KR101438221B1 - Optical sheet, backlight unit including same, and liquid crystal display - Google Patents

Abstract

The present invention relates to an optical element comprising a substrate, a plurality of protrusions located on the substrate, and an optical layer located below the substrate, the optical layer comprising a first layer comprising a polymeric material and a second layer disposed adjacent the first layer, And a second layer including a polymer material having a different refractive index from the first layer, wherein the plurality of protrusions include a first protrusion and a second protrusion, wherein a height of the first protrusion is different from a height of the second protrusion Another optical sheet is provided.

Optical sheet

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, the liquid crystal 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 with a light receiving display device.

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 protective sheet, a prism sheet, and the like.

The prism sheet among the optical sheets has a plurality of linear prism structures, and the cross section may be formed in an isosceles triangle shape.

However, the conventional prism sheet may concentrate the light emitted from the light source to increase the brightness, while there may be a portion that emits uneven light depending on the angle of the prism structure. These uneven light emissions, when visually observed, appear to be a distinctly dark area or a light interference phenomenon, such as a ring of iridescent light, as compared to other parts.

Therefore, there is a problem that a sharp image can not be provided due to the shape of the light interference caused by the regular prism structure.

Accordingly, the present invention provides an optical sheet capable of preventing a light interference phenomenon to provide a clear image, a backlight unit including the optical sheet, and a liquid crystal display device.

In order to achieve the above object, an optical sheet according to an embodiment of the present invention includes a substrate, a plurality of projections positioned on the substrate, and an optical layer positioned below the substrate, And a second layer disposed adjacent to the first layer and comprising a polymeric material having a different refractive index from the first layer, the plurality of protrusions including a first protrusion and a second protrusion And the height of the first protrusion may be different from the height of the second protrusion.

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, a plurality of projections positioned on the substrate, and an optical Wherein the optical layer comprises a first layer comprising a polymeric material and a second layer positioned adjacent the first layer and comprising a polymeric material having a different refractive index from the first layer, The height of the first protrusion may be different from the height of the second protrusion, and the protrusion of the second protrusion may include a first protrusion and a second protrusion.

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, A plurality of protrusions and an optical layer disposed under the substrate, the optical layer comprising a first layer comprising a polymeric material and a second layer disposed adjacent the first layer and having a refractive index different from that of the first layer, Wherein the plurality of protrusions include a first protrusion and a second protrusion, and a height of the first protrusion may be different from a height of the second protrusion.

INDUSTRIAL APPLICABILITY The optical sheet of the present invention, the backlight unit including the same, and the liquid crystal display device have an advantage of improving light efficiency and preventing a light interference phenomenon and providing a clear image.

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

1A and 1B are views of an optical sheet according to an embodiment of the present invention.

1A and 1B, an optical sheet 100 according to an embodiment of the present invention includes a substrate 110, a plurality of protrusions 120 positioned on the substrate 110, Wherein the optical layer 130 comprises a first layer 131 comprising a polymeric material and a second layer 131 disposed adjacent to the first layer 131, And a second layer (132) including a polymer material having different refractive indexes, wherein the plurality of protrusions (120) include a first protrusion (121) and a second protrusion (122) 121 may be different from the height h2 of the second protrusion 122. In this case,

More specifically, the substrate 110 serves to transmit light incident from the light source. To this end, the substrate 110 must be capable of transmitting light incident from a light source, and therefore, it is preferable that the substrate 110 be made of a light transmissive material, for example, a material selected from the group consisting of polyethylene terephthalate, polycarbonate, polypropylene, polyethylene, polystyrene and polyepoxy But it is not limited thereto.

The plurality of protrusions 120 may function to condense the light incident from the light source.

The plurality of protrusions 120 include a first protrusion 121 and a second protrusion 122. The height h1 and the width w1 of the first protrusion 121 are equal to the height h1 and the width w1 of the second protrusion 122, The height h2 and the width w2.

In addition, the plurality of protrusions 120 may be linearly formed along the longitudinal direction of the protrusions, but are not limited thereto.

In the cross-section of the plurality of protrusions 120, the protrusions 120 may have different cross-sectional shapes, and may have a triangular shape, for example, an isosceles triangle or an equilateral triangle. However, the present invention is not limited thereto, and they may have the same cross-sectional shape.

