1. Technical Field
The disclosure generally relates to a backlight module, and more particularly, to a backlight module incorporating a light-diffusion and light-conversion plate.
2. Description of Related Art
Nowadays LEDs (light emitting diodes) are applied widely in displays for illumination. A type of display, generally called direct-light display, uses a plurality of LEDs to directly illuminate the screen thereof. The LED often includes a blue light-emitting chip, an encapsulant sealing the chip and a yellow phosphor layer doped in the encapsulant and covering the chip. Thus, blue light emitted from the chip can activate the phosphor to emit yellow light, which mixes with the blue light to produce white light.
However, the blue light emitted from the chip passes through the phosphor layer in different pathways. A part of the blue light having a large light-emergent angle may activate more phosphor in a long pathway to produce more yellow light, while another part of the blue light having a small light-emergent angle may activate less phosphor in a short pathway to produce less yellow light. Thus, the blue light and the yellow light cannot be mixed uniformly, resulting in color aberration of the white light.
Furthermore, a lens may be mounted over the LED for diffusing the white light emitted from the LED. Nevertheless, the lens has different light-refraction levels for the blue light and the yellow light. As a result, the blue light and the yellow light are refracted by the lens to be separated from each other, thereby aggravating the color aberration of the white light. When such white light emitted from the LED is used to be diffused by a diffusion plate to illuminate a screen of a display such as an LCD (liquid crystal display), the color aberration of the white light causes the color of the image shown on the screen to be distorted.
What is needed, therefore, is a backlight module which can address the limitations described.
Many aspects of the present embodiments can be better understood with reference to the following drawing. The components in the drawing are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawing, like reference numerals designate corresponding parts throughout the view.
The only one drawing FIGURE shows a backlight module and a screen in accordance with an embodiment of the present disclosure.
Referring to
The backlight module includes a board 20, an LED 30 mounted on a top face of the board 20, a lens 40 fixed on the top face of the board 20 and covering the LED 30 and a diffusion and conversion plate 50 above the lens 40.
The board 20 may be a circuit board for supplying power to the LED 30. Preferably, the board 20 may be a metal-core circuit board which has a metal plate sequentially covered by an insulating layer and an electrical route (not shown). Thus, the board 20 can further provide heat dissipation for the LED 30 mounted thereon.
The LED 30 includes a base 36, a light-emitting chip 32 mounted on the base 36 and an encapsulant 34 sealing the chip 32. The base 36 may be made of heat conductive and electrical-insulating materials such as ceramic. The chip 32 may be made of semiconductor materials such as GaN, InGaN, AlInGaN. The chip 32 emits blue light when powered. The encapsulant 34 may be made of transparent materials such as silicone, polycarbonate or polymethylmethacrylate. The encapsulant 34 is attached on the base 36 to seal the chip 32 from an outside environment.
The lens 40 is made of transparent materials such as silicone, glass, polycarbonate or polymethylmethacrylate. The lens 40 has a light-incident face 42, a light-emergent face 44 opposite to the light-incident face 42 and a supporting face 46 connecting the light-incident face 42 and the light-emergent face 44. In this embodiment, the light-incident face 42 is a concave face, the light-emergent face 44 is a convex face, and the supporting face 46 is a flat face. The light-incident face 42 has a curvature larger than that of the light-emergent face 44. The supporting face 46 of the lens 40 is attached on the top face of the board 20 to fix the lens 40 over the LED 30. The lens 40 can diffuse the blue light from the LED 30 towards the diffusion and conversion plate 50.
The diffusion and conversion plate 50 may be made of transparent materials such as polymethylmethacrylate or polystyrene by injection-molding. The diffusion and conversion plate 50 includes a plurality of light-diffusion particulates 52 and phosphor particulates 54 doped therein. The light-diffusion particulates 52 may be made of silicone, polymethylmethacrylate, polystyrene or the like. An average diameter of the light-diffusion particulates 52 may range between 0.5 μm-20 μm. The phosphor particulars 54 may be made of YAG (Yttrium aluminum garnet), silicate or other suitable materials which can emit yellow light when excited by the blue light from the LED 30. Alternatively, the phosphor particulates 54 may also be made of two different materials which can emit red and green light when excited by the blue light from the LED 30. Thus, the red and green light excited from the phosphor particulates 54 can mix with the blue light to generate white light having a high color rendering index. The phosphor particulates 54 may have an average diameter ranging between 1 μm˜20 μm. In this embodiment, the average diameter of the phosphor particulates 54 is larger than that of the light-diffusion particulates 52. The light-diffusion particulates 52 and the phosphor particulates 54 may be dipped in a liquid material of the diffusion and conversion plate 50 before molding the diffusion and conversion plate 50, and then churned together with the liquid material of the diffusion and conversion plate 50. Thus, the light-diffusion particulates 52 and the phosphor particulates 54 are uniformly distributed in the liquid material of the diffusion and conversion plate 50. Finally, the liquid material of the diffusion and conversion plate 50 is injected into a mold and cured therein to form the diffusion and conversion plate 50 containing therein the uniformly distributed light-diffusion particulates 52 and phosphor particulates 54. The light-diffusion particulates 52 and the phosphor particulates 54 are totally doped in an interior of the diffusion and conversion plate 50 without covering any surface of the diffusion and conversion plate 50.
When the LED 30 is activated, the blue light is generated. The blue light passes through the lens 40 towards the diffusion and conversion plate 50 and is diffused beforehand by the lens 40. After entering the diffusion and conversion plate 50, the blue light strikes the light-diffusion particulates 52 and is reflected and refracted by the light-diffusion particulates 52 to diffuse towards various directions. The diffused blue light excites the phosphor particulates 54 to generate yellow light. The yellow light further strikes the light-diffusion particulates 52 to diffuse towards various directions. The blue light and the yellow light can sufficiently mix with each other after multiple striking with the light-diffusion particulates 52. Thus, the white light mixed by the blue light and yellow light in the diffusion and conversion plate 50 can have a high uniformity.
Since the blue light and the yellow light are diffused multiple times by the light-diffusion particulates 52 in the diffusion and conversion plate 50, they can be sufficiently mixed to produce uniform white light. Thus, color aberration of the white light is reduced or even prevented.
It is to be understood, however, that even though numerous characteristics and advantages of the present embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Number | Date | Country | Kind |
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101144664 | Nov 2012 | TW | national |