Light emission method, coating material for mechanoluminescence, and method for producing mechanoluminescenct coating material

Abstract

Provided are a light emission method which uses a coating material for mechanoluminescence not known in the past, and a coating material for mechanoluminescence and a method for producing the same. In the light emission method, a coating material provided with a light-emitting layer containing a photoluminescent compound, the photoluminescent compound exhibiting mainly an amorphous phase while having crystal regions in parts, is prepared and mechanoluminescence is generated from the light-emitting layer by applying mechanical stimulation to the coating material.

Description

Method for luminescence, and coating material for mecanorluminescence and method for manufacturing a mecanorluminescence coating material.

[0001] The present invention relates to a method for emitting light, as well as a coating material for mecanorluminescence and a method for manufacturing a mecanorluminescence coating material.

[0002] Mechanoluminescence (ML) is a phenomenon in which light is emitted in response to mechanical stimuli (mechanical actions) such as fracture, shattering, and friction. Unlike photoluminescence (PL), ML does not require light excitation to generate an excited state. Therefore, ML materials are attractive materials for mechanically responsive materials that visualize stress and damage applied to materials, self-generating light-emitting devices, and energy conversion methods (see Non-Patent Documents 1-9).

[0003] It has been reported that ML emission occurs when the crystals of fluorescent or phosphorescent PL compounds are fractured (Non-Patent Documents 1, 3, 5, 7, 9). However, the ML emission of PL compounds by crystal fracture exhibits significant attenuation of emission intensity, and controlling the crystal structure and establishing a reproducible crystallization method is difficult. Therefore, the application of ML emission by crystal fracture of PL compounds is limited.

[0004] In contrast, Patent Document 1 proposes an amorphous triboluminescent material comprising a luminescent phosphorus, defined as a substance that produces light emission including fluorescence, phosphorescence, and long afterglow caused by light irradiation, and a polymer. This amorphous triboluminescent material is formed by compounding luminescent phosphorus molecules and polymer molecules without forming crystals with a regular spatial arrangement. Prior to the disclosure of Patent Document 1, it was widely believed that triboluminescence, a type of mechanorluminescence, was a rare phenomenon that occurred only under very specific conditions in certain materials. However, Patent Document 1 overturned that idea. The amorphous triboluminescent material described in Patent Document 1 was the first to disclose that triboluminescence, which is a non-destructive mechanical stimulus, is possible even in an amorphous state where crystalline and microcrystalline phases do not exist, by incorporating a luminescent phosphorus into a polymer sheet.

[0005] Special Announcement No. 2024-530783

[0006] Bunzli, J.-C. G.; Wong, K.-L., Lanthanide mechanoluminescence. Journal of Rare Earths 2018, 36 (1), 1-41.Jha, P.; Chandra, B. P., Survey of the literature on mechanoluminescence from 1605 to 2013. Luminescence 2014, 29 (8), 977-993.Mukherjee, S.; Thilagar, P., Renaissance of Organic Triboluminescent Materials. Angew. Chem. Int. Ed. 2019, 58 (24), 7922-7932.Olawale, D. O.; Uddin, J.; Yan, J.; Dickens, T.; Okoli, O., Triboluminescence. Springer: 2016.Sage, I.; Bourhill, G., Triboluminescent materials for structural damage monitoring. J. Mater. Chem. 2001, 11 (2), 231-245.Su, L.; Wang, H. J.; Zi, Y. L., Recent progress of triboelectrification-induced electroluminescence: from fundaments to applications. J Phys-Mater 2021, 4 (4), 042001.Xie, Y.; Li, Z., Triboluminescence: Recalling Interest and New Aspects. Chem 2018, 4 (5), 943-971.Zhuang, Y.; Xie, R. J., Mechanoluminescence Rebrightening the Prospects of Stress Sensing: A Review. Adv. Mater. 2021, 33 (50), e2005925.Zink, J. I., Triboluminescence. Acc. Chem. Res. 1978, 11 (8), 289-295.Karimata, A.; Fayzullin, RR; Khusnutdinova, JR, Versatile Method of Generating Triboluminescence in Polymer Films Blended with Common Luminophores. ACS Macro Lett. 2022, 11 (8), 1028-1033.

[0007] As mentioned above, mechanorluminescence is a phenomenon with a wide range of potential applications, including mechanically responsive materials, self-generating light-emitting devices, and energy conversion methods. However, the details of its light-emitting mechanism, particularly the principle of light emission when amorphous materials are used, are still under investigation. The influence of the amorphous or crystalline structure of ML materials, and even what kind of mechanical stimuli cause ML materials to emit light depending on their crystalline state, remain unknown.

[0008] Therefore, this disclosure aims to provide a method for luminescence using a new coating material for mecanorluminescence, as well as a coating material for mecanorluminescence and a method for manufacturing the same.

[0009] Under these circumstances, the inventors diligently conducted research and completed the light emission method, as well as the coating material for mecanorluminescence and the method for manufacturing the mecanorluminescence coating material, as described below. The gist of these components is as follows.

[0010] (1) A method for generating light, comprising: preparing a coating material having a light-emitting film containing a photoluminescent compound, wherein the light-emitting film mainly exhibits an amorphous phase but has a crystalline region in part, and generating mechanorluminescence from the light-emitting film by applying a non-destructive mechanical stimulus to the coating material.

[0011] (2) The light emission method according to (1) above, wherein the non-destructive mechanical stimulus is applied by friction of the member against the coating material.

[0012] (3) The light-emitting method according to (1) above, wherein the non-destructive mechanical stimulus is applied by bringing a member into contact with the coating material and then peeling off the member.

[0013] (4) The light-emitting method according to (1) above, wherein the non-destructive mechanical stimulus is applied by one or both of bending and twisting the coating material.

[0014] (5) The light-emitting method according to (1) above, wherein the coating material further comprises a protective film that is releasably contacted on the surface of the light-emitting film, and the non-destructive mechanical stimulus is applied by peeling the protective film from the light-emitting film.

[0015] (6) The light-emitting method according to any one of (1) to (5) above, wherein mechanoluminescence is generated from the light-emitting film under air.

[0016] (7) The light-emitting method according to any one of (1) to (6) above, wherein the light-emitting film comprises a polymer matrix.

[0017] (8) The light-emitting method according to (7) above, wherein the content of the photoluminescence compound in the light-emitting film is more than 30 wt%.

[0018] (9) The light-emitting method according to any one of (1) to (8) above, wherein the photoluminescence compound is an organic compound.

[0019] (10) A coating material for mechanoluminescence that emits light under non-destructive mechanical stimulus, comprising a light-emitting film containing a photoluminescence compound, wherein the light-emitting film mainly exhibits an amorphous phase and partially has a crystalline region.

[0020] (11) The coating material for mechanoluminescence according to (10) above, wherein the light-emitting film comprises a polymer matrix.

[0021] (12) The coating material for mechanoluminescence according to (11) above, wherein the content of the photoluminescence compound in the light-emitting film is more than 30 wt%.

[0022] (13) The coating material for mechanoluminescence according to any one of (10) to (12) above, wherein the photoluminescence compound is an organic compound.

[0023] (14) A coating material for mechanorluminescence according to any one of (10) to (13) above, further comprising a protective film provided on the surface of the light-emitting film.

[0024] (15) The protective film is a mechanorluminescent coating material according to (14) above, which is peelably brought into contact with the surface of the light-emitting film.

[0025] (16) The mecanorluminescent coating material according to any one of (10) to (15) above, wherein the nondestructive mechanical stimulus is friction of a member against the mecanorluminescent coating material.

[0026] (17) The mecanorminescent coating material according to any one of (10) to (15) above, wherein the non-destructive mechanical stimulus is contact-peeling between the member and the mecanorminescent coating material.

[0027] (18) The mechanorluminescent coating according to any one of (10) to (15), wherein the nondestructive mechanical stimulus is either bending or twisting of the mechanorluminescent coating or both.

[0028] (19) The mechanorluminescent coating material according to (15), wherein the non-destructive mechanical stimulus is the peeling of the protective film from the light-emitting film.

[0029] (20) A method for producing a mechanorluminescent coating, comprising: a first step of preparing a solution containing a photoluminescent compound; and a second step of applying the solution and drying it to obtain a light-emitting film, wherein the light-emitting film mainly exhibits an amorphous phase and has a crystalline region in part.

