color toners (yellow toner, magenta toner, cyan toner, black toner), the following Patent Document 1 discloses that an aliphatic polyester resin having an alcohol component as a binder resin is used. A technique has been proposed in which the toner used contains organic bentonite as a charge control agent, thereby improving the uniform fine dispersion of the charge control agent in the toner and improving the charging characteristics of the toner. As a result, the charging characteristics and the like are improved, an image free of background stains can be obtained even at high-speed development, toner scattering in the developing device can be reduced, and a stable image can be obtained from the beginning to the end of development. Technology is disclosed.

  On the other hand, in order to solve the problem relating to the dispersion characteristics of the yellow toner in the master batch, the following Patent Document 2 discloses a monoazo yellow pigment having a good hue as a main pigment, and a specific disazo yellow pigment and / or monoazo yellow pigment. A technique is disclosed in which, by containing a part thereof, crystal growth during preparation of the masterbatch can be prevented, and a masterbatch with good dispersion and good transparency can be obtained.

JP2004-4207 JP 2003-253188 A

  The polyester resin in which the alcohol component used as the binder resin described in Patent Document 1 is an aliphatic resin is inferior to the humidity resistance environment characteristics than the polyester resin in which the alcohol component is an aromatic resin, so that sufficient charging stability is achieved. It is predicted that sex will not be obtained. For this reason, as the image is repeatedly formed, problems such as image contamination and internal contamination due to toner scattering are assumed.

  Further, Patent Document 1 discloses nothing about the optimization of the master batch that is a resin kneaded material and a resin that is a raw material of the toner, and there is no suggestion about any problems such as controlling pigment dispersion and color reproduction. Not touched. Furthermore, there is no suggestion of a combination of a pigment and a charge control agent. Therefore, problems such as poor pigment dispersion and inability to obtain good color reproduction and charging characteristics are also assumed.

  On the other hand, Patent Document 2 does not suggest any optimization of the resin and the charge control agent, which are as important as the yellow pigment in suppressing crystallization in the masterbatch. Chargeability is a concern.

  Therefore, the present invention provides a yellow toner for electrophotography that can reproduce a stable and uniform image for a long time without being affected by changes in temperature and humidity even when repeated development is performed by continuous use. With the goal.

  Another object of the present invention is to provide an electrophotographic yellow toner that is excellent in at least transparency and has good color reproducibility when used as a full-color yellow toner.

  The toner of the present invention that solves the above problems is a toner comprising at least a binder resin, a colorant, and a charge control agent, wherein the binder resin is a polyester resin comprising an aromatic alcohol component, The charge control agent includes organic bentonite, and as the colorant, a monoazo yellow main pigment represented by the following general formula (1), a disazo yellow pigment represented by the following general formula (2) and / or the following general formula (3 And a monoazo yellow pigment represented by the following formula:

[In the chemical formulas 5 to 7, R ¹ and R ² represent different hydrogen atoms, chlorine atoms, nitro groups, methyl groups or methoxy groups, and R ³ , R ⁴ and R ⁵ are the same or different. Represents a hydrogen atom, a chlorine atom, a methyl group, a methoxy group or an ethoxy group, R ⁶ and R ⁷ represent a methyl group or a meoxy group, and Q ^{1 to} Q ⁴ each independently represent a hydrogen atom, a lower group having 1 to 2 carbon atoms. Represents an alkyl group, a lower alkoxy group or a hydroxyl group, W is a substituent selected from the group represented by Chemical Formula 8, m represents an integer of 0 or 1, and A and B each independently represent —NH—. Y is a group represented by Y—SO ₃ H or —OH group, where Y is a group selected from an ethylene group, a phenylene group and a naphthylene group, and may contain a substituent. . ]

  According to the electrophotographic yellow toner having the above-described configuration, the polyester resin obtained by reacting the aromatic alcohol component as the binder resin contains a specific charge control agent, thereby impairing the properties of the polyester resin. In the toner, the charge control agent can be uniformly finely dispersed, and by combining with the yellow pigment described above, a master batch with uniform pigment dispersibility can be produced.

  Therefore, by melt-kneading with the toner material having the above-described configuration, the charge control agent and the yellow pigment can be uniformly and finely dispersed in the toner, and it has excellent transparency, color reproducibility, and charge amount characteristics. A yellow toner is obtained.

  For example, compared to a polyester resin composed of an aliphatic alcohol component, a polyester resin composed of an aromatic alcohol component can control the amount of charge easily with less change in the resistance of the toner due to a change in the external environment. The charging characteristics (life characteristics) are stable even after repeated development by continuous use. Aromatic polyester resins having an alcohol component that is aliphatic are more hydrophobic and therefore have higher moisture resistance. In addition, the polyester resin comprising the dispersed aromatic alcohol component of the yellow pigment of the present invention is better and more transparent. This difference is largely due to the chemical structure of the resin.

  Furthermore, by using organic bentonite as a charge control agent in the resin, it is possible to provide a toner having good flowability and sharp charge distribution even in repeated development by continuous use.

Hereinafter, the present invention will be described in detail.
As the binder resin constituting the electrophotographic yellow toner of the present invention, a conventionally known polyester resin in which the alcohol component is aromatic can be used, and one or a combination of two or more can be used.

  The binder resin constituting the yellow toner for electrophotography of the present invention will be described. Examples of the aromatic alcohol component for obtaining a polyester resin that is a binder resin according to the present invention include bisphenol A, polyoxyethylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, Polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.2) -polyoxyethylene- (2.0) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (6) -2,2-bis (4-hydroxyphenyl) propane, Polyoxypropylene- (2.2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene- (2.4) -2, - bis (4-hydroxyphenyl) propane, polyoxypropylene - (3.3) -2,2-bis (4-hydroxyphenyl) propane and derivatives of these, and the like, bisphenol A is preferred.

