JP2014192441A - Light-emitting device and projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light-emitting device with high luminance and a projector.SOLUTION: A light-emitting device comprises: an excitation light source consisting of a solid light-emitting element including GaN; and a phosphor layer for absorbing at least a part of excitation light emitted from the excitation light source, and emitting first light.

Description

  The present invention relates to a light emitting device and a projector.

  As light emitting devices for projectors, solid light sources such as light emitting diodes and laser diodes have been actively used. Solid light sources have excellent features such as being small and long-life, fast response speed, being able to turn on / off instantaneously, and being environmentally friendly without mercury. In particular, light-emitting diodes are inexpensive and do not generate noise due to interference, such as laser light, so they are the mainstream light source for small projectors.

JP 2005-85810 A

  Although it is a light emitting diode with the above features, since the emitted light beam per unit area is smaller than other light sources, it is necessary to increase the drive current in order to obtain high output. As the current increases, heat generation increases and the temperature of the light emitting diode increases. Along with this, there has been a problem that the luminous efficiency is lowered. In particular, the material used for red light emitting diodes (AlInGaP) has a significant efficiency drop due to temperature. In order to solve this, Patent Document 1 attempts to suppress the temperature rise by devising a cooling structure. However, since a certain amount of thermal resistance remains in the light emitting layer up to the light emitting diode mounting substrate that can be cooled from the outside, there is a limit to cooling from the outside. For this reason, there has been a problem that the drive current cannot be increased and a large emitted light beam cannot be obtained.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a high-luminance light-emitting device and a projector.

  Application Example 1 A light-emitting device of this application example emits first light by absorbing at least a part of excitation light emitted from a solid-state light-emitting element containing GaN and excitation light emitted from the excitation light source. And a phosphor layer.

  According to this configuration, the light emission efficiency decrease of the GaN-based material is small and the efficiency is maintained higher than that of the AlInGaP material system under a driving condition using a large current and a high-temperature temperature condition. Output is obtained.

  Application Example 2 In the light-emitting device according to the application example, the solid-state light-emitting element includes a light-emitting diode layer containing GaN, and the light-emitting diode layer is formed on a Ga-based substrate.

  According to this configuration, the crystal defect density of the light emitting layer is low, and high light emission efficiency can be obtained. Further, since the conductivity of the GaN substrate is high, current injection into the light emitting layer can be performed perpendicularly to the PN junction surface, so that the resistance is small and it is easy to flow a large current. Further, the amount of heat generated can be suppressed, and an output of a high luminous flux can be obtained by suppressing the temperature rise of the solid state light emitting device.

Application Example 3 In the light emitting device according to the application example described above, the Ga-based substrate may be GaN or Ga ₂ O ₃ .
According to this configuration, it is possible to obtain a film having a small crystal defect with a lattice constant close to that of the epitaxial layer containing GaN forming the light emitting diode.

Application Example 4 In the light emitting device according to the application example described above, the excitation light may be blue light or ultraviolet light.
According to this configuration, the luminous efficiency of the solid state light emitting device and the conversion efficiency by the phosphor can be increased, and high output light can be obtained. Further, it becomes easy to obtain a desired color light in the visible range.

Application Example 5 In the light emitting device according to the application example, it is preferable that the first light includes at least one of red light and green light.
According to this configuration, it becomes easy to align the three primary colors used for the display.

  Application Example 6 A projector according to this application example emits the first light source device including the light emitting device according to the application example described above and second light including a wavelength region different from the wavelength region of the first light. A second light source device, a third light source device that emits third light including a wavelength region of the first light and a wavelength region different from the wavelength region of the second light, and a first light modulation device , Second light modulator, third light modulator, light from the first light modulator, light from the second light modulator, and from the third light modulator. A cross prism for combining light and a projection optical system;

  According to this configuration, a high-luminance output can be obtained even under a large current driving condition and a high temperature operating condition by using the light emitting device using the solid light emitting element containing the GaN material and the phosphor as the light source of the projector. . In addition, when displaying white because the output of the red light source is insufficient, it is necessary to reduce the output of green and blue, but the increase in red luminous flux increases the output of green and blue during white display. The output of the projector can be increased.

