JP2001022118A - Electrophotographic color toner, its production and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of voids in a solid image, surface stain and filming. SOLUTION: At least silica and titania as two inorganic oxides are added as additives to a matrix toner consisting essentially of a bonding resin and a coorant to obtain the objective electrophotographic color toner having 4.0-9.0 μm weight average diameter. The liberation rate of silica in the color toner is 0.5-8%, that of titania is 0.5-5% and image density D0.6 after fixation in 0.60 mg/cm2 coating weight of the toner on a transfer material is 1.2-2.0. When the matrix toner is mixed with the additives, the peripheral speed of agitating blades is 15-35 m/sec and mixing time for each of silica and titania is >=50 sec.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color toner which is applied to an electrophotographic method, an electrostatic recording method, an electrostatic printing method and the like, and has little occurrence of white spots, background stains and filming. The present invention relates to a method for producing the toner and an image forming method using the toner.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat.
27691, JP-B-42-23910 and JP-B-43-24748 describe various methods. These methods generally utilize a photoconductive material to form an electrical latent image on the photoconductive support by various means and then develop the latent image with toner to obtain a visible image. Alternatively, if necessary, a powder image is transferred onto paper or the like, and then fixed by heating, pressing, or solvent vapor to obtain a visible image.

A full-color electrophotographic method for obtaining a color multicolor image is disclosed in US Pat. No. 2,962,374.
As described in the above publication, at least an image is decomposed into three color signals of yellow, magenta, and cyan and exposed, and the above-mentioned steps are performed at least using a process color toner of at least yellow, magenta, and cyan. The toner image is developed repeatedly, and the toner images are superimposed to obtain a multicolor image of color.

In recent years, hard copy technology using an electrophotographic method has been rapidly developed from black and white to full color, and demands for higher image quality, higher reproducibility, and higher stability have been increasing. ing. In response to these requirements, it is often practiced to improve the image quality by reducing the particle size of the toner. Although reducing the particle size of the toner is effective for improving the image quality, it increases the charge amount per unit weight, thereby deteriorating the developability, lowering the image density and deteriorating the durability. Tends to occur.

Further, since the non-electrostatic adhesion of the toner is increased, the amount of the toner non-electrostatically adhering to a non-image portion such as a photosensitive member or an intermediate transfer member is increased, which causes an increase in background smear. ing. Further, as the non-electrostatic adhesive force increases, the cohesiveness of the toner also increases, thereby lowering the fluidity. In addition, when the coagulated toner is present on the photoreceptor or the intermediate transfer member in the development of a solid portion, Is difficult to transfer around the agglomerated toner, causing transfer unevenness and white spots. In particular, in the case of color toner, the image area of a document used for copying is generally larger than that of a conventional toner, and the document also has a large number of solid images such as photographs, catalogs, maps, and paintings. Therefore, transfer unevenness and white spots greatly deteriorate image quality.

Further, the smaller the particle size of the toner, the harder it is for the additive to adhere thereto, and the toner to which the additive does not adhere and the free additive cause soiling, filming of the photoreceptor, and in-machine contamination. Furthermore, as the toner particle size becomes smaller, the specific surface area of the toner increases, so the amount of the additive must be increased. However, this also increases the amount of free additive, which causes filming on the photoreceptor and contamination in the machine. Cause.

Here, additives used in the toner include:
For the purpose of imparting fluidity and heat-resistant storage stability, inorganic oxides such as silica and titania are often used. But,
The loose additive that has weak adhesion to the base toner or does not adhere to the toner easily develops on the photoconductor together with the toner when the electric latent image formed on the photoconductor is developed by the toner. Often remains on the photoreceptor even after it has been transferred from the photoreceptor to a transfer material such as paper, and adheres to the photoreceptor without being cleaned. When these additives accumulate on the photoreceptor, filming occurs on the photoreceptor, causing image defects and a decrease in image density of the toner image transferred to the transfer material, resulting in poor durability. In addition, the surface of the photoreceptor may be damaged, thereby shortening the life of the photoreceptor. Further, when the electric latent image on the photoreceptor is developed with toner, there is a problem that these additives spill out of the developing device and contaminate the inside of the copying machine. Further, a toner having a weak adhesive force of such an additive is
When a stress is applied in the developing device, a change in the adhesion state from the initial state is large, and when the toner is added in the developing device, the charge level is different from that of the additional toner.

On the other hand, if the adhesion to the base toner is too strong, the additive is embedded in the toner, the proportion of fine particles that can function effectively decreases, and the fluidity also decreases. Therefore, in order to obtain desired toner characteristics, the amount of addition must be further increased.
Alternatively, since the amount of the unattached free additive increases, the ratio of migration to the photoconductor and adhesion thereof increases, and image defects may occur.

In order to solve the above problems, it is conceivable to increase the molecular weight of the binder resin so that the additive is not embedded. However, in general, the color toner is different from the black toner for black-and-white printing when the fixing is heated.
It is necessary to increase the heat melting property, lower the viscosity, and obtain gloss and transparency.However, even if the resin having a high molecular weight has a high softening temperature and a high fixing temperature, the viscosity does not decrease, and the viscosity is sufficient. Gloss or transparency cannot be obtained.

Incidentally, toners using additives are disclosed in, for example, Japanese Patent Publication No. 2-27664,
JP-A-2-129866, JP-A-2-43564, JP-A-8-194335 and JP-A-9-14
No. 6293 describes a toner to which silica and titania are added and adhered. However, Tokuhei 2
Japanese Patent Application Publication No. 27664/1987 and Japanese Patent Application Laid-Open No. 62-129866 do not describe at all how much these additives adhere to the base toner, and these toners have improved charge stability and fluidity. It is intended to prevent white spots, background stains, filming, and the like from being disclosed.

Further, Japanese Patent Application Laid-Open Nos. 2-43564, 8-194335 and 9-146293 have been disclosed.
The toner described in Japanese Patent Application Laid-Open No. 2-43304 uses fine particles having different sizes as these additives.
Japanese Patent Application Publication No. 564-564 does not disclose to what extent these additives adhere to the base toner, and the toner is intended to prevent fogging.
The toners described in 194335 and JP-A-8-146293 have a high ratio of free additives and cannot sufficiently prevent white spots, background stains, filming, and the like.

For the reasons described above, satisfactory color toners for electrophotography have been obtained which are less likely to cause white spots, background stains, filming, etc. in solid images, which are particularly remarkable in toners having a small particle size. There is no present.

