JPWO2010140419A1 - Light emitting device - Google Patents

Abstract

The subject of this invention is reducing the color shift of a light-emitting device compared with the past. The light emitting device 1 of the present invention includes an LED chip 2 that emits blue light and a phosphor 35 that converts blue light into yellow light, and is disposed on the optical path of the emitted light from the LED chip 2. The light-emitting phosphor element 3 is provided, and the blue light transmitted through the phosphor element 3 and the yellow light generated by the phosphor 35 are overlapped to emit white light. The phosphor element 3 includes a plate-like substrate 30 and a microlens array formed on the light incident surface 300 of the substrate 30.

Description

  The present invention relates to a light emitting device.

  2. Description of the Related Art Conventionally, as a light emitting device that emits white light, there is one provided with an LED chip 100 that emits blue light and a phosphor plate 101 containing a yellow phosphor 102, as shown in FIG. In this light emitting device, blue light from the LED chip 100 is incident on the phosphor plate 101, and blue light transmitted between the phosphors 102 and yellow light converted from blue light to yellow light by the phosphor 102 are combined. By overlapping and emitting, white light is emitted.

  Here, FIG. 6 shows an example in which the yellow phosphor 102 is dispersed in the base material constituting the phosphor plate 101, but as another form, the phosphor is placed on the base material having a lens shape. There are also known a technique for producing a phosphor element by depositing a phosphor (see, for example, Patent Document 1) and a technique for forming a phosphor element by dispersing a phosphor in a lens-shaped base material (for example, a patent). Reference 2). As a technique for forming a phosphor layer on a substrate, for example, a method of forming a non-particulate phosphor film using sputtering (for example, see Patent Document 3), or as described in Patent Document 1, There is known a method of obtaining a phosphor film on a base material without a binder at a high filling rate by a method called an aerosol deposition method.

  In addition, a microlens group (also called a microlens array) is formed on the light extraction side of the phosphor plate as a method for increasing the axial luminous intensity of white light (mixed light of blue light and yellow light) emitted from the phosphor plate. Thus, a technique for improving the light condensing performance has been proposed (see, for example, Patent Document 4).

JP 2006-339217 A JP 2006-339336 A Japanese Patent Laid-Open No. 11-46015 JP 2007-123437 A

  However, in the light emitting device as described above, there is a problem in that the light distribution is different between blue light and yellow light, and so-called color shift occurs. Specifically, such a problem is that the blue light emitted from the LED chip 100 toward the phosphor plate 101 is concentrated in the front direction even after passing through the phosphor plate 101, and thus the light distribution of light is This is because yellow light generated as fluorescence from the phosphor 102 is emitted in a wide range starting from the phosphor 102, and thus has a wider light distribution than blue light. And in the area | region where a radiation | emission angle is large among the radiation | emission area | regions of a light-emitting device, emitted light will appear yellow rather than white.

  In particular, in the case where the light emitting device is used for an application such as a headlight of an automobile, even if the light collecting performance is improved by the technique described in Patent Literature 1, 2, or 4, the off-axis light increases as the distance from the light emitting device increases. The phenomenon of coloring from white to yellow occurs. Since off-axis light from automobile headlights may affect the appearance of signs and signal colors, a particular solution has been sought.

  Such a problem of color misregistration can be achieved by using the technology described in Patent Document 1, 2, or 4 described above to make the phosphor element into a lens shape, or by providing a lens group on the light extraction surface of the phosphor element to improve the light collecting performance. However, since blue light and yellow light are similarly refracted, the color distribution cannot be reduced by bringing the light distribution of these lights close to each other. The fundamental solution was not reached. Therefore, the problem that off-axis light is colored when the distance from the light source is still left, such as automobile headlights that need to irradiate light to a long distance using LEDs with very high illuminance In applications, further improvements have been demanded.

  Accordingly, an object of the present invention is to provide a light emitting device capable of reducing color misregistration as compared with the conventional art.

