JP2977628B2 - Magnetic carrier particles for electrophotographic development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to magnetic carrier particles for electrophotographic development. More particularly, the present invention relates to resin-coated magnetic carrier particles used particularly for magnetic brush development.

[0002]

2. Description of the Related Art Conventionally, as one of magnetic carrier particles used in magnetic brush development for electrophotographic development, iron powder or so-called ferrite particles having a core and resin coating applied thereto are used.

By the way, such magnetic carrier particles cause the toner to electrostatically adhere by frictionally charging the toner, and move the toner onto the photosensitive member during development. Specifically, the magnetic carrier particles are agitated with the toner, thereby imparting a charge to the toner.

[0004] Therefore, it is required that the carrier particles have a large triboelectric charge amount, have a uniform chargeability, and take up and deposit the toner effectively and uniformly. Further, the carrier particles must have good transportability in a developing machine, and are required to exhibit good fluidity as a powder. further,
The carrier particles function as one electrode in the developed part,
It serves to make the electric field uniform, and by changing the composition of the magnetic particles to be resin-coated,
By changing the composition of the resin, it is required to have a desired resistance according to the copying machine in the range of 10 ⁵ to 10 ¹² Ω. Moreover, it is desired that the electric resistance does not decrease under high humidity.

[0005] These characteristics need to be maintained and exhibited even when the carrier particles are agitated together with the toner in the developing machine, that is, they need to have excellent stirring stability. For this purpose, it is necessary that the coating has sufficient film strength and the carrier particles have sufficient durability.

The above resin coating is usually formed by dissolving a resin used for coating in an appropriate solvent, and adhering the obtained resin solution to the core surface by spraying or dipping. The solvent used in such a case is an organic solvent, which is often harmful and not preferable from the viewpoint of preventing pollution.

From the viewpoint of pollution prevention, water is used as a dispersion medium,
There is a method of forming a coating using a dispersion containing polymer particles. However, in this method, the film strength of the coating is insufficient and the stirring stability is also insufficient.

By the way, various coatings using a fluorine-based polymer have been proposed (JP-A-58-5858).
208754) and fluorine-based polymers are often used as carrier particles particularly suitable for positively chargeable toners. Thus, the present applicant has conducted various studies on a coating containing a fluorine-based polymer, and found that when the content of the fluorine-based polymer is large, the charge amount becomes too high and the stirring stability is poor. In addition, it is necessary to increase the thickness of the coating in order to obtain sufficient stirring stability. If the thickness is increased, then the resistance becomes high, resulting in a decrease in image density, occurrence of carrier adhesion, and an increase in cost. Occurs. Further, the problem that the stirring stability is poor is particularly remarkable in some kinds of fluoropolymers.

On the other hand, the present applicant has previously proposed that an emulsion obtained by emulsion-polymerizing a monoethylenic monomer using a polymerizable emulsifier as a resin coating material (Japanese Patent Application Laid-Open No. 61-1986). No. 27069, 62-15
561, 62-23054 and the like).

The carrier particles provided with such a resin coating exhibit stable electric resistance and flow characteristics, can arbitrarily control the triboelectric charge amount for a negatively chargeable toner, and have a high moisture resistance. It was found that stirring stability was inferior to the charging toner.

[0011] In view of the above, it is desired to further improve the material, manufacturing method and the like of the resin coating.

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to provide excellent stirring stability, sufficient coating film strength and excellent durability, and an initial charge amount within a suitable range. An object of the present invention is to provide magnetic carrier particles for electrophotographic development suitable for a positively chargeable toner having a sufficient image density.

[0013]

The above object is achieved by the following (1).
This is achieved by the configuration of (5).

(1) The magnetic particles have a resin coating on the surface thereof,
This resin coating is formed using a mixture of an emulsified dispersion of a copolymer obtained by emulsion polymerization of a monoethylenic monomer using a polymerizable emulsifier, and a dispersion of fluoropolymer particles. Magnetic carrier particles for electrophotographic development, characterized in that they are present.

(2) The resin coating is formed by coating the copolymer with 2
The magnetic carrier particles for electrophotographic development according to the above (1), which contain 0 to 90% by weight and 80 to 10% by weight of the fluoropolymer.

(3) The polymerizable emulsifier is one or more of allyl alcohol derivatives, acrylic acid derivatives, itaconic acid derivatives, maleic acid derivatives, fumaric acid derivatives, ethylene derivatives and styrene derivatives. The magnetic carrier particles for electrophotographic development according to the above (1) or (2), wherein the monoethylenic monomer is one or more of an acrylic vinyl monomer, a styrene vinyl monomer and a cyan vinyl monomer.

(4) The above polymerizable emulsifier is contained in the above copolymer in an amount of 1 to 15% by weight.
The magnetic carrier particles for electrophotographic development according to any one of the above.

(5) The thickness of the resin coating is 0.1 to 5
The magnetic carrier particles for electrophotographic development according to any one of the above (1) to (4), which have a size of μm.

[0019]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The resin coating in the present invention comprises an emulsion of a copolymer obtained by emulsion polymerization of a monoethylenic monomer using a polymerizable emulsifier (sometimes referred to as a synthetic resin emulsion) and fluoropolymer particles. It is formed using a mixture with a dispersion.

In the present invention, the polymerizable emulsifier for preparing the emulsified dispersion of the copolymer includes allyl alcohol derivatives, acrylic acid derivatives, itaconic acid derivatives, maleic acid derivatives, fumaric acid derivatives, ethylene derivatives and styrene derivatives. Of these, one or more are preferred.

Hereinafter, these specific examples are shown for each type of compound.

I. Allyl alcohol derivatives include those shown in Chemical formula 1 (JP-B-49-4629).
No. 1, JP-A-58-203960).

[0024]

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In the chemical formula 1, R ₁ , R ₂ , A, n, M and m are as follows. R ₁ : hydrogen or methyl group R ₂ : hydrocarbon group or hydrocarbon group having a substituent or organic group containing oxyalkylene group A: alkylene group having 2 to 4 carbon atoms or substituted alkylene group n: 0 or positive Number M: alkali or alkaline earth metal, ammonium, organic amine base or organic quaternary ammonium base, etc. m: valence or ionic valence of M Specific examples of the allyl alcohol derivative include the following compounds I-1 to I-5 in Chemical formula 1. I-1 n = 0, R ₁ = H, R ₂ = C ₁₂ H ₂₅ , M = N
a, m = 1 I-2 n = 1, A = CH ₂ CH (OH) CH ₂ , R _{1
= H, R 2 = C 12} H 25, M = Na, m = 1 I-3 n = 1, A = CH 2 CH (OH) CH 2, R 1
_{= H, R 2 = C 18} H 37, M = Na, m = 1 I-4 n = 1, A = CH 2 CH (OH) CH 2, R 1
_{= H, R 2 = C 18} H 37, M = NH 4, m = 1 I-5 n = 0, R 1 = H, R 2 = CH 2 CH (C 9 H
₁₉₎ (C ₇ H ₁₅₎

II. As the acrylic acid derivative, first, a compound represented by the following formula (1) may be mentioned (Japanese Patent Publication No.
12472). Formula (1) R ₁ CH = C (R ₂ ) CONH—SO ₃ M In the formula (1), R ₁ , R ₂ and M are
It is shown below. R ₁ , R ₂ : hydrogen atom or 1
An organic residue having from 10 to 10 carbon atoms, preferably a hydrocarbon residue, more preferably an alkyl or aryl group, even more preferably a methyl or phenyl group M: an alkali metal, preferably potassium Specific examples include the compounds of II-1 to II-3 shown below in the formula (1). 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 II. As the acrylic acid derivative, the formula (2)
(JP-A-55-1152).
No. 5).

[0027]

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In the formula (2), R ₁ , R ₂ , R
₃ and M are as shown below. R ₁ , R ₂ : hydrogen atom or methyl group R ₃ : alkyl group or alkenyl group having 7 to 21 carbon atoms M: alkali metal or ammonium group Further, as a specific example of formula (2) of formula 2, formula (2) )), The following compounds II-4 to II-6: II-4 R ₁ = H, R ₂ = H, R ₃ = C ₇ H ₁₅ , M = N
a II-5 R ₁ = H, R ₂ = CH 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 = N
a. Further, as the acrylic acid derivative, a compound represented by the formula (3) of Chemical formula 3 can be mentioned (JP-A-55-1).
No. 1525).

[0029]

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In the formula (3), R ₁ , R ₂ , R
₃ and M are as shown below, respectively. R ₁ , R ₂ : a hydrogen atom or a methyl group R ₃ : a saturated or unsaturated aliphatic hydrocarbon group having 1 to 21 hydrogen atoms M: an alkali metal or ammonium group Further, specific examples of the formula (3) And compounds of II-7 to II-9 represented by the following formula (3). 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 Further, II. As the acrylic acid derivative, formula (4)
(JP-A-56-28208).
issue).

[0031]

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In the formula (4), R ₁ , R ₂ ,
X, Y and Z are as shown below. R ₁ , R ₂ : hydrogen atom or methyl group X, Y, Z: 0 or an integer of 100 or less, and 1 ≦ X
+ Y + Z ≦ 100 is satisfied. Specific examples of the formula (4) in the chemical formula (4) include compounds of the following formulas (II-10) to (II-12) in the formula (4). II-10 R ₁ = H, R ₂ = CH ₃ , X = 20, Y = 2
0, 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 = 2
0, Z = 30 Also, II. As the acrylic acid derivative, the formula (5)
(JP-A-53-4168).
No. 4).

[0033]

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In the formula (5), R ₁ , R ₂ and n are as shown below. R ₁ : hydrogen, lower alkyl, phenyl or halogen R ₂ : hydrogen or lower alkyl n: an integer of 5 to 25 As a specific example of formula (5) of formula 5, II- 13 to II-15. 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. As the itaconic acid derivative,
(JP-B-46-34894).
issue).

[0036]

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In the chemical formula 6, R, M, m and n are as follows. R: alkyl group having 1 to 22 carbon atoms, structure (I) [CH ₂ (CF ₂ ) _x H
(Where x is an even integer from 2 to 10)] or a group having the structure (II) of Chemical Formula 7 (where z is an integer from 1 to 40)

[0038]

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M: hydrogen or an alkali metal m: z: an integer from 4 to 4 n: 1 or a specific example of the compound represented by the formula: Is mentioned. III -1 R = structure (I), x = 10, M = K, m =
3, n = 1 III-2 R = structure (I), x = 5, M = K, m = 3,
n = 1 III -3 R = structure (II), x = 12, M = Na, m =
3, n = 1 Further, examples of III. Itaconic acid derivatives include those shown in Chemical formula 8 (JP-B-51-44157).

[0040]

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In the formula 8, R and M are as shown below. R: a hydrocarbon group having 8 to 22 carbon atoms M: an alkali metal or ammonium group Specific examples of the compound represented by Chemical formula 8 include the following compounds in Chemical formula 8: III-4 to III-6 . _{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 Further, III. Itaconic acid derivatized 9 (JP-A-51-30284).

[0042]

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In the chemical formula 9, R ₁ , R ₂ , m, R ₃ and M are as follows. 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 1 ≦ m ≦ 150 R ₃ : when H, n = 1 to 3 methyl group n = 2 M: a monovalent cation such as an alkali metal or ammonium base.
Compounds of III-7 to III-9 are mentioned. 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. As the maleic acid derivative, the one shown in Chemical formula 10 can be mentioned first (JP-B-51-44157).

[0044]

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In the above formula, R and M are as shown below. R: a hydrocarbon group having 8 to 22 carbon atoms M: an alkali metal or ammonium group Specific examples of Chemical formula 10 include the following IV-1 to IV-3 in Chemical formula 10. _{IV-1 R = C 12 H} 25, M = NaIV-2 R = C
₁₈ H ₃₇ , M = K IV-3 R = C ₁₈ H ₃₇ , M = NH ₄ Also, examples of the maleic acid derivative include those shown in Chemical formula 11 (JP-A-51-30284).

[0046]

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In the formula 11, R ₁ , R ₂ , m, R ₃ and M are as follows. 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 when a methyl group n = 2 M: monovalent cation such as an alkali metal or ammonium base. Specific examples of Chemical formula 11 include the following IV-4 to IV-6 in Chemical formula 11. IV-4 R ₁ = H, 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 Further, examples of IV. Maleic acid derivatives also include those shown in Chemical formula 12.

[0048]

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In the chemical formula 12, R ₁ , R ₂ and M are
Each is shown below. (Japanese Patent Publication No. 56-296
No. 57). R ₁ : a residue of an aliphatic alcohol, aromatic alcohol or ether alcohol having 6 to 22 carbon atoms R ₂ : n = 2 when H, 3 = n when methyl group M: hydrogen, alkali metal or ammonium, etc. Specific examples of Chemical formula 12 include the following IV-7 to IV-9 in Chemical formula 12. _{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. Examples of fumaric acid derivatives include those shown in Chemical Formula 13 (Japanese Patent Application Laid-Open No. 30285/1979).

[0050]

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In the formula, R ₁ , R ₂ and M are
Each is shown below. R ₁ : a residue of an aliphatic alcohol, aromatic alcohol or ether alcohol having 1 to 22 carbon atoms R ₂ : n = 1 to 3 for H, n = 2 for a methyl group M: 1 such as alkali metal or ammonium base Valent cations Specific examples of Chemical formula 13 include the following V-1 to V-3 in Chemical formula 13. _{V-1 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 Further, examples of V. fumaric acid derivatives include those shown in Chemical formula 14 (Japanese Patent Application Laid-Open No. 30284/1979).

[0052]

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In the chemical formula 14, R ₁ , R ₂ , m, R ₃ and M are as follows. 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 when a methyl group n = 2 M: monovalent cation such as an alkali metal or ammonium group. Specific examples of Chemical formula 14 include V-4 to V-6 described below in Chemical formula 14. _{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 derivatives include those shown in Chemical formula 15.

[0054]

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In Formula 15, M is as shown below. M: Monovalent cation such as an alkali metal or ammonium group Specific examples of Chemical formula 15 include VI-1 and VI-2 shown below in Chemical formula 15. VI-1 M = NH ₄ VI-2 M = Na VII. Examples of ethylene derivatives include those shown in Chemical Formula 16.

[0056]

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In Formula 16, M is as shown below. M: a monovalent cation such as an alkali metal or an ammonium group. Specific examples of Chemical formula 16 include VII-1 described below in Chemical formula 16. VII -1 M = NH _4, especially allyl alcohol derivative in the polymerizable emulsifier is preferred.

These polymerizable emulsifiers are used singly or in combination of two or more. The amount of the polymerizable emulsifier used is 1 to 15% by weight, more preferably 1 to 15% by weight of the copolymer in the synthetic resin emulsion.
Preferably, it is set to 10 to 10% by weight. If the amount is less than 1% by weight, emulsion polymerization becomes difficult. If the amount exceeds 15% by weight, the humidity dependency of the resistance increases, and the charge amount further decreases, which causes inconvenience.

Incidentally, a general non-polymerizable emulsifier can be used in combination.

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 copolymer contains a monoethylenic monomer as a copolymer component in addition to the polymerizable emulsifier.

Specific examples of the ethylenic monomer used include the following.

A. Acrylic vinyl monomers (meth) acrylic acid; esters of (meth) acrylic acid with alcohols such as alkyl alcohols, halogenated alcohols, alkoxy alcohols, aralkyl alcohols, and alkenyl alcohols (specific examples of the alcohols include methyl alcohol and 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,
Alkyl alcohols such as nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, and hexadecyl alcohol; halogenated alkyl alcohols obtained by partially halogenating these alkyl alcohols; methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethoxyethyl alcohol, methoxypropyl alcohol;
Alkoxyalkyl alcohols such as ethoxypropyl alcohol; aralkyl alcohols such as benzyl alcohol, phenylethyl alcohol and phenylpropyl alcohol; alkenyl alcohols such as allyl alcohol and crotonyl alcohol. )

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

C. Cyanic vinyl monomer Acrylonitrile; α-alkylacrylonitrile such as methacrylonitrile and α-ethylacrylonitrile; α-halogenated acrylonitrile such as α-chloroacrylonitrile and α-bromoacrylonitrile; vinylidene cyanide;

These A to C styrene-based, acrylic-based,
One or more cyan vinyl monomers are contained. When two or more kinds are contained, their ratio is arbitrary.

Of these, A.I. One or more acrylic vinyl monomers; and one or more acrylic vinyl monomers; One or more styrenic vinyl monomers may be combined in any quantitative ratio; and up to 50% by weight of C.I. A combination of one or more cyanic vinyl monomers is preferred.

Further, in addition to the monostyrenic monomer,
As the ethylenic monomer, a monomer having a functional group having a crosslinking effect may be contained in an amount of 20% by weight or less.

Examples of the ethylenic monomer having a functional group having a cross-linking effect include an epoxy-containing monomer having an epoxy group-containing group such as glycidyl; a methacryloyl, acryloyl, allyloxy, vinyl, allyl or other terminal having a double bond. A polyfunctional monomer having a plurality of groups; a hydroxy-containing monomer having a group containing a hydroxy group such as methylol and hydroxyl; a basic monomer containing an amino group such as carbamoyl and dialkylamino, and an imino group; Carboxy-containing monomer having a carboxy group; β-diketone-containing monomer having a β-diketone group such as acetoacetoxy; organic metal such as silyl group such as triethoxysilyl, triethoxymethoxysilyl, trimethoxysilyl, and acetoxysilyl Organometallic monomers containing groups are suitable.

The monomer skeleton includes acrylic acid,
Methacrylic acid, ethylene and the like are preferred.

In addition to these emulsifying polymerizing agents and monoethylenic monomers, other vinyl monomers, oligomers and the like may be used as needed for the purpose of adjusting the glass transition point Tg, improving the adhesion to magnetic particles, and the like. You. The use amount is desirably 50% by weight or less.

Examples of such vinyl monomers include fatty acid vinyl esters such as vinyl acetate and vinyl propionate; olefins such as ethylene, propylene, butylene and butadiene; vinyl chloride, vinyl bromide, vinyl fluoride, and vinylidene chloride. And halogenated olefins such as vinylidene bromide and vinylidene fluoride; and amides such as acrylamide and methacrylamide.

These may be contained by blending with the copolymer of the present invention, or may be contained in the copolymer.

The emulsified dispersion (synthetic resin emulsion) of the above copolymer is produced by an emulsion polymerization method. As the emulsion polymerization method, a batch polymerization method, a drop polymerization method (monomer or emulsified monomer), a seed polymerization method, and a multi-stage polymerization method, which is an advanced type of these methods, are employed depending on the purpose.

The synthetic resin emulsion thus produced usually has a synthetic resin (copolymer) content of 5 to 60.
% By weight. The particle size of the synthetic resin emulsion is 0.0
It is about 1 to 1 μm, preferably about 0.02 to 1 μm.

The solvent is water or an alcohol such as methyl alcohol, ethyl alcohol and isopropyl alcohol, or a mixture thereof.

The glass transition point Tg of the synthetic resin in such a synthetic resin emulsion is 130 ° C. or less, especially 40 to
It is preferably 130 ° C.

When a film-forming aid is added to the emulsion, a more uniform continuous film is formed. In this case, as a film-forming aid to be 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, hexanol, shellsol, 3-methoxybutyl acetate, ethylene glycol acetate, benzyl alcohol, furfuryl alcohol and derivatives thereof; and aromatics such as toluene and xylene And other hydrocarbons.

The amount of the film-forming aid used is preferably 1 to 20% by weight.

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

On the other hand, in the present invention, the fluorine-based polymer used for the dispersion may be either a homopolymer or a copolymer containing a fluorine atom, and specific examples thereof include the following. .

Polyvinyl fluoride, polyvinylidene fluoride, poly (ethylene trifluoride) chloride, polytetrafluoroethylene, ethylene tetrafluoride-propylene hexafluoride copolymer,
Ethylene tetrafluoride-ethylene copolymer, ethylene trifluoride ethylene-ethylene copolymer, ethylene tetrafluoride-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-propene hexafluoride copolymer rubber, polyfluoro An alkyl group-containing acrylic (or methacrylic) acid ester-based copolymer.

Further, the following homopolymers and copolymers are preferably used.

A) A homopolymer containing a monomer represented by the following formula (a) as a constitutional unit. Formula (a) CH ₂ ＣＨCHXR _{f In the} formula (a), X represents —O— or —OCO—, and R _f represents a fluoroalkyl group, a fluorooxyalkyl group, or a fluoroalkenyl group.

B) At least one kind of the monomer represented by the above formula (a), and (b) tetrafluoroethylene (TFE), trifluoroethylene (TrFE), chlorotrifluoroethylene (CTFE) and hexafluoropropylene ( A copolymer comprising at least one monomer selected from HFP) as a constituent unit in an arbitrary ratio.

C) at least one kind of the monomer represented by the above formula (a), at least one kind of the monomer selected from the above (b), and (c) vinyl ethers (methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether) , Chloroethyl vinyl ether, etc.): Vinyl esters (vinyl acetate, vinyl benzoate, vinyl persatic acid, vinyl trichloroacetate, etc.): (meth) acrylic monomers (methyl acrylate, methyl methacrylate, cyclohexyl methacrylate, etc.):
A copolymer containing at least one monomer selected from ethylene, propylene, styrene, vinyl chloride, vinylidene chloride and vinyl silane as a constituent unit in an arbitrary ratio. However, the proportion of the monomer (c) is preferably not more than 30 mol%.

In A), B) and C), the formula (a)
Specific examples of the monomer represented by the formula include those represented by the formula (17).

[0088]

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Further, specific examples of the copolymer (B) or (C) include those shown in Chemical Formula 18.

[0090]

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As the fluorine-based polymer, the following homopolymers and copolymers are preferably used.

D) Homopolymer having a monomer represented by formula 19 as a constitutional unit.

[0093]

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In the chemical formula 19, R ₁ is H, —CH ₃ , F
Or represents Cl. Y is shown in Chemical formula 20. R
_f represents a fluoroalkyl group having 1 to 20 carbon atoms.

[0095]

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Specific examples of the monomer represented by Chemical formula 19 include those represented by Chemical formulas 21 and 22.

[0097]

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[0098]

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[0099]

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E) at least one or more monomers represented by Chemical formula 19 and (d) an α, β-unsaturated double bond,
At least one of monomers having a carboxylic acid group or a carboxylic anhydride group in a side chain (eg, acrylic acid, methacrylic acid, itaconic acid, maleic anhydride, fumaric acid, maleic acid, α-fluoroacrylic acid, α-chloroacrylic acid, etc.) A copolymer containing at least any of the following as a structural unit. However, the proportion of the monomer (d) is preferably 15% by weight or less.

In the above E), in addition to the monomer shown in Chemical formula 19 and the monomer (d), a copolymer further containing the following copolymerizable monomer as a constitutional unit may be used. However, such a monomer is represented by the following formula.
3 of the total weight of the monomer shown in
Preferably, it is contained in a range of 0% or less. Examples of such a monomer include those shown below. Styrenes such as styrene, α-methylstyrene and chloromethylstyrene; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, 2-chloroethyl acrylate, α-methyl methyl acrylate, ethyl α-fluoroacrylate, methyl α-chloroacrylate,
Alkyl (meth) acrylates such as methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate, and 2-chloroethyl methacrylate Ethyl vinyl ether, 2-chloroethyl vinyl ether, propyl vinyl ether, butyl vinyl ether,
Vinyl ethers such as octyl vinyl ether and phenyl vinyl ether; vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate, and vinyl benzoate; methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone, butyl vinyl ketone, and phenyl vinyl ketone Vinyl ketones; olefins such as ethylene, propylene, isobutylene, butadiene and isoprene; N-vinylpyrrolidone, N-vinylcarbazole, 4-
Nitrogen-containing compounds such as vinylpyridine, acrylonitrile and methacrylonitrile; vinyl fluoride, vinylidene fluoride, ethylene trifluoride,
Haloolefins such as ethylene tetrafluoride, vinyl chloride, and vinylidene chloride.

The fluoropolymer of the present invention can be synthesized according to a known method, and a commercially available product can be used as it is. Further, only one kind may be used, or two or more kinds may be used in combination.

Such a fluoropolymer is used as a dispersion. As the dispersion medium at this time, for example, water, various alcohols, various ketones, water-alcohol, water-ketone, and the like are preferable. Is preferred.

The average particle size of the fluoropolymer as the dispersoid is preferably 0.1 to 1.0 μm, and the particles are preferably uniform. The dispersion amount of the fluoropolymer in the dispersion may be about 10 to 60% by weight of the entire dispersion. Various surfactants may be added to the dispersion for the purpose of controlling charging.

The fluorine-based polymer in the present invention is commercially available in the form of a dispersion, and in such a case, it can be used as it is.

The resin coating in the present invention is formed by using a mixture of the emulsified dispersion and the dispersion as described above, and the content of the copolymer of the monoethylenic monomer in the resin coating is 20 to 20. 90% by weight, preferably 30 to 70% by weight, and the content of the fluoropolymer is 1%
It is good to be 0 to 80% by weight, preferably 30 to 70% by weight.

The effect of the present invention is improved by setting the content as described above.

The content of the copolymer of the monoethylenic monomer and the content of the fluoropolymer with respect to the whole resin component in the mixture are almost the same as those in the resin coating.

Further, for the purpose of adjusting the charge amount of the magnetic particles, an azine compound, a quaternary ammonium salt,
A charge controlling agent such as a polyamine resin may be used if necessary. The use amount is desirably 15% by weight or less.

It is preferable that the resin coating contains conductive fine particles mainly for the purpose of controlling resistance.

As the material, carbon black, titanium oxide, tin oxide and the like can be used, and carbon black is particularly preferable.

The average particle size of the conductive fine particles is 0.0
The BET value is about 300-150 μm.
It is preferably about 0 m ² / g.

The lower limit of the thickness of the resin coating is 0.1 μm,
More preferably, it is 0.5 μm, particularly preferably 0.8 μm, and the upper limit is preferably 5 μm, particularly preferably 3 μm. The resin coating is preferably a continuous film.

The resin coating preferably contains conductive fine particles in an amount of 0.5 to 50% by weight, more preferably 2 to 20% by weight.

Further, in the present invention, it is preferable that a large number of conductive fine particles be present on the outer surface side of the resin coating rather than on the magnetic particle side. By making the conductive fine particles rich on the outer surface side, a sharp charge amount distribution for the positively chargeable toner is realized.

In such a case, the resin coating is
When divided, the concentration of the conductive fine particles in the resin coating on the one third of the magnetic particle side is preferably 30% or less of the concentration of the conductive fine particles in the resin coating from the outer surface to one third. It is preferable that the concentration of the conductive fine particles in the resin coating on the magnetic particle side 1/3 is substantially 0.

When forming such a concentration difference of the conductive fine particles, a resin coating can be provided by multi-layer coating.

In such a case, a second resin coating containing a polymer and conductive fine particles may be provided on the first resin coating containing only the polymer.

As described above, the first resin coating substantially containing no conductive fine particles and the second resin coating containing conductive fine particles are used.
When the resin coating is laminated, the conductive fine particles are contained in an amount of 1 to 50 parts by weight, more preferably 3 to 20 parts by weight, per 100 parts by weight of the polymer as the resin component in the second resin coating. Is preferred.

The thickness of the first resin coating is particularly 0.5 to 3 μm, and the thickness of the second resin coating is particularly 0.3
It is preferably about 2 μm.

It is preferable that the composition of the polymer or copolymer of the first and second resin coatings is the same,
Depending on the case, it may be different.

Further, the resin coating may contain about 0.1 to 30% by weight of a metal complex or the like as a charge control agent.

In the present invention, the above-mentioned various additives which can be contained in the resin coating can be appropriately added to an emulsified dispersion or a dispersion, or a mixture obtained by mixing them to be used.

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

Examples of oxides having a spinel structure include soft ferrites such as so-called 2-3 spinel and 1-3 spinel, magnetite (Fe ₃ O ₄ ), and maghemite (γ
—Fe ₂ O ₃ ).

Further, as soft ferrite, N
Any material having at least one of i, Mn, Mg, Zn, Cu, Co and the like may be used.

The oxide having a hexagonal structure may be Ba ferrite or Sr ferrite, or an oxide obtained by substituting a part of Ba, Sr or Fe of Ba or Sr ferrite with another metal.

These magnetic particles are produced by a known method as particles having an average particle diameter of 10 to 200 μm. There is no particular limitation on the particle size distribution.

The surface of the magnetic particles may be subjected to a base treatment with various coupling agents before resin coating. In this case, the coupling agent may be added to the emulsion or the dispersion.

In order to form the resin coating on the surface of the magnetic particles, the resin coating is heated under heating in a vessel in which a fluidized layer or a tumbling layer is formed.
The mixed solution of the emulsion and the dispersion may be coated using a nozzle spray, and may be dried if necessary.

The heating temperature is 70 to 90 ° C., the coating temperature is 40 to 80 ° C., and the drying temperature is about 40 to 80 ° C.

In the present invention, the coating is usually carried out continuously. In particular, in the case where conductive fine particles are contained, when the first and second resin coatings are laminated as described above, The coating may be dried once and then coated again.

As described above, it is preferable to form a resin coating on the magnetic particles by a nozzle spray or the like and in some cases, by multi-layer coating, and if necessary, dry and then heat-treat.

The heat treatment temperature is determined by the glass transition point T of the synthetic resin.
g or more, preferably 120 to 300 ° C, more preferably 160 to 240 ° C, and the heat treatment time is about 6 to 90 minutes.

Such a heat treatment may be performed by a fluidized bed, a box type drier, a continuous drying oven, a rotary kiln, or the like.

By such a heat treatment, the charge amount distribution of the carrier particles is sharpened, and the film strength is further improved.

Further, the magnetic carrier particles of the present invention may have 5 to 4 particles.
It has a charge of 5 μC / g. And the stirring stability is also good.

The fluidity per 50 g is 20 to 3
Indicates a value of 5 sec.

[0139] In this case, the fluidity is the falling speed of 50 g of the carrier obtained by weighing out 50 g of the carrier and using a powder rheometer.

Further, the electric resistance shows a value of about 10 ¹² to 10 ⁵ Ω in the range of 100 to 1000 ^V.

The carrier particles have a saturation magnetization of 35 to 35.
It is about 95 emu / g.

The magnetic carrier particles of the present invention are preferably used in combination with a positively charged toner for development for electrophotography.

There are no restrictions on the type of the positively chargeable toner used, the amount of toner added, and the like.

In obtaining an electrostatic copy image, there is no limitation on the magnetic brush developing system or the type of the photosensitive member to be used.

[0145]

The present invention will be specifically described below with reference to examples.

Example 1 (1) Preparation of Synthetic Resin Emulsion A monoethylenic monomer having a copolymer composition (parts by weight) shown in Table 1 and a polymerizable material having a ratio shown in Table 1 with respect to this copolymer composition A synthetic resin emulsion using an emulsifier (the compound I-1) was prepared.

The average particle size of the resin in each emulsion was 0.1.
04 μm, and the resin content in the emulsion is 35 to
It was 45% by weight.

In the emulsion, butyl carbitol acetate was used as a film-forming aid. 5% by weight
It is.

[0149]

[Table 1]

(2) Dispersion of fluoropolymer
Emissions F-1: Dispersion [dispersing medium of the polymer mainly comprising a fluoroalkyl methacrylate; water, the proportion of the resin component to the total; 22% by weight, trade name FM-300;
F-2: Dispersion of a copolymer containing vinylidene fluoride as a main component [dispersion medium; water, ratio of resin component to the whole; 20% by weight, trade name VP-850; Daikin Industries, Ltd.] (Manufactured by Corporation)

(3) Ferrite particles having an average particle diameter of 65 μm (composition: MgO 23 mol%, CuO 5 mol%, Zn
O 20 mol%, Fe ₂ O ₃ 52 mol%, σ _m = 60
emu / g, Hc = 2.0 Oe). The ferrite particles were placed in a vessel in which a fluidized bed was formed, and preheated to 50 ° C.

The emulsions shown in Table 1 and the above-mentioned dispersions were appropriately used and mixed at the ratios shown in Table 2 at 50 ° C. using a fluidized bed coating apparatus.
Spray coated with 1 hour and heat treated for 1 hour
8, 12 were obtained.

The carriers 9 to 11, 13, 1 and 2 were formed in the same manner as described above, except that the following was used as the resin coating.
4 was obtained (Table 2). AD-3: Dispersion of copolymer of emulsion A-3 (dispersion medium; water, ratio of copolymer to total; 3)
AS-3: 5% by weight solution of a copolymer of emulsion A-3 [solvent: methyl ethyl ketone-acetone (50: 5)
0) Mixed solvent] FS-1: 5% by weight of the polymer of the dispersion F-1
Solution [solvent: methyl ethyl ketone-acetone (50: 5
0) Mixed solvent]

Next, the following compositions were prepared. Styrene-acrylic resin (Mitsui Toatsu Chemicals XPA-3115) 89.0 parts by weight Polypropylene wax (Sanyo Chemical Industries Co., Ltd. Viscol 550P) 4.0 parts by weight Positive charge control agent 2.0 parts by weight (Orient Chemical 5.0 parts by weight of carbon black (MA-100, manufactured by Mitsubishi Kasei Kogyo Co., Ltd., average particle size: 20 μm) The above composition was blended, melted, kneaded, cooled, and coarsely ground with a hammer mill. . Then finely pulverize with a jet mill,
After classification, toner particles having a volume average particle diameter of 10 μm were obtained.

60 parts by weight of the above toner was weighed with respect to 940 parts by weight of each carrier, and this was stirred at 100 rpm for 1 hour to prepare a developer.

For each of the developers thus prepared, the initial value of the charge amount (initial charge amount) and the initial image density when each developer was used were examined. Further, the stirring stability and the film strength of each carrier were examined. These characteristics were evaluated as follows. Table 2 shows the results. In the table, ◎, 〇, △, etc. are shown, and the standards are also described below.

(1) Initial Charge Amount The developer prepared by stirring for 1 hour was sampled and measured by a blow-off charge amount meter manufactured by Toshiba Chemical Corporation. In this case, the measured value is a value after stirring for 10 seconds in the measuring instrument. ◎: charge amount 10.5-12.0 μC / g (proper value) 〇; charge amount 9.0-10.4 μC / g, 12.1-1
4.0 μC / g (out of appropriate value range) Δ: charge amount 7.5 to 8.9 μC / g, 14.1 to 17.
0μC / g (outside the appropriate value range)

(2) Initial Image Density An electrostatic latent image was developed by a copying machine having an OPC photosensitive member. Image density was measured with a Macbeth reflection densitometer. ◎: image density 1.28 to 1.36 (appropriate value) 〇; image density 1.22 to 1.27, 1.37 to 1.42
(Out of appropriate value range) Δ: Image density 1.15 to 1.21, 1.43 to 1.47
(Further out of proper value range)

(3) Stirring Stability 60 parts by weight of the toner was weighed with respect to 940 parts by weight of the carrier, and the stirring amount was measured at 100 rpm for 3 minutes after stirring and 90 minutes after stirring to compare the charge amount. Judged. ◎; difference 0 to 1.5 μC / g 〇; difference 1.6 to 4.5 μC / g △; difference 4.6 to 9.0 μC / g Also, for carriers 1 to 6 and 9 to 11, stirring time FIG. 1 and FIG. 2 are graphs showing the relationship between
Shown in

(4) Film Strength (Durability) After each carrier was stirred for 100 hours by a ball mill, the film strength before and after stirring was compared to determine the film strength. ◎: less than 1% of film peeling 〇: 1 to 5% of film peeling Δ: 6 to 10% of film peeling The thickness of the resin coating of the carriers 1 to 14 shown in the table is about 1.5 μm. is there.

[0161]

[Table 2]

From the results in Table 2, the effect of the present invention is clear. Further, the initial charge amount and the stirring stability are supported by the results shown in FIGS.

[0163]

The carrier particles of the present invention are excellent in initial properties and stirring stability, and have sufficient film strength and durability.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship between a stirring time and a charge amount.

FIG. 2 is a graph showing a relationship between a stirring time and a charge amount.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G03G 9/113

Claims (5)

(57) [Claims] 1. A resin coating on a surface of a magnetic particle, wherein the resin coating comprises an emulsion dispersion of a copolymer obtained by emulsion polymerization of a monoethylenic monomer using a polymerizable emulsifier;
Magnetic carrier particles for electrophotographic development, formed using a mixture of a fluoropolymer particle and a dispersion. 2. The method according to claim 1, wherein the resin coating covers the copolymer by 20 to 20.
90% by weight, 80 to 10% by weight of the fluoropolymer
2. The magnetic carrier particles for electrophotographic development according to claim 1, which contain. 3. The polymerizable emulsifier is one or more of allyl alcohol derivatives, acrylic acid derivatives, itaconic acid derivatives, maleic acid derivatives, fumaric acid derivatives, ethylene derivatives and styrene derivatives. The magnetic carrier particles for electrophotographic development according to claim 1 or 2, wherein the ethylenic monomer is one or more of an acrylic vinyl monomer, a styrene vinyl monomer, and a cyan vinyl monomer. 4. The magnetic carrier particle for electrophotographic development according to claim 1, wherein the polymerizable emulsifier is contained in the copolymer in an amount of 1 to 15% by weight. 5. The resin coating has a thickness of 0.1 to 5 μm.
The magnetic carrier particles for electrophotographic development according to any one of claims 1 to 4, wherein