JP5081702B2 - Magenta toner for electrophotography and method for producing the same - Google Patents

Description

  The present invention relates to an electrophotographic magenta toner used in an image forming apparatus using a so-called electrophotographic method, such as an electrostatic copying machine or a laser beam printer, and a manufacturing method thereof, and more specifically, color reproducibility and light fastness. The present invention relates to a full-color electrophotographic magenta toner capable of forming a high-quality image stably without impairing chargeability even during long-term running and a method for producing the same.

  2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic system, an electrostatic printing system, or the like has been widely used for a copying machine, a printer, a facsimile machine, and the like. For example, in an electrophotographic image forming apparatus, a photoconductor having a photosensitive layer containing a photoconductive material formed on the surface is used as an image carrier, and image information is obtained on the photoconductor through various image forming processes. After forming an electrostatic latent image based on the image, developing the electrostatic latent image with a developer supplied from a developing device and containing a toner to form a visible image, and transferring the visible image to a recording material such as paper. Then, the image is formed on the recording paper by being heated and pressed by the developing roller and fixed on the recording material.

  In such an image forming apparatus, toner is used to visualize the electrostatic latent image formed on the image carrier. As a dry development method using toner, development methods by frictional charging such as a powder craft method, a cascade method, and a magnetic brush method are generally used. Among these, the magnetic brush method is widely used because the development operation can be easily controlled and a recorded image having high image quality can be obtained. The magnetic brush method includes a one-component development method in which a magnetic brush is formed only with toner containing a magnetic substance and development is performed, and a magnetic brush is formed with a two-component developer containing toner and magnetic particles called carriers, and development is performed. There are two-component development methods to be performed, and in both cases, toner to which a predetermined charge is applied on the magnetic brush is transferred to the electrostatic latent image on the photosensitive member by the coulomber and is developed.

  The toner is obtained by dispersing a colorant in a binder resin. As the binder resin, for example, various types of synthetic resins having appropriate electric detection and binding properties such as a styrene resin and a polyester resin. A resin is used, and as the colorant, carbon black, an organic colorant, an inorganic colorant, or the like is used. The developed image is transferred onto paper and then fixed to form an image.

In a full-color image, colors are reproduced by the human eye recognizing light absorbed and reflected by each toner layer by superimposing cyan, magenta, and yellow toners.
In recent years, the technology of hard copy using an electrophotographic method has changed from monochrome copy to full color copy. As full-color copies have become widespread, their uses have become complicated and diversified, and the image quality is required to be higher than that of photographic images.

  In order to satisfy the characteristics required of toners for achieving high image quality, there are increasing technical demands for expanding the color reproduction region and reducing the particle size of toners. In order to widen the color reproduction gamut, it is necessary to select a color material having a wider color reproduction gamut as the color material becomes highly dispersed. For high image quality, it is necessary to reduce the toner particle size and reduce the amount of toner adhering to the paper. In order to exhibit the same color development performance with the reduced toner, it is contained in the toner. It is necessary to increase the amount of color material. In order to show the same color developability as before while increasing the amount of color material, it is necessary to improve the dispersion state of the color material, but it is very difficult, and the degree of coloring is high, that is, the amount of color material added is increased. There is an increasing demand for selection of a color material that can obtain the same image density without the need.

In addition, with the diversification of uses for electrophotography such as advertisements and posters, there is an increasing demand for color materials having high weather resistance and high light resistance. In order to diversify these uses, color materials and surface treatment agents have been studied. For example, Patent Document 1 discloses a toner containing a quinacridone-based color material. These conventional toners are difficult to change in color by light, but have a problem that the hue is slightly weaker in blue and the color gamut is narrow, and the coloring power is low.
In addition, as a method of compensating for the problems while taking advantage of each color material, an attempt has been made to obtain a toner having high coloring degree and high light resistance while expanding the color reproduction range by using two or more color materials together. .
For example, in Patent Document 2, C.I. I. Pigment red 81, C.I. I. Pigment Red 48 is used in combination, that is, a toner using a rhodamine color material and a monoazo color material in combination. According to this publication, a red developer that does not impair the chargeability can be obtained by using these color materials together. However, this publication does not describe color reproducibility. C. I. The monoazo color material typified by CI Pigment Red 48 has a low reflectance in a short wavelength region of 400 nm to 500 nm in spectral reflectance characteristics, and is a so-called low bluish color material, so that the magenta color reproducibility is extremely low. . Therefore, a toner with strong redness can be obtained by using the two kinds of color materials together.

