JP2002194349A - Stress-induced light-emitting material and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stress-induced light-emitting material capable of effectively emitting the light with good repeatability, when a mechanical external force is applied to the material, and to provide a method for producing the same. SOLUTION: This stress-induced light-emitting material is formed by using an oxide expressed by the formula: MN2O4 (M is one or more metal elements selected from the group consisting of Mg, Sr, Ba, and Zn; and N is one or more metal elements selected from the group consisting of Ga and Al) as a base material and adding one or more elements selected from rare earth elements or transition metals which emit the light when carries excited with mechanical energy return to the ground state as emission centers to the base material, wherein the element constituting the emission center is contained in an amount of 0.001-20 mol% based on the amount of the element expressed by M.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the stress light-emitting material, with particularly it is possible to convert the mechanical force directly visible, and novel stress-luminescent material or mechanochemical luminescent material having excellent reproducibility The present invention relates to the manufacturing method.

[0002]

2. Description of the Related Art Heretofore, a phenomenon in which a substance emits visible light at around room temperature when an external stimulus is applied thereto is known as a so-called fluorescent phenomenon. A substance that causes such a fluorescent phenomenon, that is, a phosphor, is used in an illumination lamp such as a fluorescent lamp or a display such as a CRT (Cathode Ray Tube), a so-called cathode ray tube. External stimuli that cause this fluorescence phenomenon are usually given by ultraviolet rays, electron beams, X-rays, radiation, electric fields, chemical reactions, etc., but until now, they have been deformed by applying stimuli such as mechanical external forces. Materials that emit more intensely are not known. In particular, there has been a problem in that the change in light emission luminance due to mechanical stimulation has been small, and the light emission intensity has been greatly attenuated by repeated stress, and there is no reproducibility of the light emission intensity due to mechanical external force. Has not been converted.

[0003]

DISCLOSURE OF THE INVENTION The present inventors have conducted long-term research on a material that emits light efficiently and with good reproducibility when stimulated by a mechanical external force or the like.
An oxide represented by MN ₂ O ₄ (M and N are Mg, S
It is not only effective to add a luminescent center to a base material composed of at least one metal element selected from the group of r, Ba, Zn, and the group of Ga, Al, They found a means for controlling lattice defects in the base material and an appropriate addition amount and an appropriate addition method of the luminescent center, and as a result, succeeded in significantly improving the efficiency of converting mechanical energy into light energy.

[0004] The present invention is based on such knowledge, and the technical problem of the present invention is to efficiently emit light with good reproducibility by mechanical external forces such as frictional force, shear force, impact force, pressure and tension. Another object of the present invention is to provide a novel stress-stimulated luminescent material of a type different from those known hitherto and a method for producing the same.

[0005]

In order to achieve the above object, a stress-stimulated luminescent material according to the present invention comprises a compound represented by MN ₂ O ₄ (M and N are groups of Mg, Sr, Ba, Zn, And at least one selected from the group of Ga and Al
One or more elements selected from rare earths or transition metals that emit light when carriers excited by mechanical energy return to the ground state. And a luminescent center element is added to the base material, and the mole% of the luminescent center element with respect to the metal element represented by M is set to 0.001 to 20%.

In the stress-stimulated luminescent material, MgGa ₂ O ₄ , ZnGa ₂ O ₄ , ZnAl ₂ O is used as a base material.
₄ , SnZn ₂ O ₄ , BaAl ₂ O ₄ or MgAl ₂
The use of an oxide represented by O ₄ is particularly effective for obtaining efficient and reproducible light emission. Further, the stress-stimulated luminescent material of the present invention comprises the above oxide as a host material and has a lattice defect of 0.0001 to 20 mol% with respect to M or N, or a compound having a spinel structure as the host material. In some embodiments, a pseudo spinel or inverse spinel structure may be included.

On the other hand, the production method of the stress light-emitting material of the present invention for achieving the above object, the base material consists of an oxide represented by the MN ₂ O _4, carriers excited by mechanical energy When at least one kind of rare earth or transition metal that emits light when the element returns to the ground state is used as an emission center, the mole% of the metal element represented by M is 0.0
After adding and mixing so as to have a concentration of 01 to 20%, the mixture is fired at 300 to 1800 ° C. in an oxidizing atmosphere, and then fired at 400 to 1800 ° C. in a reducing atmosphere to dope the emission center. Is what you do.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The stress-stimulated luminescent material according to the present invention
Basically, it is configured by adding a luminescent center to a base material.
As the base material, in particular, MN₂O₄Compounds represented by in
(M and N are, Mg, Sr, Ba, a group of Zn, and
At least one selected from the group consisting of Ga and Al
Material consisting of one or more of the above metal elements)
Emission intensity when using them is stronger than other substances
I know that. Therefore, the base material is
You will have to choose later. The above stress-stimulated luminescent materials
In addition, as shown in the examples described later,
As a matrix material, MgGa₂O₄, ZnGa₂O₄, Z
nAl₂O₄, SnZn ₂O₄, BaAl₂O₄Or
MgAl₂O₄It is more efficient to use an oxide represented by
This is effective for obtaining light emission with good reproducibility.

Further, the above-mentioned base material includes mechanical energy.
Field where carriers excited by the energy return to the ground state
Luminescence centers of rare earths and transition metals
When pressurized, it is possible to further higher luminance emission intensity
You. As a material serving as a light emission center, Ce, Pr, Nd,
Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, T
rare earths of m, Yb, Lu, and Ti, Zr, V, C
r, Mn, Sn, Fe, Co, Ni, Cu, Zn, N
b, Mo, Ta, W
Others are suitable to use more, but formation of the base material
Optimum emission center by crystal structure is different. For example, base material
The material is ZnAl₂O ₄Is particularly effective in the case of
BaAl₂O₄In the case of Ce, Sm, Eu, Mn, etc.
Is effective. In general, Eu, Ce,
Selected from the group of Sm, Tb, Dy, Nd, Mn, Sn
One or more elements are used as emission centers.

The luminescent color of the stress-stimulated luminescent material differs depending on the luminescent center to be added. Therefore, by selecting the kind of the luminescent center, full-color, that is, various colors of light can be obtained. The amount of the material to be added as the emission center is 0.001 to 2 with respect to the metal element represented by M.
It can be selected within the range of 0 mol%. It is 0.0
If the amount is less than 01 mol%, the emission intensity is insufficiently improved. On the other hand, if the amount is more than 20 mol%, the crystal structure of the base material cannot be maintained, and the luminous efficiency is lowered, which is not suitable for practical use.

Further, in the MN ₂ O ₄ compound, the stress emission intensity can be further remarkably improved by controlling the concentration of lattice defects with respect to M or N. The control of the defect concentration is achieved by adjusting the charging ratio and controlling the firing conditions. Is easy Reducing advance the composition ratio of M or N in the time of charging, defect type compound of M or N is obtained by firing in a reducing atmosphere. This defect-type material has high luminance stress emission characteristics. As the defect concentration, the defect can be selected in the range of 0.0001 to 20 mol%. If the content is less than 0.0001 mol%, the emission intensity is insufficiently improved.
When the content is 0 mol% or more, the crystal structure of the base material cannot be maintained, and the luminous efficiency decreases, which is not suitable for practical use.

The luminous intensity of the stress-stimulated luminescent material depends on the nature of the mechanical force acting as an excitation source. Generally, the greater the applied mechanical force, the higher the luminous intensity.
Therefore, by measuring the light emission characteristics, the mechanical acting force applied to the material can be known. As a result, the stress state applied to the material can be detected in a non-contact manner, and the stress state can be visualized. Therefore, application in a stress detector and other wide fields can be expected.

[0013] The stress-luminescent material under various environmental, it is physically and chemically stable. The carrier at the emission center is excited by the deformation by applying a mechanical external force, and emits light when returning to the base. This can be applied in various environments. For example, light can be emitted by a mechanical external force not only in the atmosphere but also in various solution environments of water, an inorganic solution, and an organic solution as well as in a vacuum, the atmosphere, a reducing or oxidizing atmosphere.
Therefore, it is effective for stress detection under various environments.

When the stress-stimulated luminescent material is mixed or embedded in an organic material such as resin or plastic at an arbitrary ratio to form a composite material, when a mechanical external force is applied to the composite material, the luminescent material becomes Light emission can be caused by mechanical deformation. Furthermore, the above-mentioned stress-stimulated luminescent material can be applied on the surface of another material. In this case, when a mechanical external force is applied to the material, the light emitting material layer on the surface of the material emits light by deformation. With such a method, light emission in a large area can be obtained with a small amount of light-emitting material.

[0015] In the production of the stress-stimulated luminescent material,
In the base material composed of the oxide represented by MN ₂ O _4, at least one kind of rare earth or transition metal which emits light when carriers excited by mechanical energy return to the ground state is used as a light emission center. After adding and mixing well, bake at 300-1800 ° C. in an oxidizing atmosphere, and then 400-1800 ° C. in a reducing atmosphere.
By baking for 30 minutes or more, doping of the luminescent center is achieved. Further, by adding a flux such as boric acid, the light emission characteristics can be improved.

[0016]

Examples of the present invention will be described below.

[SrAl₂O₄System] Sample 1-1 Using strontium carbonate, alumina and tin oxide as raw materials
Yes, Sn_0.01Sr _0.99Al₂O₄The composition of
After weighing them and mixing well, first in air
And fired at 600 ° C for 1 hour.
And then 5% H₂11 in a reducing atmosphere of Ar
It was baked at 00 ° C. for 4 hours. The obtained compound was used as a sample 1-1.
And

To examine the stress-stimulated luminescent properties of this stress-stimulated luminescent material, the obtained powder sample was molded into the following form. 1) solidified powder sample in a mold, and molded by hydrostatic pressure of 3 GPa, by calcining 1300 ° C. 4 h, the molded pellets produced were emission measurements described below. 2) powder sample and the weight ratio of the epoxy resin were mixed 1: 1 to prepare a composite material pellets were emission measurement. For the measurement of the luminescence characteristics, luminescence was measured for mechanical stimuli such as friction and compression using these molded bodies. The emission spectrum was measured simultaneously by a spectrometer.

FIG. 1 shows that Sn _0.01 Sr _0.99 Al
1 m of the molded pellet of ₂ O ₄ was measured with a friction tester.
4N load with a friction speed of 40c
The time-dependent change of light emission when friction is applied at m / s is shown. The light emitted was strong enough for the naked eye to clearly see blue light emission.

[0020] FIG. 2, the _Sn 0.01 _{Sr 0.99}
The time-dependent change of stress light emission when a mechanical action force of 1000 N is applied to a molded pellet of Al ₂ O ₄ by a material tester is shown. The light emitted was strong enough for the naked eye to clearly see blue light emission. FIG. 3 shows the above Sn
For composite pellets with _0.01 Sr _0.99 Al ₂ O ₄ and the resin, showing the correlation between stress luminescent intensity and the stress against compression. The luminescence intensity showed a correlation that increased with increasing stress.

Samples 1-2 to 1-13 These samples were prepared in the same manner as described above, and the luminescence was measured. Result _(change ratio of _{M x Sr 1-x Al 2} O 4 -system intensity _{I 0} in the case of the emission intensity I and non-stimulated by mechanical stimulation: I / _{I 0)} is shown in Table 1.

[0022]

[Table 1]

The other systems were prepared similarly. Table 2
Table 6 shows that the material systems having particularly high emission intensities were BaAl ₂ O ₄ , MgAl ₂ O ₄ , and MgGa.
The results of ₂ O ₄ , ZnAl ₂ O ₄ , and ZnGa ₂ O ₄ (the ratio of change in emission intensity due to mechanical stimulation of each system) are shown.

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

[Table 4]

[0027]

[Table 5]

[0028]

[Table 6]

Further, it has been confirmed from experiments relating to the present invention that the above-mentioned material systems having appropriate crystal defects have higher emission intensity than the pure phase crystal structure. FIG. 4 shows the crystal structures of two ZnAl ₂ O ₄ : Mn samples. The sample B in the figure has a pure phase ZnAl ₂ O ₄ spinel structure, while the sample A has a pseudo-spinel peak together with the spinel structure. This pseudo spinel peak is considered to be due to partial inverse spinel. Samples A and B were heat-treated at 1250 ° C. and 900 ° C. in 1% H ₂ —N ₂ , respectively.

FIG. 5 shows the stress emission intensity of Sample A and Sample B. The emission intensity of Sample A is much higher than that of Sample B. In addition, many stress-stimulated luminescent materials having crystal defects have high afterglow intensity. FIG. 6 shows the decay time dependence of the emission intensity and the afterglow intensity of Sample A after irradiation with an ultraviolet lamp. Sample B showed a similar tendency, but the emission intensity value was two orders of magnitude lower than Sample A.

The defect concentration was evaluated by thermoluminescence measurement. FIG. 7 shows a measurement example of thermoluminescence in ZnAl ₂ O ₄ : Mn samples A and B. Since the area of the peak was proportional to the defect concentration, it was found that Sample A had two orders of magnitude more crystal defects than Sample B. This crystal defect was caused by pseudo spinel (partially reverse spinel), and it was found that the stress-stimulated luminescence intensity could be dramatically improved.

The defect concentration of a crystal can be optimized in various ways. For example, methods such as firing conditions such as firing temperature and firing atmosphere, charged composition ratio of starting materials for preparation, and additives are effective. For ZnAl ₂ O ₄ : Mn, heat treatment in a reducing atmosphere is particularly effective. FIG. 8 shows that Z was fired at various temperatures shown in the drawing in a reducing atmosphere.
The crystal structure of the nAl ₂ O ₄ : Mn sample is shown. 1150 ° C
When calcined as described above, a pseudo spinel phase appears, and 13
When firing at 00 ° C. or more, the Al ₂ O ₃ impurity phase is significantly increased. As a result of thermogravimetric analysis, it was found that Zn was sublimated when firing at a temperature of 1100 ° C. or more in a reducing atmosphere. Thus, by firing at various temperatures in a reducing atmosphere, the crystal defects of ZnAl ₂ O ₄ : Mn could be controlled.

FIGS. 9A and 9B show the correlation between the crystal structure of the ZnAl ₂ O ₄ : Mn sample treated at various temperatures and the emission intensity. Pure phase spinel has low emission intensity due to too few defects. In addition, when the crystal is largely broken, the number of defects is too large, so that the emission intensity is low. With spinel structure, towards samples with pseudo spinel or partial inverse spinel is, in order to have a proper defect concentration while maintaining the crystal structure, the sample calcined at 1,140-1,280 ° C. represents the highest stress luminous intensity I understood that.
The stress emission intensity is proportional to the afterglow intensity. FIG.
Al ₂ O _4: shows an example of measurement of the relationship between stress luminescent intensity and afterglow intensity in the Mn samples. From this measurement, it was found that the ratio I / I ₀ between the emission intensity I changed by the stress and the afterglow intensity I ₀ when no stress was applied was constant.

Further, in water, ethanol, acetone, 0.1.
The same tendency was obtained under an environment such as a 1 molar hydrochloric acid solution. In the table, the stress emission intensity, the emission center wavelength, and the color for the frictional force and the compressive force are shown at the same time. In addition, the stress luminescence intensity with respect to the tensile force obtained the same result as in the case of compression. Optical properties of various environmental media (scattering coefficient, refractive index, absorption coefficient, etc.)
Although the measured values of the luminescence intensity differ depending on the type, the same tendency as shown in FIGS. 1 and 2 in the atmosphere was obtained in each case.

[0035]

As described above in detail, according to the present invention, a stress-luminescent material which emits light in full color with high luminance by a mechanical external force such as a frictional force, a shearing force, an impact force, and a pressure, and a method of manufacturing the same. In addition, since the above mechanical external force can be directly converted into light by the light emission of the material itself acting on it, in various environments, it can be used as a completely new optical element. Wide application can be expected in the control process of

[Brief description of the drawings]

FIG. 1 shows Sn _0.01 Sr _0.99 Al _{2 according to the} present invention.
Molding pellets O _4, is a graph showing changes over time in light emission when added friction.

FIG. 2 shows Sn _0.01 Sr _0.99 Al _{2 according to the} present invention.
Molding pellets O _4, is a graph showing the variation with time of the stress luminescent when multiplied by the mechanical action force.

FIG. 3 shows Sn _0.01 Sr _0.99 Al _{2 according to the} present invention.
Of O ₄ for the composite pellet, it is a graph showing the correlation between the stress light-emitting intensity and the stress against compression.

FIG. 4 shows a sample A of ZnAl ₂ O ₄ : Mn according to the present invention.
Shows the (spinel structure and pseudo spinel structure) and Sample B X-ray diffraction pattern of the crystal structure of (ZnAl ₂ O ₄ spinel structure phase pure).

FIG. 5 is a graph showing the stress luminescence intensity of Sample A and Sample B of FIG.

FIG. 6 is a graph showing the decay time dependence of the emission intensity and the afterglow intensity of Sample A after irradiation with an ultraviolet lamp.

7 is a graph showing an example of measurement of thermo-luminescence in the sample A and sample B.

FIG. 8: Z calcined at various temperatures in a reducing atmosphere
nAl ₂ O _4: is a diagram showing the crystal structure of the Mn sample by X-ray diffraction pattern.

FIGS. 9 (a) and (b) are graphs showing the correlation between the crystal structure of a ZnAl ₂ O ₄ : Mn sample treated at various temperatures and the emission intensity.

FIG. 10 is a graph showing a measurement example of the relationship between the stress emission intensity and the afterglow intensity in the ZnAl ₂ O ₄ : Mn sample.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuhiro Nonaka 807-1, Nonoshita, Jukucho, Tosu-shi, Saga Prefecture Inside the Kyushu Institute of Industrial Technology (72) Inventor Hiroshi Tateyama Hiroshi Tateyama Jukucho, Tosu-shi, Saga 807 No. 1 F-term in Kyushu Institute of Technology (reference) 4H001 CA02 CA04 CF02 XA00 XA08 XA12 XA13 XA30 XA31 XA38 XA50 XA56 YA22 YA25 YA26 YA27 YA28 YA29 YA30 YA40 YA50 YB52 YB62

Claims (10)

[Claims] A compound represented by MN ₂ O ₄ (M and N
Is composed of an oxide composed of at least one metal element selected from the group consisting of Mg, Sr, Ba, and Zn, and the group consisting of Ga and Al) as a base material, and a carrier excited by mechanical energy. Adding at least one element selected from rare earths or transition metals, which emits light when the element returns to the ground state, to the base material as an emission center; Was set to 0.001 to 20%. 2. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by MgGa ₂ O ₄ is used as a base material. 3. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by ZnGa ₂ O ₄ is used as a base material. 4. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by ZnAl ₂ O ₄ is used as a base material. 5. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by SnZn ₂ O ₄ is used as a base material. 6. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by BaAl ₂ O ₄ is used as a base material. 7. The stress-stimulated luminescent material according to claim 1, wherein an oxide represented by MgAl ₂ O ₄ is used as a base material. 8. A compound represented by MN ₂ O ₄ (M and N
Is an oxide composed of at least one metal element selected from the group consisting of Mg, Sr, Ba and Zn, and the group consisting of Ga and Al). having 0001-20 mole% of lattice defects,
A stress-stimulated luminescent material, comprising: 9. The stress-stimulated luminescent material according to claim 1, wherein the host material is composed of a compound having a spinel structure and includes a pseudo spinel or an inverse spinel structure. 10. An oxide represented by MN ₂ O ₄ (M and N represent a group of Mg, Sr, Ba, Zn, Ga, Al
A base material composed of at least one metal element selected from the group consisting of: a rare earth element or a transition metal that emits light when carriers excited by mechanical energy return to a ground state. As a center, the mole% of the metal element represented by M above is 0.0
After adding and mixing so as to have a concentration of 01 to 20%, the mixture is fired at 300 to 1800 ° C. in an oxidizing atmosphere, and then fired at 400 to 1800 ° C. in a reducing atmosphere to dope the emission center. Of producing a stress-stimulated luminescent material.