JP7633512B2 - Light-emitting device - Google Patents

Description

The present invention relates to a light-emitting device.

Known light-emitting devices that use light-emitting elements such as light-emitting diodes (LEDs) include light-emitting elements that emit blue light and light-emitting devices that emit mixed color light using phosphors that are excited by light from the light-emitting elements and emit light. Such light-emitting devices are used in a wide range of fields, such as general lighting, vehicle lighting, displays, and liquid crystal backlights.

In recent years, attention has been focused on light-emitting devices that take into account their impact on humans. For example, it is known that when humans perceive light, the luminosity of the human eye changes between dark and bright places. In bright environments (photopic vision), color perception is possible through the action of cone cells, which are the photoreceptor cells (photoreceptor cells) of the human eye. In dark environments (scotopic vision), many colors cannot be perceived because cone cells do not function, but luminosity is improved through the action of rod cells.

The peak wavelength of visual sensitivity due to cone cells, which are active in bright places, is 555 nm, while the peak wavelength of visual sensitivity due to rod cells, which are active in dark places, is 507 nm, and it is known that the peak of visual sensitivity differs between dark and bright places. This phenomenon is known as the Purkinje phenomenon, in which colors on the longer wavelength side appear more vivid in bright places and colors on the shorter wavelength side appear more vivid in dark places.

For example, Patent Document 1 proposes a lighting device that utilizes the Purkinje phenomenon, in which a road light emits white light that provides high visibility to drivers on the sidewalk side and high visibility to pedestrians in a mesopic environment with intermediate brightness between dark and bright places, and makes it difficult to perceive color spots on the roadway side and the sidewalk side. Patent Document 1 states that the higher the S/P ratio, which is the ratio of scotopic vision to photopic vision, the higher the visibility of the light in a mesopic environment.

JP 2017-220312 A

However, if the S/P ratio is too high, the human eye may perceive the light as dark in photopic vision and bright in scotopic vision. In addition, the light-emitting device may be required to emit a light color that can evoke a specific state, such as charging a portable device, and it is necessary to consider the effect of the light emitted by such a light-emitting device on humans.
One aspect of the present invention aims to provide a light-emitting device that is bright in both scotopic and photopic vision, emits an emission color that can evoke an image of a specific state or the like, and takes into consideration its effects on humans.

One aspect of the present invention is a light emitting device including: a light emitting element having a dominant wavelength in the range of 400 nm to 500 nm; and a wavelength conversion member that is disposed on a light emission side of the light emitting element and contains a rare earth aluminate phosphor having a composition represented by the following formula (I):
(Lu _1-p-n Ln _p Ce _n ) ₃ (Al _1-m Ga _m ) _5k O ₁₂ (I)
(In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and k, m, n, and p satisfy 0.95≦k≦1.05, 0.05≦m≦0.70, 0.002≦n≦0.050, and 0≦p≦0.30, respectively.)
Emitting light having a dominant wavelength in the range of 475 nm or more and 500 nm or less;
The light emitting device has an S/P ratio, which is the ratio of luminous flux in scotopic vision to luminous flux in photopic vision, derived from the following formula (1) of 6.5 or less.
(In formula (1), the constant K is 6831 (lm/W), the constant K' is 1700 (lm/W), and within the wavelength λnm range of 360 nm or more and 830 nm or less, V(λ) is the standard spectral luminous efficiency for human photopic vision, V'(λ) is the standard spectral luminous efficiency for human scotopic vision, and Φ _e (λ) is the spectral total radiant flux of light emitted from the light emitting device.)

Another aspect of the present invention is a light emitting device including: a light emitting element having a dominant wavelength in the range of 400 nm to 500 nm; and a wavelength conversion member disposed on a light emission side of the light emitting element, the wavelength conversion member including a rare earth aluminate phosphor having a composition represented by the following formula (I):
(Lu _1-p-n Ln _p Ce _n ) ₃ (Al _1-m Ga _m ) _5k O ₁₂ (I)
(In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and k, m, n, and p satisfy 0.95≦k≦1.05, 0.05≦m≦0.70, 0.002≦n≦0.050, and 0≦p≦0.30, respectively.)
Emitting light having a dominant wavelength in the range of 475 nm or more and 500 nm or less;
The light-emitting device has a melanopic ratio, calculated from the following formula (2), of 3.4 or less.
(In formula (2), in the wavelength range of 380 nm or more and 730 nm or less, "Lamp x Circadian" is a circadian response included in the spectral distribution of the light emitting device, "Lamp x Visual" is a luminosity response included in the spectral distribution of the light emitting device, "Lamp" is the spectral distribution of the light emitting device, "Circadian" is a sensitivity curve of intrinsic photosensitive retinal ganglion cells, which are photoreceptors in the retina of mammals, "Visual" is a luminosity curve in human photopic vision, and "1.218" is a constant (lux factor).)

According to an aspect of the present invention, it is possible to provide a light-emitting device that is bright in both scotopic and photopic vision, emits a light color that evokes an image of a specific state, such as when charging, and takes into consideration its effect on humans.

FIG. 1 is a diagram showing standard spectral luminous efficiency V(λ) for photopic vision and standard spectral luminous efficiency V'(λ) for scotopic vision. FIG. 2 is a diagram showing the sensitivity curve (Circadian) of intrinsically photosensitive retinal ganglion cells, which are photoreceptors in the mammalian retina, and the luminosity curve (Visual) in human photopic vision. FIG. 3 is a diagram showing an area A1 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. FIG. 4 is a diagram showing area A2 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. FIG. 5 is a diagram showing area A3 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. FIG. 6A is a schematic plan view of a light emitting device according to a first configuration example. FIG. 6B is a schematic cross-sectional view of the light emitting device of the first configuration example. FIG. 7 is a schematic cross-sectional view of a light emitting device according to the second configuration example. FIG. 8 is a schematic cross-sectional view of a light emitting device according to the third configuration example.

The light-emitting device according to the present invention will be described below based on an embodiment. However, the embodiment shown below is an example for realizing the technical idea of the present invention, and the present invention is not limited to the light-emitting device described below. The relationship between the color name and the chromaticity coordinate, and the relationship between the wavelength range of light and the color name of monochromatic light, follow JIS Z8110. Furthermore, when there are multiple substances corresponding to each component in the composition, the content of each component in the composition means the total amount of multiple substances present in the composition, unless otherwise specified.

Light-emitting device One embodiment of the light-emitting device is a light-emitting device including a light-emitting element having a dominant wavelength in the range of 400 nm or more and 500 nm or less, and a wavelength conversion member that is arranged on the light emission side of the light-emitting element and contains a rare earth aluminate phosphor having a composition represented by formula (I) described later, wherein the light-emitting device emits light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and has an S/P ratio of 6.5 or less, which is derived from formula (1) described later and which is the ratio of luminous flux in photopic vision to luminous flux in scotopic vision.

The dominant wavelength of a light-emitting element refers to the wavelength at the point where a line connecting the chromaticity coordinates (x=0.3333, y=0.3333) of white light in the CIE 1931 chromaticity diagram defined by the CIE (Commission International de l'Eclairage) and the chromaticity coordinates ( _xE , _yE ) of the light-emitting color of the light-emitting element intersects with the spectrum locus. The spectrum locus is a curve obtained by connecting the chromaticity points of monochromatic (pure) light on the chromaticity diagram. The dominant wavelength of a light-emitting device refers to the wavelength at the point where a line connecting the chromaticity coordinates (x=0.3333, y=0.3333) of white light in the CIE 1931 chromaticity diagram and the chromaticity coordinates (x, y) of the light-emitting color of the light-emitting device intersects with the spectrum locus.

The light emitting device includes a light emitting element having a dominant wavelength in the wavelength range from blue to blue-green, and a phosphor having an emission peak wavelength in the wavelength range of green, and emits light having a dominant wavelength in the wavelength range from blue to green including blue-green. It is known that the higher the S/P ratio, which is the ratio of the luminous flux in scotopic vision to the luminous flux in photopic vision, the higher the human visibility. Figure 1 is a diagram showing the standard spectral luminous efficiency V(λ) for photopic vision and the standard spectral luminous efficiency V'(λ) for scotopic vision. The standard spectral luminous efficiency V(λ) for photopic vision and the standard spectral luminous efficiency V'(λ) for scotopic vision are specified by the CIE. As shown in Figure 1, the peak wavelength in the standard spectral luminous efficiency V(λ) for photopic vision is 555 nm, and the peak wavelength in the standard spectral luminous efficiency V'(λ) for scotopic vision is 507 nm, and the peak of luminosity is different between dark and bright places. It is known that the peak wavelength of the luminosity of the human eye differs between bright and dark places, and that the human eye sees colors on the long wavelength side more vividly in bright places and colors on the short wavelength side more vividly in dark places due to the Purkinje phenomenon. When the S/P ratio of a light-emitting device that emits light having a dominant wavelength in the purple to green wavelength range is increased to improve visibility, the colors on the short wavelength side may become too vivid and appear too bright when viewed in a dark place. The light-emitting device according to the embodiment of the present invention has an S/P ratio of 6.5 or less even when emitting light having a dominant wavelength in the blue to green wavelength range including blue-green, and is considered to be able to reduce the difference between the luminous flux in a dark place and the luminous flux in a bright place, appear bright in both scotopic and photopic vision, and maintain excellent visibility.

The S/P ratio, which is the ratio of luminous flux in a dark place to luminous flux in a bright place, can be derived from the following formula (1).

In formula (1), the constant K is 6831 (lm/W), the constant K' is 1700 (lm/W), and within the wavelength λnm range of 360 nm or more and 830 nm or less, V(λ) is the standard spectral luminous efficiency for human photopic vision, V'(λ) is the standard spectral luminous efficiency for human scotopic vision, and Φ _e (λ) is the total spectral radiant flux of light emitted from the light-emitting device.

The S/P ratio, which is the ratio of the luminous flux in scotopic vision to the luminous flux in photopic vision of the light emitted from the light-emitting device, is 6.5 or less, preferably 6.0 or less, preferably 2.0 or more, and more preferably 3.0 or more. By reducing the S/P ratio of the light emitted from the light-emitting device to 6.5 or less and reducing the difference between the luminous flux in scotopic vision and the luminous flux in photopic vision, it is believed that even a light-emitting device that emits light having a dominant wavelength in the wavelength range from blue to green, including blue-green, can emit light that reduces the difference in brightness felt by humans in scotopic vision and photopic vision while maintaining excellent visibility that appears bright in both scotopic vision and photopic vision. The dominant wavelength, luminous flux, chromaticity coordinates (x, y) in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram described later, and total spectral radiant flux of the light emitted from the light-emitting device can be measured using an optical measurement system that combines a spectrophotometer (e.g., PMA-11, manufactured by Hamamatsu Photonics K.K.) and an integrating sphere.

