JP7707616B2 - Wavelength conversion member and light emitting device - Google Patents

Description

The present invention relates to a wavelength conversion material that converts the wavelength of light emitted by a light-emitting diode (LED) or a laser diode (LD) to another wavelength, and a light-emitting device that uses the wavelength conversion material.

In recent years, light-emitting devices using LEDs and LDs have been attracting attention as the next generation of light-emitting devices to replace fluorescent lamps and incandescent lamps, from the viewpoints of low power consumption, small size and light weight, and easy light intensity adjustment. As an example of such a light-emitting device, for example, the following Patent Document 1 discloses a light-emitting device in which a wavelength conversion member is disposed on an LED that emits blue light, which absorbs part of the light from the LED and converts it to yellow light. This light-emitting device emits white light, which is a composite light of the blue light emitted from the LED and the yellow light emitted from the wavelength conversion member.

Light-emitting devices using LEDs and LDs have been proposed not only for general lighting applications, but also for sensing applications in combination with wavelength conversion materials and sensors. For example, the following Patent Document 2 discloses a light source for a methane gas sensor that includes a light-emitting element that emits ultraviolet light and/or visible light and a phosphor layer provided on the light-emitting element.

JP 2000-208815 A JP 2013-170205 A

If the excitation light leaks out together with the fluorescence, it may adversely affect the sensor's function. Furthermore, ultraviolet light, when its wavelength is small, is likely to have adverse effects on the human body. For this reason, in the light-emitting device described in Patent Document 2, a filter that does not transmit the excitation light but transmits only the fluorescence is formed on the surface of the phosphor layer. However, forming such a filter on the surface of the phosphor layer causes problems in that the manufacturing process becomes complicated, leading to increased costs.

In view of the above, the present invention aims to provide a wavelength conversion material and a light-emitting device using the wavelength conversion material that can efficiently excite phosphors even when ultraviolet light is used as the excitation light, and that can suppress deterioration of surrounding materials and effects on the human body due to leakage of ultraviolet light.

The wavelength conversion member of the present invention is a wavelength conversion member for converting the wavelength of excitation light emitted from a light source, comprising: a first layer composed of a first glass matrix and phosphor particles dispersed in the first glass matrix; and a second layer formed on the first layer and composed of a second glass matrix, wherein the first layer is provided on the light source side, and a difference |T A -T _B | between a transmittance T _A of the first glass matrix and a transmittance T _B of the second glass matrix at an excitation wavelength is larger than a difference |L _A -L _B | between a transmittance L _A of the first glass matrix and a transmittance L _B of the second _glass matrix at a fluorescence wavelength, and T _A >T _B.

In the present invention, the difference between the transmittance difference at the excitation wavelength and the transmittance difference at the fluorescence wavelength, |T _A -T _B |-|L _A -L _B |, is preferably 20% or more.

In the present invention, it is preferable that the transmittance _TA of the first glass matrix at an excitation wavelength is 20% or more, and the transmittance _TB of the second glass matrix at an excitation wavelength is 65% or less.

In the present invention, it is preferable that the first glass matrix has a transmittance _LA at a fluorescent wavelength of 50% or more, and the second glass matrix has a transmittance _LB at a fluorescent wavelength of 50% or more.

In the present invention, it is preferable that the second layer does not substantially contain phosphor particles.

In the present invention, it is preferable that the thickness of the second layer is greater than the thickness of the first layer.

In the present invention, it is preferable that the thickness ratio of the second layer to the first layer (second layer/first layer) is 1 or more and 30 or less.

In the present invention, it is preferable that the excitation light is UV light.

In the present invention, it is preferable that the fluorescence is visible light.

The light-emitting device according to the present invention is characterized by comprising a light source that emits excitation light and a wavelength conversion member configured according to the present invention.

The present invention provides a wavelength conversion material and a light-emitting device using the wavelength conversion material that can efficiently excite phosphors even when UV light is used as the excitation light, and that can suppress deterioration of surrounding materials and effects on the human body due to leakage of UV light without the use of an external filter.

FIG. 1 is a schematic front cross-sectional view showing a wavelength conversion member according to one embodiment of the present invention. FIG. 2 is a diagram showing an example of the transmittance spectrum of the first glass matrix and the second glass matrix. FIG. 3 is a schematic front cross-sectional view showing a light-emitting device according to one embodiment of the present invention. FIG. 4 is a schematic front cross-sectional view showing a modified example of a light-emitting device according to an embodiment of the present invention. FIG. 5 is a diagram showing an example of an energy distribution spectrum of light emitted from the exit surface side of a wavelength conversion member when irradiated with a UVLED.

The following describes preferred embodiments. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. In addition, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

[Wavelength conversion material]
Fig. 1 is a schematic front cross-sectional view showing a wavelength conversion member according to one embodiment of the present invention. As shown in Fig. 1, the wavelength conversion member 1 of this embodiment has a rectangular plate shape. However, the wavelength conversion member 1 may have a substantially circular plate shape, and the shape is not particularly limited.

The wavelength conversion member 1 comprises a first layer 2 and a second layer 3. The first layer 2 has a first main surface 2a and a second main surface 2b. The second layer 3 is provided on the first main surface 2a of the first layer 2. The second main surface 2b of the first layer 2 is the surface on which the light source 7 is provided. Therefore, the second layer 3 is provided on the side opposite the light source 7.

