JPS62153960A - Electrostatic image developing carrier - Google Patents

Abstract

PURPOSE:To obtain the titled carrier having improved properties of durability, electrostatic chargeability and image density by providing with a coating layer contg. a copolymer of a vinylidene fluoride and a tetrafluoroethylene and a copolymer contg. a specific vinylether monomer unit substd. with a fluorine atom in a side chain thereof as a main component to the titled carrier. CONSTITUTION:The copolymerization molar ratio of the copolymer of the vinylidene fluoride and the tetrafluoroethylene contg. in the coating layer of the carrier is a range of (75:25)-(95:5), preferably (5:25)-(87.5:12.5). As the ratio of the polymer blend, the fluorated vinylidene fluoride/tetrafluoroethylene is preferably 50-95wt%, more preferably 70-95wt%, and the polymer contg. the vinylether monomer unit shown by the formula, and substd. the side chain thereof with the fluorine atom is 50-5wt%, further preferably 30-5wt%. Thus, the titled carrier having the improved properties of durability, the electrostatic charge and the image density is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a carrier that constitutes an electrostatic image developer together with a toner, and in particular to a method for obtaining high-quality images by coating a carrier core material with a specific resin. This invention relates to a carrier for developing electrostatic images.

[Background of the Invention] In electrophotography, a photoreceptor made of a photoconductive element is given a uniform surface charge in a dark place, an electrostatic image is formed by imagewise exposure, and this electrostatic image is developed. A visible image is formed.

Generally, methods for developing such electrostatic images are broadly classified into wet developing methods and dry developing methods. The wet development method uses a liquid developer made by dispersing various pigments and dyes as fine particles in an insulating organic liquid, while the dry development method uses carbon black in a natural or synthetic resin. This is a developing method that uses a fine powder called a toner containing a dispersed coloring agent such as the following. This dry developing method includes a so-called bristle brush method using a developer containing only the above-mentioned toner as a main component;
In addition to the impression method and the powder cloud method, there are the so-called magnetic brush method and the cascade method, which use a mixture of the toner and a carrier made of iron powder or glass beads as a developer.

By these developing methods, electrostatic particles such as toner particles having electric charge contained in the developer adhere to the electrostatic image to form a visible image. This visible image is transferred directly onto a photoreceptor or onto paper or other image support by heat, pressure, solvent vapor, etc., and then fixed.

The present invention relates to a developer carrier used in the magnetic brush droplet and cascade methods among the above-mentioned development methods, that is, a carrier that imparts a desired charge to the toner by being stirred together with the toner.

Generally, carriers are broadly classified into conductive carriers and insulating carriers.

Oxidized or unoxidized iron powder is usually used as the conductive carrier, but in a developer containing this iron powder carrier, the triboelectricity of the toner is unstable, and the formation by the developer is unstable. There is a drawback that fog occurs in the visible image. That is, as toner particles adhere to the surface of iron powder carrier particles as a developer is used, the electrical resistance of the carrier particles increases and the bias current decreases, and the triboelectric charging properties become unstable, resulting in the formation of toner particles. The image density of the visible image decreases and fog increases. Therefore, if a developer containing an iron powder carrier is used for continuous copying with an electronic copying device, the developer deteriorates after a few copies, making it necessary to replace the developer early, so that good images can continue to be produced. I can't get it.

In addition, typical insulating carriers are carriers in which the surface of a carrier core material made of a ferromagnetic material such as iron, nickel, or ferrite is uniformly coated with an insulating resin. In developers using this insulating carrier, toner particles are less likely to fuse to the carrier surface than in the case of conductive carriers, and at the same time, the frictional electrification between the toner and carrier can be controlled, resulting in increased durability. is relatively excellent. Another advantage is that it can be used in high-speed electronic copying machines. However, in this insulating carrier, it is necessary that the coating layer covering the surface of the carrier core material has sufficient abrasion resistance (durability) and that the coating layer is good enough to prevent toner from forming a film on the carrier surface. It is required to have anti-sticking properties and to be able to obtain a charged state of a desired magnitude and polarity by friction with a specific toner used together with a carrier (charging property).

That is, the insulating carrier is rubbed against other carrier particles, toner particles, and the wall of the device in the developing device, but when the coating layer is worn away by this friction, the stability of the charging characteristics caused by the friction with the toner is lost. As a result, it is not possible to impart a desired charging state to the toner particles. Furthermore, even if the coating layer of the insulating carrier has sufficient abrasion resistance, if its adhesion to the core material is poor, the coating layer will peel off or crumble due to the above-mentioned friction, resulting in a similar loss of charging characteristics. It becomes like this. Furthermore, if toner adheres to the surface of the coating layer to form a film, the charging characteristics will become unstable. In either case, the entire developer needs to be replaced with a new one at an early stage.

Conventionally, as a method to improve such drawbacks, a technique of coating the surface of the carrier core material with a blended polymer (Japanese Patent Application Laid-Open No.
4-110839) and carriers in which the surface of the core material is coated with a vinylidene fluoride/tetrafluoroethylene copolymer or a polymer blend of these copolymers and a second polymer are known ( Japanese Patent Publication No. 58-208754
No. 60-176048, No. 60-176049, No. 60-176050, No. 60-176051,
(See Publications No. 60-176052, No. 60-176053, No. 60-176054, and No. 60-176055).

Furthermore, carriers using acrylates having fluorine atoms in their side chains as coating resins are also known (Special Publication No. 60-1
(Refer to Publication No. 6617), and the present applicant also filed a patent application in 1984-2.
No. 40758, No. 59-240759, No. 59-24
In the specification of No. 0763 and No. 59-240762,
We have previously proposed technology for this type of carrier.

[Problems to be Solved by the Invention] However, in the case of carriers coated with vinylidene fluoride/tetrafluoroethylene copolymer, the disadvantage is that the coating layer is abraded and lacks durability because the resin is soft. There is.

Furthermore, in the case of a carrier coated with a polymer blend of vinylidene fluoride/tetrafluoroethylene copolymer and a second polymer, the blend of the second polymer certainly increases the adhesion with the core, and the resin itself It also became harder and showed improved durability. However, blending the second polymer has the disadvantage that the amount of charge decreases or becomes unstable.

Furthermore, in the case of a carrier coated with an acrylate having a fluorine atom in the side chain, there is a drawback that the band TL amount is insufficient.
For example, in the case of the carrier described in Japanese Patent Publication No. 60-16617, there is clearly a lack of charge and vinegar, and also in the carrier described in Japanese Patent Application No. 59-240758 filed by the present applicant, the amount of charge is However, it is still insufficient and has the disadvantage that the amount of charge becomes unstable during long-term copying.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a carrier for electrostatic image development that has excellent durability and chargeability, has little fogging, and is capable of increasing image density.

Means for Solving Problem E] The carrier for electrostatic image development according to the present invention that can achieve the above object is made of a vinylidene fluoride/tetrafluoroethylene copolymer and a side chain substituted with fluorine atoms. It is characterized by having a coating layer mainly composed of a polymer containing a vinyl ether monomer unit.

The present invention will be explained in detail below.

The copolymerization molar ratio of vinylidene fluoride/tetrafluoroethylene copolymer contained in the coating layer of the carrier of the present invention is 75:
The range is preferably 25 to 95:5, more preferably 75:5.
:25-87.5 :12.5 range. When the molar composition ratio of the copolymer is within the above range, the solvent solubility will be improved, and the film formability and film strength will be improved, thereby ultimately improving the durability. Note that even if the solvent solubility improves, if the molecular weight becomes too high, the viscosity of the solution will increase too much, causing problems such as uneven film formation and durability, which is undesirable. Furthermore, if the molecular weight is low, the resin Since durability problems arise due to a decrease in strength, the intrinsic viscosity (in methyl ethyl ketone, 30°
C) is preferably in the range of 0.1 d-cross/g to 5 d-cross/g.

As the vinyl ether monomer unit containing a fluorine atom substituted in the side chain contained in the coating layer of the carrier of the present invention, a monomer unit represented by the following general formula (1) is preferably used.

General formula (1) % formula %) [In the formula, R represents an alkyl group or an aralkyl group substituted with at least one fluorine atom.] The vinyl ether monomer unit shown in the above general formula (1) As a preferred embodiment of the constituent monomers, the following general formula (2
) to (6).

General formula (2) %formula% General formula (3) CIl□=CH 0-CI+2-R.

General formula (4) % formula % (: General formula (5) General formula (6) % formula % [In the formula, R1 has a carbon number of 1 to 21, preferably 2 to 12,
Particularly preferably represents 2 to 8 fluoroalkyl groups, R
2 is an alkyl group having 2 to 8 carbon atoms, and half of the hydrogen atom -L
Represents those substituted with fluorine, ×1, X2,
L is selected from a halogen atom or a hydrogen atom and always contains one or more fluorine atoms, and l is O, ■, 2
or 3, and n represents 1 or 2.

As specific monomers, for example, those listed below can be used.

M-(1) CF211CF20C112C1120
C1l=CII.

M-(2) CF3CF2Cl120C112C11
,0CII=CI+2M-(3) CF211CF2
0CII□C1120C112Ctl□-OC1l=C
112M - (4) CF3CF2Cl120CII=
C11□M - (5) CF30F20CF2CF2C
1120CIl=CII2M-(6) CF, CF,
CF20CPtChC1l□OCfl=CLM −(7
) CF, +110Cll=CH2-(8) CF30
CIl=CI+2M-(9) CF30CIl=CI
+2 In the present invention, the monomer component used in the polymer contained in the coating layer together with the vinylidene fluoride/tetrafluoroethylene copolymer (hereinafter referred to as the polymer used in the present invention) has fluorine atoms substituted. The vinyl ether may contain only the vinyl ether, but it may also contain other components. Other ingredients here include, for example, acrylic (methacrylic) acid, methyl acrylic (methacrylate), acrylic (methacrylic)
Ethyl acrylate, butyl acrylate (methacrylate), benzyl acrylate (methacrylate), acrylic (methacrylic) acid amide, cyclohexyl acrylate (methacrylate), glycidyl acrylate (methacrylate), hydroxyethyl acrylate (methacrylate), styrene, vinyl acetate , ethylene, propylene, isoprene, etc.

Specific examples of the polymer used in the present invention include, but are not limited to, the following.

[Exemplary Compound 1 Polymer (1) -((R2-CH)- OCR2CH20CF 20F 2H Polymer (5) 1+CH2-cl()- [OCR2CF 2CF 200F 20F 3 The polymer blend ratio in the present invention is preferably 50 to 95% by weight of vinylidene fluoride/tetrafluoroethylene copolymer,
It is more preferably 70 to 95% by weight, and the polymer containing vinyl ether monomer units substituted with fluorine atoms in the side chain is preferably 50 to 5% by weight, more preferably 30 to 5% by weight. . Polymer blend ratio is 50:5
If it is 0 or more, the compatibility of the resin is good, the charge distribution becomes uniform, and the absolute value of the charge amount increases. Further, if the ratio is within 95:5, the coating layer is hard and therefore less likely to be worn out, which is preferable from the viewpoint of durability. The amount is preferably 0 to 30% by weight.

The coating layer of the carrier of the present invention contains a polymer made of the above-mentioned polymer blend, but it is also possible to contain a tertiary component, etc., if necessary.

In producing the carrier of the present invention, a coating liquid is prepared by dissolving or dispersing the vinylidene fluoride/tetrafluoroethylene copolymer and a polymer containing vinyl ether monomer units substituted with fluorine atoms in an organic solvent. The carrier of the present invention is obtained by preparing the coating layer, applying it to the surface of the carrier core material by, for example, a dry spray method to form a coating layer, and then heating or leaving it to stand.

