JPH08217487A - Wavelength-changing glass material - Google Patents

Abstract

PURPOSE: To obtain a readily producible wavelength-changing glass material having excellent conversion ratio and handleability by adding holmium chloride to a chloride glass base material comprising specific compounds as a glass forming agent and a glass forming auxiliary. CONSTITUTION: This wavelength-changing glass material is obtained by adding holmium chloride to a chloride glass base material comprising gadolinium chloride as a glass forming agent and an alkaline earth metal chloride as a glass forming auxiliary. The amount of gadolinium chloride required is an amount as a main component of the glass parent material and is at least about 40mol%, usually >=50mol% based on the whole composition of the glass material. Barium chloride, strontium chloride or calcium chloride is preferable as the alkaline earth metal chloride. Since the wavelength-changing glass material is a glass material, it is produced easier than that of crystal and is readily processed into products of various shapes such as fiber.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength conversion material which converts infrared light and red light into visible light having a shorter wavelength.
More specifically, the present invention relates to a wavelength conversion glass material that has excellent conversion efficiency and handleability, is easy to manufacture, and can be widely applied as a material for a phosphor for display, an infrared light detector, an up-conversion laser, and the like.

[0002]

2. Description of the Related Art Generally, in fluorescence emission, the emitted light has a longer wavelength than the incident light (excitation light), but some rare earth ion-containing substances emit light of a shorter wavelength than the excitation light by up-conversion. Some exhibit fluorescence.
This is because the electrons of the rare earth ions are excited by two-step absorption of photons or the like. For example, a phosphor that emits visible light using infrared light as excitation light is known,
In addition to being used as a material for identifying the optical path of infrared light that is invisible to the naked eye, it is expected to be used as a compact visible light laser light source in combination with a phosphor for display or a semiconductor laser in the infrared or red region. ing.

In particular, recently, an up-conversion material that emits light of a shorter wavelength has been sought in response to higher density of optical storage, and a phosphor that emits blue light by using infrared light or red light as excitation light has been demanded. Consideration is in progress. For example,
Blue laser oscillation due to up-conversion has been observed in a YLiF ₄ crystal doped with Tm ³⁺ .
(Applied Optics, 28,17, 3553-3555, 1989). But,
Crystals are difficult to form into arbitrary shapes such as fibers, and it is often difficult to produce large single crystals.
In addition, the crystal has a high symmetry of the ligand field, so the luminescence transition probability is low, and the absorption width is narrow. Therefore, when excited by a laser such as a semiconductor laser in which the wavelength of the excitation light is likely to change, absorption occurs. There is a problem that the fluctuation of efficiency is large.

Therefore, in recent years, amorphous, that is, glassy phosphors have been proposed. Phosphors made of transparent glass materials are (i) easier to make materials with less loss and scattering when generating visible light than crystals, (ii) can be molded into any shape such as fiber, (iii) excitation Since the fluctuation of the absorption efficiency due to the fluctuation of the wavelength of light is small, there is an advantage that a relatively stable output can be obtained even when a semiconductor laser whose output wavelength is apt to change due to the influence of temperature or current is used as the excitation light. . As this kind of glass phosphor, a phosphor in which zirconium fluoride glass is doped with Ho ³⁺ is known, and there is a reported example of green laser oscillation at room temperature.
(Electron. Lett., 26 , 261-263, 1990), or a phosphor obtained by doping a fluoride glass with Ho ³⁺ and further adding Yb ³⁺ as a sensitizer (JP-A-6-219777). Has been. In addition, ZBLAN (glass containing zirconium fluoride as a main component from each fluoride of Zr, Ba, La, Al and Na) is doped with Tm ³⁺ , or Eu ³⁺ is further added as a sensitizer. Phosphors have been proposed (for example, S.
G. Grubb et al., Electron. Lett., 28, 1243, 1992).