Another embodiment of the light emitting device is a light emitting device that includes a light emitting element having a dominant wavelength in the range of 400 nm to 500 nm, and a wavelength conversion member that is disposed on the light emission side of the light emitting element and contains a rare earth aluminate phosphor having a composition represented by formula (I) described below, and emits light having a dominant wavelength in the range of 475 nm to 500 nm, and has a melanopic ratio of 3.4 or less as calculated from formula (2) below.

In formula (2), in the wavelength range of 380 nm or more and 730 nm or less, "Lamp × Circadian" is the circadian response included in the spectral distribution of the light-emitting device, "Lamp × Visual" is the luminosity response included in the spectral distribution of the light-emitting device, "Lamp" is the spectral distribution of the light-emitting device, "Circadian" is the sensitivity curve of intrinsically photosensitive retinal ganglion cells (ipRGCs), which are photoreceptors in the retina of mammals, "Visual" is the luminosity curve in human photopic vision, and "1.218" is a constant (lux factor). The spectral distribution (emission spectrum) of a light-emitting device can be measured using an optical measurement system that combines a spectrophotometer (e.g., PMA-11, manufactured by Hamamatsu Photonics K.K.) and an integrating sphere. For "Visual," the standard spectral luminous efficiency V(λ) for human photopic vision defined by the CIE can be used (Visual = V(λ)).

In addition to cone cells and rods, the presence of intrinsically photosensitive retinal neurons (ipRGCs) containing the visual pigment melanopsin has been discovered in the photoreceptor cells (photoreceptor cells) of the human retina. These ipRGCs respond to light stimuli even when alone, and also respond to light stimuli by receiving input from cones and rods, thereby influencing the human circadian rhythm. Figure 2 shows the sensitivity curve (circadian action curve) of ipRGCs and the visual sensitivity curve of human photopic vision. The peak wavelength in the visual sensitivity curve of human photopic vision is 555 nm, and the melanopsin output from ipRGCs has a peak sensitivity wavelength in the range of 480 nm to 500 nm. Melanopsin is also involved in the secretion and suppression of melatonin, a sleep-promoting hormone. Furthermore, the melanopsin output of ipRGC is also projected to the imaging pathway from the lateral geniculate body, which transmits visual information, to the visual cortex, and may affect the visual system, such as image perception. For example, the melanopic ratio is a value derived from the spectral distribution of the light-emitting device, the sensitivity curve (absorbance) of the ipRGC, and the luminosity curve in human photopic vision. The higher the melanopic ratio, the stronger the stimulation given to the human circadian rhythm. If the melanopic ratio of the light emitted from the light-emitting device is 3.4 or less, it is thought that it can evoke a specific image as a signal color that indicates a specific state of the device, such as when charging, without significantly affecting the human circadian rhythm.

The melanopic ratio of the light emitted from the light-emitting device may be 3.3 or less, or may be 3.2 or less, and is preferably 1.4 or more, and more preferably 1.5 or more. If the melanopic ratio of the light emitted from the light-emitting device is within the range of 1.4 to 3.4, it is believed that the light can evoke a specific image, for example, as a light that emits a signal color that indicates a specific state, such as when charging, without significantly affecting human circadian rhythms.

The light emitting device preferably emits light within an area A1 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the chromaticity coordinates (x, y) of which are (x=0.0082, y=0.5384) as a first point, (x=0.1096, y=0.0868) as a second point , (x=0.210, y=0.190) as a third point, and (x=0.260, y=0.380) as a fourth point in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. Fig. 3 shows the area A1 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting device preferably emits light within an area A1 surrounded by straight lines connecting the first and second points, the second and third points, the third and fourth points, and the fourth and first points in Fig. 3. The light emitting device emits light within the area A1 in Fig. 3, and the light within the area A1 has a dominant wavelength within a range of 475 nm or more and 500 nm or less, and exhibits an emission color ranging from blue to green, including blue-green.

The light emitting device preferably emits light within an area A2 defined by chromaticity coordinates (x, y) of (x=0.0350, y=0.4127) as a first point, (x=0.0800, y=0.2149) as a second point, (x=0.2150, y=0.2106) as a third point, and (x=0.2550, y=0.3550) as a fourth point in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, a first line connecting the first point and the second point , a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point. Figure 4 shows the area A2 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting device preferably emits light within an area A2 surrounded by straight lines connecting the first and second points, the second and third points, the third and fourth points, and the fourth and first points in Fig. 4. The light emitting device emits light within the area A2 in Fig. 4, and the light within the area A2 has a dominant wavelength within a range of 475 nm or more and 500 nm or less, and exhibits an emission color of blue to blue-green.

It is more preferable that the light emitting device emits light within an area A3 defined by the chromaticity coordinates (x, y) of (x=0.1825, y=0.3252) as the first point, (x=0.1550, y=0.2149) as the second point, (x=0.1930, y=0.2106) as the third point, and (x=0.2205, y=0.3209) as the fourth point in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, a first line connecting the first point and the second point , a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point. Figure 5 shows the area A3 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting device preferably emits light within an area A3 surrounded by straight lines connecting the first and second points, the second and third points, the third and fourth points, and the fourth and first points in Fig. 5. The light emitting device emits light within the area A3 in Fig. 5, and the light within the area A3 has a dominant wavelength within a range of 475 nm or more and 500 nm or less, and exhibits an emission color of blue to blue-green.

In the emission spectrum of the light-emitting device, the ratio Ib/Ia of the integral value Ib in the wavelength range of 380 nm to 531 nm to the integral value Ia in the wavelength range of 380 nm to 780 nm is preferably in the range of 0.6 to 0.95, more preferably in the range of 0.65 to 0.94, even more preferably in the range of 0.70 to 0.93, and particularly preferably in the range of 0.75 to 0.92. In the emission spectrum of the light-emitting device, when the ratio Ib/Ia of the integral values is in the range of 0.6 to 0.95, light having a dominant wavelength in the wavelength range of blue to green including blue-green is emitted from the light-emitting device, and it is considered that light can be emitted that reduces the difference in brightness felt by humans in both scotopic and photopic vision while maintaining excellent visibility that appears bright in both scotopic and photopic vision. The emission spectrum of the light emitting device, the integral value Ia in the wavelength range of 380 nm to 780 nm in the measured emission spectrum, and the integral value Ib in the wavelength range of 380 nm to 531 nm in the measured emission spectrum can be measured using an optical measurement system that combines a spectrophotometer (e.g., PMA-11, manufactured by Hamamatsu Photonics K.K.) and an integrating sphere. The integral ratio Ib/Ia can be calculated from the measured integral values Ia and Ib.

The light-emitting element can be, for example, _a light-emitting diode _(LED) chip or _a laser diode (LD: Laser Diode) chip, which is a semiconductor light-emitting element using a nitride-based semiconductor represented by the composition formula InXAlYGa1-X-YN (0≦X, 0≦Y, X+Y≦1), and it is preferable to use an LED chip.

The light-emitting element has a dominant wavelength in the range of 400 nm to 500 nm. The dominant wavelength of the light emitted from the light-emitting element is preferably in the range of 420 nm to 495 nm, and more preferably in the range of 430 nm to 490 nm.

The light-emitting element preferably has an emission peak wavelength in the range of 380 nm to 500 nm, more preferably has an emission peak wavelength in the range of 390 nm to 495 nm, even more preferably has an emission peak wavelength in the range of 400 nm to 490 nm, and particularly preferably has an emission peak wavelength in the range of 420 nm to 490 nm.

The light-emitting element is provided with a p-electrode and an n-electrode. The p-electrode and n-electrode of the light-emitting element may be formed on the same side of the light-emitting element, or may be provided on different sides. The light-emitting element may be flip-chip mounted.

Rare Earth Aluminate Phosphor The rare earth aluminate phosphor contained in the light emitting device has a composition represented by the following formula (I).
(Lu _1-p-n Ln _p Ce _n ) ₃ (Al _1-m Ga _m ) _5k O ₁₂ (I)
(In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and k, m, n, and p satisfy 0.95≦k≦1.05, 0.05≦m≦0.70, 0.002≦n≦0.050, and 0≦p≦0.30, respectively.)

The rare earth aluminate having the composition represented by formula (I) is excited by light from a light-emitting element having a dominant wavelength in the range of 400 nm to 500 nm, converts the wavelength of the light emitted from the light-emitting element, and emits light from the light-emitting device having a dominant wavelength in the range of 475 nm to 500 nm.

In the formula (I), the molar ratio of Ce is the product of the variable n and 3. The variable n is 0.002 or more, may be 0.003 or more, may be 0.004 or more, may be 0.005 or more, may be 0.050 or less, may be 0.045 or less, may be 0.040 or less, may be 0.035 or less, or may be 0.030 or less. Ce acts as an activator for the rare earth aluminate phosphor. In the formula (I), the variable n may be in the range of 0.002 to 0.045 (0.002≦n≦0.045), 0.002 to 0.040 (0.002≦n≦0.040), 0.003 to 0.040 (0.003≦n≦0.040), or 0.003 to 0.035 (0.003≦n≦0.035). The molar ratio of Ce in 1 mole of the rare earth aluminate phosphor having the composition represented by the formula (I) is preferably in the range of 0.006 to 0.15. When the molar ratio of Ce is in the range of 0.006 to 0.15, the luminescence brightness is high and the desired luminescence color can be obtained.

In the formula (I), the molar ratio of Ga is the product of the variable m, the variable k in the range of 0.95 to 1.05, and 5. The variable m is in the range of 0.05 to 0.70 (0.05≦m≦0.70), may be in the range of 0.10 to 0.70 (0.10≦m≦0.70), or may be in the range of 0.10 to 0.60 (0.10≦m≦0.60). The variable m may be 0.20 or more, 0.30 or more, 0.55 or less, or 0.50 or less. The molar ratio of Ga in 1 mole of the rare earth aluminate phosphor having the composition represented by the formula (I) is preferably in the range of 0.2375 to 3.15. In the formula (I), the molar ratio of Ga, together with Al, is expressed as the product of the variables k, m, and 5. By adjusting the variable m to be within the range of 0.05 to 0.70, the emission peak wavelength of the phosphor can be changed, and when used in a light-emitting device, the desired emission color can be obtained.

In the formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb. The rare earth element Ln acts as a coactivator together with the activator Ce. Ln may be at least one rare earth element selected from the group consisting of Y, La, and Gd, and Ln may be Y. In the formula (I), the molar ratio of the at least one rare earth element Ln selected from the group consisting of Y, La, Gd, and Tb is the product of the variable p and 3. In the formula (I), the rare earth element Ln may not be included. In the formula (I), the variable p may be in the range of 0 to 0.20 (0≦p≦0.20). In the formula (I), the variable p may be in the range of 0.001 to 0.20 (0.001≦p≦0.20).

In the formula (I), it is preferable that m, n, and p satisfy the following conditions: 0.10≦m≦0.70, 0.002≦n≦0.040, and 0≦p≦0.20, respectively. By adjusting the molar ratio of Ce, which acts as an activator, the molar ratio of Ga, and, if necessary, the molar ratio of the rare earth element Ln, the desired emission color can be obtained when used in a light-emitting device.

Method for Producing Rare Earth Aluminate Phosphor The rare earth aluminate phosphor can be produced by heat treating a raw material mixture of compounds containing each element, such as oxides containing each element of Lu, Ce, Al, Ga, and at least one rare earth element Ln selected from the group consisting of Y, La, Gd, and Tb as necessary, or carbonates or hydroxides that become oxides by thermal decomposition. A raw material mixture obtained by mixing only the raw materials before heat treatment may be called a first raw material mixture. The rare earth aluminate phosphor can also be produced by using a coprecipitate containing all or part of each element constituting the rare earth aluminate phosphor. For example, a coprecipitate containing the elements can be obtained by adding an aqueous solution of an alkali or carbonate to an aqueous solution containing at least one element selected from the group consisting of Lu, Ce, Al, Ga, and at least one element selected from the group consisting of Y, La, Gd, and Tb as necessary. The rare earth aluminate phosphor can also be produced by drying and heat treating the coprecipitate. The rare earth aluminate phosphor may be produced by using a flux, and the flux is preferably a fluoride containing the element constituting the rare earth aluminate phosphor. The flux may be at least one selected from the group consisting of BaF ₂ , AlF ₃ and CeF _3. The flux is preferably used in an amount of 0.1 to 10 parts by mass, and may be used in an amount of 0.5 to 8.0 parts by mass, per 100 parts by mass of the raw material mixture (or the first raw material mixture). The mixture of the raw material mixture (or the first raw material mixture) and the flux may be referred to as the first mixture.

The heat treatment temperature is preferably in the range of 1000°C to 1800°C, and may be in the range of 1100°C to 1750°C, 1200°C to 1700°C, 1300°C to 1650°C, or 1400°C to 1600°C. For example, an electric furnace, a gas furnace, etc. may be used for the heat treatment.

The heat treatment atmosphere is preferably a reducing atmosphere. The heat treatment can be performed in a reducing atmosphere containing at least one of nitrogen, hydrogen, a reducing compound, and ammonia. In a highly reducing atmosphere, the raw material mixture becomes highly reactive, and a fired product can be obtained by firing under atmospheric pressure without applying pressure. Also, by heat treating the raw material mixture in a highly reducing atmosphere, tetravalent Ce (Ce ⁴⁺ ) is reduced to trivalent Ce (Ce ³⁺ ), and a fired product can be obtained in which the proportion of trivalent Ce that contributes to luminescence in the fired product is increased.

The heat treatment time varies depending on the heating rate, heat treatment atmosphere, etc., but is preferably at least 1 hour, more preferably at least 2 hours, and even more preferably at least 3 hours after the heat treatment temperature is reached, and is preferably within 20 hours, more preferably within 18 hours, and even more preferably within 15 hours.

In the method for producing a rare earth aluminate phosphor, the fired product obtained by heat-treating the raw material mixture is called the first fired product, and the first fired product, a compound containing Lu, a compound containing Ce, a compound containing Al, a compound containing Ga, and a compound containing the rare earth element Ln as necessary are mixed, and the second fired product obtained by the second heat treatment may be obtained as a rare earth aluminate phosphor. A mixture of a compound containing Lu, a compound containing Ce, a compound containing Al, a compound containing Ga, and a compound containing the rare earth element Ln as necessary, not including the first fired product, is called the first raw material mixture, and heat-treating the first raw material mixture may be called the first heat treatment. A mixture of a flux mixed into the first raw material mixture is also called the first mixture. A raw material mixture of a compound containing Lu, a compound containing Ce, a compound containing Al, a compound containing Ga, and a compound containing the rare earth element Ln as necessary, other than the first fired product, which is mixed with the first fired product, is also called the second raw material mixture. The content of the first fired product in the total amount of the second fired product and the second raw material mixture is preferably in the range of 10% by mass to 90% by mass, and may be in the range of 20% by mass to 80% by mass. The mixture of the first fired product and the second raw material mixture may contain a flux. A mixture containing the first fired product, the second raw material mixture, and optionally a flux is also called a second mixture. When a flux is contained, it is preferably used in the range of 0.1 parts by mass to 10 parts by mass, and may be used in the range of 0.5 parts by mass to 8.0 parts by mass, per 100 parts by mass of the second raw material mixture.

The first heat treatment and the second heat treatment can be carried out at the same heat treatment temperature, heat treatment atmosphere, and heat treatment time as described above. The fired product obtained after the first heat treatment is also called the first fired product. The fired product obtained after the second heat treatment is also called the second fired product.

The first fired product and the second fired product may be subjected to a dispersion treatment. The dispersion treatment is performed by wet dispersion, wet sieving, dehydration, drying, dry sieving, etc. As a solvent for wet dispersion, for example, deionized water can be used. The time for wet dispersion varies depending on the solid dispersion medium and solvent used, but is preferably 30 minutes or more, more preferably 60 minutes or more, even more preferably 90 minutes or more, even more preferably 120 minutes or more, and is preferably 420 minutes or less. The dispersion treatment can improve the dispersibility of the rare earth aluminate phosphor in the manufacturing process of the light emitting device.

The first or second fired product after the dispersion treatment may be subjected to an acid treatment in which the product is brought into contact with an acidic solution or a base treatment in which the product is brought into contact with a basic solution. By bringing the first or second fired product into contact with an acidic or basic solution, decomposition products contained in the first or second fired product that have been decomposed during the heat treatment can be removed. The acidic substance contained in the acidic solution may be an inorganic acid such as hydrofluoric acid, nitric acid, or hydrochloric acid, or may be hydrogen peroxide. The basic substance contained in the basic solution may be a hydroxide containing an alkali metal or ammonia. The time for which the first or second fired product is brought into contact with the acidic or basic solution is, for example, 10 minutes to 30 hours, preferably 30 minutes to 25 hours, and more preferably 1 hour to 25 hours, in order to remove thermal decomposition products contained in the first or second fired product. In addition, the temperature at which the first or second fired product is contacted with the acidic or basic solution is preferably from room temperature (about 20° C.) to 300° C., more preferably from 30° C. to 200° C., and even more preferably from 40° C. to 150° C., in order to efficiently remove decomposition products contained in the first or second fired product. After the acid or base treatment, a step of washing the first or second fired product with a liquid medium may be included.

The resulting first fired product and second fired product are rare earth aluminate phosphors having the composition represented by formula (I).

In addition to the rare earth aluminate phosphor having a composition represented by formula (I), the light emitting device preferably includes at least one phosphor selected from the group consisting of a halosilicate phosphor having a composition represented by formula (II), a β-sialon phosphor having a composition represented by formula (III), an oxynitride phosphor having a composition represented by formula (IV), an alkaline earth metal aluminate phosphor having a composition represented by formula (V), an alkaline earth metal sulfide phosphor having a composition represented by formula (VI), a first silicate phosphor having a composition represented by formula (VII), a second silicate phosphor having a composition represented by formula (VIII), a third silicate phosphor or germanate phosphor having a composition represented by formula (IX), and a fourth silicate phosphor having a composition represented by formula (X).
(Ca, Sr, Ba) ₈ MgSi ₄ O ₁₆ (F, Cl, Br) ₂ :Eu (II)
Si _6-z Al _z O _z N _8-z :Eu (0<z≦4.2) (III)
_{BaSi2O2N2 :} Eu ( _IV )
Sr ₄ Al ₁₄ O ₂₅ :Eu (V)
(Sr,Ca,Ba) _{Ga2S4 :} Eu (VI)
(Ba, Sr, Ca) ₂ SiO ₄ :Eu (VII)
(Ba, Sr)ZrSi ₃ O ₉ :Eu (VIII)
_Ca3Sc2 (Si,Ge) _{3O12 : Ce} (IX)
_{( ALi3SiO4} )n:Eu (A is at least one element selected from the group consisting of Li, Na, K, Rb and Cs, and n is an integer from 1 to 8) (X)

In this specification, in the composition formula showing the composition of the phosphor, the multiple elements separated by a comma (,) mean that at least one of these multiple elements is contained in the composition, and two or more of the multiple elements may be contained in combination. In addition, in the formula showing the composition of the phosphor, the part before the colon (:) represents the elements constituting the host crystal and their molar ratio, and the part after the colon (:) represents an activating element. It is understood that the molar amount of the activating element written after the colon (:) does not have to be the same molar amount as the molar amount of the element written before the colon. "Molar ratio" represents the molar amount of an element in 1 mole of the composition of the phosphor.

A halo silicate phosphor having a composition represented by the formula (II), a β-sialon phosphor having a composition represented by the formula (III), an oxynitride phosphor having a composition represented by the formula (IV), an alkaline earth metal aluminate phosphor having a composition represented by the formula (V), an alkaline earth metal sulfide phosphor having a composition represented by the formula (VI), a first silicate phosphor having a composition represented by the formula (VII), a second silicate phosphor having a composition represented by the formula (VIII), a third silicate phosphor having a composition represented by the formula (IX), or a germane At least one phosphor selected from the group consisting of a rare earth aluminate phosphor and a fourth silicate phosphor having a composition represented by the formula (X) is excited by light from a light emitting element having a dominant wavelength in the range of 400 nm to 500 nm, and together with the rare earth aluminate phosphor having a composition represented by the formula (I), converts the wavelength of the light from the light emitting element to emit light from the light emitting device having a dominant wavelength in the range of 475 nm to 500 nm, and having an S/P ratio represented by the formula (1) of 6.5 or less or a melanopic ratio represented by the formula (2) of 3.4 or less.

