Light source unit including color conversion sheet, and display and lighting device including same

Abstract

To provide a color conversion sheet with an excellent color reproductivity and durability.SOLUTION: A light source unit includes a light source, a color conversion sheet, and an optical film. The color conversion sheet has a compound which discharges delay fluorescence. The optical film has a reflectance in a range between 20% and 95%, both inclusive, in a wavelength band in a range from a peak wavelength of the absorption spectrum of the compound which discharges the delay fluorescence to a peak wavelength of an emission spectrum of the compound which discharges the delay fluorescence.SELECTED DRAWING: None

Description

[Technical Field]

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

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

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

[0004] One of the challenges for liquid crystal displays that use such materials is achieving both color reproducibility and durability. A technique for improving the color reproducibility of liquid crystal displays has been proposed in which an organic light-emitting material is used as a component of a color conversion sheet. Examples of techniques for using an organic light-emitting material as a component of a color conversion sheet include those using coumarin derivatives (see, for example, Patent Document 1), rhodamine derivatives (see, for example, Patent Document 2), and pyrromethene derivatives (see, for example, Patent Document 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-273440 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-164245 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-241160 Summary of the Invention [Problem to be solved by the invention]

[0006] However, conventional techniques using organic light-emitting materials have not been sufficient in improving color reproducibility and have also lacked durability. Therefore, an object of the present invention is to provide a color conversion sheet that is excellent in color reproducibility and durability. [Means for solving the problem]

[0007] In order to overcome the above-mentioned problems, the light source unit according to the present invention is a light source unit comprising a light source, a color conversion sheet, and an optical film, wherein the color conversion sheet contains a compound that emits delayed fluorescence, and the optical film is an optical film having a reflectance of 20% or more and 95% or less in a wavelength band ranging from the peak wavelength of the absorption spectrum of the compound that emits delayed fluorescence to the peak wavelength of the emission spectrum of the compound that emits delayed fluorescence. [Effects of the Invention]

[0008] The color conversion sheet according to the present invention has the effect of being excellent in color reproducibility and durability. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view showing a first example of a light source unit according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic cross-sectional view showing a second example of a light source unit according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic cross-sectional view showing a third example of a light source unit according to an embodiment of the present invention. [Figure 4]FIG. 4 is a schematic cross-sectional view showing a fourth example of a light source unit according to an embodiment of the present invention. [Figure 5] FIG. 5 is a schematic cross-sectional view showing a first example of a color conversion sheet. [Figure 6] FIG. 6 is a schematic cross-sectional view showing a second example of the color conversion sheet. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a third example of the color conversion sheet. [Figure 8] FIG. 8 is a schematic cross-sectional view showing a fourth example of the color conversion sheet. [Figure 9] FIG. 9 is a graph showing the reflectance of the LED-side surface of each optical film used in the examples. [Figure 10] FIG. 10 shows the emission spectrum of the color conversion member according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes in detail the embodiments of the present invention, but the present invention is not limited to the following embodiments and can be modified in various ways depending on the purpose and application.

[0011] <Light source unit> The light source unit of the present invention comprises a light source, a color conversion sheet, and an optical film, wherein the color conversion sheet has a compound that emits delayed fluorescence, and the optical film has a reflectance of 20% or more and 95% or less in a wavelength band ranging from the peak wavelength of the absorption spectrum of the compound that emits delayed fluorescence to the peak wavelength of the emission spectrum of the compound that emits delayed fluorescence.

[0012] By having the reflectance of 20% or more, the light emitted from the compound that emits delayed fluorescence can be reflected back to the color conversion sheet, narrowing the emission spectrum of the compound that emits delayed fluorescence (increasing color purity) and adjusting the emission peak wavelength. This is because the self-absorption of the compound that emits delayed fluorescence can be promoted, shifting the emission spectrum to a longer wavelength. This action results in the effect of improving color reproducibility.

[0013] Generally, increasing the number of excitations of a light-emitting material by reflection accelerates its decomposition, as described below. In contrast, compounds that emit delayed fluorescence are less susceptible to deterioration, as described below. Therefore, according to the present invention, it is possible to improve color reproducibility while maintaining durability.

[0014] However, if the reflectance is too high, the effect of deterioration will appear even if a compound that emits delayed fluorescence is used. Therefore, the reflectance is 95% or less. The range of the reflectance is preferably 25 to 90%, and more preferably 30 to 85%.

[0015] When the color conversion sheet contains two or more compounds that emit delayed fluorescence, the optical film may have the above reflectance in relation to at least one compound that emits delayed fluorescence.

[0016] Two or more types of optical films may be included in the light source unit. In that case, it is sufficient that the reflectance of all the optical films combined is within the above range. Note that even when optical films are provided on both the viewing side and the opposite side of the color conversion sheet, it is sufficient that the reflectance of all the optical films combined is within the above range.

[0017] For optical films whose reflectance is angle-dependent, the average value of the reflectance at the angle showing the maximum reflectance and the reflectance at the angle showing the minimum reflectance is used. When the reflectance of the optical film differs significantly between the front and back sides, the reflectance of the surface facing the color conversion sheet should be measured.

[0018] Fig. 1 is a schematic cross-sectional view showing an example of a light source unit. As shown in Fig. 1, the light source unit 100 in this example is a light source unit configured by a light source section including a substrate 6, a reflective layer 5, and a light source 4, a diffuser plate 3, a color conversion sheet 1, and a diffuser film 21, which is a type of optical film.

[0019] The light source unit shown in FIG. 1 has a so-called direct type configuration, but the arrangement of the light source is not particularly limited.

[0020] In the color conversion sheet according to the embodiment of the present invention, it is preferable that I0 / A0, which is the ratio of the emission peak height I0 resulting from the emission of singlet oxygen in the fluorescence spectrum of the color conversion sheet to the absorbance A0 at the peak wavelength of the absorption spectrum of the color conversion sheet when the peak wavelength of the absorption spectrum is used as the excitation wavelength, is smaller than I' / A', which is the ratio of the emission peak intensity I' resulting from the emission of singlet oxygen in the fluorescence spectrum of the resin sheet to the absorbance A' at the peak wavelength of the absorption spectrum of the resin sheet when the peak wavelength of the absorption spectrum of a resin sheet containing 0.05 wt% rose bengal in the resin is used as the excitation light.

[0021] When the color conversion sheet has multiple peaks in its absorption spectrum, the sum of the absorbances is taken as A0, for example, when the color conversion sheet is a laminate of two or more color conversion layers that convert light to different colors.

[0022] More details will be provided later in the section on color conversion layers, but organic fluorescent materials generally generate singlet oxygen from their excited state, and when the singlet oxygen reacts with the fluorescent material, the fluorescent material deteriorates, causing a change in chromaticity. However, luminescent materials with an I0 / A0 ratio smaller than I' / A' generate less singlet oxygen, suppressing deterioration of the luminescent material and ensuring good durability of the color conversion sheet. Both the absorbance A and the emission peak height I resulting from singlet oxygen emission are proportional to concentration, so I / A indicates the singlet oxygen generation capacity independent of the luminescent material's concentration.

[0023] Rose Bengal is a well-known material that generates singlet oxygen and is a relatively readily available dye material. If the amount of singlet oxygen generated by an organic fluorescent material is less than that of Rose Bengal, then even if the number of excitations is increased due to reflection by the optical film, the amount of singlet oxygen generated will be small. Therefore, the number of organic fluorescent materials decomposed by singlet oxygen is reduced, and the color conversion sheet exhibits good durability.

[0024] The amount of singlet oxygen generated is expressed as I / A and I' / A'. If (I / A) / (I' / A')<1, the amount of singlet oxygen generated is small, the fluorescent material in the color conversion layer is less likely to deteriorate, and good durability of the color conversion sheet can be obtained, but it is particularly preferable that (I / A) / (I' / A')<1 / 10.

[0025] Near-infrared fluorescence spectroscopy for measuring singlet oxygen emission is sensitive, and the absolute value of the emission peak may vary depending on the measurement device. Therefore, measurements of I / A and I' / A to determine the value of (I / A) / (I' / A') must be performed using the same device, a near-infrared fluorescence spectrophotometer.

[0026] Because rose bengal has high polarity, it is necessary to use a binder resin that can disperse rose bengal in the resin. When forming rose bengal into sheets, the binder resin is preferably an acrylic resin, and particularly preferably polymethyl methacrylate (PMMA).

[0027] (light source) Any light source can be used as long as it emits light in a wavelength range that can be absorbed by the delayed fluorescent material. For example, any light source can be used, in principle, including hot cathode tubes, cold cathode tubes, fluorescent light sources such as inorganic EL, organic electroluminescence element light sources, LED light sources, incandescent light sources, and sunlight. Among these, LEDs are preferred, and for display and lighting applications, blue LEDs with a light source wavelength in the 430 to 500 nm range are even more preferred because they can enhance the color purity of blue light.

[0028] The light source may have one emission peak or two or more emission peaks, but in order to improve color purity, it is preferable to use a light source having one emission peak. It is also possible to use a combination of multiple light sources with different emission peaks.

[0029] The arrangement of the light source and the color conversion sheet is not particularly limited, and the light source and the color conversion sheet may be closely attached to each other, or may be separated from each other in a remote phosphor configuration. Furthermore, the light source unit may further include a color filter to enhance color purity.

[0030] (Optical film) Examples of optical films that can be used in the light source unit of the present invention include polarized reflective films, light diffusing films, prism sheets, wavelength-selective reflective films, microlens films, cut films, etc. Among these, these optical films have the function of returning a portion of the light emitted from the color conversion sheet to the color conversion layer by diffusion or reflection.

