KR20070088117A - Backlight unit and liquid crystal display using the same - Google Patents

Abstract

A backlight unit and an LCD(Liquid Crystal Display) using the same are provided to achieve the improved optical efficiency even though a lamp cover is removed by extending and bending a first reflecting plate disposed under a light guide plate to lower and side surfaces of a lamp and disposing a second reflecting plate so as to cover a portion of an upper side of the light guide plate and upper and side surfaces of the lamp. A light guide plate(260) converts a light incident from a light source into a planar light source. A first reflecting plate(220) is disposed under the light guide plate. One end of the first reflecting plate is bent and extends in a direction parallel to a light entrance surface of the light guide plate so as to surround the light source disposed at the light entrance surface of the light guide plate. A second reflecting plate(230) is disposed in a portion of the light guide plate and over the light source. One end of the second reflecting plate is bent and extends in a direction parallel to a light entrance surface of the light guide plate so as to surround the light source disposed at the light entrance surface of the light guide plate.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY USING THE SAME}

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

FIG. 2 is a sectional view of a section taken at line A-A in FIG. 1; FIG.

3 is a schematic perspective view of a backlight unit according to a second embodiment of the present invention;

4 is a cross-sectional view showing a section taken at the line B-B in FIG.

5 is a schematic exploded perspective view of a liquid crystal display device using the backlight unit according to the present invention.

<Explanation of symbols for main parts of the drawings>

200: lower chassis 220a: first reflective surface

220b: second reflective surface 220: first reflective plate

230a: third reflective surface 230b: fourth reflective surface

230: second reflector 240: lamp

260: light guide plate 280: diffuser plate

300: prism sheet

The present invention relates to a backlight unit and a liquid crystal display device having the same, and more particularly, to a backlight unit having a lamp cover removed and a liquid crystal display device having the same.

In general, the liquid crystal display (LCD) is expanding its application range due to features such as lightweight, thin, low-power drive, full-color, high-resolution implementation. Currently, liquid crystal displays are used in computers, notebooks, PDAs, telephones, TVs, and audio / video devices. In such a liquid crystal display device, a light transmittance is adjusted according to an image signal applied to a plurality of control switches arranged in a matrix to display a desired image on a panel of the liquid crystal display device.

Such a liquid crystal display device displays a desired image on a screen by adjusting the amount of light transmitted according to image signals applied to a plurality of control switches arranged in a matrix form, and operates an LCD panel that directly displays an image. LCD driver IC, a backlight unit used as a light source of the liquid crystal display device, and a chassis for fastening each component of the liquid crystal display device into one unit, wherein the backlight unit is disposed on one side of the plane of the panel to form a front surface of the panel. It is divided into a direct method of dimming the light source and an edge method of reflecting and diffusing light to a light guide plate and a reflecting plate by disposing a light source on one side or a plurality of side surfaces of the panel.

Conventional liquid crystal display devices using the edge method of the direct method and the edge method include, for example, a lamp provided on the side of the light guide plate and a lamp cover surrounding the lamp. The lamp cover transmits the light emitted from the lamp to the light guide plate as efficiently as possible, protects the lamp, makes the temperature of the lamp uniform, and at the same time prevents a problem of inconsistency caused by the light guide plate. However, even with the above advantages, the lamp cover is a factor of the cost increase. Therefore, the present applicant intends to reduce the cost by removing the lamp cover.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a backlight unit having improved light efficiency even when the lamp cover is removed.

Another object of the present invention is to provide a backlight unit having a reliable optical sheet mounting structure.

In order to achieve the above object, the present invention provides a light source, a light guide plate for converting light incident from the light source into a surface light source, and a lower portion of the light guide plate, and one end of the light guide plate to surround the light source provided on the incident surface of the light guide plate. It provides a backlight unit comprising a first reflecting plate which is bent and extended parallel to the incident surface of the light guide plate.

In this case, the second reflector may be disposed on a portion of the light guide plate and an upper part of the light source, and the second reflector may be bent in parallel with the incident surface of the light guide plate so as to surround the light source installed on the incident surface of the light guide plate. .

The light source may further include a lower chassis for accommodating the light source, the light guide plate, and the first and second reflector plates, wherein the first reflector may include a first reflecting surface provided under the light guide plate, And a second reflecting surface formed in parallel with the incident surface, wherein the second reflecting plate A third reflecting surface provided on a portion of the light guide plate and the light source, and a fourth reflecting surface formed on the third reflecting surface in parallel with the incident surface of the light guide plate, wherein the fourth reflecting surface is the second half. It may be provided between the slope and the lower chassis.

In this case, the light guide plate may further include a diffusion plate and a prism sheet provided on the light guide plate, and the prism sheet may overlap at least a portion on the third reflective surface.

The light guide plate may include at least one light source, a light guide plate for converting light incident from the light source into a surface light source, and a light guide plate disposed below the light guide plate, and one end of the light guide plate to surround the light source provided on the incident surface of the light guide plate. It provides a liquid crystal display device comprising a backlight unit including a first reflecting plate bent to extend parallel to the incident surface of the light emitting device, and a liquid crystal display panel for displaying an image using the light supplied from the backlight unit .

In this case, the second reflector may be disposed on a portion of the light guide plate and an upper part of the light source, and the second reflector may be bent in parallel with the incident surface of the light guide plate so as to surround the light source installed on the incident surface of the light guide plate. .

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

However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art to fully understand the scope of the invention. It is provided to inform you. Like reference numerals in the drawings refer to like elements.

1 is an exploded perspective view of a backlight unit according to a first embodiment of the present invention, Figure 2 is a cross-sectional view showing a cross section taken on line A-A of FIG.

As shown in FIG. 1 and FIG. 2, the backlight unit according to the first exemplary embodiment of the present invention includes a light guide plate 260, a lamp 240 disposed at a side of the light guide plate 260, and generates light. 260 and a first reflector 220 provided below the lamp 240 and extending to the side of the lamp 240. In this case, the diffusion plate 280 and the prism sheet 300 may be further included on the light guide plate 260, and the light guide plate 260, the lamp 240, the first reflecting plate 220, and the diffusion plate ( 280 and the lower chassis 200 for accommodating the prism sheet 300 may be further included.

The light guide plate 260 converts a line light source from the lamp 240 into a surface light source, and is made of a transparent material having a constant refractive index, such as polyolefin or polycarbonate, which is a polymethymethacrylate (PMMA), which is an acrylic resin. . At this time, the light emitted from the lamp 240 is incident to the side of the light guide plate 260 is emitted to the top.

Meanwhile, the light guide plate 260 as described above includes at least one of a molded light guide plate, a light scattering light guide plate, and a hollow light guide plate. The molded light guide plate is a method of applying a fine concavo-convex dot pattern on the light guide itself instead of printing the scattering material on the back surface of the light guide acrylic resin, and thus a printing process is unnecessary. In addition, the back surface of the light guide is simultaneously molded into a pattern like a prism sheet, and excellent in front luminance characteristics. The light scattering light guide plate requires an angle correction prism for correcting the light propagation direction in the front direction by distributing the light scattering polymer in the light guide instead of the scattering printed dot pattern on the back surface of the light guide acrylic resin. The hollow light guide plate empties the center of the light guide, diffuses light from a light source, traps the light in a space, and emits the light through a diffusion sheet, thereby enabling a large screen and a high brightness wide viewing angle.

The lamp 240 may be installed at a side of the light guide plate 260 and may be supported by a lamp supporter (not shown). The lamp 240 includes a light source such as an electroluminescent lamp (EL), a light emitting diode (LED), and a cold cathode fluorescent lamp (CCFL). Use a lamp. However, the present invention is not limited thereto, and any light source may be used without departing from the object of the present invention.

The cold cathode fluorescent lamp includes a glass tube, inert gases contained in the glass tube, and a negative electrode and a positive electrode provided at both ends of the glass tube. At this time, a phosphor is coated on the inner wall of the glass tube, and light is generated by a driving voltage applied from the outside.

The diffusion plate 280 directs the light incident from the lamp 240 toward the front of the liquid crystal display panel (not shown), and diffuses the light to have a uniform distribution in a wide range so as to irradiate the liquid crystal display panel. As the diffusion plate 280, it is preferable to use a film made of a transparent resin coated with a predetermined light diffusion member on both surfaces.

The prism sheet 300 serves to change the light incident at an oblique angle among the light incident to the prism sheet 300 to be emitted vertically. This is because the light efficiency increases when the light incident on the liquid crystal display panel is perpendicular to the liquid crystal display panel. Therefore, at least one prism sheet 300 may be disposed between the diffuser plate 280 and the liquid crystal display panel to vertically convert the light emitted from the diffuser plate 280.

The lower chassis 200 surrounds and protects the side and bottom surfaces of the lamp 240 unit and the light guide plate 260. The lower chassis 200 is formed in a box shape of a rectangular parallelepiped with an open upper surface, so that a storage space having a predetermined depth is formed therein. Is formed.

The first reflecting plate 220 is to increase the light utilization efficiency by reflecting the light incident from the lamp 240 as a light source to the light emitting surface of the backlight, by adjusting the amount of reflection of the entire incident light, the entire light emitting surface of the backlight is uniform Have a luminance distribution.

The first reflecting plate 220 surrounds the light guide plate 260 and the first reflecting surface 220a provided under the lamp 240 and the lamp 240 disposed on the side surface of the light guide plate 260. The second reflective surface 220b extends from the first reflective surface 220a in the same direction as the lateral direction of 260. That is, the first reflecting plate 220 is bent in a '' '' shape. In the present invention, the lamp cover of the conventional backlight unit is not used, and a part of the first reflecting surface 220a and the second reflecting surface 220b of the first reflecting plate 220 replace the lamp cover.

As the first reflecting plate 220, a plate having a high light reflectivity is used, which is installed to contact the bottom surface of the lower chassis 200. Although the first reflecting plate 220 is illustrated as having a flat shape in the drawing, the first reflecting plate 220 may be manufactured in a curved shape having a reference reflecting surface and a triangular protrusion protruding from the reference reflecting surface. When the lamp 240 is formed at both side surfaces of the light guide plate 260, the first reflector 220 as described above may be installed at the other side surface of the light guide plate 260.

As described above, according to the present invention in which the first reflecting plate 220 including the second reflecting surface 220b is extended and bent, the first reflecting surface 220a serves as a conventional lamp cover. 220 is done. Accordingly, the lamp 240 may be protected from impact as in the conventional lamp cover, and the light emitted from the lamp 240 may be transmitted to the light guide plate 260 as efficiently as possible. In addition, the high temperature portion of the lamp 240, that is, the heat of the lamp electrode to the low temperature portion can be solved a lot of defects caused by the heat emission is not solved, it is possible to solve the bright line which is a chronic problem caused by using the light guide plate 260. . Furthermore, the present invention does not use a lamp cover, and thus extends the first reflecting plate 220 to replace the lamp cover, thereby reducing the cost.

Next, a backlight unit according to a second embodiment of the present invention will be described. The description overlapping with the above-described first embodiment will be omitted.

3 is a schematic perspective view of a backlight unit according to a second exemplary embodiment of the present invention, and FIG. 4 is a cross-sectional view illustrating a cross section taken along line B-B of FIG. 3.

As shown in FIGS. 3 and 4, the backlight unit according to the second exemplary embodiment of the present invention includes a light guide plate 260, a lamp 240 installed at a side surface of the light guide plate 260 to generate light, and the light guide plate. 260 and a first reflecting plate 220 provided below the lamp 240 and bent to extend to a side surface of the lamp 240, and a second half of the upper portion of the lamp 240 and the first reflecting plate 220. The second reflector 230 covers the slope 220b. In this case, the diffusion plate 280 and the prism sheet 300 may be further included on the light guide plate 260, and the light guide plate 260, the lamp 240, and the first and second reflector plates 220 and 230 may be further included. The lower chassis 200 may further include a diffusion plate 280 and a prism sheet 300.

As shown in FIGS. 3 and 4, the first reflecting plate 220 is disposed on the first reflecting surface 220a provided under the light guide plate 260 and the lamp 240 and on the side surface of the light guide plate 260. The second reflecting surface 220b extends from the first reflecting surface 220a in the same direction as the side direction of the light guide plate 260 to surround the lamp 240. In this case, the second reflector 230 is also composed of the third and fourth reflecting surfaces 230a and 230b, similarly to the first reflecting plate 220, and the third reflecting surface 230a is an upper portion of the lamp 240. The fourth reflecting surface 230b is disposed in the third reflecting surface 230a in the same direction as that of the side surface of the light guide plate 260 so as to surround the lamp 240 disposed on the side of the light guide plate 260. Extends from. In addition, the third reflecting surface 230a of the second reflecting plate 230 covers an upper portion of the lamp 240 and a portion of the upper portion of the light guide plate 260. That is, the second reflecting plate 230 is manufactured in a "b" shape to sandwich the fourth reflecting surface 230b between the side wall of the lower chassis 200 and the second reflecting surface 220b of the first reflecting plate 220. A third reflective surface 230a is mounted on the lamp 240 and the light guide plate 260. However, the present invention is not limited thereto, and the fourth reflecting surface 230b of the second reflecting plate 230 may be provided between the second reflecting surface 220b of the first reflecting plate 220 and the lamp 240.

Meanwhile, the backlight unit according to the second embodiment of the present invention overlaps the optical sheet such as the prism sheet 300 on the third reflective surface 230a mounted on the light guide plate 260. In this case, the diffusion plate 280 preferably does not overlap on the third reflection surface 230a of the second reflection plate 230 to compensate for the height difference due to the thickness of the second reflection plate 230. In addition, the second reflector 230 is preferably the same thickness as the diffusion plate 280 to match the thickness of the diffusion plate 280.

The second reflector 230 may be made of the same material as the first reflector 220, but is not limited thereto. That is, a white pad may be used.

As described above, the backlight unit according to the second embodiment of the present invention using the first and second reflecting plates 220 and 230 solves reliability by securing a stable length of the optical sheet even in a product having a short structure to overlap the optical sheet. In addition, since the optical sheet has an extended effect than the existing length, it is possible to prevent the optical sheet from falling out. Furthermore, in the conventional art, the optical sheet is inevitably opened even if it is disadvantageous in light leakage, foreign matter, etc. in a product having a short structure to overlap the optical sheet. However, in the second embodiment of the present invention, this problem is caused by using the second reflecting plate 230. Solved.

Next, a liquid crystal display using the backlight unit according to the present invention will be described. The liquid crystal display device according to the present invention described below will be mainly described with a configuration different from the above-described backlight unit, and descriptions overlapping with the above-described backlight unit will be omitted.

5 is a schematic exploded perspective view of a liquid crystal display using the backlight unit according to the present invention.

Referring to FIG. 5, a liquid crystal display according to the present invention includes a liquid crystal display panel 2200, a backlight unit including a light guide plate 260, a mold frame 2000 for accommodating the backlight unit, and a liquid crystal display panel. 2200 and an upper chassis 2400 for wrapping a predetermined area and a side of the upper portion of the backlight unit.

In the above, the liquid crystal display panel 2200 may include a thin film transistor substrate 2220, a data side and gate side tape carrier package (TCP) 2260a and 2280a connected to the thin film transistor substrate 2220, and data. Data side and gate side printed circuit boards 2260b and 2280b connected to the side and gate side tape carrier packages 2260a and 2280a, respectively, a color filter substrate 2240 corresponding to the thin film transistor substrate 2220, and a thin film transistor. And a liquid crystal layer (not shown) injected between the substrate 2220 and the color filter substrate 2240. In addition, the display device may further include a polarizer (not shown) formed to correspond to the upper portion of the color filter substrate 2240 and the lower portion of the thin film transistor substrate 2220, respectively.

The color filter substrate 2240 is a substrate in which RGB pixels, which are color pixels in which a predetermined color is expressed while light passes, are formed by a thin film process. A common electrode (not shown) made of a transparent conductor such as indium tin oxide (ITO) or indium zinc oxide (IZO), which is a transparent conductive thin film, is formed on the front surface of the color filter substrate 2240. It is.

The thin film transistor substrate 2220 is a transparent glass substrate in which thin film transistors (TFTs) and pixel electrodes are formed in a matrix form. The data line is connected to the source terminal of the thin film transistors, and the gate line is connected to the gate terminal. Also, a pixel electrode (not shown) made of a transparent electrode made of a transparent conductive material is connected to the drain terminal. When an electrical signal is input to the data line and the gate line, each thin film transistor is turned on or turned off to apply an electrical signal necessary for pixel formation to a drain terminal.

That is, as described above, when power is applied to the gate terminal and the source terminal of the thin film transistor substrate 2220 and the thin film transistor is turned on, an electric field is formed between the pixel electrode and the cavity electrode of the color filter substrate 2240. Due to this electric field, the arrangement of the liquid crystal injected between the thin film transistor substrate 2220 and the color filter substrate 2240 is changed, and the light transmittance is changed according to the changed arrangement to obtain a desired image.

The data side and gate side tape carrier packages 2260a and 2280a are respectively connected to data lines and gate lines of the thin film transistor substrate 2220 to apply a data driving signal and a gate driving signal to the thin film transistor. In this case, an integrated circuit (IC) may be mounted in the data side and gate side tape carrier packages 2260a and 2280a. The data side and gate side printed circuit boards 2260b and 2280b are connected to the data side and gate side tape carrier packages 2260a and 2280a to apply external image signals and gate driving signals.

The backlight unit is provided on the light guide plate 260, a side surface of the light guide plate 260, and generates a light 240, and is provided below the light guide plate 260 and the lamp unit 240. A first reflecting plate 220 bent and extended to a side of the second reflecting plate 220, a second reflecting plate 230 covering the upper portion of the lamp 240 and the second reflecting surface 220b of the first reflecting plate 220, and the light guide plate ( The diffusion plate 280 and the prism sheet 300 disposed above the 260, the first and second reflection plates 220 and 230, the lamp 240, the diffusion plate 280, and the prism sheet 300 are disposed. A lower chassis 200 for receiving and a lamp driving circuit (not shown) for driving the lamp 240. The lamp 240 driving circuit includes a plurality of driving voltage generators (not shown) which are disposed on the rear surface of the lower chassis 200 to generate driving voltages. Here, the driving voltage generation unit includes at least one inverter for boosting the low voltage AC voltage applied from the outside to the high voltage AC voltage for driving the lamp 240. The driving voltage generator and the lamp 240 are electrically connected by wires.

The mold frame 2000 is formed in a rectangular frame shape and includes a planar portion and sidewall portions bent at right angles therefrom. A mounting portion (not shown) may be formed on the flat portion to allow the liquid crystal display panel 2200 to be mounted thereon. The seating part may use a fixing protrusion for contacting and aligning the edge side surfaces of the liquid crystal display panel 2200, respectively, or may be formed using a predetermined stepped step surface. In the mold frame 2000, a prism sheet 300, a diffusion plate 280, a light guide plate 260, a lamp unit 240, and first and second reflecting plates 220 and 230 are positioned between the lower chassis 200. It is fixed.

The upper chassis 2400 is configured in the form of a rectangular window frame having a flat portion and sidewall portions bent at right angles therefrom. The planar portion of the upper chassis 2400 supports a portion of an edge of the liquid crystal display panel 2200 at a lower portion thereof, and the sidewall portion is coupled to face the sidewalls of the lower chassis 200. The upper chassis 2400 and the lower chassis 200 are preferably made of metal having excellent strength, light weight, and low deformation.

Although described above with reference to the drawings and embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit of the invention described in the claims below. I can understand.

As described above, the present invention extends and bends the first reflector provided in the lower part of the light guide plate to the lower part and the side of the lamp, and removes the lamp cover by installing a part of the upper part of the light guide plate and a second reflector covering the upper part and the side part of the lamp. A backlight unit and a liquid crystal display device having improved light efficiency can be provided.

In addition, the present invention can provide a backlight unit and a liquid crystal display device having a reliable optical sheet mounting structure in which an optical sheet does not fall by providing a second reflecting plate covering a portion of the light guide plate as described above.

Claims (6)

Light source, A light guide plate for converting light incident from the light source into a surface light source; And a first reflecting plate disposed under the light guide plate, the first reflecting plate having one end bent in parallel with the incidence surface of the light guide plate so as to surround a light source installed on the light incident surface of the light guide plate. The method according to claim 1, A second reflecting plate disposed on a portion of the light guide plate and an upper portion of the light source, the second reflecting plate having one end bent in parallel with the incidence surface of the light guide plate so as to surround the light source installed on the incidence surface of the light guide plate; Backlight unit. The method according to claim 2, Further comprising a lower chassis for receiving the light source, the light guide plate and the first and second reflecting plate, The first reflecting plate includes a first reflecting surface provided under the light guide plate, and a second reflecting surface formed parallel to the incident surface of the light guide plate at the first reflecting surface. The second reflector is A third reflective surface provided on a portion of the light guide plate and the light source, and a fourth reflective surface formed parallel to the incident surface of the light guide plate at the third reflective surface, And the fourth reflecting surface is provided between the second reflecting surface and the lower chassis. The method according to claim 3, Further comprising a diffusion plate and a prism sheet provided on the light guide plate, And the prism sheet overlaps at least a portion of the third reflective surface. At least one light source, a light guide plate for converting the light incident from the light source into a surface light source, and disposed at a lower portion of the light guide plate, one end of which is parallel to the incident surface of the light guide plate so as to surround the light source provided at the incident surface of the light guide plate; A backlight unit including a first reflecting plate which is bent to extend; And a liquid crystal display panel which displays an image by using light supplied from the backlight unit. The method according to claim 5, A second reflecting plate disposed on a portion of the light guide plate and an upper portion of the light source, the second reflecting plate having one end bent in parallel with the incidence surface of the light guide plate so as to surround the light source installed on the incidence surface of the light guide plate; Liquid crystal display.

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