Wavelength conversion member The wavelength conversion member preferably includes a wavelength conversion body containing a phosphor and a light-transmitting material, and more preferably includes a light-transmitting body on which the wavelength conversion body is arranged. The wavelength conversion body preferably includes a phosphor and a light-transmitting material described later. The wavelength conversion body may be formed in a plate-like, sheet-like or layer-like shape. The wavelength conversion member may include a wavelength conversion body in a form other than a plate-like, sheet-like or layer-like shape. A plate-like wavelength conversion sintered body can also be used as the wavelength conversion member. The plate-like wavelength conversion sintered body can be obtained, for example, by the method disclosed in JP 2018-172628 A using a mixture of a phosphor and an inorganic oxide as a raw material. As the inorganic oxide, for example, aluminum oxide (Al ₂ O ₃ ) can be used.

In the light emitting device, the rare earth aluminate phosphor having the composition represented by formula (I) and the phosphor other than the rare earth aluminate phosphor preferably constitute a wavelength converter together with a translucent material. The wavelength converter may constitute a wavelength conversion member together with a translucent body. The wavelength converter preferably contains the rare earth aluminate phosphor having the composition represented by formula (I) in the range of 1 part by mass to 800 parts by mass, more preferably in the range of 10 parts by mass to 750 parts by mass, and even more preferably in the range of 15 parts by mass to 700 parts by mass, per 100 parts by mass of the translucent material. The light emitting device includes a wavelength conversion member having a wavelength converter containing the rare earth aluminate phosphor represented by formula (I) excited by the light emitted by the light emitting element, and by disposing the wavelength conversion member on the light emission side of the light emitting element, the light from the light emitting element can be efficiently wavelength converted by the rare earth aluminate phosphor having the composition represented by formula (I) contained in the wavelength converter.

In the rare earth aluminate phosphor having a composition represented by the formula (I), when the molar ratio of Ce represented by the product of the variable n and 3 is in the range of 0.018 to 0.150, and the variable n is 0.006≦n≦0.050, the content of the rare earth aluminate phosphor contained in the wavelength converter may be in the range of 10 parts by mass to 800 parts by mass, 20 parts by mass to 780 parts by mass, 30 parts by mass to 750 parts by mass, or 40 parts by mass to 700 parts by mass, relative to 100 parts by mass of the translucent material.

The wavelength converter may contain two or more rare earth aluminate phosphors having different compositions, each of which has a composition represented by the formula (I). In the rare earth aluminate phosphors having different compositions, the molar ratio of Ce represented by the product of the variable n and 3 in the composition represented by formula (I) is in the range of 0.018 to 0.150, and the variable n is 0.006≦n≦0.050. In this case, the total content of the two or more rare earth aluminate phosphors contained in the wavelength converter may be in the range of 10 to 800 parts by mass, 20 to 780 parts by mass, 30 to 750 parts by mass, or 40 to 700 parts by mass, relative to 100 parts by mass of the translucent material.

In the rare earth aluminate phosphor having a composition represented by the formula (I), when the molar ratio of Ga is in the range of 0.5 to 3.0 and the molar ratio of Ce is in the range of 0.015 to 0.040, the content of the rare earth aluminate phosphor contained in the wavelength converter may be in the range of 20 to 700 parts by mass, 40 to 650 parts by mass, 60 to 600 parts by mass, or 80 to 560 parts by mass, relative to 100 parts by mass of the translucent material. In the rare earth aluminate phosphor having a composition represented by the formula (I), when the molar ratio of Ga is in the range of 0.5 to 3.0 and the variable k is in the range of 0.95 to 1.05 (0.95≦k≦1.05), the variable m is in the range of 0.095 to 0.631 (0.095≦m≦0.631). In the rare earth aluminate phosphor having the composition represented by formula (I), when the molar ratio of Ce is within the range of 0.015 to 0.040, the variable n is within the range of 0.005 to 0.013 (0.005≦n≦0.013).
In the rare earth aluminate phosphor having a composition represented by the formula (I), when the molar ratio of Ga is in the range of 0.5 to 2.0 and the molar ratio of Ce is in the range of 0.018 to 0.040, the content of the rare earth aluminate phosphor contained in the wavelength converter may be in the range of 20 to 500 parts by mass, 30 to 400 parts by mass, or 40 to 300 parts by mass, relative to 100 parts by mass of the translucent material. In the rare earth aluminate phosphor having a composition represented by the formula (I), when the molar ratio of Ga is in the range of 0.5 to 2.0 and the variable k is in the range of 0.95 to 1.05 (0.95≦k≦1.05), the variable m is in the range of 0.095 to 0.421 (0.095≦m≦0.421). In the rare earth aluminate phosphor having the composition represented by formula (I), when the molar ratio of Ce is within the range of 0.018 to 0.040, the variable n is within the range of 0.006 to 0.013 (0.006≦n≦0.013).

In addition to the rare earth aluminate phosphor represented by formula (I), the wavelength converter may contain at least one phosphor selected from the group consisting of a halosilicate salt phosphor having a composition represented by formula (II), a β-sialon phosphor having a composition represented by formula (III), an oxynitride phosphor having a composition represented by formula (IV), an alkaline earth metal aluminate phosphor having a composition represented by formula (V), an alkaline earth metal sulfide phosphor having a composition represented by formula (VI), a first silicate phosphor having a composition represented by formula (VII), a second silicate phosphor having a composition represented by formula (VIII), a third silicate phosphor or germanate phosphor having a composition represented by formula (IX), and a fourth silicate phosphor having a composition represented by formula (X). The wavelength converter may contain a total amount of phosphors in the range of 1 part by mass to 900 parts by mass, 10 parts by mass to 850 parts by mass, or 15 parts by mass to 800 parts by mass, per 100 parts by mass of the translucent material.

Translucent material The translucent material may be at least one selected from the group consisting of resin, glass, and inorganic material. The resin is preferably at least one selected from the group consisting of epoxy resin, silicone resin, phenolic resin, and polyimide resin. The inorganic material may be at least one selected from the group consisting of aluminum oxide and aluminum nitride. In addition to the phosphor and the translucent material, the wavelength converter may contain a filler, a colorant, and a light diffusing material as necessary. Examples of the filler include silicon oxide, barium titanate, titanium oxide, and aluminum oxide. The content of other components other than the phosphor and the translucent material contained in the wavelength converter can be in the range of 0.01 parts by mass to 100 parts by mass, and may be in the range of 0.1 parts by mass to 80 parts by mass, or may be in the range of 0.5 parts by mass to 75 parts by mass, based on 100 parts by mass of the translucent material, in terms of the total content of the other components.

Light-transmitting body The wavelength conversion member may include a light-transmitting body. The light-transmitting body may be a plate-shaped body made of a light-transmitting material such as glass or resin. Examples of glass include borosilicate glass and quartz glass. Examples of resin include silicone resin and epoxy resin. The thickness of the light-transmitting body may be any thickness that does not reduce the mechanical strength during the manufacturing process and can sufficiently support the wavelength conversion body.

Light Emitting Device-First Configuration Example A configuration example of a light emitting device is shown. FIG. 6A is a schematic plan view of a light emitting device 100 of the first configuration example. FIG. 6B is a schematic cross-sectional view of the light emitting device 100 shown in FIG. 6A along the line VI-VI'. The light emitting device 100 includes a light emitting element 10 having a dominant wavelength in the range of 400 nm to 500 nm, and a wavelength conversion member 30 including a wavelength conversion body 31 containing at least one phosphor that is excited by light from the light emitting element 10 to emit light, and a light-transmitting body 32 in which the wavelength conversion body 31 is arranged. The light emitting element 10 is flip-chip mounted on a substrate 70 via bumps that are conductive members 60. The wavelength conversion body 31 of the wavelength conversion member 30 is provided on the light emitting surface of the light emitting element 10 via an adhesive layer 80. The light emitting element 10 and the wavelength conversion member 30 have their sides covered by a covering member 90 that reflects light. The wavelength conversion body 31 contains a phosphor that is excited by light from the light emitting element 10 and has at least one emission peak wavelength in a specific wavelength range. The wavelength converter 31 may contain two or more phosphors having different wavelength ranges of emission peak wavelengths. The light emitting element 10 can emit light by receiving power from the outside of the light emitting device 100 through wiring and a conductive member 60 formed on a substrate 70. The light emitting device 100 may include a semiconductor element 50 such as a protective element for protecting the light emitting element 10 from destruction due to application of an excessive voltage. The covering member 90 is provided so as to cover, for example, the semiconductor element 50. Each member used in the light emitting device will be described below. For details, the disclosure of, for example, JP 2014-112635 A may be referred to.

Substrate The substrate is preferably made of an insulating material that is difficult to transmit light from the light emitting element or external light. Examples of the substrate material include ceramics such as aluminum oxide and aluminum nitride, and resins such as phenol resin, epoxy resin, polyimide resin, bismaleimide triazine resin (BT resin), and polyphthalamide (PPA) resin. Ceramics are preferred as a substrate material because of their high heat resistance.

Adhesive layer An adhesive layer is interposed between the light emitting element and the wavelength conversion member, and fixes the light emitting element and the wavelength conversion member. The adhesive constituting the adhesive layer is preferably made of a material that can optically connect the light emitting element and the wavelength conversion member. The material constituting the adhesive layer is preferably at least one resin selected from the group consisting of epoxy resin, silicone resin, phenol resin, and polyimide resin.

Semiconductor elements Semiconductor elements that are provided as necessary in a light-emitting device include, for example, transistors for controlling light-emitting elements and protective elements for preventing damage to or performance degradation of light-emitting elements due to application of excessive voltage. An example of the protective element is a Zener diode.

Covering member It is preferable to use an insulating material as the material of the covering member. More specifically, phenol resin, epoxy resin, bismaleimide triazine resin (BT resin), polyphthalamide (PPA) resin, and silicone resin can be mentioned. A colorant, a phosphor, and a filler may be added to the covering member as necessary.

Conductive Member As the conductive member, a bump can be used, and as the material of the bump, Au or its alloy can be used, and as other conductive members, eutectic solder (Au-Sn), Pb-Sn, lead-free solder, etc. can be used.

Manufacturing method of light emitting device - First configuration example An example of a manufacturing method of a light emitting device will be described. For details, the disclosure of, for example, JP 2014-112635 A or JP 2017-117912 A can be referenced. The manufacturing method of the light emitting device preferably includes a step of arranging a light emitting element, a step of arranging a semiconductor element as necessary, a step of forming a wavelength conversion member including a wavelength converter, a step of bonding the light emitting element and the wavelength conversion member, and a step of forming a covering member.

