JP2003241434A - Electrophotographic cyan toner and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic cyan toner which realizes both of formation of a high density image and a wide range of color reproduction and which is also excellent in light transmitting property. <P>SOLUTION: The electrophotographic cyan toner comprises at least a binder resin and a coloring cyan pigment and has 3 to 10 μm volume average particle size D<SB>50</SB>. When a deposition amount M<SB>0</SB>of the toner in a single layer formed on the surface of a transfer medium is defined by preliminarily determined formula, the toner satisfies: 0.015≤(C×M<SB>0</SB>)≤0.05 with respect to the product (C×M<SB>0</SB>) of the concentration C of the coloring cyan pigment and the toner deposition amount M<SB>0</SB>; 0.95≤X<SB>(1.5)</SB>/X<SB>(0.5)</SB>, wherein X<SB>(1.5)</SB>and X<SB>(0.5)</SB>represent chroma X when the toner deposition amount in a transferred toner solid part is 1.5M<SB>0</SB>and 0.5M<SB>0</SB>, respectively; and 0.60≤L*<SB>(1.5)</SB>/L*<SB>(0.5)</SB>, wherein L*<SB>(1.5)</SB>and L*<SB>(0.5)</SB>represent lightness index L* when the toner deposition amount in a transferred toner solid part is 1.5M<SB>0</SB>and 0.5M<SB>0</SB>, respectively. <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 one-component developing device or a two-component developing device used for developing an electric latent image or a magnetic latent image in an image forming apparatus such as an electrophotographic copying machine and a printer. Color toner, especially cyan toner, and a method for producing the same.

[0002]

2. Description of the Related Art The electrophotographic image forming technology was a black and white image with black toner at the beginning of its development, but in response to the progress of digital processing technology of image information, full color image formation is progressing. It is used to create proposals and presentation materials such as OHP (Over Head Projector).

However, it is difficult to say that the image quality of a full-color electrophotographic image is comparable to that of a printed image, and further higher image quality is desired. Conventionally, as one approach for improving the image quality of a full-color electrophotographic image, an attempt has been made to increase the pigment concentration in order to make the image high concentration, but by increasing the pigment concentration, the toner composition is increased. There are problems that the pigments are likely to aggregate, the charging performance of the toner is deteriorated, and the saturation and the color reproduction range are reduced due to diffuse reflection of light due to the aggregated pigments.

Under such circumstances, prior arts that attempt to improve the image quality of full-color electrophotographic images include, for example, Japanese Patent Laid-Open Nos. 9-114127 and 11-338.
There are 190 publications and the like.

Japanese Unexamined Patent Publication No. 9-114127 discloses that by optimizing the toner particle size, pigment content and toner adhesion amount, both high image quality and developability can be achieved. Further, Japanese Patent Laid-Open No. 11-338190 discloses that good translucency and color reproducibility can be obtained by limiting the lightness and saturation of a color toner containing an oil-soluble dye to a specific range.

[0006]

However, the above-mentioned prior art has the following problems. JP-A-9-1
In the technology disclosed in Japanese Patent No. 14127, the toner particle size,
Although it is possible to obtain a high-density image by optimizing the pigment content and the toner adhesion amount, there is a problem that a decrease in saturation and a decrease in the reproduction range of secondary colors cannot be avoided. In the technique disclosed in Japanese Patent Application Laid-Open No. 11-338190, no consideration is given to the change in hue during image formation, and since a dye-based coloring agent is used, light resistance is poor and sufficient coloring power can be obtained. There is a problem such as not.

When an image is formed using a conventional color toner, since the content of the colorant is low, the toner layer must be thickened to obtain a desired image density. There is a problem in that an electrophotographic image in which the granular feeling of the toner remains, as compared with the lithographic printing image. As a result of earnest studies to improve such problems, the present inventors have found that in image formation using a color toner having a high pigment concentration, a high dispersion treatment of the pigment in the toner composition is performed to form a granular toner. The present invention has been achieved based on the finding that it is possible to improve the concealment of feeling and to form a high-density image and a wide color reproduction range at the same time.

An object of the present invention is to provide a cyan toner for electrophotography which is capable of forming a high density image and a wide color reproduction range at the same time and is excellent in translucency, and a method for producing the same.

[0009]

The present invention has at least the following conclusions.
Containing a resin and a cyan pigment for coloring, and having a volume average particle diameter D ₅₀
Odor of cyan toner for electrophotography whose size is 3 to 10 μm
Layer is formed on the surface of the transfer medium onto which the toner is transferred.
The toner adhesion amount is given by the following formula (1),     M₀[Mg / cm²] = (1-ε) ・ (4/3) ・ (D₅₀/ 2) ρ ... (1) Here, ε: in a toner single-layer formed image in a square arrangement
Porosity on two-dimensional plane (= 0.215) ρ: True specific gravity of toner The cyan pigment concentration C for coloring satisfies the following formula (2),       0.015 ≦ C ・ M₀≤0.05 (2)     Where 0 <C <1     C = (parts by weight of pigment in toner composition) / (total parts by weight of all toner compositions) The saturation X given by the following equation (3) is related to the following equation (4).
Satisfied the clerk,       X = (a^{* 2}+ B^{* 2})^1/2                                 … (3)     Where a^*, B^*: Chromaticity index       (X_(1.5)/ X_(0.5)) ≧ 0.95 (4) Where X_(1.5): Toner adhesion amount is 1.5M₀Is
Mushroom saturation X_(0.5): Toner adhesion amount is 0.5M₀Saturation when Lightness index L specified in Japanese Industrial Standard Z8729^*Is below
Electrophotography characterized by satisfying the relation of expression (5)
Cyan toner for use.       (L^* _(1.5)/ L^* _(0.5)) ≧ 0.60 (5) Where L^* _(1.5): Toner adhesion amount is 1.5M₀Is
Lightness index when L^* _(0.5): Toner adhesion amount is 0.5M₀Ming when
Degree index

According to the present invention, the volume average particle diameter D of the toner is
₅₀ , the saturation C and the lightness index L so that the concentration C of the cyan pigment for coloring and the toner adhesion amount M ₀ in the toner composition are in the optimum ranges and the toner adhesion amount increases when forming the image layer. Design cyan toner for electrophotography so that the deterioration of ^* is within a certain range. As a result, in full-color electrophotographic image formation, it is possible to obtain excellent image quality with high density and excellent reproduction of intermediate tones and a wide color reproduction range.

Further, the present invention is characterized in that the concentration C of the coloring cyan pigment is 4 to 20% by weight.

According to the present invention, since the concentration C of the cyan pigment for coloring is selected within a suitable range, it is possible to form a high-concentration image which is excellent in translucency and concealment of toner graininess, and is wide. A cyan toner for electrophotography having a color reproduction range and excellent fixability is realized.

In the present invention, the cyan pigment for coloring is
C. I. Pigment Blue 15: 3 or 15: 4 phthalocyanine pigment.

According to the present invention, the cyan pigment for coloring includes
C. I. Since a phthalocyanine pigment of Pigment Blue 15: 3 or 15: 4 is used, a high quality and stable quality image can be obtained.

Further, the invention is characterized in that the binder resin is a polyester resin or a polyether polyol resin.

According to the present invention, since the polyester resin or the polyether polyol resin is used as the binder resin, it is possible to obtain the electrophotographic cyan toner excellent in the translucency and the secondary color reproducibility.

According to the present invention, the volume resistance value is 10 ¹¹ Ω · c.
It is characterized by being m or more. According to the present invention, since the electrophotographic cyan toner retains a high volume resistance value, the amount of charge does not decrease and toner scattering and image fog are suppressed.

Further, according to the present invention, a first kneading roll having heating means and spirally forming grooves on the outer peripheral surface thereof, and a second kneading roll having cooling means and spirally forming grooves on the outer peripheral surface thereof. And arranging the first kneading roll and the second kneading roll so that a gap is formed by the outer peripheral surfaces facing each other and their axes are parallel to each other in the same plane. The roll and the second kneading roll are rotated about their axes by providing a peripheral speed difference in different directions,
Glass transition temperature T of the main component resin that constitutes the binder resin
Melt kneading dispersion treatment is carried out by passing a mixture containing at least a binder resin and a cyan pigment for coloring through a gap formed by the first and second kneading rolls at a temperature not more than 2 times g. And a method for producing a cyan toner for electrophotography.

According to the present invention, the mixture containing at least the binder resin and the cyan pigment for coloring passes through the gap between the first and second kneading rolls which rotate about the axis in different directions, respectively, whereby a high shearing force is exerted. It is kneaded while receiving. The temperature of the mixture when kneading is 2 times the glass transition temperature Tg of the main resin constituting the binder resin.
It is kept at a low temperature of less than double. By kneading the mixture as described above, the coloring cyan pigment contained in a high concentration can be uniformly and highly dispersed in the binder resin, and thus the high concentration, a wide color reproduction range and the light transmitting property are excellent. It is possible to produce an electrophotographic cyan toner capable of forming an image.

Further, the present invention is characterized in that the melt-kneading dispersion treatment is carried out after the preliminary dispersion treatment of previously dispersing the coloring cyan pigment in the binder resin.

According to the present invention, a preliminary dispersion treatment for preliminarily dispersing the coloring cyan pigment in the binder resin by a treatment such as masterbatch or flashing is carried out, and then the melt-kneading dispersion treatment is carried out. It becomes possible to disperse the pigment in the binder resin more uniformly and highly.

Further, the present invention comprises a visible image forming means for forming a visible image on a recording medium and a conveying means for conveying the recording medium, the visible image forming means having the developing unit containing the cyan toner for electrophotography described above. An image forming apparatus including the above.

According to the present invention, the developing unit provided in the visible image forming means contains the electrophotographic cyan toner, and the electrophotographic cyan toner is used for developing the image.
High-quality image formation can be realized.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION To reproduce each color in a full-color electrophotographic image, three colors of yellow (Y) toner, magenta (M) toner and cyan (C) toner are used, and these toners should be mixed. Each color is represented by. However, since it is difficult to reproduce black with the above-mentioned three colors, black (B) toner is generally used for expressing black.

In a full-color electrophotographic image, a wide color reproduction range including halftones controls not only the toner image forming method and the toner adhesion amount, but also the toner hue, saturation X and lightness index L ^*. It is realized by doing.

The cyan toner for electrophotography (hereinafter simply referred to as cyan toner) according to the embodiment of the present invention is
It contains at least a binder resin and a cyan pigment for coloring, has a volume average particle diameter D _{50 of 3} to 10 μm, and gives a toner adhesion amount which is further formed on the surface of a transfer medium on which the toner is transferred, given by the following formula (1). is ^{_{time, M 0 [mg / cm 2}} ] = (1-ε) · (4/3) · (D 50/2) ρ ... (1) where, epsilon: the toner 1 layer forming images in square arrangement Porosity on two-dimensional plane (= [(2r) ² −πr ² ] / (2r) ² = 0.2
15 r: Radius of toner particles) ρ: Cyan pigment concentration C for coloring true specific gravity of toner satisfies the following expression (2), and the saturation X given by the following expression (3) has a relationship of the following expression (4). And the lightness index L ^* specified in Japanese Industrial Standard Z8729 satisfies the relationship of the following expression (5). 0.015 ≦ C · M ₀ ≦ 0.05 (2) where 0 <C <1 C = (concentration of pigment in toner composition) / (total part by weight of all toner compositions) X = (a ^{* 2} + b ^{* 2} ) ^1/2 (3) where a ^* , b ^* : chromaticness index (X _(1.5) / X _(0.5) ) ≥ 0.95 (4) where X _{(1.5 )} : Saturation when toner adhesion amount is 1.5M ₀ X _(0.5) : Saturation when toner adhesion amount is 0.5M ₀ (L ^* _(1.5) / L ^* _(0.5) ) ≧ 0.60 (5) where L ^* _(1.5) : Lightness index when the toner adhesion amount is 1.5M ₀ L ^* _(0.5) : When the toner adhesion amount is 0.5M ₀ Brightness index of

The toner adhesion amount M defined by the above formula (1) is defined as the adhesion amount of the solid portion formed by the monochromatic toner such as the cyan toner adhered on the transfer medium by the development according to the present embodiment. _A sufficient image density can be obtained by designing it to be about 1.5 times ₀ . Further, the portion where the image density is low is generally about 0.5 times the toner adhesion amount M ₀ . Therefore, the saturation X and the lightness index L ^* of the developed image with cyan toner are
By designing the development amount to be a desired value in the range of 1.5M ₀ to 0.5M ₀ , it is possible to realize high quality of a developed image.

The reasons for limiting each range in designing the cyan toner of this embodiment will be described below.

When (X _(1.5) / X _(0.5) ) is less than 0.95 and (L ^* _(1.5) / L ^* _(0.5) ) is less than 0.60, the toner layer formed by development is light-sensitive. Since it is not possible to secure a sufficient transmission and absorption characteristic, it is not possible to secure a desired hue and color reproduction width, and the color developability is also poor. Further, there is a possibility that the gradation in the halftone portion may not be obtained due to the hue change during image formation. Therefore, (X _(1.5) / X _(0.5) ) ≧ 0.95 and (L ^* _(1.5) / L ^* _{( 0.5)} ) ≧ 0.60.

If the product C · M ₀ of the concentration C of the coloring cyan pigment and the toner adhesion amount M ₀ is less than 0.015, a sufficient image density cannot be obtained, which is desired due to the influence of the transfer medium. Cannot secure the color gamut of. Further, the graininess of the toner cannot be sufficiently hidden. If it exceeds 0.05, the toner layer formed by development cannot secure sufficient light transmission / absorption characteristics, so that a desired hue and color reproduction range cannot be secured. Therefore, 0.015 or more and 0.05 or less.

The range of the L ^* a ^* b ^* color system (CIE1976) (CIE: International Commission on Illumination) of the solid portion of the cyan toner is such that the lightness index L ^* is 30 or more, preferably 40 or more, The chromaticity index a ^* is minus (−) 10 or less and the b ^* is −40 or less. The saturation X is 50 or more, preferably 60 or more. However, the chromaticness indices a ^* and b ^* are not limited to the above-mentioned numerical values because it is necessary to consider the balance with other colors of magenta and yellow.

Further, the desirable spectral reflection characteristic of the solid portion by the cyan toner is such that the reflectance at the maximum reflection wavelength is 40% or more, preferably 60% or more, and the reflectance at the maximum absorption wavelength is 10% or less, preferably 5. % Or less.

The volume average particle diameter D ₅₀ of the cyan toner is 3 to 10 μm, preferably 5 to 8 μm as described above. If it is less than 3 μm, the individual toner particles cannot have sufficient chargeability, and toner scattering and image fog occur during the developing operation. If it exceeds 10 μm, the toner layer of the image formed by development becomes thicker,
It becomes difficult to hide the graininess of the toner. Therefore, it is set to 3 μm or more and 10 μm or less.

The particle size distribution of cyan toner is from 3 to
It is better to have a higher ratio belonging to the range of 10 μm,
Even those having a particle size distribution which can be obtained by an ordinary pulverization method can be used. However, with respect to the volume average particle diameter D ₅₀ , it is desirable that particles of 0.5 × D ₅₀ or less are 20 pop% or less and particles of 2 × D ₅₀ or more are 2 vol% or less.

Cyan pigments for coloring are C.I. I. Pigment Blue 15: 3 or 15: 4 phthalocyanine pigment, and the concentration C of the colored cyan pigment in the cyan toner composition is C.
Is 4 to 20% by weight. Although phthalocyanine pigments that are widely used generally have α-type and β-type, they are chemically and thermally stable β-type C.I. I. By using Pigment Blue 15: 3 or 15: 4, it is possible to realize uniform color reproduction and suppress pigment aggregation to obtain a high dispersion state.

When the concentration C of the coloring cyan pigment in the cyan toner composition is less than 4% by weight, the light-transmitting property is good, but the concealing property of toner graininess is not sufficient, and a uniform high-density image is obtained. I can't. If it exceeds 20% by weight, the saturation X and the lightness index L ^* are insufficient, so that a sufficient color reproduction area cannot be secured, and the fixing strength is deteriorated due to a relative decrease in the binder resin content. Come on. Therefore, it is set to 4% by weight or more and 20% by weight or less.

Examples of the binder resin include styrene resins such as polystyrene and polystyrene-acrylic acid ester copolymers, vinyl chloride resins, phenol resins, epoxy resins, polyester resins, polyether polyol resins, polyurethane resins and polyvinyl butyral resins. One or more selected from the group may be used. However, since the polyester resin or the polyether polyol resin is excellent in thermal properties such as resin elasticity, it is desirable to use them as the binder resin.

The cyan toner containing at least a binder resin and a coloring cyan pigment has a volume resistance value of 10 ¹¹ Ω.
cm or more. When the concentration C of the cyan pigment for coloring in the cyan toner composition is increased to increase the density of the image, the content of the conductive substance in the cyan toner composition is increased. The value will be reduced. However, as will be described later in detail, the formation of conductive paths in the cyan toner composition can be suppressed by sufficiently dispersing the coloring cyan pigment in the binder resin. It is possible to increase the volume resistance and maintain a high volume resistance value. When the volume resistance value of cyan toner is less than 10 ¹¹ Ω · cm,
Since image fog and the like may occur due to a decrease in the amount of charge, it is set to 10 ¹¹ Ω · cm or more.

The cyan toner of the present embodiment may contain other additives such as a charge control agent, waxes or external additives in addition to the cyan pigment for coloring and the binder resin. As the charge control agent used for color toners such as cyan toner, it is desirable to use a colorless one such as a quaternary ammonium salt if it has a positive charge property and a metal salt of alkylsalicylic acid if it has a negative charge property. .

Examples of waxes include synthetic waxes such as polyethylene and polypropylene, natural waxes such as carnauba wax and rice wax, silicone-based waxes, higher fatty acids,
Polyolefin type and low molecular weight polymers are preferably used.

Inorganic fine powders such as silica fine powder, titanium oxide fine powder, and alumina fine powder are preferably used as the external additive added for the purpose of adjusting the charge and adjusting the surface resistance. These inorganic fine powders include silicone varnishes, various modified silicone varnishes, silicone oils, various modified silicone oils, silane coupling agents, silane coupling agents having a functional group, and other organic silicons for the purpose of hydrophobizing and controlling electrostatic properties. It may be treated with a treating agent such as a compound.

As other additives, for example, polytetrafluoroethylene, zinc stearate zinc, polyvinylidene fluoride, silicone oil particles (about 40%) can be used as a lubricant.
(Containing silica) are preferably used, and as the developability improver, white fine particles having a polarity opposite to that of the toner particles are used.

FIG. 1 is a perspective view showing a simplified structure of a kneading / dispersing apparatus 1 which is preferably used in a cyan toner manufacturing method according to another embodiment of the present invention. The kneading / dispersing apparatus 1 includes a heating means 2 and a first kneading roll 4 in which a plurality of grooves 3 are spirally formed on the outer peripheral surface, and a cooling means 5.
And a plurality of grooves 6 are spirally formed on the outer peripheral surface of the second
And a kneading roll 7.

The first and second kneading rolls 4 and 7 have a substantially rectangular parallelepiped outer shape and a first side wall 9 of a casing 8 which is a hollow container having an opening on only one surface, and a second side wall facing the first side wall 9.
The inner surface of the side wall 10 is rotatably supported by a bearing (not shown). At this time, the first kneading roll 4 and the second kneading roll 7 are arranged such that a gap is formed between the outer peripheral surfaces facing each other and the respective axes are parallel to each other in the same plane.

The first and second kneading rolls 4 and 7 are connected to driving means such as an electric motor through gears and the like.
As a result, the first kneading roll 4 and the second kneading roll 7 can rotate around the axis in different directions, that is, opposite directions shown by the arrow 11 and the arrow 12.

The heating means 2 provided in the first kneading roll 4 is
A first supply source 15 for supplying hot water or hot oil, which is a heating medium for heating the first kneading roll 4, pipe lines 16a, 16b for supplying the heating medium, and a pipe line 16
Flow rate adjusting valve 1 provided in a for adjusting the supply amount of the heating medium
7, a heater 19 provided in the first supply source 15 for heating the heating medium, and a temperature sensor 1 for detecting the temperature of one end 51 of the first kneading roll 4, which is a supply side of a mixture to be described later.
3a and the temperature sensor 13b for detecting the temperature of the other end 52 on the discharge side of the mixture, and the temperature sensors 13a, 13
In response to the detection output of b, the energization of the heater 19 is o
a first controller 14 for controlling the n-off.

A liquid-tight space is formed inside the first kneading roll 4, a supply port and a discharge port for the liquid-tight space are further formed, a pipe line 16a is connected to the supply port, and a pipe line 1 is connected to the discharge port.
By connecting 6b, the first kneading roll 4 can be heated by the configuration of the heating means 2 described above. The temperature sensors 13a and 13b may be of a contact type or a non-contact type such as a radiation thermometer, and the first control power supply 14 operates in response to the detection output of the temperature sensors 13a and 13b. 1 One end 51 of the kneading roll 4
And, it becomes possible to maintain the temperature of the other end portion 52 at a desired value.

The cooling means 5 provided in the second kneading roll 7 is
A second supply source 53 for supplying a cooling medium, such as water, for cooling the second kneading roll 7, pipe lines 54a, 54b for supplying the cooling medium, and a supply amount of the cooling medium provided in the pipe line 54a are adjusted. Flow rate adjusting valve 55 and a coolant 56 provided in the second supply source 53 for cooling the cooling medium.
A temperature sensor 59a for detecting the temperature of one end 57 of the second kneading roll 7 and a temperature sensor 59b for detecting the temperature of the other end 58, and the operation of the coolant 56 in response to the detection outputs of the temperature sensors 59a, 59b. And a second control device 60 for controlling the.

Similar to the first kneading roll 4, a liquid-tight space is formed inside the second kneading roll 7, a supply port and a discharge port for the liquid-tight space are formed, and a pipe line 54a is connected to the supply port. By connecting the pipe line 54b to the discharge port,
The second kneading roll 7 can be cooled by the configuration of the cooling means 5 described above. By the operation of the second controller 60 in response to the detection output of the temperature sensors 59a and 59b,
The temperatures of the one end 57 and the other end 58 of the second kneading roll 7 can be maintained at desired values.

A mixture containing at least a binder resin and a cyan cyan pigment is supplied from, for example, a charging device 18 in the vicinity of the gap formed by the first and second kneading rolls 4 and 7. The first and second kneading rolls 4 and 7 that rotate about their axes with peripheral speed differences in opposite directions are provided with the feeding device 1 by the grooves 3 and 6 formed on the outer peripheral surface, respectively.
The mixture supplied from 8 is kneaded while applying high shear stress.

By the first kneading roll 4 and the second kneading roll 7, the mixture is supplied from one side of the first and second kneading rolls 4 and 7 indicated by the arrow 61 to the discharge side which is the other side. The cyan pigment for coloring is dispersed in the binder resin because the coloring cyan pigment is repeatedly subjected to a shearing action during the process of sequentially compressing, melting, and uniformly dispersing while being conveyed in the direction toward.
At this time, by controlling the temperature of the first kneading roll 4, the temperature of the mixture is maintained at twice the glass transition temperature Tg of the main component resin constituting the binder resin, that is, the polyester resin or the polyether polyol resin. It In addition, the mixture subjected to the melt-kneading dispersion treatment is indicated by arrow 6
It is discharged from the gap between the first and second kneading rolls 4 and 7 in the direction indicated by 2.

As described above, the temperature is controlled so that the viscosity of the binder resin in the molten state during the kneading / dispersing process does not decrease too much, and the melt-kneading / dispersing process is performed while applying high shear stress to the mixture. Even when the content of the coloring cyan pigment in the product is large, the coloring cyan pigment can be uniformly and highly dispersed in the binder resin. The cyan toner in which a high content cyan pigment for coloring is uniformly and highly dispersed in a binder resin enables high-density image formation with a wide color reproduction range and excellent light-transmitting properties.

The kneading / dispersing apparatus includes, for example, TEM-
100B (manufactured by Toshiba Machine Co., Ltd.), PCM-65 / 87
An open roll type one such as a uniaxial or biaxial extruder such as (made by Ikegai Co., Ltd.) or Needix (made by Mitsui Mining Co., Ltd.) is preferably used.

The cyan pigment for coloring is preliminarily dispersed in a binder resin or a colorless resin different from the binder resin by, for example, masterbatch or flashing, and then mixed with the binder resin. Melt kneading dispersion treatment can also be performed. For example, 20 to 60% by weight of a dry coloring cyan pigment and 40 to 80% by weight of a binder resin or a colorless resin different from the binder resin are heated and kneaded under pressure, or a cyan pigment paste 30 for water-containing coloring is used.
˜80 wt% and a binder resin or 20-70 wt% of a colorless resin different from the binder resin are heated and kneaded under pressure to carry out a preliminary dispersion treatment for dispersing the pigment in the resin, such as a treatment for removing water. After that, a mixture containing at least the obtained pigment dispersion and a predetermined binder resin is melt-kneaded and dispersed. This makes it possible to disperse the coloring cyan pigment in the binder resin more uniformly and highly, and thus it is possible to obtain a cyan toner excellent in coloring power and translucency.

The mixture containing at least the binder resin and the cyan pigment for coloring is preliminarily dispersed by dry-mixing additives such as a charge control agent, waxes and a dispersant with a mixer or the like, and then You may perform melt-kneading dispersion processing. Henschel mixers (manufactured by Mitsui Mining Co., Ltd.), super mixers (manufactured by Kawata Co., Ltd.), mechano-mills (manufactured by Okada Seiko Co., Ltd.), and Ong Mills (Hosokawa Micron Co., Ltd.) Made),
A hybridization system (manufactured by Nara Machinery Co., Ltd.), a cosmo system (manufactured by Kawasaki Heavy Industries, Ltd.) and the like can be preferably used.

The mixture that has been melt-kneaded and dispersed is pulverized to produce toner particles. For the crushing process,
A collision type air flow crusher using a jet air flow or a mechanical crusher can be used. The toner particles after pulverization are classified by, for example, wind force so as to have the desired particle size as described above.

The production of the cyan toner is not limited to the melt-kneading and dispersing treatment as described above, but it may be carried out by a suspension method of forming particles in an aqueous solution or a solvent, an emulsion aggregation method,
A so-called polymerization method such as an in-liquid drying method may be used.

FIG. 2 is a schematic sectional view showing a simplified structure of an image forming apparatus 20 according to still another embodiment of the present invention.

The image forming apparatus 20 is for forming a full-color electrophotographic image, and has four sets of visible image forming means 21B (black), 2 for forming a visible image on the recording paper 39.
1C (cyan), 21M (magenta), 21Y (yellow), a recording paper tray 31 for accommodating the recording paper 39, and a conveying means 32 for conveying the recording paper 39. The recording paper tray 31 is arranged on the most upstream side in the transport direction of the recording paper 39 shown by the arrow 33, and the recording paper 39 is placed and stored.
When forming an image, the recording paper 39 is separated and fed one by one. 4 sets of visible image forming means 21B, 21C, 2
1M and 21Y are provided along the transporting means 32 in this order from the upstream side to the downstream side in the transport direction of the recording paper 39 shown by the arrow 33.

Cyan toner visible image forming means 21C
Is the photoconductor 22, the charging roller 23, and the laser irradiation unit 2
4, a developing unit 25, a transfer roller 26, and a cleaning unit 27. The photoconductor 22 is rotatably provided on the body of the image forming apparatus 20, and an electrostatic latent image is formed on the surface thereof. The charging roller 23 is disposed so as to face the photoconductor 22, and uniformly charges the surface of the photoconductor 22. Laser irradiation unit 24
Laser-exposes the surface of the photoconductor 22 in accordance with image information to form an electrostatic latent image.

The developing section 25 is arranged to face the photoconductor 22 with a predetermined interval, and supplies the cyan toner of the present invention to the photoconductor 22 to develop the electrostatic latent image and visualize it. The transfer roller 26 is arranged to face the photoconductor 22 via an endless belt 34, which will be described later, and a bias voltage opposite to that of the toner is applied to the transfer roller 26 to form a toner image on the surface of the photoconductor 22 on the recording paper 39. Transfer to. After the toner image is transferred from the photoconductor 22 onto the recording paper 39, the cleaning unit 27 removes the toner remaining on the surface of the photoconductor 22 and cleans the surface of the photoconductor 22 in preparation for the next development. The other visible image forming means 21B, 21M, 21Y have the same configuration as the visible image forming means 21C except that the toner is different.

The conveying means 32 includes a driving roller 35, an idling roller 36, and an endless belt 34 stretched around the driving roller 35 and the idling roller 36 so as to be rotatable. The drive roller 35 is rotationally driven by an electric motor or the like around an axis line in the direction perpendicular to the plane of FIG. Although the idling roller 36 does not have a driving source, the rotational driving force of the driving roller 35 is transmitted by the endless belt 34, and is driven and rotated around the axis line in the same direction as the driving roller 35. The endless belt 34 stretched between the drive roller 35 and the idling roller 36 rotates in the direction indicated by the arrow 33 with the rotation of the drive roller 35, and electrostatically adsorbs the recording paper 39 for conveyance. To do.

Recording paper 39 after the transfer of the toner image is completed
Is separated from the endless belt 34 by the curvature formed in the driving roller 35 and is conveyed to the fixing unit 40. The fixing unit 40 includes a heating roller 41 and a pressure roller 42,
The recording paper 39 on which the toner image is transferred is nipped and conveyed between the heating roller 41 and the pressure roller 42 to perform the fixing process.

In the image forming apparatus 20, an image is formed as follows. The recording paper 39 fed one by one from the recording paper tray 31 is indicated by the arrow 3 by the endless belt 34.
It is transported in three directions. In the visible image forming means 21C, the surface of the photoconductor 22 is uniformly charged by the charging roller 23, and then the surface of the photoconductor 22 is laser-exposed by the laser irradiation unit 24 according to the image information to form an electrostatic latent image. Is formed. A cyan toner image is developed on the electrostatic latent image on the photoconductor 22 by the developing unit 25, and the visualized cyan toner image is transferred by a transfer roller 26 to which a bias voltage having a polarity opposite to that of the toner is applied. It is transferred onto the recording paper 39 on the endless belt 34.

On the recording paper 39, while being conveyed in the direction indicated by the arrow 33, toner of each color is applied by the other visible image forming means 21B, 21M and 21Y arranged along the conveying means 32. It is transcribed multiple times. After the transfer by the four sets of visible image forming means 21B, 21C, 21M, and 21Y is completed, the recording paper 39 is conveyed to the fixing section 40 and is pinched between the heating roller 41 and the pressure roller 42. Appropriate temperature and pressure are applied, the toner of each color is melted and fixed on the recording paper 39, and a robust image is formed.

In the image forming apparatus 20 of the present embodiment, the cyan toner of the present invention is used for developing an electrostatic latent image in the developing section 25 provided in the visible image forming means 21C, so that a high quality image is obtained. The formation can be realized.

(Examples) Examples of the present invention will be described below.

Example 1 In this example, a cyan toner was manufactured as follows. Both cyan toners
For the binder resin, the glass transition temperature Tg: 60 ° C., 1/2
A polyester resin having characteristics of a flow softening temperature Tm: 110 ° C. is used, and as a cyan pigment for coloring, C.I. I. Pigment Blue 15: 3 was used. The cyan pigment for coloring was used in the production of a cyan toner as a kneaded product (hereinafter referred to as a cyan kneaded product for convenience) which was pre-dispersed in a binder resin at a concentration of 40% by weight. A charge control agent was further added to the binder resin and the cyan kneaded product at the compounding ratio shown in Table 1 in a Henschel mixer and mixed for 10 minutes to prepare a mixture. The obtained mixture was melt-kneaded and dispersed with Kneedex MOS140-800 manufactured by Mitsui Mining Co., Ltd. Table 2 shows the conditions of the melt-kneading dispersion treatment. The temperature of the mixture during the melt-kneading / dispersion treatment was measured by an infrared non-contact thermometer, and as a result, for all cyan toners, 120
It was below ℃. That is, the glass transition temperature Tg of the polyester resin as the binder resin was not more than twice the glass transition temperature Tg of 60 ° C.

[0069]

[Table 1]

[0070]

[Table 2]

The mixture after the melt-kneading and dispersion treatment was cooled, roughly crushed, and then finely crushed by a jet crusher. After finely pulverizing, air classification was performed, and the volume average particle diameter D ₅₀ was 3 to 10 μm while confirming the particle size with a Coulter Multisizer II (manufactured by Beckman Coulter, Inc.), and 0.5 × D _50.
The following particles were adjusted so as to be a cyan toner powder having 20 pop% or less and 2 × D ₅₀ or more particles having a particle size distribution of 2 vol% or less.

100 parts by weight of the obtained cyan toner powder, and a hydrophobic silica fine powder (BET) surface-treated with a silane coupling agent and dimethyl silicone oil.
0.5 parts by weight of a specific surface area of 120 m ² / g) was mixed to prepare a cyan toner having negative triboelectricity.

By changing the cyan pigment concentration C for coloring and the volume average particle diameter D ₅₀ in producing the cyan toner, the sample samples 11 to 11 satisfying all the requirements of the present invention.
17 cyan toners and comparative example samples 61 and 62 cyan toners that do not satisfy any of the requirements of the present invention were obtained.
The true specific gravities ρ of the produced cyan toners were 1.1 g / cm ³ .

Each of the prepared cyan toners and a silicone-coated ferrite core carrier having an average particle size of 60 μm were adjusted and mixed so that the cyan toner concentration would be 5% by weight to prepare a two-component developer. . AR-C150 manufactured by Sharp Corporation is used as the image forming apparatus, and full-color dedicated paper (product number: PP1) manufactured by Sharp Corporation is used as the recording paper.
06A4C), each two-component developer prepared as described above was adjusted so as to have a predetermined toner adhesion amount of 1.5 M ₀ , and the same image was developed. After development, fixing processing was further performed using a separate fixing device to form an evaluation image to be used in the test. Using an X-Rite 938 spectrophotometric densitometer (manufactured by X-Rite), the chromaticity and the optical density indicating the image density of the evaluation image were measured.

The image quality is evaluated by color tone, image density and HAZ.
The evaluation was carried out by E value and comprehensive evaluation combining them.
The color tone uses the saturation X of the evaluation image as an evaluation index, and the saturation X is 5
A value of 0 or more was rated as good (◯), and a value of less than 50 was rated as bad (x).

A solid image formed on an OHP sheet with a toner of 1.5 M ₀ is fixed at a temperature of 170 ° C., and a haze meter (TC-HI) compliant with Japanese Industrial Standard K7105.
II type; manufactured by Tokyo Denshoku Co., Ltd., the Haze value defined by the formula (6) was measured, and the Haze value was used as an evaluation index of translucency and pigment dispersibility. The Haze value indicates that the smaller the value is, the more excellent the light-transmitting property is, and that the pigment is well dispersed. If the Haze value is less than 25, the quality is good, and if it is 25 or more, the quality is bad. Haze (%) = (amount of diffuse transmitted light / amount of total transmitted light) × 100 (6)

The results are shown in Table 3. In the example samples 11 to 17 satisfying the formula (2), the formula (4) and the formula (5) which are the requirements of the present invention, all of the color tone, the image density and the translucency are good, and the high density is obtained. And a high-definition image was obtained.

On the other hand, C · M ₀ = 0.100, which deviates the requirement of the formula (2) to the higher side, and (X _{( 1.5)} / X _(0.5) ) =
In Comparative Example Sample 61, in which 0.86 and (L ^* _(1.5) / L ^* _(0.5) ) = 0.53, which deviates from the above formulas (4) and (5) to the lower side, although the image density is high, The color tone and translucency were poor. In addition, (X _(1.5) / X _(0.5) ) is X
The ratio may be referred to as (L ^* _(1.5) / L ^* _(0.5) ) and may be referred to as the L ^* ratio. Further, C · M ₀ = 0.012, and the above formula (2)
The image density was low in the comparative sample 62 which deviated to the lower side.

[0079]

[Table 3]

(Example 2) C.I. I.
A cyan toner having a cyan pigment concentration C of 10% by weight and a volume average particle diameter D _{50 of} 6.5 μm was produced in the same manner as in Example 1 except that Pigment Blue 15: 4, 15: 1 was used. Then, using the produced cyan toners, the cyan toner concentration was adjusted to be 5% by weight and mixed to prepare a two-component developer. In this way, C.I. I. Pigment Blue 15: 4 as an example sample 18 and a cyan pigment for coloring as C.I. I. Pigment Blue 15: 1 and Comparative Example Sample 63 were obtained. The example sample 14 prepared in the example 1 together with the example sample 18 and the comparative example sample 63 was also subjected to the following test. In this example, three samples (denoted by suffixes a, b, and c) each having a different production lot were prepared from one example sample or comparative sample, and the cyan pigment for coloring was used as an image. The effect on quality stability was tested.

Using the same image forming apparatus and recording paper as in Example 1, the same evaluation image is formed by adjusting each two-component developer to a predetermined toner adhesion amount of 1.5M _0. did. Using the X-Rite 938 spectrophotometric densitometer as in Example 1, the saturation X was determined for the evaluation image.

The test results were evaluated as follows.
Saturation X is obtained for each sample of each two-component developer manufactured in different lots, and the average value Xav of the saturation X obtained in the three lots (a, b, c) and three lots (a, b, The saturation Xi (i
Is the difference ΔX (= Xi−Xav: this Δ
X is sometimes called the difference from the average value). When the absolute value of the difference ΔX from the average value is 0.5 or less, it is determined that the image stability is good, and when the absolute value of the difference ΔX of the average value exceeds 0.5, it is determined that the image stability is poor. did.

The test results are shown in Table 4. A cyan pigment for coloring is C.I. I. Pigment Blue 15: 4 was used as Example Sample 18 and a cyan pigment for coloring. I. Pigment Blue 15: 3 produced in Example Sample 14
Then, the absolute value of the difference ΔX from the average value was 0.3 or less, and good image stability could be obtained. On the other hand, C.I. I. In the comparative sample 63 manufactured using Pigment Blue 15: 1, the absolute value of the difference ΔX from the average value was more than 2.0, and the image stability was poor.

[0084]

[Table 4]

(Example 3) A glass transition temperature Tg = 60 ° C., a half flow softening temperature Tm = 110 ° C. was added to a binder resin.
Cyan pigment concentration for coloring C: 10% by weight, volume average particle diameter D ₅₀ : 6.5 μm, in the same manner as in Example 1 except that a styrene-butylmethacrylate resin having the above characteristics was used.
Comparative cyan sample 64 was obtained. Comparative sample 64 and example sample 14 prepared in Example 1
The effect of the binder resin on the light-transmitting property was tested with the cyan toner of No. 1 (in this example, the cyan toner before being adjusted to a two-component developer is also abbreviated as Example sample 14 for convenience). The test was conducted as follows. Each of the example sample 14 and the comparative example sample 64 was pressed and melted while being heated to prepare a thin film sample adjusted to have a thickness of 5 μm. The spectrophotometer U-3000 (manufactured by Hitachi, Ltd.) was used to measure the spectral transmittance (%) in the maximum transmission wavelength region of the thin film sample. The measured transmittance (%) is 88.
% Or more is said to have excellent translucency, and the transmittance (%) is 8
Those with less than 8% were evaluated as inferior in translucency.

The results are shown in Table 5. In the example sample 14 in which the polyester resin is used as the binder resin, the maximum transmission wavelength is 48
Although it has a transmittance of 91% at 5 nm and is excellent in translucency, the maximum transmittance wavelength of 490 is obtained in Comparative Example Sample 64 using styrene-butyl methacrylate resin as the binder resin.
The transmittance was only 82% in nm, which was the result of poor light transmission.

[0087]

[Table 5]

Example 4 The same procedure as in Example 1 was carried out except that a twin-screw extruder PCM-35 (manufactured by Ikegai Co., Ltd.) was used in the melt-kneading dispersion treatment, and the cyan pigment concentration C for coloring was C: 1.
A cyan toner having 0% by weight and a volume average particle diameter D _{50 of} 6.5 μm was manufactured to obtain a comparative example sample 65. The melt-kneading and dispersing treatment conditions of the twin-screw extruder are as follows: cylinder temperature 80 ° C., spindle speed 250 min ⁻¹ , mixture supply rate 10 kg / ho.
It was ur. The temperature of the mixture during the melting, kneading and dispersing treatment of Comparative Sample 65 was 128 ° C., which was measured by an infrared non-contact thermometer.

Also, a kneading / dispersing apparatus Kneedex MO
S140-800 (manufactured by Mitsui Mining Co., Ltd.), except that the supply side temperature of the first kneading roll was set to 70 ° C. and 80 ° C., the cyan pigment concentration C for coloring was C: 1 in the same manner as in Example 1.
A cyan toner having 0% by weight and a volume average particle diameter D _{50 of} 6.5 μm was manufactured, and Example sample 19 and Comparative example sample 66 were obtained. As a result of measuring the temperature of the mixture during this melt-kneading dispersion treatment with an infrared non-contact thermometer, it was 120 ° C. in Example sample 19 in which the supply side temperature of the first kneading roll was set to 70 ° C. It was 135 ° C. in Comparative Example Sample 66 in which the supply side temperature was set to 80 ° C. Example sample 14 made in Example 1 together with Example sample 19 and Comparative example samples 65 and 66 was also subjected to the following test.

In this example, Example samples 14 and 19 were used.
Also, the sample number indications of the comparative example samples 64 and 65 are used as a general name of each cyan toner manufactured under the above-described conditions and the two-component developer prepared by using each cyan toner.

The test was conducted as follows. The cyan toner indicated by each sample number was made to have a thickness of 5 μm in the same manner as in Example 3.
Prepare a thin film sample adjusted to m, and spectrophotometer U-300
The spectral transmittance (%) in the maximum transmission wavelength region of the thin film sample was measured by 0. The translucency was evaluated in the same manner as in Example 3.

Further, the cyan toner indicated by each sample number was pressed to form a pellet, and the volume resistance value of the pellet-like formed body was measured by a dielectric loss measuring device (manufactured by Ando Electric Co., Ltd.). The volume resistance value of 10 ¹¹ Ω · cm or more was evaluated as good.

The cyan toner indicated by each sample number and a silicone-coated ferrite core carrier having an average particle size of 60 μm were adjusted to a cyan toner concentration of 5% by weight and mixed by a ball mill to prepare two components. A developer was prepared. The cyan toner charge amount of each of the prepared two-component developers was measured by a blow-off charge amount measuring device (manufactured by Toshiba Chemical Co., Ltd.). Charge amount is 20 μc / g
Those having the above values were evaluated as good, and those having less than 20 μc / g were evaluated as poor.

Further, the two-component developers prepared as described above were used in the image forming apparatus AR-
When the cyan toner was scattered into the developing tank provided in C150 (manufactured by Sharp Corporation) and the two-component developer was stirred in the developing tank, it was visually observed whether or not the cyan toner was scattered from the surface of the developing sleeve. When no scattering of cyan toner was observed, it was judged as good (○), and when scattering was observed, it was judged as bad (x).
It was evaluated.

The results are shown in Table 6. In the sample samples 14 and 19, the transmittance (%) in the maximum transmission wavelength region is high and the light transmittance is excellent, the volume resistance value reaches 10 ¹¹ Ω · cm, the toner has a sufficient charge amount, and the toner scatters. Is not admitted.

On the other hand, melt-kneading dispersion treatment was carried out with a twin-screw extruder, and the mixture temperature at the time of treatment exceeded twice glass transition temperature Tg: 60 ° C. of polyester resin as a binder resin 1.
The comparative sample 65, which had a temperature of 28 ° C., has a transmittance of only 85% in the maximum transmission wavelength range, and is inferior in translucency. Open roll type kneading / dispersion equipment Kneedex MO
Even when treated with S140-800, the temperature of the mixture during the treatment is 135 ° C., which is more than twice the glass transition temperature Tg of the polyester resin as the binder resin: 60 ° C.
In Comparative Example Sample 66, the transmittance in the maximum transmission wavelength range was only 83% and the light transmittance was poor, and the volume resistance value was 1.
Since it was only 0 ¹⁰ Ω · cm, the toner charge amount was low, and toner scattering was also observed.

[0097]

[Table 6]

Example 5 The coloring cyan pigment and the binder resin were directly loaded into a kneading and dispersing treatment apparatus without preparing a cyan kneaded product by predispersing the coloring cyan pigment and the binder resin. A cyan toner having a cyan pigment concentration C of 10% by weight and a volume average particle diameter D _{50 of} 6.5 μm was manufactured in the same manner as in Example 1 except that the toner was added. Binding with the comparative sample 67 and the cyan toner of the example sample 14 prepared in the example 1 (in this example, the cyan toner before being adjusted to the two-component developer is also abbreviated as the example sample 14 for convenience). The effect of the predispersion treatment of the resin and the cyan toner on the translucency was tested.

In the test, the cyan toners of Example sample 14 and Comparative example sample 67 were processed in the same manner as in Example 3 to have a thickness of 5 μm.
Prepare a thin film sample adjusted to, and spectrophotometer U-3000
The spectral transmittance (%) in the maximum transmission wavelength region of the thin film sample was measured by. The translucency was evaluated in the same manner as in Example 3.

The results are shown in Table 7. In Example Sample 14,
In Comparative Example Sample 67, which has a transmittance of 91% at the maximum transmission wavelength of 485 nm and is excellent in translucency, the binder resin and the cyan pigment for coloring are not pre-dispersed.
The transmittance was only 86% at the maximum transmission wavelength of 485 nm, and the result was inferior in translucency.

[0101]

[Table 7]

[0102]

According to the present invention, the volume average particle diameter D _{50 of} the toner, the concentration C of the cyan cyan pigment for coloring in the toner composition and the toner adhesion amount M ₀ are set in the optimum ranges, and the image layer is formed. The cyan toner for electrophotography is designed so that the saturation X and the decrease in the lightness index L ^* with respect to the increase in the amount of adhered toner during the formation of are within a certain fixed range. As a result, in full-color electrophotographic image formation, it is possible to obtain excellent image quality with high density and excellent reproduction of intermediate tones and a wide color reproduction range.

Further, according to the present invention, since the concentration C of the coloring cyan pigment is selected within a suitable range, it is possible to form a high-concentration image excellent in light-transmitting property and concealment of toner graininess.
Further, an electrophotographic cyan toner having a wide color reproduction range and excellent fixing properties can be realized.

Further, according to the present invention, the cyan pigment for coloring includes C.I. I. Pigment Blue 15: 3 or 15: 4
Since this phthalocyanine pigment is used, an image with high image quality and stable quality can be obtained.

Further, according to the present invention, since a polyester resin or a polyether polyol resin is used as the binder resin, it is possible to obtain a cyan toner for electrophotography which is excellent in translucency and secondary color reproducibility. .

According to the present invention, since the cyan toner for electrophotography retains a high volume resistance value, the charge amount does not decrease and toner scattering and image fog are suppressed.

Further, according to the present invention, the mixture containing at least the binder resin and the cyan pigment for coloring passes through the gap between the first and second kneading rolls rotating about the axis in different directions, so that high shearing occurs. It is kneaded while receiving power. The temperature of the mixture at the time of kneading is the glass transition temperature T of the main resin constituting the binder resin.
It is kept at a low temperature of less than twice g. By kneading the mixture as described above, the coloring cyan pigment contained in a high concentration can be uniformly and highly dispersed in the binder resin, and thus the high concentration, a wide color reproduction range and the light transmitting property are excellent. It is possible to produce an electrophotographic cyan toner capable of forming an image.

According to the present invention, the pre-dispersion treatment for preliminarily dispersing the coloring cyan pigment in the binder resin by a treatment such as masterbatch or flashing is carried out, and then the melt-kneading dispersion treatment is carried out. It becomes possible to disperse the cyan pigment in the binder resin more uniformly and highly.

Further, according to the present invention, the developing section provided in the visible image forming means contains the electrophotographic cyan toner, and since the electrophotographic cyan toner is used for developing the image, a high quality image is obtained. The formation can be realized.

[Brief description of drawings]

FIG. 1 is a perspective view showing a simplified configuration of a kneading / dispersing apparatus 1 that is preferably used in a method for producing a cyan toner according to another embodiment of the present invention.

FIG. 2 is a schematic sectional view showing a simplified configuration of an image forming apparatus 20 according to still another embodiment of the present invention.

[Explanation of symbols]

1 Kneading and dispersion processing equipment 20 image forming apparatus

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Ariyoshi             22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka             Inside the company F-term (reference) 2H005 AA01 AA21 AB04 CA08 CA15                       CA21 EA01 EA07 EA10

Claims (8)

[Claims] 1. An electrophotographic cyan toner containing at least a binder resin and a coloring cyan pigment and having a volume average particle diameter D _{50 of 3} to 10 μm, which is further formed on the surface of a transfer medium onto which the toner is transferred. toner adhesion amount is given by the following formula _{(1), M 0 [mg} / cm 2] = (1-ε) · (4/3) · (D 50/2) ρ ... (1) where, epsilon: Porosity on a two-dimensional plane in a toner single-layer formed image in a square arrangement (= 0.215) ρ: true density of toner cyan pigment concentration C satisfies the following expression (2), and 0.015 ≦ C M ₀ ≦ 0.05 (2) where 0 <C <1 C = (parts by weight of pigment in toner composition) / (total parts by weight of all toner compositions) given by the following formula (3). The saturation X satisfies the relationship of the following expression (4), and X = (a ^{* 2} + b ^{* 2} ) ^1/2 (3) where a ^* , b ^* : Chromaticity index (X _(1.5) / X _(0.5) ) ≧ 0.95 (4) where X _(1.5) : Saturation X _(0.5) when the toner adhesion amount is 1.5M ₀ : A cyan toner for electrophotography, characterized in that, when the toner adhesion amount is 0.5 M ₀ , the saturation lightness index L ^* defined in Japanese Industrial Standard Z8729 satisfies the relationship of the following expression (5). (L ^* _(1.5) / L ^* _(0.5) ) ≧ 0.60 (5) where L ^* _(1.5) : Lightness index L ^* _(0.5) when the toner adhesion amount is 1.5M ₀ : Lightness index when the amount of toner attached is 0.5M ₀ 2. The cyan toner for electrophotography according to claim 1, wherein the concentration C of the coloring cyan pigment is 4 to 20% by weight. 3. The cyan pigment for coloring is C.I. I. Pigment Blue 15: 3 or 15: 4 phthalocyanine pigment, The cyan toner for electrophotography according to claim 1, wherein the cyan toner is a pigment. 4. The cyan toner for electrophotography according to claim 1, wherein the binder resin is a polyester resin or a polyether polyol resin. 5. The cyan toner for electrophotography according to claim 1, which has a volume resistance value of 10 ¹¹ Ω · cm or more. 6. A first kneading roll provided with heating means and having spiral grooves formed on its outer peripheral surface, and a second kneading roll having cooling means provided with spiral grooves formed on its outer peripheral surface. Then, the first kneading roll and the second kneading roll are arranged such that a gap is formed by the outer peripheral surfaces facing each other and their axes are parallel to each other in the same plane. The two kneading rolls are rotated about their axes by providing circumferential speed differences in different directions, and the glass transition temperature T of the main component resin constituting the binder resin
Melt kneading dispersion treatment is performed by passing a mixture containing at least a binder resin and a cyan pigment for coloring through a gap formed by the first and second kneading rolls at a temperature not more than 2 times g. Method for producing cyan toner for electrophotography. 7. The production of a cyan toner for electrophotography according to claim 6, wherein the melt-kneading dispersion treatment is carried out after a preliminary dispersion treatment in which a coloring cyan pigment is dispersed in a binder resin in advance. Method. 8. A visible image forming means for forming a visible image on a recording medium, comprising a developing section containing the cyan toner for electrophotography according to claim 1, and a conveying means for conveying the recording medium. An image forming apparatus comprising: