JPS59104664A - Electrostatic charge image developing carrier - Google Patents

Abstract

PURPOSE:To obtain an electrostatic charge image developing carrier superior in humidity resistance, small in deterioration of triboelectrification characteristics, and capable of stable development in a long term by coating the surface of a core material with a specified polymethacrylate. CONSTITUTION:A polymer used for the carrier is obtained by polymerizing cycloalkyl methacrylate, such as cyclohexyl methacrylate, and has >=about60 deg.C glass transition point. It may be a copolymer of said monomer and styrene or vinyl acetate. A carrier core material, such as sand, glass powder, or iron powder having about 30-1,000mum particle diameter, is coated with a soln. of said polymer and dried to form a coating layer made of said polymer on the surface of the core material, serviceable as a carrier.

Description

[Detailed description of the invention] The present invention relates to a carrier for developing electrostatic images.

Generally, in the electrophotographic method or the Seikiki, Recording method, etc.

In order to develop an electrostatic charge image formed on a support made of a photoconductive photoreceptor or a dielectric material, a developer consisting of toner, which is a colored fine powder, and a carrier is used. This present l
constitutes an agent. During the conveyance process, the toner is rubbed against the carrier, and a charge of the opposite polarity to the electrostatic charge image is induced in the toner, and during the development process with a developer, the toner electrostatically adheres to the image support. A visible image is formed.

Therefore, although the toner in the developer in the developing device is consumed each time development is performed, the developing device is replenished with new toner accordingly, so that the toner in the developing device is constantly updated. However, the carrier is one that is initially prepared and used repeatedly over a long period of time, and therefore, as development is repeated, the characteristics of the carrier deteriorate. For example, some of the toner may become fused to the surface of the carrier, resulting in so-called spent toner, reducing the triboelectric charging properties of the carrier, or when adjusting image quality by applying a bias voltage to the developer. effect cannot be obtained, and good development cannot be achieved.

Generally, inorganic powder or granules are used as they are as carriers, but if the surface condition is hydrophilic, this is not possible.
The moisture resistance of the agent is reduced and similarly good performance cannot be achieved.

As a means to solve the above problems, it is known that, for example, inorganic particles are used as a carrier core material, and a coating layer made of a resin that has excellent triboelectric charging characteristics with toner is formed on the surface of the carrier core material. As the primary resin for forming such a coating layer, a homopolymer containing methacrylic acid ester as a monomer component or a copolymer with styrene or the like is known, for example, from JP-A-47-18954. There is.

However, not all polymers containing methacrylic acid ester as a monomer component are suitable as materials for forming the coating layer of the carrier. In other words, due to the difference in the type of hydrocarbon group bonded to the ester acid group of the methacrylic ester, the hygroscopicity, glass transition temperature, and other thermal properties of the methacrylic ester polymer are different. The properties of the carrier formed with the Yotsuko coating layer are affected, particularly the triboelectric charging properties and fluidity properties of the toner. In particular, if the hydrophilicity of the hydrocarbon group bonded to the ester acid group of the methacrylic ester is large, the hygroscopicity of the polymer using this methacrylic ester monomer will not be large. A carrier whose coating layer is made of a polymer with high viscosity gradually absorbs moisture, and its triboelectric charging properties and fluidity properties deteriorate, making it impossible to achieve stable development over a long period of time. For example, methyl methacrylate has a methyl group as the hydrocarbon group that binds to the ester acid group of the methacrylate ester.Since the methyl group is the most hydrophilic among alkyl groups, this methyl methacrylate is used as a monomer. A carrier in which a coating layer is formed using a polymer as a component has high hygroscopicity, and therefore its triboelectric charging properties deteriorate significantly over time.

In addition, a carrier in which a coating layer is formed of a polymer of a monomer having a methylated alkyl group other than a methyl group as a hydrocarbon group bonded to an ester acid group of a methacrylic acid ester,
When using the above-mentioned polymer of methyl methacrylate monomer, the hygroscopicity is small, but it does not necessarily have sufficient moisture resistance, and furthermore, it does not have a suitable glass transition temperature, so it is thermally They have some drawbacks in terms of properties, particularly in that they adversely affect the flow characteristics of the carrier. That is, if the glass transition temperature is low, the characteristics change, especially due to heat, in the atmosphere inside the copying machine.

Further, when heat is generated due to friction between the carriers or friction between the carriers and the wall of the developing device, the resin becomes sticky and its fluidity deteriorates.

The present invention has been made based on the above circumstances.
b. The purpose is to have a coating layer with excellent moisture and thermal properties, and therefore have high triboelectric properties and flow properties, and can achieve good development over a long period of time. An object of the present invention is to provide a carrier for electrostatic charge development.

The above object is achieved by a carrier for forming an electrostatic charge gap, in which a coating layer of a polymer containing methacrylic acid cycloalkyl ester as a monomer component is formed on the surface of a carrier core material.

The present invention will be explained in detail below.

In the present invention, a resin made of a homopolymer or copolymer of a methacrylic acid cycloalkyl ester monomer in which the hydrocarbon group bonded to the ester acid group is a cycloalkyl group is used as the material for forming the coating layer of the carrier. A carrier is formed by dissolving this in, for example, a solvent, applying this solution to the surface of the carrier core material, and drying it.

Note that methods for applying the resin solution to the carrier core material include a dipping method, a spray method, a fluidized bed method, and the like.

In the carrier of the present invention, a polymer containing methacrylic acid cycloalkyl ester as a monomer component is used as a material for the coating layer, and this polymer has a hydrocarbon group bonded to the ester acid group that is cycloalkyl methacrylate. Because the carrier has low hydrophilicity, it has low hygroscopicity and therefore has excellent moisture resistance.Therefore, the carrier has little deterioration in triboelectric charging properties and can be stably used for development over a long period of time. Become. Furthermore, since the polymer has a good glass transition temperature and can be easily obtained, the polymer can have good thermal properties, and therefore the carrier can have high fluidity properties. .

Furthermore, polymers of monomers in which the hydrocarbon group bonded to the ester acid group is an aromatic hydrocarbon group such as a phenyl group have a negative effect on the triboelectric properties of the cow Yaria.
Polymers of methacrylic acid cycloalkyl ester monomers can exhibit good triboelectric charging properties for toners that have such drawbacks.

In the present invention, the carrier core material has a particle size of 80 to 1
000 microns, preferably 80-200 microns, conventional carrier core materials such as sand, glass, or metals such as cobalt, iron, copper, nickel, ferrite, zinc, aluminum, ferrite, or their alloys or oxides thereof. You can actually use what is used as .

It is selected as appropriate according to the current four methods to be adopted. The carrier core is preferably spherical.

The methacrylic acid cycloalkyl ester which is a monomer component of the polymer used in the coating layer of the core material in the carrier of the present invention is one having 8 to 7 carbon atoms forming a substituted or unsubstituted cycloalkyl ring. Preferred examples include cyclopropyl methacrylate, cyclobutyl methacrylate, cyclopentyl methacrylate, cycloP-hexyl methacrylate, and cycloheptyl methacrylate, among which cyclohexyl methacrylate is particularly preferred.

The polymer for forming the carrier coating layer is a homopolymer of the above-mentioned methacrylic acid cycloalkyl ester monomer or a copolymer with other monomers such as styrene, vinyl acetate, vinyl chloride, etc. and mixtures thereof.

In addition, the glass transition temperature of the coating polymer is at least 60C.
It is preferable that the carrier of the present invention has an absolute value of 5% under normal usage conditions of 1% to the toner used together with the carrier.
Preferably, it provides a charge of ˜40 microcolons/g.