  Application Example 7 A projector according to this application example emits the first light source device including the light-emitting device according to the application example described above and second light including a wavelength region different from the wavelength region of the first light. From the second light source device, the third light source device that emits third light including a wavelength region different from the wavelength region of the first light and the wavelength region of the second light, and the first light source device Color combining means for combining the light from the second light source device and the light from the third light source device, a light modulating device for modulating the light emitted from the color combining means, A projection optical system.

  According to this configuration, in particular, a field sequential color drive system in which the first to third light source devices are sequentially switched on and displayed, and an image corresponding to each light source device is displayed on the light modulation device in synchronization with the switching timing. In this case, since it is necessary to flow a large current value, the efficiency is remarkably lowered, which is an effective means for increasing the brightness.

Application Example 8 In the light emitting device according to the application example described above, the phosphor layer absorbs part of the excitation light and emits the first light, and transmits or reflects the remainder of the excitation light.
According to this configuration, since the light of the first light source device that excites the phosphor can be used, it can be used as a light source device that emits two colored lights.

Application Example 9 In the light emitting device according to the application example, the excitation light is blue light.
Thus, it can be used as blue light necessary for video display.

Application Example 10 In the light emitting device according to the application example, the first light includes at least one of red light and green light.
Thus, it can be used as blue light and another color light necessary for video display.

Application Example 11 A projector according to this application example includes a first light source device including the light emitting device according to the application example described above, and a wavelength region different from a wavelength region of light emitted from the first light source device. A second light source device that emits second light, a first light modulation device, a second light modulation device, a third light modulation device, light from the first light modulation device, and A cross prism that combines light from the second light modulation device and light from the third light modulation device; and a projection optical system.
According to this configuration, it is not necessary to separately provide a blue light source device by using the light of the excitation light source, and the optical system of the projector can be reduced in size.

Application Example 12 A projector according to this application example includes a first light source device including the light emitting device according to the application example described above, and a wavelength region different from a wavelength region of light emitted from the first light source device. A second light source device that emits second light, a color composition unit that synthesizes light from the first light source device, and light from the second light source device, and emitted from the color composition unit A light modulation device for modulating light; and a projection optical system.
According to this configuration, the configuration on the light source device side can be simplified even in the configuration of a projector using one light modulator.

It is sectional drawing which shows the structure of the light-emitting device of 1st Embodiment. It is a top view which shows the 1st structural example of the projector using the light-emitting device of 1st Embodiment. It is a top view which shows the 2nd structural example of the projector using the light-emitting device of 1st Embodiment. It is a top view which shows the 3rd structural example of the projector using the light-emitting device of 1st Embodiment. It is sectional drawing which shows the light-emitting device of 2nd Embodiment. It is a top view which shows the 1st structural example of the projector using the light-emitting device of 2nd Embodiment. It is a top view which shows the 2nd structural example of the projector using the light-emitting device of 2nd Embodiment. It is a top view which shows the 3rd structural example of the projector using the light-emitting device of 2nd Embodiment.

Hereinafter, a projector according to an embodiment of the invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiment, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

[First Embodiment]
FIG. 1 is a cross-sectional view showing the configuration of the light emitting device of this embodiment.
The light emitting device 19 of this embodiment includes a solid light emitting element 30 and a phosphor 31 that absorbs light from the solid light emitting element 30 and emits light having a wavelength different from that of the light from the solid light emitting element 30.

The solid state light emitting element 30 emits blue light (peak of emission intensity: around 460 nm). As long as the phosphor can be excited, light having a peak wavelength other than 460 nm may be emitted. For example, a material that emits ultraviolet light such as 405 nm or 365 nm may be used.
The phosphor 31 has a particulate phosphor (phosphor particle 18) that absorbs excitation light emitted from the solid state light emitting device and emits fluorescence. Depending on the type of phosphor used, green light (wavelength near 530 nm) or red light (wavelength near 630 nm) can be extracted as fluorescence.

As the phosphor particles 18, a silicon nitride material such as CaAlSiN ₃ can be used for red, and a LAG (lutetium, aluminum, garnet) phosphor can be used for green. The phosphor material is an example, and other materials can be used as long as they emit fluorescence in the green and red wavelength bands.

