JPS622311B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dry developer for electrophotography, and particularly aims to prevent deterioration of its characteristics. Conventionally, there have been two-component electrophotographic developers in which toner particles and carrier particles are mixed to develop an electrostatic image, such as a cascade development method or a magnetic brush development method, and a so-called one-component development method consisting only of toner particles. A method of developing an electrostatic charge image using an agent is known. When any of the above-mentioned developers is repeatedly developed, for example, an electrostatic latent image on the same electrophotographic photoreceptor, the binder used in the toner particles on the photoreceptor or carrier Colorants and the like can accumulate and impair the sensitivity of the photoreceptor, and can also cause undesirable stains on the resulting copies.
There was a drawback that the charging characteristics of the toner particles changed. For this reason, various developers have been proposed in which abrasive particles and the like are added and mixed with the developer. For example, toners in which alkylated silane is added, fatty acid metal salts and colloidal silica are added, phthalic acid and its salts are added, and crosslinked polyvinylidene fluoride powder is added are known. . However, when these developers are used continuously, hard fine powder may damage the surface of the photoreceptor or accumulate on the carrier surface due to electrical force, reducing the original triboelectric charging ability of the developer. This caused a new problem of impairing durability. The present invention aims to solve such problems, and has the general formula Rf-(CH ₂ ) _o -X or (RfO) _n -Ar-Xw, where n=0-2 m=1-3 w=1, 2 Rf = carbon fluoride group Ar = aryl group or aralkyl group This is a dry type developer for electrophotography. Note that the fluorinated carbon group herein refers to a group having at least one fluorine atom, such as an alkyl group, an alkenyl group, or an allyl group in which at least one hydrogen is substituted with fluorine. In other words, the present invention maintains the effects of adding hard fine powder to the developer, such as preventing filming on the photoreceptor and improving fluidity, and also improves hardness by surface treatment. By reducing the critical surface energy of the fine powder or changing the triboelectric charging series, it prevents adhesion to the carrier or photoreceptor surface and improves the durability of the developer. Hard fine powders that can be used in the present invention include oxides such as cerium oxide, chromium oxide, aluminum oxide, magnesium oxide, silicon oxide, tin oxide, zirconium oxide, iron oxide, and titanium oxide; calcium sulfate, barium sulfate, and sulfuric acid. Sulfates such as aluminum; silicates such as calcium silicate and magnesium silicate; titanides such as boron titanide and titanium titanide; carbides such as silicon carbide, titanium carbide, boron carbide, tungsten carbide, and zirconium carbide; zirconium boride , borides such as titanium boride, and the like. The particle size of these hard fine powders is preferably about 1 mμ to 1 μm. Further, two or more of these hard fine powders may be used simultaneously as necessary. In addition, examples of compounds corresponding to the above general formula include RfCOOH, RfCH ₂ CH ₂ COOH,

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[Formula] RfSO ₃ H,

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[Formula] etc. Since such a compound is a surfactant and has a low resistance of 10 ⁷ Ωcm or less and a low surface energy of 30 dynes/cm or less, by applying it to the surface of the hard fine powder,
This produces the effects described above. Next, examples will be described. Example 1 Aluminum oxide abrasive 15 was added to 500 g of a 0.1% methanol solution of an organic acid represented by _{C9F17COOH .}
g was immersed, then taken out and methanol was evaporated to obtain an additive used in the present invention. A developer of the present invention was obtained by adding 0.5 wt % of this additive to a normal two-component developer (for copying machine "PPC-900" manufactured by Ricoh Co., Ltd.). This developer has significantly improved fluidity, and when 20,000 copies were made continuously using this developer, the images obtained were clear and free of background smudges, and the image density was low.
1.25, and the skin density was 0.08. This image was almost the same as the initial image. When the developer was taken out and the toner charge amount was measured by blow-off, it was (10) 19.7 μC/g. Further, there was no toner filming on the photoreceptor at all. Comparative Example 1 When a similar test was conducted using untreated aluminum oxide in Example 1, the image density decreased and the image was blurry with background smudges, and the image quality was significantly deteriorated compared to the initial image. was. At this time, the image density was 0.75 and the background density was 0.23. Further, the toner charge amount was (10) 4.3 μC/g. Example 2

After immersing 30 g of silicon oxide abrasive material in 1000 g of a 0.05% methanol solution of an organic acid represented by the formula, it was taken out and the methanol was evaporated to obtain the additive used in the present invention. This additive is used in toner (Ricoh Co., Ltd. copier “PPC”).
-900"), the fluidity of the toner was significantly improved. This toner was mixed with a carrier to make a developer, and this was used in the same manner as in Example 1 to continuously copy 20,000 sheets. As a result, the obtained image was clear and free of density loss and background smudge.The image density was 1.19 and the background density was 0.07.The amount of toner charge was measured (10) 17.0μC/
It was hot at g. Comparative Example 2 When a similar test was conducted using untreated silicon oxide in Example 1, the image density decreased and the image was blurry with background smudges, with the image quality significantly deteriorating compared to the initial image. Ta. At this time, the image density was 0.65 and the background density was 0.30. Also, when we measured the toner charge amount, it was found that (10)
It was 2.3μC/g. Example 3 After immersing 30 g of boron titanide abrasive material in 1000 g of a 0.1% methanol solution of an organic acid represented by C ₉ F ₁₇ SO ₃ H, it was taken out and the methanol was evaporated.
An additive used in the present invention was obtained. This additive is used in toner (Ricoh Co., Ltd. copier “PPC”).
-900"), the fluidity of the toner was significantly improved. This toner was mixed with a carrier to make a developer, and this was used in Example 1.
When 20,000 sheets were continuously copied in the same manner as above, the images obtained were clear and free of density loss and background smearing. The image density was 1.18 and the background density was 0.07. The amount of toner charge was measured (10) 20.3μ
It was C/g. Example 4 0.1 of an organic acid expressed as C ₉ F ₁₇ CH ₂ CH ₂ COOH
% titanium carbide powder 30g in 1000g methanol solution
After immersing the sample, the sample was taken out and methanol was evaporated to obtain the additive used in the present invention. This additive is used in toner (Ricoh Co., Ltd. copier “PPC”).
-900), the fluidity of the toner was significantly improved. This toner was mixed with EFV iron powder (manufactured by Nippon Tetsuko Co., Ltd.) to make a developer, and when 20,000 sheets were continuously copied in the same manner as in Example 1, the images obtained were clear and the density decreased. And it was clean. Image density 1.24,
The skin density was 0.08. When the toner charge amount was measured (10), it was 18.7 μC/g. Example 5

50 g of barium sulfate powder was immersed in 1000 g of a 0.2% methanol solution of an organic acid represented by the formula, taken out, and the methanol was evaporated to obtain an additive used in the present invention. This additive is used in toner (Ricoh Co., Ltd. copier “PPC”).
-900"), the fluidity of the toner was significantly improved.
It was mixed with EFV iron powder to form a developer, and when 20,000 sheets were continuously copied in the same manner as in Example 1 using this, the images obtained were clear and free of density loss and background smudge. Image density 1.19, background density
It was 0.06. Measurement of toner charge amount (10)
It was 20.3μC/g.

Claims (1)

[Claims] 1 General formula Rf-(CH ₂ ) _o -X or (RfO) _n -Ar-Xw where n=0-2 m=1-3 w=1,2 Rf=carbon fluoride group A dry developer for electrophotography, characterized in that it contains a hard fine powder surface-treated with an organic acid having a fluorinated carbon group represented by Ar=aryl group or aralkyl group and X=carboxyl group or sulfonic acid group. .