JP2005353650A - Led optical source and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inexpensive liquid crystal display device in which a color filter usually arranged in liquid crystal is not required when a highly efficient LED optical source where loss of light is suppressed is combined with a liquid crystal panel. <P>SOLUTION: In the LED optical source formed of a light guide plate 102 and LED 101, phosphor layers 103 and 104 of a plurality of colors are periodically arranged on the surface on which light from LED 101 is radiated. The phosphor layers 103 and 104 are excited by light from LED 101 and emit light whose wavelength is converted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a low-cost liquid crystal display device that does not require a highly efficient LED light source and color filter.

  As an example of a conventional planar light source, there is one in which LED light is incident from an edge portion of a light guide plate and a phosphor is disposed on the back side of a light exit surface of the light guide plate (for example, Patent Document 1).

FIG. 7 shows a conventional LED light source and liquid crystal display device described in Patent Document 1. In FIG. In FIG. 7, light from the blue LED 1 propagates through the light guide plate 2, is wavelength-converted by the phosphor scattering layer 3, and is emitted from the surface of the light guide plate opposite to the phosphor layer.
Japanese Patent No. 2868085 (see FIG. 2)

  However, in the configuration of FIG. 7, since the light whose wavelength has been converted by the phosphor layer is emitted from the opposite surface of the light guide plate, it is emitted through at least the light guide plate. Was.

  Moreover, in order to improve the uniformity of the light emitting surface, the light diffusing plate 5 may be inserted. In this case, there is a problem that the light use efficiency is further reduced.

  In addition, when used as a liquid crystal backlight in combination with a liquid crystal, the blue LED light is converted into white by a phosphor and then color-separated by an RGB color filter in the liquid crystal, resulting in light loss in the color filter. There is also a problem.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly efficient LED light source that suppresses light loss. Alternatively, it is intended to provide a low-cost liquid crystal display device that does not require a color filter installed in the liquid crystal when combined with a liquid crystal panel.

  In order to solve the above-described conventional problems, an LED light source and a liquid crystal display device according to the present invention is a LED light source composed of a light guide plate and an LED, and a plurality of color phosphor layers are periodically formed on a surface from which light from the LED is emitted. The phosphor layer is excited by light from the LED and emits wavelength-converted light.

  In a preferred embodiment, the LED is a blue LED, the phosphor layer is excited by blue light to emit green and red, and the phosphor layer is formed on at least a part of the light guide plate. There are parts that are not.

  In a preferred embodiment, the LED is an ultraviolet LED, and the phosphor layer emits blue, green, and red when excited by ultraviolet light.

  In a preferred embodiment, the phosphor layers are arranged in a line on the surface of the light guide plate.

  In a preferred embodiment, the phosphor layers are arranged in a dot shape on the surface of the light guide plate.

  In a preferred embodiment, the LED light source is combined with a liquid crystal panel, and the position of the phosphor layer and the position of the electrode corresponding to each cell of the liquid crystal are substantially coincident.

  In a preferred embodiment, the liquid crystal display device has no color filter in each pixel.

  As described above, according to the present invention, in the LED light source including the light guide plate and the LED, the phosphor layers of a plurality of colors are periodically arranged on the surface from which the light from the LED is emitted, A highly efficient LED light source can be provided by a configuration that emits light that is excited by light from the LED and wavelength-converted.

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1)
Fig.1 (a) shows the outline of the LED light source in the 1st Embodiment of this invention. In FIG. 1A, the blue LED modules 101 are installed side by side so as to be optically coupled to the edge portion of the light guide plate 102, and blue light from the LEDs is efficiently introduced into the light guide plate 102. In addition, a heat sink 301 and a fan 302 are installed on the back surface of the blue LED module 101 to dissipate heat generated from the LED module.

  Here, the light guide plate 102 is made of a translucent material, and is made of, for example, transparent acrylic.

  In addition, a reflection plate 105 is installed in close contact with the back surface of the light guide plate 102 (in FIG. 1, it is separated but actually in close contact), and light emitted from the light guide plate 102 is returned into the light guide plate. ing.

  Phosphor layers 103 and 104 are formed on the opposite surface of the reflector 105 across the light guide plate 102. This surface is called a light emitting surface, and light from the LED is emitted from this surface.

  Here, the structure of the blue LED module 101 will be described in detail with reference to FIG. A schematic diagram is shown in FIG. FIG. 2A shows a top view of the LED module 101 (view of the light exit surface). In practice, this surface is optically coupled to the light guide plate 102. The 10 mm square LED module 101 has 16 (= 4 × 4) LED chips 201 of 0.3 mm square mounted on a substrate (not shown) of one module. A reflector 202 is installed around each LED chip, and emits light with narrow directivity so that the emitted light of the LED can be efficiently introduced into the light guide plate.

  FIG. 2B shows a cross-sectional view of the LED module. The LED chip 201 is flip-chip mounted via a bump (not shown) on a substrate 203 mainly made of a material having high thermal conductivity such as aluminum, copper, or ceramic. In addition, a reflecting plate 202 whose surface is coated with or made of a material having high reflectivity such as aluminum or silver is provided. The LED chip 201 is sealed with a sealing resin 204 (for example, silicone resin) with little light deterioration.

In addition, when an LED of about 0.3 mm square is used, it is mounted at a density of about 10 to 100 / cm ² per mounting board area. For example, if the rated power per LED is 0.1 W, the power density is about 1 to 10 W / cm ² .

Further, for example, when LEDs of about 1 mm square are used, they are mounted at a density of about 1 to 10 / cm ² per mounting board area. If the rated power per LED is 1 W, the power density is about 1 to 10 W / cm ² .

In this embodiment, 0.3 mm square LED chips are mounted at a density of 16 / cm ² .

  The heat dissipation structure of the LED module 101 configured as described above will be described in detail below. As shown in FIG. 1, a heat sink 301 and a fan 302 are installed on the back surface of the blue LED module 101. A detailed cross-sectional view is shown in FIG. The blue LED module 101 and the heat sink 301 are installed so as to be in contact with each other using silicon grease, and efficiently transmit heat from the blue LED module 101 to the heat sink. The heat sink 301 is installed so that heat is released to the air by the air blown from the fan 302. Here, the reason why the fans are arranged with almost no gap is to reduce the fan noise and reduce the amount of air blown per fan, that is, the rotational speed. Thus, noise reduction during cooling of the fan due to the configuration in which a large number of fans are rotated at a low speed is very effective.

  As described above, when the LEDs are mounted at a very high density, it is preferable to cool the LEDs as necessary in order to prevent a decrease in the luminous efficiency of the LEDs due to heat. With such a configuration, it is possible to operate the LED light source without causing a decrease in the efficiency of the LED. In addition, the groove | channel of a heat sink is formed in the substantially perpendicular direction so that the hot air in a heat sink may circulate easily at the time of use. It should be noted that the heat sink and the fan may be appropriately used depending on the amount of heat generated from the LED, and are not necessarily required.

  Next, the phosphor layers 103 and 104 formed on the exit surface of the light guide plate 102 will be described in detail. Light collected in the light guide plate 102 emits blue light from a portion where the phosphor layer is not coated, green light from the phosphor layer 103, and red light from the phosphor layer 104. The phosphor layers 103 and 104 formed on the light guide plate 102 are periodically formed throughout the light guide plate in a line with a uniform pitch or width of several tens of μm to several mm. In the case of the present embodiment, the portion having the same width of about 100 μm and not coated with the phosphor layer, the portion coated with the phosphor layer 103 that emits green light, and the phosphor layer 104 that emits red light. The painted parts are formed periodically (the emission colors are in the order of BGR). The distance between the phosphor layers 103 and 104 is about 10 μm. For example, light emission portions for 1024 cycles are formed on the light guide plate 102 with the light emission portion of the BGR as one cycle. FIG. 1B shows an enlarged view of the phosphor layer formed on the surface of the light guide plate.

  Here, the phosphor layers 103 and 104 are obtained by dispersing a phosphor in a translucent resin, and are excited by the light of a blue LED and emit light in each color. In addition, the emitted light from the phosphor layer is adjusted so that the blue light from the LED is absorbed almost without passing through the phosphor layer, and only the emission color of the phosphor is almost the same. It is. By preventing blue light from escaping in this way, it is possible to suppress a decrease in purity of light emitted from the phosphor layer and to obtain an image with high color reproducibility when combined with the following liquid crystal.

Here, the green phosphor layer 103 is selected from, for example, SrGa ₂ S ₄ : Eu ²⁺ (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ and Y ₃ Al ₅ O ₁₂ : Ce ³⁺ in a silicone resin. The phosphor contains a concentration of 2 to 50 wt%, and the thickness of the phosphor layer is 10 to 1000 μm.

The red phosphor layer 104, similarly to the resin 103, for example, _{^{CaS: Eu2 +, CaSiN 2:}} Eu 2+ and ^{_{Sr 2 Si 5 N 8: Eu}} 2+ or _{(Sr, Ca) 2 SiO 4} : from ^{Eu 2+} The phosphor contains a selected phosphor at a concentration of 1 to 50%, and the thickness of the phosphor layer is 10 to 1000 μm. The concentration of the phosphor and the thickness of the phosphor layer are appropriately adjusted according to the LED output and the light output from the exit surface of the light guide plate so that the light from the LED hardly transmits.

  In the configuration shown in FIG. 1, the LED light source can be used for general illumination. This is because the distance between the object to be irradiated and the LED light source of the present embodiment, which is about several tens of centimeters to several meters, is as short as 100 μm in the width of each emission color. Since RGB is completely mixed and becomes radiation with suppressed color unevenness, it can be sufficiently used for general illumination. In this case, an LED light source having an arbitrary color temperature and chromaticity can be obtained by adjusting the phosphor type, the phosphor concentration of the phosphor layer, and the thickness of the phosphor layer. Further, even when the light output of the LED changes, there is a feature that the color change is small because the emission of green and red from the phosphor layer is also reduced.

  When used for general illumination, blue light may be transmitted from the phosphor layer as long as the light after color mixing satisfies the target chromaticity and color temperature.

  In addition, an embodiment in combination with a liquid crystal panel will be described below. FIG. 4 shows a part of the cross section in the X direction of FIG. 1 of the liquid crystal display device when the LED light source of FIG. 1 is combined with liquid crystal. In FIG. 4, light converted into each color of GR by the phosphor layers 103 and 104 on the surface of the light guide plate 102 becomes light emission having a BGR light emission pattern. Here, each color is directly incident on each pixel of the liquid crystal panel 401 by installing so that the position of each pixel of the liquid crystal panel 401 configured in the order of BGR and the light emission pattern on the surface of the light guide plate 102 match. I can do it.

  For this reason, a color filter required for a general liquid crystal panel is not required, and a simpler structure can be achieved, thereby reducing costs. In addition, since the color filter does not absorb light, a liquid crystal display device that is highly efficient and does not generate heat in the color filter portion can be obtained.

  Here, the pixel position of the liquid crystal panel 401 and the positions of the phosphor layers 103 and 104 coincide with each other when the position of the electrode 402 arranged in each cell for driving the liquid crystal is the same as the position of the phosphor layers 103 and 104. It is that I have done.

(Embodiment 2)
Next, an LED light source and a liquid crystal display device according to the second embodiment of the present invention will be described with reference to FIG.

  The LED light source shown in FIG. 5 has the same configuration as that of the LED light source of FIG. 1, and the phosphor layers 502 and 503 have almost no gap on the light guide plate 102 in FIG. , 504 are different. The phosphor layers 502, 503, and 504 are periodically formed on the line with a uniform width or pitch. In the present embodiment, the phosphor layer 502 that emits blue light with the same width of about 100 μm. The phosphor layer 503 that emits green light and the phosphor layer 504 that emits red light are periodically formed. Each phosphor layer is installed with a distance of about 10 μm.

  The LED has an emission center wavelength of 365 to 400 nm, and the other structures such as the substrate and the reflector are the same as those shown in the first embodiment.

  Next, the phosphor contained in the phosphor layer will be described. The phosphor of the present embodiment is a phosphor that is excited by ultraviolet rays from an LED and converts into each color.

The phosphor contained in the blue phosphor layer 502 is a phosphor selected from BaMgAl ₁₀ O ₁₇ : Eu ²⁺ and (Ba, Sr, Ca, Mg) ₁₀ (PO ₄ ) ₆ C ₁₂ : Eu ²⁺ at a concentration of 2. The thickness of the phosphor layer is 10 to 1000 μm.

The phosphors contained in the green phosphor layer 503 are BaMgAl ₁₀ O ₁₇ : Eu ²⁺ , Mn ²⁺ , (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ , Y ₂ SiO ₅ : Ce ³⁺ , and Te ^3+. The selected phosphor contains a concentration of 2 to 50 wt%, and the thickness of the phosphor layer is 10 to 1000 μm.

The phosphor contained in the red phosphor layer 503 includes CaSiN ₂ : Eu ²⁺ , Sr ₂ Si ₅ N ₈ : Eu ²⁺ , (Sr, Ca) ₂ SiO ₄ : Eu ^2+, and La ₂ O ² S: Eu. A phosphor selected from ³⁺ , 3.5MgO.0.5MgF ₂ .GeO ₂ : Mn ⁴⁺ is contained at a concentration of 2 to 50 wt%, and the thickness of the phosphor layer is 10 to 1000 μm.

  The LED light source configured as described above can obtain a highly efficient light source as in the first embodiment.

  Although not shown in the figure, each color is directly incident on each pixel of the liquid crystal by matching the position of the phosphor layer and the position of each pixel (cell) of the liquid crystal as shown in FIG. 4 of the first embodiment. I can do it. For this reason, the color filter required for the liquid crystal is not required, and a liquid crystal display device having a simple structure with lower cost and no optical loss in the color filter can be obtained. In the case of the present embodiment, since BGR has 1024 lines, liquid crystal can be combined with a liquid crystal having a resolution of 1024 pixels in the direction crossing the line, and a liquid crystal display device with high definition, high efficiency, and high brightness can be obtained. I can do it. Note that the resolution in the line direction is determined by the resolution of the liquid crystal.

  In the present embodiment, an acrylic resin is used as the light guide plate material and a silicone resin is used as the LED sealing resin. However, soda glass, quartz, and the like have the same effect.

  In particular, when an ultraviolet LED is used as the LED module, it is preferable to use soda glass, quartz or the like from the viewpoint of resin deterioration.

(Embodiment 3)
Next, an LED light source and a liquid crystal display device according to a third embodiment of the present invention will be described. FIG. 6A shows the same configuration as that of the LED light source shown in FIG. 1, and only the shape of the phosphor layer formed on the surface of the light guide plate is different. FIG. 6 shows an enlarged view of the phosphor layer on the light guide plate, which is a portion corresponding to FIG. 1B of the first embodiment. The green phosphor dot layer 601 and the red phosphor dot layer 602 have a size of 100 × 300 μm and are formed in a dot shape with a thickness of 100 μm. The gap between the phosphor layers 601 and 602 is 10 μm. Even with such a configuration, the same effect as in the first embodiment can be obtained. In addition, by matching the size of the phosphor layer with the size of each color cell of the liquid crystal panel, the phosphor layer is formed corresponding to each cell. Can be solved in principle.

  In addition, although the case where the phosphor layers of the present embodiment are separated from each other with a distance of 10 μm is shown, the phosphor layers may be formed without a gap. However, when formed without gaps, the phosphor resin may be mixed at the phosphor layer interface, and the process of forming the phosphor resin becomes complicated, such as the need to form after solidifying each resin, It is preferable to form a gap of 5 μm or more between the phosphor layers. Further, as described above, light emission to the adjacent liquid crystal cell is eliminated in principle, which is preferable. Also in this case, it is preferable to form a gap of 5 μm or more between the phosphor layers.

  According to the present invention, a highly efficient LED light source can be provided.

(A) is the schematic of the LED light source in Embodiment 1 of this invention, (b) is a partially expanded view of an LED light source. (A) is the top view of the LED module part in Embodiment 1 of this invention, (b) is sectional drawing of an LED module part, (c) is the schematic of an LED module part Sectional drawing which shows the cooling structure of the LED module part in Embodiment 1 of this invention The figure which shows the cross section of the liquid crystal display device in Embodiment 1 of this invention. The figure which shows the outline of the LED light source in Embodiment 2 of this invention. The enlarged view of the light emission surface of the LED light source in Embodiment 3 of this invention The figure which shows the section of the conventional planar light source

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 LED module 102 Light guide plate 103 Green fluorescent substance layer 104 Red fluorescent substance layer 105 Reflective plate 201 LED chip 202 Reflective plate 203 Substrate 204 Sealing resin 301 Heat sink 302 Fan 401 Liquid crystal panel 402 Liquid crystal drive electrode 403 arranged in each cell Common electrode for driving liquid crystal 404 Glass 405 Liquid crystal layer 406 Glass 501 LED module 502 Blue phosphor layer 503 Green phosphor layer 504 Red phosphor layer 601 Green light emitting dot layer 602 Red light emitting dot layer 1 Blue LED
2 Light guide plate 3 Phosphor scattering layer 4 Reflecting layer 5 Light diffusion plate 6 Scattering reflecting layer 7 Al base

Claims (7)

In an LED light source consisting of a light guide plate and LEDs,
A phosphor layer of a plurality of colors is periodically arranged on the surface that emits light from the LED,
The LED light source, wherein the phosphor layer emits light that is excited by light from the LED and wavelength-converted. The LED is a blue LED,
The phosphor layer is excited by blue light and emits green and red,
The LED light source according to claim 1, wherein at least a part of the light guide plate includes a portion where the phosphor layer is not formed. The LED is an ultraviolet LED,
3. The LED light source according to claim 1, wherein the phosphor layer emits blue, green, and red when excited by ultraviolet light. 4. The LED light source according to claim 1, wherein the phosphor layers of the respective emission colors are arranged in a line on the surface of the light guide plate. 5. 4. The LED light source according to claim 1, wherein the phosphor layers of the respective emission colors are arranged in a dot shape on the surface of the light guide plate. 5. The LED light source is combined with a liquid crystal panel,
6. The liquid crystal display device according to claim 1, wherein a position of the phosphor layer and a position of an electrode corresponding to each cell of the liquid crystal substantially coincide with each other. The liquid crystal display device according to claim 6, wherein each pixel has no color filter.

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