JP2003231881A - Phosphor, method for producing phosphor and cathode- ray tube - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor suitable for a cathode-ray tube capable of affording an image of high luminance with high resolution and a method for production thereof. <P>SOLUTION: The phosphor has a granular shape, comprises a principal component which is a Y2SiO5 crystal phase containing an activator dispersed therein and has 2-7% ratio of the content of a γ-Y2Si2O7 crystal phase to the content of a Y2SiO5 crystal phase and <0.1% ratio of the content of a β-Y2Si2O7 phase. The phosphor is prepared by carrying out a sphering treatment with a thermal plasma and then heat-treating the resultant spherical material at 1,500-1,700°C. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a yttrium silicate phosphor and a cathode ray tube using the phosphor.

[0002]

2. Description of the Related Art As a large-screen television for general household use, a CRT-type projection display, which is cost-effective, is in widespread use. This is a red, green, blue monochrome CR
It is a display of a system in which T (cathode ray tube) is used as a projection tube and each image is enlarged and projected on a screen through a lens system. Monochrome CR used as a projection tube
The T is required to have higher brightness and higher resolution than a normal CRT.

Monochrome CRTs have respective emission colors (RGB) on the irradiation surface of an electron beam emitted from an electron gun.
It has a phosphor layer coated with a suitable phosphor, and the characteristics of the phosphor layer greatly influence the image quality of the monochrome CRT.

A typical phosphor used for the phosphor layer of the projection tube is luminance and a luminance saturation characteristic under high current density excitation, and as a red phosphor, europium-activated yttrium oxide (Y2O3: Eu), Terbium-activated yttrium silicate (Y2SiO5: Tb) is used as the green phosphor, and silver-activated zinc sulfide (ZnS: Ag) is used as the blue phosphor. Of these, the green phosphor has the largest contribution to brightness, and the characteristics of this Y2SiO5: Tb are regarded as important.

The brightness of the projection tube depends not only on the luminous efficiency of the phosphor itself, but also on the film quality such as the thickness and packing density of the phosphor layer and the smoothness of the surface (phosphor surface) of the phosphor layer. Is also affected by. On the other hand, the resolution depends on the size of light scattering in the phosphor layer, and is influenced by the size of the phosphor particles, the film thickness of the phosphor layer, the packing density, and the like.

Japanese Unexamined Patent Publication (Kokai) No. 8-109375 discloses a spherical phosphor in which the particles of the phosphor are made spherical by using a method of exposing the phosphor particles to high temperature thermal plasma (thermal plasma treatment). ing. When the phosphor is made spherical, the dispersibility is improved and a phosphor layer having a high packing density can be formed. Therefore, when used as the phosphor layer of the projection tube, the resolution of the image can be improved.

Japanese Patent Laid-Open No. 11-43672 discloses that a yttrium silicate (Y2SiO5: Tb) -based material used as a green phosphor can also obtain a spherical phosphor by thermal plasma treatment.

[0008]

However, since the thermal plasma treatment required to make the phosphor spherical is subjected to the process of exposing the phosphor to high temperature plasma and quenching it at the same time, the phosphor immediately after the thermal plasma treatment is processed. Has poor crystallinity. In particular, in a multi-element silicate such as yttrium silicate phosphor, a part of it is decomposed and evaporated during the thermal plasma treatment, and the emission characteristics are unavoidably deteriorated.

With respect to this problem, the above-mentioned JP-A-11-4
In 3672, 1300 to 1 after thermal plasma treatment.
It is described that the heat treatment at 700 ° C. improves the crystallinity of the spherical phosphor and restores the luminous efficiency.

However, the luminous efficiency of the yttrium silicate spherical phosphor after the heat treatment shown in the publication is improved by the densification effect of the phosphor layer due to the spherical shape of the phosphor, and the existing non-spherical shape. Several% for phosphor layer using phosphor
However, in order to use it as a phosphor layer of a projection tube of a projection type display, further improvement in brightness is required.

In view of the above-mentioned problems, an object of the present invention is to provide an yttrium silicate-based phosphor capable of obtaining a high-resolution and high-luminance image when used as a phosphor layer of a cathode ray tube, and a method for producing the same. Is to provide.

Further, another object of the present invention is to provide a cathode ray tube having a phosphor layer made of yttrium silicate based phosphor which can obtain a screen with high resolution and high brightness.

[0013]

The first feature of the phosphor of the present invention is that it has a spherical shape and the main component is a Y2SiO5 crystal phase in which an activating element is solid-dissolved. The ratio of the content of γ-Y2Si2O7 crystal phase to the content is 2 to 7%, β
-The ratio of the content of the Y2Si2O7 crystal phase is to be less than 0.1%.

