JP2021118163A - Illuminating device - Google Patents

Abstract

To provide an illuminating device that has high conversion efficiency of excitation light for illumination light.SOLUTION: An illuminating device 1 comprises: a board 21 comprising a first reflecting surface 21a; a first layer 11 comprising a first wavelength conversion member 31; a second layer 12 located along the first layer 11 above the first layer 11, and comprising a second wavelength conversion member 32; a third layer 13 located between the first layer 11 and the second layer 12; and a light emitting device 40 for emitting excitation light 71 from an emitting point 13a located inside the third layer 13. The first wavelength conversion member 31 converts at least a portion of the incident excitation light 71 into first converted light. The first reflecting surface 21a reflects the first converted light toward the second layer 12. The second wavelength conversion member 32 converts at least a portion of the incident excitation light into second converted light. The second layer 12 transmits at least a portion of the second converted light and at least a portion of the first converted light incident from the first layer, outward.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a lighting device.

A lighting device having a phosphor unit that receives excitation light emitted from a semiconductor laser and emits fluorescence having a wavelength different from that of the excitation light, and a fiber bundle that waveguides at least a part of the fluorescence emitted from the phosphor unit. Is known (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-252440

In the illumination light, it is required to increase the conversion efficiency of the excitation light.

The lighting device according to the embodiment of the present disclosure includes a substrate having a first reflecting surface, a first layer, a second layer, a third layer, and a light emitting device. The first layer is located on the first reflecting surface and has a first wavelength conversion member. The second layer is located above the first layer along the first layer and has a second wavelength conversion member. The third layer is located between the first layer and the second layer. The light emitting device emits excitation light from an emission point located inside the third layer. The first wavelength conversion member converts at least a part of the excitation light incident on the first layer into the first conversion light specified by a spectrum different from the excitation light. The first reflecting surface reflects the excitation light that has not been converted by the first wavelength conversion member toward the second layer. The second wavelength conversion member converts at least a part of the excitation light incident on the second layer from the first layer into a second conversion light specified by a spectrum different from the excitation light. The second layer transmits at least a part of the second conversion light and at least a part of the first conversion light incident from the first layer toward the outside.

According to the lighting device according to the embodiment of the present disclosure, the conversion efficiency of the excitation light is high.

It is a schematic diagram which shows the structural example of the lighting apparatus which concerns on one Embodiment. It is sectional drawing which shows the structural example of the wavelength conversion member. It is a graph which shows an example of the spectrum of the illumination light which concerns on this embodiment. It is a graph which shows an example of a filter characteristic.

(Configuration of lighting device 1)
As shown in FIG. 1, the lighting device 1 according to the embodiment includes a first layer 11, a second layer 12, a third layer 13, a substrate 21, and a light emitting device 40. The substrate 21 extends along the XZ plane. The first layer 11, the second layer 12, and the third layer 13 are located along the substrate 21 and extend along the XZ plane. Of the first layer 11, the second layer 12, and the third layer 13, the first layer 11 is located on the side closest to the substrate 21. The second layer 12 is located on the side farthest from the substrate 21. The third layer 13 is located between the first layer 11 and the second layer 12. That is, each layer is located in the order of the first layer 11, the third layer 13, and the second layer 12 when viewed from the substrate 21. It can be said that each layer is located in the order of the first layer 11, the third layer 13, and the second layer 12 from the negative direction side of the Y axis to the positive direction side. It can be said that the first layer 11, the third layer 13, and the second layer 12 are laminated on the substrate 21 in this order.

The substrate 21 has a first reflecting surface 21a located on the side facing the first layer 11 (the side in the positive direction of the Y axis). The first reflecting surface 21a reflects the incident light. The light reflected by the first reflecting surface 21a passes through the first layer 11 and travels toward the third layer 13 and the second layer 12. The substrate 21 having the first reflecting surface 21a is also referred to as a first reflecting member. It can be said that the first layer 11 is located on the substrate 21 or on the first reflecting surface 21a. The first layer 11 may come into contact with the first reflecting surface 21a, or may be positioned at a predetermined distance from the first reflecting surface 21a. The illuminating device 1 may have other members located between the first layer 11 and the substrate 21 or the first reflecting surface 21a. That is, the position of the first layer 11 may or may not be directly above the substrate 21 or the first reflecting surface 21a.

