JP2005008704A - Yttrium silicate spherical phosphor and cathode ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a spherical phosphor of yttrium silicate having further excellently improved luminance and luminance deterioration properties by electron beam irradiation while keeping excellent luminance saturation properties, temperature properties and high resolution in excitation at a high current density. <P>SOLUTION: The spherical phosphor of yttrium silicate exhibits a spherical state having ≥1.0 and ≤1.2 ratio (major axis/minor axis), ≥2μm and ≤10μm average particle diameter and a composition represented by chemical formula (Y,Ln)<SB>2</SB>O<SB>3</SB>-SiO<SB>2</SB>(1) (Ln is at least one kind of Tb and Ce; x is in a range of 1.011≤x≤1.090). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４０】
比較例１，２は、（長径／短径）比が１．２を越えており球状ではなく、比較例３はＳｉＯ_２過少の組成である。
【００４１】
次に、比較例１〜３および実施例１〜３の蛍光体を用いて投写管を作製し、それらの特性を比較した。
【００４２】
まず、バリウム水溶液と水ガラスとを用いた沈降法により、対角７インチのガラスバルブ内に蛍光膜を形成した。この際、１ｃｍ^２当たりの塗布量は４．０ｍｇとした。次に、蒸着法により、膜厚約０．２μｍのアルミニウム膜を成膜した。さらに、アノードおよび電子銃を取りつけて、投写管が完成する。
【００４３】
こうして得られた投写管の構成を表わす概略図を図１に示す。図示するように、フェースプレート１の内面には、蛍光膜２および反射膜となるアルミニウム膜３が順次形成されている。また、蛍光膜２に電子線を照射するために、アノード５を介して電子銃４が設けられている。
【００４４】
投写管の特性としては、スポット径、相対輝度および輝度維持率を調べた。
【００４５】
投写管に加速電圧３２ｋＶを印加して、スポット径（５％幅）を測定することにより解像度を評価した。スポット径が小さいほど、分解能が優れていることを表わす。輝度特性は、３．５ｍＡのビーム電流でラスターを描かせた際の輝度を測定し、比較例１の蛍光体を用いた投写管の輝度を基準として、相対輝度を求めた。
【００４６】
さらに、次のように輝度維持率を求めて、蛍光膜の寿命特性を判断した。具体的には、加速電圧３２ｋＶを印加し、１ｍＡのビーム電流で１０Ｈｒラスターを描かせた。この際の電流照射直後および１０時間後それぞれにおける輝度を測定し、直後と比較した照射後の輝度維持率を蛍光膜の寿命とした。照射後の輝度維持率が大きいほど、寿命が長いことになる。各投写管の特性を下記表２にまとめる。
【００４７】
【表２】

【００４８】
表２に示されるように、実施例１〜３はスポット径が１５０μｍ以下であるのに対し、比較例１，２では２２０μｍを越えている。これは、蛍光体の形状に起因するものであり、球状蛍光体を用いることにより分解能が飛躍的に向上することがわかる。
【００４９】
さらに、比較例３と実施例１〜３とを比較すると、実施例では８〜１５％以上の輝度改善効果が得られ、寿命特性も８〜１０％以上改善されている。比較例３では、ＳｉＯ_２の組成比（ｘ値）が０．９９２と、１．０１１≦ｘ≦１．０９０の範囲から外れているからである。しかも、比較例３は、Ｙ_２Ｏ_３相の異相率が５％であるために、輝度および輝度維持率（寿命）特性が実施例よりも劣っている。
【００５０】
（比較例４，５、実施例４，５）
（長径／短径）比が１．３８で、平均粒径５．８μｍの（Ｙ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を比較例４とした。（長径／短径）比が１．３８なので、この粒子は球状ではない。また、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析法による組成分析を行なったところ、比較例４の蛍光体におけるＳｉＯ_２組成はｘ＝１．１０３であった。また、Ｃｕ−Ｋα線によるＸ線回折測定の結果、この蛍光体中にはγ−Ｙ_２Ｓｉ_２Ｏ_７相が４．２％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が３．２％であることが確認されたが、Ｙ_２Ｏ_３相およびβ−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００５１】
比較例４の蛍光体に、比較例３と同様の手法により球状化処理および熱処理を施して比較例５の球状蛍光体を作製した。この蛍光体の（長径／短径）比は１．０５であり、平均粒径は６．３μｍであった。また、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析を行なったところ、ＳｉＯ_２組成はｘ＝１．０９７であった。また、Ｃｕ−Ｋα線によるＸ線回折測定の結果、この球状蛍光体中にはγ−Ｙ_２Ｓｉ_２Ｏ_７相が３．８％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が３％含まれていることが確認されたが、Ｙ_２Ｏ_３相およびβ−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００５２】
一方、共沈法により（Ｙ，Ｃｅ）_２Ｏ_３とＳｉＯ_２を合成し、これを原料としてフラックスを用いる方法により、（Ｙ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を作製した。具体的には、平均粒径が６．１μｍ、（長径／短径）比が１．４２、ＳｉＯ_２組成がｘ＝１．０３９である（Ｙ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を作製した。
【００５３】
この蛍光体を原料として、実施例１と同様の手法により球状化処理および熱処理を施して、実施例４の球状蛍光体を作製した。得られた蛍光体の（長径／短径）比は１．１０であり、平均粒径は６．５μｍであった。また、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析の結果、ＳｉＯ_２組成はｘ＝１．０１５であった。この蛍光体中に含まれる異相率を分析したところ、Ｙ_２Ｏ_３相およびＹ_２Ｓｉ_２Ｏ_７相は、いずれも０．１％未満で検出できなかった。
【００５４】
また、平均粒径が５．９μｍ、（長径／短径）比が１．４２、ＳｉＯ_２組成がｘ＝１．０９７であるセリウム付活ケイ酸イットリウム蛍光体を原料として用い、実施例１と同様の手法により球状化処理および熱処理を施して、実施例５の球状蛍光体を作製した。得られた蛍光体の（長径／短径）比は１．０６であり、平均粒径は６．２μｍであった。また、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析の結果、ＳｉＯ_２組成はｘ＝１．０７９であった。さらに、この蛍光体中に含まれる異相率を分析したところ、この球状蛍光体に含まれる異相率はγ−Ｙ_２Ｓｉ_２Ｏ_７相が１％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が１％で、Ｙ_２Ｏ_３相およびβ−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００５５】
比較例４，５、および実施例４，５の蛍光体の特性を下記表３にまとめる。
【００５６】
【表３】

【００５７】
比較例４は、（長径／短径）比が１．２を越えており球状ではなく、比較例５はＳｉＯ_２過剰の組成である。
【００５８】
次に、比較例４，５、および実施例４，５の蛍光体を用いて、前述と同様の手法により投写管を作製し、それらの特性を比較した。相対輝度値は、比較例４を基準（１００）として求めた。各投写管の特性を、下記表４にまとめる。
【００５９】
【表４】

【００６０】
表４に示されるように、実施例４，５ではスポット径が１６０μｍ以下であるのに対し、比較例４では２２０μｍを越えている。これは、蛍光体の形状に起因するものであり、球状蛍光体を用いることにより分解能が飛躍的に向上することがわかる。
【００６１】
さらに、比較例５と実施例４，５とを比較すると、実施例では、約１０％の輝度改善効果が得られ、輝度維持率も約５％程度向上している。比較例５では、組成比（ｘ値）が１．０１１≦ｘ≦１．０９０の範囲から外れているからである。しかも、比較例５は、Ｙ_２Ｓｉ_２Ｏ_７相の合計異相率が６．８％であるために、輝度維持率（寿命）特性が劣っている。
【００６２】
（比較例６，７、実施例６，７）
（長径／短径）比が１．４０で、平均粒径６．１μｍの（Ｙ，Ｔｂ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を比較例６とした。（長径／短径）比が１．４０なので、この粒子は球状ではない。また、Ｔｂ濃度は４原子％であり、Ｃｅ濃度は０．１原子％であった。この蛍光体に含まれるＳｉＯ_２組成はｘ＝１．０１０であった。異相に関しては、Ｙ_２Ｏ_３相が３．５％、γ−Ｙ_２Ｓｉ_２Ｏ_７相が３．１％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が１．２％で、β−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００６３】
比較例６の蛍光体に、比較例３と同様の手法により球状化処理および熱処理を施して、比較例７の球状蛍光体を作製した。この蛍光体の（長径／短径）比は１．１２であり、平均粒径は６．７μｍであった。また、Ｔｂ濃度は４原子％であり、Ｃｅ濃度は０．１原子％であった。この蛍光体のＩＣＰ発光分析を行なったところ、この蛍光体に含まれるＳｉＯ_２組成はｘ＝１．００１であった。異相に関しては、Ｙ_２Ｏ_３相が４．３％、γ−Ｙ_２Ｓｉ_２Ｏ_７相が２．７％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が０．５％で、β−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００６４】
一方、共沈法により（Ｙ，Ｔｂ，Ｃｅ）_２Ｏ_３を合成し、ＳｉＯ_２とともに原料として用いて、フラックスを用いる方法により（Ｙ，Ｔｂ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を作製した。具体的には、平均粒径が６．２μｍ、（長径／短径）比が１．５１、ＳｉＯ_２組成がｘ＝１．１０２である（Ｙ，Ｔｂ，Ｃｅ）_２Ｏ_３・ｘＳｉＯ_２蛍光体を作製した。
【００６５】
この蛍光体を原料として、実施例１と同様の手法により球状化処理および熱処理を施して、実施例６の球状蛍光体を作製した。得られた蛍光体の（長径／短径）比は１．１３であり、平均粒径は６．５μｍであった。また、Ｔｂ濃度は４原子％であり、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析の結果、ＳｉＯ_２組成はｘ＝１．０８２であった。異相に関しては、γ−Ｙ_２Ｓｉ_２Ｏ_７相が１．５％、δ−Ｙ_２Ｓｉ_２Ｏ_７相が０．９％であり、Ｙ_２Ｏ_３相およびβ−Ｙ_２Ｓｉ_２Ｏ_７相は０．１％未満で検出できなかった。
【００６６】
また、平均粒径が５．７μｍ、（長径／短径）比が１．２９、ＳｉＯ_２組成がｘ＝１．０３８であるテルビウム、セリウム付活ケイ酸イットリウム蛍光体を原料として用い、実施例１と同様の手法により球状化処理および熱処理を施して、実施例７の球状蛍光体を作製した。得られた蛍光体の（長径／短径）比は１．０４であり、平均粒径は６．１μｍであった。また、Ｔｂ濃度は４原子％であり、Ｃｅ濃度は０．１原子％であった。ＩＣＰ発光分析の結果、ＳｉＯ_２組成はｘ＝１．０１３であった。異相に関しては、Ｙ_２Ｏ_３相およびＹ_２Ｓｉ_２Ｏ_７相は、いずれも０．１％未満で検出できなかった。
【００６７】
比較例６，７、および実施例６，７の蛍光体の特性を下記表５にまとめる。
【００６８】
【表５】

【００６９】
比較例６は、（長径／短径）比が１．２を越えており球状ではなく、比較例７はＳｉＯ_２組成比が本発明の範囲よりも少ない。
【００７０】
次に、比較例６，７、および実施例６，７の蛍光体を用いて、前述と同様の手法により投写管を作製し、それらの特性を比較した。相対輝度値は、比較例６を基準（１００）として求めた。各投写管の特性を、下記表６にまとめる。
【００７１】
【表６】

【００７２】
表６に示されるように、実施例６，７ではスポット径が１６０μｍ以下であるのに対し、比較例６では２２０μｍ程度である。これは、蛍光体の形状に起因するものであり、球状蛍光体を用いることにより分解能が飛躍的に向上することがわかる。
【００７３】
さらに、比較例７と実施例６，７とを比較すると、実施例では、約１３％の輝度改善効果が得られ、輝度維持率も約６％程度向上している。比較例５では、組成比（ｘ値）が１．００１と、１．０１１≦ｘ≦１．０９０の範囲から外れているからである。しかも、比較例５は、Ｙ_２Ｏ_３相の異相率が４．３％であるために、輝度および輝度維持率（寿命）特性が劣っている。
【００７４】
【発明の効果】
以上詳述したように、本発明の一態様によれば、高電流密度励起下での良好な輝度飽和特性、温度特性、および高分解能を維持しつつ、輝度および電子線照射による輝度劣化特性を更に良好に改善したケイ酸イットリウム球状蛍光体が提供される。本発明の他の態様によれば、デジタルテレビに対応し得る高解像度の陰極線管が提供される。
【図面の簡単な説明】
【図１】本発明の一実施形態にかかる投写管の概略断面図。
【符号の説明】
１…フェースプレート，２…蛍光膜，３…アルミニウム膜，４…電子銃，５…アノード。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a phosphor, and more particularly to a phosphor suitable for a cathode ray tube, particularly a projection tube.
[0002]
[Prior art]
As a large-screen television for general home use, a CRT-type projection display which is superior in price is widely used. This is a display of a system that uses three red, green and blue monochrome CRTs (projection tubes) to enlarge and project an image of the projection tube on a screen via a lens system. In order to realize an image with a large screen and higher brightness, a high voltage and a high current are applied to a fluorescent screen of a projection tube used in this display. Therefore, the following characteristics are required for the phosphor constituting the phosphor screen.
[0003]
First, the phosphor applied to the inner surface of the projection tube is required to have a luminance current saturation characteristic in which the luminance is not saturated even when a high current is passed. Next, it is necessary to stably emit light with high brightness even at high temperatures. That is, since a high-power electron beam is incident on the fluorescent screen of the projection tube, energy not used for light emission is converted into heat, and the phosphor forming the fluorescent screen is heated to 100 ° C. or higher. For this reason, the phosphor is required to be less susceptible to a decrease in luminance even at high temperatures. Furthermore, even if it is used under such a large current application condition, crystal breakdown is unlikely to occur and a phosphor having a stable crystal structure is required.
[0004]
The brightness of the projection tube depends on the luminous efficiency of the phosphor, but is also affected by the film quality of the phosphor screen such as the thickness, packing density, and smoothness of the phosphor screen. On the other hand, the resolution depends on the size of light scattering in the phosphor screen, and is affected by the size of the phosphor particles, the thickness of the phosphor screen, the packing density, and the like.
[0005]
Incidentally, it has been proposed to produce a spherical phosphor by a thermal plasma method (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). These spherical phosphors can form fluorescent films with high packing density due to the good shape and dispersibility of the individual phosphor particles, improving resolution when used on the phosphor screen of projection tubes can do.
[0006]
A typical phosphor used in a projection tube is red with europium activated yttrium oxide (Y) due to luminance and luminance saturation characteristics under high current density excitation. ₂ O ₃ : Eu), green is terbium-activated yttrium silicate (Y ₂ SiO ₅ : Tb), and the blue color is silver activated zinc sulfide (ZnS: Ag). In particular, since the green phosphor has the largest contribution to the luminance of the color screen among these, the above-described characteristics are regarded as important.
[0007]
[Patent Document 1]
JP-A-8-109375
[0008]
[Patent Document 2]
Japanese Patent Laid-Open No. 11-43672
[0009]
[Patent Document 3]
JP 2002-105450 A
[0010]
[Problems to be solved by the invention]
In the future digital television era, a higher-definition projection tube is required, and the number of scanning lines increases, the scanning lines become thinner, and the excitation current density of the phosphor increases. For this reason, the luminance life characteristics of current yttrium silicate spherical phosphors are becoming insufficient. There is a need for a yttrium silicate spherical phosphor that can improve the luminance life characteristics and has higher luminance than the present one.
[0011]
Accordingly, the present invention provides a yttrium silicate spherical phosphor that further improves the luminance and luminance degradation characteristics due to electron beam irradiation while maintaining good luminance saturation characteristics, temperature characteristics, and high resolution under high current density excitation. The purpose is to provide.
[0012]
It is another object of the present invention to provide a high-resolution cathode ray tube that can be applied to a digital television.
[0013]
[Means for Solving the Problems]
The yttrium silicate spherical phosphor according to one embodiment of the present invention has a sphere having a (major axis / minor axis) ratio of 1.0 or more and 1.2 or less, an average particle diameter of 2 μm or more and 10 μm or less. It has the composition represented.
[0014]
(Y, Ln) ₂ O ₃ ・ XSiO ₂ (1)
(In the general formula (1), Ln is at least one of Tb and Ce, and x is in the range of 1.011 ≦ x ≦ 1.090.)
A cathode ray tube according to an aspect of the present invention includes a screen including the above-described yttrium silicate spherical phosphor.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
[0016]
The inventors have determined that the composition of the yttrium silicate spherical phosphor, specifically SiO 2 ₂ As a result, the present inventors have found that there is an optimum composition ratio that deviates from the stoichiometric composition ratio, and thus achieved the present invention.
[0017]
The yttrium silicate spherical phosphor according to the embodiment of the present invention has a (major axis / minor axis) ratio of 1.0 to 1.2. If this ratio is greater than 1.2, more particles are no longer considered spherical, and the packing density of the phosphor screen is reduced. As a result, the desired sufficient light emission characteristics cannot be obtained mainly with respect to resolution. The ratio (major axis / minor axis) was defined as follows. First, a phosphor particle image is observed with a scanning electron microscope or the like, and a plurality of particles are selected at random. About each particle | grain, the largest diameter and the minimum diameter were measured, the ratio was calculated | required, and what averaged the ratio value about each particle | grain was defined as ratio (major axis / minor axis).
[0018]
The average particle size of the phosphor is specified to be 2 μm or more and 10 μm or less. If it is less than 2 μm, the luminance is lowered, and if it exceeds 10 μm, the image quality deteriorates, for example, the resolution is lowered when used in a projection tube. As the definition of the particle size, the particle size when the integrated distribution curve obtained from the particle size distribution takes a value of 50%, that is, the 50% size was adopted. Specifically, a 50% diameter measured by a LA-910W type particle size distribution measuring apparatus manufactured by Horiba Seisakusho using a laser diffraction method is used.
[0019]
Furthermore, the spherical phosphor according to the embodiment of the present invention has a composition represented by the general formula (1).
[0020]
As long as it shows the same crystal structure as yttrium silicate, a part of yttrium (Y) may be substituted with at least one rare earth element such as gadolinium (Gd), lanthanum (La), or lutetium (Lu). . Even when substituted with such elements, (Y, Ln) ₂ O ₃ ・ XSiO ₂ The light emission characteristics and effects similar to the above can be expected, so substantially (Y, Ln) ₂ O ₃ ・ XSiO ₂ Can be regarded as the same.
[0021]
The emission color of the phosphor is determined according to the element contained as the activator Ln. For example, in the case of terbium (Tb), it becomes a green light emitting phosphor, and in the case of cerium (Ce), it becomes a blue light emitting phosphor. Further, when terbium (Tb) and cerium (Ce) are simultaneously activated, a green light emitting phosphor is obtained.
[0022]
In the yttrium silicate spherical phosphor according to the embodiment of the present invention, the SiO 2 rather than the stoichiometric ratio. ₂ Is contained in excess. Specifically, SiO ₂ Is defined within the range of 1.011 ≦ x ≦ 1.090.
[0023]
Conventional Y ₂ O ₃ Powder and SiO ₂ When producing yttrium silicate by high-temperature solid phase reaction with powder, ₂ If the composition is excessive, P.I. J. et al. Born et al. : J. Mater. Sci. Let. 4, 97 (1985), inevitably disilicate [(Y, Ln) in the phosphor. ₂ Si ₂ O ₇ ] Is generated. On the contrary, SiO ₂ In the case where the amount is too small, (Y, Ln) is unavoidable in the phosphor. ₂ O ₃ A phase is formed.
[0024]
That is, when x = 0.980, (Y, Ln) is 2% or more. ₂ O ₃ When a phase is formed and x = 1.010, 1% or more (Y, Ln) ₂ Si ₂ O ₇ A phase is generated in proportion to the value of x.
[0025]
The present inventors have found that when a spherical yttrium silicate phosphor is produced, a phase different from the conventional one is generated. That is, when x = 1.000 which is a stoichiometric composition, (Y, Ln) ₂ O ₃ A phase was formed, and when x = 1.01, the heterogeneous phase was significantly reduced, and when x = 1.02, the heterogeneous phase was most decreased. Further, up to x = 1.090, (Y, Ln) than a normal phosphor ₂ Si ₂ O ₇ There is little increase in phase. More preferably, x is 1.050 or less. Furthermore, the inventors have determined that this (Y, Ln) ₂ O ₃ The phase has also been found to have a very detrimental effect on the luminance and lifetime properties of the phosphor. (Y, Ln) ₂ Si ₂ O ₇ The phase also adversely affects the luminance and lifetime properties of the yttrium silicate spherical phosphor, but (Y, Ln) ₂ O ₃ Not as much as the phase.
[0026]
Based on these findings, SiO of the yttrium silicate spherical phosphor according to the embodiment of the present invention ₂ The composition (x) was defined within the range of 1.011 ≦ x ≦ 1.090. In addition, SiO ₂ The composition of can be calculated as the atomic ratio of Y, Ln and Si by measuring the amounts of Y, Ln and Si by ICP emission analysis.
[0027]
Inevitable Y ₂ O ₃ The heterogeneous ratio of the phase is preferably 3% or less, and β-Y ₂ Si ₂ O ₇ , Γ-Y ₂ Si ₂ O ₇ , And δ-Y ₂ Si ₂ O ₇ It is preferable that the total amount of the different phase ratios of the phases is 5% or less. The ratio of such a different phase can be defined as follows by the intensity ratio of the X-ray diffraction lines when measured with Cu-Kα rays.
[0028]
In JCPDS card, γ-Y ₂ Si ₂ O ₇ Then, the diffraction line of d = 3.099 mm (corresponding to the diffraction line of (121) according to the JCPDS card) intensity Y ₂ SiO ₅ Is calculated as a ratio to the diffraction line intensity of d = 2.912A corresponding to (402). δ-Y ₂ Si ₂ O ₇ Then, β = Y of d = 2.872 mm (corresponding to the diffraction line (221) according to the JCPDS card). ₂ Si ₂ O ₇ Then, it is calculated as the diffraction line intensity ratio of d = 3.219 (corresponding to the diffraction line (021) according to the JCPDS card). In addition, the above β, γ, δ-Y ₂ Si ₂ O ₇ It is clear that a part of yttrium can be substituted with another rare earth element such as an activator in view of the generation process.
[0029]
The spherical phosphor having the shape and average particle diameter as described above can be manufactured by a thermal plasma method or the like. Specifically, for example, a non-spherical yttrium silicate phosphor having a (major axis / minor axis) ratio of 1.25 to 1.5 is used as a raw material, and spheroidizing treatment is performed using high-frequency thermal plasma. Thereafter, heat treatment is performed in an argon atmosphere to obtain a yttrium silicate spherical phosphor having a predetermined shape, average particle diameter, and composition.
[0030]
The yttrium silicate spherical phosphor according to the embodiment of the present invention has a SiO 2 rather than a stoichiometric composition. ₂ Is excessively contained, it was possible to obtain a phosphor screen having higher luminance than conventional yttrium silicate phosphors, stable luminance deterioration characteristics, and long life.
[0031]
【Example】
Hereinafter, the present invention will be described in more detail with reference to specific examples.
[0032]
(Comparative Examples 1-3, Examples 1-3)
(Y, Tb) having a (major axis / minor axis) ratio of 1.42 and an average particle diameter of 6.7 μm ₂ O ₃ ・ XSiO ₂ The phosphor was set as Comparative Example 1. Since the (major axis / minor axis) ratio is 1.42, the particles are not spherical. The Tb concentration was 4 atomic%. When composition analysis was performed by ICP emission analysis, SiO in the phosphor of Comparative Example 1 was analyzed. ₂ The composition was x = 1.003. In addition, as a result of X-ray diffraction measurement using Cu-Kα rays, this phosphor contains Y ₂ O ₃ 4% phase, γ-Y ₂ Si ₂ O ₇ 2% phase, δ-Y ₂ Si ₂ O ₇ It was confirmed that the phase contained 1%, but β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0033]
Next, (Y, Tb) having a (major axis / minor axis) ratio of 1.36 and an average particle diameter of 6.3 μm ₂ O ₃ ・ XSiO ₂ The phosphor was designated as Comparative Example 2. Since the (major axis / minor axis) ratio is 1.36, this particle is also not spherical. The Tb concentration was 4 atomic%. Composition analysis by ICP emission analysis was performed. ₂ The composition was x = 1.105. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, this phosphor contains γ-Y ₂ Si ₂ O ₇ 5% phase, δ-Y ₂ Si ₂ O ₇ Phase is 3%, β-Y ₂ Si ₂ O ₇ It was confirmed that the phase contained 1%, but Y ₂ O ₃ The phase was not detectable below 0.1%.
[0034]
Further, the phosphor of Comparative Example 1 was spheroidized by high-frequency thermal plasma, and heat-treated at 1600 ° C. for 5 hours in an argon atmosphere to produce the spherical phosphor of Comparative Example 3. This phosphor had a (major axis / minor axis) ratio of 1.08 and an average particle diameter of 7.1 μm. The Tb concentration was 4 atomic%. When ICP emission analysis was performed, SiO ₂ The composition was x = 0.992. In addition, as a result of X-ray diffraction measurement using Cu-Kα rays, this phosphor contains Y ₂ O ₃ Phase is 5%, γ-Y ₂ Si ₂ O ₇ Phase is 1%, δ-Y ₂ Si ₂ O ₇ It was confirmed that the phase contained 1%, but β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0035]
On the other hand, a phosphor different from Comparative Examples 1 and 2 was prepared as a raw material. Specifically, the average particle size is 5.9 μm, the (major axis / minor axis) ratio is 1.3, SiO ₂ Using the terbium-activated yttrium silicate phosphor having a composition of x = 1.034 as a raw material, it was spheroidized by high-frequency thermal plasma, and was subjected to heat treatment at 1500 ° C. for 5 hours in an argon atmosphere. The body was made. The phosphor obtained had a (major axis / minor axis) ratio of 1.06 and an average particle diameter of 6.2 μm. The Tb concentration was 4 atomic%. When the ICP emission analysis of this phosphor was performed, SiO ₂ The composition was x = 1.015. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, Y ₂ O ₃ Phase and Y ₂ Si ₂ O ₇ None of the phases were detectable below 0.1%.
[0036]
Average particle diameter is 6.1 μm, (major axis / minor axis) ratio is 1.5, SiO ₂ Using a terbium-activated yttrium silicate phosphor having a composition of x = 1.043 as a raw material, spheroidizing treatment and heat treatment were performed in the same manner as in Example 1 to produce the spherical phosphor of Example 2. did. The phosphor obtained had a (major axis / minor axis) ratio of 1.05 and an average particle diameter of 6.5 μm. The Tb concentration was 4 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.025. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, γ-Y ₂ Si ₂ O ₇ The phase was confirmed to be 1.3%, but Y ₂ O ₃ Phase, δ-Y ₂ Si ₂ O ₇ Phase, β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0037]
Average particle size is 5.7 μm, (major axis / minor axis) ratio is 1.45, SiO ₂ Using a terbium-activated yttrium silicate phosphor having a composition of x = 1.102 as a raw material, spheroidizing treatment and heat treatment were performed in the same manner as in Example 1 to produce the spherical phosphor of Example 3 did. The obtained phosphor (ratio of major axis / minor axis 9 was 1.08, average particle size was 6.3 μm, and Tb concentration was 4 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.087. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, γ-Y ₂ Si ₂ O ₇ Phase is 1.5%, δ-Y ₂ Si ₂ O ₇ The phase was confirmed to be 1% but Y ₂ O ₃ Phase, β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0038]
The characteristics of the phosphors of Comparative Examples 1 to 3 and Examples 1 to 3 are summarized in Table 1 below.
[0039]
[Table 1]

[0040]
Comparative Examples 1 and 2 have a (major axis / minor axis) ratio exceeding 1.2 and are not spherical. Comparative Example 3 is SiO 2 ₂ Under composition.
[0041]
Next, projection tubes were prepared using the phosphors of Comparative Examples 1 to 3 and Examples 1 to 3, and their characteristics were compared.
[0042]
First, a fluorescent film was formed in a 7 inch diagonal glass bulb by a sedimentation method using an aqueous barium solution and water glass. At this time, 1cm ² The coating amount per unit was 4.0 mg. Next, an aluminum film having a thickness of about 0.2 μm was formed by vapor deposition. Further, the projection tube is completed by attaching the anode and the electron gun.
[0043]
A schematic diagram showing the configuration of the projection tube thus obtained is shown in FIG. As shown in the figure, a fluorescent film 2 and an aluminum film 3 serving as a reflective film are sequentially formed on the inner surface of the face plate 1. In addition, an electron gun 4 is provided via an anode 5 to irradiate the fluorescent film 2 with an electron beam.
[0044]
As the characteristics of the projection tube, the spot diameter, relative luminance, and luminance maintenance rate were examined.
[0045]
The resolution was evaluated by applying an acceleration voltage of 32 kV to the projection tube and measuring the spot diameter (5% width). The smaller the spot diameter, the better the resolution. As for the luminance characteristics, the luminance when a raster was drawn with a beam current of 3.5 mA was measured, and the relative luminance was obtained on the basis of the luminance of the projection tube using the phosphor of Comparative Example 1.
[0046]
Further, the luminance maintenance ratio was obtained as follows, and the life characteristics of the fluorescent film were judged. Specifically, an acceleration voltage of 32 kV was applied, and a 10 Hr raster was drawn with a beam current of 1 mA. At this time, the luminance was measured immediately after the current irradiation and 10 hours after the current irradiation, and the luminance maintenance rate after the irradiation compared with the current irradiation was defined as the lifetime of the fluorescent film. The longer the luminance maintenance rate after irradiation, the longer the lifetime. The characteristics of each projection tube are summarized in Table 2 below.
[0047]
[Table 2]

[0048]
As shown in Table 2, in Examples 1 to 3, the spot diameter is 150 μm or less, while in Comparative Examples 1 and 2, it exceeds 220 μm. This is due to the shape of the phosphor, and it can be seen that the resolution is dramatically improved by using the spherical phosphor.
[0049]
Further, when Comparative Example 3 and Examples 1 to 3 are compared, in the example, a brightness improvement effect of 8 to 15% or more is obtained, and the life characteristics are also improved by 8 to 10% or more. In Comparative Example 3, SiO ₂ This is because the composition ratio (x value) is 0.992, which is out of the range of 1.011 ≦ x ≦ 1.090. Moreover, Comparative Example 3 is Y ₂ O ₃ Since the heterogeneous ratio of the phases is 5%, the luminance and luminance maintenance rate (life) characteristics are inferior to those of the examples.