Japanese Patent Publication No.49-46951 Japanese Patent No. 3226993

  The present invention has been made in view of the above prior art, has good color reproducibility, high light resistance and strong coloring power, and does not impair the charge amount even during long-term running, and image deterioration such as ground fogging. An object of the present invention is to provide an electrophotographic magenta toner capable of forming a high-quality image stably without any defects, and a method for producing the same.

  As a result of intensive studies, the present inventors have determined that C.I. I. Pigment red 122, C.I. I. Pigment Red 81 is used in combination, and a negatively chargeable charge control agent is used, and the amount of addition and ratio thereof are taken into consideration, and various investigations are made in consideration of dispersibility. As a result, the following [1] The inventors have found that the above-mentioned problems can be solved by the invention described in [14]. Hereinafter, the present invention will be specifically described.

[1]: The above-described problem is in an electrophotographic magenta toner containing at least a binder resin, a magenta color material, and a charge control agent.
The magenta color material is C.I. I. Pigment red 122, C.I. I. Pigment Red 81 mixed color material, the charge control agent is a salicylic acid metal salt,
C. above. I. A magenta toner for electrophotography, wherein the weight ratio (R / C) of the addition amount (R) of Pigment Red 81 and the addition amount (C) of the charge control agent is 1.1 to 2.0. Solved.

  [2]: The electrophotographic magenta toner described in [1] above, wherein the salicylic acid metal salt is zinc salicylate.

  [3]: In the magenta toner for electrophotography according to the above [1] or [2], the C.I. I. Pigment red 122, C.I. I. The total addition amount of the mixed color material with Pigment Red 81 is 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin.

  [4]: In the magenta toner for electrophotography according to any one of [1] to [3], C.I. I. Pigment red 122, C.I. I. The mixing ratio with Pigment Red 81 is 2: 8 to 8: 2.

  [5]: The electrophotographic magenta toner according to any one of [1] to [4], wherein the binder resin is a polyester resin.

  [6]: The electrophotographic magenta toner according to any one of [1] to [5], wherein the electrophotographic magenta toner further contains a colorant dispersant.

  [7]: The electrophotographic magenta toner according to [6], wherein the colorant dispersant is a fatty acid ester.

  [8]: The electrophotographic magenta toner according to [6] or [7], wherein the colorant dispersant has a melting point lower than a softening point of the binder resin.

  [9]: The electrophotographic magenta toner according to the above [8], wherein the colorant dispersant has a melting point of 70 ° C. to 105 ° C.

  [10]: In the magenta toner for electrophotography according to any one of [6] to [9], the addition amount of the colorant dispersant is 0.5 parts by weight to 100 parts by weight of the binder resin. 5 parts by weight.

  [11]: The electrophotographic magenta toner according to any one of [6] to [10], wherein the colorant dispersant has an acid value of 5 to 30 mgKOH / g.

  [12]: The electrophotographic magenta toner according to any one of [1] to [11], wherein the electrophotographic magenta toner further contains a wax.

[13]: The above problem is a method for producing a magenta toner for electrophotography according to any one of [1] to [12],
A mixing step of mixing at least a binder resin, a magenta coloring material, and a raw material containing a charge control agent, and a mixture obtained by the mixing step is melt-kneaded using an open roll type kneader in which the kneading part is an open system. And a melt-kneading step, and the melt-kneaded product obtained in the melt-kneading step is pulverized and classified to obtain a toner.

  [14]: A masterbatch prepared by previously melt-kneading a predetermined amount of the magenta colorant and the binder resin in the mixing step in the method for producing a magenta toner for electrophotography according to [13] above. It is characterized by using.

According to the magenta toner for electrophotography of the present invention, C.I. I. Pigment red 122, C.I. I. Pigment Red 81 and a salicylic acid metal salt as a charge control agent are used. I. Since the weight ratio (R / C) of the addition amount (R) of Pigment Red 81 and the addition amount (C) of the charge control agent is regulated to 1.1 to 2.0, color reproducibility is good. In addition, the light resistance and coloring power are strong, and a decrease in charge amount is suppressed even in long-term running, and image formation such as ground fog does not occur and high-quality image formation can be stably performed. Further, when a montanic acid ester is used as a pigment dispersant, a toner having better color reproducibility can be obtained.
According to the method for producing an electrophotographic magenta toner of the present invention, by using an open roll type kneader as a melt kneader, a kneading force can be imparted to the raw material mixture because it can be kneaded at a relatively low temperature. And can be dispersed well to obtain a toner with good color reproducibility. Furthermore, by using the master batch, the dispersibility of the color material is further increased, and a toner with high color reproducibility and high coloring power can be obtained.