The toner constituting the present iron agent together with the carrier of the present invention is made by dispersing a colorant in a resin, and a thermoplastic resin such as Umemi is used as the binder resin. Specific examples include styrenes such as styrene, parachlorostyrene, and α-methylstyrene; methyl acrylate, ethyl acrylate, n-propyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, and methyl methacrylate. , ethyl methacrylate, n-butyl methacrylate, lauryl methacrylate, methacrylic acid? -α-methylene aliphatic monocarboxylic acid esters such as ethylhexyl; vinyl nitriles such as acrylonitrile and methacrylonitrile; 2-vinylpyridine;
Vinyl pyridines such as 4-vinyl pyridine: vinyl methyl ether, vinyl isobutyl ether, etc.
L ethers; Vinyl ketones such as vinyl methyl ketone, vinyl ethyl ketone, and methyl isopropenyl ketone; Unsaturated hydrocarbons such as ethylene, propylene, isoprene, butadiene, and their halides, and halogen-based unsaturated hydrocarbons such as chloroprene. or copolymers obtained by combining two or more of these monomers, mixtures thereof, or, for example, rosin-modified phenol-formalin resins, oil-modified epoxy resins, polyester resins, polyurethane resins. .

Examples include non-vinyl condensation resins such as polyimide resins, cellulose resins, and polyether resins, or mixtures of these and the vinyl resins.

Specific examples of the colorant include carbon black, nigrosine dye, aniline blue, calco oil blue, chrome yellow, ultramarine blue, methylene blue, rose bengal, phthalocyanine blue, or mixtures thereof. .

As described above, the present invention uses a polymer coating whose monomer component is methacrylic acid cycloalkyl ester, which has excellent moisture resistance and thermal properties, and forms a coating layer on the surface of the carrier core material. , has high triboelectric charging properties and high flow properties, and therefore can achieve good electrostatic charge development stably over a long period of time at °C.

Of course, various additives such as charge polarity control agents and the like can be added to the carrier of the present invention as required.

The present invention will be explained below with reference to examples, but the present invention is not limited to these examples.

Example: Styrene and cyclohexyl methacrylate in a weight ratio of 70.
:30 to synthesize a styrene-cyclohexyl methacrylate copolymer, and 12 g of this copolymer was used to prepare spherical iron powder (L'DSP1 manufactured by Dowa Iron Powder Co., Ltd.) with an average particle size of 100μ.
35c, l) l# with a thickness of approx. 2 using the fluidized bed method.
A carrier of the present invention was manufactured by forming a coating layer of μ.

To 98 parts by weight of this carrier, 2 parts by weight of toner for U-Bix 4500 (manufactured by Konishiroku Photo Industry Co., Ltd.) was mixed to prepare a developer.
% high-temperature, high-humidity atmosphere (hereinafter referred to as "atmosphere ■") and a temperature of 10°C and a relative humidity of 20% (hereinafter referred to as "atmosphere ■"). (manufactured by Photo Industry Co., Ltd.), and the maximum image density of the formed visible images was investigated. In addition, in the triboelectric charge amount test, the developer was shaken for several minutes to be triboelectrically charged, and then a known 10-off method was used.

On the other hand, for comparison, a styrene-methyl methacrylate copolymer was synthesized by reacting styrene and methyl methacrylate at a weight ratio of 70:80, and a similar experiment was conducted.

The experimental results are shown in Tables 1 and 2, and the results of the triboelectrification test are shown in terms of the amount of charge per gram of toner (represented by Q in the table), and the results of the maximum both edge density test are shown. The results are shown by the relative density of the developed image (expressed as Dmax in the table) when the image density of the original image is set to 2. Table 1 shows the results in atmosphere IK, and Table 2 shows the results in atmosphere ■.

Table 1 Table 2 Results of this experiment 1 It can be seen that the developer using the carrier according to the example of the present invention has stable triboelectric charging characteristics even in a high temperature and high humidity atmosphere.

Note that the carrier obtained in the same manner as in Example except that styrene-phenyl methacrylate copolymer was used instead of styrene-cyclohexyl methacrylate copolymer had a low original charge amount and could not be used for practical use. Ta.

Claims (1)

[Scope of Claims] 1) A carrier for developing electrostatic images, characterized in that a coating layer made of a polymer containing methacrylic acid cycloalkyl ester as a monomer component is formed on the surface of a carrier core material. 2) The carrier for electrostatic image development according to claim 1, wherein the methacrylic acid cycloalkyl ester is cyclohexyl methacrylate.