KR20210082756A - Fluorescence sheet and display device having thereof - Google Patents

Abstract

According to the present invention, provided is an optical sheet to prevent color shift in an area between LEDs. A fluorescent sheet includes: a first fluorescent layer which converts input monochromatic light into white light and a second fluorescent layer thereon; and a first intermediate layer disposed between the first fluorescent layer and the second fluorescent layer.

Description

Fluorescent sheet and display device having same {FLUORESCENCE SHEET AND DISPLAY DEVICE HAVING THEREOF}

The present invention relates to a fluorescent sheet and a display device having the same, and more particularly, to a fluorescent sheet capable of preventing color shift and a display device having the same.

The flat panel display device is being applied not only to various portable electronic devices such as mobile phones, tablet PCs, and notebook computers, but also to large-area electronic devices such as TVs. The flat panel display includes a liquid crystal display and an organic light emitting display.

Among these flat panel displays, liquid crystal displays are widely used due to their advantages such as light weight, thinness, and low power consumption, but have disadvantages in that they have lower contrast and luminance compared to organic light emitting displays.

The present invention has been made in view of the above points, and by providing a mini LED or microphone LED that emits monochromatic light and a fluorescent sheet that converts monochromatic light into white light, a fluorescent sheet and display capable of reducing manufacturing cost and improving luminance and contrast ratio The purpose is to provide a device.

Another object of the present invention is to provide a fluorescent sheet and a display device capable of minimizing the color shift of light in the region between the LEDs by outputting white light to the region between the LEDs by scattering from the fluorescent sheet, thereby preventing image quality deterioration due to the color shift. will do

In order to achieve the above object, a fluorescent sheet according to the present invention includes a first fluorescent layer for converting input monochromatic light into white light and a second fluorescent layer thereon; and a first intermediate layer disposed between the first fluorescent layer and the second fluorescent layer.

The input monochromatic light may be a blue monochromatic light, the first fluorescent layer and the second fluorescent layer may each be a yellow fluorescent material, the input monochromatic light may be a blue monochromatic light, and the first fluorescent layer and the second fluorescent layer may be a red fluorescent material and a green light, respectively. It may be composed of a fluorescent material. In addition, the input monochromatic light is ultraviolet light, and the first fluorescent layer and the second fluorescent layer may be composed of a green fluorescent material and a blue fluorescent material, respectively.

The first and second fluorescent layers and the first intermediate layer have different refractive indices, and in this case, the first intermediate layer is made of PET (PolyEthylene Terephthalate). Scattering particles may be distributed on at least a surface of the second fluorescent layer, and at least one second intermediate layer and a third fluorescent layer disposed on the second fluorescent layer may be alternately disposed.

In addition, a display device according to the present invention includes a display panel; a plurality of LEDs disposed under the display panel to emit monochromatic light; and a fluorescent sheet disposed between the display panel and the LED to convert monochromatic light emitted from the LED to white light and output the fluorescent sheet.

The LED may be a mini LED or a micro LED, and may be an LED emitting blue light or an LED emitting ultraviolet light.

An upper portion of the optical sheet further includes a luminance enhancement film that transmits P waves among white light output from the optical sheet and reflects and scatters S waves, wherein the luminance enhancement film is Advanced Polarizing Collimaton Film (APCF) or Double Brightness Enhancement (DBEF). film).

In the present invention, a mini LED or a microphone LED emitting monochromatic light is provided, and a fluorescent sheet is provided on the upper part to convert the light emitted from the LED into white light and supply it to the liquid crystal panel. Compared to that, it is possible to reduce the manufacturing cost and improve the luminance and contrast ratio.

Furthermore, in the present invention, the fluorescent sheet is composed of a plurality of fluorescent layers and an intermediate layer therebetween so that the white light that is converted from the monochromatic light emitted from the LED and is outputted is scattered, so that the output white light is supplied through the region between the adjacent LEDs. do. Accordingly, since the white light is mixed with the color-shifted light output from the region between the adjacent LEDs and supplied to the liquid crystal panel, it is possible to minimize the deterioration of image quality due to the color shift in this region.

1 is an exploded perspective view of a display device according to a first embodiment of the present invention.
2 is a cross-sectional view of a display device according to a first embodiment of the present invention;
3A is a plan view of a liquid crystal panel according to the present invention, and FIG. 3B is a cross-sectional view taken along line II′ of FIG. 3A.
4 is a cross-sectional view showing the structure of an LED according to the present invention.
FIG. 5 is an enlarged cross-sectional view of area A of FIG. 2 .
6 is an enlarged cross-sectional view of a partial region of a display device according to a second exemplary embodiment of the present invention.
7 is a view illustrating that light is supplied to a liquid crystal panel in the display device according to the first embodiment of the present invention.
8 is a view illustrating that light is supplied to a liquid crystal panel in the display device according to the second embodiment of the present invention.
9 is a spectrum of light in the region between LEDs in the first embodiment of the present invention.
10 is a view showing transmission and reflection of light in a luminance-enhanced film according to a second embodiment of the present invention;
11 is a view showing a fluorescent sheet according to a third embodiment of the present invention.
12 is a view showing a fluorescent sheet according to a fourth embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the technical field to which the present invention belongs It is provided to fully inform the possessor of the scope of the invention, and the scope of the rights of the present invention should be determined by the appended claims.

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

1 is an exploded perspective view of a display device 100 according to a first embodiment of the present invention, and FIG. 2 is an assembled cross-sectional view.

1 and 2 , the display device 100 according to the present invention includes a display panel 200 and a backlight for supplying light to the display panel.

