Stress luminescent material and stress luminescent resin composition

Abstract

Disclosed are: a stress luminescent material which has an afterglow luminance of 17 mcd / m2 or less at one minute after being irradiated for 20 minutes with light having an illuminance of 200 lx using a standard light source D65; a stress luminescent material which has a composition represented by SrpEuqM1rAl2 + tO4 + u; and a stress luminescent material which has a composition represented by SrpEuqLarM2sAl2 + tO4 + u.

Description

Stress-luminescent material and stress-luminescent resin composition

[0001] The present disclosure relates to a stress-luminescent material and a stress-luminescent resin composition.

[0002] A stress-stimulated luminescent material is a material that emits luminescence in response to an external mechanical stimulus (for example, compression, displacement, friction, impact, etc.).

[0003] A typical mechanoluminescent material is strontium aluminate, SrAl ２ O ４ :Eu ２＋ (Patent Documents 1 and 2) have been reported.

[0004] Strontium aluminate based SrAl ２ O ４ is EU ２＋ and Dy ３＋ It is known that adding SrAl to aluminates makes them phosphorescent materials (Patent Document 3), and they have also been reported as mechanoluminescent materials (Non-Patent Document 1). ２ O ４ is EU ２＋ It has also been reported that adding Dy, Ce, Er, La, or Tm in addition to the above makes it possible to obtain a stress-stimulated luminescent material with high luminescence intensity (Patent Document 4).

[0005] Patent Document 1: Japanese Patent No. 3511083 Patent Document 2: Japanese Patent No. 5007971 Patent Document 3: Japanese Patent No. 2543825 Patent Document 4: Japanese Patent Laid-Open No. 2004-352797

[0006] Non-patent document 1: M. Akiyama, CN.

[0007] The strontium aluminate-based SrAl ２ O ４Stimuli-luminescent materials that use this as a base material often have high luminescence properties, but also have afterglow properties. When a mechanoluminescent material has afterglow properties, when the mechanoluminescent state is photographed with a camera, the difference in brightness between the areas that emit light due to stress and the areas that emit light due to afterglow is small, making it difficult to measure minute sensitivity.

[0008] Therefore, in recent years, the mechanoluminescence index (hereinafter referred to as ML index), which is obtained by subtracting the afterglow intensity from the mechanoluminescence intensity, has been defined as an index of ease of recognition (Non-Patent Document 2). In addition, the mechanoluminescence difference intensity (hereinafter referred to as ML Diff. int.), which is obtained by subtracting the afterglow intensity from the mechanoluminescence intensity, is also defined as an index of ease of recognition.

[0009] The present disclosure has been made in view of the above circumstances, and relates to providing a stress-stimulated luminescent material and a stress-stimulated luminescent resin composition having a high ML index or a high ML Diff. int., in which afterglow characteristics are suppressed while having high stress-stimulated luminescent characteristics.

[0010] As a result of examining various phosphors, the inventors have found that a strontium aluminate phosphor activated with a specific element has a characteristic ML index or ML Diff. int. and is useful as a stress-stimulated luminescent material.

[0011] The present disclosure includes the following aspects: <1> Using a standard light source D65, after irradiating light with an illuminance of 200 lx for 20 minutes, the afterglow luminance after 1 minute has elapsed is 17 mcd / m ２ A mechanoluminescent material having the following properties: <2> Sr ｐ EU ｑ M1 ｒ Al ２＋ｔ O ４＋ｕ <3> A mechanoluminescent material according to <2>, having a composition represented by the formula: <1>, wherein M1 is at least one element selected from the group consisting of La, Mg, Cr, and Fe, and p+q+r=1, 0.7<p<1, 0<q<0.3, 0<r<0.3, -0.2<t<0.4, and -0.2<u<0.4. <4> A mechanoluminescent material according to <2>, wherein M1 is La. <5> A mechanoluminescent material according to <3>, wherein M1 is La. <6> A mechanoluminescent material according to <2>, having a composition represented by the formula: <1>, wherein M1 is at least one element selected from the group consisting of La, Mg, Cr, and Fe, and wherein p+q+r=1, 0.7<p<1, 0<q<0.3, 0<r<0.3, -0.2<t<0.4, and -0.2<u<0.4. <7> A mechanoluminescent material according to <2>, wherein M1 is La. <8> A mechanoluminescent material according to <2>, ｐ EUｑ La ｒ M2 ｓ Al ２＋ｔ O ４＋ｕ wherein M2 is at least one element selected from the group consisting of Mg, Cr, and Fe, and p+q+r+s=1, -0.2<t<0.4, and -0.2<u<0.4. <5> The stress-stimulated luminescent material according to <4>, wherein M2 is Cr. <6> The stress-stimulated luminescent material according to <4>, wherein M2 is Fe. <7> A stress-stimulated luminescent resin composition comprising the stress-stimulated luminescent material according to any one of <1> to <6>.

