JP2005134508A - Color filter for liquid crystal display device, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color filter for a liquid crystal display device restraining a change in color temperature and further preventing the lowering of lightness at the time of white display without narrowing a color reproducing region even in the case of using a white LED as the light source of a backlight, and to provide a liquid crystal display device. <P>SOLUTION: In the color filter for the liquid crystal display device constituted of colored pixels of three primary colors, the transmittance in wavelength 585 nm of the red pixel is 43 to 53%, the transmittance in wavelength 600 nm of the green pixel is 27 to 37% and the transmittance in wavelength 495 nm thereof is 46 to 56%, and the transmittance in wavelength 530 nm of the blue pixel is 52 to 62%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a liquid crystal display device, and particularly to a color filter for a liquid crystal display device and a liquid crystal display device that display a suitable color when a white LED is used as a light source.

  In a segment type liquid crystal display device used in a digital display instrument or the like, the color display of the liquid crystal display device that is directly viewed is, for example, specified in a shape corresponding to the segment electrode outside the liquid crystal display element as an optical shutter. Color filter patterns are provided, and color display is performed so that each segment portion is displayed in a specific color.

  Further, in a matrix type liquid crystal display device widely used for notebook PCs, color TVs, and the like, a large number of pixel electrodes are regularly arranged in the horizontal and vertical directions so that arbitrary characters and images can be displayed. In addition, corresponding to this pixel electrode, red (R), green (G), and blue (B) color filter pixels, which are the three primary colors of light, are regularly provided inside the liquid crystal display element to provide a full color display. Is going.

  If this pixel is sufficiently subdivided, it will not be recognized as each color of red (R), green (G), and blue (B) because it will exceed the resolution of the eye if it is separated by a certain distance or more. , Recognized as a mixed color.

  That is, in a matrix-type liquid crystal display device, an intermediate color of an arbitrary character or image is displayed by spatially mixing three pixels of red (R), green (G), and blue (B). doing. Color display is performed by so-called juxtaposed additive color mixing.

  Among liquid crystal display devices that are directly viewed, a transmissive liquid crystal display device generally uses a white light source as a backlight that is a light source. The liquid crystal display element functions as an achromatic black and white shutter, and by electrically controlling the degree of opening and closing of the black and white shutter of each pixel, the transmitted light amount of each pixel is changed to express a halftone, and a full color display Is going.

  The color gamut, color temperature, brightness during white display, and the like of this transmissive liquid crystal display device are substantially determined by the emission spectrum of the backlight, the spectral transmittance of the color filter, and the electro-optical characteristics of the liquid crystal.

  A three-wavelength light emitting fluorescent lamp (three-wave tube) with excellent color rendering properties is widely used as the light source for the backlight, and a pigment-dispersed color filter with excellent heat resistance and light resistance is used as the color filter. Widely used.

  In recent years, the color reproduction range of transmissive liquid crystal display devices has been studied in terms of the emission spectrum of a three-wavelength tube and the spectral transmittance of a color filter. The filter composition has been devised to have a color gamut equivalent to that of a CRT.

  The range of colors that can be reproduced by the color CRT of a color television receiver is surrounded by three chromaticity points on the chromaticity diagram of the three primary colors emitted by the phosphors of red (R), green (G), and blue (B). The inside of the triangle.

  For example, the area of a triangle on the chromaticity diagram surrounded by three chromaticity points according to the standard value of the NTSC (National Television System Committee) system is the color gamut in the NTSC system.

The standard values of the three primary colors of the red (R), green (G), and blue (B) of the NTSC system in the chromaticity diagram of the CIE 1931 standard display system are shown below.

Rx = 0.67, Ry = 0.33
Gx = 0.21, Gy = 0.71
Bx = 0.14, By = 0.08

In addition, the following shows a mathematical formula for obtaining a color reproduction range (a triangular area (S) formed by three chromaticity points) in the standard value of the NTSC system on the chromaticity diagram of the CIE 1931 standard display system.

S = | Ry (Gx−Bx) + Gy (Bx−Rx) + By (Rx−Gx) | /2=0.1582.

The color gamut% (NTSC ratio) with respect to the color gamut 100% of the standard value of the NTSC system of a certain liquid crystal display device (i) is obtained by the following formula.

(S _i / S) × 100
Here, S _i : a triangle on the CIE chromaticity diagram of a certain liquid crystal display device (i)
area
S: 0.1582

The NTSC ratio in the present invention refers to the above (S _i / S) × 100.

  FIG. 1 shows an emission spectrum of an example of a three-wavelength region-emitting fluorescent lamp (three-wave tube) widely used as a light source for a backlight of a liquid crystal display device.

  As shown in FIG. 1, this three-wavelength tube has respective peak wavelengths in the red, green, and blue wavelength regions. The chromaticity coordinates of this three-wavelength tube are Wx = 0.295, Wy = 0.302, and the color temperature is about 8000K.

  FIG. 2 shows the spectral transmittance of an example of a pigment dispersion type color filter widely used as a color filter for liquid crystal display devices.

  As shown in FIG. 2, the red pixel constituting the color filter for the liquid crystal display device has a transmittance of about 72 at a wavelength of 585 nm, the green pixel has a transmittance of about 41% at a wavelength of 600 nm, and a transmittance of 56% at a wavelength of 495 nm. The blue pixel has a transmittance of about 51% at a wavelength of 530 nm.

  The performance of the liquid crystal display device using the three-wavelength tube shown in FIG. 1 as the light source of the backlight and the color filter for liquid crystal display device (CF-1) shown in FIG. 2 as the color filter for color reproduction is as follows. It becomes.

  That is, the color gamut is about 27.7% in NTSC ratio, the chromaticity coordinates are Wx = 0.290, Wy = 0.296, the color temperature is about 8800K, and the brightness during white display is Y = 41.5. It has excellent display quality as a liquid crystal display device.

  On the other hand, in recent years, the brightness of blue emitting LEDs (Light Emitting Diodes) has been greatly improved, and instead of three-wavelength tubes, LEDs with excellent color rendering and high chroma have begun to be used as light sources for backlights of liquid crystal display devices. .

  This LED also has advantages such as low power consumption and long life. For example, a blue light emitting LED and a yellow light emitting phosphor are combined as a backlight light source of a liquid crystal display device for a mobile phone. Types of white LEDs are in practical use.

  GaN is mainly used as the material of the blue LED that constitutes the white LED, and YAG (Itium Aluminum Garnet) is used as the material of the yellow phosphor.

  This white LED is formed by molding a LED element with a phosphor-containing resin in which a yellow phosphor such as YAG is dispersed in a transparent resin such as an epoxy resin, and effectively converts the light emission in the ultraviolet region of the LED to yellow, It is made white by mixing with blue.

  FIG. 3 shows an emission spectrum of an example of a white LED that is practically used as a light source of a backlight of a liquid crystal display device.

  As shown in FIG. 3, the white LED has a dominant wavelength of blue light emission near a wavelength of 470 nm and a dominant wavelength of yellow light emission near a wavelength of 570 nm, and white color is obtained by this color mixture.

  The chromaticity coordinates of the white LED are Wx = 0.313, Wy = 0.313, and the color temperature is about 6600K.

  The performance of the liquid crystal display device using the white LED shown in FIG. 3 as the backlight light source and the color filter (CF-1) for the liquid crystal display device shown in FIG. 2 as the color filter for color reproduction is as follows. It becomes.

  That is, the color gamut is as narrow as about 25.3% in NTSC ratio, the chromaticity coordinates are Wx = 0.302, Wy = 0.305, and the color temperature is significantly low, about 7500K. The brightness during white display is slightly low, Y = 41.1. Therefore, the display quality as a liquid crystal display device is deteriorated.

  Here, in general, the white color of the display device is preferred to the blue color rather than the yellow color, and the change in the color temperature to the low temperature side is not a preferable direction.

  The present invention has been made in view of the above problems, and even when a white LED is used as a light source of a backlight of a liquid crystal display device, a decrease in color temperature is suppressed while suppressing a decrease in color reproduction range to the same extent. It is another object of the present invention to provide a color filter for a liquid crystal display device that is excellent in color during white display.

  In addition, the present invention suppresses the decrease in color temperature while suppressing the narrowing of the color reproduction range to the same color even when white LEDs are used as the light source of the backlight of the liquid crystal display device. An object is to provide an excellent liquid crystal display device.

  The present invention is a color filter for a liquid crystal display device composed of colored pixels of three primary colors, wherein the transmittance of a red pixel at a wavelength of 585 nm is 43% to 53%, and the transmittance of a green pixel at a wavelength of 600 nm is 27%. A color filter for a liquid crystal display device, characterized in that the transmittance at a wavelength of 495 nm is 46% to 56%, and the transmittance of a blue pixel at a wavelength of 530 nm is 52% to 62%.

  According to another aspect of the present invention, there is provided a liquid crystal display device using a white LED as a light source of a backlight and using the color filter for a liquid crystal display device according to claim 1 as a color filter for color reproduction.

In the present invention, the transmittance of a red pixel at a wavelength of 585 nm is 43% to 53%, the transmittance of a green pixel at a wavelength of 600 nm is 27% to 37%, and the transmittance at a wavelength of 495 nm is 46% to 56%. Since the color filter for a liquid crystal display device has a transmittance of 52% to 62% at a wavelength of 530 nm for a blue pixel, a white LED is used as a light source for the backlight.
However, it is preferable that the color reproduction range is narrowed to the same extent as when the resist is not improved, while the color temperature drop is suppressed, and the white display color tone is prevented from becoming yellowish. Therefore, the color filter for a liquid crystal display device that maintains the tendency of blueness is obtained.

  Further, the present invention is a liquid crystal display device using a white LED as a light source of a backlight and using the above color filter for a liquid crystal display device as a color filter for color reproduction, and therefore does not improve the resist for narrowing the color reproduction range. The liquid crystal display device is excellent in color at the time of white display while suppressing a decrease in color temperature while suppressing to the same extent as in the case.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 4 shows the spectral transmittance of one embodiment of the color filter for a liquid crystal display device according to the present invention.

  As shown in FIG. 4, the red pixel constituting the color filter (CF-2) for the liquid crystal display device has a transmittance of about 44 at a wavelength of 585 nm, the green pixel has a transmittance of about 30% at a wavelength of 600 nm, and a wavelength of 495 nm. The blue pixel has a transmittance of about 60% at a wavelength of 530 nm.

  Such a color filter for a liquid crystal display device is based on the pigment composition of each color photoresist used when forming red, green, and blue pixels having the spectral transmittance shown in FIG. 2, and is shown in FIG. In order to realize the spectral transmittance, it can be obtained by adjusting the composition ratio in the basic composition or changing the pigment concentration.

  In the case of red pixels, when preparing a pigment-dispersed red photoresist used to form red pixels, the composition ratio of several types of red pigments used was adjusted to suppress brightness and reduce yellowness. Yes.

  In addition, in the case of green pixels, when preparing a pigment-dispersed green photoresist used to form a green pixel, the composition ratio of several types of green pigments to be used is adjusted, the brightness is suppressed, and the redness is reduced. Yes.

  In the blue pixel, when preparing a pigment-dispersed blue photoresist used for forming the blue pixel, the lightness as the blue pixel is improved by changing the pigment concentration.

  As described above, the transmittance at the wavelength of 585 nm of the red pixel is 43% to 53% by adjusting the composition ratio or changing to a preferable pigment, and the wavelength of the green pixel at 600 nm. The transmittance is 27% to 37%, the transmittance at a wavelength of 495 nm is 46% to 56%, and the transmittance of a blue pixel at a wavelength of 530 nm is 52% to 62%.

  A liquid crystal display device using a white LED having an emission spectrum shown in FIG. 3 as a light source of a backlight and a color filter (CF-2) having a spectral transmittance shown in FIG. 4 as a color filter for color reproduction. The performance of is as follows.

  That is, the color gamut is about 25.3% in NTSC ratio, the chromaticity coordinates are Wx = 0.291, Wy = 0.305, the color temperature is about 8400K, and the brightness during white display is Y = 39.7. In addition, by keeping the color temperature high, yellowing at the time of white display is prevented, and the liquid crystal display device has excellent display quality.

  As white LED used for this invention, the Nichia Chemical Co., Ltd. product and LED-b2 (product number) are mention | raise | lifted, for example.

  The performance of a liquid crystal display device using the three-wavelength tube shown in FIG. 1 as a light source of a backlight and the color filter for liquid crystal display device (CF-1) shown in FIG. 2 as a color filter for color reproduction, and FIG. The performance of the liquid crystal display device using the white LED shown in FIG. 3 as the light source of the backlight and the color filter for liquid crystal display device (CF-1) shown in FIG. 2 as the color filter for color reproduction is shown in FIG. Table 1 shows the performance of a liquid crystal display device using the white LED shown as a backlight light source and the color filter for liquid crystal display device (CF-2) having the spectral transmittance shown in FIG. 4 as a color filter for color reproduction. Shown in

An emission spectrum of an example of a three-wavelength region-emitting fluorescent lamp (three-wave tube) is shown. The spectral transmittance of an example of a pigment dispersion type color filter is shown. The light emission spectrum of an example of white LED currently used as a light source of the backlight of a liquid crystal display device is shown. FIG. 5 shows the spectral transmittance of an embodiment of a color filter for a liquid crystal display device according to the present invention. FIG.

Explanation of symbols

R: Spectral transmittance of red pixel G: Spectral transmittance of green pixel B: Spectral transmittance of blue pixel

Claims (2)

  A color filter for a liquid crystal display device composed of colored pixels of three primary colors, wherein the transmittance of a red pixel at a wavelength of 585 nm is 43% to 53%, and the transmittance of a green pixel at a wavelength of 600 nm is 27% to 37%. A color filter for a liquid crystal display device, wherein the transmittance at a wavelength of 495 nm is 46% to 56%, and the transmittance of a blue pixel at a wavelength of 530 nm is 52% to 62%.   2. A liquid crystal display device using a white LED as a light source of a backlight and using the color filter for a liquid crystal display device according to claim 1 as a color filter for color reproduction.

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