JPS6228772A - Dry developing agent - Google Patents

Abstract

PURPOSE:To make it possible to use a 2-component type dry developer stably for a long period and to form a good-quality image through development by incorporating fine spherical particles of titanium oxide amorphous in crystal form. CONSTITUTION:The 2-component type dry developer contains in a toner or in the coat of a carrier, fine spherical particles of titanium oxide amorphous in the crystal form, having an average particle diameter of 0.01-1.0mum, preferably, 0.02-0.3mum. The addition of such fine particles permits trouble, such as deterioration due to pulverization of the toner caused by collision of the toner particles with the carrier particles and the change of electrifiability of the carrier particles, to be extremely reduced, and consequently, dispersibility and agglomeration tendency not to be changed from those in the initial stage even after a durability test over 100,000 copies, and a good image to be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a dry type developer, and more specifically, a two-component dry type developer containing amorphous, spherical titanium oxide fine particles can be used stably for a long period of time. The present invention relates to a dry developer which can be used and which produces developed images of good quality.

(Prior art and problems to be solved by the invention) 2 as a developer used to develop an electrical latent image formed by electrophotography, electrostatic recording, electrostatic printing, etc. into a visible image. A two-component dry developer is widely known, that is, a two-component dry developer consisting of a toner carrier and a toner carrier.

Various proposals have been made for each of these components to satisfy the required characteristics. For example, there is a method in which the toner contains a magnetic material and conductive fine powder to prevent the toner from deteriorating due to the collision of the toner particles and carrier particles, which causes the toner to be crushed and fused to the carrier surface. Japanese Patent Publication No. 58-216256)
. However, this method has new problems such as an adverse effect on image quality because the dispersibility of the magnetic material used is insufficient.

Furthermore, regarding the resin composition used to coat the surface of carrier particles, it has been proposed to use a silicone resin containing titanium oxide particles as a coating layer in order to prevent deterioration of the charging characteristics of carrier particles due to so-called spent formation. (Japanese Unexamined Patent Publication No. 12558/1983). However, the dispersibility of titanium oxide particles in the resin composition is insufficient, and the problem of aggregation of carrier particles remains unsolved.

[Means for solving problems]

It is an object of the present invention to solve the above-mentioned problems in two-component dry developers and to provide a developer that has excellent durability and provides visible images of excellent quality.

That is, the present invention relates to a two-component dry developer characterized by containing amorphous, spherical titanium oxide fine particles.

The amorphous, spherical titanium oxide fine particles used in the present invention can be produced, for example, by the method described in Japanese Patent Application No. 60-41828.

It has been revealed by X-ray diffraction analysis that the crystal form t of the titanium oxide fine particles used in the present invention is amorphous, and moreover, they are spherical. There is no particular restriction on the particle size of the titanium oxide fine particles, and various types may be used, but preferably the average particle size is 0.01 to 1.
The thickness is about 0 μm, particularly preferably 0.02 to 0.3 μm. Further, titanium oxide fine particles having a specific surface area of various ranges can be used, but for example, in the case of titanium oxide fine particles having an average particle size of 0.02 to 0.3 μm, the specific surface area is about 100 to 30'Og/g (BET method ).

The titanium oxide fine particles may be added to either the toner or the carrier, or to both.

As mentioned above, when a two-component dry type developer is operated and used continuously, the toner particles collide with the carrier particles, and the toner is finely ground (pulverized), which is fused to the surface of the carrier and becomes part of the developer. In addition to causing deterioration and scattering of finely divided particles to the surrounding area, the chargeability of the carrier particles changes, resulting in local differences in adsorption force, resulting in uneven images. The present invention completely eliminates this problem.As a result, the durability of the developer is good and the quality of visible images is improved.Furthermore, it has the advantage of having excellent charging characteristics even under high humidity and not coagulating. Furthermore, the use of the titanium oxide fine particles according to the present invention improves the fluidity of the developer.

As mentioned above, various advantages can be obtained by blending specific titanium oxide fine particles into a two-component dry developer.
When the titanium oxide fine particles are added to the toner, not only is there an effect of lowering the insulation property, but also it is possible to effectively prevent the toner particles from being crushed or scattered due to collision with carrier particles. Furthermore, when a magnetic substance is included in the toner, effects such as improving the dispersibility of the magnetic substance can be achieved. In addition, the titanium oxide fine particles have good dispersibility (and a toner with excellent fluidity can be obtained. As for the toner components, any known components can be used. For example, binder resin such as polystyrene, carbon blank, etc.) In addition to the above-mentioned coloring agent, the above-mentioned magnetic substance, etc. can be added as appropriate. There are no special conditions for the amount of titanium oxide fine particles to be added to the toner, and it may be appropriately determined in consideration of the intended use of the product, etc.