  The polybasic acid component of the polyester resin includes succinic acid, adipic acid, sebacic acid, azelaic acid, dodecenyl succinic acid, n-dodecyl succinic acid, malonic acid, maleic acid, fumaric acid, citraconic acid, itaconic acid, glutaconic acid. , Dibasic acids such as cyclohexanedicarboxylic acid, orthophthalic acid, isophthalic acid, terephthalic acid, acids having three or more bases such as trimellitic acid, trimetic acid, pyromellitic acid, and anhydrides thereof, and lower alkyl esters. From the viewpoint of heat-resistant aggregation, terephthalic acid or its lower alkyl ester is preferred.

  The acid value of the polyester resin constituting the yellow toner for electrophotography of the present invention is preferably within the following range. For example, the acid value of the polyester resin is preferably 5 to 30 mgKOH / g. When the acid value is less than 5 mgKOH / g, the charging characteristics of the resin are lowered, and the organic bentonite as the charge control agent is difficult to disperse in the polyester resin. This adversely affects the charge amount stability of repeated development due to rising of the charge amount or continuous use.

  On the other hand, when the acid value is 2 mgKOH / g or less, the dispersion of the organic bentonite is deteriorated, and the charging characteristics of the resin are further deteriorated. Therefore, the charging characteristics of repeated development due to continuous use are not stable and toner scattering increases. Further, the pigment dispersion is deteriorated and the color reproducibility is narrowed.

  On the other hand, when the acid value exceeds 35 mgKOH / g, moisture adsorption in a high-temperature and high-humidity environment increases and the moisture content increases. As a result, the resistance of the toner is lowered, and even when a charge control agent is added, it is difficult to stably control the charge amount against environmental changes, and the charging characteristics of repeated development by continuous use are not stabilized.

  Here, the acid value was measured according to the method described in JIS K 0070-1992.

  The melting temperature of the polyester resin constituting the above-described electrophotographic yellow toner of the present invention is one of the important factors for achieving transparency. For example, when used as a color toner, it is necessary to melt sufficiently so that the boundaries between the toners disappear when the toners of the respective colors are stacked. Therefore, the melting temperature of the polyester resin is preferably 90 ° C to 135 ° C. If the melting temperature of the binder resin is less than 90 ° C., the toner cohesive force is too low and high temperature offset tends to occur. On the other hand, if the temperature is higher than 135 ° C., it becomes difficult to eliminate the boundary between the toner particles and provide sufficient transparency.

Here, the melting temperature of the above-mentioned resin was measured using a flow tester CFT-500 type (manufactured by Shimadzu Corporation) with a sample amount of 1.0 g, a die size of 1.0 × 1.0, an extrusion load of 20 kgf / cm ² , and a temperature increase. Under the conditions of a speed of 6 ° C./min and a starting temperature of 60 ° C. and a preheating time of 300 seconds, the temperature at the 1/2 stroke when measured was defined as the melting temperature.

Next, the charge control agent constituting the yellow toner for electrophotography of the present invention will be described. As this charge control agent, organic bentonite is used. The organic bentonite is a substance produced mainly from an organic cation-forming compound and bentonite, and bentonite is a viscosity having a layered structure mainly composed of SiO ₂ and Al ₂ O ₃ and mainly composed of montmorillonite. It is a mineral. Bentonite, which is such a natural layered compound, can take in organic molecules between layers by ion exchange or the like. Between the bentonite layers, inorganic metal cations such as sodium and potassium originally exist, but by exchanging these ions, organic cations such as alkylammonium ions are intercalated (inclusion), and organic and inorganic substances are separated. Alternating composites (interlayer compounds) are produced. The organic bentonite used as a charge control agent in the present invention is obtained by exchanging inorganic cations in bentonite with organic cations generated from an organic cation-forming compound.

  A known compound can be used as the organic cation-forming compound for producing the organic bentonite. For example, dodecyltrimethylammonium chloride, lauryltrimethylammonium chloride, hexadecyltrimethylammonium chloride, dodecylammonium chloride, dodecylammonium bromide, dimethyldistearylammonium chloride, stearyldimethylbenzylammonium chloride, tetrabutylammonium chloride, tetrapentylammonium fluorophosphate, There are quaternary ammonium salts such as tetraethylammonium benzoate, tetraethylammonium acetate, tetrabutylammonium iodide, triethylmethylammonium iodide, and the like.

  Further, there are pyrididium salts such as isopropylpyridinium chloride, butylpyridinium chloride, heptylpyridinium chloride, decylpyridinium chloride, dodecylpyridinium bromide, cetylpyridinium chloride, and the like.

  Furthermore, polyalkyleneimines such as polyethyleneimine, poly- (4-vinylpyridine), polyallylamine, aminoacetylated polyvinyl alcohol, poly- (L) -lysine, chitosan, polypyrrole, or amino groups such as diethylaminoethyl methacrylate There is a polymeric ammonium salt obtained from a copolymer with a vinyl monomer containing a containing acrylate.

  The anion component of the organic cation-forming compound for producing the organic bentonite is not particularly limited, but from the viewpoint of safety or environmental protection, chromium, cobalt, copper, nickel, molybdenum, lead, mercury, It is preferable that it is an anion which does not contain heavy metals, such as.

  It does not specifically limit as a method for preparing the organic bentonite used by this invention, It can manufacture by the ion exchange operation used conventionally. For example, it is obtained by immersing bentonite in water, a mixture of water and an organic solvent, or adding an organic cation-forming compound thereto, leaving it for a certain period of time, filtering and washing it, and drying. Can do.

  Furthermore, the organic bentonite used in the present invention preferably has a salt structure composed of alkaline bentonite and an organic cation. Thereby, even in a small amount, the charge imparting function to the toner can be sufficiently exhibited.

