JPH0679168B2 - Negatively charged blue toner for electrophotography - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic toner, and more particularly to a blue electrophotographic toner that can be used for developing a positively charged image.

2. Description of the Related Art As a toner for electrophotography, a toner in which a colorless pigment such as carbon black is dispersed in a fixing resin binder is generally used. Therefore, those obtained by dispersing various chromatic colorants in a fixing resin binder have been gradually used.

Among such color toners, as the blue toner, those using a phthalocyanine-based dye such as copper phthalocyanine are mainly used from the viewpoint of sharpness, but such a phthalocyanine-based dye is used for the toner itself. It has a drawback that it tends to be positively charged and cannot be used for a photosensitive plate having a positive electrostatic image such as a selenium photosensitive plate.
Of course, it is conceivable to add a charge control agent that gives a negative chargeability to the copper phthalocyanine toner, but the addition of a large amount of charge control agent makes the toner itself sensitive to humidity, Alternatively, there are inevitable drawbacks such as deterioration of its electrical characteristics.

SUMMARY OF THE INVENTION AND OBJECTS The present inventors have found that when an indanthrone dye is used as a colorant for a blue toner, it has a vivid blue hue and also has the effect of significantly improving the negative chargeability of the toner. I found it.

An object of the present invention is to provide an electrophotographic toner having a negative blue charge and a clear blue hue.

Another object of the present invention is to provide a blue toner in which the negative charging property is remarkably improved without adversely affecting the moisture resistance, fluidity or electrical characteristics of the toner particles.

According to the present invention, a fixing resin binder and the following chemical structure as a colorant and a charge control agent are provided. And an indanthrone-based dye having (excluding the case of using a copper phthalocyanine-based pigment).

In this toner, the indanthrone dye is 2 to 12 parts by weight, particularly 5 to 10 parts by weight, per 100 parts by weight of the fixing resin binder.
It is preferable to be present in a proportion of parts by weight.

Features and operational effects of the invention Indanthrone dyes are vat dyes obtained by oxidatively condensing 2-aminoanthraquinone in a melting agent mainly composed of causticari and anhydrous sodium acetate, and if necessary purified with sulfuric acid. And CI Bat Blue (C.
I.69800) and has the following formula It is a dye having a chemical structure shown by.

This dye is insoluble in most solvents such as water, alcohol or xylene, is chemically stable and is particularly suitable as a colorant for toner.

Moreover, this indanthrone-based dye has a negative polarity triboelectrification performance, which is exceptional among blue colorants.

The following Table 1 shows various blue colorants 10g and iron powder carrier S
The results obtained by mixing 90 g of TV-25T (manufactured by Nippon Iron Powder Co., Ltd.) with a roll mill for 1 hour and measuring the charge amount (microcoulomb / g) by the blow-off method are shown.

From the results in Table 1 above, it is clear that the indanthrone type dye has an exceptional negative charging ability as a blue dye, and the present invention utilizes this characteristic for a blue toner.

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to its preferable modes.

As the fixing resin binder, among various thermoplastic or thermosetting resins, all the resins used in this field can be used, for example, styrene resin, acrylic resin, olefin resin, vinyl resin. Resin, saturated polyester resin, polyamide resin, alkyd resin, epoxy resin,
A xylene resin or the like is used alone or in combination of two or more kinds.

The indanthrone-based dye is preferably used in the above-mentioned quantitative ratio per the binder. If the amount ratio is less than the above range, the negative charging property or the coloring degree, that is, the image density tends to decrease, and if it exceeds the above range, the toner cleaning property or the fixing property tends to decrease.

To the toner of the present invention, it is of course possible to add known toner compounding agents, for example, other colorants (except copper phthalocyanine pigments) for adjusting the color tone, and electric resistance adjustment. Therefore, an inorganic conductive agent, for example, a tin oxide-antimony oxide based conductive agent can be blended. Further, silicone oil, low molecular weight olefin resins, various waxes and the like may be used for the purpose of assisting the releasing property.

