KR100900043B1 - Backlight Unit for Liquid Crystal Display - Google Patents

Abstract

The present invention relates to a backlight unit of a liquid crystal display device, wherein the backlight unit for a liquid crystal display device includes: a sub-diffusion plate disposed behind the liquid crystal panel; A main diffusion plate disposed at a rear of the sub diffusion plate at a predetermined distance; A transparent electrode pattern formed to have a predetermined pattern formed on a rear surface of the main diffusion plate; A plurality of light emitting diodes (LEDs) attached to the transparent electrode patterns and electrically connected to the transparent electrode patterns; A backlight unit for a liquid crystal display device including a reflector disposed at a rear of the main diffusion plate at a distance for obtaining a microcavity effect from the light emitting diode and reflecting light emitted from the light emitting diode to the front. Is provided.

According to the present invention, since the light emitted backward from the light emitting diode is reflected by the front reflecting by the reflecting plate and emitted, the light diffusion and uniformity is improved, the color mixing efficiency is improved, and the microcavity ( The microcavity effect can be obtained, which results in better light efficiency.

Backlight, Light Emitting Diode, LED, Microcavity Effect

Description

Back-light unit for Liquid Crystal Device

1 is a cross-sectional view schematically showing the structure of a conventional backlight unit for a direct type liquid crystal display device

2A is a cross-sectional view schematically showing the configuration of a first embodiment of a backlight unit for a direct type liquid crystal display device according to the present invention;

FIG. 2B is a view illustrating a state in which light emitted from a light emitting diode of the backlight unit of FIG. 2A is reflected by a reflector;

3 is a cross-sectional view schematically showing the configuration of a second embodiment of a backlight unit for a direct type liquid crystal display device according to the present invention;

4 is a cross-sectional view schematically showing the configuration of a third embodiment of a backlight unit for a direct type liquid crystal display according to the present invention.

5 is a cross-sectional view schematically showing the configuration of a fourth embodiment of a backlight unit for a direct type liquid crystal display according to the present invention.

6 is a cross-sectional view schematically showing the configuration of a fifth embodiment of a backlight unit for a direct type liquid crystal display device according to the present invention;

7 is a cross-sectional view schematically showing the configuration of a sixth embodiment of a backlight unit for a direct type liquid crystal display device according to the present invention;

8 is a cross-sectional view schematically showing the configuration of a seventh embodiment of a backlight unit for a direct type liquid crystal display device according to the present invention;

9 and 10 are cross-sectional views illustrating embodiments of a reflective pattern implemented on a reflector of the backlight unit according to the present invention.

11 and 12 illustrate the results of simulating the light efficiency of the backlight unit according to the present invention.

Explanation of symbols on the main parts of the drawings

11: sub diffusion plate 12: main diffusion plate

13: reflector 14: light emitting diode

15 ITO transparent electrode pattern 16 phosphor

The present invention relates to a backlight unit of a liquid crystal display device, and more particularly, to a backlight unit for a direct type liquid crystal display device using a light emitting diode (LED) as a light source.

As is well known, a liquid crystal display (LCD), which is one of the flat panel display devices, has excellent visibility and a lower average power consumption than a CRT having the same screen size as compared to the cathode ray tube (CRT). Along with plasma display pannels (PDPs) and field emission displays, they have recently been in the spotlight as display devices of mobile phones, computer monitors and televisions.

Since the LCD does not emit light by itself, a separate light source device is positioned behind the LCD. The back light unit is a light source device that illuminates the entire LCD screen uniformly from the back of the LCD panel that does not have a self-luminous ability to view characters or images on the LCD.

The backlight unit, which is a light source device, must be used for all types of LCD panels such as TN, STN, and TFT, and is transmitted by the brightness (luminance, cd / m2) and uniformity (uniformity,%) of the light source for emitting light. The amount of light and the uniformity of the entire screen are determined.

In recent years, as the screen is enlarged and the demand for high quality increases, the direct type of the light source is placed directly behind the liquid crystal panel rather than the light source on the side or the upper and lower edges. Many backlight units are used.

1 of the accompanying drawings shows a structure of a conventional direct backlight unit, the conventional direct backlight unit is a sub-diffusion plate (1) disposed behind the liquid crystal panel (not shown) disposed in front, and A main diffusion plate 2 disposed at a rear of the sub diffusion plate 1 at a predetermined distance, a reflection plate 3 disposed at a rear of the main diffusion plate 2 at a predetermined distance, and the reflection plate 3; It is configured to include a plurality of light emitting diodes (4) which are installed at a predetermined interval.