In the step of arranging the light emitting element, the light emitting element is arranged on the substrate and mounted. The light emitting element and the semiconductor element are mounted on the substrate by, for example, flip chip mounting.

In the step of forming a wavelength conversion member containing a wavelength converter, the wavelength conversion member may be obtained by forming a plate-shaped, sheet-shaped or layer-shaped wavelength conversion member on one surface of a transparent body by a printing method, an adhesion method, a compression molding method or an electrodeposition method. For example, the printing method can print a composition for a wavelength conversion member containing a phosphor and a resin serving as a binder or a solvent on one surface of a transparent body to form a wavelength conversion member containing a wavelength conversion member.

Step of Adhering Light Emitting Device and Wavelength Conversion Member In the step of adhering the light emitting device and the wavelength conversion member, the wavelength conversion member is opposed to the light emitting surface of the light emitting device and is bonded onto the light emitting device by an adhesive layer.

In the process of forming the covering member, the side surfaces of the light-emitting element and the wavelength conversion member except for the light-emitting surface are covered with a composition for the covering member, and a covering member is formed on the side surfaces of the light-emitting element and the wavelength conversion member except for the light-emitting surface. This covering member is for reflecting light emitted from the light-emitting element, and is formed so as to cover the side surfaces without covering the light-emitting surface of the wavelength conversion member and to embed the semiconductor element.

In this manner, the light-emitting device shown in Figures 6A and 6B can be manufactured.

Light-emitting device - second configuration example Fig. 7 is a schematic cross-sectional view of a light-emitting device 200 of a second configuration example. The light-emitting device 200 is the same as the light-emitting device 100, except that the light-emitting device 200 includes a wavelength conversion member 30 made of a wavelength converter 31 containing at least one phosphor that emits light when excited by light from the light-emitting element 10. In Fig. 7, the same members as those in the light-emitting device 100 are given the same reference numerals. The wavelength conversion member 30 may be made of the wavelength converter 31 without including the translucent body 32.

Manufacturing method of light emitting device - second configuration example The manufacturing method of the light emitting device of the second configuration example can be manufactured in the same manner as the manufacturing method of the light emitting device of the first configuration example, except that in the wavelength conversion member forming step, a wavelength conversion member made of a wavelength converter is formed. The wavelength converter is formed in advance in a plate-like, sheet-like or layer-like shape by curing a composition for wavelength converters containing a phosphor and a translucent material, and is then cut into individual pieces of a size that can be arranged on the light emitting element, to prepare a wavelength conversion member made of a plate-like, sheet-like or layer-like wavelength converter. In this manner, the light emitting device of the second configuration example can be manufactured. As described above, the wavelength conversion member can also be a plate-like wavelength conversion sintered body.

Light-emitting device - third configuration example FIG. 8 is a schematic cross-sectional view of a light-emitting device 300 of a third configuration example. The light-emitting device 300 includes, for example, a molded body 41, a light-emitting element 11, and a wavelength conversion member 33. The molded body 41 is formed by integrally molding a first lead 51, a second lead 52, and a resin part 42 containing a thermoplastic resin or a thermosetting resin. The molded body 41 forms a recess having a bottom surface and a side surface, and the light-emitting element 11 is placed on the bottom surface of the recess. The light-emitting element 11 has a pair of positive and negative electrodes, and the pair of positive and negative electrodes are electrically connected to the first lead 51 and the second lead 52 via wires 63, respectively. The light-emitting element 11 is covered with a wavelength conversion member 33. The wavelength conversion member 33 includes a phosphor 21 that converts the wavelength of light from the light-emitting element 11 and a translucent material. The phosphor 21 is excited by light from the light-emitting element to have at least one emission peak wavelength in a specific wavelength range, and may include two or more phosphors having different wavelength ranges of emission peak wavelengths. The first lead 51 and the second lead 52 connected to a pair of positive and negative electrodes of the light emitting element 11 have portions exposed toward the outside of the package constituting the light emitting device 300. Through these first lead 51 and second lead 52, power can be supplied from the outside to cause the light emitting device 300 to emit light.

The translucent material used in the wavelength conversion member may be the same as the translucent material used in the wavelength conversion member of the first or second configuration example. In addition, the wavelength conversion member may contain a filler, a colorant, and a light diffusing material as necessary, similar to the wavelength conversion members of the first and second configuration examples.

Manufacturing method of light emitting device - third configuration example A manufacturing method of a light emitting device of the third configuration example will be described. For details, the disclosure of JP 2010-062272 A can be referred to. The manufacturing method of the light emitting device preferably includes a molded body preparation step, a light emitting element arrangement step, a wavelength conversion member composition arrangement step, and a resin package formation step. When an aggregate molded body having a plurality of recesses is used as the molded body, a singulation step of separating the resin packages of each unit area may be included after the resin package formation step.

In the step of preparing a molded body, a plurality of leads are integrally molded using a thermosetting resin or a thermoplastic resin to prepare a molded body having a recess having a side surface and a bottom surface. The molded body may be a molded body made of an aggregate base including a plurality of recesses.
In the light-emitting element arrangement step, the light-emitting element is arranged on the bottom surface of the recess of the molded body, and the positive and negative electrodes of the light-emitting element are connected to the first lead and the second lead by wires.
In the step of placing the composition for a wavelength conversion member, the composition for a wavelength conversion member is placed in the recess of the molded body.
In the resin package molding process, the composition for wavelength conversion member arranged in the recess of the molded body is cured to form a resin package, and a light emitting device is manufactured. When a molded body made of an aggregate base having a plurality of recesses is used, after the resin package forming process, the aggregate base having a plurality of recesses is separated into each resin package of each unit area in a singulation process, and individual light emitting devices are manufactured. In this manner, the light emitting device of the third configuration example shown in FIG. 8 can be manufactured.

The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples.

Rare earth aluminate phosphor A
Preparation of raw materials Lutetium oxide (Lu ₂ O ₃ ), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), and gallium oxide (Ga ₂ O ₃ ) were used as raw materials, and raw materials consisting of each compound were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound satisfied the following composition to obtain a raw material mixture. 7.0 mass% of barium fluoride (BaF ₂ ) was added as a flux relative to the total amount of 100 mass%, and each raw material was mixed in a ball mill to obtain a mixture. The raw materials were prepared so that the charged composition was (Lu _0.987 Ce _0.012 ) ₃ (Al _0.9 Ga _0.1 ) ₅ O ₁₂ .
Heat Treatment The resulting mixture was placed in an alumina crucible and heat treated at 1600° C. for 10 hours in a reducing atmosphere to obtain a fired product.
Dispersion treatment The obtained fired material, alumina balls as a dispersion medium, and deionized water were placed in a container and dispersed for 4 hours while rotating. After that, coarse particles were removed by wet sieving. Then, sedimentation classification was performed to remove fine particles.
Acid Washing Treatment The fired product obtained by sedimentation classification was washed with an aqueous hydrochloric acid solution having a hydrochloric acid concentration of 17% by mass, then washed with water, separated and dried, and the fired product after the acid washing treatment was obtained as rare earth aluminate phosphor A.

Rare earth aluminate phosphor B
Rare earth aluminate phosphor B was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound satisfied the following composition. The raw materials were prepared so that _{the charged} composition was ( _{Lu0.987Ce0.013} ) ₃ ( _Al0.8Ga0.2 ) _{5O12 .}

Rare earth aluminate phosphor C
Rare earth aluminate phosphor C was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound had the following composition: _{( Lu0.987Ce0.013} ) _{3 ( Al0.7Ga0.3 )5O12 .}

Rare earth aluminate phosphor D
Rare earth aluminate phosphor D was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared from the respective compounds of Lu, Ce, _Al and Ga so that the respective elements satisfied the following composition. The raw materials were prepared so that the charged composition was ( _{Lu0.987Ce0.013} ) _{3 ( Al0.6Ga0.4} ) _{5O12 .}

Rare earth aluminate phosphor E
Raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound had the following composition. Rare earth aluminate phosphor E was obtained in the same manner as for rare earth aluminate phosphor A, except that the heat treatment was performed at ₁₅₀₀ ° C. for 10 hours. The raw materials were prepared so that the charged composition was ( _{Lu0.995Ce0.005} ) _{3 ( Al0.6Ga0.4} ) _{5O12 .}

Rare earth aluminate phosphor F
Rare earth aluminate phosphor F was obtained in the same manner as for rare earth aluminate phosphor E, except that raw materials were prepared so that the elements Lu, Ce, Al _, and Ga contained the following compounds: The raw materials were prepared so that the charged composition was ( _{Lu0.995Ce0.005} ) _{3 ( Al0.5Ga0.5} ) _{5O12 .}

Rare Earth Aluminate Phosphor G
Rare earth aluminate phosphor G was obtained in the same manner as for rare earth aluminate phosphor E, except that raw materials consisting of each compound of Lu, Ce, _Al and Ga were prepared so that each element satisfied the following composition. The raw materials were prepared so that the charged composition was ( _{Lu0.995Ce0.005} ) _{3 ( Al0.4Ga0.6} ) _{5O12 .}

Rare earth aluminate phosphor H
Rare earth aluminate phosphor H was obtained in the same manner as for rare earth aluminate phosphor E, except that the heat treatment was performed in an air atmosphere at 1500° C. for 10 hours. The raw materials were prepared so that the charged composition was (Lu _0.995 Ce _0.005 ) ₃ (Al _0.6 Ga _0.4 ) ₅ O ₁₂ .

Rare Earth Aluminate Phosphor I
Preparation of raw materials (first mixture)
Lutetium oxide (Lu ₂ O ₃ ), cerium oxide (CeO ₂ ), aluminum oxide (Al ₂ O ₃ ), and gallium oxide (Ga ₂ O ₃ ) were used as raw materials, and raw materials consisting of each compound were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound satisfied the following composition. 7.0 mass% of barium fluoride (BaF ₂ ) was added as a flux relative to the total amount of 100 mass%, and each raw material was mixed in a ball mill to obtain a first mixture. The raw materials were prepared so that the charged composition was (Lu _0.995 Ce _0.005 ) ₃ (Al _0.6 Ga _0.4 ) ₅ O ₁₂ .
First Heat Treatment The obtained first mixture was placed in an alumina crucible and heat-treated at 1500° C. for 10 hours in a reducing atmosphere to obtain a first fired product.
Second mixture The obtained first fired product, lutetium oxide ( _Lu2O3 ), cerium oxide ( _CeO2 ), _aluminum oxide ( _Al2O3 ), and gallium oxide ( _Ga2O3 ) _were used as raw materials, and raw materials consisting of each compound were prepared so that the elements Lu, _Ce , Al, and Ga contained in the first fired product and each compound satisfied the above composition, and a second raw material mixture was obtained by adding 7.0 mass% of barium fluoride ( _BaF2 ) as a flux relative to the total amount of 100 mass%. The first fired product and the second raw material mixture were mixed using a ball mill so that the mass ratio was 7:3, and a second mixture was obtained.
The obtained second mixture was placed in an alumina crucible and heat-treated in a reducing atmosphere at 1500° C. for 10 hours to obtain a second fired product. This second fired product was subjected to a dispersion treatment and an acid washing treatment in the same manner as for the rare earth aluminate A to obtain rare earth aluminate phosphor I.

