KR20110071993A - Light guiding panel and back light unit using the same - Google Patents

Abstract

PURPOSE: A light guiding panel and a backlight unit using the same are provided to improve the displaying quality of a liquid crystal display device by improving the uniformity and the brightness of light applied to a liquid crystal panel. CONSTITUTION: A body includes a light incident side. A first prism pattern(120) is formed on the upper side of the body in order to collect light from the body and emit the collected light to the outside. A second prism pattern(110) is formed in a dot shape at the lower side of the body. The second prism pattern includes sub-prisms. The cross section of the sub-prisms includes a pre-set shape. The first prism pattern and the second prism pattern are orthogonally formed.

Description

Light guiding panel and back light unit using the same}

The present invention relates to a light guide plate and a backlight unit using the same, and more particularly, to a light guide plate of a liquid crystal display device and a backlight unit using the same, which improves the brightness, uniformity, condensing property, and visibility of light, and also reduces manufacturing cost of the liquid crystal display device. It is about.

Recently, various types of flat panel display devices have been developed and applied to portable information devices and IT products. Among the flat panel display devices, liquid crystal display devices (LCDs) have advantages such as light weight, thinness, and low power consumption. As a result, its application range is widening.

The liquid crystal display device displays a desired image on the screen of the liquid crystal panel by adjusting the light transmittance of the liquid crystal cell according to an image signal applied to control switches (TFTs) arranged in a matrix form. Here, the liquid crystal panel displaying an image receives light through the backlight unit because it does not emit light. The backlight unit has an edge type in which the light source is located in the side direction of the liquid crystal panel according to the arrangement of the light source. edge light type) and a direct light type in which a light source is located on the back of the liquid crystal panel.

1 is a perspective view illustrating an edge type backlight unit according to the prior art, and FIG. 2 is a cross-sectional view of the edge type backlight unit according to the prior art, and is a cross-sectional view taken along line AA ′ of FIG. 1.

1 and 2, the edge type backlight unit according to the related art includes a light source 10, a light guide plate 20, upper and lower diffusion sheets 30 and 60, and upper and lower prism sheets 40 and 50. It includes.

The light source 10 generates light irradiated onto a liquid crystal panel (not shown). In general, a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED) that generates white light with low power consumption is generated. Emitting Diode) is used.

The light guiding plate 20 is formed on the side of the light source 10, and serves to convert the linear or pointed light generated by the light source 10 and incident through the side into surface light to be emitted to the front of the liquid crystal panel. That is, the light incident on the side surface of the light guide plate 20 is changed in the traveling angle inside the light guide plate 20 so that the light is emitted toward the liquid crystal panel.

A lower diffuser sheet 30 is formed on the upper surface of the light guide plate 20 and serves to uniform light emitted through the light guide plate 20. The upper and lower prism sheets 40 and 50 diffuse through the lower diffusion sheet 30 to refract and collect light having a reduced brightness, thereby increasing the brightness of the light. The upper diffusion sheet 60 is located on the upper surface of the upper prism sheet 50 to prevent scratches of the upper prism sheet 50, and emits light emitted from the prism sheets 40 and 50 formed in two layers in the vertical and horizontal directions. It evenly outputs to prevent moire effects that occur when the upper and lower prism sheets 40 and 50 are applied.

The liquid crystal panel is positioned above the backlight unit, and the liquid crystal panel controls the transmittance of light emitted from the backlight unit to implement an image. There are many things to consider in order to improve the quality of the image displayed on the liquid crystal panel, but representative ones are uniformity and luminance of light supplied to the liquid crystal panel. That is, high brightness and uniform light are supplied to the liquid crystal panel through the backlight unit to express a high quality image.

The edge type backlight unit according to the related art having the above-described configuration converts linear or pointed light into surface light through the light guide plate 20 and emits the light, but as shown in FIG. 3, the luminance of the light emitted in the horizontal (H) direction is emitted. It cannot be secured enough. In particular, the luminance of the light emitted in the vertical (V) direction is biased to one side has a disadvantage of low uniformity.

