JP5803137B2 - Light source device and projector - Google Patents

Description

  The present invention relates to a light source device and a projector.

  Conventionally, in a projector, a discharge lamp such as an ultra-high pressure mercury lamp is generally used as a light source. However, this type of discharge lamp has problems such as a relatively short life, difficulty in instantaneous lighting, and ultraviolet light emitted from the lamp deteriorates the liquid crystal light bulb. In view of this, a projection type image display apparatus using a light source instead of a discharge lamp has been proposed.

  As such a light source, a method of forming white light using fluorescence is known. For example, a light source device that extracts white light as emitted light (fluorescence) by illuminating a phosphor using an LED that emits ultraviolet light has been proposed (see Patent Document 1).

  However, in the apparatus of Patent Document 1, since the light energy per unit area of the LED is small, it is necessary to arrange many LEDs side by side in order to increase the amount of emitted light. Then, when considering a plurality of LEDs as the light source, the etendue (a parameter given by the product of the light emitting area of the light source and the condensing solid angle) is larger than that of a conventional projector light source, so that the light use efficiency decreases. End up.

  Therefore, a light source device using a laser light source as a high output light source instead of the LED has been proposed (for example, see Patent Documents 2 and 3). The light source devices of Patent Documents 2 and 3 include a laser light source that is a light source of excitation light (blue light) that excites the phosphor, and a phosphor that emits a plurality of color lights corresponding to the three primary colors of light. Fluorescence emitted by irradiating a plurality of phosphors with laser light while rotating the disc while arranging the phosphors of a plurality of types on the disc in the circumferential direction and dividing the region for each type. Is different for each hour. Thus, a light source device that emits white light by time-integrating a plurality of color lights and mixing the colors is obtained.

JP 2005-274957 A JP 2009-277516 A US Pat. No. 7,547,114

  However, while the devices of Patent Documents 2 and 3 can reduce the etendue, there are the following problems.

  First, when the light source device uses a laser light source that emits blue light as excitation light, and the blue light and color light (fluorescence) emitted from the phosphor are mixed to form white light, the fluorescence is Lambertian. In contrast, the blue light, which is a laser beam, is highly linear and does not diffuse so much (the degree of scattering is small), and therefore emits light in different diffusion states. Then, when the formed white light is enlarged and irradiated on the screen, color unevenness (luminance unevenness) occurs. Lambertian is a light emission distribution in which the distribution of the emission intensity with respect to the observation angle is proportional to the observation angle cos (cosine).

  Second, since the fluorescence emitted from the phosphor is emitted in all directions, the fluorescence emitted by the laser light irradiation is emitted outside the phosphor film after propagating in the phosphor film in the in-plane direction. Therefore, even if the spot diameter of the laser light irradiated to the fluorescent film is small, the spot diameter of the emitted fluorescence is enlarged and the etendue is increased.

  The present invention has been made in view of such circumstances, and it is an object of the present invention to solve at least one of the above-described problems and to provide a light source device with low color unevenness and high light utilization efficiency. It is another object of the present invention to provide a projector having such a light source device and capable of displaying a high-quality image.

In order to solve the above problems, a light source device according to the present invention includes a laser light source that emits excitation light in a visible light region and a part of the excitation light that is transmitted and excited by the excitation light in the visible light region. A light-emitting element that emits fluorescence, and the light-emitting element includes a light-transmitting base material, a plurality of phosphor particles included in the base material, and a light-transmitting property included in the base material. a light-emitting layer including a plurality of filler particles, a with the total volume of the plurality of phosphor particles and the plurality of filler particles, Ri 45% der less than 35% of the volume of the light-emitting layer, wherein The refractive index of the plurality of phosphor particles and the plurality of filler particles is 1.2 times or more the refractive index of the material of the base material, and the film thickness of the light emitting layer is that of the plurality of phosphor particles. and wherein 10 times the thickness of der Rukoto an average particle size That.
In order to solve the above problems, a light source device according to the present invention includes a laser light source that emits excitation light in a visible light region and a part of the excitation light that is transmitted and excited by the excitation light in the visible light region. A light-emitting element that emits fluorescence, and the light-emitting element includes a light-transmitting base material, a plurality of phosphor particles included in the base material, and a light-transmitting property included in the base material. And a plurality of filler particles having a light emitting layer.

  According to this configuration, the light emitted from the light source device is light having a color in which excitation light and fluorescence are mixed. At that time, the excitation light is scattered and diffused by being partially reflected and refracted on the surface of the phosphor particles and filler particles in the light emitting layer. For this reason, excitation light having high straightness is more diffused and spread than when filler particles are not included, and thus approaches the spread of fluorescence. In addition, fluorescence emitted isotropically from the phosphor particles is scattered by being partially reflected and refracted on the surfaces of the phosphor particles and filler particles in the light emitting layer, and proceeds toward the exit surface of the light source device. The fluorescence component increases. Therefore, compared with the case where filler particles are not included, the distance in a plan view in which the fluorescence travels in the light emitting layer in a direction parallel to the emission surface of the light source device can be suppressed, and the spot diameter of the emitted fluorescence is increased. Can be suppressed. As a result, it is possible to obtain a light source device in which color unevenness is suppressed and light utilization efficiency is high.

In the present invention, it is desirable that an average particle diameter of the plurality of filler particles is a size for geometrically optically scattering the excitation light.
According to this configuration, in the filler particles, backscattering is less likely to occur in the excitation light and fluorescence having a longer wavelength than the excitation light. Therefore, a light source device with high light utilization efficiency can be obtained.

In the present invention, the average particle diameter of the plurality of filler particles is preferably 5 μm or more.
According to this configuration, it is possible to effectively cause geometric optical scattering and suppress backscattering.

In the present invention, it is desirable that an average particle diameter of the plurality of phosphor particles is a size for geometrically optically scattering the excitation light.
According to this configuration, in the phosphor particles as well as the filler particles, backscattering is less likely to occur in the excitation light and fluorescence having a longer wavelength than the excitation light. Therefore, a light source device with high light utilization efficiency can be obtained.

