Preparation of epsilon copper phthalocyanine of small primary particle size and narrow particle size distribution by kneading

Abstract

A process of preparing copper phthalocyanine particles exhibiting an epsilon crystallographic form, comprising a kneading step by kneading at at least two different temperatures copper phthalocyanine particles wherein more than or equal to 50 wt % of the particles exhibit an alpha crystallographic form in presence of a liquid and of at least one inorganic salt.

Description

[0001] This application claims the benefit of European Patent Application No. 07120738.5 filed November 15, 2007, which is hereby incorporated by reference. technical field [0002] The present invention relates to a method for preparing ε crystal form copper phthalocyanine (ε-CuPc) particles with small primary particle size and narrow particle size distribution, ε crystal form copper phthalocyanine particles obtainable according to the method and their use Use in the manufacture of blue color filter pigments for liquid crystal display (LCD) devices. Background technique [0003] Of all the pigments, copper phthalocyanine is especially stable and excellent in various fastnesses. In addition, copper phthalocyanine has various crystal forms. Among these crystal forms, those known to have found practical use include α, β, and ε crystal forms of copper phthalocyanine. It is common practice to use the beta form to produce a greenish blue and the alpha form to produce a reddish ...

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Problems solved by technology

[0014] However, the aforementioned methods of preparing ε crystal form copper phthalocyanine in the prior art have a problem that they require too much time for crystal phase transformation and particle size reduction

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