Stimulus-responsive, slow-acting liquid light-emitting material, and its applications

Abstract

This invention provides a stimulus-responsive, slow-acting, room-temperature liquid luminescent material whose emission wavelength changes in response to external stimuli, a method for controlling the rate of change of its emission wavelength, and a luminescent ink using these materials. [Solution] The stimulus-responsive, slow-acting liquid light-emitting material contains an imide compound represented by formula (1) and a π-conjugated compound. TIFF2026081871000023.tif3374 [Ring A represents an aromatic hydrocarbon ring with 6 to 20 nuclear atoms, which may be substituted. X 1 X represents an alkylene group having 1 to 6 carbon atoms, which may be substituted with one or more specific groups. 2 X represents an oxygen atom or a nitrogen atom; X 2 If it is an oxygen atom, then m is 1. 2 If it is a nitrogen atom, then m represents 1 or 2. 1 This represents an alkyl group with 8 to 18 carbon atoms, in which one or more -CH2- groups may be replaced by -O-, -S-, or -(SiMe2)-.

Description

[Technical Field]

[0001] This disclosure relates to a stimulus-responsive, slow-acting liquid light-emitting material containing an imide compound that is liquid at room temperature and a π-conjugated compound, wherein the emission wavelength changes in response to an external stimulus, as well as a method for controlling the response rate thereof, and its applications. [Background technology]

[0002] In recent years, materials whose emission wavelength changes in response to physical stimuli such as temperature, light, electric current, and magnetic fields, or external stimuli such as changes in the chemical environment such as pH and the concentration of chemical substances, have attracted attention because they can be applied to sensors, anti-counterfeiting inks, recording media, and the like.

[0003] In particular, liquid light-emitting materials whose emission wavelength changes in response to external stimuli can be used as inks, and are therefore used as anti-counterfeiting inks and temperature sensors.

[0004] Patent Document 1 and Non-Patent Document 1 disclose that a room-temperature liquid material consisting of a tetracarboxylic acid diimide skeleton becomes a liquid light-emitting material exhibiting luminescence properties when a naphthalene derivative is dissolved in it, and ceases to emit light when the naphthalene derivative is evaporated by heating, thus making the liquid light-emitting material useful as a temperature sensor.

[0005] Non-patent document 2 discloses that a liquid luminescent material, obtained by adding 0.5 mol% of 9,10-bis(phenylethynyl)anthracene and 5.0 mol% of tris(1,3-diphenyl-1,3-propanedione)mono(1,10-phenanthroline)europium(III) as dopants to a room-temperature liquid material consisting of an anthracene skeleton, exhibits a change in emission wavelength with temperature and is therefore useful as a temperature sensor.

[0006] Non-patent document 3 discloses that a liquid light-emitting material having a diketopyrrolopyrrole skeleton changes from a liquid to a crystal when shear stress is applied, and that the emission wavelength changes accordingly.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Non-Patent Documents

[0008]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, the liquid light-emitting materials having stimulus responsiveness reported so far are only those in which the emission wavelength changes immediately after an external stimulus is applied, that is, the response speed shows instantaneity. Also, there is no quantitative description regarding the response speed in any of the prior art documents.

[0010] Currently, there is a need for a technology that can freely control the response speed, not only for the conventional liquid light-emitting materials having instantaneity stimulus responsiveness. Among them, liquid light-emitting materials having delayed stimulus responsiveness with a reduced response speed to external stimuli can enhance the anti-counterfeiting effect when used as anti-counterfeiting ink in combination with liquid light-emitting materials having instantaneity stimulus responsiveness.

[0011] In addition, liquid light-emitting materials having delayed stimulus responsiveness can change the color tone of a painting over time when used in inks for artworks such as ornaments and paintings, etc., so that they can provide attractive optical properties and high added value to ornaments and artworks.

[0012] Based on the above, one aspect of the present disclosure provides a stimulus-responsive, delayed-release liquid light-emitting material in which the emission wavelength changes after a certain period of time following the application of an external stimulus, an ink containing the same, and a method for generating delayed-release light. [Means for solving the problem]

[0013] The inventors have discovered that a liquid luminescent material, prepared by dissolving an imide compound and a π-conjugated compound that are liquid at room temperature, exhibits a change in emission wavelength after a certain period of time in response to an external stimulus. Furthermore, they have found that the response speed of the change in emission wavelength after the application of an external stimulus can be controlled by adjusting the type and concentration of the π-conjugated compound, thus completing the present invention.

