JP2870846B2 - Two-component developer for electrostatic image development - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a two-component developer for developing electrostatic images used in the field of electrophotography and the like. More specifically, the present invention relates to a two-component developer for developing an electrostatic image, which has good charge stability of a toner in a developing tank and little change in image density and excellent durability.

[Prior art] Conventionally, a two-component developer composed of a carrier and a toner and a carrier are required as a developer for developing an electrostatic image formed on a latent image holding surface such as an electrophotographic photosensitive member. One-component developers are known.

The toner particles that constitute these developers are usually resins,
Colored fine particles containing a colorant, a charge control agent and the like as components.

When a developer composed of these toner particles is used repeatedly in a plain paper copying machine or the like, there is a problem that the frictional charge amount of the toner is not stabilized, and the image quality of a copy is lowered, the image density is lowered, and fogging occurs. As attempts to improve these disadvantages, for example, a method of coating a carrier with various resins, a method of adding an oxide dielectric fine powder such as SiO ₂ as an external additive, and the like are known.

[Problems to be Solved by the Invention] However, in the two-component developer for developing an electrostatic image, there is a problem that the carrier coated with the resin has a high resistance, so that the edge effect is strong and the solid portion is not uniform. I have.
In addition, in the case of adding oxide dielectric fine powder, the fluidity of the developer is increased and image quality without image unevenness is obtained. However, since the oxide dielectric fine powder itself has a relatively strong chargeability, toner While it is effective for improving the charging characteristics of the toner, when added to a toner having the same polarity, the image density decreases, and when added to a toner having the opposite polarity, fog and toner scattering may occur. Had difficulties.

[Object of the Invention] The present invention has been made to solve the above-mentioned problems of the conventional two-component developer for developing an electrostatic image, and an object thereof is to improve the fluidity of the toner and the developer. Improves the image quality and keeps the toner charge amount stable during repeated use, that is, maintains a constant image density without causing a change in image density, and reduces fog and toner scattering to copy images. An object of the present invention is to provide a two-component developer for developing an electrostatic image which does not cause contamination.

Means for Solving the Problems In order to achieve the above object, the present invention is directed to coating a toner for developing an electrostatic image containing a binder resin and a colorant with a toner containing an oxide dielectric fine powder and a resin. In a two-component developer for developing an electrostatic image, which is obtained by mixing a carrier material, the particle diameter of the oxide dielectric fine powder is 0.005 to 3.0 μm, and at least a part of the surface of the fine powder has a volume. General formula MO · nFe ₂ O _{3 with a} specific resistance of 10 ⁹ ohm · cm or less (where n is a number from 1 to 6, M is Fe, Zn, Mg, Mn, Cu, Ba, Ni, Co or Cd ) Is covered with one or more compounds represented by the following formula:

(Function) The two-component developer for developing a positive charge image of the present invention is obtained by coating a specific conductive substance on the surface of an oxide dielectric fine powder which is usually used for the purpose of improving fluidity. The feature is that the chargeability is suppressed without impairing the effect of improving the fluidity of the body, the chargeability of the toner is always stable, the image density can be kept extremely stable for a long time, and the image quality is deteriorated Problem was solved. Known oxide dielectric fine powders are used. For example, SiO ₂ , TiO ₂ , Al ₂ O ₃ , BaTiO ₃ , SrTiO _3, etc., which have been widely used as a fluidity improving agent of a conventional toner, can be used.

The dielectric substance covering the surface of these oxide dielectric fine powders has a general formula of MO · nFe ₂ O ₃ having a volume resistivity of 10 ⁹ ohm · cm or less.
(Where n is a number from 1 to 6, M is Fe, Zn, Mg, Mn,
As long as it is a compound represented by Cu, Ba, Ni, Co or Cd), there is no problem even if oxides, composite oxides and various combinations thereof are used. These are appropriately selected depending on the type, particle size, shape, and the like of the oxide dielectric.

In the specification of the present application, a substance having a volume resistivity of 10 ⁹ ohm · cm or less is referred to as a conductive substance.

As a surface coating method using a conductive substance according to the present invention, for example, an aqueous solution based on chloride metal ions is converted into complex salt water by a galvanic treatment method, raw material particles are mixed into the metal ion aqueous solution, and then neutralized with alkali. There is a composite metal oxide surface coating method or the like in which a metal oxide is formed on the surface in the form of reducing the raw material particles as nuclei. In any case, a method capable of covering at least a part or the entire surface of the oxide dielectric surface can be adopted.

The particle diameter of the oxide dielectric is 0.005 to 3.0 μm, and preferably 0.01 to 1.0 μm. If it is too fine, the chargeability becomes too high, and the roller does not function as a roller for improving the fluidity of the toner. On the other hand, if it is too large, the problem of scattering occurs.

The surface coating amount of the conductive material depends on the type of oxide dielectric serving as a nucleus, the shape and the type of conductive material to be coated, but usually 0.01 to 50 wt. %, Preferably 0.1 to 30% by weight. If the amount is too small, the effect cannot be exhibited, and if it is too large, the conductivity becomes too large and the image quality deteriorates.

