JPH05204186A - Production of toner for electrostatic copying machine - Google Patents

Abstract

PURPOSE:To produce a toner hardly causing scattering and fogging during continuous printing and capable of giving a uniform dot image and a halftone dense image excellent in image quality. CONSTITUTION:Magnetite or hydrotalcite is added to toner particles and mixed. Silica or titanium is further added to the mixture and mixed. The objective toner for an electrostatic copying machine is produced by adding the additives in two stages.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner used in an electrophotographic apparatus such as an electrostatic transfer copying machine or a laser printer. More specifically, it relates to improvement of the external addition process of toner.

[0002]

2. Description of the Related Art For example, in an electrostatic transfer type copying machine (hereinafter referred to as a copying machine) which uses a two-component developer composed of a toner and a carrier, an electrophotographic toner (hereinafter referred to as a toner) is a carrier. Is mixed in advance and stored as a developer in the developing device, while toner for replenishment is stored in the toner hopper. The toner contained during the development is supplied to the photoconductor through the magnet roller.

Further, the toner in the toner hopper is replenished to the developing device when a decrease in the toner concentration in the developing device is detected by the toner concentration detecting device based on the principle of the magnetic center, and then in the developing device. It is mixed with a carrier and similarly supplied to the photoreceptor. The toner supplied to the photoconductor is attracted to the electrostatic latent image formed on the photoconductor and then transferred to the transfer paper. As a result, a desired image can be obtained.

The above-mentioned toner is usually obtained by the steps of mixing, kneading, pulverizing and classifying materials such as a binder resin agent, a colorant, a charge control agent and a releasing agent, on the surface of toner particles. It is molded by attaching an external additive that imparts electrostatic properties.

[0005]

Conventionally, in the so-called external addition step of attaching the external additive, the external additive having different functions is usually mixed together with the toner in a mixer or the like to remove the externally added toner. It has gained. However, when the mixing time is short, an external additive having a large particle size (average particle size of 0.1 to 5 μm) (for example, hydrotalcite and imidazole for the purpose of charging, and magnetite for the purpose of increasing the concentration, etc.) ) Does not disperse throughout the toner. On the other hand, if the mixing time is too long, there is a drawback that the effect of the external additive (such as silica, titanium, alumina) having a small particle size (average particle size of 10 to 100 μm) for the purpose of fluidity is deteriorated. Furthermore, since the particles are small, they penetrate into the toner and the fluidity effect is reduced. Therefore, when continuous printing is performed, there are problems in image quality such as uniformity of halftone dot images, gradation reproducibility, and halftone density. Further, there are drawbacks such as large scattering of toner and poor fluidity.

For example, Japanese Patent Laid-Open No. 3-41464 discloses that
Although a toner containing an external additive is disclosed, it has a problem in image quality. That is, an object of the present invention is to solve these problems described above, and to provide a method for producing an electrophotographic toner having good fluidity, little toner scattering, and an image of stable image quality. is there.

[0007]

As a result of intensive studies on the above problems, the inventors of the present invention have carried out a surface treatment in two or more steps in the step of externally adding the toner, whereby the toner is less scattered and the fluidity is improved. Succeeded in obtaining an excellent externally added toner, and completed the present invention. That is,

The method for producing a toner for an electrostatic copying machine according to the present invention comprises adding and mixing different external additives in at least two stages in the external addition step of adding the external additive to the toner particle powder. ..

Examples of the external additive used in the present invention include magnetite, imidazole, hydrotalcite, silica, titanium oxide, tin oxide, aluminum oxide and the like. A feature of the present invention is that two or more kinds of external additives selected from these external additives are added to the toner in several stages and mixed to perform the surface treatment of the toner particles. A preferred method is to first mix the toner particle powder with magnetite or hydrotalcite, and then add silica or titanium oxide for processing. (Details are shown in Examples.)