[0050]
(Comparative Examples 4 and 5, Examples 4 and 5)
(Y, Ce) having a (major axis / minor axis) ratio of 1.38 and an average particle diameter of 5.8 μm ₂ O ₃ ・ XSiO ₂ The phosphor was designated as Comparative Example 4. Since the (major / minor) ratio is 1.38, the particles are not spherical. The Ce concentration was 0.1 atomic%. Composition analysis by ICP emission analysis was performed. As a result, SiO in the phosphor of Comparative Example 4 ₂ The composition was x = 1.103. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, this phosphor contains γ-Y ₂ Si ₂ O ₇ Phase 4.2%, δ-Y ₂ Si ₂ O ₇ The phase was confirmed to be 3.2% but Y ₂ O ₃ Phase and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0051]
The phosphor of Comparative Example 4 was subjected to spheronization treatment and heat treatment in the same manner as in Comparative Example 3 to produce the spherical phosphor of Comparative Example 5. The phosphor had a (major axis / minor axis) ratio of 1.05 and an average particle diameter of 6.3 μm. The Ce concentration was 0.1 atomic%. When ICP emission analysis was performed, SiO ₂ The composition was x = 1.097. Further, as a result of X-ray diffraction measurement by Cu-Kα ray, this spherical phosphor contains γ-Y ₂ Si ₂ O ₇ 3.8% phase, δ-Y ₂ Si ₂ O ₇ It was confirmed that 3% of the phase was contained. ₂ O ₃ Phase and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0052]
On the other hand, by coprecipitation method (Y, Ce) ₂ O ₃ And SiO ₂ And using a flux as a raw material, (Y, Ce) ₂ O ₃ ・ XSiO ₂ A phosphor was prepared. Specifically, the average particle size is 6.1 μm, (major axis / minor axis) ratio is 1.42, SiO 2 ₂ The composition is x = 1.039 (Y, Ce) ₂ O ₃ ・ XSiO ₂ A phosphor was prepared.
[0053]
Using this phosphor as a raw material, a spheroidizing treatment and a heat treatment were performed in the same manner as in Example 1 to produce a spherical phosphor of Example 4. The phosphor obtained had a (major axis / minor axis) ratio of 1.10 and an average particle diameter of 6.5 μm. The Ce concentration was 0.1 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.015. When the heterogeneous ratio contained in this phosphor was analyzed, Y ₂ O ₃ Phase and Y ₂ Si ₂ O ₇ None of the phases were detectable below 0.1%.
[0054]
Further, the average particle diameter is 5.9 μm, the (major axis / minor axis) ratio is 1.42, SiO 2 ₂ Using a cerium-activated yttrium silicate phosphor having a composition of x = 1.097 as a raw material, a spheroidizing treatment and a heat treatment were performed in the same manner as in Example 1 to produce a spherical phosphor of Example 5. The phosphor obtained had a (major axis / minor axis) ratio of 1.06 and an average particle diameter of 6.2 μm. The Ce concentration was 0.1 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.079. Furthermore, when the heterogeneous ratio contained in this phosphor was analyzed, the heterogeneous ratio contained in this spherical phosphor was γ-Y ₂ Si ₂ O ₇ 1% phase, δ-Y ₂ Si ₂ O ₇ Phase is 1%, Y ₂ O ₃ Phase and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0055]
The characteristics of the phosphors of Comparative Examples 4 and 5 and Examples 4 and 5 are summarized in Table 3 below.
[0056]
[Table 3]

[0057]
Comparative Example 4 has a (major axis / minor axis) ratio exceeding 1.2 and is not spherical, and Comparative Example 5 is SiO 2. ₂ Excess composition.
[0058]
Next, using the phosphors of Comparative Examples 4 and 5 and Examples 4 and 5, a projection tube was produced by the same method as described above, and their characteristics were compared. The relative luminance value was obtained with Comparative Example 4 as a reference (100). The characteristics of each projection tube are summarized in Table 4 below.
[0059]
[Table 4]

[0060]
As shown in Table 4, in Examples 4 and 5, the spot diameter is 160 μm or less, while in Comparative Example 4, it exceeds 220 μm. This is due to the shape of the phosphor, and it can be seen that the resolution is dramatically improved by using the spherical phosphor.
[0061]
Further, when the comparative example 5 is compared with the examples 4 and 5, in the example, the luminance improvement effect of about 10% is obtained, and the luminance maintenance rate is also improved by about 5%. This is because in Comparative Example 5, the composition ratio (x value) is out of the range of 1.011 ≦ x ≦ 1.090. Moreover, Comparative Example 5 is Y ₂ Si ₂ O ₇ Since the total phase ratio of the phases is 6.8%, the luminance maintenance factor (life) characteristic is inferior.
[0062]
(Comparative Examples 6 and 7, Examples 6 and 7)
(Y, Tb, Ce) having a (major axis / minor axis) ratio of 1.40 and an average particle diameter of 6.1 μm ₂ O ₃ ・ XSiO ₂ The phosphor was designated as Comparative Example 6. Since the (major axis / minor axis) ratio is 1.40, the particles are not spherical. Moreover, Tb density | concentration was 4 atomic% and Ce density | concentration was 0.1 atomic%. SiO contained in this phosphor ₂ The composition was x = 1.010. For different phases, Y ₂ O ₃ Phase is 3.5%, γ-Y ₂ Si ₂ O ₇ 3.1% phase, δ-Y ₂ Si ₂ O ₇ The phase is 1.2% and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0063]
The phosphor of Comparative Example 6 was subjected to spheronization treatment and heat treatment in the same manner as in Comparative Example 3 to produce the spherical phosphor of Comparative Example 7. This phosphor had a (major axis / minor axis) ratio of 1.12 and an average particle diameter of 6.7 μm. Moreover, Tb density | concentration was 4 atomic% and Ce density | concentration was 0.1 atomic%. When the ICP emission analysis of this phosphor was performed, the SiO contained in this phosphor was analyzed. ₂ The composition was x = 1.001. For different phases, Y ₂ O ₃ Phase is 4.3%, γ-Y ₂ Si ₂ O ₇ 2.7% phase, δ-Y ₂ Si ₂ O ₇ The phase is 0.5% and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0064]
On the other hand, by coprecipitation method (Y, Tb, Ce) ₂ O ₃ Is synthesized into SiO ₂ (Y, Tb, Ce) ₂ O ₃ ・ XSiO ₂ A phosphor was prepared. Specifically, the average particle size is 6.2 μm, (major axis / minor axis) ratio is 1.51, SiO 2 ₂ The composition is x = 1.102 (Y, Tb, Ce) ₂ O ₃ ・ XSiO ₂ A phosphor was prepared.
[0065]
Using this phosphor as a raw material, a spheroidizing treatment and a heat treatment were performed in the same manner as in Example 1 to produce a spherical phosphor of Example 6. The phosphor obtained had a (major axis / minor axis) ratio of 1.13 and an average particle diameter of 6.5 μm. Moreover, Tb density | concentration was 4 atomic% and Ce density | concentration was 0.1 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.082. For heterogeneous phase, γ-Y ₂ Si ₂ O ₇ Phase is 1.5%, δ-Y ₂ Si ₂ O ₇ The phase is 0.9% and Y ₂ O ₃ Phase and β-Y ₂ Si ₂ O ₇ The phase was not detectable below 0.1%.
[0066]
Further, the average particle diameter is 5.7 μm, the (major axis / minor axis) ratio is 1.29, SiO 2 ₂ Using the terbium and cerium activated yttrium silicate phosphors whose composition is x = 1.038 as raw materials, spheroidizing treatment and heat treatment were performed in the same manner as in Example 1 to produce the spherical phosphor of Example 7 did. The phosphor obtained had a (major axis / minor axis) ratio of 1.04 and an average particle diameter of 6.1 μm. Moreover, Tb density | concentration was 4 atomic% and Ce density | concentration was 0.1 atomic%. As a result of ICP emission analysis, SiO ₂ The composition was x = 1.003. For different phases, Y ₂ O ₃ Phase and Y ₂ Si ₂ O ₇ None of the phases were detectable below 0.1%.
[0067]
The characteristics of the phosphors of Comparative Examples 6 and 7 and Examples 6 and 7 are summarized in Table 5 below.
[0068]
[Table 5]

[0069]
Comparative Example 6 has a (major axis / minor axis) ratio exceeding 1.2 and is not spherical, and Comparative Example 7 is SiO 2. ₂ The composition ratio is less than the range of the present invention.
[0070]
Next, using the phosphors of Comparative Examples 6 and 7 and Examples 6 and 7, projection tubes were produced by the same method as described above, and their characteristics were compared. Relative luminance values were determined using Comparative Example 6 as a reference (100). The characteristics of each projection tube are summarized in Table 6 below.
[0071]
[Table 6]

[0072]
As shown in Table 6, in Examples 6 and 7, the spot diameter is 160 μm or less, while in Comparative Example 6, it is about 220 μm. This is due to the shape of the phosphor, and it can be seen that the resolution is dramatically improved by using the spherical phosphor.
[0073]
Further, comparing the comparative example 7 with the examples 6 and 7, in the example, the luminance improvement effect of about 13% is obtained, and the luminance maintenance rate is also improved by about 6%. In Comparative Example 5, the composition ratio (x value) is 1.001, which is out of the range of 1.011 ≦ x ≦ 1.090. Moreover, Comparative Example 5 is Y ₂ O ₃ Since the heterogeneous ratio of the phases is 4.3%, the luminance and luminance maintenance ratio (life) characteristics are inferior.
[0074]
【The invention's effect】
As described above in detail, according to one aspect of the present invention, while maintaining good brightness saturation characteristics, temperature characteristics, and high resolution under high current density excitation, brightness and brightness degradation characteristics due to electron beam irradiation are maintained. A further improved yttrium silicate spherical phosphor is provided. According to another aspect of the present invention, a high-resolution cathode ray tube capable of supporting a digital television is provided.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of a projection tube according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Face plate, 2 ... Fluorescent film, 3 ... Aluminum film, 4 ... Electron gun, 5 ... Anode.

Claims (4)

Yttrium silicate spherical fluorescence having a (major axis / minor axis) ratio of 1.0 to 1.2, an average particle size of 2 to 10 μm, and a composition represented by the following chemical formula body.
(Y, Ln) ₂ O ₃ .xSiO ₂ (1)
(In the general formula (1), Ln is at least one of Tb and Ce, and x is in the range of 1.011 ≦ x ≦ 1.090.) _{2. The} yttrium silicate spherical phosphor according to claim 1, wherein a heterogeneous ratio of the Y ₂ O ₃ phase is 3% or less. The total amount of heterogeneous ratios of β-Y ₂ Si ₂ O ₇ , γ-Y ₂ Si ₂ O ₇ , and δ-Y ₂ Si ₂ O ₇ phases is 5% or less. Yttrium silicate spherical phosphor described in 1. A cathode ray tube comprising a screen comprising the yttrium silicate spherical phosphor according to any one of claims 1 to 3.

Images