KR20090123749A - Optical sheet, back light unit and liquid crystallization display comprising thereof - Google Patents

Abstract

PURPOSE: An optical sheet, back light unit and liquid crystallization display comprising thereof are provided to improve the spread efficiency of the light by forming the first spreader. CONSTITUTION: The reflection-type polarizing film(110) 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. A part of the light which is income from the light source transmits the reflection-type polarizing film. In a part of the light which is income from the light source is the reflection-type polarizing film, it is reflected to the light source direction of the lower part. The light reflected to the light source is again income to the reflection-type polarizing film. The first spreader(120) diffuses the light which is income through the first spreading particle(122) from the external light source. The first spreader comprises the resin(121) having the predetermined adhesive property. The first spreading particle formed inside the first spreader is formed into the first bead.

Description

Optical Sheet, Back Light Unit And Liquid Crystallization Display Comprising Thereof}

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 capable of improving light diffusion efficiency, a backlight unit including the same, and a liquid crystal display device.

In order to achieve the above object, the optical sheet according to an embodiment of the present invention is located on one surface of the reflective polarizing film and the reflective polarizing film, and includes a first diffuser including a plurality of first diffusion particles, When the particle diameter of the particles that occupy the largest volume among the total volume of the first diffusion particles is X μm, the volume of particles having a particle size in the range of X-2 μm to X + 2 μm is applied to the total volume of the first diffusion particles. About 40 to 80%.

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 is disposed on one surface of the reflective polarizing film and the reflective polarizing film, and includes a plurality of first It includes a first diffusion portion including diffusion particles, when the particle diameter of the particles occupying the largest volume of the total volume of the first diffusion particles is X㎛, having a particle size in the range of X-2㎛ to X + 2㎛ The volume of particles may be 40 to 80% of the total volume of the first diffusion particles.

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 includes a reflective polarizing film and the reflective type. Located on one side of the polarizing film, including a first diffusion comprising a plurality of first diffusion particles, when the particle diameter of the particles occupying the largest volume of the total volume of the first diffusion particles is X㎛, X-2㎛ The volume of particles having a particle size in the range of from X to 2 μm may be 40 to 80% of the total volume of the first diffusion particles.

In addition, the optical sheet according to an embodiment of the present invention includes a reflective polarizing film and a first diffusion part positioned on the reflective polarizing film and including a plurality of first diffusion particles, and the plurality of first diffusions. The particles have a plurality of particle diameters, each of the diffusion particles corresponding to the plurality of particle diameters has a respective volume, when the particle diameter of the diffusion particles corresponding to the largest volume of each volume is X㎛, X- The volume of particles having a particle size in the range of 2 μm to X + 2 μm may be 40 to 80% of the total volume of the first diffusion particles.

Therefore, the optical sheet of the present invention, the backlight unit and the liquid crystal display including the same include the optical sheet which can improve the light diffusion efficiency, there is an advantage that can improve the brightness of the light.

Hereinafter, with reference to the accompanying drawings a specific embodiment according to an embodiment of the present invention will be described.

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

Referring to FIG. 1, an optical sheet 100 according to an embodiment of the present invention is positioned on a reflective polarizing film 110 and a reflective polarizing film 110, and includes a plurality of first diffusion particles 122. It may include a first diffusion portion 120 including.

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 of the reflection In the 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 first diffuser 120 may diffuse light incident from an external light source through the first diffused particles 122 formed therein.

The first diffusion part 120 may be formed to include a resin 121 having a predetermined adhesive property. Here, as the resin, 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, metyrol acrylamide, glycidyl methacrylate, ethyl acrylate, isobutyl acrylate, normal butyl acrylate, 2-ethylhexyl acrylate polymer Or acrylic, urethane, epoxy, melamine, or the like, such as copolymers or terpolymers, may be used, but is not limited thereto.

The first diffusion particles 122 formed in the first diffusion part 120 may be a first bead, and may be any one or more selected from the group consisting of polymethyl methacrylate (PMMA), polystyrene, and silicon.

Here, the first diffusion particles 122 with respect to the resin 121 may be included in 10 to 50 parts by weight. If the content of the first diffusion particles 122 with respect to the resin 121 is 10 parts 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. When the content of the first diffusion particles 122 is 50 parts by weight or less, there is an advantage in that the transmittance of light incident from the light source is lowered.

In addition, the particle diameters of the first diffusion particles 122 distributed in the resin 121 may not be uniform and may have an irregular distribution.

The shape of the first diffusion particles 122 may be circular, elliptical, snowman-shaped, bumpy circular, or the like, but is not limited thereto.

In addition, the first diffusion particles 122 distributed in the resin 121 may have an irregular distribution without having a regular distribution in the resin 121.

The diameter of the first diffusion particles 122 may be 0.5㎛ to 10㎛. If the diameter of the first diffusion particles 122 is small, the density of the first diffusion particles 122 may be increased in the first diffusion part 120 to improve the light diffusion rate of the optical sheet 100, but If the diameter of the first diffusion particles 122 is too small, interference of light incident from an external light source may occur. For this reason, as mentioned above, by making the diameter of the said 1st diffuse particle 122 more than 0.5 micrometer, the light-diffusion rate can be improved as much as possible without the interference of light generate | occur | producing.

In addition, when the diameter of the first diffusion particles 122 is large, a problem arises in that a thickness of the first diffusion part 120 needs to be formed to secure the light diffusion rate of the optical sheet 100. A problem arises that it is difficult to manufacture 100). For this reason, as mentioned above, by making the diameter of the said 1st diffused particle 122 into 10 micrometers or less, thickness reduction of the optical sheet 100 can be achieved within the limit that a light-diffusion rate does not fall.

The plurality of first diffusion particles 122 has a particle size of X-2 μm to X + 2 μm when the particle diameter of the particles that occupy the largest volume among the total volumes of the first diffusion particles 122 is X μm. The volume of the particles having a particle size may be 40 to 80% of the total volume of the first diffusion particles 122.

In other words, the plurality of first diffusion particles 122 has a plurality of particle diameters, and each of the diffusion particles corresponding to the plurality of particle diameters has a respective volume, and corresponds to the largest volume of the respective volumes. When the particle diameter of the diffusing particles is X μm, the volume of the particles having a particle size in the range of X-2 μm to X + 2 μm may be 40 to 80% of the total volume of the first diffused particles.

In more detail, with reference to Figure 2 which is a graph showing the volume distribution according to the particle size of the first diffusion particles 122 for all the first diffusion particles 122 included in the first diffusion unit 120. . Here, the horizontal axis represents the particle diameter (μm) of the first diffusion particles 122, and the vertical axis represents the volume (%) occupied by the first diffusion particles 122 corresponding to each particle diameter.

Referring to FIG. 2, X-2 μm to X + 2 μm based on the first diffused particle 122 corresponding to the particle size X μm of the particles having the largest volume among the entire volumes of the first diffused particles 122. It can be seen that the volume occupied by the first diffusion particles 122 corresponding to the particle size in the range of about 40 to 80% of the total volume of the diffusion particles. Here, the minimum particle diameter of the first diffusion particles 122 is 0.5㎛, the maximum particle diameter may be 10㎛, X may be 3 to 6㎛.

The first diffused particles 122 having a particle size of X μm occupy about 30% of the volume of the entire first diffused particles 122, and the first diffused particles 122 having a particle size of X −2 μm are about 10 μm. %, The first diffusion particles 122 having a particle size of X + 2㎛ may occupy about 10% of the volume.

For example, when the total volume of the first diffusion particles 122 present in the first diffusion unit 120 is 100%, when the particle diameter of the diffusion particles occupying the largest volume with respect to the total volume is 5㎛, 3 The volume occupied by the diffusion particles in the range of 7 to 7 μm is 40 to 80%. On the contrary, when the particle diameter of the diffusion particles occupying the largest volume with respect to the total volume is 3㎛, the volume occupied by the diffusion particles in the range of 1 to 5㎛ may be 40 to 80%.

Table 1 shows the results of measuring the diffusion effect and the brightness of the optical sheet according to the volume of the first diffusion particles corresponding to the particle size in the range of 3㎛ 7㎛ when X is 5㎛.

% Volume of first diffusing particles having a particle size in the range of 3 μm to 7 μm Diffusion effect Luminance 20 × ◎ 30 × ◎ 40 ○ ◎ 50 ○ ○ 60 ○ ○ 70 ◎ ○ 80 ◎ ○ 90 ◎ ×

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

Referring to Table 1, in an embodiment of the present invention, among the plurality of first diffusion particles included in the first diffusion part, diffusion particles having a particle diameter of 5 μm that occupy the largest volume with respect to the total volume of the first diffusion particles are selected. As the center, when the volume occupied by the first diffusion particles corresponding to the particle size in the range of 3 μm to 7 μm is in the range of about 40 to 80%, it can be seen that the diffusion effect and the brightness are excellent.

