JPH03186856A - Carrier for developer - Google Patents

Abstract

PURPOSE:To improve an electric charge imparting characteristic by forming at least the carrier in such a manner that the carrier has the potassium salt of the boron complex of specific ketocarboxylic acid on the surface. CONSTITUTION:This carrier has at least the potassium salt of the boron complex of the ketocarboxylic acid expressed by formula I on the surface. In the formula I, R1, R2 denote a hydrogen atom, alkyl group and aryl group which may be the same or different. Such carrier is obtd. by coating the core material of the carrier with a coating liquid obtd. by dissolving or dispersing the potassium salt of the boron complex of the ketocarboxylic acid expressed by the formula I together with a coating resin at need in a solvent or dispersion medium. The characteristics to impart charges to a toner are improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a carrier for a developer used in electrophotography and the like.

[Conventional technology]

The electrophotographic method using a two-component developer mixes toner, which is colored resin particles with a colorant dispersed in bound citrus, and a magnetic carrier made of iron powder, ferrite, etc. Supplied onto a developing sleeve with a magnet inside,
A toner image is formed on the photosensitive layer by forming a magnetic brush made of this composition and rubbing the magnetic brush against the photosensitive layer that is separated from the photoconductive material having the electrostatic latent image. The toner acquires a desired triboelectric charge through friction with the magnetic carrier, and the toner on the magnetic brush moves and adheres to the electrostatic latent image on the photosensitive layer due to electrostatic force, and the electrostatic latent image is developed. The toner image on the photosensitive layer obtained by development is transferred onto a transfer material such as transfer paper, and is fixed onto the transfer material by heat or pressure to form an image.

It is important that the toner used to develop electrostatic latent images in electrophotography has charging characteristics controlled to the desired polarity, and for this purpose, a charge control agent is added to the toner particles. is being carried out.

[Problem to be solved by the invention]

However, the charge control agent is easily detached from the toner surface due to friction between the toners and collision with the carrier, which contaminates the carrier surface and deteriorates the charging property.

Further, if the developing operation is repeated for a long period of time, the developer deteriorates and good charge control cannot be performed.

If good charging cannot be performed in this way, problems such as fogging, toner scattering, etc. occur, and resolution and fine line reproducibility deteriorate.

Therefore, in order to solve such problems, it has been proposed to improve the charge imparting characteristics to the toner not only by the charge control agent in the toner but also from the carrier side. That is, various carriers having charge control agents on their surfaces are provided. However, none has yet shown satisfactory performance, and the above-mentioned problems still occur, and there is a need for carriers with further improved charge imparting properties.

As a result of extensive research, the present inventors have discovered that a carrier having a potassium salt of a ketocarboxylic acid boron complex on its surface has excellent charge imparting properties.

Therefore, an object of the present invention is to provide a developer carrier with improved charge imparting properties.

[Structure of the invention]

According to the present invention, the above-mentioned problem is solved by a carrier for a developer characterized in that it has at least a potassium salt of a ketocarboxylic acid boron complex represented by the following formula on its surface.

(In the formula, R and R2 represent a hydrogen atom, an alkyl group, or an aryl group, which may be the same or different.) [Preferred Embodiment of the Invention] The carrier for a developer of the present invention is a ketocarboxylic compound represented by the above-mentioned -formation. It can be obtained by coating a carrier core material with a coating liquid obtained by melting or dispersing a potassium salt of an acid boron complex together with a coating resin as required in a solvent or dispersion medium.

The usage ratio of the potassium salt of the ketocarboxylic acid boron complex represented by the above-mentioned - formation is 0.00001 to 5% by weight, preferably 0.0% by weight, based on the carrier core material described below.
001 to 1% by weight. If the amount used is less than the above range, it will be difficult to give the toner sufficient charging characteristics, and if the amount used is too large, the amount of charging will be too high.
This causes a decrease in image density and carrier adhesion. Also, when used with a coating resin, the coating resin should be 0%
．． It is preferable to use at least 0.001% by weight, especially at least 0.01% by weight.

