JPH0327053A - Electrostatic charge developing carrier - Google Patents

Abstract

PURPOSE:To enhance film strength, adhesion to a core material, chargeability characteristics of a carrier coating layer by coating the core material with a polymer having specified structural units or a composition containing said polymer. CONSTITUTION:This carrier to be used is formed by coating the core material, such as a ferrite powder, with the polymer having the structural units each represented by formula I (each of X1 and X5 is H, halogen, 1 - 3 C alkyl, or the like) or a composition containing the polymer. As the monomer of the structural units of formula I, trifluorostyrene and the like can be used, and copolymerizable other polymers, such as vinyl acetate, can be used in combination.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a carrier for electrostatic charge development (hereinafter referred to as carrier) which constitutes a two-component dry electrostatic developer together with a toner in an electrophotographic copying machine.

Conventional technology and its problems Conventionally, in two-component developers consisting of toner and carrier, a carrier core material has been used for the purpose of controlling the triboelectricity of the toner, preventing deterioration of the carrier, and preventing toner from accumulating in the carrier. Polymer coated.

JP-A-60-176055 and JP-A-62-2291 disclose materials in which the surface of a core material is coated with a fluorine-containing polymer as a carrier that imparts positive chargeability to toner.
It is disclosed in Publication No. 58 and the like. However, these carriers have soft coatings that are easily scratched, lack adhesion, have poor friction durability when used at high speeds for long periods of time, and do not retain sufficient charge, making them difficult to copy. There is a problem in that it causes so-called fog, unevenness, etc.

Means for Solving the Problems As a result of repeated research in view of the problems of the prior art as described above, the present inventor has discovered that a polymer containing a specific monomer as an essential component has excellent properties as a carrier film. It was discovered that

That is, the present invention provides the following carrier for electrostatic charge development: Carrier for charge development.'' The monomers providing the structural unit represented by the general formula (1) used in the present invention may be used alone, or two or more types may be used in combination. Examples of the monomer include the following.

? 3 [In the formula, X, X2, X3, X4 and shows. ] CH,, CH2 Cl, CICF2 = CF
C.F. =CFCF2 =CF
CF2=CFCF,=CF? C, F■7 etc.

The polymer used in the present invention may contain other monomers that can be copolymerized with the monomer in order to improve the glass transition temperature (Tg), solubility in solvents, charging characteristics, etc. of the polymer. May contain. Examples of such monomers include, but are not limited to, the following: *Aromatic vinyl compounds such as styrene, α-methylstyrene, and p-methylstyrene; *Methyl acrylate, ethyl acrylate , Probyl acrylate, Butyl acrylate, Trifluoroethyl acrylate, Pentafluoroprobyl acrylate, Methyl methacrylate, Ethyl methacrylate, Probyl methacrylate, Butyl methacrylate, Trifluoroethyl methacrylate, Pentafluoropropylacrylate methacrylate Pills etc. (meth)
Acrylic esters; *Vinyl esters such as vinyl acetate; *Olefins such as ethylene, propylene, 1,3-butadiene, vinyl chloride, 1,1,2-trichlorobutadiene, tetrafluoroethylene, chlorotrifluoroethylene, etc. etc.

The molecular weight of the polymer in the present invention is a weight average molecular weight,
It is about 5,000 to 1,000,000.

As a method for producing the polymer, a usual radical polymerization method is employed, and bulk polymerization, suspension polymerization, emulsion polymerization, solution polymerization, etc. are performed.

As the polymerization initiator, peroxides such as diisopropyl peroxydicarbonate and ammonium persulfate, azonitrile such as azobisisobutyronitrile, and the like can be used. The polymerization temperature is not particularly limited, but is 40 to 1
The temperature is preferably about 50°C. As the solvent used in solution polymerization, benzene, toluene, xylene, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, acetonitrile, methyl ethyl ketone, methyl isobutyl ketone, dioxane, ethyl acetate, butyl acetate, etc. can be used.

The coating material for the carrier core material may be a combination of the above polymers, dyes, pigments, surfactants, silica powder, natural resins, fluororesins, silicone resins, acrylic resins, etc., which are conventionally used as carrier additives. It is possible to use a material to which an additive such as a resin is added. The amount of these additives used is preferably 50% or less of the total weight of the polymer.

As the carrier core material used in the present invention, all known materials can be used, and there are no particular limitations. Specifically, metals such as ferrite, magnetite, iron, cobalt, nickel, and aluminum; powders of alloys or compounds containing these metals; glass beads, silica sand, and the like are exemplified. The particle size of such carrier is usually 30 to 1000
The thickness is about μm, more preferably about 50 to 500 μm.

The coating on the carrier core material is carried out in substantially the same manner as a conventional method. For example, a polymer containing monomer (1) as an essential component or a mixture containing the polymer and an additive may be dissolved or dispersed in an organic solvent to achieve a solid content concentration of 0. 1-30
A coating liquid of 1% to 5% by weight is prepared, and the core material is coated by a dipping method, a dry spray method, a fluid spray method using a flow coater, etc., and then dried.

If necessary, heat treatment may be performed after the coating is formed.

As the organic solvent, a wide variety of solvents can be used, unlike when conventional fluororesins are used.

More specifically, ketone solvents such as acetone, methyl ethyl ketone, methyl probyl ketone, methyl isopropyl ketone, and methyl isobutyl ketone; acetate ester solvents such as ethyl acetate, cellosolp acetate, and n-butyl acetate; tetrahydrofuran, dioxane cyclic ethers such as monochlorobenzene, toluene, xylene, etc.; halogenated hydrocarbons such as tetrachloroethylene, trichloroethylene, methylene chloride; methyl alcohol, ethyl alcohol, butyl alcohol, tert-butyl alcohol, isoprovil Alcohols such as alcohol; 1,1,2-trifluorotrichloroethane, ■,2-difluorotetrachloroethane, hexafluorometa-xylene, 1,1,2,
Examples include fluorine-containing solvents such as 3.4-hexafluorotetrachlorobutane. These solvents may be used alone or in combination of two or more. From the viewpoint of evaporation rate, etc., it is more preferable that the solvent has a boiling point of about 60 to 140°C.

The thickness of the coating layer is usually about 0.05 to 20 μm, preferably about 1 to 5 μm. If it is less than 0.05 μm, the durability is insufficient, and if it exceeds 20 μm,
The adhesion of the coating film to the carrier core material decreases.

The carrier of the present invention is used in electrostatic development in combination with known toners. Such a toner is obtained by dispersing a colorant in a binder resin.

Examples of the binder resin include resins such as polystyrene, styrene-acrylic copolymer, polyester resin, polybutyral resin, ethylene-vinyl acetate copolymer, polyamide, and epoxy resin; Rikiichi Bon Black, Spirit Black, Nigrosine, Benzidine Yellow, Toners include colorants such as quinacridone, rhedamine, phthalocyan blue, and oil blue; charge control agents; and fluidizing agents.

The carrier of the present invention and such toner are usually the former 1
00 parts by weight, the latter 0.00 parts by weight. They are mixed in a proportion of about 3 to 20 parts by weight and used for electrostatic image development such as magnetic brush method and cascade method.

Effects of the Invention The carrier coating layer made of a polymer or a compound containing the same used in the present invention has excellent film strength, good adhesion to the core material, and excellent abrasion resistance and durability. Moreover, it is possible to provide a carrier with excellent charge retention properties.

EXAMPLES Examples and comparative examples are shown below to further clarify the features of the present invention.

Example 1 Trifluorostyrene 20g 1 ammonium persulfate 15
0 ■ and 2 g of n-dodecylamine hydrochloride in 100 of water.
ml, and a polymerization reaction was carried out for 7 hours in a constant temperature bath at 60° C. in a nitrogen stream. The reaction solution was poured into water containing potassium alum to precipitate a polymer.

The polymer was washed repeatedly with water and then dried under vacuum.

The weight average molecular weight of the obtained polymer was 470,000 (
Gel permeation chromatography, polystyrene equivalent).

The above polymer was dissolved in monochlorobenzene and 3% by weight was obtained.
A solution was prepared. The obtained coating liquid was used as a carrier core material (ferrite spherical powder DSPR-141, Dowa Iron Powder Industries Co., Ltd.)
Co., Ltd.) using a flow coater to produce a carrier with a coating layer of 2 μm.

With respect to 100 parts by weight of the obtained carrier, styrene/
100 parts by weight of acrylic copolymer (Himer SBM73, manufactured by Sanyo Chemical Industries, Ltd.), 10 parts by weight of carbon plaque (Regal 660R, manufactured by Cabot Corporation), and low molecular weight polypropylene (Viscol 660P, manufactured by Sanyo Chemical Industries, Ltd.). Toner 3 with an average particle size of 10 μm made by Co., Ltd.)
A developer was prepared by mixing parts by weight.

Example 2 15 g of trifluorostyrene, 10 g of vinyl acetate
100 ml of ammonium persulfate, 2.9 g of n-dodecylbenzenesulfonic acid and 20 ml of sodium bisulfite were added to 100 ml of water, and a polymerization reaction was carried out in a constant temperature bath at 40 DEG C. for 20 hours in a nitrogen stream. The reaction solution was poured into methanol to precipitate a polymer (weight average molecular weight = 800,000, gel permeability chromatography, calculated as boristyrene; trifluorostyrene 72.1 mol % in the polymer).

Thereafter, a carrier having a coating layer of 2 μm was manufactured in the same manner as in Example 1, and a developer was prepared.

Comparative Example 1 Vinylidene fluoride/tetrafluoroethylene (80 moles = 20 moles) copolymer (weight average molecular weight =
200,000) and dissolving it in a mixed solvent of methyl ethyl ketone/acetone (4:6).
A developer was prepared in the same manner as above.

Test Example 1 The amount of triboelectric charge (Q/M, μc/g) of the toner of the developer obtained in Examples 1 to 2 and Comparative Example 1 was measured using a blow-off charge amount measuring device (TB-200, Toshiba Chemical Corporation). made)
Each was measured.

The results are shown below.

Example 1 +32 2 +28 Comparative Example 1 +22 Furthermore, regarding the developer stirred in a blender for 20 hours,
When the surface of the carrier was observed with a scanning electron microscope, no abnormality was observed in the coating film of the carrier of Examples 1 and 2, whereas the coating film of the carrier of Comparative Example 1 showed some defects. Peeling was observed.

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Claims (1)

[Claims] (1) Formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ [In the formula, X_1, X_2, X_3, X_4 and X_5
are the same or different and represent a hydrogen atom, a halogen atom, an alkyl group having 1 to 3 carbon atoms, a halogenated alkyl group, an alkoxy group, or a halogenated alkoxy group. ] A carrier for electrostatic charge development comprising a carrier core material coated with a polymer containing a structural unit represented by the following or a composition containing the polymer.