Polarizing film, polarized luminescent film, polarized luminescent plate and display device containing water-soluble naphthalimide compound or its salt

Abstract

To provide a polarized light emitting film which offers high transmittance in the visible light region and high durability in harsh environments, and to provide a polarized light emitting plate and a display device.SOLUTION: Provided herein is a polarized light emitting film containing a water-soluble naphthalimide compound represented by formula (1) below or a salt thereof. (In formula (1), A represents a naphthalimide skeleton that may have a substituent, X represents a sulfo group or carboxy group, and n represents an integer of 1 to 3.)SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a novel polarizing film and polarized luminescent film containing a water-soluble naphthalimide compound or a salt thereof, and a dye-based polarized luminescent plate and display device equipped with the same. [Background technology]

[0002] Polarizing plates, which have the ability to transmit and block light, are fundamental components of displays such as liquid crystal displays (LCDs), along with liquid crystals, which have the ability to switch light. The application of LCDs has expanded from small devices such as calculators and clocks in the early days to include laptops, word processors, LCD projectors, LCD televisions, car navigation systems, and indoor and outdoor measuring instruments. Polarizing plates can also be applied to lenses with polarizing properties, such as sunglasses with improved visibility and, more recently, polarized glasses compatible with 3D televisions. As the range of uses for polarizing plates has expanded, their operating conditions have also become more diverse, ranging from low to high temperatures, low to high humidity, and low to high light levels. This has created a demand for polarizing plates with high polarization performance and durability.

[0003] Generally, polarizing films constituting polarizing plates are produced by stretching and orienting a film of polyvinyl alcohol or its derivatives containing iodine or a dichroic dye, or by dehydrochlorinating a polyvinyl chloride film or dehydrating a polyvinyl alcohol film to produce and orient a polyene. Polarizing plates constructed from such conventional polarizing films have low transmittance in the visible light range because they use a dichroic dye that absorbs light in the visible light range. For example, the transmittance in the visible light range of commercially available general polarizing plates is 35 to 45%. Using a polarizing plate with low transmittance in the visible light range in a display or the like reduces the transmittance of the entire display, so methods for obtaining polarized light without using conventional polarizing plates have been researched. Patent Documents 1 to 3 disclose techniques for emitting polarized light. However, these technologies use rare and special metals, such as lanthanide metals such as europium (Eu) and terbium (Tb), as materials that emit polarized light (hereinafter referred to as "polarized luminescence"). These metals are extremely difficult to manufacture and therefore unsuitable for mass production. Furthermore, the polarized light emitted is weak, making them difficult to apply to displays. Therefore, there is a need to develop new materials that exhibit polarized luminescence without using conventional polarizers, have high transmittance in the visible light range, and can be applied to liquid crystal displays and other devices that require durability in harsh environments. Meanwhile, naphthalimide compounds are known to emit fluorescence, and for example, Patent Document 4 describes their use as fluorescent brightening agents, and Patent Document 5 describes their use as water-soluble fluorescent inks. Patent Document 6 describes the use of naphthalimide compounds as oil-soluble dyes to be dissolved in liquid crystal for use in guest-host liquid crystal display elements. Patent Documents 7, 8, and 9 also describe the use of naphthalimide compounds as oil-soluble fluorescent dyes to be dissolved in liquid crystal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-224854 [Patent Document 2] Patent No. 5849255 [Patent Document 3] Patent No. 5713360 [Patent Document 4] Special Publication No. 47-047978 [Patent Document 5] International Publication No. 2004 / 096928 [Patent Document 6] Japanese Patent Application Publication No. 58-057488 [Patent Document 7] Japanese Patent Application Laid-Open No. 2014-527092 [Patent Document 8] Chinese Patent Application Publication No. 101942210 [Patent Document 9] Chinese Patent Application Publication No. 109180654 Summary of the Invention [Problem to be solved by the invention]

[0005] However, these documents all relate to oil-soluble dichroic naphthalimide compounds that exhibit dichroism when a voltage is applied to a liquid crystal to drive it, but do not disclose water-soluble naphthalimide compounds. Furthermore, there have been no examples of applying naphthalimide compounds as water-soluble dichroic dyes to polarized luminescent films and polarized luminescent plates. An object of the present invention is to provide a polarized light-emitting film, a polarized light-emitting plate, and a display device that have high transmittance in the visible light region and high durability under harsh environments. [Means for solving the problem]

[0006] The present inventors have discovered that a specific water-soluble naphthalimide compound or a salt thereof exhibits polarized luminescence in the visible light region when irradiated with light in the ultraviolet to visible region, for example, light of 300 to 600 nm. They have also discovered that a polarized luminescent film and a polarized luminescent plate containing such a compound or a salt thereof have polarizing properties in the visible light region, high transmittance in the visible light region, and excellent durability even under harsh environments. The present invention was completed based on these findings.

[0007] That is, the present invention relates to the following [1] to [7]. [1] A polarizing film containing a water-soluble naphthalimide compound represented by the following formula (1) or a salt thereof:

[0008] [ka]

[0009] (In formula (1), A represents a naphthalimide skeleton which may have a substituent, X represents a sulfo group or a carboxy group, and n represents an integer of 1 to 3.) [2] The polarizing film according to item [1] above, wherein the water-soluble naphthalimide compound or a salt thereof is represented by the following formula (2):

[0010] [ka]

[0011] (In formula (2), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent; Q represents a hydrogen atom, a halogen atom, a sulfur atom which may have a substituent, an oxygen atom which may have a substituent, or a nitrogen atom which may have a substituent; and n represents an integer of 1 to 3. [3] The polarizing film according to item [1] above, wherein the water-soluble naphthalimide compound or a salt thereof is represented by the following formula (3):

[0012] [ka]

[0013] (In formula (3), R 1 represents a hydrocarbon group having 1 to 12 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 12 carbon atoms. [4] The polarizing film according to any one of the above items [1] to [3], further comprising at least one organic dye or fluorescent dye other than the water-soluble naphthalimide compound or its salt. [5] The polarizing film according to any one of the preceding items [1] to [4], wherein the water-soluble naphthalimide compound or the salt thereof, and optionally the organic dye or the fluorescent dye, are contained in a substrate made of a polyvinyl alcohol resin or a derivative thereof. [6] A polarized light-emitting film, wherein the polarizing film according to any one of the above items [1] to [5] exhibits polarized light-emitting properties. [7] A polarized light-emitting plate comprising the polarized light-emitting film according to the above item [6] and a transparent protective layer provided on at least one surface thereof. [8] A display device comprising the polarized light-emitting film according to the preceding item [6] or the polarized light-emitting plate according to the preceding item [7]. [Effects of the Invention]

[0014] The polarized luminescent film and polarized luminescent plate containing the water-soluble naphthalimide compound having a specific structure or a salt thereof of the present invention have high transmittance in the visible light region and high durability under harsh environments, and are therefore useful for display devices. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, embodiments of the present invention will be described in detail, but the present invention is not limited to the embodiments shown below. In the following, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Unless otherwise specified, the compounds represented by each formula and the compounds shown in each compound example are shown in the form of free acid (not forming a salt), but their salts are also included within the technical scope of the present invention. Furthermore, unless otherwise specified, for convenience, the term "water-soluble naphthalimide compound or a salt thereof" may be abbreviated simply as "water-soluble naphthalimide compound." When the carbon number is, for example, 1 to 4, it may be abbreviated as C1-4.

[0016] [Naphthalimide compounds] The water-soluble naphthalimide compound according to an embodiment of the present invention is represented by the following formula (1).

[0017] [ka]

[0018] (In formula (1), A represents a naphthalimide skeleton which may have a substituent, X represents a sulfo group or a carboxy group, and n represents an integer of 1 to 3.)

[0019] In the above formula (1), A represents a naphthalimide skeleton which may have a substituent. Examples of the substituent which A may have include a heterocyclic amino group, a fused heterocyclic amino group, an alkoxy group, an aryloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylcarbonyloxy group, an arylcarbonyloxy group, an alkylcarbonyl group, an arylcarbonyl group, an alkylcarbamoyl group, an arylcarbamoyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, an alkylsulfonylamino group, an arylsulfonylamino group, an alkylsulfamoyl group, an arylsulfamoyl group, an alkylsulfonyl group, an arylsulfonyl group, an alkylthio group, an arylthio group, an alkylureido group, an arylureido group, an alkoxycarbonylamino group, an aryloxycarbonylamino group, an alkylamino group, an arylamino group, a hydroxy group (—OH), a cyano group (—CN), a nitro group (—NO), a mercapto group (—SH), and a halogen atom. Preferred are an alkoxy group, an aryloxy group, an alkylcarbonylamino group, an arylcarbonylamino group, an alkylcarbamoyl group, an arylcarbamoyl group, an alkylsulfonylamino group, an arylsulfonylamino group, an alkylsulfamoyl group, an arylsulfamoyl group, an alkylthio group, an arylthio group, an alkylamino group, an arylamino group, a nitro group (—NO2), and a halogen atom.

[0020] The heterocyclic amino group includes a 5- or 6-membered heterocyclic amino group containing 1 to 3 heteroatoms selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom. Specific examples of such heterocyclic amino groups include: 5-membered heteroalicyclic amino groups such as pyrrolidinylamino, tetrahydrofurylamino, tetrahydrothiophen-2-ylamino, and tetrahydrothiophen-3-ylamino; 6-membered heteroalicyclic amino groups such as piperidinylamino, piperazinylamino, dioxan-2-ylamino, morpholinylamino, and thiomorpholinylamino; 5-membered aromatic heterocyclic amino groups such as pyrroleamino, pyrazoleamino, imidazoleamino, triazoleamino, furylamino, thiophen-2-ylamino, thiophen-3-ylamino, oxazoleamino, and thiazoleamino; or Examples thereof include 6-membered aromatic heterocyclic amino groups such as pyridylamino, pyrazylamino, pyridazinylamino, and triazinylamino. The heterocyclic group preferably has an aromatic heterocyclic moiety, and the heteroatom constituting the heterocyclic ring is preferably selected from the group consisting of a nitrogen atom and a sulfur atom.

