KR20110062294A - Light mixing element and lcd backlight unit using the same - Google Patents

Abstract

PURPOSE: An optical mixing member and an LCD backlight unit including the same are provided to mix light from a light source uniformly, by forming a number of reflection layers in the optical mixing member. CONSTITUTION: An optical mixing member(1) has a first plane(10) and a second plane(20). A light is incident on the first plane. The second plane outputs the light. The optical mixing member is formed with an optical transmission material. A number of holes(30) are formed on the first plane. A first reflection layer(15) is formed in the first plane. A second reflection layer(25) is formed in the second plane. At least more than one reflection layer(40) is intervened between the first and the second reflection layer.

Description

LIGHT MIXING ELEMENT AND LCD BACKLIGHT UNIT USING THE SAME

The present invention relates to a light mixing member and an LCD backlight unit including the same, and more particularly, a light mixing member for uniformly mixing light emitted from a light source, so that no lamp mura is obtained and uniform white light is obtained. And it relates to an LCD backlight unit comprising the same.

Cold Cathode Fluorescent Lamps (CCFLs), which are commonly used as light sources for backlight units of LCDs, use mercury gas, which may cause environmental pollution, slow response speed, and high color reproducibility. There was a problem of low. Accordingly, in recent years, a light emitting diode (LED) is replaced with a backlight light source instead of the CCFL.

A backlight unit employing an LED light source generally arranges red light (R) LEDs, green light (G) LEDs, and blue light (B) LEDs in a matrix to form a light source unit, and emits light emitted from the LED on the light source unit. Optical sheets, such as a light mixing plate for mixing, a diffusion sheet for diffusing light, and a light collecting sheet for condensing light in a specific direction, are sequentially stacked.

On the other hand, the LED light source is eco-friendly because it does not emit environmental pollutants such as mercury, low power consumption, fast response time of several nanoseconds, high color response, and excellent color reproducibility. Although it has advantages, it emits white light by mixing red light, green light and blue light emitted from each LED element, so that if the light is not uniformly mixed, the desired light cannot be obtained, and the color of either side is noticeably There is a problem that appears. In addition, the lamp mura phenomenon occurs due to the difference in brightness between the portion where the LED is present and the portion where the LED is not present, and there is a problem that the image quality of the display is deteriorated.

In general, such non-uniform mixing of light and lamp mura can be solved by increasing the light propagation distance, but when increasing the thickness of the light mixing plate or increasing the distance between the optical sheets in order to increase the light propagation distance, There is a problem that the thickness of the backlight unit becomes thick, and as a result, the thickness of the entire LCD device becomes thick, which is counter to the trend of slimming the LCD.

The present invention is to solve the above problems, by forming a plurality of reflective layers in the light mixing member to increase the propagation distance of the light, uniformly mixing the light emitted from the light source, to improve the lamp mura phenomenon and color degradation The present invention provides a light mixing member capable of manufacturing a thin LCD and a backlight unit using the same.

To this end, the present invention is made of a light-transmitting material, and has a first surface on which light is incident and a second surface on which light is emitted, a plurality of holes for light incident on the first surface; A first reflection layer formed inside of the first surface; A second reflection layer formed inside the second surface so as to face the first reflection layer; And at least one reflective layer interposed between the first reflective layer and the second reflective layer.

In this case, the first reflecting layer preferably has a reflectance of 90 to 100%, and the second reflecting layer and at least one or more reflecting layers inserted between the first reflecting layer and the second reflecting layer have a transmittance of 10% to 90%. It is preferable.

In addition, the first reflection layer, the second reflection layer, and at least one reflection layer inserted between the first reflection layer and the second reflection layer may be formed of a metal layer or a dielectric layer.

On the other hand, the light mixing member may further include light diffusing particles, wherein the light diffusing particles are inorganic particles selected from the group consisting of silica, alumina and titania, thermosetting resins such as polyurethane, epoxy and polyethylene, It may be made of one or more organic polymer particles or a combination thereof selected from the group consisting of thermoplastic resins such as polypropylene, polystyrene, vinyl chloride, acryl and the like.

