β-type sialon phosphor, its manufacturing method, and light-emitting device

Abstract

In an X-ray photoelectron spectrum obtained using Al-Kα radiation as an excitation X-ray source, this β-sialon phosphor satisfies the relationship 2.5>Y / X, where X is the photoelectron intensity at a binding energy of 103.5 eV and Y is the photoelectron intensity at a binding energy of 102.0 eV.

Description

[Technical Field]

[0001] The present invention relates to a β-sialon phosphor, a method for producing the same, and a light-emitting device. [Background technology]

[0002] Light-emitting devices that combine a light-emitting element that emits primary light with a phosphor that absorbs the primary light and emits secondary light are attracting attention as next-generation light-emitting devices that are expected to have low power consumption, small size, high brightness, and a wide range of color reproducibility, and research and development into these devices is being actively conducted.For example, a light-emitting device has been proposed that combines a light-emitting element that emits short-wavelength visible light from blue to purple with a phosphor, and obtains white light by mixing the light emitted by the light-emitting element with light whose wavelength has been converted by the phosphor (Patent Document 1).

[0003] In recent years, there has been a demand for higher brightness in light-emitting devices such as backlights for liquid crystal displays, lighting, and flat panel displays, and this has led to an increase in the output power of light-emitting devices. Higher output power of light-emitting devices leads to an increase in heat generation, which in turn reduces the luminescence intensity associated with an increase in the temperature of the phosphor, thereby reducing the reliability of the light-emitting device. Therefore, phosphors with excellent durability (particularly heat resistance) are in demand, and nitride or oxynitride phosphors, such as β-sialon phosphors, which have a stable crystal structure, have been attracting attention.

[0004] A known method for producing a β-sialon phosphor is to mix silicon nitride, aluminum nitride, and an optically active element compound such as europium oxide in a predetermined molar ratio, fire the mixture at a temperature of about 2000°C, pulverize the resulting fired product, and then acid-treat the powdered fired product (Patent Document 2).Another known method involves performing heat treatment in a nitrogen atmosphere and a rare gas atmosphere after firing the raw materials (Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4769132 [Patent Document 2] Patent No. 4210761 [Patent Document 3] Patent No. 5508817 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the β-sialon phosphors produced by known methods such as those described in Patent Documents 2 and 3 do not have sufficient durability (particularly heat resistance) in their original state, and there is a problem that the reliability is reduced when this β-sialon phosphor is used in a light emitting device.

[0007] The present invention has been made to solve the above problems, and an object of the present invention is to provide a β-sialon phosphor that allows for the production of a highly reliable light emitting device, and a method for producing the same. Another object of the present invention is to provide a highly reliable light emitting device. [Means for solving the problem]

[0008] As a result of intensive research conducted by the inventors to solve the above problems, they discovered that by heat-treating a β-sialon phosphor under specific conditions to modify its surface, a β-sialon phosphor with excellent durability (particularly heat resistance) that provides a highly reliable light-emitting device can be obtained, and this led to the completion of the present invention. Furthermore, the inventors performed X-ray photoelectron spectroscopy on a β-sialon phosphor having the above-described properties and found that in the X-ray photoelectron spectroscopy spectrum using Al-Kα radiation as the excitation X-ray source, the ratio of photoelectron intensities (Counts / s) at binding energies at two specific positions falls within a specific range, leading to the completion of the present invention.

[0009] That is, in the X-ray photoelectron spectroscopy spectrum obtained by using Al-Kα radiation as an excitation X-ray source, the β-sialon phosphor according to the embodiment of the present invention satisfies 2.5>Y / X, where X is the photoelectron intensity when the binding energy is 103.5 eV and Y is the photoelectron intensity when the binding energy is 102.0 eV. Furthermore, a light emitting device according to an embodiment of the present invention includes the above-described β-sialon phosphor. Furthermore, in a method for producing a β-sialon phosphor according to an embodiment of the present invention, in a state where water of 0.5 mass % or more relative to the total mass of the β-sialon phosphor and water is present, 1.62 Gauge pressure of MPa or more, 200 At temperatures above ℃ 48~168 hours, The β-sialon phosphor is heat-treated. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a β-sialon phosphor that can be used to manufacture a highly reliable light emitting device, and a method for manufacturing the same. Furthermore, according to the present invention, a highly reliable light emitting device can be provided. [Brief explanation of the drawings]

[0011] [Figure 1] 1 shows X-ray photoelectron spectroscopy spectra of β-sialon phosphors of Example 1 and Comparative Example 1. [Figure 2] 1 shows spectra of Kubelka-Munk function values ​​(KM values) measured by FT-IR for the β-sialon phosphors of Example 1 and Comparative Examples 1 and 2. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of a β-sialon phosphor, a method for manufacturing the same, and a light-emitting device according to the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in the following embodiments. For example, some components may be deleted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0013] In this specification, the term "β-type sialon phosphor" refers to a solid solution in which Al is partially substituted at the Si position and O is partially substituted at the N position of β-type silicon nitride (Si3N4), and has the general formula: Si 6-z Al z O z N 8-z In the formula, z is 0 to 4.2. The β-sialon phosphor is excited by a wide wavelength range from ultraviolet light to visible light, and emits green light.

