JP2009194161A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projection image display device which has a superior color reproduction range and stability of display colors, can be made compact, and can have sufficient on-screen luminance. <P>SOLUTION: The image display device includes a plurality of light sources emitting light beams having different wavelengths. The image display device further includes, as the light sources: a first light source comprising a semiconductor laser device emitting red light; a second light source comprising a semiconductor laser device emitting blue light; and a third light source which includes a semiconductor laser device emitting pump light and a β type sialon phosphor absorbing the pumping light and emitting fluorescent light, and which emits green light in which the pump light has a shorter wavelength than the fluorescent light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a projection type image display apparatus using a wavelength conversion material.

  In recent years, competition has intensified in the field of development of projection-type image display devices. Various types of projection-type image display apparatuses have been proposed so far, but no system that satisfies brightness, color stability, and color reproducibility (NTSC ratio) at the same time has been found.

  Currently, a discharge lamp such as a high-pressure mercury lamp is mainly used as a projection light source in a projection-type image display device as disclosed in Japanese Patent Application Laid-Open No. 2000-347153 (Patent Document 1). Although these projection light sources have the advantage of high brightness, they have a problem that they have a short lifespan and have a poor color reproducibility (NTSC ratio) because the red reproduction range cannot be expanded so much.

  Therefore, a projection-type image display device in which a high-pressure mercury lamp and a red semiconductor laser device are combined with a projection light source has been proposed as disclosed in JP-A-2005-25101 (Patent Document 2). However, the projection-type image display device as shown in Patent Document 2 has a complicated structure, and the high-pressure mercury lamp is a white light source. Therefore, a dichroic mirror for separating light into the three primary colors of light is used. A color separation illumination optical system is required, and it is difficult to reduce the size of the projection type image display apparatus.

In order to overcome such problems, there has been proposed a laser display type projection type image display apparatus using laser light of at least three primary colors of red, green and blue which can be primary colors for color expression for image formation. . As a light source for emitting the laser light, a gas semiconductor laser device and a semiconductor laser pumped SHG (second harmonic generation) solid-state semiconductor laser device have been proposed. Here, among the three primary colors of light, a light source that emits green laser light is not practically used, so an SHG solid-state laser is used. However, the gas semiconductor laser device has a problem that the energy conversion efficiency is generally as low as about 0.1% and a cooling mechanism is required. As a result, the projection type image display device becomes large and expensive. On the other hand, in the semiconductor laser pumped SHG solid-state semiconductor laser device, noise is generated in the laser beam as the output is increased, which causes problems in terms of efficiency, size reduction, and cost.
JP 2000-347153 A JP 2005-25101 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a projection that is excellent in color reproduction range and stability of display color, and that can achieve downsizing and sufficient on-screen luminance. Type image display device.

  In order to solve the above-mentioned problems, the present inventors use, for example, a red semiconductor laser diode as a red light source, a blue semiconductor laser diode as a blue light source, and a semiconductor laser device that emits excitation light as a green light source, When using a light source combined with a β-sialon phosphor that absorbs light and emits longer-wavelength fluorescence than the excitation light, it achieves excellent on-screen brightness and excellent color reproduction range and display color stability. It has been found that a possible projection type image display device is realized. That is, the present invention is as follows.

  The present invention is an image display device including a plurality of light sources that emit light of different wavelengths, and the light source emits blue light and a first light source that is a semiconductor laser device that emits red light. A second light source composed of a semiconductor laser device, a semiconductor laser device that emits excitation light, and a β-sialon phosphor that absorbs excitation light and emits fluorescence, and the excitation light has a shorter wavelength than fluorescence. And a third light source that emits green light.

  In the image display device of the present invention, it is preferable that the excitation light has a peak wavelength in a wavelength range of 380 nm to 460 nm, and it is particularly preferable that the excitation light has a peak wavelength in a wavelength range of 390 nm to 410 nm. .

  In the image display device of the present invention, the semiconductor laser device that emits excitation light is preferably a laser diode.

  In the image display device of the present invention, the β-type sialon phosphor is preferably a solid solution in which Eu is dissolved.

  In the image display device of the present invention, the β-type sialon phosphor is preferably a solid solution having an oxygen content of 0.8% by mass or less.

  In the image display device of the present invention, the fluorescence preferably has a peak wavelength in the range of 520 nm to 550 nm, and the fluorescence particularly preferably has a peak wavelength in the range of 520 nm to 535 nm.

  In the image display device of the present invention, the β sialon phosphor preferably has a full width at half maximum of the emission spectrum of 55 nm or less.

