JP3164453B2 - Toner for developing electrostatic images - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toner for developing an electrostatic image (electrostatic latent image) such as electrophotography and electrostatic recording.

[0002]

2. Description of the Related Art Originally, an electrostatic latent image can be developed and visualized by applying toner by its electrostatic attraction. Agents are widely used. This dry developer
A toner having an average particle diameter of 10 to 15 μm in which a colorant, a charge control agent, a fluidizing agent, and the like are dispersed in a natural resin or a synthetic resin;
An average particle obtained by dispersing a two-component developer composed of a mixture of a carrier such as iron powder or ferrite powder of 0 to 200 μm and a colorant, a charge control agent, a fluidizing agent, a magnetic substance, and the like in a natural resin or a synthetic resin. It can be roughly classified into a one-component developer consisting of only a toner having a diameter of 7 to 10 μm.

[0003] A two-component developer achieves development by causing toner charged by friction with a carrier to adhere to an electrostatic latent image, and a one-component developer includes a toner instead of a carrier. Brush-like with the same function as
A toner charged by friction with a plate-shaped friction member is known, and recently, a toner charged by mutual friction with the magnetic fine powder while keeping the magnetic fine powder in a dispersed state is known. I have. Thus, these developing toners maintain positive or negative charges according to the polarity of the electrostatic latent image to be developed. In order for the toner to retain the charge,
It has also been proposed to utilize the triboelectricity of the resin, which is the main component of the toner. However, in this method, the resulting image is easily fogged and unclear because the toner has a small chargeability and a large solid surface resistance. It becomes something.

[0004] In order to impart a desired triboelectrification property to a toner, one of the practical applications in the art today is to apply a positive charge to the toner.
There is a nigrosine-based oil-soluble dye and the like shown in JP-A-1-2427 and the like, and when a negative charge is imparted, JP-B-41-20153, JP-B-43-17955, and JP-B-45-175. No. 26478, and the like.

[0005]

With these charge control agents, the function of simply applying charge is not sufficient, and it is required to control the charge amount of the toner to a constant value. It is necessary that the toner be controlled so that it is always triboelectrically charged to a constant charge amount under any environment and during long-term use, and as a result, a stable and high-quality image is obtained. Therefore, the conventional toner cannot satisfy the above various requirements, and a charge control agent is required to be improved.

Accordingly, it is an object of the present invention to provide a toner which is excellent in durability and can always obtain a stable image even when used continuously for a long period of time. It is another object of the present invention to provide a charge control agent which has a quick charge rise and provides a high quality image which is stable from the beginning.

[0007]

According to the present invention, in a toner for developing an electrostatic image comprising at least a binder resin, a colorant and a charge control agent, the charge control agent comprises a rhodamine dye and an extender pigment. A lake pigment having a ratio (weight ratio) of the dye to the extender pigment of 0.1 to 1 obtained by the synthesis, and the charge control agent is 0 to 100 parts by weight of the binder resin. 0.05 to 10 parts by weight of the toner for developing an electrostatic image.

Hereinafter, the toner for developing an electrostatic image of the present invention will be described in detail. In the present invention, a laked pigment is used as a charge control agent, and the constituent components of the pigment include a dye, an extender pigment, and a precipitant, and the ratio (weight ratio) of the dye to the extender pigment is set to 0. 1 to
1, and the ratio of the charge control agent in the toner is in the range of 0.05 to 10 parts by weight with respect to 100 parts by weight of the binder resin.
The extender includes clay, gypsum, zinc white, lithopone, lead white, and the like. In the present invention, at least one selected from aluminum hydroxide, barium sulfate, and calcium carbonate may be used as the extender. preferable.

[0009] Specific reaction steps for constitutional synthesis and lake formation are described below. As a general reaction mode, a sulfate band, barium chloride, and sodium carbonate are reacted to synthesize aluminum hydroxide and barium sulfate, and rhodamine, a dye, is added thereto to form a constitution. Further, after phosphorus, tungsten and molybdic acid are added as a precipitant to form a lake, the precipitate is filtered, washed with water, dried, pulverized and toned to obtain a lake pigment. Stability as a charge control agent can be obtained by setting the proportion of the dye in the range of 0.1 to 1 (weight ratio) of barium sulfate and aluminum hydroxide as extenders in the above reaction step. Becomes It is presumed that by increasing the amount of the extender pigment that is insoluble in water, the water content of the finished lake pigment is controlled to be low, and as a result, the charge stability as a charge control agent is obtained.

The ratio of the dye to the extender (weight ratio)
If it is less than 0.1, characteristics as a lake pigment cannot be obtained, and as a result, there is no charge stability. If the ratio exceeds 1, the constitutional reaction becomes insufficient,
The water content of the finished lake pigment increases, and the charge stability as a charge control agent cannot be obtained. Further, the ratio of the charge control agent used in the present invention in the toner is in the range of 0.05 to 10 parts by weight with respect to 100 parts by weight of the binder resin, but is less than 0.05 part by weight. On the other hand, it is difficult to obtain the charging stability and the charging start-up characteristic, which are the objects of the present invention. Conversely, if it exceeds 10 parts by weight, it will be added more than necessary, resulting in poor dispersion in the binder resin.

The binder resin used in the present invention includes polystyrene, styrene / acrylic acid copolymer, styrene / methacrylic acid copolymer,
Styrene / acrylate copolymer, styrene / methacrylate copolymer, styrene / butadiene copolymer, saturated polyester resin, unsaturated polyester resin, epoxy resin, phenol resin, maleic acid resin,
Coumarone resins, chlorinated paraffins, xylene resins, vinyl chloride copolymers, and mixtures thereof.

Further, additives can be added to the toner of the present invention as needed. As an additive, for example, Teflon, a lubricant such as zinc stearate, or a polishing agent such as cerium oxide, silicon carbide, strontium titanate, or a fluidity imparting agent such as colloidal silica, aluminum oxide, or a low molecular weight polyethylene, There are fixing aids such as low molecular weight polypropylene and various waxes.

When the toner of the present invention is used as a two-component developer, it is used by mixing with a carrier powder.
In this case, the mixing ratio of the toner and the carrier powder is preferably 0.5 to 10% by weight, particularly 2 to 4% by weight as the toner concentration. As the carrier that can be used in the present invention, all known carriers can be used, for example, iron powder, ferrite powder,
Examples include magnetic powders such as nickel powder, glass beads and the like, and those obtained by treating the surfaces thereof with a resin or the like.

The coloring agents used in the present invention include:
Any suitable pigment or dye is used. Toner colorants are well known, for example, carbon black as a pigment,
Examples include aniline black, acetylene black, naphthol yellow, hansa yellow, rhodamine lake, alizarin lake, bengalara, phthalocyanine blue, and indanthrene blue. These are used in an amount necessary and sufficient to maintain the optical density of the fixed image.
0.1 to 20 parts by weight, preferably 2 to 10 parts by weight per part by weight
Good addition amount by weight. A dye is further used for the same purpose. For example, there are azo dyes, anthraquinone dyes, xanthene dyes, methine dyes and the like, and the addition amount is preferably 0.1 to 3 parts by weight based on 100 parts by weight of the binder resin.

In order to prepare the toner for developing an electrostatic image according to the present invention, a resin composition, a charge control agent and a pigment or dye as a colorant, additives, and the like are thoroughly mixed by a ball mill, a super mixer, or another mixer. And then the heating roll,
Melting, kneading and kneading using a hot kneader such as a kneader or extruder, dispersing or dissolving the pigments or dyes while the resins are mutually compatible, cooling and solidifying, pulverizing and classifying and then averaging. A toner having a particle size of 5 to 20 μm can be obtained.

Hereinafter, the present invention will be described in more detail with reference to Examples, but this does not limit the present invention in any way.
All parts in the following formulations are parts by weight.

Example 1 Aqueous solution of rhodamine dye 100 parts Extender pigment (BaSO ₄ , Al (OH) ₃ ) 150 parts After the above composition was synthesized at room temperature, phosphorus, tungsten and molybdic acid were used as a lake-forming agent. A 1.2-fold molar amount is added to the dye and laked at 90 ° C. The resulting precipitate is filtered, washed with water, dried, pulverized and toned to obtain the desired lake pigment (charge control agent).

To 1 part of the obtained charge control agent, 100 parts of polyester resin, 10 parts of carbon black and 1 part of low molecular weight polypropylene are added, mixed well, melt-kneaded by a hot roll mill, cooled, and coarsely ground by using a hammer mill. Then, the mixture is finely pulverized by an air jet type pulverizer. The obtained fine powder was classified to have a particle size of 5 to 15 μm, and then 0.1 part of titanium oxide was mixed with 100 parts of the classified toner to obtain a toner. A developer was prepared by mixing 2.1 parts of the toner and 97.9 parts of spherical ferrite powder coated with a silicon resin and 0.002 parts of titanium oxide as an additive.