[0014] A first aspect of this disclosure is a stimulus-responsive, slow-acting liquid light-emitting material comprising an imide compound represented by formula (1) and a π-conjugated compound. [ka] [In formula (1), Ring A represents an aromatic hydrocarbon ring with 6 to 20 nuclei, which may be substituted (it may be a monoring, a fused ring, or a linked ring containing multiple rings). X 1 Each of these independently represents an alkylene group having 1 to 6 carbon atoms, which may be substituted with one or more groups selected from the group consisting of a sulfanyl group, an alkylthio group, a hydroxyl group, a carboxyl group, an amino group, an amide group, a guanidino group, an imidazolyl group, a phenyl group, a hydroxyphenyl group, and an indolyl group. X 2 represents an oxygen atom or a nitrogen atom; X 2 If it is an oxygen atom, then m is 1. X 2 If it is a nitrogen atom, then m represents either 1 or 2. R 1represents a linear or branched alkyl group having 8 to 24 carbon atoms, or a linear alkyl group having 8 to 18 carbon atoms in which one or more -CH2- may be replaced by -O-, -S-, or -(SiMe2)-, provided that two or more -O- and three or more -S- do not appear consecutively.

[0015] The second aspect of the present disclosure is a stimulus-responsive delayed liquid luminescent material in which, in formula (1), the above ring A is represented by the following formula (2) or formula (3). [Chemical formula] [Chemical formula] [In formulas (2) and (3), R 2 and R 3 each independently represent a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group having 1 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 12 nuclear atoms, or a heteroaromatic group having 3 to 6 nuclear atoms. * represents the bonding position.

[0016] The third aspect of the present disclosure is a stimulus-responsive delayed liquid luminescent material in which, in formula (1), R 2 and R 3 each independently represent a hydrogen atom or a bromine atom. [Advantages of the Invention]

[0017] According to the present disclosure, there are provided a stimulus-responsive delayed liquid luminescent material whose emission wavelength changes after a certain period of time has elapsed after an external stimulus is applied, an ink containing the same, and a method for generating delayed luminescence. [Brief Description of the Drawings]

[0018] [Figure 1] It is a diagram showing the appearance at 25°C of (A-3-a) to (A-3-c) prepared in Examples 1 to 3.

[0019] [Figure 2] This figure shows the changes in emission wavelength and emission color after applying (A-3-a), prepared in Example 1, to a glass substrate and then applying an external stimulus at 25°C.

[0020] [Figure 3] This figure shows the changes in emission wavelength and emission color after applying (A-3-a) and (A-3-b), prepared in Examples 4 and 5, to a glass substrate and then applying an external stimulus at 25°C.

[0021] [Figure 4] This figure shows the changes in emission wavelength and emission color after coating (A-3-c), prepared in Example 6, onto a glass substrate, without applying any external stimuli at 25°C.

[0022] [Figure 5] This figure shows the changes in emission wavelength and emission color after applying (A-3-a), prepared in Example 7, to a paper substrate and then applying an external stimulus at 25°C.

[0023] [Figure 6] This figure shows the changes in emission wavelength and emission color after applying (A-3-c), prepared in Reference Example 1, to a glass substrate and then applying an external stimulus at 25°C. [Modes for carrying out the invention]

[0024] Preferred embodiments of this disclosure are described in detail below.

[0025] <Imide compounds> The imide compound of this embodiment is a compound represented by formula (1) (hereinafter sometimes referred to as "imide compound (1)"). [ka] (In formula (1), rings A, X 1 , X 2 , R 1 (And m have the same meaning as above.)

[0026] Examples of aromatic hydrocarbon rings with 6 to 20 nuclear atoms represented by ring A include benzene rings, biphenyl rings, naphthalene rings, anthracene rings, phenanthrene rings, tetracene rings, chrysene rings, or perylene rings. It is preferable that the aromatic hydrocarbon ring has 6 to 16 nuclear atoms because the raw materials are readily available, and more preferably that it is a benzene ring, naphthalene ring, or anthracene ring. Ring A may be substituted with one or more groups selected from the group consisting of hydrogen atoms, chlorine atoms, bromine atoms, iodine atoms, C1-C6 alkyl groups, 6-C12 aromatic hydrocarbon groups, and 3-C6 heteroaromatic groups. The C1-C6 alkyl group may be linear, branched, or cyclic, and examples include methyl group, ethyl group, propyl group, isopropyl group, butyl group, 2-methylpropyl group, 2-methylcyclopropyl group, 3-methylpropyl group, pentyl group, 2-methylbutyl group, 3-methylbutyl group, 4-methylbutyl group, hexyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 2,3-dimethylbutyl group, 3-ethylpentyl group, etc. The aforementioned aromatic hydrocarbon group having 6 to 12 nuclear atoms represents a monovalent group obtained by removing one hydrogen atom from an aromatic hydrocarbon. The number of nuclear atoms in the aromatic hydrocarbon group is preferably 6 to 10. The aromatic hydrocarbon group may be a monocyclic aromatic hydrocarbon group, an aromatic hydrocarbon group in which two or more aromatic rings are linked, or a fused aromatic hydrocarbon group. Examples of aromatic hydrocarbon groups include phenyl group, biphenylyl group, naphthyl group, etc. The heteroaromatic group having 3 to 6 nuclear atoms may be a monocyclic heteroaromatic group, a heteroaromatic group in which two or more aromatic rings are linked, or a fused heteroaromatic group. If the heteroaromatic group has multiple aromatic rings, at least one of the aromatic rings must contain a heterocyclic atom (e.g., an oxygen atom, a nitrogen atom, a sulfur atom, etc.). Examples of heteroaromatic groups include pyrrolyl group, thienyl group, furyl group, imidazolyl group, pyrazolyl group, thiazolyl group, isothiazolyl group, thiadiazolyl group, oxazolyl group, isoxazolyl group, oxadiazolyl group, pyridyl group, pyrimidyl group, pyrazyl group, 1,3,5-triazinyl group, etc.

