JP3232540B2 - Rare earth phosphor for monochrome CRT - Google Patents

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 (Literature
quid Crystal Color Shutter CRT, hereafter referred to as LCS. ) Is attracting attention. this is,
Briefly, the B, G, and R components of the monochrome CRT are separated by a polarizer (polarizer) of a liquid crystal color shutter and a π cell disposed on the front of the monochrome CRT, and the components are superimposed and the brightness of the CRT is changed. Various colors are displayed by this.

[0003] 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. In the case of LCS, this can be achieved with one electron gun. Therefore, there is an advantage that the resolution is excellent. Further, the display surface is gray in the shadow mask type, whereas the LCS has an advantage that the display surface is black because the liquid crystal color shutter is arranged on the front surface of the CRT, and the contrast is very good.

[0004] However, since the LCS of the liquid crystal color shutter 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. However, there is a disadvantage in that

[0005] A phosphor used for an LCS monochrome CRT is required to emit approximately white light by a single substance, and it is particularly preferable to emit light of three colors, G, B and R. This is because if the phosphor is a mixed phosphor, color unevenness occurs due to a spot hit by the electron beam. Further, it is necessary to match the peak ratio of the emission wavelength of the phosphor to the used polarizer. JEDEC, P represented by (Y, Tb) ₂ O ₂ S as a phosphor that can satisfy the conditions to some extent
Forty-five phosphors are known. In addition to this,
(Y, Tb, Sm) ₂ O ₂ disclosed in US Pat.
S phosphors can also be used.

FIG. 1 shows (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, a peak near 545 nm as a yellow-green component, and a peak near 608 nm as an orange component of the phosphor are taken out, and these colors can be displayed by separating and synthesizing these. it can.

[0007]

As described above, as described above, LC
Since the brightness of the S display depends on the brightness of the monochrome CRT on the rear surface, that is, the brightness of the phosphor, the current density must be increased to excite the phosphor. However, conventional phosphors have poor current characteristics, so that improvement in luminance cannot be expected. In other words, even if the phosphor is excited by increasing the current density, the brightness does not increase beyond a certain level.
Monochrome CRTs have a problem in that current saturation occurs, and when excitation is continued at a high current density, a phenomenon called “burning” occurs in the phosphor, discoloring the phosphor and lowering the luminance. In fact, no improvement in brightness could be expected.

Accordingly, 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 burn.
This realizes a monochrome CRT with high luminance even when used in a high current density region for CS.

[0009]

The present inventors have conducted a number of experiments to improve the current saturation and burn of rare-earth phosphors. As a result, these problems were solved by adding a trace amount of Ce. The present inventors have found out what can be done, and have accomplished the present invention. That is, the rare earth phosphor of the present invention is a rare earth phosphor represented by the general formula (Y _{1 -XYZ} , Ce _X , Tb _Y , Sm _Z ) ₂ O ₂ S, wherein X is 0 <X ≦ 1 × ^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 .

[0010] The phosphor of the present invention can be obtained by an ordinary method for producing a rare earth phosphor. For example, yttrium oxide,
After weighing rare earth oxide raw materials such as terbium oxide, cerium oxide, and samarium oxide so as to have a predetermined molar ratio, sulfur and a suitable flux (such as alkali metal or alkaline earth metal such as sodium carbonate and lithium fluoride) are used. (Halides, carbonates, etc.) by dry mixing and firing. Also, after dissolving the weighed oxide in an acid, adding an oxalic acid solution to precipitate as an oxalate, calcinating the oxalate to form an oxide, and further calcining by adding sulfur and a flux or hydrogen sulfide It can also be obtained by firing in an atmosphere.

[0011]

[Effect] FIG. 2 shows (Y _{1 -X} Ce _X Tb 0.0025 Sm 0.0008)
FIG. 4 is a diagram showing current characteristics of a ₂ O ₂ S phosphor, where A indicates an X value of 4;
× 10 ^-5 , B is 2 × 10 ^-5 , C is 1 × 10 ^-5 , D is 5 ×
10 ⁻⁶ and E are the phosphors of the present invention with 2.5 × 10 ⁻⁶ . In this figure, the luminance of each of the A to E phosphors at each current density is such that a phosphor film is formed of each of the A to E phosphors, and the phosphor film is subjected to an acceleration voltage of 16 kV and a current density of 0.5 μA / cm.
It is expressed as a relative value when the luminance at the time of excitation in step ² is 100%.
The acceleration voltage at each current density was fixed at 16 kV.