[0030] (21) The method for producing a mechanoluminescent coating material according to (20), wherein in the first step, the photoluminescent compound and the polymer are mixed to prepare the solution.

[0031] (22) A method for manufacturing a mechanorluminescent coating material according to (20) or (21) above, further comprising a third step of providing a protective film on the surface of the light-emitting film after the second step.

[0032] This disclosure provides a method for luminescence using a coating material for mecanorluminescence that was previously unknown, as well as a coating material for mecanorluminescence and a method for manufacturing the same.

[0033] This is a schematic diagram of a coating material for mechanorluminescence according to one embodiment. This is a schematic diagram of a light emission method according to one embodiment. This is one aspect of a light emission method by friction. This is one aspect of a light emission method by contact-peeling. This is one aspect of a light emission method by bending and twisting. This is one aspect of a light emission method by peeling. This is the XRD pattern in Experimental Example 1. This is an ML photograph in Experimental Example 1. These are the PL spectrum and ML spectrum in Experimental Example 1. These are the ML spectra in Experimental Example 1 and Reference Experimental Example 1. This is an ML photograph by friction through a protective film in Experimental Example 1. This is an ML photograph by contact-peeling in Experimental Example 1. This is an ML photograph by peeling in Experimental Example 1. This is an ML photograph by bending and twisting in Experimental Example 2. This is the XRD pattern in Reference Experimental Example 1. This is an ML photograph in Reference Experimental Example 1. These are the PL spectrum and ML spectrum in Reference Experimental Example 1. This is an ML photograph by friction through a protective film in Reference Experimental Example 1. This is an ML photograph by contact-peeling in Reference Experimental Example 1. This is an ML photograph taken due to delamination in Reference Experiment Example 1. This is an ML photograph taken due to bending and twisting in Reference Experiment Example 2. This is the XRD pattern in Additional Experiment Example 1. These are the PL spectrum and ML spectrum in Additional Experiment Example 1. These are the PL spectrum and ML spectrum in Additional Experiment Example 1.

[0034] Embodiments of the present invention will be described in detail below with reference to the drawings. In principle, identical components will be given the same reference numeral and their descriptions will be omitted. Furthermore, the drawings are schematic for illustrative purposes and do not accurately reflect actual dimensions or proportions. In this specification, numerical ranges may be expressed using "X to Y" instead of "greater than or equal to" or "less than or equal to," in which case the numerical values ​​X and Y are included as the lower and upper limits, respectively.

[0035] (Mechanorluminescent coating) Refer to the schematic cross-sectional view in Figure 1. Hereinafter, the mechanorluminescent coating may be referred to as the mechanorluminescent coating, ML coating, or simply the coating. The mechanorluminescent coating (ML coating) 10 that emits light by non-destructive mechanical stimulation according to the embodiments of this disclosure comprises a light-emitting film 1 containing a photoluminescent compound. As illustrated in Figure 1, the ML coating 10 may further comprise a protective film 2 provided on the surface of the light-emitting film 1, or it may further comprise any film not shown. The photoluminescent compound contained in the light-emitting film 1 mainly exhibits an amorphous phase, while having a crystalline region in part. Referring also to the schematic diagram in Figure 2 for illustrative purposes, in this embodiment, the light-emitting film 1 of the ML coating 10 is provided by being coated on the surface of a substrate 20. In this embodiment, a protective film 2 is provided on the surface of the light-emitting film 1, and a gap 3 exists between both ends of the light-emitting film 1 and the protective film 2. This ML coating material 10 emits light in response to non-destructive mechanical stimulation and is a novel mechanorluminescence coating material not previously known. In the example shown in Figure 2, ML emission is achieved by rubbing the light-emitting layer 1 through the protective film 2. The details of each component will be explained in order below.

[0036] <Emitting Film> The emissive film 1 contains at least a photoluminescent (PL) compound. The emissive film 1 may consist only of the PL compound, but the emissive film 1 may further contain a polymer matrix and may further contain optional additives.

[0037] Here, we will specifically describe a state in which the light-emitting film 1 mainly exhibits an amorphous phase while having a crystalline region in part. In this state, the light-emitting film 1 as a whole does not form crystals with a regular spatial arrangement, and is mainly an amorphous phase. That is, in the light-emitting film 1, the PL compound as a whole does not crystallize and forms an amorphous phase, or the PL compound is molecularly dispersed in the polymer matrix and as a whole does not crystallize and forms an amorphous phase. However, in this state, the light-emitting film 1 locally includes a crystalline region in part in which the PL compound is arranged with a regular spatial arrangement. The state in which the light-emitting film 1 mainly exhibits an amorphous phase while having a crystalline region in part can be quantified by determining the degree of crystallinity using a commercially available differential scanning calorimeter (DSC) and a known method. In this case, if we quantitatively express the above state, the degree of crystallinity is less than 50%, preferably 40% or less, and may be 30% or less, but is greater than 0%. This condition can also be confirmed by X-ray diffraction, and in the X-ray diffraction pattern, it can be judged from the coexistence of a broad halo pattern originating from the amorphous phase and peaks originating from the crystalline phase.

[0038] <<Photoluminescent Compounds>> Photoluminescent compounds are compounds that exhibit at least one of the following light emission phenomena in response to photoexcitation: fluorescence, delayed fluorescence, phosphorescence, and long afterglow. There are no particular limitations as long as such light emission phenomena are exhibited, but they are preferably organic compounds, and also preferably metal complexes. The light-emitting film 1 may contain one or more photoluminescent compounds.

[0039] Examples of photoluminescent compounds composed of such organic compounds include aromatic compounds, heteroaromatic compounds, organometallic compounds, and metal complexes. In this specification, "aromatic compound" means a compound containing at least one aromatic ring. In this specification, "heteroaromatic compound" means a compound containing at least one heteroaromatic ring. The aromatic rings and heteroaromatic rings may be monocyclic or fused rings having a polycyclic structure. Examples of heteroatoms constituting the heteroaromatic rings include nitrogen atoms, oxygen atoms, and sulfur atoms.

[0040] <<<Aromatic Compounds>>> Examples of aromatic compounds include aromatically substituted unsaturated hydrocarbons, condensed polycyclic aromatic compounds having a polycyclic aromatic ring formed by the condensation of two or more benzene rings, and compounds having a structure in which two or more aromatic rings (e.g., benzene rings) are linked by a π-conjugated linking group. At least one hydrogen atom in each of the aromatic ring and the π-conjugated linking group may be substituted by a substituent. Specific examples of the ring skeleton of condensed polycyclic aromatic compounds include anthracene rings and pyrene rings. π-conjugated linking groups are linking groups that form a conjugated system with the double bond of the aromatic ring, and include ethenylene groups, 1,3-butadiene-1,4-diyl groups, and linking groups having a polyene structure.

[0041] Examples of aromatic substituents include phenyl, naphthyl, anthryl, tolyl, xylyl, and biphenylyl groups. Examples of substituents on aromatic rings and π-conjugated groups include: alkyl groups (preferably with 1 to 50 carbon atoms), alkylene groups (preferably with 1 to 50 carbon atoms), alkynyl groups (preferably with 1 to 50 carbon atoms), alkoxy groups (preferably with 1 to 50 carbon atoms), nitro groups, cyano groups, halogen atoms, hydroxyl groups, thiol groups, acyl groups (preferably with 1 to 50 carbon atoms), silyl groups (preferably with 1 to 50 carbon atoms), amino groups, aldehyde groups, isocyanate groups, thiazolyl groups, aryl groups (preferably with 6 to 50 carbon atoms), heterocycloalkyl groups (preferably with 3 to 50 carbon atoms), and heteroaryl groups (preferably with 3 to 50 carbon atoms). These groups may be further substituted. Examples of such further substituents include aralkyl groups, haloalkyl groups, and alkoxysilyl groups. The substituents on the aromatic ring and the π-conjugated linkage may include carboxyl bonds, carboxyamide bonds, ester bonds, amide bonds, sulfide bonds, disulfide bonds, and the like. These exemplified groups may be further substituted. Such further substituents include aralkyl groups, haloalkyl groups, and alkoxysilyl groups. The substituents on the aromatic ring and the π-conjugated linkage may include carboxyl bonds, carboxyamide bonds, ester bonds, amide bonds, sulfide bonds, disulfide bonds, and the like.

