JP2009212275A - Backlight source for liquid crystal display device - Google Patents

Abstract

A light-emitting diode light source used in a conventional backlight for a liquid crystal display device needs to have a certain size or more in order to perform color mixing, which has hindered miniaturization or thinning of the liquid crystal display device.
Blue, green and red light are composed of a blue light source using a blue light emitting diode, a green light source combining a blue light emitting diode and a green phosphor, and a red light source combining a blue light emitting diode and a red phosphor. These are one package covered with a diffusion layer.
[Selection] Figure 1

Description

  The present invention relates to a backlight light source for a liquid crystal display device using a light emitting diode. More specifically, the present invention relates to a backlight light source for a liquid crystal display device using a light emitting diode capable of emitting a plurality of colors by combining a phosphor and a light emitting diode.

  Conventionally, a cold cathode tube has been used as a backlight source used in a liquid crystal display device. However, the cold cathode tube has problems that Hg is used, power consumption is large, and it is difficult to make it thinner. Therefore, in recent years, the use of light emitting diodes that can solve this problem in place of cold cathode tubes is increasing.

  Among light sources using light-emitting diodes, development of white light-emitting diodes that combine phosphors and light-emitting diode elements is particularly active. In addition, various phosphor components have been devised so that light other than white can be emitted.

Patent Document 1 discloses an RGB light source including a blue light source using a blue light emitting diode element, a green light source combining a blue light emitting diode element with a green phosphor, and a red light source combining a blue light emitting diode element with a red phosphor. Has been. This light source has the advantage of suppressing chromaticity changes due to temperature rise.
JP 2006-309209 A

  The technique described in Patent Document 1 does not have a configuration for use in a backlight for a liquid crystal display device in mind. Therefore, when the distance from the light source to the light guide plate, which is one of the components constituting the backlight light source, is short, there is a problem that the color mixing property of each color of blue, green, and red deteriorates.

  In the present invention, the above-described problems have been solved by the structure described in the claims. That is, the present invention relates to a first light source including a first blue light emitting diode element, a second blue light emitting diode element, and a second blue light emitting diode element covering the second blue light emitting diode element. A phosphor that emits green upon being excited by blue light; a third blue light emitting diode element that covers a third blue light emitting diode element; and a third blue light emitting diode element that covers the third blue light emitting diode element. A light source including a third light source including a phosphor that is excited by blue light and emits red, and a first light source, a second light source, and a diffusion layer covering the third light source.

  With the configuration of the present invention, it is possible to obtain a light source with good color mixing of light of each color even if the distance to the light guide plate is short, while maintaining the advantage of suppressing chromaticity change due to temperature rise, and thus a liquid crystal display device. Can be made thinner and smaller. In addition, since all the blue light emitting diode elements are in a thermally coupled state and the temperature difference between the blue light emitting diode elements is reduced, the change in light emission efficiency between chips due to the temperature difference is reduced.

  FIG. 1 shows the basic configuration of the present invention. At least three blue light emitting diode elements 1 are arranged on the substrate 6. On the substantial light emitting surface of the blue light emitting diode element 1, a color conversion layer made of a phosphor that absorbs blue light emitted from this element and converts it into a different light emission color is formed. In this example, a green phosphor layer 2 that performs color conversion from blue light to green light and a red phosphor layer 3 that performs color conversion from blue light to red light are disposed. The blue light directly emitted from the blue light emitting diode element 1 (from the blue light emitting diode element at the center in FIG. 1) and the green light and the red light color-converted by the phosphor from the blue light are mixed to obtain white light. Each phosphor layer is formed using a so-called printing method using a stencil or the like, a spray method, or the like so as to substantially cover the light emitting surface of each corresponding blue light emitting diode element 1.

  The three blue light emitting diode elements 1 in FIG. 1 are wired so that they can be driven individually, and are individually wired when it is necessary to dimm the luminescent color or to shine each luminescent color independently. . In this example, it is a so-called 3in1 configuration in which one light source is included in one package for each color of blue, green, and red. However, when it is desired to obtain a stronger green light emission intensity, a configuration called 4in1 in which another green light emission part is added may be used. Although the reflection ring 5 is shown in the figure, this is mainly for reflecting the emitted light in the lateral direction in the front direction (upward in the figure), and is not an essential component.

  In the configuration of FIG. 1, the periphery of the light emitting portion is further covered with a diffusion layer 4 containing a diffusion material. As for the shape of the diffusion layer 4, the shape of the light emitting surface on the upper surface may be smooth as shown in FIG. 1. Further, even if the light emitting diode elements are bridged by the diffusion layer 4 as shown in FIG. 2, the three light emitting diode elements 1 are covered with the diffusion layers as shown in FIG. 3, and the green phosphor layer is formed thereon. 2. A red phosphor layer 3 may be disposed. Further, although not shown, for example, it may be a dome shape or a so-called crisp shape in which the linear axis direction is aligned with the arrangement of the blue light emitting diode elements 1.

As the blue light emitting diode element 1, a gallium nitride compound semiconductor light emitting element can be preferably used. The emission wavelength is about 450 to 470 nm. In addition, the green phosphor layer 2 excited by this element is obtained by mixing, for example, (Ba, Ca) ₂ SiO ₄ : Eu or (Ca, Sr) Ga ₂ S ₄ : Eu with an appropriate binder resin such as silicone. Can be used. Furthermore, the red phosphor layer 3 is, for example CaAlSiN 3: _Eu-or sialon-based phosphor or the like can be used a mixture in silicones suitable binder resin.

The diffusion layer 4 may be a mixture of SiO ₂ particles, Al ₂ O ₃ particles, TiO ₂ particles and the like having an average particle diameter of about 5 to 50 μm in a binder resin such as silicone or epoxy. The reflection ring 5 may be made of ceramic such as AlN or Al ₂ O _3, metal whose surface is coated with a metal having high reflectivity such as aluminum or silver, and the like. Furthermore, the substrate 6 can be a ceramic or metal substrate.

It is one Embodiment of this invention. It is a modification of this invention. It is another modification of this invention.

DESCRIPTION OF SYMBOLS 1 Blue light emitting diode element 2 Green fluorescent substance layer 3 Red fluorescent substance layer 4 Diffusion layer 5 Reflecting ring 6 Board | substrate

Claims (1)

A first light source comprising a first blue light emitting diode element;
A second light source comprising: a second blue light-emitting diode element; and a phosphor that covers the second blue light-emitting diode element and emits green when excited by blue light from the second blue light-emitting diode element;
A third light source comprising: a third blue light emitting diode element; and a phosphor that coats the third blue light emitting diode element and emits red light when excited by blue light from the third blue light emitting diode element;
A light source including a first light source, a second light source, and a diffusion layer covering the third light source.

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