JPS61110161A - Carrier for electrophotography - Google Patents

Abstract

PURPOSE:To increase the increasing rate of electrostatic charge and to eliminate the decrease of electrostatic charge quantity in the stage of running by coating the surface of a core material with a material exhibiting <=20dyne/cm critical surface energy thereby preparing a carrier for electrophotography. CONSTITUTION:A soln. dissolved with (1) a mixture composed of a fluoropolymer and polymer having positive electrostatic chargeability and (2) a random, block or graft copolymer of a fluoromonomer and positive- electrostatic chargeable monomer or the like into a suitable solvent is prepd. The core material is immersed into such soln. and is subjected to desolvating, drying and high-temp. baking to coat the layer exhibiting <=20dyne/cm critical surface energy on the core material by which the carrier for electrophotography is obtd. The amt. of the polymer to be coated on the core material is adequately 0.05-3.0wt%. The core material includes glass beads, aluminum powder, etc. and the powder having about 10-500mu grain size is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing carrier used for developing electrostatic latent images in electrophotography and electrostatic recording. More specifically, the present invention provides a carrier for magnetic brush development, which is composed of a magnetic core material and a coating resin layer, and is excellent in charging properties, surface contamination resistance, mechanical strength, adhesion between the core and the coating layer, etc. It is.

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. A method of attaching and visualizing the image is generally adopted.

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 the former is more immersive when considering developer life, so 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 required characteristics, the coat carriers used in the past still have problems that need to be improved.
No complete version is known at this time. For example, fluorinated vinyl polymers have excellent surface stain resistance, but are negatively charged and have problems in adhesion to the core, and acrylic polymers have poor mechanical strength, adhesion to the core, Although it is satisfactory in terms of positive chargeability, it is said that there is a problem in surface contamination resistance. One of the reasons is that it has the same level as toner, that is, 35 to 45 dyn.
It can be mentioned that it has a critical surface energy of /cII+. In any case, the current situation is that we are forced to use coating materials that have advantages and disadvantages.

In view of the current situation, the present inventors conducted various studies and examinations in order to improve the conventional drawbacks, and as a result, the use of a specific coating material met the various requirements of the coat carrier. The present inventors have discovered that this method is effective in improving properties, and have completed the present invention.

SUMMARY OF THE INVENTION Accordingly, the main object of the present invention is to provide a new magnetic brush development carrier used for developing electrostatic latent images in electrophotography and electrostatic recording.

Another object of the present invention is that since the charging rate is high and the surface contamination resistance is good, the amount of charging does not decrease during running, and as a result, there is no early fogging or internal contamination. Another object of the present invention is to provide a carrier for magnetic brush development that has excellent adhesion between the core material and the coating layer.

Structure of the Invention The above and other objects of the present invention are such that the core material has two surfaces.
This can be achieved by coating with a material that exhibits a critical surface energy of 0 clyn/am or less and at the same time exhibits positive chargeability.

In order to obtain a coating that has both a low critical surface energy coating surface of 2Qdyn/am or less and positive chargeability, the following four methods can be used, but the method by the former champion in particular shows good results with little change over time. give.

■ Mix a fluoropolymer and a positively chargeable polymer to form a coating layer.

(2) Random, block or graft copolymerization of a fluorine-based monomer and a positively chargeable monomer to form a coating layer.

(2) The lower layer is coated with a positively chargeable polymer, and the upper layer is coated with a fluoropolymer layer.

(2) Adding a positive charge control agent to the fluoropolymer and coating it.

Specific examples of monomers constituting a fluoropolymer that provides a critical surface energy of 2Qdyn/cn+ or less include:
For example, tetrafluoroethylene, trifluoromethyltrifluoroethylene, heptafluoropropylethylene, l-
(1-trifluoromethyltetrafluoroethoxymethyl)
Examples include fluorinated alkylenes such as -1-methylethylene, fluorinated acryls such as fluorinated alkyl acrylates, and fluorinated alkyl methacrylates. Considering copolymerizability with other monomers, solvent solubility, etc., these fluorinated acrylic esters are preferred.

More specifically, the following can be used as the fluorinated alkyl acrylate or fluorinated alkyl methacrylate in the present invention.

That is, 1. of acrylic acid or methacrylic acid. l-dihydroperfluoroethyl, 1. l-dihydroperfluoropropyl, l,l-'; hydroperfluorohexyl, l,1-
dihydroperfluorooctyl, 1,1-dihydroperfluorodecyl, I, l-'; hydroper 70 lolauryl,
l, l, 2.2-tetrahydroperfluorobutyl, 1.
1,2.2-tetrahydroperfluorohexyl, 1.1
．． 2゜2-Tetrahydroperfluorobutinope 1,1゜2.2-Tetrahydroperfluorodecyl, 1,1゜2.
2-Tetrahydroperfluorolauryl, l.

1.2.2-tetrahydroperfluorostearyl, 2,
2,3.3-tetrafluoropropyl, 2,2°3.3,
4.4-hexafluorobutyl, ■, 1°ω-trihydroperfluorohexyl, 1,1. ω-trihydroperfluorooctyl, 1,1. 1゜3.3.3-hexafluoro-2-propyl, 3-perfluorononyl-2-acetylpropyl, 3-perfluorolauryl-2-acetylpropyl, N-perfluorohexylsulfonyl-N-methylaminoethyl, N-perfluorohexylsulfonyl-N
-Methylaminoethyl, N-perfluorooctylsulfonyl-N-methylaminoethyl, N-bar70octylsulfonyl-N-ethylaminoethyl, N-perfluorooctylsulfonyl-N-butylaminoethyl, N
-bar 70 decylsulfonyl-N-methylaminoethyl N -/<-fluorodecylsulfonyl-N-ethylaminoethyl, N-bar 70 decylsulfonyl-N-
Ester compounds such as butylaminoethyl, N-per70 lolaurylsulfonyl-N-methylaminoethyl, N-bar70 lolaurylsulfonyl-N-ethylami/ethyl, and N-perfluorolaurylsulfonyl-N-butylaminoethyl are listed. It will be done.

As a specific example of the positively chargeable coating material, as a polymer of an addition polymerizable monomer, a single or copolymer of an acrylic ester, a methacrylic ester, or a nitrogen-containing vinyl heptamer is suitable. Specific examples of acrylic esters and methacrylic esters include acrylic acid, methacrylic acid and alcohols, such as evaporative methyl alcohol, ethyl alcohol, flobyl alcohol, phthyl alcohol, amyl alcohol, heptyl alcohol, heptyl alcohol, and octyl alcohol. , nonyl alcohol,
Alkyl alcohols such as dodecyl alfur, tetradenyl alcohol, hexadenyl alcohol, methoxyethyl alcohol, ethoxyethyl alcohol, ethoxyethyl alcohol, ethquinethyl alcohol, metquinpropyl alcohol, ethquinpropyl, which are partially alkoxylated versions of these alkyl alcohols. Examples include esterification products with alkoxyalkyl alcohols such as alcohol, aralkyl alcohols such as benzyl alcohol, phenylethyl alcohol, and phenylpropyl alcohol, and alkenyl alcohols such as allyl alcohol and crotonyl alcohol.

Further, specific examples of nitrogen-containing vinyl monomers include 2-vinylpyridine, 4-vinylpyridine, 2-vinyl-6-
Methylpyridine, 2-vinyl-5-methylpyridine, 4
-Butenylpyridine, 4-pentylpyridine, N-vinylpiperidine, 4-vinylpiperidine, 4-vinylpiperidine, N-vinyldihydropyridine, N-vinylpyrrole, 2-vinylpyrrole, N-vinylpyroline, N-
Vinylpyrrolidine, 2-vinylpyrrolidine, N-vinyl-2-pyrrolidone, N-vinyl-21,'IJton,
Examples include N-vinylcarbazole. These can be used alone or in combination of two or more.

Specific examples of the positively chargeable condensation polymer include polyamide, cellulose resin, Epoquin resin, silicone resin, and modified products thereof.

Specific examples of the fluoropolymer that is coated on the upper layer to form the release layer include polyvinylidene fluoride, polytetrafluoroethylene, polytetrafluoroethylene-hexafluoropropylene copolymer, and polychlorotrifluoroethylene. , fluorinated silicone resins, fluorinated epoxy resins, fluorinated alkyl acrylate polymers, fluorinated alkyl methacrylate polymers, and the like.