That is, when the volume occupied by the first diffusion particles corresponding to the particle size in the range of X-2 μm to X + 2 μm is 40% or more, the diffusion effect of light incident from the light source to the optical sheet may be improved.

When the volume of the first diffusion particles corresponding to the particle size in the range of X-2 μm to X + 2 μm is 80% or less, the volume of the first diffusion particles having the same particle diameter is increased to prevent the luminance from falling. There is an advantage to that.

Therefore, by forming the first diffusion particles having a volume of 40 to 80% of the first diffusion particles corresponding to the particle diameter in the range of X-2 μm to X + 2 μm, the light incident from the light source is formed. There is an advantage to spread.

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 diffusion particles of the first diffusion part to change the path, and the other part of the light passes through the exit surface of the first diffusion part to the liquid crystal panel.

The light whose path is changed by hitting the first diffuser is hit by another adjacent first diffuser and the path is changed again, and some of them are propagated to the liquid crystal panel through the exit surface of the first diffuser, and some of the other first diffuser are The path is changed again.

Finally, the light passing through the exit surface of the first diffusion part is evenly incident on the liquid crystal panel.

As described above, the light incident on the optical sheet is reflected by the plurality of first diffusion particles formed inside the first diffusion part and diffused while changing its propagation path, thereby improving luminance uniformity.

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

Referring to FIG. 3, the optical sheet 200 according to another embodiment of the present invention is positioned on the reflective polarizing film 210 and the reflective polarizing film 210, and has a plurality of first diffusion particles 222. It may include a first diffusion unit 220 including a.

The optical sheet 200 according to another embodiment of the present invention may further include a first adhesive layer 230 between the reflective polarizing film 210 and the first diffuser 220.

As a method of forming the first diffuser 220 on the reflective polarizing film 210, a resin 221 and a plurality of first diffused particles 222 are mixed and applied onto the reflective polarizing film 210. Forming or coating may be a method.

Meanwhile, the resin 221 and the plurality of first diffusion particles 222 may be formed in a film form by extrusion or injection, and then formed on the reflective polarizing film 210 by using an adhesive. . In this case, the first adhesive layer 230 may be coated on the reflective polarizing film 210, and the first diffusion part 220 may be formed.

The first adhesive layer 230 may be formed to have a thickness of 1 to 10 μm in consideration of light transmittance and adhesiveness, but is not limited thereto.

On the other hand, the reflective polarizing film 210 may serve to transmit or reflect the light incident from the light source, as described above. The reflective polarizing film 210 may include a first layer 211 including a polymer material and a material including a polymer material positioned adjacent to the first layer 211 and having a refractive index different from that of the first layer 211. It may include two layers 212. Since the detailed description has been given above, the description thereof is omitted in the present embodiment.

As described above, the first diffuser 220 may diffuse light incident from an external light source through the first diffused particles 222 formed therein.

The first diffusion part 220 may be formed to include a resin 221 having a predetermined adhesive property.

The first diffusion particles 222 formed in the first diffusion part 220 may be first beads, and may be any one or more selected from the group consisting of polymethyl methacrylate (PMMA), polystyrene, and silicon.

Herein, the first diffusion particles 222 may be included in an amount of 10 to 50 parts by weight based on the resin 221. If the content of the first diffusion particles 222 is 10 parts by weight or more with respect to the resin 221, it is possible to prevent a problem that light incident from the light source is difficult to be diffused by the beads. When the content of one diffusion particle 222 is 50 parts by weight or less, there is an advantage in that the transmittance of light incident from the light source is lowered.

The diameter of the first diffusion particles 222 may be 0.5㎛ to 10㎛. When the diameter of the first diffusion particles 222 is small, the density of the first diffusion particles 222 may be increased in the first diffusion unit 220 to improve the light diffusion rate of the optical sheet 200, but If the diameter of the first diffusion particles 222 is too small, interference of light incident from an external light source may occur. For this reason, as mentioned above, by making the diameter of the said 1st diffuse particle 222 or more into 0.5 micrometer, the light-diffusion rate can be improved as much as possible without the interference of light.

In addition, when the diameter of the first diffusion particles 222 is large, a problem arises in that the first diffusion part 220 needs to be thickened to secure the light diffusion rate of the optical sheet 200. Problems arise that are difficult to manufacture. For this reason, as mentioned above, by making the diameter of the said 1st diffuse particle 222 into 10 micrometers or less, thickness reduction of the optical sheet 200 can be achieved within the limit that a light-diffusion rate does not fall.

The plurality of first diffusion particles 222 has a particle size of the first diffusion particles 222 having a largest volume with respect to the total volume of the first diffusion particles 222 is X㎛, X-2㎛ to X + 2 The volume of the first diffusion particles 222 having a particle size in the range of μm may be 40 to 80% of the volume of the first diffusion particles 222.

Therefore, the light incident on the optical sheet is reflected by the plurality of first diffusion particles formed inside the first diffusion part and diffuses while changing its propagation path, thereby improving the uniformity of luminance.

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

Referring to FIG. 4, the optical sheet 300 according to an embodiment of the present invention may include a reflective polarizing film 310, a first adhesive layer 330 disposed on the reflective polarizing film 310, and an adhesive layer ( Located on 330, the first diffusion part 320 may include a plurality of first diffusion particles 322.

The optical sheet 300 according to another embodiment of the present invention further includes a second adhesive layer 340 and a second diffuser 350 disposed on the second adhesive layer 340 under the reflective polarizing film 310. It may include.

In the present exemplary embodiment, descriptions of the reflective polarizing film 310, the first adhesive layer 330, and the first diffusion part 320 are omitted.

The second adhesive layer 340 is for bonding the reflective polarizing film 310 and the second diffuser 350 to be the same as the first adhesive layer 330 described above.

The second diffuser 350 may be the same as the first diffuser 350 described above. In more detail, the second diffusion unit 350 may diffuse light incident from an external light source through the second diffusion particles 352 formed therein.

The second diffusion part 350 may be formed to include a resin 351 having a predetermined adhesive property. Here, as the resin 351, 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 acrylate, 2-ethylhexyl Acrylic, urethane, epoxy and melamine such as acrylate polymers or copolymers or terpolymers may be used, but are not limited thereto.

The second diffusion particles 352 formed in the second diffusion unit 350 may be beads, and may be any one or more selected from the group consisting of polymethyl methacrylate (PMMA), polystyrene, and silicon.

Here, the second diffusion particles 352 with respect to the resin 351 may be included in 10 to 50 parts by weight. If the content of the second diffusion particles 352 with respect to the resin 351 is 10 parts 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. When the content of the two diffusion particles 352 is 50 parts by weight or less, there is an advantage in that the transmittance of light incident from the light source is lowered.

In addition, the particle diameter of the second diffusion particles 352 distributed in the resin 351 may not be uniform and may have an irregular distribution.

The shape of the second diffusion particles 352 may be circular, elliptical, snowman-shaped, bumpy circular, or the like, but is not limited thereto.

In addition, the second diffusion particles 352 distributed in the resin 351 may have an irregular distribution without having a regular distribution in the resin 351.

The diameter of the second diffusion particles 352 may be 0.5 μm to 10 μm. When the diameter of the second diffusion particles 352 is small, the density of the second diffusion particles 352 may be increased in the second diffusion part 350 to improve the light diffusion rate of the optical sheet 300. If the diameter of the second diffusion particles 352 is too small, interference of light incident from an external light source may occur. For this reason, as mentioned above, by making the diameter of the said 2nd diffuser particle 352 or more into 0.5 micrometer, the light-diffusion rate can be improved as long as the interference of light does not generate | occur | produce.

In addition, when the diameter of the second diffusion particles 352 is large, a problem arises in that the second diffusion part 350 needs to be thickly formed in order to secure the light diffusion rate of the optical sheet 300. Problems arise that are difficult to manufacture 300). For this reason, as mentioned above, by making the diameter of the said 2nd diffused particle 352 into 10 micrometers or less, thinning of the optical sheet 300 can be achieved within the limit that a light-diffusion rate does not fall.

