JPH04102863A - Electrophotographic color toner - Google Patents

Abstract

PURPOSE:To obtain images having excellent color reproducibility and good color tones by forming color toner particles to a sharp grain size distribution and to a spherical shape, confining the average grain size to small sizes and within a specific range and incorporating a proper ratio of a quinacridone yellow pigment into the particles. CONSTITUTION:The color toner consists essentially of the substantially spherical resin with which the particles having >=0.8 sphericity occupy >=80 wt.% of the entire part. The quinacridone yellow pigment which has 3 to 8mum average grain size D and with which the particles having the diameter within the 0.5 to 3D range occupy >=70% of the entire part in number average is incorporated at 1 to 25wt.% into the toner. The toner constituted of such particle shape, grain size, grain size distribution, and color material has the sharp grain size distribution and the spherical shape and the surface smoothing characteristic of the toner layer after fixing is improved to improve the neutral tint reproducibility of the images. Further, the toner having the optimum hue and saturation to expand the neutral hue region from red to blue centering at magenta is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention is applicable to electrophotographic copying machines, laser printers,
This invention relates to a toner used in a developer such as the following. More specifically, the present invention relates to process color toners used for forming color images, and particularly relates to toners colored magenta.

(Prior art) In general, electrophotography involves photoconductive materials (often processed into a drum shape) made of inorganic materials such as selenium, amorphous silicon, and zinc oxide, or organic materials such as diazo compounds and dyes. (: photosensitive drum) is first charged in a negative manner,
Next, an electrostatic latent image is formed by irradiating image-modulated light, and developed by attaching powder to the electrostatic latent image using electrostatic force. After transferring the powder to the surface, it is fixed by applying pressure, heating, or other methods. Electrophotography is currently available in copying machines,
Widely used in laser printers, etc.

In electrophotography, a powder that develops an electrostatic latent image on a photosensitive drum and is ultimately transferred to a base material such as paper or film to form an image is called a toner. These toners usually have carrier particles (carrier) such as iron powder or ferrite.
It is used as a so-called developer.

Color toners used to form color images are generally colored in predetermined tones called process colors, that is, toners colored in the three subtractive primary colors of yellow, magenta, and cyan.

In particular, colorants for magenta coloring include nitro, azo, stilbene azo, diphenylmethane, quinoline, methine, thiazole, anthraquinone, isoindolinone, anthrapyrimidine, and flavanthrone. organic dyes or pigments, or inorganic pigments such as manganese violet, cobalt violet, etc., or metal salts of acidic dyes, basic dyes and phosphoric acid,
Lake pigments represented by salts with molybdic acid, tungstic acid, etc. are known.

Conventionally, toners used in electrophotographic developers include:
Particles have been used that are produced by a so-called pulverization method, in which a coloring agent, a charge control agent, a fluidity modifier, a pulverization aid, etc. are added to a thermoplastic resin, the mixture is kneaded, and then pulverized and further classified. Alternatively, in recent years, some studies have been conducted on toners using emulsion polymerization, suspension polymerization, seed polymerization, and the like.

These toners are required to have various physical or chemical properties. Furthermore, in recent years, there has been a tendency for toners to be required to have the quality of copied images, particularly good color image reproducibility.

(Problem to be solved by the invention) Conventional red color toners have poor color image reproducibility,
It is not satisfactory in terms of image retention, safety and hygiene, etc.

Many of the conventionally known inorganic pigments have safety and health problems, and as a practical matter, it is impossible to use toners containing these in general copiers, printers, and the like. Some organic coloring materials also have safety and health problems, and the materials that can actually be used as coloring materials are limited. Even if there are no health and safety issues, there are many that have problems with image retention. That is, many organic coloring materials undergo discoloration and fading due to exposure to ultraviolet rays, and there are few that are particularly satisfactory in terms of color image retention.

The above are problems with coloring materials, but the color image reproducibility of color toners is not determined solely by the coloring materials used.