As described above, the electrophotographic magenta toner in the present invention is an electrophotographic magenta toner containing at least a binder resin, a magenta color material, and a charge control agent.
The magenta color material is C.I. I. Pigment red 122, C.I. I. Pigment Red 81 mixed color material, the charge control agent is a salicylic acid metal salt,
C. above. I. The weight ratio (R / C) of the addition amount (R) of Pigment Red 81 and the addition amount (C) of the charge control agent is 1.1 to 2.0.

  In the present invention, C.I. I. Pigment red 122, C.I. I. Pigment Red 81 uses both quinacridone colorant with good magenta color reproducibility, excellent fastness (light resistance) but weak coloring power, high coloring power, and very good color reproducibility This is because a rhodamine color material having poor light resistance is used in combination for the rake color material, and the problems are complemented while taking advantage of each other's excellent points.

  Further, a salicylic acid metal salt is used as a charge control agent, and C.I. I. The reason why the weight ratio (R / C) of the addition amount (R) of Pigment Red 81 and the addition amount (C) of the charge control agent is 1.1 to 2.0 is as follows. That is, C.I. I. Pigment Red 81 has a dye having an amine group at its end insolubilized (raked) with phosphorus-tungsten-molybdenum, so it has a very positive chargeability. By adding it to the toner, the negative polarity toner is charged. The amount is reduced, causing problems such as ground fog and toner scattering. Accordingly, a white or colorless charge control agent having a negative chargeability that hardly affects the color reproducibility of the toner is disclosed in C.I. I. It is necessary to add according to the addition amount of pigment red 81. Here, C.I. I. If the weight ratio (R / C) between the addition amount (R) of Pigment Red 81 and the addition amount (C) of the charge control agent is less than 1.1, the charge amount of the toner is too high, resulting in a decrease in image density. On the other hand, if R / C is larger than 2, the charge amount is too low, so the effect of the charge control agent is low, and problems such as ground fog and toner scattering occur.

In the magenta toner for electrophotography of the present invention, the C.I. I. Pigment red 122, C.I. I. It is preferable that the total addition amount of the mixed color material with Pigment Red 81 is 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin.
The addition amount of the mixed color material for magenta is 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin. If the color material is less than 5 parts by weight, the color development as magenta is weak and the image Magenta toner with low density and saturation. On the other hand, when the amount is more than 15 parts by weight, it becomes difficult to disperse the color material, and the toner has low saturation.

In the electrophotographic magenta toner of the present invention, C.I. used as a colorant for magenta. I. Pigment red 122, C.I. I. The mixing ratio with Pigment Red 81 is preferably 2: 8 to 8: 2.
C. I. If the addition ratio of Pigment Red 81 is greater than 8, the influence of rhodamine fading is large, and the influence on the color reproducibility of the toner is large. In addition, the charge amount is reduced, and toner scattering and ground fog are likely to occur. On the other hand, C.I. I. When the pigment red 122 addition ratio is greater than 8, the coloring power is low and the toner has a low image density.

  In the electrophotographic magenta toner of the present invention, the binder resin is preferably a polyester resin. That is, since the polyester resin has high transparency and high negative chargeability, the color reproducibility is high, and it is possible to obtain a toner having a stable chargeability that does not cause toner scattering or fogging.

The electrophotographic magenta toner of the present invention preferably further contains a color material dispersant, and a fatty acid ester can be favorably used as the color material dispersant.
In the present invention, the fatty acid ester is used as the colorant dispersant because the wettability with the colorant is improved if it has an ester group, although the reason is not clear. Since it is compatible with the carboxylic acid of the binder resin, it can be effectively dispersed.

In the magenta toner for electrophotography of the present invention, it is preferable that the melting point of the colorant dispersant is lower than the softening point of the binder resin.
Since the melting point of the color material dispersant is lower than the softening point of the binder resin, the color material dispersant can be melted earlier than the binder resin and cover the color material surface at the time of melt-kneading. It is considered that the dispersibility of the colorant is further improved since the effect as a colorant is easily obtained.