Specifically, the carrier core is raised to an equilibrium height by a rising pressurized gas flow, for example in a fluidized bed apparatus, and then the coating liquid is sprayed on by the time the core falls again. This application is repeated to form a coating layer in advance. Incidentally, if there is agglomerated carrier, it can be sieved to finally obtain the carrier of the present invention having a desired film thickness.

The organic solvent used in the above production may be any solvent as long as it dissolves the copolymer of the present invention and the resin containing the copolymer as a main component, but examples include acetone, ketones such as methyl ethyl ketone, tetrahydrofuran, dioxane, dimethyl A solvent consisting of a sulfoxide, fluorine and/or halogen-substituted hydrocarbon compound, or a mixed solvent thereof is used.

In the present invention, the N content of the carrier coating layer is 0.05 lI.
range of I to 20 l, preferably 0.1 m to 2Ii,
The range is 11. If the thickness of the coating layer exceeds 20 gm, the solvent will remain in the coating layer for a long period of time, which will adversely affect chargeability, and at the same time, toner film formation will occur on the carrier surface, which is undesirable. 05 pL!
If it is less than 1, it is not preferable because it causes problems in charging stability due to pinholes and durability due to friction.

As the material of the carrier core material in the present invention, materials commonly used as carrier core materials such as sand, glass, and metal can be used, but in particular, materials that are strongly magnetized in the direction of a magnetic field, such as ferrite, Ferromagnetic metals such as magnetite, iron, cobalt, and nickel, or alloys or compounds containing these metals; alloys that do not contain ferromagnetic elements but become ferromagnetic through appropriate heat treatment; For example, alloys called Heusler alloys such as manganese-copper-aluminum or manganese-copper-tin, chromium dioxide, and the like can be mentioned as suitable examples. The particle size of these carrier core materials is preferably 30 to 1000 lm, more preferably 50 to 500 #1.1. It is preferable that the carrier of the present invention imparts a charge of 5 to 40 #LCog in absolute value to the toner used therewith under normal usage conditions.

The carrier of the present invention can constitute a two-component developer with any toner. Among them, the preferred toner is:
Examples include those using polyester resin and/or styrene/acrylic resin as the binder.

Polyester resin is obtained by condensation polymerization of alcohol and carboxylic acid, and the alcohols used include, for example, ethylene glycol, diethylene glycol,
Diols such as triethylene glycol, 1,2-7'ropylene glycol, l,3-propylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-butynediol, 1,4-bis(hydroxymethyl ) Cyclohexane, etherified hisphenols such as bisphenol A, hydrogenated bisphenol A, polyoxyethylated bisphenol A, polyoxypropylenated bisphenol A, and other dihydric alcohol monomers.

Examples of carboxylic acids include maleic acid, fumaric acid, mesaconic acid, citraconic acid, itaconic acid, glutaconic acid, phthalic acid, isophthalic acid, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, cepatic acid, malonic acid, Examples include anhydrides of these acids, dimers of lower alkyl esters and lysyl ric acid, and other divalent organic acid monomers.

As the polyester resin used in the present invention, it is preferable to use not only a polymer made only of the above difunctional monomers, but also a polymer containing a component made of a polyfunctional monomer having a unifunctional or higher functionality. Examples of such polyfunctional monomers, such as trivalent or higher polyhydric alcohol monomers, include sorbitol, 1, and 2.3.

B-hexanetetrol, 1,4-sorbitan, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2.4-butanetriol, 1,2.5-pentanetriol, glycerol,
2-methylpropanetriol, 2-methyl-1,2,
Examples include 4-butanetriol, trimethylolethane, trimethylolpropane, 1,3.5-trihydroxymethylbenzene, and others.

In addition, as the trivalent or higher polyvalent carboxylic acid monomer, for example, 1
, 2.4-benzenetricarboxylic acid, 1,3.5-benzenetricarboxylic acid, 1,2.4-cyclohexanetricarboxylic acid, 2,5.7-naphthalenetricarboxylic acid,
1,2.4-naphthalenetricarboxylic acid, 1.2.4-
Butanetricarboxylic acid, 1,2.5-hexanetricarboxylic acid, 1,3-dicarboxyl-2-methyl-2-methylenecarboxypropane, tetra(methylenecarboxyl)methane, 1,2,7.8-octanetetracarboxylic acid , empol trimer acid, and anhydrides of these acids,
Others can be mentioned.

It is desirable that the polyfunctional monomer component as mentioned above is contained in a proportion of 20 to 30 mol % in each of the alcohol component or acid component as a structural unit in the polymer.

As for styrene/acrylic resin, JP-A-50-13
Contains the α,β-unsaturated ethylenic monomer described in Publication No. 4652 as a structural unit, and has a weight average molecular weight (
MW)/number average molecular weight (Mn) of 3.5 to 40 can be used.

The content of the polyester resin and/or styrene/acrylic resin is preferably 30 to 95% by weight based on the total amount of the toner.

In order to produce the toner used in the present invention, the binder contains a coloring agent, various additives are added as necessary, and the binder is mixed with a ball mill or the like, kneaded, pulverized,
The toner used in the present invention can be obtained through each step of classification.

Note that it can also be obtained by a manufacturing method other than the above, such as spray drying, interfacial polycondensation, suspension polycondensation, or solution polycondensation.

The particle size of the toner obtained by the above method is 1 to 50 p-m.
and preferably 5 to 30 ILm.

Specific examples of the colorant contained in the toner include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or a mixture thereof. can.

Further, the above-mentioned toner may contain fine powder of hydrophobic silica or fatty acid metal salt. Regarding silica fine powder,
Although it is described in Japanese Patent Publication No. 54-16219 and No. 54-16220, a preferable example is "Aerosil R972J, r Silica D-1" manufactured by Nippon Aerosil Co., Ltd.
7J etc. can be mentioned. As fatty acid metal salts,
For example, metal salts of maleic acid and zinc, magnesium, calcium, etc.; stearic acid and zinc, cadmium, barium, lead, iron, nickel, cobalt, copper, aluminum,
Metal salts with magnesium, etc.; dibasic lead stearate;
Oleic acid and zinc, magnesium, iron, cobalt, copper,
Metal salts with lead, calcium, etc.: metal salts of palmitic acid with aluminum, calcium, etc.; lead caprylate; lead caproate; metal lead with linoleic acid and zinc, cobalt, etc.; calcium ricinoleate; ricylic acid and zinc, Examples include metal salts with cadmium and mixtures thereof. The content is 0.01-10% by weight based on the toner. As the addition method, a so-called external addition method is preferably used.

Further, examples of additives that may be added as necessary include offset inhibitors, charge control agents, and the like.

The developer is obtained by mixing the carrier of the present invention and the toner, and the mixing ratio thereof is preferably 0.3 to 20 parts by weight per 100 parts by weight of the carrier.

[Effects of the Invention] According to the present invention, as is clear from the Examples described below, it is possible to provide a carrier with excellent durability and chargeability, and also to increase image density, with no or almost no fogging occurring. There is an effect that there is no.

[Examples] Examples of the present invention will be described below, but the embodiments of the present invention are not limited thereto.

Manufacture of carrier and toner First, carrier A-I and comparative carrier A were prepared as follows.
-C, toner AB was produced.

Carrier A Vinylidene fluoride/tetrafluoroethylene copolymer r VT
-100J (copolymerization molar ratio 80:20, intrinsic viscosity 0
, fl15db/g) (manufactured by Daikin Industries, Ltd.) 13g and Exemplary Polymer (1) (intrinsic viscosity 0.50db/g) 2g
acetone-methyl ethyl ketone (1:I) mixed solvent 5
A coating liquid is prepared by dissolving or dispersing it in
5c J (manufactured by Dowa Iron Powder Industries Co., Ltd.) IKg was coated using a fluidized bed apparatus to produce carrier A having a film thickness of 2 μm.

Carrier B Said vinylidene fluoride/tetrafluoroethylene copolymer r
Carrier B was prepared in the same manner as carrier A except that a coating liquid was prepared using 12 g of VT-1004 and 3 g of exemplary polymer (4) (intrinsic viscosity 0.58 du/g).
was manufactured.

Carrier C: the vinylidene fluoride/tetrafluoroethylene copolymer rV
Carrier C was produced in the same manner as carrier A except that a coating liquid was prepared using 14 g of T-100J and Exemplary Polymer (5) (intrinsic viscosity: 0.47 du/g) Ig.

Carrier D Vinylidene fluoride and tetrafluoroethylene in a molar ratio of 75:
Vinylidene fluoride/tetrafluoroethylene copolymer obtained by reaction in 25 (intrinsic viscosity 0.88 dJ1/g) sg
and Exemplary Polymer (3) (Intrinsic Viscosity Q, flGd/g)
Carrier D was produced in the same manner as carrier A except that 3 g was used.

Carrier E Vinylidene fluoride and tetrafluoroethylene in a molar ratio of 90:
Vinylidene fluoride/tetrafluoroethylene copolymer obtained by reaction with IQ (intrinsic viscosity 1, 14 dJL/g)
14g and exemplary polymer (2) (intrinsic viscosity 0.55dl
/g) Carrier E was manufactured in the same manner as Carrier A except that Ig was used.

Carrier F Said vinylidene fluoride/tetrafluoroethylene copolymer rV
Carrier F was produced in the same manner as Carrier A except that 8 g of T-100J and 7 g of Exemplified Polymer (1) were used.

Carrier G In the production of Carrier A, vinylidene fluoride and tetrafluoroethylene were used in place of rVT-1004 at a molar ratio of 70:3.
Carrier G was produced in the same manner except that the vinylidene fluoride/tetrafluoroethylene copolymer obtained by the reaction in Example 0 was used.

Carrier H In the production of carrier A, the amount of rVT-1004 was
Carrier H was produced in the same manner except that the amount of Example Polymer (1) was changed to 0.5 g and 4.5 g.

In the production of Carrier E-Carrier A, the amount of rVT-100J was
Carrier I was produced in the same manner except that the amount of Example Polymer (1) was changed to 0.8 g.

Comparative Carrier A Said vinylidene fluoride/tetrafluoroethylene copolymer rV
Comparative Carrier A was manufactured in the same manner as Carrier A except that only 15 g of T-100J was used and no fluorinated vinyl ether polymer was used.

Comparative Carrier B Said vinylidene fluoride/tetrafluoroethylene copolymer rV
Comparative carrier B was manufactured in the same manner as carrier A except that a coating liquid was prepared using 13 g of T-1004 and 2 g of methyl methacrylate copolymer "Acrivet MF" (manufactured by Mitsubishi Rayon Co., Ltd.).

Comparative Carrier C Comparative Carrier C was produced in the same manner as in the production of Carrier A except that 15 g of Exemplary Polymer (1) was used.

Toner A 332g of terephthalic acid and polyoxypropylene (2,2
)-2,2-bis(4-hydroxyphenyl)propane (90 g) and bisphenol A 5B (7 g) using a thermometer,
A round-bottomed flask equipped with a stainless steel stirrer, a glass nitrogen gas inlet tube, and a flow-down condenser is set in a mantle heater, and nitrogen gas is introduced through the nitrogen gas inlet tube to maintain an inert atmosphere inside the flask. The temperature was raised. Then, 0.05 g of dibutyltin oxide was added, and the reaction was carried out at a temperature of 200° C. while monitoring the reaction at the softening point to produce a polyester resin.

100 parts by weight of this polyester resin, 10 parts by weight of carbon black "Regal B+30RJ (manufactured by Capot), low molecular weight polypropylene "Viscol 1 (80P)"
J (manufactured by Sanyo Chemical Industries, Ltd.) 2 heavy equipment parts and ethylene bisstearoylamide "2 parts by weight of Hoechst Wax GJ (manufactured by Hoechst Corporation) were mixed in a ball mill, and through the steps of kneading, pulverization, and classification, a toner with an average particle size of 10 pm was obtained. Particles are produced, and hydrophobic silica fine powder [Aerosil R-
Toner A was prepared by mixing 0.4% by weight of 812J (manufactured by Nippon Aerosil Co., Ltd.) and 0.1% by weight of zinc stearate.

Toner B Styrene/methyl methacrylate/n-methacrylate obtained by reacting styrene, methyl methacrylate, and n-butyl methacrylate at a molar ratio of 50:20:30
- 100 parts by weight of butyl copolymer, 10 parts by weight of carbon black "Regal 880RJ (manufactured by Capot),
3 parts by weight of low molecular weight polypropylene [Viscol 8BOPJ (manufactured by Sanyo Chemical Industries, Ltd.) is mixed in a ball mill, and through the steps of kneading, pulverization, and classification, toner particles with an average particle size of 117411 are produced, and to this is added hydrophobic silica fine powder. "Aerosil R-972J (manufactured by Nippon Aerosil Co., Ltd.) 0.5
Toner B was prepared by mixing % by weight and 0.2% by weight of zinc stearate.

Examples and Comparative Examples Carrier A-I and toner A-B of the present invention were mixed in combinations shown in Table 1 at a toner concentration of 2% to prepare a total of 11 types of developers N001 to 11.

On the other hand, for comparison, a total of three types of developer No.
12-14 were prepared.

Next, an electrophotographic copying machine rU-Bix 4000J (Konishi Roku Photo Using a modified machine (manufactured by Kogyo Co., Ltd.), continuous copying of up to 100,000 sheets was performed for each developer. The results are shown in Table 1.

In the table, "charge amount" is the amount of triboelectric charge per gram of toner measured by a known blow-off method, and "maximum image density" is the value of the amount of triboelectric charge per gram of toner measured by a known blow-off method, and "maximum image density" is the value of the amount of triboelectric charge per gram of toner measured by a known blow-off method. It is expressed by relative density, and "durability" is expressed by the number of copies made when fogging occurs and the image quality begins to deteriorate significantly. At this time, only the carrier is removed from the developer and the coverage is measured, and the coverage of new carrier is measured. "Film peeling/abrasion" was evaluated by comparing with the ratio. However, 0: No film peeling/wear, ○: Film peeling/wear less than 5%, △:
Film peeling/wear is 5% or more and less than 10%, X: Film peeling/wear is 10% or more.

As is clear from Table 1 above, the developer using the carrier of the present invention has an appropriate toner charge amount, has a high maximum image density, has good durability, and has little or no peeling or abrasion. It doesn't happen at all.

On the other hand, the developer using a comparative carrier causes fogging, film peeling, and abrasion, and has poor durability.

Claims (5)

[Claims] (1) It is characterized by having a coating layer mainly composed of vinylidene fluoride/tetrafluoroethylene copolymer and a polymer containing vinyl ether monomer units substituted with fluorine atoms in the side chains. Carrier for electrostatic image development. (2) Claim 1, characterized in that the copolymerization molar ratio of vinylidene fluoride/ethylene tetrafluoride copolymer is vinylidene fluoride:ethylene tetrafluoride = 75:25 to 95:5. Carrier for electrostatic image development as described in . (3) Electrostatic image development according to claim 1 or 2, characterized in that the vinyl ether monomer unit formed by substituting a fluorine atom in the side chain is represented by the following general formula (1). carrier. General formula (1) ▲There are numerical formulas, chemical formulas, tables, etc.▼ [In the formula, R_f represents an alkyl group or an aralkyl group substituted with at least one fluorine atom. ] (4) The vinylidene fluoride/tetrafluoroethylene copolymer is 50 to 95% by weight, and the polymer containing vinyl ether monomer units substituted with fluorine atoms in the side chain is 50 to 95% by weight.
Claim 2, characterized in that the amount is 5% by weight.
The carrier for electrostatic image development according to item 1 or 3. (5) The vinylidene fluoride/tetrafluoroethylene copolymer is 70 to 95% by weight, and the polymer containing vinyl ether monomer units substituted with fluorine atoms in the side chain is 30% by weight.
Claim 4 characterized in that the amount is 5% by weight.
Carrier for electrostatic image development as described in .