KR20180056582A - liquid crystal display device for improving brightness and composite sheet for liquid crystal display - Google Patents

Abstract

The present invention relates to a liquid crystal display device having enhanced brightness and including a backlight unit and a liquid crystal panel. The backlight unit comprises: a reflection plate for preventing loss of light; a light source for generating the light; a light guide plate for converting the light emitted from the light source into the light of a surface light source and emitting the converted light to the liquid crystal panel; and an optical sheet positioned above the light guide plate to change optical characteristics of the light emitted from the light guide plate. The optical sheet includes a dual brightness enhancement film (DBEF), a prism sheet, and a high-brightness film containing 10 to 40 wt% of a LuAG phosphor.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a composite sheet for a liquid crystal display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display (LCD) having improved brightness, and more particularly, to a liquid crystal display including a dual brightness film (DBEF: Dual Brightness Enhancement Film) A liquid crystal display device having improved brightness and a composite sheet for a liquid crystal display device.

Recently, the display market is evolving from a large-size and high-resolution competition to a color competition, and therefore, interest in displays capable of achieving excellent color is increasing.

OLED (Organic Light-Emitting Diode), which is widely regarded as the next generation display, can achieve the color reproduction rate up to 100% of NTSC. However, the present LCD shows 70% color reproduction rate to be.

Accordingly, although a method using a quantum dot is applied to improve the color gamut of an LCD, there is a problem that a sealing process through a barrier film must be accompanied by inherent characteristics of quantum dots susceptible to moisture and oxygen.

On the other hand, in the LCD, a luminance enhancement film is applied in order to increase the contrast. The brightness enhancement film can be attached to a back light unit (BLU) using a light shielding tape. The reflection type polarizing film is a film in which a high refractive index layer and a low refractive index layer are alternately repeatedly laminated, and commercially available is a dual brightness enhancement film (DBEF) ) Are used.

1, the conventional LCD structure includes a white LED 21 as a light source, a diffuser plate 31, a prism sheet 41, and a DBEF (not shown) sequentially disposed in front of the white LED 21 51 and a liquid crystal panel 61. Therefore, the light emitted from the white LED 21 is diffused by the diffusion plate 31, is condensed through the prism sheet 41, and the brightness is improved while passing through the DBEF 51.

However, recently, as the resolution of the display is increased, the number of pixels is increased, and the luminance is decreased. In particular, since the structure of the backlight is structurally impossible to further apply the LED for improving the luminance of the structure of the display, the necessity of the LCD structure capable of improving the brightness even under the low power is more urgently required to be.

Korean Patent Publication No. 10-2013-0072792 Korean Patent No. 10-1663280

It is an object of the present invention to provide a liquid crystal display device having improved luminance including a high luminance film using a LuAG-based phosphor together with a double luminance film (DBEF).

According to an aspect of the present invention, there is provided a liquid crystal display including a light guide plate, a prism sheet, a DBEF, and a liquid crystal panel, wherein the light guide plate and the DBEF A high brightness film is disposed on at least one of the prism sheet and the DBEF, and the high brightness film includes a LuAG-based phosphor in the base film.

In this case, the liquid crystal display may further include a light source, and the light source may be a blue LED.

In this case, the high-luminance film may contain 10 to 40 wt% of LuAG-based fluorescent material in the base film.

In this case, the LuAG base phosphor _{Lu 3 Al 5 O 12: Ce} 3 +, Tb 3 Al 5 O 12: Ce 3 + or _{Lu 2 CaMg 2 Si 3 O 12} : be at least one selected from Ce ³⁺ have.

In this case, the light guide plate, the high luminance film, the prism sheet, and the DBEF may be sequentially arranged in the liquid crystal display device.

In this case, the light guide plate, the prism sheet, the high luminance film, and the DBEF may be sequentially arranged in the liquid crystal display device.

In this case, the high-brightness film may include a back coating layer including PMMA and an antistatic agent on one side.

In this case, the PMMA may include 0.1 to 5 wt%.

In this case, the antistatic agent may include 0.01 to 3 wt%.

The present invention also provides a composite sheet for a liquid crystal display, comprising a high luminance film containing a LuAG-based phosphor, a prism sheet and a DBEF in the base film, wherein the high luminance film, the prism sheet and the DBEF are laminated together to provide.

In this case, the high-brightness film may include a back coating layer including PMMA and an antistatic agent on one side.

The high-luminance film of the present invention is a film which plays a role of increasing the luminance by the phosphor being expressed in Blue LED by adding the phosphor in the base film. In order to improve the brightness, a brightness enhancement film is disposed between the light source and the prism sheet in the LCD structure in which the DBEF is applied, so that the light emitted from the light source is provided to the prism sheet in an improved brightness by the brightness enhancement film, The viewing angle can be improved.

