JPH0542674B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a carrier that constitutes an electrostatic image developer together with a toner, and in particular to an electrostatic image that has improved durability and stabilized triboelectric charging characteristics by coating the carrier core material with a resin. Regarding carriers for development. [Prior art] In electrophotography, a tourist object made of a photoconductive element is given a uniform surface charge in a dark place, and then an electrostatic charge image is formed by imagewise exposure, and this electrostatic charge 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, which contains a colorant such as the following dispersed therein. In addition to the so-called bristle brush method, impression method, and powder cloud method using a developer containing only the above-mentioned toner as a main component, this dry development method includes a method in which the above-mentioned toner is mixed with a carrier made of iron powder or glass beads, etc. There are the so-called magnetic brush method and the cascade method, which use the body as a developer. By these developing methods, electrostatic particles such as toner particles containing charges contained in the developer adhere to the electrostatic charge 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 method and cascade method among the above-mentioned development methods, that is, a carrier for imparting 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 iron powder formed by the developer is unstable. The disadvantage is 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 times, so it is necessary to replace the developer early to maintain a stable image quality. I can't keep getting it. A typical example of an insulating carrier is a carrier 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 a developer using this insulating carrier, toner particles are less likely to fuse to the carrier surface than in the case of a conductive carrier, and at the same time, the frictional electrification between the toner and the carrier can be controlled, making it durable. It also has the advantage that it has relatively good properties and 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 charging 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, the container wall, etc. in the developing device, but when the coating layer is worn away by this friction,
The stability of charging characteristics caused by friction with the toner is lost, and 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 friction described above, and the charging characteristics will similarly deteriorate. become lost. Furthermore, if toner adheres to the surface of the coating layer to form a film, the charging characteristics will become unstable. In either case, it becomes necessary to quickly replace the entire developer with a new one. Conventionally, as a technique for improving such defects, a technique is known in which the surface of the carrier core material is coated with a fluoro compound such as perfluoroalkane or perfluoroalkyl (see Japanese Patent Laid-Open No. 117638/1983). However, in this technology, since the compound containing the coating layer has a relatively low molecular weight, the coating strength is weak and the abrasion resistance has not been significantly improved, resulting in poor durability and unstable triboelectric charging properties. It was hot. Therefore, as a technique for increasing coating strength, a technique is known in which the coating is coated with a polymer containing a fluorinated acrylate or methacrylate having a specific structure as a monomer component. (Refer to Japanese Patent Application Laid-Open No. 53-97435). However, although this technology uses a high-molecular weight polymer to increase coating strength, its adhesion and film-forming properties are insufficient, resulting in the coating layer peeling off during repeated use at high speeds and over long periods of time, and due to frictional electrification. The disadvantage was that the properties became unstable and the durability was inferior. In particular, it has been found that the peeling object that causes this does not cause the coating layer to peel off from the surface of the core material, but rather causes the film to peel off from the middle of the coating layer. [Objective of the Invention] The object of the present invention is to provide an electrostatic charge coating layer that has good film-forming properties and adhesion to the carrier core material, is durable even during high-speed and urinary use, and has stable triboelectric charging properties. An object of the present invention is to provide a carrier for image development. Other objects of the invention will become apparent from the following description of the specification. [Summary of the Invention] The carrier for developing electrostatic images according to the present invention is characterized in that a carrier core material is coated with a composition consisting of at least the following (a) and (b). (a) A monomer represented by the following general formula (1) and an aziridenyl group (

[Structure of the invention]

The composition of the present invention contains as a component a copolymer consisting of at least a monomer having a fluorine atom in its side chain and a monomer having an azidenyl group in its side chain, and further contains the above-mentioned azidenyl group as a component b. It consists of at least a crosslinking agent that can react with the side chain of the monomer. By bonding fluorine atoms to the side chains, it is possible to adjust solvent solubility, charging characteristics, film properties, etc., and it is easier to handle and has better properties than polymers in which fluorine atoms are directly bonded to the main chain. The top is also excellent. Structurally, it is necessary to use two or more atoms, preferably three or more atoms, from the main chain carbon atoms. For example, as the monomer having the fluorine atom in its side chain, monomers listed in the following general formulas (2) to (14) can be used. General formula (2) General formula (3) General formula (4) General formula (5) General formula (6) General formula (7) General formula (8) General formula (9) General formula (10) General formula (11) General formula (12) General formula (13) General formula (14) General formula (15) In the formula, R ₁ represents a hydrogen atom or a methyl group,
R2 represents a fluoroalkyl group having 1 to 21 carbon atoms, preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms;
R ₃ represents an alkyl group having 2 to 8 carbon atoms in which more than half of the hydrogen atoms are substituted with fluorine,
X ₁ , X ₂ , and X ₃ are each selected from a halogen atom or hydrogen, and always contain one or more fluorine atoms, m represents 0, 1, 2, or 3, and n represents 1 or 2. . Among the monomers represented by the above general formulas, monomers of general formulas (2) to (5) are preferably used. As specific monomers, for example, those listed below can be used.

【table】

〔Effect of the invention〕

Since the carrier of the present invention uses a copolymer containing a monomer having a side chain with a fluorine atom as a monomer component as a material for its coating layer, it has good negative triboelectrification characteristics. In addition, since the aziridinyl groups in the copolymer and the crosslinking agent react to form crosslinks, the resin itself has excellent film-forming properties, and also has good adhesion to the carrier core material, which makes it possible to reduce triboelectrification. Its properties are extremely stable and highly durable.
It has this effect. In addition, since the copolymer of the present invention has high solubility in organic solvents, it also has the effect of being easy to manufacture since a dry spray method or a dipping method can be adopted. In other words, for carriers coated with conventional fluorine-based resins, since fluorine-based resins have low solvent solubility, firing methods were used as a means of fixing the core material and resin in the manufacturing method. There was a drawback. For example, a technology to coat the surface of the carrier core material with a copolymer of tetrafluoroethylene and hexafluoropropylene as a fluorocarbon resin, and an epoxy resin or polyurethane as a modifier (Japanese Patent Application Laid-open No.
47-17435), a non-adhesive fluororesin is bonded to the surface of the core material by blending a cross-linking resin such as epoxy or polyurethane and baking it. Also, in the technique of coating the surface of the carrier core material with a primer containing chromium or phosphoric acid as an adhesive using tetrafluoroethylene as a fluorocarbon resin (see Japanese Patent Application Laid-Open No. 48-90238), In order to improve the adhesive, it is coated with a primer containing chromium and phosphoric acid, and then coated with a fluorine-based resin and fired. Both of these require firing at a high temperature of 300 to 400 degrees Celsius. There were drawbacks in manufacturing, such as the adhesion and the triboelectric properties of the developer changing depending on the temperature conditions. In contrast, the present invention does not have the above-mentioned drawbacks and can exhibit the various effects described above. [Example] Examples of the present invention will be described below, but the present invention is not limited thereto. Example 1 2 parts by weight of the copolymer shown in Exemplary Compound a-(1) as a copolymer and b-(6) (Epicoat) as a crosslinking agent.
152 (manufactured by Ciel Kagaku Co., Ltd.) in a mixed solvent of acetone and methyl ethyl ketone to prepare a coating solution. After coating with 100 parts by weight of "DSP135C" (manufactured by Dowa Iron Powder Industries Co., Ltd.) and heat-treating in an air circulation oven at about 150°C for 5 minutes, the aggregates were sieved to form the carrier of the present invention with a film thickness of about 2 μm. Obtained. 100 parts by weight of the carrier of this invention and styrene.
100 parts by weight of acrylic copolymer "Himer SBM73" (manufactured by Sanyo Chemical Industries, Ltd.), 10 parts by weight of carbon black "Regal 660R" (manufactured by Cabot Corporation), and 3 parts by weight of low molecular weight polypropylene "Viscol 660P" (manufactured by Sanyo Chemical Industries, Ltd.) 2 parts by weight of toner having an average particle size of 10 μm obtained through the steps of kneading, pulverizing, and classifying were mixed in a ball mill to prepare a developer. Using this developer, an electrophotographic copying machine "U −Bix3000” (manufactured by Konishiroku Photo Industry Co., Ltd.)
A live-action test was conducted using a modified machine. As a result, a clear copy image without fog was obtained even after 50,000 continuous copies, and the maximum image density (relative density when the image density of the original image is 2) after this continuous copying was 1.3. . In addition, the charge amount of this developer at the initial stage was 21.4 microcoulombs/g, and even after 50,000 copies, it remained 19.7 microcoulombs/g, showing almost no fluctuation and was found to be an excellent developer. Example 2 In Example 1, copolymer exemplified compound a-(1)
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that a copolymer of exemplified compound a-(2) was used instead. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 3 In Example 1, copolymer exemplified compound a-(1)
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that a copolymer of exemplified compound a-(3) was used instead. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 4 In Example 1, copolymer exemplified compound a-(1)
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that a copolymer of exemplified compound a-(4) was used instead of . Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 5 b-(6) used as a crosslinking agent in Example 1
b-(6) (Epicote 152) instead of (Epicote 152)
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that a carrier of the present invention was used. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 6 b-(6) used as a crosslinking agent in Example 1
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that b-(4) was used instead of (Epicote 152). Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 7 b-(6) used as a crosslinking agent in Example 1
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that b-(2) was used instead of (Epicote 152). Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 8 In Example 1, copolymer exemplified compound a-(1)
A copolymer of exemplified compound a-(5) was used instead of b-(6) (Epicote 152) used as a crosslinking agent.
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that b-(18) (n=2) was used instead of . Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 9 In Example 1, copolymer exemplified compound a-(1)
A copolymer of exemplified compound a-(7) was used instead of b-(6) (Epicote 152) used as a crosslinking agent.
A carrier of the present invention was obtained in exactly the same manner as in Example 1 except that b-(19) was used instead of. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 10 In Example 1, copolymer exemplified compound a-(1)
A copolymer of exemplified compound a-(6) was used instead of b-(6) (Epicote 152) used as a crosslinking agent.
A carrier of the present invention was obtained in exactly the same manner as in Example 1, except that b-(4) (QT-3476, manufactured by Dow Chemical Company) was used instead of. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Example 11 In Example 1, instead of the spherical iron powder "DSP135C" (manufactured by Dowa Iron Powder Kogyo Co., Ltd.) used as the carrier core material, spherical iron powder "Shinto 100M-1" (manufactured by Shinto Blater Co., Ltd.) was used. Except for the above, a carrier of the present invention was obtained in exactly the same manner as in Example 1. Using this carrier, a developer was prepared in the same manner as in Example 1, and a photocopying test was conducted. As in Example 1, good copied images were obtained. Comparative Example 1 The fluorine-containing monomer component and the third component were polymerized to obtain the following copolymer (not containing a monomer component having an aziridenyl group). A coating solution was prepared by dissolving 2 parts by weight of the above copolymer in an acetone-methyl ethyl ketone mixed solvent,
Using this coating liquid, 100 parts by weight of spherical iron powder "DSP135C" (manufactured by Dowa Iron Powder Industries Co., Ltd.) was coated using a fluidized bed method to obtain a comparative carrier having a film thickness of about 2 μm. Using this carrier for comparison, a developer was prepared in the same manner as in the case of the carrier of the present invention in Example 1, and an actual photographic test was conducted. As a result, clear images with no fog were obtained in the initial stage, and the maximum image density at this time was 1.4, but the number of copies was
From around 12,000 sheets, fogging was observed.
Image quality has significantly decreased. When this developer was observed under an electron microscope, it was found that the carrier film had peeled off. Comparative Example 2 A comparative carrier was obtained in exactly the same manner as in Example 1, except that b-(6), a crosslinking agent, was not added to the coating liquid. Using this carrier for comparison, a developer was prepared in the same manner as in the case of the carrier of the present invention in Example 1, and an actual photographic test was conducted. As a result, a clear image with no fog was obtained in the initial stage, with a maximum image density of 1.2, but fogging occurred after 50,000 continuous copies, and the maximum image density at that time was 0.7. It dropped to .

Claims (1)

[Scope of Claims] 1. A carrier for developing electrostatic images, comprising a carrier core material coated with a composition consisting of at least the following (a) and (b). (a) A copolymer whose essential main components are a monomer represented by the following general formula (1) and a monomer having an aziridenyl group ([formula]) in the side chain that can be copolymerized with the monomer. . General formula (1) [In the formula, R represents a hydrogen atom or a methyl group, and
represents an oxygen atom, a COO group, or a CO group, and Rf represents a fluoroalkyl group. ] (b) A crosslinking agent selected from acids, acid anhydrides, epoxies, and amines.