The melting point of the colorant dispersant is preferably 70 ° C to 105 ° C.
The reason for setting the melting point of the color material dispersant to 70 ° C. to 105 ° C. is that, even if the color material dispersant is partially compatible, it is present in a domain, and the color material is dispersed when the toner is pulverized. Since the agent domain is used as an interface and is often pulverized, the probability of existing on the toner surface is increased. Here, if the melting point is lower than 70 ° C., the colorant dispersant present on the surface deteriorates the storage stability of the toner, or the running characteristics under high temperature and high humidity causes a charging failure and the accompanying ground fog, etc. Can not provide. On the other hand, when the temperature is higher than 105 ° C., the color material surface cannot be uniformly covered during melt kneading, and sufficient color material dispersibility cannot be obtained.

In the electrophotographic magenta toner of the present invention, the amount of the colorant dispersant added is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin.
The amount of the color material dispersant added is 0.5 parts by weight or more. If the amount is less than 0.5 parts by weight, the color material surface cannot be sufficiently covered and sufficient color material dispersibility cannot be obtained. . On the other hand, if the amount is more than 5 parts by weight, the presence of the colorant dispersant present on the surface increases as described above, so the colorant dispersant present on the surface deteriorates the storage stability of the toner, or running under high temperature and high humidity. In terms of characteristics, poor charging and accompanying ground cover occur.

In the electrophotographic magenta toner of the present invention, the colorant dispersant preferably has an acid value of 5 to 30 mgKOH / g.
The reason for setting the acid value of the colorant dispersant to 5 to 30 mgKOH / g is that if the acid value is less than 5 mgKOH / g, it will not be compatible with the binder resin and will not act as a dispersant. Can't get. On the other hand, if it is higher than 30 mgKOH / g, the hygroscopicity of the colorant dispersant exposed on the surface is increased, the storage stability is deteriorated, or the running characteristics under high temperature and high humidity causes a charging failure and the accompanying ground cover, and the like. Can not provide the toner.

A method for producing an electrophotographic magenta toner in the present invention is a method for producing the above-described electrophotographic magenta toner, which includes a mixing step of mixing at least a binder resin, a magenta color material, and a charge control agent. A melt-kneading step of melt-kneading the mixture obtained in the mixing step using an open roll kneader having an open system in the kneading part, and pulverizing and classifying the melt-kneaded product obtained in the melt-kneading step Thus, a toner is obtained.
The open roll type kneader is used because the present kneader can knead the heat generated during toner kneading while dissipating the heat to the outside, so that it can be kneaded at a relatively low temperature. Since it is possible to knead in a highly elastic state by kneading at a low temperature, a strong elasticity can be imparted to the raw material.

Here, in the mixing step, it is preferable to use a master batch prepared by previously melt-kneading a magenta color material and a predetermined amount of a binder resin.
By using the master batch, it is possible to obtain a toner having higher colorant dispersibility, higher color reproducibility of color superposition, and higher coloring power.

The embodiment of the present invention will be further described in detail.
The toner production method of the present invention includes a mixing step of mixing at least a binder resin, a magenta color material, and a raw material containing a charge control agent, and an open roll in which a kneaded portion of the mixture obtained in the mixing step is an open system At least a melt-kneading step of melt-kneading using a mold kneader, for example, comprising the steps of mixing, melt-kneading, cooling, crushing, crushing, classifying and externally adding raw materials as described below Can do.
(1) Mixing step of mixing raw materials including at least a binder resin, a magenta color material, and a charge control agent (2) Using an open roll type kneader in which the mixture obtained in the mixing step is an open system (3) Cooling step for cooling and solidifying the melt-kneaded product obtained in the melt-kneading step (4) Crushing step for coarsely crushing the cooled / solidified product obtained in the cooling step ( 5) A pulverizing step for pulverizing the coarsely pulverized product obtained in the coarse pulverizing step. (6) A classification step for classifying the pulverized product obtained in the pulverizing step. (7) An external additive is applied to the surface of the classified toner base particles. External addition process to attach

  The raw material mixer is not limited as long as it can stir the raw material, but is preferably a high rotation speed capable of being cooled by a jacket, such as a Henschel mixer (Mitsui Mine). Etc.). The melt kneader may be any one that can be heated and melted and kneaded, such as a single-screw kneader, a twin-screw extruder kneader, or an open roll kneader, but an open roll kneader is preferably used. The open roll type kneader is preferably a kneader having at least one pair of two rolls arranged close to each other. From the viewpoint of production efficiency and simplification of equipment, a continuous two open roll type kneader is more preferable. preferable.

