JP7722121B2 - Method for manufacturing wavelength conversion member - Google Patents

Description

The present invention relates to a method for manufacturing a wavelength conversion member that converts the wavelength of light emitted by light-emitting diodes (LEDs), laser diodes (LDs), etc. to another wavelength.

In recent years, light-emitting devices using LEDs and LDs have been attracting increasing attention as next-generation light-emitting devices to replace fluorescent lamps and incandescent lamps, due to their low power consumption, small size and light weight, and easy light intensity adjustment. Patent Document 1, for example, discloses an example of such a light-emitting device in which a wavelength conversion member is placed on an LED that emits blue light, and the wavelength conversion member 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.

Wavelength conversion materials have traditionally been made by dispersing phosphor particles in a resin matrix. However, when exposed to the heat and light emitted by LEDs and LDs, the resin matrix of such wavelength conversion materials can discolor and deform, causing a decrease in the performance of the wavelength conversion material.

In response to this, wavelength conversion materials have been proposed that are made from completely inorganic solids, in which phosphor particles are dispersed and fixed in a glass matrix instead of a resin matrix (see, for example, Patent Documents 2 and 3). Such wavelength conversion materials have the advantage that the glass matrix that serves as the base material is less susceptible to degradation due to the heat and light emitted from the LED, making them less susceptible to problems such as discoloration and deformation.

Japanese Patent Application Laid-Open No. 2000-208815 Japanese Patent Application Laid-Open No. 2003-258308 Patent No. 4895541

Wavelength conversion members such as those described in Patent Documents 2 and 3 can be manufactured, for example, by molding a mixture of glass powder and phosphor particles and then firing it. In this case, if the lot of glass powder or phosphor particles is changed, the chromaticity of the wavelength conversion member obtained may deviate from the target chromaticity even with the same concentration settings as before the lot change due to differences in particle size distribution, etc. This presents a problem in that it is difficult to consistently obtain wavelength conversion members with the desired chromaticity.

The object of the present invention is to provide a method for manufacturing wavelength conversion materials that enables the stable production of wavelength conversion materials with the desired chromaticity.

In a broad aspect, the method for manufacturing a wavelength conversion member according to the present invention is a method for manufacturing a wavelength conversion member by firing a molded body containing phosphor particles, and is characterized by comprising the steps of: preparing a preform containing phosphor particles and determining the correlation between the firing temperature of the preform and the chromaticity after firing; setting a main firing temperature corresponding to the target chromaticity of the wavelength conversion member to be obtained based on the correlation; and firing the molded body containing phosphor particles at the main firing temperature.

The present invention preferably includes the steps of: pre-firing some of a plurality of molded bodies containing phosphor particles and applying the chromaticity determined by the pre-firing to the correlation to set a main firing temperature corresponding to the target chromaticity of the wavelength conversion member to be obtained; and firing the remaining molded bodies of the plurality of molded bodies at the main firing temperature.

In the present invention, when the chromaticity obtained by the pre-firing is higher than the target chromaticity, the main firing temperature may be set higher than the pre-firing temperature.

In the present invention, when the chromaticity obtained by the pre-firing is lower than the target chromaticity, the main firing temperature may be set lower than the pre-firing temperature.

In the present invention, it is preferable that the molded body further contains glass powder.

In the present invention, it is preferable that the molded body has the same composition as the pre-molded body.

In the present invention, the molding is preferably sheet molding or press molding.

Another broad aspect of the method for manufacturing a wavelength conversion member of the present invention is a method for manufacturing a wavelength conversion member by firing a molded body containing phosphor particles, characterized by comprising the steps of: preparing a preform containing phosphor particles; determining the correlation between the firing conditions of the preform and the chromaticity after firing; setting main firing conditions corresponding to the target chromaticity of the wavelength conversion member to be obtained based on the correlation; and firing the molded body containing phosphor particles under the main firing conditions.

The present invention preferably includes a step of setting main firing conditions corresponding to the target chromaticity of the wavelength conversion member obtained by pre-firing some of the multiple molded bodies containing phosphor particles and applying the chromaticity determined by the pre-firing to the correlation, and a step of firing the remaining multiple molded bodies under the main firing conditions.

In the present invention, the firing conditions are preferably firing time, atmospheric pressure, or temperature rise/fall rate.

The present invention provides a method for manufacturing wavelength conversion materials that enables wavelength conversion materials with the desired chromaticity to be consistently obtained.

