KR20090119552A - Optical sheet, back light unit and liquid crystal display device comprising the same - Google Patents

Abstract

PURPOSE: An optical sheet, a backlight unit including the same, and a liquid crystal display device are provided to improve display quality by uniformly diffusing the light on the whole surface of the display region of the liquid crystal panel. CONSTITUTION: A base(110) includes a first surface(111a) and a second surface(111b) to face each other. A prime unit(120) is positioned on the base. The H1 is a vertical distance from one point of the first surface to the second surface. The H2 is a vertical distance from the other point of the first surface to the second surface. At least one side of the first surface and the second surface of the base has a wave shape. The prism unit includes a plurality of beads and a base part(125).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical sheet, a backlight unit including the optical sheet, and a liquid crystal display

The present invention relates to an optical sheet, a backlight unit including the optical sheet, and a liquid crystal display.

2. Description of the Related Art Recently, a display field for visually expressing various electrical signal information has been rapidly developed. Various flat panel displays (FPDs) having excellent characteristics such as thinning, light weight, and low power consumption have been developed Has been introduced to replace CRT (Cathode Ray Tube).

Examples of such flat panel display devices include a liquid crystal display (LCD), a plasma display panel (PDP), a field emission display (FED), an electroluminescence display (ELD) Among them, the liquid crystal display device has a high contrast ratio and is excellent in moving picture display and is currently being used most actively in a display screen for a notebook, a monitor, and a TV.

In general, a liquid crystal display device classified as a light-receiving-type display device may include a backlight unit disposed below the liquid crystal panel for providing light to the liquid crystal panel, in addition to a liquid crystal panel for displaying an image.

The backlight unit may include a light source, an optical sheet, or the like to provide light to the liquid crystal panel. Here, the optical sheet may include a diffusion sheet, a prism sheet, or a protective sheet.

On the other hand, if the luminance uniformity of the light provided to the liquid crystal panel from the backlight unit is decreased, the display quality of the liquid crystal display device is deteriorated.

In order to prevent this, conventionally, a diffusion sheet is used to uniformly diffuse light over the entire display area of the liquid crystal panel. However, it is difficult to secure not only the luminance uniformity but also a high light diffusion rate as described above.

The present invention provides an optical sheet, a backlight unit including the optical sheet, and a liquid crystal display device capable of improving luminance uniformity and light diffusivity through shape change of a base material.

In order to achieve the above object, an optical sheet according to an embodiment of the present invention includes a substrate including a first surface and a second surface opposed to each other, and a prism portion located on the substrate, The vertical distance H ₁ from any one point on one surface to the second surface may be different from the vertical distance H ₂ from another point on the first surface of the substrate to the second surface.

Further, a backlight unit according to an embodiment of the present invention includes a light source and an optical sheet positioned on the light source, wherein the optical sheet includes a substrate including a first surface and a second surface opposed to each other, Wherein a vertical distance H ₁ from any point on the first surface of the substrate to the second surface is defined as a vertical distance H from a different point on the first surface of the substrate to the second surface, ₂ < / RTI >

According to another aspect of the present invention, there is provided a liquid crystal display comprising a light source, an optical sheet positioned on the light source, and a liquid crystal panel positioned on the optical sheet, And a prism portion located on the substrate, wherein a vertical distance H ₁ from any one point of the first surface of the substrate to the second surface is greater than a vertical distance H ₁ between the first surface of the substrate and the second surface, And the vertical distance H ₂ from the point to the second surface.

The optical sheet, the backlight unit including the optical sheet, and the liquid crystal display device according to an embodiment of the present invention can improve the luminance uniformity and the light diffusivity through the optical sheet. Therefore, there is an advantage that the display quality of the liquid crystal display device can be improved.

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

1 and 2 are sectional views of an optical sheet according to an embodiment of the present invention.

Referring to FIGS. 1 and 2, an optical sheet 100 according to an embodiment of the present invention may include a substrate 110 and a prism portion 120 disposed on the substrate 110.

 The substrate 110 serves to transmit light incident from a light source. To this end, the substrate 100 must be capable of transmitting light incident from a light source and thus may be selected from the group consisting of light-transmitting materials such as polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polystyrene and polyepoxy But it is not limited thereto.

The substrate 110 may be formed such that at least one of the first and second surfaces 111a and 111b facing each other, for example, the first surface 111a has a curved surface. Here, the entire first surface 111a may be formed to have a curved surface, or a part of the first surface 111a, for example, a curved surface other than the edges of the first surface 111a may be formed.

The first surface 111a of the substrate 110 may be formed to have, for example, a wave shape so that the acid and the valley may be alternately formed.

The pitch of the acid formed on the first surface 111a of the substrate 110 may be constant. In addition, the height difference between the mountains and the valleys formed adjacent to the first surface 111a may be constant. At this time, the pitch of the acid and the difference in height of the acid and the valley formed adjacent to each other are not limited because they should be appropriately selected according to the thickness and size of the substrate 110, the desired luminance uniformity, the light diffusion rate,

The substrate 110 may be formed such that the first surface 111a of the substrate 110 has a curved surface through any one of methods such as calendering, injection molding, and casting molding, But is not limited thereto.

The substrate 110 may be formed to have a thin thickness, for example, a thickness of 50 to 250 mu m in response to the thinning of the backlight unit. Here, the thickness of the substrate 110 means an average value of the distance from the first surface 111a to the second surface 111b and the distance from the first surface 111a to the second surface 111b can do.

It is possible to make the backlight unit as thin as possible as long as the mechanical properties and heat resistance of the optical sheet 100 are not deteriorated by making the base material 110 have a thickness of 50 mu m or more. Further, by making the base material 110 have a thickness of 250 占 퐉 or less, the thickness of the backlight unit can be reduced, and the mechanical properties and heat resistance of the optical sheet 100 can be maximized.

On the other hand, the vertical distance H ₁ from one point on the first surface 111a of the base 110 to the second surface 111b is the distance from the other surface of the first surface 111a of the base 110 to the second surface the vertical distance H ₂ of up to 111b) may be different from each other.

That is, the vertical distance H ₁ from one point on the first surface 111a of the substrate 110 to the second surface 111b is the distance from the other surface of the first surface 111a of the substrate 110 to the second surface 111b) vertical distance H ₂ is 0.1㎛ ≤ │H ₁ - may satisfy the relational expression of H ₂ │≤ 10㎛.

Table 1 below shows the results of measuring the diffusion effect and luminance of the optical sheet according to the relationship between the vertical distance H ₁ and the vertical distance H ₂ .

The value (占 퐉) of | H ₁ - H ₂ | Diffusion effect Luminance 0.05 × ◎ 0.1 ○ ◎ One ○ ◎ 3 ○ ○ 5 ○ ○ 7 ○ ○ 9 ◎ ○ 10 ◎ ○ 15 ◎ ×

                                         X: poor, o: good, o: very good

Referring to Table 1, there is an advantage in that a curved surface is formed on one surface of the substrate 110 to diffuse the light incident from the light source when 0.1 탆 ≤ H ₁ - H ₂ │, and │H ₁ - H ₂ │ 10 mu m, there is an advantage that the step difference of the curved surface of the base material 110 is too large and the luminance is prevented from being lowered.

The prism section 120 may function to condense the light incident from the light source.

The prism portion 120 may have a triangular cross section. The prism portion 120 may be linearly formed along the longitudinal direction of the prism portion 120 so that the prism portion 120 may be formed in a triangular prism bar shape. However, the present invention is not limited thereto.

The prism portion 120 includes a plurality of mountains 121 and valleys 122 and may further include a bottom portion 125 at a lower portion of the valley 122. The base portion 125 may be integrated with the prism portion 120 and may be positioned below the valley 122 in the prism portion 120.

The base portion 125 may have a thickness of 5 to 50% of the height of the peak 121 of the prism portion 120. Here, when the base portion 125 is 5% or more of the height of the peak 121, it is possible to prevent the base 110 from being damaged by the pressure when the shape of the prism portion 120 is manufactured, Is 50% or less of the height of the mountain 121, there is an advantage that the base 125 is too thick and the transmittance of light incident on the light source is prevented from being lowered.

Although the optical sheet 100 described above is an example in which the first surface 111a of the substrate 110 is curved, the second surface 111b of the substrate 110 may also be curved And the second surface 111b of the substrate 110 may have a curved surface.

Hereinafter, embodiments of the optical sheet described below disclose that the first surface 111a of the substrate 110 has a curved surface, but it is also applicable to the optical sheet having a curved surface on the second surface 111b of the substrate 110 .

3 is a cross-sectional view of an optical sheet according to another embodiment of the present invention.

3, an optical sheet 200 according to another embodiment of the present invention includes a base 210 and a prism 220 disposed on the base 210 and including a plurality of first beads 230 ).

The substrate 210 may have a vertical distance H ₁ from one point on the first surface 211a of the substrate 210 to the second surface 211b at a distance from the other point on the first surface 211a of the substrate 210 And the vertical distance H ₂ to the second surface 211b.

Here, the substrate 210 is the same as the above-described embodiment, and a detailed description thereof will be omitted.

The prism portion 220 may include a base 225, a resin 235, and a plurality of first beads 230. Here, the base unit 225 is the same as the above-described embodiment, and a description thereof will be omitted.

The resin 235 may be an acrylic resin, for example, an unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butyl methyl methacrylate, Acrylates such as methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyethyl acrylate, acrylamide, methylol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, Acrylate, 2-ethylhexyl acrylate polymer, copolymer or terpolymer, acrylic, urethane, epoxy, melamine and the like can be used.

The plurality of first beads 230 serve to diffuse and transmit light incident from the light source.

For this, the first beads 230 may be organic and inorganic particles having high light transmittance and high light diffusivity. For example, there may be mentioned methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, n-butyl methacrylate, n-butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, Acrylate, methacrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate polymer or copolymer or tertiary Olefin-based particles such as acrylic, polyethylene, polystyrene, and polypropylene, copolymers of acrylic and olefin, and multi-layered multicomponent particles formed by forming monopolymer particles and then covering them with different kinds of monomers Can be used. As the first light-diffusing particles 124b, inorganic particles such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, and magnesium fluoride may be used.

Here, the first beads 230 may be included in 1 to 10 parts by weight with respect to the resin 235. If the content of the first beads 230 is more than 1 part by weight with respect to the resin 235, it is possible to prevent the problem that the light incident from the light source is difficult to be diffused by the beads, When the content of the beads 230 is 10 parts by weight or less, there is an advantage that the transmittance of light incident from the light source can be prevented from being lowered.

At this time, the particle diameters of the plurality of first beads 230 distributed in the resin 235 may be irregular and irregular, and the first beads 230 may be all included in the surface of the resin 235 .

Therefore, the backlight unit including the optical sheet according to the embodiments of the present invention operates as follows.

Light emitted from the light source is incident on the optical sheet. A part of the light incident on the optical sheet collides with the first bead of the prism portion to change the path and another portion of the light travels to the liquid crystal panel through the exit surface of the prism portion.

Light whose path is changed by colliding with the first bead is hit by another adjacent first bead and its path is changed again and a part of the light advances to the liquid crystal panel through the outgoing surface of the prism portion and part of the light is hit by another first bead, Is changed.

Finally, light passing through the exit surface of the prism portion is uniformly incident on the liquid crystal panel.

As described above, the light incident on the optical sheet is reflected by the plurality of first beads formed inside the prism portion and diffused while changing its traveling path, so that the light can be condensed to improve the brightness.

4A and 4B are views showing an optical sheet according to another embodiment of the present invention.

4A and 4B, an optical sheet 300 according to another embodiment of the present invention includes a substrate 310 and a substrate 310, and includes an acid 321 and a valley 322 And a prism portion 320 for guiding the light.

The substrate 310 may be formed such that the vertical distance H ₁ from one point on the first surface 311a of the substrate 310 to the second surface 311b is greater than the vertical distance H1 from another point on the first surface 311a of the substrate 310 And the vertical distance H ₂ to the second surface 311b.

Here, the base material 310 is the same as the above-described embodiment, and a detailed description thereof will be omitted.

The cross section of the prism section 320 may have a triangular shape and the pitch between the peaks 321 of the prism section 320 may be 20 to 300 mu m.

The mountains 321 of the prism portion 320 may have a shape that is serpentine along the longitudinal direction of the prism portion 320. In this case, the average horizontal amplitude of the mountains 321 of the prism portion 320 is 1 Lt; / RTI >

In addition, the valleys 322 of the prism portion 320 may be formed in a serpentine shape, and the average horizontal amplitude of the valleys 322 of the prism portion 320 may be 1 to 20 탆.

The height of the peak 321 from the bottom surface of the prism portion 320 may vary randomly or periodically in the longitudinal direction of the prism portion 320. For example, the average height difference of the acid 321 may be 1 to 20 占 퐉. In addition, the height of the trough 322 may be varied randomly or periodically in the longitudinal direction of the prism portion 320.

Therefore, it is difficult for the optical sheet 300 to visually easily detect defects such as the crushing of the peak 321 of the prism portion 320 by physical contact with other sheets in contact with the upper portion of the optical sheet 300, The image quality of the liquid crystal display device may not be affected.

5 is a cross-sectional view of an optical sheet according to another embodiment of the present invention.

5, an optical sheet 400 according to another embodiment of the present invention includes a base material 410, a prism portion 420 disposed on the base material 410, And may include a protective layer 430.

The substrate 410 has a vertical distance H ₁ from one point on the first surface 411a of the substrate 410 to the second surface 411b is greater than the vertical distance H ₁ from another point on the first surface 411a of the substrate 410 And the vertical distance H ₂ to the second surface 411b.

Here, the prism portion 420 including the base material 410 and the base portion 425 is the same as the above-described embodiment, and a detailed description thereof will be omitted.

The protective layer 430 may improve the heat resistance of the optical sheet 400. More specifically, the protective layer 430 may include a plurality of second beads 432 dispersed within the resin 431 and the resin 431.

The resin 431 may be an acrylic resin having transparency and excellent heat resistance and mechanical properties, and may be the same as the resin of the above-described embodiment.

The second bead 432 may be manufactured using the same or different resin as the resin 431 and may be included in the resin 431 in an amount of 10 to 50 parts by weight.

The size of the second bead 432 may be appropriately selected according to the thickness of the substrate 410, and may be 2 to 10 占 퐉.

In an embodiment of the present invention, the size of the second bead 432 may be substantially the same, and the distribution within the resin 431 may be regular. Alternatively, the sizes of the second beads 432 are different from each other, and the distribution in the resin 431 may be irregular.

The first bead and the second bead 432 may be made of the same material or may be different from each other.

As described above, the protective layer 430 can prevent the optical sheet from being deformed due to heat generated in the light source. That is, the optical sheet is not wrinkled by the resin 431 having high heat resistance, and even if the optical sheet is deformed at a high temperature, the restoring force of returning from the normal temperature state back to the original optical sheet shape is excellent.

In addition, the protective layer 430 may prevent scratches on the optical sheet due to an external impact or other physical force.

6A and 6B are an exploded perspective view and a cross-sectional view for explaining a configuration of a backlight unit including an optical sheet according to embodiments of the present invention.

In FIG. 6A, an edge type backlight unit is shown as a backlight unit, and since the prism sheet of the present invention is the same as the above-described optical sheet, the overlapping description is omitted.

Referring to FIGS. 6A and 6B, the backlight unit 500 according to an exemplary embodiment of the present invention may be provided in a liquid crystal display device, and may provide light to a liquid crystal panel included in a liquid crystal display device.

The backlight unit 500 may include a light source 520 and a prism sheet 530. The backlight unit 500 may further include a light guide plate 540, a reflector 550, a bottom cover 560, and a mold frame 570.

The light source 520 can generate light using driving power applied from the outside, and can emit the generated light.

The light source 520 may be formed on at least one side of the light guide plate 540 along the major axis direction of the light guide plate 540 or may be formed on at least one side of each side of the light guide plate 540 . The light emitted from the light source 520 may be directly incident into the light guide plate 540 or may be incident on a portion of the light source 520 such as a light source housing 522 formed to surround about 3/4 of the outer circumferential surface of the light source 520 And then may be incident into the light guide plate 540.

Specifically, the light source 520 includes a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL), and a light emitting diode Light emitting diodes (LEDs), and the like.

The optical sheet 530 may be disposed above the light guide plate 540. The optical sheet 530 may function to condense the light incident from the light source 520.

The optical sheet 530 includes a base including a first surface and a second surface opposed to each other and a prism portion located on the base, and the prism portion located on one side of the base, The vertical distance H ₁ may be different from the vertical distance H ₂ from the other side of the first side of the substrate to the second side and all of the optical sheets of the above embodiments may be applied.

Therefore, the optical sheet 530 has an advantage that the luminance uniformity and the light diffusivity can be improved by changing the shape of the base material. As a result, the display quality of the backlight unit 500 according to an embodiment of the present invention can be improved.

The light guide plate 540 may be disposed to face the light source 520 and may guide the light so that the light incident from the light source 520 is emitted upward.

The reflection plate 550 may be disposed under the light guide plate 540 and may reflect upward the light emitted downward through the light guide plate 540 out of the light emitted from the light source 520.

The bottom cover 560 includes a bottom portion 562 and a side portion 564 extending from the bottom portion 562 to form a storage space. The storage space includes a light source 520, an optical sheet 530, The light guide plate 540, and the reflection plate 550 can be accommodated.

The mold frame 570 is formed in a substantially rectangular shape and can be fastened to the bottom cover 560 from the top side of the bottom cover 560 in a top down manner.

7A and 7B are an exploded perspective view and a cross-sectional view illustrating a configuration of a backlight unit according to an embodiment of the present invention.

7A and 7B show a direct-type backlight unit as a backlight unit, the present invention is not limited thereto. Meanwhile, the backlight unit shown in FIGS. 7A and 7B is substantially the same as the backlight unit shown in FIGS. 6A and 6B, except for the arrangement of the light sources and the change of the components thereof, , And only those features will be described.

Referring to FIGS. 7A and 7B, the backlight unit 600 according to an exemplary embodiment of the present invention may be provided in a liquid crystal display device, and may provide light to a liquid crystal panel included in a liquid crystal display device.

The backlight unit 600 may include a light source 620 and an optical sheet 630. The backlight unit 600 may further include a reflection plate 650, a bottom cover 660, a mold frame 670, and a diffusion plate 680.

At least one light source 620 may be disposed under the diffusion plate 680. Therefore, the light emitted from the light source 620 can be directly incident on the diffusion plate 680.

The optical sheet 630 may be disposed above the diffuser plate 680. The optical sheet 630 may function to condense the light incident from the light source 620.

The optical sheet 630 includes a base including a first surface and a second surface opposed to each other and a prism portion located on the base, The vertical distance H ₁ may be different from the vertical distance H ₂ from the other side of the first side of the substrate to the second side and all of the optical sheets of the above embodiments may be applied.

Therefore, the optical sheet 630 has an advantage that the luminance uniformity and the light diffusivity can be improved by changing the shape of the base material. As a result, the display quality of the backlight unit 600 according to an embodiment of the present invention can be improved.

The diffuser plate 680 may be disposed between the light source 620 and the optical sheet 630 and may diffuse the light incident from the light source 620 upward. This is to prevent the shape of the light source 620 from being visible through the backlight unit 600 and further diffuse the light.

8A and 8B are an exploded perspective view and a cross-sectional view illustrating a configuration of a liquid crystal display device according to an embodiment of the present invention. 8A and 8B show the backlight unit shown in Figs. 6A and 6B as a backlight unit, the present invention is not limited thereto, and the backlight unit shown in Figs. 7A and 7B may be employed as the backlight unit. 8A and 8B are the same as those described above, so that overlapping descriptions will be omitted and only the features will be described.

8A and 8B, the liquid crystal display device 900 according to the embodiment of the present invention can display an image using the electro-optical characteristic of the liquid crystal.

The liquid crystal display 700 may include a backlight unit 710 and a liquid crystal panel 810.

The backlight unit 710 may be mounted under the liquid crystal panel 810 and may provide light to the liquid crystal panel 810.

The backlight unit 710 may include a light source 720 and an optical sheet 730. The backlight unit 710 may further include a light guide 740, a reflector 750, a bottom cover 760, and a mold frame 770.

The liquid crystal panel 810 is fixed on the mold frame 770 by a top cover 820 which is coupled with the bottom cover 760 in a top-down manner.

The liquid crystal panel 810 can display an image using light provided from the backlight unit 710, specifically, light emitted from the light source 720.

The liquid crystal panel 810 may include a color filter substrate 812 and a thin film transistor substrate 814 facing each other with a liquid crystal therebetween.

The color filter substrate 812 can realize the color of the image to be displayed through the liquid crystal panel 810. [

The color filter substrate 812 may include a color filter array formed as a thin film on a transparent substrate such as glass or plastic, for example, an red / green / blue color filter. Here, the upper polarizer may be disposed on the color filter substrate 812.

The thin film transistor substrate 814 is electrically connected to a printed circuit board 718 on which a plurality of circuit components are mounted via a driving film 716. [ The thin film transistor substrate 814 may apply a driving voltage provided from the printed circuit board 718 to the liquid crystal in response to a driving signal provided from the printed circuit board 718.

The thin film transistor substrate 814 may include a thin film transistor and a pixel electrode formed as a thin film on another substrate of a transparent material such as glass or plastic.

Here, a lower polarizer may be attached to a lower portion of the thin film transistor substrate 814.

As described above, the optical sheet according to one embodiment of the present invention, the backlight unit including the optical sheet, and the liquid crystal display device may include a plurality of diffusion particles in the prism portion to diffuse the light, There is an advantage.

In addition, the backlight unit and the liquid crystal display device including the optical sheet according to the embodiments of the present invention have an advantage of bending the shape of the mountain and the valley of the prism portion to prevent damage by other sheets contacting the upper portion of the prism portion have.

In addition, the optical sheet according to one embodiment of the present invention, the backlight unit including the same, and the liquid crystal display device have an advantage that the heat resistance and the mechanical strength of the optical sheet can be improved by further including a protective layer below the optical sheet.

The optical sheet according to one embodiment of the present invention, the backlight unit including the same, and the liquid crystal display device may further include a substrate having a curved surface on at least one of a first surface and a second surface opposed to each other, and a prism portion There is an advantage that the luminance uniformity and the light diffusivity can be improved by changing the shape of the base material.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

1 and 2 are sectional views of an optical sheet according to an embodiment of the present invention.

3 is a cross-sectional view of an optical sheet according to another embodiment of the present invention;

4A and 4B show an optical sheet according to another embodiment of the present invention.

5 is a sectional view of an optical sheet according to another embodiment of the present invention;

6A and 6B illustrate a backlight unit according to an embodiment of the present invention.

7A and 7B illustrate a backlight unit according to another embodiment of the present invention.

8A and 8B illustrate a liquid crystal display according to an embodiment of the present invention.

Claims (13)

A substrate comprising a first side and a second side facing each other; And And a prism portion located on the substrate, Wherein a vertical distance H ₁ from any one point on the first surface of the substrate to the second surface is different from a vertical distance H ₂ from another point on the first surface of the substrate to the second surface. The method according to claim 1, Wherein at least one of the first surface and the second surface of the base material has a wave shape and the mountains and the valleys are alternately formed. The method according to claim 1, Wherein the prism portion includes a plurality of first beads. The method according to claim 1, Wherein the prism portion includes a plurality of mountains and a valley, and further comprises a base at a lower portion of the valley. 5. The method of claim 4, And the base portion has a thickness of 5 to 50% of the height of the peak of the prism portion. The method according to claim 1, Wherein the optical sheet further comprises a protective layer at the bottom of the substrate. The method according to claim 6, Wherein the protective layer comprises a resin and a plurality of second beads. The method according to claim 1, Wherein the prism portion includes a plurality of mountains and a valley, Wherein at least one of the acid and the valley meanders left and right. The method according to claim 1, Wherein the prism portion includes a plurality of mountains and a valley, Wherein at least one of the acid and the valley varies in height along a longitudinal direction of the prism portion. The method according to claim 1, Wherein at least one of the first surface and the second surface of the substrate has a curved surface. The method according to claim 1, Wherein the vertical distance H ₁ and the vertical distance H ₂ satisfy a relation of 0.1 탆 | H ₁ -H _{2 |} ≤ ₁₀ 탆. Light source; And And an optical sheet positioned on the light source, Wherein the optical sheet comprises a substrate including a first surface and a second surface opposite to each other and a prism portion located on the substrate, wherein a vertical distance from any one point of the first surface of the substrate to the second surface Wherein H ₁ is different from a vertical distance H ₂ from another point on the first surface of the substrate to the second surface. Light source; An optical sheet positioned on the light source; And And a liquid crystal panel positioned on the optical sheet, Wherein the optical sheet comprises a substrate including a first surface and a second surface opposite to each other and a prism portion located on the substrate, wherein a vertical distance from any one point of the first surface of the substrate to the second surface Wherein H ₁ is different from a vertical distance H ₂ from another point on the first surface of the substrate to the second surface.

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