However, in consideration of application to visible light laser oscillation, the above glass material is insufficient in wavelength conversion efficiency from excitation light to upconversion fluorescence. That is, in the fluoride glass, the maximum energy of lattice vibration is as large as 400 to 500 cm ⁻¹ even in the above ZBLAN, but generally, when the lattice vibration energy is large, there is a problem that the multiphonon relaxation time becomes short (JP van der Ziel et.
al. J. Appln. Phys. 60, (1986) 4262-67). That is,
The electrons of the light-emitting source ion are excited by receiving excitation energy directly or through the sensitizer, but when the lattice vibration energy is large, the average residence time at the excitation level is short, and therefore the excitation is further increased. A two-step excitation process in which energy is absorbed and excited to a higher energy level is less likely to occur, and up-conversion efficiency decreases.

[0006]

The present invention solves the above problems in up-conversion glass useful as a wavelength conversion material, is easy to vitrify, has a high emission intensity, and excites semiconductor laser light in the infrared or red wavelength region. An object of the present invention is to provide a wavelength conversion glass material that emits green or blue light with a strength and stability that can withstand practical use as light.

[0007]

The present invention uses chloride glass as a base material in place of conventionally known fluoride glass, and uses gadolinium chloride (Gd chloride), which does not vitrify alone, as a glass base material. Holmium (H
o) A wavelength conversion glass material having a strong blue emission intensity is achieved by containing ions. Since Gd chloride alone does not vitrify by itself, conventionally, a chloride glass having Gd chloride as a base material has not been known, but the present inventors have added an alkaline earth chloride to Gd chloride as a glass forming aid. It was found that a chloride glass can be obtained by this method (Japanese Patent Application No. 6-95477). The present invention is based on the above findings, and by containing Ho ions as an emission center in this Gd-alkaline earth chloride-based glass, infrared light or red light is used as excitation light to emit green or blue light having strong emission intensity. A chloride glass material that gives rise to is obtained.

That is, according to the present invention, there is provided a wavelength conversion glass material having the following constitution. (1) A wavelength conversion glass material obtained by containing holmium chloride in a chloride glass base material using gadolinium chloride as a glass forming agent and alkaline earth chloride as a glass forming aid. (2) The wavelength conversion glass material according to (1) above, wherein the glass forming aid is one or a combination of two or more of barium chloride, strontium chloride and calcium chloride. (3) 35-93 mol% gadolinium chloride, 6-49 mol% barium chloride and 0.01-33 holmium chloride
The wavelength conversion glass material of (2) above, which is composed of mol%. (4) Gadolinium chloride 48 to 83 mol%, strontium chloride 15 to 47 mol% and holmium chloride 0.0
The wavelength conversion glass material according to (2) above, which comprises 1 to 20 mol%. (5) Gadolinium chloride 51-82 mol%, calcium chloride 16-47 mol% and holmium chloride 0.01-
The wavelength conversion glass material according to (2) above, which comprises 18 mol%. (6) Gadolinium chloride 35 to 90 mol%, barium chloride 1 to 48 mol%, strontium chloride 1 to 46 mol%
And 0.01 to 28 mol% of holmium chloride,
The total amount of barium chloride and strontium chloride is 6 to 49
The wavelength conversion glass material of (2) above, which is in mol%. (7) Gadolinium chloride 40 to 90 mol%, barium chloride 1 to 48 mol%, calcium chloride 1 to 46 mol%, and holmium chloride 0.01 to 28 mol%, and the total amount of barium chloride and calcium chloride is 6 ~ 49 mol%
The wavelength conversion glass material according to (2) above. (8) Gadolinium chloride 50 to 83 mol%, strontium chloride 1 to 46 mol%, calcium chloride 1 to 46 mol% and holmium chloride 0.01 to 20 mol%, and the total amount of strontium chloride and calcium chloride is 1
The wavelength conversion glass material according to the above (2), which is 5 to 47 mol%. (9) gadolinium chloride 35 to 91 mol%, barium chloride 1 to 47 mol%, strontium chloride 1 to 46 mol%, calcium chloride 1 to 46 mol% and holmium chloride 0.01 to 30 mol%, and barium chloride The wavelength conversion glass material according to the above (2), wherein the total amount of strontium chloride and calcium chloride is 7 to 49 mol%.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the glass material of the present invention, gadolinium chloride (GdCl ₃ ) is used as the glass forming agent. Gd chloride is required as the main component of the glass base material,
It accounts for at least about 40 mol% and usually at least 50 mol% of the total composition of the glass material. Since chloride glass has a lower multiphonon relaxation rate than fluoride glass, high conversion efficiency is realized in visible light conversion. A typical example of the conventionally known chloride glass is zinc chloride (ZnCl).
_{Although 2} ) is used as a glass base material, the glass having ZnCl ₂ as a base material has a practical difficulty in that it has a remarkable deliquescent property. The glass material of the present invention containing Gd chloride as a base material does not have such a defect.