FIG. 1 is a schematic front cross-sectional view showing a wavelength conversion member manufactured by a method for manufacturing a wavelength conversion member according to one embodiment of the present invention. FIG. 2 is a graph showing an example of the correlation between the firing temperature and chromaticity in the method for producing a wavelength conversion member according to one embodiment of the present invention. FIG. 3(a) is a schematic diagram showing the state of a molded body containing glass powder and phosphor particles before firing, and FIG. 3(b) is a schematic diagram showing the state after firing. FIG. 4 is a graph showing the correlation between the firing temperature and the chromaticity in Example 1.

Preferred embodiments are described below. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. Furthermore, in each drawing, components having substantially the same functions may be referred to by the same reference numerals.

(Wavelength conversion member)
Fig. 1 is a schematic front cross-sectional view showing a wavelength conversion member manufactured by a method for manufacturing a wavelength conversion member according to one embodiment of the present invention. As shown in Fig. 1, the wavelength conversion member 1 is a phosphor glass comprising a glass matrix 2 and phosphor particles 3. In this embodiment, the phosphor particles 3 are dispersed in the glass matrix 2. In this embodiment, the wavelength conversion member 1 has a rectangular plate shape. However, in the present invention, the shape of the wavelength conversion member 1 is not particularly limited.

There are no particular limitations on the glass matrix 2, as long as it can be used as a dispersion medium for phosphor particles 3, such as inorganic phosphors. For example, borosilicate glass, phosphate glass, tin phosphate glass, bismuthate glass, tellurite glass, etc. can be used as the glass matrix 2.

Examples of borosilicate glasses include those containing, by mass%, 30% to 85% _SiO2 , 0% to ₃₀ % _Al2O3 , 0% to 50% _B2O3 , 0% to ₁₀ % _Li2O + _Na2O + _K2O , and 0% to 50% MgO+CaO+SrO+BaO. Examples of tin phosphate glasses include those containing, by mole%, 30% to 90% SnO _and 1% to 70% _P2O5 . Examples of tellurite-based glasses include those containing, in mole percent, 50% or more TeO ₂ , 0% to 45% ZnO, 0% to 50% RO (R is at least one selected from Ca, Sr, and Ba), and 0% to 50% La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ .

The softening point of the glass matrix 2 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 glass matrix 2 is too low, the mechanical strength and chemical durability of the wavelength conversion material 1 may be reduced. Furthermore, because the heat resistance of the glass matrix 2 itself is low, there is a risk of softening and deformation due to heat generated by the phosphor particles 3. On the other hand, if the softening point of the glass matrix 2 is too high, when a firing process is included during manufacturing, the phosphor particles 3 may deteriorate, resulting in a decrease in the luminescence intensity of the wavelength conversion material 1. From the perspective of further enhancing the chemical stability and mechanical strength of the wavelength conversion material 1, the softening point of the glass matrix 2 is preferably 500°C or higher, more preferably 600°C or higher, even more preferably 700°C or higher, particularly preferably 800°C or higher, and most preferably 850°C or higher. Examples of glasses that constitute such glass matrix 2 include borosilicate glasses. However, as the softening point of the glass matrix 2 increases, the firing temperature also increases, which tends to result in higher manufacturing costs. Furthermore, if the phosphor particles 3 have low heat resistance, they may be degraded by firing. Therefore, when manufacturing the wavelength conversion member 1 more inexpensively or when the phosphor particles 3 have lower heat resistance, the softening point of the glass matrix 2 is preferably 550°C or lower, more preferably 530°C or lower, even more preferably 500°C or lower, particularly preferably 480°C or lower, and most preferably 460°C or lower. Examples of glasses that can constitute such a glass matrix 2 include tin phosphate-based glasses, bismuthate-based glasses, and tellurite-based glasses.

A ceramic matrix may be used instead of the glass matrix 2. The use of a ceramic matrix can improve the heat resistance of the wavelength conversion member 1. Examples of ceramics that form the ceramic matrix include Al ₂ O ₃ , MgO, and AlN.

The phosphor particles 3 are not particularly limited as long as they emit fluorescence when exposed to excitation light. Examples of phosphor particles 3 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-based compound phosphors. These phosphors may be used alone or in combination. When blue light is used as the excitation light, for example, a phosphor that emits yellow light as fluorescence can be used. An example of a phosphor that emits yellow light as fluorescence is a YAG phosphor.

