JP2009157203A - Mixture toner for electrostatic charge image development - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mixture toner for electrostatic charge image development, the mixture toner that comprises a combination of a toner containing a condensed azo pigment and a toner containing a halogenated copper phthalocyanine pigment and can maintain a hue of an image constant even in continuous printing, and to provide a method for manufacturing the toner, and an image forming method that uses the toner. <P>SOLUTION: The mixture toner for electrostatic charge image development comprises a toner (A), containing a binder resin and a condensed azo pigment and a toner (B), containing a binder resin and a halogenated copper phthalocyanine pigment, wherein the toner (A) and the toner (B) contain a chromium complex of a salicylic acid compound, and a chromium ionic strength ratio (chromium ionic intensity of toner (A)/chromium ionic strength of toner (B)) of the toner (A) to the toner (B) is in the range of 1.30 to 2.50. A method for manufacturing the toner is disclosed, and an image forming method which uses this mixture toner for an image forming apparatus, employing a hybrid developing system, is disclosed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a mixed toner for developing an electrostatic image used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method and the like, a method for producing the same, and an image forming method using the toner About.

Various technologies for mixing two or more color toners with different colors have been studied for the purpose of manufacturing custom color toners that can meet various user requirements and two-color printing that can simplify the equipment. . For example, in Patent Document 1, an attempt is made to homogenize the toner surface while paying attention to the toner surface treatment agent.
JP-A-2005-316124

  However, in the combination of a toner containing a condensation type azo pigment and a toner containing a copper halide phthalocyanine pigment, even if the toner surface is homogenized by the method described in Patent Document 1, the change in hue associated with continuous printing is prevented. Can not do it.

  An object of the present invention is a mixed toner in which a toner containing a condensation type azo pigment and a toner containing a copper halide phthalocyanine pigment are combined, and the static of the image can be maintained constant even in continuous printing. An object of the present invention is to provide a mixed toner for developing a charge image, a method for producing the same, and an image forming method using the toner.

The present invention
[1] A mixed toner for developing an electrostatic image comprising a toner (A) containing a binder resin and a condensation type azo pigment, and a toner (B) containing a binder resin and a halogenated copper phthalocyanine pigment. The toner (A) and the toner (B) further contain a chromium complex of a salicylic acid compound, and the ratio of the chromium ions of the toner (A) and the toner (B) (the chromium ion strength of the toner (A) / the toner ( B) a mixed toner for developing an electrostatic charge image having a chromium ion intensity) of 1.30 to 2.50,
[2] Manufacture of a mixed toner for developing an electrostatic charge image comprising a step of mixing a toner (A) containing a binder resin and a condensation type azo pigment and a toner (B) containing a binder resin and a copper phthalocyanine halide. The toner (A) and the toner (B) further contain a chromium complex of a salicylic acid compound, and a chromium ion intensity ratio between the toner (A) and the toner (B) (the chromium of the toner (A)). A method for producing a mixed toner for developing an electrostatic charge image having an ionic strength / chromium ionic strength (toner (B)) of 1.30 to 2.50, and [3] image formation by hybrid development using the mixed toner described in [1] above The present invention relates to an image forming method used in an apparatus.

  The mixed toner for developing an electrostatic image obtained by combining the toner containing the condensation type azo pigment of the present invention and the toner containing the copper halide phthalocyanine pigment can maintain the hue of the image constant even in continuous printing.

  The mixed toner for developing an electrostatic image of the present invention contains a toner (A) containing a condensation type azo pigment and a toner (B) containing a halogenated copper phthalocyanine pigment, and the toner (A) and the toner (B) are Further, it is characterized in that it contains a chromium complex of a salicylic acid compound, and the ratio of the chromium ion intensity between the toner (A) and the toner (B) is in a specific range. In general, when two or more types of color toners having different colors are mixed, it is considered that the toner is developed more uniformly as the charge amount and the toner surface are more uniform. However, in the combination of the color toner of the present invention containing the specific colorant, even if the dispersion state of the charge control agent on the toner surface is uniform, the change in hue due to continuous printing cannot be suppressed. Was found to be due to scattering of the toner (A) containing the condensation type azo pigment. However, in the present invention, in the combination of toners further containing a chromium complex of a salicylic acid compound as a charge control agent, the chromium ion intensity of the toner (A) is larger than that of the toner (B), and the chromium ion intensity ratio of both toners When the (chromium ion intensity of toner (A) / chromium ion intensity of toner (B)) is 1.30 to 2.50, preferably 1.32 to 2.40, more preferably 1.35 to 2.30, it is remarkable for suppression of hue change. An effect is produced. The chromium ion strength of the toner can be adjusted by the kneading conditions of the binder resin and the charge control agent and the addition amount of the charge control agent.

  In the present invention, the condensation type azo pigment contained in the toner (A) is represented by the formula (I):

(Wherein R ¹ , R ² , R ³ and R ⁵ are each independently a hydrogen atom, a halogen atom or an alkyl group having 1 to 3 carbon atoms, and R ⁴ and R ⁶ are each independently , A hydrogen atom, a halogen atom, a trifluoromethyl group, a ClCH ₂ CH ₂ OCO— group or a (CH ₃ ) ₂ CHOCO— group)
The compound represented by these is preferable. Although the reason is unknown, the toner (A) containing such a condensation type azo pigment has a small fading due to light irradiation and a small change in charge amount due to a change in environment. Therefore, vivid image quality with excellent color developability can be maintained over a long period of time.

  In the formula (I), examples of the halogen atom include a chlorine atom, a fluorine atom, a bromine atom and an iodine atom. Among these, a chlorine atom is preferable. Examples of the alkyl group having 1 to 3 carbon atoms include a methyl group, an ethyl group, a propyl group, and an isopropyl group. Among these, a methyl group is preferable.

  Examples of the condensed azo pigment represented by the formula (I) include CI Pigment Red 144, CI Pigment Red 221, CI Pigment Red 220, CI Pigment Red 242, CI Pigment Red 214, CI Pigment Red 166. These may be used alone or in combination of two or more. In the present invention, from the viewpoint of light resistance and chargeability of the toner, the formula (Ia):

C.I. Pigment Red 242 and Formula (Ib):

C.I. Pigment Red 221 represented by the following formula is preferred, and C.I. Pigment Red 242 is more preferred.

  The content of the condensation type azo pigment in the toner (A) is preferably 1 to 20 parts by weight, more preferably 5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  On the other hand, as the halogenated copper phthalocyanine pigment contained in the toner (B), the formula (II):

(In the formula, X ^{1 to} X ⁴ are each independently a halogen atom, p 1 to p 4 are integers of 0 to 4, X p represents p pieces of X, and each X is the same or different. (Except when p is all 0)
The compound represented by these is preferable. In the formula (II), examples of the halogen atom include a chlorine atom, a fluorine atom, a bromine atom and an iodine atom. Among these, a chlorine atom and a bromine atom are preferable.

  Examples of the halogen copper phthalocyanine pigment represented by the formula (II) include the formula (IIa):

C.I. Pigment Green 7, represented by formula (IIb):

C.I. Pigment Green 36 represented by the formula (1) or the like, and these may be used alone or in admixture of two or more.

  The content of the copper halide phthalocyanine pigment in the toner (B) is preferably 1 to 20 parts by weight and more preferably 5 to 10 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner (A) may contain a colorant other than the condensed azo pigment, and the toner (B) may contain a colorant other than the halogenated copper phthalocyanine pigment as long as the effects of the present invention are not impaired.

  As a chromium complex of a salicylic acid compound contained as a charge control agent in toner (A) and toner (B), formula (III):

(In the formula, R ⁷ , R ⁸ and R ⁹ are each independently a hydrogen atom, a linear or branched alkyl group having 1 to 10 carbon atoms or an alkenyl group having 2 to 10 carbon atoms, and m is 2 or more. Integer, n represents an integer of 1 or more)
The compound represented by these is preferable.

In the formula (III), R ⁸ is preferably a hydrogen atom, and R ⁷ and R ⁹ are preferably a branched alkyl group, more preferably a tert-butyl group.

Examples of commercially available chromium complexes of salicylic acid compounds in which R ⁸ is a hydrogen atom and R ⁷ and R ⁹ are tert-butyl groups preferably used in the present invention include “Bontron E-81” (Orient Chemical Industries, Ltd.). Manufactured).

  The content of the chromium complex of the salicylic acid compound in the toner (A) and the toner (B) is preferably 0.1 to 5.0 parts by weight, and 0.3 to 4.0 parts by weight with respect to 100 parts by weight of the binder resin, from the viewpoint of charge rising property. Is more preferable. From the viewpoint of adjusting the chromium ion strength, as the content of the chromium complex of the salicylic acid compound is reduced, the chromium complex of the salicylic acid compound present on the toner surface decreases and the chromium ion strength tends to decrease.

  The toner (A) and the toner (B) may appropriately contain a charge control agent other than the chromium complex of the salicylic acid compound as long as the effects of the present invention are not impaired.

  Examples of the binder resin contained in the toner (A) and the toner (B) include vinyl resins such as polyester and styrene-acrylic resins, epoxy resins, polycarbonates, polyurethanes, and hybrid resins having two or more resin components. Although not particularly limited, polyester is preferable from the viewpoint of good dispersibility of the additive in the toner. The content of the polyester is preferably 50 to 100% by weight, more preferably 70 to 100% by weight, and still more preferably 100% by weight in the binder resin.

  The polyester is obtained by polycondensing a known alcohol component and a known carboxylic acid component such as a carboxylic acid, a carboxylic acid anhydride, or a carboxylic acid ester as raw material monomers.

  Examples of the alcohol component include alkylenes of bisphenol A such as polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane and polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane. (Carbon number 2 to 3) Oxide (average added mole number 1 to 16) adduct, ethylene glycol, propylene glycol, glycerin, pentaerythritol, trimethylolpropane, hydrogenated bisphenol A, sorbitol, or alkylene thereof (carbon number 2 -4) Oxide (average added mole number 1-16) adduct and the like.

  The carboxylic acid component includes dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, adipic acid and succinic acid, alkyl groups having 1 to 20 carbon atoms such as dodecenyl succinic acid and octenyl succinic acid, or carbon. Trivalent or higher polyvalent carboxylic acids such as succinic acid, trimellitic acid and pyromellitic acid substituted with alkenyl groups having 2 to 20 carbon atoms, anhydrides of these acids and alkyls of these acids (1 to 3 carbon atoms) ) Esters and the like. The acids as described above, and anhydrides and alkyl esters of these acids are collectively referred to herein as carboxylic acid compounds.

  The alcohol component may contain a monovalent alcohol, and the carboxylic acid component may contain a monovalent carboxylic acid compound as appropriate from the viewpoints of molecular weight adjustment and offset resistance improvement.

  The polyester is obtained, for example, by subjecting an alcohol component and a carboxylic acid component to condensation polymerization at a temperature of 180 to 250 ° C. in an inert gas atmosphere, if necessary, in the presence of an esterification catalyst.

  From the viewpoint of durability and fixability, the softening point of the polyester is preferably 80 to 165 ° C, the glass transition point is preferably 50 to 85 ° C, and the acid value is preferably 0.5 to 60 mgKOH / g.

  In the present invention, the polyester may be a polyester modified to such an extent that the characteristics are not substantially impaired. Examples of the modified polyester include grafting and blocking with phenol, urethane, epoxy and the like by the methods described in JP-A-11-133668, JP-A-10-239903, JP-A-8-20636, and the like. Polyester.

  Further, the toner (A) and the toner (B) have additives such as a release agent, a conductivity adjusting agent, an extender pigment, a reinforcing filler such as a fibrous substance, an antioxidant, an anti-aging agent, and a magnetic substance. These may be added as appropriate.