Rare earth aluminate phosphor J
Rare earth aluminate phosphor J was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared from the respective compounds of Lu, Ce, _Al and Ga so that the respective elements satisfied the following composition. The raw materials were prepared so that the charged composition was ( _{Lu0.993Ce0.007} ) _{3 ( Al0.6Ga0.4} ) _{5O12 .}

Rare earth aluminate phosphor K
Rare earth aluminate phosphor K was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained _in each compound satisfied the following composition. The raw materials were prepared so that the _charged composition was ( _{Lu0.992Ce0.008} ) ₃ ( _Al0.6Ga0.4 ) _{5O12 .}

Rare earth aluminate phosphor L
Rare earth aluminate phosphor L was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound had _the following composition: _{( Lu0.990Ce0.010} ) _{3 ( Al0.6Ga0.4} ) _5O12 .

Rare earth aluminate phosphor M
Rare earth aluminate phosphor M was obtained in the same manner as for rare earth aluminate phosphor A, except that raw materials were prepared from the respective compounds of Lu, Ce, _Al and Ga so that the respective elements satisfied the following composition. The raw materials were prepared so that the charged composition was ( _{Lu0.988Ce0.012} ) _{3 ( Al0.6Ga0.4} ) _{5O12 .}

Rare earth aluminate phosphor N
Rare earth aluminate phosphor N was obtained in the same manner as for rare earth aluminate phosphor A _, except that raw materials were prepared so that the elements Lu, Ce, Al, and Ga contained in each compound had the following composition: The raw materials were prepared so that the charged composition was ( _{Lu0.987Ce0.013} ) _{3 ( Al0.6Ga0.4} ) _{5O12 .}

Evaluation of Rare Earth Aluminate Phosphor The obtained rare earth aluminate phosphor was evaluated as follows. The evaluation results are shown in Table 1. In Table 1, Ga (molar ratio) and Ce (molar ratio) are the molar ratios of each element in the charged composition.

Luminescence characteristics The luminescence characteristics of each phosphor were measured. The luminescence characteristics of the phosphors were measured by irradiating each phosphor with an excitation light having a wavelength of 420 nm using a quantum efficiency measuring device (QE-2000, manufactured by Otsuka Electronics Co., Ltd.) and measuring the emission spectrum at room temperature (25°C ± 5°C). From the emission spectrum of each phosphor, the chromaticity coordinates (x, y) and luminance (%) in the chromaticity coordinate system in the CIE chromaticity diagram were obtained for each phosphor.

Examples 1-1 to 1-3
A light emitting device was manufactured using rare earth aluminate A. For the manufacturing method of the light emitting device, the disclosure of JP 2010-062272 A can be referred to. Specifically, a molded body having a first lead, a second lead, and a recess having a bottom surface and a side surface was prepared. A light emitting element using a nitride semiconductor having a dominant wavelength of 455 nm was prepared, and the light emitting element was placed on the bottom surface of the recess and connected to the first lead and the second lead by wire. A composition for wavelength converter containing rare earth aluminate phosphor A in the amount shown in Table 2 (Example 1-1: 20 parts by mass, Example 1-2: 40 parts by mass, Example 1-3: 60 parts by mass) per 100 parts by mass of silicone resin as a light transmissive material was prepared, and the composition for wavelength converter was filled in the recess of the molded body. The composition for wavelength converter was cured by heating at 150° C. for 4 hours, and a wavelength conversion member made of a wavelength converter covering the light emitting element was formed to form a resin package, thereby manufacturing a light emitting device.

Examples 2-1 to 2-3
A light emitting device was manufactured using rare earth aluminate phosphor B. A composition for a wavelength converter containing rare earth aluminate phosphor B in the amount shown in Table 2 (Example 2-1: 20 parts by mass, Example 2-2: 40 parts by mass, Example 2-3: 60 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Examples 3-1 to 3-3
A light emitting device was manufactured using rare earth aluminate phosphor C. A composition for a wavelength converter containing rare earth aluminate phosphor C in the amount shown in Table 2 (Example 3-1: 40 parts by mass, Example 3-2: 60 parts by mass, Example 3-3: 80 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Comparative Example 4-1, Examples 4-2 to 4-5
A light emitting device was manufactured using rare earth aluminate phosphor D. A composition for a wavelength converter containing rare earth aluminate phosphor D in the amount shown in Table 2 (Comparative Example 4-1: 20 parts by mass, Example 4-2: 40 parts by mass, Example 4-3: 60 parts by mass, Example 4-4: 90 parts by mass, Example 4-5: 120 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Comparative Example 1
A light emitting element using a nitride semiconductor with a dominant wavelength of 454 nm was prepared, and a light emitting device of the first embodiment was manufactured in the same manner as in Example 1-1, except that no phosphor was used.

Comparative Example 2
A light emitting element using a nitride semiconductor with a dominant wavelength of 484 nm was prepared, and a light emitting device of the first embodiment was manufactured in the same manner as in Example 1-1, except that no phosphor was used.

Comparative Example 3
A light emitting element using a nitride semiconductor with a dominant wavelength of 495 nm was prepared, and a light emitting device of the first embodiment was manufactured in the same manner as in Example 1-1, except that no phosphor was used.

The following evaluations were performed for each light-emitting element and each light-emitting device. The evaluation results for each light-emitting device are shown in Table 2.

Evaluation of light-emitting element (dominant wavelength of light-emitting element)
For each of the light-emitting elements used in the examples and comparative examples, the chromaticity coordinates (x, y) in the chromaticity coordinate system of the CIE 1931 chromaticity diagram were measured using an optical measurement system combining a spectrophotometer (PMA-11, Hamamatsu Photonics K.K.) and an integrating sphere. A line was drawn to connect the chromaticity coordinates (x E , y E ) of white light in the CIE 1931 chromaticity diagram to the chromaticity coordinates (x _E , y _E ) of the emitted color of each light-emitting element, and the wavelength at the point where the extended line intersects with the spectral locus was determined as the dominant wavelength.

Evaluation of light-emitting device Luminous flux, luminous flux ratio, radiant flux (spectral total radiant flux), and chromaticity coordinates (x, y) of light-emitting device
For each light-emitting device, the luminous flux, radiant flux (spectral total radiant flux: mW), and chromaticity coordinates (x, y) in the chromaticity coordinate system of the CIE 1931 chromaticity diagram were determined using an optical measurement system combining a spectrophotometer (PMA-11, Hamamatsu Photonics K.K.) and an integrating sphere.

Dominant wavelength λd of the light emitting device
The dominant wavelength of each light-emitting device was determined by drawing a line connecting the chromaticity coordinates (x = 0.3333, y = 0.3333) of white light on the CIE 1931 chromaticity diagram with the chromaticity coordinates (x, y) of the emitted color of each light-emitting device, and finding the wavelength at the point where the extended line intersected with the spectral locus.

S/P Ratio For each light emitting device, the S/P ratio, which is the ratio of luminous flux in scotopic vision to luminous flux in photopic vision, was calculated based on the above formula (1).

Emission spectrum of the light-emitting device The emission spectrum of each light-emitting device was measured at room temperature (25°C ± 5°C) using an optical measurement system combining a spectrophotometer (PMA-11, Hamamatsu Photonics K.K.) and an integrating sphere. The relative emission spectrum of each light-emitting device was calculated by taking the maximum emission intensity in the emission spectrum of each light-emitting device as 1.

Melanopic Ratio The melanopic ratio was calculated based on the above formula (2) from the spectral distribution of each light-emitting device, the sensitivity curve (absorbance) of ipRGC, and the luminosity curve in human photopic vision.

Ratio of integral values of emission spectrum Ib/Ia
In the relative emission spectrum of each light emitting device, the ratio Ib/Ia of the integral Ib in the wavelength range of 380 nm to 531 nm to the integral Ia in the wavelength range of 380 nm to 780 nm was determined.

The light emitting device of each embodiment emits light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and the S/P ratio, which is the ratio of the luminous flux in scotopic vision to the luminous flux in photopic vision, was 6.5 or less. Even when emitting light having a dominant wavelength in the wavelength range of blue to green, including blue-green, the light emitting device of each embodiment reduces the difference between the luminous flux in a dark place and the luminous flux in a bright place, appears bright in both scotopic and photopic vision, and is considered to be able to maintain excellent visibility.

The light emitting device of each embodiment emitted light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and had a melanopic ratio of 3.4 or less. The light emitting device of each embodiment was considered to be unlikely to have a significant effect on human circadian rhythms, and to be capable of emitting light having a dominant wavelength in the wavelength range from blue to green, including blue-green, which can evoke a specific image as a signal color indicating a specific state of a device, such as when charging.

The light emitted from the light emitting device of each example and having a dominant wavelength in the range of 475 nm to 500 nm exhibited an emission color in the region A1 shown in FIG. 3 and the region A2 shown in FIG. 4 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting devices of Examples 3-2, 4-2, 4-3, 4-4, and 4-5 exhibited an emission color of blue to blue-green in the region A3 shown in FIG. 5, within the regions A1 and A2.

The light emitting device of each embodiment has an integral value ratio Ib/Ia in the range of 0.6 to 0.95, and is considered to be capable of emitting light that reduces the difference in brightness perceived by humans in both scotopic and photopic vision, while maintaining excellent visibility that appears bright in both scotopic and photopic vision.

