KR20160077482A - Liquid crystal display device - Google Patents

Abstract

The present invention relates to a liquid crystal display device using an LED as a light source, and more particularly, to a liquid crystal display device of which the luminance and color gamut are improved. According to the feature of the present invention, a quantum dot sheet, which emits light which is not emitted from an LED including a B-LED chip, is placed on an upper side of the LED such that the light emitted from the LED is mixed with the light emitted from the quantum dot sheet, thereby implementing white color light having an excellent light property of high luminance and high color gamut. Specifically, even though light does not pass through both side ends of a PCB, an LED emitting white color light is placed on both side ends of a PCB, a side reflection plate on which phosphor is coated is placed on an opposite light introducing surface of a light guiding plate and both side surfaces, or phosphor is coated along at least one edge of an optical sheet, such that blue light may be prevented from being leaked through an edge of the quantum dot sheet from which the quantum dot property is removed.

Description

[0001] Liquid crystal display device [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device using an LED as a light source, and more particularly to a liquid crystal display device with improved luminance and color reproduction rate.

In recent years, the use of light emitting diodes (LEDs) having features such as small size, low power consumption and high reliability as light sources has been increasing. Such LEDs have been utilized for various lighting purposes, and their use ranges from a display portion of an electronic product to various display devices, a lighting device of a vehicle, and the like.

In particular, LEDs may artificially generate white light to replace fluorescent lamps for general illumination, and LEDs that emit white light are receiving the spotlight as backlight units of liquid crystal displays (LCDs).

1 is a cross-sectional view of a liquid crystal display including a backlight unit of a general edge type using an LED as a light source.

A liquid crystal display device 1 including a backlight unit 20 of a general edge type includes a liquid crystal panel 10, a backlight unit 20, a guide panel 30, a cover bottom 50, And a top cover 40.

The liquid crystal panel 10 is constituted by first and second substrates 12 and 14 which are in contact with each other with a liquid crystal layer interposed therebetween, which plays a key role in image display.

And reference numerals 19a and 19b denote polarizers attached to the front and back surfaces of the liquid crystal panel 10 to control the polarization direction of light, respectively.

A backlight unit 20 is provided behind the liquid crystal panel 10.

The backlight unit 20 includes an LED assembly 29 arranged along the longitudinal direction of at least one edge of the guide panel 30 and composed of a PCB 29b on which a plurality of LEDs 29a and LEDs 29a are mounted, A reflector 25 of white or silver color resting on the bottoms 50 and a light guide plate 23 resting on the reflector 25 and an optical sheet 21 located thereon.

The liquid crystal panel 10 and the backlight unit 20 are covered with a top cover 40 covering the top edge of the liquid crystal panel 10 with the edges thereof being surrounded by a rectangular guide panel 30, The cover bottoms 50 are integrally joined to each other through the guide panel 30.

On the other hand, the LED 29a in which a G (green) phosphor is mixed with a B (blue) LED chip that emits blue light to the backlight unit 20 is used according to a consumer's demand for higher luminance and color reproduction ratio Studies have been actively carried out to improve the brightness and color gamut of the liquid crystal display device 1 through an optical sheet (not shown, hereinafter referred to as a quantum dot spot) using a quantum dot.

However, the liquid crystal display device 1 including the backlight unit 20 including a quantum dot sheet (not shown) causes blue leakage phenomenon at the edge of the screen.

In the blue light leakage phenomenon, moisture and oxygen penetrate into the edge portions of the quantum dot sheet (not shown) during cutting of the quantum dot sheet (not shown), so that the quantum dot characteristic is removed at the edge portions of the quantum dot sheet A blueish color appears on the edge portion of the quantum dot sheet (not shown) as it is as an image.

This blue light leakage phenomenon causes a problem of lowering the display quality of the liquid crystal display device 1. [

In the liquid crystal display device 1 having a narrow bezel, which is a non-display area other than the display area, the bezel area is expanded while the display area which is recently required to exhibit such blue light leakage phenomenon is expanded It becomes deepened.

SUMMARY OF THE INVENTION It is a first object of the present invention to improve the brightness and color gamut of a liquid crystal display device.

A second object of the present invention is to prevent the blue light leakage phenomenon from occurring at the edge of the image.

A third object of the present invention is to provide a liquid crystal display device having improved screen display quality.

In order to achieve the above object, according to the present invention, there is provided a liquid crystal display device comprising a liquid crystal panel, an optical sheet positioned under the liquid crystal panel, and a liquid crystal layer disposed below the optical sheet and having one of red, A quantum dot sheet that emits a first light mixed with at least two lights, a light guide plate positioned below the quantum dot sheet, and a plurality of first and second LEDs and a plurality of first And a reflector positioned below the light guide plate, wherein the first LED includes a second light mixed with the first light to realize white light, And the second LEDs are positioned at both ends of the PCB in the longitudinal direction to implement white light.

At this time, the white light realized from the second LED passes through the edge of the quantum dot sheet, and each of the second LEDs is provided at each end in the longitudinal direction of the PCB, or two or three LEDs are respectively provided.

The present invention relates to a liquid crystal display device, which comprises a liquid crystal panel, an optical sheet positioned under the liquid crystal panel, and a liquid crystal layer disposed under the optical sheet and having at least one of red, green, and blue, A light guide plate disposed below the quantum dot sheet, a plurality of LEDs disposed corresponding to light incident surfaces of the light guide plate and emitting a second light, and a PCB on which the plurality of LEDs are mounted, And a side reflector which is disposed on both sides of the light guide plate and on the light receiving surface of the light guide plate and is coated with a phosphor that emits a third light mixed with the second light and emits white light, A display device is provided.

Here, the phosphor is applied to one side of the side reflector so as to face the light-incident side and both sides of the light guide plate.

According to another aspect of the present invention, there is provided a liquid crystal display comprising: a liquid crystal panel; a quantum dot sheet disposed below the liquid crystal panel and emitting a first light having at least two of red, green, and blue mixed with at least two red, And a PCB on which the plurality of LEDs are mounted, and a reflector positioned at a lower portion of the light guide plate. The LED assembly includes a plurality of light emitting diodes (LEDs) And at least one optical sheet coated with a phosphor that is disposed on the quantum dot sheet and emits a third light that is mixed with the second light and emits white light.

Here, the first light and the second light are mixed to realize white light.

As described above, according to the present invention, a quantum dot sheet that emits light that does not emit light from an LED is placed on top of an LED including a B-LED chip, and light emitted from the LED and light emitted from the quantum dot sheet are mixed And white light having excellent light characteristics having a high luminance and a high color recall ratio can be realized by implementing white light.

Particularly, it is possible to position the LED, which emits white light, without passing through the quantum dot sheet at both ends of the PCB, to position the side reflector coated with the fluorescent material on the light receiving surface and both sides of the light guide plate, Accordingly, by applying the fluorescent material, it is possible to prevent blue light leakage from occurring in the image corresponding to the edge portion of the quantum dot sheet from which the quantum dot characteristic is removed.

1 is a cross-sectional view of a liquid crystal display including a backlight unit of a general edge type using an LED as a light source.
2 is a perspective view schematically showing a liquid crystal display device according to an embodiment of the present invention.
3 is a graph showing a color coordinate according to a color reproduction rate of a liquid crystal display device according to an embodiment of the present invention.
4 is a perspective view schematically showing a backlight unit according to the first embodiment of the present invention.
5A is a photograph showing a light leakage phenomenon of a general liquid crystal display device.
5B is a photograph of the liquid crystal display according to the first embodiment of the present invention in which light leakage phenomenon does not occur.
6A to 6B are perspective views schematically showing a modified example of the LED assembly according to the first embodiment of the present invention.
7 is a perspective view schematically showing a backlight unit according to a second embodiment of the present invention.
8 is a perspective view schematically showing a backlight unit according to a third embodiment of the present invention.

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

2 is a perspective view schematically showing a liquid crystal display device according to an embodiment of the present invention.

The liquid crystal display 100 according to the embodiment of the present invention mainly includes a liquid crystal panel 110, a backlight unit 120, a guide panel 130, a top cover 140, a cover bottom 150, .

For the sake of convenience, the backlight unit 120 is disposed behind the liquid crystal panel 110 under the assumption that the display surface of the liquid crystal panel 110 faces forward, The top cover 140 is positioned in front of the liquid crystal panel 110 and the cover bottom 150 is positioned on the back surface of the backlight unit 120 in a state in which the guide- And are integrated.

Let's take a closer look at each of these.

First, the liquid crystal panel 110 is a part that plays a key role in image display of the liquid crystal display device 100 and includes a first substrate 112 and a second substrate 114 which are bonded to each other, And a liquid crystal layer (not shown).

Although not shown in the figure, a plurality of gate lines and data lines cross each other on the inner surface of a first substrate 112 called a lower substrate or an array substrate, pixels are defined, and a thin film transistor (TFT) : TFT) are connected in one-to-one correspondence with the transparent pixel electrodes formed in the respective pixels.

On the inner surface of the second substrate 114 called an upper substrate or a color filter substrate, color filters of red (R), green (G), and blue (B) And a black matrix for covering the gate lines, the data lines, and the thin film transistors.

In addition, color filters of red (R), green (G), and blue (B) colors and transparent common electrodes covering the black matrix are provided.

An upper and a lower alignment film (not shown) for determining the initial alignment direction of the liquid crystal are interposed at the boundary between the first and second substrates 112 and 114 and the liquid crystal layer (not shown) A seal pattern (not shown) is formed along the edges of the substrates 112 and 114 to prevent leakage of a liquid crystal layer (not shown) filled between the substrates 112 and 114.

A polarizing plate (not shown) for selectively transmitting only specific light is attached to the outer surfaces of the first and second substrates 112 and 114, respectively.

A printed circuit board 117 is connected to at least one edge of the liquid crystal panel 110 via a connection member 116 such as a flexible circuit board or a tape carrier package (TCP) And is brought into close contact with the side surface of the guide panel 130 or the back surface of the cover bottom 150.

Accordingly, when the thin film transistor selected for each gate line is turned on by the on / off signal of the thin film transistor which is transferred to the gate line, the liquid crystal panel 110 supplies the image signal And the alignment direction of the liquid crystal molecules is changed by the electric field between the pixel electrode and the common electrode which is generated thereby, and the difference in transmittance is shown.

In the liquid crystal display device 100 according to the present invention, a backlight unit 120 is provided to supply light from the rear surface of the liquid crystal display device 100 so that a difference in transmittance represented by the liquid crystal panel 110 is externally expressed.

The backlight unit 120 includes an LED assembly 129, a white or silver reflective plate 125, a light guide plate 123 seated on the reflective plate 125, a quantum dot sheet 122 interposed therebetween, (121).

The LED assembly 129 is a light source of the backlight unit 120 and is disposed at one side of the light guide plate 123 so as to face the light incident surface 123a of the light guide plate 123. The LED assembly 129 includes a plurality of LEDs 129a 129b, and a PCB 129b on which a plurality of LEDs 129a are mounted with a predetermined spacing therebetween.

The light guide plate 123 on which the light emitted from the plurality of LEDs 129a of the LED assembly 129 is incident is incident on the light guide plate 123 while the light incident from the LED 129a travels through the light guide plate 123, So that the liquid crystal panel 110 is provided with a surface light source.

The light guide plate 123 may include a pattern of a specific shape on the lower surface to supply a uniform surface light source. The pattern may be formed in various shapes such as an elliptical pattern, a polygon pattern, a hologram pattern, and the like in order to guide light incident into the light guide plate 123. The pattern is formed on the lower surface of the light guide plate 123 by a printing method or an injection method.

The reflection plate 125 is disposed on the back surface of the light guide plate 123 and reflects light passing through the back surface of the light guide plate 123 toward the liquid crystal panel 110 to improve the brightness of light.

The optical sheet 121 on the light guide plate 123 diffuses or condenses the light that has passed through the light guide plate 123 so that a more uniform surface light source is incident on the liquid crystal panel 110.

Particularly, in the liquid crystal display 100 of the present invention, the quantum dot sheet 122 is further disposed above the light guide plate 123 of the backlight unit 120, and the quantum dot sheet 122 is connected to the LED 129a Green light and white light according to the hue of the light emitted from the blue light emitting diode (LED) 129a. In the case where the LED 129a is a blue LED chip emitting blue light and the quantum dot sheet 122 has no separate phosphor, And a red and green (RG) quantum dot sheet for emitting both red light and green light.

When the LED 129a emits blue light and the green phosphor is applied to the upper portion of the B-LED chip, the quantum dot sheet 122 emits R (red) quantum dots, which emit red light, In the case of the LED 129a in which the LED chip emits UV light and does not have a separate phosphor, the quantum dot sheet 122 may be formed of RGB (red and green and blue) quantum dot sheets emitting red, green, have.

Accordingly, the light emitted from the LED 129a and the light emitted from the quantum dot sheet 122 are mixed to realize uniform white light.

Here, the quantum dot sheet 122 absorbs light of a first wavelength including blue light or ultraviolet light, and emits light of a second wavelength and light of a third wavelength.

This quantum dot sheet 122 is constituted by uniformly arranging quantum dot fluorescent powders corresponding to light of the second wavelength and light of the third wavelength on silicon.

Quantum confinement effect occurs when the individual quantum dots QD of the quantum dot fluorescent powder are smaller than the Bohr radii of excitons formed by electrons and holes excited by light or electricity. The energy gap has a large energy level and the size of the energy gap is changed. Further, the charge is confined within the quantum dots, so that it has a high luminous efficiency.

In addition, the quantum dots differ in fluorescence wavelength depending on the particle size, unlike a general fluorescent dye. That is, as the size of the particles decreases, the light of a short wavelength is emitted, and the size of the particles can be controlled to produce fluorescence in a visible light region of a desired wavelength.

In addition, since the extinction coefficient is very large and the quantum yield is higher than that of a general dye, highly fluorescent light is generated.

The quantum dots of the quantum dot sheet 122 may have a core-shell structure. In the case of the core, a material selected from the group consisting of CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe, And a material selected from the group consisting of CdSe, CdTe, CdS, ZnSe, ZnTe, ZnS, HgTe, and HgS in the case of a shell.

Accordingly, the liquid crystal display device 100 according to the embodiment of the present invention realizes a high color gamut by the white light realized by mixing the light emitted from the LED 129a and the light emitted from the quantum dot sheet 122. Let's take a closer look at this later.

The liquid crystal panel 110 and the backlight unit 120 are modularized through the top cover 140, the guide panel 130 and the cover bottom 150. The top cover 140 is disposed on the top edge of the liquid crystal panel 110, So as to cover the side surface.

Here, the top cover 140 is opened to cover the top and side edges of the liquid crystal panel 110, so that the top cover 140 is formed in a rectangular shape having a "B" .

The guide panel 130 supports the edges of the liquid crystal panel 110 and has a rectangular shape for covering the edges of the backlight unit 120. The guide panel 130 includes a liquid crystal panel 110 and vertical parts 131 surrounding the sides of the backlight unit 120 And a horizontal part 133 for separating the position of the liquid crystal panel 110 and the backlight unit 120 from the vertical part 131.

The guide panel 130 is mounted on the cover bottom 150. The cover bottom 150 includes a horizontal surface 151 and an edge portion 153 having a vertically bent edge.

The guide panel 130 and the cover bottom 150 and the top cover 140 are formed by laminating the top edges of the liquid crystal panel 110 and the backlight unit 120 in a state in which the edges of the liquid crystal panel 10 and the backlight unit 120 are covered with the guide panel 130 The cover top 140 covering the back cover 140 and the cover bottom 150 covering the back surface of the backlight unit 120 are combined at the front and rear sides to be modularly integrated through the guide panel 130. [

Here, the top cover 140 may be referred to as a case top or a top case, and the guide panel 130 may be referred to as a support main or main support or a mold frame. The cover bottom 150 may be referred to as a bottom cover or a bottom cover I will.

At this time, the top cover 140 may be omitted in order to implement the lightweight and thin liquid crystal display device which is recently required in the liquid crystal display device 100 having the above-described structure. The liquid crystal display device 100 can be made light and thin by eliminating the top cover 140, and the process can be simplified.

In addition, the elimination of the top cover 140 made of a metal material may reduce the process cost.

The backlight unit 120 according to an embodiment of the present invention may be configured such that a quantum dot sheet 122 for emitting light corresponding to light not emitting light from the LED assembly 129 is positioned above the light guide plate 123, The light emitted from the LED 129a of the light emitting diode 129 and the light emitted from the quantum dot sheet 122 are mixed to realize white light, thereby realizing white light having excellent optical characteristics.

In particular, the backlight unit 120 according to the embodiment of the present invention achieves a high color gamut.

As a result, the color reproduction rate of the ATSC (International Television Standards Committee) can be more satisfied. Therefore, it is possible to provide a high quality screen to the user.

3 is a graph illustrating a color coordinate according to a color recall ratio of a liquid crystal display device according to an exemplary embodiment of the present invention.

Here, in order to explain the effect of the liquid crystal display (100 of FIG. 2) according to the embodiment of the present invention, the color coordinates of the white light emitted from the backlight unit including the color coordinates of the ATSC system and the conventional general LED assembly are shown together .

Prior to the description, Sample 1 shows the color reproduction rate of white light emitted from a conventional LED assembly. The blue light emitted from a backlight unit using an LED coated with a yellow (Y) And the color reproduction ratio of the white light.

2, the LED assembly (129 in FIG. 2) as the light source of the backlight unit (120 in FIG. 2) according to the embodiment of the present invention is formed so as to include the G phosphor on the B-LED chip emitting blue light, 2 shows the color reproduction ratio of the white light emitted from the backlight unit (120 in Fig. 2) in which the R quantum dot sheet (122 in Fig. 2) emitting red light in front of the LED (129a in Fig.

Here, the color gamut refers to a range of colors that can be expressed by a display device including a liquid crystal display (100 in Fig. 2). The color gamut is represented by the color coordinates of red (R), green (G), and blue (B) , And the color reproduction ratio can be obtained for the three primary colors based on the measurement.

Coordinates of red (700 nm), green (546.1 nm) and blue (435.8 nm) are assigned to the International Commission on Illumination (CIE) ) On the coordinate system designated in 1931.

More specifically, the color reproduction ratio can be calculated by connecting the color coordinates of each of red (R), green (G) and blue (B) determined on the color coordinate system. It can be calculated by comparing with the area of ATSC (International TV Standards Committee) color coordinate.

That is, the color recall ratio is expressed as a ratio of the relative area when assuming that the value of the color coordinate area of the ATSC is 100.

Referring to FIG. 3, if the color reproduction ratio of the ATSC system is 100%, the color reproduction ratio of red, green, and blue of the white light emitted from the backlight unit including the typical LED assembly of Sample 1 is 103%.

It can be confirmed that the color reproduction rate of red (R), green (G) and blue (B) of Sample 2 according to the embodiment of the present invention is 135.2%, which is 32.2% higher than that of Sample 1.

As described above, since the white light emitted from the liquid crystal display (100 of FIG. 2) according to the embodiment of the present invention has a much higher color reproduction rate than the white light emitted from the backlight unit including the general LED assembly, .

On the other hand, the liquid crystal display (100 in Fig. 2) including the quantum dot sheet (122 in Fig. 2) Oxygen is infiltrated and the QD characteristic is removed. As the QD characteristic is removed, the circulation of light at the edge of the QD sheet becomes unreliable and blue light leakage phenomenon is caused.

In the blue light leakage phenomenon, the light of the blueish color in the edge portion of the screen is seen as an image as it is.

This causes a problem of lowering the display quality of the liquid crystal display device (100 in Fig. 2).

Here, the liquid crystal display (100 of FIG. 2) according to the embodiment of the present invention uses the quantum dot sheet (122 of FIG. 2) The occurrence of the phenomenon can be prevented.

Hereinafter, each embodiment will be described in detail.

- First Embodiment

FIG. 4 is a perspective view schematically illustrating a backlight unit according to the first embodiment of the present invention, FIG. 5A is a photograph of a light leakage phenomenon of a general liquid crystal display device, FIG. 5B is a cross- This is a photograph of a state in which the light leakage phenomenon of the liquid crystal display device does not occur.

6A to 6B are perspective views schematically showing a modified example of the LED assembly according to the first embodiment of the present invention.

As shown in the figure, the LED assembly 129 is positioned along the light-incoming surface 123a of the light guide plate 123, and the LED assembly 129 includes a B-LED chip and a G fluorescent material And a plurality of second LEDs 129c including B-LED chips and Y-phosphors are mounted on the PCB 129b at a predetermined interval.

The optical sheet 121 is positioned above the R quantum dot sheet 122 and is disposed at a lower portion of the light guide plate 123. The R- (125).

Here, the plurality of second LEDs 129c are positioned at both ends in the longitudinal direction of the PCB 129b, and are positioned corresponding to both longitudinal edges of the light guide plate 123.

The cyan light mixed with the blue light emitted from the B-LED chip and the green light emitted by the G phosphor from the plurality of first LEDs 129a of the LED assembly 129 is incident on the light incidence surface 123a of the light guide plate 123, And enters the light guide plate 123 through the light guide plate 123.

A plurality of second LEDs 129c located at both ends in the longitudinal direction of the PCB 129b of the LED assembly 129 emit white light mixed with blue light emitted from the B-LED chip and yellow light emitted from the Y- And enters the light guide plate 123 through the light incidence surface 123a of the light guide plate 123. [

At this time, the cyan light incident into the light guide plate 123 is incident on the central portion of the light guide plate 123, and the white light is incident on the both side edges in the longitudinal direction of the light guide plate 123.

The cyan light and the white light incident on the light guide plate 123 are uniformly distributed in the wide area of the light guide plate 123 while traveling in the light guide plate 123 by the total internal reflection in the light guide plate 123, And is emitted to the surface light source through the upper surface.

The cyan light and the white light passing through the upper surface of the light guide plate 123 pass through the R quantum dot sheet 122. The cyan light passes through the R quantum dot sheet 122 and passes through the red quantum dot sheet 122, And processed into white light excellent in optical characteristics having high luminance and high color reproduction ratio, and is provided to the liquid crystal panel (110 in Fig. 2) via the optical sheet 121. [

The white light passes through the rim portion of the R quantum dot sheet 122. The edge of the R quantum dot sheet 122 has a blueish color due to the elimination of the quantum dot characteristic. The blueish color is canceled by the white light passing through the edge portion of the light guide plate.

Accordingly, the white light passes through the R quantum dot sheet 122 as it is, and is supplied to the liquid crystal panel (110 in Fig. 2) via the optical sheet 121. [

That is, the cyan light and the white light generated from the first and second LEDs 129a and 129c of the LED assembly 129 are processed as a planar light source through the light guide plate 123 and then transmitted through the R quantum dot sheet 122, (FIG. 2) 110 through the optical sheet 121 through the R quantum dot sheet 122 as it is.

As a result, the liquid crystal panel (110 in FIG. 2) is provided with white light having a high luminance and a high color reproduction rate, so that a high quality screen can be provided to the user.

In addition, it is possible to prevent the blue light leakage phenomenon caused by eliminating the quantum dot characteristic at the edge portion of the R quantum dot sheet 122, thereby further improving the display quality of the liquid crystal display (100 in Fig. 2).

5A and 5B. FIG. 5A is a photograph of a blue light leakage phenomenon occurring at an edge of an image of a liquid crystal display device including a general quantum dot sheet. It can be confirmed that a blue light leakage phenomenon occurs.

This is because water and oxygen permeate the edge portion of the quantum dot sheet during the cutting of the quantum dot sheet, and the quantum dot characteristic is removed at the edge portion of the quantum dot sheet, so that the circulation of light is unnecessarily blueish, As a result, a blueish color generated at the edge portion of the quantum dot sheet can be seen as an image.

On the other hand, FIG. 5B is a photograph showing an image of a liquid crystal display according to the first embodiment of the present invention, and it can be confirmed that no blue light leakage phenomenon occurs at the edge of the image.

This is because the second LED 129c that emits white light is positioned at both ends in the longitudinal direction of the PCB 129b of the LED assembly 129 and the white light emitted from the second LED 129c is incident on the quantum dot sheet 122 This is because the blueish color which is formed at the edge portion is canceled out to be removed, so that white light is provided to the edge portion of the liquid crystal panel (110 in FIG. 2).

Therefore, the display quality of the liquid crystal display (100 in Fig. 2) can be further improved.

In the first embodiment of the present invention, the second LEDs 129c formed of the B-LED chips and the Y-phosphors are disposed on only one side of the PCB 129b in the longitudinal direction of the PCB 129b, As shown in the figure, the second LED 129c may be positioned at two ends in the longitudinal direction of the PCB 129b, or the second LED 129c may be positioned at the PCB 129b In the longitudinal direction.

In the first embodiment of the present invention, the first LED 129a is formed of a B-LED chip and the G fluorescent material, the second LED 129c is formed of a B-LED chip and a Y fluorescent material, The first LED 129a is formed of only the B-LED chip, and the second LED 129c is formed of the B-LED chip and the RG fluorescent material. And the RG quantum dot sheet may be positioned on the upper side of the light guide plate 123.

When the first LED 129a is formed of a UV chip and there is no separate phosphor, the second LED 129c is a mixture of the UV chip and the RGB phosphor, and the RGB quantum dot sheet is positioned on the upper side of the light guide plate 123 .

As described above, the liquid crystal display (100 in Fig. 2) according to the first embodiment of the present invention is configured such that the LEDs 129a and 129c including the B-LED chip are not emitted from the LEDs 129a and 129b The light emitted from the LEDs 129a and 129c and the light emitted from the quantum dot sheet 122 are mixed by placing the quantum dot sheet 122 for emitting light so that the optical characteristics having high brightness and high color recall ratio Excellent white light can be realized.

Particularly, by positioning the LED 129c emitting white light without passing through the quantum dot sheet 122 at both ends of the PCB 129b, the blue light leakage corresponding to the edge portion of the quantum dot sheet 122 from which the quantum dot characteristic is removed Can be prevented.

- Second Embodiment -

7 is a perspective view schematically showing a backlight unit according to a second embodiment of the present invention.

As shown in the drawing, the LED assembly 129 including the reflection plate 125, the light guide plate 123, the PCB 129b on which the LED 129a and the LED 129a are mounted, and the quantum dot sheet 122 and the optical sheets 121 are stacked to form a backlight unit 120. FIG.

The plurality of LEDs 129a of the LED assembly 129 emit cyan light by being provided with a B-LED chip and a G fluorescent material that realize high brightness, and the quantum dot sheet 122 located above the light guide plate 123 And an R quantum dot sheet emitting red light.

In the backlight unit 120 according to the second embodiment of the present invention, a side reflector 127 is attached to three edges except the light incidence surface 123a of the light guide plate 123. The side reflector 127 is provided with an R phosphor 127a.

The light guide plate 123 may be made of a plastic material such as polymethylmethacrylate (PMMA) or a polycarbonate (PC) such as acrylic transparent resin, which is one of transparent materials capable of transmitting light, ) Series. PMMA, which has excellent transparency, weatherability, and colorability, and induces light diffusion when light is transmitted, is the most widely used.

The light guide plate 123 includes a light incident surface 123a corresponding to the LED assembly 129 and a light incident surface 123b corresponding to the light incident surface 123a and a light incident surface 123a and a light incident surface 123b, A lower surface 123f facing the surface 123e and the reflection plate 125 and opposite side surfaces 123c and 123d facing each other.

The side reflector 127 to which the R phosphor 127a is applied is attached to the light receiving surface 123b and the both side surfaces 123c and 123d of the light guide plate 123. The side reflector 127 includes an R phosphor 127a The coated one surface is attached so as to face the light-incoming surface 123b and both the side surfaces 123c and 123d of the light guide plate 123. [

The cyan light emitted from the plurality of LEDs 129a of the LED assembly 129 is incident into the light guide plate 123 through the light incident surface 123a of the light guide plate 123, The light is uniformly distributed to the wide area of the light guide plate 123 through the light guide plate 123 and emitted to the surface light source through the upper surface 123e of the light guide plate 123 by total reflection.

At this time, when the cyan light proceeding inside the light guide plate 123 reaches the light receiving surface 123b and the both side surfaces 123c and 123d of the light guide plate 123, the cyan light emitted from the R fluorescent material 127a And the light is output through the edge of the upper surface 123e of the light guide plate 123.

Therefore, the cyan light emitted to the planar light source through the upper surface 123e of the light guide plate 123 is processed into white light excellent in optical characteristics having a high luminance and a high color reproduction rate in the process of passing through the R quantum dot sheet 122, (110 in Fig. 2) via the liquid crystal panel 122.

The white light emitted along the edge of the upper surface 123e of the light guide plate 123 passes through as it is while canceling the blueish color of the edge portion of the R-point spot sheet 122 from which the Q- 121) to the liquid crystal panel (110 in Fig. 2).

As a result, the liquid crystal panel (110 in FIG. 2) is provided with white light having a high luminance and a high color reproduction rate, so that a high quality screen can be provided to the user.

In addition, it is possible to prevent the blue light leakage phenomenon caused by eliminating the quantum dot characteristic at the edge portion of the R quantum dot sheet 122, thereby further improving the display quality of the liquid crystal display (100 in Fig. 2).

In the second embodiment of the present invention, the LED 129a is formed of a B-LED chip and a G fluorescent material, and the R quantum dot sheet 122 is positioned above the light guide plate 123, The LED 129a is formed of only the B-LED chip, the RG quantum dot sheet is positioned above the light guide plate 123, and the RG fluorescent material is applied to the side reflector 127 have.

When the LED 129a is formed of a UV chip and there is no separate phosphor, the RGB quantum dot sheet may be positioned above the light guide plate 123 and the RGB fluorescent material may be applied to the side reflector 127. [

- Third Embodiment -

8 is a perspective view schematically showing a backlight unit according to the third embodiment of the present invention.

As shown in the drawing, the LED assembly 129 including the reflection plate 125, the light guide plate 123, the PCB 129b on which the LED 129a and the LED 129a are mounted, and the quantum dot sheet 122 and the optical sheets 121 are stacked to form a backlight unit 120. FIG.

The plurality of LEDs 129a of the LED assembly 129 emit cyan light by being provided with a B-LED chip and a G fluorescent material that realize high brightness, and the quantum dot sheet 122 located above the light guide plate 123 And an R quantum dot sheet emitting red light.

The backlight unit 120 according to the third embodiment of the present invention is characterized in that the R fluorescent material 128 is applied along one edge of the optical sheet 121 positioned above the R quantum dot sheet 122.

The optical sheet 121 on the light guide plate 123 includes a diffusion sheet and at least one light condensing sheet and diffuses or condenses light that has passed through the light guide plate 123 and is reflected by the liquid crystal panel 110 The R fluorescent material 128 is applied along the edge of the optical sheet 121 which is closest to the quantum dot sheet 122 among them.

Therefore, the liquid crystal display (100 of FIG. 2) according to the third embodiment of the present invention can prevent the blue light leakage phenomenon from occurring at the edge portion of the screen by the quantum dot sheet 122 while having high luminance and high color recall ratio have.

That is, the blue light emitted from the B-LED chip and the cyan light mixed with the G phosphor are emitted from the LED assembly 129 and are incident into the light guide plate 123 through the light entrance surface 123a of the light guide plate 123, The cyan light entering the inside of the light guide plate 123 spreads in the wide area of the light guide plate 123 and travels through the upper surface of the light guide plate 123, It will come out.

The cyan light emitted to the planar light source through the upper surface of the light guide plate 123 is processed into the white light excellent in optical characteristics having a high luminance and a high color reproduction rate in the course of passing through the R quantum dot sheet 122, 121) to the liquid crystal panel (110 in Fig. 2).

At this time, the cyan light passing through the rim portion of the R quantum dot sheet 122 having no quantum dot characteristic is separated from the R quantum dot sheet 122 by a sieve which cancels the blueish color appearing at the edge portion of the R quantum dot sheet 122 The cyan light is mixed with the R phosphor 128 coated along one edge of the optical sheet 121 in the course of passing through the optical sheet 121 and processed into white light And passes through the optical sheet 121.

Therefore, white light processed while passing through the optical sheet 121 is provided to the liquid crystal panel (110 in Fig. 2) along with the white light processed through the R quantum dot sheet 122, Only one white light is provided.

Accordingly, it is possible to provide a high-quality screen to the user and prevent the blue light leakage phenomenon caused by eliminating the quantum dot characteristic at the edge portion of the R quantum dot sheet 122, The display quality can be further improved.

In the third embodiment of the present invention, the LED 129a is composed of a B-LED chip and a G fluorescent material, and the R quantum dot sheet 122 is positioned above the light guide plate 123, The LED 129a is formed of only the B-LED chip, the RG quantum dot sheet is positioned on the upper side of the light guide plate 123, and the RG fluorescent material is coated on the optical sheet 121 .

When the LED 129a is formed of a UV chip and there is no separate phosphor, the RGB quantum dot sheet may be positioned on the light guide plate 123 and the RGB phosphor may be coated on the optical sheet 121. [

As described above, the liquid crystal display (100 in Fig. 2) according to the first to third embodiments of the present invention is configured such that light emitted from the LED 129a to the upper portion of the LED 129a including the B- And the light emitted from the LED 129a and the light emitted from the quantum dot sheet 122 are mixed to realize white light so that white light having high brightness and high color reproducibility, Can be implemented.

Particularly, it is possible to position the LEDs (129c in FIG. 4) where white light is emitted even though the quantum dot sheet 122 does not pass through both ends of the PCB 129b, (127 in Fig. 7) coated with the phosphor (127a in Fig. 7) is placed on the side surface (123c and 123d in Fig. 7) of the optical sheet 121, or the fluorescent material 128 It is possible to prevent blue light leakage from being generated corresponding to the edge portions of the quantum dot sheet 122 from which the quantum dot characteristic is removed.

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.

120: Backlight unit
121: Optical sheet
122: Quantum dot sheet
123: light guide plate 123a (light incidence surface)
125: reflector
129: LED assembly (129a: first LED, 129b: PCB, 129c: second LED)

Claims (7)

A liquid crystal panel;
An optical sheet positioned under the liquid crystal panel;
A quantum dot sheet disposed at a lower portion of the optical sheet and emitting first light having one of red, green, and blue or at least two of red, green, and blue mixed;
A light guide plate positioned below the quantum dot sheet;
An LED assembly including a PCB on which a plurality of first and second LEDs and a plurality of first and second LEDs are mounted, the LED assembly being positioned corresponding to the light incident surface of the light guide plate;
And a reflector disposed under the light guide plate,
Wherein the first LED includes a second light mixed with the first light to realize white light and the second LED is disposed at both ends in the longitudinal direction of the PCB to realize a white light, .
The method according to claim 1,
And the white light realized from the second LED passes through the edge of the quantum dot sheet.
The method according to claim 1,
And the second LEDs are provided at one or both ends in the longitudinal direction of the PCB, respectively, or two or three LEDs are provided at each end of the PCB.
A liquid crystal panel;
An optical sheet positioned under the liquid crystal panel;
A quantum dot sheet disposed at a lower portion of the optical sheet and emitting first light having one of red, green, and blue or at least two of red, green, and blue mixed;
A light guide plate positioned below the quantum dot sheet;
An LED assembly including a plurality of LEDs corresponding to light incident surfaces of the light guide plate and emitting a second light, and a PCB on which the plurality of LEDs are mounted;
A reflector positioned below the light guide plate;
A side reflector disposed on both sides of the light guide plate and on both sides of the light guide plate and coated with a phosphor that emits a third light that is mixed with the second light and emits white light,
And the liquid crystal display device.
5. The method of claim 4,
Wherein the phosphor is applied to one side of the side reflector so as to face the light-incident side and both sides of the light guide plate.
A liquid crystal panel;
A quantum dot sheet disposed at a lower portion of the liquid crystal panel and emitting a first light of at least two of red, green, and blue or at least two of red, green, and blue;
A light guide plate positioned below the quantum dot sheet;
An LED assembly including a plurality of LEDs corresponding to light incident surfaces of the light guide plate and emitting a second light, and a PCB on which the plurality of LEDs are mounted;
A reflector positioned below the light guide plate;
And at least one optical sheet coated with a phosphor that emits a third light that is mixed with the second light and emits white light,
And the liquid crystal display device.
The method of any of claims 4 and 6,
Wherein the first light and the second light are mixed to realize white light.

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