Optical: systems and elements – Absorption filter
Reexamination Certificate
2003-01-29
2004-01-13
Dunn, Drew (Department: 2872)
Optical: systems and elements
Absorption filter
C252S582000, C430S007000
Reexamination Certificate
active
06678099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a color filter, and more particularly, to a reflective color filter which has green pixels containing a green pigment and C.I. Pigment Yellow 138 and satisfies the requirements of both high color purity and high light transmittance.
2. Description of the Related Art
In recent years, displays to be mounted on portable terminals such as mobile telephones and game playing machines need to exhibit low electric power consumption. Because of this, reflective liquid crystal devices requiring no backlight are suitable for the displays used for the portable terminals. In order to realize low electric power consumption, it is suitable to decrease a concentration of pigment contained in colored pixels of a color filter. However, the decreased concentration of the pigment raises a problem in that color purity is lowered. Conversely, increased concentration of the pigment poses a problem in that light transmittance is lowered although color purity is improved.
Conventionally, among the colored pixels (normally red pixels, green pixels, and blue pixels) of a color filter, the green pixels contain, as a colored component, a combination of C.I. Pigment Green 36, which is a green pigment, and a yellow pigment mixed in a proper ratio.
As the yellow pigment, PY-139, PY-150 and the like are mainly used. However, when such yellow pigments have been used in reflective color filters, it has been difficult to fulfill the requirements of both low electric power consumption and high color purity.
SUMMARY OF THE INVENTION
The present invention has been accomplished in order to solve the problems associated with the prior art. Therefore, it is an object of the invention to provide a reflective color filter that displays high contrast, clear color tone and high light transmittance, realizes low electric power consumption, and has green pixels exhibiting high color purity.
The invention provides a reflective color filter comprising a substrate having disposed thereon two or more kinds of patterned colored pixels exhibiting mutually different color hues, wherein at least one kind of the colored pixels is a green pixel that contains a green pigment and C.I. Pigment Yellow 138, a value y expressed in the x-y system is 0.37 or greater when chromaticity of the green pixel is measured with a D65 light source, and a value Y in the CIE 1931 color system is 87 or greater.
DESCRIPTION OF THE INVENTION
A reflective color filter according to the present invention will be explained in detail below.
The reflective color filter according to the invention comprises a substrate having disposed thereon two or more kinds of patterned colored pixels exhibiting mutually different color hues, wherein at least one kind of the colored pixels is a green pixel that contains a green pigment and C.I. Pigment Yellow 138, a value y expressed in the x-y system is 0.37 or greater when chromaticity of the green pixel is measured with a D65 light source, and a value Y in the CIE 1931 color system is 87 or greater.
It is preferable that the green pixel comprise a colored photosensitive composition containing: a pigment dispersion composition that includes a green pigment, C.I. Pigment Yellow 138 and a resin; a polyfunctional monomer having two or more ethylenically unsaturated double bonds; and a photopolymerization initiator.
<Pigment Dispersion Composition>
The pigment dispersion composition to be incorporated in the colored photosensitive composition which forms the reflective color filter of the invention will be explained below.
In the invention, the pigment dispersion composition contains a green pigment, C.I. Pigment Yellow 138, and a resin.
—Pigments to be Incorporated in Green Pixels—
C.I. Pigment Yellow 138, that is a yellow pigment, is used as an essential component in the green pixels of the reflective color filter of the invention. C.I. Pigment Yellow 138 is used as a green colorant in combination with a green pigment in the green pixels. Specific examples of the green pigment that can suitably be used include C.I. Pigment Green 7, C.I. Pigment Green 36, and C.I. Pigment Green 37.
Use of the pigment dispersion composition that contains the C.I. Pigment Yellow 138, the green pigment and a resin makes it possible to obtain the green pixels which have a thin layer and a high light transmittance and fulfill the requirements of both low electric power consumption and high color purity.
The content of the green pigment in the pigment dispersion composition is preferably 5 to 20% by mass, and more preferably 8 to 18% by mass, based on a total mass of the pigment dispersion composition. The content of C.I. Pigment Yellow 138 in the pigment dispersion composition is preferably 5 to 20% by mass, and more preferably 8 to 18% by mass, based on a total mass of the pigment dispersion composition.
In the invention, although other yellow pigments than C.I. Pigment Yellow 138 may be used together, the content of C.I. Pigment Yellow 138 is preferably 99 to 10% by mass, and more preferably 90 to 50% by mass, based on the content of the yellow pigments other than C.I. Pigment Yellow 138 used together. As the proportion of the yellow pigment other than the C.I. Pigment Yellow 138 increases, light transmittance of the color filter may occasionally be lowered.
Suitable examples of the yellow pigment other than C.I. Pigment Yellow 138, that can be used together, include C.I. Pigment Yellow 2, C.I. Pigment Yellow 10, C.I. Pigment Yellow 12, C.I. Pigment Yellow 17, C.I. Pigment Yellow 20, C.I. Pigment Yellow 24, C.I. Pigment Yellow 55, C.I. Pigment Yellow 60, C.I. Pigment Yellow 65, C.I. Pigment Yellow 75, C.I. Pigment Yellow 83, C.I. Pigment Yellow 86, C.I. Pigment Yellow 87, C.I. Pigment Yellow 90, C.I. Pigment Yellow 93, C.I. Pigment Yellow 95, C.I. Pigment Yellow 99, C.I. Pigment Yellow 104, C.I. Pigment Yellow 109, C.I. Pigment Yellow 110, C.I. Pigment Yellow 114, C.I. Pigment Yellow 116, C.I. Pigment Yellow 117, C.I. Pigment Yellow 123, C.I. Pigment Yellow 125, C.I. Pigment Yellow 127, C.I. Pigment Yellow 137, C.I. Pigment Yellow 139, C.I. Pigment Yellow 147, C.I. Pigment Yellow 148, C.I. Pigment Yellow 150, C.I. Pigment Yellow 152, C.I. Pigment Yellow 153, C.I. Pigment Yellow 154, C.I. Pigment Yellow 156, C.I. Pigment Yellow 162, C.I. Pigment Yellow 165, C.I. Pigment Yellow 166, C.I. Pigment Yellow 168, C.I. Pigment Yellow 169, C.I. Pigment Yellow 180, C.I. Pigment Yellow 181, C.I. Pigment Yellow 182, C.I. Pigment Yellow 183, C.I. Pigment Yellow 185, C.I. Pigment Yellow 191, C.I. Pigment Yellow 193, etc.
Among the above listed pigments, C.I. Pigment Yellow 139, C.I. Pigment Yellow 150, and C.I. Pigment Yellow 180 are more preferable.
The content of the green pigment is preferably 90 to 10% by mass, and more preferably 80 to 20% by mass, relative to the yellow pigment (a total of C.I. Pigment Yellow 138 and other yellow pigments to be used together).
—Resin—
The resin to be incorporated in the pigment dispersion composition is preferably a polymer having an acidic group. Use of the polymer having an acidic group as the resin is preferable because the polymer imparts steric repulsion to the pigment and thus improves dispersion stability of the pigment and enhances developability with alkali when the dispersion is used as the colored photosensitive composition. Examples of the polymer having an acidic group include a (meth)acrylic acid/(meth)acrylic ester copolymer, a styrene/maleic anhydride copolymer, a reaction product between a styrene/maleic anhydride copolymer and an alcohol, etc. The polymer may be used singly or in combination of two or more kinds thereof. Among the above-mentioned polymers, preferred is a polymer that is excellent in pigment dispersibility, excellent in compatibility with a polyfunctional monomer and a photopolymerization initiator, and has a suitable degree of solubility in an alkaline developing solution, a sufficient solubility in an organic solvent, strength, softening temperature, etc. when the polymer is used in the colored p
Boutsikaris Leo
Dunn Drew
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