The first layer 2 is a phosphor glass composed of a first glass matrix 4 and phosphor particles 5. In this embodiment, the phosphor particles 5 are dispersed in the first glass matrix 4. The second layer 3 is composed of a second glass matrix 6.

In this embodiment, as shown in FIG. 1, excitation light A from a light source 7 is emitted to the wavelength conversion member 1. The excitation light A is incident on the first layer 2 from the second main surface 2b side. When the excitation light A is irradiated onto the first layer 2 in which the phosphor is arranged, fluorescence B is emitted. The fluorescence B passes through the second layer 3 and is emitted from the wavelength conversion member 1.

2 is a diagram showing an example of the transmittance spectrum of the first glass matrix 4 and the second glass matrix 6 constituting such a wavelength conversion member 1. Note that FIG. 2 shows the transmittance spectrum of each of the first glass matrix 4 and the second glass matrix 6 alone. The transmittance spectrum of the first glass matrix 4 and the second glass matrix 6 is measured for a glass plate having a thickness of 1 mm. This glass plate can be produced by vacuum firing a compact of glass powder (average particle size 2.5 μm) which is the raw material of the first glass matrix 4 or the second glass matrix 6 at the softening point of the glass powder + 50°C to obtain a sintered body, and then cutting, lapping, or polishing the obtained sintered body to a thickness of 1 mm. The transmittance shown in this patent refers to the total light transmittance of a sintered body having a thickness of 1 mm that has been polished and polished, and can be measured by a method conforming to JIS K7105. The transmittance spectrum of the first glass matrix 4 and the second glass matrix 6 can be measured by a spectrophotometer.

As shown in FIG. 2, in this embodiment, the absolute value |T _A -T _B | of the difference between the transmittance T _A of the first glass matrix 4 and the transmittance T _B of the second glass matrix 6 at the excitation wavelength is larger than the absolute value |L _A -L _B | of the difference between the transmittance L _A of the first glass matrix 4 and the transmittance L _B of the second glass matrix 6 at the fluorescence wavelength. More specifically, the transmittance T _A of the first glass matrix 4 is larger than the transmittance T _B of the second glass matrix 6 at the excitation wavelength. On the other hand, at the fluorescence wavelength, the transmittance L _A of the first glass matrix 4 and the transmittance L _B of the second glass matrix 6 are both large, and the difference between them is small. In the present invention, the excitation wavelength means the wavelength at which the emission intensity of the excitation light source is maximum, and the fluorescence wavelength means the wavelength at which the fluorescence intensity is maximum. In this embodiment, the transmittance of the excitation wavelength means the transmittance of UV light, specifically, at a wavelength of 200 nm to 380 nm. The transmittance of the fluorescent wavelength refers to the transmittance of visible light, specifically, at wavelengths of 380 nm to 800 nm.

When UV light as excitation light A is incident on the wavelength conversion member 1 using the first glass matrix 4 and the second glass matrix 6 having such optical properties, the absorption of the excitation light A by the glass can be reduced because the transmittance of the first glass matrix 4 constituting the first layer 2 at the excitation wavelength is high, and the wavelength can be efficiently converted to fluorescence in the first layer 2. On the other hand, in the second layer 3, the transmittance of the second glass matrix 6 constituting the second layer 3 at the excitation wavelength is low, so that the UV light as the excitation light A can be blocked in the second layer 3. Therefore, deterioration of surrounding materials and effects on the human body due to leakage of UV light can be suppressed. In addition, since the transmittance of the first glass matrix 4 and the second glass matrix 6 constituting the first layer 2 and the second layer 3 at the fluorescent wavelength is high, fluorescence can be efficiently emitted. Therefore, according to the wavelength conversion member 1 of this embodiment, even when UV light is used as the excitation light A, the phosphor can be efficiently excited, and deterioration of surrounding materials and effects on the human body due to leakage of UV light can be suppressed.

In the present invention, the difference |T _A -T _B |-|L _A -L _B | between the transmittance difference at the excitation wavelength and the transmittance difference at the fluorescence wavelength is preferably 20% or more, more preferably 40% or more, even more preferably 60% or more, and particularly preferably 75% or more. When the difference |T _A -T _B |-|L _A -L _B | is equal to or more than the lower limit, the phosphor can be excited more efficiently while further suppressing deterioration of surrounding members and effects on the human body due to leakage of UV light. The upper limit of the difference |T _A -T _B |-|L _A -L _B | is not particularly limited, but can be, for example, 95%.

In the present invention, it is preferable that the thickness of the second layer 3 is greater than the thickness of the first layer 2. In this case, it is possible to more reliably block UV light while further increasing the efficiency of fluorescent light emission.

In particular, the thickness ratio of the second layer 3 to the first layer 2 (second layer 3/first layer 2) is preferably 1 or more, more preferably 1.5 or more, even more preferably 2 or more, and preferably 30 or less, more preferably 10 or less, and even more preferably 7 or less. When the thickness ratio (second layer 3/first layer 2) is equal to or greater than the lower limit, UV light can be more reliably blocked while the emission efficiency of the fluorescent light can be further increased. On the other hand, when the thickness ratio (second layer 3/first layer 2) is equal to or less than the upper limit, the luminous intensity of the wavelength conversion member can be further increased.

