JPH081527B2 - Magnetic carrier particles for electrophotographic development - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic carrier particles for electrophotographic development.

More particularly, it relates to magnetic carrier particles, particularly those used in magnetic brush development.

2. Related Art and its Problems Conventionally, as one of magnetic carrier particles used for magnetic brush development for electrophotographic development, iron powder or so-called ferrite particles coated with a resin have been used.

By the way, such magnetic carrier particles electrostatically adhere the toner by frictionally charging the toner,
The donor is moved onto the photoreceptor during development.

For this reason, it is required that the carrier particles have a large triboelectric charge amount, have a uniform chargeability, and effectively and uniformly pick up and deposit the toner.

In this case, it is desired that the charge amount be within the range of 15 to 40 μC / g. Furthermore, it is desirable to keep the charge amount within the above range even when using various toners,
At present, the charge amount is controlled by a charge amount control agent added to the toner, and there are problems of high cost, stability of the charge amount, and humidity dependency.

On the other hand, the carrier particles must have good transportability in the developing machine and are required to exhibit good fluidity as powder.

In this case, it is desired that the falling speed of 50 g of the powder, which is an index of fluidity, be as small as possible within the range of 25 to 35 seconds.

Further, the carrier particles function as one of the electrodes in the developing portion and have a function of making the electric field uniform.
By changing the composition of the magnetic particles to be coated with a resin, or by changing the composition of the resin, 10 ⁵ to 10 ¹²
In the range of Ω, it is required to have a desired resistance according to the copying machine.

Moreover, it is desired that this electric resistance does not decrease under high humidity.

In addition, the carrier particles are required to have durability for stably maintaining and exhibiting the above-mentioned various characteristics in the developing machine.

However, the conventional resin coat material does not satisfy these characteristics in all respects.

From such circumstances, the present inventors have previously proposed that a polymerizable emulsifier is used as a resin coat material and an emulsion obtained by emulsion-polymerizing a monoethylenic monomer is used (special feature). No. 60-112491).

The carrier particles provided with such a resin coating exhibit stable electrical resistance and flow characteristics, the triboelectric charge amount can be arbitrarily controlled, and the moisture resistance is high.

However, in terms of durability, further improvement is desired.

II Object of the Invention An object of the present invention is to provide a magnetic carrier particle for electrophotographic development, which has stable electric resistance and flow characteristics, can control the amount of triboelectric charge arbitrarily, and has sufficiently large moisture resistance and durability. It is in.

III DISCLOSURE OF THE INVENTION Such an object is achieved by the present invention described below.

That is, the present invention uses a polymerizable emulsifier on the surface of magnetic particles, and a monoethylenic monomer containing one or more of a styrene vinyl monomer, an acrylic vinyl monomer and a cyan vinyl monomer, Epoxy-containing monomer, polyfunctional monomer, hydroxy-containing monomer,
Synthesis obtained by emulsion-polymerizing a functional monomer containing one or more of a basic monomer, a carboxy-containing monomer, a β-diketone-containing monomer and a silyl group-containing monomer A magnetic carrier particle for electrophotographic development, characterized in that a resin coating is formed.

IV Specific Configuration of the Invention Hereinafter, the specific configuration of the present invention will be described in detail.

The magnetic carrier particles for electrophotographic development of the present invention have a resin coating on the surface of the magnetic particles.

The coating is formed using a synthetic resin emulsion obtained by emulsion-polymerizing a monoethylenic monomer and a functional monomer using a polymerizable emulsifier.

As the polymerizable emulsifier, an acrylic alcohol derivative,
One or more of acrylic acid derivative, itaconic acid derivative, maleic acid derivative, fumaric acid derivative, ethylene derivative and styrene derivative are preferable. Specific examples of the polymerizable emulsifier are shown below.