The light emitting device of Comparative Example 1 emitted light having a dominant wavelength of less than 475 nm and an S/P ratio of more than 6.5, and it was assumed that the light emitting device of Comparative Example 1 may be perceived as being too bright when viewed in a dark place. In addition, the light emitting device of Comparative Example 1 emitted light having a dominant wavelength of less than 475 nm and had a melanopic ratio of more than 3.4, and it was considered that the light emitting device of Comparative Example 1 may affect the human circadian rhythm. In addition, the light emitting device of Comparative Example 1 emitted light having a dominant wavelength of less than 475 nm and did not exhibit the emission color within the region A1 shown in Figure 3. In addition, the light emitting device of Comparative Example 1 had an integral value ratio Ib/Ia of more than 0.95, and it was assumed that the light emitting device of Comparative Example 1 may be perceived as being too bright in a dark place.

The light emitting device of Comparative Example 2 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, but the S/P ratio exceeded 6.5, and it was assumed that the light may be perceived as too bright when viewed in a dark place. The light emitting device of Comparative Example 2 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, and the melanopic ratio exceeded 3.4, and it was considered that the light may affect the human circadian rhythm. The light emitting device of Comparative Example 2 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, and exhibited the emission color in the region A1 shown in Figure 3, but did not exhibit the emission color in the region A2 shown in Figure 4 or the region A3 shown in Figure 5. The light emitting device of Comparative Example 2 also had an integral value ratio Ib/Ia exceeding 0.95, and it was assumed that the light may be perceived as too bright in a dark place.

The light emitting device of Comparative Example 3 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, but the S/P ratio exceeded 6.5, and it was assumed that the light may be perceived as too bright when viewed in a dark place. The light emitting device of Comparative Example 3 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, and the melanopic ratio exceeded 3.4, and it was considered that the light may affect the human circadian rhythm. The light emitting device of Comparative Example 3 emitted light having a dominant wavelength in the range of 475 nm to 500 nm, and this light exhibited the emission color in the region A1 shown in FIG. 3 and the region A2 shown in FIG. 4, but did not exhibit the emission color in the region A3 shown in FIG. The light emitting device of Comparative Example 3 also had an integral value ratio Ib/Ia exceeding 0.95, and it was assumed that the light may be perceived as too bright in a dark place.

In the light emitting device of Comparative Example 4-1, the molar ratio of Ga in the composition of rare earth aluminate phosphor D contained in the wavelength conversion member is relatively high, and the molar ratio of Ce is also relatively high. As a result, the emission peak wavelength of rare earth aluminate phosphor D changes compared to phosphors with a low molar ratio of Ga, and when the content of rare earth aluminate phosphor D is low, light having a dominant wavelength in the range of 475 nm to 500 nm is not emitted.

Comparative Examples 5-1 to 5-2, Examples 5-3 to 5-7
A light emitting device was manufactured using rare earth aluminate phosphor E. A composition for a wavelength converter containing rare earth aluminate phosphor E in the amount shown in Table 3 (Comparative Example 5-1: 20 parts by mass, Comparative Example 5-2: 40 parts by mass, Example 5-3: 60 parts by mass, Example 5-4: 90 parts by mass, Example 5-5: 120 parts by mass, Example 5-6: 200 parts by mass, Example 5-7: 280 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Comparative Examples 6-1 to 6-4, Examples 6-5 to 6-9
A light emitting device was manufactured using rare earth aluminate phosphor F. A composition for a wavelength converter containing rare earth aluminate phosphor F in the amount shown in Table 3 (Comparative Example 6-1: 20 parts by mass, Comparative Example 6-2: 40 parts by mass, Comparative Example 6-3: 60 parts by mass, Comparative Example 6-4: 100 parts by mass, Example 6-5: 200 parts by mass, Example 6-6: 300 parts by mass, Example 6-7: 400 parts by mass, Example 6-8: 450 parts by mass, Example 6-9: 550 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Comparative Examples 7-1 to 7-4, Examples 7-5 to 7-11
A light emitting device was manufactured using rare earth aluminate phosphor G. A composition for wavelength converter containing rare earth aluminate phosphor G in the amount shown in Table 3 (Comparative Example 7-1: 20 parts by mass, Comparative Example 7-2: 40 parts by mass, Comparative Example 7-3: 60 parts by mass, Comparative Example 7-4: 150 parts by mass, Example 7-5: 250 parts by mass, Example 7-6: 350 parts by mass, Example 7-7: 450 parts by mass, Example 7-8: 560 parts by mass, Example 7-9: 600 parts by mass, Example 7-10: 650 parts by mass, Example 7-11: 700 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for wavelength converter was used.

Comparative Examples 8-1 to 8-4, Examples 8-5 to 8-8
A light emitting device was manufactured using rare earth aluminate phosphor H. A composition for a wavelength converter containing rare earth aluminate phosphor H in the amount shown in Table 3 (Comparative Example 8-1: 20 parts by mass, Comparative Example 8-2: 40 parts by mass, Comparative Example 8-3: 60 parts by mass, Comparative Example 8-4: 100 parts by mass, Example 8-5: 200 parts by mass, Example 8-6: 300 parts by mass, Example 8-7: 400 parts by mass, Example 8-8: 450 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Comparative Examples 9-1 to 9-2, Examples 9-3 to 9-6
A light emitting device was manufactured using rare earth aluminate phosphor I. A composition for a wavelength converter containing rare earth aluminate phosphor I in the amount shown in Table 3 (Comparative Example 9-1: 20 parts by mass, Comparative Example 9-2: 40 parts by mass, Example 9-3: 60 parts by mass, Example 9-4: 120 parts by mass, Example 9-5: 200 parts by mass, Example 9-6: 300 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 1-1, except that this composition for a wavelength converter was used.

Each light-emitting device was evaluated in the same manner as in Example 1-1. The results are shown in Table 3.

The light emitting device of each embodiment emits light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and the S/P ratio, which is the ratio of the luminous flux in scotopic vision to the luminous flux in photopic vision, is 6.5 or less. Even when emitting light having a dominant wavelength in the wavelength range of blue to green, including blue-green, the light emitting device of each embodiment reduces the difference between the luminous flux in a dark place and the luminous flux in a bright place, appears bright in both scotopic and photopic vision, and is thought to be able to maintain excellent visibility and reduce the difference in brightness perceived by humans.

The light emitting device of each embodiment emitted light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and had a melanopic ratio of 3.4 or less. It was considered that the light emitting device of each embodiment could emit light having a dominant wavelength in the wavelength range from blue to green, including blue-green, which can evoke a specific image as a signal color indicating a specific state of a device, such as when charging, without significantly affecting human circadian rhythms.

The light emitted from the light emitting device of each example and having a dominant wavelength in the range of 475 nm to 500 nm exhibited an emission color in the region A1 shown in FIG. 3 and the region A2 shown in FIG. 4 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting devices of Example 5-5, Example 5-6, Examples 6-6 to 6-9, Examples 7-7 to 7-11, Examples 8-5 to 8-8, and Example 9-5 exhibited an emission color of blue to blue-green in the region A3 shown in FIG. 5, within the regions A1 and A2.

The light emitting device of each embodiment has an integral value ratio Ib/Ia in the range of 0.6 to 0.95, and is considered to be capable of emitting light that reduces the difference in brightness perceived by humans in both scotopic and photopic vision, while maintaining excellent visibility that appears bright in both scotopic and photopic vision.

In the light emitting devices of Comparative Examples 5-1 to 5-2, 6-1 to 6-4, 7-1 to 7-4, 8-1 to 8-3, and 9-1, the molar ratio of Ga is relatively high and the molar ratio of Ce is low in the compositions of the rare earth aluminate phosphors E to I contained in the wavelength conversion member, so that the luminance is low, and when the content of the rare earth aluminate phosphors E to I is low, light having a dominant wavelength of less than 475 nm is emitted, and the S/P ratio exceeds 6.5, and it is assumed that when viewed in a dark place, it may be perceived as being too bright. In addition, each of the light emitting devices of Comparative Examples 5-1 to 5-2, 6-1 to 6-4, 7-1 to 7-4, 8-1 to 8-3, and 9-1 emits light having a dominant wavelength of less than 475 nm, and the melanopic ratio exceeds 3.4, and there is a possibility that it may affect the human circadian rhythm. In the light emitting devices of Comparative Example 8-4 and Comparative Example 9-2, the molar ratio of Ga in the composition of the rare earth aluminate phosphor H or I contained in the wavelength conversion member is relatively high, so the emission peak wavelength of the rare earth aluminate phosphor H or I changes compared to phosphors with a low molar ratio of Ga, and when the content of the rare earth aluminate phosphor H or I is low, light having a dominant wavelength in the range of 475 nm to 500 nm is not emitted.

Example 10-1, Comparative Examples 10-2 to 10-3
A light emitting device having the embodiment shown in FIG. 6A and FIG. 6B was manufactured.
In the process of arranging the light-emitting element, a ceramic substrate made of aluminum nitride was used as the substrate. The light-emitting element used was a light-emitting element in which a nitride-based semiconductor layer having a dominant wavelength of 450 nm was laminated. The size of the light-emitting element was a roughly square shape of about 1.0 mm square in plan view, and the thickness was about 0.11 mm. The light-emitting element was arranged so that the light-emitting surface was on the substrate side, and flip-chip mounted by bumps using a conductive material made of Au. In addition, the semiconductor element was flip-chip mounted by bumps using a conductive material made of Au with a gap between the light-emitting element and the semiconductor element.

In the process of forming a wavelength converter including a wavelength conversion member, rare earth aluminate phosphor A was used. A composition for a wavelength converter was prepared containing rare earth aluminate phosphor A in the amount shown in Table 4 (Example 10-1: 100 parts by mass, Comparative Example 10-2: 150 parts by mass, Comparative Example 10-3: 200 parts by mass) relative to 100 parts by mass of silicone resin as a translucent material, and 15 parts by mass of aluminum oxide as a filler. As a translucent body, a translucent body was prepared that was made of borosilicate glass, had a planar shape of approximately 1.15 mm square, was approximately 0.15 mm larger in length and width than the planar shape of the light-emitting element, and had a thickness of approximately 0.10 mm. The composition for the wavelength converter was printed by a printing method on one surface of the approximately square shape of the translucent body, and then heated at 180°C for 2 hours to harden the composition for the wavelength converter, forming a layered wavelength converter with a thickness of approximately 80 μm, forming a wavelength conversion member in which the layered or plate-shaped wavelength converter and the translucent body are integrated.

In the process of bonding the light-emitting element and the wavelength conversion member, one surface of the wavelength conversion member, which has a planar shape of approximately 1.15 mm square, and one surface of the light-emitting element, which has a planar shape of approximately 1.0 mm square, are bonded together using an adhesive containing silicone resin, forming an adhesive layer between the light-emitting element and the wavelength conversion member.

