JP2003223013A - Electrophotographic color toner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic color toner which stably develops an image of sharp tone. <P>SOLUTION: The color toner is obtained by mixing two or more kinds of toners selected from a plurality of toners having different tones and comprising at least binder resins and coloring agents. The two or more kinds of toners contain white conductive fine particles different in at least either the content or the material. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color toner for electrophotography, and particularly to yellow, magenta,
The present invention relates to a color toner for electrophotography, which is characterized by a structure for stabilizing the developability of a color toner obtained by mixing two or more kinds of toner selected from cyan, black toner and the like.

[0002]

2. Description of the Related Art The electrophotographic method is a technology widely used in image forming apparatuses such as copying machines, electrophotographic facsimiles, and electrophotographic printers. As the electrophotographic method, for example, US Pat. No. 2,297,691 is cited. As described, photoconductive insulator-based schemes are commonly used.

In this method, a photoconductive insulator charged by a corona discharge or a charge supply roller is irradiated with light from a laser, an LED, or the like to form an electrostatic latent image, which is called a toner. A resin powder colored with a pigment or a dye is electrostatically adhered to the electrostatic latent image to develop it to form a visualized toner image, which is then transferred onto a recording medium such as paper or film. It is transcribed.

However, since the toner image at this time is a powder image which is simply placed on the recording medium, it is necessary to fix the toner image on the recording medium. Therefore, in the final step, the toner is fused on the recording medium by heat, pressure, light or the like and then solidified to finally obtain a toner image fixed on the recording medium.

As described above, the fixing of the toner means that the toner, which is a powder containing a thermoplastic resin (hereinafter referred to as a binder resin) as a main component, is melted by heat and fixed on the recording medium. Well-known methods include a heat roll method in which a recording medium on which a toner image is formed is directly heated and pressed by a roller, and a flash fixing method in which toner is fixed on the recording medium by flash light irradiation such as a xenon flash lamp. There is.

In order to obtain a color image, three color toners of yellow toner, magenta toner, and cyan toner, or four color toners of black toner in addition to the three color toners are developed and superposed. Printing method for performing color printing according to Japanese Patent Laid-Open No. 61-13
As described in Japanese Patent No. 2959, there is known a printing method for performing color printing by superposing two colors or two or more colors of black toner or color toner.

In the former printing method, color toners of yellow toner, magenta toner, cyan toner, and black toner are set in a yellow developing device, a magenta developing device, a cyan developing device, and a black developing device, respectively. Is formed. In this case, even if the physical properties of the respective color toners are different, it is possible to make the developing characteristics the same by optimizing the developing conditions, but on the other hand, the device structure becomes complicated and the high cost device is used. Becomes

On the other hand, in the latter printing method, if at least one developing device for developing color toner is used, color printing can be performed, the structure of the device is simple, and the device is low cost.

In the latter printing method, Japanese Patent Laid-Open No.
As described in Japanese Patent Laid-Open No. 348101, there is known a printing apparatus having a fluidized bed for uniformly mixing toners having substantially the same physical properties and different colors at a set ratio.

Further, conventionally, the electric resistance of the toner is adjusted by a method of adding a conductive additive to the toner,
In a two-component developer including a toner and a magnetic carrier, the electrical resistance is controlled by adjusting the conductivity of the core material and the coating material of the magnetic carrier combined with the toner.

For example, as described in JP-A-5-19525 or JP-A-11-327192, a method of adding a conductive additive to the toner is a method for controlling the electric resistance of the toner. Are known. In this method, a conductive additive is added to the toner by internal addition or external addition to change the electric resistance of the color toner.

A printed image can be obtained by using a color toner obtained by mixing two or more kinds of toner selected from such yellow toner, magenta toner, cyan toner, black toner and the like.

[0013]

However, when a printed image is obtained by using a color toner obtained by mixing two or more kinds of toners selected from yellow toner, magenta toner, cyan toner, black toner and the like. However, there arises a problem that the color tone of the printed image becomes unstable.

That is, yellow toner, magenta toner,
Colorants used for cyan toner, black toner, etc., such as color pigments, dyes, carbon black, etc., have different electric resistances and addition amounts. Therefore, yellow toners, magenta toners, cyan toners, and black toners having different electric resistances can be used. can get.

Incidentally, carbon black, which is usually used for black toner, has an extremely lower resistance than that of color pigments used for color toners, so that the electric resistance of black toner becomes low, and also for color pigments, cyan toner is used. The copper phthalocyanine pigment used has a relatively low resistance as compared with other pigments.

When the color toners obtained by combining and mixing the color toners having different electric resistances as described above are printed, the combined color toners are unevenly developed, and the color tone of the printing becomes unstable. .

Therefore, in order to precisely adjust the electric resistance of the yellow toner, the magenta toner, the cyan toner, the black toner, and the like, which respectively contain colorants such as yellow pigment, magenta pigment, cyan pigment, and carbon black, which have different electric resistances. Method is necessary.

In the above-mentioned Japanese Patent Laid-Open No. 6-348101, it is necessary to equalize the physical properties of the toners to be mixed, but it is necessary to precisely control the electric resistance of the toners. The method is completely unclear.

Therefore, an object of the present invention is to provide a color toner capable of stably developing an image having a vivid color tone, an image forming apparatus using the color toner, and the like.

[0020]

Means for solving the problems of the present invention will now be described with reference to FIG. 2. FIG. 2 shows R _H / R of print evaluation results of each color toner.
It is a figure which shows _L dependence. In order to achieve the above-mentioned object, in the present invention, in the electrophotographic color toner, two or more kinds of toners selected from a plurality of toners having different color tones including at least a binder resin and a colorant are mixed. The color toner thus obtained is characterized in that the two or more types of toner contain white electroconductive fine particles whose content and / or material are different from each other.

As described above, the electric resistance of each toner can be made substantially equal by changing the amount or material of the white conductive fine particles mixed in each toner, thereby stabilizing the color tone of the printed image. It becomes possible to do.