[0012] According to the present disclosure, there are provided a stress-stimulated luminescent material and a stress-stimulated luminescent resin composition having a high ML index or a high ML Diff. int., which exhibits high stress-stimulated luminescent properties while suppressing afterglow properties.

[0013] Fig. 1 is a graph showing mechanoluminescence spectra of the mechanoluminescent material in Example 10 according to the present disclosure when a scratching stress is applied. Fig. 2 is a graph showing ML index characteristics calculated from the afterglow characteristics and mechanoluminescence characteristics of the mechanoluminescent materials in Example 16 according to the present disclosure and Comparative Example 1. Fig. 3 is a graph showing ML Diff. int. characteristics calculated from the afterglow characteristics and mechanoluminescence characteristics of the mechanoluminescent materials in Example 16 according to the present disclosure and Comparative Example 1.

[0014] An embodiment of the present disclosure will be described in detail below. However, the present disclosure is not limited to the following embodiment. In the following disclosure, components (including element steps, etc.) are not essential unless otherwise specified. The same applies to numerical values ​​and their ranges, and do not limit the present disclosure.

[0015] In the present disclosure, when a numerical range is indicated using "to", the numerical values ​​before and after "to" are included as the lower and upper limits, respectively. In the present disclosure, when a numerical range is described in stages, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another staged numerical range. Furthermore, in the present disclosure, the upper or lower limit of that numerical range may be replaced with a value shown in the examples. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the content of each component refers to the total content of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, when multiple elements are listed using "or", this does not exclude the combination of multiple elements unless a technical contradiction occurs, unless otherwise specified. In the present disclosure, when an element is described in the singular, this does not exclude the presence of multiple elements unless a technical contradiction occurs, unless otherwise specified. In the present disclosure, multiple exemplary embodiments described separately may be combined with each other to form a new embodiment, unless mutually contradictory.

[0016] <Stress-luminescent material> (Stress-luminescent material of first embodiment) The stress-luminescent material of the first embodiment of the present disclosure was irradiated with light of 200 lx illuminance for 20 minutes using a standard light source D65, and after 1 minute, the afterglow luminance was 17 mcd / m ２ In the present disclosure, the afterglow brightness after 1 minute is 17 mcd / m or less. ２ If it is below this, it can be said that the afterglow characteristics are suppressed.

[0017] In the stress-stimulated luminescent material of the first embodiment, after 20 minutes of irradiation with light of 200 lx using a standard light source D65, the afterglow luminance after 1 minute was 15 mcd / m ２ It is preferable that the density is 10 mcd / m or less. ２ More preferably, it is 5 mcd / m or less. ２ It is more preferable that:

[0018] In the stress-stimulated luminescent material of the first embodiment, after 20 minutes of irradiation with light of 200 lx using a standard light source D65, the afterglow luminance after 10 minutes was 5 mcd / m ２ Preferably, it is less than 3 mcd / m ２ More preferably, it is 1 mcd / m or less. ２ It is more preferable that:

[0019] (Stress-stimulated luminescent material of second embodiment) The stress-stimulated luminescent material of the second embodiment of the present disclosure is a material containing Sr ｐ EU ｑ M1 ｒ Al ２＋ｔ O ４＋ｕ wherein M1 is at least one element selected from the group consisting of La, Mg, Cr, and Fe, and p+q+r=1, 0.7<p<1, 0<q<0.3, 0<r<0.3, −0.2<t<0.4, and −0.2<u<0.4.

[0020] In the stress-stimulated luminescent material according to the second embodiment of the present disclosure, it is preferable that p+q+r=1, 0.8<p<1, 0<q<0.2, 0<r<0.2, −0.2<t<0.4, and −0.2<u<0.4.

[0021] In the stress-stimulated luminescent material of the second embodiment, Sr, Al, and O are elements constituting the base material, Eu is a luminescence center, and M1 is an additive that increases trap centers or lattice defects (oxygen defects, cation defects, antisite defects, etc.). In the stress-stimulated luminescent material of the second embodiment, the trap level (the energy position of the trap center M1 or the energy position of a lattice defect) generated by adding M1, i.e., at least one element selected from the group consisting of La, Mg, Cr, and Fe, is located at a depth appropriately separated from the band edge, so that light energy can be stored and the stored energy can be released by stress to emit light. Furthermore, since p, q, r, t, and u are within the above-mentioned predetermined numerical ranges, the material has high stress-stimulated luminescence properties while suppressing afterglow characteristics.

[0022] In the stress-stimulated luminescent material of the second embodiment, M1 is preferably La from the viewpoint of achieving high stress-stimulated luminescent properties and suppressing afterglow properties.

[0023] The total amount of Eu and M1 added in the stress-stimulated luminescent material of the second embodiment is preferably 0.002% to 30% in mole percent relative to Sr, more preferably 0.01% to 10% in mole percent, and even more preferably 1% to 5% in mole percent, in order to achieve a high ML index and ML Diff. int. Alternatively, the total amount of Eu and M1 added in the stress-stimulated luminescent material of the second embodiment is preferably 0.001% to 20% in mole percent relative to Sr, more preferably 0.01% to 10% in mole percent, and even more preferably 1% to 5% in mole percent, in order to achieve a high ML index and ML Diff. int.

[0024] The mechanoluminescent material of the second embodiment is irradiated with light of 200 lx illuminance for 20 minutes using a standard light source D65, and the afterglow luminance after 1 minute is 17 mcd / m ２ Preferably, it is 15 mcd / m or less. ２ More preferably, it is 10 mcd / m or less. ２ More preferably, it is 5 mcd / m or less. ２ It is particularly preferred that:

[0025] The mechanoluminescent material of the second embodiment is irradiated with light of 200 lx illuminance for 20 minutes using a standard light source D65, and after 10 minutes the afterglow luminance is 5 mcd / m ２ Preferably, it is less than 3 mcd / m ２ More preferably, it is 1 mcd / m or less. ２ It is more preferable that:

[0026] (Stress-stimulated luminescent material of the third embodiment) The stress-stimulated luminescent material of the third embodiment of the present disclosure is a material containing Sr ｐ EU ｑ La ｒ M2 ｓ Al ２＋ｔ O ４＋ｕ wherein M2 is at least one element selected from the group consisting of Mg, Cr, and Fe, and p+q+r+s=1, −0.2<t<0.4, and −0.2<u<0.4.

[0027] In the stress-stimulated luminescent material of the third embodiment, Sr, Al, and O are elements constituting the base material, Eu is a luminescence center, and La and M2 are additives that increase trap centers or lattice defects (oxygen defects, cation defects, antisite defects, etc.). In the stress-stimulated luminescent material of the third embodiment, trap levels (energy positions of the La trap center, energy positions of the M2 trap center, or energy positions of lattice defects) generated by adding La and M2, i.e., La and at least one element selected from the group consisting of Mg, Cr, and Fe, are located at depths appropriately separated from the band edge, allowing light energy to be stored and the stored energy to be released by stress, resulting in light emission. Furthermore, since p, q, r, s, t, and u are within the above-mentioned predetermined numerical ranges, the material has high stress-stimulated luminescence properties while suppressing afterglow characteristics.

[0028] In the stress-stimulated luminescent material of the third embodiment, M2 is preferably Cr or Fe from the viewpoint of achieving high stress-stimulated luminescent properties and suppressing afterglow properties.

[0029] Sr in the stress-stimulated luminescent material according to the third embodiment of the present disclosure ｐ EU ｑ La ｒ M2 ｓ Al ２＋ｔ O ４＋ｕ In the third embodiment of the present disclosure, p, q, r, and s each satisfy the following conditions: p+q+r+s=1, -0.2<t<0.4, and -0.2<u<0.4. In the third embodiment of the present disclosure, p, q, r, and s each satisfy the following conditions: 0.7<p<1, 0<q<0.3, 0<r<0.3, and 0≦s<0.3. In the third embodiment of the present disclosure, p, q, r, and s each satisfy the following conditions: 0.7<p<1, 0<q<0.2, 0<r<0.2, and 0<s<0.2.

[0030] The total amount of Eu, La, and M2 added in the stress-stimulated luminescent material of the third embodiment is preferably 0.002% to 30% in mole percent relative to Sr, more preferably 0.01% to 10% in mole percent, and even more preferably 1% to 5% in mole percent, in order to achieve a high ML index and ML Diff. int. Alternatively, the total amount of Eu, La, and M2 added in the stress-stimulated luminescent material of the third embodiment is preferably 0.002% to 30% in mole percent relative to Sr, more preferably 0.005% to 10% in mole percent, and even more preferably 0.01% to 5% in mole percent, in order to achieve a high ML index and ML Diff. int.

[0031] The stress-stimulated luminescent material of the third embodiment is irradiated with light of 200 lx illuminance for 20 minutes using a standard light source D65, and the afterglow luminance after 1 minute is 17 mcd / m ２ Preferably, it is 15 mcd / m or less. ２ More preferably, it is 10 mcd / m or less. ２ More preferably, it is 5 mcd / m or less. ２ It is particularly preferred that:

[0032] The stress-stimulated luminescent material of the third embodiment is irradiated with light of 200 lx illuminance for 20 minutes using a standard light source D65, and after 10 minutes, the afterglow luminance is 5 mcd / m ２ Preferably, it is less than 4 mcd / m ２ More preferably, it is 2 mcd / m or less. ２ It is more preferable that:

[0033] (Synthesis of Stress-Stimulated Luminescent Material) An example of a method for synthesizing the stress-stimulated luminescent material according to the first to third embodiments of the present disclosure will be described below. The raw material for the stress-stimulated luminescent material according to the first to third embodiments is, for example, strontium carbonate (SrCO 3 ) as a raw material for strontium (Sr). ３ ), and aluminum oxide (Al) as a raw material for aluminum (Al) ２ O ３ ) and europium oxide (Eu) as a raw material for europium (Eu). ２ O ３) and optionally lanthanum oxide (La) as a source of lanthanum (La). ２ O ３ ), magnesium carbonate (MgCO ) as a raw material for magnesium (Mg) ３ ), chromium oxide (Cr) as a raw material for chromium (Cr) ２ O ３ ) and / or iron oxide (Fe ２ O ３ ) are prepared. These raw materials of the mechanoluminescent material and the flux are mixed in predetermined amounts to produce a mixed powder of raw materials. Here, carbonates and oxides are exemplified as raw materials, but hydroxides, for example, may also be selected.

[0034] When a flux is used, the flux may be, for example, sodium carbonate (Na ２ CO ３ ) and sodium bicarbonate (NaHCO ３ ), alkali metal carbonates such as lithium phosphate (Li ３ P.O. ４ ), potassium phosphate (K ３ P.O. ４ ) and potassium hydrogen phosphate (K ２ HPO ４ ), phosphates such as boric acid (H ３ BO ３ ), as well as boron compounds such as potassium sulfate (K ２ SO ４ ) and the like can be suitably used.

[0035] In the process of mixing the raw materials of the mechanoluminescent material with the flux, for example, the raw material powders are placed in a pot containing alumina balls and mixed by ball milling to produce a uniform mixed powder. This mixed powder is then filled into a heat-resistant container such as an alumina crucible. This may be further placed in a larger quartz crucible to form a double crucible. The mixed powder filled in the crucible is placed in an electric furnace and fired at a temperature range of 1200°C to 1800°C, preferably 1300°C to 1600°C, for 1 hour to 20 hours, preferably 4 hours to 15 hours. The firing atmosphere is preferably a reducing atmosphere containing a reducing gas. After this firing process, the material is subjected to appropriate processes such as crushing, washing, drying, and sieving to obtain a mechanoluminescent material of a desired particle size.

[0036] (Evaluation of Stimuli-Luminescent Materials) In the present disclosure, mechanoluminescent materials are evaluated by the ML index or ML Diff. int., which is measured by the following method. An example of a method for evaluating the properties of a mechanoluminescent material is shown below. First, a coating material containing a mixture of a mechanoluminescent material and a binder is applied to the surface of an object to be tested to prepare a test coating sample. Examples of binders include acrylic resins, urethane resins, and epoxy resins. The test coating sample is irradiated with light to store light energy. After waiting for the afterglow intensity to decrease, mechanical energy such as tensile stress is applied to observe the mechanoluminescent intensity. Using a CCD camera or C-MOS camera as a luminescence intensity detector, the afterglow intensity and mechanoluminescent intensity after blocking the excitation light are measured. The value obtained by dividing the measured mechanoluminescent intensity (ML) by the afterglow intensity (AG) at the start of stress application is defined as the ML index, and the value obtained by subtracting ML by AG is defined as the ML Diff. int. (Non-Patent Document 2): [ML index]=[ML] / [AG] (1) [ML Diff. int.]=[ML]-[AG] (2)

[0037] <Stress-luminescent composition> The stress-luminescent composition of the present disclosure includes any one of the stress-luminescent material of the first embodiment, the stress-luminescent material of the second embodiment, or the stress-luminescent material of the third embodiment of the present disclosure.

[0038] The mechanoluminescent composition of the present disclosure may contain a binder, such as an acrylic resin, a urethane resin, or an epoxy resin.

[0039] The mechanoluminescent composition of the present disclosure may further contain additives, such as ultraviolet absorbers, colorants, softeners, antistatic agents, heat stabilizers, light diffusing agents, fluorescent brighteners, antioxidants, dispersants, coupling agents, surfactants, anti-fogging agents, anti-settling agents, anti-sagging agents, anti-rust agents, and emulsifiers.

[0040] The stress-stimulated luminescent composition of the present disclosure may be a stress-stimulated luminescent resin composition containing any one of the stress-stimulated luminescent material of the first embodiment, the stress-stimulated luminescent material of the second embodiment, or the stress-stimulated luminescent material of the third embodiment of the present disclosure.

[0041] (Preparation of Stimuli-Luminescent Composition) The mechanoluminescent composition can be used to confirm mechanoluminescent properties, etc. An example of a method for preparing a mechanoluminescent composition is shown below. A target mechanoluminescent material and a binder are mixed in a mass ratio of 1:9, and the mixture is applied to a white paper or polycarbonate film, and then allowed to dry naturally to obtain a coating sample, which is a composition for observing mechanoluminescence intensity.

[0042] Hereinafter, the present disclosure will be described more specifically with reference to examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[0043] Example 1 As a raw material, 119.8 g of strontium carbonate (SrCO ３ ), 82.3 g of aluminum oxide (Al ２ O ３ ), 1.46 g of europium oxide (Eu ２ O ３ ) and 1.35 g of lanthanum oxide (La ２ O ３ ) were weighed, and the above raw materials were thoroughly mixed using a ball mill. This mixture was filled into an alumina crucible and fired in an electric furnace in a hydrogen / nitrogen 3% reducing atmosphere at 1450°C for 6 hours. After that, it was cooled to room temperature, and after being recovered from the crucible, it was milled using alumina beads with a diameter of 2 mm. After a drying process and a sieving process, Sr ０．９８９ EU０．００１ La ０．０１ Al １．９５ O ３．９３ A powdery compound represented by the following formula was obtained.

[0044] Examples 2 to 13 Compounds shown in Table 1 were obtained in the same manner as in Example 1, except that the elements and their molar ratios were changed as shown in Table 1.

[0045] Comparative Example 1: As an existing mechanoluminescent material, Sr ０．９８ EU ０．０１ La ０．０１ Al ２ O ４ The compound represented by the formula:

[0046]

[0047] It should be noted that Examples 1 to 13 are the stress-stimulated luminescent materials of the first embodiment, the second embodiment, and the third embodiment of the present disclosure.

[0048] Example 14 As a raw material, 114.2 g of strontium carbonate (SrCO ３ ), 87.4 g of aluminum oxide (Al ２ O ３ ), 1.40 g of europium oxide (Eu ２ O ３ ), 1.30 g of lanthanum oxide (La ２ O ３ ) and 0.6724 g of magnesium carbonate (MgCO ３ The raw materials were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain Sr ０．９７ EU ０．０１ La ０．０１ Mg ０．０１ Al ２．１５ O ４．２３ The compound represented by the formula:

[0049] Example 15 As a raw material, 115.1 g of strontium carbonate (SrCO ３ ), 87.2 g of aluminum oxide (Al ２ O ３ ), 1.40 g of europium oxide (Eu２ O ３ ), 1.30 g of lanthanum oxide (La ２ O ３ ) and 0.0060 g of chromium oxide (Cr ２ O ３ The raw materials were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain Sr ０．９７９９ EU ０．０１ La ０．０１ Cr ０．０００１ Al ２．１５ O ４．２３ The compound represented by the formula:

[0050] Example 16 As a raw material, 115.1 g of strontium carbonate (SrCO ３ ), 87.2 g of aluminum oxide (Al ２ O ３ ), 1.40 g of europium oxide (Eu ２ O ３ ), 1.30 g of lanthanum oxide (La ２ O ３ ) and 0.0064 g of iron(III) oxide (Fe ２ O ３ The raw materials were thoroughly mixed using a ball mill. This mixture was treated in the same manner as in Example 1 to obtain Sr ０．９７９９ EU ０．０１ La ０．０１ Fe ０．０００１ Al ２．１５ O ４．２３ The results of Examples 14 to 16 are shown in Table 2.

[0051]

[0052] It should be noted that Examples 14 to 16 are the stress-stimulated luminescent materials of the first embodiment, the second embodiment, and the third embodiment of the present disclosure.

[0053] [Measurement of Mechanoluminescence Spectrum] First, for Example 10, the mechanoluminescence spectrum from 350 nm to 800 nm was measured using a multichannel spectrometer (Model: PMA-12, silicon photodiode detector, manufactured by Hamamatsu Photonics). A mixture of the target mechanoluminescent material and transparent screen ink (VG screen ink; 000 Medium, manufactured by Teikoku Ink Mfg. Co., Ltd.) in a mass ratio of 1:9 was applied to white paper and allowed to dry naturally to obtain a coating sample. The coating film was formed to a thickness of 150 μm. The obtained coating sample was irradiated with ultraviolet light using a UV lamp (peak emission wavelength 365 nm) for 1 minute to enter an excited state, and then scratch stress was applied, and the mechanoluminescence spectrum was measured using the multichannel spectrometer. The results are shown in Figure 1. From the obtained mechanoluminescence spectrum, Eu ２＋ It can be seen that the material exhibits stress-induced luminescence with a peak at around 520 nm, which is characteristic of the material.

[0054] [Visual Evaluation of Stimuli-Luminescent Sensitivity] Next, visual evaluation of mechanoluminescent sensitivity was carried out for Examples 1 to 13 and Comparative Example 1. In the same manner as above, a mixture of the target mechanoluminescent material and transparent screen ink was applied to white paper to obtain a coating sample with a coating thickness of 150 μm. Each of the obtained coating samples was irradiated with ultraviolet light using an ultraviolet lamp (peak emission wavelength 365 nm) for 1 minute to induce an excited state. Immediately after the end of irradiation, a scratching stress was applied so as to apply the same pressure, and the mechanoluminescent intensity was observed visually. The results of the mechanoluminescent sensitivity evaluation for Examples 1 to 13 and Comparative Example 1 are shown in Table 3. For the mechanoluminescent sensitivity evaluation, the mechanoluminescent intensity was visually judged, and the relative mechanoluminescent intensity is shown, with Comparative Example 1 being set at 100.

[0055] [Afterglow Characteristics] Next, the afterglow characteristics were examined for Examples 1 to 13 and Comparative Example 1. The target mechanoluminescent materials were filled into aluminum sample containers and then left in a dark place for two days to remove the afterglow. Using a standard light source D65 as the excitation light source, the samples from which the afterglow had been removed were irradiated with light at an illuminance of 200 lx for 20 minutes (excitation conditions described in JIS Z 9107 Safety Signs - Performance Classification, Performance Standards and Test Methods (ISO 17398 2004)). The afterglow brightness was measured 1 minute and 10 minutes after the end of irradiation using a 2D color luminance meter (model: UA-200AWS, manufactured by Topcon). The afterglow brightness for Examples 1 to 13 and Comparative Example 1 is shown in Table 3.

[0056]

[0057] The results shown in Table 3 show that the mechanoluminescent materials of Examples 1 to 13 according to the present disclosure all exhibit lower afterglow luminance than Comparative Example 1. Due to the suppression of the afterglow luminance, the mechanoluminescent materials of Examples 1 to 13 according to the present disclosure can all exhibit a high ML index or a high ML Diff. int., even though they have a weaker mechanoluminescent intensity than Comparative Example 1.

[0058] Similarly, visual mechanoluminescence sensitivity evaluation and afterglow luminance measurement were carried out for Examples 14 to 16. Table 4 shows the mechanoluminescence sensitivity evaluation and relative afterglow luminance when Comparative Example 1 is set to 100.

[0059]

[0060] [Stimuli-Luminescent Properties] Next, the mechanoluminescent properties were examined for Examples 2, 5, and 10, which showed low afterglow brightness and good results in the mechanoluminescent sensitivity evaluation shown in Table 3, as well as Comparative Example 1. A mixture of the target mechanoluminescent material and transparent screen ink (VG Screen Ink; 000 Medium, manufactured by Teikoku Ink Mfg. Co., Ltd.) at a mass ratio of 1:9 was applied to a polycarbonate film and allowed to dry naturally to obtain a coating sample. The coating film was formed to a thickness of 150 μm. Both ends of each obtained coating sample were fixed to the jigs of a small tabletop testing machine (manufactured by Tokyo Koki Testing Machine Co., Ltd.). The jigs were fixed with a gap between them so that the length of the coating sample was 40 mm so that luminescence could be observed. The upper jig moved up and down, allowing tensile and compressive stress to be applied, and the distance (mm) of the rise and fall and the stress (N) could be measured simultaneously. After fixation, the coating sample was irradiated with light from a spot UV irradiation device (manufactured by Ushio Inc.) as an excitation light source for 5 minutes. Five minutes after the end of irradiation, the upper jig was raised at a speed of 10 mm / min to apply tensile stress. Using a photomultiplier tube (manufactured by Hamamatsu Photonics), the afterglow intensity after the end of irradiation and the mechanoluminescence intensity when tensile stress was applied were measured.

[0061] [ML index calculation] Next, the ML index was calculated from the afterglow characteristics and mechanoluminescence characteristics obtained for Examples 2, 5, and 10, and Comparative Example 1. As shown in the above formula (1), the ML index was calculated by dividing the mechanoluminescence intensity (ML: strains of 3000 μST and 6000 μST) by the afterglow intensity (AG) at the start of stress application (5 minutes after the end of irradiation). The results of the ML index for Examples 2, 5, and 10, and Comparative Example 1 are shown in Table 5.

[0062] [ML Diff. int.] As shown in the above formula (2), the mechanoluminescence intensity (ML: strains of 3000 μST and 6000 μST) was subtracted by the afterglow intensity (AG) at the start of stress application (5 minutes after the end of irradiation) to obtain the ML Diff. int. When the ML Diff. int. of Comparative Example 1 at a strain of 3000 μST was set to 100, the relative ML Diff. int. of Examples 2, 5, and 10 and Comparative Example 1 are shown in Table 5.

[0063]

[0064] The results shown in Table 5 show that the ML index and relative ML Diff. int. of Examples 2, 5, and 10 according to the present disclosure all exhibit higher values ​​than those of Comparative Example 1.

[0065] The afterglow and mechanoluminescence properties were investigated for Examples 15 and 16 as described above. The ML index was calculated from the results, and the relative ML Diff. int., where the ML Diff. int. for Comparative Example 1 at an applied strain of 3000 μST is set to 100, is shown in Table 6. The ML index characteristics of Example 16 and Comparative Example 1 are shown in FIG. 2, and the relative ML Diff. int. characteristics of Example 16 and Comparative Example 1 are shown in FIG. 3.

[0066]

[0067] From the results shown in Table 6 and FIGS. 2 and 3, it can be seen that the ML index and relative ML Diff. int. of Examples 15 and 16 according to the present disclosure all exhibit higher values ​​than those of Comparative Example 1.

[0068] As described above, the mechanoluminescent materials according to the first to third embodiments of the present disclosure are mechanoluminescent materials that exhibit high ML index and high ML Diff. int characteristics due to low afterglow characteristics. Therefore, unlike conventional mechanoluminescent materials, the mechanoluminescent materials according to the first to third embodiments of the present disclosure exhibit a large difference in brightness between areas that emit light due to stress and areas that emit light due to afterglow when photographed in a mechanoluminescent state, making it possible to measure minute sensitivity.

[0069] The disclosure of Japanese Patent Application No. 2024-134660, filed on August 9, 2024, is incorporated herein by reference in its entirety. In addition, all documents, patent applications, and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard were specifically and individually indicated to be incorporated by reference.

[0070] The mechanoluminescent materials of the first to third embodiments of the present disclosure are capable of measuring luminescence due to mild compression, tension, and expansion / contraction, and are therefore expected to be applied to new sensing technologies. They can visualize strain distribution across an entire surface in two dimensions, enabling real-time observation of dynamic deformation and stress changes. They respond repeatedly to even minute changes and enable non-contact measurement. Furthermore, they can be applied to a variety of materials, including metals, resins, wood, glass, and ceramics. By mixing, coating, or impregnating structural materials as pigments or fillers, they demonstrate utility in fields such as architecture, civil engineering, transportation equipment, robotics, and wearables. Specifically, by applying the mechanoluminescent materials of the first to third embodiments of the present disclosure to the surface of an object, stress-induced luminescence can be detected at stress-initiated stress concentrations, potential defects, and cracks due to aging. Examples of such objects include automobiles, automobile body parts, aircraft body parts, ships, machine tool-related parts, buildings, bridges, tunnel interior walls, and tanks. It can also be applied to reliability testing and evaluation in the automotive and aerospace industries, as well as safety management of tunnels and bridge structures. It can also be applied to toys, educational materials, art, sporting goods, and more, contributing to entertainment value and safety improvements. It can also be used for safety management in the automotive and aerospace industries and infrastructure, making it applicable to a wide range of industrial fields.

Claims

Using standard light source D65, after irradiating light of 200 lx for 20 minutes, the afterglow brightness after 1 minute is 17 mcd / m ２ The following stress-luminescent material: Sr ｐ EU ｑ M1 ｒ Al ２＋ｔ O ４＋ｕ It has a composition represented by M1 is at least one element selected from the group consisting of La, Mg, Cr, and Fe, and the mechanoluminescent material satisfies p+q+r=1, 0.7<p<1, 0<q<0.3, 0<r<0.3, −0.2<t<0.4, and −0.2<u<0.

4. The mechanoluminescent material according to claim 2 , wherein M1 is La. Sr ｐ EU ｑ La ｒ M2 ｓ Al ２＋ｔ O ４＋ｕ It has a composition represented by M2 is at least one element selected from the group consisting of Mg, Cr, and Fe, and the mechanoluminescent material satisfies p+q+r+s=1, −0.2<t<0.4, and −0.2<u<0.

4. The mechanoluminescent material according to claim 4 , wherein M2 is Cr. 　 The mechanoluminescent material according to claim 4 , wherein M2 is Fe. 　 A stress-stimulated luminescent resin composition comprising the stress-stimulated luminescent material according to any one of claims 1 to 6.

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