JPH0578830B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an electrophotographic toner,
More specifically, the present invention relates to a toner that can impart strong positive charging characteristics without adversely affecting the hue of the toner. The present invention also relates to a color toner, particularly a translucent color toner that can be subjected to overlapping development processing and can be advantageously used for producing color copies, transparency for overhead projects, and the like.

(Prior Art and Technical Problems of the Invention) It is important that the charging characteristics of the toner used to develop an electrostatic latent image in electrophotography be controlled to have a polarity opposite to that of the electrostatic image. . For example, in developing a negatively charged image, it is important that the toner particles have positive charging characteristics, and for this purpose, it is necessary to incorporate a positive charge control agent into the toner particles. Most of the conventionally used positive charge control agents are dye-based,
For example, oil-soluble dyes are used, and these dyes inevitably color the toner itself in a unique hue.
In particular, in the case of color toners, the mixing of dyes for charge control into regular colorants has a negative effect on the color tone of the color toners. In some cases, the sharpness of the colors will be lost.

Positive charge control agents that do not exhibit a unique hue are already known; for example, in Japanese Patent Publication No. 53-22447,
It has been proposed to use aminosilane-treated metal oxide powders as positive charge control agents in toners.

(Summary of the Invention and Objectives of the Invention) The present inventors surface-treated vapor phase silica with a specific surface area of 50 m ² /g or more with a vinyl group-containing silane, and then treated it with an amino group-containing ethylenically unsaturated monomer. It has been found that the grafted fine particles exhibit an extremely strong positive charge control effect when incorporated into toner particles, and are also excellent in the sustainability and stability of the positive charge control effect.

That is, an object of the present invention is to provide an electrophotographic toner containing a control agent that has an extremely strong positive charge control effect and is excellent in sustainability and stability of the positive charge control effect.

Another object of the present invention is to provide an electrophotographic toner containing a control agent having the above-mentioned effect without coloring the toner particles in a specific color tone.

Still another object of the present invention is to provide a color toner that has excellent light transmittance and is capable of superimposed development processing.

(Structure of the Invention) According to the present invention, vapor-phase silica having a specific surface area of 50 m ² /g or more is surface-treated with a vinyl group-containing silane,
Next, there is provided an electrophotographic toner characterized by containing fine coated particles formed by graft bonding of an ethylenically unsaturated monomer containing an amino group.

(Characteristics and Effects of the Invention) The present invention employs a two-step reaction method in which vapor phase silica is first reacted with a vinyl group-containing silane and then reacted with an ethylenically unsaturated monomer containing an amino group. This is based on the knowledge that this reaction product exhibits an extremely strong positive charge control effect when incorporated into toner particles, and also has excellent sustainability and stability of the positive charge control effect. .

Vapor-phase silica, commonly known as Aerosil, has one of the smallest particle sizes among various inorganic fillers, has excellent dispersibility in resin binders, and is itself transparent. It has the property of not impairing its sex. Vapor-phase silica, like ordinary amorphous silica, itself has a negative chargeability, while organic compounds containing basic nitrogen atoms generally have a positive chargeability. ing. In the present invention, from this point of view, the surface of the fine amorphous silica particles described above is treated with an organic compound containing a basic nitrogen atom and not itself having a chromophore, that is, amines. It is important for the purpose of the present invention to react the phase-grown silica with a vinyl group-containing silane and then graft polymerize the amino group-containing ethylenically unsaturated monomer using the vinyl group as a polymerization initiation point.

First, the vinyl group-containing silanes used in the present invention are characterized by being easily reactive with silanol groups on the silica surface and having a carbon-carbon double bond that serves as a polymerization initiation point. In this way, if vinyl silane is reacted with vapor-phase silica and then an ethylenically unsaturated monomer containing an amino group is reacted with it, a graft reaction occurs using the double bonds of vinyl silane as polymerization initiation points, and the silica surface By chemically bonding amines to the silica, a high concentration of amino groups can be fixed on the silica surface. Vapor-phase silica has a significantly lower concentration of surface silanol groups than normal amorphous silica, such as wet-process silica, and therefore, when aminosilanes are directly applied, the aminosilanes are chemically fixed. This is considered to be the reason why it is difficult to obtain a sufficiently large positive charge control effect and the connectivity and stability are insufficient.

In contrast, according to the present invention, even when the surface silanol concentration of vapor-phase silica is low and the amount of silanes fixed is relatively small, a large amount of amino groups can be absorbed due to the polymerization initiating properties of vinyl groups. It becomes possible to graft containing monomers and increase the concentration of amino groups chemically bonded to the silica surface.

Furthermore, when the positive charge control agent of the present invention is used, it is free from coloring and has excellent transparency, so it can be advantageously used for translucent color applications. Furthermore, there is an advantage that the amount of expensive silanes used can be reduced, thereby reducing the cost of the charge control agent.

(Preferred Embodiment of the Invention) In the present invention, the vapor-phase silica used has a specific surface area of 50 m ² /g or more, particularly 150 m ² /g or more. This vapor phase silica may be silica alone or may contain some amount of A ₂ O ₃ or TiO ₂ . The particle size of silica particles is
The particle size is desirably within the range of 0.2 μm or less, particularly 0.05 μm or less.

As the vinyl group-containing silane, trichlorosilane or trialkoxysilane having a vinyl group, acryloxyalkyl group, methacryloxyalkyl group, propenylaminoalkyl group, etc. bonded to a silicon atom is used, and suitable examples thereof are as follows. That's right.

Vinyltrichlorosilane, vinyltriethoxysilane, vinyl-tris(β-methoxyethoxy)silane, γ-methacryloxypropyltrimethoxysilane, γ-propenylaminopropyltrimethoxysilane.

The amino group-containing ethylenically unsaturated monomer used in the grafting process is a compound that has both an ethylenically unsaturated monomer such as a vinyl group, an acrylic group, or a methacryl group, and an amino group. The following can be mentioned:

3-aminopropyl acrylate, 3-N,N-diethylaminopropyl acrylate, 3-aminopropyl methacrylate, 3-N,N-diethylamino methacrylate, 3-(2-aminoethyl)aminopropyl methacrylate, 3-(2-N, N-diethylaminoethyl)aminopropyl methacrylate, aminostyrene, dimethylaminostyrene, vinylpyridine, vinylcarbazole, diethylvinylamine.

Surface treatment of vapor phase silica with vinyl group-containing silane is carried out by bringing the silane or its solution into sufficient contact with the silica, and this treatment can be easily carried out by, for example, the stirring pouring method, stirring spray method, etc. It will be held in Grafting of the amino group-containing substance onto vinylsilane-treated silica is easily carried out by allowing the monomer to act in a solvent in the presence of a radical initiator. As the radical initiator, peroxides such as cumene hydroperoxide and di-t-butyl peroxide, and azo compounds such as azobisisobutyronitrile can be used, and the graft reaction is carried out in an inert atmosphere. Although the reaction proceeds satisfactorily at room temperature, the reaction can be accelerated if necessary by heating. The reaction treatment is
They may be carried out sequentially in the same container, or may be carried out in different containers.

The amount of the vinyl group-containing silane added to the vapor-phase silica can vary over a wide range, but is generally in the range of 0.01 to 10% by weight, particularly 0.1 to 5% by weight, based on the silica. The appropriate amount of addition is 0.005 to 5% by weight, particularly 0.05 to 0.5% by weight. Unreacted components are washed,
It can be removed by means such as extraction.

It is also important to use the above-mentioned charge control agent in an amount of 0.1 to 20% by weight, especially 0.2 to 15% by weight, based on the fixing resin; if the amount is less than the above, the desired charge control effect may not be obtained. On the other hand, if the amount exceeds the above range, the light transmittance tends to be impaired.

In the present invention, it is preferable to use organic pigments or dyes with a particle size of 0.2 μm or less, particularly 0.05 μm or less as the colorant, thereby imparting translucency to the final toner image and enabling superimposed development processing. I can do it. Many inorganic pigments have particle sizes considerably larger than the above particle size range and are not suitable for the purpose of the present invention. Furthermore, if the particle size of the organic pigment is larger than the above-mentioned particle size, the light transmittance will be significantly impaired.

The type of organic pigment is not particularly limited as long as it has the above-mentioned particle size, but examples include blue-green phthalocyanine pigments, yellow-red azo pigments,
Metal complex pigments, triphenylmethane pigments, pigments closely related to butt dyes, etc. are used. The organic pigment having the above particle size can be obtained by crystallizing the pigment to form fine crystals in the final stage of pigment production. Furthermore, as the dye, oil-soluble dyes used for coloring plastics are used.

