JP2009007536A - Porous silica-based phosphor and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous silica-based phosphor having excellent stability. <P>SOLUTION: The porous silica-based phosphor is a porous silica-based phosphor composed of a matrix containing porous silica-based particulates having an average particle size of 5-100 nm and a specific surface area of 100-1,000 m<SP>2</SP>/g, wherein the matrix contains an activator in an amount of 0.01-0.6 mass% in terms of carbon atoms relative to 100 mass% of the matrix. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a porous silica phosphor and a method for producing the same.

  Examples of inorganic phosphors include various compounds such as calcium halophosphate, alkali halides, oxides, oxyacid salts, and fluorides, and activated phosphors to which manganese or antimony is added as an activator are also known.

  Many techniques have already been known for these phosphors and their production methods. For example, as a phosphor containing zinc oxide and silica, Patent Document 1 discloses an invention related to a fluorescent material based on zinc silicate doped with manganese having a short decay time, and the fluorescent material is zinc oxide, It is described that it can be produced by drying an aqueous suspension composed of silica gel and manganese carbonate and treating the resulting dried product in an oven.

  In Patent Document 2, in a ZnO: Zn phosphor that is used as a low-energy electron beam-excited phosphor and has high emission luminance, a metal zinc powder in which silica is coated on the surface of a metal zinc powder fine particle is disclosed as ZnO: Zn fluorescence. Mixing or adhering to the body is disclosed.

  As described above, various types of phosphors containing silica and their production methods have already been proposed, but those methods are complicated in production process, and in special limited applications, Even if it can be used, it has not been used as a general-purpose inorganic phosphor.

Therefore, it has been desired to develop an inorganic phosphor that is excellent in powder characteristics and economy and can be used in various applications.
Patent Document 3 discloses an invention relating to a nitrogen-doped zinc oxide-silica-based inorganic porous phosphor characterized in that zinc oxide fine particles containing nitrogen are encapsulated in pores of a silica-based inorganic porous material. ing. By encapsulating nitrogen-containing zinc oxide particles in the pores of the silica-based inorganic porous material, the phosphor is excellent in powder characteristics such as stability and handling properties and economical efficiency, and in various applications. It is disclosed as one of the usable inorganic phosphors. In addition, a production method is described in which zinc ions or a zinc compound is introduced into pores of a silica-based inorganic porous material modified with a silane compound having an amino group, and then heated and fired.

This silica-based inorganic porous body describes that the average pore diameter measured by nitrogen adsorption is preferably 1 nm or more, more preferably 3 nm or more.
Patent Document 4 discloses an invention relating to a light-emitting substance characterized in that a porous inorganic particle having an average pore size of 5 to 500 nm contains a fluorescent complex, and the porous inorganic particle having a specific pore diameter is disclosed. It is described that a substance containing a fluorescent complex can be used in various devices such as a luminescent substance having high emission intensity and high color rendering properties or a wide color reproduction range and a light emitting device using the same. Yes. In particular, the porous inorganic particles are silica particles, the average particle diameter of the silica particles is in the range of 1 to 300 μm, the specific surface area is 50 to 800 m ² / g, and the pore volume is 0.6 to 1.6 ml. There is a description that particles having a / g are advantageous for handling and deterioration. It is described that the obtained phosphor can be effectively used as functional fillers and pigments for special paints, inks, cosmetics, paper and the like in the field of opelectronics.

In Patent Document 5, a) a silica-based porous particle having an aspect ratio of at least 2 and b) an optically active substance encapsulated in the porous particle are contained in a physiologically acceptable medium. An invention relating to a cosmetic composition is disclosed, wherein the silica-based porous particles have an average particle diameter of 1 to 100 μm, and the optically active substance is an ultraviolet shielding substance There is a description that it is selected from fluorescent substances and photochromic substances.

  Patent Document 6 relates to a chemical substance adsorbing sheet characterized by containing a powder of a substance capable of adsorbing to a chemical substance, cellulose fibers, fine fibrillated cellulose and a fluorescent agent, and being made into a sheet by papermaking. There is a description about the invention, and the substance having an adsorbing ability with respect to the chemical substance is porous ceramics, and an example thereof is porous silica.

In US Pat. No. 6,057,033, a porous matrix that conceals at least a portion of the light emitting diode, and a response luminescence emitted when interacting with the excitation luminescence emitted by the diode, is packed in the porous matrix. An invention relating to a semiconductor-based light-emitting device containing a substance is disclosed, and it is described that the porous matrix is a sol-gel material.

  Patent Document 8 discloses an invention related to a conjugate comprising a porous particle on which a functional substance is adsorbed or non-adsorbed, and a polymer molecule based on a water-soluble polymer chain segment immobilized on the particle surface. The porous particles are organic or inorganic particles having an average particle diameter of 10 nm to 10 mm and pores having a pore diameter of 10 μm to 1 nm, and may be composed of silica. ing.

As described above, in recent years, the use as an inorganic phosphor has been rapidly expanding, and therefore, an inorganic phosphor having excellent stability that can be used for various purposes, in particular, a minute inorganic phosphor. Development of was desired.
Japanese Patent No. 3195054 JP-A-5-117654 JP 2005-132964 A Japanese Patent Laid-Open No. 2005-41942 JP 2005-53846 A Japanese Patent No. 3734517 JP-T-2006-518111 International Publication WO2005 / 005548

  An object of the present invention is to provide a porous silica-based phosphor excellent in stability.

The porous silica-based phosphor of the present invention is a porous silica-based phosphor comprising a matrix containing porous silica-based fine particles, and the average particle diameter of the porous silica-based fine particles is in the range of 5 to 100 nm, The specific surface area is in the range of 100 to 1000 m ² / g, and the activator is contained in an amount of 0.01 to 0.6% by mass in terms of carbon atoms in the matrix (100% by mass).

The matrix is preferably an aggregate of porous silica-based fine particles.
Moreover, it is preferable that the average particle diameter of the said porous silica type fluorescent substance exists in the range of 0.1 micrometer-100 micrometers.

  The porous silica-based fine particles are selected from the group consisting of silicon and elements of Group IIIa, Group IIIb, Group IVa, Group IVb, Group Va, Group Vb and Group VIa of the periodic table. It is preferably obtained by removing a part other than silicon from the composite oxide fine particles containing other elements.

The method for producing a porous silica-based phosphor of the present invention comprises dispersing porous silica-based fine particles having an average particle diameter in the range of 5 to 100 nm and a specific surface area in the range of 100 to 1000 m ² / g in a dispersion medium. A mixture is prepared by adding carbon or an organic compound to the porous silica-based sol, and the mixture is dried at 100 to 150 ° C. and further baked at 300 to 700 ° C.

  The porous silica-based phosphor of the present invention is composed of a matrix containing porous silica-based fine particles activated with carbon or an organic compound, and the activator is dispersed inside the porous silica-based fine particles. Excellent stability.

Hereinafter, the porous silica phosphor of the present invention and the production method thereof will be described in more detail. <Porous silica-based phosphor>
The porous silica-based phosphor of the present invention is a dry-type phosphor comprising a matrix containing porous silica-based fine particles, and carbon or an organic compound is dispersed in the matrix. It is.
<Porous silica-based fine particles>
The average particle diameter of the porous silica-based particles is 5 to 100 nm, preferably 25 to 80 nm, a specific surface area of 100~1000m ² / g, preferably 300~800m ² / g.

If the average particle diameter and specific surface area of the porous silica-based fine particles are within the above ranges, carbon or an organic compound tends to be sufficiently dispersed in the pores of the fine particles.
When the average particle diameter of the porous silica-based fine particles exceeds 100 nm, since the porous silica-based fine particles are large, in the case of an aggregate, the total specific surface area is reduced, and the relative particle size is smaller than when the porous fine particles are small. In particular, the dispersibility of carbon or organic compounds tends to decrease.

  On the other hand, when the average particle diameter of the porous silica-based fine particles is less than 5 nm, the porous silica-based fine particles are extremely small, and therefore the dispersibility of carbon or organic compounds in the porous silica-based fine particles tends to be low. This is presumably because the pores of the porous silica fine particles are too small for carbon or organic compounds to enter.

When the specific surface area of the porous silica-based fine particles is less than 100 m ² / g, the dispersibility and persistence of the carbon or organic compound is lowered, so that the stability as the porous silica-based phosphor is lowered.

In addition, the value of the said average particle diameter and the value of a specific surface area are the values at the time of measuring by the method as described in the Example mentioned later, respectively.
The porous silica-based fine particles used in the present invention include silicon and elements of Group IIIa, Group IIIb, Group IVa, Group IVb, Group Va, Group Vb and Group VIa of the periodic table. Fine particles obtained by removing a part of elements other than silicon from composite oxide fine particles containing an element other than silicon selected from the group consisting of:
<Activator>
The activator used in the present invention can be suitably used as long as it is water-soluble. Examples include, but are not limited to, citric acid, fumaric acid, malic acid, lactic acid and the like.

Examples of carbon include carbon powder provided with hydrophilic substituents.
Other examples of organic compounds include monobasic carboxylic acids or polybasic carboxylic acids. As the monobasic carboxylic acid, a fatty acid having 1 to 24 carbon atoms is usually used, and the fatty acid may be linear or branched, and may be saturated or unsaturated. Good. Specifically, for example, formic acid, acetic acid, propionic acid, linear or branched butanoic acid, linear or branched pentanoic acid, linear or branched hexanoic acid, linear or branched Heptanoic acid, linear or branched octanoic acid, linear or branched nonanoic acid, linear or branched decanoic acid, linear or branched undecanoic acid, linear or branched Dodecanoic acid, linear or branched tridecanoic acid, linear or branched tetradecanoic acid, linear or branched pentadecanoic acid, linear or branched hexadecanoic acid, linear or branched Heptadecanoic acid, linear or branched octadecanoic acid, linear or branched hydroxyoctadecanoic acid, linear or branched nonadecanoic acid, linear Or branched icosanoic acid, linear or branched heicosanoic acid, linear or branched docosanoic acid, linear or branched tricosanoic acid, linear or branched tetracosanoic acid, etc. Fatty acids are mentioned.

  Further, acrylic acid, linear or branched butenoic acid, linear or branched pentenoic acid, linear or branched hexenoic acid, linear or branched heptenoic acid, linear or branched Octenoic acid, linear or branched nonenoic acid, linear or branched decenoic acid, linear or branched undecenoic acid, linear or branched dodecenoic acid, linear or branched Tridecenoic acid, linear or branched tetradecenoic acid, linear or branched pentadecenoic acid, linear or branched hexadecenoic acid, linear or branched heptadecenoic acid, linear or branched Octadecenoic acid, linear or branched hydroxyoctadecenoic acid, linear or branched nonadecenoic acid, linear or branched icosenoic acid, Chain or branched henicosenoic acid, straight-chain or branched docosenoic acid, unsaturated fatty acids such as straight-chain or branched tricosenoic acid, or a linear or branched tetracosenoic acid. These can be used individually by 1 type or in combination of 2 or more types.

  Examples of the polybasic carboxylic acid include dibasic acid, citric acid, and trimellitic acid. The dibasic acid may be either a chain dibasic acid or a cyclic dibasic acid. In the case of a chain dibasic acid, it may be linear or branched, or may be saturated or unsaturated.

  As the chain dibasic acid, a chain dibasic acid having 2 to 16 carbon atoms is preferable. Specifically, for example, ethanedioic acid, propanedioic acid, linear or branched butanedioic acid, linear or branched pentanedioic acid, linear or branched hexanedioic acid, linear Or branched heptanedioic acid, linear or branched octanedioic acid, linear or branched nonanedioic acid, linear or branched decanedioic acid, linear or branched undecanedioic acid Acid, linear or branched dodecanedioic acid, linear or branched tridecanedioic acid, linear or branched tetradecanedioic acid, linear or branched heptadecanedioic acid, linear or Branched hexadecanedioic acid, linear or branched hexenedioic acid, linear or branched heptenedioic acid, linear or branched octenedioic acid, linear or branched nonenedioic acid ,straight Linear or branched decenedioic acid, linear or branched undecenedioic acid, linear or branched dodecenedioic acid, linear or branched tridecenedioic acid, linear or branched tetradecene Examples thereof include diacids, linear or branched heptacene diacids, linear or branched hexadecene diacids, and mixtures thereof. Examples of the cyclic dibasic acid include 1,2-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and aromatic dicarboxylic acid.

Among these carbon or organic compounds, carboxylic acid compounds such as citric acid are preferable because they are easily available.
The concentration of the activator in which carbon or an organic compound contained in the matrix (100% by mass) is activated is 0.01 to 0.6% by mass, preferably 0.03 to 0.5% by mass in terms of carbon atoms. It is. If it is less than 0.01% by mass, sufficient light emission may not be achieved. If it exceeds 0.6 mass%, the emission intensity tends to decrease due to the concentration quenching phenomenon.
<Matrix>
The porous silica-based phosphor of the present invention comprises a matrix containing the porous silica-based fine particles.

Examples of the form of the matrix include aggregates or powders of the porous silica-based fine particles.
This matrix is preferably an aggregate of the porous silica-based fine particles.

  Since the matrix made of the aggregate is an aggregate of fine porous silica fine particles having an average particle diameter in the range of 5 to 100 nm, carbon or an organic compound is introduced into the matrix including the inside of the pores of the porous silica fine particles. It can be sufficiently dispersed and activated. As a result, a porous silica phosphor having excellent stability can be obtained.

[Method for producing porous silica-based phosphor]
The method for producing the porous silica-based phosphor of the present invention is described below.
<Manufacture of porous silica-based fine particles>
The porous silica-based fine particles can be produced by a known production method, for example, a production method comprising the following first step and second step.

First, the first step will be described.
An alkali aqueous solution (hereinafter also referred to as “raw material aqueous solution a1”) that is a raw material of silicon in the porous silica-based fine particles and an alkaline aqueous solution that is a raw material of elements other than silicon (hereinafter also referred to as “raw material aqueous solution a2”) are prepared. These prepared aqueous solutions are gradually added to an alkaline aqueous solution having a pH of 10 or more while stirring to obtain a reaction solution (hereinafter also referred to as “reaction solution a”). Alternatively, an alkaline aqueous solution (hereinafter also referred to as “raw material aqueous solution b”) containing a raw material of silicon and a raw material of an element other than silicon in the porous silica-based fine particles is prepared, and the prepared alkaline aqueous solution is added to an alkaline aqueous solution having a pH of 10 or more. The mixture is gradually added with stirring to obtain a reaction liquid (hereinafter also referred to as “reaction liquid b”).

When the reaction solution is filtered through an ultrafiltration membrane and washed, a composite oxide precursor sol is obtained.
As a raw material of silicon, alkali metal, ammonium or silicate of organic base is used. Sodium silicate (water glass) or potassium silicate is used as the alkali metal silicate. Examples of the organic base include quaternary ammonium salts such as tetraethylammonium salt, and amines such as monoethanolamine, diethanolamine, and triethanolamine. Examples of the ammonium silicate or organic base silicate include an alkaline solution in which ammonia, quaternary ammonium hydroxide, an amine compound, or the like is added to a silicic acid solution.

In addition, alkali-soluble inorganic compounds are used as raw materials for elements other than silicon. For example, an alkali metal salt or alkaline earth of a metal or non-metal oxo acid selected from Group IIIa, Group IIIb, Group IVa, Group IVb, Group Va, Group Vb, Group VIa of the Periodic Table Examples thereof include metal salts, ammonium salts, and quaternary ammonium salts. Preferred is Group IIIa. More specifically, sodium aluminate, sodium tetraborate, zirconyl ammonium carbonate, potassium antimonate, potassium stannate, sodium aluminosilicate, sodium molybdate, cerium ammonium nitrate, and sodium phosphate are suitable.

  Although the pH value of the reaction solution a or b changes simultaneously with the addition of the raw material aqueous solution a1, a2 or b, in the present invention, an operation for controlling this pH value within a predetermined range is not particularly required. The final pH value of the reaction solution a or b is determined by the type of raw material and the mixing ratio. In order to control the pH value within a predetermined range, for example, an acid may be added to the reaction solution a or b. In this case, since the added acid generates a metal salt of the raw material of the composite oxide, the stability of the sol may be lowered. In addition, there is no special restriction | limiting in the addition rate of the aqueous solution at this time.

In this method for producing a composite oxide precursor sol, a dispersion of seed particles can be used as a starting material. The seed particles are not particularly limited, and for example, inorganic oxides such as SiO ₂ , Al ₂ O ₃ , TiO ₂ or ZrO ₂ or fine particles of these composite oxides are used. Usually, these sols are used as the seed particle dispersion, but sols obtained by the above-described production method may be used.

  The raw material aqueous solution a1, a2 or b is added to the seed particle dispersion adjusted to pH 10 or higher with stirring in the same manner as in the method of adding the aqueous alkali solution described above. In the present invention, an operation for controlling the pH value of the dispersion within a predetermined range is not particularly required. As described above, when the composite oxide particles are grown using the seed particles as nuclei, it is easy to control the particle size of the grown particles, and particles with uniform particle sizes can be obtained.

  The above-described silicon raw material and raw materials of elements other than silicon have high solubility on the alkali side. However, when both are mixed in this highly soluble pH region, the solubility of oxo acid ions such as silicate ions and aluminate ions decreases, and these composites precipitate and grow into fine particles, or on the seed particles. Precipitates into particles and causes particle growth. Therefore, it is not always necessary to perform pH control as in the conventional method for precipitation and growth of fine particles.

  The composite ratio of silicon and elements other than silicon (silicon (mol) / elements other than silicon (mol)) in the first step is preferably in the range of 0.5 to 20. Within this range, the smaller the proportion of silicon, the more complex oxide fine particles become porous and the greater the specific surface area. However, when the molar ratio is less than 0.5, the specific surface area of the composite oxide fine particles tends to hardly increase. On the other hand, when the molar ratio exceeds 20, the pore volume decreases, and the specific surface area tends to decrease.

Next, the second step will be described.
At least a part of elements other than silicon is selectively removed from the composite oxide fine particles of the composite oxide precursor sol obtained in the first step. Specific removal methods include dissolution removal using a mineral acid or organic acid, or ion exchange removal in contact with a cation exchange resin.

The composite oxide fine particles of the composite oxide precursor sol obtained in the first step are particles having a network structure in which elements other than silicon and silicon are bonded through oxygen. By removing elements other than silicon from such composite oxide fine particles, porous silica-based fine particles having a higher porosity and a larger specific surface area can be obtained. However, if it is removed excessively, the strength of the porous silica-based fine particles is weakened, and finally the shape cannot be maintained. Therefore, it is desirable that the final composite ratio (molar ratio) of silicon to elements other than silicon is about 1000 or less.
<Production of porous silica-based phosphor>
A porous silica-based sol can be obtained by dispersing the porous silica-based fine particles obtained in the previous step in an aqueous solvent. Carbon or an organic compound is added to the obtained porous silica-based sol.

  As for the amount of carbon or organic compound added to the porous silica-based fine particles, as long as the carbon atom content in the porous silica-based phosphor is added in the range of 0.01 to 0.6% by mass, It is not particularly limited.

Usually, a water-soluble organic compound is added to an aqueous porous silica sol to prepare a mixture.
Further, the mixture is dried at 100 to 150 ° C., preferably 100 to 120 ° C., and further fired at 300 to 700 ° C., preferably 400 to 600 ° C., to obtain an aggregate of porous silica-based fine particles.

Since carbon or an organic compound and porous silica-based fine particles are mixed in an aqueous system, the activator can be sufficiently dispersed inside the pores of the porous silica-based fine particles.
As for the drying temperature, if it is less than 100 ° C., the drying efficiency is low, which is not practical. Temperatures above 150 ° C are not necessarily required. When the firing temperature is within the above range, an aggregate of porous silica-based fine particles having good properties can be obtained. Here, the good property means, for example, that carbon is not attached to the surface of the porous silica fine particles. When carbon adheres to the surface of the porous silica fine particles, the tendency of the phosphor particles to become black increases. When the firing temperature is less than 300 ° C., aggregates may not be easily generated. Although it is possible to heat at a temperature exceeding 700 ° C., it is economically desirable to carry out at a temperature of 700 ° C. or less for practical use.

  When the obtained porous silica-based phosphor is put into practical use, it is usually pulverized and further pressure-molded. Although it does not restrict | limit especially about a shaping | molding shape, For example, it shape | molds in a disk shape or plate shape. Although the pressure at the time of pressure molding is not specifically limited, For example, it is the range of 5-15 KPa. The pulverization method is not particularly limited, and a mixer, a mill or a mortar can be used.

In order to make the particle diameter of the pulverized porous silica-based phosphor uniform, a sieve or a filter can be used.
The average particle size of the porous silica-based phosphor of the present invention varies depending on the average particle size, the firing temperature and the firing time of the porous silica-based fine particles, but can be adjusted from several μm to several hundred μm. Usually, it is preferable to adjust to the range of 0.1 μm to 100 μm by means such as pulverization and sieving as described above.

Depending on the application, the porous silica phosphor obtained by pulverization may be used as it is, or may be used by blending with other curable compositions.
<Characteristics of porous silica phosphor>
The porous silica-based phosphor of the present invention emits light when irradiated with ultraviolet rays in the near ultraviolet region where the wavelength of the light source is 200 to 380 nm, for example. For example, when irradiated with ultraviolet rays of 254 nm or 365 nm, light is emitted from bluish white to white. When the light source is irradiated with ultraviolet rays of 320 nm, an emission spectrum is observed.
[Example]
[1] Measurement of specific surface area by nitrogen adsorption method and calculation of average particle diameter Silica sol 50 ml was adjusted to pH 3.5 with HNO ₃ , 40 ml of 1-propanol was added, and the sample dried at 110 ° C. for 16 hours was crushed in a mortar The sample for measurement was baked at 500 ° C. for 1 hour in a muffle furnace. And the specific surface area was measured by the BET 1-point method from the amount of adsorption | suction of nitrogen using the nitrogen adsorption method (BET method) using the specific surface area measuring apparatus (The product made from Yuasa Ionics, model number multisorb 12).

  Specifically, 0.5 g of a sample is placed in a measurement cell, degassed for 20 minutes at 300 ° C. in a mixed gas stream of 30% by volume of nitrogen and 70% by volume of helium, and then the sample is mixed with the above mixed gas stream. The liquid nitrogen temperature is maintained in the sample, and nitrogen is allowed to equilibrate to the sample. Next, the sample temperature was gradually raised to room temperature while flowing the mixed gas, the amount of nitrogen desorbed during that time was detected, and the specific surface area of the silica sol was measured with a calibration curve prepared in advance.

The average particle size of the silica sol was calculated from the following formula (1).
D = 6000 / (ρ × SA) (1)
(D: Average particle diameter (nm), ρ: Sample density (g / cm ³ ), SA: Specific surface area (m ² / g)
)
[2] Content measurement of C (carbon) The carbon content in the porous silica-based phosphor was measured with EMIA-320V (manufactured by Horiba, Ltd.). The analysis principle is based on high-frequency heating combustion in an oxygen stream-infrared absorption method. The minimum reading sensitivity was 0.01 ppm, the analysis time was 30 to 60 seconds, the anode output was 2.3 kW, and the frequency was 18 MHz. The combustion furnace method was a high frequency induction heating furnace method with a combustion control function.
[3] Ultraviolet irradiation device Handy UV Lamp SLUV-6 (variable emission wavelength 254 nm / 365 nm) manufactured by AS ONE was used.
[4] Emission spectrum measurement
A Perkin Elmer LS50B spectrofluorometer was used. As a sample, a porous silica-based phosphor powder molded into a disk shape at a pressure of 10 to 11 Kpa was used. The measurement wavelength range was 300 to 800 nm.

(First step)
A mixture of 100 g of silica sol having an average particle size of 5 nm (catalyst chemical industry, Cataloid SI-550, SiO ₂ : 20% by mass, water: 80% by mass) and 1900 g of pure water is heated to 80 ° C. and reacted. A mother liquor was obtained.

The pH of this reaction mother liquor was 10.5. In this reaction mother liquor, 9000 g of a sodium silicate aqueous solution containing 1.5% by mass of silicon in terms of SiO ₂ and 9000 g of a sodium aluminate aqueous solution containing 0.5% by mass of aluminum in terms of Al ₂ O ₃ were simultaneously added. This was added to obtain a reaction solution. Meanwhile, the temperature of the reaction solution was kept at 80 ° C. Immediately after the addition, the pH of the reaction solution rose to 12.5 and remained almost unchanged thereafter. After completion of the addition, the reaction solution is cooled to room temperature, filtered through an ultrafiltration membrane and washed to obtain a SiO ₂ · Al ₂ O ₃ composite oxide precursor sol (A) having a solid content concentration of 20% by mass. It was.
(Second step)
1,700 g of pure water was added to 500 g of the SiO ₂ / Al ₂ O ₃ composite oxide precursor sol (A) obtained in the first step and heated to 98 ° C., while maintaining this temperature, sodium silicate 3,000 g of a silicic acid solution (silica concentration: 3.5% by mass) obtained by dealkalizing the aqueous solution with a cation exchange resin was added. The sol was washed with an ultrafiltration membrane and 1,125 g of pure water was added to 500 g of the sol having a solid content of 13% by mass, and concentrated hydrochloric acid (35.5% by mass) was added dropwise to adjust the pH to 1.0. Dealumination treatment was performed. Next, the aluminum salt dissolved in the ultrafiltration membrane was separated while adding 10 liters of hydrochloric acid aqueous solution of pH 3 and 5 liters of pure water, and the SiO ₂ · Al ₂ O ₃ composite oxide precursor sol from which a part of aluminum was removed. (B) was obtained.

The average particle size of the porous silica-based fine particles contained in the SiO ₂ / Al ₂ O ₃ composite oxide precursor sol (B) was 30 nm, and the specific surface area was 600 m ² / g.
100 g of SiO ₂ · Al ₂ O ₃ composite oxide precursor sol (B) obtained in the second step (
To the silica concentration: 5% by mass, 0.05 g of citric acid monohydrate was added, stirred at room temperature, and dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour, pulverized in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped porous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is 0.04 mass%.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 KPa. When this molded body was irradiated with ultraviolet rays having a wavelength of 254 nm or 365 nm, it was confirmed that light emission was bluish white. Further, it was found that the emission spectrum when the excitation light wavelength was 320 nm had a peak at 520 nm.

0.5 g of citric acid monohydrate was added to 100 g (silica concentration: 5% by mass) of the same SiO ₂ .Al ₂ O ₃ composite oxide precursor sol (B) prepared in the second step of Example 1. In addition, the mixture was stirred at room temperature and dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour, pulverized in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped porous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is 0.10 mass%.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. When this molded body was irradiated with ultraviolet rays of 254 nm or 365 nm, it was confirmed that light was emitted in white. Further, it was found that the emission spectrum when the excitation light wavelength was 320 nm had a peak at 520 nm.

  The carbon-doped porous silica particle powder was stored at room temperature for 6 months, and the emission characteristics were measured in the same manner as described above. As a result, the same emission characteristics were confirmed.

The same SiO ₂ · Al ₂ O ₃ composite oxide precursor sol (B) 100 g (silica concentration: 5% by mass) as that prepared in the second step of Example 1 was charged with 1.0 g of citric acid monohydrate. In addition, the mixture was stirred at room temperature and dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour, pulverized in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped porous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is 0.14 mass%.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. When this molded body was irradiated with ultraviolet rays of 254 nm or 365 nm, it was confirmed that light was emitted slightly. Further, the emission spectrum when the excitation light wavelength was 320 nm did not have a peak at 520 nm.

5 g of citric acid monohydrate was added to 100 g (silica concentration: 5 mass%) of the same SiO ₂ .Al ₂ O ₃ composite oxide precursor sol (B) prepared in the second step of Example 1. The mixture was stirred at room temperature and dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour, pulverized in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped porous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is carbon content: 0.17 mass%.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. When this molded body was irradiated with ultraviolet rays of 254 nm or 365 nm, it was confirmed that light was emitted slightly. Further, the emission spectrum when the excitation light wavelength was 320 nm did not have a peak at 520 nm.

[Comparative Example 1]
10 g of citric acid monohydrate was added to 100 g (silica concentration: 5 mass%) of the same SiO ₂ .Al ₂ O ₃ composite oxide precursor sol (B) prepared in the second step of Example 1. The mixture was stirred at room temperature and dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour, pulverized in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped porous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is 0.68 mass%.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. It was confirmed that no light was emitted when the molded body was irradiated with ultraviolet rays of 254 nm or 365 nm. Further, the emission spectrum when the excitation light wavelength was 320 nm did not have a peak at 520 nm.

[Comparative Example 2]
100 g (silica concentration: 5% by mass) of the same SiO ₂ · Al ₂ O ₃ composite oxide precursor sol (B) as that prepared in the second step of Example 1 was dried at 110 ° C. for 12 hours. The dried product was baked at 500 ° C. for 1 hour and pulverized in a mortar to obtain porous silica particle powder having a particle size of 90 μm or less with a sieve (carbon content: 0.00 mass%).

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. It was confirmed that no light was emitted when the molded body was irradiated with ultraviolet rays of 254 nm or 365 nm. Further, the emission spectrum when the excitation light wavelength was 320 nm did not have a peak at 520 nm.

[Comparative Example 3]
Citric acid monohydrate 0, 100 g of silica sol having an average particle size of 25 nm (catalyst chemical industry, Cataloid SI-50, SiO ₂ : 20% by mass, water: 80% by mass, specific surface area 90m ² / g) 05 g was added, stirred at room temperature, and dried at 110 ° C. for 12 hours. Further, baking was performed at 500 ° C. for 1 hour, pulverization was performed in a mortar, and the particle diameter was reduced to 90 μm or less with a sieve to obtain carbon-doped nonporous silica particle powder. About this powder, when carbon content was measured by content measurement of said [3] C (carbon), it was confirmed that it is 0.001 mass% or less.

  The powder obtained above was molded into a disc shape (diameter 5 cm, thickness 1 cm) by applying a pressure of 10 to 11 MPa. It was confirmed that no light was emitted when the molded body was irradiated with ultraviolet rays of 254 nm or 365 nm. Further, the emission spectrum when the excitation light wavelength was 320 nm did not have a peak at 520 nm.

  The porous silica phosphor of the present invention is suitable for illumination, cathode ray tube, printing, X-ray sensitization, and fluorescent display tube.

Claims (5)

A porous silica-based phosphor comprising a matrix containing porous silica-based fine particles, wherein the average particle diameter of the porous silica-based fine particles is in the range of 5 to 100 nm, and the specific surface area is in the range of 100 to 1000 m ² / g. A porous silica-based phosphor comprising 0.01 to 0.6% by mass of an activator in terms of carbon atoms with respect to 100% by mass of the matrix.   2. The porous silica-based phosphor according to claim 1, wherein the matrix is an aggregate of porous silica-based fine particles.   3. The porous silica-based phosphor according to claim 2, wherein an average particle diameter is in a range of 0.1 μm to 100 μm.   The porous silica-based fine particles are selected from the group consisting of silicon and elements of Group IIIa, Group IIIb, Group IVa, Group IVb, Group Va, Group Vb and Group VIa of the periodic table The porous silica-based phosphor according to any one of claims 1 to 3, wherein the porous silica-based phosphor is obtained by removing a part of elements other than silicon from composite oxide fine particles containing elements other than the above. Carbon or an organic compound is added to a porous silica-based sol in which porous silica-based fine particles having an average particle diameter of 5 to 100 nm and a specific surface area of 100 to 1000 m ² / g are dispersed in a dispersion medium. A method for producing a porous silica-based phosphor comprising adding the mixture to prepare a mixture, drying the mixture at 100 to 150 ° C., and firing at 300 to 700 ° C.