I Allyl alcohol derivatives R _{1 is} hydrogen or methyl R _{2 is a} hydrocarbon group or an organic group containing a hydrocarbon having a substituent or an oxyalkylene group A: an alkylene group having 2 to 4 carbon atoms or a substituted alkylene group n: 0 or a positive number M: alkali or alkaline earth metal, ammonium,
Organic amine base or organic quaternary ammonium base, etc. m: M atomic or ionic value 1-1 n = 0, R ₁ = H, R ₂ = C ₁₂ H ₂₅ , Ml / m = Na, 1-2 n = 1, A = CH ₂ CH (OH) CH ₂ , R ₁ = H, R ₂ = C ₁₂ H ₂₅ , M1 / m = Na, I-3 n = 1, A = CH ₂ CH (OH) CH ₂ , R ₁ = H, R ₂ = C ₁₈ H ₃₇ , M1 / m = Na, 1-4 n = 1, A = CH ₂ CH (OH) CH ₂ , R ₁ = H, R ₂ = C ₁₈ H ₃₇ , M1 / m = NH ₄ , 1-5 n = 0, R ₁ = H, R ₂ = CH ₂ CH (C ₉ H ₁₉ ) (C ₇ H ₁₅ ) II acrylic acid derivative R ₁ CH = C (R ₂ ) CONH-SO ₃ M (Japanese Patent Publication No. 46-12472) R ₁ , R ₂ : hydrogen atom or an organic residue having 1 to 10 carbon atoms, preferably a hydrocarbon residue, more preferably an alkyl or aryl group. And more preferably a methyl or phenyl group M: alkali metal-preferably potassium II-1 R ₁ = H, R ₂ = C ₁₀ H ₂₁ , M = K, II-2 R 1 = H, R 2 = C 10 H 21, M = Na, II-3 R 1 = H, R 2 = CH 2, M = K, R ₁ , R ₂ : hydrogen atom or methyl group R ₃ : alkyl or alkenyl group having 7 to 21 carbon atoms M: alkali metal or ammonium group II-4 R ₁ = H, R ₂ = H, R ₃ = C _{7 H 15, M = Na II-} 5 R 1 = H, R 2 = H 3 R 3 = C 21 H 43, M = NH 4 II-6 R 1 = H, R 2 = H, R 3 = C 18 H ₃₅ , M = Na R ₁ , R ₂ : hydrogen atom or methyl group R ₃ : saturated or unsaturated aliphatic hydrocarbon group having 1 to 21 hydrogen atoms M: alkali metal or ammonium group II-7 R ₁ = H, R ₂ = CH ₃ , _{R 3 = C 12 H 25,} M = Na, II-8 R 1 = H, R 2 = H, R 3 = C 12 H 25, M = K, II-9 R 1 = CH 3, R 2 = CH ₃ , R ₃ = C ₁₈ H ₃₇ , M = NH ₄ , R ₁ , R ₂ : Hydrogen atom or methyl group X, Y, Z: O or an integer of 100 or less, and the following function holds: 1≤X + Y + Z≤100 II-10 R ₁ = H, R ₂ = CH ₃ , X = 20, Y = 20, Z = 30 II-11 R 1 = H, R 2 = H, X = 30, Y = 30, Z = 40 II-12 R 1 = H, R 2 = CH 3, X = 30, Y = 20, Z = 30 R ₁ : hydrogen, lower alkyl, phenyl or halogen R ₂ : hydrogen or lower alkyl n: integer of 5 to 25 II-13 R ₁ = CH ₃ , R ₂ = H, n = 2 II-14 R ₁ = CH ₃ , R ₂ = H, n = 5 II-15 R ₁ = CH ₃ , R ₂ = H, n = 9 III Itaconic acid derivative R: an alkyl group having 1 to 22 carbon atoms, a group having a structure I CH ₂ (CF ₂ ) _x H (where x is an integer of 2 to 10) Structure II (Where z is an integer of 1 to 40) M: hydrogen or an alkali metal m: an integer of Z to 4 n: 1 or 2 III-1 R = 1, x = 10, M = K, m = 3 , N = 1 III-2 R = I, x = 5, M = K, m = 3, n = 1 III-3 R = II, z = 12, M = Na, m = 3, n = 1 R: Hydrocarbon group having 