Using this developer, repeated copying of 100,000 sheets was performed with a copying machine FT-4830 manufactured by Ricoh Co., Ltd., but the image was clear from the beginning and no deterioration in copy quality was observed. Further, the change in the charge amount of the developer was also gradual. The charging rise of this toner was measured as follows. That is, the toner and the carrier were mixed so that the toner concentration became 2.1%, and the mixture was stirred for a certain period of time in a ball mill pot, the toner was taken out, and the toner was blown with a blowing device to measure the charge amount. Table 1 shows the amount of charge at that time.
Shown in

Example 2 A lake was formed in the same manner as in Example 1 except that the amount of the extender in Example 1 was changed to 300 parts to obtain a desired charge control agent. A mixture of a polyester resin and a styrene / acrylic copolymer in 0.5 part of the obtained charge control agent was used.
After 0 parts, 10 parts of carbon black and 1 part of low molecular weight polypropylene were added and mixed well, kneading, pulverization, classification and mixing were carried out in the same manner as in Example 1 to obtain a toner having a particle size of 5 to 15 μm. 2.0 parts of this toner was mixed with 98 parts of spherical ferrite powder coated with a silicone resin and 0.002 parts of hydrophobic silica to prepare a developer.

Using this developer, a copying machine F manufactured by Ricoh Co., Ltd.
Repeated copying of 100,000 sheets was performed at T-4820, but the image was clear from the beginning, and no deterioration in copy quality was observed. Further, the change in the charge amount of the developer was also gradual. Table 1 shows the charging rise.

Example 3 To 2 parts of the charge control agent obtained in Example 1, 80 parts of a polyester resin, 20 parts of a styrene / acrylic copolymer, 8 parts of carbon black and 2 parts of low molecular weight polypropylene were added, and mixed well. In the same manner as in Example 1, kneading, pulverization, classification, and mixing were performed to obtain a toner having a particle size of 5 to 15 μm. 2.0 parts of the toner was mixed with 98 parts of spherical ferrite powder coated with a silicone resin and 0.002 part of titanium oxide to prepare a developer.

Using this developer, in the same manner as in Example 1,
Repeated copying was performed, but the image was clear from the beginning, and no reduction in copy quality was observed.

Comparative Example 1 A lake was formed in the same manner as in Example 1 except that the amount of the extender in Example 1 was changed to 80 parts to obtain a desired charge control agent. To 1 part of the obtained charge control agent, 80 parts of the same polyester resin as in Example 2, 20 parts of a styrene / acrylic copolymer, and 12 parts of carbon black were added and mixed well.
Kneading, pulverizing, classifying and mixing in the same manner as in Example 1, 5 to 15
A toner having a particle size of μm was obtained.

When this toner was repeatedly copied in the same manner as in Example 1, a good image was obtained in the initial copy, but an unclear copy image was obtained after 50,000 continuous copies.

Comparative Example 2 A kneading, pulverization, classification, mixing, and mixing were carried out in the same manner as in Example 3 except that the amount of the charge control agent in Example 3 was changed to 0.03 parts. When this toner was repeatedly copied in the same manner as in Example 1, a good image was obtained in the initial copy, but the image became unclear after 30,000 continuous copies, and the charge amount of the developer was reduced. .

The results of the examples of the present invention are listed in Table 1 below.

[Table 1]

[0028]

According to the first aspect of the present invention, the toner for developing an electrostatic charge image uses a specific pigment as an extender in the production process of the charge control agent to be used, and adjusts the ratio of the dye to the extender within a specific range. By controlling the water content of the resulting lake pigment, a stable product can be obtained. Further, the charge control agent is added to the toner at a specific ratio, so that the charge stability is good and the durability is good. It is excellent in performance and can always obtain a stable image even when used continuously for a long time. In addition, since the charging rises quickly, a stable image free from background contamination can be obtained from the beginning.

In the toner for developing an electrostatic charge according to the second aspect, since a specific extender is selected, a high-performance charge control agent can be easily obtained, and as a result, the charge stability becomes better.

Claims (2)

(57) [Claims] 1. An electrostatic image developing toner comprising at least a binder resin, a colorant and a charge control agent, wherein the charge control agent is obtained by synthesizing a rhodamine dye and an extender pigment. Ratio to extender pigment (weight ratio)
Is in the range of 0.1 to 1 and the charge control agent is 0.1 to 100 parts by weight of the binder resin.
A toner for developing an electrostatic image, which is contained in an amount of from 0.05 to 10 parts by weight. 2. The extender pigment is aluminum hydroxide,
2. The electrostatic image developing toner according to claim 1, wherein the toner is at least one selected from barium sulfate and calcium carbonate.