Radiation imagery chemistry: process – composition – or product th – Radiation modifying product or process of making – Screen other than for cathode-ray tube
Reexamination Certificate
2001-08-17
2004-05-11
McPherson, John A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation modifying product or process of making
Screen other than for cathode-ray tube
C430S270100
Reexamination Certificate
active
06733935
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a colored resist material set used to form colored resists of three colors (red (R), Green (G) and blue (B)) in a color filter which is preferably used in color televisions, liquid crystal display elements, cameras and the like and also to a color filter formed with colored resists by the colored resist material set.
In these days, there is a tendency that demands for liquid crystal displays, especially, color liquid crystal displays are increasing along with the progress of, particularly, portable personal computers. Because the color liquid crystal display is expensive, there is increasing needs to lower the cost, particularly increasing needs to lower the cost of a color filter occupying a large part of the cost of the color liquid crystal display.
In such a color filter, generally colored resists of three primary colors of red (R), green (G) and blue (B) respectively are provided and a liquid crystal works as a shutter by switching electrodes corresponding to each pixel of R, G and B on and off whereby light passes through each resist of R, G and B to display colors.
The following method is among methods of producing such a color filter. Specifically, a resist material (light-sensitive resin) containing a photoinitiator is applied every color on a transparent substrate. A mask in which only the area to be colored is made transparent is brought into contact with the resist material and the mask is irradiated with light to thereby cause a difference in solubility between the part irradiated with light and the part non-irradiated with light. Namely, only the resist material corresponding to the part irradiated with light is cured by the action of the aforementioned photoinitiator (exposure step). Next, the resist material is developed to form a pattern (developing step), followed by post-baking (film-forming step) to form a monocolor resist pattern. This operation for each resist material of R, G and B is repeated three times to form a colored layer.
As the photoinitiator used in this method, those which can cure the resist material in a shorter time, namely those absorbing light having a wide range of wavelengths have been used.
However, the photoinitiator is a type which is left unremoved in the resist after the resist material is cured with the result that the following problems sometimes arise.
It is supposed that a resist material is cured by making the resist material absorb light having a wavelength shorter than 440 nm. Specifically, in the case of forming a red (R) resist, green (G) resist and blue (B) resist respectively by using a resist material containing a photoinitiator having a photoabsorption region on the side of wavelengths shorter than 440 nm, the photoinitiator left in the formed resists having three colors respectively absorbs light having wavelengths shorter than 440 nm even after the resists are formed, namely in the case where these resist materials function as a color filter.
Here, generally the light having wavelengths of about 400 to 570 nm represents blue light, the light having wavelengths of about 460 to 650 nm represents green light and the light having wavelengths of about 570 to 700 nm represents red light.
Therefore, when three color (R, G and B) resists are formed using the aforementioned photoinitiator (absorbing light having wavelengths shorter than 440 nm), there is no influence on the light transmittance of each of the red (R) resist and the green (G) resist, even if the photoinitiator is contained (because this photoinitiator is a type which does not absorb light having wavelengths longer than 440 nm). However, in the blue (B) resist, the photoinitiator resultantly absorbs a part the blue light which is transmitting through the resist, which causes the light transmittance of the blue resist to decrease consequently.
The reduction in the light transmittance of the blue resist leads to the upset of the white balance (the balance of chromaticity and/or luminance between R, G and B) of whole pixels, giving rise to the problem concerning the luminance and tint of a liquid crystal display and the like.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems and it is an object of the present invention to provide a colored resist material set which prevents a reduction in the light transmittance of each colored resist and also to provide a color filter which is not reduced in the light transmittance of a colored resist by using the above set.
The above objects are achieved by the following inventions. According to a first aspect of the present invention, there is provided a colored resist material set comprising at least colored resist materials having three colors consisting of a red resist material, a green resist material and a blue resist material, each resist material containing a reactive monomer, a photoinitiator and a dye and/or a pigment, wherein the photoinitiator contained in the red resist material has a photoabsorption region on the side of wavelengths shorter than 570 nm, the photoinitiator contained in the green resist material has a photoabsorption region on the side of wavelengths shorter than 460 nm and the photoinitiator contained in the blue resist material has a photoabsorption region on the side of wavelengths shorter than 400 nm, each photoinitiator using at least two or more photoinitiators.
In the present invention, the photoinitiator to be used in each colored resist material is combined according to the wavelength of each color. Since the photoabsorption region of the photoinitiator used to cure each resist material is on the side of wavelengths shorter than the wavelength of each color (R, G and B), the photoinitiator does not decrease the light transmittance of the resist after the resist is formed, whereby the luminance and tint of, for example, a liquid crystal display can be exhibited to the maximum.
In the present invention, the photoinitiators contained in the red resist material and the green resist material respectively are preferably the same photoinitiator having a photoabsorption region on the side of wavelengths shorter than 460 nm.
Because many photoinitiators used currently have a photoabsorption region on the side of shorter wavelengths, blue light having the shortest wavelength among three primary color lights is much affected by the photoinitiator. Therefore, if only the photoinitiator contained in the blue resist material has a photoabsorption region on the side of wavelengths shorter than 400 nm and the photoinitiators contained in other two colored resist materials are the same photoinitiator having a photoabsorption region on the side of wavelengths shorter than 460 nm, the effect of the present invention can be produced, specifically, a reduction in the light transmittance of each resist can be prevented, whereby the luminance and tint of, for example, a liquid crystal display can be exhibited to the maximum.
In the present invention, preferably the photoinitiators contained in the red resist material and the green resist material respectively are 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 and the photoinitiator contained in the blue resist material is 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one.
This is because 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1 is placed on the market as Irgacure 369 (trademark, manufactured by Ciba Specialty Chemicals) and 2-methyl-1[4-(methylthio)phenyl]-2-morpholinopropan-1-one is placed on the market as Irgacure 907 (trademark, manufactured by Ciba Specialty Chemicals) and the both are therefore easily available and can be used conveniently.
Further, according to a second aspect of the present invention, there is provided a color filter comprising forming a colored resist by using the aforementioned colored resist material set.
The color filter provided with the colored resists formed using the colored resist material set according to the present invention ensures that the light transmittance of the colo
Kishimoto Takehide
Watanabe Miho
Dai Nippon Printing Co. Ltd.
Ladas & Parry
McPherson John A.
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