In the process of forming the covering member, a composition for the covering member was prepared, which contained dimethyl silicone resin and titanium oxide particles with an average particle size (catalog value) of 0.28 μm, and contained 30 parts by mass of titanium oxide particles per 100 parts by mass of dimethyl silicone resin. The side surfaces of the light emitting element and the wavelength conversion member including the wavelength conversion body and the light transmitting body arranged on the substrate were covered with the composition for the covering member, and the composition for the covering member was filled so that the semiconductor element was completely embedded in the composition for the covering member, and the composition for the covering member was cured to form the covering member, forming a resin package, and the light emitting device was manufactured.

Examples 11-1 to 11-2, Comparative Example 11-3
A light emitting device was manufactured by mixing rare earth aluminate phosphor A and rare earth aluminate phosphor H in a weight ratio of 50:50. A composition for a wavelength converter containing a mixture of rare earth aluminate phosphor A and rare earth aluminate phosphor H in the amount shown in Table 4 (Example 11-1: 200 parts by mass, Example 11-2: 300 parts by mass, Comparative Example 11-3: 500 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 10-1, except that this composition for a wavelength converter was used.

Examples 12-1 to 12-3
A light emitting device was manufactured using rare earth aluminate phosphor H. A composition for a wavelength converter containing rare earth aluminate phosphor H in the amount shown in Table 4 (Example 12-1: 400 parts by mass, Example 12-2: 500 parts by mass, Example 12-3: 600 parts by mass) was prepared, and a light emitting device was manufactured in the same manner as in Example 10-1, except that this composition for a wavelength converter was used.

The light emitting device of each embodiment emits light having a dominant wavelength in the range of 475 nm or more and 500 nm or less, and the S/P ratio, which is the ratio of the luminous flux in scotopic vision to the luminous flux in photopic vision, is 6.5 or less. Even when emitting light having a dominant wavelength in the wavelength range of blue to green, including blue-green, the light emitting device of each embodiment reduces the difference between the luminous flux in a dark place and the luminous flux in a bright place, appears bright in both scotopic and photopic vision, and is thought to be able to maintain excellent visibility and reduce the difference in brightness perceived by humans.

The light emitting device of each embodiment emitted light having a dominant wavelength in the range of 475 nm to 500 nm, and had a melanopic ratio of 3.4 or less. The light emitting device of each embodiment emitted light having a dominant wavelength in the wavelength range of blue to green, including blue-green, which is unlikely to have a significant effect on human circadian rhythms and can evoke a specific image as a signal color indicating a specific state of a device, such as when charging.

The light emitted from the light emitting device of each example and having a dominant wavelength in the range of 475 nm to 500 nm exhibited an emission color in the region A1 shown in FIG. 3 and the region A2 shown in FIG. 4 in the xy chromaticity coordinate system of the CIE 1931 chromaticity diagram. The light emitting device of Example 12-3 exhibited an emission color of blue to blue-green in the region A3 shown in FIG. 5, among the regions A1 and A2.

The light emitting device of each embodiment has an integral value ratio Ib/Ia in the range of 0.6 to 0.95, and is considered to be capable of emitting light that reduces the difference in brightness perceived by humans in both scotopic and photopic vision, while maintaining excellent visibility that appears bright in both scotopic and photopic vision.

In the light emitting devices of Comparative Examples 10-2 to 10-3 and Comparative Example 11-3, the rare earth aluminate phosphor A contained in the wavelength converter had high brightness, and when the content of the rare earth aluminate phosphor was too high, light with a dominant wavelength exceeding 500 nm was emitted, and light with a dominant wavelength in the range of 475 nm to 500 nm was not emitted.

The light-emitting device according to one aspect of the present invention can be used as a light-emitting device for general lighting, a light-emitting device for vehicles, a display device, a lighting fixture, a display, etc.

10, 11: Light-emitting element, 21: Phosphor, 30, 33: Wavelength conversion member, 31: Wavelength conversion body, 32: Light-transmitting body, 41: Molded body, 42: Resin part, 50: Semiconductor element, 51: First lead, 52: Second lead, 60: Conductive member, 63: Wire, 70: Substrate, 80: Adhesive layer, 90: Covering member, 100, 200, 300: Light-emitting device.

Claims (11)

A light emitting element having a dominant wavelength in the range of 400 nm to 500 nm;
a wavelength conversion member disposed on a light emission side of the light emitting element, the wavelength conversion member including a rare earth aluminate phosphor having a composition represented by the following formula (I):
(Lu _1-p-n Ln _p Ce _n ) ₃ (Al _1-m Ga _m ) _5k O ₁₂ (I)
(In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and k, m, n, and p satisfy 0.95≦k≦1.05, 0.05≦m≦0.70, 0.002≦n≦0.050, and 0≦p≦0.30, respectively.)
Emitting light having a dominant wavelength in the range of 475 nm or more and 500 nm or less;
A light emitting device having an S/P ratio, which is a ratio of luminous flux in scotopic vision to luminous flux in photopic vision, derived from the following formula (1) of 6.5 or less.

(In formula (1), the constant K is 6831 (lm/W), the constant K' is 1700 (lm/W), and within the wavelength λnm range of 360 nm or more and 830 nm or less, V(λ) is the standard spectral luminous efficiency for human photopic vision, V'(λ) is the standard spectral luminous efficiency for human scotopic vision, and Φ _e (λ) is the spectral total radiant flux of light emitted from the light emitting device.) A light emitting element having a dominant wavelength in the range of 400 nm to 500 nm;
a wavelength conversion member disposed on a light emission side of the light emitting element, the wavelength conversion member including a rare earth aluminate phosphor having a composition represented by the following formula (I):
(Lu _1-p-n Ln _p Ce _n ) ₃ (Al _1-m Ga _m ) _5k O ₁₂ (I)
(In formula (I), Ln is at least one rare earth element selected from the group consisting of Y, La, Gd, and Tb, and k, m, n, and p satisfy 0.95≦k≦1.05, 0.05≦m≦0.70, 0.002≦n≦0.050, and 0≦p≦0.30, respectively.)
Emitting light having a dominant wavelength in the range of 475 nm or more and 500 nm or less;
A light-emitting device having a melanopic ratio, calculated from the following formula (2), of 3.4 or less.

(In formula (2), in the wavelength range of 380 nm or more and 730 nm or less, "Lamp x Circadian" is a circadian response included in the spectral distribution of the light emitting device, "Lamp x Visual" is a luminosity response included in the spectral distribution of the light emitting device, "Lamp" is the spectral distribution of the light emitting device, "Circadian" is a sensitivity curve of intrinsic photosensitive retinal ganglion cells, which are photoreceptors in the retina of mammals, "Visual" is a luminosity curve in human photopic vision, and "1.218" is a constant (lux factor).) 3. The light emitting device according to claim 1, wherein in an xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, a first point is (x=0.0082, y=0.5384), a second point is (x=0.1096, y=0.0868), a third point is (x=0.210, y=0.190), and a fourth point is (x=0.260, y=0.380), and the light emitting device emits light within an area A1 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point , the light emitting device according to claim 1, wherein the light emitting device emits light within an area A1 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the light emitting device according to claim 1, The light emitting device of claim 1 , wherein the S/P ratio is 6.0 or less. The light emitting device according to claim 1 , wherein the S/P ratio is 3.0 or more. The light emitting device of claim 2 , wherein the melanopic ratio is 1.4 or greater. The light emitting device according to any one of claims 1 to 6, wherein the ratio Ib/Ia of the integral Ib of the emission spectrum in the wavelength range of 380 nm to 531 nm to the integral Ia of the emission spectrum in the wavelength range of 380 nm to 780 nm in the emission spectrum of the light emitting device is in the range of 0.6 to 0.95. 8. The light emitting device according to claim 1, wherein in an xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, a first point is (x=0.0350, y=0.4127), a second point is (x=0.0800, y=0.2149), a third point is (x=0.2150, y=0.2106), and a fourth point is (x=0.2550, y=0.3550), and the light emitting device emits light within an area A2 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the light emitting device according to claim 1, wherein the light emitting device emits light within an area A2 defined by a first line connecting the second point and the third point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the light emitting device according to claim 1, 9. The light emitting device according to claim 1, wherein in an xy chromaticity coordinate system of the CIE 1931 chromaticity diagram, a first point is (x=0.1825, y=0.3252), a second point is (x=0.1550, y=0.2149), a third point is (x=0.1930, y=0.2106), and a fourth point is (x=0.2205, y=0.3209), and the light emitting device emits light within an area A3 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the light emitting device according to claim 1, wherein the light emitting device emits light within an area A3 defined by a first line connecting the first point and the second point, a second line connecting the second point and the third point, a third line connecting the third point and the fourth point, and a fourth line connecting the fourth point and the first point, the light emitting device according to claim 1, 10. The light emitting device according to claim 1 , further comprising at least one phosphor selected from the group consisting of a rare earth aluminate phosphor having a composition represented by formula (I), a halosilicate phosphor having a composition represented by formula (II), a β-sialon phosphor having a composition represented by formula (III), an oxynitride phosphor having a composition represented by formula (IV), an alkaline earth metal aluminate phosphor having a composition represented by formula (V), an alkaline earth metal sulfide phosphor having a composition represented by formula (VI), a first silicate phosphor having a composition represented by formula (VII), a second silicate phosphor having a composition represented by formula (VIII), a third silicate phosphor or germanate phosphor having a composition represented by formula (IX), and a fourth silicate phosphor having a composition represented by formula (X).
(Ca, Sr, Ba) ₈ MgSi ₄ O ₁₆ (F, Cl, Br) ₂ :Eu (II)
Si _6-z Al _z O _z N _8-z :Eu (0<z≦4.2) (III)
_{BaSi2O2N2 :} Eu ( _IV )
Sr ₄ Al ₁₄ O ₂₅ :Eu (V)
(Sr,Ca,Ba) _{Ga2S4 :} Eu (VI)
(Ba, Sr, Ca) ₂ SiO ₄ :Eu (VII)
(Ba, Sr)ZrSi ₃ O ₉ :Eu (VIII)
_Ca3Sc2 (Si,Ge) _{3O12 : Ce} (IX)
_{( ALi3SiO4} )n:Eu (A is at least one element selected from the group consisting of Li, Na, K, Rb and Cs, and n is an integer from 1 to 8) (X) The light-emitting device according to any one of claims 1 to 10, wherein k, m, n, and p in formula (I) satisfy 0.95≦k≦1.05, 0.3≦m≦0.5, 0.002≦n≦0.04, and 0≦p≦0.20, respectively.

Images