Accordingly, the backlight unit diffuses and mixes light emitted forward through the light emitting diodes 4 in order through the main diffusion plate 2 and the sub-diffusion plate 1 in sequence, and thus, the front liquid crystal panel (not shown). Is provided.

However, since the conventional direct type backlight unit is emitted while the light emitted from the light emitting diode (LED), which is a light source, is diffused at a predetermined angle, the light emitted from the light emitting diodes is emitted from the entire surface of the diffusion plate. In order to spread evenly over a distance from the light emitting diode to the diffusion plate must be secured. Therefore, there is a limit in reducing the thickness of the backlight unit, which makes it difficult to thin the entire LCD.

Of course, reducing the distance between the light emitting diodes can reduce the distance between the diffusion plate and the light emitting diodes to some extent, but in this case, the number of light emitting diodes increases, resulting in a problem of increased power consumption and cost.

In addition, the conventional direct backlight unit has a Gaussian distribution in which the luminance of light emitted from each light emitting diode (LED) is concentrated in the center, and thus, does not provide uniform luminance and difficult color mixing. have.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a uniform and high brightness light using a small number of light emitting diodes, and for the direct type liquid crystal display device, which is easy to thin the backlight unit. It is to provide a backlight unit.

The present invention for achieving the above object, the main diffusion plate disposed behind the liquid crystal panel; A plurality of light emitting diodes (LEDs) attached to a rear surface of the main diffusion plate and emitting light backwards; A backlight unit for a liquid crystal display device is provided at a rear of the main diffusion plate at a predetermined distance from the light emitting diode and includes a reflecting plate for reflecting light emitted from the light emitting diode to the front.

According to an aspect of the present invention, there is provided a sub-diffusion plate disposed behind the liquid crystal panel; A main diffusion plate disposed at a rear of the sub diffusion plate at a predetermined distance; A transparent electrode pattern formed on a rear surface of the main diffusion plate to have a predetermined pattern; A plurality of light emitting diodes (LEDs) attached to the transparent electrode patterns and electrically connected to the transparent electrode patterns; A backlight unit for a liquid crystal display device including a reflector disposed at a rear of the main diffusion plate at a distance for obtaining a microcavity effect from the light emitting diode and reflecting light emitted from the light emitting diode to the front. Is provided.

According to the present invention, since the light emitted backward from the light emitting diode is reflected to the front by the reflecting plate and emitted, the light diffusion and uniformity are improved to improve the color mixing efficiency.

In addition, since the microcavity effect can be obtained between the main diffusion plate and the reflecting plate according to the distance between the light emitting diode and the reflecting plate, there is an advantage in that excellent light efficiency can be obtained with a small number of light emitting diodes.

Hereinafter, exemplary embodiments of a backlight unit for a liquid crystal display according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2A illustrates a structure of a backlight unit for a liquid crystal display according to a first embodiment of the present invention, wherein the backlight unit includes a sub-diffusion plate 11 disposed behind a liquid crystal panel (not shown), and the sub-diffusion plate 11. A main diffusion plate 12 disposed at a rear of the diffusion plate 11 at a predetermined distance, an ITO transparent electrode pattern 15 formed to have a predetermined pattern formed on a rear surface of the main diffusion plate 12, and A plurality of light emitting diodes (LEDs) 14 attached to the ITO transparent electrode patterns 15 and emitting light backwards, and the light emitting diodes 14 behind the main diffusion plate 12. And a reflecting plate 13 disposed at a distance to obtain a microcavity effect and reflecting light emitted from the light emitting diodes 14 to the front. Yellow or red phosphor 16 is deposited on the front surface of the main diffusion plate 12.

The sub-diffusion plate 11 may be configured using a transparent plate, a diffusion sheet, a prism sheet, a DBEF (DUAL BRIGHTNESS ENHANCE FILM) sheet, or the like.

The main diffusion plate 12 may be made of transparent glass, polycarbonate (PC), polymethyl methacrylate (PMMA), or the like.

In this embodiment, the light emitting diodes 14 are all composed of a single color light emitting diode which emits light of blue color, but a single color of other green or red or white lines. The light emitting diodes emitting light may be formed of light emitting diodes, and light emitting diodes emitting light of various colors, that is, red (R), green (G), and blue (B) colors may be alternately arranged.

In addition, the ITO transparent electrode pattern 15 is connected to an external power source. The light emitting diodes 14 may be attached to the ITO transparent electrode pattern 15 by soldering, Ag, Au, Cu paste or tape, or by using a conductive resin.

Referring to the operation of the backlight unit for a liquid crystal display device of the present invention configured as described above are as follows.

As shown in FIGS. 2A and 2B, when power is applied to the light emitting diodes 14 from the outside through the ITO transparent electrode pattern 15, the light emitting diodes 14 emit light back at a predetermined angle. Release. The emitted light is diffused forward by being reflected by the rear reflector 13.

