Fluorescent light source device

Abstract

To provide a fluorescent light source device which includes a light source for excitation and a phosphor, and which can generate light showing a high color rendering property.SOLUTION: A fluorescent light source device includes: an excitation light source for emitting excitation light in a blue region; a fluorescent plate which includes a phosphor in which Ce is activated, and which generates long wavelength fluorescent light by receiving the excitation light; a collimating optical system which at least reduces a divergence angle of the fluorescent light; and a notch filter where light emitted from the collimating optical system passes. In the notch filter, a light incident surface is arranged in the direction substantially orthogonal to an optical axis of a main light ray of the light emitted from the collimating optical system, and as for a cut wavelength region, a central wavelength of the cut wavelength region belongs to the range of 553 nm to 575 nm and a half value width is within the range of 17 nm to 41 nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fluorescent light source device that converts the wavelength of incident excitation light and emits generated fluorescent light. [Background technology]

[0002] In a light source device that generates illumination light, there is a market demand for high color rendering properties of the illumination light.

[0003] Patent Document 1 below discloses a light source device including an excitation light-emitting element formed of a GaN-based LED element and a wavelength control optical element containing a phosphor that receives light emitted from the light-emitting element and emits fluorescence. The wavelength control optical element disclosed in Patent Document 1 has a multilayer structure, specifically including a first wavelength conversion layer in which a green fluorescent dye is dispersed within a matrix resin, a second wavelength conversion layer in which a red fluorescent dye is dispersed within a matrix resin, and a wavelength selection layer in which a light-absorbing dye is dispersed within a matrix resin.

[0004] According to Patent Document 1, the wavelength control optical element having the above structure can improve color rendering by absorbing yellow light, which reduces color rendering, with a light-absorbing pigment and a red fluorescent pigment, and emitting red light with the red fluorescent pigment.

[0005] Furthermore, Patent Document 2 discloses a technique for cutting light in the red range using a dichroic mirror that functions as a notch filter in order to improve color reproducibility. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2017-138534 [Patent Document 2] Patent No. 5928383 Summary of the Invention [Problem to be solved by the invention]

[0007] The method of Patent Document 1 improves color rendering by absorbing light in the visible range using a phosphor or a dye-absorbing dye. As a result, a large amount of light is absorbed in the wavelength control optical component, and as a result, the output of the excitation light source needs to be increased to obtain a high light output, resulting in insufficient light utilization efficiency.

[0008] Furthermore, the method of Patent Document 2 has a structure in which a dichroic mirror functions as a notch filter, and is arranged at a 45° inclination with respect to the optical axis. A notch filter is formed by stacking multiple dielectric layers with different refractive indices. To narrow the cut wavelength range of the notch filter, it is necessary to increase the number of layers (number of films). On the other hand, if the number of films is too large, stress on the substrate holding the dielectric multilayer film increases, which may induce deformation or cracking of the substrate. For this reason, there is a natural limit to the number of layers that can be stacked as a dielectric multilayer film.

[0009] When a notch filter is positioned with its light incident surface tilted 45° with respect to the optical axis, the chief ray of light incident on the notch filter passes through the notch filter at a 45° inclination with respect to the lamination direction of the dielectric multilayer film. This means that, compared to when the chief ray of light is incident in the normal direction of the light incident surface of the notch filter, in order to pass the same optical path length through the notch filter, the thickness of the notch filter must be increased; in other words, the number of layers must be increased. However, as mentioned above, there is a limit to the number of layers that can be stacked in a dielectric multilayer film. Therefore, a notch filter with its light incident surface tilted 45° with respect to the optical axis cannot structurally narrow the cutoff wavelength range sufficiently.

[0010] As a result of intensive research by the inventors, it has been confirmed that the color rendering property decreases as the cutoff wavelength range becomes wider. For these reasons, it is difficult to realize a light source device that exhibits extremely high color rendering property with the technology proposed in Patent Document 2.

[0011] In view of the above-mentioned problems, an object of the present invention is to enable the generation of light exhibiting high color rendering properties in a light source device including an excitation light source and a phosphor. [Means for solving the problem]

[0012] The fluorescent light source device according to the present invention comprises: an excitation light source that emits excitation light in the blue region; a fluorescent plate containing a Ce-activated phosphor, which receives the excitation light and generates fluorescence having a wavelength longer than that of the excitation light; a collimating optical system that reduces at least the divergence angle of the fluorescence; a notch filter through which the light emitted from the collimating optical system passes, the notch filter is disposed such that a light incident surface thereof is oriented substantially perpendicular to an optical axis of a chief ray of light emitted from the collimating optical system; The cut wavelength range of the notch filter has a center wavelength in the range of 553 nm to 575 nm and a half width in the range of 17 nm to 41 nm; The first feature of this invention is that the light guided to the downstream optical system via the notch filter is a composite light of the fluorescent light and light in the blue region, and has an average color rendering index (Ra value) of 85 or more.

[0013] Furthermore, the fluorescent light source device according to the present invention comprises: an excitation light source that emits excitation light; a fluorescent plate containing a Ce-activated phosphor, which receives the excitation light and generates fluorescence having a wavelength longer than that of the excitation light; a collimating optical system that reduces at least the divergence angle of the fluorescence; a notch filter through which light emitted from the collimating optical system passes; a blue light source that inputs superimposed light in a blue range onto an optical path of the fluorescence emitted from the fluorescent plate, the notch filter is disposed such that a light incident surface thereof is oriented substantially perpendicular to an optical axis of a chief ray of light emitted from the collimating optical system; The cut wavelength range of the notch filter has a center wavelength in the range of 553 nm to 575 nm and a half width in the range of 17 nm to 41 nm; The second feature is that the light guided to the downstream optical system via the notch filter is a composite light of the fluorescent light and light in the blue region, and has an average color rendering index (Ra value) of 85 or more.

[0014] The phosphor may be a Ce-activated oxide phosphor or a Ce-activated nitride phosphor. A specific example is LSN (La3Si6N 11 :Ce 2+ ,(La, Y)3Si6N 11 :Ce 2+ ), CSO(CaSc2O4:Ce 3+ ), LuAG(AlO 12 Lu3:Ce 2+ ), and YAG(AlO 12 Y3:Ce 2+ Among the materials listed above, LSN is particularly preferred.

[0015] In addition to Ce-activated phosphors, there are also Eu-activated and Gd-activated phosphors. However, compared to Ce, the electron orbitals of Eu and Gd are more susceptible to thermal influences, making them more susceptible to de-excitation. This results in significant thermal quenching and reduced luminous efficiency. Therefore, from the perspective of achieving both high color rendering and high brightness, it is preferable to use Ce as the activated material in the phosphor.

[0016] According to the above structure, the divergence angle of the fluorescence emitted from the fluorescence plate is reduced through the collimating optical system, and then the fluorescence is incident on the notch filter, whose light incident surface is oriented substantially perpendicular to the optical axis of the chief ray. As a result, the wavelength range of the fluorescence that is cut by the notch filter can be narrowed.

[0017] Specifically, the cut wavelength range of the notch filter can be set so that the center wavelength falls within the range of 553 nm to 575 nm and the half-width falls within the range of 17 nm to 41 nm. By providing such a notch filter, the color rendering of the light that passes through the filter and then enters the downstream optical system is improved. The light that enters this optical system is a composite of fluorescent light and light in the blue region, and achieves an extremely high general color rendering index (Ra value) of 85 or more. This Ra value is a high value that has not been easily achieved with conventional fluorescent light source devices that include a phosphor and an excitation light source. The chromaticity y of the composite light is preferably within the range of 0.283 to 0.373.

[0018] The Ra value of the combined light can be measured by a method conforming to the method specified in JIS Z 8726 (method for evaluating the color rendering properties of light sources), and the chromaticity y value of the combined light can be measured by a method conforming to the method specified in JIS Z 8724 (method for measuring color - light source color), for example.

[0019] Here, "the light incident surface of the notch filter is substantially perpendicular to the optical axis of the chief ray of the light emitted from the collimating optical system" means that the angle between the normal to the light incident surface and the optical axis of the chief ray of the light emitted from the collimating optical system is within the range of -5° to +5°, and more preferably within the range of -3° to +3°.

[0020] An example of the fluorescent plate is one in which particulate fluorescent material is dispersed in a binder made of an inorganic compound such as CaF2, BaF2, MgF2, ZnS, Al2O3, MgO, ZrO2, ZnO, or TiO2, and then sintered. Among the inorganic compounds listed above, oxide materials are particularly preferred as binder materials, with Al2O3 being particularly preferred. When a nitride fluorescent material is used as the fluorescent material, MgO is particularly preferred as binder material.

[0021] In the first characteristic configuration in which a light source emitting blue light is used as the excitation light source, the light source device may emit a composite light of the blue light emitted from the excitation light source and the fluorescence emitted from the fluorescent plate. In addition, in this configuration, a separate blue light source that emits blue light may be provided, and the blue light emitted from the blue light source may be superimposed on the fluorescence emitted from the fluorescent plate, and the resulting composite light may be emitted from the light source device.

[0022] On the other hand, in the second characteristic configuration, a separate blue light source that emits blue light is provided, and the blue light emitted from the blue light source is superimposed on the fluorescence emitted from the fluorescent plate, and the resulting combined light is emitted from the light source device. Therefore, the excitation light source does not necessarily have to be a light source that emits light in the blue range, and may be a light source that emits, for example, violet light or ultraviolet light. Furthermore, the position at which the light in the blue range is superimposed may be between the notch filter and the fluorescent plate or at a position subsequent to the fluorescent plate.

[0023] The collimating optical system may have a light entrance surface or a light exit surface formed as a flat surface, and the notch filter may be disposed on the flat surface.

[0024] According to the above configuration, the collimating optical system and the notch filter can be integrated, thereby reducing the size of the device. [Effects of the Invention]

[0025] The fluorescent light source device of the present invention can generate light that exhibits high color rendering properties. [Brief explanation of the drawings]

[0026] [Figure 1] 1 is a diagram schematically illustrating a configuration of an embodiment of a fluorescent light source device. [Figure 2] 1 is a diagram showing an example of a transmission spectrum of a notch filter. [Figure 3] FIG. 2 is a schematic cross-sectional view illustrating the structure of a fluorescent plate. [Figure 4] FIG. 4 is a partially enlarged view of FIG. 3. [Figure 5] 10 is a graph in which the spectrum of synthetic light L1 and the transmission spectrum of notch filter 20 are superimposed when blue light source 9 is an LED. [Figure 6] 10 is a graph in which the spectrum of synthesized light L1 and the transmission spectrum of notch filter 20 are superimposed when blue light source 9 is a laser diode. [Figure 7] 10 is a graph showing the relationship between the y value and the Ra value of the combined light L1 measured when the blue light source 9 is an LED and the material of the phosphor 16 contained in the phosphor plate 10 and the presence or absence of the notch filter 20 are changed. [Figure 8] 10 is a graph showing the relationship between the y value and the Ra value of the combined light L1 when the blue light source 9 is a laser diode and the material of the phosphor 16 contained in the phosphor plate 10 and the presence or absence of the notch filter 20 are changed. [Figure 9] 10 is a graph showing the relationship between the half width of the cut wavelength range of the notch filter 20 and the Ra value of the synthetic light L1. [Figure 10] 10 is a graph showing the relationship between the minimum transmittance of light within the cut wavelength band of the notch filter 20 and the Ra value of the combined light L1. [Figure 11] 10 is a graph showing the relationship between the center wavelength of the cut wavelength range of the notch filter 20 and the Ra value of the synthetic light L1. [Figure 12] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 13] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 14] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 15] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 16] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 17] 10 is a diagram schematically illustrating a configuration example of another embodiment of a fluorescent light source device. [Figure 18] 10 is a graph in which the spectrum of combined light L1 and the transmission spectrum of notch filter 20 are superimposed when blue light source 9 is an LED and the fluorescent plate contains two types of fluorescent materials. DETAILED DESCRIPTION OF THE INVENTION

[0027] The configuration of the fluorescent light source device of the present invention will be described with reference to the drawings. Note that in the following drawings, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the numbers on the drawings do not necessarily match the actual numbers.

[0028] 1 is a diagram illustrating the configuration of one embodiment of a fluorescent light source device. The fluorescent light source device 1 shown in Fig. 1 includes an excitation light source 5, a collimating optical system 7, a fluorescent plate 10, and a notch filter 20.

[0029] Furthermore, the fluorescent light source device 1 of this embodiment includes a blue light source 9 that emits blue light, a reflecting mirror 41, and a dichroic mirror 43.

[0030] In this embodiment, the emission wavelength of the excitation light source 5 is not limited as long as it is a wavelength that can excite the phosphors mounted on the fluorescent plate 10, but is typically in the blue, violet, or ultraviolet range. As a specific example, the excitation light source 5 is configured to include a semiconductor laser element that emits light in the blue range with a wavelength of 445 nm to 465 nm. The excitation light source 5 may also include an optical system such as a collimating lens, if necessary.

[0031] Dichroic mirror 43 is designed to reflect at least blue light and transmit light with wavelengths longer than blue light. In this specification, blue light refers to light in the wavelength range of 420 nm to 500 nm, violet light refers to light in the wavelength range of 370 nm to 420 nm, and ultraviolet light refers to light in the wavelength range less than 370 nm.

[0032] In the fluorescence light source device 1 of this embodiment shown in Fig. 1, excitation light L5 in the blue range emitted from the excitation light source 5 is guided to one main surface of the fluorescence plate 10 (the main surface opposite to the side on which the substrate 11 is disposed) via a reflecting mirror 41 and a dichroic mirror 43. The phosphor contained in the fluorescence plate 10 is excited by the excitation light L5 and emits fluorescence L10. The fluorescence L10 has its divergence angle reduced by a collimating optical system 7, is typically converted into parallel light, and then passes through a notch filter 20.

[0033] The notch filter 20 significantly reduces the light intensity of components of the incident light within a designed cutoff wavelength range, while barely reducing the light output of wavelength components outside the cutoff wavelength range. The cutoff wavelength range of the notch filter 20 is designed so that the center wavelength falls within the range of 553 nm to 575 nm and the half-width falls within the range of 17 nm to 41 nm. In other words, the cutoff wavelength range of the notch filter 20 included in the fluorescent light source device 1 is an extremely narrow band. Figure 2 shows an example of the transmission spectrum of the notch filter 20.

[0034] 1, fluorescence L10 converted into nearly parallel light by the collimating optical system 7 is incident on the notch filter 20. In other words, the light incident surface of the notch filter 20 is oriented in a direction substantially perpendicular to the optical axis of the chief ray of fluorescence L10 emitted from the collimating optical system 7. Therefore, unlike the configuration of Patent Document 2, the cut wavelength range of the notch filter 20 can be narrowed.

[0035] Fluorescence L10, which has passed through notch filter 20 and has had the light intensity of components in the cut wavelength range reduced, is combined with blue light L9 emitted from blue light source 9. This combined light L1 is guided to a subsequent utilization optical system 50. An LED or a laser diode can be used as blue light source 9. The utilization optical system 50 is any optical system that utilizes combined light L1 emitted from fluorescence light source device 1.

[0036] In the example shown in FIG. 1, a collimating optical system 45 that reduces the divergence angle of the blue light L9 emitted from the blue light source 9 is provided, but it is optional whether or not to provide this collimating optical system 45.

[0037] An example of the fluorescent plate 10 included in the fluorescent light source device 1 of this embodiment will be described with reference to Figs. 3 and 4. Fig. 3 is a cross-sectional view schematically showing the configuration of the fluorescent plate 10 and the substrate 11. Fig. 4 is an enlarged view of a part of Fig. 3.

[0038] In the example shown in FIG. 3, the fluorescent plate 10 is fixed to the substrate 11 via the bonding layer 12 .

[0039] Substrate 11 is provided to dissipate heat generated by fluorescent plate 10 and is made of a material with a thermal conductivity of, for example, 90 [W / m·K] or higher, specifically, 230 to 400 [W / m·K]. Examples of such materials include Cu, copper compounds (such as MoCu and CuW), Al, and AlN. Substrate 11 has a thickness of, for example, 0.5 mm to 5 mm. From the perspective of heat dissipation, the surface area of ​​substrate 11 is preferably larger than the surface area of ​​fluorescent plate 10.

[0040] The bonding layer 12 is a layer that bonds the substrate 11 and the fluorescent plate 10, and is made of, for example, a solder material. From the viewpoint of heat dissipation, it is preferable that the material that constitutes the bonding layer 12 has, for example, a thermal conductivity of 40 [W / m·K] or more. More specifically, for example, cream solder, which is made by mixing flux and other impurities with materials such as Sn and Pb to form a cream (paste), Sn-Ag-Cu solder, Au-Sn solder, etc. can be used. The thickness of the bonding layer 12 is, for example, 20 μm to 200 μm.

[0041] Although not shown, in order to further enhance the bond between substrate 11 and bonding layer 12, a metal film made of Ni / Au film formed by, for example, a plating method may be formed between substrate 11 and bonding layer 12. The thickness of this metal film may be, for example, Ni / Au=1000 nm to 5000 nm / 30 nm to 1000 nm.

[0042] In the example shown in FIG. 1, the surface of the fluorescent plate 10 onto which excitation light L5 is incident and the surface onto which fluorescence L10 is extracted and utilized from the fluorescent plate 10 are the same surface. In other words, even if fluorescence L10 is emitted from the surface of the fluorescent plate 10 facing the substrate 11, utilization of this fluorescence L10 is not anticipated, resulting in reduced utilization efficiency. From this perspective, in the example shown in FIG. 3, a reflective layer 13 is provided on the upper surface of the substrate 11. The reflective layer 13 is provided to reflect the fluorescence L10 generated by the fluorescent plate 10 that travels toward the substrate 11 and guide it to the light extraction principal surface. The reflective layer 13 can be formed, for example, of a metal film such as Al or Ag, or an enhanced reflection film in which a dielectric multilayer film is formed on the metal film.

[0043] However, as will be described later with reference to FIG. 16, if the surface of the fluorescent plate 10 onto which the excitation light L5 is incident and the surface from which the fluorescent light L10 is extracted are different, the reflective layer 13 is not necessary.

[0044] For example, the fluorescent plate 10 has a rectangular flat plate structure when viewed from a direction perpendicular to the surface of the substrate 11. The fluorescent plate 10 has a thickness of, for example, 0.05 mm to 1 mm. In the example shown in FIG. 4, the fluorescent plate 10 includes phosphors 16, binders 17, and pores 18. As shown in FIG. 3, the fluorescent plate 10 may have a moth-eye structure 15 formed by processing fine protrusions and recesses on the main surface on the light extraction side.

[0045] The phosphor 16 is a Ce-activated oxide phosphor or a Ce-activated nitride phosphor. A specific example is LSN (La3Si6N 11 :Ce 2+ ,(La, Y)3Si6N 11:Ce 2+ ), CSO(CaSc2O4:Ce 3+ ), LuAG(AlO 12 Lu3:Ce 2+ ), and YAG(AlO 12 Y3:Ce 2+ Among the materials listed above, LSN is particularly preferred.

[0046] As shown in Fig. 4, phosphor 16 is present in the form of particles dispersed in binder 17. The particle size of 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. There is no particular lower limit for the particle size of phosphor 16, but it is generally 1 µm or more.

[0047] The binder 17 is composed of an inorganic compound. Specific examples of the binder 17 include one or more of CaF2, BaF2, MgF2, ZnS, Al2O3, MgO, ZrO2, ZnO, and TiO2. Among the above-mentioned materials, alumina (Al2O3) is preferred. When a nitride phosphor is used in combination, MgO is particularly preferred as the material for the binder 17. The fluorescent plate 10 is a sintered body of inorganic particles, which are the constituent material of the binder 17, and particles of the constituent material of the phosphor 16. The pores 18 contained in the fluorescent plate 10 are generated during the sintering process, but by changing the profile of the sintering process, it is possible to achieve a structure that is completely free of pores 18.

[0048] The mass percentage of the binder 17 contained in the phosphor plate 10 is preferably 30 mass % to 70 mass % or less, and more preferably 50 mass % to 90 mass %. The mass percentage of the binder 17 contained in the phosphor plate 10 refers to the ratio of the mass of the binder 17 to the total mass of the phosphor 16 and the binder 17.

[0049] The relative density of the phosphor plate 10 is preferably 80.4% to 99.5%. The relative density of the phosphor plate 10 is the ratio of the apparent density to the theoretical density of the phosphor plate 10, which is a sintered body, and can be measured, for example, by a method conforming to JIS R 1634 (Method for Measuring Density and Open Porosity of Sintered Fine Ceramics). In other words, the phosphor plate 10 may contain pores 18 with a content of 0.5% to 19.6%. The inclusion of the pores 18 in the phosphor plate 10 creates a refractive index difference at the interface between the phosphor 16 or binder 17 and the pores 18, making it easier to refract the fluorescence L10 generated within the phosphor plate 10 toward the light-extraction principal surface.

[0050] 5 is a graph superimposing the spectrum of synthetic light L1 and the transmission spectrum of notch filter 20 when phosphor 16 contained in fluorescent plate 10 is LSN (fluorescence peak wavelength 535 nm), binder 17 is alumina, and blue light source 9 is an LED with a peak wavelength of 455 nm. A filter with the transmission spectrum shown in FIG. 2 was used as notch filter 20. As described above, synthetic light L1 is light that has passed through notch filter 20, and therefore the light intensity in the vicinity of 553 nm to 575 nm, which is the cut wavelength range of notch filter 20, is significantly reduced.

[0051] When the resulting synthetic light L1 was measured according to JIS Z 8724 (Method for measuring color - Light source color), the chromaticity y value was 0.33. Furthermore, when the synthetic light L1 was measured according to JIS Z 8726 (Method for evaluating the color rendering properties of light sources), an extremely high average color rendering index (Ra value) of 92 was obtained.

[0052] 6 is a graph superimposing the spectrum of synthetic light L1 and the transmission spectrum of notch filter 20 when phosphor 16 contained in fluorescent plate 10 is LSN (fluorescence peak wavelength 535 nm), binder 17 is alumina, and blue light source 9 is a laser diode with a peak wavelength of 460 nm. A filter with the transmission spectrum shown in FIG. 2 was used as notch filter 20. As described above, synthetic light L1 is light that has passed through notch filter 20, and therefore the light intensity in the vicinity of 553 nm to 575 nm, which is the cut wavelength range of notch filter 20, is significantly reduced.

[0053] When the resulting synthetic light L1 was measured using a method conforming to JIS Z 8724, the chromaticity y value was 0.34. Furthermore, when the synthetic light L1 was measured using a method conforming to JIS Z 8726, an extremely high Ra value of 89.8 was obtained.

[0054] Although it is not clear why extremely high color rendering properties are obtained by the combined light L1 obtained by the fluorescent light source device 1 of this embodiment, it is presumed that this is because the spectrum of the fluorescence L10 generated by excitation with the excitation light L5 has reduced intensity in the wavelength range between the green and red ranges, around 553 nm to 575 nm. The combined light L1 obtained by combining the fluorescence L10, whose light intensity in the cutoff wavelength range around 553 nm to 575 nm is significantly reduced, with the blue light L9 essentially simulates the superposition of blue light, green light, and red light, and is therefore presumed to have high color rendering properties.

[0055] Figure 7 is a graph showing the relationship between the y value and the Ra value measured when the phosphor 16 contained in the phosphor plate 10 is made of YAG or LSN and when a notch filter 20 is provided and when a notch filter 20 is not provided. The y value was changed by adjusting the relative values ​​of the light output of the excitation light source 5 and the blue light source 9 to change the target color temperature. The Ra value was measured using a method based on JIS Z 8726 for the synthesized light. An LED with a peak wavelength of 455 nm was used as the blue light source 9.

[0056] When the notch filter 20 was provided, verification was performed using four types of phosphors 16 contained in the fluorescent plate 10: LSN (referred to as "LSN-1"), in which the peak wavelength of the fluorescence L10 was set to 535 nm; LSN (referred to as "LSN-2"), in which the peak wavelength of the fluorescence L10 was set to 540 nm; YAG (referred to as "YAG-1"), in which the peak wavelength of the fluorescence L10 was set to 540 nm; and YAG (referred to as "YAG-2"), in which the peak wavelength of the fluorescence L10 was set to 545 nm. On the other hand, when the notch filter 20 was not provided, verification was performed using two types of phosphors 16 contained in the fluorescent plate 10: YAG-1 and LSN-1.

[0057] FIG. 7 confirms that when notch filter 20 is not provided, the Ra value of combined light L1 is below 80 regardless of the y value. On the other hand, when notch filter 20 is provided, it can be seen that, for all phosphors, an extremely high Ra value of 85 or higher is obtained when the chromaticity y value of combined light L1 is within the range of 0.283 to 0.396. Furthermore, when comparing the phosphors using YAG and LSN, a higher Ra value was obtained with LSN. This is thought to be because the fluorescence L10 emitted from LSN contains more red components than the fluorescence L10 emitted from YAG. Note that when the chromaticity y value is within the range of 0.283 to 0.396, the color temperature of combined light L1 is 5100K to 9100K.

[0058] FIG. 8 is a graph showing the relationship between the y value and the Ra value measured in the same manner as in FIG. 7 using a laser diode with a peak wavelength of 460 nm as the blue light source 9. As shown in FIG. 8, when the blue light source 9 is a laser diode, as in the case of an LED, the Ra value of the combined light L1 is below 80 regardless of the y value when notch filter 20 is not provided. On the other hand, when notch filter 20 is provided, an extremely high Ra value of 85 or more is obtained for all phosphors when the chromaticity y value of the combined light L1 is within the range of 0.280 to 0.373. When the chromaticity y value is within the range of 0.283 to 0.373, the color temperature of the combined light L1 is 5400K to 8300K.

[0059] Table 1 shows the relationship between the half-width of the cut wavelength range of the notch filter 20 and the Ra value of the synthetic light L1 when the half-width is changed in a case where an LED with a peak wavelength of 462 nm is used as the blue light source 9 and LSN-2 is used as the phosphor 16 contained in the fluorescent plate 10. Note that Fig. 9 is a graph showing the results when the center wavelength of the cut wavelength range of each notch filter 20 is fixed at 564 nm and only the half-width is changed.

[0060] 9, by designing the cut wavelength range of notch filter 20 to have a half-width of 17 nm to 41 nm, the Ra value of synthetic light L1 can be increased. If the half-width is too narrow, light components in the wavelength range that should be cut to achieve high color rendering are not cut, which is thought to result in a deterioration of color rendering. Conversely, if the half-width is too wide, light components in the wavelength range that should not be cut to achieve high color rendering are cut, which is thought to result in a deterioration of color rendering.

[0061] [Table 1]

[0062] From Table 1, the following results can be obtained:

[0063] When the center wavelength of the cut wavelength range of notch filter 20 is 553 nm, if the half width of the cut wavelength range is set to 19 nm to 23 nm, the Ra value of synthetic light L1 exceeds 85. If the half width is 18 nm, the Ra value is 84.4, which can be considered to be substantially equivalent to 85. By setting the half width to 17 nm to 25 nm, the Ra value can be made 84 or higher. Even when the Ra value is in the range of 84 to 85, the color rendering value is lower than when the Ra value is 85 or higher, but this is a high value that could not easily be achieved with conventional fluorescent light source devices that include a phosphor and an excitation light source.

[0064] When the center wavelength of the cut wavelength range of notch filter 20 is 555 nm, and the half width of the cut wavelength range is set to 18 nm to 27 nm, the Ra value of synthetic light L1 exceeds 85. Note that when the half width is 17 nm, the Ra value is 84.9, which can be considered to be substantially equivalent to 85. By setting the half width to 17 nm to 28 nm, the Ra value can be made 84 or higher. Even when the Ra value is in the range of 84 to 85, the color rendering value is lower than when the Ra value is 85 or higher, but this is a high value that could not easily be achieved with conventional fluorescent light source devices that include a phosphor and an excitation light source.

[0065] When the center wavelength of the cut wavelength range of notch filter 20 is 560 nm, if the half width of the cut wavelength range is 17 nm to 31 nm, the Ra value of synthetic light L1 exceeds 85. In particular, if the half width is 23 nm to 25 nm, the Ra value of synthetic light L1 reaches approximately 90. Note that if the half width is 16 nm or 32 nm, Ra is 84.5, which can be considered to be 85 when rounded to the nearest whole number. By setting the half width to 16 nm to 32 nm, the Ra value can be made 84 or higher.

[0066] When the center wavelength of the cut wavelength range of notch filter 20 is 565 nm, if the half width of the cut wavelength range is set to 18 nm to 35 nm, the Ra value of synthetic light L1 exceeds 85. In particular, if the half width is set to 23 nm to 29 nm, the Ra value of synthetic light L1 reaches approximately 90. Note that when the half width is 17 nm, Ra is 84.5, which can be considered to be 85 when rounded to the nearest whole number. By setting the half width to 17 nm to 36 nm, the Ra value can be made 84 or higher.

[0067] When the center wavelength of the cut wavelength range of notch filter 20 is 570 nm, if the half width of the cut wavelength range is set to 21 nm to 39 nm, the Ra value of synthetic light L1 exceeds 85. In particular, if the half width is set to 28 nm to 32 nm, the Ra value of synthetic light L1 reaches approximately 90. Note that when the half width is 20 nm or 40 nm, Ra is 84.8, which can be considered to be 85 when rounded to the nearest whole number. By setting the half width to 20 nm to 41 nm, the Ra value can be made 84 or higher.

[0068] When the center wavelength of the cut wavelength range of notch filter 20 is 575 nm, if the half width of the cut wavelength range is 32 nm or 34 nm, the Ra value of synthetic light L1 exceeds 85. If the half width is 30 nm or 36 nm, Ra is 84.8, and if rounded to the first decimal place, Ra can be considered to be 85. Furthermore, by setting the half width to 30 nm to 36 nm, Ra can be made 84 or higher.

[0069] On the other hand, when the center wavelength of the cut wavelength range of notch filter 20 is 550 nm or 580 nm, the Ra value of synthetic light L1 could not be increased to 83 or more even by adjusting the half width of the cut wavelength range.

[0070] 10 is a graph evaluating the effect on the Ra value of synthetic light L1 when the degree of reduction in light belonging to the cut wavelength range of notch filter 20 is changed when an LED with a peak wavelength of 462 nm is used as blue light source 9 and LSN-2 is used as phosphor 16 contained in fluorescent plate 10. Specifically, the horizontal axis represents the transmittance for light of the center wavelength in the cut wavelength range of notch filter 20, and the vertical axis represents the Ra value of synthetic light L1.

[0071] According to FIG. 10, it can be seen that if the transmittance is at least 33% or less, a synthetic light L1 exhibiting a high Ra value can be obtained.

[0072] 11 is a graph evaluating the effect on the Ra value of the synthetic light L1 when the center wavelength of the cut wavelength range of the notch filter 20 is changed, when an LED with a peak wavelength of 462 nm is used as the blue light source 9 and LSN-2 is used as the phosphor 16 contained in the fluorescent plate 10. Specifically, each notch filter 20 was designed so that the half width of the cut wavelength range of the notch filter 20 was fixed at 25 nm and only the center wavelength was changed.

[0073] According to FIG. 11, it is confirmed that the Ra value of the synthetic light L1 can be increased by designing the notch filter 20 so that the center wavelength of the cut wavelength range is within the range of 553 nm to 575 nm.

[0074] [Another embodiment] The following describes another embodiment of the fluorescent light source device 1. In the following drawings, elements common to those in FIG. 1 are given the same reference numerals.

[0075] <1> As in the fluorescent light source device 1 shown in Fig. 12, the notch filter 20 may be disposed after the location where the blue light L9 is combined with the fluorescent light L10. In the example of Fig. 12, the notch filter 20 is disposed after the dichroic mirror 43.

[0076] <2> The notch filter 20 may be disposed in a state where it is integrated into a refractive optical system that changes the traveling direction of light.

[0077] 13 includes a condensing optical system 46. This condensing optical system 46 is disposed for the purpose of condensing and guiding the combined light L1 generated by the fluorescent light source device 1 toward a downstream utilization optical system 50. If this condensing optical system 46 is a lens having a flat surface, a notch filter 20 may be disposed on this flat surface.

[0078] Furthermore, as shown in FIG. 14, a notch filter 20 may be disposed on the light exit surface of the lens that constitutes the collimating optical system 7.

[0079] <3> The fluorescence light source device 1 may be configured to emit blue light as excitation light L5 from the excitation light source 5 and to combine this blue light with fluorescence L10 to produce combined light L1. In this case, as shown in Fig. 15, the fluorescence light source device 1 does not need to include a blue light source 9.

[0080] 16, an excitation light source 5 may emit excitation light L5 incident on the rear surface of the fluorescent plate 10, and a portion of the excitation light L5 transmitted through the fluorescent plate 10 and the fluorescence L10 emitted from the fluorescent plate 10 may be guided as combined light L1 to the utilization optical system 50. In this case, in order to prevent attenuation of the excitation light L5, it is preferable that the fluorescent plate 10 be used without being held by the substrate 11, unlike the configuration described above with reference to FIG. 3. Furthermore, the reflective layer 13 is not required.

[0081] 17, excitation light L5 may be incident from the excitation light source 5 obliquely onto the fluorescent plate 10. In this case, a portion of the excitation light L5 reflected by the light incident surface of the fluorescent plate 10 is superimposed on the fluorescent light L10 to obtain composite light L1.

[0082] <4> The structures of the fluorescent light source device 1 shown in FIGS. 12 to 17 can be combined as appropriate.

[0083] <5> The fluorescent plate 10 may include multiple types of fluorescent materials 16. Fig. 18 is a graph superimposing the spectrum of the composite light L1 and the transmission spectrum of the notch filter 20 when the fluorescent material 16 contained in the fluorescent plate 10 is a mixture of LuAG (peak fluorescence wavelength 517 nm) and LSN (peak fluorescence wavelength 556 nm), the binder 17 is alumina, and the blue light source 9 is an LED with a peak wavelength of 455 nm. A filter with the transmission spectrum shown in Fig. 2 was used as the notch filter 20.

[0084] When the resulting synthetic light L1 was measured according to JIS Z 8724, the chromaticity y value was 0.38. Furthermore, when the synthetic light L1 was measured according to JIS Z 8726 (method for evaluating the color rendering properties of light sources), an extremely high Ra value of 90.4 was obtained.

[0085] 5 and 6, the y value of the composite light L1 is higher than when the phosphor 16 is made of a single type of material. This suggests that by providing the fluorescent light source device 1 with the fluorescent plate 10 containing multiple types of phosphors 16 that produce fluorescence L10 with different wavelengths, it is possible to generate composite light L1 that exhibits a high Ra value while maintaining a low color temperature. [Explanation of symbols]

[0086] 1: Fluorescent light source device 5: Excitation light source 7: Collimated optical system 9: Blue light source 10: Fluorescent plate 11: Substrate 17: Binder 20: Notch filter 41: Reflective mirror 43:Dichroic mirror 45: Collimated optical system 46: Condensing optical system 50: Optical system used L1: Synthetic light L10: Fluorescence L5: Excitation light L9: Blue light

Claims

1. an excitation light source that emits excitation light in the blue region; a fluorescent plate that includes a Ce-activated phosphor and receives the excitation light to generate fluorescence having a wavelength longer than that of the excitation light; a collimating optical system that reduces at least the divergence angle of the fluorescence; a notch filter through which the light emitted from the collimating optical system passes, the notch filter is disposed such that a light incident surface thereof is oriented substantially perpendicular to an optical axis of a chief ray of light emitted from the collimating optical system; The cut wavelength range of the notch filter has a center wavelength in the range of 553 nm to 575 nm and a half width in the range of 17 nm to 41 nm, a fluorescent light source device, characterized in that the light guided to a downstream utilization optical system via the notch filter is a composite light of the fluorescent light and light in the blue region, and has an average color rendering index (Ra value) of 85 or more.

2. an excitation light source that emits excitation light; a fluorescent plate that includes a Ce-activated phosphor and receives the excitation light to generate fluorescence having a wavelength longer than that of the excitation light; a collimating optical system that reduces at least the divergence angle of the fluorescence; a notch filter through which light emitted from the collimating optical system passes; a blue light source that inputs superimposed light in a blue range onto an optical path of the fluorescence emitted from the fluorescent plate, the notch filter is disposed such that a light incident surface thereof is oriented substantially perpendicular to an optical axis of a chief ray of light emitted from the collimating optical system; The cut wavelength range of the notch filter has a center wavelength in the range of 553 nm to 575 nm and a half width in the range of 17 nm to 41 nm, a fluorescent light source device, characterized in that the light guided to a downstream utilization optical system via the notch filter is a composite light of the fluorescent light and light in the blue region, and has an average color rendering index (Ra value) of 85 or more.

3. 3. The fluorescent light source device according to claim 1, wherein the notch filter has a transmittance of 33% or less for light having a central wavelength in the cut wavelength range.

4. 3. The fluorescent light source device according to claim 1, wherein the combined light has a chromaticity y in the range of 0.283 to 0.

373.

5. the collimating optical system has a light incident surface or a light exit surface formed as a flat surface, 3. The fluorescent light source device according to claim 1, wherein the notch filter is disposed on the flat surface.

6. 3. The fluorescent light source device according to claim 1, wherein the fluorescent plate is composed of a binder made of an inorganic material and a sintered body of a Ce-activated oxide phosphor or a Ce-activated nitride phosphor dispersed in the binder.

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