[0013]

SUMMARY OF THE INVENTION It is a first object of the present invention to provide an electrophotographic color toner in which the occurrence of white spots (so-called fireflies) in a solid image, which is particularly conspicuous in a toner having a small particle size, is small. It is to provide a manufacturing method and an image forming method. A second object of the present invention is to provide a color toner for electrophotography with less occurrence of background stain and filming, and a method for producing the toner and an image forming method. A third object of the present invention is to provide a color toner for electrophotography having an appropriate glossiness and little transfer dust and toner scattering, and a method for producing the toner and an image forming method.

[0014]

According to the present invention, a weight average particle diameter is obtained by adding at least two kinds of inorganic oxides composed of silica and titania as additives to a base toner composed of at least a binder resin and a colorant. Is 4.0 to 9.0 μm, the image density D _0.6 after fixing is 1.2 to 2.0 when the amount of toner adhered on the transfer material is 0.60 mg / cm ² . And a release ratio of silica of 0.5 to 8% and a release ratio of titania of 0.5 to 5%. Further, according to the present invention, the peripheral speed of the stirring blade at the time of mixing the base toner and the additive is 15 to 35 m / sec. And the mixing time of at least 50 sec. For either silica or titania added as an additive. A method for producing the above electrophotographic color toner is provided. Further, according to the present invention, an electrostatic latent image corresponding to the recorded image is formed on the latent image carrier, and the formed electrostatic latent image is developed using toner to form a toner image on the latent image carrier. An image forming method for forming and transferring a formed toner image onto a transfer material via an intermediate transfer member to obtain a recorded image, wherein the color toner for electrophotography is used as the toner. A method is provided.

That is, the color toner for electrophotography of the present invention is obtained by adding at least two kinds of inorganic oxides composed of silica and titania as additives to a base toner composed of at least a binder resin and a colorant. Average diameter is 4.0
The image density D _0.6 after fixing is 1.2 to 2.0 when the toner adhesion amount on the transfer material is 0.60 mg / cm ² , and the release rate of silica is 0.1 to 9.0 μm. 5
-8%, and a titania release rate of 0.5-5%.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The electrophotographic color toner of the present invention has a weight average diameter of 4.0 to 9.0 μm, preferably 5.0.
８8.0 μm. If the average diameter is smaller than 4.0 μm, the developability will be reduced and the durability will not be sufficiently obtained. On the other hand, if it is larger than 9.0 μm, the reproducibility of the dots deteriorates because the gradation is remarkably reduced. The weight average diameter of the electrophotographic color toner of the present invention can be measured by, for example, a Coulter Multisizer.

The image density D _0.6 of the toner of the present invention after fixing when the amount of toner adhered on the transfer material is 0.60 mg / cm ² is 1.2 to 2.0. When _D0.6 is lower than 1.2, the coloring power of the toner is low, and the image density of the solid portion is reduced. If the amount of toner adhered to the transfer material is increased to solve this problem, the amount of toner consumption increases, so it is necessary to frequently supply the toner to the developing device. It is difficult to perform uniform agitation, soiling is likely to occur, and when a solid image is output, unevenness is likely to occur on the image, making it difficult to obtain a uniform solid image.
Further, when the amount of toner adhered is increased, toner dust tends to occur in a thin line portion called a transfer dust, particularly when two or more colors of toner are overlapped and developed like a thin line portion of a color image. , The trend becomes more pronounced. When D _0.6 is higher than 2.0, a minute electrostatic latent image on the photoreceptor must be developed with a very small amount of toner, especially when reproducing a halftone portion.
Roughness in the halftone portion tends to be conspicuous, and in addition, background dirt tends to be conspicuous.

Here, the image density D _{0.6 corresponds} to 1 on the transfer material.
This is the image density measured after forming a solid image to which 0.60 ± 0.05 mg of toner is attached per cm ² and fixing the solid image so that the glossiness of the solid image after fixing becomes 10% or more. . Here, the glossiness was measured at an incident angle of 60 ° using a gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. The image density was measured using, for example, a measuring instrument such as X-Rite 938.

It is necessary that the color toner for electrophotography of the present invention further comprises at least two kinds of inorganic oxides composed of silica and titania. By using two kinds of inorganic oxides composed of silica and titania, appropriate fluidity can be obtained, and under high temperature and high humidity,
While maintaining the charge amount of toner required for development, uniformity of charge on the surface of toner particles, speed of charge exchange between toner particles is improved, charging speed is improved, and charge distribution can be sharpened. As a result, the environmental dependency of the charge amount of the toner composition can be significantly improved. In addition, silica and titania need to have a release rate of silica of 0.5 to 8% and a release rate of titania of 0.5 to 5%.

If the release rate of silica is 8% or the release rate of titania is higher than 5%, the released silica or titania adheres to the photoreceptor, the developing roller, the carrier, etc. This is likely to cause development troubles such as filming, and also tends to cause background contamination and a decrease in developability due to poor charging of the developer. On the other hand, if the release ratio of silica and titania is lower than 0.5%, sufficient fluidity cannot be obtained because the additive strongly adheres to the base toner and is embedded in the surface of the base toner. As in the case of the toner of the present invention, when the liberation rate of silica is in the range of 0.5 to 8% and the liberation rate of titania is in the range of 0.5 to 5%, filming of the photoreceptor or the developing roller and film formation on the carrier are performed. Contamination due to adhesion is unlikely to occur.

Here, the liberation rate of silica and titania was measured using the following formula using PT1000 manufactured by Yokogawa Electric Corporation.

(Equation 1)

(Equation 2)

The measurement conditions at this time are shown below. Analysis wavelength: Si element: 288.160 nm Ti element: 334.900 nm C element: 247.860 nm Spectroscope used: Si element: No. 1 or No. 2 (blaze wavelength: 25
0 nm) Ti element: No. 1 or No. 2 (blaze wavelength: 25
0 nm) C element: No. 3 or No. 4 (blaze wavelength: 400
nm) Measurement gas: O ₂ 0.1% He gas Number of C element detected in one scan: 500 to 1500 Noise cut level: 1.5 or less Sort time: 20 digits Here, the main component of C element is mother toner. Also, when using silica and titania surface-treated with a silane coupling agent or the like as an additive, the substantial addition amount is at most about several parts by weight, and the detection amount of the C element by the silane coupling agent is Since it is almost insignificant as compared with the base toner, the liberation rate of silica and titania used as an additive can be determined from the above equation.