The particle size of the toner particles is generally in the range of 3 to 25 microns, preferably 5 to 20 microns.
In order to improve the fluidity of the toner particles, the surface of the toner particles can be sprinkled with fine particles such as fumed silica by a means known per se.

Toner particles are manufactured by uniformly kneading the above-mentioned components,
This kneaded composition is cooled, then pulverized and optionally kneaded. Alternatively, as another method, the toner can be manufactured by a so-called spray granulation method in which the above-mentioned components are dissolved and dispersed in an organic solvent such as toluene, and the dispersed solution is sprayed in a dry atmosphere to granulate.

In the electrostatographic copying method using the toner of the present invention, formation of an electrostatic latent image can be carried out by any method known per se, for example, after uniformly charging a photoconductive layer on a conductive substrate, An electrostatic latent image can be formed by imagewise exposure.

Development of the electrostatic image is facilitated by mixing the toner with a magnetic carrier and bringing the magnetic brush of the toner into contact with the substrate. The toner image formed by the development is transferred onto a copy sheet, and the toner image is fixed by bringing it into contact with a heating roll.

The mixing ratio of the toner and the magnetic carrier may be the same as that of a normal black toner, and is generally 3: 100 to 10: 100.
The range of is desirable.

The invention is illustrated by the following example.

Example 1 100 parts by weight of PRIORITE ACL (styrene-acrylic copolymer, manufactured by Goodyear), 8 parts by weight of Slenblue IRN, and 3 parts by weight of low molecular weight polypropylene 550P (manufactured by Sanyo Kasei Co., Ltd.) were uniformly mixed with a Henschel mixer. Is melt-kneaded with a twin-screw extruder, allowed to cool, and then roughly crushed with a cutting mill. Approximately 25 of this coarsely pulverized product is ultrasonically jet milled.
It was finely pulverized to a size of not more than micron and cut to a size of 5 microns or less by an air classifier to obtain a blue toner having a size of 5 to 25 microns. Furthermore, hydrophobic silica R-972 is used to improve fluidity.
(Manufactured by Nippon Aerosil Co., Ltd.) was applied to the toner surface with a Henschel mixer in an amount of 0.1% by weight based on the total amount.

After 80 g of this blue toner and 720 g of iron powder carrier were mixed by stirring for one hour by a roll mill, the triboelectric charge amount of the toner was measured by the blow-off method to be −17.7 μc / g. This developer was put in a commercially available dry copying machine DC-232 (manufactured by Mita Kogyo Co., Ltd.), and the developing machine and Se drum were continuously rotated (aged) for 10 hours with the developing bias applied, and then the developer on the developing sleeve was collected. Then, the triboelectric charge was measured to be -16.8 μc /
g, toner concentration was 9.8%.

In addition, 120g of this blue toner and 1200g of iron powder carrier were mixed with a roll mill to use as a starter, and a commercially available dry copying machine was used.
It was put in DC-A2 (manufactured by Mita Kogyo Co., Ltd.) and 5000 sheets were continuously copied (A2 size). First copy quality is brush mark,
It was a clear blue image with no trailing, there was almost no deterioration in image quality after 5000 sheets, and there was almost no toner scattering. The image density (ID) and fog density (FD) of the first 5000th sheet are as shown below.

1st 5000th ID 0.95 0.93 FD 0.001 0.001 Comparative Example 1 100 parts by weight of Pliolite ACL, Cyanine Blue G-3148
A blue toner was obtained from 3 parts by weight of 550P3 by weight in the same manner as in Example.

When an aging test was conducted with DC-232 as in the example, the toner charge amount was −10.1 μc / g.

However, when copying was performed using this toner in the same manner as in Example 1, it was confirmed that fogging was remarkably generated and the fog density (FD) reached 0.1.

Claims (2)

[Claims] 1. A fixing resin binder and the following chemical structure as a colorant and a charge control agent. And an indanthrone-based dye having (excluding the case where a copper phthalocyanine-based pigment is used). 2. The negative electrode type electrophotography according to claim 1, wherein the indanthrone dye is present in an amount of 2 to 12 parts by weight per 100 parts by weight of the fixing resin binder. For blue toner.