[0042] <<<Heteroaromatic Compounds>>> Suitable heteroaromatic compounds for PL compounds include compounds containing heterocycles such as pyridine rings, pyrrole rings, imidazole rings, thiazole rings, oxazole rings, furan rings, and thiophene rings. These heterocycles may be monocyclic or fused with multiple heterocycles or aromatic rings. In heteroaromatic compounds as well, hydrogen atoms on the ring may be substituted with the substituents mentioned above.

[0043] <<<Metal Complexes>>> Suitable organometallic compounds and metal complexes as PL compounds include complexes having at least one central metal selected from the group consisting of Cu, Al, Ir, Ru, and Eu. Ligands for these organometallic compounds and metal complexes include ligands containing heteroaromatic rings such as pyridine rings or pyrrole rings, ligands having a phosphine structure, and diketone ligands.

[0044] The heteroaromatic ring in the ligand may be a monocyclic ring, or it may be a fused ring in which one or more heteroaromatic rings are fused with one or more aromatic rings or heterocycles. At least one hydrogen atom of the heteroaromatic ring may be substituted with the substituents described above.

[0045] -Specific Examples- Specific examples of PL compounds applicable to this disclosure are shown below. However, it should be understood that the PL compounds usable in the present invention are not limited to these specific examples.

[0046]

[0047] In the above formula, AlQ ３ is tris(8-quinolinolato)aluminum, BBOT is 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene, CBP is 4,4'-bis(9H-carbazole-9-yl)biphenyl, Cu(dmp)DPE is bis[2-(diphenylphosphino)phenyl]-ether(2,9-dimethyl-1,10-phenanthroline)tetrafluoroborate copper(I), DPVBi is 4,4'-bis(2,2-diphenylvinyl)biphenyl, and Ru(phen) ３ PF ６ It is tris(1,10-phenanthroline)ruthenium(II)bis(hexafluorophosphate), and Eu(dpm) ３ (phen) is tris(dibenzoylmethane)mono(1,10-phenanthroline)europium(lll), Eu(dbm) ４TBA is tetrakis(dibenzoylmethane)europium(III)tetrabutylammonium, TPBD is 1,1,4,4-tetraphenyl-1,3-butadiene, TPP is 2,4,6-triphenylpyryllium tetrafluoroborate, and VB2TB is vitamin B2 tetrabutyrate.

[0048] <<Polymer Matrix>> The light-emitting film 1 preferably includes a polymer matrix as a base material for dispersing the PL compound. In this case as well, the light-emitting film 1 mainly exhibits an amorphous phase while having a crystalline region in part.

[0049] Specific examples of polymers applicable to the polymer matrix include polyacrylate, polymethacrylate, polystyrene, poly(ε-caprolactone), polycarbonate (poly(bisphenol A) carbonate), polyvinyl chloride, polyurethane, polyester, polyamide, polylactone, polyalkylene oxide, polysiloxane, polydimethylsiloxane, polylactide, polyolefin, polyisobutylene, polyamide-imide, polybutadiene, epoxy resin, polyacetylene, and vinyl polymers. Of these polymers, polyacrylate, polymethacrylate, polystyrene, poly(ε-caprolactone), polycarbonate (poly(bisphenol A) carbonate), and polyvinyl chloride are preferred. Poly(ε-caprolactone) is preferred for its high biocompatibility. Polyacrylate is preferably polyalkyl acrylate, and polymethacrylate is preferably polyalkyl methacrylate. The number of carbon atoms in the alkyl groups of these polyalkyl acrylates and polyalkyl methacrylates is typically 1 to 40, more preferably 1 to 20, and even more preferably 1 to 6. The molecular weight of the polymer is not particularly limited and can be selected from a range of, for example, 1,000 to 300,000, more preferably 5,000 to 50,000. In addition, one or more polymers may be used to obtain the polymer matrix.

[0050] <<Optional Additives>> The light-emitting film 1 may further contain any additives such as adhesives, tackifiers, stabilizers, plasticizers, compatibilizers, and sensitizers, depending on the desired purpose. However, even in this case, the light-emitting film 1 mainly exhibits an amorphous phase while having a crystalline region in part.

[0051] <<<PL Compound Content>>> The content of the photoluminescent compound in the light-emitting film 1 is preferably more than 30 wt% by total weight, may be 50 wt% or more, or 80 wt% or more. If the light-emitting film 1 consists only of the photoluminescent compound, the content of the photoluminescent compound is theoretically 100 wt%, but the exclusion of unavoidable impurities is not intended. The content of the polymer matrix or other optional additives can be appropriately adjusted so that the light-emitting film 1 mainly exhibits an amorphous phase while having a crystalline region in part. The content of the polymer matrix in the light-emitting film 1 may be 30 wt% or less by total weight, may be 20 wt% or less, or may be 10 wt% or less. If the light-emitting film 1 does not contain a polymer matrix, its content is 0 wt%. In addition, the total content of the optional additives in the light-emitting film 1 may be 10 wt% or less, may be 5 wt% or less, or may be 3 wt% or less. If the light-emitting film 1 does not contain any optional additives, the content is 0 wt%.

[0052] <Protective Film> Refer again to Figure 1. It is preferable that a protective film 2 be provided on the surface of the light-emitting film 1, and the protective film 2 may be provided via any film different from the light-emitting film 1 and the protective film 2. The protective film 2 may be peelably in contact with the surface of the light-emitting film 1, may be adhered to or bonded to the surface of the light-emitting film 1, may be placed on the surface of the light-emitting film 1, or may be electrostatically adsorbed to the surface of the light-emitting film 1. The protective film 2 is not particularly limited, but may be made of a polymer, for example, and may be a crystalline polymer or an amorphous polymer. Examples of crystalline polymers include polyethylene (PE), polypropylene (PP), polyamide (PA), polyacetal (POM), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), liquid crystal polymer, and polytetrafluoroethylene (PTFE). Examples of amorphous polymers are described in the specific examples of polymers applicable to the polymer matrix.

[0053] <Optional Additional Films> The ML coating material 10 may also have a multilayer structure comprising one or more light-emitting films different from the light-emitting film 1. For convenience, the light-emitting film 1 may be referred to as the "first light-emitting film," and the light-emitting films different from the light-emitting film 1 may be referred to as the "second light-emitting film," the "third light-emitting film," etc. Each of the films may be made of the same material or different materials. Similarly, the ML coating material may also comprise one or more protective films different from the protective film 2. For convenience, the protective film 2 may be referred to as the "first protective film," and the protective films different from the protective film 2 may be referred to as the "second protective film," the "third protective film," etc. Each of the films may be made of the same material or different materials. Furthermore, the ML coating material may comprise one or more arbitrary films different from the light-emitting film and the protective films. Examples of such arbitrary films include adhesive films and bonding films for joining different types of films together.

[0054] -Film Thickness- The film thickness of the light-emitting film 1 is preferably determined appropriately according to the application, within the range of 10 nm to 5 mm. If it is thicker than 10 nm, it can prevent tearing due to friction, and if it is less than 5 mm, it can be used without using a polymer matrix. The film thickness of the light-emitting film 1 may be 100 nm to 100 μm, or 1 μm to 10 μm or less, and these upper and lower limits may be combined as appropriate. In addition, when a protective film 2 is used, its film thickness may be in the range of 10 nm to 5 mm, and it is preferable to make it thinner. In addition, the total film thickness of the ML coating material 10 may be 10 nm to 5 mm, or 100 nm to 100 μm, or 1 μm to 10 μm or less, and these upper and lower limits may be combined as appropriate.

[0055] -Non-destructive mechanical stimulation- The ML coating material 10 described above emits light in response to non-destructive mechanical stimulation. Non-destructive mechanical stimulation refers to a load that exerts a mechanical effect without damaging the structure of the object, and includes friction, contact-peeling, bending, twisting, and peeling, and may also include pressure, tension, vibration, and other non-destructive stimuli.

[0056] --Friction-- As illustrated using Figure 3, mechanorluminescence can be generated from the light-emitting film 1 of the ML coating material 10 by non-destructive mechanical stimulation caused by friction with the ML coating material 10 by a member. Mechanorluminescence can be generated whether the light-emitting film 1 is directly rubbed with the member or rubbed through the protective film 2. It is thought that the light-emitting film 1 emits light due to the electric field generated when electron transfer occurs between the light-emitting film 1 and the member or protective film due to friction, and the light-emitting film and the member or the light-emitting film and protective film are charged oppositely (positively and negatively) at the friction interface.

