JP3115057B2 - 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 for using a toner containing a specific polyester as a binder resin to keep the electrostatic image forming body and the developer in non-contact, and to apply a voltage between the electrostatic image forming body and the developer carrier No. 62-178277).

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 body, and the alternating electric field formed in the developing area is conveyed. The action causes the toner particles to fly and adhere to the electrostatic image of the electrostatic image forming body, so when the particle size distribution of the toner particles is wide, large-sized particles preferentially adhere to the electrostatic image. Selective development occurs in which particles having a small particle size do not contribute to development. As a result, there is a problem in that image reproducibility is poor, fogging occurs in the image, and toner scattering occurs.

On the other hand, as a toner constituting a developer,
It is effective to use a toner having a small particle diameter obtained by a polymerization method in order to increase the resolution and improve the image quality. From this point of view, the following techniques have been conventionally proposed. Japanese Patent Application Laid-Open No. 62-266559 discloses a method in which fine particles are once prepared, and a monomer system containing a polymerization initiator is added dropwise to a dispersion medium system, and coalesced under a temperature condition of 70 to 90 ° C. to form an amorphous form. A toner having improved cleaning properties has been proposed. Japanese Patent Application Laid-Open No. 2-51164 proposes a technique in which particles having a particle size of 10 μm or less are formed into amorphous aggregated particles having a particle size of 5 to 25 μm, and a polyvinyl alcohol having a saponification degree of 60 to 85% is added to obtain a toner. . The reaction temperature of the primary particles is 65 ° C.

[0006]

However, Japanese Patent Application Laid-Open No. Sho 62-62
In the technique of 266559, it takes time to uniformly disperse the polymerization initiator, and it is difficult to obtain a small-diameter amorphous toner having a wide particle size distribution and good cleaning properties. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 2-51164, there is a problem that the environmental stability of chargeability is large due to polyvinyl alcohol as a suspension stabilizer, and fog and toner scattering are likely to occur.

Accordingly, 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 with good cleaning properties.

[0008]

To achieve the above object, according to an aspect of the image forming method of the present invention, the polymerizable monomer to the aqueous medium
Particles and colorant dispersion formed by polymerization reaction in
Are mixed, and the average particle diameter obtained by performing agglomeration is 0.5 to
3.0 μm, average particle size obtained by aggregating polymer particles a having a degree of dispersion of 1.1 to 1.8, 3.0 to 7.0 μm, degree of dispersion 1.1 to 1.8, degree of irregularity A two-component developer containing 1.3 to 3.0 agglomerated particles b as a toner is carried on a developer carrier, and the two-component developer is charged in such a manner that the two-component developer is not in contact with the electrostatic image forming member. The method is characterized in that the method includes a step of transporting between the formed body and the developer carrying member, and developing by applying an alternating electric field between the electrostatic image forming body and the developer carrying member.

Hereinafter, the present invention will be described specifically. [Description of Toner] In the present invention, the average particle diameter is 0.5 to
The polymer particles a having a size of 3.0 μm were aggregated to form an average particle size of 3.0.
７7.0 μm, degree of dispersion 1.1 to 1.8, degree of irregularity 1.
Aggregated particles b of 3 to 3.0 are produced, 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 value measured by a laser diffraction type particle size distribution analyzer “HELOS” (manufactured by SYMPATEC). The degree of dispersion σ is given by σ = Dv / Dp
(Dv: volume average particle diameter, Dp: number average particle diameter) In the present invention, it refers to a value measured by the above “HELOS”. The degree of irregularity is defined by the following formula 1, and the BET measurement value and the measured particle size are measured by Micromeritics, Flowsorb 2300II (flow type automatic measuring apparatus for specific surface area; manufactured by Shimadzu Corporation). It was done.

[0010]

(Equation 1)

The average particle size of the aggregated particles b is 3.0 to 7.0 μm.
When it is within the range of m, it is possible to reproduce high-quality images with excellent resolution and good cleaning properties. On the other hand, when the average particle size of the aggregated particles b is less than 3.0 μm,
Cleaning failure is likely to occur. On the other hand, when the average particle size of the aggregated particles b exceeds 7.0 μm, high image quality cannot be obtained, and the resolution is 5 lines / mm or less.

When the degree of dispersion of the agglomerated particles b is in the range of 1.1 to 1.8, good image quality without fog and toner scattering can be reproduced. On the other hand, when the degree of dispersion of the aggregated particles b is less than 1.1, production becomes difficult due to the temperature and concentration gradient of the apparatus and the solvent, and it is practically very difficult to obtain a toner with a high yield. On the other hand, when the degree of dispersion of the agglomerated particles b exceeds 1.8, selective development in which large-sized toner particles adhere preferentially to the electrostatic image forming body and small-sized toner particles do not contribute to development. And fog and toner scattering occur.

The degree of irregularity of the aggregated particles b is from 1.3 to 3.0.
When the ratio is within the range, the cleaning property of the toner is improved, and the fluctuation of the particle size distribution is small, and the stable charging property is exhibited. On the other hand, when the degree of irregularity of the aggregated particles b is less than 1.3, cleaning failure occurs. On the other hand, when the degree of irregularity of the aggregated particles b exceeds 3.0,
Since the toner is easily disintegrated in the developing device, the particle size distribution fluctuates and the chargeability changes.

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.

The polymerization degree of dispersion of the particles a, from the viewpoint of narrowing the particle size distribution of aggregated particles b, is in the range of 1.1 to 1.8
You.

[0016]

[0017]

[0018]

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, methyl isopropenyl ketone, etc., 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 a (meth) acrylate of an aliphatic alcohol 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.

Further, 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, and 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, dibasic acids such as anhydrides of these acids or lower alcohol esters thereof and derivatives thereof, glycerin, trimethylolpropane And trivalent or more carboxylic acids such as trimellitic acid and pyromellitic acid.

As the coloring agent contained in the polymer particles a,
Various organic pigments (azo pigments, polycyclic pigments, acidic or basic dyes), inorganic pigments (oxides, hydroxides, sulfides, selenides, ferrocyanides, chromates, sulfates, carbonates, (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, mixtures thereof, and the like. Among 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 polymer particles a may contain a release agent. Examples of such a release agent include, for example,
No. 6,110,946 can be used. Specifically, polyolefin wax, paraffin wax, paraffin oxide wax, fatty acid ester wax, partially saponified fatty acid ester wax, 00
01 mid wax, microcrystalline wax and other waxes. Among these, polyolefin wax is preferred. Particularly, polypropylene wax and polyethylene wax are preferable. Further, a polypropylene wax modified with a carboxylic acid such as maleic acid is preferable. Further, several kinds of polyolefin waxes may be used in combination.

Commercially available polyolefin waxes include Viscol 330P, Viscol 550P, Viscol 660P (these are polypropylene waxes manufactured by Sanyo Chemical Industries, Ltd.), High Wax 320P, and High Wax 3
10P, high wax 410P, high wax 405
P, high wax 400P, high wax 200P (the above, polyethylene wax manufactured by Mitsui Petrochemical Co., Ltd.), sun wax 131P, sun wax 151P, sun wax 161P, sun wax 165P, sun wax 17
1P (the above, manufactured by Sanyo Chemical Industries, polyethylene wax), polywax 400, polywax 500, polywax OH465, polywax 1040 (the above, manufactured by Toyo Petrolite Co., polyethylene wax).

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

In 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 sulfates 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, if 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 based on 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 necessary. 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 ~
The polymerization reaction is performed for 5 hours to produce core particles. Instead of producing the core particles by the polymerization reaction as described above, polymerized fine particles of styrene type, acrylic type, epoxy type, etc. may be used.

The reaction liquid containing the core particles obtained as described above is mixed with a dispersion of a coloring agent and, if necessary, a dispersion of a release agent. The polymer particles a are produced by performing a proper dispersion and agglomeration. In this agglomeration, the average particle size of the polymer particles a is adjusted to 0.5 to 3.0 μm. The reaction is stopped by adjusting the temperature and pH of the dispersion so that the degree of dispersion of the polymer particles a is preferably 1.1 to 1.8. The dispersion containing the polymer particles a is further heated to a high temperature of 50 to 90 ° C. to promote agglomeration, and the average particle size is 3.0 to 7.0 μm,
The degree of dispersion is 1.1 to 1.8, and the degree of irregularity is 1.3 to 3.0.
Is obtained. Further, a fluidizing agent may be externally added to and mixed with the toner.

[Explanation of Carrier] In the present invention, the carrier used in combination with the toner is preferably a carrier whose surface is coated with a resin such as iron powder and ferrite powder. 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 unit that generates a DC corona discharge is disposed 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 to which the toner image has been transferred in the transfer step is subjected to a fixing process by a heat fixing device, a pressure fixing device or the like, thereby forming an image.

[0045]

[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 vessel equipped with a homomixer. A dispersion liquid in which 10 parts of carbon black is dispersed,
A dispersion liquid in which 2 parts of polypropylene is dispersed is added, and 4
The polymerization reaction was carried out at 0 ° C. for 4 hours to obtain polymer particles a. At this time, the pH was adjusted to 5.0 with hydrochloric acid. When the particle size of the polymer particles a was measured by the above “HELOS”, the average particle size was 2.2 μm and the degree of dispersion was 1.6.

Further, the temperature was raised to 60 ° C. and the temperature was maintained for 6 hours to cause coagulation. To adjust the pH to 7, ammonia water was added to control the coagulation reaction, and the average particle size was 5.1 μm. Agglomerated particles b having a degree of 1.4 and an irregularity of 2.0 were obtained. Also, [volume average particle size of aggregated particles b /
(Volume average particle diameter of polymer particles a x degree of dispersion of polymer particles a)]
Was 3. The main conditions for the polymer particles a and the aggregated particles b 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 carrying member so as to be in non-contact with the electrostatic image forming member is moved between the electrostatic image forming member and the developer carrying member. And a copy image formed by an electrophotographic copying machine “DC8028” (manufactured by Konica Corporation) employing a system for developing by applying an alternating electric field between the electrostatic image forming body and the developer carrier. The following items were evaluated 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.

[Cleaning Property] The surface of the photoreceptor was visually observed and evaluated by the number of copies at the time when cleaning failure occurred.

[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.

[0054]

[ Examples 2 to 5] In the same manner as in Example 1, except that the conditions were changed.
Aggregated particles b having the average particle size, degree of dispersion, and degree of irregularity shown in Table 1 below were obtained. A developer was prepared using the agglomerated particles b in the same manner as in Example 1, and an actual printing test was performed. As a result, the results shown in Table 2 below were obtained.

[Comparative Examples 1 to 6] Agglomerated particles b having the average particle diameter, the degree of dispersion, and the degree of irregularity shown in Table 1 below were obtained in the same manner as in Example 1 except that the reaction conditions were changed. .
A developer was prepared using the particles b in the same manner as in Example 1, and an actual printing test was performed. As a result, the results shown in Table 2 below were obtained.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

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) Good cleaning properties.

[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

Continued on the front page (72) Inventor Mayumi Tanaka 2970, Ishikawacho, Hachioji-shi, Tokyo Inside Konica Corporation (56) References JP-A-63-282749 (JP, A) JP-A-3-113465 (JP, A) JP-A-1-92759 (JP, A) JP-A-4-324868 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. A polymerization reaction of a polymerizable monomer in an aqueous medium.
The core particles and the colorant dispersion are mixed and aggregated.
The average particle size obtained by coagulating polymer particles a having an average particle size of 0.5 to 3.0 μm and a dispersity of 1.1 to 1.8 is 3.0 to 7.0 μm. , The degree of dispersion 1.1 to 1.
8. A two-component developer containing agglomerated particles b having a degree of irregularity of 1.3 to 3.0 as a toner is carried on a developer carrier, and the two-component developer is brought into non-contact with the electrostatic image forming body. Transporting between the electrostatic image forming body and the developer carrier so as to form an alternating electric field between the electrostatic image forming body and the developer carrier to develop. Image forming method.