WO2013161462A1

WO2013161462A1 - Solid-state lighting device

Info

Publication number: WO2013161462A1
Application number: PCT/JP2013/058174
Authority: WO
Inventors: 善久池田; 順一木下
Original assignee: 東芝ライテック株式会社
Priority date: 2012-04-25
Filing date: 2013-03-21
Publication date: 2013-10-31
Also published as: JP2013229174A

Abstract

This solid-state lighting device has a light source section, a waveguide, a light-guiding body, a wavelength conversion layer, and an outer tube section. The light source section has semiconductor lasers and drive circuits, and emits multiple laser beams in a wavelength range of blue-violet to blue. The waveguide respectively guides the multiple laser beams. The light-guiding body, which comprises a first surface, a second surface, and a side surface, scatters the multiple laser beams introduced through the first surface while guiding the laser beams toward the second surface, and emits the resulting light through the side surface. The wavelength conversion layer has an inner edge and an outer edge, and fluorescent particles are distributed in a scattered manner inside the wavelength conversion layer. The wavelength conversion layer emits, through the outer edge, the wavelength-converted light and scattered light that results from multiple scattering of residual light, that is, a portion of the light that is emitted through the side surface without being absorbed by the fluorescent particles. The outer tube section is provided so as to surround the outer edge of the wavelength conversion layer, scatters the scattered light and the wavelength-converted light by means of a rough surface, and emits the resulting light as mixed light through the outer surface thereof.

Description

Solid state lighting device

Embodiments of the present invention relate to a solid state lighting device.

White solid-state lighting (SSL: Solid-State Lighting) devices using solid-state light-emitting elements are mainly LEDs (Light Emitting Diodes).

However, the white light emitting part having a phosphor and the LED chip are often provided close to each other. For this reason, a substrate for heat dissipation and power supply of the LED chip is required.

Further, the high-luminance LED has a chip size of 0.5 mm × 0.5 mm or more, a Lambert distribution, and a wide emission angle. For this reason, light tends to diverge and it is difficult to efficiently irradiate the phosphor layer.

High-brightness and high-intensity light sources are necessary for lighting devices such as liquid crystal projectors, searchlights, headlights, stage lighting, and street lamps. However, it is difficult to configure a light emitting unit that is small, light, and has a low calorific value with LEDs.

JP 2007-52957 A

する Provide a solid-state lighting device that emits incoherent light and has improved safety.

The solid-state lighting device according to the embodiment includes a light source unit, a waveguide, a light guide, a wavelength conversion layer, and an outer tube unit. The light source unit includes a semiconductor laser and a drive circuit that controls the semiconductor laser, and emits a plurality of laser beams in a blue-violet to blue wavelength range. The waveguide guides the plurality of laser beams. The light guide has a first surface and a second surface and a side surface opposite to the first surface, and introduces the plurality of laser beams from the first surface. The light is scattered while being guided toward the surface, and emitted from the side surface. The wavelength conversion layer has an inner edge surrounding the side surface of the light guide and an outer edge opposite to the inner edge, and the phosphor particles are arranged in a dispersed manner. The wavelength conversion layer includes wavelength-converted light emitted from the phosphor particles that have absorbed light emitted from the side surface, and residual light that is not absorbed by the phosphor particles among the light emitted from the side surface. Scattered light generated by multiple scattering is emitted from the outer edge. The outer tube portion is provided so as to surround the outer edge of the wavelength conversion layer, has an outer surface provided with a rough surface, and scatters the scattered light and the wavelength converted light by the rough surface. The mixed light is emitted from the outer surface.

A solid state lighting device with improved safety by emitting incoherent light is provided.

It is a model perspective view which shows the structure of the solid-state lighting device concerning 1st Embodiment. 2A is a schematic cross-sectional view along the central axis of the multiple scattering converter, FIG. 2B is a schematic cross-sectional view along the line AA, and FIG. 2C is a partially enlarged wavelength conversion layer. It is a schematic cross section. 3A is a schematic diagram for explaining a speckle contrast measurement system, and FIG. 3B is an emission spectrum diagram of mixed light. FIG. 4A is a photograph of speckle noise generated on the observation surface by coherent light, and FIG. 4B is a photograph of the observation surface by incoherent light. 5A is a speckle contrast observation surface of a blue LED, FIG. 5B is a speckle contrast observation surface of a blue semiconductor laser, and FIG. 5C is a speckle contrast observation of an illumination device including four semiconductor lasers. FIG. 5D is a graph showing a speckle contrast observation surface of an illumination device including 20 semiconductor lasers. It is a graph of the dependence of speckle contrast on operating current. FIG. 7A is a graph of the optical output with respect to the operating current of the blue semiconductor laser, FIG. 7B is a graph of the emission spectrum in the low current region, and FIG. 7C is the emission spectrum in the high current region. FIG. It is a schematic cross section of the solid-state lighting device concerning 2nd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic perspective view illustrating the configuration of the solid-state lighting device according to the first embodiment.
The solid state lighting device includes a light source unit 10, a waveguide 20, a light guide 39, a wavelength conversion layer 32, and an outer tube unit 34.

The light source unit 10 is made of a nitride-based semiconductor material, and a plurality of semiconductor lasers 11 that can emit laser light in a blue-violet to blue wavelength range (405 to 490 nm), and a drive that can drive each of the plurality of semiconductor lasers 11. Circuit 12 (12a, 12b, 12c, 12d). A semiconductor laser (LD: Laser Diode) 11 can be optically coupled to the light guide 20 efficiently. The light emitting point of the end face of the chip of the semiconductor laser 11 has a size of 10 μm or less, and its radiation angle (beam divergence) is as narrow as about 25 ° × 40 °.

The drive circuit 12 controls the operation mode by changing the voltage or current of the semiconductor laser 11. It can also be controlled to achieve a predetermined light output.

The waveguide 20 guides each of the plurality of laser beams G1 toward the light guide 39. The waveguide 20 can be, for example, an optical fiber 24. The optical fiber 24 may be provided for each laser beam or may be common.

The light guide 39, the wavelength conversion layer 32, and the outer tube portion 34 constitute a multiple scattering conversion unit 30. The multiple scattering conversion unit 30 scatters the plurality of semiconductor laser beams G1 to generate scattered light, and generates wavelength converted light by the wavelength conversion layer 32 that has absorbed the plurality of semiconductor laser beams G1, and illuminates incoherent light. It can be emitted as light. The multiple scattering conversion unit 30 has a central axis 39d.

2A is a schematic cross-sectional view along the central axis of the multiple scattering converter, FIG. 2B is a schematic cross-sectional view along the line AA, and FIG. 2C is a partially enlarged wavelength conversion layer. It is a schematic cross section.
The light guide 39 has a first surface 39a, a second surface 39b opposite to the first surface 39a, and a side surface 39c. The four laser beams g1 to g4 are incident from the first surface 30a, guided to the second surface 39b, and emitted outward from the side surface 39c. In the first embodiment, the number of semiconductor lasers 11 is four, but the number of semiconductor lasers 11 is not limited to this. The number of semiconductor lasers 11 will be described in detail later.

Each of the incident laser beams g1 to g4 is scattered by reflection inside the light guide 39 while being guided toward the second surface 39b of the light guide 39. The wavelength conversion layer 32 has an inner edge 32a surrounding the side surface 39c of the light guide 39, and an outer edge 32b on the side opposite to the inner edge 32a. In the wavelength conversion layer 32, phosphor particles 32c made of YAG (Yttrium Aluminum Garnet) phosphor or the like are dispersed and arranged.

The light emitted from the side surface 39 c of the light guide 39 irradiates the wavelength conversion layer 32. The phosphor particles 32c that have absorbed the irradiation light emit wavelength-converted light gc. The remaining light that is not absorbed by the phosphor particles 32c becomes scattered light gs with reduced coherence by being multiple-reflected or diffused by the phosphor particles 32c in the wavelength conversion layer 32.

Further, as shown in FIG. 2C, when the light diffusion particles 32d containing a material having a high diffusion transmittance are dispersed and arranged in the wavelength conversion layer 32, the scattering increases and the coherence can be further reduced. The light scattering particles 32d can contain polymethyl methacrylate, calcium carbonate, or the like.

When the particle diameters of the phosphor particles 32c and the light diffusion particles 32d are equal to or greater than the wavelength, Mie scattering is mainly generated. Further, when the particle diameter is smaller than the wavelength, Rayleigh scattering is mainly generated. In the first embodiment, in the wavelength conversion layer 32, incident light is scattered mainly by particles to reduce coherence.

The outer tube portion 34 is provided so as to surround the outer edge 32 b of the wavelength conversion layer 32. A rough surface is provided on the outer surface 34 b of the outer pipe portion 34. The wavelength conversion light gc and the scattered light gs are emitted from the outer edge 32 b of the wavelength conversion layer 32 and enter the outer tube portion 34. The scattered light gs and the wavelength converted light gc are scattered by the rough surface and emitted from the outer surface 34b as the mixed light GT. In the first embodiment, by roughening the outer surface 34b of the outer tube portion 34 serving as a light emitting surface, blue-violet to blue light can be further reduced in coherency. The wavelength conversion layer 32 may be provided on the inner edge 34a of the outer tube portion 34 by coating or the like.

The light guide 39 and the outer tube 34 may include glass (including quartz), ceramics, and the like. The surface can be roughened by, for example, frost treatment. If the outer tube portion 34 is made of YAG ceramics, it can be made transparent in the ultraviolet to infrared region. Further, the hardness can be increased and the mechanical strength of the lighting device can be increased.

Also, ceramics and including Al ₂ O ₃ or the like of the hexagonal system having the optical anisotropy to an internal or external surface 34b, it is possible to further improve the scattering.

The solid-state lighting device of the first embodiment can emit a light beam exceeding 1100 lumens with a diameter of several millimeters or less, and can realize a high-intensity, high-intensity white light source. In addition, since the heat generation region in the multiple scattering conversion layer 30 is only the wavelength conversion layer 32, it can be made small and lightweight.

As described above, the illumination device using the semiconductor laser 11 is easy to be small, light, and have a low calorific value. On the other hand, safety management in accordance with the provisions of the International Electrotechnical Commission (IEC) is required for devices using laser light. Hereinafter, a result of evaluating which class of the IEC standard the illumination light of the first embodiment corresponds to will be described in detail.

3A is a schematic diagram for explaining a speckle contrast measurement system, and FIG. 3B is an emission spectrum diagram of mixed light.
As shown in FIG. 3A, the mixed light GT emitted from the outer surface 34 b of the outer tube portion 34 enters the filter 54 that transmits blue-violet to blue light through the slit 52. The light transmitted through the filter 54 is collected by the lens 56 and projected onto the screen 58. The projection on the screen 58 forms an image on a 1/2 inch CCD (Charge Coupled Device) via a pin hole with a diameter of 0.8 mm that allows light with a solid angle of 2 m radians to pass through and a condenser lens 62. Note that speckle refers to a random interference phenomenon that occurs when a scattered light is randomly scattered by a rough object and scattered light from each point overlaps at each point on the observation surface (CCD light receiving surface) ([Non-patent Reference 1]).

Further, as shown in FIG. 3B, the emission spectrum of the mixed light GT includes a wavelength in the vicinity of 450 nm and wavelength-converted light having a broad spectrum with a center wavelength of 560 nm.

FIG. 4A is a photograph of speckle noise generated on the observation surface by coherent light, and FIG. 4B is a photograph of the observation surface by incoherent light.
Speckle contrast Cs, using average intensity E (I) and the standard deviation sigma _I, it shall be expressed by Equation (1).

Cs = σ _I / E (I) Formula (1)

In the observation plane, by mean intensity E (I) and obtaining a standard deviation sigma _I, the speckle contrast Cs, is calculated from equation (1). This makes it possible to evaluate whether the illumination light is closer to the class to which the laser light that is coherent light belongs or the class to which the LED light that is incoherent light belongs.

5A is a speckle contrast observation surface of a blue LED, FIG. 5B is a speckle contrast observation surface of a blue semiconductor laser, and FIG. 5C is a speckle contrast observation of an illumination device including four semiconductor lasers. FIG. 5D is a graph showing a speckle contrast observation surface of an illumination device including 20 semiconductor lasers.
The vertical axis of the three-dimensional display is the relative intensity of speckle contrast Cs. In the two-dimensional display, the relative intensity is planarly displayed.

As shown in FIG. 5A, the speckle contrast Cs of the blue LED having a wavelength of 445 nm was 1.8% when the operating current was 0.16A and 1.8% when the operating current was 1A. That is, the speckle contrast Cs is low and the change with respect to the operating current is small.

On the other hand, as shown in FIG. 5B, the speckle contrast Cs of the blue semiconductor laser having a wavelength of 455 nm is 83.3% when the operating current is 0.16 A, and the operating current is 1 A (light output is approximately 1.3 W). 27%. That is, it was higher by one digit or more than the speckle contrast Cs of the blue LED. In addition, when the operating current was increased, the speckle contrast could be reduced. When the transmission wavelength of the filter 54 is changed within the visible light wavelength range, the speckle contrast Cs can be measured for each visible light component of the mixed light.

As shown in FIG. 5C, in the case of the illumination device having the four semiconductor lasers 11, the speckle contrast Cs is 15.8% when the operating current is 0.16A and 3.4% when the operating current is 1A. there were. In this case, the luminous flux was 1100 lumens and the color temperature was 4000K.

Further, as shown in FIG. 5D, in the case of an illumination device having 20 semiconductor lasers 11, the speckle contrast Cs is 2.4% when the operating current is 0.16 A and 1.7 when the operating current is 1 A. %Met. That is, when the operating current is 1 A, when the number of semiconductor lasers 11 is increased from 4 to 20, the speckle contrast Cs can be halved. In this case, the speckle contrast Cs of the illumination device is substantially the same as that of the LED, and can be said to be incoherent light. The luminous flux was 5000 lumens, and the color temperature was 5000K.

The wavelengths of the plurality of laser beams may be substantially the same. For example, when the semiconductor laser 11 is formed on the same wafer or the MQW (Multi Quantum Well) structure of the light emitting layer is the same, the difference between the maximum value and the minimum value of the oscillation longitudinal mode wavelength Can be approximately 15 nm or less. In this case, since the semiconductor laser 11 has substantially the same characteristics, the drive circuit 12 can be easily designed and the price can be reduced. Note that the oscillation longitudinal mode wavelength is represented by a wavelength at which the emission spectrum intensity peaks in a broad emission spectrum.

On the other hand, the oscillation longitudinal mode wavelengths of the plurality of semiconductor lasers 11 may be widely distributed in the range of 405 to 490 nm. For example, if the difference between the maximum value and the minimum value of the oscillation longitudinal mode wavelength is 50 nm or more, it is easier to reduce the coherence.

FIG. 6 is a graph showing the dependence of speckle contrast on the operating current.
The vertical axis represents speckle contrast Cs (%), and the horizontal axis represents operating current (A). The speckle contrast Cs of the solid state lighting device (solid line) with 20 semiconductor lasers 11 is substantially equal to the speckle contrast Cs of the LED (dashed line) in the operating current range of 1.2 A or less. Further, the speckle contrast Cs of the solid state lighting device (dot line) having four semiconductor lasers 11 increases and approaches the blue semiconductor laser (chain line). The speckle contrast Cs (chain line) of the semiconductor laser 11 increases at an operating current lower than 0.3A. From FIG. 6, if the maximum value of the speckle contrast Cs is 10% or less, low coherence can be achieved, and safety for human eyes can be ensured.

FIG. 7A is a graph of the optical output with respect to the operating current of the blue semiconductor laser, FIG. 7B is a graph of the emission spectrum in the low current region, and FIG. 7C is the emission spectrum in the high current region. FIG.
As shown in FIG. 7B, in the region where the operating current is lower than 0.3 A, the longitudinal mode arrangement is close to the single longitudinal mode oscillation, and the emission spectrum has high coherence. On the other hand, as shown in FIG. 7C, when the operating current is 0.3 A or more, the mode is completely the multi-longitudinal mode, the emission spectrum width is widened, and low coherence is achieved. That is, the drive circuit 12 can achieve low coherence by controlling each semiconductor laser 11 to operate at 0.3 A or more, as shown by a solid line in FIG. Note that the luminance can be controlled by changing the operating current in the range of 0.3 A or more by the drive circuit 12.

Thus, by making the laser light incident on the multiple scattering conversion unit 30 low coherence, it becomes easier to convert the illumination light into incoherent light.

In addition, when the speckle contrast Cs is used, the effect of roughening the outer surface 39b of the light guide 39 can be known. For example, when the outer tube portion 34 is made of quartz, the speckle contrast Cs is 13.7%. On the other hand, when the outer tube portion 34 is made of YAG ceramics, the speckle contrast Cs can be reduced to 6%. That is, it has been found that YAG ceramics can be easily made to have lower coherence than quartz.

FIG. 8 is a schematic cross-sectional view of a solid-state lighting device according to the second embodiment.
The solid state lighting device includes a light source unit 10, a waveguide 20, a light guide 39, a wavelength conversion layer 32, and a reflection layer 38. In addition, although the cross section of the light guide 39 is a rectangle, this invention is not limited to this. The cross section may be a circle, an ellipse, a polygon, or the like.

The light guide 39 has a first surface, a second surface opposite to the first surface, an upper surface 39f, and a lower surface 39e opposite to the upper surface 39f. The plurality of laser beams g5 are reflected and scattered inside the light guide 39 while being guided inside the light guide 39, and are mainly emitted from the upper surface 39f and the lower surface 39e.

Further, the wavelength conversion layer 32 in which the phosphor particles are dispersedly disposed is provided in contact with the lower surface 39e of the light guide 39. The light emitted from the lower surface 39e irradiates the wavelength conversion layer 32. The phosphor particles 32c that have absorbed the irradiation light emit wavelength-converted light gc. The remaining light that is not absorbed by the phosphor particles 32 c is reflected or diffused by the phosphor particles in the wavelength conversion layer 32 and becomes scattered light gs. The reflective layer 38 reflects the wavelength-converted light gc and the scattered light gs upward. Further, if light diffusing particles containing a material having a high diffusion transmittance are dispersed and arranged in the wavelength conversion layer 32, the coherence can be further reduced.

If a rough surface is provided on the upper surface 39f of the light guide 39, the wavelength converted light gc and the scattered light gs can be further scattered to further reduce the coherence. The light guide 39 may include any of glass (including quartz) and ceramics.

However, lighting devices such as LEDs, halogen light bulbs, high intensity light sources such as HID (High Intensity Discharge), and lighting devices such as projectors have large housings due to the heat generated by the light sources. In particular, the projector includes a cooling fan and the like, and optical components such as a liquid crystal and a lens, a circuit, and the like are integrally incorporated in the housing. It is also necessary to take measures against heat dissipation from these expensive parts. In addition, when a projector is placed on a desk, the exhaust heat from the cooling fan is uncomfortable and the sound of the fan is loud. On the other hand, in the present embodiment, it is possible to provide a small and lightweight large-intensity high-luminance lighting device that is easy to dissipate.

In addition, the solid-state lighting device of the present embodiment emits a light beam exceeding 1100 lumens with a diameter of several millimeters or less, and can realize a high-intensity high-intensity white light source. The heat generating region in the multiple scattering conversion unit 30 is only the phosphor layer 32, and a small and lightweight white light emitting region can be realized.

Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

Claims

A light source unit that has a semiconductor laser and a drive circuit that controls the semiconductor laser, and that emits a plurality of laser beams in a blue-violet to blue wavelength range;
A waveguide for guiding each of the plurality of laser beams;
A first surface and a second surface opposite to the first surface; and a plurality of laser beams are introduced from the first surface and guided toward the second surface. A light guide that scatters and emits light from the side surface;
A wavelength conversion layer having an inner edge surrounding the side surface of the light guide and an outer edge opposite to the inner edge, the phosphor particles being dispersed and arranged, the light emitted from the side surface The wavelength-converted light emitted from the absorbed phosphor particles and the scattered light generated by multiple scattering of the remaining light that is not absorbed by the phosphor particles out of the light emitted from the side surface, from the outer edge A wavelength converting layer to be emitted;
The outer surface of the wavelength conversion layer is provided so as to surround the outer edge, and has an outer surface provided with a rough surface. The scattered light and the wavelength converted light are scattered by the rough surface and mixed light from the outer surface. As the outer tube part discharging as
A solid state lighting device.
The solid state lighting device according to claim 1, wherein the difference between the maximum value and the minimum value of the oscillation longitudinal mode wavelength of the plurality of laser beams is 50 nm or more.
The solid state lighting device according to claim 1, wherein the difference between the maximum value and the minimum value of the oscillation longitudinal mode wavelength of the plurality of laser beams is 15 nm or less.
The solid-state lighting device according to claim 1, wherein the driving circuit drives the semiconductor lasers so that the plurality of laser beams are in a multi-longitudinal mode.
The solid-state lighting device according to claim 1, wherein a speckle contrast of a visible light component in the mixed light is 10% or less.
A light source unit that has a semiconductor laser and a drive circuit that controls the semiconductor laser, and that emits a plurality of laser beams in a blue-violet to blue wavelength range;
A waveguide for guiding each of the plurality of laser beams;
A first surface and a second surface opposite to the first surface; an upper surface and a lower surface; and introducing the plurality of laser beams from the first surface toward the second surface. A light guide that scatters and emits light from the upper surface and the lower surface, the light guide having a rough surface on the upper surface,
A wavelength conversion layer provided on the lower surface of the light guide and arranged to disperse phosphor particles, the wavelength converted light emitted from the phosphor particles absorbing the light emitted from the lower surface, and A wavelength conversion layer that emits scattered light generated by multiple scattering of the remaining light that is not absorbed by the phosphor particles among the light emitted from the lower surface;
With
The scattered light and the wavelength-converted light are solid state lighting devices that are emitted as mixed light while being scattered by the rough surface.
The reflective layer provided in contact with the wavelength conversion layer or at least one of the upper surface and the lower surface of the light guide, and capable of reflecting the scattered light and the wavelength converted light. 6. The solid state lighting device according to 6.
The solid state lighting device according to claim 6, wherein a difference between a maximum value and a minimum value of the oscillation longitudinal mode wavelength of the plurality of laser beams is 50 nm or more.
The solid state lighting device according to claim 6, wherein a difference between a maximum value and a minimum value of oscillation longitudinal mode wavelengths of the plurality of laser beams is 15 nm or less.
The solid-state lighting device according to claim 6, wherein the driving circuit drives the semiconductor lasers so that the plurality of laser beams are in a multi-longitudinal mode.
The solid-state lighting device according to claim 6, wherein a speckle contrast of a visible light component in the mixed light is 10% or less.