The display panel 200 is a liquid crystal panel. Although not shown in the drawing, the liquid crystal panel 200 is composed of a first substrate and a second substrate and a liquid crystal layer therebetween to realize an image as a signal is applied from the outside.

The backlight is disposed on the lower side of the liquid crystal panel 200 and includes an LED substrate 130 on which a plurality of Light Emitting Devices (LEDs) 140 emitting monochromatic light are mounted, and an LED disposed under the liquid crystal panel 200 . A diffusion plate 132 for diffusing the light emitted from 140, a fluorescent sheet 150 disposed on the diffusion plate 132 to convert the monochromatic light emitted from the LED 140 into white light, and the liquid crystal An optical sheet (134a) disposed between the panel 200 and the fluorescent sheet 150 to diffuse the white light converted by the fluorescent sheet 150 again and a prism sheet 134b to collect the diffused light ( 134).

After the LED substrate 130, the diffuser plate 132, the fluorescent sheet 150, and the optical sheet 134 of the backlight are accommodated in the lower cover 160, the lower cover 160 is connected to the guide panel 162 and the upper part. It is assembled as it is coupled with the cover 164 .

A liquid crystal panel 200 , a diffusion plate 132 , a fluorescent sheet 150 and an optical sheet 134 are disposed on the guide panel 162 . The guide panel 162 is formed in a rectangular frame having a predetermined width, and multi-stage steps are formed so that edge regions of the diffusion plate 132 , the fluorescent sheet 150 , and the optical sheet 134 are placed on the steps, respectively. In addition, the edge region of the liquid crystal panel 200 is placed on the upper surface of the guide panel 162 and assembled.

At this time, although not shown in the drawings, a double-sided adhesive is disposed on the upper surface of the guide panel 162 so that the liquid crystal panel 200 can be attached to the upper surface of the guide panel 162 to be fixed.

3A is a plan view of the liquid crystal panel 200, and FIG. 3B is a cross-sectional view taken along line I-I' of FIG. 3A. Substantially, N×M pixel areas are arranged in a matrix in the liquid crystal panel 200 according to the present invention, but only one pixel area is shown in the drawings for convenience of explanation.

As shown in FIG. 3A , the liquid crystal panel 200 includes a plurality of gate lines 203 and data lines 205 defining a plurality of pixel regions, thin film transistors disposed in each pixel region, and the pixel region. It is composed of a common electrode 222 and a pixel electrode 224 disposed on the .

The thin film transistor has a gate electrode 211 connected to the gate line 203 to which a scan signal is applied from the outside, and is disposed on the gate electrode 211 and is activated as a scan signal is applied to the gate electrode 211 to activate a channel. The semiconductor layer 213 forming the semiconductor layer 213 is disposed on the semiconductor layer 213 and, when the semiconductor layer 213 is activated, an image signal applied through the data line 205 is supplied to the pixel electrode 224 of the pixel region. and a source electrode 215 and a drain electrode 216 .

The common electrode 222 is formed to have substantially the same shape as the shape of the pixel area over the entire area of the pixel area, and a common electrode line 223 is disposed between adjacent pixel areas to form a common electrode line 223 disposed in adjacent pixel areas. Electrodes 222 are electrically connected.

The pixel electrode 224 is disposed to overlap the common electrode 222 with an insulating layer interposed therebetween. In this case, a portion of the pixel electrode 224 is removed to form a plurality of strip-shaped slits 224a in a direction parallel to the gate line 203 or slightly inclined to the gate line 203 . When an image signal is applied to the pixel electrode 224 through the source electrode 215 and the drain electrode 216 of the thin film transistor, the two long sides of the slit 224a of the pixel electrode 224 and the common electrode 222 below An electric field substantially perpendicular to the surface of the display panel is generated therebetween, and by this electric field, liquid crystal molecules of the liquid crystal layer are aligned, and an image can be realized by adjusting the transmittance of light passing through the liquid crystal layer.

As shown in FIG. 3B , a thin film transistor is formed on the first substrate 230 . The thin film transistor includes a gate electrode 211 formed on the first substrate 230 , a gate insulating layer 232 formed over the entire first substrate 230 on which the gate electrode 211 is formed, and the gate insulating layer 232 . ) formed on the semiconductor layer 213 , and a source electrode 215 and a drain electrode 216 formed on the semiconductor layer 213 .

The gate insulating layer 232 may be made of an inorganic insulating material having good interfacial and insulating properties, such as SiNx or SiOx, and the gate electrode 211 is formed of Cr, Mo, Ta, Cu, Ti, Al or Al alloy. It may be made of the same metal. In addition, the semiconductor layer 213 may be formed of an amorphous semiconductor layer such as a-Si or a polycrystalline semiconductor layer such as p-Si. Also, the semiconductor layer 213 may be formed of an oxide semiconductor layer. The source electrode 215 and the drain electrode 216 may be formed of a metal such as Cr, Mo, Ta, Cu, Ti, Al, or an Al alloy.

A common electrode 222 is formed on the gate insulating layer 232 . In this case, the common electrode 222 is made of a transparent conductive material such as indium tin oxide (ITO) or indium tin oxide (IZO) and has a shape similar to that of the pixel region over the entire pixel region. The common electrode 222 may be formed on the first substrate 230 .

A passivation layer 236 is formed over the entire first substrate 230 on which the thin film transistor is disposed, and a pixel electrode 224 is disposed on the passivation layer 236 . The protective layer 236 may be formed of an organic insulating material such as photoacrylic, and the pixel electrode 224 may be formed of a transparent conductive material such as ITO or IZO, or an opaque metal. The pixel electrode 224 is provided with a plurality of slits 224a. The slit 224a is formed by etching a portion of the pixel electrode 224 in a band shape having a set width. Although a specific number of slits 224a are formed in the pixel area in the drawing, the number of slits 224a is not limited to a specific number, and may be determined by various factors such as the size or resolution of the display device, and a cell gap.