In another aspect, the invention provides a plurality of point light source; And a plurality of holes formed of a light transmissive material, each having a first surface on which light is incident and a second surface on which light is emitted; A first reflection layer formed inside of the first surface; A second reflection layer formed inside the second surface so as to face the first reflection layer; And a light mixing member including at least one reflective layer interposed between the first reflective layer and the second reflective layer.

In this case, the point light source is preferably an LED light source.

On the other hand, the light mixing member may further include light diffusing particles therein as necessary.

The backlight unit may further include a lens configured to insert the plurality of point light sources into the plurality of holes or to concentrate light emitted from the point light source into the hole in front of the point light source. It can be made, including.

Since the light diffusing member of the present invention is provided with a plurality of reflective layers and uniformly mixed with the light reflected inside the light diffusing member, the lamp mura phenomenon can be improved and excellent color mixing effect can be obtained.

In addition, the light diffusing member of the present invention can achieve uniform light mixing without increasing the thickness of the backlight unit by using the reflective layer, which is advantageous for manufacturing a thin LCD.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

1 shows an embodiment of the light mixing member of the present invention. As shown in FIG. 1, the light mixing member 1 of the present invention has a first surface 10 through which light is incident and a second surface 20 through which light is emitted. The hole 30 and the first reflection layer 15 for light incident of the second reflection layer 25 are formed on the second surface. Meanwhile, at least one reflective layer (hereinafter referred to as 'third reflective layer') 40 is interposed between the first reflective layer 15 and the second reflective layer.

The light mixing member 1 of the present invention is a light transmitting material, for example, polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl chloride (PVC), poly A first light incident surface formed of one or more materials selected from the group consisting of esters, polymethyl methacrylates, polystyrenes, polyester sulfones, polybutadienes, polyether ketones and polyurethanes, and formed in a light source (not shown) direction. The surface 10 and the 2nd surface 20 which is a light emission surface formed in the liquid crystal panel (not shown) direction are provided.

Meanwhile, a plurality of holes 30 and a first reflection layer 15 are formed in the first surface 10. The plurality of holes 30 are intended to allow light emitted from the light source to be incident into the light mixing member 1. For example, as shown in FIG. 5, an LED light source is inserted into the hole 30, or as shown in FIG. 6, light emitted from each LED light source is incident through the hole 30. By doing so, the light emitted from the light source can be incident into the light mixing member 1.

The shape of the hole 30 is not particularly limited, and for example, may be formed in a circular, square or other polygonal shape.

On the other hand, the first reflection layer 15 is for reflecting light in the direction of the second surface, and is formed in the region of the first surface where the hole 30 is not formed. The first reflection layer 15 may be formed of a metal such as silver, aluminum, platinum, chromium, nickel, and copper; Inorganic dielectrics such as silica, hafnium oxide and zinc oxide; Organic series dielectrics such as PET, PC, PVC, polyester, polymethylmethacrylate, polystyrene, polyestersulfone, polybutadiene, polyetherketone and polyurethane; Or a combination thereof.

In this case, the reflectance of the first reflective layer is preferably about 90 to 100%, and from the aspect of light efficiency, the closer to 100%, the more preferable. The reflectance of the first reflective layer can be adjusted in an appropriate manner depending on the material used, which is well known to those skilled in the art. For example, when the first reflection layer is made of metal, the reflectance (or transmittance) may be adjusted by adjusting the thickness of the metal layer. When the first reflection layer is made of organic or inorganic dielectric material, the refractive index and the thickness of the medium may be varied. Reflectance can be realized.

Next, the light mixing member 1 of the present invention includes a second reflection layer 25 on the second surface 20. The second reflection layer 25 is for reflecting light toward the first surface, and like the first reflection layer, metals such as silver, aluminum, platinum, chromium, nickel, and copper, or silica, hafnium oxide, and zinc oxide Inorganic series dielectrics; Organic series dielectrics such as PET, PC, PVC, polyester, polymethylmethacrylate, polystyrene, polyestersulfone, polybutadiene, polyetherketone and polyurethane, or combinations thereof.