Regarding color reproducibility as a process color, the hue of toner obtained by coloring with a coloring material is one of the important factors. However, the color reproducibility when a plurality of colors are superimposed cannot be evaluated simply by the hue of the toner. The color mixing mechanism in systems such as electrostatic photography, in which color reproduction is performed as an aggregate of colored particles of a certain size, is not simple additive or subtractive color mixing, but is extremely complex. Subtractive color mixing is mainly performed in areas where toners of different colors overlap, and additive color mixing is performed in areas where toners of different colors or colors generated by overlapping different colors are placed side by side in a plane, depending on the area ratio. Mainly done. The hue of toner is determined by taking into consideration such a complex color reproduction mechanism.

However, in toners obtained by conventional pulverization methods, the average particle size itself is large and the particle size distribution is wide and broad, so additive color mixing according to the area ratio of the parts where different colors are placed side by side is not sufficient. I can't do it. As a result, when an image is actually observed with the naked eye, a problem arises in that a fine color cast occurs and the texture of the image becomes coarse.

In addition, the particle size distribution of the toner particles is wide (and the shape is irregular), which causes problems with the surface properties of the toner layer after fixing. In other words, the image surface and the interface between the overlapping parts of toners of different colors, etc. Due to the poor smoothness of the surface, surface scattering or interfacial scattering of incident light occurs, and therefore sufficient subtractive color mixing cannot be performed.As a result, additive color mixing according to the area ratio becomes dominant in the overall color mixing mechanism. Problems such as the color reproduction range being significantly narrowed due to color mixing have arisen.

In view of this situation, the inventors of the present invention have conducted intensive research to obtain a magenta color toner with excellent color reproducibility, especially as a Colort 6 toner. Incidentally, the inventors have discovered that toner colored with a specific coloring material exhibits extremely excellent color image reproducibility, and the following invention has been achieved.

(Means for Solving the Problems) That is, the present invention provides that, among color toners used to realize color images in an electrophotographic system, particularly yellow color toner, the color toner has sphericity (breadth and short diameter). Particles whose main component is substantially spherical resin, in which particles with a length ratio of 0.8 or more account for 80% by weight or more of the whole, and the average particle size of the particles are 3 to 8 μm, and the average particle size is D
In this case, particles having a diameter in the range of 0.5D to 2D account for 70% or more of the total on a number average, and contain 1 to 25% by weight of a quinacridone magenta pigment. This is a color toner for electrophotography.

In the present invention, the resin that is the main component of the particles is not particularly limited, but includes styrene/acrylic resin,
Epoxy resins, polyester resins, etc. can be used, but in particular, from the viewpoint of adhesion to paper, fixing properties, transparency, etc., it is preferable to use resins whose main component is polyester resin consisting of polyol and polycarboxylic acid. is preferred.

The glass transition point of the resin used in the present invention is preferably 4°C or higher. When the glass transition point is lower than this, there is a tendency to aggregate during handling or storage, which may cause problems in storage stability.

Furthermore, the softening point of the resin used in the present invention is 80 to 150°C.
It is preferable that it is in the range of . Toners in which the softening temperature of the resin is kept lower than this tend to aggregate during handling or storage, and fluidity may deteriorate significantly, especially during long-term storage. If the softening point is higher than this, fixing performance will be impaired. Further, since it is necessary to heat the fixing roll to a high temperature, the material of the fixing roll and the material of the base material to be copied are limited.

In the present invention, 80% by weight of the particles constituting the toner
The sphericity (ratio of short axis to long axis) needs to be 0.8 or more. Further, the average particle size of the particles needs to be in the range of 3 to 8 μm. Furthermore, the particle size distribution is so sharp that, when the average particle size is D, particles with diameters in the range of 0.5D to 2D account for more than 80% of the total number average. There is a need. particle shape,
When the average particle size and particle size distribution are not within the predetermined range, problems occur in color image reproducibility, particularly in intermediate color reproducibility.