The average particle diameter of the phosphor particles 3 is preferably 1 μm or more, and more preferably 5 μm or more. If the average particle diameter of the phosphor particles 3 is too small, the quantum efficiency tends to be poor and the luminescence intensity tends to decrease. On the other hand, if the average particle diameter of the phosphor particles 3 is too large, the dispersion state within the matrix tends to be poor, and the luminescent color tends to become non-uniform. Therefore, the average particle diameter of the phosphor particles 3 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 analyzer.

The content of phosphor particles 3 in the wavelength conversion member 1 is preferably 1 vol% or more, more preferably 1.5 vol% or more, and even more preferably 2 vol% or more. The content of phosphor particles 3 in the wavelength conversion member 1 is preferably 70 vol% or less, more preferably 50 vol% or less, and even more preferably 30 vol% or less. If the content of phosphor particles 3 is too low, the thickness of the wavelength conversion member 1 must be increased to obtain the desired emitted color, which may result in increased internal scattering in the wavelength conversion member 1 and reduced light extraction efficiency. On the other hand, if the content of phosphor particles 3 is too high, the thickness of the wavelength conversion member 1 must be reduced to obtain the desired emitted color, which may reduce the mechanical strength of the wavelength conversion member 1.

The thickness of the wavelength conversion member 1 is preferably 0.01 mm or more, more preferably 0.03 mm or more, even more preferably 0.05 mm or more, particularly preferably 0.075 mm or more, and most preferably 0.1 mm or more. The thickness of the wavelength conversion member 1 is preferably 1 mm or less, more preferably 0.5 mm or less, even more preferably 0.35 mm or less, particularly preferably 0.3 mm or less, and most preferably 0.25 mm or less. If the wavelength conversion member 1 is too thick, light scattering and absorption in the wavelength conversion member 1 may become too great, resulting in low fluorescence emission efficiency. If the wavelength conversion member 1 is too thin, it may be difficult to obtain sufficient luminescence intensity. Furthermore, the mechanical strength of the wavelength conversion member 1 may be insufficient.

The following describes a method for manufacturing a wavelength conversion member of the present invention, such as wavelength conversion member 1.

(Method for manufacturing wavelength conversion member)
The method for manufacturing a wavelength conversion member according to the present invention is a method for manufacturing a wavelength conversion member by firing a molded body containing phosphor particles. Specifically, first, a preform containing phosphor particles is prepared, and the correlation between the firing temperature of the preform and the chromaticity after firing is determined. Next, based on the determined correlation, a main firing temperature corresponding to the target chromaticity of the resulting wavelength conversion member is set. Next, the molded body containing phosphor particles is fired at the set main firing temperature. This adjusts the chromaticity of the resulting wavelength conversion member so that it approaches the target chromaticity.

The method for manufacturing a wavelength conversion material according to the present invention has the above-described configuration, so that wavelength conversion materials with the desired chromaticity can be reliably obtained even when manufacturing conditions such as raw material lots are changed. This is explained in detail below.

In the past, when changing the lot of glass powder or phosphor particles, the chromaticity of the wavelength conversion material obtained could deviate from the target chromaticity due to differences in particle size distribution, even when the same concentration setting was used. This made it difficult to consistently obtain wavelength conversion materials with the desired chromaticity.

In response to this, the inventors focused on the firing temperature of a molded body containing phosphor particles and discovered that the chromaticity of the resulting wavelength conversion member can be adjusted by changing the firing temperature. In particular, they found that by determining the correlation between the firing temperature and the chromaticity after firing in advance and setting the firing temperature based on this correlation, the chromaticity of the resulting wavelength conversion member can be adjusted to approach the target chromaticity. More specifically, as shown in Figure 2, an example of the correlation, they found that the higher the firing temperature, the lower the chromaticity, and the lower the firing temperature, the higher the chromaticity. The reason why the chromaticity of the resulting wavelength conversion member can be adjusted by changing the firing temperature can be explained as follows, with reference to Figure 3.

Figure 3(a) is a schematic diagram showing the state of a molded body containing glass powder and phosphor particles before firing, and Figure 3(b) is a schematic diagram showing the state after firing.

As shown in Figure 3(a), in the molded body 4 before firing, the glass powder 2A and phosphor particles 3 exist in the form of particle clumps, with interfaces between each particle. On the other hand, as shown in Figure 3(b), in the wavelength conversion member 1 after firing, the glass powder 2A has melted to form a glass matrix 2, and the phosphor particles 3 are dispersed within the glass matrix 2.

