JP5783510B2 - Fluorescent silica - Google Patents

Description

  The present invention relates to fluorescent silica.

  Silica is a material having a low refractive index, chemical stability, etc. Currently, silica, alumina powder, etc. are used in various discharge lamps such as xenon lamps and fluorescent lamps for the purpose of chemical protection. Many.

There have been many reports on fluorescent silica containing rare earth elements. For example, Patent Documents 1 and 2 listed below include fluorescent silica for fine binders containing 4 mol% or 9 mol% of Tb ₂ O and Y ₂ O ₃ , respectively. Examples of making and using in a lamp are described. However, in recent years, rare earth elements such as Tb and Y have been rising in price due to resource depletion, and therefore, there is a need for fluorescent silica that does not use them. Silica doped with semiconductor fine particles or organic molecules exhibits strong light emission without using rare earth elements, but has a drawback of severe deterioration due to ultraviolet irradiation.

  On the other hand, silica sintered by doping Cu into porous silica glass exhibits strong fluorescence, and it is reported that the fluorescence intensity is increased by adding Al, Zn or the like (Patent Document 3, non-patent document). Reference 1 etc.).

  However, when Al is doped in addition to Cu, the fluorescence intensity is enhanced, but there is a problem that the emission peak shifts to around 470 nm in the blue region where the visibility is low and the luminance is lowered. For this reason, fluorescent silica having high fluorescence intensity and emitting light at a longer wavelength side is desired.

US6531074 US2001 / 0048966 JP 2004-331442 A

Zhang Q, CHEMICAL PHYSICS LETTERS, 482 Vol: 4-6 228-233 (2009)

  The present invention has been made in view of the current state of the prior art described above, and its main object is a fluorescent silica containing no rare earth element, which has a high fluorescence intensity and provides a high brightness material. It is to be.

  The present inventor has intensively studied to solve the above problems. As a result, the material obtained by doping Ga with Cu into porous silica, the main component of which is silica, and then firing it in a reducing atmosphere is fluorescent compared to the material fired by doping only Cu. As the intensity greatly increased, the peak of the fluorescence intensity shifted to the long wavelength side where the visibility was high, ie, 480 nm to 500 nm, and it was found that the luminance was greatly improved, and the present invention was completed here.

That is, this invention provides the following fluorescent silica and its manufacturing method.
Item 1. A fluorescent silica comprising SiO ₂ as a main component and Cu and Ga.
Item 2. SiO ₂ as a main component, 0.4 weight Cu% to 1.2 wt% and fluorescent silica, characterized in that it contains 0.6 to 1.75% by weight of Ga.
Item 3. Item 2. The method for producing fluorescent silica according to Item 1, wherein porous silica containing SiO ₂ as a main component is impregnated with an aqueous solution containing Cu and Ga, and then fired in a reducing atmosphere.
Item 4. Item 4. The method for producing fluorescent silica according to Item 3, wherein an aqueous solution containing 0.04 mol / L to 0.15 mol / L of Cu and 0.05 to 0.15 mol / L of Ga is used.
Item 5. Item 5. The method for producing fluorescent silica according to Item 3 or 4, wherein firing is performed at 900 to 1050 ° C in a nitrogen gas atmosphere to which a mixed gas of hydrogen gas containing 1 to 5 vol% of hydrogen gas and Ar gas is added.

Hereinafter, the fluorescent silica of the present invention and the production method thereof will be specifically described.
Method for producing fluorescent silica
The fluorescent silica of the present invention can be produced by doping porous silica containing SiO ₂ as a main component with Cu and Ga and then firing in a reducing atmosphere. Hereinafter, this manufacturing method will be described.

(1) Porous silica The porous silica used in the method for producing fluorescent silica of the present invention may be porous silica containing SiO ₂ as a main component, and contains about 90 mol% or more of SiO _2. Preferably, it is more preferably about 95 mol% or more. In the porous silica, components other than SiO ₂ are not particularly limited, but elements such as Al and B may be contained depending on the production method.

  The pore diameter of the porous silica is preferably about 1 nm to 10 nm, more preferably about 2 nm to 6 nm, and still more preferably about 2 nm to 3 nm. By using porous silica having a pore diameter in this range, Cu and Ga can be uniformly doped to the inside of the porous body, and a phosphor having high fluorescence intensity and high luminance can be obtained. If the pore diameter is too small, the amount of Cu doping decreases, and the probability that Cu and Ga are adjacent to each other decreases, so that the fluorescence intensity and the luminance are likely to decrease. On the other hand, if the pore diameter is too large, copper tends to aggregate, which is not preferable.

The specific surface area of the porous silica is preferably about 400 m ² / g to 800 m ² / g, and the pore volume is preferably 0.3 cm ³ / g or more. A larger pore volume is preferable, but if it is too large, copper is likely to precipitate, and it becomes difficult to maintain the shape as silica, so the upper limit of the pore volume should be about 0.8 cm ³ / g. preferable.

  In the present specification, the average pore diameter and the specific surface area are values obtained by the BET method based on nitrogen adsorption.

  In the present invention, as long as the porous silica satisfies the above-described conditions, the production method and the like are not particularly limited. For example, commercially available porous silica can be used as it is.

(2) Doping process of additive element In the fluorescent silica of the present invention, first, the porous silica described above is doped with Cu as a luminescent element and Ga as an enhancer.

  A method for doping these elements is not particularly limited, and for example, a method of doping by a vapor phase method such as a CVD method, a method of immersing porous silica in a solution containing the above-described elements, and the like can be applied. In particular, the method of immersing in a solution is advantageous in that the element is easily uniformly doped.

  In the method of immersing the porous silica in the solution, each element may be doped so that the concentration range of each element in the fluorescent silica described later is obtained.

  As a solvent for the solution containing the element to be doped, water is usually used, but organic solvents such as ethanol and acetone can also be used as appropriate. When water is used as a solvent, each element may be dissolved in water as a water-soluble compound such as nitrate or chloride.

  Although the concentration of each element in the solution is not particularly limited, for example, the concentration of Cu is usually preferably about 0.01 mol / L to 0.3 mol / L, and 0.04 mol / L to 0.15 mol / L. More preferably, it is about. The concentration of Ga is preferably about 0.01 mol / L to 0.3 mol / L, and more preferably about 0.05 mol / L to 0.15 mol / L.

  As a specific dipping method, the porous glass may be dipped in a solution containing each of the above elements and allowed to stand. The temperature of the solution may be about room temperature, and the immersion time may be about 2 minutes to 40 minutes.

(3) Firing step After adding porous silica to the above-mentioned solution containing Cu and Ga and impregnating the solution into the multi-light silica, the porous silica is taken out from the solution and dried. Thereafter, by firing in a reducing atmosphere, the pores of the porous silica disappear, and fluorescent silica containing Cu and Ga therein is obtained.
There is no particular limitation on the method for extracting the porous silica from the solution containing Cu and Ga. For example, a method such as filtration may be used.

  Although there is no limitation in particular about drying temperature, Usually, what is necessary is just to dry at about 110-500 degreeC.

  The glass is then fired in a reducing atmosphere. The reducing atmosphere is not particularly limited, and examples thereof include a method of firing in an atmosphere of a reducing gas such as hydrogen gas, and a method of firing in an alumina crucible containing carbon.

In particular, the nitrogen gas, in the case of firing hydrogen gas in an atmosphere with the addition of hydrogen gas and Ar gas and mixed gas containing about 1～5Vol% can be fluorescence intensity and brightness obtain high fluorescence silica. At this time, for example, the flow rate of the nitrogen stream is preferably 20 cc / min to 40 cc / min, and the amount of the mixed gas of hydrogen gas and Ar gas added to the nitrogen stream is 0.01 cc / min to 0.1 cc. It is preferable to be about / min.

  At this time, if the amount of the mixed gas of hydrogen gas and Ar gas is too large, copper precipitates, and if the amount of the mixed gas of hydrogen gas and Ar gas is too small, copper becomes divalent and the fluorescence intensity decreases, which is not preferable. .

  The firing temperature is preferably about 850 to 1100 ° C, more preferably about 900 to 1050 ° C. By setting the firing temperature within this range, a fluorescent glass with high fluorescence intensity and high brightness can be obtained.

Fluorescent silica The fluorescent silica of the present invention is obtained by uniformly dispersing and fixing Cu and Ga in a material mainly composed of SiO ₂ obtained by firing porous silica. Among these components, Cu is an element that becomes a light emission center that generates fluorescence by ultraviolet excitation. In addition, Ga acts as a sensitizer for increasing the fluorescence intensity, and at the same time, has the effect of shifting the maximum value of the emission peak to the long wavelength side of about 480 nm to 500 nm where the visibility is high. High-intensity fluorescent glass can be obtained.

  If the Cu content is too small, it is difficult to obtain a sufficient fluorescence intensity, and if it is too high, the luminance may decrease due to concentration quenching. With respect to the Ga content, if the amount is too small, sufficient luminance cannot be obtained, and if it is too large, there is a disadvantage that the luminance is lowered.

  From the above viewpoint, the Cu content is preferably about 0.4 to 1.2% by weight, and more preferably about 0.5 to 0.65% by weight, based on the entire fluorescent silica. Further, the Ga content is preferably about 0.6 to 1.75% by weight, and more preferably about 0.7 to 1.2% by weight. The contents of Cu and Ga in the fluorescent silica of the present invention can be determined by ICP emission by decomposing the fluorescent silica with hydrofluoric acid and hydrochloric acid.

In the fluorescent silica of the present invention, the content of SiO ₂ is preferably about 90% by weight or more.

  Since the fluorescent silica of the present invention is dispersed with good uniformity without agglomeration of Cu and Ga, the fluorescent silica exhibits very strong high-luminance emission when excited by ultraviolet light. Therefore, according to the fluorescent glass of the present invention, ultraviolet rays can be converted to visible light with high efficiency.

  Furthermore, the fluorescent silica of the present invention is excellent in heat resistance, chemical durability, mechanical strength and the like because the matrix is a stable oxide. Therefore, there is an advantage that defects due to ultraviolet light irradiation are hardly generated.

  Furthermore, the fluorescent silica of the present invention produces strong fluorescence without containing a rare earth element component, and has high brightness. For this reason, according to this invention, the luminescent material which shows strong light emission can be manufactured at low cost.

  The fluorescent silica of the present invention has an excellent function as described above. For this reason, for example, it can be used as a protective film for a lamp, a fluorescent agent for biodiagnosis, and the like.

  The fluorescent silica of the present invention is a high-intensity fluorescent material having high fluorescence intensity, is a low-cost phosphor that does not contain rare earth elements, and is excellent in heat resistance, chemical durability, and the like.

The graph which shows the relationship between the Ga density | concentration in the impregnating liquid of Cu density | concentration 0.06 mol / L measured in Example 1, and a fluorescence spectrum. The graph which shows the fluorescence spectrum of the Cu-Ga dope fluorescence silica and Cu-Al dope fluorescence silica which were measured in Example 2. FIG.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
As an impregnating solution, 1.5 mL of an aqueous solution in which copper chloride and gallium nitrate were dissolved at the concentrations shown in Table 1 and Table 2 below, 0.3 g of porous silica (trade names: Silicia 530 manufactured by Fuji Silysia, and manufactured by Fuji Silysia) were used. , With a specific surface area of 588.76 m ² / g and a pore diameter of 2.3 nm (determined by the BET method)) and left at room temperature for 0.5 hour to impregnate the porous silica with an aqueous solution containing copper chloride and gallium nitrate . Next, the porous silica was collected by filtration and dried at 110 ° C.

The dried porous silica was placed on a quartz dish, introduced into an atmosphere control furnace, and N ₂ was allowed to flow at 30 cc / min. Flow therein by a mixed gas of H ₂ and Ar containing H ₂ 3 vol% by adding 0.2 cc / min, was carried out for 3-4 hours baking at 1000 ° C..

  About the sample after baking, it excited by the ultraviolet-ray with a wavelength of 254 nm, and measured the fluorescence spectrum. After measurement, 20 mg of each sample is taken, decomposed by microwave irradiation in 1 ml of hydrofluoric acid and 1 ml of hydrochloric acid, the decomposition solution is diluted 50 times, and the concentrations of Cu and Ga are quantified by ICP emission. The content in silica was determined.

Tables 1 and 2 below show the analytical values of the Cu and Ga concentrations in the impregnating solution and the Cu and Ga concentrations in the glass after firing. In addition, the maximum intensity and maximum wavelength of the fluorescence spectrum are shown. FIG. 1 shows fluorescence spectra of the obtained phosphors when an aqueous solution having a CuCl ₂ concentration of 0.06 mol / L is used and the concentration of Ga (NO ₃ ) ₃ is changed.

  As is clear from the above results, in Examples 1 to 11, phosphors having strong fluorescence intensity and an emission peak at 480 nm or more were obtained. In contrast, the phosphor of Comparative Example 1 did not show fluorescence because Ga was not added.

Example 2
Each impregnating solution uses an aqueous solution containing 0.06 mol / L copper chloride solution and 1 mol / L gallium nitrate, or 1.5 mL of an aqueous solution containing 0.06 mol / L copper chloride solution and 1 mol / L aluminum nitrate as the impregnating solution. 0.5 g of porous silica (trade name: Fuji Silysia 530, Fuji Silysia, specific surface area 588.76 m ² / g, pore size 2.3 nm (determined by BET method)) was added to room temperature. The porous silica was impregnated with an aqueous solution containing copper chloride and gallium nitrate or an aqueous solution containing copper chloride and aluminum nitrate. Next, the porous silica was collected by filtration and dried at 110 ° C.

The dried porous silica was placed on a quartz dish, introduced into an atmosphere control furnace, and N ₂ was allowed to flow at 30 cc / min. While flowing therein by a mixed gas of H ₂ and Ar containing H ₂ 3 vol% by adding 0.2 cc / min, it was 4 hours firing at 1000 ° C..

  About the sample after baking, it excited by the ultraviolet-ray with a wavelength of 254 nm, and measured the fluorescence spectrum. This fluorescence spectrum is shown in FIG.

  From FIG. 2, it can be seen that the wavelength at which the maximum fluorescence intensity of the silica doped with Cu and Ga shifts to the longer wavelength side compared with the silica doped with Cu and Al.

These silica powders are put in a quartz cell, excited by ultraviolet rays with a wavelength of 254 nm from an angle of 45 degrees, and measured for luminance using a luminance meter (Cannon LS-100), a commercially available phosphor (LaPO ₄ : Ce , Tb). As a result, the luminance of silica doped with Cu and Al is 0.08 cd / m ^2, the luminance of silica doped with Cu and Ga is 0.12 cd / m ^2, more silica doped with Cu and Ga is increased luminance It was.

Claims (5)

A fluorescent silica containing 90% by weight or more of SiO ₂ and containing Cu and Ga. 2. The fluorescent silica according to claim 1, comprising 0.4 to 1.2% by weight of Cu and 0.6 to 1.75% by weight of Ga. The method for producing fluorescent silica according to claim 1, wherein porous silica containing 90 mol% or more of SiO ₂ is impregnated with an aqueous solution containing Cu and Ga, and then fired in a reducing atmosphere. The method for producing fluorescent silica according to claim 3, wherein an aqueous solution containing 0.04 mol / L to 0.15 mol / L of Cu and 0.05 to 0.15 mol / L of Ga is used. The method for producing fluorescent silica according to claim 3 or 4, wherein firing is performed at 900 to 1050 ° C in a nitrogen gas atmosphere to which a mixed gas of hydrogen gas containing 1 to 5 vol% of hydrogen gas and Ar gas is added.

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