JP7119600B2 - fluorescent light emitting element - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fluorescent light-emitting device containing a phosphor.

BACKGROUND ART Conventionally, a fluorescent light source device is known which includes an excitation light source composed of a semiconductor laser element and a fluorescent light emitting element containing a phosphor, and irradiates the phosphor with light (laser light) emitted from the excitation light source to generate fluorescence. (see, for example, Patent Document 1 below). Fluorescence generated in such a fluorescence light source device is used, for example, as a light source for a projector.

Japanese Patent No. 5900563

In recent years, there has been an increasing market demand for smaller, brighter projectors. When using the fluorescence emitted from the fluorescence light source device as a light source for a projector, it is necessary to increase the luminance of the fluorescence generated in the fluorescence light source device. From the viewpoint of increasing the brightness of the fluorescence, it is preferable to reduce the spot diameter of the fluorescence generated by the phosphor.

Further, the optical system included in the projector is generally configured so as to be able to take in only light beams having an étendue within a predetermined range. In other words, when the fluorescent spot diameter is large, only part of the extracted light can be used, and the light utilization efficiency is low, making it difficult to realize a high-brightness projector. Note that this problem is not limited to projector applications, and can occur in general optical components that utilize fluorescence extracted from the fluorescence light source device.

SUMMARY OF THE INVENTION In view of the above problems, an object of the present invention is to provide a fluorescent light-emitting device capable of achieving high luminance with a limited light-emitting area.

The inventor of the present invention has found through intensive research that a fluorescent light-emitting device having the following structure can realize a high-luminance fluorescent light-emitting device.

That is, the fluorescent light-emitting device according to the present invention is
Having a plate-shaped fluorescent plate containing a phosphor and a binder made of a material different from the phosphor,
The thermal conductivity of the binder material is 8 W / (m K) or more,
a refractive index difference between the material of the phosphor and the material of the binder is 0.25 or more;
The fluorescent plate is characterized by having a moth-eye structure presenting an uneven shape on at least one surface of the fluorescent plate.

As described above, by configuring the binder with a material having a thermal conductivity of 8 W / (m K) or more, even when the fluorescent light emitting element is fixed to the member of the light source device and used, Heat can be discharged with high efficiency, and the occurrence of temperature quenching is suppressed. That is, it is not necessary to attach the fluorescent light emitting element to a wheel or the like having a rotation drive mechanism and rotate it for cooling.

As described above, by setting the refractive index difference between the material of the phosphor and the material of the binder to be 0.25 or more, out of the light (fluorescence) generated by the phosphor, substantially It is possible to easily change the traveling direction of the light traveling in the parallel direction to the side of the light extraction surface of the fluorescent plate. That is, the fluorescent spot diameter on the light extraction surface of the fluorescent plate can be reduced, and the brightness on the light extraction surface can be enhanced.

Furthermore, as described above, by forming the moth-eye structure on at least one surface of the fluorescent plate, when the light generated by the phosphor is guided to the extraction surface side, the reflection on the surface is suppressed. Therefore, the light extraction efficiency is enhanced. The surface on which the moth-eye structure is formed may be at least the light extraction surface of the fluorescent plate.

More specifically, the fluorescent light emitting element includes a substrate and a bonding layer formed on the substrate, and the fluorescent plate is fixedly bonded to the substrate via the bonding layer. can be

In the fluorescent light emitting device, the volume ratio of the phosphor contained in the fluorescent plate may be 50% or more. With such a configuration, the intensity of fluorescence generated by the fluorescence emitting element can be increased.

In the fluorescent light emitting element, the particle size of the phosphor contained in the fluorescent plate may be 10 μm or less. In this specification, the term "particle size of the phosphor" refers to the average particle size of the primary particles that make up the phosphor. Means the average value of the measured values of the particle diameter (long axis length) of the particles.

The fluorescent plate may contain pores with a volume ratio of 0.8% to 5%. By including pores in the fluorescent screen, a large refractive index difference occurs between the phosphor and the pores, and between the binder and the pores. can be directly directed toward the surface of the fluorescent plate (light extraction surface).

