KR100961858B1 - Reflecttive plarizer, backlight unit and liquid crystal including the same - Google Patents

Abstract

The present invention relates to a broadband reflective polarizer, a backlight unit having the same, and a liquid crystal display device.

The broadband reflective polarizer of the present invention transmits the first polarized light and the second polarized light of at least one or more unpolarized light of the white light emitted from the light source and forms a wavelength band having a greater light intensity than the other wavelength bands, while remaining of the remaining unpolarized light. A reflective polarizing film that transmits one polarized light and reflects the second polarized light; And an absorbing polarizing film that transmits the first polarized light incident from the reflective polarizing film and absorbs the second polarized light.

Therefore, the present invention has an advantage that the optimum color expression can be expected because the unpolarized light having a large light intensity is emitted from the reflective polarizing film and the absorbing polarizing film appropriately from the white light emitted from the light source.

Reflective polarizer, reflective polarizing film, absorption polarizing film, optical sheet, diffusion sheet.

Description

Broadband reflective polarizer, backlight unit and liquid crystal display having the same {REFLECTTIVE PLARIZER, BACKLIGHT UNIT AND LIQUID CRYSTAL INCLUDING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadband reflective polarizer, a backlight unit having a same, and a liquid crystal display device. More particularly, a broadband reflective polarizer capable of expecting optimal color expression by appropriately adjusting any polarization having a large light intensity, and a backlight having the same A unit and a liquid crystal display device.

Generally, a liquid crystal display injects a liquid crystal between the glass plates in which the transparent electrode was formed, and has a structure which arrange | positioned the polarizing film before and behind the said glass plate. The polarizing film used for such a liquid crystal display is manufactured by making an iodine, a dichroic dye, etc. adsorb | suck to a polyvinyl alcohol film, and extending this in a fixed direction.

However, the polarizing film manufactured as described above absorbs light vibrating in one direction and passes only light vibrating in the other direction to make linearly polarized light. Therefore, the efficiency of a polarizer cannot theoretically exceed 50%, and becomes the biggest factor which lowers the efficiency of a liquid crystal display.

Therefore, a technique of using a cholesteric liquid crystal having a circularly polarized light separation function as a reflective polarizing film has been proposed. Such a cholesteric liquid crystal has a spiral rotational direction and a circular polarization direction of the liquid crystal, and a wavelength of the spiral pitch of the liquid crystal. It has the characteristic of selective reflection reflecting only light of circularly polarized light. Therefore, by using such selective reflection characteristics, it is possible to manufacture a highly efficient polarizing film by transmitting and separating only specific circularly polarized light of natural light of a certain wavelength band and reflecting and reusing the rest.

At this time, the transmitted circularly polarized light is converted into linearly polarized light by passing through the λ / 4 wave plate, and the liquid crystal display device having a high transmittance can be obtained by matching the direction of the linearly polarized light with the transmission direction of the absorption type polarizer used in the liquid crystal display. . In other words, when the cholesteric liquid crystal film is used as a linear polarizer in combination with a λ / 4 wave plate, there is no theoretical loss of light. Therefore, a theory of the cholesteric liquid crystal film used in comparison with the case of using a conventional absorption type polarizer that absorbs 50% of light alone is theoretical. In the image, the brightness can be improved by 2 times.

In the prior art using such a cholesteric liquid crystal, the cholesteric liquid crystal film layers, each of which is provided with selective reflection characteristics by inducing horizontal alignment, are laminated in the order of short wavelength to long wavelength so that the visible light region is selected as the selective reflection wavelength region. A broadband cholesteric liquid crystal film manufacturing technology (application number: 10-1998-0000498, 10-1999-0065640, 10-2004-0078416, 10-2004-0060853) is proposed.

In addition, two or more cholesteric liquid crystal polymer layers are stacked on each other in a state of being in close contact with each other in a long and short order based on the center wavelength of the reflected light, and the long-wavelength side of the circularly polarized light separating layer having the spiral pitch in the thickness direction and the center wavelength of the reflected light Also disclosed is a polarizer manufacturing technique (application number: 10-1998-0043207, 10-1998-0017719, 10-1999-0006902, 10-1998-0019146, 10-2005-7015572) including a phase difference layer disposed in the same.

FIG. 1 is an exemplary view of a liquid crystal display device including the above-described conventional reflective polarizer, and the conventional liquid crystal display device includes a backlight element A and a liquid crystal panel B, as shown in FIG. The backlight device A includes a light guide plate 12 and a diffusion plate 13 that diffuse and emit light incident from the LED light source 11, and a prism sheet that collects and emits light incident from the diffusion plate 13. (15), a reflective polarizing film 16 for selectively reflecting light incident from the prism sheet 15, and a phase delay layer 18 for converting circularly polarized light transmitted through the reflective polarizing film 16 into linearly polarized light. do.

 In FIG. 1, reference numeral 12a denotes a reflecting plate, and 19 denotes an absorption type reflective polarizing film.

The conventional reflective polarization film 16 constituting such a liquid crystal display device has a selective reflection function for all of the blue, green, and red light to secure the function of the broadband reflective polarizer whose wavelength range is the visible light region. .

When using a blue LED coated with a yellow phosphor, which is widely used as a light source of the liquid crystal display device described above, the intensity of light is different in the blue, green, and red wavelength bands, respectively. That is, in general, the light emitted from the LED has a light intensity of about 2 times greater than the light intensity of the blue and red wavelength bands, and when the light of such wavelength bands passes through the reflective polarizer and enters the liquid crystal panel, The difference is left.

Therefore, the above-described difference in light intensity causes a problem of color expression in the liquid crystal display device. Therefore, in a liquid crystal cell of a general liquid crystal panel, a component or device for controlling the intensity of the emitted blue light must be separately provided. Due to the complexity of the backlight device, there was a problem leading to the delay of assembly labor.

The present invention has been made to solve the above-mentioned conventional problems, the object of the present invention is to adjust the polarization of any one of the large light intensity, with the optimal color expression, simplifying the backlight unit and shortening the assembly labor. It is an object of the present invention to provide a broadband reflective polarizer, a backlight unit and a liquid crystal display device having the same.

In order to achieve the above object, the present invention is to transmit the first and second polarized light of at least one or more unpolarized light of the white light emitted from the light source, the wavelength band having a greater light intensity than other wavelength band, A reflective polarizing film for transmitting the first polarized light and reflecting the second polarized light; The first polarized light incident from the reflective polarizing film is transmitted, and the second polarized light is absorbed.

Here, the reflective polarizing film is made of a polymer film stretched to transmit and reflect the polarization by the refractive index, the reflective polarizing film is laminated in two or more layers, any one or more layers of the stacked reflective polarizing film is birefringent Contains substances.

In addition, it is preferable that the reflective polarizing film laminated with two or more layers as described above generates a refractive index difference for each wavelength band according to one or more refractive index components.

Meanwhile, the reflective polarizing film transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity and transmits the first polarized light of any of the other unpolarized light and reflects the second polarized light. A first cholesteric liquid crystal layer; A second cholesteric liquid crystal layer that transmits the first polarization and the second polarization of the unpolarized light having a large light intensity while transmitting the first polarized light of the other unpolarized light and reflecting the second polarized light; It includes.

Optionally, the reflective polarizing film transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity while transmitting the first polarized light of the remaining unpolarized light and reflects the second polarized light. It may be composed of a single cholesteric liquid crystal layer having a long wavelength or short wavelength pitch while going upward.

On the other hand, the reflective polarizing film transmits the first polarized light and the second polarized light of the unpolarized light of the wavelength band having a large light intensity while transmitting the first polarized light of the remaining unpolarized light and reflects the second polarized light, At least one surface of the base film having a metal grid is made of a wire grid polarizing film arranged.

The present invention further includes an optical sheet disposed to focus polarized light emitted from the reflective polarizing film, and on one surface of the optical sheet, optical sheets having different patterns are laminated so as to cross the pattern of the optical sheet. It is preferable that the pitch of the pattern which comprises such an optical sheet consists of 10-100 micrometers.

In addition, the vertex angle of the pattern constituting the optical sheet is made of 70 ~ 110 °, each pattern may be arranged non-linearly along the longitudinal direction.

The present invention also provides a backlight unit having the above-mentioned broadband reflective polarizer and a liquid crystal display device having such a backlight unit.

According to the present invention implemented by the above means, out of the white light emitted from the light source, the unpolarized light with a large light intensity is appropriately emitted from the reflective polarizing film and the absorbing polarizing film so that the optimal color expression can be expected as well. Therefore, there is a very useful effect that can be expected to simplify the device and shorten the assembly time.

In addition, the present invention is because the intensity of the light emitted from the light source through the reflective polarizing film and the absorption polarizing film is substantially the same, it is not necessary to adjust the light intensity through a separate component or device as in the prior art, and thus economical As a result, cost savings can be expected.

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

The broadband reflective polarizer 3 of the present invention transmits the first polarized light and the second polarized light of the unpolarized light, which form a wavelength band having a greater light intensity than the other wavelength bands of the white light emitted from the light source 100, while remaining unpolarized light. A reflective polarizing film 300 which transmits the first polarized light and reflects the second polarized light; It consists of an absorption polarizing film 500 which transmits the first polarized light which is input from the reflective polarizing film 300 and absorbs the second polarized light. The term “unpolarized light” refers to unpolarized light, that is, random polarized light in which various polarization states are randomly mixed as usual definition.

The light source 100 emitting white light is implemented by any one of a method of mixing R, G, and B light, a method of using R, G, and B phosphors in UV light, and a method of applying a yellow phosphor to a blue LED. In the present invention, it will be described by implementing a blue LED coated with a yellow phosphor, which is currently the most widely used as a light source.

The reflector 200 is disposed below the light source 100 to reflect the light reflected from the reflective polarization film 300 in the direction of the reflective polarization film 300.

The reflective polarizing film 300 selectively transmits the unpolarized light of the white light incident from the light source 100 while remaining unpolarized light having a large light intensity as it is. That is, the first polarization and the second polarization, which are one or two unpolarized lights, which form a wavelength band having a greater light intensity than the other wavelength bands, are transmitted as they are, while the first polarized light, which is the remaining unpolarized light with small light intensity, is transmitted and is transmitted. Polarization is reflection.

3 is a conceptual diagram conceptually illustrating the operation of the reflective polarizing film 300. As shown in FIG. 3, the reflective polarizing film 300 may include a first polarized light having no polarized light constituting the G-R wavelength band. While transmitting, the second polarized light is reflected, the first polarized light and the second polarized light of the unpolarized light forming the B wavelength band are transmitted as it is.

That is, the white light emitted from the blue LED coated with the yellow phosphor is unpolarized light in the R, G, and B wavelength bands, and the unpolarized light includes the first polarized light in one direction and the second polarized light in a different direction. In this case, the reflective polarizing film 300 transmits the first polarized light in one direction and reflects the second polarized light in the other direction among the G or R unpolarized light, while the first polarized light and the second polarized light of the B unpolarized light are All is to pass.

The second polarized light of G and R selectively reflected as described above is reflected by the reflector 200 to be converted into the first polarized light and the second polarized light, and the first polarized light thus transmitted passes through the reflective polarized film 300 and is formed. The two polarized light is reflected, and as the series of processes are repeated continuously, G and R eventually pass through the reflective polarizing film 300 in the form of the first polarized light.

The above-mentioned reflective polarizing film 300 is preferably implemented by the stretched polymer film. For example, a polymer film obtained by adsorbing iodine, dichroic dye, or the like onto a polyvinyl alcohol film is stretched in a predetermined direction to produce the same. The polymer film thus prepared has a function of transmission and selective reflection using refractive index.

In addition, the reflective polarizing film 300 may be formed of two or more layers, one or more of the layers having a birefringent material. In addition, two or more adjacent layers generate a difference in refractive index for each of the R, G, and B wavelength bands according to one or more refractive index components. Will have

Here, the stretched polymer film is preferably made of a thermoplastic polymer, the thermoplastic polymer is polyolefin (polyethylene, polypropylene, etc.), polynorbornene-based polymer, polyester, polyvinyl chloride, polystyrene, polyacrylonitrile, poly Sulfone, polyallylate, polyvinyl alcohol, polymethacrylic acid ester, polyacrylic acid ester, cellulose ester and copolymers thereof.

Optionally, as described above, the reflective polarizing film 300 transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity, and transmits the unpolarized light of any one of the remaining polarized light. A first cholesteric liquid crystal layer 310 that transmits first polarized light and reflects second polarized light; A second cholesteric liquid crystal layer that transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity while transmitting the first polarized light of the other unpolarized light and reflecting the second polarized light ( 320); may be implemented by stacking.

For example, the first cholesteric liquid crystal layer 310 transmits the first polarized light and the second polarized light of the unpolarized light of the B wavelength band as it is, while transmitting the first polarized light of the unpolarized light of the G wavelength band and the second polarized light. Is a reflection. The second cholesteric liquid crystal layer 320 transmits the first polarized light and the second polarized light of the unpolarized light of the B wavelength band as it is, while transmitting the first polarized light of the unpolarized light of the R wavelength band and the second polarized light. To reflect.

Here, the reflective polarizing film 300 can be implemented by changing the stacking order of the first and second cholesteric liquid crystal layers 310 and 320, as well as two to selectively reflect light of different wavelength bands. Obviously, the above-described cholesteric liquid crystal layer may be laminated.

In addition, the first and second cholesteric liquid crystal layers 310 and 320 are made of a mixture of a curable nematic liquid crystal material and a curable chiral material, depending on the composition of the two materials. To be adjustable. The curable nematic liquid crystal material and the curable chiral material may be used as long as the liquid crystal material includes a mesogenic group representing a nematic liquid crystal. In addition, the chiral material may be any material having chiral carbon in a conventional nematic liquid crystal, and is not limited to a specific material. Here, the curable includes a material having a thermosetting or photocurable reactive group in its molecular structure. For example, in the case of thermosetting, a combination of monomers including vinyl groups such as vinyl group, acrylic group and methacryl group, or having various reactive groups capable of condensation polymerization may be used. As the photocurable, a reactive group crosslinkable by ultraviolet rays such as a vinyl group, an acryl group, and an aryl group may be used.

On the other hand, the reflective polarizing film 300 may be implemented as a single cholesteric liquid crystal layer. The single cholesteric liquid crystal layer transmits the first and second polarized light of unpolarized light having a large light intensity while transmitting the first polarized light of the remaining unpolarized light and reflects the second polarized light. It is implemented as a cholesteric liquid crystal layer having a long wavelength or short wavelength pitch while going from bottom to top. That is, the first polarized light and the second polarized light of the unpolarized light forming the B wavelength band are transmitted as it is, while the first polarized light of the unpolarized light forming the G-R wavelength band is transmitted and the second polarized light is transmitted.

In general, when the nematic liquid crystal material and the chiral material are mixed to form the cholesteric liquid crystal layer, the higher the content of the chiral liquid crystal material is mixed, the wavelength of the selective reflection is shifted to a shorter wavelength.

On the other hand, the reflective polarizing film 300 transmits the first polarized light and the second polarized light of the unpolarized light of the wavelength band having a large light intensity while transmitting the first polarized light of the remaining unpolarized light and reflecting the second polarized light, It may be implemented as a wire grid polarizing film in which a metal grid is arranged on at least one surface of the base film having light transmittance.

On the other hand, the reflective polarizing film 300 may be implemented by arbitrarily combining the stretched film, cholesteric liquid crystal and the wire grid listed as described above.

Referring to FIG. 3, the operation of the reflective polarizing film 300 is further described as follows.

As shown in FIG. 3A, the R, G, and B unpolarized light of the visible light wavelength band emitted from the blue LED coated with the yellow phosphor is incident on the reflective polarizing film 300. At this time, the B unpolarized light of the wavelength band having the largest light intensity is composed of the first polarized light B1 and the second polarized light B2, and the G unpolarized light of the wavelength band having a smaller light intensity than the B unpolarized light Is the first polarized light G1 and the second polarized light G2, and the R unpolarized light consists of the first polarized light R1 and the second polarized light R2, respectively. Here, each of the above-described first polarized light R1 (G1) B1 is polarized light in one direction, and the second polarized light R2 (G2) B2 is polarized light in a different direction.

Accordingly, the reflective polarizing film 300 transmits both the first polarized light B1 and the second polarized light B2 for the unpolarized light in the B wavelength band, but the first polarized light for the unpolarized light in the G and R wavelength bands. Only G1 and R1 are transmitted, and the second polarized light G1 and R2 are reflected.

Subsequently, as illustrated in FIG. 3B, the second polarized light G2 and R2 reflected by the reflective polarizing film 300 are reflected while hitting the reflecting plate 200 to be first polarized light G1a and R1a. And second polarized light G2a (R2a), the first polarized light G1a (R1a) thus converted is transmitted back to the reflective polarization film 300, and the second polarized light G2a (R2a) is reflected polarized light. It hits the film 300 and is reflected again.

Through the above-described series of transmission and reflection processes, as shown in FIG. 3C, the first polarized light B1 and the second polarized light B2 of the B wavelength band having a large light intensity are reflected. Only the first polarized light G1 (R1) is transmitted through the polarizing film 300, and the G and R wavelength bands are transmitted. The first polarized light G1 (R1) thus transmitted is repeatedly transmitted and reflected as described above. After the final transmission through the reflective polarizing film 300. That is, in the case of the G wavelength band, the first polarized light G1 transmitted is “G1, G1a, G1b, G1c ...”, and in the case of the R wavelength band, the first polarized light R1 transmitted is “R1, R1a, R1b, R1c ... ”.

Optionally, the reflective polarizing film 300 transmits the first polarized light R1 (G1) and the second polarized light R2 (G2) of the R or G wavelength band having a large light intensity as it is, among white light emitted from the light source. The first polarized light B1 of the B wavelength band may be transmitted and the second polarized light B2 may be reflected.

On the contrary, the reflective polarizing film 300 transmits the first polarized light R1 (B2) and the second polarized light R2 (B2) of the R · B wavelength band having a large light intensity as it is, among white light emitted from the light source. It is clear that the first polarization G1 of the G wavelength band can be transmitted and the second polarization G2 can be reflected.

The absorbing polarizing film 500 is disposed on the reflective polarizing film 300 to transmit the first polarized light R1 (G1) and B1 incident from the reflective polarizing film 300 as it is, and the second non-polarized light is transmitted. Polarized light B2 absorbs. That is, 50% of the light in the B wavelength band absorbs (second polarized light) and transmits the remaining light (first polarized light). As a result, the intensity of the light in the G-R wavelength band transmitted through the absorption polarizing film 500 remains unchanged, but the intensity of the light in the B wavelength band decreases.

That is, conventionally, when the light intensity of the B wavelength band of the R, G, and B wavelength bands transmitted through the absorption polarizing film 500 is lowered, it becomes difficult to optimize the expression of white light in the liquid crystal display device. The G / B light intensity is appropriately adjusted to optimize the white light due to the harmonious mixing of the R, G, and B light.

On the other hand, Figure 5 is a cross-sectional view showing another embodiment of the broadband reflective polarizer 3 of the present invention, the optical sheet 400 is disposed on the reflective polarizing film 300, such an optical sheet 400 Efficiently suppress the scattering phenomenon of the light passing through the reflective polarizing film 300 to improve the brightness. And a microstructure, that is, a pattern is formed on the upper portion of the optical sheet 400, the cross-sectional shape of the pattern is preferably formed in a prism or arc shape.

Optionally, another optical sheet may be further stacked on the upper surface or the lower surface of the optical sheet 400 so that the patterns may cross each other, and the stacked optical sheets may more effectively realize horizontal and vertical viewing angles.

In addition, the pitch (interval between each pattern) of the pattern of the optical sheet 400 is preferably made of about 10 ~ 100㎛ to maximize the light collection efficiency. And the vertex angle (θ) of each pattern is made of 70 ~ 110 ° to improve the brightness.

In addition, the optical sheet 400, but each pattern is preferably linearly arranged in parallel in the longitudinal direction, each pattern may be arranged in a non-linear chaos pattern along the longitudinal direction, if necessary.

4 is an exemplary view showing a liquid crystal display device having the broadband reflective polarizer 3 configured as described above, and the liquid crystal display device having the broadband reflective polarizer 3 of the present invention is a backlight unit 1. And the liquid crystal panel 2.

Here, the backlight unit 1 includes a light source 100 that emits white light, a light guide plate 110 that distributes the light generated by the light source 100 to an entire area, and light incident from the light guide plate with uniform brightness. And a diffusing sheet 600 for deforming to a surface light source of light, and an optical sheet 400 for condensing light incident from the diffusing sheet 600 and outputting the light to the reflective polarizing film 300.

The diffusion sheet 600 diffuses the light emitted from the light source 100 into the surface light source, and the light transmitted through the diffusion sheet 600 is uniformly diffused into the entire area and is transformed into the surface light source. The diffusion sheet 600 is implemented by applying a resin layer containing a plurality of beads (not shown) to the bottom surface of the base film (not shown), and the light is emitted in various directions through the beads, the light diffusion effect You can expect.

The foregoing descriptions are merely illustrative of one preferred embodiment according to the present invention, and the present invention is not limited to the above-described embodiments, and may be variously modified and implemented within the scope of the appended claims.

1 is an exemplary view of a liquid crystal display device including a conventional reflective polarizer.

2 is a cross-sectional view showing a broadband reflective polarizer of the present invention.

3 is a conceptual diagram conceptually showing the operation of the reflective polarizing film of the present invention.

4 is a cross-sectional view showing a backlight unit of the present invention.

5 is a cross-sectional view showing a reflective polarizer according to another embodiment of the present invention.

6 is a cross-sectional view showing an embodiment of a reflective polarizing film of the present invention.

♠ Explanation of symbols on the main parts of the drawing ♠

100: light source 200: reflector

300: reflective polarizing film 400: optical sheet

500 absorption polarizing film 600 diffusion sheet

Claims (15)

The first polarized light and the second polarized light of the unpolarized light of one or two wavelength bands of which R, G, and B wavelength bands of white light emitted from the light source are larger than other wavelength bands are transmitted, and none of the remaining wavelength bands are transmitted. A reflective polarizing film for transmitting the first polarized light of the polarized light and reflecting the second polarized light; And An absorption polarizing film that transmits the first polarized light incident from the reflective polarizing film and absorbs the second polarized light; Broadband reflective polarizer comprising a. The method according to claim 1, The reflective polarizing film is a broadband reflective polarizer, characterized in that made of a polymer film stretched to transmit and reflect polarized light by the refractive index. The method according to claim 2, The reflective polarizing film is a broadband reflective polarizer, characterized in that laminated in two or more layers. The method according to claim 3, And at least one of the reflective polarizing films stacked in at least two layers comprises a birefringent material. The method according to claim 3, The reflective polarizer film laminated with two or more layers is a broadband reflective polarizer, characterized in that for generating a difference in refractive index for each wavelength band according to one or more refractive index components. The method according to claim 1, Reflective polarizing film, A first cholesteric liquid crystal layer that transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity and transmits the first polarized light of any one of the other unpolarized light and reflects the second polarized light; A second cholesteric liquid crystal layer that transmits the first polarization and the second polarization of the unpolarized light having a large light intensity while transmitting the first polarized light of the other unpolarized light and reflecting the second polarized light; Broadband reflective polarizer comprising a. The method according to claim 1, The reflective polarizing film transmits the first polarized light and the second polarized light of the unpolarized light having a relatively large light intensity, transmits the first polarized light of the unpolarized light of the remaining wavelength band, and reflects the second polarized light. A broadband reflective polarizer, characterized in that it consists of a single cholesteric liquid crystal layer whose pitch monotonously changes from top to top. The method according to claim 1, The reflective polarizing film transmits the first polarized light and the second polarized light of the unpolarized light having a large light intensity, and transmits the first polarized light of the remaining unpolarized light and reflects the second polarized light. A broadband reflective polarizer comprising a wire grid polarizing film in which a metal lattice is arranged on at least one side of the film. The method according to claim 1, And a first optical sheet disposed to collect polarized light emitted from the reflective polarizing film. The method according to claim 9, And a second optical sheet having a different pattern so as to intersect the pattern of the first optical sheet on one surface of the first optical sheet. The method according to claim 9 or 10, The pitch of the pattern provided in the first optical sheet is a broadband reflective polarizer, characterized in that consisting of 10 ~ 100㎛. The method according to claim 9 or 10, The vertex angle of the pattern provided in the first optical sheet is a broadband reflective polarizer, characterized in that consisting of 70 ~ 110 °. The method according to claim 9 or 10, The pattern provided in the first optical sheet is a broadband reflective polarizer, characterized in that arranged in a non-linear along the longitudinal direction. A backlight unit having the broadband reflective polarizer of any one of claims 1 to 10. A liquid crystal display device having a backlight unit of claim 14.

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