In the present invention, the total amount of the two inorganic oxides of silica and titania is preferably 1.2 to 2.0 parts by weight, particularly preferably 100 parts by weight of the base toner. , 1.4 to 1.8 parts by weight. When the addition amount is less than 1.2 parts by weight, the fluidity and charge amount of the toner are not sufficient, and when a solid image is output, unevenness is likely to be generated on the image, and it is difficult to obtain a uniform solid image. . When the amount is more than 2.0 parts by weight, although the fluidity is improved, poor cleaning of the photoreceptor such as chattering and turning up of the blade and filming on the photoreceptor due to an additive released from the toner are liable to occur. And the durability of the photoreceptor decreases. Furthermore, toner dust tends to occur in a thin line portion called a transfer dust, and this tendency becomes more remarkable particularly when two or more colors of toner are developed in a superposed manner as in a color thin line.

Here, the addition amounts of silica and titania can be measured by various methods, but are generally determined by X-ray fluorescence analysis. That is, a calibration curve is created by a fluorescent X-ray analysis method for a toner having a known addition amount of silica or titania, and the addition amount of silica or titania is determined using the calibration curve.

Further, the electrophotographic color toner of the present invention comprises:
It is preferable that the added amount of titania is larger than the added amount of silica. This is because when the particle size of the toner is reduced, the surface area per unit weight increases, and excessive charging due to rubbing is liable to occur. On the other hand, if the added amount of silica is larger than the added amount of titania, the charge imparting ability of silica itself is also high,
The charge increases further, but titania is added,
By setting the added amount of titania to be larger than the added amount of silica, it is possible to control the charging to an appropriate level, and it is possible to suppress the dependence of charging on the environment.

Further, the silica and titania used in the present invention are preferably subjected to a surface treatment with a hydrophobizing agent or the like. This surface treatment makes it possible to impart sufficient fluidity to the toner. Here, typical examples of the hydrophobizing agent include the following.

Dimethyldichlorosilane, trimethylchlorosilane, methyltrichlorosilane, allyldimethyldichlorosilane, allylphenyldichlorosilane, benzyldimethylchlorosilane, bromomethyldimethylchlorosilane, α-chloroethyltrichlorosilane, p-chloroethyl Trichlorosilane, chloromethyldimethylchlorosilane, chloromethyltrichlorosilane, p-chlorophenyltrichlorosilane, 3-chloropropyltrichlorosilane, 3-chloropropyltrimethoxysilane,
Vinyltriethoxysilane, vinylmethoxysilane, vinyltris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, vinyltriacetoxysilane, divinyldichlorosilane, dimethylvinylchlorosilane, octyltrichlorosilane, decyltrichlorosilane, Nonyltrichlorosilane, (4-
(t-propylphenyl) trichlorosilane, (4-t-
Butylphenyl) trichlorosilane, diventyldichlorosilane, dihexyldichlorosilane, dioctyldichlorosilane, dinonyldichlorosilane, didecyldichlorosilane, didodecyldichlorosilane, dihexadecyldichlorosilane, (4- (t-butylphenyl) octyldichlorosilane, dioctyldichlorosilane, didecenyldichlorosilane, dinonenyldichlorosilane, di-2
-Ethylhexyldichlorosilane, di-3,3-dimethylbenzyldichlorosilane, trihexylchlorosilane, trioctylchlorosilane, tridecylchlorosilane, dioctylmethylchlorosilane, octyldimethylchlorosilane, (4-t-propylphenyl ) Diethylchlorosilane, isobutyltrimethoxysilane, methyltrimethoxysilane, octyltrimethoxysilane, trimethoxy (3,3,3-trifluoropropyl) silane, hexamethyldisilazane, hexaethyldisilazane, diethyltetramethyldisilazane, Hexaphenyldisilazane, hexatolyldisilazane and the like. In addition, titanate-based coupling agents and aluminum-based coupling agents can also be used.

The average primary particle size of the silica used in the present invention is preferably about 0.005 to 0.05 μm, more preferably 0.01 to 0.03 μm. The average primary particle size of titania is 0.005 to 0.2 μm.
m, and more preferably 0.01 to 0.05 μm. Average primary particle size of silica is 0.05μ
m or the average primary particle size of titania is 0.1.
If it is larger than 2 μm, the charge of the toner becomes non-uniform due to poor fluidity, and as a result, background contamination, toner scattering and the like occur. On the other hand, when the average primary particle size of silica or titania is smaller than 0.005 μm, the additive is easily embedded on the surface of the base toner, and the durability is reduced. This tendency is more remarkable when used for a color toner having a sharp melt property.

The toner of the present invention may further contain other additives within a range that does not substantially adversely affect the toner, for example, lubricant powders such as Teflon powder, zinc stearate powder, and polyvinylidene fluoride powder; cerium oxide powder, Silicon carbide powder,
Abrasives such as strontium titanate powder; conductivity-imparting agents such as carbon black powder, zinc oxide powder, tin oxide powder, and the like; and fine particles of white fine particles and black fine particles of opposite polarity may be used in small amounts as a developing property improver. it can.

The binder resin used in the toner of the present invention is:
Although any of those usually used for electrophotographic toner are used, the softening point thereof is preferably 110 to 130 ° C. If the softening point of the binder resin is lower than 110 ° C., offset tends to occur, blocking tends to occur during storage of the toner, and unevenness tends to occur on the image when a solid image is output. It is difficult to obtain a solid image. Conversely, if the temperature is higher than 130 ° C., sufficient gloss and transparency cannot be obtained. The softening point of the binder resin was measured as follows. That is, using an elevated flow tester (CFT-500) (manufactured by Shimadzu Corporation), the diameter of the pores of the die was 1 mm, and the pressure was 20 kg /
The temperature corresponding to 温度 of the height from the outflow start point to the outflow end point when a 1 cm ³ sample was melted and discharged under the conditions of cm ² and a heating rate of 6 ° C./min was defined as the softening point.

The binder resin used in the toner of the present invention is made of a polyester resin, a polyol resin, or a mixture of a polyester resin and a polyol resin, because the resin is excellent in gloss, transparency, and offset resistance. ,
Particularly preferred. When two or more different binder resins are used, these resins need to be compatible with each other during kneading, and if there is an interface between the resins without being compatible with each other, the refraction of light is reduced. It often occurs at the interface and the transparency often deteriorates. Here, the determination of the compatibility state between the binder resins was performed based on an enlarged photograph at a magnification of 100,000 times using a transmission electron microscope.

