JPH09279139A - Infrared excitable and stimulable fluorescent substance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an infrared excitable and stimulable fluorescent substance, comprising a mixture of alkaline earth sulfides as a matrix and bismuth, etc., as activators, capable of emitting a fluorescence consisting essentially of a blue to a green regions, excellent in visibility even in the light and useful as an infrared ray detector, etc. SOLUTION: This infrared excitable and stimulable fluorescent substance comprises a mixture of alkaline earth sulfides such as the one of magnesium sulfide with strontium sulfide as a matrix and bismuth and samarium as activators in an amount of respective 10<-5> to 10<-3> mol based on 1 mol mixture of the sulfides and is capable of emitting fluorescence consisting essentially of a blue to a green regions with infrared exciting light. Furthermore, the content of the magnesium is preferably 70-30mol% and that of the strontium is preferably 30-70mol% in the alkaline earth sulfides.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an infrared excitation stimulable phosphor. More specifically, the invention relates to a stimulated phosphor that emits blue to green stimulated emission with excellent visibility when irradiated with near-infrared light and is particularly useful as a fluorescent base material used in an infrared light detector or the like.

[0002]

2. Description of the Related Art A stimulated phosphor stores light energy in advance in the phosphor (preliminary excitation), and then emits the stored energy by irradiation with near infrared light or visible light to emit visible light.
It has a property of (stimulated luminescence). It is used in infrared light detectors and the like by utilizing the property of converting infrared light, which cannot be visually recognized by the naked eye, into visible light, and is used for infrared light leakage and optical axis adjustment of optical fibers.

A sulfide phosphor is used as such a stimulable phosphor.
(ZnS, CaS) is widely known, but as an example, calcium sulfide is used as a matrix, and samarium (Sm) and europium (Er) are added as activators to the matrix (Jpn.J. .Appl.Phys., 32, 3187 (1993)). However, since the emission color of this phosphor is mainly orange, there is a problem that visibility is poor in a bright place, and it is difficult to determine the presence or absence of light emission.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in conventional infrared-excited stimulable phosphors, and produces bright fluorescent light mainly in the blue to green region, which is highly visible even in a bright place. An exhaust phosphor is provided.

That is, according to the present invention, there is provided a stimulable phosphor having the following constitution. (1) Infrared-excited photostimulation characterized in that a mixture of alkaline earth sulfides is used as a matrix, bismuth and samarium are included as activators, and that fluorescence from blue to green is mainly generated by infrared excitation light. Phosphor. (2) The stimulated phosphor according to the above (1), wherein the contents of bismuth and samarium are each 10 ⁻⁵ to 10 ⁻³ mol with respect to 1 mol of the sulfide mixture.

The above-described stimulated phosphor of the present invention includes an embodiment in which the following mixed sulfide is used as a matrix. (3) Mixture of magnesium sulfide and strontium sulfide
The stimulable phosphor according to (1) or (2) above, which has (Mg _x Sr _1-x S) as a matrix. (4) In the above sulfide, 70 to 30 mol% of magnesium and 30 to 70 mol% of strontium are contained (3)
The stimulated phosphor described in 1.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically. A mixture of alkaline earth metal sulfides is used for the matrix of the stimulable phosphor of the present invention. Specifically, the general formula Mg _x S in which sulfides of magnesium and strontium coexist.
A mixture represented by r _1-x S is used. By using this mixed sulfide as a base material and containing bismuth and samarium as an activator, a stimulated phosphor that emits fluorescence mainly in the blue to green wavelength region having high emission intensity and high visibility can be obtained.

[0008] As shown in the comparative sample described later, those having calcium sulfide, magnesium sulfide, or strontium sulfide as the sole matrix produce purple or green fluorescence by infrared light (about 1300 nm). The strength is weak and cannot be put to practical use. In addition, even if it is a combination of alkaline earth metal sulfides, those that have a combination of magnesium and strontium, calcium and strontium as a matrix, as well as those that have a single sulfide as a matrix, infrared light (About 1300 nm) produces purple or green fluorescence, but this emission intensity is weak and is not practical. From these results, the preferred alkaline earth metal combination is magnesium and strontium.

In the above phosphor having a mixture of magnesium sulfide and strontium sulfide (Mg _x Sr _1-x S) as a matrix,
A preferred quantitative ratio is 70 to 30 mol% magnesium and 30 to 70 mol% strontium, that is, Mg _x S.
In r _1-x S, x is in the range of 0.3 ≦ x ≦ 0.7. When the molar ratio (x) of magnesium is in the range of 0.7 to 0.5, highly visible green fluorescence is produced, and when the molar ratio is in the range of 0.5 to 0.3, visibility is similarly good. It produces a blue-green fluorescence. It should be noted that when the molar ratio of magnesium exceeds 0.7, yellow-green fluorescent light is obtained, and when the molar ratio of magnesium is less than 0.3, blue fluorescent light is obtained, and thus visibility is reduced,
The emission intensity also decreases.

The sulfide phosphor contains two kinds of activators, bismuth (Bi) and samarium (Sm). With bismuth alone and samarium alone, the emission intensity is weak and the desired sufficient fluorescence cannot be obtained. The addition amount of each of these is 10 ^-5 to 10 ^-3 mol with respect to 1 mol of the sulfide matrix. If the addition amount is less than this, there is no luminous property and almost no stimulable fluorescence is exhibited. If the amount added exceeds the above range, concentration quenching occurs. It is preferable to use bismuth and samarium in the same amount.

The stimulable phosphor of the present invention can be obtained by an ordinary manufacturing method. Specifically, for example, a commercially available alkaline earth carbonate or the like is used as a raw material, and bismuth such as bismuth sulfate and a samarium source such as samarium oxide, samarium carbonate, or samarium acetate are added to the raw material, and a mixture of NaCO ₃ and sulfur is added. It can be obtained by heating and melting at 900 to 1100 ° C. in a reducing atmosphere.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention are shown below together with comparative examples. It should be noted that these are examples and do not limit the scope of the present invention.

Example 1 Commercially available magnesium carbonate in the amount ratio shown in Table 1,
Calcium carbonate and strontium carbonate are blended, bismuth sulfate and samarium acetate are added to give the dope amount to be displayed, and the mixture is heated and melted at 1000 ° C. in a hydrogen sulfide atmosphere to give calcium and strontium, magnesium and strontium, A sulfide phosphor having a mixed sulfide matrix in which magnesium and calcium coexist was used as a matrix.

After pre-exciting these phosphors, their fluorescent color and emission intensity were examined using infrared light (1300 nm) as an excitation source. The results are summarized in Table 1. For comparison, magnesium sulfide (MgS), strontium sulfide (Sr
The fluorescent color and the emission intensity were similarly examined for the phosphors having S) and calcium sulfide (CaS) alone as the matrix. The result is shown in comparison with Table 1.

As shown in Table 1, the phosphor having MgS and CaS alone as a base material produces purple fluorescence with low visibility and has a weak emission intensity. Further, a phosphor having SrS alone as a base emits green fluorescence, but its emission intensity is extremely weak and is not practical. Note that the phosphors based on calcium sulfide and magnesium sulfide, and the phosphors based on calcium sulfide and strontium sulfide are both stronger than the phosphors based on single sulfide, but still not practically strong. There is a shortage. On the other hand, any of the phosphors of the present invention, which has a mixture of magnesium and strontium sulfide as a base material, can obtain blue-green to green fluorescence and has a high emission intensity.

Example 2 The sample of Example 1 (Mg _0.7 Sr _0.3 S: Bi, Sm) was pre-excited and then excited with infrared laser light having a wavelength of 1300 nm, and its emission spectrum was examined. The result is shown in FIG. As shown in the figure, although a fluorescence peak partially occurs at 565 to 570 nm, it was confirmed that the main fluorescence wavelength is around 480 nm (blue region).

[0017]

[Table 1]

[0018]

The stimulable phosphor of the present invention emits green to blue-green fluorescence with excellent visibility when excited by infrared light. Therefore, when the phosphor of the present invention is used as a phosphor matrix of an infrared light detector, a detector with good visibility in a bright place can be obtained. Currently used as a wavelength for optical communication 1300
Since it exhibits good stimulated fluorescence for infrared light of wavelength nm and infrared light of wavelength 780 nm used in FA equipment, it is necessary to check the leakage of infrared light in the optical fiber, align the optical axis of FA equipment, etc. Useful for.

[Brief description of drawings]

FIG. 1 is an emission spectrum diagram of the phosphor of the present invention.

Claims (4)

[Claims] 1. A mixture of alkaline earth sulfides is used as a matrix, and bismuth and samarium are included as activators.
An infrared-excited stimulable phosphor, which emits fluorescence mainly in the blue to green region by infrared excitation light. 2. The stimulated phosphor according to claim 1, wherein the contents of bismuth and samarium are 10 ⁻⁵ to 10 ⁻³ mol, respectively, relative to 1 mol of the mixture of sulfides. 3. The photostimulable phosphor according to claim 1, which comprises a mixture of magnesium sulfide and strontium sulfide (Mg _x Sr _1-x S) as a matrix. 4. The magnesium sulfide in the above sulfide
The stimulable phosphor according to claim 3, wherein the stimulable phosphor is -30 mol% and strontium 30-70 mol%.