At this time, the second reflection layer is configured to transmit a certain degree without reflecting light at 100%. This is because when the light is reflected at 100% in the second reflection layer, the light does not reach the liquid crystal panel and thus the display device cannot be implemented. Preferably, the second reflective layer has a transmittance of 10 to 90%. This is because when the transmittance of the second reflection layer is less than 10%, the amount of light absorbed by the reflective layer increases, so that the light loss rate increases, and when the transmittance exceeds 90%, sufficient light mixing may not occur. However, the transmittance may be appropriately selected in consideration of the material of the second reflective layer, the desired degree of light mixing, and the like.

As described above, the reflectance of the second reflective layer can be adjusted by an appropriate method depending on the material used. For example, when the second reflection layer is made of metal, the reflectance (or transmittance) can be adjusted by adjusting the thickness of the metal layer, and when the second reflection layer is made of organic or inorganic dielectric material, the refractive index and thickness of the medium can be varied. Reflectance can be realized.

As in the present invention, when the second reflection layer 25 having a transmittance of 10 to 90% is formed on the second surface 20, some of the light generated from the light source is transmitted, and the remaining light is formed of the first reflection layer. It is reflected back in one direction. The reflected light is reflected back from the first reflecting layer to travel in the direction of the second reflecting layer, some of the light reaching the second reflecting layer is transmitted, and the remaining light is reflected again and proceeds to the first reflecting layer. This process is repeated indefinitely inside the light mixing member, and the light propagation path is lengthened by this internal reflection, so that the light is uniformly mixed in the light mixing member.

On the other hand, it is preferable that the third reflection layer 40 interposed between the first reflection layer and the second reflection layer has a transmittance of 10 to 90% similarly to the second reflection layer. As such, when the additional reflective layer 40 is provided, more internal reflection occurs inside the light mixing member 1, resulting in a longer light propagation path, and as a result, light may be mixed more uniformly.

Meanwhile, FIG. 1 illustrates a case in which only one reflective layer is interposed between the first reflective layer and the second reflective layer, but as illustrated in FIG. 2, two or more reflective layers may be interposed.

These additional reflective layers 40a and 40b may be made of a metal layer or a dielectric layer similarly to the first reflective layer, the second reflective layer, and the third reflective layer, and the transmittance thereof is preferably about 10 to 90%.

As described above, the light mixing member of the present invention having a plurality of reflective layers can be manufactured by various methods. For example, the light mixing member of the present invention may be manufactured by a method of alternately stacking a reflective layer and a light transmitting polymer material layer. More specifically, the light mixing member having three reflecting layers forms a reflecting layer made of a metal layer or a plurality of dielectric layers, and thereafter laminated and cured a light-transmitting polymer material such as an acrylic resin thereon, and a metal layer or a plurality of layers thereon. It can be prepared by laminating a dielectric layer of to form a reflective layer, and then laminating and curing the translucent material thereon, and again forming a reflective layer thereon. In this case, the reflective layer made of a metal layer may be formed by depositing metal particles on the light-transmissive material by, for example, e-beam or thermal vapor deposition, chemical vapor deposition, or sputtering, and the reflective layer made of a dielectric layer may be formed by stacking dielectric materials. Can be prepared. In addition, when the reflective layer is to be further formed, the above-described transparent polymer material layer and the reflective layer stacking process may be further performed.

On the other hand, the light mixing member of the present invention can also be produced by sequentially stacking a substrate made of a commercially available reflective sheet and a translucent material without directly forming a substrate or a reflective layer as described above.

Meanwhile, another embodiment of the present invention is shown in FIGS. 3 and 4. 3 and 4, the light mixing member 1 of the present invention may include a light diffusing particle 50 therein.

In this case, as shown in FIG. 3, the light diffusing particles 50 may be present in a form dispersed in the light transmitting resin forming the light mixing member, and as shown in FIG. 4, only a part of the light mixing member may be used. May exist

When the light diffusing particles 50 are included in the light mixing member, the light is mixed while being scattered by the light diffusing particles, and thus there is an advantage that the light can be efficiently mixed.