The cross-section of the first protrusion 121 and the cross-section of the second protrusion 122 may be different from each other, but they may be the same shape.

The height h1 and the width w1 of the first protrusion 121 of the plurality of protrusions 120 may be different from the height h2 and the width w2 of the second protrusion 122, May be the same.

Here, the plurality of protrusions 120 may have a height of 20 to 500 탆. The plurality of protrusions 120 may have different widths, and preferably have a width of 1 to 100 탆.

Accordingly, the plurality of protrusions 120 have a height of 20 to 500 mu m and a width of 1 to 100 mu m, so that the characteristic of condensing light incident from the lower light source can be improved.

Although it is described that the plurality of protrusions 120 described above may have different heights and widths, they are not limited thereto but may be regular and may be the same.

The optical layer 130 may serve to transmit or reflect light incident from the light source. The optical layer 130 includes a first layer 131 comprising a polymeric material and a second layer 130 disposed adjacent to the first layer 131 and including a polymeric material having a refractive index different from that of the first layer 131, (132).

Here, the first layer 131 and the second layer 132 may be alternately and repeatedly disposed. In this case, the first layer 131 may be polymethylmethacrylate (PMMA), and the second layer 132 may be formed of a polyester.

Further, the optical layer 130 preferably has a thickness of 120 to 450 mu m.

Accordingly, a part of the light incident from the light source is transmitted through the optical layer 130 and a part of the light is reflected from the optical layer 130 toward the lower light source. At this time, the light reflected toward the light source is reflected again and is incident on the optical layer 130. A part of the light incident on the optical layer 130 transmits through the optical layer 130, As shown in FIG.

That is, the optical layer 130 alternately stacks polymer layers having different refractive indexes, uses a principle of orienting the molecular orientation of the polymer in one direction, transmitting only polarized light in the other direction, and reflecting polarized light in the same direction, The efficiency of light incident from the light source can be improved.

An adhesive layer 140 may be further disposed between the substrate 110 and the optical layer 130.

The adhesive layer 140 may serve to bond the substrate 110 and the optical layer 130, and may be made of acrylic resin.

As described above, the optical sheet according to an embodiment of the present invention includes the plurality of irregularly formed protrusions and the optical layer, thereby improving the efficiency of light incident from the light source, and refracting the light incident from the light source irregularly So that the optical interference phenomenon can be prevented and the sharpness of the image can be improved.

Hereinafter, various structures of the optical sheet according to one embodiment of the present invention will be described in detail. The optical sheet described below can be applied to all the embodiments described below without need of disclosing the protrusion.

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

Referring to FIGS. 2A to 2C, an optical sheet 300 according to another embodiment of the present invention includes a substrate 310, a plurality of protrusions 320 disposed on the substrate 310, And an optical layer (330) underlying the substrate (310), the optical layer (330) comprising a first layer (331) comprising a polymeric material and a second layer And a second layer 332 including a polymer material having a different refractive index from the layer 331. The plurality of protrusions 320 includes a first protrusion 321 and a second protrusion 322, The height of the first protrusion 321 may be different from the height of the second protrusion 322.

The plurality of protrusions 320 may be continuously bent.

More specifically, the plurality of protrusions 320 may have a random zigzag shape on the left and right, and the average horizontal amplitude of the protrusions 320 may be 1 to 20 占 퐉.

The plurality of protrusions 320 includes a valley 325 where the protrusions 320 meet with each other, and the valleys 325 may have a random zigzag shape on both sides, and the average horizontal amplitude of the valleys 325 May be 1 to 20 mu m.

The protrusions 320 may have different heights in the longitudinal direction of the protrusions 320. That is, the protrusions 320 may vary periodically from the bottom of each protrusion 320, and may vary irregularly. At this time, the average height difference of the protrusions 320 may be 1 to 20 占 퐉.

Further, the depths of the troughs 325 may be different from each other. However, the depths of the valleys 325 may be equal to each other and are not limited thereto.

The horizontal amplitude of the protrusion 320 or the valley 325 of the optical sheet 300 according to another embodiment of the present invention changes at random and the height of the protrusion 320 or the depth of the valley 325 varies Or irregularly.

Therefore, it is difficult for the defects such as the crushing of the protrusion 320 to be visually easily detected by the physical contact with the other sheets in contact with the upper portion of the optical sheet 300, Lt; / RTI >

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

3A and 3B, an optical sheet 400 according to one embodiment of the present invention includes a substrate 410, a plurality of protrusions 420 positioned on the substrate 410, And an optical layer 430 underlying the substrate 410. The optical layer 430 includes a first layer 431 comprising a polymeric material and a first layer 431 disposed adjacent the first layer 431, And a second layer 432 including a polymer material having a different refractive index from the layer 431. The plurality of protrusions 420 include a first protrusion 421 and a second protrusion 422, The height of the first protrusion 421 may be different from the height of the second protrusion 422.

The plurality of protrusions 420 may further include a plurality of first beads 450.

Here, the first beads 450 may be included in a range of 1 to 10 parts by weight with respect to the plurality of protrusions 420. Therefore, it is possible to prevent the problem that the light incident from the light source is difficult to be diffused by the first bead 450, and the transmittance of the light incident from the light source can be prevented from being lowered.

At this time, the particle diameters of the first beads 450 may not be uniform but irregular. In addition, the first beads 450 may have an irregular distribution without having a regular distribution in the plurality of protrusions 420.

At this time, the first bead 450 may be completely contained in the protrusion 420 so as not to be exposed on the surface of the plurality of protrusions 420.

As described above, the optical sheet according to the embodiment of the present invention has the advantage that the diffusing characteristics of the optical sheet can be improved by including the plurality of first beads in the plurality of protrusions, and the viewing angle can be improved.

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

4A and 4B, an optical sheet 500 according to another embodiment of the present invention includes a substrate 510, a plurality of protrusions 520 disposed on the substrate 510, And an optical layer 530 disposed under the substrate 510. The optical layer 530 includes a first layer 531 including a polymer material and a second layer 531 disposed adjacent to the first layer 531, And a second layer 532 including a polymer material having a refractive index different from that of the first layer 531. The plurality of protrusions 520 includes a first protrusion 521 and a second protrusion 522 And the height of the first protrusion 521 may be different from the height of the second protrusion 522.

The optical sheet 500 according to another embodiment of the present invention may further include a protective layer 550 including a plurality of second beads 552 under the optical layer 530. [

The protective layer 550 may improve the heat resistance of the optical sheet 500. More specifically, the protective layer 550 may include a resin base material 551 and a plurality of second beads 552 dispersed in the base material 551.

The base material 551 is transparent and acrylic resin having excellent heat resistance and mechanical properties can be used. The acrylic resin may be, for example, polyacrylate or polymethyl methacrylate.

The second beads 552 may be manufactured using the same or different resins as the base material 551 and may be included in the base material 551 in an amount of 10 to 50 parts by weight.

The size of the second bead 552 may be appropriately selected according to the thickness of the substrate 510, and may be 1 to 10 탆.

In an embodiment of the present invention, the size of the second beads 552 may be substantially the same, and the distribution in the base material 551 may be regular. Alternatively, the sizes of the second beads 552 are different from each other, and the distribution in the base material 551 may also be irregular.

In addition, the second beads 552 referred to in the embodiment of the present invention may be the same as the first beads described above, but they are not limited thereto and may be different from each other.

The protective layer 550 can prevent the optical sheet from being deformed by heat generated in the light source. That is, the optical sheet is not wrinkled by the base material 551 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 550 can also prevent scratches on the optical sheet due to an external impact or other physical force.

5A and 5B are an exploded perspective view and a cross-sectional view for explaining a configuration of a backlight unit including an optical film according to embodiments of the present invention.

In Fig. 5A, an edge type backlight unit is shown as a backlight unit, and since the optical sheet of the present invention is the same as the above-mentioned optical sheet, the overlapping description is omitted.

5A and 5B, the backlight unit 700 according to an 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 700 may include a light source 720 and an optical sheet 730. The backlight unit 700 may further include a light guide plate 740, a reflector 750, a bottom cover 760, and a mold frame 770.

The light source 720 can generate light using driving power applied from the outside and emit the generated light.

The light source 720 may be formed on at least one side of the light guide plate 740 along the major axis direction of the light guide plate 740 or may be formed on each side of the light guide plate 740 . The light emitted from the light source 720 may be incident directly into the light guide plate 740 or may be incident on the light source housing 722 formed to surround a part of the light source 720, for example, about 3/4 of the outer peripheral surface of the light source 720 And then may be incident into the light guide plate 740.

Specifically, the light source 720 includes a cold cathode fluorescent lamp (CCFL), a hot cathode fluorescent lamp (HCFL), an external electrode fluorescent lamp (EEFL) (Light Emitting Diode) (LED), but the present invention is not limited thereto.

The optical sheet 730 may be disposed above the light guide plate 740. The optical sheet 730 may function to condense the light incident from the light source 720.

The optical sheet 730 includes a substrate, a plurality of protrusions located on the substrate, and an optical layer positioned below the substrate, wherein the optical layer comprises a first layer comprising a polymeric material and a second layer adjacent to the first layer And a second layer including a polymer material having a refractive index different from that of the first layer, wherein the plurality of protrusions include a first protrusion and a second protrusion, and a height of the first protrusion is larger than a height of the second protrusion It may be different from height.

Therefore, when light is incident from the bottom of the optical sheet 730, the incident light is reflected or transmitted through the optical layer. Therefore, efficiency of light incident from the light source can be improved.

Further, the light transmitted through the optical layer can be irregularly refracted at the plurality of protrusions. Therefore, the plurality of protruding portions can prevent the occurrence of optical interference phenomenon, thereby improving the sharpness of the image.

As a result, the display quality of the backlight unit 700 according to an embodiment of the present invention can be improved.

The light guide plate 740 may be disposed to face the light source 720 and guide the light so that the light incident from the light source 720 is emitted upward.

The reflection plate 750 may be disposed below the light guide plate 740 and may reflect upward the light emitted downward through the light guide plate 740 out of the light emitted from the light source 720.

The bottom cover 760 includes a bottom portion 762 and a side portion 764 extending from the bottom portion 762 to form a storage space. The storage space includes a light source 720, an optical sheet 730 The light guide plate 740, and the reflection plate 750 can be accommodated.

The mold frame 770 is formed in a substantially rectangular shape and can be fastened to the bottom cover 760 in a top down manner from above the bottom cover 760.

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

All. 6A and 6B show a direct-type backlight unit as a backlight unit, the present invention is not limited thereto. Meanwhile, the backlight unit shown in Figs. 6A and 6B is substantially the same as the backlight unit shown in Figs. 5A and 5B, 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. 6A and 6B, the backlight unit 800 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 800 may include a light source 820 and an optical sheet 830. The backlight unit 800 may further include a reflection plate 850, a bottom cover 860, a mold frame 870, and a diffusion plate 880.

At least one light source 820 may be disposed below the diffusion plate 880. Therefore, the light emitted from the light source 820 can be directly incident on the diffusion plate 880.

The optical sheet 830 may be disposed above the diffuser plate 880. The optical sheet 830 may function to condense the light incident from the light source 820.

The optical sheet 830 includes a substrate, a plurality of protrusions located on the substrate, and an optical layer positioned below the substrate, wherein the optical layer comprises a first layer comprising a polymeric material and a second layer adjacent to the first layer And a second layer including a polymer material having a refractive index different from that of the first layer, wherein the plurality of protrusions include a first protrusion and a second protrusion, and a height of the first protrusion is larger than a height of the second protrusion It may be different from height.

Therefore, when light is incident from the bottom of the optical sheet 830, the incident light is reflected or transmitted through the optical layer. Therefore, efficiency of light incident from the light source can be improved.

Further, the light transmitted through the optical layer can be irregularly refracted at the plurality of protrusions. Therefore, the plurality of protruding portions can prevent the occurrence of optical interference phenomenon, thereby improving the sharpness of the image.

As a result, the display quality of the backlight unit 800 according to an embodiment of the present invention can be improved.

The diffuser plate 880 may be disposed between the light source 820 and the optical sheet 830 and may diffuse the light incident from the light source 820 upward. This is to prevent the shape of the light source 820 from being visible through the backlight unit 800 and to further diffuse the light.

7A and 7B 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. In FIGS. 7A and 7B, the backlight unit shown in FIGS. 5A and 5B is shown as a backlight unit, but the present invention is not limited thereto, and the backlight unit shown in FIGS. 6A and 6B may be employed as the backlight unit. 7A and 7B are the same as those described above, so that redundant description will be omitted and only the features will be described.

Referring to FIGS. 7A and 7B, a liquid crystal display 900 according to an embodiment of the present invention can display an image using electro-optical characteristics of a liquid crystal.

