JPH01116563A - White toner - Google Patents

Abstract

PURPOSE:To obtain a white toner having a fluidity which is not impaired at high temp. and high humidity, and having stable triboelectric characteristic by using TiO2 having >=99% TiO2 content as white pigment for the white toner wherein the surface of the TiO2 is not treated with hydrous oxide(s) of Al and/or Si. CONSTITUTION:A white pigment of the title toner is TiO2 of high purity which is not surface-treated with hydrous oxide(s) of Al and/or Si, and a blue colorant to be used is a hydrophobic blue pigment. In a medium for fixing resin to be used for dispersing the TiO2 pigment, conventional resin used for the production of toner of this kind, particularly, those derived from several mono- or diethylenic unsatd. monomers, most pref. homopolymers of copolymers of (a) vinyl aromatic monomers, (b) acrylic monomers, may be used. By this constitution, a white toner causing no coagulation even at high temp. and high humidity, having also stable triboelectric characteristic as well as high whiteness, is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a white toner used in electrophotography.

(Prior Art and its Problems) In the field of electrophotography, a method of copying an image on colored paper using white toner is known as a simple method for obtaining a reverse image, that is, a negative image.

Generally, white toner is obtained by dispersing a white pigment such as titanium oxide in a fixing resin medium.

However, this conventionally used white toner has a yellowish tinge and is not completely satisfactory in terms of whiteness.

Therefore, we first proposed a toner in which the yellowish color was corrected to white by blending a blue-based coloring agent, which is a complementary color to yellow (Japanese Patent Application Laid-Open No. 61-2536
28).

However, although the problem of color tint has been solved in this proposal, there is still room for improvement in terms of humidity dependence.

That is, titanium oxide pigments conventionally used as white pigments have been surface-treated with hydrous oxides of aluminum or silicon to adjust their oil absorption and water absorption in order to increase their dispersion in solvents. When this surface-treated titanium oxide is used in a toner, the toner exhibits some hygroscopicity and aggregates in the developing device, resulting in insufficient agitation and a failure to obtain a uniform amount of triboelectric charge. As a result, image density may sometimes decrease,
Problems such as background capri and image blurring occurred.

In addition, the blue dye used as the blue coloring agent also exhibits hygroscopicity, so it has the same problems as titanium oxide.

(Objective) Therefore, an object of the present invention is to provide a white toner that does not agglomerate even under adverse high-temperature environments, exhibits stable charging characteristics at a high level, and has excellent whiteness. .

(Means for Solving the Problems) The white toner of the present invention contains a white pigment and a blue colorant in a fixing resin medium, and is surface-treated with a hydrous oxide of at least one of aluminum and silicon as the white pigment. Using titanium oxide with 99% or more of TiO□ components,
In addition, a hydrophobic blue pigment is used as a blue coloring agent.

(Function) The titanium oxide used in the present invention is high purity (Tie: 99% or more) titanium oxide that has not been surface-treated with a hydrous oxide such as aluminum or silicon during its manufacturing process.

When using titanium oxide as a white pigment for toner,
There is almost no difference in the dispersibility of the pigment in the fixing resin medium melt during melt-kneading between those that have been surface-treated with hydrous oxides of aluminum or silicon and those that have not been surface-treated. In fact, it was found that when a surface-treated pigment is used, it affects the fluidity of the powder when it is melted, kneaded, cooled, and pulverized to form fine particles. Another feature of the present invention is that the purity of the titanium oxide pigment is 99% or more. A10z during the manufacturing process
, Sing, CaO, etc., adsorption of water molecules to the impurities occurs, resulting in hygroscopicity. Therefore, it is important to use titanium oxide pigments with few impurities. A titanium oxide pigment suitable for the purposes of the present invention is available from Ishiya Sangyo Co., Ltd. under the trade name High Purity Titanium Oxide CR-EL. That is, Tie without surface treatment, the ingredients are 9
The white toner of the present invention, in which high-purity titanium oxide containing 9% or more is dispersed in a fixing resin medium, does not contain hydrous oxides such as aluminum or silicon, so it does not exhibit hygroscopicity and is resistant to high temperature and high humidity conditions. It has sufficient fluidity even in environmental conditions, and can be uniformly stirred without agglomeration in the developing device, resulting in stable charging characteristics. Therefore, even after long-term copying, clear images without image smearing or background capri can be obtained. This was recognized.

On the other hand, the colorant to be combined with the above-mentioned titanium oxide is also a hydrophobic colorant. In such a combination, all the materials constituting the white toner have excellent moisture resistance, and it is possible to make the white toner free from humidity dependence.

(Preferred Embodiment of the Invention) As the fixing resin medium in which the titanium oxide pigment is dispersed in the present invention, resins used in the production of this type of toner are used, and particularly preferred ones include various materials or resins. Diethylene-based unsaturated monomers, particularly homopolymers and copolymers of (a) vinyl aromatic monomers and (b) acrylic monomers, are used.

Examples of the monomer (a) above include styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene, vinylxylene, vinylnaphthalene, etc.
Monomers (b) include methacrylic acid, ethyl acrylate, methyl methacrylate, butyl acrylate, butyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 3-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 3-aminopropyl acrylate, 3-N,N
-diethylaminopropyl acrylate, acrylamide and the like.

Other monomers used in combination with these monomers (a) or (b) or alone include butadiene, isoprene, chloroprene, maleic anhydride, fumaric acid, crotonic acid, Examples include other ethylenically unsaturated carboxylic acids such as itaconic acid or their esters, vinyl esters such as vinyl acetate, vinylpyridine, vinylpyrrolidone, vinyl ethers, acrylonitrile, vinyl chloride, vinylidene chloride, and the like. The molecular weight of these resins is preferably in the range of 3.000 to 300,000, particularly 5.000 to 200.000 (7).

Further, in the present invention, the titanium oxide pigment which has not been surface-treated with a hydrous oxide of at least one of aluminum and silicon is used in an amount of 1 to 50 parts by weight, particularly 2 to 30 parts by weight, per 100 parts by weight of the fixing resin medium. Ru. If the amount used is more than the above range, there will be problems such as a decrease in fixing properties, and if it is less than the above range, it will be difficult for 1 to sufficiently express white color.

Furthermore, in the present invention, a blue colorant is blended in order to correct the yellowish color to white, and this blue colorant is of a hydrophobic pigment type.

Examples of blue pigments include navy blue, cobalt blue, alkali blue lake, Victoria blue lake, phthalocyanine blue, metal-free phthalocyanine blue, partially chlorinated phthalocyanine blue, fast sky blue,
Examples include Indan Stremburu-BC.

These blue coloring agents are used at 5 parts by weight per 100 parts by weight of the fixing resin.
It is used within a proportion of 0.001 to 2 parts by weight, particularly 0.001 to 2 parts by weight. When used in an amount larger than this range, the white color of the toner is adversely affected and the toner becomes bluish. Most preferably, it is used in an amount of 1/10 or less of the weight of the white pigment within the above range.

Other compounding agents include white or substantially colorless toner compounding agents that do not adversely affect the color of the toner, such as charge control agents, anti-offset agents, pressure fixability imparting agents, and conductivity imparting agents according to well-known formulations. can do.

As charge control agents, organic compounds having basic nitrogen atoms, such as polynuclear polyamine compounds, aminosilanes, or fillers treated with the same, are used for the purpose of controlling positive charges, and as negative charge control agents, organic compounds having basic nitrogen atoms are used. , hydrophobic carboxy group-containing compounds, such as alkyl salicylic acid metal chelates, are used. Specific examples include zinc chelates of alkylsalicylic acids.

It is preferable to use these charge control agents in an amount of 1 to 10 parts by weight per toner. In addition, in the method of fixing the toner with a hot roll, offset prevention agents such as silicone oil, low molecular olefin resins, various waxes, etc. 2 per toner
It can be used in amounts ranging from 15 parts by weight. Further, in applications where the toner is fixed with a pressure roll, a pressure fixing property imparting agent such as paraffin wax, various animal/vegetable waxes, fatty acid amide, etc. may be used in an amount of 5 to 30 parts by weight per toner.

In the present invention, a white pigment dispersed in a fixing resin medium is formed into particles having a particle size of 5 to 50 IJm to form a toner.

The toner is produced by any means known per se. For example, a charge control agent is added to a fixing resin medium along with other additives if necessary, and the mixture is kneaded evenly and uniformly, and then granulated to form a toner.

For molding, after cooling the above-mentioned kneaded mixture,
It can be obtained by pulverizing this and, if necessary, sieving it. Of course, rapid mechanical stirring may be used to round off irregularly shaped particles.

Alternatively, the fixing resin medium is dissolved in a solvent such as toluene or xylene, and the scaly pigment is dispersed therein.
By spray-drying and granulating the resulting stock solution, toner in the form of spherical particles can be obtained.

Furthermore, a toner can also be obtained by dispersing a white pigment in a solvent that dissolves the monomer but not the resulting polymer, and polymerizing the monomer in this system in the presence of a radical initiator. be able to. As monomers, those exemplified above are preferably used.

(Example) The content of the present invention will be explained in detail below using examples.

Toner 1 (Example) Titanium oxide pigment: CR-EL (manufactured by Ishihara Sangyo Co., Ltd.) 20 parts by weight, styrene-acrylic resin: PA-525 (manufactured by Mitsui Toatsu Chemical Co., Ltd.) 100 parts by weight, monochlorocopper phthalocyanine pigment Nidiane Blue 〇-314 (manufactured by Yamama Shiki Co., Ltd.) Low molecular weight polypropylene: Viscol 550P (manufactured by Sanyo Chemical Co., Ltd.) 2.0 parts by weight, white charge control agent: Bontron E8
4 (manufactured by Orient Chemical Co., Ltd.) and mixed uniformly with a Henschel mixer FM20B (manufactured by Mitsui Miike Kakoki Co., Ltd.), and then melted and mixed in a twin screw extruder DCM45 (manufactured by Bumen Tekko Co., Ltd.) and allowed to cool. Rear cutting mill ■DS-5 type (
(manufactured by Nippon Pneumatic Co., Ltd.). Fine powder was removed from this finely pulverized product using an Alpine classifier 132MPL (manufactured by Yasuyo Denki Co., Ltd.) to obtain a toner having an average particle size of 12 μm. Furthermore, in order to improve fluidity, 0.25 parts by weight of hydrophobic silica: R-972 (manufactured by Nippon Aerosil Co., Ltd.) was added, the mixture was stirred with a Henschel mixer FM20B, the surface was treated, and finally aggregates were removed with a vibrating sieve. It was made into a product toner. This white toner and a ferrite carrier (average particle size: 50 μm, manufactured by Nippon Tetsuko Co., Ltd.) are mixed using a Nauta mixer (manufactured by Hosogumi Micron Co., Ltd.) to obtain a developer having a toner concentration of 5%.

Toner 2 (Comparative Example 1) Except for replacing the titanium oxide pigment in Toner 1 with R-615 (manufactured by Ishihara Sangyo Co., Ltd.) and replacing cyanine blue G-314 with a commercially available blue dye (C, 1, Acid Blue 158). A developer was prepared in exactly the same manner as Toner I.

Toner 3 (Comparative Example 2) A developer was obtained in exactly the same manner as Toner 2 except that the toner formulation in Toner 2 did not contain C,1 acid blue.

The titanium oxide pigments used in Examples and Comparative Examples are as shown in Table 1 below.゛Table-1 The above developer was tested at room temperature (20℃, 65%) and at high temperature.
Copies were made in a copying machine DC-111 manufactured by Sanda Kogyo Co., Ltd. under a high temperature environment (35° C., 85%).

As a result, toner 1 produced clear images with no background fogging or image smearing under any environment, but toners 2 and 3 had problems such as background fogging and image smearing under high temperature and high humidity environments. Occurred.

Furthermore, the image obtained with Toner 3 had a yellowish tinge.

(Effects of the Invention) According to the present invention, it is possible to obtain a white toner with stable triboelectric charging characteristics that does not impair fluidity and does not aggregate in a developing device even in a high temperature and high humidity environment, thereby reducing background fog and image formation. Good copies without bleeding can be obtained.

Claims (4)

[Claims] (1) In a white toner containing a white pigment and a blue colorant in a fixing resin medium, the white pigment is high-purity titanium oxide that is not surface-treated with a hydrous oxide of at least one of aluminum and silicon; A white toner characterized in that the blue colorant is a hydrophobic blue pigment. (2) The white toner according to claim 1, wherein the blue colorant is blended in an amount of 1/10 or less of the weight of the white pigment. (3) The white toner according to claim 1, wherein the titanium oxide pigment has a purity of 99% or more. (4) The titanium oxide pigment is 1 to 5 per fixing resin medium.
The white toner according to claim 1, wherein the white toner is dispersed in a proportion of 0 parts by weight.