KR20090122718A - 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 improving light diffusing rate and luminance uniformity through an optical sheet. CONSTITUTION: An optical sheet(100) includes a material(110) and a lens part(120) positioned in a top part of the material. The material transmits a light emitted from a light source. The material is made of one selected in groups composed of polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polystyrene, and polyepoxy, and has a first surface(111a) and a second surface(111b). At least one of the first surface and the second surface has a curved surface. A vertical distance(H1) from one point of the first surface to the second surface is different from a vertical distance(H2) from the other point of the first surface to the second surface.

Description

Optical Sheet, Back Light Unit And Liquid Crystal Display Device Comprising The Same}

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

Recently, the display field for visually expressing various electrical signal information is rapidly developing, and in response to this, various flat panel displays (FPDs) with excellent characteristics such as thinness, light weight, and low power consumption are being developed. It is introduced and rapidly replaced the existing CRT (Cathode Ray Tube).

Examples of such flat panel displays include liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and electroluminescence displays (ELDs). The liquid crystal display has a large contrast ratio and is excellent in moving image display, and is currently used most widely in the field of display screens, monitors, and TVs for notebook computers.

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

The backlight unit may include a light source, an optical sheet, and 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, when the luminance uniformity of the light provided from the backlight unit to the liquid crystal panel is inferior, there is a problem that the display quality of the liquid crystal display device is degraded.

In order to prevent this, in the past, light is uniformly diffused over the entire display area of the liquid crystal panel using a diffusion sheet, but only the diffusion sheet is difficult to secure not only the above-described brightness uniformity but also a high light diffusion rate.

The present invention provides an optical sheet, a backlight unit including the same, and a liquid crystal display device, which may improve luminance uniformity and light diffusion rate by changing a shape of a substrate.

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 facing each other and a lens unit positioned on the substrate, the first of the substrate The vertical distance H ₁ from any point of the face to the second face may be different from the vertical distance H ₂ from another point of the first face of the substrate to the second face.

In addition, the 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 first and second surfaces facing each other and on the substrate. Wherein the vertical distance H ₁ from any point on the first side of the substrate to the second side is different from the vertical distance H ₂ from another point on the first side of the substrate to the second side. Can be.

In addition, the liquid crystal display according to an exemplary embodiment of the present invention includes a light source, an optical sheet positioned on the light source, and a liquid crystal panel positioned on the optical sheet, wherein the optical sheet has a first surface and a first surface facing each other. And a lens portion positioned on the substrate, wherein the vertical distance H ₁ from one point of the first face to the second face of the substrate is determined from the other point of the first face of the substrate. It can differ from the vertical distance H ₂ to two sides.

An optical sheet, a backlight unit including the same, and a liquid crystal display device according to an exemplary embodiment of the present disclosure may improve luminance uniformity and light diffusion rate through the optical sheet. Therefore, there is an advantage that the display quality of the liquid crystal display device can be improved.

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

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

1 and 2, an optical sheet 100 according to an embodiment of the present invention may include a substrate 110 and a lens unit 120 positioned on the substrate 110.

 The substrate 110 serves to transmit the light incident from the light source. To this end, since the substrate 100 must be able to transmit light incident from the light source, any one selected from the group consisting of a light transmissive material, for example, polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polystyrene and polyepoxy It may be made of one, but not limited to.

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 may be formed to have a curved surface except for an edge of the first surface 111a.

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

The pitch of the peaks formed on the first surface 111a of the substrate 110 may be constant. In addition, the height difference between the hill and the valley formed to be adjacent to each other on the first surface 111a may be constant. In this case, the pitch of the peaks, and the height difference between the peaks and valleys formed to be adjacent to each other should be appropriately selected according to the thickness and size of the substrate 110, the desired luminance uniformity, the light diffusion rate, and the like, and are not limited thereto.

The substrate 110 may be formed such that the first surface 111a of the substrate 110 has a curved surface through any one of a method such as calendering processing, injection processing, and casting molding. It is not limited to this.

The substrate 110 may be formed to have a thin thickness, for example, 50 μm to 250 μm 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 peak of the first surface 111a to the second surface 111b and the distance from the valley of the first surface 111a to the second surface 111b. can do.