The organic bentonite, which is a charge control agent used in the present invention, can improve the charging characteristics of the toner by improving the dispersibility (uniformly dispersing) in the polyester resin as the binder resin described above. To that end, the volume average particle diameter D ₅₀ of the organic bentonite, is preferably adjusted to 8μm or less. As a result, the charge control agent is present on the toner surface almost uniformly with a fine diameter, and is difficult to separate from the toner particles, so that the toner can be excellent in charge amount rise characteristics, charge life stability, and the like. When the volume average particle diameter D ₅₀ exceeds 8 μm, the charge control agent is uniformly dispersed in the toner, but the size becomes non-uniform and the charging efficiency slightly decreases. Therefore, it is preferable that the volume average particle diameter D ₅₀ of about 8μm or less. Here, if the volume average particle diameter D ₅₀ is to be finely pulverized to 1 μm or less, considerable time and energy are required, resulting in poor productivity and an increase in cost. However, if the object of the present invention is achieved in consideration of dispersibility, one having a volume average particle diameter D ₅₀ of 1 μm or less can be used. Also, if an object to inexpensively produce a toner, it may be used more than 1μm a volume average particle diameter D _50.

  The organic bentonite according to the present invention has a great influence on charging characteristics and color reproducibility in yellow toner or the like depending on the amount of the organic bentonite added. Therefore, the amount of organic bentonite added is preferably 0.5% by weight to 5% by weight with respect to the total amount of toner. For example, when the addition amount is less than 0.5% by weight, image quality deterioration and toner scattering in the apparatus are likely to occur due to a decrease in charge amount rise characteristic of the toner and deterioration in charge amount life stability. On the other hand, if it exceeds 5% by weight, the color reproducibility of the toner starts to deteriorate, which is not desirable. A more preferable range is 0.8 to 3% by weight. By making it within such a range, the color reproducibility is improved and the charging performance is not easily lowered. In the present invention, other charge control agents can be used in combination.

  The yellow pigment and master batch constituting the yellow toner for electrophotography of the present invention will be described. First, the yellow pigment according to the present invention uses the yellow pigment described in Patent Document 2. The yellow pigment is composed of a monoazo yellow main pigment represented by the following general formula (1), a disazo yellow pigment represented by the following general formula (2) and / or a monoazo yellow yellow represented by the following general formula (3). It is characterized by containing pigments.

  In order to use the monoazo yellow main pigment as a masterbatch, in addition to improving the optical properties while maintaining the original properties of these monoazo main pigments, it is necessary to increase the crystal stability against heat and so on. Necessary for preventing deterioration. In order to solve this problem, the monoazo yellow main pigment is different in structure from the monoazo yellow main pigment, and the disazo yellow pigment represented by the general formula (2) containing a sulfonic acid group and / or By introducing and mixing the monoazo yellow pigment represented by the formula (3), it is possible to prevent crystal growth in the process of preparing a masterbatch containing the monoazo yellow pigment, and the polyester in which the alcohol component of the present invention is aromatic By using the resin as a resin binder, the pigment can be uniformly and finely dispersed.

[In the chemical formulas 9 to 11, R ¹ and R ² represent different hydrogen atoms, chlorine atoms, nitro groups, methyl groups or methoxy groups, and R ³ , R ⁴ and R ⁵ are the same or different. Represents a hydrogen atom, a chlorine atom, a methyl group, a methoxy group or an ethoxy group, R ⁶ and R ⁷ represent a methyl group or a meoxy group, and Q ^{1 to} Q ⁴ each independently represent a hydrogen atom, a lower group having 1 to 2 carbon atoms. Represents an alkyl group, a lower alkoxy group, or a hydroxyl group, W represents a substituent selected from the group represented by Chemical Formula 12, m represents an integer of 0 or 1, and A and B each independently represent —NH—. Y is a group represented by Y—SO ₃ H or —OH group, where Y is a group selected from an ethylene group, a phenylene group and a naphthylene group, and may contain a substituent. . ]

  The blending ratio of the monoazo yellow main pigment represented by the general formula (1) is preferably 98 to 80 mol%, and the disazo yellow pigment represented by the general formula (2) and / or the monoazo yellow represented by the following general formula (3) The blending ratio of the pigment is preferably 2 to 20 mol%. Moreover, the primary particle diameter of these yellow main pigments and yellow pigments is set to a small numerical value of 0.15 to 0.2 μm or less to prevent crystal growth in the process of preparing a masterbatch containing a monoazo yellow pigment. be able to.

The introduction of the specific yellow pigment represented by general formula (2) and / or general formula (3) containing these sulfonic acid groups into the monoazo yellow main pigment represented by general formula (1) is a coupling reaction synthesis. It can sometimes be introduced by mixing or blending pigments synthesized separately or in a paste or powder state. When introduced at the time of synthesis, the base represented by the general formula (4) (preferably 98 to 80 mol%) and the base represented by the general formula (5) and / or the general formula (6) (preferably 2 to 20). The diazonium salt may be prepared simultaneously or separately using a mol%) and then a coupling reaction with the coupler represented by the general formula (7) may be carried out. In the case of performing synthesis, a pigment is synthesized by separately performing a coupling reaction using the pigment of the general formula (1), the general formula (2) and / or the general formula (3), and then preferably 2 to 20 mol%. What is necessary is just to mix and mix | blend so that it may become.

  In this case, after the coupling reaction synthesis of the pigment represented by the general formula (1), a predetermined amount of the pigment paste of the general formula (2) and / or the general formula (3) is added and mixed to finish the pigment of the present invention. Alternatively, a predetermined amount of each powder pigment may be blended and finished.

  Here, examples of the base represented by the general formula (4) include 3-nitro-4-toluidine, p-chloro-o-nitroaniline, p-nitroaniline, o-nitroaniline, p-methoxy-o-. Examples thereof include nitroaniline and m-nitro-o-anisidine.

