JP2007023221A - Coated illuminant and its utilization - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated illuminant which is not deteriorated with water, has high brightness, and has a long light emission life. <P>SOLUTION: This method for producing the coated illuminant comprises (I) a process for coating an illuminant with a coating material, (II) a process for dispersing the coated illuminant in a solvent to obtain a dispersion, and (III) a process for separating the dispersion into a solid phase and a liquid phase, wherein the processes (II) and (III) are repeated until to give an electric conductivity of ≤100 μS/cm to the liquid phase. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coated illuminant having high luminance and less moisture deterioration, a method for producing the same, and use of the illuminant. Specifically, the present invention relates to a luminance or The present invention relates to a luminescent material having an excellent luminescent lifetime, a manufacturing method thereof, and use of the luminescent material.

It is known that a light-emitting body used for a light-emitting portion in various lighting devices and / or display devices is deteriorated by moisture, and the light emission power and / or luminance is reduced. For this reason, the phosphor has been conventionally coated with a silica film (for example, see JP-A-61-2678). However, the method described in Patent Document 1 has not been sufficient for preventing deterioration. Further attempts have been introduced to produce a dense coating film for the purpose of solving such moisture degradation (see, for example, Patent Documents 2 to 4).
JP 61-23678 (released February 1, 1986) JP-A-6-306356 (published on November 1, 1994) JP 2002-69442 A (published March 8, 2002) JP 2003-261869 A (published on September 19, 2003)

  However, even when the techniques described in Patent Documents 2 to 4 are used, preferable results are not obtained. The reason is considered that the denseness of the formed film was still insufficient.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a coated illuminator provided with a coating having a density sufficient to prevent moisture deterioration.

  As a result of intensive studies, the present inventors have found that when a film is produced using specific conditions for a light emitter, moisture degradation of the coated light emitter can be prevented.

That is, a method for producing a coated illuminant in which a illuminant is coated with a coating material according to the present invention,
(I) a step of coating the illuminant with a coating material;
(II) a step of obtaining a dispersion in which the coated phosphor is dispersed in a solvent; and (III) a step of separating the dispersion into a solid phase and a liquid phase, the electric conductivity of the liquid phase being It is characterized by repeating steps (II) and (III) until it becomes 100 μS / cm or less.

  In the method according to the present invention, the solvent is preferably water or an organic solvent.

  In the method according to the present invention, the separating step is preferably performed by centrifugation.

  In the method according to the present invention, the coating material is preferably silica.

  The coated illuminant according to the present invention is manufactured by the above method.

  The coated illuminant according to the present invention is a coated illuminant in which an illuminant is coated with a coating material, and the elution of the illuminant through the film is 100 ppm or less.

  In the coated illuminant according to the present invention, the coating material is preferably silica.

  By using the present invention, it is possible to obtain a coated illuminant having a dense coating film, having a low risk of moisture approaching the coated illuminant, having no reduction in luminance, and having a long emission lifetime.

  As a result of intensive studies, the present inventors have been able to suppress moisture intrusion into the coated illuminant by removing impurities as much as possible from the dispersion of the coated illuminant. It has been found that a reduction in luminance can be prevented.

  The factor that could almost completely suppress the intrusion of moisture into the coated phosphor was to remove as much of the solution, unreacted reagent, salt, alkali component, and acid component as possible after the coating reaction, followed by firing. This is probably because the process was performed. In the prior art, unreacted reaction system, alkali component, and acid component remain on the film, thereby promoting hydrolysis by heating, and as a result, only a film with insufficient denseness can be obtained. It was.

  The fact that there is almost no impurities in the dispersion means that the pure coating completely covers the surface of the internal material, which suppresses moisture intrusion into the coated illuminant and reduces brightness. Is considered to be suppressed. In addition, the light emission of the light emitter largely contributes to the surface, but the surface of a normal coated light emitter has many defective portions, and therefore, the luminance is likely to be lowered. However, it is considered that by obtaining a coated illuminant having almost no impurities, defects on the illuminant surface can be complemented, and as a result, a decrease in luminance is suppressed.

  The present invention provides a method for producing a coated illuminant in which the illuminant is coated with a coating material. The method for producing a coated illuminant according to the present invention comprises: (I) a step of coating the illuminant with a coating material; (II) a step of obtaining a dispersion in which the coated illuminant is dispersed in a solvent; and (III) It includes a step of separating the dispersion into a solid phase and a liquid phase, and the steps (II) and (III) are repeated until the electric conductivity of the liquid phase becomes 100 μS / cm or less.

  According to the manufacturing method according to the present invention, it is possible to manufacture a coated illuminant that can almost completely suppress moisture intrusion into the coated illuminant. In other words, the coated illuminant according to the present invention has a feature that it has a coating that can almost completely suppress moisture intrusion into the interior.

  It is considered that such a film was obtained because the unreacted reagent, remaining salt, alkali component, acid component, and remaining solvent were removed as much as possible after the coating reaction. In the prior art, the presence of an unreacted reaction system, an alkali component, and an acid component resulted in accelerated hydrolysis by heating, and it was assumed that a substantially pure film could not be obtained.

  In conventional coated phosphor manufacturing methods, particles after coating were washed using decantation or gel filtration, but the importance of removing unreacted reagents remaining after coating as much as possible It was not so recognized and the degree of cleaning was ambiguous.

  Until the electrical conductivity of the liquid phase reaches a desired level, it is necessary to re-disperse the coated illuminant and then separate it again in a solvent. In the method for producing a coated illuminant according to the present invention, the electric conductivity of the liquid phase separated from the coated illuminant is preferably 100 μS / cm or less, more preferably 20 μS / cm or less, and more preferably 10 μS / cm. Most preferably, it is cm or less.

  As used herein, the term “luminescent material” includes phosphors, phosphors, and phosphors, and by irradiating ultraviolet rays, X-rays, electron beams, etc., “phosphor” Chemicals that fluoresce are intended, “phosphor” is intended to be a substance that fluoresces lasting after removal of irradiation energy (ie, “phosphorescence”), and “phosphor” can accumulate light energy. Substances that emit stored energy by self-luminous are intended. The amount of light emitted from the light emitter is proportional to the amount of irradiation energy.

  The light emitter can be manufactured using various methods known in the art. Also, as the coating step, various methods known in the art such as a sol / gel method and a gas phase method can be employed.

  As the shape of the illuminant, various shapes such as a needle shape, a plate shape, a spherical shape, a granular shape, an elliptical shape, and a cubic shape can be used. The particle shape is a nucleic acid from a coated illuminant to which a nucleic acid is bound. Since it is easy to influence the elution of, it is preferably spherical or granular.

  The average particle size of the luminescent material is preferably in the range of 0.01 to 100 μm, more preferably in the range of 0.02 to 1 μm.

  The phosphor used in the present invention is preferably a phosphor. Examples of the phosphor include those based on zinc sulfide (ZnS), calcium sulfide (CaS), strontium sulfide (SrS), and the like, but are not particularly limited as long as the phosphor is mainly composed of an inorganic substance. In addition, such a material to be coated may be added with various activators and / or coactivators such as copper, silver, and manganese for the purpose of increasing the color and brightness.

  As used herein, “coating material” is intended to be a material that has a certain degree of transparency to light in the wavelength range used. Examples of the coating material include oxides (eg, silica, titania, ceria, yttria, etc.), double oxides (eg, barium titanate, strontium titanate, etc.), fluorides (eg, calcium fluoride, magnesium fluoride, etc.) However, it is not limited to these.

  Examples of the coating process include a low temperature CVD (Chemical Vapor Deposition) method, a low pressure CVD method, a plasma CVD method, a low temperature sol-gel method, and the like. If it is a film | membrane method), it will not specifically limit.

  As used herein, the “solvent” is not particularly limited as long as it can uniformly disperse the coated phosphor, and water or an organic solvent is preferable. Examples of the organic solvent include, but are not limited to, alcohol (for example, methanol, ethanol, propanol, pentanol and the like), ether, ketone, and polyhydric alcohols (for example, ethylene glycol, propylene glycol, diethylene glycol and the like). From the viewpoint of reaction rate control, preferred organic solvents are alcohols, more preferably ethanol. The organic solvents can be used alone or in combination.

  Examples of means for separating the dispersion (that is, colloidal solution) into a solid phase and a liquid phase include centrifugation, decantation, and Kel filtration.

  It is also preferable to perform sonication in the dispersion, and it is more preferable that the sonication is performed a plurality of times.

  The coated illuminant according to the present invention has a coating film that is so dense that the illuminant does not substantially elute, and specifically, the illuminant elution through the film is 100 ppm or less, more preferably 10 ppm or less. obtain.

  That is, an object of the present invention is to provide a light-emitting body having a coating capable of preventing moisture deterioration and excellent in luminance and light-emission life and a method for producing the same, and is specifically described in this specification. It does not depend on conditions such as the shape, type and manufacturing method of the phosphor, and coating method.

  It should be noted that the specific embodiments made in the section of the best mode for carrying out the invention and the following examples are merely to clarify the technical contents of the present invention, and to such specific examples. It is not to be construed as limiting in any way whatsoever, and those skilled in the art can implement the invention within the spirit of the invention and the scope of the appended claims.

  Moreover, all the academic literatures and patent literatures described in this specification are incorporated herein by reference.

[Example 1]
10 g of commercially available phosphor (copper, aluminum-doped zinc sulfide (manufactured by Toshiba)) was collected, and 100 ml of ethanol (manufactured by Wako Pure Chemical Industries), 5 ml of ion-exchanged water, 7 ml of 28% ammonia water (manufactured by Wako Pure Chemical Industries) Was dispersed in the resulting solution. While stirring this dispersion, 5 g of tetraethyl orthosilicate (manufactured by Wako Pure Chemical Industries, Ltd.) in 50 ml of ethanol was added to this dispersion, and stirring was continued for 8 hours to obtain a dispersion of silica-coated phosphor.

  This silica-coated phosphor dispersion was centrifuged at about 470 × g for 10 minutes, the supernatant was removed, and then the precipitate was suspended in 150 ml of methanol (manufactured by Wako Pure Chemical Industries, Ltd.) and sufficiently shaken by hand. And centrifuged in the same manner. These operations were performed once more. After removing the supernatant, the precipitate was washed in 150 ml of water, and the electric conductivity of the supernatant obtained by centrifuging at about 470 × g for 10 minutes was measured. Washing was repeated until the electrical conductivity reached 10 μS / cm or less. Subsequently, after drying under reduced pressure using a diaphragm type vacuum pump until there was no change in weight, it was baked in a dryer at 300 ° C. for 8 hours.

[Example 2]
A silica-coated phosphor was obtained in the same manner as in Example 1 except that 10 g of silver-doped zinc sulfide (manufactured by Toshiba) was used instead of the phosphor.

Example 3
10 g of the silica-coated phosphor obtained in Example 2 was further subjected to the same silica coating treatment as in Example 1 to obtain a silica-coated phosphor with a thicker silica coating.

[Comparative Example 1]
The commercially available phosphor used in Example 1 was used without being coated with silica.

[Comparative Example 2]
The commercially available phosphor used in Example 2 was used without being coated with silica.

<A. Elution evaluation of component elements>
1 g of the coated phosphor (Examples 1 to 3) or the uncoated phosphor (Comparative Examples 1 and 2) is fractionated and immersed in 500 ml of 1 mol% nitric acid aqueous solution (manufactured by Wako Pure Chemical Industries) for 20 minutes, and the supernatant liquid The amount of zinc contained in was measured using an atomic absorption analyzer (manufactured by Shimadzu Corporation).

<B. Luminance evaluation>
Using a fluorescent phosphor (manufactured by Perkin Elmer), each phosphor was filled in a powder holder, and an emission spectrum was measured at an excitation wavelength of 320 nm, and peak intensities were compared.

<C. Water resistance evaluation>
After immersion in ion exchange water at 70 ° C. for 48 hours, the luminance was evaluated, and the peak intensity ratio before and after the water resistance test was calculated.

なお、比較例１および２では、輝度が低下していた。

In Comparative Examples 1 and 2, the luminance was lowered.

  By using the present invention, it is possible to obtain a coated illuminant having a dense film, having a low risk of moisture approaching the coated illuminant, causing no reduction in luminance, and having a long emission lifetime. It can contribute to the development of fields such as medical X-ray intensifying screens and bioimaging and related industries.

Claims (7)

A method for producing a coated illuminant, in which the illuminant is coated with a coating material,
(I) a step of coating the illuminant with a coating material;
(II) a step of obtaining a dispersion in which the coated phosphor is dispersed in a solvent; and (III) a step of separating the dispersion into a solid phase and a liquid phase, the electric conductivity of the liquid phase being A method characterized by repeating steps (II) and (III) until it becomes 100 μS / cm or less.   The method according to claim 1, wherein the solvent is water or an organic solvent.   The method of claim 1, wherein the separating is by centrifugation.   The method of claim 1, wherein the coating material is silica.   A coated illuminator produced by the method according to claim 1.   A coated illuminant in which a illuminant is coated with a coating material, and the elution of the illuminant through the coating material is 100 ppm or less.   The coated light-emitting body according to claim 4, wherein the coating material is silica.