According to one aspect of the invention,
An LED that emits light of a first predetermined wavelength;
A phosphor that converts the light having the first predetermined wavelength into light having the second predetermined wavelength, and a translucent phosphor element disposed on the optical path of the light emitted from the LED. ,
In the light emitting device that emits the light having the first predetermined wavelength transmitted through the phosphor element and the light having the second predetermined wavelength generated in the phosphor in an overlapping manner,
The phosphor element is
A substrate,
And a microlens array formed on the light incident surface of the substrate.

In the light emitting device of the present invention,
It is preferable that the phosphor is disposed closer to the substrate than the microlens array.

In the light emitting device of the present invention,
Each microlens in the microlens array has a focal point inside the phosphor element, and the phosphor is preferably localized in the vicinity of the focal point of the microlens.

  As one form of localizing the phosphor in the vicinity of the focal point of the microlens, the phosphor is localized so as to be discontinuous in a direction substantially perpendicular to the optical axis of the emitted light of the LED. The form to make is mentioned as a preferable form. For example, it may be localized in a substantially semi-ellipsoidal shape having an end surface on the light incident surface side of the substrate.

As another form of localizing the phosphor in the vicinity of the focal point of the microlens,
A preferred form is a form in which the phosphor is localized in a layered manner in a direction substantially orthogonal to the optical axis of the emitted light of the LED.

In the light emitting device of the present invention,
The light having the first predetermined wavelength and the light having the second predetermined wavelength are each visible light, and preferably have a complementary color relationship with each other.

  In particular, it is preferable that the light having the first predetermined wavelength is blue light, and the light having the second predetermined wavelength is yellow light.

  As a result of further studies, the present inventors have found that the above-described problem of color misregistration is that the light emitted from the LED and the phosphor are separated from each other, so that the first predetermined wavelength of light emitted from the LED is emitted. This is largely due to the fact that the light emitting point of the light having the second predetermined wavelength emitted from the phosphor is separated, and the light emitting point of the LED and the light emitting point of the phosphor are brought close to each other. We focused on the fact that it can solve the problem of color misregistration.

  According to the present invention, since the microlens array is formed on the light incident surface of the substrate, the light having the first predetermined wavelength emitted from the LED is refracted by the microlens array and enters the phosphor element. . Thereafter, some of the light of the first predetermined wavelength is incident on the phosphor to excite the phosphor to generate excitation light, and other light passes through the phosphor element as it is, The light is emitted from the phosphor element. At that time, due to the refractive action (condensing action) of the microlens, a part of the transmitted light of the first predetermined wavelength is emitted from the phosphor element as light having a wide light distribution. On the other hand, the light of the second predetermined wavelength generated in the phosphor is emitted with a wide light distribution. Accordingly, since the alignment distribution of the light having the first predetermined wavelength can be made closer to the alignment distribution of the light having the second predetermined wavelength, the color shift can be reduced as compared with the conventional case.

  In another aspect, by providing the microlens array on the incident surface side of the phosphor element, the light of the first predetermined wavelength is focused at a position closer to the phosphor than the LED by the light collecting action. Become. As a result, the apparent light emission point (focal point of the microlens) for the light having the first predetermined wavelength can be brought closer to the light emission point (phosphor) for the light having the second predetermined wavelength. In addition, color misregistration can be reduced. That is, the light of the first predetermined wavelength emitted from the LED is condensed on the apparent light emission point (the focal point of the microlens) and diffused from this light emission point, so that the orientation distribution can be widened. .

  Further, when the entire light incident surface of the phosphor element is formed into one lens shape as in Patent Documents 1 and 2, it is a case where the condensing action is strengthened in order to bring the focal point position and the phosphor position close together. However, the thickness of the phosphor element is increased, but by using the microlens array, the effect of the present invention can be obtained without increasing the size of the apparatus.

It is sectional drawing which shows schematic structure of the light-emitting device which concerns on this invention. It is sectional drawing which shows a phosphor element. It is a figure which shows the schematic block diagram of an aerosol deposition film-forming apparatus. It is sectional drawing and the top view of the light-emitting device of the Example of this invention, and a comparative example. It is a graph which shows the light distribution in the light-emitting device of an Example and a comparative example. It is sectional drawing which shows schematic structure of the conventional light-emitting device.

  Hereinafter, a light emitting device according to the present invention will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a light emitting device 1 according to the present embodiment.

  As shown in this figure, the light emitting device 1 includes an LED chip 2 and a phosphor element 3 containing a phosphor 35.

  The LED chip 2 emits light having a first predetermined wavelength. In the present embodiment, the LED chip 2 emits blue light. However, the wavelength of the LED chip 2 of the present invention and the wavelength of the emitted light from the phosphor are not limited, and the wavelength of the emitted light from the LED chip 2 and the synthesized light with the wavelength of the emitted light from the phosphor being complementary. Is the most suitable combination, but a combination of LED emission light and phosphor emission light that emits light other than white light may be used.

In addition, as such LED chip 2, various well-known LED chips can be used. In particular, when white light is obtained by the light emitting device 1, a blue LED chip can be preferably used. As the blue LED chip, any existing one including In _x Ga _1-x N system can be used. The emission peak wavelength of the blue LED chip is preferably 440 to 480 nm.

  In addition, as a form of the LED chip, the LED chip is mounted on the substrate and directly radiated upward or laterally, or the blue LED chip is mounted on a transparent substrate such as a sapphire substrate, and bumps are formed on the surface thereof. It can be applied to any form of LED chip, such as the so-called flip chip connection type, which is flipped over and connected to the electrode on the substrate, but it is suitable for the manufacturing method of high brightness type or lens type A type is more preferable.

  The phosphor element 3 is a translucent optical element disposed on the optical path of light emitted from the LED chip 2, and includes a substrate 30 and a microlens array 31. In the following description, the substrate 30 and the microlens array 31 are described as separate members for the sake of convenience, but may be integrated members.

  Among these, the board | substrate 30 is a member arrange | positioned perpendicular | vertical with respect to the center (it is also called an optical axis) of the advancing direction of the emitted light from LED chip 2, Comprising: Flat form or lens form may cover LED chip 2. It may have such a dome shape, or may have a flat plate shape in which the light emission surface 301 is formed in a lens shape.

  On the other hand, the microlens array 31 has a plurality of microlenses 310 arranged on the light incident surface 300 of the substrate 30. Here, each microlens 310 in the present embodiment is a convex lens having a focal point inside the phosphor element 3. However, as the shape of the microlens, a shape designed as desired in consideration of light collection characteristics, light distribution characteristics, and the like such as a substantially hemispherical shape, a dome shape, an aspherical shape, and a cylindrical shape can be arbitrarily used. Moreover, the shape etc. which have a hollow in the center of a lens can also be used arbitrarily. The thickness, diameter, etc. are not particularly limited.

  However, when the size of the lens is reduced with respect to the wavelength, the original performance of the microlens is not exhibited due to the influence of diffraction. Therefore, it is desirable that the lens diameter L is larger than the peak wavelength of the light emitted from the LED chip 2.

  The phosphor element 3 described above contains a phosphor 35.

  The phosphor 35 converts light having a first predetermined wavelength emitted from the LED chip 2 into light having a second predetermined wavelength. In the present embodiment, the phosphor 35 emits blue light emitted from the LED chip 2. Light is converted to yellow light.

  The phosphor 35 is disposed closer to the substrate 30 than the light incident surface 311 of the microlens array 31 in the phosphor element 3. In the present embodiment, the phosphor 35 is disposed on the entire substrate 30 and the microlens array 31. It is in a state of being uniformly dispersed. However, as shown in FIGS. 2A and 2B, the phosphor 35 may be dispersed in only one of the substrate 30 and the microlens array 31.

  Such a phosphor 35 uses an oxide or a compound that easily becomes an oxide at a high temperature as a raw material of Y, Gd, Ce, Sm, Al, La, and Ga. Mix to obtain the raw material. Alternatively, a coprecipitated oxide obtained by calcining a solution obtained by coprecipitation of oxalic acid with a solution obtained by dissolving a rare earth element of Y, Gd, Ce, and Sm in an acid at a stoichiometric ratio, and aluminum oxide and gallium oxide Mix to obtain a mixed raw material. An appropriate amount of fluoride such as ammonium fluoride is mixed with this as a flux and pressed to obtain a molded body. The compact can be packed in a crucible and fired in air at a temperature range of 1350 to 1450 ° C. for 2 to 5 hours to obtain a sintered body having the phosphor emission characteristics.

  The above phosphor element 3 uses glass or a light-transmitting resin as a binder of the phosphor 35, and the substrate 30 and the microlens array 31 are integrally formed by injection molding a mixed material of the binder and the phosphor 35. It is formed to become. However, after the substrate 30 is formed by injection molding, the microlens array 31 may be formed on the light incident surface 300 of the substrate 30 by a dropping method.

  As the binder, for example, a resin having good thermoplasticity and light transmittance such as an epoxy resin, a cyclic polyolefin resin, and a polycarbonate resin can be used. Moreover, it is preferable to use glass from a heat resistant viewpoint. In the case where the phosphor 35 is kneaded and molded into glass, for example, the technique disclosed in Japanese Patent Application Laid-Open No. 2000-258308 can be used.

  Next, the operation of the light emitting device 1 will be described.

  First, when the LED chip 2 emits blue light toward the phosphor element 3, the blue light is refracted by the microlens array 31 and enters the phosphor element 3.

  Next, of the blue light incident on the phosphor element 3, a part of the light is converted into yellow light by the phosphor 35 and emitted, while the remaining light is transmitted between the phosphors 35.

  As a result, the blue light transmitted through the phosphor element 3 and the yellow light generated by the phosphor 35 are superimposed and emitted as white light.

  In addition, the above light-emitting device 1 can be used as a light for automobiles.

  According to the light emitting device 1 described above, since the microlens array 31 is formed on the light incident surface 300 of the substrate 30, the blue light emitted from the LED chip 2 is refracted by the microlens array 31 and is fluorescent. The light enters the body element 3 and is emitted from the phosphor element 3. Therefore, since the light distribution of blue light can be made closer to the light distribution of yellow light generated in the phosphor 35 inside the phosphor element 3, the color shift can be reduced as compared with the prior art.

  Further, compared to the case where a microlens separate from the phosphor element 3 is disposed between the LED chip 2 and the phosphor element 3, an apparent light emitting point for blue light (the focal position of the microlens 310). ) And the light emitting point (phosphor 35) for yellow light can be brought close to each other, so that color shift can be reduced more reliably.

  In addition, since the phosphor 35 is disposed closer to the substrate 30 than the light incident surface 311 of the microlens array 31 in the phosphor element 3, the microlens array 31 can exert a refracting action on only blue light. . Therefore, since the light distribution of blue light can be reliably brought close to the light distribution of yellow light, color misregistration can be reliably reduced.

  In addition, since the microlens array 31 is formed on the light incident surface 300 of the substrate 30 as described above, unlike the case where the entire light incident surface 300 has a single lens shape, the light condensing action is increased. Even if it exists, since it can prevent that the thickness of the phosphor element 3 becomes large, it can prevent that the light-emitting device 1 enlarges.

<Second Embodiment>
Next, a second embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component similar to the said 1st Embodiment, and the description is abbreviate | omitted.

  The light emitting device 1A according to the second embodiment is different from the light emitting device 1 according to the first embodiment in that a phosphor element 3A is provided instead of the phosphor element 3, as shown in FIG. Different. Hereinafter, this point will be described in detail.

  The phosphor element 3 </ b> A includes a substrate 30 </ b> A and a microlens array 31. Note that the microlens array 31 in the present embodiment does not contain the phosphor 35.

  A phosphor 35 is stacked on the light incident surface 300 of the substrate 30A. Thereby, the phosphor 35 in the present embodiment is in a state of being localized in layers so as to be substantially orthogonal to the optical path of the emitted light from the LED chip 2. In FIG. 2C and FIG. 2D described later, a state in which only one phosphor 35 is provided is illustrated, but a plurality of layers may be provided.

  Next, a method for depositing the phosphor 35 on the substrate 30A will be described.

  In order to form the phosphor 35 in layers, a so-called aerosol deposition method is used in which fine particles of the phosphor 35 as a raw material collide with the substrate 30A as a substrate at high speed to form a film.

  As a film forming apparatus using the aerosol deposition method, a configuration disclosed in “Applied Physics”, Vol. 68, No. 1, page 44, Japanese Patent Laid-Open No. 2003-215256, and the like can be used.

  FIG. 3 is a diagram showing a schematic configuration diagram of an aerosol deposition film forming apparatus. As shown in this figure, the aerosol deposition film forming apparatus has a holder 209 for holding a substrate 210 (substrate 30A), an XYZθ stage 211 for operating the holder 209 in three dimensions with XYZθ, and a narrow opening for ejecting raw materials to the substrate. A nozzle 208 provided, a chamber 207 provided with a pipe 206 connecting the nozzle 208 to the aerosolization chamber 204, a high-pressure gas cylinder 201 for storing a carrier gas, an aerosolization chamber 204 in which the fine particle raw material and the carrier gas are stirred and mixed, and It is comprised by the piping 202 which connects these. Numbers 203 and 205 are valves. A temperature control mechanism using a Peltier element is installed on the back surface of the stage, and the substrate can be maintained at an optimum temperature.

  Furthermore, the particulate raw material in the aerosolization chamber 204 is formed on the substrate 210 by the following procedure.

  The fine particle raw material having a particle diameter of preferably 0.02 to 5 μm, more preferably 0.1 to 2 μm filled in the aerosolization chamber 204 passes through a pipe from a high-pressure gas cylinder 201 for storing a carrier gas, and is converted into an aerosolization chamber. It is introduced into 204 and is agitated and agitated together with the carrier gas.

  As a method for measuring the particle size of raw material particles, a general laser diffraction particle size measuring device can be mentioned. Specifically, HELOS (manufactured by JEOL), Microtrac HRA (manufactured by Nikkiso Co., Ltd.), SALD-1100 (manufactured by Shimadzu Corporation) And Coulter Counter (manufactured by Coulter). Particularly preferred is Microtrac HRA.

  The aerosolized fine particle raw material passes through the pipe 206 and is sprayed together with the carrier gas from the nozzle 208 having a narrow opening in the chamber 207 to form a coating film. The chamber 207 is evacuated by a vacuum pump or the like, and the degree of vacuum in the chamber 207 is adjusted as necessary. In the present invention, the degree of vacuum is preferably 0.01 to 10000 Pa, more preferably 0.1 to 1000 Pa. Furthermore, since the holder 209 of the substrate 210 can be moved three-dimensionally by the XYZθ stage 211, a phosphor layer having a necessary thickness can be formed on a predetermined portion of the substrate 210. A sealing layer can be provided on the phosphor layer formed on the substrate 210 as necessary.

  The aerosolized raw material particles are preferably transported by a carrier gas having a flow rate of 100 to 400 m / sec and can be deposited by colliding with the substrate 210. The particles carried by the carrier gas are bonded to each other by impact of collision to form a film.

  In the film forming method of the present invention, an inert gas such as nitrogen gas or He gas is preferable as the carrier gas for accelerating / blowing the raw material particles. Nitrogen gas can be particularly preferably used.

  Moreover, it is preferable to hold | maintain the temperature of the board | substrate 210 with which raw material fine particles collide -100 degreeC or more and 200 degrees C or less. When the substrate temperature is heated to 300 ° C. or higher, the film may become cloudy, and light may not be extracted, resulting in a decrease in brightness of the white LED.

  The formation of the phosphor layer requires at least the fine particles of the phosphor, and may further mix fine particles of a transparent inorganic oxide as necessary. The aerosol distribution chamber 204 of the film forming apparatus is provided for the phosphor and the transparent inorganic oxide, and the phosphor distribution in the phosphor layer can be controlled by appropriately switching the feed materials. The transparent inorganic oxide can control the phosphor concentration in the phosphor layer by appropriately mixing with the phosphor. When a layer of only transparent inorganic oxide is formed on the outermost surface, it can be used as a transparent sealing layer.

  In the above film forming method, phosphor particles are deposited by colliding with the surface of the substrate 30A at high speed to form a phosphor layer. Therefore, pretreatment may be performed so that the phosphor layer does not peel off. In particular, when the substrate 30A is made of a resin, it is also preferable to form a phosphor layer by previously applying a base layer containing a hard material or a binder to the surface of the substrate 30A for the purpose of imparting adhesiveness of the phosphor particles. This is one aspect.

  As the hard material in this case, for example, a metal can be used, and these fine particles, for example, Al, Cu, Ni, Ti, Pt, Au, Ag, Si, and the like are dispersed in a binder such as polyvinyl alcohol, and this is used. The base layer is coated on the resin substrate 30A to improve the adhesion to the substrate 30A. In this case, in order not to lose the transparency, the metal fine particles need to be extremely fine, preferably have a particle size of 100 nm or less, and more preferably 10 nm or less.

  According to the light emitting device 1A described above, the same effect as that of the light emitting device 1 in the first embodiment can be obtained, and the phosphor 35 is localized in layers so as to be substantially orthogonal to the optical path. Therefore, yellow light can be generated by reliably applying blue light to the phosphor 35. Accordingly, the amount of the phosphor 35 can be reduced as compared with the case where the phosphor 35 is uniformly dispersed in the phosphor element 3, so that the manufacturing cost can be reduced. In addition, since the yellow light emission point can be aligned in the direction orthogonal to the optical axis direction (the deviation of the yellow light emission point in the optical axis direction can be reduced), optical control of the emitted light can be facilitated. .

  In the second embodiment, the phosphor 35 is described as being laminated on the light incident surface 300 of the substrate 30A. However, as shown in FIG. 2D, the light emitting surface 301 of the substrate 30A. It is good also as laminating. In this case, since the phosphor 35 is located outside the light emitting surface 301 of the substrate 30A, yellow light generated in the phosphor 35 may be reflected by the light emitting surface 301 to the inside of the phosphor element 3A. Absent. Therefore, since yellow light can be reliably emitted and overlapped with blue light, color misregistration can be more reliably reduced. Also in this case, the microlens array is designed so that its focal point is in the vicinity of the phosphor 35.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In addition, the same code | symbol is attached | subjected to the component similar to the said 1st Embodiment, and the description is abbreviate | omitted.

  The light emitting device 1B according to the third embodiment is different from the light emitting device 1 according to the first embodiment in that a phosphor element 3B is provided instead of the phosphor element 3, as shown in FIG. Different. Hereinafter, this point will be described in detail.

  The phosphor element 3B includes a substrate 30 and a microlens array 31B. Note that the substrate 30 in the present embodiment does not contain the phosphor 35.

  The microlens array 31 </ b> B has a plurality of microlenses 310 </ b> B arranged on the light incident surface 300 of the substrate 30. Here, each microlens 310B in the present embodiment is a convex lens having a focal point inside the microlens 310B.

  These microlenses 310 </ b> B contain a phosphor 35. The phosphor 35 is localized in the vicinity of the focal point of the microlens 310B. More specifically, the phosphor 35 is discontinuously localized in a direction substantially orthogonal to the optical axis direction (the optical path direction from the LED chip 2). Specifically, it is localized in a substantially semi-ellipsoidal shape having an end surface on the light incident surface 300 side. In the present embodiment, the vicinity of the focal point of the microlens 310B is a range in which the distance from the focal point of the microlens 310B to the phosphor 35 is ½ or less of the distance between the apex of the microlens 310B and the focal point. Say.

  The microlens 310B described above can be formed by forming a U-shaped lens when viewed in cross section by embossing or the like and then disposing the phosphor 35 in the depression of the lens.

  According to the light emitting device 1B described above, it is possible to obtain the same effect as that of the light emitting device 1 in the first embodiment, and each microlens 310B in the microlens array 31 is provided inside the phosphor element 3B. Since the phosphor 35 is localized in the vicinity of the focus of the microlens 310B, yellow light can be generated by reliably applying blue light to the phosphor 35. Accordingly, the amount of the phosphor 35 can be reduced as compared with the case where the phosphor 35 is uniformly dispersed in the phosphor element 3, so that the manufacturing cost can be reduced. In addition, since the light emission points of yellow light can be aligned in the direction orthogonal to the optical axis direction, optical control over the emitted light can be facilitated.

  It should be noted that the present invention should not be construed as being limited to the above-described embodiment, and of course can be modified or improved as appropriate.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these.

<Sample (1)>
As the light-emitting device of the sample (1), the one in which the phosphor element 3 in the first embodiment is arranged on the optical path of the LED chip 2 was created as a simulation model. In this phosphor element 3, the phosphors 35 are uniformly dispersed, and the microlens array 31 is formed on the light incident surface 300 of the substrate. The configuration of the sample (1) is shown in FIG. 4, and the phosphor element 3 has a microlens array 31 on the bottom surface, and the whole is housed in the LED cup 4. The LED chip 2 is embedded in the bottom surface of the LED cup 4.

  In more detail, the following conditions were used.

Particle refractive index of phosphor: 1.83
Phosphor particle radius: 5 μm
Particle density of phosphor: 45000 / mm ³
Diameter of phosphor element: 2 mm
Phosphor element thickness: 500 μm
Optical characteristics of phosphor element side surface: Complete diffusion surface Refractive index of binder: 1.6
Microlens thickness: 50 μm
Micro lens curvature radius: 70μm
Microlens pitch: 140 μm
LED chip size: 1mm ²
LED chip light distribution: Uniform emission at 0 to 10 degrees, intensity 0 above
Distance between LED chip and microlens: 20 μm
In the above light-emitting device, the relationship between the emission angle of the blue light emitted from the phosphor element and the light intensity was obtained by simulation, and the result shown in the graph of “▲” in FIG. 5A was obtained. . Here, the emission angle is an angle with respect to the normal line of the phosphor element. In the drawing, the abbreviation “MLA” indicates a microlens array.

<Sample (2)>
As the light emitting device of the sample (2), the same light emitting device as the sample (1) was created as a simulation model, and the relationship between the emission angle of yellow light emitted from the phosphor element and the light intensity was determined. In (a), the results shown in the “x” graph were obtained. Other conditions are the same as those of the sample (1).

<Sample (3)>
As a light emitting device of the sample (3), a light emitting device in which the microlens array is removed from the light emitting device of the sample (1) was used to obtain the relationship between the emission angle of blue light and the light intensity. The result shown in the graph of “◆” was obtained. In addition, about the other conditions, the conditions similar to said sample (1) were used.

<Sample (4)>
As a light emitting device of sample (4), a light emitting device in which a microlens array is taken from the light emitting device of sample (1) was used to determine the relationship between the emission angle of yellow light and the light intensity. The results shown in the graph of “□” were obtained. In addition, about the other conditions, the conditions similar to said sample (1) were used.

FIG. 5B is a diagram showing the light emission state of the light emitting device with and without the sample (1) and the sample (3), that is, with the microlens array, as a _YIE value in the CIE chromaticity diagram. In FIG.5 (b), the relationship between each graph and a symbol is as follows.

“▲” sample (1) X value of light emitting device with microlens array “×” sample (1) Y value of light emitting device with microlens array “◆” sample (3) X of light emitting device without microlens array Value “□” Sample (3) Y value of light emitting device without microlens array <Summary>
In FIG. 5A, the blue light is such that the curve with the microlens array (sample 1) exceeds the curve with no microlens array (sample 3) at an angle of about 25 degrees. This can be seen as a distribution of blue light spread by the effect of the microlens array. In yellow light, such a reversal of light intensity does not occur, but the light intensity is larger in the case of the microlens array (sample 1). This phenomenon is also caused by the fact that blue light that is converted into yellow light by the phosphor diverges with a wider light distribution, so that more blue light obliquely passes through the phosphor element, and the amount of blue light that is compared with the phosphor of the blue light. This is probably because the encounter probability has increased. Therefore, it can be seen that by providing the microlens array on the LED side, the light distribution of blue light is broadened and the angle dependency of blue light and yellow light is reduced.

  In FIG. 5B, the curve of the X value and Y value without the microlens array has a steep inclination at an angle of 10 to 40 degrees, whereas the curve of the X value and Y value with the microlens array is steep. It has become gentle. In addition, the difference between the CIE values of the curves at an angle of 10 degrees and an angle of 40 degrees is clearly smaller with the microlens array. Therefore, it can be said that the light emitting device with the microlens array has less angle dependency and less color shift.

  As described above, by forming a microlens array on the light incident surface of the phosphor element, the light distribution of blue light can be made closer to the light distribution of yellow light. It was found that it can be reduced.

1 Light Emitting Device 2 LED Chip (LED)
3 Phosphor element 30 Substrate 31 Micro lens array 35 Phosphor 300 Light incident surface 301 Light exit surface 310 Micro lens

Claims (8)

An LED that emits light of a first predetermined wavelength;
A phosphor that converts the light having the first predetermined wavelength into light having the second predetermined wavelength, and a translucent phosphor element disposed on the optical path of the light emitted from the LED. ,
In the light emitting device that emits the light having the first predetermined wavelength transmitted through the phosphor element and the light having the second predetermined wavelength generated in the phosphor in an overlapping manner,
The phosphor element is
A substrate,
And a microlens array formed on the light incident surface of the substrate. The light-emitting device according to claim 1.
The phosphor is
A light-emitting device, which is disposed closer to the substrate than the microlens array. The light-emitting device according to claim 2.
Each microlens in the microlens array is
Having a focal point inside the phosphor element;
The phosphor is
A light-emitting device that is localized near the focal point of the microlens. The light emitting device according to claim 3.
The phosphor is
The light emitting device is localized so as to be discontinuous in a direction substantially orthogonal to the optical axis of the emitted light of the LED. The light-emitting device according to claim 4.
The light emitting device, wherein the phosphor is localized in a substantially semi-ellipsoidal shape having an end surface on the light incident surface side of the substrate. The light emitting device according to claim 3.
The phosphor is
A light emitting device characterized by being localized in a layered manner in a direction substantially perpendicular to the optical axis of the emitted light of the LED. In the light-emitting device as described in any one of Claims 1-5,
The light of the first predetermined wavelength and the light of the second predetermined wavelength are visible light and have a complementary color relationship with each other. In the light-emitting device as described in any one of Claims 1-7,
The light of the first predetermined wavelength is blue light;
The light of the second predetermined wavelength is yellow light.