JP3235851B2 - Image forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electrophotography, electrostatic recording,
The present invention relates to an image forming method applied to electrostatic printing or the like.

[0002]

2. Description of the Related Art In an example of electrophotography, generally,
An electrostatic charge image was formed on the surface of the electrostatic charge image forming body by charging and imagewise exposure, and then the electrostatic charge image was developed with toner, and the obtained toner image was usually transferred to a recording material such as paper. Thereafter, the image is fixed by a heat roller fixing device or the like to form an image. . On the other hand, the toner remaining on the electrostatic image forming body after the transfer step is cleaned by a cleaning blade or the like and used for forming the next image.

Conventionally, the following techniques have been proposed as means for developing an electrostatic charge image. Means for keeping the electrostatic image forming body and the developer in a non-contact state and applying a voltage between the electrostatic image forming body and the developer carrier (Japanese Patent Application Laid-Open No. 59-121077). Means for developing by using a two-component magnetic developer and applying an alternating electric field in a developing area (Japanese Patent Laid-Open No. 59-67565). Means of developing by applying an alternating electric field in a developing area using a two-component developer (Japanese Patent Application Laid-Open No. 2-79863).

[0004]

However, in the above-mentioned conventional developing means, the developer layer on the developer carrier is transported to the developing area at a thickness that does not directly contact the electrostatic image forming member, and the developing layer is conveyed to the developing area. In order to cause the toner particles to fly and adhere to the electrostatic image of the electrostatic image forming body by the action of the alternating electric field formed in
When the particle size distribution of the toner particles is wide, selective development occurs in which large-sized particles preferentially adhere to the electrostatic charge image and small-sized particles do not contribute to development. There is a problem that reproducibility is poor, fogging occurs in an image, and toner scattering occurs.

On the other hand, in the toner constituting the developer, it is effective to use polymer particles having a small particle diameter obtained by a polymerization method as the toner in order to increase the resolution and achieve high image quality. Further, in order to form an image having a high image density, it is necessary to uniformly disperse the colorant in the toner. From this point of view, a technique of adding a colorant emulsion when aggregating primary particles obtained by a polymerization method to obtain secondary particles has been proposed (Japanese Patent Application Laid-Open No. Sho 63-282849). ). However, this
The technique disclosed in Japanese Patent No. 282749 has problems that it is difficult to uniformly disperse the colorant, the image density is low, and the reproducibility of intermediate colors is low in a color image.

Therefore, the present invention aims at the following matters. (1) To provide an image forming method in which selective development does not occur. (2) To provide an image forming method capable of forming an image with high resolution. (3) To provide an image forming method capable of forming an image without fog. (4) To provide an image forming method capable of forming an image having a high image density. (5) To provide an image forming method capable of forming an image having high reproducibility of intermediate colors of a color image.

[0007]

In order to achieve the above object, the image forming method of the present invention uses an average particle size of 0.5 to 3.0.
A dispersion of the colorant dispersed such that the particle size of the colorant is 2 to 10 times the primary particle size is added to the dispersion of the polymer particles a of μm, and the colorant is fixed on the surface of the polymer particles a. It is characterized in that a two-component developer containing, as a toner, aggregated particles b having an average particle size of 3.0 to 7.0 μm, which is obtained by agglomeration after the formation, is used. Further, in the image forming method, the developer carried on the developer carrying member so as not to contact the electrostatic image forming body is transported between the electrostatic image forming body and the developer carrying body, The method is characterized by including a step of developing by applying an alternating electric field between the electrostatic image forming body and the developer carrier. Further, the ratio of the colorant is preferably 2 to 10 parts by weight based on 100 parts by weight of the polymer particles a.

Hereinafter, the present invention will be described specifically. [Description of Toner] In the present invention, the average particle diameter is 0.5 to
The dispersion of the polymer particles a having a particle diameter of 1
A dispersion of a coloring agent dispersed so as to have a secondary particle diameter of 2 to 10 times is added, and the coloring agent is fixed on the surface of the polymer particles a and then aggregated to have an average particle diameter of 3.0 to 7.0 μm. And the aggregated particles b are used as toner. Here, the average particle size refers to a volume average particle size, and in the present invention, a laser diffraction type particle size distribution analyzer “HELOS”
(Manufactured by SYMPATEC). The primary particle size of the colorant is an average particle size calculated from the size and number of the colorant particles by an electron micrograph, and the particle size of the colorant in the dispersion is “DLS-700” (Otsuka Electronics (Manufactured by Co., Ltd.).

The average particle diameter of the aggregated particles b is 3.0 to 7.0 μm.
When it is in the range of m, high-quality reproduction with excellent resolution becomes possible. On the other hand, when the average particle diameter of the aggregated particles b is less than 3.0 μm, the colorant is insufficiently dispersed, and the image density is likely to be reduced. On the other hand, when the average particle size of the aggregated particles b exceeds 7.0 μm, the color reproducibility is poor, high image quality cannot be obtained, and the resolution is 5 lines / mm or less.

The average particle size of the polymer particles a is 0.5 to 3.0 μm.
When it is in the range of m, a toner (aggregated particles b) having a small environment dependence of charging and a uniform particle size distribution can be stably produced by the emulsion polymerization method. On the other hand, when the average particle diameter of the polymer particles a is less than 0.5 μm, the amount of the surfactant becomes large when the emulsion polymerization method is applied, the subsequent reaction is inhibited, and the toner (aggregation) The environmental dependence of the charging of the particles b) increases. On the other hand, when the average particle size of the polymer particles a exceeds 3.0 μm, stable production becomes difficult depending on the emulsion polymerization method, and the particle size distribution of the toner (aggregated particles b) becomes wide.

In the dispersion of the colorant, the dispersion of the colorant in the aggregated particles b is sufficiently uniform by previously dispersing the colorant so that the particle size of the colorant is 2 to 10 times the primary particle size. And a toner capable of forming an image having high image density and high reproducibility of an intermediate color of a color image. When the particle size of the colorant in the dispersion of the colorant is less than twice the primary particle size, the image density becomes low. On the other hand, the particle size of the colorant is 10% of the primary particle size.
When the ratio is more than twice, the content of the colorant increases, and the environmental dependency of the toner increases, and it is difficult to achieve both transparency and reflectivity when a color toner is used.

The polymerizable monomer for obtaining the polymer particles a may be any one capable of synthesizing a thermoplastic resin for toner, but is preferably a monomer used for obtaining a vinyl polymer. As the polymerizable monomer for obtaining the vinyl polymer, for example, those described in JP-A-56-106250 can be used. Specifically, styrene, o-methylstyrene, m- Methylstyrene, p-methylstyrene, α-methylstyrene, p-ethylstyrene, 2,4-dimethylstyrene, pn-butylstyrene, p-tert-butylstyrene, pn-hexylstyrene, pn- Styrenes such as octylstyrene, pn-nonylstyrene, pn-decylstyrene, pn-dodecylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, and 3,4-dichlorostyrene Monomers.

Other vinyl monomers include ethylenically unsaturated monoolefins such as ethylene, propylene, butylene and isobutylene, vinyl chlorides such as vinyl chloride, vinylidene chloride, vinyl bromide and vinyl fluoride, and acetic acid. Vinyl esters such as vinyl, vinyl propionate, vinyl benzoate, and vinyl butyrate, methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, propyl acrylate, and n-acrylate
Octyl, dodecyl acrylate, lauryl acrylate,
2-ethylhexyl acrylate, stearyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, α-methyl methyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate Α-methylene aliphatic monocarboxylic acids such as n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, stearyl methacrylate, phenyl methacrylate, dimethylaminoethyl methacrylate, and diethylaminoethyl methacrylate Esters, acrylic acid or methacrylic acid derivatives such as acrylonitrile, methacrylonitrile, acrylamide, vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether Vinyl ethers such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N-vinyl pyrrole; N-vinyl carbazole; N-vinyl indole;
Examples thereof include N-vinyl compounds such as N-vinylpyrrolidene, and vinylnaphthalenes.

When a polymerization reaction or the like is carried out on the acidic side, a monomer having an acidic polar group can be used simultaneously with the vinyl monomer. As the monomer having an acidic polar group,
Acrylic acid, methacrylic acid, fumaric acid, maleic acid,
Carboxyl groups (-COO) such as itaconic acid, cinnamic acid, monobutyl maleate, monooctyl maleate, and salts thereof such as metal salts such as Na and Zn.
H) having an α, β-ethylenically unsaturated compound, sulfonated styrene, its Na salt, allyl sulfosuccinic acid,
Α, β-ethylenically unsaturated compounds having a sulfone group (—SO ₃ H), such as octyl allylsulfosuccinate and its Na salt. In addition, an anionic surfactant, a nonionic surfactant, and the like described below can be used together with the vinyl monomer.

