JP2014001300A - Fluophor and method of producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of producing a fluophor with high fluorescence quantum yield and high crystallinity by using an inexpensive material with high supply stability and low environmental load, and such a fluophor.SOLUTION: A fluophor contains only boron and aluminium as a metal, a molar ratio between a boron atom and an aluminium atom is in the range of 1:4.5-1:5.5, and a molar ratio between a boron atom and an oxygen atom is in the range of 1:8.0-1:9.5.

Description

  The present invention relates to a phosphor containing only boron and aluminum as metals and a method for producing the same.

  The phosphor has been conventionally used for a fluorescent tube, a nocturnal display panel, and the like, and in recent years, studies as a color conversion agent for LED are also progressing. Various phosphors are still being researched and developed to solve problems such as diversification of emission color, improvement of emission intensity, and improvement of economy.

  For example, a β-type sialon phosphor using Mn, Ce, Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, Yb or the like as an emission center element is known (see Patent Document 1). The use of these luminescent center elements has problems from the viewpoints of supply stability of raw materials, production costs, environmental burden at the time of disposal, and the like.

  Therefore, research on phosphors using raw materials with high supply stability, low cost, and low environmental load is underway. For example, a phosphor composed only of boron, carbon, nitrogen, and oxygen (see Patent Documents 2 and 3), a phosphor using aluminum oxide (see Patent Document 4), and the like have been reported.

JP 2009-19213 A International Publication No. 2008/126500 International Publication No. 2010/67767 International Publication No. 2010/114002

  The phosphors described in Patent Documents 2 to 4 are advantageous from the viewpoints of supply stability of raw materials, production cost, environmental load at the time of disposal, and the like. However, since the phosphors described in Patent Documents 2 and 3 have low crystallinity, there is a high possibility that stability during long-term use becomes a problem. Further, the phosphor described in Patent Document 4 has a low fluorescence quantum yield of 40% or less.

  In view of such circumstances, the object of the present invention is to obtain a phosphor having high crystallinity and high fluorescence quantum yield, which is obtained from a raw material having high supply stability, low cost, and low environmental load, and the phosphor. It is to provide a manufacturing method.

According to the present invention, the above object is [1] containing only boron and aluminum as metals, and the molar ratio of boron atom to aluminum atom is in the range of 1: 4.5 to 1: 5.5, A phosphor having a molar ratio of boron atom to oxygen atom in the range of 1: 8.0 to 1: 9.5;
[2] Boric acid (chemical formula: B (OH) ₃ ), boric anhydride (chemical formula: B ₂ O ₃ ), metaboric acid (chemical formula: (HBO ₂ ) _n ) and hypoboric acid (chemical formula: (B (OH)) ₂ ) The fluorescence of [1] above, wherein a mixture of at least one boric acid selected from the group consisting of ₂ ) (hereinafter simply referred to as “boric acid”), an aluminum-containing compound and a dispersant is baked in the presence of oxygen. Body manufacturing method;
[3] The method for producing a phosphor according to the above [2], wherein the number of moles of aluminum atoms contained in the aluminum-containing compound is 5.5 times or less of the number of moles of boron atoms contained in boric acids; and [4] dispersion The production method of the above [2] or [3], wherein the agent is a nitrogen-containing polymer compound;
Is achieved by providing

  According to the present invention, a phosphor with high fluorescence quantum yield and high crystallinity can be provided from a raw material having high supply stability, low cost, and low environmental load.

2 is an emission spectrum of the phosphor obtained in Example 1 by ultraviolet excitation. 2 is an X-ray analysis spectrum of the phosphor obtained in Example 1. FIG. 2 is an electron micrograph of the phosphor obtained in Example 1. FIG. 2 is an emission spectrum of the phosphor obtained in Example 2 by ultraviolet excitation. 3 is an X-ray analysis spectrum of the phosphor obtained in Example 2.

  Hereinafter, modes for carrying out the present invention will be described.

The phosphor of the present invention contains only boron and aluminum as metals. In this specification, the metal means a group 1 element excluding hydrogen; a group 2 element; a group 3 element including lanthanoids and actinoids; a group 4 to 13 element; a group 14 element excluding carbon; and 15 excluding nitrogen and phosphorus. Group elements: Group 16 elements excluding oxygen, sulfur and selenium. Boron and aluminum are included in group 13 elements. The molar ratio of boron atom to aluminum atom in the phosphor of the present invention is in the range of 1: 4.5 to 1: 5.5, preferably in the range of 1: 4.7 to 1: 5.2. . When the number of moles of aluminum atoms is less than 4.5 times the number of moles of boron atoms, the obtained phosphor contains a large amount of boron oxide. When the number of moles exceeds 5.5 times, aluminum oxide is contained in the obtained phosphor. Aggregate. For this reason, if the molar ratio of boron atoms to aluminum atoms is out of the range of 1: 4.5 to 1: 5.5, the fluorescence intensity decreases. The molar ratio of boron atom to oxygen atom in the phosphor of the present invention is in the range of 1: 8.0 to 1: 9.5, preferably in the range of 1: 8.3 to 1: 9.2. is there. In the phosphor of the present invention, it is presumed that boron atoms and aluminum atoms are mainly contained as a crystal structure of Al ₅ BO ₉ . Since the phosphor of the present invention contains a large amount of the crystal structure, the phosphor has high structural stability and excellent long-term stability. When the number of moles of oxygen atoms is less than 8.0 times the number of moles of boron atoms, the crystal structure has more defects, and when the number of moles of oxygen atoms exceeds 9.5 times the number of moles of boron atoms Since the oxidation numbers of boron atoms and aluminum atoms in the phosphor increase, the structural stability tends to decrease.

  The phosphor of the present invention may contain nitrogen and / or carbon as an element other than boron, aluminum, and oxygen. The content of these elements is preferably 5% by mass or less, more preferably 3% by mass or less of the phosphor of the present invention.

The phosphor of the present invention can be obtained by firing a mixture of boric acids, an aluminum-containing compound and a dispersant in the presence of oxygen. During firing, it is considered that boric acids react with the aluminum-containing compound when the temperature in the temperature raising process is lower than 200 ° C., and the dispersant is decomposed when the temperature is 200 ° C. or higher. By producing by such a method, it is considered that defects of aluminum and oxygen accompanying the decomposition of the dispersant are generated in the crystal structure of Al ₅ BO ₉ and function as a phosphor.

  The boric acids used in the method for producing the phosphor of the present invention may be selected from the group consisting of boric acid, boric anhydride, metaboric acid and hypoboric acid, and may be used alone or in combination. May be mixed and used. The boric acids are preferably boric acid or anhydrous boric acid from the viewpoints of availability and supply stability.

  Examples of the aluminum-containing compound used in the phosphor production method of the present invention include aluminum salts of organic acids such as aluminum acetate and aluminum butyrate; aluminum salts of mineral acids such as aluminum sulfate, aluminum nitrate and aluminum phosphate; aluminum chloride , Aluminum bromide, aluminum iodide, and the like; aluminum oxide; aluminum hydroxide; and the like. Aluminum oxide and aluminum hydroxide are preferred from the viewpoint of availability and supply stability. These may be used individually by 1 type, and may mix and use multiple types.

  The dispersant used in the method for producing the phosphor of the present invention is added in order to increase the dispersibility of the boric acids and the aluminum-containing compound and increase the uniformity of the reaction. As the dispersant, a compound that can be strongly coordinated with the aluminum-containing compound and decomposes in the range of 200 to 400 ° C. is preferable. Specifically, for example, nitrogen-containing polymer compounds such as polyethyleneimine, polyvinylamine, polyallylamine, polyaniline, polyacrylonitrile, polyvinylpyrrolidone, polyvinylpyridine, and polyurea are preferable, and polyethyleneimine and polyurea are more preferable because of their availability. preferable. The weight average molecular weight (Mw) of the nitrogen-containing polymer compound is usually in the range of 2000 to 750,000, preferably in the range of 2200 to 500000, and the number average molecular weight (Mn) is usually 1200 to 60000. It is a range, Preferably it is the range of 1500-50000. In addition, Mw and Mn in this specification are values in terms of standard polystyrene measured by gel permeation chromatography (GPC). These dispersing agents may be used individually by 1 type, and may use multiple types together.

  The amount of boric acid and aluminum-containing compound used depends on the type of compound used, the firing temperature, the time, etc., but is usually included in the aluminum-containing compound with respect to the number of moles of boric acid atoms contained in the boric acid. The number of moles of aluminum atoms is preferably in the range of 5.5 times or less, and more preferably in the range of 0.3 to 5.2 times. When the number of moles of aluminum atoms contained in the aluminum-containing compound exceeds 5.5 times the number of moles of boric acid atoms contained in boric acids, aluminum oxide aggregates in the resulting phosphor and the fluorescence intensity decreases. Tend to.

  The amount of dispersant used depends on the type of compound, firing temperature, firing time, etc., but is usually preferably in the range of 0.1 to 500 parts by weight with respect to 100 parts by weight of the aluminum-containing compound. The range of parts by mass is more preferable, and the range of 2 to 50 parts by mass is more preferable from the viewpoint of energy efficiency during production.

