JP2011032488A - Production method for composite nitride phosphor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a composite nitride phosphor of a powdered form, low in baking cost and high in emission intensity. <P>SOLUTION: There is provided the method of producing the composite nitride phosphor represented by general formula (I) and containing a small amount of oxygen, by baking a powder of mixed raw materials containing a monomer and/or a compound of an activating element M<SP>1</SP>, a nitride of a divalent metal M<SP>2</SP>, a nitride of a trivalent metal M<SP>3</SP>and a nitride of a tetravalent metal M<SP>4</SP>. The powder of mixed raw materials is baked on a state of the bulk density of ≥0.05 g/cm<SP>3</SP>and ≤1 g/cm<SP>3</SP>, at a baking temperature of ≥1,200°C and ≤1,750°C, and in the presence of the oxygen in the raw material to be baked and of ≥1% and ≤20% molar number of oxygen to the total molar number of nitrogen and oxygen in the raw material to be baked. M<SP>1</SP><SB>a</SB>M<SP>2</SP><SB>b</SB>M<SP>3</SP><SB>c</SB>M<SP>4</SP><SB>d</SB>N<SB>e</SB>O<SB>f</SB>(I), (wherein 0.00001≤a≤0.15, 0.5≤b≤2, 0.5≤c≤2, 0.5≤d≤2, 1.5≤e≤6, 0<f≤1.2, and 0<f/(e+f)≤0.2). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a composite nitride phosphor. More specifically, the present invention relates to a method for producing a composite nitride phosphor containing a trace amount of oxygen.

  Phosphors are used in fluorescent lamps, fluorescent display tubes (VFD), field emission displays (FED), plasma display panels (PDP), cathode ray tubes (CRT), white light emitting diodes (LEDs) and the like. In any of these applications, in order to make the phosphor emit light, it is necessary to supply the phosphor with energy for exciting the phosphor, and the phosphor is not limited to vacuum ultraviolet rays, ultraviolet rays, visible rays, electron beams, etc. When excited by an excitation source having high energy, it emits ultraviolet rays, visible rays, and infrared rays.

However, the phosphor has a problem that the luminance of the phosphor is reduced as a result of being exposed to the excitation source as described above, and there is a demand for a phosphor having no luminance reduction. Therefore, instead of conventional phosphors such as silicate phosphor, phosphate phosphor, aluminate phosphor, borate phosphor, sulfide phosphor, oxysulfide phosphor, etc. As a nitride phosphor, a Ca-alpha sialon phosphor activated with Eu ²⁺ ions has been proposed.

The Ca-alpha sialon phosphor activated with Eu ²⁺ ions is manufactured by a manufacturing process generally described below. First, raw material powders of silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and europium oxide (Eu ₂ O ₃ ) are mixed at a molar ratio of Si: Al: Eu = 13: 9: 1, Eu-alpha sialon is manufactured by calcining the raw material mixed powder in a state of compression molding by applying a pressure of 200 atmospheres by a hot press method in which the raw material mixture powder is kept at a temperature of 1700 ° C. for 1 hour in a nitrogen gas atmosphere of 1 atmosphere. Separately, raw material powders of silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), and calcium oxide (CaO) are mixed so that the molar ratio is Si: Al: Ca = 13: 9: 3, and the raw material mixed powder In a state of compression molding by applying a pressure of 200 atm, Ca-alpha sialon is manufactured by firing by a hot press method of keeping at 1700 ° C. for 1 hour in nitrogen gas at 1 atm. The Eu-alpha sialon powder and Ca-alpha sialon powder thus obtained were mixed at a molar ratio of 50:50 and held at 1700 ° C. for 1 hour in nitrogen gas at 1 atm. The hot-press method is used to obtain a Ca-alpha sialon phosphor activated with the target Eu ²⁺ ions (see, for example, Patent Document 1).

It has been reported that Ca-alpha sialon activated by Eu ²⁺ ions obtained by this process becomes a phosphor that emits yellow light having a wavelength of 550 nm to 600 nm when excited by blue light having a wavelength of 450 nm to 500 nm.

  However, for applications such as white LEDs and plasma displays that use ultraviolet light or blue light as an excitation source, there is a demand for phosphors that emit light other than yellow, particularly phosphors that emit red light with a wavelength of 600 nm or more. It was done.

  Moreover, since the phosphors obtained in this way are low in the reactivity of the raw material powder used, they were compression-molded at a high temperature for the purpose of promoting the solid phase reaction between the raw material mixed powders during firing. In this state, since the contact area between the raw material mixed powders is increased and heated, it is synthesized in the state of a very hard sintered body. However, in order to obtain a phosphor in a powder state suitable for the above phosphor use, it is necessary to pulverize the sintered body made of the phosphor thus obtained to a fine powder state. However, when a phosphor made of a hard sintered material is mechanically pulverized over a long period of time and with a large amount of energy using a jaw crusher or a ball mill, a large number of defects are generated in the phosphor crystal matrix. As a result, there is a disadvantage that the emission intensity of the phosphor is significantly reduced.

  For this reason, a method of firing in a powder state without compression molding at the time of heating has been attempted, but since the solid phase reaction between the nitride powders of the raw material is not promoted at a low temperature, the target phosphor is not generated. It was necessary to synthesize the phosphor at a high temperature of 1800 ° C. or higher. However, when firing at such a high temperature, there arises a disadvantage that a decomposition reaction accompanied by desorption of nitrogen from the nitride raw material occurs, and thus firing is performed in a nitrogen gas atmosphere of 5 atm or more for the purpose of suppressing it. Therefore, not only high firing energy is required, but also a very expensive high-temperature and high-pressure firing furnace is required, which increases the manufacturing cost of the phosphor.

JP 2002-363554 A

  It is an object of the present invention to have an emission color different from that of a conventional rare earth activated sialon phosphor, in particular, a fluorescence characteristic of emitting a long wavelength red light when activated by Eu, and a bulk density without compression molding. Low-cost firing because it can be fired in a low-powder state at a relatively low temperature under low atmospheric gas pressure, and a fine-powder composite nitride phosphor with high emission intensity by short-time grinding without applying large grinding energy The present invention intends to provide a method for manufacturing a product at low cost.

In view of the above circumstances, the present inventors have conducted extensive research on a method for producing a composite nitride phosphor, and as a result, by selecting the following production methods (1) to (6), A method for producing a small amount of composite nitride phosphor at low cost has been found, and the present invention has been completed. In particular, among composite nitride phosphors, phosphors typified by CaAlSiN ₃ : Eu containing a small amount of oxygen are efficiently excited by excitation light from ultraviolet to green and emit red light with high luminance. The method of the invention is suitable for the production method of this phosphor.

(1) A raw material mixed powder containing a single element and / or compound of an activating element, a bivalent metal nitride, a trivalent metal nitride, and a tetravalent metal nitride is fired, and the following general a method of producing a composite nitride phosphor containing trace oxygen formula (I), the raw material mixed powder was used as a bulk density of 0.05 g / cm ³ or more 1 g / cm ³ or less states, the firing temperature Firing at 1200 ° C. or higher and 1750 ° C. or lower, in which oxygen is present in the raw material to be fired so that the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen in the raw material to be fired is 1% or more and 20% or less. A method for producing a composite nitride phosphor characterized.
_{^{M 1 a M 2 b M 3}} c M 4 d N e O f (I)
(In general formula (I), M ¹ is an activating element, M ² is a divalent metal element, M ³ is a trivalent metal element, M ⁴ is a tetravalent metal element, and a, b, c, d, e, and f are values in the following ranges, respectively.
0.00001 ≦ a ≦ 0.15
0.5 ≦ b ≦ 2
0.5 ≦ c ≦ 2
0.5 ≦ d ≦ 2
1.5 ≦ e ≦ 6
0 <f ≦ 1.2
0 <f / (e + f) ≦ 0.2)

(2) activating element ^{M 1} is Cr, Mn, Fe, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and be one or more elements selected from the group consisting of Yb , divalent metal elements ^{M 2} is Mg, Ca, Sr, Ba, and at least one element selected from the group consisting of Zn, 3-valent metal element ^{M 3} is Al, Ga, in, and from Sc And the tetravalent metal element M ⁴ is one or more elements selected from the group consisting of Si, Ge, Sn, Ti, Zr, and Hf. The method for producing a composite nitride phosphor according to (1) above.

(3) The method of producing a composite nitride phosphor according to (1) or (2) the activator elements M ¹ is characterized in that it comprises at least Eu.

(4) is a divalent metal elements ^{M 2} of 50 mol% or more Ca and / or Sr, a trivalent 50 mol% or more Al metal elements ^{M 3,} 50 of the tetravalent metal elements ^{M 4} Mol% or more is Si, The manufacturing method of the composite nitride fluorescent substance in any one of said (1)-(3) characterized by the above-mentioned.

  (5) The method for producing a composite nitride phosphor according to any one of (1) to (4), wherein an Eu raw material containing europium oxide is used.

  (6) The composite nitride fluorescence according to any one of (1) to (5), wherein the firing atmosphere is an inert atmosphere or a reducing atmosphere, and the gas pressure during firing is 9 atm or less. Body manufacturing method.

  In the following, the ratio (percentage) of the number of moles of oxygen to the total number of moles of nitrogen and oxygen in the raw material to be fired in the present invention may be referred to as “the ratio of oxygen present in the raw material”.

  In the present invention, the oxygen content ratio in the raw material is the ratio (percentage) of the number of moles of oxygen to the total number of moles of nitrogen and oxygen present in the raw material to be fired at the time of firing. Nitrogen derived from the raw material powder, on the other hand, oxygen includes oxygen previously incorporated in the raw material powder and oxygen taken into the material to be fired from the firing atmosphere during firing. The proportion of oxygen in the raw material can be determined by measurement using an oxygen nitrogen analyzer.

  The production method of the present invention makes it possible to provide a composite nitride phosphor that exhibits high-luminance emission and little deterioration during use at low cost. In other words, in the present invention, since firing is performed in the presence of oxygen such that the oxygen content in the predetermined raw material described above is present, firing is performed at an excessively high temperature in a relatively low bulk density state without performing compression molding. In addition, a phosphor having excellent light emission characteristics can be produced at low cost by smoothly promoting a solid-phase reaction between nitride materials at a relatively low firing temperature and firing pressure without performing high-pressure firing.