As shown in FIG. 2, two or more types of toner
The resistance R of the toner with the highest resistance _HAnd the lowest resistance
Toner resistance R_LRatio R_H/ R_LLess than 2.5,
It is more preferable to set it to 2.0 or less, and
Good stability can be obtained. Tona to be mixed
Electrical resistance ratio R_H/ R_LWhen the value exceeds 2.5, mixing
Since the developed toner is unevenly developed and consumed, the printing color
The tone becomes unstable.

The mixing ratio of the white conductive fine particles is 2
It is preferably 0% by weight or less, and if it exceeds 20% by weight, the white turbidity of the toner becomes remarkable and it becomes difficult to realize high saturation.

Further, it is desirable that the white conductive fine particles have an aspect ratio of 10 or more and a major axis diameter of 4 μm or less. By virtue of such a needle-like shape, a large addition amount can be obtained with a small addition amount. You can get sex.
It is desirable that all the white conductive fine particles satisfy the above condition, but it is sufficient that half or more of the white conductive fine particles satisfy the above condition.

The electric resistance of the white conductive fine particles is 1 to 10 in order to effectively control the electric resistance of the toner.
It is preferably 0 Ω · cm, and if it is less than 1 Ω · cm, the chargeability of the toner is lowered and fogging occurs, which is 100
If it exceeds Ω · cm, sufficient conductivity cannot be obtained.

Examples of such white conductive fine particles include Zn
O, TiO₂, SnO₂, Al₂O ₃, In₂O₃, S
iO₂, MgO, BaO, MoO₃, Out of WO
It is desirable that it is a metal oxide of some kind, and such a metal
By using an oxide, the color tone of the color toner can be improved.
It is possible to reduce the influence of the influence.

In particular, when TiO ₂ particles are used as the white conductive fine particles, in order to effectively control the electric resistance of the toner with a small addition amount, the major axis diameter is 1 μm or more,
It is desirable that the TiO ₂ particles having a minor axis diameter of 0.1 μm or less account for 50% by weight or more of the entire TiO ₂ particles.

In this case, SnO is formed on the surface of the TiO ₂ particles.
It is desirable to provide a conductive layer composed of ₂ and Sb ₂ O ₃ , particularly a conductive layer in which the amount of Sb ₂ O ₃ is 10 to 25 wt% with respect to SnO ₂ , and it is preferable that the conductive layer is less than 10 wt%. Is insufficient, and if it exceeds 25 weights, the white conductive fine particles themselves become dark and the saturation of the image is lowered.

As white conductive fine particles, SnO ₂
In the case of using particles, in order to effectively control the electric resistance of the toner with a small addition amount, SnO ₂ particles having a major axis diameter of 1 μm or more and a minor axis diameter of 0.1 μm or less are used as 50% of the total SnO ₂ particles. The content is preferably at least wt%, and it is particularly desirable to use SnO ₂ particles having a conductive layer made of Sb ₂ O _{3 on the} surface.

As the color toners having different hues, it is preferable to use toners having hues of yellow, magenta, cyan and black, and toners having hues of green, blue, red, white and gray. May be used.

Stable image quality can be realized by accommodating the color toner in which two or more kinds of toner are mixed in the toner cartridge and setting the toner cartridge in the image forming apparatus.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION Now, a preferred procedure of the embodiment of the present invention will be described. The color toner of the present invention can be manufactured by a conventionally known manufacturing method, and at least a binder resin, a colorant, white conductive fine particles, and if necessary, a charge control agent and wax are added to obtain a raw material.

This raw material is kneaded by, for example, a pressure kneader, a roll mill, an extruder or the like to be uniformly dispersed, and then pulverized by a pulverizer, a jet mill or the like into fine powder and classified by an air classifier, etc. A toner having a desired particle size distribution is obtained.

Then, two or more kinds of toners selected from the yellow toner, magenta toner, cyan toner, and black toner obtained by the above method are appropriately mixed according to the color tone to be obtained, and, for example, By uniformly mixing with a Henschel mixer or the like, the electrophotographic color toner of the present invention can be obtained. The color toners may be mixed in the step of coating the surface of the toner with inorganic fine particles as an external additive.

Each color toner in this case has, for example, 75 to 100 parts by weight of the binder resin when the total amount of the toner is 100 parts by weight.
It is desirable that the amount of the coloring agent is 95 parts by weight and the colorant is 0.1 to 20 parts by weight, preferably 0.5 to 15 parts by weight.

The binder resin used in the present invention is not particularly limited, and thermoplastic resins made of various natural or synthetic polymer substances can be used. For example, epoxy resin, styrene-acrylic resin, polyamide resin. , A polyester resin, a polyvinyl resin, a polyurethane resin, a polybutadiene resin and the like, which are used alone or in combination.

The colorant contained in the color toner of the present invention is not particularly limited, and a known colorant can be used. For example, a monoazo red pigment, a disazo yellow pigment, a quinacridone magenta pigment, an anthraquinone dye, a nigrosine dye, a quaternary ammonium salt, a monoazo metal complex salt dye, or the like can be used. May be.

More specifically, for example, aniline blue (C.I. No. 50405), chalco oil blue (C.I. No. azoic Blue3), chrome yellow (C.I. No. 14090), ultra. Marine blue (C.I. No. 77103), DuPont oil red (C.I. No. 26105), quinoline yellow (C.I. No. 47005), methylene blue chloride (C.I. No. 52015), phthalocyanine. Blue (C.I. No. 74160), Malachite Green Oxalate (C.I. No. 42000), Food Red No. 2 (Amaranth, C.I. No. 16185),
Edible Red No. 3 (Erythrosin, CI No. 4543
0), Edible Red No. 40 (Arla Red AC, CIN
o. 16035), food red No. 102 (new coccin, CI No. 16255), food red No. 104 (phloxine, CI No. 45410), food red No. 105 (rose bengal, CI No. .4544
0), food red No. 106 (acid red, CIN)
o. 45100), <Yellow> Food Yellow No. 4 (Tartrazine, CI No. 19140), Food Yellow No. 5 (Sunset Yellow FCF, CI No. 15985),
<Green> Edible Green No. 3 (First Green FCF,
C. I. No. 42053), <Blue> Edible Blue No. 1 (Brilliant Blue FCF, CI No. 4209)
0), food blue No. 2 (indigo carmine, CIN
o. 73015) and the like can be used.

