KR20110049550A - Backlight unit and liquid crystal display device using the same - Google Patents

Abstract

PURPOSE: A backlight unit and liquid crystal display device using the same are provided to prevent the deformation of an optical sheet and a reflective sheet and to increase the deformation of an optical sheet and a reflective sheet by efficiently using the light of LED light source. CONSTITUTION: A light source unit irradiates the light. One or more light guide plate(17) is separated from the light source unit and changes the light researched from the light source into the plane light source. A light reflective unit reflects the light which is incident from the light source unit. The light reflective unit is incident to the light incident plate of the light guide plate.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

The present invention relates to a backlight unit and a liquid crystal display using the same.

BACKGROUND ART Liquid crystal display devices have tended to be gradually widened due to their light weight, thinness, and low power consumption. The liquid crystal display device is used as a portable computer such as a notebook PC, office automation equipment, audio / video equipment, indoor and outdoor advertising display devices, and the like. The transmissive liquid crystal display device, which occupies most of the liquid crystal display device, displays an image by controlling an electric field applied to the liquid crystal layer to modulate the light incident from the backlight unit.

The backlight unit is roughly divided into a direct type and an edge type. The direct type backlight unit has a structure in which a plurality of light sources are arranged in a row on the lower surface of the diffuser plate so that light is directly directed to the front of the liquid crystal display. In contrast, the edge type backlight unit has a structure in which a light source is disposed to face the side of the light guide plate, and a plurality of optical sheets are disposed between the liquid crystal display panel and the light guide plate. In the edge type backlight unit, a light source irradiates light on one side of the light guide plate, and the light guide plate converts the linear light or the point light emitted from the light source into planar light, thereby advancing the light toward the front of the liquid crystal display.

Such an edge type backlight is installed at the bottom of the liquid crystal display panel to guide the bottom cover, a light source for supplying light from one side of the bottom cover, a light source housing for receiving and protecting the light source, and guide light from the light source to the liquid crystal display panel. A light guide plate, a reflection sheet for reflecting light reflected from the lower part of the light guide plate to the front surface of the light guide plate, an optical sheet stacked on the light guide plate to supply uniform light to the liquid crystal display panel, and a guide panel for supporting the liquid crystal display panel. do.

Conventionally, a cold cathode tube (CCFL) has been used as a light source of the backlight unit. However, in recent years, since it can be driven at a low voltage, the LED has low power consumption, excellent color reproducibility, contrast ratio, and long life. "Is in the spotlight."

However, in the edge type backlight, since the luminance specification is determined by the efficiency of light incident on the light incident part of the light guide plate, the incident efficiency of light incident on the light incident part of the light guide plate is very important.

In general, a backlight using LED as a light source is designed to have the same thickness of the light guide plate and the thickness of the LED in order to increase the efficiency of light incident on the light guide plate. When the LED is used as a light source, the LED is mounted on a printed circuit board, and the light source housing is provided to protect and maintain the printed circuit board on which the LED is mounted. The light source housing is formed to have a side wall facing the side wall of the bottom cover and a bottom wall facing the bottom wall of the bottom cover so that the LED does not flow. However, considering the size of the printed circuit board on which the LED is mounted, the height of the side wall of the light source housing may be thicker than the thickness of the light guide plate. As a result, spaces are formed in the upper and lower portions of the light guide plate. In general, a reflective sheet is attached to the lower part of the light guide plate, and light incident into the light guide plate along the light incident surface of the light guide plate is reflected by the reflective sheet toward the upper surface of the light guide plate, thereby suppressing the loss of light. On the other hand, since the light of the LED incident into the space between the lower part of the light guide plate and the light source housing is reflected by the reflection sheet attached to the lower part of the light guide plate, the light is not directed into the light guide plate and is lost. In addition, the light of the LED incident into the space between the upper part of the light guide plate and the guide panel is incident on the side surface of the optical sheet on the upper part of the light guide plate to reduce the uniformity of the light incident to the liquid crystal display panel. In addition, the light incident from the LED into the upper and lower spaces has a constant energy, and the optical sheet and the reflective sheet are vulnerable to heat, and thus, wrinkles are generated or deformed, thereby degrading the efficiency of the backlight.

An object of the present invention is to solve the problems of the prior art, by effectively using the light of the LED light source emitted into the space formed between the light guide plate and the light source housing and the space formed between the light guide plate upper surface and the guide panel. The present invention provides a backlight unit capable of increasing the efficiency of light incident on an optical surface and suppressing deformation of the reflective sheet and the optical sheet, and a liquid crystal display device using the same.

In order to achieve the above object, the backlight device of the present invention is a light source for irradiating light, at least one light guide plate for converting the light emitted from the light source spaced from the light source unit into a planar light source, formed between the light source and the light guide plate And at least one portion of the upper and lower portions of the space part to reflect the light incident from the light source part and to enter the incident surface of the light guide plate.

In the above configuration, the light source unit irradiates light to the light guide plate, at least one light source disposed to face the light incident surface of the light guide plate, a printed circuit board on which the light source is mounted, and the printed circuit board on which the light source is mounted. A light source housing for receiving.

The light source housing may include a side wall to which the printed circuit board is attached, a bottom wall bent from the side wall to extend toward the lower side of the light guide plate, and a support part supporting a lower end of the light guide plate by protruding upward from the bottom wall toward the light guide plate. And a first through hole formed in the bottom wall between the support part.

In addition, the backlight unit according to the embodiment of the present invention is disposed on the light guide plate and the optical sheet which is emitted from the light source unit to diffuse the light incident through the light incident surface of the light guide plate upward, and disposed below the light guide plate A reflection sheet for reflecting light toward the optical sheet toward the bottom of the light guide plate, a first bending portion, a second bending portion for preventing and supporting the flow of the light guide plate on the opposite side of the first bending portion, and the first bending portion; The cover bottom may further include a horizontal part connecting the second bending part and a second through hole formed in the horizontal part to correspond to the first through hole of the light source housing.

The light reflection part may include a first light reflection part that emits light emitted from the light source part and directed toward the light incident surface of the light guide plate to totally reflect the light toward the light incident surface of the light guide plate, and a light emitted to the light source part and directed downward to the light incident surface of the light guide plate. And a second light reflecting portion that totally reflects to the light incident surface of the light guide plate, wherein the second light reflecting portion extends downwardly from the body and the body contacting the bottom wall of the light source housing, and the first through hole and the cover of the light source housing. An extension part formed to pass through the second through hole of the bottom, and extending in the radial direction of the extension, and the engaging step formed to be coupled to the outside of the horizontal portion of the peripheral portion of the second through hole of the cover bottom.

In addition, the liquid crystal display device according to an embodiment of the present invention, a liquid crystal display panel for displaying an image, a light source unit for supplying light to the liquid crystal display panel, and the light emitted from the light source unit spaced apart from the light source unit is converted into flat light At least one light guide plate and a backlight having a light reflecting portion for totally reflecting the light incident from the light source portion to at least one portion of the upper and lower portions of the space formed between the light source portion and the light guide plate to enter the light incident surface of the light guide plate; It is characterized by.

In addition, the liquid crystal display device of the present invention is disposed on the light guide plate and an optical sheet which is emitted from the light source portion to diffuse the light incident through the light incident surface of the light guide plate upward, and disposed below the light guide plate A reflection sheet for reflecting light toward the bottom of the optical sheet toward the optical sheet, a side wall, and a bottom wall bent from a lower end of the side wall to extend in a horizontal direction, the liquid crystal display panel supporting the liquid crystal display panel; A guide panel for maintaining a constant distance between the optical sheet, a first bending part for supporting the guide panel, a second bending part for preventing and supporting the flow of the light guide plate on the opposite side of the first bending part; The cover bottom may further include a horizontal portion connecting the first bending portion and the second bending portion.

The present invention totally reflects the light incident from the light source portion to at least one portion of the upper and lower portions of the space portion formed between the light source portion and the light guide plate and enters the light incident portion of the light guide plate. Therefore, the effect of increasing the efficiency of light incident on the light incident part of the light guide plate and suppressing deformation of the reflective sheet and the optical sheet can be obtained.

Hereinafter, a backlight unit and a liquid crystal display using the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals denote like elements throughout the specification.

First, an edge type backlight according to an exemplary embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3. 1 is an exploded perspective view schematically illustrating a backlight unit according to an exemplary embodiment of the present invention, FIG. 2 is a cross-sectional view illustrating a state in which the backlight unit of FIG. 1 is assembled, and FIG. 3 is a portion A of the liquid crystal display of FIG. It is an expanded sectional drawing which shows typically how the light radiate | emitted from a light source part is used efficiently.

1 to 3, an edge type backlight unit according to an exemplary embodiment of the present invention is disposed under a light guide plate 17 and a light guide plate 17 that convert light emitted from the light source and the light source into planar light to be emitted to the front. The reflective sheet 19, the plurality of optical sheets 21 disposed on the light guide plate 17, the first reflecting part 27 and the first reflecting portions formed on the upper side and the lower side of the space formed between the light source unit and the light guide plate 16, respectively. 2 includes a reflector 31 and a cover bottom 23 coupled to the lower part of the light source unit.

The light source unit includes at least one LED light source 11 (hereinafter referred to as a light source), a light source housing 15 accommodating a printed circuit board 13 and a printed circuit board 13 on which the light source 11 is mounted. The LED 11 used as the light source may be formed of red, green, and blue light emitting diodes emitting red (R), green (G), and blue (B) light so as to face the light incident part of the light guide plate 17. Are arranged. The light source housing 15 includes a side wall 15a to which the printed circuit board 13 on which the light source 11 is mounted is attached, a bottom wall 15b that is bent from the side wall 15a and extends to the lower side of the light guide plate 17. A support portion 15c protruding upward from the bottom wall 15b toward the light guide plate 17 to support a lower end portion of the light guide plate 17 adjacent to the light source 11; and a bottom between the side wall 15a and the support portion 15c. And a through hole 15d formed in the wall 15b.

The light guide plate 17 is supported by the support part 15c and the cover bottom 23 of the light source housing 15. The light guide plate 17 functions to direct light incident from the light source 11 into the light incident part of the light guide plate 1 toward the upper direction of the light guide plate 17, that is, the screen direction. To this end, a diffusion pattern (not shown) is formed on the bottom of the light guide plate 17 to scatter light directed toward the bottom to face upward. That is, the light guide plate 17 converts the light incident from the light source 11 into uniform planar light and emits the light to the plurality of optical sheets 21 disposed on the light guide plate 16. As the light guide plate 17, a material having good refractive index and transmittance, for example, polymethylenemethacrylate (PMA), polycarbonate (PC: polycarbonate), polyethylene (PE: polyethylene), cycloolefin resin (COP) And the like, but are not limited to these materials.

The reflective sheet 19 is disposed under the light guide plate 17 and receives light that is incident from the light source 11 through the light incident part of the light guide plate 17 and proceeds downward of the light guide plate 17, that is, in the opposite direction to the screen. The efficiency of light is increased by reflecting the light guide plate 17 toward the front surface, that is, the screen direction.

The optical sheets 21 are disposed on the light guide plate 17, increase the uniformity of the light projected through the light guide plate 17, and increase the luminance by refracting and condensing the light.

The cover bottom 23 has a first bending portion 23a for supporting the guide panel 12 to be described later, and a second portion for preventing and supporting the flow of the light guide plate 17 on the opposite side of the first bending portion 23a. The horizontal portion 23b connecting the bending portion 23c, the first bending portion 23a and the second bending portion 23c, and the horizontal portion so as to correspond to the through hole 15d of the light source housing 15. The through hole 23c formed in the part 23b is provided.

The guide panel 25 includes a side wall 25a contacting the upper wall of the case top to be described later, and a bottom wall 25b that is bent from the lower end of the side wall 25a and extends in the horizontal direction. The guide panel 25 is a rectangular mold frame in which glass fibers are mixed in a synthetic resin such as polycarbonate (polycabonate). The guide panel 25 surrounds the upper edge and side surfaces of the liquid crystal display panel to be described later and surrounds the side surface of the backlight unit. The guide panel 25 supports the liquid crystal display panel and keeps the gap between the liquid crystal display panel and the optical sheets 21 constant.

The first reflecting portion 27 is attached to the guide panel 25 at a position between the light source housing 15 and the optical sheets 21. The first reflecting portion 27 includes a first total reflection film 29 attached to an upper surface thereof to totally reflect light from the light source 11.

The second reflecting portion 31 includes a body portion 31a positioned on the bottom wall 15b at a position between the side wall 15a of the light source housing 15 and the support portion 20c, and the body portion 31a of the body portion 31a. An extension portion 31b extending vertically from the lower surface and a latching jaw 31c extending radially from an end portion of the extension portion 31b are provided. In addition, the second reflecting portion 31 includes a second total reflection film 33 attached to the upper surface of the body portion 31a to totally reflect the light from the light source 11. The extension portion 21b of the second reflecting portion passes through the through hole 15d formed in the bottom wall 15b of the light source housing 15 and the through hole 23d formed in the horizontal portion 23b of the cover bottom 23. Is formed. The latching jaw 31c of the second reflecting portion 31 is configured to be coupled to the outside of the horizontal portion 23b of the periphery of the through hole 23d of the cover bottom 23 so that the second reflecting portion 31 is connected to the light source housing 20. ) And the cover bottom 23 to be firmly coupled.

According to the backlight unit according to the embodiment of the present invention, it is possible to obtain an effect that the utilization efficiency of the light incident on the light incident part of the light guide plate is considerably improved. Hereinafter, the light utilization efficiency will be described in detail with reference to FIG. 3.

3 is an enlarged cross-sectional view of portion A of the backlight unit according to the exemplary embodiment of the present invention shown in FIG. 2.

Referring to FIG. 3, light directed toward the front of the light incident part 17a of light emitted from the light source 11 facing the light incident part 17a of the light guide plate 17 is incident into the light guide plate 17 as it is. . However, the width of the light source housing 15 for accommodating the printed circuit board 13 on which the light source 11 is mounted and the printed circuit board 13 is larger than the thickness of the light guide plate 17 due to the working margin. Therefore, the light emitted from the upper end and the lower end of the light source 11 is directed to the space above and below the light guide plate 17. According to the backlight unit according to the exemplary embodiment of the present invention, since the light directed toward the upper and lower spaces of the light guide plate 17 is totally reflected by the first reflecting unit 2 and the second reflecting unit 31, the light of the light guide plate 17 is reflected. It enters into the incident part 17a and is recycled. In addition, since the light directed to the upper and lower spaces of the light guide plate 17 is recycled, thermal energy is not directly supplied to the optical sheet 21 on the light guide plate 17 and the reflective sheet 19 under the light guide plate 17. It is possible to prevent the phenomenon that deformation occurs in these sheets 17 and 19.

Next, the liquid crystal display device having the backlight unit according to the embodiment of the present invention described above will be described with reference to FIGS. 4 and 5.

4 is an exploded perspective view of a liquid crystal display device having a backlight unit according to an exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view of the liquid crystal display device of FIG. 4 assembled. For simplicity of description, members having the same function as each member shown in FIGS. 1 to 3 are given the same reference numerals and description thereof will be omitted.

4 and 5, the liquid crystal display device 100 includes a liquid crystal display panel 110, a backlight assembly 10, and a case top 120.

The liquid crystal display panel 110 serves to display an image, and may include an upper glass substrate, a lower glass substrate, and a liquid crystal layer formed between the substrates, and may be implemented in any liquid crystal mode.

The backlight unit 10 for supplying light to the liquid crystal display panel 110 is arranged under the liquid crystal display panel 110. Since the backlight unit 10 has been described in detail with reference to FIGS. 1 to 3, it will be omitted below.

The case top 120 is made of a metal material such as a galvanized steel sheet and has a structure that surrounds the side wall 25a of the guide panel 25. The case top 120 includes a hook or a screw on at least one of the guide panel 25 and the cover bottom 23. It is fixed to (not shown). The case top 120 accommodates the liquid crystal display panel 110 and the backlight unit 10 therein together with the cover bottom 23, and defines an effective display area of the liquid crystal display panel 110.

Modified Example

In the present exemplary embodiment, the first reflecting portion 27 is separately prepared and formed on the bottom wall 25b of the guide panel 25, but the first reflecting portion 27 is formed on the guide panel 25. It may be formed as a molding integral with the bottom wall 25b of the guide panel 25 so as to protrude from the bottom wall 25b. In addition, in the present exemplary embodiment, the first total reflection film 29 is formed on the upper surface of the first reflection part 27, but the entire first reflection part 27 may be formed of a total reflection material.

In addition, in the present exemplary embodiment, the second reflecting unit 31 is separately prepared and described in combination with the light source housing 15 and the cover bottom 23, but the second reflecting unit 31 and the light source housing 15 are described. It may be formed as a molding integral with the bottom wall 15b so as to protrude from the bottom wall 15b. In this case, the through hole 20d formed in the bottom wall 15b of the light source housing 15 and the through hole 23d formed in the horizontal portion 23b of the cover bottom 23 can be omitted. In addition, through fastening means such as a screw, the outside of the cover bottom 23 is formed in the through hole 23d formed in the horizontal portion 23b of the cover bottom 23 and the bottom wall 15b of the light source housing 15. The second reflector 31, the cover bottom 23, and the light source housing 15 may be coupled to each other through the formed through hole 20d. In addition, in the present exemplary embodiment, the second total reflection film 33 is formed on the upper surface of the second reflection part 31, but the entire second reflection part 31 may be formed of a total reflection material.

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.

1 is an exploded perspective view of a backlight unit according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the backlight unit of FIG. 1 assembled; FIG.

3 is a partially enlarged cross-sectional view of part A of the backlight unit shown in FIG. 2;

4 is an exploded perspective view of a liquid crystal display device having a backlight unit according to an exemplary embodiment of the present invention.

FIG. 5 is a cross-sectional view of the liquid crystal display of FIG. 4 assembled; FIG.

Description of the Related Art

10: backlight unit 21: optical sheet

15 light source housing 17 light guide plate

19: reflector 23: cover bottom

25: guide panel 27: first reflecting portion

29: first total reflection film 31: second reflecting portion

33: second total reflection film 100: liquid crystal display device

110: liquid crystal display panel 113: case top

Claims (9)

A light source unit for irradiating light; At least one light guide plate spaced apart from the light source unit and converting light emitted from the light source into a planar light source; And a light reflection part which totally reflects the light incident from the light source part and enters the light incident surface of the light guide plate in at least one portion of the upper and lower portions of the space formed between the light source part and the light guide plate. The method of claim 1, The light source unit, At least one light source irradiating light onto the light guide plate and disposed to face the light incident surface of the light guide plate; A printed circuit board on which the light source is mounted; And And a light source housing accommodating the printed circuit board on which the light source is mounted. The method of claim 2, The light source housing, Sidewalls to which the printed circuit board is attached; A bottom wall bent from the side wall and extending toward the lower side of the light guide plate; A support part protruding upward from the bottom wall toward the light guide plate to support a lower end of the light guide plate; And a first through hole formed in the bottom wall between the side wall and the support part. The method of claim 3, wherein An optical sheet disposed on an upper portion of the light guide plate and configured to diffuse light emitted from the light source unit upward through the light incident surface of the light guide plate; A reflection sheet disposed under the light guide plate and reflecting light directed toward the bottom surface of the light guide plate toward the optical sheet; And A first bending portion, a second bending portion for preventing and supporting the flow of the light guide plate on the opposite side of the first bending portion, a horizontal portion connecting the first bending portion and the second bending portion, and a first portion of the light source housing. 1. The backlight unit of claim 1, further comprising a cover bottom having a second through hole formed in the horizontal part to correspond to the through hole. The method of claim 1, The light reflection unit, A first light reflecting part which is emitted from the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate; And And a second light reflecting part which is emitted to the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate. The method of claim 4, wherein The light reflection unit, A first light reflecting part which is emitted from the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate; And A second light reflecting part which is emitted to the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate, The second light reflecting portion extends downwardly from the body and the body in contact with the bottom wall of the light source housing and extending through the first through hole of the light source housing and the second through hole of the cover bottom; And a latching jaw extending in the radial direction of the extension part and formed to be coupled to an outer side of the horizontal part of the periphery of the second through hole of the cover bottom. A liquid crystal display panel for displaying an image; A light source unit for supplying light to the liquid crystal display panel, at least one light guide plate spaced apart from the light source unit, and converting light emitted from the light source unit into planar light, and at least one upper and lower portions of a space part formed between the light source unit and the light guide plate And a backlight having a light reflecting portion for totally reflecting light incident from the light source portion to the light incident surface of the light guide plate. The method of claim 7, wherein The light reflection unit, A first light reflecting part which is emitted from the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate; And A second light reflecting part which is emitted to the light source part and totally reflects light directed toward the light incident surface of the light guide plate to the light incident surface of the light guide plate, The second light reflecting portion extends downwardly from the body and the body in contact with the bottom wall of the light source housing and extending through the first through hole of the light source housing and the second through hole of the cover bottom; And an engaging jaw extending in the radial direction of the extension part and formed to be coupled to an outer side of the horizontal part of the periphery of the second through hole of the cover bottom. The method of claim 8, An optical sheet disposed on an upper portion of the light guide plate and configured to diffuse light emitted from the light source unit upward through the light incident surface of the light guide plate; A reflection sheet disposed under the light guide plate and reflecting light directed toward the bottom surface of the light guide plate toward the optical sheet; A guide panel having a side wall and a bottom wall bent from a lower end of the side wall and extending in a horizontal direction, the guide panel supporting the liquid crystal display panel and maintaining a distance between the liquid crystal display panel and the optical sheet; A first bending part supporting the guide panel, a second bending part for preventing and supporting the flow of the light guide plate on the opposite side of the first bending part, and a horizontal part connecting the first bending part and the second bending part; A liquid crystal display further comprising a cover bottom.

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