JPH067271B2 - Negative charging color toner - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a color toner for electrophotography, and more particularly to a color toner having a good blue tint and an excellent negative electrode charging ability.

2. Description of the Related Art In electrophotography, as a toner for visualizing an electrostatic latent image, saliency and fixing particles containing various pigments in a binder resin medium are used. Among these toners, copper phthalocyanine, particularly unsubstituted copper phthalocyanine, is most excellent in terms of tint as a pigment for blue toner.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, it has been found that when this copper phthalocyanine is used as a pigment to produce a blue toner having a negative charging ability, a fatal drawback occurs. In electrophotography, a positive or negative electrostatic latent image is formed according to the characteristics of the photoconductor, but the positive electrostatic latent image is advantageous in that ozone is less generated, A toner having a negative chargeability is required as a toner applicable to this.
By the way, since copper phthalocyanine itself has a triboelectric chargeability of positive polarity, there are drawbacks that the charging of the toner becomes unstable and the charge amount is remarkably reduced during copying for a long time.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an electrophotographic color toner which retains the good tint of copper phthalocyanine as it is and also has excellent negative chargeability, that is, excellent charge retention and charge retention. To provide.

Another object of the present invention is to provide a color toner for electrophotography comprising a combination of copper phthalocyanine and a resin medium having excellent dispersibility of copper phthalocyanine.

According to the present invention, there is provided a negatively chargeable color toner for electrophotography, which is characterized by containing a blue copper phthalocyanine pigment in a styrene-acrylic resin medium having an acid value of 10 or more.

Preferred Embodiments of the Invention As the blue pigment, many blue pigments such as ultramarine blue, Victoria blue, and slen blue are known in addition to copper phthalocyanine, but copper phthalocyanine, that is, phthalocyanine blue B is the most excellent in terms of vivid blue tint. ing. Copper phthalocyanine has the following formula It is recognized that the compound has a chemical structure represented by, and has a triboelectric charging property of positive polarity due to the influence of nitrogen atoms contained in the molecule. This copper phthalocyanine has
A nuclear chlorine-substituted derivative is known, and this derivative gradually shows a negative polarity triboelectric charging property depending on the degree of chlorine substitution, but as chlorine is substituted, this pigment appears to have a hue close to green. Which is not preferable for the purpose of the present invention.

In the present invention, by using a styrene-acrylic resin having an acid value of 10 or more as the resin medium in which the copper phthalocyanine is dispersed, the excellent blue tint of the copper phthalocyanine can be used, and the toner can have negative triboelectrification characteristics. It has been successfully given. Moreover, in the combination of copper phthalocyanine and this resin medium, copper phthalocyanine can be easily and uniformly dispersed in the resin medium, and
It is possible to remarkably improve the charge retention property and the charge retention amount as a toner, and to form a color print with stable density even when repeatedly copying a large number of sheets.

It is absolutely essential that the acid value of the styrene-acrylic resin is 10 or more from the viewpoint of stable negative charge, and even if the styrene-acrylic resin is used, if the acid value is less than 10, The triboelectrification property of the toner becomes unstable.

It is also important that the resin used in the present invention is a styrene-acrylic resin. The toner resin is required to have a combination of sensible properties, fixing properties, blocking resistance, and pulverizability for toner production. Styrenic resins are excellent in electroscopic property, blocking resistance, and pulverizability, but have some problems in fixing property. Styrene resin has high electric resistance, and once it is triboelectrically charged, it is difficult for the charge to dissipate and is excellent in charge retention. However, since this resin has no polar group, it traps charge. There are disadvantages that there are few places (sites) to be charged and the amount of held electric charges, namely the amount of held surface charges is small. On the other hand, although the acrylic resin is excellent in the electrophotographic property and the fixing property, it is recognized that the acrylic resin has a problem in the releasability at the time of fixing and the blocking of the toner occurs during the operation for a long time. By using a styrene resin and an acrylic resin in the form of a copolymer, it is possible to obtain almost satisfactory combination characteristics in all respects. By incorporating it in the copolymer together with the monomer, the charge retention amount can be remarkably increased without substantially lowering the charge retention property as a toner.

The styrene-acrylic resin used in the present invention comprises an ethylenically unsaturated carboxylic acid corresponding to an acid value of 10 or more, particularly 15 to 80, an acrylic acid ester and / or a methacrylic acid ester, and a styrene monomer. Obtained by polymerizing. As the ethylenically unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic anhydride, fumaric acid, itaconic acid, crotonic acid, etc. are used, and as the esters of acrylic acid or methacrylic acid, methyl ester, ethyl ester, butyl Ester, amyl ester, 2-ethylhexyl ester, lauryl ester and the like can be mentioned. In addition to styrene, vinyltoluene, α-methylstyrene, α-chlorostyrene and the like can be used as the styrene-based monomer.

A styrene-acrylic resin particularly suitable for the purpose of the present invention contains 10 to 40% by weight of an ester of acrylic acid or methacrylic acid and 60 to 90% by weight of a styrene monomer in the polymer chain, based on the resin. It contains the amount of the ethylenically unsaturated carboxylic acid which gives the above-mentioned acid value per 100% by weight of the total amount of these.

In the present invention, copper phthalocyanine is preferably used in an amount of 1 to 30 parts by weight, particularly 5 to 25 parts by weight, per 100 parts by weight of the resin.

This toner contains, in addition to the above-mentioned components, a compounding agent known per se, for example, a low molecular weight polyolefin wax,
A mold release agent such as various waxes may be blended. Further, in order to control the fluidity of the toner particles, vapor phase silicon oxide,
A fluidity modifier such as vapor phase aluminum oxide may be blended on the surface of the toner particles.

Further, in such a color toner, due to its color tone, carbon black cannot be blended, the electric resistance of the developer as a whole becomes too high, and as a result, an edge effect is likely to occur. It is desirable to add a substantially non-colored conductive agent such as an antimony-based conductive agent or a zinc oxide-based conductive agent in an amount of 0.5 to 20% by weight based on 100 parts by weight of the resin.

To produce the toner particles, the above-mentioned respective components are blended, kneaded at a temperature equal to or higher than the softening point of the resin, and the kneaded composition is pulverized,
Then, it is easily subjected to a classification operation.
The particle size of the toner particles is preferably such that the average particle size is in the range of 7 to 15 microns.

The color toner particles of the present invention are used as a magnetic brush for developing a positive electrostatic latent image in the form of a two-component developer mixed with a magnetic carrier such as iron powder, and have a high density and a clear blue image. Can be formed.

Example 1. The mixture having the above formulation was premixed with a Henschel mixer, then melt-kneaded with a twin-screw extruder and allowed to cool. This mixture was roughly crushed with a cutting mill, finely crushed with an ultrasonic jet mill, and cut with an Alpine classifier to a particle size of 5 μm or less to obtain a blue toner having an average particle size of 11.0 μm in the range of 5 to 25 μm. It was Further, 0.2 wt% of hydrophobic silica (R-972, manufactured by Nippon Aerosil Co., Ltd.) for improving fluidity was treated on the toner surface with a Henschel mixer. When 80 g of this blue toner and 720 g of iron powder carrier (STV-25T; manufactured by Nippon Iron Powder Co., Ltd.) were rotatively mixed by a roll mill for 1 hour to prepare a developer, and a blow-off triboelectric charge amount was measured.
It was 17.5 μc / g. This developer is a commercial copying machine (DC
-161; manufactured by Mita Kogyo Co., Ltd.) and a copy test was performed on 10,000 sheets. When the charge amount after copying 10,000 sheets was measured, it was -15.9 µc / g, and in the copied image, the initial image density (ID) was 1.08 and the fog density (FD) was 0.6.
On the 000th and 10,000th sheets, the image density was 1.09 and the fog density was 0.001 with almost no change, and a blue image with no tailing brush mark and excellent in resolution and sharpness was obtained.

Example 2. A blue toner was obtained in the same manner as in Example 1 except that a styrene-acrylic resin having an acid value of 35.4 was used.

The charge amount after mixing with the carrier was −24.3 μc / g. As a result of performing the copy test in the same manner as in Example 1, the charge amount after copying 10,000 sheets was −22.7 μc / g, which was almost unchanged.

On the other hand, in the copied image, the initial ID is 1.01 and the FD is 0.000, and the I.D. D was 1.03 and FD was 0.000, and clear images could be obtained as in Example 1.

Further, a developer was prepared and an image forming experiment was conducted in the same manner as in Example 1 except that styrene-acrylic resins having acid values of 10.2 and 12.0 were used. The results are shown in Tables 1 and 2 together with the results of Example 1. In the image output experiment of Example 1 and the like, the calculation of the transfer efficiency and the observation of the stain inside the machine were also performed, and the results are also shown.

Comparative Example A blue toner was obtained in the same manner as in Example 1 except that the styrene-acrylic resin having an oxidation of 3.5 was used.

The charge amount after mixing with the carrier was -12.1 μc / g. When a copy test was conducted in the same manner as in Example 1, the charge amount after copying 10,000 sheets decreased to -6.4 μc / g.

Also, in the case of copied images, the initial ID 1.08 and FD 0.001
On the other hand, after 10,000 sheets, the density was decreased to 0.91 and the FD was 0.014, and the fog increased. In particular, as the number of copies increased, trailing and brush marks increased extremely, toner scattering inside the machine was remarkable, and fogging due to dirt on the optical system occurred.

Further, a developer was prepared and an image forming experiment was conducted in the same manner as in Example 1 except that styrene-acrylic resins having acid values of 6.1 and 9.3 were used. The results are shown in Tables 1 and 2.

Claims (1)

[Claims] 1. A negatively chargeable color toner for electrophotography, comprising a blue copper phthalocyanine pigment contained in a styrene-acrylic resin medium having an acid value of 10 or more.