The plurality of second diffusion particles 352 are the same as the first diffusion particles 322 described above, and the particle diameter of the second diffusion particles 352 occupying the largest volume with respect to the entire volume of the second diffusion particles 352. The volume of the second diffusion particles 352 having a particle size in the range of X μm and X−2 μm to X + 2 μm may be 40 to 80% of the total volume of the second diffusion particles 352. Here, X may be 3 to 6㎛.

That is, when the volume of the second diffusion particles 352 corresponding to the particle diameter in the range of X-2 μm to X + 2 μm is 40% or more, the diffusion effect of light incident from the light source to the optical sheet 300 may be improved. Can be.

In addition, when the volume of the second diffusion particles 352 corresponding to the particle size in the range of X-2 μm to X + 2 μm is 80% or less, the volume of the second diffusion particles 352 having the same particle diameter is increased and the luminance is increased. There is an advantage that can prevent the fall.

Therefore, by forming the second diffusion particles having a volume of 40 to 80% of the second diffusion particles corresponding to the particle size in the range of X-2 μm to X + 2 μm, the light incident from the light source is formed. There is an advantage to spread.

5 to 7 are exploded perspective views and cross-sectional views for explaining the configuration of a backlight unit including an optical sheet according to embodiments of the present invention.

5 to 7 illustrate an edge type backlight unit 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.

5 to 7, the backlight unit 400 according to an exemplary embodiment of the present invention may be provided in the liquid crystal display and may provide light to the liquid crystal panel provided in the liquid crystal display.

The backlight unit 400 may include a light source 420 and an optical sheet 430. In addition, the backlight unit 400 may further include a light guide plate 440, a reflective plate 450, a bottom cover 460, and a mold frame 470.

The light source 420 may generate light by using driving power applied from the outside, and may emit the generated light.

For example, at least one light source 420 may be formed on one side of the light guide plate 440 along the long axis direction of the light guide plate 440, or at least one light source 420 may be formed on each side of the light guide plate 440. . Here, the light emitted from the light source 420 is incident directly into the light guide plate 440, or the light source housing 422 formed to surround a portion of the light source 420, for example, about 3/4 of the outer peripheral surface of the light source 420. After reflection, the light may enter the light guide plate 440.

Specifically, the light source 420 may include 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 430 may be disposed on the light guide plate 440.

The optical sheet 430 is disposed on one surface of the reflective polarizing film 430a and the reflective polarizing film 430a, and includes a first diffuser 430b including a plurality of first diffused particles. When the particle diameter of the particles that occupy the largest volume among the total volume of the diffusion particles is X µm, the volume of particles having a particle diameter in the range of X-2 µm to X + 2 µm is 40 to the total volume of the first diffusion particles. 80%.

In addition, as shown in FIG. 6, the second diffusion part 430c including a plurality of second diffusion particles is included on the other surface of the reflective polarizing film 430a, and the most of the total volumes of the second diffusion particles are included. When the particle diameter of the particles occupying a large volume is X μm, the volume of the particles having a particle size in the range of X-2 μm to X + 2 μm may be 40 to 80% of the total volume of the second diffusion particles.

Therefore, the optical sheet 430 improves the light efficiency in the reflective polarizing film 430a and diffuses the light in the diffusion parts 430b and 430c, thereby improving the uniformity of the brightness of the light. . As a result, display quality of the backlight unit 400 according to an exemplary embodiment may be improved.

Meanwhile, one or more of the diffusion sheet 432 and the prism sheet 431 may be included between the light guide plate 440 and the optical sheet 430. In addition, the prism sheet 431 or the diffusion sheet 432 may be located on the optical sheet 430, and the positions thereof are not limited thereto.

The light guide plate 440 may be disposed to face the light source 420, and may guide the light so that light incident from the light source 420 is emitted upward.

The reflection plate 450 may be disposed under the light guide plate 440, and may reflect light emitted downward from the light source 420 through the light guide plate 440 upward.

The bottom cover 460 may include a bottom portion 462 and a side portion 464 formed to extend from the bottom portion 462 to form an accommodation space, and the light source 420 and the optical sheet 430 may be formed in the accommodation space. The light guide plate 440 and the reflective plate 450 may be accommodated.

The mold frame 470 may be formed in a substantially rectangular frame shape and may be fastened with the bottom cover 460 from the top of the bottom cover 460 in a top down manner.

8 to 10 are exploded perspective views and cross-sectional views for describing the configuration of a backlight unit according to an embodiment of the present invention.

