KR20150027974A - Backlight unit and method for manufacturing of the same, liquid crystal display device comprising the same - Google Patents

Abstract

A backlight unit according to an embodiment of the present invention includes a light guide plate which guides light, a first light source part located on one side of the light guide plate and a second light source part located on the other side of the light guide plate, and a reflection plate which is located on the lower part of the light guide plate and reflects light. The light guide plate ha a plate shape and includes a protrusion part corresponding to the second light source part.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY DEVICE COMPRISING THE SAME Technical Field The present invention relates to a backlight unit,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide plate, and more particularly, to a backlight unit capable of reducing color difference and manufacturing cost, a manufacturing method thereof, and a liquid crystal display including the same.

BACKGROUND ART [0002] Liquid crystal display devices (LCDs) are widely used because of advantages such as low power driving, thin structure, and excellent image quality. In such a liquid crystal display device, a liquid crystal panel comprising two substrates facing each other and liquid crystal interposed therebetween is used. The liquid crystal panel displays an image by changing the arrangement of the liquid crystal by the electric field generated between the liquid crystal panels.

Such a liquid crystal panel requires a light supply device such as a backlight unit (BLU) in order to display an image as a non-light emitting type display panel. In general, a liquid crystal display device includes a liquid crystal panel and a backlight unit ). Such a backlight unit is divided into an edge type BLU and a bottom type BLU according to the position of a light source. Further, the backlight unit (BLU) includes a light guide plate and various kinds of optical sheets so as to efficiently transmit and use the light supplied to the light source to the liquid crystal panel.

1 is a cross-sectional view showing a conventional liquid crystal display device. 1, the liquid crystal display 10 includes a light source 20 for providing light, a light guide plate 30 for guiding light of the light source 20, and a surface light source for emitting light from the light guide plate 30 And a liquid crystal panel 50 for displaying an image by receiving a surface light source from the optical sheet 40 and the optical sheet 40. [

However, due to the characteristics of the injection method for manufacturing the light guide plate 30, the resin density of the light input portion 34 of the light guide plate is higher than that of the light input portion 32, The amount of absorption of the blue region increases from the light-incident portion 32 toward the light-incident portion 34, so that it becomes relatively yellow. Such a problem has a problem in that the larger the light guide plate for application to a large screen becomes, the larger the difference in color feeling becomes, and the display quality is greatly affected.

The present invention provides a backlight unit, a method of manufacturing the same, and a liquid crystal display device including the same, which can reduce color difference and reduce manufacturing cost.

In order to achieve the above object, a backlight unit according to an embodiment of the present invention includes a light guide plate for guiding light, a first light source part located at one side of the light guide plate, a second light source part located at the other side of the light guide plate, And a reflector disposed at a lower portion of the light guide plate and reflecting the light, wherein the light guide plate has a plate shape and includes protrusions corresponding to the second light source portion.

The first light source unit includes a plurality of light sources, and the light is emitted to one side of the light guide plate.

The first light source unit includes at least one light source and emits light to the protrusions.

And the protrusion is integrated with the light guide plate.

And the protruding portion is located at the center of the other side of the light guide plate.

A method of manufacturing a backlight unit according to an embodiment of the present invention includes a light guide plate, a first light source unit disposed on one side of the light guide plate, a second light source unit disposed on the other side of the light guide plate, Wherein the light guide plate has a plate shape and includes protrusions corresponding to the second light source portion, the method comprising the steps of: providing at least one cavity, a gate leading to the cavity, and a resin Preparing a mold having an injection port to be injected, connecting a cylinder for resin injection to the injection port, supplying resin to the cylinder to melt the resin and fill the cavity of the mold with resin, After cooling, the gap between the gate and the injection port is cut, and a light guide plate having a protrusion on one side The method comprising the steps of:

According to another aspect of the present invention, there is provided a liquid crystal display device including a light guide plate for guiding light, a first light source unit disposed on one side of the light guide plate, a second light source unit disposed on the other side of the light guide plate, A liquid crystal panel disposed on the backlight unit, and a bottom cover and a top cover for accommodating the backlight unit and the display panel, wherein the light guide plate has a plate shape, And a protrusion corresponding to the second light source unit.