  The gap between the two rolls arranged close to each other can be freely set. Further, the two rolls may be parallel or non-parallel. By making the roll gap on the discharge side of the kneaded material wider than the roll gap on the raw material input side, the kneading force of the open roll type kneader, which normally applies a strong shearing force over the entire kneading part, In the latter part, the generation of the kneading heat itself can be suppressed by mainly mixing by melting, so that the effect is further increased. It is preferable that one of the two rolls arranged close to each other is a heating roll through which a heating medium is passed, and the other is a cooling roll through which a cooling medium is passed. The temperature of the heating medium is preferably within a temperature range of ± 30 ° C. softening point of the binder resin. The structure, size, material, and the like of the roll are not particularly limited, and the roll surface may be any of smooth, corrugated, uneven and the like. The rotation speed of the roll is preferably 2 to 100 m / min in peripheral speed, and the rotation speed ratio (the rotation speed of the cooling roll / the rotation speed of the heating roll) is preferably 1/10 to 9/10. The kneading temperature and the number of roll rotations can be adjusted to a desired kneading force.

  In the present invention, the binder resin used is not particularly limited, but a polyester resin is preferably used. As the polyester resin, a resin having a preferable acid value can be easily selected. Moreover, it is preferably used for full color from the viewpoint of control of thermal characteristics.

  Specifically, the polyester resin can be synthesized from the following polyhydric alcohol and polyvalent carboxylic acid component. Examples of the polyhydric alcohol component include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, diethylene glycol, triethylene glycol, and 1,5-pentanediol. 1,6-hexanediol, neopentylene glycol, 1,4-cyclohexanedimethanol, dipropylene glycol, polyethylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene And dihydric alcohols such as bisphenol A alkylene oxide adducts such as bisphenol A.

  In addition, a trihydric or higher polyhydric alcohol can be used to make the polymer non-linear to such an extent that no tetrahydrofuran-insoluble matter is generated. Examples of the trivalent or higher alcohol component include glycerin, sorbitol, 1,2,3,6-hexanetetraol, 1,4-sorbitan, pentaerythritol, 1,2,4-butanetriol, 1,2,5- Examples include pentanetriol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene.

  Examples of the polyvalent carboxylic acid component include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, terephthalic acid, isophthalic acid, cyclohexanedicarboxylic acid, malonic acid, and succinic acid. And dibasic carboxylic acids such as adipic acid, sebacic acid, glutaric acid, alkyl succinic acid (for example, n-octyl succinic acid, n-dodecenyl succinic acid), acid anhydrides and alkyl esters thereof. The acid value of the binder resin used in the present invention is not particularly limited, but is preferably 10 to 30 mgKOH / g in consideration of dispersibility of the color material and environmental characteristics.

  The softening point of the resin was measured by using a high and low flow tester (Shimadzu Corporation: CFT-500D), applying a load of 1.96 MPa with a plunger while heating a 1 g sample at a heating rate of 6 ° C./min. Extrusion was performed from a nozzle having a length of 1 mm and a length of 1 mm. The amount of plunger drop of the flow tester was plotted against the temperature, and the temperature at which half of the sample flowed out was taken as the softening point.

As described above, the colorant of magenta toner is classified into C.I. I. Pigment red 81 and C.I. I. Pigment Red 122 is used in combination.
Further, as described above, in the present invention, a fatty acid ester can be preferably used as a colorant dispersant. The fatty acid ester can be produced, for example, by subjecting a fatty acid to oxidative purification and then adding an alcohol to esterify it. The fatty acid ester selected is not particularly limited, but may be any solid at room temperature, that is, a melting point of 40 ° C. or higher, preferably 70 ° C. to 105 ° C., lauric acid having 12 or more carbon atoms, Esters such as myristic acid, palmitic acid, stearic acid, behenic acid, lignoceric acid, and montanic acid are preferred.
Considering storage stability and running stability under high temperature and high humidity, a montanic acid ester having a melting point of 80 ° C. or higher is more preferable. The addition amount is favorably determined by the addition amount of the pigment, but 0.5 to 5 parts by weight is preferable in consideration of the storage stability of the toner and the running characteristics under high temperature and high humidity.