When the molded body 4 is fired in the state shown in Figure 3(a), interfaces are present during firing, which act as light scattering elements, and the degree of scattering is thought to change depending on the firing temperature. Specifically, the firing temperature changes the state of fusion between the glass powder 2A, which changes the scattering state within the wavelength conversion member 1, changing the degree of incidence of excitation light on the phosphor particles 3, and therefore changing the chromaticity.

In particular, the higher the firing temperature, the more the glass powder particles 2A fuse together, reducing the number of interfaces and scattering within the wavelength conversion member 1, making it easier for the excitation light to pass through the wavelength conversion member 1 as is. As a result, the amount of excitation light incident on the phosphor particles 3 decreases, reducing the amount of light emitted, which is thought to result in a decrease in chromaticity. Furthermore, the lower the firing temperature, the more the glass powder particles 2A fuse together, increasing the number of interfaces and scattering of the excitation light within the wavelength conversion member 1, increasing the amount of excitation light incident on the phosphor particles 3. As a result, the amount of light emitted increases, which is thought to result in an increase in chromaticity.

It is also believed that the degree of scattering changes depending on the firing time. Specifically, the firing time changes the state of fusion between the glass powder particles 2A, which changes the scattering state within the wavelength conversion member 1 and changes the degree of incidence of excitation light on the phosphor particles 3, resulting in a change in chromaticity.

In particular, the longer the firing time, the more the glass powder particles 2A fuse together, reducing the number of interfaces and scattering within the wavelength conversion member 1, making it easier for the excitation light to pass through the wavelength conversion member 1 as is. As a result, the amount of excitation light incident on the phosphor particles 3 decreases, reducing the amount of light emitted, which is thought to result in a decrease in chromaticity. Furthermore, the shorter the firing time, the more the glass powder particles 2A fuse together, increasing the number of interfaces and scattering of the excitation light within the wavelength conversion member 1, increasing the amount of excitation light incident on the phosphor particles 3. As a result, the amount of light emitted increases, which is thought to result in an increase in chromaticity.

In this way, in the present invention, the firing temperature may be set based on the correlation between the firing temperature and the chromaticity after firing, or the firing time may be set based on the correlation between the firing time and the chromaticity after firing. In other words, the firing conditions may be set based on the correlation between firing conditions such as the firing temperature and firing time and the chromaticity after firing.

The firing temperature may be set based on the correlation between the firing temperature and the color after firing, and the firing time may be set based on the correlation between the firing time and the color after firing.

Firing conditions other than firing temperature and firing time may be set based on the correlation between the chromaticity after firing and other firing conditions. Such firing conditions include atmospheric pressure and temperature rise/fall rate.

In this case, the amount of bubbles remaining inside the wavelength conversion material 1 changes depending on the atmospheric pressure during firing, which in turn changes the scattering state inside the wavelength conversion material 1, changing the degree of incidence of excitation light on the phosphor particles 3, and therefore changing the chromaticity.

For example, if the firing atmosphere is a reduced pressure atmosphere and the pressure is lower, the number of bubbles remaining inside the wavelength conversion material 1 decreases, scattering inside the wavelength conversion material 1 also decreases, and excitation light is more likely to pass through the wavelength conversion material 1 as is. As a result, the amount of excitation light incident on the phosphor particles 3 decreases, reducing the amount of light emitted, which is thought to result in a decrease in chromaticity. Furthermore, if the firing atmosphere is a reduced pressure atmosphere and the pressure is higher, the number of bubbles remaining inside the wavelength conversion material 1 increases, increasing the scattering of excitation light inside the wavelength conversion material 1 and increasing the amount of excitation light incident on the phosphor particles 3. As a result, the amount of light emitted increases, which is thought to result in an increase in chromaticity.

Alternatively, if the firing atmosphere is a pressurized atmosphere and the pressure is higher, the green compact 4 is compressed, and the air bubbles remaining inside the wavelength conversion material 1 are compressed and smaller, making it easier to obtain a dense sintered body. This reduces scattering within the wavelength conversion material 1, making it easier for excitation light to pass through the wavelength conversion material 1 as is. As a result, the amount of excitation light incident on the phosphor particles 3 decreases, reducing the amount of light emitted, which is thought to result in a decrease in chromaticity. Furthermore, if the firing atmosphere is a pressurized atmosphere and the pressure is lower, the air bubbles remaining inside the wavelength conversion material 1 are less likely to be compressed, making it harder to obtain a dense sintered body. This increases scattering of excitation light within the wavelength conversion material 1, increasing the amount of excitation light incident on the phosphor particles 3. As a result, the amount of light emitted increases, which is thought to improve chromaticity.

In addition, the fusion state between the glass powder particles 2A changes depending on the rate of temperature rise and fall during firing (the rate of temperature rise until the firing temperature (maximum temperature) is reached and the rate of temperature fall from the firing temperature). This changes the scattering state within the wavelength conversion member 1, which in turn changes the degree of excitation light incident on the phosphor particles 3, resulting in a change in chromaticity.

For example, as the heating rate or cooling rate (absolute value) increases, fusion between the glass powder particles 2A is suppressed and the number of interfaces increases, and scattering of excitation light within the wavelength conversion member 1 also increases, increasing the amount of excitation light incident on the phosphor particles 3. As a result, the amount of light emitted increases, which is thought to improve chromaticity. Furthermore, as the heating rate or cooling rate (absolute value) decreases, fusion between the glass powder particles 2A progresses and the number of interfaces decreases, which also reduces scattering within the wavelength conversion member 1, making it easier for excitation light to pass through the wavelength conversion member 1 directly. As a result, the amount of excitation light incident on the phosphor particles 3 decreases, reducing the amount of light emitted, which is thought to lower chromaticity.

As mentioned above, in addition to the firing temperature, the firing time, atmospheric pressure, or temperature increase/decrease rate can also be selected as firing conditions. When these firing conditions are selected, the main firing conditions will be the main firing time, main atmospheric pressure, or main temperature increase/decrease rate, respectively.

Details of each process are explained below.

Preparation of calibration curves;
A preform containing glass powder and phosphor particles is prepared, and the correlation between the firing temperature of the prepared preform and the chromaticity after firing is determined.

Specifically, the preform is fired and its chromaticity is measured, and the correlation between firing temperature and chromaticity is determined based on the firing temperature and chromaticity. For example, the firing temperature is changed and the chromaticity at each firing temperature is plotted to create a calibration curve such as the graph shown in Figure 2. This makes it possible to determine the correlation between the firing temperature of the preform and the chromaticity after firing. Note that while two plots may be used to create the graph, three or more plots are preferred in order to obtain a more accurate correlation between firing temperature and chromaticity.

From Figure 2, it can be seen that the calibration curve created shows that the higher the firing temperature, the lower the chromaticity. On the other hand, the lower the firing temperature, the higher the chromaticity. Therefore, it can be seen that the chromaticity of the resulting wavelength conversion material can be controlled by changing the firing temperature.

The chromaticity of the wavelength conversion member can be obtained by irradiating one main surface of the wavelength conversion member with excitation light from the light source used and measuring the light emitted from the other main surface of the wavelength conversion member with a colorimeter.

Pre-firing;
Next, a mixture containing glass powder and phosphor particles is prepared, and multiple molded bodies are formed from the prepared mixture. It is desirable to mass-produce the mixture containing glass powder and phosphor particles and form multiple molded bodies from the same mixture. It is also desirable that the glass powder and phosphor particles are from the same lot as the phosphor particles and glass powder used to prepare the preform. It is also desirable that the molded bodies be made to have the same composition as the preform. The number of multiple molded bodies can be, for example, 4 or more and 1,000 or less.

In pre-firing, a portion of the multiple molded bodies produced is pre-fired, and the chromaticity after firing is measured. If there is a discrepancy between the chromaticity obtained by pre-firing and the target chromaticity, the firing temperature is set based on the correlation described above to bring the chromaticity closer to the target chromaticity. This firing temperature can be used as the main firing temperature. Note that the portion of the molded bodies pre-fired can be, for example, 25% or less of the multiple molded bodies produced. For example, it can be 1 to 250 of the multiple molded bodies produced.

In particular, when manufacturing conditions are changed, such as when using phosphor particles or glass powder from a different lot than those used to make the preform, it is preferable to perform the above-mentioned pre-firing step.

Main firing;
In the main firing, the remaining molded bodies among the plurality of molded bodies made using the mixture containing the glass powder and the phosphor particles are fired at the main firing temperature set as described above, thereby adjusting the chromaticity of the wavelength conversion member obtained so as to approach the target chromaticity.

