KR101167310B1 - Prism sheet and the backlight unit using it - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a prism sheet and a backlight unit using the same.

According to the present invention, the viewing angle characteristic is improved by making the cross section of the outer pattern of the prism sheet in the streamlined shape and making the cross section of the central pattern the triangle in the backlight unit.

Prism Sheet, Backlight Unit, Uneven Pattern

Description

Prism sheet and the backlight unit using it}

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

2 is a graph showing viewing angle characteristics of a liquid crystal panel according to a backlight unit using a prism sheet having a triangular cross-sectional shape.

3 is a block diagram showing a configuration of a backlight unit according to the present invention.

4A and 4B are perspective and cross-sectional views of the prism sheet according to the present invention.

Description of the Related Art [0002]

111: first pattern

112: second pattern

140: Prism Sheet

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display, and more particularly, to a prism sheet and a backlight unit using the same.

In general, a liquid crystal display (hereinafter referred to as an LCD) includes a plurality of liquid crystal cells arranged in a matrix and a plurality of control switches for switching a video signal to be supplied to each of the liquid crystal cells. The transmittance of the light beam supplied from the backlight unit is controlled by the liquid crystal panel configured to display a desired image on the screen.

On the other hand, in order to enable the display in such a liquid crystal display device, light must be sufficiently considered. This is because the liquid crystal does not generate light by itself, but is a light receiving element that only serves to adjust the transmittance of light supplied after being generated from the outside.

At this time, the display characteristics of the liquid crystal display are changed according to the light supplied to the liquid crystal. In other words, when light with a very uniform brightness is supplied to the liquid crystal display device, the display characteristics are very good, whereas when light with a non-uniform brightness is supplied to the liquid crystal display device, the display characteristics are very poor. For this reason, light having a very uniform brightness should be used in the liquid crystal display.

However, in general, it is very difficult to implement a light having a uniform luminance (hereinafter, referred to as a 'plane light source') within a constant area.

1 is a schematic diagram illustrating a configuration of a general backlight unit.

In a general liquid crystal display device, a lamp 10 having a line light source distribution is mainly used as shown in FIG. 1.

At this time, while the lamp 10 is easy to implement, there is a disadvantage that the luminance deviation is very large according to the distance from the light source. That is, it means that it is difficult to form a light having a uniform brightness with only the lamp 10.

For this reason, in the liquid crystal display device 100, a light distribution changing device called the light guide plate 20 is used as shown in FIG.

Specifically, the light guide plate 20 receives the light having the linear light source distribution incident from the lamp 10 and changes the surface light source distribution.

At this time, after the line light source distribution is changed to the surface light source distribution in the light guide plate 20, the emitted light is perpendicular to the light exit surface of the light guide plate 20 according to the law of refraction, that is, based on the surface of the light guide plate 20. As shown in Fig. 1, the light exits at a great inclination angle of 75 ° to 83 ° with respect to the vertical. This phenomenon occurs because the refractive index of the light guide plate 20 is 1.49 and the refractive index of air is 1, for example.

In this way, since the light emitted from the light guide plate 20 is emitted in a state inclined with respect to the direction perpendicular to the surface of the light guide plate 20, the luminance at the front viewing angle is greatly reduced. That is, the brightness of the displayed image is very low at the front viewing angle. This, in turn, means that the display cannot be performed normally.

Therefore, the light emitted from the light guide plate in such a state as to be greatly inclined as described above is sequentially spread on the upper surface of the light guide plate 20 as shown in FIG. 1, the first prism sheet 43, and the second prism. It spreads by the prism sheet 40 comprised of the sheet | seat 46, etc., and changes it to a front direction.

The diffusion sheet 30, the first prism sheet 43, and the second prism sheet 46 are all inclined at an angle of 75 ° to 83 ° with respect to the front surface of the light guide plate 20. Change it to incense.

The cross section of the first prism sheet and the second prism sheet has a triangular mountain shape.

Herein, reference numeral 15 denotes a reflecting plate, 50 denotes a protective sheet, and reference numeral 60 denotes a liquid crystal display panel which performs display by controlling liquid crystal.

2 is a graph showing viewing angle characteristics of a liquid crystal panel according to a backlight unit using a prism sheet having a triangular cross-sectional shape.

Referring to the graph of FIG. 2, 0 ° in the X axis is defined as the front viewing angle, and the front viewing angle is lowered toward the X axis direction.

First, the graph indicated by reference numeral a is luminance for each viewing angle of light emitted from the light guide plate 20. The graph shown by reference numeral b is luminance for each viewing angle of light passing through the light guide plate 20 to the diffusion sheet 30.

Lastly, the graph indicated by reference numeral c is luminance for each viewing angle of light passing through the light guide plate 20, the diffusion sheet 30, and the first and second prism sheets 50 and 60.

At this time, referring to the graph a, in the case of the light passing through the light guide plate 20, the luminance at the front viewing angle was greatly decreased, and the luminance at the viewing angle of 70 ° to 80 ° was the highest.

In this way, the light having weak luminance at the front viewing angle while passing through the light guide plate 20 passes through the diffusion sheet 30, and the luminance distribution that is directed to either side is uniformly changed as shown in graph b. Subsequently, the light passing through the first and second prism sheets 43 and 46 has the highest luminance of the front viewing angle as shown in graph c.

As such, the light whose direction is corrected while passing through the diffusion sheet 30 and the first and second prism sheets 43 and 46 is displayed by the liquid crystal display panel assembly 60 to display a desired image. Will perform.

As described above, the backlight unit using the prism sheet having a triangular cross-sectional shape maximizes the condensing effect and increases the front brightness, but the half-angle is relatively narrowed by the condensing effect and the brightness at the specific viewing angle is sharply reduced. There is a problem in that the viewing angle characteristic deterioration such as a cut-off phenomenon occurs.

An object of the present invention is to provide a prism sheet and a backlight unit using the same in which the cross section of the outer pattern of the prism sheet is streamlined and the cross section of the central pattern is triangular in the backlight unit.

In order to achieve the above object, the present invention provides a prism sheet in which an uneven pattern is formed at an outer portion and a center, and the outer uneven pattern has a streamlined cross-sectional structure, and the uneven pattern at the center has a triangular cross-sectional structure. Characterized in having a.

In addition, in order to achieve the above object, a backlight unit according to the present invention comprises a light guide plate configured to irradiate uniform light on the rear surface of a liquid crystal display panel; A reflector reflecting light from the lower end of the light guide plate to the liquid crystal display panel; A light source configured at one side of the light guide plate to emit light; A diffusion plate disposed above the light guide plate to diffuse light; The first and second prism sheets having a concave-convex pattern having a streamlined cross section in the outer portion and a concave-convex pattern having a triangular cross section in the central portion thereof are formed at the outer side of the diffusion plate.

The first and second prism sheets are arranged to be perpendicular to each other.

The uneven pattern is characterized in that formed long from one side to the other.

The streamlined cross-sectional structure is a circular, oval, characterized in that the cross-sectional structure of the rounded triangle vertices.

The outer portion is characterized in that less than 1/4 point of the full width from the edge.

Hereinafter, a backlight unit according to the present invention will be described in detail with reference to the accompanying drawings.

3 is a block diagram showing a configuration of a backlight unit according to the present invention.

As shown in FIG. 3, the backlight unit 130 according to the present invention serves to supply light to the liquid crystal display panel 160.

Although not shown, the liquid crystal display panel 160 includes upper and lower polarizers respectively disposed on upper and lower portions thereof, and the liquid crystal display panel 160 includes a TFT substrate, a color filter substrate, and the TFT substrate on which electrodes are formed. And a liquid crystal layer injected between the color filter substrates.

In addition, the backlight unit 130 is easy to implement, has a long life, and a lamp 110 having a line light source distribution having various advantages such as generating white light, or an LED having a point light source distribution is mainly used.

In addition, the backlight unit 130 includes a light guide plate 120 which is a light distribution changing device so that light generated from the lamp or LED which is the light source has a uniform brightness.

Specifically, the light guide plate 120 serves to change the light having the line light source distribution or the point light source distribution incident from the lamp 110 to the surface light source distribution.

At this time, after the line light source distribution is changed to the surface light source distribution in the light guide plate 120, the emitted light is perpendicular to the surface of the light guide plate 120, that is, the surface of the light guide plate 120 according to the law of refraction. Emitted with a great inclination at an angle of 75 ° to 83 °. This phenomenon occurs because the refractive index of the light guide plate 120 is 1.49 and the refractive index of air is 1, for example.

The light emitted from the light guide plate in a highly inclined state as described above is arranged on the upper surface of the light guide plate 120 in order of a prism sheet including a diffusion sheet 125, a first prism sheet 143, and a second prism sheet 146. 140) and spread in the front direction.

The diffusion sheet 125, the first prism sheet 143, and the second prism sheet 146 all receive light inclined at an angle of 75 ° to 83 ° with respect to the front surface of the light guide plate 120. To.

In this case, one surface of the first prism sheet 143 and the second prism sheet 146 is formed of irregularities, and has first and second patterns 111 and 112.

The cross-sectional shape of the first pattern 111 has a triangular mountain shape, and the cross-sectional shape of the second pattern 112 has a streamlined shape.

In this case, the first pattern 111 is disposed at the central portion A of the first and second prism sheets 143 and 146, and the second pattern 112 is the first and second prism sheets 143 and 146. It is preferable to arrange | position to the outer periphery (B) of ().

The first pattern 111 collects light to increase front brightness, and the second pattern 112 collects and diffuses light to increase side brightness, which is a function of the liquid crystal display panel 160. It serves to improve the overall viewing angle characteristics.

On the other hand, the outer portion (B) of the prism sheet 140 is characterized in that it refers to the point of m / 4 or less at the edge with respect to the overall width (m).

The first prism sheet 143 and the second prism sheet 146 are formed such that their arrangement directions are perpendicular to each other.

4A is a perspective view of a prism sheet according to the present invention, and FIG. 4B is a cross-sectional view taken along the line II ′ of FIG. 4A.

As shown in FIGS. 4A and 4B, the prism sheet 140 according to the present invention has first and second patterns 111 and 112 having irregularities on one surface thereof.

The first pattern 111 may be disposed at the central portion A of the prism sheet 140, and the second pattern 112 may be disposed at the outer portion B of the prism sheet 140.

The first pattern 111 has a triangular cross-sectional shape and is elongated from one side to the other, and the second pattern 112 has a streamlined cross-sectional shape and is elongated from one side to the other.

In this case, the second pattern 112 may be formed in various shapes such as a cross-section, a circle, an oval, a triangle having a vertex streamlined, and the like.

The first pattern 111 condenses light to increase front luminance, and the second pattern 112 condenses and diffuses light to increase side luminance, which is the overall viewing angle of the liquid crystal display panel. It serves to improve the luminance characteristic of the.

On the other hand, the outer portion (B) of the prism sheet 140 is characterized in that it refers to the point of m / 4 or less at the edge with respect to the overall width (m).

The prism sheet 140 having the first and second patterns 111 and 112 as described above is formed of a first prism sheet and a second prism sheet, and the first prism sheet and the second prism sheet are orthogonal to each other in an arrangement direction. Is arranged to.

Therefore, since the streamlined second pattern 112 is formed at a position where the first prism sheet and the second prism sheet intersect with each other, the streamlined second pattern 112 diffuses and condenses light on four outer surfaces of the liquid crystal display panel, thereby improving luminance. have.

Although the present invention has been described with reference to the embodiments illustrated in the drawings, this is merely exemplary, and it will be understood by those skilled in the art that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

The present invention has the effect of uniformly improving the luminance even in the front and side of the liquid crystal display panel using a prism sheet having a triangular and streamlined cross-sectional pattern.

Claims (9)

In the prism sheet in which the irregularities in the center region and the outer region formed on both sides of the center region are different from each other, The outer region concave-convex pattern has a streamlined cross-sectional structure, the concave-convex pattern in the central region has a triangular cross-sectional structure, The boundary between the outer region and the center region is the same distance from the edge of the prism sheet. The method of claim 1, The uneven pattern is formed from one side to the other long elongated prism sheet. The method of claim 1, The streamlined cross-sectional structure is a prism sheet, characterized in that the cross-sectional structure of a round, oval, apex rounded triangle. The method of claim 1, The outer region is a prism sheet, characterized in that less than 1/4 point of the full width from the edge. A light guide plate configured on a rear surface of the liquid crystal display panel to irradiate uniform light; A reflector reflecting light from the lower end of the light guide plate to the liquid crystal display panel; A light source configured at one side of the light guide plate to emit light; A diffusion plate disposed above the light guide plate to diffuse light; And first and second prism sheets having a concave-convex pattern having a triangular cross section in a central region at an upper side of the diffusion plate, and a concave-convex pattern having a streamlined cross section in a peripheral region formed at both sides of the central region. And a boundary between the outer region and the central region is the same distance from the edge. 6. The method of claim 5, And the first and second prism sheets are orthogonal to each other. 6. The method of claim 5, The uneven pattern is a backlight unit, characterized in that formed long from one side to the other. 6. The method of claim 5, The streamlined cross-sectional structure is a backlight unit, characterized in that the cross-sectional structure of a round, oval, apex rounded triangle. 6. The method of claim 5, The outer area is a backlight unit, characterized in that less than 1/4 point of the full width from the edge.

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