In order to solve this problem, the diffusion sheets 30 and 60 and the prism sheets 40 and 50 are disposed on the light guide plate 20 to diffuse and condense the light emitted from the light guide plate 20 to uniform light. The liquid crystal panel is irradiated. However, since the light emitted from the light guide plate 20 passes through the plurality of diffusion sheets 30 and 60 and the plurality of prism sheets 40 and 50, the luminance of the light irradiated onto the liquid crystal panel is reduced.

In addition, the thickness of the backlight unit is increased by disposing the plurality of diffusion sheets 30 and 60 and the plurality of prism sheets 40 and 50 on the light guide plate 20. In particular, the prism sheet and the diffusion sheet occupy about 30% of the manufacturing cost of the backlight unit constituting the liquid crystal display device. Therefore, as in the prior art, when the backlight unit is configured to include the plurality of diffusion sheets 30 and 60 and the plurality of prism sheets 40 and 50, there is a disadvantage in that a high cost is generated in manufacturing the liquid crystal display device.

An object of the present invention is to provide a light guide plate of a liquid crystal display device and a backlight unit using the same, which can improve the brightness, uniformity, light condensing property, and visibility of light supplied to the liquid crystal panel.

An object of the present invention is to provide a light guide plate of a liquid crystal display device and a backlight unit using the same, which can improve brightness, uniformity, light condensation, and visibility of light without disposing a prism sheet and a diffusion sheet on the light guide plate.

An object of the present invention is to provide a light guide plate capable of reducing the manufacturing cost of an edge type liquid crystal display device and a backlight unit using the same.

The light guide plate according to an embodiment of the present invention for achieving the above object is a body having a side on which light is incident; First prism patterns extending in a direction parallel to a direction in which the light is incident and formed in an upper portion of the body such that a cross section has a predetermined shape; And second prism patterns formed in a lower portion of the body in a dot form from one side to the other side to which the light is incident, each of the second prism patterns including sub-prisms having a predetermined shape in cross section. do.

The second prism patterns of the light guide plate according to the embodiment of the present invention are characterized by including sub-prisms having different densities.

The second prism patterns of the light guide plate according to the exemplary embodiment of the present invention are formed such that the density of the inner sub-prism increases as the light enters the side.

The second prism patterns of the light guide plate according to the embodiment of the present invention are formed such that the density of the inner sub-prism increases from the center portion to the edge.

The sub-prisms of the second prism patterns of the light guide plate according to the embodiment of the present invention are an isosceles triangle, a triangle whose vertex is curved, an isosceles triangle, a trapezoid, a polygon, an ellipse, and one surface is a straight one of the curves. Characterized in that it is formed to have a shape.

In the light guide plate according to the embodiment of the present invention, the sub-prisms of the second prism patterns have a triangular cross section, and vertices of adjacent sub-prisms are formed to have different angles.

According to an exemplary embodiment of the present invention, the uniformity, brightness, and visibility of light supplied to a liquid crystal panel may be improved without applying a prism sheet and a diffusion sheet on the light guide plate.

According to an exemplary embodiment of the present invention, the display quality of the liquid crystal display may be improved by improving the uniformity and brightness of light supplied to the liquid crystal panel.

According to an exemplary embodiment of the present invention, a backlight unit may be configured without applying a prism sheet and a diffusion sheet on a light guide plate, thereby reducing the manufacturing cost of the liquid crystal display.

According to the exemplary embodiment of the present invention, the thickness of the backlight unit may be reduced by configuring the backlight unit without applying the prism sheet and the diffusion sheet on the light guide plate.

Hereinafter, the technical objects and features of the present invention will be apparent from the description of the accompanying drawings and the embodiments. Looking at the present invention in detail.

Prior to the description with reference to the drawings, in order to increase the quality of light supplied to the liquid crystal panel, the light exit angle of the light emitted from the light guide plate should be changed to improve the uniformity, light condensing property, and luminance of the light in front of the liquid crystal panel.

4 is a perspective view illustrating a light guide plate according to an exemplary embodiment of the present invention, and FIG. 5 is a cross-sectional view of a light guide plate according to an exemplary embodiment of the present invention and a line B-B ′ of FIG. 4.

4 and 5, the light guide plate 100 according to the embodiment of the present invention includes a body having an incident surface on which light is incident from a light source; A plurality of lower prism patterns 110 formed in a dot shape at the bottom of the body 100 to reflect light incident on the light guide plate 100 to the upper side of the light guide plate 100; And a plurality of upper prism patterns 120 formed on the upper portion of the body 100 to collect light emitted from the body 100 and to emit the light to the outside.