The total thickness of the wavelength conversion member 1 is preferably 0.1 mm or more, more preferably 0.125 mm or more, even more preferably 0.15 mm or more, particularly preferably 0.175 mm or more, and most preferably 0.2 mm or more. The total thickness of the wavelength conversion member 1 is preferably 1.5 mm or less, more preferably 1 mm or less, even more preferably 0.75 mm or less, particularly preferably 0.5 mm or less, and most preferably 0.3 mm or less. When the total thickness of the wavelength conversion member 1 is equal to or greater than the lower limit, the luminescence intensity and mechanical strength of the wavelength conversion member 1 can be further increased. When the thickness of the wavelength conversion member 1 is equal to or less than the upper limit, the scattering and absorption of light in the wavelength conversion member 1 can be further suppressed, and the emission efficiency of the fluorescence can be further increased.

As described below, the first glass matrix 4 and the second glass matrix 6 are basically produced by stacking and simultaneously firing green sheets that are the raw materials for each layer, so it is preferable that the difference in softening point between the glass powder used in the first glass matrix 4 and the glass powder used in the second glass matrix 6 is small. The difference in softening point between the glass powder used in the first glass matrix 4 and the glass powder used in the second glass matrix 6 is preferably 200°C or less, more preferably 100°C or less, even more preferably 50°C or less, and particularly preferably 10°C or less, and it is most preferable that the softening points of both are the same.

(First Layer)
The first layer 2 is composed of a first glass matrix 4 and phosphor particles 5 dispersed in the first glass matrix 4 .

A first glass matrix;
The first glass matrix 4 is made of glass that can be used as a dispersion medium for phosphor particles 5 such as inorganic phosphors. The first glass matrix 4 is also made of glass that transmits UV light and fluorescent light (UV light transmitting glass).

The transmittance _TA of the first glass matrix 4 at the excitation wavelength is preferably 20% or more, more preferably 40% or more, even more preferably 60% or more, and particularly preferably 80% or more. When the transmittance _TA of the first glass matrix 4 at the excitation wavelength is equal to or more than the above lower limit, the absorption of excitation light by the glass can be further reduced, and fluorescence can be emitted more efficiently in the first layer 2. The upper limit of the transmittance _TA of the first glass matrix 4 at the excitation wavelength is not particularly limited, and can be, for example, 95%.

The transmittance _LA of the first glass matrix 4 at the fluorescent wavelength is preferably 50% or more, more preferably 75% or more, and further preferably 80% or more. When the transmittance _LA of the first glass matrix 4 at the fluorescent wavelength is equal to or more than the above lower limit, the first layer 2 can emit fluorescent light more efficiently. The upper limit of the transmittance _LA of the first glass matrix 4 at the fluorescent wavelength is not particularly limited, and can be, for example, 95%.

The glass constituting the first glass matrix 4 is not particularly limited as long as it has the above-mentioned optical properties, and examples that can be used include borosilicate glass, phosphate glass, tin phosphate glass, bismuthate glass, and tellurite glass.

A specific example of the glass constituting the first glass matrix 4 may be glass containing, in mole percent, 40% to 60% SiO ₂ , 0.1% to 35% B ₂ O ₃ , 0.1% to 10% Al ₂ O ₃ , 0% to 10% Li ₂ O , 0% to 10% Na ₂ O , ₀ % to 10% K _{2 O , 0.1% to 10% Li 2 O + Na 2 O +} K 2 O , 0% to 45% MgO , 0% to 45% CaO , 0% to 45% SrO , 0% to 45% BaO , 0.1% to 45% MgO + CaO + SrO + BaO , and 0% to 15% ZnO.

The glass constituting the first glass matrix 4 may be glass containing, in mass %, 55% to 75% _{SiO 2} , 1% to 10% Al ₂ O ₃ , 10% to 30% B ₂ O 3 , 0% to 5% CaO, 0% to 5% BaO, and 1% to 15% Li ₂ O + Na ₂ O + K ₂ O.

Furthermore, the glass constituting the first glass matrix 4 may be glass containing, in mass %, 60% to 90% SiO ₂ +B ₂ O ₃ , 0% to 20% Li ₂ O +Na ₂ O +K ₂ O, and 0% to 20% MgO +CaO +SrO +BaO.

If the glass constituting the first glass matrix 4 contains _Fe2O3 or _TiO2 , the transmittance of UV light tends to decrease, so the content of these _elements is preferably small, and it is preferable that they are not contained substantially at all. Here, "substantially not contained" means that the raw material is not intentionally contained, and objectively means that the content is less than 1000 ppm.

In this specification, "x+y+..." means the total amount of each component.

The softening point of the first glass matrix 4 is preferably 250°C to 1000°C, more preferably 300°C to 950°C, and even more preferably 500°C to 900°C. If the softening point of the first glass matrix 4 is too low, the mechanical strength and chemical durability of the wavelength conversion member 1 may decrease. In addition, since the heat resistance of the first glass matrix 4 itself is low, there is a risk of softening and deformation due to heat generated from the phosphor particles 5. On the other hand, if the softening point of the first glass matrix 4 is too high, when a firing process is included in the manufacturing process, the phosphor particles 5 may deteriorate and the luminescence intensity of the wavelength conversion member 1 may decrease. From the viewpoint of further increasing the chemical stability and mechanical strength of the wavelength conversion member 1, the softening point of the first glass matrix 4 is preferably 500°C or higher, more preferably 600°C or higher, and even more preferably 650°C or higher. However, if the softening point of the first glass matrix 4 is high, the firing temperature also increases, which tends to result in higher manufacturing costs. Furthermore, if the heat resistance of the phosphor particles 5 is low, there is a risk of deterioration due to firing. Therefore, in order to manufacture the wavelength conversion member 1 more inexpensively or in order to manufacture the phosphor particles 5 with lower heat resistance, the softening point of the first glass matrix 4 is preferably 550°C or less, more preferably 530°C or less, even more preferably 500°C or less, particularly preferably 480°C or less, and most preferably 460°C or less.

