KR20130037446A - Liquid crystal display device - Google Patents

Abstract

PURPOSE: A liquid crystal display is provided to improve color reproductivity by using the green color filter pattern of a color filter layer which is made of a mixture of green 58 pigment and yellow 138 pigment. CONSTITUTION: A liquid crystal panel includes an array substrate(112) having a thin film transistor and a color filter substrate(114) having an RGB color filter pattern(134). A backlight unit includes a reflecting plate located in the lower part of the liquid crystal panel, an LED arranged on the reflecting plate, and an optical sheet located in the upper part of the LED. A green color filter pattern is made of a mixture of green 58 pigment and yellow 138 pigment.

Description

[0001] Liquid crystal display device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to an improvement in luminance and color reproducibility of a liquid crystal display using an LED as a light source.

Liquid crystal display devices (LCDs), which are used for TVs and monitors due to their high contrast ratio and are advantageous for displaying moving images, are characterized by optical anisotropy and polarization of liquid crystals. The principle of image implementation by

Such a liquid crystal display is an essential component of a liquid crystal panel bonded through a liquid crystal layer between two side-by-side substrates, and realizes a difference in transmittance by changing an arrangement direction of liquid crystal molecules with an electric field in the liquid crystal panel. do.

However, since the liquid crystal panel does not have its own light emitting element, a separate light source is required to display the difference in transmittance as an image. To this end, a backlight having a light source is disposed on the back surface of the liquid crystal panel.

Here, as a light source of the backlight unit, a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp, a light emitting diode (LED) .

Among them, LEDs are particularly widely used as light sources for displays with features such as small size, low power consumption, and high reliability.

1 is a cross-sectional view of a liquid crystal display device using a general LED as a light source.

As illustrated, a general liquid crystal display device includes a liquid crystal panel 10, a backlight unit 20, a support main 30, a cover bottom 50, and a top cover 40.

The liquid crystal panel 10 is a part that plays a key role in image expression and is composed of first and second substrates 12 and 14 bonded to each other with a liquid crystal layer interposed therebetween.

Although not shown in the drawings, a thin film transistor (TFT) is provided on a first substrate 12, which is usually called a lower substrate or an array substrate, and a second substrate 14 called an upper substrate or a color filter substrate On the inner surface, for example, a color filter pattern of red (R), green (G), and blue (B) colors and a black matrix are provided.

A backlight unit 20 is provided behind the liquid crystal panel 10.

The backlight unit 20 includes an LED assembly 29 arranged along the longitudinal direction of at least one side edge of the support main body 30, a white or silver reflective plate 25 seated on the cover bottom 50, A light guide plate 23 that is seated on the light guide plate 25, and a plurality of optical sheets 21 interposed therebetween.

The LED assembly 29 is formed on one side of the light guide plate 23 and includes a plurality of LEDs 29a for emitting white light and an LED PCB 29b for mounting a plurality of LEDs 29a, Quot;).

The LED assembly 29 is fixed in position by an adhesive or the like so that the light emitted from the plurality of LEDs 29a faces the light-incoming portion of the light guide plate 23. [

The liquid crystal panel 10 and the backlight unit 20 are covered with a top cover 40 and a backlight unit 20 which surround the top edge of the liquid crystal panel 10 in a state in which the edge is surrounded by the support main body 30 having a rectangular- And the cover bottom 50 covering the back surface of the cover main body 30 are joined to each other through the support main body 30.

Here, reference numerals 19a and 19b denote polarizers attached to the front and rear surfaces of the liquid crystal panel 10 to control the polarization direction of light, respectively.

Therefore, the light emitted from the backlight unit 20 is displayed in the form of a color image by reflecting the color combination of the color filter pattern in the process of passing through the liquid crystal panel 10.

On the other hand, the LED (29a) used as a light source of the liquid crystal display device is composed of a light emitting LED chip and a phosphor, and when light is emitted from the LED chip, the emitted light excites the phosphor to emit white light.

Such LED 29a is a trend to use a lot of yellow phosphor in recent years to improve the brightness.

However, the liquid crystal display device using the LED 29a using the yellow phosphor as a light source has a problem that the luminance is increased but the color reproduction rate is decreased.

That is, as the white light emitted from the LED 29a using the yellow phosphor penetrates the color filter patterns of red (R), green (G), and blue (B) colors of the liquid crystal panel 10, In particular, the color gamut of the wavelength range from 480 to 580 nm does not satisfy the color coordinate of BT.709, which is a color coordinate system representing color gamut of HDTV (High Definition Television).

The present invention has been made to solve the above problems, and an object thereof is to improve luminance and color reproducibility of a liquid crystal display device using an LED including a yellow phosphor as a light source.

In order to achieve the above object, the present invention provides a liquid crystal panel comprising an array substrate having a thin film transistor and a color filter substrate on which color filter patterns of red (R), green (G) and blue (B) are formed; ; And a backlight unit including a reflective plate positioned below the liquid crystal panel, an LED arranged on the reflective plate, and an optical sheet positioned above the LEd, wherein the green (G) color filter pattern includes a green 58 pigment; Provided is a liquid crystal display device formed by using a green (G) pigment mixed with Yellow 138.

At this time, the Green 58 pigment and Yellow 138 pigment is mixed in a ratio of 70:30 or 80:20, the LED includes a blue LED chip and a yellow phosphor.

And a light guide plate under the optical sheet, wherein the LED is positioned to face the light incident part of the light guide plate, and the gate and data crossing the inner surface of the array substrate to define a pixel region. And a thin film transistor connected to the two wires, a pixel electrode connected to the thin film transistor, and an inner surface of the color filter substrate, a black matrix corresponding to the gate and data wiring and the thin film transistor; A common electrode covering the color filter pattern and the black matrix is formed.

As described above, the present invention is formed by forming a green (G) color filter pattern of the color filter layer with a green (G) pigment mixed with a mixture of Green 58 pigment and Yellow 138 in a ratio of 70:30 or 80:20. The color reproducibility of the liquid crystal display using the light source as a light source is improved, and the color coordinates of BT.709 are satisfied.

1 is a sectional view of a liquid crystal display device using a general LED as a light source.
2 is an exploded perspective view of a liquid crystal display module according to an embodiment of the present invention.
3 is an exploded perspective view of a part of a liquid crystal panel;
4 is a simulation result of measuring the function of the wavelength of the green pigment in spectral transmittance.
Fig. 5 is a graph showing the BT.709 overlap ratio on the color coordinate;

Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings.

FIG. 2 is an exploded perspective view of a liquid crystal display device according to an embodiment of the present invention, and FIG. 3 is a partially exploded perspective view of the liquid crystal panel of FIG.

As shown, the liquid crystal display device includes a liquid crystal panel 110, a backlight unit 220, a support main body 230, a cover bottom 250, and a top cover 240.

3, which is a partially exploded perspective view of the liquid crystal panel 110, a plurality of data lines 118 and a plurality of gate lines 116 are vertically and horizontally crossed on one surface of an array substrate 112, And defines an area P.

The thin film transistor T is provided at the intersection of the two wirings 116 and 118 so as to be connected one-to-one with the transparent pixel electrode 124 provided in each pixel region P. FIG.

A data line 118 and a gate line 116 of the array substrate 112 and a non-display element such as a thin film transistor T are formed on one surface of the color filter substrate 114 facing the liquid crystal layer 150, Shaped black matrix 132 that covers the pixel region P so as to expose only the pixel electrode 124 while covering the pixel electrode 124. [

In addition, a transparent common electrode covering the red (R), green (G), and blue (B) color filter layers 134 and all of them are sequentially arranged in order to correspond to each pixel region P in the lattice. 136.

At this time, the green (G) color filter pattern of the red (R), green (G), blue (B) color filter layer 134 of the present invention, the ratio of Green 58 pigment and Yellow 138 is 70:30 or 80:20 It is characterized by being formed as a green (G) pigment mixed with. Through this, the liquid crystal display of the present invention satisfies the color coordinate of BT.709, which is the color coordinate system representing the color reproduction of HDTV (High Definition Television).

We will discuss this in more detail later.

On each of the outer surfaces of the array substrate 112 and the color filter substrate 114, polarizing plates 119a and 119b for selectively transmitting only specific light are attached.

Although not clearly shown in the figure, the upper and lower alignment films for determining the initial alignment direction of the liquid crystal are interposed at the boundary between the array substrate 112 and the color filter substrate 114 and the liquid crystal layer 150, A seal pattern (not shown) is formed along the edges of both substrates 112 and 114 to prevent leakage of the liquid crystal layer 150 filled between the array substrate 112 and the color filter substrate 114.

At this time, the array substrate 112 has a size larger than that of the color filter substrate 114, and one side edge of the array substrate 112 is exposed to the outside at the time of adhering them, A plurality of connected data pads 122 and a plurality of gate pads (not shown) connected to the plurality of gate lines 116 are located. The plurality of data pads 122 and gate pads (not shown) are connected to an external printed circuit board 218 via a connection member 216 such as a tape carrier package (TCP) The circuit board 218 is mounted with a timing controller, a gamma voltage generator, and the like that processes various kinds of signal information input from an external device such as a computer and supplies signal voltages necessary for image display.

The printed circuit board 218 is brought into close contact with the side of the support main body 230 or the backside of the cover bottom 250 during the modularization process.

An image signal transmitted to the data line 118 of the liquid crystal panel 110 and a gate line 116 are transmitted to the connection member 216 through the signal voltage transmitted from the printed circuit board 218, And a gate driver IC for generating and outputting a scan signal including an on / off signal of an on / off switch (not shown).

Accordingly, the signals for turning on / off the thin film transistor T are sequentially scanned and applied to the gate wiring 16, so that the image signal of the data wiring 118 is selected. When the image signal is transmitted to the electrode 124, the liquid crystal molecules between the array substrate and the color filter substrates 112 and 114 are driven by the electric field therebetween, and various images can be displayed by the change in the transmittance of light. .

In addition, the liquid crystal display module according to the present invention is provided with a backlight unit 220 for supplying light from the rear side of the liquid crystal panel 110 so that the difference in transmittance is expressed to the outside.

The backlight unit 220 includes an LED assembly 229, a white or silver reflector 225, a light guide plate 223 seated on the reflector 225, and a plurality of optical sheets 221 interposed thereon. Include.

The LED assembly 229 is disposed at one side of the light guide plate 223 so as to face the light incident portion of the light guide plate 223. The LED assembly 229 includes a plurality of LEDs 229a for emitting light, 229a are spaced apart from each other by a predetermined distance.

Here, the LED 229a is composed of an LED chip (not shown) and a phosphor (not shown) that emits large light. When light is emitted from the LED chip (not shown), the emitted light excites the phosphor (not shown). It will shine.

At this time, the LED 229a is a yellow phosphor of a YAG: Ce (T3Al5O12: Ce) -based yttrium (Y) aluminum (Al) garnet doped with a blue LED chip (not shown) and cerium (Ce) to improve luminance. Not shown).

Here, the yellow phosphor has an emission wavelength band in which red of the wavelength band of 645 to 655 nm, green of the wavelength band of 520 to 530 nm, and yellow of the wavelength band of 550 to 560 nm are mixed.

The light guide plate 223 evenly spreads the light incident from the LED 229a to a wide area of the light guide plate 223 while propagating through the light guide plate 223 by several total reflections to provide the surface light source to the liquid crystal panel 110.

The light guide plate 223 may include a pattern of a specific shape on the back surface to supply a uniform surface light source.

The reflective plate 225 is disposed on the rear surface of the light guide plate 223 to further reflect the light passing through the rear surface of the light guide plate 223 toward the liquid crystal panel 110 to further improve the brightness of the light.

The plurality of optical sheets 221 formed on the light guide plate 223 include a diffusion sheet, at least one light collecting sheet, and the like, and diffuse or collect light passing through the light guide plate 223 to provide a more uniform surface light source. To be incident on (110).

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 130, the support main 140, and the cover bottom 150, which surrounds the edges of the liquid crystal panel 110 and the backlight unit 120. The support main 140 has a rectangular frame shape.

In addition, the cover bottom 150 provides a horizontal surface 151 on which the backlight unit 120 including the liquid crystal panel 110 and the support main 140 are seated to support the entire liquid crystal display and simultaneously generate light loss. It serves as a lower frame to minimize the thing, the edge of the horizontal plane 151 is vertically bent to form a side (153).

In this case, the cover bottom 150 may stably guide the support main 140 to prevent shaking of the modular liquid crystal display and maintain a stable fixed state.

In addition, the top cover 130 prevents the liquid crystal panel 110 and the backlight unit 120 from being removed from the front and removes light leakage that may occur in the gap between the liquid crystal panel 110 and the support main 140. It will play the role of the upper frame.

The top cover 130 has a rectangular frame having a cross section bent in a shape of “a” so as to cover the top edge and side surfaces of the liquid crystal panel 110. The top cover 130 opens the front surface of the top cover 130 in the liquid crystal panel 110. It is configured to display an image to be implemented.

Therefore, the top cover 130, the support main 140, and the cover bottom 150 of the present invention are assembled and fastened to each other to integrally modularize the liquid crystal panel 110 and the backlight unit 120. In this case, the top cover 240 may be referred to as a case top or a top case, and the support main 230 may be referred to as a guide panel or a main support or a mold frame. The cover bottom 250 may be referred to as a bottom cover or a bottom cover I will.

Meanwhile, in the liquid crystal display of the present invention, even when the LED 229a including the yellow phosphor (not shown) is used as a light source of the backlight unit 220, the white light emitted from the LED 229a is used to improve the luminance. BT.709, which is a color coordinate system representing the color reproduction rate of HDTV (High Definition Television), as the color reproduction rate realized by passing through the color filter layer 134 of red (R), green (G), and blue (B) colors of 110). The color coordinate of is more satisfied than before.

This is because the green (G) color filter pattern of the color filter layer 134 of the present invention is formed of a green (G) pigment mixed with a mixture of Green 58 pigment and Yellow 138 in a ratio of 70:30 or 80:20.

That is, the liquid crystal display device using the LED 229a including the yellow phosphor (not shown) of the present invention as a light source of the backlight unit 220 may use a pigment forming a green (G) color filter pattern of the color filter layer 134. This is because it is newly formulated to satisfy the color coordinates of BT.709.

In detail, the green (G) color filter pattern of the color filter layer 134 is composed of a green (G) pigment in which Green 58 pigment and Yellow 138 are mixed and blended at a ratio of 70:30 or 80:20. , Yellow 138 pigment has a higher transmittance than Yellow150 pigment.

Accordingly, by mixing the Green 58 pigment and the Yellow 138 pigment in a ratio of 70:30 or 80:20, the green (R) pigment of the present invention is improved in transmittance.

That is, FIG. 4 is a value obtained by measuring the function of the color matching function of green designated by the International Commission on Illumination (CIE) in 1931 and the wavelength of the green pigment as a spectral transmittance.

Here, isochromat function is a value that defines three color matching functions corresponding to human vision in CIE as a function of wavelength, and quantifies the difference in wavelength between spectral sensitivity and luminous efficiency function. It is said to be excellent when it is below 3%, and is said to be bad when it is above 8%.

Currently, red (R), green (G), and blue (B) color pigments of the color filter pattern 134 being used all have an orange color function of 3% or less.

In this case, G1 represents a function of the wavelength of the general green (G) pigment, G2 represents a function of the wavelength of the green (G) pigment according to an embodiment of the present invention.

Referring to the graph, it can be seen that the transmittance of G2 is higher than that of G1.

That is, in the present invention, the green 58 pigment and the yellow 138 are mixed in a ratio of 70:30 or 80:20, and the green (G) pigment is more improved than the general green (G) pigment. It can be seen that the color matching function value of green is more satisfied.

Here, the improvement of the transmittance of the green (G) pigment of the present invention can be examined in more detail through the following Table (1) and Table (2), Table (1) is the green (G) pigment of the present invention The color coordinates and transmittance of the conventional green (G) pigments are compared.

Pigment x y Y Transmittance Green G1 0.273 0.572 59.65 - G2 0.273 0.572 60.96 2.2% improvement

Referring to Table (1), it can be seen that the Y value of G1 and G2 has changed, and the G2 has a 2.2% improvement in transmittance compared to G1. Through this, the green (G) pigment of the present invention can be seen that the transmittance is improved compared to the conventional green (G) pigment.

Table 2 below shows the color coordinates of the green (G) pigment of the present invention and the existing green (G) pigment when the white light emitted from the LED including the yellow phosphor used as the light source of the liquid crystal display device is combined, and It is a simulation result comparing and measuring the transmittance.

Green Pigment Light source X y Y Transmittance G1 Yellow phosphor 0.306 0.594 198.6 - G2 Yellow phosphor 0.306 0.594 204.0 2.7% improvement

Referring to Table (2), it can be seen that the Y values of G1 and G2 have been changed, and G2 has a 2.7% improvement in transmittance compared to G1.

That is, referring to Tables (1) and (2), when comparing only G1 and G2, it can be seen that G2 improves the transmittance by 2.2% compared to G1. The LED including a yellow phosphor as a light source of the liquid crystal display device When using as a light source, G2 can be seen that the transmittance is improved 2.7% compared to G1.

Here, the liquid crystal display of the present invention uses the LED including the yellow phosphor as a light source, thereby substantially increasing the transmittance by 2.7%.

Therefore, the present invention forms a green (G) pigment mixed with a Green 58 pigment and a Yellow 138 pigment in a ratio of 70:30 or 80:20 in a green (G) color filter pattern, thereby making it suitable for existing green (G) pigments. Since the transmittance is improved, it can be seen that the color matching function of green (G) specified by the CIE is more satisfied.

As described above, the green pigment of the present invention has improved transmittance to satisfy the green color equivalent value specified by CIE, thereby forming a green (G) color filter pattern through the green (G) pigment of the present invention. Color gamut can be more satisfying the color coordinate of BT.709.

The following table (3) shows the color coordinates of the liquid crystal display device in which the green (G) color filter pattern is formed through the green (G) pigment of the present invention, and the green (G) through the conventional green (G) pigment This is shown in comparison with the color coordinates of the liquid crystal display device in which the color filter pattern is formed.

Dry Red Green Blue White BT.709
Nesting ratio Ryox y Y X y Y X y Y x Y Y 0.6362 0.3364 84.0 0.3041 0.6026 360.7 0.1509 0.0578 50.2 0.2749 0.2883 494.89 96.9% 0.6362 0.3364 84.0 0.3011 0.6024 367.4 0.1509 0.0578 50.2 0.2903 0.2903 501.57 97.3%

G1 represents color coordinates of each color implemented through a liquid crystal display device in which a green (G) color filter pattern is formed through a general green (G) pigment, and G2 represents a green (G) pigment according to an embodiment of the present invention. The color coordinates of each color implemented through the liquid crystal display device in which the green (G) color filter pattern is formed are shown.

Referring to Table (3), there is no difference in the red and blue color coordinates of G1 and G2, but it can be seen that the difference appears in the green color coordinates.

That is, it can be seen that the green (G) pigment and the general green (G) pigment in which the Green 58 pigment and the Yellow 138 of the present invention are mixed at a ratio of 70:30 or 80:20 have a difference in color coordinates.

In addition, as the color coordinates of the green (G) fluctuate, it can be seen that the overlap ratio of BT.709 is different. The BT.709 overlap ratio of G2 is 97.3%, which is higher than the BT.709 overlap ratio of 96.9% of G1. Able to know.

Through this, white light emitted from the LED 229a including the yellow phosphor (not shown) is transmitted through the color filter layer 134 of red (R), green (G), and blue (B) colors of the liquid crystal panel 110. As can be seen, the color gamut implemented in the color coordinate system of BT.709, which represents the color gamut of HDTV (High Definition Television), is more satisfactory than before.

Here, the color recall ratio refers to a range of colors that a display device including a liquid crystal display device can express, which measures the color coordinates and luminance of red (R), green (G), and blue (B) Color Reproduction can be obtained for 3 Primary Colors.

The color coordinates are the scientific quantities that are typically displayed to measure the color and then distinguish each, and coordinate values of red (700 nm), green (546.1 nm), and blue (435.8 nm) are displayed on the coordinate system specified by CIE in 1931 will be.

In more detail about the color reproducibility, as shown in Figure 5 by connecting the color coordinates of each of the red (R), green (G), blue (B) determined on the color coordinates, it is possible to calculate the area of the triangle, The color gamut can be calculated by comparing the area above with the area of the NTSC color coordinates.

That is, the color recall ratio is expressed as a ratio of the relative area when assuming that the value of the color coordinate area of NTSC is 100.

Accordingly, if the color coordinate of BT.709, which is the color coordinate system representing the color reproduction ratio of HDTV (High Definition Television), is implemented as the area of A, a liquid crystal display including a general green (G) pigment is implemented as the area of B on the color coordinate. In addition, the liquid crystal display device including the green (G) pigment according to the embodiment of the present invention is implemented to the area of C.

Accordingly, the BT.709 overlap ratio refers to the amount overlapping the area of A on the color coordinates, and the area of C overlaps the area of A by about 0.5% more than the area of B.

Through this, the liquid crystal display device including the green pigment of the present invention satisfies the color coordinate of BT.709, which is the color coordinate system indicating the color reproduction ratio of HDTV (High Definition Television), and the color reproduction ratio is It can be seen that compared to the liquid crystal display device containing a green (G) pigment. As described above, according to the present invention, the green (G) color filter pattern of the color filter layer 134 is formed of a green (G) pigment in which Green 58 pigment and Yellow 138 are mixed in a ratio of 70:30 or 80:20, The color reproducibility of the liquid crystal display device using the LED 229a including the yellow phosphor as a light source is improved.

Accordingly, the color coordinate system of BT.709, which is a color coordinate system indicating the color reproduction ratio of HDTV (High Definition Television), is satisfied.

The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

Claims (5)

A liquid crystal panel including an array substrate having a thin film transistor and a color filter substrate on which color filter patterns of red (R), green (G), and blue (B) are formed;
A backlight unit comprising a reflector plate positioned below the liquid crystal panel, an LED arranged on the reflector plate, and an optical sheet positioned above the LEd.
Wherein the green (G) color filter pattern is formed using a green (G) pigment in which Green 58 pigment and Yellow 138 are mixed.
The method of claim 1,
Wherein the Green 58 pigment and Yellow 138 pigment are mixed at a ratio of 70:30 or 80:20.
The method of claim 1,
The LED includes a blue LED chip and a yellow phosphor.
The method of claim 1,
Further comprising a light guide plate disposed under the optical sheet, wherein the LED is positioned to face the light entrance portion of the light guide plate.
The method of claim 1,
On the inner surface of the array substrate,
A gate electrode and a data line crossing each other and defining a pixel region, the thin film transistor connected to the two lines, and the pixel electrode connected to the thin film transistor,
On the inner surface of the color filter substrate,
A black matrix corresponding to the gate and data lines and the thin film transistor, and a common electrode covering the color filter pattern and the black matrix.

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