According to the first feature of the phosphor of the present invention, the ratio of the content of the β-Y2Si2O7 crystal phase, which becomes a factor for inhibiting the improvement of luminous efficiency, is less than 0.1%, and the γ-Y2Si2O7 crystal phase is included. Since the ratio of the content of is 2 to 7%, higher luminous efficiency can be obtained. Therefore, if the phosphor of the present invention is used for a phosphor layer (phosphor surface) of a cathode ray tube, a fine phosphor layer can be formed due to its spherical shape, so that an image with high resolution can be obtained, and High luminance can be achieved by high luminous efficiency.

In this specification, the numerical value (%) of the content ratio of the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal phase is C
It is defined by the intensity ratio of X-ray diffraction lines when measured by u-Kα ray. That is, the diffraction line intensity at the interplanar spacing d = 2.912Å corresponding to the (402) crystal face of Y2SiO5 is Im, and the diffraction line intensity at d = 3.219Å corresponding to the (021) crystal face of β-Y2Si2O7 is Iβ. , Γ-Y2S
When the diffraction line intensity Iγ at d = 3.099Å of the (121) crystal plane of i2O7 (all of them are based on the JCPDS card), it is determined by the following formula.

Β-Y2Si2O7 phase content ratio (%) = Iβ / Im × 100 (f1) γ-Y2Si2O7 phase content ratio (%) = Iγ / Im × 100 (f2) Phosphor of the present invention The second feature is that the surface of the phosphor having the above-mentioned first feature is coated with an alkaline earth metal polyphosphate film.

According to the second feature of the phosphor of the present invention described above, the aggregation of phosphor particles is reduced and the dispersibility is improved by the alkaline earth metal polyphosphate film covering the surface of the phosphor. , The fluidity of the phosphor is improved. Therefore, when the phosphor layer is formed, the packing density of the phosphor is improved, so that a denser layer can be formed. Therefore, if it is used as a phosphor layer of a cathode ray tube, an image with higher resolution can be provided.

The first feature of the method for producing a phosphor of the present invention is a thermal plasma treatment step of exposing phosphor particles whose main component is Y2SiO5 in which an activating element is solid-soluted to a thermal plasma, and the above thermal plasma. The phosphor particles after the treatment are treated at 1500 ° C. to 170 ° C.
A heat treatment at a temperature of 0 ° C.

According to the first feature of the method for producing a phosphor of the present invention, the phosphor particles can be made spherical by performing the thermal plasma treatment. Furthermore, by the heat treatment process at 1500 ° C. to 1700 ° C. after the thermal plasma treatment process,
Under the condition that the effect of spherical shape can be maintained or recovered, while improving the crystallinity of Y2SiO5 which is the main component of the phosphor,
The ratio of the content of β-Y2Si2O7 crystal phase in the phosphor is 0.1%
The ratio of the content of the γ-Y2Si2O7 crystal phase can be 2 to 7%. The phosphor thus obtained has good crystallinity and contains almost no β-Y2Si2O7 crystal phase, which hinders the improvement of the luminous efficiency, and thus has high luminous efficiency and also has a spherical effect. Therefore, if it is used for the phosphor layer (fluorescent surface) of a cathode ray tube, a dense phosphor layer can be formed due to its spherical shape, so that an image with high resolution can be obtained and high luminous efficiency due to its high luminous efficiency. Can be realized.

A second feature of the method for producing a phosphor of the present invention is that, in addition to the method for producing a phosphor of the present invention having the first feature, the surface of the phosphor after the above heat treatment is an alkaline earth metal polyphosphate. It has a step of coating with salt.

According to the second feature of the method for producing a phosphor of the present invention, even if the phosphor which has been spheroidized by the thermal plasma treatment is impaired in sphericity and dispersibility to some extent due to the effect of heat treatment, By coating with a polyphosphate, the fluidity of the phosphor can be increased, and when forming the phosphor layer of the cathode ray tube, the packing density of the phosphor can be improved. Therefore, since the effect of the spherical shape can be complemented and the densification of the phosphor can be promoted, higher resolution can be obtained.

A feature of the cathode ray tube of the present invention is a cathode ray tube having an electron gun as a cathode ray generating source and a phosphor layer irradiated with the cathode ray, wherein the phosphor layer has a spherical shape, The main component is the Y2SiO5 crystal phase in which the activating element is dissolved, and the ratio of the content of the γ-Y2Si2O7 crystal phase to the content of the above Y2SiO5 crystal phase is 2 to 7%, and the ratio of the content of the β-Y2Si2O7 phase. Is less than 0.1%. The definition of the content ratio of each crystal phase is the same as the definition in the phosphor having the first feature of the present invention described above.

According to the features of the cathode ray tube of the present invention, since the phosphor layer having a spherical phosphor having a high luminous efficiency is provided, an image having high resolution and high brightness can be provided.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(First Embodiment) The phosphor according to the first embodiment of the present invention has Y2SiO5: Ln as a main component, and yttrium silicate in which each particle is processed into substantially spherical shape by plasma treatment. System spherical phosphor. As the activator Ln dispersed in the host crystal, any of lanthanoid elements (hereinafter, referred to as Ln) except La, preferably Tb or Ce can be used. When Tb is used as an activator, it can be used as a green phosphor, and when Ce is used, it can be used as a blue phosphor.