  If it is the said structure, since the semiconductor laser apparatus is used for the light source, size reduction of an apparatus can be implement | achieved and sufficient on-screen brightness | luminance can be implement | achieved. In addition, since a two-color laser light source that can be a primary color for color expression and a high-luminance light source that combines a laser light source and a phosphor are used, color reproducibility is improved.

  Since the image display device of the present invention uses a semiconductor laser device as a light source, the image display device can be reduced in size and sufficient on-screen luminance can be realized.

  The image display device of the present invention is a combination of a first light source and a second light source, each composed of a semiconductor laser device that emits two primary colors of light that can be primary colors for color expression, and a semiconductor laser device and a phosphor. Since a high-intensity light source including the third light source is provided, color reproducibility is good.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. In addition, dimensional relationships such as length, size, and width in the drawings are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensions.

FIG. 1 is a schematic diagram illustrating an image display apparatus according to the present embodiment.
Hereinafter, a description will be given based on FIG.

  The image display apparatus of this embodiment includes at least a plurality of light sources that emit light of different wavelengths. The light sources include a first light source 1a that emits red light, a second light source 1b that emits blue light, and a third light source 1d that emits green light. The first light source 1a and the second light source 1b are composed of a semiconductor laser device, the third light source 1d is a semiconductor laser device 1c that emits excitation light, and a β-type sialon that absorbs the excitation light and emits fluorescence. And phosphor 2. In the present embodiment, the β-type sialon phosphor 2 is supported by the mold resin 3. The excitation light has a shorter wavelength than the fluorescence.

  In the image display apparatus according to the present embodiment, as shown in FIG. 1, each light source is installed around a dichroic prism 4 that combines the first light source 1a, the second light source 1b, and the third light source 1d. The projection lens 5 is installed on the remaining surface. Then, white light for projection is emitted from the projection lens 5. However, the form of the present invention is not particularly limited as long as the light source includes at least the first light source 1a, the second light source 1b, and the third light source 1d. Therefore, for example, the first light source 1a and the second light source 2b are used as light sources, whether it is a transmissive image display device such as a liquid crystal television or a projection image display device such as a liquid crystal projection. By providing the third light source 3c, the image display device of the present invention is configured.

  In the present embodiment, of the light sources, only the third light source 1d that emits green light is a combination of the semiconductor laser device 1c and the β-type sialon phosphor 2. The β-type sialon phosphor 2 absorbs excitation light and emits green fluorescence. There are a plurality of phosphors that emit green fluorescence. In the present embodiment, the β-sialon phosphor 2 is selected among them. In the present embodiment, the third light source 1d is used because the phosphor has a light emission peak wavelength in a wavelength range of 520 nm or more and 550 nm or less and a sharp emission spectrum whose full width at half maximum is 55 nm or less. This is because it is preferable to select the β-type sialon phosphor 2 as a constituent.

  By adopting the above configuration, it is possible to provide an image display device with high luminance and good color reproducibility.

  Hereafter, the NTSC ratio is the NTSC (National) of the area of a triangle obtained by connecting the chromaticity coordinates of red, green, and blue colors in the CIE1976UCS chromaticity coordinates (u ′, v ′) in the CIE1976 color system. The chromaticity coordinates (u ′, v ′) (red (0.498, 0.519), green (0.076, 0.576), blue (0) of each color of red, green, and blue determined by the Television System Committee .152, 0.196)) is the ratio to the area of the triangle obtained.

  In the present invention, the light wavelength is a value measured with a fluorescence spectrum measuring apparatus MCPD-7000 manufactured by Otsuka Electronics.

<First light source>
In the present embodiment, the first light source 1a is a semiconductor laser device, and is particularly preferably a semiconductor laser device. A semiconductor laser diode is preferably selected as the semiconductor laser device. The first light source 1a emits red light. Here, in the present invention, red light means light having a wavelength of 600 nm or more and 750 nm or less.

  Since the semiconductor laser device as the first light source 1a directly emits red light, it is not particularly necessary to adjust the emission wavelength with a phosphor or the like.

As the first light source 1a, for example, a general formula of In _x (Ga _{1 -y} Al _y ) _1-x P (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1 on a GaAs substrate is used. ) Can be selected.

<Second light source>
In the present embodiment, the second light source 1b is a semiconductor laser device. A semiconductor laser diode is preferably selected as the semiconductor laser device. The second light source 1b emits blue light. Here, in the present invention, blue light refers to light having a wavelength of 430 nm or more and 490 nm or less.

  Since the semiconductor laser device as the second light source 1b directly emits blue light, it is not particularly necessary to adjust the emission wavelength with a phosphor or the like.

The second light source 1b, for example, GaN, Si, SiC, In x Al y Ga 1-xy N (0 ≦ x ≦ 1,0 ≦ y ≦ 1,0 ≦ on a substrate made of Al ₂ O ₃ A semiconductor layer having a general formula of x + y ≦ 1) is stacked. The well layer of the active layer is made of In _x Ga _1-x N (0.05 ≦ x ≦ 0.20), and the active layer is The first and second barrier layers made of In _x Ga _1-x N (0 ≦ x ≦ 0.1) can be selected.

<Third light source>
The third light source 1d of this embodiment includes the semiconductor laser device 1c and the β-type sialon phosphor 2 supported by the mold resin 3 as described above. The wavelength of the excitation light emitted from the semiconductor laser device 1c is shorter than the fluorescence emitted by the β-type sialon phosphor 2 by absorbing the excitation light. The third light source emits green light. Here, in this invention, green light shall mean light with a wavelength of 520 nm or more and 550 nm or less.

The semiconductor laser device 1c is particularly preferably a semiconductor laser diode. When the semiconductor laser device 1c is a semiconductor laser diode, for example, the well layer of the active layer is Al _x In _y Ga _1-xy N (0 ≦ x ≦ 0.1, 0 ≦ y ≦ 0.15). , X + y <1), and the first and second barrier layers sandwiching the active layer are Al _x In _y Ga _1-xy N (0 ≦ x ≦ 0.25, 0 ≦ y ≦ 0.1, x + y <1) can be selected. This is because in this embodiment, by using such a semiconductor laser diode, a peak wavelength can be obtained in a wavelength range of 380 nm to 460 nm. The excitation light emitted from the semiconductor laser device 1c in the present embodiment preferably has a peak wavelength in the range of 380 nm to 460 nm, and particularly preferably has a peak wavelength in the range of 390 nm to 410 nm. This is because when the peak wavelength of the excitation light emitted from the semiconductor laser device 1c is less than 380 nm, the energy as ultraviolet light increases, and the mold resin 3 may be greatly deteriorated, and the peak wavelength of the excitation light is 460 nm. This is because if it exceeds, the overlap between the emission spectrum of the semiconductor laser device 1c and the emission spectrum of the β-type sialon phosphor 2 becomes large, which may reduce the NTSC ratio.

  As the β-type sialon phosphor 2, it is preferable to select one that is efficiently excited by near-UV to blue excitation light from 350 nm to 470 nm, and Eu-activated β-type that is a solid solution in which Eu is dissolved. It is preferable to select a sialon phosphor. The β-type sialon phosphor 2 of the present embodiment has Eu and Si, Al, O, and N elements in a specific composition region range, a specific solid solution state, and a specific crystal phase, and has a wavelength of 520 nm or more. A phosphor having a sharp emission peak in a range of 550 nm or less is preferable. If the emission peak is less than 520 nm, the overlap between the emission spectrum of the second light source 1b and the emission spectrum of the β-type sialon phosphor 2 may increase, possibly reducing the NTSC ratio, exceeding the wavelength of 550 nm. In this case, the overlap between the emission spectrum of the first light source 1a and the emission spectrum of the β-type sialon phosphor 2 is increased, which may reduce the NTSC ratio.

The β-sialon phosphor 2 of the present embodiment is preferably one in which a nitride or oxynitride having a β-type Si ₃ N ₄ crystal structure is used as a base crystal and a divalent Eu ion is added as an emission center. And it is especially preferable that the fluorescence emitted from the β-type sialon phosphor 2 has a peak wavelength in the wavelength range of 520 nm to 535 nm. Further, the β-type sialon phosphor preferably has a full width at half maximum of the emission spectrum of the emitted fluorescence of 55 nm or less. This is because the color reproducibility (NTSC ratio) can be further increased.

  In addition, the β-type sialon phosphor is preferably a solid solution prepared so that the oxygen content contained in the crystal constituting the phosphor is 0.8% by mass or less. The oxygen content can be measured with a TC436 type oxygen-nitrogen analyzer manufactured by LECO. This is because if the oxygen content exceeds 0.8% by mass, the full width at half maximum of the fluorescence emission spectrum may increase. Thus, the β-sialon phosphor 2 in which the amount of oxygen in the crystal is adjusted is particularly preferable because it has an effect of reducing the full width at half maximum of the fluorescence emission spectrum.