In the present invention, particles having a sphericity (ratio of short axis to long axis) of 0.8 or more account for 80% by weight or more of the whole, and whose main component is a substantially spherical resin, and the average particle size of the particles is 3. ~8μ
m, and when the average particle size is D, the number average of particles with a diameter in the range of 0.5D to 2D is 80% of the total.
As a method for obtaining resin particles with a sharp particle size distribution that accounts for more than 0.8 to 2.
An example of a method for manufacturing by polymerizing 0 can be exemplified.

Here, the polyester resin mainly consists of a dicarboxylic acid resin and a glycol component. Examples of the dicarboxylic acid component include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, and 1,5-naphthalic acid, and aromatic oxycarboxylic acids such as p-oxybenzoic acid and p-(hydroxyethoxy)benzoic acid. , aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, fumaric acid, maleic acid,
Examples include unsaturated aliphatic acids such as itaconic acid, hexahydrophthalic acid, and tetrahydrophthalic acid, and alicyclic dicarboxylic acids.

If necessary, a small amount of tri- and tetracarboxylic acids such as trimellitic acid, trimesic acid, and pyromellitic acid may be included.

Glycol components include, for example, ethylene glycol, propylene glycol, 1,3-propanediol, 1,
4-butanediol, 1,5-bentanediol, 1,
6-hexanediol, neohentyl glycol, diethylene glycol, dipropylene glycol, 2,2.
4-trimethyl-1,3-bentanediol, 1,4-
Cyclohexane dimetatool, spiroglycol, 1°4-phenylene glycol, ethylene oxide adduct of 1,4-phenylene glycol, diols such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, ethylene oxide adduct of bisphenol A, and propylene oxide adduct,
Examples include ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol A.

If necessary, a small amount of triol and tetraol such as trimethylolethane, trimethylolpropane, glycerin, and pentanylthritol may be included.

Other examples of polyester polyols include lactone-based polyester polyols obtained by ring-opening polymerization of lactones such as ε-caprolactone.

The ionic groups contained in the polyester resin include anionic groups such as carboxyl groups, sulfonic acid groups, sulfuric acid groups, phosphoric acid groups, or salts thereof, or cationic groups such as primary to tertiary amine groups. and preferably a sulfonic acid metal base.

Examples of the aromatic dicarboxylic acid containing a sulfonic acid metal group that can be copolymerized with polyester include sulboterepthalic acid, 5-
Examples include metal salts of sulfoisophthalic acid, 4-sulfophthalic acid, 4-sulfonaphthalene-2,7dicarboxylic acid, and 5[4-sulfophenoxyfisophthalic acid. Metal salts include Li1Na1Kz Mgt Cai
Examples include salts such as Cus Fe. Particularly preferred is 5-sodium sulfoisophthalic acid.

The amount of the aromatic dicarboxylic acid containing a sulfonic acid metal group is not limited as long as the aqueous dispersion can be obtained.
Appropriately, the range is approximately 20 to 5 oo equivalents/1,000,000 g.

In the present invention, the polyester resins can be used alone or in combination of two or more if necessary.

Further, it can be mixed with amino resins, epoxy resin isocyanate compounds, etc. in a molten state or a solution state, and furthermore, it can be partially reacted with these compounds. The obtained partial reaction product can also be used as a raw material for an aqueous dispersion.

The aqueous dispersion containing the ionic group-containing polyester resin of the present invention as a main component can be produced by any known method. That is, a polyester resin and a water-soluble organic compound are mixed in advance at 50 to 200°C and water is added to this, or a mixture of a polyester resin and a water-soluble organic compound is added to water and stirred at 40 to 120°C. Manufactured by Alternatively, by adding polyester resin to a mixed solution of water and a water-soluble organic compound,
It is also produced according to Table 9, a method of stirring and dispersing at 00'C.