[0027] It is especially preferable that ring A is a ring represented by formula (2) or formula (3) below. [ka] [ka] (In equations (2) and (3), R 2 , R 3 And * have the same meaning as above. R 2 and R 3 Each of these independently represents a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group having 1 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 12 nuclei, or a heteroaromatic group having 3 to 6 nuclei.

[0028] R 2 and R 3 The alkyl groups having 1 to 6 carbon atoms, aromatic hydrocarbon groups having 6 to 12 nuclear atoms, and heteroaromatic groups having 3 to 6 nuclear atoms, as represented by R 2 and R 3 It is synonymous with R. 2 and R 3 This represents either a hydrogen atom or a bromine atom, and a hydrogen atom is preferred because the raw material is readily available.

[0029] X 1Examples of alkylene groups having 1 to 6 carbon atoms represented by the following formulas (a-1) to (a-19) are shown below, but in this embodiment X 1 The group is not limited to this. The group represented by (a-1), (a-2), (a-3), (a-4), (a-5), or (a-16) is more preferred in that the synthesis of the imide compound (1) is easy, and the group represented by (a-1), (a-2), (a-3), (a-4), or (a-5) is particularly preferred. [ka]

[0030] In imide compound (1), from the viewpoint of ease of synthesis, X 1 It is preferable that these are the same group. Note that the divalent linking group represented by formula (ap) (where p is an integer from 2 to 18) is assumed to encompass both of the two optical isomers. That is, since the divalent methine carbons in formulas (a-2) to (a-19), excluding formula (a-1), are chiral carbons, there may be two optical isomers for each: the R-form represented by formulas (a-2R) to (a-19R) and the S-form represented by formulas (a-2S) to (a-19S). Assume that the divalent methine carbon is directly bonded to a nitrogen atom on the left side and to a carbon atom on the right side. [ka] [ka] In this specification, for convenience, the formulas are denoted as (ap), and these include the R and S optical isomers described above. The divalent linking group represented by formula (ap) contains at least one of the optical isomers represented by formulas (a-pR) and (a-pS), and may contain both of the optical isomers represented by formulas (a-pR) and (a-pS).

[0031] X 2 represents an oxygen atom or a nitrogen atom, and an oxygen atom is preferred because the imide compound (1) is liquid at room temperature.

[0032] R 1 The C8-C24 alkyl group represented by may be linear or branched, and may be an octyl group, 2-octyl group, 2-ethylhexyl group, 5-methylheptyl group, nonyl group, decyl group, 2-ethyloctyl group, 3,7-dimethyloctyl group, undecyl group, dodecyl group, 2-ethyldecyl group, tridecyl group, tetradecyl group, 2-butyldodecyl group, 2-(hexa-2-yl)-5-methyloctyl group, Examples include pentadecyl group, 3,7,11-trimethyldodecyl group, hexadecyl group, 2-hexyldodecyl group, heptadecyl group, octadecyl group, nanodecyl group, eicosyl group, 2-hexyltetradecyl group, 2-octyldodecyl group, henicosyl group, docosyl group, 2-octyltetradecyl group, tricosyl group, tetracosyl group, 2-octylhexyldecyl group, 2-decyltetradecyl group, etc. In terms of ease of synthesis, R 1 The group is preferably an alkyl group having 8 to 22 carbon atoms, more preferably a branched alkyl group having 8 to 22 carbon atoms, even more preferably a group represented by the following formulas (b-1) to (b-8), and especially preferably a group represented by (b-2). [ka]

[0033] R 1 One or more -CH2- groups represented by can be replaced with -O-, -S-, or -(SiMe2)-, but examples of linear alkyl groups having 8 to 18 carbon atoms that do not have two or more consecutive -O- groups or three or more consecutive -S- groups include the groups shown in the following formulas (C-1) to (C-48). [ka] TIFF2026081871000012.tif110110

[0034] As the imide compound (1) of this embodiment, for example, compounds represented by (A-1) to (A-10) are preferred in that they are easy to synthesize, compounds represented by (A-1), (A-2), (A-3), (A-4), (A-5), or (A-8) are more preferred, and (A-3) is particularly preferred. Note that the imide compound (1) of this embodiment is not limited to the compounds exemplified below. [ka]

[0035] <Method for producing imide compound (1)> The imide compound (1) can be synthesized according to the method disclosed in Patent Document 1 (JP 2024-109062 A) or Japanese Patent Application No. 2024-38536.

[0036] <Method for manufacturing a stimulus-responsive, slow-acting liquid light-emitting material> The stimulus-responsive, slow-acting liquid light-emitting material of this embodiment comprises an imide compound (1) and a π-conjugated compound.

[0037] Examples of π-conjugated compounds included in the stimulus-responsive, slow-acting liquid light-emitting material of this embodiment include naphthalene, anthracene, tetracene, pyrene, triphenylene, phenanthrene, perylene, coronene, stilbene, phenylenevinylene, phenyleneethynylene, phenanthrene, fluorene, tetraphenylethene, thiophene, 2,2'-bithiophene, 2,2':5',2''-terthiophene, pyrrole, furan, silole, thiazole, thiadiazole, pyridine, pyrazine, triazine, quinoxaline, phenazine, or triphenylamine. In terms of exhibiting a slow response rate, substituted ethene compounds represented by the following formula (4) are preferred. [ka] (In formula (4), Ar 1 Ar 2 Ar 3 and Ar 4 (This expresses the same meaning as above.) Ar 1 Ar 2 Ar 3 and Ar 4 The aromatic hydrocarbon groups represented by , with 6 to 20 nuclear atoms, are not particularly limited, but examples include phenyl, biphenylyl, terphenylyl, naphthylphenyl, naphthyl, acenaphthyrenyl, phenanthryl, anthranyl, fluoranthenyl, pyrenyl, triphenylenyl, chrysenyl, fluorenyl, triptycenyl, and perilenyl groups, and the bond position is not limited. Furthermore, the substitution position is not limited. Ar 1 Ar 2 Ar 3 and Ar 4 The heterocyclic aromatic groups represented by 5 to 10 nuclear atoms are not particularly limited, but examples include pyrrolyl, thienyl, furyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, thiadiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, pyridyl, pyrimidyl, pyrazyl, and 1,3,5-triazinyl groups.

[0038] Ar 1 Ar 2 and Ar 3 It is preferable that the group is a phenyl group in that it allows the stimulus-responsive, slow-acting liquid light-emitting material to exhibit a delayed response rate. 4 The phenyl group is preferably a substituted phenyl group, more preferably a phenyl group substituted with a bromine atom or a formyl group, in terms of exhibiting a delayed response rate in the stimulus-responsive, slow-acting liquid light-emitting material, and the π-conjugated compound is particularly preferably a substituted ethene compound represented by the following formula (4-a) or formula (4-b). [ka] The π-conjugated compounds may be used individually or in any ratio. Therefore, as the stimulus-responsive, slow-acting liquid light-emitting material of this embodiment, a combination of any compound represented by formulas (A-1) to (A-10) and a compound represented by formula (4-a) or formula (4-b) is preferred.

[0039] The content of the π-conjugated compound in the imide compound (1) contained in the stimulus-responsive slow-acting liquid light-emitting material of this embodiment is not particularly limited as long as the π-conjugated compound is uniformly dissolved in the imide compound (1). However, in order to exhibit a slow response rate, it is preferably in the range of 0.01 to 10.0 mol%, and more preferably in the range of 0.1 to 2.0 mol%.

[0040] The stimulus-responsive, slow-acting liquid luminescent material of this embodiment can be produced by kneading an imide compound (1) and a π-conjugated compound. General kneading methods such as stirring, shaking, and ball milling can be used. Furthermore, during kneading, the mixture can be heated for 5 minutes or more at a temperature appropriately selected from 20°C to 250°C. However, for ease of preparation of the stimulus-responsive, slow-acting liquid luminescent material of this embodiment, it is preferable to heat the mixture for 5 minutes or more at a temperature appropriately selected from 100°C to 220°C.

[0041] In this embodiment, delayed emission refers to the characteristic of the stimulus-responsive, delayed-acting liquid light-emitting material in which the emission wavelength changes after a certain period of time has elapsed following the application of an external stimulus. The time required for the change in emission wavelength is preferably 5 seconds to 24 hours, and more preferably 10 seconds to 1 hour from the viewpoint of exhibiting a delayed response speed. Immediate emission refers to the characteristic in which the emission wavelength changes immediately after the application of an external stimulus.

[0042] The stimulus-responsive, slow-acting liquid light-emitting material of this embodiment is liquid at least at room temperature. In this specification, room temperature refers to a temperature range of 5°C to 40°C, and liquid refers to all substances in a liquid state, regardless of their viscosity. More specifically, since the decomposition temperature of the imide compound (1) in this disclosure is 300°C or higher, it can maintain its liquid state over a wide temperature range from room temperature to the decomposition temperature. Since the stimulus-responsive, slow-acting liquid light-emitting material of this embodiment can maintain its liquid state over the processing temperature range for inks, no change in properties occurs during processing. Furthermore, since the stimulus-responsive, slow-acting liquid light-emitting material of this embodiment can maintain its liquid state over the temperature range in which ordinary inks are used, high reliability can be ensured.

[0043] <Method for manufacturing slow-release luminescence ink> The slow-acting luminescent ink of this embodiment comprises the stimulus-responsive slow-acting liquid luminescent material and solvent of the present disclosure.

[0044] The content of the stimulus-responsive slow-acting liquid light-emitting material in the slow-acting light-emitting ink of this embodiment is preferably in the range of 30 to 70% by weight, based on the total amount of the light-emitting ink, in order to obtain good light-emitting properties.

[0045] The solvents contained in the slow-release ink of this embodiment include, but are not limited to, alcohols, acetone, hexane, dichloromethane, chloroform, ethyl acetate, toluene, acetonitrile, C2-C6 alcohols, C6-C10 isoparaffinic hydrocarbons, and C6-C14 alicyclic hydrocarbons. These may be used individually or in combination of two or more.

[0046] The C2-C6 alcohols may be used individually or in combination of two or more. Examples of C2-C6 alcohols include methyl alcohol, ethyl alcohol, propyl alcohol, isopropyl alcohol, butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, pentanol, 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, 3-methoxy-butanol, and the like.

[0047] The isoparaffinic hydrocarbons may be used as the main component of the solvent, either individually or in combination of two or more. Isoparaffinic hydrocarbons having 6 to 10 carbon atoms can be obtained by refining and / or synthesizing petroleum raw materials.

[0048] Examples of commercially available isoparaffinic hydrocarbons include IP Solvent 1016, IP Solvent 1620, IP Solvent 2028, and IP Solvent 2835 (all manufactured by Idemitsu Kosan Co., Ltd., trade names), the Isosol series (manufactured by ENEOS Corporation, trade name), Shellsol TG, Shellsol TK, and Shellsol TM (all manufactured by Showa Shell Sekiyu Co., Ltd., trade names), Isopar E, and Isopar G (manufactured by ExxonMobil Corporation, trade names).

[0049] The alicyclic hydrocarbons having 6 to 14 carbon atoms may be used as the main component of the solvent, either individually or in combination of two or more. Examples of alicyclic hydrocarbons having 6 to 14 carbon atoms include methylcyclohexane and ethylcyclohexane.

[0050] The slow-acting luminescent ink of this embodiment is obtained by mixing the stimulus-responsive slow-acting liquid luminescent material of this disclosure with a solvent, preferably by heating at a temperature appropriately selected from 20°C to 60°C for 5 minutes or more. The mixing method can be a general method such as stirring, shaking, or ball milling. <Method for generating delayed-effect luminescence> The method for generating delayed luminescence in this embodiment includes the steps of (a) applying the stimulus-responsive delayed liquid luminescent material or delayed luminescent ink of this embodiment to a substrate, (b) applying an external stimulus to the substrate obtained in step (a) (hereinafter sometimes referred to as "substrate a"), and (c) irradiating the substrate obtained in step (b) (hereinafter sometimes referred to as "substrate b") with UV light. Examples of substrates used in step (a) include glass substrates, paper substrates, and plastic substrates, with glass substrates or paper substrates being preferred in terms of generating delayed luminescence. In step (a), there are no particular restrictions on the method of applying the stimulus-responsive slow-acting liquid light-emitting material or slow-acting light-emitting ink of this embodiment to the substrate. Methods well known to those skilled in the art, such as spin coating, dip coating, bar coating, brush coating, roller coating, and spraying, can be used. Brush coating or spin coating is preferred because it is easy to apply. In step (b), examples of external stimuli applied to the substrate a include compression, friction, shearing, bending, stretching, scratching, twisting, vibration, heat, light, cold air, and humidification. Compression, friction, shearing, bending, stretching, scratching, and twisting are preferred because they easily exhibit a delayed reaction rate in the change of emission wavelength due to the external stimuli, with friction, shearing, and scratching being more preferred, and scratching being particularly preferred. Two or more of these external stimuli may be applied in combination. In step (b), the temperature at which an external stimulus is applied to the substrate a can be appropriately selected from 0°C to 100°C, but 10°C to 50°C is preferred because it is easier to exhibit a slow reaction rate. In step (b), an external stimulus may be applied to the substrate a, but it is preferable to apply it to the surface in order to obtain a sensitive change in the emission wavelength. The surface of the substrate a to which the stimulus-responsive slow-acting liquid light-emitting material or slow-acting light-emitting ink of this embodiment is applied is referred to as the surface.