The white electroconductive fine particles added to control the electric resistance preferably have an aspect ratio of 10 or more and a major axis diameter of 4 μm or less, and the white electroconductive fine particles of 20% by weight or less. It is preferable to contain them in a mixing ratio. As described above, since the shape of the white conductive fine particles is needle-like, the number of contact points of the white conductive fine particles is large even if the amount of addition is small, so that the electric resistance is lowered, and the addition amount is 20% by weight or less. As a result, high saturation can be realized without causing the toner to become cloudy.

In this case, the toner is obtained by mixing the toner.
Yellow toner used for the color toner of the present invention,
Electrodes such as magenta toner, cyan toner, and black toner
Air resistance is the highest toner resistance R_H, Lowest tona
Resistance of R_LThen, R _H/ R_LIs less than 2.5,
More preferably, R_H/ R_LWhite to 2.0 or less
It is desirable to adjust the material and amount of color conductive particles.
Yes.

The white conductive fine particles may be contained in all toners of yellow, magenta, cyan, black, etc., or may be contained in only one of the toners. By adjusting the content of the white conductive fine particles according to the resistance, the resistance of the toner can be controlled, and the development stability can be dramatically improved.

In particular, in addition to controlling the electric resistance of the toner by the white conductive fine particles, the volume resistivity of the toner is from 1 × 10 ⁹ to
It was found that good chargeability can be imparted when the range is 1 × 10 ¹² Ω · cm.

The white conductive fine particles have an electric resistance of 1 to
When it is 100 Ω · cm, good charging characteristics can be obtained. That is, when the white conductive fine particles having a resistance of less than 1 Ω · cm are used, the toner having a sufficient specific charge cannot be obtained because the surface resistance of the toner is too low. On the other hand, when the white conductive fine particles having a conductivity of more than 100 Ω · cm are used. However, the amount of the conductive fine particles added must be increased to a high concentration of 20% by weight or more, and the color of the toner becomes turbid, so that a printed image with high saturation cannot be obtained.

Examples of such white conductive fine particles include Zn
O ₂ , TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ ,
When the metal oxide is selected from SiO ₂ , MgO, BaO, MoO ₃ , and WO, good developability and a vivid image can be realized. This is because the metal oxide has a color that has a small effect on the color of the color toner.

Of these, when TiO ₂ is used, when the major axis diameter is 1 μm or more and the minor axis diameter is 0.1 μm or less, 50% by weight or more of the whole TiO ₂ particles, Particularly good developability and a vivid image can be realized. This is effective for resistance control with a particularly small amount of acicular TiO ₂ , and a shape having a major axis diameter of 1 μm or more and a minor axis diameter of 0.1 μm or less is also effective for resistance control.

That is, the shape of the white conductive fine particles is better as the shape is longer and narrower, and the larger the aspect ratio is, the smaller the added amount is, the lower the electric resistance of the toner is, and the longer the diameter is 1 μm or more. And the minor axis diameter is 0.1
It is particularly effective when TiO ₂ particles having a particle size of μm or less are present in an amount of 50% by weight or more based on the whole.

[0047] Further, it is possible to realize a vivid image with particularly good developability when the surface of the TiO ₂ is TiO ₂ particles having a conductive layer made of SnO ₂ and Sb ₂ O _3. This is because the conductive layer is particularly effective for resistance control, and the addition amount can be further suppressed.

[0048] In this case, with respect to both SnO ₂ of Sb ₂ O _3, as Sb ₂ O _3, it is possible to realize a vivid image with particularly good developability when 10 to 25% by weight. This is because the resistance of TiO ₂ can be minimized at the above weight ratio.

[0049] In the case of using a SnO ₂ as a white conductive fine particles, a long axis diameter is not less 1μm or more, and, 50 SnO ₂ particles overall SnO ₂ particle minor axis diameter of 0.1μm or less by weight When it is at least%, particularly good developability and a vivid image can be realized. This is effective for resistance control with a particularly small amount of needle-shaped SnO ₂ , and a shape having a major axis diameter of 1 μm or more and a minor axis diameter of 0.1 μm or less is also effective for resistance control. .

[0050] Further, it is possible to realize a vivid image with particularly good developability when a SnO ₂ particles having a conductive layer made of Sb ₂ O ₃ on the surface of the SnO _2. This is because the conductive layer is particularly effective for resistance control, and the addition amount can be further suppressed.

Next, a method for measuring the electric resistance of such white conductive fine particles will be described. First, 1 white conductive fine particles
A columnar green compact having a diameter of 20 mm and a thickness of 1 to 5 mm is formed by molding at a pressure of 00 kg / cm ² , its DC electric resistance is measured, and the electric resistance of the white conductive fine particles is calculated from the following formula. Electric resistance (Ω · cm) = measured value × (cross-sectional area / thickness) The electric resistance in this case is HV-MEASURE
UNIT (KEITHLEY237: KEYTHLEY
It was measured using the product name manufactured by the company.

A charge control agent may be added to the color toner of the present invention for the purpose of imparting chargeability and reducing a change in charge amount under different temperature and humidity environments. The charge control agent is colorless. To light-colored ones are preferred.

As such a charge control agent, for example, 4
Well-known positively and negatively chargeable charge control agents such as a quaternary ammonium salt compound, a salicylic acid compound, a boron complex, and a carboxylic acid compound can be used.

Further, in order to improve the fluidity of the color toner of the present invention, inorganic fine particles may be coated on the surface of the toner as an external additive, and the external additive usable here is
Particle size is 5 nm to 2 μm, preferably 5 nm to 500
is a particle in the range of nm, also, it is preferable that the specific surface area by the BET method is 20m ² / g~500m ² / g.

The proportion of the external additive mixed in the color toner of the present invention is 0.1 to 5 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the toner.
2.0 parts by weight.