In the present invention, the average particle diameter of the plurality of phosphor particles is preferably 5 μm or more.
According to this configuration, it is possible to effectively cause geometric optical scattering and suppress backscattering.

In the present invention, it is desirable that the film thickness of the light emitting layer is not more than 10 times the average particle diameter of the plurality of phosphor particles.
According to this configuration, it is possible to suppress an increase in the spot diameter of the emitted fluorescence.

In the present invention, the plurality of filler particles are preferably made of a material having a refractive index larger than that of the substrate.
According to this configuration, since the total reflection on the filler particle surface is suppressed, the backscattered light can be reduced and the light utilization efficiency can be increased.

In the present invention, the plurality of filler particles are preferably made of a material having a refractive index that is 1.2 times or more and 1.3 times or less of the refractive index of the substrate.
According to this configuration, it is possible to effectively promote forward scattering while suppressing backscattering of excitation light, and suppress color unevenness. Further, it is possible to effectively promote the scattering of fluorescence, suppress the increase in etendue, and increase the light utilization efficiency.

In the present invention, the plurality of phosphor particles are preferably made of a material having a refractive index larger than that of the substrate.
According to this configuration, since total reflection on the surface of the phosphor particles is suppressed, backscattered light can be reduced and light utilization efficiency can be increased.

In the present invention, the plurality of phosphor particles are preferably made of a material having a refractive index that is 1.2 times or more and 1.3 times or less of the refractive index of the base material.
According to this configuration, it is possible to effectively promote forward scattering while suppressing backscattering of excitation light, and suppress color unevenness. Further, it is possible to effectively promote the scattering of fluorescence, suppress the increase in etendue, and increase the light utilization efficiency.

In the present invention, it is desirable that the total volume of the plurality of phosphor particles and the plurality of filler particles is 35% to 45% of the volume of the light emitting layer.
According to this configuration, the light distribution characteristic related to the forward scattered light of the excitation light is sufficient, and the back scattered light is also reduced. Therefore, it is possible to provide a light source device that has no color unevenness and high light use efficiency. It becomes possible. Moreover, the expansion of the spot diameter of the emitted fluorescence can be suppressed.

In the present invention, it is preferable that the light emitting element has a wavelength selection film that transmits the excitation light and reflects the fluorescence on a surface of the light emitting layer on which the excitation light is incident.
According to this configuration, since the fluorescent backscattered light can be reflected forward, it is possible to provide a light source device with high light utilization efficiency.

In the present invention, the base material is preferably a resin composition.
According to this configuration, the light emitting layer can be easily formed and processed.

In the present invention, it is desirable that the base material is made of an inorganic material.
According to this configuration, since it is possible to modify in the vacuum process after the formation of the light emitting layer, it becomes easy to form various functional structures such as an antireflection film and a wavelength selection film on the surface of the light emitting layer, and the degree of freedom in design. Becomes higher.

According to another aspect of the invention, there is provided a projector comprising: the light source device described above; a light modulation element that modulates light emitted from the light source apparatus; and a projection optical system that projects light modulated by the light modulation element. It is characterized by.
According to this configuration, since the above-described light source device is provided, it is possible to provide a projector capable of displaying high-quality images while suppressing color unevenness on the projection surface.

It is a schematic diagram which shows the light source device and projector of 1st Embodiment. It is a graph which shows the light emission characteristic of a light source device and a light emitting layer. It is a schematic explanatory drawing of a light emitting element. It is a schematic explanatory drawing of a polarization conversion element. It is a schematic diagram which shows the behavior of the light inside a light emitting layer. It is a schematic diagram which shows the light source device of 2nd Embodiment. It is explanatory drawing of the measuring apparatus used in an Example. It is explanatory drawing of the measuring apparatus used in an Example. It is explanatory drawing of the measuring apparatus used in an Example. It is a graph which shows the measurement result of an Example.

[First Embodiment]
The light source device and projector according to the first embodiment of the present invention will be described below with reference to FIGS. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

  FIG. 1 is a schematic diagram illustrating a light source device 100 and a projector PJ according to the present embodiment. As shown in the figure, the projector PJ includes a light source device 100, a color separation optical system 200, liquid crystal light valves (light modulation elements) 400R, 400G, and 400B, a color composition element 500, and a projection optical system 600.

  The projector PJ generally operates as follows. The light emitted from the light source device 100 is separated into a plurality of color lights by the color separation optical system 200. The plurality of color lights separated by the color separation optical system 200 are incident on the corresponding liquid crystal light valves 400R, 400G, and 400B and modulated. A plurality of color lights modulated by the liquid crystal light valves 400R, 400G, and 400B are incident on the color synthesis element 500 and synthesized. The light synthesized by the color synthesizing element 500 is enlarged and projected by a projection optical system 600 onto a screen SCR such as a wall or a screen, and a full-color projection image is displayed. Hereinafter, each component of the projector PJ will be described.

  The light source device 100 has a configuration in which a laser light source 10, a condensing optical system 20, a light emitting element 30, a collimating optical system 60, lens arrays 120 and 130, a polarization conversion element 140, and a superimposing lens 150 are arranged in this order.

  The laser light source 10 emits blue (light emission intensity peak: about 445 nm, see FIG. 2A) laser light as excitation light for exciting a fluorescent material included in the light emitting element 30 described later. In FIG. 2A, reference numeral B denotes a color light component emitted from the laser light source 10 as excitation light. Note that a plurality of laser light sources 10 (three in the drawing) may be provided, or only one laser light source may be used. In addition, a laser light source that emits colored light having a peak wavelength other than 445 nm may be used as long as it has a wavelength that can excite a fluorescent material to be described later.

  The condensing optical system 20 includes a first lens 22 that is a plurality of convex lenses, and a second lens 24 that is a convex lens through which light through the plurality of first lenses 22 is incident in common. The condensing optical system 20 is disposed on the beam axis of the laser light emitted from the laser light source 10 and condenses the excitation light emitted from the plurality of laser light sources 10.

  The light emitting element 30 transmits a part of the excitation light (blue light) emitted from the laser light source 10 and absorbs the remaining part to give yellow (emission intensity peak: about 550 nm, see FIG. 2B) fluorescence. Has a function to convert.

