KR20080098209A - Backlight unit and liquid crystal display using the same - Google Patents

Abstract

A backlight unit and an LCD device using the same are provided to improve the display quality efficiently by controlling the number of lamp, thereby reducing power consumption. A backlight unit of an LCD device comprises a plurality of lamps(112), a reflecting plate(126) facing the lower part and side part of lamps, and a cover member including the reflecting plate and lamps. At the reflecting plate, the curvature of the bottom part of the lamps is smaller than that of side part of the lamp. Under the above curvature rate condition between bottom part of the lamp and side part of the lamp, curvature rate of the reflection plate is between 0.2~0.9.

Description

Back light unit and liquid crystal display using the same

1 is a diagram illustrating a liquid crystal display including a direct type backlight.

FIG. 2 is a cross-sectional view of the backlight unit illustrated in FIG. 1.

3 is an experimental result image of measuring the luminance of the backlight unit shown in FIG.

4 is a graph showing experimental results of measuring luminance of the backlight unit illustrated in FIG. 1.

5 is a view showing a liquid crystal display device according to an embodiment of the present invention.

6 is a cross-sectional view of the LCD shown in FIG. 5.

7A to 7B are diagrams showing optical paths that vary depending on the curvature of the reflecting member disposed under the lamp.

8A to 8C are diagrams showing experimental results using the reflective member of FIG. 7A.

9A to 9C are diagrams showing experimental results using the reflective member of FIG. 7B.

10 is a test result image showing the lamp brightness of the backlight unit according to an embodiment of the present invention.

11 is a graph showing experimental results of measuring luminance of a backlight unit according to an exemplary embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

Lamp: 12,112 Bottom cover: 2,52

Top case: 8,58 Panel guide: 6,56

Optical sheets: 4,54 Support side: 18,118

Diffusion Plate: 16,116 Liquid Crystal Display Panel: 20,120

Color filter array substrate: 20a, 120a Reflector: 33,93

Thin film transistor array substrate: 20b, 120b reflective member: 66, 126

Gate tape carrier package: 22,122

Data Tape Carrier Package: 24,124

The present invention relates to a liquid crystal display device, and more particularly to a backlight unit and a liquid crystal display device using the same to increase the light uniformity.

 In general, the liquid crystal display device has a trend that the application range is gradually widened due to the characteristics such as light weight, thin, low power consumption. According to this trend, liquid crystal displays are widely applied to various electronic devices such as office automation equipment and audio / video equipment.

Since the liquid crystal display is not a self-luminous display, a separate light source such as a back light unit is required.

The backlight unit is divided into a direct type and an edge type according to the position of the light source. The edge type backlight is provided with a light source facing the side of the light guide plate, and irradiates the liquid crystal display panel with light incident from the light source through the light guide plate and the plurality of optical sheets. In the direct type backlight, as shown in FIG. 1, a plurality of light sources are disposed under the liquid crystal display, and light incident from the light sources is irradiated onto the liquid crystal display panel through the diffusion plate and the plurality of optical sheets.

Recently, the application range of the direct type backlight has been expanding, mainly on large display devices such as LCD TVs, compared to the edge type. 1 and 2, the liquid crystal display device surrounds an edge of the liquid crystal display panel 20, a panel guide 6 supporting the liquid crystal display panel 20, and a liquid crystal display panel 20. A top case 8 and a direct backlight unit 37 for irradiating light to the liquid crystal display panel 20 are provided.

The direct type backlight unit 37 includes a plurality of lamps 12 disposed below the liquid crystal panel 30, a reflection sheet 33 disposed below the lamp 12, and reflecting light, and a reflection sheet 33. The bottom cover 2 includes a diffusion plate 16 disposed on the lamps 12, and a plurality of optical sheets 4 disposed between the diffusion plate 16 and the liquid crystal panel 20.

The direct type backlight unit 37 has a problem in that the lamps 12 are shown in a bright line in the display image because the brightness between the lamps 12 and the brightness of the lamps 12 are increased. 3 and 4 are experimental results showing bright lines. In order to solve the problem of lowering the optical uniformity of the liquid crystal display due to such bright lines, the distance between the lamps can be reduced by increasing the number of lamps in the direct type backlight unit, but power consumption is inevitably increased.

Accordingly, the present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a backlight unit and a liquid crystal display device using the same to increase the light uniformity.

In order to solve the above object, the backlight unit according to an embodiment of the present invention comprises a plurality of lamps; A reflective member facing the bottom and side surfaces of the lamps; And a cover member in which the lamps and the reflective member are accommodated.

In the reflecting member, the curvature of the portion facing the bottom of the lamp is smaller than the curvature of the portion facing the side of the lamp.

The curvature of the reflective member is determined to be between 0.2 and 0.9 under a condition that the curvature of the portion of the reflective member opposite the lamp is less than the curvature of the other portion of the reflective member opposite the side of the lamp.

The reflective member is a plastic molded body formed with a groove below the lamp and facing the side of the lamp; And a metal film formed into a groove of the plastic molded body.

The distance between the reflective member and the lamp is determined to be between 0mm and 10mm.

An end of the reflecting member facing the side of the lamp is inclined at an angle of 5 ° to 30 ° with respect to a horizontal reference plane parallel to the bottom surface of the cover member.

Liquid crystal display device according to an embodiment of the present invention; And a backlight for irradiating light to the liquid crystal display panel using a plurality of lamps disposed under the liquid crystal display panel, a reflective member facing the bottom and side surfaces of the lamps, and a cover member in which the lamps and the reflective member are accommodated. With a unit.

 Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 5 to 9.

5 and 6 illustrate a liquid crystal display according to an exemplary embodiment of the present invention.

5 and 6, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal display panel 120, a panel guide 56 supporting the liquid crystal display panel 120, and a liquid crystal display panel ( A top case 58 surrounding the edge of the 120 and a direct backlight unit 97 for irradiating light to the liquid crystal display panel 20 are provided.

The direct type backlight unit 97 includes a plurality of lamps 112, a support side 118 on which the lamps 112 are mounted, and a bottom cover 52 engaged with the support side 118. ), A reflective sheet 93 disposed under the lamps 98, a diffuser plate 116 positioned on the top of the lamps 112, and a plurality of optical sheets positioned on the diffuser plate 116. 54 is provided.

The liquid crystal display panel 120 includes a color filter array substrate 120a as an upper substrate and a thin film transistor array substrate 120b as a lower substrate. A color filter, a common electrode, a black matrix, and the like are formed on the upper substrate. In addition, a plurality of data lines and a plurality of signal lines and pixel electrodes are formed on the lower substrate of the liquid crystal display panel 120, and thin film transistors (“TFTs”) are formed at intersections of the data lines and the gate lines. "Is formed. In the in-plane switching mode (IPS), the common electrode is not formed on the upper substrate, but the common electrode is formed together with the pixel electrode on the lower substrate. The TFT switches the data signal to be transmitted from the data line toward the liquid crystal cell in response to the scan signal (gate pulse) from the gate line. The pixel electrode is formed in the pixel region between the data line and the gate line. In addition, pads connected to the data lines and the gate lines may be formed at one side of the lower substrate, and the pads may include a gate tape carrier package 122 in which a gate integrated circuit for generating a gate signal is mounted. And a data tape carrier package 124 on which a data integrated circuit for generating a data signal is mounted. The gate integrated circuit and the data integrated circuit, which are drive integrated circuits, may be attached to the glass substrate in a chip on glass manner or may be directly formed on the glass substrate together with the signal wiring and the TFTs of the pixel region.

The direct backlight unit 97 includes a plurality of lamps 112, a support side 118 on which the lamps 112 are mounted, and a bottom cover 52 engaged with the support side 118. , A reflective sheet 93 disposed under the lamps 112, a diffuser plate 116 positioned above the lamps 112, and a plurality of optical sheets positioned above the diffuser plate 116 ( 54).

The lamps 112 are preferably an external electrode fluorescent lamp (EEFL) as a light source, but may be replaced with a fluorescent lamp (CCFL) or a light emitting diode (LED).

The bottom cover 52 is formed to have a bottom surface and an inclined surface that extends in one direction of the bottom surface so as to provide a space to accommodate the lamps 112. In addition, the bottom cover 52 has a reflective sheet attached to the inner bottom surface and the side, and the support side 118 is located in the side region. That is, the support side 118 is fixed to both sides of the bottom cover 52 through a screw. The support side 118 is provided with a common electrode in which the external electrodes of the plurality of external electrode fluorescent lamps EEFL are electrically connected in common. AC driving power is supplied to the external electrode fluorescent lamps EEFL through the common electrode.

 The reflective member 126 is disposed between the bottom cover 52 and the lamps. The reflective members 126 are formed to have an elliptical cross section so as to surround lower and lower sides of the lamps 112 except for the upper parts of the lamps 112 facing the liquid crystal display panel 120. The lamps 112 face the reflective member 126 at intervals of 0 mm to 10 mm. In order to increase the reflection efficiency of the light and to quickly dissipate the heat of the lamps 112, the reflecting member 126 is made of a highly reflective metal or a metal having a high reflectance on the lamp facing surface of the reflecting member 126. It is preferred to be coated. For example, in order to manufacture the reflective member 126, the method of manufacturing the reflective member 126 according to the embodiment of the present invention molds the plastic into the shape of the reflective member 126, and oxidizes to the lamp facing surface of the plastic molded body Titanium can be coated.