  The mixture of boric acids, aluminum-containing compound and dispersant used in the production method of the present invention may further contain a solvent. By uniformly dissolving or dispersing boric acids, an aluminum-containing compound, and a dispersant in the solvent, the uniformity of the obtained phosphor can be further enhanced. Examples of the solvent that can be used include water such as ultrapure water, pure water, ion exchange water, and distilled water; alcohols such as methanol and ethanol; ethers such as tetrahydrofuran, tetrahydropyran, and 1,4-dioxane; From the viewpoint of safety, water is preferable.

  If the solvent contains an alkali metal, an alkaline earth metal, a heavy metal or a compound containing these elements, the luminous performance of the resulting phosphor may be adversely affected. In addition, when a halogen or a halogen-containing compound is contained in the solvent, decomposition of the dispersant is accelerated, which is not preferable. From this point of view, when the mixture contains a solvent, the content of alkali metal, alkaline earth metal, heavy metal and halogen in the solvent is preferably 5000 ppm by mass or less, and 1000 ppm by mass. The following is more preferable.

  The amount of the solvent used depends on the type of compound, the firing temperature, the firing time, etc., but is usually preferably in the range of 0.1 to 50000 parts by weight with respect to 100 parts by weight of the aluminum-containing compound, and 1 to 10000 parts by weight. The range of parts is more preferable, and the range of 2 to 5000 parts by mass is more preferable from the viewpoint of increasing the energy efficiency during production.

  The boric acids, aluminum-containing compounds and dispersants and optional solvent mixtures are ball mills, turbo mills, jet mills, mortars, etc. when the mixture does not contain a solvent, and the mixture contains a solvent. Can be prepared by mixing using a hot stirrer, magnetic stirrer, ultrasonic stirrer or the like. In addition, when a mixture contains a solvent, you may mix, after distilling a solvent off by methods, such as spray drying.

  In the method for producing a phosphor of the present invention, the mixture thus prepared is baked in the presence of oxygen (sometimes referred to as “baking step” in this specification). When the mixture uses a solvent, it is preferable to heat in a nitrogen atmosphere until the evaporation of the solvent is completed, and then perform baking in the presence of oxygen. The firing method is, for example, a heating and firing furnace such as a moving bed such as a rotary kiln furnace or a conical kiln furnace, a continuous fixed bed such as a roller hearth furnace or a pusher furnace, or a batch fixed bed such as an atmosphere adjustment furnace. A thermal decomposition furnace such as a spray method may be used.

  The maximum temperature in the firing step depends on the amount of boric acid, aluminum-containing compound and dispersant used, but is usually preferably in the range of 600 to 1000 ° C, from the viewpoint of promoting decomposition of the dispersant and energy efficiency. The range of 980 ° C is more preferable, and the range of 750 to 950 ° C is more preferable.

  Although the temperature increase rate in a baking process is not restrict | limited in particular, Considering the load to a manufacturing apparatus, the range of 1-80 degree-C / min is preferable normally, and the range of 2-50 degree-C / min is more preferable.

  In the firing step, the retention time at the maximum temperature depends on the amount of the dispersant used and the like, but is usually preferably in the range of 0 to 180 minutes. From the viewpoint of homogeneity and crystallinity of the obtained phosphor, 1 The range of -150 minutes is more preferable, and the range of 5-120 minutes is more preferable.

  The firing step needs to be performed in the presence of oxygen, and is usually performed in an air atmosphere.

  The rate of temperature decrease from the maximum temperature in the firing step is not particularly limited, but is usually preferably in the range of 1 to 80 ° C./min, more preferably in the range of 2 to 50 ° C./min in consideration of the load on the production apparatus. .

  The temperature lowering (cooling) operation can be performed, for example, in an inert gas atmosphere such as nitrogen or a rare gas (eg, helium, argon, etc.) or an air atmosphere, but in an inert gas atmosphere in consideration of safety. It is preferable to lower the temperature. Further, when the temperature is lowered at 300 ° C. or lower, it is preferable to lower the temperature in a dry gas atmosphere in order to suppress adhesion of moisture to the target phosphor surface.

  The fired product obtained by the above firing step becomes the phosphor of the present invention. In order to suppress aggregation of the phosphor and improve uniformity, it is preferable to pulverize and mix. At this time, a dispersant may be added again. The pulverization and mixing can be performed using, for example, a ball mill, a turbo mill, a jet mill, or a mortar.

  The pulverized product obtained by the above pulverization and mixing may be fired, cooled and pulverized and mixed again. By repeating firing, cooling, and pulverization and mixing, the uniformity of the obtained phosphor is increased.

  The pulverized product obtained by pulverization and mixing may be further adjusted to a desired particle size by crushing and classification.

Hereinafter, the present invention will be described in detail with reference to examples. In each example, phosphors having various compositions were produced, and X-ray diffraction (XRD) of the obtained phosphors, emission spectra due to ultraviolet excitation at a wavelength of 365 nm, and fluorescence quantum yield were measured. XRD is measured by an X-ray diffraction test apparatus (Rigaku Corporation, Rint 2200V), emission spectrum by ultraviolet excitation at a wavelength of 365 nm is measured by a spectrofluorometer (Shimadzu Corporation, RF-5300PC), and the fluorescence quantum yield is absolute PL quantum. It measured with the yield measuring apparatus (Hamamatsu Photonics Co., Ltd., C9920-02). Moreover, surface observation was performed with the electron microscope (Keyence Corporation, VE-8800). In addition, this invention is not limited to a following example.
In this specification, the “fluorescence quantum yield” is the ratio between the number of photons emitted from a phosphor excited by incident light having a wavelength of 350 nm and the number of photons of incident light. Preferred as a body.

[Example 1]
In a 100 ml beaker, 0.9 g (0.015 mol) of boric acid, 0.8 g (0.010 mol) of aluminum hydroxide, 4 g of polyethyleneimine (weight average molecular weight: 2000, decomposition temperature: 240 ° C.) and 20 g of ultrapure water The mixture was stirred and dissolved using a hot stirrer (rotation number: 500 rpm) (the number of moles of aluminum atoms contained in aluminum hydroxide relative to the number of moles of boric acid atoms contained in boric acid: 0.67 times). The resulting solution was transferred to a crucible, heated in a heating furnace to 400 ° C. in 30 minutes in an air atmosphere, held at 400 ° C. for 60 minutes, then heated to 900 ° C. in 30 minutes, and further at 900 ° C. Hold for 30 minutes. Thereafter, the temperature was lowered to 500 ° C. for 30 minutes in an air atmosphere, held at 500 ° C. for 30 minutes, then lowered to 100 ° C. for 1 hour under a nitrogen atmosphere, and further naturally cooled to room temperature to obtain a phosphor. .
The measurement test result of the emission spectrum of the obtained phosphor by ultraviolet excitation at a wavelength of 365 nm is shown in FIG. 1, the measurement test result of the fluorescence quantum yield is shown in Table 1, and the measurement result of X-ray diffraction is shown in FIG. Since a sharp peak is observed in FIG. 2, it can be said that the obtained phosphor has high crystallinity. In addition, acicular crystals are observed in the electron micrograph (FIG. 3). Table 2 shows the result of component analysis by fluorescent X-ray.

[Example 2]
In Example 1, the same operation as in Example 1 was performed except that 0.5 g (0.005 mol) of aluminum oxide was used instead of 0.8 g of aluminum hydroxide (boric acid contained in boric acid) The number of moles of aluminum atoms contained in the aluminum oxide relative to the number of moles of atoms: 0.67 times), a phosphor was obtained.
The measurement result of the emission spectrum of the obtained phosphor by ultraviolet excitation at a wavelength of 365 nm is shown in FIG. 4, the measurement test result of the fluorescence quantum yield is shown in Table 1, and the measurement result of X-ray diffraction is shown in FIG. Since a sharp peak is observed in FIG. 5, it can be said that the obtained phosphor has high crystallinity. Table 2 shows the result of component analysis by fluorescent X-ray.

[Comparative Example 1]
In Example 1, the same operation as in Example 1 was performed except that boric acid was not added. The obtained fired product was aluminum oxide, and no fluorescence was observed.

[Comparative Example 2]
In Example 1, it carried out like Example 1 except not having added aluminum hydroxide. The obtained fired product was boric anhydride and no fluorescence was observed.

  According to the present invention, it is possible to provide a phosphor with high fluorescence quantum yield and high crystallinity using a raw material with high supply stability, low cost, and low environmental load. In addition, an industrially advantageous production method of the phosphor can be provided.

Claims (4)

  The metal contains only boron and aluminum, the molar ratio of boron atom to aluminum atom is in the range of 1: 4.5 to 1: 5.5, and the molar ratio of boron atom to oxygen atom is 1: 8. A phosphor in the range of 0 to 1: 9.5.   2. A mixture of at least one boric acid selected from the group consisting of boric acid, boric anhydride, metaboric acid and hypoboric acid, an aluminum-containing compound and a dispersant is calcined in the presence of oxygen. A method for producing the phosphor according to 1.   The method for producing a phosphor according to claim 2, wherein the number of moles of aluminum atoms contained in the aluminum-containing compound is 5.5 times or less of the number of moles of boron atoms contained in the boric acid.   The production method according to claim 2 or 3, wherein the dispersant is a nitrogen-containing polymer compound.