WO2010024610A2

WO2010024610A2 - Light guide plate and backlight unit based on same

Info

Publication number: WO2010024610A2
Application number: PCT/KR2009/004795
Authority: WO
Inventors: 박정호
Original assignee: 주식회사 엘엠에스
Priority date: 2008-08-28
Filing date: 2009-08-27
Publication date: 2010-03-04
Also published as: KR20100025759A; KR100983332B1; WO2010024610A3

Abstract

The present invention relates to a backlight unit of a liquid crystal display (LCD) apparatus and particularly to a light guide plate that can provide enhanced brightness and a wide viewing angle without applying a diffusion film and prism sheet, and a backlight unit based on the same. The present invention relates to a light guide plate whereon a plurality of engraved optical patterns are formed at the bottom mode; said optical pattern has a horseshoe shape in both cross sections, and the inner face formed inside the horseshoe shape of said optical pattern and the outer face formed outside it are respectively formed so as to have an inner base angle and an outer base angle, but the inner faces of said optical patterns are arranged so as to face in one direction.

Description

Light guide plate and backlight unit using the same

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight unit of a liquid crystal display (LCD) device, and more particularly, to a light guide plate and a backlight unit using the same without providing a diffusion film and a prism sheet.

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. .

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

As shown in FIG. 1, the backlight unit 10 includes a reflecting plate 1, a light guide plate 2, a diffusion film 3, a first fine pattern sheet 4, a second fine pattern sheet 5, and a protective sheet ( 6) and the light source 7.

After the light emitted from the light source 7 is incident on the light guide plate 2, the light is generated by total reflection inside the light guide plate 2 and scattered by the reflection pattern formed on the lower surface of the light guide plate 2. Among the light scattered by the reflection pattern, light incident on the surface of the light guide plate at an angle of incidence smaller than the critical angle is transmitted without being totally reflected, and thus is emitted upward and downward. In general, the emission angle of the light emitted through the light guide plate 2 is very low, about 30 degrees with respect to the upper surface of the light guide plate 2.

The reflecting plate 1 reflects the light emitted downward and re-enters the light guide plate 3 to improve the light efficiency.

The diffusion film 3 diffuses and condenses the light emitted through the upper surface of the light guide plate 2 to make the luminance uniform and to widen the viewing angle. However, the light passing through the diffusion film 4 is sharply lowered in brightness.

Since the first fine pattern sheet 4 refracts the light incident from the diffuser film 4 at a low angle, the first fine pattern sheet 4 concentrates and emits the light so that the first fine pattern sheet 4 enters the LCD element vertically, and thus the luminance and emission angle sharply dropped by the diffuser film 4. Increase In general, the first fine pattern sheet 4 has a plurality of prism patterns arranged on the upper surface of the first fine pattern sheet 4 so as to emit light incident from the diffusion film 4 perpendicularly 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 5 collects and emits the secondary light in order to increase the luminance uniformity of the light primarily collected in the first fine pattern sheet 4 and to increase the emission angle.

Usually, the emission angle of the light emitted from the light guide plate 2 is approximately 30 degrees with the surface of the light guide plate 2. Therefore, the first fine pattern sheet 4 and the second fine pattern sheet 5 receive light emitted through the diffusion film 3 and collect and emit the light so that the emission angle of the light is approximately 90 degrees.

In order to improve the uniformity of luminance, the first fine pattern sheet 5 and the second fine pattern sheet 6 are generally disposed such that the respective prism patterns are vertical. Only the fine pattern sheet 4 may be used, or both may be used.

The protective film 6 is positioned on the first fine pattern sheet 4 or the second fine pattern sheet 5 and scratches on the first fine pattern sheet 4 or the second fine pattern sheet 5. To prevent it from happening.

As described above, in the conventional backlight unit, light incident on the bottom of the LCD element must be provided vertically. However, since the emission angle of light based on the light guide plate emitted from the light guide plate is very low, about 30 degrees, a diffusion sheet and at least one fine pattern sheet are required, which makes it difficult to reduce the backlight unit.

In addition, in the conventional backlight unit, since the diffusion film 3 having the high thermal expansion coefficient and the first fine pattern filter 4 and the second fine pattern filter 5 are stretched by the heat generated by the light source, wrinkles occur and the characteristic decreases. There was a problem that could occur.

In addition, the use of the micropattern sheets and the diffusion sheet of the conventional backlight unit not only complicates the backlight unit assembly process but also has a problem that may cause a defect in cutting and assembly.

Accordingly, an object of the present invention is to form an intaglio horseshoe-shaped optical pattern on the lower surface of the light guide plate, and to form a diffused or condensed pattern on the upper surface of the light guide plate to provide improved luminance and wide viewing angle without applying a diffusion film and a prism sheet. An object of the present invention is to provide a light guide plate and a backlight unit using the same.

The light guide plate of the present invention for achieving the above object; In the light guide plate in which a plurality of optical patterns are formed intaglio on the lower surface, the optical pattern has a horseshoe shape having both end surfaces, the inner surface and the outer surface formed on the inside of the horseshoe shape of the optical pattern It is formed to be inclined to have an inner bottom angle and an outer bottom angle, respectively, characterized in that the inner surface of the optical patterns are arranged so as to face in one direction.

Here, the cross section of the horseshoe-shaped optical pattern is preferably formed in a triangular shape or trapezoidal shape.

Both end surfaces of the horseshoe-shaped optical pattern are preferably inclined toward the front.

It is preferable that the inner bottom angle is formed to be 10 degrees to 80 degrees, and the outer bottom angle is formed to be 10 degrees to 50 degrees.

It is preferable to form an additional pattern on the upper surface corresponding to the upper side of the trapezoidal optical pattern.

It is preferable to form diffusion or condensation patterns on an upper surface of the light guide plate.

A backlight unit according to another embodiment of the present invention; In the backlight unit comprising a light guide plate having a light source located on one side and an optical pattern of the negative surface on the lower surface, the optical pattern has a horseshoe shape having both end surfaces, the optical pattern is formed inside the horseshoe-shaped optical pattern The inner surface and the outer surface formed on the outer side is formed to be inclined so as to have an inner bottom angle and an outer bottom angle, respectively, characterized in that the inner surface of the optical pattern is arranged to face the side on which the light source is disposed.

As described above, the present invention can diffuse and condense the light emitted from the light source with only the light guide plate without the optical film such as the diffusion film and the fine pattern sheet, thereby reducing the backlight thickness.

In addition, the present invention has the effect of reducing the manufacturing cost according to the reduction of the number of parts and the number of processes constituting the backlight.

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

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

3 is a view showing the configuration of a horseshoe-shaped optical pattern of the trapezoidal cross section according to the present invention;

4 is a cross-sectional view of the horseshoe-shaped optical pattern of FIG.

5 is a view showing the curvature of the arc formed by the inner surface of the horseshoe-shaped optical pattern of FIG.

6 is a view showing an example of the optical path according to the light reflection in the optical pattern according to the present invention

7 is a view showing an example of the optical path according to the light condensing on the inner surface of the optical pattern according to the present invention

8 is a view showing the optical path of the light transmitted through the optical pattern and the light incident from the light portion according to the present invention

9 is a view showing an optical path of light incident from the light guide portion and other optical patterns according to the present invention;

10 is a view showing a first arrangement example of the horseshoe-shaped optical pattern according to the present invention

11 is a view showing a second arrangement example of the horseshoe-shaped optical pattern according to the present invention;

12 is a view showing a case in which an additional pattern is formed on the upper surface of the horseshoe-shaped optical pattern according to the present invention

13 is a view showing the configuration of a horseshoe-shaped optical pattern having a triangular cross section according to the present invention

14 is a cross-sectional view of the horseshoe-shaped reflection pattern of FIG.

15 is a view showing a case in which the prism pattern is provided on the upper surface of the light guide plate according to the present invention.

16 is a view showing a case in which a semi-cylindrical pattern is provided on the upper surface of the light guide plate according to the present invention.

17 is a view illustrating a case in which a semi-circular sphere pattern is provided on an upper surface of a light guide plate according to the present invention;

18 to 22 is a view showing the brightness and viewing angle characteristics according to the change of the inner bottom angle of the horseshoe-shaped optical pattern of the present invention

23 to 27 is a view showing the brightness and viewing angle characteristics according to the change of the outer bottom angle of the horseshoe-shaped optical pattern of the present invention

28 to 34 are views showing the luminance and viewing angle characteristics according to the change in the curvature (W: H) of the arc formed by the inner surface of the horseshoe-shaped optical pattern of the present invention

Hereinafter, a configuration of a 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 backlight unit according to the present invention.

The backlight unit 20 according to the present invention includes a light source 11, a reflective sheet 12, a light guide plate 13, and a protective sheet 14.

The light source 11 is a part which first emits light. As the light source 11, a light emitting diode (LED), a cold cathode fluorescent lamp (CCFL), or the like is used.

The light guide plate 13 is provided with a horseshoe-shaped optical pattern 14 according to the present invention at the lower end of the light guide plate scatters and condenses the light emitted from the light source 11 to emit upward. Specifically, the light emitted from the light source 11 is incident to the light guide plate 13, and then proceeds to cause total reflection inside the light guide plate 13, and a horseshoe shape is formed in an intaglio form on the lower surface of the light guide plate 13 according to the present invention. Impinges on the optical pattern 14 and is reflected and collected according to the incident angle of light. Since the light collected by the horseshoe-shaped optical pattern 14 is incident on the upper surface of the light guide plate 13 at an angle of incidence smaller than the critical angle, it is transmitted without being totally reflected and emitted upward. In addition, the light is scattered therein, and when the light is incident on the inner surface of the light guide plate 13 at an angle of incidence smaller than the critical angle, the light passes through the light guide plate 13 and is emitted upward and downward. At this time, the light emitted to the upper side of the light guide plate 13 is incident to the protective sheet 15, the light emitted to the lower side is incident to the reflective sheet 12.

The reflective sheet 12 reflects light incident from the lower side of the light guide plate 13 and reenters the light guide plate 13.

The protective sheet 15 prevents scratches from occurring in the light guide plate 13 and diffuses the light emitted from the light guide plate 13 to emit in a direction perpendicular to the LCD element.

Although not shown in FIG. 2, a fine pattern sheet or a diffusion sheet may be additionally configured between the light guide plate 13 and the protective sheet 15 to increase the viewing angle, increase luminance, or improve luminance uniformity.

3 is a view showing a cross-section of the horseshoe-shaped optical pattern according to the invention has a trapezoidal shape, Figure 4 is a view showing a cross-sectional view of the horseshoe-shaped optical pattern according to the present invention, Figure 5 according to the present invention Fig. 6 is a view showing the curvature of the arc formed by the inner surface of the horseshoe-shaped optical pattern, Figure 6 is a view showing an example of the optical path according to the light reflection in the optical pattern according to the present invention, Figure 7 is a view of the optical pattern according to the present invention 8 is a view showing an example of the optical path according to the light condensing on the inner surface, Figure 8 is a view showing an example of the light path incident from the light transmitted through the horseshoe-shaped optical pattern and the light portion according to the invention, Figure 9 Figure 1 shows an example of the optical path by the outer surface of the horseshoe-shaped optical pattern according to the invention. 10 is a view showing a first arrangement example of the horseshoe-shaped optical pattern according to the present invention, Figure 11 is a view showing a second arrangement example of the horseshoe-shaped optical pattern according to the present invention. Hereinafter, the horseshoe-shaped optical pattern structure according to the present invention will be described with reference to FIGS. 3 to 11.

The horseshoe-shaped optical pattern 14 according to the present invention has a cross section, that is, a trapezoidal cross section as shown in FIG. 4, and may be formed to have a base length of 50 μm and a height of 40 μm. The horseshoe-shaped optical pattern 14 having a trapezoidal cross section has an upper surface 21, a lower surface 22, a first front end surface 23, and a second front end surface 24 as shown in FIG. It consists of a side surface 25 and an outer surface 26.

The inner surface 25 is configured to have a shape lying inclined with respect to the front side, that is, the side direction in which the light source 11 is located. Referring to the cross section of the horseshoe-shaped optical pattern of FIG. 4, the inner surface 25 has a concave shape toward the front while maintaining the inclination by the inner bottom angle α, which is the inner bottom angle of the reflective pattern 14 of FIG. 4. It is formed to have. As shown in FIG. 5, the inner surface 25 may have a curved surface having a curvature determined by the width W and the height H, or may be formed in a continuous plane as shown in FIG. 7. The inner surface 25 formed as described above collects light in total reflection or scattering in the light guide plate 13 and emits the light to the upper side of the light guide plate 13 as shown in FIGS. 6 to 9. In other words, the inner side surface 25 performs the function of condensing and diffusing light to improve the left and right viewing angles.

Among the lights reflected by the inner surface 25, light incident on the light guide plate 13 at an angle of incidence smaller than a critical angle as shown in FIG. 12 is transmitted through the light guide plate 13 and is emitted in a direction perpendicular to the LCD element. do.

The outer side 26 is also configured to have a shape lying at a certain inclination. Referring to FIG. 4, the outer surface 26 is formed to have a convex shape toward the rear while maintaining the inclination by the outer base angle β. The outer surface 26 thus formed reflects the light in progress while totally reflecting, or reflects the light in scattering again. Specifically, referring to FIGS. 8 and 9, light having an incident angle smaller than the critical angle, such as the light 411 of FIG. 8, may transmit the reflection pattern 14 and the transmitted light 411-1. The silver is reflected by the reflective sheet 12, and the reflected light 411-2 is refracted by the outer surface 26 to be emitted above the light guide plate 13. Further, the total reflection or the light 413 reflected from the light facing part opposite to where the light source 11 is located among the scattered light is reflected by the outer surface 26 and proceeds above the light guide plate 13. In addition, as shown in FIG. 9, the light that is reflected and incident on the light portion except for the inner surface 25 and the other pattern is reflected through the outer surface 26 having a circular convex shape, and then proceeds toward the light guide plate 13. That is, the outer surface 26 forms an even reflecting surface for the light incident from all directions except the light incident on the inner surface 25.

On the other hand, when the cross section of the horseshoe-shaped optical pattern has a trapezoidal shape, the first front end face 23 and the second front end face 24 also have a trapezoidal shape. The first front end surface 23 and the second front end surface 24 may be formed to have the same shape and the same size, and may be configured to lie at a predetermined inclination θ with respect to the light incident direction. The upper sides of the first front end surface 23 and the second front end surface 24 correspond to both ends of the upper surface 21, respectively, and the lower sides correspond to both ends of the lower surface 22, respectively. The first front end surface 23 and the second front end surface 24 reflect light scattered during total reflection or re-reflect light scattered. The inclination θ may have the same value as the outer base angle or the inner base angle.

The method of forming the horseshoe-shaped optical pattern 14 includes hot press, etching and the like.

18 to 22 are views showing the brightness and viewing angle characteristics according to the change of the inner bottom angle of the horseshoe-shaped optical pattern of the present invention, Figures 23 to 27 are the brightness and viewing angle according to the change of the outer bottom angle of the horseshoe-shaped optical pattern of the present invention It is a figure which showed the characteristic.

18 to 22 measure luminance and viewing angle characteristics of the outer base angle at 80 degrees, the curvature at 5: 1, and the inner base angle at 30 degrees, 40 degrees, 42.5 degrees, 45 degrees, and 50 degrees. 23 to 27 show that the inner bottom angle is 42.5 degrees, the curvature is fixed at 5: 1, and the outer bottom angle is measured in luminance and viewing angle characteristics at intervals of 10 degrees in a range of 40 degrees to 80 degrees.

As described above, in the horseshoe-shaped optical pattern 14 according to the present invention, the inner bottom angle α, which is the inclination of the inner surface 25, and the outer bottom angle β, which is the inclination of the outer surface 26 serve as important factors.

As shown in FIG. 18, when the inner bottom angle α is 30 degrees, the main exit angle is +10 degrees. In the case of 40 degrees as shown in FIG. 19, the main exit angle is +5 degrees. In the case of almost 0 degrees and 45 degrees as shown in Fig. 21, the main exit angle is -5 degrees to -7 degrees. In addition, as shown in FIG. 22, when the inner angle is 50 degrees, it has a light condensing effect and luminance characteristics evened from -20 degrees to +60 degrees, and the main emission angle is -10 degrees. If the other angle, that is, the inner bottom angle α is less than 30 degrees or more than 5 degrees, it can be seen that the main exit angle is 10 degrees.

Therefore, the inner bottom angle α is formed at an arbitrary angle between 30 degrees and 50 degrees so that the main emission angle in the vertical direction is within +10 degrees compared to the vertical (0 degrees) in consideration of the light collecting effect as shown in FIG. 9. It is desirable to.

In FIG. 23, when the outer base angle is 40 degrees, the light condensing effect of the upper portion of the viewing angle is reduced, and thus, the luminance decrease of about 30% occurs compared to 80 degrees.

Therefore, the outer base angle β is preferably formed at any angle between 50 degrees and 90 degrees with a large light converging effect in consideration of the viewing angle distribution as shown in FIG. 10.

28 to 35 show the luminance and viewing angle characteristics according to the curvature change of the inner surface of the horseshoe-shaped optical pattern of the present invention, while fixing the inner bottom angle at 42.5 degrees and the outer bottom angle at 80 degrees and changing the curvature, It shows what measured. The black part in the center represents the distribution of red light.

As shown in FIGS. 28 to 35, when the curvature W: H of the inner surface of the horseshoe-shaped optical pattern 14 is 5: 2, 5: 3, 5: 4 and 4: 1, the left and right viewing angle distributions split, When the curvatures are 5: 1, 6: 1, 10: 1 (5: 0.5) and 20: 1, it can be seen that the left and right viewing angle distributions do not diverge. In other words, when the curvature is less than 4: 1 and more than 20: 1, the gap of the central red light distribution shown in black is large, indicating that the left and right viewing angle distributions are divided, and 5: 1 to 20: 1. Since the gap of the central red light distribution shown in black is small in between, it can be seen that the left and right viewing angle distributions do not split. Therefore, in the present invention, it is preferable that the width-to-height ratio of the curvature of the left and right viewing angles not to be divided, that is, the light converging effect is good, be 5: 1 or more and 20: 1 or less.

The horseshoe-shaped optical pattern 14 may be arranged at a predetermined distance up, down, left, and right as shown in FIG. 10, or may be arranged in a continuous form at a left and right at a predetermined distance as shown in FIG. 11. In addition, the optical pattern 14 may be arranged while decreasing the distance in steps as the distance from the light source (11).

12 is a view showing a case in which the additional pattern is formed on the upper surface of the horseshoe-shaped optical pattern of the trapezoidal cross section according to the present invention.

Referring to FIG. 12, in order to additionally condense light, which is totally reflected or scattered, on the horseshoe-shaped upper surface 21 corresponding to the upper side of the trapezoidal shape, which is a cross section of the optical pattern 14 in the present invention, as shown in FIG. 12. An additional pattern in the form of a triangular prism is formed. In addition to the additional pattern, a polygonal pattern, a semi-cylindrical pattern, or the like may be formed.

13 and 14 illustrate a cross section of a horseshoe-shaped optical pattern according to the present invention. FIG. 13 illustrates a horseshoe-shaped optical pattern having a triangular cross section, and FIG. 14 shows a cross section of a horseshoe-shaped optical pattern. The figure shown.

13 and 14, the horseshoe-shaped optical pattern 14 having a triangular cross section includes a first front end face 31, a second front end face 32, an inner face 33, and an outer face 34. And a lower surface 35.

13 and 14, except that the upper surface 21 is not illustrated in FIG. 3, since the remaining shapes and functions are the same, overlapping descriptions thereof will be omitted.

The horseshoe-shaped optical patterns having a triangular cross section as shown in FIGS. 13 and 14 may also be arranged in the same manner as the horseshoe-shaped optical patterns having a trapezoidal cross section shown in FIGS. 6 and 7.

15 to 17 is a view showing a diffusion pattern or a light collecting pattern provided on the upper surface of the light guide plate according to the present invention.

15 to 17, diffusion patterns or condensing patterns are further formed on the top surface of the horseshoe-shaped light guide plate 13 according to the present invention, thereby diffusing or condensing the light collected in the light guide plate 13. A prism pattern may be formed as shown in FIG. 15, and a semi-circle cylinder as shown in FIG. 16 and a semi-sphere pattern as shown in FIG. 17 may be formed. By further configuring the above-described diffusion pattern and condensing pattern on the upper surface of the light guide plate 13, it is possible to improve luminance, luminance uniformity, and viewing angle.

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.

Recently, liquid crystal display (LCD) has been increasingly used in display devices such as mobile phones, TVs, navigation, and various monitors, and this trend is expected to continue in the future. In particular, as display devices become more complex, compactness and simplicity are important factors.

In view of this aspect, the light guide plate used in the liquid crystal display device according to the present invention can provide improved luminance and wide viewing angle without applying a diffusion film and a prism sheet, thereby miniaturizing and simplifying the product and finally improving the quality of the product. Can contribute. For this reason, the light guide plate of the present invention is considered to be widely used in a display device in the future.

Claims

In the light guide plate in which a plurality of optical patterns are formed intaglio on the lower surface,

The optical pattern has a horseshoe shape having both end faces, and the inner surface formed on the inside of the horseshoe shape of the optical pattern and the outer surface formed on the outside are inclined to have an inner bottom angle and an outer bottom angle, respectively, A light guide plate, characterized in that the side is arranged to face in one direction.
The method of claim 1,

The light guide plate, characterized in that the cross section of the horseshoe-shaped optical pattern is formed in a triangular shape.
The method of claim 1,

The light guide plate, characterized in that the cross section of the horseshoe-shaped optical pattern is formed in a trapezoidal shape.
The method of claim 1,

A light guide plate, characterized in that both end surfaces of the horseshoe-shaped optical pattern is inclined toward the front.
The method of claim 1,

The inner light guide plate is characterized in that the 30 to 50 degrees.
The method of claim 1,

The outer light guide plate is characterized in that 40 to 80 degrees.
The method of claim 3,

The light guide plate, characterized in that the additional pattern is formed on the upper surface corresponding to the upper side of the trapezoidal shape of the optical pattern
The method according to any one of claims 1 to 7,

The light guide plate, characterized in that the diffusion or condensing pattern is formed on the upper surface of the light guide plate.
The method of claim 1,

The inner light guide plate is formed to have a curvature between 5: 1 to 20: 1.
In the backlight unit comprising a light guide plate having a light source located on one side and an intaglio optical pattern on the bottom surface,

The optical pattern has a horseshoe shape having both end surfaces, and the inner surface formed on the inner side of the horseshoe-shaped optical pattern and the outer surface formed on the outer side are formed to be inclined so as to have an inner bottom angle and an outer bottom angle, respectively. Back side of the light source, characterized in that the light source is arranged facing the side arranged.