  Mold release agents include polypropylene wax, polyethylene wax, synthetic wax such as Fischer Tropu, coal wax such as montan wax, petroleum wax such as paraffin wax, wax such as alcohol wax, carnauba wax, rice wax, candelilla Natural ester waxes such as wax may be mentioned, and these may be used alone or in admixture of two or more. The content of the release agent is preferably 0.5 to 10 parts by weight and more preferably 1 to 8 parts by weight with respect to 100 parts by weight of the binder resin.

  The toner (A) and the toner (B) are preferably pulverized toners. For example, a binder resin, a colorant, a charge control agent and the like are mixed with a mixer such as a Henschel mixer and a ball mill, and then a sealed kneader or a single screw or A classifier using a swirling airflow, melt-kneaded with a twin-screw extruder, etc., cooled, coarsely pulverized with a hammer mill, etc., and further finely pulverized with a fine pulverizer or mechanical pulverizer using a jet stream. And obtained by classification to a predetermined particle size using a classifier using the Coanda effect. The higher the kneading temperature, the smaller the share of the material to be kneaded and the lower the dispersibility of the internal additive such as the charge control agent, so that the chromium complex of the salicylic acid compound present on the toner surface decreases, and the chromium There is a tendency for the ionic strength to decrease.

  The toner surface may be surface-treated with an external additive. Examples of the external additive include inorganic fine particles such as silica, alumina, titania, zirconia, tin oxide, and zinc oxide. Among these, silica having a small specific gravity is preferable from the viewpoint of preventing embedding.

  From the viewpoint of environmental stability, the silica is preferably hydrophobic silica that has been subjected to a hydrophobic treatment. The hydrophobizing method is not particularly limited, and examples of the hydrophobizing agent include hexamethyldisilazane (HMDS), dimethyldichlorosilane (DMDS), silicone oil, methyltriethoxysilane, and the like. Dichlorosilane (DMDS) is preferred.

  The content of the external additive is preferably 0.01 to 10 parts by weight and more preferably 0.1 to 5 parts by weight with respect to 100 parts by weight of the toner before being processed with the external additive.

  The surface treatment step using the external additive is preferably a dry mixing method in which the external additive and the toner are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, a V-type blender, or the like. The external additives may be mixed in advance and added to a high-speed stirrer or a V-type blender, or may be added separately.

The volume median particle size (D ₅₀ ) of the toner (A) and the toner (B) is preferably 3 to 12 μm, and more preferably 4 to 10 μm.

  The toner (A) and the toner (B) are mixed using a high-speed stirrer such as a Henschel mixer or a super mixer, a V-type blender, or the like to obtain the mixed toner for developing an electrostatic image of the present invention. The mixing ratio of the two toners is appropriately determined according to the color of the target mixed toner.

  The mixed toner of the present invention can be used as a one-component developing toner as it is, or as a two-component developing toner used by mixing with a carrier, in either a one-component developing method or a two-component developing method. The mixed toner of the invention can be suitably used as a two-component developing toner because it can cope with high-speed printing, and can also be suitably used for an image forming apparatus of a hybrid developing system. The hybrid developing system includes a magnetic roller, a developing roller, and a photosensitive drum carrying an electrostatic latent image on a peripheral surface, and a two-component developer composed of a non-magnetic toner and a magnetic carrier is added to the periphery of the magnetic roller. The two-component developer held on the magnetic roller is brought into contact with the developing roller to electrostatically adhere nonmagnetic toner to the peripheral surface of the developing roller. This is a developing method using an image forming apparatus configured to cause magnetic toner to fly onto the peripheral surface of the photosensitive drum and to visualize the electrostatic latent image on the photosensitive drum as a toner image.