On the second substrate 240 , a black matrix 242 for preventing image quality from being deteriorated due to light transmission to an area on which an image is not displayed and a color filter layer 244 for realizing actual colors are disposed, and the first substrate The liquid crystal layer 250 is formed between the 230 and the second substrate 240 to complete the liquid crystal panel 200 .

Although not shown in the drawings, a first polarizing plate and a second polarizing plate are respectively provided on the lower surface and the upper surface of the liquid crystal panel 200 . In this case, the optical axis directions of the first polarizing plate and the second polarizing plate may be perpendicular to each other or may be horizontal. The light supplied from the backlight to the liquid crystal panel 200 is input as first polarized light by the first polarizing plate, and the polarization state of the light is changed while passing through the liquid crystal layer of the liquid crystal panel 200 and output through the second polarizing plate. An image is realized by adjusting the transmittance of the light.

Referring back to FIGS. 1 and 2 , the LED 140 disposed under the liquid crystal panel 200 is a mini LED or a micro LED that emits monochromatic light. In general, LEDs emitting white light are manufactured and supplied in the form of a package. For example, since such a white LED package is composed of an LED element emitting monochromatic light and a fluorescent layer, the unit price is increased. Moreover, since a typical white LED package is configured in a size of about 1000 μm, when applied to a liquid crystal display device, only about tens to hundreds of them can be used due to the limited size of the liquid crystal display device, and more white LED packages are arranged There was a limit to what could be done.

On the other hand, since the mini LED or micro LED is a device emitting monochromatic light, the manufacturing cost is relatively low compared to the white LED package. In addition, since the mini LED has a size of about 200 to 700 μm and the micro LED has a size of 100 μm or less, when applied as a backlight for a liquid crystal display, a much larger number, for example, thousands, is used in the backlight compared to a white LED package. can be provided. Accordingly, the liquid crystal display employing the mini-LED or micro-LED can significantly improve the luminance and contrast ratio compared to the liquid crystal display employing the general white LED package.

Hereinafter, the LED employed in the present invention will be described in detail with reference to the referenced drawings.

4 is a diagram showing the structure of the LED 140 applied to the display device according to the present invention.

As shown in FIG. 4, the LED 140 of the display device according to the present invention is a mini-LED having a size of about 200 to 700 μm or a micro LED having a size of 100 μm or less, including an undoped GaN layer 144, the An n-type GaN layer 145 disposed on a GaN layer 144, an active layer 146 having a Multi-Quantum-Well (MQW) structure disposed on the n-type GaN layer 145, the active layer 146, the A p-type GaN layer 147 disposed on the active layer 145, an ohmic contact layer 148 formed of a transparent conductive material and disposed on the p-type GaN layer 147, a portion of the ohmic contact layer 148 A portion of the n-type GaN layer 145 exposed by etching a portion of the p-type electrode 141 , the active layer 146 , the p-type GaN layer 147 and the ohmic contact layer 148 in contact with It consists of an n-type electrode 143 in contact.

The n-type GaN layer 145 is a layer for supplying electrons to the active layer 146 and is formed by doping the GaN semiconductor layer with an n-type impurity such as Si.

The active layer 146 is a layer in which injected electrons and holes are combined to emit light. Although not shown in the drawing, in the multi-quantum well structure of the active layer 146, a plurality of barrier layers and well layers are alternately arranged, and the well layer is composed of an InGaN layer and the barrier layer is composed of GaN, but is limited thereto. no.

The p-type GaN layer 147 is a layer for injecting holes into the active layer 146 , and is formed by doping a GaN semiconductor layer with p-type impurities such as Mg, Zn, and Be.

The ohmic contact layer 148 is for ohmic contact between the p-type GaN layer 147 and the p-type electrode 141, and includes Indium Tin Oxide (ITO), Indium Galium Zinc Oxide (IGZO), A transparent metal oxide such as Indium Zinc Oxide (IZO) may be used.

The p-type electrode 141 and the n-type electrode 143 may be formed of a single layer or a plurality of layers made of at least one of Ni, Au, Pt, Ti, Al, and Cr or an alloy thereof. .

In the LED 140 having this structure, as a voltage is applied to the p-type electrode 141 and the n-type electrode 143 , the active layer 146 is formed from the n-type GaN layer 145 and the p-type GaN layer 147 . ), when electrons and holes are respectively injected into the active layer 146, excitons are generated in the active layer 146, and as these excitons decay, the lowest unoccupied molecular orbital (LUMO) and highest occupied molecular orbital (HOMO) of the emission layer are formed. The light corresponding to the energy difference is generated and emitted to the outside.

At this time, the wavelength of the light emitted from the LED 140 can be controlled by adjusting the thickness of the barrier layer of the multi-quantum well structure of the active layer 146 .

Although not shown in the drawings, the LED 140 is manufactured by forming a buffer layer on a substrate and growing a GaN thin film on the buffer layer. In this case, as a substrate for the growth of the GaN thin film, sapphire, silicon (Si), GaN, silicon carbide (SiC), gallium arsenide (GaAs), zinc oxide (ZnO), or the like may be used.

In addition, the buffer layer prevents quality deterioration due to lattice mismatch that occurs when the n-GaN layer 120, which is an epi layer, is directly grown on the substrate when the GaN thin film growth substrate is made of a material other than the GaN substrate. For this purpose, AlN or GaN may be used.

The n-type GaN layer 145 may be formed by growing a GaN layer 144 undoped with impurities and then doping an n-type impurity such as Si on the undoped thin film. In addition, the p-type GaN layer 147 may be formed by growing an undoped GaN thin film and then doping p-type impurities such as Mg, Zn, and Be.

