JP5750775B2 - Method for coating phosphor using SiOx - Google Patents

Description

The present invention relates to a phosphor coating method for coating SiO _{2 on} a phosphor surface using SiO _x .

  Various lighting sources such as incandescent bulbs and fluorescent lamps are used around us. In recent years, white LEDs that have characteristics such as low power consumption, long life, and safety have attracted attention as alternative lighting for incandescent bulbs and fluorescent lamps. Further, the phosphor used in the white LED is also required to have higher performance in terms of light emission efficiency and durability (see Non-Patent Documents 1 to 3).

By the way, phosphors have the property of being easily deteriorated. For example, Zn ₂ SiO ₄ : Mn ²⁺ is known as a green phosphor applicable to the use of a plasma display panel (PDP). However, there is a problem that the surface of the base crystal deteriorates due to ion collisions under Xe plasma and the luminance deteriorates.

In order to suppress this deterioration, it has been attempted to coat the surface of the phosphor with silica (SiO ₂ ). As a typical example, the phosphor surface can be coated by the sol-gel method. However, the reagent (organometallic compound) in the solution used in this method is very expensive, and this method can be handled in a reducing atmosphere gas. Therefore, it is not satisfactory in terms of cost and manufacturing process, and has not yet reached a practical effect of suppressing deterioration.

On the other hand, the present inventors have already been able to synthesize silicate phosphors while supplying SiO _x , which is a part of the starting material, in a gas phase state, and obtained using this gas phase method. It has been found that non-patent document 4 discloses that the phosphor exhibits better light emission characteristics than the phosphor obtained by the conventional solid phase method.

  However, the technique of Non-Patent Document 4 discloses a method of manufacturing a phosphor from a raw material while incorporating a gas phase method into a solid phase method. For a commercially available phosphor or a previously manufactured phosphor, It does not disclose a technique for coating the surface to prevent deterioration.

Satoshi Watanabe, “Current Status and Applications of InGaN High Power LEDs”, Applied Physics, Vol. 74, No. 11, 2005 Edited by the Society of Phosphors, “Phosphor Handbook”, Ohm Co., Ltd., 1991 Thomas L. Barry, J.M. Electrochem. Soc. , Volume 115, Issue 11, pp. 1181-1184, (1968) Kenji Toda and 4 other authors, “Synthesis of Silicate Phosphors by Solid Vapor Phase Method”, Fall of 2010, 71st JSAP Scientific Lecture Meeting, Proceedings of Japan Society of Applied Physics, August 30, 2010 Day

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a phosphor coating method for coating the phosphor surface with SiO ₂ in a reducing atmosphere at a low cost.

As a result of intensive studies, the present inventors made a phosphor already synthesized as a nucleus and reacted (heat treatment) while bringing SiO _x gas or SiO _x powder into contact with the periphery of the phosphor. _The present inventors have found that ₂ ) can be coated with high density and have completed the present invention.

That is, the present invention has the following configuration / features.
[1] A phosphor powder synthesized in advance is placed in a reducing atmosphere gas, and SiO _x (0.8 ≦ x ≦ 1.2) in a gas phase is supplied toward the phosphor powder, A phosphor coating method comprising coating the outer peripheral surface of a phosphor powder with SiO ₂ .
[2] Solid powdery SiO _x is placed on the inflow side of the reducing atmosphere gas, the reducing atmosphere gas is heated to 1200 to 1700 ° C. to volatilize the solid powdery SiO _x, and the gas phase The method for coating a phosphor according to [1], wherein SiO _x in a state is supplied.
[3] A phosphor powder synthesized in advance and a solid powdery SiO _x (0.8 ≦ x ≦ 1.2) are mixed, and the mixture is heated while flowing a gas, thereby the phosphor powder. A method of coating a phosphor, characterized in that SiO ₂ is coated on the outer peripheral surface of the phosphor.
[4] The heating temperature of the mixture, the phosphor coating methods having the constitution [3] to be within the scope of 800 to 1300 ° C..

According to the phosphor coating method of the present invention, a commercially practical silica (SiO ₂ ) coating is applied to the phosphor surface in order to utilize SiO _x which is inexpensive and can be handled in a reducing atmosphere. Is possible.

Further, according to the method of the present invention, the phosphor powder having a certain size is used as a core, and the outer peripheral surface is coated with high-density SiO ₂ so as to surround the core. In other words, according to the present invention, a phosphor powder having a core-shell structure can be produced. The high-density SiO ₂ coating contributes to further improvement of the emission intensity of the phosphor.

Further, since the SiO _x powder is a stable material, the phosphor coating method of the present invention can be carried out using a normal apparatus used for phosphor synthesis or the like.

In addition, the phosphor to be coated by the coating method of the present invention is not particularly limited, and can be applied to any kind of phosphor. For example, Ba ₂ SiO ₄ : Eu ²⁺ and SrAl ₂ O ₄ : Eu ^{2+, which} are promising as LED phosphors, have a weak point that they are vulnerable to water, and these phosphor surfaces are coated to protect them. Is also possible.

It is the figure which showed the X-ray-diffraction measurement result of the sample coat | covered by the Example. It is the figure which showed the fluorescence characteristic of the sample coat | covered by the Example.

  Hereinafter, the present invention will be described based on the following specific embodiments with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

In the phosphor coating method according to the present invention, a phosphor powder synthesized in advance is placed in a reducing atmosphere gas, and SiO _x (0.8 ≦ x ≦ 1. 2), and the outer peripheral surface of the phosphor powder is coated with SiO ₂ . More preferably, solid powdery SiO _x is placed on the inflow side of the reducing atmosphere gas, and the reducing atmosphere gas is heated to 1200 to 1700 ° C. to volatilize the solid powdery SiO _x, thereby Phase-phase SiO _x is supplied.

According to the verification to date by the present inventors, since the SiO _x the state close to SiO acts more favorably, it is preferable that the range of x in SiO _x is 0.8 ≦ x ≦ 1.2, More preferably, 0.95 ≦ x ≦ 1.1. Such suitable high purity SiO is commercially available from, for example, Osaka Titanium Technologies Co., Ltd. or Sanyo Trading Co., Ltd.

Solid SiO _x can be sublimated and heated to a gas phase by heating to 1200 to 1700 ° C., preferably 1400 to 1700 ° C. in a reducing gas atmosphere. This high-temperature and vapor-phase SiO _x is supplied to the phosphor powder for reaction, and SiO ₂ is deposited and coated on the outer peripheral surface of the phosphor powder.

Examples of the reducing gas atmosphere include an inert gas atmosphere such as nitrogen and argon, an oxidizing atmosphere such as air, oxygen, oxygen-containing nitrogen, and oxygen-containing argon, and hydrogen-containing nitrogen and hydrogen containing 0.1 to 10% by volume of hydrogen. For example, a reducing atmosphere such as hydrogen-containing argon containing 0.1 to 10% by volume. In order to advance the gas phase-solid phase reaction of the present invention in a high yield, the carrier gas for supplying SiO _x and the atmosphere during firing include hydrogen containing nitrogen containing 0.1 to 10% by volume of hydrogen, A reducing atmosphere such as hydrogen-containing argon containing 0.1 to 10% by volume of hydrogen is particularly preferable.

In addition, the phosphor powder prepared as a target for the coating treatment is already synthesized in advance, and for example, an available commercially available phosphor powder may be used. Here, the phosphor that is a candidate for coating is not particularly limited as long as it can be coated with silica (SiO ₂ ) according to the present invention, and various phosphors may be mentioned. It is very useful to apply the high-density silica coating of the present invention to Ba ₂ SiO ₄ : Eu ²⁺ , SrAl ₂ O ₄ : Eu ²⁺ , and Zn ₂ SiO ₄ : Mn ²⁺ , which are weak phosphor materials.

The phosphor coating method according to the present invention can also be achieved by the method described below. That is, the phosphor powder synthesized in advance and solid powder SiO _x (0.8 ≦ x ≦ 1.2) are directly mixed, and the mixture is heated while flowing the gas. The outer peripheral surface of this is coated with SiO ₂ . At this time, the heating temperature of the mixture is preferably in the range of 800 to 1300 ° C. in order to efficiently solid-phase synthesize SiO ₂ on the outer peripheral surface. The gas to be circulated includes air for ease of handling, but is not necessarily limited thereto.

The phosphor coated with SiO _{2 according to the} example of the present invention was manufactured by the following method. ZnO (High-Purity Chemical Laboratory 4N), MnCO ₃ (High-Purity Chemical Laboratory 3N), and SiO ₂ (Wako Pure Chemical Industries, Ltd. 3N) were mixed as the phosphor material, and air The phosphor Zn ₂ SiO ₄ : Mn ²⁺ powder was synthesized in advance by firing in an inside (furnace filled with air) at 1200 ° C. for 6 hours. This pre-synthesized Zn ₂ SiO ₄ : Mn ²⁺ and SiO powder were weighed according to the stoichiometric ratio and wet-mixed with acetone in an agate mortar. After mixing, this mixture was placed on an alumina boat, and this time the mixture was heated (fired) at a temperature of 1200 ° C. for 6 hours in such a state that air was constantly flowing through the furnace using a gas cylinder.

(Sample identification)
In the demonstration test in the examples, a powder X-ray diffractometer (manufactured by Mac Science Co., Ltd., MX-Labo) was used for sample identification. FIG. 1 shows the result of X-ray diffraction (XRD) measurement of the sample before and after the above-described firing. In addition, the top result shows the XRD pattern for reference of Zn ₂ SiO ₄ obtained from the inorganic crystal structure database (ICSD) provided by the Japan Society for Chemical Information (JACI).

When observing FIG. 1, the peak position of the XRD pattern of the sample fired according to the above example is the peak position of the XRD pattern of the sample before firing, the peak position of the reference XRD pattern of Zn ₂ SiO ₄ , and Both agree well. Therefore, it can be said that the target product, Zn ₂ SiO ₄ : Mn ^2+, is obtained in the main phase without being destroyed even if this heat treatment is performed.

(Evaluation of fluorescence characteristics)
FIG. 2 is a diagram showing an excitation emission spectrum of Zn ₂ SiO ₄ : Mn ²⁺ manufactured according to the example. In addition, the spectrofluorimeter (JASCO Corporation, FP-6500) was used for the measurement of excitation and the emission spectrum. In FIG. 2, the curve group drawn on the left side shows the excitation spectrum under each test condition, and the curve group drawn on the right side shows the emission spectrum when excited at the optimum excitation wavelength.

  Here, each curve shown with a broken line shows the excitation spectrum and emission spectrum about the sample before baking. The solid line indicates the excitation spectrum and emission spectrum of the sample after firing.

As is clear from FIG. 2, the sample fired according to the example of the present invention showed higher emission intensity than the sample before firing. This increase in emission intensity is thought to be due to the fact that SiO ₂ is coated on the outer peripheral surface of the phosphor powder with high density, so that the amount of Mn ²⁺ increases and the light extraction efficiency is improved.

The embodiment described above, by using the coating method of the phosphor of the present invention, the phosphor powder as nuclei, it is possible to carry out the coating of dense SiO ₂ on the outer peripheral surface thereof Thus, the phosphor The emission intensity can be further increased, and the phosphor can be prevented from being deteriorated and protected against water.

In the coating method of the present invention, the phosphor to be coated is not particularly limited, and can be applied to any kind of phosphor. Further, the phosphor coated according to the present invention is applicable not only to white LEDs but also to a wide range of uses such as display panel display devices such as CRT, PDP and FED, and illumination devices such as fluorescent lamps. Therefore, the present invention has very high industrial applicability.

Claims (4)

A phosphor powder synthesized in advance is placed in a reducing atmosphere gas, and SiO _x (0.8 ≦ x ≦ 1.2) in a gas phase is supplied toward the phosphor powder, and the phosphor powder is supplied. A method of coating a phosphor, characterized in that SiO ₂ is coated on the outer peripheral surface of the phosphor. The solid powdery SiO _x is placed on the inflow side of the reducing atmosphere gas, the reducing atmosphere gas is heated to 1200 to 1700 ° C. to volatilize the solid powdered SiO _x, and the gas phase SiO _{x 2.} The phosphor coating method according to claim 1, wherein _x is supplied. The phosphor powder synthesized in advance and solid powdery SiO _x (0.8 ≦ x ≦ 1.2) are mixed, and the mixture is heated while flowing the gas, and the outer peripheral surface of the phosphor powder A method of coating a phosphor, comprising coating SiO ₂ on the substrate.   The method for coating a phosphor according to claim 3, wherein the heating temperature of the mixture is in the range of 800 to 1300 ° C.

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