As the carrier to be mixed with the toner of the present invention, a carrier with low saturation magnetization that weakens the contact with the magnetic brush is preferable from the viewpoint of image characteristics. Saturation magnetization of the carrier is preferably ^{40~100Am 2 / kg, 50~90Am 2 /} kg is more preferable. The saturation magnetization is preferably 100 Am ² / kg or less from the viewpoint of adjusting the hardness of the magnetic brush and maintaining gradation reproducibility, and preferably 40 Am ² / kg or more from the viewpoint of preventing carrier adhesion and toner scattering. The saturation magnetization of the carrier is measured by the method described in Examples described later.

  As the core material of the carrier, those made of known materials can be used without particular limitation, for example, ferromagnetic metals such as iron, cobalt, nickel, magnetite, hematite, ferrite, copper-zinc-magnesium ferrite, Examples include alloys and compounds such as manganese ferrite and magnesium ferrite, and glass beads. Among these, iron powder, magnetite, ferrite, copper-zinc-magnesium ferrite, manganese ferrite, and magnesium ferrite are preferable from the viewpoint of chargeability. From the viewpoint of image quality, ferrite, copper-zinc-magnesium ferrite, manganese ferrite and magnesium ferrite are more preferable.

  In the two-component developer obtained by mixing the mixed toner and the carrier, the weight ratio of the mixed toner to the carrier (mixed toner / carrier) is preferably 1/99 to 10/90, and 2/98 to 8/92. More preferred.

  In the image forming method of the present invention, an image is formed through a known process except that the developing process for developing the electrostatic latent image is performed by a hybrid developing system. As a process other than the development process, for example, a process of forming an electrostatic latent image on the surface of the photoreceptor (charging / exposure process), a process of transferring the developed toner image to a transfer material such as paper (transfer process), transfer There are a step of fixing the toner image (fixing step), a step of removing toner remaining on a developing member such as a photosensitive drum (cleaning step), and the like.

  The mixed toner of the present invention can be suitably used for a high-speed image forming apparatus having a linear velocity of preferably 750 mm / sec or more, more preferably 1000 mm / sec. Here, the linear speed refers to the process speed of the image forming apparatus, and is determined by the paper feed speed of the fixing unit.

[Softening point of resin]
Using a flow tester (Shimadzu Corp., CFT-500D), a 1 g sample was heated at a heating rate of 6 ° C / min, and a 1.96 MPa load was applied by a plunger, and extruded from a nozzle with a diameter of 1 mm and a length of 1 mm. . The amount of plunger drop of the flow tester is plotted against the temperature, and the temperature at which half of the sample flows out is taken as the softening point.

[Glass transition point of resin]
Using a differential scanning calorimeter (Seiko Denshi Kogyo Co., Ltd., DSC210), the temperature was raised to 200 ° C, and the sample was cooled to 0 ° C at a temperature drop rate of 10 ° C / min. The temperature at the intersection of the extended line of the baseline below the maximum peak temperature of endotherm and the tangent line indicating the maximum slope from the peak rising portion to the peak apex.

[Resin acid value]
Measured according to the method of JIS K0070. However, only the measurement solvent was changed from the mixed solvent of ethanol and ether specified in JIS K0070 to the mixed solvent of acetone and toluene (acetone: toluene = 1: 1 (volume ratio)).

[Volume-median particle diameter of toner (D ₅₀ )]
Measuring machine: Coulter Multisizer II (Beckman Coulter, Inc.)
Aperture diameter: 50μm
Analysis software: Coulter Multisizer AccuComp version 1.19 (Beckman Coulter)
Electrolyte: Isoton II (Beckman Coulter, Inc.)
Dispersion: Emulgen 109P (manufactured by Kao Corporation, polyoxyethylene lauryl ether, HLB: 13.6) is dissolved in the electrolytic solution to a concentration of 5% by weight to obtain a dispersion.
Dispersion conditions: 10 mg of a measurement sample is added to 5 ml of the dispersion, and dispersed for 1 minute with an ultrasonic disperser, then 25 ml of an electrolyte is added, and further dispersed for 1 minute with an ultrasonic disperser. Prepare a dispersion.
Measurement conditions: After adjusting the particle size of 30,000 particles to a concentration that can be measured in 20 seconds by adding the sample dispersion to 100 ml of the electrolyte solution, 30,000 particles are measured, Determine the volume median particle size (D ₅₀ ).