[0031] These optical films are preferably provided on one or both sides of the color conversion sheet, and more preferably on both sides, depending on the purpose and use. Also, an optical unit is preferred in which an optical film is provided on at least the viewer side of the color conversion sheet, and a diffuser plate is further provided on the side opposite to the viewer side of the color conversion sheet.

[0032] The diffuser plate is a rigid plate with a textured surface. By placing the diffuser plate on the light source's emission side, the light from the light source is reflected and diffused to make the amount of light uniform. There are no particular restrictions on the thickness of the diffuser plate, but a thickness of 0.5 cm to 3 cm is preferable.

[0033] The optical film and the diffuser plate promote light reflection. Therefore, when optical films are provided on both sides of the color conversion sheet, or when an optical film is provided on at least the viewer-side surface and a diffuser plate is provided on the surface opposite the viewer-side, light is repeatedly reflected between the optical films or between the optical film and the diffuser plate, which can further increase the number of excitations of the luminescent material. Increasing the number of excitations enhances the effect of promoting self-absorption of the luminescent material and shifting the spectrum to longer wavelengths, thereby further improving color reproducibility. Here, the viewer-side surface refers to the display surface side in display applications and the light-emitting surface side in lighting applications.

[0034] From the viewpoints of thinning the light source unit, productivity, and light durability, it is preferable to provide three or more optical films on the viewing side of the color conversion sheet. By providing three or more optical sheets, light reflection can be promoted, thereby achieving good in-plane uniformity.

[0035] The color conversion sheet and the optical film may be spaced apart or laminated, but are preferably laminated, because the longer the air layer distance r, the greater the attenuation of light, which results in a decrease in the light utilization efficiency and can be a factor in a decrease in the brightness of the entire light source unit.

[0036] (polarized reflective film) The light source unit according to the present invention preferably has a polarizing reflective film on the light-emitting surface of the color conversion sheet. The polarizing reflective film has polarization separation ability in addition to its reflective function, and can emit light of a preferred polarization while reflecting light of other polarizations. The reflected light is recycled by reflection from the color conversion layer or other optical films, thereby increasing the brightness of the light source unit. Preferred polarizing reflective films include a cholesteric reflective polarizer, a cholesteric reflective polarizer with a quarter-wave retarder, a DBEF reflective polarizer available from 3M Company, or a DRPF reflective polarizer available from 3M Company.

[0037] (light diffusion film) Light diffusion films are used to reduce unevenness and diffuse light evenly by reflecting light from a light source. Light diffusion films also have the same light-condensing effect as prism sheets (described below), contributing to improved brightness in the front direction. Light diffusion films also have the effect of reducing the directionality of light emitted from the light source and making it easier for light emitted from the organic light-emitting material to be extracted to the outside of the color conversion sheet, thereby optimizing the ratio of light emitted from the light source to light emitted from the organic light-emitting material.

[0038] Examples of light diffusion films include Light Up and Chemical Matte (manufactured by Kimoto Co., Ltd.), Opalus (manufactured by Keiwa Co., Ltd.), D Series (manufactured by Tsujiden Co., Ltd.), and CH / JS (manufactured by SKC Haas Display Films).

[0039] (Prism sheet) The prism sheet is used to condense the light emitted from the light source, thereby improving the brightness in the front direction and making the brightness of the backlight uniform.

[0040] Prism sheets generally have a structure in which a prism pattern in the shape of an isosceles triangle with a 90-degree apex angle or a microlens shape is formed on a transparent PET film. There is no particular limit to the number of prism sheets used as long as it is one or more, but to further improve the front brightness, it is preferable to use two prism sheets orthogonal to each other. When used in combination with the aforementioned light diffusion film, the effect of improving front brightness is even more pronounced.

[0041] Examples of prism sheets include the BEF series (manufactured by 3M), Diaart (manufactured by Mitsubishi Rayon Co., Ltd.), and the GTL5000 / GTL6000 series (manufactured by Goyo Paper Co., Ltd.).

[0042] (wavelength selective reflective film) Suitable specific examples of wavelength-selective reflective films include those described in International Publication No. 2017 / 164155 and Japanese Patent Application Laid-Open No. 2018-81250.

[0043] (microlens film) A microlens film is a microfabricated film with multiple convex lenses arranged on its surface. It focuses light irradiated from a light source, achieving improved brightness and in-plane uniformity. The convex lenses may be arranged regularly or randomly. Regular arrangement refers to a close-packed arrangement, for example. The lens shape is not particularly limited to either spherical or aspherical, and the shape and size are appropriately selected depending on the desired light-focusing and light-diffusion performance. The lens diameter D of each microlens is preferably approximately 4 to 200 μm, and the lens height h' is preferably approximately 2 to 100 μm. In this study, lenticular lenses are also included in the microlens film.

[0044] (Cut film) The cut film absorbs part of the light emitted from the light source or the color conversion sheet, thereby improving color reproducibility.

[0045] 2 to 4 show some specific examples of the light source unit of the present invention.

[0046] In the configuration shown in FIG. 2, a diffusion film 21 is placed on the color conversion sheet 1.

[0047] 3, there are two color conversion sheets 1, each consisting of a base layer 10 and a color conversion layer 11, and the color conversion layer sides of these sheets are integrated via an adhesive layer 8. In addition, a diffusion film 21 is provided between the color conversion sheet 1 and the light source 4.

[0048] The configuration shown in FIG. 4 is such that two prism sheets 22 and a polarizing reflective film 23 are provided on the viewing side of the color conversion sheet 1, and a diffusion film 21 is provided on the light source side.

[0049] (Color conversion sheet) The color conversion sheet converts incident light into light with a wavelength different from that of the incident light. Here, converting into light with a wavelength different from that of the incident light preferably means converting into light with a wavelength longer than that of the incident light.

[0050] The color conversion sheet includes a color conversion layer that is a layer made of the color conversion composition described below or a cured product thereof. The cured product of the color conversion composition is preferably included in the color conversion sheet as a layer obtained by curing the color conversion composition (a layer made of the cured product of the color conversion composition). Typical structural examples of color conversion sheets include the following four, for example.

[0051] Fig. 5 is a schematic cross-sectional view showing a first example of a color conversion sheet. As shown in Fig. 5, this first example of color conversion sheet 1A is a single-layer sheet composed of a color conversion layer 11. Color conversion layer 11 is a layer made of a cured product of the color conversion composition described above.

[0052] Fig. 6 is a schematic cross-sectional view showing a second example of a color conversion sheet. As shown in Fig. 6, this second example of color conversion sheet 1B is a laminate of a base layer 10 and a color conversion layer 11. In this structural example of color conversion sheet 1B, color conversion layer 11 is laminated on base layer 10.

[0053] Fig. 7 is a schematic cross-sectional view showing a third example of a color conversion sheet. As shown in Fig. 7, the color conversion sheet 1C of this third example is a laminate of multiple base material 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 base material layers 10.

[0054] Fig. 8 is a schematic cross-sectional view showing a fourth example of a color conversion sheet. As shown in Fig. 8, this fourth example of a color conversion sheet 1D is a laminate of multiple base layers 10, a color conversion layer 11, and multiple barrier films 12. In this structural example of color conversion film 1D, color conversion layer 11 is sandwiched between multiple barrier films 12, and this laminate of color conversion layer 11 and multiple barrier films 12 is further sandwiched between multiple base layers 10. In other words, color conversion sheet 1D may have a barrier film 12 as shown in Fig. 4 to prevent deterioration of color conversion layer 11 due to oxygen, moisture, or heat.

[0055] The thickness of the color conversion sheet is preferably 30 to 300 μm. Here, the thickness of the color conversion sheet refers to the combined thickness of all layers included in the color conversion sheet, and refers to the film thickness (average film thickness) measured based on Method A of the thickness measurement by mechanical scanning in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods. By making the thickness of the color conversion sheet 30 μm or more, the toughness of the sheet can be improved, and by making it 300 μm or less, cracking can be suppressed.

[0056] (color conversion layer) In the present invention, the color conversion layer contains a compound that emits delayed fluorescence (hereinafter, may be referred to as "delayed fluorescent material").

[0057] The thickness of the color conversion layer is not particularly limited, but is preferably 10 μm to 1000 μm. The lower limit of the color conversion layer thickness is more preferably 30 μm or more. The upper limit is more preferably 200 μm or less, even more preferably 100 μm or less, and particularly preferably 50 μm or less. The thickness of the color conversion film in the present invention refers to the thickness (average thickness) measured in accordance with Method A, a thickness measurement method using mechanical scanning, in JIS K7130 (1999) Plastics - Films and Sheets - Thickness Measurement Methods.

[0058] The color conversion layer can be formed by applying the color conversion composition prepared by the method described above onto an underlayer such as a substrate layer or a barrier film, and drying it.

[0059] The color conversion layer may be one layer or two or more layers. In addition to the delayed fluorescent material and binder resin described above, the color conversion layer may contain other components (additives), such as a light stabilizer, an antioxidant, a processing and heat stabilizer, a light resistance stabilizer such as an ultraviolet absorber, scattering particles, silicone fine particles, and a silane coupling agent.

[0060] (Delayed fluorescence emitting compound) Compounds that emit delayed fluorescence are discussed on pages 87-103 of "State-of-the-Art Organic EL" (edited by Adachi Chinaya and Fujimoto Hiroshi, published by CMC Publishing). The document explains that by bringing the energy levels of the singlet and triplet excited states of an emitting material close together, reverse energy transfer from the triplet excited state, which normally has a low transition probability, to the singlet excited state occurs with high efficiency, resulting in the appearance of thermally activated delayed fluorescence (TADF). Furthermore, Figure 5 in the document explains the mechanism by which delayed fluorescence occurs. Delayed fluorescence emission can be confirmed by transient photoluminescence (PL) measurements.

[0061] It has also been reported that matching the energy levels of the single excited state and triplet excited state of an emissive material can speed up the reverse energy transfer from the triplet excited state to the singlet excited state (Nature Photonics volume 14, pages 643-649 (2020)). Furthermore, active research is being conducted on compounds whose triplet excited state energy level is higher than that of the single excited state of the emissive material.

[0062] In this specification, a compound that emits fluorescence by transitioning from a triplet excited state to a singlet excited state with high efficiency, including a compound that exhibits thermally activated delayed fluorescence, is referred to as a "compound that emits delayed fluorescence."

[0063] Usually, fluorescent light is emitted from a singlet excited state generated after photoexcitation of a light-emitting material, and the triplet excited state of a light-emitting material generated by intersystem crossing is thermally deactivated in a room temperature environment and does not emit fluorescence. On the other hand, as described above, in a compound that emits delayed fluorescence, even if a triplet excited state is generated, it is quickly converted to a singlet excited state and then emits fluorescence. Therefore, the triplet excited state, which cannot contribute to light emission in ordinary fluorescent materials, can also contribute to fluorescent light emission. Therefore, highly efficient light emission can be obtained.

[0064] The triplet excited state of compounds that emit delayed fluorescence quickly converts to the singlet excited state, making it difficult to generate singlet oxygen. This feature has been found to prevent degradation of the luminescent material, suppress changes in chromaticity over time, and improve durability. This mechanism will be explained in detail below.

[0065] First, we will explain the degradation mechanism of luminescent materials. The chromaticity change of a color-converting composition is caused by degradation of the luminescent material, which is brought about by singlet oxygen. Singlet oxygen is an oxygen molecule in a singlet state where the two electrons occupying the π* orbitals (antibonding π orbitals) of the oxygen molecule's molecular orbital have opposite spin directions, i.e., an excited state where the total spin quantum number is zero. This excited state exists in two states: the Σ1 state, in which each of the two π* orbitals is occupied by an electron with an opposite spin direction, and the Δ1 state, in which only one of the π* orbitals is occupied by two electrons with opposite spin directions. In the Δ1 state, the vacant electron orbital of singlet oxygen has strong electrophilicity and strong oxidizing power. Therefore, singlet oxygen is thought to cause oxidative degradation of luminescent materials.

[0066] Next, we will discuss the mechanism by which singlet oxygen is generated. It is thought that singlet oxygen is unlikely to be generated by direct photoexcitation of ground-state triplet oxygen. This is because the transition from ground-state triplet oxygen to excited-state singlet oxygen is a spin-forbidden transition, and therefore the transition probability is extremely low.

[0067] Therefore, it is believed that the generation of singlet oxygen in the color-changing composition is due to dye sensitization. In other words, it is believed that singlet oxygen is generated by the exchange of electrons and energy between the triplet excited state of the light-emitting material and triplet oxygen molecules in the ground state. The generation mechanism is believed to be as follows.

[0068] First, photoexcitation transforms a ground-state singlet luminescent material into an excited-state singlet luminescent material, and then, through intersystem crossing, the excited-state singlet luminescent material transforms into an excited-state triplet luminescent material. The transition from the excited triplet luminescent material to the ground-state singlet luminescent material is a spin-forbidden transition, so the transition probability is usually low and the excited state has a long lifetime. However, when ground-state triplet oxygen coexists, the spin forbidden state is lifted by the excitation from ground-state triplet oxygen to excited-state singlet oxygen, allowing the triplet luminescent material to quickly deactivate to the ground-state singlet luminescent material. This mechanism is called the Dexter mechanism (electron exchange mechanism).

[0069] For the Dexter mechanism to proceed, electron exchange via intermolecular wave function overlap is required, and therefore it is thought that a direct collision between the energy donor molecule (in this case, the excited triplet luminescent material) and the energy acceptor molecule (in this case, triplet oxygen in the ground state) is required.

[0070] As mentioned above, compounds that emit delayed fluorescence have the property that the triplet excited state quickly converts to the singlet excited state, i.e., the lifetime of the triplet excited state is short. This reduces the probability of direct collision between the triplet excited state of the luminescent material and triplet oxygen in the ground state, making it difficult for singlet oxygen to be generated.

[0071] Molecular design that brings the energy levels of the singlet excited state and the triplet excited state closer together is effective in linking an electron donor skeleton and an electron acceptor skeleton within the same molecule. This allows the HOMO (highest occupied molecular orbital) orbital and the LUMO (lowest unoccupied molecular orbital) orbital to be separated within the molecule. The electron donor skeleton and the electron acceptor skeleton may be bonded directly or via a linking group. In this case, the linking group is preferably a skeleton containing an aromatic hydrocarbon.

[0072] Examples of the electron donor skeleton include a skeleton having an amine nitrogen atom. Among them, a skeleton containing diarylamine or triarylamine, a skeleton containing carbazole, a skeleton containing benzocarbazole, a skeleton containing indolocarbazole, a skeleton containing phenoxazine, and a skeleton containing phenothiazine are preferred. Among these, a skeleton containing carbazole, a skeleton containing benzocarbazole, a skeleton containing indolocarbazole, and a skeleton containing phenoxazine are more preferred, and a skeleton containing carbazole and a skeleton containing phenoxazine are even more preferred.

[0073] On the other hand, electron-accepting skeletons typically include skeletons containing electron-withdrawing substituents. Electron-withdrawing groups, also known as electron-accepting groups, are groups that attract electrons from the substituted atomic group due to inductive or resonance effects in organic electronics. Examples of electron-withdrawing groups include those with a positive Hammett's substituent constant (σp(para)). The Hammett's substituent constant (σp(para)) can be found in the 5th Revised Edition of the Basic Chemistry Handbook (page II-380).

[0074] Although there are cases where a phenyl group also takes a positive value, the phenyl group is not included in the electron-withdrawing groups of the present application.

[0075] Examples of electron-withdrawing groups include -F (σp: +0.20), -Cl (σp: +0.28), -Br (σp: +0.30), -I (σp: +0.30), and -CO2R. 12 (σp:R 12 is an ethyl group, +0.45), -CONH2 (σp: +0.38), -COR 12 (σp:R 12 is a methyl group, +0.49), -CF3 (σp: +0.51), -SO2R 12 (σp:R 12 When R is a methyl group, the value is +0.69), and -NO2 (σp: +0.81). 12 each independently represents a hydrogen atom, a substituted or unsubstituted aromatic hydrocarbon group having 6 to 30 ring carbon atoms, a substituted or unsubstituted heterocyclic group having 5 to 30 ring atoms, a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, or a substituted or unsubstituted cycloalkyl group having 1 to 30 carbon atoms. Specific examples of each of these groups include the same examples as above.

[0076] Among these, preferred are skeletons containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, skeletons containing a fluorinated substituent, skeletons containing a cyano group, skeletons containing a carbonyl group, skeletons containing a sulfoxide or disulfoxide, and skeletons containing a phosphine oxide group. Among these, skeletons containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, skeletons containing a fluorinated substituent, and skeletons containing a cyano group are more preferred from the viewpoint of the stability of the compound.

[0077] Among skeletons containing a heteroaryl group having a partial structure in which a carbon atom and a nitrogen atom are bonded by a double bond, specifically, skeletons containing pyridine, pyrimidine, pyrazine, triazine, quinoline, quinoxaline, quinazoline, or phenanthroline are preferred, and among these, skeletons containing pyrimidine, triazine, quinoxaline, or quinazoline are more preferred, and skeletons containing triazine are even more preferred.

[0078] Among the skeletons containing fluorinated substituents, skeletons containing fluorinated aryl groups or fluoroalkyl groups are more preferred.As the skeleton containing fluorinated aryl groups, fluorinated benzene rings are preferred, and specifically, skeletons containing fluorobenzene, difluorobenzene, trifluorobenzene, tetrafluorobenzene or pentafluorobenzene are more preferred.As the skeleton containing fluoroalkyl groups, skeletons containing benzene rings substituted with trifluoromethyl groups are preferred, and among these, skeletons containing mono(trifluoromethyl)benzene or bis(trifluoromethyl)benzene are more preferred.

[0079] Among the skeletons having a cyano group, skeletons containing cyanobenzene, dicyanobenzene, and tricyanobenzene are more preferred.

[0080] Examples of compounds in which the above-described electron donor skeleton and electron acceptor skeleton are combined are shown below, but are not limited to these. Note that the compounds shown here are known to emit delayed fluorescence according to previous literature.

[0081] [ka]

[0082] In addition to the compounds in which an electron donor skeleton and an electron acceptor skeleton are bonded together, compounds represented by the general formula (1) or (2) are preferred as compounds that emit delayed fluorescence.

[0083] [ka]

[0084] In general formula (1) or (2), ring Za, ring Zb, and ring Zc are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl ring having 6 to 30 ring carbon atoms. Z 1 and Z2 are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra), or a sulfur atom. 1 When R a is NRa, R a may be bonded to ring Z a or ring Z b to form a ring. 2 When is NRa, Ra may be bonded to ring Za or ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom having a substituent Ra), or P=O. E 1 and E 2 are each independently BRa (a boron atom having a substituent Ra), PRa (a phosphorus atom having a substituent Ra), SiRa2 (a silicon atom having two substituents Ra), P(=O)Ra2 (a phosphine oxide having two substituents Ra) or P(=S)Ra2 (a phosphine sulfide having two substituents Ra), S(=O) or S(=O)2. E 1 When is BRa, PRa, SiRa2, P(=O)Ra2 or P(=S)Ra2, Ra may be bonded to ring Za or ring Zb to form a ring. 2 When is BRa, PRa, SiRa2, P(=O)Ra2, or P(=S)Ra2, Ra may combine with ring Za or ring Zc to form a ring. Each Ra is independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

[0085] In all of the above groups, hydrogen may be replaced with deuterium. The same applies to the compounds or partial structures thereof described below.

[0086] In the following description, for example, a substituted or unsubstituted aryl group having 6 to 40 carbon atoms means that the number of carbon atoms included in the substituents substituted on the aryl group is 6 to 40, and the same applies to other substituents that specify the number of carbon atoms.

[0087] The term "unsubstituted" in the context of "substituted or unsubstituted" means that a hydrogen atom or a deuterium atom has been substituted. The same applies to the term "substituted or unsubstituted" in the compounds or partial structures thereof described below.

[0088] In all of the above groups, the substituent when substituted is an alkyl group, a cycloalkyl group, a heterocyclic group, an alkenyl group, a cycloalkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a hydroxyl group, a thiol group, an alkoxy group, an alkylthio group, an aryl ether group, an aryl thioether group, a halogen atom, a cyano group, an aldehyde group, a carbonyl group, a carboxyl group, an oxycarbonyl group, an amide group, a sulfonyl group, a sulfonate ester group, a sulfonamide group, an amino group, a nitro group, a silyl group, a siloxanyl group, a boryl group, or a phosphine oxide group. These substituents may be further substituted with the above-mentioned substituents.

[0089] The alkyl group refers to a saturated aliphatic hydrocarbon group such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, or a tert-butyl group, which may or may not have a substituent. When substituted, the additional substituent is not particularly limited, and examples thereof include an alkyl group, a halogen, an aryl group, and a heteroaryl group, which also applies to the following description. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 1 to 20, more preferably 1 to 8, in terms of availability and cost.

[0090] The cycloalkyl group refers to a saturated alicyclic hydrocarbon group, such as a cyclopropyl group, a cyclohexyl group, a norbornyl group, an adamantyl group, or the like, which may or may not have a substituent. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0091] The heterocyclic group refers to an aliphatic ring having atoms other than carbon atoms in the ring, such as a pyran ring, a piperidine ring, or a cyclic amide, which may or may not have a substituent. The number of carbon atoms in the heterocyclic group is not particularly limited, but is preferably in the range of 2 to 20.

[0092] The alkenyl group refers to an unsaturated aliphatic hydrocarbon group containing a double bond, such as a vinyl group, an allyl group, or a butadienyl group, which may or may not have a substituent. The number of carbon atoms in the alkenyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0093] The cycloalkenyl group refers to an unsaturated alicyclic hydrocarbon group containing a double bond, such as a cyclopentenyl group, a cyclopentadienyl group, or a cyclohexenyl group, which may or may not have a substituent. The number of carbon atoms in the cycloalkenyl group is not particularly limited, but is preferably in the range of 3 to 20.

[0094] The alkynyl group refers to an unsaturated aliphatic hydrocarbon group containing a triple bond, such as an ethynyl group, which may or may not have a substituent. The number of carbon atoms in the alkynyl group is not particularly limited, but is preferably in the range of 2 to 20.

[0095] The alkoxy group refers to a functional group in which an aliphatic hydrocarbon group is bonded via an ether bond, such as a methoxy group, an ethoxy group, or a propoxy group, and this aliphatic hydrocarbon group may or may not have a substituent. The number of carbon atoms in the alkoxy group is not particularly limited, but is preferably in the range of 1 to 20.

[0096] An alkylthio group is an alkoxy group in which the oxygen atom of the ether bond is replaced with a sulfur atom. The hydrocarbon group of the alkylthio group may or may not have a substituent. The number of carbon atoms in the alkylthio group is not particularly limited, but is preferably in the range of 1 to 20.

[0097] The aryl ether group refers to a functional group to which an aromatic hydrocarbon group, such as a phenoxy group, is bonded via an ether bond, and the aromatic hydrocarbon group may or may not have a substituent. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0098] An aryl thioether group is an aryl ether group in which the oxygen atom of the ether bond is substituted with a sulfur atom. The aromatic hydrocarbon group in the aryl ether group may or may not have a substituent. The number of carbon atoms in the aryl ether group is not particularly limited, but is preferably in the range of 6 to 40.

[0099] The aryl group refers to an aromatic hydrocarbon group such as a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a benzofluorenyl group, a dibenzofluorenyl group, a phenanthryl group, an anthracenyl group, a benzophenanthryl group, a benzanthracenyl group, a chrysenyl group, a pyrenyl group, a fluoranthenyl group, a triphenylenyl group, a benzofluoranthenyl group, a dibenzoanthracenyl group, a perylenyl group, or a helicenyl group. Among these, a phenyl group, a biphenyl group, a terphenyl group, a naphthyl group, a fluorenyl group, a phenanthryl group, an anthracenyl group, a pyrenyl group, a fluoranthenyl group, or a triphenylenyl group is preferred. The aryl group may or may not have a substituent. The number of carbon atoms in the aryl group is not particularly limited, but is preferably in the range of 6 to 40, more preferably 6 to 30.

[0100] The heteroaryl group refers to a cyclic aromatic group having one or more atoms other than carbon in the ring, such as a pyridyl group, a furanyl group, a thiophenyl group, a quinolinyl group, an isoquinolinyl group, a pyrazinyl group, a pyrimidyl group, a pyridazinyl group, a triazinyl group, a naphthyridinyl group, a cinnolinyl group, a phthalazinyl group, a quinoxalinyl group, a quinazolinyl group, a benzofuranyl group, a benzothiophenyl group, an indolyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a carbazolyl group, a benzocarbazolyl group, a carbolinyl group, an indolocarbazolyl group, a benzofurocarbazolyl group, a benzothienocarbazolyl group, a dihydroindenocarbazolyl group, a benzoquinolinyl group, an acridinyl group, a dibenzoacridinyl group, a benzimidazolyl group, an imidazopyridyl group, a benzoxazolyl group, a benzothiazolyl group, or a phenanthrolinyl group. Here, the naphthyridinyl group refers to any of a 1,5-naphthyridinyl group, a 1,6-naphthyridinyl group, a 1,7-naphthyridinyl group, a 1,8-naphthyridinyl group, a 2,6-naphthyridinyl group, and a 2,7-naphthyridinyl group. The heteroaryl group may or may not have a substituent. The number of carbon atoms in the heteroaryl group is not particularly limited, but is preferably in the range of 2 to 40, more preferably 2 to 30.

[0101] Halogen refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0102] The carbonyl group, carboxyl group, oxycarbonyl group, and carbamoyl group may or may not have a substituent. Examples of the substituent include an alkyl group, a cycloalkyl group, an aryl group, and a heteroaryl group, and these substituents may be further substituted.

[0103] The amino group is a substituted or unsubstituted amino group. In the case of substitution, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, and a branched alkyl group. Preferred aryl and heteroaryl groups are a phenyl group, a naphthyl group, a pyridyl group, and a quinolinyl group. These substituents may be further substituted. The number of carbon atoms is not particularly limited, but is preferably in the range of 2 to 50, more preferably 6 to 40, and particularly preferably 6 to 30.

[0104] The silyl group refers to, for example, alkylsilyl groups such as trimethylsilyl, triethylsilyl, tert-butyldimethylsilyl, propyldimethylsilyl, and vinyldimethylsilyl, and arylsilyl groups such as phenyldimethylsilyl, tert-butyldiphenylsilyl, triphenylsilyl, and trinaphthylsilyl. The substituent on the silicon atom may be further substituted. The number of carbon atoms in the silyl group is not particularly limited, but is preferably in the range of 1 to 30.

[0105] The siloxanyl group refers to a silicon compound group bonded via an ether bond, such as a trimethylsiloxanyl group, etc. The substituent on the silicon may be further substituted.

[0106] The boryl group is a substituted or unsubstituted boryl group. When substituted, examples of the substituent include an aryl group, a heteroaryl group, a linear alkyl group, a branched alkyl group, an aryl ether group, an alkoxy group, and a hydroxyl group, and among these, an aryl group and an aryl ether group are preferred.

[0107] The phosphine oxide group is -P(=O)R 10 R 11 R 10 R 11 is R 1 ~R 9 is selected from the same group as

[0108] Any two adjacent substituents may be bonded to each other to form a conjugated or non-conjugated fused ring. The fused ring may contain, in addition to carbon, an element selected from nitrogen, oxygen, sulfur, phosphorus, and silicon. The fused ring may further be fused with another ring.

[0109] Examples of the substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms in ring Za, ring Zb, and ring Zc include aromatic hydrocarbon rings such as a benzene ring, a naphthalene ring, a phenanthrene ring, a chrysene ring, an anthracene ring, and a pyrene ring, among which a benzene ring is preferred from the viewpoint of ensuring solubility. Examples of the heteroaryl ring having 5 to 30 ring carbon atoms include aromatic heteroaryl ring structures such as a pyridine ring, a quinoline ring, and a phenanthroline ring, among which a pyridine ring is preferred from the viewpoint of ease of raw material availability and difficulty of synthesis.

[0110] Ra is preferably a group having 6 to 40 carbon atoms including the substituent. Ra is more preferably a substituted or unsubstituted aryl group. Examples of the substituted or unsubstituted aryl group include a substituted or unsubstituted phenyl group, a substituted or unsubstituted biphenyl group, a substituted or unsubstituted fluorenyl group, a substituted or unsubstituted naphthyl group, and a substituted or unsubstituted phenanthrenyl group, and a substituted or unsubstituted phenyl group is more preferred.

[0111] Rb is preferably a group having 6 to 40 carbon atoms including the substituent, and more preferably a substituted or unsubstituted aryl group or a substituted or unsubstituted alkyl group.

[0112] Z 1 and Z 2 is preferably an oxygen atom or NRa, because the π-conjugated system of the compound represented by general formula (1) or (2) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0113] E is preferably a boron atom, E1 and E 2 is preferably BRa, because the π-conjugated system of the compound represented by general formula (1) or (2) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0114] Ring Za, ring Zb, and ring Zc are preferably benzene rings, because the π-conjugated system of the compound represented by general formula (1) or (2) is efficiently expanded, and reverse intersystem crossing from the triplet excited state to the singlet excited state occurs more efficiently, thereby further improving durability.

[0115] The compound represented by general formula (1) or (2) is a molecule that can separate the HOMO orbital and the LUMO orbital by the multiple resonance effect by optimally arranging the electron-donating amine nitrogen atom and the electron-accepting boron atom, as described in, for example, the literature Adv. Mater., 2016, 28, 2777-2781. From the viewpoint of clearly separating the HOMO orbital and the LUMO orbital, bringing the singlet excited state and the triplet excited state closer to each other and facilitating the emission of delayed fluorescence, it is preferable that E is a boron atom with strong electron-accepting properties and Z is a boron atom with strong electron-accepting properties. 1 and Z 2 are preferably both NRa, which are groups with strong electron donating properties.

[0116] Furthermore, due to the multiple resonance effect, compounds represented by general formula (1) or (2) have sharper emission spectra than compounds combining an electron donor skeleton and an electron acceptor skeleton, resulting in emission of higher color purity. In other words, compounds represented by general formula (1) or (2) are advantageous for improving the color gamut of displays and are therefore preferred. Furthermore, compounds represented by general formula (1) or (2) have rings Za, Zb, and Zc around the E atom in general formula (1) or (2), where the LUMO orbital is primarily localized. This allows the LUMO orbital to be delocalized from the E atom to each ring. Delocalizing the LUMO orbital efficiently utilizes the multiple resonance effect, resulting in emission of higher color purity.

[0117] Furthermore, a structure in which Ra in general formula (1) or (2) is bonded to at least one of rings Za, ring Zb, and ring Zc is more preferred. This is because Ra is bonded to at least one of rings Za, ring Zb, and ring Zc, and thus E in general formula (1) or E in general formula (2) is bonded to at least one of rings Za, ring Zb, and ring Zc. 1 and E 2 This is because it is expected that the steric protection effect of the compound will be further enhanced, and the effect of suppressing a decrease in the fluorescence quantum yield will be further improved.

[0118] Examples of compounds represented by general formula (1) or (2) are shown below, but the compounds are not particularly limited to these.

[0119] [ka]

[0120] The delayed fluorescent material is preferably at least one of the following light-emitting materials (a) and (b). (a) A luminescent material that emits light with a peak wavelength observed in the region of 500 nm or more and less than 580 nm when excited with light having a wavelength in the range of 430 nm or more and 500 nm or less. (b) A luminescent material that, when excited by either or both of excitation light having a wavelength in the range of 430 nm to 500 nm and the emission from the luminescent material (a), exhibits luminescence with a peak wavelength observed in the range of 580 nm to 750 nm.

[0121] Hereinafter, the emission observed in the region with a peak wavelength of 500 nm or more and less than 580 nm will be referred to as "green emission," and the emission observed in the region with a peak wavelength of 580 nm or more and 750 nm or less will be referred to as "red emission."

[0122] When at least one of the luminescent material (a) and the luminescent material (b) is a compound that emits delayed fluorescence, the durability of the color-converting composition can be improved. 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 not, the durability of not only the luminescent material (a) itself but also the luminescent material (b) can be improved, and as a result, the durability of the entire color-converting composition can be improved.

[0123] This is because, as will be described in detail later, when at least one of the luminescent materials (a) and (b) is a compound that emits delayed fluorescence, it becomes possible to suppress the generation of singlet oxygen, which causes deterioration of the luminescent material. By suppressing the generation of singlet oxygen, not only the deterioration of compounds that emit delayed fluorescence but also the deterioration of compounds that do not emit delayed fluorescence is suppressed.

[0124] The light-emitting material (a) is preferably a light-emitting material that emits light with a peak wavelength of 500 nm or more and 550 nm or less when excited with light having a wavelength in the range of 430 nm or more and 500 nm or less.

[0125] The luminescent material (b) is preferably a luminescent material that, when excited by either or both of excitation light having a wavelength in the range of 430 nm to 500 nm and the emission from the luminescent material (a), emits luminescence with a peak wavelength observed in the range of 580 nm to 680 nm.

[0126] Because a portion of excitation light in the wavelength range of 430 nm to 500 nm is partially transmitted through the color conversion sheet of the present invention, when a blue LED with a sharp emission peak is used, it exhibits a sharply shaped emission spectrum in each of the blue, green, and red colors, resulting in white light with excellent color purity. As a result, a wider color gamut with more vivid colors can be efficiently produced, particularly in displays. Furthermore, in lighting applications, the sheet offers improved emission characteristics, particularly in the green and red regions, compared to white LEDs that combine a blue LED with a yellow phosphor, which is currently the mainstream, resulting in improved color rendering and making it a desirable white light source.

[0127] The content of the luminescent material (a) and the luminescent material (b) in the color-changing composition of the present invention can be selected depending on the molar absorption coefficient, fluorescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness and transmittance of the sheet to be produced. Here, the content of the luminescent material (a) and the luminescent material (b) refers to the total content when two or more types of the luminescent material (a) and the luminescent material (b) are contained. The content of the luminescent material (a) and the luminescent material (b) is 1.0 × 10 per 100 parts by weight of the binder resin. -2 Parts by weight to 5 parts by weight are preferred.

[0128] (Other luminescent materials) In addition to compounds that emit delayed fluorescence, examples of luminescent materials used as the luminescent material (a) and the luminescent material (b) include inorganic phosphors, fluorescent pigments, fluorescent dyes, quantum dots, etc. Two or more of these may be contained. To achieve highly efficient color conversion, materials that exhibit luminescent properties with high quantum yield are preferred, and quantum dots and organic luminescent materials are preferred, with organic luminescent materials being more preferred.

[0129] Examples of organic light-emitting materials include: Compounds having a fused aryl ring, such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, naphthacene, triphenylene, perylene, fluoranthene, fluorene, and indene, and derivatives thereof; Compounds having a heteroaryl ring, such as furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyridine, pyrazine, naphthyridine, quinoxaline, and pyrrolopyridine, and derivatives thereof; Borane derivatives; stilbene derivatives such as 1,4-distyrylbenzene, 4,4'-bis(2-(4-diphenylaminophenyl)ethenyl)biphenyl, and 4,4'-bis(N-(stilben-4-yl)-N-phenylamino)stilbene; Aromatic acetylene derivatives, tetraphenylbutadiene derivatives, aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives; Coumarin derivatives such as Coumarin 6, Coumarin 7, and Coumarin 153; Azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and triazole, and their metal complexes; cyanine compounds such as indocyanine green; Xanthene and thioxanthene compounds such as fluorescein, eosin, and rhodamine; Polyphenylene compounds, naphthalimide derivatives, phthalocyanine derivatives and their metal complexes, porphyrin derivatives and their metal complexes; oxazine compounds such as Nile Red and Nile Blue; Helicene-based compounds; Aromatic amine derivatives such as N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine; and Organometallic complex compounds such as iridium (Ir), ruthenium (Ru), rhodium (Rh), palladium (Pd), platinum (Pt), osmium (Os), and rhenium (Re); The following are suitable examples.

[0130] The organic light-emitting material may be a fluorescent material or a phosphorescent material, but fluorescent materials are preferred to achieve high color purity. Among them, pyrromethene derivatives are preferred because they provide high fluorescence quantum yield and have better chromaticity durability.

[0131] (binder resin) The binder resin forms a continuous phase and may be any material that is excellent in moldability, transparency, heat resistance, and the like. Examples of binder resins include known materials such as photocurable resist materials having reactive vinyl groups, such as acrylic acid-based, methacrylic acid-based, polyvinyl cinnamate-based, and cyclic rubber-based materials, epoxy resins, silicone resins (including organopolysiloxane cured products (crosslinked products) such as silicone rubber and silicone gel), urea resins, fluororesins, polycarbonate resins, acrylic resins, urethane resins, melamine resins, polyvinyl resins, polyamide resins, phenolic resins, polyvinyl alcohol resins, cellulose resins, aliphatic ester resins, aromatic ester resins, aliphatic polyolefin resins, and aromatic polyolefin resins. Copolymer resins of these resins may also be used as the binder resin. By appropriately designing these resins, binder resins useful for the color-converting compositions and color-converting sheets according to embodiments of the present invention can be obtained. Among these resins, thermoplastic resins are more preferred because of the ease of film formation. Among thermosetting resins, epoxy resins, silicone resins, acrylic resins, ester resins, olefin resins, or mixtures thereof can be preferably used from the viewpoints of transparency, heat resistance, etc. Furthermore, from the viewpoint of durability, particularly preferred thermoplastic resins are acrylic resins, ester resins, and cycloolefin resins.

[0132] Suitable specific examples of binder resins include those described in WO 2016 / 190283, WO 2017 / 61337, WO 2018 / 43237, WO 2019 / 21813, and WO 2019 / 188019.

[0133] The binder resin may contain additives such as dispersants and leveling agents for stabilizing the coating film, or may contain adhesion promoters such as silane coupling agents as film surface modifiers.The binder resin may also contain inorganic particles such as silica particles and silicone microparticles as agents for inhibiting the precipitation of color conversion materials.

[0134] (solvent) The color-changing composition may contain a solvent. The solvent is not particularly limited as long as it can adjust the viscosity of the resin in a fluid 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, and propylene glycol monomethyl ether acetate. Two or more of these solvents may also be mixed and used. Among these solvents, toluene is particularly preferred because it does not affect the deterioration of the compound represented by general formula (1) or (2) and leaves little residual solvent after drying.

[0135] The amount of solvent remaining in the color conversion layer containing the color conversion composition or its cured product after drying 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, from the viewpoint of further improving the durability of the color conversion sheet.

[0136] Furthermore, from the viewpoint of improving the quantum yield of the color conversion sheet, the amount of the remaining 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.

[0137] (Other ingredients) In addition to the compound represented by the general formula (1) or (2) and the binder resin, the color-changing composition may contain other components (additives), such as a light stabilizer, an antioxidant, a processing and heat stabilizer, a light resistance stabilizer such as an ultraviolet absorber, scattering particles, silicone microparticles, and a silane coupling agent.

[0138] Examples of light stabilizers include, but are not limited to, tertiary amines, catechol derivatives, nickel compounds, complexes containing at least one transition metal selected from the group consisting of Sc, V, Mn, Fe, Co, Cu, Y, Zr, Mo, Ag, and lanthanoids, and salts with organic acids. These light stabilizers may be used alone or in combination.

[0139] Examples of the antioxidant include, but are not limited to, phenolic antioxidants such as 2,6-di-tert-butyl-p-cresol and 2,6-di-tert-butyl-4-ethylphenol. These antioxidants may be used alone or in combination.

[0140] Examples of processing and heat stabilizers include, but are not limited to, phosphorus-based stabilizers such as tributyl phosphite, tricyclohexyl phosphite, triethyl phosphine, and diphenylbutyl phosphine. These stabilizers may be used alone or in combination.

[0141] Examples of the light resistance stabilizer include, but are not limited to, benzotriazoles such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole and 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole. These light resistance stabilizers may be used alone or in combination.

[0142] As the scattering particles, inorganic particles having a refractive index of 1.7 to 2.8 are preferred, and examples thereof include titania, zirconia, alumina, ceria, tin oxide, indium oxide, iron oxide, zinc oxide, aluminum nitride, aluminum, tin, titanium or zirconium sulfide, and titanium or zirconium hydroxide.

[0143] The content of these additives in the color-changing composition depends on the molar absorption coefficient, luminescence quantum yield, and absorption intensity at the excitation wavelength of the compound, as well as the thickness and transmittance of the color-changing film to be produced, but is usually 1.0 × 10 -3 The content of these additives is preferably 1.0×10 to 30 parts by weight based on 100 parts by weight of the binder resin. -2 It is more preferable that the amount is 1.0×10 parts by weight or more and 15 parts by weight or less. -1 It is particularly preferable that the amount is from 1 part by weight to 10 parts by weight.

[0144] (Haze value of color conversion sheet) The color conversion sheet preferably has a haze value of 40% or more and 95% or less. By having the haze value within the above range, the in-plane uniformity of the color conversion sheet can be improved without significantly impairing the durability of the color conversion sheet. High in-plane uniformity of color is preferable because it can suppress color unevenness and increase contrast. The haze value is more preferably 40% or more and 75% or less. The haze value can be measured in accordance with ASTM D 1003 (2013).

[0145] The method for adjusting the haze value of the color conversion sheet to the above range is not particularly limited, but examples include incorporating scattering particles into the color conversion layer, providing a light-scattering layer separately from the color conversion layer, and increasing the surface roughness of the base material constituting the color conversion sheet. Among these, incorporating scattering particles into the color conversion layer is more preferred.

[0146] (Method of producing color-changing composition) An example of a method for producing a color-converting composition for producing a color-converting layer is described below. The delayed fluorescent material, binder resin, and, if necessary, additives and solvents are mixed to a predetermined composition, and then the color-converting composition is obtained by homogenizing or kneading the mixture using a stirrer / kneader. Examples of stirrers / kneaders include homogenizers, planetary stirrers, three-roller stirrers, ball mills, planetary ball mills, and bead mills. After mixing or dispersing, or during the mixing or dispersing process, degassing under vacuum or reduced pressure is also preferred. It is also possible to premix certain components or perform aging or other treatments. The desired solids concentration can also be achieved by removing the solvent using an evaporator.

[0147] (base material layer) Examples of the substrate layer include glass and resin films. Examples of resin films include plastic films such as polyethylene terephthalate (PET), polyphenylene sulfide, polycarbonate, polypropylene, and polyimide. To facilitate easy peeling of the film, the surface of the substrate layer may be subjected to a release treatment in advance. The thickness of the substrate layer is not particularly limited, but the lower limit is preferably 25 μm or more, and more preferably 38 μm or more. The upper limit is preferably 5000 μm or less, and more preferably 3000 μm or less.

[0148] (barrier layer) The barrier layer is preferably one that prevents oxygen, moisture, heat, etc. from penetrating into the color conversion layer, and two or more barrier layers may be provided. A barrier layer may be provided on both sides of the light conversion layer, or on one side.

[0149] Examples of films 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; metal oxide thin films or metal nitride thin films containing these with added elements; and films containing various resins such as polyvinylidene chloride, acrylic resins, silicone resins, melamine resins, urethane resins, fluorine-containing resins, and polyvinyl alcohol resins such as saponified vinyl acetate. Two or more of these may be included. Examples of films with moisture barrier properties include films containing various resins such as polyethylene, polypropylene, nylon, polyvinylidene chloride, copolymers of vinylidene chloride and vinyl chloride, copolymers of vinylidene chloride and acrylonitrile, fluorine-containing resins, and polyvinyl alcohol resins such as saponified vinyl acetate.

[0150] The color conversion sheet of the present invention may further have an auxiliary layer having a light diffusion layer, an adhesive layer, an anti-reflection function, an anti-glare function, an anti-reflection and anti-glare function, a hard coat function (abrasion resistance function), an anti-static function, an anti-fouling function, an electromagnetic wave shielding function, an infrared ray blocking function, an ultraviolet ray blocking function, a polarizing function, or a color-tuning function, depending on the required functions.

[0151] <Manufacturing method of color conversion sheet> Next, an example of a method for producing a color conversion sheet will be described. The color conversion composition prepared by the above-described method is applied to a substrate and dried to form a color conversion layer. When the binder resin contains a thermosetting resin, the color conversion composition may be applied to the substrate and then heat-cured to form the color conversion layer. When the binder resin is a photocurable resin, the color conversion composition may be applied to the substrate and then photocured to form the color conversion layer.

[0152] Coating can be carried out using a reverse roll coater, blade coater, comma coater, slit die coater, direct gravure coater, offset gravure coater, kiss coater, natural roll coater, air knife coater, roll blade coater, two-stream coater, rod coater, wire bar coater, applicator, dip coater, curtain coater, spin coater, knife coater, etc. In order to obtain a uniform thickness of the color conversion layer, coating with a slit die coater, comma coater or dip coater is preferred.

[0153] The color conversion layer can be dried using a common heating device such as a hot air dryer or an infrared dryer. In this case, the heating temperature is preferably 60 to 200°C, and the heating time is preferably 2 minutes to 4 hours. It is also possible to heat and cure the layer in stages using a method such as step curing.

[0154] When the color conversion layer is formed by heat curing, a hot air oven or the like can be used as the heating device. The heating conditions can be selected depending on the binder resin. For example, the heating temperature is preferably 100°C to 300°C, and the heating time is preferably 1 minute to 2 hours.

[0155] When forming a color conversion layer by photocuring, it is preferable to irradiate with high-energy light such as ultraviolet light. The light irradiation conditions can be selected depending on the binder resin. For example, the wavelength of the irradiated light is preferably 200 nm to 500 nm, and the irradiation dose is 10 mJ / cm. 2 ~10J / cm 2 is preferred.

[0156] After the color conversion layer is produced, the substrate can be changed as needed. In this case, simple methods include a method of replacing the substrate using a hot plate, or a method using a vacuum laminator or a dry film laminator.

[0157] The color conversion sheet is preferably a color conversion sheet including at least one of the following layers (A) and (B). Layer (A): A layer containing a light-emitting material (a) as a compound that emits delayed fluorescence. (B) Layer: A layer containing a luminescent material (b) as a compound that emits delayed fluorescence.

[0158] One example of a color conversion sheet is a color conversion sheet that includes one or more color conversion layers, in which the luminescent material (a) and the luminescent material (b) are included in the same layer.

[0159] One example of the color conversion sheet is a color conversion sheet that includes two or more color conversion layers, in which the light-emitting material (a) and the light-emitting material (b) are included in different layers. A specific example of such a color conversion layer is a color conversion sheet that includes at least the following (A') layer and (B') layer. Layer (A'): A layer containing at least a light-emitting material (a) and a binder resin. Layer (B'): A layer containing at least the light-emitting material (b) and a binder resin.

[0160] <Displays, lighting equipment> The display and lighting according to the embodiment of the present invention include at least the above-described light source unit. For example, the above-described light source unit is used as a backlight unit in a display such as a liquid crystal display. The liquid crystal display of the present invention preferably includes a liquid crystal cell equipped with a color filter in addition to the light source unit according to the present invention. [Example]

[0161] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0162] <Reflectance measurement> The reflectance of the optical film was measured using the CM-2600d (Konica Minolta) with the SCI method, measuring the relative reflectance based on barium sulfate. Each measurement was performed three times. Since angle dependency exists in the measurement of the prism sheet, the reflectance was calculated as the average value of the reflectance at angle θ where the reflectance is maximum and the reflectance at angle θ' where the reflectance is minimum.

[0163] <Preparation of Rose Bengal-Containing Resin Sheet> 100 parts by weight of BR-85 as a binder resin were mixed with 0.005 parts by weight of compound R-3 (rose bengal) and 300 parts by weight of ethyl acetate as a solvent, and then the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing device "MAZERSTAR" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition.

[0164] Next, the obtained resin composition was applied to a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm) using a slit die coater, and heated and dried at 120°C for 20 minutes to form a resin layer with an average thickness of 20 μm, thereby producing a rose bengal-containing resin sheet.

[0165] <Absorbance measurement> The absorption spectra of the color conversion sheet and the rose bengal-containing resin sheet were obtained by measuring the absorption spectra of resin films formed by individually applying the compositions for forming each layer onto a PET film.

[0166] The compositions for producing each layer were applied to a "Lumirror" U48 (Toray Industries, Inc., thickness 50 μm) using a Baker-type applicator to an average film thickness of 18 μm, and then heated at 140°C for 1 hour and dried to form a resin film for measurement. The absorption spectrum of the formed resin sheet was measured using a U-3010 (Hitachi High-Tech Science).

[0167] <Measurement of near-infrared fluorescence> The absorption spectra of the color conversion sheet and the rose bengal-containing resin sheet were obtained by measuring the absorption spectra of resin films formed by individually applying the compositions for forming each layer onto a PET film.

[0168] The compositions for preparing each layer were applied to Lumirror U48 (Toray Industries, Inc., 50 μm thick) using a Baker-type applicator to an average film thickness of 18 μm, and then heated and dried at 140°C for 1 hour to form a resin film for measurement. The near-infrared fluorescence spectrum of the formed resin sheet was measured using a modular near-infrared high-speed fluorescence spectrometer NanoLog (Horiba, Ltd.) with the peak wavelength of the absorption spectrum of the formed resin sheet as the excitation light, and I0 / A0 and I' / A' were calculated using equation (1).

[0169] <Haze measurement> The haze of the color conversion sheets prepared in the examples and comparative examples was measured using an NDH7000 (manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with ASTM D 1003 (2013). The measurement was performed once for each sheet.

[0170] <Measurement of color conversion characteristics> Each color conversion sheet to be evaluated was placed on a light-emitting device equipped with a blue LED (USHIO EPITEX; model number SMBB450H-1100, emission peak wavelength: 450 nm) and a diffuser plate on its emission surface. A current of 100 mA was passed through the light-emitting device to light up the blue LED, and the emission spectrum, emission intensity at the peak wavelength, and chromaticity were measured using a spectroradiometer (Konica Minolta CS-1000). The distance between each color conversion sheet and the blue LED element was 3 cm.

[0171] <Evaluation of in-plane uniformity> A BenQ LCD monitor (SW2700PT) was disassembled, and the color conversion sheet produced in the Examples and Comparative Examples described below was inserted in place of the built-in color conversion sheet, and then the monitor was reassembled. The backlight unit was configured as "reflective film / light guide plate / diffusion film / color conversion sheet / prism sheet / polarized reflective film." Nine color coordinates u' and v' were measured using a spectroradiometer (CS-1000, manufactured by Konica Minolta), and the in-plane variation 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 If Δu'v' is 0.035 or less, it is considered good, and if it is 0.025 or less, it is considered extremely good.

[0172] <Light durability test> Each color conversion sheet to be evaluated was placed on a light-emitting device equipped with a blue LED (USHIO EPITEX; Model No. SMBB450H-1100, emission peak wavelength: 450 nm) and a diffuser plate on its emission surface. A current of 100 mA was passed through the light-emitting device to turn on the blue LED, and the peak intensity at the color-converted emission wavelength was measured using a spectroradiometer (Konica Minolta CS-1000). Each color conversion sheet was placed 3 cm away from the blue LED element. The sheets were then continuously irradiated with light from the blue LED element under an environment of 50°C and 80% RH. The durability of the color conversion sheets was evaluated by observing the time it took for the emission intensity of the phosphor to decrease by 10% from its initial value. A time of 250 hours or more for the emission intensity of the phosphor to decrease by 10% from its initial value was considered good, and a time of 450 hours or more was considered extremely good. The materials used in the examples are listed below.

[0173] <Light-emitting materials> In the following examples and comparative examples, compounds G-1 to G-3 and R-1 to R-3 are the compounds shown below, where G-1, G-3, and R-1 are compounds that emit delayed fluorescence, and R-3 is rose bengal.

[0174] [ka]

[0175] [ka]

[0176] The physical properties of each compound are shown in Table 1.

[0177] [Table 1]

[0178] <Resin> Polymethyl methacrylate resin BR-85 (manufactured by Mitsubishi Chemical Corporation) and acrylic resin Oricox KC-7000 (manufactured by Kyoeisha Chemical Co., Ltd.) were used as binder resins. Polyester resin "Vylon" (registered trademark) 630 (Toyobo Co., Ltd.) was used as the resin for the adhesive layer.

[0179] <Scattered particles> JR-301 (titanium oxide particles manufactured by Teika Corporation, average particle diameter 300 nm) was used as scattering particles.

[0180] <Optical film> The LCD monitor UN65JS9500F (manufactured by SAMSUNG) was disassembled and the built-in prism sheet and polarized reflective film were used. In addition, "Chemical Matte" 125PW (manufactured by Kimoto Co., Ltd., thickness 138 μm) was used as a diffusion film. Figure 9 shows the reflectance of the LED-side surface of each optical film.

[0181] Example 1 A mixture of 100 parts by weight of BR-85 as a binder resin, 0.27 parts by weight of compound G-1 as a light-emitting material (a), 2 parts by weight of JR-301 as scattering particles, and 300 parts by weight of ethyl acetate as a solvent was then mixed, and the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing device "MAZERSTAR" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing a green color conversion layer.

[0182] Next, the obtained resin composition for preparing a green color conversion layer was applied using a slit die coater onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm), and heated and dried at 120°C for 20 minutes to form a green color conversion layer with an average film thickness of 20 μm.

[0183] Next, 100 parts by weight of BR-85 as the binder resin, 0.0028 parts by weight of compound R-1 as the luminescent material (b), 2 parts by weight of JR-301 as scattering particles, and 300 parts by weight of ethyl acetate as the solvent were mixed, and then the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing device "MAZERSTAR" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing a red color conversion layer.

[0184] Next, the obtained resin composition for preparing a red color conversion layer was applied to a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm) using a slit die coater, and heated and dried at 120°C for 20 minutes to form a red color conversion layer with an average film thickness of 20 μm.

[0185] Next, 100 parts by weight of "Vylon" 630 as the resin was mixed with 300 parts by weight of ethyl acetate as the solvent, and the mixture was then stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing device "Mazerustar" KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing an adhesive layer.

[0186] Next, the resin composition for forming an adhesive layer was applied onto the red color conversion layer using a slit die coater, and heated and dried at 120° C. for 20 minutes to form an adhesive layer with an average thickness of 20 μm.

[0187] Next, the two units were heat-laminated so that the green color conversion layer and adhesive layer were directly laminated to create a color conversion sheet. The haze value, in-plane uniformity, and durability of the resulting color conversion sheet were evaluated using the methods described above. Furthermore, an optical film was heat-laminated onto the color conversion sheet to form the configuration shown in Table 2, producing a color conversion component with a "polarized reflective film / prism sheet / prism sheet / color conversion sheet / diffusion film" configuration. With this configuration, the reflectance of the entire optical film at wavelengths of 510 nm and 610 nm was 80.96% and 81.55%, respectively. Furthermore, as can be seen from Figure 9, the reflectance of each film constituting the optical film does not change significantly in the wavelength range from 500 nm to 740 nm, indicating that the reflectance of the optical film in this wavelength range is approximately 81%. The durability of the resulting color conversion sheet was evaluated using the methods described above.

[0188] When this color conversion member was used to convert blue LED light with a peak emission wavelength of 450 nm, the emission spectrum showed sharp emission peaks in the red, green, and blue regions as shown in Figure 10, and white light with an XY color coordinate of (X, Y) = (0.25, 0.22) was obtained. Extracting only the green light emission region, high-color-purity green light emission with a peak wavelength of 530 nm was obtained. Extracting only the red light emission region, high-color-purity red light emission with a peak wavelength of 642 nm was obtained. The color gamut area in the (u', v') color space was 95% of the color gamut area of ​​the BT.2020 standard. The evaluation results for Example 1 are shown in Table 2 below. In Table 2, "color coordinates (X, Y)" are the values ​​of the XY color coordinates. "Color gamut area" is the area of ​​the color gamut in the (u', v') color space. Additionally, "A" to "D" in the "Color Gamut Area" column indicate the evaluation results of the area of ​​this color gamut, with A being 90% or more, B being 80-89%, C being 70-79%, and D being below that. This is the same for each table.

[0189] (Examples 2 to 4, Comparative Examples 1 to 4) The same procedures as in Example 1 were carried out to prepare a color conversion sheet, measure the haze value, measure the in-plane uniformity, prepare a color conversion member, calculate the color gamut area of ​​the color conversion member, and evaluate its durability, except that the optical film was as shown in Table 2.

[0190] A comparison of Examples 1-3 with Comparative Examples 1-2 shows that for the combination of G-1 and R-1, the higher the reflectance of the optical film, the larger the color gamut area, and color reproducibility and durability were particularly good when the reflectance was 20-95%. Furthermore, a comparison of Examples 1-2 with Example 4 and Comparative Examples 3-4 shows that durability is further improved by satisfying (I0 / A0) / (I' / A')<1 / 10.

[0191] Comparing Example 3 with Comparative Example 1, it was found that the provision of at least one optical film further improved color reproducibility and durability.

[0192] Comparing Example 1 with Example 3, it was found that providing at least three optical films on the viewing side significantly improved color reproducibility and durability.

[0193] [Table 2]

[0194] Example 5 A mixture of 100 parts by weight of BR-85 as a binder resin, 0.27 parts by weight of compound G-1 as a light-emitting material (a), 1 part by weight of JR-301 as scattering particles, and 300 parts by weight of ethyl acetate as a solvent was then mixed, and the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing device "Mazerustar" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing a green color conversion layer.

[0195] Next, the obtained resin composition for preparing a green color conversion layer was applied using a slit die coater onto a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm), and heated and dried at 120°C for 20 minutes to form a green color conversion layer with an average film thickness of 20 μm.

[0196] Next, 100 parts by weight of BR-85 as the binder resin, 0.0028 parts by weight of compound R-1 as the luminescent material (b), 1 part by weight of JR-301 as scattering particles, and 300 parts by weight of ethyl acetate as the solvent were mixed, and then the mixture was stirred and degassed at 1000 rpm for 20 minutes using a planetary stirring and degassing device "MAZERSTAR" (registered trademark) KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing a red color conversion layer.

[0197] Next, the obtained resin composition for preparing a red color conversion layer was applied to a polyester film "Lumirror" (registered trademark) U48 (manufactured by Toray Industries, Inc., thickness 50 μm) using a slit die coater, and heated and dried at 120°C for 20 minutes to form a red color conversion layer with an average film thickness of 20 μm.

[0198] Next, 100 parts by weight of "Vylon" 630 as the resin was mixed with 300 parts by weight of ethyl acetate as the solvent, and the mixture was then stirred and degassed at 300 rpm for 20 minutes using a planetary stirring and degassing device "Mazerustar" KK-400 (manufactured by Kurabo Industries, Ltd.) to obtain a resin composition for producing an adhesive layer.

[0199] Next, the resin composition for forming an adhesive layer was applied onto the red color conversion layer using a slit die coater, and heated and dried at 120° C. for 20 minutes to form an adhesive layer with an average thickness of 20 μm.

[0200] Next, the above two units were heat-laminated so that the green color conversion layer and adhesive layer were directly laminated to create a color conversion sheet. The haze value, in-plane uniformity, and durability of the resulting color conversion sheet were evaluated using the methods described above. The color conversion sheet was further heat-laminated to create a color conversion member with a "polarized reflective film / prism sheet / prism sheet / color conversion sheet / diffusion film" configuration. The durability of the resulting color conversion member was evaluated using the methods described above. The results are shown in Table 3.

[0201] Examples 6 to 9 The same procedures as in Example 5 were carried out except that the amount of diffusing particles added was as shown in Table 3, and the preparation of a color conversion sheet, measurement of haze value, measurement of in-plane uniformity, preparation of a color conversion member, calculation of the color gamut area of ​​the color conversion member, and durability evaluation were carried out.

[0202] Furthermore, a comparison of Examples 5 to 9 revealed that the larger the haze value, the better the in-plane uniformity. However, as shown in Example 9, when the haze value exceeds 95%, although the in-plane uniformity is good, the light durability is significantly reduced compared to Example 8.

[0203] [Table 3] [Explanation of symbols]

[0204] 1 Color conversion sheet 3 Diffuser 4 light source 5 Reflective layer 6 PCB 8 Adhesive layer 10 Base material layer 11 Color conversion layer 12 Barrier film 21 Diffusion film 22 Prism sheet 23 Polarized Reflective Film 100 Light Source Unit

Claims

1. A light source unit including a light source, a color conversion sheet, and an optical film, the color conversion sheet contains a compound that emits delayed fluorescence, the optical film has a reflectance of 20% or more and 95% or less in a wavelength band ranging from a peak wavelength of an absorption spectrum of the compound that emits delayed fluorescence to a peak wavelength of an emission spectrum of the compound that emits delayed fluorescence, The compound that emits delayed fluorescence contains a compound represented by general formula (1) or (2). 【Chemistry 1】 In general formula (1) or (2), ring Za, ring Zb, and ring Zc are each independently a substituted or unsubstituted aryl ring having 6 to 30 ring carbon atoms, or a substituted or unsubstituted heteroaryl ring having 6 to 30 ring carbon atoms. Z 1 and Z 2 are each independently an oxygen atom, NRa (a nitrogen atom having a substituent Ra) or a sulfur atom. When Z 1 is NRa, Ra may be bonded to ring Za or ring Zb to form a ring. When Z 2 is NRa, Ra may be bonded to ring Za or ring Zc to form a ring. E is a boron atom, a phosphorus atom, SiRa (a silicon atom having a substituent Ra), or P=O. E1 and E2 are each independently BRa (a boron atom having a substituent Ra), PRa (a phosphorus atom having a substituent Ra), SiRa2 (a silicon atom having two substituents Ra), P(=O)Ra2 (a phosphine oxide having two substituents Ra), P(=S)Ra2 (a phosphine sulfide having two substituents Ra), S(=O) or S(=O)2. When E1 is BRa, PRa, SiRa2, P(=O)Ra2, or P(=S)Ra2, Ra may be bonded to ring Za or ring Zb to form a ring. When E 2 is BRa, PRa, SiRa 2 , P(═O)Ra 2 or P(═S)Ra 2 , Ra may be bonded to ring Za or ring Zc to form a ring. Each Ra is independently a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted alkyl group.

2. The emission peak height I resulting from the emission of singlet oxygen in the fluorescence spectrum of the color conversion sheet when the peak wavelength of the absorption spectrum of the color conversion sheet is used as the excitation wavelength. ０ and absorbance A at the peak wavelength of the absorption spectrum of the color conversion sheet. ０ is the ratio of I ０ / A ０ and, When the peak wavelength of the absorption spectrum of a resin sheet containing 0.05 wt % of rose bengal in the resin is used as excitation light, the ratio I' / A' of the emission peak intensity I' resulting from the emission of singlet oxygen in the fluorescence spectrum of the resin sheet to the absorbance A' at the peak wavelength of the absorption spectrum of the resin sheet is (I ０ / A ０ ) / (I' / A')<1 / 10 The light source unit according to claim 1 , wherein

3. 3. The light source unit according to claim 1, wherein the optical film is provided on at least a viewer side surface of the color conversion sheet, and a diffusion plate is further provided on a surface of the color conversion sheet opposite to the viewer side.

4. The light source unit according to claim 1 , wherein the optical film is provided on both sides of the color conversion sheet.

5. 5. The light source unit according to claim 1, wherein the optical film comprises at least one of a polarizing reflective film, a light diffusing film, a prism sheet, a wavelength selective reflective film, a microlens film, and a cut film.

6. 6. The light source unit according to claim 1, wherein three or more of the optical films are provided on the viewer side of the color conversion sheet.

7. 7. The light source unit according to claim 1, wherein the color conversion sheet and the optical film are laminated together.

8. 8. The light source unit according to claim 1, wherein the optical film includes a diffusion film, and the diffusion film is laminated on one or both surfaces of the color conversion sheet.

9. 9. The light source unit according to claim 1, wherein the optical film includes a prism sheet and a polarizing reflective film, and the prism sheet and the polarizing reflective film are provided on the light exit surface of the color conversion sheet.

10. 10. The light source unit according to claim 1, wherein the haze value of the color conversion sheet is 40% or more and 95% or less.

11. The light source unit according to any one of claims 1 to 10, wherein the compound that emits delayed fluorescence is at least one of the following light-emitting materials (a) and (b): (a) A luminescent material that emits light with a peak wavelength observed in the region of 500 nm or more and less than 580 nm when excited with light having a wavelength in the range of 430 nm or more and 500 nm or less. (b) A luminescent material that emits luminescence with a peak wavelength observed in the range of 580 nm to 750 nm when excited by either or both of excitation light having a wavelength in the range of 430 nm to 500 nm and the luminescence from the luminescent material (a).

12. The light source unit according to claim 11 , wherein the color conversion sheet includes at least one of the following layers (A) and (B): (A) A layer containing the light-emitting material (a) as the compound that emits delayed fluorescence (B) A layer containing the light-emitting material (b) as the compound that emits delayed fluorescence.

13. 13. The light source unit according to claim 1, wherein the light source is a light emitting diode having a maximum emission in the range of 400 nm to 500 nm.

14. A display comprising the light source unit according to any one of claims 1 to 13.

15. An illumination device comprising the light source unit according to any one of claims 1 to 13.

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