8 to 22 carbon atoms M: Alkali metal or ammonium group III-4 R = C ₁₂ H ₂₅ , M = Na, III-5 R = C ₁₈ H ₃₇ , M = Na, III-6 R = C ₁₂ H ₂₅ , M = NH ₄ , R ₁ : hydrogen or an alkyl group having 1 to 4 carbon atoms R ₂ : hydrogen or an alkyl group having 1 to 22 carbon atoms m: an integer of m ≤ 150 ≤ R ₃ : when H: n = 1 to 3 methyl group n = 2 M: monovalent cation such as alkali metal or ammonium base III-7 R ₁ = H, R ₂ = C ₁₂ H ₂₅ , R ₃ = H, M = Na, m = 5, n = 3 III- 8 R ₁ = H R ₂ = C ₁₈ H ₃₇ , R ₃ = H, M = Na, m = 3, n = 1 III-9 R ₁ = H R ₂ = C ₁₂ H ₂₅ , R ₃ = H, M = NH ₄ , m = 5, n = 3 IV Maleic acid derivative R: Hydrocarbon group having 8 to 22 carbon atoms M: Alkali metal or ammonium group IV-1 R = C ₁₂ H ₂₅ , M = Na, IV-2 R = C ₁₈ H ₃₇ , M = K IV-3 R = C ₁₈ H ₃₇ , M = NH ₄ R ₁ : hydrogen or an alkyl group having 1 to 4 carbon atoms R ₂ : hydrogen or an alkyl group having 1 to 22 carbon atoms m: an integer of 5 ≦ m ≦ 150 R ₃ : when H: n = 1 to 3 methyl group n = 2 M = 1 monovalent cation IV-4 R ₁ = H, such as an alkali metal or ammonium _{salt, R 2 = C 12 H 25} , R 3 = H, m = 5, n = 2, M = Na IV- 5 R ₁ = H, R ₂ = C ₁₈ H ₃₇ , R ₃ = H, m = 5, n = 2, M = Na IV-6 R ₁ = H, R ₂ = C ₁₂ H ₂₅ , R ₃ = H , M = 5, n = 2, M = NH ₄ R _{1 is} a residue of an aliphatic alcohol, aromatic alcohol, or ether alcohol having 6 to 22 carbon atoms R ₂ : When H is n = 2,3 When methyl group is n = 2 M: Hydrogen, alkali metal or ammonium, etc. monovalent cation _{IV-7 R 1 = C 8} H 17, R 2 = H, n = 3, M = Na IV-8 R 1 = C 12 H 25, R 2 = H, n = 3, M = K IV-9 R ₁ = C ₁₆ H ₃₃ , R ₂ = H, n = 3, M = NH ₄ V fumaric acid derivative R ₁ : Residue of aliphatic alcohol, aromatic alcohol or ether alcohol having 1 to 22 carbon atoms R ₂ : When n is 1 to 3 when H is methyl group, n = 2 M: 1 such as alkali metal or ammonium base valent cation V-1 of _{R 1 = C 8 H 17,} R 2 = H, M = Na, n = 2 V-2 R 1 = C 12 H 25, R 2 = H, M = Na, n = 2 V -3 R ₁ = C ₁₆ H ₃₃ R ₂ = H, M = Na, n = 2 R ₁ : hydrogen or an alkyl group having 1 to 4 carbon atoms R ₂ : hydrogen or an alkyl group having 1 to 22 carbon atoms m: 5 integer of m ≦ 150 R ₃ : when n is 1 to 3 when H is n = 2 M: monovalent cation such as alkali metal or ammonium base V-4 R ₁ = H, R ₂ = C ₁₂ H ₂₅ , R ₃ = H, m = 5, n = 2, M = Na V-5 _{R 1 = H, R 2 =} C 18 H 37, R 3 = H, m = 5, n = 2, M = Na V-6 R 1 = H, R 2 = C 12 H 25, R 3 = H, m = 5, n = 2, M = NH ₄ VI styrene derivative M: monovalent cation such as alkali metal or ammonium group VI-1 M = NH ₄ IV-2 M = Na VII ethylene derivative M: Monovalent cation such as alkali metal or ammonium group VII-1 M = NH _{4 Of the} above polymerizable emulsifiers, allyl alcohol derivatives are particularly preferable.

These polymerizable emulsifiers are used alone or in combination of two or more, and the amount thereof is 1 to 15 wt%, more preferably 1 to 10 wt% based on the monoethylenic monomer in the synthetic resin emulsion. .

If it is less than 1 wt%, there is no effect, and if it exceeds 15 wt%, the humidity dependency of the resistance becomes large, and further the charge amount decreases, which causes inconvenience.

It is also possible to use a general non-polymerizable emulsifier together.

Examples of the non-polymerizable emulsifier used in combination include sodium lauryl sulfate, ammonium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium dodecylbenzenesulfonate, sodium dioctylsulfosuccinate, and polyoxyethylene nonylphenyl ether.

The following are specific examples of the main monoethylenic monomer used.

A. Styrene-based vinyl monomers Styrene; α- or β-alkyl-substituted styrenes such as α-methylstyrene and β-ethylstyrene; Nuclear-alkyl-substituted styrenes such as 4-methylstyrene, 2-ethylstyrene and 4-hexylstyrene; Nuclear halogen substituted styrenes such as chlorostyrene, dichlorostyrene, fluorostyrene, bromostyrene; nuclear alkoxy substituted styrenes such as methoxystyrene; nuclear acyl substituted styrenes such as acetylstyrene; nitrostyrene and the like.

B. Acrylic vinyl monomers (meth) acrylic acid; esters of (meth) acrylic acid with alcohols such as alkyl alcohols, halogenated alcohols, alkoxy alcohols, aralkyl alcohols, alkenyl alcohols (as specific examples of the above alcohols, methyl Alcohol, ethyl alcohol, propyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, amyl alcohol, hexyl alcohol, 2-ethyl-hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, dodecyl alcohol, tetradecyl Alcohols, alkyl alcohols such as hexadecyl alcohol; halogenated alkyl alcohols obtained by partially halogenating these alkyl alcohols; methoxy ether Alkoxyalkyl alcohols such as chill alcohol, ethoxyethyl alcohol, ethoxyethoxyethyl alcohol, methoxypropyl alcohol, ethoxypropyl alcohol; aralkyl alcohols such as benzyl alcohol, phenylethyl alcohol, phenylpropyl alcohol; allyl alcohol, crotonyl alcohol, etc. C. Cyan-based vinyl monomer acrylonitrile; α-alkyl acrylonitrile such as methacrylonitrile and α-ethyl acrylonitrile; α-halogenated acrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; Vinylidene cyanide, etc.

These monoethylenic monomers may be used alone or in combination of two or more, and more preferably methylmethacrylate-acrylonitrile, styrene-acrylonitrile, and methylmethacrylate-styrene are preferable.

The functional monomer used in combination with the polymerizable emulsifier and the monoethylenic monomer is a monomer having a functional group having a crosslinking effect.

As the functional group and functional monomer having a crosslinking effect, I. Epoxy-containing monomer having an epoxy group-containing group such as glycidyl II. Methacryloyl, acryloyl, allyloxy, vinyl, allyl, etc. Polyfunctional Monomers Having Multiple Bonded Groups III. Hydroxy-Containing Monomers Having Hydroxy Group-Containing Groups such as Methylol and Hydroxyl IV. Bases Containing Amino and Imino Groups such as Carbamoyl and Dialkylamino Monomers V. Carboxy-containing monomers containing carboxy groups such as carboxy and carboxymethyl VI. Β-containing β-diketone groups such as acetoacetoxy
-Diketone-containing monomer VII. Silyl group-containing monomers containing a silyl group such as triethoxysilyl, triethoxymethoxysilyl, trimethoxysilyl, acetoxysilyl are preferred.

In addition, acrylic acid, methacrylic acid, ethylene and the like are preferable as the monomer skeleton.

 Preferred specific examples of the functional monomer will be given below.

I Epoxy-containing monomer α, β-ethylenically unsaturated glycidyl ester or ether, preferably glycidyl (meth) acrylate, diglycidyl itaconate, diglycidyl allate (fumarate), glycidyl alkyl itaconate, glycidyl alkyl malate ( Fumarate) [where alkyl group has 1 to 6 carbon atoms] Allyl glycidyl phthalate, mixed glycidyl allyl ether of allyl glycidyl succinate bisphenol A, allyl glycidyl ether, etc. II Polyfunctional monomer Ethylene glycol di (meth) ) Acrylate, butanediol di (meth) acrylate, trimethylolpropane di-, tri- (meth) acrylate, pentaerythritol di-, tree, tetra-, (meth) acrylate, polymethylene group Calls di (meth) acrylate, polyalkylene ether glycol di (meth)
Polyesters such as acrylates, erythritol, mannitol and sorbitol, polyhydric alcohols such as polymethacrylates and ethylenically unsaturated acid polyesters such as saccharides, ethylene glycol divinyl ether, butanediol divinyl ether, trimethylolpropane di-,
Or polyvinyl alcohols such as tri-vinyl ether, di-, tri-, or tetra-vinyl ether of pentaerythritol, polyvinyl ether such as sorbitol, erythritol, and mannitol, and polyvinyl ethers such as sugars, diallyl fumarate (malate) tri Allyl trimellitate, diallyl phthalate, diallyl isophthalate, dimethallyl phthalate, dimethallyl isophthalate, diallyl monohydrogen phosphate, triallyl phosphate, diallyl monomethyl phosphate, diallyl monoethyl phosphate, diallyl monophenyl phosphate, diallyl monobenzyl phosphate , Diallyl monohydrogen phosphite, triallyl phosphite, diallyl monomethyl phosphite, diallyl monophenyl Ruphosphite, diallyl monobenzyl phosphite, trimethylolpropane di- or triallyl ether, pentaerythritol di-, tri-, or tetra-allyl ether, erythritol polyallyl ether, erythritol polymethallyl ether, arabino's polyallyl Ether, arabitol polyallyl ether, xylose polyallyl ether, glycose polyallyl ether, mannose polyallyl ether, mannitol polyallyl ether, sorbitol polyallyl ether, inositol polyallyl ether, sucrose polyallyl ether, (poly Polyallyl or polymethallyl ethers such as polyhydric alcohols and sugars) triallyl cyanurate, triallyl isocyanurate, methylenebisacrylamide Polyunsaturated acid amides such as methacrylamide, ethylenebis (meth) acrylamide, dihydroxyethylenebisacrylamide, tris (acryloyl) hexahydro-s-triazine, divinyl ketone, diallyl chlorendate, diarylidene pentaerythritol, diallyl cyanamide , Divinylbenzene, tetraallyloxyethane, etc. III Hydroxy-containing monomer 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate , 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 5-hydroxypentyl (meth) acrylate, 6-hydroxyhexyl (meth Acrylate, thio neopentyl glycol mono (meth) acrylate, 3-
Butoxy-2-hydroxypropyl (meth) acrylate, 2-hydroxy-1-phenylethyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, glycerin mono (meth) acrylate, N-
Methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, Nn-propoxymethyl (meth) acrylic acid, N-isopropoxymethyl (meth) acrylamide, Nn-butoxymethyl (meth) acrylamide, N -Sec-butoxymethyl (meth) acrylamide, Nt-butoxymethyl (meth) acrylamide, N-isobutoxymethyl (meth)
N-methylol compounds of α, β-monoethylenically unsaturated carboxylic acid amides such as acrylamide IV Basic monomers Diacetone acrylamide, (meth) acrylamide, N, N-dimethyl acrylamide, Nn-butoxymethyl acrylamide , N-vinylpyrrolidone, N-vinylimidazole, 2-methyl-N-vinylimidazole, 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 2-dinyl-5-ethylpyridine, dimethylaminoethyl acrylate, dimethyl. Aminoethyl methacrylate, diethylaminoethyl (meth) acrylate, butylaminoethyl acrylate (methacrylate), dimethylallylamine, diallylamine, 7-
Amino-3,7-dimethyloctyl (meth) acrylate, 2-methyl-5-vinylpyridine, 3-methyl-5
-Vinyl pyridine, 2-butyl-5-vinyl pyridine, etc. V Carboxy-containing monomer α, β- such as aconitic acid, acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and crotonic acid
Monoethylenically unsaturated carboxylic acids, etc. VI β-diketone-containing monomers Allyl acetoacetate, acryl acetoacetate, methacryl acetoacetate, (meth) acrylethyl acetoacetate, (meth) acrylpropyl acetoacetate, etc. VII silyl group-containing unit Body Vinyltrichlorosilane, Nyltrimethoxysilane,
Vinyltriethoxysilane, vinyltriethoxymethoxysilane, vinyltrisacetoxysilane, γ-methacryloxypropyltrimethoxysilane, etc. These functional monomers are used alone or in combination of two or more. In the resin emulsion, the amount is 1 to 20% by weight, more preferably 3 to 10% by weight, based on the monoethylenic monomer.

If it is less than 1 wt%, there is no effect, and if it exceeds 20 wt%, the emulsion polymerization stability is lowered, and further, the moisture resistance and durability of the film are lowered, and other disadvantages occur.

In addition to the main monoethylenic monomers and functional monomers, other vinyl monomers, oligomers, etc. are used as necessary for the purpose of adjusting the glass transition point Tg and improving the adhesion to magnetic particles. To be done. The amount used is preferably 50 wt% or less.

