Color conversion sheet, light source unit containing the same, display and lighting 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

[Technical Field]

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

[0002] There is much research into applying multi-color technology using color conversion methods to liquid crystal displays, organic EL displays, lighting devices, and other applications. Color conversion refers to the process of converting light emitted from a light source into longer wavelength light, such as converting blue light to green or red light.

[0003] This color-converting composition (hereinafter referred to as the color-converting composition) can be formed into a sheet and combined with, for example, a blue light source 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 formed by combining such a blue light source with a color-converting sheet (hereinafter referred to as the color-converting sheet) can be used as a light source unit such as a backlight unit, and by combining this light source unit with a liquid crystal drive unit and a color filter, it becomes possible to manufacture a full-color display. Furthermore, a white light source formed by combining a blue light source with a color-converting sheet can also be used as a white light source such as LED lighting.

[0004] One challenge for liquid crystal displays utilizing color conversion methods is improving color reproducibility and durability. To improve color reproducibility, it is effective to narrow the full width at half maximum of the blue, green, and red emission spectra of the light source unit and increase the color purity of each color. As a means of solving this, for example, color conversion materials containing pyromethene compounds have been proposed (see, for example, Patent Documents 1-2). Furthermore, as a technique to improve durability, a technique of adding a light stabilizer has been proposed (see, for example, Patent Document 3), but this technique still resulted in insufficient durability. Therefore, as a technique to improve both color reproducibility and durability, light-emitting materials having electron-withdrawing groups have been proposed (see, for example, Patent Document 4). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2010-61824 [Patent Document 2] Japanese Patent Publication No. 2014-136771 [Patent Document 3] Japanese Patent Publication No. 2019-50381 [Patent Document 4] International Publication No. 2016 / 190283 [Overview of the project] [Problems that the invention aims to solve]

[0006] The technology described in Patent Document 4 makes it possible to obtain a color conversion composition that has excellent color reproducibility and durability with minimal brightness degradation even when used continuously for long periods of time. However, in response to the recent demands for further miniaturization and high resolution, it has been found that conventional color conversion sheets using color conversion compositions have a new problem: the chromaticity changes slightly with prolonged use.

[0007] The present invention has been made in view of the above circumstances, and its first objective is to provide a color conversion sheet with excellent chromaticity durability. The second objective of the present invention is to provide a light source unit, a display, and a lighting device including the color conversion sheet. [Means for solving the problem]

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

[0009] In addition, in the color conversion sheet according to the present invention, in the above invention, 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, and is characterized by this.

[0010]

Chemical formula

[0014] , 4 , , ,

[0012] , , 1 , 3 , , 3 , ,

[0013] , and Z 2 may be the same as or different from each other, and is a hydrogen atom or an organic group having 1 or more and 20 or less carbon atoms. In the general formula (4), Y<00000​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​Furthermore, 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 light-emitting material (a) and light-emitting material (b). Light-emitting material (a): A light-emitting material that exhibits emission observed in the region of 500 nm to less than 580 nm when excitation light in the wavelength range of 430 nm to 500 nm is used. Light-emitting material (b): A light-emitting material that, when excited by excitation light in the wavelength range of 430 nm to 500 nm, or by emission from the light-emitting material (a), or both, exhibits emission observed in the region of 580 nm to 750 nm with a peak wavelength.

[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] [ka] (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. 1 and Z 2 These are, independently, an oxygen atom, an NRa (a nitrogen atom with a substituent Ra), or a sulfur atom. 1 If it is NRa, the substituent Ra may bond to ring Za or ring Zb to form a ring. 2 If is NRa, the substituent Ra may bond to ring Za or ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom with substituent Ra), or P=O. 1 and E 2These are, independently, BRa (a boron atom with substituent Ra), PRa (a phosphorus atom with substituent Ra), SiRa2 (a silicon atom with two substituent Ra), C=O, P(=O)Ra2 (a phosphine oxide with two substituent Ra), or P(=S)Ra2 (a phosphine sulfide with two substituent Ra), S(=O), or S(=O)2. 1 If is BRa, PRa, SiRa2, P(=O)Ra2, or P(=S)Ra2, the substituent Ra may bond to ring Za or ring Zb to form a ring. 2 If is BRa, PRa, SiRa2, P(=O)Ra2, or P(=S)Ra2, the substituent Ra may bond to ring Za or ring Zc to form a ring. Each substituent Ra is independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

[0017] Furthermore, the color conversion sheet according to the present invention is characterized in that the compound that emits delayed fluorescence is a compound represented by the general formula (1), where E in the general formula (1) is a boron atom, and Z 1 and Z 2 Each of them is independently NRa, or the compound that emits delayed fluorescence is a compound represented by the general formula (2), and E in the general formula (2) 1 and E 2 It is characterized in that each of them is independently BRa.

[0018] Furthermore, the light source unit according to the present invention is characterized by including a light source and a color conversion sheet described in any one of the above inventions.

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

[0020] Furthermore, the display according to the present invention is characterized by comprising the light source unit described in the above invention.

[0021] Furthermore, the lighting device according to the present invention is characterized by comprising the light source unit described in the above invention. [Effects of the Invention]

[0022] The present invention provides a color conversion sheet with excellent chromaticity durability. The color conversion sheet of the present invention improves durability against changes in chromaticity. Furthermore, by including the color conversion sheet, the light source unit, display, and lighting device of the present invention can improve durability against changes in chromaticity. [Brief explanation of the drawing]

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

[0024] The following describes preferred embodiments of the color conversion sheet, light source unit, display, and lighting device according to the present invention. However, 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-emitting element such as a light source into light of a different wavelength than the incident light, and includes at least a color conversion layer containing 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. Hereinafter, "converting to light of a different wavelength than the incident light" means that it is preferable to convert the incident light into light with a longer wavelength than 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 which is a layer made of a color conversion composition or its cured product, as described below. Preferably, the cured product of the color conversion composition is 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). Four typical structural examples of the color conversion sheet of the present invention are as follows.

[0027] Figure 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 Figure 1, this first example of a 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 according to the present invention.

[0028] Figure 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 Figure 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 the color conversion sheet 1B, the color conversion layer 11 is laminated on top of the base layer 10.

[0029] Figure 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 Figure 3, this third example of a color conversion sheet 1C is a laminate of a plurality of substrate layers 10 and a color conversion layer 11. In this structural example of the color conversion sheet 1C, the color conversion layer 11 is sandwiched between the plurality of substrate layers 10.

[0030] Figure 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 Figure 4, this fourth example of a color conversion sheet 1D is a laminate of a plurality of base material layers 10, a color conversion layer 11, and a plurality of barrier films 12. In this structural example of the color conversion sheet 1D, the color conversion layer 11 is sandwiched between a plurality of barrier films 12, and furthermore, this laminate of the color conversion layer 11 and the plurality of barrier films 12 is sandwiched between a plurality of base material layers 10. That is, the color conversion sheet 1D may have barrier films 12 as shown in Figure 4 to prevent deterioration of the color conversion layer 11 due to oxygen, moisture, and 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 total thickness of all layers contained in the color conversion sheet, and is the film thickness (average film thickness) measured according to Method A of the mechanical scanning method for measuring thickness in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Method. By setting the thickness of the color conversion sheet of the present invention to 30 μm or more, the toughness of the color conversion sheet can be improved. Furthermore, by setting the thickness of the color conversion sheet of the present invention to 300 μm or less, cracks in the color conversion sheet can be suppressed.

[0032] (Color conversion layer) In the present invention, the color conversion layer (for example, the color conversion layer 11 shown in Figures 1 to 4) contains a compound that emits delayed fluorescence (hereinafter sometimes abbreviated as "delayed fluorescence material"), a binder resin, and a trace amount of solvent. This 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. Furthermore, 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. In this invention, the thickness of the color conversion layer refers to the film thickness (average film thickness) measured according to Method A of the mechanical scanning method for measuring thickness in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods.

[0034] The color conversion layer described above can be formed by applying the color conversion composition prepared by the method described later to a substrate layer or barrier film and drying it.

[0035] In the color conversion sheet of the present invention, the color conversion layer may consist of one layer or two or more layers. In addition to the delayed fluorescence material and binder resin described above, the color conversion layer may also contain other components (additives) such as light stabilizers, antioxidants, processing and heat stabilizers, light-resistant stabilizers such as ultraviolet absorbers, scattering particles, silicone fine particles, and silane coupling agents.

[0036] (Compounds that emit delayed fluorescence) Compounds that emit delayed fluorescence (delayed fluorescence materials) are explained on pages 87-103 of "Cutting-Edge Organic EL" (edited by Chihaya Adachi and Hiroshi Fujimoto, published by CMC Publishing). In that document, it is explained that by bringing the energy levels of the singlet excited state and the triplet excited state of the luminescent material close together, the reverse energy transfer from the triplet excited state to the singlet excited state, which normally has a low transition probability, occurs with high efficiency, and thermally activated delayed fluorescence (TADF) is expressed. Furthermore, the mechanism of delayed fluorescence generation is explained in Figure 5 of the same document. The emission of delayed fluorescence can be confirmed by transient PL (Photo Luminescence) measurement.

[0037] Furthermore, it has been reported that by matching the energy levels of the singlet excited state and the triplet excited state of a luminescent material, the reverse energy transfer from the triplet excited state to the singlet excited state can be accelerated (Nature Photonics volume 14, pages 643-49 (2020)). In addition, research is actively being conducted on compounds in which the energy level of the triplet excited state is higher than the energy level of the singlet excited state of the luminescent material.

[0038] In this specification, compounds that exhibit thermally activated delayed fluorescence, including compounds that transition efficiently from a triplet excited state to a singlet excited state and emit fluorescence, are referred to as "compounds that emit delayed fluorescence" or abbreviated as "delayed fluorescence materials."

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

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

[0041] First, let's explain the degradation mechanism of the luminescent material. The change in chromaticity of a color conversion composition is caused by the degradation of the luminescent material. This degradation of the luminescent material is caused by singlet oxygen. Singlet oxygen is an oxygen molecule in an excited state where the spins of two electrons in the π* orbital (antibonding π orbital) of the molecular orbital of the oxygen molecule are oriented in opposite directions, i.e., the total spin quantum number is 0. In such excited states, there are two states: the Σ1 state, where each of the two π* orbitals is occupied by one electron with opposite spin directions, and the Δ1 state, where only one of the π* orbitals is occupied by two electrons with opposite spin directions. In the Δ1 state, the empty electron orbital of singlet oxygen has strong electrophilicity and strong oxidizing power. Therefore, it is thought that singlet oxygen causes the degradation of the luminescent material through oxidation.

[0042] Next, we will discuss the mechanism of singlet oxygen generation. Singlet oxygen is unlikely to be generated by directly photoexciting the 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 very low.

[0043] Therefore, the generation of singlet oxygen in the color conversion composition is thought to be due to the sensitizing effect of the dye. In other words, singlet oxygen is thought to be generated by the exchange of electrons and energy between the triplet excited state luminescent material and the ground state triplet oxygen molecule. The generation mechanism is thought 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 lifetime of the triplet excited state is long. However, if ground-state triplet oxygen is present, the spin forbidden transition is released by excitation from the ground-state triplet oxygen to the excited-state singlet oxygen, and the luminescent material can be rapidly deactivated from the triplet excited state to the singlet ground state. This mechanism is called the Dexter mechanism (electron exchange mechanism).

[0045] For the Dexter mechanism to proceed, electron exchange via the overlap of wave functions between molecules is necessary. Therefore, it is thought that a direct collision is required between the energy donor molecule (in this case, a luminescent material in a triplet excited state) and the energy acceptor molecule (in this case, triplet oxygen in a ground state).

[0046] As mentioned earlier, delayed fluorescence materials have the property that the triplet excited state is rapidly converted to the singlet excited state, meaning the lifetime of the triplet excited state is short. Therefore, the probability of a direct collision between the luminescent material in the triplet excited state and the triplet oxygen in the ground state is reduced, making it less likely for singlet oxygen to be generated.

[0047] To design molecules that bring the energy levels of the singlet excited state and the triplet excited state close together, it is effective to bond an electron donor skeleton and an electron acceptor skeleton within the same molecule. This allows for the separation of the HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) orbitals within the molecule. The electron donor skeleton and the electron acceptor skeleton may be directly bonded or bonded via a linking group. In this case, the linking group is preferably a skeleton containing aromatic hydrocarbons.

[0048] Examples of electron-donating skeletons include skeletons having an amine nitrogen atom. Among these, skeletons containing diarylamines or triarylamines, skeletons containing carbazoles, skeletons containing benzocarbazoles, skeletons containing indrocarbazoles, skeletons containing phenoxazines, and skeletons containing phenothiazines are preferred. Of these, skeletons containing carbazoles, skeletons containing benzocarbazoles, skeletons containing indrocarbazoles, and skeletons containing phenoxazines are more preferred, and skeletons containing carbazoles and skeletons containing phenoxazines are even more preferred.

[0049] On the other hand, electron-accepting skeletons typically 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 the substituted atomic group through inductive or resonance effects in organic electron theory. Examples of electron-withdrawing groups include those whose substituent constant (σp(para)) in Hammett's rule takes a positive value. The substituent constant (σp(para)) in Hammett's rule can be quoted from the Chemical Handbook, Basic Edition, 5th Revised Edition (II-380). Although there are examples where the phenyl group also takes a positive value, the phenyl group is not included in the electron-withdrawing groups of this application.

[0050] Examples of electron-withdrawing groups include -F (σp: +0.20), -Cl (σp: +0.28), -Br (σp: +0.30), -I (σp: +0.30), and -CO2R. 12 (σp:R 12 When it is an ethyl group, +0.45), -CONH2 (σp: +0.38), -COR 12 (σp:R 12 When it is a methyl group, it is +0.49), -CF3 (σp: +0.51), -SO2R 12 (σp:R 12 Examples include when it is a methyl group (+0.69), -NO2 (σp: +0.81), etc. 12Each of these independently represents a hydrogen atom, a substituted or unsubstituted ring-forming aromatic hydrocarbon group having 6 to 30 carbon atoms, a substituted or unsubstituted ring-forming heterocyclic group having 5 to 30 carbon atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and a substituted or unsubstituted cycloalkyl group having 1 to 30 carbon atoms. Specific examples of each of these groups are similar to the substituents in the compounds represented by general formula (1) or general formula (2) described later.

[0051] Among the skeletons containing electron-withdrawing groups, skeletons containing heteroaryl groups having a substructure in which a carbon atom and a nitrogen atom are bonded by a double bond, skeletons containing fluorinated substituents, skeletons containing cyano groups, skeletons containing carbonyl groups, skeletons containing sulfoxides or disulfoxides, and skeletons containing phosphine oxide groups are preferred. Of these, skeletons containing heteroaryl groups having a substructure in which a carbon atom and a nitrogen atom are bonded by a double bond, skeletons containing fluorinated substituents, and skeletons containing cyano groups are even more preferred from the viewpoint of the stability of the delayed fluorescence material.

[0052] Among skeletons containing heteroaryl groups having a substructure in which a carbon atom and a nitrogen atom are bonded by a double bond, skeletons containing pyridine, pyrimidine, pyrazine, triazine, quinoline, quinoxaline, quinazoline, or phenanthroline are particularly preferred. Of these, skeletons containing pyrimidine, triazine, quinoxaline, or quinazoline are more preferred, and skeletons containing triazine are even more preferred.

[0053] Among skeletons containing fluorinated substituents, skeletons containing aryl fluoride groups or fluoroalkyl groups are more preferred. Among skeletons containing aryl fluoride groups, fluorinated benzene rings are preferred, and specifically, skeletons containing fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, or pentafluorobenzene are more preferred. Among 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 containing cyano groups, skeletons containing cyanobenzene, dicyanobenzene, and tricyanobenzene are more preferred.

[0055] Examples of compounds combining the electron donor and electron acceptor skeletons described above are shown below, but the compounds are not limited to these examples. It should be noted that the compounds shown here are known to emit delayed fluorescence, according to previous literature.

[0056] [ka]

[0057] Furthermore, as a delayed fluorescence material, in addition to the compounds formed by combining the electron donor skeleton and the electron acceptor skeleton described above, compounds represented by the following general formula (1) or general formula (2) are preferred.

[0058] [ka]

[0059] 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.

[0060] In general formula (1), Z 1 and Z 2 These are, independently, an oxygen atom, an NRa (a nitrogen atom with a substituent Ra), or a sulfur atom. 1 If it is NRa, the substituent Ra may bond to ring Za or ring Zb to form a ring. 2 If is NRa, the substituent Ra may bond to a ring Za or a ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom with substituent Ra), or P=O.

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

[0062] Each of the substituents Ra described above is 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 replaced with deuterium. This is also true for the compounds or substructures described below. Furthermore, in the following descriptions, for example, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms refers to an aryl group whose total carbon number, including the substituents substituted on the aryl group, is between 6 and 40. The same applies to other substituents that specify the carbon number.

[0064] In the phrase "substituted or unsubstituted," "unsubstituted" means that a hydrogen atom or a deuterium atom has been substituted. The same applies to the phrase "substituted or unsubstituted" in the compounds or substructures described below.

[0065] Furthermore, in all of the above groups, the substituents that may be substituted are alkyl groups, cycloalkyl groups, heterocyclic groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, aryl groups, heteroaryl groups, hydroxyl groups, thiol groups, alkoxy groups, alkylthio groups, aryl ether groups, arylthioether groups, halogens, cyano groups, aldehyde groups, carbonyl groups, carboxyl groups, oxycarbonyl groups, amide groups, sulfonyl groups, sulfonic acid ester groups, sulfonamide groups, amino groups, nitro groups, silyl groups, siloxanyl groups, boryl groups, or phosphine oxide groups. These substituents may also be further substituted with the substituents mentioned above.

[0066] Alkyl groups refer to saturated aliphatic hydrocarbon groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl groups, and may or may not have substituents. There are no particular restrictions on additional substituents when substitution occurs; for example, alkyl groups, halogens, aryl groups, heteroaryl groups, etc., are examples, and this point is also common to the following description. Furthermore, the number of carbon atoms in the alkyl group is not particularly limited, but from the standpoint of availability and cost, it is preferably in the range of 1 to 20, more preferably 1 to 8.

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

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

[0069] An 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 substituents. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

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

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

[0072] An alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether linkage, such as a methoxy group, ethoxy group, or propoxy group. This aliphatic hydrocarbon group may or may not have substituents. 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 a group in which the oxygen atom of the ether bond of an alkoxy group is replaced by a sulfur atom. The hydrocarbon group of the alkylthio group may or may not have substituents. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0074] An 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 substituents. 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 arylthioether group is an aryl ether group in which the oxygen atom in the ether bond is replaced by a sulfur atom. The aromatic hydrocarbon group in the arylthioether group may or may not have substituents. The number of carbon atoms in the arylthioether group is not particularly limited, but is preferably in the range of 6 to 40.

[0076] The aryl group refers to aromatic hydrocarbon groups such as phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzofluorenyl, dibenzofluorenyl, phenanthryl, anthracenyl, benzophenanthryl, benzoanthracenyl, chrysenyl, pyrenyl, fluoranthenyl, triphenylenyl, benzofluoranthenyl, dibenzoanthracenyl, perilenyl, and hericenyl groups. Among these, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracenyl, pyrenyl, fluoranthenyl, and triphenylenyl groups are preferred. The aryl group may or may not have substituents. 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] Heteroaryl groups include, for example, pyridyl, furanyl, thienyl, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidyl, pyridadinyl, triazinyl, naphthilidinyl, synnolinyl, phthalazinyl, quinoxalinyl, quinazolinyl, benzofuranyl, benzothienyl, indolyl, dibenzofuranyl, dibenzothienyl, carbazolyl, and benzocarbazolyl groups. This refers to cyclic aromatic groups having one or more non-carbon atoms in the ring, such as a 1,5-naphthilidinyl group, a 1,6-naphthilidinyl group, a 1,7-naphthilidinyl group, a 1,8-naphthilidinyl group, a 2,6-naphthilidinyl group, or a 2,7-naphthilidinyl group. The heteroaryl group may or may not have substituents. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably in the range of 2 to 40, more preferably 2 to 30.

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

[0079] An amino group is a substituted or unsubstituted amino group. Examples of substituents include aryl groups, heteroaryl groups, linear alkyl groups, and branched alkyl groups. Preferred aryl and heteroaryl groups are phenyl, naphthyl, pyridyl, and quinolinyl groups. 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 most preferably 6 to 30.

[0080] The silyl group refers to alkylsilyl groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, as well as arylsilyl groups such as phenyldimethylsilyl, tert-butyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The substituents 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] A 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. A boryl group refers to a substituted or unsubstituted boryl group. Examples of substituents include aryl groups, heteroaryl groups, linear alkyl groups, branched alkyl groups, aryl ether groups, alkoxy groups, and hydroxyl groups. Among these, aryl groups and aryl ether groups are preferred.

[0082] A phosphine oxide group is -P(=O)R 10 R 11 It is a group represented by . The R of the phosphine oxide group 10 R 11 The following group is selected. For details, see R 10 , R 11These may be the same or different, and are selected from a candidate group consisting of hydrogen atoms, alkyl groups, cycloalkyl groups, heterocyclic groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, hydroxyl groups, thiol groups, alkoxy groups, alkylthio groups, aryl ether groups, arylthioether groups, aryl groups, heteroaryl groups, halogens, cyano groups, aldehyde groups, carbonyl groups, carboxyl groups, acyl groups, ester groups, amide groups, carbamoyl groups, amino groups, nitro groups, silyl groups, siloxanyl groups, boryl groups, sulfo groups, sulfonyl groups, phosphine oxide groups, and fused rings and aliphatic rings formed between adjacent substituents.

[0083] R 10 R 11 When the aryl group is substituted or unsubstituted, the aryl group is preferably a phenyl group, biphenyl group, terphenyl group, naphthyl group, fluorenyl group, phenanthryl group, or anthracenyl group, and more preferably a phenyl group, biphenyl group, terphenyl group, or naphthyl group. Even more preferably, it is a phenyl group, biphenyl group, or terphenyl group, with the phenyl group being particularly preferred.

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

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

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

[0087] Furthermore, in compounds represented by general formula (1) or general formula (2), any two adjacent substituents may bond to each other to form a conjugated or unconjugated fused ring. The constituent elements of the fused ring may include elements selected from nitrogen, oxygen, sulfur, phosphorus, and silicon, in addition to carbon. The fused ring may also be further fused with another ring.

[0088] Examples of substituted or unsubstituted ring-forming aryl rings with 6 to 30 carbon atoms in rings Za, Zb, and Zc include aromatic hydrocarbon rings such as benzene, naphthalene, phenanthrene, chrysene, anthracene, and pyrene rings. Among these, the benzene ring is preferred from the viewpoint of ensuring solubility. Examples of heteroaryl rings with 6 to 30 carbon atoms that form the ring include aromatic heteroaryl ring structures such as pyridine, quinoline, and phenanthroline rings. Among these, the pyridine ring is preferred from the viewpoint of ease of obtaining raw materials and difficulty of synthesis.

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

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

[0091] Z in general formula (1) 1 and Z 2 It is preferable that the atom is an oxygen atom or NRa. This is 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 general formula (1) is preferably a boron atom, and E in general formula (2) 1 and E 2It is preferable that the compound is BRa. This is 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] In other words, the above-mentioned delayed fluorescence material is a compound represented by general formula (1), wherein E in general formula (1) is a boron atom, and Z 1 and Z 2 Preferably, each of them is an oxygen atom or NRa independently. Alternatively, the delayed fluorescence material is a compound represented by general formula (2), wherein E in general formula (2) 1 and E 2 It is preferable that each of them be independently BRa.

[0094] Furthermore, it is preferable that rings Za, Zb, and Zc are benzene rings. This is 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] Compounds represented by general formula (1) or general formula (2) are molecules that can separate the HOMO and LUMO orbitals by multiple resonance effects by optimally arranging an electron-donor amine nitrogen atom and an electron-acceptor boron atom, as described, for example, in reference Adv. Mater., 2016, 28, 2777-2781. From the perspective of clearly separating the HOMO and LUMO orbitals and bringing the singlet excited state and triplet excited state closer together to facilitate delayed fluorescence emission, in general formula (1), E is a boron atom with strong electron-acceptor properties, and Z 1 and Z 2 It is preferable that both are NRa groups, which are groups with strong electron donor properties. That is, when the delayed fluorescence material is a compound represented by general formula (1), E is a boron atom and Z 1 and Z 2 It is preferable that it be NRa.

[0096] Furthermore, the emission spectra of compounds represented by general formula (1) or general formula (2) are sharper than those of compounds that combine an electron donor skeleton and an electron acceptor skeleton due to the multiple resonance effect of the compound. Therefore, by using a compound represented by general formula (1) or general formula (2) as a delayed fluorescence material, high color purity emission can be obtained. In other words, 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 fluorescence materials. In addition, in compounds represented by general formula (1) or general formula (2), since rings Za, Zb, and Zc exist around the E atom in general formula (1) or general formula (2) where the LUMO orbital is mainly localized, the LUMO orbital can be delocalized from the E atom across each ring. By delocalizing the LUMO orbital, the multiple resonance effect works efficiently, resulting in higher color purity emission. Note that the above E atom is the E atom in general formula (1) and E in general formula (2). 1 and E 2 These are the atoms of [the plant].

[0097] Furthermore, it is more preferable that the substituent Ra of general formula (1) or general formula (2) forms a ring structure bonded to at least one of the rings of ring Za, ring Zb, and ring Zc. This is because the bonding of the substituent Ra to at least one of the rings of ring Za, ring Zb, and ring Zc allows for the formation of E in general formula (1) and E in general formula (2). 1 and E 2 This is because the steric protection effect of E and E is expected to 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 steric protection, it is even more preferable if the compound represented by general formula (1) is the compound represented by general formula (2).

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

[0099] [ka]

[0100] Furthermore, the delayed fluorescence material is preferably at least one of the following light-emitting materials (a) and (b). That is, it is preferable that at least one of the light-emitting materials (a) and (b) is a compound that emits delayed fluorescence.

[0101] Light-emitting material (a) is a light-emitting material that exhibits emission observed in the region of peak wavelength between 500 nm and 580 nm when excited by excitation light in the wavelength range of 430 nm to 500 nm. Light-emitting material (b) is a light-emitting material that exhibits emission observed in the region of peak wavelength between 580 nm and 750 nm when excited by excitation light in the wavelength range of 430 nm to 500 nm, emission from light-emitting material (a), or both. Hereafter, emission observed in the region of peak wavelength between 500 nm and 580 nm will be referred to as "green emission," and emission observed in the region of peak wavelength between 580 nm and 750 nm will be referred to as "red emission."

[0102] (solvent) In the color conversion sheet of the present invention, the color conversion layer contains a residual solvent, which is a trace amount of 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 above the above lower limit is thought to be as follows.

[0103] The triplet excited delayed fluorescence materials contained in the color conversion layer include charge-delocalized excited species in which positively charged holes 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 a triplet excited state to a singlet excited state in delayed fluorescence materials occurs when the energy levels of the neutral excited species (a type of triplet excited state) and the excited species in the singlet excited state are close. This is in accordance with the quantum mechanical law that conversion between singlet and triplet excited states, or vice versa, only occurs between excited species with different charge distributions. In other words, whether the reverse conversion occurs at room temperature depends on the energy difference between the excited species when the charge distributions of 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 include 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 the stabilization of the energy state of the light-emitting material by including a solvent. Generally, the more polar a molecule is, the greater the effect of the solvent effect on stabilizing its energy state.

[0106] The stabilization of the excitation energy of the luminescent material occurs through the solvent effect. However, 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 its excitation energy by the solvent effect. As a result, the difference between the energy levels of 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] Furthermore, from the viewpoint of suppressing oxidative degradation of the delayed fluorescence material, the upper limit of the residual solvent amount in the color conversion layer is 30,000 ppm by mass or less, preferably 10,000 ppm by mass or less, and more preferably 5,000 ppm by mass or less. When the residual solvent amount is below the above upper limit, the fluidity of the resin in the color conversion layer decreases, which reduces the probability of contact between the luminescent material in the color conversion layer and singlet oxygen. This reduces the reaction rate of the luminescent material that undergoes oxidative degradation due to contact with singlet oxygen. The residual solvent amount in the color conversion layer can be measured by gas chromatography.

[0108] To include residual solvent in the color conversion layer, for example, the solvent content in the color conversion layer can be adjusted to a minute amount by drying the color conversion layer. Drying of the color conversion layer can be done using a general 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 within the above 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. In addition, when drying the color conversion layer, it is also possible to heat-cur the color conversion layer in stages using methods such as step curing.

[0109] Furthermore, from the viewpoint of further improving the durability of the color conversion sheet, it is preferable that the residual solvent in the color conversion layer has functional groups with an SP value of 11.0 to 20.0. Having functional groups within this SP value range in the residual solvent increases the solvent effect described above, thereby promoting the reverse conversion from the triplet excited state to the singlet excited state of the delayed fluorescence material, and thus further improving the durability of the color conversion sheet. The SP value of the functional groups in the residual solvent can be calculated using the Fedors method from the following formula. SP value (δ) = (E / V) 1 / 2

[0110] In the formula for the SP value above, E represents the molar heat of vaporization (cal / mol), and V represents the molar volume (cm³).3 This represents ( / mol). In other words, the unit of the SP value of the functional group in the residual solvent in the color conversion layer is (cal / cm³). 3 ) 1 / 2 That is the case.

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

[0112] Examples of solvents included 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. A list of the functional groups and SP values ​​of these solvents is shown in Tables 1-1 and 1-2.

[0113] [Table 1-1]

[0114] [Table 1-2]

[0115] Among these solvents, highly polar solvents are preferred from the viewpoint of improving the durability of the color conversion sheet. For example, toluene, 1-methoxy-2-propanol, 2-propanol, ethyl acetate, ethanol, methyl ethyl ketone, and acetone are preferred. Furthermore, from the viewpoint of improving the durability of the color conversion sheet, solvents having functional groups with an SP value of 11.0 to 20.0 are more preferred. Specifically, 1-methoxy-2-propanol, ethyl acetate, methyl ethyl ketone, and acetone are more preferred. Ethyl acetate is particularly preferred because it does not affect the degradation of the delayed fluorescence material and makes it easy to adjust the amount of residual solvent after drying the color conversion layer to 10 ppm to 30,000 ppm by mass.

[0116] (Binder resin) The binder resin forms a continuous phase and can be any material that has excellent moldability, transparency, heat resistance, etc. Examples of binder resins include, for example, photocurable resist materials having reactive vinyl groups such as acrylic acid-based, methacrylic acid-based, polyvinyl cinnamate-based, and ring rubber-based resins, 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 even more preferred because the sheet formation process is easy. Among thermoplastic resins, epoxy resins, silicone resins, acrylic resins, ester resins, olefin resins, or mixtures thereof can be suitably used from the viewpoint of transparency, heat resistance, etc. Furthermore, from the viewpoint of durability, acrylic resins, ester resins, and cycloolefin resins are particularly preferred thermoplastic resins.

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

[0118] Furthermore, the binder resin is preferably a resin that contains a substructure represented by general formula (3) and a substructure represented by general formula (4) in its molecular structure. In particular, in the color conversion sheet of the present invention, the binder resin in the color conversion layer contains a substructure represented by general formula (3) and a substructure represented by general formula (4) in its molecular structure, and the residual solvent in the color conversion layer has an SP value of 11.0 (cal / cm³). 3 ) 1 / 2 More than 20.0(cal / cm 3 ) 1 / 2 It is preferable that the following functional groups be present.

[0119] [ka]

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

[0121] The delayed fluorescence material contained in the color conversion sheet of the present invention is excited by light, but since the delayed fluorescence material in the excited state is highly reactive, if excited delayed fluorescence material is in close proximity to other excited delayed fluorescence material, the degradation of the delayed fluorescence material is accelerated. Therefore, in order to improve the durability of the delayed fluorescence material contained in the color conversion sheet, it is preferable that the delayed fluorescence material is well dispersed in the binder resin without agglomerating.

[0122] To effectively disperse the delayed fluorescence material in the binder resin, it is preferable that the binder resin in the color conversion layer contains both substructures with high compatibility with the delayed fluorescence material and substructures with low compatibility. A more preferred form of such a binder resin is a copolymer that randomly contains substructures with high and low compatibility with the delayed fluorescence material.

[0123] The delayed fluorescence material contained in the color conversion sheet of the present invention has the characteristic of having good compatibility with the substructure represented by general formula (3) in the molecular structure of the binder resin, but poor compatibility with the substructure represented by general formula (4). Therefore, by having both the substructure represented by general formula (3) and the substructure represented by general formula (4) in the binder resin, the light-emitting material such as the delayed fluorescence material can be well dispersed in the binder resin within the color conversion layer. As a result, it is possible to achieve high durability of the color conversion sheet. This effect is even greater when the delayed fluorescence material is an organic light-emitting material.

[0124] The delayed fluorescence material contained in the color conversion sheet of the present invention may undergo radical oxidation by radicals derived from functional groups and hygroscopic moisture contained in the molecules of the binder resin, resulting in decomposition or degradation. For this reason, 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 substructure represented by general formula (3) in the binder resin, Z 1 It is preferably a hydrogen atom or a methyl group, and more preferably a methyl group.

[0125] Furthermore, from the viewpoint of improving the heat resistance of the binder resin, in the substructure represented by general formula (3) in the binder resin, Z 2is 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 arylthioether group, an aryl group or a heteroaryl group. Further, these groups may be further substituted by the above-described substituents. Among these, Z in the partial structure represented by the general formula (3) 2 is more preferably a methyl group from the viewpoints of availability and cost.

[0126] The description of "alkyl group" and the like in the binder resin and the description of "unsubstituted" in the case of "substituted or unsubstituted" are the same as those described for the above-mentioned delayed fluorescence material.

[0127] Further, from the viewpoint of enhancing the heat resistance of the binder resin, in the partial structure represented by the general formula (4) in the binder resin, 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 arylthioether group, an aryl group or a heteroaryl group. Further, these groups may be further substituted by the above-described substituents.

[0128] However, Y in the general formula (4) 1 ~Y 4At least one of them is a group containing an aliphatic cyclic hydrocarbon structure. Examples of the aliphatic cyclic hydrocarbon structure include a substituted or unsubstituted saturated cyclic hydrocarbon (cycloalkyl) structure, an unsaturated cyclic hydrocarbon (cycloalkenyl) structure, and the like. Among these, from the viewpoint of durability, a saturated cyclic hydrocarbon (cycloalkyl) structure is preferred. The number of carbon atoms constituting such an aliphatic cyclic 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 having the number of carbon atoms constituting the aliphatic cyclic hydrocarbon structure within the above range, high durability can be obtained while ensuring the compatibility between the partial structure represented by the general formula (4) in the binder resin and the light-emitting material.

[0129] Specific examples of the saturated cyclic hydrocarbon (cycloalkyl) structure include, for example, structures obtained by hydrogenating the aromatic ring portions of polymers of aromatic vinyl monomers 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 vinyl monomers 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 in the general formula (4) 1 ~Y 4 As long as at least one of them is a group containing an aliphatic cyclic hydrocarbon structure, there is no particular limitation on the combination of these Y 1 ~Y 4 Particularly, from the viewpoints of availability and cost, at least one of Y 1 ~Y 4 in the general formula (4) is preferably a substituted or unsubstituted cyclohexyl group. Also, Y 1 ~Y 4It is more preferable that one of these is a substituted or unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0131] The content of repeating units of the substructure 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% by weight or more, more preferably 50% by weight or more, even more preferably 60% by weight or more, and particularly preferably 70% by weight or more, of the total amount of the binder resin. By having the content of repeating units of the substructure represented by general formula (3) in a range above the lower limit of the above, compatibility between the substructure represented by general formula (3) and the delayed fluorescence material can be ensured, and as a result, higher durability can be obtained.

[0132] Furthermore, the content of repeating units of the substructure 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 keeping the content of repeating units of the substructure represented by general formula (3) within the range of the above upper limit, a color conversion sheet with excellent crack resistance can be obtained.

[0133] The content of repeating units of the substructure represented by general formula (4) in the binder resin contained in the color conversion sheet of the present invention is not particularly limited, but it is preferably 5% by weight or more, more preferably 10% by weight or more, and particularly preferably 15% by weight or more of the total amount of the binder resin. By keeping the content of repeating units of the substructure represented by general formula (4) above the lower limit of the above value, 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 repeating units of the substructure represented by general formula (4) in the binder resin contained in the color conversion sheet of the present invention is preferably 70% by weight or less, more preferably 50% by weight or less, and particularly preferably 30% by weight or less, of the total amount of the binder resin. By keeping the content of repeating units of the substructure represented by general formula (4) within the range of the above upper limit, compatibility between the substructure represented by general formula (4) and the delayed fluorescence 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. If the weight-average molecular weight is within the above upper and lower limits, 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 this invention is a value measured by gel permeation chromatography (GPC). Specifically, the sample is filtered through a membrane filter with a pore size of 0.45 μm, and then the value is determined by converting it to polystyrene equivalent using a GPC apparatus (HLC-82A, manufactured by Tosoh Corporation) (developing solvent: toluene, development rate: 1.0 ml / min, column: TSKgelG2000HXL, 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 above binder resin can be measured using a commercially available measuring instrument, such as a differential scanning calorimeter manufactured by Seiko Electronics Industries (product name DSC6220, heating rate 0.5°C / min).

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

[0140] Furthermore, the binder resin may be modified with additives such as dispersants and leveling agents to stabilize the coating film, or with adhesive aids such as silane coupling agents to modify the color conversion layer surface. In addition, inorganic particles such as silica particles or silicone microparticles may be added to the binder resin as a color conversion material settling inhibitor.

[0141] In the color conversion composition for producing the color conversion sheet of the present invention, it is preferable to include a hydrosilylation reaction retarder such as acetylene alcohol as an additional component in the binder resin to suppress curing at room temperature and extend the pot life. Furthermore, the binder resin may optionally contain fine particles such as fumed silica, glass powder, or quartz powder, inorganic fillers such as titanium dioxide, zirconia oxide, barium titanate, or zinc oxide, pigments, flame retardants, heat resistant agents, antioxidants, dispersants, solvents, adhesion promoters such as silane coupling agents or titanium coupling agents, etc., to the extent that the effects of the present invention are not impaired.

[0142] (Other additives) In addition to the delayed fluorescence material, binder resin, and residual solvent described above, the color conversion sheet of the present invention may also contain other components (additives) such as light stabilizers, antioxidants, processing and heat stabilizers, lightfastness stabilizers such as ultraviolet absorbers, scattering particles, silicone fine particles, and silane coupling agents.

[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 lanthanides. These light stabilizers may be used individually or in combination.

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

[0145] Examples of processing and heat stabilizing agents include phosphorus-based stabilizers such as tributyl phosphite, tricyclohexyl phosphite, triethylphosphine, and diphenylbutylphosphine, but are not limited to these. These stabilizers may be used individually or in combination.

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

[0147] As scattering particles, inorganic particles having a refractive index of 1.7 to 2.8 are preferred. Examples of such inorganic particles include titania, zirconia, alumina, ceria, tin oxide, indium oxide, iron oxide, zinc oxide, aluminum nitride, aluminum, tin, titanium or zirconium sulfides, titanium or zirconium hydroxides, and the like.

[0148] In the color conversion sheet of the present invention, the content of these additives depends on the molar extinction coefficient, emission 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 made, but is usually 1.0 × 10 per 100 parts by weight of the binder resin. -3 It is preferable that the amount is between parts by weight and 30 parts by weight. Furthermore, the content of these additives should be 1.0 × 10 per 100 parts by weight of the binder resin. -2 It is more preferably between parts by weight and 15 parts by weight, and 1.0 × 10 -1 It is particularly preferable that the amount is between parts by weight and 10 parts by weight.

[0149] (Method for manufacturing color-changing compositions) The following describes an example of a method for producing a color conversion composition for creating a color conversion layer contained in the color conversion sheet of the present invention. In this method, predetermined amounts of the aforementioned delayed fluorescence material, binder resin, solvent, and optionally additives are mixed. After mixing these components to a predetermined composition, the color conversion composition can be obtained by homogenizing the mixture using a stirring / kneading machine. Examples of stirring / kneading machines include homogenizers, orbital stirring machines, three-roller machines, ball mills, planetary ball mills, and bead mills. Degassing under vacuum or reduced pressure conditions is also preferably performed after mixing or dispersion, or during the mixing or dispersion process. In addition, certain components may be mixed in advance, or treatments such as aging may be performed. It is also possible to remove the solvent using an evaporator to obtain the desired solid content concentration.

[0150] (base material layer) Examples of the substrate layer in the color conversion sheet of the present invention (for example, the substrate layer 10 shown in Figures 2-4) include glass and resin films. Preferred resin films are plastic films such as polyethylene terephthalate (PET), polyphenylene sulfide, polycarbonate, polypropylene, and polyimide. The substrate layer may be pre-treated for release due to its ease of peeling. While there are no particular restrictions on the thickness of the substrate layer, a minimum of 25 μm is preferred, and a minimum of 38 μm is more preferred. A maximum of 5000 μm is preferred, and a minimum of 3000 μm is more preferred.

[0151] (Barrier film) The barrier film in the color conversion sheet of the present invention (for example, the barrier film 12 shown in Figure 4) is used as appropriate when it is necessary to improve the gas barrier properties of the color conversion layer. Preferably, this barrier film (also called the barrier layer) 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 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 illustrated by the barrier film 12 in Figure 4, or it 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 carbide nitride; metal oxide thin films and metal nitride thin films obtained by adding other elements to these; or films containing various resins such as polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, urethane resins, fluororesins, and polyvinyl alcohol resins such as saponified vinyl acetate. The barrier film may contain two or more of these. Examples of barrier films having a barrier function against moisture 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, fluororesins, and polyvinyl alcohol 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-reflective function, an anti-glare function, an anti-reflective 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 cut function, an ultraviolet cut function, a polarization function, a color tuning function, etc., depending on the required function.

[0154] (Other films) The color conversion sheet of the present invention may further comprise a polarizing reflective film, a diffusion sheet, a prism sheet, a wavelength selective reflective film, and the like. Suitable examples of the wavelength selective reflective film include, for example, those described in International Publication No. 2017 / 164155 and Japanese Patent Application Publication No. 2018-81250.

[0155] <How to manufacture a color conversion sheet> Next, an example of a method for manufacturing the color-converting sheet of the present invention will be described. In this method for manufacturing the color-converting sheet, the color-converting composition prepared by the method described above is applied to a substrate such as a base layer or a barrier layer and dried. This forms a color-converting layer. If the binder resin contained in the color-converting composition is a thermosetting resin, the color-converting layer may be formed by applying the color-converting composition to a substrate such as a base layer and then heat-curing it. If the binder resin contained in the color-converting composition is a photocurable resin, the color-converting layer may be formed by applying the color-converting composition to a substrate such as a base layer and then photocuring it.

[0156] The color conversion 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. To obtain uniform film thickness of the color conversion layer, it is preferable to apply it using a slit die coater, comma coater, or dip coater.

[0157] The color conversion layer can be dried using a general 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-cur the color conversion layer in stages using methods such as step curing.

[0158] When forming a color conversion layer by heat curing, a hot air oven or the like is used as the heating device. The heating conditions for the heat curing of the color conversion layer can be selected according to 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 according to the binder resin. For example, the wavelength of the irradiated light is preferably 200 nm to 500 nm, and the light irradiation dose is 10 mJ / cm². 2 ~10J / cm 2 It is preferable that this be the case.

[0160] After creating the color conversion layer, it is also possible to change the substrate layer as needed. In this case, simple methods include, for example, using a hot plate to replace the layer, or using a vacuum laminator or 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-mentioned color conversion composition or color conversion sheet. The light source included in the light source unit of the present invention is the source of the above-mentioned excitation light. The arrangement of the light source and the color conversion sheet is not particularly limited; the light source and the color conversion sheet may be in close contact, or a remote phosphor configuration may be adopted in which the light source and the color conversion sheet are separated. Furthermore, the light source unit of the present invention may also be configured to include a color filter for the purpose of improving color purity.

[0162] (light source) The light source unit of the present invention can use any light source as long as it emits light in the wavelength range absorbable by the delayed fluorescence material. For example, any excitation light source such as a hot cathode tube, cold cathode tube, inorganic electroluminescent (EL) light source, organic EL element light source, LED light source, incandescent light source, or sunlight can be used in principle. Among these, an LED light source is preferred. For display and lighting applications, a blue LED light source having maximum emission in the wavelength range of 430 nm to 500 nm is even more preferred because it can enhance the color purity of blue light.

[0163] The above light source may have one type of emission peak or two or more types of emission peaks, but to improve color purity, one with one type of emission peak is preferable. It is also possible to use multiple light sources with different types of emission peaks in any combination.

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

[0165] <Displays, lighting equipment> A display according to an embodiment of the present invention comprises 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 light source and a color conversion sheet described above as a backlight unit. Furthermore, a lighting device according to an embodiment of the present invention comprises 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 a light source unit with a color conversion sheet that converts the blue light from the blue LED light source into light with a longer wavelength. [Examples]

[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 in the examples and comparative examples will be explained.

[0167] <Durability Evaluation> In the durability evaluation, for each example and comparative example, a light-emitting device equipped with the fabricated color conversion sheet and a blue LED element (USHIO EPITEX; model number SMBB450H-1100, emission peak wavelength: 450 nm) was illuminated by passing a 30 mA current through the blue LED element, and the initial emission peak intensity of green light and red light was measured using a spectroradiometer (CS-1000, Konica Minolta). The distance between the color conversion sheet and the blue LED element in each light-emitting device was set to 3 cm. Subsequently, after 1000 hours of continuous irradiation with light from the blue LED element in a 50°C environment, the emission peak intensity of green light and red light were measured in the same manner. The durability of the chromaticity of the color conversion sheet was evaluated by comparing these obtained emission peak intensities of green and red light with the initial emission peak intensities of green and red light, and calculating the retention rate of the emission peak intensity for each of the green and red lights. The retention rate of the emission peak intensity can be calculated using the following formula. Emission peak intensity maintenance rate Z (%) = Y / X × 100 In the above equation, 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 prepared color conversion sheet was cut into 8 mm squares to prepare a sample, and the fluorescence quantum yield was measured when the sample was excited with excitation light at a wavelength of 450 nm using an absolute fluorescence quantum yield analyzer (Quantaurus-QY, Hamamatsu Photonics).

[0169] <Measurement of residual solvent volume> The amount of residual solvent in the color conversion layer was measured by the following procedure. Specifically, first, a color conversion layer was formed on a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick). Next, the formed color conversion layer was peeled off the polyester film, and 20 mg of the obtained color conversion layer was weighed out. Then, this 20 mg of color conversion layer was dissolved in 2 mL of NMP to prepare 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℃ Carrier gas: He Carrier gas flow rate: 6 mL / min Heating conditions: After holding at 40°C for 4 minutes, the temperature is raised to 260°C at a heating rate of 8°C / minute, and then held for 16 minutes.

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

[0171] [ka]

[0172] [ka]

[0173] <Binder resin> In each example and comparative example, the following resins A, B, C, and D were used as binder resins.

[0174] (Resin A) In this specification, resin A is resin F as described in International Publication No. 2019 / 021813. Resin A is a binder resin containing 95.0% by weight of a substructure represented by general formula (3) and 5.0% by weight of a substructure represented by general formula (4). In this resin A, the substructure Y represented by general formula (4) 1 ~Y 4 Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

[0175] (Resin B) In this specification, resin B is resin G (Optimas 6000 (PMMA-hydrogenated styrene copolymer manufactured by Mitsubishi Gas Chemical Co., Ltd.)) as described in International Publication No. 2019 / 021813. Resin B is a binder resin containing 61.0% by weight of a substructure represented by general formula (3) and 39.0% by weight of a substructure represented by general formula (4). In this resin B, the substructure Y 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) In this specification, resin C is resin H (Optimas 7500 (PMMA-hydrogenated styrene copolymer manufactured by Mitsubishi Gas Chemical Co., Ltd.)) as described in International Publication No. 2019 / 021813. Resin C is a binder resin containing 77.0% by weight of a substructure represented by general formula (3) and 23.0% by weight of a substructure represented by general formula (4). In this resin C, the substructure Y 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) In this specification, resin D is resin I as described in International Publication No. 2019 / 021813. Resin D is a binder resin containing 75.7% by weight of a substructure represented by general formula (3) and 24.3% by weight of a substructure represented by general formula (4). In this resin D, Y of the substructure represented by general formula (4) 1 ~Y 4 Of these, one is an unsubstituted cyclohexyl group, and the other three are hydrogen atoms.

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

[0179] (Examples 1-4) In Examples 1 to 4, 100 parts by weight of a binder resin (resin A, resin B, resin C, or resin D) shown in Table 2 below was mixed with 0.40 parts by weight of compound G-1 as luminescent material (a), 0.01 parts by weight of compound R-1 as luminescent material (b), and 300 parts by weight of ethyl acetate as a solvent. These mixtures were then stirred and defoamed at 1000 rpm for 20 minutes using a planetary stirring and defoaming device "Mazelstar KK-400" (manufactured by Kurabo Corporation) to obtain a color conversion composition as a resin liquid for producing a color conversion layer.

[0180] Similarly, polyester resin "Vylon630" (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. These mixtures were then stirred and defoamed at 300 rpm for 20 minutes using a planetary stirring and defoaming device "Mazelstar KK-400" (manufactured by Kurabo Corporation), thereby obtaining a resin composition for use as an adhesive composition.

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

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

[0183] Next, the two units described above were laminated by heating so that the color conversion layer and the adhesive layer were directly stacked, thereby creating a color conversion sheet with the configuration of "substrate layer / color conversion layer / adhesive layer / substrate layer / light diffusion layer". Various evaluations of the obtained color conversion sheet were performed using the method described above. The configuration and evaluation results of the color conversion sheets in each of Examples 1 to 4 are shown in Table 2.

[0184] (Example 5) In Example 5, the same method as in Example 1 was used to prepare the color conversion sheet and to perform various evaluations of the color conversion sheet, except that compound R-2 was used as the luminescent material (b). The composition of the color conversion sheet in Example 5 and the evaluation results are shown in Table 2.

[0185] (Example 6) In Example 6, the same method as in Example 1 was used to prepare the color conversion sheet and to perform various evaluations of the color conversion sheet, except that compound G-2 was used as the light-emitting material (a). The composition of the color conversion sheet in Example 6 and the evaluation results are shown in Table 2.

[0186] (Examples 7-13) In Examples 7 to 13, the same method as in Example 1 was used for the preparation of color conversion sheets and various evaluations of the color conversion sheets, except that the drying temperature and drying time were changed as shown in Table 3 below. The composition of the color conversion sheets and the evaluation results for each of Examples 7 to 13 are shown in Table 3.

[0187] (Example 14) In Example 14, the same method as in Example 1 was used for the preparation of the color conversion sheet and various evaluations of the color conversion sheet, except that toluene was used as the solvent and the drying temperature and drying time were changed as shown in Table 3. The composition of the color conversion sheet in Example 14 and the evaluation results are shown in Table 3.

[0188] (Comparative Example 1) In Comparative Example 1, the same method as in Example 1 was used to prepare a color conversion sheet and to perform various evaluations of the color conversion sheet, except that compound G-2 was used as the light-emitting material (a) and compound R-2 was used as the light-emitting material (b). The composition of the color conversion sheet in Comparative Example 1 and the evaluation results are shown in Table 4.

[0189] (Comparative Example 2) In Comparative Example 2, the same method as in Example 1 was used to prepare the color conversion sheet and to perform various evaluations of the color conversion sheet, except that the drying temperature and drying time were changed as shown in Table 4. The composition of the color conversion sheet in Comparative Example 2 and the evaluation results are shown in Table 4.

[0190] (Comparative Example 3) In Comparative Example 3, the same method as in Comparative Example 1 was used for the preparation of the color conversion sheet and various evaluations of the color conversion sheet, except that the drying temperature and drying time were changed as shown in Table 4. The composition of the color conversion sheet in Comparative Example 3 and the evaluation results are shown in Table 4.

[0191] [Table 2]

[0192] [Table 3]

[0193] [Table 4]

[0194] In Tables 2-4, "Maintenance of green light emission peak intensity" refers to the durability evaluation result of the chromaticity of the light-emitting material (a) included in the color conversion sheet. "Maintenance of red light emission peak intensity" refers to the durability evaluation result of the chromaticity of the light-emitting material (b) included in the color conversion sheet. [Industrial applicability]

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

[0196] 1A, 1B, 1C, 1D Color Conversion Sheet 10 Base material layer 11 Color Conversion Layers 12 Barrier film

Claims

1. A color conversion sheet that converts incident light into light of a different wavelength than the incident light, The material includes at least a color conversion layer containing a compound that emits delayed fluorescence and a binder resin, The amount of solvent in the color conversion layer is 10 ppm by mass or more and 30,000 ppm by mass or less. The solvent in the color conversion layer has functional groups with an SP value of 11.0 (cal / cm³) 1 / 2 or more and 20.0 (cal / cm³) 1 / 2 or less. A color conversion sheet characterized by the following features.

2. The binder resin has a substructure represented by general formula (3) and a substructure represented by general formula (4) in its molecular structure. The color conversion sheet according to feature 1. 【Chemistry 1】 (In general formula (3), Z 1 and Z 2 These may be the same or different from each other, and are hydrogen atoms or organic groups having 1 to 20 carbon atoms. In general formula (4), Y 1 ~Y 4 These may be the same or different, and are a hydrogen atom or an organic group having 1 to 20 carbon atoms, and Y 1 ~Y 4 At least one of these groups contains an aliphatic cyclic hydrocarbon structure.

3. In the general formula (4) above, Y 1 ~Y 4 At least one of them is a substituted or unsubstituted cyclohexyl group. The color conversion sheet according to feature 2.

4. 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. The color conversion sheet according to feature 2.

5. The compound that emits delayed fluorescence is at least one of the following light-emitting materials (a) and (b): The color conversion sheet according to feature 1. Light-emitting material (a): A light-emitting material that exhibits emission observed in the region of 500 nm to less than 580 nm when excitation light in the wavelength range of 430 nm to 500 nm is used. Light-emitting material (b): A light-emitting material that, when excited by excitation light in the wavelength range of 430 nm to 500 nm, or by emission from light-emitting material (a), or both, exhibits emission observed in the region of 580 nm to 750 nm with a peak wavelength.

6. The compound that emits delayed fluorescence contains a compound represented by the following general formula (1) or general formula (2). The color conversion sheet according to feature 1. 【Chemistry 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. 1 and Z 2 These are, independently, an oxygen atom, an NRa (a nitrogen atom with a substituent Ra), or a sulfur atom. 1 If is NRa, the substituent Ra may bond to ring Za or ring Zb to form a ring. 2 If is NRa, the substituent Ra may bond to a ring Za or a ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom with substituent Ra), or P=O. 1 and E 2 These are, independently, BRa (a boron atom with a substituent Ra), PRA (a phosphorus atom with a substituent Ra), and SiRa 2 (Silicon atom with two substituents Ra), C=O, P(=O)Ra 2 (Phosphine oxide having two substituents Ra) or P(=S)Ra 2 (Phosphine sulfide having two substituents Ra), S(=O) or S(=O) 2 It is. E 1 is BRa, PRa, SiRa 2 , P(=O)Ra 2 Or P(=S)Ra 2 In this case, the substituent Ra may bond to ring Za or ring Zb to form a ring. 2 is BRa, PRa, SiRa 2 , P(=O)Ra 2 Or P(=S)Ra 2 In this case, the substituent Ra may bond to ring Za or ring Zc to form a ring. Each substituent Ra is independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

7. The compound that emits delayed fluorescence is a compound represented by the general formula (1), wherein E in the general formula (1) is a boron atom, and Z 1 and Z 2 Each of them is independently NRa, or the compound that emits the delayed fluorescence is a compound represented by the general formula (2), and E in the general formula (2) 1 and E 2 Each of them is independently BRa. The color conversion sheet described in feature 6.

8. Light source and A color conversion sheet according to any one of claims 1 to 7, A light source unit characterized by including the following.

9. The light source is a light-emitting diode that has maximum emission in the wavelength range of 400 nm to 500 nm. The light source unit according to claim 8.

10. A light source unit as described in claim 8, A display characterized by the following features.

11. A light source unit as described in claim 8, A lighting device characterized by the following features.

Images