In the fluorescent light emitting device,
the phosphor comprises _La3Si6N11 : _Ce or (La _{, Y} ) _3Si6N11 : _Ce ,
The binder may be made of a fluoride material.

In this specification, a phosphor defined by La ₃ Si ₆ N ₁₁ :Ce or (La, Y) ₃ Si ₆ N ₁₁ :Ce may be referred to as an “LSN phosphor”. More specifically, the phosphor can be a material defined by _La3Si6N11 : _Ce2 ⁺ or (La, _Y ⁾ _3Si6N11 : _{Ce2 +} . Fluoride materials constituting the binder include CaF ₂ and BaF ₂ . For example, an LSN phosphor made of La ₃ Si ₆ N ₁₁ :Ce has a refractive index of 2.0 and a binder made of CaF ₂ has a refractive index of 1.39. At this time, the refractive index difference between the two is 0.61.

According to the fluorescent light-emitting device of the present invention, the light-emitting area is limited, and high-brightness fluorescent light with a small spot diameter can be generated.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows typically the structure of the fluorescence light source device of one Embodiment containing the fluorescence light emitting element of this invention. It is a sectional view showing typically composition of a fluorescent light emitting element. 2 is a cross-sectional view schematically showing the structure of a fluorescent plate; FIG. 4 is a graph showing the relationship between the peak fluorescence intensity and the volume content of the phosphor in the fluorescence light-emitting device made of each material of Example 1, Comparative Example 1, and Reference Example 1. FIG. 4 is a graph showing the relationship between the peak fluorescence intensity and the particle size of the phosphor in the fluorescence light-emitting device made of the material of Example 1. FIG. 4 is a graph showing the relationship between the peak fluorescence intensity and the volume content of the phosphor in the phosphor plates made of the materials of Examples 1, 2, 3, and 4. FIG. 5 is a graph showing the relationship between the peak fluorescence intensity and the volume content of the phosphor in the phosphor plates made of the materials of Example 1, Example 5, Example 6, Comparative Example 2, and Reference Example 2. FIG.

The configuration of the fluorescent light emitting device of the present invention will be described with reference to the drawings. Note that in the following figures, the dimensional ratios on the drawings and the actual dimensional ratios do not necessarily match.

FIG. 1 is a drawing schematically showing the configuration of a fluorescence light source device of one embodiment, including fluorescence light emitting elements. A fluorescence light source device 1 shown in FIG.

The excitation light source 2 includes, for example, a semiconductor laser element that emits light in the blue region with a wavelength of 445 nm or more and 465 nm or less. The excitation light source 2 can be provided with an optical system such as a collimating lens as required.

The fluorescent light emitting element 10 contains a phosphor and a binder, which will be described later. When the fluorescence light emitting element 10 is irradiated with the excitation light 21 emitted from the excitation light source 2 , the phosphor contained in the fluorescence light emitting element 10 is excited, and fluorescence 22 is emitted from the fluorescence light emitting element 10 . The fluorescence 22 is light with a longer wavelength than the excitation light 21, and has a wavelength of 470 nm or more and 700 nm or less, for example.

In the fluorescence light source device 1 shown in FIG. 1, the dichroic mirror 3 is configured to transmit excitation light 21 emitted from the excitation light source 2 and reflect fluorescence 22 emitted from the fluorescence light emitting element 10. The dichroic mirror 3 is arranged such that the mirror surface is inclined at an angle of 45° with respect to the incident angle of the excitation light 21, for example. With such a configuration, the fluorescence 22 is taken out of the fluorescence light source device 1 and enters, for example, a subsequent optical system (not shown).

As will be described later, the fluorescent light-emitting device 10 includes a binder with high thermal conductivity, and thus has high heat exhausting properties. Therefore, the fluorescent light emitting element 10 does not need to be installed on a separate rotating wheel or the like for cooling, and can be fixedly installed at a predetermined location of the device.

FIG. 2 is a cross-sectional view schematically showing the configuration of the fluorescent light emitting device 10. As shown in FIG. The fluorescent light emitting device 10 has a substrate 11, a bonding layer 12, a reflective layer 13, and a fluorescent plate .