Phosphor particles;
The phosphor particles 5 are not particularly limited as long as they emit fluorescence when excitation light is incident on them. Examples of the phosphor particles 5 include oxide phosphors, nitride phosphors, oxynitride phosphors, chloride phosphors, oxychloride phosphors, sulfide phosphors, oxysulfide phosphors, halide phosphors, chalcogenide phosphors, aluminate phosphors, halophosphate chloride phosphors, and garnet compound phosphors. These phosphors may be used alone or in combination. Examples of phosphors that absorb UV light and emit visible light include Lu ₃ Al ₅ O 12 (fluorescence wavelength 550 nm), Si _6-z Al _z O _z N _8-z :Eu (0<z<4.2) (=β-SiAlON:Eu) (fluorescence wavelength 545 nm), and La ₃ Si ₆ N _{11 :} Ce (fluorescence wavelength 535 nm).

The average particle diameter of the phosphor particles 5 is preferably 1 μm or more, and more preferably 5 μm or more. If the average particle diameter of the phosphor particles 5 is too small, the quantum efficiency tends to be poor and the luminous intensity tends to decrease. On the other hand, if the average particle diameter of the phosphor particles 5 is too large, the dispersion state in the first glass matrix 4 tends to be poor and the luminous color tends to be non-uniform. Therefore, the average particle diameter of the phosphor particles 5 is preferably 50 μm or less, and more preferably 25 μm or less.

In this specification, the average particle size refers to the average particle size _D50 measured by a laser diffraction particle size distribution measuring device.

The content of phosphor particles 5 in the first layer 2 is preferably 1 vol% or more, more preferably 3 vol% or more, and even more preferably 5 vol% or more. The content of phosphor particles 5 in the first layer 2 is preferably 70 vol% or less, more preferably 65 vol% or less, and even more preferably 50 vol% or less. If the content of phosphor particles 5 is too small, the thickness of the first layer 2 needs to be increased to obtain the desired fluorescence intensity, and as a result, the light extraction efficiency may decrease due to increased internal scattering of the wavelength conversion member 1 and absorption by the matrix. On the other hand, if the content of phosphor particles 5 is too large, the proportion of glass decreases relatively, and the force of the glass to support the phosphor is weakened, so the mechanical strength of the wavelength conversion member 1 may decrease.

In this embodiment, the second glass matrix 6 is made of a powder sintered body of only glass powder, but is not limited thereto. For example, the second glass matrix 6 may contain other inorganic powders such as filler powder for the purpose of adjusting the thermal expansion coefficient and obtaining a light scattering effect. In this way, the thermal expansion coefficients of the first layer 2 and the second layer 3 can be easily matched, and the occurrence of warping, cracks, etc. of the wavelength conversion member 1 caused by the difference in thermal expansion coefficient can be further suppressed. In addition, the light scattering effect of the filler powder can further improve the luminous intensity of the wavelength conversion member 1. Furthermore, by containing a filler powder with high thermal conductivity, the heat dissipation efficiency of the wavelength conversion member 1 can be further improved. Examples of the filler powder include MgO, Al ₂ O ₃ , BN, and AlN. Among them, MgO, Al ₂ O ₃ , and BN are preferable because they have excellent transmittance in the visible range.

A first layer;
The thickness of the first layer 2 is not particularly limited, but is preferably 0.01 mm or more, more preferably 0.03 mm or more, and preferably 0.5 mm or less, and more preferably 0.3 mm or less. When the thickness of the first layer 2 is equal to or more than the above lower limit, the luminous intensity and mechanical strength of the wavelength conversion member 1 can be further increased. When the thickness of the first layer 2 is equal to or less than the above upper limit, the scattering and absorption of light in the first layer 2 can be further suppressed, and the emission efficiency of the fluorescence can be further increased.

(Second Layer)
The second layer 3 is made of a second glass matrix 6. The second glass matrix 6 is made of glass (UV light blocking glass, etc.) that blocks excitation light (e.g. UV light) and transmits fluorescence.

The transmittance T _B of the second glass matrix 6 at the excitation wavelength is preferably 65% or less, more preferably 40% or less, even more preferably 20% or less, and particularly preferably 10% or less. When the transmittance T _B of the second glass matrix 6 at the excitation wavelength is equal to or less than the above upper limit, the second layer 3 can more reliably block the excitation light, and when the excitation light is, for example, UV light, deterioration of surrounding members and effects on the human body due to leakage of the excitation light can be more reliably suppressed. The lower limit of the transmittance T _B of the second glass matrix 6 at the excitation wavelength is not particularly limited, but can be, for example, 0%.