[0051] In step (c), when substrate b is irradiated with UV light, a change in emission wavelength is obtained compared to the emission when substrate a is irradiated with UV light. As delayed emission, it is preferable that the emission wavelength changes in the range of 5 seconds to 24 hours after the application of an external stimulus, and more preferably in the range of 10 seconds to 1 hour. In step (c), the change in emission wavelength due to the application of an external stimulus may be in the range of 10 to 200 nm, and may change to a shorter or longer wavelength compared to before the application of the external stimulus. However, it is preferable that the change is in the range of 50 to 80 nm and towards the shorter wavelength, as this makes the change in emission wavelength easier to detect.

[0052] There are no restrictions on the wavelength of the UV light used in step (c), but 250 to 500 nm is preferred, and 300 to 450 nm is more preferred, as it makes it easier to observe changes in the emission wavelength. There are no particular restrictions on the UV light source, but examples include white fluorescent lamps, LEDs (white, blue, green, red, etc.), halogen lamps, incandescent bulbs, mercury lamps, etc.

[0053] The stimulus-responsive, slow-acting liquid light-emitting material or slow-acting light-emitting ink of this embodiment can be used for any suitable purpose. For example, it can be used as fluorescent paint for inkjet printing, fluorescent ink for anti-counterfeiting, fluorescent ink for writing instruments, fluorescent dye for clothing, medical dyes, light-emitting materials or wavelength conversion materials for electroluminescent devices, etc.

[0054] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In addition, 1 For 1H-NMR measurements, a Bruker ASCEND HD (400MHz; manufactured by Bruker) was used. 1 ¹H-NMR was performed using deuterated chloroform (CDCl3) as the measurement solvent and tetramethylsilane (TMS) as the internal standard.

[0055] [Synthesis Reference Example 1: Imide Compound (A-3)] [ka] Under an argon atmosphere, (2S,2'S)-2,2'-(1,3,5,7-tetraoxo-5,7-dihydropyrrolo[3,4-f]isoindole-2,6(1H,3H)-diyl)bis(3-methylbutyrate) (1.04 g, 2.5 mmol), 2-hexyl-1-decanol (1.33 g, 5.5 mmol), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (1.05 g, 5.5 mmol), and 4-dimethylaminopyridine (0.92 g, 7.5 mmol) were suspended in 50 mL of dichloromethane. After stirring this mixture at room temperature for 24 hours, water was added to the reaction solution and extracted with chloroform. Sodium sulfate was added to the combined organic layer to dehydrate it, and the resulting organic layer was collected by filtration and the low-boiling components were removed by distillation. The resulting crude material was purified using silica gel column chromatography (hexane / ethyl acetate), and then vacuum-dried to obtain the target tetracarboxylic acid diimide compound (A-3) as a colorless, viscous liquid (1.12 g, 56.0%). 1 H-NMR(400MHz,CDCl3)δ(ppm)8.31(s,2H),4.68(d,8.3Hz,2H),4.07(d,5.6Hz,5H),2.79(s,2H),1.20(m,66H),0.88(m,22H).

[0056] <Examples 1-3: Stimulus-responsive, delayed-acting liquid light-emitting materials (A-3-a)-(A-3-c)> The imide compound (A-3) and the π-conjugated compound were mixed in the proportions (mass) shown in Table 1 and heated at each temperature for 5 minutes to obtain stimulus-responsive, slow-acting liquid light-emitting materials (A-3-a) to (A-3-c). [Table 1] Table 1: Formulation amounts and heating temperatures (°C) for Examples 1-3

[0057] The appearance of (A-3-a) to (A-3-c) prepared in Examples 1 to 3 at 25°C was captured by irradiating them with UV light and photographing them using a high-resolution digital color camera (Nikon D750, Nikon Corporation). The results are shown in Figure 1 and will be described later.

[0058] Using a fluorescence spectrophotometer (JASCOFP-8500, manufactured by JASCO Corporation; excitation bandwidth: 5 nm, fluorescence bandwidth: 5 nm, response: 10 msec, sensitivity: Manual, scanning mode: continuous scan, scanning speed: 100 nm / min), the maximum wavelength was determined from the emission spectrum (A-3-a) and this was used as the emission wavelength. The results are shown in Figure 2 and will be described later.

[0059] <Examples 4-7: Evaluation of stimulus-responsive, delayed-acting liquid light-emitting materials (A-3-a)-(A-3-c)> Examples 4-6 After applying (A-3-a) to (A-3-c) onto a glass substrate with a spatula, the surface was scratched with a spatula at 25°C to apply an external stimulus. Subsequently, UV light (365 nm, Funakoshi Co., Ltd., UVGL-15) was irradiated, and the color change was visually observed while measuring the time. The time measurement started from the time after the application of the external stimulus, and the time required for the change in emission wavelength, i.e., the change in emission color, was defined as the time required for the change in emission wavelength. The results are shown in Figures 3 to 5 and will be described later. Furthermore, the appearance of delayed emission in Examples 4 to 67, in which an external stimulus was applied, was compared with A-3-a), (4-a), and (4-b) of Reference Examples 1 to 3, in which no external stimulus was applied, to confirm the change in emission wavelength, i.e., the change in emission wavelength. The results are shown in Figures 3 and 4 and will be described later.

[0060] Example 7 (A-3-a) was impregnated into filter paper (Kiriyama Manufacturing Co., Ltd., Kiriyama Funnel Filter Paper No. 5C) using a spatula, and then an external scratching stimulus was applied using a spatula at 25°C. After that, UV light (365 nm) was irradiated, and the change in emission wavelength was visually observed while measuring the time. The time measurement was taken from the start of the application of the external stimulus, and the time required for the change in emission wavelength, i.e., the change in emission color, was visually observed was defined as the time required for the change in emission wavelength. The results are shown in Figure 5 and will be described later.

[0061] From Figure 1, it was confirmed that (A-3-a) to (A-3-c) exhibited luminescence at room temperature. From the results in Figures 1 to 6, it was confirmed that (A-3-a) to (A-3-c) exhibited the fluorescence wavelengths and emission colors shown in Table 2 below. [Table 2] Table 2: Changes in emission wavelength and emission color before and after application of external stimuli in Examples 4-7, and the time required for the change in emission wavelength.

[0062] [Example 4] When (A-3-a) was applied to a glass substrate, the surface was scratched, and after applying an external stimulus, the emission wavelength changed from 550 nm (orange emission) to 475 nm (light blue emission). Since the time required for the change in emission wavelength was 15 seconds, it was revealed that it is a stimulus-responsive, slow-acting liquid light-emitting material with delayed stimulus response.

[0063] [Example 5] When (A-3-b) was applied to a glass substrate, the surface was scratched and an external stimulus was applied. The emission wavelength changed from 550 nm (orange emission) to 475 nm (light blue emission), and the time required for the change in emission wavelength was 532 seconds. This revealed that it is a stimulus-responsive, slow-acting liquid light-emitting material with delayed stimulus response.

[0064] [Example 6] When (A-3-c) was applied to a glass substrate, its surface was scratched, and after applying an external stimulus, the emission wavelength changed from 539 nm (yellow emission) to 479 and 520 nm (yellow-green emission). The time required for the change in emission wavelength was 14 hours, which revealed that it is a stimulus-responsive, slow-acting liquid light-emitting material with delayed stimulus response.

[0065] [Reference example 1] When (A-3-a) was applied to a glass substrate, no change in emission wavelength (550 nm, orange emission) was observed after 14 hours without the application of external stimuli. This revealed that, in order to exhibit a delayed stimulus response, the emission wavelength must change in response to external stimuli.

[0066] [Example 7] When (A-3-a) was applied to a paper substrate, the emission color changed from orange to light blue after an external scratching stimulus was applied, and the time required for the change in emission wavelength was 3475 seconds. This revealed that it is a stimulus-responsive, slow-acting liquid light-emitting material with delayed stimulus responsiveness. In other words, it was confirmed that a stimulus-responsive, slow-acting liquid light-emitting material with delayed stimulus responsiveness can be realized using (A-3-a) to (A-3-c) of this disclosure.