In the present invention, the "vinyl monomer containing a counterionic group" refers to an ionic group opposite to the ionic group contained in the polyester resin (a counterion when the ionic group contained in the polyester resin is an anionic group). The cationic group means a vinyl monomer having a cationic group, and when the ionic group contained in the polyester resin is a cationic group, the counterionic group is an anionic group. Such ionic groups are essential for forming a stable aqueous dispersion of polyester resin.

The amount of counterionic groups in the polymer obtained by polymerizing vinyl polymerizable monomers is 0.8 to 2 in equivalent ratio to the amount of ionic groups in the polyester resin.
．． 0, preferably in the range of 0.85 to 1.5. When the lower limit of this range is not reached, coalescence and growth of the fine particles are difficult to occur, and even when the upper limit is exceeded, it not only does not contribute to the growth of the fine particles, but also may cause problems such as a decrease in the water resistance of the resin particles.

As the cationic group-containing vinyl monomer, for example, 2
-aminoethyl (meth)acrylate, 2-N,N-dimethylaminoethyl (meth)acrylate, 2-N,N
-diethylaminoethyl (meth)acrylate, 2-N
, N-dipropylamino (meth)acrylate, 2-N
, t-butylaminoethyl (meth)acrylate, 2-
(4-morpholino)-ethyl (meth)acrylate, 2
-Vinylpyridine, 4-vinylpyridine, aminoethylene pyridine.

In addition, examples of anionic group-containing vinyl monomers include (meth)acrylic acid, itaconic acid, furotic acid, maleic acid,
Monomers containing carboxyl groups or their salts such as fumaric acid, styrenesulfonic acid, vinyltoluenesulfonic acid, vinylethylbenzenesulfonic acid, isopropenylbenzenesulfonic acid, 2-chlorostyrenesulfonic acid, 2-methyl-4-chlorostyrene Sulfonic acid groups, such as sulfonic acid, vinyloxybenzenesulfonic acid, vinylsulfonic acid, (meth)allylsulfonic acid, sulfoethyl or sulfopropyl ester of (meth)acrylic acid, 2-acrylamido-2-methylpropanesulfonic acid, or Monomers containing its salts, phosphorus such as azidophosphoxyethyl (meth)acrylate, azidophosphoxypropyl (meth)acrylate 3-chloro-2-azidophosphoxypropyl methacrylate, bis(meth)acryloxyethyl phosphate, vinyl phosphate, etc. Examples include monomers containing acid groups or salts thereof.

In order to achieve the object of the present invention, a combination of a cationic group-containing vinyl monomer and an anionic group-containing polymer is more desirable. In addition, there is no problem in appropriately using known nonionic monomers.

There are no particular restrictions on the polymerization initiator used when polymerizing vinyl monomers, and examples include organic peroxides such as benzoyl peroxide and acetyl peroxide, 2,2'-azobisisobutyronitrile, 2,2'- Azo compounds such as azobis(2,4-dimethylvaleronitrile), persulfates, hydrogen peroxide,
Inorganic peroxides such as permanganates, water-soluble redox systems of the inorganic peroxides and reducing agents such as sulfites, bisulfites, metasulfites, hydrosulfites, thiosulfates, iron salts, oxalic acid, etc. Examples include initiators, but water-soluble redox initiators are preferred from safety and industrial viewpoints. The amount of polymerization initiator used is approximately 0.1 to 0.1 to vinyl monomer.
It is within the range of 3% by weight.

Although it is difficult to define the polymerization temperature unambiguously, it is possible to
In order to coalesce and grow into a spherical shape as the vinyl monomer polymerizes, it is desirable to adopt a temperature condition higher than the glass transition point (Tg) of the polyester resin; conditions below this temperature tend to produce amorphous particles. By using a solvent or a plasticizer for the polyester resin, the apparent glass transition point (or minimum film-forming temperature) of the polyester resin can be lowered, and polymerization can be carried out at a temperature higher than this temperature. The types of solvents and plasticizers are not limited, and are appropriately selected from known ones depending on the type of polyester resin, as long as they do not inhibit polymerization.

