JP3306730B2 - Dry two-component developer for electrophotography - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dry two-component developer for electrophotography.

[0002]

2. Description of the Related Art A dry two-component developer for electrophotography (hereinafter sometimes simply referred to as "developer") comprises a carrier and a toner. In the conventional developer, the use of a carrier having a large particle diameter is bad against background contamination, and the specific surface area is reduced, so that the setting range of the toner concentration is narrowed. As a result, there is a disadvantage that carrier scattering and carrier adhesion easily occur. It has been difficult to simultaneously solve the problems such as an increase in the margin for background contamination caused by the inappropriate particle diameter of the carrier, carrier scattering, and carrier adhesion.

[0003] In addition, there are some problems in the conventional mixing of carriers. First, in the case of two or more types of mixed carriers having different average particle diameters, carrier adhesion on the small particle diameter side is concerned, so that an applied voltage cannot be set to a high bias and the saturation magnetization decreases. On the other hand, on the large particle size side, the resolution cannot be increased and the specific surface area is small, so that the toner density cannot be set over a wide range and the solid density is insufficient. However, JP-A-48-68235 uses a small particle size carrier having a value obtained by adding 5 μm to the average particle size of the toner in addition to a normal carrier. Only two types of carriers (average particle size is 1 to 10 μm)
m) is mixed and used.
In any case, carrier scattering and carrier adhesion tend to occur, and the range of the set margin on the machine side is narrowed. Similarly, Japanese Patent Application Laid-Open No. Sho 60-144759 uses two or more different ferrite carriers having a coercive force in a mixed manner. However, this also causes carrier scattering and carrier adhesion to occur when the overall particle size is reduced. Become. Further, Japanese Patent Laid-Open No. 2-7
No. 4955 uses a mixture of two types of carriers having different average particle diameters and different saturation magnetizations. However, the saturation magnetization cannot be adjusted by resin coating due to the physical properties of the core material itself, and the above problem can be easily solved. Can not.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-component dry developer capable of solving the above-mentioned problems and obtaining a good image.

[0005]

According to the present invention, there is provided a dry two-component developer for electrophotography comprising carrier particles and toner particles, wherein the carrier has a small particle size, a low electric resistance carrier (A) and a large particle size. With high electrical resistance carrier (B)
And the average particle size of the carrier (A) is 30.
The average particle size of the carrier (B) is 50 to 80 μm at 〜60 μm.
m, and the average particle size of the carrier (A) is the carrier (B)
And the carrier (B) is larger than the average particle size by at least 1/2.
Has an average particle size larger than the average particle size of the carrier (A) by 20 μm or more.
The dynamic electric resistance of the carrier (B) is 7.0 to 11.0 log Ω at 0 to 10.5 log Ω, and the dynamic electric resistance of the carrier (B) is 0.3 lo than the dynamic electric resistance of the carrier (A).
It is characterized by being larger than gΩ. Here, the weight ratio of the carrier (A) to the carrier (B) is 1:12 to 1
It is preferably 0: 1 , more preferably in the range of 1:10 to 5: 1.

The present inventors have paid attention to electric resistance, which is one of the characteristics of carriers, in solving the above problem. The high electrical resistance emphasizes the edge effect, and the image uniformity is not good, but the intermediate reproducibility is good, while the low electrical resistance has a margin against background dirt, and the edge effect is eliminated and the image uniformity is reduced. It was also confirmed that the above-mentioned problems could be solved by bringing about a phenomenon such as improvement in the goodness and the like, and subsequently linking it to a mixed carrier of a large particle size carrier and a small particle size carrier. The present invention has been made based on this.

Hereinafter, the present invention will be described in more detail. The carrier can be manufactured by coating a carrier core material such as iron powder and glass beads with a resin in both (A) and (B). The carrier core material is magnetite (Fe ₃
O ₄ ) and / or ferrite. As the release resin for carrier coating used here, a polyolefin resin, for example, polyethylene,
Polypropylene, chlorinated polyethylene, and chlorosulfonated polyethylene; polyvinyl and polyvinylidene-based resins, for example, polystyrene, acrylic resin (for example, polymethyl methacrylate), polyacrylonitrile, polyvinyl acetate, polyvinyl alcohol, polyvinyl butyral, polyvinyl chloride, polyvinyl carbazole, Polyvinyl ethers and polyvinyl ketones; vinyl chloride-vinyl acetate copolymers; styrene-acrylic acid copolymers; silicone resins such as straight silicone resins comprising organosiloxane bonds, or modified products thereof (for example, alkyd resins, polyesters, epoxy resins, Modified product by polyurethane etc.); Fluororesin such as polytetrafluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polychlorotrif Oroechiren; polyamides; polyesters such as polyethylene terephthalate; polyurethanes; polycarbonates; amino resins such as urea - formaldehyde resins, epoxy resins and the like.

Among them, preferred are acrylic resins, silicone resins or modified products thereof, and fluororesins from the viewpoint of preventing the spent toner from adhering to the carrier, and particularly preferred are silicone resins or modified products thereof. Commercially available silicone resins (straight silicone resin) include KR271, KR255, and KR251 manufactured by Shin-Etsu Chemical Co., Ltd., and SR2400 and SR2408 manufactured by Toray Silicon Co., Ltd. Commercially available modified silicone resins include KR206 (modified alkyd resin) and KR30 manufactured by Shin-Etsu Chemical Co., Ltd.
93 (modified acrylic resin), ES1001N (modified epoxy resin), SR2115 manufactured by Toray Silicon
(Modified epoxy resin) and SR2110 (modified alkyd resin).

The amount of the coating resin to be used is suitably 0.1 to 50 parts by weight, preferably 0.5 to 30 parts by weight per 100 parts by weight of the carrier core material.

An appropriate amount of the following conductive substances is added to the coating resin so that the carriers (A) and (B) have a predetermined dynamic electric resistance (Ω). (A) White conductive material ECT-52 (TiO ₂ system) KV400 (TiO ₂ system) manufactured by Titanium Industry Co., Ltd. ECR-72 (TiO ₂ system) manufactured by Titanium Industry Co., Ltd. ECTR-82 (TiO ₂ system) manufactured by Titanium Industry Co., Ltd. Industrial 500W (TiO ₂ system) Ishihara Sangyo 300W (TiO ₂ system) Ishihara Sangyo S-1 (TiO ₂ system) Ishihara Sangyo W-1 (SnO ₂ system) Mitsubishi Metals 23K (ZnO ₂ ) Conductive zinc white No.1 (ZnO) manufactured by Hakusui Chemical Co., Ltd. Conductive zinc white No.2 (ZnO) manufactured by Honjo Chemical Co., Ltd. W-10 (TiO ₂ system) manufactured by Honjo Chemical Denthol WK-100 (Mitsubishi Metals) conductive fiber) manufactured by Otsuka Chemical Co. DENTALL WK-200 (conductive fiber) manufactured by Otsuka Chemical Co. DENTALL WK-300 (conductive fiber) manufactured by Otsuka Chemical Co. MEC300 (SnO ₂ system) Teikoku Kako Co. ME 500 (SnO ₂ system) Teikoku Kako Co., Ltd. (ii) Carbon Black Pearls 2000, VULCANX
C-72 (manufactured by Cabot) Ketchen black EC / DJ500, Ketchen black EC / DJ600
(Lion Akzo Co., Ltd.) DENKA black granules, DENKA black powder (made by Denki Kagaku Kogyo Co., Ltd.) CONDUCTEX975, CONDUCTEX SC
(Made by Columbia Carbon)

"Dynamic electric resistance" in this specification is calculated by the following measuring method. That is, a DC voltage is applied to a doctor plate installed on the sleeve while stirring the coated carrier with a conductive sleeve containing a magnet. At this time, the value of the current flowing from the sleeve to the ground is measured, and the measured value is substituted into the following equation to determine the dynamic electric resistance. Dynamic electrical resistance (Ω) = applied voltage / current

The amount of the conductive substance is 0.05 to 7 with respect to 100 parts by weight of the coating resin (preferably silicon resin).
0 parts by weight, more preferably 0.1 to 50 parts by weight.
If necessary, a silane coupling agent may be added to the coating resin layer to improve the adhesive strength of the coating layer and further to improve the dispersibility of the conductive substance. The coating resin layer can be formed on the surface of the carrier core material by a spraying method, a dipping method, or the like, as in the related art.

[0013]

EXAMPLES The present invention will be described below more specifically with reference to examples. All parts here are by weight.

(Preparation of Toner for Measurement) Carbon black (# 44, manufactured by Mitsubishi Kasei Co., Ltd.) was added to 100 parts of polyester resin.
3 parts and 3 parts of a charge control agent (Pontron E84, manufactured by Orient Chemical Co., Ltd.) were added, and the mixture was placed on a two-roll mill at 120 ° C.
, Kneaded under heating, cooled and ground and classified.
A toner of 5 μm was prepared, and 0.6 part of silica fine powder (R972, manufactured by Nippon Aerosil Co., Ltd.) was externally added to 100 parts of the toner to prepare a toner for measurement.

(Preparation of Carrier (A) -1) A coating solution was prepared as a carrier coating material according to the following formulation. Silicone resin liquid (manufactured by Toray Silicone Co., Ltd., SR2406, solid content: 20%) 300 parts Toluene 1500 parts Average particle size of about 5 in a rotating disk type fluidized bed particle coating apparatus
5,000 parts of a ferrite carrier of 0 μm is put therein, the coating solution of the above-mentioned formulation is sprayed under heating at 80 ° C. while flowing, and the applied material is taken out of the coating apparatus, placed in a thermostat, and heated at 200 ° C. for 2 hours. Then, the silicone film was cured to prepare Carrier (A) -1. Its dynamic electric resistance was 8.8 logΩ.

(Preparation of Other Carrier (A)) Carrier (A) -1 except that the carrier core material and its average particle size were changed.
A plurality of carriers (A) as shown in Table 1 in the same manner as
Was prepared.

[Table 1]

(Preparation of Carrier (B) -1) A coating solution was prepared according to the following formulation as a carrier coating material. Silicone resin liquid (manufactured by Toray Silicone Co., Ltd., SR2406, solid content: 20%) 600 parts Toluene 1500 parts Average particle diameter of about 7 in a rotating disk type fluidized bed particle coating apparatus
5,000 parts of a ferrite carrier of 0 μm is put therein, the coating solution of the above-mentioned formulation is sprayed under heating at 80 ° C. while flowing, and the applied material is taken out of the coating apparatus, placed in a thermostat, and heated at 200 ° C. for 2 hours. Then, the silicone film was cured to prepare Carrier (B) -1. Its dynamic electric resistance was 9.2 logΩ.

(Preparation of Other Carrier (B)) Carrier (B) -1 except that the carrier core material and its average particle size were changed.
And a plurality of carriers (B) as shown in Table 2
Was prepared.

[Table 2]

Embodiment 16And Comparative Examples 1 to3  Two kinds of the above carriers are mixed, and the mixed carrier is mixed.
Dry two-component development by mixing 95 parts of toner for measurement with 5 parts
An agent was prepared. Then, the developer is transferred to an electrophotographic copying machine.
(Ricoh Imagio MF530)
And the results shown in Tables 3 and 4 were obtained.
Obtained. Tables 3 and 4 show mixed carriers (Comparative Examples).2Passing
And3Indicates a single carrier).

[0020]

[Table 3] (Note) Background dirt, carrier scattering and carrier adhesion: ◎ does not occur, は hardly occurs, Δ slightly occurs, and × occurs.

[0021]

[Table 4] (Note) Evaluation of background contamination, carrier scattering and carrier adhesion is the same as Table 3.

[0022]

According to the first aspect of the present invention, it is possible to obtain a large number of high quality copies free from background contamination, carrier scattering and carrier adhesion. According to the second aspect of the present invention, more preferable effects can be obtained.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-215559 (JP, A) JP-A-3-131869 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 9/10 G03G 9/08

Claims (2)

(57) [Claims] 1. A dry two-component developer for electrophotography comprising carrier particles and toner particles, wherein the carrier has a small particle size and low electric resistance (A) and a large particle size and high electric resistance carrier the average particle size of the carrier (a) in made by mixing (B) and the average particle size of the carrier (B) in 30~60μm is 50 to 80 [mu] m, an average particle diameter of the carrier (a) is a carrier 1 / Than the average particle size of (B)
2 or more, and the average particle size of the carrier (B) is at least 20 μm larger than the average particle size of the carrier (A), and the dynamic electric resistance of the carrier (A) is 6.0 to 10.5 logΩ.
And the dynamic electric resistance of the carrier (B) is 7.0 to 11.0 lo.
A dry two-component developer for electrophotography, wherein the dynamic electric resistance of the carrier (B) is 0.3 logΩ or more than the dynamic electric resistance of the carrier (A). 2. The dry two-component developer for electrophotography according to claim 1, wherein the weight ratio of the carrier (A) to the carrier (B) is in the range of 1:12 to 10: 1.