1 is a schematic view of a structure of a liquid crystal display device according to the prior art
2 is a schematic view of a structure of a liquid crystal display device according to Embodiment 1 of the present invention.
3 is a schematic view of a liquid crystal display device according to a second embodiment of the present invention.
4 is a view showing a high luminance film of the liquid crystal display structure shown in FIG.
FIG. 5 is a graph showing the structure of a conventional liquid crystal display device and the luminance according to the viewing angle according to the structure of the liquid crystal display device according to the present invention.
6 is a schematic view showing a manufacturing process of the composite sheet according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic view of a liquid crystal display device according to a first embodiment of the present invention, FIG. 3 is a schematic view of a liquid crystal display device according to a second embodiment of the present invention, and FIG. FIG. 2 is a view showing a high-luminance film of a liquid crystal display device structure.

2 and 3, a liquid crystal display device according to the present invention includes a reflection plate 20 for preventing light loss, a light source 30 for generating light, a light source 30 for converting light emitted from the light source into a surface light source A light guide plate 40 for emitting the light to the liquid crystal panel, and optical sheets positioned on the light guide plate and changing the optical characteristics of light emitted from the light guide plate.

The optical sheets include a double luminance film (DBEF) 60, a prism sheet 50, and a high luminance film containing 10 to 40 wt% of LuAG-based fluorescent material.

2, the light source 30 emits light used for realizing visual information through the liquid crystal panel 70. The liquid crystal display 70 includes a liquid crystal display Structure, and a blue LED may be used as the light source 30 in the present invention.

In this case, the light guide plate 40 may be disposed between the light source 30 and the high luminance film 10 to guide the light emitted from the light source 30 to the high luminance film 10.

2, only the light source 30 is disposed in a direct-type configuration, but it is also possible to configure the light source 30 in an edge-type configuration.

The prism sheet 50 is disposed in front of the light guide plate 40 for condensing light guided by the light guide plate 40.

The DBEF 60 is disposed in front of the prism sheet 50 for improving the brightness of the liquid crystal display device.

In this case, the prism sheet 50 and the DBEF 60 can be disposed in the opposite manner. That is, the DBEF 60 may be disposed in front of the light guide plate 40, and the prism sheet 50 may be disposed in front of the DBEF 60.

In addition, the high-brightness film 10 according to the present invention may be disposed between the prism sheet 50 and the DBEF 60 as shown in FIG.

The liquid crystal panel 70 is disposed at the forefront of the liquid crystal display device structure for converting light into visual information and emitting the light to the outside.

The light source 30, the prism sheet 50, the DBEF 60, the liquid crystal panel 70, the reflection plate 20, and the light guide plate 40, which are commonly used, can be applied as they are, , And is not particularly limited.

The high brightness film 10 is provided between the light guide plate 40 and the prism sheet 50, between the light guide plate 40 and the DBEF 60, between the prism sheet 50 and the DBEF 60, Or the like.

Specifically, the high-luminance film 10 includes the LuAG-base phosphor 116 in the base film 100 as shown in Fig.

The base film 100 may be selected from a polyethylene terephthalate (PET) film, a triacetylcellulose (TAC) film, a polycarbonate (PC) film, a polyimide film, or an acrylic film , And the present invention is not limited to the above examples.

LuAG based fluorescent material 116 is to be added to improve the _{brightness, Lu 3 Al 5 O 12:} Ce 3+, Tb 3 Al 5 O 12: Ce 3 + or _{Lu 2 CaMg 2 Si 3 O 12} : Ce 3 + And the like.

If the content of the LuAG-based fluorescent material 116 is less than 10 wt%, the desired luminance enhancement effect can not be exhibited. If the content of the LuAG-based fluorescent material 116 is more than 40 wt% The color reproduction rate may be lowered.

In addition, the present invention may further comprise a back coating layer on the high-luminance film.

The high brightness film is provided with concavity and convexity by the particles contained in the back coating layer to prevent blocking with other optical sheets to improve workability and to prevent static electricity caused by friction in the process.

The coating solution used for the back coating layer comprises conventional urethane acrylate oligomer, monofunctional monomer, photoinitiator, leveling agent, dispersant and PMMA particles.

The PMMA particles are preferably contained in an amount of 0.1 to 5 wt% with respect to the entire back coating layer. When the amount of the PMMA particles is less than 0.1 wt%, sufficient irregularities can not be formed on the back surface of the high-brightness film. When the amount of the PMMA particles is more than 5 wt%, the transmitted light loss due to the high haze occurs. .

An anti-static additive may be added to the back coat layer as needed. The surface resistance can be controlled by adding the antistatic agent. The antistatic agent is preferably contained in an amount of 0.01 to 3 wt% with respect to the total amount of the back coat layer. When the content of the antistatic agent is less than 0.01 wt%, the surface resistance for preventing static electricity is insufficient. When the antistatic agent content is more than 3 wt%, an excessive amount of the antistatic agent is added excessively. It is preferable to adjust the resistance to be in the range of 10 ¹⁰ to 10 ¹² Ohm / □. When the surface resistance is in the range of 10 ¹⁰ to 10 ¹² Ohm / □, it is possible to prevent the film from being damaged in the dynamic state, and there is an effect that the charging phenomenon immediately after charging is immediately attenuated.

Back coating of the back coating layer can be performed by a method such as bar coating and slot-die coating.

The thickness of the coating layer upon back coating is preferably 1 to 10 mu m. When the thickness is less than 1 占 퐉, sufficient irregularities are not formed on the back surface of the optical film, preventing blocking. On the other hand, when the thickness is more than 10 占 퐉, there is a problem of transmission light loss due to high haze.

The high-brightness film 10 as described above may be selected from the group consisting of polyethylene terephthalate (PET), triacetylcellulose (TAC), polycarbonate (PC), polyimide, and acrylic at least any one of resin, _{Lu 3 Al 5 O 12: Ce} 3 +, Tb 3 Al 5 O 12: Ce 3 + or _{Lu 2 CaMg 2 Si 3 O 12} : Ce , at least one of LuAG-base phosphor is selected from the ³⁺ (114) are mixed by 10 to 40 wt% to prepare a mixture.

The mixture is prepared by a casting process in a conventional film manufacturing method to prepare a base film 100 containing the LuAG-based phosphor 116.

In the conventional casting process according to the present invention, a thermoplastic chip produced through a polymerization process is melted and a certain width is discharged onto a T-die to form a sheet, followed by biaxial stretching to produce a stretched film.

The liquid crystal display of the present invention can be used as a composite sheet in which a prism sheet, a DBEF, and a high luminance film included in a backlight unit are adhered together by a common lamination process in a backlight unit. Sheet, DBEF, and high-brightness film can be manufactured by adhering with an adhesive in the lamination process, and it is preferable to use a transparent adhesive (OCA, Optical Clear Adhesive) or a direct bonding (full lamination) .

In particular, the direct bonding method has a lower yield compared to the air gap bonding method, but has the advantage of high visibility due to excellent optical characteristics and low power consumption.

The lamination process is performed by the manufacturing process shown in FIG.

The first supply film F1 is supplied through the first supply roller R1 and the second supply film F2 is supplied through the second supply roller R2. The first supply film F1 passes through the adhesive application roller R3 and is coated on at least one surface of the first supply film with the adhesive A and then passes through the second roller film R4 via the second supply film F2, And the laminated film (F3) is completed.

The first supply film F1 or the second supply film F2 refers to at least one film selected from a prism sheet, a DBEF, or a high-luminance film.

Therefore, the composite film F3 in which at least one of the first supply film F1 and the second supply film F2, which are selected from a prism sheet, a DBEF, or a high-luminance film, is laminated is formed by laminating a prism sheet and a high- Or a laminated film of a DBEF film and a high-luminance film, or a laminated film (F3) of a prism sheet and a DBEF film laminated together.

The composite film (F3) in which the prism sheet and the high-brightness film are laminated, the DBEF film and the high-brightness film are laminated, or the prism sheet and the DBEF film are laminated is made of at least one selected from a prism sheet, DBEF, And the lamination process are repeated to form a composite sheet including a prism sheet, a DBEF film, and a high luminance film.

As described above, the present invention can be applied to a liquid crystal display by fabricating a plurality of films into a single composite sheet through at least one lamination process for convenience of processing.

Hereinafter, the present invention will be described in more detail with reference to the following embodiments. It is to be understood that the same is by way of illustration and example only and is not to be taken by way of limitation.

Manufacturing example

Manufacturing example  One

900 kg of a PET chip of Mw = 40,000 g / mol prepared by the polymerization process was melted and 100 kg of Lu ₃ Al ₅ O ₁₂ : Ce ^{3 +} phosphor was precisely dispersed in a melted PET chip with a high-temperature mixer, To form a sheet, and a PET film containing 10 wt% of Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is prepared through a biaxial stretching process.

Manufacturing example  2

800 kg of a PET chip of Mw = 40,000 g / mol prepared by the polymerization process was melted and 200 kg of Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor was precisely dispersed in a melted PET chip using a high-temperature mixer. To form a sheet, and a PET film containing 20 wt% of Lu ₃ Al ₅ O ₁₂ : Ce ^{3 +} phosphor is prepared through a biaxial stretching process.

Manufacturing example  3

700 kg of a PET chip of Mw = 40,000 g / mol prepared by a polymerization process was melted and 300 kg of Lu ₃ Al ₅ O ₁₂ : Ce ^{3 +} phosphor was precisely dispersed in a melted PET chip using a high-temperature mixer. To form a sheet, and a PET film containing 30 wt% of Lu ₃ Al ₅ O ₁₂ : Ce ^{3 +} phosphor is prepared through a biaxial stretching process.

Manufacturing example  4

600 kg of a PET chip of Mw = 40,000 g / mol prepared by a polymerization process was melted and 400 kg of Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor was precisely dispersed in a melted PET chip with a high-temperature mixer. To form a sheet, and a PET film containing 40 wt% of Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is prepared through a biaxial stretching process.

The brightness and color reproducibility of the PET films produced by Production Examples 1 to 4 are shown in Table 1 below.

Luag
Content wt% Production Example 1 Production Example 2 Production Example 3 Production Example 4 Luminance [nit] 610 660 690 720 Color Reproduction [%] 81.1 82.4 82.1 81.1

It can be seen that the luminance increases as the content of the LuAG-based phosphor increases.

Example

Example  One

The PET film prepared in Production Example 1 was cut into A4 size, and then a high brightness film (HBF) was placed on a blue LED device (LCD module with the structure shown in FIG. 2) and a POP film (Prism on Prism) (DBEF) was placed thereon, and the luminance of the fluorescent substance-containing base film was measured through a luminance measuring device (BM-7 FAST color intensity meter, Japan Topcon) to obtain a front luminance of 764.7 nit there was.

Example  2

The PET film prepared in Production Example 1 was cut into A4 size, and then a POP module (Prism on Prism) was placed on a blue LED device using a LCD module and a panel as shown in FIG. 3, (DBEF) was prepared, and the luminance of the fluorescent substance-containing base film was measured through a luminance measuring apparatus (BM-7 FAST color intensity meter, Topcon, Japan) to obtain a front luminance of 609.8 nit.

Comparative Example

1, the brightness of the fluorescent substance-containing base film was measured through a luminance measuring device (BM-7 FAST color intensity meter, Topcon, Japan), and the luminance of the front face of 469.2 nit I could get the brightness

As can be seen from Examples 1 and 2, when the DBEF and the luminance enhancement film are applied together with the conventional LCD TV, the brightness enhancement effect is further maximized.

10: high luminance film 20: reflector
30: light source 31: white LED
40: light guide plate 41: diffusion plate
50, 51: prism sheet 60, 61: DBEF
70, 71: liquid crystal panel 100: substrate film
116: LuAG-based phosphor R1: first supply roller
R2: second supply roller R3: adhesive application roller
R4: Lapping roller R5: Wrapping roller
r: Guide roller A: Adhesive
F1: first supply film F2: second supply film
F3: Laminating film

Claims (12)

In a liquid crystal display including a light guide plate, a prism sheet, a backlight unit including a DBEF, and a liquid crystal panel,
A high luminance film is disposed between at least one of the light guide plate and the prism sheet, between the light guide plate and the DBEF, and between the prism sheet and the DBEF, and the high luminance film includes a LuAG base phosphor in the base film A liquid crystal display device having improved brightness. The method according to claim 1,
Wherein the liquid crystal display window further comprises a light source, and the light source is a blue LED. The method according to claim 1,
Wherein the high-luminance film contains the LuAG-based phosphor in an amount of 10 to 40 wt% in the base film.
The method according to claim 1,
The LuAG base phosphor _{Lu 3 Al 5 O 12: Ce} 3 +, Tb 3 Al 5 O 12: Ce 3 + or _{Lu 2 CaMg 2 Si 3 O 12} : in that the at least one selected from Ce ^3+, characterized A liquid crystal display device having improved brightness. The method according to claim 1,
Wherein the light guide plate, the high luminance film, the prism sheet, and the DBEF are sequentially arranged in the liquid crystal display device. The method according to claim 1,
Wherein the light guide plate, the prism sheet, the high luminance film, and the DBEF are sequentially arranged in the liquid crystal display device. The method according to claim 1,
Wherein the high-brightness film includes a back coating layer including PMMA and an antistatic agent on one surface thereof. 8. The method of claim 7,
And the PMMA is contained in an amount of 0.1 to 5 wt%. 8. The method of claim 7,
Wherein the antistatic agent comprises 0.01 to 3 wt% of the antistatic agent. [8] The liquid crystal display of claim 7, wherein the thickness of the back coating layer is 1 to 10 [mu] m. A composite sheet for a liquid crystal display device, comprising a high luminance film including a LuAG-based phosphor, a prism sheet and DBEF in the base film, wherein the high brightness film, the prism sheet and the DBEF are laminated together. 12. The method of claim 11,
Wherein the high brightness film comprises a back coating layer including PMMA and an antistatic agent on one side thereof.

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