As described above, Gd chloride does not vitrify alone, but as the present inventors have made clear in Japanese Patent Application No. 6-95477, a certain amount of alkaline earth chloride is added to glass together with Gd chloride. Gd chloride can be vitrified by using it together as a forming aid. As the alkaline earth chloride used in combination, Ba chloride, Sr chloride, and Ca chloride are preferable. You may use these 2 or more types together. If two or more of these are used, a more stable glass material can be obtained. Ba chloride is commonly used as a glass forming aid in ZnCl ₂ type glass and the like, but Ba chloride itself does not vitrify, and an example of combined use with Gd chloride has not heretofore been known. A glass material composed of Gd chloride and Ba chloride was first proposed by the present inventors (the above-mentioned Japanese Patent Application No. 6-95477).
issue). Sr chloride is conventionally used as a glass forming aid, but an example of using it together with Gd chloride is not known. The same applies to Ca chloride. Of these glass forming aids, BaCl ₂ is most preferable because it provides a stable glass material having the highest glass transition point.

Ho ions are contained in the above glass material as a luminescent center. Ho ions emit blue light (wavelength approximately 410 to 490 nm) by excitation light in the red wavelength region (wavelength 640 to 665 nm).
) Becomes the emission center. When the content of Ho ions is too small, the emission intensity becomes weak, so that it is preferably 0.01 mol% or more, more preferably 0.05 mol% or more in terms of Ho chloride. On the other hand, if the amount of Ho ions is excessive, the energy transfer between the ions becomes dominant and the concentration quenching lowers the light emission efficiency, and vitrification is hindered. Therefore, the content is up to about 30 mol in terms of Ho chloride. % Is suitable, and 8 mol% or less is preferable. In addition, green light (520 to 560 nm) can be obtained by using infrared light (810 to 840 nm) as an excitation light source.

An example of the composition range of the blue light emitting glass material according to the present invention is shown in FIG. Figure 1 is GdCl ₃ -BaCl ₂ -
It is a ternary system graph showing the composition range of the glass material made of HoCl _3, and the glass material of the present invention is obtained in the composition range of the shaded portion in FIG. 1. If it goes out of the composition range of the shaded area,
Since the crystallization rate becomes very high, vitrification becomes difficult even if the raw material is heated and melted and then rapidly cooled, resulting in devitrification (crystallization). The upper and lower limits of each component in the vitrification range shown in the shaded area are: GdCl ₃ 35 to 93 mol%, BaCl ₂ 6 to 49
Mol% and HoCl ₃ 0.01 to 33 mol%. In particular, the emission intensity of blue light and green light is high in the range of Gd chloride of 52 to 89 mol%, Ba chloride of 10 to 40 mol%, and Ho chloride of 0.05 to 8 mol%, and glass can be prepared relatively stably. This composition range is most suitable because it can be obtained.

In the present specification and the accompanying drawings, the glass composition is represented by chlorides such as GdCl ₃ , BaCl ₂ and HoCl ₃ , which are cations (Gd ion, Ba ion and Ho ion) in the glass. ) And an anion (chloride ion) content ratio in terms of chloride, and each component forms a network structure in which they are mutually bonded in the same manner as a normal glass structure.