Examples of such external additives include silica, alumina, titanium oxide, barium titanate, magnesium titanate, calcium titanate, strontium titanate, zinc oxide, silica sand, clay, mica, wollastonite. It is possible to use fine particles of diatomaceous earth, chromium oxide, cerium oxide, red iron oxide, antimony trioxide, magnesium oxide, zirconium oxide, barium sulfate, barium carbonate, calcium carbonate, silicon carbide, silicon nitride and the like. Among these, it is particularly preferable to use fine silica particles, and it is preferable to use those external additives whose surface is treated to be hydrophobic.

Next, a method for measuring the electric resistance of the color toner manufactured by the above procedure and materials will be described. First, the toner particles are compression-molded at a pressure of 5000 kg / cm ² to obtain a cylindrical green compact having a diameter of 13 mm and a thickness of 200 to 500 μm, which is then measured using a dielectric loss measuring device (manufactured by Ando Electric Co., Ltd.). The electric conductivity was measured, and the electric resistance was calculated from the following formula. Electric resistance (Ω · cm) = S / (L · d) where S is the bottom area [cm ² ] of the cylindrical green compact, d is the thickness [cm] of the cylindrical green compact, and L is the columnar It is the electric conductivity [Ω ⁻¹ ] of the green compact.

Next, a printing test is conducted using this color toner. In this case, the process speed of the image forming apparatus is 1
A 100 mm / s high-speed development type color laser printer, for example, F6708B (trade name, manufactured by Fujitsu Ltd .; 50 sheets / minute) is used to print, for example, 100,000 sheets or more to evaluate image stability.

Here, with reference to FIG. 1, the conceptual configuration of the used color laser printer will be described. See FIG. 1. FIG. 1 is a conceptual configuration diagram of a color laser printer used in a print test. A photoconductor 1 made of amorphous silicon is shown.
0 around the charger 20, the exposing means 30, the developing means 4
0, a transfer device 50, a cleaner 60, a static eliminator 70, a flash fixing device 80 having a xenon flash lamp 81, and the like.

The developing means 40 includes a developer container 41, a developing roller 43, and a stirring blade (not shown), and brings the toner particles TO and the carrier particles CA in the developer container 41 into contact with each other to impart a predetermined charge amount to the toner. It is supposed to be done. Further, the color toner of the present invention is set in advance in the toner hopper 45, and when the toner concentration in the developing container decreases due to printing, the color toner is supplied from the toner hopper 45 to the developing container 41. Further, by changing the color toner set in the toner hopper 45 and the developing container 41, it is possible to print toner of various color tones. Hereinafter, the color toner of the present invention will be described more specifically based on Examples.

Based on the above matters, in the following,
Specific examples of the present invention and comparative examples for clarifying the effects of the examples of the present invention will be described together. First, various individual toner preparation methods that are the premise of each example and each comparative example are described. Will be explained. (Toner 1) First, in order to produce a yellow toner, binder resin: polyester resin (manufactured by Kao) 88 parts by weight Colorant: yellow pigment (Toner Yellow HG; product name of Clariant) 5 parts by weight Negative charge control agent: E-89 (trade name, manufactured by Orient Chemical Co., Ltd.) 2 parts by weight Conductive agent: acicular titanium oxide (FT-1000; trade name, manufactured by Ishihara Sangyo Co., Ltd.) 15 parts by weight or more of the materials are charged into a Henschel mixer and premixed. After that, the mixture is kneaded by an extruder, then roughly crushed by a hammer mill, finely crushed by a jet mill, and classified by an air stream classifier to have a volume average particle size of about 8.
Toner 1 consisting of 5 μm yellow toner is obtained. The acicular titanium oxide (FT-1000; trade name of Ishihara Sangyo Co., Ltd.) has a major axis diameter of 1.7 μm and a minor axis diameter of 0.1.
It is needle-like fine particles having an aspect ratio of 17 μm.

Next, 0.5 part by weight of hydrophobic silica fine particles (H2000 / 4; trade name of Clariant Co., Ltd.) was added to this toner 1 as an external additive, and the mixture was externally added by stirring with a Henschel mixer. When the surface of Toner 1 is coated with an external additive, the electric resistance of the toner is 12 GΩ.
It was cm (1.2 × 10 ¹⁰ Ω · cm).

(Toners 2 and 3) Next, the addition amount of acicular titanium oxide (FT-1000; trade name of Ishihara Sangyo Co., Ltd.) was changed to
The toner 1 described above is used except that the amounts are 5 parts by weight and 0 parts by weight, respectively.
Toner 2 and Toner 3 were produced in exactly the same manner as in.
The electric resistances of the toner 2 and the toner 3 are 55 GΩ respectively.
-Cm and 150 GΩ-cm.

(Toners 4 and 5) Next, 5 parts by weight of a magenta pigment (Toner Magenta EB; trade name of Clariant) was added as a colorant, and acicular titanium oxide (FT-1000; trade name of Ishihara Sangyo Co., Ltd.). Toners 4 and 5 which are magenta toners were manufactured in exactly the same manner as Toner 1 except that the addition amounts of (1) and (2) were changed to 10 parts by weight and 0 parts by weight, respectively. The electric resistances of the toner 4 and the toner 5 are 8 GΩ · cm and 100 GΩ · cm, respectively.
It was cm.

(Toners 6 and 7) Next, as a colorant, a cyan pigment (Lionol Blue ES [CI.
gment Blue 15: 3]; 5 parts by weight of Toyo Ink Mfg. Co., Ltd.), and the addition amount of needle-shaped titanium oxide (FT-1000; Ishihara Sangyo Co., Ltd.).
The toner 1 described above is used except that the amounts are 5 parts by weight and 0 parts by weight, respectively.
Cyan toners Toner 6 and Toner 7 were prepared in the same manner as in. The electric resistances of the toner 6 and the toner 7 were 15 GΩ · cm and 60 GΩ · cm, respectively.

(Toner 8) Next, 10 parts by weight of carbon black (Mogar L; trade name manufactured by Cabot) was added as a colorant, and needle-shaped titanium oxide (FT-100) was added.
Toner 8, which is a black toner, was prepared in exactly the same manner as Toner 1 except that the addition amount of 0: Ishihara Sangyo Co., Ltd.) was 0 parts by weight. The electric resistance of this toner 8 was 10 GΩ · cm.