[0057] --Contact-Separation-- Furthermore, as illustrated in Figure 4, mechanorluminescence can also be generated from the light-emitting film 1 of the ML coating material 10 by non-destructive mechanical stimulation through contact-separation between the member and the ML coating material 10. Mechanorluminescence can be generated whether the member and the light-emitting film 1 are directly contacted and separated, or whether the member and the light-emitting film 1 are contacted and separated via the protective film 2. Figure 4 also shows a separator to facilitate contact-separation with the member. Note that this ML emission due to contact-separation occurs at the moment the member is separated from the ML coating material 10, and is different from emission due to pressure. It is thought that when the light-emitting film 1 is in contact, electron transfer occurs between the light-emitting film and the member or between the light-emitting film and the protective film, and at the contact interface the light-emitting film and the member or the light-emitting film and the protective film become charged to opposite poles (positive and negative). At the moment of separation, a discharge occurs due to the electric field generated by the charging at the contact interface, causing the light-emitting film to emit light. Because it emits light upon contact and peeling, it can be used in fashion items and decorations that emit light upon mechanical stimulation, as well as in detection technology for static electricity and triboelectric charging that can cause malfunctions in precision equipment. In one aspect of this disclosure, ML emission occurs not only when the light-emitting film and the protective film are peeled apart, but also when they are initially in contact. In another aspect of this disclosure, ML emission does not occur when the light-emitting film and the protective film are in contact, but occurs when they are peeled apart.

[0058] --Bending or Twisting-- Furthermore, as illustrated with Figure 5, mechanorluminescence can also be generated from the light-emitting film 1 of the ML coating material 10 by non-destructive mechanical stimulation by bending (bending) and / or twisting (twisting) of the ML coating material 10. In this case, such mechanorluminescence can be generated regardless of whether the protective film 2 is present or not. It is thought that when the light-emitting film 1 is bent or twisted, it is rubbed or comes into contact with and peels off the protective film or substrate 20, causing electron transfer, and the electric field generated when the light-emitting film and the protective film or substrate 20 are charged opposite electrodes (positively and negatively) at the friction interface causes the light-emitting film to generate mechanorluminescence. Since it emits light by bending or twisting, it can also be used as a sheet that displays light by mechanical stimulation, a fashion item, or a decoration.

[0059] --Detachment-- Furthermore, as illustrated in Figure 6, mechanorluminescence can also be generated from the light-emitting film 1 by non-destructive mechanical stimulation, which involves detaching the protective film 2, which is placed on the substrate 20, from the light-emitting film 1. When the light-emitting film 1 comes into contact with the protective film 2 or the substrate 20, electron transfer occurs between the light-emitting film 1 and the protective film 2 or between the light-emitting film 1 and the substrate 20, and the light-emitting film 1 and the protective film 2 or the light-emitting film 1 and the substrate 20 become charged oppositely (positively and negatively) at the contact interface. It is thought that at the moment of detachment, a discharge occurs at the interface due to the electric field generated by the charging at the contact interface, causing the light-emitting film 1 to emit light.

[0060] As described above, the coating material for mechanorluminescence according to this disclosure can be used for ML emission in various applications that were previously impossible.

[0061] -Modification- In Figure 1, a gap 3 was shown between the light-emitting film 1 and the protective film 2. However, the presence or absence of the gap 3 is optional. The protective film 2 may be in close contact with the light-emitting film 1 so as to eliminate the gap 3, or the edges of the light-emitting film 1 may be left open. Furthermore, the protective film 2 does not need to cover the entire surface of the light-emitting film 1; partial coverage is sufficient. As mentioned earlier, the protective film 2 is not an essential component but is a preferred film.

[0062] (Structure) Referring again to Figure 1, it can also be said that the mecanorluminescence structure 100 has the above-mentioned mecanorluminescence coating material 10 provided on the surface of the base material 20. This mecanorluminescence structure 100 can also generate mecanorluminescence from the light-emitting film 1 by applying the above-mentioned non-destructive mechanical stimulation. The material of the base material 20 is not particularly limited, and in addition to flat base materials such as glass plates, silicone sheets, plastic sheets, metal plates, and ceramic plates, columnar members such as tubes and fibers may also be used as base materials. When the latter columnar member is used as the base material 20, it can also be used as a woven fabric by coating the columnar member with the mecanorluminescence coating material 10.

[0063] Next, embodiments of the manufacturing method for the ML coating material described above and embodiments of the light emission method using the ML coating material described above will be explained. Note that explanations of components that overlap with those of the ML coating material described above will be omitted.

[0064] (Method for manufacturing a mechanorluminescent coating) Refer to Figures 1 and 2. The method for manufacturing a mechanorluminescent coating 10 according to this embodiment of the present disclosure includes at least a first step of preparing a solution containing a photoluminescent compound, and a second step of applying and drying this solution to obtain a light-emitting film 1. A third step may be further included after the second step, in which a protective film 2 is provided on the surface of the light-emitting film 1, and any additional steps may be included before or after each step. The light-emitting film obtained in the second step mainly exhibits an amorphous phase, while having a crystalline region in part. Details of each step will be described below.

[0065] <Step 1> As described above, in Step 1, a solution containing a photoluminescent compound is prepared. In order to form the polymer matrix described above, the photoluminescent compound and the polymer may be mixed in Step 1 to prepare the solution. A solvent may or may not be used when preparing the solution. In addition, any additives may be mixed in during preparation.

[0066] -Solvent- Examples of solvents that can be used to prepare this solution include aromatics such as benzene, toluene, xylene, and chlorobenzene; ethers such as diethyl ether, dibutyl ether, tetrahydrofuran, 1,4-dioxane, dimethoxyethane, and diethylene glycol dimethyl ether; esters such as methyl acetate, ethyl acetate, butyl acetate, and ethyl propionate; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; hydrocarbons such as hexane, heptane, octane, and nonane; halogens such as dichloromethane, chloroform, and 1,2-dichloroethane; hydrocarbons; organic acids such as formic acid, acetic acid, and propionic acid; polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methylpyrrolidone; water; and mixtures of these solvents.

[0067] <Second Step> In the second step, the solution prepared in the first step is applied to any substrate 20 and dried to obtain a light-emitting film 1. The method of applying the prepared solution onto the substrate is not particularly limited, and known wet processes such as spin coating and casting can be employed. Furthermore, the applied solution may be dried in the atmosphere, under an inert atmosphere, or under a reduced pressure atmosphere, or these methods may be combined over time.

[0068] <Third Step> After the second step, a third step may be performed in which a protective film 2 is provided on the surface of the light-emitting film 1. The protective film 2 may be provided on the surface of the light-emitting film 1 using an adhesive, glue, etc., or the protective film 2 may simply be brought into contact with the surface of the light-emitting film 1, or it may be placed on top of the surface. The protective film 2 may be peelably brought into contact with or adhered to the surface of the light-emitting film 1, or it may be placed on the surface of the light-emitting film 1 and attached by electrostatic attraction.

[0069] Furthermore, when PL compounds are mixed with a well-miscible polymer matrix, film formation improves, but it may become more difficult to form a crystalline phase. Also, when a light-emitting film is prepared without using a polymer matrix, it may not form a "film" on the substrate surface, but instead become a powdery solid. Therefore, the degree of film formation and crystallization from a solution containing PL compounds is adjusted appropriately according to the PL compound, by adjusting the melting and solidification conditions of the PL compound, the coating conditions, and the drying conditions after coating, so that the light-emitting film obtained in the second step mainly exhibits an amorphous phase while having some crystalline regions.

[0070] (Method of Light Emission) Refer to Figures 1 and 2. In the method of light emission according to this embodiment based on the present disclosure, a coating material 10 is prepared which comprises a light-emitting film 1 containing a photoluminescent compound. The light-emitting film 1 in this coating material 10 mainly exhibits an amorphous phase, but has a crystalline region in part. Mechanorluminescence is generated from the light-emitting film 1 by applying a non-destructive mechanical stimulus to the coating material 10.

[0071] Mechanorluminescence can be generated by applying non-destructive mechanical stimulation through friction between the component and the coating material 10 (Figure 3). Mechanorluminescence can be generated by applying non-destructive mechanical stimulation by bringing the component into contact with the coating material 10 and then peeling the component off (Figure 4). Mechanorluminescence can be generated by applying non-destructive mechanical stimulation through bending and / or twisting of the coating material 10 (Figure 5). The coating material 10 may further include a protective film 2 that is peelably in contact with the surface of the light-emitting film 1, in which case mechanorluminescence can be generated by applying non-destructive mechanical stimulation by peeling the protective film 2 from the light-emitting film 1 (Figure 6).

[0072] In the preferred light emission method according to this embodiment, mecanorluminescence is generated from the light-emitting film 1 under air. Alternatively, mecanorluminescence may be generated from the light-emitting film 1 under an inert gas atmosphere such as argon.

[0073] As previously described in the embodiments of the mechanorluminescence coating material 10, the light-emitting film 1 may contain a polymer matrix, the content of the photoluminescence compound in the light-emitting film 1 may be more than 30 wt%, and the photoluminescence compound may be an organic compound.

[0074] While embodiments based on this disclosure have been described above, the compounds and configurations exemplified herein are merely examples and do not limit the technical scope of the present invention to them. Other compounds and components that produce equivalent effects can be arbitrarily combined by those skilled in the art, including the modifications and known technologies described herein, and such changes and modifications are included within the technical scope of the present invention. Furthermore, the present invention can be used in combination with existing known technologies, and such forms are also included within the scope of the present invention.

[0075] The following examples illustrate the inventions based on this disclosure in more detail, but the present invention is not limited in any way to the following examples.

[0076] [Experiment 1] (Experiment Summary) A study was conducted to investigate whether ML light emission occurs when a coating material is obtained using a known PL compound. The PL compounds employed in the experiment are tetrakis(dibenzoylmethane) europium(III) tetrabutylammonium (Eu(dbm) ４ TBA), tris(dibenzoylmethane) mono(1,10-phenanthroline) europium(III) (Eu(dpm) ３ (phen)), 2,4,6-triphenylpyrylium tetrafluoroborate (TPP), 1,1,4,4-tetraphenyl-1,3-butadiene (TPBD), and vitamin B2 tetrabutyrate (VB2TB). A thin film was formed by spin-coating these PL compounds onto a glass plate, and crystallinity and ML light emission were confirmed.

[0077] <PL Compounds> Among the above PL compounds, Eu(dpm) ３ (phen), TPP, TPBD, and VB2TB were purchased from Tokyo Chemical Industry Co., Ltd. Eu(dbm) ４ TBA was synthesized according to the procedure reported in known Reference 1.

[0078] <Preparation of Samples on Glass Plates> A spin coating solution was prepared by dissolving each of the above PL compounds as a solute in chloroform or a chloroform-acetonitrile mixture, and the solution (0.20 mL) was spin-coated onto a glass plate (76 mm×52 mm×1 mm) at room temperature, followed by vacuum drying at room temperature for 24 hours to produce a thin film and obtain a sample. No additives were used in any case. The spin coating conditions were as follows: rotation speed 500 rpm, time 6-9 seconds, and drop volume 0.20 mL. When the film thickness of the thin film obtained on the glass plate was measured with a profilometer, the film thickness of the thin film was in the range of 0.3 μm to 1.1 μm.

[0079] The method for preparing the spin coating solution was as follows. Eu(dbm) ４ TBA: 10 mg of powder was dissolved in chloroform-acetonitrile (4:1 / volume ratio) (0.20 mL) with stirring at room temperature. Eu(dbm) ３(Phen): 10 mg of powder was dissolved in chloroform (0.20 mL) at room temperature by stirring. TPP: 10 mg of powder was dissolved in acetonitrile (0.20 mL) at room temperature by stirring. TPBD: 10 mg of powder was dissolved in chloroform (0.20 mL) at 30°C for 10 minutes by stirring. VB2TB: 10 mg of powder was dissolved in chloroform (0.20 mL) at room temperature by stirring.

[0080] <XRD> The presence of a crystalline phase in the thin films of each sample was investigated by X-ray diffraction analysis. X-ray diffraction analysis of each sample was performed using a Bruker D8 Discover diffractometer with Cu Kα rays. For micro-angle incident X-ray diffraction (GID) measurements, a Goebel mirror was used, and the fixed incident angle was approximately 0.1°. The results are shown in Figure 7. Eu (dbm) ３ phen, Eu (dbm) ４ In all cases—TBA, TPBD, TPP, and VB2TB—it was confirmed that the thin films on the glass plate mainly exhibited an amorphous phase while also having crystalline regions in some areas.

[0081] <ML Emission Confirmation> When the surface of a thin film on a glass plate was directly rubbed (i.e., rubbed) with a silicone rod in a dark glove box under an Ar atmosphere, visible emission due to ML was observed. ML observation photographs were taken with a Sony α7SII, FE 2.8 / 50 macro objective lens, and an exposure time of 10 seconds. Figure 8 shows the photographs where emission was observed. In Figure 8, the ML observation photographs during friction of the thin film surface of each sample are shown as the main image, with the emission photographs under a UV lamp before friction displayed as an inset. Eu (dbm) ３ Phen thin film and Eu (dbm) ４ The TBA thin film emitted red light, the TPBD thin film emitted blue light, and the VB2TB thin film emitted yellow light. However, the TPP thin film did not emit any light through friction in this Ar atmosphere. The same results were obtained for all samples when friction was performed using a PFA rod instead of a silicone rod.

[0082] <PL and ML Spectra> The PL and ML spectra of each sample on a glass plate were measured under an Ar atmosphere. The PL spectrum was measured in a reflectance / backscatter configuration using a QE-Pro6200 spectrometer. The ML spectrum was recorded under an Ar gas atmosphere by rubbing the surface of the thin film on the glass plate with a transparent perfluoroalkoxyalkane (PFA) rod into which an optical fiber probe was inserted, and detecting the emission signal with a QE-Pro6200 spectrometer. The results are shown in Figure 9. In the graph, Eu (dbm) ３ (phen) and Eu (dbm) ４ The emission peaks of TBA are indicated by arrows. The ML spectra of each sample correspond to their respective PL spectra, confirming that the excited states of the photoluminescent compounds are generated by friction on the thin film surface (Figure 9). However, the TPP sample did not exhibit ML emission under direct friction in an Ar atmosphere.

[0083] <ML Luminescence Experiment> Next, ML luminescence experiments were performed on each sample using various non-destructive mechanical stimuli.

[0084] <<ML emission by friction>> In the previous experiment, the conditions were Ar atmosphere. However, for each sample on a glass plate, ML emission was induced by friction with a glass tube containing an optical fiber probe in humid air (24°C, relative humidity 37%) through a protective film made of polyvinyl chloride (PVC) (thickness 20-30 μm) in air (see also Figure 3 above). The spectrum of ML generated by this friction was measured using the spectrometer described above. Figure 10 shows the ML spectra due to friction for each sample. This figure also shows the results of Reference Experiment 1 described later. Figure 11 shows ML photographs from each sample on a glass plate due to friction through the PVC protective film. Specifically, it was generated by friction of a silicone rod (diameter 10 mm) against the thin film of each sample through the PVC protective film in humid air (25°C, relative humidity: 31-34%). The camera exposure time was 10 seconds. Eu (dbm) ３ Phen thin film and Eu (dbm) ４ The TBA thin film emitted red light, the TPBD thin film emitted blue light, and the TPP thin film and VB2TB thin film emitted yellow light.

[0085] <<ML emission by contact-peel>> A silicone sheet spacer and a PVC protective film were placed on each sample thin film on a glass plate. In the dark, a soft silicone rod (10 mm in diameter) was brought into contact with the PVC protective film every second, and then removed, applying non-destructive mechanical stimulation to the sample thin film to generate ML (see also Figure 4 above). This ML generation was repeated and recorded with a CCD camera under humid air (25°C, relative humidity: 31-34%). A representative example is Eu (dbm). ３ Figure 12 shows ML photographs (30 fps) from the (phen) thin film and the TPP thin film. In addition, an intensity distribution image of the ML emission generated by contact-detachment with this silicone rod and the time profile of the emission during repeated contact-detachment were recorded using a Thorlabs CCD camera and analyzed using Image J. As a result, no significant attenuation of ML due to contact-detachment of the rod on the coating film was observed even after more than 90 cycles.

[0086] <<ML emission due to peeling>> Under humid conditions (25°C, relative humidity: 31-34%), a PVC protective film (thickness: approximately 10-20 μm) was attached to a sample thin film on a glass plate. When the PVC protective film was peeled off from the thin film, ML emission was observed (see Figure 6 above). The imaging conditions were the same as for the contact-peeling experiment described above, and the photographs were taken at 30 fps. Eu (dbm) is a representative example. ３ ML photographs from (phen) thin films, TPBD thin films, and TPP thin films are shown in Figure 13. Note that ML was not observed when adhesive tape and Post-it® notes were directly attached to the thin films and then peeled off.

[0087] <Discussion> - From the Triboluminescence Experiment - A sharp peak was measured in the near-infrared region of the ML spectrum shown in Figure 9. This is thought to be due to gas discharge emission from the surrounding Ar gas. This suggests that the strong electric field generated at the contact surface with the thin film due to triboelectric charging is involved in ML. Furthermore, ML was also generated when the surface was rubbed with rods made of polyacetal (POM), polytetrafluoroethylene (PTFE), and perfluoroalkoxyalkane (PFA), which are known to become negatively charged by friction compared to other polymer materials. In addition, when a PVC protective film (thickness: 20-30 μm) was attached to the sample thin film, ML was generated from PL compounds in humid air when the thin film was rubbed through the protective film with a glass rod or silicone rod (Figures 10 and 11). Attaching a protective film to the thin film surface is useful because it can suppress damage to the thin film due to friction, adhesion of other materials to the thin film, and adhesion from the thin film material to other materials. In addition, in the triboluminescence through the protective film in air, nitrogen gas discharge emission was also observed in the ultraviolet region of the ML spectrum (Figure 10).

[0088] In the TPP thin film, no ML (metabolic filtration) was observed when the thin film surface was directly rubbed in an Ar atmosphere (Figure 9). However, ML was observed when the TPP thin film was rubbed through a PVC protective film in humid air. Therefore, it was confirmed that rubbing the thin film made from the PL compound through a protective film is more effective in generating ML than rubbing it directly.

[0089] -From the Contact-Peel Experiment- When a protective film was placed on a thin film, it was confirmed that ML (luminescence emission) was generated by contact-peeling between the protective film and the silicone rod (Figure 12). This phenomenon indicates that ML could be generated without friction. This is because the rod can move both vertically and parallel to the contact interface between the protective film and the silicone rod. Furthermore, as mentioned above, even after more than 90 cycles of ML generation by this contact-peeling method, no significant attenuation of ML was observed. Such a luminescence phenomenon has not been reported before and is a first discovery by the inventors.

[0090] -From the peeling experiment- Furthermore, ML was also generated by peeling off a PVC protective film attached to a sample thin film under humid air (Figure 13). This phenomenon is also the first discovery of luminescence caused by contact and peeling of a PL compound, which does not contain adhesive or bonding additives, with other materials. It has been reported that luminescence occurs at the peeling interface when adhesive tape is peeled off (Reference 2), but in this experiment, the luminescence originating from the PL compound is generated by contact and peeling of a non-adhesive PL compound and a non-adhesive polymer film, which is novel.

[0091] -Comparison with publicly known reports- Reports that similar ML generation was induced by contact-delamination with a component are limited to cases where semiconductor particles of ZnS:Cu, which are well known as ML materials, are embedded in polydimethylsiloxane (Reference 3). Also, SrAl ２ O ４ :Eu ２＋ Non-contact electrostatically induced luminescence has also been reported (Reference 4). However, both of these involved ML emission from crystalline particles, and there have been no reports to date of generating ML emission when a light-emitting film, which mainly exhibits an amorphous phase but has a crystalline region in part, is separated from a component such as a rod or protective film. The mechanorluminescent coating material and the coating material and amorphous phase according to this disclosure can also serve as direct light sources. Furthermore, in certain embodiments of this disclosure, these light sources do not need to exhibit ML emission in the crystalline state. In addition, in the aforementioned References 3 and 4, crystalline inorganic particles were used as the ML source. These are crystalline particles having trap levels. On the other hand, in certain embodiments of this disclosure, the crystalline region is composed of a molecular crystal. This molecular crystal does not need to have trap levels and may be composed of a photoluminescent compound.

[0092] In summary, the mechanorluminescent coating material and novel light-emitting method using the coating material disclosed herein not only enable the development of unprecedented non-destructive mechanically responsive fibers, sheets, and devices, but also enable applications such as mechanical sensors that can visualize friction and contact-peeling, self-generating displays, energy conversion devices, luminescent toys, decorative paints, anti-counterfeiting applications for banknotes, and the development of electrostatic detection sensing systems, and their applications are endless.

[0093] [Experiment 2] The inventors conducted further experiments to investigate non-destructive mechanical stimulation. Unless otherwise specified, the experimental conditions were the same as those in Experiment 1 described above.

[0094] <Sample Preparation> TPBD and Eu(dbm) used as PL compounds in Experiment 1. ３ (Phen) was used in each case. A PL compound was applied to a polyethylene terephthalate (PET) film as a substrate by spin coating to form a PL compound thin film, and a flexible ML film was produced.

[0095] <ML Observation> ML was generated when the surface of the PL compound film coated on the PET film was rubbed with a material. Furthermore, a laminated film was created by covering the surface of the coated PET film on the PL compound film side with a protective silicone sheet and a PVC sheet, respectively. Under humid air conditions (27°C, relative humidity: 31%), ML was observed in both the case of the silicone sheet and the PVC sheet by bending or twisting the laminated film (see Figure 5 above). Figure 14 shows photographs of the ML observation. The camera exposure time was set to 5 seconds.

[0096] These laminated films emitted light when bent or twisted, but did not emit light when simply shaken. Furthermore, luminescence (ML) was not observed when there was no protective film covering the surface of the PL compound thin film on the PET film. This suggests that the emission is based on contact charging due to contact-peelback between the PL compound and the protective film.

[0097] [Reference Experiment 1] The inventors also conducted experiments with other types of PL compounds. Unless otherwise specified, the experimental conditions were the same as in Experiment 1 described above.

[0098] (Experiment Overview) The PL compound used in this reference experiment was tris(8-quinolinolato)aluminum (AlQ ３ ), 2,5-bis(5-tert-butyl-2-benzoxazolyl)thiophene (BBOT), 4,4'-bis(9H-carbazole-9-yl)biphenyl (CBP), bis[2-(diphenylphosphino)phenyl]-ether(2,9-dimethyl-1,10-phenanthroline) copper(I) tetrafluoroborate (Cu(dmp)DPE), 4,4'-bis(2,2-diphenylvinyl)biphenyl (DPVBi), tris(1,10-phenanthroline)ruthenium(II)bis(hexafluorophosphate) (Ru(phen) ３ PF ６ ) Among these, AlQ ３ CBP is known as an amorphous solid that is applied to organic light-emitting devices (OLEDs) (see known references 5-8).

[0099] Of the above PL compounds, AlQ ３ , BBOT, CBP, DPVBi, Ru(phen) ３ PF ６ The product was purchased from Tokyo Chemical Industry Co., Ltd. Cu(dmp)DPE was prepared by mixing Cu(I) chloride and 1 equivalent of bis[2-(diphenylphosphino)phenyl] ether in a THF-MeCN solution at 70°C for 1 hour, and then mixing 1 equivalent of 2,9-dimethyl-1,10-phenanthroline hemihydrate with 1.1 eq of NaBF ４ The mixture was synthesized by adding [the specified ingredient]. The resulting mixture was then crystallized and purified with acetonitrile to obtain crystalline Cu(dmp)DPE.

[0100] <Sample preparation on glass plate> A thin film was prepared and a sample was obtained by spin-coating the above PL compound onto a glass plate in the same manner as in Experiment 1.

[0101] The spin-coating solution was prepared as follows: 50 mg of Cu(dmp)DPE powder was dissolved in chloroform (0.20 mL) at room temperature with stirring. ３ 30 mg of powder was dissolved in chloroform (0.60 mL) by stirring at 40°C for 20 minutes. CBP: 20 mg of powder was dissolved in chloroform (0.60 mL) by stirring at 40°C. Ru(phen) ３ (PF ６ ) ２ 8.0 mg of powder was dissolved in chloroform-acetonitrile solution (3:1 / volume ratio) (0.20 mL) by stirring at 30°C. BBOT: 10 mg of powder was dissolved in chloroform (0.20 mL) by stirring at room temperature. DPVBi: 10 mg of powder was dissolved in chloroform (0.20 mL) by stirring at 30°C for 10 minutes.

[0102] <XRD> Similar to Experiment 1, the presence of a crystalline phase in the thin film of each sample was investigated by X-ray diffraction analysis. The results are shown in Figure 15. AlQ ３ , BBOT, CBP, Cu(dmp)DPE, DPVBi, Ru(phen) ３ PF ６ In all cases, the XRD patterns did not show crystalline peaks, indicating amorphous solids.

[0103] <Confirmation of ML Emission> Similar to Experiment 1, when the surface of a thin film on a glass plate was directly rubbed (i.e., rubbed) with a silicone rod in a dark glove box under an Ar atmosphere, visible emission due to ML was observed. A photograph showing the observed emission is shown in Figure 16. AlQ ３ The thin film and Cu(dmp)DPE thin film emitted yellow light, the BBOT thin film and DPVBi thin film emitted blue light, and the CBP thin film emitted purple light. However, Ru(phen) ３ PF ６ The thin film did not emit light through friction under this Ar atmosphere.

[0104] <PL and ML spectra> Similar to Experiment 1, the PL and ML spectra of each sample on a glass plate were measured under an Ar atmosphere. The results are shown in Figure 17. The ML spectrum of each sample corresponds to its respective PL spectrum, and, similar to Experiment 1, it can be confirmed that the excited state of the photoluminescent compound is generated by friction on the thin film surface (Figure 17). However, Ru(phen) ３ PF ６ The sample did not exhibit ML emission under direct friction in an Ar atmosphere.

[0105] <ML Luminescence Experiment> In Reference Experiment 1, ML luminescence experiments were also performed on each sample using various non-destructive mechanical stimuli.

[0106] <<ML emission by friction>> Similar to Experiment 1, each sample on a glass plate was subjected to friction in humid air using a glass tube containing an optical fiber probe, with a protective film made of polyvinyl chloride (PVC) in the air, to induce ML emission (see also Figure 3 above). The ML spectra generated by this friction were measured using a spectrometer. The ML spectra due to friction for each sample are shown in Figure 10 above. Also, representative examples of ML photographs from each sample on a glass plate due to friction through the PVC protective film are shown in Figure 18. AlQ ３ The thin film and Cu(dmp)DPE thin film emitted yellow light, the BBOT thin film and DPVBi thin film emitted blue light, and the CBP thin film emitted purple light.

[0107] <<ML emission by contact-peeling>> Similar to Experiment 1, a silicone sheet spacer and a PVC protective film were placed on each sample thin film on a glass plate. In the dark, a soft silicone rod was brought into contact with the PVC protective film every second, and then removed, applying non-destructive mechanical stimulation to the sample thin film to generate ML. This ML generation was repeated and recorded with a CCD camera (30 fps) under humid air. As representative examples, ML photographs from Cu(dmp)DPE thin film and DPVBi thin film are shown in Figure 19(a). In addition, the intensity distribution image of the ML emission generated by contact-peeling with this silicone rod and the emission time profile during repeated contact-peeling were recorded using a Thorlabs CCD camera and analyzed with Image J. Figures 19(b) and (c) show the emission distribution and time profile of ML of Cu(dmp)DPE during peeling. Even after more than 90 cycles, no significant attenuation of ML due to contact peeling of the rod on the coating film was observed. Furthermore, a weak luminescence was observed not only during peeling but also during contact.

[0108] <<ML emission due to peeling>> Similar to Experiment 1, a PVC protective film was attached to a sample thin film on a glass plate under a humid atmosphere, and when the PVC protective film was peeled off from the thin film, ML was observed (see Figure 6 above). The imaging conditions were the same as in the contact-peel experiment described above, and the photographs were taken at 30 fps. As representative examples, ML photographs from BBOT thin film, Cu(dmp)DPE thin film, and DPVBi thin film are shown in Figure 20. Note that, similar to Experiment 1, when adhesive tape and Post-it® notes were attached to the thin film before peeling, no such ML was observed.

[0109] <Discussion> - From the Triboluminescence Experiment - Similar to Experiment 1, a sharp peak was measured in the near-infrared region of the ML spectrum shown in Figure 17. This is thought to be due to gas discharge emission from the surrounding Ar gas. This also suggests that the strong electric field generated around the contact surface with the thin film by triboelectric charging is involved in ML. Similar to Experiment 1, ML was also generated when the surface was rubbed with rods made of POM, PTFE, PFA, etc. Also, similar to Experiment 1, ML was generated from the PL compound in humid air when the thin film was rubbed with a glass rod or silicone rod through a protective film (Figures 10 and 18).

[0110] Similar to the phenomenon observed in the TPP thin film in Experiment 1, Ru(phen) ３ PF ６ In thin films, no ML was observed when the thin film surface was directly rubbed in an Ar atmosphere (Figure 17), but Ru(phen) was observed through a PVC protective film in humid air. ３ PF ６ ML was observed when the thin film was rubbed. Therefore, this experiment also confirmed that rubbing the thin film made from the PL compound through a protective film is more effective in generating ML than rubbing it directly.

[0111] -From the Contact-Peel Experiment- Similar to Experiment 1, when a protective film was placed on the thin film, it was confirmed that ML was generated by contact-peeling between the protective film and the silicone rod (Figure 19). Furthermore, as mentioned above, even after more than 90 cycles of ML generation due to this contact-peeling, no significant decrease in ML was observed.

[0112] -From the peeling experiment- Furthermore, ML was also generated by peeling off the PVC protective film attached to the sample thin film under humid air conditions (Figure 20).

[0113] [Reference Experiment 2] The inventors conducted Reference Experiment 2 immediately following Reference Experiment 1, similar to Experiment 2. Unless otherwise specified, the experimental conditions were the same as those for Experiment 2 described above.

[0114] <Sample Preparation> Cu(dmp)DPE and DPVBi, which were used in Experiment Reference 1, were used as PL compounds. A flexible ML film was prepared by forming a PL compound thin film on a PET film substrate using the spin coating method.

[0115] <ML Observation> Similar to Experiment 2, ML was generated when the surface of the PET film was rubbed with a material. Furthermore, the coated PET film surface was covered with a protective silicone sheet and a PVC sheet to form a laminated film. In this case, as in Experiment 2, ML was observed by bending and twisting the laminated film (see Figure 5 above). Figure 21 shows photographs of the ML observations.

[0116] Similar to Experiment 1, these laminated films glowed when bent or twisted, but did not glow when simply shaken. Furthermore, ML was not observed when there was no protective film covering the PET film.

[0117] [Reference Experiment 3] The inventors further conducted experiments in which the PL compound was molecularly dispersed in a polymer matrix. In the experiment, PMMA (polymethyl methacrylate) was used, and AlQ was used as the PL compound. ３ Using Cu(dmp)DPE and DPVBi, thin films were formed on a glass plate by spin coating, and a PVC film was used as a protective layer. The PMMA content was also adjusted. Unless otherwise specified, other experimental conditions were the same as those described in Experiment 1 and Reference Experiment 1. That is,

[0118] <AlQ ３ > When the thin film was rubbed directly with a silicon rod, no ML (luminescence emission) was generated in air, but when rubbed through a PVC film, visible ML was generated. In the PMMA-containing film, no significant difference in ML emission intensity was observed even when the amount was adjusted within the range of 10 to 100 wt%. Similarly, in the ML emission intensity when the thin film was rubbed directly with a silicon rod under an Ar gas atmosphere, no significant difference was observed even when the amount of PMMA-containing film was adjusted within the range of 10 to 100 wt%.

[0119] <Cu(dmp)DPE> When the PVC protective film was peeled off a Cu(dmp)DPE thin film on a glass plate, ML (luminescence emission) occurred. When a thin film was formed on the PVC protective film and placed on a glass plate, ML of the Cu(dmp)DPE was also generated by rubbing the thin film from the PVC protective film side. It was confirmed that the ML intensity decreased when the Cu(dmp)DPE content was reduced in the PMMA-containing film (90 wt%, 70 wt%, 50 wt%, 30 wt%, 10 wt%). The pure Cu(dmp)DPE thin film without PMMA showed the strongest ML emission when rubbed in air through the PVC protective film.

[0120] <DPVBi> In PMMA-containing films, when DPVBi was mixed with PMMA at a concentration of 90-30 wt%, the ML emission intensity was better than that of the PMMA-free case, both under Ar atmosphere and air conditions, regardless of whether friction was performed using a silicone rod or a PFA rod.

[0121] AlQ ３ In all cases—the thin film, the Cu(dmp)DPE thin film, and the DPVBi thin film—frictional luminescence due to friction with a metal spatula was observed under Ar gas.