The transmittance L _B of the second glass matrix 6 at the fluorescent wavelength is preferably 50% or more, more preferably 75% or more, and even more preferably 80% or more. When the transmittance L _B of the second glass matrix 6 at the fluorescent wavelength is equal to or more than the above lower limit, the wavelength conversion member 1 can emit fluorescence more efficiently. The upper limit of the transmittance L _B of the second glass matrix 6 at the fluorescent wavelength is not particularly limited, and can be, for example, 95%.

The glass constituting the second glass matrix 6 is not particularly limited as long as it has the above-mentioned optical properties, and examples that can be used include borosilicate glass, phosphate glass, tin phosphate glass, bismuthate glass, and tellurite glass.

A specific example of the glass constituting the second glass matrix 6 may be glass containing, in mole percent, 40% to 60% SiO ₂ , 0.1% to 35% B ₂ O ₃ , 0.1% to 10% Al ₂ O ₃ , 0% to 10% Li ₂ O , 0% to 10% Na ₂ O , ₀ % to 10% K _{2 O , 0.1% to 10% Li 2 O + Na 2 O +} K 2 O , 0% to 45% MgO , 0% to 45% CaO , 0% to 45% SrO , 0% to 45% BaO , 0.1% to 45% MgO + CaO + SrO + BaO , 0% to 15% ZnO , and 0.001% to 10% CeO ₂ .

The glass constituting the second glass matrix 6 may be glass containing, in mass %, 30% to 85% SiO ₂ , 0% to 30% Al ₂ O ₃ , 0% to 50% B ₂ O ₃ , 0% to 10% Li ₂ O + Na ₂ O + K ₂ O , and 0% to 50% MgO + CaO + SrO + BaO.

The softening point of the second glass matrix 6 is preferably 250°C to 1000°C, more preferably 300°C to 950°C, and even more preferably 500°C to 900°C. If the softening point of the second glass matrix 6 is too low, the mechanical strength and chemical durability of the wavelength conversion member 1 may decrease. On the other hand, if the softening point of the second glass matrix 6 is too high, the phosphor particles 5 may deteriorate and the luminescence intensity of the wavelength conversion member 1 may decrease if a firing process is included in the manufacturing process.

A second layer;
The thickness of the second layer 3 is not particularly limited, but is preferably 0.05 mm or more, more preferably 0.1 mm or more, and preferably 1 mm or less, and more preferably 0.5 mm or less. When the thickness of the second layer 3 is equal to or greater than the lower limit, the second layer 3 can more reliably block the excitation light, and when the excitation light is UV light, for example, deterioration of the surrounding members and effects on the human body due to leakage of the excitation light can be more reliably suppressed. When the thickness of the second layer 3 is equal to or less than the upper limit, scattering and absorption of light in the second layer 3 can be more reliably suppressed, and the emission efficiency of the fluorescence can be more improved.

It is preferable that the second layer 3 does not substantially contain phosphor particles. However, the second layer 3 may contain phosphor particles.

(Method of manufacturing wavelength conversion member)
An example of a method for producing a wavelength conversion member will be described below.

First, a green sheet for forming the first layer is prepared. Specifically, a slurry containing glass particles and phosphor particles 5 that will become the first glass matrix 4 is prepared. The above slurry usually contains a binder resin and a solvent. Next, the prepared slurry is applied onto a supporting substrate, and a doctor blade that is placed at a predetermined distance from the substrate is moved relative to the slurry to form a green sheet for forming the first layer. For example, a resin film such as polyethylene terephthalate can be used as the supporting substrate.

Next, a green sheet for forming the second layer is prepared. Specifically, a slurry containing glass particles that will become the second glass matrix 6 is prepared, and a green sheet for forming the second layer is obtained in the same manner as described above.

The material of the glass particles that will become the first glass matrix 4 and the second glass matrix 6 can be the same as the material of the first glass matrix 4 and the second glass matrix 6 described above. The average particle diameter of the glass particles is preferably 0.1 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. If the average particle diameter of the glass particles is too small, the production cost tends to increase and the handling property tends to decrease. On the other hand, if the average particle diameter of the glass particles is too large, air bubbles tend to remain in the glass matrix after firing in the obtained wavelength conversion member 1, and the light extraction efficiency of the wavelength conversion member 1 may decrease. Therefore, the average particle diameter of the glass particles is preferably 100 μm or less, more preferably 50 μm or less, even more preferably 20 μm or less, and particularly preferably 10 μm or less. It is desirable that the average particle diameter of the phosphor particles is within the range described in the first layer 2 above.

Next, the green sheet for forming the first layer and the green sheet for forming the second layer are laminated by thermocompression or the like to obtain a laminate. The laminate is then fired at a temperature between the softening point of the glass particles and the softening point of the glass particles + 100°C to obtain a wavelength conversion member 1 consisting of a sintered body in which the first layer 2 and the second layer 3 are laminated. The firing is preferably performed in a reduced pressure atmosphere, and more preferably in a vacuum atmosphere. In this case, a wavelength conversion member 1 with even greater density can be obtained. It is also preferable to fire the laminate while sandwiched between a pair of restraining members. In this case, the flatness of the wavelength conversion member 1 (particularly the flatness of the interface between the first layer 2 and the second layer 3) is improved, making it easier to process to the desired thickness in the subsequent polishing process. In addition, it is preferable to perform a debindering process at a temperature lower than the softening point of the glass particles before firing. In this case, the organic component residue that causes light absorption and scattering can be reduced in the obtained wavelength conversion member 1, and the luminous intensity can be further improved.