The core materials used in the present invention include glass peas, aluminum powder, iron powder, iron oxide powder, carbonyl iron powder,
Examples include powders such as magnetite, nickel, and ferrite, and usually 10 to 50
A particle size of 0 μm is used.

The carrier particles of the present invention are obtained by surface-treating the magnetic core material as described above with the polymer according to the present invention as described above, and forming a coating layer of the copolymer on the surface of the core material by chemical bonding or adsorption. You can be humiliated by this.

For surface treatment of the core material, for example, the core material is immersed in a solution obtained by dissolving one or more of the above-mentioned polymers in a suitable solvent, followed by desolvation, drying, and high temperature treatment. A method of baking, or a method of suspending the core material in a fluidized bed, spraying the polymer solution, drying, and baking at a high temperature can be used. In these methods, high temperature baking treatment is not necessarily required.

The amount of the polymer coated is usually 0.05 to 3% of the core material.
．． Preferably it is 0% by weight.

The carrier of the present invention thus obtained is mixed with a toner and used as a magnetic brush developer for developing electrostatic latent images.

The toner is not particularly limited and may be any negatively charged toner that has a colorant dispersed in a binder resin and is commonly used in electrophotography.

According to the carrier for magnetic brush development of the present invention, the magnetic core material is coated with a specific polymer (including a copolymer), and various effects such as those described below can be achieved. Become.

First of all, since the charging speed is high and the amount of charging does not decrease during running, there is no early fogging or contamination inside the machine, and the adhesion between the core material and the coating is excellent (internal destruction of the coating layer). (no peeling is observed), mechanical strength is high, and toner contamination is suppressed due to the low surface energy material coating, extending the life of the carrier and the life of the developer. It can be manufactured by a simple process such as spray application of a solution or heat treatment if necessary.

``01'' The present invention will now be explained in more detail with reference to Examples. However, the present invention is not limited to these examples.

Example-1 6 parts by weight of a polymer consisting of 20 parts by weight of N-perfluorooctylsulfonyl-N-aminoethyl methacrylate, 65 parts by weight of methyl methacrylate, and 15 parts by weight of styrene were dissolved in 100 parts by weight of toluene. This solution was coated with an average particle size of 60 μm using a fluidized bed coating device.
The carrier according to the present invention was coated on 1,000 weight IIN of spherical iron oxide powder of m.

Comparative Example A control carrier was obtained in the same manner as in Example 1 except that the use of fluorinated alkyl methacrylate in Example 1 was discontinued and 85 parts by weight of ethyl methacrylate was used.

Example-2 20-weight methacrylic acid ester of 1,1,2,2-tetrahydroperfluorooctyl alcohol! Part, 80 parts by weight of methyl methacrylate triple copolymer! parts, 20 parts by weight of styrene, 80 parts by weight of methyl methacrylate ff1
Dissolve 7 parts of the copolymer R in methyl isobutyl ketone,
This solution was coated with an average particle size of 1 using a fluidized bed coating device.
A carrier according to the present invention was obtained by coating 00 μm spherical iron oxide powder.

1000 of each carrier obtained in Examples-1 to 2 and Comparative Example
A developer was prepared by mixing 30 parts by weight of a negatively charged toner (comprised of a styrene-butyl acrylate copolymer, carbon black, and a chromium complex dye charge control agent). When these developers were subjected to a continuous copying test using Fuji Xerox 4370, the following results were obtained.

The amount of charge is measured using a blow-off measuring device.

The peeling of the coating material and the degree of toner adhesion on the carrier surface were determined by scanning electron microscopy.

The lifespan is 1. Oa is less than 0.7 and white area is 0
．． When the value is 03 or higher, it is determined that the lifespan has expired.

The critical surface energy of various organic liquids is determined by the Zisman
Obtained from Plot.

Claims (1)

[Claims] A positively chargeable electrophotographic carrier characterized in that a core material is coated with a material whose surface exhibits a critical surface energy of 20 dyn/cm or less.