With respect to the glass material of the present invention, the preferable composition range when Sr chloride and Ca chloride are used as glass forming aids instead of Ba chloride is shown below. _{(1) GdCl 3 -SrCl 2 -HoCl} 3 chloride Gd: forty-eight to eighty-three mol%, preferably 52 to 79 mol% chloride Sr: fifteen to forty-seven mol%, preferably 20 to 40 mol% chloride Ho: 0.01 to 20 mol%, preferably 0.05
~ 8 mol%

(2) GdCl ₃ —CaCl ₂ —HoCl ₃ Gd chloride: 51 to 82 mol%, preferably 52 to 79 mol% Ca chloride: 16 to 47 mol%, preferably 20 to 40 mol% Ho chloride 0: 0 0.01 to 18 mol%, preferably 0.05
~ 8 mol%

By using two or more glass forming aids, a more stable glass material can be obtained. However, the total amount of glass forming aids is less than 50 mol%. Examples of such glass materials include Gd-Ba-Sr-Ho and Gd.
-Ba-Ca-Ho or Gd-Sr-Ca-Ho quaternary glass composed of chloride, or Gd-Ba-
A quinary glass made of each chloride of Sr-Ca-Ho can be mentioned.

With respect to the glass material of the present invention, a suitable composition range in the case of containing two or more kinds of these glass forming aids is shown below. _{(3) GdCl 3 -BaCl 2 -SrCl} 2 -HoCl
₃ chloride Gd: 35 to 90 mol%, preferably 52 to 89 mol% chloride Ho: 0.01-28 mol%, preferably 0.05
-8 mol% Total amount of Ba chloride and Sr chloride: 6-49 mol%, preferably 10-40 mol%

(4) GdCl ₃ —BaCl ₂ —CaCl
_2- HoCl ₃ Gd chloride: 40 to 90 mol%, preferably 52 to 89 mol% Ho chloride: 0.01 to 28 mol%, preferably 0.05
-8 mol% Total amount of Ba chloride and Ca chloride: 6-49 mol%, preferably 10-40 mol%

[0019] _{(5) GdCl 3 -SrCl 2 -CaCl} 2 -HoCl
₃ chloride Gd: 50 to 83 mol%, preferably 52 to 79 mol% chloride Ho: 0.01 to 20 mol%, preferably 0.05
~ 8 mol% Total amount of Sr chloride and Ca chloride: 15 to 47 mol%, preferably 20 to 40 mol%

(6) GdCl ₃ —BaCl ₂ —SrCl
₂ -CaCl ₂ -HoCl ₃ chloride Gd: thirty-five to ninety-one mol%, preferably 52 to 89 mol% chloride Ho: 0.01 to 30 mol%, preferably 0.05
-8 mol% Total amount of Ba chloride, Sr chloride and Ca chloride: 7 to 49
Mol%, preferably 10-40 mol%

The above glass forming aids (BaCl ₂ , SrCl ₂ , Ca
Cl ₂ ) together with LiCl, NaCl, KCl, RbCl,
A more stable glass material can be obtained by using CsCl, PbCl ₂ and TlCl in combination. The addition amount of these is about 40 mol% or less. In addition, the glass forming aid (Ba
Cl ₂ , SrCl ₂ , CaCl ₂ ) together with these LiCl and NaC
l, KCl, RbCl, CsCl, PbCl ₂ and T
The introduction of lCl into the glass composition lowers the glass transition point.

The chloride glass material of the present invention is obtained by heating and melting a mixed powder prepared by mixing a predetermined amount of purified and dried chloride powder as a raw material under a chlorine gas atmosphere or under vacuum and then rapidly cooling it to a temperature below the glass transition point. The cooling rate is 60 K / s or more.
If the cooling rate is less than the above value, devitrification may occur due to some crystal formation. As shown in FIG. 2, the X-ray diffraction curve of the obtained quenched body does not show a specific peak as seen in the crystalline body, which shows that it is vitreous. Further, no peaks corresponding to the composition of each raw material salt were observed, and it can be confirmed that these are not simply mixtures of these.
Further, a glass transition point is recognized as illustrated in the differential thermal analysis curve of FIG. 3, and it can be seen that it is also glassy. The glass of the present invention can be produced by a known amorphous forming method such as a vapor phase growth method in addition to the above-described melt cooling process.