Tables 1 and 2 summarize the compositions of the toners 1 to 8.

[Table 1]

[Table 2]

Next, Examples 1 to 5 and Comparative Examples 1 and 2 relating to color toners prepared by mixing the above toners 1 to 8 will be described. Example 1 Toner 1 (yellow toner) 50 parts by weight Toner 6 (cyan toner) 50 parts by weight were mixed using a Henschel mixer to obtain a green color toner. In this green toner, the ratio R _H / R _L of the electric resistance of the toner 6 having a relatively high electric resistance to the electric resistance of the toner 1 having a relatively low electric resistance is R _H / R _L = 15 GΩ · cm / 12 GΩ / cm = 1.2
It is 5.

Using this two-component developer consisting of green toner and carrier, a printing test of 10 sheets was conducted using the above-mentioned color laser printer, and the toner specific charge, the density of the printed image, and the saturation were investigated. did. The two-component developer used here was an evaluation test using 5 parts by weight of the color toner produced in the above process and 95 parts by weight of silicone resin-coated magnetite carrier (Kanto Denka Kogyo) mixed in a ball mill. As a result, it was possible to stably obtain a vivid color image. In this case, the variation rate of the toner specific charge was within 20%.

Example 2 Toner 1 (yellow toner) 50 parts by weight Toner 4 (magenta toner) 50 parts by weight were mixed using a Henschel mixer to obtain a vermilion color toner. In this vermilion toner, the ratio R _H / R _L of the electric resistance of the toner 1 having a relatively high electric resistance to the electric resistance of the toner 4 having a relatively low electric resistance is R _H / R _L = 12 GΩ · cm / It is 8 GΩ · cm = 1.5.

This vermilion toner was subjected to a printing test on 10 sheets as a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined, and a vivid color tone was obtained. The image of was able to be obtained stably.

Example 3 Toner 4 (magenta toner) 70 parts by weight Toner 6 (cyan toner) 30 parts by weight were mixed using a Henschel mixer to obtain a purple color toner. In this purple toner, the ratio R _H / R _L of the electric resistance of the toner 6 having a relatively high electric resistance to the electric resistance of the toner 4 having a relatively low electric resistance is R _H / R _L = 15 GΩ · cm / It is 8 GΩ · cm≈1.88.

A printing test was performed on 10 sheets of this purple toner using a two-component developer as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined, and a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

Example 4 Toner 2 (yellow toner) 50 parts by weight Toner 7 (cyan toner) 50 parts by weight were mixed using a Henschel mixer to obtain a light green color toner. In this light green toner,
Ratio of electric resistance of toner 7 having relatively high electric resistance to electric resistance of toner 2 having relatively low electric resistance R _H / R
_L is R _H / R _L = 60 GΩ · cm / 55 GΩ · cm≈1.0
It is 9.

A printing test was performed on 10 sheets of the thin green toner using a two-component developer in the same manner as in Example 1 above.
When the toner specific charge, the density of the printed image, and the saturation were investigated, it was possible to stably obtain an image with a vivid color tone. In this case, the change rate of the toner specific charge is 20%.
It was within.

(Example 5) Toner 1 (yellow toner) 30 parts by weight Toner 4 (magenta toner) 60 parts by weight Toner 8 (black toner) 10 parts by weight were mixed using a Henschel mixer to obtain a brick-colored mixture. Color toner was obtained. In this brick color toner,
Ratio of electrical resistance of toner 1 having relatively high electrical resistance to electrical resistance of toner 4 having relatively low electrical resistance R _H / R
_L is R _H / R _L = 12 GΩ · cm / 8 GΩ · cm = 1.5.

This brick-color toner was subjected to a printing test on 10 sheets using a two-component developer in the same manner as in Example 1 above.
When the toner specific charge, the density of the printed image, and the saturation were investigated, it was possible to stably obtain an image with a vivid color tone. In this case, the change rate of the toner specific charge is 20%.
It was within.

Comparative Example 1 Toner 3 (yellow toner) 50 parts by weight Toner 7 (cyan toner) 50 parts by weight were mixed using a Henschel mixer to obtain a blue-green color toner. In this blue-green toner, the ratio R _H / R _L of the electric resistance of the toner 3 having a relatively high electric resistance to the electric resistance of the toner 7 having a relatively low electric resistance is R _H / R _L = 150 GΩ · cm / 60 GΩ · cm = 2.
It is 5.

Example 1 described above was applied to this blue-green toner.
Similarly to the above, a printing test was performed on 10 sheets using a two-component developer, and the toner specific charge, the density of the printed image, and the saturation were investigated, and the color tone was unstable, and a blue-green image was initially obtained. , Gradually became a greenish image with a strong yellow color.

Further, when the printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to the decrease of the image density, and it is clear that the toner has low development stability and color tone stability. is there. It is considered that this is because toners having different electric resistances were mixed.

(Comparative Example 2) Toner 3 (yellow toner) 30 parts by weight Toner 5 (magenta toner) 60 parts by weight Toner 8 (black toner) 10 parts by weight were mixed using a Henschel mixer to obtain a brick color. Color toner was obtained. In this brick color toner,
The ratio R _H / R of the electric resistance of the toner 3 having a relatively high electric resistance to the electric resistance of the toner 8 having a relatively low electric resistance.
_L is R _H / R _L = 150 GΩ · cm / 10 GΩ · cm = 1
It is 5.0.

A printing test was performed on 10 sheets of this brick color toner using a two-component developer in the same manner as in Example 1 above.
When the toner specific charge, the density of the printed image, and the saturation were investigated, the color tone was unstable, and a brick-colored image was initially obtained, but the color tone gradually became a vermilion-colored image with a strong yellow tint.

Further, when the printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light red image due to the decrease in the image density, and it is clear that the toner has low development stability and color tone stability. is there. Also in this case, it is considered that toners having different electric resistances were mixed.

FIG. 2 shows a summary of the above results. Again referring to FIG. 2, from this result, it is possible to obtain good development stability and color tone stability by setting the ratio R _H / R _L to less than 2.5, and more preferably to 2.0 or less. It is understood that it is possible.