The titanium oxide fine particles according to the present invention can also be blended into a carrier, and in this case, they are added to the coating layer of the core particles of the carrier. Particles of metals such as iron, copper, cobalt, nickel, zinc, and aluminum or oxides of these metals, and inorganic particles such as sand and glass beads are used as core particles, and in order to improve the charging characteristics of the core particles. The surface is coated with synthetic resin. There are various synthetic resins that can be used for this purpose, including styrene/methacrylate copolymers, polystyrene, and silicone resins with low surface tension. Furthermore, various substances are blended into synthetic resin for the purpose of improving the surface properties when the core particle surface is coated with synthetic resin, but when the specific titanium oxide fine particles mentioned above are blended, aggregation of carrier particles is prevented. However, in addition to solving the problem of uneven distribution of carriers, since the specific gravity of the titanium oxide fine particles is small, the dispersibility in the resin is maintained well. Therefore, it is difficult for the carrier to become spent, and it is possible to provide high-quality images over a long period of time. The amount of titanium oxide fine particles to be blended may be appropriately determined in consideration of the purpose of use, as in the case of toner.

In addition, the above-mentioned core particles generally have an average particle diameter of 10 to 1
The core particles are coated with the resin composition by a conventional method such as coating or spraying.

〔Effect of the invention〕

The dry developer of the present invention has extremely few troubles caused by collisions between toner particles and carrier particles, and the chargeability of the carrier is stable, so it can be used in a stable state for a long period of time, and the visible Image quality is good.

Therefore, the dry developer of the present invention is suitable for electrophotography.

It is used as a developer in electrostatic recording methods, electrostatic printing methods, etc.

〔Example〕

Next, the present invention will be explained in detail with reference to examples.

Example 1 65 parts by weight of polystyrene, 5 parts by weight of carbon black,
20 parts by weight of magnetic material and amorphous.

After kneading 5 parts by weight of spherical titanium oxide (average particle size: 0.02 μm) at 150°C for 20 minutes in a roll mill, the mixture was pulverized using a jet mill to reduce the average particle size to 0.02 μm.
A toner of 5 to 0.7 μm was obtained.

200g of the above toner and carrier (manufactured by Nippon Steel Powder, EFV)
250/400) was mixed to prepare a two-component residual dry developer.
-900), and a 100,000-sheet durability test was conducted. The toner scattering on a white paper (5 cm x 5 cm) placed under the apparatus was 0.11 mm as measured by a Macbeth densitometer. Further, it was confirmed that the dispersibility of the magnetic material in the toner was unchanged from the initial state, and no aggregation of titanium oxide fine particles occurred.

Example 2 In Example 1, 5 parts by weight of nigrosine dye was added as a toner component and the durability test of the developer was improved to 150.0.
The same procedure as in Example 1 was carried out except that the number of sheets was 00. As a result, the toner scattering was 0.18. Furthermore, the dispersibility of the magnetic material in the toner and the agglomeration of the titanium oxide fine particles were the same as in Example 1.

Comparative Example 1 The same procedure as in Example 2 was carried out except that SnO□ (manufactured by Mitsubishi Metals, T-1) was used instead of the titanium oxide fine particles as a toner component. As a result, toner scattering on white paper was 0.
It was 55. Furthermore, in this case, the quality of the visible image deteriorated due to poor dispersion of the magnetic material.

Example 3 Amorphous, spherical titanium oxide fine particles (average particle size 0
, 02 μm) 1 part by weight, silicone resin (manufactured by Shin-Etsu Chemical)
130 parts by weight and 130 parts by weight of toluene were mixed and stirred to obtain a resin solution. This solution has a particle size of 50 to 150 μm.
500 parts by weight of steel beads were coated to obtain carrier particles. The thickness of the coating layer at this time was 0.91 μm.

2800 g of the carrier particles were mixed with 200 g of the toner obtained in Example 1 to prepare a two-component dry developer for eight rounds.

When a test was conducted in the same manner as in Example 1 using this developer, no change was observed in the image quality of copies in the 100,000-sheet test. In addition, the thickness of the coating layer on the carrier particles after this test was measured and was found to be 0.9
0) Lln.

Example 4 2,800 g of the carrier particles obtained in Example 3 were mixed with 200 g of toner (87 parts by weight of styrene-n-butyl methacrylate copolymer, 10 parts by weight of carbon blank, and 3 parts by weight of Sennoazu dye, average particle size of 6 μm). A developer was obtained.

- No change was observed in the image quality. Further, even after the test was completed, the coating layer of carrier particles was hardly worn away.

Comparative Example 2 A carrier was prepared in the same manner as in Example 3 except that crystalline titanium oxide (manufactured by Nippon Aerosil Co., Ltd., P-25) was used as the titanium oxide fine particles. The thickness of the coating layer at this time was 0.89 μm.

A developer was obtained in the same manner as in Example 4 using these carrier particles.

When a test was conducted using this developer in the same manner as in Example 1, the image quality of the copies after the 100,000-sheet test was degraded, and the coating layer of the carrier particles was significantly worn after the test.

Claims (3)

[Claims] (1) A two-component dry developer characterized by containing amorphous, spherical titanium oxide fine particles. (2) The dry developer according to claim 1, which contains amorphous, spherical titanium oxide fine particles in the toner. (3) The dry developer according to claim 1, which contains amorphous, spherical titanium oxide fine particles in the carrier coating layer.