KR100637283B1 - Transflective Liquid Crystal Display Device - Google Patents

Abstract

The present invention is a liquid crystal layer interposed between the upper and lower plates of the transparent material spaced apart from each other, the transparent electrode positioned between the upper and lower plates, the transparent electrode positioned between the lower plate and the liquid crystal layer, between the transparent electrode and the liquid crystal layer A reflection plate having a transmissive portion and a reflection portion, a first color filter layer disposed between the liquid crystal layer and the upper plate, and formed at a position corresponding to the reflection portion of the reflection plate, and at the same layer as the first color filter layer. Provided is a reflective liquid crystal display device formed at a position corresponding to the transmissive portion, the second color filter layer having a higher pigment density than the first color filter layer, and a backlight mounted under the lower plate.

Description

Reflective Liquid Crystal Display Device             

1 is a diagram showing the transmittance of each layer of light emitted from the backlight.

2 is a cross-sectional view showing an operation along a cross section of a general reflective transmissive liquid crystal display device;

3 is a cross-sectional view showing an operation in accordance with the transmission of the color filter of the general reflection-transmissive liquid crystal display device.

4A is a graph showing the spectrum when passing through a color filter once.

4B is a graph showing the spectrum when passing through the color filter twice.

FIG. 5 is a diagram illustrating CIE color coordinates when a color filter and a color filter are transmitted once or twice in a transmissive liquid crystal display; FIG.

6 is a cross-sectional view of a transflective liquid crystal display device according to an exemplary embodiment of the present invention.

7 is a plan view of a reflective transmissive color filter of the present invention.

<Explanation of symbols for main parts of drawing>

100: lower substrate 110: reflecting unit                 

120: transmission part 200: upper substrate

250: liquid crystal layer 300: backlight

400: transmissive color filter 401: reflective color filter

403: transmissive color filter II: reflector

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display device, and more particularly, to a transflective liquid crystal display device capable of reflective and transmissive modes. In particular, the present invention relates to a reflective transmissive liquid crystal display device that eliminates color differences that occur between reflective and transmissive modes.

Recently, as the information society has progressed rapidly, a display field for processing and displaying a large amount of information has been developed.

Until modern times, cathode ray tube (CRT) has become the mainstream of display devices and has been developing.

However, in recent years, the need for a flat panel display has emerged in order to meet the times of miniaturization, light weight, and low power consumption. Accordingly, a thin film transistor-liquid crystal display (hereinafter referred to as TFT-LCD) having excellent color reproducibility and thinness has been developed.

Referring to the operation of the TFT-LCD, when any pixel is switched by the thin film transistor, the switched arbitrary pixel makes it possible to adjust the light transmittance of the lower light source.

The switching element is mainly composed of an amorphous silicon thin film transistor (a-Si: H TFT) in which a semiconductor layer is formed of amorphous silicon. This is because the amorphous silicon thin film can be formed at a low temperature on a large insulating substrate such as a low-cost glass substrate.

Commonly used TFT-LCDs have used a method of representing an image by the light of a light source called a backlight located under the panel.

However, TFT-LCDs are very inefficient light modulators that transmit only 3-8% of the light incident by the backlight.

45% of the two polarized light transmittance, 94% of the glass of the lower plate and the top plate, about 65% of the TFT array and pixel, 27% of the color filter, the light transmittance of the TFT-LCD About 7.4%.

1 is a diagram schematically illustrating transmittance of each layer of light emitted from a backlight.

As described above, since the amount of light actually seen through the TFT-LCD is about 7% of the light generated in the backlight, the brightness of the backlight should be bright in the high brightness TFT-LCD, and the power consumption by the backlight is large.

Therefore, in order to supply sufficient backlight power, a battery having a large weight has been used by increasing the capacity of the power supply device. However, this also has a limited use time.

In order to solve the above problem, a reflective TFT-LCD which does not use backlight light has recently been studied. Since it operates by using natural light, the power consumption of the backlight can be greatly reduced, so that it can be used in a portable state for a long time, and the aperture ratio is also superior to that of a conventional backlight TFT-LCD.

That is, the reflective TFT-LCD has a structure that reflects external light by using a material having an opaque reflective characteristic in the pixel portion formed of the transparent electrode in the conventional transmissive TFT-LCD.

The reflective TFT-LCD as described above can be used for a long time because it is driven using natural light or an external artificial light source without using an internal light source such as a backlight. That is, the reflective TFT-LCD reflects external natural light to the reflective electrode and uses the reflected light. Therefore, only power required for driving the reflective TFT-LCD is the liquid crystal drive and the drive circuit.

However, natural or artificial light sources do not always exist. That is, the reflective TFT-LCD may be used in an office or a building in which daylight is present, or an external artificial light is present, but the reflective TFT-LCD may be used in a dark environment in which there is no natural light. There will be no.

Therefore, in order to solve the above problems, recently, a transflective TFT-LCD using the advantages of the reflective TFT-LCD using natural light and the transmissive TFT-LCD using backlight light has been researched and developed.                         

The reflective transmissive TFT-LCD is free to switch to the reflective or transmissive mode according to the user's will.

2 is a cross-sectional view illustrating one pixel of the above-described reflective transparent TFT-LCD. Referring to FIG. 2, a general reflective transparent TFT-LCD will be described below.

The lower plate 50 includes a switching element (not shown), a pixel electrode 54, and a reflective electrode 52, and an upper plate 60 having a color filter 61 formed thereon.

In addition, the liquid crystal layer 80 is positioned in the form of the lower plate 50 and the upper plate 60. In addition, the backlight 70 is positioned under the lower plate 50.

As the reflective electrode 52 formed on the lower plate 50, a conductive material having excellent reflectance is mainly used to reflect the external light 74.

In addition, a plurality of holes 53 are present in the reflective electrode 52 in plan view and have a length of ΔL in cross section.

That is, the pixel electrode 54 is positioned where the hole 53 is formed to transmit the backlight light 72 formed from the backlight 70.

Referring to the above, the operation of the reflective transmission TFT-LCD is described in detail. In the reflective mode, the reflective electrode 52 reflects the light 74 incident from the outside to the upper plate 60.

In the transmissive mode, the light 72 generated by the backlight 70 is transmitted to the upper plate 60 through the pixel electrode 54 positioned in the hole formed in the reflective electrode 52.

At this time, when a signal is applied to the reflective electrode 52 to the pixel electrode 54 by the action of a switching element (not shown), the phase of the liquid crystal layer 80 is changed, at which time the liquid crystal layer is transmitted through The reflected light may be colored by the color filter 61 formed on the upper plate 60 and viewed as a color screen.

As described above, since the reflection-transmitting TFT-LCD has a reflection mode and a transmission mode, there is an advantage that it can be used regardless of day / night or place.

Referring to FIG. 3 presented as a structure of a general reflection type TFT-LCD, it is as follows.

As shown in FIG. 3, in the reflection mode TFT-LCD, in the reflection mode, the external light 74 is reflected through the reflection part 52 among the reflection part 52 and the transmission part 53 which constitute the reflection plate I. The light passes through the color filter 61 two times before being incident and released to the outside. That is, once when the external light is incident, and once when it is reflected by the reflecting portion 52 and emitted again to the outside.

In the transmission mode, the backlight light 72 passes through the color filter 61 only once through the transmission part 53.

As a result, the user feels different colors in the reflection mode and the transmission mode.

4A and 4B are diagrams illustrating spectra of light wavelengths when the color filter is transmitted once and twice.

As shown in FIG. 4A, when the light passes through the color filter once, it can be seen that red (R), green (G), and blue (B) light are not clearly distinguished.

The wavelength range of visible light visible to the human eye is limited to a small wavelength range between 400 and 700 nm. In this case, red of the visible light corresponds to a wavelength of 660nm, green corresponds to 530nm, and blue corresponds to a wavelength of 470nm. That is, the pitch of the liquid crystals can be artificially manipulated, and the artificial liquid crystal mode enables the display of high purity color by selectively reflecting only the unique wavelength of the color corresponding to each pixel of visible light.

In the drawing illustrated in FIG. 4A, when the blue color filter is described as an example, the blue color filter should absorb colors other than blue, but the transmittance of blue light having a wavelength around 470 nm is high overall. It can be seen. That is, it can be seen that green light is also transmitted through the blue color filter.

FIG. 4B is a diagram analyzing the spectrum when the color filter is transmitted twice, and the light transmittance distribution of each color (red, green, blue) is more even than the spectrum when the color filter is transmitted once. Since the curve corresponding to the intrinsic wavelength is steep, wavelengths other than the intrinsic wavelength are filtered out well.

As described above, FIG. 4A corresponds to a transmission mode and FIG. 4B corresponds to a reflection mode.

Therefore, the colors that can be combined with each other in the reflection mode and the transmission mode are different. For example, in the reflection mode and the transmission mode, even though the same green color is expressed, dark green is represented in the reflection mode and light green in the transmission mode. It can be expressed.

FIG. 5 is a diagram illustrating color coordinates when passing through a color filter once and passing through it twice, and the number of colors that can be combined when passing through the color filter once as shown in the illustrated figure is twice. It can be seen that less than the number of colors when passing through.

As a result, when the same voltage is applied to the pixel electrode, the combined color in the reflection mode and the transmission mode is different.

The above problem is caused by the characteristics of the color filter. In general, the color filter used in the case of a transflective liquid crystal display device is based on a reflection mode as a design reference. Therefore, in order to increase the luminance in the reflection mode, the color filter for the reflection mode weakly forms the purity of the color, so that the purity of the color is decreased in the transmission mode that transmits the color filter once.

In order to solve the above problems, an object of the present invention is to effectively remove the color difference generated between the reflection mode and the transmission mode in the reflective liquid crystal display device.

Furthermore, it can be said to implement high quality TFT-LCD.

In the present invention to achieve the above object and the top and bottom of the transparent material facing each other spaced apart; A liquid crystal layer interposed between the upper plate and the lower plate; A transparent electrode disposed between the lower plate and the liquid crystal layer; A reflection plate disposed between the transparent electrode and the liquid crystal layer, the reflection plate having a transmission portion and a reflection portion; A first color filter layer disposed between the liquid crystal layer and the upper plate and formed at a position corresponding to the reflecting portion of the reflecting plate; A second color filter layer formed on the same layer as the first color filter layer at a position corresponding to the transmissive portion of the reflecting plate, and having a higher pigment density than the first color filter layer; Provided is a reflective liquid crystal display device including a backlight mounted under the lower plate.

The first and second color filters are made of the same resin component, and a plurality of pixels are defined in the reflective plate, and the transmissive part is positioned in each pixel, and the reflecting part surrounds the transmissive part, and the first color is disposed in the reflective plate. The filter layer is located outside the second color filter layer.

Hereinafter, the configuration and operation according to the embodiment of the present invention will be described with reference to the accompanying drawings.

6 is a cross-sectional view showing a cross section corresponding to one pixel portion of the reflective liquid crystal display device according to the present invention.

First, the backlight 300 used in the transmissive mode is positioned under the lower substrate 100.

The lower substrate 100 has a thin film transistor substrate 150 on which a thin film transistor (not shown) used as a switching element of a liquid crystal display device is formed, a transparent electrode 130 in a transmissive mode, and a reflective mode on the transparent electrode 130. The reflection unit 110 is formed, and the reflection plate II includes the reflection unit 120 and the transmission unit 120 so that light generated by the backlight 300 can pass therethrough.

In addition, an upper substrate 200 spaced at a predetermined interval is formed on the lower substrate 100, and the upper substrate 200 is located at a portion opposite to the reflector 110 formed on the lower substrate 100. The reflective color filter 401 is configured to face the transmissive portion 120 such that the transmissive color filter 400 having a higher pigment density than the reflective color filter 401 is located.

The reason for different pigment densities of the two types of color filters is that when light passes through the color filter once, the transmittance is higher and the color purity is lower than when it passes twice (see FIGS. 4A and 4B). Therefore, the transmittance can be reduced and the color purity can be increased, thereby reducing the color difference between the two modes.

That is, in the process of the color filter, by using the same resin, by controlling the amount of the R, G, B pigment, the transmittance and color purity can be adjusted.

The liquid crystal layer 250 is positioned between the lower substrate 100 and the upper substrate 200.

FIG. 7 is a plan view of a reflective color filter 403 corresponding to each of the R, G, and B filters of the present invention. For reference, the positions of the reflective part 110 and the transmissive part 120 are defined by the reflective electrode of the lower plate. It depends on the structure.

As shown, the reflective color filter 401 of the reflective transmissive color filter 403 is positioned to surround the transmissive part 400, that is, the reflective color filter 401 is the transmissive color filter 400. It is located on the outside of the floor.                     

The reflective transmissive color filter 403 of the present invention is processed at a higher pigment density of the transmissive color filter than the reflective type, and is not necessarily limited to the same resin component.

That is, the reflective color filter 403 of the present invention is to provide a high quality reflective transmission liquid crystal display device in accordance with the color purity and transmittance most suitable for the light source used in each mode.

Since the final quality of the transmissive LCD depends on the color, eliminating the color difference is an important issue.

As described above, when the color filter of the reflection-transmission TFT-LCD is manufactured in the reflection transmission type according to the embodiment of the present invention, the color difference generated between the reflection mode and the transmission mode is eliminated so that the user does not see a difference in color feeling. It is possible to provide a TFT-LCD.

Claims (3)

A top plate and a bottom plate of transparent material spaced apart from each other; A liquid crystal layer interposed between the upper plate and the lower plate; A transparent electrode disposed between the lower plate and the liquid crystal layer; A reflection plate disposed between the transparent electrode and the liquid crystal layer, the reflection plate having a transmission portion and a reflection portion; A first color filter layer disposed between the liquid crystal layer and the upper plate and formed at a position corresponding to the reflecting portion of the reflecting plate; A second color filter layer formed on the same layer as the first color filter layer at a position corresponding to the transmissive portion of the reflecting plate, and having a higher pigment density than the first color filter layer; Backlight mounted on the lower plate Reflective liquid crystal display device comprising a. The method of claim 1, And the first and second color filters are the same resin component. The method of claim 1, A plurality of pixels are defined in the reflective plate, and the transmissive part is positioned in each pixel, and the reflective part surrounds the transmissive part, and the first color filter layer is positioned on the outer side of the second color filter layer. Device.

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