Color conversion chip, including its light source unit, display and lighting device

Abstract

As one embodiment of the present invention, the color conversion sheet is a color conversion sheet that converts incident light into light with a wavelength different from the incident light, and includes a color conversion layer containing a compound that emits delayed fluorescence. The haze value of the color conversion sheet is 20% or more and 99% or less.

Description

Technical Field

[0001] This invention relates to a color conversion sheet, a light source unit including the color conversion sheet, a display, and an illumination device. Prior Technology

[0002] Multicolor conversion technology based on color conversion methods is being actively researched for applications in liquid crystal displays (LCDs), organic electroluminescence (EL) displays, lighting devices, and more. Color conversion refers to the conversion of light emitted from a light source into light with a longer wavelength; examples include converting blue light into green or red light.

[0003] By chipping a component with this color conversion function (hereinafter referred to as a color conversion component) and combining it with, for example, a blue light source, the three primary colors of blue, green, and red can be obtained from the blue light source, that is, white light can be obtained. This white light source, formed by combining a blue light source with a component with a color conversion function (hereinafter referred to as a color conversion component), can be used as a light source unit such as a backlight unit. Furthermore, by combining this light source unit with a liquid crystal driving section and a color filter, a full-color display can be manufactured. In addition, the white light source formed by combining a blue light source with a color conversion component can also be directly used as a white light source for light-emitting diode (LED) illumination.

[0004] As a problem with liquid crystal displays utilizing color conversion, examples include: color deviation in the light-emitting area of ​​the backlight device due to the light source; or insufficient durability. As a means to solve this problem, a technique has been proposed to increase the content of color conversion material per unit area in the peripheral portion of the color conversion sheet of the display (for example, see Patent Document 1). Furthermore, a technique has been disclosed to add a light stabilizer to prevent the degradation of the organic light-emitting material and improve durability (for example, see Patent Document 2). [Existing Technical Documents] [Patent Literature]

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-195583 Patent Document 2: Japanese Patent Application Publication No. 2011-241160 Summary of the Invention

[0006] [The problem that the invention aims to solve]

[0007] However, in the technology described in Patent Document 1, due to the increased content of color conversion material, there are problems such as reduced brightness due to phosphor aggregation, or insufficient durability. In addition, in the technology described in Patent Document 2, the in-plane uniformity of color cannot be ensured, and the balance between in-plane uniformity and durability is insufficient.

[0008] The present invention was made in view of the above circumstances, and aims to provide a color conversion sheet for use in light source units, displays and lighting devices, etc., and has excellent in-plane uniformity and durability of color. [Methods for solving problems]

[0009] In order to solve the aforementioned problems and achieve the objectives, the color conversion sheet involved in the present invention is a color conversion sheet that converts incident light into light with a wavelength different from that incident light. The color conversion sheet is characterized in that it includes a color conversion layer containing a compound that emits delayed fluorescence, and the haze value is 20% or more and 99% or less.

[0010] Furthermore, the color conversion layer of the present invention is characterized in that: in the invention, the color conversion layer contains scattering particles.

[0011] Furthermore, the color conversion sheet involved in this invention is characterized in that, in the invention, the absolute value of the zeta potential of the scattering particles at any value in the range of pH 4 or higher and 10 or lower is 20 mV or higher and 100 mV or lower.

[0012] Furthermore, the color conversion sheet involved in this invention is characterized in that, in the invention, the average particle size of the scattering particles is 100 nm or more and 700 nm or less.

[0013] Furthermore, the color conversion sheet involved in this invention is characterized in that, in the invention, the refractive index of the scattering particles is 1.4 or higher and 2.8 or lower.

[0014] Furthermore, the color conversion sheet involved in this invention is characterized in that: in the invention, the color conversion layer further comprises an adhesive resin, and when the adhesive resin is set to 100 parts by weight, the content of the scattering particles in the color conversion layer is 1.0 × 10⁻³ parts by weight or more and 30 parts by weight or less.

[0015] Furthermore, the color conversion sheet involved in this invention is characterized in that: in the invention, the scattering particles are at least one selected from aluminum oxide, titanium dioxide and zirconium oxide.

[0016] Furthermore, the color conversion sheet involved in this invention is characterized in that: in the invention, the scattering particles are titanium dioxide particles.

[0017] Furthermore, the color conversion sheet involved in this invention is characterized in that, in the invention, the compound that emits delayed fluorescence is at least one of the following luminescent materials (a) and (b). Luminescent material (a): A luminescent material that exhibits luminescence in a region with a peak wavelength of 500 nm or more but less than 580 nm when excited by excitation light in the range of 430 nm or more but less than 500 nm. Luminescent material (b): a luminescent material that exhibits luminescence in a region with a peak wavelength of 580 nm or more and 750 nm or less, by being excited by either or both of excitation light in the range of 430 nm or more and 500 nm or by luminescence from said luminescent material (a).

[0018] Furthermore, the color conversion sheet involved in this invention is characterized in that: in the invention, the compound that emits delayed fluorescence contains a compound represented by the following general formula (1) or general formula (2).

[0019] [Chemistry 1] In general formula (1) or general formula (2), rings Za, Zb, and Zc are independently substituted or unsubstituted rings forming aryl rings with 6 to 30 carbon atoms, or substituted or unsubstituted rings forming heteroaryl rings with 6 to 30 carbon atoms; Z1 and Z2 are independently oxygen atoms, NRa (nitrogen atoms with substituent Ra), or sulfur atoms; when Z1 is NRa, substituent Ra can bond with rings Za or Zb to form a ring; when Z2 is NRa, substituent Ra can bond with rings Za or Zc to form a ring; E is a boron atom, a phosphorus atom, SiRa (silicon atoms with substituent Ra), or P=O; E1 and E2 are independently BRa (boron atoms with substituent Ra), PRa (phosphorus atoms with substituent Ra), SiRa2 (silicon atoms with two substituent Ra), or P(=O)Ra. 2 (phosphine oxide with two substituents Ra) or P(=S)Ra 2 (phosphine sulfide with two substituents Ra), S(=O) or S(=O) 2; when E 1 is BRa, PRa, SiRa 2, P(=O)Ra 2 or P(=S)Ra 2, the substituent Ra can bond with ring Za or ring Zb to form a ring; when E 2 is BRa, PRa, SiRa 2, P(=O)Ra 2 or P(=S)Ra 2, the substituent Ra can bond with ring Za or ring Zc to form a ring; the substituent Ra is independently a substituted or unsubstituted aryl, a substituted or unsubstituted heteroaryl, or a substituted or unsubstituted alkyl.

[0020] Furthermore, the color conversion layer of the present invention is characterized in that: in the invention, the color conversion layer includes at least one of the following layers (A) and (B). (A) Layer: A layer containing the luminescent material (a) as the compound that emits delayed fluorescence. (B) Layer: A layer containing the luminescent material (b) as the compound that emits delayed fluorescence.

[0021] Furthermore, the color conversion sheet involved in this invention is characterized in that: in the invention, at least one of the (A) layer and the (B) layer contains scattering particles.

[0022] Furthermore, the light source unit involved in this invention is characterized by comprising: a light source, and a color conversion sheet as described in any one of the inventions.

[0023] Furthermore, the light source unit involved in this invention is characterized in that, in the invention, the light source is a light-emitting diode that has extremely high luminescence in the wavelength range of 400 nm or more and 500 nm or less.

[0024] Furthermore, the display according to the present invention is characterized by including: the light source unit described in the invention.

[0025] Furthermore, the lighting device according to the present invention is characterized by including: the light source unit described in the invention. [The effects of the invention]

[0026] The color conversion sheet involved in this invention exhibits excellent in-plane color uniformity and durability. Simple Explanation of the Diagram

[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. 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 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 is a schematic cross-sectional view showing a fourth example of a color conversion sheet according to an embodiment of the present invention. Implementation

[0028] The preferred embodiments of the color conversion sheet, the light source unit including the color conversion sheet, the display and the lighting device involved in the present invention will be described in detail below. However, the present invention is not limited to the following embodiments and can be implemented in various ways depending on the purpose or use.

[0029] Color conversion sheet The color conversion sheet according to the embodiments of the present invention is a color conversion sheet that converts incident light from a light source or other light-emitting body into light with a wavelength different from the incident light, and includes a color conversion layer containing a compound that emits delayed fluorescence. The haze value of the color conversion sheet is 20% or more and 99% or less. Here, "converting into light with a wavelength different from the incident light" preferably means converting the incident light into light with a wavelength longer than the incident light. Hereinafter, the color conversion sheet according to the embodiments of the present invention will sometimes be simply referred to as the color conversion sheet of the present invention.

[0030] The color conversion sheet of the present invention includes a layer comprising a color conversion composition or a cured form thereof, as described later, namely a color conversion layer. Preferably, the cured form of the color conversion composition is contained within the color conversion sheet as a layer obtained by curing the color conversion composition (a layer containing the cured form of the color conversion composition). As representative structural examples of the color conversion sheet of the present invention, the following four examples can be cited.

[0031] 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, the first example of the color conversion sheet 1A is a single-layer sheet composed of a color conversion layer 11. The color conversion layer 11 is a layer of hardened material containing the color conversion composition of the present invention.

[0032] 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, the color conversion sheet 1B of this second example is a laminate of a substrate 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 the substrate layer 10.

[0033] Figure 3 is a schematic cross-sectional view showing a third example of the color conversion sheet according to an embodiment of the present invention. As shown in Figure 3, the color conversion sheet 1C of this third example is a laminate of multiple 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 multiple substrate layers 10.

[0034] Figure 4 is a schematic cross-sectional view showing a fourth example of the color conversion sheet according to an embodiment of the present invention. As shown in Figure 4, the color conversion sheet 1D of this fourth example is a laminate of multiple substrate layers 10, a color conversion layer 11, and multiple barrier films 12. In this structural example of the color conversion sheet 1D, the color conversion layer 11 is sandwiched between multiple barrier films 12, and furthermore, the laminate of the color conversion layer 11 and the multiple barrier films 12 is sandwiched between multiple substrate layers 10. That is, in the color conversion sheet 1D, in order to prevent the color conversion layer 11 from deteriorating due to oxygen, moisture, or heat, as shown in Figure 4, a barrier film 12 may also be provided.

[0035] 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, specifically the film thickness (average film thickness) measured by method A of mechanical scanning thickness measurement in Japanese Industrial Standards (JIS) K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods. By setting the thickness of the color conversion sheet of the present invention to 30 μm or more, the strength and 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, cracking of the color conversion sheet can be suppressed.

[0036] (Color conversion layer) In this invention, the color conversion layer (for example, color conversion layer 11 shown in Figures 1-4) contains a compound that emits delayed fluorescence (hereinafter, sometimes referred to as "delayed fluorescence material"). In addition, the color conversion layer may further contain an adhesive resin.

[0037] There is no particular limitation on the thickness of the color conversion layer, but it is preferably 10 μm or more and 1000 μm or less. The lower limit of the color conversion layer thickness is more preferably 30 μm or more. Furthermore, the upper limit of the color conversion layer thickness is preferably 200 μm or less, 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 by method A of mechanical scanning thickness measurement in JIS K7130 (1999) Plastics – Films and Sheets – Thickness Measurement Methods.

[0038] The aforementioned color conversion layer can be formed by coating a color conversion composition prepared by the method described later onto a substrate such as a substrate layer or a barrier film and allowing it to dry.

[0039] In the color conversion sheet of the present invention, the color conversion layer may be one layer or two or more layers. In addition to containing the aforementioned delayed fluorescence material and adhesive resin, the color conversion layer may also contain other components (additives) such as light stabilizers, antioxidants, processing and heat stabilizers, lightfastness stabilizers such as ultraviolet absorbers, silicone microparticles and silane coupling agents.

[0040] (A compound that emits delayed fluorescence) Compounds emitting delayed fluorescence (delayed-fluorescent materials) are explained on pages 87-103 of "The Most Advanced Organic Electron Microscopy" (edited by Chihaya Adachi and Hiroshi Fujimoto, published by CMC). This literature explains that by bringing the energy levels of the singlet and triplet excited states of a luminescent material closer together, reverse energy transfer from the low-probability triplet excited state to the singlet excited state is typically generated efficiently, exhibiting thermally activated delayed fluorescence (TADF). Furthermore, Figure 5 in this literature illustrates the mechanism of delayed fluorescence generation. The emission of delayed fluorescence can be confirmed by transition PL (photoluminescence) measurements.

[0041] In addition, the report states that by aligning 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 (Vol. 14, pp. 643-649 (2020))). Furthermore, research is actively underway on compounds with higher energy levels in the triplet excited state than in the singlet excited state of the luminescent material.

[0042] In this specification, compounds that include thermally activated delayed fluorescence and that efficiently transition from triplet excited state to singlet excited state and emit fluorescence are described as "delayed fluorescence compounds" or simply "delayed fluorescence materials".