As shown in FIG. 1, the phosphor of the present invention has a Y
Is replaced by Ce, the luminance increases with the increase of the current density, and the phenomenon of current saturation as in the related art is not observed. In addition, the effect of Ce is remarkably exhibited by replacing only a very small amount.

FIG. 3 shows (Y _{1 -X} Ce _X Tb 0.0025 Sm 0.000
8) Regarding the phosphor of the present invention which was produced by changing the amount of cerium (X value) of the ₂ O ₂ S phosphor, the current density was plotted on the horizontal axis and the relative luminance was plotted on the vertical axis as in FIG. FIG. 7 is a diagram showing a comparison between a conventional phosphor and current characteristics. 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, the fluorescent film is formed by a conventional (Y0.9967Tb0.0025Sm0.0008) ₂ O ₂ S phosphor, the accelerating voltage 16kV and the fluorescent film
In the above, the luminance when excited at the same current density as the phosphor of the present invention is expressed as a relative value with 100% as the luminance.

As shown in FIG. 3, the phosphor of the present invention is Ce
In the low current density region, the initial luminance is lower than that of the conventional phosphor, but as the current density is increased, the conventional phosphor has a current saturation phenomenon and the luminance is lower. While the phosphor does not increase, the phosphor of the present invention does not cause a current saturation phenomenon, the luminance gradually increases from a low current density region, and has a current characteristic higher than that of a conventional phosphor in a 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 current saturation due to an increase in the current density tends to be improved when the Ce amount, that is, the X value, is larger than 0. At the same time, the brightness tends to decrease in the low current density range, so that a 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 particularly 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, in consideration of a decrease in the initial luminance at 0.5 μA / cm ² , the upper limit of the phosphor of the present invention is set to an X value of 1 × 10 ⁻⁴ as a practical range.

The Tb amount, ie, the Y value is about 1 × 10 ⁻³ or more, and peaks near 418 nm and 545 nm shown in FIG. 1 are obtained. As the amount increases, the peak value at 545 nm increases, and the peak at 418 nm increases. The value decreases. A preferable range for maintaining white light emission based on the balance between both peaks is a range of 1 × 10 ⁻³ ≦ Y ≦ 5 × 10 ⁻³ . As another effect, by increasing the amount of Tb, it is possible to compensate for a decrease in luminance of Ce and improve luminance.

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

[0018]

【Example】

Examples 1 to 5 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 out as shown in Table 1, and they are sufficiently dry-mixed.
Calcination was performed at 3 ° C. for 3 hours. After firing, the phosphor was washed several times to remove the flux, and then dried at 120 ° C. for 5 hours to obtain the phosphor of the present invention. These phosphors are shown in FIGS.
These are the same as the phosphors A to E shown by.

These phosphors were applied to a slide glass together with a binder, and the acceleration voltage was 27 kV and the current density was 10 μm.
When forcibly excited at A / cm ² for 30 minutes, all the coated surfaces did not change color at all, and the luminance was the same as before excitation, and no burning occurred.

[0020]

[Table 1]

[0021]

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

[Brief description of the drawings]

FIG. 1 is a view 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 one embodiment 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 relation to current density and relative luminance.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsunori Uchimura 491-100 Kaminakacho Oka, Anan-shi, Tokushima Prefecture Nichia Chemical Industry Co., Ltd. Examiner Hiroko Fujiwara (56) JP-A-52-117290 (JP, A) JP-A-57-78478 (JP, A) JP-A-62-253684 (JP, A) JP-A-64-22986 (JP, A) 130172 (JP, A) JP-B 53-28146 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C09K 11/84 CPD

Claims (1)

(57) [Claims] (1) When the general formula is (Y ₁ -XYZ, Ce _X , Tb
_Y, a rare-earth phosphor represented by _{Sm Z) 2 O 2 S,} X is in the range of ^{0 <X ≦ 1 × 10 -4} , Y is ^{1 × 10 -3 ≦ Y ≦ 5} × 10 - located on the ^third range, Z is 0 <Ri range near the Z ≦ 5 × ^{10 -2,} around 418 nm, and the emission peak near 545nm pressurized
The emission spectrum has an emission peak of Sm around 608 nm.
A rare earth phosphor for a monochrome CRT , comprising: