Stress luminescent film and method for forming the same, and strain / stress / load distribution detection system and strain / stress / load distribution detection method using the stress luminescent film

Abstract

To provide a stress luminescent film capable of detecting the strain of a target object, the stress of the target object or a load applied to the target object by luminescence even in the presence of visible light, a method for forming the same, a strain / stress / load distribution detection system using the stress luminescent film, and a strain / stress / load distribution detection method.SOLUTION: And a visible-light-blocking layer provided on a side of the light-emitting layer opposite to the target object, wherein the light-emitting layer contains a mechanoluminescent material that emits specific-wavelength electromagnetic waves having wavelengths in a range of 850nm to 2500nm, and the visible-light-blocking layer blocks 80% to 100% of the electromagnetic waves having wavelengths in the range of 360nm to 830nm and transmits 50% to 100% or more of the specific-wavelength electromagnetic waves emitted from the light-emitting layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a mechanoluminescent film that can visualize the strain, stress, or load on an object by emitting light even in an environment where artificial lighting or the like is present, a method for forming the same, and a strain, stress, and load distribution detection system and method using the mechanoluminescent film. [Background technology]

[0002] A variety of industrial fields have long required technology to measure strain, stress, and force (load) applied to a reference surface, especially small strain, stress, and load. For example, in fields such as mechanical testing and strength testing that involve changes in shape (fracture, deformation, etc.), particularly in strength testing of structural materials such as CFRP (carbon fiber reinforced plastics), automobile collision tests, and ship mooring strength evaluation, there is a demand for technology that can detect even smaller strains.

[0003] One such technique is a method for measuring stress distribution using a mechanoluminescent material, which is characterized by applying stress to a subject containing a mechanoluminescent material that itself emits light in proportion to stress, and visualizing the stress distribution in the subject based on the luminescence intensity of the mechanoluminescent material in the subject (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-215157 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the mechanoluminescence (electromagnetic waves) emitted from a mechanoluminescent material often falls within the visible light range (visible light region) with wavelengths of 360 nm to 830 nm.

[0006] Therefore, in an environment where external visible light (electromagnetic waves emitted from artificial lighting, etc.) is present, such as indoors illuminated by artificial lighting, the intensity of the external visible light is greater than the intensity of the electromagnetic waves emitted from the stress-luminescent material, and the electromagnetic waves emitted from the stress-luminescent material are drowned out by the external visible light reflected from the surface of the subject or the surface of the coating film containing the stress-luminescent material.

[0007] As a result, in an environment where external visible light with a higher intensity than the electromagnetic waves emitted from the stress-stimulated luminescent material is present (for example, an environment with an illuminance of 3 lux or more), the measurement method of Patent Document 1 has the problem of being unable to detect the electromagnetic waves emitted from the stress-stimulated luminescent material.

[0008] In particular, JIS Z9110 (General Provisions for Lighting Standards) specifies lighting requirements for various human activities, and factories, workplaces, etc. cannot be left in the dark (environments with illuminance below 100 lux) for long periods of time. In other words, in factories, workplaces, etc., there was a problem in that the conventional measurement method using mechanoluminescent materials could not detect (visualize) the strain distribution of a target object, the stress of a target object, or the load acting on a target object using the measurement method of Patent Document 1.

[0009] In the conventional measurement methods using mechanoluminescent materials described above, the mechanoluminescence emitted from the mechanoluminescent material was limited to the visible light region because it was primarily intended to be visible to the human eye. Recent research and development has aimed to differentiate the wavelength of external visible light from the wavelength of the electromagnetic waves emitted from mechanoluminescent materials, and materials that exhibit mechanoluminescence of specific electromagnetic wavelengths in the wavelength region of 850 to 2500 nm have been developed (see Japanese Patent Nos. 6249477 and 6345676).

[0010] The inventors of the present invention have also conducted extensive research and development into a method for measuring the strain, stress, or load of a target object in an environment where external visible light with an intensity higher than the intensity of the mechanoluminescence emitted from a mechanoluminescent material is present. As a result, they discovered a problem: when mechanoluminescent materials emitting electromagnetic waves in the 850-2500 nm wavelength range are irradiated with artificial light containing the excitation wavelength of the mechanoluminescent material, they emit fluorescence through a mechanism different from mechanoluminescence. That is, when irradiated with artificial light, mechanoluminescent materials emit fluorescence (fluorescence) even when the target object is not strained, stressed, or under load. As a result, when irradiated with artificial light, the intensity of the electromagnetic waves emitted from the mechanoluminescent material does not change solely in response to the strain, stress, or load of the target object, making it impossible to detect (visualize) these changes. This issue of fluorescence through a mechanism different from mechanoluminescence has not been reported before, and is a new problem (challenge) discovered by the inventors of the present invention.

[0011] In view of the above circumstances, the present invention aims to provide a mechanoluminescent film that can detect strain, stress, or load on an object by emitting light even in the presence of visible light such as artificial lighting, as well as a method for forming the same, and a strain, stress, and load distribution detection system and method using the mechanoluminescent film.