  The composite nitride phosphor produced by the production method of the present invention emits light with higher luminance than the conventional sialon phosphor, and particularly when Eu is selected as an activator, emits red light with high luminance and a long wavelength. Show. Further, even when exposed to an excitation source, this phosphor provides a useful phosphor that is suitably used for fluorescent lamps, VFDs, FEDs, PDPs, CRTs, white LEDs, and the like, without a decrease in luminance. Is.

By firing a raw material mixed powder containing a single element and / or compound of an activator element, a divalent metal nitride, a trivalent metal nitride, and a tetravalent metal nitride, An embodiment of a method for producing a composite nitride phosphor of the present invention for producing a composite nitride phosphor represented by the general formula (I) will be described in detail.
_{^{M 1 a M 2 b M 3}} c M 4 d N e O f (I)
(In general formula (I), M ¹ is an activating element, M ² is a divalent metal element, M ³ is a trivalent metal element, M ⁴ is a tetravalent metal element, and a, b, c, d, e, and f are values in the following ranges, respectively.
0.00001 ≦ a ≦ 0.15
0.5 ≦ b ≦ 2
0.5 ≦ c ≦ 2
0.5 ≦ d ≦ 2
1.5 ≦ e ≦ 6
0 <f ≦ 1.2
0 <f / (e + f) ≦ 0.2)

The method of manufacturing a composite nitride phosphor of the present invention, the activating element M ^1, can be used, emitting ions that can be contained various crystal matrix of the composite nitride phosphor, Cr, Mn When one or more elements selected from the group consisting of Fe, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb are used, a phosphor with high emission characteristics can be manufactured. preferable. Further, it is highly bright red that contains at least Eu as the activating element M ¹ , in particular, contains Eu at least 10 mol%, preferably at least 50 mol%, more preferably at least 80 mol% of the activating element M ^1. Since the fluorescent substance which shows light emission can be obtained, it is preferable. Further, in order to provide a variety of functions such as to impart the or phosphorescent increasing the luminance may be one or to more containing coactivator in addition to Eu as activator elements M ^1.

M ² is a divalent metal element, but when it is at least one element selected from the group consisting of Mg, Ca, Sr, Ba, and Zn, a phosphor having high emission characteristics can be obtained. since preferred, is preferably more than 50 mol% of ^{M 2} are mixed raw material so that the Ca and / or Sr, more than 80 mole% of ^{M 2} is more preferable to be Ca and / or Sr, More preferably, 90 mol% or more is Ca and / or Sr, and most preferably all M ² is Ca and / or Sr.

M ³ is a trivalent metal element, but is preferably at least one element selected from the group consisting of Al, Ga, In, and Sc because a phosphor with high emission characteristics can be obtained. Among them, it is preferable to mix the raw materials so that 50 mol% or more of M ³ is Al, 80 mol% or more of M ³ is preferably Al, and 90 mol% or more is more Al. Preferably, all of M ³ is Al.

M ⁴ is a tetravalent metal element, but is preferably at least one element selected from Si, Ge, Sn, Ti, Zr, and Hf because a phosphor with high emission characteristics can be obtained. In particular, it is preferable to mix the raw materials so that 50 mol% or more of M ⁴ is Si, 80 mol% or more of M ⁴ is preferably Si, and 90 mol% or more is more preferably Si. Preferably, all of M ⁴ is Si.

In particular, 50 mol% or more of M ² is Ca and / or Sr, 50 mol% or more of M ³ is Al, and 50 mol% or more of M ⁴ is Si. It is preferable because a phosphor having particularly high emission characteristics can be produced.

  A in the general formula (I) is 0.00001 ≦ a ≦ 0.15, and the lower limit of the value of a is preferably a ≧ 0.0001, and a ≧ 0.001. More preferably, a ≧ 0.005 is more preferable, and a ≧ 0.008 is most preferable. The upper limit of the value of a is preferably a ≦ 0.1, more preferably a ≦ 0.05, further preferably a ≦ 0.04, and a ≦ 0.02. Most preferred.

  Although b is 0.5 ≦ b ≦ 2, the lower limit of the value of b is preferably b ≧ 0.7, and more preferably b ≧ 0.9. As an upper limit of the value of b, b ≦ 1.5 is preferable, and b ≦ 1.2 is more preferable. Most preferably, b = 1.

  c is 0.5 ≦ c ≦ 2, but the lower limit of the value of c is preferably c ≧ 0.7, and more preferably c ≧ 0.9. As an upper limit of the value of c, c ≦ 1.5 is preferable, and c ≦ 1.2 is more preferable. Most preferably c = 1.

  d is 0.5 ≦ d ≦ 2, but the lower limit of the value of d is preferably d ≧ 0.7, and more preferably d ≧ 0.9. As an upper limit of the value of d, d ≦ 1.5 is preferable, and d ≦ 1.2 is more preferable. Most preferably, d = 1.

  Although e is 1.5 ≦ e ≦ 6, the lower limit of the value of e is preferably e ≧ 2.1, and more preferably e ≧ 2.7. The upper limit of the value of e is preferably e ≦ 4.5, and more preferably e ≦ 3.6.

The amount of solid solution of oxygen f is in the range of 0 <f ≦ 1.2. However, as the amount of oxygen in the crystal phase increases, the amount of nitrogen decreases, and accordingly, the trivalent metal element M ³ is reduced. The tetravalent metal element M ⁴ increases and decreases. If f exceeds 1.2, the emission wavelength shifts to a short wavelength, which is not preferable. On the other hand, a phosphor containing no oxygen is not preferable because it requires a very high firing temperature and a high pressure firing atmosphere, which increases the production cost. The lower limit of the value of f is preferably f ≧ 0.03, more preferably f> 0.03, still more preferably f ≧ 0.06, and most preferably f ≧ 0.09. As an upper limit of the value of f, f ≦ 0.8 is preferable, f ≦ 0.5 is more preferable, and f ≦ 0.3 is most preferable.

  In the general formula (I), f / (e + f) representing the ratio of the molar amount of oxygen to the total molar amount of oxygen and nitrogen satisfies the relationship of 0 <f / (e + f) ≦ 0.2. When f / (e + f) exceeds 0.2, the emission intensity is significantly lowered and the emission wavelength is shifted to a short wavelength, which is not preferable. On the other hand, a phosphor containing no oxygen of f / (e + f) = 0 is not preferable because a very high baking temperature and a high pressure baking atmosphere are required, and the manufacturing cost is high. The lower limit of the value of f / (e + f) is preferably 0.01 ≦ f / (e + f), more preferably 0.01 <f / (e + f), still more preferably 0.02 ≦ f / (e + f), 0 0.03 ≦ f / (e + f) is most preferable. The upper limit of the value of f / (e + f) is preferably f / (e + f) ≦ 0.2, more preferably f / (e + f) ≦ 0.15, and most preferably f / (e + f) ≦ 0.1.

  In the method for producing a composite nitride phosphor of the present invention, the element and / or compound of the activator used as a raw material may be a metal (element), oxide, nitride, sulfide, or halide of the activator. In addition to hydrides, activating elements such as inorganic acid salts such as nitrates, sulfates and carbonates, organic acid salts such as oxalates and acetates, and organometallic compounds are incorporated into the phosphor crystal matrix at high temperatures. Anything can be used, and there are no restrictions on its type. However, from the viewpoint of good reactivity with other nitride materials, metals, oxides, nitrides and halides of activators are preferred, and in particular, the materials can be obtained at low cost and the synthesis temperature of the phosphor can be lowered. An oxide is preferable at this point.

When at least Eu is used as the activating element, the Eu raw material is Eu metal having Eu as a constituent element, europium oxide such as EuO and Eu ₂ O ₃ , EuN, EuH ₃ , Eu ₂ S ₃ , EuF ₂ , EuF ₃ , EuCl ₂ , EuCl ₃ , Eu (NO ₃ ) ₃ , Eu ₂ (SO ₄ ) ₃ , Eu ₂ (CO ₃ ) ₃ , Eu (C ₂ O ₄ ) ₃ , Eu (O-i-C ₃ H ₇ ) One or more of various compounds such as ₃ can be used, but Eu halides such as EuF ₂ , EuF ₃ , EuCl ₂ and EuCl ₃ are preferable because they have an effect of promoting crystal growth. Eu ₂ O ₃ and Eu metal are also preferable because phosphors having high characteristics can be synthesized. Among them, Eu ₂ O ₃ that can synthesize a high-luminance phosphor at a relatively low temperature with low raw material cost and low deliquescence is particularly preferable.

As a raw material of an element other than the activator element, that is, a raw material of a divalent, trivalent or tetravalent metal element, those nitrides are usually used, but as a divalent metal nitride, for example, One or more of Mg ₃ N ₂ , Ca ₃ N ₂ , Sr ₃ N ₂ , Ba ₃ N ₂ , Zn ₃ N _{2 and the} like can be mentioned. Examples of the trivalent metal nitride include AlN, One or more of GaN, InN, ScN and the like can be mentioned, and examples of the tetravalent metal nitride include Si ₃ N ₄ , Ge ₃ N ₄ , Sn ₃ N ₄ , Ti ₃ N ₄ , and Zr. One or two or more of ₃ N ₄ , Hf ₃ N _{4 and the} like can be mentioned, and it is preferable to use those powders because a phosphor having high emission characteristics can be produced.

  In particular, as a raw material for a divalent element other than the activator element, using a highly active and highly reactive nitride raw material having a mole number of oxygen of 1% to 20% with respect to the total mole number of nitrogen and oxygen, The solid phase reaction between the nitride raw material mixed powders can be significantly advanced, and as a result, the firing temperature and the atmospheric gas pressure during firing can be lowered without compression molding the raw material mixed powder. For the same reason, as a raw material of a divalent element other than the activator element, a nitride raw material in which the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen is 2% to 15%, particularly 3% to 12%. It is even more preferable to use the nitride raw material.

Metal element composition of the raw material mixed powder containing these activation element and the metal element, the molar ratio of M ¹ element raw material mixed powder a ', the molar ratio of M ² element b', of M ³ element the molar ratio c when ', the molar ratio of M ⁴ element d' was preferable since a high phosphor characteristics to the composition the following ranges can be produced in good yield.
0.00001 ≦ a ′ ≦ 0.15
0.5 ≦ b ′ ≦ 2
0.5 ≦ c ′ ≦ 2
0.5 ≦ d ′ ≦ 2

Moreover, a phosphor with good light emission characteristics can be obtained even if the metal element composition in the raw material mixed powder is adjusted so as to have the following metal element composition ratio.
0.00001 ≦ a ′ ≦ 0.15
a ′ + b ′ = 1
0.2 ≦ c ′ ≦ 10
0.2 ≦ d ′ ≦ 5

  In the above metal element composition, if a 'is smaller than 0.00001, sufficient light emission intensity cannot be obtained. When a 'is larger than 0.15, concentration quenching increases and the emission intensity decreases. For the same reason, the lower limit is preferably a ′ ≧ 0.0001, more preferably a ′ ≧ 0.001, more preferably a ′ ≧ 0.005, and mixing of raw materials so that a ′ ≧ 0.008. It is most preferable to adjust the metal element composition of the powder. As an upper limit, a ′ ≦ 0.1 is preferable, a ′ ≦ 0.05 is more preferable, a ′ ≦ 0.04 is further preferable, and the metal element composition of the raw material mixed powder is set so that a ′ ≦ 0.02. Is most preferably adjusted.

The raw material mixture composition is adjusted so that the sum of a ′ and b ′ becomes 1 because the activating element M ¹ replaces the atomic position of the divalent metal element M ² in the crystal base of the phosphor.

c 'tends to yield during manufacture of the phosphor is lowered represented by less than 0.2 and ^{_{M 1 a M 2 b M 3}} c M 4 d N e O f. On the other hand, when the ratio is larger than 10, the yield of the phosphor tends to be low. Accordingly, the raw materials are usually mixed so that c ′ is in the range of 0.2 ≦ c ′ ≦ 10. However, from the viewpoint of emission intensity, the lower limit of c ′ is preferably c ′ ≧ 0.4, more preferably c ′ ≧ 0.5, still more preferably c ′ ≧ 0.6, and c ′ ≧ 0.8. Is most preferred. As an upper limit, c ′ ≦ 5 is preferable, c ′ ≦ 2.5 is more preferable, c ′ ≦ 2 is further preferable, and c ′ ≦ 1.8 is most preferable.

and d 'is less than 0.2, the phosphor of the yield expressed by ^{_{M 1 a M 2 b M 3}} c M 4 d N e O f in the general formula (I) tends to be low. On the other hand, when d ′ is larger than 5, the yield of the phosphor tends to be low. Therefore, the raw materials are usually mixed so that d is in the range of 0.2 ≦ d ′ ≦ 5. However, from the viewpoint of emission intensity, the lower limit of d ′ is preferably d ′ ≧ 0.4, more preferably d ′ ≧ 0.5, further preferably d ′ ≧ 0.6, and d ′ ≧ 0.8. Is most preferred. As an upper limit, d ′ ≦ 2.5 is preferable, d ′ ≦ 2 is more preferable, d ′ ≦ 1.7 is further preferable, and ≦ d ′ ≦ 1.2 is most preferable.

By adjusting the composition of the raw material mixed powder so that the metal element composition ratio is as described above, M ¹ _a M ² _b M ³ _c M ⁴ _d N _e O of the general formula (I) having high light emission characteristics It becomes possible to produce the phosphor represented by _f with good yield.

Incidentally, the amount the preparation of raw material mixed powder, ^{may _{M 1 a M 2 b M 3}} c M 4 d N e O f impurities other than phosphor represented by the desired Formula (I) is produced some, but as this case, the amount of the desired ^{_{M 1 a M 2 b M 3}} c M 4 d N e O f phosphor represented by the general formula (I), and 20 wt% or more It is preferable to adjust the metal element composition of the raw material mixed powder. Further, the amount of the desired ^{_{M 1 a M 2 b M 3}} c M 4 d N e O f phosphor represented by the general formula (I), the raw material mixed powder so that 50 wt% or more metals it is more preferable to adjust the elemental composition, the fluorescence expressed by more preferably be adjusted to be 80 wt% or more, it does not contain impurities ^{_{M 1 a M 2 b M 3}} c M 4 d N e O f It is most preferable to adjust the metal element composition of the raw material mixed powder so that the body is formed as a single phase.

  In the present invention, the metal element composition of the raw material mixed powder is preferably adjusted as described above, and oxygen is present during firing so that the oxygen content in the raw material is 1% to 20%. The solid phase reaction between the raw material powders is promoted, and the phosphor can be produced at a low temperature.

  Here, if the oxygen content in the raw material is less than 1%, the solid phase reaction between the nitride raw materials is not promoted, and it becomes difficult to synthesize the phosphor at a relatively low temperature. On the other hand, if the oxygen content in the raw material exceeds 20%, the emission intensity of the phosphor is lowered and a preferable emission color cannot be obtained. In particular, in the case of a phosphor containing at least Eu as an activating element, if the proportion of oxygen in the raw material exceeds 20%, the emission wavelength becomes short and a phosphor exhibiting a desired red emission cannot be obtained. For the same reason, the oxygen content in the raw material is preferably 2% or more and 15% or less.

As a method of causing oxygen to exist at such a ratio of oxygen in the raw material during firing,
(1) A method of using a raw material nitride containing oxygen in a desired concentration as a raw material to be fired
(2) A method in which a raw material nitride is heated in advance in an oxygen-containing atmosphere to contain oxygen in a desired concentration to obtain a raw material to be fired.
(3) Method of mixing raw material nitride powder with oxygen-containing compound powder to make raw material to be fired
(4) The method includes introducing oxygen into the material to be fired by adding oxygen to the firing atmosphere when oxidizing the material nitride and oxidizing the material nitride during firing. In order to produce a high-luminance phosphor, (1) a method of using a raw material nitride containing a desired concentration of oxygen as a raw material to be fired, and (3) a raw material nitride powder containing an oxygen-containing compound powder It is preferable to use a raw material containing oxygen in a desired concentration as a raw material nitride by combining the method (1) and the method (3). In addition, a method in which the raw material nitride powder is mixed with the oxygen-containing compound powder is more preferable.

  In this case, the oxygen-containing compound powder is selected from substances that become metal oxides during firing. These materials include each metal, that is, an oxide of metal constituting the raw material nitride, an inorganic acid salt such as nitrate, sulfate and carbonate, an organic acid salt such as oxalate and acetate, and an oxygen-containing organic material. Although a metal compound etc. can be used, it is preferable to use a metal oxide from the point which can control oxygen concentration easily and can suppress the accompanying of impurity gas in a calcination atmosphere low.

  The proportion of oxygen present in the raw material can be easily determined by performing a chemical analysis of all raw materials. In particular, the ratio of nitrogen and oxygen can be determined by analyzing the concentration of nitrogen and oxygen. Further, e and f and the ratio f / (e + f) in the general formula can be determined from the analysis values.

  The raw materials can be mixed by a normal method in which the raw material powders can be mixed sufficiently uniformly after being pulverized using a dry pulverizer such as a hammer mill, a roll mill, a ball mill, or a jet mill. Examples of these methods include a method using a dispersion medium such as a ball mill, a pearl mill, and a vibrating ball mill, a method using gravity such as a V-type blender, and a method using a mixer having stirring blades such as a ribbon blender and a Henschel mixer. It is done. When mixing the raw materials, there is a dry method of pulverizing and mixing the raw material powder using a dry pulverizer, or a method of adding the raw material powder in a medium such as water and pulverizing and mixing using a wet pulverizer, When using a raw material powder that easily reacts with water, such as calcium nitride, dry mixing is preferred.

  As the container used for firing the raw material mixed powder, various heat-resistant containers that have been conventionally used in high-temperature firing can be used, but among these, when using a heat-resistant container such as a crucible or tray made of boron nitride, This is preferable because a phosphor with good emission characteristics can be obtained because of its low reactivity and low impurity concentration.

  As a baking apparatus, various high-temperature baking furnaces that can maintain an inert atmosphere or a reducing atmosphere are usually used. Among them, a high-temperature firing furnace capable of precisely controlling the oxygen concentration is preferable, and the oxygen concentration is 0.1% or less, preferably 100 ppm or less, more preferably 10 ppm or less in a firing furnace having a carbon heater and a carbon heat insulating material. A firing furnace having a controllable sealed vessel is particularly preferred.

In the present invention, a raw material mixed powder comprising a single element and / or compound of an activator element, a divalent metal nitride, a trivalent metal nitride, and a tetravalent metal nitride is mixed with a bulk density of 0. .05g / cm ³ is fired as the state of more than 1 g / cm ³ or less. If the bulk density of the raw material mixed powder at the time of firing is too small, the contact area between the raw material powders is small, so that the solid phase reaction is difficult to proceed, and a large amount of impurity phase that cannot synthesize a preferred phosphor remains. On the other hand, if the bulk density is too large, the resulting phosphor becomes a hard sintered body, which not only requires a long pulverization step after firing, but also causes a problem that the brightness of the phosphor is lowered. . When firing the raw material mixed powder as the state of less bulk density 0.05 g / cm ³ or more 1 g / cm ³ has less impurity phase, and the phosphor obtained after calcination, a large amount of crystalline phase of a preferred emission characteristics In addition, a phosphor fine powder with high luminance can be obtained from the powder obtained by firing by a relatively short grinding process. For the same reason, the lower limit of the bulk density of the raw material mixed powder during firing is preferably 0.15 g / cm ³ or more, and more preferably 0.25 g / cm ³ or more. The upper limit is preferably 0.8 g / cm ³ or less, 0.6 g / cm ³ or less is more preferable.

  In the present invention, the firing temperature of the raw material mixed powder is set to 1200 ° C. or higher and 1750 ° C. or lower. When the firing temperature is less than 1200 ° C., even if the raw material mixed powder is heated, the solid phase reaction is difficult to proceed and the target phosphor cannot be synthesized. On the other hand, when firing at a temperature exceeding 1750 ° C., not only wasteful firing energy is consumed, but also the volatilization of nitrogen from the starting material and the generated material increases, and the pressure of nitrogen that becomes a part of the atmospheric gas is greatly reduced. The target phosphor cannot be produced unless it is too high. For the same reason, the lower limit of the firing temperature is preferably 1300 ° C. or higher, more preferably 1400 ° C. or higher, and further preferably 1500 ° C. or higher. The upper limit is preferably 1700 ° C. or less, more preferably 1650 ° C. or less, and further preferably 1650 ° C. or less.

  In the present invention, the firing atmosphere of the raw material mixed powder is basically an inert atmosphere or a reducing atmosphere, but an atmosphere containing a trace amount of oxygen having an oxygen concentration in the range of 0.1 to 10 ppm. This is preferable because phosphors can be synthesized at a relatively low temperature. However, when firing in an oxidizing atmosphere such as an oxygen-containing gas or in the air where the oxygen concentration exceeds 0.1%, the volatilization of nitrogen from the raw materials and products increases, and the target phosphor cannot be obtained.

  Moreover, the pressure of the atmospheric gas at the time of baking shall normally be 20 atmospheres (2 MPa) or less. In order to achieve a pressure exceeding 20 atmospheres, a high-temperature baking facility composed of a robust heat-resistant container is required, which increases the cost required for baking, which is not preferable. In order to reduce the apparatus cost of the high-temperature pressure-resistant firing furnace, the atmospheric gas pressure is preferably 10 atm (1 MPa) or less, more preferably less than 10 atm, and 9.5 atm (0.95 MPa) or less. Is more preferably 9 atm (0.9 MPa) or less. Further, in order to reduce the apparatus cost and prevent the volatilization of nitrogen, the pressure is preferably set to 0.5 atm (0.05 MPa) or more and 2 atm (0.2 MPa) or less. In order to further reduce the equipment cost of the firing furnace, the atmospheric gas pressure is more preferably 0.9 atm (0.09 MPa) to 1.5 atm (0.15 MPa). In order to prevent oxygen from being mixed in the atmosphere, it is particularly preferable that the pressure is slightly over 1 atm (0.1 MPa) and 1.2 atm (0.12 MPa) or less. If the firing furnace is poorly sealed, if it is 1 atm (0.1 MPa) or less, a large amount of oxygen is mixed and it is difficult to obtain a phosphor with high characteristics.

  The holding time at the maximum temperature during firing is usually 1 minute to 100 hours. If the holding time is too short, the solid phase reaction between the raw material mixed powders does not proceed sufficiently and the target phosphor cannot be obtained. In addition, when the holding time is too long, not only wasteful heating energy is consumed, but also nitrogen is desorbed from the surface of the phosphor and the fluorescence characteristics are deteriorated. For the same reason, the lower limit of the holding time is preferably 10 minutes or more, and more preferably 30 minutes or more. The upper limit is preferably 24 hours or less, and more preferably 12 hours or less.

  The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

[Example 1]
As raw material powders, Eu ₂ O ₃ powder, Ca ₃ N ₂ powder having an oxygen content of 9 mol% represented by the number of moles of oxygen relative to the total number of moles of nitrogen and oxygen, Si ₃ N ₄ having the same oxygen content of 2 mol% Each powder uses AlN powder having the same oxygen content of 2 mol%, and the metal element composition ratio (molar ratio) is Eu: Ca: Al: Si = 0.008: 0.992: 1: 1. Were weighed and mixed to obtain a raw material mixed powder. The oxygen content indicated by the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen of this raw material mixed powder was 5 mol%. The Ca ₃ N ₂ powder contains oxygen by using a material containing oxygen in a desired concentration as a raw material to be fired, and the Si ₃ N ₄ powder contains oxygen in a desired concentration. Oxygen is contained by using a raw material to be fired, and the AlN powder contains oxygen by using a raw material containing oxygen in a desired concentration.

This raw material mixed powder was put into a boron nitride crucible so as to have a bulk density of 0.35 g / cm ³ without being compressed, and the nitrogen pressure was adjusted to 1.1 atm in a high purity nitrogen atmosphere with an oxygen concentration of 10 ppm or less. Firing was performed at 1600 ° C. for 10 hours using an electric furnace. At this time, the proportion of oxygen present in the raw material during firing is 5 mol% by calculation from the oxygen concentration in each raw material and the mixing proportion of each raw material.

As a result of identifying a crystal phase generated in the obtained phosphor by a powder X-ray diffraction method, it was confirmed that a crystal of CaAlSiN ₃ was generated. When the fluorescence characteristics of the phosphor by excitation with a wavelength of 465 nm were measured with a fluorescence spectrophotometer, when the peak intensity of a commercially available Ce-activated yttrium aluminum garnet phosphor was 100, the peak intensity of the obtained phosphor was The emission intensity was as high as 128, and red light having a peak wavelength of 652 nm was shown. In addition, 20 mg of the obtained phosphor sample was put into a tin capsule, and this was put into a nickel basket, and the TC-436 type oxygen-nitrogen analyzer manufactured by LECO was used to measure the nitrogen and oxygen in the powder sample. When the concentration was analyzed, the total of nitrogen and oxygen contained 94 mol% nitrogen and 6 mol% oxygen (that is, f / (e + f) = 0.06).

[Example 2]
A phosphor powder was obtained in the same manner as in Example 1 except that EuF ₃ was used instead of Eu ₂ O ₃ . The oxygen content indicated by the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen of this raw material mixed powder was 5 mol%. Moreover, the oxygen existing ratio in the raw material at the time of baking is 5 mol% by calculating from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identifying a crystal phase generated in the obtained phosphor by a powder X-ray diffraction method, it was confirmed that a crystal of CaAlSiN ₃ was generated. When the fluorescence characteristics of the phosphor by excitation with a wavelength of 465 nm were measured with a fluorescence spectrophotometer, when the peak intensity of a commercially available Ce-activated yttrium aluminum garnet phosphor was 100, the peak intensity of the obtained phosphor was The emission intensity was as high as 114, and red light having a peak wavelength of 650 nm was shown. In addition, 20 mg of the obtained phosphor sample was put into a tin capsule, and this was put into a nickel basket, and the TC-436 type oxygen-nitrogen analyzer manufactured by LECO was used to measure the nitrogen and oxygen in the powder sample. When the concentration was analyzed, the total of nitrogen and oxygen contained 95 mol% nitrogen and 5 mol% oxygen (that is, f / (e + f) = 0.05).

[Example 3]
A phosphor powder was obtained in the same manner as in Example 1 except that EuN was used instead of Eu ₂ O ₃ and the firing time was 2 hours. The oxygen content indicated by the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen of this raw material mixed powder was 5 mol%. Moreover, the oxygen existing ratio in the raw material at the time of baking is 5 mol% by calculating from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identifying a crystal phase generated in the obtained phosphor by a powder X-ray diffraction method, it was confirmed that a crystal of CaAlSiN ₃ was generated. When the fluorescence characteristics of the phosphor by excitation with a wavelength of 465 nm were measured with a fluorescence spectrophotometer, when the peak intensity of a commercially available Ce-activated yttrium aluminum garnet phosphor was 100, the peak intensity of the obtained phosphor was The emission intensity was high at 112, and red light with a peak wavelength of 649 nm was shown. In addition, 20 mg of the obtained phosphor sample was put into a tin capsule, and this was put into a nickel basket, and the TC-436 type oxygen-nitrogen analyzer manufactured by LECO was used to measure the nitrogen and oxygen in the powder sample. When the concentration was analyzed, the total of nitrogen and oxygen contained 95 mol% nitrogen and 5 mol% oxygen (that is, f / (e + f) = 0.05).

[Example 4]
A phosphor powder was obtained in the same manner as in Example 1 except that EuN was used instead of Eu ₂ O ₃ , the nitrogen pressure was 10 atm, and the firing time was 2 hours. The oxygen content indicated by the number of moles of oxygen with respect to the total number of moles of nitrogen and oxygen of this raw material mixed powder was 5 mol%. Moreover, the oxygen existing ratio in the raw material at the time of baking is 5 mol% by calculating from the oxygen concentration in each raw material and the mixing ratio of each raw material.

As a result of identifying a crystal phase generated in the obtained phosphor by a powder X-ray diffraction method, it was confirmed that a crystal of CaAlSiN ₃ was generated. When the fluorescence characteristics of the phosphor by excitation with a wavelength of 465 nm were measured with a fluorescence spectrophotometer, when the peak intensity of a commercially available Ce-activated yttrium aluminum garnet phosphor was 100, the peak intensity of the obtained phosphor was The emission intensity was as high as 109, and red light having a peak wavelength of 650 nm was shown. In addition, 20 mg of the obtained phosphor sample was put into a tin capsule, and this was put into a nickel basket, and the TC-436 type oxygen-nitrogen analyzer manufactured by LECO was used to measure the nitrogen and oxygen in the powder sample. When the concentration was analyzed, the total of nitrogen and oxygen contained 95 mol% nitrogen and 5 mol% oxygen (that is, f / (e + f) = 0.05).

  The results are summarized in Table 1.

  According to the method for producing a composite nitride phosphor of the present invention, it is possible to provide a composite nitride phosphor that exhibits high-luminance emission and little deterioration during use at low cost. The composite nitride phosphor produced by the production method of the present invention emits light with higher luminance than the conventional sialon phosphor, and particularly when Eu is selected as an activator, emits red light with high luminance and a long wavelength. Show. Further, even when the phosphor is exposed to an excitation source, the luminance does not decrease. Therefore, the composite nitride phosphor produced according to the present invention is suitably used for fluorescent lamps, VFDs, FEDs, PDPs, CRTs, white LEDs and the like.

Claims (1)

A raw material mixed powder containing a single element and / or compound of an activator element, a divalent metal nitride, a trivalent metal nitride, and a tetravalent metal nitride is fired, and the following general formula (I And a method for producing a composite nitride phosphor containing a trace amount of oxygen represented by:
Raw material mixed powder was used as a following state bulk density of 0.05 g / cm ³ or more 1 g / cm ^3,
The firing temperature is 1200 ° C. or higher and 1750 ° C. or lower,
A composite nitride phosphor characterized by firing in the presence of oxygen in the raw material to be fired so that the number of moles of oxygen relative to the total number of moles of nitrogen and oxygen in the raw material to be fired is 1% to 20% Manufacturing method.
_{^{M 1 a M 2 b M 3}} c M 4 d N e O f (I)
(In general formula (I), M ¹ is an activating element, M ² is a divalent metal element, M ³ is a trivalent metal element, M ⁴ is a tetravalent metal element, and a, b, c, d, e, and f are values in the following ranges, respectively.
0.00001 ≦ a ≦ 0.15
0.5 ≦ b ≦ 2
0.5 ≦ c ≦ 2
0.5 ≦ d ≦ 2
1.5 ≦ e ≦ 6
0 <f ≦ 1.2
0 <f / (e + f) ≦ 0.2)