KR20110073087A - Light guide panel and lcd back light unit using the same - Google Patents

Abstract

PURPOSE: A light guide plate for a liquid crystal display backlight unit and the liquid crystal display backlight unit using the same are provided to enhance brightness and regularity of light intensity forming more than two kinds of stripe pattern vertically crossing each other. CONSTITUTION: A side(10c) of a light guide plate(100) makes a light incident. A front side(10b) of the light guide plate emits the light. A backside of the light guide plate reflects the light. The first and the second stripe pattern(1,2) are formed in the backside of the light guide plate in order to cross each other vertically. A cross sectional shape of the first stripe pattern is a circle, an ellipsoid or an R prism.

Description

LIGHT GUIDE PANEL AND LCD BACK LIGHT UNIT USING THE SAME}

The present invention relates to a light guide plate for a liquid crystal display backlight unit. More specifically, the present invention provides a liquid crystal display capable of effectively eliminating hot spots of LEDs and improving luminance compared with a printed LGP by forming two or more stripe patterns that cross each other at right angles to the rear surface of the LGP for a LCD unit. A light guide plate for a device backlight unit and a backlight unit including the same.

In general, a liquid crystal display device refers to a device in which a liquid crystal, which is a liquid and a solid intermediate material, is injected between two glass substrates formed of electrodes to display a number or an image by applying an electric field. LCDs have the advantages of light weight, low power consumption, and thin product. Due to these features, the application range of thin-screen TVs, monitors, portable displays, etc. is gradually increasing. In particular, in the TV market, which has become larger, achieving low power consumption and high brightness becomes an important problem.

The part which is closely related to such power consumption and high brightness is especially a backlight unit. The backlight unit includes a direct type method of irradiating light by arranging lamps on a lower surface of the liquid crystal panel, and an edge type method of installing a light guide plate under the liquid crystal panel and irradiating light from a lamp at one end of the light guide plate. The edge type backlight unit is composed of a light source that emits light, a light guide plate for guiding the emitted light and spreading the light evenly on the front surface of the backlight, a diffusion sheet for condensing the light emitted from the light guide plate in the front direction, and a prism sheet. . Typically, a circular reflective layer is printed on the bottom of the light guide plate to spread the light from the light source to the front of the backlight. Light from the light source is totally reflected in the light guide plate and scattered by the printed reflective layer. A part of the scattered light is emitted at a low angle from the light guide plate, and the light emitted at a low angle is focused in the front direction by the diffusion sheet and the prism sheet.

In the conventional light guide plate lower surface printing method, part of the light emitted from the light source positioned at the side of the backlight is totally reflected in the light guide plate, and part of the light is scattered by the reflective layer on the bottom surface of the light guide plate and is emitted from the light guide plate. The size and density of the reflective layer on the lower surface of the light guide plate are adjusted according to the position of the light guide plate so that the light emitted from the light source is uniformly emitted from the front surface of the light guide plate. The light emitted at a low angle from the light guide plate is collected in the center direction by the diffusion sheet and finally collected by the prism sheet. However, there is a disadvantage in that it is impossible to improve the central luminance by adjusting the viewing angle of the light emitted from the structure of the conventional printed light guide plate, diffusion sheet, and prism sheet.

In order to increase the central luminance by narrowing the viewing angle of the emitted light, there is a method of improving the luminance by forming a geometric pattern on the upper and lower surfaces of the light guide plate instead of the printed light guide plate and combining the lenticular films. However, this method has a problem in that a hot spot of the LED occurs when the LED is used as a light source. In order to remove such hot spots, a method of printing or forming a pattern on the light incident part of the light guide plate has been used. In addition, since the technology for forming the upper and lower surface patterns of the light guide plate has not been developed, it is difficult to mass-produce it into an actual product.

Accordingly, there is a need for development of a light guide plate that can easily form a light guide plate and effectively remove hot spots of LEDs and improve luminance compared to a printed light guide plate only by pattern formation of a cross section instead of an upper and a lower surface pattern.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light guide plate for a liquid crystal display backlight unit that can not only effectively remove a hot spot of an LED but also has excellent brightness.

Another object of the present invention is a light guide plate for a liquid crystal display backlight unit that is not only easy to form a pattern, but also has excellent luminance by only forming a pattern of a cross section rather than an upper and a lower pattern, and is easy to manufacture and reduce manufacturing cost. To provide.

Another object of the present invention is to provide a light guide plate for a liquid crystal display backlight unit that can improve the appearance and appearance of moire.

Another object of the present invention is to provide a light guide plate for a liquid crystal display backlight unit having excellent light uniformity and visibility.

Another object of the present invention is to provide a backlight unit of a liquid crystal display device using the light guide plate.

Technical problems to be achieved by the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

One aspect of the present invention relates to a light guide plate for a liquid crystal display backlight unit. The light guide plate includes a side on which light is incident, a front surface connected to the side surface, and a rear surface reflecting light, and two or more stripe patterns crossing at right angles to the rear surface. Characterized in that formed.

In a specific embodiment, a first stripe pattern in a direction perpendicular to the light source and a second stripe pattern in a direction parallel to the light source are formed on the rear surface, and the first stripe pattern and the second stripe pattern cross each other at right angles on the same plane. Characterized in that.

In embodiments, the first stripe pattern may have a curved surface shape having a circular cross section, an ellipse, an R-prism, or a combination thereof.

In embodiments, the first stripe pattern may have a pitch to height ratio of 0.7 or less.

In exemplary embodiments, a gap GAP may be formed between the first stripe patterns. In the first stripe pattern, a gap GAP between the patterns may be 200 μm or less.

In embodiments, the second stripe pattern may include a prism, a trapezoid, an inverted groove, an ellipse, a lenticular, or a combination thereof.

In embodiments, when the cross section of the second stripe pattern is a prism, the hypotenuse angle may be 5 to 30 °.

In one embodiment, the second stripe pattern may have a variable pitch structure in which the distance between the patterns becomes narrower as the light source moves away from the light source.

In another embodiment, the second stripe pattern may have a structure in which the inclination angle increases as the distance from the light source increases.

In another embodiment, the second stripe pattern may have a structure in which the distance between the patterns becomes narrower and the hypotenuse angle increases as the distance from the light source increases.

The light guide plate may have a plurality of beads dispersed therein. The beads may be included in 0 to 0.1% by weight of the total weight of the light guide plate.

Another aspect of the present invention relates to a liquid crystal display backlight unit including the light guide plate. In an embodiment, the liquid crystal display backlight unit may include the light guide plate; And a light source disposed on one side or both sides of the light guide plate.

In an embodiment, a light collecting sheet may be provided on the front surface of the light guide plate.

The light collecting sheet may have a stripe pattern and may be in a vertical or horizontal direction with the second stripe pattern of the light guide plate. In addition, the light collecting sheet may have a prism, an ellipse, a circle, a trapezoid, an inverse groove, a lenticular, an R-prism, or a combination thereof.

The light collecting sheet may have a prism cross section. At this time, the hypotenuse angle may be 25 to 50 °.

According to the present invention, two or more stripe patterns crossing each other at right angles are formed on the rear surface of the light guide plate so that hot spots of LEDs can be effectively removed, and brightness can be improved compared to the printed light guide plate. It is easy to manufacture by pattern molding and can reduce manufacturing cost, improve moire phenomenon and appearance, and have excellent light uniformity and visibility. Therefore, it is possible to configure the backlight unit by omitting all or any one of the diffusion film and the prism film used in the existing backlight unit.

The configuration of the present invention will be apparent with reference to the accompanying drawings. In the drawings, the sizes of components constituting the invention are exaggerated for clarity and are not limited thereto.

1 is a perspective view illustrating a light guide plate for a liquid crystal display backlight unit according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the light guide plate 100 for a liquid crystal display backlight unit according to an exemplary embodiment of the present invention has a side surface 10c through which light is incident and a front surface 10b connected to the side surface to emit the light. And a back surface 10a that reflects light, and two or more stripe patterns 1 and 2 intersecting at right angles to each other are formed on the back surface.

The light guide plate 100 for the liquid crystal display backlight unit of the present invention is generally made of a transparent acrylic material having high strength, less cracking or deformation, and light weight and high visible light transmittance.

In an exemplary embodiment, the light guide plate 100 includes a light guide plate body 10, a first stripe pattern 1, and a second stripe pattern 2.

The light guide plate body 10 has a side surface 10c through which light is incident, a front surface 10b connected to the side surface 10c, and facing a panel (not shown) of the liquid crystal display device, and a side surface 10c. ) And a rear surface 10a facing the front surface 10b. The original dictionary meaning of the side surface 10c means the side surface of the object, but in the present invention, it is defined as the surface from which light is incident from the light source 20.

A first stripe pattern 1 perpendicular to the light source and a second stripe pattern 2 parallel to the light source are formed on the rear surface 10a, and the first stripe pattern and the second stripe pattern are the same. They intersect at right angles to each other on a plane. The term 'vertical to the light source' refers to a direction perpendicular to the direction in which the light sources are arranged, and the term 'parallel to the light source' refers to a direction parallel to the direction in which the light sources are arranged.

The first stripe pattern 1 in a direction perpendicular to the direction in which the light sources are arranged serves to remove LED hot spots by uniformly spreading the light from the light source. In an embodiment, the first stripe pattern 1 has a curved shape in which the cross-sectional shape includes a circle, an ellipse, an R-prism, or a combination thereof in order to uniformly spread the light from the light source. 2 is a specific example showing a cross section in the light source direction of the light guide plate of the present invention. As illustrated, the first stripe pattern 1 has a curved cross section, and a gap GAP may be formed between the patterns.

In one embodiment, the first stripe pattern has a higher pitch: height ratio, and preferably, may be 0.2 to 0.7. Within this range, the luminance is improved and the LED hot spot is also removed.

In addition, the first stripe pattern may have a gap (GAP) between the patterns of 200 μm or less, preferably 5 to 150 μm. The light can be emitted from the light guide plate while removing the LED hot spot within the above range.

As the height of the first stripe pattern 1 increases, the light emitted from the light source is uniformly spread, so that the LED hot spot can be effectively removed. However, if the height of the circular pattern is high, it is difficult to form the pattern, which causes a limitation in mass production of the light guide plate, and there is a problem in that the luminance is lowered. Therefore, the LED hot spot should be removed without the luminance decrease. In one embodiment, the height of the first stripe pattern 1 is 1 to 100 µm, preferably 10 to 85 µm, more preferably 30 to 75 µm. LED Hot Spot can be effectively removed within the above range, there is an easy advantage in terms of pattern molding.

The second stripe pattern is a direction parallel to the direction in which the light sources are arranged, and serves to cause the light emitted from the light source to be emitted to the upper surface of the light guide plate.

That is, the light emitted by the light source is incident on the light guide plate of the present invention, is totally reflected, and is refracted by the second stripe pattern in a direction parallel to the direction in which the light sources are arranged, and is then emitted to the outside of the light guide plate.

In embodiments, the second stripe pattern may include a prism, a trapezoid, an inverted groove, an ellipse, a lenticular, or a combination thereof. 3 illustrates various examples of cross-sectional shapes of the second stripe pattern. FIG. 3 (a) shows the prism shape of the cross section of the second stripe pattern, and FIG. 3 (b) shows the shape of the ellipse cross section of the second stripe pattern.

In an embodiment, when the cross-section of the second stripe pattern is a prism, the central luminance may be improved since the light emitted is focused as the inclination angle of the prism pattern becomes smaller. However, when the rain variance is too small, the amount of light cannot be emitted so that the amount of light is lowered. Therefore, it is necessary to optimize the rain variance so that the amount of light is minimized and minimized. In a preferred embodiment of the present invention the hypotenuse angle may be 5 to 30 °, preferably 10 to 30 °. It has an excellent central luminance within the above range, it is possible to minimize the amount of light loss.

In an exemplary embodiment, the second stripe pattern may have a variable pitch structure in which the interval of the pattern is changed according to the position from the light source so that the light is uniformly emitted to the entire surface of the backlight. 3C to 3E illustrate various embodiments of the variable pitch structure of the second stripe pattern.

In one embodiment, as shown in FIG. 3 (c), the second stripe pattern may have a structure in which the distance between the patterns becomes narrower as it moves away from the light source. In such a structure, light may be more uniformly emitted to the front surface of the backlight.

In another embodiment, as shown in FIG. 3 (d), the second stripe pattern may have a structure in which an oblique angle α increases as the distance from the light source increases. In such a structure, the light may be uniformly emitted to the entire surface of the backlight while the pitch of the stripe pattern is constant.

In another embodiment, as shown in FIG. 3E, the second stripe pattern may have a structure in which the distance between the patterns becomes narrower and the hypotenuse angle α increases as the distance from the light source increases. In such a structure, the pitch and the angle of inclination (α) of the stripe pattern are adjusted so that the light is uniformly emitted to the front surface of the backlight while condensing the light to improve brightness.

In another embodiment, as shown in FIG. 3 (f), the cross-section of the second stripe pattern may have an inverse groove shape having a predetermined radius of curvature on the side surface. In an embodiment, the side surface may have a positive radius of curvature as shown in the left side of FIG. 3 (f), and the side surface may have a negative radius of curvature as shown in the right side of FIG. Alternatively, although not shown, one side may have a positive radius of curvature and the other side may have a negative radius of curvature.

In an embodiment, the height of the first stripe pattern 1 may be greater than the height of the second stripe pattern 2. In another embodiment, the height of the first stripe pattern 1 may be smaller than the height of the second stripe pattern 2. In another embodiment, the height of the first stripe pattern 1 and the height of the second stripe pattern 2 may be the same.

In one embodiment, the light guide plate may have a plurality of beads dispersed therein. 4 is a cross-sectional view of the light guide plate to which the beads 11 are added. When the beads are added in this way, the moire phenomenon and the appearance may be improved. The amount of beads can be determined according to the purpose of the user. By adjusting the amount of the bead added, it is possible to adjust the brightness and the uniformity of the amount of light on the front surface of the light guide plate. In one embodiment of the present invention, the beads may be included in 0 to 0.1% by weight of the total weight of the light guide plate. It is effective to remove the LED hot spot of the light guide plate within the above range, and is also advantageous to improve the external space and moire removal of the light guide plate. It also improves the brightness and uniformity of the amount of light on the front surface of the light guide plate.

Another aspect of the present invention relates to a liquid crystal display backlight unit including the light guide plate. In an embodiment, the liquid crystal display backlight unit may include the light guide plate; And a light source disposed on one side or both sides of the light guide plate.

In an embodiment, a light collecting sheet may be provided on the front surface of the light guide plate. 5 is an exploded perspective view of a liquid crystal display backlight unit provided with a light collecting sheet 200 on a front surface of the light guide plate 100.

The light collecting sheet 200 may have a stripe pattern. In an embodiment, the stripe pattern of the light collecting sheet 200 may have a vertical or horizontal direction with the second stripe pattern of the light guide plate. In addition, the light collecting sheet may have a prism, an ellipse, a circular shape, a trapezoidal shape, an inverse groove shape having a predetermined radius of curvature, a lenticular shape, an R-prism, or a combination thereof.

In one embodiment, the light collecting sheet may have a prism cross section. The hypotenuse angle may be 15 to 50 °, preferably 25 to 45 °. Within the above range, the light emitted from the light guide plate may be focused in the vertical direction, and the light reflected from the upper DBEF sheet may be focused to re-reflect light reflected from the reflective sheet.

The light collecting sheet may be manufactured in a UV resin pattern molding structure on a PET film, and may be manufactured by an extrusion method using PS and PC resins. The thickness is 100 to 500 mu m, preferably 200 to 500 mu m.

In another embodiment, the liquid crystal display backlight unit of the present invention may further include a brightness enhancement film 300 on the light collecting sheet 200. FIG. 6A is an exploded perspective view of a liquid crystal display backlight unit provided with a brightness enhancing film 300 according to an embodiment of the present invention. The brightness enhancement film 300 is a reflective polarization prism sheet having a multi-layered structure that emits light by condensing and polarizing light, and a dual brightness enhancement film (DBEF ™, manufacturer 3M) may be preferably applied.

In another embodiment, as shown in FIG. 6 (b), the liquid crystal display backlight unit of the present invention may further include a prism sheet 210 and a brightness enhancement film 300 on the light collecting sheet 200. The prism sheet has a triangular prism pattern (not shown) for condensing and emitting light and having a constant arrangement. The hypotenuse angle of the prism pattern may be 40 to 50 °. In an embodiment, a brightness enhancement film (Brightness Enhancement Film-III, BEF-III ™, manufacturer 3M) may be used as the prism sheet.

In another embodiment, as shown in FIG. 6 (c), the liquid crystal display backlight unit of the present invention has a structure in which a prism sheet 210 and a brightness enhancement film 300 are stacked on the light guide plate 100 of the present invention. It can have

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the embodiments make the disclosure of the present invention complete, and those skilled in the art to which the present invention pertains. It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims.

Example 1

The cross section of the first stripe pattern of the patterned light guide plate was circular (pitch 200um, height 50um, gap between lenses 100um), the second stripe pattern was a prism pattern, and the hypotenuse angle was 11 °. The material was PMMA and thickness was 4 mm. A light collecting sheet having a prism pattern having a commutation angle of 30 degrees was positioned on the pattern light guide plate, and the pattern of the light collecting sheet was horizontal to the second stripe pattern. A prism film (MAS, Cheil Industries) and a DBEF film (3M) were attached to the top of the light collecting sheet to prepare a backlight unit.

Example 2

The same procedure as in Example 1 was performed except that the hypotenuse angle of the prism pattern of the light collecting sheet was 32 degrees.

Example 3

The same procedure as in Example 1 was performed except that the hypotenuse angle of the prism pattern of the light collecting sheet was 34 degrees.

Comparative Example 1

A printed light guide plate (material PMMA, thickness 4mm)), a diffusion film (PTD737, Shinhwa), a prism film (MAS, Cheil Industries), and a DBEF film (3M) were sequentially stacked and compared.

Comparative Example 2

The same process as in Example 3 was performed except that the first stripe pattern was not formed.

Sheet structure Pattern LGP Pattern Condensing Sheet Second stripe pattern First stripe pattern Prism angle of prism Example 1 The hypotenuse angle: 11 degrees Pitch 200um, Height 50um, Gap 100um between Lenses 30 degrees Example 2 The hypotenuse angle: 11 degrees Pitch 200um, Height 50um, Gap 100um between Lenses 32 degrees Example 3 The hypotenuse angle: 11 degrees Pitch 200um, Height 50um, Gap 100um between Lenses 34 degrees Comparative Example 1 Printing Light Guide Plate + Diffusion Film + Prism Film Comparative Example 2 The hypotenuse angle: 11 degrees - 34 degrees

Relative luminance and viewing angle distribution photographs (simulation data, LightTools) for Examples 1 to 3 and Comparative Examples 1 to 2 are shown in FIG. 7. As shown in FIG. 7, in Examples 1 to 3, the luminance is improved by 30% or more compared to Comparative Example 1. In addition, it can be seen that the central luminance increases and the vertical viewing angle and the left and right viewing angles decrease because the condensation angle of the prism pattern of the light collecting sheet increases. Therefore, the viewing angle and brightness can be adjusted by adjusting the pattern of the light guide plate and the pattern of the light collecting sheet, and it can be confirmed that the center brightness can be optimized while satisfying the viewing angle according to the user's purpose.

Example 3 and Comparative Example 2 were simulated using LightTools, and the LED hot spot measurement results are shown in FIG. 8. As shown in FIG. 8, in Comparative Example 2, since the light emitted from the LED does not spread uniformly because the first stripe pattern does not exist, the luminance is increased at the LED position, which means that the LED hot spot is large. (LED Hot Spot is visible). In the case of Example 3, it can be seen that the light emitted from the LED is uniformly spread to remove the LED Hot Spot.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention belongs may have the technical idea of the present invention. However, it will be understood that other specific forms may be practiced without changing the essential features. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

1 is a perspective view illustrating a light guide plate for a liquid crystal display backlight unit according to an exemplary embodiment of the present invention.

Figure 2 is one embodiment showing a cross section of the first stripe pattern of the present invention.

3 (a) to 3 (b) show various cross-sectional shapes of the second stripe of the present invention, and FIGS. 3 (c) to 3 (e) show various embodiments of the variable pitch structure of the second stripe pattern. f) shows a shape in which the side surface of the pattern cross section has an inverse groove shape having a predetermined radius of curvature.

4 is a cross-sectional view of the light guide plate to which the beads of the present invention are added.

5 is an exploded perspective view of a liquid crystal display backlight unit having a light collecting sheet on a front surface of the light guide plate.

6 (a) to 6 (c) are other specific examples of the liquid crystal display backlight unit of the present invention.

7 is a photograph showing relative luminance and viewing angle distribution for Examples 1 to 3 and Comparative Examples 1 to 2. FIG.

8 is a graph showing the degree of LED Hot Spot for Example 3 and Comparative Example 2.

<Explanation of symbols for the main parts of the drawings>

1: first stripe pattern 2: second stripe pattern

10: light guide plate body 20: light source

100: light guide plate 200: light collecting sheet

300: brightness enhancement film

Claims (19)

2. A light guide plate for a liquid crystal display device comprising a side on which light is incident, a front surface connected to the side to emit light, and a back surface to reflect light, wherein the back surface crosses at right angles to each other. A light guide plate for a backlight unit of a liquid crystal display device, characterized in that more than one stripe pattern is formed. The light emitting device of claim 1, wherein a first stripe pattern in a direction perpendicular to the light source and a second stripe pattern in a direction parallel to the light source are formed on the rear surface, and the first stripe pattern and the second stripe pattern are disposed on the same plane. A light guide plate for a liquid crystal display backlight unit, characterized by crossing at right angles. The light guide plate of claim 2, wherein the first stripe pattern has a curved shape including a cross section, an ellipse, an R-prism, or a combination thereof. 4. The light guide plate of claim 3, wherein the first stripe pattern has a pitch: height ratio of 0.7 or less. The light guide plate of claim 4, wherein a gap (GAP) is formed between the patterns of the first stripe pattern. The light guide plate of claim 5, wherein the first stripe pattern has a gap (GAP) of 200 μm or less. The light guide plate of claim 2, wherein the second stripe pattern comprises a prism, a trapezoid, an inverted groove, an ellipse, a lenticular, or a combination thereof. The light guide plate according to claim 7, wherein the commutation angle is 5 to 30 degrees when the cross section of the second stripe pattern is a prism. The light guide plate of claim 7, wherein the second stripe pattern has a variable pitch structure in which a distance between the patterns becomes narrower as the second stripe pattern moves away from the light source. The light guide plate of claim 7, wherein the second stripe pattern has a structure in which the inclination angle increases with distance from the light source. The light guide plate of claim 7, wherein the second stripe pattern has a structure in which the distance between the patterns decreases as the distance from the light source increases, and the hypotenuse angle increases. The light guide plate of claim 1, wherein the height of the first stripe pattern is greater than the height of the second stripe pattern. The light guide plate of claim 12, wherein a plurality of beads are dispersed therein. The light guide plate of claim 13, wherein the bead is included in an amount of 0 to 0.1 wt% based on the total weight of the light guide plate. The light guide plate of any one of Claims 1-14; And A light source disposed on one side or both sides of the light guide plate; Liquid crystal display backlight unit comprising a. The liquid crystal display backlight unit of claim 15, wherein a light collecting sheet is provided on the entire surface of the light guide plate. The liquid crystal display backlight unit of claim 16, wherein the light collecting sheet has a stripe pattern and is perpendicular to the second stripe pattern of the light guide plate. 18. The backlight unit of claim 17, wherein the light collecting sheet has a prism, an ellipse, a circle, a trapezoid, an inverse groove, a lenticular, an R-prism, or a combination thereof. 19. The liquid crystal display backlight unit of claim 18, wherein the light collecting sheet has a prism cross section and has a hypotenuse angle of 25 to 50 degrees.

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