Examples of the Eu-activated β-sialon phosphor described above include, for example, a metal compound powder containing an optically active element Eu such as Eu ₂ O ₃ and EuN, an aluminum nitride (AlN) powder, and a silicon nitride powder (Si ₃ N ₄ ) can be uniformly mixed and fired at a temperature of about 1800 to 2000 ° C. The mixing ratio of these raw material powders is appropriately selected in consideration of the composition ratio of the phosphor after firing.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Example 1>
Hereinafter, a description will be given based on FIG. In this example, a laser diode having an emission peak wavelength at 630 nm was used as the first light source 1a, and a laser diode having an emission peak wavelength at 450 nm was used as the second light source 1b. As the third light source 1d, a laser diode having an emission peak wavelength at 405 nm is used as the semiconductor laser device 1c, and a composition represented by Eu _0.027 Si _12.15 Al _0.49 O _0.04 N _15.32 is used as the β-type sialon phosphor 2. A silicone resin was used as the mold resin 3. Further, the β-type sialon phosphor 2 was dispersed in the mold resin 3 so that β-type sialon phosphor: mold resin = 1: 18 (mass ratio).

  A rectangular parallelepiped dichroic prism 4 was prepared, and the first light source 1a, the second light source 1b, and the third light source 1d were arranged as shown in FIG. The dichroic prism 4 was installed so that the projection lens 5 came to one surface where no light source was arranged.

An image display device was manufactured as described above.
<Comparative Example 1>
In this comparative example, an LED (light emitting diode) having an emission peak wavelength at 630 nm is used instead of the first light source 1a in Example 1, and an LED having an emission peak wavelength at 450 nm is used instead of the second light source 1b. An image display device was produced in the same manner as in Example 1 except that was used.

<Comparative Example 2>
In this comparative example, a high-pressure mercury lamp (manufactured by Philips) was used as the light source in place of the first light source 1a, the second light source 1b, and the third light source 1d in the first example. An image display device was produced in the same manner as described above. The high-pressure mercury lamp was installed so that the emitted white light was separated into the three primary colors of red, green and blue and then synthesized again by the dichroic prism.

<Examination results>
FIG. 2 is a diagram illustrating an emission spectrum emitted from the projection lens when the image display apparatus in Example 1 is driven. FIG. 3 is a diagram illustrating an emission spectrum emitted from the projection lens when the image display apparatus in Comparative Example 1 is driven. FIG. 4 is a diagram showing an emission spectrum emitted from the projection lens when the image display device in Comparative Example 2 is driven.

  Table 1 shows the NTSC ratio at the white point (u ′, v ′) = (0.206, 0.475) of the image display devices of Example 1 and Comparative Examples 1-2.

  First, FIG. 2 shows that the emission intensity of Example 1 is higher than that of Comparative Example 1 and has high luminance. From Table 1, the image display device of Example 1 achieved an NTSC ratio of 103% at the white point (u ′, v ′) = (0.206, 0.475). It was also shown that the color reproduction range is excellent. Further, in Example 1 and Comparative Example 1 using a β-type sialon phosphor as a green light source, both showed an NTSC ratio exceeding 100% and an excellent color reproduction range.

  The embodiments and examples disclosed this time can be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a schematic diagram which shows the image display apparatus of embodiment in this invention. It is a figure which shows the emission spectrum emitted from a projection lens at the time of driving the image display apparatus in Example 1. FIG. It is a figure which shows the emission spectrum emitted from a projection lens at the time of driving the image display apparatus in the comparative example 1. It is a figure which shows the emission spectrum emitted from a projection lens at the time of driving the image display apparatus in the comparative example 2.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1a 1st light source, 1b 2nd light source, 1c Semiconductor laser apparatus, 1d 3rd light source, 2 beta-type sialon fluorescent substance, 3 mold resin, 4 dichroic prism, 5 projection lens

Claims (9)

An image display device comprising a plurality of light sources that emit light of different wavelengths,
The light source includes
A first light source comprising a semiconductor laser device that emits red light;
A second light source comprising a semiconductor laser device emitting blue light;
A semiconductor laser device that emits excitation light; and a β-type sialon phosphor that absorbs the excitation light and emits fluorescence. The excitation light has a shorter wavelength than the fluorescence, and emits green light. An image display device including a light source.   The image display apparatus according to claim 1, wherein the excitation light has a peak wavelength in a wavelength range of 380 nm to 460 nm.   The image display apparatus according to claim 1, wherein the excitation light has a peak wavelength in a wavelength range of 390 nm to 410 nm.   The image display device according to claim 1, wherein the semiconductor laser device that emits the excitation light is a laser diode.   The image display device according to claim 1, wherein the β-type sialon phosphor is a solid solution in which Eu is dissolved.   The image display device according to claim 1, wherein the β-type sialon phosphor is a solid solution having an oxygen content of 0.8 mass% or less.   The image display device according to claim 1, wherein the fluorescence has a peak wavelength in a wavelength range of 520 nm to 550 nm.   The image display device according to claim 1, wherein the fluorescence has a peak wavelength in a range of a wavelength of 520 nm or less and 535 nm or more.   The image display device according to claim 1, wherein the β sialon phosphor has a full width at half maximum of an emission spectrum of 55 nm or less.

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