The yttrium silicate-based spherical phosphor is
Preferably, the ratio of the major axis to the minor axis is adjusted to be in the range of 1.0 to 1.2. Under this condition, due to the effect of the spherical shape of each particle, when the phosphor layer is formed, a dense layer having a high packing density can be formed. Therefore, when this phosphor layer is used as the phosphor layer of the projection tube, the resolution of the image can be increased. Here, the ratio of the major axis and the minor axis of the spherical phosphor, the phosphor particle image is observed by a scanning electron microscope or the like, and a plurality of particles are randomly selected from among these, and the maximum diameter of each particle is determined. The minimum diameter is measured and the ratio is determined, and the ratio values for each particle are averaged.

The yttrium silicate-based spherical phosphor according to the first embodiment of the present invention further comprises a host crystal as a main component.
The feature is that the content of yttrium silicate phase other than Y2SiO5 (hereinafter referred to as "heterogeneous phase") is suppressed to a very small amount. Specifically, the ratio of the content of the β-Y2Si2O7 crystal phase to the content of the host crystal Y2SiO5 (hereinafter, simply referred to as “content rate”) is less than 0.1%, and the same as γ-Y2Si2.
The ratio of the content of the O7 crystal phase (hereinafter, simply referred to as "content rate") is set to 7% or less, for example, 7% to 2%.

In general, the spherical phosphor that has just been subjected to the plasma treatment has deteriorated the crystallinity of the phosphor due to the process of rapid heating and quenching by the plasma treatment, and inevitably contains various different phases in addition to the host crystal. It The deterioration of crystallinity and the presence of heterogeneous crystals lower the luminous efficiency of the phosphor, and when used as the phosphor layer of the projection tube, the spherical shape effect can increase the resolution, but high brightness cannot be obtained. Have difficulty.

It is known that the luminous efficiency can be improved by recovering the crystallinity of the host crystal by heat treatment. However, the inventors of the present invention have found that the phosphor composition and the characteristics of the phosphor depend on the heat treatment conditions after the plasma treatment. By more specifically studying the above relationship, it was found that the luminous efficiency of the phosphor can be improved by adjusting the content of the different phase in the phosphor. That is, among the different phases contained, β-Y2Si2O7
It was found that the luminous efficiency can be significantly improved when the content of the crystal phase is less than 0.1%. It is also desirable to reduce the content of the γ-Y2Si2O7 crystal phase,
It was confirmed that the lower the content of the β-Y2Si2O7 crystal phase does not contribute to the improvement of the luminous efficiency, and that the luminous efficiency improving effect can be obtained, for example, in the range of 7% or less, or in the range of 7% to 2%.

Therefore, the phosphor obtained by the heat treatment after the plasma treatment is γ-Y2S other than the host crystal Y2SiO5.
By setting the i2O7 crystal phase content to 7% to 2% and the β-Y2Si2O7 crystal phase content to less than 0.1%, the effect due to the spherical shape of the phosphor can be maintained and the luminous efficiency is greatly improved. it can.

Therefore, if the phosphor layer of the projection tube, which is a cathode ray tube for a projection type display, is formed of the phosphor according to the first embodiment, a high resolution can be obtained due to the shape effect of the spherical phosphor. At the same time, high brightness can be achieved.

In order to obtain the effect of this embodiment described above, it is preferable that the average particle diameter of the phosphor is 2 to 10 μm. When used as a phosphor layer of a projection tube, if the particle size is larger than 10 μm, the image quality is deteriorated such as the resolution is deteriorated, and if the particle size is smaller than 2 μm, the transmissivity of the fluorescent film is deteriorated and the brightness is deteriorated. The problem arises. The particle size of the phosphor shown here is
It means the particle size when the integrated distribution curve obtained from the particle size distribution has a value of 50%, that is, the 50% size. For example, here, the 50% diameter measured by a Horiba Seisakusho LA-920 type particle size distribution measuring apparatus by a laser diffraction method is shown.

Next, a method of manufacturing the phosphor according to the first embodiment of the present invention will be described.

First, a commercially available phosphor Y2SiO5: Tb or Y2
A yttrium silicate phosphor raw material having an average particle diameter of 2 μm to 10 μm is prepared by milling (grinding) SiO 5: Ce or using a known flux method or the like. It should be noted that, for example, the content of β-phase Y2Si2O7 is reduced by firing at a high temperature of 1500 ° C or higher, or the stoichiometric ratio during synthesis is strictly controlled to reduce the amount of different phases at the raw material stage. It is desirable to set it.

Next, these phosphor raw materials are introduced into high-frequency thermal plasma and subjected to thermal plasma treatment to make the particle shape spherical. Raw material particles are introduced into a chamber of a high frequency plasma apparatus together with an inert gas such as Ar gas, and the particles in a floating state are exposed to a high temperature plasma of several thousand degrees Celsius. If the average temperature of the plasma is too low, the raw material is not completely melted and the spheroidization is insufficient. Note that it is preferable to suppress the electric power of the thermal plasma and suppress the plasma temperature so that the generation of different phases is minimized.

Next, the spherical phosphor after the thermal plasma treatment is
Heat treatment is performed at a high temperature of about 1500 to 1700 ° C. This heat treatment is preferably performed in an atmosphere of an inert gas such as Ar.

The yttrium silicate phosphor immediately after the thermal plasma treatment undergoes a rapid heating and quenching process, so that the main component Y2SiO5 is used.
The crystallinity of Y2O3, SiO2, β-Y inevitably deteriorates.
Although the 2Si2O7 phase, the γ-Y2Si2O7 phase, and the like are also generated, the above heat treatment improves the crystallinity of Y2SiO5, which is the host crystal of the phosphor, and reduces the β-Y2Si2O7 crystal phase content to 0.
The content of the γ-Y2Si2O7 crystal phase can be adjusted to 1% or less and 2 to 7%.

As described in "Prior Art", in Japanese Patent Laid-Open No. 11-43672, heat treatment at 1300 to 1700 ° C. is performed after thermal plasma treatment to improve crystallinity and increase luminous efficiency. However, this publication does not mention the composition of the crystal phase of the phosphor.

On the other hand, the inventors of the present application have studied more concretely the relationship between the heat treatment conditions after the plasma treatment and the characteristics of the phosphors, and as a result, the temperature conditions under which the β-phase Y2Si2O7 can be made less than 0.1%, that is, It has been found that the heat treatment at 1500 ° C. or higher can significantly improve the luminous efficiency of the phosphor layer.

If the heat treatment temperature exceeds 1700 ° C., the particles of the phosphor will sinter and a plurality of particles will agglomerate, making it difficult to separate the individual particles by a simple milling process. However, in order to maintain the effect of the spherical shape of the phosphor, it is not desirable to raise the temperature higher than 1700 ° C. Therefore, the heat treatment temperature is 1500 ° C to 1700 ° C.
And the heat treatment atmosphere is preferably an inert gas atmosphere such as Ar or N2.

It is preferable that the content of the γ-Y2Si2O7 crystal phase is also small, but the heat treatment temperature is set to about 1400 ° C. and only the content of the γ-Y2Si2O7 crystal phase is reduced, the effect of improving the luminous efficiency is small. . Heat treatment temperature is 1500 ℃ ~
At 1700 ° C, the content of the γ-Y2Si2O7 crystal phase rather increases to the range of 2% to 7%, but the β phase Y2Si2O7 is added to 0.1%.
When it is less than%, a good effect of improving the luminous efficiency can be obtained.

Therefore, the heat treatment temperature is 1500 ° C. to 1 ° C.
By adjusting the temperature within the range of 700 ° C, the effect due to the spherical shape of the phosphor, that is, the denseness obtained when the phosphor layer is formed, is maintained and the luminous efficiency is improved, and it is used for the phosphor layer of the projection tube. In this case, both high resolution and high brightness can be satisfied.

The phosphor according to the first embodiment is
Since it has Y2SiO5: Ln (where Ln is either Tb or Ce) as a main component, a small amount of impurities may be mixed. For example, the content of Y2SiO5: Ln may be 95 wt% or more. Even if a part of yttrium (Y) of Y2SiO5: Ln is replaced with at least one of rare earth elements such as gadolinium (Gd), lanthanum (La), and lutetium (Lu), the same crystal structure as that of yttrium silicate is obtained. As far as shown, the same effects as Y2SiO5: Ln can be obtained, so that it can be regarded as a material equivalent to Y2SiO5: Ln.

Also in the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal phase, it is clear that some of the yttrium can be replaced with other rare earth elements such as an activator, considering the formation process thereof.

(Second Embodiment) The phosphor according to the second embodiment of the present invention is the same as the phosphor according to the first embodiment of the present invention, except that the surface of the phosphor according to the first embodiment is alkaline earth such as calcium polyphosphate. It is provided with a polyphosphate coating of a metal. That is, this phosphor is obtained by coating the surface of the phosphor with a polyphosphoric acid film after high-temperature heat treatment at 1500 ° C. to 1700 ° C. following spheroidization by thermal plasma treatment.

As described above, the phosphor according to the first embodiment of the present invention is the yttrium silicate spherical phosphor in which the heterophase crystal phase is reduced after the phosphor is spheroidized by the thermal plasma treatment. In order to obtain it, heat treatment is performed at 1500 ° C. to 1700 ° C., but at this time, a phenomenon occurs in which particles are lightly sintered and aggregated. This sintering caused by the heat treatment at 1700 ° C. or less is slight, and the particles can be separated from each other by milling or the like, and the characteristics of the spherical phosphor are not significantly impaired.

However, by milling, only a part of the particles are crushed into non-spherical particles, or the particles cannot be completely separated from each other, and a small part of the particles remain in an aggregated form. It can happen. When the phosphor layer is formed by using such a phosphor, the packing density of the phosphor screen is slightly reduced as compared with the case where the original spherical phosphor is used. As a result, although the resolution when used as the fluorescent layer of the projection tube is improved as compared with the case where the non-spherical phosphor is used, the improvement effect becomes lower than that of the spherical phosphor with less aggregation.

In the phosphor according to the second embodiment, a surface of yttrium silicate spherical phosphor after milling is provided with a polyphosphate coating film of alkaline earth metal such as calcium polyphosphate. The polyphosphate coating covering the phosphor surface improves the fluidity of the phosphor. Therefore, the dispersibility of the phosphor particles can be improved and a dense phosphor layer can be formed.

As a method for producing a polyphosphoric acid film, for example, a spherical phosphor is immersed in pure water in which sodium metaphosphate or the like is dissolved, and the suspension is stirred to suspend an alkaline earth such as calcium nitrate in a solution. It is possible to use a method of forming a polyphosphate coating film on the surface of the spherical phosphor by dropping an aqueous solution of a nitrate of a similar metal to cause a reaction.

It should be noted that US Pat. No. 5,739,632 discloses a method of forming a polyphosphate film on the surface of a zinc sulfide-based phosphor and using it as a protective film for preventing deterioration due to electron beam irradiation. There is. Also, US Pat.
No. 998,047 discloses that an aluminate phosphor is surface-treated with a polyphosphate such as calcium, magnesium or zinc. In this case as well, the purpose is to reduce the deterioration of the phosphor. Has become.

On the other hand, in the case of the yttrium silicate phosphor according to the second embodiment, the degree of deterioration due to electron beam irradiation or the like is extremely smaller than that of the zinc sulfide-based phosphor or the like, so that the polyphosphate coating film is used. Is not required as a protective film, and a structure in which a polyphosphate film is formed on the surface of a yttrium silicate phosphor is not known.

However, since the yttrium silicate phosphor of the second embodiment is subjected to high-temperature heat treatment or milling treatment after being spheroidized by the thermal plasma treatment, the polyphosphate coating film has roughened particles. Adds fluidity to the surface,
The effect of improving the dispersibility of the phosphor particles and forming a dense phosphor layer, which is completely different from the above-described deterioration prevention, is exhibited. In addition, a function as a protective film may occur as a secondary effect.

The surface treatment itself of the phosphor with the polyphosphate is 0.005 when the surface treatment amount is expressed by the weight ratio of the alkaline earth metal to the weight of all the phosphors.
It is preferably about 0.1% by weight. When the treatment amount is higher than the upper limit value, when the phosphor is caused to emit light by electron beam excitation, the ratio of the excited electron beam absorbed by the surface-treated product increases, so that the brightness decreases and the treatment amount becomes the lower limit. If it is less than the value, the effect of improving the packing density at the time of forming the fluorescent film becomes small.

(Third Embodiment) The third embodiment of the present invention includes a phosphor layer formed of the phosphor according to the above-described first and second embodiments. The projection tube of the projection display will be described.

FIG. 1 is an explanatory view showing the structure of a projection tube according to the third embodiment. For convenience of description, a cross-sectional view is shown above the break line and an external view is shown below the break line. As shown in the figure, the projection tube has a substantially rectangular face plate 1 serving as an exit surface of a projected image on the front surface of a vacuum glass bulb 10, and the inner surface of the face plate 1 has the first or second embodiment. It has a laminated structure composed of a phosphor layer 4 formed of the phosphor according to the embodiment and an aluminum film 5. An electron gun 3 and an anode 2 are provided in the glass bulb 10, and an electron beam (cathode ray) emitted from the electron gun 3 is applied to the phosphor layer 4. The aluminum film 5 has a function as a reflection layer for projecting light emitted from the phosphor layer to the outside and a function for applying a potential for irradiating the phosphor layer with an electron beam.

Phosphor layer 4 on inner surface of face plate 1
In the formation of, the known precipitation method using a barium salt aqueous solution and water glass can be used. Further, the aluminum film can be formed by a vacuum evaporation method or the like.

The thickness of the phosphor layer 4 is preferably about 2 to 3 times the average particle diameter of the phosphor in consideration of the penetration depth of the electron beam and the output balance of the image light, for example, about several tens of μm. Is preferred.

When the phosphor layer 4 is formed using the phosphor according to the first embodiment, due to the spherical shape of the phosphor,
A dense phosphor layer can be obtained, an image with high resolution can be obtained, and the image brightness can be greatly improved as compared with the case where a conventional spherical phosphor is used.

Furthermore, when the phosphor layer 4 is formed by using the phosphor according to the second embodiment, the phosphor according to the first embodiment is produced due to the effect of the polyphosphoric acid film formed on the surface of the phosphor. Phosphor layer 4 that is more compact than when a body is used
Therefore, the resolution of the video can be further improved.