[0023]

EXAMPLES AND COMPARATIVE EXAMPLES Examples of the present invention are shown below together with comparative examples. It should be noted that the present embodiment is merely an example and does not limit the scope of the present invention.

Example 1 GdCl _{3 as a} glass base material and HoCl as a luminescent substance
₃ powders are commercially available Gd ₂ O ₃ or Ho ₂ O _{3 respectively.}
Was synthesized by a conventional method, heated, melted, blown with chlorine gas, and completely dehydrated and purified. As the glass forming aid BaCl ₂ , high-purity anhydrous crystals dried in a drying container at 320 ° C. for 2 days were used. These raw material powders were mixed in a ratio of 70.6 mol% GdCl ₃ , 28.0 mol% BaCl ₂ and 1.4 mol% HoCl ₃ to prepare a mixed powder of transparent quartz glass tube (inner diameter 1.5 mm, wall thickness 0.6 mm, length 200 mm) was vacuum-sealed to prepare an ampoule, which was melted in a heating furnace at 600 ° C. for 15 minutes. Immediately cool the obtained melt with the ampoule to 250 ° C (cooling rate 80
(K / s) After annealing for 2 hours, it was gradually cooled at 1 K / min to obtain a pale orange transparent body.

When the obtained transparent body was visually inspected,
No crystal precipitation was observed inside or on the surface. When the transparent body was measured by X-ray diffraction, the graph of the scattering intensity thereof was not glassy, as shown in FIG. 2, and it was confirmed that the transparent body was glassy. . Further, as shown in FIG. 3, a glass transition point (Tg) was observed in the differential thermal analysis curve of this transparent body at around 250 ° C., and it was confirmed from this measurement that it was vitreous.

Examples 2-38 SrCl ₂ and CaCl treated as in Example 1 using the same GdCl ₃ and HoCl ₃ powders as in Example 1.
_Two powders were mixed in a molar ratio shown in Table 1, and this mixed powder was treated in the same manner as in Example 1 to obtain the following glass material. _{GdCl 3 -BaCl 2 -HoCl 3 GdCl 3} -SrCl 2 -HoCl 3 GdCl 3 -CaCl 2 -HoCl 3 GdCl 3 -BaCl 2 -SrCl 2 -HoCl 3 GdCl 3 -SrCl 2 -CaCl 2 -HoCl 3 GdCl 3 -CaCl ₂ -BaCl ₂ -HoCl ₃ resulting glass material is transparent, was observed with the naked eye, precipitation of crystals on the surface to the inside was observed.
It was confirmed that the transparent body was a glass body in the same manner as in Example 1.

[0027]

[Table 1]

Measurement of Emission Spectra The glass material obtained in Example 1 was taken out from a quartz ampoule, cut into a cylindrical shape having a length of about 5 mm, and the cut portion was surface-polished, and a semiconductor laser (5 mW) having a wavelength of 650 nm was applied to the sample. Upon irradiation, it was confirmed that blue light was emitted inside the glass material.
This emission spectrum is shown by the solid line in FIG. Fluoride glass (52ZrF ₄・ 20BaF ₄・ 4La manufactured by a conventional method is used.
The _{F 3 · 3AlF 3 · 20NaF ·} 1HoF 3) was prepared in the same shape,
The same measurement was performed on a comparative sample obtained by cutting and surface polishing. The results are as shown in FIG. 4 (broken line), and the glass material of this example exhibits strong blue light emission near the wavelength of 490 nm, and this intensity is about 20 times higher than that of the conventional fluoride glass (wavy line). On the other hand, the conventional fluoride glass containing Ho ions has the highest emission intensity in the green wavelength region of 550 nm and does not emit blue light. When the same measurement was carried out for each sample of the other examples, the blue light intensity near the wavelength of 490 nm was several times to 20 times that of the above-mentioned fluoride glass as in Example 1.

Comparative Examples 1 to 7 Mixed powders obtained by mixing the same raw materials as those used in Examples in the molar ratios shown in Table 2 were heated and melted under the same conditions as in Example 1 and quenched. A transparent glass material was obtained. When the obtained transparent body was observed with the naked eye, no precipitation of crystals was found inside or on the surface. In addition, it was confirmed that the transparent body was glassy in the same manner as in Example 1. However, when the obtained glass was cut into the same shape as in Example 1 and the spectrum was similarly measured, the blue intensity near a wavelength of 490 nm was about 1/20 times that of the fluoride glass.

