JP2000250251A - Alumina powder and developer containing same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain alumina powder for a toner additive adaptable to the increase of the amount of a toner used due to the colorization of an electronic photograph, upgrading an image, having good durability and excellent in grinding performance in an electrophotographic developer used in an electrophotographic device and to obtain a developer using the alumina powder. SOLUTION: The alumina powder comprises polyhedral α-alumina particles substantially having no crushed face. The ratio (D/H) of the maximum particle diameter D of the particles parallel to a hexagonal close-packed lattice face of α-alumina to the particle diameter H perpendicular to the hexagonal close- packed lattice face is 0.5-3.0. The number average particle diameter of the α-alumina particles is 0.1-1.0 μm. The ratio (D90/D10) of the particle diameter D90 of cumulative 90% of the cumulative particle size distribution from the fine particle side to the particle diameter D10 of cumulative 10% is <=7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alumina powder for a toner additive and an electrophotographic developer using the same.

[0002]

2. Description of the Related Art In electrophotography, a photoconductor (drum) using a photoconductive substance is charged by corona discharge or the like, and an image is formed thereon by an optical lens or an image is drawn by a laser beam. A potential drop occurs to form an electrostatic latent image, and then the latent image is developed using a developer, and the toner image is transferred to a transfer material such as paper, and then fixed by heat, pressure, etc. And record. In such an electrophotographic method, when used for a long time, drum filming in which toner accumulates on the drum occurs, and there is a problem that the quality of an image deteriorates. To solve this problem, a method of adding a powder having a polishing effect to a developer has been disclosed. For example, Japanese Patent Application Laid-Open No. 7-92720 discloses that the toner powder has a low bulk density of 0.3 to 0.6 g / cm ³ and a high bulk density of 0.6 to 0.
A method of adding 9 g / cm ³ of alumina is disclosed. Further, Japanese Patent Application Laid-Open No. Hei 8-22139 discloses a method in which alumina having an average primary particle diameter of 400 nm or less is added.

[0003]

However, since the use of color toners is expected to increase the amount of toner used, and further improvements in image quality and durability are expected, development of abrasives having excellent polishing performance has been developed. Is required.
SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic developer used in an electrophotographic apparatus capable of coping with an increase in the amount of toner used due to colorization of electrophotography, improving image quality and improving polishing performance with good durability. An object of the present invention is to provide an excellent alumina powder for a toner additive and an electrophotographic developer using the same.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the toner to which a specific alumina powder is added shows good durability as an electrophotographic developer. I found that it was completed.

That is, the present invention provides the following (1) and (2). (1) polyhedral particles having substantially no crushed surface,
When the maximum particle diameter parallel to the hexagonal lattice plane of α-alumina, which is the hexagonal close-packed lattice, is D, and the particle diameter perpendicular to the hexagonal close-packed lattice is H, the D / H ratio is 0.5 or more and 3.0. Α-alumina particles having a number average particle diameter of 0.1 μm or more and 1.0 μm or less, and the particle diameters of 10% and 90% of the cumulative particle size distribution from the fine particle side in the cumulative particle size distribution, respectively. An alumina powder for a toner additive having a particle size distribution of D90 / D10 of 7 or less when D10 and D90 are defined as D10 and D90. (2) An electrophotographic developer containing the alumina powder described in the above (1).

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. In the present invention, the alumina powder used as an abrasive is composed of polyhedral particles having substantially no crushed surface, and has a maximum particle diameter D parallel to the hexagonal lattice plane of α-alumina, which is a hexagonal close-packed lattice, and a hexagonal maximum particle diameter. Let the particle diameter perpendicular to the dense lattice plane be H
When α / alumina particles have a D / H ratio of 0.5 or more and 3.0 or less, the α-alumina particles have a number average particle size of 0.1 μm or more and 1.0 μm or less and have a cumulative particle size distribution of Is an alumina powder having a particle size distribution in which the value of D90 / D10 is 7 or less when the particle diameters of 10% and 90% from the fine particle side are D10 and D90, respectively.

The alumina powder used in the present invention comprises 1
After wet filtration at 0 μm, the amount of coarse particles of 10 μm or more is 2
0 ppm or less is preferable. When this is used as an abrasive, scratches generated on the drum are almost zero.