When a polymerization reaction is carried out on the basic side,
A monomer having a basic polar group can be used simultaneously with the vinyl monomer. Examples of the monomer having a basic polar group include (meth) acrylates of aliphatic alcohols having 1 to 12, preferably 2 to 8, particularly preferably 2 carbon atoms having an amine group or a quaternary ammonium group, (Meth) acrylic amide or optionally (meth) acrylic amide mono- or di-substituted by an alkyl group having 1 to 18 carbon atoms on N, vinyl substituted by a heterocyclic group having N as a ring member Compound, N, N-
Diallyl-alkylamine or a quaternary ammonium salt thereof. Among them, the amine group or 4
(Meth) of aliphatic alcohol having quaternary ammonium group
Acrylic esters are preferred. In addition, a cationic surfactant, a nonionic surfactant, and the like described below can be used together with the vinyl monomer.

A crosslinking agent may be used in combination with the polymerizable monomer. Examples of such a crosslinking agent include aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene and derivatives thereof, ethylene glycol dimethacrylate, diethylene glycol methacrylate, triethylene glycol methacrylate, trimethylolpropane triacrylate, allyl methacrylate, and t-butylaminoethyl. Methacrylate, tetraethylene glycol dimethacrylate, diethylenic carboxylic acid esters such as 1,3-butanediol dimethacrylate,
Examples thereof include divinyl compounds such as N, N-divinylaniline, divinyl ether, divinyl sulfide, and divinyl sulfone, and compounds having three or more vinyl groups.
These may be used alone or as a mixture.

Other crosslinking agents include ethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol,
4-butanediol, neopentyl glycol, 1,4
-Butenediol, 1,4-bis (hydroxymethyl)
Dihydric alcohols such as cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethylenated bisphenol A, polyoxypropylene bisphenol A, maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid Acids, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid, anhydrides of these acids or dibasic acids such as lower alcohol esters thereof and derivatives thereof, glycerin, trimethylolpropane And trivalent or more carboxylic acids such as trimellitic acid and pyromellitic acid.

Examples of the coloring agent include various organic pigments (azo pigments, polycyclic pigments, acidic or basic dyes), inorganic pigments (oxides, hydroxides, sulfides, selenides, ferrocyanides, chromic acids) Salt, sulfate, carbonate, silicate, phosphate, metal powder), carbon and the like. Specifically, carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, Dupont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate, lamp black, rose bengal, , And others. Of these, carbon black is preferred as the black colorant, disazo pigments are preferred as the yellow colorant, quinacridone pigments are preferred as the magenta colorant, and copper phthalocyanine pigments are preferred as the cyan colorant. The proportion of the colorant is preferably 2 to 10 parts by weight based on 100 parts by weight of the polymer particles a. With such a ratio, a toner having a high image density and low environmental dependency can be obtained.

The aggregated particles b may contain a charge control agent. Examples of such charge control agents include metal complex dyes, nigrosine dyes, and ammonium compounds.

When producing the polymer particles a, an anionic, cationic, amphoteric or nonionic surfactant may be used, if necessary. For example, to obtain a negatively chargeable toner, it is preferable to use an anionic surfactant, and to obtain a positively chargeable toner, it is preferable to use a cationic surfactant. In order to further improve the dispersion stability, it is preferable to use a nonionic surfactant in combination.

Examples of the anionic surfactant include fatty acid salts such as sodium oleate and castor oil, alkyl sulfate esters such as sodium lauryl sulfate and ammonium lauryl sulfate, alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate, and alkylnaphthalene. Sulfonates, dialkyl sulfosuccinates, alkyl phosphates, naphthalene sulfonic acid formalin condensates, polyoxyethylene alkyl sulfates, and the like.

Examples of the cationic surfactant include alkylamine salts such as laurylamine acetate and stearylamine acetate, and quaternary ammonium salts such as lauryltrimethylammonium chloride and stearyltrimethylammonium chloride.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene fatty acid ester, sorbitan fatty acid ester, polyoxysorbitan fatty acid ester, polyoxyethylene alkylamine, glycerin, fatty acid ester, and the like. Oxyethylene-oxypropylene block polymer and the like.

Examples of the amphoteric surfactant include lauryl trimethyl ammonium chloride and the like.
The amount of the surfactant used is 0.01 to the polymerizable monomer.
10 to 10% by weight is preferred, and particularly 0.5 to 5% by weight is preferred. If the amount of the surfactant is too small, stable emulsion polymerization may be difficult, and if the amount of the surfactant is excessive, the moisture resistance of the toner may be deteriorated.