It is also preferable to polish the first layer 2 in the obtained sintered body to a desired thickness. Specifically, it is preferable to polish the first layer 2 in the sintered body to a predetermined thickness to adjust the chromaticity of the wavelength conversion member 1. The second layer 3 in the obtained sintered body may also be polished to a desired thickness.

The method for manufacturing the wavelength conversion member 1 is not limited to the above method. For example, the first layer-forming green sheet and the second layer-forming green sheet may be fired separately, and then the resulting fired bodies may be bonded by thermocompression or with an adhesive to obtain the wavelength conversion member 1.

[Light-emitting devices]
Fig. 3 is a schematic front cross-sectional view showing a light-emitting device according to one embodiment of the present invention. As shown in Fig. 3, the light-emitting device 11 includes the wavelength conversion member 1 according to the embodiment described above, and a light source 7 that emits excitation light A to the wavelength conversion member 1. In the light-emitting device 11, the light source 7 is disposed so that the excitation light A is directly incident on the wavelength conversion member 1 from the first layer 2 side.

By providing the first layer 2 and the second layer 3 in the wavelength conversion member 1 of the light-emitting device 11, the phosphor can be excited efficiently while suppressing the deterioration of surrounding materials and the effects on the human body due to leakage of UV light.

The arrangement of the light source 7 is not limited to the above. For example, in the modified example shown in FIG. 4, a light guide plate 12 is arranged between the light source 7 and the wavelength conversion member 1. The light source 7 is arranged so that the excitation light A is directly incident on the light guide plate 12. The excitation light A emitted from the light source 7 passes through the light guide plate 12 and is incident on the wavelength conversion member 1. Specifically, the excitation light A enters from an end face of the light guide plate 12, exits from the main surface of the light guide plate 12, and enters the wavelength conversion member 1. Here, the light guide plate 12 uses a material that absorbs the excitation light A as little as possible.

The light-emitting device 11 can be suitably used, for example, as a light-emitting device for sensing and for high color rendering lighting.

The present invention will be described in more detail below based on specific examples. The present invention is not limited to the following examples, and can be modified as appropriate within the scope of the gist of the invention.

Example 1
As glass particles to form the first glass matrix, glass particles _A (softening point: 690°C, thermal expansion coefficient: 86.1 x _10-7 /°C, average particle size: 2.5 μm) having a composition, in mole percent, of SiO2 ₄₅ %, _{Al2O3 4} %, _B2O3 18%, _Li2O 1.5%, _Na2O 1.5%, ^{K2O 1.5} %, BaO 25%, and ZnO 3.5% were prepared.

Next, a slurry-like mixture was obtained by kneading glass particles A, phosphor particles (Lu ₃ Al ₅ O ₁₂ , average particle size: 15 μm), binder resin (Kyoeisha Chemical Co., Ltd., Oricox), plasticizer (dioctyl adipate), dispersant (Kyoeisha Chemical Co., Ltd., Flowren G-700), and organic solvent (methyl ethyl ketone). The obtained slurry-like mixture was formed into a sheet by a doctor blade method and dried at room temperature to obtain a green sheet for forming the first layer. The amount of phosphor particles added was adjusted to be 30 volume % in the first layer.

Next, glass particles X (softening point: 690°C, thermal expansion coefficient _: 86.1 x 10-7/°C, average particle size: 2.5 µm) having a composition, in mol%, of _{SiO2 45} %, _{Al2O3 4} %, _B2O3 18%, _Li2O 1.5%, _Na2O 1.5%, K2O 1.5%, BaO 25%, ZnO ₃ ^% , and CeO2 0.5% were prepared as glass particles to form a second glass matrix.

Next, a slurry-like mixture was obtained by kneading glass particles X, a binder resin (Oricox, manufactured by Kyoeisha Chemical Co., Ltd.), a plasticizer (dioctyl adipate), a dispersant (Florene G-700, manufactured by Kyoeisha Chemical Co., Ltd.), and an organic solvent (methyl ethyl ketone). The resulting slurry-like mixture was formed into a sheet by the doctor blade method and dried at room temperature to obtain a green sheet for forming the second layer.

Next, the green sheet for forming the first layer and the green sheet for forming the second layer were cut to a predetermined size, and then the two were thermocompressed together. The resulting laminate was degreased in an electric furnace, and then vacuum-fired in a vacuum gas replacement furnace at 740°C (the softening point of the glass particles that form the first glass matrix and the glass particles that form the second glass matrix + 50°C). The resulting fired body was polished on each side to the desired layer thickness, thereby obtaining a wavelength conversion member in which the first layer and the second layer were laminated. The thickness of the first layer was 40 μm, and the thickness of the second layer was 160 μm.

Example 2
As glass particles to be the first glass matrix, _glass particles B (softening point: 700° C., thermal expansion coefficient: 41.9× ₁₀ ⁻⁷ /° C., average particle size: 2.5 μm) having a composition, by mass%, of _SiO 2 68%, Al ₂ O 3 4%, B ₂ O ₃ 19%, Na ₂ O ₇ %, K 2 O 1%, and F 2 1% were prepared.

