JP2010174181A - Phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of a phosphor, which particularly emits green light. <P>SOLUTION: The phosphor is an oxynitride phosphor exhibiting a ratio of 85% to 105% of the emission intensity expressed by a photon number at 300K to the emission intensity expressed by a photon number at 4K, and contains a crystal phase having a chemical composition expressed by formula [I]: Ba<SB>3-x</SB>Eu<SB>x</SB>Si<SB>6</SB>O<SB>12</SB>N<SB>2</SB>. In formula [I], x represents a number satisfying 0.00001≤x≤3. The phosphor is preferably produced through a step of firing a phosphor precursor in the presence of a flux and an annealing step. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a phosphor. Specifically, the present invention relates to a phosphor that emits green light when irradiated with light from an excitation light source such as a semiconductor light emitting element.

  In recent years, phosphor materials having excellent characteristics have been developed for multi-component nitrides and oxynitrides based on silicon nitride. These phosphor materials are known to emit yellow to red light when excited by a blue LED or a near ultraviolet LED. A light emitting device that emits white light can be configured by a combination of such a blue LED or near-ultraviolet LED and these phosphors.

  White light, often used in lighting and display applications, is generally obtained by combining blue, green and red emission by the additive mixing principle of light. In a backlight for color liquid crystal display devices, which is one field of display applications, in order to efficiently reproduce a wide range of colors on the chromaticity coordinates, each of the blue, green and red light emitters has an emission intensity as much as possible. High durability, good color purity, and high durability are desirable so that lighting and displays can be used for a long time.

As a green phosphor suitable for these uses, a Ba ₃ Si ₆ O ₁₂ N ₂ : Eu phosphor has been found as disclosed in Patent Document 1. This phosphor has a wavelength near 400 nm and 450 nm.
Green light having an emission peak wavelength of around 525 nm is shown with respect to nearby excitation light, which is excellent in terms of emission intensity.

JP 2008-138156 A

It is desirable that the green light emitters for illumination and display have a light emission peak wavelength of around 525 nm, high luminous efficiency, and high durability. However, the conventional green phosphor Ba ₃ Si ₆ O ₁₂ N ₂ : Eu described in Patent Document 1 has high conversion efficiency with respect to blue light or near-ultraviolet light, and has good color purity, but has durability. It was insufficient. For this reason, improvement in durability of this green phosphor has been desired.

  The present invention has been made in view of the above problems, and an object thereof is to provide a highly durable green phosphor.

  The present inventors succeeded in synthesizing a highly durable green phosphor by reducing crystal defects that affect the temperature quenching characteristics at a temperature lower than room temperature by annealing after firing using a flux. .

That is, the gist of the present invention is that the ratio of the emission intensity at 300 K to the emission intensity at 4 K represented by the number of photons is 85% or more and 105% or less, and has a chemical composition represented by the following formula [I]. It exists in the oxynitride fluorescent substance characterized by containing a crystal phase.
Ba _3-x Eu _x Si ₆ O ₁₂ N ₂ [I]
(However, in the above formula [I], x represents a number satisfying 0.00001 ≦ x ≦ 3.)

  ADVANTAGE OF THE INVENTION According to this invention, the conversion efficiency with respect to blue light or near-ultraviolet light is high, the point of color purity is also favorable, and the highly durable fluorescent substance which can light-emit green can be provided.

It is a figure which shows the temperature dependence of the number of emitted photons in the low temperature below room temperature of Comparative Examples 1-2 of this invention and Examples 1-3. It is a figure which shows the thermoluminescence glow curve of the comparative example 1 of this invention. It is a figure which shows the FT-IR spectrum of Comparative Examples 1-2 of this invention, and Examples 1-3. It is an enlarged view of 900 cm < ^-1 > vicinity of the FT-IR spectrum (FIG. 3) of Comparative Examples 1-2 of this invention, and Examples 1-3. It is a figure which shows the thermoluminescence glow curve of the comparative example 2 of this invention. It is a figure which shows the thermoluminescence glow curve of Example 1 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the scope of the present invention.