(Embodiment 6) Next, the toner 1 (yellow toner) and the toner 6 (cyan toner) of the above-described embodiment 1 are used.
The white conductive fine particles in Fig. ₂ are needle-shaped SnO ₂ (FS-10
P: trade name of Ishihara Sangyo Co., Ltd.) A green toner of Example 6 was prepared in exactly the same manner as in Example 1 except that 8 parts by weight were replaced. The needle-shaped SnO ₂ (FS-10P; trade name manufactured by Ishihara Sangyo) has a volume resistivity of 70 Ω · cm and a major axis diameter =
It is needle-like fine particles having an aspect ratio of 75 with a minor axis diameter of 0.02 μm and a diameter of 1.5 μm.

A printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. As a result, a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

As described above, it is understood from Example 6 that the effect of obtaining the image stability does not depend on the material of the white conductive fine particles, and in addition to TiO ₂ or SnO ₂ , the color tone of the color toner can be improved. ZnO, Al ₂ O ₃ , which has no influence,
In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , W
A metal oxide such as O is preferable, and a metal oxide having no conductivity is SnO ₂ or Sb ₂ O on the surface.
It is understood that it may be covered with a conductive layer made of ₃ or a mixture thereof.

Next, the shape of the white conductive fine particles to be added, such as the aspect ratio, and the amount added were examined. (Embodiment 7) As white conductive fine particles in the toner 1 (yellow toner) and the toner 6 (cyan toner) of the above-mentioned Embodiment 1, the volume resistivity is 10 Ω · cm, the major axis diameter is 2 μm, and the minor axis diameter is. A green toner of Example 7 was manufactured in exactly the same manner as in Example 1 except that acicular TiO ₂ having an aspect ratio of 10 of 0.2 μm was used and the addition amount was 20% by weight.

A print test was performed on 10 sheets of this green toner using a two-component developer as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were investigated, and a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

(Embodiment 8) Toner 1 of Embodiment 1 described above
As the white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the volume resistivity is 10 Ω.
cm, the major axis diameter was 4 μm, the minor axis diameter was 0.08 μm, and the acicular TiO ₂ having an aspect ratio of 50 was used, and the addition amount was 5% by weight. 8 green toner was prepared.

A print test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were investigated. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

Example 9 Toner 1 of Example 1 described above
The volume resistivity is 8 Ω · c as white conductive fine particles in (yellow toner) and toner 6 (cyan toner).
m, the major axis diameter is 2 μm or more, and the minor axis diameter is 0.2 μm.
With the following proportion of the TiO ₂ fine particles the proportion of the total TiO ₂ particles used in 50 wt% acicular TiO _2, except that the added amount of 8 wt% green Example 9 in the same manner as in Example 1 A toner was prepared.

A printing test was performed on 10 sheets of this green toner using a two-component developer as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined, and a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

Comparative Example 3 Toner 1 of Example 1 described above
Example 1 except that 5% by weight of spherical TiO ₂ particles having an aspect ratio of 2 or less was added as TiO ₂ particles in (yellow toner) and toner 6 (cyan toner).
A green toner of Comparative Example 3 was manufactured in exactly the same manner as in.

A print test was conducted on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. Stable and initially got a turquoise image,
Gradually, the image became a greenish image with a strong yellow tint.

Further, when printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to the decrease in image density, and it is clear that the toner has low development stability and color tone stability. is there. This is presumably because the white conductive fine particles having a small aspect ratio were used, the fine particles were not sufficiently contacted with each other, and the electric resistance was not sufficiently reduced.

Comparative Example 4 Toner 1 of Example 1 described above
As (yellow toner) and the toner 6 TiO ₂ fine particles in (cyan toner) and a long axis diameter of 5 [mu] m, minor axis diameter is 0.1 [mu] m, except that the aspect ratio was added 50 acicular TiO ₂ fine particles of 5 wt% In the same manner as in Example 1, a green toner of Comparative Example 4 was produced.

When a printing test was performed on 10 sheets of this green toner using a two-component developer as in Example 1 above, image defects such as fog occurred. This is TiO ₂
It is considered that the long axis diameter of the fine particles is too long, and it becomes difficult to mix with other toner constituent materials, so that a good toner specific charge cannot be realized.

Comparative Example 5 Toner 1 of Example 1 described above
A green toner of Comparative Example 5 was manufactured in exactly the same manner as in Example 1 except that the addition amount of TiO ₂ fine particles in (yellow toner) and toner 6 (cyan toner) was changed to 25% by weight.

When a printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, a decrease in image saturation was observed. It is considered that this is because the effect of white turbidity appears because the amount of TiO ₂ particles added is too large.

Comparative Example 6 Toner 1 of Example 1 described above
As white conductive fine particles in (yellow toner) and toner 6 (cyan toner), needle-like TiO ₂ fine particles having a major axis of 1 μm or more and a minor axis diameter of 0.1 μm or less are 30 wt% of the entire TiO ₂ fine particles. A green toner of Comparative Example 6 was manufactured in exactly the same manner as in Example 1 except that 5% by weight of white conductive fine particles were added.

A printing test was conducted on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. Stable and initially got a turquoise image,
Gradually, the image became a greenish image with a strong yellow tint.

Further, when the printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to the decrease of the image density, and it is clear that the toner has low development stability and color tone stability. is there. It is considered that this is because the amount of TiO ₂ fine particles having a large aspect ratio is small, so that the fine particles are insufficiently contacted with each other and the electric resistance is not sufficiently reduced.

Comparative Example 7 Toner 1 of Example 1 described above
As the white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the volume resistivity is 70Ω.
cm, a spherical SnO ₂ (SN-
A green toner of Comparative Example 7 was prepared in exactly the same manner as in Example 1 except that 100 P; Ishihara Sangyo's trade name) was used in an amount of 8% by weight.

A printing test was performed on 10 sheets of this green toner using a two-component developer as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. Stable and initially got a turquoise image,
Gradually, the image became a greenish image with a strong yellow tint.

Further, when printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to a decrease in image density, and it is clear that the toner has low development stability and color tone stability. is there. This is the comparative example 3 described above.
Similarly, regardless of the material of the white conductive fine particles, it is considered that sufficient conductivity cannot be obtained when the aspect ratio is small.

(Comparative Example 8) Toner 1 of Example 1 described above
The volume specific resistance of the white conductive fine particles in (yellow toner) and toner 6 (cyan toner) is 0.08.
A green toner of Comparative Example 8 was produced in exactly the same manner as in Example 1 except that 5% by weight of Ω · cm TiO ₂ particles was added.

When a printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, image defects such as fogging occurred. It is considered that this is because the white electrically conductive fine particles have too low a volume specific resistance, so that the charging property of the toner is lowered.

Comparative Example 9 Toner 1 of Example 1 described above
(White toner) and toner 6 (cyan toner) have white specific resistance of 200Ω as white conductive fine particles.
A green toner of Comparative Example 9 was manufactured in exactly the same manner as in Example 1 except that 5% by weight of TiO ₂ fine particles of cm was added.

A printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. Stable and initially got a turquoise image,
Gradually, the image became a greenish image with a strong yellow tint.

Further, when printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to a decrease in image density, and it is clear that the toner has low development stability and color tone stability. is there. It is considered that this is because the volume specific resistance of the white conductive fine particles is too high, and sufficient conductivity as a toner cannot be obtained.

The results of Examples 6 to 9 and Comparative Examples 3 to 9 are summarized in FIG. Referring to FIG. 3, judging from the results shown in FIG. 3, Example 6 and Comparative Example 7
From the comparison with Example 1 and Comparative Example 3 described above, it is considered that the effect of adding the white conductive fine particles does not depend on the material but on the volume resistivity and shape thereof.

From the comparison between Examples 7 and 8 and Comparative Example 3, it is considered that the lower limit of the aspect ratio of the white conductive fine particles is 10, and the upper limit of the major axis diameter of the white conductive fine particles is 4 μm. Is considered to be.

Further, from the comparison between Example 7 and Comparative Example 5,
The upper limit of the amount of white conductive fine particles added is considered to be 20% by weight, and if it is added in excess of that amount, the problem of reduced saturation due to cloudiness becomes a problem.

From the comparison between Example 9 and Comparative Example 8,
The lower limit of the ratio of the white conductive fine particles having a large aspect ratio is considered to be 50% by weight, and if it is less than 50%, the decrease in conductivity becomes a problem.

From the comparison between each example and Comparative examples 8 and 9, the volume specific resistance of the white conductive fine particles is 1 to 100Ω.
.Cm is desirable, and when it is less than 1 .OMEGA.cm, the chargeability of the toner is lowered and an image defect such as fogging occurs.
If it exceeds 100 Ω · cm, the conductivity becomes insufficient.

Example 10 Toner 1 of Example 1 described above
As white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the amount of Sb ₂ O ₃ is SnO.
Example 1 except that 5% by weight of needle-like TiO ₂ fine particles having a major axis diameter of 1.7 μm and a minor axis diameter of 0.1 μm, the surface of which was coated with a conductive layer mixed with the amount of ₂ by 10% by weight, were added.
A green toner of Example 10 was manufactured in exactly the same manner as in.

A printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. As a result, a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

Example 11 Toner 1 of Example 1 described above
As white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the amount of Sb ₂ O ₃ is SnO.
Example 1 except that 5% by weight of acicular TiO ₂ fine particles having a major axis diameter of 1.7 μm and a minor axis diameter of 0.1 μm, the surface of which was coated with a conductive layer mixed in an amount of 25% by weight with respect to the amount of ₂ , were added.
A green toner of Example 11 was manufactured in exactly the same manner as in.

A printing test was performed on 10 sheets of this green toner using a two-component developer as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were investigated, and a vivid color tone was obtained. The image of was able to be obtained stably. In this case, the variation rate of the toner specific charge was within 20%.

Comparative Example 10 Toner 1 of Example 1 described above
As white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the amount of Sb ₂ O ₃ is SnO.
Example 1 except that 5% by weight of acicular TiO ₂ fine particles having a major axis diameter of 1.7 μm and a minor axis diameter of 0.1 μm, the surface of which was coated with a conductive layer mixed in an amount of 5% by weight with respect to ₂ , was added. A green toner of Comparative Example 10 was produced in exactly the same manner as in.

A printing test was performed on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were examined. Stable and initially got a turquoise image,
Gradually, the image became a greenish image with a strong yellow tint.

Further, when printing is continued, the toner is overcharged, and after about 100,000 sheets, it becomes a light green image due to a decrease in image density, and it is clear that the toner has low development stability and color tone stability. is there. This is because, in the case of the addition amount of about 5% by weight, if the mixing ratio of Sb ₂ O ₃ is too small, the volume resistivity of the white conductive fine particles does not decrease and the sufficient conductivity as a toner cannot be obtained. it is conceivable that.

Comparative Example 11 Toner 1 of Example 1 described above
As white conductive fine particles in (yellow toner) and toner 6 (cyan toner), the amount of Sb ₂ O ₃ is SnO.
Example 1 except that 5% by weight of acicular TiO ₂ fine particles having a major axis diameter of 1.7 μm and a minor axis diameter of 0.1 μm, the surface of which was coated with a conductive layer mixed in an amount of 40% by weight with respect to the amount of ₂ , were added.
A green toner of Comparative Example 11 was produced in exactly the same manner as in.

A print test was conducted on 10 sheets of this green toner using a two-component developer in the same manner as in Example 1 above, and the toner specific charge, the density of the printed image, and the saturation were investigated. Has decreased in saturation. It is considered that this is because the amount of Sb ₂ O ₃ in the conductivity that coats the surface of the white conductive fine particles is too large and the white conductive fine particles themselves become black, which adversely affects the color tone of the color toner.

FIG. 4 summarizes the above results. See FIG. 4 Judging from the results shown in FIG. 4, when the surface of the white conductive fine particles is coated with a conductive layer to reduce the amount of the white conductive fine particles added, the amount of Sb ₂ O ₃ of SnO ₂
The amount based on the amount of 10 to 25% by weight is suitable.
If it is less than 0% by weight, the conductivity becomes insufficient, while
If it exceeds 25% by weight, blackening occurs and the deterioration of saturation becomes a problem.