[0021] The fused heterocyclic amino group includes a fused 5- or 6-membered heterocyclic amino group in which one benzene ring is fused to a 5- or 6-membered heterocyclic group containing 1 to 3 heteroatoms selected from the group consisting of a nitrogen atom, an oxygen atom, and a sulfur atom. Specific examples of such a fused heterocyclic amino group include, for example, fused heteroalicyclic amino groups in which the heterocyclic moiety is a five-membered alicyclic ring, such as phthalanylamino; fused heteroalicyclic amino groups in which the heterocyclic moiety is a six-membered alicyclic ring, such as benzopyranylamino; a fused aromatic heterocyclic amino group in which the heterocyclic moiety is an aromatic 5-membered ring, such as benzpyrroleamino, benzpyrazoleamino, benzimidazoleamino, benzotriazoleamino, benzofuranylamino, benzothiophen-2-ylamino, benzothiophen-3-ylamino, benzoxazoleamino, or benzothiazoleamino; or Examples thereof include fused aromatic heterocyclic amino groups in which the heterocyclic moiety is an aromatic 6-membered ring, such as quinolinylamino, cinnolinylamino, phthalazinylamino, quinazolinylamino, and quinoxalinylamino. The heterocyclic group preferably has an aromatic heterocyclic moiety, and the heteroatom constituting the heterocyclic ring is preferably selected from the group consisting of a nitrogen atom and a sulfur atom.

[0022] The alkoxy group may be a linear, branched, or cyclic alkoxy group, preferably a C1-10 alkoxy group. Specific examples of the C1-10 alkoxy group include, for example, Straight-chain C1-10 alkoxy groups such as methoxy, ethoxy, n-propoxy, n-butoxy, n-pentoxy, n-hexyloxy, n-heptoxy, n-octyloxy, n-nonyloxy, and n-decyloxy; branched C3-10 alkoxy groups such as isopropoxy, isobutoxy, sec-butoxy, t-butoxy, isoamyloxy, t-amyloxy, isohexyloxy, t-hexyloxy, isoheptoxy, t-heptoxy, isooctyloxy, t-octyloxy, 2-ethylhexyloxy, isononyloxy, and isodecyloxy; or Examples include cyclic C3-7 alkoxy groups such as cyclopropoxy, cyclobutoxy, cyclopentoxy, cyclohexyloxy, cycloheptoxy, etc. Among these, linear or branched alkoxy groups are preferred.

[0023] The aryloxy group is preferably a C6-12 aryloxy group, and specific examples include phenoxy, naphthyloxy, biphenyloxy, etc.

[0024] The alkylcarbonylamino group may be a linear, branched, or cyclic alkylcarbonylamino group, preferably a C1-10 alkylcarbonylamino group. Specific examples of the C1-10 alkylcarbonylamino group include, for example, Straight-chain C1-10 alkylcarbonylamino groups such as methylcarbonylamino, ethylcarbonylamino, n-propylcarbonylamino, n-butylcarbonylamino, n-pentylcarbonylamino, n-hexylcarbonylamino, n-heptylcarbonylamino, n-octylcarbonylamino, n-nonylcarbonylamino, and n-decylcarbonylamino; branched-chain C3-10 alkylcarbonylamino groups such as isopropylcarbonylamino, isobutylcarbonylamino, sec-butylcarbonylamino, t-butylcarbonylamino, isoamylcarbonylamino, t-amylcarbonylamino, isohexylcarbonylamino, t-hexylcarbonylamino, isoheptylcarbonylamino, t-heptylcarbonylamino, isooctylcarbonylamino, t-octylcarbonylamino, 2-ethylhexylcarbonylamino, isononylcarbonylamino, and isodecylcarbonylamino; or Examples include cyclic C alkylcarbonylamino groups such as cyclopropylcarbonylamino, cyclobutylcarbonylamino, cyclopentylcarbonylamino, cyclohexylcarbonylamino, cycloheptylcarbonylamino, etc. Among these, linear or branched alkylcarbonylamino groups are preferred, and linear alkylcarbonylamino groups are more preferred.

[0025] The arylcarbonylamino group is preferably a C6-12 arylcarbonylamino group, and specific examples include phenylcarbonylamino, naphthylcarbonylamino, biphenylcarbonylamino, and the like.

[0026] The alkylcarbonyloxy group may be a linear, branched, or cyclic alkylcarbonyloxy group, preferably a C1-10 alkylcarbonyloxy group. Specific examples of the C1-10 alkylcarbonyloxy group include, for example, Straight-chain C1-10 alkylcarbonyloxy groups such as methylcarbonyloxy, ethylcarbonyloxy, n-propylcarbonyloxy, n-butylcarbonyloxy, n-pentylcarbonyloxy, n-hexylcarbonyloxy, n-heptylcarbonyloxy, n-octylcarbonyloxy, n-nonylcarbonyloxy, and n-decylcarbonyloxy; branched-chain C3-10 alkylcarbonyloxy groups such as isopropylcarbonyloxy, isobutylcarbonyloxy, sec-butylcarbonyloxy, t-butylcarbonyloxy, isoamylcarbonyloxy, t-amylcarbonyloxy, isohexylcarbonyloxy, t-hexylcarbonyloxy, isoheptylcarbonyloxy, t-heptylcarbonyloxy, isooctylcarbonyloxy, t-octylcarbonyloxy, 2-ethylhexylcarbonyloxy, isononylcarbonyloxy, and isodecylcarbonyloxy; or Examples include cyclic C alkylcarbonyloxy groups such as cyclopropylcarbonyloxy, cyclobutylcarbonyloxy, cyclopentylcarbonyloxy, cyclohexylcarbonyloxy, cycloheptylcarbonyloxy, etc. Among these, linear or branched alkylcarbonyloxy groups are preferred, and linear alkylcarbonyloxy groups are more preferred.

[0027] The arylcarbonyloxy group is preferably a C6-12 arylcarbonyloxy group, and specific examples include phenylcarbonyloxy, naphthylcarbonyloxy, biphenylcarbonyloxy, and the like.

[0028] The alkylcarbonyl group may be a straight-chain, branched-chain, or cyclic alkylcarbonyl group, preferably a C1-10 alkylcarbonyl group. Specific examples of the C1-10 alkylcarbonyl group include, for example, Straight-chain C1-10 alkylcarbonyl groups such as methylcarbonyl, ethylcarbonyl, n-propylcarbonyl, n-butylcarbonyl, n-pentylcarbonyl, n-hexylcarbonyl, n-heptylcarbonyl, n-octylcarbonyl, n-nonylcarbonyl, and n-decylcarbonyl; branched C3-10 alkylcarbonyl groups such as isopropylcarbonyl, isobutylcarbonyl, sec-butylcarbonyl, t-butylcarbonyl, isoamylcarbonyl, t-amylcarbonyl, isohexylcarbonyl, t-hexylcarbonyl, isoheptylcarbonyl, t-heptylcarbonyl, isooctylcarbonyl, t-octylcarbonyl, 2-ethylhexylcarbonyl, isononylcarbonyl, and isodecylcarbonyl; or Examples include cyclic C alkylcarbonyl groups such as cyclopropylcarbonyl, cyclobutylcarbonyl, cyclopentylcarbonyl, cyclohexylcarbonyl, cycloheptylcarbonyl, etc. Among these, linear or branched alkylcarbonyl groups are preferred, and linear alkylcarbonyl groups are more preferred.

[0029] The arylcarbonyl group is preferably a C6-12 arylcarbonyl group, and specific examples include phenylcarbonyl (benzoyl), naphthylcarbonyl, biphenylcarbonyl, and the like.

[0030] The alkylcarbamoyl group may be a linear, branched, or cyclic monoalkylcarbamoyl group or dialkylcarbamoyl group. The monoalkylcarbamoyl group is preferably a mono-C alkylcarbamoyl group, and specific examples include: straight-chain mono-C1-10 alkylcarbamoyl groups such as methylcarbamoyl, ethylcarbamoyl, n-propylcarbamoyl, n-butylcarbamoyl, n-pentylcarbamoyl, n-hexylcarbamoyl, n-heptylcarbamoyl, n-octylcarbamoyl, n-nonylcarbamoyl, and n-decylcarbamoyl; branched mono-C alkylcarbamoyl groups such as isopropylcarbamoyl, isobutylcarbamoyl, sec-butylcarbamoyl, t-butylcarbamoyl, isoamylcarbamoyl, t-amylcarbamoyl, isohexylcarbamoyl, t-hexylcarbamoyl, isoheptylcarbamoyl, t-heptylcarbamoyl, isooctylcarbamoyl, t-octylcarbamoyl, 2-ethylhexylcarbamoyl, isononylcarbamoyl, and isodecylcarbamoyl; or Examples of such cyclic mono-C alkylcarbamoyl groups include cyclopropylcarbamoyl, cyclobutylcarbamoyl, cyclopentylcarbamoyl, cyclohexylcarbamoyl, cycloheptylcarbamoyl, etc. Among these, linear or branched monoalkylcarbamoyl groups are preferred, and linear monoalkylcarbamoyl groups are more preferred.

[0031] The dialkylcarbamoyl group is preferably a diC alkylcarbamoyl group, and specific examples include, straight-chain di-C1-10 alkylcarbamoyl groups such as dimethylcarbamoyl, diethylcarbamoyl, di-n-propylcarbamoyl, di-n-butylcarbamoyl, di-n-pentylcarbamoyl, di-n-hexylcarbamoyl, di-n-heptylcarbamoyl, di-n-octylcarbamoyl, di-n-nonylcarbamoyl, and di-n-decylcarbamoyl; a branched di-C alkylcarbamoyl group having two branched chains, such as diisopropylcarbamoyl, diisobutylcarbamoyl, di-sec-butylcarbamoyl, di-t-butylcarbamoyl, diisoamylcarbamoyl, di-t-amylcarbamoyl, diisohexylcarbamoyl, di-t-hexylcarbamoyl, diisoheptylcarbamoyl, di-t-heptylcarbamoyl, diisooctylcarbamoyl, di-t-octylcarbamoyl, di-(2-ethylhexyl)carbamoyl, diisononylcarbamoyl, or diisodecylcarbamoyl; or Examples of such cyclic di-C alkylcarbamoyl groups include dicyclopropylcarbamoyl, dicyclobutylcarbamoyl, dicyclopentylcarbamoyl, dicyclohexylcarbamoyl, dicycloheptylcarbamoyl, etc. Among these, linear or branched dialkylcarbamoyl groups are preferred, and linear dialkylcarbamoyl groups are more preferred.

[0032] The arylcarbamoyl group may be a monoarylcarbamoyl group or a diarylcarbamoyl group. The monoarylcarbamoyl group is preferably a mono-C6-12 arylcarbamoyl group, and specific examples include phenylcarbamoyl, naphthylcarbamoyl, and biphenylcarbamoyl.

[0033] The diarylcarbamoyl group is preferably a diC6-12 arylcarbamoyl group, and specific examples include diphenylcarbamoyl, dinaphthylcarbamoyl, di(biphenyl)carbamoyl, and the like.