[Composition of phosphor]
The oxynitride phosphor of the present invention (hereinafter appropriately referred to as “the phosphor of the present invention”) is an oxynitride phosphor containing a crystal phase having a chemical composition represented by the following formula [I]. is there.
Ba _3-x Eu _x Si ₆ O ₁₂ N ₂ [I]
(However, in the above formula [I], x represents a number satisfying 0.00001 ≦ x ≦ 3.)

In the above formula [I], x is a numerical value in the range of 0.00001 or more and 3 or less. Among these, x is preferably 0.03 or more, more preferably 0.06 or more, further preferably 0.12 or more, particularly preferably 0.18 or more, and particularly preferably 0.27 or more. On the other hand, if the content of the activating element Eu is too large, concentration quenching may occur. Therefore, it is preferably 1.5 or less, more preferably 1.2 or less, still more preferably 0.9 or less, and particularly preferably 0.8. 7 or less, still more preferably 0.45 or less.

[Phosphor production method]
In the phosphor of the present invention, the phosphor raw material powder and / or a fired product obtained by mixing and firing them (in the present specification, these are collectively referred to as “phosphor precursor”) are present in flux. It is obtained through a step of firing below (firing step) and a subsequent annealing step. The phosphor raw material and the phosphor production method at this time are as follows.

As a method for producing the phosphor of the present invention, in the general formula [I], the raw material of the activation element Eu (hereinafter referred to as “Eu source” as appropriate), the Ba raw material (hereinafter referred to as “Ba source” as appropriate), and , Si raw materials (hereinafter referred to as “Si source” as appropriate) are prepared as phosphor raw materials, these phosphor raw materials are mixed (mixing step), and the resulting mixture (raw material mixture) is fired (firing step). The method of manufacturing by this is mentioned.
As the Eu source, a compound containing Eu is appropriately selected, but Eu ₂ O ₃ or EuF ₃ is preferable. As the Ba source, a compound containing Ba is appropriately selected, and BaCO ₃ is preferable. As the Si source, a compound containing Si is appropriately selected, but SiO ₂ and Si ₃ N ₄ are preferable.

  In the mixing step, the phosphor raw materials are weighed so as to obtain the target composition, and these are mixed before firing. At this time, it is preferable that the mixing is sufficiently performed using a ball mill or the like.

By firing the obtained mixture, a phosphor having a target composition is obtained (firing step). In this firing step, the phosphor material is filled in a container such as a crucible and fired at a predetermined temperature (eg, 1200 ° C. to 1350 ° C.). Examples of the atmosphere for performing the firing step include a hydrogen-containing nitrogen atmosphere, a nitrogen atmosphere, and an argon atmosphere, and among them, a hydrogen-containing nitrogen atmosphere is preferable. Moreover, the pressure at the time of performing a baking process is normally atmospheric pressure.
In the firing step, it is preferable that a flux coexists in the reaction system. Further, the firing process may be divided and fired twice or more.

  The phosphor of the present invention is characterized by a reheating (annealing) step after the heat treatment in the above-described firing step, and if necessary, pulverized, washed, dried, and classified before or after annealing. Etc. are made.

The annealing process is a process in which the phosphor obtained in the firing process is heat-treated at a temperature lower than the firing temperature. In order to improve the durability of the phosphor, it is necessary to have this step.
The heat treatment temperature in the annealing step is usually lower than 1150 ° C., preferably 1050 ° C. or lower, preferably 300 ° C. or higher, preferably 400 ° C. or higher, more preferably 500 ° C. or higher, although it depends on the atmosphere during the heat treatment. Preferably it is 600 degreeC or more, Most preferably, it is 700 degreeC or more.

As an atmosphere during the heat treatment in the annealing step, an oxygen-containing inert gas such as air or oxygen-containing nitrogen, or hydrogen can be used in addition to the same atmosphere as described in the section of the baking step. Among the atmospheres exemplified above, it is preferable to perform the annealing step in an atmosphere containing hydrogen. In this case, the hydrogen content should be 2% by volume or more and 5% by volume or less in consideration of safety. Is preferred.
Further, the heat treatment may be performed a plurality of times by changing the atmosphere.