And the protruding portion is protruded outside the liquid crystal panel.

The top cover further includes a groove key positioned at one edge of the top cover, and the groove key is positioned to face the protrusion.

A backlight unit and a liquid crystal display device including the same according to an embodiment of the present invention can improve brightness uniformity of a liquid crystal display device and improve display quality by forming a protrusion on a light guide plate and making light from the second light source incident on a protrusion There is an advantage. In addition, there is an advantage that the disposal cost and the like can be reduced by utilizing the projecting portion removed from the light guide plate.

1 is a sectional view showing a conventional liquid crystal display device.
2 is an exploded perspective view illustrating a liquid crystal display device according to an embodiment of the present invention.
3 is a plan view showing a light guide plate.
4 is a cross-sectional view taken along line I-I 'of FIG. 2;
FIGS. 5A and 5B are views illustrating a manufacturing method of a light guide plate according to an embodiment of the present invention.
6 is a plan view showing each region of the liquid crystal display device of the present invention.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, well-known functions or constructions are not described in detail to avoid unnecessarily obscuring the subject matter of the present invention.

FIG. 2 is an exploded perspective view illustrating a liquid crystal display device according to an embodiment of the present invention, FIG. 3 is a plan view illustrating a light guide plate, and FIG. 4 is a sectional view taken along line I-I 'of FIG.

2, a liquid crystal display 100 according to an exemplary embodiment of the present invention includes a liquid crystal panel 110, a backlight unit 130, a support main 140, a bottom cover 150, a top cover 160, .

The liquid crystal panel 110 is mounted on the panel support portion of the support main body 140 to adjust the transmittance of light supplied from the backlight unit 130 to realize an image. The liquid crystal panel 110 includes a first substrate 111 and a second substrate 112 which are bonded together with a liquid crystal layer (not shown) interposed therebetween. Although not shown in the drawings, a plurality of pixels may be defined on the first substrate 111, which is referred to as a TFT array substrate, by intersecting a plurality of scan lines and data lines in a matrix form. Each pixel is provided with a thin film transistor (TFT) capable of turning on / off a signal, and a pixel electrode connected to the thin film transistor may be positioned.

The second substrate 112, which is referred to as a color filter substrate, includes red (R), green (G), and blue (B) color filters respectively corresponding to a plurality of pixels, A black matrix for covering non-display elements such as transistors may be provided. Further, a transparent common electrode covering them may be provided. In the present embodiment, the pixel electrode is provided on the first substrate and the common electrode is provided on the second substrate. However, the present invention is not limited to this, and both the pixel electrode and the common electrode may be provided on the first substrate.

The printed circuit board 116 is connected to at least one side of the liquid crystal panel 110 via a connection member 114 such as a flexible circuit board or a tape carrier package (TCP) 140 or on the back surface of the bottom cover 150. [

In the liquid crystal panel 110 having the above structure, when the selected thin film transistor is turned on for each scan line by the on / off signal of the gate drive circuit transmitted from the scan line, the data voltage of the data drive circuit is transmitted through the data line The alignment direction of the liquid crystal molecules is changed by the electric field between the pixel electrode and the common electrode, and the difference in transmittance can be exhibited.

The support main 140 covers the edges of the light guide plate 200, the optical sheet 139 and the reflection plate 128 and the light guide plate 200, the optical sheet 139 and the reflection plate 128 to the bottom cover 150 And a function of supporting the liquid crystal panel 110. Here, the role of the support main body 140 may be replaced or omitted by the structure added to the top cover 160 and the bottom cover 150.

The liquid crystal display 100 of the present invention may include a backlight unit 130 capable of providing light from the back surface of the liquid crystal panel 110 to the liquid crystal panel 110. The backlight unit 130 includes the light sources 120 and 125, the white or silver reflection plate 128, the light guide plate 200 positioned on the reflection plate 128, and a plurality of optical sheets 139).

