JP2951358B2 - Up conversion glass - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an up-conversion glass suitable as a material for a display, a detector for infrared rays and an infrared laser, or an up-conversion laser.

[Prior Art] A substance that converts irradiated infrared light into visible light and emits it as fluorescence or laser light (hereinafter referred to as an up-conversion substance) is a display, a detector of infrared and infrared lasers, a visible light laser, or the like. Because of its high utility value as a material, various research and development have been promoted.

For example, Patent Application Publication No. 63-503495 discloses a crystal containing calcium fluoride as a main component and doped with Er ³⁺ as an active ion.

In addition, "Electronic Letters (ELECTRONICS
LETTERS) Vol. 23, No. 1 "(pages 32 to 34, 1987, January 1)
Moon) describes that in a fluoride glass and a CaF ₂ crystal doped with Yb ³⁺ and Er ³⁺ , visible light emission due to up-conversion of Er ³⁺ was observed.

Among these up-conversion materials, up-conversion materials using glass as a medium (hereinafter referred to as up-conversion glasses) are easier to manufacture than up-conversion materials using crystals such as CaF ₂ crystals as their medium, However, it has advantages such as low fiber density and the possibility of fiberization. Further, in the up-conversion glass, since the absorption spectrum of rare earth ions in the glass is broad, the fluctuation of the absorption efficiency due to the wavelength fluctuation of the excitation light is small, so that the output wavelength tends to fluctuate due to the influence of temperature, current, and the like. Even when a semiconductor laser is used as the excitation light, there is an advantage that a relatively stable output can be obtained.

[Problems to be Solved by the Invention] However, the conventional up-conversion glass using fluoride glass as a medium has a conversion efficiency comparable to the conversion efficiency between infrared light and visible light of an up-conversion material using CaF ₂ crystal as a medium. From this point, it can be said that it is practical, but fluoride glass is difficult to be put to practical use because of its low chemical durability and mechanical strength. Further, in the fluoride glass, there is a problem that the composition region in which the glass can be generated stably is extremely narrow, and it is difficult to change the composition to greatly change the characteristics. Further, the fluoride glass also has a problem that it is difficult to control the atmosphere and form the glass when producing the glass.

In addition, Yb ³⁺
The measurement results of the conversion efficiency of infrared-visible light in silicate glass and phosphate glass doped with Er ³⁺ are described, but the conversion efficiency of infrared-visible light in these glasses is However, it is about 1 / 100,000 to 1/10000 of up-conversion glass using fluoride glass as a medium, and it cannot be said that an up-conversion phenomenon has occurred.

Therefore, an object of the present invention is to provide an up-conversion glass having practical infrared-visible light conversion efficiency, which has excellent chemical durability and mechanical strength, and is easy to produce and mold. Is to do.

Means for Solving the Problems The present invention has been made to achieve the above object, and the upconversion glass of the present invention is composed of an oxide glass containing a heavy metal oxide and a rare earth element oxide. The maximum energy of lattice vibration of the oxide glass is 1000 cm ^-1 or less.

 Hereinafter, the present invention will be described in detail.

The upconversion glass of the present invention is made of an oxide glass as described above, and this oxide glass contains a heavy metal oxide.

PbO, CdO, Bi ₂ O ₃ , Ga ₂ O ₃ , Te
O ₂ , Sb ₂ O ₃ , As ₂ O ₃ , GeO _{2 and the} like are mentioned, and the up-conversion glass of the present invention contains at least one of these heavy metal oxides. The content of heavy metal oxides is from 20 to
Preferably it is 85 mol%. If it is less than 20 mol%, it becomes difficult to substantially reduce the maximum energy of lattice vibration to 1000 cm ^-1 or less, and if it exceeds 85 mol%, it becomes difficult to form glass. Particularly preferred heavy metal oxide content is
25-82 mol%.

The up-conversion glass of the present invention also contains a rare earth element oxide. Then, the rare earth element constituting the rare earth element oxide becomes an ion (upconversion active ion) for causing an upconversion phenomenon in the glass.

As rare earth elements, Ce, Pr, Nd, Pm, Sm, Eu, Tb,
Dy, Ho, Er, Tm, Yb, and Lu may be mentioned, and the rare earth element oxide may be any oxide of these rare earth elements. The content of the rare earth oxide is preferably 0.1 to 30 mol%. If it is less than 0.1 mol%, the conversion efficiency between infrared light and visible light is low and it is not practical. If it exceeds 30 mol%, molding of glass becomes difficult. A particularly preferred content of the rare earth element oxide is 1 to 20 mol%.

In the upconversion glass of the present invention, as components other than the above-mentioned heavy metal oxide and rare earth element oxide, alkali metal oxides such as Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, etc. Substances, alkaline earth metal oxides such as MgO, CaO, SrO, BaO, etc., SiO ₂ , Al ₂ O ₃ , P ₂ O ₅ , ZnO, WO ₃ , MoO
Components commonly used as glass components such as ₃ can be contained.

Further, the maximum energy of the lattice vibration of the up-conversion glass of the present invention is limited to 1000 cm ⁻¹ or less. The reason for limiting the maximum energy of lattice vibration to 1000 cm ^-1 or less is as follows.

In an up-conversion glass made of an oxide glass, as the phonon energy involved in multi-phonon relaxation is smaller, the intensity of light emitted by the conversion between infrared light and visible light increases. The phonon energy involved in this multi-phonon relaxation is, for example, in an up-conversion glass containing Eu ³⁺ , when the excitation spectrum of the glass is measured while monitoring the emission (612 nm) due to the ⁵ D ₀ → ⁷ F ₂ transition. corresponding to an energy difference between the peak of the emerging electronic transitions ⁽⁷ F ₀ → ⁵ D ₂ transition) peak and phonon sidebands appear in the higher energy side of the electron transition peak. Note that also in an up-conversion glass made of an oxide glass containing a rare earth element other than Eu, the energy difference between the electron transition peak and the peak of the phonon side band corresponds to the phonon energy involved in multiphonon relaxation.

These electron transition peaks and phonon sideband peaks can be measured using a normal spectrofluorometer, but in glasses containing rare earth elements other than Eu as rare earth elements, phonon sidebands appear. Since there is an electron transition of a rare earth ion at the energy position and the phonon sideband is hidden by the band based on the electron transition, it is difficult to specify the phonon sideband. In addition, the phonon energy of glass does not depend on the type of rare earth element contained therein, so the phonon energy of glass containing a rare earth element other than Eu is the same as the phonon energy of glass obtained by replacing only the rare earth element in this glass with Eu. It is not easy to produce a plurality of glasses having the same composition except for the rare earth elements, except for the simultaneous production of these glasses. Therefore, as a rare earth element
In glasses containing rare earth elements other than Eu, it is difficult to accurately measure the phonon energy involved in multiphonon relaxation.

By the way, the value of the phonon energy involved in the multiphonon relaxation can also be obtained from the value of the lattice vibration energy obtained from the Raman scattering spectrum of glass [Physical Review B16]
(Page 10, 1977). Also in this case, as in the case of the phonon energy involved in the multi-phonon relaxation described above, as the maximum energy of the lattice vibration is smaller, the intensity of the light emitted by the conversion between infrared light and visible light increases. In an up-conversion glass made of an oxide glass, if the maximum energy of the lattice vibration of the glass exceeds 1000 cm ⁻¹ , the up-conversion phenomenon does not appear or becomes very weak even if it appears.

Therefore, in the up-conversion glass of the present invention, the maximum energy of the lattice vibration of the glass is 1000 cm
Limited to ^-1 or less. When the maximum energy of lattice vibration of glass is 1000 cm ^-1 or less, the energy loss due to non-radiative transition from the excitation level of rare earth ions excited by infrared light becomes small, and the up conversion phenomenon appears remarkably I do.

