JPS589415B2 - Dry toner for electrostatic image development - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in color toners for dry electrophotography.

Conventionally, cyan toners for dry electrophotography have been made by dispersing phthalocyanine organic pigments such as C-I Pigment Blue 15, 1, 6, 1, 7, etc. in styrene thread resin.

Although this product has excellent color properties, it does not show positive polarity due to friction with the carrier during use, so in order to create a positive polarity toner, other polarity control agents are added as constituents of the toner, so the following steps are required: There were drawbacks such as:

For example, the compatibility between the polarity control agent and the base resin is poor, resulting in decreased transparency.

In addition, the polarity control agent deteriorates the spectral characteristics.

Furthermore, since the phthalocyanine pigment has negative polarity, it is unstable even if it is controlled to positive polarity using a control agent, and the amount of charge decreases in high humidity.

The purpose of the present invention is to improve such drawbacks, and in the dry toner for electrostatic development which mainly consists of a resin and a colorant, the colorant is represented by two general formulas: R1, R3, R5, R6 represents hydrogen or a lower alkyl group, and R2, R, each represents a lower alkyl group.

This is a dry toner for electrostatic image development, characterized in that it has a pigment obtained by turning a basic dye represented by the following into a lake, and contains 1 to 20% by weight of an oil-soluble phenol resin based on the total amount of the resin.

Examples of the basic dyes used in the present invention include those shown below.

C. I. Basic Blue 1 (Product name: Eisen Basic Cyanine 6GH, manufactured by Hodogaya Chemical) C. I. Basic Blue 5 (trade name: Primocyanin BX conc, manufactured by Sumitomo Chemical Co., Ltd.) The dye is formed into a lake by a known method.

That is, an aqueous solution of a lake forming agent such as phosphotungstic acid, phosphotungsten molybdic acid, phosphomolybdic acid, or oxalic acid is added to an acetic acid solution of the dye to precipitate the lake pigment, which is washed separately with water, dried, and pulverized.

Pigments obtained by turning the above-mentioned dyes into lakes are commercially available, and include the following, for example.

Astrazon Blue Lake (AstrazonB
Lue Lake) (manufactured by Shinko Chemical Co., Ltd.) Fastel Bremen Blue Splat (Fast
e l, Bremen Blue Supra) (
manufactured by Imperial Chemical Co.) Irgalite Azure Blue TCR (Irgalite Azure)
i teAzure Blue TCR')
(manufactured by Geigy) Such pigments have traditionally been widely used as binders. If the resin is dispersed only in the styrene resin, the dispersion will be poor and the color properties and charging stability will be insufficient, so oil-soluble phenol resins are particularly suitable for the present invention.

Typical oil-soluble phenol resins include baraphenyl phenol resins, which are available as commercial products, such as PP-811, PP-1008 (manufactured by Gunei Kagaku Co., Ltd.), and UCC #5 2 (product name). 5 4 (manufactured by Union Carbide), etc.

Resins traditionally used as binders can be used in combination with oil-soluble phenolic resins.

Such resins include polystyrene, polyacrylic ester, styrene acrylic ester copolymer, polyvinyl chloride, polyvinyl acetate, alkyd resin, epoxy resin, polyvinyl acetal, unsaturated polyester resin, and the like.

The content of the lake pigment in the present invention is preferably 1 to 10 parts by weight, preferably 2 to 5 parts by weight, based on the total amount of the toner.

This lake pigment is a substance that causes the toner to be strongly and positively triboelectrified, and by using an oil-soluble phenol resin as the resin, it is possible to improve the dispersibility of this lake pigment in the resin. Among these, it is a substance that has a relatively strong tendency to be negatively charged.

From this point of view, it is appropriate that the content of the oil-soluble phenol resin be 1 to 20 parts by weight, more preferably 5 to 10 parts by weight, based on the total resin amount.

The lake pigment of the present invention is well dispersed in a resin and has excellent charging properties, and exhibits particularly strong positive charging properties when included in a toner containing an oil-soluble phenol resin as a binder.

It also exhibits excellent humidity resistance and spectral properties.

Further, the oil-soluble phenol resin has an appropriate softening point and hardness when used as a toner resin.

Examples and comparative examples are shown below.

Examples Styrene normal butyl methacrylate copolymer (trade name: Hymer SBM73, manufactured by Sanyo Kasei Co., Ltd.) 95 parts by weight Varaphenylphenol resin (trade name: PP-811, manufactured by Gunei Chemical Co., Ltd.) 5 parts by weight Astrazone Blue Lake ( (manufactured by Shinko Chemical Co., Ltd.) 3 parts by weight or more were melt-kneaded in a roll mill, cooled, pulverized in a jet mill, and classified to obtain particles of 5 to 20 μm.

This was mixed with iron powder of 150 to 250 mesh to prepare a developer.

When a negative latent image formed on zinc oxide photosensitive paper was developed using this developer by a conventional method, a clear positive image was obtained.

Further, when the amount of triboelectric charge of the toner in this developer was measured by a blow-off method, it was found to be +15 μc/g.

Then, this developer was left in a high temperature and high humidity atmosphere of 30°C and 90% for 6 hours, and the amount of charge was measured after that.
There was no change at +15 μc/g, and a clear positive image was obtained in the development test.

Comparative Example A cyan toner was prepared using a phthalocyanine pigment as a coloring agent and a polyamide resin as a polarity control resin as shown below.

Styrene normal butyl methacrylate copolymer (product name: Hymer SBM 73, manufactured by Sanyo Chemical Co., Ltd.) 95 parts by weight Polyamide resin (product name: Polymide A-5, manufactured by Sanyo Chemical Co., Ltd.) 5 parts by weight Cap cyanine pigment (product name) :LiondBlueKL (manufactured by Toyo Ink Co., Ltd.) A toner containing 3 parts by weight or more was produced in the same manner as in the example, and mixed with iron powder to obtain a developer.

In the development test and charge amount measurement using this developer, the same results as in the example were obtained, but the charge amount after being left at high temperature and high humidity was +2.
It decreased to .mu.c/g, and in the development test, there was a very large amount of background smudge.

The properties of the toners of Examples and Comparative Examples are summarized in the table below.

(Note) (1), (2), (3) H
, M, and L. (Note) (4)...The value obtained by measuring the cloudiness of the toner film using an integrating sphere turbidity meter and subtracting it from the factor of 100.

As described above, the toner of the comparative example had a decreased charge amount after being left at high temperature and high humidity, and also had poor compatibility between polystyrene and polyamide resin, resulting in decreased transparency.

Claims (1)

[Scope of Claims] 1. A color toner for dry electrophotography containing a resin and a colorant as main components, in which a basic dye represented by the following general formula is used as the colorant, provided that in the above formula, R1 , R3 , R5 , Ra
represents hydrogen or a lower alkyl group, R2 represents a lower alkyl group, and R4 represents a lower alkyl group. Contains a laked pigment, and 1% of the total amount of resin.
A dry toner for electrostatic image development, characterized in that it contains up to 20% by weight of an oil-soluble phenolic resin.