As the polyester resin used as the binder resin in the present invention, various types can be used, but the following are particularly preferable as the polyester resin used in the present invention. (A) The following general formula (I)

Embedded image (Wherein, R ¹ is an alkylene group having 2 to 4 carbon atoms;
x and y are positive integers, and the average value of the sum is 2 to 16. ) And a component selected from the group consisting of (b) a divalent or higher polycarboxylic acid, an anhydride thereof and a lower alkyl ester thereof.

Examples of the diol represented by the general formula (I) in the above (a) include polyoxypropylene (2,2)-
2,2-bis (4-hydroxyphenyl) propane, polyoxyethylene (2) -2,2-bis (4-hydroxyphenyl) propane, polyoxypropylene (6)-
Examples thereof include 2,2-bis (4-hydroxyphenyl) propane and polyoxypropylene (16) -2,2-bis (4-hydroxyphenyl) propane. It should be noted that a bifunctional or higher polyhydroxy compound as described below may be used as the diol component in an amount of about 5 mol% or less. Ethylene glycol, propylene glycol, glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or etherified polyhydroxyl compounds thereof.

Specific examples of the above (b) include phthalic acid, isophthalic acid, terephthalic acid, maleic acid, fumaric acid and anhydrides thereof, and lower alkyl esters thereof, trimellitic acid or anhydrides thereof. Containing acid, n-dodecenyl succinic acid, n-dodecyl succinic acid,
Succinic acid derivatives such as n-butylsuccinic acid, iso-dodecenylsuccinic acid, iso-octylsuccinic acid and the like can be mentioned.
By introducing these succinic acid derivatives, the fixability of the toner at a low temperature becomes sufficient, and the gloss is further improved.

The above polyester resin is usually prepared by mixing a polyol component and a polycarboxylic acid component in an inert gas atmosphere.
It can be produced by condensation polymerization at a temperature of 80 to 250 ° C.

As the polyol resin, various types can be used, but the following are particularly preferred as the resins used in the present invention. Particularly, as a polyol resin, an epoxy resin, an alkylene oxide adduct of a dihydric phenol or a glycidyl ether thereof, a compound having one active hydrogen that reacts with an epoxy group in a molecule, and an active hydrogen that reacts with an epoxy group in a molecule. It is preferable to use a polyol obtained by reacting a compound having two or more compounds with each other.

Further, the epoxy resin is particularly preferably at least two or more bisphenol A type epoxy resins having different number average molecular weights. This polyol resin gives good gloss and transparency, and is effective in offset resistance. The epoxy resin used in the present invention is preferably one obtained by combining bisphenol such as bisphenol A or bisphenol F with epichlorohydrin. Epoxy resins have at least two different molecular weights to obtain stable fixing characteristics and gloss.
It is preferable that the number average molecular weight of the low molecular weight component is 360 to 2,000 and the number average molecular weight of the high molecular weight component is 3,000 to 10,000 in at least one kind of bisphenol A type epoxy resin. 20-50 wt% low molecular weight component
%, And the high molecular weight component is preferably 5 to 40 wt%. When there are too many low molecular weight components, or when the molecular weight is lower than 360, glossiness may be too high and storage stability may be deteriorated. When the amount of the high molecular weight component is too large, or when the molecular weight is higher than 10,000, the gloss may be insufficient or the fixability may be deteriorated.

As the compound used in the present invention,
Examples of the alkylene oxide adduct of a dihydric phenol include the following. That is, a reaction product of ethylene oxide, propylene oxide, butylene oxide, and a mixture thereof with a bisphenol such as bisphenol A or bisphenol F can be used. The obtained adduct may be glycidylated with epichlorohydrin or β-methylepichlorohydrin before use. In particular, a diglycidyl ether of an alkylene oxide adduct of bisphenol A represented by the following general formula (II) is preferable.

Embedded image (Wherein, R represents —CH ₂ —CH ₂ —, —CH ₂ —CH (C
H ₃ ) — or —CH ₂ —CH ₂ —CH ₂ —, and n and m are the number of repeating units, each being 1 or more, and n + m = 2 to 6. In addition, it is preferable that an alkylene oxide adduct of dihydric phenol or glycidyl ether is contained in an amount of 10 to 40% by weight based on the polyol resin. Here, if the amount is smaller than this, problems such as increase in curl occur, and if n + m is 7 or more, and if the amount is larger than this, gloss becomes too high, and furthermore, the storage stability deteriorates. there is a possibility.

The compound having one active hydrogen which reacts with the epoxy group in the molecule used in the present invention includes 1
There are polyhydric phenols, secondary amines and carboxylic acids.
The following are illustrated as monohydric phenols. That is, phenol, cresol, isopropylphenol, aminophenol, nonylphenol, dodecylphenol, xylenol, p-cumylphenol and the like can be mentioned. Secondary amines include diethylamine, dipropylamine, dibutylamine, N-methyl (ethyl) piperazine, piperidine and the like. Examples of the carboxylic acids include propionic acid and caproic acid.

Examples of the compound having two or more active hydrogens that react with the epoxy group in the molecule used in the present invention include dihydric phenols, polyhydric phenols, and polycarboxylic acids. Examples of the dihydric phenol include bisphenols such as bisphenol A and bisphenol F. As polyhydric phenols, ortho-cresol novolaks, phenol novolaks,
Tris (4-hydroxyphenyl) methane, 1- [α-
Methyl-α- (4-hydroxyphenyl) ethyl] benzene is exemplified. Polycarboxylic acids include malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid,
Fumaric acid, phthalic acid, terephthalic acid, trimellitic acid,
An example is trimellitic anhydride.

In order to obtain a polyol resin having an epoxy resin part and an alkylene oxide part in the main chain of the present invention, various combinations of raw materials are possible. For example,
It can be obtained by reacting an epoxy resin having a glycidyl group at both ends and an alkylene oxide adduct of a dihydric phenol having a glycidyl group at both ends with dihalide, diisocyanate, diamine, dithiol, polyhydric phenol, or dicarboxylic acid. Of these, the reaction with dihydric phenol is most preferable in terms of reaction stability. It is also preferable to use a polyhydric phenol or a polycarboxylic acid together with a dihydric phenol within a range not causing gelation. Here, the amount of the polyhydric phenols and polycarboxylic acids is 15% or less, preferably 10% or less based on the total amount.

When these polyester resins and polyol resins have a high crosslinking density, it is difficult to obtain transparency and glossiness. Preferably, they are non-crosslinked or weakly crosslinked (THF insoluble content is 5% or less). Is preferred.