The present invention has been described above with reference to the first to third embodiments, but the present invention is not limited to these descriptions, and various modifications and substitutions can be made by those skilled in the art. It is self-explanatory.

Further, the phosphor of the present invention is not limited to the phosphor layer of the projection tube, but can be used for other cathode ray tubes, plasma displays,
Alternatively, it is obvious to those skilled in the art that it can be used as a phosphor layer of a fluorescent lamp or the like.

[0062]

EXAMPLES Examples and comparative examples of the present invention will be described below. In addition, Examples 1-5 and Comparative Examples 1-4,
The present invention relates to a green phosphor using Tb as an activator, and Example 6 and Comparative Example 5 relate to a blue phosphor using Ce as an activator. In addition, the numerical value (%) of the content rate of the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal in the following description corresponds to the ratio of the content determined along the definition formula (f1) (f2) of the present specification. To do.

Example 1 A commercially available Y2SiO5: Tb phosphor (Comparative Example 1) having a non-spherical particle size of 8.7 μm was prepared.
After heat treatment at 550 ° C. for 1.5 hours, milled material was used as a raw material and spheroidized by high frequency thermal plasma. Subsequently, heat treatment was performed at 1550 ° C. for 5 hours in an argon atmosphere. The ratio of the major axis to the minor axis of this phosphor is 1.
The average particle size was 06 and the average particle size was 7.0 μm.

When the X-ray diffraction measurement of the phosphor of Example 1 was carried out, the results shown in the table of FIG. 1 were obtained. β-Y2Si2O7
If the content of crystalline phase is less than 0.1%, it cannot be detected, and γ-Y2Si2
The O7 crystal phase was included at 5.4%.

Example 2 Prepared by the coprecipitation method (Y, Tb)
Y2 having a Tb concentration of 4 atomic% at a calcination temperature of 1600 ° C. was prepared by a known method using a flux of 2O3 and SiO2 as raw materials.
A SiO5: Tb phosphor was prepared. Spheroidization and heat treatment were performed in the same manner as in Example 1 except that this phosphor was used as a raw material.
The spherical phosphor of Example 2 was produced. The ratio of major axis to minor axis of this phosphor was 1.03, and the average particle diameter was 7.4 μm. The γ-Y2Si2O7 crystal phase contained in this phosphor was 2.9%, but the content of the β-Y2Si2O7 crystal phase was 0.1%.
It could not be detected in less than 1%.

Example 3 The spherical phosphor 100 of Example 1
0.20 g sodium metaphosphate and 0.35 g per g
Using g of calcium nitrate, a calcium polyphosphate coating film was formed on the surface of the phosphor particles by the following method to prepare the phosphor of Example 3. That is, first, 0.2 g of sodium metaphosphate was dissolved in 250 ml of pure water, and 1
00 g of the spherical phosphor was added, and the mixture was stirred for 20 minutes or more to suspend it. 7 ml of a 5% calcium nitrate aqueous solution was added dropwise to the suspension to start the reaction, and the stirring was continued for another 60 minutes, and then the stirring was stopped. After standing for 10 minutes, the supernatant is discarded and the phosphor is recovered by filtration.
Dried at ~ 120 ° C. Thus, a phosphor whose surface was coated with calcium polyphosphate was obtained. When the amount of calcium polyphosphate attached was analyzed as the amount of calcium contained in the phosphor, it was 0.016% by weight.
The ratio of the major axis to the minor axis and the average particle diameter of this phosphor were the same as in Example 1. Further, the contents of the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal phase were the same as in Example 1.

Example 4 A spherical phosphor of Example 4 was produced in the same manner as in Example 1 except that heat treatment was performed at 1650 ° C. for 4 hours in an argon atmosphere after spheroidizing. The ratio of the major axis to the minor axis of this phosphor was 1.06, and the average particle diameter was 7.
It was 6 μm. The γ-Y2Si2O7 crystal phase contained in this phosphor was 1.6%, but the content of the β-Y2Si2O7 crystal phase was less than 0.1% and could not be detected.

(Example 5) The spherical phosphor of Example 2 was surface-treated with calcium polyphosphate in the same manner as in Example 3 to prepare a phosphor of Example 5. When the amount of calcium polyphosphate attached was analyzed as the amount of calcium contained in the phosphor, it was 0.018%. The ratio of the major axis to the minor axis and the average particle diameter of this phosphor were the same values as in Example 2. In addition, the contents of the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal phase were the same as in Example 2.

Comparative Example 1 A commercially available Y2SiO5: Tb phosphor having a particle shape of 8.7 μm, which is not spherical, was used as Comparative Example 1. This phosphor was subjected to X-ray diffraction measurement using Cu-Kα rays, and the amount of different phases was examined as a diffraction line intensity ratio. Γ-Y2S
The i2O7 crystal phase was 3% and the β-Y2Si2O7 crystal phase was 0.5%.

