KR20100025759A - Light guide panel and backlight unit using the same - Google Patents

Abstract

PURPOSE: A light guide panel and a backlight unit using the same are provided to make a back light thin by implementing diffusion and concentration of light emitted from a light source only with a light guide panel. CONSTITUTION: A plurality of reflection patterns(14) are engraved on the lower face of a light guide plate. A reflection pattern has a horseshoe shape having amount end face. An inner face(25) and an outer face(26) of the reflection pattern are formed to slope in order to have the inner side basic angle and the outer side basic angle. The inner side is arranged in order to face one direction.

Description

LIGHT GUIDE PANEL 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 diffuser 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 condenses and emits the second condensed 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 defects in cutting and assembly.

Accordingly, an object of the present invention is to form a negative horseshoe reflection 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 reflective patterns are formed intaglio on the lower surface, the reflective 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 reflective pattern is 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 reflective patterns are arranged so as to face in one direction.

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

Both end surfaces of the horseshoe-shaped reflection 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 reflection pattern.

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

A backlight unit according to another embodiment of the present invention; A backlight unit including a light guide plate having a light source located on one side and a negative reflection pattern on a lower surface thereof, wherein the reflection pattern has a horseshoe shape having both end surfaces and is formed inside the horseshoe shape reflection 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 reflective patterns are 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.

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 includes the horseshoe-shaped reflection patterns 14 according to the present invention at an inner bottom thereof to scatter and condense 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. The light incident on the reflective pattern 14 is reflected and collected according to the incident angle of light. Since the light collected by the horseshoe-shaped reflection 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 is 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.

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

The horseshoe-shaped reflective pattern 14 according to the present invention has a cross section, that is, a trapezoidal cross section, as shown in FIG. 3b, and may be formed to have a width W of 50 μm and a height H of 40 μm. The horseshoe-shaped reflection 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. 3A. 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 reflection pattern of FIG. 3B, 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. 3B. It is formed to have. The inner surface 25 may be formed as a curved surface having a curvature determined by the width W and the height H as shown in FIG. 3C or in a continuous portion of the partial plane as in FIG. 4B. As described above, the inner side surface 25 collects light in total reflection or scattering in the light guide plate 13 and emits the light toward the upper side of the light guide plate 13 as shown in FIG. 4. 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. 4A 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. 3B, 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. In detail, referring to FIGS. 4C and 4D, the light having the incident angle smaller than the critical angle, such as the light 411 of FIG. 4C, 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. 4D, 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 proceeds upwards to 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 reflection pattern is trapezoidal, the first front end surface 23 and the second front end surface 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 reflection pattern 14 includes hot press, etching and the like.

9 is a view showing the brightness and viewing angle characteristics according to the change of the inner bottom angle of the horseshoe shape reflection pattern of the present invention, Figure 10 is a view showing the brightness and viewing angle characteristics according to the change of the outer bottom angle of the horseshoe shape reflection pattern of the present invention. to be.

FIG. 9 measures luminance and viewing angle characteristics at an outer bottom angle of 80 degrees, a curvature of 5: 1, and an inner bottom angle of 30 degrees, 40 degrees, 42.5 degrees, 45 degrees, and 50 degrees. In addition, FIG. 10 measures luminance and viewing angle characteristics at intervals of 10 degrees at an inner bottom angle of 42.5 degrees, a curvature of 5: 1, and an outer bottom angle of 40 degrees to 80 degrees.

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

As shown in FIG. 9A, 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. 9B, the main exit angle is +5 degrees. In the case of almost 0 degrees and 45 degrees as shown in Fig. 9d, the main exit angle is -5 degrees to -7 degrees. In addition, as shown in FIG. 9E, 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 base angle α is less than 30 degrees or more than 5 degrees, it can be seen that the main exit angle is ㅁ 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 ㅁ 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. 10A, when the outer base angle is 40 degrees, the light condensing effect of the upper portion of the viewing angle is lowered, and thus, the luminance decrease of about 30% compared to 80 degrees occurs.

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.

11 is a view illustrating brightness and viewing angle characteristics according to a curvature change of an inner surface of a horseshoe-shaped reflection pattern of the present invention. The luminance and viewing angle characteristics are measured while changing the curvature while fixing the inner bottom angle at 42.5 degrees and the outer bottom angle at 80 degrees. It is shown.

As shown in FIG. 11, when the curvature W: H of the inner surface of the horseshoe reflection pattern 14 is 5: 2, 5: 3, 5: 4, and 4: 1, the left and right viewing angle distributions are split, and the curvature is At 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 left and right viewing angle distributions are split, and between 5: 1 and 20: 1, the left and right viewing angle distributions are 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 reflection pattern 14 may be arranged at a predetermined distance up, down, left, and right as shown in FIG. 5A, or may be arranged in a continuous form at a left and right at a predetermined distance as shown in FIG. 5B. In addition, the reflective patterns 14 may be arranged while decreasing the distance in steps as the distance from the light source 11 increases.

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

Referring to FIG. 6, in order to additionally collect 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 reflective pattern 14 in FIG. 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.

7 is a cross-sectional view of the horseshoe-shaped reflection pattern according to the present invention is a triangle, Figure 7a shows a horseshoe-shaped reflection pattern of the triangle cross-section, Figure 7b is a view showing a cross section of the horseshoe-shaped reflection pattern to be.

Referring to FIG. 7, the horseshoe-shaped reflective pattern 14 having a triangular cross section includes a first front end surface 31, a second front end surface 32, an inner surface 33, an outer surface 34, and a lower portion. It consists of the face 35.

Since the reflective pattern according to FIG. 7 has the same function as the remaining shapes except for the absence of the upper surface 21 in FIG. 3, redundant description thereof will be omitted.

The horseshoe-shaped reflection patterns having a triangular cross section as shown in FIG. 7 may also be arranged in the same manner as the horseshoe-shaped reflection patterns having a trapezoidal cross section shown in FIGS. 4A and 4B.

8 is a view illustrating a diffusion pattern or a light collecting pattern provided on an upper surface of the light guide plate according to the present invention.

Referring to FIG. 8, 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. 8A, and a semi-cylindrical shape as shown in FIG. 8B and a semi-circular pattern as shown in FIG. 8C 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 the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

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;

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

3B is a cross-sectional view of the horseshoe shape reflection pattern of FIG. 3A;

Figure 3c is a view showing the curvature of the arc formed on the inner surface of the horseshoe shaped reflection pattern of Figure 3a

4A illustrates an example of an optical path according to light reflection in a reflection pattern according to the present invention;

4B is a view showing an example of an optical path according to condensing on the inner surface of the reflective pattern according to the present invention;

Figure 4c is a view showing the optical path of the light passing through the reflection pattern and the light incident in accordance with the present invention;

4d is a view showing an optical path of light incident on a light portion and another reflection pattern according to the present invention;

5A is a view showing a first arrangement example of a horseshoe-shaped reflection pattern according to the present invention;

Figure 5b is a view showing a second arrangement example of the reflection pattern of the horseshoe shape according to the present invention

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

Figure 7a is a view showing the configuration of a horseshoe-shaped reflective pattern of the triangle is a cross section according to the present invention

FIG. 7B is a cross-sectional view of the horseshoe shape reflection pattern of FIG. 7A; FIG.

8A is a view illustrating a case where a prism pattern is provided on an upper surface of a light guide plate according to the present invention.

8B 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;

8C 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;

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

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

11 is a view showing the luminance and viewing angle characteristics according to the change in curvature (W: H) of the arc formed on the inner surface of the horseshoe-shaped reflection pattern of the present invention

※ Explanation of codes for main parts of drawing

1, 12: reflection sheet 2, 13: light guide plate

3: diffusion sheet 4: first fine pattern sheet

5: 2nd fine pattern sheet 6, 15: protective sheet

7, 11: light source 14: reflection pattern

21: upper surface 22, 35: lower surface

23, 31: first front end face 24, 32: second front end face

25, 33: inner side 26, 34: outer side

Claims (10)

In the light guide plate in which a plurality of reflective patterns are formed intaglio on the lower surface, The reflective pattern has a horseshoe shape having both end faces, and the inner surface formed on the inner side of the horseshoe shape of the reflective 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 reflective 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 reflective pattern is formed in a trapezoidal shape. The method of claim 1, The light guide plate, characterized in that both end surfaces of the horseshoe-shaped reflection pattern is inclined toward the front. The method of claim 1, The inner light guide plate is characterized in that the 30 degrees to 50 degrees. The method of claim 1, The outer light guide plate is characterized in that the 40 to 80 degrees. The method of claim 3, The light guide plate is formed on the upper surface corresponding to the upper side of the trapezoidal shape of the reflective pattern The method according to any one of claims 1 to 7, The light guide plate, characterized in that the diffusion 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 including a light guide plate having a light source located on one side and a negative reflective pattern on the lower surface,  The reflective pattern has a horseshoe shape having both end faces, and the inner surface and the outer surface formed on the outside of the horseshoe-shaped reflection pattern 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.

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