By making the substrate 110 have a thickness of 50 μm or more, the backlight unit can be made as thin as possible without the mechanical properties and the heat resistance of the optical sheet 100 falling. In addition, by making the substrate 110 have a thickness of 250 μm or less, thickness reduction of the backlight unit may be achieved, and mechanical properties and heat resistance of the optical sheet 100 may be maximized.

On the other hand, the vertical distance H ₁ from one point of the first surface 111a of the substrate 110 to the second surface 111b is the second surface (from the other point of the first surface 111a of the substrate 110. And may differ from the vertical distance H ₂ to 11b).

That is, the vertical distance H ₁ from one point of the first surface 111a of the substrate 110 to the second surface 111b is the second surface (from the other point of the first surface 111a of the substrate 110. The vertical distance H ₂ to 11b) may satisfy a relational equation of 0.1 μm ≦ H ₁ -H _{2 |} ≦ 10 μm.

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

Value of │H ₁ -H ₂ │ Diffusion effect Luminance 0.05 × ◎ 0.1 ○ ◎ One ○ ◎ 3 ○ ○ 5 ○ ○ 7 ○ ○ 9 ◎ ○ 10 ◎ ○ 15 ◎ ×

                                      ×: bad, ○: good, ◎: very good

Referring to Table 1, if 0.1 µm ≤ H ₁ -H ₂ │, a curved surface is formed on one surface of the substrate 110 to diffuse light incident from the light source, and H ₁ -H ₂ │ If it is ≦ 10 μm, there is an advantage that the level difference of the curved surface of the substrate 110 is too large to prevent the luminance from decreasing.

The lens unit 120 may be formed of a transparent polymer resin to transmit light incident from the outside. Here, the polymer resin may be any one selected from the group consisting of acrylic, polycarbonate, polypropylene, polyethylene, and polyethylene terephthalate.

The lens unit 120 may further include a base 125. The base 125 is positioned below the inside of the lens unit 120 and may be integrated with the lens unit 120.

Base 125 may be formed of a height (H ₃₎ of 5 to 50% of the height (H ₄₎ of the lens section 120. The

Table 2 below shows the results of measuring the defects of the optical sheet and the light transmission characteristics according to the height H ₄ of the lens unit 120 and the height H ₃ of the base 125.

Height of base part to height of lens part (%) Light transmission characteristics Defective One ◎ ○ 3 ◎ ○ 5 ◎ × 10 ○ × 20 ○ × 30 ○ × 40 ○ × 50 ○ × 60 × × 70 × × 80 × ×

                        Light transmission characteristic- ×: Poor, ○: Good, ◎: Very good

                           Bad or not-○: Bad, ×: Bad

Referring to Table 2, when the height H ₃ of the base portion 125 is 5% or more of the height H ₄ of the lens portion 120, when manufacturing the shape of the lens portion 120, the substrate 110 may be used. Can be prevented from being damaged by pressure, and if the height H ₃ of the base 125 is less than or equal to 50% of the height H ₄ of the lens 120, the base 125 is too thick to enter the light source. There is an advantage that the transmittance of light can be prevented from being lowered.

Therefore, the height H ₃ of the base 125 may be 5 to 50% of the height H ₄ of the lens unit 120.

3A to 3D are views illustrating the shape of the lens unit. Referring to this, the lens unit 120 may serve to condense the light incident from the light source.

The lens unit 120 may be a micro lens or a lenticular lens.

The micro lens may be formed to have an embossed hemispherical surface on one surface of the substrate 110.

The microlens may vary in the degree of diffusion, the degree of refraction, the light condensation, etc. according to the size and the density of the lens. Accordingly, the microlens may have a constant or irregular diameter of the lens, and may have a constant or irregular height of the lens.

In addition, the lens diameter of the micro lens may be formed to 20 ㎛ ~ 200 ㎛, but is not limited thereto. The distribution of the lens in the total area may be formed to have 50% to 90% or more, but is not limited thereto.

If the microlenses are formed to have an embossed hemispherical surface, as described above, some of the light incident from the outside, for example, from under the microlens, is uniformly refracted at all azimuth angles in the hemispherical surface to produce the microlenses. Permeable. For this reason, some of the light incident from the lower part of the microlens can be uniformly diffused upward and can be focused.

The lenticular lens has a semicircular cross-sectional shape and may be continuously formed in the longitudinal direction instead of a pattern shape like the aforementioned micro lens. For example, the semi-cylindrical cylinder may have a shape lying down on the substrate 110.

In the lenticular lens, the pitch of the lens may be constant or irregular, and the height of the lens may also be constant or irregular, but is not limited thereto.

Although the above-described optical sheet 100 discloses an embodiment in which the first surface 111a of the substrate 110 is curved, as shown in FIG. 2, the optical sheet 100 may also be curved in the second surface 111b of the substrate 110. In addition, the present invention is not limited thereto, and a curved surface may exist only on the second surface 111b of the substrate 110.

Hereinafter, embodiments of the optical sheet to be described below disclose that the curved surface is present on the first surface 111a of the substrate 110, but it is also applicable to the optical sheet having the curved surface on the second surface 111b of the substrate 110. Do. In addition, although the shape of the lens part 120 discloses that it is a lenticular lens, it may be a micro lens.

4 is a cross-sectional view of an optical sheet according to another exemplary embodiment of the present disclosure.

4, the optical sheet 200 according to another embodiment of the present invention is positioned on the substrate 210 and the substrate 210, and includes a lens unit 220 including a plurality of first beads 230. ) May be included.

The substrate 210 may be formed such that at least one of the first and second surfaces 211a and 211b facing each other, for example, the first surface 211a has a curved surface.

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

The lens unit 220 may be a lenticular lens or a micro lens, and may include a base layer 225, a resin 235, and a plurality of first beads 230.

Resin 235 may be an acrylic resin, for example, unsaturated polyester, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, Methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxy ethyl acrylate, acrylamide, methrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl Acrylic, urethane, epoxy, melamine, etc., such as an acrylate, a 2-ethylhexyl acrylate polymer, a copolymer, or a terpolymer, can be used.

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

To this end, the first bead 230 may be organic and inorganic particles having a high light transmittance and a high light diffusion rate. For example, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, normal butyl methyl methacrylate, acrylic acid, methacrylic acid, hydroxyethyl methacrylate, hydroxypropyl methacrylate Acrylate, hydroxy ethyl acrylate, acrylamide, metyrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate polymer or copolymer or terpolymer Olefin-based particles such as acrylic, polyethylene, polystyrene, polypropylene, etc., copolymers of acrylic and olefins, homopolymer-like particles, and multi-layered multi-component particles made by covering the layers with other monomers Organic particles of can be used. In addition, inorganic particles such as silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, and magnesium fluoride may be used as the first light diffusing particles 124b.

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

In this case, the particle diameters of the plurality of first beads 230 distributed in the resin 235 may not be uniform but have an irregular distribution, and the first beads 230 may be included without protruding from the surface of the resin 235. Can be.

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

Light generated 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 lens part to change the path, and the other part of the light travels to the liquid crystal panel through the exit surface of the lens part.

Light hitting the first bead and whose path is changed is hit by another adjacent bead, and the path is changed again, and some of them are propagated to the liquid crystal panel through the exit surface of the lens part, and a part of the first bead is hit by another first bead again. Is changed.

Finally, the light passing through the exit surface of the lens portion is incident evenly into the liquid crystal panel.

As described above, since the light incident on the optical sheet is reflected by the plurality of first beads formed inside the lens unit several times and diffuses while changing its propagation path, the light may be focused to improve luminance.

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

Referring to FIG. 5, an optical sheet 300 according to another embodiment of the present invention may be located on a base 310, a lens unit 320 positioned on the base 310, and a lower portion of the base 310. The protective layer 330 may be included.

The substrate 310 may be formed such that at least one of the first and second surfaces 311a and 311b facing each other, for example, the first surface 311a has a curved surface.

Here, the lens unit 320 including the base 310 and the base layer 325 is the same as the above-described embodiment and a detailed description thereof will be omitted.

The protective layer 330 may serve to improve heat resistance of the optical sheet 300. In more detail, the protective layer 330 may include a resin 331 and a plurality of second beads 332 dispersed in the resin 331.