Although the LED 140 is formed in a specific structure in the drawing, the present invention is not applied only to the LED 140 having this structure, but may be applied to LEDs of various structures such as a vertical structure LED and a horizontal structure LED.

Referring back to FIGS. 1 and 2 , the monochromatic light emitted from the LED 140 is supplied to the liquid crystal panel 200 through the diffusion plate 132 , the fluorescent sheet 150 , and the optical sheet 134 .

FIG. 5 is an enlarged cross-sectional view of region A of FIG. 2 , showing the LED 140 , the diffusion plate 132 , the fluorescent sheet 150 , and the optical sheet 134 . A structure disposed on the LED 140 will be described in detail with reference to this drawing.

As shown in FIG. 5 , the diffusion plate 132 is disposed on the LED 140 to be spaced apart from each other by a predetermined distance. The diffusion plate 132 is disposed to prevent lattice mura. When the LED 140 is disposed under the liquid crystal panel 200 to supply light to the liquid crystal panel 200 as in the present invention, the luminance of the liquid crystal panel 200 varies according to the position of the LED 140 . .

That is, when the distance between the LED 140 and the LED 140 is too large because the spreading angle of the light emitted from the LED 140 is narrow, the light output from the LED 140 to the region is relatively small. Therefore, the luminance of the region between the adjacent LEDs 140 decreases the luminance of the region above the LED 140 (eg, the region included in the light divergence angle of the LED 140 ). In addition, when the distance between adjacent LEDs 140 is too small, dark lines and bright lines are formed in a grid shape in which the luminance of the region between the LEDs 140 is greater than the luminance of the region above the LED 140 due to the overlap of emitted light. lattice failure occurs.

The diffusion plate 132 diffuses the light input from the LED 140 to prevent such a grid failure. As the diffusion plate 132, an acrylic resin having good light transmittance and light resistance, a styrene-acrylic copolymer resin, a styrene resin, a styrene-acrylonitrile resin, a polycarbonate resin, etc. may be used alone or in combination of two or more. However, the present invention is not limited thereto.

In addition, a plurality of light diffusion particles may be dispersed inside the diffusion plate 132 , and an optical pattern for scattering incident and emitted light may be formed on an upper surface and/or a lower surface of the diffusion plate 132 . In this case, the optical pattern may be a concave groove or a convex part. The optical pattern may be uniformly or non-uniformly formed over the entire upper and/or lower surface of the diffusion plate 132 , and may be formed only in a region corresponding to the LED 140 .

A fluorescent sheet 150 is disposed on the diffusion plate 132 . The fluorescent sheet 150 converts the monochromatic light emitted from the LED 140 into white light. In the present invention, an LED that emits blue light is used as the LED 140 and a fluorescent sheet that converts blue light into white light is used as the fluorescent sheet 150, but the present invention is not limited thereto. It is also possible to use a fluorescent sheet that converts the

The fluorescent sheet 150 includes a fluorescent material. The fluorescent material absorbs a part of the monochromatic light output from the LED 140 and is excited to output light of a different wavelength, and the monochromatic light input from the LED 140 and transmitted and light of another wavelength generated by being excited are mixed to produce a final result. white light is output.

When the LED 140 emits blue light, the fluorescent sheet 150 may be composed of a yellow fluorescent material, and the fluorescent sheet 150 may be composed of a red fluorescent material and a green fluorescent material. Alternatively, when the LED 140 emits ultraviolet light, the fluorescent sheet 150 may be composed of a green fluorescent material and a blue fluorescent material.

Although not shown in the drawings, the fluorescent material of the fluorescent sheet 150 may be applied to a transparent film. At this time, as the transparent film, silicone resin, polymethyl pentene resin, polyether sulfon resin, polyether imide resin, polyarylate resin, polymethyl It may be composed of a methacrylate (polymethyl methacylate) resin and a mixture thereof, but is not limited thereto.

The fluorescent sheet 150 may be formed to have a thickness of about 250-350 μm, preferably about 280-320 μm, but is not limited thereto.

In addition, the fluorescent sheet 150 is formed to have the same size as that of the liquid crystal panel 200 . That is, the fluorescent sheet 150 is formed in a size large enough to cover all of the plurality of LEDs 140 disposed below, so that the monochromatic light emitted from the plurality of LEDs 140 is all in one fluorescent sheet 150 . ), then converted to white light and output.

In the case of a general white light LED package that emits white light rather than a mini LED or micro LED, a fluorescent layer must be formed on each LED package, thereby increasing the manufacturing cost. On the other hand, in the present invention, if only a plurality of monochromatic LEDs 140 and a single fluorescent sheet 150 are provided, all the monochromatic light output from the plurality of LEDs 140 can be converted into white light, which greatly reduces the overall manufacturing cost. be able to do

An optical sheet 134 is disposed on the fluorescent sheet 150 . The optical sheet 134 improves the efficiency of white light output from the fluorescent sheet 160 and supplies it to the liquid crystal panel 200 . The optical sheet 134 includes a diffusion sheet 134a for diffusing the light output from the fluorescent sheet 160 and a prism for condensing the light diffused by the diffusion sheet so that uniform light is supplied to the liquid crystal panel 200 . made of a sheet 134b. At this time, the diffusion sheet 134a is provided with one sheet, but the prism sheet 134b is composed of two prism sheets in which prisms cross each other perpendicularly in the x and y-axis directions, and refracts light in the x, y-axis directions. to improve the straightness of the light.

