JPH06332233A - Electrophotographic toner - Google Patents

Abstract

PURPOSE:To prevent the filming of a toner on the surface of a carrier, sleeve and photosensitive body and to obtain the toner having a stabilized triboelectrifying characteristic and without forming a white dot on a picture by depositing a specifed titanium oxide particle on the toner surface. CONSTITUTION:The particle of titanium oxide exemplified by TiOx (x<2) is deposited on the surface of a toner contg. binder resin and colorant. The diameter of the particle is preferably controlled to 0.5mum, and carbon black, magnetite or ferrite can be incorporated as a colorant. Such a particle has the grinding effect, chargeability and fluidity improving effect of titanium oxide. Accordingly, when the toner is used, the excessive increase in the charge of the toner is suppressed since the titanium oxide having higher conductivity than the binder resin is deposited, and contact of the toner base particle with the carrier, sleeve, etc., is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner for developing an electrostatic charge image formed by electrophotography, electrostatic printing, electrostatic recording or the like.

[0002]

2. Description of the Related Art A method for developing an electrostatic latent image with toner is roughly classified into a developing method using a two-component developer mainly composed of toner and carrier, or a developing method using a one-component developer consisting of only toner. There are various methods, and various proposals have been made for each developing method. The method of using a two-component developer is a method of developing an electrostatic latent image by applying an electric charge to the toner by frictional charging between the toner and the carrier. Therefore, if the mixing property of the toner and the carrier and the charging property are not good, sufficient charging property cannot be obtained, and good image quality cannot be obtained. Further, when a large number of sheets are copied, the toner is electrically attached or mechanically fused to the surface of the carrier and the surface of the carrier is changed, so that the characteristics of the developer are changed and the triboelectric charging speed becomes slow, resulting in various problems. Occur. Specifically, when the charge distribution of the developer spreads and the toner of the opposite charge is generated, the fogging phenomenon to the image background portion and the toner scattering from the developing layer become remarkable, and the characteristics of the developer change due to the selective development. The toner consumption may increase due to a decrease in image density, or a decrease in charging property and an increase in image density.

Further, in the case of the one-component toner, a method of charging the toner by frictional charging between the toner and the sleeve or the charging blade is used, but a phenomenon similar to the above-mentioned phenomenon occurring on the carrier surface occurs on the sleeve. Then
After all, the developability changes. As a means for solving these problems, conventionally, powdered relatively conductive inorganic fine powder such as magnetite, carbon black, titanium oxide, alumina, or ceramics is externally added to the toner surface to coat the surface of the carrier or the sleeve. A method of maintaining the image quality by polishing or by utilizing the conductive property of these additives to leak the charge accumulated in the toner to prevent an increase in the charge amount is used. It is known that by adhering the conductive inorganic fine powder to the surface of the toner as described above, it is possible to obtain the effect of polishing the photosensitive member, the sleeve, or the carrier, and the effect of preventing an increase in the charge amount.

Conventionally, titanium oxide has been suitably used as a conductive inorganic fine powder used for the above purpose.
The fine particles of titanium oxide are effective in imparting fluidity to the toner, have less influence on the charging characteristics of the toner, and have a better environmental characteristic of the toner than colloidal silica which is generally used. This is preferable because it has little effect. However, since conventional fine particles of titanium oxide are easily aggregated even if the primary particle size is small, aggregates having a large particle size of several tens of μm exist. These agglomerates are less likely to electrostatically adhere to the toner surface, and a large amount of energy is required to fix them on the toner surface. However, if a method of applying strong energy to fix these particles to the toner surface is taken, these fine powders will be buried in the toner surface, and the expected effect may not be fully exhibited. However, the intended effect was not sufficiently obtained. If these fine powders are not adhered to the toner surface, they will be desorbed from the toner in the developing device and not only will not be sufficient effect, but also coarse particles of large particle size will accumulate in the developer, However, there were problems such as white spots on the image due to white coarse particles after fixing.

[0005]

SUMMARY OF THE INVENTION The present invention solves the problems of the above-mentioned conventional electrophotographic developers, and prevents the filming of toner on the carrier, sleeve, photosensitive member surface, etc. The present invention provides a toner for electrophotography, which has stable triboelectric charging characteristics during copying and has good quality with no white spots on an image.