Various types of binder resins can be used as the binder resin of the toner component. Examples thereof include polystyrene, chloropolystyrene, poly-α-methylstyrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, and styrene-butadiene copolymer. Copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer (styrene-methyl acrylate copolymer, styrene-ethyl acrylate copolymer) Polymers, styrene-butyl acrylate copolymer, styrene-octyl acrylate copolymer, styrene-phenyl acrylate copolymer, etc.), styrene-methacrylic ester copolymer (styrene-methyl methacrylate copolymer, Styrene-ethyl methacrylate copolymer, styrene-methac Le butylmethacrylate copolymers and styrene - phenyl methacrylate copolymer), styrene -
α-methyl methacrylate copolymer and styrene
Styrene resins such as acrylonitrile-acrylic acid ester copolymers (homopolymers or copolymers containing styrene or styrene substituents), vinyl chloride resins, rosin-modified maleic resins, phenolic resins, epoxy resins, polyester resins, High molecular weight polyethylene, low molecular weight polypropylene, ionomer resin, polyurethane resin, silicone resin, ketone resin, ethylene-ethyl acrylate copolymer, xylene resin, polyvinyl butyral resin, etc. Base resin, saturated or unsaturated polyester resin and epoxy resin.
In addition, the above resins are not limited to being used alone, and two or more resins can be used in combination.

The charge control of the toner may be performed by the binder resin or the colorant itself, but if necessary, a charge control agent including a known one may be used. For example, there are nigrosine dyes for positive charging, quaternary ammonium salts, polyamine resins and the like, and for negative charging Cr, Co, metal-containing azo dyes such as Al,
Metal salts of alkylsalicylic acid and the like are known. The amount used is preferably 0.1 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the binder resin. The charge control agent may be used in a form mixed with the binder resin or attached to the surface of the toner particles.

As a coloring agent, for example, carbon black, TiO 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 0.1 to 30 parts by weight, more preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the binder resin.

In the two-component developer for developing an electrostatic image of the present invention, the oxide dielectric fine powder surface-coated with a conductive substance is not more than 1 part by weight, more preferably not more than 1 part by weight, based on 100 parts by weight of the toner.
It is preferable to add in the range of 0.05 to 0.5 part by weight.

In addition, auxiliary agents such as various plasticizers and release agents can be added to the toner for the purpose of adjusting thermal characteristics, physical characteristics, and the like. The addition amount is suitably from 0.1 to 10 parts by weight based on 100 parts by weight of the binder resin.

A general method for producing a two-component developer for developing an electrostatic image 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. Subsequently, the finely pulverized material is classified by a dispersion classifier, a zigzag classifier or the like. afterwards,
External additives such as oxide dielectric fine powder are dispersed in the toner particles as a classifier using a Henschel mixer or the like. Further, depending on the case, a process of embedding the oxide dielectric fine powder into the toner particles to some extent may be performed using a hybridizer or the like.

As the carrier used in combination with the toner for developing an electrostatic image of the present invention, iron powder having an average particle diameter in the range of 20 to 200 μm, ferrite powder, magnetite powder, magnetic powder resin dispersion carrier and the like are preferable. Can be 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 of the Invention] Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

 Note that “parts” in the examples indicates “parts by weight”.

Example A conductive substance surface-coated oxide dielectric fine powder was produced by the following method.

Oxide dielectric fine powder (1): Adhesion of Fe ₃ O ₄ to 3 wt% surface of silicon oxide (trade name: Aerosil # 200; manufactured by Nippon Aerosil Co., Ltd.) with a particle size of about 12 nm by wet method based on iron chloride ion I let it.

Oxide dielectric fine powder (2): CuO.Fe ₂ O ₃ is added to silicon oxide (trade name: Nipsil SS-50; manufactured by Nippon Silica Co., Ltd.) with a particle size of about 1.3 μm by a wet method based on iron chloride ion.
wt% on the surface.

The Fe ₃ O ₄ was attached to 3 wt% surface by the base and the wet process iron chloride ions; (manufactured by Teikoku Kako trade name MT500B) titanium oxide having a particle diameter of about 35 nm: oxide dielectric fine powder (3).

Oxide dielectric fine powder (4): Fe ₃ O ₄ is adhered to a surface of 10 wt% on a silicon oxide (trade name: Aerosil R972; manufactured by Nippon Aerosil Co., Ltd.) with a particle size of about 16 nm by a wet method based on iron chloride ions. Was.

<Example 1> 100 parts of styrene resin SMB-600 (manufactured by Sanyo Chemical) 5 parts of carbon black MA-8 (manufactured by Mitsubishi Kasei) 2 parts of chromium alkylsalicylate complex E-81 (2 parts of Orient Chemical) 2 parts of polypropylene wax 550P ( The material having the above formulation was melt-kneaded with a hot roll mill, cooled, coarsely crushed using a hammer mill, and then finely crushed with an air jet fine crusher. The resulting fine powder was classified to select a particle size of 5 to 20 μm. After that, 0.3% by weight of the oxide dielectric fine powder (1) was externally added by a Henschel mixer to obtain a toner.

