JP2637102B2 - Phosphor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to an improvement in europium-activated yttrium phosphor.

(Prior Art) As is well known, europium-activated yttrium oxysulfide, europium-activated yttrium oxide, europium-activated yttrium vanadate phosphor, and the like are known as red light-emitting phosphors for color televisions. In particular, europium-activated yttrium oxysulfide phosphors are widely used, particularly because the emission color is sufficiently red for practical use, and furthermore, the emission luminance is high and stable under use conditions.

(Problems to be Solved by the Invention) With these phosphors, when the voltage is increased, the light emission luminance is increased, that is, the voltage characteristics are not always sufficient.

An object of the present invention is to provide a novel phosphor which eliminates the above-mentioned disadvantages, and in particular, to provide a phosphor excellent in voltage characteristics without practically changing the fluorescent color at all.

[Configuration of the invention]

(Means for solving the problems) formula to achieve this objective (Y, Gd) ₂ 0 ₂ by applying the red light emitting phosphor represented by the S / Eu, limit the content of the gadolinium 10~2000ppm Adopt a method to do.

(Operation) As described above, the host of the red light-emitting phosphor according to the present invention is a phosphor represented by (Y, Gd) ₂ O ₂ S / Eu in which part of yttrium (Y) is replaced by gadolinium (Gd). And the content of gadolinium was set to 10 to 2000 ppm.

That is, if the gadolinium content is less than 10 ppm, the increase in emission luminance with the applied voltage is insufficient compared to the phosphor containing no gadolinium, and conversely, the phosphor containing no gadolinium does not contain gadolinium at a content exceeding 2000 ppm. In comparison, an increase in emission luminance with an increase in applied voltage cannot be obtained as expected.

Therefore, the present invention is based on this fact.

FIG. 1 shows a voltage-luminance characteristic curve depending on whether or not a part of yttrium in the europium-activated yttrium oxysulfide phosphor is replaced with gadolinium. The vertical axis represents a relative value with the luminance at an applied voltage of 10 kV as 100, and the horizontal axis represents the applied voltage.

As is evident from this curve, it is obvious that there is a difference in the voltage-luminance characteristics depending on the presence or absence of a certain amount of gadolinium substitution.

On the other hand, in a current color picture tube, as a means for improving the contrast of an image, a pigment (eg, bengara, selenium sulfide) is used.
It has been confirmed that a phosphor coated with gadolinium) is used, and that the pigment does not affect the voltage-luminance characteristics.

In the production of this red light emitting phosphor, a certain amount of yttrium oxide, gadolinium oxide and europium oxide raw material may be mixed by physical means,
Since the mixing amount of gadolinium oxide is very small, the mixing by physical means deteriorates the uniformity, and further affects the characteristics of the product. Therefore, it is advisable to use a rare earth oxide obtained by once dissolving these raw materials in a nitric acid solution, adding oxalic acid and coprecipitating them as oxalates, extracting the raw materials, and firing them.

In forming the oxalate, 10 to 40 ppm of terbium may be added to help improve the emission luminance of the cathode ray tube (see Japanese Patent Publication No. 47-13243).

The rare-earth coprecipitated oxide thus obtained can be easily mixed with sulfur and a flux, fired and washed to produce a red light-emitting phosphor.

In this way, the voltage characteristics of the red light-emitting phosphor can be improved by manufacturing a part of the europium-activated sulfated yttrium phosphor by substituting the aforementioned amount of gadolinium.

In FIG. 2, the horizontal axis represents the amount of Gd added, and the vertical axis represents the luminance ratio (10 kV and 30 kV).
The ratio of the measured luminance value in kV, that is, the 30 kV luminance value / 10 kV luminance value) is shown, and it is clearly shown that the content of Gd is too large or too small, and the voltage characteristics are all deteriorated. The effect of the red light emitting phosphor according to the present invention is clear.

(Examples) (1) 999.9 g of yttrium oxide and 0 gadolinium oxide.
1 g and 61.5 g of europium oxide are added to a solution obtained by adding 720 cc of concentrated nitric acid to deionized water 3 and then heated to 70 to 90 ° C. to dissolve.

Meanwhile, 2.5 kg of oxalic acid heated to 70 ° C in deionized water 5
The mixture was gradually added to a solution containing yttrium, gadolinium and europium, and after completion of stirring, stirring was continued for another 30 minutes.Oxalate of yttrium, gadolinium and europium was formed and coprecipitated in this solution, Next, the solution containing coprecipitated oxalate
The precipitate is filtered by repeating the Decantaition and washing with deionized water having a pH of 5 or more.

This precipitate is dried at 130 ° C. for 12 hours, and then thermally decomposed at 900 ° C. for 3 hours to convert oxalate to an oxide. 100 g of the oxide thus obtained was mixed with 50 g of sulfur, 50 g of sodium carbonate and 8 g of potassium phosphate, and mixed well.
It is housed in a closed crucible and fired at 1150 ° C. for 6 hours. The sintered body is thoroughly washed with water and an acid, and then washed again with water, filtered and dried.

The phosphor obtained by this method obtained (Y, Gd) ₂ O ₂ S / Eu containing 100 ppm of gadolinium, and the emission luminance was improved by 11% as compared with the phosphor not containing gadolinium. It is a measurement result at an applied voltage of 30 kV.

(2) 999 g of yttrium oxide and 1 g of gadolinium oxide
Further, 61.5 g of europium oxide was treated in exactly the same manner as in Example 1 to obtain a (Y, Gd) ₂ O ₂ S / Eu phosphor, and the emission luminance at an applied voltage of 300 kV was lower than that of a cadmium-less phosphor. It improved to 7.7%. The content of gadolinium is 1000 ppm.

(3) 999 g of yttrium oxide, 2 g of gadolinium oxide and 61.5 g of europium oxide were treated in the same manner as in Example 1 to contain 2000 ppm of gadolinium (Y, G
d) to produce a ₂ O ₂ S / Eu, the emission luminance at an applied voltage 30kV compared with the phosphor of gadolinium less was improved 3.3%.

(4) 999 g yttrium oxide, 0.01 gadolinium oxide
g and europium oxide (61.5 g) were treated in exactly the same manner as in the above example to give (Y, Gd) ₂ O ₂ S with gadolinium content of 10 ppm.
/ Eu was manufactured, and the emission luminance at an applied voltage of 30 kV was improved by 5% as compared with the gadolinium-less phosphor.

(5) 999 g of yttrium oxide, 61.5 g of gallium oxide, 61.5 g of europium oxide and 0.02 g of terbium oxide were treated in the same manner as in Example 1 to obtain 100 pp of gadolinium.
m, (Y, Gd) ₂ O ₂ S / Eu containing terbium 20 ppm,
The emission luminance was improved by 11% compared to the gadolinium-less phosphor. This value is a measured value at an applied voltage of 30 kV.

It has been confirmed that the same effect can be obtained even when the content of terbium is 10, 30, or 40 ppm.

As described above, the phosphor according to the present invention contains a small amount of Gd, and as a result, focuses on the fact that the luminance increases with a change in the applied voltage, and a predetermined red color tone is obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a curve diagram showing voltage luminance characteristics of europium-activated yttrium oxysulfide with and without gadolinium, and FIG. 2 is a 30 kV luminance value / 10 kV luminance value of the europium-activated yttrium oxysulfide phosphor. FIG. 4 is a curve diagram showing the vertical axis and the horizontal axis for the amount of Gd added.

Claims (1)

(57) [Claims] 1. A phosphor represented by the general formula (Y, Gd) ₂ O ₂ S / Eu, wherein the phosphor contains gadolinium (Gd) in an amount of 10 to 2000 ppm.