[0043] Typically, fluorescence is emitted from a singlet excited state generated when a self-luminescent material is photoexcited. Triplet excited states of luminescent materials generated through intersystem crossing are thermally deactivated at room temperature. Therefore, fluorescence is not emitted from the triplet excited state of such luminescent materials. On the other hand, as mentioned above, in delayed-emission materials, even if a triplet excited state is generated, it quickly transitions to a singlet excited state before emitting fluorescence. Therefore, in conventional luminescent materials, triplet excited states that would not contribute to luminescence can still contribute to fluorescence. Thus, highly efficient luminescence can be obtained.

[0044] Delayed-emission fluorescent materials (DEF) are characterized by a rapid transition from triplet excited states to singlet excited states, making it difficult to generate singlet oxygen. Furthermore, it has been found that this characteristic can prevent the degradation of the luminescent material, suppress time-dependent changes in chromaticity, and thus improve durability against chromaticity variations. This mechanism will be explained in detail below. Furthermore, hereafter, durability against chromaticity variations will sometimes be referred to simply as "chromaticity durability" or simply "durability."

[0045] First, the degradation mechanism of luminescent materials is explained. The chromaticity change of the color-converting components is caused by the degradation of the luminescent material. This degradation is caused by singlet oxygen. Singlet oxygen refers to an oxygen molecule in an excited state where the two electrons in the π* orbitals (anti-bonding π orbitals) of the oxygen molecule have different spin orientations. In this excited state, there are Σ1 states (where electrons with different spin orientations each occupy one of the two π* orbitals) and Δ1 states (where only one of the two electrons with different spin orientations occupies a π* orbital). Singlet oxygen in the Δ1 state has strong electrophilicity due to its empty electron orbitals and strong oxidizing power. Therefore, it is believed that singlet oxygen causes the degradation of luminescent materials due to oxidation.

[0046] Next, the generation mechanism of singlet oxygen will be described. It is believed that singlet oxygen cannot be directly generated into triplet oxygen in the fundamental state through photoexcitation. The reason is that the transition from triplet oxygen in the fundamental state to singlet oxygen in the excited state is a spin-forbidden transition, and therefore the transition probability is very low.

[0047] Therefore, it is believed that the generation of singlet oxygen in the color conversion composition is caused by pigment sensitization. That is, it is believed that singlet oxygen is generated through the exchange of electrons and energy between the luminescent material in the triplet excited state and the triplet oxygen molecule in the base state. The generation mechanism is believed to be as follows.

[0048] First, the luminescent material is photoexcited to transition from a singlet fundamental state to a singlet excited state. Then, a portion of the luminescent material undergoes intersystem crossing to transition from a singlet excited state to a triplet excited state. The transition from the triplet excited state to the singlet fundamental state is a spin-forbidden transition, therefore typically with a low probability and a long lifetime in the triplet excited state. However, in the presence of triplet oxygen in the fundamental state, the spin forbidden state is lifted by the excitation of triplet oxygen from the fundamental state to singlet oxygen in the excited state, allowing the luminescent material to rapidly deactivate from the triplet excited state back to the singlet fundamental state. This mechanism is known as the Dexter mechanism (electron exchange mechanism).

[0049] For the Dexter mechanism to proceed, electron exchange via overlapping wave functions between molecules is required. Therefore, it is assumed that 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 base state) need to collide directly.

[0050] As previously described, delayed-emission fluorescent materials exhibit the property of rapidly transitioning from triplet excited states to singlet excited states, meaning the lifetime of triplet excited states is short. Therefore, the probability of a direct collision between a triplet excited material and triplet oxygen in its base state is reduced, making it difficult to generate singlet oxygen.

[0051] As a molecular design approach to approximate the energy levels of singlet and triplet excited states, an effective method is to bond the electron donor and electron acceptor skeletons within the same molecule. This allows for the separation of HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) orbitals within the molecule. The electron donor and electron acceptor skeletons can be directly bonded or bonded via a linker group. Preferably, the linker group is a skeleton containing an aromatic hydrocarbon.

[0052] Examples of electronic donor skeletons include skeletons having amine nitrogen atoms. Preferably, these include skeletons containing diarylamines or triarylamines, skeletons containing carbazole, skeletons containing benzo[a]carbazole, skeletons containing indole[a]carbazole, skeletons containing phenoxazine, and skeletons containing phenoxazine. Among these, skeletons containing carbazole, skeletons containing benzo[a]carbazole, skeletons containing indole[a]carbazole, and skeletons containing phenoxazine are more preferred, and even more preferably, skeletons containing carbazole and skeletons containing phenoxazine.

[0053] On the other hand, as an electron-accepting skeleton, skeletons that typically include electron-withdrawing substituents (i.e., electron-withdrawing groups) can be listed. An electron-withdrawing group, also known as an electron-accepting group, is, in organic electronic theory, an atomic group that attracts electrons from the substituted atomic group through an inducible effect or resonance effect. Electron-withdrawing groups can be listed as those that take a positive value according to Hammett's rule for the substituent constant (σp(para)). The Hammett's rule for the substituent constant (σp(para)) can be cited from the revised 5th edition of the Handbook of Chemistry (II-380). Furthermore, although there are examples of phenyl groups taking a positive value, the electron-withdrawing group in this application does not contain a phenyl group.

[0054] Examples of electron-withdrawing groups include: -F (σp: +0.20), -Cl (σp: +0.28), -Br (σp: +0.30), -I (σp: +0.30), -CO 2R 12 (σp: +0.45 when R 12 is ethyl), -CONH 2 (σp: +0.38), -COR 12 (σp: +0.49 when R 12 is methyl), -CF 3 (σp: +0.51), -SO 2R 12 (σp: +0.69 when R 12 is methyl), -NO 2 (σp: +0.81), etc. R 12 independently represents a hydrogen atom, an aromatic hydrocarbon group with 6 to 30 carbon atoms (substituted or unsubstituted), a heterocyclic group with 5 to 30 carbon atoms (substituted or unsubstituted), an alkyl group with 1 to 30 carbon atoms (substituted or unsubstituted), or a cycloalkyl group with 1 to 30 carbon atoms (substituted or unsubstituted). Specific examples of these groups can be given as examples of substituents that are the same as those in compounds represented by general formula (1) or general formula (2) described below.

[0055] Among the frameworks containing electron-withdrawing groups, it is preferable to have a framework containing a heteroaryl group with a partial structure formed by carbon and nitrogen atoms bonded by double bonds, a framework containing a fluorinated substituent, a framework containing a cyano group, a framework containing a carbonyl group, a framework containing a monoxide or a dimonoxide, and a framework containing a phosphine oxide group. From the viewpoint of delaying the stability of the fluorescent material, it is even more preferable to have a framework containing a heteroaryl group with a partial structure formed by carbon and nitrogen atoms bonded by double bonds, a framework containing a fluorinated substituent, and a framework containing a cyano group.

[0056] In the skeleton containing a heteroaryl group having a partial structure in which carbon and nitrogen atoms are bonded by double bonds, specifically, it is preferably a skeleton containing pyridine, pyrimidine, pyrazine, triazine, quinoline, quinoxaline, quinazoline, or benzeline. Among these, it is more preferably a skeleton containing pyrimidine, triazine, quinoxaline, or quinazoline, and even more preferably a skeleton containing triazine.

[0057] In the skeleton containing fluorinated substituents, it is more preferably a skeleton containing fluorinated aryl or fluoroalkyl groups. As a skeleton containing fluorinated aryl groups, a fluorinated benzene ring is preferred; specifically, a skeleton containing fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene, or pentafluorobenzene is more preferred. As a skeleton containing fluoroalkyl groups, a skeleton containing a benzene ring substituted with a trifluoromethyl group is preferred; among these, a skeleton containing mono(trifluoromethyl)benzene or bis(trifluoromethyl)benzene is more preferred.

[0058] In the cyano skeleton, it is more preferably a skeleton containing cyanobenzene, dicyanobenzene, or tricyanobenzene.

[0059] The following is an example of a compound formed by bonding an electron donor backbone with an electron acceptor backbone as described above, but the compound is not particularly limited to these. Furthermore, the compound shown here is known from previous literature to emit delayed fluorescence.

[0060] [Chemistry 2]

[0061] In addition, as a delayed fluorescence material, besides containing the compound formed by bonding an electron donor backbone and an electron acceptor backbone, it is also preferred to contain a compound represented by the following general formula (1) or general formula (2).

[0062] [Chemistry 3]

[0063] In general formula (1) or general formula (2), ring Za, ring Zb and ring Zc are independently substituted or unsubstituted rings forming aryl rings with 6 to 30 carbons, or substituted or unsubstituted rings forming heteroaryl rings with 6 to 30 carbons.

[0064] In general formula (1), Z1 and Z2 are independently oxygen atoms, NRa (nitrogen atoms with substituent Ra), or sulfur atoms, respectively. When Z1 is NRa, the substituent Ra can bond with ring Za or ring Zb to form a ring. When Z2 is NRa, the substituent Ra can bond with ring Za or ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (silicon atoms with substituent Ra), or P=O.

[0065] In general formula (2), E1 and E2 are independently BRa (boron atom with substituent Ra), PRa (phosphorus atom with substituent Ra), SiRa2 (silicon atom with two substituent Ra), P(=O)Ra2 (phosphine oxide with two substituent Ra) or P(=S)Ra2 (phosphine sulfide with two substituent Ra), S(=O) or S(=O)2. When E1 is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra can bond with ring Za or ring Zb to form a ring. When E2 is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra can bond with ring Za or ring Zc to form a ring.

[0066] The substituent Ra is independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

[0067] In all of the aforementioned groups, hydrogen may be deuterium. This also applies to the compounds described below or parts thereof. Furthermore, in the following description, for example, substituted or unsubstituted aryl groups with 6 to 40 carbon atoms also include aryl groups with 6 to 40 carbon atoms, including those contained in substituents that have substituted the aryl group. The same applies to other substituents that specify the number of carbon atoms.

[0068] When referring to "substituted or unsubstituted," "unsubstituted" means that either hydrogen or deuterium atoms have been substituted. The same applies to references to "substituted or unsubstituted" in the compounds or parts thereof described below.

[0069] Furthermore, among all the aforementioned groups, the substituents used when substituted are alkyl, cycloalkyl, heterocyclic, alkenyl, cycloalkenyl, alkynyl, aryl, heteroaryl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl thioether, halogen, cyano, aldehyde, carbonyl, carboxyl, oxycarbonyl, acetylamino, sulfonyl, sulfonate, sulfonylamino, amino, nitro, silylalkyl, siloxyalkyl, oxoboryl, or phosphine oxide. Additionally, these substituents may be further substituted by the aforementioned substituents.

[0070] The term "alkyl" refers to saturated aliphatic hydrocarbon groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl, dibutyl, and tributyl, which may or may not have substituents. There are no particular limitations on the additional substituents added in the case of substitution; examples include alkyl, halogen, aryl, and heteroaryl groups, and this will be consistent with the following description. Furthermore, there is no particular limitation on the number of carbon atoms in the alkyl group; however, for ease of acquisition or cost considerations, a range of 1 to 20 is preferred, and more preferably 1 to 8.

[0071] The term cycloalkyl refers to saturated alicyclic hydrocarbon groups such as cyclopropyl, cyclohexyl, norbornyl, and adamantyl, which may or may not have substituents. The number of carbon atoms in the alkyl moiety is not particularly limited, but is preferably in the range of 3 to 20.

[0072] A heterocyclic group, for example, refers to an aliphatic ring such as a pyran ring, piperidine ring, or cyclic amide ring, which has atoms other than carbon atoms within the ring. It may or may not have substituents. There is no particular limitation on the number of carbon atoms in the heterocyclic group, but it is preferably in the range of 2 to 20.

[0073] The term alkenyl refers to unsaturated aliphatic hydrocarbon groups containing double bonds, such as vinyl, allyl, and butadienyl. These groups 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.

[0074] The term "cycloalkenyl" refers to unsaturated alicyclic hydrocarbon groups containing a double bond, such as cyclopentenyl, cyclopentadienyl, and cyclohexenyl. These groups 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.

[0075] The term alkynyl refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as ethynyl. It may or may not have substituents. There is no particular limitation on the number of carbon atoms in the alkynyl group, but it is preferably in the range of 2 to 20.

[0076] The term alkoxy refers to a functional group such as methoxy, ethoxy, or propoxy that is bonded to an aliphatic hydrocarbon group via an ether bond. This aliphatic hydrocarbon group may or may not have substituents. There is no particular limitation on the number of carbon atoms in the alkoxy group, but it is preferably in the range of 1 to 20.

[0077] An alkathioyl group refers to a group in which the oxygen atom in the ether bond of an alkoxy group is replaced by a sulfur atom. The hydrocarbon group of an alkathioyl group may or may not have substituents. There is no particular limitation on the number of carbon atoms in the alkathioyl group, but it is preferably in the range of 1 to 20.

[0078] The term "aryl ether" refers to a functional group, such as a phenoxy group, to which an aromatic hydrocarbon group is bonded via an ether bond. The aromatic hydrocarbon group may or may not have substituents. There is no particular limitation on the number of carbon atoms in the aryl ether group, but it is preferably in the range of 6 to 40.

