JPH1172949A - Developing agent for electrophotography and image forming method using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing agent for electrophotography, which has excellent fluidity and storage stability and is almost free from lowering the image quality caused by the change of the circumstance, and to provide an image forming method using the agent. SOLUTION: This non-magnetic one component developing agent is obtained by stirring the core monomers comprised of styrene and n-butyl acrylate and carbon black, etc., to mix and disperse homogeneously, polymerizing the mixture thus obtained, adding methyl methacylate to the polymer thus obtained, again polymerizing to obtain a dispersion of polymer particles for developing agent, then adjusting the pH of the dispersion to 5.5 by the addition of sulfuric acid, further, after dehydrating the polymer particles with a continuous belt filter and washing, again dispersing the polymer particles into water, centrifugally dehydrating the dispersion by using a siphon pillar centrifuge having a filter layer comprised of the polymer particles for filtration, which have a volume average particle diameter of about 7.8 μm, to isolate the polymer particles with the water content of 15%, drying the polymer particles to obtain polymer particles for the developing agent, furthermore adding a silica, which has been treated to be hydrophobic, to the polymer particles, and finally mixing to fix the silica on the surface of the polymer particles by using a Henschel mixer.

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 particularly, to a developer having excellent fluidity and preservability.
Also, the present invention relates to a developer which is less likely to deteriorate in image quality due to environmental fluctuations and its use.

[0002]

2. Description of the Related Art An electrostatic latent image formed in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus is first developed with a developer, and then the formed developer image is used as required. After being transferred onto a transfer material such as paper, it is fixed by various methods such as heating, pressing, and solvent vapor.

[0003] The image formed by the electrophotographic apparatus is required to have higher definition year by year. Conventionally, the developer used for the apparatus is a pulverization method developer in which a resin containing a colorant or the like is melted, pulverized, and classified, but a particle size control is easy, and complicated particle size control and the like are complicated. Attention has been paid to polymerization-type developers, which are said to require no production process. As a polymerization method developer, the polymerization method developer is dispersed in 20 ml of water having conductivity σ1 at a ratio of 1 g of the developer, sufficiently stirred to be in an equilibrium state, and a filtrate obtained by filtering the polymerization method developer is used. Conductivity D
5 μS / cm ≦ D2−σ1 ≦ 50 μS / cm
(Japanese Patent Laid-Open No. 8-2)
No. 48676). This polymerization method developer is charged by friction with magnetic iron powder, and is a so-called two-component developer. However, when this two-component developer is 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 is largely dependent on the environment, and image quality is degraded due to environmental fluctuations. On top of
Fluidity and storage stability were also low. As a non-magnetic one-component developer, the present applicant has previously proposed a polymerization developer in which the content of metal ions derived from a poorly water-soluble metal compound is 1000 ppm or less (Japanese Patent Application Laid-Open No. 8-160661). . In this developer, image quality deterioration due to environmental fluctuations has been greatly improved, but further improvements have been demanded in terms of storability and fluidity.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electrophotographic developer which is excellent in fluidity and preservability, and in which image quality is hardly deteriorated due to environmental fluctuations, and an image forming method using the same. . The present inventors have conducted intensive studies to achieve the above object, and found that the above object can be achieved by using a developer having a specific range of pH or a non-magnetic one-component developer having a specific range of conductivity. Have been found, and based on this finding, the present invention has been completed.

[0005]

Thus, according to the present invention, there are provided (1) a polymer particle for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the surface of the particle. An electrophotographic developer is provided, wherein the pH of an aqueous extract of the developer obtained by the following procedure is about 4 to 7. 100 g of ion-exchanged water having a pH of about 7 and 6 g dispersed therein
Is heated and boiled for 10 minutes. To this, add separately boiled ion-exchanged water having a pH of about 7 to replenish the evaporated water, return to the original volume, and cool to room temperature. Obtain an aqueous extract. Further, according to the present invention, there is provided (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, the developer comprising: Conductivity of the aqueous extract of the developer obtained by the method described above is 20 μS / cm or less;
An electrophotographic developer having -σ1 of 10 μS / cm or less is provided. 6 g of ion-exchanged water 100 having a conductivity of σ1
g, and boil it for 10 minutes, then add separately boiled ion-exchanged water with a pH of about 7 to replenish the evaporated water, return to the original volume, and cool to room temperature. To obtain a water extract.

The following are provided as preferred embodiments of the developer of the present invention. (3) A developer comprising polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive adhered to the surface of the particles, the method comprising the following steps: Conductivity of the aqueous extract of the developer obtained by
0 μS / cm or less, and the conductivity of ion-exchanged water is σ1
The electrophotographic developer according to the above (1), wherein σ2−σ1 is 10 μS / cm or less. (4) A developer comprising polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the particle surface, wherein 1 g of the developer is added to 20 ml of water having a conductivity of σ1. To obtain a dispersion, and the dispersion is sufficiently stirred to be in an equilibrium state. When the conductivity of the filtrate obtained by filtering the dispersion is defined as D2, D2-σ1 is less than 5 μS / cm. The electrophotographic developer according to the above (1), (2) or (3). (5) The electrophotographic developer according to any one of the above (1) to (4), wherein the electrophotographic developer is a non-magnetic one-component developer.

(6) The polymerizable monomer according to any one of the above (1) to (5), wherein the polymerizable monomer contains a styrene monomer, an ester of acrylic acid or methacrylic acid, and a crosslinkable monomer. The described developer. (7) The developer according to (6), further comprising a macromonomer in the polymerizable monomer. (8) The above (1) to wherein the external additive is silicon dioxide particles.
The developer according to any one of (7).

(9) The external additive has a number average particle size of 5 to 20 n.
m, preferably particles of 7 to 18 nm, suitably inorganic oxide particles, and a number average particle diameter of more than 20 nm and 2 nm or less, preferably 30 nm to 1 μm, suitably inorganic oxide particles. The developer according to any one of the above (1) to (8). (10) The developer according to any one of (1) to (9) above, wherein the polymer particles for a developer contain a colorant, a charge control agent, and a release agent. (11) The above (1) to (9), wherein the fixing temperature is 80 to 140 ° C.
The developer according to any one of (10).

(12) Volume average particle size (dv) is 1 to 20
The developer according to any one of the above (1) to (11), which is μm. (13) Volume average particle size (dv) / number average particle size (dp)
The developer according to any one of the above (1) to (12), wherein is not more than 1.7. (14) The ratio (rl / rs) between the major axis rl and the minor axis rs is
The developer according to any one of (1) to (13), which is 1 to 1.2.

Further, according to the present invention, (15) the electrostatic latent image is developed using the developer according to any one of (1) to (14) to obtain a developer image, and And a developing method for transferring and fixing the developer image.

[0011]

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

The polymer particles for a developer are obtained by polymerizing a polymerizable monomer. Particularly preferred polymerizable monomers used for obtaining the polymer particles for a developer constituting the present invention include monovinyl monomers. Specific examples of the monovinyl monomer include, as the most preferred example, a monovinyl monomer. Specifically, styrene monomers such as styrene, vinyltoluene, and α-methylstyrene; acrylic acid and methacrylic acid;
Methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, dimethylaminoethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate,
Derivatives of acrylic acid or methacrylic acid such as dimethylaminoethyl methacrylate, acrylonitrile, methacrylonitrile, acrylamide, and methacrylamide; ethylenically unsaturated monoolefins such as ethylene, propylene, and butylene; 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 ketones such as vinyl methyl ketone and methyl isopropenyl ketone; 2-vinyl pyridine, 4-vinyl pyridine and N Monovinyl monomers such as nitrogen-containing vinyl compounds such as vinylpyrrolidone; These monovinyl monomers may be used alone, or a plurality of monomers may be used in combination. Of these monovinyl monomers, styrene monomers or derivatives of acrylic acid or methacrylic acid are preferably used.

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 esters such as ethylene glycol dimethacrylate and diethylene glycol dimethacrylate; N, N-divinylaniline, divinyl ether and the like A divinyl compound; a compound having three or more vinyl groups; and the like. These crosslinkable monomers can be used alone or in combination of two or more. These crosslinkable monomers are
It is used in an amount of usually 0.05 to 5 parts by weight, preferably 0.1 to 2 parts by weight, based on 100 parts by weight of a non-crosslinkable 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 the preservability, the offset property and the low-temperature fixing property. The macromonomer has a vinyl polymerizable functional group at a terminal of a molecular chain and has a number average molecular weight of usually 1,000 to 30,000.
0 oligomer or polymer. 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 decreases. Conversely, when a polymer having a large number average molecular weight is used, the meltability of the macromonomer is deteriorated, and the fixability is lowered.

The macromonomer preferably has a glass transition temperature higher than the glass transition temperature of the polymer obtained by polymerizing the monovinyl monomer. In addition, Tg of the macromonomer is a value measured by a measuring instrument such as a usual differential calorimeter (DSC).

Specific examples of the macromonomer used in the present invention include a polymer obtained by polymerizing styrene, a styrene derivative, a methacrylate ester, an acrylate ester, acrylonitrile, methacrylonitrile, or a mixture of two or more of them. A macromonomer having a polysiloxane skeleton, which has a polymerizable double bond at the polymer terminal disclosed on pages 4 to 7 of JP-A-3-203746;
Examples having an arbitrary repeating structural unit can be given.

Among these macromonomers, a polymer having a high glass transition temperature, in particular, a polymer obtained by polymerizing styrene, methacrylate or acrylate alone or in combination thereof is suitable for the present invention. When a macromonomer is used, its amount is usually 0.01 to 100 parts by weight of the monovinyl monomer.
To 1 part by weight, preferably 0.03 to 0.8 part by weight.
If the amount of the macromonomer is too small, the preservability and the offset property are not improved. When the amount of the macromonomer is extremely large, the fixing property is reduced.

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

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

Further, as dyes for magnetic color toners, 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. Modant 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. Modant Blue 7, C.I. I.
Direct Gulin 6, C.I. I. Basic Green 4,
C. I. Basic Glin 6 etc. are pigments such as graphite, cadmium yellow, mineral first yellow, navel yellow, neftol yellow S, hanziero G, permanent yellow NCG, tartrazine lake, red mouth graphite,
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, Alkaline Blue Lake, Victoria Blue Lake, Phthalocyanine Blue, Fast Sky Blue, Induslen Blue B
C, chrome grin, chromium oxide, pigment grin B,
Malachite green lake, final yellow logulin G and the like.

Examples of the magenta coloring pigment for full-color toner 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 etc. are magenta dyes 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. Oil-soluble dyes such as Disperse Violet 1;
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; 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. Acid Blue 45 and a copper phthalocyanine pigment in which 1 to 5 phthalimidomethyl groups are substituted on the phthalocyanine skeleton.

Further, yellow coloring pigments for full-color toners include 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 and the like.

As the charge control agent, a commonly used positive or negative charge control agent can be used. For example, a metal complex of an organic compound having a carboxyl group or a nitrogen-containing group, a metal-containing dye, nigrosine and the like can be mentioned. More specifically, Spiron Black TRH
(Made by Hodogaya Chemical Co., Ltd.), T-77 (made by Hodogaya Chemical Co., Ltd.),
Bontron S-34 (Orient Chemical), Bontron E-84 (Orient Chemical), Bontron N-0
1 (manufactured by Orient Chemical Co.), Copy Blue-PR (manufactured by Hoechst), a quaternary ammonium salt-containing resin, and a sulfonic acid group-containing resin. The charge control agent is based on 100 parts by weight of the polymerizable monomer.
Usually, 0.01 to 10 parts by weight, preferably 0.03 to 5 parts by weight
Use parts by weight.

As the release agent, low molecular weight polyethylene,
Examples include low molecular weight polyolefins such as low molecular weight polypropylene and low molecular weight polybutylene, and waxes. The release agent is usually 0.1 to 20 parts by weight, preferably 1 to 20 parts by weight, based on 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 such as oleic acid, stearic acid or the like, or a metal salt of a metal such as Na, K, Ca, Mg, Zn or the like is used for the purpose of uniform dispersion of the colorant in the toner particles. A dispersing aid such as a silane-based or titanium-based coupling agent; and the like may be used. Such lubricants and dispersants are 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 and 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; and halogenated hydrocarbons such as carbon tetrachloride and carbon tetrabromide. These molecular weight regulators can be added before the start of polymerization or during the polymerization. The molecular weight modifier is usually 0.01 to 1 based on 100 parts by weight of the monomer.
0 parts 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. Examples of poorly water-soluble metal compounds include 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; metal hydroxides of aluminum hydroxide, magnesium hydroxide, and ferric hydroxide; and the like.
Among them, a dispersant containing a colloid of a poorly water-soluble metal hydroxide is preferable because it can narrow the particle size distribution of the polymer particles and improves the sharpness of an image.

The polymerization of the polymerizable monomer is usually performed 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 a suspension polymerization method. The dispersant used in the suspension polymerization method is preferably a dispersant containing a colloid of a poorly water-soluble metal hydroxide, and is not limited by its production method. Colloids of poorly water-soluble metal hydroxide obtained by adjusting to about 7 or more, especially poorly water-soluble metal hydroxide formed by the reaction of a water-soluble polyvalent metal compound with an alkali metal hydroxide in an aqueous phase. It is preferable to use a colloid of a substance.

The colloid of the poorly water-soluble metal compound 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 (9% of the number particle size distribution).
(0% cumulative value) is preferably 1 μm or less.

The dispersant is generally used in a proportion of 0.1 to 20 parts by weight based on 100 parts by weight of the composition such as a monomer described below. If this proportion is less than 0.1 part by weight, it is difficult to obtain sufficient polymerization stability, and a polymer aggregate is easily generated. Conversely, if the amount exceeds 20 parts by weight, the viscosity of the aqueous solution increases, and the polymerization stability decreases.

In the present invention, if necessary, a dispersant containing a water-soluble polymer can be used. 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 for stably performing suspension polymerization within a range in which the environmental dependence of charging characteristics does not become large.

The polymer particles thus obtained have a volume average particle size of usually 2 to 10 μm, preferably 2 to 9 μm.
m, particularly preferably 3 to 8 μm. Further, volume average particle diameter (dv) / number average particle diameter (dp) is usually
1.7 or less, preferably 1.5 or less, more preferably 1.3 or less colored fine particles are obtained. Further, the particles obtained in this way, further polymerizable monomer, polymerization initiator,
A charge controlling 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 defined as a shell. As a monomer constituting the monomer for the shell, it is possible to use a monomer which forms a polymer having a glass transition temperature exceeding 80 ° C., such as styrene and methyl methacrylate, alone or in combination of two or more. it can. It is necessary to set the glass transition temperature of the polymer composed of the shell monomer 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 120 ° C or lower, preferably higher than 60 ° C and 110 ° C or lower, more preferably, in order to improve the storage stability of the polymerization toner. 80
Exceeding 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.
It is more preferably at least 30 ° C.

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

The monomer for the shell is not particularly limited by the solubility in water at 20 ° C., but a monomer having a solubility in water at 20 ° C. of 0.1% by weight or more and having a high solubility in water is promptly added to the core particles. , It is easy to obtain polymer particles having good storage properties. Monomers having a solubility in water at 20 ° C. of 0.1% by weight or more include (meth) acrylates such as methyl methacrylate and methyl acrylate; amides such as acrylamide and methacrylamide; and cyanides 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 the monomer is used in an amount of less than% by weight, the transfer to the core particles becomes slow. 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 prepare a single monomer for the shell. The body moves to the core particles quickly, and it becomes easier to obtain polymer particles having good storage stability. The solubility in water at 20 ° C. is 0.
Less than 1% by weight of the shell monomer includes styrene, butyl acrylate, 2-ethylhexyl acrylate,
Examples include ethylene and propylene.

The solubility in water at 20 ° C. is 0.1% by weight.
Examples of the organic solvent preferably used when less than the shell monomer is 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; 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 a dispersion medium (total amount of water and the organic solvent) of 0.1.
An amount of 1% by weight or more is added. Although the specific amount of the organic solvent varies depending on the type and amount of the organic solvent and the shell monomer, it is usually 0.1 to 100 parts by weight of the aqueous dispersion medium.
It is 1 to 50 parts by weight, preferably 0.1 to 40 parts by weight, 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, but in order to facilitate the transfer of the shell monomer to the core particles and to easily obtain polymer particles having good storability, It is preferable to add the organic solvent first, and then add the shell monomer.

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

In the present invention, after mixing the charge controlling agent with the shell monomer, it is preferable to add the mixture to the reaction system and polymerize the mixture 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 chargeable charge control agents can be used. Specific examples of the charge control agent include Bontron N01 (Nigrosine, manufactured by Orient Chemical), Nigrosine EX (manufactured by Orient Chemical),
Spiron Black TRH (Hodogaya Chemical), T-7
7 (manufactured by Hodogaya Chemical Co., Ltd.), Bontron S-34 (manufactured by Orient Chemical Co., Ltd.), Bontron E-84 (manufactured by Orient Chemical Co., Ltd.), and charge control resins such as quaternary ammonium salt-containing resins and sulfonic acid group-containing resins. be able to. The charge control agent is used in an amount of usually 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 for polymerizing the shell monomer in the presence of the core particles, a method for continuously adding the shell monomer to the reaction system of the polymerization reaction for obtaining the core particles is described. Or a method in which core particles obtained in another reaction system are charged, a monomer for a shell is added thereto, and polymerization is carried out in a stepwise manner. The monomer for the shell component can be added to the reaction system all at once, or can be added continuously or intermittently using a pump such as a plunger pump.

(Polymerization initiator for shell) In the polymerization method toner of the present invention, it is easy to obtain core-shell type polymer particles by adding a water-soluble radical initiator when adding a monomer for shell. It is preferable to When a 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 considered that this is because a shell is easily formed.

Examples of the water-soluble polymerization initiator include persulfates such as potassium persulfate and ammonium persulfate; 4,4-azobis (4-cyanovaleric acid) and 2,2-azobis (2-amidinopropane) dihydrochloride Azo-based 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 the core particles) to the monomer for shell is usually 8%.
0/20 to 99.9 / 0.1. Within this range, the storage stability will be 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,
As the size decreases, 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 is covered with the shell. The core particle diameter and shell thickness can be obtained by directly measuring the particle size and shell thickness selected at random from an observation photograph when observable with an electron microscope. When it is difficult to observe the above, it can be calculated from the particle size of the core particles and the amount of the monomer forming the shell.

The external additives constituting 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, methacrylate polymer particles, acrylate polymer particles, styrene-methacrylate copolymer particles, styrene-acrylate copolymer particles, the core is a methacrylate polymer, the shell Are core-shell particles formed of a styrene polymer. Of these, inorganic oxide particles, particularly silicon dioxide particles, are preferred. Moreover, the surface of these particles can be subjected to a hydrophobic treatment, and silicon dioxide particles subjected to the hydrophobic treatment are particularly suitable. The amount of the external additive is not particularly limited, but is usually 0.1 to 100 parts by weight of the toner particles.
６6 parts by weight.

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

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

The developer of the present invention thus obtained has a pH of about 4 to 7, preferably about 4.5 to 6.5, in an extract obtained by subjecting it to the ion exchange water boiling extraction method. It is. When the pH is less than about 4 or more than about 7, the environment dependence of the charge amount of the non-magnetic one-component developer becomes large, and the image quality is deteriorated due to the environmental change. In the present invention, "about" in the numerical value of pH refers to a value that is rounded off to one digit and falls within the numerical value. For example, pH of about 7 means pH 6.5 to 7.4, and pH of about 6.5. Means pH 6.45 to 6.54. In the ion-exchanged water boiling extraction method, 6 g of the developer is subjected to a cation exchange treatment and an anion exchange treatment to a pH of about 7;
Is dispersed in 100 g of ion-exchanged water, which is heated, boiled, and the boiling state is maintained for 10 minutes (boiled for 10 minutes) to extract the water-soluble component from the developer. Add the ion-exchanged water whose pH has been brought to about 7 by the cation exchange treatment and the anion exchange treatment that has been boiled back to the volume before boiling, and cool to room temperature (about 25 ° C) to obtain the extract. Is the way. pH is
This is a value obtained by measuring the extract obtained by this method using a pH meter.

The developer of the present invention has a conductivity σ2 of 20 μS / c of an extract obtained by using the ion-exchanged water having a conductivity of σ1 in the above-mentioned ion-exchanged water boiling extraction method.
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 increases, and the image quality is reduced due to environmental fluctuations (changes in temperature and humidity). Become.

Further, the developer of the present invention comprises the developer 1
g was dispersed in 20 ml of cation-exchanged and anion-exchanged ion-exchanged water having a conductivity of σ1 to obtain a dispersion, and the dispersion was sufficiently stirred. 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 increases, the dependence of the charge amount of the non-magnetic one-component developer on the environment increases, and the image quality decreases due to environmental changes (changes in temperature and humidity).

The developer of the present invention has a volume average particle diameter (d
v) is usually 1 to 20 μm, preferably 1.5 to 15 μm.
μm, and more preferably 1.5 to 8 μm. Also,
The volume average particle size (dv) / number average particle size (dp) is usually 1.7 or less, preferably 1.5 or less.

The developer of the present invention has a major axis rl and a minor axis r
The ratio (rl / rs) to s is usually 1 to 1.2, preferably 1 to 1.1. When this ratio increases, 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 at the same time as the toner increases, so that the external additive may be peeled off. , The durability tends to decrease.

The method for producing the developer of the present invention is not particularly limited. Preferably, an aqueous dispersion of polymer particles for a developer obtained by suspension polymerization of a polymerizable monomer is used. A step of filtering and dehydrating through a filter cake layer comprising a polymer particle for filtration having a volume average particle diameter larger than the volume average particle diameter of the united particles, washing, drying the washed developer polymer particles, developer Adhering an external additive to the surface of the polymer particles for use.

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, larger than the volume average particle diameter of the polymer particles for the developer.
It has a large volume average particle size. When the polymer particles for filtration are smaller than the polymer particles for developer, the filter cake layer is densely packed, the voids between the particles are eliminated, the dehydration becomes worse, and the water content of the obtained polymer particles is increased. As a result, the dependence on the environment such as the amount of charge may increase.

The polymer particles for filtration are not particularly limited by the kind of the polymer constituting them, but are composed of the same polymer as the developer polymer particles in order to minimize the contamination of the developer with foreign substances. And those containing a colorant, a charge control agent, a release agent and the like are preferred. Specific examples of the polymer include a copolymer of a styrene monomer and a derivative of acrylic acid or methacrylic acid, particularly, styrene and (meth)
A copolymer with an alkyl acrylate is preferably used.

In the production method of the present invention, filtration and dehydration are performed 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 used. Among these, the centrifugal filtration method is preferred.
Examples of the filtration and dewatering device include peeler centrifugation and siphon peeler centrifugation. In the centrifugal filtration method, centrifugal gravity is
Usually 400-3000G, preferably 800-200G
Set to 0G. The water content after dehydration is usually 5 to 30% by weight, preferably 8 to 25% by weight. If the water content is high, the drying step requires a long time, and even if the impurity concentration in the water is low, if the water content is high, the impurities are concentrated by drying, and the environment dependency of the developer increases.

The water content referred to here is 2 g of water-containing particles.
Sample on an aluminum dish and weigh it precisely (W ₀[G]) and 10
Leave in a dryer set at 5 ° C for 1 hour, cool down, and weigh
(W₁[G]), and is a value calculated by the following equation. Water content = ((W₀-W₁) / W₀) × 100

The pH of the polymer particle dispersion for a developer obtained by suspension polymerization is usually from 8 to 12, preferably from 8.5 to 11.
belongs to. If the pH is too low, the particle size distribution of the polymer particles for the developer becomes wide. Further, it is preferable to adjust the pH of the aqueous dispersion of polymer particles for a developer at the time of filtration and dehydration to 6.5 or less. For adjustment, a mineral acid such as sulfuric acid or hydrochloric acid; or an organic acid such as carboxylic acid is used. Particularly, sulfuric acid is preferred.

In the above-mentioned method for producing the developer of the present invention, the fixing temperature is usually from 80 to 140 ° C., preferably from 80 to 130 ° C.
This method is suitable as a method for obtaining a so-called low-temperature fixing developer having a low temperature of, in particular, a low-temperature fixing non-magnetic one-component developer. 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 a low-temperature fixing developer comprising a core having a low glass transition temperature and a shell having a high glass transition temperature. What is comprised by the following core-shell type polymer particles is suitable. 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 illustrating one embodiment of the image forming apparatus. In the image forming apparatus, a photosensitive drum 1 as a photosensitive member is rotatably mounted in the direction of arrow A. The photosensitive drum 1 has 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.

Around the photosensitive drum 1, along a 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, 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. By applying a voltage to the charging roll and bringing the charging roll into contact with the photosensitive drum, the surface of the sightseeing drum is changed. It is charged. The charging roll 3 can be replaced by charging means using corona discharge. The laser light irradiating device 4 irradiates light corresponding to an image signal onto the surface of the uniformly charged photosensitive drum in a predetermined pattern, and forms an electrostatic latent image on the irradiated portion (reversal development). in the case of). In addition, an electrostatic latent image is formed on a portion not irradiated with light (in the case of regular development)
There are also things to do. As another electrostatic latent image forming means, an electrostatic latent image forming means including an LED array and an optical system can be used. The developing roll is for applying a developer to the electrostatic latent image on the photosensitive drum 1 for development. In the reversal development, the developer is applied only to the light-irradiated portion. A bias voltage is applied between the developing roll and the photosensitive drum so that only the developer adheres.

Next to the developing roll, a developing roll 8 and a supply roll 1 are placed in a casing 11 in which a developer 10 is stored.
2 are provided. The developing roll is arranged close to and in contact with the photosensitive drum, and rotates in a direction B opposite to the photosensitive drum. The supply roll 12 contacts the developing roll and rotates in the same direction C as the developing roll,
The developer is supplied to the outer periphery of the developing roll. Around the developing roll, a developing roll blade 9 as a layer thickness regulating means is disposed at a position between a contact point with the supply roll and a contact point with the photosensitive drum.
The blade 9 is made of conductive rubber or stainless steel, and is applied with a voltage of | 200 V | to | 600 V | to perform charge injection into the developer on the developing roll. For this purpose, the electrical resistivity of the blade 9 is preferably 10 6 Ωcm or less.

The above-described developer 10 is accommodated in a casing 11 of the image forming apparatus. Since the developer of the present invention is excellent in fluidity and preservability, the developer does not agglomerate in the casing 11 and does not cause image defects such as blurring and fog.

The transfer roll 6 is for transferring the developer image on the surface of the photosensitive drum formed by the developing roll to the transfer material 7. Examples of the transfer material include paper and a resin such as an OHP sheet. Examples of the transfer unit 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 fixing means. The fixing means usually comprises a heating means and a pressure bonding means. The developer transferred to the transfer material is heated by heating means to melt the developer, and the melted developer is pressed and fixed to the surface of the transfer material by pressure bonding means. In the image forming apparatus of the present invention, since the above-mentioned developer is used, even if the heating temperature by the heating unit is low, the toner is easily melted, and when pressed lightly by the pressure bonding unit, the developer becomes a smooth state. Since it is fixed to the transfer material surface,
Printing or copying at high speed is possible. Also, it has excellent OHP permeability.

The cleaning device 2 is for cleaning the transfer residual developer remaining on the surface of the photosensitive drum, and includes, for example, a cleaning blade. Note that this cleaning device does not necessarily need to be installed when adopting a method of performing cleaning at the same time as development by the developing roll.

[0069]

EXAMPLES The present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to only these examples. Parts and percentages are by weight unless otherwise specified.

In this example, evaluation was made by the following method. (Particle size) The polymer particles for development and filtration have a volume average particle size (unit: μm) measured by Multisizer (manufactured by Coulter Inc.). The measurement by the Multisizer was as follows: aperture diameter: 100 μm, medium: Isoton II, concentration 1
The measurement was performed under the conditions of 0% and the number of measured particles: 50,000.

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

(PH) 6 g of the developer was dispersed in 100 g of ion-exchanged water having a pH of about 7 by the cation exchange treatment and the anion exchange treatment, and this was heated and boiled.
After maintaining the boiling state for 10 minutes (10 minutes boiling), subsequently, ion-exchanged water having a pH of about 7 due to the cation exchange treatment and the anion exchange treatment, which had been separately boiled for 10 minutes, was added to the mixture before boiling. It is a value measured by using a pH meter for the extract which was returned to the volume and cooled to room temperature (about 25 ° C.).

(Conductivity σ2) 6 g of the developer is dispersed in 100 g of ion-exchanged water having a pH of about 7 by the cation exchange treatment and the anion exchange treatment, and this is heated and boiled. After holding for 10 minutes (boil for 10 minutes), add ion-exchanged water whose pH has been brought to about 7 by cation exchange treatment and anion exchange treatment, which has been separately boiled for 10 minutes, and return to the volume before boiling. , Room temperature (about 25
(° C.) was measured for the conductivity σ2 of the extract. Σ1-σ1 was calculated assuming that the conductivity of ion-exchanged water having a pH of about 7 by the cation exchange treatment and the anion exchange treatment was σ1.

(Conductivity D2) 1 g of the developer was dispersed in 20 ml of ion-exchanged water subjected to cation exchange treatment and anion exchange treatment with a conductivity of σ1 to obtain a dispersion, and the dispersion was thoroughly stirred. And the conductivity D2 of the filtrate obtained by filtering the dispersion.
Was measured. D2-σ1 was calculated assuming that the conductivity of the ion-exchanged water whose pH became about 7 by the cation exchange treatment and the anion exchange treatment was σ1.

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

(Fluidity) The openings were 150 μm and 75 μm, respectively.
Three types of sieves of μm and 45 μm are stacked in this order from the top, and 4 g of the developer to be measured is precisely weighed and placed on the uppermost sieve. Next, the three types of sieves thus stacked were vibrated for 15 seconds using a powder measuring device (trade name “Powder Tester” manufactured by Hosokawa Micron Co., Ltd.) under the condition of a vibration intensity of 4 and then remained on each sieve. The weight of the developer is measured. Each measured value is put into the following equation to calculate the value of the fluidity. The measurement was performed three times per sample, and the average value was determined. 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 Flowability (%) = 100− (a + b + c)

(Preservability) The developer is placed in a sealable container, and after sealing, the container is immersed in a thermostatic water bath maintained at a temperature of 55 ° C. After a lapse of 8 hours, the container is taken out of the thermostatic bath, 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 to the sieve so as not to destroy the aggregated structure of the developer in the container. After the sieve was vibrated for 30 seconds under the condition of a vibration intensity of 4.5 using the above-mentioned powder measuring machine, the weight of the developer remaining on the sieve was measured and defined as the weight of the aggregation developer. The ratio (% by weight) of the weight of the aggregation developer to the weight of the developer initially placed in the container was calculated. The measurement was performed three times for one sample, and the average value was used as an index of the storage stability.

(Environmental Dependency of Charge Amount) L / L environment of temperature 10 ° C. and humidity 20% RH or temperature 35 ° C. and humidity 80% R
In a H / H environment of H, the developer is put into a non-magnetic one-component developing system printer (four-sheet machine), left for one day and night, and five halftone print patterns are printed, and then, The developer 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. The state of the environmental change of the developer was evaluated from the change of the charge amount under each environment.

(Environment Dependency of Image Quality) Using the above-described modified printer, continuous printing was performed from the beginning in each environment of 35 ° C. × 80 RH% (H / H) and 10 ° C. × 20 RH% (L / L). Continuous printing that can maintain image quality with a print density of 1.3 or more with a reflection densitometer (manufactured by Macbeth) and a fog of 10% or less in non-image areas measured with a whiteness meter (manufactured by Nippon Denshoku) The number of sheets was examined, and the environmental dependency of image quality due to the developer was evaluated based on 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 image quality is 5,000 or more and less than 10,000, ×: The number of continuous prints that can maintain the image quality is less than 5000.

Example 1 A core monomer obtained from 78 parts of styrene and 22 parts of n-butyl acrylate (calculated Tg of the obtained copolymer =
50 ° C.), 7 parts of carbon black (trade name “Printex 150T” manufactured by Degussa Co., Ltd.), and a charge controlling agent (trade name “Spiron Black TRH” manufactured by Hodogaya Chemical Co., Ltd.) 1
Part, divinylbenzene 0.3 part, polymethacrylic acid ester macromonomer (Toa Gosei Chemical Industry Co., Ltd., trade name “AA6”, Tg = 94 ° C.) 0.8 part, pentaerythritol = tetrastearate 10 parts and t- A homomixer (TK type, manufactured by Tokushu Kika Co., Ltd.) capable of mixing 4 parts of butylperoxy-2-ethylhexanoate with high shearing force is stirred and mixed at a rotation speed of 12000 rpm to be uniformly dispersed, A monomer mixture for a core was obtained.

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

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

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

While stirring the aqueous dispersion of the core-shell type polymer particles for a developer thus obtained, the system
H was adjusted to about 5.5, and acid washing (25 ° C., 10 minutes) was performed. Next, dewatering was performed using a continuous belt filter (trade name “Eagle Filter” manufactured by Sumitomo Heavy Industries, Ltd.), and after dewatering, washing was performed by sprinkling washing water.

After washing with water, the polymer particles for the developer were dispersed again in water, and then centrifugal gravity was 1200 G and layer pressure was changed using a siphon peeler centrifuge (trade name “HZ40Si” manufactured by Mitsubishi Kakoki Co., Ltd.). 10 mm, layer area 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 (Obtained by suspension polymerization of 7 parts of Monarch 120 manufactured by Cabot Corporation and 1 part of charge control agent (brand name: Spiron Black TRH) manufactured by Hodogaya Chemical Co., Ltd.) Exchange water 40 parts /
The polymer particles for developer having a water content of 15% were separated by centrifugal filtration and dehydration under the conditions of a supply amount of an aqueous dispersion of 120 parts / hour, and finally dried at 45 ° C. for 2 days and nights in a drier. 100 parts of the polymer particles for the developer were treated with silica subjected to hydrophobization treatment (trade name “AEROSIL R-17 manufactured by Nippon Aerosil Co., Ltd.).
0 ", 1 part of number average particle diameter 15 nm, and hydrophobicized silica (manufactured by Nippon Aerosil Co., Ltd., trade name" AEROSI ")
LRX-50 ", a number average particle size of 40 nm) 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 size (dv) of the polymer particles for a developer is 6.9 μm, and the ratio of the volume average particle size to the number average particle size (dv / dp).
Is 1.27, which is the ratio of the major axis to the minor axis of the toner (rl /
rs) was 1.1. In the image evaluation, high temperature and high humidity (H
In both the (/ H) environment and the low-temperature and low-humidity (L / L) environment, very good images having good color tone, high image density and no fog were obtained. Other evaluation results are shown in Table 1.

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

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

Comparative Example 1 In Example 2, the filtering polymer particles having a volume average particle diameter of 6.1 μm (constitution = styrene 85)
Parts, 15 parts of n-butyl acrylate, 0.3 parts of divinylbenzene, 2 parts of a release agent, 7 parts of carbon black (manufactured by Cabot Corporation, trade name "Monarch 120") and a charge control agent (trade name, manufactured by Hodogaya Chemical Co., Ltd., trade name) "Spiron Black TR
Example 2 except that 1 part of "H" was subjected to suspension polymerization).
A developer was obtained in the same manner as described above. The centrifugal filter quickly clogged, making continuous operation difficult. The water content of the polymer particles obtained by the filtration and dehydration was 28%. Table 1 shows the evaluation results.

Comparative Example 2 After washing with a continuous belt filter, a developer was obtained in the same manner as in Example 2 except that the developer was not dispersed again in water, and dehydration by centrifugal filtration was not performed. Table 1 shows the evaluation results.

Comparative Example 3 In Example 1, the pH of the dispersion of the polymer particles for a developer was adjusted to about 6.9 with sulfuric acid, and acid washing was performed (25 ° C., 10 minutes).
The polymer particles for filtration having a volume average particle diameter of 6.3 μm (constitution = 85 parts of styrene, n-butyl acrylate 15
Parts, divinylbenzene 0.3 parts, release agent 2 parts, carbon black (manufactured by Cabot Corporation, trade name "Monarch 120")
Example 1 except that one part obtained by suspension polymerization was used.
A developer was obtained in the same manner as described above. The centrifugal filter quickly clogged, making continuous operation difficult. Table 1 shows the evaluation results.
It was shown to.

[0092]

[Table 1]

[0093]

According to the present invention, the charge amount does not change so much in a low-temperature and low-humidity environment, and in a high-temperature and high-humidity environment, and the image quality is almost degraded. Since it is not stable, it can be suitably used for a non-magnetic one-component developing system printing machine and copying machine.

[0094]

[Brief description of the drawings]

FIG. 1 is a diagram illustrating one embodiment of an image forming layer value.

[0001]

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum 3 ... Charging roll 6 ... Transfer roll 8 ... Developing roll 10 ... Developer

Claims (3)

[Claims] 1. A developer comprising a polymer particle for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the particle surface, wherein the developer obtained by the following procedure is provided. An electrophotographic developer wherein the pH of an aqueous extract of the agent is about 4 to 7. 6 g is dispersed in 100 g of ion-exchanged water having a pH of about 7, heated, and boiled for 10 minutes. After that, the water which has been boiled with ion-exchanged water having a pH of about 7 is added to supplement the evaporated water. To the original volume, and further cooled to room temperature to obtain a water extract. 2. A developer comprising polymer particles for a developer obtained by polymerizing a polymerizable monomer and an external additive attached to the particle surface, wherein the developer obtained by the following procedure An electrophotographic developer in which the aqueous extract of the agent has a conductivity σ2 of 20 μS / cm or less and σ2−σ1 of 10 μS / cm or less. 6 g is dispersed in 100 g of ion-exchanged water having a conductivity of σ1, heated and boiled for 10 minutes, and then separately added with boiled ion-exchanged water having a pH of about 7 to replenish the evaporated water. To the original volume, and further cooled to room temperature to obtain a water extract. 3. A development forming method for developing an electrostatic latent image using the developer according to claim 1 or 2 to obtain a developer image, transferring the developer image to a transfer material, and fixing the same.