TWI416223B - Backlight unit - Google Patents

Abstract

A backlight unit includes an LED, a light-diffusion sheet, a prism sheet and a polarizing sheet. The light emitted from the LED radiates through the light-diffusion sheet, the prism sheet and the polarizing sheet. The prism sheet has a surface which is located at on the light pathway of the LED, being coated with phosphor. The backlight can have a uniform light-mixing effect.

Description

Backlight module

The invention relates to a backlight module, in particular to a light-emitting diode backlight module.

The display screen is an electronic device that can display text and images and is widely used in people's daily life. The current display screens can be mainly divided into two types according to their materials: one is an organic light-emitting display (OLED), and the other is a thin film transistor (TFT). Due to the high cost of the OLED screen, although there are many advantages, the scope of application is limited. The TFT screen, with its large price advantage, still dominates the application. However, the TFT screen itself does not have a light-emitting function, so it is usually necessary to equip it with a corresponding backlight module for illumination.

The light source used in the conventional backlight module is usually a cold cathode fluorescent lamp (CCFL) and a light emitting diode (LED). Due to its early appearance and relatively mature technology, cold cathode fluorescent tubes are still the first choice for most display backlight modules. The technology of light-emitting diodes started late, and currently only related applications on some display screen products. However, due to the many advantages compared to cold cathode fluorescent tubes, such as small size, light weight, low energy consumption, no pollution, etc., the application of future light-emitting diodes It will gradually expand, and it is imperative to replace the cold cathode fluorescent tube.

Since the display screen requires white light for illumination, white light is not directly generated for the light-emitting diode of a single wafer, and therefore white light is usually synthesized by mixing light. The current mainstream light mixing method is a blue light emitting chip plus yellow phosphor powder. However, since the volume of the light-emitting diode is small, the distribution of the phosphor powder doped in the package is uneven, and the output white light is discolored, thereby affecting the display effect of the display screen.

Therefore, it is necessary to provide a backlight module with uniform light mixing.

A backlight module includes a light emitting diode, a diffusing plate, a cymbal piece and a polarizing plate, and the light emitted by the light emitting diode is emitted through the diffusing plate, the cymbal piece and the polarizing plate, and the cymbal piece is in the light propagation path of the light emitting diode Fluorescent powder is provided on the surface.

Since the phosphor powder is disposed on the surface of the bract, the larger area ensures uniform distribution of the phosphor powder, thereby evenly mixing the light and avoiding the phenomenon of color cast.

10‧‧‧Light guide plate

12‧‧‧Into the glossy surface

14‧‧‧Glossy

20‧‧‧Lighting diode

30‧‧‧Diffuser

32‧‧‧Into the glossy surface

34‧‧‧Glossy

40‧‧‧ Picture

42‧‧‧Into the glossy surface

44‧‧‧Glossy

50‧‧‧Polar plate

60‧‧‧Yellow Fluorescent Powder

62‧‧‧Red Fluorescent Powder

64‧‧‧Green Fluorescent Powder

FIG. 1 is a schematic diagram of a backlight module according to a first embodiment of the present invention.

2 is a schematic view of a backlight module according to a second embodiment of the present invention.

FIG. 3 is a schematic diagram of a backlight module according to a third embodiment of the present invention.

Referring to FIG. 1, a backlight module according to a first embodiment of the present invention is shown. The backlight module is used for illuminating a display screen (not shown) to facilitate the user to observe the content displayed on the display screen. The backlight module includes a light guide plate 10 and a plurality of guides The light-emitting diodes 20 at opposite ends of the light plate 10, a diffusion plate 30 disposed above the light guide plate 10, a cymbal plate 40 disposed above the diffusion plate 30, and a polarizing plate 50 disposed above the cymbal plate 40.

The light guide plate 10 can be made of a highly transparent material such as acrylic resin or polycarbonate resin. The light guide plate 10 has a rectangular shape, and the two sides of the light-emitting diode 20 are the light-incident surface 12, and the top surface thereof is the light-emitting surface 14. The light emitted from the LED 20 enters the light guide plate 10 through the light incident surface 12 of the light guide plate 10, and part of the light is directly emitted from the light exit surface 14. The other portion of the light is totally reflected by the bottom surface of the light guide plate 10 and then exits from the light exit surface 14. . In order to prevent light from leaking from the bottom surface of the light guide plate 10, a bottom surface of the light guide plate 10 may further form a reflective layer (not shown). The reflective layer can be made of a metal material such as silver, aluminum, gold, or the like. In addition, a plurality of diffusion points (not shown) may be formed on the bottom surface of the light guide plate 10 for diffusing light. These diffusion points can be formed by screen printing or other means from high reflectivity ink materials such as titanium dioxide or ceria. These diffusion points can be arranged in a specific pattern to achieve different astigmatism effects. The function of the light guide plate 10 is to adjust the direction of the light emitted from the level of the light-emitting diode 20 to propagate upward.

These light-emitting diodes 20 are disposed in the vicinity of the light incident surface 12 of the light guide plate 10. Each of the light-emitting diodes 20 in this embodiment is a blue light-emitting diode using a blue light-emitting chip (not shown). The blue light-emitting chip can be made of a semiconductor light-emitting material such as gallium nitride, indium gallium nitride or aluminum indium gallium nitride. The light emitting diode 20 is directed to the light incident surface 12 of the light guide plate 10 to inject light into the light guide plate 10. The light-emitting diode 20 can be directly bonded to the light-incident surface 12 of the light guide plate 10, or can be bonded by a transparent gel (not shown) to reduce the loss of light during propagation.

The diffusion plate 30 is disposed above the light guide plate 10. The diffusion plate 30 may be made of polycarbonate or polymethyl methacrylate doped with diffusion particles. The diffusing plate 30 diffuses the light incident from the light-emitting surface 14 of the light guide plate 10 by the diffusing particles inside, and causes the light to be uniformly emitted from the light-emitting surface 34 toward the cymbal 40.

The crotch panel 40 is disposed above the diffuser plate 30. The cymbal sheet 40 may be made of a transparent material such as a polyester or polycarbonate. The crotch panel 40 is formed with a plurality of continuous triangular corners (not shown) on its light exit surface 44. The spacing between adjacent vertex vertices is preferably between 24 μm and 110 μm, and the angle of each corner is preferably between 90 and 110 degrees. The cymbal 40 is used to adjust the angle of the light incident from the diffuser plate 30, and collimate the light scattered by the diffuser plate 30 to be defined to be emitted within a specific viewing angle range, thereby increasing the luminance in the range of the viewing angle. Each corner of the cymbal 40 is coated with a layer of yellow phosphor 60 for varying the color of the output light. In the embodiment, the yellow phosphor powder 60 may be made of a fluorescein material having a radiation spectrum such as yttrium aluminum garnet, citrate compound, nitride or oxynitride in a yellow light band. Since the light is reflected and refracted multiple times on the edges to achieve the collimation effect, the yellow light emitted by the yellow phosphor 60 applied to each corner can be sufficiently mixed with the blue light to obtain uniformity. High white light. Further, since the area of the light-emitting surface 44 of the cymbal 40 is much larger than the area of the light-emitting diode 20, the yellow phosphor powder 60 can be applied more uniformly, thereby further ensuring uniformity of light mixing. Of course, the position of the yellow phosphor 60 is not limited to the corners on the light-emitting surface 44 of the cymbal 40, and it can also be applied to the light-incident surface 42 of the cymbal 40, which can also achieve the purpose of uniform light mixing.

The polarizing plate 50 is located above the cymbal 40. The polarizing plate 50 is composed of a multi-layer composite film for polarizing the light output from the cymbal 40 to cause light in a certain polarization direction. Pass through to filter light in other directions.

It can be understood that the above yellow phosphor powder 60 can also be applied to the light incident surface 32 of the diffusion plate 30 as shown in FIG. 2 . Uniform light mixing can also be achieved by multiple refractions and reflections of light in the diffuser plate 30. In addition, in order to compensate for the problem of insufficient color rendering of the yellow-blue synthesized white light, a light-emitting surface 44 or a light-incident surface 42 of the cymbal 40 may be coated with a layer of red phosphor 62 (Fig. 2 is coated on the cymbal). 40 on the light surface 44). The red phosphor powder 62 can be made of a phosphor material having an emission spectrum of an alkaline earth metal sulfide, a zinc sulfide type sulfide, a niobate compound, an aluminate compound, or an oxynitride in a red light band. By adding red phosphor powder 62, the color rendering of the final white light can be raised from the original 70 to 80 up and down.

It can also be understood that in order to further improve the color rendering of the output white light, white light can also be synthesized by mixing RGB three primary colors. For example, red fluorescent light may be applied to any two of the light-emitting surface 34 and the light-incident surface 32 of the diffusing plate 30, the light-emitting surface 44 of the cymbal 40, the light-incident surface 42 and the light-emitting surface 14 of the light guide plate 10, respectively. Powder 62 and green phosphor 64. One of the various combinations described above is shown in FIG. 3, that is, the red phosphor powder 62 is located on the light exit surface 44 of the web 40, and the green phosphor powder 64 is located on the light exit surface 14 of the light guide plate 10. The green phosphor powder 64 can be made of a fluorescent material such as yttrium aluminum garnet, an aluminate compound, a nitride, or an oxynitride in a green light band. Through the combination of three kinds of light, red, green and blue, the color rendering of the output white light can be increased to 90~100, so as to adapt to the lighting requirements of certain display screens.

Further, the above various phosphors 60, 62, 64 may be previously doped inside the respective elements during the manufacturing process described above, and are not limited to being applied to the surfaces of the respective elements.

In addition, in each of the above embodiments, the light-emitting diodes 20 are provided in a side-emitting manner. Therefore, the light guide plate 10 is required to change the light direction of the light-emitting diode 20 so as to be emitted upward. It can be understood that the light emitting diode 20 can also be disposed in a direct type, even if the light emitting direction of the light emitting diode 20 is directly upward, thereby eliminating the light guide plate 10, and further saving cost.

In summary, the present invention complies with the requirements of the invention patent and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims.

10‧‧‧Light guide plate

12‧‧‧Into the glossy surface

14‧‧‧Glossy

20‧‧‧Lighting diode

30‧‧‧Diffuser

32‧‧‧Into the glossy surface

34‧‧‧Glossy

40‧‧‧ Picture

42‧‧‧Into the glossy surface

44‧‧‧Glossy

50‧‧‧Polar plate

60‧‧‧Yellow Fluorescent Powder

Claims (8)

A backlight module includes a light emitting diode, a diffusing plate, a cymbal piece and a polarizing plate, and the light emitted by the light emitting diode is emitted through the diffusing plate, the cymbal piece and the polarizing plate, and the improvement is that the cymbal piece is located in the light emitting diode The surface of the light propagation path is provided with phosphor powder, and the light-emitting surface of the bracts has a plurality of corners, and the phosphor powder is disposed on the edges and corners, and the phosphor powder on the adjacent corners is discontinuously distributed. The backlight module of claim 1, wherein the radiation spectrum of the phosphor disposed on the exit surface of the cymbal is in the yellow light band. The backlight module of claim 1, wherein the diffusing surface of the diffusing plate is also provided with phosphor powder. The backlight module of claim 3, wherein the radiation spectrum of the phosphor powder on the light incident surface of the diffusing plate is in the yellow light band. The backlight module of claim 4, wherein the radiation spectrum of the phosphor powder disposed on the surface of the cymbal is in the red light band. The backlight module of claim 1, further comprising a light guide plate disposed on a side of the light guide plate adjacent to the light guide plate. The backlight module of claim 6, wherein the light-emitting surface of the light guide plate is provided with green phosphor powder, and the phosphor powder disposed on the surface of the breeze sheet is red phosphor powder. The backlight module of any one of claims 1 to 7, wherein the light emitting diode is a blue light diode.