The phosphor particles 18 can be formed by a means of mixing with a resin 17 such as silicone, applying the mixture on the solid light emitting element 30, and then thermally curing (at 150 ° C. for 2 hours).
Here, it is desirable to use the solid light emitting element 30 obtained by epitaxially growing a light emitting diode layer on a GaN substrate. Compared with a sapphire substrate, the lattice constant is uniform, so that the crystal defect density is small and the luminous efficiency is high. Further, since the GaN substrate has high conductivity, an electrode can be formed below the GaN substrate, so that current can be injected perpendicularly to the bonding surface of the light emitting layer, and the current density can be made uniform easily. In addition, since the resistance from the n-side electrode to the light emitting layer can be reduced, it is possible to drive with a large current without increasing the amount of heat generation.

  In the first embodiment, a structure in which a GaN substrate used as a substrate for forming a light emitting diode layer is used as it is has been described. However, the present invention is not limited to this, and the light emitting diode layer is removed from the GaN substrate as necessary. It is also possible to take means for placing the layer on another ceramic substrate (such as AlN) or a metal substrate (copper). It is also effective to apply a technique used in a light emitting diode such as forming an uneven structure on the surface in order to increase the light extraction efficiency.

  Next, the configuration of the projector using the light emitting device according to the embodiment of the invention will be described with reference to FIG. In the configuration of FIG. 2, the red light source device 50R including the light emitting device using red fluorescence excited by the blue solid light emitting element is used, but the green light source device 50G is green excited by the blue solid light emitting element. A light source device that emits fluorescence may be used. The light source device 50B for blue used a normal solid light emitting element (light emitting diode) that does not use a phosphor. Green light, red light, and blue light emitted from the light source devices 50R, 50G, and 50B are substantially collimated by a collimator lens, enter the cross dichroic prism 22, and are combined into one optical path.

  The cross dichroic prism 22 has a substantially square shape in plan view in which four right-angle prisms are bonded. A dielectric multilayer film is formed on the substantially X-shaped interface to which the right-angle prism is bonded. The dielectric multilayer film formed at one of the substantially X-shaped interfaces reflects red light, and the dielectric multilayer film formed at the other interface reflects blue light. By these dielectric multilayer films, red light and blue light are bent, and the traveling direction of green light is aligned, so that three color lights are synthesized.

  The green light, red light, and blue light synthesized by the cross dichroic prism 22 are incident on a fly eye integrator composed of the first fly eye lens array 23 and the second fly eye lens array 24, and the light quantity distribution is made uniform. Green light, red light, and blue light emitted from the fly eye integrator are converted into linearly polarized light whose polarization direction is aligned in one direction by the polarization conversion element 25, and the light modulation device 21R, 21G and 21B are superimposed and illuminated. Since the fly-eye integrator and the polarization conversion element are well-known techniques whose details are disclosed in, for example, Japanese Patent Laid-Open No. 8-304739, detailed description thereof is omitted.

  The color separation light guide optical system includes a blue dichroic mirror, a green dichroic mirror, a reflection mirror, and a relay lens. The color separation light guide optical system separates the light combined by the dichroic prism into red light, green light, and blue light, and the red light, green light, and blue light are respectively modulated into the light modulation device 21R, the light modulation device 21G, and the light modulation. It has a function of guiding light to the device 21B.

  A blue dichroic mirror and a green dichroic mirror are mirrors in which a wavelength selective transmission film made of a dielectric multilayer film that reflects light in a predetermined wavelength region and transmits light in another wavelength region is formed on a substrate. . Specifically, the blue dichroic mirror reflects a blue light component and transmits a red light component and a green light component. The green dichroic mirror reflects the green light component and transmits the red light component.

  The reflection mirror is a mirror that reflects incident light. The color light component separated by the dichroic mirror is reflected and guided to the light modulation device.

  The blue light reflected by the blue dichroic mirror is reflected by the reflecting mirror and enters the image forming area of the light modulator 21B for blue light. The green light transmitted through the blue dichroic mirror is reflected by the green dichroic mirror and enters the image forming area of the light modulator 21G for green light. The red light transmitted through the green dichroic mirror enters the image forming area of the light modulator 21R for red light through the incident-side reflection mirror, the relay lens, and the emission-side reflection mirror.

  As the light modulation device 21R, the light modulation device 21G, and the light modulation device 21B, those generally known can be used. For example, a light modulation device such as a transmissive liquid crystal light valve having a liquid crystal element and two polarizing elements sandwiching the liquid crystal element is used. The two polarizing elements have, for example, a configuration in which the transmission axes are orthogonal to each other (crossed Nicol arrangement).

  The light modulation device 21R, the light modulation device 21G, and the light modulation device 21B modulate the incident color light according to image information to form a color image, and are illumination targets of the light source devices 50R, 50G, and 50B. . The light modulation device 21R, the light modulation device 21G, and the light modulation device 21B perform light modulation of the incident color light.

  For example, the light modulation device 21R, the light modulation device 21G, and the light modulation device 21B are transmission type light modulation devices in which liquid crystal is hermetically sealed in a pair of transparent substrates, and given image information using a polysilicon TFT as a switching element. Accordingly, the polarization direction of one type of linearly polarized light emitted from the incident side polarization element is modulated.

  Subsequently, the three color lights are synthesized by the second cross dichroic prism.

  The color image emitted from the second cross dichroic prism is enlarged and projected by the projection optical system 27 to form an image on the screen.

As described above, according to the projector 500 of the present embodiment described in detail, the emitted light beam is increased by using a solid-state light emitting element and a phosphor that have a small temperature dependency of the emitted light beam and can be driven with a large current. Can do.
In particular, this is effective for increasing the brightness of the projector when displaying white in which the red output is a bottleneck.

Next, in the present embodiment, a configuration using one light modulation device 21W as shown in FIG. 3 is also possible. A method called a color field sequential method is used which obtains a color image by sequentially flashing red, green, and blue light sources and sequentially displaying an image corresponding to each color light on the light modulation device in accordance with the timing of light emission. it can. Further, as the light modulation device 21W, a device having a pixel structure including at least red, green, and blue color filters inside the light modulation device described above may be used.
When these methods are used, there are few optical system parts, the configuration is simple, and the projector can be miniaturized.

  The light modulation device 21W can use not only a liquid crystal light valve but also a digital micromirror device as in the configuration shown in FIG. In this configuration, an example in which the rod integrator 29 in which four mirrors are combined is used instead of the fly-eye integrator is shown, but any uniformizing means may be used.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIG.
Compared to the structure of the first embodiment in FIG. 1, the thickness of the phosphor layer 32 is thin (for example, 100 μm), or the weight concentration of the phosphor particles 18 is small (for example, 30%). The solid light emitting element 30 uses blue light (near 460 nm). A part of the light emitted from the solid light emitting element 30 is absorbed by the phosphor layer 32 formed on the solid light emitting element 30 and converted into red fluorescence.
On the other hand, the remaining light that has not been absorbed is transmitted and diffused through the phosphor layer 32 and is emitted from the light source device 19. In this case, two color lights of blue and red (green when a green phosphor is used) can be extracted from the light source device 19.

  FIG. 6 shows a configuration of a projector when the light emitting device of the second embodiment is used. Lights from the light source device 50RB and the green light source device 50G each having a light emitting device that emits red and blue light are substantially collimated by a collimator lens and incident on a dichroic mirror 221. The dichroic mirror 221 reflects green and transmits other color light. A configuration in which the light source devices are replaced is also possible. In that case, a dichroic mirror that transmits green and reflects other color light is used. After being synthesized by the dichroic mirror 221, after being uniformed by the fly-eye integrator system and modulated by the light modulation device as in the first embodiment, synthesized by the cross dichroic prism and projected by the projection optical system 27. . Compared with the first embodiment, the configuration of the light source device is simplified, which is advantageous when the projector is downsized.

  FIG. 7 shows a configuration example of a projector in the case where there is one light modulation device. A light modulator in which red, green, and blue color filters are formed is used. The optical system configuration other than the light source device can use the same method as in the first embodiment. On the other hand, in the case of the second embodiment, since the excitation blue and the fluorescent red light are emitted simultaneously and cannot be switched in time sequence, the light modulation device excludes the color field sequential method.