The maximum energy of the lattice vibration of the glass determined from the Raman scattering spectrum in this specification is 10 × 25
When a sample with a size of × 4 mm is polished on six surfaces, and one surface of the polished sample is irradiated with a laser beam having an incident angle of 45 ° and a wavelength of 514.5 nm and an output of 60 mW, and the scattered light is detected by a Raman spectrophotometer. Was obtained as a wave number corresponding to the peak position of the scattering band present on the highest wave number side in the Raman scattering spectrum.

Heavy metal oxide and rare earth element oxide as essential components,
The upconversion glass of the present invention in which the maximum energy of the lattice vibration of the glass is 1000 cm ^-1 or less, as a starting material of the heavy metal oxide, an oxide of a heavy metal to be contained, a carbonate, a nitrate, and the like, and a rare earth element. Rare earth oxides, carbonates, and nitrates to be contained can be used as starting materials for the oxides. In addition, if necessary, ordinary glass materials such as oxides, carbonates, nitrates and the like as starting materials such as alkali metal oxides and alkaline earth metal oxides which are optional components can be used. And
These starting materials can be obtained from a mixture prepared so that the composition of the finally obtained glass becomes a desired composition in the same manner as in the production of an oxide glass by a usual melting method.

Therefore, the up-conversion glass of the present invention uses a fluoride glass as a medium without causing a problem that it is difficult to control or mold an atmosphere generated when obtaining an up-conversion glass using a fluoride glass as a medium. It is possible to obtain upconversion glasses of various shapes having better chemical durability and mechanical strength than the upconversion glass. Further, since the composition region in which glass can be produced is wide, up-conversion glass having various characteristics can be obtained by changing the composition.

[Examples] Hereinafter, examples of the present invention will be described, but the present invention is not limited to these examples.

Example 1 These starting materials were finalized using TeO ₂ as a starting material for heavy metal oxides, Er ₂ O ₃ as a starting material for rare earth oxides, and Na ₂ CO ₃ as a starting material for optional components. The mixture obtained by blending so that the composition of the resulting glass is as shown in Table 1 is heated at 900 ° C. for 60 minutes in the air to form a glass melt. After pouring onto an iron plate, solidifying, and then cooled at a rate of about 30 ° C./h, an oxide up-conversion glass was obtained.

A sample having a size of 10 × 25 × 4 mm was cut out from the thus obtained up-conversion glass, and after polishing this sample on six sides, an incident angle was applied to one side of the sample.
A laser beam with a wavelength of 514.5 nm and an output of 60 mW is irradiated at 45 °, and the scattered light at this time is NR-1000 manufactured by JASCO Corporation.
Raman scattering spectra detected by the type Raman spectrophotometer, the maximum energy of the lattice vibration of the glass by the method described above (hereinafter, referred to as the maximum energy of the lattice vibration) was sought, as shown in FIG. 1, 680 cm ^- It was determined to be ¹ . The peak near 1300 nm (the peak portion is not shown) in FIG. 1 is due to the fluorescence of Er ³⁺ .

Further, using the sample polished on the above-mentioned six surfaces, which was used for measuring the maximum energy of the lattice vibration, and when the fluorescence spectrum of the sample was irradiated with an infrared semiconductor laser having a wavelength of 800 nm as excitation light, As shown in FIG. 2, the fluorescence spectrum at this time was confirmed to have fluorescence attributable to infrared-visible light conversion, having a peak at a wavelength of 550 nm. In this case, as shown in FIG. 3, the fluorescence spectrum was measured by irradiating a laser beam from an excitation light source (infrared semiconductor laser) 1 with a pulse from a chopper 2 to a sample 4 by a mirror 3,
Visible light (fluorescence) from the sample 4 is condensed by the lens 5 and the spectrometer [R32 manufactured by Jobin-Yvon] is used.
[0 monochromator] 6 for spectroscopy.
The result of detection by the photomultiplier (Hamamatsu Photonics Co., Ltd. R2228) 7 of the light separated by the liquid nitrogen cooled by liquid nitrogen is amplified by a lock-in amplifier (EG & G 5208) 8 and then recorded by the recorder 9. Was performed. Note that the lock-in amplifier 8 is also connected to the chopper 2 to match the phases of the signal light and the reference light.

Furthermore, the intensity of fluorescence (hereinafter, referred to as “fluorescence”) due to infrared-visible light conversion at room temperature of the obtained up-conversion glass
Infrared light-visible light converted fluorescence intensity), chemical durability and fracture toughness were measured in the following manner. Table 1 shows the measurement results.

・ Infrared light-visible light conversion fluorescence intensity 10 × 25 × 4m from the obtained up-conversion glass
A sample having a size of m was cut out, and after polishing this sample on six surfaces, the fluorescence spectrum obtained when an infrared semiconductor laser having a wavelength of 800 nm was irradiated as excitation light on one surface of the sample using the apparatus shown in FIG. It was measured.

・ Chemical durability Water resistance based on the chemical durability measurement method (powder method) of optical glass specified in Japan Optical Glass Industrial Association standard JOGIS-1975
Dw (unit: wt%) was measured.

・ Fracture toughness The fracture toughness [K _IC (unit: MPam ^1/2 )] is obtained by cutting a sample of 5 × 5 × 30 mm from the obtained up-conversion glass, polishing one surface of the rectangle, and polishing the surface. Cracks of a certain size were generated and the bending strength was determined by a three-point bending test, and the strength was normalized by the shape of the cracks.

Examples 2 to 7 As starting materials for heavy metal oxides, Ga ₂ O ₃ , PbO, Bi ₂ O ₃ , G
eO ₂ and TeO ₂ , and Er ₂ O ₃ as a starting material for a rare earth element oxide, and as necessary, Na ₂ CO ₃ , SrCO ₃ , WO ₃ and Li ₂ CO ₃ as a starting material for optional components A mixture obtained by mixing these starting materials so that the composition of the glass finally obtained has the composition shown in Table 1 is heated at 1100 to 1200 ° C. for 30 to 60 minutes in the air. Into a glass melt, and pour the obtained glass melt onto an iron plate,
After solidification, the solid was cooled at a rate of about 30 ° C./h to obtain an oxide up-conversion glass.

The maximum energy of lattice vibration, infrared-visible light converted fluorescence intensity, chemical durability and fracture toughness of each of the thus obtained up-conversion glasses were measured in Example 1.
Table 1 shows the measurement results in the same manner as in Example 1.

Comparative Example 1 ZrF ₄ , BaF ₂ , LaF ₃ , AlF ₃ , NaF and E as starting materials
using rF _3, the composition of the glass obtained these starting materials finally are mixtures obtained by blended to achieve the composition shown in Table 1, 60 minutes at 875 ° C., and heated in an argon atmosphere A glass melt is obtained, and the obtained glass melt is
By cooling at a rate of 30 ° C./h, a fluoride up-conversion glass was obtained.

The maximum energy of the lattice vibration, the infrared-visible light converted fluorescence intensity, the chemical durability and the fracture toughness of the thus obtained up-conversion glass were measured in Examples 1 to 4.
Table 1 shows the measurement results in the same manner as in Example 7.

Comparative Example 2 P ₂ O ₅ , Al ₂ O ₃ , K ₂ CO ₃ , MgCO ₃ , BaCO ₃ and Er ₂ O ₃ were used as starting materials. The mixture obtained by mixing so as to have the composition shown in FIG. 1 was heated at 1200 ° C. for 60 minutes in the air to form a glass melt, and the obtained glass melt was poured out onto an iron plate and solidified. The mixture was gradually cooled at a rate of 30 ° C./h to obtain a phosphate glass.

Maximum energy of lattice vibration in the phosphate glass thus obtained, infrared-visible light converted fluorescence intensity,
Table 1 shows the results of measuring the chemical durability and fracture toughness in the same manner as in Examples 1 to 7.

As is clear from Table 1, the maximum energy of the lattice vibration of each of the up-conversion glasses of Examples 1 to 7 is:
In each case, the fluorescence intensity of infrared-visible light conversion at room temperature is 1000 cm ^-1 or less, which is comparable to that of the fluoride up-conversion glass of Comparative Example 1 at room temperature. It was confirmed that it had a practical conversion efficiency between infrared light and visible light.

In addition, the Dw value of each of the up-conversion glasses of Examples 1 to 7 was 0.02 to 0.11 wt%, which was significantly smaller than the Dw value (0.24 wt%) of the fluoride up-conversion glass of Comparative Example 1. It turns out that it is excellent in chemical durability.

Further, K _IC value of K value of _IC is 0.5~0.7MPam ^1/2, upconversion glass of fluoride of Comparative Example 1 of the up-conversion glasses of Examples 1 to 7 (0.5 MPa
m ^1/2 ) or more, indicating that the steel has excellent fracture toughness. Further, it can be seen from this that the mechanical strength is excellent.

The phosphate glass of Comparative Example 2 is superior to each of the up-conversion glasses of Examples 1 to 7 and Comparative Example 1 in terms of chemical durability and fracture toughness, but is converted from infrared light to visible light. The strength was hardly 5 × 10 ^−8, and it was not substantially an up-conversion glass.

In addition, the infrared-visible light conversion fluorescence intensity in each of the up-conversion glasses of Examples 1 to 7 has a small change due to the fluctuation of the external environment temperature, in other words, a low temperature dependency and a high temperature dependency. It was confirmed that infrared-to-visible light converted fluorescence with stable emission intensity could be obtained as compared with an up-conversion glass using a fluoride glass as a medium.

[Effects of the Invention] As described above, the up-conversion glass of the present invention has a practical infrared-visible light conversion efficiency,
It is an up-conversion glass that has excellent chemical durability and mechanical strength, is easy to manufacture and mold, and has low temperature dependence of its infrared-visible light conversion fluorescence intensity.

Therefore, according to the present invention, it is possible to easily obtain an up-conversion glass that can withstand practical use as a material for a display, a detector of an infrared ray and an infrared laser, or an up-conversion laser even at room temperature while appropriately selecting characteristics. Become.

[Brief description of the drawings]

FIG. 1 is a Raman scattering spectrum diagram for obtaining the lattice vibration energy of the up-conversion glass of the present invention obtained in Example 1, and FIG. 2 is a diagram of the up-conversion glass of the present invention obtained in Example 1. FIG. 3 is a fluorescence spectrum diagram, and FIG. 3 is a schematic diagram showing an apparatus used in obtaining the fluorescence spectrum diagram shown in FIG. 4. Sample (up-conversion glass)

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Torkei Kura 2-7-5 Nakaochiai, Shinjuku-ku, Tokyo Inside Soya Co., Ltd. (72) Keiko Okada 2-7.5-7 Nakaochiai, Shinjuku-ku, Tokyo No. Hoya Corporation (56) References Tanabe et al. , Journal of Non-Crys talline Solids, June 1990, Vol. 122, no. 1, p. 59-65, 79-82 Kazuyuki Hirao et al., Proceedings of the Ceramic Society of Japan 1990 Annual Meeting, Japan Ceramics Association, May 23, 1990, p. 287 (58) Field surveyed (Int. Cl. ⁶ , DB name) C03C 3/00-3/32 C03C 4/12

Claims (2)

(57) [Claims] 1. An up-conversion glass comprising an oxide glass containing a heavy metal oxide and a rare earth element oxide, wherein the maximum energy of lattice vibration of the oxide glass is 1000 cm ^-1 or less. 2. The up-conversion glass according to claim 1, which contains 20 to 85 mol% of a heavy metal oxide and 0.1 to 30 mol% of a rare earth element oxide.