As such vinyl monomers, vinyl acetate, fatty acid vinyl esters such as vinyl propionate; olefins such as ethylene, propylene, butylene, butadiene; vinyl chloride, vinyl bromide, vinyl fluoride, vinylidene chloride, bromide. There are halogenated olefins such as vinylidene and vinylidene fluoride; amides such as acrylamide and methacrylamide.

Further, a charge amount adjusting agent such as an azine compound, a quaternary ammonium salt, or a polyamine resin may be used if necessary for the purpose of adjusting the charge amount of the magnetic particles. Used amount is 15wt%
The following is desirable.

The synthetic resin emulsion used for coating the magnetic particles is produced by an emulsion polymerization method. As the emulsion polymerization method, a batch polymerization method, a drop polymerization method (monomer or emulsion monomer), a seed polymerization method, and a multi-stage polymerization method, which is a development of these methods, are adopted for the purpose.

The synthetic resin emulsion thus produced has a synthetic resin content of 5 to 6 wt%.

The particle size of the synthetic resin emulsion is 0.01 to 10 μm, preferably about 0.02 to 1 μm.

The solvent is water or an alcohol type such as methyl alcohol, ethyl alcohol, isopropyl alcohol, or a mixture thereof. The glass transition point Tg of the synthetic resin in such a synthetic resin emulsion is preferably 130 ° C. or lower, and particularly preferably 20 to 130 ° C.

If the Tg exceeds 130 ° C, it will be industrially expensive to uniformly coat the synthetic resin emulsion on the magnetic particles, and it will be difficult to form a uniform coating film.

When Tg is less than 20 ° C, the fluidity of the magnetic carrier particles is very poor, and the humidity dependence of the electric resistance becomes large.

The coating made of such synthetic resin is formed as a continuous coating with a thickness of 2 to 10 μm.

In order to form such a coating on the surface of the magnetic particles, the emulsion solution may be coated with a nozzle spray under heating in a container in which a fluidized bed or a rolling layer is formed, and dried.

The heating temperature is 70 to 90 ° C, and the drying temperature is about 70 to 100 ° C.

In addition, a more uniform continuous film is formed by adding a film forming aid. In this case, as the film forming aid used, diethylene glycol monobutyl ether acetate, butyl carbitol acetate, cellosolve, cellosolve acetate, butyl cellosolve, butyl cellosolve acetate, phenyl cellosolve, carbitol, carbitol acetate, butyl carbitol, diethyl carbitol, Mono- or polyhydric alcohols such as dibutyl carbitol, hexylene glycol, texanol, shell sol, 3-methoxybutyl acetate, ethylene glycol acetate, benzyl alcohol and furfuryl alcohol, or derivatives thereof; or aromatics such as toluene and xylene. There are hydrocarbons.

 The amount of the film-forming auxiliary used is preferably 1 to 20 wt%.

By using the film-forming aid, the resin component swells in the emulsion, and it becomes possible to coat the synthetic resin having a high glass transition point.

On the other hand, the material of the magnetic particles used in the present invention is not particularly limited, but is usually iron powder or oxide powder having a spinel structure or a hexagonal structure.

As an oxide having a spinel structure, so-called 2-3
Spinel and 1-3 soft ferrite spinel, magnetite (Fe ₃ O _4), maghemite (γ-Fe ₂ O ₃₎ may be any.

As soft ferrite, Ni, Mn, Mg, Zn, Cu, C
Any of those having one or more of o and the like may be used.

Examples of oxides having a hexagonal structure include Ba ferrite and Sr.
It may be ferrite, or one in which Ba, Sr, or Fe of Ba or Sr ferrite is partially replaced with another metal.

Then, these magnetic powders are prepared by a known method to
Produced as particles with an average particle size of ~ 200 μm. The particle size distribution is not particularly limited.

Such magnetic carrier particles of the present invention have a content of 15-40 μC / g.
It has a charge amount of.

 Further, the fluidity per 50 g shows a value of 28 to 34 sec.

In this case, the fluidity is the dropping speed of 50 g of the carrier, which was obtained by weighing 50 g of the carrier and measuring the powder flow form.

Furthermore, the electric resistance is 10 ^{12 in} the range of 100 to 500 V.
Shows a value of about 10 ⁵ Ω.

In this case, the electric resistance of the carrier particles is measured as follows, simulating the magnetic brush development method.

That is, the N pole and the S pole are opposed to each other with a gap of 7 mm between the magnetic poles. In this case, the surface magnetic flux density of the magnetic pole is 1500 Gaus
s, the area of the facing magnetic pole is 10 × 30 mm. A non-magnetic parallel plate electrode is arranged between the magnetic poles with a gap between the electrodes of 5 mm, and 200 mg of the sample is put between the electrodes and held by magnetic force. Then, the resistance may be measured with an insulation resistance meter or an ammeter.

The saturation magnetization of carrier particles is about 40 to 80 emu / g.

V Specific Actions of the Invention The magnetic carrier particles of the present invention, in combination with a toner,
It is used for developing for electrophotography.

 There is no limitation on the type of toner used.

It should be noted that there is no limitation on the magnetic brush development method or the type of the photoconductor used in obtaining the electrostatically copied image.

VI Specific effects of the present invention The following effects can be obtained by the present invention.

The charge amount of the magnetic carrier particles can be controlled by adjusting the type and addition amount of the polymerizable emulsifier, and the control range is as large as 15 to 35 μC / g.

As described above, since the charge amount of the magnetic carrier particles themselves can be controlled, the charge amount becomes stable.

Further, it is almost unnecessary to add an expensive charge amount control agent to the toner, and the cost of the developer can be reduced.

By using a functional monomer, the variation in the charge amount of the magnetic carrier particles is reduced, the durability of the coating layer is improved, and a stable charge amount and electric resistance are exhibited against changes in the external environment. .

The fluidity shows a good value of 34 seconds or less per 50 g.

The electric resistance is 10 ⁵ to 10 ¹² Ω regardless of the charge amount.
Can be controlled. Furthermore, the humidity dependence of the electric resistance is small, and high humidity (85% R) under low humidity (30% RH)
Electric resistance at H) below, until 1/10 ^2-5 / 10 ³ with no magnetic carrier particles the resin coating, each non-polymerizable emulsifier-magnetic carrier particles to 1/10 ^2-1 / 10 ³ using Compared with the decrease, in the magnetic carrier particles using the polymerizable emulsifier
It is only decreasing from 1/10 to 5/10 ² .

Therefore, the resistance can be optimized for various copying machines, and stable and good image quality can be obtained against changes in the external environment.

By using the polymerizable emulsifier, the durability of the coating layer is further improved.

Since an aqueous emulsion is used, it is characterized by no pollution and low cost as compared with the case of using a conventional solvent type resin.

VII Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown to explain the present invention in more detail.

Example 1 Ferrite particles having a particle diameter of about 60 μm as magnetic particles (composition: NiO 20 mol%, ZnO 28 mol%, Fe ₂ O ₃ 52 mol%,
σ _m = 50 emu / g, Hc = 2.00 e) was used.

The ferrite particles were placed in a container having a fluidized bed and preheated to 80 ° C. for about 15 minutes.

After this, the synthetic resin emulsion A1 shown in Table 1 below.
~ A10 was sprayed using a two-fluid nozzle and dried.

 The drying temperature was 60-100 ° C.

In addition, butyl carbitol acetate was used as a film forming aid. The amount used is 5 wt%.

A uniform continuous film of 3 to 5 μm was formed on the ferrite surface.

For each of these carrier particles, a commercially available toner and carrier particles were mixed at a ratio of 5 to 100 (weight ratio), triboelectrically charged, and the charge amount was measured using a blow-off charge amount measuring device manufactured by Toshiba Chemical Corporation.

The results are shown in Fig. 1. In the figure, curves I and II correspond to samples A1 to A4 and A5 to A8, respectively.

The measurement results of the electric resistance of each carrier particle at 30 ° C. and 50% are shown in FIG. In the figure, curves I and II correspond to samples A1 to A4 and A5 to A8, respectively.

Furthermore, 50 g of each carrier particle is weighed, and 50 particles of carrier particles are
The falling speed of g was measured and used as the fluidity.

 The results are shown in Table 2.

In addition, in Table 2, 30 ° C, 30% for 30% electric resistance
The ratio (%) of the electric resistance of 85% is shown.

 Further, Table 2 shows the durability of the carrier particles.

For durability, a magnetic brush is formed only on carrier particles on the magnet roll in the developing box, and the magnet roll is rotated at a speed of 100 rpm for 20 hours. indicate.

In this case, practically, the carrier particles preferably satisfy the following durability criteria.

