KR20110111087A - Backlight unit and display unit including the same - Google Patents

Abstract

The present invention relates to a structure of a backlight unit and a reflector of a display device including the same.
The present invention is a printed circuit board fixed to the light source; A light guide plate provided on one side of the light source and scattering light projected from the light source body; A diffusion plate provided on the first surface of the light guide plate to diffuse the light emitted from the light guide plate at a predetermined angle; A first reflector provided on a second surface of the light guide plate to totally reflect light lost from the light guide plate into the light guide plate; And a second reflecting plate surrounding the printed circuit board and the light source and in contact with the side surface of the diffusion plate.
Therefore, since no optical loss occurs in the backlight unit, the brightness of the display device is improved, and the printed circuit board on which the light source is fixed is fixed to a frame made of metal, thereby sufficiently supporting a load of a light emitting diode or the like.

Description

Backlight unit and display device including the same {Backlight unit and display unit including the same}

The present invention relates to a backlight unit and a display device including the same, and more particularly, to a structure of a reflecting plate of a backlight unit.

Recently, the demand for liquid crystal display (Liquid crystal display) is a display device that displays an image by controlling the amount of light coming from the outside by using the liquid crystal injected between the TFT (Thin film transistor) substrate and the color filter substrate .

In addition, since the liquid crystal display has no self-light emitting capability, a separate backlight unit for irradiating light to the panel is required.

As a light source of a conventional backlight unit, a cold cathode fluorescent lamp (CCFL) having a rod shape or a light emitting diode (LED) having a dot shape is mainly used.

However, the cold cathode ray tube lamp has a high brightness and a long life, and has a very low heat generation value compared to an incandescent lamp, but has poor brightness uniformity. Therefore, a backlight using a light emitting diode as a light source is widely used.

A light emitting diode is a light emitting device using a group 3-5 or group 2-6 compound semiconductor material of a conductor, and can realize various colors such as red, green, blue, and ultraviolet rays, and is efficient by using fluorescent materials or combining colors. Good white light is also possible.

However, the above-described conventional LED backlight has the following problems.

The light emitted from the light emitting diode is incident on the light guide plate, and is refracted or scattered in the direction toward the liquid crystal display while undergoing total reflection inside the light guide plate. In this case, the light emitting diode used for a large screen of 40 inches or more should be provided at least 0.8 mm (mm) or more due to a thermal problem with the light guide plate.

In addition, some of the light emitted from the light emitting diode may leak into the space between the light guide plate and cause optical loss. This optical loss leads to a decrease in luminance of the display device with a backlight.

In addition, the backlight used for a large screen of 40 inches or more has a problem in that the number of light emitting diodes and other components used is increased, thereby increasing the load applied to the printed circuit board on which the light emitting diodes are packaged.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem, and an object of the present invention is to reduce optical loss between the light source and the light guide plate in the backlight unit and thus decrease the luminance of the display device.

Another object of the present invention is to provide a backlight having a rigid structure that withstands a load such as a light emitting diode applied to a printed circuit board in a backlight used for a large screen display.

The present invention to solve the above problems is a printed circuit board with a light source is fixed; A light guide plate provided on one side of the light source and scattering light projected from the light source body; A diffusion plate provided on the first surface of the light guide plate to diffuse the light emitted from the light guide plate at a predetermined angle; A first reflector provided on a second surface of the light guide plate to totally reflect light lost from the light guide plate into the light guide plate; And a second reflecting plate surrounding the printed circuit board and the light source and in contact with the side surface of the diffusion plate.

According to another embodiment of the present invention, a printed circuit board having a light source fixed thereto, a light guide plate provided on one side of the light source and scattering the light projected from the light source body, and a first surface of the light guide plate provided in the light guide plate A diffusion plate for diffusing the emitted light at a predetermined angle, a first reflection plate provided on the second surface of the light guide plate to totally reflect the light lost from the light guide plate, and surrounding the printed circuit board and the light source, A backlight unit including a second reflector in contact with a side surface; A panel realizing an image by the light projected by the optical system; And a color filter provided on the front surface of the panel and selectively transmitting any one of red, green, and blue light.

Here, the second reflector may contact the side surface of the first reflector.

The second reflecting plate may be provided in a 'c' shape and may surround at least one of the diffusion plate and the first reflecting plate, and may surround the light guide plate.

The second reflector may include aluminum (Al) or silver (Ag).

In addition, the second reflector may be formed by coating aluminum or silver on the metal frame.

The second reflector may be doped with at least one of titanium (Ti), chromium (Cr), and zirconium (Zr).

In addition, the light source may be a light emitting diode.

The effects of the backlight unit and the display device including the same according to the present invention described above are as follows.