In this way, in the manufacturing method of this embodiment, a main firing temperature corresponding to the target chromaticity of the wavelength conversion member to be obtained is set based on a predetermined correlation between firing temperature and chromaticity, and the molded body is fired at that main firing temperature. This makes it possible to obtain a wavelength conversion member that is adjusted to approach the target chromaticity. Therefore, in the manufacturing method of this embodiment, even when manufacturing conditions such as the raw material lot of glass powder or phosphor particles are changed, color variation in the emitted color (chromaticity variation) is unlikely to occur, and wavelength conversion members with the desired chromaticity can be obtained stably and accurately.

For example, it is preferable that the variation in chromaticity (Cx) of the resulting wavelength conversion member relative to the target chromaticity be within ±0.0100, more preferably within ±0.0050, even more preferably within ±0.0025, and particularly preferably within ±0.0015. Furthermore, when manufacturing conditions such as raw material lots are changed, it is preferable that the variation in chromaticity (Cx) of the wavelength conversion member before and after the lot change be within ±0.0100, more preferably within ±0.0050, even more preferably within ±0.0025, and particularly preferably within ±0.0015. However, it is more preferable that the chromaticity of the resulting wavelength conversion member be the same as the target chromaticity.

It is also possible to perform a second pre-firing before the main firing to check the chromaticity and fine-tune the main firing temperature determined in the first pre-firing. In this way, it is possible to obtain a wavelength conversion member with the desired chromaticity with even greater stability and precision.

In the present invention, the green body can be formed in each manufacturing step by, for example, sheet molding. Specifically, the green body can be produced using a slurry containing glass powder, which forms the glass matrix, phosphor particles, and, if necessary, organic components such as a binder resin and a solvent. For example, the green body can be formed by applying the slurry to a resin film such as polyethylene terephthalate using a doctor blade method or the like, and then heating and drying the resulting film. Alternatively, the green body can be formed by applying the slurry to a substrate to form a film, and then drying the resulting film. The green body can also be formed by press molding a powder mixture containing glass powder and phosphor particles. In this way, sheet molding or press molding is preferable.

In the present invention, the glass powder material can be the same as the glass matrix material described above. The average particle size of the glass powder 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 size of the glass powder is too small, production costs tend to increase and handling tends to be difficult. On the other hand, if the average particle size of the glass powder is too large, air bubbles are likely to remain in the glass matrix after firing in the resulting wavelength conversion member, which may reduce the light extraction efficiency of the wavelength conversion member. Therefore, the average particle size of the glass powder 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 also desirable that the average particle size of the phosphor particles be within the range described above for the wavelength conversion member.

In the present invention, the firing temperature in each manufacturing step is preferably within ±150°C of the softening point of the glass powder, and more preferably within ±100°C of the softening point of the glass powder. If the firing temperature is too low, the glass powder may not soften and flow, and a dense sintered body may not be obtained. On the other hand, if the firing temperature is too high, the phosphor particles may dissolve into the glass, reducing the luminescence intensity, or the phosphor components may diffuse into the glass, causing the glass to become colored and reducing the luminescence intensity. Furthermore, the firing time (holding time at the maximum temperature) in each manufacturing step can be, for example, 5 minutes or more and 120 minutes or less. Furthermore, it is preferable to appropriately adjust the firing time (holding time at the maximum temperature) in the manufacturing step between 10 minutes and 60 minutes.

As mentioned above, the fusion state between the glass powder particles can be changed by appropriately adjusting the heating rate up to the firing temperature and the cooling rate from the firing temperature, thereby adjusting the color. The heating rate is preferably adjusted between +0.1°C/min and +10°C/min, or even between +0.5°C/min and +5°C/min. The cooling rate is preferably adjusted between -0.1°C/min and -50°C/min, or even between -1°C/min and -30°C/min.

Furthermore, the firing is preferably carried out in a reduced pressure atmosphere. Specifically, the atmosphere during firing is preferably less than 1.013 × 10 ⁵ Pa, more preferably 1000 Pa or less, and even more preferably 400 Pa or less. This reduces the amount of bubbles remaining in the resulting wavelength conversion member. As a result, the scattering factor in the resulting wavelength conversion member can be reduced, and the light extraction efficiency can be improved.