In the description of each of the above embodiments,
Although toners of three hues of yellow, magenta, and cyan and black toners are used in combination as color toners, color toners of a different hue system may be used. That is, for example, toners of hues such as green, blue, red, white, and gray may be combined.

Here, the detailed features of the present invention will be described again. (Supplementary Note 1) A color toner obtained by mixing two or more kinds of toner selected from a plurality of toners having different color tones, each of which is composed of at least a binder resin and a colorant, and contains two or more kinds of toner. A color toner for electrophotography, characterized in that the electroconductive color toner contains white conductive fine particles having at least one of different amounts or materials. (Supplementary Note 2) The ratio R _H / R _L between the resistance R _{H of the} toner having the highest resistance and the resistance R _{L of the} toner having the lowest resistance among the above two or more types of toner is set to less than 2.5. The color toner for electrophotography according to appendix 1, characterized by: (Supplementary Note 3) The mixing ratio of the white conductive fine particles is 20.
3. The color toner for electrophotography according to appendix 1 or 2, characterized in that the content is at most% by weight. (Supplementary Note 4) The electrophotographic color toner according to any one of Supplementary Notes 1 to 3, wherein the white conductive fine particles have an aspect ratio of 10 or more and a major axis diameter of 4 μm or less. (Supplementary Note 5) The white conductive fine particles have an electric resistance of 1 to
The color toner for electrophotography according to any one of appendices 1 to 4, which has a resistance of 100 Ω · cm. (Supplementary Note 6) The white conductive fine particles are ZnO, TiO.
₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , M
6. The color toner for electrophotography according to any one of appendices 1 to 5, which is a metal oxide of any one of gO, BaO, MoO ₃ , and WO. (Supplementary Note 7) The white conductive fine particles are TiO ₂ particles, and have a major axis diameter of 1 μm or more and a minor axis diameter of 0.1 μm.
The following TiO ₂ particles m of the total TiO ₂ particles 50 wt%
The electrophotographic color toner according to appendix 6, which is the above. (Supplementary Note 8) The white conductive fine particles are SnO ₂ and S.
8. The color toner for electrophotography according to appendix 7, which is TiO ₂ particles having a conductive layer made of b ₂ O ₃ on the surface. (Supplementary Note 9) The amount of Sb ₂ O ₃ relative to SnO ₂ is
10 to 25% by weight, The electrophotographic color toner according to appendix 8. (Supplementary Note 10) The white conductive fine particles are SnO ₂ particles, and have a major axis diameter of 1 μm or more and a minor axis diameter of 0.1.
7. The color toner for electrophotography according to appendix 6, wherein the SnO ₂ particles having a particle size of μm or less accounts for 50% by weight or more of the entire SnO ₂ particles. (Supplementary Note 11) The SnO ₂ particles, electrophotographic color toners of Appendix 10, wherein it is a SnO ₂ particles having a conductive layer made of Sb ₂ O ₃ on the surface. (Supplementary Note 12) In any one of supplementary notes 1 to 11, wherein the hue of the toner having a different color tone is selected from the group consisting of yellow, magenta, cyan, black, green, blue, red, white, and gray. The described color toner for electrophotography. (Supplementary Note 13) A toner cartridge which is set and used in an image forming apparatus for fixing a color toner image onto a recording medium, and stores the electrophotographic color toner according to any one of Supplementary Notes 1 to 12. Toner cartridge characterized by having. (Supplementary Note 14) An image forming apparatus in which color toner image fixing is performed on a recording medium, wherein the electrophotographic color toner according to any one of Supplementary Notes 1 to 12 is used. .

[0129]

According to the present invention, when two or more kinds of toner selected from a plurality of color toners and black toners are mixed to form a developer, the material of the white conductive particles to be added to each toner. Alternatively, since the electric resistance of each toner is made substantially equal by controlling the addition amount, the mixed toner is consumed evenly and a stable printed image can be obtained.
As a result, it greatly contributes to the spread of high-quality image forming apparatuses.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a schematic configuration of a two-component developing type image forming apparatus.

FIG. 2 is a print evaluation result R in the embodiment of the present invention.
It is explanatory drawing of _H / _RL ratio dependence.

FIG. 3 is an explanatory diagram of a shape and an addition amount dependency of white conductive fine particles in a print evaluation result in the embodiment of the present invention.

FIG. 4 is an explanatory diagram of Sb ₂ O ₃ ratio dependency in a coating layer of a print evaluation result in the embodiment of the present invention.

[Explanation of symbols]

10 photoconductor 20 charger 30 exposure means 40 developing means 41 developer container 43 Developing roller 45 toner hopper 50 transfer device 60 cleaner 70 Static eliminator 80 Flash fixer 81 xenon flash lamp

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Katsuharu Hu             4-1, Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 1 within Fujitsu Limited F-term (reference) 2H005 AA06 AA21 CB07 CB13 EA01                       EA10

Claims (5)

[Claims] 1. A color toner obtained by mixing two or more kinds of toner selected from a plurality of toners having different color tones, which are composed of at least a binder resin and a colorant, and the two or more kinds of toner are A color toner for electrophotography, characterized in that it contains white electroconductive fine particles having at least one of content and / or material different from each other. 2. The ratio R _H / R _L of the resistance R _{H of the} toner having the highest resistance and the resistance R _{L of the} toner having the lowest resistance of the two or more types of toner is less than 2.5. The color toner for electrophotography according to claim 1, wherein 3. The color toner for electrophotography according to claim 1, wherein the white conductive fine particles have an aspect ratio of 10 or more and a major axis diameter of 4 μm or less. 4. The white conductive fine particles are ZnO, Ti.
O ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ ,
The color toner for electrophotography according to any one of claims 1 to 3, which is a metal oxide of any one of MgO, BaO, MoO ₃ , and WO. 5. The color toner for electrophotography according to claim 4, wherein the white conductive fine particles are TiO ₂ particles having a conductive layer made of SnO ₂ and Sb ₂ O ₃ on the surface.