  Examples of the base represented by the general formula (5) include 3,3′-dimethyl-4,4′-diaminobiphenyl-6,6′-disulfonic acid, 3,3′-dimethoxy-4,4′-diamino. Biphenyl-6,6'-disulfonic acid is mentioned.

The base represented by the general formula (6) has A and B which are each independently a group represented by —NH—Y—SO ₃ H or —OH group, and Y represents an ethylene group, phenylene It may be a group selected from a group and a naphthylene group and may contain a substituent. Representative examples used as —NH—Y—SO ₃ H include taurine, sulfanilic acid, metanilic acid, alternilic acid, naphthionic acid, tobias acid, 2-aminophenol-4-sulfonic acid, and 2-methoxyaniline. -5-sulfonic acid, 4-chloroaniline-3-sulfonic acid, 2-nitroaniline-3-sulfonic acid, 2-nitroaniline-4-sulfonic acid, 4B acid (p-toluidine-m-sulfonic acid), 2B Acid (o-chloro-p-toluidine-m-sulfonic acid), C acid (3-amino-6-chlorotoluene-4-sulfonic acid), CB acid (3-amino-6-chlorobenzoic acid-4-sulfone) Acid), gamma acid (2-amino-8-naphthol-6-sulfonic acid) and the like.

  As the base preparation method represented by the general formula (6), the following two methods (a) and (b) are representative, and an outline thereof is shown below.

(I) First, 1.0 mol of the diamine represented by the general formula (8) is reacted with 1.0 mol of cyanuric chloride, and then the reaction product is represented by —NH—Y—SO ₃ H such as taurine. What is necessary is just to make 1.0-2.0 mol of compounds to react.

(B) First, 1.0 mol of cyanuric chloride is reacted with 1.0 to 2.0 mol of a compound represented by —NH—Y—SO ₃ H such as taurine, and then, in general formula (8) What is necessary is just to make it react with 1.0 mol of diamine shown. Various preparation methods other than the methods shown in (a) and (b) can be used.

  As the coupler represented by the general formula (7), acetoacetylanilide, acetoacetyl-o-chloro-anilide, acetoacetyl-o-anisidide, acetoacetyl-p-anisidide, acetoacetyl-o-toluidide, acetoacetyl- Examples thereof include m-xylide, 2,5-dimethoxy-4-chloro-acetoacetylanilide, 2,5-dimethyl-acetoacetylanilide, acetoacetyl-p-phenitidide and the like.

  In order to obtain the master batch of the present invention, 98-80 mol% of the monoazo yellow main pigment represented by the general formula (1), the disazo yellow pigment represented by the general formula (2) containing a sulfonic acid group, and / or the general It is preferable to introduce and mix the monoazo yellow pigment represented by the formula (3) in an amount of 2 to 20 mol%, preferably 3 to 15 mol%. If the introduction amount of the disazo yellow pigment and / or monoazo yellow pigment is less than 2 mol%, the primary particle diameter of the pigment becomes large and the optical properties are not improved sufficiently. It impairs the vividness of the hue, impairs the optical properties, adversely affects it, and makes it difficult to obtain a good masterbatch.

  The content of these yellow pigments is preferably 2% by weight to 20% by weight. Within this range, it is possible to obtain a high-density image that is excellent in transparency, coloring power, color reproducibility, and fixability and is uniform throughout the image. When the pigment concentration is less than 2% by weight, the transparency is good, but the coloring power is not sufficient, and a uniform high density image cannot be obtained. On the other hand, if it exceeds 20% by weight, a sufficient color reproduction range cannot be ensured due to insufficient lightness and saturation, and the fixing strength deteriorates due to a decrease in resin components. More preferably, it is 2 to 15% by weight. By setting it within this range, sufficient color reproducibility can be secured and there is little deterioration in fixing properties.

  The electrophotographic yellow toner of the present invention may contain a conventionally known wax. As this wax, it can be used 1 type or in combination of 2 or more types. Specifically, petroleum wax such as paraffin wax, oxidized paraffin wax, microcrystalline wax, mineral wax such as montan wax, animal and plant wax such as beeswax, carnauba wax, polyolefin wax (polyethylene, polypropylene, etc.) Synthetic waxes such as oxidized polyolefin wax, Fischer-Tropsch wax and the like, but are not necessarily intended to be limited thereto.

  The wax can be contained in an amount of 0.1 to 15% by weight, preferably 1 to 10% by weight, based on the binder resin, whereby good fixing offset performance can be obtained. When the content is less than 0.1 parts by weight, the offset resistance is liable to be impaired, and when the content is more than 15% by weight, the fluidity of the toner tends to be deteriorated.

  In the yellow toner for electrophotography of the present invention, various external additives such as a fluidizing agent and a surface resistance adjusting agent can be used as necessary. Examples of external additives that can be used in the present invention include inorganic fine powders such as silicon dioxide, titanium oxide, aluminum oxide, cerium oxide, zinc oxide, tin oxide, and zirconium oxide, and silicon oil, silane coupling agents, and the like. And surface treated with a hydrophobizing agent, resin fine powders such as polystyrene, acrylic, styrene acrylic, polyester, polyolefin, cellulose, polyurethane, benzoguanamine, melamine, nylon, silicon, phenol, vinylidene fluoride, and the like. These can be used alone or in combination of two or more.

  The yellow toner for electrophotography of the present invention can be used alone, but the yellow toner for electrophotography of the present invention and a carrier can be mixed and used as a two-component developer.

  In general, a carrier in which magnetic material particles are coated with a resin is used, and this can also be used in the present invention. As the resin covering the carrier surface, styrene-acrylic acid ester copolymer, styrene-methacrylic acid ester copolymer, acrylic acid ester copolymer, methacrylic acid ester copolymer, silicon resin, fluorine-containing resin, polyamide resin , Ionomer resins, polyphenylene sulfide resins, and mixtures thereof can be used.

  As the magnetic material for the carrier core, oxides such as ferrite, iron-rich ferrite, magnetite and γ-iron oxide, metals such as iron, cobalt and nickel, or alloys thereof can be used. The elements contained in these magnetic materials are iron, cobalt, nickel, aluminum, copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, cadmium, calcium, manganese, selenium, titanium, tungsten, vanadium. Etc.

  The carrier is generally made of a magnetic material particle coated with a resin, but in addition to this, other types of carriers such as particles made only of a magnetic material or magnetic particles dispersed in resin particles are used. It may be used in the invention.

  The binder resin, charge control agent, and external additive used in the present invention constituting the electrophotographic yellow toner have been described above. In addition to this configuration, other color toners, for example, magenta, cyan, and black toners are used to obtain a full color image. As the colorant constituting these toners, conventionally known colorants can be used. Each color can be used alone or in combination of two or more.

  The yellow toner for electrophotography of the present invention is not particularly limited in a toner production method using a melt kneading process. Here, when it is intended to obtain a high-quality and high-density image, the volume average particle diameter of the obtained toner is preferably in the range of 4 μm to 8 μm. By reducing the particle size to this range, a high image density can be obtained even with a small amount of adhesion, and the toner consumption can be reduced. When the particle diameter is less than 4 μm, the individual particles cannot have sufficient chargeability, and toner scattering, image fogging, and the like become remarkable and cannot be used in actual use. On the other hand, if the thickness exceeds 8 μm, the layer thickness of the formed image is increased, and an image having a remarkably graininess is undesirable.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not specifically limited unless the summary is exceeded.

(1) Production Example of Charge Control Agent A bentonite suspension is prepared by dispersing 10 g of bentonite having a pH of 7 to 12 in 300 ml of deionized water at 80 ° C. and stirring for 1 hour. Next, 5.3 g of 77% aqueous distearyldimethylammonium chloride (DSDMAC) solution was adjusted to pH 9 with dilute NaOH solution, added to the bentonite suspension, stirred at 80 ° C. for 1 hour, filtered Separately, after washing several times with deionized water, it was dried at 60 ° C. under vacuum and subjected to a particle size reduction treatment to produce charge control agents (organic bentonites) having different average volume particle sizes D ₅₀ . The average volume particle diameter D ₅₀ of the charge control agent prepared is as respective Examples and Comparative Examples described in Table 1.

(2) Pigment Production Example 1
In a mixed solution of 700 g of water and 315 g (3.02 mol) of 35% hydrochloric acid, 181.4 g (1.08 mol) of m-nitro-o-anisidine and 68.8 g (0.12 mol) of base A were added. Stir to disperse. To this dispersion, about 600 g of ice was added and cooled, and then a solution in which 87 g (1.26 mol) of sodium nitrite was dissolved in 100 g of water was added and stirred for 1 hour while maintaining at 10 ° C. or lower. Excess nitrous acid was eliminated, followed by filtration to obtain a diazotized solution.

  On the other hand, the coupler solution was prepared as follows. After dissolving 100 g (0.74 mol) of sodium acetate in 8900 g of water, 256.7 g (1.24 mol) of acetoacetyl-o-anisidide was added and dispersed, and then 185 g (1.39 mol) of 30% caustic soda was added. ) Was added and dissolved in 110 g (1.47 mol) of 80% acetic acid to adjust the pH to 6, and the temperature was adjusted to 25 ° C. to obtain a coupler solution. The diazotization liquid was dropped into this coupler liquid in 120 minutes to complete the coupling reaction. Next, it heated up to 90 degreeC and heat-processed for 30 minutes. Thereafter, filtration and washing were performed to remove by-product salts and the like, followed by drying at 80 ° C. with a dryer. The average particle diameter of the yellow pigment A obtained by pulverizing this dry pigment was 0.07 μm.

(3) Pigment production example 2
To a mixed solution of 700 g of water and 315 g (3.02 mol) of 35% hydrochloric acid, 185.5 g (1.10 mol) of m-nitro-o-anisidine and 45.3 g (0.10 mol) of base B were added. Stir and disperse. To this dispersion, about 600 g of ice was added and cooled, and then a solution in which 87 g (1.26 mol) of sodium nitrite was dissolved in 100 g of water was added and stirred for 1 hour while maintaining at 10 ° C. or lower. After the nitrous acid had disappeared, filtration was performed to obtain a diazotized liquid.

  On the other hand, the coupler solution was prepared as follows. After 100 g (0.74 mol) of sodium acetate was dissolved in 8900 g of water, 256.7 g (1.24 mol) of acetoacetyl-o-anisidide was added and dispersed, and then 185 g (1.39 mol) of 30% caustic soda was added. 110% (1.47 mol) of 80% acetic acid was added dropwise to the solution dissolved by adding to pH 6 and adjusted to a temperature of 25 ° C. to obtain a coupler solution. The diazotization liquid was dropped into this coupler liquid in 120 minutes to complete the coupling reaction. Next, it heated up to 90 degreeC and heat-processed for 30 minutes. Thereafter, filtration and washing were performed to remove by-product salts and the like, followed by drying at 80 ° C. with a dryer. The average particle diameter of the yellow pigment B obtained by pulverizing this dry pigment was 0.12 μm.

(4) Production Example of Masterbatch 60% by weight of the resin and 40% by weight of the pigment were charged into a kneader and gradually heated while being mixed for sales. The material was stirred and kneaded at a material temperature of 90 ° C. for about 20 minutes. Thereafter, the temperature was gradually raised, and the material temperature was 100 ° C. for 90 minutes to disperse the pigment. Next, the contents were discharged from the kneader, and after cooling, a kneading and dispersing process was performed with a roll of about 30 × 10 ⁵ Pa using a three roll heated to 110 ° C.
The dispersion-treated product was cooled and pulverized to prepare a master batch having a pigment concentration of 40%.

Example 1
・ Polyester resin (acid value: 21 mgKOH / g) [Resin A]
Aromatic alcohol components: PO-BPA and EP-BPA
Acid components: fumaric acid and merit anhydride
79.9% by weight
Master batch (yellow pigment A: 40% by weight, resin A: 60% by weight)
(Contains 5% by weight of pigment) 12.6% by weight
Nonpolar paraffin wax (DSC peak 78 ° C., Mw 8.32 × 10 ² )
6% by weight
・ Organic bentonite (volume average particle diameter 2 μm created in the above production example)
1.5% by weight
The nonpolar paraffin wax Mw exhibits a weight average molecular weight as is well known.

  Each of the above constituent materials was premixed with a Henschel mixer and then melt-kneaded with a twin-screw extrusion kneader. The kneaded material was coarsely pulverized with a cutting mill, then finely pulverized with a jet mill, and then classified with an air classifier to prepare toner base particles having an average particle diameter of 6.5 μm. Next, 1.0% by weight of hydrophobized silica fine particles was added to the classified toner and mixed with a Hensyl mixer, followed by external addition treatment to produce a yellow toner for evaluation.

(Example 2)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 5 mg KOH / g as shown in Table 1 below.

(Example 3)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 28 mg KOH / g as shown in Table 1.

Example 4
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 4 mg KOH / g as shown in Table 1.

(Example 5)
A toner was prepared in the same manner as in Example 1 except that the acid value of the polyester resin was changed to 31 mg KOH / g as shown in Table 1.

(Example 6)
A toner was prepared in the same manner as in Example 1 except that the volume average particle size of the organic bentonite as the charge control agent was changed to 7 μm as shown in Table 1.

(Example 7)
A toner was prepared in the same manner as in Example 1 except that the volume average particle size of the organic bentonite as the charge control agent was changed to 9 μm as shown in Table 1.

(Example 8)
A toner was prepared in the same manner as in Example 1 except that the number of parts by weight of the organic bentonite as the charge control agent was changed to 0.4% by weight as shown in Table 1.

Example 9
A toner was prepared in the same manner as in Example 1 except that the weight part of the organic bentonite as the charge control agent was changed to 0.6% by weight as shown in Table 1.

(Example 10)
A toner was prepared in the same manner as in Example 1 except that the weight part of the organic bentonite as the charge control agent was changed to 4% by weight as shown in Table 1.

(Example 11)
A toner was prepared in the same manner as in Example 1 except that the number of parts by weight of the organic bentonite as the charge control agent was changed to 6% by weight as shown in Table 1.

(Example 12)
A toner was prepared in the same manner as in Example 1 except that the pigment was changed to yellow pigment B as shown in Table 1.

(Example 13)
A toner was prepared in the same manner as in Example 1 except that the pigment content was changed to 14% by weight as shown in Table 1.

(Example 14)
A toner was prepared in the same manner as in Example 1 except that the pigment content was changed to 18% by weight as shown in Table 1.

(Example 15)
A toner was prepared in the same manner as in Example 1 except that the pigment content was changed to 2% by weight as shown in Table 1.

(Example 16)
A toner was prepared in the same manner as in Example 1 except that the pigment content was changed to 1.5% by weight as shown in Table 1.

  A comparative example for comparison and comparison with the toner of the present invention according to each embodiment prepared as described above will be described below.

(Comparative Example 1)
A toner was prepared in the same manner as in Example 1 except that the binder resin of the master batch was changed to a polyester resin (resin B below) composed of an aliphatic alcohol component as shown in Table 1.
[Resin B]
Alcohol component: Ethylene glycol and dierylene glycol and neopentyl glycol Acid component: Naphrene dicarboxylic acid and terephthalic acid

(Comparative Example 2)
A toner was prepared in the same manner as in Example 1 except that the polyester resin was changed to a polyester resin (resin B) comprising an aliphatic alcohol component as shown in Table 1.
Alcohol component: Ethylene glycol and dierylene glycol and neopentyl glycol Acid component: Naphrene dicarboxylic acid and terephthalic acid

(Comparative Example 3)
A toner was prepared in the same manner as in Example 1 except that the charge control agent was changed to a zirconium compound of salicylic acid as shown in Table 1.

(Comparative Example 4)
A toner was prepared in the same manner as in Example 1 except that the charge control agent was changed to a zirconium compound of salicylic acid as shown in Table 1.

(Comparative Example 5)
As shown in Table 1, C.I. I. A toner was prepared in the same manner as in Example 1 except that the pigment yellow 180 was used.

(Comparative Example 6)
As shown in Table 1, C.I. I. A toner was prepared in the same manner as in Example 1 except that the pigment yellow 155 was used.

(Comparative Example 7)
As shown in Table 1, C.I. I. A toner was prepared in the same manner as in Example 1 except that the pigment yellow 74 was used.

  The toners of Examples 1 to 16 and Comparative Examples 1 to 7 prepared above and a silicon-coated ferrite core carrier having an average particle diameter of 60 μm were prepared so that the toner concentration was 5% by weight, and a two-component developer was prepared. .

In the following Table 1, the particle size indicates volume average particle diameter D _50. The organic bentonite has a salt structure composed of alkaline bentonite and an organic cation, and is obtained in the above production example.

