Pigmented magenta inks and their use in electrophotographic printing
Publication Date: 2004-Aug-25
The IP.com Prior Art Database
Certain Quinacridone magenta pigments (solid solution of C.I. Pigment Violet 19/C.I. Pigment Red 202) provide good colour brilliance when used as toners for multicolour electrophoto-graphic printing. Colour reproduction is improved when using them in combination with a CMYK (Cyan (C), Magenta (M), Yellow (Y), Black (K)) toner set.
The present publication relates to pigmented magenta toners that are especially suitable for electrophotographic printing. By the electrophotographic printing method, images and characters are usually printed by subtractive colour mixing of toners of four colours, namely Yellow (Y), Magenta (M), Cyan (C) and Black (K). In many applications, toners are subject to high demands in terms of their optical density, colour brilliance and fastness to humidity, light and atmospheric pollutants. In practice, the electrophotographic process competes with other printing processes such as ink jet in the home and office, and lithography in short run commercial printing. In both these areas, pigmented inks are used to give optimised light and weather fastness. In lithography Pigment Red 57:1 is the most commonly used magenta pigment, but where very high fastness properties are required, high performance pigments such as C.I. Pigment Red 122 (2,9-dimethylquinacridone), C.I. Pigment Red 202 (2,9-dichloroquinacridone) or C.I. Pigment Violet 19 (Quinacridone) are used. However, it is well known that it is difficult to match the colour strength of Red 57:1 based inks with 2,9-dimethylquinacridone pigments having a very small particle size (less than 100 nm) are increasingly used because of their improved colouristic properties. However, a need still exists for high fastness magenta toners with increased colour strength for multicolour electrophotographic printing.
Certain Quinacridone magenta pigments enable to formulate magenta toners with outstanding colour brilliance. The obtained toners are expected to improve colour reproduction when used in combination with a CMYK toner set or with a CMYK toner set already complemented with additional colour toners, such as Light Cyan, Light Magenta, Orange, Green or Red toners. Quinacridone pi...