As the carrier core material used in the present invention, carrier core materials for electrophotographic developers known per se used in this field can be used, such as iron oxide, reduced iron, copper, ferrite, nickel, cobalt. etc., and alloys of these with zinc, alumium, etc., but ferrite-based particles are preferable because their electrical resistance changes little in the environment and over time, and can form soft spikes. For example, Zn-based ferrite, Ni
ferrite, Cu ferrite, Mn ferrite,
Ni-Zn ferrite, Mn-Mg ferrite, C
u-Mg-based ferrite, Mn-Zn-based ferrite,
Examples include Mn-Cu-Zn-based ferrite. Among these, Mn-Cu-Zn ferrite is particularly preferred. The particle size of these core materials is 10 to 200 μm, preferably 30 to 150 μm, and the saturation magnetization is 35 to 7 Qemu/g, particularly 40 to 65 emu/g.
/g is preferably used.

Further, in the present invention, as the coating resin used with the potassium salt of the ketocarboxylic acid boron complex represented by the above-mentioned - formation, a known carrier coating resin is used, such as acrylic resin, styrene resin, polyester resin, One or more of epoxy resin, silicone resin, urethane resin, polyacetal resin, boria resin, polycarbonate resin, phenol resin, vinyl acetate resin, cellulose resin, polyolefin resin, fluorine resin, amino resin, etc. are used in combination. It will be done.

In addition, in the present invention, as a solvent for dissolving the potassium salt of the ketocarboxylic acid boron complex represented by the above general formula, aromatic hydrocarbons such as toluene and xylene, and halogens such as l-lichloroethylene and perchloroethylene are used. Carbonized hydrocarbons, acetones such as acetone and methyl ethyl ketone, cyclic ethers such as tetrahydrofuran, alcohols such as methanol, ethanol, and isopropyl alcohol, etc. can be used, and the concentration of the compound is 1 to 10% by weight. It is preferable that there be. When used together with a coating resin, the coating resin and the compound may be dissolved in the above-mentioned appropriate solvent.

In this case, the resin solution has a resin content of 0.05 to 50% by weight.
, preferably at a concentration of about 0.1 to 40% by weight.

Examples of processing machines used for coating include mixers that are known per se, such as Henschel mixer (manufactured by Mitsui Miike Seisakusho), Type B blender (manufactured by Fuji Powder Co., Ltd.), Nauta mixer (manufactured by Micron Co., Ltd. for wire use), etc. Another method is to apply the obtained solution to the surface of the carrier core material by a method such as a dipping method, a spray method, or a fluidized bed method, and then heat and dry it to evaporate the solvent. After the solvent has evaporated, heat treatment can be further performed for curing.

Further, in the heating and drying steps, it is preferable to perform the heating temperature at a temperature of 30 to 150°C, although this varies depending on the type of solvent. In the curing reaction after heating and drying, generally 80
It is preferable to carry out the reaction at a temperature of 100 to 400°C, particularly 100 to 400°C.

Further, the carrier of the present invention may contain other additives in the coating layer, such as silica, alumina, carbon black, fatty acid metal salts, barium titanate, and the like.

The carrier of the present invention thus obtained has an electrical resistance of 104 to 1014 Ω·cm, particularly 10' to 1012
It is preferable to adjust it within the range of Ω·cm, and it can be adjusted by variously changing the electrical resistance of the carrier core material itself used, the thickness of the coating layer, and the type and amount of additives.

The carrier of the present invention is mixed with a toner, which is a resin particle having a particle size of 5 to 25 μm, in which a known additive such as a coloring agent is dispersed in a known insulating fixing resin. do. The mixing ratio of the carrier and toner of the present invention is preferably adjusted to a range of 99:1 to 85:15. Further, at this time, external additives known per se used in this field, such as silica, alumina, tin oxide, strontium oxide, and various resin powders, can be mixed at the same time to prepare the developer.

[Experiment example]

The present invention will be explained below based on experimental examples.

(Example 1) Potassium salt of a ketocarboxylic acid boron complex represented by the following general formula (1) was mixed with Mn-Cu-Zn having an average particle size of 100 μm.
ferrite core material at a ratio of 1:10,000, and was coated on the surface by stirring for 10 minutes with a V-type blender.

Styrene-acrylic copolymer 85 parts by weight Carbon black 10 parts by weight (Printex L manufactured by Dexa) Charge control agent 2 parts by weight (Nigrosine Base EX manufactured by Orient) Low molecular weight polypropylene 3 parts by weight (Viscol 550P manufactured by Sanyo Kaisha) ) A mixture consisting of the above formulation was premixed using a Henschel mixer, then melt-kneaded using a twin-screw extruder and allowed to cool. This kneaded product was coarsely pulverized with a cutting mill, finely pulverized with an ultrasonic jet mill, and cut to particles with a particle size of 5 μm or less using an Albine classifier to obtain toner with an average particle size of 12 μm in the range of 8 to 15 μm. Ta. This toner and hydrophobic silica (R972 manufactured by Nippon Aerosil 0 Co., Ltd.) were stirred at a ratio of 1000:1 to impart fluidity.