Examples of the pressure during the heat treatment in the annealing step are the same as those described in the section of the firing step.
Here, when it is necessary to desorb hydrogen taken into the phosphor crystal during heating in the annealing step, it is preferable to use a reduced pressure condition.
At this time, when the phosphor is heated to 1000 ° C. in a vacuum, the H ₂ gas emission amount measured using a temperature-programmed desorption gas analyzer is usually 1 cm ³ / g or less with respect to the phosphor, preferably When the atmosphere, pressure, and time during the annealing step are appropriately adjusted so as to be 0.2 cm ³ / g or less, more preferably 0.1 cm ³ / g or less, a phosphor having high luminance and high durability can be obtained. It is done.
The heat treatment time in the annealing step is usually 0.1 hour or more, preferably 0.5 hour or more, and from the viewpoint of productivity, usually 100 hours or less, preferably 50 hours or less, more preferably 24 hours or less. More preferably, it is 12 hours or less.

  By having this annealing step, the excess hydrogen in the phosphor crystal, distortion and defects of the crystal are reduced, the crystallinity of the phosphor is improved, and the phosphor surface can be expected to be modified. It is thought that it contributes to the improvement of durability.

[Characteristics of phosphor]
The phosphor of the present invention preferably has the following characteristics.
When the annealing step is performed once or more in an atmosphere containing hydrogen, a phosphor having the following characteristics can be obtained. Although these features will be described in detail in the examples described later, they are considered to contribute to the improvement of durability in the durability test.
The phosphor of the present invention preferably satisfies the following (1), and particularly preferably satisfies any of the following (2) to (4) in addition to the following (1).

(1) Temperature quenching rate The phosphor of the present invention preferably has a small temperature quenching rate from 4K to 300K.
In general, when the emission intensity at 4K (number of photons) is compared with the emission intensity at 300K, the emission intensity at 300K is smaller. This is called temperature quenching, and large temperature quenching is considered to indicate that there are many non-radiation deactivation paths such as crystal defects.
The phosphor subjected to the annealing treatment tends to have a low temperature quenching and is considered to have few non-radiation deactivation paths, and is preferable not only in terms of luminous efficiency but also in terms of durability.
When the ratio of the emission intensity (number of photons) at 300K to the emission intensity (number of photons) at 4K is “temperature quenching rate”, the temperature quenching rate is usually 85% or more, preferably 91% or more, more preferably 96%. In addition, it is usually 105% or less, more preferably 100% or less.
The temperature extinction rate can be measured by the method described in Examples described later.

(2) Thermoluminescence The phosphor of the present invention preferably has a small subpeak of the thermoluminescence glow curve.
The phosphor of the present invention has a peak from room temperature to around 200 ° C. in the thermoluminescence glow curve. In addition, the temperature which shows a peak is dependent on measurement conditions, especially a temperature increase rate.
The conventional phosphor represented by the formula [I] usually has a minute peak (hereinafter referred to as “sub-peak”) on the low temperature side of the peak (hereinafter referred to as “main peak”). . On the other hand, a phosphor obtained by performing the annealing process in an atmosphere containing hydrogen tends to have a small intensity of the sub-peak. This is probably because phosphors subjected to an annealing process in an atmosphere containing hydrogen have few or no shallow traps presumed to adversely affect durability.
The phosphor of the present invention has a TL subpeak ratio of 0.05% in a thermoluminescence glow curve measured at a heating rate of 20 K / min, where the ratio of the subpeak intensity to the main peak intensity is “TL subpeak ratio”. Or less, more preferably 0.02% or less, and most preferably no TL subpeak is present.
In addition, thermoluminescence can be measured by the method as described in the below-mentioned Example.

(3) Infrared absorption (FT-IR) spectrum It is preferable that the phosphor of the present invention has a reduced absorbance in the vicinity of 900 cm ^-1 in the infrared absorption (FT-IR) spectrum.
Phosphor of the present invention, the FT-IR spectrum has an absorption peak considered to be derived from Si-OH in the vicinity of 900 cm ^-1. A phosphor subjected to an annealing process in an atmosphere containing hydrogen tends to have a small absorption in the vicinity of 900 cm ⁻¹ . This is considered because there are few Si-OH groups estimated to have a bad influence on a fluorescence characteristic.
That is, the phosphor of the present invention, the FT-IR spectrum, absorption peak intensity near 900 cm ^-1 in the case of normalizing the absorption peak of 750 cm ^-1 as 100% preferably small is preferred. In other words, 900 cm (in which the minimum value of the transmittance.) ^-1 near the absorption peak located at (850～930Cmcm ^-1) is larger is preferable.
Specifically, the phosphor of the present invention, the FT-IR spectrum, absorption peak intensity near 900 cm ^-1 in the case of normalizing the absorption peak of 750 cm ^-1 as 100% (i.e., the minimum value of the transmittance) Is preferably 90% or more, more preferably 92% or more, and particularly preferably 94% or more.

(4) Durability test The phosphor of the present invention has a property that its light emission intensity is hardly lowered even when used for a long time. As a specific range, the phosphor of the present invention is usually 200 hours or more, preferably 500 hours or more, more preferably 600 hours or more in a durability test under an environment where the temperature is 85 ° C. and the relative humidity is 85%. Particularly preferably, it is stable for 800 hours or more. In this case, the longer the stable time, the better. However, 1000 hours is usually sufficient. Here, “stable” means that the ratio of the emission intensity after the durability test to the emission intensity before the durability test is 70% or more. The durability can be evaluated by energizing 20 mA in an environment with a temperature of 85 ° C. and a relative humidity of 85% using an LED aging system of Yamakatsu Electronics Co., Ltd. May be.

Among them, the phosphor of the present invention obtained through the annealing step is obtained by dispersing the phosphor of the present invention in a silicone resin at a concentration of 6% by weight, under an environment where the temperature is 85 ° C. and the relative humidity is 85%, the current density. The chromaticity coordinate CIE chromaticity coordinate value y based on JIS Z 8701 after energizing for 500 hours at 255 mA / mm ² and the light emission output of 0.25 to 0.35 W / mm ² is JIS Z before energization.
The chromaticity coordinate CIE chromaticity coordinate value y based on 8701 is usually a value within a range of ± 30%, preferably within a range of ± 25%, and more preferably within a range of ± 20.

  For example, C460EZ290 (manufactured by Cree, wavelength range 455 nm to 457.4 nm) may be energized with 20 mA as the above-described current density and light emission output excitation light, and the phosphor may be irradiated with excitation light. Moreover, as a silicone resin which disperse | distributes fluorescent substance at this time, Shin-Etsu Chemical Co., Ltd. SCR1101 is mentioned.

  The reason why the phosphor of the present invention can exhibit excellent durability as described above by having an annealing step is not clear, but according to the study by the present inventors, electrons and holes excited by light are not present. This is probably because the number of lattice defects trapped is reduced.

Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless departing from the gist thereof.
[Measurement method of phosphor]
In Examples and Comparative Examples described later, various evaluations of the phosphor particles were performed by the following methods unless otherwise specified.
(Measurement method of emission spectrum)
The emission spectrum was measured using a fluorescence measuring apparatus (manufactured by JASCO Corporation) equipped with a 150 W xenon lamp as an excitation light source and a multi-channel CCD detector C7041 (manufactured by Hamamatsu Photonics) as a spectrum measuring apparatus. The light from the excitation light source was passed through a diffraction grating spectrometer having a focal length of 10 cm, and only the excitation light having a wavelength of 455 nm was irradiated to the phosphor through the optical fiber. The light generated from the phosphor by the irradiation of the excitation light is dispersed by a diffraction grating spectroscope having a focal length of 25 cm, the emission intensity of each wavelength is measured by a spectrum measuring device in a wavelength range of 300 nm to 800 nm, and a personal computer is used. An emission spectrum was obtained through signal processing such as sensitivity correction.