As the binder resin, the following resins can be used, if necessary, in addition to the binder resin having the characteristics of the present invention. Polystyrene, poly-p-chlorostyrene, homopolymers of styrene such as polyvinyltoluene and substituted products thereof; styrene-p-chlorostyrene copolymer,
Styrene-propylene copolymer, styrene-vinyltoluene copolymer, styrene-vinylnaphthalene copolymer,
Styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-methyl methacrylate copolymer, styrene-ethyl methacrylate Copolymer, styrene-butyl methacrylate copolymer, styrene-α-chloromethyl methacrylate copolymer, styrene-acrylonitrile copolymer, styrene-vinyl methyl ether copolymer, styrene-vinyl ethyl ether copolymer, Styrene-vinyl methyl ketone copolymer, styrene-butadiene copolymer, styrene-isoprene copolymer, styrene-acrylonitrile-
Styrene copolymers such as indene copolymer, styrene-maleic acid copolymer, styrene-maleic acid ester copolymer; polymethyl methacrylate, polybutyl methacrylate, polyvinyl chloride, polyvinyl acetate, polyethylene, polypropylene, polyurethane ,polyamide,
Epoxy resin, polyvinyl butyl butyral, polyacrylic acid resin, rosin, modified rosin, terpene resin, phenol resin, etc.

Next, as the colorant used in the toner of the present invention, dyes and pigments capable of obtaining yellow, magenta, cyan and black toners usually used for electrophotographic color toners can be used. For example, carbon black, lamp black, aniline black, ultramarine, aniline blue, phthalocyanine blue, phthalocyanine green, hansa yellow G, rhodamine 6G, lake, calco oil blue, chrome yellow, quinacridone, benzidine yellow, rose bengal, triallylmethane Any conventionally known dyes and pigments such as dyes and the like can be used alone or in combination. The content of these colorants is usually 1 to 30% by weight based on the binder resin,
Preferably it is 1 to 10% by weight.

In the toner of the present invention, it is preferable to include a charge control agent in order to impart appropriate charge to the toner. As the charge control agent in this case, a charge control agent that can add a transparent to white substance that does not impair the color tone of the color toner and stabilize the chargeability of the toner to a negative or positive polarity is preferable. Among them, the addition of a metal salt of a salicylic acid derivative is particularly effective in stabilizing the chargeability of the toner to the negative polarity.

The metal salt of the salicylic acid derivative used herein includes a compound represented by the following general formula (III).

Embedded image (Wherein, R ¹ , R ² and R ³ represent a hydrogen atom or a carbon atom
It represents 10 alkyl groups or allyl groups, and particularly preferably a hydrogen atom or an alkyl group or allyl group having 1 to 6 carbon atoms. Here, R ¹ , R ² and R ³ may be the same or different at the same time. Me represents any metal selected from zinc, nickel, cobalt, copper, and chromium. )

The metal salt of the salicylic acid derivative is CLA
RK, J. et al. L. Kao, H (1948) J. Amer.
Chem. Soc. 70, 2151. For example, 2 mol of salicylic acid sodium salt (including the sodium salt of salicylic acid derivative) and 1 mol of zinc chloride are added to a solvent, mixed, heated and stirred to obtain a zinc salt. This metal salt is a white crystal.
It does not show coloring even when dispersed in a toner binder. Regarding metal salts other than zinc salts,
It can be manufactured according to the above method. Table 1 shows specific examples of particularly preferred compounds among the metal salts of the salicylic acid derivatives.

[0048]

[Table 1]

The metal salt of the above-mentioned salicylic acid derivative has a good dispersibility in a binder resin, and does not easily film on a developing roller or the like. The content of the metal salt of the salicylic acid derivative is preferably 0.5 to 8% by weight.

Further, in the toner of the present invention, a releasing agent can be contained in order to improve the releasability of the toner from the fixing member at the time of fixing and to improve the fixing property of the toner. . As the release agent in this case, any material can be used as long as it is incompatible with the binder resin. In particular, an ester-based or olefin-based wax is preferable as the release agent. Since these release agents are more uniformly dispersed in the binder resin, they exhibit excellent offset resistance, and are particularly effective when a polyester resin or a polyol resin is used as the binder resin. Here, the ester wax refers to a wax having an ester bond, and includes natural waxes such as candelilla wax, carnauba wax, and rice wax.Examples of the olefin wax include polyethylene wax, polypropylene wax, Fischer-Tropsch wax and the like. The content of these release agents is usually 1 to 20% by weight, preferably 2 to 10% by weight, based on the binder resin.

Further, the toner of the present invention contains a magnetic material and can be used as a magnetic toner. Specific magnetic materials include iron oxides such as magnetite, hematite, and ferrite, metals such as cobalt and nickel, or aluminum and copper, lead, magnesium, tin, zinc, antimony, beryllium, bismuth, and cadmium. , Calcium, manganese, selenium, titanium, tungsten, alloys with metals such as vanadium, and mixtures thereof. These magnetic substances preferably have an average particle size of about 0.1 to 2 μm, and the amount contained in the toner is 20 to 200 parts by weight, particularly preferably 1 to 100 parts by weight of the binder resin.
It is 40 to 150 parts by weight with respect to 00 parts by weight.

In the digital full-color electrophotographic method, arithmetic processing is performed on the obtained optical information, and masking processing and UCR processing are performed. In particular, in the UCR processing, three primary color toners of yellow, magenta, and cyan are conventionally used. Since the superimposed black part can be replaced with black toner, the gray balance of the image is improved,
Further, the thickness of the toner layer can be reduced. But,
In general, the smaller the amount of adhesion, the lower the image density and gloss. Therefore, if the thickness of the black toner layer is small, the image density and gloss of the image are reduced only in that portion, which is a major cause of deteriorating the quality of the entire image.

The electrophotographic color toner of the present invention is used as a full-color toner composed of at least yellow, magenta, cyan, and black toners in a full-color copying machine or printer using a digital full-color electrophotographic method. In this case, it is preferable that the image density D _0.6 after fixing when the adhesion amount of the black toner on the transfer material is 0.60 mg / cm ² is higher than that of other toners, and that the glossiness of the black toner is higher than that of other toners. Is preferably higher than that of the toner.

The toner of the present invention is generally produced as follows. The above-mentioned binder resin, pigment or dye as a colorant, or if necessary, a charge control agent, a lubricant, other additives, and the like are sufficiently mixed by a mixer such as a Henschel mixer. A batch type twin roll, a Banbury mixer or a continuous type twin screw extruder such as a KTK type twin screw extruder manufactured by Kobe Steel, a TEM type twin screw extruder manufactured by Toshiba Machine Co., a twin screw extruder manufactured by KCK, PCM type twin screw extruder manufactured by Ikegai Iron Works,
The constituent materials are kneaded well using a KEX type twin screw extruder manufactured by Kurimoto Tekkosho Co., Ltd. or a continuous single screw kneader such as a kneader manufactured by Buss. After cooling the kneaded material, coarsely pulverized using a hammer mill or the like,
Further, the powder is finely pulverized by a fine pulverizer or a mechanical pulverizer using a jet airflow, and classified to a predetermined particle size by a classifier using a swirling airflow or a classifier using the Coanda effect, to obtain a base toner.

The toner of the present invention can be produced by other methods such as a polymerization method and a capsule method. The outline of these production methods is described below. (Polymerization toner) A polymerizable monomer, and if necessary, a polymerization initiator, a colorant, and the like are granulated in an aqueous dispersion medium. The granulated monomer composition particles are classified into an appropriate particle size. The monomer composition particles having a specified internal particle diameter obtained by the classification are polymerized. After an appropriate treatment to remove the dispersant, the polymerization product obtained above is filtered, washed with water and dried to obtain a base toner.

(Capsule Toner) A resin, magnetic powder and the like, if necessary, are kneaded with a kneader or the like to obtain a molten toner core material. The toner core is placed in water and stirred vigorously to produce a fine particle core. The core material fine particles are put in a shell material solution, and a poor solvent is dropped with stirring, and the core material is encapsulated by covering the core material surface with the shell material. The capsule obtained above is filtered and dried to obtain a base toner.

Next, the base toner and additives such as inorganic oxides are sufficiently mixed by a mixer such as a Henschel mixer (manufactured by Mitsui Miike), a mechanofusion system (manufactured by Hosokawa Micron), a mechanomill (manufactured by Okada Seiko). And, if necessary, pass through a sieve having an opening of about 100 μm or less,
Removal of coarse particles, aggregated particles, etc.

Here, in the method of producing a color toner for electrophotography according to the present invention, the peripheral speed of the stirring blade at the time of mixing the base toner and the additive is 15 to 35 m / sec. And
The mixing and stirring time is at least 50 sec. For both silica and titania added as additives. It is preferable that it is above. The peripheral speed of the stirring blade at the time of mixing the base toner and the additive is 15 m / sec. When the mixing time is lower, or the mixing and stirring time of either silica or titania added as an additive is 50 sec. If the length is shorter, sufficient mixing is not performed, so that the additives are not uniformly mixed, and the released additives adhere to the photoreceptor, the developing roller, the carrier, etc., and fill the photoreceptor and the developing roller. It tends to cause development troubles such as filming and the like, and tends to cause background contamination and deterioration in developability due to poor charging of the developer.
Conversely, the peripheral speed of the stirring blade at the time of mixing the base toner and the additive is 35 m / sec. If the value is higher, the additive strongly adheres to the base toner and is easily embedded in the surface of the base toner, so that sufficient fluidity cannot be obtained. In addition, the toner may be melted by heat generated during mixing. Particularly, in the case of a color toner, a low-softening binder resin having a large amount of low molecular weight components is generally used. The trend is more pronounced.

The color toner for electrophotography of the present invention is applicable to both one-component toner and two-component toner. When used as a two-component toner, it is used as a mixture with a carrier. As the carrier that can be used in the present invention, known powders such as iron powder, ferrite powder, magnetic powder such as nickel powder, and glass beads can all be used. It is preferred to coat with. In this case, examples of the resin used for coating include polyfluorocarbon, polyvinyl chloride, polyvinylidene chloride, phenol resin, polyvinyl acetal, acrylic resin, and silicone resin. As a method for forming the resin coating layer, a resin may be applied to the surface of the carrier by a spraying method, a dipping method, or the like, as in the related art. Here, the average particle size of these carriers is usually 10 to 100 μm.
m, preferably 30 to 60 μm. The amount of the resin used is usually 1 to 100 parts by weight of the carrier.
10% by weight. Further, the mixing ratio of the toner and the carrier is generally 0.1 parts by weight of the toner to 100 parts by weight of the carrier.
About 5 to 7.0 parts by weight is appropriate.

Next, an embodiment in which the image forming method of the present invention is applied to an electrophotographic copying machine (hereinafter, referred to as a copying machine) will be described. First, the configuration and operation of a copying machine according to an embodiment of the present invention will be described with reference to FIG. The copying machine 201
It comprises a scanner 101 as image reading means and a printer 112 as image output means. The above scanner 1
Numeral 01 is for reading an original image optically, and includes a contact glass 209 as an original mounting table, an exposure lamp 210, a reflection mirror 211, an imaging lens 212,
And a CCD image sensor 213 and the like. As the exposure lamp 210, a halogen lamp is generally used. Reading of a document image by the scanner 101 is performed as follows.

The original placed on the contact glass 209 is irradiated with light by an exposure lamp 210, and the reflected light from the original is reflected by an image forming lens 212 by a reflecting mirror 211 and the like.
Lead to. The reflected light is converted by the imaging lens 212 into a CCD.
An image is formed on the image sensor 213. The CCD image sensor 213 converts the reflected light into a digital electric signal corresponding to a document image. The CCD image sensor 213 is a full-color image sensor, and separates a given optical signal into, for example, R (red), G (green), and B (blue) colors, and outputs a digital electric signal corresponding to each color. Is output. The CCD image sensors 213 are arranged in rows in a direction perpendicular to the drawing (this direction is also referred to as a main scanning direction). CC above
The digital electric signal output from the D image sensor 213 is subjected to image processing such as color conversion processing in an image processing unit to be described later, and cyan (Cyan: hereinafter, referred to as C) and magenta (Magenta: hereinafter, referred to as M). , Yellow (hereinafter, referred to as Y) and black (hereinafter, BK)
) Color image data. On the basis of these color image data, C,
Visualization is performed using M, Y, and BK toners, and the obtained toner images are superimposed to form a full-color image.

At substantially the center of the printer 112, a photosensitive member 215 as an image carrier is arranged. The photoconductor 215 is an organic photoconductor (OPC) drum, and its outer diameter is about 120 mm. Around the photoreceptor,
Charging device 207 for uniformly charging the photoreceptor surface, BK developing unit 202, C developing unit 203, M developing unit 204, Y developing unit 205, intermediate transfer belt 20
6, a cleaning device 214, and the like.
The scanner 101 is located above the photoconductor.
A laser optical system 208 that generates a light beam based on the above-described color image data and optically scans the uniformly charged surface of the photoconductor 215 is provided below.
The laser optical system 208 includes a laser diode that generates a light beam, a polygon mirror that deflects the light beam, and the like.