The light emitting device 40 emits the excitation light 71 from a predetermined point 13a located inside the third layer 13. The predetermined point 13a from which the excitation light 71 is emitted is also referred to as an emission point. The light emitting device 40 may include a light source 41 that emits excitation light 71. The light source 41 may be located at a predetermined point 13a. The light emitting device 40 may include a fiber 42 that propagates the excitation light 71 emitted from the light source 41 to the predetermined point 13a. The excitation light 71 travels from the predetermined point 13a toward the first layer 11 or the second layer 12.

The first layer 11 includes a first wavelength conversion member 31. The second layer 12 includes a second wavelength conversion member 32. The first wavelength conversion member 31 and the second wavelength conversion member 32 are also collectively referred to as a wavelength conversion member 30. The wavelength conversion member 30 converts the excitation light 71 specified in a predetermined spectrum into light specified in a different spectrum and emits it. The light converted and emitted by the first wavelength conversion member 31 and the second wavelength conversion member 32 is also referred to as first conversion light and second conversion light, respectively. The first conversion light and the second conversion light are also collectively referred to as conversion light. The spectrum that identifies the excitation light 71 is also referred to as an excitation light spectrum. The spectra that specify the first conversion light and the second conversion light are also referred to as the first conversion light spectrum and the second conversion light spectrum, respectively.

The first wavelength conversion member 31 converts at least a part of the incident excitation light 71 into the first conversion light and emits it. The second wavelength conversion member 32 converts at least a part of the incident excitation light 71 into the second conversion light and emits it. The excitation light 71 incident on the wavelength conversion member 30 may be emitted as the excitation light 71 without being converted into other light. The excitation light 71 emitted as it is without being converted by the first wavelength conversion member 31 or the second wavelength conversion member 32 is also referred to as unconverted light. The spectrum of the unconverted light is the same as the spectrum of the excitation light 71. That is, the unconverted light is specified by the excitation light spectrum.

The light incident on the first layer 11 is reflected by the first reflecting surface 21a of the first layer 11 or the substrate 21 and travels toward the second layer 12. The light reflected by the first layer 11 or the first reflecting surface 21a and traveling toward the second layer 12 is also referred to as the first reflected light 72. The first reflected light 72 includes the first converted light converted by the first wavelength conversion member 31 and the unconverted light not converted by the first wavelength conversion member 31.

At least a part of the light incident on the second layer 12 passes through the second layer 12 and is emitted to the outside of the illuminating device 1. The light transmitted through the second layer 12 and emitted to the outside of the illuminating device 1 is also referred to as transmitted light 73. It can be said that the second layer 12 transmits the transmitted light 73 toward the outside of the lighting device 1. Of the light incident on the second layer 12, the light that has not passed through the second layer 12 is reflected by the second layer 12 and travels toward the first layer 11. The light reflected by the second layer 12 and traveling toward the first layer 11 is also referred to as the second reflected light 74. The transmitted light 73 and the second reflected light 74 include the second converted light converted by the second wavelength conversion member 32 and the unconverted light not converted by the second wavelength conversion member 32.

The first reflected light 72 may include second converted light or unconverted light incident from the second layer 12. The transmitted light 73 and the second reflected light 74 may include the first converted light or the unconverted light incident from the first layer 11.

<Light emitting device 40>
The light source 41 of the light emitting device 40 emits excitation light 71. In the present embodiment, the excitation light 71 is assumed to be a laser beam having a peak wavelength in the wavelength region from 360 nm to 430 nm. The wavelength region from 360 nm to 430 nm is also referred to as a violet light region. Light having a peak wavelength included in the violet light region is also referred to as violet light. That is, in the present embodiment, it is assumed that purple light is used as the excitation light 71. Purple light is included in visible light. Human luminosity factor for violet light is lower than that of other colors of visible light. By using purple light as the excitation light 71, the control of the intensity of the excitation light 71 is less likely to affect the color rendering property. By using a laser beam as the excitation light 71, the monochromaticity and directivity of the excitation light 71 can be enhanced. The energy of the excitation light 71 is easily controlled, and the traveling direction of the excitation light 71 is easily controlled.

The light source 41 may include a semiconductor laser such as an LD (Laser Diode). The light source 41 is not limited to this, and may be configured to include various other devices such as an LED (Light Emitting Diode). The light source 41 may be located outside the third layer 13 or inside the third layer 13.

The fiber 42 of the light emitting device 40 has a core that propagates light and a clad that totally reflects the light and confine it in the core. The fiber 42 has a first end and a second end. The fiber 42 is connected to the light source 41 at the first end and propagates the excitation light 71 incident from the light source 41. The excitation light 71 is emitted from the second end of the fiber 42. The second end of the fiber 42 is located inside the third layer 13. Since the second end of the fiber 42 is located inside the third layer 13, the excitation light 71 can propagate to the inside of the third layer 13 with low loss. The position of the second end of the fiber 42 corresponds to the position of the predetermined point 13a. The fiber 42 has flexibility. That is, the fiber 42 may be bent.

<Board 21>
The substrate 21 having the first reflecting surface 21a may be composed of various materials such as ceramics, resins, semiconductors, and metals. In this embodiment, the substrate 21 is made of ceramic. The reflectance of light on the first reflecting surface 21a is determined based on the special material made of the material constituting the substrate 21. When the substrate 21 is made of ceramic, the reflectance of visible light on the first reflecting surface 21a can be, for example, 90% or more. When the substrate 21 is made of ceramic, the light incident on the first reflecting surface 21a can be diffusely reflected. The substrate 21 may include a heat radiating member. The heat radiating member may include, for example, aluminum and copper. Examples of the shape of the heat radiating member include those with a heat pipe and those with fins. The thermal conductivity of the heat-dissipating member may be at least higher than the thermal conductivity of air. Since the substrate 21 includes a heat-dissipating member, the heat generated in the first layer 11 is likely to be dissipated to the substrate 21. As a result, the temperature of the first wavelength conversion member 31 included in the first layer 11 is less likely to rise.

<Wavelength conversion member 30>
As shown in FIG. 2, the wavelength conversion member 30 includes a phosphor 35. The wavelength conversion member 30 may further include a translucent member 38 having translucency. The translucent member 38 may hold the phosphor 35 in a substantially uniformly dispersed state by containing the phosphor 35 inside.

The phosphor 35 is excited by the excitation light 71 incident on the wavelength conversion member 30 and emits fluorescence. The fluorescence emitted by the phosphor 35 has a peak wavelength included in the wavelength region from 360 nm to 780 nm. The wavelength region from 360 nm to 780 nm is also referred to as a visible light region. Light having a peak wavelength included in the visible light region is also referred to as visible light. When the phosphor 35 emits fluorescence, the wavelength conversion member 30 converts purple light as excitation light 71 into visible light as conversion light.

The translucent member 38 may be formed of, for example, a translucent insulating resin such as a fluororesin, a silicone resin, an acrylic resin or an epoxy resin, or a translucent glass material or the like.

The phosphor 35 may convert violet light into light specified in the spectrum having a peak wavelength included in, for example, a wavelength region from 400 nm to 500 nm, that is, blue light. In this case, the phosphor 35 is, for example, BaMgAl ₁₀ O ₁₇ : Eu, or (Sr, Ca, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : Eu, (Sr, Ba) ₁₀ (PO ₄ ) ₆ Cl ₂ : It may be configured to include Eu and the like.

The phosphor 35 may convert violet light into light specified in the spectrum having a peak wavelength included in, for example, a wavelength region from 450 nm to 550 nm, that is, blue-green light. The phosphor 35 may be composed of, for example, (Sr, Ba, Ca) ₅ (PO ₄ ) ₃ Cl: Eu, Sr ₄ Al ₁₄ O ₂₅ : Eu and the like.

The phosphor 35 may convert violet light into light specified in the spectrum having a peak wavelength included in, for example, a wavelength region from 500 nm to 600 nm, that is, green light. The phosphor 35 may contain, for example, SrSi ₂ (O, Cl) ₂ N ₂ : Eu, (Sr, Ba, Mg) ₂ SiO ₄ : Eu ²⁺ , or ZnS: Cu, Al, Zn ₂ SiO ₄ : Mn. It may be configured to include.

The phosphor 35 may convert violet light into light specified in the spectrum having a peak wavelength included in, for example, a wavelength region from 600 nm to 700 nm, that is, red light. The phosphor 35 may contain, for example, Y ₂ O ₂ S: Eu, Y ₂ O ₃ : Eu, SrCaClAlSiN ₃ : Eu ²⁺ , CaAlSiN ₃ : Eu, CaAlSi (ON) ₃ : Eu, and the like. ..

The phosphor 35 may convert violet light into light specified in the spectrum having a peak wavelength included in, for example, a wavelength region from 680 nm to 800 nm, that is, near infrared light. Near-infrared light may include light in the wavelength range from 680 to 2500 nm. The phosphor 35 may be composed of, for example, 3Ga ₅ O ₁₂ : Cr or the like.

The phosphor 35 is not limited to the materials described above, and may be configured to include other types of materials. The phosphor 35 may be formed by arbitrarily combining a plurality of types of materials. The combination of materials for the phosphor 35 is not particularly limited.

The wavelength conversion member 30 may include one type of phosphor 35. The wavelength conversion member 30 may include the first phosphor 35a and the second phosphor 35b as the phosphor 35. The peak wavelength of the light converted by the first phosphor 35a and the peak wavelength of the light converted by the second phosphor 35b may be different from each other.

The wavelength conversion member 30 converts the excitation light 71 into conversion light specified by a spectrum different from the excitation light spectrum and emits it. The spectrum that identifies the converted light may have various peak wavelengths depending on the combination of the phosphors 35. By appropriately selecting the type of the phosphor 35 included in the wavelength conversion member 30, the wavelength conversion member 30 can be converted into light specified in various spectra, light having various colors, or various types of light. Can emit light with a color temperature.

The lighting device 1 emits transmitted light 73 including the first converted light and the second converted light to the outside as illumination light. The spectrum of the first conversion light and the spectrum of the second conversion light can be different spectra from each other. Therefore, the spectrum of the illumination light is a spectrum obtained by adding the spectrum of the first conversion light and the spectrum of the second conversion light. The illumination light may further include unconverted light. When the illumination light includes unconverted light, the spectrum of the illumination light becomes a spectrum obtained by further adding the spectrum of the unconverted light.

The lighting device 1 can improve the conversion efficiency of converting the excitation light 71 into visible light or the like. Therefore, the lighting device 1 can improve the efficiency of conversion of the excitation light 71 to the light of a desired color even in the endoscope, general lighting, and vehicle-mounted lighting. Further, the illumination device 1 having high conversion efficiency can bring the spectrum of illumination light closer to the spectrum of white light in which the intensities of each wavelength included in the visible light region are uniformly approached. As a result, the illuminating device 1 can enhance the color rendering property of the illuminating light. The illuminating device 1 brings the spectrum of the illuminating light close to the spectrum of various lights such as direct sunlight from the sun, sunlight reaching a predetermined depth in the sea, light emitted by a candle flame, or light of a firefly. You can also do it. In other words, the illuminating device 1 can make the illuminating light into light having various colors or light having various color temperatures.

The higher the conversion efficiency of the excitation light 71 in the wavelength conversion member 30, the less the unconverted light and the more the converted light. In the lighting device 1 according to the present embodiment, the unconverted light that has not been converted in the first layer 11 can become the converted light in the second layer 12. Further, the unconverted light that has not been converted even in the second layer 12 can be reflected and re-entered into the first layer 11 or the second layer 12 to become the converted light. By doing so, the conversion efficiency of the excitation light 71 in the lighting device 1 according to the present embodiment is increased. By improving the conversion efficiency of the excitation light 71, the intensity of the excitation light 71 emitted by the light emitting device 40 may be reduced. As a result, the energy input for emitting the excitation light 71 to the light emitting device 40 can be reduced. Further, by improving the conversion efficiency of the excitation light 71, the color rendering property of the illumination light can be improved.

<Comparison with comparative example>
In the apparatus according to the comparative example, it is assumed that the excitation light 71 passes through the wavelength conversion member 30 only once. On the other hand, in the lighting device 1 according to the present embodiment, the excitation light 71 is more likely to pass through the wavelength conversion member 30 twice or more. In this case, at the peak wavelength of the excitation light 71 represented by λp in the spectrum of the illumination light illustrated in FIG. 3, the intensity of the illumination light of the illumination device 1 according to the present embodiment is the intensity of the illumination light of the apparatus according to the comparative example. It is less than the intensity of the illumination light. Therefore, the lighting device 1 according to the present embodiment can improve the conversion efficiency of the excitation light 71 as compared with the device according to the comparative example.

Further, in the wavelength range including the wavelength range of the spectrum of the first conversion light or the wavelength range of the spectrum of the second conversion light represented by λc, the intensity of the illumination light of the illumination device 1 according to the present embodiment is compared. It is higher than the intensity of the illumination light of the device according to the example. Therefore, the lighting device 1 according to the present embodiment can enhance the color rendering property of the lighting light as compared with the device according to the comparative example.

(Other embodiments)
Hereinafter, other embodiments will be described.

<Structure of third layer 13>
The third layer 13 located between the first layer 11 and the second layer 12 transmits the excitation light 71, the unconverted light, the first converted light, and the second converted light. In other words, the third layer 13 transmits the excitation light 71, the first reflected light 72, and the second reflected light 74. The third layer 13 may be an air layer. The third layer 13 may be made of a translucent member such as glass or a transparent resin. Since the third layer 13 is an air layer or is composed of a member having translucency, the light passing through the third layer 13 is less likely to be absorbed by the third layer 13 and less likely to be attenuated by the third layer 13. Become. Since the light is not easily attenuated in the third layer 13, the intensity of the first converted light that advances toward the second layer 12 and is transmitted to the outside through the second layer 12 can be increased, and the wavelength conversion member 30 can be increased. The intensity of the excitation light 71 or the unconverted light incident on the light may increase. As a result, the conversion efficiency of the excitation light 71 can be improved, and the intensity of the illumination light emitted by the illumination device 1 can be increased.

The third layer 13 may be composed of the wavelength conversion member 30. The wavelength conversion member 30 constituting the third layer 13 is also referred to as a third wavelength conversion member. It is assumed that the density of the phosphor 35 included in the third wavelength conversion member is smaller than the density of the phosphor 35 contained in the first wavelength conversion member 31 and the second wavelength conversion member 32. By doing so, the light passing through the third layer 13 is less likely to be converted into other light. The density of the phosphor 35 is calculated from, for example, the area occupancy of the phosphor 35 in a certain cross section of the wavelength conversion member 30, or the mass of only the portion of the wavelength conversion member 30 excluding the phosphor 35 in the same volume. Can be calculated by comparing with the mass of the substance containing the phosphor 35 and the like.

The predetermined point 13a from which the excitation light 71 is emitted is located inside the third layer 13. The excitation light 71 emitted from the predetermined point 13a travels inside the third layer 13 while spreading at a predetermined solid angle. Then, the closer to the predetermined point 13a, the higher the intensity of the excitation light 71.

It can be said that the phosphor 35 absorbs the excitation light 71 and emits the conversion light. The phosphor 35 generates heat by absorbing the excitation light 71.

It is assumed that the density of the phosphor 35 contained in the third wavelength conversion member is higher than the density of the phosphor 35 contained in the first wavelength conversion member 31 or the second wavelength conversion member 32. In this case, in the vicinity of the predetermined point 13a of the third layer 13, the third wavelength conversion member absorbs the high-intensity excitation light 71 by the high-density phosphor 35 and generates heat. Then, the third wavelength conversion member locally becomes hot in the vicinity of the predetermined point 13a. The heat generated locally in this way is difficult to dissipate. In addition, the reliability of the illuminating device 1 may decrease due to the occurrence of a local temperature distribution.

On the other hand, in the present embodiment, due to the low density of the phosphor 35 of the third wavelength conversion member, the excitation light 71 easily dissipates heat to the substrate 21 having a large heat capacity, or the first wavelength conversion member 31 or It becomes easy to reach the second wavelength conversion member 32 which easily dissipates heat to the outside air. By doing so, the portion that generates heat inside the lighting device 1 is dispersed, and the heat generation is easily dissipated. As a result, the local temperature distribution can be reduced and the reliability of the lighting device 1 can be improved.

Further, since the predetermined point 13a from which the excitation light 71 is emitted is located inside the third wavelength conversion member having a low density of the phosphor 35, the excitation light 71 is the first wavelength conversion member 31 and the second wavelength conversion member 32. Will be easier to reach. As a result, the intensities of the first conversion light and the second conversion light can be easily controlled.

Further, the direction in which the excitation light 71 emitted from the predetermined point 13a travels has a predetermined spread. The excitation light 71 is specified by a radiant intensity representing energy radiated in a certain direction. The radiation intensity of the excitation light 71 may differ depending on the traveling direction of the excitation light 71. That is, the radiation intensity of the excitation light 71 may have a distribution. In the present embodiment, the traveling direction in which the radiation intensity of the excitation light 71 is maximized may be the direction from the predetermined point 13a toward the first layer 11. In other words, the radiant intensity of the excitation light 71 emitted from the predetermined point 13a may be maximized in the direction from the predetermined point 13a toward the first layer 11. The direction from the predetermined point 13a toward the first layer 11 can be said to have a component in the negative direction of the Y-axis. By maximizing the radiation intensity of the excitation light 71 in the direction from the predetermined point 13a toward the first layer 11, the excitation light 71 can pass through both the first wavelength conversion member 31 and the second wavelength conversion member 32. .. By doing so, the excitation light 71 can be converted into the first conversion light by the first wavelength conversion member 31, and the second wavelength conversion even if the first wavelength conversion member 31 passes through the unconverted light as it is. It can be converted into the second conversion light by the member 32. As a result, the probability that the excitation light 71 is converted into the first conversion light or the second conversion light can be increased. That is, the conversion efficiency of the excitation light 71 can be increased.

<Second reflective surface 22a>
The illuminating device 1 may further include, but are not required, a spacer member 22 that defines the spacing between the first layer 11 and the second layer 12. The spacer member 22 is located along the substrate 21 along with the third layer 13. The third layer 13 may be surrounded by the spacer member 22. When the third layer 13 is surrounded by the spacer member 22, the end of the third layer 13 in the direction along the substrate 21 (X-axis direction in FIG. 1) is specified by the spacer member 22. In this case, the spacer member 22 has an end face in contact with the end of the third layer 13, and reflects light incident from the side of the third layer 13 on the end face. The end surface of the spacer member 22 is also referred to as a second reflecting surface 22a. It can be said that the second reflecting surface 22a intersects in the direction in which the third layer 13 extends (the X-axis direction in FIG. 1).

The first layer 11 and the second layer 12 can be arranged in a narrow range by the second reflecting surface 22a reflecting the light incident from the third layer 13. By doing so, the illuminating device 1 can emit the transmitted light 73 as the illuminating light from the second layer 12 having a narrow area. As a result, the brightness of the illumination light can be increased and the illumination device 1 can be miniaturized.

The normal vector 22n of the second reflecting surface 22a is a direction in which the components in the direction in which the first layer 11 and the second layer 12 spread (the X-axis direction in FIG. 1) and the first layer 11 and the second layer 12 are laminated. It has a component (in the Z-axis direction of FIG. 1). The second reflecting surface 22a may be configured such that the component of the normal vector 22n in the Z-axis direction is directed toward the second layer 12. By doing so, among the light reflected by the second reflecting surface 22a, the light directed to the second layer 12 is larger than the light directed to the first layer 11. By increasing the amount of light directed to the second layer 12, the intensity of the transmitted light 73 transmitted through the second layer 12 and emitted to the outside can be increased. As a result, the intensity of the illumination light can be increased.

<Arrangement of phosphor 35>
It is assumed that in the illuminating device 1, a plurality of types of phosphors 35 are required in order to obtain a desired spectrum of illumination light. In this case, the first wavelength conversion member 31 contains some types of phosphors 35, while the second wavelength conversion member 32 contains other types of phosphors 35, so that the illumination device 1 as a whole contains illumination light. The spectrum can be the desired spectrum.

The first wavelength conversion member 31 can dissipate heat to the substrate 21. The second wavelength conversion member 32 can dissipate heat to the outside air. When the heat is more easily dissipated to the substrate 21 than the outside air, the second wavelength conversion member 32 tends to have a higher temperature than the first wavelength conversion member 31. The heat-resistant temperature of the second wavelength conversion member 32 may be higher than the heat-resistant temperature of the first wavelength conversion member 31. By doing so, the phosphor 35 as a whole of the lighting device 1 is less likely to deteriorate. As a result, the reliability of the lighting device 1 can be improved. The heat-resistant temperature is a temperature at which the substance can maintain its physical properties, and if it is a wavelength conversion member 30, it is a temperature at which the function as the wavelength conversion member 30 can be maintained.

The heat resistant temperature of the phosphor 35 is determined by the type of the phosphor 35. For example, the heat-resistant temperature of the green phosphor 35 is lower than the heat-resistant temperature of the phosphors 35 of other colors. For example, the heat-resistant temperature of the blue phosphor 35 is higher than the heat-resistant temperature of the phosphors 35 of other colors. The heat resistant temperature of the phosphor 35 of each color can be increased in the order of, for example, green, yellow or orange, red, and blue.

The heat resistant temperature of the wavelength conversion member 30 is determined by the type of the phosphor 35 included in the wavelength conversion member 30. The second wavelength conversion member 32 may contain less green phosphor 35 than the first wavelength conversion member 31 so that the heat resistant temperature thereof is higher than the heat resistant temperature of the first wavelength conversion member 31. That is, the density of the green phosphor 35 contained in the second wavelength conversion member 32 may be lower than the density of the green phosphor 35 contained in the first wavelength conversion member 31. The green phosphor 35 is also referred to as a green phosphor.

In the present embodiment, the excitation light 71 traveling from the predetermined point 13a toward the first layer 11 can be converted into the first conversion light by the first wavelength conversion member 31. The first conversion light is reflected by the first reflection surface 21a or the first wavelength conversion member 31 and travels toward the second layer 12 to reach the second wavelength conversion member 32. The first conversion light can be further converted by the second wavelength conversion member 32 to become the second conversion light. Here, it is assumed that the peak wavelength of the light emitted by the phosphor 35 included in the first wavelength conversion member 31 is longer than the peak wavelength of the light emitted by the phosphor 35 included in the second wavelength conversion member 32. .. By doing so, the wavelength of the first conversion light can be longer than the peak wavelength of the light emitted by the phosphor 35 included in the second wavelength conversion member 32. As a result, the first conversion light is less likely to be converted into the second conversion light by the second wavelength conversion member 32. Therefore, the ratio of the intensities of the first converted light and the second converted light can be easily controlled.

<Configuration example including filter 50>
As shown in FIG. 1, the illuminating device 1 may further include, but is not required, a filter 50 located outside the second layer 12. The filter 50 is located on the side opposite to the side facing the first layer 11 when viewed from the second layer 12. Based on the vertical relationship of FIG. 1, the filter 50 is located above the second layer 12. Based on the coordinate system of FIG. 1, the filter 50 is located on the positive side of the Y-axis with respect to the second layer 12.

It can be said that the filter 50 is located on the second layer 12. The filter 50 may abut on the second layer 12 or may be located at a predetermined interval with respect to the second layer 12. The illuminating device 1 may further have other members located between the filter 50 and the second layer 12. That is, the position of the filter 50 may or may not be directly above the second layer 12.

The filter 50 has a predetermined reflection characteristic. The filter 50 may have, for example, the reflection characteristics shown in FIG. The reflection characteristic represents the relationship between the wavelength of the incident light and the reflectance of the light of each wavelength. In the example of FIG. 4, the reflectance of the filter 50 may be made larger in the wavelength range (λex) including the peak wavelength (λp) of the excitation light 71 than in the other wavelength range (λc). In other words, the reflectance of the filter 50 may be maximized in the wavelength range including the peak wavelength of the excitation light 71. By increasing the reflectance of the filter 50 in the wavelength range including the peak wavelength of the excitation light 71, the excitation light 71 as the unconverted light is reflected toward the first layer 11 or the second layer 12 and is again second. It can enter the first layer 11 or the second layer 12 and be converted into converted light by the wavelength conversion member 30. As a result, the conversion efficiency of the excitation light 71 can be increased. Further, by increasing the reflectance of the filter 50 in the wavelength range including the peak wavelength of the excitation light 71, among the illumination lights emitted to the outside of the illumination device 1, the excitation light emitted as the unconverted light is emitted. The proportion of 71 is reduced. As a result, the intensity of purple light, which does not contribute much to the improvement of the color rendering property of the illumination light, can be reduced, or the conversion efficiency to the illumination light of a desired color can be improved.

The filter 50 has predetermined transmission characteristics. The transmission characteristic represents the relationship between the wavelength of the incident light and the transmittance of the light of each wavelength. The transmittance of the filter 50 may be smaller in the wavelength range including the peak wavelength of the excitation light 71 than in other wavelength ranges. In other words, the transmittance of the filter 50 may be minimized in the wavelength range including the peak wavelength of the excitation light 71. By lowering the transmittance of the filter 50 in the wavelength range including the peak wavelength of the excitation light 71, among the illumination lights emitted to the outside of the illumination device 1, the excitation light 71 emitted as the unconverted light The proportion is reduced. As a result, the intensity of purple light, which does not contribute much to the improvement of the color rendering property of the illumination light, can be reduced, or the conversion efficiency to the illumination light of a desired color can be improved.

The figure illustrating the embodiment according to the present disclosure is schematic. The dimensional ratios on the drawings do not always match the actual ones.

Although the embodiments according to the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications or modifications based on the present disclosure. It should be noted, therefore, that these modifications or modifications are within the scope of this disclosure. For example, the functions and the like included in each component and the like can be rearranged so as not to be logically inconsistent, and a plurality of components and the like can be combined or divided into one.

In the present disclosure, the descriptions such as "first" and "second" are identifiers for distinguishing the configuration. The configurations distinguished by the descriptions such as "first" and "second" in the present disclosure can exchange numbers in the configurations. For example, the first conversion light can exchange the identifiers "first" and "second" with the second conversion light. The exchange of identifiers takes place at the same time. Even after exchanging identifiers, the configuration is distinguished. The identifier may be deleted. The configuration with the identifier removed is distinguished by a code. Based solely on the description of identifiers such as "first" and "second" in the present disclosure, it shall not be used as a basis for interpreting the order of the configurations and for the existence of identifiers with smaller numbers.

In the present disclosure, the X-axis, Y-axis, and Z-axis are provided for convenience of explanation and may be interchanged with each other. The configuration according to the present disclosure has been described using a Cartesian coordinate system composed of the X-axis, the Y-axis, and the Z-axis. The positional relationship of each configuration according to the present disclosure is not limited to being orthogonal.

1 Lighting device 11 1st layer 12 2nd layer 13 3rd layer 13a Predetermined point 21 Substrate (21a: 1st reflective surface)
22 Spacer member (22a: second reflecting surface, 22n: normal vector)
30 Wavelength conversion member (31: first wavelength conversion member, 32: second wavelength conversion member, 35: phosphor, 35a: first phosphor, 35b: second phosphor, 38: translucent member)
40 Light emitting device (41: light source, 42: fiber)
50 Filter 71 Excitation light 72 First reflected light 73 Transmitted light 74 Second reflected light

Claims (16)

A substrate having a first reflective surface and
A first layer located on the first reflecting surface and having a first wavelength conversion member, and
A second layer located above the first layer along the first layer and having a second wavelength conversion member,
A third layer located between the first layer and the second layer,
A light emitting device that emits excitation light from an injection point located inside the third layer is provided.
The first wavelength conversion member converts at least a part of the excitation light incident on the first layer into the first conversion light specified by a spectrum different from the excitation light.
The first reflecting surface reflects the excitation light that has not been converted by the first wavelength conversion member toward the second layer.
The second wavelength conversion member converts at least a part of the excitation light incident on the second layer from the first layer into a second conversion light specified by a spectrum different from the excitation light.
The second layer is an illuminating device that transmits at least a part of the second converted light and at least a part of the first converted light incident from the first layer toward the outside. The lighting device according to claim 1, wherein the third layer has a translucent member. The third layer has a third wavelength conversion member and has a third wavelength conversion member.
The claim that the density of the phosphor contained in the third wavelength conversion member is smaller than the density of the phosphor contained in the first wavelength conversion member and the density of the phosphor contained in the second wavelength conversion member. The lighting device according to 1 or 2. The lighting device according to claim 1, wherein the third layer is an air layer. Further provided is a spacer member having a second reflective surface intersecting the extending direction of the third layer.
The lighting device according to any one of claims 1 to 4, wherein the second reflecting surface reflects light incident from the third layer toward the third layer. The lighting device according to claim 5, wherein the normal vector of the second reflecting surface has a component toward the second layer. The lighting device according to any one of claims 1 to 6, wherein the heat-resistant temperature of the second wavelength conversion member is higher than the heat-resistant temperature of the first wavelength conversion member. The first wavelength conversion member and the second wavelength conversion member each include a green phosphor that converts the excitation light into green light.
The one according to any one of claims 1 to 7, wherein the density of the green phosphor contained in the second wavelength conversion member is lower than the density of the green phosphor contained in the first wavelength conversion member. Lighting device. The illuminating device according to any one of claims 1 to 8, wherein the peak wavelength of the spectrum that identifies the first converted light is longer than the peak wavelength of the spectrum that specifies the second converted light. Any of claims 1 to 9, wherein the light emitting device is located outside the third layer and has a light source that emits the excitation light and a fiber that propagates the excitation light from the light source to the emission point. The lighting device according to one item. The lighting device according to claim 10, wherein the radiation intensity of the excitation light emitted from the injection point is maximized in the direction toward the first layer. The lighting device according to any one of claims 1 to 11, wherein the light emitting device emits laser light as the excitation light. Further provided with a filter located on the second layer,
The lighting device according to any one of claims 1 to 12, wherein the reflectance of the filter is the largest in the wavelength range including the peak wavelength of the spectrum for specifying the excitation light. Further provided with a filter located on the second layer,
The lighting device according to any one of claims 1 to 12, wherein the transmittance of the filter is the smallest in the wavelength range including the peak wavelength of the excitation light. The lighting device according to any one of claims 1 to 14, wherein the peak wavelength of the excitation light is 360 nm or more and 430 nm or less. The lighting device according to any one of claims 1 to 15, wherein the substrate includes a heat-dissipating member.

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