KR102013498B1 - Liquid Crystal Display device using high brightness film and composite sheet for liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a composite sheet for a liquid crystal display device using a high brightness film characterized in that it further comprises DBEF in a high brightness film coated with a coating layer comprising a YAG-based phosphor and a LuAG-based phosphor on the base film.

Description

Liquid crystal display device using high brightness film and composite sheet for liquid crystal display}

The present invention relates to an LCD structure using a high brightness film to which a phosphor is applied. Specifically, a composite for a liquid crystal display device and a liquid crystal display device using a high brightness film to improve luminance and color reproducibility of an LCD by using YAG and LuAG phosphors in a film. It is about a sheet.

In the past, 40-inch TVs were the mainstream, but now many consumers buy 50-inch and 60-inch TVs. After such size competition, competition for the manufacture of displays having excellent brightness and color has recently emerged.

In particular, a liquid crystal display (LCD) displays an image by using the optical characteristics of the liquid crystal. Since the liquid crystal panel displaying the image is a non-light emitting device that does not emit light by itself, the liquid crystal panel is disposed on the rear side of the liquid crystal panel together with the liquid crystal panel. It has a structure including a backlight unit (BLU) for supplying light to.

The BLU serves to illuminate the display image evenly so that the display image is visible from the back of the LCD which does not emit light. This BLU uses a direct-lit BLU, a method of evenly arranging the LED BLU behind the LCD panel, and uses the LED BLU at the left and right corners to distribute the light from the LED evenly throughout the screen. Edge type (Edge-lit BLU) is a method that reflects the reflection, but the edge type is more advantageous for slimming, which is a recent issue.

Conventional liquid crystal display device applies a brightness enhancement film to increase the contrast (contrast), the brightness enhancement film may be attached to the backlight unit by a light shielding tape. A reflective polarizing film is used as a brightness enhancing film. A reflective polarizing film is a film in which a high refractive index layer and a low refractive index layer are alternately laminated. Commercially, 3M's Dual Brightness Enhancement Film (DBEF) is used.

Conventional LCD TV using the brightness enhancement film is formed in the structure as shown in FIG. White LED layer, diffuser plate, prism sheet, DBEF film, and panel are formed in a stacked structure from the bottom. That is, the light emitted from the white LED is condensed through the prism sheet and the brightness is improved through the DBEF film.

However, there has been a need to develop a material having better brightness enhancement performance than a conventional brightness enhancement film DBEF film.

In order to improve the problems of the prior art as described above, the present invention is to provide a liquid crystal display device and a composite sheet for a liquid crystal display device using a high brightness film with a DBEF film to improve the brightness.

At this time, the liquid crystal display is characterized in that it comprises both a high brightness film and a DBEF film containing a phosphor.

The present invention provides a liquid crystal display device and a composite sheet for a liquid crystal display device using a high brightness film further comprising DBEF in a high brightness film coated with a YAG-based phosphor and a LuAG-based phosphor on a base film as a means for solving the problems. do.

In the liquid crystal display device using the high brightness film of the present invention, the amount of the YAG-based fluorescent material and the LuAG-based fluorescent material is mixed with respect to the entire coating layer, and the YAG-based fluorescent material is 10 to 40 wt%, and the LuAG-based fluorescent material is mixed by 1 to 20 wt%. .

In addition, the coating thickness of the coating layer is characterized in that 10 to 100 μm.

In addition, YAG-based phosphor is Y ₃ A1 ₅ 0 ₁₂ : Ce ^{3 +} (YAG: Ce), Tb ₃ A1 ₅ 0 ₁₂ : Ce ^{3 +} (TAG: Ce), Ca ₃ (Sc, Mg) ₂ Si ₃ O ₁₂ : Ce ³⁺ and _{Y 3 Mg 2 AlSi 2 O 12} : characterized in that the at least one of a Ce ^{+ 3.}

Also, LuAG base phosphor Lu ₃ Al ₅ O _12: characterized in that the at least one of a ^{Ce 3 +: Ce 3 +,} Tb 3 Al 5 O 12: Ce 3 + and _{Lu 2 CaMg 2 Si 3 O 12} .

