JP2002080847A - Rare earth silicate phosphor and luminescent screen using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rare earth silicate phosphor improved in luminance and a luminescent screen. SOLUTION: This rare earth silicate phosphor is represented by the formula: (Ln1-xLn'x)2O3.nSiO2 (Ln denotes at least one kind of rare earth element selected from among Y, La, Gd, and Lu; Ln' denotes at least one kind of rare earth element selected from among Tb, Ce, and Eu; 0.95<=n<=2.5; and 5×10-3<=x<=2×10-1) and contains carbon (C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare-earth silicate which emits light with high luminance when excited by an electron beam, has good current-luminance characteristics (.gamma. Characteristics), and particularly has excellent light-emitting characteristics for projection televisions. The present invention relates to a phosphor and a luminescent screen.

[0002]

2. Description of the Related Art With the enlargement of color televisions (color TVs), projection is performed by projecting images from a plurality of cathode ray tubes, each of which emits a different color of light, onto a single screen to synthesize and observe the images. Shaped color TVs are beginning to spread. A CRT used in a projection type color TV needs to have higher luminance than a general CRT in order to perform enlarged projection, and is operated at a higher current density than a CRT for a general TV.

Accordingly, a phosphor used in a projection type color TV cathode-ray tube generally has a high emission luminance and a good correlation between the current density of the irradiated electron beam and the emission luminance, that is, the current luminance characteristic. (Γ characteristics) is good,
Various characteristics such as not deteriorating by long-time excitation and good temperature characteristics are required.

[0004] In addition to the CRT for a projection type TV,
In recent years, the cathode ray tube has become higher definition, and it has been necessary to narrow the spot of each color electron beam. Therefore, for the phosphor, the current density of the irradiated electron beam has increased.
Since the load increases, there is a demand for a phosphor that is less deteriorated by electron beam irradiation than the current phosphor.

At present, as phosphors for projection tubes, red-light-emitting Y ₂ O ₃ : Eu phosphors and green-light-emitting Y ₃ (Al, G
a) ₅ O ₁₂ : Tb phosphor, Y ₃ Al ₅ O ₁₂ : Tb phosphor, Y ₂ SiO ₅ : Tb phosphor, LaOCl: Tb phosphor, blue light emitting ZnS: Ag, Al, etc. are used. However, among these phosphors, phosphors having a rare earth silicate as a host, particularly Y ₂ SiO ₅ : Tb exhibiting green light emission
The phosphor has a current density of about 10 μm for the irradiated electron beam.
In a relatively low current density region of A / cm 2 or less,
Luminescent luminance increases almost in proportion to the current density, the current luminance characteristics (γ characteristics) are excellent, and the temperature characteristics of the phosphor are small with respect to temperature changes. Is a high phosphor.

However, the rare earth silicate phosphors such as Y ₂ SiO ₅ : Tb do not always have satisfactory luminous luminance in practical use, and further improvement in luminous luminance is desired.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a rare earth silicate phosphor and a light emitting screen having improved emission luminance.

[0008]

In order to achieve the above-mentioned object, the present inventors have focused on details of a change in emission luminance of a rare-earth silicate phosphor when the phosphor contains various metal elements. As a result of the investigation, a specific amount of carbon (C) was contained in this phosphor.
It was found that the emission luminance was improved by containing.

That is, the present invention has the following configuration. (1) The composition formula is (Ln _1-x Ln ′ _x ) ₂ O ₃ .nS
A rare earth silicate phosphor represented by iO ₂ and containing carbon (C). (However, Ln is Y, L
a, Gd and Lu represent at least one rare earth element, and Ln ′ represents at least one of Tb, Ce and Eu.
Represents a rare earth element, and n and x are each 0.1.
95 ≦ n ≦ 2.5 and 5 × 10 ⁻³ ≦ x ≦ 2 × 10 ⁻¹
Is a number that satisfies the following condition). (2) The rare earth silicate phosphor according to (1), wherein the content of the carbon (C) is 5 to 500 ppm.

(3) The content of the carbon (C) is 10 to
The rare earth silicate phosphor according to the above (2), wherein the content is 350 ppm. (4) The rare earth silicate phosphor according to any one of (1) to (3), wherein Ln ′ is Tb. (5) The rare-earth silicate phosphor according to any one of (1) to (4), wherein the n value is a number satisfying a condition of 0.95 ≦ n ≦ 1.5. (6) A luminescent screen, comprising a support and a phosphor film made of the rare earth silicate phosphor according to any one of (1) to (5) formed on the support.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The phosphor of the present invention is manufactured as follows. Examples of the phosphor material include oxides of Ln, compounds of Ln such as nitrates, sulfates, carbonates, and oxalates of Ln which can be thermally decomposed into Ln oxides by heating at a high temperature; Oxide or Ln ′ nitrate, sulfate,
A compound of Ln ′ which can be thermally decomposed by heating at a high temperature to be converted to an oxide of Ln ′, such as carbonate and oxalate, a silicon compound such as silicon dioxide, and

Using a carbon-containing compound such as carbon powder, sucrose, and coconut shell activated carbon, these phosphor raw materials are stoichiometrically (Ln _1-x Ln ′ _x ) ₂ O ₃ .nSiO ₂ (where Ln is Y , La, Gd and Lu
Ln ′ represents at least one rare earth element among Tb, Ce and Eu, and n and x are 0.95 ≦ n ≦ 2.5 and 5 × 10 ⁻³ ≦
x ≦ 2 × 10 ⁻¹ ), and, if necessary, further blending a barogenide of an alkali metal and / or an alkaline earth metal with the mixture as a flux. And mix well by wet or dry method. Further, it is possible to improve and control the particle shape and the particle size distribution of the phosphor obtained by using a material constituting the base material having a spherical shape and a narrow particle size distribution.
-59233).

Next, this raw material mixture is filled in a heat-resistant container such as an alumina crucible and fired at least once in a neutral atmosphere or a reducing atmosphere at a temperature of 1000 to 1700 ° C. for 1 to 12 hours. In the case where the fired product once fired is once cooled to room temperature and then fired again, and is manufactured through a plurality of firing processes, the second and subsequent firings are performed at 1100 ° C. to 1700 ° C.
You can do it in The fired product obtained in this manner is pulverized, washed with a dilute mineral acid such as dilute hydrochloric acid, washed with water, and then dried.
The phosphor of the present invention is obtained by sieving to make the particle diameter uniform.
In addition, the phosphor obtained as described above has a further 400
By performing annealing at a relatively low temperature of about 900 ° C., the emission luminance may be further improved.

FIG. 1 shows a composition formula, (Y _0.93 Tb)
₁₀ is a graph illustrating the correlation between the content of carbon (C) in a rare earth silicate phosphor represented by _0.07 ) ₂ SiO ₅ and the emission luminance of the phosphor under electron beam excitation. FIG.
In the graph, the content of carbon (C) on the horizontal axis represents the ratio of carbon (C) contained in the phosphor to the weight of the phosphor (pp
m), each phosphor is melted and extracted in a high-frequency heating furnace,
The gas generated in an oxygen atmosphere was guided to a detector by a carrier gas, and the gas was quantified by detecting with an infrared detector (gas fusion analysis). The emission luminance on the vertical axis indicates that the phosphor has an acceleration voltage of 20 kV and a current density of 1 μA / c.
It was measured by irradiating an electron beam of m ^2.

As is apparent from FIG. 1, the emission luminance of the Tb-activated yttrium silicate phosphor of the present invention when irradiated with an electron beam is as follows: when the C content is about 5 to 500 ppm, the conventional C-free yttrium silicate phosphor does not contain C. Emission luminance is higher than that of the Tb-activated yttrium silicate phosphor, and particularly the content of C is 10 to 10.
It can be seen that the emission luminance is particularly high when it is in the range of 350 ppm. Although not illustrated, the rare earth element Ln is G
d, La, and Lu, Ln 'is also Eu.
Also in the case of Ce, it was confirmed that the relationship between the content of C in the phosphor and the emission luminance under the electron beam excitation was similar to that of FIG. However, the phosphor illustrated in FIG. 1 emitted green light, whereas when Ln ′ was Eu, it emitted red light, and when Ln ′ was Ce, it emitted blue light.

Further, in the rare earth silicate phosphor of the present invention, the ratio (n value) of SiO _{2 to} (Ln _1-x Ln ′ _x ) ₂ O ₃ is irrespective of the type of Ln and Ln ′.
When it is in the range of 0.95 ≦ n ≦ 2.5, practically sufficient light emission luminance is shown, and when it is in the range of 0.95 ≦ n ≦ 1.5, light emission of particularly high luminance is exhibited.

It should be noted that the rare earth silicate phosphor of the present invention, as described above, emits high-luminance under excitation by an electron beam, and also emits high-luminance under excitation by ultraviolet rays or X-rays. It can be suitably used for X-ray applications such as a fluorescent film of a lamp and an intensifying screen.

The luminescent screen of the present invention is a fluorescent screen comprising a rare earth silicate phosphor of the present invention on a support such as glass by a conventionally known coating method such as a photolithography method, a sedimentation coating method or a slurry coating method. It can be manufactured by forming a film. For example, when used as a projection type color TV screen, a phosphor slurry in which the rare earth silicate phosphor of the present invention is suspended in water containing potassium silicate or the like is applied to the entire inner surface of the face plate of a cathode ray tube. Then, it is allowed to stand, drained, and dried to form a fluorescent film on the inner surface of the face plate (support).

[0019]

[Example 1]

Yttrium oxide (Y ₂ O ₃ ) 21.0 g Terbium oxide (Tb ₄ O ₇ ) 2.6 g Silicon dioxide (SiO ₂ ) 6.0 g Carbon powder 0.003 g The above raw materials are sufficiently mixed by a ball mill, and the mixture is put in an alumina crucible. The sintering was performed for 2 hours in an electric furnace maintained at a temperature of 1600 ° C. while passing nitrogen gas containing 2% hydrogen gas. The obtained fired product was subjected to pulverization, washing with water, drying and sieving to obtain a Tb-activated yttrium silicate phosphor of Example 1. As a result of chemical analysis, this phosphor was found to have (Y _0.93 Tb
_0.07 ) ₂ SiO _{5. The} content of carbon (C) was analyzed by gas fusion analysis.
It contained 0 ppm carbon (C).

The phosphor of Example 1 was applied to the test piece by sedimentation, and the luminescent screen of Example 1 was irradiated with an electron beam having an acceleration voltage of 20 KV and a current density of 1 μA / cm ² .
The emission luminance when emitting light from the phosphor film surface was improved by 5% as compared with the phosphor of Comparative Example 1 containing no carbon element, which was measured under the same conditions.

[Comparative Example 1] As a phosphor material, 0.00
After obtaining a rare earth silicate phosphor of Comparative Example 1 in the same manner as in the phosphor of Example 1 except that 3 g of powdered carbon was not used, a luminescent screen comprising the phosphor of Comparative Example 1 in the same manner as in Example 1 Was measured, and the results are shown in Table 1.

[Examples 2 to 8] Phosphor raw materials of the respective compounds were used so as to have the composition formulas shown in Table 1, respectively.
Only in the case of the phosphor of Example 5, carbon (C) was applied to each phosphor in the same manner as in Example 1 except that the nitrogen gas containing 2% hydrogen gas was not ventilated and calcined in air. Was obtained in the amounts shown in Table 1 to obtain rare earth silicate phosphors of Examples 2 to 8. The luminous brightness of the luminescent screen composed of these phosphors was measured in the same manner as in Example 1, and the results were measured. The results were the same as those of the phosphors of each example except that they did not contain carbon (C). The relative values with respect to the emission luminances of the phosphors of Comparative Examples 2 to 8 are shown in Table 1 below.

Comparative Examples 2 to 8 Rare earth silicate phosphors of the composition formulas shown in Table 1 were prepared in the same manner as in the phosphors of Examples 2 to 8 except that powdered carbon was not used as the phosphor material. After obtaining Comparative Examples 2 to 8), Comparative Example 2 was performed in the same manner as in Example 1.
The luminous brightness of the luminescent screens composed of the phosphors of Nos. 1 to 8 was measured, and the following relative values were obtained with respect to the luminous brightness of the phosphors of Examples 2 to 8 having the same composition formula except that they contained carbon (C). The results are shown in Table 1.

[0024]

[Table 1]

As described above, in Table 1, the emission luminance of each of the phosphors of Examples 1 to 8 is shown as a relative value to the emission luminance of each of the phosphors of Comparative Examples 1 to 8 corresponding to each of the examples. Therefore, it is not possible to make a relative comparison of the emission luminances between the phosphors of the examples and the comparative examples.

As can be seen from Table 1, the luminance of the phosphors of Examples 1 to 8 is higher than that of Comparative Examples 1 to 8, which have the same composition except that they do not contain carbon (C). Is high.

[0027]

According to the present invention, by adopting the above structure, the brightness is higher than that of a conventional rare-type silicate phosphor,
The luminescent screen of the present invention composed of this phosphor is a projection type T
It can be applied to high-brightness cathode ray tubes such as V.

[0028]

[Brief description of the drawings]

FIG. 1 is a graph illustrating the correlation between the carbon (C) content and the emission luminance under electron beam excitation in a rare-earth silicate phosphor.

Claims (6)

[Claims] 1. The composition formula is (Ln _1-x Ln ′ _x ) ₂ O ₃
· NSiO represented by _2, and a rare earth silicate phosphor which is characterized by containing carbon (C). (Where Ln represents at least one rare earth element among Y, La, Gd and Lu, Ln ′ represents at least one rare earth element among Tb, Ce and Eu, and n and x represent 0.95 ≦ n ≦ 2.5 and 5 × 10 ⁻³ ≦ x ≦ 2 × 1 respectively
0 ^-1 a satisfying number made). 2. The carbon (C) content is 5 to 500 p.
2. The rare earth silicate phosphor according to claim 1, wherein the phosphor is pm. 3. The carbon (C) content is 10 to 350.
The rare earth silicate phosphor according to claim 2, wherein the content is ppm. 4. The rare earth silicate phosphor according to claim 1, wherein said Ln ′ is Tb. 5. The rare earth silicate phosphor according to claim 1, wherein the n value is a number satisfying a condition of 0.95 ≦ n ≦ 1.5. 6. A light-emitting screen comprising a support and a phosphor film comprising the rare-earth silicate phosphor according to claim 1 formed on the support.