[0034] The alkoxycarbonyl group may be a linear, branched, or cyclic alkoxycarbonyl group, preferably a C1-10 alkoxycarbonyl group. Specific examples of the C1-10 alkoxycarbonyl group include: For example, straight-chain C1-C alkoxycarbonyls such as methoxycarbonyl, ethoxycarbonyl, n-propoxycarbonyl, n-butoxycarbonyl, n-pentoxycarbonyl, n-hexyloxycarbonyl, n-heptoxycarbonyl, n-octyloxycarbonyl, n-nonyloxycarbonyl, and n-decyloxycarbonyl. 10 alkoxycarbonyl groups; branched C3-10 alkoxycarbonyl groups such as isopropoxycarbonyl, isobutoxycarbonyl, sec-butoxycarbonyl, t-butoxycarbonyl, isoamyloxycarbonyl, t-amyloxycarbonyl, isohexyloxycarbonyl, t-hexyloxycarbonyl, isoheptoxycarbonyl, t-heptoxycarbonyl, isooctyloxycarbonyl, t-octyloxycarbonyl, 2-ethylhexyloxycarbonyl, isononyloxycarbonyl, and isodecyloxycarbonyl; or Examples include cyclic C alkoxycarbonyl groups such as cyclopropoxycarbonyl, cyclobutoxycarbonyl, cyclopentoxycarbonyl, cyclohexyloxycarbonyl, cycloheptoxycarbonyl, etc. Among these, linear or branched alkoxycarbonyl groups are preferred, and linear alkoxycarbonyl groups are more preferred.

[0035] The aryloxycarbonyl group is preferably a C6-12 aryloxycarbonyl group, and specific examples include phenoxycarbonyl, naphthyloxycarbonyl, biphenyloxycarbonyl, and the like.

[0036] The alkylsulfonylamino group may be a linear, branched, or cyclic alkylsulfonylamino group, preferably a C1-10 alkylsulfonylamino group. Specific examples of the C1-10 alkylsulfonylamino group include, for example, Straight-chain C1-10 alkylsulfonylamino groups such as methylsulfonylamino, ethylsulfonylamino, n-propylsulfonylamino, n-butylsulfonylamino, n-pentylsulfonylamino, n-hexylsulfonylamino, n-heptylsulfonylamino, n-octylsulfonylamino, n-nonylsulfonylamino, and n-decylsulfonylamino; branched-chain C3-10 alkylsulfonylamino groups such as isopropylsulfonylamino, isobutylsulfonylamino, sec-butylsulfonylamino, t-butylsulfonylamino, isoamylsulfonylamino, t-amylsulfonylamino, isohexylsulfonylamino, t-hexylsulfonylamino, isoheptylsulfonylamino, t-heptylsulfonylamino, isooctylsulfonylamino, t-octylsulfonylamino, 2-ethylhexylsulfonylamino, isononylsulfonylamino, and isodecylsulfonylamino; or Examples thereof include cyclic C alkylsulfonylamino groups such as cyclopropylsulfonylamino, cyclobutylsulfonylamino, cyclopentylsulfonylamino, cyclohexylsulfonylamino, cycloheptylsulfonylamino, etc. Among these, linear or branched alkylsulfonylamino groups are preferred, and linear alkylsulfonylamino groups are more preferred.

[0037] The arylsulfonylamino group is preferably a C6-12 arylsulfonylamino group, and specific examples include phenylsulfonylamino, toluenesulfonylamino, naphthylsulfonylamino, biphenylsulfonylamino, and the like.

[0038] The alkylsulfamoyl group may be a linear, branched, or cyclic monoalkylsulfamoyl group or dialkylsulfamoyl group. The monoalkylsulfamoyl group is preferably a mono-C alkylsulfamoyl group, and specific examples include: straight-chain mono-C1-10 alkylsulfamoyl groups such as methylsulfamoyl, ethylsulfamoyl, n-propylsulfamoyl, n-butylsulfamoyl, n-pentylsulfamoyl, n-hexylsulfamoyl, n-heptylsulfamoyl, n-octylsulfamoyl, n-nonylsulfamoyl, and n-decylsulfamoyl; branched-chain mono-C alkylsulfamoyl groups such as isopropylsulfamoyl, isobutylsulfamoyl, sec-butylsulfamoyl, t-butylsulfamoyl, isoamylsulfamoyl, t-amylsulfamoyl, isohexylsulfamoyl, t-hexylsulfamoyl, isoheptylsulfamoyl, t-heptylsulfamoyl, isooctylsulfamoyl, t-octylsulfamoyl, 2-ethylhexylsulfamoyl, isononylsulfamoyl, and isodecylsulfamoyl; or Examples of such groups include cyclic mono-C alkylsulfamoyl groups such as cyclopropylsulfamoyl, cyclobutylsulfamoyl, cyclopentylsulfamoyl, cyclohexylsulfamoyl, and cycloheptylsulfamoyl. Among these, linear or branched monoalkylsulfamoyl groups are preferred, and linear monoalkylsulfamoyl groups are more preferred.

[0039] The dialkylsulfamoyl group is preferably a diC alkylsulfamoyl group, and specific examples include, straight-chain di-C1-10 alkylsulfamoyl groups such as dimethylsulfamoyl, diethylsulfamoyl, di-n-propylsulfamoyl, di-n-butylsulfamoyl, di-n-pentylsulfamoyl, di-n-hexylsulfamoyl, di-n-heptylsulfamoyl, di-n-octylsulfamoyl, di-n-nonylsulfamoyl, and di-n-decylsulfamoyl; a branched di-C alkylsulfamoyl group having two branched chains, such as diisopropylsulfamoyl, diisobutylsulfamoyl, di-sec-butylsulfamoyl, di-t-butylsulfamoyl, diisoamylsulfamoyl, di-t-amylsulfamoyl, diisohexylsulfamoyl, di-t-hexylsulfamoyl, diisoheptylsulfamoyl, di-t-heptylsulfamoyl, diisooctylsulfamoyl, di-t-octylsulfamoyl, di-(2-ethylhexyl)sulfamoyl, diisononylsulfamoyl, or diisodecylsulfamoyl; or Examples of such groups include cyclic di-C alkylsulfamoyl groups having two rings, such as dicyclopropylsulfamoyl, dicyclobutylsulfamoyl, dicyclopentylsulfamoyl, dicyclohexylsulfamoyl, and dicycloheptylsulfamoyl. Among these, linear or branched dialkylsulfamoyl groups are preferred, and linear dialkylsulfamoyl groups are more preferred.

[0040] The arylsulfamoyl group may be a monoarylsulfamoyl group or a diarylsulfamoyl group. The monoarylsulfamoyl group is preferably a mono-C6-12 arylsulfamoyl group, and specific examples include phenylsulfamoyl, naphthylsulfamoyl, and biphenylsulfamoyl.

[0041] The diarylsulfamoyl group is preferably a diC6-12 arylsulfamoyl group, and specific examples include diphenylsulfamoyl, dinaphthylsulfamoyl, di(biphenyl)sulfamoyl and the like.

[0042] The alkylsulfonyl group may be a linear, branched, or cyclic alkylsulfonyl group, preferably a C alkylsulfonyl group. Specific examples of the C alkylsulfonyl group include, for example, Straight-chain C1-12 alkylsulfonyl groups such as methylsulfonyl, ethylsulfonyl, n-propylsulfonyl, n-butylsulfonyl, n-pentylsulfonyl, n-hexylsulfonyl, n-heptylsulfonyl, n-octylsulfonyl, n-nonylsulfonyl, n-decylsulfonyl, n-undecylsulfonyl, and n-dodecylsulfonyl; branched-chain C alkylsulfonyl groups such as isopropylsulfonyl, isobutylsulfonyl, sec-butylsulfonyl, t-butylsulfonyl, isoamylsulfonyl, t-amylsulfonyl, isohexylsulfonyl, t-hexylsulfonyl, isoheptylsulfonyl, t-heptylsulfonyl, isooctylsulfonyl, t-octylsulfonyl, 2-ethylhexylsulfonyl, isononylsulfonyl, isodecylsulfonyl, isoundecylsulfonyl, t-undecylsulfonyl, isododecylsulfonyl, and t-dodecylsulfonyl; or Examples include cyclic C alkylsulfonyl groups such as cyclopropylsulfonyl, cyclobutylsulfonyl, cyclopentylsulfonyl, cyclohexylsulfonyl, cycloheptylsulfonyl, etc. Among these, linear or branched alkylsulfonyl groups are preferred, and linear alkylsulfonyl groups are more preferred.

[0043] The arylsulfonyl group is preferably a C6-12 arylsulfonyl group, and specific examples include phenylsulfonyl, naphthylsulfonyl, biphenylsulfonyl, and the like.

[0044] The alkylthio group may be a linear, branched, or cyclic alkylthio group, preferably a C1-10 alkylthio group. Specific examples of the C1-10 alkylthio group include, for example, Straight-chain C1-10 alkylthio groups such as methylthio, ethylthio, n-propylthio, n-butylthio, n-pentylthio, n-hexylthio, n-heptylthio, n-octylthio, n-nonylthio, and n-decylthio; branched C3-10 alkylthio groups such as isopropylthio, isobutylthio, sec-butylthio, t-butylthio, isoamylthio, t-amylthio, isohexylthio, t-hexylthio, isoheptylthio, t-heptylthio, isooctylthio, t-octylthio, 2-ethylhexylthio, isononylthio, and isodecylthio; or Examples include cyclic C alkylthio groups such as cyclopropylthio, cyclobutylthio, cyclopentylthio, cyclohexylthio, cycloheptylthio, etc. Among these, linear or branched alkylthio groups are preferred, and linear alkylthio groups are more preferred.

[0045] The arylthio group is preferably a C6-12 arylthio group, and specific examples include phenylthio, naphthylthio, biphenylthio, etc.

[0046] The alkylureido group may be a linear, branched, or cyclic monoalkylureido group or dialkylureido group. The monoalkylureido group is preferably a mono-C alkylureido group, and specific examples include: linear mono-C1-10 alkylureido groups such as methylureido, ethylureido, n-propylureido, n-butylureido, n-pentylureido, n-hexylureido, n-heptylureido, n-octylureido, n-nonylureido, and n-decylureido; branched mono-C alkylureido groups such as isopropylureido, isobutylureido, sec-butylureido, t-butylureido, isoamylureido, t-amylureido, isohexylureido, t-hexylureido, isoheptylureido, t-heptylureido, isooctylureido, t-octylureido, 2-ethylhexylureido, isononylureido, and isodecylureido; or Examples of such alkylureido groups include cyclic mono-C alkylureido groups such as cyclopropylureido, cyclobutylureido, cyclopentylureido, cyclohexylureido, cycloheptylureido, etc. Among these, linear or branched alkylureido groups are preferred, and examples thereof include linear alkylureido groups.

[0047] The dialkylureido group is preferably a diC alkylureido group, and specific examples thereof include, for example, Straight-chain di-C1-10 alkylureido groups such as dimethylureido, diethylureido, di-n-propylureido, di-n-butylureido, di-n-pentylureido, di-n-hexylureido, di-n-heptylureido, di-n-octylureido, di-n-nonylureido, and di-n-decylureido; Branched chain di-C3-C alkyl esters with two branched chains, such as diisopropyl ureide, diisobutyl ureide, di-sec-butyl ureide, di-t-butyl ureide, diisoamyl ureide, di-t-amyl ureide, diisohexyl ureide, di-t-hexyl ureide, diisoheptyl ureide, di-t-heptyl ureide, diisooctyl ureide, di-t-octyl ureide, di-(2-ethylhexyl) ureide, diisononyl ureide, and diisodecyl ureide 10 an alkylureido group; or Examples of such alkylureido groups include cyclic di-C alkylureido groups having two rings, such as dicyclopropylureido, dicyclobutylureido, dicyclopentylureido, dicyclohexylureido, dicycloheptylureido, etc. Among these, linear or branched dialkylureido groups are preferred, and linear dialkylureido groups are more preferred.

[0048] The arylureido group may be a monoarylureido group or a diarylureido group. The monoarylureido group is preferably a mono-C6-12 arylureido group, and specific examples include phenylureido, naphthylureido, and biphenylureido.

[0049] The diarylureido group is preferably a diC6-12 arylureido group, and specific examples include diphenylureido, dinaphthylureido, di(biphenyl)ureido and the like.

[0050] The alkoxycarbonylamino group may be a linear, branched, or cyclic alkoxycarbonylamino group, preferably a C1-10 alkoxycarbonylamino group. 10Specific examples of the alkoxycarbonylamino group include, for example, straight-chain C1-10 alkoxycarbonylamino groups such as methoxycarbonylamino, ethoxycarbonylamino, n-propoxycarbonylamino, n-butoxycarbonylamino, n-pentoxycarbonylamino, n-hexyloxycarbonylamino, n-heptoxycarbonylamino, n-octyloxycarbonylamino, n-nonyloxycarbonylamino, and n-decyloxycarbonylamino; branched-chain C3-10 alkoxycarbonylamino groups such as isopropoxycarbonylamino, isobutoxycarbonylamino, sec-butoxycarbonylamino, t-butoxycarbonylamino, isoamyloxycarbonylamino, t-amyloxycarbonylamino, isohexyloxycarbonylamino, t-hexyloxycarbonylamino, isoheptoxycarbonylamino, t-heptoxycarbonylamino, isooctyloxycarbonylamino, t-octyloxycarbonylamino, 2-ethylhexyloxycarbonylamino, isononyloxycarbonylamino, and isodecyloxycarbonylamino; or Examples thereof include cyclic C alkoxycarbonylamino groups such as cyclopropoxycarbonylamino, cyclobutoxycarbonylamino, cyclopentoxycarbonylamino, cyclohexyloxycarbonylamino, cycloheptoxycarbonylamino, etc. Among these, linear or branched alkoxycarbonylamino groups are preferred, and linear alkoxycarbonylamino groups are more preferred.

[0051] The aryloxycarbonylamino group is preferably a C6-12 aryloxycarbonylamino group, and specific examples include phenylcarbonylamino, naphthylcarbonylamino, biphenylcarbonylamino, and the like.

[0052] The alkylamino group may be a linear, branched, or cyclic monoalkylamino group or dialkylamino group. The monoalkylamino group is preferably a mono-C alkylamino group, and specific examples include: straight-chain mono-C1-10 alkylamino groups such as methylamino, ethylamino, n-propylamino, n-butylamino, n-pentylamino, n-hexylamino, n-heptylamino, n-octylamino, n-nonylamino, and n-decylamino; branched-chain mono-C alkylamino groups such as isopropylamino, isobutylamino, sec-butylamino, t-butylamino, isoamylamino, t-amylamino, isohexylamino, t-hexylamino, isoheptylamino, t-heptylamino, isooctylamino, t-octylamino, 2-ethylhexylamino, isononylamino, and isodecylamino; or Examples thereof include cyclic mono-C alkylamino groups such as cyclopropylamino, cyclobutylamino, cyclopentylamino, cyclohexylamino, cycloheptylamino, etc. Among these, linear or branched mono alkylamino groups are preferred, and linear mono alkylamino groups are more preferred.

[0053] The dialkylamino group is preferably a di-C alkylamino group, and specific examples thereof include: straight-chain di-C1-10 alkylamino groups such as dimethylamino, diethylamino, di-n-propylamino, di-n-butylamino, di-n-pentylamino, di-n-hexylamino, di-n-heptylamino, di-n-octylamino, di-n-nonylamino, and di-n-decylamino; a branched di-C alkylamino group having two branched chains, such as diisopropylamino, diisobutylamino, di-sec-butylamino, di-t-butylamino, diisoamylamino, di-t-amylamino, diisohexylamino, di-t-hexylamino, diisoheptylamino, di-t-heptylamino, diisooctylamino, di-t-octylamino, di-(2-ethylhexyl)amino, diisononylamino, or diisodecylamino; or Examples include cyclic di-C alkylamino groups having two rings, such as dicyclopropylamino, dicyclobutylamino, dicyclopentylamino, dicyclohexylamino, dicycloheptylamino, etc. Among these, linear or branched dialkylamino groups are preferred, and linear dialkylamino groups are more preferred.

[0054] The arylamino group may be a monoarylamino group or a diarylamino group. The monoarylamino group is preferably a mono-C6-12 arylamino group, and specific examples include phenylamino (anilino), naphthylamino, and biphenylamino.

[0055] The diarylamino group is preferably a di-C6-12 arylamino group, and specific examples include diphenylamino, dinaphthylamino, di(biphenyl)amino, etc.

[0056] Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom, with a fluorine atom, a chlorine atom, or a bromine atom being preferred.

[0057] In formula (1), X represents a sulfo group or a carboxy group, and is preferably a sulfo group, and n represents an integer of 1 to 3, and is preferably 1. If chemically possible, the sulfo group or carboxy group may be bonded to any position on the naphthalimide skeleton which may have a substituent represented by A, and the desired polarized luminescence effect is obtained regardless of the position at which the group is bonded. A preferred substitution position is the 5th position when the imide ring is positioned at positions 1, 2, and 3, and is the meta position relative to the carbonyl substitution position when viewed from the naphthalene skeleton.

[0058] The water-soluble naphthalimide compound represented by the above formula (1) or a salt thereof is preferably a compound represented by the following formula (2) or a salt thereof.

[0059] [ka]

[0060] In the above formula (2), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent; Q represents a hydrogen atom, a sulfur atom which may have a substituent, an oxygen atom which may have a substituent, or a nitrogen atom which may have a substituent; and n represents an integer of 1 to 3.

[0061] Examples of the hydrocarbon group having 1 to 12 carbon atoms (also referred to as "C1-12") include linear hydrocarbon groups such as methyl, ethyl, n-butyl, and n-octyl; branched hydrocarbon groups such as isobutyl and tert-butyl; and cyclic hydrocarbon groups such as cyclohexyl, cycloheptyl, phenyl, 2,6-dimethylphenyl, 2,6-diisopropylphenyl, and naphthyl. Q is preferably a nitrogen atom. n is preferably 1. The substituents for the hydrocarbon having 1 to 12 carbon atoms which may have a substituent, the substituents for the sulfur atom which may have a substituent, the oxygen atom which may have a substituent, and the substituents for the nitrogen atom which may have a substituent are the same as the substituents that A may have. The sulfo group can be bonded to any position of the naphthalimide skeleton, which may have a substituent represented by A, if chemically possible, and the desired polarized luminescence effect is obtained regardless of the position at which the sulfo group is bonded.

[0062] The water-soluble naphthalimide compound represented by the above formula (1) is more preferably a compound represented by the following formula (3) or a salt thereof.

[0063] [ka]

[0064] In the above formula (3), R 1 represents a hydrocarbon group having 1 to 12 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 12 carbon atoms. 1 The hydrocarbon group having 1 to 12 carbon atoms may be the same as that described in the section on formula (2). 2Examples of the hydrocarbon group having 1 to 12 carbon atoms include linear hydrocarbon groups such as a methyl group, an ethyl group, an n-butyl group, and an n-octyl group; branched hydrocarbon groups such as an isobutyl group and a tert-butyl group; and cyclic hydrocarbon groups such as a cyclohexyl group, a cycloheptyl group, a phenyl group, a 2,6-dimethylphenyl group, a 2,6-diisopropylphenyl group, and a naphthyl group. The sulfo group can be bonded to any position of the naphthalimide skeleton, which may have a substituent represented by A, if chemically possible, and the desired polarized luminescence effect is obtained regardless of the position at which the sulfo group is bonded.

[0065] The salts of the water-soluble naphthalimide compounds represented by the above formulas (1) to (3) refer to a state in which the free acid of the water-soluble naphthalimide compounds represented by the above formulas (1) to (3) forms a salt together with an inorganic cation or an organic cation. The inorganic cations include cations of alkali metals, such as lithium, sodium, and potassium, or ammonium (NH4 + Examples of organic cations include organic ammoniums represented by the following formula (4):

[0066] [ka]

[0067] In formula (4), Z1 to Z4 each independently represent a hydrogen atom, an alkyl group, a hydroxyalkyl group, or a hydroxyalkoxyalkyl group, and at least one of Z1 to Z4 is a group other than a hydrogen atom.

[0068] In formula (4), specific examples of Z1 to Z4 include, for example, C1-6 alkyl groups such as methyl, ethyl, butyl, pentyl, hexyl, etc., preferably C1-4 alkyl groups; hydroxy C1-6 alkyl groups such as hydroxymethyl, 2-hydroxyethyl, 3-hydroxypropyl, 2-hydroxypropyl, 4-hydroxybutyl, 3-hydroxybutyl, 2-hydroxybutyl, preferably hydroxy C1-4 alkyl groups; or Examples thereof include hydroxy C1-6 alkoxy C1-6 alkyl groups such as hydroxyethoxymethyl, 2-hydroxyethoxyethyl, 3-hydroxyethoxypropyl, 3-hydroxyethoxybutyl, and 2-hydroxyethoxybutyl, and preferably hydroxy C1-4 alkoxy C1-4 alkyl groups.

[0069] Among these inorganic cations or organic cations, cations such as sodium, potassium, lithium, monoethanolamine, diethanolamine, triethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, and ammonium are more preferred, and inorganic cations such as lithium, ammonium, and sodium are particularly preferred.

[0070] As described above, the water-soluble naphthalimide compounds represented by formulas (1) to (3) according to embodiments of the present invention have at least one naphthalimide skeleton in the molecule and no azo bond. Because of the naphthalimide skeleton, the water-soluble naphthalimide compounds exhibit luminescence upon irradiation with ultraviolet or visible light, particularly light in the 300 to 600 nm wavelength range. On the other hand, because the water-soluble naphthalimide compounds do not have azo bonds in the molecule, light absorption due to azo bonds is suppressed. Due to this specific structure, these water-soluble naphthalimide compounds can absorb ultraviolet or visible light and utilize the resulting energy to emit polarized light in the visible light range. Therefore, by using such naphthalimide compounds or salts thereof, novel polarized luminescent films and polarized luminescent plates can be provided that have polarizing properties from the ultraviolet to visible light range and exhibit polarized luminescence in the visible light range, without using rare lanthanide metals or the like.

[0071] Next, a method for synthesizing the above-mentioned water-soluble naphthalimide-based compound will be described. Although there is no particular limitation, for example, the water-soluble naphthalimide-based compound represented by the formulas (1) to (3) can be synthesized by carrying out the synthesis reaction shown below.

[0072] The water-soluble naphthalimide compounds represented by the above formulas (1) to (3) or salts thereof can be produced according to known sulfonation or carboxylation methods. Furthermore, the introduction of substituents can be achieved, for example, by the method described in JP-A-50-119023. The compounds to be subjected to sulfonation or carboxylation are water-insoluble naphthalimide compounds that have a naphthalimide skeleton and may have the above-mentioned substituents. These compounds may be commercially available or may be synthesized according to known methods.

[0073] [Polarized luminescent film] The present invention also includes a polarized light-emitting film that contains a water-soluble naphthalimide compound represented by any one of the above formulas (1) to (3) or a salt thereof and exhibits polarized light-emitting properties. In a preferred embodiment of the present invention, the polarized luminescent film includes a substrate containing a water-soluble naphthalimide compound represented by any of the above formulas (1) to (3) or a salt thereof. Such a substrate is preferably a film obtained by forming a hydrophilic polymer capable of adsorbing the water-soluble naphthalimide compound or a salt thereof. The hydrophilic polymer is not particularly limited, but examples thereof include polyvinyl alcohol resins, amylose resins, starch resins, cellulose resins, and polyacrylate resins. Among these resins, polyvinyl alcohol resins or their derivatives are preferred from the viewpoints of dye adsorption, processability, and orientation properties of water-soluble naphthalimide compounds and the like. Any polyvinyl alcohol resin derivative generally known in this technical field can be used. Examples of polyvinyl alcohol resin derivatives that can be used include, but are not limited to, modified polyvinyl alcohol resins obtained by copolymerizing unsaturated carboxylic acids or unsaturated sulfonic acids, such as crotonic acid, acrylic acid, methacrylic acid, and maleic acid, with olefins, such as ethylene and propylene. The shape of the substrate is not particularly limited, and can be any shape, such as a film, sheet, flat plate, curved plate, or hemisphere. The thickness of the substrate is usually 10 μm to 100 μm, and preferably 20 μm to 80 μm. The substrate may contain one or more water-soluble naphthalimide compounds or salts thereof represented by the above formulas (1) to (3).

[0074] In the polarized luminescent film, the blending ratio of the water-soluble naphthalimide compound or its salt contained in the substrate is preferably adjusted to fall within the preferred range described below, but is not particularly limited. The polarization performance of the polarized luminescent film varies depending not only on the blending ratio of the naphthalimide compound contained in the polarized luminescent film but also on various factors such as the swelling degree of the substrate to which the compound is adsorbed, the stretching ratio, the dyeing time, the dyeing temperature, the pH during dyeing, and the influence of salt. Therefore, the blending ratio of the naphthalimide compound contained in the polarized luminescent film can be determined depending on the swelling degree of the substrate, the dyeing temperature, the dyeing time, the pH, the type and concentration of salt, and even the stretching ratio. Adjustment of such blending ratio can be appropriately performed based on the explanation described below.

[0075] The polarized light-emitting film may further contain one or more organic dyes or fluorescent dyes other than the water-soluble naphthalimide compounds represented by Formulas (1) to (3) or their salts to adjust the transmittance, emission color, etc., without impairing the polarized light-emitting function of the polarized light-emitting film. The other organic dyes or fluorescent dyes used in combination are not particularly limited, but are preferably dyes that have high dichroism or luminescence brightness and little effect on the polarized light-emitting function of the polarized light-emitting film containing the compounds represented by Formulas (1) to (3). Examples of such other organic dyes include CI Direct Yellow 12, CI Direct Yellow 28, CI Direct Yellow 44, CI Direct Orange 26, CI Direct Orange 39, CI Direct Orange 71, CI Direct Orange 107, CI Direct Red 2, CI Direct Red 31, CI Direct Red 79, CI Direct Red 81, CI Direct Red 247, CI Direct Blue 69, CI Direct Blue 78, CI Direct Green 80, and CI Direct Green 59. These other organic dyes may be in the form of free acids, alkali metal salts (such as Na, K, and Li salts), ammonium salts, or salts of amines.

[0076] When the above-mentioned other organic dyes or fluorescent dyes are added, the type of dye to be added varies depending on the intended use, such as a polarized luminescent film with a neutral gray hue, a polarized luminescent film having a polarizing function at a specific wavelength (for example, a color polarized luminescent film for a liquid crystal projector), or other color polarized luminescent films used in sunglasses, etc. Therefore, the blending ratio of the other organic dyes is not particularly limited, but it is generally preferable to include at least one of these dyes in a total amount ranging from 0.01 to 10 parts by mass per part by mass of the naphthalimide-based compound of the above formulas (1) to (3).

[0077] <Method of manufacturing polarized luminescent film> A method for producing the polarized luminescent film will now be described. The method for producing the polarized luminescent film according to the present invention is not limited to the following method, but mainly includes the steps of preparing a substrate, immersing the substrate in a swelling liquid to stretch the substrate by swelling, impregnating the swollen substrate in a dyeing solution containing at least one water-soluble naphthalimide compound represented by any of the above formulae (1) to (3) or a salt thereof, and optionally other organic dyes or fluorescent dyes (hereinafter collectively referred to as "polarizing dye") to adsorb the polarizing dye onto the substrate, immersing the adsorbed substrate in a solution containing boric acid to crosslink the polarizing dye within the substrate, uniaxially stretching the substrate with the crosslinked polarizing dye in a specific direction to align the polarizing dye in a specific direction, and, if necessary, washing the stretched substrate with a washing liquid and drying the washed substrate.

[0078] (Preparation of substrate) A substrate is prepared to contain the water-soluble naphthalimide compound represented by any one of the formulas (1) to (3) or its salt, and optionally other organic dyes or fluorescent dyes. The substrate may be, for example, a film made of a commercially available polyvinyl alcohol resin or its derivative, or may be prepared by forming a polyvinyl alcohol resin film. The method for forming a polyvinyl alcohol resin film is not particularly limited, and known film-forming methods can be used, such as melt extrusion of hydrous polyvinyl alcohol, casting film-forming, wet film-forming, gel film-forming (a polyvinyl alcohol aqueous solution is cooled to gel, and then the solvent is extracted and removed), cast film-forming (a polyvinyl alcohol aqueous solution is poured onto a substrate and dried), and combinations thereof.

[0079] (Swelling process) Next, the substrate is subjected to a swelling treatment. The swelling treatment is preferably carried out by immersing the substrate in a swelling liquid at 20 to 50°C for 30 seconds to 10 minutes, and the swelling liquid is preferably water. The stretching ratio of the substrate in the swelling liquid is preferably adjusted to 1.00 to 1.50 times, and more preferably 1.10 to 1.35 times.

[0080] (Polarizing dye adsorption and impregnation process) Subsequently, at least one polarizing dye containing the water-soluble naphthalimide compound or a salt thereof is adsorbed onto and impregnated into the substrate obtained by the swelling treatment described above. The method for carrying out this step is not particularly limited as long as it allows the polarizing dye to be adsorbed onto and impregnated into the substrate. For example, it is preferable to immerse the substrate in a dyeing solution (aqueous dyeing solution) containing the polarizing dye. Alternatively, the polarizing dye can be adsorbed onto the substrate by applying the dyeing solution. The concentration of the polarizing dye in the dyeing solution is not particularly limited as long as the polarizing dye is sufficiently adsorbed into the substrate. For example, it is preferable that the concentration of the polarizing dye in the dyeing solution be 0.0001 to 3% by mass, and more preferably 0.001 to 1% by mass.

[0081] The temperature of the dye solution in the polarizing dye adsorption / impregnation step is preferably 5 to 80° C., more preferably 20 to 50° C., and particularly preferably 40 to 50° C. The time for immersing the substrate in the dye solution can be appropriately adjusted, and is preferably adjusted between 30 seconds and 20 minutes, and more preferably between 1 and 10 minutes.

[0082] As the polarizing dye contained in the dye solution, the water-soluble naphthalimide compounds or salts thereof represented by the above formulas (1) to (3) may be used alone or in combination of two or more. The water-soluble naphthalimide compounds or salts thereof represented by the above formulas (1) to (3) emit different colors of light, so by incorporating two or more of these compounds into the substrate, the emitted light color can be appropriately adjusted to a desired color. Furthermore, if necessary, the dye solution may further contain one or more of the other organic dyes or fluorescent dyes described above.

[0083] The dyeing solution may further contain a dyeing assistant, if necessary, in addition to the polarizing dye. Examples of dyeing assistants include sodium carbonate, sodium bicarbonate, sodium chloride, sodium sulfate (mirabilite), anhydrous sodium sulfate, and sodium tripolyphosphate, with sodium sulfate being preferred. The content of the dyeing assistant can be adjusted as desired by the immersion time and the temperature of the dyeing solution based on the dyeing properties of the polarizing dye used, but is preferably 0.1 to 10% by mass, more preferably 0.1 to 2% by mass in the dyeing solution.

[0084] After the polarizing dye adsorption / impregnation process, a preliminary cleaning process can be optionally performed to remove the dye solution that has adhered to the surface of the substrate during this process. Performing the preliminary cleaning process can prevent the organic dye remaining on the surface of the substrate from migrating into the subsequent processing solution. In the preliminary cleaning process, water is generally used as the cleaning solution. The preferred cleaning method is to immerse the dyed substrate in the cleaning solution. Alternatively, the substrate can also be cleaned by applying the cleaning solution to it. The cleaning time is not particularly limited, but is preferably 1 to 300 seconds, more preferably 1 to 60 seconds. The temperature of the cleaning solution in the preliminary cleaning process must be such that the material constituting the substrate does not dissolve; cleaning is generally performed at 5 to 40°C. The preliminary cleaning process can be omitted because it does not significantly affect the performance of the polarized luminescent film.

[0085] (Crosslinking process) After the polarizing dye adsorption / impregnation step or the pre-cleaning step, the polarizing dye in the substrate can be crosslinked. A preferred method for crosslinking the polarizing dye in the substrate is to immerse the substrate in a treatment solution containing a crosslinking agent. Alternatively, the treatment solution may be coated or spread on the substrate. A solution containing boric acid is preferably used as the crosslinking agent in the treatment solution. The solvent in the treatment solution is not particularly limited, but water is preferred. The concentration of boric acid in the treatment solution is preferably 0.1 to 15% by mass, more preferably 0.1 to 10% by mass. The temperature of the treatment solution is preferably 30 to 80°C, more preferably 40 to 75°C. Furthermore, the treatment time for this crosslinking step is preferably 30 seconds to 10 minutes, more preferably 1 to 6 minutes. In a preferred embodiment of the present invention, the method for producing a polarized luminescent film includes this crosslinking step, and the resulting polarized luminescent film emits polarized light with high brightness and a high degree of polarization. This is an excellent effect that was completely unexpected from the function of boric acid, which has been used in prior art to improve water resistance or light transmittance. Furthermore, if necessary, the crosslinking process may be further subjected to a fixation treatment using an aqueous solution containing a cationic polymer compound. This fixation treatment enables the polarizing dye to be fixed. Examples of cationic polymer compounds that can be used include cationic ions, dicyanide-based compounds such as dicyanamide and formalin polymer condensates, polyamine-based compounds such as dicyandiamide-diethylenetriamine polycondensates, and polycation-based compounds such as epichlorohydrin-dimethylamine addition polymers, dimethyldiallylammonium chloride-dioxide ion copolymers, diallylamine salt polymers, dimethyldiallylammonium chloride polymers, allylamine salt polymers, and dialkylaminoethyl acrylate quaternary salt polymers.

[0086] (Stretching process) After the crosslinking step, a stretching step is carried out. The stretching step is carried out by uniaxially stretching the substrate in a certain direction. The stretching method may be either a wet stretching method or a dry stretching method. The stretching ratio is preferably 3 times or more and less than 10 times, and more preferably 5 to 9 times.

[0087] In the dry stretching method, when the stretching heating medium is air, the substrate is preferably stretched at a temperature of the air medium of room temperature to 180°C. The humidity is preferably 20 to 95% RH in the atmosphere. Examples of methods for heating the substrate include inter-roll zone stretching, roll heating stretching, hot rolling stretching, and infrared heating stretching, but the method is not limited to these stretching methods. The dry stretching step may be performed in one stretching stage or in two or more multi-stage stretching stages.

[0088] In the wet stretching method, the substrate is preferably stretched in water, a water-soluble organic solvent, or a mixture thereof. More preferably, the substrate is stretched while immersed in a solution containing at least one crosslinking agent. The crosslinking agent may be, for example, boric acid, as used in the crosslinking agent step. Preferably, the stretching is performed in the treatment solution used in the crosslinking step. The stretching temperature is preferably 40 to 70°C, more preferably 45 to 60°C. The stretching time is usually 30 seconds to 20 minutes, preferably 2 to 7 minutes. The wet stretching step may be performed in a single stretching step or in a multi-stage stretching step of two or more stages. The stretching may optionally be performed before the polarizing dye adsorption / impregnation step. In this case, the orientation of the dye can be simultaneously performed at the time of dyeing.

[0089] (Cleaning process) After the stretching step, precipitation of the crosslinking agent or adhesion of foreign matter to the surface of the substrate may occur, so a washing step can be carried out to wash the surface of the substrate. The washing time is preferably 1 second to 5 minutes. The washing method is preferably to immerse the substrate in a washing liquid. Alternatively, washing can be carried out by applying or coating the washing liquid onto the substrate. Water is preferred as the washing liquid. The washing treatment may be carried out in one stage or in a multi-stage treatment of two or more stages. The temperature of the washing solution in the washing step is not particularly limited, but is usually 5 to 50°C, preferably 10 to 40°C, and may be room temperature.

[0090] In addition to water, examples of solvents for the solutions or treatment liquids used in the above-described steps include alcohols such as dimethyl sulfoxide, N-methylpyrrolidone, methanol, ethanol, propanol, isopropyl alcohol, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. The solvents for the solutions or treatment liquids are not limited to these, but water is most preferred. Furthermore, these solvents for the solutions or treatment liquids may be used alone or in combination of two or more.

[0091] (drying process) After the washing step, the substrate is subjected to a drying step. The drying process can be carried out by natural drying. To further increase the drying efficiency, it is possible to carry out the drying by compressing with a roll or removing moisture from the surface with an air knife or water-absorbing roll, or it is also possible to carry out air drying. The temperature for the drying process is preferably 20 to 100°C, more preferably 60 to 100°C. The drying time is preferably 30 seconds to 20 minutes, more preferably 5 to 10 minutes.

[0092] Polarized light-emitting films can be produced according to the methods exemplified above. Also, polarized light-emitting films having various colors, such as neutral gray, can be produced by mixing the water-soluble naphthalimide compounds represented by formulas (1) to (3) with liquid crystals and orienting them, or by orienting them by a shear coating method.

[0093] [Polarized luminescent plate] The present invention also includes a polarized light-emitting plate including the polarized light-emitting film. In a preferred embodiment of the present invention, the polarized luminescent plate includes a transparent protective layer together with the polarized luminescent film, and typically has a transparent protective layer on at least one surface of the polarized luminescent film. The transparent protective layer is used to improve the water resistance and handleability of the polarized luminescent film. Therefore, it is preferable that the transparent protective layer does not have any effect on the polarized luminescence function exhibited by the polarized luminescent film.

[0094] The transparent protective layer is preferably a transparent protective layer excellent in optical transparency and mechanical strength. Furthermore, the transparent protective layer preferably has a layer shape that can maintain the shape of the polarized luminescent film. In addition to transparency and mechanical strength, the transparent protective layer is also preferably excellent in thermal stability, moisture blocking properties, and the like. Examples of materials for forming such a transparent protective layer include cellulose acetate films, acrylic films, fluorine-based films such as tetrafluoroethylene / hexafluoropropylene copolymers, polyester resins, polyolefin resins, and polyamide resins. Triacetyl cellulose (TAC) films and cycloolefin films are preferred. The thickness of the transparent protective layer is preferably in the range of 1 μm to 200 μm, more preferably 10 μm to 150 μm, and particularly preferably 40 μm to 100 μm. The polarized luminescent plate having a transparent protective layer is not particularly limited, but can be produced, for example, by overlaying the transparent protective layer on the polarized luminescent film and laminating them according to a known formulation.

[0095] The polarized luminescent plate may further include an adhesive layer between the transparent protective layer and the polarized luminescent film for bonding the transparent protective layer to the polarized luminescent film. The adhesive for forming the adhesive layer is not particularly limited, but examples thereof include polyvinyl alcohol-based adhesives, urethane emulsion-based adhesives, acrylic adhesives, and polyester-isocyanate-based adhesives, and a polyvinyl alcohol-based adhesive is preferably used. After bonding the transparent protective layer and the polarized luminescent film with the adhesive, the polarized luminescent plate can be produced by drying or heat-treating them at an appropriate temperature.

[0096] In addition, the polarized light-emitting plate may be appropriately provided with various known functional layers such as an anti-reflection layer, an anti-glare layer, and an additional transparent protective layer, and these layers are typically provided on the exposed surface of the transparent protective layer.When preparing such layers with various functions, it is preferable to coat materials with various functions on the exposed surface of the transparent protective layer, for example.In addition, such layers or films with functions can also be attached to the exposed surface of the transparent protective layer via an adhesive or pressure-sensitive adhesive.

[0097] Examples of the additional transparent protective layer include a hard coat layer of an acrylic type, a urethane type, a polysiloxane type, or the like. Furthermore, in order to further improve the single-piece transmittance, an antireflection layer can be provided on the exposed surface of the transparent protective layer. The antireflection layer can be formed, for example, by subjecting a substance such as silicon dioxide or titanium oxide to vapor deposition or sputtering treatment on the exposed surface of the transparent protective layer, or by thinly coating a fluorine-based substance on the exposed surface of the transparent protective layer.

[0098] The polarized light-emitting plate may further include a support, if necessary. Such a support preferably has a flat surface to which the polarized light-emitting plate is attached. Furthermore, from the viewpoint of optical applications, it is preferable that the support be transparent. Transparent supports can be divided into inorganic and organic supports. Examples of inorganic supports include supports made of inorganic materials such as soda glass, borosilicate glass, quartz, sapphire, and spinel. Examples of organic supports include supports made of organic materials such as acrylic, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, and cycloolefin polymer. The thickness and size of the support are not particularly limited and can be determined appropriately. Furthermore, in polarized light-emitting plates having a support, it is preferable to provide an anti-reflection layer on one or both of the support surface and the polarized light-emitting plate surface to further improve the single-piece transmittance. To bond the polarized light-emitting plate to the flat surface of the support, a transparent adhesive (pressure-sensitive adhesive) is applied to the flat surface of the support, and then the polarized light-emitting plate is attached to this coated surface. The adhesive or pressure-sensitive adhesive used is not particularly limited, and commercially available adhesives or pressure-sensitive adhesives can be used, with acrylate-based adhesives or pressure-sensitive adhesives being preferred.

[0099] The polarized light-emitting plate can also be converted into a circularly polarized light-emitting plate or an elliptically polarized light-emitting plate by attaching a retardation plate. For example, when a support is further provided on the polarized light-emitting plate, these circularly or elliptically polarized light-emitting plates can be produced by using a retardation plate as the support. Retardation plates generally include, but are not limited to, those having a retardation value of 1 / 4λ or 1 / 2λ relative to the absorption wavelength or emission wavelength of light. By having a retardation value of 1 / 4λ, the plate functions as a circularly polarized light-emitting plate or a circularly polarized light-emitting plate for that wavelength, and by having a retardation value of 1 / 2λ, the plate can be used to convert polarized light to a 90° direction. Thus, various functional layers, supports, etc. can be further provided on the polarized light-emitting plate, and such polarized light-emitting plates can be used in various products such as liquid crystal projectors, calculators, clocks, laptops, word processors, LCD televisions, car navigation systems, indoor and outdoor measuring instruments and displays, lenses, or glasses.

