WO2010047557A2 - Optical film, and backlight unit using same - Google Patents

Abstract

The present invention relates to a direct type backlight unit for a liquid crystal display (LCD), and more particularly, to an optical film comprising glass bubbles having hollow holes for enhancing brightness uniformity and viewing angle characteristics and for rendering a backlight unit thin. The present invention also relates to the backlight unit using the optical film. The optical film of the present invention comprises a plate type base unit, and a refraction structure unit including microstructures elongated in one direction and disposed side by side on the upper surface of the base unit. The microstructures have interiors in which glass bubbles having hollow holes are diffused.

Description

Optical film and backlight unit using same

The present invention relates to a direct backlight unit of a liquid crystal display (LCD) device, and more particularly to an optical film that can thin a backlight unit while improving brightness uniformity and viewing angle characteristics, including glass bubbles having hollows. It relates to a backlight unit using the same.

In general, LCD devices are electronic devices that change various electrical information generated by various devices into visual information by using a change in liquid crystal transmittance according to an applied voltage. LCD devices display various information and cannot be visualized without their own light source. Accordingly, liquid crystal displays used in televisions and laptops include a back-light unit (BLU) that uniformly provides light vertically to the entire LCD element from the rear thereof in order to visualize information displayed on the LCD element. .

In general, the backlight unit is classified into a direct type and an edge type according to the position of the light source. In the edge type, the light source is disposed on the side of the backlight unit, and is applied to a liquid crystal display (LCD) such as a notebook requiring a thin shape. In the direct type, the light source is disposed at the lower side of the backlight unit, and is applied to a large liquid crystal display device requiring high brightness such as an LCD television.

1 is a view showing a schematic configuration of a general direct type backlight unit.

As shown in FIG. 1, the direct type backlight unit includes a reflecting plate 20, a light source unit 10, a diffusion plate 30, a diffusion sheet 40, a first prism sheet 50, and a second prism sheet 60. It consists of.

The light source unit 10 includes a plurality of light sources arranged in parallel in one direction to emit light in an upward direction. The light source may be a hot cathode fluorescent lamp (HCFL) or a cold cathode fluorescent lamp (CCFL).

The lamp cover 20 reflects the light emitted downward from the light source unit 10 upward to improve the light efficiency. In addition, the lamp cover 20 protects the light source unit 10 from external impact.

The diffusion plate 30 diffuses the light emitted from the plurality of light sources of the light source unit 10, that is, the plurality of lamps to remove the light and dark portions generated according to the arrangement of the plurality of lamps.

The diffusion sheet 40 evenly disperses the light raised through the diffusion plate 30 to further remove the light and dark portions. Typically, the diffusion sheet 40 has a bead type, hemispherical shape, and semi-cylindrical shape. In general, the light diffusion effect of the semi-cylindrical diffusion sheet is determined by the width (W) and the height (H) of the cross-section of the semi-cylindrical pattern, which is referred to as fine (= H / W). In general, increasing the fine equipment improves the diffusion effect.

Since the first fine pattern sheet 50 refracts the light incident from the diffusion sheet 40 at a low angle, the first fine pattern sheet 50 is focused on the LCD element so that the first fine pattern sheet 50 is vertically incident on the LCD device, and thus the luminance and the emission angle sharply dropped by the diffusion sheet 40. Increase In general, the first fine pattern sheet 50 is arranged in parallel with the prism patterns extending in one direction on the upper surface in order to emit light incident from the diffusion sheet 40 perpendicular to the LCD element. Typically, the prism pattern is formed in a triangular shape having a vertex angle of about 90 degrees.

The second fine pattern sheet 60 collects and emits the secondary light in order to increase the luminance uniformity of the light primarily collected in the first fine pattern sheet 50 and to increase the emission angle.

Each micropattern sheet converges light incident on a plane perpendicular to the longitudinal direction of the prism patterns in the normal direction of the micropattern sheet, and does not collect light incident on a plane parallel to the longitudinal direction of the prism patterns. Therefore, in order to focus light in the vertical and horizontal directions, the first fine pattern sheet 50 and the second fine pattern sheet 60 are generally disposed such that the respective prism patterns are vertical.

In addition, a scratch is generated on the first fine pattern sheet 4 or the second fine pattern sheet 5 by being positioned on the first fine pattern sheet 50 or the second fine pattern sheet 60. A protective sheet for preventing may be further provided.

As described above, the conventional direct type backlight unit must include a diffusion plate and a diffusion sheet to remove the dark portion and the ridge caused by the light sources extending side by side in one direction on the lower side, and the front face lowered by the diffusion plate and the diffusion sheet. Since a plurality of fine pattern sheets must be provided to increase the brightness, it is difficult to reduce the thickness of the backlight unit.

As described above, a cylindrical diffusion sheet is used to remove light and shadow generated by lamps by improving light condensing and uniformity in the direct backlight unit, but fabricating a structure having fine equipment for obtaining a desired diffusion effect. There was a difficult problem.

That is, in order to obtain a sufficient diffusion effect to the desired degree, as described above, it is necessary to make a thin device of semi-cylindrical pattern large enough. However, as the size of the semi-cylindrical pattern is increased, the angle of the side of the semi-cylindrical pattern becomes closer to the vertical. As a result, the side of the adjacent semi-cylindrical pattern becomes very close, which causes a lot of difficulties in manufacturing.

In addition, in the conventional direct type backlight unit, two or more diffusion sheets must be used to solve such a problem, thereby increasing production cost and making it difficult to reduce the thickness of the backlight unit.

In addition, the conventional backlight unit not only complicates the backlight unit assembly process by using a plurality of optical sheets such as diffusion sheets and fine pattern sheets in addition to the diffusion plate, but also has a problem that may cause defects during cutting and assembly.

Accordingly, an object of the present invention is to provide an optical film and a backlight unit using the same, which can reduce the thickness of the backlight unit while improving brightness uniformity and viewing angle characteristics, including glass bubbles having hollows.

The optical film of the present invention for achieving the above object; It includes a base plate and a refractive structure that is arranged side by side in the microstructure extending in one direction on the base upper surface, characterized in that the glass bubbles having a hollow inside the microstructure is diffused.

The diameter of the hollow is preferably formed to have a 4 ~ 30um in consideration of the transmittance and reflectance of the glass bubble.

The glass bubbles are preferably formed to have a density of 40% to 70% of the total volume inside the microstructure.

The microstructure is characterized in that the chaotic shape irregularly twisted to the left and right with respect to the longitudinal direction.

When the microstructure is a semi-cylindrical or lenticular shape, it is preferable to form the thin equipment of the semi-cylindrical cylinder and the lenticular to be 0.1 to 1.

The microstructure is characterized in that the winding side to side in the longitudinal direction.

The backlight unit of the present invention for achieving the above object is a light source unit having a plurality of light sources arranged side by side in one direction, disposed on the light source portion, the base portion of the plate, and extends in parallel to the one direction on the base portion upper surface The microstructures include a refractive structure that is arranged side by side, characterized in that it comprises an optical film in which glass bubbles having a hollow inside the microstructure is diffused.

The diameter of the hollow is preferably formed to have a 4 ~ 30 um in consideration of the transmittance and reflectance of the glass bubble.

The glass bubbles are preferably formed to have a density of 40% to 70% of the total volume inside the microstructure.

The microstructure is characterized in that the chaotic shape irregularly twisted to the left and right with respect to the longitudinal direction.

As described above, the present invention provides a diffusion effect and luminance and luminance that can remove the dark and dark areas generated by a plurality of light sources with one optical film without an optical sheet such as a diffusion plate, a diffusion sheet and a fine pattern sheet. Uniformity can be improved and the backlight unit can be thinned.

In addition, since the present invention reduces the number of parts and the number of processes constituting the backlight unit, manufacturing cost can be saved, and the defect rate occurring in the assembly process can be reduced.

1 is a view showing a schematic configuration of a general direct type backlight unit

2 is a view showing a schematic configuration of a direct type backlight unit according to the present invention;

3 is a cross-sectional view of a semi-cylindrical optical film according to the present invention;

4 is a cross-sectional view of the glass bubble of FIG.

5 and 6 are views showing the diffusion effect of the glass beads according to the present invention and the general bead

7 to 11 is a view showing the transmittance and reflectance according to the size of the glass bubble of the present invention

12 is a graph showing the transmittance and reflectance characteristics according to the size of the glass bubble of the present invention

13 is a view showing the configuration of a direct backlight unit to which an optical film having a semi-cylindrical structure according to the present invention is applied.

14 is a view showing the configuration of a direct backlight unit to which the microstructure according to the present invention is applied an optical film of a prism type.

15 is a view showing the configuration of a direct backlight unit to which a microstructure according to the present invention is applied to an optical film having a chaotic semi-cylindrical shape.

16 is a view showing the configuration of a direct backlight unit to which the microstructure according to the present invention is applied to the optical film of the chaotic triangular prism type

17 shows luminance uniformity characteristics of the present invention and the prior art;

18 is a view showing the viewing angle characteristics of the present invention and the prior art.

Hereinafter, a configuration of a direct type backlight unit according to the present invention will be described with reference to the drawings.

2 is a view showing a schematic configuration of a direct type backlight unit according to the present invention.

2, the backlight unit according to the present invention includes a light source unit 110, a lamp cover 120, an optical film 140, and a fine pattern sheet 150.

The light source unit 110 emits light for the first time, and is composed of a plurality of light sources, that is, lamps, extending in one direction. Hot Cathode Fluorescent Lamp (HCFL) or Cold Cathode Fluorescent Lamp (CCFL) is used as the lamp.

The lamp cover 120 has a structure capable of fixing the light source unit 110, and is configured to surround left and right sides and a lower side, and increases light efficiency by reflecting light emitted from the light source unit 110 to the lower side and the left side upward. , To protect the light source 110.

The optical film 140 is positioned above the light source unit 110 and diffuses and condenses the light emitted from the light source unit 110.

The prism sheet 150 collects the light diffused from the optical film 140 to improve luminance characteristics.

3 is a cross-sectional view of the semi-cylindrical optical film according to the present invention, Figure 4 is a view showing a cross-section of the glass bubble of FIG. Hereinafter, the configuration of the optical film 140 of FIG. 2 will be described in detail with reference to FIGS. 3 and 4.

The optical film 140 has a plate-shaped base portion 141 positioned on the upper portion of the light source unit 110 and microstructures 142 extending in one direction on the upper surface of the plate-shaped base portion 141 arranged side by side to be incident. It consists of a refractive structure 145 for diffusing and condensing the light to be emitted. The microstructures 142 are curved to the left and right with respect to the longitudinal direction of the chaotic semi-cylindrical shape and the triangular prism shape in which the semi-cylindrical shape, the triangular prism shape, and the semi-cylindrical shape are meandering from side to side in the longitudinal direction as shown in FIG. It may be a chaotic shape or the like that is formed to be serpentine.

The optical film 140 may be disposed to coincide with one direction of lamps in which the length direction of the microstructure 142 extends. The microstructure 142 may be made of a resin such as polymethylmethacrylate, polyamide, polypropylene, and polyurethane.

Inside the microstructures 142, as shown in FIG. 4, glass bubbles 143 having hollows 146 formed therein are diffused. The light emitted from the light source 110 and incident through the base 141 is reflected and transmitted by the hollow 144 to be diffused and collected, and secondly diffused and collected at the surface of the microstructure 142. The glass bubble 143 is typically composed of glass, and may be composed of polyester resin, polyacrylic resin, polystyrene resin, and polycarbonate resin having high transparency. The thickness (D1-D2) / 2 of the glass bubble 143 may be formed to have a value of 1/2 or less of the outer diameter D1 of the glass bubble. That is, the thickness of the glass bubble is preferably formed thin within 50% of the outer diameter (D1). When the thickness of the glass bubble has a value of 1/2 or more, the diffusion effect and luminance uniformity are reduced.

5 is a view showing the diffusion effect by the beads in the general bead-type diffusion sheet, Figure 6 is a view showing the diffusion effect by the glass bubble having a hollow according to the present invention.

In FIG. 6, the glass bubble 143 according to the present invention diffuses into the microstructure 142, but the glass bubble 143 of the present invention diffuses into the general resin layer in order to compare the diffusion effect of the beads in the general bead type diffusion sheet. The case was shown.

FIG. 6 shows that although the glass bubble 146 having the hollow 144 according to the present invention is diffused into the resin layer as shown in FIG. 5 without diffusing into the microstructure 142, the glass bubble 143 of the present invention is It can be seen that the diffusion effect is better than that of the beads.

Referring to FIG. 6, light passes through four medium boundaries in the course of passing through the glass bubble 143. That is, the boundary between air and the glass material exists twice from the outside of the glass bubble 143 to the center of the glass bubble 143, and from the center of the glass bubble 143 to the outside of the glass bubble 143. In the process of exiting, the boundary exists twice, and as a result, the light is refracted four times, so that the diffusion effect is greatly increased.

As a result, when the glass bubble 143 having the hollow 144 is diffused into the microstructure 142 of the present invention, the light diffused by the glass bubble 143 is secondaryly diffused and condensed. The film 140 may further improve luminance uniformity and diffusion effect than the general bead type diffusion sheet.

In the above, the diffusion effect and luminance uniformity are described in comparison with the base material, thickness, and general beads of the glass bubble 143. Hereinafter, a method of determining the diameter D1 of the glass bubble according to the present invention will be described with reference to FIGS. 7 to 11.

FIG. 7 illustrates the reflection and transmission characteristics when the diameter of the glass bubble is 600 nm and is diffused into the microstructure 142 at a water density of approximately 700 million / μs. FIG. 8 shows the diameter D1 of the glass bubble is 800 nm. , Reflectance and transmission characteristics when diffused to a density of 295,358,650 pieces / ,, Figure 9 shows the reflection and transmission characteristics when the diameter (D1) of the glass bubble is diffused to a water density of 151,187,900 / ㎣ 10 shows the reflection and transmission characteristics when the diameter D1 of the glass bubble is 3 μm and is diffused at a water density of 5,600,000 pieces / ㎣, and FIG. 11 shows a diameter D1 of 6 μm and 700,000 pieces / ㎣. This shows the reflection and transmission characteristics when diffused to a density of, and the reflection and transmission characteristics when the volume of the glass bubbles 146 in the microstructure 142 is the same. 12 is a view showing the reflectance and transmittance according to the diameter (D1) of the glass bubble 146 according to the present invention.

As shown in FIG. 7, when the diameter D1 of the glass bubble 146 is 600 nm, the light irradiated from the light source 10 may not be transmitted through the optical film and may be reflected. As shown in FIG. 8, the diameter D1 may be reflected. Even at 800 nm, only a part of the light is transmitted, and most of the light is reflected.

In addition, as shown in FIG. 9, even when the diameter D1 of the glass bubble 146 is 1 μm, the light transmittance is lower although some light is transmitted than when the diameter D1 is 800 nm.

On the contrary, when the diameter D1 of the glass bubble 146 is 3 μm as shown in FIG. 10, the reflectance and the transmittance are similar. When the diameter D1 of the glass bubble is 6 μm as shown in FIG. 11, the reflectance is 6 μm. It can be seen that the transmittance is greater than.

Referring again to FIG. 12, it can be seen that as the diameter D1 of the glass bubble 146 increases, the transmittance increases and the reflectance decreases. In the optical film of the present invention, since the diffusion effect and the uniformity of luminance are important, the diameter D1 having a transmittance of 50% or more and a reflectance of 5% or more is selected.

Therefore, it can be seen from FIG. 12 that the diameter D1 of the glass bubble 146 satisfying the condition that the transmittance is 50% or more and the reflectance is 5% or more is 4um to 30um. Therefore, the glass bubble 143 is preferably formed to have a diameter (D1) of 4um to 30um.

In addition, the glass bubbles 143 having the diameter D1 determined as described above are diffused to have a density of 40% to 70% of the total volume inside the microstructure 142 in the microstructure 142 in consideration of luminance. It is preferable. That is, by adjusting the number density of the glass bubble within the range of 40% to 70% can obtain the desired light diffusion effect.

Compared to the prior art, when the microstructure 142 is a semi-cylindrical shape as shown in FIG. 3, the width W and the height H of the semi-cylindrical column are obtained in order to obtain a desired diffusion effect, that is, desired luminance uniformity and viewing angle. Although it was necessary to adjust the fine equipment (H / W) determined by), in the present invention, the glass bubble 144 having a hollow 146 diffused inside the microstructure 142 without having to adjust the fine equipment to obtain a desired diffusion effect. The diffusion effect can be controlled by adjusting the density of water. However, it may be adjusted to further improve the diffusion effect by adjusting the thin equipment. Therefore, the present invention can more easily obtain the desired diffusion effect. In general, when the microstructure 142 has a semi-cylindrical shape, the width (W) and the height (H) of the cross section of the microstructures are formed to have a thickness of 1 um to 200 um.

As such, when the diffusion effect is increased by using the glass bubble 144, a sufficient diffusion effect can be obtained without increasing the equipment to the extent that manufacturing is difficult, so the manufacturing process can be simplified and the thickness of the optical film can be reduced. A more advantageous effect can also be obtained in terms of thinning of the unit.

FIG. 13 is a perspective view of a backlight unit to which an optical film having a semi-cylindrical microstructure according to the present invention is applied, and FIG. 14 is a perspective view of a backlight unit to which an optical film having a prismatic microstructure according to the present invention is applied. Drawing. And Figure 8 shows the diffusion effect according to the number density of the glass bubble having a hollow diffused in the microstructure of the present invention.

As shown in FIG. 13, the microstructures may have a semi-cylindrical shape, and as shown in FIG. 14, the microstructures may have a prism shape.

Glass bubbles 142 having a hollow 146 is preferably diffused to have a density of 40% to 70% of the total volume inside the microstructure 142 as described above.

When the microstructure 142 is configured in the shape of a prism, in order to increase the light collecting efficiency of the light diffused by the glass bubble 142, the vertex angle of the prism is preferably formed at 40 to 110 degrees. In addition, the microstructures may be formed in a lenticular, that is, semi-spherical lens shape. The size of the lenticular is preferably formed such that the width-to-height ratio (h / w: thin equipment) has a value between 0.1 and 1. If the size is smaller than this, the diffusion effect and luminance uniformity are reduced due to the large curvature of the pattern. If larger than this, the processing of the pattern is not only difficult but also the diffusion effect is reduced as the curvature is reduced, the luminance uniformity is also worsened. Even when the microstructure is semi-cylindrical, it is preferable that the thin equipment is formed to have a value between 0.1 and 1.

15 and 16, the semi-cylindrical and triangular prism-shaped microstructures 142 are irregularly twisted from side to side in the longitudinal direction (hereinafter referred to as "chaos shape"), and wet (wet-out). , Newton ring and moire can be improved. Specifically, since the chaos pattern has a serpentine shape in the left and right and up and down directions, the pattern shape having periodicity can be avoided, thereby reducing the moire. Since the contact portion of the irregularity can be made more effective in improving the wet and Newton ring.

13 to 16, the optical film 140 according to the present invention is preferably disposed so that the longitudinal direction of the lamp and the longitudinal direction of the microstructure.

17 is a view comparing luminance uniformity characteristics of the backlight unit to which the optical film according to the present invention is applied and luminance uniformity characteristics of the backlight unit to which the diffusion plate 30 is applied according to the related art.

As shown in FIG. 17A, although the diffusion plate 30 is applied to the backlight according to the related art, the light and dark portions caused by the lamps are clearly seen. Therefore, in this case, the diffusion sheet must be additionally applied to the upper part of the diffusion plate. However, as shown in (b) of FIG. 17, although the present invention does not apply the diffusion plate, it can be seen that the light and dark portions generated by the lamps of the light source unit 110 are not visible. That is, it can be seen that the light diffusion and luminance uniformity characteristics of the light emitted from the optical film 140 of the present invention are better than the light diffusion and luminance uniformity characteristics of the conventional diffusion plate 30.

18 is a view comparing the viewing angle characteristics of the backlight unit to which the optical film according to the present invention is applied and the viewing angle characteristics of the backlight unit to which the diffusion plate is applied according to the prior art.

As shown in (a) of FIG. 18, the backlight unit according to the prior art has an upper and lower viewing angle of about 80 degrees, and as shown in (b), the backlight unit according to the present invention has an upper and lower viewing angle of about 90 degrees, and the present invention. It can be seen that the viewing angle of the backlight unit is better than that of the conventional backlight unit. Left and right viewing angles can also be seen that the backlight unit of the present invention is better than the conventional backlight unit.

On the other hand, the present invention is not limited to the above-described typical preferred embodiment, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions in the art Anyone who has this can easily understand it. If such improvement, change, substitution or addition is carried out within the scope of the appended claims, the technical spirit should also be regarded as belonging to the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct backlight unit of a liquid crystal display (LCD) device, and is generated by a plurality of light sources with one optical film without an optical sheet such as a diffusion plate, a diffusion sheet, and a fine pattern sheet. And it is possible to improve the diffusion effect and brightness and brightness uniformity to remove the dark portion, and to reduce the backlight unit, it is possible to reduce the manufacturing cost by reducing the number of parts and processes constituting the backlight unit, It is a useful technology in the backlight field because it can reduce the defect rate occurring in the assembly process.

Claims (10)

The base of the plate, It includes a refractive structure in which the micro-structures extending in one direction are arranged side by side on the base upper surface, Optical film, characterized in that the glass bubbles having a hollow in the microstructure is diffused. The method of claim 1, Optical film, characterized in that the diameter of the glass bubble is 4 ~ 30 um. The method of claim 1, And the glass bubbles are diffused to have a density of 40% to 70% of the total volume inside the microstructure. The method of claim 1, The microstructure of the optical film, characterized in that the semi-cylindrical, prismatic or lenticular shape. The method of claim 4, wherein When the microstructure is a semi-cylindrical or lenticular shape, the optical film, characterized in that the fine equipment of the semi-cylindrical cylinder and the lenticular is 0.1 to 1. The method of claim 1, The micro-structure is an optical film, characterized in that the chaotic shape bent irregularly curved to the left and right with respect to the longitudinal direction. A light source unit having a plurality of light sources arranged side by side in one direction, Is disposed above the light source portion, and includes a plate-shaped base portion and the refractive structure portion is arranged in parallel to the microstructure extending in parallel to the base surface on the base portion, wherein the glass bubbles having a hollow inside the microstructure is diffused The direct type backlight unit comprising an optical film. The method of claim 7, wherein The direct type backlight unit, characterized in that the diameter of the glass bubble 4 ~ 30 um. The method of claim 7, wherein And the glass bubbles are diffused to have a density of 40% to 70% of the total volume inside the microstructure. The method of claim 7, wherein And a chaotic shape in which the microstructures are irregularly twisted from side to side in the longitudinal direction.

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