Comparative Example 2 Using the phosphor of Comparative Example 1 as a raw material, spheroidizing was performed by high-frequency thermal plasma, and 1400 ° C. in a mixed atmosphere of 2 vol% hydrogen and 98 vol% nitrogen.
A spherical phosphor of Comparative Example 2 was produced by performing heat treatment for 5 hours. The ratio of the major axis to the minor axis of this phosphor was 1.05, and the average particle diameter was 8.8 μm. When the X-ray diffraction measurement of this phosphor was performed, the results shown in the table of FIG. 2 were obtained. From this result, it was found that the β-Y2Si2O7 crystal phase was included in an amount of 4.0%, but the γ-Y2Si2O7 crystal phase was less than 0.1% and could not be detected.

Comparative Example 3 The spherical phosphor 100 of Comparative Example 2
0.20 g sodium metaphosphate and 0.35 g per g
Using g of calcium nitrate, a calcium polyphosphate coating was formed on the surface of the phosphor particles in the same manner as in Example 3 to prepare the phosphor of Comparative Example 3.

The amount of calcium polyphosphate attached was analyzed as the amount of calcium contained in the phosphor and was 0.0.
It was 17%. The ratio of the major axis to the minor axis and the average particle diameter of this phosphor were the same as those in Comparative Example 2. Further, the content rates of the β-Y2Si2O7 crystal phase and the γ-Y2Si2O7 crystal phase were the same as in Comparative Example 2.

(Comparative Example 4) The phosphor of Comparative Example 1 was replaced by 1550.
After heat treatment at 1.5 ° C. for 1.5 hours, milling was performed using a ball mill as a raw material. The raw material was spheroidized and heat treated in the same manner as in Comparative Example 2 to obtain the spherical phosphor of Comparative Example 4. It was made. The ratio of the major axis to the minor axis of this phosphor is 1.
The average particle size was 06 and the average particle size was 6.5 μm. The β-Y2Si2O7 crystal phase contained in this phosphor was 4.6%, and the γ-Y2Si2O7 crystal phase was 0.7%.

(Characteristics of Projection Tube) Next, the above-mentioned Examples 1 to 1
No. 5 and Comparative Examples 1 to 4 were used to fabricate a projection tube, and their characteristics were compared. The projection tube was manufactured by the following procedure. That is, a well-known sedimentation method using an aqueous solution of barium and water glass was used to put 1
A phosphor layer having a coating amount of 4.0 mg per cm ² was formed. Then, an aluminum film having a thickness of about 0.2 μm was formed on the phosphor layer by using a vapor deposition method. After this, a projection tube was manufactured through a process of attaching an electron gun. When evaluating the characteristics, an acceleration voltage of 32 kV was applied to the prototype projection tube, and 3.
The brightness when a raster was drawn with a beam current of 5 mA was measured, and the relative brightness was determined using the brightness of the projection tube using the phosphor of Comparative Example 1 as a reference (100). In addition, a straight line was drawn with a beam current of 1 mA, the brightness profile was measured, and the spread of the line having a brightness of 5% of the brightness at the center of the straight line was defined as the spot diameter, which was used as a scale of resolution. The smaller the spot diameter, the better the resolution. The characteristics of the prototype projection tube are shown in the table of FIG.

As described above, in the terbium-activated yttrium silicate spherical phosphors of Comparative Examples 2 to 4, the spot diameter was reduced, that is, the resolution was improved as compared with Comparative Example 1, but the brightness improving effect was 10%. It was less than less than. On the other hand, in Examples 1 to 5, a brightness improvement effect of 10% or more was obtained as compared with Comparative Example 1, and improvement in resolution was also recognized.

Example 6 Prepared by the coprecipitation method (Y, Ce)
The Ce concentration was 0.1 atomic% at a calcination temperature of 1600 ° C. by a known method using a flux of 2O3 and SiO2 as raw materials
Y2SiO5: Ce phosphor, which is the above, was heat-treated at 1550 ° C. for 1.5 hours and then milled, and used as a raw material, and spheroidizing treatment and heat treatment were performed in the same manner as in Example 1. The surface treatment of calcium polyphosphate was carried out in the same manner as in Example 3 to prepare the Y2SiO5: Ce spherical phosphor of Example 6. Analysis of the amount of calcium polyphosphate deposited as the amount of calcium contained in the phosphor gives 0.018
% By weight. The ratio of the major axis to the minor axis of this phosphor is 1.0.
3 and the average particle size was 7.6 μm. Further, the γ-Y2Si2O7 crystal phase contained in this phosphor was 5.0%, but the β-Y2Si2O7 crystal phase content was less than 0.1% and could not be detected.

(Comparative Example 5) Prepared by the coprecipitation method (Y, Ce)
The Ce concentration was 0.1 atomic% at a calcination temperature of 1600 ° C. by a known method using a flux of 2O3 and SiO2 as raw materials.
A Y2SiO5: Ce phosphor of Comparative Example 5 was prepared. The average particle size of this phosphor is 8.0 μm, and γ contained in this phosphor is
-Y2Si2O7 crystal phase is 6.2%, β-Y2Si2O7 crystal phase is 0.1%
% Was not detected.

