JPH069957A - Blue-emitting phosphor - Google Patents

Abstract

PURPOSE:To obtain the title phosphor having a good color purity and a high luminescent intensity by giving thereto a structure in which thulium is used as an activator and a specified tantalate is used as a matrix. CONSTITUTION:The phosphor is represented by the formula: (La1-xTmx)Ta7O19 wherein x is 1X10<-2> or greater and is desirably in the range: 5X10<-2=x<=5X10<-1>. By adopting the above matrix composition, a blue-emitting phosphor activated by highly concentrated thulium can be realized, and is desirably used in electron tubes, lamps and sensitized papers. This phosphor can be obtained by weighing out a specified amount of an La compound such as lanthanum oxide or lantham carbonate, a specified amount of a Tm compound such as thulium oxide or thulium carbonate and a specified amount of a Ta compound such as tantalum pentaoxide or tantalum chloride, mixing these compounds with a flux such as ammonium chloride, packing the resulting mixture into a heat-resistant container such as a crucible, firing the mixture in air or a neutral atmosphere, grinding, water-washing and drying the fired product, and sieving the dried product.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to electron beams, ultraviolet rays and X-rays.
The present invention relates to a thulium-activated lanthanum tantalate phosphor that emits blue light when excited by a line.

[0002]

2. Description of the Related Art Thulium (Tm ³⁺ ) and cerium (C
Since phosphors using e ³⁺ ) as an activator generally emit blue light with good color purity, various studies have been conducted. Especially T
As a phosphor that is being put into practical use as an m-activated phosphor, for example, a thulium-activated yttrium aluminate phosphor (YAlO ₃ : Tm) is known. However, although the YAlO ₃ : Tm phosphor exhibits good color purity, it is insufficient in terms of brightness, and therefore a phosphor with higher brightness has been demanded.

[0003]

Therefore, the inventors of the present invention have conducted research to obtain a high-luminance phosphor that is a blue light-emitting phosphor that has Tm as an activator and has good color purity. It has been found that when the activity is increased, the emission intensity should originally be increased, but the concentration quenching phenomenon occurs due to the structure of the phosphor matrix, and the emission intensity is not increased.

That is, in order to improve the emission intensity of the Tm-activated phosphor, it is important to consider how the concentration quenching does not start even if a large amount of Tm is incorporated into the matrix as an emission center. is there. This is the cause of concentration quenching. Cross relaxation by resonance transfer 2. It is necessary to consider energy migration to non-radiative centers due to resonance transfer. Since the resonance transfer is proportional to R ⁻ⁿ of the distance R between Tm ions, the distance between sites where Tm ions are replaced is required to be long in the mother body in order to suppress the resonance transfer. However, it is considered difficult to determine the distance between sites in the matrix itself such that resonance transfer between Tm ions does not occur, or to replace Tm ions with such a distance at equal intervals. Then, the next issue is how to suppress the energy migration to the non-radiative center due to resonance transmission. The larger the “volume of the space in the crystal in which the excitation energy can be transferred within a certain period of time” due to energy migration, the greater the chance of meeting non-radiative centers such as defects. At this time, if the Tm ions, which are the luminescence centers, are arranged in a lower dimension (one-dimensional or two-dimensional) in the crystal, the probability that the excitation energy visits the same lattice point increases, so that the “movable volume” is small. Therefore, the migration of the excitation energy to the non-radiative centers is suppressed.

From the above points, in the case of an oxide, what is considered to be suitable as a matrix of a phosphor having Tm as an activator is that the sites where the Tm ions, which are the emission centers, are substituted. It is a compound having a crystal structure such that it is separated by a cluster formed by other cations and oxygen ions, and is arranged in a low dimension. As such a compound, borate, phosphate, etc. are generally considered,
The inventors of the present invention have determined that a specific tantalate salt, which is considered to be excellent in high-temperature stability, chemical stability, etc., is the most suitable as a base material, and has Tm with good emission intensity and color purity as an activator. The present invention is intended to provide a tantalate blue phosphor.

[0006]

The present invention has the general formula (La
_1-XTm_x) Ta₇O₁₉And x in the formula is 1 × 10
^-2It is a blue light emitting phosphor characterized by the above.
The novel phosphor of the present invention is capable of exciting electron rays, ultraviolet rays and X-rays.
It emits blue light when it starts. The phosphor of the present invention is as follows.
Can be synthesized.

As the phosphor raw material, 1) lanthanum compounds such as lanthanum oxide, lanthanum oxalate and lanthanum carbonate. 2) Thulium compounds such as thulium oxide, thulium oxalate, and thulium carbonate 3) Weigh a predetermined amount of tantalum compounds such as tantalum pentoxide and tantalum chloride, add a flux of ammonium chloride, ammonium fluoride, etc., and mix the raw material mixture sufficiently. Wet or dry mix. The lanthanum and the rare earth thulium may be mixed by coprecipitation.

This mixture is filled in a heat-resistant container such as a crucible and fired once or more at 800 to 1600 ° C. in air or a neutral atmosphere for 1 to 12 hours. The final firing is always 1
The temperature is 100 ° C or higher. This fired product is crushed, washed with water, dried,
By performing sieving, the blue light emitting tantalate phosphor of the present invention can be obtained.

[0009]

FIG. 1 shows (La of the present invention._1-xTm_x) Ta₇O
₁₉Well-known (Y) _1-xTm_x) AlO₃firefly
When the light body (marked with Δ) is excited by ultraviolet rays (365 nm)
It is a figure which shows the relationship between emission intensity and Tm density | concentration (x). Figure
As is clear from No. 1, in the phosphor of the present invention, x is 1 × 10.^-2Since
The above shows significant emission intensity, and x is 5 × 10.^-2more than
Well known (Y_1-xTm_x) AlO₃Emitted compared to phosphor
The light intensity is high. Especially, the upper limit of x is 1 × 10^-1, More preferred
3 × 10^-1Is. In addition, a part of La can
It may be replaced with a group such as Y, Gd, Lu and the like.

FIG. 2 shows the emission spectrum of the (La _0.9 Tm _0.1 ) Ta ₇ O _{1 9} phosphor of the present invention under the excitation of 365 nm ultraviolet light. The emission showed a blue emission spectrum having a good color purity peculiar to Tm ion having a peak at 456 nm.

[0011]

[Example] (Example)

[0012]

Table 1 Table 1 La ₂ O ₃ 2.6 g (0.008 mol) Tm ₂ O ₃ 0.77 g (0.002 mol) Ta ₂ O ₅ 30.9 g (0.07 mol) NH ₄ Cl 0. 3 g (0.006 mol)

The above raw materials were thoroughly mixed in a nitric acid solution, evaporated to dryness, and then calcined in air at 400 ° C. for 3 hours. After pulverizing the obtained fired product, it is further fired at 1200 ° C. for 4 hours,
The phosphor was obtained by crushing, washing with water, drying and sieving. The composition of this phosphor is (La _0.8 Tm _0.2 ) Ta ₇ O ₁₉ ,
The emission spectrum shown in FIG. 1 was obtained under the excitation of ultraviolet rays of 365 nm.

[0014]

EFFECTS OF THE INVENTION The present invention makes it possible to provide a bright blue phosphor having a high Tm concentration by adopting the above-mentioned base composition, which is suitable for electron tubes, lamps and intensifying screens. was gotten.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between Tm concentration (x) and emission intensity.

FIG. 2 is a graph showing an emission spectrum of a (La _0.8 Tm _0.2 ) Ta ₇ O ₁₉ phosphor.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Shimada Aoba, Aoba-ku, Sendai-shi, Miyagi Aoba Aoba Tohoku University Faculty of Engineering

Claims (2)

[Claims] 1. A general formula is represented by _{(La 1-X Tm x)} Ta 7 O 19, a blue-emitting phosphor, wherein the x in the formula is 1 × 10 ^-2 or more. 2. The blue light-emitting phosphor according to claim 1, wherein x is in the range of 5 × 10 ⁻² ≦ x ≦ 5 × 10 ⁻¹ .