  3A and 3B are schematic explanatory views of the light emitting element 30. FIG. 3A is a plan view, FIG. 3B is a cross-sectional view taken along line AA in FIG. 3A, and FIG. ) Is a schematic diagram of a light emitting layer 42 included in the light emitting element 30.

  As shown in FIG. 3A, the light-emitting element 30 includes a disc 40 and a single light-emitting layer 42 continuously formed on the disc 40 in the circumferential direction. ), A wavelength selection film 44 provided between the disc 40 and the light emitting layer 42 is provided. The light emitting element 30 is disposed so that the side of the disc 40 on which the light emitting layer 42 is not formed faces the condensing optical system 20 side, and the focal position of the excitation light condensed by the condensing optical system 20 is It arrange | positions so that the light emitting layer 42 may overlap. For example, the diameter of the circular light emitting element 30 is 50 mm, and the light emitting element 30 is provided so that excitation light is incident at a position about 22.5 mm away from the center of the light emitting element 30 in plan view.

  The disk 40 is made of a material that transmits blue light, which is excitation light, and can be made of, for example, quartz glass, quartz, sapphire (single crystal corundum), transparent resin, or the like. Among these, quartz glass, quartz, and sapphire, which are inorganic materials, are preferably used so as not to be deformed by heating with excitation light.

  The light emitting layer 42 transmits a part of the excitation light (blue light) emitted from the laser light source 10 and absorbs the remaining part to produce yellow fluorescence (peak of emission intensity: about 550 nm, see FIG. 2B). Convert. The light emitted from the light emitting layer 42 forms white light by mixing blue excitation light and yellow fluorescence. 2B is a color light component that can be used as red light in the yellow light emitted from the light emitting layer 42. Similarly, the component indicated by G is green light. Available color light components. The configuration of the light emitting layer 42 will be described in detail later.

  The wavelength selection film 44 has wavelength selectivity that transmits blue light and reflects light having a longer wavelength than blue light (for example, light having a longer wavelength than 480 nm). Such a wavelength selection film 44 is formed of, for example, a dielectric multilayer film. Excitation light, which is blue light, passes through the wavelength selection film 44 and irradiates the light emitting layer 42.

  Further, as shown in FIG. 3C, the light emitting layer 42 includes a light-transmitting base material 421, a plurality of fluorescent particles 422 emitting fluorescence, and a plurality of light-transmitting particulate substances. Filler particles 423.

  The substrate 421 includes a plurality of phosphor particles 422 and a plurality of filler particles 423. As a material for forming the substrate 421, a resin material (resin composition) having optical transparency can be used, and among them, a silicone resin having a high heat resistance (refractive index: about 1.4) is preferably used. it can.

  The resin material to be used may be a composition (resin composition) in which two or more kinds of resin materials are mixed as long as it is a substance that transmits blue light as excitation light as described above. Further, in addition to the phosphor particles 422 and filler particles 423, for example, a composition containing an additive for the purpose of improving mechanical strength may be used.

The phosphor particles 422 are particulate fluorescent substances that absorb excitation light emitted from the laser light source 10 shown in FIG. 1 and emit fluorescence. For example, the phosphor particle 422 contains a substance that emits fluorescence when excited by blue light having a wavelength of about 445 nm, and a part of the excitation light emitted by the laser light source 10 is shown in FIG. As described above, the light is converted into light including the red wavelength band to the green wavelength band and emitted. As such phosphor particles 422, those having an average particle diameter of about 1 μm to several tens of μm are known to exhibit high luminous efficiency. As the phosphor particles 422, a commonly known YAG (yttrium, aluminum, garnet) phosphor can be used. For example, a YAG phosphor having a composition represented by (Y, Gd) ₃ (Al, Ga) ₅ O ₁₂ : Ce having an average particle diameter of 10 μm (refractive index: about 1.8) can be used.

  Note that the material for forming the phosphor particles 422 may be one type, or a mixture of particles formed using two or more types of forming materials may be used as the phosphor particles 422.

The filler particles 423 have a function of diffusing excitation light incident on the light emitting layer 42 and fluorescence emitted from the phosphor particles 422. As a forming material of the filler particles 423, a wide variety of materials such as a resin material and an inorganic material can be used as long as they are particulate substances having light transmittance. Among them, an inorganic material having high heat resistance can be suitably used. For example, Al ₂ O ₃ (refractive index: about 1.8) having an average particle diameter of 10 μm can be used.

  The total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is prepared to be 35% to 45% of the volume of the light emitting layer 42. The volume of the phosphor particles 422 is set according to the required fluorescence intensity and fluorescence wavelength, and the amount of the filler particles 423 is adjusted so that the total volume is 35% to 45% of the volume of the light emitting layer 42. Yes. Here, the volume of the light emitting layer 42 is the sum of the total volume of the plurality of phosphor particles 422, the total volume of the plurality of filler particles 423, and the volume of the base material 421.

  Returning to FIG. 1, the light emitting element 30 is provided with a motor 50 connected to the center of the disc 40 and is rotatable about a normal passing through the center of the disc 40 as a rotation axis. The motor 50 rotates the light emitting element 30 at, for example, 7500 rpm when in use. In this case, the region (beam spot) irradiated with the excitation light on the light emitting element 30 moves at about 18 m / second. That is, the motor 50 functions as a position displacement unit that displaces the position of the beam spot on the light emitting element 30. Thereby, since excitation light does not continue irradiating the same position on the light emitting element 30, thermal degradation of the irradiation position can be prevented and the life of the apparatus can be extended.

  The collimating optical system 60 includes a first lens 62 that suppresses the spread of light from the light emitting element 30 and a second lens 64 that substantially collimates the light incident from the first lens 62. It collimates the emitted light. The first lens 62 and the second lens 64 are configured as convex lenses.

