JPH0216916B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a developing powder for electrophotography. Electrophotography generally involves forming an electrostatic latent image on a photoconductor made of a photoconductive substance, developing this image with a powder developer to make it visible, and then fixing it with heat or a solvent. be.

As a developer for such electrophotography, a mixture of a fine particle powder called a toner consisting of a resin and a colorant, and a microscopic glass bead or iron powder called a carrier is used.

The present invention relates to this developing powder called toner.

The photoconductor layer can be positively or negatively charged so that exposure under the original produces a positive or negative electrostatic latent image. Therefore, if the negative electrostatic latent image is developed with positively charged developer powder, a positive-positive image matching the original is generated. However, when a positively electrostatic latent image is developed with negatively charged developer powder, the black and white tones are reversed, resulting in a negative image of the original, that is, a positive-negative image. As described above, there are two types of developer powder for electrophotography: positively charged developer powder and negatively charged developer powder.

The present invention relates to negatively charged developer powder.

Generally, developer powder is a fine powder made by mixing synthetic resin with coloring agents such as dyes and pigments.

In order to charge the developing powder negatively, the dye mixed therein plays an important role not only in coloring but also in its electrostatic properties as a charge control agent. In particular, most of the dyes and pigments conventionally used as coloring agents are positively charged, and even if they are negatively charged, their chargeability is weak, resulting in mixed mirror images or fog, resulting in sharp images. I couldn't get an image.

The present inventors focused on this point and developed a dye that has negative characteristics and particularly has extremely good compatibility with the resin used. As a result, it was possible to produce a developing powder with excellent electrostatic properties that improved all the drawbacks of conventionally used colorants. That is, the present invention provides the following formula {In the formula, X represents a nitro group, a sulfonamide group, or a halogen atom, Y represents a hydrogen atom, a halogen atom, or a nitro group (excluding cases where both X and Y are nitro groups), and M represents a chromium or cobalt atom. represent } This is an electrophotographic developing powder containing a 2:1 type metal complex dye represented by the following as a charge control agent and a colorant.

The above dye has the property of being negatively charged electrostatically,
Therefore, a negatively charged developing powder can be obtained very easily by mixing with a suitable developing resin in a desired ratio.

In addition, there are many 2:1 type metal complex dyes as toner colorants similar to the dye represented by formula (1) above, as detailed below, but the dye according to the present invention is more effective than known dyes. , has particularly good compatibility with developing powder resins. Therefore, the developer powder is uniformly distributed in each of the fine particles. This is an important point regarding the charging characteristics of the developing powder. Furthermore, the dye of the present invention itself has an extremely large amount of negative charge.

Examples of using 2:1 type metal complex dyes in toners include, for example, Japanese Patent Publication No. 41-6397;
No. 41-12915, Japanese Patent Publication No. 41-20153, Japanese Patent Publication No. 43-27596, Japanese Patent Publication No. 51-29827, Japanese Patent Application Publication No. 47-5637, Japanese Patent Publication No. 49-21151 and Publication No. 49-27229 can be mentioned. However, in all of these known dyes, the counter ion to the negative charge of the dye matrix structure is an alkali metal ion, an alkaline earth metal ion, an ammonium ion, an aliphatic ammonium ion, an alicyclic ammonium ion, or a heterocyclic ammonium ion. It is different from the counter ion H of the dye according to the present invention.

As a result of various studies, the present inventors have completed the present invention by discovering that by using H as the counter ion of the dye, the compatibility with the resin becomes extremely good.
The reason why the dye of the present invention has particularly good compatibility with resin is not necessarily clear, but it is due to the fact that the dye of the present invention has a particularly low bulk specific gravity and the dye particles are soft and easily divided. It seems to be.

The dye of formula (1) used in the developing powder of the present invention is expressed by the following formula (2). A monoazo dye obtained from a 2-aminophenol derivative represented by the formula (wherein X and Y are as defined above) and β-naphthol is treated with a chromium or cobalt imparting agent by a known method. It will be done. Generally, the following formula (3) (where X and Y are as defined previously, and A
represents an alkali metal ion or an ammonium ion. ) can be easily obtained by dispersing a 2:1 type metal complex dye represented by the formula in aqueous alcohol and adding a stoichiometrically slightly excess amount of hydrochloric acid or sulfuric acid, with the counter ion being H. In this case, lower alcohols such as methanol, ethanol, propanol, and butanol can be suitably used as the alcohol, and the alcohol concentration is preferably in the range of 30 to 50%.

The dye according to the present invention obtained in this way is
The crystals are very soft and can be made into a product by omitting the pulverization step after drying. Even more surprisingly, the bulk specific gravity is extremely small, being 1/3 to 1/6 compared to known dyes. This shows that it has very good compatibility with the developing powder resin as a charge control agent and coloring agent for toner. Moreover, the dye according to the present invention exhibits negative results in a mutagenicity test (Ames test).

The developing powder of the present invention is prepared by melting and blending the dye of formula (1) in a weight ratio of 1 to 50% based on the synthetic resin, solidifying it, and then pulverizing it with a ball mill or other pulverizer, or by adding it to the synthetic resin monomer. It can be produced by adding a polymerization initiator, adding thereto a dye in a weight ratio of 1 to 50% based on the monomer, and polymerizing the mixture while suspending it in water. At this time, other colorants or carbon black may be added as a dye. The developer powder produced in this way provides an amount of charge suitable for developing an electrostatic image through friction with the carrier, and the amount of charge remains constant even after repeated development, and the charge distribution is uniform. held constant. Therefore, images developed using this developing powder have uniform and constant density, and are much clearer than conventional negative developing powders.

The present invention will be explained in detail below with reference to Examples.

Example 1 Disperse 10 parts of the dye represented by the above formula in 75 parts of a 50% ethanol aqueous solution, add 1.5 parts of 36% hydrochloric acid while stirring vigorously, stir for 5 hours, pour into 100 parts of water, and filter. Wash the dye cake with 50 parts of water;
Dried and the following structural formula 9.4 parts of a dye of the formula was obtained. The bulk specific gravity of this dye was reduced to 1/3 compared to the dye used as the raw material. Next, 6 parts of carbon black and 5 parts of the above dye were added to 100 parts of styrene synthetic resin, mixed well, heated and melted, cooled and ground in a ball mill to obtain a fine, negatively charged developing powder. . Next, this developing powder colored black was mixed in a weight ratio of 5:100.
A developer was obtained by mixing it with iron powder having a diameter of 100 to 150μ. A positive electrostatic latent image was formed on a selenium photosensitive plate charged by +5000 V corona discharge, and developed by a magnetic brush method using the above developer to obtain a positive image. A +5000V corona discharge was applied to this positive image to transfer it to paper, and by heating and fixing, a clear image without fogging was obtained. Further, during running (10,000 times), there was no significant change in the development characteristics of the toner. The amount of charge on the toner was measured using the blow-off method and was -19μc/g on average.
The charge distribution was approximately uniform at -18.5 to -19.4 μc/g.

On the other hand, for comparison, in this example, the following known dye was used instead of the dye of the present invention. When using the toner, the obtained image had background smudges and became unclear, and during running (10,000 times), the development characteristics of the toner changed significantly, making it impossible to form a practical image. The average charge amount of this toner is -13μc/
g, and the charge amount distribution was non-uniform at -2.5 to -28 μc/g.

Note that in place of the 2:1 type metal complex dye in Example 1, a dye having the structure shown below could be used.

Furthermore, in place of the styrene resin in Example 1, an epoxy resin, a polyester resin, a styrene-acrylic copolymer, and a polyolefin resin could be used.

Claims (1)

[Claims] Linear formula {In the formula, X represents a nitro group, a sulfonamide group, or a halogen atom, Y represents a hydrogen atom, a halogen atom, or a nitro group (excluding cases where both X and Y are nitro groups), and M represents a chromium or cobalt atom represents. } An electrophotographic developing powder characterized by containing a 2:1 metal complex dye represented by the following as a charge control agent and a colorant.