[0008] The particle size of the alumina powder particles is 0.1.
1 μm or more and 1.0 μm or less, preferably 0.2 μm or less.
It is not less than μm and not more than 0.7 μm. A particle size of 0.1 μm or less is not preferred because the particles are likely to aggregate and the polishing efficiency is low. A particle size of 1 μm or more is not preferred because problems such as excessive polishing efficiency and scratches on the drum occur.

The method for producing alumina powder according to the present invention is described in, for example, JP-A-6-191833 and JP-A-6-191.
Nos. 836 and 7-206430 can be used.

The amount of the alumina powder of the present invention added to a developer for electrophotography is preferably from 0.1 to 1.0 part by weight based on 100 parts by weight of the toner. Below this, the polishing effect is not sufficient, and above this, there is a problem that the drum is scratched.

The surface of the alumina powder particles of the present invention may be subjected to a surface treatment, if necessary. Although not limited, a silicon coupling agent, a titanium coupling agent, or the like can be used.

As the alumina of the present invention, for example, AA03 (primary particle size: 0.3 μm), AA04 (primary particle size: 0.4 μm), and AA manufactured by Sumitomo Chemical Co., Ltd.
05 (primary particle size 0.5 μm), AA07 (primary particle size 0.5 μm).
7 μm). All of these have a purity of 99.9.
9 wt% or more.

Next, the method for producing the developer of the present invention will be described. The binder resin and colorant used for the developer may be those usually used. If necessary, a release agent or a charge control agent can be added to prevent offset, and an external additive can be added to improve fluidity.

Examples of the binder resin include, but are not limited to, natural wax, polyethylene wax, low molecular weight polypropylene, ethylene-vinyl acetate copolymer, styrene-acrylic copolymer, polyester, polystyrene, epoxy, polyamide, polymethyl methacrylate, Poalivinyl butyral, an acrylic resin, or the like can be used.

The colorant is not limited, but carbon black and organic and inorganic pigments can be used. For example, carbon black includes furnace black, channel black, acetylene black, and the like. Pigments include benzidine yellow pigment, followin yellow, acetoacetic anilide-based insoluble azo pigment, monoazo dye, azomethine dye, xanthene-based magenta dye, naphthol-based insoluble azo pigment, anthraquinone-based dye, thioindigo, naphthol-based insoluble azo pigment, copper Phthalocyanine pigments and the like can be mentioned.

The release agent includes, but is not limited to, low molecular weight polypropylene and low molecular weight polyethylene. Examples of the charge control agent include a nigrosine dye, a fatty acid metal salt, a quaternary ammonium salt, an azo metal-containing dye, chlorinated paraffin, and chlorinated polyester. Examples of the external additive include colloidal silica, titanium oxide, and a fatty acid metal salt.

The developer is prepared by mixing a binder and a colorant, heat-melting and kneading, coarsely crushing, finely crushing and classifying.
It can be produced by adding and mixing alumina and, if necessary, a release agent, a charge control agent, and an external additive.

The method of heat-melt kneading includes a screw-type kneader, a heat kneader, a roller and the like, the method of coarse crushing includes a hammer mill and a cutter mill, and the method of fine crushing includes a jet mill. As the classification, wind classification can be usually used.
Usually, a high-speed fluid mixer is used for mixing with the alumina powder.

The developer obtained in the present invention can be applied to all developing methods currently used. For example, there are developing methods such as a cascade developing method, a two-component magnetic brush developing method, a one-component insulating toner developing method, and a one-component conductive toner developing method.

By using the developer to which the alumina powder of the present invention is added, the drum surface is appropriately polished with the alumina powder, so that drum filming hardly occurs. Filming occurs in about 100,000 sheets with the developer and 150,000 sheets in the conventional developer to which alumina powder is added. By using the developing solution of the present application, drum filming can be performed to about 200,000 sheets or more. Does not occur.

Next, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

Various measuring methods in the present invention will be described below. (1) Measurement of number average particle diameter of primary particle diameter Scanning electron microscope (SEM, JEOL Ltd .: T-30)
0), taking a photograph of the powder particles, selecting 50 to 100 particles from the photograph and performing image analysis;
The average value was obtained. (2) Measurement of D10 and D90 (Measurement of Weight Cumulative Particle Size Distribution) It was measured by a laser diffraction scattering method using a master sizer (manufactured by Malvern). The alumina slurry prepared for the measurement was prepared by adding 25 g of a 0.5% by weight aqueous solution of sodium hexametaphosphate to 2.5 g of alumina powder.
The mixture was added, and the mixed solution was subjected to ultrasonic wave for 2 hours with a homogenizer.
And irradiated for 5 minutes.

(3) Wet sieve After 1000 g of distilled water was added to 1000 g of alumina, an ultrasonic bath having a capacity of 6 liters (frequency: 28 kHz,
Ultrasonic waves were irradiated while stirring at an output of 200 W) for 30 minutes to prepare a slurry. In a beaker filled with distilled water, immerse a bag-shaped mesh of 10 μm nylon mesh,
The entire amount of the alumina slurry prepared above was poured into the nylon mesh bag, and the entire beaker was irradiated with ultrasonic waves using an ultrasonic bath. This causes the alumina particles to move through the nylon mesh and into the beaker. After 20 minutes, the nylon mesh bag was pulled up, the outside of the bag was sufficiently washed, dried, and the weight increase was measured. The increase in weight was divided by the charged amount of alumina, 1000 g, to obtain a 10 μm sieve residue.

(4) Measurement of D / H ratio Scanning electron microscope (SEM, JEOL Ltd .: T-30)
A photograph of the powder particles was taken using 0), 5 to 10 particles were selected from the photograph, and image analysis was performed, and the average value was obtained. (5) Evaluation of Drum Filming The number of printed sheets at which drum filming starts to occur using the actually manufactured developer was examined.

Example 1 Using 100 parts by weight of polystyrene as a binder and 5 parts by weight of acetylene black as a coloring agent, kneading them with a kneader, pulverizing them with a hammer mill, finely pulverizing them with a jet mill, and classifying them by wind power to obtain a toner. Manufactured. 0.2 parts by weight of Sumicoundum AA03 manufactured by Sumitomo Chemical Co., Ltd. was added thereto and mixed with a high-speed fluid mixer to produce a developer. Using this developer, drum filming did not occur even when the number of printed sheets was 200,000.

Example 2 Example 1 was repeated except that the amount of alumina added was 0.1 part by weight.
When a developer is manufactured in the same manner as described above, drum filming does not occur even when the number of printed sheets is 200,000.

Example 3 Example 1 was repeated except that the amount of alumina was changed to 0.5 part by weight.
When a developer is manufactured in the same manner as described above, drum filming does not occur even when the number of printed sheets is 200,000.

Example 4 When a developer is manufactured in the same manner as in Example 1 except that AA04 is used as alumina, drum filming does not occur even when the number of printed sheets is 200,000.

Example 5 When a developer is manufactured in the same manner as in Example 1 except that AA07 is used as alumina, drum filming does not occur even when the number of printed sheets is 200,000.

Comparative Example 1 A developer was produced in the same manner as in Example 1, except that alumina produced by the alum method was used as the alumina. Drum filming began to occur when the number of prints exceeded 150,000.

Comparative Example 2 When no alumina was added, the drum filming was 10
It starts to occur when the number of copies exceeds 10,000.

Comparative Example 3 Sumicorundum A manufactured by Sumitomo Chemical Co., Ltd. as alumina
When a developer is manufactured in the same manner as in Example 1 except that A2 is used, drum filming starts to occur when the number of printed sheets exceeds 100,000.

Table 1 shows the results of Example 1 and Comparative Example 1.

[0034]

[Table 1]

[0035]

By using the alumina for toner additives of the present invention, it is possible to obtain a developer without drum filming, to cope with an increase in the amount of toner used, and to improve the image quality and durability. As a developer for electrophotography.

Claims (4)

[Claims] 1. A polyhedral particle having substantially no crushed surface, having a maximum particle diameter D parallel to the hexagonal lattice plane of α-alumina, which is a hexagonal close-packed lattice, and a particle perpendicular to the hexagonal close-packed lattice plane. When the diameter is H, α-alumina particles having a D / H ratio of 0.5 or more and 3.0 or less, the number average particle diameter of the α-alumina particles is 0.1 μm or more and 1.0 μm or less, An alumina powder for a toner additive having a particle size distribution in which the value of D90 / D10 is 7 or less when the particle diameters of 10% and 90% from the fine particle side in the cumulative particle size distribution are D10 and D90, respectively. 2. The alumina powder according to claim 1, wherein coarse particles having a size of 10 μm or more have a content of 20 ppm or less. 3. An electrophotographic developer containing the alumina powder according to claim 1. 4. The developer according to claim 3, wherein the content of the alumina powder is 0.01 to 0.1 part by weight based on 100 parts by weight of the toner.