The printer 11 performed by such a configuration
The image forming operation in No. 2 will be described below by taking as an example a case based on BK image data. The latent image formed on the surface of the photoconductor 215 by the light beam based on the BK image data from the laser optical system 208 is developed by the BK developing unit 202 to become a BK toner image. This toner image is transferred to the intermediate transfer belt 2
No. 06 (hereinafter, transfer of the toner image from the photoconductor 215 to the intermediate transfer belt 206 is referred to as belt transfer). The above-described series of operations of latent image formation, development, and belt transfer are performed for the four colors C, M, Y, and BK, and a four-color superimposed toner image is formed on the intermediate transfer belt 206. You. The four-color superimposed toner image is collectively transferred by a transfer bias roller 217 onto a recording medium, for example, recording paper fed from a paper supply unit 216. The recording medium on which the four-color superimposed toner image is formed is
The sheet is conveyed to the fixing device 219 by the conveyance belt 218. The fixing device 219 melts the four-color superimposed toner image by heating and pressing, and fixes the toner image on a recording medium. The recording medium on which the fixing is completed is discharged onto the paper discharge tray 220.

On the other hand, the toner remaining on the surface of the photoconductor 215 is collected by the cleaning device 214, and the surface of the photoconductor 215 is cleaned. The surface of the photoconductor 215 after the cleaning is neutralized by the neutralization device. Further, after transferring the four-color superimposed image from the intermediate transfer belt 206 onto the recording medium, the toner remaining on the intermediate transfer belt 206 is collected by the belt cleaning device 222, and the surface of the intermediate transfer belt 206 is cleaned. .

[0065]

The present invention will be specifically described below with reference to examples. The present invention is not limited to these examples.
The parts in the examples represent parts by weight.

Example 1 Production of Toner <Binder Resin> Polyester resin (polyester resin synthesized from propylene oxide adduct of bisphenol A, terephthalic acid, succinic acid derivative, softening point: 103 ° C.) 60 parts Styrene-acrylic resin Resin (styrene / n-butyl methacrylate copolymer, softening point 94 ° C.) 40 parts <Colorant> Pigment for yellow toner (non-benzine disazo yellow pigment: CI Pigment Yellow 180) 4.0 parts Pigment for magenta toner (Quinacridone magenta pigment: CI Pigment Red 122) 3.5 parts Pigment for cyan toner (copper phthalocyanine blue pigment: CI Pigment Blue 15: 3) 1.7 parts Pigment for black toner (carbon black: C) I. Pigmen The Black7) 3.0 parts The above materials were mixed in a Henschel mixer for each color, and melt-kneaded using a biaxial kneader heated to 140 ° C.. The kneaded material was water-cooled, coarsely pulverized by a cutter mill, pulverized by a fine pulverizer using a jet stream, and then a base toner of each color having a weight average diameter shown in Table 2 was obtained using an air classifier.

[0067]

[Table 2]

Here, the particle size distribution of the toner can be measured by various methods. In Example 1, the measurement was performed using a Coulter Multisizer. That is, a Coulter Multisizer IIe type (manufactured by Coulter) is used as a measuring device, and an interface (manufactured by Nikkaki) for outputting a number distribution and a volume distribution is connected to a personal computer.
As the electrolyte, a 1% aqueous NaCl solution was prepared using primary sodium chloride. As a measuring method, the electrolytic solution 100
0.1 to 5 ml of a surfactant, preferably an alkylbenzene sulfonate, was added as a dispersant to ~ 150 ml, and 2 to 20 mg of a measurement sample was further added, and a dispersion treatment was performed for about 1 to 3 minutes with an ultrasonic disperser. . Further, 100 to 200 ml of the aqueous electrolytic solution was placed in another beaker, the sample dispersion liquid was added thereto to a predetermined concentration, and 50,000 pieces of the 50,000 samples were used as the aperture by the Coulter Multisizer IIe using a 100 μm aperture. This was done by measuring the average of the particles.

Next, the base toner of each color was put into a Henschel mixer, and the stirring blade peripheral speed was set to 25 m / sec. And mixed for 120 seconds, and then an additive having the following composition <additive> silica (hexamethyldisilazane surface-treated product, average primary particle diameter: 0.01 μm) 0.6 part titania (isobutyl) Trimethoxysilane surface-treated product, average primary particle diameter: 0.015 μm) 0.4 part was added to 100 parts of the base toner, and the stirring blade peripheral speed was 25 m / sec. With a Henschel mixer. The mixture was mixed for 100 seconds, and then air-sieved with a sieve having openings of 75 μm to obtain toner of each color.

Examples 2 to 9 and Comparative Examples 1 to 7 In the same manner as in Example 1, color toners for electrophotography were obtained. Here, the formulations, particle diameters, and mixing conditions for mixing the base toner and the additives of the respective Examples and Comparative Examples are summarized in Tables 3 to 15. In Comparative Example 5, only titania was added first, mixed for 80 seconds, further added silica, and mixed for 20 seconds. In Comparative Example 6, only silica was added first, and after mixing for 80 seconds, titania was further added and mixing was performed for 20 seconds.

Manufacture of Carrier Core Material Cu-Zn Ferrite (Average Particle Diameter 45 μm) 100 parts Coating Material Silicone Resin (SR-2411, solid content 20% by weight, manufactured by Dow Corning Toray Silicone Co., Ltd.) 1.2 parts Core Material 100 Then, 1.2 parts of the coating material was coated using a fluidized bed, followed by baking at 210 ° C. for 2 hours to obtain a carrier coated with the resin.

Production of Developer A toner for electrophotography was obtained by mixing 5 parts of each of the toners obtained in Examples 1 to 9 and Comparative Examples 1 to 7 with 95 parts of the above-mentioned carrier using a turbuler mixer.

With respect to the electrophotographic color toners of these Examples and Comparative Examples, the toner adhesion amount on the transfer material was 0.6.
The image density D _0.6 after fixing at 0 mg / cm ² and the release ratio of silica and titania were determined. Table 1 shows the results
2 to 15. In addition, the electrophotographic color toner and the electrophotographic developer of these Examples and Comparative Examples were used in a full-color copying machine (PRETER550, manufactured by Ricoh Company) (FIG. 1).
And the following various evaluations were performed. The results at this time are shown in Tables 12 to 15. Here, ◎, ○, in Table 4
、 And × are four-level evaluations of each evaluation item, ◎ is a very good level, は is a good level, △ is a level that has no practical problem, and × is a level that has practical problem. Is shown. In addition, in this series of evaluations, if there are any special items, those contents are described in the remarks column of Tables 12 to 15.