(Measurement method of emission peak wavelength, chromaticity coordinates, emission peak intensity, luminance)
The emission peak wavelength was read from the obtained emission spectrum. Chromaticity coordinates x and y (hereinafter sometimes referred to as CIEx and CIEy, respectively) are chromaticity coordinates in the XYZ color system defined by JIS Z8701, and from the data in the wavelength region of 480 nm to 800 nm, It calculated by the method according to JISZ8724.
The peak emission intensity read from the emission spectrum was expressed as a relative value with the peak intensity at the time of excitation at 365 nm wavelength of LP-B4 manufactured by Kasei Optonix as a reference value of 100.
The luminance was calculated as follows. The stimulus value Y of the XYZ color system calculated when calculating the chromaticity coordinates was obtained. The stimulation value Y at the time of excitation of wavelength 365 nm of LP-B4 manufactured by Kasei Optonics Co. was calculated by the above method, and the relative value of the Y value of the phosphor when the Y value of LP-B4 was 100 was defined as the luminance. .
(Measurement method of temperature extinction rate)
A hole having a diameter of 1.2 mm and a depth of 1 mm was formed in the copper block, and painted with a black paint so as not to reflect the excitation light. The hole was filled with phosphor powder and covered with 1 mm thick quartz glass so as not to spill the phosphor powder, to obtain a phosphor-filled test piece for measuring the temperature quenching rate.

Cryostat (Iwatani Corporation Ltd., Model CRT-006-RK01) equipped with the phosphor filling test piece, and vacuum evacuating the system until 10 ^-4 Torr stand until 4K using liquid nitrogen and liquid helium Cooled down. In this state, light from a semiconductor laser having a wavelength of 403 nm (manufactured by Nichia Corporation, model NDHV220APAE1) is irradiated as excitation light. Inc., USB2000). The light irradiation density of the semiconductor laser was about 1 microwatt / cm ² .

Next, after changing the temperature to 20 K and waiting for about 5 minutes, the fluorescence spectrum was measured. Similarly, the fluorescence spectrum was measured while changing the temperature in increments of 20K up to 300K. A temperature quenching curve was obtained by graphing the relationship between the number of photons and the temperature estimated from the fluorescence spectra at each temperature thus obtained.

  In addition, as an index for comparing the tendency of temperature quenching, the ratio of the emission intensity at 4K to the emission intensity at 300K was used. Usually, the emission intensity is compared by the number of emission energy, but the emission intensity here is the number of emitted photons. The reason is that the spectrum shape changes by lowering the temperature, so it is preferable to compare by the number of photons in order to compare correctly.

(Measurement method of thermoluminescence)
A hole having a diameter of 1.2 mm and a depth of 1 mm was formed in the copper block, and painted with a black paint so as not to reflect the excitation light. The hole was filled with phosphor powder, and covered with quartz glass having a thickness of 1 mm so as not to spill the phosphor powder, to obtain a test piece for thermoluminescence measurement.

The test piece was mounted at a predetermined position of a cryostat (model I / T, manufactured by Iwatani Corporation, model CRT-006-RK01). The inside of the apparatus was evacuated to the 10 ⁻⁴ Torr level and cooled to −180 ° C. (93 K) with liquid nitrogen.
A region of 1.2 cm in diameter on the sample surface of the test piece was irradiated with a deep ultraviolet lamp (USHIO Inc., model UER20H-222B) having a wavelength of 222 nm for 30 minutes. After the end of the deep ultraviolet lamp irradiation, the sample was waited for 1 minute, and after the emission of the afterglow component was not detected, the temperature of the sample was increased at a rate of 20 ° C./min. The light generated while the temperature is raised to about 300 K after irradiation with the deep ultraviolet lamp is spectroscopically analyzed by a diffraction grating spectrometer (manufactured by Retsu Applied Optics Co., Ltd., model MC-30N) at 520 nm.
The light was taken out and the intensity was measured with a photomultiplier tube (Hamamatsu Photonics Co., Ltd., H8259-10 type). The relationship between temperature and emission intensity was graphed to obtain a thermoluminescence glow curve.

(Fourier transform infrared spectroscopy (FT-IR) measurement method)
The phosphor sample was mixed at a ratio of 1% by weight with respect to the alkali metal halide compound (KBr). The obtained phosphor mixed powder is finely pulverized and attached to a Fourier transform infrared spectrophotometer (manufactured by JASCO Corporation, FT / IR-4000 type) in a state where the tablet molding machine is fixed. Measurements were made.

(Durability test method)
A blue light emitting diode (C460EZ290: manufactured by Cree) was used as the first light emitter, and die bonding was performed on the electrode at the bottom of the recess of the frame using silver paste as an adhesive. After heating at 150 ° C. for 2 hours to cure the silver paste, the blue LED and the frame electrode were wire-bonded. A gold wire with a diameter of 25 μm was used as the wire.

  To 0.08 g of each phosphor dried at 150 ° C. for 2 hours, 1.415 g of a silicone resin (SCR1011: manufactured by Shin-Etsu Chemical Co., Ltd.) was mixed to prepare a phosphor slurry. The slurry was poured into a concave portion of the frame, and cured by heating at 70 ° C. for 1 hour and further at 150 ° C. for 5 hours to form a phosphor-containing portion, thereby producing a surface mount green light emitting device.

  The obtained light emitting device was driven to emit light by energizing the blue LED with 20 mA in an environment of a temperature of 85 ° C. and a humidity of 85%. The CIE chromaticity coordinate value y, which is a chromaticity coordinate having a high influence on green, was measured every 25 hours at room temperature of 25 ° C., and the ratio when the value immediately after the start of energization was taken as 100 was determined as the CIEy retention rate.

[Comparative Example 1]
BaCO ₃ (293 g), SiO ₂ (149 g) are used as the phosphor material so that the charged composition of each material of the phosphor is Ba: Si: Eu = 2.7: 4.5: 0.3 (molar ratio). And Eu ₂ O ₃ (29 g) were thoroughly mixed with stirring and then filled into an alumina crucible. This is placed in a resistance heating electric furnace with a temperature controller, heated to 1100 ° C. at a heating rate of 4 ° C./min in an atmospheric atmosphere at atmospheric pressure, held at that temperature for 6 hours, and then allowed to cool to room temperature. did. The obtained sample was pulverized to 100 μm or less on an alumina mortar.

The sample (177 g) obtained above and Si ₃ N ₄ (34 g) were sufficiently stirred and mixed, and then filled into an alumina crucible as primary firing, and this was filled with a hydrogen-containing nitrogen atmosphere (nitrogen) under atmospheric pressure. : Hydrogen = 96: 4 (volume ratio), hereinafter referred to as “mixed gas of 96% by volume of nitrogen + 4% by volume of hydrogen”.) Heated to 1170 ° C. under a flow rate of 3 liters / minute, and at that temperature, 6 After holding for a period of time, it was allowed to cool to room temperature. The obtained fired powder was pulverized on an alumina mortar until it became 100 μm or less.

200 g of the fired powder obtained by the primary firing, BaF ₂ (3 g) as the flux, B
After agitation and mixing with aHPO ₄ (6 g), it is filled in an alumina crucible with molybdenum lining, and as a secondary firing, 3 liters of mixed gas of 96 volume% nitrogen + 4 volume% hydrogen under atmospheric pressure. The mixture was heated to 1320 ° C. under a flow rate of 1 minute, held at that temperature for 20 hours, and then allowed to cool to room temperature. The obtained fired powder was pulverized on an alumina mortar until it became 100 μm or less.

The sample obtained by the secondary firing (200 g), the flux BaF ₂ (4 g), BaCl ₂ (20 g), and BaHPO ₄ (10 g) were sufficiently stirred and mixed, and then put into an alumina crucible. Filled and heated to 1170 ° C. under a flow of 3 liters / minute of mixed gas of 96% by volume of nitrogen and 4% by volume of hydrogen at the atmospheric pressure as the third firing, held at that temperature for 6 hours, and then allowed to cool to room temperature. .
The obtained fired powder is slurried and dispersed using glass beads, and after separating 60 μm or less with a sieve, it is washed with 1N hydrochloric acid, dehydrated and dried, and sieved to 60 μm or less. A green phosphor having a chemical composition of Ba _2.7 Eu _0.3 Si ₆ O ₁₂ N ₂ was obtained.

FIG. 1 shows the temperature dependence (temperature quenching) of the number of emitted photons at a low temperature of room temperature or lower, together with the results of other comparative examples and examples. The ratio of the emission intensity at 4K to the emission intensity at 300K (compared by the number of photons) of this phosphor was 61%. Since this phosphor has a large temperature quenching, it is considered that there are many non-radiative deactivation centers.

  In addition, a thermoluminescence glow curve measured at a heating rate of 20 K / min of this phosphor is shown in FIG. The ratio of the sub-peak intensity appearing near 60 ° C. to the main peak intensity appearing near 200 ° C. (TL sub-peak ratio) was 0.07%.

FIG. 3 shows an FT-IR spectrum of this phosphor, and FIG. 4 shows an enlarged view thereof. In the FT-IR spectrum, this phosphor had a large absorption peak estimated to be derived from Si—OH appearing at 800 to 940 cm ⁻¹ . That is, the minimum value of the transmittance from 800 to 940 cm ⁻¹ when normalized with the absorption peak near 750 cm ⁻¹ as 100% was 89%.
For this reason, it is considered that a relatively large amount of OH groups are present on the surface of the phosphor.
The chromaticity coordinate value y maintenance rate after 500 hours of the LED lighting test of this phosphor was as low as 65%.
These other analytical values, durability evaluation results, and light emission characteristics are shown together with other comparative examples and examples in Table 1.

[Comparative Example 2]
The phosphor of Comparative Example 2 was obtained by heating the phosphor obtained in Comparative Example 1 in air at 700 ° C. for 20 hours under atmospheric pressure.
The ratio of the emission intensity at 4K to the emission intensity at 300K of this phosphor (compared by the number of photons) was 83%. Since this phosphor has a slightly large temperature quenching, it is considered that there are a few more radiationless deactivation centers.

  When the thermoluminescence of this phosphor was measured at a heating rate of 20 K / min, as shown in FIG. 5, the ratio of the sub-peak intensity appearing near 10 ° C. to the main peak intensity appearing near 160 ° C. (TL sub-peak ratio) is It was 0.7%. Compared with Comparative Example 1, a large sub-peak is detected, and it is considered that crystal defects are generated by the heat treatment in air, which is considered to be a cause of a decrease in luminance.

When the FT-IR spectrum of this phosphor was measured, this phosphor had a large absorption peak that was considered to be derived from Si—OH appearing at 800 to 940 cm ⁻¹ . That is, 75
The minimum value of transmittance at 900 cm ⁻¹ when normalized with an absorption peak near 0 cm ⁻¹ is 87%.
was. It is considered that a relatively large amount of OH groups are present on the phosphor surface.

[Example 1]
The phosphor of Example 1 was obtained by heating the phosphor obtained in Comparative Example 2 at 930 ° C. for 20 hours in a hydrogen (100%) flow atmosphere at atmospheric pressure.
The ratio of the emission intensity at 4K to the emission intensity at 300K of this phosphor (compared by the number of photons) was 95%. Since this phosphor has a small temperature quenching, it is considered that there are few non-radiation deactivation centers.

  FIG. 6 shows a glow curve of thermoluminescence measured at a heating rate of 20 K / min of this phosphor. Unlike Comparative Example 1 and Comparative Example 2, no peak was present on the low temperature side of the main peak appearing near 160 ° C. This is considered to indicate that the crystal defects disappeared by the heat treatment (annealing step) in a hydrogen-containing atmosphere.

Moreover, in the FT-IR spectrum, this phosphor had a small absorption peak that was considered to be derived from Si—OH appearing at 800 to 940 cm ⁻¹ . That is, the minimum value of the transmittance of 900 cm ^-1 when normalized by the absorption peak around 750 cm ^-1 was 96%. The surface of this phosphor is considered to have fewer OH groups than the phosphors of Comparative Example 1 and Comparative Example 2, and this has an effect on improving durability in the durability test. Conceivable.
The chromaticity coordinate value y retention rate after 500 hours in the durability test is 65% for the phosphor of Comparative Example 1, whereas the chromaticity coordinate value y retention rate of the phosphor of this example is 88%. was.

[Example 2]
The phosphor of Example 2 was obtained by heating the phosphor of Comparative Example 1 at 930 ° C. for 20 hours in a hydrogen (100%) flow atmosphere under atmospheric pressure.
The ratio of the emission intensity at 4K to the emission intensity at 300K of this phosphor (compared by the number of photons) was 98%. Since this phosphor has low temperature quenching, it is considered that there are few non-radiative deactivation centers.

  When the thermoluminescence of this phosphor was measured at a heating rate of 20 K / min, no peak was present on the low temperature side of the main peak appearing near 160 ° C., as in Example 1. This is considered to show that the crystal defects disappeared by the heat treatment in hydrogen.

In the FT-IR spectrum of this phosphor, the phosphor had a small absorption peak that appears to be derived from Si—OH appearing at 800 to 940 cm ⁻¹ . That is, the minimum value of the transmittance of 900 cm ^-1 when normalized by the absorption peak around 750 cm ^-1 was 96%.
Compared with Comparative Example 1 and Comparative Example 2, the surface of this phosphor is considered to have fewer OH groups.
These are considered to have an effect on durability improvement in the lighting test. In addition, the chromaticity coordinate value y maintenance rate after 500 hours in the durability test of the phosphor of this example was 78%.

[Example 3]
The phosphor of Example 3 was obtained by heating the phosphor of Comparative Example 1 at 1000 ° C. for 10 hours in an atmosphere of 4% by volume hydrogen + 96% by volume nitrogen under atmospheric pressure.
The ratio of the emission intensity at 4K to the emission intensity at 300K (compared by the number of photons) of this phosphor was 89%. Since this phosphor has a small temperature quenching, it is considered that there are few non-radiation deactivation centers.

  When the thermoluminescence of this phosphor was measured at a heating rate of 20 K / min, no peak was present on the low temperature side of the main peak appearing near 160 ° C., as in Example 1. This is considered to indicate that the crystal defects disappeared by the heat treatment in the hydrogen nitrogen mixed gas.

In the FT-IR spectrum of this phosphor, the phosphor had a small absorption peak that appears to be derived from Si—OH appearing at 800 to 940 cm ⁻¹ . That is, the minimum value of the transmittance of 900 cm ^-1 when normalized by the absorption peak around 750 cm ^-1 was 94%.
Compared with Comparative Example 1 and Comparative Example 2, the surface of this phosphor is considered to have fewer OH groups.
This is considered to have an effect on the durability improvement in the durability test. In addition, the chromaticity coordinate value y maintenance rate after 500 hours of the durability test of the phosphor of this example was 87%.

The phosphor of the present invention can be used in any industrial field, for example, in a light emitting device. Among them, the phosphor of the present invention is suitable for use in a white light-emitting device because the decrease in light emission efficiency accompanying a temperature rise is usually smaller than that of a YAG: Ce phosphor that has been widely used in white light-emitting devices. is there.

  The phosphor of the present invention is widely used and can be used in the field of image display devices such as lighting or displays. Among them, the LED for general illumination is particularly suitable for the purpose of realizing a high-power lamp, particularly a white LED for backlight having a high luminance and a wide color reproduction range.

Claims (1)

The ratio of the emission intensity indicated by the number of photons at 300K to the emission intensity indicated by the number of photons at 4K is 85% or more and 105% or less, and
An oxynitride phosphor containing a crystal phase having a chemical composition represented by the following formula [I].
Ba _3-x Eu _x Si ₆ O ₁₂ N ₂ [I]
(However, in the above formula [I], x represents a number satisfying 0.00001 ≦ x ≦ 3.)

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