[0079] The term "aryl sulfide" refers to an aryl ether group in which the oxygen atom of the ether bond is replaced by a sulfur atom. The aromatic hydrocarbon group in an aryl sulfide group may or may not have substituents. There is no particular limitation on the number of carbon atoms in the aryl sulfide group, but it is preferably in the range of 6 to 40.

[0080] The term "aryl" can refer to aromatic hydrocarbon groups such as phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, benzo[fluorenyl], dibenzo[fluorenyl], phenanthryl, anthracene, benzo[phenanthryl], benzo[anthryl], 1,2-benzo[phenanthryl], pyrene, fluoranthenyl group, triphenylenyl group, benzo[anthryl], dibenzo[anthryl], peryl, and helicenyl group. Among these, phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, anthracene, pyrene, fluoranthenyl, and triphenyl 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, and more preferably in the range of 6 to 30.

[0081] The term "heteroaryl" refers to cyclic aromatic groups, such as pyridyl, furanyl, thiophene, quinolinyl, isoquinolinyl, pyrazinyl, pyrimidinyl, pyridazinyl, triazinyl, naphridinyl, cinnamyl, phthalazinyl, quinoxolinyl, quinazolinyl, benzofuranyl, benzothiophene, indolyl, dibenzofuranyl, dibenzothiophene, carbazoyl, benzocarbazoyl, carbolinyl group, indolocarbazoyl, benzofuranocarbazoyl, benzothiophenocarbazoyl, dihydroindocarbazoyl, benzoquinolinyl, acridineyl, dibenzoacridyl, benzoimidazoyl, imidazopyridyl, benzooxazolyl, benzothiazoyl, and phenolinyl, which have atoms other than carbon atoms in one or more rings. The term "naphthidyl" refers to any one of 1,5-naphthidyl, 1,6-naphthidyl, 1,7-naphthidyl, 1,8-naphthidyl, 2,6-naphthidyl, or 2,7-naphthidyl. 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, and more preferably in the range of 2 to 30.

[0082] The term "halogen" refers to an atom selected from fluorine, chlorine, bromine, and iodine. Furthermore, carbonyl, carboxyl, oxycarbonyl, and aminomethyl groups may or may not have substituents. Examples of substituents include alkyl, cycloalkyl, aryl, and heteroaryl groups, which can be further substituted.

[0083] The term "amine group" refers to an amine group, whether substituted or unsubstituted. Examples of substituents used for substitution include aryl, heteroaryl, straight-chain alkyl, and branched alkyl groups. Phenyl, naphthyl, pyridyl, and quinolinyl are preferred aryl and heteroaryl groups. These substituents may also be further substituted. The number of carbon atoms is not particularly limited, but is preferably in the range of 2 to 50, more preferably in the range of 6 to 40, and most preferably in the range of 6 to 30.

[0084] The term "silyl" can refer to, for example, alkylsilyl such as trimethylsilyl, triethylsilyl, tributyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, or arylsilyl such as phenyldimethylsilyl, tributyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The substituents on the silicon may also 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.

[0085] The term "siloxane" refers to, for example, a silicon compound group via an ether bond, such as trimethylsiloxane. Substituents on the silicon may also be further substituted. Additionally, "oxoboroyl" refers to an substituted or unsubstituted oxoboroyl group. Examples of substituents used for substitution include: aryl, heteroaryl, straight-chain alkyl, branched alkyl, aryl ether, alkoxy, and hydroxyl. Among these, aryl and aryl ether groups are preferred.

[0086] The term phosphonooxide refers to the group represented by -P(=O)R 10R 11. R 10 and R 11 of the phosphonooxide group are selected from the following groups. Specifically, R 10 and R 11 may be the same or different, and are selected from the candidate groups including hydrogen atoms, alkyl, cycloalkyl, heterocyclic, alkenyl, cycloalkenyl, alkynyl, hydroxyl, thiol, alkoxy, alkylthio, aryl ether, aryl thioether, aryl, heteroaryl, halogen, cyano, aldehyde, carbonyl, carboxyl, acetyl, ester, acetaminophen, aminomethyl, amino, nitro, silyl, siloxyalkyl, oxoboryl, sulfonyl, sulfonyl, phosphonooxide, and condensed rings and aliphatic rings formed with adjacent substituents.

[0087] When R10 and R11 are substituted or unsubstituted aryl groups, the preferred aryl group is phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, or anthracene; more preferably, it is phenyl, biphenyl, terphenyl, or naphthyl. Further preferably, it is phenyl, biphenyl, or terphenyl; most preferably, it is phenyl.

[0088] When each substituent is further substituted with an aryl group, the aryl group is preferably phenyl, biphenyl, terphenyl, naphthyl, fluorenyl, phenanthryl, or anthracene, more preferably phenyl, biphenyl, terphenyl, or naphthyl. Phenyl is particularly preferred.

[0089] When R10 and R11 are substituted or unsubstituted heteroaryl groups, the preferred heteroaryl group is pyridyl, furanyl, thiophene, quinolinyl, pyrimidinyl, triazine, benzofuranyl, benzothiophene, indolyl, dibenzofuranyl, dibenzothiophene, carbazoyl, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, or benzirolinyl; more preferably pyridyl, furanyl, thiophene, or quinolinyl. Pyridyl is particularly preferred.

[0090] When each substituent is further substituted with a heteroaryl group, the heteroaryl group is preferably pyridyl, furanyl, thiophene, quinolinyl, pyrimidinyl, triazine, benzofuranyl, benzothiophene, indolyl, dibenzofuranyl, dibenzothiophene, carbazole, benzimidazolyl, imidazopyridyl, benzoxazolyl, benzothiazolyl, or benzirolinyl; more preferably pyridyl, furanyl, thiophene, or quinolinyl. Pyridyl is particularly preferred.

[0091] 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 non-conjugated condensation ring. The constituent elements of this condensation ring may include, in addition to carbon, elements selected from nitrogen, oxygen, sulfur, phosphorus, and silicon. Furthermore, this condensation ring may further condense with other rings.

[0092] Examples of aryl rings with 6 to 30 carbon atoms that form substituted or unsubstituted rings in rings Za, Zb, and Zc include: benzene rings, naphthalene rings, phenanthrene rings, 1,2-benzophenanthrene rings, anthracene rings, pyrene rings, and other aromatic hydrocarbon rings. Among these, a benzene ring is preferred from the viewpoint of ensuring solubility. Additionally, examples of heteroaryl rings with 6 to 30 carbon atoms include: pyridine rings, quinoline rings, benzyline rings, and other aromatic heteroaryl ring structures. Among these, a pyridine ring is preferred from the viewpoint of ease of obtaining starting materials or ease of synthesis.

[0093] In general formula (1), the substituent Ra is preferably a group having 6 to 40 carbon atoms, including the substituent. The substituent Ra is more preferably a substituted or unsubstituted aryl group. Examples of substituted or unsubstituted aryl groups include: substituted or unsubstituted phenyl, substituted or unsubstituted biphenyl, substituted or unsubstituted fluorenyl, substituted or unsubstituted naphthyl, substituted or unsubstituted phenanthryl, etc. Among these, a substituted or unsubstituted phenyl group is more preferred.

[0094] In addition, in general formula (2), the substituent Ra is preferably a group that also includes substituents and has 6 to 40 carbon atoms. The substituent Ra is more preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl group.

[0095] In general formula (1), Z1 and Z2 are preferably oxygen atoms or NRa. The reason is that the π-conjugation system of the compound represented by general formula (1) expands well and further efficiently causes inverse intersystem crossover from triplet excited state to singlet excited state, thus further improving durability.

[0096] In addition, E in general formula (1) is preferably boron atom, and E1 and E2 in general formula (2) are preferably BRa. The reason is that the π-conjugation system of the compound represented by general formula (1) or general formula (2) has good expansion efficiency, and further efficiently causes inverse intersystem crossover from triplet excited state to singlet excited state, thus further improving durability.

[0097] In addition, rings Za, Zb, and Zc are preferably benzene rings. The reason is that the π-conjugation system of the compound represented by general formula (1) or general formula (2) has a good expansion efficiency, and further efficiently causes inverse intersystem crossover from triplet excited state to singlet excited state, thus further improving durability.

[0098] The compounds represented by general formula (1) or general formula (2), for example as described in the literature "Advanced Materials" (2016, 28, 2777-2781), are molecules in which the HOMO orbital and LUMO orbital can be separated by the multiple resonance effect through the optimal configuration of electron donor amine nitrogen atoms and electron acceptor boron atoms. From the viewpoint of making it easier to emit delayed fluorescence by clearly separating the HOMO orbital and LUMO orbital and making the singlet excited state and triplet excited state closer, it is preferable that in general formula (1), E is a boron atom with strong electron acceptor, and Z1 and Z2 are both groups with strong electron donor, namely NRa.

[0099] Furthermore, the emission spectrum of compounds represented by general formula (1) or general formula (2) becomes sharper than that of compounds formed by bonding an electron donor backbone and an electron acceptor backbone due to the multiple resonance effect of the compound. Therefore, by using compounds represented by general formula (1) or general formula (2) as delayed fluorescent materials, high color purity emission can be obtained. That is, compounds represented by general formula (1) or general formula (2) are beneficial for improving the color gamut of displays, and are therefore better as delayed fluorescent materials. In addition, regarding 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), which are mainly locally present in LUMO orbitals, the LUMO orbitals from the E atom to each ring can be non-localized. By making the LUMO orbitals non-localized, the multiple resonance effect works efficiently, and thus higher color purity emission can be obtained. Furthermore, the E atom in general formula (1) is the atom of E, and in general formula (2) it is each atom of E1 and E2.

[0100] Furthermore, the substituent Ra in general formula (1) or general formula (2) is preferably a structure formed by bonding with at least one ring of ring Za, ring Zb, and ring Zc. The reason is that by bonding the substituent Ra with at least one ring of ring Za, ring Zb, and ring Zc, the stereoprotective effect of E in general formula (1) or E1 and E2 in general formula (2) is further improved, and the effect of suppressing the decrease in fluorescence quantum yield can be expected to be further improved.

[0101] Hereinafter, an example of a compound represented by general formula (1) or general formula (2) is shown. However, the compound is not particularly limited to these.

[0102] [Chemistry 4]

[0103] Furthermore, the delayed fluorescence material is preferably at least one of the following luminescent materials (a) and (b). That is, preferably at least one of the luminescent materials (a) and (b) is a compound that emits delayed fluorescence and is contained in the color conversion layer of the color conversion sheet of the present invention.

[0104] The luminescent material (a) is a luminescent material that emits light in a region with a peak wavelength of 500 nm or more and less than 580 nm when excited by excitation light in the range of 430 nm or more and 500 nm or less. The luminescent material (b) is a luminescent material that emits light in a region with a peak wavelength of 580 nm or more and less than 750 nm when excited by either or both of excitation light in the range of 430 nm or more and 500 nm or by light emitted from the luminescent material (a). Hereinafter, light emitted in the region with a peak wavelength of 500 nm or more and less than 580 nm will be referred to as "green light emitted," and light emitted in the region with a peak wavelength of 580 nm or more and less than 750 nm will be referred to as "red light emitted."

[0105] By using at least one of the luminescent material (a) and luminescent material (b) as a compound that emits delayed fluorescence, the durability of the color conversion composition of the present invention can be improved. The color conversion composition of the present invention refers to the color conversion composition constituting the color conversion layer contained in the color conversion sheet of the present invention. Here, according to the present invention, for example, when the luminescent material (a) is a compound that emits delayed fluorescence and the luminescent material (b) is a compound other than the compound that emits delayed fluorescence (i.e., a compound other than a delayed fluorescence material), not only the durability of the luminescent material (a) itself can be improved, but also the durability of the luminescent material (b). As a result, the overall durability of the color conversion composition of the present invention can be improved.

[0106] The improvement in durability will be described in detail later, and the reason for this is that by ensuring that at least one of the luminescent materials (a) and (b) is a compound that emits delayed fluorescence, the generation of singlet oxygen, which is a cause of degradation of the luminescent material, can be suppressed. By suppressing the generation of singlet oxygen, not only the degradation of the compound that emits delayed fluorescence is suppressed, but also the degradation of compounds that are not such compounds is suppressed.

[0107] The luminescent material (a) is preferably a luminescent material that exhibits luminescence with a peak wavelength of 500 nm or more and 550 nm or less by using excitation light in the range of 430 nm or more and 500 nm or less.

[0108] In addition, the luminescent material (b) is preferably a luminescent material that exhibits luminescence in a region with a peak wavelength of 580 nm or more and 680 nm or less by being excited by either or both of excitation light in the range of 430 nm or more and 500 nm or by luminescence from the luminescent material (a).

[0109] A portion of the excitation light in the wavelength range of 430 nm to 500 nm is transmitted through a portion of the color conversion sheet of the present invention. Therefore, when using a blue LED with a sharp emission peak as the source of this excitation light, white light exhibiting a sharp emission spectrum in blue, green, and red, and with good color purity, can be obtained. As a result, especially in displays, more vibrant colors and a wider color gamut can be efficiently produced. Furthermore, in lighting applications, compared to the currently mainstream white LEDs that combine blue LEDs with yellow phosphors, the luminescence characteristics, especially in the green and red regions, are improved, thus enhancing color rendering and achieving a superior white light source.

[0110] The content of luminescent material (a) and luminescent material (b) in the color conversion composition of the present invention can be selected based on the molar absorptivity, fluorescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness or transmittance of the color conversion sheet to be manufactured. Here, the content of luminescent material (a) and luminescent material (b), when containing two or more luminescent materials (a) and luminescent material (b), refers to their total content. Relative to 100 parts by weight of the binder resin contained in the color conversion composition of the present invention, the content of luminescent material (a) and luminescent material (b) is preferably 1.0 × 10⁻² parts by weight or more and 5 parts by weight or less.

[0111] (Other luminescent materials) Either luminescent material (a) or luminescent material (b) may be a luminescent material other than a compound that emits delayed fluorescence (another luminescent material). Examples of luminescent materials used in either luminescent material (a) or luminescent material (b) besides compounds that emit delayed fluorescence include, for example, inorganic phosphors, fluorescent pigments, fluorescent dyes, quantum dots, etc. This other luminescent material may also contain two or more of these. To achieve high-efficiency color conversion, this other luminescent material is preferably a material exhibiting high quantum yield luminescence properties. Specifically, quantum dots and organic luminescent materials are preferred, and organic luminescent materials are even more preferred.

[0112] As organic light-emitting materials, preferred examples include compounds or derivatives of condensed aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, 1,2-benzophenanthrene, condensed tetraphenylene, triphenylene, perylene, fluoranthene, fluorene, and indene.

[0113] In addition, as organic light-emitting materials, preferred examples include compounds or derivatives of compounds with heteroaryl rings such as furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenocyanate, pyridine, pyrazine, naphthidine, quinoxaline, and pyrrolopyridine.

[0114] In addition, preferred organic light-emitting materials include, for example, borane derivatives, stilbene derivatives, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, aldazine derivatives, pyrrole methylene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, and coumarin derivatives. Examples of stilbene derivatives include 1,4-stilbeneylbenzene, 4,4'-bis(2-(4-diphenylaminophenyl)vinyl)biphenyl, and 4,4'-bis(N-(stilbene-4-yl)-N-phenylamino)stilbene. Examples of coumarin derivatives include coumarin 6, coumarin 7, and coumarin 153.

[0115] In addition, as organic light-emitting materials, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and triazole, as well as their metal complexes, are preferred.

[0116] In addition, as organic light-emitting materials, anthocyanin compounds, xanthones, or thioxanthates are preferred examples. Examples of anthocyanin compounds include indocyanine green. Examples of xanthones or thioxanthates include fluorescent yellow, eosin, and rose red.

[0117] In addition, preferred organic light-emitting materials include, for example, polyphenylene compounds, naphthalenedimethylimine derivatives, phthalocyanine derivatives and their metal complexes, porphyrin derivatives and their metal complexes, oxazine compounds, and helical hydrocarbon compounds. Examples of oxazine compounds include, for instance, Nile red or Nile blue.

[0118] Furthermore, aromatic amine derivatives and organometallic complexes are preferred organic light-emitting materials. Examples of aromatic amine derivatives include N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine. Examples of organometallic complexes include iridium (Ir), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re).

[0119] The organic light-emitting material can be either a fluorescent or phosphorescent material, but a fluorescent material is preferred to achieve high color purity. Pyrrole methylene derivatives are preferred for imparting high fluorescence quantum yield and better color durability.

[0120] (Haze value of the color conversion filter) In this invention, as described above, the haze value of the color conversion sheet is 20% or more and 99% or less. By keeping the haze value within this range, both the in-plane uniformity of the color and the durability of the color conversion sheet can be improved. The haze value is an indicator of the degree of light scattering in the color conversion layer contained in the color conversion sheet. In the color conversion sheet, from the viewpoint of in-plane uniformity of color, it is preferable to scatter light moderately. If the haze value of the color conversion sheet is less than 20%, the scattering of light in the color conversion layer is insufficient, and the in-plane uniformity of the color of the color conversion sheet decreases. On the other hand, if the haze value of the color conversion sheet exceeds 99%, even if a delayed fluorescence material is used in the color conversion layer, the degradation of the delayed fluorescence material will be observed, and the durability of the color conversion sheet decreases. The lower limit of the haze value of the color conversion sheet is preferably 50% or more. In addition, the upper limit of the haze value of the color conversion sheet is preferably 95% or less, and more preferably 75% or less. The haze value can be determined according to the method of American Society of Testing Materials (ASTM) D 1003 (2013).

[0121] There are no particular limitations on the method for setting the haze value of the color conversion sheet of the present invention within the stated range, and the following methods can be listed: a method of including scattering particles in the color conversion layer; a method of providing a light scattering layer separately from the color conversion layer; a method of increasing the surface roughness of the substrate contained in the color conversion sheet. Among these, the method of including scattering particles in the color conversion layer is more preferred. In this specification, scattering particles refer to particles that scatter light.

[0122] (Scattered particles) In the color conversion sheet of the present invention, the color conversion layer preferably contains scattering particles. As described above, by including scattering particles in the color conversion layer, the haze of the color conversion sheet including the color conversion layer can be controlled. Hereinafter, the scattering particles contained in the color conversion layer of the color conversion sheet of the present invention will sometimes be referred to as "scattering particles of the present invention".

[0123] As scattering particles of the present invention, at least one of organic and inorganic particles can be listed. Specifically, as scattering particles of the present invention, particles composed of glass, titanium dioxide, silicon dioxide, aluminum oxide, silicone resin, zirconium oxide, cerium oxide, aluminum nitride, silicon carbide, silicon nitride, barium titanate, acrylic resin, etc., can be listed. The scattering particles of the present invention can be used alone or in combination with two or more of these particles. From the viewpoint of easy availability, particles composed of silicon dioxide, aluminum oxide, titanium dioxide, zirconium oxide, acrylic resin, silicone resin, etc., are preferred as scattering particles of the present invention. When the color conversion layer contains an adhesive resin, from the viewpoint of dispersibility in the adhesive resin, the scattering particles of the present invention are preferably selected from at least one of aluminum oxide, titanium dioxide, and zirconium oxide, and more preferably titanium dioxide particles.

[0124] Furthermore, from the viewpoint of improving dispersibility in the color conversion layer, the scattering particles of the present invention are preferably surface-treated. Regarding surface treatment methods for the scattering particles, surface treatments using inorganic or organic substances can be cited. Specifically, methods such as: surface treatment (coating) of the scattering particles using aqueous oxides of inorganic oxides such as alumina or silicon dioxide; or surface treatment of the scattering particles using polyol compounds, alkanolamine compounds, silicon compounds, etc.

[0125] From the viewpoint of hydrophobicity and weather resistance, surface treatment of the scattering particles using alumina and silicon dioxide is preferred. For example, in the case where the color conversion layer contains an adhesive resin, the adhesive resin can be filled with the scattering particles of the present invention. The adhesive resin to which the scattering particles are filled is typically hydrophobic. Therefore, the scattering particles, whose surfaces are hydrophobically treated by the aforementioned surface treatment method, exhibit better compatibility with the adhesive resin and better dispersibility within the adhesive resin. In particular, regarding the titanium dioxide particles in the scattering particles, from the viewpoint of suppressing the generation of reactive oxygen species, surface treatment using alumina and silicon dioxide is preferred.

[0126] Furthermore, in this invention, the zeta potential of the scattering particles is preferably 20 mV or more in absolute terms. That is, the scattering particles of this invention are preferably scattering particles such that, when dispersed in a solution, the absolute value of the zeta potential is 20 mV or more when the pH of the solution is set to 4 or more and 10 or less. Here, "the absolute value of the zeta potential is 20 mV or more when the pH is set to 4 or more and 10 or less" means "the absolute value of the zeta potential is 20 mV or more at any pH value within the range of 4 or more and 10 or less." Because the zeta potential of the scattering particles of this invention is within this range, the electrostatic repulsion between the particles increases. Therefore, in the color conversion composition used to fabricate the color conversion layer of this invention, the aggregation of scattering particles with each other, or the aggregation of scattering particles with delayed fluorescent materials, can be suppressed. As a result, the brightness of the color conversion sheet of this invention can be improved. Furthermore, the delayed fluorescent material has high polarization in its structure. Therefore, by controlling the zeta potential of the scattering particles as described above, the aggregation of scattering particles with delayed fluorescent materials can be suppressed.

[0127] In the color conversion composition of the present invention, the filler resin preferably has a high glass transition temperature. This is because a higher glass transition temperature of the binder resin suppresses the movement of the delayed fluorescent material encapsulated within it. However, when the binder resin is filled with scattering particles, the movement of the delayed fluorescent material within the binder resin is suppressed by the scattering particles because their zeta potential is within the aforementioned range. Therefore, even with a binder resin having a low glass transition temperature, the aggregation of the delayed fluorescent materials within the binder resin, as well as the aggregation of the scattering particles with the delayed fluorescent material, can be suppressed. Hereinafter, "aggregation of the delayed fluorescent materials" and "aggregation of the scattering particles with the delayed fluorescent material" will sometimes be collectively referred to as "aggregation of the delayed fluorescent material."

[0128] Furthermore, in color conversion sheets containing delayed fluorescent materials and scattering particles in the color conversion layer, the fact that the zeta potential of the scattering particles is within the aforementioned range also contributes to achieving high color purity. This is believed to be due to the following reason: Because delayed fluorescent materials have a highly planar structure, if the delayed fluorescent materials are not sufficiently dispersed in the color conversion layer, excimer emission is easily observed, and the half-width at half maximum (WWHM) of the emission peak in the emission spectrum becomes wider. In contrast, when the scattering particles of the present invention are included in the color conversion layer, the aggregation of the delayed fluorescent materials in the color conversion layer is suppressed by the action of these scattering particles, thereby narrowing the WWHM of the emission peak of the delayed fluorescent materials. As a result, high color purity of the color conversion sheet can be achieved.

[0129] Furthermore, in this invention, there is no particular limitation on the upper limit of the zeta potential of the scattering particles, but it is preferably 100 mV or less in absolute terms. Specifically, the scattering particles of this invention are preferably scattering particles such that, when dispersed in a solution, the absolute value of the zeta potential is 100 mV or less when the pH of the solution is set to 4 or higher and 10 or lower. That is, the absolute value of the zeta potential of the scattering particles of this invention is preferably 20 mV or higher and 100 mV or less when the pH value is within any range of 4 or higher and 10 or lower.

[0130] The zeta potential can be measured using an electrophoretic light scattering spectrophotometer. For example, the zeta potential of the scattering particles of the present invention can be determined by using scattering particles dispersed in an aqueous solution containing 10 mmol / dm³ of NaCl electrolyte and measuring the electroosmotic flow at 25°C and pH 4-10. An electrophoretic light scattering spectrophotometer such as the ELS-8000 manufactured by Otsuka Electronics Co., Ltd. can be used in this case. Regarding the scattering particles used, even if they are extracted from a color conversion sheet, the effect on the zeta potential value is minimal.

[0131] The average particle size of the scattering particles of the present invention is not particularly limited if it is within the range of haze values, but is preferably 100 nm or more and 700 nm or less. By having the average particle size of the scattering particles within this range, the dispersion of the scattering particles in the color conversion layer becomes better, and the light scattering efficiency of the delayed fluorescent material is improved.

[0132] Furthermore, when the color conversion sheet of the present invention has at least one of the following color conversion layers: a color conversion layer containing a delayed fluorescent material that emits light in a peak wavelength region of 510 nm or more and less than 540 nm, and a color conversion layer containing a delayed fluorescent material that emits light in a peak wavelength region of 610 nm or more and less than 670 nm, the average particle size of the scattering particles contained in the color conversion layer of the color conversion sheet is preferably 500 nm or less, and more preferably 300 nm or less. In the combination of delayed fluorescent material having an emission peak wavelength range and scattering particles having an average particle size range, the light scattering range is expanded due to the generation of backscattering and sidescattering of light. This increases the scattering intensity and further improves the light scattering efficiency. In this specification, the average particle size of the scattering particles refers to the mode obtained from the particle size distribution measured by dynamic light scattering.

[0133] The refractive index of the scattering particles of the present invention is preferably 1.4 or higher and 2.8 or lower. By having a refractive index of 1.4 or higher, the reflectivity at the interface between the adhesive resin and the scattering particles increases, thus improving the light scattering effect. On the other hand, by having a refractive index of 2.8 or lower, the efficiency of light extraction after color conversion is prevented from decreasing, further improving brightness.

[0134] Here, the refractive index of the scattering particles of the present invention refers to the numerical average of the refractive indices of 30 randomly selected scattering particles, using sodium D-rays (589 nm) as the light source, at a temperature of 25°C, measured by an Abbe refractometer (DR-M2, manufactured by ATAGO) and by the immersion method (Becke line method).

