JP4910151B2 - Phosphor mixture - Google Patents

Description

  The present invention relates to a phosphor mixture and a method for producing the same, and relates to the development of a phosphor composition that can be used for illumination, display media, and the like.

White calcium halophosphate phosphors are used in white fluorescent lamps that have been widely used as illumination light sources. However, there is a problem in that the red light component is poor in the emission spectrum and the color rendering properties are poor. Therefore, recently, for the purpose of improving the color rendering properties and light output of the fluorescent lamp, a three-wavelength fluorescent lamp using an appropriate mixture of a red phosphor, a green phosphor and a blue phosphor has been put into practical use. Patent Documents 1 to 3 disclose a method of manufacturing a phosphor mixture by combining four or more kinds of phosphors in order to realize light emission with better color rendering than three-wavelength light emission. In order to realize a light emission color with no color unevenness, it is necessary to uniformly mix these plural types of phosphor powders without agglomeration. As a solution to this problem, Patent Document 4 discloses a method of preventing aggregation by synthesizing single spherical phosphor particles using a uniform precipitation method.
2006-63233 2004-269845 2002-198008 Hei 8-143305

  However, in the method of manufacturing a phosphor mixture by combining a plurality of types of phosphors as disclosed in Patent Documents 1 to 3, a plurality of types of phosphors are uniformly mixed to prevent color unevenness, There is a problem that it is not easy to finely adjust the relative proportions of the various phosphor mixed powders to set the required chromaticity.

  Further, the method for preventing aggregation using the uniform precipitation method disclosed in Patent Document 4 has a problem that the manufacturing process becomes complicated because precise temperature adjustment and solution concentration adjustment are required during synthesis. .

  The present invention has been made in view of the above-described conventional situation, and a phosphor mixture in which a plurality of types of phosphors are uniformly mixed can be obtained by a simple manufacturing process by selecting an appropriate chemical composition and temperature / pressure. Providing is a problem to be solved.

  According to the first aspect of the present invention, a fluorescent material is characterized in that a multiphase mixture synthesized in a region where a plurality of solid phases are stably coexisting is selected as a base material of a phosphor by selecting an appropriate chemical composition and temperature / pressure. Body mixture and method for producing the same.

  According to the present invention, by selecting an appropriate chemical composition and temperature / pressure, a multi-phase mixture synthesized in a region where a plurality of solid phases stably coexist is used as a matrix of the phosphor, so that a plurality of types of phosphors can be obtained. Can be mixed in a uniform process and a chromaticity-adjusted phosphor mixture can be produced by a simple process.

By selecting the appropriate chemical composition and temperature / pressure, multiple types of phosphor mixtures synthesized in a region where multiple solid phases coexist stably are produced by uniformly dispersing each phosphor. Is unnecessary or can be omitted significantly.
Furthermore, if the average chemical composition changes even slightly in the multiphase coexistence region, the proportion of the coexisting phase (phase composition) changes under the influence, and as a result, the emission spectrum of the entire phosphor mixture changes. That is, by manipulating the average chemical composition of the phosphor mixture, the chromaticity of the entire phosphor mixture can be finely adjusted.

  In addition, when the chemical composition and crystal structure of the coexisting multiphase mixture are similar, the coexisting fluorescence is compared with the phosphor blend produced by mixing phosphors having completely different chemical compositions and crystal structures. It can be expected that the difference in speed at which the body deteriorates with time is small and the color balance is not easily lost.

  In the conventional method for producing a phosphor mixture composed of a plurality of types of phosphors, it is necessary to synthesize various phosphors separately and then uniformly mix the plurality of types of phosphor powders at a predetermined ratio. It was. According to the method for producing a phosphor mixture according to the present invention, a plurality of uniformly dispersed phosphor mixtures are obtained as a result of the production process, so that the mixing process is unnecessary or can be greatly omitted.

  In the conventional phosphor mixture, in order to adjust the chromaticity, it is necessary to mix plural kinds of phosphors at a predetermined ratio. However, in the present invention, the emission spectrum or chromaticity of the entire phosphor mixture can be adjusted by manipulating the average chemical composition of the phosphor mixture.