The light guide plate 100 may be formed of a material such as polycarbonate (PC), polymethymethacrylate (PMMA), zeolite (COP), norbornene resin (ARTON), or the like.

The plurality of lower prism patterns 110 and the plurality of upper prism patterns 120 may be formed in directions perpendicular to each other or may have different directions. Such a plurality of lower prism patterns 110 and a plurality of upper prism patterns 120 will be described in detail with reference to FIGS. 8 to 16 to be described later.

6 is a perspective view illustrating a light guide plate and a backlight unit using the light guide plate according to an exemplary embodiment of the present invention, and FIG. 7 is a cross-sectional view taken along line C-C 'of FIG. 6.

6 and 7, a backlight unit according to an embodiment of the present invention includes a light guide plate 100; A light source 140 disposed at a side of the light guide plate 100 to irradiate light to the light guide plate 100; And a diffusion sheet 130 disposed on the light guide plate 100 to diffuse light emitted from the light guide plate 100 to irradiate the liquid crystal panel.

In addition, the backlight unit according to the embodiment of the present invention may further include a reflective sheet (not shown) disposed on the light guide plate 100 to reflect the light traveling to the back of the light guide plate 100 to reduce the loss of light. Can be.

6 illustrates that the light source 140 is formed only on one side of the light guide plate 100, the light source 140 may be disposed on both sides of the light guide plate 100 so as to face each other, or may be disposed on each side of the light plate 140. have.

As the light source 140, a light emitting diode (LED) having advantages of low power consumption and high life is used, and as another embodiment, a cold cathode fluorescent lamp (CCFL) and an external electrode fluorescent lamp (CFL) are used. External Electrode Fluorescent Lamp (EEFL) may be used.

Hereinafter, the plurality of lower prism patterns 110 and the plurality of upper prism patterns 120 formed on the light guide plate 100 according to the exemplary embodiment of the present invention will be described with reference to FIGS. 8 to 16.

As illustrated in FIG. 8, each of the plurality of upper prism patterns 120 according to an exemplary embodiment may be formed in a straight line shape so as to be parallel with the light emitted from the light source 140 in a horizontal direction.

As illustrated in FIG. 9, each of the plurality of upper prism patterns 120 according to an embodiment of the present disclosure may have the other side from one side from which light is incident from the light source 140 to correspond to a direction parallel to the light emitted from the light source 140. As an example to have a predetermined curvature, it may be arranged to have a shape of 'S' when viewed from above.

Although not shown in the drawing, each of the plurality of upper prism patterns 120 according to another embodiment may be formed in a mixture of straight lines and curves.

Here, the cross section of each of the plurality of upper prism patterns 120 has a predetermined shape, and the adjacent upper prism patterns 120 may be formed without a separation distance or may be spaced apart at regular intervals.

Each of the plurality of upper prism patterns 120 is formed in an intaglio shape, as shown in FIGS. It may be formed in a polygonal or circular shape, or may be formed in an intaglio shape including a first inclined surface in a straight form and a second inclined surface in a curved form.

On the other hand, when the upper prism pattern 120 has a triangular cross section, the vertex angle of the upper prism pattern 120 is preferably formed in the range of 30 ~ 140 °.

In addition, the interval d between the adjacent upper prism patterns 120 is formed to have a range of 0 to 1000 μm, and the height h of the upper prism pattern 120 is formed to have a range of 0 to 500 μm. It is preferable. Here, the distance d between the adjacent upper prism patterns 120 and / or the height h of the upper prism pattern 120 may be formed uniformly over the entire surface of the light guide plate 100. Meanwhile, scattering agents (SiO 2 and TiO 2) that scatter light may be formed on a surface of the upper prism pattern 120.

If the upper prism pattern 120 is not formed, the shape of the lower prism pattern 110 may be irradiated to the liquid crystal panel as it is and may cause a moire phenomenon. In the present invention, by separating the shape of the lower prism pattern 110 formed on the lower side of the light guide plate 100 through the upper prism pattern 120 to prevent the moire phenomenon and improves visibility. In addition, the uniformity, condensing degree, and luminance of light emitted from the light guide plate 100 may be improved.

11 and 12, the lower prism pattern 110 formed on the lower side of the light guide plate 100 may be formed in a dot shape over the entire lower side of the light guide plate 100 from one side to which light is incident.

The light emitted from the light source 140 enters the light guide plate through the incident surface of the light guide plate 100, and then proceeds in a random path within the light guide plate 100, and the emission condition is determined by Chanel's law. If satisfied, the top view of the light guide plate 100 is emitted to the rear.

The lower prism pattern 110 changes the traveling angle of the light incident on the light guide plate 100 to vertically emit the light incident on the liquid crystal panel direction, that is, the light guide plate 100. In addition, the light emitted to the rear surface of the light guide plate 100 is reflected by the lower prism pattern 110 formed in a dot form on the lower side of the light guide plate 100 to the upper side of the light guide plate 100 to improve the brightness and uniformity of the light emitted. do.

Here, each of the lower prism patterns 110 is formed to include the sub-prisms 112, and the sub-prisms 112 are formed in a direction perpendicular to the light emitted from the light source (orthogonal to the upper prism pattern). In this case, the sub-prisms 112 may be arranged in a straight line or a curved shape, as shown in FIG. 12, as shown in FIG. 11.

Although not shown in the drawings, in another embodiment of the present disclosure, the lower prism pattern 110 may be formed in a mixture of a straight line and a curved array.

The lower prism pattern 110 is formed by varying the size and density of the sub-prism 112 included therein as the light emitted from the light guide plate 100 increases away from the light source in order to improve uniformity, condensing property, and brightness. can do.

For example, as shown in FIG. 13, the lower prism pattern 110 may be formed in a form in which the density of the sub-prism 112 included therein increases as the distance from the light source increases.

Meanwhile, in another embodiment of the present invention, the lower prism pattern 110 may be formed in a shape in which size and density increase from the center portion to the edge.

When viewed from above, the lower prism pattern 110 may be formed in the shape of a circle, an ellipse, a rectangle, a rhombus, a trapezoid, or the like, as shown in FIG. 14. Here, the sub-prism 112 inside the lower prism pattern 110 may be formed not only intaglio but also embossed. In addition, the lower prism pattern 110 may include scattering agents (SiO 2 and TiO 2) that scatter light.

Although not illustrated, in another embodiment of the present invention, the size of the prism pattern 110 is the same, and as the distance from the light source increases, the number of sub-prisms 112 included in the prism pattern 110 may increase.

15A to 15H, the sub-prisms 112 inside the lower prism pattern 110 may have an isosceles triangle, a vertex triangle, an isosceles triangle, a trapezoid, a polygon, an ellipse, and one side of a straight line. The surface may be formed in a curved shape, both surfaces curved. Here, in the case where the sub-prism inside the lower prism pattern 110 has a triangular shape, the vertex angle may be formed at 30 to 140 °.

Referring to FIG. 16, the lower prism pattern 110 may be formed to include a plurality of sub-prisms 112 having different shapes in cross section. As an example, the lower prism pattern 110 may be formed to include a plurality of sub-prisms 112 having an isosceles triangle, a triangle having a vertex curved shape, and a trapezoidal shape.

Here, when the cross section of the sub-prism 112 in the lower prism pattern 110 has a triangular shape, the vertex angle of the sub-prism 112 may be formed in the range of 30 ~ 140 °, the adjacent sub-prism 112 The vertex angles of) may be formed such that the angles are different from each other. That is, vertices of adjacent sub-prisms 112 in the lower prism pattern 110 may be formed to have different angles of θ ₁ , θ ₂ , and θ ₃ .

In addition, when the sub-prisms 112 have a triangular shape in which the vertices are curved, the curvatures of the vertices of adjacent sub-prisms may be formed differently.

As described above, when the vertices or vertices of vertices of adjacent sub-prisms 112 in the lower prism pattern 110 are formed differently, the light guide plate 100 may be formed through the sub-prisms 112 having different angles or curvatures. The angle of the emitted light is adjusted to prevent the emitted light from being concentrated on one side. Therefore, the light guide plate 100 according to the embodiment of the present invention forms different vertices or curvatures of adjacent sub-prisms 112 in the lower prism pattern 110, thereby improving the uniformity of the light emitted from the light guide plate 100. Can be improved.

As described above, the upper prism pattern 120 and the lower prism pattern 110 of the light guide plate 100 according to the embodiment of the present invention have an isosceles triangle, an isosceles triangle, a vertex triangle, an isosceles triangle, Trapezoidal, polygonal, elliptical, one side is straight one side may be formed by a rolling method using a roller formed with a curved pattern. In addition, in the form of an intaglio or embossed cross section, an isosceles triangle, a vertex triangle, an isosceles triangle, a trapezoid, a polygon, an oval, and one side is a press press method using a press formed with a curved pattern. Can be formed.

In the description with reference to FIG. 16, the sub-prisms 112 are illustrated and described to be formed at a predetermined distance. However, this is an example, and in another embodiment of the present invention, the sub-prisms 112 are adjacent to each other without being spaced apart from each other. Can be formed.

17 and 18 illustrate profiles of light emitted from the light guide plate 100 according to the exemplary embodiment of the present invention including the lower prism pattern 110 and the upper prism pattern 120 described above.

17 and 18 are compared with FIG. 3, which is a light profile of a light guide plate according to the prior art, the light guide plate according to the prior art has a low luminance of the outgoing light in the horizontal direction and the light emitted in the vertical direction, as shown in FIG. 3. This is biased to one side. Therefore, it can be seen that light is emitted unbalanced in the horizontal and vertical directions, and sufficient luminance cannot be obtained.

Due to such a disadvantage, in the prior art, the light emitted from the light guide plate cannot be directly used as a backlight of the liquid crystal panel, and a plurality of prism sheets and a plurality of diffusion sheets are disposed on the light guide plate to improve the emission angle and uniformity of the light. Since the light is emitted through the optical sheet of the light emitted from the center of the light guide plate has a disadvantage of low brightness.

On the other hand, the light guide plate 100 according to the embodiment of the present invention, as shown in FIG. 17 through the upper prism pattern 120 and the lower prism pattern 110 described above, emits light uniformly across the entire surface of the light guide plate. The light condensing property and the luminance may be improved by allowing the light incident in the horizontal direction to be emitted in the vertical direction.

In particular, it focuses light in the center of the liquid crystal panel, improves visibility and uniformity of light in the horizontal (H) and vertical (V) directions, and emits light of high luminance to provide the quality of light supplied to the liquid crystal panel. Can improve.

Therefore, as in the prior art, it is possible to improve the uniformity, condensing property, and luminance of the light supplied to the liquid crystal panel without applying a plurality of prism sheets and optical sheets on the light guide plate.

In addition, when the backlight unit is configured by applying one diffusion sheet on the light guide plate 100 according to the embodiment of the present invention, as shown in FIG. 18, the uniformity of light in the horizontal and vertical directions is further improved. The quality of light supplied to the liquid crystal panel can be improved.

Therefore, as in the prior art, the uniformity, condensing property and brightness of light supplied to the liquid crystal panel are improved without applying a plurality of prism sheets and optical sheets on the light guide plate, the display quality of the liquid crystal display device is improved, and the liquid crystal display device is Can reduce the manufacturing cost.

In the above description, the light guide plate 100 includes the upper prism pattern 120 and the lower prism pattern 110. However, this is an example, and in another embodiment of the present invention, the light guide plate 100 is the upper prism. It may be formed to include only the pattern 120 or the lower prism pattern 110.

The present invention described above is not limited to the embodiments and the accompanying drawings, and those skilled in the art to which the present invention pertains have various substitutions, modifications, and changes without departing from the spirit or essential features of the present invention. You will understand that it is possible.

Therefore, the embodiments described in the present invention are not limited, and the scope of the present invention is indicated by the following claims rather than the detailed description. Accordingly, all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

1 is a perspective view showing an edge-type backlight unit according to the prior art.

2 is a cross-sectional view of the edge-type backlight unit according to the prior art, a cross-sectional view of the AA 'line of FIG.

3 is a view showing a profile of light emitted from the light guide plate of the edge type backlight unit according to the prior art.

4 is a perspective view illustrating a light guide plate according to an exemplary embodiment of the present invention.

FIG. 5 is a cross-sectional view of the light guide plate according to the embodiment of the present invention, and taken along line BB ′ of FIG. 4.

6 is a perspective view illustrating a light guide plate and a backlight unit using the light guide plate according to an exemplary embodiment of the present invention.

FIG. 7 is a cross-sectional view of a light guide plate and a backlight unit using the light guide plate according to the embodiment of the present invention, and FIG.

8 and 9 are plan views of upper prism patterns formed on the light guide plate.

10A to 10G are cross-sectional views of the C-C ′ line of FIG. 6, illustrating a top prism pattern formed on the light guide plate.

11 and 12 are rear views of the light guide plate according to the embodiment of the present invention.

FIG. 13 is a view illustrating a density change of a sub prism included in a lower prism pattern formed under the light guide plate. FIG.

14 is a plan view showing a shape of a lower prism pattern formed under the light guide plate.

15 and 16 are cross-sectional views of a lower prism pattern formed under the light guide plate.

17 is a view showing a profile of light emitted from a light guide plate according to an embodiment of the present invention.

18 is a diagram illustrating a profile of light emitted from a backlight unit according to an exemplary embodiment of the present invention.

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

100: light guide plate 110: lower prism pattern

120: upper prism pattern 130: diffusion sheet

140: light source

Claims (20)

A body having a side on which light is incident; First prism patterns extending in a direction parallel to a direction in which the light is incident and formed in an upper portion of the body such that a cross section has a predetermined shape; A second prism pattern formed in a lower portion of the body in a dot form from one side to the other side to which the light is incident; Each of the second prism patterns includes sub-prisms having a predetermined shape in cross section. The method of claim 1, And the second prism patterns include sub-prisms having different densities. The method of claim 2, The second prism patterns are formed such that the density of the sub-prism inside increases as the distance from the one side to which the light is incident. The method of claim 1, The second prism patterns are formed so that the density of the inner sub-prism increases from the central portion to the edge. The method of claim 1, The sub-prisms of the second prism patterns are formed such that the cross section is an isosceles triangle, a vertex is a triangle, an isosceles triangle, a trapezoid, a polygon, an ellipse, and one side is a straight line and one surface is curved. Light guide plate. The method of claim 5, The sub-prisms of the second prism patterns have a triangular cross section, the vertex of the adjacent sub-prism is formed to have a different angle. The method of claim 5, The vertex of the sub-prisms of the second prism pattern has a curved cross section, the vertex of the adjacent sub-prism is formed to have a different curvature. The method of claim 5, The vertex angle of the sub-prism of the second prism pattern is formed in the light guide plate 30 ~ 140 °. The method of claim 1, wherein the first prism pattern is The light guide plate, characterized in that arranged in a form of a straight line, having a predetermined curvature or a mixture of the straight line and the predetermined curvature so as to have a length from one side to the other side to which the light is incident. The method of claim 1, The first prism pattern and the second prism pattern is formed in a direction orthogonal to each other. The method of claim 1, The first prism pattern and the second prism pattern is formed in the form of an intaglio or embossed light guide plate. The method of claim 1, The second prism patterns are arranged to have a circular, elliptical, square, rhombus, trapezoidal shape. The method of claim 1, The sub-prisms adjacent to each other in the second prism patterns are formed to have different shapes in cross section. The method of claim 13, The vertex angle of the adjacent sub-prism is formed to have a different angle. The method of claim 13, The vertex of the adjacent sub-prism is formed to have different curvature. A light guide plate according to any one of claims 1 to 15; And a light source disposed at a side of the light guide plate to irradiate light to the light guide plate. The method of claim 16, And a diffusion sheet disposed on the light guide plate to diffuse light emitted from the light guide plate. The method of claim 16, The light source is a backlight unit, characterized in that formed on one side or a plurality of side surfaces of the light guide plate. The method of claim 16, And a reflective sheet disposed under the light guide plate to reflect light emitted to the rear surface of the light guide plate to an upper surface of the light guide plate. A light guide plate according to any one of claims 1 to 15; A light source disposed at a side of the light guide plate to irradiate light to the light guide plate; And a liquid crystal panel configured to display an image by adjusting a transmission amount of light emitted from the light guide plate at an upper portion of the light guide plate.

Images