Claims

1. A stimulus-responsive, slow-acting liquid light-emitting material containing an imide compound represented by formula (1) and a π-conjugated compound. 【Chemistry 1】 [In formula (1), Ring A represents an aromatic hydrocarbon ring (which may be a monoring, a fused ring, or a linked ring containing multiple rings) having 6 to 20 nuclei, and which may be substituted. X １ Each of these independently represents an alkylene group having 1 to 6 carbon atoms, which may be substituted with one or more groups selected from the group consisting of a sulfanyl group, an alkylthio group, a hydroxyl group, a carboxyl group, an amino group, an amide group, a guanidino group, an imidazolyl group, a phenyl group, a hydroxyphenyl group, and an indolyl group. X ２ represents an oxygen atom or a nitrogen atom; X ２ If it is an oxygen atom, then m is 1. X ２ If it is a nitrogen atom, then m represents either 1 or 2. R １ This is a linear or branched alkyl group having 8 to 24 carbon atoms, or one or more -CH groups. ２ -, -O-, -S-, or -(SiMe ２ ) - may be substituted, but it represents a linear alkyl group having 8 to 18 carbon atoms where there are no consecutive -O- or -S- atoms.

2. The stimulus-responsive, slow-acting liquid light-emitting material according to claim 1, wherein in formula (1), the ring A is the following formula (2) or formula (3). 【Chemistry 2】 【Transformation 3】 In formula (2) and formula (3), R ２ and R ３ each independently represents a hydrogen atom, a chlorine atom, a bromine atom, an iodine atom, an alkyl group having 1 to 6 carbon atoms, an aromatic hydrocarbon group having 6 to 12 nuclear atoms, or a heteroaromatic group having 3 to 6 nuclear atoms. * indicates the joining position.

3. R ２ and R ３ The stimulus-responsive, slow-acting liquid light-emitting material according to claim 2, wherein each atom is independently a hydrogen atom or a bromine atom.

4. The stimulus-responsive, slow-acting liquid light-emitting material according to any one of claims 1 to 3, wherein the π-conjugated compound is a substituted ethene compound represented by the following formula (4). 【Chemistry 4】 [In formula (4), Ar １ Ar ２ Ar ３ and Ar ４ Each of these independently represents an aromatic hydrocarbon group with 6 to 20 optionally substituted nuclear atoms or a heterocyclic aromatic group with 5 to 20 optionally substituted nuclear atoms.

5. Ar ４ The stimulus-responsive, slow-acting liquid light-emitting material according to claim 4, wherein is a phenyl group substituted with a bromine atom or a formyl group.

6. The stimulus-responsive, slow-acting liquid light-emitting material according to claim 1, wherein the content of the imide compound represented by formula (1) is in the range of 0.01 to 10.0 mol%.

7. The stimulus-responsive, slow-acting liquid light-emitting material according to claim 1, wherein the emission wavelength changes in response to an external stimulus.

8. The stimulus-responsive, slow-acting liquid light-emitting material according to claim 1, wherein the emission wavelength changes in response to one or more external stimuli selected from the group consisting of compression, friction, shearing, bending, stretching, scratching, and twisting.

9. The stimulus-responsive, slow-acting liquid light-emitting material according to claim 7, wherein the change in emission wavelength upon application of an external stimulus is 10 to 200 nm.

10. A stimulus-responsive, delayed-acting liquid light-emitting material according to claim 1 or claim 7, wherein the emission wavelength changes 5 seconds or more after the application of an external stimulus.

11. A slow-acting light-emitting ink comprising the stimulus-responsive slow-acting liquid light-emitting material and solvent described in claim 1.

12. The slow-acting luminescent ink according to claim 11, wherein the solvent is at least one organic solvent selected from the group consisting of alcohols having 2 to 6 carbon atoms, isoparaffinic hydrocarbons having 6 to 10 carbon atoms, and alicyclic hydrocarbons having 6 to 14 carbon atoms, and the content of the stimulus-responsive slow-acting liquid luminescent material is in the range of 30 to 70% by weight.

13. A method for producing delayed luminescence, comprising the following steps (a) to (c). (a) A step of applying the stimulus-responsive slow-acting liquid light-emitting material described in claim 1 or the slow-acting light-emitting ink described in claim 11 to a substrate. (b) A step of applying an external stimulus to the substrate obtained in step (a). (c) A step of irradiating the substrate obtained in step (b) with UV light.

14. A fluorescent paint for inkjet printing, a fluorescent ink for anti-counterfeiting, a fluorescent ink for writing instruments, a fluorescent dye for clothing, a pigment for medical devices, a light-emitting material for electroluminescent devices, or a wavelength conversion material, containing the stimulus-responsive slow-acting liquid light-emitting material described in claim 1 or the slow-acting light-emitting ink described in claim 10.

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