The light sources 120 and 125 are mounted on a light source circuit board and are driven by a power source to generate light. The light sources 120 and 125 may be formed of any one of a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), and an external electrode fluorescent lamp (EEFL) The light emitted from the light sources 120 and 125 is incident into the light guide plate 200 and is supplied to the liquid crystal panel 110 by the light guide plate 200, the optical sheet 139 and the reflection plate 128. The light sources 120 and 125 are formed to face at least one side of the light guide plate 200.

 The light sources 120 and 125 of the present invention include a first light source unit 120 located at one side of the light guide plate 200 and a second light source unit 125 located at the other side of the light guide plate 200. [ The LED assembly is disposed on one side of the light guide plate 200 and includes a plurality of LED light sources 121 and LED light sources 121 spaced apart from each other at regular intervals 122 and the bottom cover 150. The support base 123 is provided on the bottom cover 150,

On the other hand, in the present invention, it is advantageous that the backlight unit 130 is configured as an edge type. The light guide plate of the present invention induces the light emitted from the light source 120 to be totally reflected by not only the upper pattern and the light collecting sheet but also the lower pattern, thereby improving the brightness and preventing hot spots and bright lines.

The optical sheet 139 condenses or diffuses light emitted through the light guide plate 200 to be transmitted to the liquid crystal panel 110. To this end, the optical sheet 139 is configured to include at least one of a diffusion sheet or a light condensing sheet. The diffusion sheet prevents the light emitted through the light guide plate 200 from being concentrated in a part of the region and disperses light to be transmitted to the liquid crystal panel 110 with a uniform distribution. The light collecting sheet condenses the light emitted from the light guide plate 200 and allows light to be vertically transmitted to the liquid crystal panel 110. In particular, the light collecting sheet of the present invention may be constituted by a reverse prism sheet on which a sheet pattern is formed on the surface facing the light guide plate 200.

The reflection plate 128 is disposed on the lower side or the side surface of the light guide plate 200 and reflects light emitted to the exit surface or the lower surface of the light guide plate 200 into the light guide plate 200. The reflection plate 128 may be formed in different positions depending on the arrangement of the light sources 120 and 125. For example, as shown in FIG. 2, the edge type backlight unit may be disposed on the lower surface of the light guide plate 200, that is, on the surface facing the liquid crystal panel 110 with the light guide plate 200 interposed therebetween. The direct-type backlight unit may be formed on the side surface of the light guide plate 200 or may be omitted if necessary. The light guide plate 200 may be deformed by various allowances such as the arrangement of the light sources 120 and 125 without being limited thereto.

The light guide plate 200 spreads the light incident from the light sources 120 and 125 into the wide area of the light guide plate 200 while traveling in the light guide plate 200 by total reflection to provide a primary surface light source to the liquid crystal panel 110 Can play a role. The light guide plate 200 may include a pattern of a specific shape on the back surface to supply a uniform surface light source.

The liquid crystal panel 110 and the backlight unit 130 may be modularized through the top cover 160, the support main 140 and the bottom cover 150. [ The top cover 160 may have a rectangular frame shape covering the top and side surfaces of the liquid crystal panel 110 and may open the front surface of the top cover 160 to display an image formed on the liquid crystal panel 110. In this embodiment, the top cover 160 may have a home key 162 formed at one edge thereof. The bottom cover 150 serves as a base for the liquid crystal display device by coupling the liquid crystal panel 110 and the backlight unit 130, and may be formed into a rectangular plate shape.

Referring to FIG. 3, the light guide plate 200 of the present invention has a plate-like planar shape. As described above, the light guide plate 200 has the protrusion 210 protruding from the light guide plate 200 of the present invention. More specifically, the first light source unit 120 is located on one side of the light guide plate 200, and the second light source unit 125 is located on the other side. The first light source unit 120 is a main light source that substantially provides light to the light guide plate 200, and includes a plurality of LEDs. The second light source unit 125 is a sub light source for providing light to the light guide plate 200, and at least one LED is provided.

In particular, the second light source 125 is formed to correspond to the protrusion 210 of the light guide plate 200. The second light source unit 125 provides light to the light guide plate 200 through the protrusion 210 of the light guide plate 200 and provides light to the keypad (not shown) of the top cover disposed on the protrusion 210.

More specifically, referring to FIG. 4, the light guide plate 200 is housed in the bottom cover 150. The first light source unit 120 is located on one side of the light guide plate 200 and the second light source unit 125 is located on the other side. A reflection plate 128 is disposed below the light guide plate 200 and an optical sheet 139 is disposed above the light guide plate 200. The liquid crystal panel 110 is positioned on the optical sheet 139 and the top cover 160 is coupled to the bottom cover 150 on the liquid crystal panel 110 to constitute the liquid crystal display device 100. [

The second light source unit 125 is positioned at a position corresponding to the protrusion 210 of the light guide plate 200 and provides light to the light guide plate 200 through the protrusion 210. [ Therefore, the light provided by the second light source unit 125 is incident on the light guide plate 200 in addition to the light provided by the first light source unit 120. The second light source unit 125 is provided adjacent to the light input / output unit of the conventional light guide plate 200 and the light emitted from the light guide plate 200 is yellowed by the second light source unit 125 . The top cover 160 corresponding to the protruding portion 210 has a groove key 162 thereon. The light provided to the protruding portion 210 through the second light source portion 125 is illuminated to the home key 162 of the top cover 160. [

Hereinafter, a manufacturing method of the light guide plate will be described. 5A and 5B are views showing a manufacturing method of a light guide plate according to an exemplary embodiment of the present invention.

Referring to FIG. 5A, the light guide plate of the present invention is manufactured using a mold. In more detail, a mold (MD) provided with at least one cavity (CV) acting as a frame of the light guide plate is prepared. The mold MD is provided with an injection port IP through which resin as a material of the light guide plate can be injected and a gate GA through which the resin is injected to the cavity CV through the injection port IP. Then, a cylinder SL for injecting resin into the mold MD is prepared. The cylinder SL may be provided with a heating means for filling the resin into the mold MD and additionally for melting the resin. In addition, the resin constituting the light guide plate may be a transparent resin such as PMMA or PET, but it may preferably be made of PMMA.

The previously prepared resin is supplied to the cylinder SL. The resin supplied to the cylinder SL may be a resin in a pellet state. When resin is supplied to the cylinder SL, the cylinder SL is extruded and heat-treated at the same time to deform the resin into a liquid or gel phase capable of being extruded. Next, after the cylinder SL is mounted on the injection port IP of the mold MD, the resin in the cylinder SL is injected to fill the mold MD. At this time, the resin is injected into the injection port IP of the mold MD and filled in the respective cavities CV through the gate GA. When filling of the resin ends, remove the cylinder, cool the mold (MD) and remove the mold (MD).

As shown in Fig. 5B, the light guide plates 200 connected by the gate GA are separated from the mold MD. Then, the light guide plate 200 is finally formed by cutting along the cut line CL so that a part of the gate GA is left in the light guide plate 200. [ The light guide plate 200 thus formed may be provided with a protrusion 210 on one side like the light guide plate 200 of FIG.

Generally, in the manufacturing process of the light guide plate 200, all of the light guide plate 200 is cut without leaving the gate GA, and discarded. However, in the present invention, a part of the gate (GA) is used as the protrusion 210 of the light guide plate 200 to reduce the color difference of the light guide plate 200 and to use the light as a hometown illumination. Thereby, there is an advantage that cost for disposal of the gate (GA) can be reduced and display quality can be improved.

Table 1 below shows the measured brightness, chromaticity coordinate, and chromaticity standard deviation of each region of the conventional liquid crystal display device shown in FIG. 1, and Table 2 shows brightness, chromaticity coordinates, and chromaticity coordinates of the liquid crystal display according to the present invention, And the standard deviation of the color coordinate is measured and shown. The numbers 1 to 9 in the following Tables 1 and 2 mean the respective regions of the liquid crystal display device shown in FIG.

Luminance
Color coordinates u ' v ' △ u'v ' One 12392 0.2052 0.4416 0.00401278 2 10792 0.2056 0.4455 0.00504337 3 10648 0.2055 0.4456 0.00515275 4 11008 0.2055 0.4454 0.0049763 5 11966 0.2054 0.4420 0.00164012 6 11822 0.2054 0.4423 0.001853 7 11694 0.2049 0.4405 0.000455695 8 11834 0.2051 0.4407 0.00022091 9 11718 0.2051 0.4409 Minimum (min) 10648 0.2049 0.4402 Max (max) 12392 0.2056 0.4456 Average (avg) 11542 0.2053 0.4427 0.0052 Uniformity 86%

Luminance
Color coordinates u ' v ' △ u'v ' One 12910 0.206 0.439 0.00296357 2 13246 0.207 0.441 0.00329555 3 12642 0.207 0.441 0.00325121 4 12734 0.207 0.442 0.00364981 5 12494 0.206 0.438 0.00065894 6 12370 0.206 0.439 0.00125436 7 11888 0.206 0.438 0.00113635 8 12668 0.206 0.439 0.00010382 9 11888 0.206 0.439 Minimum (min) 11888 0.206 0.438 Max (max) 13246 0.207 0.442 Average (avg) 12538 0.206 0.440 0.0036 Uniformity 90%

Referring to Tables 1 and 2, in the case of the conventional liquid crystal display device not including the protruding portion and the second light source, the luminance uniformity is about 86% and the standard deviation of the color coordinates is 0.0052. However, It can be confirmed that the liquid crystal display device provided with two light sources remarkably improved brightness uniformity of about 90% and standard deviation of color coordinates of 0.0036.

As described above, the backlight unit and the liquid crystal display device including the same according to the embodiment of the present invention improve the luminance uniformity of the liquid crystal display device by forming protrusions on the light guide plate and causing the light of the second light source portion to enter the protrusions, There is an advantage that it can be improved. In addition, there is an advantage that the disposal cost and the like can be reduced by utilizing the projecting portion removed from the light guide plate.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the present invention should not be limited to the details described in the detailed description, but should be defined by the claims.

100: liquid crystal display device 110: liquid crystal panel
120: light source 128: reflector
130: backlight unit 140: guide panel
150: bottom cover 160: top cover
200: a light guide plate 210:

Claims (9)

A light guide plate for guiding light;
A first light source part located at one side of the light guide plate and a second light source part located at the other side of the light guide plate; And
And a reflection plate positioned below the light guide plate and reflecting light,
Wherein the light guide plate includes a plate-shaped protrusion corresponding to the second light source unit.
The method according to claim 1,
Wherein the first light source unit includes a plurality of light sources and emits light to one side of the light guide plate.
The method according to claim 1,
Wherein the first light source unit includes at least one light source, and emits light to the protrusion.
The method according to claim 1,
Wherein the protrusion is integrated with the light guide plate.
The method according to claim 1,
And the protruding portion is located at the center of the other side of the light guide plate.
A light guide plate, a first light source part disposed on one side of the light guide plate, a second light source part positioned on the other side of the light guide plate, and a reflector positioned below the light guide plate to reflect light, wherein the light guide plate has a plate shape In a method of manufacturing a backlight unit including a protrusion corresponding to a second light source portion,
Preparing a mold having at least one cavity, a gate leading to the cavity, and an injection port into which the resin is injected;
Connecting a cylinder for resin injection to the injection port;
Supplying resin to the cylinder to melt the resin and fill the cavity of the mold with resin; And
And cooling the resin to cut off the gap between the gate and the injection port to produce a light guide plate having a protrusion on one side thereof.
A backlight unit including a light guide plate for guiding light, a first light source unit positioned at one side of the light guide plate, a second light source unit positioned at the other side of the light guide plate, and a reflector positioned below the light guide plate to reflect light;
A liquid crystal panel positioned on the backlight unit; And
And a bottom cover and a top cover for accommodating the backlight unit and the display panel,
Wherein the light guide plate includes a plate-shaped protrusion corresponding to the second light source unit.
8. The method of claim 7,
And the protruding portion is protruded to the outside of the liquid crystal panel.
9. The method of claim 8,
Wherein the top cover further includes a groove key positioned at one edge of the top cover, and the groove key is positioned to face the projection.

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