JP2015119046A - Light-emitting device and light source for projector using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the output of a reflection type light-emitting device using a light source emitting laser light and especially, and to provide a light-emitting device capable of obtaining high output as a light source for green color.SOLUTION: The light-emitting device includes a light source 10 emitting laser light and a light-emitting part 20 arranged spatially away from the light source. The light-emitting part includes a substrate 30, a phosphor layer 21 arranged on the substrate, and a reflection layer 22 arranged between the substrate and the phosphor layer. Further, the light-emitting device includes optical path adjustment means for changing the propagation direction of the laser light propagating through the phosphor layer. The optical path adjustment means is, for instance, an interpolation material dispersed in the phosphor layer or a white ceramic layer arranged in contact with the phosphor layer.

Description

  The present invention relates to a light emitting device that combines a light source that emits laser light and a phosphor that uses laser light as excitation light and emits light of a different wavelength, and more particularly to a high-output light emitting device that reduces light loss in the phosphor. .

  As semiconductor light emitting devices have increased in output, their applications are expanding to light sources for general lighting, LCD backlights, and vehicle headlamps. Among applications that use a high-power light source, projectors require a particularly high output because they project an image on a screen, and high-voltage discharge has been used in the past. Has come to be used.

  In the light source for a projector, light sources of three primary colors of RGB (red, green, blue) are required to reproduce colors. Conventionally, a blue light source and a red light source have a high output LD or LED, but there is no green light source capable of obtaining a high output comparable to these.

As a phosphor used for a green light source, for example, a phosphor described in Patent Document 1 is known. Patent Document 1 proposes a green phosphor composed of a first phase made of Al ₂ O ₃ and a second phase made of LuAG containing Ce, and the second phase when combined with a blue LED. It is described that when the ratio of is in a specific range, higher emission intensity can be obtained than when the second phase is 100%.

  On the other hand, Patent Document 2 discloses a light source device in which a laser light source and a phosphor are arranged at spatially separated positions as a light source device capable of obtaining high output. In the technique described in Patent Document 2, by extracting light from the phosphor layer by a reflection method, a thermal light source efficiency is improved as compared with a conventional transmissive light source, and a high-luminance light source device is provided.

JP 2012-62444 A JP 2012-226986 A

  In Patent Document 1, the light emission intensity is examined when the green phosphor is a transmissive device using an LED, but the reflection type or combination with a laser light source is not studied. In Patent Document 2, a device such as a reflective layer is provided between the phosphor layer and the substrate in order to increase the luminance. However, the reflective layer has a wavelength dependency, and simply providing a reflective layer. It is not always possible to increase the brightness.

  An object of the present invention is to increase the output of a reflective light-emitting device using a light source that emits laser light, and in particular to provide a light-emitting device that can obtain high output as a green light source.

  A light-emitting device of the present invention that solves the above problems includes a light source that emits laser light and a light-emitting unit that is spatially spaced from the light source, and the light-emitting unit is disposed on the substrate and the substrate. And an optical path adjusting means for changing the propagation direction of the laser light propagating through the phosphor layer, the phosphor layer having a reflection layer disposed between the substrate and the phosphor layer. Features.

  In the present invention, the optical path adjusting means for changing the propagation direction of the laser light can take several forms. One aspect of the optical path adjusting means is an interpolation material contained in the phosphor layer in addition to the phosphor. Another embodiment is a white ceramic layer in contact with the phosphor layer.

  According to the study by the present inventors, in a light emitting device in which a total reflection layer is provided in the light emitting portion, the light emission output of the light emitting portion increases as the phosphor concentration increases, and the maximum is obtained when the phosphor concentration is 100%. It becomes. However, when a reflection layer is provided with an enhanced reflection film or a total reflection film to improve the reflection characteristics of the reflection layer, when a phosphor plate with a phosphor concentration of 100% is used, the fluorescence with a phosphor concentration of less than 100% is used. It has been found that the output is lower than when a body plate is used. This phenomenon is considered to be caused by the following phosphor excitation mechanism.

  The intensity distribution of the laser light is a Gaussian distribution with a high center and a sharp weakening in the periphery. For this reason, the laser light that vertically enters the phosphor plate and reaches the reflection layer is reflected to the light emission side along the same optical path as the incident light. As a result, it is considered that the phosphor is excited and saturated, and the fluorescence output does not increase (fluorescence efficiency does not improve).

  In the present invention, by providing means for changing the propagation direction of light propagating in the phosphor layer, it is possible to cause a deviation between the incident optical path and the reflected optical path, thereby preventing excitation saturation, High brightness can be achieved.

The figure which shows the whole light-emitting device outline | summary of this invention Sectional drawing which shows the fluorescent substance plate of 1st Embodiment (A)-(c) is a figure which shows the example of a change of the fluorescent substance plate of 1st Embodiment, respectively. The figure which shows the structure of the light-emitting device of 2nd Embodiment. The figure which shows the outline | summary of the light source device for projectors of 3rd Embodiment. The graph which shows the reflection spectrum of the antireflection layer of Example 1 The graph which shows the incident angle dependence of the reflection layer of Example 1 The graph which shows the reflection spectrum of the reflection layer of Example 1 The figure which shows the outline | summary of the fluorescent substance output measuring apparatus used in the Example

Hereinafter, an embodiment of a light emitting device of the present invention will be described with reference to the drawings.
First, an outline of a light emitting device to which the present invention is applied will be described with reference to FIG. A light emitting device 100 shown in FIG. 1 includes a laser light source 10 and a light emitting unit 20, and the laser light source 10 and the light emitting unit 20 are arranged spatially separated from each other by a support structure (not shown). The laser light source 10 is a light source that emits laser light of a predetermined wavelength, and for example, a laser diode (LD) that emits a blue light laser is used. The LD constituting the laser light source 10 may be singular or plural.