The geometry of the reflective member 126 should be optimized so that the light incident from the lamps 126 in the reflective member 126 can be reflected at a wide angle. For this purpose, the curvature of the deepest bottom surface of the reflective member 126 facing the lower surface of the lamp 112 should be smaller than the curvature of the sides of the reflective member 126 opposite to the side of the lamp 112 as shown in 7b. do. In addition, the side ends of the reflective member 126 should be at an angle of about 5 ° to 30 ° with respect to a horizontal reference plane parallel to the horizontal bottom surface of the bottom cover 52 so that light can spread widely as shown in FIG. 7B. On the contrary, as shown in FIG. 7A, when the curvature of the lowest bottom surface of the reflecting member 126 is equal to or larger than the curvature of the sides of the reflecting member 126, the side end angle of the reflecting member 126 is greater than 30 °. The geometric angle narrows the diffusion angle of the light from the reflecting member 126. Therefore, the reflective member of the shape as shown in Figure 7a can further deepen the bright line.

By controlling the curvature of the bottom and side of the reflective member 126 to control the path of the light to remove the bright line between the lamp 112 and the lamp 112 to increase the light uniformity. In addition to the external electrode fluorescent lamps (EEFL, 112), the reflective member 126 has an advantage that it is easy to mount to a cold cathode fluorescent lamp (CCFL). In addition, the use of the reflective member 126 has the same brightness as that of a conventional lamp with a small number of lamps 112, so that the screen quality is not degraded and there is an advantage in that power consumption by using a small number of lamps 112 is reduced.

The diffusion plate 116 includes a plurality of beads and scatters light incident through the lamps 112 by using the beads, thereby displacing the lamps 112 on the display surface of the liquid crystal display panel 120. The luminance difference does not occur at the position of and the position between the lamps 112. Since the diffusion plate 116 is manufactured in a structure in which beads are dispersed in a medium having the same refractive index, light cannot be collected. The diffusion plate 116 is formed of a polymethylmethacrylate (PMMA) material or a glass for preventing deformation due to heat generated from the lamp 112.

The optical sheets 54 include one or more diffusion sheets and one or more prism sheets to uniformly irradiate the light incident from the diffusion plate 116 to the entire liquid crystal display panel 120 and to be perpendicular to the display surface. This function is to condense the light to the front of the display surface by folding the light path.

8A to 8C are diagrams showing experimental results using the reflective member as shown in FIG. 7A, and FIGS. 9A to 9C are diagrams showing experimental results using the reflective member as shown in FIG. 7B. 10 and 11 show the light quantity distribution as quantitative data as a result of the experiment using the reflective member as shown in FIG. 7B.

According to these experiments, in order to prevent the bright line from being visible in the direct backlight unit, the curvature of the portion of the reflective member 126 facing below the lamp 112 is opposite to the side of the lamp 112. Under conditions smaller than the curvature of the side portions of 126, the reflecting surface curvature of the reflecting member 126 should be determined between 0.2 and 0.9.

As described above, the backlight unit and the liquid crystal display device using the same according to the present invention are disposed under the lamp to reflect the member having a reflecting surface below the lamp and facing the side of the lamp to diffuse the light from the lamps at a wide angle It is possible to solve the problem of increase in power consumption due to the increase in the number of lamps because the brightness of the display is not only improved, but the desired brightness can be obtained with only a few lamps.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (6)

Multiple lamps; A reflective member facing the bottom and side surfaces of the lamps; And A cover member in which the lamps and the reflecting member are accommodated; And a curvature of a portion of the reflective member that faces below the lamp is smaller than a curvature of a portion of the reflective member that faces the side of the lamp. The method of claim 1, A curvature of the reflective member is between 0.2 and 0.9 under a condition that a curvature of a portion of the reflective member opposite the lamp is less than a curvature of another portion of the reflective member opposite the side of the lamp unit. The method of claim 1, The reflective member, A plastic molded body formed with a groove below the lamp and opposed to a side surface of the lamp; And And a metal film formed into a groove of the plastic molded body. The method of claim 1, And a distance between the reflective member and the lamp is between 0 mm and 10 mm. The method of claim 1, The end of the reflective member facing the side of the lamp is inclined at an angle of 5 to 30 degrees with respect to the horizontal reference plane parallel to the bottom surface of the cover member. A liquid crystal display panel; And A backlight unit irradiating light to the liquid crystal display panel using a plurality of lamps disposed under the liquid crystal display panel, a reflective member facing the bottom and side surfaces of the lamps, and a cover member in which the lamps and the reflective member are accommodated. Equipped with And a curvature of a portion of the reflective member that faces below the lamp is smaller than a curvature of a portion of the reflective member that faces the side of the lamp.

Images