JP2018106814A - Lighting device and vehicle lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make light emission distribution uniform and reduce optical loss.SOLUTION: A lighting device includes: a laser light source for radiating laser light; a condenser lens for condensing laser light from the laser light source; and a wavelength conversion member having a diffuser panel for diffusing laser light that is condensed by the condenser lens and enters the panel and a wavelength conversion layer for converting laser light diffused by the diffuser panel into a desired wavelength. The diffuser panel has a diffusion degree that is configured so as to become high in the incident center of laser light depending on intensity distribution of laser light and becomes lower as being separated from the incident center of laser light.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an illumination device that irradiates light with a desired wavelength by converting light emitted from an element such as a laser diode (LD) by a wavelength conversion member, and a vehicular lamp including the illumination device.

  2. Description of the Related Art There is known an illumination device that uses a part of light from a laser diode (LD) as illumination light after being converted into light having a desired wavelength by a wavelength conversion member. In Patent Document 1, blue light emitted from an LD is incident on a wavelength conversion member composed of a light scattering layer (also referred to as a light diffusion plate) and a wavelength conversion layer arranged in the direction of blue light irradiation, An illuminating device is disclosed in which blue light is diffused in a light scattering layer and then converted into white light in a wavelength conversion layer and emitted to the outside. When using an LD as a light source as in the illumination device of Patent Document 1, it is easy to condense light with a lens due to monochromaticity and coherency of laser light, and the light collection efficiency is higher than when using an LED as a light source, There is an advantage that a high-luminance lighting device can be realized. In addition, in such an illumination device, heat is generated from the LD during light emission, and heat is generated from the wavelength conversion layer when the wavelength of the blue light of the LD is converted, so that the wavelength conversion efficiency is reduced. is there. Therefore, by disposing the LD and the wavelength conversion member at positions separated from each other, the heat generated by each of the LD and the wavelength conversion member is dispersed to suppress the deterioration of the light emission characteristics of the lighting device.

Japanese Patent Laid-Open No. 2006-9963

  By the way, when the LD is applied as the light source of the illuminating device, the intensity of the laser light exhibits a Gaussian distribution, so that the light output is strongest at the center of the beam, and the light output becomes weaker as the distance from the center increases. Therefore, when laser light is incident on the wavelength conversion member, problems such as color unevenness on the light emitting surface, luminance saturation, and heat saturation occur. For this reason, the light scattering layer is required to diffuse the blue light incident from the LD and uniformly enter the wavelength conversion layer.

  However, when the diffusion concentration of the scattering agent in the light scattering layer is low, the blue light from the LD cannot be sufficiently diffused, so the blue light is incident on the wavelength conversion layer with a light density distribution, Color unevenness occurs in the wavelength conversion layer. On the other hand, when the diffusion density of the light scattering layer is high, the blue light is sufficiently diffused and the color unevenness on the light emitting surface of the wavelength conversion layer is eliminated, but the light returned to the incident side by the light scattering layer (rear side) Scattering) is large, resulting in light loss, and the amount of light as an illumination device decreases. As described above, the color unevenness and the light amount are in a trade-off relationship, and it is necessary to appropriately maintain the diffusion concentration of the scattering agent in the light scattering layer.

  The present invention has been made in view of the above circumstances, and an object thereof is to make the light emission distribution uniform and reduce light loss.

  One embodiment of the present invention includes a laser light source that emits laser light, a condensing lens that condenses the laser light from the laser light source, and a diffusion plate that diffuses the incident laser light that is collected by the condensing lens. And a wavelength conversion member having a wavelength conversion layer that converts the laser light diffused in the diffusion plate into a desired wavelength, and the diffusion concentration of the scattering agent of the diffusion plate is set according to the intensity distribution of the laser light. The illumination device is configured such that the incident center of laser light is high and the distance from the incident center of laser light is low.

  According to the present invention, the light emission distribution can be made uniform and light loss can be reduced.

It is sectional drawing which shows schematic structure of the illuminating device which concerns on the 1st Embodiment of this invention. It is explanatory drawing which shows the relationship between the light which injects with respect to the diffuser plate of the wavelength conversion member in the illuminating device which concerns on the 1st Embodiment of this invention, and a diffusion degree, (A) is a case where diffusion density is small, (B) is The case where the diffusion concentration is large is shown. It is explanatory drawing which shows the relationship between the light which injects with respect to the diffuser plate of the wavelength conversion member in the illuminating device which concerns on the 1st Embodiment of this invention, and a diffusion degree, (A) is a structure of a wavelength conversion member, (B) Shows the intensity distribution when laser light is incident on the wavelength conversion member of (A). It is explanatory drawing which shows the heat flow in the wavelength conversion member in the illuminating device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows schematic structure of the illuminating device which concerns on the 2nd Embodiment of this invention. FIG. 7A is a cross-sectional view illustrating a schematic configuration when the lighting device according to the first embodiment is applied to a vehicle lamp according to a first modification of each embodiment of the present invention, and FIG. It is sectional drawing which shows schematic structure at the time of applying the illuminating device which concerns on this embodiment to a vehicle lamp. (A)-(H) are related with the modification 2 of embodiment of this invention, and are reference figure sectional drawings which show the other example of the wavelength conversion member applied to an illuminating device.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings shown below, hatching is appropriately omitted even in a cross-sectional view for easy understanding and improved visibility. In the following description, the same components are denoted by the same reference numerals, and the description thereof is omitted.

(First embodiment)
An illumination device according to the first embodiment of the present invention will be described.
As shown in FIG. 1, the illumination device according to the present embodiment includes a laser light source 11 that irradiates laser light housed in a housing 5, a condenser lens 12 that condenses the laser light from the laser light source, A wavelength conversion member 13 that diffuses and converts the incident laser light collected by the condenser lens 12 into light having a desired wavelength, a reflection member 14 that covers the periphery of the wavelength conversion member, and the wavelength conversion member 13 and the reflection member 14. And a support substrate 15 disposed on the lower surface of the substrate.

  The housing 5 accommodates the laser light source 11 on the bottom surface, holds the condenser lens 12 in the optical axis direction of the light emitted from the laser light source 11, and emits the light condensed by the condenser lens 12. An opening 5A is provided. A wavelength conversion member 13 and a reflection member 14 supported by a support substrate 15 described later are disposed at the edge of the opening 5A.

  As the laser light source 11 (hereinafter, simply referred to as “LD”), for example, a packaged CAN type semiconductor laser light source including a laser diode can be applied. As the laser light source 11, a light source that emits light in a blue region (for example, an emission wavelength of 450 nm), a near ultraviolet region (for example, an emission wavelength of 405 nm), or other wavelengths can be applied. The LD 11 is housed in the housing 5, so that oxidation is prevented and deterioration of the LD 11 due to oxidation is suppressed.

  The condensing lens 12 condenses the light emitted from the laser light source 11 and makes it incident on a wavelength conversion member 13 described later in order to improve the luminance of the illumination device. The support substrate 15 radiates heat generated in the wavelength conversion member 13 by the support substrate 15. Therefore, the support substrate 15 is desirably as large as possible. Therefore, here, the diameter of the aperture of the support substrate 15 through which the laser beam passes is made as small as possible, and the spot diameter of the laser beam with respect to the wavelength conversion member 13 is set to a desired size that can pass through the aperture diameter of the support substrate by the condenser lens 12. Thus, the size of the support substrate 15 is secured.

The wavelength conversion member 13 includes a diffusion plate 31 that diffuses the incident laser light collected by the condenser lens 12 and a wavelength conversion layer 32 that converts the laser light diffused by the diffusion plate 31 to a desired wavelength. .
The diffusion plate 31 is configured by a scattering agent or a member including a structure that acts as a scattering agent. The scattering agent or the structure acting as a scattering agent is preferably a size not less than the wavelength of the laser beam. Due to the structure that acts as a scattering agent or a scattering agent, the diffuser plate 31 causes the incident laser light to be forward scattered and simultaneously backscattered. Further, by adjusting the concentration of the scattering agent or the structure acting as a scattering agent (diffusion concentration), the degree of light diffusion or the degree of scattering (scattering intensity) can be adjusted, and the larger the diffusion concentration of the scattering agent, etc. The degree of light scattering is large.

For example, as the scattering agent, an additive such as particles and fillers, or air bubbles, which are dispersed in a matrix material such as resin, glass, or ceramics can be used as the diffusion plate 31. Particles and fillers can be made of resin, glass, ceramics or metal. As the structure acting as a scattering agent, a crystal grain boundary can be used. For example, ceramics including crystal grain boundaries can be used as the diffusion plate 31. It is desirable that the member used as the diffusing plate 31 has a characteristic that does not absorb the laser beam and does not melt or deform even at the temperature reached when the laser beam is irradiated. Specifically, an alumina sintered body containing bubbles and grain boundaries, or a diffusion plate composed of YAG / Al ₂ O ₃ polycrystals in which YAG crystal grain boundaries and Al ₂ O ₃ crystal grain boundaries coexist. 31 can be used.

  Here, since the intensity of the laser light from the LD 11 incident on the diffusion plate 31 exhibits a Gaussian distribution, there is a characteristic that the light intensity is strongest at the center of the beam and the light intensity becomes weaker as the distance from the center increases. For this reason, when the diffusion degree in the diffusion plate 31 is uniformly low, the light from the LD 11 cannot be sufficiently diffused, and the light from the LD 11 is incident on the wavelength conversion layer with a light intensity distribution. As a result, color unevenness occurs in the wavelength conversion layer (FIG. 2A). On the other hand, when the diffusion degree of the diffusion plate 31 is uniformly high, the light from the LD is sufficiently diffused and uneven color on the light emitting surface of the wavelength conversion layer is eliminated. The returned light (backscattering) becomes a large loss of light, which not only reduces the amount of light as an illumination device, but also affects the operation of the LD 11.

  Therefore, in the present embodiment, the diffusion plate 31 has a diffusion degree indicating a degree of diffusing the light incident on the diffusion plate 31 with a high incident center of the laser light according to the intensity distribution of the incident laser light, The distance from the incident center is lower.

  In order to increase the incident center of the laser beam according to the intensity distribution of the incident laser beam and lower the distance from the incident center of the laser beam, the diffusion plate 31 has a configuration having at least two diffusion layers having different diffusion degrees. can do. For example, as shown in FIG. 3A, the first diffusion layer 31A having a relatively low diffusion degree and the second diffusion layer 31B having a relatively high diffusion degree may be stacked.

  In this case, among the two or more diffusion layers 31A and 31B, a diffusion layer having a high diffusion concentration in which the thickness of the incident center of the incident laser beam is the hottest and becomes thinner as it goes away from the center, that is, the diffusion degree is relatively high. The high second diffusion layer 31B is laminated so as to be positioned at the center of incidence of the laser beam. In the example of FIG. 3A, the second diffusion layer 31B has inclined surfaces in which the incident surface of the laser light is inclined to the left and right around the incident center of the laser light. That is, the second diffusion layer 31B can be shaped to have a thickness corresponding to the intensity distribution of the laser light, and the first diffusion layer 31A can be disposed around the second diffusion layer 31B. In the first diffusion layer 31A and the second diffusion layer 31B, the second diffusion layer 31B having a high degree of diffusion is preferably higher in refractive index than the first diffusion layer 31A.

  By configuring the diffusion plate 31 in this way, as shown in FIG. 3B, first, light from the LD 11 enters the diffusion plate 31 and enters the first diffusion layer 31A located on the lower surface of the diffusion plate 31. Thus, the first diffusion layer 31A is diffused, that is, isotropically scattered. Since the first diffusion layer 31A has a small diffusion degree, the degree of isotropic scattering is small, the back scattering is small, and the light loss is small (the broken line A in FIGS. 3A and 3B). At this time, as shown in FIG. 3B, the incident light has a high incident center.

  Subsequently, a part of the light from the LD 11 reaches the second diffusion layer 31B (broken line B in FIG. 3), and is isotropically scattered in the slope of the second diffusion layer 31B and in the second diffusion layer 31B. The At this time, light scattering is first started from the vicinity of the center where the light intensity is strong. By completely transmitting through the second diffusion layer 31B, the laser light is diffused sufficiently and uniformly before reaching the wavelength conversion layer 32. Further, most of the light scattered on the slope of the second diffusion layer 31B reaches the side surface of the diffusion plate 31 and is reflected to the wavelength conversion layer 32 side, so that it is scattered to the incident side and becomes return light. The amount of light reaching the wavelength conversion layer 32 is small and the amount of light reaching the wavelength conversion layer 32 can be increased. A dichroic mirror for reflecting the excitation light converted in the wavelength conversion layer 32 to be described later can be provided in the lower layer of the diffusion plate 31.

  The wavelength conversion layer 32 converts the light irradiated from the LD 11 and diffused by the diffusion plate 31 into a desired wavelength and irradiates the outside. As the wavelength conversion layer 32, a phosphor can be applied. For example, a plate-like body in which phosphor particles are dispersed in a binder, phosphor crystal, phosphor glass, or phosphor ceramic can be used. When the light from the LD 11 is in the blue region (e.g., emission wavelength 450 nm), a phosphor that emits yellow light is applied to the wavelength conversion layer 32 or in the near ultraviolet region (e.g., emission wavelength 405 nm). Can be used as a lighting device that emits white light by combining phosphors that emit three colors of red, green, and blue.

  For example, Ce-doped YAG is used as the phosphor that emits yellow light. For the purpose of further diffusing the light from the LD 11, alumina as a diffuser can be used in combination with the phosphor. For example, alumina and Ce-doped YAG may be mixed. A dichroic mirror for reflecting the excitation light converted in the wavelength conversion layer 32 may be provided below the wavelength conversion layer 32.

  The reflection member 14 is provided so as to cover the periphery of the wavelength conversion member 13 and shields light emitted from the side surface of the wavelength conversion layer 32. As the reflecting member 14, a white resin in which titanium oxide particles are dispersed in a resin can be used.

  The support substrate 15 supports the wavelength conversion member 13 and functions as a heat dissipation member that radiates heat generated when the wavelength of the light from the LD 11 is converted in the wavelength conversion layer 32 of the wavelength conversion member 13. As the support substrate 15, a metal having high thermal conductivity can be used, and ceramics can be applied to match the wavelength conversion member 13 and the thermal expansion coefficient. Metal bonding or a resin material is used for bonding the support substrate 15 and the wavelength conversion member 13.

  The wavelength conversion layer 32 generates heat when irradiating the light whose wavelength is converted by absorbing the light from the LD 11. The arrows in FIG. 4 indicate the heat flow at this time. Since the wavelength conversion efficiency of the wavelength conversion layer 32 is reduced by heat, it is necessary to dispose the support substrate 15 having a heat dissipation function. As shown in FIG. 4, since the heat generated in the wavelength conversion layer 32 is radiated by the support substrate 15 through the diffusion plate 31, it is preferable to increase the area of the support substrate 15. On the other hand, it is necessary to provide the support substrate 15 with an opening 15A for allowing the laser light from the LD 11 to enter the diffusion plate 31, and the larger the opening diameter, the smaller the incident light loss. Thus, since the aperture diameter and the area of the support substrate 15 are in a trade-off relationship, the incident light loss is reduced by narrowing the laser beam to a desired spot diameter by the condenser lens 12, and the support substrate is reduced. A size of 15 is secured.

  According to the illuminating device according to the present embodiment, with respect to the diffusion plate 31, the degree of diffusing the light incident on the diffusion plate 31 is set such that the incident center of the laser light is increased according to the intensity distribution of the incident laser light, The first diffusion layer 31A having a lower degree of diffusion and a lower diffusion degree is disposed on the incident surface as the distance from the incident center increases. As a result, the light incident on the diffusion plate is first diffused and isotropically scattered in a portion having a low diffusion degree. At this time, since the diffusion degree of the first diffusion layer 31A is low, the degree of isotropic scattering is small, the back scattering is small, and the light loss is small. Subsequently, the laser light reaches a portion with a high degree of diffusion. First, light scattering starts from the vicinity of the center where the light intensity is strong, and reaches the wavelength conversion layer by passing through all the portions with a high degree of diffusion of the diffusion plate. It is possible to increase the amount of light that is scattered evenly and reaches the wavelength conversion layer. Therefore, it is possible to reduce the light loss while making the light emission distribution uniform.

(Second Embodiment)
In the above-described first embodiment, the example in which the laser beam from the LD 11 is condensed by the condenser lens 12 and then directly incident on the diffusion plate 31 has been described. As shown in FIG. 5, in the present embodiment, an example in which laser light from the LD 11 is collected by the condenser lens 12 and then incident on the diffusion plate 31 through the fiber 20 will be described.

The housing 5 accommodates the laser light source 11 on the bottom surface, holds the condenser lens 12 in the optical axis direction of the light emitted from the laser light source 11, and emits the light condensed by the condenser lens 12. An opening 5A is provided. One end of a fiber 20 is attached to the edge of the opening 5A via a ferrule 6.
The other end of the fiber 20 is held by the support member 7 via the ferrule 6, and guides the laser light from the LD 11 to the wavelength conversion member 13 provided on the support member 7.

  According to the present embodiment, by using the fiber 20, it is possible to guide the light to the diffusion plate 31 in a state where the light loss of the laser light from the LD 11 is reduced and the light loss is reduced. When the fiber 20 is used, the intensity distribution of light incident on the diffusion plate 31 has a conical shape. Therefore, it is preferable that the second diffusion layer has a shape matching this, and the first diffusion layer is disposed around the second diffusion layer.

(Modification 1)
The illuminating device in each embodiment mentioned above can be used as a light source device of a vehicle lamp. As shown in FIGS. 6A and 6B, a reflector 3 that reflects the light emitted from the illumination device and a lens 4 that collects or diffuses the light reflected by the reflector 3 are provided.
Thereby, the light of the desired wavelength irradiated from the illumination device is reflected by the reflector, and is irradiated to the outside through the lens 4 as a light beam having a desired shape.

(Modification 2)
In each of the embodiments described above, the diffusion plate 31 of the wavelength conversion member 13 has the second diffusion layer having a relatively high diffusion degree and a slope, and the diffusion degree provided around the incident surface and the second diffusion layer. The configuration including the first diffusion layer lower than the second diffusion layer has been described. The diffusion plate 31 is not limited to the configuration described above, and the shape of the second diffusion layer 31B is appropriately changed as shown in FIGS. 7A to 7E, and the first diffusion layer 31A is changed to the second diffusion layer. It can be set as the shape provided so that the circumference | surroundings of 31B might be covered. Further, as shown in FIGS. 7F to 7H, the second diffusion layer has a higher degree of diffusion than the first diffusion layer 31A between the first diffusion layer 31A and the second diffusion layer 31B. A third diffusion layer 31C lower than 31B can also be provided.

DESCRIPTION OF SYMBOLS 5 ... Case, 6 ... Ferrule, 7 ... Support member, 11 ... Laser light source, 12 ... Condensing lens, 13 ... Wavelength conversion member, 14 ... Reflective member, DESCRIPTION OF SYMBOLS 15 ... Support substrate, 31 ... Diffusing plate, 31A ... 1st diffused layer, 31B ... 2nd diffused layer, 31C ... 3rd diffused layer, 32 ... Wavelength conversion Layer (phosphor)

Claims (8)

A laser light source for irradiating laser light;
A condensing lens that condenses the laser light from the laser light source;
A wavelength conversion member having a diffusion plate for diffusing the incident laser light collected by the condenser lens, and a wavelength conversion layer for converting the laser light diffused in the diffusion plate to a desired wavelength,
An illuminating device in which a diffusion degree of the diffusion plate is configured such that the incident center of the laser beam is high according to the intensity distribution of the laser beam and decreases as the distance from the incident center of the laser beam increases.   The lighting device according to claim 1, wherein the diffusion plate has at least two diffusion layers having different diffusion degrees.   The illuminating device according to claim 2, wherein the diffusion plate has a diffusion layer having a high diffusion degree arranged at an incident center of incident laser light among two or more diffusion layers.   The illuminating device according to claim 3, wherein a diffusion layer having a lower diffusion degree than the diffusion layer having a higher diffusion degree is disposed on the entire incident surface of the laser beam on the diffusion plate.   The lighting device according to claim 3 or 4, wherein the diffusion layer having a high diffusion degree has a higher refractive index than other diffusion layers.   The illumination device according to claim 2, wherein the diffusion layer having a high diffusion degree has an inclined surface with respect to an incident surface of incident laser light.   The lighting device according to claim 1, further comprising a reflection member that covers the periphery of the wavelength conversion member.   A vehicular lamp provided with the illumination device according to any one of claims 1 to 7.

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