JPS60208765A - Electrostatic charge image developing carrier - Google Patents

Abstract

PURPOSE:To enhance close adhesion to a core material and mechanical strength and to improve chargeability and uniformity of charge distribution by forming a coating layer made of a copolymer of methyl methacrylate, vinyl pyridine, and a diene compd. on the core material. CONSTITUTION:The surface of the core material is treated with a copolymer made from at least methyl methacrylate, vinyl pyridine, a diene compd., such as 1,3-butadiene, etc., as copolymn. components, and a coating layer is formed on the surface of the core material by the chemical combination or adsorption. Such a coating layer can be obtained by dissolving said copolymer into a solvent, immersing the core material into the obtained soln., and baking it at high temp. The coated carrier thus obtained has superior intimate adhesion between the core material and the coating film, high mechanical strength, low stainability with the toner, and a long carrier life, uniform chargeability, uniform charge distribution, shortened saturation charging time, and sharp charge distribution free from different polarity charge.

Description

[Detailed description of the invention] Industrial applications.

The present invention relates to electrostatic image developing carrier particles used for developing electrostatic latent images in electrophotography and electrostatic recording. More specifically, the present invention provides carrier particles for developing electrostatic images, which are composed of a core and a coating resin and have excellent chargeability and uniformity of charge distribution.

In conventional electrophotography, a photoconductive substance such as selenium is used as a photoreceptor, an electrical latent image is formed using various means, and toner is applied to this latent image using a magnetic brush development method or the like. Generally, a method is adopted in which the material is attached and visualized.

In this development process, carrier particles called carriers are used to impart an appropriate amount of positive or negative electricity to the toner. Carriers are generally classified into coated carriers and non-coated carriers, but since the former is superior when considering developer life, various types of coated carriers have been developed and put into practical use. has been done.

There are various characteristics required for coat carriers, but
Particularly important properties include appropriate chargeability, impact resistance, abrasion resistance, good adhesion between the core and coating material, and uniform charge distribution.
Examples include gender.

Considering the above-mentioned H required characteristics, the coated carriers that have been used in the past still have problems that need to be improved.
No complete version is known at this time. For example, fluorinated vinyl primers have excellent chargeability, but
There are problems with adhesion to the core, and acrylic/
Although IJmers are satisfactory in terms of mechanical strength and adhesion to the core, they are said to have problems in charging properties.

In any case, the current situation is that we are forced to use coating materials that have advantages and disadvantages.

Purpose of the Invention In view of the current situation, the present inventors have conducted various studies and examinations to improve the various drawbacks of the conventional art, and have found that the use of a specific coating material can improve the various required characteristics of the coated carrier. The present invention has been completed based on the discovery that the method is effective in the following.

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide a carrier for developing electrostatic images which has improved the above-mentioned conventional drawbacks, particularly in chargeability, uniformity of charge distribution, strength, and adhesion to the core.

Structure of the Invention These and other objects of the invention can be achieved by treating the core material with a copolymer containing at least methyl methacrylate, vinyl pyridine and diene as copolymer components.

That is, the present invention relates to a carrier for developing electrostatic images comprising a core material and a coating layer thereon of a copolymer containing at least methyl methacrylate, vinylpyridine and a diene as copolymer components.

The proportions of each copolymer component of the coating material are methyl methacrylate deff, q~gQ weight t, vinylpyricine θ, l~
It is preferable that lθ weight fc and diene/-10' @ weight.

The coating material of the present invention can contain monomer components other than those mentioned above, and the proportion thereof is preferably up to 30% by weight.
The amount used is within the above range, and therefore the amount of other monomer components added corresponds to the reduced amount of methyl methacrylate.

In the present invention, vinylyl pyridine includes, for example, corvinylpyridine, darpinylpyridine, corvinyl-6-
Examples include methylpyridine, cobinyl-S-methylpyridine, couptenylpyridine, and gouhentenylpyridine.

In addition, the diene components include /, 3-butadiene, /, 3
Examples include -pentadiene, -1methyl-1, 3-butadiene, co,3-dimethyl-1,3-butadiene, co,couhexadiene, 3-methyl-141-hexazoe, and the like.

Furthermore, other monomer components include styrene derivatives,
For example, styrene, methylstyrene, dimethylstyrene,
Alkylstyrenes such as trimethylstyrene, ethylstyrene, dimethylstyrene, triethylstyrene, propylstyrene, butylstyrene, hexylstyrene, heptylstyrene, octylstyrene, fluorostyrene,
Chlorostyrene, glomosterene, dimethylstyrene,
Halogenated styrenes such as mead styrene, Nido-n-styrene, acetylstyrene, methoxystyrene, etc.; Unsaturated cardanic acids such as acrylic acid, methacrylic acid, α-
Addition-polymerizable unsaturated aliphatic monocarps such as ethyl acrylic acid, crotonic acid, α-methyl crotonic acid, α-ethyl crotonic acid, isocrotonic acid, tiglic acid, and ungellic acid? Addition-polymerizable unsaturated aliphatic dicardic acid such as phosphoric acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, mesaconic acid, glutaconic acid, dihydromuconic acid; the addition-polymerizable unsaturated carnic acid and alcohol, 1' lJ, t hamethyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol, amyl alcohol, hexyl alcohol, heptyl alcohol, octyl alcohol,
Alkyl alcohols such as nonyl alcohol, dodecyl alcohol, tetradecyl alcohol, and hexadecyl alcohol, halodanated alkyl alcohols obtained by partially converting cholera alkyl alcohols, methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethoxyethyl alcohol, methoxypropyl alcohol,
Esters of alkoxyalkyl alcohols such as ethoxyethyl alcohol, aralkyl alcohols such as benzyl alcohol, phenylethyl alcohol, phenylpurpyl alcohol, alkenyl alcohols such as allyl alcohol and crotonyl alcohol; amides and nitriles derived from; and olefins, e.g.
! --, ychloroethylene, l,2-dibromoethylene, l,2-short ethylene, ingropenyl chloride, isozobenyl bromide, allyl chloride, allyl bromide, vinylidene chloride, vinylidene fluoride, vinyl fluoride, and other halogens aliphatic olefins, etc. can be used. These monomers can be used alone or in combination of 21i or more.

On the other hand, the core materials used in the present invention include iron oxide powder,
Examples include carbunyl iron powder, chromium dioxide, metal powders such as iron, nickel, and cobalt, particles such as glass beads, magnetite, and ferrite, which are commonly used as core materials for carrier particles for developing electrostatic images. Generally, those having a size of about 0 to 00 μm are used.

The carrier particles for developing electrostatic images of the present invention are prepared by surface-treating the core material as described above with the copolymer containing at least methyl methacrylate, vinylpyricine, and diene as copolymer components, and forming a chemical bond or bond on the surface of the core material. It can be obtained by forming a coating layer of the copolymer by adsorption.

The molecular weight (Mn) of the copolymer is 5.00θ to 10O1
θOθ is preferably in the range of 70.000 to go, ooθ.

For surface treatment of the core material, for example, the copolymer produced as described above is dissolved in a suitable solvent, the core material is immersed in the resulting solution, and then the solvent is removed, dried, and baked at high temperature. Alternatively, a method can be used in which the core material is suspended in a fluidized bed, sprayed with a copolymer solution, dried, and baked at a high temperature. In these methods,
Although high-temperature baking treatment is not necessarily required, from the viewpoint of increasing the adhesion strength between the core material and the copolymer coating, it is preferable to perform high-temperature baking treatment at about IO θ to 200 oc.

The amount of the copolymer coated is preferably about 0.0[theta]/~0.5 parts by weight based on 700 parts by weight of the core material.

The carrier of the invention thus obtained is mixed with a toner,
Used as a developer for electrostatic latent images.

As the toner, any toner in which a colorant is dispersed in a binder resin and which is commonly used in electrophotography can be used, and there is no particular limitation.

Effects of the invention The carrier of the invention makes it possible to achieve various effects based on the coating of the core particles with specific copolymers. First, compared to conventional coated carriers, it is superior in chargeability and uniformity of charge distribution, that is, the charging saturation time is significantly shortened, and the charge distribution is sharp and does not contain charges of different polarity. Further, since the adhesion between the core material and the coating is excellent, the mechanical strength is high, and contamination by toner is suppressed based on the coating, the carrier has a long life, and as a result, a developer with a long life can be obtained. Further, the carrier of the present invention can be manufactured by a simple process such as immersion in a solution or spray application of a solution, or, if necessary, heat treatment.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. However, the present invention is not limited to these Examples in any way.

Example-7 Iron powder with an average particle size of 100 μm was mixed with methyl methacrylate/
Vinylpyridine/butadiene copolymer (copolymerization ratio 93.
! ; l/, θ+5. , t) to serve as a carrier. The coating amount is 0.00 parts by weight per 700 parts by weight of carrier.
It was 1 part by weight. Styrene/butyl methacrylate copolymer (copolymerization ratio 6θ:1) was added to 100 parts by weight of this carrier.
Io) qo weight% and car? Toner 3 with an average particle size of 72 μm and consisting of 10% by weight of black! A certain amount was mixed to prepare a developer.

When this developer was used to perform magnetic brush development on a photoreceptor on which an electrostatic latent image had been formed, copies with high image density and little capri were obtained. A further 50,000 copies were made, but there was no change in image density or fog from the initial state. When the surface of the carrier was observed after copying 50,000 copies, no peeling of the coating agent occurred, and no adhesion of toner to the surface of the carrier was observed.

Table 1 shows the results of examining the triboelectric charging properties of this developer.

Example - Methyl methacrylate as a carrier coating material)/4!
-Vinylpyridine/butadiene/styrene copolymer (copolymerization ratio S'!, 0:6.Ot 10.0 + 301
The same procedure as in Example-/ was carried out except that . The image after 50,000 copies had good image density and fog, and was unchanged from the initial image. Moreover, neither peeling of the coating material nor adhesion of toner was observed.

Comparative Example: The same procedure as Example 1 was carried out except that a methyl methacrylate polymer was used as the carrier coating material.

The image density began to decrease and the fog density began to increase after making too many copies, and at 2,000 copies, both the image density and the capri density exceeded the allowable limits. When the carrier was observed at this time, peeling of the coating material and adhesion of the toner were observed.

Claims (1)

[Claims] A carrier for developing an electrostatic image, comprising a core material and a coating layer thereon of a copolymer containing at least methyl methacrylate, vinylpyricine and a diene as copolymer components.