The above carrier and toner were mixed to prepare a developer with a toner concentration of 4.5%, and 1. OOOO0
A printing durability test was conducted on the sheets.

(Example 2) The potassium salt of the ketocarboxylic acid boron complex represented by the general formula CI) and the styrene-acrylic resin were dissolved in toluene at a ratio of 1:100 to obtain a 3% solution. A Ni-Zn ferrite core material having an average particle size of 80 μm was immersed in this solution, and then heated and dried to produce a ferrite carrier whose surface was coated with potassium salt of a boron ketocarboxylic acid complex.

A developer with a toner concentration of 4.5% was prepared using the above carrier and the toner of Example 1, and a developer with a toner concentration of 4.5% was prepared in the same manner as in Example 1.
A printing durability test of 000 sheets was conducted.

(Example 3) A potassium salt of a ketocarboxylic acid boron complex represented by the following general formula (II) was prepared in a ratio of 1:5000 with a Cu-based ferrite core material having an average particle size of 90 μm, and mixed with a Nauta mixer at a ratio of 30 μm. By stirring for several minutes, the surface was coated and a carrier was obtained.

A developer with a toner concentration of 4.5% was prepared using the above carrier and the toner of Example 1, and a developer with a toner concentration of 4.5% was prepared in the same manner as in Example 1.
A printing durability test of 000 sheets was conducted.

(Example 4) A potassium salt of a ketocarboxylic acid boron complex represented by the general formula [■] and a silicone resin were dissolved in xylene at a ratio of 1:50 to obtain a 3% solution. This solution has an average particle size of 10
Spray on 0 μm Mn-Zn ferrite core material,
By heating and drying, a ferrite carrier whose surface was coated with a potassium salt of a boron ketocarboxylic acid complex was produced.

A developer with a toner concentration of 4.5% was prepared using the above carrier and the toner of Example 1, and a developer with a toner concentration of 4.5% was prepared in the same manner as in Example 1.
A printing durability test of 000 sheets was conducted.

(Comparative Example 1) A developer with a toner concentration of 4.5% was prepared using an uncoated Mn-Cu-Zn ferrite carrier with an average particle size of 90 μm and the toner of Example 1, and a developer with a toner concentration of 4.5% was prepared in the same manner as in Example 1.
A printing durability test of 00,000 sheets was conducted.

(Comparative Example 2) A 3% solution obtained by dissolving silicone resin in xylene was sprayed onto a Mn-Zn-based ferrite core material with an average particle size of 100 μm, and the surface was coated with silicone resin by heating and drying. A ferrite carrier was fabricated.

A developer with a toner concentration of 4.5% was prepared using the above carrier and the toner of Example 1, and 100% was prepared in the same manner as in Example 2.
A printing durability test of 000 sheets was conducted.

Table 1 shows the results of the printing durability test of Examples 1 to 4 and Comparative Examples 1 to 2 above. In the table, 100 is 1oooooo,
50 represents 50,000 pieces.

3. As is clear from Table 1, Examples 1 to 4, which used a carrier having a potassium salt of a ketocarboxylic acid boron complex on the surface, had very little fogging and toner scattering, and had excellent fine line reproducibility and resolution. There is. On the other hand, in Comparative Examples 1 and 2, which used carriers that did not have a potassium salt of a boron ketocarboxylic acid complex on the surface, toner scattering and fogging occurred, and fine line reproducibility and resolution were also poor.

〔Effect of the invention〕

According to the present invention, the carrier having the potassium salt of the ketocarboxylic acid boron complex represented by the above general formula on the surface significantly improves the charge imparting characteristics to the toner, reduces the occurrence of fogging and toner scattering, and improves resolution and fine line reproducibility. The decrease in

Claims (1)

[Scope of Claims] A carrier for a developer, characterized in that it has at least a potassium salt of a ketocarboxylic acid boron complex represented by the following general formula on its surface. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (In the formula, R_1 and R_2 represent a hydrogen atom, an alkyl group, or an aryl group, which may be the same or different.)