JP2007304391A - Color filter and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color filter which has such a film thickness of colored pixels in the color filter as to cause no overhang on side surfaces of the colored pixels and permits a liquid crystal display device satisfying a color reproduction region according to EBU method, and to provide a liquid crystal display device provided with the color filter. <P>SOLUTION: The liquid crystal display device is provided with: a pseudo white color LED which is composed of a blue-color light emission LED and a yellow-color light emission fluorescent body and has a ratio of the emission peak intensity of blue color light emission to the emission peak intensity of yellow color light emission of 1/(0.20 to 0.50); and a color reproduction color filter which has a film thickness of respective colored pixels of 1.0 μm to 2.0 μm and contains C. I. Pigment Yellow 7 and C. I. Pigment Yellow 185 as pigments for a green colored pixel. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device that uses a pseudo white LED as a light source and can satisfy a color reproduction range of NTSC standard values.

Since the liquid crystal display device is not a self-luminous display device, the display needs light from the other, for example, a backlight is provided behind the display, and the display is performed by the light from the back. In such a transmissive liquid crystal display device, white light from a backlight provided behind the transmissive liquid crystal display device passes through the colored pixels of the color filter to become colored light, and is emitted outside the front of the liquid crystal display device to be viewed. It has become so. If the coloring pixels are sufficiently subdivided, the resolution of the eye is exceeded, so that they are not recognized as red (R), green (G), and blue (B) colors, but are recognized as mixed colors. .
Color display is performed by so-called juxtaposed additive color mixing.

In a transmissive liquid crystal display device, a white light source is generally used as a backlight which 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 cathode ray fluorescent tube excellent in color rendering is widely used as a light source for the backlight, and a pigment-dispersed color filter excellent in heat resistance and light resistance is widely used as the color filter.
The pseudo white LED is used as a light source for mobile devices including mobile phones because of its small size and light weight.

  In a mobile device, in order to reduce power consumption, a color filter of a liquid crystal display device used in the mobile device is required to have high brightness. For this reason, in the case of a color filter of a liquid crystal display device used in a mobile device, for example, the film thickness of the colored pixel of the color filter is reduced, the hue of green (G) is yellowed, and the saturation is reduced. , Was raising the brightness.

As a result, the liquid crystal display device used in the mobile device can be reduced in power consumption without lowering the brightness. However, the color gamut of this liquid crystal display device is about 48% (about 67% by EBU ratio) in NTSC ratio.
The NTSC ratio refers to the ratio of the color gamut of the liquid crystal display device to the color gamut of the NTSC standard value chromaticity diagram in the liquid crystal display device. Similarly, the EBU ratio refers to the ratio of the color reproduction range of the liquid crystal display device to the color reproduction range of the standard value of the EBU method in the liquid crystal display device.

In recent years, since the brightness of the pseudo white LED has been greatly improved, as described above, the thickness of the colored pixel is not reduced, that is, the thickness of the colored pixel of the color filter that uses the thickness of the colored pixel for the TV. It has become possible to use a color filter that has been returned to the saturation state and used for a liquid crystal display device for mobile devices.
As a result, in a liquid crystal display device used for a mobile device, the brightness is maintained without increasing the power consumption, and the color reproduction range is improved compared with the NTSC ratio of about 48%, and the NTSC ratio is about 72% (EBU). The ratio was about 100%).

  However, for example, the resolution of mobile phones is comparable to that of digital cameras, the response speed corresponding to TV video, etc., and the network environment and the enhancement of content have expanded the use of mobile devices as network terminals. However, liquid crystal display devices used for mobile devices have been required to have a color gamut equivalent to that used for TVs.

When the color gamut of a liquid crystal display device used in a TV is compared with the NTSC standard, a cathode-ray fluorescent tube (CCFL) is used as the light source of the backlight, and the spectral transmission of the color filter is applied to the spectral distribution of the cathode-ray fluorescent tube. By using the color filter (CF-1) adjusted to match the rate, a liquid crystal display device satisfying the NTSC standard has been obtained (see Table 1, Table 2, LCD-1).
In the present invention, satisfying the NTSC standard means 72% or more in terms of NTSC ratio (100% or more in terms of EBU ratio).

図１には、液晶表示装置のバックライトの光源として広く用いられている陰極線蛍光管（ＣＣＦＬ）の一例の発光スペクトルを示してある。図１に示すように、この陰極線蛍光管の発光スペクトルのピーク波長は、青色の波長領域で４４０ｎｍ付近、緑色の波長領域で５５０ｎｍ付近、赤色の波長領域で６１０ｎｍ付近にあり、輝線のピークを有している。
尚、図１において、縦軸は発光スペクトルの強度を表している。

FIG. 1 shows an emission spectrum of an example of a cathode ray fluorescent tube (CCFL) widely used as a light source of a backlight of a liquid crystal display device. As shown in FIG. 1, the peak wavelength of the emission spectrum of this cathode ray fluorescent tube is around 440 nm in the blue wavelength region, around 550 nm in the green wavelength region, and around 610 nm in the red wavelength region, and has an emission line peak. is doing.
In FIG. 1, the vertical axis represents the intensity of the emission spectrum.

FIG. 2 shows the spectral transmittance of an example of a pigment dispersion type color filter widely used as a color filter of a liquid crystal display device used for TV.
As shown in FIG. 2, the spectral transmittance of the red pixel constituting the color filter (CF-1) is approximately 35 at a wavelength of 585 nm, the green pixel is approximately 20% at a wavelength of 600 nm, and the wavelength is 495 nm. The blue pixel has a transmittance of about 20% at a wavelength of 530 nm.

This color filter (CF-1) adjusts the blue and red peak wavelengths of the color filter to match the emission line of the cathode ray fluorescent tube, that is, the peak wavelength and the second peak wavelength in the wavelength region of each color. In addition, the green color is obtained by adjusting the chromaticity coordinates in order to match the NTSC standard.
The cathode ray fluorescent tube shown in FIG. 1 is used as the light source of the backlight, and the color filter (CF-1) of the liquid crystal display device used in the TV shown in FIG. 2 is used as the color filter for color reproduction (LCD-1). Is approximately 74.6% in terms of NTSC ratio, and has excellent display quality as a liquid crystal display device used for TV.

  Here, the pseudo-white LED whose luminance is greatly improved is used as a backlight light source in place of the cathode ray fluorescent tube (CCFL), and the color filter (CF-1) is used as a color filter for color reproduction. As a result, the NTSC ratio is about 66.8%, and a liquid crystal display device satisfying the NTSC standard cannot be obtained. (See Table 1, Table 2, LCD-2).

FIG. 5 shows an emission spectrum of an example of a pseudo-white LED that is practically used as a light source of a backlight of a liquid crystal display device or the like used in a mobile device and has the luminance greatly improved. InGaN is mainly used as the material of the blue LED constituting the pseudo white LED, and YAG (Itium Aluminum) is used as the material of the yellow phosphor.
Garnet) is used.
In this pseudo white LED, a phosphor is applied to a blue LED, the phosphor is excited with blue light to form yellow light, and white light is obtained by mixing the yellow light and the blue light. As shown in FIG. 5, this pseudo white LED has a peak wavelength of blue light emission near a wavelength of 460 nm and a peak wavelength of yellow light emission near a wavelength of 565 nm, and white color is obtained by this color mixture.

  When the pseudo white LED is used as a light source of a backlight and the color filter (CF-1) is used as a color filter for color reproduction, the pseudo white LED has a wavelength range of each color in the cathode ray fluorescent tube. Since there is no second peak wavelength in the above, the spectral range of the color filter (CF-1) has a wide wavelength range for transmission, and the saturation is lowered. In other words, a liquid crystal display device satisfying the NTSC standard cannot be obtained by simple diversion.

FIG. 3 shows the spectral transmittance of the color filter (CF-2) in which the wavelength region of each color in the color filter (CF-1) is narrowed.
This color filter (CF-2) is formed using the same colored composition as the colored composition used to form the color filter (CF-1). This is an attempt to narrow the wavelength region and improve the saturation by increasing the thickness of the colored pixels from 1.8 μm to 2.1 μm (see Table 3).

図３に示すように、着色画素の膜厚を厚くすることによって、青色の波長領域は狭くなり、短波長側へシフトしたものとなっている。緑色の波長領域は狭くなっている。また、赤色の波長領域は狭くなり、長波長側へシフトしたものとなっている。
前記疑似白色ＬＥＤをバックライトの光源として用い、色再現のカラーフィルタとして、図３に示すカラーフィルタ（ＣＦ−２）を用いた液晶表示装置（ＬＣＤ−３）の色再現域はＮＴＳＣ比で約７２％であり、ＮＴＳＣ規格を満たした液晶表示装置が得られている（表１、表２、ＬＣＤ−３参照）。

As shown in FIG. 3, by increasing the thickness of the colored pixels, the blue wavelength region is narrowed and shifted to the short wavelength side. The green wavelength region is narrow. Further, the red wavelength region is narrowed and shifted to the long wavelength side.
The color reproduction range of the liquid crystal display device (LCD-3) using the pseudo white LED as a backlight light source and the color filter (CF-2) shown in FIG. 3 as a color filter for color reproduction is about NTSC ratio. A liquid crystal display device that is 72% and satisfies the NTSC standard is obtained (see Tables 1, 2 and LCD-3).

  However, the cross-sectional shape of the colored pixels constituting the color filter (CF-2) is an overhang shape (14) as shown in FIG. This is because, since the colored composition forming the colored pixel (12) is thick, the exposure light when forming the colored pixel is attenuated in the colored composition (photoresist), and is formed at the bottom of the colored composition. This is because a sufficient amount of light did not reach and the side surface near the bottom of the colored pixel was dissolved by the development process.

When the side surface of the colored pixel has such an overhang shape (14), the transparent conductive film (13) provided on the colored pixel (12) is cracked or disconnected (15), and the display of the liquid crystal display device It will adversely affect quality.
FIG. 7 shows a case where the color pixel has a small film thickness, and shows a cross-sectional shape of the color pixel that is normally formed without the side surface of the color pixel (2) being overhanged. Since the side surface of the colored pixel is not overhanged, the transparent conductive film (3) is not cracked or disconnected.
JP 2002-244122 A

The present invention has been made in view of the above problems, and when using a pseudo white LED as a light source of a backlight and using a pigment-dispersed color filter as a color filter for color reproduction,
The liquid crystal display device in which the color pixel thickness of the color filter does not cause an overhang on the side surface of the color pixel, that is, a thickness less than 2.1 μm and satisfies the color reproduction range of the NTSC standard value It is an object of the present invention to provide a color filter that enables the above. It is another object of the present invention to provide a liquid crystal display device using a pseudo white LED and the color filter and satisfying the NTSC standard color reproduction range.

  The present invention is a color reproduction color filter composed of colored pixels of the three primary colors, and each color colored pixel has a film thickness of 1.0 μm to 2.0 μm. I. Pigment Yellow 7, and C.I. I. It is a color filter characterized by containing Pigment Yellow 185.

Further, the present invention is a pseudo white LED composed of a blue light emitting LED and a yellow light emitting phosphor, which emits a blue light emission peak in a wavelength range of 450 nm to 470 nm and emits a yellow light in a wavelength range of 550 nm to 600 nm. A pseudo white LED having an emission peak, wherein the ratio of the emission peak intensity of blue emission to the emission peak intensity of yellow emission is 1: (0.20 to 0.50);
A liquid crystal display device comprising the color filter according to claim 1.

  The present invention is a color reproduction color filter composed of colored pixels of the three primary colors, and each color colored pixel has a film thickness of 1.0 μm to 2.0 μm. I. Pigment Yellow 7, and C.I. I. Since it is a color filter containing Pigment Yellow 185, it is a pseudo white LED composed of the color filter, a blue light emitting LED and a yellow light emitting phosphor, and has a blue light emission peak in a wavelength range of 450 nm to 470 nm. A pseudo white LED having a yellow light emission peak in the wavelength range of 550 nm to 600 nm and a ratio of the blue light emission peak intensity to the yellow light emission peak intensity being 1: (0.20 to 0.50); In the liquid crystal display device, the color pixel of the color filter has a thickness that does not cause an overhang on the side surface of the color pixel, and color reproduction that can satisfy the color reproduction range of the standard value of the EBU method A liquid crystal display device having a region is obtained.

Hereinafter, embodiments of the present invention will be described in detail.
FIG. 4 shows the spectral transmittance of an embodiment of the color filter according to the present invention. As shown in FIG. 4, the red pixel constituting the color filter (CF-3) shown in this embodiment has a transmittance of about 89% at a wavelength of 610 nm and a transmittance of about 96% at a wavelength of 650 nm. The transmittance at a wavelength of 450 nm is about 0%, the transmittance at a wavelength of 525 nm is about 82%, the transmittance at a wavelength of 650 nm is about 7%, the transmittance of a blue pixel at a wavelength of 450 nm is about 70%, and the wavelength is 550 nm. The transmittance at is about 0%.

  Such a color filter (CF-3) has a pigment composition (coloring composition 1 shown in Table 3) of each color photoresist used when forming red, green, and blue pixels having the spectral transmittance shown in FIG. In order to realize the spectral transmittance shown in FIG. 4, the composition ratio shown in FIG. 4 is adjusted, or the composition ratio is adjusted or added to a preferable pigment. Can do.

For red pixels, when preparing a pigment-dispersed red photoresist used to form red pixels, some of the several red pigments used are changed, the composition ratio is adjusted, and the color purity of the red pixel is increased. It has been improved and the yellowness is reduced.
Table 4 shows the pigments used in the colored composition 1 and the composition ratio. Table 5
Represents the pigment and the composition ratio in the colored composition 2 in which the composition ratio in the basic composition is adjusted or changed to a preferred pigment or added.

また、緑色画素においては、緑色画素の形成に用いる顔料分散型緑色フォトレジストを調製する際に、用いている数種類の赤色顔料に、好ましい顔料の添加を行い、組成比を調整し、緑色画素としての色純度を向上させ、黄色味を低減させたものとしている。具体的には、表５に示すように、表４に示す着色組成物１の組成に、Ｃ．Ｉ．Ｐｉｇｍｅｎｔ Ｙｅｌｌｏｗ ７、及びＣ．Ｉ．Ｐｉｇｍｅｎｔ Ｙｅｌｌｏｗ １８５を添加し４種の組成比を調整した。

In the case of green pixels, when preparing a pigment-dispersed green photoresist used to form a green pixel, a preferred pigment is added to several types of red pigments used, the composition ratio is adjusted, and green pixels are obtained. The color purity is improved and the yellow color is reduced. Specifically, as shown in Table 5, the composition of the colored composition 1 shown in Table 4 was changed to C.I. I. Pigment Yellow 7, and C.I. I. Pigment Yellow 185 was added to adjust the composition ratio of the four kinds.

  In the case of blue pixels, the color purity of the blue pixel is improved by adjusting the composition ratio of the blue pigment used when preparing the pigment-dispersed blue photoresist used to form the blue pixel. It is said.

  In the color filter (CF-3) in which colored pixels of each color are formed with a film thickness of 1.75 μm using the colored composition 2 shown in Table 5, no overhang is generated on the side surface. Further, the transparent conductive film provided on the colored pixels is free from cracks and breaks, and the resistance value of the transparent conductive film is 23Ω / □ (see Table 6).

図５に示す疑似白色ＬＥＤは、前記のように、波長４６０ｎｍ近辺に青色発光のピーク波長を有し、波長５６５ｎｍ近辺に黄色発光のピーク波長を有し、この混色により白色が得られる。この青色発光の発光ピーク強度と黄色発光の発光ピーク強度の比は１：０．３５程度のものである。
尚、本発明に用いられる疑似白色ＬＥＤとしては、例えば、日亜化学工業（株）製、ＬＥＤ−ｂ５（品番）があげられる。

As described above, the pseudo white LED shown in FIG. 5 has a peak wavelength of blue light emission near a wavelength of 460 nm and a peak wavelength of yellow light emission near a wavelength of 565 nm, and white color is obtained by this color mixture. The ratio of the emission peak intensity of blue light emission to the emission peak intensity of yellow light emission is about 1: 0.35.
Examples of the pseudo white LED used in the present invention include LED-b5 (product number) manufactured by Nichia Corporation.

  The color reproduction range of the liquid crystal display device (LCD-4) using the pseudo white LED shown in FIG. 5 as the light source of the backlight and the color filter (CF-3) shown in FIG. A liquid crystal display device having an NTSC ratio of about 72% and satisfying the NTSC standard has been obtained (see Tables 1, 2 and LCD-4).

1 shows an emission spectrum of an example of a cathode ray fluorescent tube (CCFL) widely used as a light source of a backlight of a liquid crystal display device. The spectral transmittance of an example of the color filter of the liquid crystal display device used for TV is shown. The spectral transmittance of the color filter (CF-2) having a narrow wavelength region is shown. The spectral transmittance of the Example of the color filter in this invention is shown. The light emission spectrum of an example of pseudo white LED of the liquid crystal display device used for a mobile device is shown. It is explanatory drawing of the overhanging side surface of a coloring pixel. It is explanatory drawing of the normal side surface of a coloring pixel.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Black matrix 2, 12 ... Colored pixel 3, 13 ... Transparent conductive film 10 ... Glass substrate 14 ... Overhang shape 15 ... Disconnection CCFL ... Cathode ray fluorescent tube LED ..Pseudo white LED
R: Spectral transmittance of red pixel G: Spectral transmittance of green pixel B: Spectral transmittance of blue pixel

Claims (2)

  A color reproduction color filter composed of three primary color pixels, wherein the color of each color pixel is in the range of 1.0 μm to 2.0 μm. I. Pigment Yellow 7, and C.I. I. A color filter containing Pigment Yellow 185. A pseudo white LED composed of a blue light emitting LED and a yellow light emitting phosphor, having a blue light emission peak in a wavelength range of 450 nm to 470 nm, and a yellow light emission peak in a wavelength range of 550 nm to 600 nm, A pseudo white LED in which the ratio of the emission peak intensity of blue emission to the emission peak intensity of yellow emission is 1: (0.20 to 0.50);
A liquid crystal display device comprising the color filter according to claim 1.

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