JP2985534B2 - Positively chargeable magnetic one-component toner - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic toner for visualizing an electrostatic image such as an electrophotographic method. More specifically, the present invention relates to a positively chargeable magnetic one-component toner that visualizes a negatively charged electrostatic image and provides a high-quality image.

[0002]

2. Description of the Related Art Conventionally, as an electrophotographic method, US Pat.
Although many methods are known, such as the specification of No. 297691,
In principle, a photoconductive substance is used to form an electrostatic latent image on the photoreceptor surface by various means, and then developed using an electrostatic toner to form a visible image. Further, if necessary, the image is transferred to a transfer material such as paper, and a fixed image is obtained by applying heat, pressure and the like.

As methods for visualizing an electrostatic latent image, a magnetic brush method (US Pat. No. 2,870,463), a cascade method (US Pat. No. 2,221,776), and a method using a conductive magnetic toner (US Pat. No. 3,909,258). Specification), a method using an insulating magnetic toner (Japanese Patent Publication No. 41-9)
475) have been devised. At present, methods mainly used in practice are a magnetic brush method called a two-component developing method and a method using an insulating magnetic toner called a one-component developing method.The two-component developing method mixes toner particles and carrier particles. The carrier particles deteriorate due to long-term use, and it is necessary to replace the developer. Further, since it is necessary to always maintain the mixing ratio of the toner particles and the carrier particles at a constant level, a technique is required for controlling the toner concentration, and there is a problem that the machine becomes large and complicated. A method devised to solve these problems is a one-component development method using an insulating magnetic toner. Since this method does not require carrier particles, the method does not require replacement of the developer and control of the toner concentration at all, thereby improving the above-mentioned problem.

On the other hand, a selenium-based or cadmium sulfide-based photosensitive member has conventionally been used as a photosensitive member for forming an electrostatic latent image. Since these have positive charging properties, toners for visualizing an electrostatic latent image are mainly of negative charging properties. However, selenium or cadmium sulfide used in this type of photoreceptor has a problem in terms of safety and health for human bodies, and is currently being replaced with a photoreceptor using an organic material. The main organic materials include phthalocyanine-based compounds, which have a negative charge property. Therefore, a positively chargeable toner is used as a toner for visualizing an electrostatic latent image.

[0005] The toner used in the one-component developing method is obtained by dispersing a dye, a pigment, a magnetic powder and the like in a binder resin, and pulverizing and classifying the particles to 1 to 30 µm. It is known that the addition of hydrophobic colloidal silica to this toner improves the prevention of aggregation and the fluidity. However, when dry colloidal silica is added to the positively chargeable toner, the flowability is improved, but the charge amount of the toner is reduced, causing a reduction in image density and a fogging phenomenon, thereby deteriorating the image quality. In order to solve these problems, it has been proposed to add a metal oxide which acts as a charging aid in combination with dry colloidal silica to prevent a reduction in charge amount, that is, a deterioration in image quality. The metal oxide referred to here is aluminum oxide,
Titanium oxide, calcium titanate, mug stearate
Nesium, strontium titanate, magnetite, zinc oxide, tin oxide and the like can be mentioned.

However, since these conventional metal oxides generally have an irregular shape, the photosensitive member is damaged by the pressure of a blade or a fur brush in a cleaning section for removing residual toner. Further, since the volume average particle diameter is often 0.1 μm or less, when added to the toner, physical adhesion such as van der Waals force is large. Therefore, the toner tends to adhere firmly to the surface of the toner, and as a result, the fluidity of the toner tends to decrease. This decrease in toner fluidity inhibits the formation of a favorable sleeve layer pressure, leading to a decrease in image density. Therefore, these metal oxides cannot sufficiently compensate for the adverse effects caused by the addition of dry colloidal silica.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to provide a toner which can prevent a decrease in charge amount and does not cause a decrease in fluidity in a one-component developing method using a positively chargeable toner. It is an object. Further, the present invention provides a toner capable of minimizing damage to the photoreceptor and prolonging the life of the photoreceptor and stably obtaining a high-quality image.

[0008]

According to the present invention, there is provided a volume average particle size obtained by subjecting a zeolite to acid treatment, washing with water, and baking one-component toner particles mainly composed of a binder resin, magnetic powder and a positive charge control agent. The present invention relates to a positively-chargeable magnetic one-component toner comprising amorphous silica-alumina-based composite oxide particles of 0.1 to 10 μm and dry colloidal silica. Dry colloidal silica is produced by hydrolyzing silicon tetrachloride gas in a flame of hydrogen and oxygen, and is generally represented by Formula 1.

