JP2007077283A - Phosphor, method for preparing the same and light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor safe, low price and of high luminous brightness, to provide a method for preparing the phosphor, and to provide a light-emitting element. <P>SOLUTION: The matrix comprises Ca<SB>12</SB>Al<SB>14</SB>O<SB>33</SB>or Sr<SB>12</SB>Al<SB>14</SB>O<SB>33</SB>, wherein a predetermined concentration Eu is contained at the inclusion site of the cage-like lattice. The phosphor is prepared by ordinary firing. The light-emitting element comprises the phosphor. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a phosphor, a manufacturing method thereof, and a light emitting element including the phosphor.

  Today, in the display field, a cathode ray tube (CRT) is shifting to a thin flat panel display (FPD), and various displays such as liquid crystal display, plasma display panel (PDP), organic EL display, field emission display (FED), etc. FPD has been developed. Among them, the FED emits light by causing an electron beam generated from the cathode to collide with the phosphor of the anode on the same light emission principle as that of the CRT. The PDP emits light by irradiating a phosphor with vacuum ultraviolet rays emitted from a discharge gas. It is desirable that the phosphor serving as the light source has excellent characteristics such as light emission luminance, color purity, and lifetime. The phosphors mainly used in the conventional CRT and the current FED and PDP are high cost, are deleterious, cause a decrease in luminous efficiency due to phosphor surface deterioration, Of the three colors of red, green, and blue, blue has problems to be solved such as low brightness of the material itself, and alternative materials have been actively developed. However, there are still no satisfactory ones.

Examples of the phosphor include a formula: M ¹ ₁₂ M ² ₁₄ O ₃₃ (wherein M ¹ is one or more selected from the group consisting of Ca, Sr and Ba, and M ² is a group consisting of Al and Ga). Ln (Ln is Ce, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Mn) as an activator for the compound represented by the formula (1). In which one or more selected from the group consisting of the above-mentioned groups is contained (for example, see Patent Document 1). This phosphor is for an ultraviolet light emitter element.
JP 2004-300261 A (Claims)

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. Instead of the phosphors currently used in CRT, FED, PDP, etc., a safe and inexpensive phosphor with high emission luminance and its production. It is an object to provide a method and a light-emitting device comprising the phosphor.

In the development process of the phosphor, the present inventors have a safe constitutional element and are composed of abundant elements with higher Clark number (Ca: 5th, Al: 3rd, O: 1th). When a compound represented by Ca ₁₂ Al ₁₄ O ₃₃ is used as a phosphor base material and europium (Eu) is contained as an activator, it emits red light by ultraviolet irradiation and emits blue light by electron beam irradiation. As a result, the present invention has been completed.

The phosphor of the present invention comprises a compound having a composition represented by Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ as a base material, and contains Eu as an activator. It emits red light and emits blue light when irradiated with an electron beam.

  The Eu is contained in the inclusion site of the mother cage lattice.

The base Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ has a cage lattice as a basic structure in the crystal structure. In this matrix, there are three types of occupied sites of the elements to be activated, which are the inclusion of trivalent Al sites and divalent Ca sites (or Sr sites) constituting the cage lattice, and the inclusion of the cage lattice. It is a site. It is known that Eu emits red light when excited with a valence of +3 and emits blue light when excited with a valence of +2. Therefore, when Eu is added to both the Al site and the Ca site (or Sr site) and each emits light, it should not emit two colors, but emit purple light by adding red and blue. .

  However, in the phosphor of the present invention, it is surprising that two-color light emission occurs, that is, red light emission by ultraviolet irradiation and blue light emission by electron beam irradiation. The mechanism of this two-color light emission can be explained as follows.

  First, Eu is +2 and enters the inclusion site of the cage lattice, and when irradiated with ultraviolet light, it is in the +3 state where one electron is emitted, and the electron continues to be excited without time to return. To do. However, in the electron beam irradiation, the charges around Eu are in a state of being charged up by irradiation, and it is impossible for Eu to emit electrons and become +3 valence, and therefore it continues to emit blue light at +2 valence. Since the activator is not added to the matrix Al site and Ca site of the matrix, but is added to the inclusion site of the matrix cage lattice of the matrix, the excitation energy obtained by electron beam and ultraviolet irradiation is stored in the cage. This makes it easy to stay within the lattice and enables highly efficient light emission.

The method for producing a phosphor for an electron beam-excited light emitting device according to the present invention includes Ca or Sr, a compound that can be decomposed during firing to become calcium oxide or strontium oxide, and Al, and is used during firing. A compound that can be decomposed to become an aluminum oxide is blended so that the atomic equivalent ratio of Ca or Sr to Al is 12:14, and Eu element or oxide thereof is converted into the element, Ca _{Based on 12} Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ , 0.001 to 10 atomic%, preferably 0.1 to 4.0 atomic% is mixed, and the resulting mixture is fired to obtain the formula: ( Ca ₁₂ Al ₁₄ O _{33) 100} or _{(Sr 12 Al 14 O 33)} 100: in Eu _x (where fluorescent x is 0.001 to 10, represented by preferably 0.1 to 4.0) To get the body And butterflies.

  Compounds that can be decomposed during the calcination to become calcium oxide or strontium oxide and compounds that can be decomposed during the calcination to become aluminum oxide include oxides, hydroxides, carbonates, nitrates, halides, and the like. It is a compound selected from oxalates. It is preferable that the compound that can be decomposed during the calcination to become calcium oxide or strontium oxide is a carbonate, and the compound that can be decomposed during the calcination to become aluminum oxide is an oxide.

  The light emitting device of the present invention comprises the phosphor.

According to the present invention, a compound represented by Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ is used as a phosphor base material, and by containing a predetermined amount of Eu as an activator, inclusion is performed. Eu added to the site is not purple light emission that is the sum of red and blue, but two-color light emission, that is, red light emission with high luminance by ultraviolet irradiation, and blue light emission with high luminance by electron beam irradiation. There is an effect.

  According to the phosphor of the present invention, since a complex oxide of Ca and Al, which is rich in resources, is used as a base material, it is possible to realize a low environmental load and a low cost compared to a conventionally used deleterious substance such as ZnS. There is an effect.

  In addition, the phosphor of the present invention has an effect that it can be produced by an easy process by ordinary firing.

  Furthermore, since the light emitting device comprising a phosphor exhibiting excellent light emission luminance and color purity of the present invention produces two-color light emission with high luminance, it can be expected to be used for FPD such as FED and cathode ray tube (CRT) displays. There is an effect.

  Embodiments of the present invention will be described below.

According to the present invention, there is provided a phosphor having a compound having a composition represented by Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ as a base, and adding and containing a predetermined amount of Eu as an activator. By providing a phosphor that emits red light when irradiated with ultraviolet light and emits blue light when irradiated with an electron beam, the intended purpose can be achieved.

The addition amount of the activator used in the present invention is 0.001 to 10 atomic%, preferably 0.1 to 4.0 atomic%, based on the base compound Ca ₁₂ Al ₁₄ O ₃₃ . If it is less than 0.001 atomic% and more than 10 atomic%, the luminance is remarkably lowered.

  Hereinafter, a method for producing the phosphor of the present invention will be described.

  The method for producing the phosphor of the present invention is not particularly limited. For example, it can be produced by firing a mixture of a compound containing calcium (or strontium) and / or aluminum constituting the base and Eu element or its oxide. Compounds containing the elements constituting this matrix include oxides, hydroxides, carbonates, nitrates, halides, oxalates, etc. that decompose at the firing temperature to produce calcium (or strontium) / aluminum oxides. The compound which can become a thing can be used, These compounds are mix | blended and used so that it may become the predetermined | prescribed composition of a base material. It is also possible to prepare the target phosphor by preparing only the matrix first and then firing the mixture obtained by adding the activator to the matrix.

  According to the present invention, the compound containing the element constituting the matrix and the Eu element or oxide thereof are weighed together with the composition of the target phosphor, and a known ball mill, jet mill, V-type mixer, Mixing and pulverizing using a stirrer etc., the resulting mixture, for example, inert gas atmosphere (rare gas such as argon or atmosphere such as nitrogen), oxidizing gas atmosphere (air, oxygen, oxygen atom-containing gas, etc.) And a reducing gas atmosphere (an atmosphere of a hydrogen atom-containing gas such as hydrogen gas) at 1000 to 1500 ° C. (preferably 1200 to 1300 ° C.) for a predetermined time to obtain a target phosphor. be able to. Of these firing atmospheres, a nitrogen gas atmosphere is most preferable from the viewpoint of luminance.

Specifically, according to the present invention, for example, calcium carbonate (CaCO ₃ ) or strontium carbonate (SrCO ₃ ) and aluminum oxide (Al ₂ O ₃ ) are mixed at an atomic ratio of Ca or Sr and Al. Equivalent ratio is 12:14, and europium (Eu) or its oxide is converted into Eu element, based on Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ , After mixing and pulverizing the mixed powder thus obtained in a ball mill, this is preferably 1200 to 1300 ° C. (for example, 1200 ° C.) in an inert gas atmosphere, an oxidizing gas atmosphere or a reducing gas atmosphere. The desired phosphor can be obtained by baking with.

  The phosphor of the present invention obtained as described above has emission luminance superior to that of conventional phosphors and emits two colors. Using this phosphor, a light emitting device can be manufactured by a known manufacturing method. Of the FED and CRT light-emitting elements that use this phosphor, the FED light-emitting element will be briefly described below as an example.

  For example, the phosphor paste of the present invention is prepared by dispersing particles of the phosphor of the present invention in an organic solvent solution of a binder made of a polymer compound (eg, cellulose compound, polyvinyl alcohol, etc.). This phosphor paste is applied to the surface of a front substrate on which a conductive film (for example, ITO (indium tin oxide)) is formed (this conductive film is used as an anode electrode) by a known application method such as screen printing. This phosphor layer and a back substrate provided with an electron source (for example, carbon nanotube, graphite nanotube) and a cathode electrode are laminated and bonded together with a spacer for securing a vacuum region interposed therebetween. Next, the target FED model can be manufactured by evacuating the inside and vacuum-sealing to form an electron flight space.

  Hereinafter, the present invention will be described in detail by way of examples, but the present invention is not limited to these examples.

CaCO ₃ and Al ₂ O ₃ are mixed so that the atomic equivalent ratio of Ca and Al is 12:14. To this, europium oxide (Eu ₂ O ₃ ) is converted into Eu, and Ca ₁₂ Al _{Based on 14} O ₃₃ , 0.48 atomic% ((Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 ) was added, and the dry pulverized and stirred powder was raised to 1200 ° C. in the air for 1 hour and 30 minutes. Warm, hold at this temperature for 4 hours and fire.

FIG. 1 shows a powder XRD diffraction spectrum of (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 obtained by firing as described above. In the figure, a sample having a very good single phase was prepared as can be seen from the peak obtained from the crystal structure data shown in the lower part of the figure. In the figure, C12A7 means _Ca 12 _Al 14 _{O 33.}

  Next, the fluorescence characteristic evaluation of the obtained fired powder will be described.

  As preparation of a measurement sample, first, 0.01 g of the fired powder was put into a beaker into which 20 cc of ethanol was injected, and sufficiently stirred. A glass substrate on which a conductive ITO film was formed was placed in the beaker, and the ethanol mixture was dried. The powder deposited by this method was irradiated with ultraviolet rays having a wavelength of 254 nm or an electron beam with an acceleration voltage of 3 kV, and the fluorescence characteristics were evaluated with a spectrophotometer.

FIG. 2 shows an emission spectrum when the (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 sample is irradiated with ultraviolet light having a wavelength of 254 nm. This emission spectrum had a sharp peak at a wavelength of about 615 nm, and the color coordinates showed high-quality red emission located at x = 0.636 and y = 0.361 on the CIE chromaticity diagram. FIG. 3 shows an emission spectrum when (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 is irradiated with an electron beam with an acceleration voltage of 3 kV. This emission spectrum had a peak at a wavelength of about 395 nm, and the color coordinates showed blue light emission located at x = 0.186 and y = 0.054 on the CIE chromaticity diagram. This is equivalent to the color coordinates x = 0.146 and y = 0.074 of ZnS: Ag, which is a conventional blue phosphor for CRT, and it was confirmed that the chromaticity was comparable to ZnS: Ag.

In accordance with the method described in Example 1, CaCO ₃ and Al ₂ O ₃ were mixed so that the atomic equivalent ratio of Ca and Al was 12:14, and europium oxide (Eu ₂ O ₃ ) was added thereto. _{Based on 12} Al ₁₄ O ₃₃ standard, converted to Eu and added in a range of 0 to 10 atomic%, the dry pulverized and stirred powder was heated to 1200 ° C. in the air for 1 hour and 30 minutes, It was kept at this temperature for 4 hours and fired. Eu with respect to the emission luminance (arbitrary unit) when the phosphor represented by the formula: (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _x (x = 0 to 10) is irradiated with ultraviolet light having a wavelength of 254 nm. The concentration dependency and the Eu concentration dependency on the emission luminance (arbitrary unit) when irradiated with an electron beam with an acceleration voltage of 3 kV were evaluated, and the results are shown in FIG. As is apparent from this figure, it can be seen that the luminance is maximized when the concentration of Eu as an activator is around 1.6 atomic% in both ultraviolet excitation and electron beam excitation. As apparent from the lower part of FIG. 4, in the case of electron beam excitation, if the Eu concentration exceeds 0.48 atomic%, red light emission starts to be mixed and the blue purity is lowered. Preferably, about 0.05 to 0.5 atomic% seems optimal for obtaining two-color emission. However, even if the Eu concentration is infinitely close to 0 atomic%, two-color light emission occurs.

The phosphor represented by the formula: (Sr ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 prepared under the same conditions using SrCO ₃ instead of CaCO ₃ in Example 1 is the same as in Example 1. When the fluorescence characteristics were evaluated, almost the same results were obtained (FIG. 5). In the figure, C12A7 is as defined above, S12A7 is or means _Sr 12 _Al 14 _{O 33.} As is clear from this figure, it can be seen that there are broad peaks around 395 nm and around 600 nm.

(Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 was obtained according to the method described in Example 1 except that the firing time in Example 1 was changed to four types of 1, 2, 4 and 8 hours. In this case, 1200 ° C. in air, 1300 ° C. in air, _{N 2} 1200 ° C. gas, and with calcined in _{N 2} four atmosphere 1300 ° C. gas was also performed for the exhaust fired by a rotary pump. The phosphor thus obtained was evaluated for the firing time dependence on the emission luminance (arbitrary unit) when the electron beam was irradiated with an acceleration voltage of 3 kV, and the result is shown in FIG. As can be seen from FIG. 6, a phosphor having a substantially satisfactory luminance can be obtained at a firing time of 1 to 8 hours, and in particular, a phosphor having a higher luminance can be obtained at 2 to 4 hours. As the firing atmosphere, there was a tendency to obtain a phosphor having higher luminance in the case of N ₂ gas.

According to the present invention, a compound represented by Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ is used as a phosphor base material, and Eu as an activator having a predetermined concentration is used as an inclusion site of a cage lattice. In the present invention, it is possible to provide a phosphor exhibiting excellent emission luminance and color purity by two-color emission and a light-emitting element comprising the phosphor. Therefore, the present invention provides a thin FPD (liquid crystal display, PDP, organic EL display, FED, etc.), particularly in the field of display such as FED and CRT.

The upper graph shows the X-ray diffraction spectrum of (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 obtained in Example 1, and the lower graph shows the peak position and intensity determined from the known crystal structure. An emission spectrum when (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 obtained in Example 1 is irradiated with ultraviolet light having a wavelength of 254 nm. An emission spectrum when (Ca ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 obtained in Example 1 is irradiated with an electron beam at an acceleration voltage of 3 kV. It is a graph which shows the dependence of Eu density | concentration with respect to light-emitting luminance about the fluorescent substance obtained in Example 2, the upper stage is a graph at the time of ultraviolet irradiation, and the lower stage is a graph at the time of electron beam irradiation. An emission spectrum when (Sr ₁₂ Al ₁₄ O ₃₃ ) ₁₀₀ : Eu _0.48 obtained in Example 3 was irradiated with an electron beam at an acceleration voltage of 3 kV. 6 is a graph showing the dependency of the phosphor obtained in Example 4 on the baking conditions with respect to the luminance.

Claims (5)

A phosphor comprising a compound having a composition represented by Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O ₃₃ as a base material, and Eu added thereto as an activator. The phosphor emits red light when irradiated with ultraviolet rays. A phosphor that emits blue light when irradiated with an electron beam.   2. The phosphor according to claim 1, wherein the Eu is contained in an inclusion site of a mother cage lattice. A compound containing Ca or Sr and capable of decomposing upon firing to form calcium oxide or strontium oxide, and a compound containing Al and capable of decomposing upon firing to form aluminum oxide include Ca or Sr and Al. The elemental equivalent ratio is 12:14, and the Eu element or oxide thereof is converted into the element in terms of Ca ₁₂ Al ₁₄ O ₃₃ or Sr ₁₂ Al ₁₄ O _{33 on the} basis of 0.1. 001-10 mixed atomic%, by calcining the resulting mixture, the _{formula: (Ca 12 Al 14 O 33} ) 100 or _{(Sr 12 Al 14 O 33)} 100: Eu x ( wherein, x is 0. A method for producing a phosphor, characterized in that a phosphor represented by (001 to 10) is obtained.   Compounds that can be decomposed during the calcination to become calcium oxide or strontium oxide and compounds that can be decomposed during the calcination to become aluminum oxide include oxides, hydroxides, carbonates, nitrates, halides, and the like. The method for producing a phosphor for an electron beam-excited light emitting device according to claim 3, wherein the phosphor is a compound selected from oxalates.   A light emitting device comprising the phosphor according to claim 1 or 2, or the phosphor produced by the production method according to claim 3 or 4.

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