[0014] The β-sialon phosphor of this embodiment satisfies 2.5>Y / X, where X is the photoelectron intensity at a binding energy of 103.5 eV and Y is the photoelectron intensity at a binding energy of 102.0 eV in an X-ray photoelectron spectroscopy spectrum using Al-Kα radiation as an excitation X-ray source. If 2.5≦Y / X, the durability of the β-sialon phosphor is not sufficiently improved, making it impossible to obtain a highly reliable light-emitting device. Here, X-ray photoelectron spectroscopy can identify functional groups, etc., from the bond energy value of each photoelectron intensity. Photoelectron intensity at a bond energy of 103.5 eV indicates the presence of a Si-N bond, and photoelectron intensity at a bond energy of 102.0 eV indicates the presence of a Si-O bond.

[0015] When 2.5 > Y / X is satisfied, the ratio of Si-O bonds to Si-N bonds becomes high, which is thought to result in hydrolysis of the surface of the β-SiAlON phosphor, resulting in the formation of a sufficient oxide layer (i.e., sufficient surface modification). The formation of a sufficient oxide layer on the surface of the β-SiAlON phosphor suppresses further hydrolysis. As a result, when the temperature of the β-SiAlON phosphor rises in a light-emitting device, the generation of ionic substances such as ammonium ions is suppressed, improving the reliability of the light-emitting device.

[0016] The X-ray photoelectron spectroscopy spectrum can be obtained by X-ray photoelectron spectroscopy (XPS). The measurement conditions are as follows: Measurement equipment: X-ray photoelectron spectrometer (ULVAC-PHI PHI5000VersaProbeII) Output: 15kV-50W Measurement area: 200μmφ Pass energy: 187 eV Step size: 50ms

[0017] The β-sialon phosphor of this embodiment has a wave number of 3650 cm in a spectrum of the Kubelka-Munk (hereinafter, sometimes abbreviated as "KM") function value (KM value) obtained by FT-IR. -1 The KM value is A and the wave number is 2600 cm -1 If the KM value at this time is D, then 0.15 Here, in this specification, the "value of the Kubelka-Munk function" is a function that converts the reflectance of a substance into a value that serves as an index of the absorption specific to the substance, and can be obtained by dividing the extinction coefficient by the scattering coefficient (extinction coefficient / scattering coefficient). The Kubelka-Munk function (KM value) spectrum using FT-IR can identify functional groups from the wavenumber value. -1 The KM value at this point indicates a Si-OH bond, and the wavenumber is 2600 cm -1 The KM value at this time shows a peak derived from the structure of the β-sialon phosphor. ​

[0018] 0.15

[0019] The Kubelka-Munk function (KM value) spectrum can be obtained by Fourier transform infrared absorption analysis (FT-IR). Measurements were performed using a PerkinElmer Spectrum One. The measurement sample can be prepared by pelletizing the β-sialon phosphor without diluting it.

[0020] The β-sialon phosphor of this embodiment has a wave number of 3650 cm in the spectrum of the Kubelka-Munk function value (KM value) obtained by FT-IR. -1 The KM value is A and the wave number is 3400 cm -1 If the KM value at this time is B, then 0.2 Here, the wave number is 3400 cm -1 The KM value at this point indicates the OH bond of adsorbed water. 0.2

[0021] The β-sialon phosphor of this embodiment has a wave number of 3200 cm in the spectrum of the Kubelka-Munk function value (KM value) obtained by FT-IR. -1 The KM value is C and the wave number is 3400 cm -1 ​​​When the KM value at this time is B, it is preferable to satisfy 0.7 < C / B. Here, the KM value at a wave number of 3200 cm -1 indicates the Al-OH bond of the oxide layer. When 0.7 < C / B is satisfied, the ratio of the Al-OH bond of the oxide layer becomes higher than that of the O-H bond of the adsorbed water. Therefore, it is considered that the surface of the β-sialon phosphor is hydrolyzed and the oxide layer is sufficiently formed. Therefore, when the temperature of the β-sialon phosphor rises in the light-emitting device, it becomes difficult for ionic substances such as ammonium ions to be generated, and the reliability of the light-emitting device is improved.

[0022] The β-sialon phosphor of the present embodiment having the above characteristics can be produced by heat-treating the β-sialon phosphor at a temperature of 150 °C or higher in a state where 0.5% by mass or more of water coexists with respect to the total mass of the β-sialon phosphor and water. If the amount of water coexisting is less than 0.5% by mass or the heating temperature is less than 150 °C, the hydrolysis of the surface of the β-sialon phosphor becomes insufficient and the oxide layer is not sufficiently formed.

[0023] The method for making 0.5% by mass or more of water coexist with respect to the total mass of the β-sialon phosphor and water is not particularly limited. For example, after mixing the β-sialon phosphor and water, the mixture (water content 0.5% by mass or more) may be sealed.

[0024] The pressure conditions during the heat treatment are not particularly limited, but it is preferable to perform the heat treatment under a gauge pressure of 0.05 MPa or more. By performing the heat treatment under the above pressure conditions, the hydrolysis of the surface of the β-sialon phosphor can be efficiently performed. The method for performing the heat treatment under such pressure conditions is not particularly limited. For example, a sealed container may be used and the heat treatment may be performed in a sealed state.

[0025] The β-sialon phosphor before the heat treatment is not particularly limited, and may be one obtained by a known method. Specifically, the β-sialon phosphor before the heat treatment can be obtained by firing a mixed raw material powder containing silicon nitride, aluminum nitride, and an optically active element compound such as europium oxide, and pulverizing the resulting fired product. The β-sialon phosphor before the heat treatment may be subjected to an acid treatment or heat treatment in an inert atmosphere as necessary. Alternatively, a commercially available product may be used as the β-sialon phosphor before the heat treatment.

[0026] After the above heat treatment, further heat treatment may be performed in the atmosphere at 100° C. or higher, preferably 100 to 600° C. By performing the further heat treatment, it is possible to remove adsorbed water and crystal water from the β-sialon phosphor, thereby improving the reliability of the light emitting device.

[0027] The β-sialon phosphor of this embodiment obtained in this manner is useful for use in light-emitting devices because it is less likely to generate ionic substances such as ammonium ions when the temperature inside the light-emitting device rises.

[0028] The light emitting device of this embodiment includes the above-described β-sialon phosphor. In this light emitting device, the β-sialon phosphor is generally used in the light emitting member. The light emitting member can be obtained by mixing the β-sialon phosphor with a sealing material (e.g., silicone resin) and curing the mixture. The light emitting member may also include a phosphor other than the β-sialon phosphor. The light emitting device of this embodiment may include various light emitting elements. The light emitting element is not particularly limited, but is preferably an ultraviolet LED or blue LED that emits light with a wavelength of 240 to 480 nm, and more preferably a blue LED that emits light with a wavelength of 440 to 470 nm. For example, the above-mentioned β-sialon phosphor can be combined with an ultraviolet LED or a blue LED to obtain a white light emitting device (white LED).

[0029] The light emitting device of this embodiment having the above-described characteristics is highly reliable because it contains a β-sialon phosphor that is less likely to generate ionic substances such as ammonium ions when the temperature inside the light emitting device rises. [Example]

[0030] The present invention will be explained in more detail below using examples and comparative examples, but the present invention is not limited to the following examples as long as it does not deviate from the gist of the invention. Examples 5 and 6 are reference examples.

[0031] Example 1 95% by mass of β-sialon phosphor (GR-SW529B manufactured by Denka Co., Ltd.) and 5% by mass of ion-exchanged water were mixed. Next, 20 g of the mixture was placed in a Teflon-lined SUS316 container (50 cc) and heat-treated in a sealed state at 200°C for 168 hours. The gauge pressure inside the container during the heat treatment was measured and found to be 1.62 MPa. Next, the heat-treated β-sialon phosphor was passed through a nylon sieve (150 μm mesh) while pouring ion-exchanged water over it, and then filtered using filter paper with a pore size of 10 μm or less. The filtered residue was washed with 3 L of ion-exchanged water and filtered again, and then dried at 80°C for 25 hours to obtain the β-sialon phosphor of Example 1.

[0032] Example 2 A β-sialon phosphor of Example 2 was obtained by treating under the same conditions as in Example 1, except that the heat treatment was carried out at 200°C for 48 hours. The gauge pressure in the container during the heat treatment was measured and found to be 1.62 MPa.

[0033] Example 3 The β-sialon phosphor of Example 2 was further heat-treated in the air at atmospheric pressure at 150° C. for 5 hours, thereby obtaining a β-sialon phosphor of Example 3.

[0034] Example 4 The β-sialon phosphor of Example 2 was further heat-treated in the air at atmospheric pressure at 80° C. for 5 hours, thereby obtaining a β-sialon phosphor of Example 4.

[0035] Example 5 A β-sialon phosphor of Example 5 was obtained by carrying out the treatment under the same conditions as in Example 1, except that the heat treatment was carried out at 150° C. for 48 hours. The gauge pressure measured during the heat treatment was 0.52 MPa.

[0036] Example 6 A β-sialon phosphor of Example 6 was obtained by treating under the same conditions as in Example 2, except that 99.5 mass % of a β-sialon phosphor (GR-SW529B manufactured by Denka Co., Ltd.) and 0.5 mass % of ion-exchanged water were mixed. The gauge pressure during the heat treatment was measured to be 0.68 MPa.

[0037] (Comparative Example 1) The β-sialon phosphor (GR-SW529B manufactured by Denka Co., Ltd.) before the heat treatment was used as Comparative Example 1.

[0038] (Comparative Example 2) A β-sialon phosphor (GR-SW529B manufactured by Denka Co., Ltd.) was heat-treated in the air at atmospheric pressure at 200°C for 168 hours. Next, the heat-treated β-sialon phosphor was passed through a nylon sieve (mesh opening: 150 μm) while pouring ion-exchanged water over it, and then filtered using filter paper with a pore size of 10 μm or less. The filtered material was washed with 3 L of ion-exchanged water and filtered again, and then dried at 80°C for 25 hours to obtain a β-sialon phosphor of Comparative Example 2.

[0039] (Comparative Example 3) A β-sialon phosphor of Comparative Example 3 was obtained by carrying out the treatment under the same conditions as in Example 1, except that the heat treatment was carried out at 100°C for 48 hours. The gauge pressure measured during the heat treatment was 0.13 MPa.

[0040] Comparative Example 4 A β-sialon phosphor of Comparative Example 4 was obtained by carrying out the treatment under the same conditions as in Example 1, except that the heat treatment was carried out at 50° C. for 48 hours. The gauge pressure measured during the heat treatment was 0.02 MPa.

[0041] (Comparative Example 5) A β-sialon phosphor of Comparative Example 5 was obtained by carrying out treatment under the same conditions as in Example 2, except that 20 g of the β-sialon phosphor (GR-SW529B manufactured by Denka Co., Ltd.) was used without mixing with water. The gauge pressure during the heat treatment was measured and found to be 0.06 MPa.

[0042] The heat treatment conditions in the above examples and comparative examples are summarized in Table 1.

[0043] [Table 1]

[0044] The β-sialon phosphors obtained in the above examples and comparative examples were subjected to X-ray photoelectron spectroscopy analysis, Fourier transform infrared absorption analysis, and reliability evaluation. The X-ray photoelectron spectroscopy and Fourier transform infrared absorption analysis were performed under the conditions described above. The reliability was evaluated as follows.

[0045] <Reliability evaluation> 2.5 g of the β-sialon phosphor obtained in each of the examples and comparative examples and 47.5 g of silicone resin (OE6656, manufactured by Toray Dow Corning Co., Ltd.) were mixed in a rotation-revolution mixer (Thinky Corporation's Awatori Rentaro® ARE-310). Next, a light-emitting element (LED) was placed at the bottom of a recessed package body and wire-bonded to the electrodes on the substrate. The mixture was then injected from a microsyringe to cover the light-emitting element and cured at 150°C. This was followed by post-curing at 110°C for 10 hours, sealing, and forming an LED package. The light-emitting element used had an emission peak wavelength of 448 nm and dimensions of 1.0 mm x 0.5 mm. Next, the LED package connected to a DC stabilized power supply was placed in a constant temperature and humidity chamber at 85°C and 85% RH, and exposed for 1000 hours with a current of 90 mA applied and the LED turned on. The total luminous flux of the LED package was measured before and after exposure, and the total luminous flux retention of the LED package after exposure was calculated. A total luminous flux retention of 93% or higher can be considered to be highly reliable. The results of the above evaluations are shown in Table 2.

[0046] [Table 2]

[0047] As representative examples of the results of the X-ray photoelectron spectroscopy and Fourier transform infrared absorption analysis, the X-ray photoelectron spectroscopy spectra of the β-sialon phosphors of Example 1 and Comparative Example 1 are shown in Fig. 1. Also, the spectra of the Kubelka-Munk function values ​​(KM values) of the β-sialon phosphors of Example 1 and Comparative Examples 1 and 2 are shown in Fig. 2.

[0048] As shown in Table 2, the β-sialon phosphors of Examples 1 to 6 had a Y / X ratio of 2.5>Y, and highly reliable LED packages with total luminous flux retention of 93% or more were obtained. In contrast, the β-sialon phosphor of Comparative Example 1 was not heat-treated, so an oxide layer was not sufficiently formed on the surface, resulting in a Y / X ratio of 2.5≦Y / X (the ratio of Si-O bonds to Si-N bonds was low). As a result, this β-sialon phosphor generates ionic substances such as ammonium ions when the temperature rises, which is thought to have reduced the total luminous flux retention (reliability) of the LED package.

[0049] The β-sialon phosphor of Comparative Example 2 was heat-treated in the atmosphere, so surface hydrolysis did not progress sufficiently. The β-sialon phosphors of Comparative Examples 3 and 4 were heat-treated at too low a temperature, so surface hydrolysis did not progress sufficiently. Furthermore, the β-sialon phosphor of Comparative Example 5 was heat-treated without allowing 0.5% by mass or more of water to coexist with the total mass of the β-sialon phosphor and water, so surface hydrolysis did not progress sufficiently. Therefore, these β-sialon phosphors did not have a sufficient oxide layer formed on their surfaces, resulting in a Y / X ratio of 2.5≦Y / X (the ratio of Si-O bonds to Si-N bonds was low), which is thought to have reduced the total luminous flux retention (reliability) of the LED package.

[0050] Furthermore, comparing Example 2 and Example 3, further heat treatment in the atmosphere at a temperature of 100°C or higher after the heat treatment improved the total luminous flux retention (reliability) of the LED package. This is thought to be because the further heat treatment removed the adsorbed water in the β-sialon phosphor. In fact, looking at the spectrum of the Kubelka-Munk function value (KM value), the KM value B, which indicates the OH bond of the adsorbed water, decreased, while the values ​​of A / B and C / B increased. Even when a further heat treatment was performed, if the heat treatment temperature was less than 100° C. as in Example 4, the total luminous flux retention (reliability) of the LED package could not be sufficiently improved.

[0051] As can be seen from the above results, the present invention can provide a β-sialon phosphor and a method for manufacturing the same that can be used to manufacture a highly reliable light emitting device. Also, the present invention can provide a highly reliable light emitting device. [Industrial Applicability]

[0052] The β-sialon phosphor of the present invention can be used in various light-emitting devices, such as white light-emitting devices and colored light-emitting devices. Examples of white light-emitting devices include liquid crystal displays, backlights for liquid crystal panels, lighting devices, traffic lights, and image display devices. The β-sialon phosphor and light-emitting device of the present invention can also be used in projectors.

Claims

1. A β-sialon phosphor that satisfies the relationship 2.5>Y / X, where X is the photoelectron intensity when the binding energy is 103.5 eV and Y is the photoelectron intensity when the binding energy is 102.0 eV in an X-ray photoelectron spectroscopy spectrum using Al-Kα radiation as an excitation X-ray source.

2. In the spectrum of the Kubelka-Munk function value (KM value) using FT-IR, the wave number is 3650 cm -1 The KM value is A and the wave number is 2600 cm -1 2. The β-sialon phosphor according to claim 1, wherein A / D satisfies 0.15<A / D, where D is the KM value at this time.

3. In the spectrum of the Kubelka-Munk function value (KM value) using FT-IR, the wave number is 3650 cm -1 The KM value is A and the wave number is 3400 cm -1 3. The β-sialon phosphor according to claim 1, wherein, when the KM value at the time is B, A / B satisfies 0.2<A / B.

4. In the spectrum of the Kubelka-Munk function value (KM value) using FT-IR, the wave number is 3200 cm -1 The KM value at this time is C, and the wave number is 3400 cm -1 4. The β-sialon phosphor according to claim 1, wherein, when the KM value at this time is B, 0.7<C / B is satisfied.

5. A light emitting device comprising the β-sialon phosphor according to any one of claims 1 to 4.

6. A method for producing a β-sialon phosphor, comprising heat-treating a β-sialon phosphor at a gauge pressure of 1.62 MPa or more and a temperature of 200°C or more for 48 to 168 hours in the presence of water in an amount of 0.5 mass% or more relative to the total mass of the β-sialon phosphor and water.

7. The method for producing a β-sialon phosphor according to claim 6 , wherein after the heat treatment, a further heat treatment is carried out in the atmosphere at a temperature of 100° C. or higher.

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