JPH05302083A - Rare earth phosphor - Google Patents

Abstract

PURPOSE:To provide the title phosphor improved in luminance saturation and prevention of scorch and thereby realize a monochromatic CRT having a high luminance even when used in a range of high-current density. CONSTITUTION:The title phosphor is represented by the general formula: (Y1-X-Y-Z, CeX, TbY, SmZ)2O2S (wherein 0<X<=1X10<-4>, 1X10<-3=Y<=5X10<-3>, and 0<=Z<=5X10<-2>).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rare earth phosphor used in a cathode ray tube (CRT), and more particularly to a rare earth phosphor having improved current saturation which can be used in a liquid crystal color shutter CRT.

[0002]

2. Description of the Related Art Recently, a liquid crystal color shutter CRT (Li
quid Crystal Color Shutter CRT, hereinafter referred to as LCS. The CRT called)) is attracting attention. this is,
Briefly, the B, G, and R components of the monochrome CRT are separated by the polarizer and the π cell of the liquid crystal color shutter placed in front of the monochrome CRT, and they are superimposed, and the brightness of the CRT is changed. By this, many colors are displayed.

On the other hand, a shadow mask type CRT uses three electron guns to form one color with three dots of G, B, and R, but in the case of LCS, this can be done with one electron gun. Therefore, there is an advantage that the resolution is excellent. Further, while the display surface is gray for the shadow mask type, the LCS has an advantage that the display surface is black because the liquid crystal color shutter is arranged in front of the CRT, and the contrast is very good.

However, since the liquid crystal color shutter of the LCS has poor transparency, if it is desired to display the same brightness as that of a normal CRT, the brightness of the monochrome CRT on the rear surface must be increased, which imposes a burden on the phosphor. There is a drawback that

A fluorescent substance used for a monochrome CRT of LCS is required to have a white light emission by a single substance, and it is particularly preferable that it emits wavelengths of G, B and R three colors. This is because a mixed fluorescent substance causes color unevenness due to a spot hit by an electron beam. In addition, it is necessary to match the peak ratio of the emission wavelength of the phosphor with a polarizer that uses it. As a phosphor capable of satisfying the condition to some extent, JEDEC, P represented by (Y, Tb) ₂ O ₂ S
Forty-five phosphors are known. In addition to this, Japanese Patent Publication Sho 53
-28146 (Y, Tb, Sm) ₂ O ₂
S phosphors can also be used.

In FIG. 1, (Y0.967Tb0.0025Sm0.0008) ₂
3 shows an emission spectrum of an O ₂ S phosphor. In the LCS, for example, a peak near 418 nm as a blue component of this phosphor, a peak near 545 nm as a yellow-green component, and a peak near 608 nm as an orange component are extracted, and these are separated and combined to display each color. it can.

[0007]

As described above, the LC
Since the brightness of the S display all depends on the brightness of the monochrome CRT on the rear surface, that is, the brightness of the phosphor, it is necessary to raise the current density to excite the phosphor. However, since the conventional phosphor has poor current characteristics, improvement in brightness could not be expected. In other words, even if the current density is increased to excite the phosphor, the brightness does not rise above a certain level.
Since there is a problem that current saturation occurs, and that the phosphor is discolored due to a phenomenon called "burning" when the phosphor is continuously excited at a high current density, and the brightness is reduced, the monochrome CRT has a problem. The reality is that no improvement in brightness can be expected.

Therefore, the present invention has been made in view of such circumstances, and an object of the present invention is to provide a rare earth phosphor having improved current saturation and burntness.
Even if it is used for CS in a high current density range, it realizes a monochrome CRT with high brightness.

[0009]

The present inventors have conducted various experiments in order to improve the current saturation and the burning of the rare earth phosphor, and as a result, the problems have been solved by containing an extremely small amount of Ce. The inventors have newly found what can be done and have completed the present invention. That is, the rare earth phosphor of the present invention is a rare earth phosphor represented by the general formula of (Y _{1 -XYZ} , Ce _x , Tb _Y , Sm _Z ) ₂ O ₂ S, where X is 0 <X ≦ 1 ×. Is in the range of 10 ⁻⁴ , Y is in the range of 1 × 10 ⁻³ ≦ Y ≦ 5 × 10 ⁻³ , and Z
Is in the range of 0 ≦ Z ≦ 5 × 10 ^-2 .

The phosphor of the present invention can be obtained by an ordinary method for producing a rare earth phosphor. For example yttrium oxide,
Rare earth oxide raw materials such as terbium oxide, cerium oxide, and samarium oxide are weighed so as to have a predetermined molar ratio, and then sulfur and a suitable fluxing agent (sodium carbonate, lithium fluoride, or another alkali metal or alkaline earth metal (Halides, carbonates, etc.) are dry mixed and fired. Also, after dissolving the weighed oxide in acid, add an oxalic acid solution to precipitate it as an oxalate, and calcinate the oxalate to form an oxide, and then add sulfur or a flux, and calcine, or hydrogen sulfide. It can also be obtained by firing in an atmosphere.

[0011]

[Operation] Fig. 2 shows (Y _1-X Ce _X Tb0.0025Sm0.0008)
FIG. ₂ is a diagram showing current characteristics of a ₂ O ₂ S phosphor, where A has an X value of 4
^{X10 -5} , B is ^{2x10 -5} , C is ^{1x10 -5} , D is 5x
10 ⁻⁶ and E are phosphors of the present invention containing 2.5 × 10 ⁻⁶ mol of cerium. In this figure, the brightness at each current density of the A to E phosphors is obtained by forming a phosphor film with each of the A to E phosphors and exciting the phosphor film at an acceleration voltage of 16 kV and a current density of 0.5 μA / cm ^2. Is expressed as a relative value with the luminance of 100% as 100%. The acceleration voltage at each current density is 1
It was fixed at 6 kV.

As shown in this figure, the phosphor of the present invention is Y
By substituting a part of Ce with Ce, the brightness increases as the current density increases, and the conventional phenomenon of current saturation is not seen. Moreover, the effect of Ce is conspicuous when only a very small amount is replaced.

FIG. 3 shows (Y _1-X Ce _X Tb0.0025Sm0.000
8) With respect to the phosphor of the present invention manufactured by changing the cerium amount (X value) of the ₂ O ₂ S phosphor, the horizontal axis represents the current density and the vertical axis represents the relative luminance, and Ce is not included, as in FIG. It is a figure which compares and shows a current characteristic with the conventional fluorescent substance. The phosphors A to E are the same as the phosphors shown in FIG. In this figure, the brightness at each current density of the phosphor of the present invention is as follows. A conventional (Y0.9967Tb0.0025Sm0.0008) ₂ O ₂ S phosphor is used to form a phosphor film, and the phosphor film is accelerated at an acceleration voltage of 16 kV.
In the above, the value is expressed as a relative value with the luminance when excited at the same current density as the phosphor of the present invention being 100%.

As shown in FIG. 3, the phosphor of the present invention is Ce.
In the low current density region because it contains the initial brightness is lower than the conventional phosphor, as the current density is increased, the conventional phosphor causes a current saturation phenomenon and the brightness is Whereas the phosphor of the present invention does not increase, the current saturation phenomenon does not occur, the brightness gradually increases from the low current density region, and the phosphor of the present invention has current characteristics superior to those of the conventional phosphor in the high current density region. ..

From the above, the general formula is (Y _{1 -XYZ} , Ce _X , T
In the phosphor of the present invention represented by b _Y , Sm _Z ) ₂ O ₂ S, the amount of Ce, that is, the X value tends to improve the current saturation due to the increase of the current density in the range of more than 0. At the same time, since the luminance tends to decrease in the low current density region, the practical value is preferably 1 × 10 ⁻⁴ or less, more preferably 2.5 × 10 ⁻⁶ or more and 4 × 10 ⁻⁵ or less. .. Although not shown in FIG. 3, the X value is 1 × 1.
0 ^-4 and a phosphor, a current density of 0.5 .mu.A / luminance in cm ² is about 80%, the luminance in 50 .mu.A / cm ² is 115%
Therefore, the X value of 1 × 10 ⁻⁴ was set as the upper limit of the phosphor of the present invention as a practical range in consideration of the decrease in initial luminance at 0.5 μA / cm ² .

The amount of Tb, that is, the Y value is about 1 × 10 ^-3 or more, and the peaks near 418 nm and 545 nm shown in FIG. 1 are obtained. As the amount is increased, the peak value at 545 nm increases and the peak at 418 nm. The value becomes smaller. A preferable range for maintaining white light emission from the balance of both peaks is 1 × 10 ⁻³ ≦ Y ≦ 5 × 10 ⁻³ . Further, as another effect, by increasing the amount of Tb, it is possible to compensate for the decrease in the brightness of Ce and improve the brightness.