[0012] These problems (issues) do not preclude the existence of other problems. Furthermore, each aspect of the present invention described below does not necessarily solve all of these problems (issues). Furthermore, other problems (issues) may be identified from the description of the specification, drawings, or claims. [Means for solving the problem]

[0013] As a result of intensive research into the above-mentioned problems, the inventors of the present invention have discovered the following revolutionary mechanoluminescent film, a method for forming the same, a strain / stress / load distribution detection system, and a strain / stress / load distribution detection method.

[0014] A first aspect of the present invention for solving the above-mentioned problems is a stress-stimulated luminescent film provided on the surface of a target object, which emits electromagnetic waves with a specific wavelength of 850 nm to 2500 nm in response to strain, stress, or load on the target object, the stress-stimulated luminescent film comprising: a light-emitting layer provided on the surface of the target object; and a visible-light-shielding layer provided on the surface of the light-emitting layer opposite the target object, the light-emitting layer containing a stress-stimulated luminescent material that emits electromagnetic waves with a specific wavelength in response to strain, stress, or load on the target object, and the visible-light-shielding layer blocks 80% to 100% of electromagnetic waves with a wavelength of 300 nm to 780 nm and transmits 50% to 100% of the electromagnetic waves with a specific wavelength emitted from the light-emitting layer.

[0015] According to the first aspect, since electromagnetic waves of a specific wavelength (electromagnetic waves with a wavelength of 850 nm to 2500 nm) are detected, they are less susceptible to the influence of reflection of external visible light such as artificial lighting, etc. As a result, even in the presence of external visible light, it is possible to detect the distribution of strain on the target object, stress on the target object, or load acting on the target object.

[0016] Furthermore, since the stress-stimulated luminescent film is composed of a light-emitting layer provided on the surface of the target object and a visible light-shielding layer provided on the surface of the light-emitting layer, even if external visible light is incident on the surface of the stress-stimulated luminescent film, it is blocked by the visible light-shielding layer and hardly reaches the light-emitting layer. As a result, the above-mentioned fluorescence (fluorescence by a mechanism different from stress-stimulated luminescence) can be prevented.

[0017] The second aspect of the present invention is that the stress luminescent material is SrAl2O4:Eu,Cr,Nd (Japanese Patent No. 6345676), SrAl2O4:Eu,Er (http: / / iopscience.iop.org / 1757 - 899X / 18 / 21 / 212013), Sr3Sn2O7:Nd (Japanese Patent No. 6249477), Li 0.10 , Na X NbO3:Nd (0.10 ≦ X ≦ 0.98) (Japanese Patent No. 7320888), ZnO:Nd (International Publication No. 2022 / 186378), CaZnOS:Nd (https: / / doi.org / 10.1021 / acsami.8b02530), CaZnOS:Er (https: / / doi.org / 10.1016 / j.nanoen.2019.104413), SrZnSO:Nd (https: / / doi.org / 10.1016 / j.nanoen.2019.104329) or Li X Zn 1-X O:Nd (0.0001 < X < 0.7) (International Publication No. 2022 / 186378), which is the stress luminescent film according to the first aspect, characterized in that.

[0018] According to such a second aspect, since specific wavelength electromagnetic waves included in the range of 850 nm to 2500 nm can be radiated with high intensity, even in the presence of high - intensity visible light (for example, 3 lux to 1000 lux), the strain of the target object, the stress of the target object or the distribution regarding the load applied to the target object can be detected.

[0019] The third aspect of the present invention is that the visible - light shielding layer includes at least one of a near - infrared transmitting material (manufactured by artience Co., Ltd., SVSS IP BLACK), a near - infrared transmitting black dispersion liquid (manufactured by Tokushiki Co., Ltd., IRBK - 0003), Y 0.90 Zn 0.10 MnO3, a mixture of YMnO3 and Mn3O4 or at least one of the azo pigments described in International Publication No. WO2015 / 125224, or has at least one of a germanium thin film, a silicon thin film or a zinc sulfide thin film, which is the stress luminescent film according to the first aspect, characterized in that.

[0020] According to the third aspect, electromagnetic waves with wavelengths of 300 nm to 780 nm can be blocked with a higher blocking rate, so that the strain of the target object, the stress of the target object, or the distribution of the load acting on the target object can be detected even in the presence of high-intensity external visible light.

[0021] A fourth aspect of the present invention is the stress-luminescent film structure according to the third aspect, characterized in that the visible light-shielding layer has a thickness of 0.0001 mm to 0.1 mm.

[0022] According to the fourth aspect, electromagnetic waves with wavelengths of 300 nm to 780 nm can be blocked with an even higher blocking rate, so that the strain of the target object, the stress of the target object, or the distribution of the load acting on the target object can be detected even in the presence of external visible light with a higher intensity.

[0023] A fifth aspect of the present invention is a strain / stress / load distribution detection system for visualizing a strain distribution in a target object, a stress distribution in the target object, or a load distribution acting on the target object, characterized in that the strain / stress / load distribution detection system comprises a mechanoluminescent film according to any one of the first to fourth aspects and a detection unit for detecting electromagnetic waves of a specific wavelength emitted from the mechanoluminescent film.

[0024] According to the fifth aspect, by detecting electromagnetic waves of a specific wavelength, it is less susceptible to the influence of reflection of external visible light contained in artificial lighting, etc. As a result, even in the presence of external visible light, it is possible to detect the distribution of strain on the target object, stress on the target object, or load acting on the target object.

[0025] Furthermore, since the stress-stimulated luminescent film is composed of a light-emitting layer provided on the surface of the target object and a visible light-shielding layer provided on the surface of the light-emitting layer, even if external visible light is incident on the surface of the stress-stimulated luminescent film, it is blocked by the visible light-shielding layer and the external visible light hardly reaches the light-emitting layer. As a result, the above-mentioned fluorescence (fluorescence by a mechanism different from stress-stimulated luminescence) can be prevented.

[0026] A sixth aspect of the present invention is a strain / stress / load distribution detection system characterized in that the detection unit detects only electromagnetic waves of a specific wavelength.

[0027] According to the sixth aspect, the detection unit detects only electromagnetic waves of a specific wavelength, making it less susceptible to the influence of reflected external visible light. As a result, the strain, stress, and load distribution detection system can easily visualize strain, stress, and load distributions even in the presence of external visible light.

[0028] A seventh aspect of the present invention resides in the strain / stress / load distribution detection system according to the fifth aspect, characterized in that it includes a load unit that applies a load to the target object and causes the stress-luminescent film to emit electromagnetic waves of a specific wavelength.

[0029] According to the seventh aspect, a load can be reliably applied to the target object, and therefore the distribution of strain in the target object, stress in the target object, or load applied to the target object can be reliably detected.

[0030] An eighth aspect of the present invention is a strain / stress / load distribution detection method for visualizing a strain distribution in a target object, a stress distribution in the target object, or a load distribution acting on the target object, the strain / stress / load distribution detection method comprising: a stress-luminescent film formation step of forming a stress-luminescent film according to any one of the first to fourth aspects on the target object; and a light emission step of applying a load to the target object and causing the stress-luminescent film to emit electromagnetic waves of a specific wavelength.

[0031] According to the eighth aspect, since electromagnetic waves of a specific wavelength are detected, it is less susceptible to the influence of reflection of external visible light contained in artificial lighting, etc., and therefore it is possible to detect the strain of a target object, the stress of a target object, or the distribution of a load acting on a target object even in the presence of external visible light.

[0032] Furthermore, since the stress-stimulated luminescent film is composed of a light-emitting layer provided on the surface of the target object and a visible light-shielding layer provided on the surface of the light-emitting layer, even if external visible light is incident on the surface of the stress-stimulated luminescent film, it is blocked by the visible light-shielding layer and the external visible light hardly reaches the light-emitting layer. As a result, the above-mentioned fluorescence (fluorescence by a mechanism different from stress-stimulated luminescence) can be prevented.

[0033] A ninth aspect of the present invention is a method for forming a stress-stimulated luminescent film according to any one of the first to fourth aspects on a surface of a target object, the method comprising: a light-emitting layer forming step of forming a light-emitting layer on the surface of the target object; and a visible-light-shielding layer forming step of forming a visible-light-shielding layer on the surface of the light-emitting layer.

[0034] According to the ninth aspect, the stress-stimulated luminescent film according to the present invention can be easily produced. [Brief explanation of the drawings]

[0035] [Figure 1] FIG. 1 is a schematic diagram of a strain / stress / load distribution detection system according to the first embodiment. [Figure 2] FIG. 2(a) is a backscattered electron image of a cross section of a stress-stimulated luminescent film in this example, and FIG. 2(b) is an enlarged backscattered electron image of the boundary between the luminescent layer and the visible light-shielding layer. [Figure 3] FIG. 3 is a photograph of an aluminum alloy piece attached to a tensile strength tester in the example. [Figure 4] FIG. 4 is a bar graph showing the mechanoluminescence intensity (stimuli-luminescence intensity) obtained by subtracting the intensity of the electromagnetic waves with a specific wavelength measured when an aluminum alloy piece was pulled using a tensile strength tester from the intensity of the electromagnetic waves with a specific wavelength measured before the tensile test in the examples (under a bright environment and a dark environment). [Figure 5] FIG. 5 is a bar graph showing the intensity (baseline intensity) of electromagnetic waves of a specific wavelength immediately before pulling an aluminum alloy piece with a tensile strength tester in Examples (under a bright environment and under a dark environment). DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, embodiments of a mechanoluminescent film and a strain / stress / load distribution detection system using the same according to the present invention will be described with reference to the accompanying drawings. Note that the present invention is not limited to the following embodiments.

[0037] (Embodiment 1) As shown in FIG. 1, the strain / stress / load distribution detection system 1 according to this embodiment is composed of a stress-luminescent film 10 provided on the surface of a target object 100, and a detection unit 50.

[0038] First, we will explain the stress-stimulated luminescent film 10. The stress-stimulated luminescent film 10 has a light-emitting layer 11 provided on the surface of the target object 100, and a visible light-shielding layer 12 provided on the surface of the light-emitting layer 11 opposite to the target object 100.

[0039] The light-emitting layer 11 is not particularly limited as long as it contains a stress-luminescent material that can emit electromagnetic waves with a specific wavelength of 850 nm to 2500 nm in response to the strain of the target object 100, the stress of the target object 100, or the load applied to the target object 100. Examples of the light-emitting layer 11 include a layer made by uniformly mixing such a stress-luminescent material with an epoxy resin, a urethane resin, an acrylic resin, or a silicone resin, a curing agent and a solvent for controlling the crosslinking and curing reaction of these resins, and a dispersant and an auxiliary agent for uniformly dispersing these materials, and then applying and curing the mixture to the surface of the target object 100.

[0040] Here, the stress luminescent material, unlike the fluorescent material, is not particularly limited as long as it emits specific wavelength electromagnetic waves with wavelengths in the range of 850 nm to 2500 nm in response to the strain of the target object, the stress of the target object, or the load applied to the target object. That is, when the strain of the target object, the stress of the target object, or the load applied to the target object is large, the stress luminescent material has a high emission intensity of specific wavelength electromagnetic waves, and when the stress of the target object or the load applied to the target object is small, the emission intensity of the specific wavelength electromagnetic waves becomes small. Examples of such stress luminescent materials include SrAl2O4 (SrAl2O4:Eu,Cr,Nd) co-doped with Eu, Cr, and Nd, which exhibits stress luminescence in the wavelength range of 850 nm to 1450 nm, SrAl2O4 (SrAl2O4:Eu,Er) co-doped with Eu and Er, which exhibits stress luminescence in the wavelength range of 1400 nm to 1600 nm, Sr3Sn2O7 (Sr3Sn2O7:Nd) doped with Nd, which exhibits stress luminescence in the wavelength range of 850 nm to 1450 nm, Li 1-X Na X NbO3 (Li 1-X Na X NbO3:Nd, 0.10 ≤ X ≤ 0.98), ZnO (ZnO:Nd) doped with Nd, which exhibits stress luminescence in the wavelength range of 850 nm to 1450 nm, CaZnOS (CaZnOS:Nd) doped with Nd, which exhibits stress luminescence in the wavelength range of 850 nm to 1450 nm, CaZnOS (CaZnOS:Er) doped with Er, which exhibits stress luminescence in the wavelength range of 850 nm to 1650 nm, SrZnSO (SrZnSO:Nd) doped with Nd, which exhibits stress luminescence in the wavelength range of 850 nm to 1450 nm, or Li X Zn 1-X O (Li X Zn 1-X O:Nd, 0.0001 < X < 0.7), etc.

[0041] The concentration (weight ratio) of the stress-stimulated luminescent material contained in the light-emitting layer 11 is not particularly limited, but is preferably in the range of 20 wt% to 90 wt% because it can emit light with sufficient luminous intensity (brightness), and is more preferably in the range of 40 wt% to 80 wt% because it is easy to handle and can emit light with high luminous intensity. The thickness of the stress-stimulated luminescent film 10 is also not particularly limited, but is preferably in the range of 1 μm to 1 mm in terms of luminous intensity and ease of handling, and is more preferably in the range of 10 μm to 500 μm in terms of luminous intensity and ease of handling.

[0042] Although there are no particular limitations on the materials other than the stress-stimulated luminescent material contained in the light-emitting layer 11, it is preferable that the materials do not absorb electromagnetic waves of a specific wavelength of 850 nm to 2500 nm (for example, materials with a transmittance of 50% to 100% or 80% to 100% for electromagnetic waves of a specific wavelength). By using such materials, the electromagnetic waves of a specific wavelength emitted from the stress-stimulated luminescent material can be emitted from the light-emitting layer 11 without being significantly attenuated.

[0043] Next, the visible light-shielding layer 12 will be described. The visible light-shielding layer 12 is not particularly limited as long as it blocks 80% to 100% of electromagnetic waves with wavelengths of 300 nm to 780 nm and transmits 50% to 100% of electromagnetic waves with a specific wavelength. Preferably, the visible light-shielding layer 12 blocks 85% to 100% of electromagnetic waves with wavelengths of 300 nm to 780 nm and transmits 70% to 100% of electromagnetic waves with a specific wavelength, and particularly preferably blocks 90% to 100% of electromagnetic waves with wavelengths of 300 nm to 780 nm and transmits 80% to 100% of electromagnetic waves with a specific wavelength.

[0044] The visible light blocking layer 12 may be made of, for example, a near-infrared transmitting material (manufactured by Artience Co., Ltd.), a near-infrared transmitting black dispersion (manufactured by Tokushiki Co., Ltd.), or Y 0.90 Zn 0.10Examples include MnO3, a mixture of YMnO3 and Mn3O4, a black azo pigment having multiple chromophores of azomethine groups and azo groups (for example, the azo pigments described in International Publication No. WO2015 / 125224), and an infrared-transmitting film selected from one or more of a germanium thin film, a silicon thin film, and a zinc sulfide thin film. Furthermore, compositions in which these materials are blended with resins, glass, organic solvents, or water that transmit electromagnetic waves of a specific wavelength may also be used.

[0045] Furthermore, the visible light-shielding layer 12 may be composed of a single layer or multiple layers. For example, an infrared light-transmitting filter in which germanium thin films and zinc sulfide thin films are alternately stacked may be used (Japanese Patent Laid-Open Publication No. 63-294501). Furthermore, by combining materials having the ability to shield and transmit electromagnetic waves in different wavelength ranges, it is possible to construct a visible light-shielding layer 12 that is limited to an arbitrary wavelength range and can transmit only a specific wavelength region (e.g., 780 nm to 1600 nm) by blocking electromagnetic waves in a predetermined wavelength range 1 (e.g., 300 nm to 780 nm) and blocking electromagnetic waves of a specific wavelength in a predetermined wavelength range 2 (e.g., 1600 nm to 2500 nm).

[0046] The thickness of the visible light-shielding layer 12 is not particularly limited, but is preferably in the range of 0.1 μm to 100 μm, particularly preferably 0.5 μm to 50 μm, from the viewpoint of ease of handling.

[0047] Next, the detection unit 50 will be described. The detection unit 50 is not particularly limited as long as it can detect electromagnetic waves of a specific wavelength. Examples of the detection unit 50 include a commercially available near-infrared camera. The detection unit 50 may be connected to an image processing device (such as a personal computer), and the distribution state of the electromagnetic waves of a specific wavelength detected by the detection unit 50 (the strain distribution of the target object 100, the stress distribution of the target object 100, or the load distribution acting on the target object 100) may be image-processed so that it can be recognized by a human.

[0048] The arrangement (distance, position) of the detection unit 50 from the stress-stimulated luminescent film 10 is not particularly limited as long as it can detect the electromagnetic wave of the specific wavelength emitted from the light-emitting layer 11 of the stress-stimulated luminescent film 10. Alternatively, the arrangement (distance, position) of the detection unit 50 from the stress-stimulated luminescent film 10 may be determined depending on the combination of the light-collecting range of the detection unit 50 and the light-collecting device provided in the detection unit 50. For example, when a commercially available near-infrared camera is used, the optimal arrangement is determined depending on the imaging range of the target object 100 and the lens performance that has high transparency to the electromagnetic wave of the specific wavelength. As described above, the optimal arrangement (distance, position) varies depending on the size of the subject and the type of device used for the detection unit 50, but does not affect the imaging of the stress-stimulated luminescent intensity of the stress-stimulated luminescent film 10 related to the strain of the target object 100, the stress of the target object 100, or the load applied to the target object 100.

[0049] The target object 100 is not particularly limited, and examples include structural materials and manufactured products installed in material testing machines, press dies in automobile factories, electronic circuit boards, bridges, buildings, hydrogen cylinders, femurs, artificial bones, etc.

[0050] <Method for creating mechanoluminescent films> The stress-stimulated luminescent film 10 is fabricated by forming a visible light blocking layer 12 on the surface of a light emitting layer 11 .

[0051] The luminescent layer 11 may be formed directly on the surface of the target object 100 (by applying a solution and curing), or may be formed on the surface of the target object 100 by attaching an already formed luminescent layer 11 (such as a nonwoven fabric mixed with a stress-luminescent material) to the surface of the target object 100.

[0052] In addition, the visible light-blocking layer 12 may be formed directly on the surface of the light-emitting layer 11, or may be formed on the surface of the light-emitting layer 11 by attaching an already formed visible light-blocking layer 12 to the surface of the light-emitting layer 11.

[0053] Furthermore, as a method for forming the visible light blocking layer 12 on the surface of the light emitting layer 11, for example, a near-infrared transmitting material (manufactured by Artience Co., Ltd.), a near-infrared transmitting black dispersion (manufactured by Tokushiki Co., Ltd.), Y 0.90 Zn 0.10 When using a dispersion of a material (visible light blocking material) that has the function of blocking visible light, such as MnO3, a mixture of YMnO3 and Mn3O4, or a black azo pigment having multiple chromophores of azomethine groups and azo groups, a spin coater, screen printing, spray coating, a bar coater, a doctor blade, etc. can be used.

[0054] Furthermore, when a metal thin film such as germanium, silicon, or zinc sulfide is used as the visible light-shielding layer 12, a known film formation method such as electron beam evaporation or sputtering can be used, but a formation method in which the visible light-shielding material is dispersed uniformly within the visible light-shielding layer 12 is preferred.

[0055] Furthermore, a visible light blocking layer 12 may be formed in advance on the surface of a light emitting layer 11 (such as a nonwoven fabric mixed with a stress-luminescent material), and then the layer may be attached to the surface of the target object 100 to form a stress-luminescent film 10 on the surface of the target object 100.

[0056] <Operation of strain, stress, and load distribution detection system> First, the stress-luminescent film 10 is provided on the surface of the target object 100, and then the target object 100 is attached to a load unit such as a tensile strength tester. Then, the detection unit 50 is placed at a predetermined position and operated.