[0122] From the above, it was confirmed that the presence of a polymer matrix does not contribute to ML emission. However, since using a polymer matrix is ​​useful for coating PL compounds, this disclosure does not intend to exclude the use of polymer matrices.

[0123] (Note) Based on the above reference experiments 1 to 3, the following embodiments are also possible based on this disclosure. This disclosure is also applicable to coating materials in which the light-emitting film exhibits an amorphous phase but does not have a crystalline region. In such cases as well, the fact that ML emission can be confirmed by contact-peeling with a non-adhesive member is a discovery made by the inventors for the first time, and such a method is useful. Similarly, the fact that ML emission can be confirmed by further providing a non-adhesive protective film that is peelably in contact with the surface of the light-emitting film and peeling this protective film from the light-emitting film is a discovery made by the inventors for the first time, and such a method is useful.

[0124] [Additional Experiment 1] (Preparation of PMMA film containing PL compound) 80 mg of PMMA (polymethyl methacrylate) powder was dissolved in dichloromethane (1.0 mL). The PL compound powder (20 mg) used in Experiment 1 and Reference Experiment 1 was dispersed in the dichloromethane solution. In other words, the PL compound content was 20 wt%. Next, this dispersion was placed on a glass petri dish (50 mm in diameter) and air-dried for 2 to 3 hours, and then vacuum-dried for 1 day to obtain a PMMA film. The PL compound used in the experiment was AlQ ３ , BBOT, CBP, DPVBi, Ru(phen) ３ PF ６ These are TPBD, TPP, and VB2TB.

[0125] The XRD patterns of PMMA films containing PL compounds were measured in the same manner as in Experiment 1 and Reference Experiment 1. Specifically, an automated Bruker D8 Discover diffractometer equipped with an EIGER R 500K detector was used. Cu Kα1 radiation was used. The thickness of each sample was approximately 0.05–0.08 mm. Each sample was placed in a Si-low-background holder. The diffraction patterns were recorded in 0.015° increments, starting from 5° in the 2θ range. The exposure time was 0.5 seconds. In addition, the background XRD pattern and the XRD pattern of PMMA alone were also measured. The results are shown in Figure 22. In all cases, a broad peak of amorphous PMMA was observed, indicating that this film is mainly in the amorphous phase, and peaks originating from the crystalline phase were also observed.

[0126] Furthermore, the ML spectra of the PL compound-containing PMMA film were measured under an Ar atmosphere in the same manner as in Experiment 1 and Reference Experiment 1. The results are shown in Figures 23 and 24.

[0127] Based on the experimental results above, in addition to the luminescent film without a polymer matrix confirmed in Experiment 1, ML luminescence was also confirmed in the case of a luminescent film containing a polymer matrix in this additional Experiment 1.

[0128] ―References― Reference 1: Richter, MM; Bard, AJ, Electrogenerated Chemiluminescence. 58. Ligand-Sensitized Electrogenerated Chemiluminescence in Europium Labels. Anal. Chem. 1996, 68 (15), 2641-2650. Reference 2: EN Harvey, Science 1939, 89, 460-461. Reference 3: Park, H.-J.; Kim, S.; Lee, JH; Kim, HT; Seung, W.; Son, Y.; Kim, TY; Khan, U.; Park, N.-M.; Kim, S.-W., Self-Powered Motion-Driven Triboelectric Electroluminescence Textile System. ACS Applied Materials & Interfaces 2019, 11 (5), 5200-5207. Reference 4: Kikunaga, K.; Terasaki, N., Demonstration of static electricity induced luminescence. Scientific Reports 2022, 12 (1), 8524. Reference 5: Wang, M.-H.; Konya, T.; Yahata, M.; Sawada, Y.; Kishi, A.; Uchida, T.; Lei, H.; Hoshi, Y.; Sun, L.-X., Thermal change of organic light-emitting ALQ3 thin films. J. Therm. Anal. Calorim. 2010, 99 (1), 117-122. Reference 6: Schrogel, P.; Tomkevi?ien?, A.; Strohriegl, P.; Hoffmann, ST; Kohler, A.; Lennartz, C., A series of CBP-derivatives as host materials for blue phosphorescent organic light-emitting diodes. J. Mater. Chem. 2011, 21(7), 2266-2273. Reference 7: So, SK; Choi, WH; Cheung, CH, Thin-film transistor as a probe to study carrier transport in amorphous organic semiconductors. J. Photonics Energy 2011, 1, 011011 / 1. Reference 8: Shibata, M.; Sakai, Y.; Yokoyama, D., Advantages and disadvantages of vacuum-deposited and spin-coated amorphous organic semiconductor films for organic light-emitting diodes. J Mater Chem C 2015, 3 (42), 11178-11191.

[0129] According to the present invention, it is possible to provide a method for emitting light using a coating material for mecanorluminescence that was not previously known, as well as a coating material for mecanorluminescence and a method for manufacturing the same, which is useful.

[0130] 1. Light-emitting film (thin film) 2. Protective film 3. Void 10. Coating material 20. Substrate 100. Structure

Claims

1. A coating material comprising a light-emitting film containing a photoluminescent compound, wherein the light-emitting film mainly exhibits an amorphous phase while having a crystalline region in part, and a method for generating mechanorluminescence from the light-emitting film by applying a non-destructive mechanical stimulus to the coating material.

2. The light emission method according to claim 1, wherein the non-destructive mechanical stimulus is applied by friction of the member against the coating material.

3. The light emission method according to claim 1, wherein the member is brought into contact with the coating material, and then the member is peeled off to apply the non-destructive mechanical stimulus.

4. The light emission method according to claim 1, wherein the non-destructive mechanical stimulus is applied by bending and / or twisting of the covering material.

5. The light emission method according to claim 1, wherein the coating material further comprises a protective film that is peelably in contact with the surface of the light-emitting film, and the non-destructive mechanical stimulus is applied by peeling the protective film from the light-emitting film.

6. A method for generating light according to any one of claims 1 to 5, wherein mecanorluminescence is generated from the light-emitting film in the presence of air.

7. The light-emitting method according to claim 1, wherein the light-emitting film includes a polymer matrix.

8. The light-emitting method according to claim 7, wherein the content of the photoluminescent compound in the light-emitting film is more than 30 wt%.

9. The light emission method according to claim 1, wherein the photoluminescent compound is an organic compound.

10. A coating material for mechanorluminescence that emits light upon non-destructive mechanical stimulation, comprising a light-emitting film containing a photoluminescent compound, wherein the light-emitting film mainly exhibits an amorphous phase while having a crystalline region in part.

11. The coating material for mechanorluminescence according to claim 10, wherein the light-emitting film comprises a polymer matrix.

12. The coating material for mechanorluminescence according to claim 11, wherein the content of the photoluminescent compound in the light-emitting film is more than 30 wt%.

13. The coating material for mechanorluminescence according to claim 10, wherein the photoluminescent compound is an organic compound.

14. The coating material for mechanorluminescence according to claim 10, further comprising a protective film provided on the surface of the light-emitting film.

15. The coating material for mechanorluminescence according to claim 14, wherein the protective film is in peelable contact with the surface of the light-emitting film.

16. The mecanorluminescent coating material according to any one of claims 10 to 15, wherein the non-destructive mechanical stimulus is friction of a member against the mecanorluminescent coating material.

17. The mecanorminescent coating according to any one of claims 10 to 15, wherein the non-destructive mechanical stimulus is contact-peeling between the member and the mecanorminescent coating.

18. The mechanorluminescent coating according to any one of claims 10 to 15, wherein the non-destructive mechanical stimulus is either bending or twisting of the mechanorluminescent coating or both.

19. The mechanorluminescent coating material according to claim 15, wherein the non-destructive mechanical stimulus is the peeling of the protective light-emitting film from the protective coating material.

20. A method for producing a mechanoluminescent coating, comprising: a first step of preparing a solution containing a photoluminescent compound; and a second step of applying the solution and drying it to obtain a light-emitting film, wherein the light-emitting film mainly exhibits an amorphous phase and has a crystalline region in part.

21. The method for producing a mechanoluminescent coating material according to claim 20, wherein in the first step, the photoluminescent compound and the polymer are mixed to prepare the solution.

22. A method for manufacturing a mecanorluminescent coating material according to claim 20 or 21, further comprising a third step of providing a protective film on the surface of the light-emitting film after the second step.

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