8 to 10 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. 8 to 10 is substantially the same as the backlight unit illustrated in FIGS. 5 to 7 except for arrangement of a light source and a change in components thereof, and thus, redundant descriptions thereof are omitted. Only its features will be described.

8 to 10, the backlight unit 500 according to an exemplary embodiment of the present invention may be provided in the liquid crystal display, and may provide light to the liquid crystal panel provided in the liquid crystal display.

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 reflection plate 550, a bottom cover 560, a mold frame 570, and a diffusion plate 580.

At least one light source 520 may be disposed under the diffuser plate 580. For this reason, the light emitted from the light source 520 may be incident directly to the diffuser plate 580.

The optical sheet 530 may be disposed on the diffuser plate 580. The optical sheet 530 may serve to condense the light incident from the light source 520.

The optical sheet 530 is disposed on one surface of the reflective polarizing film 530a and the reflective polarizing film 530a and includes a first diffuser 530b including a plurality of first diffused particles. When the particle diameter of the particles which occupy the largest volume of the total volume of the diffused particles is Xum, the volume of particles having a particle size in the range of X-2um to X + 2um is 40 to 80% of the total volume of the first diffused particles. Can be.

In addition, as shown in FIG. 9, the second diffuser 530c including a plurality of second diffused particles is formed on the other surface of the reflective polarizing film 530a, and the most of the total volumes of the second diffused particles are included. When the particle diameter of the particles occupying a large volume is X μm, the volume of the particles having a particle size in the range of X-2 μm to X + 2 μm may be 40 to 80% of the total volume of the second diffusion particles.

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

Meanwhile, one or more of the diffusion sheet 532 and the prism sheet 531 may be included between the diffusion plate 580 and the optical sheet 530. In addition, the prism sheet 531 or the diffusion sheet 532 may be located on the optical sheet 530, and the positions thereof are not limited thereto.

The diffusion plate 580 may be disposed between the light source 520 and the optical sheet 530, and may diffuse light incident from the light source 520 upward. This is to prevent the shape of the light source 520 from being visible through the backlight unit 500 and to further diffuse the light.

11 to 13 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. 11 to 13 illustrate the backlight unit illustrated in FIGS. 5 to 7 as the backlight unit, the present invention is not limited thereto, and the backlight unit illustrated in FIGS. 8 to 10 may be employed as the backlight unit. Meanwhile, since the backlight units illustrated in FIGS. 11 to 13 are the same as described above, overlapping descriptions are omitted and only the features thereof will be described.

11 to 13, the liquid crystal display 600 according to an exemplary embodiment may display an image by using the electro-optical characteristics of the liquid crystal.

The liquid crystal display device 600 may include a backlight unit 610 and a liquid crystal panel 710.

The backlight unit 610 may be mounted under the liquid crystal panel 710 and may provide light to the liquid crystal panel 710.

The backlight unit 610 may include a light source 620 and an optical sheet 630.

The optical sheet 630 is disposed on one surface of the reflective polarizing film 630a and the reflective polarizing film 630a and includes a first diffuser 630b including a plurality of first diffused particles. When the particle diameter of the particles that occupy the largest volume among the total volume of the diffusion particles is X µm, the volume of particles having a particle diameter in the range of X-2 µm to X + 2 µm is 40 to the total volume of the first diffusion particles. 80%.

In addition, as shown in FIG. 12, a second diffusion part 630c including a plurality of second diffusion particles is formed on the other surface of the reflective polarizing film 630a, and the most of the total volumes of the second diffusion particles are included. When the particle diameter of the particles occupying a large volume is X μm, the volume of the particles having a particle size in the range of X-2 μm to X + 2 μm may be 40 to 80% of the total volume of the second diffusion particles.

Therefore, the optical sheet 630 improves the light efficiency in the reflective polarizing film 630a and serves to diffuse the light in the diffusion parts 630b and 630c, thereby improving the uniformity of the brightness of the light. . As a result, display quality of the backlight unit 600 according to an exemplary embodiment may be improved.

In addition, the backlight unit 610 may further include a light guide plate 640, a reflective plate 650, a bottom cover 660, and a mold frame 670.

In addition, one or more of the diffusion sheet 632 and the prism sheet 631 may be included between the light guide plate 640 and the optical sheet 630. In addition, the prism sheet 631 or the diffusion sheet 632 may be positioned on the optical sheet 630, and the positions thereof are not limited thereto.