Other polymerization conditions are carried out according to conventional methods, but the method of charging the vinyl monomer in advance into an aqueous dispersion of polyester resin fine particles, and then dropping the polymerization initiator dropwise causes rapid coalescence and aggregation of the polyester resin fine particles. This is preferable because there is no problem.

The obtained aqueous dispersion of polyester resin particles is filtered,
It is extracted as a dry powder using conventional methods such as freeze drying and spray drying.

Thus, particles with a sphericity of 0.8 or more, which are the main components of the color toner for electrophotography in the present invention, are present in at least 80% of the total, and have an average particle size of 3 to 8 μm. It is possible to industrially produce polyester resin particles having a sharp distribution in which particles having a diameter in the range of 0.5D to 2D account for 70% or more of the total number on average.

Another essential requirement in the present invention is to contain 1 to 25% by weight of a quinacridone magenta pigment. Specific examples of the quinacridone pigment include C,1, Pigment Violet 19, C,1, Pigment Violet 30, and C,1, Pigment Red 122.

Among these, C,1, Pigment Red 122 is preferred from the viewpoint of color reproducibility.

The method for dispersing the present pigment into the main particles of the toner is not particularly limited, but preferably, the pigment is kneaded into the resin in advance before obtaining the aqueous dispersion for producing the resin particles described above. Examples include a method in which the pigment is placed in an aqueous dispersion, or a method in which the pigment is allowed to coexist as an aqueous dispersion when the fine particles coalesce and grow, thereby being incorporated into the particles at the same time as the fine particles coalesce.

In the present invention, there is no restriction on the supplementary use of known existing coloring agents such as pigments or dyes for adjusting the hue. From the viewpoint of spectral transmission characteristics, it is preferable to use a dye, and the hue may be adjusted using a disperse dye, a basic dye, a cationic dye, a dispersed cationic dye, or the like.

In the electrophotographic toner of the present invention, a charge control agent may be used to provide stable charge. Charge control agents that positively charge the toner through friction with carrier particles include, for example, titanates such as N Ca1Ba, carbonates, alkoxylated amines, polyamide resins such as nylon, phthalocyanine blue, quinacridone red, and azo. Pigments with positive zeta potential such as metal complex green, azine compounds, stearic acid-modified azine compounds, oleic acid-modified azine compounds, azine pigments such as nigrosine, quaternary ammonium salt compounds, etc. .

Examples of the charge control agent that imparts a negative charge to the toner through friction with carrier particles (carrier) include pigments with a negative zeta potential such as carbon black, halogenated phthalocyanine green, flavanstone yellow, and perylene red, copper, Examples include metal-containing azo compounds such as zinc, lead, and iron.

In the toner of the present invention, a fluidity modifier such as fine alumina particles or fine silica particles may be added.

The amount added is not particularly limited, but from the viewpoint of imparting appropriate fluidity, it is preferably 0.00 to the toner.
The amount is about 0.01 to 5% by weight, more preferably about 0.1 to 2% by weight.

The method of treating particles with the colorant, charge control agent, fluidity modifier, etc. described above is not particularly limited, and any known existing treatment method can be used. For example, these may be dispersed in the particles, adsorbed onto the particles, or coated on the particles.

As mentioned above, the color mixing mechanism in systems such as electrophotography, where color reproduction is performed as an aggregate of colored particles with a certain size, is mainly due to subtractive color mixing in areas where toners of different colors overlap. In areas where toners of different colors or colors generated by overlapping different colors are juxtaposed on a plane, additive color mixing is mainly performed in accordance with the area ratio.

The color toner of the present invention has a small average particle size and, above all, a sharp particle size distribution, so it has excellent additive color mixing properties according to the area ratio of the parts where different colors are juxtaposed, and the image can be seen with the naked eye. When observed, the "texture of the image" becomes extremely fine.