[0006]

According to the present invention, in a toner containing at least a binder resin and a colorant, titanium oxide particles represented by the general formula TiO _x (where X is less than 2) are attached to the surface. It is preferable that the titanium oxide particles have a particle diameter of 0.5 μm, and carbon black, magnetite, or ferrite can be contained as a coloring agent.

The general formula T for adhering to the toner surface of the present invention
The titanium oxide particles represented by io _x (where X is less than 2) have the polishing effect, the charging property, and the fluidity imparting effect that titanium oxide itself has. Therefore, when this toner is used, since titanium oxide, which is relatively more conductive than the binder resin, adheres to the surface of the toner, an excessive increase in charge of the toner is suppressed and the image density is stabilized. Further, the contact between the toner mother particles and the carrier or sleeve is suppressed, and the generation of spent toner is reduced. Further, even if toner filming occurs on the carrier, sleeve, or photoreceptor, the filming substance is polished by the polishing effect of titanium oxide, and an effect that a fresh state is always obtained is obtained. The general formula TiO used in the present invention
Titanium oxide particles represented by _X (where X is less than 2) have a dark blue (purple) color (black), and even if coarse particles are present, they are the dark color described above, and therefore are mixed with black toner. Even if it is developed in the developed state, it cannot be visually discriminated, so that it has an advantage that it does not appear as an image defect.

The titanium oxide particles used in the present invention are generally represented by the general formula TiO _x (where X is less than 2) obtained by subjecting titanium dioxide, which is generally white, to a reduction treatment to remove a part of oxygen. It is a secondary titanium oxide (hereinafter abbreviated as low-order titanium oxide). As this low-order titanium oxide, titanium black product name (20M, 13
M, 13R, 12S, 10S), black titanium oxide trade name {T-1 (X = 1.86), S-1 (X =
1.86)} and the like. These low-order titanium oxides have a bluish or purplish black color. The addition amount of the low-order titanium oxide particles used in the present invention is the general formula TiO _x (where X =
The optimum content of titanium oxide represented by (less than 2) is 0.1 to 2 parts by weight. If the amount is less than 0.1 parts by weight, it is difficult to maintain good triboelectric charging characteristics of the toner and the polishing effect is not sufficient. On the other hand, if the amount is more than 2 parts by weight, there arises a problem that the charging property of the toner itself is hindered.

As the colorant used in the present invention, at least one kind of colorant such as carbon black, magnetite fine particles, ceramic fine particles and black dye, which is a colorant for a black toner, is used.

The low-order titanium oxide used in the present invention has an average particle diameter (average body area by an image analyzer) of 0.5 μm.
m or less is desirable. If the particle size exceeds 0.5 μm and becomes large, the agglomerated particles become too coarse, resulting in poor transfer when developed together with the toner, or the coarse titanium oxide transferred onto the transfer paper due to the fixing offset is desorbed. As a result, white spots in the image occur, which is not preferable.

The means for adhering the black titanium oxide to the surface of the toner used in the present invention is achieved by mixing the toner and the black titanium oxide and then mixing and stirring with a stirrer capable of applying a high shearing force. For this reason, for example, Henschel mixer, super mixer, turbulizer, hybridizer of Nara Machinery Co., Ltd., which is generally used as a surface reforming machine for powders, Ong mill of Hosokawa Micron Co., turbo mill of Turbo Kogyo Co., etc. can give.

As the binder resin contained in the toner, styrene resin, styrene-acrylic acid ester copolymer resin, styrene-butadiene copolymer resin, polyester resin, epoxy resin and the like can be used. As other constituent components of the toner constituting the present invention, other colorants,
A charge control agent, and other additives as required, are included. A toner is obtained by mixing these materials and a binder resin in a desired composition, melt-kneading, cooling, solidifying, and pulverizing and classifying. . Further, it may be obtained as a so-called polymerization method toner prepared by mixing the above materials at the time of polymerizing the binder resin. Examples of the charge control agent include nigrosine dyes, quaternary ammonium salts, monoazo metal complex dyes, and the like. Other additives added as necessary include polyolefins such as polypropylene as a release agent, and hydrophobic silica and colloidal silica as a fluidizing agent.