Evaluation 1: White spots (fireflies) Fireflies were evaluated in four steps visually after the continuous output of 10 sheets of full-size solid cyan images of A3 size. did. Table 12 shows the results at this time.
-15.

Evaluation 2: Background Stain The background stain was evaluated by visually evaluating the degree of background stain in the non-image area in four stages. Table 12-
The results are shown in FIG.

Evaluation 3: Filming In the evaluation of filming, the degree of filming of the photoreceptor of a 10,000-sheet continuous copying machine was visually evaluated in four stages. The results at this time are shown in Tables 12 to 15.

Evaluation 4: Glossiness Full-color copier (PRETER550 manufactured by Ricoh Company)
(FIG. 1), using a copying machine (type 6000-70W,
Ricoh Co., Ltd.) has an adhesion amount of 1.0 ± 0.1 mg / cm ² consisting of a single color of yellow, magenta, cyan and black.
To create a solid image, and the fixing roller surface temperature is 160 ° C
The glossiness of this single-color solid image at the time of was measured using a gloss meter manufactured by Nippon Denshoku Industries Co., Ltd. at an incident angle of 60 °. As for the gloss, the higher the value, the more the glossiness appears. Moderate gloss is preferred for full-color copy images, 15 to 15
About 40% is preferable. The results are shown in Tables 12 to 15.

Evaluation 5: Transfer Chile The transfer chile was evaluated by observing the image when a one-dot blue line was output with a microscope VH-5910 (manufactured by Keyence Corporation) equipped with a 200 × lens (VH-200). The degree of dust on one line in the visual field was evaluated in four steps. The results at this time are shown in Tables 12 to 15.

Evaluation 6: Toner Scattering Toner scattering was evaluated by visual evaluation of the degree of toner scattering in a copying machine after 10,000 sheets were continuously copied. The results at this time are shown in Tables 12 to 15.

[0080]

[Table 3]

[0081]

[Table 4]

[0082]

[Table 5]

[0083]

[Table 6]

[0084]

[Table 7]

[0085]

[Table 8]

[0086]

[Table 9]

[0087]

[Table 10]

[0088]

[Table 11]

[0089]

[Table 12]

[0090]

[Table 13]

[0091]

[Table 14]

[0092]

[Table 15]

[0093]

According to the present invention, the occurrence of white spots, background stains, filming, etc. in a solid image, which is particularly conspicuous in a toner having a small particle diameter, is extremely small, and there is no transfer dust and toner scattering. Color toner for use, a method for producing the toner, and an image forming method using the toner.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an electrophotographic copying machine according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 101 Scanner 112 Printer 201 Copier 202 Black developing unit 203 Cyan developing unit 204 Magenta developing unit 205 Yellow developing unit 206 Intermediate transfer belt 207 Charging device 208 Laser optical system 209 Contact glass 210 Exposure lamp (halogen lamp) 211 Reflection mirror 212 Image formation Lens 213 CCD image sensor 214 Cleaning device 215 Photoconductor 216 Paper feed unit 217 Transfer bias roller 218 Conveying belt 219 Fixing device 220 Paper discharge tray 221 Bias roller 222 Belt cleaning device

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 9/08 374 381 (72) Inventor Yasuo Asahina 1-3-6 Nakamagome, Ota-ku, Tokyo Co., Ltd. Inside Ricoh (72) Inventor Minoru Masuda 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company (72) Inventor Tomomi Suzuki 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Company (Reference) 2H005 AA01 AA06 AA08 AA21 AB10 CA08 CA15 CA21 CA25 CB07 CB13 DA02 DA04 EA03 EA05 EA07 EA10 FB01 FC01 2H030 AD01 AD04 BB63

Claims (10)

[Claims] 1. A weight average diameter of 4.0 to 9.0 μm in which at least two types of inorganic oxides composed of silica and titania are added as additives to a base toner composed of at least a binder resin and a colorant. In the electrophotographic color toner, the amount of toner attached on the transfer material is 0.60 mg / cm.
^2, the image density D _0.6 after fixing is 1.2 to 2.0, the liberation rate of silica is 0.5 to 8%, and the liberation rate of titania is 0.5 to 5%. Color toner for electrophotography. 2. The electronic device according to claim 1, wherein the total amount of the two inorganic oxides is 1.2 to 2.0 parts by weight based on 100 parts by weight of the base toner. Photographic color toner. 3. The color toner for electrophotography according to claim 1, wherein the added amount of the titania is larger than the added amount of the silica. 4. The softening point of the binder resin is 110 to 13
The color toner for electrophotography according to claim 1, wherein the temperature is 0 ° C. 5. 5. The color toner for electrophotography according to claim 1, wherein the binder resin comprises a polyester resin and / or a polyol resin. 6. The color toner for electrophotography according to claim 1, further comprising a salicylic acid derivative metal salt as a charge control agent. 7. The electrophotographic color toner is a full-color toner composed of at least yellow, magenta, cyan, and black toners, and the black toner has a toner adhesion amount of 0.60 mg on a transfer material.
/ Cm ² image density D _0.6 after fixing in the electrophotographic color toner according to any one of claims 1 to 6, wherein the higher than said D _0.6 Other toners. 8. The electrophotographic color toner is a full-color toner composed of at least yellow, magenta, cyan, and black toners, and the black toner has a toner adhesion amount of 0.60 mg on a transfer material.
/ Glossiness after fixing in cm ² is, color toners for electrophotography according to any one of claims 1 to 7, characterized in that above the glossiness of the other toner. 9. A stirring blade having a peripheral speed of 15 to 35 m / sec. When mixing a base toner and an additive. And, for any of silica and titania added as an additive,
The mixing and stirring time is at least 50 sec. The method for producing an electrophotographic color toner according to any one of claims 1 to 8, wherein: 10. An electrostatic latent image corresponding to a recorded image is formed on a latent image carrier, and the formed electrostatic latent image is developed using toner to form a toner image on the latent image carrier. An image forming method for transferring a formed toner image onto a transfer material via an intermediate transfer member to obtain a recorded image, wherein the color toner for electrophotography according to claim 1 is used as the toner. An image forming method comprising: