KR20090123755A - Optical sheet, back light unit and liquid crystal display device comprising the same - Google Patents

Abstract

PURPOSE: An optical sheet, back light unit and liquid crystal display device comprising the same are provided to improve the diffusion characteristic by forming the optical sheet. CONSTITUTION: The optical sheet(100) comprises the reflection-type polarizing film(110), and the material(120) and protrusion(130). The reflection-type polarizing film plays the role of transmitting the light which is income from the light source and the role of reflecting. The reflection-type polarizing film comprises the first layer(111) and the second layer(112) including polymer. The second layer comprises the polymer having the different refractive index with the first layer. The materials plays the role of transmitting the light which is income from the light source. The material is composed of the light transmitting material. The protrusion is located on the top of the materials. The protrusion plays the role of serving as and diffusing of condensing the light which is income from the light source.

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.

Such a backlight unit is composed of an optical sheet made up of a plurality of sheets for diffusing and condensing light emitted from a light source, but there are many limitations in achieving improvement in manufacturing yield and brightness of the backlight unit.

Accordingly, the optical sheet of the present invention, a backlight unit and a liquid crystal display including the same, provide an optical sheet having a uniform distribution of luminance, a backlight unit and a liquid crystal display including the same.

In order to achieve the above object, the optical sheet according to an embodiment of the present invention is a reflective polarizing film, a substrate which is located on one surface of the reflective polarizing film, including a first surface and a second surface facing each other and A protrusion located on the substrate, wherein the thickness T ₁ from any point of the first face to the second face of the substrate is from the other point of the first face to the second face of the substrate. The thickness T ₂ is different from each other, and the thickness T ₁ and the thickness T ₂ may satisfy a relational equation of 0.1 μm ≦ │T ₁ -T _{2 |} ≦ ₁₀ μm.

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, and the optical sheet is disposed on one surface of the reflective polarizing film and the reflective polarizing film and faces each other. A substrate comprising a first side and a second side and a protrusion located on the base, wherein a thickness T ₁ from any point of the first side of the base to the second side is determined by the first side of the base. The thickness T ₂ from the other point of the plane to the second plane is different from each other, and the thickness T ₁ and the thickness T ₂ may satisfy a relational equation of 0.1 μm ≦ │T ₁ -T _{2 |} ≦ ₁₀ μm.

In addition, the liquid crystal display device according to an 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 is a reflective polarizing film and the reflective type. Located on one side of the polarizing film, and comprising a substrate comprising a first surface and a second surface facing each other and a projection located on the substrate, from any point of the first surface of the substrate to the second surface The thickness T ₁ of the substrate is different from the thickness T ₂ from another point of the first surface of the substrate to the second surface, and the thickness T ₁ and the thickness T ₂ are 0.1 μm ≦ │T ₁ -T ₂ │ ≦ A relation of 10 μm may be satisfied.

The optical sheet of the present invention, the backlight unit and the liquid crystal display including the same as the substrate having a curved surface, can improve the diffusion characteristics of the optical sheet, thereby providing a backlight unit and a liquid crystal display device having a uniform distribution of luminance. There is an advantage to this.

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

1A to 1C illustrate an optical sheet according to an embodiment of the present invention.

1A to 1C, the optical sheet 100 according to an embodiment of the present invention includes a reflective polarizing film 110, a substrate 120 and a substrate positioned on one surface of the reflective polarizing film 110. It may include a protrusion 130 located on the 120.

The reflective polarizing film 110 may serve to transmit or reflect light incident from the light source. The reflective polarizing film 110 may include a first layer 111 including a polymer material and a material including a polymer material positioned adjacent to the first layer 111 and having a refractive index different from that of the first layer 111. It may include two layers 112.

Here, the first layer 111 and the second layer 112 may be a structure that is alternately positioned repeatedly. In this case, the first layer 111 may be polymethyl methacrylate (PMMA), and the second layer 112 may be made of polyester.