  When a mixed powder consisting of multiple types of phosphors is mounted on a product, there is a difference in the durability of each phosphor, and each phosphor exhibits a different deterioration with time, resulting in the loss of the overall color balance. There was a problem. However, in the phosphor mixture according to the present invention, when the chemical composition and crystal structure of the coexisting phosphors are similar, the phosphor blend produced by mixing phosphors having completely different chemical compositions and crystal structures. Compared to the above, there can be expected an advantage that the difference in the rate of deterioration of the coexisting phosphors with time is small and the color balance is not easily lost.

  Some phosphors have a structure in which impurity ions called activators are dispersed in a base crystal. The luminescent ion species as the activator is limited to some ions such as rare earth, while the base crystal can be diverted to different applications by changing the concentration and type of the activator. Therefore, the phosphor mixture provided by claims 1 to 6 is not a phosphor limited to the luminescent ions used in the present example, but is activated if it is an element that can generate a luminescent center. It can be used as an agent. Furthermore, the phosphor mixture provided by claims 1 to 6 is not a light emitting material limited to ultraviolet excitation at a wavelength of 200 nm to 400 nm, but emits light by excitation of vacuum ultraviolet light, electron beam, electric field, etc. It can be used as a display medium or a phosphor for illumination, and can be applied to liquid crystal displays, plasma displays, field emission displays, full-color fluorescent display tubes, electroluminescence, and the like.

  Embodiments 1 and 2 of the present invention will be described below in detail with reference to the drawings. In this example, a phosphor mixture in which two types of phosphors are uniformly dispersed and coexist is manufactured, but these are examples, and a phosphor mixture in which three or more types of phosphors coexist is manufactured. However, it goes without saying that the present invention is established.

  Further, in this example, a phosphor sintered powder is obtained after synthesizing and pulverizing a crystalline sintered body sample, and the fluorescence characteristics are evaluated. However, a thin film or glass or other shape sample is synthesized. However, it goes without saying that the present invention is established.

  In addition, after synthesizing a single solid phase or a uniform single solid phase in a region where a single solid phase or a single liquid phase is stable, a plurality of solid phases can be formed by manipulating temperature or pressure. A phosphor mixture in which multiple solid phases coexist is produced by changing to a stable temperature and pressure range and causing phase separation such as spinodal decomposition or homogeneous nucleation / growth or heterogeneous nucleation / growth. Even in this case, it goes without saying that the present invention is established.

In this example, a phosphor mixture obtained by activating Eu in a mixture in which two phases of an α phase and a β ′ phase coexist in a binary system of Ca ₃ (PO ₄ ) ₂ —Sr ₃ (PO ₄ ) ₂ The manufacturing method will be described.

Non-patent document 1 reports the phase composition of Ca _3-x Sr _x (PO ₄ ) ₂ which is a Ca ₃ (PO ₄ ) ₂ -Sr ₃ (PO ₄ ) ₂ binary composition. According to this, it is said that the α phase and the β ′ phase are stable in the chemical composition range (2.31 ≦ x) where the value of x is 2.31 or more. However, since the α phase has a structure equivalent to Sr ₃ (PO ₄ ) ₂ (x = 3), it is considered that the α single phase is stable in the chemical composition region where the value of x is close to 3. Therefore, first, the two-phase coexistence region of α phase and β ′ phase in the binary system of Ca ₃ (PO ₄ ) ₂ —Sr ₃ (PO ₄ ) ₂ was determined.
Chemistry of Materials, Vol.14, No.7, 3197 (2002) Using calcium carbonate (CaCO3), strontium carbonate (SrCO3), and ammonium dihydrogen phosphate (NH4H2PO4) as starting materials, 0.06: 2.94: 2 and 0.05: Mixed at 2.95: 2 (molar ratio). The ratios of these starting materials are the ratios in which the chemical compositions with the average chemical composition of Ca0.06Sr2.94 (PO4) 2 (x = 2.94) and Ca0.05Sr2.95 (PO4) 2 (x = 2.95) are produced. It is. Next, these mixed powders were uniaxially pressed into pellets with a diameter of about 12 mm and a height of about 3 mm, heated in the atmosphere at 400 ° C. for 1 hour, then removed from the electric furnace and cooled to room temperature. After pulverizing and mixing the obtained sample, it was uniaxially pressed into pellets with a diameter of about 12 mm and a height of about 3 mm, heated in the atmosphere at 1300 ° C for 3 hours, the electric furnace was turned off and the furnace was turned on. Cooled to room temperature over about 3 hours.

