GB2182165A - Trichromatic colour filter comprising a substituted phthalocyanine - Google Patents

Abstract

A trichromatic colour filter, suitable for use in a flat bed display, has a green pigment which is an optionally substituted octa-4,5-phthalocyanine, e.g. copper octa-4,5-phenyl-phthalocyanine. The colour filter may be prepared on a substrate e.g. an amorphous silicon thin film transistor.

Description

SPECIFICATION Colour filter This specification describes an invention relating to trichromaticcolourfilterssuitableforuseinflatbed displays incorporating red, blue and green pigments and more particularlyto a colourfilter in which the green pigment is a substituted phthalocyanine.

A green pigment for use in flat bed displays preferably has a transmission maximum, with a transmittance of at least 50%, and more preferably at least 70%,centred on 530 #2 0m m and a reasonably narrow band width i.e. preferably not greater than 250m m and more preferably notgreaterthan 150m m at 50% of peak height when deposited in a thin layer on a suitable substrate.

According to the present invention there is provided a trichromatic colourfilter suitable for use in a flat bed display in which the green pigment is an op tionallysubstituted octa-4,5-phthalocyanine.

The OPPc may be substituted in the phenyl rings or the phthalocyanine nucleus. Preferred substituents on the phenyl rings are non-ionic groups, such as halogeno, alkyl, alkoxy, amino and substituted amino, hydroxy and nitro in which the alkyl groups are preferably C1 20-al kyl. Preferred substituents for the phthalocyanine nucleus are, alkyl, especially C1 20-alkyl, such substituents being present in the 3 or6 position or both the 3 and 6 positions on each ofthe peripheral benzene rings of the phthalocyanine nucleus.

The OPPc may be metal-free or it may be com plexedwith a metal oroxy-metal derivative. Examples of suitable metals are Zn, GaOH,VO, Ni, Pd, Pb, Mg, Ca, Co and especially Cu.

An especially preferred pigmentiscopperocta- 4,5-phenyl-phthalocyaninewhich has a symmetrical transmission peak at 530m m with a transmittance, substantially independent of layer thickness up to 1 clam, of at least 90%.

The OPPc may be prepared from the correspond.

ing 4,5-diphenylphthalic anhydride by reaction with urea in an inertsolventin the presence ofcupric chloride and methods for the preparation of the start- ing material are given in UK 683770.

The colour filter can be prepared in the usual manner for such devices by sequential application of the red, blue and green pigments to a suitable sub stratesuch as an amorphous silicon thin film transis tor. In order to obtain arrays ofsmall dots ofthethree pigments over the surface of the substrate it is convenientto employ a photolithographictechnique whereby each pigment is deposited on a photoetched polymer surface and the pigment and polymer are removed from the un-irradiated areas by washing with a solvent.

The invention is further illustrated by the following Example.

Example A layer of the green pigment, copper octa-4,5phenyl-phthalocyanine, at a thickness of 0.1 #m, was formed on a glass plate by vacuum evaporation. The pigment evaporated satisfactorily and deposited in a layer of substantially even thickness on the glass plate.

The transmission spectrum ofthe layer, plotted with a spectrophotometer, had a transmission peak of 95% at 530m m with a band width at 50% peak height of 200mpWm.

The layers of pigment were substantially resistant to washing with a solvent comprising a mixture of iso-propanol and methylisobutylketone.

Claims (3)

1. Atrichromatic colour filter suitable for use in a flat bed display in which the green pigment is an op tionallysubstituted octa-4,5-phthalocyanine.

2. Afilter according to claim 1 wherein the pigment is copper octa-4,5-phenylphthalocyanine.

3. Afilter as claimed in claim 1 substantially as hereinbefore described with reference to the Example.