Method for manufacturing wavelength conversion member

Abstract

To provide a method of manufacturing a wavelength conversion member in which the wavelength conversion member which has desired chromaticity can be obtained.SOLUTION: There is provided a method of manufacturing a wavelength conversion member 1 by burning a compact 4 including phosphor particles 3, and the method of manufacturing the wavelength conversion member 1 comprises the processes of: manufacturing a pre-compact including the phosphor particles 3, and finding correlation relationship between a burning temperature of the pre-compact and chromaticity after the burning; setting a main burning temperature corresponding to target chromaticity of the obtained wavelength conversion member 1 based upon the correlation relationship; and burning the compact 4 including the phosphor particles 3 at the main burning temperature.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for producing a wavelength conversion member that converts the wavelength of light emitted by a light emitting diode (LED), a laser diode (LD), or the like into another wavelength. [Background technology]

[0002] 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 disposed 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.

[0003] Wavelength conversion materials have traditionally been made by dispersing phosphor particles in a resin matrix, but when exposed to heat and light emitted by LEDs and LDs, the resin matrix can discolor and deform, causing a decrease in the performance of the wavelength conversion material.

[0004] Therefore, wavelength conversion members made of a completely inorganic solid in which phosphor particles are dispersed and fixed in a glass matrix instead of a resin matrix have been proposed (see, for example, Patent Documents 2 and 3). Such wavelength conversion members have the advantage that the glass matrix, which is the base material, is less likely to deteriorate due to the heat and irradiated light of the LED, and are less likely to suffer from problems such as discoloration and deformation. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-208815 [Patent Document 2] Japanese Patent Application Laid-Open No. 2003-258308 [Patent Document 3] Patent No. 4895541 Summary of the Invention [Problem to be solved by the invention]

[0006] Wavelength conversion members such as those described in Patent Documents 2 and 3 can be manufactured by, for example, molding a mixture of glass powder and phosphor particles and then firing the molded product. In this case, if the lots of the glass powder or phosphor particles are 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.

[0007] An object of the present invention is to provide a method for manufacturing a wavelength conversion member that makes it possible to stably obtain a wavelength conversion member having a desired chromaticity. [Means for solving the problem]

[0008] 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, characterized by comprising the steps of: preparing a preform containing phosphor particles; determining a 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.

[0009] In the present invention, it is preferable to include a step of setting a main firing temperature 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 obtained to the correlation, and a step of firing the remaining molded bodies of the multiple molded bodies at the main firing temperature.

[0010] In the present invention, when the chromaticity determined by the pre-firing is higher than the target chromaticity, the main firing temperature may be set higher than the pre-firing temperature.

[0011] In the present invention, when the chromaticity determined by the pre-firing is lower than the target chromaticity, the main firing temperature may be set lower than the pre-firing temperature.

[0012] In the present invention, it is preferable that the molded body further contains glass powder.

[0013] In the present invention, it is preferable that the molded body has the same composition as the pre-molded body.

[0014] In the present invention, the molding is preferably sheet molding or press molding.

[0015] 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 a 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.

[0016] In the present invention, it is preferable to include 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 obtained to the correlation, and a step of firing the remaining molded bodies of the multiple molded bodies under the main firing conditions.

[0017] In the present invention, the firing conditions are preferably firing time, atmospheric pressure, or temperature increase / decrease rate. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a method for manufacturing a wavelength conversion member that makes it possible to stably obtain a wavelength conversion member having a desired chromaticity. [Brief explanation of the drawings]

[0019] [Figure 1] 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. [Figure 2] FIG. 2 is a graph showing an example of the correlation between the firing temperature and chromaticity in a method for producing a wavelength conversion member according to one embodiment of the present invention. [Figure 3] 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. [Figure 4] FIG. 4 is a graph showing the correlation between the firing temperature and chromaticity in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0020] Preferred embodiments will be described below. 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.

[0021] (wavelength conversion material) 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.

[0022] The glass matrix 2 is not particularly limited as long as it can be used as a dispersion medium for the 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.

[0023] Examples of borosilicate glasses include those containing, by mass%, 30% to 85% SiO2, 30% to 30% Al2O, 30% to 50% B2O, 0% to 10% Li2O + Na2O + K2O, and 0% to 50% MgO + CaO + SrO + BaO. Examples of tin phosphate glasses include those containing, by molar%, 30% to 90% SnO and 51% to 70% P2O. Examples of tellurite glasses include those containing, by molar%, 50% or more TeO2, 0% to 45% ZnO, 0% to 50% RO (R is at least one selected from Ca, Sr, and Ba), and 30% to 50% La2O3 + Gd2O3 + Y2O.

[0024] 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 member 1 may be reduced. Furthermore, since 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 step is included in the manufacturing process, the phosphor particles 3 may be deteriorated, and the luminescence intensity of the wavelength conversion member 1 may be reduced. Note that, from the viewpoint of further improving the chemical stability and mechanical strength of the wavelength conversion member 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 constituting such glass matrix 2 include borosilicate glasses. However, if the softening point of the glass matrix 2 is high, the firing temperature also becomes high, which tends to result in higher manufacturing costs. Furthermore, if the heat resistance of the phosphor particles 3 is low, there is a risk of deterioration due to firing. Therefore, in order to manufacture the wavelength conversion member 1 more inexpensively or if the heat resistance of the phosphor particles 3 is even lower, 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.

[0025] 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 Al2O3, MgO, and AlN.

[0026] The phosphor particles 3 are not particularly limited as long as they emit fluorescence when excitation light is incident on them. Examples of the 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. One type of these phosphors may be used alone, or multiple types may be used 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.

[0027] The average particle diameter of the phosphor particles 3 is preferably 1 μm or more, 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 luminous 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 luminous color tends to become non-uniform. Therefore, the average particle diameter of the phosphor particles 3 is preferably 50 μm or less, more preferably 25 μm or less.

[0028] In this specification, the average particle size is the average particle size D measured by a laser diffraction particle size distribution analyzer. 50 This refers to the following.

[0029] 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 needs to 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 needs to be reduced to obtain the desired emitted color, which may result in reduced mechanical strength of the wavelength conversion member 1.

[0030] 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 a 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.

[0031] A method for producing a wavelength conversion member of the present invention such as wavelength conversion member 1 will now be described.

[0032] (Method of 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.

[0033] The method for producing a wavelength conversion member according to the present invention has the above-mentioned configuration, and therefore can stably produce a wavelength conversion member with a desired chromaticity even when production conditions such as raw material lots are changed. This will be described in detail below.

[0034] In the past, when changing the lot of glass powder or phosphor particles, the chromaticity of the wavelength conversion member obtained could deviate from the target chromaticity due to differences in particle size distribution, etc., even when the same concentration setting was used. This made it difficult to consistently obtain a wavelength conversion member with the desired chromaticity.

[0035] In response to this, the present 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 the determined correlation, the chromaticity of the resulting wavelength conversion member can be adjusted to approach the target chromaticity. More specifically, as shown in an example of the correlation in FIG. 2, 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 FIG. 3.

[0036] 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.

[0037] As shown in Fig. 3(a), in the molded body 4 before firing, the glass powder 2A and the phosphor particles 3 exist in the form of particle clumps, with interfaces between the particles. On the other hand, as shown in Fig. 3(b), in the wavelength conversion member 1 after firing, the glass powder 2A is melted to form a glass matrix 2, and the phosphor particles 3 are dispersed within the glass matrix 2.

[0038] 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 fusion state between the glass powders 2A, which changes the scattering state inside the wavelength conversion member 1, and changes the degree of incidence of excitation light on the phosphor particles 3, which is thought to result in a change in chromaticity.

[0039] In particular, the higher the firing temperature, the more the glass powder 2A fuses together, the fewer the interfaces, and the less scattering occurs inside 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 2A fuses together, the more the interfaces increase, increasing the scattering of excitation light inside the wavelength conversion member 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.

[0040] It is also believed that the degree of scattering changes depending on the firing time. Specifically, it is believed that the firing time changes the fusion state between the glass powder 2A particles, which changes the scattering state inside 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.

[0041] In particular, the longer the firing time, the more the glass powder 2A fuses together, the fewer the interfaces, and the less scattering there is inside 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 2A fuses together, the more the interfaces increase, increasing the scattering of excitation light inside the wavelength conversion member 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 improvement in chromaticity.

[0042] 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 the firing conditions, such as the firing temperature and firing time, and the chromaticity after firing.

[0043] The baking temperature may be set based on the correlation between the baking temperature and the chromaticity after baking, and the baking time may be set based on the correlation between the baking time and the chromaticity after baking.

[0044] The firing conditions other than the firing temperature and firing time may be set based on the correlation between the chromaticity after firing and other firing conditions, such as atmospheric pressure and temperature rise / fall rate.

[0045] 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 causing a change in chromaticity.

[0046] 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 member 1 decreases, scattering inside the wavelength conversion member 1 also decreases, and excitation light is more likely to pass through the wavelength conversion member 1 as it 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 member 1 increases, increasing the scattering of excitation light inside the wavelength conversion member 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.

[0047] Alternatively, if the firing atmosphere is a pressurized atmosphere and the pressure is higher, the molded body 4 is compressed, and the bubbles remaining inside the wavelength conversion member 1 are compressed and smaller, making it easier to obtain a dense sintered body. This reduces scattering inside the wavelength conversion member 1, making it easier for 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, if the firing atmosphere is a pressurized atmosphere and the pressure is lower, the bubbles remaining inside the wavelength conversion member 1 are less likely to be compressed, making it harder to obtain a dense sintered body. This increases scattering of excitation light inside the wavelength conversion member 1, increasing the amount of excitation light incident on the phosphor particles 3. As a result, it is thought that the chromaticity is improved because the amount of light emitted increases.

[0048] Furthermore, the fusion state of the glass powder 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 is thought to change the scattering state inside the wavelength conversion member 1 and the degree of incidence of excitation light on the phosphor particles 3, resulting in a change in chromaticity.

[0049] For example, as the heating rate or cooling rate (absolute value) increases, the fusion of the glass powder 2A particles to each other is suppressed, the number of interfaces increases, and the scattering of excitation light inside 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, the fusion of the glass powder 2A particles to each other progresses, the number of interfaces decreases, and scattering inside the wavelength conversion member 1 also decreases, 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, which reduces the amount of light emitted, which is thought to lower chromaticity.

[0050] As described above, in addition to the firing temperature, the firing time, atmospheric pressure, or temperature increase / decrease rate can be selected as firing conditions. When these firing conditions are selected, the main firing conditions are the main firing time, main atmospheric pressure, or main temperature increase / decrease rate, respectively.

[0051] Each step will be described in detail below.

[0052] 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.

[0053] 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.

[0054] From Figure 2, it can be seen that the higher the firing temperature, the lower the chromaticity in the created calibration curve. On the other hand, it can be seen that the lower the firing temperature, the higher the chromaticity. Therefore, it can be seen that the chromaticity of the obtained wavelength conversion member can be controlled by changing the firing temperature.

[0055] The chromaticity of the wavelength conversion member can be obtained by irradiating excitation light from the light source used onto one main surface of the wavelength conversion member and measuring the light emitted from the other main surface of the wavelength conversion member with a colorimeter.

[0056] 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 be 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.

[0057] In the 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 above correlation so as to bring the chromaticity closer to the target chromaticity. This firing temperature can be the main firing temperature. Note that the portion of the molded bodies to be 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.

[0058] In particular, when manufacturing conditions are changed, such as when phosphor particles or glass powder from a different lot than those used to prepare the preform are used, it is preferable to perform the above-mentioned pre-firing process.

[0059] 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.

[0060] As described above, 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 the 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 lots of glass powder and 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.

[0061] For example, the variation in chromaticity (Cx) of the wavelength conversion member obtained relative to the target chromaticity is preferably 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, the variation in chromaticity (Cx) of the wavelength conversion member before and after the lot change is preferably 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 wavelength conversion member obtained is the same as the target chromaticity.

[0062] Before the main firing, a second pre-firing may be performed to check the chromaticity and fine-tune the main firing temperature determined in the first pre-firing. In this way, a wavelength conversion member with the desired chromaticity can be obtained more stably and accurately.

[0063] In the present invention, the molded body in each manufacturing step can be formed, for example, by sheet molding. Specifically, the molded body can be produced using a slurry containing glass powder as a glass matrix, phosphor particles, and, if necessary, organic components such as a binder resin and a solvent. For example, the molded 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 applied slurry to produce a green sheet. Alternatively, the molded body can be formed by applying the slurry to a substrate to form a film, and then drying the resulting film. Alternatively, the molded body can be formed by producing a compact (press molding) of a mixed powder containing glass powder and phosphor particles. In this way, molding by sheet molding or press molding is preferable.

[0064] 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 impaired. On the other hand, if the average particle size of the glass powder is too large, bubbles tend 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 for the wavelength conversion member described above.

[0065] 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 (retention 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 (retention time at the maximum temperature) in the manufacturing step between 10 minutes and 60 minutes.

[0066] As described above, the fusion state between the glass powder particles can be changed by appropriately adjusting the rate of temperature increase up to the firing temperature and the rate of temperature decrease from the firing temperature, thereby adjusting the chromaticity. The rate of temperature increase is preferably adjusted between +0.1°C / min and +10°C / min, and more preferably between +0.5°C / min and +5°C / min. The rate of temperature decrease is preferably adjusted between -0.1°C / min and -50°C / min, and more preferably between -1°C / min and -30°C / min.

[0067] The firing is preferably carried out in a reduced pressure atmosphere. 5 The pressure is preferably less than 1000 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.

[0068] On the other hand, when firing is performed in a pressurized atmosphere, the molded body is compressed, and the bubbles remaining inside the wavelength conversion member 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, the bubbles remaining in the resulting wavelength conversion member can be compressed and reduced in size. As a result, the scattering factor in the resulting wavelength conversion member can be reduced, and the light extraction efficiency can be improved. However, from the perspective of effectively reducing the scattering of excitation light in the wavelength conversion member, it is more preferable to perform firing in a reduced-pressure atmosphere.

[0069] Furthermore, in the present invention, polishing may be performed before measuring the chromaticity in each step. 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 may be used.

[0070] It is desirable that the firing conditions in each manufacturing step and the polishing method, if any, be standardized.

[0071] The present invention will be described in more detail below with reference to specific examples. The present invention is not limited to the following examples, and can be practiced with appropriate modifications within the scope of the present invention.

[0072] Example 1 Preparation of calibration curves; As the glass powder, a glass powder (average particle diameter D ) having a composition of SiO 2 61.4%, B 2 O 3 5.3%, Al 2 O 3 3.6%, CaO 13.2%, BaO 12%, and ZnO 4.5% in mole percent was used. 50 The phosphor particles used were YAG phosphor particles (average particle diameter D 50The glass powder and phosphor particles were mixed to obtain a mixture. The content of the phosphor particles in the mixture was 8 mass %.

[0073] The resulting mixture was kneaded with 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) to obtain a slurry. The resulting slurry was formed into a sheet using a doctor blade method and dried at room temperature to obtain a green sheet-like preform. Three preforms were fabricated, 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 plotted to create a calibration curve, and the correlation shown in Figure 4 was obtained.

[0074] 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.

[0075] Two of the produced compacts were pre-fired at 900°C (holding time at maximum temperature: 20 minutes), which is the firing temperature corresponding to the target chromaticity (0.279) obtained 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.

[0076] Main firing; In the main firing, the remaining 98 of the 100 compacts were placed in a reduced pressure atmosphere (1.013 × 10 1The material was fired at a set firing temperature of 910°C (maximum temperature holding time: 20 minutes) under a pressure of 100 Pa, and the chromaticity after firing was measured. As a result, the chromaticity of the wavelength conversion material obtained by firing had an average deviation of +0.0003 from the target chromaticity (amount of deviation from pre-firing: -0.0035), confirming that the deviation in chromaticity had been suppressed.

[0077] The chromaticity was calculated as follows: The wavelength conversion member, which was a molded product after firing, was placed under a light source with an excitation wavelength of 450 nm. The light emitted from the underside of the wavelength conversion member 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 determine the tristimulus values XYZ. Chromaticity x = X / (X+Y+Z) was calculated from these tristimulus values XYZ.

[0078] Example 2 Preparation of calibration curves; The phosphor particles used were YAG phosphor particles (average particle diameter D 50 A green sheet-like preform was obtained in the same manner as in Example 1, except that a phosphor particle (e.g., 20 μm) was used and the content of 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 the chromaticity. Then, the chromaticity at each firing temperature was plotted to create a calibration curve, and the correlation shown in the graph in FIG. 4 was obtained, as in Example 1.

[0079] 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.

[0080] 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) obtained 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.

[0081] Main firing; In the main firing, the remaining 98 of the 100 molded bodies produced were fired at the set main firing temperature of 905°C (holding time at maximum temperature: 20 minutes), and the chromaticity after firing was measured. As a result, the chromaticity of the wavelength conversion material obtained by main firing had an average deviation from the target chromaticity of +0.0001 (variation from pre-firing: +0.0026), confirming that the chromaticity deviation had been suppressed. [Explanation of symbols]

[0082] 1...Wavelength conversion material 2...Glass matrix 2A: Glass powder 3...Phosphor particles 4...Molded body

Claims

1. 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:

2. A process of setting a main firing temperature corresponding to a target chromaticity of the wavelength conversion member obtained by pre-firing some of a plurality of molded bodies containing glass powder and phosphor particles and applying the chromaticity determined by the pre-firing 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:

3. 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.

4. 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.

5. 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.

6. A method for manufacturing a wavelength conversion member described in any one of claims 1 to 5, wherein the molded body is formed by sheet molding or press molding.

7. 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.

8. A process of setting main firing conditions corresponding to the target chromaticity of the wavelength conversion member obtained by pre-firing some of a plurality of molded bodies containing glass powder and phosphor particles and applying the chromaticity obtained to the correlation; firing the remaining compacts among the plurality of compacts under the main firing conditions; The method for manufacturing a wavelength conversion member according to claim 7 , comprising:

9. A method for manufacturing a wavelength conversion member described in any one of claims 1 to 8, wherein the glass powder is composed of borosilicate glass, phosphate glass, tin phosphate glass, bismuthate glass, or tellurite glass, and the SiO 2 content in the borosilicate glass is 61.4 mol% or less.

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