[Chromium ion strength of toner]
Measuring device: TOF-SIMS IV (made by ION-TOF)
Measurement conditions: Primary ion Bi3 25kV [0.5pA], Cycle Time 100μs
Bunching mode, positive ion detection
Measurement area 300 × 300μm, integration 50sec
Analysis method: Chromium (Cr) ionic strength ratio is m / z 52 ionic strength
Obtained by normalizing with total ion intensity.

[Charge amount of toner]
Measure using a Q / M meter (Epping). After adding 3.0 g of toner and 47.0 g of a silicone-coated ferrite carrier (manufactured by Kanto Denka Kogyo Co., Ltd., average particle size 60 μm) to a 50 ml plastic bottle, using a paint shaker (manufactured by TOYOSEIKI) and stirring for 30 minutes, Q / A specified amount of developer is put into a cell attached to the M meter, and only the toner is sucked for 90 seconds through a sieve having a mesh size of 32 μm (made of stainless steel, twill, wire diameter: 0.0035 mm). The voltage change on the carrier generated at that time is monitored, and the value of [total amount of electricity after 90 seconds (μC) / amount of attracted toner (g)] is calculated as the charge amount (μC / g).

Resin production example 1
1040 g polyoxypropylene (2.2) -2,2-bis (4-hydroxyphenyl) propane, 10 g polyoxyethylene (2.0) -2,2-bis (4-hydroxyphenyl) propane, 199 g terephthalic acid, and dibutyltin oxide 4 g was reacted at 230 ° C. under normal pressure for 5 hours under a nitrogen atmosphere, and further reacted under reduced pressure. After cooling to 210 ° C., 209 g of fumaric acid and 1 g of hydroquinone were added and reacted for 5 hours, and further reacted under reduced pressure to obtain a polyester (resin A). The obtained resin A had a softening point of 107.5 ° C., an acid value of 21.3 KOH mg / g, and a glass transition point of 64.4 ° C.

[Carrier saturation magnetization]
(1) Fill a plastic case with a lid of 7 mm outer diameter (6 mm inner diameter) and 5 mm height while tapping the carrier, and calculate the mass of the carrier from the difference between the weight of the plastic case and the weight of the plastic case filled with the carrier. .
(2) Set a plastic case filled with a carrier in the sample holder of the magnetic property measuring device “BHV-50H” (VSMAGNETOMETER) of RIKEN ELECTRONICS CO., LTD., While vibrating the plastic case using the vibration function, Saturation magnetization is measured by applying a magnetic field of 79.6 kA / m. The obtained value is converted into saturation magnetization per unit mass in consideration of the mass of the filled carrier.

Examples 1-5 and Comparative Examples 1-5
(Manufacture of toner (A))
100 parts by weight of resin A as a binder resin, 8 parts by weight of a condensation azo pigment “NOVOPERM SCARLET 4RF” (Clariant, CI Pigment Red 242) as a colorant, and the amount of salicylic acid compound used in Table 1 as a charge control agent 2 parts of polypropylene complex "Bontron E-81" (manufactured by Orient Chemical Industries) and 1 part by weight of polypropylene wax "High Wax NP-055" (manufactured by Mitsui Chemicals) as a release agent are mixed with a Henschel mixer, and then a twin-screw kneader Using “PCM-43” (manufactured by Ikegai Co., Ltd.), the mixture was melt-kneaded under the temperature conditions shown in Table 1, cooled with a drum flaker, and then roughly pulverized with a cutter mill. Thereafter, the mixture was finely pulverized with a jet mill and classified with an airflow classifier to obtain toner base particles having a volume median particle size (D ₅₀ ) of 8.5 μm.

  100 parts by weight of the obtained toner base particles and 0.6 parts by weight of hydrophobic silica “R-972” (manufactured by Nippon Aerosil Co., Ltd., hydrophobizing agent: DMDS) are mixed, stirred for 90 seconds with a Henschel mixer, and then opened A red toner was obtained by sieving with a 100 μm wire mesh.

(Production of toner (B))
Except for using 8 parts by weight of a copper halide phthalocyanine pigment `` HOSTPERM GREEN GG01 '' (manufactured by Clariant, CI Pigment Green 7) instead of the condensed azo pigment as a colorant, the same as in the toner (A), A green toner was obtained.

  50 parts by weight of toner (A) and 50 parts by weight of toner (B) were mixed with a Henschel mixer to obtain a mixed toner.

Examples 6 and 7
In the preparation of the mixed toner, the weight ratio of toner (A) to toner (B) ((A) / (B)) was changed to 70/30 in Example 6 and 30/70 in Example 7, respectively. In the same manner as in Example 1, a mixed toner was obtained.

Test example 1
5kg of ferrite carrier (average particle size: 60μm, saturation magnetization: 68Am ² / kg) is put into the image development device "Vario Stream 9000" (linear speed: 1000mm / sec) manufactured by Osse Printing System. The mixed toner was replenished so that the toner concentration was 6% by weight, and the mixture was stirred for 10 minutes to prepare a two-component developer, and then an image with a printing rate of 0.5% was printed on 200,000 sheets. At that time, the hue of the image printed on the paper was compared with the initial printing (100 sheets), and the change in hue (ΔE) was measured by the following method. The results are shown in Table 1.

[Measurement of ΔE]
The L ^* value, a ^* value, and b ^* value are measured using a color meter “SPM50” (manufactured by Gretag). The color difference (ΔE) is calculated according to the following formula, and the change in hue is evaluated.

(In the formula, L ₁ ^* , a ₁ ^* and b ₁ ^* represent initial values of printing, and L ₂ ^* , a ₂ ^* and b ₂ ^* represent values after printing 200,000 sheets, respectively.)

  From the above results, it can be seen that Examples 1 to 7 have much higher effects on hue change suppression than Comparative Examples 1 to 5. Further, from the results of Comparative Example 1 in which the charge amounts of the combined toners are substantially equal and the comparison between Example 1 and Comparative Example 5 in which the charge amounts of the respective toners are substantially equal, the effect of suppressing the change in hue is Regardless of the adjustment of the charge amount, it is clear that it is influenced by the chromium ion intensity ratio.

  The mixed toner for developing an electrostatic image of the present invention is used for developing a latent image formed in an electrophotographic method, an electrostatic recording method, an electrostatic printing method or the like.

Claims (4)

  An electrostatic charge image developing mixed toner comprising a toner (A) containing a binder resin and a condensation-type azo pigment, and a toner (B) containing a binder resin and a halogenated copper phthalocyanine pigment, the toner (A) and toner (B) further contain a chromium complex of a salicylic acid compound, and the chromium ion intensity ratio of toner (A) and toner (B) (chromium ion intensity of toner (A) / toner (B) A mixed toner for developing electrostatic images having a chromium ion intensity of 1.30 to 2.50.   A method for producing a mixed toner for developing an electrostatic image, comprising a step of mixing a toner (A) containing a binder resin and a condensation type azo pigment and a toner (B) containing a binder resin and a copper halide phthalocyanine. In addition, the toner (A) and the toner (B) further contain a chromium complex of a salicylic acid compound, and a ratio of chromium ion strength between the toner (A) and the toner (B) (chromium ion strength / toner (A) / A method for producing a mixed toner for developing an electrostatic charge image, wherein the chromium ion intensity of the toner (B) is 1.30 to 2.50.   An image forming method using the mixed toner according to claim 1 in an image forming apparatus of a hybrid development system.   The image forming method according to claim 3, wherein a linear velocity of the image forming apparatus is 750 mm / sec or more.