Electric resistance: 65% or more Flow rate: 90% or more Charge amount: 80% or more From these results, it is understood that according to the present invention, by adjusting the addition amount of the polymerizable emulsifier, the charge amount can be controlled while maintaining the electric resistance and the fluidity of the carrier particles at favorable values.

 Further, it can be seen that the moisture resistance is also very good.

Furthermore, it is understood that the wear resistance of the carrier particles is improved by adding the functional monomer.

Example 2 The same magnetic particles as in Example 1 were used, and as in Example 1, the resin coating shown in Table 3 was applied.

In addition, butyl carbitol acetate was used as a film forming aid. The amount used is 5 wt%.

The charge amount of each of these carrier particles is shown in FIG. 3, and the electrical resistance at 30 ° C. and humidity of 50% RH is shown in FIG.

Furthermore, the charge amount control range when changing the ratio of the electric resistance of each carrier particle under high humidity (80% RH) to the electric resistance under low humidity (30% RH) and the amount of emulsifier added, and the carrier The durability of the particles is shown in Table 4.

From these results, according to the present invention, by changing the type of the polymerizable emulsifier, while maintaining characteristics such as electric resistance of the carrier particles in a good state, it is possible to control the charge amount, further, the carrier particles It can be seen that the humidity resistance is small and the electric resistance is stable and the wear resistance is good.

Example 3 The coatings shown in Table 5 were formed in the same manner as in Example 2 and the characteristics were measured. The results are shown in Table 6.

Butyl carbitol acetate was used as a film forming aid.

 The amount used is 5 wt%.

From the results shown in Table 6, the effect of the present invention is clear.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the addition amount of the polymerizable emulsifier and the charge amount. FIG. 2 is a graph showing the relationship between the amount of polymerizable emulsifier added and the electrical resistance. FIG. 3 is a graph showing the relationship between the type of emulsifier and the charge amount. FIG. 4 is a graph showing the relationship between the type of emulsifier and the electrical resistance.

Claims (11)

[Claims] 1. A polymerizable emulsifier is used on the surface of magnetic particles,
Monoethylenic monomer containing one or more of styrene vinyl monomer, acrylic vinyl monomer and cyan vinyl monomer, and epoxy-containing monomer, polyfunctional monomer, hydroxy-containing monomer Body, a basic monomer, a carboxy-containing monomer, a β-diketone-containing monomer, and a silyl group-containing monomer, and a functional monomer containing one or more of them are subjected to emulsion polymerization. Magnetic carrier particles for electrophotographic development, characterized in that a coating of the obtained synthetic resin is formed. 2. A polymerizable emulsifier is an allyl alcohol derivative,
The magnetic carrier particle for electrophotographic development according to claim 1, which is one or more of an acrylic acid derivative, an itaconic acid derivative, a maleic acid derivative, a fumaric acid derivative, an ethylene derivative and a styrene derivative. 3. The magnetic carrier particles for electrophotographic development according to claim 1 or 2, wherein the polymerizable emulsifier is contained in an amount of 1 to 15 wt% with respect to the monoethylenic monomer. 4. The magnetic carrier for electrophotographic development according to claim 1, wherein the functional monomer is contained in an amount of 1 to 20 wt% with respect to the monoethylenic monomer. particle. 5. The magnetic carrier particles for electrophotographic development according to claim 1, wherein the coating of the synthetic resin is formed by using an emulsion of the synthetic resin. 6. The magnetic carrier particles for electrophotographic development according to claim 5, wherein the synthetic resin content is 5 to 60 wt%. 7. The magnetic carrier particles for electrophotographic development according to claim 1, wherein the glass transition point of the synthetic resin is 130 ° C. or lower. 8. The magnetic carrier particles for electrophotographic development according to claim 1, wherein the coating has a thickness of 2 to 10 μm. 9. The magnetic carrier particles for electrophotographic development according to claim 1, wherein the magnetic particles are iron or an oxide of spinel structure or hexagonal structure. 10. A synthetic resin emulsion containing a film-forming aid in an amount of 1 to 1.
Magnetic carrier particles for electrophotographic development according to any one of claims 5 to 9, wherein 20 wt% is added. 11. The magnetic carrier particles for electrophotographic development according to claim 10, wherein the film-forming auxiliary is one or more of alcohols and their derivatives, and aromatic hydrocarbons.