[0030]

[Table 2]

[0031]

Since the wavelength conversion material of the present invention is a glass material, it is easier to manufacture than a crystalline wavelength conversion material, and can be processed into various shaped products such as fibers. Further, since the absorption of rare earth ions is broader than that of the crystal body, the fluctuation of the absorption efficiency is small even if the wavelength of the excitation light fluctuates, and thus the fluctuation of the emission efficiency is small. Therefore, a relatively stable output can be obtained even when a semiconductor laser whose output wavelength is apt to change due to the influence of temperature or current is used as the excitation light. Further, in the present invention, Gd chloride and a chloride of an alkaline earth metal are used as the glass base material, and the glass transition point is 200 ° C. or higher. Therefore, the conventional chloride glass (the glass transition point is about 175 ° C.) is used. Compared with this, it has a much higher glass transition point and is stable. Further, the wavelength conversion glass material of the present invention has, as its greatest feature, much higher light conversion efficiency in the blue region than conventional fluoride wavelength conversion glass materials. Therefore, it can be applied to a wide range of fields such as displays and blue lasers using the up-conversion method.

[Brief description of drawings]

FIG. 1 is a graph showing the ternary vitrification range of Gd chloride-Ba chloride-Ho chloride according to the present invention.

FIG. 2 is an X-ray diffraction chart of the glass material of Example 1.

FIG. 3 is a graph showing a differential thermal analysis curve of the glass material of Example 1.

FIG. 4 is a spectrum diagram showing the emission intensity of the glass material of Example 1 and a conventional fluoride glass.

Claims (9)

[Claims] 1. A wavelength conversion glass material obtained by containing holmium chloride in a chloride glass base material using gadolinium chloride as a glass forming agent and alkaline earth chloride as a glass forming aid. 2. The wavelength conversion glass material according to claim 1, wherein the glass forming aid is one or a combination of two or more of barium chloride, strontium chloride and calcium chloride. 3. Gadolinium chloride 35 to 93 mol%, barium chloride 6 to 49 mol%, and holmium chloride 0.01
The wavelength conversion glass material according to claim 2, which comprises ˜33 mol%. 4. The wavelength conversion glass material according to claim 2, which comprises 48 to 83 mol% of gadolinium chloride, 15 to 47 mol% of strontium chloride and 0.01 to 20 mol% of holmium chloride. 5. Gadolinium chloride 51-82 mol%, calcium chloride 16-47 mol% and holmium chloride 0.
The wavelength conversion glass material according to claim 2, which comprises 01 to 18 mol%. 6. Gadolinium chloride 35-90 mol%, barium chloride 1-48 mol%, strontium chloride 1-46
Molium and 0.01-28 mol% holmium chloride, and the total amount of barium chloride and strontium chloride is 6%.
The wavelength conversion glass material according to claim 2, which is ˜49 mol%. 7. Gadolinium chloride 40 to 90 mol%, barium chloride 1 to 48 mol%, calcium chloride 1 to 46 mol% and holmium chloride 0.01 to 28 mol%, wherein the total amount of barium chloride and calcium chloride is 6-49
The wavelength conversion glass material according to claim 2, which is in mol%. 8. Gadolinium chloride 50 to 83 mol%, strontium chloride 1 to 46 mol%, calcium chloride 1 to 4
The wavelength conversion glass material according to claim 2, which comprises 6 mol% and 0.01 to 20 mol% of holmium chloride, and the total amount of strontium chloride and calcium chloride is 15 to 47 mol%. 9. Gadolinium chloride 35-91 mol%, barium chloride 1-47 mol%, strontium chloride 1-46.
Mol%, calcium chloride 1 to 46 mol% and holmium chloride 0.01 to 30 mol%, and the total amount of barium chloride, strontium chloride and calcium chloride is 7 to 49
The wavelength conversion glass material according to claim 2, which is in mol%.