In producing the polymer particles a, a water-soluble polymerization initiator may be used as necessary. Examples of such a water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate, hydrogen peroxide, 4,4′-azobiscyanovaleric acid, and 2,2′-azobis (2-amidinopropane) dihydrochloride. , T-butyl hydroperoxide,
Cumene hydroperoxide and the like. These water-soluble polymerization initiators may be used in combination with a reducing agent. As the reducing agent, generally known agents such as sodium metabisulfite and ferrous chloride can be used. It is not necessary to use the reducing agent, but when it is used, it is preferable to use it in an equivalent amount or less with respect to the water-soluble polymerization initiator. The amount of the polymerization initiator used is preferably 0.01 to 10% by weight, particularly preferably 0.1 to 5% by weight, based on the polymerizable monomer. If the amount of the polymerization initiator is too small, the polymerizable monomer does not completely polymerize and remains in the toner, possibly deteriorating the properties of the toner.

In the toner used in the present invention, a fluidizing agent may be externally added and mixed as needed. Such fluidizing agents include inorganic oxides, inorganic nitrides, carbides,
Organic fine particles are exemplified. These may be used in combination as appropriate.

[Production Example of Toner] Hereinafter, a specific production example of the toner will be described. A polymerizable monomer such as a styrene-based or acrylic-based polymer is formed into an emulsion in an aqueous medium to which a polymerization initiator, a cross-linking agent, a surfactant, and the like are added as necessary, and the emulsion is maintained at a temperature of 50 to 100 ° C. 0.5 ~
After 5 hours of polymerization reaction, the average particle size is 0.5 to
A 3.0 μm polymer particle a is produced. Instead of producing the polymer particles a by performing a polymerization reaction as described above, polymer fine particles of styrene, acrylic, epoxy, or the like may be used. On the other hand, a colorant is dispersed in an aqueous medium to which a surfactant has been added. In this dispersion, the particle size of the dispersed colorant is adjusted to be 2 to 10 times the primary particle size.

The dispersion of the polymer particles a obtained as described above is mixed with the dispersion of the colorant, and while the pH is adjusted, the dispersion is uniformly performed by a stirrer to give polymer particles a.
The colorant is fixed on the surface of the glass and further raised to a high temperature of 50 to 90 ° C. to promote agglomeration, and the average particle size is 3.0 to 7.0 μm.
Is obtained. Further, a fluidizing agent may be externally added to and mixed with the toner.

[Explanation of Carrier] In the present invention, as the carrier used in combination with the toner, a carrier whose surface such as iron powder or ferrite powder is coated with a resin is preferable. Examples of the coating resin include a styrene-acrylic resin, a fluorine resin, and a silicone resin. Further, the form of the carrier may be spherical or irregular.

[Explanation of Image Forming Process] In the image forming method of the present invention, an image is formed using a two-component developer containing the toner. In particular, the developer carried on the developer carrying member so as to be in non-contact with the electrostatic image forming member is transported between the electrostatic image forming member and the developer carrying member. It is preferable to include a step of developing by applying an alternating electric field between the developer and the developer carrier.

FIG. 1 is a schematic view of a main part of an apparatus which can be used in the image forming method of the present invention.
Is a developer carrier, 3 is a two-component developer, 4 is a layer thickness regulating member, 5 is a development area, 6 is a developer layer, and 7 is a power supply for forming an alternating electric field. The developer is carried on the developer carrier 2 by magnetic force, is regulated to a predetermined thickness by the layer thickness regulating member 4, and is conveyed to the development area 5. The developer carrier 2 includes a developing sleeve 2A and an internal magnet body 2B. In the developing area 5, the developer layer 6
So as not to directly rub the electrostatic image forming body 1
The thickness of the developer layer 6 on the developer carrier 2 is controlled by the thickness regulating member 4.
Regulated by

The minimum gap Dsd of the developing area 5 is larger than the thickness of the developer layer 6 conveyed to the developing area 5, for example, about 100 to 1000 μm. The thickness B _H of the developer layer 6 on the developer carrier 2 is, for example, about 50 to 900 μm. As the power source 7 for forming the alternating electric field, an alternating current having a frequency of 1 to 10 kHz and a voltage of 1 to 3 kV _PP is preferable. The power source 7 may have a configuration in which a direct current is added to an alternating current as necessary. As a direct current, a voltage of 300 to 8
00V is preferred.

The toner image formed on the electrostatic image forming body in the developing step is transferred to a transfer material in the transferring step. In this transfer step, any of an electrostatic transfer method and a bias transfer method can be applied, and particularly, the electrostatic transfer method can be preferably used. Specifically, for example, a transfer device for generating a DC corona discharge is arranged so as to face the electrostatic image forming body via the transfer material, and the DC charge is applied to the transfer material from the back surface side to cause an electrostatic charge. The toner image carried on the surface of the image forming body is transferred to the surface of the transfer material. In addition, in order to facilitate the transfer, it is preferable to add, for example, a charging / exposure step before the transfer step.

The developer remaining on the electrostatic image forming body without being transferred in the transfer step is cleaned by a cleaning step. Although the cleaning means is not particularly limited, a cleaning device having a cleaning blade in contact with the surface of the electrostatic image forming body is preferable. According to this cleaning device, the residual developer is scraped off by rubbing the surface of the electrostatic charge image forming body with the cleaning blade. Note that, in the preceding stage of the cleaning step, it is preferable to add a charge elimination step for eliminating the charge on the surface of the electrostatic charge image forming body in order to facilitate the cleaning. This static elimination step can be performed by, for example, a static eliminator that generates an AC corona discharge.

The transfer material on which the toner image has been transferred in the transfer step is subjected to a fixing process by a heat fixing device or a pressure fixing device, thereby forming an image.

[0036]

[Example 1]

Styrene monomer 85 parts Butyl acrylate 15 parts Acrylic acid 5 parts Water 500 parts Nonionic surfactant (polyoxyethylene alkyl ether) 2 parts Cationic surfactant (dimethylammonium chloride) 2 parts Polymerization initiator (Potassium persulfate) was added to the mixed aqueous solution. K. The mixture was stirred while being kept at 80 ° C. in a container equipped with a homomixer to produce polymer particles a having an average particle size of 2.2 μm.

In the same apparatus as above, 100 parts of water, 10 parts of carbon black (colorant) and 2 parts of an anionic surfactant (alkylbenzene) were added. K. The mixture was stirred at 10,000 rpm with a formula homomixer to make the particle size of the dispersed particles of carbon black three times the primary particle size.

In a dispersion containing 100 parts of the above polymer particles a,
The above-mentioned dispersion liquid containing 10 parts of carbon black (coloring agent) was mixed and kept at 40 ° C. for 4 hours to fix the carbon black on the surface of the polymer particles a. On this occasion,
The pH was adjusted to 5.0 with hydrochloric acid. Further, when the temperature is 60 ° C
, And held for 6 hours to perform aggregation, and ammonia water was added to adjust the pH to 7 to control the aggregation reaction, thereby obtaining aggregated particles b having an average particle size of 5.1 μm. Above polymer particles a, dispersion of carbon black, aggregated particles b
The main conditions for are summarized in Table 1 below.

The aggregated particles b were washed with water and dried to obtain a toner. To this toner, 2% by weight of silica and 1% by weight of titanium oxide were added and mixed, and 5 parts of this externally added toner and 95% of ferrite particles (carrier) 95 whose surface was coated with a methyl methacrylate / styrene copolymer. Were mixed to prepare a two-component developer.

Using this two-component developer, a developer carried on a developer carrier so as to be in non-contact with the electrostatic image forming body is moved between the electrostatic image forming body and the developer carrier. The electrophotographic copying machine “DC8028” (manufactured by Konica Corporation), which employs a system for developing by applying an alternating electric field between the electrostatic image forming body and the developer carrier, is transported to a negative organic material. A real image test for forming a copy image was performed using a machine modified so that the photosensitive member could be used, and the following items were evaluated. The results are as shown in Table 2 below.

The minimum gap Dsd of the developing area is 500
μm, the thickness B _H of the developer layer on the developer carrier is 400 μm.
m. In order to form an alternating electric field, an alternating current having a frequency of 2 kHz and a voltage of 2 kV _PP was used. further,
A DC voltage of 500 V was applied in series to the AC.

[Resolution] A copy image of the thin line chart was formed, and the determination was made based on the number of identifiable thin lines per 1 mm.

[Fog] Under normal temperature and normal humidity environment (temperature 20 ° C.,
A continuous copy image is formed at a relative humidity of 60%, and the reflection density of a white background portion is measured with a “Sakura Densitometer” (manufactured by Konica Corporation). When the reflection density exceeds 0.02 Fog was judged by the number of copies.

[Coloring degree of toner] A toner is adhered to a white label in a single layer, and the reflection density of this toner layer is measured with a “Sakura Densitometer” (manufactured by Konica Corporation). The case of 1.3 or more was evaluated as ○, and the case of less than 1.3 was evaluated as ×.

[Change in particle size distribution] 1/3 of the volume average particle size
The following toner number% was evaluated. The volume average particle size is measured by the above “HELOS”. The measurement was performed at the start of the actual shooting test and at the time of fogging or 50,000 copies, and the change with time was examined. If the number% of the toner having a volume average particle diameter of 1/3 or less is 10% or more, the chargeability of the toner is impaired.

Example 2 Polymer particles a having an average particle size of 0.9 μm were obtained in the same manner as in Example 1. To a dispersion containing 100 parts of the polymer particles a, a dispersion containing 10 parts of carbon black (colorant) obtained in the same manner as in Example 1 was mixed, and further, 85 parts of a styrene monomer and 15 parts of butyl acrylate were added. And a mixture of 5 parts of acrylic acid and 2 parts of a polymerization initiator (potassium persulfate) was added dropwise at a temperature of 60 ° C. to 6 parts.
Polymerization was carried out over time to obtain aggregated particles b having an average particle size of 3.0 μm. The aggregated particles b were washed with water and dried to obtain a toner. In the same manner as in Example 1, an external additive was added to the toner, and a carrier was further mixed to prepare a developer. A real-image test was performed using this developer in the same manner as in Example 1, and the results shown in Table 2 below were obtained.

[Examples 3 to 6] In Example 1, the average particle diameter of the polymer particles a, the kind of the colorant, the ratio of the particle diameter to the primary particle diameter of the colorant in the colorant dispersion, the aggregated particles b
A developer was prepared in the same manner as in Example 1 except that the average particle size was as shown in Table 1 below, and an actual printing test was performed. As a result, the results shown in Table 2 below were obtained. The following items were further evaluated for the color toner. [Reproducibility of intermediate colors in color images] Measure the L ^* a ^* b ^* color system using a color difference meter (Macbeth, manufactured by Minolta Co., Ltd.), and evaluate the image using the color chart published by the Institute of Electrophotography. The color difference ΔE from the original chart was measured. It is good if ΔE is 20 or less. The original chart is printed using the same pigment.

[Comparative Examples 1 to 6] In Example 1, the average particle size of the polymer particles a, the kind of the colorant, the ratio of the particle size to the primary particle size of the colorant in the colorant dispersion, the aggregated particles b
A developer was prepared in the same manner as in Example 1 except that the average particle size was as shown in Table 1 below, and an actual printing test was performed. As a result, the results shown in Table 2 below were obtained. For the color toner, the reproducibility of the intermediate color of the color image was evaluated in the same manner as described above.

[0049]

[Table 1]

[0050]

[Table 2]

[0051]

As described in detail above, according to the image forming method of the present invention, the following effects can be obtained. (1) No selective development occurs. (2) A high-resolution image can be formed. (3) An image without fog can be formed. (4) An image having a high image density can be formed. (5) It is possible to form an image having high reproducibility of an intermediate color of a color image.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing an example of a developing device that can be used for performing a developing step in an image forming method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrostatic image forming body 2 Developer carrier 2A Developing sleeve 2B Magnet 3 Developer 4 Layer thickness regulating member 5 Developing area 6 Developer layer 7 Power supply

Continuation of the front page (72) Inventor Mayumi Tanaka 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (56) References JP-A-2-61650 (JP, A) JP-A-63-186253 (JP, A (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 9/08 381

Claims (4)

(57) [Claims] 1. A dispersion of a colorant dispersed in a dispersion of polymer particles a having an average particle size of 0.5 to 3.0 μm such that the particle size of the colorant is 2 to 10 times the primary particle size. Is added, and a colorant is fixed on the surface of the polymer particles a. Then, the two-component developer containing the aggregated particles b having an average particle diameter of 3.0 to 7.0 μm and obtained as a toner is used. Image forming method. 2. The image forming method according to claim 1, wherein the two-component developer carried on the developer carrier so as to be in non-contact with the electrostatic image body is supported by the electrostatic image body and the developer carrier. An image forming method comprising the steps of: transporting the developer between the developer and the developer; and applying an alternating electric field between the developer and the developer to develop the image. 3. The image forming method according to claim 1, wherein the proportion of the colorant is 2 to 10 based on 100 parts by weight of the polymer particles a.
An image forming method characterized in that it is a weight part. 4. The image forming method according to claim 2, wherein the ratio of the colorant is 2 to 10 based on 100 parts by weight of the polymer particles a.
An image forming method characterized in that it is a weight part.