On the other hand, if firing is carried out in a pressurized atmosphere, the molded body is compressed, and any air bubbles remaining inside the wavelength conversion material are compressed and reduced in size, making it easier to obtain a dense sintered body. Specifically, the atmosphere during firing is preferably 20 MPa or higher, more preferably 40 MPa or higher, and even more preferably 100 MPa or higher. In this case, too, any air bubbles remaining in the resulting wavelength conversion material can be compressed and reduced in size. As a result, the scattering factor in the resulting wavelength conversion material can be reduced, and the light extraction efficiency can be improved. However, from the perspective of effectively reducing scattering of excitation light in the wavelength conversion material, it is more preferable to carry out firing in a reduced-pressure atmosphere.

In addition, in the present invention, polishing may be performed before measuring the color in each process. The polishing method is not particularly limited, and can be performed by lapping or mirror polishing. Lapping has the advantage of being faster than mirror polishing. On the other hand, mirror polishing can improve the precision of the polished surface more than lapping. Any polishing method that results in a surface condition (surface roughness) equivalent to that of the finished surface of the final product should be used.

It is desirable that the firing conditions and polishing methods used in each manufacturing process be standardized.

The present invention will now be described in more detail based on specific examples. The present invention is not limited to the following examples, and can be modified and implemented as appropriate without departing from the spirit and scope of the invention.

Example 1
Preparation of calibration curves;
The glass powder used was a glass powder (average particle diameter _D50 : ₂ μm, _softening point 850°C) with a composition (mol%) of SiO2 61.4%, _{B2O3 5.3} %, _Al2O3 3.6%, CaO 13.2%, BaO 12%, and ZnO 4.5%. The phosphor particles used were YAG phosphor particles (average particle diameter _D50 : 25 μm). A mixture was obtained by mixing this glass powder and the phosphor particles. The phosphor particle content in the mixture was 8 mass%.

The resulting mixture was kneaded with binder resin (Oricox, manufactured by Kyoeisha Chemical Co., Ltd.), plasticizer (dioctyl adipate), dispersant (Florene G-700, manufactured by Kyoeisha Chemical Co., Ltd.), and organic solvent (methyl ethyl ketone) to obtain a slurry. The resulting slurry was formed into a sheet using the doctor blade method and dried at room temperature to obtain a green sheet-like preform. Three preforms were produced, and each preform was fired at 890°C, 900°C, and 910°C, respectively, to determine its chromaticity. The chromaticity at each firing temperature was then plotted to create a calibration curve, yielding the correlation shown in the graph in Figure 4.

Pre-firing;
Using glass powder and phosphor particles from lots different from those used in creating the calibration curve, 100 green sheet-like molded bodies were obtained in the same manner as in the preparation of the preformed bodies.

Two of the produced compacts were pre-fired at 900°C (maximum temperature holding time: 20 minutes), which is the firing temperature corresponding to the target chromaticity (0.279) determined using the calibration curve, and the chromaticity after firing was measured. As a result, it was confirmed that the chromaticity obtained by pre-firing deviated from the target chromaticity by an average of +0.0038. Therefore, based on the correlation in Figure 4, the main firing temperature was set to 910°C, 10°C higher than the pre-firing temperature, in order to bring the chromaticity closer to the target chromaticity.

Main firing;
In the main firing, the remaining 98 molded bodies out of the 100 produced molded bodies were fired in a reduced pressure atmosphere (1.013 × 10 ¹ Pa) at a set main firing temperature of 910°C (holding time at maximum temperature: 20 minutes), and the chromaticity after firing was measured. As a result, the chromaticity of the wavelength conversion member obtained by the main firing had an average deviation of +0.0003 from the target chromaticity (variation from the pre-firing: -0.0035), confirming that the chromaticity deviation had been suppressed.

The chromaticity was calculated as follows: The wavelength conversion element, which was a fired molded body, was placed under a light source with an excitation wavelength of 450 nm. Light emitted from the underside of the wavelength conversion element was captured inside an integrating sphere and then guided to a spectroscope calibrated with a standard light source to measure the light energy distribution spectrum. Next, the above spectrum was integrated using the CIE 1931 2-deg, x(_), y(_), z(_) color matching functions to find the tristimulus values XYZ. Chromaticity x = X/(X + Y + Z) was calculated from these tristimulus values XYZ.