[0135] The shape of the scattering particles of the present invention is not particularly limited, and examples include: spherical, ellipsoidal, needle-shaped, polygonal, star-shaped, etc. In addition, the shape of the scattering particles can be a shape with unevenness or pores on the particle surface, or it can be a hollow shape.

[0136] Furthermore, in the color conversion sheet of the present invention, when the color conversion layer contains not only the delayed fluorescent material but also an adhesive resin, and the adhesive resin is set to 100 parts by weight, the content of scattering particles in the color conversion layer is preferably 1.0 × 10⁻³ parts by weight or more and 30 parts by weight or less. By having the content of scattering particles at 1.0 × 10⁻³ parts by weight or more, the scattering particles are uniformly dispersed in the color conversion layer (i.e., in the color conversion composition constituting the color conversion layer), resulting in a sufficient optical path length and thus further improving the color conversion efficiency. Additionally, the light diffusion increases in the color conversion layer, thereby increasing the number of photoexcitations of the delayed fluorescent material and further improving the brightness.

[0137] Furthermore, typically, the more photoexcitations a luminescent material undergoes, the more severe the degradation of the luminescent material associated with photoexcitation becomes. However, in the case of the delayed phosphor material contained in the color conversion layer of the color conversion sheet of the present invention, as described above, the degradation of the luminescent material associated with photoexcitation can be suppressed. Therefore, in cases where the number of photoexcitations is low or equal to or greater, it is preferable to include scattering particles in the color conversion layer containing the delayed phosphor material to improve brightness without compromising durability.

[0138] On the other hand, by using scattering particles of the present invention at a content of 30 parts by weight or less, the scattering particles do not aggregate and settle in the color conversion composition, resulting in a further improvement in color conversion efficiency. More preferably, the content of scattering particles is 1.0 × 10⁻² parts by weight or more and 15 parts by weight or less, and particularly preferably 1.0 × 10⁻¹ parts by weight or more and 10 parts by weight or less, relative to 100 parts by weight of the adhesive resin. Furthermore, the total light transmittance of the color conversion layer containing the scattering particles of the present invention at 450 nm is preferably 50% or more. With this total light transmittance within the aforementioned range, it is easy to balance high beam density and high durability of the color conversion sheet.

[0139] (Adhesive resin) In the color conversion sheet of the present invention, the color conversion layer may further include an adhesive resin in addition to the aforementioned delayed fluorescence material. The adhesive resin is a material that forms a continuous phase and possesses excellent processability, transparency, and heat resistance. Examples of adhesive resins include photocurable photoresist materials containing reactive vinyl groups such as acrylic, methacrylic, polyvinyl cinnamate, and cyclic rubber; epoxy resins; silicone resins (including silicone rubber, silicone gel, and other organopolysiloxane curables (crosslinks)); 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. Furthermore, these copolymer resins may also be used as adhesive resins. By appropriately designing these resins, adhesive resins useful in the color conversion compositions and color conversion sheets involved in the embodiments of the present invention can be obtained. Among these resins, thermoplastic resins are preferred for ease of sheeting. Among thermoplastic resins, epoxy resins, silicone resins, acrylic resins, ester resins, olefin resins, or mixtures thereof are preferred for transparency and heat resistance. Furthermore, from the viewpoint of durability, acrylic resins, ester resins, and cycloolefin resins are particularly preferred thermoplastic resins.

[0140] Furthermore, from the viewpoint of suppressing the movement of delayed fluorescent material in the adhesive resin, the glass transition temperature of the adhesive resin contained in the color conversion layer (the layer of the color conversion composition of the present invention) is preferably high. For example, the glass transition temperature of such adhesive resin is preferably 100°C or higher. In the case where the delayed fluorescent material and scattering particles of the present invention are contained in the color conversion layer, the movement of the delayed fluorescent material in the adhesive resin of the color conversion layer is suppressed by the scattering particles. Therefore, even an adhesive resin with a relatively low glass transition temperature (e.g., an adhesive resin with a glass transition temperature less than 100°C) can preferably be used as the adhesive resin. In this case, the glass transition temperature of the adhesive resin is preferably 60°C or higher, and more preferably 80°C or higher. As described above, the scattering particles of the present invention refer to scattering particles whose absolute value of the zeta potential is 20 mV or higher and 100 mV or lower when the pH value of the solution in which the scattering particles are dispersed is any value within the range of 4 or higher and 10 or lower.

[0141] Preferred examples of adhesive resins include those described in International Publication Nos. 2016 / 190283, 2017 / 61337, 2018 / 43237, 2019 / 21813 and 2019 / 188019.

[0142] In addition, dispersants or leveling agents for stabilizing the coating film can be added to the adhesive resin as additives, and adhesive aids such as silane coupling agents can also be added as surface modifiers. Furthermore, inorganic particles such as silica particles or silicone microparticles can also be added to the adhesive resin as sedimentation inhibitors for color conversion materials.

[0143] In the color conversion composition used for manufacturing color conversion sheets according to the embodiments of the present invention, in order to suppress curing at room temperature and extend the service life, it is preferable to incorporate a silane hydrocracking reaction retarder such as ethynyl alcohol as another component into the adhesive resin. Furthermore, without compromising the effects of the present invention, microparticles such as silica, glass powder, and quartz powder, inorganic fillers or pigments such as titanium dioxide, zirconium oxide, barium titanate, and zinc oxide, flame retardants, heat resistant agents, antioxidants, dispersants, solvents, and adhesion promoters such as silane coupling agents or titanium coupling agents may also be incorporated into the adhesive resin as needed.

[0144] (solvent) The color conversion composition of the present invention may also include a solvent. The solvent is not particularly limited as long as it can adjust the viscosity of the resin in its flow state and does not excessively affect the luminescence and durability of the luminescent material. Examples of such solvents include: toluene, methyl ethyl ketone, methyl isobutyl ketone, hexane, acetone, terpineol, texanol, methyl cellosolve, butyl carbitol, butyl carbitol acetate, propylene glycol monomethyl ether acetate, etc. Two or more of these solvents may also be used in combination. Among these solvents, toluene is preferred, especially in that it does not affect the deterioration of the compound represented by general formula (1) or general formula (2) and leaves little residual solvent after drying.

[0145] (Other ingredients) In addition to the compound (delayed fluorescence material) and adhesive resin represented by the general formula (1) or general formula (2) in the embodiments of the present invention, the color conversion sheet may also contain light stabilizers, antioxidants, processing and heat stabilizers, lightfastness stabilizers such as ultraviolet absorbers, silicone microparticles and silane coupling agents and other components (additives).

[0146] Examples of light stabilizers include, for example, tertiary amines, catechol derivatives, and nickel compounds, or complexes or salts of at least one transition metal selected from the group consisting of Sc, V, Mn, Fe, Co, Cu, Y, Zr, Mo, Ag, and lanthanides, and organic acids; there are no particular limitations. Furthermore, these light stabilizers can be used alone or in combination.

[0147] Examples of antioxidants include phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol and 2,6-di-tert-butyl-4-ethylphenol, but these are not specifically limited to these. Furthermore, these antioxidants can be used alone or in combination.

[0148] Examples of phosphorus-based stabilizers used in processing and heat treatment include tributyl phosphite, tricyclohexyl phosphite, triethylphosphine, and diphenylbutylphosphine, but these are not specifically limited to these. Furthermore, these stabilizers can be used alone or in combination.

[0149] Examples of lightfastness 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 these are not specifically limited to. Furthermore, these lightfastness stabilizers can be used alone or in combination.

[0150] In the color conversion sheet according to the embodiments of the present invention, the content of these additives, while also depending on the molar absorptivity, luminescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness or transmittance of the produced color conversion sheet, is generally preferably 1.0 × 10⁻³ parts by weight or more and 30 parts by weight or less relative to 100 parts by weight of the adhesive resin. Furthermore, relative to 100 parts by weight of the adhesive resin, the content of these additives is more preferably 1.0 × 10⁻² parts by weight or more and 15 parts by weight or less, and particularly preferably 1.0 × 10⁻¹ parts by weight or more and 10 parts by weight or less.

[0151] Furthermore, from the viewpoint of further improving the durability of the color conversion sheet, the amount of residual solvent in the color conversion layer after drying, comprising the color conversion composition of the present invention or its cured form, is preferably 3.0% by weight or less, more preferably 1.0% by weight or less, and even more preferably 0.5% by weight or less. Furthermore, from the viewpoint of improving the quantum yield of the color conversion sheet, the amount of residual solvent is preferably 0.01% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.1% by weight or more.

[0152] (Manufacturing method of color conversion components) The following describes an example of a method for manufacturing a color conversion composition used to produce the color conversion layer contained in the color conversion sheet of the present invention. In this manufacturing method, the delayed fluorescent material, binder resin, scattering particles, additives, and solvent are mixed in predetermined amounts as needed. After mixing these components in a predetermined manner, the mixture is homogenized or kneaded using a mixer / blender to obtain the color conversion composition. Examples of mixers / blenders include: homogenizers, rotary mixers, three-roll mixers, ball mills, planetary ball mills, and bead mills. Degassing can preferably be performed under vacuum or reduced pressure conditions after mixing or during mixing or dispersion. Additionally, a specific component can be pre-mixed, or aging treatments can be performed. The desired solid component concentration can also be achieved by removing the solvent using an evaporator.

[0153] (Substrate layer) As the substrate layer in the color conversion sheet of the present invention (for example, substrate layer 10 shown in Figures 2-4), examples include glass or resin film. As the resin film, polyethylene terephthalate (PET), polyphenylene sulfide, polycarbonate, polypropylene, polyimide, and other plastic films are preferred. Regarding ease of film peeling, the substrate layer can also be pre-treated with a release agent. The thickness of the substrate layer is not particularly limited, but as a lower limit, it is preferably 25 μm or more, more preferably 38 μm or more. Furthermore, as an upper limit, it is preferably 5000 μm or less, more preferably 3000 μm or less.

[0154] (Blocking membrane) The barrier film (e.g., barrier film 12 shown in FIG. 4) in the color conversion sheet of the present invention can be suitably used to improve the gas barrier properties of the color conversion layer. This barrier film (also called a barrier layer) is preferably one that inhibits the intrusion of oxygen, moisture, heat, etc., into the color conversion layer. The color conversion sheet of the present invention may also 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 barrier film 12 in FIG. 4, or it may have a barrier film only on one side of the color conversion layer.

[0155] Examples of barrier membranes with gas barrier properties include: inorganic oxides such as silicon oxide, aluminum oxide, titanium oxide, tantalum oxide, zinc oxide, tin oxide, indium oxide, yttrium oxide, and magnesium oxide; inorganic nitrides such as silicon nitride, aluminum nitride, titanium nitride, and silicon carbonitride; or metal oxide films or metal nitride films formed by adding other elements to these; or films containing various resins such as polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, carbamate resins, fluorinated resins, and polyvinyl alcohol resins such as vinyl acetate saponification. The barrier membrane may contain two or more of these. Additionally, examples of barrier membranes with moisture barrier functions 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, fluorinated resins, and polyvinyl alcohol resins such as vinyl acetate saponification.

[0156] Depending on the required functions, the color conversion sheet of the present invention may further include a light diffusion layer, an adhesive layer, and auxiliary layers with anti-reflection, anti-glare, anti-reflection and anti-glare, hard coating (abrasion resistance), antistatic, anti-fouling, electromagnetic wave shielding, infrared cutoff, ultraviolet cutoff, polarization, and color adjustment functions.

[0157] (Other membranes) The color conversion film involved in the embodiments of the present invention may further include polarizing reflective films, diffusers, prisms, wavelength selective reflective films, etc. As preferred specific examples of wavelength selective reflective films, those described in International Publication No. 2017 / 164155 and Japanese Patent Application Publication No. 2018-81250 can be cited.

[0158] <Manufacturing Method of Color Conversion Sheets> Next, an example of a method for manufacturing the color conversion sheet of the present invention will be described. In this method, a color conversion composition prepared by the method is coated onto a substrate such as a substrate layer or a barrier layer and dried. This forms a color conversion layer. If the adhesive resin contained in the color conversion composition is a thermosetting resin, the color conversion composition can also be coated onto a substrate such as a substrate layer and then heat-cured to form the color conversion layer. If the adhesive resin contained in the color conversion composition is a photocurable resin, the color conversion composition can also be coated onto a substrate such as a substrate layer and then photocured to form the color conversion layer.

[0159] The coating of color conversion components can be performed using reverse roll coaters, blade coaters, corner wheel coaters, slot die coaters, direct gravure coaters, flatbed gravure coaters, coincident coaters, natural roll coaters, air knife coaters, roller-blade coaters, two-stream coaters, bar coaters, wire-bar coaters, applicators, dip coaters, curtain coaters, spin coaters, and doctor blade coaters. To obtain uniform film thickness of the color conversion layer, it is preferable to use slot die coaters, corner wheel coaters, or dip coaters.

[0160] The color conversion layer can be dried using common heating devices such as hot air dryers or infrared dryers. In this case, the preferred heating temperature is 60°C to 200°C, and the preferred heating time is 2 minutes to 4 hours. Alternatively, the color conversion layer can be heat-cured in stages using methods such as step cure.

[0161] When a color conversion layer is formed by heat curing, a hot air oven or similar device can be used as the heating apparatus. The heating conditions for heat curing the color conversion layer can be selected based on the adhesive resin. For example, a heating temperature of 100°C to 300°C and a heating time of 1 minute to 2 hours are preferred.

[0162] When a color conversion layer is formed by photocuring, it is preferable to irradiate the color conversion layer with high-energy light such as ultraviolet light. The light irradiation conditions during the photocuring of the color conversion layer can be selected according to the adhesive resin. For example, the wavelength of the irradiated light is preferably 200 nm to 500 nm, and the irradiation intensity is preferably 10 mJ / cm² to 10 J / cm².

[0163] After the color conversion layer is made, the substrate layer can be changed as needed. In this case, as a simple method, examples include: using a heating plate for re-lamination, or using a vacuum laminator or dry film laminator, etc.

[0164] Alternatively, as an example, the color conversion sheet of the present invention may also include one or more color conversion layers containing delayed fluorescent materials. In this case, the color conversion sheet of the present invention may be a color conversion sheet in which the luminescent material (a) and the luminescent material (b) are contained in different layers. Such a color conversion sheet is preferably a color conversion sheet in which the color conversion layer includes at least one of the following layers (A) and (B).

[0165] Specifically, layer (A) is a layer containing luminescent material (a) as a compound that emits delayed fluorescence. Layer (B) is a layer containing luminescent material (b) as a compound that emits delayed fluorescence. For example, layers (A) and (B) may be separate layers within the same color conversion layer of one or more color conversion layers in the color conversion sheet of the present invention, or they may be different color conversion layers among two or more color conversion layers. Preferably, at least one of layers (A) and (B) contains the scattering particles.

[0166] Furthermore, as a further example, the color conversion sheet of the present invention may also be a color conversion sheet comprising two or more color conversion layers, wherein each of the two or more color conversion layers, which are different from each other, contains a light-emitting material (a) and a light-emitting material (b). Such a color conversion sheet is preferably a color conversion sheet comprising at least the following (A') layer and (B') layer as two or more color conversion layers.

[0167] Layer (A') is a layer containing at least luminescent material (a) and adhesive resin. Layer (B') is a layer containing at least luminescent material (b) and adhesive resin. For example, layer (A') is one or more color conversion layers in a color conversion sheet of the present invention. Layer (B') is one or more color conversion layers that are different from layer (A'). In this case, it is preferable that at least one of the luminescent material (a) in layer (A') and the luminescent material (b) in layer (B') is a delayed fluorescence material.

[0168] <Light Source Unit> The light source unit (hereinafter, sometimes simply referred to as the light source unit of the present invention) according to embodiments of the present invention includes at least a light source and the color conversion component or color conversion sheet. The light source included in the light source unit of the present invention is the source of the excitation light. There are no particular limitations on the arrangement of these light sources and color conversion sheets; a structure in which the light source and color conversion sheet are in close contact can be adopted, or a remote phosphor form separating the light source and color conversion sheet can be adopted. Furthermore, for the purpose of improving color purity, the light source unit of the present invention may further adopt a structure including a color filter.

[0169] (light source) The type of light source included in the light source unit of the present invention can be any light source that emits light in the wavelength region that the delayed fluorescent material can absorb. For example, any light source that excites light, such as a hot cathode tube or cold cathode tube, a fluorescent light source such as inorganic electroluminescence (EL), an organic EL element light source, an LED light source, an incandescent light source, or sunlight, can be used in principle. Among these, an LED light source is preferred. For example, a light-emitting diode that emits maximum light in the wavelength range of 400 nm to 500 nm is a more preferred LED light source. In display or lighting applications, in terms of improving the color purity of blue light, a blue LED light source that emits maximum light in the wavelength range of 430 nm to 500 nm is even more preferred.

[0170] The light source may have one emission peak or two or more emission peaks. To improve color purity, it is preferable to have one emission peak. Alternatively, multiple light sources with different types of emission peaks can be combined arbitrarily.

[0171] The light source unit of this invention is effectively used in various light sources such as spatial lighting and backlighting. Specifically, the light source unit of this invention can be used in displays, lighting devices, interiors, signs, billboards, etc., and is particularly well-suited for use in displays or lighting devices.

[0172] <Displays, Lighting Fixtures> The display according to embodiments of the present invention includes at least the aforementioned light source unit. For example, in displays such as liquid crystal displays, a light source unit having the aforementioned light source and a color conversion sheet is used as a backlight unit. Furthermore, the lighting device according to embodiments of the present invention includes at least the aforementioned light source unit. For example, this lighting device is configured such that a blue LED light source serving as the light source unit is combined with a color conversion sheet that converts blue light from the blue LED light source into light with a wavelength longer than that blue light, thereby emitting white light. [Example]

[0173] The present invention will now be illustrated by examples, but the present invention is not limited to the following examples. First, the evaluation methods in the examples and comparative examples will be described.

[0174] <Haze Measurement> In the haze measurement, a haze meter (NDH7000, manufactured by Nippon Denshoku Kogyo Co., Ltd.) was used, and the haze value [%] of the color conversion sheets prepared in the examples and comparative examples was measured according to the method of ASTM D 1003 (2013). The haze value of each color conversion sheet was measured once.

[0175] <Determination of Color Conversion Characteristics> In the determination of color conversion characteristics, on a light-emitting device equipped with a blue LED element (manufactured by Ushio EPITEX; model SMBB450H-1100, peak emission wavelength: 450 nm), the color conversion sheets used as the evaluation objects were changed and configured according to each embodiment and each comparative example. A current of 100 mA was passed through the light-emitting device to illuminate the blue LED element, and the emission spectrum, luminous intensity at the peak wavelength, and chromaticity were measured using a spectroradiometer (CS-1000, manufactured by Konica Minolta). Furthermore, the distance between the color conversion sheet and the blue LED element in the light-emitting device was set to 3 cm.

[0176] <Evaluation of the in-plane uniformity of color> In evaluating the in-plane uniformity of color, a BenQ liquid crystal monitor (SW2700PT) was disassembled, and the built-in color conversion sheet, prepared as the evaluation object in each of the embodiments and comparative examples described later, was inserted instead. The liquid crystal monitor was then reassembled as is. At this time, the color conversion sheet as the evaluation object was changed and used according to each embodiment and comparative example. The backlight unit structure of this liquid crystal monitor is "reflective film / light guide plate / diffuser / color conversion sheet / prism / polarizing reflective film". Subsequently, a spectroradiometer (CS-1000, manufactured by Konica Minolta) was used to measure the 9-point color coordinates u' and v', and the in-plane deviation of color Δu'v' was calculated using the following formula. Δu' = u'(max) - u'(min) Δv' = v'(max) - v'(min) Δu'v'={(Δu') 2+(Δv') 2} 1 / 2

[0177] In the formula, u'(max) is the value of the largest color coordinate u' among the nine measured color coordinates u'. u'(min) is the value of the smallest color coordinate u' among the nine measured color coordinates u'. v'(max) is the value of the largest color coordinate v' among the nine measured color coordinates v'. v'(min) is the value of the largest color coordinate v' among the nine measured color coordinates v'. In this evaluation, if Δu'v' is less than 0.02, the in-plane uniformity of the color is judged to be good. In particular, if Δu'v' is less than 0.015, the in-plane uniformity of the color is extremely good. On the other hand, if Δu'v' is greater than or equal to 0.02, the in-plane uniformity of the color is judged to be poor.

[0178] <Evaluation of Light Durability> In the evaluation of light durability, the color conversion sheets used in each embodiment and comparative example were varied and configured on a light-emitting device equipped with a blue LED element (manufactured by Ushio EPITEX; model SMBB450H-1100, peak emission wavelength: 450 nm). A current of 100 mA was passed through the light-emitting device to illuminate the blue LED element, and the peak intensity of the light at the emission wavelength after color conversion via the color conversion sheet was measured using a spectroradiometer (CS-1000, manufactured by Konica Minolta). Furthermore, the distance between the color conversion sheet and the blue LED element in the light-emitting device was set to 3 cm. Subsequently, light from the blue LED element was continuously irradiated at 50°C and 80%RH, and the time it took for the luminous intensity of the phosphor in the color conversion sheet to decrease by 10% from its initial value was observed to evaluate the durability of the color conversion sheet. In this evaluation, if the time it takes for the luminescence intensity of the phosphor in the color conversion sheet to decrease by 10% from its initial value is 300 hours or more, the color conversion sheet is judged to have good durability. In particular, if this time is 400 hours or more, the durability of the color conversion sheet is considered extremely good. On the other hand, if this time is less than 300 hours, the durability of the color conversion sheet is judged to be poor.

[0179] <Luminescent Materials> In the following examples and comparative examples, compounds G-1, G-2, G-3, and R-1 are suitable as luminescent materials (e.g., luminescent material (a) and luminescent material (b)). Compounds G-1, G-2, G-3, and R-1 are the compounds shown below. Among these, compounds G-1, G-3, and R-1 are compounds that emit delayed fluorescence.

[0180] [Chemistry 5]

[0181] In addition, the emission peak wavelengths of each compound G-1, compound G-2, compound G-3, and compound R-1, which are luminescent materials, are shown in Table 1-1.

[0182] [Table 1-1] (Table 1-1) Luminescent materials peak wavelength (nm) G-1 481 G-2 515 G-3 519 R-1 615

[0183] <Adhesive Resins> In the following examples and comparative examples, adhesive resins P-1 and P-2, as shown below, were used as adhesive resins.

[0184] As adhesive resin P-1, polymethyl methacrylate resin "BR-85" (manufactured by Mitsubishi Chemical Corporation) is used. The glass transition temperature of adhesive resin P-1 is 105°C. As adhesive resin P-2, methyl methacrylate-ethyl methacrylate copolymer resin "M-4501" (manufactured by Nemoto Kogyo Co., Ltd.) is used. The glass transition temperature of adhesive resin P-2 is 84°C.

[0185] <Scattering particles> In the following embodiments and comparative examples, the scattering particles S-1, S-2, S-3, S-4, and S-5 shown below are used as scattering particles.

[0186] Scattering particle S-1 uses titanium dioxide particles "JR-301" (manufactured by TAYCA Corporation, average particle size 300 nm, refractive index 2.72). Scattering particle S-2 uses silicon dioxide particles "Admafine SO-E1" (manufactured by Admatechs Corporation, average particle size 250 nm, refractive index 1.46). Scattering particle S-3 uses alumina particles "Advanced Alumina (AA-04)" (manufactured by Sumitomo Chemicals Corporation, average particle size 500 nm, refractive index 1.76). Scattering particle S-4 uses titanium dioxide particles "MT-01" (manufactured by TAYCA Corporation, average particle size 10 nm, refractive index 2.50). As the scattering particle S-5, aluminum-rich andalusite particles "KM-101" (manufactured by Kyoritsu Materials Co., Ltd., with an average particle size of 1900 nm and a refractive index of 1.64) are used.

[0187] <Measurement of ζ potential> In the determination of zeta potential, an electrophoretic light scattering spectrophotometer (ELS-8000) manufactured by Otsuka Electronics Co., Ltd. was used as the measuring device. A liquid containing 1 part by weight of the scattering particles to be measured, dispersed in a 10 mmol / dm³ NaCl aqueous solution, was used as the measuring solution. The electroosmotic flow of this solution was measured at 25°C to determine the zeta potential of the scattering particles. The pH of the solution was adjusted using aqueous HCl and NaOH solutions. The pH was determined according to the pH measurement method using a glass electrode as described in JIS Z 8802 (2011) using a pH meter (D50) manufactured by Horiba Corporation. The number of zeta potential measurements was set to 3 for each scattering particle. The absolute value of the zeta potential of the scattering particle was taken as the average of these 3 measurements. The absolute values ​​of the zeta potentials of scattering particles S-1 and S-5 are shown in Table 1-2.

[0188] [Table 1-2] (Table 1-2) Scattering particles S-1 S-5 pH value 7 4 5 6 7 8 9 10 ζ potential Absolute value [mV] 40 12 10 8 5 10 16 14

[0189] (Example 1) In Example 1, adhesive resin P-1 was used, and relative to 100 parts by weight of adhesive resin P-1, 0.27 parts by weight of compound G-1 (specifically, luminescent material (a)) as a luminescent material, 3 parts by weight of scattering particles S-1, and 300 parts by weight of ethyl acetate as a solvent were mixed. Subsequently, the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing apparatus, MAZERUSTAR (registered trademark) KK-400 (manufactured by Kurashiki Textile Co., Ltd.), to obtain a color conversion composition for use as a resin composition in the production of a color conversion layer.

[0190] Next, the color conversion composition obtained as described is coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick) using a slot die coater, and then heated and dried at 120°C for 20 minutes. This forms a color conversion layer with an average film thickness of 20 μm, resulting in a unit formed by laminating these color conversion layers with the polyester film (substrate layer).

[0191] Next, using polyester resin "Vylon 630" (manufactured by Toyobo Co., Ltd.) as the adhesive layer resin, 300 parts by weight of ethyl acetate as the solvent were mixed with 100 parts by weight of the polyester resin. Then, the mixture was stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing apparatus "MAZERUSTAR" KK-400 (manufactured by Kurashiki Bosho Co., Ltd.), thereby obtaining the resin composition for the adhesive layer.

[0192] Next, using a slot die coater, the adhesive layer resin composition obtained as described is coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick), and heated and dried at 120°C for 20 minutes. This forms an adhesive layer with an average film thickness of 20 μm, resulting in a unit formed by laminating these adhesive layers with the polyester film (substrate layer).

[0193] Next, the two units are heat-laminated by directly stacking the color conversion layer and the adhesive layer to fabricate a color conversion sheet with a structure of "substrate layer / color conversion layer / adhesive layer / substrate layer". The haze, in-plane color uniformity, and durability of the obtained color conversion sheet are then evaluated using the method described above. The structure of the color conversion layer and the evaluation results of the color conversion sheet in Example 1 are shown in Table 2-1 below.

[0194] (Examples 2-13, Comparative Examples 1-5) In Examples 2 to 13 and Comparative Examples 1 to 5, except for changing the type of luminescent material or the amount of scattering particles as shown in Tables 2-1 and 2-2, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 1. The structure and evaluation results of the color conversion layers of the color conversion sheets in Examples 2 to 13 and Comparative Examples 1 to 5 are shown in Tables 2-1 and 2-2 described below.

[0195] As shown in Table 2-1, based on the comparison between Examples 1 to 8 and Comparative Example 1, it was found that, compared with Comparative Example 1, which had a haze value of less than 20%, the in-plane uniformity of color in Examples 1 to 8, which had a haze value of 20% or more, was better. Among them, the in-plane uniformity of color in Examples 1 and Examples 4 to 8, which had a haze value of 50% or more, was significantly better.

[0196] Furthermore, based on the comparison of Examples 1 to 8, it was found that the higher the haze value, the better the in-plane uniformity of the color. Additionally, it was found that although the higher the amount of scattering particles used (added amount), the lower the durability, excellent durability can be maintained if the haze value is within the range of 20% to 99%. Specifically, as shown in Comparative Example 2, it was found that if the haze value exceeds 99%, although the in-plane uniformity of the color is good, the durability is significantly reduced.

[0197] Furthermore, as shown in Table 2-1, based on the comparison between Example 1 and Comparative Example 3, it was found that, as a luminescent material used in conjunction with scattering particles, the use of compound G-1 as a delayed fluorescence material resulted in better durability of the color conversion layer containing scattering particles and luminescent material compared to the use of compound G-2, which is not a delayed fluorescence material.

[0198] Furthermore, as shown in Table 2-2, based on the comparison between Examples 9 to 13 and Comparative Example 5, it was found that when using Compound G-3, which is a delayed fluorescence material different from that in Examples 1 to 8, the same tendency as when using Compound G-1 was observed.

[0199] [Table 2-1] (Table 2-1) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Color conversion layer Luminescent materials G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-2 G-2 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 3 0.3 0.65 1 1.5 4 6 7 0.2 7.5 3 0.3 Amount of luminescent material added [Parts by weight] (vs. 100 parts by weight of resin) 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 Haze value [%] 92 20 36 51 70 93 96 99 10 99.5 91 15 In-plane uniformity (Δu'v') 0.006 0.018 0.016 0.013 0.009 0.004 0.003 0.002 0.022 0.002 0.007 0.026 Durability (reduced by 10% over time) [Hour] 520 700 680 640 600 400 350 320 720 280 200 410

[0200] [Table 2-2] (Table 2-2) Example 9 Example 10 Example 11 Example 12 Example 13 Comparative Example 5 Color conversion layer Luminescent materials G-3 G-3 G-3 G-3 G-3 G-3 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 0.2 1 1.5 3 4 0.1 Amount of luminescent material added [Parts by weight] (vs. 100 parts by weight of resin) 0.34 0.34 0.34 0.34 0.34 0.34 Haze value [%] 20 60 77 95 99 10 In-plane uniformity (Δu'v') 0.018 0.013 0.007 0.004 0.002 0.022 Durability (reduced by 10% over time) [Hour] 700 630 600 530 490 730

[0201] (Example 14) In Example 14, using adhesive resin P-1, 0.27 parts by weight of compound G-1 (as luminescent material (a)), 0.0020 parts by weight of compound R-1 (as luminescent material (b)), 3 parts by weight of scattering particles S-1, and 300 parts by weight of ethyl acetate (as solvent) were mixed relative to 100 parts by weight of adhesive resin P-1. Subsequently, the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing apparatus, "MAZERUSTAR" (registered trademark) KK-400 (manufactured by Kurashiki Textile Co., Ltd.), to obtain a color conversion composition for use as a resin composition in the production of a color conversion layer.

[0202] Next, the color conversion composition obtained as described is coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick) using a slot die coater, and then heated and dried at 120°C for 20 minutes. This forms a color conversion layer with an average film thickness of 20 μm, resulting in a unit formed by laminating these color conversion layers with the polyester film (substrate layer).

[0203] Next, using polyester resin "Vylon 630" (manufactured by Toyobo Co., Ltd.) as the adhesive layer resin, 300 parts by weight of ethyl acetate as the solvent were mixed with 100 parts by weight of the polyester resin. Then, the mixture was stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing apparatus "MAZERUSTAR" KK-400 (manufactured by Kurashiki Bosho Co., Ltd.), thereby obtaining the resin composition for the adhesive layer.

[0204] Next, using a slot die coater, the adhesive layer resin composition obtained as described is coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick), and heated and dried at 120°C for 20 minutes. This forms an adhesive layer with an average film thickness of 20 μm, resulting in a unit formed by laminating these adhesive layers with the polyester film (substrate layer).

[0205] Next, the two units are heat-laminated by directly stacking the color conversion layer and the adhesive layer to fabricate a color conversion sheet with a structure of "substrate layer / color conversion layer / adhesive layer / substrate layer". The haze, in-plane color uniformity, and durability of the obtained color conversion sheet are then evaluated using the method described above. The structure of the color conversion layer and the evaluation results of the color conversion sheet in Example 14 are shown in Table 3-1 below.

[0206] (Examples 15-23, Comparative Examples 6-10) In Examples 15-23 and Comparative Examples 6-10, except for changing the type of luminescent material or the amount of scattering particles as shown in Tables 3-1 and 3-2, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 14. The structure and evaluation results of the color conversion layer of the color conversion sheets in Examples 15-23 and Comparative Examples 6-10 are shown in Tables 3-1 and 3-2 described below.

[0207] As shown in Table 3-1, based on the comparison between Examples 14-19 and Comparative Example 6, it was found that, compared with Comparative Example 6, which had a haze value of less than 20%, the in-plane uniformity of color in Examples 14-19, which had a haze value of 20% or more, was better. Among them, the in-plane uniformity of color in Examples 14 and Examples 16-19, which had a haze value of 50% or more, was significantly better.

[0208] Furthermore, based on the comparison of Examples 14 to 19, it was found that the higher the haze value, the better the in-plane uniformity of the color. Additionally, it was found that although the higher the amount of scattering particles used (added amount), the lower the durability, excellent durability can be maintained if the haze value is within the range of 20% to 99%. Specifically, as shown in Comparative Example 7, it was found that if the haze value exceeds 99%, although the in-plane uniformity of the color is good, the light durability is significantly reduced.

[0209] Furthermore, as shown in Table 3-1, based on the comparison between Example 14 and Comparative Example 8, it was found that, as a luminescent material used in conjunction with scattering particles, the use of compound G-1 as a delayed fluorescence material resulted in better durability of the color conversion layer containing scattering particles and luminescent material compared to the use of compound G-2, which is not a delayed fluorescence material.

[0210] Furthermore, as shown in Table 3-2, based on the comparison between Examples 20 to 23 and Comparative Examples 9 and 10, it was found that when using Compound G-3, which is a delayed fluorescence material different from that in Examples 14 to 19, the same tendency as when using Compound G-1 was observed.

[0211] [Table 3-1] (Table 3-1) Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Comparative Example 6 Comparative Example 7 Comparative Example 8 Color conversion layer Luminescent materials (a) G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-2 Amount of luminescent material (a) added [Parts by weight] (vs. 100 parts by weight of resin) 0.27 0.27 0.27 0.27 0.27 0.34 0.27 0.34 0.27 Luminescent materials (b) R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 Amount of luminescent material (b) added [Parts by weight] (vs. 100 parts by weight of resin) 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 3 0.3 1.5 4 5 6 0.2 6.5 3 Haze value [%] 92 20 75 94 96 99 10 99.5 91 In-plane uniformity (Δu'v') 0.005 0.017 0.008 0.003 0.005 0.003 0.021 0.002 0.006 Durability (reduced by 10% over time) [Hour] 510 680 580 350 320 300 700 250 160

[0212] [Table 3-2] (Table 3-2) Example 20 Example 21 Example 22 Example 23 Comparative Example 9 Comparative Example 10 Color conversion layer Luminescent materials (a) G-3 G-3 G-3 G-3 G-3 G-3 Amount of luminescent material (a) added [Parts by weight] (vs. 100 parts by weight of resin) 0.34 0.34 0.34 0.34 0.34 0.34 Luminescent materials (b) R-1 R-1 R-1 R-1 R-1 R-1 Amount of luminescent material (b) added [Parts by weight] (vs. 100 parts by weight of resin) 0.002 0.002 0.002 0.002 0.002 0.002 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 0.2 1 1.5 3.5 4 0.1 Haze value [%] 20 63 83 99 99.5 15 In-plane uniformity (Δu'v') 0.018 0.013 0.006 0.003 0.002 0.026 Durability (reduced by 10% over time) [Hour] 690 620 590 490 280 700

[0213] (Example 24) In Example 24, adhesive resin P-1 was used, and relative to 100 parts by weight of adhesive resin P-1, 0.27 parts by weight of compound G-1 as luminescent material (a), 3 parts by weight of scattering particles S-1, and 300 parts by weight of ethyl acetate as solvent were mixed. Subsequently, the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing apparatus, "MAZERUSTAR" (registered trademark) KK-400 (manufactured by Kurashiki Textile Co., Ltd.), to obtain a resin composition for the production of a green color conversion layer (hereinafter referred to as the green color conversion composition).

[0214] Next, the green color conversion composition obtained as described was coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick) using a slot die coater, and then heated and dried at 120°C for 20 minutes. This formed a green color conversion layer with an average thickness of 20 μm, resulting in a unit formed by laminating these green color conversion layers with the polyester film (substrate layer).

[0215] Next, relative to 100 parts by weight of adhesive resin P-1, 0.025 parts by weight of compound R-1 (as luminescent material (b)), 3 parts by weight of scattering particles S-1, and 300 parts by weight of ethyl acetate (as solvent) were mixed. Subsequently, the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing apparatus, "MAZERUSTAR" (registered trademark) KK-400 (manufactured by Kurashiki Textile Co., Ltd.), thereby obtaining a resin composition for the production of a red color conversion layer (hereinafter referred to as the red color conversion composition).

[0216] Next, the red color conversion composition obtained as described was coated onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., 50 μm thick) using a slot die coater, and then heated and dried at 120°C for 20 minutes. This formed a red color conversion layer with an average film thickness of 20 μm, resulting in a laminate of the red color conversion layer and the polyester film (substrate layer).

[0217] Next, using a polyester resin "Vylon 630" (manufactured by Toyobo Co., Ltd.) as the adhesive layer resin, 300 parts by weight of ethyl acetate as the solvent were mixed with 100 parts by weight of the polyester resin. Then, the mixture was stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing apparatus "MAZERUSTAR KK-400" (manufactured by Kurashiki Bosho Co., Ltd.). This yielded the resin composition for the adhesive layer.

[0218] Next, the adhesive layer resin composition obtained as described is coated onto the red color conversion layer using a slot die coater, and then heated and dried at 120°C for 20 minutes. This forms an adhesive layer with an average film thickness of 20 μm, resulting in a unit formed by laminating these adhesive layers with the substrate layer and the red color conversion layer.

[0219] Next, the two units are heat-laminated by directly stacking a green color conversion layer and an adhesive layer to create a color conversion sheet with a structure of "substrate layer / green color conversion layer / adhesive layer / red color conversion layer / substrate layer". The haze, in-plane color uniformity, and durability of the obtained color conversion sheet are then evaluated using the method described above. The structure of the color conversion layer and the evaluation results of the color conversion sheet in Example 24 are shown in Table 4-1 below.

[0220] (Examples 25-33, Comparative Examples 11-15) In Examples 25-33 and Comparative Examples 11-15, except for changing the type of luminescent material or the amount of scattering particles as shown in Tables 4-1 and 4-2, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 24. The structure and evaluation results of the color conversion layer of the color conversion sheets in Examples 25-33 and Comparative Examples 11-15 are shown in Tables 4-1 and 4-2 described below.

[0221] As shown in Table 4-1, based on the comparison between Examples 24-29 and Comparative Example 11, it was found that, compared with Comparative Example 11, which had a haze value of less than 20%, Examples 24-29, with a haze value of 20% or more, exhibited better in-plane color uniformity. In particular, Examples 24 and Examples 26-29, with a haze value of 50% or more, showed significantly better in-plane color uniformity.

[0222] Furthermore, based on the comparison of Examples 24 to 29, it was found that the higher the haze value, the better the in-plane uniformity of the color. Additionally, it was found that although the durability decreases with a higher amount of scattering particles, excellent durability can be maintained if the haze value is between 20% and 99%. Specifically, as shown in Comparative Example 12, it was found that if the haze value exceeds 99%, although the in-plane uniformity of the color is good, the light durability is significantly reduced.

[0223] Furthermore, as shown in Table 4-1, based on the comparison between Example 24 and Comparative Example 13, it was found that, as a luminescent material used in conjunction with scattering particles, the use of compound G-1 as a delayed fluorescence material resulted in better durability of the color conversion layer containing scattering particles and luminescent material compared to the use of compound G-2, which is not a delayed fluorescence material.

[0224] Furthermore, as shown in Table 4-2, based on the comparison between Examples 30 to 33 and Comparative Examples 14 and 15, it was found that when using Compound G-3, which is a delayed fluorescence material different from that in Examples 24 to 29, the same tendency as when using Compound G-1 was observed.

[0225] [Table 4-1] (Table 4-1) Example 24 Example 25 Example 26 Example 27 Example 28 Example 29 Comparative Example 11 Comparative Example 12 Comparative Example 13 Color conversion layer (A) Luminescent materials (a) G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-1 G-2 Amount of luminescent material (a) added [Parts by weight] (vs. 100 parts by weight of resin) 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 0.27 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 3 0.3 1.5 4 5 6 0.2 6.5 3 Color conversion layer (B) Luminescent materials (b) R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 R-1 Amount of luminescent material (b) added [Parts by weight] (vs. 100 parts by weight of resin) 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 0.002 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 3 0.3 1.5 4 5 6 0.2 6.5 3 Haze value [%] 92 20 73 93 96 99 10 99.5 91 In-plane uniformity (Δu'v') 0.007 0.017 0.008 0.003 0.002 0.001 0.02 0.001 0.006 Durability (reduced by 10% over time) [Hour] 550 690 590 360 330 300 710 250 180

[0226] [Table 4-2] (Table 4-2) Example 30 Example 31 Example 32 Example 33 Comparative Example 14 Comparative Example 15 Color conversion layer (A) Luminescent materials (a) G-3 G-3 G-3 G-3 G-3 G-3 Amount of luminescent material (a) added [Parts by weight] (vs. 100 parts by weight of resin) 0.34 0.34 0.34 0.34 0.34 0.34 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 0.2 1 1.5 3.5 4 0.2 Color conversion layer (B) Luminescent materials (b) R-1 R-1 R-1 R-1 R-1 R-1 Amount of luminescent material (b) added [Parts by weight] (vs. 100 parts by weight of resin) 0.002 0.002 0.002 0.002 0.002 0.002 Scattering particles S-1 S-1 S-1 S-1 S-1 S-1 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 0.2 1 1.5 3.5 4 0.2 Haze value [%] 20 70 85 99 99.5 15 In-plane uniformity (Δu'v') 0.017 0.01 0.005 0.002 0.001 0.025 Durability (reduced by 10% over time) [Hour] 700 650 610 500 290 710

[0227] (Example 1, Examples 34-36, and Comparative Example 16) In Examples 1, 34-36, and Comparative Example 16, except for changing the type of scattering particles as shown in Table 5, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 1. The structure and evaluation results of the color conversion layers of the color conversion sheets in Examples 1, 34-36, and Comparative Example 16 are shown in Table 5 below.

[0228] As shown in Table 5, based on the comparison between Examples 1, 34-36 and Comparative Example 16, it was found that regardless of whether the scattering particles are titanium dioxide particles, aluminum oxide particles, or silicon dioxide particles, both the in-plane uniformity and durability of the color are good. Among these, titanium dioxide particles are preferred as the type of scattering particle, and when titanium dioxide particles are used, both the in-plane uniformity and durability of the color are particularly good.

[0229] Furthermore, a comparison between Example 1 and Example 36 revealed that when the particle size of the scattering particles is 100 nm or larger, the in-plane uniformity and durability of the color are particularly good. This is believed to be because the aggregation of the scattering particles is suppressed.

[0230] [Table 5] (Table 5) Example 1 Example 34 Example 35 Example 36 Comparative Example 16 Color conversion layer Luminescent materials G-1 G-1 G-1 G-1 G-1 Scattering particles S-1 S-2 S-3 S-4 - Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 3 3 3 3 0 Amount of luminescent material added [Parts by weight] (vs. 100 parts by weight of resin) 0.27 0.27 0.27 0.27 0.27 Haze value [%] 92 80 85 85 5 In-plane uniformity (Δu'v') 0.006 0.012 0.009 0.01 0.03 Durability (reduced by 10% over time) [Hour] 520 500 510 400 720

[0231] <Determination of Luminescent Quantum Yield> The luminescence quantum yield of the color converter was measured using an absolute PL quantum yield measurement device (Quantaurus-QY, manufactured by Hamamatsu Photonics) when the color converter was excited by excitation light with a wavelength of 460 nm.

[0232] (Examples 37 and 38) In Examples 37 and 38, except for changes in the amount of luminescent material, the type and amount of scattering particles as shown in Table 6, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 1. The structure and evaluation results of the color conversion layers of the color conversion sheets in Examples 37 and 38 are shown in Table 6 below.

[0233] As shown in Table 6, a comparison between Examples 37 and 38 reveals that the color conversion sheet, which includes a color conversion layer containing scattering particles with an absolute value of ζ potential greater than 20 mV, exhibits particularly good luminescence quantum yield. This is believed to be due to the suppression of condensation of scattering particles or delayed fluorescent materials in the color conversion layer.

[0234] [Table 6] (Table 6) Example 37 Example 38 Color conversion layer Luminescent materials G-3 G-3 Scattering particles S-1 S-5 Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 1.5 1.5 Amount of luminescent material added [Parts by weight] (vs. 100 parts by weight of resin) 1 1 Haze value [%] 75 61 In-plane uniformity (Δu'v') 0.008 0.012 Durability (reduced by 10% over time) [Hour] 550 480 Luminescent quantum yield [%] 92 85 Half-width [nm] 40 50

[0235] (Examples 11, 39, and Comparative Examples 17 and 18) In Examples 11, 39, 17, and 18, except for changes in the type and amount of luminescent material, the type of scattering particles, and the type of adhesive resin as shown in Table 7, the color conversion sheets were fabricated and various evaluations were performed using the same method as in Example 1. The structure and evaluation results of the color conversion layer of the color conversion sheets in Examples 11, 39, 17, and 18 are shown in Table 7 below.

[0236] As shown in Table 7, a comparison between Examples 11 and 39 reveals that even color conversion sheets comprising a color conversion layer using an adhesive resin P-2 with a low glass transition temperature can achieve the same good durability as color conversion sheets comprising a color conversion layer using an adhesive resin P-1 with a high glass transition temperature. Specifically, as shown in Comparative Examples 17 and 18, it was found that when the color conversion layer does not contain scattering particles, the difference in glass transition temperatures of the adhesive resins contained in the color conversion layer affects the durability of the color conversion layer. This is believed to be because the aggregation of delayed fluorescent materials in the adhesive resin is suppressed.

[0237] [Table 7] (Table 7) Example 11 Example 39 Comparative Example 17 Comparative Example 18 Color conversion layer Luminescent materials G-3 G-3 G-3 G-3 Scattering particles S-1 S-1 - - Scattering particle addition amount [Parts by weight] (vs. 100 parts by weight of resin) 1.5 1.5 - - Amount of luminescent material added [Parts by weight] (vs. 100 parts by weight of resin) 0.34 0.34 0.34 0.34 Adhesive resin P-1 P-2 P-1 P-2 Haze value [%] 77 77 8 5 In-plane uniformity (Δu'v') 0.007 0.007 0.03 0.03 Durability (reduced by 10% over time) [Hour] 600 610 730 650

[0238] In Tables 2-1, 2-2, 3-1, 3-2, 4-1, 4-2, 5, 6, and 7, unless otherwise specified, "resin" refers to adhesive resin. Furthermore, color conversion layer (A) refers to layer (A) or layer (A'). Color conversion layer (B) refers to layer (B) or layer (B'). [Industry availability]

[0239] As described above, the color conversion sheet, light source unit, display and lighting device involved in this invention are suitable for improving the in-plane uniformity and durability of color.

[0240] 1A, 1B, 1C, 1D: Color conversion sheets 10: Substrate layer 11: Color Conversion Layer 12: Barrier membrane

Claims

1. A color conversion sheet for converting incident light into light with a wavelength different from the incident light, the color conversion sheet being characterized in that: it includes a color conversion layer containing a compound that emits delayed fluorescence, and has a haze value of 20% or more and 99% or less, wherein the compound that emits delayed fluorescence contains a compound represented by the following general formula (1) or general formula (2). In general formula (1) or general formula (2), rings Za, Zb, and Zc are independently substituted or unsubstituted rings forming aryl rings with 6 to 30 carbon atoms, or substituted or unsubstituted rings forming heteroaryl rings with 6 to 30 carbon atoms; Z1 and Z2 are independently oxygen atoms, NRa (nitrogen atoms with substituent Ra), or sulfur atoms; when Z1 is NRa, substituent Ra can bond with rings Za or Zb to form a ring; when Z2 is NRa, substituent Ra can bond with rings Za or Zc to form a ring; E is a boron atom, a phosphorus atom, SiRa (silicon atoms with substituent Ra), or P=O; E1 and E2 are independently BRa (boron atoms with substituent Ra), PRa (phosphorus atoms with substituent Ra), or P=O. The substituents Ra can be: SiRa2 (silicon atom with two substituents Ra), P(=O)Ra2 (phosphine oxide with two substituents Ra), or P(=S)Ra2 (phosphine sulfide with two substituents Ra), S(=O) or S(=O)2; when E1 is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra can bond with ring Za or ring Zb to form a ring; when E2 is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, the substituent Ra can bond with ring Za or ring Zc to form a ring; the substituent Ra can be independently substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl, or substituted or unsubstituted alkyl.

2. The color conversion sheet as claimed in claim 1, wherein the color conversion layer contains scattering particles.

3. The color conversion sheet as claimed in claim 2, wherein the absolute value of the zeta potential of the scattering particles at any value in the range of pH 4 to 10 is 20 mV to 100 mV.

4. The color conversion sheet as claimed in claim 2 or claim 3, wherein the average particle size of the scattering particles is greater than 100 nm and less than 700 nm.

5. The color conversion sheet as claimed in claim 2 or claim 3, wherein the refractive index of the scattering particles is greater than 1.4 and less than 2.

8.

6. The color conversion sheet as claimed in claim 2 or claim 3, wherein the color conversion layer further comprises an adhesive resin, wherein when the adhesive resin is set to 100 parts by weight, the content of the scattering particles in the color conversion layer is 1.0 × 10⁻³ parts by weight or more and 30 parts by weight or less.

7. The color conversion sheet as claimed in claim 2 or claim 3, wherein the scattering particles are at least one selected from aluminum oxide, titanium dioxide and zirconium oxide.

8. The color conversion sheet as described in claim 2 or claim 3, wherein the scattering particles are titanium dioxide particles.

9. The color conversion sheet according to any one of claims 1 to 3, wherein the compound emitting delayed fluorescence is at least one of the following luminescent materials (a) and (b): luminescent material (a): a luminescent material that emits light in a region with a peak wavelength of 500 nm or more and less than 580 nm by using excitation light in the range of 430 nm or more and 500 nm or less; luminescent material (b): a luminescent material that emits light in a region with a peak wavelength of 580 nm or more and less than 750 nm by being excited by either or both of excitation light in the range of 430 nm or more and 500 nm or by luminescence from said luminescent material (a).

10. The color conversion sheet as claimed in claim 9, wherein the color conversion layer comprises at least one of the following layers (A) and (B): (A) layer: a layer containing the luminescent material (a) as the compound emitting delayed fluorescence; (B) layer: a layer containing the luminescent material (b) as the compound emitting delayed fluorescence.

11. The color conversion sheet as claimed in claim 10, wherein at least one of the (A) layer and the (B) layer contains scattering particles.

12. A light source unit, characterized in that it comprises: A light source, and a color conversion sheet as described in any one of claims 1 to 11.

13. The light source unit as claimed in claim 12, wherein the light source is a light-emitting diode that emits light at a maximum wavelength in the range of 400 nm and 500 nm.

14. A display, characterized in that it comprises: The light source unit as described in claim 12 or claim 13.

15. A lighting device, characterized in that it comprises: The light source unit as described in claim 12 or claim 13.

Images