  The light emitting unit 20 mainly includes a phosphor plate (phosphor layer) 21 and a substrate 30, and the phosphor plate 21 is fixed to the substrate 30 by a bonding material 40. A reflection layer 22 is formed on the substrate side of the phosphor plate 21, and an antireflection layer 25 is formed on the upper surface of the phosphor plate 21 (the side opposite to the substrate side). The surface on which the antireflection layer 25 is formed becomes the light emitting surface of the light emitting unit 20. Although FIG. 1 shows the case where the laser light is incident obliquely on the upper surface of the phosphor plate, the incident angle of the laser light with respect to the phosphor plate 21 may be 0 degrees.

The phosphor plate 21 is a member including a phosphor that absorbs laser light from the laser light source 10 and emits light having a wavelength different from that of the laser light. As the phosphor, known phosphors such as a red phosphor that emits red light, a yellow phosphor that emits yellow light, and a green phosphor that emits green light can be used. It is suitable for conversion. As the green phosphor, LuAG: Ce or LuAG: Ce + Al ₂ O ₃ can be used. Note that LuAG is a crystal having a garnet crystal structure represented by the composition formula of Lu ₃ Al ₅ O ₁₂ , where Lu is lutetium, Al is aluminum, and O is oxygen. LuAG: Ce means a crystal body in which a part of the Lu atom site of the LuAG crystal is replaced with Ce (cerium) as an activator. LuAG: Ce + Al ₂ O ₃ means a polycrystal of LuAG and Al ₂ O ₃ .

  As a form of the phosphor plate 21, a phosphor powder dispersed in glass or resin, a glass phosphor in which a luminescent center ion is added to a glass matrix, a phosphor ceramic, or the like can be used. In particular, a phosphor ceramic that is a sintered body of phosphor powder is preferable. The phosphor plate preferably has a high translucency. By using a phosphor plate with high translucency, the light extraction efficiency from the phosphor layer can be increased, and the heat generated in the phosphor plate can be diffused efficiently.

  The substrate 30 is a support member for the phosphor plate 21 and has a function of radiating heat generated by the phosphor plate 21. For this reason, it is preferable to use a metal with good thermal conductivity, such as aluminum, copper, or slenless. 1 shows a flat substrate 30, the substrate 30 may be provided with a heat dissipation structure such as fins on the side opposite to the surface to which the phosphor plate 21 is fixed, and the shape is arbitrary.

  As the bonding material 40 for fixing the phosphor plate 21 to the substrate 30, silicone resin, glass or the like can be used. When the reflective layer 22 formed on the phosphor plate 21 is a metal layer, it is also possible to use an epoxy resin, a silicone resin, solder, gold tin, or the like to which Ag filler or graphite filler with good thermal conductivity is added. When the bonding material 40 is resin or glass, it may be transparent (light transmissive) or opaque, and in the case of being transparent, it may be provided so as to cover the side surface of the phosphor plate 21. Since the transparent resin does not hinder the emission of light from the side surface of the phosphor plate 21, light from the side surface can also be used.

  As the reflection layer 22 provided on the back surface side of the phosphor plate 21, a metal reflection film, a reflection enhancement film made of a dielectric multilayer film, a combination of a metal reflection film and a reflection enhancement film, or the like can be used. Preferably, as shown in FIG. 2, a combination of a total reflection film 223, an increased reflection film 222, and a metal reflection film 221 in order from the phosphor plate 21 side is preferable.

The metal reflection film 221 is made of a metal such as Ag or Al. In particular, Ag having a high reflectance is suitable. The thickness of the metal reflective film 221 is not particularly limited, but is preferably equal to or greater than the thickness at which the reflectance of the metal used is saturated. In the case of Ag and Al, 1000 to 2000 mm (100 to 200 nm) is preferable. Further, on the outer side of the metal reflection film, a metallic protective film 26 such as Ti, Pt, Ti / Au, Pt / Au or the like, or metal oxide such as Al ₂ O ₃ , TiO ₂ , or SiO _{2 is used} to prevent metal deterioration. It is preferable to form a protective film 26 of the object.

The increased reflection film 222 is an optical multilayer film in which materials having different refractive indexes (n) are alternately stacked. The thickness of each layer is adjusted to about ¼ of the wavelength λ of incident light, and the angle dependency of incident light. In order to prevent a decrease in reflectance due to the structure, the reflection wavelength band is widened, so that a part or most of the incident light can be transmitted without being transmitted. The layer configuration is adjusted in consideration of the wavelength of the excitation light and the light emitted from the wavelength conversion member 20. It should be noted that the layer configuration can be simplified if the maximum incident angle (reflection limit angle) at which the incident light of the increased reflection film 222 can be reflected is small, and if it is large, the layer configuration becomes complicated and multi-layered. As a low refractive index material, for example, Na ₅ Al ₃ F ₁₄ (thiolite) (n = 1.33), AlF ₃ (n = 1.36), CaF ₂ (n = 1.38), SiO ₂ (n = 1.45), Al ₂ O ₃ (n = 1.64), etc. are used. As a high refractive index material, CeO ₂ (n = 2.13), Ta ₂ O ₅ (n = 2.20), Ti ₃ O ₅ (n = 2.31), TiO ₂ (n = 2.35). Nb ₂ O ₅ (n = 2.37) or the like is used. As an example suitable for this embodiment, Ta ₂ O ₅ (54 nm) / SiO ₂ (24 nm) / Ta ₂ O ₅ (54 nm) / SiO ₂ (100 nm) / Ta ₂ O ₅ (42 nm) in this order from the phosphor plate side. / SiO ₂ (54 nm)).

  The total reflection film 223 is made of a translucent material having a refractive index smaller than that of the phosphor plate 21. As a result, the incident light having the smallest incident angle (total reflection critical angle) at which the total reflection occurs among the incident light incident on the total reflection film 223 from the phosphor plate 21 can be totally reflected. That is, by providing the total reflection film 223, the reflection limit angle of the increased reflection film 222 can be reduced, and the layer configuration can be simplified.

The refractive index of the material that constitutes the total reflection film 223 is preferably a value that is smaller than the refractive index of the phosphor plate 21 and that becomes the total reflection critical angle at an angle equal to or smaller than the reflection limit angle of the increased reflection film. Specifically, if the refractive index of the phosphor plate 21 is n1, the refractive index of the total reflection film 223 is n2, and the reflection limit angle of the increased reflection film 222 is θ, the relationship of n2 ≦ sin (θ) × n1 is established. good. For example, if the refractive index of LuAG as a phosphor plate is 1.85 and the reflection limit angle of the increased reflection film is 65 °, the refractive index n2 of the total reflection film may be 1.68 or less. As such a low refractive index material, specifically, Na ₅ Al ₃ F ₁₄ (thiolite) (n = 1.33), AlF ₃ (n = 1.36), MgF ₂ (n = 1.38) , CaF ₂ (n = 1.43), SiO ₂ (n = 1.45), Al ₂ O ₃ (n = 1.64), and other dielectric materials can be used. If the refractive index of the phosphor plate is large, a dielectric material such as AlN (n = 1.9-2.2) or Si ₃ N ₄ (n = 2.03) can also be used. Of these, SiO ₂ and Al ₂ O ₃ are preferable from the viewpoints of chemical stability, refractive index, and film formability.

  The thickness of the total reflection film 223 is not limited, but when a multilayer film (increased reflection film) 222 of a dielectric layer is provided between the total reflection film 223 and the metal reflection film 221, 300 nm or more, Preferably it is 500 nm or more. The upper limit is 2 μm or less, preferably 1 μm or less. By setting the thickness to 300 nm or more, a total reflection function can be obtained without causing interference with the increased reflection film. Moreover, shortening of manufacturing time can be aimed at by setting it as 2 micrometers or less.

  The metal reflection film 221, the enhanced reflection film 222, the total reflection film 223, and the protective film 26 were formed on or on the phosphor plate 21 by a method such as sputtering, ion plating, vacuum deposition, or ion assist deposition, respectively. A film can be formed on the surface of the reflective layer.

The antireflection layer 25 provided on the light emitting surface of the phosphor plate 21 has a function of reducing the reflection of excitation light incident on the phosphor plate 21 and improving the incidence efficiency, and efficiently extracting the fluorescence emitted by the excitation. . As the antireflection layer 25, a multilayer film in which a high refractive index material (dielectric) and a low refractive index material (dielectric) are alternately laminated in multiple layers can be used. As an example suitable for the present embodiment, Ta ₂ O ₅ (23 nm) / SiO ₂ (25 nm) / Ta ₂ O ₅ (58 nm) / SiO ₂ (18 nm) / Ta ₂ O ₅ (41 nm) / An example of the multilayer film is SiO ₂ (99 nm). The antireflection layer 25 can be formed on the phosphor plate by a known method such as vapor deposition or ion plating, as with the other reflective layer 22, but vapor deposition using the ion assist function is performed at the time of vapor deposition. The substrate temperature can be lowered, which is preferable. The layer structure of the antireflection layer 25 varies depending on the wavelength to be prevented from being reflected, and is not limited to the above.

  The light emitting device 100 is bonded and fixed to the substrate 30 which is a part of the structure of the light emitting device by bonding the reflective layer 22 side of the light emitting unit 20 via the bonding material 40, and is fixed to the light emitting surface of the light emitting unit 20. It can manufacture by attaching the laser light source 10 so that a laser beam may be irradiated at an angle. The light emitting device 100 may include an optical member (not shown) such as a lens, a half mirror, and a dichroic mirror in order to adjust the optical path of the laser light emitted from the laser light source 10.

  The light emitting device of the present invention is characterized by providing means (optical path adjusting means) for preventing excitation saturation of the phosphor by the laser light incident on the phosphor plate 21 based on the structure described above. An embodiment will be described for each aspect of the optical path adjusting means.

