JPH0132873B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement in a method for manufacturing a europium-activated yttrium oxide phosphor. (Technical background of the invention and its problems) Y ₂ O ₃ :Eu phosphor, Gd ₂ O ₃ :Eu phosphor, La ₂ O ₃ :Eu phosphor as a red-emitting rare earth oxide phosphor activated with europium Known examples include (Y, Gd) ₂ O ₃ :Eu phosphor, (Y, La) ₂ O ₃ :Eu phosphor, and the like. Among these, europium-activated yttrium oxide phosphor Y ₂ O ₃ :Eu is used because its main component, yttrium, is inexpensive and its phosphor properties such as brightness and emission color when excited by electron beams and ultraviolet rays are excellent. It has been used as a red-emitting phosphor in cathode ray tubes for color televisions, and as a red-emitting phosphor in deluxe fluorescent lamps with improved color rendering for lighting. Europium-activated yttrium oxide phosphor consists of yttrium oxide (Y ₂ O ₃ ) or yttrium compounds that easily convert into yttrium oxide at high temperatures, such as carbonates and nitrates, and europium oxide (Eu ₂ O ₃ ),
Alternatively, it can be obtained by mixing europium compounds such as carbonates and nitrates that easily convert into europium oxide at high temperatures using a physical method such as a ball mill, and then firing this raw material mixture in air. It can also be obtained by chemically mixing these various raw materials in order to uniformly disperse europium, which is an activator, and improve luminous efficiency. That is, predetermined amounts of yttrium oxide and europium oxide are dissolved in hydrochloric acid or nitric acid, oxalic acid or an aqueous dimethyl oxalate solution is added to this solution to produce a coprecipitated oxalate precipitate of yttrium and europium, and then this coprecipitated oxalate is added. After the salt precipitate is filtered and dried, it is thermally decomposed in the air at a temperature of 800 to 1100°C to form a mixed rare earth oxide, and this raw material mixture is further calcined in the air at a temperature of 1200 to 1500°C to produce a mixed rare earth. A phosphor having the same composition as the oxide can be obtained. The composition of this rare earth oxide phosphor is (Y _1-x ,
Eu _x ) ₂ O ₃ (however, 10 ^-3 ≦x≦2× ^{10 -1 )} is preferable;
If it is less than 10 ⁻³ , the luminance of the obtained phosphor will be significantly lowered, which is not preferable. In recent years, improving the brightness of cathode ray tubes and fluorescent lamps for illumination has been a major challenge in the industry, and for this reason, it is desired to improve the brightness of phosphors. (Objective of the Invention) In order to satisfy the above-mentioned requirements, the present invention provides an improved manufacturing method for obtaining a europium-activated yttrium oxide phosphor with improved brightness characteristics through electron beam excitation and ultraviolet excitation. With the goal. (Summary of the Invention) As a result of repeated research using various fluxing agents, the present inventors have developed a europium-activated yttrium oxide phosphor that has high luminous efficiency under electron beam and ultraviolet excitation. It was discovered that the object could be achieved by adding a small amount of barium borate as an agent and firing, and this invention was completed. That is, the present invention provides a method for manufacturing a europium-activated yttrium oxide phosphor by firing a raw material mixture, wherein the raw material mixture contains barium borate. It's a method. The eurobium-activated yttrium oxide phosphor obtained by this invention not only improves the luminous efficiency by 1 to 8% under electron beam excitation and 0.5 to 3% ultraviolet excitation, but also improves the luminous efficiency by 1 to 8% under _ultraviolet excitation. Even when the concentration of ₃ ) is lowered, the luminous efficiency remains very high. The amount of barium borate contained in the raw material mixture is preferably 0.001 to 0.5% by weight of the raw material mixture as boron oxide (B ₂ O ₃ ).
More preferably 0.005 to 0.08% by weight. When the amount of barium borate is less than 0.001% by weight as boron oxide (B ₂ O ₃ ), no brightness improvement effect is observed, and when the amount of barium borate exceeds 0.5% by weight as boron oxide (B ₂ O ₃ ), the luminous efficiency decreases. This is not preferable because it not only lowers the temperature, but also causes sintering to become very hard. (Examples of the Invention) The present invention will be described in detail below based on Examples. Example 1 Weigh out 9.5 moles of yttrium oxide (Y ₂ O ₃ ) and 0.5 moles of europium oxide (Eu ₂ O ₃ ) and prepare a nitric acid solution.
20 and stir thoroughly to dissolve completely. Next, 13 moles of oxalic acid are added to produce coprecipitated oxalate of yztrium and europium. The coprecipitated oxalate is thoroughly washed with pure water, filtered and dried, and then thermally decomposed in air at a temperature of 900°C to obtain a mixed rare earth oxide of yttrium and europium. As a result of quantitative analysis of yttrium and europium in this mixed rare earth oxide, it was confirmed that the composition was (Y _0.95 , Eu _0.05 ) ₂ O ₃ . Next, prepare 10 weighed 200 grams each of this mixed rare earth oxide of yttrium and europium, add 0.0005 as boron oxide (B ₂ O ₃ ),
0.001, 0.005, 0.01, 0.03, 0.05, 0.08, 0.1, 0.5,
Barium tetraborate (BaB ₄ O ₇ ) in amounts of 1.0, 1.5 and 1.5% by weight are weighed and added, and each is thoroughly mixed in a pole mill. This mixture was poured into 10 quartz crucibles with lids and placed in the air.
Bake at a temperature of 1300℃ for 5 hours. On the other hand, as a comparison product, 200 g of the mixed rare earth oxide of yttrium and europium without barium tetraborate was placed in a quartz crucible with a lid, and the same was calcined in air at a temperature of 1300° C. for 5 hours. Each of the 11 baked products was crushed in a mortar, passed through 100 meshes, and thoroughly washed with warm water.
After filtering and drying and passing through 100 meshes, UV rays are applied.
The relative luminescence brightness with 254 nm excitation and the relative luminance with electron beam anode voltage 6KV excitation were evaluated and compared. The results are shown in Table 1.

