JP2012064484A - Light source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To introduce fluorescence in a phosphor ceramic in a configuration of a reflection type light source device that takes out fluorescence by a reflection method from a surface of a phosphor ceramic surface on which excitation light from a solid light source is incident. Suppress light and increase brightness sufficiently.
SOLUTION: A solid light source 5 that emits light having a predetermined wavelength in a wavelength region from ultraviolet light to visible light, and a light having a wavelength longer than the emission wavelength of the solid light source 5 that is excited by excitation light from the solid light source 5. A phosphor ceramic 2 that emits fluorescence, the solid light source 5 and the phosphor ceramic 2 are spatially separated, and the side of the phosphor ceramic 2 on which excitation light from the solid light source 5 is incident 1 is a reflective light source device 10 for extracting fluorescence from the surface of the surface of the phosphor ceramic 2 with a Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor having an internal scattering coefficient in the range of 10 / mm to 30 / mm. Is used.
[Selection] Figure 4

Description

  The present invention relates to a light source device.

  A light source device combining an optical semiconductor such as an LED and a phosphor layer has been widely used. However, in recent years, the brightness has been increased, and its application range such as general lighting and automobile headlamps has been expanded. It is considered that such light source devices will continue to be widely used in various applications by increasing the luminance.

  This tendency has spread not only to white light sources but also to monochromatic light sources. For example, currently, a high-power green light semiconductor is under development and its output is low. For example, as shown in Patent Document 1, a blue light semiconductor and a phosphor layer are combined to produce a green light source for a projector. A way to achieve this has been proposed.

  As a means for increasing the brightness of a light source device combining such an optical semiconductor and a phosphor layer, it is conceivable to increase the excitation light intensity from the optical semiconductor by supplying a large current to the optical semiconductor. Heat is generated in the phosphor layer, and in the phosphor layer, the fluorescence intensity decreases due to discoloration of the resin component or temperature quenching of the phosphor. Therefore, as a result, the emission intensity is saturated and decreased, and it is difficult to increase the luminance of the light source device that combines the optical semiconductor and the phosphor layer.

  Here, the discoloration of the resin component in the phosphor layer means that the phosphor layer is usually formed into a fixed shape with good reproducibility. This is a phenomenon in which the resin component is discolored when the resin component is heated to about 200 ° C. or higher. Since the resin component is inherently transparent, if the resin component is discolored by heat, it absorbs a part of the excitation light from the optical semiconductor and the fluorescence from the phosphor layer, which prevents high brightness. It was.

  The temperature quenching of the phosphor is a phenomenon in which the fluorescence intensity decreases when the phosphor is heated. If the fluorescence intensity decreases due to temperature quenching, the energy that has not been converted to fluorescence becomes heat, so the amount of heat generated by the phosphor increases, the temperature of the phosphor rises, temperature quenching proceeds, and the fluorescence intensity further decreases. This happens. For this reason, temperature quenching of the phosphors generated by heat has also been a factor that hinders high brightness.

  In order to solve these problems, Patent Document 2 uses a phosphor ceramic that does not substantially contain a resin component as a color conversion fan-shaped section (phosphor layer), and further the phosphor ceramic is used as a color conversion fan-shaped section. It has been proposed to use the arranged color wheel as a fluorescent rotator that is rotated by a motor. Thus, by using phosphor ceramics that do not substantially contain a resin component in the phosphor layer, problems due to discoloration of the resin component can be avoided, and by using a phosphor rotator, the phosphor layer (that is, The region where the phosphor is excited changes from moment to moment, so that overheating of the phosphor layer can be prevented and the problem of temperature quenching of the phosphor can be avoided.

