JP6256708B2 - Single crystal phosphor - Google Patents

Description

  The present invention relates to a single crystal phosphor.

  Conventionally, a light emitting element composed of an LED (Light Emitting Diode) that emits blue light and a phosphor that emits yellow light when excited by receiving the light of the light emitting element are mixed. A light emitting device that emits white light is known (see, for example, Patent Documents 1 and 2).

  In the light emitting device described in Patent Document 1, a YAG: Ce polycrystalline phosphor ceramic plate is used as a phosphor emitting yellow light.

  In the light emitting device described in Patent Document 2, cerium-activated yttrium aluminum garnet (YAG: Ce) -based polycrystalline phosphor powder is used as a phosphor emitting yellow light.

JP 2010-24278 A Japanese Patent No. 3503139

  One of the objects of the present invention is to provide a YAG-based single crystal phosphor that emits fluorescence of an unprecedented color.

In order to achieve the above object, one embodiment of the present invention provides a light emitting device according to [1] below.

[1] A light emitting element that emits blue light mounted on a substrate having wiring, and a plate-like phosphor made of one single crystal disposed through the light emitting element and a predetermined space; And the phosphor has a composition formula (Y ₁ -ab Lu _a Ce _b ) _{3 + c} Al ₅ -cO ₁₂ (0 ≦ a ≦ 0.9994, 0.0002 ≦ b ≦ 0.0067, −0 .016 ≦ c ≦ 0.315), the CIE chromaticity coordinates x, y of the emission spectrum when the peak wavelength of the excitation light is 450 nm and the temperature is 25 ° C. are −0. 4377x + 0.7384 ≦ y ≦ −0.4 377 x + 0.7504, a phosphor that absorbs part of the blue light, emits yellow light, and emits blue light. A light emitting device that emits white light by mixing the remaining yellow light. .

  According to one embodiment of the present invention, it is possible to provide a YAG-based single crystal phosphor that emits fluorescence of an unprecedented color.

FIG. 1 is a graph showing the composition distribution of the single crystal phosphor according to the first embodiment used for the evaluation. FIG. 2 is a graph showing the CIE (x, y) chromaticity distribution of the single crystal phosphor according to the first embodiment used for the evaluation. FIG. 3A is a vertical cross-sectional view of the light emitting device according to the second embodiment. FIG. 3B is an enlarged view of the light emitting element included in the light emitting device and its peripheral portion. FIG. 4 is a chromaticity diagram showing CIE chromaticity of light (fluorescence) emitted from the single crystal phosphor and CIE chromaticity of light obtained by mixing light emitted from the light emitting element and light emitted from the single crystal phosphor. FIG. 5 is a chromaticity diagram showing CIE chromaticity of mixed light emitted by a combination of a light emitting element, a single crystal phosphor, and a red phosphor. FIG. 6 shows emission spectra of the light emitting element, single crystal phosphor, and red phosphor used in the simulation. These emission spectra are called basic spectra. FIG. 7A is a vertical sectional view of the light emitting device according to the third embodiment. FIG. 7B is an enlarged view of the light emitting element included in the light emitting device and its peripheral portion. FIG. 7C is a top view of the light emitting element. FIG. 8 is a vertical sectional view of the light emitting device according to the fourth embodiment. FIG. 9 is a vertical cross-sectional view of the light emitting device according to the fifth embodiment. FIG. 10 is a vertical sectional view of the light emitting device according to the sixth embodiment.

[First Embodiment]
[Single crystal phosphor]
The single crystal phosphor according to the first embodiment is a YAG-based single crystal phosphor activated with Ce, and (Y _1-ab Lu _a Ce _b ) _{3 + c} Al _{5 -c} O ₁₂ (0 ≦ a ≦ 0.9994, 0.0002 ≦ b ≦ 0.0067, −0.016 ≦ c ≦ 0.315). Here, Ce is substituted at the Y site and functions as an activator (becomes a light emission center). On the other hand, Lu is replaced with a Y site, but does not function as an activator.

  In the phosphor composition, some atoms may occupy different positions on the crystal structure. In addition, although the value of O in the composition ratio in the above composition formula is described as 12, the above composition is slightly deviated from 12 in the composition ratio due to the presence of inevitably mixed or missing oxygen. Also includes composition. The value of c in the composition formula is a value that inevitably changes in the production of the single crystal phosphor, but the change within the numerical range of about −0.016 ≦ c ≦ 0.315 Little effect on the physical properties of the phosphor.

  The single crystal phosphor according to the first embodiment includes, for example, CZ method (Czochralski Method), EFG method (Edge Defined Film Fed Growth Method), Bridgman method, FZ method (Floating Zone Method), Bernoulli method and the like. It can be obtained by a liquid phase growth method. The single crystal phosphor ingot obtained by these liquid phase growth methods can be cut and processed into a flat plate shape, or pulverized and processed into a powder shape, which can be used in a light emitting device described later.