  The melting point of the colorant dispersant can be measured using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd .: DSC210). The sample was heated to 100 ° C. at a rate of temperature increase of 10 ° C./min, cooled to −10 ° C. at a rate of temperature decrease of 100 ° C./min, left for 3 minutes, and then heated to 25 ° C. at a rate of temperature increase of 60 ° C./min. After that, hold for 2 minutes and start measurement at a temperature rising rate of 10 ° C./min. At this time, the peak top of the endothermic peak was defined as the melting point of the colorant dispersant. The acid value was measured by the method of JIS K0070.

Further, a wax can be more preferably used for the electrophotographic magenta toner of the present invention. As wax, natural wax, animal-derived beeswax, whale wax, shellac wax, plant-derived carnauba wax, wood wax, rice bran wax (rice wax), candelilla wax, petroleum-derived paraffin wax, microcrystalline wax, mineral-derived The synthetic waxes include Fischer-Tropsch wax, polyethylene wax, oil-based synthetic waxes (esters, ketones, amides), and hydrogenated wax. In order to exhibit, what has the endothermic peak by DSC (differential scanning calorimeter) 80-110 degreeC is preferable. Although the type is not particularly limited, a hydrocarbon-based synthetic wax obtained by synthesis or a petroleum-based wax is preferable.
Hydrocarbon synthetic waxes are roughly classified into the following two types. The first type is called Fischer-Tropsch wax, which can be produced by reacting carbon monoxide with hydrogen. The other type is called polyethylene wax, which can be produced by polymerization of ethylene or thermal decomposition of polyethylene. The above waxes are used alone or in combination. Further, it can be used in combination with a colorant dispersant.

  As described above, the toner used in the embodiment of the present invention includes C.I. I. In order to supplement the positive chargeability of CI Pigment Red 81, a metal salt of salicylic acid is blended as a charge control agent. Since the metal salt of alkyl salicylic acid used is a metal complex having a carboxyl group, it has a strong negative chargeability. The metal forming the salt structure is not particularly limited, but is preferably zinc or zirconium. The amount of charge control agent added is C.I. I. It is added according to the amount of pigment red 81 added.

  The toner particles used in the embodiments of the present invention are those having an average particle diameter of 3 μm to 15 μm obtained by mixing the raw materials, kneading with the kneader, and further pulverizing and classifying. In particular, a small particle diameter toner having an average particle diameter of 9 μm or less is used for obtaining a high quality image, and a small particle diameter toner having a particle diameter of 5 μm to 8 μm is suitable for improving the image quality. Further, inorganic fine particles and resin fine particles are externally added to the toner used in the embodiment of the present invention. As the inorganic fine particles, for example, fatty acid metal salt, zinc stearate, calcium stearate, lead stearate, zinc oxide powder, aluminum oxide powder, titanium oxide powder or fine powder silica can be used. Moreover, a melamine resin can be used as the resin fine particles.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated further more concretely, these examples do not limit the scope of the present invention.

(Examples 1-24 and Comparative Examples 1-7)
2 parts by weight of wax [HNP-9 (manufactured by Nippon Seiwa)] not listed in Table 1 below, and each composition shown in Table 1 below [binder resin (abbreviated, “resin”), pigment, charge control agent and pigment Dispersants] mixed at the blending ratios shown in Table 1 are melt kneaded in a continuous open roll kneader (MOS160-560: manufactured by Mitsui Mining), pulverized and classified, and a toner having an average particle size of 7 μm. (Toner mother particles) was obtained. Further, 1.5 parts by weight of hydrophobic silica (RX200: manufactured by Nippon Aerosil Co., Ltd.) was externally added as an external additive to the surface of each obtained toner base particle, and evaluations of Examples 1 to 24 and Comparative Examples 1 to 7 were made. It was made as a toner.

Using the evaluation toners of Examples 1 to 24 and Comparative Examples 1 to 7, the ground fog, hue, and light resistance were evaluated under the following conditions. The evaluation results are shown in Table 2 below.
[Evaluation items and conditions]
[Evaluation of ground cover]
The toner obtained above and 60 μm ferrite carrier were mixed with stirring at a toner concentration of 4% for 20 minutes to obtain a two-component developer. The two-component developer was subjected to a printing durability test of 50,000 sheets at a document density of 5% using a copying machine (Imagio Neo C355) manufactured by Ricoh Co., Ltd. in an environment of a temperature of 25 ° C. and a humidity of 50%. The image densities of the formed first and 50,000th fixed images were measured with a spectrocolorimetric densitometer Xrite 938 (conditions: 2 degree visual field, D50 light source, Status A) manufactured by X-RITE.
Measure the density difference between the unused paper and the white area of the fixed image. If the density difference is less than 0.01, ◎, 0.01 to less than 0.02, ○, 0.02 to less than 0.03 Was judged as x for cases where Δ was 0.03 or more.
[Hue evaluation]
The developer produced by the above charging evaluation is Ricoh Co., Ltd. full color copying machine (Imagio Neo C600) so that the amount of adhesion on high-quality paper (type 6000 70W) for color is 0.4 mg / cm ^2. And a solid image of 2 cm × 5 cm was output. This sample was fixed at 170 ° C. with an external fixing machine in which a fixing machine of a full color copying machine (Imagio Neo C600) manufactured by Ricoh Co., Ltd. was modified so that the fixing temperature could be freely set. Spectral reflection characteristics of this fixed sample were measured with a spectrophotometer (UV3100: manufactured by Shimadzu Corporation). At this time, the rise of the reflection region of the reflection characteristics, the reflectance and its wavelength, and the difference between absorption and reflection were confirmed, and the hue and saturation were confirmed.
Those with good hue and saturation were marked with ◎, those with relatively good quality were marked with ◯, those with a little inferiority were marked with △, and those with bad hue were marked with ×. Further, a solid image of the sample was measured with a spectrocolorimetric densitometer Xrite 938 (conditions: 2 degree visual field, D50 light source, Status A) manufactured by X-RITE. Five points of the solid image were measured and the average value was calculated.
When the average value of the image density is 1.50 or more, ◎, when it is 1.40 or more and less than 1.50, ◯, when it is 1.30 or more and less than 1.40, Δ, and when it is less than 1.30, ×.
(Light resistance test)
Similarly to the hue evaluation, with a full color copying machine (Imagio Neo C600) manufactured by Ricoh Co., Ltd., adjustment was made so that the amount of adhesion on the high-quality paper for color (type 6000 70W) was 0.4 mg / cm ² , This sample was fixed at 170 ° C with an external fixing machine modified so that the fixing temperature of the full color copier (Imagio Neo C600) manufactured by Ricoh Co., Ltd. could be set freely. Produced. This sample was irradiated for 100 hours under a xenon lamp based on the standard of JIS 5600-7-7, and the color difference before and after the irradiation was measured by a spectrophotometric densitometer Xrite 938 (conditions: 2 field of view, D50 light source, The color was measured by L * a * b * in Status A) and calculated from the color difference ΔE = (L * + a * + b *) ^1/2 .
In this case, the color difference smaller than 3 was evaluated as ◎: 3 or more and less than 5, ◯, 5 or less but less than Δ, and 8 or more as x.

In the toners of Examples 1 to 6, since a color material having good color reproducibility is selected, the hue is good and the coloring power is high. In addition, C.I. I. Pigment Red 81 (Pigment Red 81) has a stable chargeability because it is supplemented by the negative chargeability of the salicylic acid compound (zinc salicylate), and it reduces ground fogging and image density due to charge reduction during long-term running. There is no.
For the toners of Examples 7 to 14, since an optimal pigment dispersant was selected and used, a toner having higher pigment dispersibility and good hue was obtained. The toner of Example 15 is C.I. I. Since the ratio of Pigment Red 122 (Pigment Red 122) is high, the coloring power is slightly lacking, but it is a level with no problem in actual use. In Example 16, since the ratio of Pigment Red 81 was high, the chargeability was slightly low, and the result of light resistance was poor, but it was a level that was not problematic in practical use. In Example 17, since a styrene acrylic copolymer resin was used as the binder resin, the negative chargeability was low, and the color reproducibility by the hue evaluation was slightly deteriorated, but it was at a level causing no problem in practical use. In Example 18, since the melting point of the pigment dispersant was higher than the melting point of the resin, a great effect by the pigment dispersant was not obtained. In Example 19, since the melting point of the pigment dispersant was high, the effect of the pigment dispersant was not obtained as in Example 18. In Example 20, since the melting point of the pigment dispersant was low, the hue was improved by improving the dispersibility. However, although the influence was high under high temperature and high humidity, ground fog and the like were generated, but the level was not problematic in practical use. In Examples 21 and 23, since the addition amount of the pigment dispersant was low and the acid value was low, a great effect of improving the hue by improving the dispersibility could not be obtained. On the other hand, in Examples 22 and 24, the dispersibility of the pigment was improved and a good hue was obtained, but the charge was lowered due to long-term running, and ground fogging occurred, but it was at a level causing no problem in practical use.
On the other hand, the toners of Comparative Examples 1 and 2 have a low charge control agent addition ratio with respect to the decrease in negative charge amount due to the addition of Pigment Red 81, so the effect of supplementing the charge is low, the negative chargeability is reduced, and the long-term Ground fog occurred during running. Further, the toners of Comparative Examples 3 and 4 had a high negative chargeability and a low image density because the addition ratio of the charge control agent was high with respect to the addition amount of Pigment Red 81. In Comparative Example 5, since potassium benzylate was used as the charge control agent, the effect of supplementing the negative chargeability was low, and ground fog occurred during long-term running. Since Comparative Examples 6 and 7 did not use Pigment Red 81 or Pigment Red 122 as the color material, it was not possible to obtain a magenta toner having a high hue.

  As can be seen from the above evaluation results, the magenta toner for electrophotography obtained by the production method of the present invention has good color reproducibility, strong light resistance and coloring power, and is free from ground fog due to a decrease in charge amount even in long-term running. There is no occurrence and stable and high-quality image formation is possible.

Claims (14)

In an electrophotographic magenta toner containing at least a binder resin, a magenta color material, and a charge control agent,
The magenta color material is C.I. I. Pigment red 122, C.I. I. Pigment Red 81 mixed color material, the charge control agent is a salicylic acid metal salt,
C. above. I. A magenta toner for electrophotography, wherein a weight ratio (R / C) of an addition amount (R) of Pigment Red 81 and an addition amount (C) of the charge control agent is 1.1 to 2.0.   The magenta toner for electrophotography according to claim 1, wherein the metal salt of salicylic acid is zinc salicylate.   C. above. I. Pigment red 122, C.I. I. 3. The magenta toner for electrophotography according to claim 1, wherein the total addition amount of the color material mixed with Pigment Red 81 is 5 to 15 parts by weight with respect to 100 parts by weight of the binder resin. .   C. in the mixed color material. I. Pigment red 122, C.I. I. The magenta toner for electrophotography according to any one of claims 1 to 3, wherein a mixing ratio with Pigment Red 81 is 2: 8 to 8: 2.   The magenta toner for electrophotography according to claim 1, wherein the binder resin is a polyester resin.   6. The electrophotographic magenta toner according to claim 1, further comprising a colorant dispersant in the electrophotographic magenta toner.   The magenta toner for electrophotography according to claim 6, wherein the colorant dispersant is a fatty acid ester.   The magenta toner for electrophotography according to claim 6 or 7, wherein a melting point of the colorant dispersant is lower than a softening point of the binder resin.   The magenta toner for electrophotography according to claim 8, wherein the melting point of the colorant dispersant is 70 ° C to 105 ° C.   The magenta for electrophotography according to any one of claims 6 to 9, wherein the addition amount of the colorant dispersing agent is 0.5 to 5 parts by weight with respect to 100 parts by weight of the binder resin. toner.   11. The electrophotographic magenta toner according to claim 6, wherein the colorant dispersant has an acid value of 5 to 30 mg KOH / g.   12. The electrophotographic magenta toner according to claim 1, further comprising a wax in the electrophotographic magenta toner. A method for producing a magenta toner for electrophotography according to any one of claims 1 to 12,
A mixing step of mixing at least a binder resin, a magenta coloring material, and a raw material containing a charge control agent, and a mixture obtained by the mixing step is melt-kneaded using an open roll type kneader in which the kneading part is an open system. A method for producing a magenta toner for electrophotography, comprising at least a melt-kneading step, wherein the melt-kneaded product obtained in the melt-kneading step is pulverized and classified into a toner.   14. The method for producing an electrophotographic magenta toner according to claim 13, wherein in the mixing step, a master batch prepared by previously melt-kneading a magenta color material and a predetermined amount of a binder resin is used. .