On the other hand, the light diffusing particles 50 may be formed of inorganic particles such as silica, alumina, titania) or organic particles made of thermosetting resins such as polyurethane and epoxy, or thermoplastic particles such as polyethylene, polypropylene, polystyrene, vinyl chloride, and acrylic. It can be used alone or in combination.

On the other hand, as shown in Figure 3, the light-diffusion member 50 is dispersed in the light mixing member, after dispersing the light-diffusing particles 50 in the light-transmitting polymer resin forming the light-mixing member, it is used It can be produced by a method of manufacturing a light mixing member, and as shown in Figure 4, the light mixing member in which the light diffusion particles 50 are located only on a part of the light mixing member, primarily using a light transmitting polymer resin After forming a substrate, coating the light diffusion particles 50 on the surface of the substrate, it can be prepared by applying a light-transmitting polymer resin thereon.

The light mixing member of the present invention made as above is particularly useful in a backlight unit having a point light source such as an LED. Hereinafter, the backlight unit of the present invention will be described.

5 and 6 are views for explaining the backlight unit of the present invention. 5 and 6, the backlight unit of the present invention is composed of a point light source 60 and the above-described light mixing member of the present invention, that is, a light transmissive material, the first surface and the light incident light A plurality of holes having light exiting the second surface, the light incidence formed on the first surface; A first reflection layer formed inside of the first surface; And a light mixing member including a second reflection layer formed inside the second surface so as to face the first reflection layer, and at least one reflection layer inserted between the first reflection layer and the second reflection layer. do.

In this case, the light mixing member may further include light diffusing particles therein as necessary. Since the details for the light mixing member are the same as those described above, the description is omitted here.

On the other hand, the point light source 60 is preferably an LED light source, the point light sources as shown in Figure 5, the plurality of point light source can be inserted into the plurality of holes. As such, when the point light sources are inserted into the holes of the light mixing member, the light emitted from the light source is incident into the 100% light mixing member, and there is an advantage that the light utilization efficiency is high because there is no leakage of light.

Meanwhile, as shown in FIG. 6, the backlight unit of the present invention does not insert the point light source 60 into the hole, but instead of the lens 70 for concentrating light to the hole of the light mixing member in front of the point light source. It can also be done by installation. In this case, by bringing the focus of the lens 70 into the hole 30, the light emitted from the light source can be incident to the light mixing member without leakage.

Hereinafter, the present invention will be described in more detail with reference to specific examples.

Comparative Example 1

Aluminum is coated on one surface of the transparent PET film using an e-beam deposition method, and then a photoresist process and aluminum etching are formed on the aluminum coating surface to form holes for light incidence, having a thickness of about 150 nm and a reflectance of about 95%. The light mixing member in which the reflecting layer which has an is formed was manufactured.

After mounting an LED on the light mixing member manufactured by the above method, the surface was image | photographed using the CCD camera. The photograph taken is shown in FIG. 7. As shown in FIG. 7, when the light mixing member of Comparative Example 1 is used, the lamp mura phenomenon is clearly seen, and the contrast ratio is also very bad.

In this case, the contrast ratio is defined as (max − min) / (max + min) when the highest luminance is max and the lowest luminance min is at the entire surface of the light mixing member.

Comparative Example 2

Aluminum is coated on one surface of the transparent PET film using an e-beam deposition method, and then a photoresist process and aluminum etching are formed on the aluminum coating surface to form holes for light incidence, having a thickness of about 150 nm and a reflectance of about 95%. Forming a first reflecting layer having a light reflecting layer, and coating aluminum on the opposite side of the PET film using an e-beam deposition method to form a second reflecting layer having a reflectance of about 50% with a thickness of about 40 nm, thereby mixing light having two reflecting layers. The member was made. In this case, the deposition thickness was reduced to a place corresponding to the second reflective layer so that the reflectance was lower than that of the first reflective layer.

After mounting an LED on the light mixing member manufactured by the above method, the surface was image | photographed using the CCD camera. The photograph taken is shown in FIG. 8. As shown in FIG. 8, when the light mixing member of Comparative Example 2 is used, the lamp mura phenomenon is slightly alleviated compared to Comparative Example 1, and the contrast ratio is also improved to some extent. However, the LED mounting portion is still brighter than the other portions, and it can be seen that the light is not uniformly mixed. The contrast ratio of Comparative Example 2 was measured to be about 80% when the contrast ratio of Comparative Example 1 was set at 100%.

