JP5293274B2 - Full color image forming method - Google Patents

Description

  The present invention relates to a full-color image forming method used in electrophotography.

In recent years, according to an electrophotographic image forming method using toner for developing an electrostatic charge image, in addition to the formation of a monochrome image (monochrome print) that has been conventionally used mainly for the creation of documents, the formation of a full color image ( Full-color printing) can be performed.
In such an electrophotographic image forming method using toner, a full color image having a desired color tone is formed by superimposing toner images of yellow toner, magenta toner, and cyan toner.

  In particular, when forming a full-color image used as a catalog or an advertisement, it is required to faithfully reproduce the original image, and accordingly, the vividness of the color of the image is further enhanced in the obtained image. In addition, it is required to widen the color reproduction range of the image.

As the electrostatic charge image developing toner for forming a full-color image, not only three types of toners, yellow toner, magenta toner and cyan toner, are used, but the highlight portion is a light color toner (light color toner), a solid portion Has proposed a method of forming an image using dark toner (dark toner).
Further, as an electrostatic charge image developing toner, a method of forming an image using a specific light color magenta toner in a highlight portion has been proposed (see Patent Document 1).

  However, in reality, it has not been possible to obtain a sufficiently wide color reproduction range with high gradation as required for a full color image to be formed.

JP-A-2005-316058

  The present invention has been made in consideration of the above-described circumstances, and the object thereof is to obtain high color reproducibility, particularly with respect to blue and red, and excellent gradation in the obtained full-color image. It is an object of the present invention to provide a full color image forming method that can be obtained.

The full-color image forming method of the present invention is a full-color image forming method for forming a full-color image using an electrostatic charge image developing toner,
As the electrostatic charge image developing toner, at least a yellow toner, a low brightness magenta toner satisfying the following condition [1], a high brightness magenta toner satisfying the following condition [2], and a cyan toner are used.
Development with the yellow toner, development with the low brightness magenta toner, development with the high brightness magenta toner, and development with the cyan toner are performed.
Condition [1]: Saturation C ^* _m1 is 45 or more and less than 65 and a lightness L ^* _m1 is 12 to 45 in a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently. .
Condition [2]: In a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently, the chroma C ^* _m2 is 80 or more and the lightness L ^* _m2 is 22 to 70.

In the full-color image forming method of the present invention, as the yellow toner, in a toner image having a toner adhesion amount of 0.6 mg / cm ² formed with yellow toner alone, the saturation C ^* _y is 85 or more, and Using a lightness L ^* _y of 70-90,
As a cyan toner, a toner image formed by using cyan toner alone and having a toner adhesion amount of 0.6 mg / cm ² has a chroma C ^* _c of 50 or more and a lightness L ^* _c of 58 to 75. It is preferable to use one.

  In the full color image forming method of the present invention, the yellow toner, the low lightness magenta toner, the high lightness magenta toner, and the cyan toner all have softening point temperatures in the range of 75 to 115 ° C. It is preferable that the difference between the softening point temperatures of any two of the types is less than 4 ° C.

  According to the full-color image forming method of the present invention, two types of magenta toners having different brightness values are used, and each of the two types of magenta toners having different brightness values has a specific brightness and a specific saturation. Therefore, in the resulting full color image, by using this high brightness magenta toner (light color magenta toner) and low brightness magenta toner (dark color magenta toner), color reproducibility without impairing the vividness of the image color. The range can be widened. As a result, high color reproducibility can be obtained and particularly excellent gradation can be obtained for the obtained full-color image, particularly with respect to blue and red.

  Specifically, by using a low lightness magenta toner at a high ratio, a dull hue can be reproduced for a full color image in a low lightness range, and by using a high lightness magenta toner at a high ratio, the lightness can be reproduced. Vivid colors can be reproduced for full-color images in a high range. More specifically, for example, by using a low-lightness magenta toner and a cyan toner, a deep blue color can be reproduced with respect to blue, which is a secondary color of magenta and cyan, and a high-lightness magenta toner and By using yellow toner, a bright red color can be reproduced for red, which is a secondary color of magenta and yellow.

It is explanatory drawing which shows an example of a structure of the tandem type full color image forming apparatus used for the full color image forming method of this invention.

Hereinafter, the present invention will be specifically described.
The full-color image forming method of the present invention is a full-color image forming method for forming a full-color image using an electrostatic image developing toner (hereinafter simply referred to as “toner”). Development using the yellow toner, development using the low brightness magenta toner, development using the high brightness magenta toner, and development using the cyan toner are performed using magenta toner, high brightness magenta toner, and cyan toner. Is.

[Low brightness magenta toner]
The low brightness magenta toner used in the full color image forming method of the present invention satisfies the following condition [1].
Condition [1]: Saturation C ^* _m1 is 45 or more and less than 65 and a lightness L ^* _m1 is 12 to 45 in a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently. .

Here, “saturation” is a value indicating the degree of vividness of the color, and specifically, L ^* a ^* b ^* color system [CIE (International Lighting Commission) 1976 (L ^* a ^* b ^* ) A value obtained from the values of a ^* and b ^* measured based on the color space] according to the following formula (1).
Here, the L ^* a ^* b ^* color system is a means that is useful for expressing a color numerically. L ^* is a coordinate in the z-axis direction and represents lightness, and a ^* and b ^* Is the coordinates of the x-axis and y-axis, respectively, a ^* indicates the hue in the red-green direction, b ^* indicates the hue in the yellow-blue direction, and both represent saturation.
Specifically, the saturation C ^* is represented by the distance from the origin O of the coordinate point (a, b).
Lightness refers to the relative brightness of colors that can be compared regardless of hue, and hue refers to shades of red, yellow, green, blue, purple, and the like.

Formula (1): Saturation C ^* = [(a ^* ) ² + (b ^* ) ² ] ^1/2

The L ^* a ^* b ^* color system for calculating the saturation C ^* is specifically a spectrophotometer “Gretag Macbeth Spectrolino” (manufactured by Gretag Macbeth), a D65 light source, and a reflection measurement. The aperture is φ4 mm, the measurement wavelength range is 380 to 730 nm at intervals of 10 nm, the viewing angle (observer) is 2 °, and the reference alignment is measured under the condition using a dedicated white tile.

When the chroma C ^* _m1 of the low brightness magenta toner is in the above range, an extremely wide color gamut can be realized for a full color image in the low brightness range.

In addition, since the lightness L ^* _m1 of the low lightness magenta toner is in the above range, a dull hue can be reproduced for a full color image in the lightness range.

[High brightness magenta toner]
The high brightness magenta toner used in the full color image forming method of the present invention satisfies the following condition [2].
Condition [2]: In a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently, the chroma C ^* _m2 is 80 or more and the lightness L ^* _m2 is 22 to 70.

When the chroma C ^* _m2 of the high lightness magenta toner is in the above range, an extremely wide color gamut can be realized for a full color image having a high lightness range.

Further, since the lightness L ^* _m2 of the high lightness magenta toner is in the above range, vivid colors can be reproduced for a full color image in the high lightness range.

The difference in lightness between the low lightness magenta toner and the high lightness magenta toner, that is, the difference between L ^* _m1 related to the low lightness magenta toner and L ^* _m2 related to the high lightness magenta toner is preferably larger than 6. More preferably, it is 8-40, More preferably, it is 10-25.
Since the difference between L ^* _m1 related to the low brightness magenta toner and L ^* _m2 related to the high brightness magenta toner is larger than 6, the color gamut represented by the magenta color material can be widened. Furthermore, when the difference is in the range of 8 to 40, it is possible to form an image having gradation in a wide color gamut.

[Yellow Toner]
The yellow toner used in the full color image forming method of the present invention preferably satisfies the following condition [3].
Condition [3]: In a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently, the chroma C ^* _y is 85 or more and the lightness L ^* _y is 70 to 90.
When the saturation C ^* _y of the yellow toner is in the above range, an extremely wide color gamut can be realized for a full color image whose lightness is in the range from halftone to high lightness.
In addition, when the lightness L ^* _y of the yellow toner is in the above range, a vivid hue can be reproduced for red, which is the secondary color of the magenta toner and the yellow toner.

[Cyan toner]
The cyan toner used in the full color image forming method of the present invention preferably satisfies the following condition [4].
Condition [4]: In a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently, the chroma C ^* _c is 50 or more and the lightness L ^* _c is 58 to 75.
When the saturation C ^* _c of the cyan toner is in the above range, an extremely wide color gamut can be realized for a full-color image having a lightness in the range from halftone to high lightness.
Further, when the lightness L ^* _c of the cyan toner is in the above range, a vivid hue can be reproduced for blue, which is the secondary color of the magenta toner and the cyan toner.

[Toner softening point temperature]
The toner according to the present invention preferably has a softening point temperature of 75 to 115 ° C., more preferably 80 to 100 ° C., for any color. And it is preferable that the difference of the softening point temperature of any two types among these four types is less than 4 degreeC.

When the toner softening point temperature is in the above range, an appropriate melting state for each toner is obtained in the fixing step, and high color reproducibility is obtained for the secondary color.
Here, “appropriate melted state for each toner” means that when a color image is formed by superimposing a toner image of one color together with a toner image of one color, In the color image region where the colorant contained and the colorant contained in the toner image relating to the other color are overlaid and fixed on the image support, the interface between the layers due to the binder resin is formed. In the state of disappearance, the colorant according to one color and the colorant according to another color are both uniformly dispersed and colored, and the colorant does not bleed out to an area outside the color image area. Say.

Here, the softening point temperature of the toner is measured as follows. That is, first, in an environment of 20 ° C. and 50% RH, 1.1 g of toner is placed in a petri dish and flattened, left to stand for 12 hours or more, and 3820 kg / Pressurize with a force of cm ² for 30 seconds to prepare a cylindrical molded sample having a diameter of 1 cm. Next, the molded sample was heated by a flow tester “CFT-500D” (manufactured by Shimadzu Corp.) under a load of 196 N (20 kgf), a starting temperature of 60 ° C., and a preheating time of 300 seconds in an environment of 24 ° C. and 50% RH. Extruding from the hole of the cylindrical die (1 mm diameter x 1 mm) at the speed of 6 ° C / min using a 1 cm diameter piston from the end of preheating, and setting the offset value to 5 mm using the melting temperature measurement method of the temperature rising method The measured offset method temperature T _offset is _defined as the softening point temperature of the toner.

  The softening point temperature of the toner should be controlled by adjusting the copolymerization ratio of the polymerizable monomer and the degree of polymerization when the binder resin constituting the toner particles described later is a vinyl copolymer. For example, in a copolymer formed using styrene and butyl methacrylate, the value of the softening point temperature can be increased by increasing the composition ratio of styrene. . Further, when the binder resin is a polyester resin, it can be controlled by selecting the type of the polymerizable monomer and adjusting the copolymerization ratio of the polymerizable monomer.

[Particle size of toner particles]
The toner particles constituting the toner have a volume-based median diameter of 3.0 to 10.0 μm, preferably 3.5 to 8.0 μm. In the case where toner particles are formed by a polymerization method, this particle size can be controlled by the concentration and addition amount of an aggregating agent, or the aggregation time, and further the composition of the polymer itself in the toner production method described later. .
When the particle diameter of the toner particles is in the above range, a change in color tone is suppressed regardless of the amount of toner adhesion, and excellent color reproducibility can be obtained. On the other hand, when the average particle size of the toner particles is less than 3.0 μm in terms of volume-based median, light scattering is likely to occur, so that the toner adhesion amount is large with a halftone image formed with a small amount of toner adhesion. There is a possibility that the color tone may be different from the solid image formed in the state.

  The volume-based median diameter of the toner is measured and calculated using a measuring apparatus in which a computer system for data processing (Beckman Coulter, Inc.) is connected to “Coulter Multisizer TA-III” (Beckman Coulter, Inc.). Is. Specifically, 0.02 g of toner is added to 20 mL of a surfactant solution (for example, a surfactant solution in which a neutral detergent containing a surfactant component is diluted 10-fold with pure water for the purpose of dispersing the toner). Then, ultrasonic dispersion was performed for 1 minute to prepare a toner dispersion, and this toner dispersion was measured in a beaker containing an electrolytic solution “ISOTONII” (manufactured by Beckman Coulter) in a sample stand. Pipette until the indicated concentration of the device is 10%. Here, by using this concentration, a reproducible measurement value can be obtained. In the measurement apparatus, the measurement particle count is 25000, the aperture diameter is 50 μm, the frequency value is calculated by dividing the measurement range of 1 to 30 μm into 256, and the volume integrated fraction is 50 % Particle diameter is defined as a volume-based median diameter.

Further, the toner according to the present invention has a coefficient of variation (CV value) in the volume-based particle size distribution of 2% or more and preferably 21% or less, particularly 5% or more and 15% or less. Preferably there is.
The CV value indicates the degree of dispersion in the particle size distribution of toner particles on a volume basis, and is calculated by the following formula (CV).
This CV value indicates that the smaller the value is, the sharper the particle size distribution is. Therefore, it means that the toner particles have the same size.

Formula (CV): CV value (%) = {(standard deviation) / (volume-based average diameter)} × 100

  By setting the CV value within the above range, the toner has a uniform toner particle size, so that it is possible to reproduce the fine dots and fine lines required in digital image formation with higher accuracy. Become. Moreover, as a photographic image, an image having high definition equivalent to or higher than that of an image formed with printing ink can be formed.

  The toners of the respective colors according to the present invention are preferably designed so that the particle diameter, CV value, and the like are the same.

In the toner used in the full color image forming method of the present invention, the toner particles constituting the toner may contain a binder resin and a colorant.
As the toner used in the full-color image forming method of the present invention, the toner particles constituting the toner particles include core particles containing a binder resin and a colorant, and a shell layer that substantially does not contain a dye covering the outer peripheral surface thereof. A core-shell structure having a shell layer made of a forming resin (hereinafter also referred to as “shell resin”) is preferable. In this case, the shell resin is a binder resin (hereinafter referred to as “core”) that constitutes the core particles. It is also referred to as a “binder resin”). By configuring the toner particles as having a core-shell structure, high production stability and storage stability can be obtained for the toner particles.
The toner particles having the core-shell structure are not limited to a form in which the shell layer completely covers the core particles, but may be those in which a part of the core particles is covered. Further, a part of the shell resin constituting the shell layer may form a domain or the like in the core particle. Furthermore, the shell layer may have a multilayer structure of two or more layers made of resins having different compositions.

[Toner Production Method]
As a method for producing the toner used in the full color image forming method of the present invention, kneading / pulverization method, suspension polymerization method, emulsion polymerization method, emulsion polymerization aggregation method, miniemulsion polymerization aggregation method, encapsulation method, and other known methods In view of the fact that it is necessary to obtain a toner with a reduced particle size in order to achieve high image quality, the manufacturing cost and the manufacturing method can be used. From the viewpoint of stability, it is preferable to use an emulsion polymerization aggregation method.

  In the emulsion polymerization aggregation method, a dispersion of fine particles (hereinafter referred to as “binder resin fine particles”) made of a binder resin produced by an emulsion polymerization method is used as a dispersion of toner particle components such as other colorant fine particles. At the same time as aggregating slowly while balancing the repulsive force of the fine particle surface by adjusting the pH and the cohesive force by adding an aggregating agent made of an electrolyte, controlling the average particle size and particle size distribution In this method, toner particles are produced by controlling the shape by fusing fine particles by heating and stirring.

  As a method for producing the toner, the binder resin fine particles formed when the emulsion polymerization aggregation method is used may be composed of two or more layers of binder resins having different compositions. A method in which a polymerization initiator and a polymerizable monomer are added to a dispersion of the first resin particles prepared by the emulsion polymerization treatment (first-stage polymerization), and the system is polymerized (second-stage polymerization). Can be adopted.

  In addition, as a method for producing toner particles having a core-shell structure, first, core resin is produced by associating, aggregating, and fusing binder resin fine particles and colorant fine particles for core formation, A binder resin fine particle for forming a shell layer is added to the dispersion, and the shell resin layer is formed on the surface of the core particle by aggregating and fusing the binder resin fine particle related to the shell layer to form a shell layer covering the surface of the core particle. The method obtained by this can be used.

[Colorant]
Examples of the colorant for the low brightness magenta toner include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 9, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 48: 3, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment Red 222 and the like can be suitably used alone, and together with these, other things such as those suitably used alone as a colorant for the high brightness magenta toner described below are combined in an appropriate mass ratio. It can also be used.
Examples of the colorant for the high brightness magenta toner include C.I. I. Solvent Red 48, C.I. I. Solvent Red 72, C.I. I. Solvent Red 73, C.I. I. Acid Red 52, C.I. I. Acid red 92, and the like, and compounds represented by the following chemical formulas (3) to (6). In addition to these, other materials such as those suitably used alone as the colorant of the low-lightness magenta toner described above can be used in combination at an appropriate mass ratio.

The colorant of the yellow toner is not particularly limited, and a known inorganic or organic colorant can be used. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment Yellow 15, Pigment Yellow 36, Pigment Yellow 65, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 138, pigment yellow 139, and the like. These can be used alone or in combination.
Further, specific examples of the yellow toner colorant satisfying the condition [3] include C.I. I. Pigment yellow 65 and C.I. I. Pigment Yellow 36 with a mass ratio of 95: 5, C.I. I. Pigment yellow 74 and C.I. I. Pigment Yellow 139 with a mass ratio of 90:10, C.I. I. Pigment yellow 74 and C.I. I. And CI Pigment Yellow 36 with a mass ratio of 80:20.

The colorant of the cyan toner is not particularly limited, and a known inorganic or organic colorant can be used. I. Pigment blue 15: 1 to 15: 3, C.I. I. And copper phthalocyanine compounds such as CI Pigment Blue 78, zinc phthalocyanine compounds, and aluminum phthalocyanine compounds. These can be used alone or in combination.
Specific examples of the cyan toner colorant that satisfies the condition [4] include compounds represented by the following general formula (I), the following chemical formula (1), and the following chemical formula (2). These can be used alone or in combination.

[In General Formula (I), M ¹ represents a silicon atom, a germanium atom, or a tin atom, and Z ¹ independently represents a hydroxy group, a chlorine atom, an aryloxy group having 6 to 18 carbon atoms, or 1 carbon atom. to 22 alkoxy group, a group represented by the following general formula (II), a ¹ ~A ⁴ each independently represent an atomic group necessary for forming a benzene ring. ]

[Wherein, Z ^{2 to} Z ⁴ each independently represents an alkyl group having 1 to 22 carbon atoms, an aryloxy group having 6 to 18 carbon atoms, or an alkoxy group having 1 to 22 carbon atoms. ]

As the colorant, a surface-modified one can also be used. As the surface modifier, conventionally known ones can be used, and specifically, silane coupling agents, titanium coupling agents, aluminum coupling agents, rosin and the like can be preferably used.
In a specific surface modification method, a colorant is dispersed in a solvent, a surface modifier is added to the dispersion, and the system is reacted by raising the temperature. After completion of the reaction, the colorant is filtered off, washed and filtered with the same solvent, and dried to obtain a colorant treated with the surface modifier.

  The addition amount of the colorant is in the range of 1 to 30% by mass, preferably 2 to 20% by mass with respect to the whole toner.

[Binder resin]
When the toner particles constituting the toner used in the full-color image forming method of the present invention are produced by, for example, a pulverization method or a dissolution suspension method, the binder resin constituting the toner is a styrenic resin, (meth) Acrylic resins, styrene- (meth) acrylic copolymer resins, vinyl resins such as olefin resins, polyester resins, polyamide resins, carbonate resins, polyethers, polyvinyl acetate resins, polysulfones, epoxy resins And various known resins such as polyurethane resins and urea resins. In particular, in order to improve transparency and color reproducibility of a superimposed image, styrene resins, acrylic resins, and polyester resins having high transparency, low melting properties, and high sharp melt properties are preferable. It is done. These can be used alone or in combination of two or more.

  Further, when the toner particles constituting the toner of the present invention are produced by, for example, suspension polymerization method, miniemulsion polymerization aggregation method, emulsion polymerization aggregation method or the like, the polymerization property for obtaining the binder resin constituting the toner is obtained. Examples of monomers include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-phenylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, p-tert-butyl. Styrene or styrene styrene derivatives such as styrene, pn-hexyl styrene, pn-octyl styrene, pn-nonyl styrene, pn-decyl styrene, pn-dodecyl styrene; methyl methacrylate, methacrylic acid Ethyl, n-butyl methacrylate, isopropyl methacrylate, isobutyl methacrylate Methacrylic acid ester derivatives such as t-butyl methacrylate, n-octyl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, lauryl methacrylate, phenyl methacrylate, diethylaminoethyl methacrylate, dimethylaminoethyl methacrylate; methyl acrylate , Ethyl acrylate, isopropyl acrylate, n-butyl acrylate, t-butyl acrylate, isobutyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, stearyl acrylate, lauryl acrylate, phenyl acrylate, etc. Acrylic ester derivatives; Olefins such as ethylene, propylene and isobutylene; Vinyl fluorides such as vinyl fluoride and vinylidene fluoride; Vinyl propionate, vinyl acetate, benzo Vinyl esters such as vinyl ethates; Vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and vinyl hexyl ketone; N-vinyl carbazole, N-vinyl indole, N-vinyl N-vinyl compounds such as pyrrolidone; vinyl compounds such as vinyl naphthalene and vinyl pyridine; and vinyl monomers such as acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, and acrylamide. These vinyl monomers can be used alone or in combination of two or more.

Moreover, it is preferable to use combining what has an ionic dissociation group as a polymerizable monomer. The polymerizable monomer having an ionic dissociation group has, for example, a substituent such as a carboxyl group, a sulfonic acid group, and a phosphoric acid group as a constituent group, and specifically includes acrylic acid, methacrylic acid, maleic acid. Acid, itaconic acid, cinnamic acid, fumaric acid, maleic acid monoalkyl ester, itaconic acid monoalkyl ester, styrene sulfonic acid, allyl sulfosuccinic acid, 2-acrylamido-2-methylpropane sulfonic acid, acid phosphooxyethyl methacrylate Etc.
Furthermore, as a polymerizable monomer, divinylbenzene, ethylene glycol dimethacrylate, ethylene glycol diacrylate, diethylene glycol dimethacrylate, diethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl A binder resin having a crosslinked structure can also be obtained using a polyfunctional vinyl such as glycol diacrylate.

  When the toner particles have a core-shell structure, styrene-acrylic resins are preferable as the core binder resin and the shell resin, respectively.

When the core binder resin is made of a copolymer, as a polymerizable monomer for obtaining the copolymer, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, It is preferable that what can make the glass transition point temperature (Tg) of the copolymer obtained low, such as 2-ethylhexyl methacrylate, is contained.
The copolymerization ratio of such a polymerizable monomer is 8 to 80% by mass, preferably 9 to 70% by mass, based on the entire polymerizable monomer that should form the core binder resin.
In addition to the specific examples given above, these polymerizable monomers may have acid anhydrides or vinyl carboxylic acid metal salt forms.

Further, when the shell resin is made of a copolymer, the glass transition point of the obtained copolymer, such as styrene, methyl methacrylate, methacrylic acid, etc., as the polymerizable monomer for obtaining the copolymer It is preferable that what can make temperature (Tg) high can be included.
The copolymer ratio of such a polymerizable monomer is 8 to 80% by mass, and preferably 9 to 20% by mass, based on the entire polymerizable monomer that should form the shell resin.
In addition to the specific examples given above, these polymerizable monomers may have acid anhydrides or vinyl carboxylic acid metal salt forms.

The binder resin constituting the toner used in the full-color image forming method of the present invention has a core-shell structure in which the toner is produced by an emulsion polymerization method, an emulsion polymerization aggregation method, a miniemulsion polymerization aggregation method, or the like. In this case, the molecular weights of the respective binder resins forming the core particles and the shell layer constituting the toner particles are preferably as follows.
That is, the binder resin constituting the core particles has a weight average molecular weight (Mw) in the range of 5,000 to 30,000 as measured by gel permeation chromatography (GPC) in which THF is soluble, and constitutes a shell layer. It is preferable that the weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) in which the binder resin is soluble in THF has a peak molecular weight in the range of 10,000 to 80,000, more preferably core particles. The weight average molecular weight (Mw) of the binder resin that constitutes a peak is in the range of 15,000 to 28,000, and the weight average molecular weight (Mw) of the binder resin that constitutes the shell layer is in a range of 10,000 to 50,000, respectively. There is a molecular weight.
The glass transition temperature (Tg) of the binder resin constituting the core particle is preferably 10 to 50 ° C., and preferably 25 to 48 ° C., and the glass transition temperature (b) of the binder resin constituting the shell layer ( Tg) is preferably 38 to 64 ° C, more preferably 40 to 54 ° C.

  On the other hand, the binder resin constituting the toner used in the method for forming a full color image of the present invention is, for example, a number obtained by gel permeation chromatography (GPC) soluble in THF when the toner does not have a core-shell structure. The average molecular weight (Mn) is preferably 3,000 to 6,000, more preferably 3,500 to 5,500, and the ratio Mw / Mn of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.0 to 6.0, preferably 2.5 to 5.5, and the glass transition temperature (Tg) is 50 to 70 ° C, preferably 55 to 70 ° C.

The molecular weight measurement by GPC was performed as follows. That is, using an apparatus “HLC-8220” (manufactured by Tosoh Corporation) and a column “TSKguardcolumn + TSKgelSuperHZM-M3 series” (manufactured by Tosoh Corporation), while maintaining the column temperature at 40 ° C., tetrahydrofuran (THF) was used as a carrier solvent at a flow rate of 0. Flow at 2 ml / min, and dissolve the measurement sample in tetrahydrofuran to a concentration of 1 mg / ml under a dissolution condition where treatment is performed for 5 minutes using an ultrasonic disperser at room temperature, and then treat with a membrane filter having a pore size of 0.2 μm. A sample solution is obtained, and 10 μL of this sample solution is injected into the apparatus together with the above carrier solvent, detected using a refractive index detector (RI detector), and the molecular weight distribution of the measurement sample is determined as a monodisperse polystyrene standard. Calculate the molecular weight using the calibration curve measured using the particles. It was. As standard polystyrene samples for preparing a calibration curve, molecular weights of 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1 manufactured by Pressure Chemical are used. .1 × 10 ⁵ , 3.9 × 10 ⁵ , 8.6 × 10 ⁵ , 2 × 10 ⁶ , 4.48 × 10 ⁶ , and at least about 10 standard polystyrene samples were measured, and a calibration curve It was created. A refractive index detector was used as the detector.

  The glass transition temperature (Tg) of the binder resin is measured using a differential scanning calorimeter “DSC-7” (manufactured by PerkinElmer) and a thermal analyzer controller “TAC7 / DX” (manufactured by PerkinElmer). Is. Specifically, 4.50 mg of toner is sealed in an aluminum pan “KITNO.0219-0041”, which is set in a sample holder of “DSC-7”, and an empty aluminum pan is used for reference measurement. Heat-cool-Heat temperature control was performed at a measurement temperature of 0 to 200 ° C. under measurement conditions of a temperature increase rate of 10 ° C./min and a temperature decrease rate of 10 ° C./min. Data on Heat is acquired, and the glass transition point is the intersection of the baseline extension before the rise of the first endothermic peak and the tangent line indicating the maximum slope between the rise of the first endothermic peak and the peak apex. It is shown as temperature (Tg). 1st. The heat was raised at 200 ° C. for 5 minutes.

  Further, the softening point temperature of the binder resin relating to the toner as described above may be a temperature at which the softening point temperature of the obtained toner falls within the above range.

〔Release agent〕
The toner particles constituting the toner according to the present invention may contain a release agent that contributes to suppression of the offset phenomenon. Here, the release agent is not particularly limited. For example, polyethylene wax, oxidized polyethylene wax, polypropylene wax, oxidized polypropylene wax, carnauba wax, sazol wax, rice wax, candelilla wax, etc. Can be mentioned.

  The content ratio of the release agent in the toner particles is usually 0.5 to 5 parts by mass, preferably 1 to 3 parts by mass with respect to 100 parts by mass of the binder resin. When the content of the release agent is less than 0.5 parts by mass with respect to 100 parts by mass of the binder resin, a sufficient offset prevention effect cannot be obtained, while on the other hand, 5 parts by mass with respect to 100 parts by mass of the binder resin If it is larger, the resulting toner has low translucency and color reproducibility.

[Charge control agent]
The toner particles constituting the toner according to the present invention may contain a charge control agent as necessary. Various known compounds can be used as the charge control agent.

As the toner particles constituting the toner according to the present invention, toner particles to which a so-called external additive is added can be used as toner particles for the purpose of improving fluidity, chargeability and cleaning properties. These external additives are not particularly limited, and various inorganic fine particles, organic fine particles and aliphatic metal salts can be used.
As the inorganic fine particles, it is preferable to use inorganic oxide particles such as silica, titania and alumina, and these inorganic fine particles are preferably hydrophobized with a silane coupling agent or a titanium coupling agent. . As the organic fine particles, spherical particles having a number average primary particle diameter of about 10 to 2000 nm can be used. As the organic fine particles, polymers such as polystyrene, polymethyl methacrylate, and styrene-methyl methacrylate copolymer can be used.

  The addition ratio of these external additives is a ratio of 0.1 to 5.0% by mass, preferably 0.5 to 4.0% by mass in the toner. In addition, various external additives may be used in combination.

(Developer)
The above toner can be used as a non-magnetic one-component developer, but may be mixed with a carrier and used as a two-component developer. When the toner of the present invention is used as a two-component developer, the carrier is made of a conventionally known material such as a metal such as iron, ferrite, or magnetite, or an alloy of such a metal with a metal such as aluminum or lead. Magnetic particles can be used, and ferrite particles are particularly preferable. Further, as the carrier, a coat carrier in which the surface of the magnetic particles is coated with a coating agent such as a resin, a binder type carrier in which a magnetic fine powder is dispersed in a binder resin, or the like may be used.
The coating resin constituting the coat carrier is not particularly limited, and examples thereof include olefin resins, styrene resins, styrene-acrylic resins, silicone resins, and fluorine resins. Moreover, it does not specifically limit as resin which comprises a resin dispersion type carrier, A well-known thing can be used, For example, a styrene-acrylic-type resin, a polyester resin, a fluororesin, a phenol resin etc. can be used.

  The volume-based median diameter of the carrier is preferably 20 to 100 μm, and more preferably 20 to 60 μm. The volume-based median diameter of the carrier can be typically measured by a laser diffraction particle size distribution measuring apparatus “HELOS” (manufactured by SYMPATEC) equipped with a wet disperser.

  Preferred carriers include a coated carrier using a silicone resin, a copolymer resin (graft resin) of an organopolysiloxane and a vinyl monomer or a polyester resin as a coating resin from the viewpoint of spent resistance. Coat carrier coated with resin obtained by reacting isocyanate with copolymer resin (graft resin) of organopolysiloxane and vinyl monomer from the viewpoint of durability, environmental stability and spent resistance Are preferable.

  Such a toner developer is used, for example, in a full-color image forming method using a full-color image forming apparatus described in detail below.

[Full-color image forming device]
FIG. 1 is an explanatory diagram showing an example of the configuration of a tandem type full-color image forming apparatus used in the full-color image forming method of the present invention.
The image forming apparatus 10 includes an image reading unit 11 and a printer unit 12. The printer unit 12 includes a plurality of (five in the example of FIG. 1) images provided along the image support conveyance belt 26. The image forming apparatus includes a forming unit 30Y, 301M, 302M, 30C, and 30K, a paper feed cassette 22, an exposure device 33 including a laser scanning device, and a fixing device 29.
In FIG. 1, reference numeral 21 denotes an image reading unit for photoelectrically reading image information of a document G.

  The image forming unit 30Y forms a toner image with yellow toner, and includes a latent image carrier made of a photoreceptor 31Y. Around the photoreceptor 31Y, a charging unit 32Y, a developing device 34Y, a transfer unit 37Y, A cleaning unit 38Y is arranged.

  Each of the image forming units 301M, 302M, 30C, and 30K forms a toner image by using low brightness magenta toner, high brightness magenta toner, cyan toner, and black toner instead of yellow toner. It has the same configuration as the forming unit 30Y.

  The image support conveyance belt 26 is stretched around a plurality of support rollers 26A and 26B and is supported so as to be able to circulate.

In the image forming apparatus 10, in the image forming units 30Y, 301M, 302M, 30C, and 30K, each of the photoconductors is charged by the charging unit and corresponds to the image signal output from the image reading unit 11 to the printer unit 12 side. The modulated laser beam is output from the exposure device 33, and the photosensitive member is scanned and exposed by the laser beam, so that the yellow color corresponding to the image information of the original G photoelectrically read by the image reading unit 21 is obtained. Electrostatic charge images (latent images) corresponding to the low lightness magenta color, high lightness magenta color, cyan color, and black color are formed on the respective photoreceptors.
The electrostatic image formed on each photoconductor is developed by each developing device with toners of yellow, low lightness magenta, high lightness magenta, cyan, and black, and can be used as a toner image. Visualized.

Next, in synchronization with the formation of each color toner image on each photoconductor, an image support such as paper housed in the paper feed cassette 22 is fed one by one by the paper feed roller 23, and the image support is conveyed. A toner image of each color (yellow color, low lightness magenta color, high lightness magenta color, cyan color, black) of each photoconductor is transferred to the image support by electrostatic adsorption on the belt 26. Are successively transferred in multiple, and a color toner image is transferred onto the image support.
Then, the image support is transported to the fixing device 29 and a fixing process is performed. As a result, a full-color image is formed on the image support, and thereafter, the image support is sandwiched between the discharge rollers 25 and discharged outside the apparatus. 27 is discharged.

  The full-color image forming apparatus used in the full-color image forming method of the present invention is not limited to the one described in detail above, and has four or more developing devices and uses four or more types of toner. Any structure can be suitably used as long as it is of a type that performs formation.

(Image support)
The image support for forming an image in the full-color image forming method of the present invention is a support for holding a toner image, and specifically, a plain paper, a high-quality paper, an art paper, a coated paper, etc. Examples thereof include, but are not limited to, coated printing paper, commercially available Japanese paper and postcard paper, plastic films for OHP, cloth, and the like.

  According to such a full-color image forming method, two types of magenta toners having different brightness values are used, and each of the two types of magenta toners having different brightness values has a specific brightness and a specific saturation. Therefore, in the resulting full color image, by using this high brightness magenta toner (light color magenta toner) and low brightness magenta toner (dark color magenta toner), color reproducibility without impairing the vividness of the image color. The range can be widened. As a result, high color reproducibility can be obtained and particularly excellent gradation can be obtained for the obtained full-color image, particularly with respect to blue and red.

  Specifically, by using a low-lightness magenta toner at a high ratio, it is possible to reproduce a dull hue for an image in a low-lightness area, and by using a high-lightness magenta toner at a high ratio, the lightness can be reduced. Vivid colors can be reproduced for high-area images. More specifically, by using low-lightness magenta toner and cyan toner, a deep blue color can be reproduced with respect to blue, which is the secondary color of magenta and cyan, and high-lightness magenta toner and yellow toner By using this, vivid red can be reproduced for red, which is the secondary color of magenta and yellow.

  Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.

[Preparation Example m1 of Magenta Colorant Fine Particle Dispersion]
Stirring and dissolving 11.5 parts by mass of sodium n-dodecyl sulfate in 160 parts by mass of ion-exchanged water. I. Pigment Red 122; 17.5 parts by mass are gradually added, and then dispersed using "Clearmix W Motion CLM-0.8" (manufactured by M Technique Co., Ltd.) to contain colorant fine particles [m1]. A magenta colorant fine particle dispersion [m1] was obtained.

[Preparation Examples of Magenta Colorant Fine Particle Dispersion Liquid m2 to m6, M1 to M10]
In Preparation Example m1 of the magenta colorant fine particle dispersion, the magenta colorant described in Table 1 is listed in Table 1 in the mass ratio described in Table 1 instead of “CI Pigment Red 122; 5 parts by mass”. Magenta colorant fine particle dispersion liquids [m2] to [m6] and magenta colorant fine particle dispersion liquids [M1] to [M10] were obtained in the same manner except that the addition amount of was used.
However, in Table 1, Colorant [D1] to Colorant [D5] are colorants related to magenta, and are dye compounds represented by the following formulas (D1) to (D5), respectively.

[Preparation Example Y1 of Yellow Colorant Fine Particle Dispersion]
In Preparation Example m1 of the magenta colorant fine particle dispersion, instead of “magenta colorant CI Pigment Red 122; 5 parts by mass”, “yellow colorant CI Pigment Yellow 74; 4.5 parts by mass and A yellow colorant fine particle dispersion [Y1] was obtained in the same manner except that “CI Pigment Yellow 139; 0.5 parts by mass” was used.

[Preparation Examples C1-C2 of Cyan Colorant Fine Particle Dispersion]
In Preparation Example m1 of the magenta colorant fine particle dispersion, instead of “magenta colorant CI Pigment Red 122; 5 parts by mass”, “cyan colorant CI Pigment Blue 15: 3; 7 parts by mass, respectively” Alternatively, cyan colorant fine particle dispersions [C1] and [C2] were obtained in the same manner except that 7 parts by mass of a silicon phthalocyanine compound represented by the following formula (C2) was used.

[Preparation Example 1 of Core Forming Resin Particles]
(1) First stage polymerization (formation of core particles):
Surface activity obtained by dissolving 4 parts by mass of an anionic surfactant represented by the following formula (P) in 3040 parts by mass of ion-exchanged water in a 5 L reaction vessel equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing device. The agent solution was charged, and the internal temperature was raised to 80 ° C. while stirring at a stirring speed of 230 rpm under a nitrogen stream.
To this surfactant solution, an initiator solution in which 10 parts by mass of a polymerization initiator (potassium persulfate; KPS) was dissolved in 400 parts by mass of ion-exchanged water was added to a temperature of 75 ° C., and then 532 parts by mass of styrene. A monomer mixture consisting of 200 parts by mass of n-butyl acrylate, 68 parts by mass of methacrylic acid, and 16.4 parts by mass of n-octyl mercaptan was added dropwise over 1 hour, and the system was heated at 75 ° C. for 2 hours. Then, polymerization (first stage polymerization) was carried out by stirring to prepare latex [A1] which is a dispersion of core particles. The weight average molecular weight (Mw) of the core particles in this latex [A1] was 16,500.

Formula (P): C ₁₀ H ₂₁ (OCH ₂ CH ₂ ) ₂ SO ₃ Na

(2) Second stage polymerization (formation of intermediate layer):
In a flask equipped with a stirrer, a monomer mixture comprising 101.1 parts by mass of styrene, 62.2 parts by mass of n-butyl acrylate, 12.3 parts by mass of methacrylic acid, and 1.75 parts by mass of n-octyl mercaptan As a release agent, 93.8 parts by mass of paraffin wax “HNP-57” (manufactured by Nippon Seiwa Co., Ltd.) was added, and the mixture was heated to 80 ° C. and dissolved to prepare a monomer solution.
On the other hand, a surfactant solution in which 3 parts by mass of the anionic surfactant represented by the above formula (P) is dissolved in 1560 parts by mass of ion-exchanged water is heated to 80 ° C., and the surfactant solution After adding 32.8 parts by mass of latex [A1] in terms of solid content, the monomer solution of the mold release agent was added by a mechanical disperser “CLEAMIX” (manufactured by M Technique Co., Ltd.) having a circulation path. A dispersion (emulsion) containing emulsified particles (oil droplets) having a dispersed particle diameter of 340 nm was prepared by mixing and dispersing for a time.
Next, an initiator solution in which 6 parts by mass of a polymerization initiator (KPS) is dissolved in 200 parts by mass of ion-exchanged water is added to this dispersion, and this system is heated and stirred at 80 ° C. for 3 hours. Polymerization (second stage polymerization) was performed to prepare latex [A2]. The latex [A2] had a weight average molecular weight (Mw) of 23,000.

(3) Third stage polymerization (formation of outer layer):
An initiator solution prepared by dissolving 5.45 parts by mass of a polymerization initiator (KPS) in 220 parts by mass of ion-exchanged water is added to the resin particles [A2] obtained as described above, and the temperature condition is 80 ° C. A monomer mixed solution composed of 293.8 parts by mass of styrene, 154.1 parts by mass of n-butyl acrylate, and 7.08 parts by mass of n-octyl mercaptan was fully consumed over 1 hour. After completion of the dropwise addition, polymerization (third stage polymerization) is performed by heating and stirring for 2 hours, followed by cooling to 28 ° C. and dispersion of the core-forming resin particles [A] composed of composite resin particles having a multilayer structure A liquid latex [A3] was obtained. The core-forming resin particles [A] had a weight average molecular weight (Mw) of 26,800. The mass average particle diameter of the composite resin particles constituting the core-forming resin particles [A] was 125 nm. The core-forming resin particles [A] had a glass transition temperature (Tg) of 28.1 ° C.
The volume-based median diameter of the composite resin particles is measured under the following measurement conditions using “MICROTRAC UPA-150” (manufactured by HONEYWELL).
Sample refractive index 1.59
・ Sample specific gravity 1.05 (in terms of spherical particles)
Solvent refractive index 1.33
Solvent viscosity 0.797 Pa · s (30 ° C), 1.002 Pa · s (20 ° C)
-Zero point adjustment Prepared by adding ion-exchanged water to the measurement cell.

[Preparation Example 1 of Resin Particles for Forming Shell]
In Preparation Example 1 of the core-forming resin particles, the monomer mixture used in the first stage polymerization (core particle formation) was 624 parts by mass of styrene, 120 parts by mass of 2-ethylhexyl acrylate, 56 parts by mass of methacrylic acid, A latex of shell-forming resin particles [F] was prepared in the same manner except that the composition was changed to 16.4 parts by mass of n-octyl mercaptan. The shell-forming resin particles [F] had a weight average molecular weight (Mw) of 16,400. The mass average particle diameter of the composite resin particles constituting the shell-forming resin particles [F] was 95 nm. The shell-forming resin particles [F] had a glass transition temperature (Tg) of 62.6 ° C.

[Toner Preparation Example m1]
(1) Formation of core particles:
420.7 parts by mass of latex [A3] of the above core-forming resin particles [A] in terms of solid content, 900 parts by mass of ion-exchanged water, and 200 parts by mass of a magenta colorant fine particle dispersion [m1], The mixture was stirred in a reaction vessel equipped with a temperature sensor, a condenser, a nitrogen introducing device, and a stirring device. After adjusting the temperature in a container to 30 degreeC, 5 mol / L sodium hydroxide aqueous solution was added to this solution, and pH was adjusted to 8-11.
Next, an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes at 30 ° C. with stirring. After standing for 3 minutes, the temperature was raised and the system was heated to 65 ° C. over 60 minutes. In this state, the particle size of the associated particles was measured with “Coulter Counter TA-II” (manufactured by Beckman Coulter), and when the volume-based median diameter became 5.5 μm, 40.2 parts by mass of sodium chloride An aqueous solution in which 1000 parts by mass of ion-exchanged water is dissolved is added to stop the growth of the particle size, and further, the fusion is continued by heating and stirring at a liquid temperature of 70 ° C. for 1 hour as an aging treatment, and the core particles [ 1] was formed. When the circularity of the core particle [1] was measured by “FPIA2000” (manufactured by Systex), the average value was 0.912.

(2) Formation of shell layer:
Next, 96 parts by mass of a latex of resin particles [F] for shell formation was added at 65 ° C., and an aqueous solution obtained by dissolving 2 parts by mass of magnesium chloride hexahydrate in 1000 parts by mass of ion-exchanged water was added over 10 minutes. After the addition, the temperature was raised to 70 ° C. (shelling temperature), stirring was continued for 1 hour, and the shell-forming resin particles [F] were fused to the surface of the core particles [1]. Aged for 20 minutes to form a shell layer.
Here, 40.2 parts by mass of sodium chloride was added, the mixture was cooled to 30 ° C. at 6 ° C./min, the produced fused particles were filtered, washed repeatedly with ion-exchanged water at 45 ° C., and then 40 ° C. By drying with warm air, a low brightness magenta toner [m1] having a shell layer formed on the surface of the core particles was produced.
The average particle diameter of the magenta toner [m1] was 6.5 μm in terms of volume-based median diameter. The volume-based median diameter of the toner is measured by the same method as described above. The same applies to the following.

[Toner Preparation Examples m2 to m6, M1 to M10, Y1, C1 to C2]
In the toner preparation example m1, the magenta colorant fine particle dispersion [m1] is changed to magenta colorant fine particle dispersion [m2] to [m6], [M1] to [M10], and the yellow colorant fine particle dispersion [Y1], respectively. , Cyan colorant fine particle dispersions [C1] to [C2], low brightness magenta toner [m2] to [m6], high brightness magenta toner [M1] to [M10], yellow toner [Y1] and cyan toners [C1] to [C2] were obtained.

[Comparative Toner Preparation Example Z1]
100 parts by mass of polyester resin and C.I. I. 6 parts by mass of Solvent Red 52 (anthraquinone dye) was premixed with a Henschel mixer, melt-kneaded with a biaxial extrusion kneader, and coarsely pulverized to about 1 to 2 mm using a hammer mill after cooling. Next, the mixture is finely pulverized by an air jet type pulverizer, the obtained finely pulverized product is classified, silica is externally added, and a high brightness magenta toner for comparison having a volume-based median diameter of 7.8 μm [Z1 ] Was obtained.

(Preparation of developer)
Low brightness magenta toner [m1] to [m6], high brightness magenta toner [M1] to [M10], yellow toner [Y1], cyan toner [C1] to [C2], comparative high brightness magenta toner [ Z1] is mixed with a silicone carrier-coated ferrite carrier having a volume average particle diameter of 50 μm so that the toner concentration is 6% by mass, and low-lightness magenta developers [m1] to [m1] to [m1] to [2] m6], high brightness magenta developer [M1] to [M10], yellow developer [Y1], cyan developer [C1] to [C2], and comparative high brightness magenta developer [Z1].

<Examples 1-11, Comparative Examples 1-3>
This low brightness magenta developer [m1] to [m6], high brightness magenta developer [M1] to [M10], yellow developer [Y1], cyan developer [C1] to [C2], high brightness for comparison The magenta developer [Z1] is mounted on each of four developing units of a commercially available multifunction machine “bizhub PRO C65hc” (manufactured by Konica Minolta Business Technologies) in the combination shown in Table 2, and “Japanese paper copy” is used as an image support. A print image forming operation was performed using “Daio” (manufactured by Ozu Sangyo Co., Ltd.), and the following (1) to (2) were evaluated. The results are shown in Table 2.

(1) Evaluation of blue and red color reproducibility The logo mark of each of the 50 manufacturers using the blue logo mark and / or the red logo mark is displayed on the computer display as detailed below from each company website. Displayed, printed on the transfer paper “Washi Copy Daio” (made by Ozu Sangyo Co., Ltd.), and randomly extracted 100 panelists in their teens to 70s, “The logo mark color of the company on the display is It was evaluated according to the following criteria according to the number of people who evaluated that it was reproduced on the transfer paper without a sense of incongruity.

[Evaluation criteria]
◎: 90 or more people evaluated as “reproduced” (excellent)
○: 80 or more and less than 90 people (good) evaluated as “reproduced”
Δ: 60 or more and less than 80 people evaluated as “reproduced” (practical)
×: Less than 60 people evaluated as “reproduced” (bad)

〔Computer〕
・ IMac (Apple Computer Co., Ltd.)
・ 24 inch wide screen LCD
・ Resolution 1920 × 1200 pixels ・ 2.16 GHz Intel Core 2 Duo processor 1
・ 4MB shared L2 cache ・ 1GB memory (2 × 512MB SO-DIMM)
・ 250GB serial ATA hard drive 2
・ 8x double layer SuperDrive (DVD + R DL, DVD ± RW, CD-RW)
・ NVIDIA GeForce 7300 GT 128MB GDDR3 memory ・ AirMac Extreme and Bluetooth 2.0 built-in ・ Apple Remote

(2) Gradation evaluation A photographic image [A] taken on a sunny day on the sunny day of a hill in which three colors of pink, magenta and purple bougainvillea bloom in Hawaii, USA, and Printed two landscape photograph images [B] taken at dusk on a clear day on a clear day, and randomly selected 100 panelists in their teens to 70s. ) Is selected as “○” (good) when the number of people who selected (b) is 80 or more, and “×” (bad) when it is less than 80. evaluated.
(A) The background and the flower color are harmonized in the photographic images [A] and [B], and the local features are expressed. The gradation is appropriate and there is no sense of incongruity.
(B) In the photographic image [A], the flower color lacks vividness in light of the background. Alternatively, in the photographic image [B], the flower color is raised with an unnatural gradation and noisily vividly.

  As described above, in Examples 1 to 11 according to the full-color image forming method of the present invention, red, which is a secondary color by a combination of magenta toner and yellow toner, and secondary by a combination of magenta toner and cyan toner. It was confirmed that excellent color reproducibility was obtained with respect to blue, which is a color, and further excellent gradation could be realized.

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 11 Image reading part 12 Printer part 21 Image reading unit 22 Paper feed cassette 23 Paper feed roller 25 Paper discharge roller 26 Image support body conveyance belt 26A, 26B Support roller 27 Paper discharge tray 29 Fixing device 30Y, 301M, 302M , 30C, 30K Image forming unit 31Y Photoconductor 32Y Charging unit 33 Exposure unit 34Y Development unit 37Y Transfer unit 38Y Cleaning unit G Original

Claims (3)

In a full-color image forming method of forming a full-color image using toner for developing an electrostatic image,
As the electrostatic charge image developing toner, at least a yellow toner, a low brightness magenta toner satisfying the following condition [1], a high brightness magenta toner satisfying the following condition [2], and a cyan toner are used.
A full-color image forming method comprising: developing with the yellow toner, developing with the low brightness magenta toner, developing with the high brightness magenta toner, and developing with the cyan toner.
Condition [1]: Saturation C ^* _m1 is 45 or more and less than 65 and a lightness L ^* _m1 is 12 to 45 in a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently. .
Condition [2]: In a toner image having a toner adhesion amount of 0.6 mg / cm ² formed independently, the chroma C ^* _m2 is 80 or more and the lightness L ^* _m2 is 22 to 70. As a yellow toner, in a toner image having a toner adhesion amount of 0.6 mg / cm ² formed by yellow toner alone, the chroma C ^* _y is 85 or more and the lightness L ^* _y is 70 to 90. Use things
As a cyan toner, a toner image formed by using cyan toner alone and having a toner adhesion amount of 0.6 mg / cm ² has a chroma C ^* _c of 50 or more and a lightness L ^* _c of 58 to 75. The full-color image forming method according to claim 1, wherein: The yellow toner, the low-lightness magenta toner, the high-lightness magenta toner, and the cyan toner all have softening point temperatures in the range of 75 to 115 ° C., and any two of these four types are softened. The full-color image forming method according to claim 1 or 2, wherein any difference in the point temperatures is less than 4 ° C.