1. Field of the Invention
This invention relates to a process for the preparation of crystalline oxytitanium phthalocyanine. Particularly, it relates to a novel process for the preparation of crystalline oxytitanium phthalocyanine suitable for use in an electrophotographic photoreceptor.
2. Description of the Prior Art
In this field, it is well known that the oxytitanium phthalocyanine may be produced either in a semi-stable .alpha.-crystal phase or in a stable .beta.-crystal phase depending on the production conditions. Further, it is also known that those two crystal phases may be converted from one to another under the influences of physical distortion, organic solvent and/or heat. For example, .alpha.-phase oxytitanium phthalocyanine can be converted into .beta.-phase by heating in an organic solvent such as N-methylpyrrolidone.
On the other hand, Japanese Patent Application Laying Open (KOKAI) No. 63-20365 discloses that crystalline oxytitanium phthalocyanine of which crystal phase can not be classified neither as the .alpha.-phase nor as the .beta.-phase and which shows an intense peak in the X-ray diffraction spectrum at a Bragg angle (2.theta.) of 27.3.degree. can be produced by forming an aqueous suspension of .alpha.-phase oxytitanium phthalocyanine obtained by the acid paste method, adding an aromatic hydrocarbon solvent into the suspension and heating the suspension, and that the obtained phthalocyanine is an useful material particularly as a recording material of an optical disc.
The object of the present invention is to provide a novel and industrially applicable process for the production of oxytitanium phthalocyanine having a crystal phase useful for various purposes such as for use in an electrophotographic photoreceptor.