Furthermore, glass particles Y (softening point: 850° C., thermal expansion coefficient: 68.0×10 −7 /° C., average particle size: 2.5 μm) having a composition, in mass%, of SiO ₂ 50%, Al ₂ O ₃ 6%, B ₂ O ₃ 5%, CaO 12%, BaO ²⁵ %, and ZnO 2% were prepared as glass particles to form the second glass matrix.

Vacuum firing was also carried out at 900°C (the higher softening point of the glass particles that will become the first glass matrix and the glass particles that will become the second glass matrix + 50°C).

Otherwise, the wavelength conversion member was obtained in the same manner as in Example 1. The thickness of the first layer was 40 μm, and the thickness of the second layer was 160 μm.

Example 3
As glass particles to form the first glass matrix, _glass particles C (softening point: ₇₃₇ °C, thermal expansion coefficient: 66.0× _10-7 ^/ °C, average particle size: 2.5 μm) having a composition, by mass%, of SiO2 ₇₁ %, _Al2O3 6%, _B2O3 13%, _Na2O 7%, K2O 1%, CaO 1%, and BaO 1% were prepared.

In addition, glass particles Y, the same as those in Example 2, were prepared as glass particles to form the second glass matrix.

Vacuum firing was also carried out at 900°C (the higher softening point of the glass particles that will become the first glass matrix and the glass particles that will become the second glass matrix + 50°C).

Otherwise, the wavelength conversion member was obtained in the same manner as in Example 1. The thickness of the first layer was 40 μm, and the thickness of the second layer was 160 μm.

The transmittance at a wavelength of 250 nm (UV-C transmittance), the transmittance at a wavelength of 280 nm (transmittance at the excitation wavelength), the transmittance at a wavelength of 300 nm (UV-B transmittance), the transmittance at a wavelength of 350 nm (UV-A transmittance), and the transmittance at a wavelength of 550 nm (VIS transmittance = transmittance at the fluorescent wavelength) of the first glass matrix and the second glass matrix used in Examples 1 to 3 were measured, and the results are shown in Table 1 below. The transmittance of the first glass matrix and the second glass matrix was measured on a glass plate having a thickness of 1 mm. This glass plate was prepared by the method described above. The transmittance of the first glass matrix and the second glass matrix was measured using a spectrophotometer (product number V-670, manufactured by JASCO Corporation).

(Comparative Example 1)
As glass particles to be the first glass matrix, glass particles X identical to those used for the second glass matrix in Example 1 were prepared.

Next, a slurry-like mixture was obtained by kneading glass particles X, phosphor particles (Lu ₃ Al ₅ O ₁₂ , average particle size: 15 μm), binder resin (Kyoeisha Chemical Co., Ltd., Oricox), plasticizer (dioctyl adipate), dispersant (Kyoeisha Chemical Co., Ltd., Flowren G-700), and organic solvent (methyl ethyl ketone). The obtained slurry-like mixture was formed into a sheet by a doctor blade method and dried at room temperature to obtain a green sheet. The amount of phosphor particles added was adjusted to be 6 volume % in the obtained wavelength conversion member.

Next, the obtained green sheet was degreased in an electric furnace, and then vacuum-sintered at 740°C in a vacuum gas replacement furnace. The obtained sintered body was polished to the desired layer thickness, thereby obtaining a wavelength conversion member consisting of only the first layer. The thickness of the wavelength conversion member was 200 μm.

(Comparative Example 2)
As glass particles to become the first glass matrix, glass particles A were prepared which were the same as the first glass matrix of Example 1. In other respects, a wavelength conversion member consisting of only a first layer was obtained in the same manner as in Comparative Example 1. The thickness of the wavelength conversion member was 200 μm.

(Comparative Example 3)
As glass particles to be the first glass matrix, glass particles A identical to the first glass matrix of Example 1 were prepared.

In addition, glass particles B, which are the same as the first glass matrix in Example 2, were prepared as glass particles to form the second glass matrix.

Vacuum firing was also performed at 750°C (the higher softening point of the glass particles that will become the first glass matrix and the glass particles that will become the second glass matrix + 50°C).

Otherwise, the wavelength conversion member was obtained in the same manner as in Example 1. The thickness of the first layer was 40 μm, and the thickness of the second layer was 160 μm.

(Comparative Example 4)
As glass particles to be the first glass matrix, glass particles X identical to those used for the second glass matrix in Example 1 were prepared.

In addition, glass particles Y, which are the same as the second glass matrix in Example 2, were prepared as glass particles to form the second glass matrix.

Vacuum firing was also carried out at 900°C (the higher softening point of the glass particles that will become the first glass matrix and the glass particles that will become the second glass matrix + 50°C).

Otherwise, the wavelength conversion member was obtained in the same manner as in Example 1. The thickness of the first layer was 40 μm, and the thickness of the second layer was 160 μm.

(evaluation)
First, the energy distribution spectrum of a UV LED (λp=280 nm) serving as an excitation light source was measured using an emission spectrum measuring device (manufactured by Ocean Photonics, Inc.) The peak intensity at this time was designated as I1.

