KR20080064507A - Backlight unit and liquid crystal display device having the same - Google Patents

Abstract

A back light unit and a liquid crystal including the same are provided to improve the luminescence of a high color reproducing cool cathode fluorescent lamp and to improve the structure of a light source. A liquid crystal display includes a liquid crystal panel(100) and a light source(330). The light source is located on the rear side of the liquid crystal panel and has a lamp emitting white light and a light emitting diode emitting green light. The light source is disposed in correspondence to the plate surface of the liquid crystal panel. The liquid crystal display includes an optical member located between the liquid crystal panel and the light source. The lamp and the light emitting diode directly face the optical member.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME}

1 is an exploded perspective view of a liquid crystal display according to a first embodiment of the present invention;

FIG. 2 is an enlarged cross-sectional view taken along II-II of FIG. 1;

3 is a graph illustrating color stimulus values of a lamp of a liquid crystal display according to a first embodiment of the present invention;

4 is a graph for explaining luminance improvement of the liquid crystal display according to the first embodiment of the present invention;

5 is an exploded perspective view of a liquid crystal display according to a second exemplary embodiment of the present invention.

* Explanation of symbols for the main parts of the drawings

100: liquid crystal panel 200: mold frame

300: backlight unit 330: light source

331: lamp 332: light emitting diode

400: lower cover 500: upper cover

The present invention relates to a backlight unit and a liquid crystal display including the same, and more particularly, to a backlight unit having an improved light source unit structure and a liquid crystal display including the same.

Recently, many flat panel displays such as liquid crystal display devices (LCDs), plasma display panels (PDPs), and organic light emitting diodes (OLEDs) have been developed in place of conventional CRTs. It is becoming.

Among them, a liquid crystal display includes a liquid crystal panel having a first substrate including a thin film transistor, a second substrate including a color filter, and a liquid crystal layer positioned between both substrates. Since the liquid crystal panel is a non-light emitting device, a backlight unit for supplying light to the liquid crystal panel is located behind the liquid crystal panel. The backlight unit includes a light source unit for emitting light.

Conventionally, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), and the like have been mainly used as the light source unit. Among them, a cold cathode fluorescent lamp which generates little heat is mainly used.

Recently, a high color reproducible cold cathode fluorescent lamp having high color reproducibility is used.

However, the high color reproducible cold cathode fluorescent lamp has a problem that the luminance is lower than that of the conventional cold cathode fluorescent lamp.

Accordingly, an object of the present invention is to provide a liquid crystal display including the backlight unit having the improved brightness by improving the structure of the light source unit and the same.

An object of the present invention can be achieved by a liquid crystal display device including a liquid crystal panel, a light source unit positioned behind the liquid crystal panel and having a lamp emitting white light and a light emitting diode emitting green light.

The light source unit may be disposed to correspond to the entire plate surface of the liquid crystal panel.

Further comprising an optical member positioned between the liquid crystal panel and the light source unit, the lamp and the light emitting diode may directly face the optical member.

The light guide plate may further include a light guide plate disposed at a rear side of the liquid crystal panel, and the light source unit may be positioned on at least one side of the light guide plate.

The lamp may comprise a barium magnesium aluminate series phosphor.

The white light emitted by the lamp may have a green color stimulus value lower than a blue color stimulus value or a red color stimulus value.

Another object of the present invention can be achieved by a backlight unit including a light source unit having a lamp for emitting white light and a light emitting diode for emitting green light.

The optical member may further include an optical member positioned on an optical path of the light source unit, and the lamp and the light emitting diode may directly face the optical member.

The lamp may comprise a barium magnesium aluminate series phosphor.

The white light emitted by the lamp may have a green color stimulus value lower than a blue color stimulus value or a red color stimulus value.

Hereinafter, the present invention will be described with reference to the accompanying drawings.

Hereinafter, the liquid crystal display device 1 according to the first embodiment of the present invention will be described with reference to FIGS. 1 to 4. Hereinafter, the optical member includes an optical sheet 310 and a diffusion plate 320, the optical member is located on the path of the light emitted from the light source unit 330.

As shown in FIG. 1, the liquid crystal display device 1 according to the first embodiment of the present invention includes a liquid crystal panel 100 for forming an image and a mold frame for supporting the edge of the liquid crystal panel 100. 200, the backlight unit 300 for supplying light to the rear surface of the liquid crystal panel 100, the lower cover 400 accommodating the backlight unit 300, and the lower cover 400 are mutually coupled to the liquid crystal panel ( It includes a top cover 500 for covering the front of the 100.

As shown in FIG. 2, the liquid crystal panel 100 faces the first substrate 110 including the thin film transistor 112 and the second substrate facing the first substrate 110 and including the color filter 123. And a liquid crystal layer 130 positioned between the first substrate 110 and the second substrate 120.

In the first substrate 110, a thin film transistor 112 is formed on the first insulating substrate 111. The thin film transistor 112 is covered by the protective layer 113, and a portion of the protective layer 113 is removed to form a contact hole 114 exposing the thin film transistor 112. The pixel electrode 115 made of a transparent conductive material is connected to the thin film transistor 112 through the contact hole 114. The first alignment layer 116 is formed on the pixel electrode 115.

In the second substrate 120, a lattice-shaped black matrix 122 is formed on the second insulating substrate 121. The black matrix 122 may be made of an organic material including a black pigment. The black matrix 122 is formed to correspond to the thin film transistor 112 of the first substrate 110.

The color filter 123 is formed between the black matrices 122. The color filter 123 may be formed of an organic material. The color filter 123 includes a first color filter 123a having a red color, a second color filter 123b having a green color, and a third color filter 123c having a blue color.

The thickness d1 of the second color filter 123b is the thickness d2 and d3 of the first color filter 123a and the third color filter 123c by the light emitting diode 332 emitting green light to be described later. Small compared to).

The common electrode 125 made of an overcoat layer 124 and a transparent conductive material is formed on the black matrix 122 and the color filter layer 123. The second alignment layer 126 is formed on the common electrode 125.

The liquid crystal layer 130 is positioned between the alignment layers 116 and 126. The molecular arrangement of the liquid crystal layer 130 is determined by both alignment layers 116 and 126.

The mold frame 200 is positioned behind the liquid crystal panel 100.

The mold frame 200 is formed along the edge of the liquid crystal panel 100, has a substantially rectangular shape, and supports the liquid crystal panel 100 spaced apart from the backlight unit 300.

Since the liquid crystal panel 100 is a non-light emitting device, a backlight unit 300 for supplying light to the liquid crystal panel 100 is positioned behind the mold frame 200.

The backlight unit 300 is positioned behind the liquid crystal panel 100 and includes an optical sheet 310, a diffusion plate 320, a light source 330, and a reflective sheet 340.

The optical sheet 310 is positioned on the rear surface of the liquid crystal panel 100 and includes a prism sheet 311 and a protective sheet 312. Here, the prism sheet 311 is formed with a triangular prism-shaped prism on the upper surface in a constant arrangement. The prism sheet 311 collects light diffused from the diffusion plate 320 to be described later in a direction perpendicular to the plate surface of the upper liquid crystal panel 100. Two prism sheets 311 are usually used, and the micro prisms formed on the prism sheets 311 form an angle. The light passing through the prism sheet 311 proceeds almost vertically to provide a uniform luminance distribution. The uppermost protective sheet 312 protects the prism sheet 311 weak to scratches. A diffuser plate 320 for diffusing light is disposed behind the prism sheet 311.

The diffusion plate 320 is disposed between the optical sheet 310 and the light source 330. The diffusion plate 320 uniformly diffuses the light supplied from the light source unit 330 toward the liquid crystal panel 100. The diffusion plate 320 may be a transparent glass material for an insulation effect, but is not limited thereto and may be a material such as a transparent polymer having an insulation effect.

The light source unit 330 is disposed behind the diffuser plate 320.

The light source unit 330 includes a plurality of lamps 331 for emitting white light, a light emitting diode 332 disposed between adjacent lamps 331 and emitting green light, and a light emitting diode substrate on which the light emitting diode 332 is mounted. 333).

The light source unit 330 extends in a first direction, which is an extension direction of the plate surface of the liquid crystal panel 100, and is disposed to correspond to the entire plate surface of the liquid crystal panel 100.

The light source unit 330 including the lamp 331 and the light emitting diode 332 directly faces the diffusion plate 320.

The lamp 331 includes a high color reproducible cold cathode fluorescent lamp containing a barium magnesium aluminate series (BAM series) phosphor.

3 is a graph showing color stimulation values of the high color reproducible cold cathode fluorescent lamps and color stimulation values of the general cold cathode fluorescent lamps.

Common cold cathode fluorescent lamps include cold cathode fluorescent lamps containing strontium calcium barium series (SCA series) phosphors.

The x-axis of FIG. 3 represents a wavelength and the y-axis represents a color stimulus value. (a) shows white light emitted by the high color reproducible cold cathode fluorescent lamp, and (b) shows white light emitted by the general cold cathode fluorescent lamp.

The white light emitted by the high color reproducible cold cathode fluorescent lamp has higher color reproducibility than the white light emitted by the general cold cathode fluorescent lamp.

However, as shown in FIG. 3, the white light (a) emitted by the high color reproducible cold cathode fluorescent lamp has a color stimulus value of green (Blue) as compared with the white light (b) emitted by the general cold cathode fluorescent lamp. It is lower than the color stimulus value of or red color stimulation value of.

On the other hand, when recognizing color with the eyes of a user, the higher the color stimulus value of green included in the color, the higher the overall luminance feels.

As a result, the lamp 331 including the high color reproducible cold cathode fluorescent lamp has high color reproducibility but low luminance.

However, the green color stimulus value of the white light emitted from the lamp 331 is compensated for by the light emitting diode 332 emitting green light.

As a result, the green color stimulus value of light emitted by the light source unit 330 including the lamp 331 and the light emitting diode 332 is improved.

The above description will be described in more detail with reference to FIG. 4.

4 shows a standard chromaticity diagram (CIE 1931 xy Chromaticity Diagram) published by the International Lighting Commission in 1931.

Where (c) represents the color of light emitted from a common cold cathode fluorescent lamp, (d) represents the color of light emitted from a high color reproducible cold cathode fluorescent lamp, and (e) represents a liquid crystal according to a first embodiment of the present invention. The light source 330 of the display device 1 represents the color of light emitted, and (f) represents a standard chromaticity diagram.

As shown in FIG. 4, the liquid crystal display according to the first exemplary embodiment of the present invention includes a lamp 331 having a high color reproducible cold cathode fluorescent lamp emitting white light and a light emitting diode 332 emitting green light. It can be seen that the light emitted from the light source unit 330 of 1) has a high chromaticity from green.

Since the green color has a high chromaticity, the luminance of the light source unit 330 is improved, thereby improving the luminance of the liquid crystal display device 1.

Referring back to FIG. 1, the reflective sheet 340 is positioned behind the light source 330.

The reflective sheet 350 is disposed between the light source 330 and the lower cover 400. The reflective sheet 350 reflects the light incident from the light source unit 330 and supplies the light toward the diffuser plate 320.

The lower cover 400 is disposed at the rear of the reflective sheet 350 and serves to accommodate the backlight unit 300.

 The upper cover 500 has a display window to expose the effective surface of the liquid crystal panel 100 to the outside, and is coupled to the lower cover 400.

Hereinafter, the liquid crystal display device 2 according to the second embodiment of the present invention will be described with reference to FIG. 5.

Hereinafter, only the characteristic parts distinguished from the first embodiment will be described and described, and the descriptions omitted will be in accordance with the first embodiment and known techniques. In addition, in the second embodiment of the present invention, for the convenience of description, the same components will be described using the same reference numerals.

As shown in FIG. 5, the backlight unit 300 of the liquid crystal display device 2 according to the second embodiment of the present invention further includes a light guide plate 350 and a light source cover 360.

The light guide plate 350 is positioned at the rear of the liquid crystal panel 100 and serves to uniformly guide the light supplied from the light source unit 330 toward the liquid crystal panel 100.

Light sources 330 are positioned on both side surfaces 350a and 350b of the light guide plate 350.

The light source unit 330 includes a plurality of lamps 331 for emitting white light and a light emitting diode 332 disposed between the adjacent lamps 331 and mounted on the light emitting diode substrate 333 and emitting green light.

The light source unit 330 extends in a second direction, which is an extension direction of both side surfaces 350a and 350b of the light guide plate 350.

The light source unit 330 including the lamp 331 and the light emitting diodes 332 directly face both side surfaces 350a and 350b of the light guide plate 350.

In another embodiment, the lamp 331 may include not only a high color reproducible cold cathode fluorescent lamp but also a general cold cathode fluorescent lamp or a hot cathode fluorescent lamp.

Although embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that the present embodiments may be modified without departing from the spirit or spirit of the invention. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a backlight unit having an improved luminance by improving the structure of the light source unit and a liquid crystal display including the same.

Claims (10)

In the liquid crystal display device, A liquid crystal panel; And a light source unit positioned behind the liquid crystal panel and having a lamp for emitting white light and a light emitting diode for emitting green light. The method of claim 1, And the light source unit is disposed corresponding to the entire plate surface of the liquid crystal panel. The method of claim 2, Further comprising an optical member located between the liquid crystal panel and the light source unit, And the lamp and the light emitting diode face the optical member directly. The method of claim 1, Further comprising a light guide plate located behind the liquid crystal panel, And the light source unit is positioned on at least one side of the light guide plate. The method according to any one of claims 1 to 4, The lamp comprises a barium magnesium aluminate-based phosphor. The method of claim 5, And wherein the white light emitted from the lamp has a green color stimulus value lower than a blue color stimulus value or a red color stimulus value. In the backlight unit, And a light source unit having a lamp emitting white light and a light emitting diode emitting green light. The method of claim 7, wherein Further comprising an optical member located on the light path of the light source unit, And the lamp and the light emitting diode face the optical member directly. The method according to claim 7 or 8, The lamp unit comprises a barium magnesium aluminate-based phosphor. The method of claim 9, The white light emitted from the lamp has a green color stimulus value lower than a blue color stimulus value or a red color stimulation value.

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