These organic pigments or dyes are preferably used in an amount of 1 to 20% by weight, especially 2 to 15% by weight, based on the fixing resin medium.

As the fixing resin medium, the resins used in the production of this type of toner are used, and particularly preferred are various mono- or diethylenically unsaturated monomers, especially (a) vinyl aromatic monomers. (b) Homopolymers and copolymers of acrylic monomers are used.

Examples of the monomer (a) above include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, etc., and vinylnaphthalene, and examples of the monomer (b) include: Acrylic acid, methacrylic acid, ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 3-
Examples include hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 3-aminopropyl acrylate, 3-N,N-diethylaminopropyl acrylate, and acrylamide.

Other monomers used in combination with these monomers (a) or (b) or alone include butadiene, isoprene, chloroprene, maleic anhydride, fumaric acid, crotonic acid, itacon, etc. Other ethylenically unsaturated carboxylic acids such as acids or their esters, vinyl esters such as vinyl acetate, vinylpyridine, vinylpyrrolidone, vinyl ethers, acrylonitrile, vinyl chloride, vinylidene chloride, etc. can also be mentioned.

The molecular weight of these resins is preferably in the range of 3,000 to 300,000, particularly 5,000 to 200,000.

The above-mentioned colorant and charge control agent are blended with this fixing resin medium along with other blending aids if necessary, and the mixture is uniformly and uniformly kneaded, and then granulated to form a toner. For example, in a method in which the developer is fixed with a heated roll, an offset preventive agent such as silicone oil, low molecular weight olefin resins, various waxes, etc. is added at a concentration of 2 to 15 times per total.
Can be used in amounts of % by weight. In addition, paraffin wax,
Pressure fixing agents such as various animal/vegetable waxes and fatty acid amides may be used in an amount of 5 to 30% by weight based on the total weight.

For granulation, the above-mentioned kneaded composition is cooled, then pulverized and, if necessary, sieved. Of course, there is no particular problem in performing rapid mechanical stirring in order to round off irregularly shaped particles. The particle size of the toner particles is related to resolution, etc., but is generally desirably within the range of 5 to 35 microns.

The toner according to the invention is used as a two-component magnetic developer for color development in combination with a magnetic carrier such as triiron tetroxide, ferrite, iron powder, etc.
It is useful for making clear and translucent multicolor copies.

The invention is illustrated by the following example.

(Example 1) Production of a charge control agent used in the toner of the present invention 1 g of vinyltriethoxysilane was dissolved in a mixed solvent consisting of 200 ml of methanol and 20 ml of water to prepare a treatment solution. 20 g of silica (Aerosil 200: primary particle average diameter 0.012 μm) was dispersed in this, and the mixture was refluxed for about 10 hours. After the reaction, it was washed twice with methanol and dried in a vacuum desiccator for 24 hours. followed by toluene
It was reacted with 0.5 g of dimethylvinylamine in 200 ml (reflux). After the reaction, it was washed twice with toluene and dried in a vacuum desiccator for 12 hours. Finally, it was pulverized to obtain a charge control agent.

Charging characteristics of the toner of the present invention Resin: Styrene resin 100 g Pigment: Butter Yellow O (manufactured by Agfa-Gevaert) 5 g Charge control agent: 5 g of the present invention The above materials were uniformly stirred and mixed in a mixer. This mixture was kneaded at 150℃ using two rolls,
Next, this was coarsely ground using a cutting mill, and then finely ground using a jet mill. Finally, classify and 5~
The toner was 25 μm (average particle size 15 μm).

Apply this toner to an iron powder carrier (manufactured by Nippon Iron Powder).
STV-25T) at a ratio of 1:20 (weight ratio) and stirred to prepare a developer. When the amount of charge of the toner of the present invention was measured by a blow-off method, it was confirmed that the toner was positively and strongly charged (21 μC/g). When the produced yellow developer was set in a modified copying machine DC-161 (manufactured by Sanda Kogyo Co., Ltd.) and a sample document was copied onto an OHP film, a clear image was obtained. At the same time, this copy had excellent translucency, and when used as an original for a projector, a bright yellow image was projected on the screen.

Claims (1)

[Claims] 1. Contains fine coated particles formed by surface-treating vapor-grown silica with a specific surface area of 50 m ² /g or more with a vinyl group-containing silane, and then grafting an amino group-containing ethylenically unsaturated monomer. Toner for electrophotography.