In addition, the reflective polarizing film 110 may have a thickness of 100 to 300 μm in a small size and 700 to 800 μm in a large size according to the size of the display device.

Therefore, a part of the light incident from the light source passes through the reflective polarizing film 110, and a part of the light is reflected from the reflective polarizing film 110 toward the lower light source. At this time, the light reflected toward the light source is reflected again to be incident to the reflective polarizing film 110, a part of the light incident on the reflective polarizing film 110 is transmitted through the reflective polarizing film 110, a part is half The sand polarizing film 110 is reflected back to the lower light source direction.

That is, the reflective polarizing film 110 alternately stacks polymer layers having different refractive indices, orients molecular orientations of the polymer in one direction, and transmits only the polarization in the other direction and reflects the polarization in the same direction. Thereby, the efficiency of the light incident from the light source can be improved.

The substrate 120 serves to transmit light incident from the light source. To this end, since the substrate 120 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 120 may have first and second surfaces 121a and 121b facing each other, and at least one of the first and second surfaces 121a and 121b, for example, the first surface ( 121a) may comprise a curved surface.

The first surface 121a of the substrate 120 may be formed to have a wave shape, for example, so that the peaks 125 and the valleys 126 may be alternately formed. Here, the peak 125 of the substrate 120 may be the highest point of the wave shape, the valley 126 of the substrate 120 may be the lowest point of the wave shape. The pitch of the peaks formed on the first surface 121a of the substrate 120 may be constant and may vary.

In addition, the height difference between the hill 125 and the valley 126 formed to be adjacent to each other on the first surface 121a may be constant and may vary. In this case, the pitch of the peaks 125 and the height difference between the peaks 125 and the valleys 126 formed to be adjacent to each other should be appropriately selected according to the thickness and size of the substrate 120, the desired luminance uniformity, and the light diffusion rate, respectively. It does not specifically limit.

The substrate 120 may include a curved surface of the first surface 121a of the substrate 120 by any one of a method such as calendering processing, injection processing, and casting molding. It is not limited.

The substrate 120 may be formed to have a thin thickness, for example, an average thickness of 50 μm to 300 μm in response to the thinning of the backlight unit. Here, the thickness of the substrate 120 means an average value of the thickness from the peak of the first surface 121a to the second surface 121b and the thickness from the valley of the first surface 121a to the second surface 121b. can do.

By having the substrate 120 have a thickness of 50 μm or more, the backlight unit can be thinned to the maximum extent within the extent that the mechanical properties and the heat resistance of the optical sheet 100 do not degrade. In addition, by making the substrate 120 have a thickness of 300 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 thickness T ₁ from one point of the first face 121a of the substrate 120 to the second face 121b is the second face 121b from the other point of the first face 121a of the substrate 120. May be different from the thickness T ₂ ).

That is, the thickness T ₁ from one point of the first face 121a of the substrate 120 to the second face 121b is different from the second face 121b of the first face 121a of the substrate 120. The thickness T ₂ up to) may satisfy a relational equation of 0.1 μm ≦ T ₁ -T 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 thickness T ₁ and the thickness T ₂ .

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

                                         ×: Poor, ○: Good, ◎: Very good

Referring to Table 1, if 0.1 µm ≤ T ₁ -T ₂ , a curved surface is formed on one surface of the substrate 110 to diffuse light incident from the light source, and T ₁ -T 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 protrusion 130 may be located on the substrate 120, and the protrusion 130 may serve to collect or diffuse light incident from the light source.

The protrusion 130 may be made 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 protrusion 130 may be a prism portion whose cross section is a triangular prism shape. Here, as shown in FIG. 1A, the protrusion 130 includes a peak 131 and a valley 132, and the peak 131 and the valley 132 are straight lines in the same length direction as the length of the protrusion 130. Can be made.

Here, the distance P between the peaks 131 of the protrusion 130 may be 20 to 60 μm, and the angle A of the peak 131 may be 70 to 110 °. In addition, the height (H ₂₎ of the projection 130 may be equal to the height (H ₂₎ of acid 131, and may be 10 to 40㎛.

In addition, as shown in FIGS. 1B and 1C, the peaks 131 or valleys 132 of the protrusion 130 may form a continuous bend along the length direction of the protrusion 130, and the bend may be regular or It may be irregular.

That is, the peak 131 of the protrusion 130 may be extended to the width (W) of the protrusion 130, the average horizontal amplitude of the peak 131 may be 1 to 20㎛.

In addition, the valley 132 of the protrusion 130 may extend the width W of the protrusion 130 in a serpentine manner, and the average horizontal amplitude of the valley 132 may be 1 to 20 μm.

In addition, the height H ₂ of the peak 131 of the protrusion 130 may vary continuously from each bottom surface, that is, a dotted line on the top of the substrate 120 in FIG. 1A, and may exhibit regular or irregular bending. Can be achieved. Here, the dotted line may be a horizontal line below the valley 132 nearest to the substrate 120.

At this time, the average height difference of the mountain 131 formed along the longitudinal direction of the protrusion 130 may be 1 to 20㎛.

The protrusion 130 may include a plurality of hills 131 and valleys 132, and may further include a base 135 below the hills 131 and valleys 132. The base 135 is positioned below the hill 131 and the valley 132 in the protrusion 130 and may be integrated with the protrusion 130, that is, the hill 131 and the valley 132.

The height H ₁ of the base 135 may be 5 to 50% of the height H ₂ of the peak 131 of the protrusion 130.

The following table 2 shows a result of measuring a defect, and whether the optical transmission characteristics of an optical sheet according to the height (H ₁₎ of the height (H ₂₎ and the base (135) of the acid 131.

Height of base at% of mountain Light transmission characteristics Badness One ◎ ○ 3 ◎ ○ 5 ◎ × 10 ○ × 20 ○ × 30 ○ × 40 ○ × 50 ○ × 60 × × 70 × × 80 × ×

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

                               Bad status-○: Bad, ×: Bad

Referring to Table 2, when the height H ₁ of the base 135 is 5% or more of the height H ₂ of the mountain 131, the substrate 120 is pressurized when manufacturing the shape of the protrusion 130. Can be prevented from being damaged, and if the height H ₁ of the base 135 is 50% or less of the height H ₂ of the mountain 131, the base 135 is so thick that the transmittance of light incident from the light source is increased. There is an advantage that can be prevented from deteriorating.

Therefore, the height H ₁ of the base 135 may be 0.1 to 20 μm.

As described above, the optical sheet according to an embodiment of the present invention has an advantage of improving the diffusion efficiency of light incident from the light source by forming a substrate having a curved surface on the reflective polarizing film.

2A to 2E are views illustrating an optical sheet according to another embodiment of the present invention.

Referring to FIG. 2A, the optical sheet 200 according to another embodiment of the present invention may include a reflective polarizing film 210, a substrate 220 and a substrate 220 positioned on one surface of the reflective polarizing film 210. It may include a protrusion 230 positioned on.

Reflective polarizing film 210 of the present embodiment is the same as the above-described embodiment and detailed description thereof will be omitted.

The substrate 220 serves to transmit light incident from the light source. To this end, since the substrate 220 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 220 may have first and second surfaces 221a and 221b facing each other, and at least one of the first and second surfaces 221a and 221b, for example, a first surface. 221a may include a curved surface.

The first surface 221a of the substrate 220 may be formed to have a wave shape, for example, so that the peaks 225 and the valleys 226 of the substrate 220 may be alternately formed. The pitch of the peaks 225 formed on the first surface 221a of the substrate 220 may be constant and may vary.

In addition, the height difference between the hill 225 and the valley 226 formed to be adjacent to each other on the first surface 221a may be constant or may vary. In this case, the pitch of the peaks 225 and the height difference between the peaks 225 and the valleys 226 formed to be adjacent to each other should be appropriately selected according to the thickness and size of the substrate 220, the desired luminance uniformity and the light diffusion rate, respectively. It is not limited.

The substrate 220 may include a curved surface of the first surface 221a of the substrate 220 through any one of a method such as calendering processing, injection processing, and casting molding. It is not limited.

The substrate 220 may be formed to have a thin thickness, for example, an average thickness of 50 μm to 300 μm in response to the thinning of the backlight unit. Here, the thickness of the base material 220 means an average value of the thickness from the peak of the first surface 221a to the second surface 221b and the thickness from the valley of the first surface 221a to the second surface 221b. can do.

By making the substrate 220 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 200 falling. In addition, by making the substrate 220 have a thickness of 300 μm or less, thickness reduction of the backlight unit may be achieved, and mechanical properties and heat resistance of the optical sheet 200 may be maximized.

On the other hand, the thickness T ₁ from one point of the first face 221a of the base material 220 to the second face 221b is the second face 221b from another point of the first face 221a of the base material 220. May be different from the thickness T ₂ ).

That is, the thickness T ₁ from one point of the first face 221a of the base material 220 to the second face 221b is the second face 221b from another point of the first face 221a of the base material 220. The thickness T ₂ up to) may satisfy a relational equation of 0.1 μm ≦ T ₁ -T ₂ ≦ 10 μm.

Here, if 0.1 μm ≤ T ₁ -T ₂ │, a curved surface is formed on one surface of the substrate 210 to diffuse the light incident from the light source, and if T ₁ -T _{2 |} ≤ 10 μm, There is an advantage that the level difference of the curved surface of the substrate 210 is too large to prevent the luminance from being lowered.

The protrusion 230 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 protrusion 230 may further include a base 235.

The height H ₁ of the base 235 may be 5 to 50% of the height H ₂ of the protrusion 230. Here, when the height H ₁ of the base 235 is 5% or more of the height H ₂ of the protrusion 230, when the shape of the protrusion 230 is manufactured, the base 220 is damaged by pressure. When the height H ₁ of the base 235 is 50% or less of the height H ₂ of the protrusion 230, the base 235 is too thick to prevent the transmittance of light incident to the light source from decreasing. There is an advantage to this.

Here, unlike the above-described embodiment, the protrusion 230 may be a micro lens or a lenticular lens.

2A to 2C, the micro lens may be formed to have an embossed hemisphere on one surface of the substrate 220.

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 diameter of the lens as shown in FIG. 2B, an irregular diameter of the lens as shown in FIG. 2C, and a constant or irregular height of the lens. .

In addition, the lens diameter of the micro lens may be formed to 20 to 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.

2D and 2E, the protrusion 230 may be a lenticular lens. 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, it may be in the form of a tunnel.

In the lenticular lens, as shown in FIG. 2D, the pitch of the lens may be constant. Alternatively, as shown in FIG. 2E, the pitch of the lens may be irregular, and the height of the lens may also be constant or irregular. It is not limited.

3A and 3B illustrate an optical sheet according to another embodiment of the present invention.

3A and 3B, the optical sheet 300 according to another embodiment of the present invention may be a reflective polarizing film 310, a substrate 320 positioned on one surface of the reflective polarizing film 310, and the It may include a protrusion 330 located on the substrate 320.

Here, since the reflective polarizing film 310 and the base portion 335 have been described in detail in the above-described embodiments, the description thereof will be omitted.

The substrate 320 serves to transmit light incident from the light source. To this end, since the substrate 320 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.

At least one of the first and second surfaces 321a and 321b facing each other, for example, the first surface 321a may include a curved surface.

For example, the first surface 321a of the substrate 320 may be formed to have a wave shape, such that the peaks 325 and the valleys 325 may be alternately formed. The pitch of the peaks 325 formed on the first surface 321a of the substrate 320 may be constant or may vary.

In addition, the height difference between the peaks 325 and the valleys 326 formed to be adjacent to each other on the first surface 321a may be constant or may vary. In this case, the pitch of the peaks 325 and the height difference between the peaks 325 and the valleys 326 formed to be adjacent to each other should be appropriately selected according to the thickness and size of the substrate 320, the desired luminance uniformity and the light diffusion rate, respectively. It is not limited.

The substrate 320 may include a curved surface of the first surface 321a of the substrate 320 by any one of a method such as calendering processing, injection processing, and casting molding. It is not limited.

The substrate 320 may be formed to have a thin thickness, for example, an average thickness of 50 μm to 300 μm in response to the thinning of the backlight unit. Here, the thickness of the substrate 320 means an average value of the thickness from the peak of the first surface 321a to the second surface 321b and the thickness from the valley of the first surface 321a to the second surface 321b. can do.

By having the substrate 320 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 300 falling. In addition, by making the substrate 320 have a thickness of 300 μm or less, thickness reduction of the backlight unit may be achieved, and mechanical properties and heat resistance of the optical sheet 300 may be maximized.

On the other hand, the thickness T ₁ from one point of the first face 321a of the substrate 320 to the second face 321b is the second face 321b from the other point of the first face 321a of the substrate 320. May be different from the thickness T ₂ ).

That is, the thickness T ₁ from one point of the first face 321a of the substrate 320 to the second face 321b is the second face 321b from the other point of the first face 321a of the substrate 320. The thickness T ₂ up to) may satisfy a relational equation of 0.1 μm ≦ T ₁ -T ₂ ≦ 10 μm.

Here, if 0.1 μm ≤ T ₁ -T ₂ │, a curved surface is formed on one surface of the substrate 310 to diffuse light incident from the light source, and if T ₁ -T ₂ │ 10 μm, In addition, there is an advantage that the level difference of the curved surface of the substrate 310 is too large to prevent the luminance from being lowered.

The protrusion 330 may include a first resin 337 and a plurality of first beads 338.

The first resin 337 may be acrylic resin, and the first bead 338 may be any one or more selected from the group consisting of polymethyl methacrylate (PMMA), polystyrene, and silicone.

In addition, the first resin 337 may further include an antistatic agent made of polyvinylbenzyl, poly (meth) acrylate, styrene- (meth) acrylate copolymer, methacrylate methacrylimide copolymer, or the like. .

The first bead 338 may be included in an amount of 1 to 10 parts by weight based on the first resin 337.

Table 3 below shows the results of measuring diffusion and luminance characteristics of the optical sheet according to the content of the first bead 338 of the first resin 337 of the protrusion 330.

Content of first bead relative to the first resin (parts by weight) Diffusion characteristics Luminance characteristics 0.1 × ◎ 0.5 × ◎ One ○ ◎ 2 ○ ○ 3 ○ ○ 5 ○ ○ 7 ○ ○ 9 ○ ○ 10 ◎ ○ 12 ◎ × 15 ◎ ×

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

Referring to Table 3, when the content of the first bead 338 relative to the first resin 337 of the protrusion 330 is 1 part by weight or more, there is an advantage in that the diffusion characteristic of the light incident from the light source is excellent. When the content of the first bead 338 is 10 parts by weight or less with respect to the resin 337, there is an advantage that the luminance can be prevented from being lowered.

Meanwhile, the particle diameter of the first bead 138 distributed in the first resin 337 may not be uniform but may have an irregular distribution.

The shape of the first bead 338 may be a circle, an oval, a snowman, an uneven circle, but is not limited thereto.

In addition, the first bead 338 distributed in the first resin 337 may have an irregular distribution without having a regular distribution in the first resin 337. In this case, the first bead 338 distributed in the first resin 337 may be completely included so as not to be exposed on the surface of the protrusion 330. That is, the first bead 338 may be embedded in the first resin 337 forming the protrusion 330.

As described above, the optical sheet 300 according to another embodiment of the present invention includes a plurality of first beads 338 in the protrusion 330, thereby diffusing the light incident from the light source, thereby providing a uniform distribution of luminance. There is an advantage that can provide an optical sheet.

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

4A and 4B, the optical sheet 400 according to another embodiment of the present invention includes a reflective polarizing film 410, a substrate 420 positioned on the reflective polarizing film 410, and It may include a protrusion 430 disposed on the substrate 420 and a protective layer 440 positioned below the reflective polarizing film 410.

Since the reflective polarizing film 410 and the base 435 have been described in detail in the above-described embodiments, the description thereof will be omitted.

The substrate 420 serves to transmit light incident from the light source. To this end, since the substrate 420 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.

At least one of the first and second surfaces 421a and 421b facing each other, for example, the first surface 421a may include a curved surface.

The first surface 421a of the substrate 420 may be formed to have a wave shape, for example, so that the peaks 425 and the valleys 426 may be alternately formed. The pitch of the peaks 425 formed on the first surface 421a of the substrate 420 may be constant or may vary.

In addition, the height difference between the hill 425 and the valley 426 formed to be adjacent to each other on the first surface 421a may be constant or may vary. In this case, the pitch of the peaks 425 and the height difference between the peaks 425 and the valleys 426 formed to be adjacent to each other should be appropriately selected according to the thickness and size of the substrate 420, the desired luminance uniformity, and the light diffusion rate. Therefore, it is not limited.

The substrate 420 may include a curved surface of the first surface 421a of the substrate 420 through any one of a method such as calendering, injection processing, and casting molding. It is not limited.

The substrate 420 may be formed to have a thin thickness, for example, an average thickness of 50 μm to 300 μm in response to the thinning of the backlight unit. Here, the thickness of the base material 420 means the thickness from the peak 425 of the first surface 421a to the second surface 421b and the valley 426 of the first surface 421a to the second surface 421b. It may mean an average value of the thickness of.

By having the substrate 420 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 400 falling. In addition, by making the substrate 420 have a thickness of 300 μm or less, thickness reduction of the backlight unit may be achieved, and mechanical properties and heat resistance of the optical sheet 400 may be maximized.

On the other hand, the thickness T ₁ from one point of the first face 421a of the base material 420 to the second face 421b is the second face 421b from another point of the first face 421a of the base material 420. May be different from the thickness T ₂ ).

That is, the thickness T ₁ from one point of the first face 421a of the base material 420 to the second face 421b is the second face 421b from another point of the first face 421a of the base material 420. The thickness T ₂ up to) may satisfy a relational equation of 0.1 μm ≦ T ₁ -T ₂ ≦ 10 μm.

Here, if 0.1 μm ≤ T ₁ -T ₂ │, a curved surface is formed on one surface of the substrate 410 to diffuse the light incident from the light source, and if T ₁ -T ₂ │ ≤ 10 μm, In addition, there is an advantage that the level difference of the curved surface of the substrate 410 is too large to prevent the luminance from being lowered.

The protrusion 430 may be made 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 protrusion 430 may be a prism portion as in the above-described embodiments, and alternatively, may be a micro lens or a lenticular lens. In addition, the protrusion 430 may include a plurality of first beads.

The protective layer 440 may serve to improve heat resistance of the optical sheet 400. In more detail, the protective layer 440 may include a second resin 441 and a plurality of second beads 442 dispersed in the resin 441.

The second resin 441 may use an acrylic resin that is transparent and has excellent heat resistance and mechanical properties, and may be the same as the first resin of the above-described embodiment. In addition, the second resin 441 may further include an antistatic agent made of polyvinylbenzyl, poly (meth) acrylate, styrene- (meth) acrylate copolymer, methacrylate methacrylimide copolymer, or the like. .

The second bead 442 may be manufactured using the same or different types of resins as the second resin 441, and may be included in an amount of 10 to 50 parts by weight based on the second resin 441.

The size of the second bead 442 may be appropriately selected according to the thickness of the reflective polarizing film 410, may be 2 to 10㎛.

In one embodiment of the present invention, the size of the second bead 442 may be substantially the same, and the distribution in the second resin 441 may be regular. In contrast, the sizes of the second beads 442 are different from each other, and the distribution in the second resin 441 may be irregular. In addition, a portion of the second bead 442 may be exposed to the outside of the second resin 441 constituting the protective layer 440, the second bead 442 is a second resin (constituting the protective layer 440 ( 441).

The first bead and the second bead 442 may use the same material as each other, and may be different from each other.

As described above, the protective layer 440 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 second resin 441 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 440 may also serve to prevent scratches on the optical sheet due to external impact or other physical force.

In addition, the protective layer 440 may improve the uniformity of luminance by diffusing light incident from the light source due to the second bead 442.

5A to 5B 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. 5A, 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 aforementioned optical sheet.

5A and 5B, 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. It may be one of (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 is located on one surface of the reflective polarizing film, the reflective polarizing film, and includes a substrate including first and second surfaces facing each other, and a protrusion located on the substrate. The thickness T ₁ from one point of the first face to the second face is different from the thickness T ₂ from another point of the first face of the substrate to the second face, and the thickness T ₁ and the thickness T ₂ may satisfy a relational expression of 0.1 μm ≦ T ₁ -T _{2 |} ≦ ₁₀ μm.

Therefore, when light is incident from the lower portion of the optical sheet 530, the incident light is reflected or transmitted in the reflective polarizing film. Therefore, the efficiency of the light incident from the light source can be improved.

In addition, the light transmitted through the reflective polarizing film is diffused by the substrate having a curved surface has the advantage that the brightness can be uniform.

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.

6A and 6B are exploded perspective views and cross-sectional views for describing the configuration of a backlight unit according to an embodiment of the present invention.

6A and 6B 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. 6A and 6B is substantially the same as the backlight unit illustrated in FIGS. 5A and 5B except for arrangement of a light source and a change in components thereof, and thus, redundant descriptions thereof will be omitted. Only its features will be described.

6A and 6B, 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 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 is located on one surface of the reflective polarizing film, the reflective polarizing film, and includes a substrate including first and second surfaces facing each other and a protrusion located on the substrate. The thickness T ₁ from one point of the first face to the second face is different from the thickness T ₂ from another point of the first face of the substrate to the second face, and the thickness T ₁ and the thickness T ₂ may satisfy a relational expression of 0.1 μm ≦ T ₁ -T _{2 |} ≦ ₁₀ μm.

Therefore, when light is incident from the lower part of the optical sheet 430, the incident light is reflected or transmitted in the reflective polarizing film. Therefore, the efficiency of the light incident from the light source can be improved.

In addition, the light transmitted through the reflective polarizing film is diffused by the substrate having a curved surface has the advantage that the brightness can be uniform.

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.

7A and 7B 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. 7A and 7B illustrate the backlight unit illustrated in FIGS. 5A and 5B as the backlight unit, but the present invention is not limited thereto, and the backlight unit illustrated in FIGS. 6A and 6B may be employed as the backlight unit. Meanwhile, since the backlight unit illustrated in FIGS. 7A and 7B is the same as described above, overlapping descriptions are omitted and only the features thereof will be described.

Referring to FIGS. 7A and 7B, the liquid crystal display 700 according to an exemplary embodiment may display an image by using 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 814 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 embodiment of the present invention have the advantage of uniformity of luminance by forming a substrate having a curved surface on the reflective polarizing film.

Therefore, an optical sheet, a backlight unit, and a liquid crystal display device including the same according to an embodiment of the present invention have an advantage of providing a backlight unit and a liquid crystal display device having a uniform distribution of luminance and improved display quality.

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.

1A to 1C illustrate an optical sheet according to an embodiment of the present invention.

2A to 2E illustrate an optical sheet according to another embodiment of the present invention.

3A and 3B illustrate an optical sheet according to another embodiment of the present invention.

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

5A and 5B 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 invention.

6A and 6B are exploded perspective views and cross-sectional views illustrating a configuration of a backlight unit according to an embodiment of the present invention.

7A and 7B 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.

Claims (18)

Reflective polarizing film; A substrate positioned on one surface of the reflective polarizing film and including a first surface and a second surface facing each other; And A protrusion located on the substrate, The thickness T ₁ from any point of the first face of the substrate to the second face is different from the thickness T ₂ from another point of the first face of the substrate to the second face, And the thickness T ₁ and the thickness T ₂ satisfy an expression of 0.1 μm ≦ T ₁ -T _{2 |} ≦ ₁₀ μm. The method of claim 1, At least one of the first surface and the second surface of the substrate is a wave-shaped optical sheet. The method of claim 1, At least one of the said 1st surface and said 2nd surface of the said base material has a serpentine curved surface. The method of claim 1, And the protrusion includes a first resin and a plurality of first beads. The method of claim 4, wherein The first bead is included 1 to 10 parts by weight based on 100 parts by weight of the first resin. The method of claim 1, The protrusion includes a plurality of hills and valleys, At least one of the acid and the valley twists side to side. The method of claim 1, The average thickness of the said substrate is 50-300 micrometers. The method of claim 1, The protrusion includes a plurality of hills and valleys, The height of at least one of the peak and the valley varies in the longitudinal direction of the protrusion. The method of claim 1, The protrusion includes a plurality of hills and valleys, An optical sheet further comprising a base under the valley. The method of claim 9, And the height of the base is 5 to 50% of the height of the mountain. The method of claim 9, The acid, the valley and the base are integral. The method of claim 1, The reflective polarizing film is an optical sheet in which the first layer and the second layer having different refractive indices are alternately stacked. The method of claim 1, An optical sheet further comprising a protective layer on the other surface of the reflective polarizing film. The method of claim 13, The protective layer includes a second resin and a plurality of second beads, The optical sheet of 10 to 50 parts by weight based on 100 parts by weight of the second resin. The method according to claim 4 or 14, At least one of the first resin and the second resin includes an antistatic agent. The method of claim 1, The protruding portion is any one selected from the group consisting of a prism portion, a micro lens and a lenticular lens. Light source; And An optical sheet positioned on the light source, The optical sheet includes a reflective polarizing film, a substrate disposed on one surface of the reflective polarizing film, a substrate including first and second surfaces facing each other, and a protrusion located on the substrate, wherein the substrate is formed of the substrate. The thickness T ₁ from one point on one face to the second face is different from the thickness T ₂ from another point on the first face of the substrate to the second face, and the thickness T ₁ and the thickness T ₂ It is 0.1㎛≤│T ₁ -T ₂ │≤10㎛ in relation backlight unit satisfying. Light source; An optical sheet positioned on the light source; And It includes a liquid crystal panel positioned on the optical sheet, The optical sheet includes a reflective polarizing film, a substrate disposed on one surface of the reflective polarizing film, a substrate including first and second surfaces facing each other, and a protrusion located on the substrate, wherein the substrate is formed of the substrate. The thickness T ₁ from one point on one face to the second face is different from the thickness T ₂ from another point on the first face of the substrate to the second face, and the thickness T ₁ and the thickness T ₂ Wherein the liquid crystal display satisfies the relation of 0.1 μm ≦ │T ₁ -T _{2 |} ≦ ₁₀ μm.

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