Example 1

Aluminum is coated on both sides of the transparent PET film (referred to as 'first film' for convenience) by using an e-beam evaporation method, with a first reflection layer having a thickness of about 150 nm and a reflectance of about 95%, and a thickness of about 50 nm. A light mixing member on which a third reflection layer having a reflectance of% was formed was prepared.

At this time, the light incident hole was formed on the surface corresponding to the first reflective layer through a photoresist process and aluminum etching.

Then, another translucent PET film (hereinafter referred to as 'second film' for convenience) is prepared, and a second reflective layer having a reflectivity of about 50% with a thickness of about 40 nm on only one surface is formed, and the surface on which the second reflective layer is not formed is A light mixing member having three reflective layers was prepared by bonding using an adhesive to be laminated on the third reflective layer of the first film.

After mounting an LED on the light mixing member manufactured by the above method, the surface is imaged using a CCD camera. The photograph taken is shown in FIG. 9. As shown in FIG. 9, it can be seen that the lamp mura phenomenon hardly occurs when there are three reflective layers. In addition, when the contrast ratio is set to 100% in Comparative Example 1, it is about 7%, it can be seen that the contrast ratio is significantly improved compared to Comparative Examples 1 and 2.

1 is a view showing a first embodiment of the light mixing member of the present invention.

2 is a view showing a second embodiment of the light mixing member of the present invention.

3 is a view showing a third embodiment of the light mixing member of the present invention.

4 is a view showing a fourth embodiment of the light mixing member of the present invention.

5 is a view illustrating an embodiment of a backlight unit of the present invention.

6 is a view showing another embodiment of a backlight unit of the present invention.

7 is a photograph of light emitted from the light mixing member of Comparative Example 1. FIG.

8 is a photograph of light emitted from the light mixing member of Comparative Example 2. FIG.

FIG. 9 is a photograph of light emitted from the light mixing member of Example 1. FIG.

Claims (11)

In a light mixing member made of a light transmitting material and having a first surface on which light is incident and a second surface on which light is emitted, A plurality of holes for light incident on the first surface; A first reflection layer formed inside of the first surface; A second reflection layer formed inside the second surface so as to face the first reflection layer; And And at least one reflective layer interposed between the first reflective layer and the second reflective layer. The method of claim 1, And the first reflection layer has a reflectance of 90 to 100%. The method of claim 1, And the at least one reflecting layer inserted between the second reflecting layer and the first reflecting layer and the second reflecting layer has a transmittance of 10 to 90%. The method of claim 1, And the at least one reflecting layer inserted between the first reflecting layer, the second reflecting layer, and the first reflecting layer and the second reflecting layer comprises a metal layer or a dielectric layer. The method of claim 1, The light mixing member further comprises light diffusing particles inside the light mixing member. The method of claim 5, The light diffusing particles include at least one inorganic particle selected from the group consisting of silica, alumina and titania; And at least one organic polymer particle selected from the group consisting of polyurethane, epoxy, polyethylene, polypropylene, polystyrene, vinyl chloride and acryl, or a combination thereof. Multiple point light sources; And A plurality of holes made of a light transmissive material and having a first surface on which light is incident and a second surface on which light is emitted, the plurality of holes being formed on the first surface; A first reflection layer formed inside of the first surface; A second reflection layer formed inside the second surface so as to face the first reflection layer; And a light mixing member including at least one reflective layer interposed between the first reflective layer and the second reflective layer. The method of claim 7, wherein The point light source is a backlight unit, characterized in that the LED light source. The method of claim 7, wherein LED backlight unit, characterized in that the light-diffusing particles are further included in the light mixing member. The method according to any one of claims 7 to 9, LED backlight unit, characterized in that the plurality of point light sources are inserted into the plurality of holes. The method according to any one of claims 7 to 9, Located in front of the point light source, LED backlight unit further comprises a lens for concentrating light emitted from the point light source to the hole.

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