First, the reflecting plate of the backlight unit is formed in a structure in which the light source and the light guide plate are in contact with each other, so that optical loss between the light source and the light guide plate does not occur and thus the brightness of the display device is not reduced.

Second, the printed circuit board on which the light source is fixed in the display of the large screen is fixed to a frame made of metal, thereby supporting a load of a light emitting diode or the like.

1 is a view showing an embodiment of a light emitting diode device,
2A is a diagram illustrating an embodiment of a backlight unit according to the present invention;
FIG. 2B is a view illustrating a light source and a second reflector of the backlight unit of FIG. 2A;
Figure 2c is a view showing the light loss of the conventional backlight unit,
3A is a view showing another embodiment of a backlight unit according to the present invention;
3B is an enlarged view of a portion of FIG. 3A;
4 is a view showing a display device provided with a backlight unit according to the present invention.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. The same components as in the prior art are given the same names and the same reference numerals for convenience of description, and detailed description thereof will be omitted.

1 is a view showing an embodiment of a light emitting diode device, Figure 2a is a view showing an embodiment of a backlight unit according to the present invention, Figure 2b is a view showing a light source and a second reflector of the backlight unit of Figure 2a to be. Hereinafter, an embodiment of a backlight unit according to the present invention will be described with reference to FIGS. 1, 2A, and 2B.

As illustrated, in the backlight unit according to the present embodiment, the light emitting diode device 100 is fixed to the printed circuit board 110. Among various light sources that may be used in the backlight unit, the present embodiment uses the light emitting diode device 100 as a light source.

The light emitting diode device 100 may implement various colors such as red, green, blue, and ultraviolet rays, and may also implement white light having high efficiency by using fluorescent materials or combining colors, and thus, the light emitting diode device 100 is preferred as a light source of a backlight.

As shown in FIG. 1, the LED device 100 includes a mount lead 11 and an inner lead 12, and the LED chip 14 is disposed on the mount lead 11. It is provided in the reflector cup 20 formed in the inside.

The n electrode and the p electrode of the LED chip 14 are electrically connected to each of the mount lead 11 and the inner lead 12 by wires 15.

The light emitting diode chip 14 is covered with a fluorescent layer in which the fluorescent material 16 is mixed with the transparent resin. In addition, the reflective cup 20 is coated with silver (Ag) and / or aluminum (Al) for high reflection of visible light.

The lens unit 17 is formed by filling and curing a liquid transparent resin on the reflective cup 20. The lens unit 17 mainly uses an epoxy or silicon material, and may also include phosphor powder. In addition, the reflective cup is shaped to spread light emitted from the light emitting device 3 widely.

In addition, the light projected by the light emitting diode device 100 is scattered by the light guide plate 130 and proceeds. Here, the light guide plate 130 scatters the light emitted from the light emitting diode device 100 so that the light is uniformly distributed over the entire area of the screen of the liquid crystal display.

Therefore, the light guide plate 130 is made of a material having good refractive index and transmittance, and may be formed of polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene (PE), or the like.

In addition, a second reflecting plate 120 is provided to surround the printed circuit board 110 and the light emitting diode device 100. Here, the second reflecting plate 120 is formed to surround the end of the light guide plate 130.

That is, as shown in FIG. 2B, the second reflecting plate 120 surrounds the printed circuit board 110 and the light emitting diode element 100 in a 'C' shape, and the 'A' and the light emitting plates 130 are formed on both sides of the light guide plate 130. Similarly, the second reflecting plate 120 is bonded.

Thus, conventionally, as shown in FIG. 2C, only part of the light emitted from the light emitting diode device 100 proceeds to the light guide plate 130, thereby proceeding to the outside of the light guide plate 130 as shown in FIG. 2A. The light is reflected by the second reflector 120 and proceeds to the light guide plate 130.

The second reflector 120 may be made of a material having excellent reflectance, and may include aluminum (Al) or silver (Ag). In addition, the second reflector 120 may be formed by coating aluminum or silver on a metal frame. That is, the material having a high reflectance may be coated on a frame such as a metal having a high strength and a low weight to support the backlight to achieve a predetermined purpose.

In addition, the second reflector 120 may be doped with at least one of titanium (Ti), chromium (Cr), and zirconium (Zr). At this time, the coating layer having a high reflectance is made of TiAl, CrAl, ZrAl and the like.

At this time, the method of doping titanium, chromium and zirconium in the above-described aluminum or silver may be performed by sputtering, etc., titanium, chromium, zirconium may be included in the 10 to 30% of the weight of aluminum or silver.

Therefore, one component of titanium, chromium, and zirconium may be added to the second reflector 120 having aluminum or silver as a main component, thereby having high reflectance and high corrosion resistance.

Although not shown, a diffusion plate may be provided on a first surface of the light guide plate 130, and a first reflecting plate may be provided on a second surface of the light guide plate 130. In this case, an end of the second reflecting plate 120 surrounding the light guide plate 130 may be in contact with the diffusion plate and the first reflecting plate, respectively. The structures of the diffusion plate and the first reflecting plate can be referred to later.

In addition, the second reflector 120 may not only surround and form the light guide plate 130, but may also form and surround the diffuser plate and the second reflector. In this case, a function of preventing light loss may be secured.

3A is a view showing another embodiment of a backlight unit according to the present invention, and FIG. 3B is an enlarged view of a portion of FIG. 3A. Hereinafter, another embodiment of the backlight unit according to the present invention will be described with reference to FIGS. 3A and 3B.

Here, the diffusion plate 150 is provided on the first surface of the light guide plate 130, and the first reflecting plate 140 is provided on the second surface of the light guide plate 130. And, as shown in the portion B, the end of the second reflecting plate 120 is characterized in that bent at the portion where the diffusion plate 150 meets.

In addition, in the embodiment illustrated in FIG. 3A, the second reflector 120 is formed on the frame 160. That is, as described in the above-described embodiment, the material having a high reflectance may be coated on the frame 160 such as a metal having a high strength and a low weight to support the backlight to form the second reflecting plate 120.

Here, an optical sheet such as a diffusion sheet, a prism sheet, or a protective sheet may be selectively stacked on the diffusion plate 150, or a micro lens array may be used. In this case, a plurality of optical sheets may be used, and the optical sheets may be made of a transparent resin such as acrylic resin, polyurethane resin, or silicone resin.

In addition, the reflector plate 140 functions to totally reflect the light reflected and lost to the lower portion of the light guide plate 130 into the light guide plate 130. In addition, the first reflection plate 140 reflects the light leaked through the bottom surface of the light guide plate 130 to the upper portion of the light guide plate 130 again.

The first reflector 140 may be formed of the same material as the second reflector 120, but a material having a high reflectance such as polyethylene terephtalate (PET) and having an ultra thin shape may be used.

Here, the other end of the second reflecting plate 120 is formed in contact with the end of the first reflecting plate 14. Therefore, due to the action of the second reflecting plate 120 in the portion B of FIG. 3A, the light emitted from the light emitting diode 100 may be propagated to the light guide plate 130.

However, there is a difference in that the second reflecting plate 120 is slightly spaced apart from the diffusion plate 150. Due to this difference, heat emitted from the light emission of the LED device 100 may be partially discharged to the outside.

4 is a view showing a display device provided with a backlight unit according to the present invention. Hereinafter, a display device provided with a backlight unit according to the present invention will be described with reference to FIG. 4.

First, the display device according to the present embodiment includes a backlight unit, a liquid crystal display device 310, and a color filter 320.

First, the backlight unit is as described above. That is, the light emitting diode device 100 is fixed to the printed circuit board 110, and the second reflecting plate 120 surrounds the light emitting diode device 100 and the printed circuit board 110.

The light emitting diode device 100 is formed of a nitride semiconductor including a p-type semiconductor layer, an active layer, and an n-type semiconductor layer on a substrate.

The n-type nitride semiconductor layer is n-doped with an Al _x In _y Ga _(1-xy) N composition formula, where 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, and 0 ≦ x + y ≦ 1. It is made of a semiconductor material, in particular n-GaN is widely used.

The active layer has a multi-quantum well (MQW) structure and may be formed of GaN or InGaN.

In addition, the p-type nitride semiconductor layer, similar to the n-type nitride semiconductor layer, Al _x In _y Ga _(1-xy) N composition formula (where 0≤x≤1, 0≤y≤1, 0≤x + y ≦ 1), and p-doped.

In addition, electrodes may be formed on the p-type nitride semiconductor layer and the n-type nitride semiconductor layer, respectively, chromium (Cr), nickel (Ni), gold (Au), aluminum (Al), titanium (Ti), and platinum ( It may be made of any one metal selected from Pt) or an alloy of the metals.

The n and p electrodes of the LED chip are electrically connected to the mount leads and the inner leads by wires. The light emitting diode chip is covered with a fluorescent layer in which a fluorescent material is mixed with a transparent resin.

In addition, the light emitted from the light emitting diode may secure straightness by the cup-shaped structure.

The second reflecting plate 120 may be formed to be in contact with the first reflecting plate 140 and bend in the vicinity of the diffusion plate 150 as shown, or may be formed to surround the light guide plate 130 as in other embodiments.

The liquid crystal display 310 is provided on the front surface of the diffusion plate 150. Here, it is obvious that other types of display devices requiring a light source besides the liquid crystal display device 310 may be provided.

In the liquid crystal display device, the liquid crystal is positioned between the glass substrates, and the polarizing plates are placed on both glass substrates in order to use polarization of light. Here, the liquid crystal has an intermediate property between a liquid and a solid, and liquid crystals, which are organic molecules having fluidity like a liquid, are regularly arranged like crystals. The liquid crystal has a structure in which the molecular arrangement is changed by an external electric field And displays an image.

The liquid crystal display device used in the display device uses an active matrix method as a switch for adjusting a voltage supplied to each pixel.

Since the structure of a specific liquid crystal display device is the same as that of the prior art, it abbreviate | omits.

In addition, a color filter 320 is provided on the front surface of the liquid crystal display 310. In this case, the color filter 320 transmits the light projected by the liquid crystal display 310, and thus only the red, green, and blue light is transmitted to each pixel, thereby displaying an image.

In the above-described backlight unit and the display device, the second reflecting plate is formed in a structure in which the light source and the light guide plate are in contact with each other, so that optical loss between the light source and the light guide plate does not occur and thus the brightness of the display device is not reduced.

In addition, in a large-screen display, a printed circuit board having a fixed light source is fixed to a frame made of metal to support a load such as a light emitting diode, and a material having a high reflectance is coated on the frame to be emitted from the light emitting diode element so that it is not incident to the light guide plate. You can re-reflect light that you can't.

As described above, the present invention has been described by way of limited embodiments and drawings, but the present invention is not limited to the above embodiments, and those skilled in the art to which the present invention pertains various modifications and variations from such descriptions. This is possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims below but also by the equivalents of the claims.

10: light emitting diode chip 11: mount lead
12: inner lead 13: light emitting diode chip
15 wire bonding 16 fluorescent material
17 lens 20 reflection cup
100: light emitting diode element 110: printed circuit board
120: second reflecting plate 130: light guide plate
140: first reflecting plate 150: diffuser plate
160: frame 310: liquid crystal display device
320: color filter

Claims (14)

A printed circuit board having a light source fixed thereto;
A light guide plate provided on one side of the light source and scattering light projected from the light source body;
A diffusion plate provided on the first surface of the light guide plate to diffuse the light emitted from the light guide plate at a predetermined angle;
A first reflector provided on a second surface of the light guide plate to totally reflect light lost from the light guide plate into the light guide plate; And
And a second reflecting plate surrounding the printed circuit board and the light source and in contact with a side surface of the diffusion plate. The method of claim 1, wherein the second reflecting plate,
And a side surface of the first reflecting plate. The method according to claim 1 or 2,
The second reflecting plate is provided with a '''shape and surrounds the light guide plate. The method according to claim 1 or 2,
The second reflecting plate is provided with a '''shape and surrounds at least one of the diffusion plate and the first reflecting plate. The method of claim 1, wherein the second reflecting plate,
A backlight unit comprising aluminum (Al) or silver (Ag). The method of claim 1, wherein the second reflecting plate,
The backlight unit, characterized in that formed on the metal frame is coated with aluminum or silver. The said 2nd reflector is a thing in any one of Claims 5-6.
And at least one of titanium (Ti), chromium (Cr), and zirconium (Zr). The method of claim 1, wherein the light source,
A backlight unit, characterized in that the light emitting diode (Light emitting diode). A printed circuit board having a light source fixed thereto, a light guide plate provided on one side of the light source and scattering light projected from the light source body, and a light guide plate provided on the first surface of the light guide plate to diffuse the light emitted from the light guide plate at a predetermined angle; And a first reflecting plate provided on a second surface of the light guide plate to totally reflect the light lost from the light guide plate into the light guide plate, and a second reflecting plate surrounding the printed circuit board and the light source and in contact with a side surface of the diffuser plate. A backlight unit;
A panel realizing an image by the light projected by the optical system; And
And a color filter provided on the front surface of the panel and selectively transmitting any one of red, green, and blue light. The method of claim 9, wherein the second reflecting plate,
And a side surface of the first reflecting plate. The method according to claim 9 or 10,
The second reflector is a display device, characterized in that provided in the '''shape surrounding the light guide plate. The method according to claim 9 or 10,
The second reflecting plate is provided with a '''shape and surrounds at least one of the diffusion plate and the first reflecting plate. The method of claim 9, wherein the second reflecting plate,
Display device characterized in that the aluminum or silver is coated on the frame. The method of claim 9, wherein the light source,
Display device, characterized in that the light emitting diode (Light emitting diode).

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