[0009]

Further, it is known to modify with dimethyldichlorosilane or the like in order to impart hydrophobicity. The amount of dry colloidal silica added is based on 100 parts by weight of toner.
It is preferably 0.01 to 3 parts by weight, particularly preferably 0.1 to 0.5 part by weight.
Parts by weight. If the amount is 0.01 part by weight or less, sufficient fluidity cannot be obtained, and the effects of the present invention cannot be obtained. Also, if it exceeds 3 parts by weight, the fluidity does not increase in proportion to the addition amount, and conversely the cost increases, which is not appropriate.

Next, details of the amorphous silica / alumina type particles will be described below. Amorphous silica / alumina particles can be obtained by treating zeolite with an acid, washing with water, and firing. The method for producing zeolite mainly includes a dry method and a wet method. The dry method is to obtain a zeolite by melting kaolin, squid and sodium carbonate and treating it with water, and the wet method is a method of mixing a sodium silicate solution and a sodium aluminate solution to form a zeolite. The main method is to dry, pulverize and sieve the gel to obtain zeolite. The general structural formula of zeolite is
It is represented by Na ₂ Al ₂ Si ₃ O ₁₀ .xH ₂ O.

[0012] Since zeolite retains its properties as an adsorbent, it has high hygroscopicity, which is not preferable from the viewpoint of stability against the environment, particularly humidity. Therefore, the zeolite obtained by any of the above production methods can be subjected to an acid treatment to shift from a strong alkali to a weak alkali, and the humidity dependency can be improved by amorphization by firing. The acid used may be an organic acid or an inorganic acid, but hydrochloric acid, sulfuric acid, nitric acid and the like are effective economically. As a means for shifting from a strong alkali to a weak alkali, ion exchange with a specific divalent metal species is also possible. The amorphous silica / alumina-based particles ion-exchanged with the divalent metal species have the following structural formula.

MMO.nNa ₂ O.pSiO ₂ .Al ₂
O ₃ .qH ₂ O (M is Ca, Mg, Zn, Ba, Sr, Cu, Sn,
Divalent metals such as Fe, Ni, and Cr, and m, n, p, and q are any positive real numbers.

The shape of the silica-alumina-based particles in the present invention is preferably a spherical or rounded cube. This is because scratches on the photoconductor in the cleaning unit can be reduced as compared with the irregular shape. The addition amount of the amorphous silica-alumina-based particles is preferably 0.01 to 3 parts by weight, particularly preferably 0.1 to 3 parts by weight, based on 100 parts by weight of the toner.
~ 1 part by weight. If the above value is more than 3 parts by weight, the photoconductor may be damaged, which is not preferable.

The volume average particle size is preferably from 0.1 to 10 μm, particularly preferably from 0.5 to 5 μm. The above numbers are
When the thickness is 0.1 μm or less, the van der Waals force increases, and when added to the toner, it firmly adheres to the surface of the toner, lowering the fluidity of the toner. On the other hand, if the thickness is 10 μm or more, the surface area decreases, and the ability to impart a charge to the toner decreases, which is not preferable. Here, the volume average particle size is a value measured by the Coulter counter method.

As the binder resin used in the present invention, polystyrene, styrene-acryl copolymer, ethylene-vinyl acetate copolymer, vinyl acetate, acrylic and the like can be used. As the positive charge control agent, a nigrosine-based oil-soluble dye is the most common, but in addition,
Crystal violet, quaternary ammonium salts and the like can also be used in the present invention. As the magnetic powder, known powders such as various ferrites, magnetite, and hematite can be used. Further, if necessary, wax and the like can be added.

[0017]

The present invention will be described in more detail with reference to the following examples. In addition, wt% in the text indicates weight%.

Example 1 Styrene resin Hymer UNI 3000 (manufactured by Sanyo Chemical Industries) 62 wt%, magnetic material MG-RF (manufactured by Mitsui Mining & Smelting) 35 w
t%, wax 550P (manufactured by Sanyo Chemical Industries) 1 wt%,
Positive charge control agent TP-302 (made by Hodogaya Chemical Co., Ltd.) 2 wt%,
Was mixed using a Henschel mixer, melt-kneaded by a twin-screw extruder, pulverized by a jet mill pulverizer, and further classified to 9 μm by an airflow classifier to obtain a base toner. With respect to 100 parts by weight of the obtained base toner, 0.5 parts by weight of dry colloidal silica R812 (manufactured by Nippon Aerosil Co., Ltd.) and amorphous silica / alumina-based particles AM having a volume average particle diameter of 0.8 μm
2 parts by weight of T-08 (manufactured by Mizusawa Chemical Industry Co., Ltd.) were added and dry-mixed with a Henschel mixer to obtain a test toner.

An image was obtained from the obtained toner using a commercially available copying machine (product name: NP-4335, manufactured by Canon Inc.) employing a one-component developing method. Use) and no fog was observed. When a further 50,000-sheet printing test was performed, the image density was the same as the initial image density even after printing 50,000 sheets.
1.35 was obtained, no fogging was observed, and a high-quality image was obtained stably.

Example 2 Dry colloidal silica R812 was used as the base toner of Example 1.
(Nippon Aerosil Co., Ltd.) 0.1 parts by weight, volume average particle size 0.8
1 part by weight of AMT-08 amorphous silica / alumina-based particles (manufactured by Mizusawa Chemical Industry Co., Ltd.) was added to obtain a test toner. Using a commercially available copying machine (trade name: NP-4335, manufactured by Canon Inc.) employing the one-component developing method, the obtained toner was used to produce an image. As a result, a sufficient image density of 1.36 was obtained, and fogging occurred. I couldn't see it. When a 50,000-sheet printing test was performed, an image density of 1.35 equivalent to the initial level was obtained after printing 50,000 sheets, and no fog was observed. I got it.

Comparative Example 1 Dry colloidal silica R812 was used as the base toner of Example 1.
Only 0.3 parts by weight (manufactured by Nippon Aerosil Co., Ltd.) was added to obtain a test toner. Using a commercially available copying machine (product name: NP-4335, manufactured by Canon Inc.) employing the one-component developing method, the obtained toner was used to produce an image.
Some fogging also occurred. When a 20,000-sheet printing test was performed, the image density was 1.10 after printing 20,000 sheets.
And fog as low as the beginning, fog worse than in the beginning,
The image became unusable for use.

Comparative Example 2 Dry colloidal silica R812 was used as the base toner of Example 1.
0.3 parts by weight (manufactured by Nippon Aerosil Co., Ltd.) and 2 parts by weight of tin oxide T-1 (manufactured by Mitsubishi Materials Corporation) were added to obtain a test toner. Using a commercially available copying machine (product name: NP-4335, manufactured by Canon Inc.) employing the one-component developing method, the obtained toner was used to produce an image. As a result, a relatively good image having an image density of 1.33 was obtained. Was. However, when a 50,000-sheet printing test was performed, white streaks were generated from around 30,000 sheets, and an image that could not be used at 50,000 sheets was obtained. When the photoreceptor was observed, it was confirmed that countless scratches occurred on the photoreceptor.

Although the mechanism of action of the present invention is not entirely clear, dry colloidal silica adheres to the toner surface and plays a role of improving the fluidity. Amorphous silica-alumina-based composite oxide particles having a diameter of 0.1 to 10 μm are frictionally charged with the toner particles by being present between the toner particles and play a role of imparting charge to the toner. It is thought to carry. That is, the effects obtained by the present invention are as follows. The drawbacks of using dry colloidal silica alone by using dry colloidal silica and the amorphous silica-alumina-based composite oxide particles in combination in the positively chargeable magnetic toner in the one-component development method Has been solved, and from the improvement of fluidity and stabilization of the charge amount, a high-quality image can be stably obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-88554 (JP, A) JP-A-2-59768 (JP, A) JP-A-3-220563 (JP, A) JP-A-3- 257462 (JP, A) JP-A-4-70847 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 9/08 CA (STN)

Claims (1)

(57) [Claims] 1. One-component toner particles containing a binder resin, a magnetic powder and a positive charge control agent as main components, and an acid treatment of zeolite,
Amorphous with a volume average particle size of 0.1 to 10 μm obtained by washing and baking
A positively-chargeable magnetic one-component toner comprising : silica-alumina-based composite oxide particles ; and dry colloidal silica.