The liquid crystal panel 710 may be seated on the mold frame 670 and may be fixed by the top cover 720 fastened to the bottom cover 660 in a top-down manner.

The liquid crystal panel 710 may display an image using light provided from the backlight unit 610, specifically, light emitted from the light source 620.

The liquid crystal panel 710 may include a color filter substrate 712 and a thin film transistor substrate 714 facing each other with the liquid crystal interposed therebetween.

The color filter substrate 712 may implement colors of the image displayed through the liquid crystal panel 710.

The color filter substrate 712 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, the upper polarizer may be disposed on the color filter substrate 712.

The thin film transistor substrate 714 is electrically connected to the printed circuit board 618 on which a plurality of circuit components are mounted through the driving film 616. The thin film transistor substrate 714 may apply a driving voltage provided from the printed circuit board 618 to the liquid crystal in response to a driving signal provided from the printed circuit board 618.

The thin film transistor substrate 714 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 714.

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 first diffusion particles in the first diffusion part, thereby diffusing light to improve uniformity of luminance. There is an advantage to this.

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 second diffuser under the reflective polarizing film, thereby further improving the uniformity of luminance of the optical sheet. There is this.

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

Figure 2 is a graph showing the volume ratio of the first diffusing particles in accordance with the particle size of the entire first diffused particles included in the first diffuser according to an embodiment of the present invention.

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

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

5 to 7 illustrate a backlight unit according to an embodiment of the present invention.

8 to 10 are views illustrating a backlight unit according to another embodiment of the present invention.

11 to 13 illustrate a liquid crystal display according to an exemplary embodiment of the present invention.

Claims (14)

Reflective polarizing film; And Located on one surface of the reflective polarizing film, and includes a first diffusion portion including a plurality of first diffusion particles, When the particle diameter of the particles that occupy the largest volume among the total volume of the first diffusion particles is X μm, the volume of particles having a particle size in the range of X-2 μm to X + 2 μm is applied to the total volume of the first diffusion particles. 40 to 80% of the optical sheet. The method of claim 1, The minimum particle diameter of the plurality of first diffusion particles is 0.5 ㎛ the optical sheet. The method of claim 1, An optical sheet having a maximum particle diameter of the plurality of first diffusion particles is 10 μm. The method of claim 1, X is 3 to 6㎛ optical sheet. The method of claim 1, And the plurality of first diffusion particles are beads. The method of claim 1, The plurality of first diffusion particles is at least one selected from the group consisting of polymethyl methacrylate (PMMA), polystyrene and silicon. The method of claim 1, The optical sheet further comprises a first adhesive layer between the reflective polarizing film and the diffusion. The method of claim 1, The optical sheet further comprises a second diffuser under the reflective polarizing film. The method of claim 8, The optical sheet further comprises a second adhesive layer between the reflective polarizing film and the second diffusion. The method of claim 8, The second diffusion part comprises a plurality of second diffusion particles. 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. Light source; And An optical sheet positioned on the light source, The optical sheet is positioned on one surface of the reflective polarizing film and the reflective polarizing film, and includes a first diffuser including a plurality of first diffused particles. When the particle size of the particles occupying the largest volume among the total volume of the first diffusion particles is X μm, the volume of particles having a particle size in the range of X-2 μm to X + 2 μm is the total volume of the first diffusion particles. 40 to 80% of the backlight unit. 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 is positioned on one surface of the reflective polarizing film and the reflective polarizing film, and includes a first diffuser including a plurality of first diffused particles. When the particle diameter of the particles that occupy the largest volume among the total volume of the first diffusion particles is X μm, the volume of particles having a particle size in the range of X-2 μm to X + 2 μm is applied to the total volume of the first diffusion particles. 40 to 80% of the liquid crystal display device. Reflective polarizing film; And Located on the reflective polarizing film, includes a first diffusion portion comprising a plurality of first diffusion particles, The plurality of first diffusion particles have a plurality of particle diameters, Each of the diffusion particles corresponding to the plurality of particle diameters has a respective volume, and when the particle diameter of the diffusion particles corresponding to the largest volume of the respective volumes is X μm, the X-2 μm to X + 2 μm The volume of particles having a particle size in the range is 40 to 80% of the total volume of the first diffusion particles.

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