The resin 331 may use an acrylic resin that is transparent and has excellent heat resistance and mechanical properties, and may be the same as the resin of the above-described embodiment.

The second bead 332 may be manufactured using the same or different types of resins as the resin 331, and may be included in an amount of 10 to 50 parts by weight based on the resin 331.

The size of the second bead 332 may be appropriately selected depending on the thickness of the substrate 310, it may be 2 to 10㎛.

In one embodiment of the present invention, the size of the second bead 332 may be substantially the same, the distribution in the resin 331 may be regular. In contrast, the sizes of the second beads 332 are different from each other, and the distribution in the resin 331 may be irregular.

In addition, the first bead and the second bead 332 described above may use the same material, and may be different from each other.

As described above, the protective layer 330 may prevent the optical sheet from being deformed by heat generated from the light source. That is, wrinkles do not occur in the optical sheet by the resin 331 having high heat resistance, and even when the optical sheet is deformed at a high temperature, the restoring force of returning to the original optical sheet shape again at room temperature is excellent.

In addition, the protective layer 330 may also prevent scratches on the optical sheet due to external impact or other physical force.

6A to 6C are exploded perspective views and cross-sectional views illustrating a configuration of a backlight unit including an optical sheet according to embodiments of the present disclosure.

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

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

The backlight unit 500 may include a light source 520 and an optical sheet 530. In addition, the backlight unit 500 may further include a light guide plate 540, a reflective plate 550, a bottom cover 560, and a mold frame 570.

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

For example, at least one light source 520 may be formed at one side of the light guide plate 540 along the long axis direction of the light guide plate 540, or at least one light source may be formed at each of both sides of the light guide plate 540. . Here, the light emitted from the light source 520 is incident directly into the light guide plate 540, or the light source housing 522 formed to surround a portion of the light source 520, for example, about 3/4 of the outer peripheral surface of the light source 520. After reflection, the light may enter the light guide plate 540.

The light source 520 may include, for example, a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL), and a light emitting diode (LED). Light Emitting Diode (LED), but is not limited thereto.

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

The optical sheet 530 includes a substrate having at least one of the first and second surfaces facing each other and a lens unit positioned on the substrate, and the optical sheets of the above-described embodiments may be applied. .

Therefore, the optical sheet 530 has an advantage of improving the brightness uniformity and the light diffusion rate by changing the shape of the substrate. As a result, display quality of the backlight unit 500 according to an exemplary embodiment may be improved.

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

The reflective plate 550 may be disposed under the light guide plate 540, and may reflect light emitted downward through the light guide plate 540 among the light emitted from the light source 520.

The bottom cover 560 may include a bottom part 562 and a side part 564 formed to extend from the bottom part 562 to form an accommodation space, and the light source 520 and the optical sheet 530 may be formed in the accommodation space. The light guide plate 540 and the reflective plate 550 may be accommodated.

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

7A to 7C are exploded perspective views and cross-sectional views for describing the configuration of a backlight unit according to an embodiment of the present invention.

7A to 7C illustrate the direct type backlight unit as the backlight unit, but the present invention is not limited thereto. Meanwhile, the backlight unit illustrated in FIGS. 7A to 7C is substantially the same as the backlight unit illustrated in FIGS. 6A to 6C except for the arrangement of the light source and the change in the components thereof. Only its features will be described.

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

The backlight unit 600 may include a light source 620 and an optical sheet 630. In addition, the backlight unit 600 may further include a reflector 650, a bottom cover 660, a mold frame 670, and a diffuser plate 680.

At least one light source 620 may be disposed under the diffuser plate 680. For this reason, the light emitted from the light source 620 may be incident directly to the diffuser plate 680.

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

The optical sheet 630 may include a substrate having a curved surface and at least one of the first and second surfaces facing each other, and a lens unit positioned on the substrate, and may apply all of the optical sheets of the above-described embodiments. .

Therefore, the optical sheet 630 has an advantage of improving the brightness uniformity and the light diffusion rate by changing the shape of the substrate. As a result, display quality of the backlight unit 600 according to an exemplary embodiment may be improved.

The diffusion plate 680 may be disposed between the light source 620 and the optical sheet 630, and may diffuse 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 to further diffuse the light.

8A and 8B are exploded perspective views and cross-sectional views illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention. 8A and 8B illustrate the backlight units illustrated in FIGS. 6A to 6C as the backlight units, but the present invention is not limited thereto, and the backlight units illustrated in FIGS. 7A to 7C may be employed as the backlight units. Meanwhile, since the backlight units illustrated in FIGS. 8A and 8B are the same as described above, overlapping descriptions are omitted and only the features thereof will be described.

8A and 8B, the liquid crystal display device 900 according to an exemplary embodiment may display an image by using the electro-optical characteristics of the liquid crystal.

The LCD 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. In addition, the backlight unit 710 may further include a light guide plate 740, a reflective plate 750, a bottom cover 760, and a mold frame 770.

The liquid crystal panel 810 may be mounted on the mold frame 770 and may be fixed by the top cover 820 fastened to the bottom cover 760 in a top-down manner.

The liquid crystal panel 810 may 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 the liquid crystal interposed therebetween.

The color filter substrate 812 may implement a color of an image displayed through the liquid crystal panel 810.

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

The thin film transistor substrate 814 is electrically connected to the printed circuit board 718 on which a plurality of circuit components are mounted through the 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 of a thin film on another substrate of a transparent material such as glass or plastic.

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

As described above, the optical sheet, the backlight unit including the same, and the liquid crystal display according to the exemplary embodiments of the present invention include a plurality of diffused particles in the lens unit, and thus may serve to diffuse and collect light. There is an advantage.

In addition, the optical sheet, the backlight unit including the same, and the liquid crystal display according to the exemplary embodiments of the present invention further include a protective layer under the optical sheet, thereby improving heat resistance and mechanical strength of the optical sheet.

In addition, in the optical sheet, the backlight unit including the same, and the liquid crystal display according to the exemplary embodiments, at least one of the first and second surfaces facing each other has a curved surface and a lens unit positioned on the substrate. By providing the optical sheet comprising, there is an advantage that can improve the brightness uniformity and the light diffusion rate through the shape change of the substrate.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the above-described technical configuration of the present invention may be embodied in other specific forms by those skilled in the art to which the present invention pertains without changing its technical spirit or essential features. It will be appreciated that it may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

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

3A to 3D are perspective views showing lens portions of the optical sheet of the present invention.

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

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

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

7A to 7C are diagrams illustrating a backlight unit according to another embodiment of the present invention.

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

Claims (12)

A substrate comprising a first side and a second side facing each other; And It includes a lens unit located on the substrate, And the vertical distance H ₁ from any point on the first side of the substrate to the second side is different from the vertical distance H ₂ from another point on the first side of the substrate to the second side. The method of claim 1, At least one of the first surface and the second surface of the substrate has a wave shape, the optical sheet formed alternately with the valleys. The method of claim 1, And the vertical distance H ₁ and the vertical distance H ₂ satisfy a relational expression of 0.1 µm≤H ₁ -H _{2 |} ≤10 µm. The method of claim 1, The lens unit is a micro lens or a lenticular lens. The method of claim 1, The lens unit includes a plurality of first beads. The method of claim 1, An optical sheet further comprising a protective layer on the lower portion of the substrate. The method of claim 6, The protective layer comprises a resin and a plurality of second beads. The method of claim 1, The lens sheet further comprises a base portion. The method of claim 8, The base portion is an optical sheet of 5 to 50% of the height of the lens portion. The method of claim 1, At least one of the said 1st surface and said 2nd surface of the said base material has a curved surface. Light source; And An optical sheet positioned on the light source, The optical sheet includes a substrate including a first surface and a second surface facing each other and a lens portion positioned on the substrate, the vertical distance H ₁ from any point of the first surface of the substrate to the second surface. Is different from the vertical distance H ₂ from another point on the first side of the substrate to the second side. Light source; An optical sheet positioned on the light source; And A liquid crystal panel positioned on the optical sheet; The optical sheet includes a substrate including a first surface and a second surface facing each other and a lens portion positioned on the substrate, the vertical distance H ₁ from any point of the first surface of the substrate to the second surface. Is different from the vertical distance H ₂ from another point on the first side of the substrate to the second side.

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