The amount of the external additive used is generally 0.01 to 5.0 for each 100 parts by weight of the toner particles.
Parts by weight are desirable. The mixing time of the external additive varies depending on the amount of the toner particles used, but is usually 30 seconds to 5 minutes. The external additive and the toner are mixed by, for example, a Henschel type super mixer. The rotation speed and other conditions are usually 100 to 1000 rpm.

The components of the toner particles before treatment with the external additive used in the production method of the present invention are a binder resin agent, a colorant, and
It consists of a charge control agent and a release agent.

Examples of the binder resin agent include polystyrene, styrene, butadiene copolymer, styrene.
Styrene-based copolymers such as acrylic copolymers, polyethylene, polyethylene-vinyl acetate copolymers, ethylene-based copolymers such as polyethylene vinyl alcohol copolymers, phenolic resins, epoxy resins, allyl phthalate resins, polyamide resins , Polyester resin, maleic acid resin and the like.

Examples of the colorant include carbon black, nigrosine dye, aniline blue, chalco oil blue, chrome yellow, ultramarine yellow, methylene blue, DuPont oil red, quinoline yellow, methylene blue chloride, phthalocyanine blue, malachite green oxalate and lambu. Black, rose bergal, etc. are also mixtures of these.

As the charge control agent, for example, quaternary ammonium salts, nigrosine, amino compounds, or organic dyes, particularly basic dyes and salts thereof are known. Benzyldimethyl-hexadecyl ammonium chloride, decyl-trimethyl ammonium Chloride, nigrosine base, nigrosine hydrochloride, safranine γ, crystal violet and the like can be used. Nigrosine base and nigrosine hydrochloride are often used as positive charge control agents.

As the release agent, polypropylene,
Polyethylene or paraffin wax can also be used. The binder, charge control agent, release agent, and colorant are not limited to the above materials, and other types of materials can be used. These toner components are usually manufactured through the steps of mixing, kneading, pulverizing and classifying. The following table is shown as an example of specific component ratios.

[0016]

[Table 1]

[0017]

In the external addition step in the production method of the present invention, since a plurality of external additives having different functions are added to the toner separately, the external additives are mixed together as in the case of mixing the external additives together. There is no sticking. Therefore, the effects of the chargeability and fluidity of each external additive are fully exhibited.

[0018]

EXAMPLES The production method of the present invention will be described below with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
The following toner was used as the toner before mixing the external additives used in Examples and Comparative Examples. That is, styrene-acrylic resin (product name: Higher-SPR15
08, 90% by weight of Sanyo Kasei Co., Ltd., and carbon black (product name: 330R, Cablack Co., Ltd.) as a colorant
5% by weight, quaternary ammonium salt (product name: P-51, manufactured by Orient Co., Ltd.) such as a charge control agent, 3% by weight, and polypropylene as a release agent (product name: Viscol 550 P) , Sanyo Kasei Co., Ltd.) was mixed with 2% by weight, and the mixture obtained by the mixing step was melted, kneaded, and integrated. Then, the kneaded material integrated in the kneading step was pulverized into particles, and the obtained particles were classified to obtain toner particles having an average particle diameter of 10 μm.

The properties of the toners obtained in Examples and Comparative Examples were measured by the following methods. Toner scattering amount: After copying 10,000 sheets continuously, copy
The amount of toner that drops to the bottom of the developing tank for 1,000 sheets (g / 1,
000 sheets). Flowability: A predetermined toner was put into a dedicated hopper of a copying machine (SF9400, manufactured by Sharp Co., Ltd.), and the toner was dropped by rotating for a certain period of time. ⊚: 25 to 29 g Δ: 21 g or more and less than 25 g x: less than 21 g Image density: Measured with a Macbeth densitometer (RD-914). A: 1.40 or more B: 1.35 or more and less than 1.40 X: less than 1.35

Example 1 2 kg of the above-mentioned toner particles having an average particle size of 10 μm were weighed and magnetite (EP having an average particle size of 0.4 μm) was used.
T-500 manufactured by Toda Kogyo Co., Ltd. was weighed in an amount of 0.2% by weight with respect to the toner, and these were mixed with a mixer (product name: Super Mixer SM
V20, manufactured by Kawata Co., Ltd. And after operating this mixer at a rotation speed of 760 γpm for 1 minute,
Furthermore, apparent specific gravity is about 50 g / l, average particle size is about 16 nm,
Silica fine powder having a specific surface area of 90 to 130 m ² / g (Product name:
R972, manufactured by Nippon Aerosil Co., Ltd., was calculated to be 0.2% by weight with respect to 2 kg of toner, charged into the mixer, and stirred at a rotation speed of 760 γpm for 1 minute to obtain a toner for an electrostatic copying machine. Obtained. Table 2 shows the measurement results of the physical properties.

Example 2 0.2% by weight of magnetite EPT500 was added to hydrotalcite DHT-4A (manufactured by Kyowa Chemical Industry Co., Ltd.) in an amount of 0.
A toner for an electrostatic copying machine of the present invention was obtained in the same manner as in Example 1 except that the content was changed to 1% by weight. The results are shown in Table 2.

Example 3 0.2% by weight of fine silica powder was mixed with titanium oxide (titanium ECC).
The toner for an electrostatic copying machine of the present invention was obtained in the same manner as in Example 1 except that the content was changed to 0.1% by weight of T-1 Titanium Industry Co., Ltd. The results are shown in Table 2.

Comparative Example 1 Silica and magnetite were externally added in the same manner as in Example 1 except that magnetite and silica were not charged to the mixer in two stages but were simultaneously charged to the mixer together with the toner and stirred for 2 minutes. Toner was obtained. The results are shown in Table 2. Comparative Example 2 Hydrotalcite and silica were externally added in the same manner as in Example 2 except that hydrotalcite and silica were not charged in two steps, respectively, and the mixture was simultaneously charged with a toner in a mixer and stirred for 2 minutes. Toner was obtained. The results are shown in Table 2.
Shown in.

Comparative Example 3 The procedure of Example 3 was repeated, except that magnetite and titanium oxide were not charged in two steps, respectively, and the toner and the toner were simultaneously charged into a mixer and stirred for 2 minutes. An added toner was obtained. The results are shown in Table 2.

Comparative Example 4 Comparative Example 1 was repeated except that the stirring time was 1 minute. The dispersion of magnetite is insufficient and the desired image density is not obtained. The results are shown in Table 2.

Comparative Example 5 The procedure of Comparative Example 2 was repeated except that the stirring time was 1 minute. Dispersion of hydrotalcite is insufficient and toner scattering is large. The results are shown in Table 2.

Comparative Example 6 The procedure of Comparative Example 3 was repeated except that the stirring time was 1 minute. The image density cannot be obtained because the dispersion of magnetite is insufficient. The results are shown in Table 2.

[0028]

[Table 2]

[0029]

The toner obtained by the novel external addition process according to the method for producing a toner for an electrostatic copying machine of the present invention has good fluidity, and has less toner scattering during continuous printing and less fog. It has an excellent effect. Therefore, in continuous printing, it is possible to obtain an image having good image quality such as uniformity of halftone dot images, gradation reproducibility, and halftone density.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshitaka Urata 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Within Sharp Corporation (72) Shintaro Hatano 22-22 Nagaike-cho, Abeno-ku, Osaka, Osaka Incorporated (72) Inventor Mirai Imoto 22-22, Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (2)

[Claims] 1. A method for producing a toner for an electrostatic copying machine, which comprises adding and mixing different external additives in at least two stages in an external addition step of adding the external additive to the toner particle powder. 2. The method according to claim 1, wherein adding and mixing the different external additives in at least two stages comprises first treating with magnetite or hydrotalcite and then treating with silica or titanium. Toner manufacturing method for electrostatic copiers.