  The lens arrays 120 and 130 make the luminance distribution of the light emitted from the collimating optical system 60 uniform. The lens array 120 includes a plurality of first small lenses 122, and the lens array 130 includes a plurality of second small lenses 132. The first small lens 122 has a one-to-one correspondence with the second small lens 132. The light emitted from the collimating optical system 60 is spatially divided and incident on the plurality of first small lenses 122. The first small lens 122 causes the incident light to form an image on the corresponding second small lens 132. Thereby, a secondary light source image is formed on each of the plurality of second small lenses 132. The outer shapes of the first small lens 122 and the second small lens 132 are substantially similar to the outer shapes of the image forming areas of the liquid crystal light valves 400R, 400G, and 400B.

  The polarization conversion element 140 aligns the polarization state of the light L emitted from the lens arrays 120 and 130. As shown in FIG. 4, the polarization conversion element 140 includes a plurality of polarization conversion cells 141. The polarization conversion cell 141 has a one-to-one correspondence with the second small lens 132. The light L from the secondary light source image formed on the second small lens 132 enters the incident region 142 of the polarization conversion cell 141 corresponding to the second small lens 132.

  Each polarization conversion cell 141 is provided with a polarization beam splitter film 143 (hereinafter referred to as a PBS film 143) and a phase difference plate 145 corresponding to the incident region 142. The light L incident on the incident region 142 is separated by the PBS film 143 into P-polarized light L1 and S-polarized light L2 with respect to the PBS film 143. One of the P-polarized light L1 and the S-polarized light L2 (here, S-polarized light L2) is reflected by the reflecting member 144 and then enters the phase difference plate 145. The S-polarized light L2 that has entered the phase difference plate 145 is converted into the polarization state of the other polarization (here, P-polarized light L1) by the phase difference plate 145, becomes P-polarized light L3, and is emitted together with the P-polarized light L1. .

  The superimposing lens 150 superimposes the light emitted from the polarization conversion element 140 in the illuminated area. The light emitted from the light source device 100 is spatially divided and then superimposed, whereby the luminance distribution is made uniform and the axial symmetry around the light axis 100ax is enhanced.

  The color separation optical system 200 includes a dichroic mirror 210, a dichroic mirror 220, a mirror 230, a mirror 240, a mirror 250, a field lens 300R, a field lens 300G, a field lens 300B, a relay lens 260, and a relay lens 270. The dichroic mirror 210 and the dichroic mirror 220 are obtained by, for example, laminating a dielectric multilayer film on a glass surface. The dichroic mirror 210 and the dichroic mirror 220 have a characteristic of selectively reflecting color light in a predetermined wavelength band and transmitting color light in other wavelength bands. Here, the dichroic mirror 210 reflects green light and blue light, and the dichroic mirror 220 reflects green light.

  The light L emitted from the light source device 100 enters the dichroic mirror 210. The red light R of the light L enters the mirror 230 through the dichroic mirror 210, is reflected by the mirror 230, and enters the field lens 300R. The red light R is collimated by the field lens 300R and then enters the liquid crystal light valve 400R.

  Green light G and blue light B in the light L are reflected by the dichroic mirror 210 and enter the dichroic mirror 220. The green light G is reflected by the dichroic mirror 220 and enters the field lens 300G. The green light G is collimated by the field lens 300G and then enters the liquid crystal light valve 400G.

  The blue light B that has passed through the dichroic mirror 220 passes through the relay lens 260 and is reflected by the mirror 240, then passes through the relay lens 270, is reflected by the mirror 250, and enters the field lens 300B. The blue light B is collimated by the field lens 300B and then enters the liquid crystal light valve 400B.

  The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B are configured by a light modulation device such as a transmissive liquid crystal light valve. The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B are electrically connected to a signal source (not shown) such as a PC that supplies an image signal including image information. The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B modulate the incident light for each pixel based on the supplied image signal to form an image. The liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B form a red image, a green image, and a blue image, respectively. The light (formed image) modulated by the liquid crystal light valve 400R, the liquid crystal light valve 400G, and the liquid crystal light valve 400B enters the color composition element 500.

  The color composition element 500 is configured by a dichroic prism or the like. The dichroic prism has a structure in which four triangular prisms are bonded to each other. The surface to be bonded in the triangular prism becomes the inner surface of the dichroic prism. On the inner surface of the dichroic prism, a mirror surface that reflects red light and transmits green light and a mirror surface that reflects blue light and transmits green light are formed orthogonal to each other. The green light incident on the dichroic prism is emitted as it is through the mirror surface. The red light and blue light incident on the dichroic prism are selectively reflected or transmitted by the mirror surface and emitted in the same direction as the emission direction of the green light. In this way, the three color lights (images) are superimposed and combined, and the combined color light is enlarged and projected onto the screen SCR by the projection optical system 600.

  Next, the behavior of light inside the light emitting layer 42 will be described with reference to FIG. FIG. 5 is a schematic diagram showing the behavior of light inside the light emitting layer 42. FIG. 5A shows the blue laser light (blue light Lb) that is the excitation light irradiated to a certain phosphor particle 422a. FIG. 5B is a diagram illustrating the behavior of the fluorescence Ly emitted from the phosphor particles 422a. Moreover, the length of the arrow which shows the blue light Lb or fluorescence Ly in the figure represents the light quantity of each light.

(Blue light)
As shown in FIG. 5A, a part of the blue light Lb that is not absorbed despite being irradiated on the phosphor particles 422a is reflected on the surface of the phosphor particles 422a, and the rest is phosphor particles. It penetrates the inside of 422a. Since the refractive index of the phosphor particles 422 is different from the refractive index of the surrounding base material 421, the light transmitted through the phosphor particles 422a is refracted on the surface of the phosphor particles 422a and combined with the reflected component is blue light. It contributes to the scattering of Lb.

  At this time, since the average particle diameter (10 μm) of the phosphor particles 422 and the filler particles 423 is 10 times or more larger than the wavelength of the blue light Lb (about 445 nm), the scattering generated in the phosphor particles 422 and the filler particles 423 is Geometric optical scattering. Since geometrical optical scattering has a feature that backscattering is much smaller than forward scattering, the probability that the blue light Lb incident on the light emitting layer 42 is lost by being reflected or refracted backward is small.

  The component scattered forward of the blue light Lb is repeatedly refracted and reflected every time it hits another phosphor particle 422 or filler particle 423. At that time, each time the blue light Lb hits the phosphor particles 422, a part of the blue light Lb is absorbed by the phosphor particles 422 and converted into fluorescence Ly or changed into heat.

  Here, when there is no filler particle 423 in the light emitting layer 42, the blue light Lb scattered inside the light emitting layer 42 decreases due to the conversion to fluorescence Ly or heat when the phosphor particles 422 are irradiated. On the other hand, the component that is transmitted in the light axis direction of the blue light Lb incident on the light emitting layer 42 includes a component that is not irradiated onto the phosphor particles 422, that is, a component that does not decrease due to conversion to fluorescence Ly or heat. For this reason, the light distribution characteristics of the blue light Lb after passing through the light emitting layer 42 are characterized in that the intensity is high in the direction of the optical axis of the incident light and the radiation angle is very small.

In contrast, in the present embodiment, filler particles 423 that do not absorb the blue light Lb and cause only reflection / refraction are added to the light emitting layer 42. Since the blue light Lb scattered by the filler particles 423 (indicated by symbol α in the figure) does not decrease, the intensity of the blue light Lb emitted in the direction of the light axis of the incident light is reduced, and the diffused blue light Lb is increased. Can contribute.
Further, when the average particle diameter of the filler particles 423 is set to 10 times or more the wavelength of the blue light Lb (about 445 nm), the scattering by the filler particles 423 becomes geometric optical scattering. Therefore, the light utilization efficiency can be further increased.
Needless to say, the influence of the average particle diameter of the phosphor particles 422 on the ratio of the back scattering to the forward scattering is the same as the influence of the average particle diameter of the filler particles 423 on the ratio of the back scattering to the forward scattering.

  Furthermore, since the blue light Lb, which is a laser beam, has coherence, when the modulated image is projected on the screen, interference fringes called speckle noise are generated on the screen, and the quality of the image is remarkably deteriorated. There is a risk of causing. However, in the present embodiment, the blue light Lb is scattered by the filler particles 423, and the light emitting layer 42 in which the filler particles 423 are embedded rotates around the normal line of the disk 40. For this reason, the blue light Lb transmitted through the light emitting layer 42 is subjected to dynamic light scattering, and an effect of reducing speckle noise of an image can be obtained.

(Yellow light)
In the blue light Lb incident on the light emitting layer 42, a part of the component irradiated to the phosphor particles 422 inside the light emitting layer 42 is absorbed by the phosphor particles 422, and a part thereof is changed into heat. The remaining components excite the electrons of the phosphor constituting the phosphor particle 422. Then, when the excited electrons return to the ground state, fluorescence Ly is emitted. The fluorescence Ly is light having a longer wavelength than the blue light Lb. The emitted fluorescence Ly is isotropically emitted from the phosphor particles 422 in all directions.

  Unlike the blue light Lb of excitation light, the fluorescence Ly emitted in the light emitting layer 42 emits light with isotropic light distribution characteristics in all directions from the phosphor particles 422a that are light emitting points. Since the wavelength selection film 44 that reflects yellow exists between the light emitting layer 42 and the disk 40 (not shown), the fluorescence Ly emitted toward the rear is reflected toward the front. However, unlike the blue light Lb incident with directivity from the outside, the fluorescence Ly is emitted from the phosphor particles 422a in all directions, and therefore propagates in the in-plane direction inside the light emitting layer 42. It is easy to go out of the light emitting layer 42 easily.

  In the light emitting element 30 of this embodiment, since the phosphor particles 422 and the filler particles 423 have a higher refractive index than the base material 421, the fluorescence Ly is difficult to totally reflect on the surfaces of the phosphor particles 422 and the filler particles 423. It has the opportunity to change the optical path through the inside of the particle and scattered by refraction. If the fluorescence Ly propagates in the light emitting layer 42 in the in-plane direction, the probability that the optical path changes due to reflection and refraction on the surface of the phosphor particles 422 and the surface of the filler particles 423 increases. Therefore, as the fluorescence Ly propagates in the in-plane direction of the light emitting layer 42, the component (indicated by the symbol α in the drawing) that goes out of the light emitting layer 42 increases. In other words, as the fluorescence Ly propagates in the in-plane direction of the light-emitting layer 42, the component that propagates in the in-plane direction through the inside of the light-emitting layer 42 decreases.

  That is, by adding filler particles 423 in the light emitting layer 42, the number of fluorescent Ly scattering sources is increased, and by increasing the amount of components going out of the light emitting layer 42, the fluorescence Ly moves in the in-plane direction inside the light emitting layer 42. It is possible to shorten the distance in plan view to propagate. As a result, the spot diameter from which the fluorescence Ly is emitted can be reduced.

  Since the fluorescence Ly propagating in the in-plane direction inside the light emitting layer 42 cannot be completely removed, the spot diameter of the fluorescence Ly on the light emitting layer 42 becomes larger than the beam spot diameter of the blue light. . The increase in the spot diameter of the fluorescence Ly in the light emitting layer 42 can be suppressed by reducing the film thickness of the light emitting layer 42 and increasing the concentrations of the phosphor particles 422 and the filler particles 423. For example, the thickness of the light emitting layer 42 is 100 μm, the total volume of the plurality of phosphor particles 422 is 30% of the volume of the light emitting layer 42, and the total volume of the plurality of filler particles 423 is 10% of the volume of the light emitting layer 42. Then, the spot diameter of the fluorescence Ly is about 70 μm.

(Addition amount of particles)
Here, when the concentration of the phosphor particles 422 and the filler particles 423 in the light emitting layer 42 is increased, the probability that the blue light Lb hits the phosphor particles 422 or the filler particles 423 further increases. Then, the blue light Lb reflected / refracted toward the wavelength selection film 44 side increases, leading to a result of increasing the light not emitted forward.

As a result of the experiment, when the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is 35% or more of the volume of the light emitting layer 42, the light distribution characteristics of the blue light Lb transmitted through the light emitting layer 42 are ( It has been found that it has a characteristic proportional to cosθ) ⁵ . Blue light Lb transmitted through the light emitting layer 42 When having such characteristics, the collimating optical system 60 shown in FIG. 1 can efficiently receive the blue light Lb, and the blue light Lb on the screen can be made uniform. Can contribute.

  Conversely, when the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is excessive, backscattering increases and the amount of blue light Lb and fluorescence Ly emitted forward from the light emitting layer 42 decreases. In the experiment, when the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 exceeds 45% of the total volume of the light emitting layer 42, the blue color that is back-scattered with respect to the total amount of blue light incident on the light emitting layer 42. It was found that the ratio of the amount of light exceeded 5%. Therefore, it is preferable to determine the addition amount of the filler particles 423 so that the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is 35% or more and 45% or less of the total volume of the light emitting layer 42.

(Refractive index of particles)
It was also found that the amount of blue light Lb backscattered by the light emitting layer 42 is affected by the refractive index of the particles contained in the light emitting layer 42. For example, when a high refractive index material having a refractive index exceeding 2 such as ZrO or TiO ₂ is used for the filler particles 423, the backscattering amount exceeds 10%. Further, it has been found that when the refractive index of the particles contained in the light emitting layer 42 is larger than 1.3 times the refractive index of the material of the base material 421, the backscattering amount is greatly increased. Further, when the refractive index of the particles contained in the light emitting layer 42 is smaller than 1.2 times the refractive index of the material of the base material 421, the backscattering amount is reduced, but the refractive index difference is not sufficient. It was found that it was difficult to cause the desired light scattering.

  Therefore, if the refractive index of the phosphor particles 422 and the refractive index of the filler particles 423 are 1.2 times or more and 1.3 times or less than the refractive index of the material of the base material 421, the blue light Lb is backscattered. The forward scattering can be effectively promoted while suppressing the unevenness, and the color unevenness can be suppressed. Further, it is possible to effectively promote the scattering of the light of the fluorescence Ly, suppress the increase in etendue, and increase the light utilization efficiency.

(Film thickness of the light emitting layer)
As the light emitting layer 42 is thinner, the amount of the phosphor particles 422 added in the thickness direction of the light emitting layer 42 varies more depending on the position of the light emitting layer 42. This is because as the film thickness of the light emitting layer 42 is thinner, the amount of the phosphor particles 422 irradiated with the blue light Lb when the blue light Lb passes through the light emitting layer 42 in the film thickness direction depends on the position of the light emitting layer 42. It means that the variation by is large. As a result, the variation in the plane of the light emitting layer 42 of the ratio of the blue light Lb and the fluorescence Ly contained in the emitted light increases. Therefore, as the light emitting layer 42 is thinner, the increase in the spot diameter of the fluorescence Ly can be suppressed, but on the other hand, it becomes difficult to control the chromaticity of light emitted from the light emitting layer 42.

  Further, if the light emitting layer 42 is thinned to about 5 times the average particle diameter of the phosphor particles 422, it becomes extremely difficult to control the film thickness, and similarly it becomes difficult to control the chromaticity of the emitted light.

  On the other hand, in this embodiment, by setting the thickness of the light emitting layer 42 to 100 μm, the chromaticity variation in the xy chromaticity diagram is suppressed to within 0.02 for both Δx and Δy.

  According to the light source device 100 configured as described above, the blue light Lb (excitation light) having high straightness is partially reflected and refracted on the surface of the phosphor particles 422 and the filler particles 423 inside the light emitting layer 42. Scatter and diffuse with Therefore, the excitation light having high straightness is diffused and spreads more than when the filler particles 423 are not included, and approaches the spread of the fluorescence Ly.

  Further, the fluorescence emitted isotropically from the phosphor particles 422 is also scattered by being partially reflected and refracted on the surfaces of the phosphor particles 422 and filler particles 423 inside the light emitting layer 42, and emitted from the light source device 100. The fluorescence component traveling in the direction of the surface increases. Therefore, compared with the case where the filler particles 423 are not included, the distance in a plan view in which the fluorescence Ly propagates in the light emitting layer 42 in the direction parallel to the emission surface of the light source device 100 can be suppressed, and the emitted fluorescence Expansion of the spot diameter of Ly can be suppressed.

  As a result, the color unevenness due to the difference between the light distribution characteristic of the blue light Lb transmitted through the light emitting layer 42 and the light distribution characteristic of the fluorescence Ly emitted from the light emitting layer 42 is suppressed, and the light source device has high light use efficiency. 100 is possible.

  Further, according to the projector PJ having the above-described configuration, it is possible to obtain a projector PJ that can suppress color unevenness on the projection surface and display a high-quality image.

  In the present embodiment, the light emitting element 30 is irradiated with blue excitation light, and yellow fluorescence is emitted. However, the present invention is not limited to this, and combinations of excitation light and fluorescence of various colors are appropriately used. You can choose.

  In the present embodiment, the light emitting element 30 is rotationally moved using the motor 50 so that the blue light condensing position does not become the same location, but this is not restrictive. For example, a condensing position can be displaced by attaching a vibration element such as an electrostrictive element to the light emitting element 30 and vibrating the light emitting layer 42 in a direction parallel to the surface direction.

[Second Embodiment]
FIG. 6 is an explanatory diagram of a light source device according to the second embodiment of the present invention, and is an explanatory diagram of a light emitting element included in the light source device of the second embodiment. FIG. 6A is a side view, and FIG. 6B is a schematic cross-sectional view of the light emitting element 70. In this embodiment, the same code | symbol is attached | subjected about the component which is common in 1st Embodiment, and detailed description is abbreviate | omitted.

  As shown in FIGS. 6A and 6B, the light-emitting element 70 includes a disk 71 in which phosphor particles and filler particles are dispersed, and a wavelength provided on the incident surface of the blue light Lb in the disk 71. A selection film 72 and an antireflection film 73 provided on an emission surface of light L (light in which blue light Lb and fluorescence Ly are mixed) in the circular plate 71 are included. In the present embodiment, the disc 71 also functions as the disc 40 and the light emitting layer 42 in the light emitting element 30 of the first embodiment.

  As shown in FIG. 6B, the disk 71 includes a light-transmitting base material 711, a plurality of fluorescent particles 422 that emit fluorescence, and a plurality of fillers that are particulate materials having light-transmitting properties. Particles 423.

  The base material 711 can use an inorganic material having optical transparency, and for example, optical glass such as borosilicate glass (refractive index: about 1.5) can be preferably used.

  As the wavelength selection film 72, a film having the same configuration as that of the wavelength selection film 44 included in the light emitting element 30 of the first embodiment can be used. The wavelength selection film 72 has wavelength selectivity that transmits blue light and reflects light having a longer wavelength than blue light (for example, light having a longer wavelength than 480 nm).

The antireflection film 73 has a function of suppressing reflection at the interface between the disk 71 and the air layer so that the light emitted from the disk 71 can be efficiently emitted to the outside. The antireflection film 73 can be formed of the generally known configuration, for example, SiO 2, _{TiO 2,} a dielectric such as niobate as a raw material, to form a dielectric multilayer film in a vacuum process Can be formed.

  As described above, in the light emitting element 70, the wavelength selection film 72 and the antireflection film 73 are provided on the surface of the disk 71. The light emitting layer 42 included in the light emitting device 30 of the first embodiment employs a resin material (resin composition) as the base material 421 for embedding phosphor particles and filler particles, and therefore has an advantage that it is easy to form. On the other hand, since the base material 421 may be damaged by a vacuum process, it is difficult to form a dielectric multilayer film after the light emitting layer 42 is formed.

  However, in the light emitting element 70, since the base material 711 for embedding the phosphor particles and filler particles in the disk 71 is an inorganic material, the dielectric multilayer film is formed after the disk 71 is formed without being damaged by a vacuum process. The wavelength selection film 72 and the antireflection film 73 can be provided on both surfaces of the disc 71.

Such a light emitting element 70 is manufactured as follows, for example.
First, the glass material used as the base material 711 is mixed with the phosphor particles 422 and the filler particles 423 as a frit (powdered) material. These mixing methods can employ either a dry method or a wet method.

  Next, the mixed powder is pressed and hardened under a temperature condition of, for example, room temperature to 50 ° C., processed into a plate shape, and then fired at a temperature at which the glass of the frit material is melted. A mixture of particles 422 and filler particles 423 is sintered. Thereby, a plate material in which the phosphor particles 422 and the filler particles 423 are uniformly dispersed therein is obtained. The plate 71 is manufactured by processing this plate into a circle.

  Next, both sides of the obtained sintered body are polished to flatten the surface, and the whole is brought close to the target thickness. In the light emitting element 70, the thinner the disc 71 is, the lighter the whole is and the less the driving power is preferable. However, if it is too thin, it is difficult to ensure the strength of the entire light emitting element 70. Therefore, the thickness of the sintered body that is the material of the disc 71 is set to about 100 μm to 500 μm, more preferably about 100 μm to 300 μm.

  Next, for example, abrasive horn processing or the like is performed so as to obtain a target disk shape. Thereafter, both surfaces of the processed disk are mirror-finished, a wavelength selection film 72 is formed on one surface, and an antireflection film 73 is formed on the other surface, so that a target light emitting element is formed. 70 can be obtained.

  In the light source device having the light emitting element 70 as described above, similarly to the light source device 100 described above, the light distribution characteristic of the blue light Lb transmitted through the disk 71 and the light distribution characteristic of the fluorescence Ly emitted from the disk 71. Color unevenness due to the difference from the above is suppressed, and a light source device with high light utilization efficiency can be obtained.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  Hereinafter, the present invention will be specifically described with reference to examples measured using model samples. In addition, this invention is not limited by these Examples.

  In the embodiment, a mixture of silicone resin, phosphor particles (YAG: Ce) and filler particles is applied onto the wavelength selection film 44 provided on the glass plate, and the silicone resin is cured, A model sample of the light emitting element in the above embodiment was manufactured.

(Evaluation method of light distribution characteristics)
A light distribution measurement system 1000 (light source light distribution measurement system IS-LI, manufactured by CYBERNET SYSTEMS) as shown in FIG. 7 was used.
The model sample S is arranged on the wall surface of the dome 1100 coated with a reflective material, and the excitation light MB emitted from the laser light source 1200 and collimated by the collimating lens 1300 is applied to the model sample S through the slit 1400. Irradiated. In the model sample S, the light emitting layer SB was irradiated with the excitation light MB from the glass plate SA side, and the distribution of transmitted light was measured with a measurement probe (not shown) provided in the dome 1100.

  In the measurement, first, the light distribution of all transmitted light is measured, and then the light distribution of the transmitted light is measured through a blue light filter of a color matching function, and the difference is included in the transmitted light. The light distribution of blue light was determined.

(Measurement method of backscattering rate)
A measuring apparatus 2000 shown in FIG. 8 was used.
The model sample S was placed on the wall surface of the integrating sphere 2100 whose interior was coated with a reflective material, and the model sample S was irradiated with excitation light emitted from the laser light source 2200 and guided by the waveguide 2300. In the model sample S, the light emitting layer SB was irradiated with excitation light from the glass plate SA side, and the amount of backscattered light was measured with the measurement probe 2400 provided in the integrating sphere 2100. The baffle 2500 is for shielding the backscattered light of the model sample S from being directly incident on the measurement probe.

  In the measurement, the amount of backscattered light was measured, and the backscattering rate was obtained by dividing by the amount of excitation light irradiated.

(Measurement method of fluorescence spread in the light emitting layer)
A measuring device 3000 shown in FIG. 9 was used.
Excitation light MB emitted from the laser light source 3100 and collimated by the collimating lens 3200 was applied to the model sample S arranged in front of the slit 3300. In the model sample S, the light emitting layer SB was irradiated with the excitation light MB from the glass plate SA side. The transmitted light was transmitted through a dichroic mirror 3400 that reflects blue light, and then imaged with an imaging device 3500 having a neutral density filter, and the spot diameter of the fluorescence on the model sample S was measured.

  Similarly, the excitation light was directly imaged by the imaging device 3500 without using the model sample S and the dichroic mirror 3400, and the spot diameter of the excitation light was measured.

(Filler particle size)
A plurality of model samples having different filler particle diameters were prepared, and the relationship with backscattering was measured. Measurement conditions are shown in Table 1, and measurement results are shown in Table 2. In the table, the volume ratio of the phosphor particles is the ratio of the total volume of the plurality of phosphor particles to the volume of the entire produced light emitting layer, and the volume ratio of the filler particles is the plurality of fillers to the volume of the entire produced light emitting layer. It is the ratio of the total volume of particles.

As a result of the measurement, it was found that the backscattering rate tends to increase when the filler diameter is smaller than 5 μm. Therefore, if the filler diameter is 5 μm or more, the light source device 100 with high light utilization efficiency can be obtained.
Although the relationship between the diameter of the filler particle 423 and the backscattering rate has been described here, the same result can be obtained for the relationship between the diameter of the phosphor particle 422 and the backscattering rate.

(Filler addition rate)
A plurality of model samples having different filler addition rates were prepared, and the relationship with each physical property value was measured. Table 3 shows the measurement conditions.

FIG. 10 is a graph showing a light distribution of blue light when the filler addition rate is changed. As shown in the figure, it can be seen that the higher the filler concentration is, the more blue light tends to diffuse. It was also found that when the filler concentration is less than 5%, the light distribution characteristic is slightly smaller than the curve of (cos θ) ⁵ . When the filler concentration is 5%, the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is 35% of the total volume of the light emitting layer 42.

  Table 4 below shows the measurement results of the backscattering rate when the addition rate of the filler is changed. From the results shown in the table, it was found that when the filler concentration exceeds 15%, the backscattering rate tends to increase beyond 5%. When the filler concentration is 15%, the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is 45% of the total volume of the light emitting layer 42. Therefore, the total volume of the plurality of phosphor particles 422 and the plurality of filler particles 423 is preferably 35% or more and 45% or less of the entire volume of the light emitting layer 42.

(Refractive index of filler)
A plurality of model samples having different refractive indexes of the fillers were produced, and the relationship with the backscattering rate was measured. Table 5 shows the measurement conditions, Table 6 shows the measurement results, and Table 7 shows the simulation results obtained by the ray tracing simulation of geometric optical scattering.

As a result of the measurement, it was found that when the refractive index of the filler particles exceeds about 2, the backscattering rate tends to increase. From the simulation results, it can be seen that when the refractive index of the filler particles is higher than 1.3 times the refractive index of the substrate, the backscattering rate tends to increase by more than 5%.
Here, the relationship between the refractive index of the filler particles 423 and the backscattering rate has been described, but the same result can be obtained for the relationship between the refractive index of the phosphor particles 422 and the backscattering rate.

(Film thickness of the light emitting layer)
A plurality of model samples having different light emitting layer thicknesses were prepared, and the relationship with the spot diameter was measured. The measurement conditions are the same as in Table 5. Table 8 shows the relationship between the amount of increase in the fluorescent spot diameter and the film thickness of the light emitting layer 42.

  As shown in Table 8, it was found that as the film thickness increased, the fluorescent spot diameter tended to be larger than the excitation light spot diameter. Therefore, if the film thickness of the light emitting layer 42 is 10 times or less the average particle diameter of the phosphor particles 422, the increase in the spot diameter of the emitted fluorescence can be suppressed.

DESCRIPTION OF SYMBOLS 10 ... Laser light source, 30, 70 ... Light emitting element (light emission means), 42 ... Light emitting layer, 44, 72 ... Wavelength selection film | membrane, 71 ... Disc (light emitting layer), 100 ... Light source device, 400R, 400G, 400B ... Liquid crystal Light valve (light modulation element), 421, 711 ... base material, 422 ... phosphor particle, 423 ... filler particle, 600 ... projection optical system, Ly ... fluorescence (fluorescence), Lb ... blue light (excitation light), PJ ... projector,

Claims (10)

A laser light source that emits excitation light in the visible light region;
A light-emitting element that transmits a part of the excitation light and emits fluorescence in the visible light region when excited by the excitation light.
The light-emitting element includes a light-transmitting base material, a plurality of phosphor particles contained in the base material, and a plurality of light-transmitting filler particles contained in the base material. Having a light emitting layer,
The total volume of the plurality of phosphor particles and the plurality of filler particles, Ri 45% der less than 35% of the volume of the light-emitting layer,
The refractive index of the plurality of phosphor particles and the plurality of filler particles is 1.2 times or more with respect to the refractive index of the material of the base material,
Thickness of the light-emitting layer, the light source and wherein an average 10 times or less in thickness der Rukoto the particle diameter of the plurality of phosphor particles.   2. The light source according to claim 1, wherein at least one of an average particle diameter of the plurality of filler particles and an average particle diameter of the plurality of phosphor particles has a size for geometrically optically scattering the excitation light. apparatus.   3. The light source device according to claim 1, wherein an average particle diameter of the plurality of filler particles is 5 μm or more.   4. The light source device according to claim 1, wherein an average particle diameter of the plurality of phosphor particles is 5 μm or more. 5. It said plurality of filler particles, a light source device according to any one of claims 1 to 4, characterized in that it consists of a material having a refractive index of 1.3 times the refractive index of the substrate. Wherein the plurality of phosphor particles, the light source device according to any one of claims 1 5, characterized in that it consists of a material having a refractive index of 1.3 times the refractive index of the substrate. The light emitting device, the surface where the excitation light in said light emitting layer is incident, any one of claims 1 to 6, characterized in that a wavelength selective film that reflects the fluorescence transmitted through the excitation light The light source device according to item. Forming material of said substrate, a light source device according to any one of claims 1 to 7, characterized in that the resin composition. Forming material of said substrate, a light source device according to any one of claims 1, characterized in that it consists of an inorganic material 7. A light source device according to any one of claims 1 to 9 ,
A color separation optical system that separates the light emitted from the light source device into fluorescence emitted from the light emitting element and a part of the excitation light transmitted through the light emitting element;
A plurality of light modulation elements corresponding to a plurality of color lights each including a part of the excitation light separated by the color separation optical system;
And a projection optical system that projects the light modulated by the light modulation element.

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