(substrate 11)
The substrate 11 is provided to dissipate heat generated by the fluorescent screen 14 . The substrate 11 is made of a material having a thermal conductivity of, for example, 90 W/(m·K) or more, specifically, 230 to 400 W/(m·K). Examples of such materials include Cu, copper compounds (MoCu, CuW, etc.), Al, AlN, and the like.

The thickness of the substrate 11 is, for example, 0.5 mm to 5 mm. Moreover, from the viewpoint of heat dissipation, etc., it is preferable that the surface area of the substrate 11 is larger than the area of the fluorescent screen 14 .

(Joining layer 12)
The bonding layer 12 is a layer that bonds the substrate 11 and the fluorescent screen 14, and is made of, for example, a solder material. From the viewpoint of heat dissipation, it is preferable to use a material having a thermal conductivity of, for example, 40 W/(m·K) or more as the material forming the bonding layer 12 . More specifically, for example, cream solder, Sn--Ag--Cu-based solder, Au--Sn-based solder, etc., which are in the form of cream (paste) by mixing flux and other impurities into materials such as Sn and Pb. can be used. The thickness of the bonding layer 12 is, for example, 20 μm to 200 μm.

In addition, although not shown, from the viewpoint of further improving the bondability between the substrate 11 and the bonding layer 12, between the substrate 11 and the bonding layer 12, a metal made of a Ni/Au film formed by, for example, a plating method A film may be formed. The thickness of this metal film can be Ni/Au=1000 nm to 5000 nm/30 nm to 1000 nm, for example.

(Reflection layer 13)
The reflective layer 13 is formed on the surface of the fluorescent screen 14 that faces the substrate 11 . The reflective layer 13 is provided to reflect the fluorescent light 22 generated by the fluorescent plate 14 and traveling toward the side opposite to the light extraction surface 14a (the substrate 11 side) and guide the fluorescent light 22 to the light extraction surface 14a. ing. The reflective layer 13 can be composed of, for example, a metal film such as Al or Ag, or a high reflection film formed by forming a dielectric multilayer film on the metal film.

Although not shown, from the viewpoint of further improving the bondability between the fluorescent plate 14 and the bonding layer 12, the surface of the fluorescent plate 14 on the substrate 11 side, more specifically, the reflective layer 13 and the fluorescent plate 14 are bonded together. A metal film made of, for example, a Ni/Pt/Au film or a Ni/Au film formed by vapor deposition may be formed between them. The thickness of this metal film can be Ni/Pt/Au=30 nm/500 nm/500 nm, for example.

(Fluorescent plate 14)
The fluorescent plate 14 is formed on the reflective layer 13 . The fluorescent plate 14 emits fluorescence 22 when the excitation light 21 emitted from the excitation light source 2 is incident thereon. As an example, the fluorescent plate 14 has a rectangular plate-like structure when viewed in a direction orthogonal to the surface of the substrate 11 . The thickness of the fluorescent plate 14 is, for example, 0.05 mm to 1 mm.

FIG. 3 is a cross-sectional view schematically showing the configuration of the fluorescent screen 14. As shown in FIG. The phosphor plate 14 shown in FIG. 3 includes a phosphor 16, a binder 17, and pores 18. As shown in FIG. Further, as shown in FIG. 2, the fluorescent plate 14 has a moth-eye structure 15 on the side opposite to the substrate 11, that is, on the side of the light extraction surface 14a.

The binder 17 is formed so as to fill the gaps between the particulate phosphors 16, as schematically illustrated in FIG. The binder 17 is made of a material exhibiting thermal conductivity λ≧8W/(m·K). Examples of such materials include CaF ₂ [λ=10 W/(m·K)], BaF ₂ [λ=12 W/(m·K)], ZnS [λ=27 W/(m·K)], Al ₂ O ₃ [λ=40 W/(m·K)] and the like.

In the phosphor 16, the difference δn (=|n ₁₆ −n ₁₇ |) between the refractive index n _{16 of the material of the phosphor 16} and the refractive index n ₁₇ of the material of the binder 17 satisfies δn≧0.25. selected from materials.

For example, when the binder 17 is CaF ₂ [n ₁₇ =1.39], BaF ₂ [n ₁₇ =1.46], or ZnS [n ₁₇ =2.2], the phosphor 16 is LSN (La _3Si6N11 : _Ce2 ⁺ , (La, Y) _3Si6N11 : _Ce2 ⁺ ) [ _n16 = 2.0], β sialon ( _SrSiAlON : _Eu2 ⁺ ) [ _n16 = 2.0 ], CSO( _CaSc2O4 : _Ce3 ⁺ )[ _n16 =1.9], _LuAG ( _Al5O12Lu3 : _Ce2 ⁺ )[ _n16 = _1.84 ], YAG( _Al5O12 Y3: _Ce2 ⁺ )[ _n16 =1.83], BOSS((Sr,Ba,Mg) _2SiO4 : _Eu2 ⁺ )[ _n16 =1.8], and BSS((Ba,Sr) SiO ₄ :Eu ²⁺ )[n ₁₆ =1.8] can be one or more selected from the group such that the refractive index difference δ _n is within a predetermined range.

Further, when the binder 17 is Al ₂ O ₃ [n ₁₇ =1.75], the phosphor 16 includes LSN [n ₁₆ =2.0], β-sialon [n ₁₆ =2.0], and CSO It may be one or more selected from the group consisting of [n ₁₆ =1.9] so that the refractive index difference δ _n falls within a predetermined range.

The particle size of the phosphor 16 is 30 μm or less, preferably 25 μm or less, more preferably 20 μm or less, and particularly preferably 10 μm or less. Although the lower limit of the particle diameter of the phosphor 16 is not particularly defined, it is generally 1 μm or more.

The volume ratio of the phosphor 16 contained in the fluorescent plate 14 is preferably 8% or more and 98% or less, more preferably 30% or more and 98% or less, and even more preferably 50% or more and 98% or less. is. The volume ratio (volume content) of the phosphors 16 contained in the phosphor plate 14 refers to the ratio of the total volume occupied by the phosphors 16 to the entire volume of the phosphor plate 14 . For example, when the fluorescent plate 14 contains the binder 17 with a volume ratio of 20% and the pores 18 with a volume ratio of 3%, the volume ratio of the phosphor 16 may be substantially 77%. The term "substantially" as used herein means that the contained impurities are not considered.

As shown in FIG. 3, in this embodiment, some pores 18 are formed in the fluorescent plate 14 . The volume ratio of the pores 18 contained in the fluorescent plate 14 is preferably 0.8% or more and 5% or less.

The fluorescent screen 14 can be manufactured, for example, by the following method. First, the particles forming the phosphor 16 and the particles forming the binder 17 are mixed using a dry mixing method such as a ball mill or V-blender to obtain mixed powder. As another method, a predetermined solvent is added to both particles to form a slurry, and the particles are mixed by a wet mixing method using a ball mill, homogenizer, ultrasonic homogenizer, twin-screw kneader, etc., and then obtained. A mixed powder is obtained by evaporating the solvent from the obtained slurry at a predetermined temperature.

After that, the obtained mixed powder is press-molded, and the obtained compact is sintered. After that, hot isostatic pressing (HIP) is applied to the obtained sintered body. The content of the pores 18 contained in the fluorescent plate 14 can be controlled by the conditions of pressurization. After that, one surface is subjected to an etching process to produce a fluorescent plate 14 including a moth-eye structure 15 having fine irregularities.

The fine uneven shape included in the moth-eye structure 15 has a nanometer-order diameter of 300 nm or more and 600 nm or less.

According to the fluorescent light emitting device 10 of the above-described embodiment, the improvement in luminance over the conventional device will be described with reference to examples. Materials of phosphors and binders used in the fluorescent plates 14 of Examples, Comparative Examples, and Reference Examples are shown in Table 1 below. Note that the volume content of the phosphor 16 and the particle size of the phosphor 16 were appropriately changed within the conditions described in Table 1 for the phosphor plates 14 of each example, comparative example, and reference example. was adopted.

(Example 1)
The fluorescent screen 14 of Example 1 includes a phosphor 16 made of LSN (La ₃ Si ₆ N ₁₁ :Ce ²⁺ ), a binder 17 made of CaF ₂ , and pores 18 having a volume content of 0.8%. A moth-eye structure 15 is formed on the side of the light extraction surface 14a.

(Example 2, Example 3, Example 7)
The fluorescent plate 14 of Example 2 was manufactured under the same conditions as the fluorescent plate 14 of Example 1, except that the volume content of pores 18 was changed to 5%. Similarly, the fluorescent plate 14 of Example 3 was produced under the same conditions as the fluorescent plate 14 of Example 1, except that the volume content of the pores 18 was changed to 0%, that is, the configuration was changed to include no pores 18. is. Similarly, the fluorescent plate 14 of Example 7 was produced under the same conditions as those of the fluorescent plate 14 of Example 1, except that the volume fraction of pores 18 was changed to 10%.

(Example 4, Example 5)
The fluorescent plate 14 of Example 4 was produced under the same conditions as the fluorescent plate 14 of Example ₁ , except that the material of the binder 17 was changed to BaF2. Similarly, the fluorescent screen 14 of Example 5 was produced under the same conditions as those of the fluorescent screen 14 of Example 1, except that the material of the binder 17 was changed to Al ₂ O ₃ .

(Example 6)
The fluorescent plate 14 of Example 4 was produced under the same conditions as the fluorescent plate 14 of Example 1, except that the material of the phosphor 16 was changed to YAG (Al ₅ O ₁₂ Y ₃ :Ce ²⁺ ). be.

(Comparative Example 1, Comparative Example 2)
Fluorescent plate 14 of Comparative Example 1 includes phosphor 16 made of YAG (Al ₅ O ₁₂ Y ₃ :Ce ²⁺ ) and binder 17 made of Al ₂ O ₃ , does not include pores 18, and has light extraction surface 14a. The moth-eye structure 15 is not formed on the side. The fluorescent plate 14 of Comparative Example 2 was manufactured under the same conditions as those of the fluorescent plate 14 of Comparative Example 1, except that pores 18 with a volume content of 3% were included.

(Reference Example 1, Reference Example 2)
Fluorescent plate 14 of Reference Example 1 is the same as Example 1 except that the volume content of pores 18 is changed to 0%, that is, no pores 18 are included, and moth-eye structure 15 is not formed on the light extraction surface 14a side. 1 is produced under the same conditions as the fluorescent plate 14 of FIG. The fluorescent plate 14 of Reference Example 2 was manufactured under the same conditions as the fluorescent plate 14 of Reference Example 1, except that the volume content of pores 18 was changed to 3%.

(Explanation of each graph)
FIG. 4 is a graph showing the relationship between the peak fluorescence intensity of the fluorescence 22 emitted from the fluorescent plate 14 made of each material of Example 1, Comparative Example 1, and Reference Example 1 and the volume content of the phosphor 16, The horizontal axis is displayed in logarithmic notation.

The values on the vertical axis shown in FIG. 4 and FIGS. 5 to 7 described later are for each fluorescent plate 14 according to the example, comparative example, or reference example described above with reference to Table 1. , correspond to the peak intensity values of the fluorescence 22 emitted from the fluorescent plate 14 when the excitation light is irradiated under the same conditions (wavelength and intensity). The values on the vertical axis (peak intensity of fluorescence 22) in FIGS. 4 to 7 are expressed as relative values with respect to the same reference value. That is, for example, the value indicated by the intensity 100 [a.u.] in the graph of FIG. 4 and the value indicated by the intensity 100 [a.u.] in the graphs of FIGS. 5 to 7 are the same value.

FIG. 4 shows that in Example 1, the particle size of the phosphor 16 is five types of 5 µm, 10 µm, 20 µm, 25 µm, and 30 µm. 5 is a graph showing the results of a simulation performed with 5 μm.

FIG. 5 is a graph obtained by extracting only the data of the fluorescent screen 14 of Example 1 from FIG. 4, plotting the particle size of the phosphor 16 on the horizontal axis and the fluorescence intensity on the vertical axis.

FIG. 6 shows the relationship between the peak fluorescence intensity of the fluorescence 22 emitted from the fluorescent plate 14 made of each material of Examples 1, 2, 3, and 4 and the volume content of the phosphor 16. 4, and the horizontal axis is displayed in logarithmic notation as in FIG. In FIG. 6, the particle size of the phosphor 16 is two types of 5 μm and 10 μm in Example 1, and the particle size of the phosphor 16 is one type of 10 μm in Examples 2 to 4. results are shown.

FIG. 7 is a graph showing the relationship between the peak fluorescence intensity and the volume content of the phosphor 16 in the phosphor plate 14 made of each material of Example 1, Example 5, Example 6, Comparative Example 2, and Reference Example 2. , and the horizontal axis is logarithmically represented as in FIG. In FIG. 7, in Example 1, the particle size of the phosphor 16 is two types of 20 μm and 25 μm, and in Example 5, Example 6, Comparative Example 2, and Reference Example 2, the particle size of the phosphor 16 is The results of a simulation performed with one grain size of 10 μm are shown.

(Verification of results)
The results shown in FIGS. 4 to 7 will be verified below.

<<1>> According to FIG. 4, in the phosphor screen 14 of Comparative Example 1, as the volume content of the phosphor 16 increases, the intensity of the emitted fluorescence light 22 gradually increases, but the degree of increase is similar to that of Example 1. Remarkably smaller than Reference Example 1. On the other hand, in the fluorescent light emitting devices of Example 1 and Reference Example 1, regardless of the particle size of the phosphor 16, it is confirmed that the fluorescence intensity increases significantly as the volume content of the phosphor 16 increases. .

In both Example 1 and Reference Example 1, the refractive index difference δn (=|n ₁₆ −n ₁₇ |) between the phosphor 16 and the binder 17 is as large as 0.61. The difference δn is as small as 0.08. When the particle size of the phosphor 16 is the same, increasing the volume ratio (volume content ratio) of the phosphor 16 contained in the phosphor plate 14 allows the phosphor 16 and the binder 17 to come into contact with each other in the same region. means more frequently.

When the refractive index difference δn between the phosphor 16 and the binder 17 is large, the fluorescence 22 that is emitted from the particles of the phosphor 16 and propagates into the binder 17 and enters the particles of the phosphor 16 that are adjacent from the binder 17 again. The emitted fluorescent light 22 changes its traveling direction each time due to the refractive index difference. As a result, even if the fluorescence 22 propagates from the phosphor 16 in a direction substantially parallel to the surface of the fluorescent plate 14, the traveling direction immediately changes and is led to the light extraction surface 14a. That is, the distance that the fluorescent light 22 moves in the direction parallel to the surface of the fluorescent plate 14 is shortened until the fluorescent light 22 is guided to the light extraction surface 14a. The luminance on the light extraction surface 14a is enhanced.

On the other hand, when the refractive index difference δn between the phosphor 16 and the binder 17 is small, the fluorescence 22 emitted from the particles of the phosphor 16 and proceeding into the binder 17 and the phosphor approaching from the binder 17 again The fluorescence 22 incident on the 16 particles hardly changes its traveling direction. Therefore, the fluorescence 22 traveling from the phosphor 16 in a direction substantially parallel to the surface of the fluorescent plate 14 continues to travel in the same direction, and as a result, is less likely to be guided toward the light extraction surface 14a. This is evident in the fact that in Comparative Example 1, even if the volume content of the phosphor 16 is increased, the intensity of the fluorescence 22 hardly changes.

As in Comparative Example 1, phosphor 16 made of YAG (Al ₅ O ₁₂ Y ₃ :Ce ²⁺ ) and binder 17 made of Al ₂ O ₃ were included. As shown in FIG. 7, it is confirmed that the intensity of the fluorescence 22 hardly changes even when the volume content of the phosphor 16 is increased.

Further, according to the results of Example 5 (particle size 10 μm, refractive index difference δn=0.25) shown in FIG. 7, Comparative Example 1 (particle size 10 μm, refractive index difference δn=0.08) shown in FIG. As compared with Example 1 shown in FIG. The upward trend is relatively low compared to This result also shows that the intensity of fluorescence 22 can be increased by increasing the volume content of phosphor 16 as the refractive index difference δn between phosphor 16 and binder 17 increases. That is, the present inventors (and others) found that when the refractive index difference δn between the phosphor 16 and the binder 17 is as small as about 0.08, the intensity of the fluorescence 22 is increased even if the volume content of the phosphor 16 is increased. Although the effect is not so good, new knowledge was found that the intensity of the fluorescence 22 can be increased by increasing the volume content of the phosphor 16 by setting the refractive index difference δn to 0.25 or more. rice field.

That is, from the above verification, by setting the refractive index difference δn between the phosphor 16 contained in the fluorescent plate 14 and the binder 17 to be 0.25 or more, the effect of increasing the intensity of the fluorescence 22 extracted from the fluorescent plate 14 can be obtained. I understand.

In Example 4 (particle size: 10 μm, refractive index difference δn=0.54) shown in FIG. 6 and Example 6 (particle size: 10 μm, refractive index difference δn=0.44) shown in FIG. As the volume content of the body 16 increases, the intensity of the emitted fluorescence 22 tends to increase to the same extent as in Example 5 or more. From these results, the refractive index difference δn between the phosphor 16 and the binder 17 contained in the fluorescent plate 14 is more preferably 0.44 or more, more preferably 0.54 or more, and more preferably 0.61 or more. is particularly preferred.

<<2>> In FIG. 4, when the results of Example 1 (with moth-eye structure 15) and Reference Example 1 (without moth-eye structure 15) are compared, regardless of the value of the volume content of phosphor 16, the fluorescent plate of Example 1 It can be seen that the intensity of the fluorescence 22 emitted from 14 is higher than the intensity of the fluorescence 22 emitted from the fluorescent plate 14 of Reference Example 1. FIG. As described above, the fluorescent plate 14 of Example 1 and the fluorescent plate 14 of Reference Example 1 were formed under the same conditions except for the presence or absence of the moth-eye structure 15 . From this result, it can be seen that providing the moth-eye structure 15 on the side of the light extraction surface 14a of the fluorescent plate 14 has the effect of further increasing the intensity of the fluorescence 22 to be extracted.

<<3>> According to FIG. 5, the intensity of the fluorescent light 22 emitted from the fluorescent screen 14 of Example 1 is such that when the volume content of the fluorescent material 16 is 8% or more, the particle diameter of the fluorescent material 16 is 5 μm to 30 μm. exceeds the maximum intensity of the fluorescence 22 emitted from the fluorescent screen 14 of Comparative Example 1 within the entire range of . Further, the intensity of the fluorescent light 22 emitted from the fluorescent screen 14 of Example 1 is maintained within the entire range of the particle diameter of the fluorescent substance 16 from 5 μm to 30 μm by setting the volume content of the fluorescent substance 16 to 50% or more. , greatly exceeds the maximum intensity of the fluorescence 22 emitted from the fluorescent screen 14 of Comparative Example 1. FIG.

Further, according to FIG. 6, the intensity of the fluorescence 22 emitted from each of the fluorescent plates 14 of Examples 2, 3, and 4 was reduced to Both are shown to greatly exceed the maximum intensity of the fluorescence 22 emitted from the fluorescent screen 14 of Comparative Example 1. Furthermore, according to FIG. 7, the intensity of the fluorescence 22 emitted from each of the fluorescent plates 14 of Examples 5, 6, and 7 was reduced to It is shown that the maximum intensity of the fluorescence 22 emitted from the fluorescent screen 14 of Comparative Example 1 is greatly exceeded.

<<4>> According to FIG. 5, in the phosphor screen 14 of Example 1, the intensity of emitted fluorescence 22 is higher as the particle size of the phosphor 16 is smaller within the range of 20 μm or less. , that the intensity of the emitted fluorescence 22 does not change much depending on the volume content of the phosphor 16 . Therefore, from the viewpoint of increasing the intensity of the fluorescence 22 extracted from the fluorescent screen 14, the particle size of the phosphor 16 is preferably 20 μm or less, more preferably 10 μm or less.

<<5>> In FIG. 6, Example 1 (particle diameter of phosphor 16: 10 μm, porosity 0.8%) and Example 2 (particle diameter of phosphor 16: 10 μm, porosity 5%) are compared. Then, it can be seen that the intensity of the fluorescence 22 emitted from the fluorescent plate 14 of Example 2 is higher than the intensity of the fluorescence 22 emitted from the fluorescent plate 14 of Example 1. FIG. On the other hand, when comparing Example 1 (particle diameter of phosphor 16: 10 μm, porosity 0.8%) and Example 3 (particle diameter of phosphor 16: 10 μm, porosity 0%), Example It can be seen that the intensity of the fluorescence 22 emitted from the fluorescent plate 14 of Example 1 is higher than the intensity of the fluorescence 22 emitted from the fluorescent plate 14 of Example 3. Further, according to the fluorescent plate 14 of Example 7 (particle diameter of phosphor 16: 10 μm, porosity of 10%) shown in FIG. .

From this result, from the viewpoint of increasing the intensity of the fluorescence 22 extracted from the fluorescent plate 14, it is preferable to include the pores 18 in the fluorescent plate 14, and it is more preferable to set the volume content ratio to 0.8% or more and 10% or less. It is preferably 5% or more and 10% or less, even more preferably.

By including the pores 18 in the fluorescent plate 14 , the phosphor 16 and the pores 18 and the binder 17 and the pores 18 are in contact in the fluorescent plate 14 . The refractive index of the pores 18 is substantially 1, which is a value different from that of the phosphor 16 and the binder 17 . Therefore, when the fluorescence 22 emitted from the particles of the phosphor 16 or traveling through the binder 17 is incident on the pores 18, the traveling direction changes due to the refractive index difference. This enhances the effect of guiding the fluorescence 22 to the light extraction surface 14a side.

From this point of view, it is preferable to include many pores 18 in the fluorescent plate 14 . On the other hand, however, if too many pores 18 are contained, the volume ratio of the phosphor 16 contained in the fluorescent plate 14 is accordingly decreased, so that the light amount of the fluorescent light 22 generated within the fluorescent plate 14 is decreased. . From this point of view, the volume content of pores 18 is preferably 10% or less.

<<6>> As the binder 17, from the viewpoint of using a material exhibiting high thermal conductivity and ensuring a large refractive index difference between the binder 17 and the phosphor 16, the binder 17 is made of _CaF2 , _BaF2 , or the like. , and the phosphor 16 is preferably made of LSN.

Reference Signs List 1: Fluorescent light source device 2: Excitation light source 3: Dichroic mirror 10: Fluorescent light emitting element 11: Substrate 12: Bonding layer 13: Reflective layer 14: Fluorescent plate 14a: Light extraction side surface of wavelength conversion layer 15: Moth-eye structure 16: Fluorescence Body 17: Binder 18: Pore 21: Excitation light 22: Fluorescence

Claims (6)

Having a plate-shaped fluorescent plate containing a phosphor and a binder made of a material different from the phosphor,
The thermal conductivity of the binder material is 8 W / (m K) or more,
a refractive index difference between the material of the phosphor and the material of the binder is 0.25 or more;
The fluorescent plate has a moth-eye structure presenting an uneven shape on at least one surface of the fluorescent plate ,
A fluorescent light-emitting device, wherein the volume ratio of the phosphor contained in the fluorescent plate is greater than 50% . 2. The fluorescent light-emitting device according to claim 1, wherein the volume ratio of said phosphor contained in said fluorescent plate is 60% or more. comprising a substrate and a bonding layer formed on the upper layer of the substrate;
3. The fluorescent light-emitting device according to claim 1 , wherein said fluorescent plate is fixedly bonded onto said substrate via said bonding layer. 4. The fluorescent light-emitting device according to claim 1, wherein the fluorescent material contained in the fluorescent plate has a particle size of 10 μm or less. The fluorescent light-emitting device according to any one of claims 1 to 4, wherein the fluorescent plate contains pores with a volume ratio of 0.8% to 5%. the phosphor comprises _La3Si6N11 : _Ce or (La _{, Y} ) _3Si6N11 : _Ce ,
The fluorescent light-emitting device according to any one of claims 1 to 5, wherein the binder is made of a fluoride material.

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