JPH07160058A - Carrier for electrostatic image development and developer - Google Patents

Abstract

(57) [Summary] [Structure] At least general formula (I) (Wherein R ¹ , R ² , R ³ and R ⁴ each represent an alkyl group, and n represents an integer of 2 or more) and the compound obtained by the reaction between the alkoxysiloxane and the silane coupling agent is contained. A carrier for developing an electrostatic charge image, which is obtained by coating at least a part of a core material with a silicone-based coating agent. [Effect] The carrier coating layer made of the silicone-based coating material of the present invention has excellent film strength and good adhesion to the core material, so that not only is it excellent in durability, but also the charging property rises quickly and is high. Gives the carrier electrostatic properties. Therefore, since the charging stability is excellent, a clear image with high image density and extremely little fog can be obtained, and the transfer efficiency of toner during image formation is increased. Further, a latent image holding member using an organic photoconductor having a low image hardness has few image defects due to abrasion of a magnetic brush, and gives a good image excellent in durability especially in a halftone image.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a carrier for developing an electrostatic charge image used in an electrophotographic copying machine, and a developer using the carrier.

[0002]

2. Description of the Related Art In a two-component developer containing a positively chargeable toner and a negatively chargeable resin-coated carrier, the carrier coating agent is a copolymer of vinylidene fluoride and tetrafluoroethylene, a fluoroalkyl methacrylate copolymer or the like. Fluorine-based resins, silicone-based resins, and the like have been conventionally proposed. (For example, JP-A-61-217068
JP-A-62-24268, JP-A-2-96770
(See each bulletin, etc.)

[0003]

Known carrier coating agents such as fluorine-based resins and silicone-based resins have drawbacks in terms of durability such as poor adhesion to the core material and easy peeling from the core material. However, they cause deterioration of image characteristics such as white background stain (fogging).

[0004]

Means for Solving the Problems As a result of repeated studies to solve the above problems, the present inventors have found that a silicone-based coating agent obtained from a specific organosiloxane is used to adhere to a core material. Properties are improved, the durability and storage stability of the coated carrier are improved, and by using the coated carrier with the silicone-based coating agent, a clear copy image with very little fog can be obtained, and the toner transfer at the time of copying The inventors have found that the efficiency is extremely improved and arrived at the present invention.

That is, the gist of the present invention is at least the general formula (I)

[0006]

[Chemical 2]

(Wherein R ¹ , R ² , R ³ and R ⁴ each represent an alkyl group, and n represents an integer of 2 or more) and the silane coupling agent is reacted with the alkoxysiloxane. A carrier for developing an electrostatic charge image is obtained by coating at least a part of a core material with a silicone coating agent containing a compound.

The present invention will be described in detail below. In the alkoxysiloxane represented by the above general formula (I),
Specific examples of R ¹ , R ² , R ³ and R ⁴ include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group,
And those having 1 to 4 carbon atoms such as a butyl group are preferred, and a methyl group and an ethyl group are preferred, and a methyl group is particularly preferred.

N is 2 to 100, more preferably 2 to 30
Are preferred, and 3 to 15 are particularly preferred. The alkoxysiloxane used in the present invention may be a mixture of alkoxysiloxanes having different n in the general formula (I). In this case, the average molecular weight of the mixture is particularly 2
50-4000, especially 300-3000 are preferable.

The alkoxysiloxane represented by the above general formula (I) can be generally obtained by reacting metallic silicon with alcohol to synthesize tetraalkoxysilane and then polymerizing the tetraalkoxysilane. Known silane coupling agents can be used. The silane coupling agent is a functional group that easily reacts with an inorganic substance such as —SiX ₃ or —SiX ₂ — (wherein, X represents a hydrolyzable substituent such as an alkoxyl group or a halogen group), a vinyl group, and an epoxy group. Group, an amino group, a (meth) acryloyl group, and an organic silicon compound having a functional group such as a mercapto group which easily reacts with an organic substance are shown in the molecule. Specific examples include trichlorovinylsilane, trimethoxyvinylsilane, and triethoxyvinylsilane. , Tris (2-methoxyethoxy) vinylsilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3- (2,2
3-epoxypropoxy) propyltrimethoxysilane, 3- (2,3-epoxypropoxy) propylmethyldiethoxysilane, 3- (2,3-epoxypropoxy) propyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane , 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3- (2-
Aminoethylamino) propylmethyldimethoxysilane, 3- (2-aminoethylamino) propyltrimethoxysilane, 3- (2-aminoethylamino) propyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltrimethoxysilane Ethoxysilane, 3-
Examples thereof include anilinopropyltrimethoxysilane, 3-chloropropyltrimethoxysilane, and 3-mercaptopropyltrimethoxysilane.

The reaction between the alkoxysiloxane represented by the general formula (I) and the silane coupling agent is a reaction in which a siloxane bond is generated by condensation. In general,
In a solvent containing a catalyst, at a temperature of 20 ° C. or higher,
React for 10 minutes to 5 hours. Specific examples of the solvent include
Tetrahydrofuran, acetone, methyl ethyl ketone and the like can be mentioned. Specific examples of the catalyst include acids such as hydrochloric acid, phosphoric acid, sulfuric acid, p-toluenesulfonic acid, and xylenesulfonic acid; tertiary amines; and quaternary ammonium salts. The amount of the catalyst is preferably 5 × 10 ⁻⁶ to 1 × 10 ⁻² parts by weight based on 1 part by weight of all the reaction compounds.

The reaction molar ratio between the alkoxysiloxane represented by the above general formula (I) and the silane coupling agent is
0.1 to 20 moles of silicon to which the hydrolyzable substituent in the silane coupling agent is directly bonded is preferable with respect to -Si (OR) ₂ -O-1 moles in the alkoxysiloxane, and 0.3 is particularly preferable. -10 mol is especially preferred. These reactions are carried out without gelation.

Further, the silicone coating material of the present invention preferably contains a vinyl resin. Examples of vinyl monomers that form vinyl resins include acrylonitriles such as acrylonitrile and methacrylonitrile; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, and vinylidene fluoride; styrene, α-
Styrenes such as methylstyrene and chloromethylstyrene; methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, amyl acrylate, hexyl acrylate, octyl acrylate, acrylic acid-
2-hydroxyethyl, hydroxypropyl acrylate, 2-chloroethyl acrylate, -2-acrylic acid
Fluoroethyl, α-methyl fluoroacrylate, α-
Ethyl fluoroacrylate, α-chloromethyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, amyl methacrylate, hexyl methacrylate, octyl methacrylate,
2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, 2-chloroethyl methacrylate,
And α-substituted or unsubstituted (meth) acrylic acid esters such as 2-fluoroethyl methacrylate; ethyl vinyl ether, 2-chloroethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, octyl vinyl ether, cyclohexyl vinyl ether, phenyl vinyl ether, etc. Vinyl ethers; vinyl esters such as vinyl acetate, vinyl chloroacetate, vinyl butyrate, vinyl pivalate, and vinyl benzoate; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, propyl vinyl ketone, butyl vinyl ketone, and phenyl vinyl ketone. Olefins such as ethylene, propylene, isobutene, butadiene, and isoprene; maleic anhydride, acrylic acid, and methacrylic acid Unsaturated carboxylic acids such as acids; maleic acid esters such as ethyl maleate and diisopropyl maleate; nitrogen-containing compounds such as N-vinylpyrrolidone, N-vinylcarbazole and 4-vinylpyridine; chlorinated vinyl chlorides Chlorinated paraffins;
In addition, chlorinated polyolefins and the like can be mentioned, and among them, vinyl halides and α-substituted or unsubstituted (meth) acrylic acid esters are preferable. The vinyl resin may be a homopolymer or a copolymer containing a repeating unit obtained from a vinyl monomer. It may also be a mixture of two or more polymers.

Further, the silicone-based coating material of the present invention may contain a resin other than the vinyl-based resin, and examples of the other resin include polyester resin, polycarbonate resin,
Epoxy resin, phenoxy resin, polyamide resin, polyimide resin, urea resin, alkyd resin, phenol resin, polysulfone resin, polyether resin, and polybutadiene resin are preferable. These may be a homopolymer or a copolymer, or may be a mixture of two or more polymers.

It is also preferable to add additives such as an inorganic fine powder, a charge control agent, a surfactant, and a lubricant to the silicone-based coating material of the present invention. Also, -Si (OR) _2-
It is also preferable to perform a curing treatment by adding a curing agent of, for example, an organic metal compound containing aluminum or tin as a curing agent; a boron compound; an organic compound such as maleic acid, succinic acid, acetic acid, oxalic acid, and phthalic acid. Examples thereof include carboxylic acid compounds; organic sulfonic acid compounds such as sulfonic acid toluenesulfonic acid and naphthalenesulfonic acid; and inorganic acid compounds such as hydrochloric acid, phosphoric acid, nitric acid, and sulfuric acid.

The method for forming a film on the carrier core material is carried out in the same manner as a conventional method. For example, the silicone coating agent of the present invention is dissolved or dispersed in an organic solvent to give a concentration of 0.
A coating liquid of 1 to 30% by weight, preferably 1 to 5% by weight is prepared, and the core material is coated by a dipping method, a dry spray method, a fluidized spray method using a flow coater, and dried.

Any organic solvent can be used as long as it dissolves the silicone-based coating agent, such as acetone, methyl ethyl ketone, methyl n-propyl ketone, and methyl i.
Ketone solvents such as so-propyl ketone, methyl butyl ketone, and cyclohexanone; Acetate solvents such as ethyl acetate, cellosolve acetate, and n-butyl acetate;
Examples include cyclic ether solvents such as tetrahydrofuran and dioxane; aromatic hydrocarbon solvents such as benzene, toluene, and xylene; and halogenated hydrocarbon solvents such as tetrachloroethylene, trichloroethylene, and chloromethylene. You may use these organic solvents in mixture of 2 or more types.

After forming the film, it is also preferable to perform heat treatment to cure the silicone-based coating agent. By the curing treatment, the adhesion of the silicone-based coating material to the core material becomes good, and a surface with less adhesion (spent) of toner particles to carrier particles can be obtained. Curing temperature is 40
-200 degreeC, Preferably it is 70-150 degreeC. The time is selected from 10 minutes to 5 hours.

The silicone-based coating material of the present invention obtained by the above method has a higher curing density than the commonly used silicone varnish, does not separate from the core material, and can be treated with the silicone-based coating material of the present invention. The coated carrier has a higher chargeability. As the core material of the carrier used in the present invention, all known core materials can be used,
There is no particular limitation. Specifically, ferrite, magnetite, and other metals exhibiting ferromagnetism such as iron, cobalt, and nickel; alloys or compounds containing these metals; not containing ferromagnetic metals, but exhibiting ferromagnetism by heat treatment. Alloys such as Mn-Cu-Al, Mn-C
Suitable examples are so-called Heusler alloys such as u-Sn; metal oxides such as CrO ₂ . The particle size of such a carrier is usually about 20 to 500 μm, more preferably about 30 to 200 μm.

The thickness of the coating layer of the carrier is
The thickness is preferably about 0.05 to 5 μm, and 0.3 to
More preferably, it is about 3 μm. If it is less than 0.05 μm, the durability is not sufficient and the charging stability is deteriorated, which is not preferable. Even if the thickness of the coating layer exceeds 5 μm, there is practically no problem in terms of performance, but the maximum value is reached in terms of performance, and the coating agent is consumed in large amounts, which is not economical.

The carrier of the present invention is used as an electrostatic image developer in combination with a known toner, especially a positively chargeable toner. Such a toner is obtained by dispersing a colorant in a binder resin. Examples of the binder resin include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, butyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate. , Α-methylene fatty acid monocarboxylic acid esters such as methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate, and 2-ethylhexyl methacrylate; vinyl nitriles such as acrylonitrile and methacrylonitrile; 2 Vinyl pyridines such as vinyl pyridine and 4-vinyl pyridine; vinyl ethers such as vinyl methyl ether and vinyl isobutyl ether; vinyl methyl ketone, vinyl ethyl metone, and methyl isopropene Vinyl ketones such as ruketone; unsaturated hydrocarbons such as ethylene, propylene, isoprene, and butadiene, and their halides; and homopolymers composed of monomers such as halogenated unsaturated hydrocarbons such as chloroprene, And a mixture of two or more kinds of these homopolymers and copolymers. Alternatively, a rosin-modified phenohil formalin resin, an oil-modified epoxy resin, a polyester resin, a polyurethane resin, a polyimide resin, a cellulose resin, a non-vinyl resin such as a polyether resin, a mixture of these non-vinyl resins and the vinyl resin, and the like. Can also be mentioned.

The above toner may further contain or be mixed with additives such as a charge control agent, waxes, inorganic fine powder, and stearate. Examples of the colorant used in the toner include carbon black, nigrosine, aniline blue, chalco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal and phthalocyanine blue.

The carrier of the present invention and such toner are
Usually, the latter is mixed in a proportion of about 0.3 to 20 parts by weight with respect to the former 100 parts by weight, and used for developing an electrostatic image by a magnetic brush method, a cascade method or the like.

[0024]

EFFECTS OF THE INVENTION The carrier coating layer comprising the silicone coating agent of the present invention has excellent film strength and good adhesion to the core material, so not only is it excellent in durability, but the charging property rises quickly. In addition, it gives the carrier high chargeability. Therefore, since the charging stability is excellent, the image density is high,
A clear image with very little fog is obtained, and the transfer efficiency of toner during image formation is increased. Further, a latent image holding member using an organic photoconductor having a low image hardness has few image defects due to abrasion of a magnetic brush, and gives a good image excellent in durability especially in a halftone image.

[0025]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. (Example 1) 236 g (1 mol, 3 equivalents) of 3- (2,3-epoxypropoxy) propyltrimethoxysilane was dissolved in 500 g of tetrahydrofuran, and 54 g (6 equivalents) of a 0.35% hydrochloric acid aqueous solution was added and mixed. The mixture was left standing at 20 ° C. for 1 hour for hydrolysis. Next, 450 g of polymethoxysiloxane mainly composed of an oligomer having a molecular weight of 500 (n = 4 in the above general formula (I)) was added and refluxed for 2 hours. Then, the temperature was raised to 150 ° C. and the solvent was allowed to flow out to obtain a silicone-based coating agent as a colorless transparent liquid. This silicone-based coating agent was dissolved in methyl ethyl ketone to a concentration of 4% by weight, and a small amount of nitric acid was added as a curing agent to prepare a coating liquid. Average particle size 100 μm
The coating solution is applied to the spherical ferrite core material of No. 2 by a fluidized spray method so that the dry film thickness is 2 μm, and the temperature is 100 ° C.
The coated carrier was obtained by heating for 1 hour for curing.

On the other hand, 100 g of a copolymer resin of styrene and n-butyl acrylate, 75 g of carbon black, 2 g of low molecular weight polypropylene, and a quaternary ammonium salt type charge control agent (Bontron P51, manufactured by Orient Chemical Co.) 2
toner having an average particle size of 10 μm, which is composed of a kneaded and pulverized product of 10 g
0 g and hydrophobic silica fine powder (R-972, manufactured by Degussa) 0.1 g were mixed by a Henschel mixer, and 4 g of silica externally added toner obtained was mixed with 100 g of the coated carrier to prepare a developer. did.

Subsequently, a commercial copying machine equipped with an organic photoconductor was used to carry out an actual copying durability test to evaluate the image density, fog, and toner transfer rate. As a result, a clear image with less fog was stably obtained from beginning to end. The toner transfer rate was also good. No peeling of the coating material from the core material was observed, indicating good durability.

Example 2 232 g (1 mol, 3 equivalents) of 3-methacryloyloxypropylmethyldiethoxysilane was used instead of 236 g of 3- (2,3-epoxypropoxy) propyltrimethoxysilane, and methylethylketone was used instead of methylethylketone. Tetrahydrofuran was used in place of 450 g of methoxysiloxane centered on an oligomer having a molecular weight of 500, and having a molecular weight of 400 (in the general formula (I), n =
A developer was prepared and evaluated in the same manner as in Example 1 except that 450 g of polymethoxysiloxane mainly containing the oligomer of 3) was used.

As a result, a clear image with less fog was stably obtained from beginning to end. The toner transfer rate was also good. Neither peeling of the coating material from the core material was observed.

(Example 3) A silicone-based coating agent was added at a concentration of 4
Instead of being dissolved in methyl ethyl ketone so that the weight% becomes, the silicone-based coating agent and vinyl chloride resin (SG-
A developer was prepared and evaluated in the same manner as in Example 1 except that a 2: 1 (weight ratio) mixture of 700, manufactured by Mitsubishi Kasei Co., Ltd.) was dissolved in tetrahydrofuran to a concentration of 3% by weight.

As a result, good image characteristics were consistently obtained. The adhesion of the coating material to the core material was also good.

Example 4 Example 1 was repeated except that an iron powder core material having an average particle size of 70 μm was used in place of the spherical ferrite core material having an average particle size of 100 μm, and 4 μm was used instead of the dry film thickness of 2 μm. A developer was prepared and evaluated in the same manner as in.
As a result, good image characteristics were consistently obtained. The adhesion of the coating material to the core material was also good.

Comparative Example A developer was prepared and evaluated in the same manner as in Example 1 except that a straight silicone varnish (KR255, manufactured by Shin-Etsu Silicone Co., Ltd.) was used in place of the silicone coating agent. As a result, only images with large fog were obtained. In addition, peeling of the silicone varnish was observed from the 10,000th photo film.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Oil Department Heihachi 4-1-1, Fushimi-cho, Chuo-ku, Osaka-shi, Osaka Mitsubishi Kasei Corporation Osaka Branch

Claims (4)

[Claims] 1. At least a compound represented by the general formula (I): (Wherein R ¹ , R ² , R ³ and R ⁴ each represent an alkyl group, and n represents an integer of 2 or more) and the compound obtained by the reaction between the alkoxysiloxane and the silane coupling agent is contained. A carrier for developing an electrostatic charge image, which is obtained by coating at least a part of a core material with a silicone-based coating agent. 2. The electrostatic charge image developing carrier according to claim 1, wherein the silicone-based coating material further contains a vinyl-based resin. 3. An electrostatic charge image developer comprising at least the electrostatic charge image developing carrier according to claim 1 and a positively chargeable toner. 4. The method for producing a carrier for developing an electrostatic charge image according to claim 1, further comprising a curing treatment after coating the core material.