Next, the wavelength conversion members produced in Examples 1 to 3 and Comparative Examples 1 to 4 were irradiated with a UV LED (λp = 280 nm), and the energy distribution spectrum of the light emitted from the emission surface side of the wavelength conversion member was measured using the same emission spectrum measuring device (Ocean Photonics). As shown in Figure 5, from the obtained energy distribution spectrum, the peak intensity of the transmitted light from the excitation light source was measured as I2, and the fluorescence peak intensity was measured as I3. The measured ratios of I2 to I1 (I2/I1) and the ratios of I3 to I1 (I3/I1) are shown in Table 2 below.

From Table 2, it can be seen that the wavelength conversion materials of Examples 1 to 3 have a small ratio (I2/I1) and are able to adequately block UV light. It can also be seen that the wavelength conversion materials of Examples 1 to 3 have a large ratio (I3/I1) and are able to efficiently excite the phosphor.

On the other hand, in the wavelength conversion materials of Comparative Examples 1 and 4, the ratio (I3/I1) was small, and the phosphor could not be excited efficiently. In addition, in the wavelength conversion materials of Comparative Examples 2 and 3, the ratio (I2/I1) was large, and the UV light could not be sufficiently blocked.

From the above, it has been confirmed that in the wavelength conversion members of Examples 1 to 3 in which the transmittance difference |T _A -T _B | between the first glass matrix and the second glass matrix at the excitation wavelength is larger than the transmittance difference |L _A -L _B | between the first glass matrix and the second glass matrix at the fluorescence wavelength and in which T _A >T _B , even when UV light is used as the excitation light, the phosphor can be efficiently excited and deterioration of surrounding materials and effects on the human body due to leakage of UV light can be suppressed without the use of an external filter.

REFERENCE SIGNS LIST 1... wavelength conversion member 2... first layer 2a... first main surface 2b... second main surface 3... second layer 4... first glass matrix 5... phosphor particles 6... second glass matrix 7... light source 11... light emitting device 12... light guide plate

Claims (11)

A wavelength conversion member for converting a wavelength of excitation light emitted from a light source,
a first layer comprising a first glass matrix and phosphor particles dispersed in the first glass matrix;
a second layer disposed on the first layer and composed of a second glass matrix; and
Equipped with
the first layer is provided on the light source side,
a difference |T _A -T _B | between a transmittance T _A of the first glass matrix and a transmittance T _B of the second glass matrix at an excitation wavelength is greater than a difference |L A -L B | between a transmittance L _A of the first glass matrix and a transmittance L _{B of} the second glass matrix at a fluorescence wavelength , and T _A >T _{B ;}
A wavelength conversion member , wherein a difference between a transmittance difference at the excitation wavelength and a transmittance difference at the fluorescence wavelength, |T _A -T _B |-|L _A -L _B |, is 20% or more . A wavelength conversion member for converting a wavelength of excitation light emitted from a light source,
a first layer comprising a first glass matrix and phosphor particles dispersed in the first glass matrix;
a second layer disposed on the first layer and composed of a second glass matrix; and
Equipped with
the first layer is provided on the light source side,
a difference | T _A -T _B | between a transmittance T _A of the first glass matrix and a transmittance T _B of the second glass matrix at an excitation wavelength is greater than a difference |L A -L B | between a transmittance L _A of the first glass matrix and a transmittance L _{B of} the second glass matrix at a fluorescence wavelength, and T _A >T _{B ;}
A wavelength conversion member, wherein the first glass matrix has a transmittance T _A of 20% or more at an excitation wavelength, and the second glass matrix has a transmittance T _B of 65% or less at an excitation wavelength. 3. The wavelength conversion member according to claim 1, wherein the first glass matrix has a transmittance L _A at a fluorescent wavelength of 50% or more, and the second glass matrix has a transmittance L _B at a fluorescent wavelength of 50% or more. The wavelength conversion member according to any one of claims 1 to 3 , wherein the second layer is substantially free of phosphor particles. The wavelength conversion member according to claim 1 , wherein the second layer has a thickness greater than a thickness of the first layer. The wavelength conversion member according to any one of claims 1 to 5 , wherein a ratio of a thickness of the second layer to that of the first layer (second layer/first layer) is 1 or more and 30 or less. The wavelength conversion member according to any one of claims 1 to 6 , wherein the excitation light is UV light. The wavelength conversion member according to any one of claims 1 to 7 , wherein the fluorescent light is visible light. The second glass matrix is composed of, in mole percent, SiO ₂ 40% to 60%, B ₂ O ₃ 0.1%~35%, Al ₂ O ₃ 0.1%~10%, Li ₂ O 0% to 10%, Na ₂ O 0% to 10%, K ₂ O 0% to 10%, Li ₂ O+Na ₂ O+K ₂ O 0.1% to 10%, MgO 0% to 45%, CaO 0% to 45%, SrO 0% to 45%, BaO 0% to 45%, MgO + CaO + SrO + BaO 0.1% to 45%, ZnO 0% to 15%, CeO ₂ The wavelength conversion member according to any one of claims 1 to 8, which is made of glass containing 0.001% to 10% of fluorine. The second glass matrix is composed of, in mass %, SiO ₂ 30%~85%, Al ₂ O ₃ 0% to 30%, B ₂ O ₃ 0% to 50%, Li ₂ O+Na ₂ O+K ₂ 9. The wavelength conversion member according to claim 1, which is made of glass containing 0% to 10% O and 0% to 50% MgO+CaO+SrO+BaO. A light source that emits excitation light;
A wavelength conversion member according to any one of claims 1 to 10 ,
A light emitting device comprising: