Color conversion sheet, light source unit including same, display, and illumination device

Abstract

A color conversion sheet according to one aspect of the present invention is for converting incident light into light having a wavelength different from that of the incident light, and includes at least a color conversion layer containing a binder resin and a compound that emits delayed fluorescence. The amount of solvent in the color conversion layer is 10-30000 mass ppm.

Description

Color conversion sheet, light source unit including same, display and lighting device

[0001] The present invention relates to a color conversion sheet, a light source unit including the same, a display, and a lighting device.

[0002] There has been active research into applying multi-color technology using color conversion methods to liquid crystal displays, organic EL displays, lighting devices, etc. Color conversion refers to converting light emitted from a light emitter into light with a longer wavelength, such as converting blue light into green or red light.

[0003] By forming this composition having color conversion function (hereinafter referred to as color conversion composition) into a sheet and combining it with, for example, a blue light source, it becomes possible to obtain the three primary colors of blue, green, and red from the blue light source, i.e., to obtain white light. A white light source combining such a blue light source with a sheet having color conversion function (hereinafter referred to as color conversion sheet) is used as a light source unit such as a backlight unit, and by combining this light source unit with a liquid crystal driving part and a color filter, it becomes possible to produce a full-color display. Furthermore, a white light source combining a blue light source with a color conversion sheet can also be used directly as a white light source for LED lighting, etc.

[0004] One of the challenges facing liquid crystal displays that utilize a color conversion system is improving color reproducibility and durability. To improve color reproducibility, it is effective to narrow the half-widths of the blue, green, and red emission spectra of the light source unit and increase the color purity of each of the blue, green, and red colors. To solve this problem, for example, color conversion materials containing pyrromethene compounds have been proposed (see, for example, Patent Documents 1 and 2). Furthermore, a technique for improving durability has been proposed in which a light stabilizer is added (see, for example, Patent Document 3), but this technique still results in insufficient durability. Therefore, a light-emitting material having an electron-withdrawing group has been proposed as a technique for improving color reproducibility and durability (see, for example, Patent Document 4).

[0005] JP 2010-61824 A JP 2014-136771 A JP 2019-50381 A International Publication No. 2016 / 190283

[0006] The technology described in Patent Document 4 makes it possible to obtain a color-converting composition that has excellent color reproducibility and excellent durability with little decrease in luminance even when used continuously for a long period of time. However, in response to the recent demand for finer and higher definition, it has been found that color-converting sheets using conventional color-converting compositions have a new problem in that chromaticity changes slightly with long-term use.

[0007] The present invention has been made in view of the above circumstances, and has as its first object to provide a color conversion sheet that has excellent chromaticity durability. The second object of the present invention is to provide a light source unit, a display, and a lighting device that include the color conversion sheet.

[0008] In order to solve the above-mentioned problems and achieve the object, the color conversion sheet of the present invention is a color conversion sheet that converts incident light into light of a wavelength different from the incident light, and is characterized in that it includes a color conversion layer containing at least a compound that emits delayed fluorescence and a binder resin, and the amount of solvent in the color conversion layer is 10 mass ppm or more and 30,000 mass ppm or less.

[0009] Furthermore, the color conversion sheet according to the present invention is characterized in that, in the above invention, the binder resin has, in its molecular structure, a partial structure represented by general formula (3) and a partial structure represented by general formula (4).

[0010] (In general formula (3), Z 1 and Z 2 may be the same or different and are a hydrogen atom or an organic group having 1 to 20 carbon atoms. 1 ~Y 4 may be the same or different and each represents a hydrogen atom or an organic group having 1 to 20 carbon atoms, and Y 1 ~Y 4 At least one of the groups is a group containing an aliphatic cyclic hydrocarbon structure.

[0011] Furthermore, in the color conversion sheet according to the present invention, Y 1 ~Y 4At least one of the groups is a substituted or unsubstituted cyclohexyl group.

[0012] Furthermore, in the color conversion sheet according to the present invention, Y 1 ~Y 4 One of the groups is a substituted or unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0013] Further, in the color conversion sheet according to the present invention, in the above invention, the solvent in the color conversion layer has an SP value of 11.0 (cal / cm 3 ) 1 / 2 More than 20.0 (cal / cm 3 ) 1 / 2 It is characterized by having the following functional groups:

[0014] The color conversion sheet according to the present invention is characterized in that, in the above invention, the compound that emits delayed fluorescence is at least one of the following luminescent material (a) and luminescent material (b): luminescent material that, when excited by excitation light having a wavelength in the range of 430 nm to 500 nm, emits light having a peak wavelength observed in the range of 500 nm to less than 580 nm; and luminescent material (b): luminescent material that, when excited by either or both of excitation light having a wavelength in the range of 430 nm to 500 nm or the emission from the luminescent material (a), emits light having a peak wavelength observed in the range of 580 nm to 750 nm.

[0015] Furthermore, the color conversion sheet according to the present invention is characterized in that, in the above invention, the compound that emits delayed fluorescence contains a compound represented by the following general formula (1) or general formula (2):

[0016] In general formula (1) or general formula (2), ring Za, ring Zb, and ring Zc are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl ring having 6 to 30 ring carbon atoms. 1 and Z 2 are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra), or a sulfur atom.1 When R is NRa, the substituent R may be bonded to the ring Za or the ring Zb to form a ring. 2 When R is NRa, the substituent R may be bonded to the ring Z or the ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom having a substituent R) or P=O. E 1 and E 2 are each independently BRa (a boron atom having a substituent Ra), PRa (a phosphorus atom having a substituent Ra), SiRa2 (a silicon atom having two substituents Ra), C=O, P(=O)Ra2 (a phosphine oxide having two substituents Ra), or P(=S)Ra2 (a phosphine sulfide having two substituents Ra), S(=O) or S(=O)2. E 1 When is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra may be bonded to ring Za or ring Zb to form a ring. 2 is BRa, PRa, SiRa2, P(=O)Ra2, or P(=S)Ra2, the substituent Ra may be bonded to ring Za or ring Zc to form a ring. The substituents Ra are each independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

[0017] Further, in the color conversion sheet according to the present invention, in the above invention, the compound emitting delayed fluorescence is a compound represented by the general formula (1), in which E in the general formula (1) is a boron atom, and Z 1 and Z 2 are each independently NRa, or the compound that emits delayed fluorescence is a compound represented by the general formula (2), and E 1 and E 2 are each independently BRa.

[0018] A light source unit according to the present invention includes a light source and the color conversion sheet according to any one of the above aspects of the present invention.

[0019] Furthermore, in the light source unit according to the present invention, in the above invention, the light source is a light emitting diode having a maximum emission wavelength in the range of 400 nm to 500 nm.

[0020] A display according to the present invention is characterized by comprising the light source unit according to the above invention.

[0021] Furthermore, a lighting device according to the present invention is characterized by comprising the light source unit according to the above invention.

[0022] The present invention has the effect of providing a color conversion sheet with excellent chromaticity durability. The color conversion sheet of the present invention can improve durability against chromaticity changes. Furthermore, the light source unit, display, and lighting device of the present invention can improve durability against chromaticity changes by including the color conversion sheet.

[0023] Fig. 1 is a schematic cross-sectional view showing a first example of a color conversion sheet according to an embodiment of the present invention. Fig. 2 is a schematic cross-sectional view showing a second example of a color conversion sheet according to an embodiment of the present invention. Fig. 3 is a schematic cross-sectional view showing a third example of a color conversion sheet according to an embodiment of the present invention. Fig. 4 is a schematic cross-sectional view showing a fourth example of a color conversion sheet according to an embodiment of the present invention.

[0024] Below, we will specifically explain preferred embodiments of the color conversion sheet of the present invention, and the light source unit, display, and lighting device including the same, but the present invention is not limited to the following embodiments and can be implemented with various modifications depending on the purpose and application.

[0025] <Color Conversion Sheet> A color conversion sheet according to an embodiment of the present invention is a color conversion sheet that converts incident light from a light source or other illuminant into light with a wavelength different from that of the incident light, and includes a color conversion layer containing at least a compound that emits delayed fluorescence and a binder resin. In the color conversion sheet, the amount of solvent in the color conversion layer is 10 ppm by mass or more and 30,000 ppm by mass or less. Here, "converting into light with a wavelength different from that of the incident light" preferably converts the incident light into light with a wavelength longer than that of the incident light. Hereinafter, the color conversion sheet according to an embodiment of the present invention may be abbreviated as the color conversion sheet of the present invention.

[0026] The color conversion sheet of the present invention includes a color conversion layer that is a layer made of the color conversion composition described below or a cured product thereof. The cured product of the color conversion composition is preferably included in the color conversion sheet as a layer obtained by curing the color conversion composition (a layer made of the cured product of the color conversion composition). Representative structural examples of the color conversion sheet of the present invention include the following four, for example.

[0027] Fig. 1 is a schematic cross-sectional view showing a first example of a color conversion sheet according to an embodiment of the present invention. As shown in Fig. 1, this first example color conversion sheet 1A is a single-layer sheet composed of a color conversion layer 11. The color conversion layer 11 is a layer made of a cured product of the color conversion composition of the present invention.

[0028] 2 is a schematic cross-sectional view showing a second example of a color conversion sheet according to an embodiment of the present invention. As shown in FIG. 2, this second example of a color conversion sheet 1B is a laminate of a base layer 10 and a color conversion layer 11. In this structural example of color conversion sheet 1B, the color conversion layer 11 is laminated on the base layer 10.

[0029] 3 is a schematic cross-sectional view showing a third example of a color conversion sheet according to an embodiment of the present invention. As shown in FIG. 3, this third example of a color conversion sheet 1C is a laminate of multiple base material layers 10 and a color conversion layer 11. In this structural example of color conversion sheet 1C, the color conversion layer 11 is sandwiched between multiple base material layers 10.

[0030] 4 is a schematic cross-sectional view showing a fourth example of a color conversion sheet according to an embodiment of the present invention. As shown in FIG. 4, this fourth example color conversion sheet 1D is a laminate of multiple base layers 10, a color conversion layer 11, and multiple barrier films 12. In this structural example of color conversion sheet 1D, the color conversion layer 11 is sandwiched between multiple barrier films 12, and this laminate of the color conversion layer 11 and the multiple barrier films 12 is further sandwiched between multiple base layers 10. That is, color conversion sheet 1D may have a barrier film 12 as shown in FIG. 4 to prevent deterioration of the color conversion layer 11 due to oxygen, moisture, or heat.

[0031] The thickness of the color conversion sheet of the present invention is preferably 30 μm or more and 300 μm or less. Here, the thickness of the color conversion sheet refers to the combined thickness of all layers included in the color conversion sheet, and refers to the film thickness (average film thickness) measured based on Method A of Measuring Thickness by Mechanical Scanning in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods. By making the thickness of the color conversion sheet of the present invention 30 μm or more, the toughness of the color conversion sheet can be improved. Furthermore, by making the thickness of the color conversion sheet of the present invention 300 μm or less, cracking of the color conversion sheet can be suppressed.

[0032] (Color conversion layer) In the present invention, the color conversion layer (for example, color conversion layer 11 shown in Figures 1 to 4) contains a compound that emits delayed fluorescence (hereinafter, may be abbreviated as "delayed fluorescence material"), a binder resin, and a trace amount of solvent. The trace amount of solvent is defined as the residual solvent in the color conversion layer.

[0033] The thickness of the color conversion layer is not particularly limited, but is preferably 10 μm or more and 1000 μm or less. The lower limit of the thickness of the color conversion layer is more preferably 30 μm or more. The upper limit of the thickness of the color conversion layer is more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. The thickness of the color conversion layer in the present invention refers to the film thickness (average film thickness) measured in accordance with Method A, a thickness measurement method by mechanical scanning, in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods.

[0034] The color conversion layer as described above can be formed by applying a color conversion composition prepared by the method described below onto an underlayer such as a substrate layer or a barrier film, and then drying it.

[0035] In the color conversion sheet of the present invention, the color conversion layer may be one layer or two or more layers. In addition to the delayed fluorescent material and binder resin described above, the color conversion layer may contain other components (additives) such as a light stabilizer, an antioxidant, a processing and heat stabilizer, a light resistance stabilizer such as an ultraviolet absorber, scattering particles, silicone fine particles, and a silane coupling agent.

[0036] (Compounds that Emit Delayed Fluorescence) Compounds that emit delayed fluorescence (delayed fluorescent materials) are discussed on pages 87-103 of "State-of-the-Art Organic EL" (edited by Adachi Chinaya and Fujimoto Hiroshi, published by CMC Publishing). The document explains that by bringing the energy levels of the singlet excited state and triplet excited state of an emitting material closer together, reverse energy transfer from the triplet excited state, which normally has a low transition probability, to the singlet excited state occurs with high efficiency, resulting in the appearance of thermally activated delayed fluorescence (TADF). Furthermore, Figure 5 in the document explains the mechanism by which delayed fluorescence occurs. Delayed fluorescence emission can be confirmed by transient photoluminescence (PL) measurements.

[0037] It has also been reported that matching the energy levels of the singlet excited state and triplet excited state of an emissive material can speed up the reverse energy transfer from the triplet excited state to the singlet excited state (Nature Photonics volume 14, pages 643-49 (2020)). Furthermore, active research is being conducted on compounds whose triplet excited state energy level is higher than that of the singlet excited state of the emissive material.

[0038] In this specification, a compound that emits fluorescence by transitioning from a triplet excited state to a singlet excited state with high efficiency, including a compound that exhibits thermally activated delayed fluorescence, is referred to as a "compound that emits delayed fluorescence" or abbreviated as a "delayed fluorescent material."

[0039] Typically, fluorescent light is emitted from a singlet excited state generated after photoexcitation of a light-emitting material, and the triplet excited state of the light-emitting material generated by intersystem crossing is thermally deactivated in a room temperature environment. Therefore, fluorescence is not emitted from the triplet excited state of the light-emitting material. On the other hand, as described above, even if a triplet excited state is generated in a delayed fluorescent material, it is quickly converted to a singlet excited state and then emits fluorescence. Therefore, the triplet excited state, which cannot contribute to light emission in ordinary fluorescent materials, can also contribute to fluorescent light emission. Therefore, highly efficient light emission can be obtained.

[0040] Delayed fluorescent materials have the characteristic of being less likely to generate singlet oxygen because their triplet excited state quickly converts to a singlet excited state. It has been discovered that this characteristic prevents degradation of the luminescent material, suppresses changes in chromaticity over time, and improves durability against chromaticity changes. This mechanism will be explained in detail below. In the following, durability against chromaticity changes may be abbreviated as "chromaticity durability" or simply "durability."

[0041] First, we will explain the degradation mechanism of luminescent materials. The chromaticity change of a color-changing composition is caused by degradation of the luminescent material. This degradation of the luminescent material is caused by singlet oxygen. Singlet oxygen is an oxygen molecule in a singlet state in which the two electrons occupying the π* orbital (antibonding π orbital) of the oxygen molecule's molecular orbital have different spin directions, i.e., an excited state in which the total spin quantum number is zero. This excited state exists in two states: the Σ1 state, in which each of the two π* orbitals is occupied by an electron with a different spin direction, and the Δ1 state, in which only one of the π* orbitals is occupied by two electrons with a different spin direction. In the Δ1 state, the vacant electron orbital of singlet oxygen has strong electrophilicity and strong oxidizing power. Therefore, singlet oxygen is thought to cause oxidative degradation of the luminescent material.

[0042] Next, we will discuss the mechanism by which singlet oxygen is generated. It is thought that singlet oxygen is unlikely to be generated by direct photoexcitation of ground-state triplet oxygen. This is because the transition from ground-state triplet oxygen to excited-state singlet oxygen is a spin-forbidden transition, and therefore the transition probability is extremely low.

[0043] Therefore, it is believed that the generation of singlet oxygen in the color-changing composition is due to dye sensitization. In other words, it is believed that singlet oxygen is generated by the exchange of electrons and energy between the light-emitting material in the triplet excited state and triplet oxygen molecules in the ground state. The generation mechanism is believed to be as follows.

[0044] First, photoexcitation causes the luminescent material to transition from the singlet ground state to the singlet excited state. Furthermore, a portion of the luminescent material transitions from the singlet excited state to the triplet excited state through intersystem crossing. The transition from the triplet excited state to the singlet ground state of the generated luminescent material is a spin-forbidden transition, so the transition probability is usually low and the triplet excited state has a long lifetime. However, when triplet oxygen in the ground state coexists, the spin forbidden state is lifted by the excitation from the ground state triplet oxygen to the excited singlet oxygen, allowing the luminescent material to rapidly deactivate from the triplet excited state to the singlet ground state. This mechanism is called the Dexter mechanism (electron exchange mechanism).

[0045] The Dexter mechanism requires electron exchange via intermolecular wave function overlap, which is thought to require direct collision between an energy donor molecule (in this case, a light-emitting material in the triplet excited state) and an energy acceptor molecule (in this case, triplet oxygen in the ground state).

[0046] As mentioned above, delayed fluorescent materials have the property that the triplet excited state is quickly converted to the singlet excited state, i.e., the lifetime of the triplet excited state is short, which reduces the probability of direct collision between the light-emitting material in the triplet excited state and triplet oxygen in the ground state, making it difficult for singlet oxygen to be generated.

[0047] In order to design a molecule so that the energy levels of the singlet excited state and the triplet excited state are close to each other, it is effective to bond an electron donor skeleton and an electron acceptor skeleton within the same molecule. By doing so, the HOMO (highest occupied molecular orbital) orbital and the LUMO (lowest unoccupied molecular orbital) orbital can be separated within the molecule. The electron donor skeleton and the electron acceptor skeleton may be bonded directly or via a linking group. In this case, the linking group is preferably a skeleton containing an aromatic hydrocarbon.

[0048] Examples of electron donor skeletons include skeletons having an amine nitrogen atom. Among them, skeletons containing diarylamine or triarylamine, skeletons containing carbazole, skeletons containing benzocarbazole, skeletons containing indolocarbazole, skeletons containing phenoxazine, and skeletons containing phenothiazine are preferred. Among these, skeletons containing carbazole, skeletons containing benzocarbazole, skeletons containing indolocarbazole, and skeletons containing phenoxazine are more preferred, and skeletons containing carbazole and skeletons containing phenoxazine are even more preferred.

[0049] On the other hand, examples of electron-accepting skeletons include skeletons containing electron-withdrawing substituents (i.e., electron-withdrawing groups). Electron-withdrawing groups, also called electron-accepting groups, are atomic groups that attract electrons from substituted atomic groups due to inductive effects or resonance effects in organic electronics theory. Examples of electron-withdrawing groups include those whose Hammett's rule substituent constant (σp(para)) takes a positive value. The Hammett's rule substituent constant (σp(para)) can be cited from the Revised 5th Edition of the Basic Chemistry Handbook (page II-380). It should be noted that, although there are examples in which phenyl groups also take a positive value, phenyl groups are not included in the electron-withdrawing groups of the present application.

[0050] Examples of the electron-withdrawing group include -F (σp: +0.20), -Cl (σp: +0.28), -Br (σp: +0.30), -I (σp: +0.30), and -COR. 12 (σp:R 12 is an ethyl group, -CONH2 (σp: +0.45), -COR 12 (σp:R 12 is a methyl group, -CF3 (σp: +0.49), -SO2R 12 (σp:R 12 is a methyl group), -NO2 (σp: +0.69), etc. 12each independently represents a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 1 to 30 carbon atoms. Specific examples of each of these groups include the same examples as the substituents in the compounds represented by general formula (1) or (2) described below.

[0051] Among the skeletons containing an electron-withdrawing group, preferred are a skeleton containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, a skeleton containing a fluorinated substituent, a skeleton containing a cyano group, a skeleton containing a carbonyl group, a skeleton containing a sulfoxide or disulfoxide, and a skeleton containing a phosphine oxide group. Among these, from the viewpoint of the stability of the delayed fluorescence material, a skeleton containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, a skeleton containing a fluorinated substituent, and a skeleton containing a cyano group are more preferred.

[0052] Among the skeletons containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, specifically, a skeleton containing pyridine, pyrimidine, pyrazine, triazine, quinoline, quinoxaline, quinazoline, or phenanthroline is preferred. Among these, a skeleton containing pyrimidine, triazine, quinoxaline, or quinazoline is more preferred, and a skeleton containing triazine is even more preferred.

[0053] Among the skeletons containing fluorinated substituents, skeletons containing fluorinated aryl groups or fluoroalkyl groups are more preferred.As the skeletons containing fluorinated aryl groups, fluorinated benzene rings are preferred, and specifically, skeletons containing fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene or pentafluorobenzene are more preferred.As the skeletons containing fluoroalkyl groups, skeletons containing benzene rings substituted with trifluoromethyl groups are preferred, and among these, skeletons containing mono(trifluoromethyl)benzene or bis(trifluoromethyl)benzene are more preferred.

[0054] Among the skeletons having a cyano group, skeletons containing cyanobenzene, dicyanobenzene, and tricyanobenzene are more preferred.

[0055] Examples of compounds in which the above-described electron donor skeleton and electron acceptor skeleton are bonded are shown below, but the compounds are not particularly limited to these. Note that the compounds shown here are known from previous literature to emit delayed fluorescence.

[0056]

[0057] In addition to the above-described compounds in which an electron donor skeleton and an electron acceptor skeleton are bonded, compounds represented by the following general formula (1) or (2) are also preferred as delayed fluorescent materials.

[0058]

[0059] In general formula (1) or general formula (2), ring Za, ring Zb, and ring Zc each independently represent a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl ring having 6 to 30 ring carbon atoms.

[0060] In general formula (1), Z 1 and Z 2 are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra), or a sulfur atom. 1 When R is NRa, the substituent R may be bonded to the ring Za or the ring Zb to form a ring. 2 When R is NRa, the substituent R may be bonded to the ring Z or the ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom having a substituent R), or P=O.

[0061] In the general formula (2), E 1 and E 2are each independently BRa (a boron atom having a substituent Ra), PRa (a phosphorus atom having a substituent Ra), SiRa2 (a silicon atom having two substituents Ra), C=O, P(=O)Ra2 (a phosphine oxide having two substituents Ra), or P(=S)Ra2 (a phosphine sulfide having two substituents Ra), S(=O) or S(=O)2. E 1 When is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra may be bonded to ring Za or ring Zb to form a ring. 2 When is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra may be bonded to ring Za or ring Zc to form a ring.

[0062] The substituents Ra are each independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

[0063] In all of the above groups, hydrogen may be deuterium. This also applies to the compounds or partial structures thereof described below. In the following description, for example, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms refers to an aryl group having 6 to 40 carbon atoms, including the number of carbon atoms contained in the substituents substituted on the aryl group. The same applies to other substituents that specify the number of carbon atoms.

[0064] The term "unsubstituted" in the context of "substituted or unsubstituted" means that a hydrogen atom or a deuterium atom has been substituted. The same applies to the term "substituted or unsubstituted" in the compounds or partial structures thereof described below.

[0065] In addition, in all of the above groups, the substituent when substituted is an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen atom, a cyano group, an aldehyde group, a carbonyl group, a carboxyl group, an oxycarbonyl group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, or a phosphine oxide group. In addition, these substituents may be further substituted with the above-mentioned substituents.

[0066] The alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group, which may or may not have a substituent. When the alkyl group is substituted, the additional substituent is not particularly limited, and examples thereof include an alkyl group, a halogen atom, an aryl group, and a heteroaryl group, and this point is also applicable to the following description. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, more preferably 1 to 8, from the viewpoints of availability and cost.

[0067] The cycloalkyl group refers to a saturated alicyclic hydrocarbon group, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, or the like, which may or may not have a substituent. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0068] The heterocyclic group refers to an aliphatic ring having atoms other than carbon atoms in the ring, such as a pyran ring, a piperidine ring, or a cyclic amide, which may or may not have a substituent. The number of carbon atoms in the heterocyclic group is not particularly limited, but is preferably in the range of 2 to 20.

[0069] The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may or may not have a substituent. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0070] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which may or may not have a substituent. The number of carbon atoms in the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0071] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may or may not have a substituent. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0072] The alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether bond, such as a methoxy group, an ethoxy group, or a propoxy group, and this aliphatic hydrocarbon group may or may not have a substituent. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0073] An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The hydrocarbon group of the alkylthio group may or may not have a substituent. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0074] The aryl ether group refers to a functional group in which an aromatic hydrocarbon group is bonded via an ether bond, such as a phenoxy group, and the aromatic hydrocarbon group may or may not have a substituent. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0075] An aryl thioether group is an aryl ether group in which the oxygen atom of the ether bond is substituted with a sulfur atom. The aromatic hydrocarbon group in the aryl thioether group may or may not have a substituent. The number of carbon atoms in the aryl thioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0076] The aryl group refers to an aromatic hydrocarbon group such as a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group. Among these, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, an anthracenyl group, a pyrenyl group, a fluoranthenyl group, or a triphenylenyl group is preferred. The aryl group may or may not have a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 30.

[0077] Examples of heteroaryl groups include pyridyl, furanyl, thienyl, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidyl, pyridazinyl, triazinyl, naphthyridinyl, cinnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothienyl, indolyl, dibenzofuranyl, dibenzothienyl, carbazolyl, and benzocarbazolyl. It refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, such as a benzoyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group. However, a naphthyridinyl group refers to a 1,5-naphthyridinyl group, a 1,6-naphthyridinyl group, a 1,7-naphthyridinyl group, a 1,8-naphthyridinyl group, a 2,6-naphthyridinyl group, or a 2,7-naphthyridinyl group. The heteroaryl group may or may not have a substituent. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably in the range of 2 or more and 40 or less, and more preferably 2 or more and 30 or less.

[0078] The term "halogen" refers to an atom selected from fluorine, chlorine, bromine, and iodine. The carbonyl group, carboxyl group, oxycarbonyl group, and carbamoyl group may or may not have a substituent. Examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, and these substituents may be further substituted.

[0079] The amino group is a substituted or unsubstituted amino group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, and a branched alkyl group. As the aryl group and the heteroaryl group, a phenyl group, a naphthyl group, a pyridyl group, and a quinolinyl group are preferred. These substituents may be further substituted. The number of carbon atoms is not particularly limited, but is preferably in the range of 2 to 50, more preferably 6 to 40, and particularly preferably 6 to 30.

[0080] The silyl group refers to, for example, alkylsilyl groups such as trimethylsilyl group, triethylsilyl group, tert-butyldimethylsilyl group, propyldimethylsilyl group, and vinyldimethylsilyl group, and arylsilyl groups such as phenyldimethylsilyl group, tert-butyldiphenylsilyl group, triphenylsilyl group, and trinaphthylsilyl group. The substituent on silicon may be further substituted. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0081] The siloxanyl group refers to a silicon compound group via an ether bond, such as a trimethylsiloxanyl group. The substituent on the silicon may be further substituted. The boryl group refers to a substituted or unsubstituted boryl group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, a branched alkyl group, an aryl ether group, an alkoxy group, and a hydroxyl group. Among these, an aryl group and an aryl ether group are preferred.

[0082] The phosphine oxide group is —P(═O)R 10 R 11 The R of the phosphine oxide group is a group represented by the formula: 10 R 11 is selected from the group shown below. 10 , R 11 may be the same or different, and are selected from the group of candidates consisting of a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, a heteroaryl group, a halogen atom, a cyano group, an aldehyde group, a carbonyl group, a carboxyl group, an acyl group, an ester group, an amido group, a carbamoyl group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, a sulfo group, a sulfonyl group, a phosphine oxide group, and a fused ring or aliphatic ring formed between adjacent substituents.

[0083] R 10 R 11is a substituted or unsubstituted aryl group, the aryl group is preferably a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, or an anthracenyl group, more preferably a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group, even more preferably a phenyl group, a biphenyl group, or a terphenyl group, and particularly preferably a phenyl group.

[0084] When each of the substituents is further substituted with an aryl group, the aryl group is preferably a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, or an anthracenyl group, more preferably a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group, and particularly preferably a phenyl group.

[0085] R 10 R 11 is a substituted or unsubstituted heteroaryl group, the heteroaryl group is preferably a pyridyl group, a furanyl group, a thienyl group, a quinolinyl group, a pyrimidyl group, a triazinyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a dibenzofuranyl group, a dibenzothienyl group, a carbazolyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group, more preferably a pyridyl group, a furanyl group, a thienyl group, or a quinolinyl group, and particularly preferably a pyridyl group.

[0086] When each substituent is further substituted with a heteroaryl group, the heteroaryl group is preferably a pyridyl group, a furanyl group, a thienyl group, a quinolinyl group, a pyrimidyl group, a triazinyl group, a benzofuranyl group, a benzothienyl group, an indolyl group, a dibenzofuranyl group, a dibenzothienyl group, a carbazolyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group, more preferably a pyridyl group, a furanyl group, a thienyl group, or a quinolinyl group, and particularly preferably a pyridyl group.

[0087] In the compound represented by general formula (1) or (2), any two adjacent substituents may be bonded to each other to form a conjugated or non-conjugated fused ring. The fused ring may contain, in addition to carbon, an element selected from nitrogen, oxygen, sulfur, phosphorus, and silicon. The fused ring may further be fused with another ring.

[0088] Examples of the substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms in ring Za, ring Zb, and ring Zc include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, a phenanthrene ring, a chrysene ring, an anthracene ring, and a pyrene ring. Of these, a benzene ring is preferred from the viewpoint of ensuring solubility. Furthermore, examples of the heteroaryl ring having 6 to 30 ring carbon atoms include aromatic heteroaryl ring structures such as a pyridine ring, a quinoline ring, and a phenanthroline ring. Of these, a pyridine ring is preferred from the viewpoints of ease of raw material availability and difficulty of synthesis.

[0089] The substituent Ra is preferably a group having 6 to 40 carbon atoms including the substituent. The substituent Ra is more preferably a substituted or unsubstituted aryl group. Examples of the substituted or unsubstituted aryl group include a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted phenanthrenyl group. Among these, a substituted or unsubstituted phenyl group is more preferred.

[0090] The substituent Ra is preferably a group having 6 to 40 carbon atoms including the substituent, and more preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl group.

[0091] Z in general formula (1) 1 and Z 2 is preferably an oxygen atom or NRa, because the π-conjugated system of the compound represented by general formula (1) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0092] Furthermore, E in the general formula (1) is preferably a boron atom, and E in the general formula (2) is preferably a 1 and E 2 is preferably BRa, because the π-conjugated system of the compound represented by general formula (1) or general formula (2) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0093] That is, the delayed fluorescent material is a compound represented by general formula (1), in which E in general formula (1) is a boron atom and Z 1 and Z 2 Alternatively, the delayed fluorescent material is a compound represented by general formula (2), and E in general formula (2) is preferably an oxygen atom or NRa. 1 and E 2 are each independently BRa.

[0094] Furthermore, ring Za, ring Zb, and ring Zc are preferably benzene rings, because the π-conjugated system of the compound represented by general formula (1) or general formula (2) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0095] The compound represented by general formula (1) or general formula (2) is a molecule that can separate the HOMO orbital and the LUMO orbital by the multiple resonance effect by optimally arranging an electron-donating amine nitrogen atom and an electron-accepting boron atom, as described in, for example, the literature Adv. Mater., 2016, 28, 2777-2781. From the viewpoint of clearly separating the HOMO orbital and the LUMO orbital and bringing the singlet excited state and the triplet excited state closer to each other, thereby facilitating the emission of delayed fluorescence, in general formula (1), E is a boron atom with strong electron-accepting properties, and Z 1 and Z 2 In other words, when the delayed fluorescent material is a compound represented by general formula (1), E is a boron atom and Z1 and Z 2 is preferably NRa.

[0096] In addition, the emission spectrum of a compound represented by general formula (1) or general formula (2) is sharper than that of a compound in which an electron donor skeleton and an electron acceptor skeleton are bonded due to the multiple resonance effect of the compound. Therefore, when the delayed fluorescent material is a compound represented by general formula (1) or general formula (2), light emission with high color purity can be obtained. That is, compounds represented by general formula (1) or general formula (2) are advantageous for improving the color gamut of displays, and are therefore preferred as delayed fluorescent materials. In addition, in compounds represented by general formula (1) or general formula (2), rings Za, Zb, and Zc are present around the E atom in general formula (1) or general formula (2), where the LUMO orbital is mainly localized, so that the LUMO orbital can be delocalized from the E atom to each ring. By delocalizing the LUMO orbital, the multiple resonance effect works efficiently, resulting in light emission with higher color purity. Note that the E atom is the E atom in general formula (1), and the E atom in general formula (2). 1 and E 2 are the atoms of

[0097] Furthermore, it is more preferable that the substituent Ra in the general formula (1) or the general formula (2) forms a ring structure bonded to at least one of the rings Za, Zb, and Zc, because the substituent Ra is bonded to at least one of the rings Za, Zb, and Zc, and thus the substituent Ra is bonded to at least one of the rings Za, Zb, and Zc, and thus the substituent Ra is bonded to at least one of the rings Za, Zb, and Zc, and thus forms a ring structure bonded to at least one of the rings Za, Zb, and Zc, and thus forms at least one of the rings Za, Zb, and Zc, and the substituent Ra is bonded to at least one of the rings Za, Zb, and Zc, and thus forms at least one of the rings Zc, Zb, and Zc, Zc, Zc, Zb, and Zc, Zc, Zc, Zb, and Zc, Zc, Zc, Zc, Zb ... 1 and E 2 This is because it is expected that the steric protection effect of E and E will be further enhanced, and the effect of suppressing the decrease in fluorescence quantum yield will be further improved. 1 and E 2 From the viewpoint of the steric protection effect, it is more preferable that the compound represented by the general formula (1) is a compound represented by the general formula (2).

[0098] Examples of compounds represented by general formula (1) or general formula (2) are shown below, but the compounds are not particularly limited to these.

[0099]

[0100] The delayed fluorescent material is preferably at least one of the following luminescent material (a) and luminescent material (b). That is, at least one of the luminescent material (a) and luminescent material (b) is preferably a compound that emits delayed fluorescence.

[0101] The luminescent material (a) is a luminescent material that exhibits luminescence with a peak wavelength observed in the range of 500 nm to less than 580 nm when excited with excitation light with a wavelength range of 430 nm to 500 nm. The luminescent material (b) is a luminescent material that exhibits luminescence with a peak wavelength observed in the range of 580 nm to 750 nm when excited with either or both of excitation light with a wavelength range of 430 nm to 500 nm and the luminescence from the luminescent material (a). Hereinafter, luminescence observed with a peak wavelength range of 500 nm to less than 580 nm will be referred to as "green luminescence," and luminescence observed with a peak wavelength range of 580 nm to 750 nm will be referred to as "red luminescence."

[0102] (Solvent) In the color conversion sheet of the present invention, the color conversion layer contains a trace amount of residual solvent, as described above. From the viewpoint of improving the durability of the color conversion sheet, the lower limit of the amount of residual solvent in the color conversion layer is 10 ppm by mass or more, preferably 100 ppm by mass or more, and more preferably 500 ppm by mass or more. The reason why the durability of the color conversion sheet is improved when the amount of residual solvent is equal to or more than the above lower limit is thought to be as follows.

[0103] The delayed fluorescent material in the triplet excited state contained in the color conversion layer includes charge-delocalized excited species in which holes, which are positive charges, can move freely within the molecule, and charge-localized excited species and neutral excited species in which holes cannot move freely within the molecule.

[0104] The reverse conversion from the triplet excited state to the singlet excited state of a delayed fluorescent material occurs when the energy levels of a neutral excited species, which is a type of triplet excited state, and an excited species in a singlet excited state are close. This is in accordance with the law of quantum mechanics, which states that the conversion or reverse conversion between a singlet excited state and a triplet excited state can only occur between excited species with different charge distributions. In other words, whether reverse conversion occurs at room temperature depends on the energy difference between the excited species when the charge distributions in the singlet excited state and the triplet excited state are different.

[0105] Here, in order to bring the energy of the excited species in the singlet excited state closer to the energy of the neutral excited species in the triplet excited state, it is preferable that the energy level of the neutral excited species in the triplet excited state is high. To achieve this, it is preferable to contain a solvent in the color conversion layer to reduce the stabilization of the neutral excited species in the triplet excited state due to the solvent effect. The solvent effect refers to stabilizing the energy state of the light-emitting material by containing a solvent. Generally, the more polar the molecule, the greater the effect of stabilizing the energy state due to the solvent effect.

[0106] The excitation energy of the light-emitting material is stabilized by the solvent effect, but when the color conversion layer contains a solvent, the neutral excited species, which has the lowest polarity among the excited species in the triplet excited state, is less susceptible to the stabilization of excitation energy due to the solvent effect. Therefore, the difference in energy level between the excited species in the singlet excited state and the neutral excited species in the triplet excited state becomes smaller, thereby improving the durability of the color conversion sheet.

[0107] In addition, from the viewpoint of suppressing oxidative degradation of the delayed fluorescent material, the upper limit of the amount of residual solvent in the color conversion layer is 30,000 mass ppm or less, preferably 10,000 mass ppm or less, and more preferably 5,000 mass ppm or less. When the amount of residual solvent is below the upper limit, the fluidity of the resin in the color conversion layer is reduced, thereby reducing the probability of contact between the luminescent material in the color conversion layer and singlet oxygen, thereby reducing the reaction rate of the luminescent material that is oxidatively deteriorated due to contact with singlet oxygen. The amount of residual solvent in the color conversion layer can be measured by gas chromatography.

[0108] To incorporate residual solvent into the color conversion layer, for example, the color conversion layer is dried to adjust the solvent content in the color conversion layer to a very small amount. Drying the color conversion layer can be performed using a common heating device such as a hot air dryer or an infrared dryer. In this case, the heating temperature is preferably 60 to 200°C, and the heating time is preferably 2 minutes to 4 hours. To adjust the amount of residual solvent in the color conversion layer to fall within the above-mentioned upper and lower limits, the heating temperature is more preferably 100 to 200°C, and the heating time is more preferably 2 minutes to 2 hours. Furthermore, when drying the color conversion layer, it is also possible to heat-cure the color conversion layer in stages using a method such as step curing.

[0109] Furthermore, from the viewpoint of further improving the durability of the color conversion sheet, the remaining solvent in the color conversion layer preferably has a functional group with an SP value of 11.0 or more and 20.0 or less. When the remaining solvent has a functional group with such an SP value range, the above-mentioned solvent effect is enhanced, thereby promoting the reverse conversion from the triplet excited state to the singlet excited state of the delayed fluorescent material, thereby further improving the durability of the color conversion sheet. The SP value of the functional group possessed by the remaining solvent can be calculated using the Fedors method from the following formula: SP value (δ) = (E / V) 1 / 2

[0110] In the above formula for the SP value, E represents the molar heat of vaporization (cal / mol), and V represents the molar volume (cm 3 That is, the unit of the SP value of the functional group of the residual solvent in the color conversion layer is (cal / cm 3 ) 1 / 2 is.

[0111] Furthermore, for E and V in the above formula for the SP value, the molar heat of vaporization (E) and molar volume (V) of the atomic group described in "POLYMER ENGINEERING AND SCIENCE, 1974, Vol. 14, No. 2, ROBERT F. FEDORS, (pp. 151-153)" can be used.

[0112] Examples of solvents contained in the color conversion sheet of the present invention include cyclohexane, hexane, toluene, 1-methoxy-2-propanol, 2-propanol, ethyl acetate, ethanol, methyl ethyl ketone, and acetone. The color conversion sheet of the present invention may contain two or more of these solvents. Tables 1-1 and 1-2 show the functional groups and SP values ​​of the solvents.

[0113]

[0114]

[0115] Among these solvents, from the viewpoint of improving the durability of the color conversion sheet, solvents with high polarity are preferred, such as toluene, 1-methoxy-2-propanol, 2-propanol, ethyl acetate, ethanol, methyl ethyl ketone, and acetone. Furthermore, from the viewpoint of improving the durability of the color conversion sheet, solvents having a functional group with an SP value of 11.0 or more and 20.0 or less are more preferred. Specifically, 1-methoxy-2-propanol, ethyl acetate, methyl ethyl ketone, and acetone are more preferred. In particular, ethyl acetate is even more preferred because it does not affect the deterioration of the delayed fluorescence material and makes it easy to adjust the amount of solvent remaining in the color conversion layer after drying to 10 ppm by mass or more and 30,000 ppm by mass or less.

[0116] (Binder Resin) The binder resin forms a continuous phase and may be any material that is excellent in moldability, transparency, heat resistance, etc. Examples of binder resins include known materials such as photocurable resist materials having reactive vinyl groups, such as acrylic acid-based, methacrylic acid-based, polyvinyl cinnamate-based, and cyclic rubber-based materials, epoxy resins, silicone resins (including organopolysiloxane cured products (crosslinked products) such as silicone rubber and silicone gel), urea resins, fluororesins, polycarbonate resins, acrylic resins, urethane resins, melamine resins, polyvinyl resins, polyamide resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, aliphatic ester resins, aromatic ester resins, aliphatic polyolefin resins, and aromatic polyolefin resins. Copolymer resins of these may also be used as the binder resin. By appropriately designing these resins, a binder resin useful for the color conversion sheet of the present invention and the color conversion composition used therein (hereinafter sometimes referred to as the color conversion composition of the present invention) can be obtained. Among these resins, thermoplastic resins are more preferred because of the ease of the sheet formation process. Among thermoplastic resins, epoxy resins, silicone resins, acrylic resins, ester resins, olefin resins, or mixtures thereof can be preferably used from the viewpoints of transparency, heat resistance, etc. Furthermore, from the viewpoint of durability, particularly preferred thermoplastic resins are acrylic resins, ester resins, and cycloolefin resins.

[0117] Suitable specific examples of binder resins include those described in, for example, WO 2016 / 190283, WO 2017 / 61337, WO 2018 / 43237, and WO 2019 / 188019.

[0118] Furthermore, the binder resin is preferably a resin containing, in its molecular structure, a partial structure represented by general formula (3) and a partial structure represented by general formula (4). In particular, in the color conversion sheet of the present invention, the binder resin in the color conversion layer contains, in its molecular structure, a partial structure represented by general formula (3) and a partial structure represented by general formula (4), and the residual solvent in the color conversion layer has an SP value of 11.0 (cal / cm 3 )1 / 2 More than 20.0 (cal / cm 3 ) 1 / 2 It is preferable that the compound has the following functional groups.

[0119]

[0120] In general formula (3), Z 1 and Z 2 may be the same or different and are a hydrogen atom or an organic group having 1 to 20 carbon atoms. 1 ~Y 4 may be the same or different and each represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. 1 ~Y 4 At least one of the groups is a group containing an aliphatic cyclic hydrocarbon structure.

[0121] The delayed fluorescent material contained in the color conversion sheet of the present invention is excited by light, and since the delayed fluorescent material in the excited state is highly reactive, when the delayed fluorescent materials in the excited state are close to each other, the deterioration of the delayed fluorescent material is promoted. Therefore, in order to improve the durability of the delayed fluorescent material contained in the color conversion sheet, it is preferable that the delayed fluorescent material is well dispersed in the binder resin without agglomeration.

[0122] In order to make the delayed fluorescent material well dispersed in the binder resin, it is preferable that the binder resin in the color conversion layer has the partial structure that is highly compatible with the delayed fluorescent material and the partial structure that is poorly compatible with the delayed fluorescent material.The more preferred form of this binder resin is preferably the copolymer that randomly comprises the partial structure that is highly compatible with the delayed fluorescent material and the partial structure that is poorly compatible with the delayed fluorescent material.

[0123] The delayed fluorescent material contained in the color conversion sheet of the present invention has the characteristic that it has good compatibility with the partial structure represented by general formula (3) in the molecular structure of the binder resin, but not good compatibility with the partial structure represented by general formula (4). Therefore, by having the binder resin have both the partial structure represented by general formula (3) and the partial structure represented by general formula (4), it is possible to well disperse a light-emitting material such as a delayed fluorescent material in the binder resin within the color conversion layer. As a result, it is possible to achieve high durability of the color conversion sheet. Note that this effect is greater when the delayed fluorescent material is an organic light-emitting material.

[0124] The delayed fluorescent material contained in the color conversion sheet of the present invention may be subjected to radical oxidation by radicals derived from functional groups contained in the binder resin molecule or hygroscopic moisture, resulting in decomposition or deterioration. Therefore, it is preferable that the binder resin in the color conversion layer is a resin with excellent heat resistance. From the viewpoint of improving the heat resistance of the binder resin, in the partial structure represented by general formula (3) in the binder resin, Z 1 is preferably a hydrogen atom or a methyl group, more preferably a methyl group.

[0125] In order to improve the heat resistance of the binder resin, the partial structure represented by general formula (3) in the binder resin may contain Z 2 is preferably a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, or a heteroaryl group. These groups may be further substituted with the above-mentioned substituents. Among these, Z in the partial structure represented by general formula (3) is 2 is more preferably a methyl group from the viewpoints of availability and cost.

[0126] The explanations of the "alkyl group" in the binder resin and the explanation of "unsubstituted" in the case of "substituted or unsubstituted" are the same as those in the explanation of the delayed fluorescence material.

[0127] In order to improve the heat resistance of the binder resin, the partial structure represented by the general formula (4) in the binder resin may contain Y 1 ~Y 4 is preferably a hydrogen atom, an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, an aryl group, or a heteroaryl group, and these groups may be further substituted with the above-mentioned substituents.

[0128] However, Y in the general formula (4) 1 ~Y 4 At least one of the groups is a group containing an alicyclic hydrocarbon structure. Examples of the alicyclic hydrocarbon structure include a substituted or unsubstituted saturated cyclic hydrocarbon (cycloalkyl) structure and an unsaturated cyclic hydrocarbon (cycloalkenyl) structure. Among these, from the viewpoint of durability, a saturated cyclic hydrocarbon (cycloalkyl) structure is preferred. The number of carbon atoms constituting such an alicyclic hydrocarbon structure is not particularly limited, but is usually preferably 4 to 30, more preferably 5 to 20, and even more preferably 5 to 15. By ensuring that the number of carbon atoms constituting the alicyclic hydrocarbon structure is within the above range, high durability can be obtained while ensuring compatibility between the partial structure represented by general formula (4) in the binder resin and the light-emitting material.

[0129] Specific examples of saturated cyclic hydrocarbon (cycloalkyl) structures include structures in which the aromatic ring moiety of a polymer of an aromatic vinyl monomer such as styrene, α-methylstyrene, β-methylstyrene, p-hydroxystyrene, p-methylstyrene, p-ethylstyrene, p-isopropylstyrene, p-divinylbenzene, alkoxystyrene, chlorostyrene, stilbene, 1-vinylnaphthalene, diphenylethylene, triphenylethylene, tetraphenylethylene, 4-vinylbiphenyl, etc. It is also possible to use a vinyl monomer having a saturated cyclic hydrocarbon structure, such as vinylcyclohexane, as a raw material.

[0130] In the present invention, when the partial structure represented by the general formula (4) is contained in the molecular structure of the binder resin, Y 1 ~Y 4 If at least one of these Y 1 ~Y 4 In particular, from the viewpoint of availability and cost, the combination of Y in the general formula (4) is １ ~Y ４ At least one of Y in general formula (4) is preferably a substituted or unsubstituted cyclohexyl group. １ ~Y ４ It is more preferable that one of the groups is a substituted or unsubstituted cyclohexyl group and the other three are hydrogen atoms.

[0131] The content of the repeating unit of the partial structure represented by general formula (3) in the binder resin contained in the color conversion sheet of the present invention is not particularly limited, but is preferably 30 wt% or more, more preferably 50 wt% or more, even more preferably 60 wt% or more, and particularly preferably 70 wt% or more of the total amount of the binder resin. By the content of the repeating unit of the partial structure represented by general formula (3) being in the range of the above lower limit or more, the compatibility between the partial structure represented by general formula (3) and the delayed fluorescent material can be ensured, and as a result, higher durability can be obtained.

[0132] Furthermore, the content of the repeating unit of the partial structure represented by general formula (3) in the binder resin contained in the color conversion sheet of the present invention is preferably 95% by weight or less, more preferably 90% by weight or less, and even more preferably 85% by weight or less, of the total amount of the binder resin. By ensuring that the content of the repeating unit of the partial structure represented by general formula (3) is within the above-mentioned upper limit or less, a color conversion sheet with excellent crack resistance can be obtained.

[0133] The content of the repeating unit of the partial structure represented by general formula (4) in the binder resin contained in the color conversion sheet of the present invention is not particularly limited, but is preferably 5 wt% or more, more preferably 10 wt% or more, and particularly preferably 15 wt% or more of the total amount of the binder resin. When the content of the repeating unit of the partial structure represented by general formula (4) is in the range of the above-mentioned lower limit or more, the dispersibility of the delayed fluorescence material in the binder resin can be ensured, and as a result, higher durability can be obtained.

[0134] Furthermore, the content of the repeating unit of the partial structure represented by general formula (4) in the binder resin contained in the color conversion sheet of the present invention is preferably 70 wt% or less, more preferably 50 wt% or less, and particularly preferably 30 wt% or less, of the total amount of the binder resin. By having the content of the repeating unit of the partial structure represented by general formula (4) in the range not exceeding the above upper limit, compatibility between the partial structure represented by general formula (4) and the delayed fluorescent material can be ensured, and as a result, a color conversion sheet with excellent luminescence intensity can be obtained.

[0135] The weight-average molecular weight (Mw) of the binder resin contained in the color conversion sheet of the present invention is preferably 5,000 or more, more preferably 15,000 or more, and particularly preferably 20,000 or more. Furthermore, the weight-average molecular weight of the binder resin is preferably 500,000 or less, more preferably 100,000 or less, and particularly preferably 50,000 or less. When the weight-average molecular weight is within the above-mentioned upper and lower limit ranges, the compatibility between the binder resin and the light-emitting material is good, and a color conversion sheet with higher durability can be obtained.

[0136] The weight-average molecular weight in the present invention is a value measured by gel permeation chromatography (GPC). Specifically, after filtering a sample through a membrane filter having a pore size of 0.45 μm, the weight-average molecular weight is determined in terms of polystyrene using a GPC apparatus (HLC-82A manufactured by Tosoh Corporation) (developing solvent: toluene, development rate: 1.0 ml / min, column: TSKgel G2000HXL manufactured by Tosoh Corporation).

[0137] The glass transition temperature (Tg) of the binder resin contained in the color conversion sheet of the present invention is preferably 50 to 200° C., and more preferably 100 to 160° C. If the glass transition temperature of the binder resin is within the above range, higher durability can be obtained in the color conversion sheet formed from the color conversion composition of the present invention.

[0138] The glass transition temperature of the binder resin can be measured by a commercially available measuring device, for example, a differential scanning calorimeter manufactured by Seiko Instruments Inc. (trade name: DSC6220, temperature rise rate: 0.5° C. / min).

[0139] The method for synthesizing the binder resin is not particularly limited, and known methods, such as copolymerizing each raw material monomer in the presence of a polymerization initiator, can be appropriately used. Commercially available products can also be used as the binder resin. Examples of commercially available products that correspond to the binder resin include, but are not limited to, Optimas 7500 and Optimas 6000 manufactured by Mitsubishi Gas Chemical Company, Inc.

[0140] The binder resin may contain additives such as dispersants and leveling agents for stabilizing the coating film, or may contain adhesive aids such as silane coupling agents as modifiers for the color conversion layer surface. The binder resin may also contain inorganic particles such as silica particles and silicone microparticles as agents for inhibiting the precipitation of the color conversion material.

[0141] In the color-converting composition for producing the color-converting sheet of the present invention, the binder resin preferably contains, as an additional component, a hydrosilylation reaction retarder such as acetylene alcohol to inhibit curing at room temperature and thereby extend the pot life. Furthermore, the binder resin may contain, as necessary, fine particles such as fumed silica, glass powder, and quartz powder, inorganic fillers and pigments such as titanium oxide, zirconia oxide, barium titanate, and zinc oxide, flame retardants, heat resistance agents, antioxidants, dispersants, solvents, and adhesion promoters such as silane coupling agents and titanium coupling agents, within the scope of the present invention.

[0142] (Other Additives) In addition to the delayed fluorescent material, binder resin, and residual solvent described above, the color conversion sheet of the present invention may contain other components (additives), such as a light stabilizer, an antioxidant, a processing and heat stabilizer, a light resistance stabilizer such as an ultraviolet absorber, scattering particles, silicone microparticles, and a silane coupling agent.

[0143] Examples of light stabilizers include, but are not limited to, tertiary amines, catechol derivatives, nickel compounds, and complexes or salts with organic acids containing at least one transition metal selected from the group consisting of Sc, V, Mn, Fe, Co, Cu, Y, Zr, Mo, Ag, and lanthanoids. These light stabilizers may be used alone or in combination.

[0144] Examples of the antioxidant include, but are not limited to, phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol and 2,6-di-tert-butyl-4-ethylphenol. These antioxidants may be used alone or in combination.

[0145] Examples of processing and heat stabilizers include, but are not limited to, phosphorus-based stabilizers such as tributyl phosphite, tricyclohexyl phosphite, triethyl phosphine, and diphenylbutyl phosphine. These stabilizers may be used alone or in combination.

[0146] Examples of the light resistance stabilizer include, but are not limited to, benzotriazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole and 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole. These light resistance stabilizers may be used alone or in combination.

[0147] The scattering particles are preferably inorganic particles having a refractive index of 1.7 to 2.8, such as titania, zirconia, alumina, ceria, tin oxide, indium oxide, iron oxide, zinc oxide, aluminum nitride, aluminum, tin, titanium or zirconium sulfide, and titanium or zirconium hydroxide.

[0148] In the color conversion sheet of the present invention, the content of these additives depends on the molar absorption coefficient, luminescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness and transmittance of the color conversion sheet to be produced. However, it is usually 1.0 × 10 -3 The content of these additives is preferably 1.0×10 to 30 parts by weight based on 100 parts by weight of the binder resin. -2 More preferably, the amount is 1.0×10 -1 It is particularly preferable that the amount is from 1 part by weight to 10 parts by weight.

[0149] (Method for Producing Color-Converting Composition) An example of a method for producing a color-converting composition for producing a color-converting layer included in the color-converting sheet of the present invention is described below. In this method, predetermined amounts of the aforementioned delayed fluorescent material, binder resin, solvent, and, if necessary, additives are mixed. These components are mixed to a predetermined composition, and then homogeneously mixed or kneaded using a stirrer / kneader to obtain a color-converting composition. Examples of stirrers / kneaders include homogenizers, planetary stirrers, three-roller stirrers, ball mills, planetary ball mills, and bead mills. After mixing or dispersing, or during the mixing or dispersing process, degassing is preferably performed under vacuum or reduced pressure conditions. It is also possible to premix certain components or perform aging or other treatments. It is also possible to remove the solvent using an evaporator to achieve a desired solids concentration.

[0150] (Substrate Layer) Examples of the substrate layer in the color conversion sheet of the present invention (for example, the substrate layer 10 shown in Figures 2 to 4) include glass and resin films. As the resin film, plastic films such as polyethylene terephthalate (PET), polyphenylene sulfide, polycarbonate, polypropylene, and polyimide are preferred. To facilitate peeling of the film, the surface of the substrate layer may be subjected to a release treatment in advance. There are no particular restrictions on the thickness of the substrate layer, but the lower limit is preferably 25 μm or more, and more preferably 38 μm or more. The upper limit is preferably 5000 μm or less, and more preferably 3000 μm or less.

[0151] (Barrier Film) The barrier film in the color conversion sheet of the present invention (for example, barrier film 12 shown in FIG. 4) is used as appropriate when improving the gas barrier properties of the color conversion layer. This barrier film (also referred to as a barrier layer) is preferably one that suppresses the penetration of oxygen, moisture, heat, etc. into the color conversion layer. The color conversion sheet of the present invention may have two or more layers of such barrier films. For example, the color conversion sheet of the present invention may have barrier films on both sides of the color conversion layer, as in the barrier film 12 exemplified in FIG. 4, or may have a barrier film on only one side of the color conversion layer.

[0152] Examples of barrier films having gas barrier properties include inorganic oxides such as silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, zinc oxide, tin oxide, indium oxide, yttrium oxide, and magnesium oxide; inorganic nitrides such as silicon nitride, aluminum nitride, titanium nitride, and silicon carbonitride; metal oxide thin films or metal nitride thin films obtained by adding other elements to these; and films containing various resins such as polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, urethane resins, fluorine-containing resins, and polyvinyl alcohol-based resins such as saponified vinyl acetate. The barrier film may contain two or more of these. Examples of barrier films having a moisture barrier function include films containing various resins such as polyethylene, polypropylene, nylon, polyvinylidene chloride, copolymers of vinylidene chloride and vinyl chloride, copolymers of vinylidene chloride and acrylonitrile, fluorine-containing resins, and polyvinyl alcohol-based resins such as saponified vinyl acetate.

[0153] The color conversion sheet of the present invention may further have an auxiliary layer having a light diffusion layer, an adhesive layer, an anti-reflection function, an anti-glare function, an anti-reflection and anti-glare function, a hard coat function (abrasion resistance function), an anti-static function, an anti-fouling function, an electromagnetic wave shielding function, an infrared ray blocking function, an ultraviolet ray blocking function, a polarizing function, a color-tuning function, or the like, depending on the required functions.

[0154] (Other Films) The color conversion sheet of the present invention may further include a polarizing reflective film, a diffusion sheet, a prism sheet, a wavelength-selective reflective film, etc. Suitable specific examples of the wavelength-selective reflective film include those described in WO 2017 / 164155 and JP 2018-81250 A.

[0155] <Method for manufacturing color conversion sheet> Next, an example of a method for manufacturing a color conversion sheet of the present invention will be described. In this method for manufacturing a color conversion sheet, the color conversion composition prepared by the above-described method is applied to an underlayer such as a base layer or a barrier layer, and then dried. This forms a color conversion layer. When the binder resin contained in the color conversion composition is a thermosetting resin, the color conversion composition may be applied to an underlayer such as a base layer, and then heat-cured to form the color conversion layer. When the binder resin contained in the color conversion composition is a photocurable resin, the color conversion composition may be applied to an underlayer such as a base layer, and then photocured to form the color conversion layer.

[0156] The color-converting composition can be applied using a reverse roll coater, blade coater, comma coater, slit die coater, direct gravure coater, offset gravure coater, kiss coater, natural roll coater, air knife coater, roll blade coater, two-stream coater, rod coater, wire bar coater, applicator, dip coater, curtain coater, spin coater, knife coater, etc. In order to obtain a uniform thickness of the color-converting layer, application using a slit die coater, comma coater or dip coater is preferred.

[0157] The color conversion layer can be dried using a common heating device such as a hot air dryer or an infrared dryer. In this case, the heating temperature is preferably 60 to 200°C, and the heating time is preferably 2 minutes to 4 hours. It is also possible to heat and cure the color conversion layer in stages using a method such as step curing.

[0158] When the color conversion layer is formed by heat curing, a hot air oven or the like can be used as the heating device. The heating conditions for heat curing the color conversion layer can be selected depending on the binder resin. For example, the heating temperature is preferably 100°C to 300°C, and the heating time is preferably 1 minute to 2 hours.

[0159] When forming a color conversion layer by photocuring, it is preferable to irradiate the color conversion layer with high-energy light such as ultraviolet light. The light irradiation conditions for photocuring the color conversion layer can be selected depending on the binder resin. For example, the wavelength of the irradiated light is preferably 200 nm to 500 nm, and the light irradiation dose is preferably 10 mJ / cm. 2 ~10 J / cm 2 It is preferable that:

[0160] After the color conversion layer is formed, the base material layer can be changed as needed. In this case, simple methods include, for example, a method of replacing the base material layer using a hot plate, or a method using a vacuum laminator or a dry film laminator.

[0161] <Light Source Unit> A light source unit according to an embodiment of the present invention (hereinafter sometimes abbreviated as the light source unit of the present invention) includes at least a light source and the above-described color conversion composition or color conversion sheet. The light source included in the light source unit of the present invention is a source of the above-described excitation light. The arrangement of the light source and the color conversion sheet is not particularly limited, and the light source and the color conversion sheet may be closely attached to each other, or a remote phosphor type in which the light source and the color conversion sheet are separated from each other may be used. Furthermore, the light source unit of the present invention may be configured to further include a color filter in order to enhance color purity.

[0162] (Light Source) The light source unit of the present invention can be equipped with any type of light source, as long as it emits light in a wavelength range that can be absorbed by the delayed fluorescent material. In principle, any excitation light source can be used, such as a hot cathode tube, a cold cathode tube, a fluorescent light source such as inorganic electroluminescence (EL), an organic EL element light source, an LED light source, an incandescent light source, or sunlight. Among these, an LED light source is a preferred light source. For display and lighting applications, a blue LED light source with a maximum emission wavelength in the range of 430 nm to 500 nm is even more preferred, as it can enhance the color purity of blue light.

[0163] The light source may have one emission peak or two or more emission peaks, but in order to improve color purity, it is preferable that the light source has one emission peak. It is also possible to use a combination of multiple light sources with different emission peaks.

[0164] The light source unit of the present invention is useful for various light sources such as spatial illumination, backlighting, etc. Specifically, the light source unit of the present invention can be used for applications such as displays, lighting devices, interiors, signs, and billboards, and is particularly suitable for use in displays and lighting devices.

[0165] <Display, Lighting Device> A display according to an embodiment of the present invention includes at least the light source unit described above. For example, a display such as a liquid crystal display uses a light source unit having the above-described light source and a color conversion sheet as a backlight unit. Furthermore, a lighting device according to an embodiment of the present invention includes at least the light source unit described above. For example, this lighting device is configured to emit white light by combining a blue LED light source as the light source unit with a color conversion sheet that converts blue light from the blue LED light source into light with a longer wavelength.

[0166] The present invention will be described below with reference to examples, but the present invention is not limited to the following examples. First, the evaluation methods used in the examples and comparative examples will be described.

[0167] <Durability Evaluation> In the durability evaluation, in each example and comparative example, a light-emitting device equipped with the prepared color conversion sheet and a blue LED element (manufactured by USHIO EPITEX Corporation; model number SMBB450H-1100, emission peak wavelength: 450 nm) was subjected to a current of 30 mA to light up the blue LED element, and the initial emission peak intensity of green light and the emission peak intensity of red light were measured using a spectroradiometer (CS-1000, manufactured by Konica Minolta). The distance between the color conversion sheet and the blue LED element in each light-emitting device was 3 cm. After that, light from the blue LED element was continuously irradiated for 1000 hours in an environment of 50°C, and the emission peak intensity of green light and the emission peak intensity of red light were similarly measured. The obtained emission peak intensities of the green light and red light were compared with the initial emission peak intensities of the green light and red light, and the maintenance rate of the emission peak intensity for each of the green light and red light was calculated to evaluate the chromaticity durability of the color conversion sheet. The emission peak intensity maintenance rate can be calculated using the following formula: Emission peak intensity maintenance rate Z (%) = Y / X × 100 In the above formula, X is the initial emission peak intensity, and Y is the emission peak intensity after 1000 hours of continuous irradiation.

[0168] <Measurement of Fluorescence Quantum Yield> In each example and comparative example, the produced color conversion sheet was cut into 8 mm squares to prepare samples, and the fluorescence quantum yield was measured when the sample was excited with excitation light having a wavelength of 450 nm using an absolute fluorescence quantum yield measurement device (Quantaurus-QY, manufactured by Hamamatsu Photonics KK).

[0169] <Measurement of Residual Solvent Amount> The amount of residual solvent in the color conversion layer was measured by the following procedure. In detail, first, a color conversion layer was formed on a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm). Subsequently, the formed color conversion layer was peeled off from the polyester film, and 20 mg of the resulting color conversion layer alone was weighed. Next, this 20 mg of color conversion layer was dissolved in 2 mL of NMP, thereby preparing a sample for measuring the amount of residual solvent in the color conversion layer. A gas chromatograph (GC-2010) manufactured by Shimadzu Corporation was used as the measuring instrument, and the amount of residual solvent in the above sample was measured under the following conditions. (Conditions) Detector: FID Column used: CP-Select 624 CB Detector temperature: 280°C Carrier gas: He Carrier gas flow rate: 6 mL / min Heating conditions: After holding at 40°C for 4 minutes, the temperature was raised to 260°C at a rate of 8°C / min, and then held for 16 minutes.

[0170] <Light-emitting material (a) and light-emitting material (b)> In the following examples and comparative examples, compounds G-1, G-2, R-1, and R-2 were used as the light-emitting material (a) and the light-emitting material (b). Compounds G-1, G-2, R-1, and R-2 are the compounds shown below. Of these, compound G-1 and compound R-1 are compounds that emit delayed fluorescence.

[0171]

[0172]

[0173] <Binder Resin> In each of the Examples and Comparative Examples, the following resins A, B, C, and D were used as binder resins.

[0174] (Resin A) Resin A in this specification was Resin F described in WO 2019 / 021813. Resin A is a binder resin containing 95.0 wt% of the partial structure represented by general formula (3) and 5.0 wt% of the partial structure represented by general formula (4). In this resin A, Y of the partial structure represented by general formula (4) 1 ~Y 4Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0175] (Resin B) Resin B in this specification was Resin G (Optimas 6000 (PMMA-hydrogenated styrene copolymer manufactured by Mitsubishi Gas Chemical Co., Ltd.)) described in WO 2019 / 021813. Resin B is a binder resin containing 61.0 wt% of the partial structure represented by general formula (3) and 39.0 wt% of the partial structure represented by general formula (4). In this resin B, Y of the partial structure represented by general formula (4) 1 ~Y 4 Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0176] (Resin C) Resin C in this specification was Resin H (Optimas 7500 (PMMA-hydrogenated styrene copolymer manufactured by Mitsubishi Gas Chemical Co., Ltd.)) described in WO 2019 / 021813. Resin C is a binder resin containing 77.0 wt% of the partial structure represented by general formula (3) and 23.0 wt% of the partial structure represented by general formula (4). In this resin C, Y of the partial structure represented by general formula (4) 1 ~Y 4 Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0177] (Resin D) Resin D in this specification was Resin I described in WO 2019 / 021813. Resin D is a binder resin containing 75.7 wt% of the partial structure represented by general formula (3) and 24.3 wt% of the partial structure represented by general formula (4). In this resin D, Y of the partial structure represented by general formula (4) 1 ~Y 4 Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0178] <Scattering Material> In the following examples and comparative examples, titanium dioxide particles "JR-301" (manufactured by Teika Co., Ltd.) were used as scattering materials.

[0179] Examples 1 to 4 In Examples 1 to 4, 0.40 parts by weight of compound G-1 as the luminescent material (a), 0.01 parts by weight of compound R-1 as the luminescent material (b), and 300 parts by weight of ethyl acetate as a solvent were mixed with 100 parts by weight of the binder resin (resin A, resin B, resin C, or resin D) shown in Table 2 below. Thereafter, these mixtures were stirred and degassed for 20 minutes at 1000 rpm using a planetary stirring and degassing device "Mazerustar KK-400" (manufactured by Kurabo Industries, Ltd.), thereby obtaining a color-changing composition as a resin liquid for producing a color-changing layer.

[0180] Similarly, polyester resin "Vylon 630" (manufactured by Toyobo Co., Ltd.) was used as the resin for the adhesive layer, and 300 parts by weight of ethyl acetate was mixed with 100 parts by weight of this polyester resin as a solvent. Thereafter, this mixture was stirred and degassed for 20 minutes at 300 rpm using a planetary stirring and degassing device "Mazerustar KK-400" (manufactured by Kurabo Industries, Ltd.), thereby obtaining a resin composition as an adhesive composition.

[0181] Next, the color-changing composition obtained as described above was applied to a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm) using a slit die coater, and dried by heating at 130° C. for 20 minutes. This formed a color-changing layer with an average thickness of 20 μm, and a unit was obtained in which this color-changing layer and polyester film (substrate layer) were laminated together.

[0182] Similarly, the resin composition obtained as an adhesive composition as described above was applied to the PET substrate layer side of a light diffusion film "Chemical Matte" 125PW (manufactured by Kimoto Co., Ltd., thickness 138 μm) using a slit die coater, and then heated and dried for 20 minutes at 130° C. This formed an adhesive layer with an average film thickness of 15 μm, and a unit was obtained in which the adhesive layer, PET substrate layer, and light diffusion film (light diffusion layer) were laminated together.

[0183] Next, the above two units were heat-laminated so that the color conversion layer and the adhesive layer were directly laminated together to produce a color conversion sheet with a structure of "substrate layer / color conversion layer / adhesive layer / substrate layer / light diffusion layer." Various evaluations of the obtained color conversion sheets were carried out using the methods described above. The structure and evaluation results of the color conversion sheets in each of Examples 1 to 4 are shown in Table 2.

[0184] In Example 5, except that compound R-2 was used as the luminescent material (b), a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Example 1. The configuration and evaluation results of the color conversion sheet in Example 5 are shown in Table 2.

[0185] In Example 6, except that compound G-2 was used as the luminescent material (a), a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Example 1. The configuration and evaluation results of the color conversion sheet in Example 6 are as shown in Table 2.

[0186] (Examples 7 to 13) In Examples 7 to 13, color conversion sheets were produced and various evaluations of the color conversion sheets were carried out in the same manner as in Example 1, except that the drying temperature and drying time were changed as shown in Table 3 below. The configurations and evaluation results of the color conversion sheets in each of Examples 7 to 13 are as shown in Table 3.

[0187] In Example 14, a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Example 1, except that toluene was used as the solvent and the drying temperature and drying time were changed as shown in Table 3. The configuration and evaluation results of the color conversion sheet in Example 14 are as shown in Table 3.

[0188] In Comparative Example 1, except that compound G-2 was used as the luminescent material (a) and compound R-2 was used as the luminescent material (b), a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Example 1. The configuration and evaluation results of the color conversion sheet in Comparative Example 1 are shown in Table 4.

[0189] (Comparative Example 2) In Comparative Example 2, a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Example 1, except that the drying temperature and drying time were changed as shown in Table 4. The configuration and evaluation results of the color conversion sheet in Comparative Example 2 are as shown in Table 4.

[0190] (Comparative Example 3) In Comparative Example 3, a color conversion sheet was produced and various evaluations of the color conversion sheet were carried out in the same manner as in Comparative Example 1, except that the drying temperature and drying time were changed as shown in Table 4. The configuration and evaluation results of the color conversion sheet in Comparative Example 3 are as shown in Table 4.

[0191]

[0192]

[0193]

[0194] In Tables 2 to 4, "green light emission peak intensity maintenance rate" refers to the evaluation result of the durability of the chromaticity of the luminescent material (a) contained in the color conversion sheet. "red light emission peak intensity maintenance rate" refers to the evaluation result of the durability of the chromaticity of the luminescent material (b) contained in the color conversion sheet.

[0195] As described above, the color conversion sheet according to the present invention, and the light source unit, display, and lighting device that include the color conversion sheet are suitable for achieving excellent durability of chromaticity.

[0196] 1A, 1B, 1C, 1D Color conversion sheet 10 Base layer 11 Color conversion layer 12 Barrier film

Claims

1. A color conversion sheet that converts incident light into light having a wavelength different from that of the incident light, comprising at least a color conversion layer containing a compound that emits delayed fluorescence and a binder resin, wherein the amount of the solvent in the color conversion layer is 10 ppm by mass or more and 30,000 ppm by mass or less, and the solvent in the color conversion layer has a functional group having an SP value of 11.0 (cal / cm3)1 / 2 or more and 20.0 (cal / cm3)1 / 2 or less, characterized in that it is a color conversion sheet.

2. The color conversion sheet according to claim 1, characterized in that the binder resin has a partial structure represented by the general formula (3) and a partial structure represented by the general formula (4) in its molecular structure.

3. 【Chemical 1】 (In general formula (3), Z 1 and Z 2 may be the same as or different from each other, and are a hydrogen atom or an organic group having 1 to 20 carbon atoms. In general formula (4), Y 1 to Y 4 may be the same as or different from each other, and are a hydrogen atom or an organic group having 1 to 20 carbon atoms, and at least one of Y 1 to Y 4 is a group containing an aliphatic cyclic hydrocarbon structure.) The color conversion sheet according to claim 2, characterized in that... Y in the general formula (4) above 1 ~Y 4 at least one of which is a substituted or unsubstituted cyclohexyl group

4. The color conversion sheet according to claim 2, characterized in that... Y in the general formula (4) 1 ~Y 4 Among them, one is a substituted or unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

5. The color conversion sheet according to claim 1, characterized in that the compound that emits delayed fluorescence is at least one of the following luminescent materials (a) and luminescent materials (b).

6. The color conversion sheet according to claim 1, characterized in that the compound that emits delayed fluorescence contains a compound represented by the following general formula (1) or general formula (2).

7. The color conversion sheet according to claim 6, characterized in that...

8. A light source unit, characterized by comprising: a light source; 【Chemical 2】 (In general formula (1) or general formula (2), ring Za, ring Zb, and ring Zc are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring-forming carbon atoms, or a substituted or unsubstituted heteroaryl ring having 6 to 30 ring-forming carbon atoms. Z 1 and Z 2 are each independently an oxygen atom, NRa (a nitrogen atom having substituent Ra), or a sulfur atom. When Z 1 is NRa, substituent Ra may be bonded to ring Za or ring Zb to form a ring. When Z 2 is NRa, substituent Ra may be bonded to ring Za or ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom having substituent Ra), or P=O. E 1 and E 2 are each independently BRa (a boron atom having substituent Ra), PRa (a phosphorus atom having substituent Ra), SiRa 2 (a silicon atom having two substituents Ra), C=O, P(=O)Ra 2 (a phosphine oxide having two substituents Ra), or P(=S)Ra 2 (a phosphine sulfide having two substituents Ra), S(=O), or S(=O) 2 is. When E 1 is BRa, PRa, SiRa 2 P(=O)Ra 2 or P(=S)Ra 2 substituent Ra may be bonded to ring Za or ring Zb to form a ring. When E 2 is BRa, PRa, SiRa 2 P(=O)Ra 2 or P(=S)Ra 2 substituent Ra may be bonded to ring Za or ring Zc to form a ring. Substituent Ra is each independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.) the color conversion sheet according to any one of claims 1 to 7. The compound that emits the delayed fluorescence is a compound represented by the general formula (1), E in the general formula (1) is a boron atom, and Z 1 and Z 2 are each independently NRa, or the compound that emits the delayed fluorescence is a compound represented by the general formula (2), and E 1 and E 2 are each independently BRa,

9. The light source unit according to claim 8, characterized in that the light source is a light-emitting diode having a maximum emission in the wavelength range of 400 nm or more and 500 nm or less.

10. A display, characterized by comprising the light source unit according to claim 8.

11. An illumination device, characterized by comprising the light source unit according to claim 8. ​ ​ ​ ​ ​ ​ ​ ​

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