The obtained sample was pulverized into a fine powder. The profile intensity in the 2θ range from 10.0 ° to 75.0 ° was measured using an X-ray powder diffractometer with CuKα ₁ line (45 kV × 40 mA) as incident light. From the obtained X-ray diffraction pattern, a sample having a composition of Ca _0.06 Sr _2.94 (PO ₄ ) ₂ (x = 2.94) coexisted with an α phase and a small amount of β ′ phase, whereas Ca _0.05 Sr _2.95 The sample of (PO ₄ ) ₂ (x = 2.95) composition was composed of α single phase. From the above, it was found that the chemical composition range of the two-phase coexistence region of α phase and β ′ phase in the Ca ₃ (PO ₄ ) ₂ -Sr ₃ (PO ₄ ) ₂ binary system is 2.31 ≦ x ≦ 2.95. .

Therefore, the inventors consider that a Ca _3-x Sr _x (PO ₄ ) ₂ composition in which two phases of α phase and β ′ phase coexist is promising as a matrix of the phosphor mixture according to the present invention, Eu Attempts were made to prepare a phosphor two-phase mixture using as an activator.

Using calcium carbonate (CaCO ₃ ), strontium carbonate (SrCO ₃ ), europium oxide (Eu ₂ O ₃ ), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ ) as starting materials, 1.00: 1.98: 0.01: 2.00 It was mixed at 0.39: 2.59: 0.01: 2.00, 0.35: 2.63: 0.01: 2.00, 0: 2.98: 0.01: 2.00 (molar ratio) to obtain four kinds of raw material mixed powder. Each raw material mixing ratio is 4 types, in which the average chemical composition is Ca _3-x Sr _x-0.02 Eu ²⁺ _0.02 (PO ₄ ) ₂ and the value of x is represented by x = 2.00 and 2.61, 2.65, 3.00 The ratio of the composition produced. The raw material mixed powder was uniaxially pressed into pellets with a diameter of about 12 mm and a height of about 3 mm, heated in the atmosphere at 400 ° C. for 1 hour, then removed from the electric furnace and cooled to room temperature. The obtained sample was pulverized and mixed, then uniaxially pressed into a pellet with a diameter of about 12 mm × height of about 3 mm, and heated at 1300 ° C for 3 hours in a mixed gas stream of 3% hydrogen and 97% argon gas. The electric furnace was turned off and cooled to room temperature in the furnace over about 3 hours.

The obtained sample was pulverized into a fine powder. The profile intensity in the 2θ range from 10.0 ° to 75.0 ° was measured using an X-ray powder diffractometer with CuKα ₁ line (45 kV × 40 mA) as the incident light. From this X-ray diffraction pattern, sample x = 2.00 was a β ′ single phase and sample x = 3.00 was an α single phase. On the other hand, sample x = 2.61 and sample x = 2.65 coexisted two phases of β ′ phase and α phase. The existence ratio of β 'phase and α phase contained in these samples was determined from the X-ray powder diffraction pattern using the Rietveld method (Non-patent Document 2). Sample x = 2.61 was 19 wt% α phase + 81 wt. % Β ′ phase and sample x = 2.65 was 22% wt α phase + 78% wt β ′ phase.
Journal of Applied Crystallography, Vol. 2, 65 (1969) Using a commercially available spectrofluorometer, the fluorescence intensity at a wavelength of 200 nm to 800 nm was measured using excitation light having a wavelength of 200 nm to 400 nm. The luminescent color was shown by the XYZ display system defined by the International Lighting Commission, and the evaluation was performed according to JIS Z8722.

  The results of evaluating the excitation spectrum and emission spectrum of sample x = 2.00 are shown in FIG. As is clear from the evaluation results shown in FIG. 1, the obtained sample x = 2.00 has an excitation peak wavelength in the ultraviolet region near 280 nm. When the emission spectrum of sample x = 2.00 was observed with ultraviolet light having an excitation wavelength of 280 nm, the fluorescence had a relatively broad spectrum with a peak at 515 nm and a half-value width of 98 nm, and a width ranging from 350 nm to 700 nm. It became a relatively broad spectrum.

  FIG. 2 shows the results of evaluating the excitation spectrum and emission spectrum of sample x = 3.00. As is apparent from the evaluation results shown in FIG. 2, the obtained sample x = 3.00 has an excitation peak wavelength in the ultraviolet region near 275 nm. When the emission spectrum of sample x = 3.00 was observed with ultraviolet light having an excitation wavelength of 275 nm, the fluorescence had a relatively sharp spectrum with a peak of 406 nm and a half-value width of 35 nm.

    Next, emission spectra of sample x = 2.00 and sample x = 3.00 were observed with ultraviolet light having an excitation wavelength of 365 nm (Fig. 3). In sample x = 2.00, the fluorescence observed a relatively broad spectrum with a peak at 515 nm and a half-value width of 85 nm, and became a relatively wide spectrum ranging from 435 nm to 685 nm. From the value of chromaticity coordinates, the emission color was classified as yellowish green (Fig. 4). That is, the europium-activated β′-phase calcium strontium phosphate phosphor obtained by the above method is a phosphor that emits yellowish green when excited by ultraviolet rays having a wavelength of 365 nm. On the other hand, for sample x = 3.00, a relatively sharp spectrum with a peak of 406 nm and a half width of 40 nm was observed. From the value of the chromaticity coordinates, the emission color was classified into bluish purple (Fig. 4). That is, the europium-activated α-phase strontium phosphate phosphor obtained by the above method is a phosphor that emits blue-violet light when excited by ultraviolet light having a wavelength of 365 nm.

  The emission spectra of sample x = 2.61 and sample x = 2.65 were observed with ultraviolet light having an excitation wavelength of 365 nm (Fig. 5). Sample x = 2.61 and sample x = 2.65 both show the characteristics of the emission spectra belonging to both phases because the two phases of β ′ phase and α phase coexist. That is, in samples x = 2.61 and x = 2.65, fluorescence peaks exist at two locations of 515 nm and 410 nm, and broad spectra ranging from 380 nm to 650 nm were observed. From the chromaticity coordinate values, the emission color of sample x = 2.61 was classified as white, and the emission color of sample x = 2.65 was classified as bluish purple (FIG. 4).

  When the emission colors of x = 2.61 and sample x = 2.65 were confirmed with the naked eye using ultraviolet rays emitted from a high-pressure mercury lamp, the emission color was uniform. From this, it was confirmed that two types of phosphors having different emission spectra were uniformly mixed.

As is clear from the chromaticity diagram shown in FIG. 4, the positions of the chromaticity coordinates of the samples x = 2.61 and x = 2.65 in which two phases of β 'and α phases coexist are composed of β' single phase. It is on a straight line connecting the position of the chromaticity coordinate (0.295, 0.569) of the sample x = 2.00 and the position of the chromaticity coordinate (0.164, 0.012) of the sample x = 3.00 made of α single phase. From this, the average chemical composition obtained by the above method has the general formula Ca _3-x Sr _x-0.02 Eu ²⁺ _0.02 (PO ₄ ) ₂ (where x is a number in the range of 2.31 ≦ x ≦ 2.95) In the phosphor mixture represented by.), Two types of phosphors with different emission spectra coexist uniformly, and the chromaticity of light emission can be determined from the chromaticity coordinates (0.295, 0.569) by manipulating the value of x. It can be arbitrarily set between chromaticity coordinates (0.164, 0.012).

In this example, Bi was activated in a composition having an average chemical composition represented by the general formula Na _2x Ca _3-x Al ₂ O ₆ (where x is a number in the range of 0.10 ≦ x ≦ 0.16). A method for producing the phosphor mixture obtained by doing so will be described.

Non-patent document 3 reports a phase composition with respect to the concentration of Na for this base crystal. According to this, the cubic crystal structure (C phase) is stable when the value of x is in the range of 0 ≦ x <0.10, and the orthorhombic crystal structure (O phase) is in the range of 0.16 <x ≦ 0.20. It is stable. On the other hand, in the range of 0.10 ≦ x ≦ 0.16, it has been clarified that two phases of a C phase having an x = 0.10 composition and an O phase having an x = 0.16 composition coexist.
Cement Chemistry; pp. 1-28. Thomas Telford Publishing, London, UK, (1997) The inventors have described that a two-phase mixture represented by the general formula Na2xCa3-xAl2O6 in the range of 0.10 ≦ x ≦ 0.16 is in accordance with the present invention. Taking the idea of being promising as a matrix of a phosphor mixture, a synthesis experiment of a phosphor two-phase mixture described below was conducted.

Calcium carbonate (CaCO ₃ ), alumina (Al ₂ O ₃ ), sodium bicarbonate (NaHCO ₃ ), bismuth oxide (Bi ₂ O ₃ ) are used as starting materials, and the average chemical composition is Na _2x Ca _2.97-x Bi _0.02 Al _It was weighed at a ratio of 8 compositions represented by ₂ O ₆ (x = 0.05, 0.10, 0.11, 0.125, 0.135, 0.15, 0.16, 0.20). These raw material mixed powders were uniaxially pressed into pellets with a diameter of about 12 mm and a height of about 3 mm, heated in the atmosphere at 925 ° C. for 1 hour, then removed from the electric furnace and cooled to room temperature. After the obtained sample was pulverized and mixed, it was uniaxially pressed into a pellet with a diameter of about 12 mm and a height of about 3 mm, heated in the atmosphere at 1200 ° C for 2 hours, taken out of the electric furnace, and cooled to room temperature. .

The obtained sample was pulverized into a fine powder. The profile intensity in the 2θ range from 10.0 ° to 60.0 ° was measured using an X-ray powder diffractometer with CuKα ₁ line (45 kV × 40 mA) as the incident light. From the obtained X-ray diffraction pattern, the sample in the range of x value 0.05 ≦ x ≦ 0.10 is the C phase, the sample in the range 0.16 ≦ x ≦ 0.20 is the O phase, and the value of x is 0.11 ≦ x It was confirmed that the sample in the range of ≦ 0.15 coexisted with two phases of C phase and O phase.

  Using a commercially available spectrofluorometer, the fluorescence intensity of wavelengths from 200 nm to 800 nm was measured using excitation light having a wavelength of 254 nm. The luminescent color was shown by the XYZ display system defined by the International Lighting Commission, and the evaluation was performed according to JIS Z8722.

  Since both sample x = 0.05 and sample x = 0.10 consisted of only the C phase, no significant difference was observed in their emission spectra. Moreover, since both sample x = 0.16 and sample x = 0.20 are composed of only the O phase, no significant difference was observed in their emission spectra. FIG. 6 shows the results of evaluating the emission spectra of sample x = 0.10 and sample x = 0.16. As is clear from the evaluation results shown in Fig. 6, in sample x = 0.10, the fluorescence observed a relatively broad spectrum with a peak at 478 nm and a half-value width of 93 nm, and a comparison of widths from 350 nm to 700 nm. Wide spectrum. The chromaticity coordinate values were (0.155, 0.235), and the emission color was classified as greenish blue (Fig. 7). That is, the bismuth-activated cubic sodium calcium aluminate phosphor obtained by the above method is a phosphor that emits greenish blue light when excited by ultraviolet light having a wavelength of 254 nm.