Further, since the toner particles have a sharp particle size distribution and are spherical, the surface smoothness of the toner layer after fixing is good. As a result, light scattering on the image surface and at interfaces where toners of different colors overlap is reduced.
Subtractive color mixing is performed almost ideally in areas where different colors overlap. These have a very favorable influence on intermediate color reproducibility, especially in high-density areas of an image.

In addition, because the particle size distribution of toner particles is sharp, low-frequency noise components can be suppressed to a low level when images are evaluated in the spatial frequency domain. Image reproduction is performed.

Furthermore, from a practical standpoint, the quinacridone-based magenta pigment used in the present invention is optimal for maximally expanding the intermediate hue range from red centered on magenta to blue in the color mixing mechanism unique to electrophotography described above. It has a beautiful hue and saturation.

(Example) The present invention will be explained in more detail by referring to Examples below, but the present invention is not limited to these in any way. In addition, the physical properties of the resin in Examples and Comparative Examples were measured by the following method.

Φ melting point, glass transition point A heating rate of 1 was measured using a differential scanning calorimeter (manufactured by Shimadzu Corporation).
Measured at 0°C/min.

・Softening point Measured according to JIS K2351.

・Number average molecular weight (vapor pressure method) It was measured using a molecular weight measuring device (newly manufactured by Hitachi Seisakusho).

・Electrical charge amount Measured using an E-Spart Analyzer (manufactured by Micron for wire use), and converted to the amount of charge per surface area assuming that the particles are true spheres.

Example 1 In an autoclave equipped with a thermometer and a stirrer, 94 parts by weight of dimethyl terephthalate, 95 parts by weight of dimethyl isophthalate, 89 parts by weight of ethylene glycol, 80 parts by weight of neopentyl glycol, and 0.1 parts by weight of tetrabutoxy titanate. Preparing the parts 1
The transesterification reaction was carried out by heating at 20-230'C for 120 minutes. Next, 6.7 parts by weight of 5-sodium sulfoisophthalic acid was added, and the reaction was continued at 220 to 230°C for 60 minutes. After the temperature was further raised to 250'C, the system pressure was reduced to 1 to 10 m
As a result of continuing the reaction at mHg for 60 minutes, a copolymerized polyester resin (A1) was obtained.

The molecular weight of the obtained copolymerized polyester resin (A1) is 2
7001 sulfonic acid metal base is 118 equivalents/1000
It was 000g. The amount of sulfonic acid metal base was determined by measuring the sulfur concentration in the copolyester resin. In addition, the composition of the copolymerized polyester resin (A1) was determined by NMR analysis to be as follows: terephthalic acid 48.5M0L%, isophthalic acid 49.0M0L%, 5-sodium sulfoisophthalic acid 2.5M0L%, alcohol component as an acid component. Ethylene glycol was 61.0M0L%, and neopentyl glycol was 39.0M0L%.

C and I as magenta organic pigments were added to 100 parts by weight of the obtained copolyester resin (AI).

Pigment Red 122 was blended in an amount of 12 parts by weight, premixed in a ball mill, and then melt-mixed in a roll mill to obtain a colored copolymerized polyester resin (AIM).

After dissolving 34 parts by weight of the obtained colored copolymerized polyester resin (AIM) and 10 parts by weight of butyl cellosolve at 110°C in a four-necked 1-liter separable flask equipped with a thermometer, condenser, and stirring blade. , 56 parts by weight of water at 80°C was added to obtain a colored copolymerized polyester aqueous dispersion (BIM).

In a four-necked 1-liter separable flask equipped with a thermometer, condenser, and stirring blade, 834 parts by weight of aqueous copolyester dispersion (BIM), 35 parts by weight of deionized water, and 5.6 parts by weight of dimethylaminoethyl methacrylate.
parts by weight were added, and the temperature was raised to 70°C. Next, 100 parts by weight of an aqueous solution containing 0.2 parts by weight of ammonium persulfate was added dropwise over 30 minutes, and the reaction was continued at 70°C for an additional 20 minutes. As a result, the copolymer with a submicron-order particle size that existed in the aqueous copolyester dispersion grew to an average particle size of 5°2 μm1 and a sphericity of 0.
．． A colored polyester particle dispersion (CIM) in which 91% by weight of the total particles are 8 or more, and 92% of the occupancy (number) of particles having a particle size in the range of 26 from 0.5D to 2D, where D is the diameter. I got it.

The obtained colored polyester particle dispersion (CIM) was cooled, filtered, washed, and dried with a spray dryer to obtain a magenta toner (TIM).

Similarly, anthraquinone organic pigments C, 1 and Pigment Yellow 108 were used as yellow coloring materials, triphenylmethane organic pigments C, R and Pigment Blue 24 were used as cyan coloring materials, yellow toner (TIY),
Cyan toner (TIG) was obtained.

1 part by weight of each of the obtained colored toners was mixed with 99 parts by weight of a carrier (spherical reduced iron powder with an average particle size of 80 μm),
A component-based electrophotographic developer was obtained.

The charge amount of the toner after mixing with the carrier was (T I Y) −105 μC/g (TIM) −111 μC/g (Tic) −118 μC/g. Using these developers, 5,000 copies were continuously made on paper using an electrophotographic color copying machine using amorphous silicon as a photoreceptor. The resulting copy was free from fog and fading, and showed a clear and good image. The resulting image has a smooth hue change in the intermediate color area, especially from red to blue, and even in areas where low-density images are reproduced, smooth midtone color reproduction with fine texture and no roughness can be achieved. there were.

Using this developer, copies were similarly made onto a transparent film for an Overherad projector. The obtained copy had excellent spectral transmission characteristics, and the image projected onto the screen by the Overherad projector showed a clear color tone without turbidity. When this developer was used, the resolution was 16 lines/frame or more. Further, no particular problems were observed in the humidity dependence of charging properties, flow properties, insulation properties, etc., as well as fixing properties, sharp melt properties, anti-offset properties, etc.

Comparative Example 1 Copolymerized polyester resin (Al
) and 10 parts by weight of the yellow pigment, magenta pigment, and cyan pigment used in Example 1, respectively, were premixed in a ball mill, melted and mixed in a roll mill, and ground and separated in a fine grinder. Colored toners (T2Y) (T2M) (T2C) having an average particle diameter of 5.8 μm were obtained. In the obtained toner, particles having a particle size of 0.5D or less accounted for 20% on average, and particles having a particle size of 2D or more accounted for 15% on average.

5 parts by weight of each of the obtained colored toners were mixed with 95 parts by weight of carrier (spherical reduced iron powder with an average particle size of 80 μm) in the same manner as in the example to obtain a two-component electrophotographic developer. The charge amount of the toner after mixing with the carrier was (T 3 Y) −72 μC/g (T3M) −81 μC/g (T2C) −64 μC/g. As in Example 1, using these developers, 5,000 copies were continuously made on paper using an electrophotographic color copying machine using amorphous silicon as a photoreceptor. The resulting copy had many scratches in the fine line areas, and a good image could not be obtained. The resolution was about 10 lines/frame.

(Effects of the Invention) As described above, the color toner according to the present invention has
Excellent in humidity dependence such as charging characteristics, flow characteristics, and insulation properties, as well as fixing properties, sharp melt properties, offset resistance, etc., and has particularly excellent image sharpness, as well as excellent color reproducibility when converting to color. This provides images with good color tone.

Claims (1)

[Claims] (1) Among the color toners used to realize color images in electrophotography, especially magenta color toner, the color toner has particles with sphericity (ratio of short axis to long axis) of 0.8 or more. These are essentially spherical resin-based particles that account for 80% or more of the total weight, and the average particle size of the particles is 3 to 8 μm, and when the average particle size is D, the diameter is 0.5D to 2D. 1. A color toner for electrophotography, characterized in that particles having a particle size falling within the range of 70% or more of the total on a number average basis, and containing 1 to 25% by weight of a quinacridone magenta pigment.