[0013]

EXAMPLES The present invention will be described below based on examples. In the examples, “part” means “part by weight”. Example 1 Preparation of toner mother particles-Styrene-acrylic acid ester copolymer resin 100 parts (manufactured by Sanyo Kasei Co., Ltd .; TB-1000) -Charge control agent 1 part (Orient Chemical Co., Ltd. trade name; Bontron S-34) ) ・ Carbon black 6.5 parts (Mitsubishi Chemical Co., Ltd. trade name; MA-100) ・ Polypropylene 3 parts (Sanyo Chemical Co., Ltd. trade name: Viscole 660P) The above raw materials are mixed with a Nippon Rigaku Kogyo super mixer. After melt kneading, the mixture was pulverized and classified to obtain negatively chargeable toner particles having an average particle diameter of 9 μm. Then, with respect to 100 parts of the toner mother particles, 0.2 part of black titanium oxide, manufactured by Ishihara Sangyo Co., Ltd., trade name M-1 (particle diameter: 0.3 to 0.4 μm) and hydrophobic silica, Nippon Aerosil Co., Ltd. Product name: R-
972) and then 0.3 parts of Hosokawa Micron Co., Ltd. to mix and mix the black titanium oxide on the surface of the toner mother particles, and screen the toner with a 200 mesh net using a gyro shifter. A toner for photography was obtained. And the average particle diameter is 60 μm
Carrier coated with silicone resin on the core material of ferrite carrier with saturation magnetization of 55 emu / g
An electrophotographic developer using the toner of the present invention was prepared by mixing 0 part of the toner with 4.5 parts of the toner.

Example 2 As low-order titanium oxide, black titanium oxide manufactured by Ishihara Sangyo Co., Ltd.,
A toner and a developer using the toner were prepared in the same manner as in Example 1 except that the trade name S-1 (particle diameter: 0.1 to 0.15 μm) was used.

Example 3 As low-order titanium oxide, titanium black manufactured by Mitsubishi Materials Co., Ltd., trade name 20M (particle diameter: 0.02 to 0.2 μm)
A toner and a developer using the same were prepared in the same manner as in Example 1 except that was used.

Example 4 As low-order titanium oxide, titanium black manufactured by Mitsubishi Materials Corp., trade name 13R (particle diameter: 0.02-0.2 μm)
A toner and a developer using the same were prepared in the same manner as in Example 1 except that was used.

Comparative Example 1 A toner and a developer using the same were prepared in the same manner as in Example 1 except that white titanium oxide, trade name MT-500B (particle size: about 0.035 μm) manufactured by Teika Corporation was used. .

Comparative Example 2 A toner and a developer using the same were prepared in the same manner as in Example 1 except that White Titanium Oxide trade name MT-600B (particle diameter: about 0.05 μm) manufactured by TAYCA was used.

Next, a commercially available copying machine (manufactured by Toshiba Corp., trade name: using the electrophotographic developers obtained in the above Examples and Comparative Examples)
BD-9110) is used to conduct a continuous copy test up to 50,000 sheets, and the number of white spots on the image at the initial stage and after copying 50,000 sheets can be visually confirmed, and the triboelectric charge amount at the initial stage and after the completion of copying of 50,000 sheets. The image density and the background fog were measured, and the results are shown in Table 1. The copied original is A4 size with a black portion of 6%, the triboelectrification amount was measured by a blow-off triboelectrification amount measuring device manufactured by Toshiba Chemical Co., and the image density was measured by a Macbeth reflection densitometer RD- 914, the ground cover is a color difference model MODE by Nippon Denshoku Industries Co., Ltd.
L Z ¥ 1001DP was used. The number of white spots is shown as an average value of five A3 whole black solid copy images.

[0020]

[Table 1]

As is clear from the results shown in Table 1, Example 1
The electrophotographic developers of Nos. 4 to 4 of the present invention had good white spots and good images and charged states. On the other hand, in the comparative example, many white spots were generated in the image after the completion of copying 50,000 sheets.

[0022]

The toner of the present invention has excellent triboelectrification characteristics and image quality, and even when copying for a long time, the phenomenon of filming on the photosensitive member, the developing sleeve or the carrier, etc.
There is no problem in other practical characteristics.

Claims (4)

[Claims] 1. A toner containing at least a binder resin and a colorant, wherein titanium oxide particles represented by the general formula TiO _x (where X is less than 2) are adhered to the surface of the toner. For toner. 2. The average particle diameter of titanium oxide particles is 0.5 μm.
The toner for electrophotography according to claim 1, wherein the toner has a thickness of m or less. 3. The electrophotographic toner according to claim 1, which contains at least carbon black as a colorant. 4. The toner for electrophotography according to claim 1, which contains at least magnetite or ferrite fine powder as a colorant.