(5) The evaluation method of an Example and a comparative example is demonstrated.
i. Initial charge amount The developer is set in a copier (Sharp Co., Ltd. AR-C160) having a commercially available two-component developing device, and after idling for 3 minutes at room temperature and humidity, the developer is collected and suction charging is performed. The charge amount was measured with a quantity measuring device (TREK: 210H-2A Q / M Meter). When the charge amount is -20 μC / g or more, it can be used, and when the charge amount is -25 μC / g or more, it is judged good.

ii. Charging Rise Characteristics A 5 ml glass bottle containing 0.95 g of carrier (silicon coated ferrite core carrier) and 0.05 g of toner was stirred for 1 minute in a rotary incubator at 32 rpm, and then the developer was collected and suction charge amount measurement was performed. The charge amount was measured with an apparatus. Further, after stirring for 3 minutes, the charge amount was measured in the same manner. It can be used when the difference between the charge amounts after 1 minute and 3 minutes is 7 μC / g or less in absolute value, and it is judged good if it is 5 μC / g or less.

iii. Attenuation characteristics of charge A 100 ml polyethylene container containing 76 g of a carrier (silicon coated ferrite core carrier) and 4 g of toner was stirred for 60 minutes with a 150 rpm ball mill, and then the charge amount of the developer was measured and exposed to high temperature and high humidity. . After 1 day, 3 days, and 10 days, the charge amount of the developer was measured. If the difference from the charge amount on the first day was 7 μC / g or less in absolute value, it was usable, and if it was 5 μC / g or less, it was judged good. .

iv. Life characteristics of charging After setting the developer in a copying machine (Sharp Co., Ltd. AR-C160) having a commercially available two-component developing apparatus and taking a real image of 50000 solid images at room temperature and humidity, the image density and The whiteness of the non-image area and the charge amount of the developer were measured. The image density was measured with an X-Rite 938 spectrocolorimetric densitometer and judged to be good if the image density was 1.4 or higher. As for whiteness, tristimulus values X, Y, and Z are obtained using an SZ90 type spectroscopic color difference meter manufactured by Nippon Denshoku Industries Co., Ltd., and the value of ΔZ (paper and non-image portion) is 0.7 or less. It was judged that it was usable when it was 0.5 or less. The charge amount of the developer was measured with a suction-type charge amount measuring device, and it was determined that the developer was usable if the difference from the initial charge amount was 7 μC / g or less in absolute value, and good if it was 5 μC / g or less.

v. Pigment dispersibility (transparency)
The toner kneaded product was cut to a thickness of 0.1 mm with a microtome and observed with an optical microscope.

The case where there was no particle of 1 μm or more was judged to be good, and the case where 1 μm or more was 5 or less in 5 mm ² area was judged to be usable.

The evaluation results from i to v are shown in Table 2. Evaluation was made in three stages: comprehensive evaluation, ◎, ○, and ×.
In addition, each evaluation standard of (double-circle), (circle), and x is as follows.
◎: Very good developer within the scope of the present invention ○: Developer within the scope of the present invention ×: Inferior to developers in the prior art

  From the results shown in Table 2, the yellow toner produced in each of Examples 1 to 16 according to the present invention has the following charging characteristics, pigment dispersion (transparency) as compared with the yellow shown in Comparative Examples 1 to 7. Etc., and stable development can be maintained.

  For example, as shown in Table 2, the electrophotographic toner according to Example 1 of the present invention had an initial charge amount of −30 μC / g and a value of −25 μC / g or more. The charge rising characteristics were -29 μC / g after 1 minute of stirring, -32 μC / g after 3 minutes of stirring, and the absolute amount difference between the charged amounts was 5 μC / g or less. Further, the attenuation characteristic was −29 μC / g on the first day, −25 μC / g after 10 days, and the absolute amount difference in charge amount was 5 μC / g or less. The charge amount after taking 5000 sheets is -28 μc / g, the difference from the initial charge amount is 5 μC / g or less, the image density is 1.50, 1.4 or more, and the whiteness is 0. 3 was 0.5 or less. Thus, it can be said that the toner has very excellent charging characteristics.

  In addition, there is no particle of 1 μm or more in the dispersion of the pigment of the toner, the pigment dispersion is good and it is sufficiently transparent, and thus the charging characteristics are also kept good. Thus, good results were obtained in all the items.

  Also, in Examples 2, 3, 6, 9, 10, 12, 13, and 15, good results were obtained in all items as in Example 1.

  In Example 4, although the acid value of the resin is as low as 4 mg KOH / g, the charging characteristics are somewhat lower than in Example 1. However, the initial charging characteristics and the charge rising characteristics can be used without being sufficiently implemented. It was an area.

  In Example 5, since the acid value of the resin was as high as 31 mg KOH / g, the charge amount attenuation at a higher temperature and higher humidity was larger than that in Example 1, but it was a usable area that could be fully used. .

  Further, in Example 7, the volume average particle diameter of the organic bentonite is as large as 9 μm, so that the charge rising property is slightly worse than that in Example 1, but it can be used. It can be said.

  In Example 8, although the amount of addition of organic bentonite was reduced to 0.4% by weight, the charging characteristics were somewhat lower than in Example 1. However, it can be used sufficiently for performance evaluation of initial charge amount, charge rising characteristics, and whiteness. It was a great area.

  In Example 11, although the whiteness was reduced because the amount of organic bentonite added was as high as 6% by weight, there was no problem with respect to other charging characteristics and the like, and the region was sufficiently usable.

  In Example 14, since the pigment content increased, there was a slight decrease in initial charging and pigment dispersion, but this was a sufficiently usable area in performance judgment.

  In Example 16, the content decreased to 1.5% by weight of the pigment, and thus the image density decreased to 1.32.

  As described above, the use of an aromatic polyester resin with an alcohol component provides excellent humidity environment characteristics and a low charge decay rate at high temperature and high humidity. In addition, since the organic bentonite is contained in the resin, the initial charge amount and the rising amount of the charge amount of the toner exhibit appropriate characteristics and the life stability is improved by the organic bentonite finely dispersed in the toner. Furthermore, by using the yellow pigment of this configuration, it is possible to obtain a toner having good pigment dispersion, high color reproducibility with high transparency, and good charging characteristics.

  On the other hand, in Comparative Example 1, since a polyester resin having an aliphatic alcohol component was used for the masterbatch, the pigment dispersion of the toner was deteriorated and good results could not be obtained.

In Comparative Example 2, since the polyester resin whose alcohol component is aliphatic is used in the masterbatch as the binder resin, the charge amount is greatly attenuated at high temperature and high humidity, and the image has a background fog having a large whiteness. Good results were not obtained.
In Comparative Example 3.4, since an object other than organic bentonite was used as the charge control agent, the initial charge amount was reduced, and an image having a background fogging with high whiteness was obtained, and the fixing characteristics were also deteriorated, and good results were not obtained. It was.

  In Comparative Example 5.6.7, a toner was prepared in the same manner as in Example 1 except for the yellow pigment of the present invention. However, the pigment dispersion was poor and the transparency was not good, and the charging characteristics were further lowered. An image with large background fogging was obtained, and good results were not obtained.

  As mentioned above, in order to satisfy both the good chargeability and the color reproducibility due to high pigment dispersion, the results of the comparison between Examples 1 to 16 and Comparative Examples 1 to 6 according to the present invention are as described above. The basic constitution is to include a polyester resin obtained by reacting an aromatic alcohol component with an organic bentonite and a specific yellow pigment.

  In addition, from the results shown in Table 2, the acid value of the polyester resin of the present invention is in the range of 4 mg KOH / g to 31 mg KOH / g in order to improve the charge amount rising property. From the results of the examples, it is proved that the range of 5 mg KOH / g to 30 mg KOH / g is a preferable range as specified. Moreover, it can be said that the range of 5 mgKOH / g-28 mgKOH / g is suitable as a more preferable range from an Example.

  Further, by using the organic bentonite which is the charge control agent of the present invention, the chargeability can be improved, and the addition amount can be in the range of 0.4 wt% to 6 wt% from the results of Table 2. From the results of the examples, it was proved that the range is 0.5% by weight to 5% by weight as specified above. Furthermore, according to the examples, it can be said that a more preferable range is 0.6% by weight to 4% by weight.

In addition, when using organic bentonite in the charge control agent of the present invention, the particle size (volume average particle size D ₅₀ ) as another requirement is a feasible range in which the chargeability is sufficiently stable up to 9 μm, As described above, it is proved from the results of the examples that 8 μm or less is good. Moreover, it can be said that the particle size is preferably 7 μm or less according to the examples. This is somewhat affected by the acid value range of the binder resin, which is another component.

  Further, by using the yellow pigment of the present invention, the pigment dispersibility can be improved, but the addition amount for that purpose can be in the range of 1.5 to 18% by weight from the results of Table 2. A range, which, as specified above, has proven to be a preferred range of 2% to 15% by weight. Furthermore, according to the examples, it can be said that a more preferable range is 2% by weight to 14% by weight.

  Further, from the result of Comparative Example 5.6.7, even when the toner base particles contain organic bentonite, the charging characteristics cannot be maintained satisfactorily by using a pigment that is not the pigment of the present invention. In this respect, according to the present invention, the yellow toner using the specific yellow pigment can be improved in charging characteristics by containing organic bentonite, and this state can be maintained. Therefore, it can be said that the use of the specific yellow pigment of the present invention for toner base particles containing organic bentonite is very useful as described above.

  As described above, when the electrophotographic yellow toner of the present invention is used and a color image is formed using magenta, cyan, and black toners, the toner particles of the superimposed colors are melted to form a boundary between the toner particles. Eliminating and obtaining sufficient transparency enables faithful color reproduction. In addition, regarding the charging characteristics, the above-described color reproducibility can be expected since the stable development can be achieved by obtaining a sufficiently stable charge amount that is rich in moisture resistance from the results shown in Table 2.

Claims (6)

A toner comprising at least a binder resin, a colorant, and a charge control agent, wherein the binder resin is a polyester resin composed of an aromatic alcohol component, the charge control agent includes organic bentonite, A monoazo yellow main pigment represented by the following formula (1) as a colorant, a disazo yellow pigment represented by the following general formula (2) and / or a monoazo yellow pigment represented by the following general formula (3) A yellow toner for electrophotography characterized by.

[In the chemical formulas ¹ to 3, R ¹ and R ² represent different hydrogen atoms, chlorine atoms, nitro groups, methyl groups or methoxy groups, and R ³ , R ⁴ and R ⁵ are the same or different. Represents a hydrogen atom, a chlorine atom, a methyl group, a methoxy group or an ethoxy group, R ⁶ and R ⁷ represent a methyl group or a meoxy group, and Q ^{1 to} Q ⁴ each independently represent a hydrogen atom, a lower group having 1 to 2 carbon atoms. Represents an alkyl group, a lower alkoxy group or a hydroxyl group, W represents a substituent selected from the group represented by Chemical Formula 4, m represents an integer of 0 or 1, and A and B each independently represent —NH—. Y is a group represented by Y—SO ₃ H or —OH group, where Y is a group selected from an ethylene group, a phenylene group and a naphthylene group, and may contain a substituent. . ]

2. The electrophotographic yellow toner according to claim 1, wherein the organic bentonite has a volume average particle diameter D ₅₀ of 9 μm or less.   2. The yellow toner for electrophotography according to claim 1, wherein an acid value of a polyester resin obtained by reacting the aromatic alcohol component is 4 mgKOH / g to 31 mgKOH / g.   2. The yellow toner for electrophotography according to claim 1, wherein a masterbatch composed of a polyester resin that reacts the colorant with the aromatic alcohol component is used.   2. The yellow toner for electrophotography according to claim 1, wherein the organic bentonite has a salt structure composed of alkaline bentonite and an organic cation.   2. The electrophotographic yellow toner according to claim 1, wherein the addition amount of the colorant is 2 wt% to 15 wt%.