Example 2
Preparation of calibration curves;
A green sheet-like preform was obtained in the same manner as in Example 1, except that YAG phosphor particles (average particle diameter D ₅₀ : 20 μm) were used as the phosphor particles and the content of the phosphor particles in the mixture was 12 mass %. Three preforms were prepared, and each of the prepared preforms was fired at 890°C, 900°C, and 910°C, respectively, to determine its chromaticity. A calibration curve was then prepared by plotting the chromaticity at each firing temperature, and the correlation shown in the graph in FIG. 4 was obtained, as in Example 1.

Pre-firing;
Using glass powder and phosphor particles from lots different from those used in creating the calibration curve, 100 green sheet-like molded bodies were obtained in the same manner as in the preparation of the preformed bodies.

Two of the produced compacts were pre-fired at 910°C (maximum temperature holding time: 20 minutes), which is the firing temperature corresponding to the target chromaticity (0.275) determined using the calibration curve, and the chromaticity after firing was measured. As a result, it was confirmed that the chromaticity obtained by pre-firing deviated from the target chromaticity by an average of -0.0025. Therefore, based on the correlation in Figure 4, the main firing temperature was set to 905°C, 5°C lower than the pre-firing temperature, in order to bring the chromaticity closer to the target chromaticity.

Main firing;
In the main firing, the remaining 98 molded bodies out of the 100 produced molded bodies were fired at the set main firing temperature of 905°C (holding time at the maximum temperature: 20 minutes), and the chromaticity after firing was measured. As a result, the chromaticity of the wavelength conversion member obtained by the main firing had an average deviation from the target chromaticity of +0.0001 (variation from the pre-firing: +0.0026), confirming that the deviation in chromaticity had been suppressed.

1... wavelength conversion member 2... glass matrix 2A... glass powder 3... phosphor particles 4... molded body

Claims (9)

A method for producing a wavelength conversion member by firing a molded body containing glass powder and phosphor particles, comprising:
a step of preparing a preform containing glass powder and phosphor particles, and determining a correlation between the firing temperature of the preform and the chromaticity after firing;
setting a firing temperature corresponding to a target chromaticity of the wavelength conversion member to be obtained based on the correlation;
firing a molded body containing glass powder and phosphor particles at the firing temperature;
A method for manufacturing a wavelength conversion member, comprising: a step of setting a main firing temperature corresponding to a target chromaticity of the wavelength conversion member to be obtained by applying chromaticities obtained by pre-firing some of a plurality of molded bodies containing glass powder and phosphor particles to the correlation;
firing the remaining compacts of the plurality of compacts at the firing temperature;
The method for manufacturing a wavelength conversion member according to claim 1 , comprising: The method for manufacturing a wavelength conversion member according to claim 2 , wherein when the chromaticity determined by the pre-firing is higher than the target chromaticity, the main firing temperature is set higher than the firing temperature of the pre-firing. 3. The method for manufacturing a wavelength conversion member according to claim 2, wherein when the chromaticity determined by the pre-firing is lower than the target chromaticity, the main firing temperature is set lower than the firing temperature of the pre-firing. The method for producing a wavelength conversion member according to any one of claims 1 to 4 , wherein the molded body has the same composition as the pre-molded body. The method for producing a wavelength conversion member according to any one of claims 1 to 5 , wherein the molded body is formed by sheet molding or press molding. A method for producing a wavelength conversion member by firing a molded body containing glass powder and phosphor particles, comprising:
a step of preparing a preform containing glass powder and phosphor particles, and determining a correlation between firing conditions of the preform and chromaticity after firing;
setting main firing conditions corresponding to the target chromaticity of the wavelength conversion member to be obtained based on the correlation;
firing a molded body containing glass powder and phosphor particles under the firing conditions;
Equipped with
The method for producing a wavelength conversion member , wherein the firing conditions are firing time, atmospheric pressure, or temperature increase/decrease rate . a step of setting a main firing condition corresponding to a target chromaticity of the wavelength conversion member to be obtained by applying chromaticities determined by pre-firing some of a plurality of molded bodies containing glass powder and phosphor particles to the correlation;
firing the remaining compacts of the plurality of compacts under the main firing conditions;
The method for manufacturing a wavelength conversion member according to claim 7 , comprising: The glass powder is composed of borosilicate glass, phosphate glass, tin phosphate glass, bismuthate glass, or tellurite glass, and SiO ₂ The method for producing a wavelength conversion member according to any one of claims 1 to 8, wherein the content of