JP2003228191A - Electrophotographic developer and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developer for electrophotography which is excellent in fluidity and storability and hardly deteriorates in image quality due to environmental fluctuation, a method for producing the same, and an image forming method using the developer. The developer comprises polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the surface of the particles, and has a conductivity of an aqueous extract of the developer. σ2 is 20 μS / cm or less and σ2-σ1 is 10 μS / c
m or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developer and its use, and more specifically, it has excellent fluidity and storability.
In addition, the present invention relates to a developer that causes little deterioration in image quality due to environmental changes and a development forming method using the developer.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an electrostatic latent image formed by exposure is first developed with a developer, and then a developer image formed by the development is If necessary, it is transferred onto a transfer material such as paper and then fixed by various methods such as heating, pressurizing, solvent vapor and the like.

The image formed by the electrophotographic apparatus is
From year to year, the demand for fineness is increasing. Conventionally, the developer used in the apparatus is a pulverized developer obtained by melting, pulverizing, and classifying a resin containing a colorant, but the particle size control is easy and complicated such as classification. Polymerization type developers, which are said to be unnecessary in various manufacturing processes, have been receiving attention. As the polymerization method developer, the polymerization method developer is dispersed in 20 ml of water having an electric conductivity of σ1 at a ratio of 1 g of the developer, sufficiently stirred to equilibrate, and then a filtrate obtained by filtering the polymerization method developer. 5 μS / cm ≦ D2−σ1 ≦ 50 μS /
Those having a relationship of cm have been proposed (Japanese Patent Laid-Open No. Hei 8 (1999) -811)
No. 248676). This polymerization method developer is a so-called two-component developer that is charged by friction with magnetic iron powder. However, this two-component developer
When used as a non-magnetic one-component developer that is charged by friction with a developing roll or a developing blade, the amount of charge greatly depends on the environment, the image quality is deteriorated due to environmental changes, and the fluidity and storage stability are low. . As a non-magnetic one-component developer, the present applicant has previously proposed a polymerization method developer having a metal ion content of 1000 ppm or less due to a poorly water-soluble metal compound (JP-A-8-160661). . Although the image quality of this developer is greatly reduced due to environmental changes, further improvement in storage stability and fluidity has been demanded.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic developer having excellent fluidity and storability, and having little deterioration in image quality due to environmental changes, and an image forming method using the same. . The present inventors, as a result of earnest research to achieve the above object, by using a non-magnetic one-component developer having a specific range of conductivity, found that the above object can be achieved, based on this finding, The present invention has been completed.

[0005]

Thus, according to the present invention, (1) polymer particles for a developer obtained by polymerizing a polymerizable monomer, and an external additive attached to the surface of the particles. The developer has a conductivity σ2 of an aqueous extract of the developer obtained by the following procedure of 20 μS / cm or less, σ2
Provided is an electrophotographic developer having −σ1 of 10 μS / cm or less. 100g of ion-exchanged water with 6g dispersed in conductivity of σ1
Is heated and boiled for 10 minutes, and then ion-exchanged water with a pH of 7 and a conductivity of σ1 is boiled separately to add evaporated water to restore the original volume, and then at room temperature. To obtain a water extract.

The following are provided as preferred embodiments of the developer of the present invention. (2) A developer comprising polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the surface of the particle, which is obtained by the following procedure. The developer for electrophotography according to (1) above, wherein the pH of the water extract is 4 to 7. After heating 6 g of ion-exchanged water having a pH of 7 in which 6 g is dispersed and boiling for 10 minutes, the ion-exchanged water having a pH of 7 is separately boiled to add evaporated water to the original content. Then, the mixture is returned to the above volume and cooled to room temperature to obtain a water extract. (3) A developer comprising polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive adhering to the surface of the particle, wherein 1 g of the developer is 20 ml of water having an electric conductivity σ1. When the conductivity of the filtrate obtained by filtering the dispersion is D2, the dispersion is D2-σ1 of less than 5 μS / cm. The electrophotographic developer according to (1) or (2) above. (4) The electrophotographic developer according to any one of (1) to (3) above, wherein the electrophotographic developer is a non-magnetic one-component developer.

(5) The polymerizable monomer contains a styrene-based monomer, an ester of acrylic acid or methacrylic acid, and a crosslinkable monomer. The developer described. (6) The developer according to (5) above, which further contains a macromonomer in the polymerizable monomer. (7) The external additive is a silicon dioxide particle (1) to
The developer according to any one of (6).

(8) The external additive has a number average particle diameter of 5 to 20 n.
m, preferably 7 to 18 nm particles, preferably inorganic oxide particles, in combination with number average particle size of more than 20 nm and 2 nm or less, preferably 30 nm to 1 μm particles, preferably inorganic oxide particles. The developer according to any one of (1) to (7) above. (9) The developer according to any one of (1) to (8) above, wherein the polymer particles for a developer contain a colorant, a charge control agent and a release agent. (10) The above (1) to which the fixing temperature is 80 to 140 ° C.
The developer according to any one of (9).

(11) The polymer particles for a developer have a volume average particle diameter (dv) of 1 to 20 μm (1) to (10).
The developer according to any one of 1. (12) Volume average particle diameter (dv) of polymer particles for developer /
The number average particle diameter (dp) is 1.7 or less (1) to
The developer according to any one of (11). (13) The ratio (rl / rs) of the major axis rl and the minor axis rs of the polymer particles for a developer is 1 to 1.2, (1) to
The developer according to any one of (12).

Further, according to the present invention, (14) the electrostatic latent image is developed using the developer described in any one of (1) to (13) above to obtain a developer image, and a transfer material is obtained. A development forming method is provided in which the developer image is transferred to and fixed on.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The developer of the present invention comprises developing polymer particles and an external additive adhering to the surface of the particles.

The polymer particles for developer are obtained by polymerizing a polymerizable monomer. As a particularly preferable polymerizable monomer used for obtaining the polymer particles for a developer constituting the present invention, a monovinyl-based monomer can be mentioned. Specific examples of monovinyl monomers include styrene and
Styrene-based monomers such as vinyltoluene and α-methylstyrene; acrylic acid, methacrylic acid; methyl acrylate,
Ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate,
Derivatives of acrylic acid or methacrylic acid such as 2-ethylhexyl methacrylate, dimethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide; ethylene, propylene,
Ethylene unsaturated monoolefins such as butylene; vinyl halides such as vinyl chloride, vinylidene chloride and vinyl fluoride; vinyl esters such as vinyl acetate and vinyl propionate; vinyl ethers such as vinyl methyl ether and vinyl ethyl ether; vinyl methyl ketone , Vinylisotone such as methyl isopropenyl ketone; nitrogen-containing vinyl compounds such as 2-vinylpyridine, 4-vinylpyridine and N-vinylpyrrolidone; and other monovinyl monomers. These monovinyl-based monomers may be used alone or in combination of a plurality of monomers. Among these monovinyl monomers, a styrene monomer or a derivative of acrylic acid or methacrylic acid is preferably used.

Further, the use of a crosslinkable monomer is effective for improving hot offset. The crosslinkable monomer is a monomer having two or more polymerizable carbon-carbon unsaturated double bonds. Specifically, aromatic divinyl compounds such as divinylbenzene, divinylnaphthalene, and derivatives thereof; diethylenically unsaturated carboxylic acid esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether, etc. And the like; compounds having 3 or more vinyl groups; and the like. These crosslinkable monomers may be used alone or in combination of two or more. These crosslinkable monomers are
It is usually used in an amount of 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of a non-crosslinking monomer such as a monovinyl monomer.

In the present invention, it is preferable to use a macromonomer as a monomer in order to improve the balance between storage stability, offset property and low temperature fixability. The macromonomer has a vinyl-polymerizable functional group at the end of the molecular chain and usually has a number average molecular weight of 1,000 to 30,000.
0 oligomers or polymers. When a polymer having a small number average molecular weight is used, the surface portion of the polymer particles becomes soft and the storage stability is deteriorated. On the other hand, when a polymer having a large number average molecular weight is used, the meltability of the macromonomer deteriorates and the fixability deteriorates.

The macromonomer preferably has a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the above-mentioned monovinyl monomer. The Tg of the macromonomer is a value measured by an ordinary measuring instrument such as a differential calorimeter (DSC).

Specific examples of the macromonomer used in the present invention include polymers obtained by polymerizing styrene, styrene derivatives, methacrylic acid esters, acrylic acid esters, acrylonitrile, methacrylonitrile, etc., alone or in combination of two or more kinds, A macromonomer having a polysiloxane skeleton, which has a polymerizable double bond at the polymer terminal disclosed in JP-A-3-203746, pages 4 to 7,
Examples thereof include those having an arbitrary repeating structural unit.

Of these macromonomers, those having a high glass transition temperature, particularly polymers obtained by polymerizing styrene, methacrylic acid ester or acrylic acid ester alone or in combination thereof are suitable for the present invention. When a macromonomer is used, its amount is usually 0.01 part by weight based on 100 parts by weight of the monovinyl-based monomer.
˜1 part by weight, preferably 0.03 to 0.8 part by weight.
When the amount of the macromonomer is small, the storage stability and the offset property are not improved. If the amount of macromonomer becomes extremely large, the fixability will decrease.

The developer polymer particles usually contain a colorant and, if necessary, a charge control agent, a release agent (wax), a colorant dispersant and the like.

In the case of carbon black, which is a black pigment, it is particularly preferable to use a colorant having a primary particle size of 20 to 40 nm as the colorant. If it is less than 20 nm, the dispersion of carbon black cannot be obtained, resulting in a toner with a large amount of fog, while if it is more than 40 nm, the amount of the polyvalent aromatic hydrocarbon compound becomes large, which may cause a safety problem. . Other black pigments include magnetic particles of triiron tetraoxide, manganese iron oxide, zinc iron oxide, nickel iron oxide, and the like.

Further, examples of dyes for magnetic color toners include C.I. I. Direct Red 1, C.I. I. Direct Red 4, C.I. I. Acid Red 1, C.I. I. Basic Red 1, C.I. I. Mordant Red 30, C.I.
I. Direct Blue 1, C.I. I. Direct Blue 2, C.I. I. Acid Blue 9, C.I. I. Acid Blue 15, C.I. I. Basic Blue 3, C.I. I. Basic Blue 5, C.I. I. Mordant Blue 7, C.I. I.
Direct grin 6, C.I. I. Basic Grin 4,
C. I. Basic Grin 6 etc. are pigments such as yellow lead, cadmium yellow, mineral first yellow, navel yellow, netotor yellow S, Hansa yellow G, permanent yellow NCG, tartrazine lake, red lead yellow lead,
Molybdenum Orange, Permanent Orange GTR, Pyrazolone Orange, Benzidine Orange G, Cadmium Red, Permanent Red 4R, Watching Red Calcium Salt, Eosin Lake, Brilliant Carmine 3B, Manganese Purple, Fast Violet B, Methyl Violet Lake, Navy Blue, Cobalt Blue, Alkali Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Induslen Blue B
C, chromegulin, chrome oxide, pigment grin B,
Examples include malachite green rake and final yellow glogin G.

Examples of magenta color pigments for full-color toners include C.I. I. Pigment Red 1, 2, 3, 4, 5,
6, 7, 8, 9, 10, 11, 12, 13, 14, 1
5, 16, 17, 18, 19, 21, 22, 23, 3
0, 31, 32, 37, 38, 39, 40, 41, 4
8, 49, 50, 51, 52, 53, 54, 55, 5
7, 58, 60, 63, 64, 68, 81, 83, 8
7, 88, 89, 90, 112, 114, 122, 12
3, 163, 202, 206, 207 and 209,
C. I. Pigment violet 19, C.I. I. Butt Red 1, 2, 10, 13, 15, 23, 29 and 3
5 and the like are magenta dyes such as C.I. I. Solvent Red 1, 3, 8, 23, 24, 25, 27, 30, 4
9, 81, 82, 83, 84, 100, 109 and 1
21, C.I. I. Disperse Red 9, C.I. I. Solvent violet 8, 13, 14, 21 and 27,
C. I. Basic Red 1, 2, 9, 12, 13, 1
4, 15, 17, 18, 22, 23, 24, 27, 2
9, 32, 34, 35, 36, 37, 38, 39 and 40, C.I. I. Basic Violet 1, 3, 7, 1
And basic dyes such as 0, 14, 15, 21, 25, 26, 27 and 28.

Cyan color pigments for full color toners include C.I. I. Pigment Blue 2, 3, 15, 16 and 17, C.I. I. Bat Blue 6, C.I. I. Examples include Acid Blue 45 and a copper phthalocyanine pigment having 1 to 5 phthalimidomethyl groups substituted on the phthalocyanine skeleton.

Further, as a yellow color pigment for full color toner, C.I. I. Pigment Yellow 1, 2, 3, 4,
5, 6, 7, 10, 11, 12, 13, 14, 15, 1
6, 17, 23, 65, 73, 83, 138 and 18
0, C.I. I. Bat yellow 1, 3, and 20 are mentioned.

As the charge control agent, it is possible to use a generally used positively chargeable or negatively chargeable charge control agent. Examples thereof include metal complexes of organic compounds having a carboxyl group or a nitrogen-containing group, metal-containing dyes, nigrosine and the like. More specifically, Spiron Black TRH
(Hodogaya Chemical Co., Ltd.), T-77 (Hodogaya Chemical Co., Ltd.),
Bontron S-34 (manufactured by Orient Chemical Company), Bontron E-84 (manufactured by Orient Chemical Company), Bontron N-0
1 (manufactured by Orient Chemical Co., Ltd.), Copy Blue-PR (manufactured by Hoechst), a quaternary ammonium salt-containing resin, a sulfonic acid group-containing resin and the like. The charge control agent is used in an amount of 100 parts by weight of the polymerizable monomer.
Usually, 0.01 to 10 parts by weight, preferably 0.03 to 5
Parts by weight are used.

As the release agent, low molecular weight polyethylene,
Examples thereof include low molecular weight polyolefins such as low molecular weight polypropylene and low molecular weight polybutylene, waxes and the like. The releasing agent is usually 0.1 to 20 parts by weight, preferably 1 to 100 parts by weight of the monovinyl monomer.
It is preferable to use 10 parts by weight.

In the present invention, a fatty acid metal salt consisting of a fatty acid such as oleic acid and stearic acid or a metal such as Na, K, Ca, Mg and Zn for the purpose of uniformly dispersing the colorant in the toner particles, A dispersion aid such as a silane or titanium coupling agent may be used. Such lubricants and dispersants, based on the weight of the colorant,
Usually, it is used at a ratio of about 1/1000 to 1/1.

In addition, a molecular weight modifier or the like can be used. Examples of the molecular weight modifier include mercaptans such as t-dodecyl mercaptan, n-dodecyl mercaptan, and n-octyl mercaptan; halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. These molecular weight modifiers can be added before the start of the polymerization or during the polymerization. The molecular weight modifier is usually 0.01 to 1 with respect to 100 parts by weight of the monomer.
It is used in an amount of 0 part by weight, preferably 0.1 to 5 parts by weight.

The dispersion stabilizer used in the present invention preferably contains a colloid of a poorly water-soluble metal compound. As the sparingly water-soluble metal compound, sulfates such as barium sulfate and calcium sulfate; carbonates such as barium carbonate, calcium carbonate and magnesium carbonate; phosphates such as calcium phosphate; metals such as aluminum oxide and titanium oxide. Oxides; aluminum hydroxide, magnesium hydroxide, ferric hydroxide metal hydroxides; and the like.
Of these, a dispersant containing a sparingly water-soluble metal hydroxide colloid is suitable because it can narrow the particle size distribution of the polymer particles and improve the sharpness of the image.

Polymerization of the polymerizable monomer is usually carried out by a suspension polymerization method, an emulsion polymerization method, a dispersion polymerization method or the like. In the present invention, it is particularly preferable to carry out the polymerization by the suspension polymerization method. The dispersant used in the suspension polymerization method is preferably a dispersant containing a colloid of a sparingly water-soluble metal hydroxide, and although it is not limited by the manufacturing method, the pH of the aqueous solution of the water-soluble polyvalent metal compound is not limited. Slightly water-soluble metal hydroxide colloid obtained by adjusting to about 7 or more, especially slightly water-soluble metal water produced by reaction of water-soluble polyvalent metal compound and alkali metal hydroxide in aqueous phase Preference is given to using oxide colloids.

The slightly water-soluble metal compound colloid used in the present invention has a number particle size distribution D50 (50% cumulative value of the number particle size distribution) of 0.5 μm or less and a D90 (number particle size distribution of 9).
The 0% cumulative value) is preferably 1 μm or less.

The dispersant is usually used in a proportion of 0.1 to 20 parts by weight with respect to 100 parts by weight of the composition such as the monomer described later. If this ratio is less than 0.1 part by weight, it is difficult to obtain sufficient polymerization stability, and polymer aggregates are easily generated. On the contrary, when it exceeds 20 parts by weight, the viscosity of the aqueous solution becomes large and the polymerization stability becomes low.

In the present invention, a dispersant containing a water-soluble polymer can be used if necessary. Examples of the water-soluble polymer include polyvinyl alcohol, methyl cellulose, gelatin and the like. In the present invention, it is not necessary to use a surfactant,
It can be used to stably carry out suspension polymerization within a range in which the environmental dependence of the charging characteristics does not increase.

The polymer particles thus obtained have a volume average particle diameter of usually 2 to 10 μm, preferably 2 to 9 μm.
m, particularly preferably 3-8 μm. Further, the volume average particle diameter (dv) / number average particle diameter (dp) is usually
Colored fine particles of 1.7 or less, preferably 1.5 or less, more preferably 1.3 or less are obtained. Further, the particles thus obtained, further polymerizable monomer, a polymerization initiator,
A charge control agent may be added and polymerized to obtain a developer having a core-shell structure, that is, a so-called capsule type developer.

In the present invention, as described above, the shell monomer can be further reacted. The colored fine particles obtained by the above-described method are core particles, and a polymer having a glass transition temperature higher than the glass transition temperature (Tg) of the polymer constituting the core particles is used as the shell. As a monomer constituting the shell monomer, it is possible to use styrene, methyl methacrylate, or another monomer forming a polymer having a glass transition temperature of higher than 80 ° C., either alone or in combination of two or more kinds. it can. It is necessary to set the glass transition temperature of the polymer comprising the shell monomer to be at least higher than the glass transition temperature of the polymer forming the core particles. The glass transition temperature of the polymer obtained from the shell monomer is usually higher than 50 ° C. and lower than 120 ° C., preferably higher than 60 ° C. and lower than 110 ° C., more preferably in order to improve the storage stability of the polymerized toner. 80
It is over 105 ° C and below 105 ° C. The difference in glass transition temperature between the polymer forming the core particles and the polymer comprising the shell monomer is usually 10 ° C. or higher, preferably 20 ° C. or higher,
More preferably, it is 30 ° C. or higher.

When the shell monomer is polymerized in the presence of the core particles (colored fine particles), it is preferable that the shell monomers be formed into droplets smaller than the number average particle diameter of the core particles. If the particle size of the droplets of the monomer for the shell is large, the shell cannot be attached uniformly, and the storage stability tends to decrease. In order to make the shell monomer into small droplets, a mixture of the shell monomer and the aqueous dispersion medium, for example, using an ultrasonic emulsifier,
Performs fine dispersion processing. It is preferable to add the obtained aqueous dispersion to the reaction system in which the core particles are present.

The shell monomer is not particularly limited by its solubility in water at 20 ° C., but a monomer having a high solubility in water at 20 ° C. of 0.1% by weight or more is used as the core particle. Since the particles easily migrate quickly, it is easy to obtain polymer particles having good storage stability. Examples of the monomer having a solubility in water at 20 ° C. of 0.1% by weight or more include (meth) acrylic acid esters such as methyl methacrylate and methyl acrylate; amides such as acrylamide and methacrylamide; and cyan such as acrylonitrile and methacrylonitrile. Vinyl compounds; nitrogen-containing vinyl compounds such as 4-vinylpyridine; vinyl acetate, acrolein and the like.

On the other hand, the solubility in water at 20 ° C. is 0.1.
When less than wt% of the monomer is used, the migration to the core particles is slowed down. Therefore, as described above, it is preferable to polymerize the monomer into fine droplets. Even when a monomer having a solubility in water at 20 ° C. of less than 0.1% by weight is used, an organic solvent having a solubility in water at 20 ° C. of 5% by weight or more is added to the reaction system to form a simple shell solvent. The monomer is rapidly transferred to the core particles, and polymer particles having good storage stability are easily obtained. Examples of the shell monomer having a solubility in water at 20 ° C. of less than 0.1% by weight include styrene, butyl acrylate, 2-ethylhexyl acrylate, ethylene and propylene.

Solubility in water at 20 ° C. is 0.1% by weight
Organic solvents that are preferably used when the following shell monomers are used include lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propyl alcohol, and butyl alcohol; ketones such as acetone and methyl ethyl ketone; tetrahydrofuran; Examples thereof include cyclic ethers such as dioxane; ethers such as dimethyl ether and diethyl ether; amides such as dimethylformamide. The organic solvent has a solubility of the shell monomer in the dispersion medium (total amount of water and organic solvent) of 0.
An amount of 1% by weight or more is added. The specific amount of the organic solvent varies depending on the type and amount of the organic solvent and the monomer for the shell, but is usually relative to 100 parts by weight of the aqueous dispersion medium.
0.1 to 50 parts by weight, preferably 0.1 to 40 parts by weight,
It is more preferably 0.1 to 30 parts by weight. The order of adding the organic solvent and the shell monomer to the reaction system is not particularly limited, in order to facilitate transfer of the shell monomer to the core particles to facilitate good storage of polymer particles, It is preferable to add the organic solvent first, and then add the shell monomer.

Solubility in water at 20 ° C. is 0.1% by weight
When a monomer of less than 0.1% by weight and a monomer of 0.1% by weight or more are used in combination, first, a monomer having a solubility in water at 20 ° C. of 0.1% by weight or more is added and polymerized, and then an organic compound is added. It is preferable to add a solvent and add a monomer having a solubility in water at 20 ° C. of less than 0.1% by weight for polymerization. According to this addition method, the T of the polymer obtained from the monomer that is polymerized in the presence of the core particles in order to adjust the fixing temperature of the polymerization toner is adjusted.
The amount of g and the amount of the monomer added can be appropriately controlled.

In the present invention, it is preferable to mix the charge control agent with the shell monomer and then add the charge control agent to the reaction system to polymerize the charge control agent in order to improve the chargeability of the toner. The charge control agent is used to improve the chargeability of the toner. As the charge control agent, various positively or negatively charged charge control agents can be used. Specific examples of the charge control agent include Bontron N01 (Nigrosine, manufactured by Orient Chemical Co., Ltd.), Nigrosine EX (manufactured by Orient Chemical Company),
Spiron Black TRH (Hodogaya Chemical Co., Ltd.), T-7
7 (manufactured by Hodogaya Chemical Co., Ltd.), Bontron S-34 (manufactured by Orient Chemical Company), Bontron E-84 (manufactured by Orient Chemical Company), quaternary ammonium salt-containing resin, sulfonic acid group-containing resin, and other charge control resins. be able to. The charge control agent is usually used in an amount of 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the shell monomer.

As a specific method of polymerizing the shell monomer in the presence of the core particles, the shell monomer is continuously added to the reaction system of the polymerization reaction carried out to obtain the core particles. And a method of charging core particles obtained in another reaction system, adding a shell monomer to the core particles, and performing stepwise polymerization. The shell component monomer can be added all at once to the reaction system, or can be added continuously or intermittently using a pump such as a plunger pump.

(Polymerization Initiator for Shell) In the polymerization toner of the present invention, it is easy to obtain core-shell type polymer particles by adding a water-soluble radical initiator when the monomer for shell is added. Is preferred. When the water-soluble polymerization initiator is added during the addition of the shell monomer, the water-soluble radical initiator enters near the outer surface of the core particle to which the shell monomer has migrated, and the polymer ( It is thought that this is because it is easy to form a shell).

As the water-soluble polymerization initiator, persulfates such as potassium persulfate and ammonium persulfate; 4,4-azobis (4-cyanovaleric acid) and 2,2-azobis (2-amidinopropane) dihydrochloride Azo initiators such as 2,2-azobis-2-methyl-N-1, 1-bis (hydroxymethyl) -2-hydroxyethylpropioamide; oil-soluble initiators such as cumene peroxide and redox catalysts Combinations; and the like. The amount of the water-soluble polymerization initiator is usually 0.01 to 20 parts by weight based on the polymerizable monomer B.

In the case of the developer of the present invention having a core-shell structure, the weight ratio of the monomer for core particles (polymer forming core particles) to the monomer for shell is usually 8
It is 0/20 to 99.9 / 0.1. Within this range, the storability is extremely good. The shell has an average thickness of 0.001 to 1.0 μm, preferably 0.003 to
It is considered to be 0.5 μm, more preferably 0.005 to 0.2 μm. As the thickness increases, the fixability decreases,
When the size becomes smaller, the storage stability decreases. In the developer having the core-shell structure of the present invention, it is not necessary that the entire core portion be covered with the shell. The core particle size and shell thickness can be obtained by directly measuring the size and shell thickness of particles randomly selected from the observation photograph, if they can be observed by an electron microscope. When it is difficult to observe and, it can be calculated from the particle size of the core particle and the amount of the monomer forming the shell.

Examples of the external additive that constitutes the developer of the present invention include inorganic particles and organic resin particles. Examples of the inorganic particles include silicon dioxide, aluminum oxide, titanium oxide, zinc oxide, tin oxide, barium titanate, and strontium titanate. As the organic resin particles, methacrylic acid ester polymer particles, acrylic acid ester polymer particles, styrene-methacrylic acid ester copolymer particles, styrene-acrylic acid ester copolymer particles, the core is a methacrylic acid ester polymer, the shell Core-shell type particles formed of a styrene polymer. Among these, inorganic oxide particles, particularly silicon dioxide particles are preferable. Further, the surface of these particles can be subjected to a hydrophobic treatment, and hydrophobically treated silicon dioxide particles are particularly preferable. The amount of the external additive is not particularly limited, but is usually 0.1 with respect to 100 parts by weight of the toner particles.
~ 6 parts by weight.

The external additives may be used in combination of two or more kinds. When the external additives are used in combination, a method of combining two kinds of inorganic oxide particles or organic resin particles having different average particle diameters is suitable. Specifically, particles having an average particle diameter of 5 to 20 nm, preferably 7 to 18 nm (preferably inorganic oxide particles), and an average particle diameter of more than 20 nm 2 μm.
It is suitable to combine and attach particles (preferably inorganic oxide particles) having a particle size of m or less, preferably 30 nm to 1 μm. The average particle diameter of the particles for the external additive is the average value of the values obtained by observing the particles with a transmission electron microscope and randomly selecting 100 particles, that is, the number average particle diameter.

The amount of the two kinds of external additives (particles) is generally 0.1 to 3 parts by weight, preferably 0.1 to 3 parts by weight, based on 100 parts by weight of toner particles. 2 to
The amount of 2 parts by weight and the average particle diameter of more than 20 nm and 2 μm or less is usually 0.1 to 3 parts by weight, preferably 0.2 to 2 parts by weight. The weight ratio of particles having an average particle diameter of 5 to 20 nm and particles having an average particle diameter of more than 20 nm and 2 μm or less is usually 1:
It is in the range of 5 to 5: 1, preferably in the range of 3:10 to 10: 3. The attachment of the external additive is usually performed by placing the external additive and the toner particles in a mixer such as a Henschel mixer and stirring the mixture.

The developer of the present invention is obtained by using the ion-exchanged water boiling extraction method described below in which the conductivity of ion-exchanged water is σ1, and the conductivity σ2 of the extract is 20 μS / c.
m, preferably 15 μS / cm, and σ2-σ1 is
It is 10 μS / cm or less, preferably 5 μS / cm or less. When σ2 is large or σ2-σ1 is large, the dependence of the charge amount of the non-magnetic one-component developer on the environment is increased, and the image quality is deteriorated due to environmental changes (changes in temperature and humidity). Become. The ion-exchanged water boiling extraction method is 10 g of ion-exchanged water whose pH has become 7 by the cation exchange treatment and the anion exchange treatment of 6 g of the developer.
The water-soluble component was dispersed in 0 g, heated and boiled, and the boiled state was kept for 10 minutes (boiled for 10 minutes) to extract the water-soluble component from the developer. This is a method in which ion-exchanged water having a pH of 7 by the ion-exchange treatment and anion-exchange treatment is added to restore the volume before boiling and then cooled to room temperature (about 25 ° C.) to obtain an extract.

In the developer of the present invention, it is desirable that the pH of the extract obtained by the ion-exchange water boiling extraction method is 4 to 7, preferably 4.5 to 6.5. When the pH is less than 4 or exceeds 7, the environmental dependency of the charge amount of the non-magnetic one-component developer becomes large, and the image quality is deteriorated due to the environmental change.

Further, the developer of the present invention is the developer 1
g was dispersed in 20 ml of ion-exchanged water that had been subjected to cation exchange treatment and anion exchange treatment with conductivity σ1 to obtain a dispersion liquid, and the dispersion liquid was sufficiently stirred, and then the dispersion liquid was filtered and the conductivity of the filtrate was filtered. When the ratio is D2, D2-σ1 is usually
It is less than 5 μS / cm, preferably 4 μS / cm or less. When D2- [sigma] 1 becomes large, the dependence of the charge amount of the non-magnetic one-component developer on the environment becomes high, and the image quality is deteriorated due to environmental changes (changes in temperature and humidity).

The volume average particle diameter (dv) of the polymer particles for a developer of the present invention is usually 1 to 20 μm, preferably 1.5 to 15 μm, more preferably 1.5 to 8 μm. The volume average particle diameter (dv) / number average particle diameter (dp) of the polymer particles for a developer of the present invention is usually 1.7 or less, preferably 1.5 or less.

The polymer particles for a developer of the present invention usually have a ratio (rl / rs) of the major axis rl to the minor axis rs of 1 to 1.
1.2, preferably 1-1.1. When this ratio becomes large, the resolution of the image tends to decrease, and when the toner is stored in the toner storage unit of the image forming apparatus, the friction between the toners becomes large, so that the external additive may peel off. Therefore, the durability tends to decrease.

The method for producing the developer of the present invention is not particularly limited, but preferably, an aqueous dispersion of polymer particles for a developer obtained by suspension polymerization of a polymerizable monomer is mixed with the above-mentioned heavy polymer for a developer. A step of filtering and dehydrating through a filter cake layer composed of polymer particles for filtration having a volume average particle diameter larger than the volume average particle diameter of the coalesced particles, and washing, a step of drying the washed polymer particles for a developer, and a developer. And a step of attaching an external additive to the surface of the polymer particles.

The polymer particles for filtration used in the above-mentioned washing step are usually 0.1 to 10 μm, preferably 0.1 to 5 μm, more than the volume average particle diameter of the polymer particles for developer.
It has a large volume average particle diameter. When the polymer particles for filtration are smaller than the polymer particles for developer, the filter cake layer is closely packed, the dehydration property is deteriorated by eliminating voids between particles, and the water content of the obtained polymer particles is increased. As a result, the environmental dependency such as the charge amount may increase.

The polymer particles for filtration are not particularly limited by the kind of the polymer constituting the same, but are composed of the same polymer as the developer polymer particles in order to minimize the inclusion of foreign matter in the developer. In addition, those containing a colorant, a charge control agent, a release agent and the like are preferable. As a specific polymer, a copolymer of a styrene-based monomer and a derivative of acrylic acid or methacrylic acid, particularly a copolymer of styrene and a (meth) acrylic acid alkyl ester is preferably used.

In the production method of the present invention, filtration and dehydration are carried out through a filter cake layer comprising the polymer particles for filtration. The thickness of the filter cake layer is usually 2 to 20 mm, preferably 5 to 15 mm.

The method of filtration and dehydration is not particularly limited. For example, a centrifugal filtration method, a vacuum filtration method, a pressure filtration method and the like can be mentioned. Of these, the centrifugal filtration method is preferable. Examples of the filter dehydrator include Peeler cent refusion and Siphon Peeler cent refusion. In the centrifugal filtration method, centrifugal gravity is usually 400 to 3000 G, preferably 800 to 2 G.
Set to 000G. The water content after dehydration is usually 5 to 3
It is 0% by weight, preferably 8 to 25% by weight. If the water content is high, the drying step will take time, and if the water content is high, the impurities will be concentrated by drying and the developer will be highly dependent on the environment even if the water content is low.

Regarding the water content, 2 g of water-containing particles were sampled in an aluminum dish, precisely weighed (W ₀ [g]), left in a dryer set at 105 ° C. for 1 hour, cooled, and then weighed precisely (W ₁ [g])
However, it is a value calculated by the following formula. Moisture content = [(W ₀ −W ₁ ) / W ₀ ] × 100

The pH of the polymer particle dispersion for a developer obtained by suspension polymerization is usually 8 to 12, preferably 8.5 to 11.
Is. If the pH is too low, the particle size distribution of the polymer particles for a developer becomes wide. It is preferable to adjust the pH of the aqueous dispersion of polymer particles for a developer during filtration and dehydration to 6.5 or less.
For the adjustment, a mineral acid such as sulfuric acid or hydrochloric acid; an organic acid such as carboxylic acid is used. Sulfuric acid is particularly suitable.

The method for producing the developer of the present invention is a method for obtaining a so-called low-temperature fixing developer having a fixing temperature of usually 80 to 140 ° C., preferably 80 to 130 ° C., particularly a low temperature fixing non-magnetic one-component developer. It is suitable. The low temperature fixing developer has a low glass transition temperature (Tg) of the entire polymer particles for a developer constituting the low temperature fixing developer, or the particles are composed of a core having a low glass transition temperature and a shell having a high glass transition temperature. Those composed of core-shell type polymer particles are preferable. The image forming method of the present invention is characterized in that an electrostatic latent image is developed using the above-mentioned developer to obtain a developer image, and the developer image is transferred to a transfer material and fixed. is there.

The image forming method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing an aspect of the image forming apparatus. The image forming apparatus includes a photosensitive drum 1 as a photoconductor.
Is mounted rotatably in the direction of arrow A. Photosensitive drum 1
Is a photoconductive layer provided on the outer peripheral surface of a conductive support drum. The photoconductive layer is composed of, for example, an organic photoconductor, a selenium photoconductor, a zinc oxide photoconductor, an amorphous silicon photoconductor, or the like.

Around the photosensitive drum 1, along the circumferential direction thereof, a charging roll 3 as a charging unit, a laser beam irradiation device 4 as an electrostatic latent image forming unit, a developing roll 8 as a developing unit, and a transfer unit. The transfer roll 6 and the cleaning device 2 are disposed.

The charging roll is for uniformly charging the surface of the photosensitive drum positively or negatively,
The surface of the photosensitive drum is charged by applying a voltage to the charging roll and bringing the charging roll into contact with the photosensitive drum. The charging roll 3 can be replaced with a charging unit that uses corona discharge. Laser light irradiation device 4
Irradiates the surface of the uniformly charged photosensitive drum with light corresponding to the image signal in a predetermined pattern, and forms an electrostatic latent image on the light-irradiated portion (in the case of reversal development). Also,
There is also one for forming an electrostatic latent image on a portion not irradiated with light (in the case of regular development). Other electrostatic latent image forming means include those composed of an LED array and an optical system. The developing roll is for developing by attaching a developer to the electrostatic latent image on the photosensitive drum 1. In the reversal development, the developer is attached only to the light irradiation portion, and in the normal development, the light non-irradiation is performed. A bias voltage is applied between the developing roll and the photosensitive drum so that the developer is attached only to the portion.

Next to the developing roll, a developing roll 8 and a supply roll 1 are provided in a casing 11 containing a developer 10.
2 is provided. The developing roll is disposed in close proximity to the photosensitive drum so as to partially contact the photosensitive drum, and is rotated in the direction B opposite to the photosensitive drum. The supply roll 12 contacts the developing roll, rotates in the same direction C as the developing roll, and supplies the developer to the outer periphery of the developing roll. Around the developing roll, a developing roll blade 9 is disposed as a layer thickness regulating means at a position between the contact point with the supply roll and the contact point with the photosensitive drum. This blade 9 is made of conductive rubber or stainless steel, and in order to inject charge into the developer on the developing roll, | 200V | to | 600
The voltage of V | is applied. To that end, the blade 9
The electric resistivity of is preferably 10 6 Ωcm or less.

The above-mentioned developer 10 is contained in the casing 11 of the image forming apparatus. Since the developer of the present invention is excellent in fluidity and storability, the developer does not aggregate in the casing 11, and image defects such as blurring and fog do not occur.

The transfer roll 6 is for transferring the developer image on the surface of the photosensitive drum formed by the developing roll onto the transfer material 7. Examples of the transfer material include paper and resins such as OHP sheets. Examples of the transfer means include a corona discharge device and a transfer belt, in addition to the transfer roll.

The developer image transferred to the transfer material is fixed to the transfer material by the fixing means. The fixing unit usually comprises a heating unit and a pressure bonding unit. The developer transferred to the transfer material is heated by the heating unit to melt the developer, and the melted developer is pressed and fixed on the surface of the transfer material by the pressure bonding unit. In the image forming apparatus of the present invention, since the above-mentioned developer is used, even if the heating temperature by the heating means is low, the toner is easily melted and the developer becomes smooth when lightly pressed by the pressing means. Since it is fixed on the surface of the transfer material,
High speed printing or copying is possible. Further, the fixed developer image has excellent OHP transparency.

The cleaning device 2 is for cleaning the transfer residual developer remaining on the surface of the photosensitive drum, and is composed of, for example, a cleaning blade. This cleaning device does not necessarily need to be installed when a system in which cleaning is performed simultaneously with development by the developing roll is adopted.

[0069]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Parts and% are based on weight unless otherwise specified.

In this example, the following method was used for evaluation. (Particle Size) The developing and filtering polymer particles are volume average particle size (unit: μm) measured by Multisizer (manufactured by Coulter Co.). Aperture diameter: 100 μm, medium: Isoton II, concentration 1
The condition was 0% and the number of measured particles: 50,000.

(Water content) 2 g of water-containing particles was sampled in an aluminum dish, precisely weighed (W ₀ [g]), left in a dryer set at 105 ° C. for 1 hour, cooled, and then weighed precisely (W 0 ₁ [g])
However, it is a value calculated by the following formula. Moisture content = [(W ₀ −W ₁ ) / W ₀ ] × 100

(PH) 6 g of the developer is dispersed in 100 g of ion-exchanged water having a pH of 7 by the cation exchange treatment and the anion exchange treatment, and this is heated and boiled, and the boiled state is maintained for 10 minutes. After (boiling for 10 minutes), continue,
Separately boiled for 10 minutes, add ion-exchanged water having a pH of 7 by cation exchange treatment and anion exchange treatment, return to the volume before boiling, and cool the extract to room temperature (about 25 ° C). , The value measured using a pH meter.

(Electrical conductivity σ2) 6 g of the developer is dispersed in 100 g of ion-exchanged water having a pH of 7 by the cation exchange treatment and the anion exchange treatment, and this is heated and boiled to a boiled state of 10 After holding for 10 minutes (boiling for 10 minutes), continue to boil for another 10 minutes, and add ion-exchanged water whose pH has become 7 by cation exchange treatment and anion exchange treatment to restore the volume before boiling to room temperature. The conductivity σ2 of the extract liquid cooled to (about 25 ° C.) was measured. [Sigma] 2- [sigma] 1 was calculated assuming that the conductivity of ion-exchanged water whose pH became 7 by cation exchange treatment and anion exchange treatment was [sigma] 1.

(Electrical conductivity D2) 1 g of the developer was dispersed in 20 ml of ion-exchanged water having an electric conductivity of σ1 which had been subjected to cation exchange treatment and anion exchange treatment to obtain a dispersion liquid, which was thoroughly stirred and then , Conductivity D2 of the filtrate obtained by filtering the dispersion
Was measured. D2- [sigma] 1 was calculated by setting the conductivity of ion-exchanged water having a pH of 7 by cation exchange treatment and anion exchange treatment to be [sigma] 1.

(Fixing Temperature) A fixing test was carried out using a commercially available non-magnetic one-component developing type printer (four-sheet machine) modified so that the temperature of the fixing roll portion could be changed. In the fixing test, the temperature of the fixing roll of the modified printer was changed, the fixing ratio at each temperature was measured, the temperature-fixing ratio relationship was determined, and the temperature at which the fixing ratio was 80% was defined as the fixing temperature. The fixing rate was calculated from the ratio of the image density before and after the tape peeling operation in the black solid area on the test paper printed by the modified printer. That is, assuming that the image density before tape peeling is before ID and the image density after tape peeling is after ID, the fixing rate can be calculated from the following equation. Fixing rate (%) = (after ID / before ID) × 100 Here, the black solid area is such that the developer is attached to all dots inside the area (lower layer controlling the printer control unit). It is the control area. The tape peeling operation is an adhesive tape (Scotch Mending Tape 810-3-1 manufactured by Sumitomo 3M Limited) on the measurement portion of the test paper.
8) is affixed, pressed with a constant pressure to be adhered, and then the adhesive tape is peeled off in a direction along the paper at a constant speed. The image density is MacBet (McBet).
h) It was measured using a reflection type image densitometer manufactured by the company.

(Flowability) Opening is 150 μm and 75, respectively.
Three kinds of sieves of μm and 45 μm are superposed in this order from the top, and 4 g of the developer to be measured is precisely weighed and placed on the top sieve. Then, the three types of sieves piled up were vibrated for 15 seconds under the condition of a vibration intensity of 4 using a powder measuring machine (manufactured by Hosokawa Micron Co., Ltd., trade name "Powder Tester"), and then remained on each sieve. Measure the weight of the developer. Each measured value is put into the following formula to calculate the fluidity value. One sample was measured three times, and the average value was calculated. Calculation formula: a = (weight of developer remaining on 150 μm sieve (g)) / 4 g
× 100 b = (weight of developer remaining on 75 μm sieve (g)) / 4 g ×
100 × 0.6 c = (weight of developer remaining on 45 μm sieve (g)) / 4 g ×
100 × 0.2 Fluidity (%) = 100− (a + b + c)

(Storability) The developer is put in a hermetically sealed container, and after hermetically sealed, the container is submerged in a constant temperature water bath kept at a temperature of 55 ° C. After 8 hours, the container is taken out from the constant temperature water tank, and the developer in the container is transferred onto a 42-mesh sieve. At this time, the developer is gently taken out of the container and carefully transferred onto a sieve so as not to destroy the aggregate structure of the developer in the container. This sieve was vibrated for 30 seconds under the condition of a vibration intensity of 4.5 using the above-mentioned powder measuring machine, and then the weight of the developer remaining on the sieve was measured and used as the weight of the cohesive developer. First, the ratio (% by weight) of the weight of the cohesive developer to the weight of the developer put in the container was calculated. One sample was measured three times, and the average value was used as an index of storability.

(Environmental Dependence of Amount of Charge) L / L environment with temperature 10 ° C., humidity 20% RH (relative humidity) or temperature 35 ° C.,
In an H / H environment with a humidity of 80% RH, put the developer in a non-magnetic one-component development type printer (four-sheet machine), leave it for one day and night, print five halftone print patterns, and then develop. The developer on the roller was sucked into a suction type charge amount measuring device, and the charge amount per unit weight was measured from the charge amount and the suction amount. From the change of the charge amount under each environment, the situation of the environmental change of the developer was evaluated.

(Environmental Dependence of Image Quality) Using the above modified printer, continuous printing is performed from the initial stage under each environment of 35 ° C. × 80 RH% (H / H) and 10 ° C. × 20 RH% (L / L). Continuous printing with a print density of 1.3 or more using a reflection densitometer (Macbeth) and a fog of 10% or less in the non-image area measured with a whiteness meter (Nippon Denshoku) The number of sheets was checked, and the environmental dependence of the image quality by the developer was evaluated according to the following criteria. ◯: The number of continuous prints that can maintain the above image quality is 10,000 or more, Δ: The number of continuous prints that can maintain the above image quality is 5,000 or more and less than 10,000, ×: The number of continuous prints that can maintain the above image quality is less than 5,000.

[Example 1] Core monomer obtained from 78 parts of styrene and 22 parts of n-butyl acrylate (calculation Tg of copolymer obtained = 50 ° C) and carbon black (trade name, manufactured by Degussa) "Printex 150T")
7 parts, charge control agent (Hodogaya Chemical Co., Ltd., trade name "Spiron Black TRH") 1 part, divinylbenzene 0.3 part,
Polymethacrylic acid ester macromonomer (trade name "AA6" manufactured by Toagosei Co., Ltd., Tg = 94 ° C) 0.8
Part, pentaerythritol = tetrastearate 10 parts and t-butylperoxy-2-ethylhexanoate 4 parts can be mixed with a high shearing force by a homomixer (TK type,
Stirring and mixing at a rotation speed of 12000 rpm was carried out by Tokushu Kika Kogyo Co., Ltd., and uniformly dispersed to obtain a core monomer mixture.

On the other hand, methyl methacrylate (calculated Tg =
(105 ° C.) 10 parts and 100 parts of water were finely dispersed by an ultrasonic emulsifying machine to obtain an aqueous dispersion of a shell monomer. The particle size of the droplets of the monomer for shell was D9 when the obtained droplets were added to a 1% sodium hexamethanephosphate aqueous solution at a concentration of 3% and measured with a Microtrac particle size distribution measuring device.
0 was 1.6 μm.

On the other hand, in an aqueous solution prepared by dissolving 9.8 parts of magnesium chloride (water-soluble polyvalent metal salt) in 250 parts of ion-exchanged water, 50 parts of ion-exchanged water and 6.9 parts of sodium hydroxide (alkali metal hydroxide). The aqueous solution in which was dissolved was gradually added under stirring to prepare a magnesium hydroxide colloid (poorly water-soluble metal hydroxide colloid) dispersion. When the particle size distribution of the purified colloid was measured with a Microtrac particle size distribution measuring device (manufactured by Nikkiso Co., Ltd.), the particle size was D50.
(50% cumulative value of number particle size distribution) is 0.38 μm, D
90 (90% cumulative value of number average particle diameter) was 0.82 μm. The measurement by this Microtrac particle size distribution measuring device was performed under the conditions of measurement range = 0.12 to 704 μm, measurement time = 30 seconds, and medium = ion-exchanged water.