At this time, the light efficiency of the light emitting diode 14 is increased by the microcavity effect in the process of reflecting the light by the reflector 13 and the main diffusion plate 12 can be obtained. That is, the light emitted from the light emitting diodes 14 is reflected by the reflecting plate 13 and then some of the light is reflected from the back of the main diffusion plate 12, at this time from the back of the main diffusion plate 12 The reflected and lost light is amplified while resonating.

Therefore, the light emitted from the light emitting diodes 14 may be more than twice as wide as the conventional one, the light uniformity is improved, and the light efficiency may be improved by the microcavity effect.

On the other hand, the light reflected by the reflecting plate 13 and passed through the main diffusion plate 12 as described above is diffused through the main diffusion plate 12, the color mixing occurs through the phosphor 16 to form a white light Next, the second diffusion through the sub-diffusion plate 11 is provided to the front liquid crystal panel (not shown).

Although not shown in the drawings, the backlight unit of the present invention may have a configuration in which another optical sheet such as a diffusion sheet or a prism sheet is additionally disposed outside the sub-diffusion plate 11.

3 shows a second embodiment of a backlight unit for a liquid crystal display device according to the present invention. The backlight unit of this second embodiment has a basic configuration substantially similar to that of the first embodiment described above. However, in this embodiment, the phosphor 16 (see FIG. 1) is not deposited on the outer surface of the main diffusion plate 212, and the phosphor is formed inside the main diffusion plate 212 in the process of forming the main diffusion plate 212. It consists of a mixed structure.

Accordingly, the light emitted backward through the light emitting diodes 14 and reflected by the reflecting plate 13 is diffused while passing through the main diffusion plate 212 and is mixed with the color to be emitted as white light. The sub-diffusion plate 11 After passing through the second diffusion is emitted to the front liquid crystal panel (not shown).

Of course, even in this case, amplification due to resonance of lost light occurs between the phosphor mixed main diffusion plate 212 and the reflection plate 13, thereby obtaining a microcavity effect of increasing light efficiency.

4 shows a third embodiment of a backlight unit for a liquid crystal display according to the present invention. The basic configuration of the backlight unit of this third embodiment is almost the same as that of the first embodiment, but the outer surface of the main diffusion plate 12 is shown. The phosphor 16 (refer FIG. 1) is not formed in the dot, and the auxiliary diffuser plate 316 in which the phosphor having a predetermined color such as yellow or red is mixed between the main diffusion plate 12 and the reflection plate 13 is formed. There is a difference.

In the backlight unit of the third embodiment configured as described above, light emitted backward through the light emitting diodes 14 passes through the auxiliary diffusion plate 316 and is simultaneously mixed with the light diffused and then reflected by the reflecting plate 13. The light reflected by the reflector 13 passes through the auxiliary diffuser 316 again and is simultaneously mixed with the second color so as to diffuse and proceed to the main diffuser 12. Therefore, even if a small amount of phosphors are mixed in the auxiliary diffusion plate 316, uniform white light can be obtained.

Meanwhile, in the above-described embodiments, the light emitting diodes 14 are all composed of only one emitting blue light. However, like the backlight unit according to the fourth embodiment of FIG. 5, the light emitting diodes 414 may be formed. All may be configured by applying white emission.

In this case, since there is no need to mix the color of the light emitted through the light emitting diode 414, there is an advantage that it is not necessary to configure a phosphor having a predetermined color.

As shown in the fifth embodiment of FIG. 6, the light emitting diodes 514 are not formed of a single color but are alternately arranged with colors of red (R), green (G), and blue (B). It may be configured.

In this case, light of various colors emitted through each of the light emitting diodes 514 is reflected and diffused by the reflecting plate 13 and mixed with the light of the adjacent light emitting diodes 514 to enter the main diffusion plate 12. The light is emitted as white light while being diffused and mixed again in the main diffusion plate 12.

The light emitted through the main diffusion plate 12 passes through the sub-diffusion plate 11 to generate secondary color mixing, thereby emitting white light closer to pure white.

7 shows a sixth embodiment of the backlight unit according to the present invention. The backlight unit of this sixth embodiment has a configuration substantially the same as that of the backlight unit of the fifth embodiment, but as in the above-described third embodiment, the main diffusion plate. An auxiliary diffusion plate 616 in which phosphors are mixed between the 12 and the reflection plate 13 is interposed.

Thus, the backlight unit of this sixth embodiment is the same as the backlight unit of the third embodiment, since the light emitted from the light emitting diodes 614 of each color is diffused and mixed by the secondary diffusion plate 616 secondarily. Mixing occurs more smoothly and white light close to pure white can be obtained.

8 shows a seventh embodiment of the backlight unit according to the present invention, in which the yellow phosphor 716 is deposited on the front surface of the main diffusion plate 12, and the main diffusion plate 12. Between the reflective plate 13 and the transparent or translucent auxiliary diffuser plate 717 in which no phosphor is mixed, the light emitting diodes 714 having the colors of red (R), green (G), and blue (B) are provided. It consists of an arranged configuration.

In the backlight unit of this embodiment, the light emitted through the light emitting diode 714 is first diffused and color-mixed while passing through the auxiliary diffusion plate 717, and the light reflected by the reflector 13 is further diffused. After passing through 717, the second diffusion and color mixing are performed, followed by the third diffusion and mixing through the main diffusion plate 12 and the phosphor 716. The light passing through the phosphor 716 is diffused and color-mixed through the sub-diffusion plate 11 and emitted as white light.

In the sixth and seventh exemplary embodiments, the backlight units of the sixth and seventh exemplary embodiments emit light of white light close to pure white because the light of the light emitting diodes 614 and 714 having various colors is diffused and mixed in four orders. There is a characteristic that can emit light.

The backlight units of the present invention have a feature of improving light efficiency by reflecting back light emitted from the light emitting diodes 14 back from the reflector plate 13. Therefore, in order to further increase the diffusivity when light is reflected from the reflector 13, a reflective pattern 18 having a specific uneven shape may be formed on the front surface of the reflector 13 as shown in FIGS. 9 and 10. have.

The reflective pattern 18 may have a prism shape, a cone shape, or a polygonal pyramid shape such as a triangular pyramid as shown in FIG. 9, or may have a hemispherical shape or a semi-cylindrical shape as shown in FIG. 10.

11 and 12 show the results of simulating the performance of the backlight unit of the present invention. The liquid crystal display device to be simulated is based on a size of 32 inches, and the total thickness of the backlight unit is 25 mm. The backlight unit has a structure of the backlight unit of the fifth embodiment shown in FIG. 6. The LEDs used were set to use 48 for emitting red (R) light, 88 for emitting green (G) light, and 48 for emitting blue (B) light as intermediate power classes. .

As a result of this simulation, it was found that white light having a uniform luminance of about 8000 nits was generally provided in the screen region except for the edge of the backlight unit.

Thus, according to the present invention, since the light emitted backward from the light emitting diode is reflected by the front reflecting by the reflecting plate and emitted, the light diffusion and uniformity is improved to improve the color mixing efficiency. Therefore, the thickness of the backlight unit can be significantly reduced, and the number of light emitting diodes used can be reduced, which is very advantageous in light weight and low power of the liquid crystal display.

In addition, since the microcavity effect can be obtained between the main diffusion plate and the reflecting plate according to the distance between the light emitting diode and the reflecting plate, there is an advantage in that excellent light efficiency can be obtained with a small number of light emitting diodes.

Claims (17)

A main diffusion plate disposed behind the liquid crystal panel; A plurality of light emitting diodes (LEDs) attached to a rear surface of the main diffusion plate and emitting light backwards; A reflector disposed at a rear of the main diffusion plate at a predetermined distance from the light emitting diode and reflecting light emitted from the light emitting diode to the front; And a sub diffusion plate disposed between the main diffusion plate and the reflection plate. The backlight unit of claim 1, wherein the distance between the light emitting diodes and the reflector is set to a distance at which a microcavity effect can be obtained. The method of claim 1, wherein the liquid crystal panel and the main diffusion plate is disposed at a predetermined distance from the main diffusion plate, characterized in that configured to include a sub-diffusion plate for secondary diffusion of light forward through the main diffusion plate. A backlight unit for a liquid crystal display device. delete The light emitting diodes of claim 1, wherein the light emitting diodes are arranged only to emit light of a single color or alternately arranged to emit light of red (R), green (G), and blue (B). Backlight unit for liquid crystal display device. The backlight unit of claim 1, wherein a phosphor having a predetermined color is formed on the main diffusion plate. delete The backlight unit of claim 1, wherein a phosphor having a predetermined color is formed in the auxiliary diffusion plate. The backlight unit of claim 1, wherein a reflective pattern having a concave-convex shape is formed on a front surface of the reflecting plate. The backlight unit of claim 9, wherein the reflective pattern has any one of a prism shape, a polygonal shape, a cone shape, a hemisphere shape, and a semi-cylindrical shape. The backlight unit of claim 1, wherein the light emitting diodes are electrically connected to a transparent electrode pattern formed on a rear surface of the main diffusion plate to have a predetermined pattern. delete delete delete delete delete delete

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