KR20080048871A - Backlight unit and liquid crystal display device using thereof - Google Patents

Abstract

A backlight unit and a liquid crystal display device having the same are provided to arrange projection parts, which are projected from a reflector, along a longitudinal direction of lamps in order to reuse the light emitted from the lamps and to increase the brightness of the liquid crystal display device. A backlight unit comprises multiple lamps(160), a reflector(141), multiple optical sheets and projection parts(141'). The reflector, placed at the lower part of the lamps, reflects the light emitted from the lamps. The optical sheets, placed at the upper part of the lamps, diffuse and collect the light reflected from the reflector. The projection parts, projected to the reflector, reflect the light emitted from the lamps to the lower side to the areas among the lamps. The projection parts correspond to the numbers of the lamps. Two surfaces of the projection part have a predetermined rake(alpha) with regard to the reflector.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE USING THEREOF}

1 is an exploded perspective view schematically illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a cross-sectional view schematically showing the shape of the reflective sheet according to the first embodiment of the present invention.

3 is a cross-sectional view schematically showing the shape of a reflective sheet according to a second embodiment of the present invention.

** Explanation of symbols for main parts of drawings **

140: backlight unit 141, 241: reflective sheet

141 ', 241': protrusion 160,260: lamp

The present invention relates to a backlight unit and a liquid crystal display device having the same, and more particularly, a backlight unit for improving overall brightness by changing a shape of a reflective sheet to reuse light that has been absorbed and extinguished by a lamp, and the same. A liquid crystal display (LCD) is provided.

In today's information society, display is more important as a visual information transmission medium, and in order to gain a major position in the future, it is necessary to satisfy requirements such as low power consumption, thinness, light weight, and high definition.

The display itself emits light such as a cathode ray tube (CRT), an electroluminescent (EL), a light emitting diode (LED), a vacuum fluorescent display (VFD), a field emission display (FED), and a plasma display panel (PDP). And it can be divided into a non-emission type that does not emit light itself, such as a liquid crystal display.

Liquid crystal display is a device that expresses image by using optical anisotropy of liquid crystal. It is superior to CRT, and it is not only smaller than CRT of screen size with the same average power consumption. It is attracting attention as a next generation display device.

The liquid crystal used in the liquid crystal display device is not a light emitting material that emits light itself, but a light source that modulates the amount of light coming from the outside to display on the screen, so that a separate light source for irradiating light to the liquid crystal display panel In other words, it requires a backlight unit.

Hereinafter, the liquid crystal display device will be described in detail.

A liquid crystal display device includes a liquid crystal display panel which largely injects liquid crystal between an array substrate and a color filter substrate to output an image, and is installed on a rear side of the liquid crystal display panel to emit light over the entire surface of the liquid crystal display panel. The backlight unit may include a plurality of case parts for fixing and coupling the liquid crystal display panel and the backlight unit to each other.

The function of the backlight unit is to make plane light with uniform brightness from a lamp used as a light source, and the thickness and power consumption of the liquid crystal display device depend largely on how thin the thickness of the unit improves the light utilization efficiency. .

Such a backlight unit is classified into an edge type and a direct type according to the position of the light source with respect to the display surface. Among these, the direct type backlight unit is widely used in large liquid crystal display devices because of its high light utilization efficiency, simple handling, and no limitation on the size of the display surface.

The direct type backlight unit does not need a light guide plate for converting the linear light of the lamp into the surface light, and reflects a plurality of lamps provided on the lower side of the display surface and the light emitted from the lamp to the display surface to prevent light loss. Located at the top of the sheet and the lamp is made of a plurality of optical sheets and the like to scatter the light to emit a uniform light.

In general, the reflective sheet of the backlight unit is flat, so that the light emitted to the lower portion of the lamp is reflected by the reflective sheet and returned to be reabsorbed by the lamp and extinguished. As a result, the luminance is lower than the set luminance, and in order to compensate for this, there is a problem of adding a lamp or applying a higher power to the lamp.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a backlight unit and a liquid crystal display device having the same, which improves the brightness of the liquid crystal display device by reusing light that is absorbed and extinguished by a lamp.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

In order to achieve the above object, the backlight unit of the present invention comprises a plurality of lamps; A reflection sheet positioned below the lamp to reflect light emitted from the lamp; A plurality of optical sheets positioned on an upper portion of the lamp to diffuse and collect light reflected from the reflective sheet; And a protrusion formed in a shape protruding from the reflective sheet immediately below the lamp to reflect light emitted downward from the lamp into an area between the lamps.

In addition, the liquid crystal display device of the present invention; A plurality of lamps emitting light to the liquid crystal display panel; A reflection sheet positioned below the lamp to reflect light emitted from the lamp; A plurality of optical sheets positioned between the lamp and the liquid crystal display panel to diffuse and collect light reflected from the reflective sheet; A protrusion formed in a shape protruding from the reflective sheet directly below the lamp to reflect light emitted downward from the lamp into an area between the lamps; And a case part for fixing and supporting the backlight unit including the liquid crystal display panel, the lamp, the reflective sheet having the protrusion, and the optical sheet.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of a backlight unit and a liquid crystal display device having the same according to the present invention.

1 is an exploded perspective view schematically illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in the figure, the liquid crystal display device is a liquid crystal display panel 110 for outputting an image, a lamp installed on the rear of the liquid crystal display panel 110 to emit light over the entire surface of the liquid crystal display panel 110 ( A backlight unit 140 including a 160, and case parts such as a mold frame 153, an upper case 151, and a lower cover 152 that accommodate and fix the liquid crystal display panel 110 and the backlight unit 140. It consists of.

In this case, the backlight unit 140 according to the embodiment of the present invention is characterized in that the plurality of lamps 160 is configured in a direct type located below the liquid crystal display panel 110.

The backlight unit 140 is disposed at both ends of the mold frame 153 and is accommodated in the lamp supporter 165 and the lamp supporter 165 for receiving and supporting both ends of the lamp 160. At least one lamp 160 positioned below the light source, a reflection sheet 141 reflecting the light emitted from the lamp 160, and between the lamp 160 and the liquid crystal display panel 110. A plurality of optical sheets 143 for diffusing and condensing the light reflected by the reflective sheet 141.

The mold frame 153 may be formed of a plastic material, and may have a storage space having a predetermined depth on an upper surface thereof, and a stepped step may be continuously formed on the upper surface bent toward the storage space. The optical sheets 143 and the liquid crystal display panel 110 are sequentially received on the stepped portion formed on the upper surface of the mold frame 153.

In addition, the lamp supporter 165 positioned at both ends of the mold frame 153 includes a plurality of lamp receiving grooves that accommodate the lamp 160 to face each other at appropriate intervals.

The lamp 160 mainly uses a Cold Cathode Fluorescent Lamp (CCFL) that is small in size and capable of high luminance. At this time, CCFL phosphors mainly use high-efficiency volatiles (Y, Ce, Tb, etc.), and for liquid crystal display devices, a mixture of phosphors of R (Red), G (Green), and B (Blue) Three wavelength types of the system are used. The most prominent features of CCFL backlights are their low power consumption and very bright white light.

In addition, the lamp 160 may be generally used in the form of a straight tube, U tube, W tube, etc., the straight tube is preferable in terms of high brightness, high uniformity.

The LCD configured as described above emits light from the lamp 160 as power is supplied from an inverter (not shown). In this case, the reflective sheet 141 disposed below the lamp 160 reflects the light emitted from the lamp 160 toward the upper optical sheets 143 and guides the light toward the liquid crystal display panel 110. The image will be displayed.

At this time, the reflective sheet 141 according to the embodiment of the present invention, as shown, by changing the shape of the reflective sheet 141 so that the protrusion 141 ′ is located directly under the lamp 160 to reduce the luminance This can be prevented, which will be described in detail with reference to FIG. 3.

2 is a cross-sectional view schematically showing the shape of the reflective sheet according to the first embodiment of the present invention.

As shown in the drawing, the reflective sheet 141 according to the first embodiment reflects the light emitted from the lamp 160 to the upper liquid crystal display panel (not shown) in the lower portion of the lamp 160. Protruding portion 141 'is provided.

In this case, the protrusion 141 ′ is formed to have a number corresponding to the number of the lamps 160 directly below the lamp 160, and the light emitted below the lamps 160 (FIG. 3). And the arrow to the area B between the lamps 160. As a result, the light that has been reabsorbed and extinguished by the existing lamp can be reused through the protrusion 141 ', so that the brightness of the LCD can be improved.

In particular, large LCDs, like the current TV models, realize high brightness using a plurality of lamps. However, if the number and arrangement of reflective sheets or lamps are not optimized, the luminance decrease due to light leakage, heat generation, and the like is greatly increased. Accordingly, the present invention minimizes the loss of light by increasing the luminance by changing the shape of the reflective sheet so that the protrusions are positioned directly under each of the corresponding lamps while forming protrusions on the reflective sheets in the number corresponding to the number of lamps. You can do it.

Here, the protrusion 141 ′ of the reflective sheet 141 may have a shape in which a mountain having a predetermined inclination angle α with respect to a flat bottom surface is arranged along the longitudinal direction of the lamp 160. (α) may vary depending on various conditions such as the size of the lamp 160 and the protrusion 141 'and the relative spacing between the reflective sheet 141 and the lamp 160 and the liquid crystal display panel, but may be 80 ° to It can have an angle of about 150 °.

The reflective sheet 141 and the protrusion 141 ′ may be formed of the same material that reflects light well, or may be formed of different materials.

In addition, the protrusion 141 ′ of the reflective sheet 141 may be changed depending on the size of the liquid crystal display panel and the lamp 160, but is about 2 mm to 20 mm high from the flat bottom surface of the reflective sheet 141. Can be formed.

At this time, the protrusion 141 ′ of the reflective sheet 141 of the first embodiment is formed so that its cross section has a triangular shape, so that two opposite surfaces form a side of the triangle, that is, a straight line. However, the present invention is not limited thereto, and two surfaces facing each of the protrusions may form a curve having a predetermined curvature, which will be described in detail with reference to the following second embodiment.

3 is a cross-sectional view schematically showing the shape of the reflective sheet according to the second embodiment of the present invention.

As shown in the figure, the reflective sheet 241 according to the second embodiment reflects the light emitted from the lamp 260 to a liquid crystal display panel (not shown) in the upper portion of the lamp 260 immediately below. Protruding portion 241 'is provided.

In this case, the protrusion 241 ′ is formed at a number corresponding to the number of the lamps 260 immediately below the lamp 260, and the protrusion 241 ′ of the second embodiment is particularly described above. Unlike the case of the first embodiment, it is characterized in that the two faces facing each other form a curve having a predetermined curvature.

The protrusion 241 ′ formed as described above may have a shape arranged along the longitudinal direction of the lamp 260.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

As described above, the backlight unit and the liquid crystal display having the same according to the present invention can obtain the effect of improving the brightness of the liquid crystal display by reusing the light that has been absorbed and extinguished by the existing lamp.

Claims (18)

Multiple lamps; A reflection sheet positioned below the lamp to reflect light emitted from the lamp; A plurality of optical sheets positioned on an upper portion of the lamp to diffuse and collect light reflected from the reflective sheet; And And a protrusion formed in a shape protruding from the reflective sheet directly below the lamp to reflect light emitted downward from the lamp into an area between the lamps. The backlight unit of claim 1, wherein the protrusion is formed in a number corresponding to the number of the lamps. The backlight unit of claim 1, wherein the protrusion has a shape arranged along a length direction of the lamp. The backlight unit of claim 1, wherein the two protruding portions each have a predetermined inclination angle with respect to the reflective sheet. The backlight unit of claim 4, wherein an inclination angle of the protrusion is 80 ° to 150 °. The backlight unit of claim 1, wherein the protrusion has a height of about 2 mm to about 20 mm. The backlight unit of claim 1, wherein the protruding portion is formed so that its cross section has a triangular shape, and two opposite surfaces form sides of the triangular surface. The backlight unit of claim 1, wherein each of the protrusions has a curved surface having two curvatures facing each other. A liquid crystal display panel; A plurality of lamps emitting light to the liquid crystal display panel; A reflection sheet positioned below the lamp to reflect light emitted from the lamp; A plurality of optical sheets positioned between the lamp and the liquid crystal display panel to diffuse and collect light reflected from the reflective sheet; A protrusion formed in a shape protruding from the reflective sheet directly below the lamp to reflect light emitted downward from the lamp into an area between the lamps; And And a case part for fixing and supporting the backlight unit including the liquid crystal display panel, a lamp, a reflective sheet having a protrusion, and an optical sheet. The liquid crystal display of claim 9, wherein the protrusion is formed in a number corresponding to the number of the lamps. 10. The liquid crystal display device according to claim 9, wherein the protrusions are arranged along the longitudinal direction of the lamp. 10. The liquid crystal display device according to claim 9, wherein the two protruding portions each have a predetermined inclination angle with respect to the reflective sheet. The liquid crystal display device according to claim 12, wherein an inclination angle of the protrusion is 80 ° to 150 °. The liquid crystal display of claim 9, wherein the reflective sheet and the protrusion are made of the same material. The liquid crystal display of claim 9, wherein the reflective sheet and the protrusion are made of different materials. The liquid crystal display of claim 9, wherein the protrusion has a height of about 2 mm to about 20 mm. 10. The liquid crystal display device according to claim 9, wherein the protruding portion is formed such that its cross section has a triangular shape, and two opposite sides form a side of the triangle. 10. The liquid crystal display device according to claim 9, wherein each of the protrusions has a curved surface with two curvatures facing each other.

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