[0057] Next, a tensile strength tester or the like is operated on the target object 100 (a load is applied). Then, the light-emitting layer 11 emits electromagnetic waves of a specific wavelength having a wavelength of 850 nm to 2500 nm in accordance with the strain of the target object 100, the stress of the target object 100, or the load applied to the target object 100. Here, the visible light-blocking layer 12 provided on the surface of the light-emitting layer 11 hardly attenuates the electromagnetic waves of the specific wavelength, so the electromagnetic waves of the specific wavelength are emitted from the stress-luminescent film 10 (the electromagnetic waves of the specific wavelength emitted from the light-emitting layer 11 are transmitted through the visible light-blocking layer 12 and then emitted). The electromagnetic waves of the specific wavelength are then detected by the detection unit 50.

[0058] Here, if the strain / stress / load distribution detection system 1 uses a detection unit 50 that detects only electromagnetic waves of a specific wavelength, such as an image sensor or detector using InGaAs as a detection material, the system will be less susceptible to the influence of external visible light reflected by the target object 100 or the mechanoluminescent film 10. Therefore, the strain / stress / load distribution detection system 1 can visualize the strain of the target object 100, the stress of the target object 100, or the load distribution acting on the target object 100, even in the presence of visible light.

[0059] As mentioned above, the detection unit 50 may be connected to an image processing device (not shown) and the distribution state of the specific wavelength electromagnetic waves detected by the detection unit 50 (strain distribution, stress distribution, load distribution on the target object 100) may be image-processed so that it can be recognized by a human.

[0060] As described above, the stress-luminescent film 10 is composed of the light-emitting layer 11 provided on the surface of the target object 100 and the visible light-blocking layer 12 provided on the surface of the light-emitting layer 11. Therefore, even if external visible light is incident on the surface of the stress-luminescent film 10, it is blocked by the visible light-blocking layer 12 and hardly reaches the light-emitting layer 11. As a result, the above-mentioned fluorescence (fluorescence by a mechanism different from stress-luminescence) can be prevented.

[0061] <Example> The target object was an aluminum alloy (A7075) piece measuring 210 mm in length, 25 mm in width, and 3 mm in thickness. First, the mechanoluminescent material SrAl2O4:Eu,Cr,Nd was dispersed in epoxy resin (manufactured by Teikoku Ink Mfg. Co., Ltd.) to prepare the above-mentioned mixed solution. This was then applied to the aluminum alloy piece and cured to form two light-emitting layers each measuring approximately 13 mm square and approximately 0.09 mm thick, emitting electromagnetic waves of specific wavelengths. Then, an infrared-transmitting ink (SVSS IP BLACK, manufactured by Artience Inc.), which blocks electromagnetic waves in the visible light range and transmits electromagnetic waves of specific wavelengths, was laminated on only one of the light-emitting layers using a spin coater to form a visible-light-shielding layer approximately 0.005 mm thick, thereby forming a mechanoluminescent film according to the present invention.

[0062] Next, we mixed the stress-luminescent material SrAl2O4:Eu in epoxy resin (manufactured by Teikoku Ink Mfg. Co., Ltd.). 2+ (manufactured by Sakai Chemical Industry Co., Ltd.) was dispersed to prepare a similar mixture, which was then coated and cured on the portion of the aluminum alloy piece below the above-mentioned mechanoluminescent film to form two comparative luminescent layers (stress-luminescent films that emit light in the visible light range of 360 nm to 830 nm in wavelength) containing a conventional mechanoluminescent material, each approximately 13 mm square and approximately 0.09 mm thick. Then, an infrared-transmitting ink (manufactured by artience Co., Ltd., SVSS IP BLACK), which blocks electromagnetic waves in the visible light range and transmits electromagnetic waves of specific wavelengths, was laminated on only one of the comparative luminescent layers using a spin coater to form a visible-light-shielding layer approximately 0.005 mm thick.

[0063] Specifically, the comparative luminescent film (A) was approximately 13 mm square and approximately 0.090 mm thick, in which only a luminescent layer made of SrAl2O4:Eu,Cr,Nd as a stress-luminescent material was formed on the surface of an aluminum alloy piece; the stress-luminescent film (B) according to the present invention was approximately 13 mm square and approximately 0.095 mm thick, in which a visible light-shielding layer was formed on a luminescent layer made of SrAl2O4:Eu,Cr,Nd as a stress-luminescent material; and the conventional SrAl2O4:Eu 2+ The comparative luminescent film (C) is made of a comparative luminescent layer using a stress-luminescent material, and has a visible light shielding layer formed on it. The film is approximately 13mm square and 0.095mm thick. The comparative luminescent film (C) is made of a comparative luminescent layer using a stress-luminescent material, and has a visible light shielding layer formed on it. The comparative luminescent film (C) is made of a comparative luminescent layer using a stress-luminescent material, and has a visible light shield 2+A comparative luminescent film (D) was prepared, which was approximately 13 mm square and approximately 0.090 mm thick and had only a comparative luminescent layer formed thereon using the above-mentioned material as a stress-luminescent material.

[0064] Here, Figure 2(a) shows a backscattered electron image of a cross section of a mechanoluminescent film (A) according to the present invention, taken using an electron microscope (Hitachi High-Tech Corporation, TM4000 PLUS II), and Figure 2(b) shows a backscattered electron image of a cross section of a mechanoluminescent film (B) according to the present invention, enlarging the area near the boundary between the visible light-shielding layer and the light-emitting layer. The backscattered electron image appears whiter and brighter for materials with higher atomic numbers and higher densities. Therefore, the white lumps in Figures 2(a) and 2(b) represent the mechanoluminescent material, which is primarily composed of metal elements, while the black areas represent the epoxy resin in the light-emitting layer and the polymeric material of the infrared-transmitting ink in the visible light-shielding layer. Observation of these backscattered electron images revealed that the mechanoluminescent film (B) according to the present invention has a thin visible light-shielding layer laminated on the light-emitting layer.

[0065] In addition, a single-axis strain gauge (manufactured by Kyowa Electronics Co., Ltd.) was attached using a special adhesive to the surface of the aluminum alloy piece opposite to the surface coated with the mechanoluminescent film (B) and the comparative luminescent films (A), (C), and (D).

[0066] 3 shows a photograph of an aluminum alloy piece provided with a total of four films, namely, a stress-stimulated luminescent film (B) and comparative luminescent films (A), (C), and (D), when the piece was attached to a tensile strength tester. In this figure, A indicates the portion provided with the comparative luminescent film (A), which is composed only of a luminescent layer that emits electromagnetic waves of a specific wavelength, B indicates the portion provided with the stress-stimulated luminescent film (B) of the present invention, C indicates the portion provided with the comparative luminescent film (C), which is a conventional comparative luminescent layer that emits visible light and has a visible light-blocking layer laminated thereon, and D indicates the portion provided with the comparative luminescent film (D), which is composed only of a conventional comparative luminescent layer that emits visible light.

[0067] The aluminum alloy piece was pulled downward at 25,000 N in the dark (0 lux) or under light irradiation from a white LED light source (100 lux, 200 lux), and the intensity of the electromagnetic waves of a specific wavelength was measured. In this tensile test, a camera (C12741-03 manufactured by Hamamatsu Photonics K.K., lens: EL1025IR manufactured by Universe Optical Co., Ltd.) was used as a detector.

[0068] The values ​​(stimuli-luminescence intensities) obtained by subtracting the intensity of the specific wavelength electromagnetic waves of each film immediately before the tensile test from the intensity of the specific wavelength electromagnetic waves measured by the tensile test for each of the mechanoluminescent film (B) and the comparative luminescent films (A), (C), and (D) are shown in Figure 4. Note that the detection unit used in this tensile test was one that detected specific wavelength electromagnetic waves with wavelengths of 950 to 1700 nm, but the detection unit is not limited to this as long as it can detect specific wavelength electromagnetic waves.

[0069] As can be seen from this figure, the mechanoluminescent film (B) of the present invention exhibits the same mechanoluminescent intensity with increasing strain of the aluminum alloy piece, whether the white LED is on (bright environment of 100 lux or 200 lux) or off (0 lux). In other words, it was found that the mechanoluminescent film (B) of the present invention can detect strain (or stress) in the presence of visible light such as artificial lighting, just as in a dark environment.

[0070] On the other hand, it was found that the mechanoluminescence intensity of the comparative luminescent film (A) increased in response to the light intensity of the white LED. In other words, it was found that the mechanoluminescence intensity of the comparative luminescent film (A) could not be measured in response to an increase in strain (or stress) of the aluminum alloy piece.

[0071] Furthermore, it was found that the comparative luminescent film (C) and the comparative luminescent film (D) do not emit electromagnetic waves of a specific wavelength, and therefore cannot detect stress on the aluminum alloy piece either in a dark environment or in a bright environment.

[0072] Furthermore, Figure 5 shows the intensities (baseline intensities) of specific wavelength electromagnetic waves before tensile testing for the mechanoluminescent film (B) and the comparative luminescent films (A), (C), and (D) when the white LED was off (0 lux) and when the white LED was on (100 lux, 200 lux). It was found that the mechanoluminescent film (B) of the present invention exhibited a baseline intensity almost the same as that in a dark environment, even in the presence of visible light such as artificial lighting. In other words, it was found that the mechanoluminescent film (B) of the present invention solved the problem of fluorescence caused by a mechanism different from mechanoluminescence.

[0073] On the other hand, it was found that the baseline of the comparative luminescent film (A), which does not have a visible light blocking layer laminated thereto, increases in proportion to the intensity of the white LED light (level of illuminance) due to the fluorescence phenomenon caused by the white LED light.

[0074] It was found that the comparative luminescent films (C) and (D) do not emit electromagnetic waves of a specific wavelength, and therefore the baseline hardly changes in either a dark or bright environment.

[0075] (Other embodiments) In the above-described embodiment, the visible light-blocking layer is directly disposed on the surface of the light-emitting layer. However, the present invention is not limited to this. For example, a layer composed of another material may be disposed between the light-emitting layer and the visible light-blocking layer. That is, the visible light-blocking layer may be disposed indirectly on the surface of the light-emitting layer. For example, by forming an intermediate layer to increase the adhesive strength between the light-emitting layer and the visible light-blocking layer, the stress-luminescent film can be used repeatedly without being destroyed even when a large strain, stress, or load is applied to the target object. An example of the intermediate layer is a layer formed from a commercially available adhesive. Needless to say, it is preferable that the layer composed of another material does not absorb electromagnetic waves of a specific wavelength (for example, one with a transmittance of electromagnetic waves of a specific wavelength of 50% to 100% or 80% to 100%). Even when a stress-luminescent film structure is configured in this manner, the same effects as those of the above-described embodiment can be obtained.

[0076] In the above-described embodiment, a load or the like is applied to the target object using a tensile strength tester or the like, but the present invention is not limited to this. For example, if the target object is a bridge, the vibration of a vehicle traveling on the bridge may be used to cause the stress-luminescent film to emit electromagnetic waves of a specific wavelength. Furthermore, if the target object is a building, the vibration of an earthquake may be used to cause the stress-luminescent film to emit electromagnetic waves of a specific wavelength.

[0077] Furthermore, in the above-described embodiment, the specific electromagnetic waves are emitted without applying any energy to the light-emitting layer of the stress-stress luminescent film. However, before or during operation of the strain / stress / load distribution detection system, the light-emitting layer may be irradiated with electromagnetic waves that penetrate the visible light-blocking layer. In this case, it goes without saying that an electromagnetic wave irradiating unit that can irradiate electromagnetic waves that penetrate the visible light-blocking layer must be provided in a position facing the stress-stress luminescent film or in the vicinity of the stress-stress luminescent film. By configuring the strain / stress / load distribution detection system in this way, the luminous intensity of the light-emitting layer of the stress-stress luminescent film can be improved. [Explanation of symbols]

[0078] 1. Strain, stress, and load distribution detection system 10 Stress-luminescent film 11 Light-emitting layer 12 Visible light shielding layer 50 Detector 100 target objects

Claims

1. A stress-luminescent film provided on a surface of a target object, which emits electromagnetic waves having a specific wavelength of 850 nm to 2500 nm in response to a strain of the target object, a stress of the target object, or a load applied to the object, a light-emitting layer provided on a surface of the target object; a visible light blocking layer provided on the surface of the light emitting layer opposite to the target object, the light-emitting layer includes a stress-luminescent material that emits the electromagnetic wave of the specific wavelength in response to a strain on the target object, a stress on the target object, or a load applied to the target object; the visible light-shielding layer blocks 80% to 100% of electromagnetic waves having a wavelength of 300 nm to 780 nm, and transmits 50% to 100% of the electromagnetic waves having the specific wavelengths emitted from the light-emitting layer; A stress-luminescent film characterized by:

2. The stress-stimulated luminescent material is SrAl ２ O ４ :Eu, Cr, Nd, SrAl ２ O ４ : Eu, Er, Sr ３ Sn ２ O ７ : Nd, Li １－Ｘ Na Ｘ NbO ３ :Nd (0.10≦X≦0.98), ZnO:Nd, CaZnOS:Nd, CaZnOS:Er, SrZnSO:Nd or Li Ｘ Zn １－Ｘ O:Nd (0.0001<X<0.7), The stress-luminescent film according to claim 1 .

3. The visible light-blocking layer is Near-infrared transmitting material (manufactured by Artience Co., Ltd.), near-infrared transmitting black dispersion (manufactured by Tokushiki Co., Ltd.), Y ０．９０ Zn ０．１０ MnO ３ , YMnO ３ and Mn ３ O ４ or at least one of the azo pigments described in International Publication No. WO 2015 / 125224; or having at least one of a germanium thin film, a silicon thin film, or a zinc sulfide thin film; The stress-luminescent film according to claim 1 ,

4. The thickness of the visible light-blocking layer is 0.1 μm to 100 μm.

4. The stress-luminescent film structure according to claim 3.

5. A strain / stress / load distribution detection system that visualizes a strain distribution of the target object, a stress distribution of the target object, or a load distribution acting on the target object, comprising: A stress-stimulated luminescent film according to any one of claims 1 to 4, a detection unit that detects the electromagnetic wave of the specific wavelength radiated from the stress-luminescent film, A strain, stress and load distribution detection system characterized by the above.

6. The detection unit detects only the electromagnetic wave of the specific wavelength. A strain, stress and load distribution detection system characterized by the above.

7. a load unit that applies a load to the target object and causes the stress-luminescent film to emit the electromagnetic wave of the specific wavelength; 6. The strain / stress / load distribution detection system according to claim 5, wherein the strain / stress / load distribution detection system comprises:

8. A strain / stress / load distribution detection method for visualizing a strain distribution of the target object, a stress distribution of the target object, or a load distribution acting on the target object, comprising: a stress-stimulated luminescent film forming step of forming the stress-stimulated luminescent film according to any one of claims 1 to 4 on the target object; a light emitting step of applying a load to the target object and causing the stress-luminescent film to radiate the electromagnetic wave of the specific wavelength. A strain, stress and load distribution detection method characterized by the above.

9. A method for forming a stress-stimulated luminescent film according to any one of claims 1 to 4 on a surface of the target object, comprising: a light-emitting layer forming step of forming the light-emitting layer on the surface of the target object; a visible light-shielding layer forming step of forming the visible light-shielding layer on a surface of the light-emitting layer, A method for forming a stress-stimulated luminescent film.

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