【table】

[Table] As can be seen from Table 1, the excitation brightness of ultraviolet rays at 254 nm is % by weight as B ₂ O ₃ for the comparative product.
However, adding 0.0005% by weight has no effect, but adding 0.001% by weight has no effect.
An improvement in brightness of 1 to 8% is observed with addition of ~0.5% by weight. The content of barium borate is more preferably within the range of 0.005 to 0.08% of the raw material mixture as boron oxide (B ₂ O ₃ ) in terms of luminance and sinterability. Addition of 0.03% by weight showed the highest improvement of 8%. However, when the amount added was 1.0% by weight or more, the brightness was lower than that of the comparative product and at the same time, it was sintered very hard. On the other hand, the electron beam 6KV excitation brightness is
Addition of less than 0.001 wt% as B ₂ O ₃ has no effect, but 0.05 to 0.5 wt% improves brightness by 0.5 to 3%, and 0.03 wt% improves brightness by 3%.
% improvement. However, when the amount added was 1.0% by weight or more, the brightness decreased as did the ultraviolet 254 nm excitation brightness. Moreover, these results are shown in FIG. As can be seen from FIG. 1, excellent effects are also shown in ultraviolet and electron beam excitation. Example 2 In order to confirm the effect of the phosphor of the present invention when the concentration of europium oxide (Eu ₂ O ₃ ), which is an activator, was changed, (Y _0.95 , Eu _0.05 ) ₂ O ₃ , (Y _0.96 , Eu _0.04 ) ₂ O ₃ , (Y _0.9
65 ,
Three types of mixed rare earth oxides having a composition of Eu _0.035 ) ₂ O ₃ were obtained. Next, barium tetraborate (BaB ₄ O ₇ ) in an amount of 0.03% by weight as boron oxide (B ₂ O ₃ ) was weighed to 500 grams each of the mixed rare earth oxides of yttrium and europium. After thoroughly mixing in a ball mill, the mixture is poured into a quartz crucible with a lid. On the other hand, as a comparative product, 500 grams of each of three types of mixed rare earth oxides without barium tetraborate were put into a quartz crucible with a lid, and both were simultaneously heated in air at a temperature of 1300℃ for 5 hours. Fire. Further, each of the fired products is crushed in a mortar and passed through 100 meshes, thoroughly washed with warm water, filtered and dried, and passed through 100 meshes. Regarding the europium-activated yttrium oxide phosphor of the present invention obtained above and the comparative phosphor, the relative luminance by ultraviolet 254 nm excitation and the relative luminance by electron beam anode voltage 6 KV excitation were evaluated and compared in the same manner as in Example 1. Table 2 shows the results of the quantitative analysis of barium Ba and boron B in the europium-activated yttrium oxide phosphor of the present invention.

[Table] As can be seen from Table 2, the phosphor of the present invention has a luminance of 8.0 to 9.3% compared to the comparative product even when the concentration of europium oxide (Eu ₂ O ₃ ) used as an activator is changed. Brightness improvement: 2.4-3.0% brightness improvement was obtained with 6KV electron beam excitation brightness. especially UV rays
At 254nm excitation brightness, the amount of very expensive europium oxide (Eu ₂ O ₃ ) is 0.05 to 0.035 mol.
Europium oxide 0.05 even when reduced by 30%
The luminance of the phosphor of the present invention was improved by 2% compared to the comparative product in terms of moles, and it was found that the phosphor is a europium-activated yttrium oxide phosphor with excellent luminous efficiency. In addition, barium Ba in the phosphor of the present invention,
Quantitative analysis of boron B confirmed that it contained 200 ppm or less and 100 ppm or less, respectively.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between the luminance of the phosphor of the present invention when excited by ultraviolet rays and electron beams and the amount of B ₂ O ₃ added.

Claims (1)

[Claims] 1. In a method of producing a europium-activated yttrium oxide phosphor by firing a raw material mixture, the raw material mixture contains barium borate, and the content of barium borate is 0.005% as boron oxide (B ₂ O ₃ ) in the raw material mixture. A method for producing a europium-activated yttrium oxide phosphor, characterized in that the europium-activated yttrium oxide phosphor is in the range of ~0.08% by weight.