[0100] In a preferred embodiment of the present invention, the polarized luminescent film and polarized luminescent plate exhibit high polarized luminescence and high transmittance in the visible light region, and also exhibit polarizing function in the ultraviolet or visible light region. Furthermore, the polarized luminescent film and polarized luminescent plate exhibit excellent durability against heat, humidity, light, and the like, and are therefore capable of maintaining their performance even in harsh environments, and are more durable than conventional iodine-based polarizers. Therefore, the polarized luminescent film and polarized luminescent plate according to a preferred embodiment of the present invention can be applied to various display devices, such as liquid crystal displays that require high transmittance in the visible light region and high durability in harsh environments, such as televisions, wearable devices, tablet devices, smartphones, in-vehicle monitors, digital signage used indoors or outdoors, and smart windows.

[0101] [Display device] The present invention also includes a display device including the polarized light-emitting film or polarized light-emitting plate. In an embodiment of the present invention, a display device exhibits polarized light emission when irradiated with light in the ultraviolet to visible range, e.g., light in the range of 300 to 600 nm, and this effect can be utilized to enable display. Because the display device according to the embodiment of the present invention has high transmittance in the visible light range, there is no decrease in transmittance in the visible light range like conventional polarizers, or even if there is a decrease in transmittance, the decrease in transmittance is significantly smaller than that of conventional polarizers. Conventional polarizers, such as iodine-based polarizers or dye-based polarizers containing other dye compounds, have a luminosity-corrected transmittance of approximately 35 to 45%. This is because conventional polarizers have both vertical and horizontal axes as light absorption axes, but absorb light incident on either the vertical or horizontal axis. That is, polarization occurs when light is absorbed along one axis and transmitted along the other axis. In such cases, light along one axis is absorbed and not transmitted, inevitably resulting in a transmittance of 50% or less. Furthermore, conventional polarizing plates are produced by stretching a film containing a dichroic dye to orient the dichroic dye. However, this manufacturing method does not necessarily result in 100% alignment of the dichroic dye, and some components that absorb light along the light transmission axis are present. Furthermore, surface reflection of this substance causes interfacial reflection. As a result, polarizing plates with high transmittance have not been obtained. In other words, a high degree of polarization could not be achieved without reducing transmittance. In contrast, the polarized luminescent film or polarized luminescent plate according to embodiments of the present invention has a light absorption band in the 300 to 600 nm range, particularly around 350 to 500 nm. That is, it absorbs light in the ultraviolet range and the short-wavelength visible range, and exhibits polarized luminescence, emitting polarized light in the visible range. Meanwhile, because absorption in the visible range, which affects luminosity, is minimal, the decrease in transmittance is significantly suppressed, resulting in very high transmittance in the visible range. Furthermore, because it exhibits polarized luminescence in the visible range, there is less light loss than with conventional polarizing plates, and the decrease in transmittance compared to conventional polarizing plates is very small. For this reason, a display device using a polarized luminescent film or polarized luminescent plate according to an embodiment of the present invention, such as a liquid crystal display, can achieve higher brightness than a display device such as a liquid crystal display using a conventional polarizing plate.Furthermore, display devices using the polarized luminescent film or polarized luminescent plate according to embodiments of the present invention have high transparency, so that, for example, a nearly transparent display can be obtained despite being a liquid crystal display. Furthermore, because the polarized luminescence can be designed to transmit when displaying characters, images, etc., a display capable of displaying characters, etc. can be obtained despite being a transparent liquid crystal display. Thus, according to embodiments of the present invention, the display device can be a transparent liquid crystal display with no optical loss, particularly a see-through display.

[0102] Furthermore, according to the embodiment of the present invention, the display device can polarize ultraviolet light, which is invisible to the human eye, and therefore can be applied to liquid crystal displays that can display images using ultraviolet light. For example, by recognizing images displayed using ultraviolet light with a computer or the like, it is possible to fabricate a simple and highly secure liquid crystal display that is visible only when irradiated with ultraviolet light.

[0103] Furthermore, the display device exhibits polarized luminescence when irradiated with ultraviolet light, and since it is possible to fabricate a liquid crystal display utilizing this polarized luminescence, it is possible to realize a liquid crystal display that uses ultraviolet light, rather than a normal liquid crystal display that uses visible light. In other words, it is possible to fabricate an emissive liquid crystal display that can display characters, images, etc., even in a dark space where ultraviolet light can be irradiated.

[0104] Furthermore, because the absorption bands of light in the visible light region and the ultraviolet light region are different, it is possible to fabricate a display that has both a liquid crystal display region that can display with light in the visible light region and a liquid crystal display region that displays with light that is polarized by ultraviolet light. While displays capable of two different displays have existed, there is no display that can display different images using separate light sources in the ultraviolet and visible light regions using the same liquid crystal panel. Therefore, the display device according to the present invention can be fabricated as a novel display by including the polarized light-emitting film or polarized light-emitting plate described above.

[0105] In the liquid crystal display according to the embodiment of the present invention, the liquid crystal cell is not limited to, for example, a TN liquid crystal cell, an STN liquid crystal cell, a VA liquid crystal cell, an IPS liquid crystal cell, etc., and the liquid crystal display can be used in any liquid crystal display mode. The polarized luminescent film or polarized luminescent plate containing the water-soluble naphthalimide compound or its salt has high durability and can therefore be used in liquid crystal displays for automotive or outdoor displays, etc.

[0106] In an embodiment of the present invention, the polarized light-emitting plate also includes a neutral gray polarizing plate, which has excellent polarized light-emitting performance and is characterized by not discoloring or decreasing its polarization performance even under high temperature and high humidity conditions such as inside a car or outdoors. [Example]

[0107] The present invention will be described in more detail below with reference to examples, but these are illustrative and do not limit the present invention in any way. Furthermore, "%" and "parts" described below are by mass unless otherwise specified. Furthermore, for compounds for which λmax (maximum absorption wavelength) was measured among the synthesized compounds, the measured value in an aqueous solution at pH 7 to 8 was shown. Furthermore, in the structural formulas of the compounds used in each example and comparative example, acidic functional groups such as sulfo groups are shown in the form of free acids.

[0108] [Example 1] (Synthesis of Water-Soluble Naphthalimide Compound: Synthesis Example 1) 27.8 parts of commercially available 4-sulfonaphthalic anhydride were added to 100 parts of water, and 150 parts of a 40% aqueous solution of methylamine were added. The mixture was refluxed for 24 hours. 50 parts of sodium chloride were added to the resulting reaction mixture, and the precipitated solid was separated by filtration and washed with 100 parts of saturated brine to obtain 20.0 parts of a wet cake. This wet cake was dried in a hot air dryer at 80°C to synthesize 6.0 parts of a water-soluble naphthalimide compound according to the present invention, represented by the following formula (5):

[0109] [ka]

[0110] (Preparation of polarized light-emitting film and polarized light-emitting plate) A 75 μm-thick polyvinyl alcohol film (VF-PS#7500 manufactured by Kuraray Co., Ltd.) was immersed in water at 40°C for 3 minutes to swell the film. The swollen film was then immersed in a 45°C aqueous solution containing 1.0 part of the water-soluble naphthalimide compound of formula (5) obtained in Synthesis Example 1, 1.0 part of sodium sulfate, and 1,000 parts of water for 3 minutes to impregnate the film with the naphthalimide compound of formula (5). The film containing the water-soluble naphthalimide compound of formula (5) was then immersed in a 3% aqueous boric acid solution at 50°C for 5 minutes and stretched 5 times its original size. The stretched film was then washed with water at room temperature for 20 seconds while maintaining tension, and then dried to produce a polarized light-emitting film. A triacetyl cellulose film (ZRD-60 manufactured by Fujifilm Corporation) (thickness: 60 μm) containing no ultraviolet absorber was laminated on both sides of the obtained polarized luminescent film using a polyvinyl alcohol adhesive to prepare a polarized luminescent plate. This polarized luminescent plate was used as the measurement sample for Example 1.

[0111] [Example 2] (Synthesis of Water-Soluble Naphthalimide Compound: Synthesis Example 2) Following the example of JP 50-119023 A, a mixture of 18.6 parts of commercially available 4-chloronaphthalic anhydride, 20.0 parts of n-butylamine, and 80 parts of N-methyl-2-pyrrolidone was reacted at 130°C for 10 hours. Next, 40 parts of methanol was added to the resulting reaction solution, which was then cooled and the precipitated solid was filtered off. The resulting precipitate was then added to 100 parts of n-butylamine and heated under reflux for 24 hours. The resulting reaction solution was poured into 200 parts of water, and the precipitated solid was filtered off and dried, yielding 5.0 parts of the following formula (6).

[0112] [ka] 5.0 parts of the obtained compound of formula (6) was added to 20 parts of 20% fuming sulfuric acid and reacted at 50°C for 4 hours, and then poured into 200 parts of ice water and salted out using sodium chloride to synthesize 2.9 parts of a water-soluble naphthalimide compound according to the present invention represented by the following formula (7).

[0113] [ka]

[0114] (Preparation of polarized light-emitting film and polarized light-emitting plate) Next, a polarized luminescent plate was prepared using the water-soluble naphthalimide compound represented by the above formula (7) in the same manner as in Example 1. This polarized luminescent plate was used as the measurement sample for Example 2.

[0115] [Example 3] (Synthesis of Water-Soluble Naphthalimide Compound: Synthesis Example 3) Following the example of JP 50-119023 A, 5.0 parts of a commercially available compound of the following formula (8) was added to 20 parts of 20% fuming sulfuric acid, and the mixture was reacted at 50°C for 4 hours. The reaction mixture was then poured into 200 parts of ice water and salted out using sodium chloride to synthesize 4.9 parts of a water-soluble naphthalimide compound of the present invention, represented by the following formula (9).

[0116] [ka]

[0117] [ka]

[0118] (Preparation of polarized light-emitting film and polarized light-emitting plate) Next, a polarized light-emitting plate was prepared using the water-soluble naphthalimide compound represented by the above formula (9) in the same manner as in Example 1. This polarized light-emitting plate was used as the measurement sample for Example 3.

[0119] [Example 4] (Synthesis of Water-Soluble Naphthalimide Compound: Synthesis Example 4) Following the example of JP 50-119023 A, 5.0 parts of a commercially available compound of formula (10) was added to 20 parts of 20% fuming sulfuric acid, and the mixture was reacted at 50°C for 4 hours. The reaction mixture was then poured into 200 parts of ice water and salted out with sodium chloride to synthesize 4.5 parts of a water-soluble naphthalimide compound according to the present invention, represented by the following formula (11):

[0120] [ka]

[0121] [ka]

[0122] (Preparation of polarized light-emitting film and polarized light-emitting plate) Next, a polarized luminescent plate was prepared using the water-soluble naphthalimide compound represented by the above formula (11) in the same manner as in Example 1. This polarized luminescent plate was used as the measurement sample for Example 4.

[0123] (Comparative Example 1) A measurement sample was prepared in the same manner as in Example 1, except that CI Direct Yellow 4 represented by the following formula (12) was used instead of the water-soluble naphthalimide compound represented by the above formula (5).

[0124] [ka]

[0125] (Comparative Example 2) A measurement sample was prepared in the same manner as in Example 1, except that the water-soluble naphthalimide compound represented by the formula (5) above was replaced with a compound represented by the following formula (13).

[0126] [ka]

[0127] (Comparative Example 3) A measurement sample was prepared in the same manner as in Example 1, except that CI Direct Orange 39 was used instead of the water-soluble naphthalimide compound represented by the formula (5) in Example 1.

[0128] [evaluation] The measurement samples obtained in Examples 1 to 4 and Comparative Examples 1 to 3 were evaluated as follows.

[0129] (a) Measurement of single transmittance Ts, parallel transmittance Tp, and perpendicular transmittance Tc The single transmittance Ts, parallel transmittance Tp, and crossed transmittance Tc of each measurement sample were measured using a spectrophotometer (Hitachi, Ltd., "U-4100"). Here, the single transmittance Ts is the transmittance at each wavelength when each measurement sample is measured using a single sheet. The parallel transmittance Tp is the spectral transmittance at each wavelength measured by preparing two identical measurement samples obtained in each Example and Comparative Example, and overlapping the two measurement samples so that their absorption axes are parallel. The crossed transmittance Tc is the spectral transmittance measured by overlapping the two measurement samples so that their absorption axes are perpendicular. The transmittances were measured over a wavelength range of 220 to 780 nm. (b) Calculation of the degree of polarization ρ The degree of polarization ρ of each measurement sample was calculated by substituting the parallel transmittance Tp and the crossed transmittance Tc into the following formula (I). A higher value of ρ indicates a better degree of polarization.

[0130]

number

[0131] (c) Luminosity-corrected single transmittance Ys and luminosity-corrected polarization degree ρy The luminosity-corrected single transmittance Ys of each measurement sample is the transmittance obtained by correcting the luminosity of the single transmittance Ts obtained at a predetermined wavelength interval dλ (here, 5 nm) in the wavelength range of 400 to 700 nm in the visible light region according to JIS Z 8722:2009. Specifically, the single transmittance Ts was calculated by substituting it into the following formula (II). In the following formula (II), Pλ represents the spectral distribution of standard light (illuminant C), and yλ represents the 2-degree visual field color matching function. The luminosity-corrected polarization degree ρy was measured using a value calculated using a spectrophotometer (Hitachi, Ltd.'s "U-4100").

[0132]

number

[0133] (d) Measurement of polarized luminescence The polarized luminescence intensity and degree of polarization of the emitted light of each measurement sample were measured using a luminescence spectrophotometer (Tokyo Instruments, Poxi-Spectra Spectropolarimeter) by the commonly known Stokes parameter method. When 375 nm light was incident on the measurement sample, the luminescence intensity (S0) obtained from the luminescence spectrophotometer was calculated, with the luminescence intensity at the maximum emission wavelength set to 1. The ratio of each wavelength was calculated, and the degree of polarization based on luminescence (DOP) was calculated using the intensity ratio (Sr0) of each wavelength and the degree of linear polarization of the emitted light (DOLP) obtained from the luminescence spectrophotometer using formula (III).

[0134]

number

[0135] Table 1 below shows the single transmittance (Ts), parallel transmittance (Tp), crossed transmittance (Tc), and degree of polarization (ρ) at the wavelength showing the maximum degree of polarization for each measurement sample obtained in Examples 1 to 4 and Comparative Examples 1 to 3, as well as the single transmittance (Ys) corrected for luminous efficacy and the degree of polarization (ρy) corrected for luminous efficacy. Note that the units of the above ratios and degrees are %.

[0136] [Table 1]

[0137] In a dark room, each of the measurement samples obtained in Examples 1 to 4 and Comparative Examples 1 to 3 was irradiated with ultraviolet light of 375 nm using a commercially available UV-LED black light with a peak wavelength of 375 nm, and the presence or absence of luminescence was observed visually. Luminescence was observed in all of the measurement samples of Examples 1 to 4, which were prepared using water-soluble naphthalimide-based compounds, whereas no luminescence was observed in all of the samples of Comparative Examples 1 to 3, which were prepared using general dichroic azo-based compounds with absorption wavelengths similar to those of the compounds of the present invention.

[0138] Figure 1 shows a graph of the DOP values ​​for each wavelength for the measurement samples obtained in Examples 1 to 4. As shown in Figure 1, the measurement samples obtained in Examples 1 to 4 exhibit high DOP values ​​centered around 510 to 550 nm, indicating polarized emission. On the other hand, in Comparative Examples 1 to 3, where no emission was observed, the emission intensity S0 could not be measured, and therefore the DOP was not calculated.

[0139] (Figure 1) TIFF0007824088000021.tif55129

[0140] Table 2 below shows the wavelengths at which the highest DOP values ​​were obtained for each of the measurement samples obtained in Examples 1 to 4, and the DOP values.

[0141] [Table 2]

[0142] As shown in Table 1 above, the measurement samples of Examples 1 to 4, which were prepared using the water-soluble naphthalimide compound having the structure of Formula (1), exhibited polarized light emission in the visible light region and functioned as polarized light-emitting films (polarized light-emitting plates) in the same region. Furthermore, the measurement samples of Examples 1 to 4 exhibited transmittance (luminosity-corrected transmittance Ys) of 85% or more in the visible light region, demonstrating that they were polarized light-emitting plates (polarized light-emitting films) that possessed polarizing function in the visible light region and high transmittance in the same region. Furthermore, as shown in FIG. 1 and Table 2, the measurement samples of Examples 1 to 4 exhibited high DOP values ​​in the wavelength region of 450 to 600 nm and had the highest DOP around 510 to 550 nm, indicating that they emitted light over a wide wavelength range in the visible light region and that the emitted light was polarized, i.e., they possessed polarized light emission properties. Furthermore, the DOP values ​​were high regardless of the transmittance (Ts) and the degree of polarization (ρ), indicating that they emitted light with polarization that was independent of the light absorption anisotropy.

[0143] (Durability test) A durability test was carried out on each of the measurement samples of Examples 1 to 4 under the following two conditions. 1)105℃, 1000 hours 2) 60°C, 90% relative humidity, 1000 hours

[0144] As a result, no change in DOP value was observed in any of the samples, which shows that the samples of Examples 1 to 4 have high durability even under severe environments. [Industrial Applicability]

[0145] As described above, the polarized luminescent film or polarized luminescent plate containing the water-soluble naphthalimide compound of the present invention not only has a polarizing function but also exhibits polarized luminescence. Furthermore, such polarized luminescent film and polarized luminescent plate have excellent durability and high transmittance in the visible light range. Therefore, a display device manufactured using such a polarized luminescent film or polarized luminescent plate has high transmittance in the visible light range and can display images by polarized luminescence for a long period of time, making it applicable to a wide range of applications, including televisions, personal computers, tablet devices, and even transparent displays (see-through displays). Furthermore, the polarized luminescent film manufactured using the above naphthalimide compound can emit light using ultraviolet light, making it applicable to displays and media requiring high security.

Claims

1. A polarized light-emitting film containing a water-soluble naphthalimide compound represented by the following formula (1) or a salt thereof, exhibiting polarized light-emitting properties. 【Chemistry 1】 (In formula (1), A represents a naphthalimide skeleton which may have a substituent, X represents a sulfo group or a carboxy group, and n represents an integer of 1 to 3.)

2. 2. The polarized luminescent film according to claim 1, wherein the water-soluble naphthalimide compound or a salt thereof is represented by the following formula (2): 【Chemistry 2】 (In formula (2), R １ represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent; Q represents a hydrogen atom, a halogen atom, a sulfur atom which may have a substituent, an oxygen atom which may have a substituent, or a nitrogen atom which may have a substituent; and n represents an integer of 1 to 3.

3. 2. The polarized luminescent film according to claim 1, wherein the water-soluble naphthalimide compound or a salt thereof is represented by the following formula (3): 【Transformation 3】 (In formula (3), R １ represents a hydrocarbon group having 1 to 12 carbon atoms, and R ２ represents a hydrocarbon group having 1 to 12 carbon atoms.

4. A polarizing film containing a water-soluble naphthalimide compound represented by the following formula (2) or a salt thereof: 【Chemistry 4】 (In formula (2), R 1 represents a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms which may have a substituent; Q represents a hydrogen atom, a halogen atom, a sulfur atom which may have a substituent, an oxygen atom which may have a substituent, or a nitrogen atom which may have a substituent; and n represents an integer of 1 to 3.)

5. A polarizing film as described in claim 4, wherein the water-soluble naphthalimide compound or its salt is represented by the following formula (3): 【Transformation 5】 (In formula (3), R 1 represents a hydrocarbon group having 1 to 12 carbon atoms, and R 2 represents a hydrocarbon group having 1 to 12 carbon atoms.)

6. 4. The polarized luminescent film according to claim 1, further comprising at least one organic dye or fluorescent dye other than the water-soluble naphthalimide compound or its salt.

7. A polarizing film as described in claim 4 or 5, further containing one or more organic dyes or fluorescent dyes other than the water-soluble naphthalimide compound or its salt.

8. 7. The polarized luminescent film according to claim 6, wherein the water-soluble naphthalimide compound or its salt, and optionally the organic dye or fluorescent dye, are contained in a substrate made of a polyvinyl alcohol resin or a derivative thereof.

9. A polarizing film as described in claim 7, which contains the water-soluble naphthalimide compound or its salt, and optionally the organic dye or fluorescent dye, in a substrate made of polyvinyl alcohol resin or a derivative thereof.

10. A polarized light-emitting film, wherein the polarizing film according to any one of claims 4, 5, 7 and 9 exhibits polarized light-emitting properties.

11. A polarized luminescent plate comprising the polarized luminescent film according to any one of claims 1 to 3, 6, 8 and 10, and a transparent protective layer on at least one surface of the polarized luminescent film.

12. A display device comprising the polarized luminescent film according to any one of claims 1 to 3, 6, 8 and 10 or the polarized luminescent plate according to claim 11.

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