JP 2010-085740 A Special table 2009-539219

  By the way, in Patent Document 2, the phosphor ceramic used in the color conversion fan-shaped section is made of a crystalline inorganic light emitting material sintered into a transparent or translucent ceramic body. However, as shown in FIG. 1, the solid light source 5 and the phosphor layer (that is, phosphor ceramics) 92 are spatially separated from each other, and excitation light from the solid light source 5 is present on the surface of the phosphor ceramics 92. In the case of a reflection type light source device that extracts fluorescence from the incident side surface by a reflection method and uses the fluorescent light condensed by the lens 50, if the transparency of the phosphor ceramic 92 is high, the inside of the phosphor ceramic 92 Fluorescent light guide (fluorescence propagation in all directions) occurs, the area of the light emitting point (light emitting spot) becomes large, and the fluorescent light emitted from the phosphor ceramic 92 cannot be efficiently collected by the lens 50. The inventor of the present application has confirmed the phenomenon that the output of illumination light decreases.

  In FIG. 1, reference numeral 6 denotes a light reflective substrate, and reference numeral 7 denotes a joint portion between the phosphor ceramic 92 and the light reflective substrate 6. That is, the light source device 90 of FIG. 1 has the light reflective substrate 7 provided on the surface of the phosphor ceramic 92 opposite to the surface on which the excitation light from the solid light source 5 is incident. The reflection ceramic light source device is configured as a reflection type light source device that extracts fluorescence by a reflection method from the surface of the phosphor ceramic 92 on the side where the excitation light from the solid light source 5 is incident.

  FIG. 2 is a view (cross-sectional view) for explaining the light guide of the fluorescence in the phosphor ceramic 92. Referring to FIG. 2, in the case where the phosphor ceramic 92 is nearly transparent, when fluorescence is generated by the excitation light from the solid light source 5 entering the phosphor ceramic 92, the fluorescence propagates in all directions. As indicated by reference numeral E in FIG. 2, the light also propagates in a direction (lateral direction) perpendicular to the direction in which the fluorescent light is extracted from the phosphor ceramic 92 (in FIG. 1, the optical axis direction of the lens 50). FIG. 3A is a diagram showing an incident spot 60 of the excitation light from the solid light source 5 to the phosphor ceramic 92, and FIG. 3B is a diagram showing the excitation light from the solid light source 5 as shown in FIG. FIG. 6 is a diagram showing a fluorescent light emission spot 61 when there is no fluorescence light guide in the phosphor ceramic 92 when it is incident on the phosphor ceramic 92. As can be seen from FIG. 3B, when there is no fluorescence light guide, the area of the fluorescent light emission spot 61 in the phosphor ceramic 92 is slightly larger (a little wider) than the area of the excitation light incident spot 60. The fluorescent light emitted from the phosphor ceramic 92 can be efficiently collected by the lens 50, and the brightness of the light source device can be increased. On the other hand, FIG. 3C shows fluorescence emission when the excitation light from the solid-state light source 5 is incident on the phosphor ceramic 92 as shown in FIG. When the fluorescent light is guided, the area of the fluorescent light emitting spot 62 in the phosphor ceramic 92 is much larger than the area of the excitation light incident spot 60 (the fluorescent light has a sign). 62a, 62b, 62c, and 62d are emitted also from the lateral direction of the phosphor ceramic 92), and the fluorescence emitted from the phosphor ceramic 92 cannot be efficiently collected by the lens 50, and the high luminance of the light source device Can not be realized.

  Thus, since the light source device of Patent Document 2 uses highly transparent phosphor ceramics, fluorescence is guided in the phosphor ceramics, and in particular, the configuration of the reflective light source device as shown in FIG. In the case where the fluorescent light emitted from the phosphor ceramic 92 is collected by the lens 50, there is a problem that there is a limit to increasing the brightness.

  The present invention provides a fluorescent light source device having a configuration of a reflective light source device that takes out fluorescence in a reflective manner from a surface of a phosphor ceramic surface on which excitation light from a solid light source is incident. An object of the present invention is to provide a light source device capable of suppressing light guiding and achieving sufficiently high luminance.

In order to achieve the above object, the invention described in claim 1 is excited by a solid light source that emits light of a predetermined wavelength in a wavelength region from ultraviolet light to visible light, and excitation light from the solid light source. A phosphor ceramic that emits fluorescence having a longer wavelength than the emission wavelength of the solid-state light source, wherein the solid-state light source and the phosphor ceramic are spatially separated from each other, and the surface of the phosphor ceramic is Lu ₃ is a reflection-type light source device that extracts fluorescence by a reflection method from a surface on which excitation light from a solid light source is incident, and has an internal scattering coefficient in the range of 10 / mm to 30 / mm in the phosphor ceramic. It is characterized by using Al ₅ O ₁₂ : Ce ³⁺ phosphor.

  According to a second aspect of the present invention, in the light source device according to the first aspect of the present invention, the thickness of the phosphor ceramic is in the range of 20 μm to 200 μm.

The invention according to claim 3 is the light source device according to claim 1 or claim 2, wherein the Ce concentration of the Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is 0.05 mol% to 1.0 mol%. It is characterized by being in range.

  According to a fourth aspect of the present invention, in the light source device according to any one of the first to third aspects, the light source device includes a fluorescent rotating body having the phosphor ceramic. It is said.

According to the first to fifth aspects of the present invention, the solid light source that emits light having a predetermined wavelength in the wavelength region from ultraviolet light to visible light, and the solid that is excited by the excitation light from the solid light source. A phosphor ceramic that emits fluorescence having a wavelength longer than the emission wavelength of the light source, wherein the solid light source and the phosphor ceramic are spatially separated from each other, and the solid light source among the surfaces of the phosphor ceramic Lu ₃ Al ₅ is a reflection type light source device that extracts fluorescence by a reflection method from the surface on which the excitation light from the light is incident, and the phosphor ceramic has an internal scattering coefficient in the range of 10 / mm to 30 / mm. Since the transparency of the phosphor ceramic is intentionally lowered using O ₁₂ : Ce ³⁺ phosphor, the surface of the phosphor ceramic is reflected from the surface where the excitation light from the solid light source is incident. In the case of the configuration of a reflection type light source device that extracts fluorescence (green light), it is possible to suppress the light guide of the fluorescence (green light) in the phosphor ceramic and to sufficiently increase the brightness of the green light. .

It is a figure which shows a reflection type light source device. It is a figure for demonstrating the light guide of the fluorescence in fluorescent substance ceramics. It is a figure for demonstrating the light guide of the fluorescence in fluorescent substance ceramics. It is a figure which shows the example of 1 structure of the light source device of this invention. It is a figure for demonstrating an internal scattering coefficient. It is a figure for demonstrating an internal scattering coefficient. It is a figure for demonstrating the problem in case the thickness L of fluorescent ceramics is thicker than 200 micrometers. It is a figure which shows the measuring system which evaluates fluorescent substance ceramics. It is a figure which shows the measurement result of the sample of fluorescent ceramics. It is a figure which shows the measurement result of the sample of fluorescent ceramics. It is a figure which shows the measurement result of the sample of fluorescent ceramics. It is a figure which shows the structural example of a reflection type fluorescence rotary body.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 4 is a diagram showing a configuration example of the light source device of the present invention. In FIG. 4, the same parts as those in FIG. Referring to FIG. 4, the light source device 10 includes a solid light source 5 that emits light having a predetermined wavelength in a wavelength region from ultraviolet light to visible light, and the solid light source 10 that is excited by excitation light from the solid light source 5. A phosphor ceramic 2 that emits fluorescence having a wavelength longer than the light emission wavelength of the light source 5 is provided, and the solid light source 5 and the phosphor ceramic 2 are arranged spatially separated from each other.

  Here, the phosphor ceramic means that the resin component normally used for forming the phosphor layer is 5 wt% or less of the phosphor layer. The phosphor ceramic is a lump of phosphor that is formed by firing a material into an arbitrary shape before firing in the manufacturing process of the phosphor. The phosphor ceramic may use an organic substance as a binder in the molding process in the manufacturing process. However, since the organic component is burned off by providing a degreasing process after the molding, the organic resin component is 5 wt. % Or less remains. Therefore, since the phosphor ceramic 2 used in the light source device 10 does not substantially contain a resin component and is composed only of an inorganic substance, discoloration due to heat does not occur. In addition, glass and ceramics made of only inorganic substances are generally advantageous in heat dissipation from the phosphor layer to the substrate because they have higher thermal conductivity than resin. That is, the phosphor ceramic 2 used for the light source device 10 is advantageous also in heat dissipation to the light reflective substrate 6 described later.

  The phosphor ceramics 2 can be obtained after being formed into a plate shape, fired, the outer shape of the fired product is controlled by dicing, and the thickness is controlled by polishing, so that the desired shape can be obtained. The apparatus actually used for processing may be a conventionally known apparatus.

  In FIG. 4, reference numeral 6 denotes a light reflective substrate, and reference numeral 7 denotes a joint portion between the phosphor ceramic 2 and the light reflective substrate 6. That is, the light source device 10 of FIG. 4 has the light reflective substrate 6 provided on the surface of the phosphor ceramic 2 opposite to the surface on which the excitation light from the solid light source 5 is incident. A reflection type in which fluorescent light is extracted from the surface of the phosphor ceramics 2 on the side on which excitation light from the solid light source 5 is incident (by the light-reflective substrate 6 being bonded to the phosphor ceramics 2). It is comprised as a light source device.

  Here, the light reflective substrate 6 also serves as a reflection surface for excitation light and fluorescence, serves to dissipate heat from the phosphor ceramic 2 to the outside, and serves as a support substrate for the phosphor ceramic 2. It is. For this reason, high light reflection characteristics, heat transfer characteristics, and workability are required. The light-reflective substrate 6 can be a metal substrate, oxide ceramics such as alumina, non-oxide ceramics such as aluminum nitride, etc., especially aluminum having both high light reflection characteristics, heat transfer characteristics, and workability. It is preferable to use a metal substrate. When a metal substrate is used as the light reflective substrate 6, a metal thin film having a higher light reflectance such as Ag may be formed on the surface thereof.

  In addition, an organic adhesive (resin), an inorganic adhesive, low-melting glass, metal brazing, or the like can be used for the joint 7 between the phosphor ceramic 2 and the light reflective substrate 6. Among these, it is desirable to use a resin having high light transparency.

Incidentally, in the present invention, as the phosphor ceramic 2, the internal scattering coefficient α is in the range of _{10 / mm~30 / mm Lu 3 Al} 5 O 12 with respect to the fluorescence: is characterized by the use of ^{Ce 3+} phosphor.

Here, the internal scattering coefficient α with respect to fluorescence is defined as the following equation (Equation 1). That is, as shown in FIG. 5, in the phosphor ceramic 2 having a thickness L (mm), it is assumed that excitation light from the solid light source 5 is incident on the point P and converted into fluorescence at the point P. Where R is R, the fluorescence transmittance T is expressed by the following equation (Equation 1). In addition, exp (...) is an exponential function.
T = (1-R) ² · exp (−αL) (Formula 1)
As can be seen from Equation 1, when the internal scattering coefficient α is 0, there is no fluorescence scattering inside the phosphor ceramic 2 and the phosphor ceramic 2 is transparent to the fluorescence. On the other hand, as the internal scattering coefficient α increases, the fluorescence transmittance T decreases, and the phosphor ceramic 2 becomes opaque to the fluorescence.

  FIG. 6A shows a case where the phosphor ceramic 2 is a crystal (only the phosphor 70), and there are no pores (hereinafter referred to as pores) in the phosphor ceramic 2. In this case, the phosphor ceramic 2 is transparent to fluorescence (transparency to fluorescence is high), and the internal scattering coefficient α is close to zero. On the other hand, FIG. 6B is a diagram showing a case where pores 71 are present in the phosphor ceramic 2 (between the phosphors 70). At this time, the phosphor ceramic 2 Becomes opaque (transparency to fluorescence decreases), and the internal scattering coefficient α increases. In other words, the internal scattering coefficient α reflects the density of pores 71 in the phosphor ceramic 2, and the higher the density of the pores 71 in the phosphor ceramic 2, the higher the internal scattering coefficient α is. The scattering coefficient α increases and the transparency to fluorescence decreases.

  As described above, if a highly transparent phosphor ceramic is used as the phosphor ceramic 2, fluorescence is guided in the phosphor ceramic 2. In particular, as shown in FIG. When the fluorescence emitted from the phosphor ceramic 2 is collected by the lens 50, there is a limit to increasing the brightness.

In the case of the configuration of the reflection type light source device in which the fluorescence is extracted from the surface of the phosphor ceramic 2 on the side where the excitation light from the solid light source 5 is incident, Is intended to suppress the light guide of the fluorescent light to sufficiently increase the brightness, and for this reason, the internal scattering coefficient α for the fluorescence of the phosphor ceramic 2 (Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor) Is made to be 10 / mm or more, and the phosphor ceramic 2 (Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor) is used with the transparency lowered intentionally. Thereby, the light guide in the phosphor ceramic 2 is suppressed, and the light collection efficiency of the lens 50 is increased, so that a green light source with higher brightness than the conventional one is realized.

However, when the internal scattering coefficient α for the fluorescence of the phosphor ceramic 2 (Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor) becomes 30 / mm or more, the internal quantum efficiency (conversion efficiency from excitation light to fluorescence) decreases. Therefore, the output of the fluorescence emitted from the phosphor ceramic 2 is reduced, and the output of the illumination light is reduced. Therefore, the internal scattering coefficient α for the fluorescence of the phosphor ceramic 2 (Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor) is preferably in the range of 10 / mm to 30 / mm.

Thus, in the present invention, since Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor having an internal scattering coefficient in the range of 10 / mm to 30 / mm is used for the phosphor ceramic, light in the phosphor ceramic 2 is used. Light can be suppressed, the light collection efficiency of the lens 50 can be increased, and a green light source with higher brightness than before can be realized. That is, in the present invention, Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor having an internal scattering coefficient in the range of 10 / mm to 30 / mm is used for the phosphor ceramic 2, and the transparency of the phosphor ceramic 2 is intentionally set. In the case of the configuration of a reflection type light source device that extracts fluorescence (green light) by a reflection method from the surface of the phosphor ceramic 2 on the side where the excitation light from the solid light source 5 is incident, The light guide of the fluorescence (green light) in the body ceramics 2 can be suppressed, the light condensing efficiency of the lens 50 can be increased, and a sufficiently high brightness of the green light can be achieved.

  In the above description, the internal scattering coefficient α is an internal scattering coefficient for fluorescence. However, in practice (in actual measurement and calculation for calculating the internal scattering coefficient α), the reflectance R of the fluorescence itself, the transmission It is not obtained by measuring the rate T, but when the internal scattering coefficient α is irradiated with light having a wavelength that is not absorbed by the phosphor ceramic, the light is fluorescently converted by pores or the like existing inside the phosphor. This is taken as an indication of the rate of loss. That is, when the phosphor ceramic 2 is irradiated with light having a wavelength that does not absorb (for example, light with a wavelength of 600 nm), the phosphor ceramic 2 and the air of the irradiation light (for example, light with a wavelength of 600 nm) to the phosphor ceramic 2 The theoretical value obtained from the difference in refractive index with respect to the reflectance R of the phosphor ceramic 2 is used as the thickness L and transmittance T of the phosphor ceramic 2, and the measured value of the irradiation light (for example, light having a wavelength of 600 nm) is used. What was obtained by calculation based on Equation 1 is the basis for the above-mentioned value (in the range of 10 / mm to 30 / mm) of the internal scattering coefficient α.

  The thickness L of the phosphor ceramic 2 is preferably in the range of 20 μm to 200 μm. That is, when the thickness L of the phosphor ceramic 2 is thinner than 20 μm, the optical path length for converting the excitation light into the fluorescence is too short, and the conversion efficiency from the excitation light to the fluorescence is low. The output of the fluorescence emitted from the phosphor ceramic 2 is reduced, and the output of the illumination light is reduced. In addition, when the thickness L of the phosphor ceramic 2 is larger than 200 μm, as shown by a symbol F in FIG. Since the fluorescent light which goes to decreases, the output of illumination light will become low. Accordingly, the thickness L of the phosphor ceramic 2 is preferably in the range of 20 μm to 200 μm.

The Ce concentration of the Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is preferably in the range of 0.05 mol% to 1.0 mol%. That is, when the Ce concentration is lower than 0.05 mol%, the Ce concentration that is a source of fluorescence is too low, and when the Ce concentration is higher than 1.0 mol%, concentration quenching occurs, so that the output of illumination light is low. It will be lower. Therefore, the Ce concentration of the Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is preferably in the range of 0.05 mol% to 1.0 mol%.

  Next, characteristics of the phosphor ceramic 2 and a measuring method thereof will be described.

  The internal scattering coefficient α indicates the efficiency with which the fluorescence in the phosphor ceramic 2 is scattered. One factor that affects the internal scattering coefficient α is considered to be pores (pores) that exist inside the phosphor ceramic 2. Therefore, the internal scattering coefficient α can be controlled by controlling the density of pores (pores) inside the phosphor ceramic 2 according to the firing temperature and the degree of vacuum when the phosphor ceramic 2 is fired. A sample having a low internal scattering coefficient α is highly transparent to fluorescence, and a sample having a high internal scattering coefficient α is a sample having low transparency to fluorescence.

  The internal scattering coefficient α is, specifically, the amount of light loss when the phosphor ceramic 2 is irradiated with light having a wavelength that is not absorbed. The reflection at the phosphor ceramic 2 and the scattering inside the phosphor ceramic 2. Assuming that the only difference is the reflectance R of the phosphor ceramic 2, the theoretical value obtained from the refractive index difference between the phosphor ceramic 2 and air is used, and the thickness L and transmittance T of the phosphor ceramic 2 are used. Can be obtained by calculation based on Equation 1.

  Further, as described above, the internal quantum efficiency indicates a ratio of converting excitation photons to fluorescent photons in the phosphor ceramic 2, and the internal quantum efficiency includes the calibrated excitation light source, integrating sphere, spectroscope, and detection. It can be obtained by using a measuring system consisting of a vessel and dividing the measured number of fluorescent photons by the number of excited photons.

  The thickness L of the phosphor ceramic 2 can be measured using a micro caliper or a laser displacement meter.

  The Ce concentration of the phosphor ceramic 2 indicates the ratio of Ce atoms contained in the phosphor composition. Specifically, the number of Ce atoms is the total number of Lu ions and Ce ions. It can be obtained by dividing and multiplying by 100. The number of atoms used in the calculation is a design value. If the firing conditions are adjusted, the Ce concentration contained in the fired product coincides with the design value.

  Next, the light source device 10 of FIG. 4 will be described in more detail.

  In the light source device 10 of FIG. 4, a light emitting diode or a semiconductor laser having a light emission wavelength from the ultraviolet light to the visible light region can be used as the solid light source 5. The present invention is not limited to these light sources because the effect is noticeable when a light source with high excitation light intensity is used. For example, the present invention is not limited to these light sources. For example, blue light of about 450 nm using a GaN-based material is used. Can be used.

Further, as described above, the phosphor ceramic 2 is made of Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ that absorbs light in the blue light region and emits green light. This phosphor ceramic 2 can be produced by a known phosphor ceramic production method, and can be produced, for example, by mixing raw materials, granulation, molding, or vacuum firing. In particular, by using particles having an average particle size of submicron or less as a starting material and uniformly forming the formed body density to be 50% or more, the transmittance T can be increased and scattering can be reduced. An example of the manufacturing method is described below.

  First, a compound of elemental elements as raw materials, for example, oxides such as lutetium oxide, aluminum oxide, and cerium oxide are weighed to a predetermined ratio, and these are mixed with a solvent such as alcohol by a ball mill to produce granulated powder. To do. Here, in order to obtain a target sample, the Ce concentration is preferably 0.1 to 2.0 mol%. Next, after forming the granulated powder and degreasing the molded body, it is fired in a vacuum atmosphere to obtain a sintered body. At this time, the granulated powder is molded by uniaxial mold molding at a pressure of about 20 MPa, and then cold isostatic pressing at a pressure of about 150 MPa. The degreasing treatment is preferably performed at 600 to 1000 ° C. Moreover, it is preferable to perform sintering at 1600-1800 degreeC in a vacuum atmosphere for 1 to 10 hours. By controlling the temperature and the degree of vacuum during sintering, it is possible to control the generation of pores that become scattering sources in the sintered body. In order to eliminate pores, it is preferable that the firing temperature is high and the degree of vacuum is high.

  The phosphor ceramics produced as described above are polished to a thickness of several tens to several hundreds of μm using an automatic polishing apparatus, and further, circular, quadrilateral, fan-shaped, or ring by dicing using a diamond cutter or laser. Cut out to a board of any shape such as shape. In the measurement described later, phosphor ceramic 2 having a size of 2.5 × 2.0 mm and a thickness L of 100 μm and 200 μm was used.

  The light-reflective substrate 6 was a flat aluminum plate coated with silver for increasing the light reflectivity. Further, a silicone resin was used for the joint 7 that joins the phosphor ceramic 2 and the light reflective substrate 6. That is, after applying a small amount of silicone resin on the light-reflective substrate 6, the phosphor ceramics 2 is placed thereon, and then left in a constant temperature bath at a temperature of 80 ° C. for 1 hour, and then at 150 ° C. The silicone resin was cured by standing at temperature for 2 hours.

  The sample thus produced (phosphor ceramic 2 disposed on the light-reflective substrate 6) was evaluated using a measurement system as shown in FIG. That is, in FIG. 8, a blue laser diode having an emission wavelength of 445 nm was used as the solid light source 5, and the phosphor ceramic 2 was excited with the blue light emitted from the solid light source 5. Sample cooling is only natural cooling. Green light emitted from the phosphor ceramic 2 was collected by a lens 75 and reflected by a pass filter 76 to separate blue light, and only green light was detected by a detector (thermopile) 77.

  The measurement conditions and measurement results are shown below.

First, as shown in FIG. 9, six samples A1, A2, A3, A4, A5, and A6 having different internal scattering coefficients were prepared, and the conditions under which the green light output was the highest were examined. The excitation energy density at the time of measurement was 3.5 W / m ² . The conditions and measurement results for the six samples A1, A2, A3, A4, A5, and A6 used in the experiment are shown in FIG. In FIG. 9, the output of green light is shown as a relative value with respect to 100, where the sample showing the highest value is 100. From the results of FIG. 9, it was found that a high output can be obtained when the internal scattering coefficient is in the range of 10 / mm to 30 / mm. This is because the internal scattering coefficient is guided in the phosphor when the internal scattering coefficient is lower than 10 / mm (high transmittance), and the internal scattering coefficient is in a trade-off relationship with the internal scattering coefficient when the internal scattering coefficient is higher than 30 / mm. It is considered that the output of the illumination light is lowered because the quantum efficiency is lowered.

Next, as shown in FIG. 10, samples B1, B2, B3, B4, B5, B6 having different thickness L from the samples A1, A2, A3, A4, A5, A6 shown in FIG. A1, A2, A3, A4, A5, and A6 have a thickness L of 100 μm, whereas samples B1, B2, B3, B4, B5, and B6 have a thickness L of 200 μm). The highest conditions were investigated. The excitation energy density at the time of measurement was 3.5 W / m ² . The conditions and measurement results of the samples B1, B2, B3, B4, B5, and B6 used in the experiment are shown in FIG. From the results of FIG. 10, it was found that a high output can be obtained when the thickness L is in the range of 200 μm or less. When the thickness L is thicker than 200 μm, as described above, it is considered that the fluorescence emitted from the lateral direction of the phosphor ceramic 2 increases and the output of the illumination light decreases.

Moreover, as shown in FIG. 11, samples C1, C2, C3, C4, and C5 having different Ce concentrations of the phosphor ceramic 2 were prepared, and the conditions under which the green light output was the highest were examined. The excitation energy density at the time of measurement was 3.5 W / m ² . The conditions and measurement results of the samples C1, C2, C3, C4, and C5 used in the experiment are shown in FIG. From the results of FIG. 11, it was found that a high output can be obtained when the Ce concentration is in the range of 1.0 mol% or less. When the Ce concentration is higher than 1.0 mol%, concentration quenching occurs, so the output of illumination light is considered to be low. However, when the Ce concentration is changed, the emission chromaticity also changes. Therefore, the result of this experiment does not preclude the use of the phosphor ceramics 2 at that concentration when the target chromaticity is at a Ce concentration of 2.0 mol%, for example.

  In the light source device 10 of FIG. 4 described above, the phosphor ceramic 2 may be fixed, but the phosphor ceramic 2 can be configured to be movable. For example, as shown in FIG. 12, it can also be configured as a reflection type fluorescent rotating body 1 in which the fluorescent ceramic 2 is rotated around a rotation axis X (rotated by a motor or the like). That is, the reflection type fluorescent rotating body 1 can be realized by connecting a phosphor ceramic 2 and a light reflective substrate 6 joined to a motor or the like. Further, in the reflection type fluorescent rotating body 1, the light reflective substrate 6 and the joint portion 7 (the joint portion 7 is not shown in FIG. 12) function as a reflection surface for excitation light and fluorescence. The shape of the light reflective substrate 6 may be a disk shape or a quadrangle. In addition, in order to ensure the stability of rotation, it is possible to cut out a part of the disk or to have a shape with a weight on the contrary.

As shown in FIG. 12, even when the phosphor ceramic 2 is configured as a reflection type fluorescent rotator 1 that is rotated around the rotation axis X (rotated by a motor or the like), the phosphor ceramic 2 has an internal scattering coefficient of 10 By using a Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor in the range of / mm to 30 / mm, light guiding in the phosphor ceramic 2 is suppressed, and the light collection efficiency of the lens 50 is reduced. And a green light source with higher brightness than before can be realized.

  Further, by configuring the phosphor ceramic 2 as the reflection type fluorescent rotating body 1 that rotates around the rotation axis X (rotated by a motor or the like), that is, the phosphor ceramic 2 is rotated with respect to the solid light source 5. Thus, it is possible to disperse the place where the excitation light from the solid light source 5 hits and suppress the heat generation in the light irradiation unit (by using this fluorescent rotating body 1, it is possible to suppress the heat generation of the phosphor in the first place) Thereby, it is possible to further increase the luminance.

  As described above, in the present invention, by installing the solid light source 5 and the phosphor ceramic 2 on the same side with respect to the light reflective substrate 6, a reflective light source device is obtained. Of course, if necessary, an optical element such as a lens can be inserted between the solid light source 5 and the phosphor ceramic 2.

  Further, by combining the above-described various light source devices of the present invention with optical components such as a predetermined lens system, it is possible to provide an illumination device capable of increasing the brightness.

  The present invention can be used for a high-luminance projector light source, an illumination light source, and the like.

DESCRIPTION OF SYMBOLS 1 Fluorescence rotary body 2 Fluorescent substance ceramics 5 Solid light source 6 Light reflective board | substrate 7 Joint part 10 Light source device 50 Lens

Claims (4)

A solid-state light source that emits light of a predetermined wavelength in a wavelength region from ultraviolet light to visible light, and a fluorescence that is excited by excitation light from the solid-state light source and emits fluorescence having a longer wavelength than the emission wavelength of the solid-state light source The solid light source and the phosphor ceramic are in a spatially separated position, and are reflected from a surface of the phosphor ceramic surface on which excitation light from the solid light source is incident. A reflection-type light source device for extracting fluorescence, wherein the phosphor ceramic is a Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor having an internal scattering coefficient in a range of 10 / mm to 30 / mm. Light source device. The light source device according to claim 1, wherein the phosphor ceramic has a thickness in a range of 20 μm to 200 μm. 3. The light source device according to claim 1, wherein a Ce concentration of the Lu ₃ Al ₅ O ₁₂ : Ce ³⁺ phosphor is in a range of 0.05 mol% to 1.0 mol%. . 4. The light source device according to claim 1, wherein the light source device includes a fluorescent rotating body having the phosphor ceramic. 5.

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