KR20060125341A - Backlight apparatus - Google Patents

Abstract

A backlight unit is provided to effectively reflect a light emitted from a light source to a display panel, thereby improving the brightness and the uniformity of light, by forming a bottom surface of a light guiding plate in a taper shape. A light source(200) is inserted into a light guiding plate across the center portion of a bottom surface of the light guiding plate. A reflective sheet(400) is installed on a lower surface of the light guiding plate. The light guiding plate includes a first light guiding plate(100) having a flat type, and a second light guiding plate(300) having a sloping bottom surface. The second light guiding plate is division-attached to a bottom surface of the first light guiding plate.

Description

Backlight apparatus

1 is a configuration diagram for explaining a general edge light type backlight device

2 is a configuration diagram illustrating a general direct type backlight device

3 is an exploded perspective view illustrating the backlight device of the present invention;

Figure 4 is an assembled state diagram for explaining the backlight device of the present invention

5 is a conceptual view illustrating a taper angle of a second light guide plate according to the backlight device of the present invention.

6 to 7 are conceptual views for explaining an example of the prism shape of the first protrusion according to the backlight device of the present invention;

8 is a conceptual diagram illustrating an angle of a prism shape constituting the first and second protrusions according to the backlight device of the present invention.

9 is a conceptual diagram illustrating a path of a light source according to the backlight device of the present invention;

FIG. 10 is a conceptual view illustrating a path of propagation of light rays at an adhesive surface between a first light guide plate and a second light guide plate according to the backlight device of the present invention; FIG.

11 is a luminance graph according to the backlight device of the present invention

12 is a luminance graph according to the conventional backlight device compared with the present invention

13 is a conceptual diagram illustrating a backlight device according to another embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

100, 300: 1st, 2nd light guide plate 100a, 400a: 1st, 2nd protrusion part

200: cold cathode tube lamp 300a: reflection pattern

400: reflective sheet

The present invention relates to a backlight device, and more particularly, to a backlight device suitable for improving light uniformity and realizing high brightness.

In general, CRT (Cathode Ray Tube) among the display devices has been steadily gaining popularity because of the ability to display a variety of colors and the brightness of the screen, but recently, the desire for large, high-resolution display devices has increased In the meantime, the development of a thin flat panel display device in place of the CRT, which is large in weight and volume, is urgently needed, and one of the flat panel display devices has been developed.

Such a liquid crystal display device requires a backlight unit (BackLight Unit), which is a separate light source because it displays a screen by using a liquid crystal (liquid crystal) that does not emit light by itself, and recently, a large area and high resolution liquid crystal display In order to implement the device, screen brightness, efficiency, power consumption, optical uniformity, color reproducibility, viewing angle, thin structure, and price competitiveness are urgently required.

The backlight unit, which is a key component of the liquid crystal display device, not only transmits light of uniform brightness to the entire screen by using a light guide plate therein to transmit light emitted from the light source to the liquid crystal layer with uniform brightness and high efficiency. Diffusion sheets and prism sheets are used on the surface to obtain more uniform and higher luminance.

The backlight unit includes a direct backlight unit that directly emits light from the rear of the liquid crystal display panel toward the front side according to the position of the cold cathode tube lamp, and the lamp is positioned at the side of the light guide plate so that the light passes through the light guide plate and faces the front side. It is divided into edge light type backlight unit.

In the edge light type backlight unit, as shown in FIG. 1, a Cold Cathode Fluorescent Lamp (CCFL) 1 serving as a light source is installed on one side of the light guide plate 3, and the light guide plate 3 is disposed. Reflective sheet 5 is installed at the bottom of the reflector to reflect the lost light to minimize the loss of the light source. In addition, the upper part of the light guide plate 3 has a primary diffusion sheet 7 for diffusing light incident on the liquid crystal display panel, and a light at an upper end of the prism sheet 9 and the prism sheet 9 for condensing the diffused light. The secondary diffusion sheet 11 which can be selectively used to diffuse the light at a predetermined angle is sequentially installed.

Such an edge light type backlight unit is mainly applied to a relatively small liquid crystal display device such as a laptop and a desktop computer.

On the other hand, the backlight unit of the direct type is composed of a light collecting optical sheet 20, a diffusion plate 22, a cold cathode tube lamp 24 and a reflecting plate 26, as shown in Figure 2, the cold cathode tube lamp ( The diffusion plate 22 positioned at an upper portion with a predetermined interval of 24 diffuses the light generated by the cold cathode tube lamp 24 to uniform the luminance distribution of the light, and the light collecting optical sheet 20 is a diffusion plate. It serves to adjust the brightness of the light emitted from (22), the reflecting plate 26 is disposed at the lower end of the cold cathode tube lamp 24 to reflect the light toward the bottom plate upwards. For reference, reference numeral 28 denotes an accommodating member for accommodating the cold cathode tube lamp.

The direct type backlight unit uses a cold cathode tube lamp as a light source as in the case of the edge light backlight unit, but the cold cathode tube lamp is disposed on the lower surface of the liquid crystal display panel, and the size of the liquid crystal display device is gradually increased. The main focus was on the structure.

However, the direct type backlight unit does not mainly use a light guide plate, and the lamp is disposed on the reflecting plate, and the diffusion plate is covered by keeping a constant distance from the lamp. The gap between the diffuser plate and the cold cathode tube lamp should be maintained so that) does not appear.

In addition, there is a problem in that the uniformity of the light emitted from the light source is poor and the quality of the screen is degraded and power consumption is increased by using a plurality of light sources.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a backlight device suitable for improving the uniformity of the light source and efficiently using the light source to minimize power consumption and at the same time achieve high brightness. Further objects and features of the present invention will be clearly understood through the preferred embodiments described below.

The backlight device of the present invention for achieving the above object is a direct-type backlight device, the light source is fitted across the center of the bottom surface, the light guide plate inclined left and right bottom surface around the light source, and the light guide plate Characterized in that comprises a reflective sheet installed on the lower surface.

In addition, the backlight device of the present invention includes a light guide plate having a flat plate-shaped first light guide plate, and a second light guide plate which is divided on left and right sides of the light source having an inclined bottom surface and adhered to a bottom surface of the first light guide plate. It is characterized in that the configuration.

In addition, the backlight device of the present invention is characterized in that the bottom surface of the second light guide plate is inclined in a tapered shape around the light source. At this time, the inclination angle of the bottom surface preferably has a range of about 0.5 ~ 30 ㅀ.

In addition, the backlight device of the present invention has a plurality of reflective patterns having a prism shape formed in the longitudinal direction of the light source on the bottom surface of the second light guide plate in order to more efficiently transmit the light incident from the lateral direction of the light source toward the first light guide plate. It is characterized in that it is formed. At this time, the bottom angle of the prism of the reflective pattern is preferably changed in the range of 0.5 ~ 45 ° according to the inclination angle of the bottom surface of the second light guide plate.

In addition, the backlight device of the present invention has at least one first protrusion protruding downward in a prism shape on the bottom surface of the first light guide plate of the portion corresponding to the light source, and the reflective sheet of the portion corresponding to the light source. And a second protrusion protruding upward in a prism shape. At this time, the height of the prism formed on the reflective sheet is at least 1/2 of the width thereof, and preferably varies according to the vertex angle of the prism shape.

In addition, the backlight device of the present invention is characterized in that the first light guide plate and the second light guide plate are bonded to each other by an adhesive resin including a light diffusing material and an acrylic resin of a light diffusing material. In this case, the light diffusing material is an inorganic diffusing material such as calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ), silica, titanium oxide (TiO ₂ ) in the form of beads and organic diffusion properties of acrylic, urethane, and silicon It is preferable to include the light-diffusion material which has.

In addition, the backlight device of the present invention is characterized in that the light source is composed of any one of a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), an external electrode lamp (EEFL).

Referring to the backlight device according to an embodiment of the present invention having the technical features as described above in more detail with reference to the accompanying drawings.

3 is an exploded perspective view of a backlight device according to an embodiment of the present invention, Figure 4 is an assembled state diagram of a backlight device according to an embodiment of the present invention.

As shown in FIGS. 3 and 4, the backlight device according to the embodiment of the present invention has a flat surface type first LGP 100 and a light source 200 therebetween, and a bottom surface of the first LGP 100. And a reflective sheet 400 provided on the bottom surface of the second light guide plate 300 and the second light guide plate 300.

Here, the second light guide plate 300 divided left and right with the light source 200 interposed therebetween has a bottom surface inclined in the shape of a taper, and portions adjacent to the light source 200 are thick and have both ends. It becomes thinner and thinner.

On the inclined bottom surface of the second LGP 300, a plurality of reflective patterns 300a having a prism shape are used to more efficiently reflect light incident from the lateral direction of the light source 200 toward the first LGP 100. ) Is formed, and the reflective pattern 300a is formed along the longitudinal direction of the light source 200. Here, the height of the prism constituting the reflective pattern 300a is preferably at least 1/2 of the prism width, which depends on the vertex angle of the prism shape.

The inclination angle Ta of the bottom surface is in a range of about 0.5 to 30 degrees (see FIG. 5), and the bottom angle of the reflection pattern 300a of the prism shape is 0.5 according to the inclination angle of the second light guide plate 300. Can vary up to ˜45 °. For reference, FIG. 5 is a conceptual view illustrating an inclination angle of the bottom surface of the backlight device of the present invention.

The top surface of the first LGP 100 is flat and its bottom surface is also generally flat, but has a first protrusion 100a protruding downward in a prism shape at a position corresponding to the light source 200. The first protrusion 100a is for reflecting light upwardly emitted from the light source 200, and is formed along the longitudinal direction of the light source 200. The light is emitted by the first protrusion 100a. Will be divided. At this time, the vertex angle (a ') of the prism has a range of about 60 ~ 140 °, preferably has a range of 70 ~ 110 °, more preferably has a range of 75 ~ 105 °.

In addition, in the backlight device according to the present invention, as shown in FIG. 6, the shape of the prism formed on the bottom surface of the first LGP 100 may be formed in an arc shape. As described above, a plurality of prismatic first protrusions 100a formed on the bottom surface of the first light guide plate 100 may be formed. At this time, when forming the prism in the shape of an arc, as shown in Figure 6, it is preferable that the value of the radius "r" of the arc portion has a range of about 0.1 ~ 2mm.

On the other hand, the second light guide plate 300, which is partly bonded to both bottom surfaces with the first protrusion 100a formed on the first light guide plate 100 interposed therebetween, may be formed of adhesive resin or acrylic resin. It is bonded to the bottom surface of the 100, the adhesive resin and the resin of the acrylic material is bead-shaped calcium carbonate (CaCO ₃ ), barium sulfate (BaSO ₄ ) to diffuse the light incident from the light source 200 And inorganic light diffusing materials such as silica and titanium oxide (TiO2) and light diffusing materials having organic diffusing properties of acrylic, urethane, and silicon. In this case, the light diffusing material includes a light diffusing material which is generally used, and the acrylic resin preferably has a refractive index in the range of about 1.4 to 1.6.

The material of the first light guide plate 100 and the second light guide plate 300 is composed of an acrylic resin such as poly carbonate (Polycabonate), polymethyl methacrylate (PMMA: Resin), etc. In the embodiment of the present invention, the material of the first and second light guide plates 300 has a refractive index in the range of about 1.5 to 1.6, and the thickness of the first light guide plate 100 has a range of about 0.25 to 5 mm.

The reflective sheet 400 installed at the lower end of the second LGP 300 is formed of a film coated with Ag coating and a reflector, and a second protrusion protruding upward in a prism shape at a position corresponding to the light source 200. 400a). In this case, the second protrusion 400a is to minimize the loss of light by reflecting the light emitted downward from the light source 200, and is formed along the longitudinal direction of the light source 200.

As shown in FIG. 8, the second protrusion 400a has a prism shape, and the vertex angle a 'of the prism has a range of about 60 to 140 °, and preferably about 70 to 110 °. And more preferably 75 to 105 °.

Meanwhile, the light source 200 fitted between the second light guide plate 300 which is divided and bonded to the bottom surface of the first light guide plate 100 to the left and right is a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). Preferably, the light emitting diode is composed of one of an LED: a light-emitting diode (LED) and an external electrode lamp (EEFL).

In the backlight device according to the embodiment of the present invention configured as described above, the light generated by the light source 200 interposed between the divided second LGP 300 as shown in FIG. ) Is emitted radially, including the left and right and up and down directions of the light source 200. At this time, the light emitted upward of the light source 200 is split and reflected toward the second light guide plate 300 by the prism-shaped first protrusion 100a formed on the bottom surface of the first light guide plate 100, and the light source ( The light emitted downward of the 200 is split and reflected toward the second light guide plate 300 by the prism-shaped second protrusion 400a formed on the reflective sheet 400.

In addition, the second light guide plate 300, which is partly bonded to the bottom surface of the first light guide plate 100, has the first and second protrusions 100a and 400a together with the light incident from the lateral direction of the light source 200. The light reflected by the incident light is reflected toward the first LGP 100. In this case, the first light guide plate 100 and the second light guide plate 300 are adhered by an adhesive resin containing a light diffusing material or an acrylic resin containing a light diffusing material, as shown in FIG. 10. In addition, light diffusion occurs in the adhesive surface between the first LGP 100 and the second LGP 300. For reference, FIG. 10 shows the emission path of the light beam according to the backlight device of the present invention, and shows the emission of Lambertian and Guassian light beams, which improves the uniformity.

Hereinafter, the brightness and uniformity improvement through the light diffusing material according to the backlight device of the present invention will be described with reference to Tables 1 and 2 and FIGS. 11 to 12.

