JPH0792734A - Magnetic toner - Google Patents

Abstract

PURPOSE:To enhance the moisture resistance of an electrostatic charge image developing toner derived from the association or aggregation of particles of a magnetic substance and a polymer by producing the polymer from soap-free emulsion polymerization in which no surfactant is included. CONSTITUTION:In the electrostatic imaging toner derived from the association or aggregation of particles of a magnetic substance and a polymer, the polymer is produced by soap-free emulsion polymerization in which no surfactant is included. An example of the soap-free polymerization used is a method using a reactive emulsifier, where a polymeric monomer is dispersed and emulsified in a medium which is chiefly water, etc., and polymerization is effected with addition of a water soluble initiator to obtain an emulsion of the polymer produced, and fine particles of the polymer containing no surfactant are obtained through subsequent dehydration and drying. The polymerizable monomer is for a radical polymer and examples of it are a monovinyl aromatic monomer and an acrylic monomer, of which one or two kinds are used in combination so that the polymer produced as the required heat and electrostatic characteristics of the toner.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a magnetic toner for electrophotography,
In particular, it relates to a magnetic toner for electrophotography having excellent moisture resistance.

[0002]

2. Description of the Related Art Electrophotography is known as one of various processes for developing and recording an electric or magnetic latent image to form an image. In this electrophotographic method, a photoconductive substance is generally used, an electric latent image is formed on a photoconductor by various means, and then the latent image is developed with a toner to form a toner image. The obtained toner image is fixed as it is, or after being transferred to paper or the like, it is fixed by means of heating, pressing or the like to form a copy. Various methods such as a powder cloud method, a touch-down method, and a magnetic brush developing method have been proposed as a method of developing using toner, and a method suitable for each image forming process is adopted.

Among these developing methods, the magnetic brush developing method is widely used because of its good image quality, easy downsizing of the apparatus, and long life. Among the magnetic brush developing methods, there are a two-component developing method using a magnetic carrier and a non-magnetic toner, a one-component developing method using only a toner, and the like, and each has its own characteristics. Among them, the developing method using the magnetic toner has the advantages that the apparatus is more compact and the toner density control is unnecessary.

Conventionally, toners used for these purposes are generally obtained by melt-kneading a coloring agent composed of a magnetic material, a dye, a pigment or the like in a thermoplastic resin to uniformly disperse the coloring agent in the resin, and then pulverizing it. By classification, a toner having a predetermined particle size distribution has been manufactured. Recently, higher resolution image formation is required, and it has been found that reducing the toner particle size is effective for this. Therefore, attempts have been made to reduce the particle size of the toner, but the average particle size of the toner obtained by the pulverization method is limited to about 7 μm. Therefore, as a method for producing a toner having a smaller particle diameter, a toner by a polymerization method has been proposed.

Examples of toner production by the polymerization method include a suspension polymerization method and a dispersion polymerization method. Although small-sized toner particles can be produced by these methods, the usual method is limited to the production of spherical particles, and it is difficult to uniformly disperse the colorant and the like in the particles. The characteristics have not been fully satisfied. Spherical particles are most unsuitable for blade cleaning, which is a general cleaning method. Therefore, an association method or an aggregation method is known as a method for producing a toner having a small particle size and an irregular shape.
In this method, a fine particle polymer is produced in advance, and necessary colorants, magnetic materials and the like are added to the fine particle polymer to be used as a toner.
The particles are associated or aggregated to have a particle size of around μm. An emulsion polymerization method in which various monomers are emulsified with a surfactant (emulsifier), a polymerization initiator is added, and heat polymerization is known as one of the methods for producing a fine particle polymer. The emulsion polymerization method is a method in which a monomer is polymerized under the action of an emulsifier using a water-soluble initiator in the presence of water, and as the emulsifier, an anionic emulsifier such as sodium higher alcohol sulfate ester, sodium alkylbenzenesulfonate and an alkylphenol are used. Nonionic emulsions such as ethylene oxide adducts and polypropylene glycol ethylene oxide adducts or cationic emulsifiers such as quaternary ammonium salts are known.

[0006]

However, since the polar groups derived from the emulsifier remain on the surface of the polymer obtained by the emulsion polymerization method, the toner using this polymer has a charge amount in a high humidity environment. However, there is a problem in that the image density decreases and the background fog increases. On the other hand, in a low humidity environment, there is a problem that the image density decreases due to an increase in the toner charge amount.

That is, since the toner produced by the emulsion polymerization method using the surfactant (emulsifier) as described above has unstable charging characteristics due to the residual surfactant, the environmental resistance is not stable. There's a problem.

An object of the present invention is to provide a magnetic toner having excellent moisture resistance.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in a magnetic toner for developing an electrostatic charge image, which comprises at least magnetic particles and a polymer associated or aggregated, The coalescence is characterized by being produced by soap-free emulsion polymerization without surfactant.

As a result of intensive studies, the inventors of the present invention have solved the above-mentioned problems by adopting a soap-free polymerization method in which the produced polymer does not contain a surfactant (emulsifier).

As the soap-free polymerization method used in the present invention, a method using a reactive emulsifier, emulsifier-free emulsification with a persulfate initiator using a relatively hydrophilic polymerizable monomer such as vinyl acetate or methyl acrylate. A method of performing polymerization, a method of copolymerizing a water-soluble special polymerizable monomer such as ionic or nonionic, a method of using a water-soluble polymer or oligomer instead of an emulsifier, a method of using a decomposable emulsifier,
There is a method using a cross-linking emulsifier. By these, the polymerizable monomer is mainly dispersed and emulsified in a medium such as water, and a water-soluble initiator is added to perform polymerization to obtain an emulsion of the produced polymer, which is then dehydrated and dried without containing a surfactant. A fine powder of polymer is obtained.

In the present invention, known magnetic materials, colorants, dispersants, polymerizable monomers, polymerization initiators (radical generators), crosslinking agents, charge control agents, fluidity modifiers, cleaning agents, fillers. Can be used.

Examples of the dispersant for the magnetic substance include the following. Examples of the silane coupling agent include γ-methacryloxypropyltrimethoxysilane and N-β- (N-vinylbenzylaminoethyl) -γ-aminopropyltrimethoxysilane hydrochloride. Further, there are titanate coupling agents such as isopropyl triisostearic titanate, sodium p-styrene sulfonate, potassium p-styrene sulfonate, calcium styrene sulfonate, acrylic acid, methacrylic acid and p-chlorostyrene.

The amount of the dispersant added is not particularly limited, but it is preferable to add it in a ratio of 0.1 to 10 parts by weight with respect to 100 parts by weight of the magnetic material.

The polymerizable monomer used in the present invention is a radical-polymerizable one, and one kind or a combination of two or more kinds is used so that the produced polymer has the required thermal characteristics and electrostatic characteristics of the toner. To be done. Examples of such monomers include monovinyl aromatic monomers, acrylic monomers, vinyl ester monomers, vinyl ether monomers, diolefin monomers, monoolefin monomers. and so on.

Monovinyl monomers include styrene and o
-Methylstyrene, m-methylstyrene, p-methylstyrene, p-methoxystyrene, p-phenylstyrene, p-chlorostyrene, p-ethylstyrene, pn
-Butyl styrene, p-tert-butyl styrene, p
-N-hexyl styrene, pn-octyl styrene,
pn-nonylstyrene, pn-decylstyrene, p
-N-dodecyl styrene, 2,4-dimethyl styrene,
Examples thereof include styrene such as 3,4-dichlorostyrene and its derivatives.

As the acrylic monomer, acrylic acid,
Methacrylic acid, methyl acrylate, ethyl acrylate,
Butyl acrylate, 2-ethylhexyl acrylate,
Cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, γ-aminopropyl acrylate, stearyl methacrylate, methacrylic acid Examples thereof include dimethylaminoethyl acid salt and diethylaminoethyl methacrylate.

The vinyl ester-based monomers include vinyl acetate, vinyl propionate and vinyl benzoate, and the vinyl ether-based monomers include vinyl methyl ether, vinyl ethyl ether, vinyl isobutyl ether and vinyl phenyl ether. . Examples of the diolefin-based monomer include butadiene, isoprene and chloroprene, and examples of the mono-olefin-based monomer include ethylene, propylene, isobutylene, butene-1, pentene-1,4-methylpentene-1 and the like.

As the radical generator and the polymerization initiator used in the present invention, known polymerization initiators can be used alone or in combination of two or more kinds. For example, 2,2′-azobisisobutyronitrile, 2,2′-azobis (2,2
4-dimethyl) valeronitrile, 2,2'-azobis 4
Polymerization can be carried out using -methoxy-2,4-dimethylvaleronitrile, benzoyl peroxide, 2,4-dichloroperoxide, isopropyl peroxycarbonate, cumene hydroperoxide, lauroyl peroxide, potassium persulfate and the like.
The amount of these polymerization initiators used is about 0.1 to 2% by weight of the monomer composition as the radical generator for dispersing the magnetic substance, and the polymerization of the polymer constituting the toner particles is not limited. For use, it is preferably about 0.1 to 5% by weight of the monomer composition.

As the cross-linking agent, a cross-linking monomer having two or more unsaturated bonds in one molecule may be used for copolymerization. Examples of the crosslinkable monomer include divinylbenzene, divinylnaphthalene, divinyl ether, diethylene glycol methacrylate, ethylene glycol dimethacrylate, polyethylene glycol dimethacrylate and diallyl phthalate. The ratio of copolymerizing these crosslinkable monomers with the polymerizable monomer,
It is preferably 0.2 to 2% by weight based on the total amount of the monomers.

As the colorant, known dyes and pigments can be used in addition to the magnetic material. For example, the dyes are nigrosine dye, CI direct red 1, CI direct red 4, CI acid red 1, CI basic red 1, CI solvent red, CI bat red, C.
I. Direct Blue 1, CI Direct Blue 2, CI
Acid Blue 15, CI Basic Blue 3, CI Solvent Blue, CI Direct Green 6, CI Solvent Red, etc. As the pigment, furnace black, acetylene black, cadmium yellow, Hansa yellow G, naphthol yellow S, pyrazolone red, permanent red 4R, molybdenum orange,
Fast violet B, phthalocyanine blue, malachite green, phthalocyanine green and the like can be mentioned. These colorants need to be contained in a ratio suitable for forming a visible image of sufficient density,
Usually, the proportion is 2 to 20% by weight with respect to the total amount of the monomer composition.

As the magnetic material, powders of ferromagnetic metals such as iron, cobalt and nickel, or alloys of these with addition of chromium, manganese, copper, zinc, aluminum, rare earth elements, their oxides magnetite and ferrite. Etc. can be used. The particle size of the magnetic material is preferably in the range of 0.1 to 2 μm. The addition amount of these magnetic materials is preferably 20 to 70% by weight based on the total weight of the toner.

Examples of charge control agents include nigrosine, quaternized ammonium salts, polyalkylamides, molybdic acid chelate pigments, metal complexes of monoazo dyes, naphthenic acid metal salts, and salicylic acid metal complexes. The amount of these charge control agents added is 0.1 to 5% by weight based on the total weight of the toner.
Is preferred.

In the present invention, in addition to the above-mentioned components, additives such as a fluidity modifier, a cleaning agent and a filler may be added if necessary. The fine polymer particles added to the surface of the polymer particles include polymers or copolymers of polyethylene, polypropylene, polystyrene, polymethylmethacrylate, polyvinylidene fluoride, polytetrafluoroethylene and the like.

The fluidity modifier is fine powder of hydrophobic silica, titanium oxide, polyvinylidene fluoride, metal soap, etc., and the cleaning aid is zinc stearate, calcium stearate, magnesium stearate, polymethyl ester. Fine powders of methacrylate, nylon, polytetrafluoroethylene, silicon carbide, etc. can be used. These additives may be used by being mixed and dispersed in the monomer composition, or may be added to the surface of the obtained toner particles.

[0026]

EXAMPLES The contents of the present invention will be described in more detail below with reference to examples. In addition, the part in an Example and a comparative example represents a weight part.

Example 1 91 parts of styrene, 8.7 parts of 2-ethylhexyl acrylate, 0.1 part of divinylbenzene.
3 parts of styrene-acryl having a size of 1 μm or less was added to an aqueous solution of 400 parts of ion-exchanged water, 1 part of hydroxypropyl cellulose, and 5 parts of potassium persulfate under stirring in a nitrogen atmosphere, followed by polymerization at 70 ° C. for 8 hours. An emulsion (solid content 20%) containing the system copolymer particles was obtained.

A silane coupling agent (SZ608 manufactured by Toray Silicon Co., Ltd.) was added to 500 parts of the above emulsion.
Disperse 80 parts of magnetic powder (MAT-305 manufactured by Toda Kogyo [Co.]) and 1 part of charge control agent (Kayacharge T-2N manufactured by Nippon Kayaku [Co.]) after surface treatment in 3), and stir 70
Hold at 3 ° C for 3 hours. In this case, since the treatment was performed at the glass transition temperature of the resin component or higher, the particles containing the polymer were aggregated to form an aggregate having an average particle diameter of 7 μm. After cooling, filtration, washing with water, and drying under reduced pressure, 0.5 parts of silica (H-2000 manufactured by Wacker [KK]) was added to the aggregate particles to obtain a magnetic toner.

Example 2 The same procedure as in Example 1 was repeated except that 70 parts of styrene and 30 parts of n-butyl acrylate were changed to an aqueous solution containing 400 parts of ion-exchanged water, 1 part of polyvinyl alcohol and 5 parts of potassium persulfate. An aggregate (magnetic toner) having an average particle size of 8 μm was obtained.

Comparative Example 1 A magnetic toner was prepared in the same manner as in Example 1 except that 1 part of anionic emulsifier (Neogen R) was used instead of 1 part of hydroxypropyl cellulose.

Comparative Example 2 A magnetic toner was prepared in the same manner as in Example 1 except that 1 part of sodium dodecyl sulfate was used in place of 1 part of hydroxypropyl cellulose.

When the above magnetic toner was evaluated by a reversal development type printer (KXP4620 manufactured by Kyushu Matsushita [KK]), the results shown in Table 1 were obtained. In Table 1, TEC
For (triboelectric charge amount), a developer adjusted to have a toner concentration of 5% by weight is mixed well, the toner is blown at a blow pressure of 1.0 kgf / cm ² , and this is blow-off powder charge amount measuring device (Toshiba Chemical Co., Ltd. ] It is the value measured by TB-200). Further, ID means image density and BG means background fog.

[0033]

[Table 1]

From Table 1, the magnetic toners obtained in Examples 1 and 2 have stable charge amounts and image densities even in a high humidity environment, no background fog occurs, and even in a low humidity environment. It can be seen that the cleaning property is good. On the other hand, in the magnetic toners of Comparative Examples 1 and 2, the charge amount and the image density are lowered in the environment of high humidity, the background fog occurs, the charge-up occurs in the environment of low humidity, and the cleaning property is remarkable. It can be seen that it has fallen to.

[0035]

EFFECTS OF THE INVENTION The present invention has the constitution and operation as described above, and in a toner produced by soap-free emulsion polymerization, a magnetic toner excellent in moisture resistance is obtained because the polymer does not contain a surfactant. be able to.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Masumi Asana 5200 Mikashiri, Kumagaya-shi, Saitama Hitachi Metals Co., Ltd. Kumagaya Plant

Claims (1)

[Claims] 1. A toner for developing an electrostatic charge image comprising at least magnetic particles and a polymer associated or aggregated with each other, wherein the polymer is produced by soap-free emulsion polymerization containing no surfactant. Magnetic toner.