FIG. 8 shows a different configuration example when the light emitting device of the second embodiment is used. The phosphor layer 32 of the light emitting device used in the light source device 50YB is composed of a yellow phosphor (YAG: yttrium aluminum garnet) or a mixture of the red phosphor particles and the green phosphor particles.
Part of the light emitted from the solid state light emitting device 30 is absorbed by the phosphor layer 32, and light of yellow fluorescence (in the case of yellow phosphor) or red and green (in the case of red and green phosphors). To emit. The remaining light that has not been absorbed is emitted from the light source device 50YB as blue light. The light source device YB is adjusted by adjusting the thickness of the fluorescent layer or the weight concentration of the fluorescent particles so that the ratio of yellow fluorescence (or red and green fluorescence) to blue light is white (for example, color temperature 6500K). The white color can be extracted from the light emitting device used in the above. The extracted white is modulated by the light modulation device and projected onto the screen in the same manner as the optical system described so far.

  DESCRIPTION OF SYMBOLS 17 ... Resin, such as silicone, 18 ... Phosphor particle, 19 ... Light source device, 21B ... Light modulation device, 21G ... Light modulation device, 21R ... Light modulation device, 21W ... Light modulation device, 22 ... Cross dichroic prism, 23 ... 1st fly-eye lens array, 24 ... 2nd fly-eye lens array, 25 ... Polarization conversion element, 26 ... Superimposing lens, 27 ... Projection lens, 28 ... Field lens, 29 ... Rod integrator combining 30 sheets, 30 ... Solid light emitting element 31 ... phosphor, 32 ... phosphor layer, 50B ... blue light source device, 50G ... green light source device, 50R ... light source device, 50RB, 50YB ... light source device, 221 ... dichroic mirror, 500 ... projector of this embodiment.

Claims (12)

An excitation light source composed of a solid-state light emitting device containing GaN;
A phosphor layer that absorbs at least part of excitation light emitted from the excitation light source and emits first light;
A light emitting device comprising: The solid state light emitting device is composed of a light emitting diode layer containing the GaN,
The light emitting device according to claim 1, wherein the light emitting diode layer is formed on a Ga-based substrate. The light emitting device according to claim ₂ , wherein the Ga-based substrate is GaN or Ga ₂ O ₃ .   The light emitting device according to any one of claims 1 to 3, wherein the excitation light is blue light or ultraviolet light.   The light emitting device according to any one of claims 1 to 4, wherein the first light includes at least one of red light and green light. A first light source device comprising the light emitting device according to any one of claims 1 to 5;
A second light source device that emits second light including a wavelength region different from the wavelength region of the first light;
A third light source device that emits third light including a wavelength region different from the wavelength region of the first light and the wavelength region of the second light;
A first light modulation device;
A second light modulation device;
A third light modulation device;
A cross prism that combines light from the first light modulation device, light from the second light modulation device, and light from the third light modulation device;
A projection optical system;
A projector comprising: A first light source device comprising the light emitting device according to any one of claims 1 to 5;
A second light source device that emits second light including a wavelength region different from the wavelength region of the first light;
A third light source device that emits third light including a wavelength region different from the wavelength region of the first light and the wavelength region of the second light;
Color synthesizing means for synthesizing light from the first light source device, light from the second light source device, and light from the third light source device;
A light modulation device for modulating the light emitted from the color synthesis means;
A projection optical system;
A projector comprising:   4. The light emitting device according to claim 1, wherein the phosphor layer emits the first light by absorbing a part of the excitation light and transmits or reflects the remainder of the excitation light. 5.   The light emitting device according to claim 8, wherein the excitation light is blue light.   The light emitting device according to claim 8, wherein the first light includes at least one of red light and green light. A first light source device comprising the light emitting device according to any one of claims 8 to 10,
A second light source device that emits second light including a wavelength region different from a wavelength region of light emitted from the first light source device;
A first light modulation device;
A second light modulation device;
A third light modulation device;
A cross prism that combines light from the first light modulation device, light from the second light modulation device, and light from the third light modulation device;
A projection optical system;
A projector comprising: A first light source device comprising the light emitting device according to any one of claims 8 to 10,
A second light source device that emits second light including a wavelength region different from a wavelength region of light emitted from the first light source device;
Color synthesizing means for synthesizing light from the first light source device and light from the second light source device;
A light modulation device for modulating the light emitted from the color synthesis means;
A projection optical system;
A projector comprising:

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