  In sample x = 0.16, the fluorescence had a relatively broad spectrum with a peak at 537 nm and a half-value width of 105 nm, and a relatively broad spectrum ranging from 350 nm to 700 nm (Fig. 6). The chromaticity coordinate values were (0.284, 0.468), and the emission color was classified as yellowish green (Fig. 7). In other words, the bismuth-activated orthorhombic sodium calcium aluminate phosphor obtained by the above method is a phosphor that emits yellowish green when excited by ultraviolet light having a wavelength of 254 nm.

  Next, the emission spectrum of a series of samples having a value of x in the range of 0.11 ≦ x ≦ 0.15 was observed (FIG. 8). In these samples, two phases of C and O phases coexist, and as the value of x increases (Na concentration increases), the peak position of the emission spectrum continuously increases from 484 nm to 528 nm. Increased.

  Using a UV light emitted from a low-pressure mercury lamp, the emission color of a series of samples having a value of x in the range of 0.11 ≦ x ≦ 0.15 was confirmed with the naked eye. From this, it was confirmed that two types of phosphors having different emission spectra were uniformly mixed.

As is clear from the chromaticity diagram shown in FIG. 7, the position of the chromaticity coordinate of the sample in which two phases of C phase and O phase coexist is the chromaticity coordinate (0.155, 0.235) of the sample consisting of C single phase. ) And the position of the chromaticity coordinates (0.284, 0.468) of the sample consisting of O single phase. From this, the average chemical composition obtained by the above method is represented by the general formula Na _2x Ca _2.97-x Bi _0.02 Al ₂ O ₆ (where x is a number in the range of 0.11 ≦ x ≦ 0.15). In the phosphor mixture, two types of phosphors with different emission spectra coexist uniformly, and the chromaticity of light emission can be changed from chromaticity coordinates (0.155, 0.235) to chromaticity coordinates (0.284) by manipulating the value of x. , 0.468) can be arbitrarily set.

  The phosphor mixture of the present invention is not a light emitting material limited to excitation of ultraviolet light having a wavelength of 200 nm to 400 nm, but can be diverted to a display medium that emits light by excitation of vacuum ultraviolet light, an electron beam, an electric field, or the like, or a phosphor for illumination. It can be used for liquid crystal displays, plasma displays, field emission displays, full-color fluorescent display tubes, electroluminescence, and the like.

FIG. 1 is a diagram showing an excitation spectrum and an emission spectrum of a sample x = 2.00 according to Example 1 of the present invention. FIG. 2 is a diagram showing an excitation spectrum and an emission spectrum of sample x = 3.00 according to Example 1 of the present invention. FIG. 3 is a diagram showing emission spectra at the excitation wavelength of 365 nm of sample x = 2.00 and sample x = 3.00 according to Example 1 of the present invention. FIG. 4 is a diagram illustrating a chromaticity diagram according to the first embodiment of the present invention. FIG. 5 is a graph showing emission spectra at the excitation wavelength of 365 nm of sample x = 2.61 and sample x = 2.65 according to Example 1 of the present invention. FIG. 6 is a graph showing emission spectra at the excitation wavelength of 254 nm of sample x = 0.10 and sample x = 0.16 according to Example 2 of the present invention. FIG. 7 is a diagram illustrating a chromaticity diagram according to the second embodiment of the present invention. FIG. 8 is a graph showing an emission spectrum at an excitation wavelength of 254 nm of a sample in which the value of x according to Example 2 of the present invention is in the range of 0.10 ≦ x ≦ 0.16.

Claims (4)

It is a matrix of a phosphor composed of a multiphase mixture synthesized in a region where a plurality of solid phases stably coexist, and the matrix has a chemical composition of the general formula Ca _3-X Sr _X (PO ₄ ) ₂ (wherein 2.31 ≦ X ≦ 2.95) . The phosphor mixture according to claim 1, wherein the phosphor mixture contains Eu as an activator . It is a matrix of a phosphor composed of a multiphase mixture synthesized in a region where a plurality of solid phases stably coexist, and the matrix has a chemical composition of the general formula Na _2X Ca _3-X Al ₂ O ₆ (however, 0 1 ≦ X ≦ 0.15) . The phosphor mixture according to claim 3, wherein the phosphor mixture contains Bi as an activator .