To the magnesium hydroxide colloidal dispersion obtained above, the above core monomer mixture was added, and T
Using a K type homomixer, high shear stirring was performed at a rotation speed of 12000 rpm to granulate droplets of the monomer mixture for core. An aqueous dispersion of the monomer mixture in which the droplets are granulated,
The mixture was placed in a reactor equipped with a stirring blade, the polymerization reaction was started at 90 ° C., and when the polymerization conversion rate reached 85%, 110 parts of the aqueous monomer dispersion for shell and 1 part of potassium persulfate were added, After continuing the reaction for 5 hours, the reaction was stopped and the pH was adjusted to 11
An aqueous dispersion of core-shell type polymer particles for a developer was obtained.

While stirring the aqueous dispersion of the core-shell type polymer particles for a developer obtained as described above, sulfuric acid was used to p-type the system.
After H was set to 5.5, acid washing (25 ° C., 10 minutes) was performed. Then, using a continuous belt filter (Sumitomo Heavy Industries, Ltd., trade name "Eagle Filter"), it was dehydrated, and after dehydration, washing water was sprinkled to wash with water.

After washing with water, the polymer particles for a developer are dispersed again in water, and then a centrifugal gravity of 1200 G and a layer pressure are applied using Siphon Peeler Centrifuge (manufactured by Mitsubishi Kakoki Co., Ltd., trade name "HZ40Si"). At 10 mm, the layer area is 0.
25 m ² filter cake layer (polymer particles for filtration: volume average particle size = 7.8 μm, composition = 85 parts styrene, 15 parts n-butyl acrylate, 0.3 parts divinylbenzene, 2 parts release agent, carbon black) (Produced by suspension polymerization of 7 parts of Cabot Co., Ltd., trade name “Monarch 120”, and 1 part of charge control agent (Hodogaya Chemical Co., Ltd., trade name of “Spiron Black TRH”), detergent ions Exchanged water 40 parts /
The polymer particles for a developer having a water content of 15% are separated by centrifugal filtration dehydration under the conditions of the time and the supply amount of the aqueous dispersion of 120 parts / hour, and finally, dried at 45 ° C. for 2 days and 2 days in a dryer, 100 parts of the polymer particles for a developer are treated with hydrophobized silica (manufactured by Nippon Aerosil Co., Ltd., trade name “AEROSIL R-17”).
0 ", 1 part of number average particle size 15 nm, and hydrophobized silica (manufactured by Nippon Aerosil Co., Ltd., trade name" AEROSI ").
L RX-50 ", number average particle size 40 nm) was added and mixed using a Henschel mixer to produce a non-magnetic one-component developer.

The volume resistivity of the developer obtained by the above formulation was 11.5 log Ω · cm. The volume average particle diameter (dv) of the polymer particles for developer is 6.9 μm, and the ratio of the volume average particle diameter to the number average particle diameter (dv / dp).
Is 1.27, and the ratio of the major axis and the minor axis of the toner (rl /
rs) was 1.1. In image evaluation, high temperature and high humidity (H
/ H) environment and a low temperature and low humidity (L / L) environment, a color tone was good, an image density was high, and an extremely good image without fog was obtained. The other evaluation results are shown in Table 1.

[Example 2] A developer was obtained in the same manner as in Example 1 except that the acid washing with sulfuric acid was carried out at pH 3.0 in Example 1. The water content after filtration was 14%.
The operability of centrifugal filtration was so good that clogging did not occur even after continuous operation for 5 hours or more. The other evaluation results are shown in Table 1.

Example 3 In Example 1, the polymer particles for filtration were polymer particles for filtration having a volume average particle diameter of 9.5 μm (constitution = 85 parts of styrene, 15 parts of n-butyl acrylate).
Part, divinylbenzene 0.3 part, release agent 2 parts, carbon black (manufactured by Cabot Co., trade name "Monarch 120")
A developer was prepared in the same manner as in Example 1 except that 7 parts and 1 part of the charge control agent (Hodogaya Chemical Co., Ltd., trade name "Spiron Black TRH") were used for suspension polymerization. Obtained. The water content after filtration was 12%. The operability of centrifugal filtration was so good that clogging did not occur even after continuous operation for 5 hours or more. The other evaluation results are shown in Table 1.

[Comparative Example 1] In Example 2, the polymer particles for filtration were polymer particles for filtration having a volume average particle size of 6.1 µm (constitution = 85 parts of styrene, 15 parts of n-butyl acrylate).
Part, divinylbenzene 0.3 part, release agent 2 parts, carbon black (manufactured by Cabot Co., trade name "Monarch 12
0 ") 7 parts and charge control agent (manufactured by Hodogaya Chemical Co., Ltd., trade name" Spiron Black TRH "1 part suspension polymerized)
A developer was obtained in the same manner as in Example 2 except that The centrifugal filter was immediately clogged, making continuous operation difficult. The water content of the polymer particles obtained by filtration and dehydration was 28%. The evaluation results are shown in Table 1.

[Comparative Example 2] A developer was obtained in the same manner as in Example 2 except that after washing with water using a continuous belt filter, it was not dispersed again in water and centrifugal filtration dehydration was not performed. The evaluation results are shown in Table 1.

[Comparative Example 3] In Example 1, acid washing was carried out (25 ° C, 10 minutes) by adjusting the pH of the dispersion of polymer particles for a developer with sulfuric acid to 6.9, and the volume average particle diameter was 6.3 µm.
m polymer particles for filtration (constitution = 85 parts styrene, 15 parts n-butyl acrylate, 0.3 parts divinylbenzene,
A developer was obtained in the same manner as in Example 1 except that 2 parts of the release agent and carbon black (manufactured by Cabot Corp., obtained by suspension polymerization of 1 part of trade name "Monarch 120") were used. The centrifugal filter was immediately clogged, and continuous operation was difficult. The evaluation results are shown in Table 1.

[0092]

[Table 1]

[0093]

According to the present invention, the preservability and fluidity are excellent, and the charge amount does not change so much in any of the low temperature and low humidity environment and the high temperature and high humidity environment, and the deterioration of the image quality is almost observed. Since it is stable without being used, it can be suitably used for a non-magnetic one-component developing type printing machine or a copying machine.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an aspect of an image forming apparatus.

[Explanation of symbols]

1 ... Photosensitive drum 3 ... Charging roll 6 ... Transfer roll 8 ... Development roll 10 ... Developer

Claims (2)

[Claims] 1. A developer comprising polymer particles for a developer, obtained by polymerizing a polymerizable monomer, and an external additive attached to the surface of the particle, which is obtained by the following procedure. A developer for electrophotography in which the conductivity σ2 of a water extract of the agent is 20 μS / cm or less and σ2-σ1 is 10 μS / cm or less. Disperse 6 g in 100 g of ion-exchanged water having a conductivity of σ1, heat and boil for 10 minutes, and then add the water that has been boiled separately to ion-exchanged water having a pH of 7 and a conductivity of σ1 Evaporated water is replenished to restore the original volume, and further cooled to room temperature to obtain a water extract. 2. A development forming method comprising developing an electrostatic latent image with the developer according to claim 1 to obtain a developer image, transferring the developer image to a transfer material, and fixing the image.