Further, although the phosphor of the present invention can emit white light only by Tb without adding Sm,
In particular, by containing the Sm amount, that is, the Z value in the range of 5 × 10 ⁻² mol or less, preferably 5 × 10 ⁻³ mol or less, the peak near 608 nm shown in FIG. 1 can be emitted, It is particularly preferable as a phosphor for LCS because it can emit light of three colors of B, G, and R. However, if the amount exceeds 5 × 10 ^-2 , the current characteristics deteriorate and the brightness tends to decrease.

[0018]

【Example】

[Examples 1-5] phosphor materials as yttrium oxide (Y ₂ O _3), cerium oxide (Ce ₂ O _3), terbium oxide (Tb ₄ O _7), samarium oxide (Sm ₂ O ₃₎ and sulfur (S ) And sodium carbonate (Na ₂ CO ₃ ) as a flux
Are weighed as shown in Table 1, thoroughly dry mixed, filled in an alumina crucible, covered with a lid 1100
It was calcined at ℃ for 3 hours. After firing, the phosphor was washed several times with water to remove the flux, and then dried at 120 ° C. for 5 hours to obtain a phosphor of the present invention. These phosphors are shown in FIGS.
It is the same as the fluorescent substance of A to E shown in.

These phosphors were coated on a slide glass together with a binder, and the accelerating voltage was 27 kV and the current density was 10 μm.
When it was forcibly excited at A / cm ² for 30 minutes, the coated surface was not discolored at all, and the brightness was the same as before the excitation, and no burning occurred.

[0020]

[Table 1]

[0021]

As described above, by incorporating Ce in the rare earth phosphor of the present invention, the current characteristics are remarkably improved and the brightness saturation and the burning can be improved. Furthermore, since the current characteristics are excellent, the chromaticity point of the phosphor does not change, and it is an extremely excellent phosphor. Therefore, when this phosphor is used for an LCS monochrome CRT,
The brightness can be improved even if the current density is increased, and the brightness of the LCS display can be made equal to the brightness of the display of a normal CRT. Further, the phosphor of the present invention is not limited to the phosphor for LCS, but may be a general monochrome CR.
It can also be used for T, and its utility value is very large.

[Brief description of drawings]

FIG. 1 is a diagram showing one emission spectrum of a (YTbSm) ₂ O ₂ S phosphor containing no cerium.

FIG. 2 is a diagram showing a relationship between current density and relative luminance of a phosphor according to an example of the present invention.

FIG. 3 is a diagram showing a comparison between a phosphor according to an embodiment of the present invention and a conventional phosphor in terms of current density and relative luminance.

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[Procedure amendment]

[Submission date] June 30, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction content]

[0011]

[Operation] Fig. 2 shows (Y _1-X Ce _X Tb0.0025Sm0.0008)
FIG. 3 is a diagram showing a current characteristic of a ₂ O ₂ S phosphor, where A has an X value of 4
^{X10 -5} , B is ^{2x10 -5} , C is ^{1x10 -5} , D is 5x
10 ⁻⁶ and E are phosphors of the present invention, which are 2.5 × 10 ⁻⁶ . In this figure, the brightness at each current density of the A to E phosphors is as follows.
It is expressed as a relative value with the luminance when excited at ² being 100%.
The acceleration voltage at each current density was fixed at 16 kV.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Further, although the phosphor of the present invention can emit white light only by Tb without adding Sm,
Particularly, by setting the Sm amount, that is, the Z value in the range of 5 × 10 ⁻² or less, preferably in the range of 5 × 10 ⁻³ or less, the peak near 608 nm shown in FIG. 1 can be emitted,
It is particularly preferable as a phosphor for LCS because it can emit B, G, and R three colors. However, when the value exceeds 5 × 10 ^-2 , the current characteristics tend to deteriorate and the luminance tends to decrease.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Koichi Kunikata 491-1, Oka, Kaminaka-cho, Anan City, Tokushima Prefecture 100 Nichia Chemical Industry Co., Ltd. Nichia Chemical Industry Co., Ltd.

Claims (1)

[Claims] 1. The general formula is (Y _{1 -XYZ} , Ce _x , Tb _Y , Sm
_Z ) ₂ O ₂ S, which is a rare earth phosphor, wherein X is in the range of 0 <X ≦ 1 × 10 ⁻⁴ and Y is 1 × 10 ⁻³ ≦ Y.
A rare earth phosphor having a range of ≦ 5 × 10 ⁻³ and a Z of 0 ≦ Z ≦ 5 × 10 ⁻² .