In addition, the upper layer of the high brightness film is characterized in that it comprises a prism sheet.

In addition, it characterized in that it comprises a composite sheet bonded to a high-brightness film and DBEF.

In addition, a liquid crystal display device using a high brightness film, characterized in that it comprises a high brightness film, a prism sheet and a composite sheet bonded to DBEF.

In addition, the high brightness film of the composite sheet is characterized in that it comprises a PMMA particles or a back coating layer containing PMMA particles and an antistatic agent.

In addition, the PMMA particles are characterized in that it comprises 0.1 to 5wt% compared to the back coating layer.

In addition, the antistatic agent is characterized in that it comprises 0.01 to 3 wt% compared to the back coating layer.

In addition, the thickness of the back coating layer is characterized in that 1 to 10 μm.

The composite sheet for a liquid crystal display device of the present invention is characterized in that a high brightness film, a prism sheet, and a DBEF coated with a coating layer including a YAG-based phosphor and a LuAG-based phosphor on a base film are sequentially laminated with an adhesive.

In addition, the amount of the YAG-based fluorescent material and LuAG-based fluorescent material is mixed with respect to the entire coating layer, YAG-based phosphor is characterized in that 10 to 40 wt%, LuAG-based phosphor is mixed 1 to 20wt%.

In addition, the coating thickness of the coating layer is characterized in that 10 to 100 ~ m.

In addition, the high-bright film is characterized in that it comprises a back coating layer containing PMMA particles or PMMA particles and an antistatic agent.

In addition, the PMMA particles are characterized in that it comprises 0.1 to 5wt% compared to the back coating layer.

In addition, the antistatic agent is characterized in that it comprises 0.01 to 3 wt% compared to the back coating layer.

In addition, the thickness of the back coating layer is characterized in that 1 to 10 ~ m.

When the combination of the optical sheet of the present invention, that is, a high brightness film including a phosphor and a DBEF film are applied to the LCD together, excellent luminance and color reproducibility can be realized compared to an LCD using only the existing DBEF film.

1 is a schematic diagram of an LCD structure according to the prior art.
2 is a schematic diagram of an LCD structure according to the present invention.
FIG. 3 is a result of comparing luminance characteristics for each viewing angle of the general LCD TV of FIG. 1 and the LCD to which the high brightness film of the present invention is applied.
It is a schematic diagram of the process of laminating the high brightness film and another optical film of this invention.

The present invention will be described in detail below, and the following embodiments or examples are merely to illustrate, but the present invention is not necessarily limited thereto.

According to the present invention, the brightness of the LCD can be improved by using a high brightness film including a phosphor together with a DBEF film. That is, the luminance of the liquid crystal display is improved through an LCD structure including a high brightness film and a DBEF film coated with a coating layer including a YAG-based phosphor and a LuAG-based phosphor on a base film.

Specifically, according to a preferred embodiment of the present invention, the phosphor is used by using a high brightness film including both YAG (Yittrium aluminum garnet) phosphor and LuAG (Lutetium aluminum garnet) phosphor emitting yellow fluorescence in combination with DBEF film. Improve.

Substrate films used in the present invention include PET, TAC, PC, Polyimide, Acryl film and the like.

In the present invention, YAC (Yittrium aluminum garnet) -based phosphors and LuAG (Lutetium aluminum garnet) -based phosphors that emit yellow fluorescence may be used together to improve luminance and color reproducibility.

The YAG-base phosphor is _{Y 3 A1 5 0 12: Ce} 3 + (YAG: Ce), Tb 3 A1 5 0 12: Ce 3 + (TAG: Ce), Ca 3 (Sc, Mg) 2 Si 3 O 12: Ce ³⁺ and _{Y 3 Mg 2 AlSi 2 O 12} : it is preferable that at least one of a Ce ^{+ 3.}

The LuAG base phosphor _{Lu 3 Al 5 O 12: Ce} 3 +, Tb 3 Al 5 O 12: Ce 3 + and _{Lu 2 CaMg 2 Si 3 O 12} : it is preferable that at least one of a Ce ^{+ 3.}

The YAG-based phosphor and the LuAG-based phosphor are mixed at a ratio of 10 wt%: 1 wt% to 40 wt%: 20 wt%.

That is, the amount of the YAG-based phosphor and the LuAG-based phosphor is mixed in the range of 10 wt% to 40 wt% of the YAG phosphor and 1 wt% to 20 wt% of the LuAG, compared to the entire coating layer.

If the lower limit of the content of the YAG-based phosphor is less than 10wt%, the effect of improving the brightness is insignificant, and if the upper limit is more than 40wt%, the color reproducibility which is important in the LCD TV is lowered, so the YAG content is preferably in the range of 10 wt% to 40 wt%.

If the lower limit of the content of the LuAG phosphor is less than 1 wt%, the brightness enhancement effect is insignificant. If the upper limit is exceeded 20 wt%, the LuAG content is preferably in the range of 1 wt% to 20 wt% because the important color reproducibility is lowered in the LCD TV. .

Improvement of Luminance and Color Reproduction Rate According to YAG and LuAG Phosphor Contents
Division Minute Ref. DBEF
(LED TV) Ref. DBEF
( QD  TV) YAG  : LuAG
content wt% YAG  10 YAG  10
LuAG  5 YAG  10
LuAG  10 YAG  10
LuAG  20 Luminance [nit] 430 450 Luminance [nit] 430 450 500 550 X 0.2730 0.2593 X 0.2350 0.2406 0.2531 0.2749 Y 0.2925 0.2911 Y 0.2577 0.2701 0.2860 0.2970 Color reproducibility [ % ] 81.6 100 Color reproducibility [ % ] 81.3 81.8 82.4 82.6 division Ref. DBEF
(LED TV) Ref. DBEF
( QD  TV) YAG  : LuAG
content wt% YAG  20 YAG  20
LuAG  5 YAG  20
LuAG  10 YAG  20
LuAG  20 Luminance [nit] 430 450 Luminance [nit] 480 520 560 600 X 0.2730 0.2593 X 0.2550 0.2606 0.2731 0.2801 Y 0.2925 0.2911 Y 0.2877 0.2801 0.2910 0.2970 Color reproducibility [ % ] 81.6 100 Color reproducibility [ % ] 82.6 82.3 82.4 82.6 division Ref. DBEF
(LED TV) Ref. DBEF
( QD  TV) YAG  : LuAG
content wt% YAG  40 YAG  40
LuAG  5 YAG  40
LuAG  10 YAG  40
LuAG  20 Luminance [nit] 430 450 Luminance [nit] 540 550 580 620 X 0.2730 0.2593 X 0.2750 0.2980 0.3031 0.3349 Y 0.2925 0.2911 Y 0.2935 0.2966 0.3140 0.3422 Color reproducibility [ % ] 81.6 100 Color reproducibility [ % ] 81.3 81.2 81.4 81.6

A coating layer including the phosphor is prepared by combining the YAC-based phosphor and the LuAG-based phosphor with a polymer matrix for securing physical properties.

Specifically, the YAG-based phosphors and LuAG-based phosphors are uniformly dispersed in the polymer matrix to prepare a coating solution including the phosphors.

The polymer matrix may include a monofunctional urethane acrylate oligomer, a monofunctional monomer, and the like, and a photoinitiator, a leveling agent, an antifoaming agent, and the like may be added.

Examples of the photoinitiator include IG184, IG907, TPO, CP4, and the like. Of these, the preferred photoinitiators are IG184, TPO.

In particular, the physical properties refer to properties such as pencil hardness, adhesion, curl, flex resistance, and the like.

Pencil hardness: Hardness evaluation by scraping the surface of pencils of various hardness with a constant load to measure the hardness of the coating layer (standard: JIS K 5400-8.4)

Adhesion: In order to measure the adhesion between the base film and the coating layer, the coating layer is scratched at regular intervals of 10 * 10 (lattice spacing 1mm), tape is peeled off, and the adhesion between the coating layer and the base layer is evaluated (standard: JIS K 5400-8.5 )

Curl: Cut the coating film into 100mm * 100mm and measure the height of the four corners of the coating film to evaluate the curl property of the film

* If curl is severe, the film curls and deteriorates workability.

Flex resistance: Flexibility evaluation of coating film and coating film by rolling the film round on a round bar

The present invention may be applied to one side of the base film to the base film with the Mayer Bar on the base film, and then cured by irradiating UV using an electrodeless lamp, thereby manufacturing a coating layer.

In the case of coating the coating layer, the thicker the coating layer, the worse the curl characteristics, so that the resin applicable to the polymer matrix is limited. Therefore, in the case of single-side coating, the thickness of the coating layer should not be too thick.

Curl according to coating thickness section Coating thickness [㎛] 5 10 30 50 70 100 120 150 Curl [mm] 0 3 4 7 10 18 22 25

When the coating layer is coated on the base film, the thickness of the coating layer is preferably 10 to 100 μm.

If the coating layer has a coating thickness of less than 10㎛ protrudes the phosphor causing a poor appearance, if it exceeds 100㎛ curl (Curl) characteristics during coating is deteriorated because the resin applicable to the polymer matrix is limited.

In the present invention, the prism sheet 13 may be used together with the high brightness film 100 including the phosphor.

The conventional LCD TV has a structure in which light emitted from a white LED is first collected through a prism sheet, and then, through a DBEF film, brightness is improved.

On the other hand, in the case of using the prism sheet in the present invention, the light emitted from the blue LED first passes through the high-bright film including the phosphor, and the luminance is improved, and then the light is collected through the prism sheet.

The prism sheet 13 is preferably used by laminating POP (Prism On Prism, two-sheet composite film) or vertical and horizontal prism sheets, respectively.

Result of luminance confirmation by application location of HBF Measurement
Structure #One #2 # 3 #4

Luminance [nit] 784.7 629.8 182.1 58.7

As shown in Table 3 above, when the High Brightness Film (HBF) 100, which is a high brightness film including the phosphor of the present invention, is applied to the LCD, the application position of the HBF is between the light source 110 and the prism sheet 13. If there is, it can be seen that the brightness enhancement effect is maximized. Therefore, it is most preferable to apply the HBF 100 between the LED light source 110 and the prism sheet 13.

In Table 4, the brightness of 469.2 nit is shown in the case of the existing LCD TV, while the brightness is 784.7 nit when the DBEF film and the HBF are applied together, and the improvement of the brightness is about 67%.

Luminance and frontal coordinate according to the presence or absence of DBEF film when applying HBF HBF  + POP HBF  + POP + DBEF Measure
rescue

Luminance 566 nit 796nit Front X coordinate 0.253 0.280 Front Y coordinate 0.291 0.353

As shown in Table 5, when the DBEF film 14 is used together with the high brightness film 100 of the present invention, it can be seen that the luminance improvement of about 40% appears compared with the case where there is no DBEF film.

In case of using DBEF and HBF together, luminance and color reproducibility according to desirable phosphor mixing ratio division YAG 10 YAG 20 YAG 40 LuAG 5 LuAG 10 LuAG 20 LuAG 5 LuAG 10 LuAG 20 LuAG 5 LuAG 10 Luminance [nit] 650 700 750 720 760 800 750 780 Color reproducibility [%] 81.8 82.4 82.6 82.3 82.4 82.6 82 81.5

In case of using DBEF and HBF together, luminance and color reproducibility according to mixing ratio other than desirable phosphor mixing ratio (1) division Ref. DBEF Ref. DBEF YAG: LuAG YAG 50 (LED TV) (QD TV) content wt% LuAG 5 LuAG 10 LuAG 20 Luminance [nit] 430 450 Luminance [ nit ] 710 730 740 Color reproducibility [%] 81.6 100 Color reproducibility [ % ] 72.3 71.3 71.3

In case of using DBEF and HBF together, luminance and color reproducibility according to mixing ratio other than desirable phosphor mixing ratio (2) division Ref. DBEF Ref. DBEF YAG: LuAG YAG 5 (LED TV) (QD TV) content wt% LuAG 5 LuAG 10 LuAG 20 Luminance [nit] 430 450 Luminance [ nit ] 480 490 530 Color reproducibility [%] 81.6 100 Color reproducibility [ % ] 79.3 79.3 78.3

The present invention may further include a back coating layer on at least one or more of an optical film such as a prism sheet, a DBEF, a viewing angle complementary sheet (lens film, a MOP, a diffusion sheet), and a high brightness film.

By providing the irregularities on the back surface of the optical film by the particles contained in the back coating to prevent blocking with other optical sheets to improve workability, there is an effect of preventing static electricity generated by the friction in the process.

The coating crude liquid used for the back coating consists of a urethane acrylate oligomer, a monofunctional monomer, a photoinitiator, a leveling agent, a dispersing agent and PMMA particles.

The PMMA particles are preferably contained 0.1 to 5 wt% based on the total back coating. If less than 0.1wt% does not form sufficient irregularities on the back of the optical film, if it is more than 5wt% caused a loss of transmitted light due to high haze, the haze of the back coating layer is adjusted to 1 to 20% by adjusting the content of PMMA particles It is desirable to.

In addition, an anti-static agent (Anti-static) may be added as an additive to the back coating as needed. The surface resistance can be adjusted by adding the antistatic agent, and the antistatic agent is preferably included in an amount of 0.01 to 3wt% relative to the entire back coating layer. When the content of the antistatic agent is less than 0.01 wt%, the surface resistance for the antistatic is insufficient, and when the content of the antistatic agent is more than 3wt%, it will result in the addition of more than necessary, the surface resistance is increased by adding 0.01 to 3wt% of the antistatic agent It is desirable to adjust the range to 10 ¹⁰ to 10 ¹² Ohm /. When the surface resistance is 10 ¹⁰ ~ 10 ¹² Ohm /, it is possible to prevent the obstacle in the dynamic state of the film, and the effect of the charging phenomenon immediately after the charging is attenuated.

Back coating can be done by bar coating or slot-die coating.

The thickness of the coating layer during the back coating is preferably 1 to 10μm. If the thickness is less than 1 μm, sufficient irregularities are not formed on the back surface of the optical film, and thus blocking is difficult to prevent. If the thickness is more than 10 μm, the problem of transmitted light loss due to high haze occurs.

The present invention can be bonded to a plurality of films constituting the LCD in the form of a single composite sheet can form a composite sheet for a liquid crystal display device. In other words, the high brightness film (HBF) 100 and other optical films are laminated with an adhesive (lamination) to produce a composite sheet can be applied to the LCD.

The optical film may be used by selecting at least one of the prism sheet 13, the DBEF 14, and a viewing angle complementary sheet (lens film, MOP, diffusion sheet).

The adhesive is preferably an optical clear adhesive (OCA), and may be bonded by direct bonding (full lamination) or air gap bonding. In particular, the direct bonding method has a lower yield than the air gap bonding method, but has excellent optical properties and high visibility and low power consumption.

The lamination is performed by the process as shown in FIG. The optical film F1 is supplied through the first feed roller R1, and the high brightness film F2 is supplied through the second feed roller R2. The optical film (F1) passes through the adhesive coating roller (R3), the adhesive (A) is applied to at least one side of the optical film and then laminated with the high-brightness film (F2) via a paper roller (R4) composite sheet (F3) ) Is completed.

On the other hand, when two or more optical films are selected and used, the high brightness film and one optical film are first laminated by the above process, and then the other one of the optical films is repeatedly subjected to the process of sequentially laminating the composite. Form a sheet.

According to the present invention, the high brightness film 100 and the prism sheet 13 are laminated by a lamination process, and then the lamination process of adhering the laminated film and the DBEF 14 is repeated to form a high brightness film, a prism sheet, and a DBEF. Form a sheet.

The composite sheet may be formed by applying an adhesive between the high brightness film and the optical film. Specifically, when only DBEF is used in the optical film, an adhesive may be applied between the high brightness film and the DBEF to form a composite sheet. When only the prism sheet of the optical film is used, a composite sheet may be formed by applying an adhesive between the high brightness film and the prism sheet. When the prism sheet and the DBEF are used in the optical film, an adhesive may be applied between the high brightness film and the prism sheet and the prism sheet and the DBEF, respectively, to form a composite sheet. When only the viewing angle supplement sheet is used among the optical films, a composite sheet may be formed by applying an adhesive between the high brightness film and the viewing angle supplement sheet. When a prism sheet and a viewing angle complementary sheet are used among the optical films, a composite sheet may be formed by applying an adhesive between the high brightness film and the prism sheet, and between the prism sheet and the viewing angle supplementary sheet, respectively.

In the present invention, a composite sheet laminated in order by applying an adhesive between the high brightness film 100 and the prism sheet 13, and between the prism sheet 13 and the DBEF 14, respectively.

Even when forming the composite sheet of the present invention, it is possible to form a back coating layer by performing a back coating on a high brightness film.

Hereinafter, an Example is given and this invention is demonstrated in detail. The following examples are only for the detailed description of the invention, it is made clear that it is not intended to limit the scope by this.

Production Example

20 wt% of the YAG-based phosphor (Y3A15012: Ce3 +) and 2 wt% of the LuAG-based phosphor (Lu3Al5O12: Ce3 +) are mixed and stirred for 60 minutes. As the polymer matrix, a monofunctional urethane acrylate oligomer and a monofunctional monomer were used. Two kinds of photoinitiators are added to the stirred phosphor and matrix mixture. As a photoinitiator, a coating liquid is prepared by mixing IG 184 and TPO two at 5: 5, respectively, and adding 5 wt%.

The coating solution thus prepared was coated with a certain thickness on one side of a PET film with a Mayer Bar, and then irradiated for about 5 seconds using an electrodeless lamp. The amount of light irradiated at this time is preferably 1000mj or less.

Example

A light guide plate, a high brightness film including a phosphor, a prism sheet, a DBEF, and a liquid crystal panel were sequentially disposed in front of a blue LED to manufacture an LCD according to the present invention as shown in FIG. 2.

Comparative example  One

LCD was manufactured in the same manner as in Example, except that DBEF was removed.

Comparative example  2

LCD was manufactured in the same manner as in Example, except that DBEF and prism sheet were removed.

The brightness and viewing angle of the LCDs prepared according to Examples, Comparative Example 1 and Comparative Example 2 were measured, and the results are shown in Table 9.

division Example Comparative Example 1 Comparative Example 2 Luminance (nit) 784.7 559.3 175.2

As shown in Table 9, it can be seen that there is a brightness improving effect when applying the high brightness film of the present invention compared to the quantum dot TV (brightness 100%), and when the DBEF and the high brightness film are applied together (Example) You can see that it is maximized.

In addition, it can be seen from FIG. 3 that when the HBF and DBEF are applied together as in FIG. 2 compared to the general LCD TV of FIG.

Luminance Measurement Method

The brightness and color reproducibility of the brightness enhancing film of the present invention are evaluated using a liquid crystal display device and Topcon BM-7FAST color luminance meter. The actual liquid crystal display used is UN55JS8500F (Samsung, 55-inch Blue-BLU), and the basic configuration is as follows. It consists of edge type blue-LED light source, light guide plate, POP film (Prism on Prism), dual brightness enhancement film (DBEF), and liquid crystal panel. In this device, the high brightness film (HBF) of the present invention is placed between the light guide plate and the POP film to evaluate brightness and color reproducibility. In the evaluation, the distance between the BM-7FAST device and the liquid crystal display device (UN55JS8500F) is kept constant at 50 cm.

11: white LED
12: diffuser plate
13: Prism Sheet
14: DBEF
15: liquid crystal panel
16: light guide plate
100: high brightness film (HBF)
110: light source
R1: first feed roller
R2: second feed roller
R3: Glue Application Roller
R4: Lamination Roller
R5: winding roller
r: guide roller
A: Adhesive
F1: optical film
F2: High Brightness Film (HBF)
F3: Composite Sheet

Claims (19)

The substrate film includes a high brightness film and DBEF coated with a YAG-based phosphor and a LuAG-based phosphor, and the YAG-based phosphor includes Tb ₃ A1 ₅ 0 ₁₂ : Ce ³⁺ (TAG: Ce), Ca ₃ (Sc , Mg) ₂ Si ₃ O ₁₂ : Ce ³⁺ and Y ₃ Mg ₂ AlSi ₂ O ₁₂ : 10 to 40wt% of at least one of Ce ³⁺ , the LuAG phosphor is Lu ₂ CaMg ₂ Si ₃ O ₁₂ : Liquid crystal display using a high brightness film comprising Ce ³⁺ 1 ~ 20wt%. delete The liquid crystal display device of claim 1, wherein the coating layer has a coating thickness of about 10 μm to about 100 μm.
delete delete The liquid crystal display device according to claim 1, further comprising a prism sheet on an upper layer of the high brightness film. The liquid crystal display device using a high brightness film according to claim 1, further comprising a composite sheet bonded to the high brightness film and DBEF.
7. A liquid crystal display device using a high brightness film according to claim 6, comprising a high brightness film, a prism sheet and a composite sheet bonded to DBEF.
The liquid crystal display device according to claim 7 or 8, wherein the high brightness film of the composite sheet comprises a back coating layer containing PMMA particles or PMMA particles and an antistatic agent. 10. The liquid crystal display device according to claim 9, wherein the PMMA particles comprise 0.1 to 5 wt% of the back coating layer. 10. The liquid crystal display device according to claim 9, wherein the antistatic agent comprises 0.01 to 3 wt% of the back coating layer. The liquid crystal display device of claim 9, wherein the back coating layer has a thickness of 1 to 10 μm. The substrate film was laminated with a high brightness film, a prism sheet, and a DBEF coated with a coating layer including a YAG-based phosphor and a LuAG-based phosphor in order with an adhesive, wherein the YAG-based phosphor is Tb ₃ A1 ₅ 0 ₁₂ : Ce ³⁺ (TAG: Ce), Ca ₃ (Sc, Mg) ₂ Si ₃ O ₁₂ : Ce ³⁺ and Y ₃ Mg ₂ AlSi ₂ O ₁₂ : 10 to 40wt% of at least one of Ce ³⁺ , the LuAG-based phosphor is Lu ₂ CaMg ₂ Si ₃ O ₁₂ : A composite sheet for a liquid crystal display device comprising 1 to 20wt% Ce ³⁺ . delete The composite sheet of claim 13, wherein the coating layer has a coating thickness of about 10 μm to about 100 μm. The composite sheet for a liquid crystal display device according to claim 13, wherein the high brightness film comprises PMMA particles or a back coating layer containing PMMA particles and an antistatic agent. The composite sheet of claim 16, wherein the PMMA particles comprise 0.1 to 5 wt% of the back coating layer. The composite sheet of claim 16, wherein the antistatic agent comprises 0.01 to 3 wt% of the back coating layer. The composite sheet of claim 16, wherein the back coating layer has a thickness of 1 to 10 μm.

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