  The range of the numerical value of b in the above composition formula representing the concentration of Ce is 0.0002 ≦ b ≦ 0.0067 because when the numerical value of b is smaller than 0.0002, the Ce concentration is too low. The problem is that the absorption of excitation light becomes small and the external quantum efficiency becomes too small, and when it is larger than 0.0067, cracks and voids occur when growing an ingot of a single crystal phosphor, and the crystal quality is low. This is because there is a high possibility of a decrease.

[Production of single crystal phosphor]
As an example of the manufacturing method of the single crystal phosphor of the present embodiment, a manufacturing method by the CZ method will be described below.

First, as a starting material, high-purity (99.99% or more) Y ₂ O ₃ , Lu ₂ O ₃ , CeO ₂ , and Al ₂ O ₃ powders are prepared and dry-mixed to obtain a mixed powder. The raw material powders of Y, Lu, Ce, and Al are not limited to the above. Further, when producing a single crystal phosphor containing no Lu, the raw material powder is not used.

  Next, the obtained mixed powder is put in an iridium crucible, and the crucible is accommodated in a ceramic cylindrical container. Then, a high-frequency coil wound around the cylindrical container supplies high-frequency energy of 30 kW to the crucible to generate an induced current, thereby heating the crucible. Thereby, the mixed powder is melted to obtain a melt.

  Next, a seed crystal that is a YAG single crystal is prepared, and the tip is brought into contact with the melt, and then pulled at a pulling speed of 1 mm / h or less while rotating at a rotation speed of 10 rpm, and a pulling temperature of 1960 ° C. or higher. The single crystal phosphor ingot is grown in the <111> direction. The single crystal phosphor ingot is grown by flowing nitrogen into the cylindrical container at a flow rate of 2 L / min in a nitrogen atmosphere under atmospheric pressure.

  Thus, for example, a single crystal phosphor ingot having a diameter of about 2.5 cm and a length of about 5 cm is obtained. By cutting the obtained single crystal phosphor ingot into a desired size, for example, a flat single crystal phosphor used in a light emitting device can be obtained. In addition, by pulverizing the single crystal phosphor ingot, a particulate single crystal phosphor can be obtained.

[Evaluation of single crystal phosphor]
A plurality of single crystal phosphors according to the first embodiment having different compositions were manufactured, and composition analysis, CIE chromaticity and internal quantum efficiency were evaluated.

  The composition analysis was performed by high frequency inductively coupled plasma (ICP) emission spectroscopy. Further, ICP mass spectrometry (ICP-MS) was used in combination with a single crystal phosphor having a very low Ce concentration.

  In the evaluation of CIE chromaticity coordinates, CIE 1931 color matching functions were used to obtain CIE chromaticity coordinates of the emission spectrum of the single crystal phosphor when the peak wavelength of the excitation light was 450 nm.

  The internal quantum efficiency was evaluated using a quantum efficiency measurement system equipped with an integrating hemisphere unit. A specific method for measuring the internal quantum efficiency of the single crystal phosphor will be described below.

  First, an excitation light spectrum is measured by irradiating barium sulfate powder as a standard sample installed in the integrating hemisphere unit with excitation light. Next, excitation light is irradiated to the single crystal phosphor placed on barium sulfate in the integrating hemisphere unit, and the excitation reflected light spectrum and the fluorescence emission spectrum are measured. Next, the excitation light diffusely reflected in the integrating hemisphere unit is irradiated to a single crystal phosphor placed on barium sulfate, and a re-excitation fluorescence emission spectrum is measured.

  Then, the difference between the photon number obtained from the fluorescence emission spectrum and the photon number obtained from the re-excitation fluorescence emission spectrum is divided by the difference between the photon number obtained from the excitation light spectrum and the photon number obtained from the excitation reflected light spectrum. Thus, the internal quantum efficiency is obtained.

  Table 1 below shows the results of the evaluation of the fluorescence wavelength and CIE chromaticity. Sample Nos. 1 to 33 in Table 1 are single crystal phosphor samples of the present embodiment, and Sample Nos. 34 to 36 are YAG polycrystals activated by Ce as a comparative example. This is a phosphor powder sample. Table 1 shows the values of a, b, and c in the composition formula of the single crystal phosphor according to the present embodiment, the peak wavelength λp (nm) of the fluorescence when the peak wavelengths of the excitation light are 440 nm, 450 nm, and 460 nm, And CIE chromaticity coordinates (x, y) when the peak wavelengths of the excitation light are 440 nm, 450 nm, and 460 nm.

As shown in Table 1, the compositional formula of the single crystal phosphor used for the evaluation (Y _1-ab Lu _a Ce _b ) _{3 + c} Al _{5 -c} O ₁₂ numerical ranges of a, b, c are respectively 0 ≦ a ≦ 0.9994, 0.0002 ≦ b ≦ 0.0067, and −0.016 ≦ c ≦ 0.315.

  Among these, the single crystal phosphor containing Lu has a numerical value range of a in the composition formula of 0.0222 ≦ a ≦ 0.9994, and the single crystal phosphor not containing Lu has a value of a in the composition formula of a = 0.

  The single crystal phosphor containing Lu has a fluorescent color close to green compared to the single crystal phosphor not containing Lu, and therefore, when combined with the red phosphor, a white light having a high color rendering property is created using a blue light source. Can do. Conversely, a single crystal phosphor that does not contain Lu can produce white light with a high color temperature using a blue light source without being combined with a red phosphor.

  In general, a single crystal phosphor containing Lu tends to have superior temperature characteristics as compared to a single crystal phosphor containing no Lu. On the other hand, since Lu is expensive, adding Lu to a single crystal phosphor increases the manufacturing cost.

  Further, according to Table 1, when the numerical ranges of a and b in the composition formula of the single crystal phosphor used for evaluation are 0 ≦ a ≦ 0.9994 and 0.0002 ≦ b ≦ 0.0067, respectively, excitation The numerical ranges of the CIE chromaticity coordinates x and y of fluorescence when the peak wavelength of light is 450 nm are 0.329 ≦ x ≦ 0.434 and 0.551 ≦ y ≦ 0.600, respectively.

  FIG. 1 is a graph showing the composition distribution of the single crystal phosphor according to the first embodiment used for the evaluation. The horizontal axis of FIG. 1 represents a (Lu concentration) in the composition formula of the single crystal phosphor, and the vertical axis represents b (Ce concentration) in the composition formula.

  FIG. 2 is a graph showing the CIE (x, y) chromaticity distribution of the single crystal phosphor according to the first embodiment used for the evaluation. The horizontal axis in FIG. 2 represents the CIE chromaticity coordinate x when the peak wavelength of the excitation light is 450 nm, and the vertical axis represents the coordinate y.

A straight line y = −0.4377x + 0.7444 in FIG. 2 is an approximate straight line of CIE chromaticity coordinates obtained by the least square method when the peak wavelength is 450 nm. The upper dotted line of this approximate straight line is a straight line represented by y = −0.4 377 x + 0.7504, and the lower dotted line is a straight line represented by y = −0.4377x + 0.7384. .

As shown in FIG. 2, the composition formula (Y _1−ab Lu _a Ce _b ) _{3 + c} Al _5−c O ₁₂ (0 ≦ a ≦ 0.9994, 0.0002 ≦ b ≦ 0.0067, −0 .016 ≦ c ≦ 0.315), the CIE chromaticity coordinates x and y of the emission spectrum when the peak wavelength of excitation light is 450 nm and the temperature is 25 ° C. −0.4377x + 0.7384 ≦ y ≦ −0.4 377 x + 0.7504 is satisfied.

Table 2 below shows the results of evaluation for internal quantum efficiency. Table 2 shows the values of a, b, c in the composition formula of the single crystal phosphor according to the present embodiment, and the internal quantum efficiency (η _{int) at} 25 ° C. when the excitation light peak wavelengths are 440, 450, 460 nm. ).

  According to Table 2, the single crystal phosphor according to the present embodiment has a high internal quantum efficiency. For example, the internal quantum efficiencies of all evaluated single crystal phosphor samples at a temperature of 25 ° C. and a peak wavelength of excitation light of 450 nm are 0.91 or more.

  As for the shape of the evaluated single crystal phosphor sample, the sample Nos. 15 and 19 are circular plates having a diameter of 10 mm and a thickness of 0.3 mm, and the sample No. 33 is a powder. The other sample is a square plate having a side length of 10 mm and a thickness of 0.3 mm. In addition, all samples except the powder sample are mirror-polished on both sides.

  The fluorescence peak wavelength λp (nm), the CIE chromaticity coordinates (x, y), and the measured values of the internal quantum efficiency are hardly affected by the shape of the sample.

[Comparison with polycrystalline phosphor]
The relationship between Ce concentration and emission color is greatly different between the YAG-based single crystal phosphor activated by Ce and the YAG-based polycrystalline phosphor powder. For example, in the patent document (Japanese Patent Laid-Open No. 2010-24278), 0.003 ≦ z ≦ for a polycrystalline phosphor powder having a composition represented by the composition formula (Y _1-z Ce _z ) ₃ Al ₅ O ₁₂ It is described that light of constant chromaticity (0.41, 0.56) is emitted in a Ce concentration range of 0.2. On the other hand, in the single crystal phosphor of the present embodiment, the chromaticity changes depending on the Ce concentration. For example, the same chromaticity (0.41, 0.56) as the polycrystalline phosphor powder of the above-mentioned patent document. the composition for emitting light is _{(Y 1-z Ce z)} 3 Al 5 O 12 (z = 0.0005).

In addition, in the patent document (Japanese Patent No. 3503139), a polycrystalline phosphor powder having a composition represented by a composition formula (Y _1-ab Lu _a Ce _b ) ₃ Al ₅ O ₁₂ has a = 0. .99, b = 0.01, the emission chromaticity is (0.339, 0.579), and when a = 0.495, b = 0.01, the emission chromaticity is (0.377, 0.570). ). The concentration of Ce contained in the polycrystalline phosphor powder is also orders of magnitude higher than the concentration of Ce contained in the single crystal phosphor of the present embodiment.

  Thus, in the single crystal phosphor, the concentration of Ce added to emit light of a desired color is extremely small compared to the polycrystalline phosphor, and the amount of expensive Ce used can be reduced. it can.

[Second Embodiment]
The second embodiment is an embodiment of a light emitting device having a single crystal phosphor according to the first embodiment.

[Configuration of light emitting device]
FIG. 3A is a vertical sectional view of the light emitting device 10 according to the second embodiment. FIG. 3B is an enlarged view of the light emitting element 100 included in the light emitting device 10 and its peripheral portion.

  The light emitting device 10 includes a substrate 11 having wirings 12 a and 12 b on the surface, a light emitting element 100 mounted on the substrate 11, a single crystal phosphor 13 provided on the light emitting element 100, and a ring surrounding the light emitting element 100. Side wall 14 and a sealing material 15 for sealing the light emitting element 100 and the single crystal phosphor 13.

Substrate 11 is made of, for example, ceramics such as _Al 2 _{O 3.} On the surface of the substrate 11, wirings 12a and 12b are formed in a pattern. The wirings 12a and 12b are made of a metal such as tungsten, for example.

  The light emitting element 100 is a flip chip type LED chip, and emits blue light. The light emission peak wavelength of the light emitting element 100 is preferably in the range of 430 to 480 nm from the viewpoint of the internal quantum efficiency of the light emitting element 100, and further from the viewpoint of the internal quantum efficiency of the single crystal phosphor 13, it is 440 to 470 nm. More preferably, it is in the range.

  In the light emitting device 100, an n-type semiconductor layer 102 made of GaN or the like, a light-emitting layer 103, and a p-type impurity are added on the first main surface 101a of the device substrate 101 made of sapphire or the like. A p-type semiconductor layer 104 made of added GaN or the like is stacked in this order. An n-side electrode 105 a is formed on the exposed portion of the n-type semiconductor layer 102, and a p-side electrode 105 b is formed on the surface of the p-type semiconductor layer 104.

  The light-emitting layer 103 emits blue light when carriers are injected from the n-type semiconductor layer 102 and the p-type semiconductor layer 104. Light emitted from the light emitting layer 103 passes through the n-type semiconductor layer 102 and the element substrate 101 and is emitted from the second main surface 101 b of the element substrate 101. That is, the second main surface 101 b of the element substrate 101 is a light emitting surface of the light emitting element 100.

  On the second main surface 101b of the element substrate 101, the single crystal phosphor 13 is disposed so as to cover the entire second main surface 101b.

  The single crystal phosphor 13 is a flat single crystal phosphor made of the single crystal phosphor according to the first embodiment. Since the single crystal phosphor 13 is composed of one single crystal, it does not include a grain boundary. The single crystal phosphor 13 has an area equal to or larger than that of the second main surface 101b. The single crystal phosphor 13 absorbs light emitted from the light emitting element 100 and emits yellowish fluorescence.

  The single crystal phosphor 13 is directly installed on the second main surface 101b of the element substrate 101 without any other member, and the first crystal phosphor 13 is a surface on the element substrate 101 side of the first crystal phosphor 13. The surface 13 a is in contact with the second main surface 101 b of the element substrate 101. The single crystal phosphor 13 and the element substrate 101 are bonded by, for example, intermolecular force.

  The n-side electrode 105a and the p-side electrode 105b of the light emitting element 100 are electrically connected to the wirings 12a and 12b through conductive bumps 106, respectively.

  The side wall 14 is made of a resin such as a silicone resin or an epoxy resin, and may include light reflecting particles such as titanium dioxide.

  The sealing material 15 is made of a translucent resin such as a silicone resin or an epoxy resin. The sealing material 15 may include particles of a red phosphor that absorbs light emitted from the light emitting element 100 and emits red fluorescence. The emission peak wavelength of the red phosphor is preferably in the range of 600 to 660 nm, more preferably in the range of 635 to 655 nm, from the viewpoint of brightness and color rendering. When the wavelength is too small, the color rendering property is deteriorated because it is close to the emission wavelength of the single crystal phosphor 13. On the other hand, if the wavelength is too large, the effect of a decrease in visibility is increased.

[Operation of light-emitting device]
When the light emitting element 100 is energized, electrons are injected into the light emitting layer 103 through the wiring 12a, the n-side electrode 105a, and the n-type semiconductor layer 102, and the wiring 12b, the p-side electrode 105b, and the p-type semiconductor layer 104 are connected. Holes are injected into the light emitting layer 103 through the light emitting layer 103, and the light emitting layer 103 emits light.

  Blue light emitted from the light emitting layer 103 passes through the n-type semiconductor layer 102 and the element substrate 101 and is emitted from the second main surface 101 b of the element substrate 101, and the first surface of the single crystal phosphor 13. Incident on 13a.

  The single crystal phosphor 13 absorbs a part of blue light emitted from the light emitting element 100 and emits yellow fluorescence.

  A part of the blue light emitted from the light emitting element 100 and traveling toward the single crystal phosphor 13 is absorbed by the single crystal phosphor 13 and wavelength-converted, and the second light of the single crystal phosphor 13 is converted into yellow light. The light is emitted from the surface 13b. Further, part of the blue light emitted from the light emitting element 100 toward the single crystal phosphor 13 is emitted from the second surface 13 b without being absorbed by the single crystal phosphor 13. Since blue and yellow are in a complementary color relationship, the light emitting device 10 emits white light in which blue light and yellow light are mixed.

  When the sealing material 15 includes a red phosphor, the red phosphor absorbs part of the blue light emitted from the light emitting element 100 and emits red fluorescence. In this case, the light emitting device 10 emits white light in which blue light, yellow light, and red light are mixed. By mixing red light, the color rendering of white light can be enhanced.

  FIG. 4 is a chromaticity diagram showing the CIE chromaticity of light (fluorescence) emitted from the single crystal phosphor 13 and the CIE chromaticity of light obtained by mixing the light emitted from the light emitting element 100 and the light emitted from the single crystal phosphor 13. is there. The eight square frames arranged in FIG. 4 are in the chromaticity range of the color temperature 2700 to 6500K defined by the chromaticity standard (ANSI C78.377).

  A curve L1 in FIG. 4 represents the relationship between the Ce concentration of the single crystal phosphor 13 and the emission chromaticity. The mark “◇” on the curve L1 indicates that the numerical value of b (Ce concentration) in the composition formula of the single crystal phosphor 13 is 0.0002, 0.0005, 0.0010, and 0.0014 in order from the left side. This is an actual measurement value of the emission chromaticity of the single crystal phosphor 13.

  A curve L2 in FIG. 4 represents the relationship between the Ce concentration of the single crystal phosphor 13 and the chromaticity of the mixed light emitted by the combination of the light emitting element 100 and the single crystal phosphor 13. The mark “●” on the curve L2 indicates, in order from the bottom, the light emitting element when the numerical value of b in the composition formula of the single crystal phosphor 13 is 0.0002, 0.0005, 0.0010, 0.0014. This is an actual measurement value of chromaticity of mixed light emitted by a combination of 100 and the single crystal phosphor 13.

These measured values are obtained when the composition of the single crystal phosphor 13 (Y _1-a-b Lu _a Ce _b ) _{3 + c} Al _{5 -c} O ₁₂ is set to 0 and b is changed to change the single crystal fluorescence. It was obtained by measuring the fluorescence spectrum of the body 13 and the combined spectrum of the light emission of the light emitting device 100 and the fluorescence of the single crystal phosphor 13.

  Note that the emission wavelength of the light-emitting element 100 used for this measurement is 450 nm. The single crystal phosphor 13 is a flat single crystal phosphor having a thickness of 0.3 mm.

  As indicated by the curves L1 and L2, Ce functions as an activator of the single crystal phosphor 13. Therefore, as the Ce concentration in the single crystal phosphor 13 increases (b increases), the light emitting device 100 and the light emitting element 100 become single. The chromaticity of the mixed light emitted by the combination of the crystal phosphors 13 approaches the chromaticity of the fluorescence of the single crystal phosphor 13. Note that, when b = 0, the single crystal phosphor 13 does not emit fluorescence, and thus becomes equal to the light emission chromaticity of the light emitting element 100 alone.

  Here, the lower limit value of the thickness of the flat single crystal phosphor 13 is 0.15 mm. From the viewpoint of mechanical strength, the thickness of the single crystal phosphor 13 is set to 0.15 mm or more.

  Since Lu does not function as an activator, even if the value of a in the composition formula of the single crystal phosphor 13 is changed, the change in chromaticity in the direction of the curve L2 hardly occurs. Similarly, even if the emission wavelength of the light emitting element 100 is changed, the change in chromaticity in the direction of the curve L2 hardly occurs.

  FIG. 5 is a chromaticity diagram showing the CIE chromaticity of the mixed light emitted by the combination of the light emitting element 100, the single crystal phosphor 13, and the red phosphor.

  A curve L2 in FIG. 5 is equal to the curve L2 in FIG. Point R represents the chromaticity (0.654, 0.345) of the fluorescence of the red phosphor. The eight square frames arranged are in the chromaticity range of the color temperature of 2700 to 6500K defined by the chromaticity standard (ANSI C78.377).

  The straight line L3 is a straight line passing through the point R and the lower end of the frame of the color temperature 2700K, and the straight line L4 is a straight line passing through the point R and the upper end of the frame of the color temperature 6500K. Point Y1 is an intersection of curve L2 and straight line L3, and point Y2 is an intersection of curve L2 and straight line L4.

  In FIG. 5, first, the Ce concentration of the single crystal phosphor is such that the chromaticity coordinates of light emission when the light emitting element 100 and the single crystal phosphor 13 are combined are located between the points Y1 and Y2 on the straight line L2. And adjust the thickness. Next, white light with a color temperature of 2700 to 6500 K can be generated by adjusting the amount of red phosphor (the concentration in the sealing material 15 when dispersed in the sealing material 15).

  At this time, since the single crystal phosphor 13 and the red phosphor also absorb the respective fluorescence, the combined chromaticity of the light emitting element 100 and the single crystal phosphor 13 with respect to the adjustment amount of the red phosphor is Although it does not change linearly with respect to the chromaticity R, white light having a target color temperature can be generated by the above method.

  Since Lu does not function as an activator, even if the value of a in the composition formula of the single crystal phosphor 13 is changed, the change in chromaticity in the direction of the curve L2 hardly occurs. Therefore, when the single crystal phosphor 13 contains Lu, the amount of the red phosphor used in combination with the light emitting element 100 and the single crystal phosphor 13 is adjusted according to the Lu concentration, so that the color temperature is 2700 to 6500K. Can produce white light.

  Similarly, even if the emission wavelength of the light emitting element 100 or the emission wavelength of the red phosphor is changed, the chromaticity in the direction of the curve L2 hardly changes, and at least the emission peak wavelength of the light emitting element 100 is in the range of 430 to 480 nm. If the emission peak wavelength of the red phosphor is in the range of 600 to 660 nm, white light having a color temperature of 2700 to 6500 K can be produced by adjusting the amount of the red phosphor by the same method. it can.

  Next, it is shown by simulation that the light emitted from the light emitting device 10 according to the present embodiment is excellent in color rendering. Here, as an example, the color rendering properties when the light emitting device 10 emits light having a color temperature of 3000 K will be described.

  FIG. 6 shows emission spectra of the light emitting element 100, the single crystal phosphor 13, and the red phosphor used in the simulation. These emission spectra are called basic spectra.

The peak wavelengths of the basic spectra of the light emitting device 100, the single crystal phosphor 13, and the red phosphor are approximately 450 nm (blue), 535 nm (yellow), and 640 nm (red). The basic spectrum of the single crystal phosphor 13 is a single crystal whose composition is (Y _1-ab Lu _a Ce _b ) _{3 + c} Al _{5 -c} O ₁₂ (a = 0, b = 0, a = 0). It is an emission spectrum of the phosphor 13.

  First, assuming that the emission spectrum of the light emitting device 10 can be approximated by the combined spectrum of the emission spectra of the light emitting element 100, the single crystal phosphor 13, and the red phosphor, the light emitting element 100, the single crystal phosphor 13, and the red fluorescence are obtained by the least square method. The fundamental spectrum of the body was fitted to a spectrum having a chromaticity corresponding to a color temperature of 3000K, and the linear combination coefficient of each fundamental spectrum was determined.

  Then, the average color rendering index Ra was calculated from the synthetic spectrum obtained by the fitting. As a result, the average color rendering index Ra when the light emitting device 10 that emits light having a color temperature of 3000 K is formed using the light emitting element 100 whose emission spectrum is the basic spectrum, the single crystal phosphor 13, and the red phosphor.

  Subsequently, the above simulation is repeated while shifting the wavelength of the basic spectrum of the light emitting device 100 and the single crystal phosphor 13 (the basic spectrum of the red phosphor is fixed), and the wavelengths of the light emitting device 100 and the single crystal phosphor 13 are changed. The average color rendering index Ra was determined. Here, the wavelength of the light-emitting element 100 was changed from the wavelength of the basic spectrum in the range of -20 to +30 nm in increments of 5 nm. The wavelength of the single crystal phosphor 13 was changed in steps of 5 nm within the range of −45 to +45 nm from the wavelength of the basic spectrum. The results are shown in Table 3 below.

  Table 3 shows that a high average color rendering index Ra of 90 or more, further 95 or more can be obtained by appropriately adjusting the wavelengths of the light emitting device 100 and the single crystal phosphor 13.

[Third Embodiment]
The third embodiment is different from the second embodiment in that the light emitting element is a face-up type LED chip. Note that the description of the same points as in the first embodiment will be omitted or simplified.

[Configuration of light emitting device]
FIG. 7A is a vertical sectional view of the light emitting device 20 according to the third embodiment. FIG. 7B is an enlarged view of the light emitting element 200 included in the light emitting device 20 and its peripheral portion. FIG. 7C is a top view of the light emitting element 200.

  The light emitting device 20 includes a substrate 11 having wirings 12 a and 12 b on the surface, a light emitting element light emitting element 200 mounted on the substrate 11, a single crystal phosphor 21 provided on the light emitting element 200, and the light emitting element 200. An enclosing annular side wall 14 and a sealing material 15 for sealing the light emitting element 200 and the single crystal phosphor 21 are included.

  The light-emitting element 100 is a face-up type LED chip, and emits blue light having a light amount peak at a wavelength of 380 to 490 nm. In the light emitting device 200, an element substrate 201 made of sapphire or the like is made of an n type semiconductor layer 202 made of GaN or the like doped with n type impurities, a light emitting layer 203, or GaN or the like doped with p type impurities. A p-type semiconductor layer 204 and a transparent electrode 207 made of ITO (Indium Tin Oxide) or the like are laminated in this order. An n-side electrode 205 a is formed on the exposed portion of the n-type semiconductor layer 102, and a p-side electrode 205 b is formed on the upper surface 207 b of the transparent electrode 207.

  The light-emitting layer 203 emits blue light when carriers are injected from the n-type semiconductor layer 202 and the p-type semiconductor layer 204. The light emitted from the light emitting layer 203 passes through the p-type semiconductor layer 204 and the transparent electrode 207 and is emitted from the upper surface 207 b of the transparent electrode 207. That is, the upper surface 207 b of the transparent electrode 207 is a light emitting surface of the light emitting element 200.

  On the upper surface 207b of the transparent electrode 207, a substantially rectangular single crystal phosphor 21 having a notch in a portion corresponding to the installation position of the n-side electrode 205a and the p-side electrode 205b is disposed.

  The single crystal phosphor 21 is a flat single crystal phosphor made of the single crystal phosphor according to the first embodiment. Since the single crystal phosphor 21 is composed of one single crystal, it does not include a grain boundary.

  The single crystal phosphor 21 is directly installed on the upper surface 207b of the transparent electrode 207 without any other member, and the first surface 21a, which is the surface of the single crystal phosphor 21 on the transparent electrode 207 side, is transparent. It is in contact with the upper surface 207b of the electrode 207.

  The n-side electrode 205a and the p-side electrode 205b of the light emitting element 200 are connected to the wiring 12a and the wiring 12b through bonding wires 206, respectively.

[Operation of light-emitting device]
When the light emitting element 200 is energized, electrons are injected into the light emitting layer 203 through the wiring 12a, the n-side electrode 205a, and the n-type semiconductor layer 202, and the wiring 12b, the p-side electrode 205b, the transparent electrode 207, and the p-type semiconductor. Holes are injected into the light emitting layer 203 through the layer 204, and the light emitting layer 203 emits light.

  Blue light emitted from the light emitting layer 203 passes through the p-type semiconductor layer 204 and the transparent electrode 207, is emitted from the upper surface 207 b of the transparent electrode 207, and enters the first surface 21 a of the phosphor 21.

  The single crystal phosphor 21 absorbs part of blue light emitted from the light emitting element 200 and emits yellow fluorescence.

  A part of the blue light emitted from the light emitting element 200 toward the single crystal phosphor 21 is absorbed by the single crystal phosphor 21 and wavelength-converted, and the second light of the single crystal phosphor 21 is converted into yellow light. The light is emitted from the surface 21b. Further, part of the blue light emitted from the light emitting element 200 toward the single crystal phosphor 21 is emitted from the second surface 21 b without being absorbed by the single crystal phosphor 21. Since blue and yellow have a complementary color relationship, the light emitting device 20 emits white light in which blue light and yellow light are mixed.

  Further, when the sealing material 15 includes a red phosphor, the red phosphor absorbs a part of the blue light emitted from the light emitting element 200 and emits red fluorescence. In this case, the light emitting device 20 emits white light that is a mixture of blue light, yellow light, and red light. By mixing red light, the color rendering of white light can be enhanced.

[Fourth Embodiment]
The fourth embodiment differs from the second embodiment in the installation position of the single crystal phosphor. Note that the description of the same points as in the second embodiment will be omitted or simplified.

  FIG. 8 is a vertical sectional view of the light emitting device 30 according to the fourth embodiment. The light emitting device 30 includes a substrate 11 having wirings 12 a and 12 b on the surface, a light emitting element light emitting element 100 mounted on the substrate 11, a single crystal phosphor 31 provided above the light emitting element 100, and the light emitting element 100. And a sealing material 15 that seals the light emitting element 100 and the single crystal phosphor 21.

  The single crystal phosphor 31 is a flat single crystal phosphor made of the single crystal phosphor according to the first embodiment. Since the single crystal phosphor 31 is composed of one single crystal, it does not include a grain boundary.

  The single crystal phosphor 31 is installed on the upper surface 14 b of the side wall 14 so as to close the opening of the annular side wall 14. Light emitted from the second main surface 101 b of the element substrate 101 of the light emitting element 100 is incident on the first surface 31 a of the single crystal phosphor 31.

  The single crystal phosphor 31 absorbs part of the blue light emitted from the light emitting element 100 and emits yellow fluorescence.

  A part of the blue light emitted from the light emitting element 100 and traveling toward the single crystal phosphor 31 is absorbed by the single crystal phosphor 31 and wavelength-converted, and the second light of the single crystal phosphor 31 is converted into yellow light. The light is emitted from the surface 31b. Further, part of the blue light emitted from the light emitting element 100 toward the single crystal phosphor 31 is emitted from the second surface 31 b without being absorbed by the single crystal phosphor 31. Since blue and yellow are in a complementary color relationship, the light emitting device 30 emits white light in which blue light and yellow light are mixed.

  When the sealing material 15 includes a red phosphor, the red phosphor absorbs part of the blue light emitted from the light emitting element 100 and emits red fluorescence. In this case, the light emitting device 30 emits white light obtained by mixing blue light, yellow light, and red light. By mixing red light, the color rendering of white light can be enhanced. Note that when the light emitting device 30 does not include a red phosphor, the light emitting device 30 may not have the sealing material 15.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 9 is a vertical sectional view of the light emitting device 40 according to the fifth embodiment. As shown in FIG. 9, in the present embodiment, the state of the phosphor and the arrangement thereof are different from those in the second embodiment. Hereinafter, constituent elements of the light-emitting device 40 having the same functions and configurations as those of the second embodiment are denoted by common reference numerals, and description thereof is omitted.

  As shown in FIG. 9, the light emitting device 40 seals the light emitting element 100 that is a light emitting element such as an LED, the substrate 11 that supports the light emitting element 100, the side wall 14 made of white resin, and the light emitting element 100. And a sealing material 15.

  In the sealing material 15, granular single crystal phosphors 41 are dispersed. The phosphor 41 is made of the single crystal phosphor according to the first embodiment, and is obtained, for example, by pulverizing the single crystal phosphor ingot manufactured in the first embodiment.

  The single crystal phosphor 41 dispersed in the sealing material 15 absorbs a part of blue light emitted from the light emitting element 100 and, for example, emits yellow fluorescence having an emission peak at a wavelength of 514 to 546 nm. To emit. Blue light not absorbed by the single crystal phosphor 41 and yellow fluorescence emitted from the single crystal phosphor 41 are mixed, and white light is emitted from the light emitting device 40.

  The single crystal phosphor 41 of the present embodiment may be applied to other embodiments. That is, the single crystal phosphor 41 of the present embodiment may be used in place of the single crystal phosphor 21 of the third embodiment.

[Sixth Embodiment]
Next, a ninth embodiment of the present invention will be described with reference to FIG. FIG. 10 is a vertical sectional view of a light emitting device 50 according to the sixth embodiment. As shown in FIG. 10, in the present embodiment, the shape of the sealing material including the particulate single crystal phosphor is different from that of the fifth embodiment. Hereinafter, constituent elements of the light emitting device 50 having the same functions and configurations as those of the fifth embodiment are denoted by common reference numerals, and description thereof is omitted.

  As shown in FIG. 11, the light emitting device 50 is provided so as to cover the light emitting element 100 that is a light emitting element such as an LED, the substrate 11 that supports the light emitting element 100, the surface of the light emitting element 100, and the upper surface of the substrate 11. And a sealing material 52.

  A particulate single crystal phosphor 51 is dispersed in the sealing material 52. The single crystal phosphor 51 is made of the single crystal phosphor of the first embodiment, and is obtained, for example, by pulverizing the single crystal phosphor ingot manufactured in the first embodiment.

  The sealing material 52 is, for example, a transparent resin such as a silicone resin or an epoxy resin, or a transparent inorganic material such as glass. Note that the sealing material 52 of this embodiment may be formed not only on the surface of the light-emitting element 100 but also on the substrate 11 in the manufacturing process using a coating method or the like. It does not have to be done.

  The single crystal phosphor 51 dispersed in the sealing material 52 absorbs a part of blue light emitted from the light emitting element 100 and, for example, emits yellow fluorescence having an emission peak at a wavelength of 514 to 546 nm. To emit. Blue light not absorbed by the single crystal phosphor 51 and yellow fluorescence emitted from the single crystal phosphor 51 are mixed, and white light is emitted from the light emitting device 50.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. In addition, the constituent elements of the above-described embodiment can be arbitrarily combined without departing from the spirit of the invention.

  The embodiments described above do not limit the invention according to the claims. In addition, it should be noted that not all the combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

  In addition, since the above embodiment is a light emitting device such as an LED light emitting device that has high energy efficiency and can realize energy saving, or a single crystal phosphor used in the light emitting device, it has an energy saving effect.

10, 20, 30, 40, 50 ... light emitting device, 13, 21, 31, 41, 51 ... single crystal phosphor, 100, 200 ... light emitting element

Claims (1)

A light-emitting element that emits blue light mounted on a substrate having wiring;
A flat phosphor composed of one single crystal disposed with a predetermined space with the light emitting element;
With
The phosphor has a composition formula (Y _1-ab Lu _a Ce _b ) _{3 + c} Al _5-c O ₁₂ (0 ≦ a ≦ 0.9994, 0.0002 ≦ b ≦ 0.0067, −0.016 ≦ c ≦ 0.315), the CIE chromaticity coordinates x and y of the emission spectrum when the peak wavelength of the excitation light is 450 nm and the temperature is 25 ° C. are −0.4377x + 0.7384. ≦ y ≦ −0.4 377 x + 0.7504, a phosphor that absorbs part of the blue light and emits yellow light, and the remaining blue light and the phosphor A light-emitting device that emits white light by mixing yellow light.

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