As described above, in the display device according to the first embodiment of the present invention, a mini LED or micro LED emitting monochromatic light is configured as a light source, and a fluorescent sheet 150 is provided thereon to emit white light to the liquid crystal panel 200 . can be supplied to Accordingly, compared to a display device having a general white light LED package that outputs white light, manufacturing cost can be significantly reduced, and luminance and contrast ratio are significantly improved.

6 is a partial cross-sectional view of a display device according to a second exemplary embodiment of the present invention, and is an enlarged view of area A of FIG. 2 . Since the structure of this embodiment is similar to that of the first embodiment shown in FIG. 2 , the description of the same configuration is omitted or only the different configuration will be simply described in detail.

As shown in FIG. 6 , in the display device of this embodiment, a plurality of LEDs 440 are disposed under the liquid crystal panel, and a diffusion plate 432 is disposed thereon. In this case, the LED 440 is a mini-LED or micro-LED that emits monochromatic light, for example, blue light.

A fluorescent sheet 450 for converting monochromatic light emitted from the LED 440 into white light is disposed on the diffusion plate 430 .

The fluorescent sheet 450 includes a first fluorescent layer 452 , a second fluorescent layer 455 , and an intermediate layer 454 therebetween.

When the LED 440 is a blue LED, the first fluorescent layer 452 and the second fluorescent layer 455 may be each made of a yellow fluorescent material or may be composed of a red fluorescent material and a green fluorescent material. Alternatively, when the LED 440 is an ultraviolet LED, the first fluorescent layer 452 and the second fluorescent layer 455 may be formed of a green fluorescent material and a blue fluorescent material, respectively. In this case, the first fluorescent layer 452 and the second fluorescent layer 455 are made of the same fluorescent material, but are not limited thereto and may be composed of different fluorescent materials.

Also, the first fluorescent layer 452 and the second fluorescent layer 455 may be formed to have the same thickness, but are not limited thereto, and may be formed to have different thicknesses.

For example, each of the first fluorescent layer 452 and the second fluorescent layer 455 may be formed to a thickness of 40-60 μm, but is not limited thereto. In addition, the intermediate layer 454 may be formed to a thickness of about 40-60 μm. In this embodiment, the fluorescent sheet 450 may be formed to a thickness of about 120-180 μm.

In the case of the first embodiment of the present invention, the fluorescent sheet 150 is formed to a thickness of about 280-320 μm, whereas in this embodiment, the fluorescent sheet 450 is formed to a thickness of about 120-180 μm. Since the thickness of the fluorescent sheet 450 of this embodiment is significantly reduced compared to the example, the thickness of the backlight of this embodiment can be reduced compared to that of the first embodiment, thereby making it possible to manufacture a thin display device.

The intermediate layer 454 is made of a material having a refractive index different from that of the first and second fluorescent layers 452 and 455 , so that light emitted from the LED 440 passes through the fluorescent sheet 450 . In this case, light is refracted and output at the interface between the first and second fluorescent layers 452 and 455 and the intermediate layer 454 . That is, in the present invention, the monochromatic light emitted from the LED 440 is not simply converted to white light in the fluorescent sheet 450 and output, but the converted white light is scattered and output. The research area is expanded.

Polyethylene terephthalate (PET) is used as the intermediate layer 454, but is not limited thereto, and other transparent resins may be used.

An optical sheet 434 including one diffusion sheet 434a and two prism sheets 434b is disposed on the fluorescent sheet 450, and a luminance enhancing film 490 is disposed thereon. The luminance enhancement film 490 is a reflective polarizing film such as Advanced Polarizing Collimaton Film (APCF) or Double Brightness Enhance Film (DBEF), and enhances the luminance of light supplied to the liquid crystal panel to improve light efficiency.

As described above, in this embodiment, the fluorescent sheet 450 is composed of two fluorescent layers 452 and 455 and an intermediate layer 454 therebetween, and a luminance enhancing film 490 is provided on the optical sheet 434. , the reason will be described with reference to FIGS. 7 and 8 as follows.

7 is a view illustrating that light is supplied to the liquid crystal panel in the display device according to the first embodiment of the present invention, and FIG. 8 is a diagram illustrating that light is supplied to the liquid crystal panel in the display device according to the second embodiment of the present invention. It is a drawing.

As shown in FIG. 7 , in the display device according to the first embodiment, blue light emitted from the LED 140 is emitted at a divergence angle of θ. In addition, the LEDs 140 are arranged at an interval of d1.

The monochromatic light emitted by the LED 140 is diffused by the diffusion plate 132 , converted into white light in the fluorescent sheet 150 , and then supplied to the liquid crystal panel through the optical sheet 134 . At this time, although the divergence angle of the light emitted from the LED 140 is θ, the area where the light is diffused from the diffusion plate 132 and the optical sheet 134 and the actual light is spread becomes larger, so that the liquid crystal in one LED 140 is The area of the light supplied to the panel becomes larger.

The most ideal light supply is when the LEDs 140 are arranged at a set interval d (d1 = d), emitted from the LED 140 and directly supplied to the liquid crystal panel through the diffusion plate 132 and the optical sheet 134 . This is to prevent the light from being overlapped with the light emitted from the adjacent LED 140 . Also, there should be no region to which the light emitted from the LED 140 is not directly supplied.

However, in order for the light emitted from the LED 140 to be directly and uniformly supplied to all regions of the liquid crystal panel as described above, the LED 140 must be disposed in the backlight at a high density. In this case, due to the increase in the number of LEDs 140 , manufacturing cost will increase.

Therefore, in the first embodiment of the present invention, the interval d1 between the LEDs 140 is made larger than the set interval d (d1 > d). In this case, the region corresponding to the region between the adjacent LEDs 140 . In the liquid crystal panel of , the light emitted from the LED 140 is not directly input, but reflected light is input.

That is, as shown in FIG. 7 , the light emitted from the LED 140 and supplied to the liquid crystal panel is reflected by the optical sheet 134 and then input to the fluorescent sheet 150 again. In addition, the light input to the fluorescent sheet 150 is reflected back by the fluorescent sheet 150 and then supplied to the liquid crystal panel. Among the light reflected from the fluorescent sheet 150 and supplied back to the liquid crystal panel, the light reflected to the region corresponding to the direct light supply region of the LED 140 , that is, the divergence angle θ of the LED 140 is the LED 140 . ), the ratio is very small compared to the light emitted from the liquid crystal panel and directly supplied to the liquid crystal panel, so the effect of the reflected light within the direct light supply region of the LED 140 is minimal.

However, since the ratio of reflected light is very large in the area corresponding to the area between the adjacent LEDs 140 , that is, in the area where the reflected light is irradiated rather than the direct light supply area of the LED 140 , the effect of the reflected light increases.

At this time, the light incident on the fluorescent sheet 150 by reflection excites the fluorescent material of the fluorescent sheet 150 , and the excited light is output from the shape sheet 150 . In the region where the light is directly supplied from the LED 140, the ratio of the light excited by reflection is much smaller than that of the directly supplied light, and is mixed with the directly input monochromatic light and output as white light, whereas between the LEDs 140 In , the light excited by reflection is not output as white light, and a color shift occurs in this region.

For example, when the LED 140 emits blue light and the fluorescent sheet 150 is made of a yellow fluorescent material, yellow light may be output in the region between the LEDs 140, and the LED 140 emits blue light, When the fluorescent sheet 150 is composed of a red fluorescent material and a green fluorescent material, a mixed light of green light and red light may be output in a region between the LEDs 140 . The supply of the color-shifted white light is an important cause of lowering the image quality of the image displayed on the liquid crystal panel.

This color shift becomes more severe as the distance between the LEDs 140 increases. 9 is a diagram illustrating a spectrum of light supplied to a region between adjacent LEDs 140 in the display device according to the first embodiment of the present invention. In this case, the horizontal axis represents the wavelength and the vertical axis represents the relative intensity of light. In addition, the green line is the spectrum when the distance between the LEDs 140 is 1.35 cm, the blue line is the spectrum when the distance between the LEDs 140 is 1.85 cm, and the red line is the spectrum when the distance between the LEDs 140 is 2.59. This is the spectrum in cm.

As shown in FIG. 9 , the intensity of the peak values of all spectra is almost the same in the blue wavelength band of about 435-445 nm, while adjacent in the green wavelength band of about 535-545 nm and the red wavelength band of 630-640 nm. As the distance between the LEDs 140 increases, the intensity of the peak value increases. This means that the intensity of green light and red light in white light increases as the distance between the adjacent LEDs 140 increases. As the distance between the adjacent LEDs 140 increases, the white light supplied to the liquid crystal panel changes to green and red. It can be seen that a color shift occurs.

In the second embodiment of the present invention, such color shift is prevented. In the display device according to the second embodiment of the present invention, the fluorescent sheet 450 includes two fluorescent layers 452 and 455 and an intermediate layer 454 therebetween. In this case, since the phosphor layers 452 and 455 and the intermediate layer 454 are made of materials having different refractive indices, light is scattered at the interface between the phosphor layers 452 and 455 and the intermediate layer 454 . That is, in the second embodiment of the present invention, scattering occurs twice at the interface between the first fluorescent layer 452 and the intermediate layer 454 and at the interface between the second fluorescent layer 455 and the intermediate layer 454 .

Accordingly, among the white light emitted from the LED 440 and directly supplied to the liquid crystal panel, the diffuser plate 432 , the fluorescent sheet 450 , and the optical sheet 434 are diffused and scattered to correspond to the region between the adjacent LEDs 440 . The amount of white light supplied to the liquid crystal panel increases. Therefore, the light output after color change by the fluorescent sheet 350 due to reflection between the adjacent LEDs 440 is not supplied to the liquid crystal panel as it is, but rather the region between the adjacent LEDs 440 by diffusion and scattering. It is supplied by mixing with the white light that is output.

At this time, since the ratio of the color shifted light by reflection by the white light emitted from the LED 450 and directly output is very low, substantially white light is supplied to the liquid crystal panel in the area between the adjacent LEDs 450, and thus the color shift Accordingly, it is possible to prevent deterioration of image quality of the display device.

The phosphor sheet 450 is formed of the phosphor layers 452 and 455 and the intermediate layer 454 having different refractive indices to scatter light at the interface. In this regard, if the intermediate layer of the fluorescent sheet 450 according to the present invention has a refractive index different from that of the fluorescent material and can transmit light without changing characteristics of light, various materials other than PET may be used.

In addition, in the present invention, color shift can be further reduced by providing the luminance enhancement film 490 in addition to the fluorescent sheet 450 , which will be described with reference to FIG. 10 .

As shown in FIG. 10 , the luminance-enhanced film 490 is a reflective polarizing plate. Among the input light, P waves are transmitted and supplied to the liquid crystal panel, and S waves are reflected. The S wave reflected from the luminance enhancing film 490 is again reflected from the upper surface of the fluorescent sheet 450 or inside the fluorescent sheet 450, that is, the first fluorescent layer 452 and the second fluorescent layer 455 and the intermediate layer ( 454) at the interface.

When the S wave incident on the fluorescent sheet 450 is reflected from the fluorescent sheet 450 , its polarization component is changed and is again input to the luminance enhancing film 490 . In addition, the P wave of the light reflected back to the luminance enhancing film 490 passes through the luminance enhancing film 490 and supplied to the liquid crystal panel, and the S wave is reflected back to the fluorescent sheet 450 .

In the present invention, by repeating the above process, all the light emitted from the LED 440 is changed to a P wave and supplied to the liquid crystal panel. That is, the white light emitted from the LED 440 and converted by the fluorescent sheet 450 repeats transmission and reflection between the fluorescent sheet 450 and the luminance enhancement film 490, so that the white light of the P-wave component is supplied to the liquid crystal panel. .

When the white light repeats transmission and reflection between the fluorescent sheet 450 and the luminance-enhanced film 490 , a portion of the white light is scattered from the fluorescent sheet 450 and the luminance-enhanced film 490 and adjacent LEDs 440 . It is input to the region between, the scattered white light and the color-shifted light from the fluorescent sheet 450 are mixed, output, and supplied to the liquid crystal panel.

Therefore, compared to the liquid crystal display of the first embodiment in which only the color-shifted light is supplied to the liquid crystal panel corresponding to the area between the adjacent LEDs 440 , white light is transmitted to the liquid crystal panel corresponding to the area between the adjacent LEDs 440 . In the liquid crystal display device of the second embodiment to which the color shifted light is supplied, it is possible to prevent image quality deterioration due to color shift.

Furthermore, in the liquid crystal display according to the second embodiment of the present invention, white light is repeatedly reflected between the fluorescent sheet 450 and the luminance-enhanced film 490, so that white light is transmitted between the fluorescent sheet 450 and the luminance-enhanced film 490. spawned several times in Accordingly, the amount of white light that is scattered and input to the region between the adjacent LEDs 440 is further increased, so that it is possible to more reliably prevent image quality deterioration due to color shift.

As described above, in the display device according to the second embodiment of the present invention, the fluorescent sheet 450 is composed of two fluorescent layers 452 and 455 and an intermediate layer 454 therebetween. The intermediate layer 454 is formed of materials having different refractive indices. Accordingly, light scattering at the interface between the first fluorescent layer 452 and the intermediate layer 454 and the second fluorescent layer 455 and the intermediate layer 454 is increased, and output from the LED 440 is directly supplied to the liquid crystal panel. By allowing the generated light to be supplied to the region between the adjacent LEDs 440, color shift in this region can be minimized.

In addition, the liquid crystal panel in the region between the LEDs 440 by providing a luminance enhancing film 490 on the fluorescent sheet 450 and repeating the reflection of light between the fluorescent sheet 450 and the luminance enhancing film 490 . It is possible to minimize the color shift of the light applied to the .

Table 1 below is a table showing the color coordinates of light output to a region between adjacent LEDs. The light output from the fluorescent sheet 150 according to the first embodiment of the present invention and the fluorescent sheet 450 according to the second embodiment of the present invention are shown in Table 1 below. ) is the color coordinate of the light output from

pitch H1.35/V1.35 H.1.85/V1.82 H2.59/V2.55 color coordinates Wx Wy Wx Wy Wx Wy first embodiment 0.203 0.181 0.209 0.194 0.216 0.208 second embodiment 0.200 0.178 0.206 0.191 0.213 0.205

At this time, the distances (pitch) between the LEDs are respectively horizontal (H) 1.35, vertical (V) 1.35, horizontal (H) 1.85, vertical (V) 1.82, horizontal (H) 2.59, vertical (V) ) is 2.55.

In the color coordinate, an increase in Wx means an increase in color shift to red, and an increase in Wy means an increase in color shift to green.

As shown in Table 1, when the pitch (interval) between LEDs increases in both the first and second embodiments, the Wx and Wy values of the color coordinates increase, so it can be seen that the red and green color shifts are severe, respectively. have. In addition, when the polarizing sheet 450 of the second embodiment is applied, the color shift of the second embodiment is lower than that of the first embodiment, regardless of the pitch between the LEDs, and compared to the first embodiment, about 3/1000 color shift is reduced.

As such, in this embodiment, the color shift of white light supplied to the liquid crystal panel corresponding to the region between adjacent LEDs can be minimized by using the two-layered fluorescent layers 452 and 455 and the intermediate layer 454 therebetween.

11 is a view showing the structure of the fluorescent sheet 550 of the liquid crystal display according to the third embodiment of the present invention.

11, the fluorescent sheet 550 of this embodiment is composed of a first fluorescent layer 552, a second fluorescent layer 555, and an intermediate layer 554 therebetween. Each of the first fluorescent layer 552 and the second fluorescent layer 555 may be composed of a yellow fluorescent material, or may be composed of a red fluorescent material and a green fluorescent material. Also, the first fluorescent layer 552 and the second fluorescent layer 555 may be formed of a green fluorescent material and a blue fluorescent material, respectively.

The intermediate layer 554 is made of a transparent resin having a refractive index different from that of the first and second fluorescent layers 552 and 555, so that light passing through the fluorescent sheet 550 can pass through the first fluorescent layer 552. ) and the intermediate layer 554 , and at the interface between the second fluorescent layer 555 and the intermediate layer 554 , scattering due to a difference in refractive index occurs. PET may be used as the intermediate layer 554, but is not limited thereto.

Scattering particles 557 are dispersed on the upper surface of the second fluorescent layer 555 . The scattering particles 557 may be composed of beads and may be uniformly or non-uniformly distributed over the entire upper surface.

The scattering particles 557 scatter the white light output through the fluorescent sheet 550 . Due to the scattering of the white light, the area to which the white light is integrated is expanded, and the white light is supplied to the area between the adjacent LEDs.

Although the scattering particles 557 are distributed on the surface of the second fluorescent layer 555 in the drawing, the scattering particles 557 may be distributed over the entire area of the second fluorescent layer 555 .

12 is a view showing the structure of the fluorescent sheet 650 of the liquid crystal display according to the fourth embodiment of the present invention.

12, the fluorescent sheet 650 of this embodiment has a first fluorescent layer 552, a first intermediate layer 654, a second fluorescent layer 655, a second intermediate layer 657, and a third fluorescent layer. Layers 658 are stacked one after the other.

In this case, each of the first to third fluorescent layers 652 , 655 , and 658 may be composed of a yellow fluorescent material, or may be composed of a red fluorescent material and a green fluorescent material. In addition, the first to third fluorescent layers 652 , 655 , and 658 may be formed of a green fluorescent material and a blue fluorescent material, respectively.

The first and second intermediate layers 654 and 657 are respectively formed between the first fluorescent layer 652 and the second fluorescent layer 655 and between the second fluorescent layer 655 and the third fluorescent layer 658 . The first and second intermediate layers 654 and 657 are each made of a transparent resin having a refractive index different from that of an adjacent fluorescent layer, so that light passing through the fluorescent sheet 650 is transmitted through the first fluorescent layer 652 and the first intermediate layer ( The interface of 654 , the interface between the second fluorescent layer 655 and the first intermediate layer 654 , the interface between the second fluorescent layer 655 and the second intermediate layer 657 , and the third fluorescent layer 658 and the second intermediate layer Scattering due to a difference in refractive index occurs between the interfaces 657 , and white light outputting the fluorescent sheet 650 is supplied to the region between the LEDs by this scattering.

In particular, compared to the fluorescent sheet 450 according to the second embodiment, since the fluorescent layer and the intermediate layer are added one by one in the fluorescent sheet 650 of the present embodiment, the white light outputting the fluorescent sheet 650 is the same as that of the second embodiment. More scattering occurs compared to the fluorescent sheet 450 . Accordingly, by outputting the fluorescent sheet 650 by scattering, the amount of white light supplied to the region between the LEDs increases, so that color shift in this region can be more effectively prevented.

As described above, in the fluorescent sheet 650 according to the present invention, the more scattering of the output white light occurs, the more the amount of white light supplied to the area between the LEDs increases, so that color shift in this area can be prevented more effectively. be able to Accordingly, only three phosphor layers 652, 655, and 658 and two intermediate layers 654 and 657 are alternately disposed in the drawing, but more phosphor layers and intermediate layers may be alternately disposed with each other.

As described above, in the present invention, a mini-LED or a microphone LED emitting monochromatic light is provided, and a fluorescent sheet is provided on the upper part to convert the light emitted from the LED into white light and supply it to the liquid crystal panel, so the existing white LED package It is possible to reduce the manufacturing cost and improve the luminance and contrast ratio compared to the case of using

Furthermore, in the present invention, the fluorescent sheet is composed of a plurality of fluorescent layers and an intermediate layer therebetween so that the white light that is converted from the monochromatic light emitted from the LED and is outputted is scattered, so that the output white light is supplied through the region between the adjacent LEDs. do. Accordingly, since the white light is mixed with the color-shifted light output from the region between the adjacent LEDs and supplied to the liquid crystal panel, it is possible to minimize the deterioration of image quality due to the color shift in this region.

130: LED substrate 132: diffuser plate
134: optical sheet 140: LED
150: fluorescent sheet 200: liquid crystal panel

Claims (14)

a first fluorescent layer for converting input monochromatic light into white light and a second fluorescent layer thereon; and
A fluorescent sheet comprising a first intermediate layer disposed between the first fluorescent layer and the second fluorescent layer.
The fluorescent sheet of claim 1 , wherein the input monochromatic light is a blue monochromatic light, and the first fluorescent layer and the second fluorescent layer are each a yellow fluorescent material.
The fluorescent sheet of claim 1, wherein the input monochromatic light is blue monochromatic light, and the first fluorescent layer and the second fluorescent layer are each composed of a red fluorescent material and a green fluorescent material.
The fluorescent sheet of claim 1 , wherein the input monochromatic light is ultraviolet light, and the first fluorescent layer and the second fluorescent layer are each composed of a green fluorescent material and a blue fluorescent material.
The fluorescent sheet of claim 1, wherein the first and second fluorescent layers and the first intermediate layer have different refractive indices.
The fluorescent sheet of claim 5, wherein the first intermediate layer is made of PET (PolyEthylene Terephthalate).
The fluorescent sheet according to claim 1, further comprising scattering particles provided on at least a surface of the second fluorescent layer.
According to claim 1,
at least one second intermediate layer disposed over the second fluorescent layer; and
The fluorescent sheet further comprising at least one third fluorescent layer alternately disposed with the second intermediate layer on the second intermediate layer.
display panel;
a plurality of LEDs disposed under the display panel to emit monochromatic light; and
A display device comprising the fluorescent sheet of claim 1 , which is disposed between the display panel and the LED and converts white light from the monochromatic light emitted from the LED to the liquid crystal panel.
The display device according to claim 9, wherein the LED is a mini LED or a micro LED.
The display device of claim 10 , wherein the LED is an LED emitting blue light or an LED emitting ultraviolet light.
The display device of claim 9 , further comprising: a luminance enhancement film disposed on the optical sheet to transmit P waves and reflect S waves among white light output from the optical sheet.
The display device of claim 12 , wherein the luminance-enhanced film is an Advanced Polarizing Collimaton Film (APCF) or a Double Brightness Enhance Film (DBEF).
10. The method of claim 9,
a diffusion plate disposed between the LED and the fluorescent sheet; and
The display device further comprising an optical sheet disposed between the fluorescent sheet and the display panel.

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