JP2814592B2 - Toner for developing electrostatic images - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a toner for developing an electrostatic image used in the field of electrophotography and the like.

More specifically, the present invention relates to a toner for developing an electrostatic image, which has a good charge stability of a toner in a developing tank, a small change in image density and an excellent durability.

[Prior Art and Problems] Conventionally, as a developer for developing an electrostatic image formed on a latent image holding surface such as an electrophotographic photosensitive member, a two-component developer comprising a carrier and a toner, One-component developers that do not require a carrier are known.

The toner particles that constitute these developers are usually resins,
Colored fine particles containing a colorant or the like as a component.

When a developer composed of these toner particles is repeatedly used in a plain paper copying machine or the like, there is a problem that the amount of triboelectricity of the toner increases and the image density of a copy decreases. As an attempt to remedy these drawbacks, there has been known a method of adding a small amount of a conductive fine powder of a metal, a metalloid, or an oxide thereof as an external additive to a toner.

These substances have a role of suppressing an increase in the amount of charge of the toner particles and always maintaining the image density at a stable level. However, these metals and metalloids and their oxides have an excessively strong polishing action, which may cause unnecessary wear of the photoconductor when cleaning the toner. In other words, streak-like polishing scratches due to the conductive fine powder on the surface of the photoreceptor cause image defects, and the film thickness of the photoreceptor becomes severe, and the electrical or optical performance of the photoreceptor decreases. There was a problem. In addition, there is a problem that these conductive substances are sometimes transferred onto paper and contaminate a copy image.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems of the conventional toner, and an object of the present invention is to provide a toner that can be repeatedly used without unnecessary wearing of the photosensitive member. An object of the present invention is to provide a toner for developing an electrostatic image, which maintains a constant image density without increasing the charge amount of the toner, that is, without lowering the image density, and which does not cause contamination of a copy image.

[Constitution of the Invention] The electrostatic image developing toner of the present invention for achieving the above object contains a binder resin, a colorant, and a charge control agent,
At least a part of the surface of the charge control agent has a volume resistivity of 10
It is characterized by being coated with a conductive material of ⁹ ohm · cm or less.

That is, the gist of the present invention is that the charge control agent itself is directly coated with a conductive substance, instead of using the conductive fine powder or the fine powder having the polarity opposite to that of the charge control agent as an additive to the toner internally or externally. By keeping the charging ability of the charge controlling agent constant at all times, the image density can be remarkably maintained for a long period of time, and the problem that the photosensitive member is deteriorated due to excessive polishing can be solved.

Known charge control agents are used. For positive charging, there are, for example, nigrosine dye, quaternary ammonium salt, polyamine resin, etc.
Metal-containing azo dyes such as o and Al, metal complex salts of alkyl salicylic acid and the like can be used.

If the conductive material that covers at least a part of the surface of these charge control agents has a volume resistivity of 10 ⁹ ohm · cm or less, use metals, metalloids, their oxides, composite oxides, and various combinations of them. There is no problem.
These are appropriately selected depending on the type, particle size, shape and the like of the charge control agent.

Specific examples of the conductive substance that can be used in the present invention include carbon; oxides such as titanium black, tin oxide, and iron oxide; and metals such as gold, copper, iron, and aluminum.

The method of coating the surface of the conductive material according to the present invention may be any method as long as the conductive material adheres to the surface of the charge control agent. Dry methods such as vacuum deposition and sputtering, and wet methods such as electroless plating. Is mentioned. As a wet method, not only the plating method but also an aqueous solution based on chloride metal ions is converted into a complex salt water by a galvanic treatment method, and the raw material particles are mixed with the metal ion aqueous solution and neutralized and reduced with alkali to nucleate the raw material particles. A composite metal oxide surface coating method of forming a metal oxide film on the surface in the form described above is also included. The coating may be performed so as to completely cover the surface of the charge control agent. However, as long as the object of the present invention is attained, the conductive material may cover only a part of the surface.

The surface coating amount of the conductive substance varies depending on the type of the charge control agent serving as the nucleus, the shape and the type of the conductive substance to be coated.
0.01-50 wt%, preferably 0.1-30 wt% is good. If the amount is too small, the effect cannot be exhibited, and if it is too large, the charging ability itself will be lost.

Examples of the binder resin include a styrene resin, an epoxy resin, and a polyester resin.

As the colorant, for example carbon black, T _i O _2,
In addition to inorganic pigments such as red iron oxide, known organic pigments and dyes such as phthalocyanine blue and dialesin red, and dyes and pigments for full-color toner can be used. The amount used is preferably 10 parts by weight or less based on 100 parts by weight of the binder resin.
A one-component magnetic toner may contain a magnetic compound such as magnetite or ferrite, but the amount of use thereof is preferably 30 to 50% by weight based on the total weight.

In the electrostatic image developing toner of the present invention, the charge control agent coated with the conductive material is added in an amount of 7 parts by weight or less, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin.

A general method for producing a toner is performed as follows.

A resin, a colorant, a charge control agent, and the like are uniformly dispersed with a Henschel mixer or the like, and the dispersion is melt-kneaded with a kneader, an extruder, a roll mill, or the like. This is roughly pulverized by a hammer mill, a cutter mill, or the like, and then finely pulverized by a jet mill, an I-type mill, or the like. Further, the finely pulverized material is classified by a dispersion classifier, a zigzag classifier or the like. afterwards,
In some cases, silica or the like is dispersed in the classified substance using a Henschel mixer or the like.

When a two-component developer is obtained, the toner for developing an electrostatic image of the present invention is used by mixing with a carrier. As the carrier, a resin dispersion carrier of iron powder, ferrite powder, magnetite powder, magnetic powder and the like having an average particle diameter in the range of 20 to 200 μm can be preferably used. Iron powder, ferrite powder, magnetite powder and the like may be a coating carrier whose surface is coated with a resin or the like.

The mixing weight ratio of the carrier and the toner is preferably 100: 1 to 10.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples.
The present invention is not limited to these examples.

 In the examples, "parts" represents "parts by weight".

Example A charge controlling agent coated on the surface of a conductive material was prepared by the following method.

Charge control agent (1): Carbon was vapor-deposited on the surface of 1 wt% of chromium-containing azo dye S-34 (manufactured by Orient Chemical) by a vacuum vapor deposition method.

Charge control agent (2): Gold was vapor-deposited on Nigrosine dye BS (manufactured by Orient Chemical) on the surface of 0.5 wt% by vacuum vapor deposition.

Charge control agent (3): chromium alkyl salicylate complex E-
3w carbon by vacuum evaporation on 81 (Orient Chemical)
t% was deposited on the surface.

Charge control agent (4): chromium alkyl salicylate complex E-
Fe ₃ O ₄ to 1 by a wet method which is based on iron chloride ions in 81
0 wt% was applied to the surface.

<Example 1> Styrene-based resin 100 parts Carbon black MA-8 (manufactured by Mitsubishi Chemical) 5 parts Charge control agent (1) 2 parts Polypropylene wax 550p (manufactured by Sanyo Chemical) 2 parts After cooling, the mixture was roughly pulverized using a hammer mill, and then finely pulverized by a pulverizer using an air jet method. The obtained fine powder was classified, and a particle size of 5 to 20 μm was selected to obtain a toner.

To 3 parts of this toner, 97 parts of a carrier (ferrite powder coated with a silicon resin and having a particle size of about 100 μm) were mixed with a V blender to prepare a developer. Using this developer, a continuous actual test was performed using a commercially available dry copying machine using selenium as a photoreceptor, and after 30,000 copies, a clear image with no image density reduction was obtained, and excellent durability was obtained. Was found to have.

The charge amount of the toner in the developer by the blow-off method was -18.3 μC / g at the initial stage and −19.0 μC / g after 30,000 sheets.

Comparative Example 1 A toner was produced in the same manner as in Example 1 except that the charge control agent (1) was changed to the chromium-containing azo dye S-34 in the toner composition of Example 1. Hereinafter, a continuous actual photographing test was performed by the same operation as in Example 1, but the image density decreased after 10,000 sheets. The charge amount of the toner in the developer by the blow-off method is −21.4 μC / g at the initial stage, and −2 after 10,000 sheets.
It changed to 5.8 μC / g.

<Example 2> Styrene-based resin 100 parts Carbon black # 40 (manufactured by Mitsubishi Chemical) 5 parts Charge control agent (2) 2 parts Polypropylene wax 550p (manufactured by Sanyo Chemical) 2 parts Except for the above composition, exactly the same as Example 1 To prepare a toner.

To 4 parts of this toner, 96 parts of a carrier (ferrite powder having a particle diameter of about 100 μm coated with a fluororesin) was mixed in a V blender to prepare a developer. Using this developer, a continuous actual test was performed using a commercially available dry photocopier using an organic photoconductor as a photoreceptor.After 30,000 copies, a clear image was obtained with clear image quality without a decrease in image density. It was found to have durability.

The charge amount of the toner in the developer by the blow-off method was +22.1 μC / g at the beginning and +23.4 μC / g after 30,000 sheets.

Comparative Example 2 A toner was produced in exactly the same manner as in Example 2, except that the charge control agent (2) in the toner composition of Example 2 was changed to the nigrosine dye BS. Hereinafter, a continuous actual photographing test was performed in the same manner as in Example 2, but the image density decreased after 8000 sheets. The charge amount of the toner in the developer by the blow-off method was +23.8 μC / g initially and +27.6 μC / g after 8000 sheets.

<Example 3> Styrene-based resin 100 parts Carbon black MA-8 (manufactured by Mitsubishi Kasei) 4 parts Charge control agent (3) 1 part Polypropylene wax 550P (manufactured by Sanyo Kasei) 2 parts A toner was produced in the same manner.

In the following, a continuous real-photographing test was conducted in exactly the same manner as in Example 1. As a result, it was found that even after 30,000 copies, a clear image with no image density reduction was obtained and excellent durability was obtained. The charge amount of the toner in the developer by the blow-off method is initially −20.6 μC / g, and −21.8 μC / g after 30,000 sheets.
g.

Comparative Example 3 A toner was produced in exactly the same manner as in Example 3, except that the charge control agent (3) was changed to the chromium alkylsalicylate complex E-81. Hereinafter, a continuous actual photographing test was performed by the same operation as in Example 3, but the image density was reduced after 10,000 sheets.

The charge amount of the toner in the developer by the blow-off method was −23.5 μC / g at the beginning and −26.7 μC / g after 10,000 sheets.

<Example 4> Polyester resin 100 parts Anthraquinone dye (CISolvent Red 52) 5 parts Charge control agent (4) 2 parts Except for the above composition, a toner was produced in exactly the same manner as in Example 1.

In the following, a continuous real-photographing test was conducted in exactly the same manner as in Example 1. As a result, it was found that even after 30,000 copies, a clear image with no image density reduction was obtained and excellent durability was obtained. The charge amount of the toner in the developer by the blow-off method is -15.4μC / g at the beginning and -16.2μC / g after 30,000 sheets.
Met.

<Comparative Example 4> A toner was produced in the same manner as in Example 4 except that the charge control agent (4) in the toner composition of Example 4 was changed to the chromium alkylsalicylate complex E-81. Hereinafter, Example 4
A continuous photographing test was performed by the same operation as described above, but the image density decreased after 3000 sheets. The charge amount of the toner in the developer by the blow-off method is -18.7 μC / g at the initial stage and −27.0 after 30,000 sheets.
μC / g.

[Effects of the Invention] As described above, the toner for developing an electrostatic image of the present invention comprises:
Since the charging ability of the direct charge control agent can be stably maintained, the photosensitive member is not unnecessarily worn as in the charge stabilization method by adding an external additive. Therefore, if the toner for developing an electrostatic image of the present invention is used, a developing method having high durability over a long period can be obtained.

Claims (1)

(57) [Claims] 1. An electrostatic image developing toner containing a binder resin, a colorant and a charge control agent, wherein at least a part of the surface of the charge control agent has a volume resistivity of 10 ⁹ ohm · cm or less. A toner for developing electrostatic images, which is coated with a substance.