Table 1 below shows luminance measurement values measured at a plurality of measurement points for the backlight device according to the present invention, and Table 2 shows luminance measurement values according to the conventional backlight device compared to the luminance measurement value according to the present invention. will be. Here, the measurement point is the same both.

TABLE 1

Y axis X axis Point1 Point2 Point3 Point1 7737 7815 7683 Point2 7466 7824 7752 Point3 7628 7586 7496

TABLE 2

Y axis X axis Point1 Point2 Point3 Point1 4577 4668 4241 Point2 4540 5070 4156 Point3 4710 4766 4797

As shown in Table 1 and Table 2 above, when comparing the luminance measurement values for the same point, it can be seen that the luminance value of the backlight device of the present invention is significantly higher than in the prior art.

In addition, in the backlight device according to the present invention, since the first LGP 100 and the second LGP 300 are bonded to each other by a light diffusing material, as shown in FIG. 11, a uniform luminance can be obtained over all sections. On the other hand, in the case of the conventional backlight device, as shown in Figure 12, it can be seen that the uniformity of the brightness is significantly reduced compared to the present invention.

Although the backlight device according to the embodiment of the present invention has been described above, various modifications and changes can be made using the above embodiment. For example, as shown in FIG. 13, it is possible to arrange | position so that several structures as shown in FIG. 4 can be arrange | positioned in a line, and it can be applicable to a large area display apparatus etc. As described above, the embodiment of the present invention can be appropriately modified and applied in the same manner. Therefore, the above description does not limit the scope of the invention as defined by the limits of the following claims.

As described above, the backlight device of the present invention has the following effects.

The bottom surface of the light guide plate is inclined in a tapered shape to more efficiently reflect the light emitted from the light source toward the panel of the display device, thereby improving the luminance and the uniformity of the light.

In addition, a prism-shaped protrusion is formed in the light guide plate and the reflective sheet disposed above and below the light source, respectively, along the longitudinal direction of the light source, so that light emitted downward from the light source is formed in the reflective sheet. And the light emitted upward from the light source is split and reflected by the prism-shaped protrusion formed in the light guide plate, so that the light emitted from the light source is almost lost. Since it is emitted as, the light can be used efficiently.

Claims (17)

In the direct type backlight device, A light guide plate fitted with a light source across the center of the bottom surface, the left and right bottom surfaces of the light source being inclined; And a reflective sheet provided on a bottom surface of the light guide plate. The method of claim 1, wherein the light guide plate, A flat plate type first light guide plate, And a second light guide plate having an inclined bottom surface and partly bonded to the bottom surface of the first light guide plate. The backlight device of claim 2, wherein the bottom surface of the second light guide plate is inclined in a tapered shape with respect to the light source. The backlight device according to claim 2 or 3, wherein a plurality of reflective patterns having a prism shape in the longitudinal direction of the light source are formed on the bottom surface of the second light guide plate. The backlight device according to claim 2 or 3, wherein at least one first protrusion protruding downward in a prism shape is formed on a bottom surface of the first light guide plate at a position corresponding to the light source. The backlight device according to claim 5, wherein the vertex angle of the prism has a range of 60 ° to 140 °. 4. The backlight device according to claim 2 or 3, wherein the reflective sheet at a position corresponding to the light source is formed with a second protrusion protruding upward in a prism shape.  The backlight device according to claim 7, wherein the prism has a height greater than or equal to 1/2 of a width thereof and varies according to a vertex angle of the prism shape. The method of claim 2 or 3, wherein the first light guide plate and the second light guide plate is bonded to each other by any one of an adhesive resin comprising a light diffusing material and a resin of an acrylic material of the light diffusing material. Backlight device. The backlight device of claim 9, wherein the first light guide plate has a thickness in the range of 0.25 to 5 mm. The backlight device of claim 1, wherein the light source is any one of a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED), and an external electrode cold cathode fluorescent lamp (EEFL). 10. The backlight device of claim 9, wherein the light diffusing material comprises a light diffusing material in the form of beads. The angle of inclination of the second LGP has a range of 0.5 to 30 °, and the base angle of the prism-shaped reflection pattern on the lower surface of the second LGP is 0.5 in accordance with the inclination angle of the second LGP. Backlight device, characterized in that variable in the range of ~ 45 °. The backlight device of claim 9, wherein the transparent acrylic resin has a refractive index in a range of 1.4 to 1.6. The backlight device of claim 4, wherein the prism-shaped reflection pattern is the same as the inclination angle of the second light guide plate. The backlight device according to claim 5, wherein the radius of the arc portion has a range of 0.1 to 2 mm when the vertex portion of the prism shape is an arc shape. 2. The backlight device according to claim 1, wherein a plurality of sets of light guide plates and reflecting plates are arranged in front, back, left, and right.

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