The liquid crystal display device 900 may include a backlight unit 910 and a liquid crystal panel 1010.

The backlight unit 910 may be mounted under the liquid crystal panel 1010 and may provide light to the liquid crystal panel 1010.

The backlight unit 910 may include a light source 920 and an optical sheet 930. The backlight unit 910 may further include a light guide 940, a reflector 950, a bottom cover 960, and a mold frame 970.

The liquid crystal panel 1010 is mounted on the mold frame 970 and can be fixed by a top cover 1020 which is coupled with the bottom cover 960 in a top-down manner.

The liquid crystal panel 1010 can display an image using light provided from the backlight unit 910, specifically, light emitted from the light source 920.

The liquid crystal panel 1010 may include a color filter substrate 1012 and a thin film transistor substrate 1014 facing each other with a liquid crystal therebetween.

The color filter substrate 1012 can realize the color of the image to be displayed through the liquid crystal panel 1010. [

The color filter substrate 1012 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 upper portion of the color filter substrate 1012.

The thin film transistor substrate 1014 is electrically connected to a printed circuit board 918 on which a plurality of circuit components are mounted via a driving film 916. The thin film transistor substrate 1014 may apply a driving voltage provided from the printed circuit board 918 to the liquid crystal in response to a driving signal provided from the printed circuit board 918.

The thin film transistor substrate 1014 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 1014.

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 to be understood, therefore, 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.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURES 1A-1B illustrate an optical sheet in accordance with an embodiment of the present invention.

2A to 2C show an optical sheet according to another embodiment of the present invention.

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

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

5A-5B illustrate a backlight unit according to an embodiment of the present invention.

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

7A and 7B illustrate a liquid crystal display device according to an embodiment of the present invention.

Claims (13)

materials; A plurality of projections positioned on the substrate; And And an optical layer located under the substrate, Wherein the optical layer comprises a first layer comprising a polymeric material and a second layer located adjacent to the first layer and comprising a polymeric material having a different refractive index from the first layer, Wherein the plurality of protrusions include a first protrusion and a second protrusion, The height of the first projection is different from the height of the second projection, Wherein each of the plurality of protrusions is continuously formed from one side to the other side of the substrate, the height of the optical sheet being variable in the longitudinal direction. The method according to claim 1, Wherein the optical layer includes the first layer and the second layer alternately and repeatedly positioned. delete The method according to claim 1, Wherein the plurality of protrusions have different widths. The method according to claim 1, Wherein the cross section of the first projecting portion and the cross section of the second projecting portion have different shapes. The method according to claim 1, The plurality of protrusions including a valley in which the protrusions meet with each other, Wherein the depths of the valleys are the same or different from each other. The method according to claim 1, And an interval between the protrusions is 1 to 10 占 퐉. The method according to claim 1, Wherein the protrusions have continuous bends different in height, and the amplitude of the left and right is randomly changed. The method according to claim 1, Wherein the plurality of protrusions further comprise a plurality of first beads. The method according to claim 1, And a protective layer below the optical layer. 11. The method of claim 10, Wherein the protective layer comprises a base material and a plurality of second beads. Light source; And And an optical sheet positioned on the light source, The optical sheet comprising a substrate, a plurality of projections located on the substrate, and an optical layer located under the substrate, Wherein the optical layer comprises a first layer comprising a polymeric material and a second layer positioned adjacent to the first layer and comprising a polymeric material having a different refractive index from the first layer, Wherein the plurality of protrusions include a first protrusion and a second protrusion, The height of the first projection is different from the height of the second projection, Wherein the plurality of protrusions are continuously formed from one side to the other side of the substrate, the height being variable in the longitudinal direction. Light source; An optical sheet positioned on the light source; And And a liquid crystal panel positioned on the optical sheet, The optical sheet comprising a substrate, a plurality of projections located on the substrate, and an optical layer located under the substrate, Wherein the optical layer comprises a first layer comprising a polymeric material and a second layer positioned adjacent to the first layer and comprising a polymeric material having a different refractive index from the first layer, Wherein the plurality of protrusions include a first protrusion and a second protrusion, The height of the first projection is different from the height of the second projection, Wherein each of the plurality of protrusions is continuously formed from one side to the other side of the substrate, wherein the height varies in the longitudinal direction.

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