KR101301516B1

KR101301516B1 - White LED Package and Liquid Crystal Display using the same

Info

Publication number: KR101301516B1
Application number: KR1020060115750A
Authority: KR
Inventors: 임우성
Original assignee: 엘지디스플레이 주식회사
Priority date: 2006-11-22
Filing date: 2006-11-22
Publication date: 2013-09-04
Also published as: KR20080046376A

Abstract

The present invention relates to a liquid crystal display device, and more particularly, to a double-sided light emitting white LED package structure used as a backlight light source.

The present invention is characterized by improving the brightness and the hot spot of the liquid crystal display device by changing the structure of the LED light emitting only one side of the prior art to emit light on both sides and use the LED housing according to this.

Description

White LED Package and Liquid Crystal Display Using the Same

1 is a schematic illustration of a white LED package used as a backlight light source according to the prior art;

2 is a view showing a light analysis result of a backlight to which a plurality of conventional white LED packages are applied.

3 schematically illustrates a vertical cutaway surface of a white LED package according to an embodiment of the invention.

4 is a view illustrating a light reflection path of a backlight to which a white LED package according to an embodiment of the present invention is applied.

5 is a perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

111: lead frame 113: blue chip

115: chip fixing wire 117: yellow phosphor

119 transparent protective layer 121 light guide plate

123: LED housing 125: printed circuit board

127: optical sheet 129: reflector

131: liquid crystal panel 133: support main

135: top cover 137: gap cover

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a structure of a double-sided light emitting white light emitting diode (LED) package used as a backlight light source.

In general, liquid crystal displays are non-light emitting devices that emit light due to external factors.

Therefore, the liquid crystal display requires a backlight which is a separate light source.

There are two types of backlight assembly constituting the backlight, an edge method and a direct method, depending on the light source arrangement.

The edge method is to install a light source outside the light guide plate, and the light emitted from the light source is incident to the entire surface of the liquid crystal panel using the transparent light guide plate, and the direct method is to place the light source on the back of the liquid crystal panel This is a method of directly examining the front of the panel.

However, when the direct method is used as a backlight assembly of a medium and small liquid crystal display device such as a notebook computer, an increase in thickness of the small liquid crystal display device cannot be avoided while pursuing a light and small size. For that reason, the structure of the backlight assembly of most medium and small sized liquid crystal displays adopts the edge method.

The backlight assembly uses a Cold Cathode Fluorescent Lamp (CCFL), an External Electrode Fluorescent Lamp (EEFL), and a Light Emitting Diode (LED) as a light source.

In particular, LEDs emit light due to a potential difference when electrons and holes recombine in a semiconductor p-n junction structure. These LEDs include gallium nitride (GaN), gallium arsenide (GaAs), gallium phosphide (GaP), gallium-arsenide-phosphorus (GaAs1-xPx), gallium-aluminum-arsenic (Ga1-xAlxAs), indium phosphide (InP), It is composed of compound semiconductor composed of indium-gallium-phosphorus (In1-xGaxP), and has low brightness, low voltage, long life and low price, and it is conventionally applied to simple information display such as display lamp or number Recently, with the development of industrial technology, especially information display technology and semiconductor technology, the application scope has been extended to the field of flat panel display (FPD), and it is expected to continue to develop as an independent information display device in the future.

Hereinafter, a white LED package used as a light source of a backlight assembly according to the prior art will be described with reference to the accompanying drawings.

1 is a view schematically showing a white LED package used as a backlight light source according to the prior art.

As shown, the white LED package 10 has a space left and right spaced apart from the lead frames 11a to 11b of the anode to cathode connected to the external power source and has the same inclined surface 13. And a compound semiconductor composed of indium-gallium-nitride (InGaN) on the LED insulation substrate 15 of sapphire (Al ₂ O ₃ ) or SiC in a space spaced left and right of the reflective frame 13. A layer (not shown) is deposited and a blue chip 17 is deposited over the semiconductor layer (not shown).

In addition, when the blue chip 17 is mounted on the positive lead frame 11a, a wire 19 connecting the blue chip 17 and the negative lead frame 11b is configured, and the blue When the chip 17 is mounted on the negative lead frame 11b, a wire 19 connecting the blue chip 17 and the positive lead frame 11a is configured.

Meanwhile, a yellow phosphor 21 made of Yttrium-Aluminum-Garnet (YAG) is enclosed around the blue chip 17, and the internal components are formed on the yellow phosphor 21 and the blue chip 17. The transparent protective layer 23 for fixing the light and transmitting light is covered.

The light emission principle of the white LED package 10 is as follows.

When power is applied to the white LED package 10, blue light is emitted from the blue chip 17, and a part of the blue light is absorbed by the yellow phosphor 21 to produce yellow light, which is not absorbed by the yellow phosphor 21. The remaining blue light and the yellow light are mixed to emit white light.

Such at least one white LED package 10 is mounted on a printed circuit board (not shown) at equal intervals and used as a light source of a backlight assembly.

The LED is a point light source, and a hot spot A in which light is concentrated and a dark area B outside the light divergence angle are generated by a characteristic of emitting light to only one surface and an angle at which light is emitted.

As shown, due to the light emitted from the white LED package 10 mounted on the printed circuit board 25 at equal intervals, the light diverging portion of the white LED package 10 and the adjacent portion of the light guide plate 27. It can be seen that hot spots A occur due to light concentration.

In addition, the contrast ratio becomes clear due to the occurrence of the hot spot A, so that the dark area B becomes clearer.

The occurrence of the hot spot A is a problem of the backlight assembly using the LED as a light source, and the hot spot A is a major cause of deterioration of the screen display quality of the LCD.

The present invention is to solve the above problems, by changing the structure of the conventional white LED package that emits only one side to emit light on both sides, by using the corresponding LED housing (Housing) of the liquid crystal display device It aims at improving luminance and improving hot spots.

In addition, an object of the present invention is to improve the screen display quality of the liquid crystal display by improving the brightness and hot spot.

In order to achieve the object as described above, the present invention includes a lead frame connected to an external power source and the center hole (Hole) is formed; A blue chip formed in the center of the hole of the lead frame and deposited on a transparent insulating substrate; A chip fixing wire applying voltage to the blue chip and connecting and fixing the blue chip and the lead frame; A yellow phosphor covering the entire blue chip; A white LED package including a transparent protective layer covering front and rear surfaces of the yellow phosphor; A light guide plate for changing a path of light emitted from the white LED package and outputting the light to the liquid crystal panel; An LED housing protecting the white LED package and reflecting light emitted from the rear side to the light guide plate; A plurality of optical sheets for uniforming the luminance of the light emitted from the light guide plate; A backlight assembly including a reflector for reflecting light leaking from the light guide plate; Provided is a liquid crystal display comprising a liquid crystal panel configured on top of the backlight assembly and including two substrates having a field generating electrode and facing each other up and down and a liquid crystal layer interposed therebetween.

The area of the hole formed in the lead frame is characterized in that the wider toward the adjacent light guide plate.

The chip fixing wire is attached to both sides of the hole inner wall of the lead frame.

The yellow phosphor is characterized as being an yttrium-aluminum-garnet compound.

The transparent protective layer covering the upper portion of the yellow phosphor is characterized in that the epoxy (Epoxy) or silicon (Silicon) resin.

The LED housing is characterized in that the silver (Ag) is applied to the polyethylene terephthalate (PET) at regular intervals to further increase the reflection efficiency for leakage light.

In addition, silver (Ag) applied to the LED housing is characterized in that located between the spaced space of the white LED package.

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

3 is a view schematically showing a vertical cut surface of a white LED package according to an embodiment of the present invention.

As shown, the white LED package 100 according to the embodiment of the present invention is configured with a lead frame 111 connected to an external power source and having a center hole formed therein. The hole of the lead frame 111 is configured to have a wider cross-sectional area toward the light guide plate (not shown) adjacent portion (the upper end of the drawing).

In the center of the hole of the lead frame 111, a blue chip 113 is deposited on a transparent insulating substrate (not shown), and a voltage is applied to the blue chip 113, and the blue chip 113 and the lead Chip fixing wires 115 for connecting and fixing the frame 111 are attached to both inner walls of the hole of the lead frame 111.

In addition, a yellow phosphor 117 composed of an yttrium-aluminum-garnet-based compound surrounds the entire blue chip 113, and a transparent protective layer 119 made of epoxy or silicone resin is used to transfer the yellow phosphor 117. It is structured to cover all of the rear side.

The light emission principle of the white LED package 100 is as follows.

When power is applied to the white LED package 100, blue light is emitted from the LED blue chip 113 in all directions, and a part of the blue light is absorbed by the yellow phosphor 117 to make yellow light, and the yellow phosphor 117. The remaining blue light and the yellow light which are not absorbed by the light are mixed to emit white light.

The white light is emitted to the rear as well as the front through the hole of the lead frame 111 of the white LED package 100.

As shown, in order to reflect the light emitted from the back of the white LED package 100 configured as shown in FIG. 3 to the light guide plate 121 region, the reflecting surface of the LED housing 123 has a reflection efficiency in PET material. High silver (Ag) is apply | coated at equal intervals and is comprised.

In this case, the coated silver (Ag) is located between the spaced apart space of the white LED package 100 serves to further increase the reflection efficiency.

That is, the light emitted to the rear surface is reflected to the light guide plate 121 region by the reflective surface of the LED housing 123, so that a larger amount of light can reach the conventional dark region (B of FIG. This is to improve the hot spot (A in Fig. 2) by conventional light concentration.

As shown, the liquid crystal display device 300 using the white LED package 100 according to an embodiment of the present invention as a backlight light source is the white LED package 100 and the white LED emitting light to both sides of the front, rear The package 100 is mounted on the printed circuit board 125 and the one side of the printed circuit board 125 mounted at equal intervals, the light guide plate 121 for changing the path of the emitted light to the liquid crystal panel 131 And the LED housing 123 which protects the white LED package 100 and reflects the light emitted to the rear side to the light guide plate 121 and is coated with silver at equal intervals.

In addition, a plurality of optical sheets 127 and a lower portion of the light guide plate 121 are formed on the light guide plate 121 to uniform the luminance of the light emitted from the light guide plate 121. It consists of a backlight assembly 200 comprising a reflector plate 129 of a white or silver sheet for reflecting the leaking light.

An upper portion of the backlight assembly 200 includes a liquid crystal panel 131 including an electric field generating electrode and two substrates facing each other up and down and a liquid crystal layer interposed therebetween.

Meanwhile, the support main 133 fixes the optical sheet 127, guides the liquid crystal panel 131, and the liquid crystal panel 131 and the backlight assembly 200 have a top cover. 135 and the bottom cover 137 is fixed.

The screen display quality of the liquid crystal display may be improved by improving luminance and dark spots of a dark region, which is a chronic problem of the backlight applying LED as a light source through the liquid crystal display 300.

The present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

As described above, by changing the structure of the conventional white LED package that emits light on only one side to emit light on both sides, and using the LED housing according to this, to improve the brightness of the liquid crystal display and improve the hot spot It works.

In addition, the present invention has the effect of improving the screen display quality of the liquid crystal display by improving the brightness and hot spots.

Claims

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A lead frame having a hole formed in a central portion thereof, a blue chip formed at a center of the hole of the lead frame and deposited on a transparent insulating substrate, and emitting light on both sides, and a voltage applied to the blue chip, A white LED package including a chip fixing wire connected to and fixed to both sides of the inner wall of the lead frame, a yellow phosphor covering the entire blue chip, and a transparent protective layer covering front and rear surfaces of the yellow phosphor;

A light guide plate configured on one side of the white LED package and configured to guide light upward;

An LED housing which protects the white LED package and reflects light emitted from the rear side to the light guide plate;

A reflection plate positioned under the light guide plate and reflecting light leaked from the light guide plate upward;

A backlight assembly disposed on the light guide plate, the backlight assembly including an optical sheet for uniforming the luminance of light emitted from the light guide plate;

A liquid crystal panel configured on an upper portion of the backlight assembly and including two substrates having a field generating electrode and facing each other up and down and a liquid crystal layer interposed therebetween

It includes, The LED housing is configured so that silver (Ag) is applied to the polyethylene terephthalate (PET) at regular intervals to further increase the reflection efficiency for leakage light, Silver (Ag) is applied to the LED housing And a space between the spaces of the white LED package.

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