(Characteristics of Projection Tube) Using the cerium-activated yttrium silicate spherical phosphor phosphors of Comparative Example 5 and Example 6 described above, the same method as in Comparative Examples 1-4 and Examples 1-5 was used. A projection tube was prototyped and their characteristics were compared. The brightness of the projection tube using the phosphor of Example 6 was as high as 115% of that of the projection tube using the phosphor of Comparative Example 5. The spot diameter of the projection tube using the phosphor of Example 6 is 235 μm.
m, which is smaller than the spot diameter of 267 μm of the projection tube using the phosphor of Comparative Example 5, and the effect of improving resolution was recognized.

[0079]

As described above, according to the phosphor of the present invention, γ-Y2Si2O7 having a Y2SiO5 crystal in which an activator is dissolved as a main component and having a spherical particle shape and a different phase is used. Since the content rates of the crystal phase and the β-Y2Si2O7 crystal phase are limited, it is possible to form a dense phosphor layer having high luminous efficiency.

According to the method for producing a phosphor of the present invention, the thermal plasma treatment is followed by a heat treatment under the temperature condition of 1500 ° C. to 1700 ° C., so that the main component of Y2SiO5 is maintained while maintaining the spherical shape. It is possible to obtain a phosphor in which the crystallinity is improved and the γ-Y2Si2O7 crystal phase and the β-Y2Si2O7 crystal phase, which are different phases, are reduced. Therefore, it is possible to form a dense phosphor layer having high luminous efficiency.

Further, according to the projection tube of the present invention, a phosphor layer having a high density and a high luminous efficiency can be formed, so that an image having high luminance and excellent resolution can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a structure of a projection tube according to a third embodiment of the present invention.

FIG. 2 is a chart showing the X-ray diffraction measurement results of the phosphor according to Example 1.

FIG. 3 is a table showing X-ray diffraction measurement results of a phosphor according to Comparative Example 1.

FIG. 4 shows conditions for producing the phosphors of Examples 1 to 5 and Comparative Examples 1 to 4 and the relative luminance and spot diameter obtained when the phosphors are used as a phosphor layer of a projection tube. It is a chart showing a relationship.

[Explanation of symbols]

1 face plate 2 anode 3 electron gun 4 Phosphor layer 5 Aluminum film 10 glass bulbs

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Ryosuke Hiramatsu             1st Komukai Toshiba-cho, Sachi-ku, Kawasaki-shi, Kanagawa             Inside the Toshiba Research and Development Center (72) Inventor Masaaki Tamaya             1 east, Komukai Toshiba Town, Saiwai-ku, Kawasaki City, Kanagawa Prefecture             Shiba Research Consulting Co., Ltd. (72) Inventor Kazuhiro Kawasaki             Kanagawa Prefecture Hiratsuka City Tamura 5893 High-frequency smelting stock             Company Shonan office (72) Inventor, Seiji Yokota             Kanagawa Prefecture Hiratsuka City Tamura 5893 High-frequency smelting stock             Company Shonan office (72) Inventor Yoshiaki Inoue             Kanagawa Prefecture Hiratsuka City Tamura 5893 High-frequency smelting stock             Company Shonan office (72) Inventor Akira Terashima             Kanagawa Prefecture Hiratsuka City Tamura 5893 High-frequency smelting stock             Company Shonan office F-term (reference) 4H001 CA02 CA04 CC12 XA08 XA14                       XA39 YA65                 5C036 CC18

Claims (5)

[Claims] 1. A Y2SiO5 crystal phase having a spherical shape, the main component of which is a solid solution of an activating element, and the ratio of the content of the γ-Y2Si2O7 crystal phase to the content of the Y2SiO5 crystal phase is A phosphor having a content ratio of 2 to 7% and a β-Y2Si2O7 crystal phase of less than 0.1%. 2. The method according to claim 1, further comprising an alkaline earth metal polyphosphate film covering the surface.
The phosphor according to 1. 3. Y2SiO5 whose main component is a solid solution of an activator element.
Thermal plasma treatment step of exposing the phosphor particles, which is a thermal plasma treatment step, to the thermal plasma;
A heat treatment at a temperature of ˜1700 ° C. 4. The method for producing a phosphor according to claim 3, further comprising a step of coating the surface with a polyphosphate of an alkaline earth metal after the heat treatment. 5. A cathode ray tube having an electron gun as a cathode ray generation source and a phosphor layer irradiated with a cathode ray emitted from the electron gun, wherein the phosphor layer has an activator element as a main component. The Y2SiO5 crystal phase is a solid solution, the content ratio of the γ-Y2Si2O7 crystal phase is 2 to 7%, and the content ratio of the β-Y2Si2O7 crystal phase is 0.1% with respect to the content of the Y2SiO5 crystal phase. Cathode ray tube having a spherical phosphor of less than%.