<First Embodiment>
The light emitting device of the present embodiment is characterized in that the phosphor plate includes an interpolation material as the optical path adjusting means. The structure of the light emitting device is the same as that shown in FIG. 1, and description of elements other than the phosphor plate is omitted. Hereinafter, the phosphor plate that is a feature of the present embodiment will be described.

The phosphor plate used by the light emitting device of this embodiment is made of phosphor ceramics obtained by sintering phosphor powder and an interpolation material. As phosphor powders, CaAlSiN ₃ : Eu ²⁺ , (Ca, Sr) AlSiN ₃ : Eu ²⁺ , (Sr, Ba) ₂ SiO ₅ : Eu ²⁺ , (Ca, Sr) ₂ Si ₅ N ₈ : Eu ²⁺ , etc. Red light-emitting phosphor, Y ₃ Al ₅ O ₁₂ : Ce ³⁺ , (Sr, Ba) ₂ SiO ₄ : Eu ²⁺ , Ca _x (Si, Al) ₁₂ (O, N) ₁₆ : Eu ²⁺ , (Ba, Sr) , Ca) ₂ SiO ₄ : Eu ²⁺ , Tb ₃ Al ₅ O ₁₂ : Ce ³⁺ , Ca-α-Sialon: Eu ^{2+ and} other yellow light-emitting phosphors, Y ₃ (Ga, Al) ₅ O ₁₂ : Ce ³⁺ , Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ , (Ba, Sr) ₂ SiO ₄ : Eu ²⁺ , Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce ³⁺ , CaSc ₂ O ₄ : Eu ²⁺ , CaSc ₂ O ₄ : Ce ³⁺ , (Si, Al) ₆ (O, N) ₈ : Eu ²⁺ , β-Sialon: Eu ²⁺ , (Sr, Ba) Si ₂ O ₂ N ₂ : Eu ²⁺ , Ba ₃ Si ₆ O ₁₂ N ₂ : A green light emitting phosphor such as Eu ²⁺ can be used. From the viewpoint of crystal structure, TAG (terbium, aluminum, garnet), YAG (yttrium, aluminum, garnet), and LuAG (rubidium, aluminum, garnet) phosphors having a garnet crystal structure are suitable. The present embodiment can be suitably applied to a green light emitting phosphor, in particular, a LuAG phosphor such as Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ .

The interpolating material is a material that imparts light diffusivity without impairing the translucency of the phosphor plate by forming a crystal phase different from the crystal phase of the phosphor in the sintered body. ) And a different refractive index are used. Specifically, a metal oxide such as Al ₂ O ₃ , SiO ₂ , AlN, Si ₃ N _{4 and the} like having an element common to the phosphor is used.

  In order to scatter laser light without impairing translucency, the grain boundary diameter of the interpolating material is such that the laser light diffracts and scatters in the traveling direction when passing through the grain boundary, that is, grains having a size of about 0.5 μm to 5 μm. The field diameter is preferred, preferably around 1 μm. When the grain boundary diameter is smaller than 0.5 μm, the diffraction scattering intensity on the rear side in the traveling direction of the laser beam increases, and the laser beam, which is the excitation light, does not reach the deep part of the phosphor plate, and the fluorescence efficiency (fluorescence output ÷ excitation light output) descend. On the other hand, if it exceeds 5 μm, the diffraction scattering angle in the traveling direction becomes narrow, the amount of light incident on the phosphor crystal decreases, and the fluorescence efficiency also decreases.

  The grain boundary shape of the interpolating material suitable for diffraction scattering of laser light is preferably a substantially spherical shape or a substantially spherical polygon shape. For this purpose, the crystal structure of the interpolating material is preferably different from that of the phosphor crystal and includes a phosphor crystal constituent element. In the interpolation material having such properties, the grain boundary of the interpolation material tends to be substantially spherical or substantially spherical polygon in the process of sintering the interpolation material and the phosphor.

  The ratio (concentration) of the interpolating material in the phosphor plate is 5 vol. % To 25 vol. % Is preferred. 5 vol. By setting the ratio to at least%, a grain boundary in which the interpolating material is dispersed in the above-described size and shape is formed in the phosphor crystal, so that scattering necessary for preventing excitation saturation of the phosphor can be obtained. In addition, 25 vol. If it exceeds 50%, the phosphor concentration decreases and the fluorescence efficiency decreases.

  The phosphor plate of the present embodiment is the same as the ordinary phosphor ceramic manufacturing method. A predetermined amount of metal oxide fine particles as an interpolation material is mixed. Thereafter, for example, after uniaxial molding with a mold or the like, cold isostatic pressing is performed to form a molded body, which is sintered in an atmosphere of inert gas, oxygen gas, reduced pressure, vacuum, or a combination thereof. After processing the sintered body into a plate shape, the reflective layer 22, the protective film 26, and the antireflection layer 25 are formed, and then diced into a predetermined shape to obtain a phosphor plate.

  The light-emitting device of the present embodiment is characterized in that the phosphor plate 21 including the interpolation material described above is used as the phosphor plate in FIG. 1, and the layer structure may be a single layer as shown in FIG. As shown in 3 (a) to (c), it may be composed of a plurality of layers (phosphor plates). FIG. 3A shows two layers, an upper layer 211 and a lower layer 212. The upper layer 211 on which laser light is incident is a phosphor plate that does not include an interpolation material, and the lower layer 212 is a phosphor plate that includes an interpolation material. FIG. 3B is a reverse of FIG. 3A, in which the upper layer 211 is a phosphor plate containing an interpolation material, and the lower layer 212 is a phosphor plate not containing an interpolation material. FIG. 3C shows a structure in which an intermediate layer 213 made of a phosphor plate not containing an interpolation material is sandwiched between upper and lower layers 214 and 215 made of a phosphor plate containing an interpolation material. The position of the phosphor plate including the interpolating material is not limited to the example shown in FIG. 3, and may be any of the upper layer, the intermediate layer, and the lower layer. In the case of such a layer structure, the concentration of the interpolation material when converted to the volume of the phosphor plate 21 is 5 vol. % To 25 vol. A phosphor plate including an interpolating material which is an upper layer, an intermediate layer, or a lower layer is formed so as to be%.

  When the phosphor plate 21 is composed of a plurality of layers, different types of phosphor plates may be joined with a joining material, or before forming the sintered body and the phosphor and interpolating material of each phosphor plate. It is good also as a single fluorescent substance plate by stacking together and sintering simultaneously.

  In the light emitting device of the present embodiment, the laser light emitted from the laser light source 10 passes through the antireflection layer 25 and enters the phosphor plate 21 of the light emitting unit 20. Here, since the phosphor plate 21 includes an upper layer, an intermediate layer, or a lower layer of the phosphor plate containing the interpolation material, the laser light incident on the light emitting unit 20 is diffracted and scattered. In this scattering, the light is not back-scattered and can go to the reflection layer 22 below the phosphor plate, so that it is reflected by the light path (outward path) to the reflection layer 22 and the reflection layer 22 and is emitted from the light exit surface. The phosphor in the phosphor plate can be sufficiently excited by the optical path (return path) up to In addition, the forward and backward paths of the laser light are different due to diffraction scattering by the interpolating material, so that the fluorescence efficiency is not lowered due to excitation saturation.

  Furthermore, in the light emitting device of this embodiment, the reflective layer 22 is composed of the metal reflective film 221, the enhanced reflective film 222, and the total reflective film 223, so that laser light and fluorescent light are emitted at the interface between the phosphor plate 21 and the reflective layer 22. Since there is no light loss and the light is reflected to the light exit surface side with an extremely high reflectance, high fluorescence efficiency (high output) can be obtained.

Second Embodiment
The light emitting device of the present embodiment is characterized in that white ceramic is used as a reflection layer in contact with the phosphor plate as an optical path adjusting means. The structure of the light emitting device is shown in FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals, and the description thereof is omitted. Although the laser light source 10 is omitted in FIG. 4, the laser light source 10 is spatially separated from the light emitting unit 20 in the same manner as the light emitting device 100 in FIG. 1.

  Also in the light emitting device of this embodiment, the light emitting unit 20 has a structure fixed on the substrate 30 by the bonding material 40. In the light emitting unit 20, an antireflection layer 25 is formed on the light emitting surface side of the phosphor plate 21, and a reflection layer 22 is formed on the opposite surface.

  The reflective layer 22 includes a white ceramic layer 225 and a metal reflective film 221 in order from the phosphor plate 21 side. The metal reflection film 221 is necessary when a metal bonding material such as solder or gold-tin is used as the bonding material 40 for fixing the light emitting unit 20 to the substrate 30, but when the bonding material 40 is a resin or glass. Can be omitted. In that case, a protective film for protecting the metal reflective film 221 can also be omitted.

  The white ceramic layer 225 diffuses or uniformly diffuses and reflects the laser light transmitted through the phosphor plate 21 and the fluorescence emitted from the phosphor plate 21 by the laser light, and from the light path (outward path) to the reflection layer 22 and the reflection layer 22. It functions as an optical path adjusting means that varies the optical path (return path) to the light exit surface. In order to provide this function, a white alumina reflective film having a high reflectance with respect to the wavelength of laser light (for example, 450 nm) and the wavelength of fluorescence (about 510 nm in the case of a green phosphor) is suitable. The white alumina reflective film has a high reflectance of 95% or more with respect to light having a wavelength of 450 nm, and diffuse reflection with less regular reflection light can be obtained.

  The ceramic layer 225 such as a white alumina reflective film can be formed on the surface of the phosphor plate 21 by plasma spraying with a film thickness accuracy of the order of μm. In addition, it can be formed by sputtering, plasma CVD, or the like, but a plasma sprayed film is preferable for forming a diffuse reflection surface or a uniform diffuse reflection surface. Moreover, what formed the white ceramic layer 27 on the predetermined base material by thermal spraying may be joined to the phosphor plate 21 via a joining material such as a transparent resin or glass. The thickness of the ceramic layer 225 is not particularly limited, but when the metal reflective film 221 is provided, the thickness may be about 1 μm to 20 μm necessary for the diffusion of laser light. In addition, when diffuse reflection is performed only by the ceramic layer 225, it is preferable to set the thickness to about 20 μm to 100 μm in order to prevent a decrease in reflectance.

  If a member having high thermal conductivity is used for the ceramic layer 225, the heat generated when the phosphor plate 21 fluoresces can be efficiently transferred to the substrate 30, so that temperature quenching of the phosphor plate 21 can be prevented. Since white alumina has a high thermal conductivity of 20 W / (m · K) to 30 W / (m · K), it is a suitable member.

  The phosphor plate 21 may be the same as that of the first embodiment, but if there is no problem of excitation saturation, the higher the phosphor concentration, the higher the fluorescence efficiency (light output) is obtained. It is preferable to use a 100% phosphor plate. A phosphor plate having a phosphor concentration of 100% means a phosphor plate that does not contain an interpolating material, and does not exclude those that contain components that are inevitably mixed. As the phosphor constituting the phosphor plate 21, the phosphor exemplified in the first embodiment can be used. Also in this embodiment, a green phosphor such as LuAG can be suitably used. The method for manufacturing the phosphor plate is the same as that in the case where the phosphor concentration is less than 100%, except that the ratio of the raw materials is different.

  The antireflection layer 25 can be omitted.

  The light emitting device according to the present embodiment uses a white ceramic layer 225 having diffuse reflectivity in a portion in contact with the phosphor plate 21 as the reflection layer 22 of the light emitting unit 20, thereby using laser light that reciprocates the phosphor plate 21. Since excitation saturation of the phosphor can be effectively prevented and high reflectivity can be maintained even for light emitted from the phosphor, high output can be obtained.

<Third Embodiment>
Next, an embodiment in which the light emitting device of the present invention is used as a light source for a projector will be described.

  FIG. 5 shows an example of a light source device for a projector. The projector light source device 800 includes a laser light source 10 that emits a blue laser, a light emitting unit 20 that includes a phosphor, a red light source 80 that emits red light, a half mirror 91, and a plurality of dichroic mirrors 92 (921 to 923). And a conversion element 94 that converts light into image light.

  The laser light source 10 is the same as the laser light source of the light emitting device 100 of FIG. 1, but here, a plurality of laser light sources that emit blue laser are used. After the light from the laser light source 10 is collected by the lens 95, a part of the light is reflected by the half mirror 91, the rest is transmitted through the half mirror 91, and further transmitted through the dichroic mirror 921 that transmits a predetermined wavelength. Incident on the part 20.

  The light emitting unit 20 includes a reflective layer on a phosphor plate containing a green phosphor, and is the same light emitting unit 20 as in either the first embodiment or the second embodiment, and receives blue laser light incident through the dichroic mirror 921. The phosphor absorbs and emits green light. The green light emitted from the light emitting unit 20 is reflected without being transmitted through the dichroic mirror 921, further reflected by the second dichroic mirror 922, transmitted through the third dichroic mirror 923, and reaches the conversion element 94. .

  The light from the laser light source 10 reflected by the half mirror 91 is further reflected by the dichroic mirror 923 and reaches the conversion element 94.

  The red light source 80 is formed of a red LED or the like, and is disposed behind the second dichroic mirror 922 having a transmission characteristic with respect to red, and the red light emitted therefrom passes through the dichroic mirror 922 and the third dichroic mirror 923. And reaches the conversion element 94.

  The conversion element 94 includes a liquid crystal element and a DLP (Digital Light Processing) element. The conversion element 94 corresponds to a large number of pixels, passes light when the element is ON, and blocks light when the element is OFF. Convert to The blue light from the laser light source 10, the green light from the light emitting unit 20, and the red light from the red light source 80 are output as image light combined at a predetermined ratio by the conversion element 94.

  In the light emitting device of the present embodiment, a high output light emitting unit that is not inferior to a high output red LED or blue LD can be used as the light emitting unit 20 that emits green light, so that a bright and good color reproducible image can be obtained. .

<Example 1>
A plurality of phosphor plates (thickness: 100 nm) containing phosphor LuAG: Ce and an interpolation material Al ₂ O ₃ and having different phosphor concentrations were prepared. The phosphor concentration was measured in Sample 1: 25 vol. %, Sample 2: 50 vol. %, Sample 3: 75 vol. %, Sample 4: 90 vol. %, Sample 5: 95 vol. %, Sample 6: 100 vol. %. The activator concentration ([Ce] / ([Lu] + [Ce] × 100)) was kept constant at 5 <atomic%.

Using a vapor deposition apparatus having an ion assist function, Ta ₂ O ₅ (23 nm) / SiO ₂ (25 nm) / Ta ₂ O ₅ (from the phosphor plate side as an antireflection layer on one surface of these phosphor plates. 58 nm) / SiO ₂ (18 nm) / Ta ₂ O ₅ (41 nm) / SiO ₂ (99 nm)). Similarly, using a vapor deposition apparatus having an ion assist function, a total reflection film (SiO ₂ , thickness: 500 nm) and an increase reflection film (Ta ₂ O ₅ (54 nm from the total reflection film side) are formed on the other surface of the phosphor plate. / SiO ₂ (24 nm) / Ta ₂ O ₅ (54 nm) / SiO ₂ (100 nm) / Ta ₂ O ₅ (42 nm) / SiO ₂ (54 nm)), adhesive layer (Al ₂ O ₃ (10 nm)), metal reflection A film (Ag (150 nm)) was formed in this order, and finally a protective film (TiO ₂ (50 nm)) was formed on the Ag film.

The reflection characteristics of the antireflection layer and the reflection layer of Example 1 were confirmed as follows.
(1) Reflectivity characteristics of antireflection layer The same multilayer film as the antireflection layer formed in Example 1 is formed on a translucent YAG substrate (refractive index 1.85), and the reflection spectrum of this antireflection layer Was measured at an incident angle of 5 ° using a reflectance measuring device. The results are shown in FIG. In FIG. 6, the horizontal axis represents wavelength (nm) and the vertical axis represents reflectance (%). As shown in the figure, the antireflection layer of this example has a reflectance of 0.4% or less with respect to light having a wavelength of 430 nm to 580 nm, and a reflectance of 0.4% with respect to blue laser light (about 450 nm) as excitation light. It was confirmed that the antireflection property was as high as 2% or less. Further, it was confirmed that the phosphor had a reflectance of 0.2% or less, that is, high transparency in the vicinity of the emission wavelength (about 510 nm) of the phosphor.

(2) Incident angle dependence of reflectivity of reflective layer Reflective layer (total reflective film + increased reflective film + metal reflective film + protective film) formed in Example 1 on a glass substrate (refractive index 1.82) The reflectance when the incident angle is changed from 0 ° to 28 ° with respect to the light having the same wavelength as the excitation light and the light having the same wavelength of 450 nm as the excitation light and the light having the same wavelength as the emission wavelength of the phosphor of 510 nm. It measured from the glass side using the measuring apparatus. The results are shown in FIG. In FIG. 7, the horizontal axis represents the incident angle (°), and the vertical axis represents the reflectance (%). As shown in the figure, the reflectance of 92% or more was shown for light of both wavelengths at all measured incident angles. Blue light (wavelength 450 nm) has a reflectivity of 97% or more with respect to an incident angle of up to about 5 ° to 10 °, and green light (wavelength 510 nm) has an angle range 0 assumed as an incident angle from a laser light source. It had a reflectivity of 95% or more with respect to an incident angle of ° to 28 °.

(3) Wavelength dependence of reflectance of reflection layer The reflection spectrum of the reflection layer of (2) above was measured at an incident angle of 5 ° using a reflectance measuring device. The results are shown in FIG. In FIG. 8, the horizontal axis represents wavelength (nm) and the vertical axis represents reflectance (%). As shown in the figure, the reflectance at a wavelength of 450 nm and the reflectance at a wavelength of 510 nm are both 98% or more, and it was confirmed that the reflection characteristics were very good.

  As described above, six types of phosphor plates with different phosphor concentrations, each having an antireflection layer on one side and a reflection layer on the other side, are cut into a predetermined size (1 mm × 1 mm) to obtain a sample piece. It was. These six sample pieces were bonded to a metal substrate (aluminum substrate, thickness 0.5 m) after UV cleaning using a transparent resin (silicone resin) and cured at 150 ° C. for 4 hours.

<Comparative Example 1>
Except for not providing the increased reflection film and the metal reflection film, six types of phosphor plate samples having different phosphor concentrations and samples after joining the metal substrate were obtained in the same manner as in Example 1.

  For each sample of Example 1 and Comparative Example 1 described above, the fluorescence output of the phosphor plate sample after metal substrate bonding was measured using a measuring apparatus 900 as shown in FIG. In FIG. 9, a laser beam from a laser light source emitting a blue laser having a wavelength of 450 nm is irradiated to a phosphor plate sample through a half mirror and a condenser lens, and the fluorescence emitted from the phosphor plate sample is emitted to the half mirror and the dichroic mirror. And detected with a thermopile sensor. The laser light output was 10 W at room temperature, and the irradiation size was about 1 mm × 1.5 mm square.

The results are shown in Table 1. The results in Table 1 are values normalized with the fluorescence output value of the phosphor concentration of Comparative Example 1 at 100%.

  As can be seen from the results shown in Table 1, in Comparative Example 1 in which the reflection-increasing film and the metal reflection film are not provided, the fluorescence output increases as the phosphor concentration increases, and becomes maximum when the phosphor concentration is 100%. On the other hand, in Example 1 provided with the increased reflection film and the metal reflection film, the fluorescence output becomes the maximum when the phosphor concentration is about 90%, and the fluorescence output decreases conversely even if the phosphor concentration is higher. However, higher phosphor outputs were obtained with the phosphor concentrations of 75%, 90%, and 95% than those with the phosphor concentration of Comparative Example 1 of 100%. This is due to the fact that the phosphor plate sample of Example 1 is provided with an increased reflection film with respect to the phosphor plate sample of Comparative Example 1, and thus the reflectance of low incident angle light is increased.

  Since the sample of Comparative Example 1 does not include the increased reflection film and the metal reflection film, the afterglow component that has not been used for excitation of the phosphor and has reached the opposite surface of the phosphor plate among the laser light incident on the phosphor plate. Is emitted and absorbed and attenuated by the joining member and the metal substrate. Therefore, the fluorescence output depends only on the phosphor concentration regardless of the presence or absence of the diffraction diffusion effect by the interpolation material.

  Since the sample of Example 1 is provided with the increased reflection film and the metal reflection film, the afterglow component that has not been used for excitation of the phosphor and has reached the opposite surface of the phosphor plate among the laser light incident on the phosphor plate. Is re-excited light that is reflected by the increased reflection film and excites the phosphor again. At this time, the phosphor concentration of 90 vol. %, The laser light diffuses and excites a wide range of phosphor grain boundaries, so that excitation saturation of the phosphor due to re-excitation light can be prevented and the fluorescence output increases. On the other hand, the phosphor concentration of 90 vol. If it exceeds about%, the diffusion of the laser beam becomes insufficient and only a narrow phosphor grain boundary is excited, so that excitation saturation of the phosphor due to re-excitation light occurs and the fluorescence output decreases.

  When the phosphor concentration is less than 90% by volume, the fluorescence output decreases, but the phosphor concentration is 75 vol. %, The fluorescence output corresponding to the re-excitation light is added, so the fluorescence output is higher than that of Comparative Example 1 that does not include the reflective reflection film and the metal reflection film.

  Since most light (90% or more) is reflected by the total reflection film and the increased reflection film, there is no need for the metal reflection film and there is no great difference in the fluorescence output.

<Example 2>
The same phosphor plate sample as the sample 6 of Example 1 (phosphor concentration 100%) was prepared, and an antireflection layer was formed on one surface thereof in the same manner as in Example 1. A white alumina layer (thickness: 30 μm) was formed on the other surface by plasma spraying. The phosphor plate sample after the formation of the white alumina layer was joined to the metal substrate on the white alumina layer side in the same manner as in Example 1 to obtain a sample of Example 2.

  In order to confirm the reflection characteristics of the white alumina layer of the sample of Example 2, when a white alumina layer was formed on a glass substrate by plasma spraying and the reflection spectrum was measured, it was 95% or more for light with wavelengths of 450 nm and 510 nm. It was confirmed that there was a reflectance of.

  When the phosphor output of the sample of Example 2 was measured in the same manner as in Example 1, it was 1.07 (value normalized by the phosphor concentration of 100% of Comparative Example 1), and high luminance was obtained. It was confirmed.

  ADVANTAGE OF THE INVENTION According to this invention, the high-intensity green light source suitable as a light source for projectors can be provided.

DESCRIPTION OF SYMBOLS 10 ... Laser light source, 20 ... Light emission part, 21 ... Phosphor plate, 22 ... Reflection layer, 25 ... Antireflection layer, 26 ... Protective film, 27 ... Ceramic layer , 30 ... substrate, 40 ... bonding material, 50 ... high frequency vibration table, 55 ... high frequency vibrator, 60 ... support member, 80 ... red light source, 91 ... half mirror , 92 (921 to 923) ... Dichroic mirror, 94 ... Conversion element 100 ... Light emitting device, 221 ... Metal reflection film, 222 ... Increase reflection film, 223 ... Total reflection film, 800: Light source device for projector.

Claims (13)

A light source that emits laser light; and a light emitting unit that is spatially spaced from the light source, wherein the light emitting unit is a substrate, a phosphor layer that is disposed on the substrate, the substrate, and the fluorescent light. A reflective layer disposed between the body layer and
A light emitting device comprising an optical path adjusting means for changing a propagation direction of laser light propagating through the phosphor layer. The light-emitting device according to claim 1,
The light-emitting device, wherein the reflective layer includes a metal reflective film, an increased reflective film, and a total reflective film in order from the substrate.   3. The light emitting device according to claim 2, wherein the optical path adjusting means is an interpolating material dispersed in the phosphor layer.   3. The light emitting device according to claim 2, wherein the phosphor layer is composed of a plurality of layers, and the optical path adjusting means is an interpolation material dispersed in at least one of the plurality of layers. Light emitting device.   5. The light-emitting device according to claim 3, wherein the interpolating material has a grain boundary diameter that diffracts and scatters laser light in a traveling direction of the laser light.   5. The light-emitting device according to claim 3, wherein the interpolating material has a grain boundary shape of a substantially spherical shape or a substantially spherical polygonal shape.   5. The light-emitting device according to claim 3, wherein the interpolating material has a crystal structure different from that of the phosphor crystal and includes a phosphor crystal constituent element. The light-emitting device according to claim 3 or 4,
The light-emitting device, wherein the laser light is a blue laser, the phosphor contained in the phosphor layer is LuAG: Ce, and the interpolating material is Al ₂ O ₃ . The light-emitting device according to claim 8,
A light-emitting device, wherein the concentration of the phosphor contained in the phosphor layer is 75 volume% or more and 95 volume% or less.   2. The light emitting device according to claim 1, wherein the reflective layer includes a metal reflective film and a white ceramic layer in order from the substrate, and the optical path adjusting means is the white ceramic layer and is in contact with the phosphor layer. A light emitting device characterized by being arranged. The light-emitting device according to claim 10,
The light emitting device, wherein the laser light is a blue laser, and the phosphor layer contains LuAG: Ce as a phosphor and substantially does not contain an interpolation material. The light emitting device according to any one of claims 1 to 11,
A light-emitting device, wherein an antireflection film is formed on the phosphor layer.   A light source for a projector, which is a combination of an LD blue light source, an LED red light source and a green light source, wherein the green light source is the light emitting device according to claim 1.

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