KR20110093292A - Backlight unit and liquid crystal display device comprising the same - Google Patents

Abstract

PURPOSE: A backlight unit and liquid crystal display device including the same are provided to fix an optical sheet while not using a silicon pad and using characteristics that the optical sheet expands under a high temperature/high humid environment. CONSTITUTION: A backlight unit includes as follows. A light source. A light guiding plate(400) is arranged in parallel with the light source. An optical sheet(300) is arranged on the light guiding plate and has a 'C' shape. The optical sheet has a bending unit(350) and the bending unit covers a side surface of the light guiding plate.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE COMPRISING THE SAME}

The embodiment relates to a backlight unit, and more particularly, to a backlight unit capable of removing a central wave phenomenon of an optical sheet under a high temperature / humidity environment, and a liquid crystal display including the same.

Display devices used in a computer monitor or TV include organic light emitting displays (OLEDs), vacuum fluorescence displays (VFDs), and electroluminescent devices (VFDs). FED (Field Emission Display), Plasma Display Panel (PDP), etc. Liquid crystal display (LCD) that does not emit light by itself and requires a light source.

A general liquid crystal display device includes two substrates provided with a field generating electrode and a liquid crystal layer having dielectric anisotropy interposed therebetween. A voltage is applied to the field generating electrode to generate an electric field in the liquid crystal layer, and the voltage is changed to adjust the intensity of the electric field to adjust the transmittance of light passing through the liquid crystal layer to display a desired image.

Liquid crystal display devices have been used in various fields as well as notebook PC and monitor market due to small size, light weight and low power consumption.

Since the LCD does not emit light by itself, a separate light source such as a backlight is required. Accordingly, the liquid crystal display device includes a liquid crystal panel and a backlight unit. The backlight unit provides light to the liquid crystal panel, and the light passes through the liquid crystal panel. In this case, the liquid crystal panel displays an image by adjusting the transmittance of the light.

The backlight unit is classified into an edge type and a direct type according to the shape of the light source. In the edge type, the light source is disposed on the side of the liquid crystal panel. In addition, the light guide plate is disposed on the rear surface of the liquid crystal panel, and guides the light provided from the side surface of the liquid crystal panel to the rear surface of the liquid crystal panel. In contrast, the direct type has a plurality of light sources on the back of the liquid crystal panel, and the light emitted from the plurality of light sources is directly provided to the back of the liquid crystal panel.

As the light source, EL (Electro Luminescence), CCFL (Cold Cathode Fluorescent Lamp), HCFL (Hot Cathode Fluorescent Lamp), Light Emitting Diode (LED) and the like are used. Among them, the light emitting diodes (LEDs) have low power consumption and excellent light emitting efficiency.

Referring to FIG. 1, in the related art, a silicon pad 220 is used on the left and right sides of the panel guide 210 to fix the optical sheet 300 of the backlight unit. However, as the left and right sides of the optical sheet 300 are fixed to fix the optical sheet 300, waves are generated at the center of the optical sheet 300 in a high temperature / humid environment. That is, the optical sheet 300 expands in a high temperature / humid environment, and since the left and right sides are fixed, the optical sheet 300 does not expand from side to side and waves are generated in the center portion. As a result, staining occurs by pressing the panel 100 with a wave at the center of the optical sheet 300, or wrinkles occur in the optical sheet 300.

In order to solve the above problems, an embodiment uses a property of expanding an optical sheet under a high temperature / humidity environment, and a backlight unit capable of fixing the optical sheet without using a silicon pad and a liquid crystal display including the same. To provide.

In one embodiment, a backlight unit includes a light source; A light guide plate disposed in parallel with the light source; And disposed on the light guide plate, characterized in that it comprises an optical sheet having a '' 'shape.

In another embodiment, a liquid crystal display includes: a liquid crystal display panel; A panel guide supporting the liquid crystal display panel; A light guide plate disposed on a rear surface of the liquid crystal display panel; A light source disposed on a side of the light guide plate; And disposed between the light guide plate and the panel guide, characterized in that it comprises an optical sheet having a '' 'shape.

The embodiment provides a backlight unit including an optical sheet having a 'c' shape. That is, the optical sheet according to the embodiment is characterized in that the edge portion is bent (bending), the bent portion surrounds the side of the light guide plate.

Therefore, the optical sheet according to the embodiment is formed integrally with the light guide plate, so that when the light guide plate expands under a high temperature / humidity environment, the optical sheet also expands together, that is, the optical sheet expands to the left and right as well as the center portion of the optical sheet. As a result, wave does not occur. In addition, since the liquid crystal display panel is not pressed, the occurrence of unevenness can be prevented.

In addition, the manufacturing cost can be reduced by not using the silicon pad to fix the optical sheet according to the embodiment, and the assembly for fixing the optical sheet to the light guide plate by forming the bending part of the optical sheet by half cutting. It is easy to integrate with a light guide plate easily.

1 is a cross-sectional view showing a conventional liquid crystal display device for fixing an optical sheet using a silicon pad.
2 is an exploded perspective view illustrating a liquid crystal display device having a backlight unit according to an exemplary embodiment.
FIG. 3 is a cross-sectional view taken along line II ′ in FIG. 2.
FIG. 4 is a view illustrating a case where the light guide plate and the optical sheet are expanded in FIG. 3.

In the description of the embodiments, each panel, member, frame, sheet, plate, or substrate is formed on or under the "on" of each panel, member, frame, sheet, plate, or substrate, and the like. When described as being "in" and "under" includes both those that are formed "directly" or "indirectly" through other components. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

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

2 is an exploded perspective view illustrating a liquid crystal display device having a backlight unit according to an exemplary embodiment. FIG. 3 is a cross-sectional view taken along line II ′ in FIG. 2. FIG. 4 is a view illustrating a case where the light guide plate and the optical sheet are expanded in FIG. 3.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment includes a liquid crystal display panel 100 displaying an image and a backlight unit 200 disposed under the liquid crystal display panel 100 to provide light. . In addition, the liquid crystal display includes a panel guide 210 that supports the edge of the liquid crystal display panel 100 and is coupled to the backlight unit 200.

Although not shown in detail, the liquid crystal display panel 100 is bonded to a thin film transistor (TFT) substrate, a color filter substrate disposed on the thin film transistor substrate, and the two so as to maintain a uniform cell gap facing each other. It includes a liquid crystal layer interposed between the substrate.

A plurality of gate lines are formed in the thin film transistor substrate, a plurality of data lines in which the plurality of gate lines intersect are formed, and a thin film transistor TFT is formed in an intersection area of the gate line and the data line. The color filter substrate disposed on the thin film transistor substrate is a substrate in which R, G, and B color filters, which display color as light passes, are formed by a thin film process, and are commonly formed of ITO on the R, G, and B color filters. The electrode is deposited.

In addition, one end of the thin film transistor substrate includes an integrated circuit chip (IC CHIP). The integrated circuit chip generates an image signal, a scan signal, and a plurality of timing signals for applying the signals, and drives the image signal and the scan signal on the gate line and the data line of the liquid crystal display panel 100. To apply.

The backlight unit 200 is disposed on the rear surface of the liquid crystal display panel 100 to provide light. The backlight unit 200 is disposed on a light source 510, a light source housing 520 surrounding the light source 510, a light guide plate 400 disposed in parallel with the light source 510, and a lower surface of the light guide plate 400. It includes a reflective sheet 600.

In addition, the backlight unit 200 includes optical sheets 300 disposed on the light guide plate 400 to diffuse and collect light.

The light source 510 is disposed in parallel with the light guide plate 400. It may be a cold cathode fluorescent lamp (CCFL) having an electrode inside both ends of the glass tube, an external electrode fluorescent lamp (EEFL) having a structure surrounding both ends of the glass tube.

In addition, although the lamp is disposed on one side of the light guide plate 400 as the light source 510, the lamp is not limited thereto, and the lamp may be disposed on both sides of the light guide plate 400, and the light source 510 emits light in addition to the lamp. Diodes (LEDs) can be used.

The light source housing 520 increases the efficiency of the light emitted from the light source 510 and prevents the loss of light. In addition, the light source housing 520 protects the light source 510.

The light guide plate 400 may be made of polymethyl methacrylate (PMMA). In addition, although not shown in detail in the drawings, the light source 510 may be formed in a wedge shape that becomes thinner away from the incident surface disposed. A prism pattern may be formed on the rear surface of the light guide plate 400 to refracted incident light toward the optical sheets 300.

The light guide plate 400 converts linear or pointed light into surface light and guides the light incident from the light source 510 toward the liquid crystal display panel 100.

The reflective sheet 600 is disposed on the lower surface of the light guide plate 400. The reflective sheet 600 reflects the light emitted to the light guide plate 400 and the optical sheets 300 when the light incident on the light guide plate 400 is emitted to the rear surface of the light guide plate 400. . The reflective sheet 600 may be made of a material such as PET having high reflectance.

The optical sheets 300 include a diffusion sheet 310 for diffusing light, a light collecting sheet 320 for collecting light, and a protective sheet 330 for protecting the light collecting sheet 320. The diffusion sheet 310, the light collecting sheet 320, and the protective sheet 330 are sequentially disposed on the light guide plate 400.

The diffusion sheet 310 may have a structure that protrudes further from the other side of the light guide plate 400 facing the area where the light source 510 is disposed than the other side of the light guide plate 400. That is, the area of the bottom surface of the diffusion sheet 310 may be larger than the top surface of the light guide plate 400.

The light collecting sheet 320 and the protective sheet 330 overlap all of the regions with the diffusion sheet 310 and the light guide plate 400. Lower surface areas of the light collecting sheet 320 and the protective sheet 330 may be larger than the upper surface area of the light guide plate 400 or may be the same as the upper surface area of the diffusion sheet 310.

Referring to FIG. 3, the optical sheets 300 have a 'c' shape. The optical sheets 300 include a bending part 350, and the bending part 350 is formed at an edge portion of the optical sheet. The bending part 350 surrounds a part of the side surface of the light guide plate 400.

That is, the optical sheets 300 surround the light guide plate 400 in a '-' shape. When the 'c' shaped optical sheets 300 are disposed on the light guide plate, the bending part 350 of the optical sheets 300 is in contact with a part of the side surface of the light guide plate 400. Other surfaces except for the bending part 350 contact the upper surface of the light guide plate 400.

Therefore, referring to FIG. 4, the optical sheets 300 may freely expand under a high temperature / humid environment. That is, when the left and right are conventionally fixed, since the left and right sides are inflated to the center part, wave, wrinkles, etc. are generated, but the optical sheets 300 according to the embodiment are not fixed to the left and right sides. It can expand freely from side to side as well as the center.

As a result, the optical sheets 300 may expand left and right in a high temperature / humidity environment, and do not expand only to a specific portion, so that wave phenomenon and wrinkles do not occur in the center portion. In addition, since the liquid crystal display panel 100 is not pressed by this, it is possible to prevent the occurrence of unevenness in the liquid crystal display panel 100.

In addition, the optical sheets 300 expand together as the light guide plate 400 expands. That is, under the high temperature / high humidity environment, the light guide plate 400 and the optical sheets 300 are integrated to expand the optical sheets 300 together when the light guide plate 400 expands. Therefore, the wave phenomenon occurring at the center of the optical sheets 300 as described above can be removed.

The bending part 350 of the optical sheets 300 may be formed by half cutting. Therefore, it is easy to make the optical sheets 300 in the '' 'shape. That is, by forming the bending part 350 of the optical sheets 300 by half cutting, the assembly for fixing the optical sheets 300 to the light guide plate 400 may be easily performed, and thus, may be easily assembled with the light guide plate 400. It can be integrated.

In addition, the silicon pads disposed on the panel guide 210 may be removed to fix the optical sheets 300 as in the related art. That is, since the silicon pad is not used to fix the optical sheets 300 according to an embodiment, manufacturing cost and assembly time may be reduced.

In addition, since the silicon pad is not used as described above, the quality of the silicon pad may be improved by removing the defect due to the detachment of the silicon pad under high temperature / humidity.

The panel guide 210 supports an edge of the liquid crystal display panel 100 and is coupled to the backlight unit 200. The optical sheets 300 are disposed between the panel guide 210 and the light guide plate 400. The optical sheets 300 are in contact with the light guide plate 400, but are spaced apart from the panel guide 210. That is, in order to expand the light guide plate 400 and the optical sheets 300, a predetermined gap is formed between the panel guide 210 and the optical sheets 300.

As a result, since the light guide plate 400 and the optical sheets 300 expand in a high temperature / humid environment, a gap between the panel guide and the optical sheet should be formed according to the expansion degree.

In one embodiment, the gap between the panel guide and the optical sheet may be 0.1 mm to 0.2 mm, preferably 0.12 mm to 0.18 mm.

Although the above description has been made with reference to the embodiments, these are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains should not be exemplified above without departing from the essential characteristics of the present embodiments. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

Claims (8)

Light source;
A light guide plate disposed in parallel with the light source; And
The backlight unit is disposed on the light guide plate, and comprises an optical sheet having a 'c' shape. The method of claim 1,
And the optical sheet has a bending portion, and the bending portion surrounds a side surface of the light guide plate. The method of claim 2,
And a bending part of the optical sheet is formed by half cutting. The method of claim 1,
And the optical sheet expands as the light guide plate expands. A liquid crystal display panel;
A panel guide supporting the liquid crystal display panel;
A light guide plate disposed on a rear surface of the liquid crystal display panel;
A light source disposed on a side of the light guide plate; And
And an optical sheet disposed between the light guide plate and the panel guide and having an 'c' shape. The method of claim 5, wherein
And the optical sheet expands as the light guide plate expands. The method of claim 5, wherein
And the optical sheet has a bending portion, and the bending portion is formed by half cutting. The method of claim 5, wherein
And a gap between the panel guide and the optical sheet is 0.1 mm to 0.2 mm.

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