To 4 parts of the toner, 96 parts of a carrier (ferrite powder having a particle diameter of about 100 μm coated with a silicone resin) was 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 −22.3 μC / g at the beginning and −24.1 μC / g after 30,000 sheets.

Comparative Example 1 A toner was produced in exactly the same manner as in Example 1 except that the oxide dielectric fine powder (1) was changed to Aerosil # 200 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 −24.4 μC / g at the initial stage, and −2 after 10,000 sheets.
It was changed to 8.8 μC / g.

<Example 2> Styrene resin SBM-600 100 parts Carbon black # 40 5 parts (Mitsubishi Chemical) Nigrosine dye N-04 2 parts (Orient Chemical) Polypropylene wax 550P 2 parts (Sanyo Chemical) The above composition is used. And oxide dielectric fine powder (2) 0.2wt
A toner was prepared in the same manner as in Example 1 except that% was externally added.

To 4 parts of this toner, 96 parts of a carrier (ferrite powder coated with a fluororesin and having a particle size of about 100 μm) was mixed in a V blender to obtain 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 +20.1 μC / g at the beginning and +21.6 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 oxide dielectric fine powder (2) in the toner composition of Example 2 was changed to Nipsil SS-50. Hereinafter, a continuous actual photographing test was performed by the same operation as in Example 2. However, after 8000 sheets, the image quality deteriorated and fog became severe. The charge amount of the toner in the developer by the blow-off method is + 17.8μC / g in the initial stage.
After 8000 sheets, it was +11.2 μC / g.

<Example 3> Styrene resin SBM-600 100 parts Carbon black MA-8 4 parts (Mitsubishi Chemical) Nigrosine dye N-07 2 parts (Orient Chemical) Polypropylene wax 550P 2 parts (Sanyo Chemical) Using oxide dielectric fine powder (3) 0.3wt
A toner was prepared in the same manner as in Example 2 except that% was externally added.

In the following, a continuous actual photographing test was performed by the same operation as in Example 2, and 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 + 19.6μC / g at the beginning and + 20.9μ after 30,000 sheets.
C / g.

Comparative Example 3 Example 3 was repeated except that the oxide dielectric fine powder (3) in the toner composition of Example 3 was changed to titanium oxide MT500B.
A toner was produced in the same manner as described above. Hereinafter, a continuous actual photographing test was performed by the same operation as in Example 3. However, after 10,000 copies, image quality such as uneven density was reduced.

The charge amount of the toner in the developer by the blow-off method was +16.3 μC / g at the beginning and +14.0 μC / g after 10,000 sheets.

<Example 4> 100 parts of polyester resin (Mw / Mn = 13000/6000) 5 parts of anthraquinone dye (CISolvent Red 52) 2 parts of charge control agent E-81 (manufactured by Orient Chemical) Dielectric fine powder (4) 0.4wt
A toner was prepared in the same manner as in Example 1 except that% was externally added.

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 -26.4 μC / g at the initial stage and -25.2 μC / g after 30,000 sheets.
g.

Comparative Example 4 A toner was produced in exactly the same manner as in Example 4, except that the oxide dielectric fine powder (4) was changed to Aerosil R972 in the toner composition of Example 4. Hereinafter, a continuous actual photographing test was performed by the same operation as in Example 4, but the image density decreased after 3000 sheets.

The charge amount of the toner in the developer by the blow-off method was −27.7 μC / g at the beginning and −37.0 μC / g after 3000 sheets.

[Effect of the Invention] As described above, the two-component developer for developing an electrostatic image of the present invention impairs the chargeability of the toner by lowering the surface of the oxide dielectric fine powder as an external additive. As a result, the fluidity of the toner and the developer is increased and the image quality such as the streak is not reduced. In addition, durability is high for a long time.

Continuation of front page (56) References JP-A-62-184473 (JP, A) JP-A-63-169666 (JP, A) JP-A-52-52639 (JP, A) JP-A-62-269151 (JP) , A) JP-A-58-40557 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08

Claims (1)

(57) [Claims] 1. An electrostatic image developing method comprising mixing a toner particle containing a binder resin and a colorant and a toner for developing an electrostatic image containing an oxide dielectric fine powder with a carrier material coated with a resin. In a two-component developer, the particle diameter of the oxide dielectric fine powder is 0.005 to 3.0 μm,
At least a part of the surface of the fine powder has a volume resistivity of 10 ⁹ o.
expressed by a general formula MO · nFe ₂ O _{3 of} hm · cm or less (where n is a number from 1 to 6 and M represents Fe, Zn, Mg, Mn, Cu, Ba, Ni, Co or Cd) A two-component developer for developing an electrostatic image, wherein the two-component developer is coated with one or more compounds.