Color conversion sheet and backlight unit including the same

Abstract

A color conversion sheet according to one embodiment of the present invention includes a wavelength conversion layer in which an organic phosphor is dispersed in a resin matrix and a light absorption layer in which an organic light absorber located on one surface of the wavelength conversion layer is dispersed in a binder resin. By absorbing short-wavelength blue light that degrades the organic phosphor without affecting the luminescence characteristics of the organic phosphor contained in the wavelength conversion layer, it is possible to use an environmentally safe organic phosphor while exhibiting excellent color reproduction rate and brightness characteristics, minimal color change during light irradiation not only at room temperature but also in high-temperature environments, excellent brightness reliability, and superior performance from the viewpoint of protecting eyesight.

Description

Technical Field

[0001] The present invention relates to a color conversion sheet using an organic phosphor and a backlight unit including the same, and more particularly, to a color conversion sheet having a light absorption layer and a backlight unit including the same.

Background Art

[0002] Conventionally, a liquid crystal display (LCD) is a light-receiving display device that cannot emit light by itself to form an image and requires light to be incident from the outside to form an image. Therefore, such a liquid crystal display requires a backlight unit (BLU) that emits light on its back.

[0003] In recent years, in order to realize high image quality of liquid crystal displays, quantum dot technology has been widely applied. Such quantum dot technology has the advantages that various colors can be realized only by adjusting the size of nano-inorganic particles, and it also has the advantage of excellent stability against light such as UV. However, in the case of conventional cadmium (Cd)-based nano-inorganic particles, there are disadvantages in terms of environmental problems and the need to use a barrier film because the nano-inorganic particles are vulnerable to moisture, resulting in limitations in the selection of substrates and the compounding with other optical films.

[0004] In order to solve such problems, much research has been conducted on the development of organic phosphors that can realize high color reproducibility and excellent luminance characteristics without including cadmium-based nano-inorganic particles. Organic phosphors have the advantage of being superior in luminous efficiency compared to nano-inorganic particles applied to quantum dot technology, and can exhibit various luminous characteristics even using the same phosphor through changes in surrounding chemical substances. In addition, organic phosphors are relatively strong against moisture, so the application of a barrier film is not required, and they also have the advantage of being easy to use various substrates and compound with other optical films.

[0005] However, in the case of organic phosphors, they may absorb and emit light from the blue LEDs of the display, and conversely, degradation may progress due to short-wavelength blue light that they cannot absorb, potentially reducing the light resistance of the display. Furthermore, short-wavelength blue light can reach the retina of the human eye, causing retinal dysfunction and potentially inducing vision loss, so the development of technology to eliminate this is currently necessary. [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention was devised to solve the above-mentioned problems and meet conventional requirements. The problem that the present invention aims to solve is to provide a color conversion sheet and a backlight unit including the same that absorbs short-wavelength blue light that degrades organic phosphors without affecting the luminescence characteristics of the organic phosphor contained in the wavelength conversion layer, and that uses environmentally safe organic phosphors while having excellent color reproduction rate and brightness characteristics, exhibiting excellent brightness reliability with little color change when irradiated with light not only at room temperature but also at high temperatures, and having excellent performance in terms of protecting eyesight.

[0007] The above and other objectives and advantages of the present invention should become apparent from the following description which illustrates preferred embodiments. [Means for solving the problem]

[0008] The aforementioned objective is achieved by a color conversion sheet comprising a wavelength conversion layer in which an organic phosphor is dispersed in a resin matrix, and a light absorption layer located on one surface of the wavelength conversion layer in which an organic light absorber is dispersed in a binder resin, wherein the light absorption layer shields more than 60% of wavelengths below 410 nm, shields more than 10% of wavelengths above 430 nm, and transmits more than 80% of wavelengths above 460 nm.

[0009] Preferably, the light-absorbing layer has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and when monomodal light with a full width at half maximum of 40 nm or less is incident, the light transmitted from the color conversion sheet satisfies the following equation 1.

[0010] (Formula 1) T1 / B1 ≥ 0.6 B1: Emission intensity at the maximum emission peak of incident light T1: Emission intensity at the maximum emission peak of transmitted light Preferably, the light-absorbing layer has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and when monomodal light with a full width at half maximum of 40 nm or less is incident, the light transmitted from the color conversion sheet satisfies the following equation 2.

[0011] (Formula 2) TS1 / TS2 ≤ 0.9 TS1: The emission intensity of light transmitted from the position with a relatively lower wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2. TS2: The emission intensity of light transmitted from the position with a relatively higher wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2. Preferably, the organic spectroscopy absorber comprises at least one selected from anthracene-based, tetracene-based, coumarin-based, porphyrin-based, diazaporphyrin-based, pyrometen-based, and benzotriazole-based compounds.

[0012] Preferably, the binder resin of the light-absorbing layer comprises at least one resin selected from ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, silicone-based, and epoxy-based resins.

[0013] Preferably, the light-absorbing layer contains 0.1 to 40 parts by weight of the organic light absorber per 100 parts by weight of the binder resin.

[0014] Preferably, the light-absorbing layer further comprises at least one selected from UV absorbers, UV stabilizers, and antioxidants.

[0015] Preferably, the organic phosphor contains at least one of a green organic phosphor and a red organic phosphor.

[0016] Preferably, the resin matrix of the wavelength conversion layer contains at least one resin selected from ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, and imide-based resins.

[0017] Preferably, the wavelength conversion layer contains 0.0001 to 10 parts by weight of the organic phosphor with respect to 100 parts by weight of the resin matrix.

[0018] Preferably, the resin matrix of the wavelength conversion layer has a glass transition temperature (Tg) of 50°C to 150°C.

[0019] Preferably, the color conversion sheet has a change in luminance L value of less than 1% after 100 hours at a temperature of 60°C.

[0020] Preferably, the light absorption layer is located in the direction in which the wavelength conversion layer is irradiated with light.

[0021] Preferably, it further includes a first polyester base material layer located on the other surface of the wavelength conversion layer.

[0022] Preferably, it further includes a second polyester base material layer located between the wavelength conversion layer and the light absorption layer or on the surface of the light absorption layer.

[0023] Moreover, the above object is achieved by a backlight unit including the above-described color conversion sheet.

Advantages of the Invention

[0024] According to the color conversion sheet and the backlight unit including the same according to the present invention, the color conversion sheet further includes a light absorption layer that absorbs short-wavelength blue light irradiated from a blue LED on one surface of a wavelength conversion layer in which an organic phosphor is dispersed, thereby preventing the organic phosphor from being deteriorated by high-energy short-wavelength blue light. Therefore, there are effects such as solving the problems of color coordinate change or reliability reduction.

[0025] Moreover, according to the color conversion sheet and the backlight unit including the same according to the present invention, the light absorption layer absorbs only short-wavelength blue light that does not affect the light emission characteristics of the organic phosphor, thereby solving the problems of luminance characteristic change and color change due to deterioration of the organic phosphor caused by blue light absorption, and also solving the problem of visual acuity reduction caused by blue light.

[0026] However, the effects of the present invention are not limited to the effects mentioned above, and other effects not mentioned should be clearly understood by those having ordinary knowledge in the technical field to which the present invention pertains from the following description.

Brief Description of the Drawings

[0027] [Figure 1] It is a cross-sectional view of a color conversion sheet according to an embodiment of the present invention. [Figure 2] It is a cross-sectional view of a color conversion sheet according to another embodiment of the present invention. [Figure 3] It is a schematic view of a backlight unit including a color conversion sheet according to an embodiment of the present invention.

Modes for Carrying Out the Invention

[0028] Hereinafter, referring to the attached drawings, embodiments of the present invention will be described in detail so that those having ordinary knowledge in the technical field to which the present invention pertains can easily implement them. However, the present invention can be embodied in various different forms and is not limited to the embodiments described here.

[0029] To clearly illustrate the present invention in the drawings, irrelevant parts have been omitted, and the same or similar components are denoted by the same reference numerals throughout the specification. In addition, thicknesses have been enlarged in the drawings to clearly represent multiple layers and regions. Furthermore, where it is stated in this specification that a component is placed "on top of" or "on top of" another component, that component may be placed directly on top of the other component, or there may be an interposed component between them. Conversely, where it is stated that a component is placed "directly on top of" or "directly on top of" another component, there may not be an interposed component.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the invention pertains. In case of any conflict, this specification, including its definitions, shall prevail. Furthermore, similar or equivalent methods and materials may be used in carrying out or testing the invention, but suitable methods and materials are described herein.

[0031] In this specification, "~-type resin," "~-type polymer," or / or "~-type copolymer" is a broad concept encompassing all "~-type resin," "~-type polymer," "~-type copolymer," or / or "derivatives of ~-type resin, polymer, or copolymer." Furthermore, in this specification, the term "polymer or copolymer crosslinked with these resins" means "polymer or copolymer crosslinked with the aforementioned resins."

[0032] In this specification, "compound" is a broad concept that includes all "monatomic molecules," "oligomers," and "polymers including homopolymers and copolymers."

[0033] In this specification, the term “inclusion” means, unless otherwise stated, that other components may be included rather than excluded.

[0034] In this specification, the term “these combinations” means a mixture or combination with one or more of the components described.

[0035] In this specification, the term "and / or" means any combination and all combinations of one or more items described in relation to each other. In this specification, the term "or" means "and / or". In this specification, expressions such as "at least one" or "one or more" preceding a component may complement the overall list of components, but not necessarily the individual components described above.

[0036] Unless otherwise stated, all percentages, parts, ratios, etc., are based on weight. Furthermore, where a quantity, concentration, or other value or parameter is given as a range, preferred range, or preferred upper and lower limit catalog, this should be understood to specifically disclose all ranges formed from any pair of any upper or preferred upper limit and any lower limit or preferred value, regardless of whether the range is disclosed separately.

[0037] Where a range of numerical values ​​is referred to herein, unless otherwise stated, that range is intended to include its endpoint and all integers and fractions within that range. The scope of the present invention is not intended to be limited to the specific values ​​referred to when defining a range.

[0038] In this specification, each component is a concept that includes both singular and plural forms.

[0039] The color change sheet according to the present invention will be described in detail below with reference to the drawings.

[0040] Referring to Figure 1, a cross-sectional view of a color conversion sheet according to one embodiment of the present invention, the color conversion sheet 100 according to one embodiment of the present invention includes a wavelength conversion layer 10 in which an organic phosphor is dispersed in a resin matrix, and a light absorption layer 20 located on one surface of the wavelength conversion layer 10 in which an organic light absorber is dispersed in a binder resin. In this case, the light absorption layer 20 can be formed by coating the light absorption composition onto one surface of the wavelength conversion layer 10 or by printing.

[0041] In one embodiment, the light-absorbing layer 20 transmits the blue light necessary for the organic phosphor of the wavelength conversion layer 10 to emit light, while shielding high-energy, short-wavelength blue light that is not needed for emission, thereby preventing the organic phosphor of the wavelength conversion layer 10 from degrading due to short-wavelength blue light. The light-absorbing layer 20 also functions to prevent the organic phosphor within the wavelength conversion layer 10 from being exposed to the outside and degrading due to unwanted elements such as moisture and oxygen in the air. Furthermore, by shielding high-energy, short-wavelength blue light that is not needed for the emission of light from the organic phosphor of the wavelength conversion layer 10, the light-absorbing layer 20 not only prevents color changes and a decrease in brightness characteristics of the display, but also solves the problem of vision deterioration caused by blue light that occurs when the display is used for a long time.

[0042] To realize the functions of the light-absorbing layer 20 as described above, it is preferable in the present invention that the light-absorbing layer 20 shields 60% or more of the wavelength region of 410 nm or less, shields 10% or more of the wavelength region of 430 nm, and transmits 80% or more of the wavelength region of 460 nm or more. Furthermore, it is even more preferable that the light-absorbing layer 20 shields 70% or more of the wavelength region of 410 nm or less, shields 20% or more of the wavelength region of 430 nm, and transmits 90% or more of the wavelength region of 460 nm or more.

[0043] This is because, if the light-absorbing layer 20 shields less than 60% of wavelengths below 410 nm and less than 10% of wavelengths below 430 nm, the organic phosphor in the wavelength conversion layer 10 will degrade over time due to high-energy short-wavelength blue light, causing changes in color coordinates and reduced reliability. The unshielded short-wavelength blue light will pass through the display liquid crystal and reach the human eye, potentially causing problems such as decreased vision.

[0044] In contrast, if the light absorption layer 20 transmits less than 80% of wavelengths above 460 nm, the amount of light required to make the organic phosphor in the wavelength conversion layer 10 emit light decreases, thereby reducing the luminescence efficiency of the organic phosphor. Furthermore, if the light absorption layer 20 transmits less than 80% of wavelengths above 460 nm, some of the light emitted from the organic phosphor in the wavelength conversion layer 10 and recycled by the optical sheet, specifically green or red light, is absorbed by the light absorption layer 20, causing a color change and a decrease in brightness characteristics.

[0045] Furthermore, it is preferable that the light-absorbing layer 20 has a light emission intensity that satisfies the following formulas 1 and 2.

[0046] First, it is preferable that the light-absorbing layer 20 has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and that the transmitted light when monomodal light is incident on it has optical properties that satisfy the following equation 1.

[0047] (Formula 1) T1 / B1 ≥ 0.6 B1: Emission intensity at the maximum emission peak of incident light T1: Emission intensity at the maximum emission peak of transmitted light As shown in Equation 1, it is preferable that the ratio of the emission intensity at the maximum emission peak of the light incident on the light absorption layer 20 to the emission intensity at the maximum emission peak of the transmitted light is 0.6 or greater. This is because if the ratio of the two is less than 0.6, not only the short-wavelength blue light region but also the long-wavelength blue light region of 440 nm or more, which is necessary for the emission of light from the organic phosphor in the wavelength conversion layer 10, is absorbed, and the luminescence efficiency of the organic phosphor can be greatly reduced.

[0048] Furthermore, it is preferable that the light-absorbing layer 20 has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and that the transmitted light when monomodal light with a full width at half maximum of 40 nm or less is incident has optical properties that satisfy the following equation 2.

[0049] (Formula 2) TS1 / TS2 ≤ 0.9 TS1: The emission intensity of light transmitted from the position with a relatively lower wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2. TS2: The emission intensity of light transmitted from the position with a relatively higher wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2. In other words, in Equation 2, TS1 and TS2 represent the emission intensity of light transmitted from the position with a relatively lower wavelength (TS1) and the emission intensity of light transmitted from the position with a relatively higher wavelength (TS2), respectively, among the two reference positions for the full width at half maximum. For example, if the maximum emission intensity of the incident light is located at a wavelength of 460 nm and the full width at half maximum is 20 nm, then TS1 represents the emission intensity at a wavelength of 450 nm and TS2 represents the emission intensity at 470 nm. Also, if the maximum emission intensity of the incident light is located at a wavelength of 450 nm and the full width at half maximum is 10 nm, then TS1 represents the emission intensity at a wavelength of 445 nm and TS2 represents the emission intensity at 455 nm.

[0050] As shown in Equation 2, the difference in emission intensity of transmitted light at the short-wavelength position and the long-wavelength position, which corresponds to half of the maximum emission intensity of light incident on the light-absorbing layer 20, is preferably 0.9 or less, and more preferably 0.8 or less. This is because the light-absorbing layer 20 blocks short-wavelength blue light and selectively transmits long-wavelength blue light, thereby preventing degradation of the organic phosphor contained in the wavelength conversion layer 10 while also preventing a decrease in luminous efficiency. In contrast, if Equation 2 exceeds 0.9, it is difficult to expect a shielding effect of short-wavelength blue light from the light-absorbing layer 20, and if it exceeds 1.0, the shielding of long-wavelength blue light, which is necessary for the emission of organic phosphor light, becomes even greater than the shielding of short-wavelength blue light, which can significantly reduce the luminous efficiency of the organic phosphor.

[0051] The organic light absorber of the light-absorbing layer 20 according to one embodiment of the present invention preferably contains at least one selected from anthracene-based, tetracene-based, coumarin-based, porphyrin-based, diazaporphyrin-based, pyrometen-based, and benzotriazole-based materials.

[0052] Furthermore, the binder resin of the light-absorbing layer 20 serves to fix the organic photoabsorber while simultaneously preventing exposure to moisture and oxygen, thereby enhancing the stability of the organic photoabsorber dispersed within the light-absorbing layer 20. The binder resin of such a light-absorbing layer 20 preferably contains at least one resin selected from ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, silicone-based, and epoxy-based resins.

[0053] In one embodiment, the light-absorbing layer 20 preferably contains 0.1 to 40 parts by weight of an organic optogenetic agent per 100 parts by weight of binder resin, and more preferably 0.5 to 40 parts by weight. This is because if the organic optogenetic agent is less than 0.1 parts by weight, the short-wavelength blue light shielding efficiency of the light-absorbing layer 20 decreases, and the degradation of the organic phosphor in the wavelength conversion layer 10 cannot be prevented. If the organic optogenetic agent exceeds 40 parts by weight, the short-wavelength blue light shielding efficiency of the light-absorbing layer 20 does not substantially increase further, but only increases manufacturing costs, and the light transmission efficiency of the light-absorbing layer 20 decreases, reducing the luminescence efficiency of the organic phosphor in the wavelength conversion layer 10.

[0054] Furthermore, the light-absorbing layer 20 may further include at least one selected from a UV absorber, a UV stabilizer, and an antioxidant. In the case of a UV absorber and a UV stabilizer, they function to prevent the degradation of the organic photoabsorber in the light-absorbing layer 20 and the organic phosphor in the wavelength-converting layer 10 from natural UV light when the color conversion sheet 100 is stored outdoors. In the case of an antioxidant, they function to prevent chain degradation of other organic photoabsorbers by removing radicals that can be generated when the organic photoabsorber in the light-absorbing layer 20 degrades during the process of absorbing light.

[0055] In one embodiment, the wavelength conversion layer 10 is located on one surface of the light absorption layer 20 and contains an organic phosphor dispersed in a resin matrix.

[0056] The resin matrix of the wavelength conversion layer 10 serves to fix the organic phosphor while simultaneously preventing exposure to moisture and oxygen, thereby preventing the degradation of the organic phosphor dispersed in the resin matrix. The resin matrix of such a wavelength conversion layer 20 preferably contains at least one of the following resins: ester, olefin, acrylic, ether, urethane, carbonate, and imide.

[0057] Furthermore, the resin contained in the resin matrix may have a number-average molecular weight (Mn) of 1,000 to 50,000 g / mol or a weight-average molecular weight (Mw) of 50,000 to 2,000,000 g / mol. This is because if the number-average molecular weight of the resin contained in the resin matrix is ​​less than 1,000 g / mol or the weight-average molecular weight is less than 50,000 g / mol, it becomes difficult to fix the organic phosphor, and aggregation of the organic phosphor due to temperature and a resulting decrease in optical properties may occur. If the number-average molecular weight exceeds 50,000 g / mol or the weight-average molecular weight exceeds 2,000,000 g / mol, the resin matrix has poor solubility in the solvent, making it difficult to form the wavelength conversion layer 20.

[0058] Furthermore, the acid value of the resin contained in the resin matrix is ​​0 to 15 mg KOH / g, preferably 0 to 10 mg KOH / g, and the hydroxyl value is 0 to 30 mg KOH / g, preferably 0 to 20 mg KOH / g, and more preferably 0 to 10 mg KOH / g. Generally, ester, olefin, acrylic, ether, urethane, carbonate, and imide resins that can be applied as the resin matrix of the wavelength conversion layer constituting the color conversion sheet may have functional groups such as hydroxyl groups and carboxylic acid groups present in these resins that accelerate the degradation of organic phosphors dispersed in the resin matrix, potentially reducing the reliability of the organic phosphors. Therefore, it is preferable to maintain the acid value and hydroxyl value within the above ranges.

[0059] More specifically, the resin matrix constituting the wavelength conversion layer 10 may include at least one of the following, or block copolymer forms thereof: polyester, modified polyester, polyethylene, polycycloolefin, poly(methyl)methacrylate, polyethylene glycol, polyurethane, polycarbonate, and polyimide.

[0060] Furthermore, the resin matrix of the wavelength conversion layer 10 preferably has a glass transition temperature (Tg) of 50°C to 150°C, more preferably 60°C to 140°C, and most preferably 70°C to 140°C. This is because if the glass transition temperature of the resin matrix is ​​less than 50°C, aggregation occurs between multiple organic phosphors over time in a high-temperature or high-temperature, high-humidity environment, resulting in a decrease in optical properties. If the glass transition temperature exceeds 150°C, the resin generally has high crystallinity and poor solubility in the solvent, which can lead to film curling due to resin crystallization during drying after coating the substrate film.

[0061] Furthermore, the organic phosphor dispersed in the resin matrix of the wavelength conversion layer 10 is a phosphor that emits light of a different wavelength from the excitation light when irradiated with excitation light. Depending on the purpose, the wavelength conversion layer 10 can emit light of various colors by containing either a green phosphor or a red phosphor, or by a combination of these.

[0062] The organic phosphor can contain multiple organic phosphors of the same hue that emit a single color in a single wavelength conversion layer 10. In this case, the multiple organic phosphors may be the same substance or different substances. For example, the wavelength conversion layer 10 can contain only one organic phosphor from among multiple green organic phosphors or multiple red organic phosphors to emit only one color of light. Also, when using an organic phosphor of a single hue in a single wavelength conversion layer, two or more wavelength conversion layers containing organic phosphors of different hues can be formed separately to emit light of various colors.

[0063] Such organic phosphors include compounds having condensed aryl rings such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, perylene, fluorantene, fluorene, and indene, and their derivatives (e.g., 2-(benzothiazol-2-yl)-9,10-diphenylanthracene and 5,6,11,12-tetraphenylnaphthalene), furan, pyrrole, thiophene, silole, 9-silafluorene, 9,9'-spirobisilafluorene, benzothiophene, benzofuran, indole, dibenzothiophene, dibenzofuran, imidazopyridine, phenanthroline, pyridine, pyrazine, naphthyridine, quinoxaline, pyrrolopyridine, thioxanthene, and other compounds having heteroaryl rings, and their derivatives, borane derivatives, distylylbenzene derivatives, and 4,4'-bis(2-(4-di This includes aminostyryl derivatives such as phenylaminophenyl)ethenyl)biphenyl and 4,4'-bis(N-(stilben-4-yl)-N-phenylamino)stilbene, aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives such as 2,3,5,6-1H,4H-tetrahydro-9-(2'-benzothiazolyl)quinolidino[9,9a,1-gh]coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, triazole and their metal complexes, and aromatic amine derivatives represented by N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine.

[0064] As an organic phosphor according to one embodiment of the present invention, the green organic phosphor absorbs blue light and emits green light, and may include the compound represented by the following chemical formula 1. [ka] Furthermore, the wavelength conversion layer 10 may include a red organic phosphor dispersed in the resin matrix. The red organic phosphor dispersed in the resin matrix of the wavelength conversion layer absorbs blue or green light and emits red light, and the red organic phosphor may include a compound represented by the following chemical formula 2. [ka] The above-mentioned organic phosphors (green organic phosphors and / or red organic phosphors) are preferably present in amounts of 0.0001 to 10 parts by weight per 100 parts by weight of resin solids in the resin matrix. This is because if the amount of organic phosphors is less than 0.0001 parts by weight, the color conversion effect to the desired hue through the color conversion sheet 100 is weak, and if it is more than 10 parts by weight, a quenching phenomenon may occur due to interactions such as aggregation of the organic phosphors.

[0065] Furthermore, the thickness of the wavelength conversion layer 10 containing the organic phosphor dispersed in the resin matrix is ​​preferably 1 to 150 μm, more preferably 1 to 100 μm, and most preferably 1 to 50 μm. This is because if the thickness of the wavelength conversion layer 10 exceeds 150 μm, it becomes difficult to remove the solvent sufficiently, and degradation of the organic phosphor can occur due to various solvents remaining in the wavelength conversion layer 10. If the thickness is less than 1 μm, the wavelength conversion layer cannot perform its function.

[0066] In the color conversion sheet according to one embodiment of the present invention, it is preferable that the light absorption layer 20 is located in the direction in which light is irradiated onto the wavelength conversion layer 10. That is, it is preferable that the light absorption layer 20 is located on one surface of the wavelength conversion layer 10 that is close to the light source. This is because, by positioning the light absorption layer 20 in the direction in which light is irradiated, short-wavelength blue light from the light source irradiated onto the wavelength conversion layer 10 can be shielded in advance, thereby more effectively preventing the deterioration of the organic phosphor in the wavelength conversion layer 10.

[0067] Furthermore, at least one surface of the wavelength conversion layer 110 and the light absorption layer 20 that is in contact with the outside may further include substrate layers 30 and 40 as needed. In the color conversion sheet 100 shown in Figure 1, the first substrate layer 30 is located on the opposite side of the surface of the wavelength conversion layer 10 on which the light absorption layer 20 is formed, i.e., on the outer surface of the wavelength conversion layer 10, and the second substrate layer 40 is located on the surface of the light absorption layer 20. In this way, in the color conversion sheet 100 according to Figure 1, the first substrate layer 30 and the second substrate layer 40 are located outside the wavelength conversion layer 10 and the light absorption layer 20, protecting the wavelength conversion layer 10 and the light absorption layer 20 from the outside.

[0068] The first base layer 30 and the second base layer 40 can be transparent and flexible polymer films, such as polyethylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyetherimide, and polyimide, but are not limited to these, and a variety of polymer films can be used.

[0069] Here, the first substrate layer 30 and the second substrate layer 40 may be a diffusion film (sheet), a prism sheet, etc., but are not limited to these, and sheets with various functions can be applied.

[0070] With this configuration, the color conversion sheet according to one embodiment of the present invention can achieve a change in brightness L value of less than 1% after 100 hours at a temperature of 60°C. If the change in brightness L value is 1% or more, the organic phosphor deteriorates significantly over time, and the reliability of the color conversion sheet decreases.

[0071] Next, with reference to Figure 2, a cross-sectional view of a color conversion sheet according to another embodiment of the present invention, a color conversion sheet according to another embodiment of the present invention will be described, and the explanation of configurations that overlap with those in Figure 1 will be omitted.

[0072] Referring to Figure 2, in the color conversion sheet 200 according to another embodiment of the present invention shown in Figure 2, a second substrate layer 40 is formed between the wavelength conversion layer 10 and the light absorption layer 20, and a first substrate layer 30 may be formed on the outer surface of the wavelength conversion layer 10 as needed.

[0073] Thus, in the color conversion sheet 200 according to another embodiment of the present invention shown in Figure 2, a first substrate layer 30 and a second substrate layer 40 are directly formed on both sides of the wavelength conversion layer 10, which can protect the organic phosphor contained in the wavelength conversion layer 10 from external moisture and air. If necessary, back coating particles can be mixed into the first substrate layer 30 and the second substrate layer 40 to function as a back coating layer.

[0074] Next, with reference to Figure 3, which is a schematic diagram of a backlight unit including a color conversion sheet according to one embodiment of the present invention, a backlight unit including a color conversion sheet according to one embodiment of the present invention will be described.

[0075] Referring to Figure 3, a backlight unit 900 including a color conversion sheet according to one embodiment of the present invention may include a light source 700, a reflector 500 that can reflect light emitted from the light source 700 to increase light efficiency, a light guide plate 300 located above the reflector plate 500 and playing a role in uniformly spreading the light emitted from the light source 700, and a color conversion sheet 100 located above the light guide plate 300. Here, the color conversion sheet may be the color conversion sheet shown in Figure 1 or Figure 2.

[0076] In this case, it is preferable that the light absorption layer 20 in the color conversion sheet 100 is positioned in a direction closer to the light source 700 from the wavelength conversion layer 10, that is, in the direction from which light is incident from the light source 700, thereby more effectively preventing the degradation of the organic phosphor in the wavelength conversion layer 10 by pre-blocking the short-wavelength blue light among the blue light irradiated onto the wavelength conversion layer 10.

[0077] The light source 700 shown in Figure 3 preferably includes at least one light source selected from edge-type light sources, side-chain light sources, and direct-type light sources, but is not limited thereto, and a variety of light sources can be used.

[0078] Furthermore, the upper (surface) of the color conversion sheet 100 may further include at least one optical sheet, such as a diffusion sheet, a prism sheet, or a brightness-enhancing film (DBEF).

[0079] The present invention will be described in more detail below with reference to examples and comparative examples. These examples are provided to further illustrate the present invention, and the scope of the present invention is not limited by these examples. [Examples]

[0080] [Example 1] Step 1: Formation of the wavelength conversion layer After preparing an organic phosphor solution by dissolving the green organic phosphor according to chemical formula 1 described above in methyl ethyl ketone, the organic phosphor solution was mixed with a polyester resin prepared by dissolving polyester chips (SK Chemical, Es-120) with an acid value of 3 mg KOH / g or less and a hydroxyl value of 2 to 6 mg KOH / g in methyl ethyl ketone. Methyl ethyl ketone was added to achieve a viscosity of 150 cps, and the mixture was stirred at 150 rpm for 30 minutes to produce a wavelength conversion layer composition. At this time, the amount of green organic phosphor was set to 0.4 parts by weight per 100 parts by weight of polyester solids. Next, the wavelength conversion layer composition was bar-coated onto the opposite side of the diffusion layer of a diffusion film (TAK, TDF12C), and then dried at 120°C for 2 minutes to form a 15 μm thick wavelength conversion layer.

[0081] Step 2: Formation of the light-absorbing layer Next, 50 parts by weight of toluene was added to the silicone resin (DOW, DC7663), and the mixture was stirred at 150 rpm for 2 hours. Then, 0.5 parts by weight of platinum catalyst (DOW, SYL-OFF 4000 CATALYST) was added and the mixture was stirred for a further 30 minutes. After that, 40 parts by weight of coumarin compound (MERCK, Coumarin 102) was added per 100 parts by weight of the solid content of the silicone resin, and the mixture was stirred at 150 rpm for 30 minutes to produce a light-absorbing layer composition. Next, the light-absorbing layer composition was bar-coated onto the top of a polyethylene terephthalate film (TAK, PH8), and then dried at 170°C for 1 minute to form a 10 μm thick light-absorbing layer.

[0082] Step 3: Manufacturing the color conversion sheet After laminating the light-absorbing layer formed in Step 2 and the wavelength-converting layer formed in Step 1 so that they were in contact with each other, a color-converting sheet was manufactured using roll lamination (GMP, EXCELAM II-355Q).

[0083] [Example 2] A color-changing sheet was manufactured using the same method as in Example 1, except that 20 parts by weight of a benzotriazole compound (BASF, Tinuvin 970) was added as an organic spectroscopy agent per 100 parts by weight of the silicon resin solids.

[0084] [Example 3] A color-changing sheet was manufactured using the same method as in Example 1, except that 0.3 parts by weight of a porphyrin compound (YAMADA Chemical, FDB-002) was added per 100 parts by weight of the silicone resin solids as an organic light absorber, and 1 part by weight of an organic light absorber (TOYO INK, NUV-240) was added per 100 parts by weight of the silicone resin solids.

[0085] [Example 4] A color-changing sheet was manufactured using the same method as in Example 1, except that a polyester resin prepared by dissolving polyester (TOYOBO, Vylon630) in methyl ethyl ketone was used for the light-absorbing layer composition.

[0086] [Example 5] A color conversion sheet was manufactured using the same method as in Example 1, except that 0.1 parts by weight of a porphyrin compound (YAMADA Chemical, FDB-002) was added as an organic light absorber per 100 parts by weight of the silicone resin solids.

[0087] [Comparative Example 1] A color conversion sheet was manufactured using the same method as in Example 1, except that the step of forming a light-absorbing layer was omitted and the polyethylene terephthalate film (TAK, PH8) was directly laminated onto the wavelength conversion layer.

[0088] [Comparative Example 2] A color conversion sheet was manufactured using the same method as in Example 1, except that 0.01 parts by weight of a porphyrin compound (YAMADA Chemical, FDB-002) was added as an organic light absorber per 100 parts by weight of the silicon resin solids.

[0089] [Comparative Example 3] A color conversion sheet was manufactured using the same method as in Example 1, except that 50 parts by weight of a coumarin-based organic spectroscopy agent (MERCK, Coumarin 102) was added per 100 parts by weight of the silicone-based resin solids.

[0090] [Comparative Example 4] A color-changing sheet was manufactured using the same method as in Example 1, except that 10 parts by weight of a coumarin compound (MERCK, Coumarin 153) was added as an organic spectroscopy agent per 100 parts by weight of the silicone resin solids, and 35 parts by weight of a benzotriazole compound (BASF, Tinuvin 970) was added per 100 parts by weight of the silicone resin solids.

[0091] Using the color conversion sheets described in Examples 1 to 5 and Comparative Examples 1 to 4, the physical properties were measured in the following experimental examples, and the results are shown in Tables 1 to 3.

[0092] [Example of experiment] 1) Measurement of light transmittance In the color conversion sheets of Examples 1 to 5 and Comparative Examples 2 to 4, the light transmittance of the light absorption layer was measured using a spectrophotometer (SHIMADZU, MPC-3100) for the configuration in which the polyethylene terephthalate film and the light absorption layer were laminated before lamination with the wavelength conversion layer. The light transmittance measured in the wavelength ranges of 410 nm, 430 nm, and 460 nm is shown in Table 1.

[0093] Furthermore, in Comparative Example 1, the light transmittance of the polyethylene terephthalate film itself was measured using the same method before laminating the wavelength conversion layer onto the polyethylene terephthalate film, and the results are shown in Table 1.

[0094] Next, using the light transmittance measured in Comparative Example 1 (light transmittance of polyethylene terephthalate film) as a baseline of 100%, the relative ratio of the measured light transmittances for a configuration in which polyethylene terephthalate film and a light-absorbing layer are laminated was calculated and recorded in Table 1 as the light transmittance of the light-absorbing layer.

[0095] 2) Measurement of changes in the blue light spectrum (emission intensity) In the color conversion sheets of the examples and comparative examples, the change in the blue light spectrum in the light absorption layer was measured using a spectroradiometer (KONICA MINOLTA, CA-S20W) before laminating the light absorption layer with the wavelength conversion layer. In this experiment, the color conversion sheet was constructed by laminating a light absorption layer coated on polyethylene terephthalate film onto the upper surface of the light guide plate of a backlight unit containing a blue LED having a maximum emission peak at a wavelength of 447 nm and a full width at half maximum of 18 nm, and then further laminating a prism sheet onto the upper surface of the light absorption layer.

[0096] This allowed us to measure the emission intensity at the maximum emission peak of the incident light (B1), the emission intensity at the maximum emission peak of the transmitted light (T1), the emission intensity of the transmitted light at a wavelength of 438 nm (short wavelength), which corresponds to half the maximum emission intensity of the incident light (TS1), and the emission intensity of the transmitted light at another position, a wavelength of 456 nm (long wavelength), which also corresponds to half the maximum emission intensity of the incident light (TS2).

[0097] 3) Measurement of changes in luminance and color coordinates For the color conversion sheets in the examples and comparative examples, the initial luminance (L) and color coordinate (x,y) values ​​were measured. Then, the change in color coordinate (Δx,Δy) and luminance (ΔLv) over 100 hours at a temperature of 60°C was measured using a spectroradiometer (KONICA MINOLTA, CA-S20W). In this experiment, the color conversion sheet was laminated on the upper surface of the light guide plate of a backlight unit containing a blue LED with a wavelength of 447 nm and a light guide plate, and a prism sheet was further laminated on top of the color conversion sheet before the experiment was conducted.

[0098] Table 1 shows the light transmittance measurement results for the light absorption layers of the examples and comparative examples. [Table 1] Of the light transmittances listed in Table 1 above, the values ​​in parentheses indicate the light transmittance of the light-absorbing layer, calculated by using the light transmittance of Comparative Example 1, which is the light transmittance of the PET film, as a reference and calculating the relative ratio of the measured light transmittances based on this reference. As shown in Table 1 above, the light transmittance of the light-absorbing layer was evaluated when it was coated on a PET film with a thickness of 100 μm. Therefore, when comparing them relatively with the light transmittance of the PET film in each wavelength region set to 100%, it can be seen that Examples 1 to 5 satisfy the conditions of shielding more than 60% in the wavelength region of 410 nm or less, shielding more than 10% in the wavelength region of 430 nm, and transmitting more than 80% in the wavelength region of 460 nm or more.

[0099] In contrast, Comparative Example 2 showed extremely low shielding efficiency at 410 nm and 430 nm due to an excessively low content of the organic light absorber. Furthermore, Comparative Example 3 showed no significant increase in shielding efficiency at 410 nm and 430 nm despite an increased content of the organic light absorber compared to Example 1.

[0100] Furthermore, while Comparative Example 4 shields more than 60% of the wavelength region below 410 nm and more than 10% of the wavelength region at 430 nm, it can be confirmed that the transmittance in the 460 nm wavelength region is extremely low.

[0101] Table 2 shows the blue light spectral measurement results of the light absorption layers in the examples and comparative examples. [Table 2] As shown in Table 2 above, it was found that all of Examples 1 to 5 satisfy Equations 1 and 2. As a result, it was confirmed that the long-wavelength blue light region from 440 nm onwards, which is necessary for the emission of light from the organic phosphor in the wavelength conversion layer 10, is not absorbed much, while short-wavelength blue light is selectively shielded in large quantities.

[0102] In contrast, in Comparative Example 2, the value of Equation 2 is close to 1.0, confirming that there is no short-wavelength blue light shielding effect. In Comparative Example 3, although both Equation 1 and Equation 2 are satisfied, there is almost no improvement in the short-wavelength blue light shielding effect with increasing organic absorber content compared to Example 1. On the other hand, it was confirmed that problems such as the deposition of organic absorber on the surface of the light absorption layer and the resulting increase in surface haze occurred due to an excessive increase in content, which can lead to problems such as a decrease in the brightness of the wavelength conversion layer.

[0103] Furthermore, in Comparative Example 4, the value of Equation 1 is less than 0.6, meaning that a large amount of light was absorbed not only in the short-wavelength blue light region but also in the long-wavelength blue light region beyond 440 nm, which is necessary for the emission of light from the organic phosphor in the wavelength conversion layer 10, thus reducing the luminescence efficiency of the organic phosphor.

[0104] Table 3 shows the results of measuring the changes in brightness and color coordinates for the examples and comparative examples. [Table 3] As shown in Table 3 above, Examples 1 to 5 demonstrate that, as a result of the light-absorbing layer satisfying both Equation 1 and Equation 2, the changes in the color coordinates of the x and y axes remain within ±0.005 even after 100 hours of treatment at a temperature of 60°C.

[0105] On the other hand, in Comparative Example 1, where no light-absorbing layer was formed, the x-axis change value was -0.002 and the y-axis change value was -0.010, confirming that these values ​​were the largest among all the examples and comparative examples.

[0106] Furthermore, in Comparative Example 2, where the light-absorbing layer does not satisfy Equation 2, a larger change in color coordinates is observed compared to Examples 1 to 5. In Comparative Example 3, although Equations 1 and 2 are satisfied, the improvement in color coordinate change with increasing organic light absorber content is significantly less compared to Example 1. In addition, in Comparative Example 4, Equation 1 is not satisfied, resulting in a decrease in the luminescence efficiency of the organic phosphor, and a relatively larger change in color coordinates is observed compared to Examples 1 to 5.

[0107] As described above, it can be confirmed that comparative examples in which the light-absorbing layer does not satisfy Equation 1 and / or Equation 2 have a greater change in color coordinates than Examples 1 to 5 in which the light-absorbing layer satisfies both Equation 1 and Equation 2.

[0108] Furthermore, while Examples 1 to 5 all showed a change in brightness of less than 1% after 100 hours of treatment at a temperature of 60°C, Comparative Example 1, which did not have a light-absorbing layer, showed a decrease in brightness, with a brightness change of 4.8% after 100 hours of treatment. Comparative Example 2, in which the light-absorbing layer could not satisfy Equation 2, also showed a decrease in brightness, with a brightness change of 4.1% after 100 hours of treatment. Comparative Example 3 satisfied Equations 1 and 2, but it was confirmed that the effect of improving brightness change with increasing organic light absorber content was very small compared to Example 1.

[0109] Thus, it was confirmed that significant color and brightness changes occur in high-temperature environments when a color conversion sheet does not form a light-absorbing layer, as in Comparative Example 1, or when it does not satisfy Equation 2, as in Comparative Example 2. In contrast, it was confirmed that when the light-absorbing layer satisfies Equations 1 and 2, color coordinate changes and brightness changes are minimal even in high-temperature environments.

[0110] The color conversion sheet according to the present invention, as described above, further incorporates a light-absorbing layer to prevent degradation of the organic phosphor due to light. By selectively blocking short-wavelength blue light and transmitting long-wavelength blue light, it is possible to prevent degradation of the organic phosphor while also preventing a decrease in luminous efficiency. This has the technical effect of solving the problems of changes in brightness characteristics and color changes associated with degradation and changes in luminous efficiency of the organic phosphor.

[0111] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements by those skilled in the art, utilizing the basic concepts of the present invention as defined in the following claims, also fall within the scope of the present invention.

Claims

1. A wavelength conversion layer in which an organic phosphor is dispersed within a resin matrix, A light-absorbing layer located on one surface of the wavelength conversion layer, in which an organic light-absorbing material is dispersed within a binder resin, Includes, The aforementioned light-absorbing layer is a color conversion sheet that shields more than 60% of wavelengths below 410 nm, more than 10% of wavelengths above 430 nm, and transmits more than 80% of wavelengths above 460 nm.

2. The light-absorbing layer has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and when monomodal light with a full width at half maximum of 40 nm or less is incident, the light transmitted from the color conversion sheet satisfies the following formula 1, as described in claim 1: (Formula 1) T1 / B1 ≥ 0.6 B1: Emission intensity at the maximum emission peak of incident light T1: Emission intensity at the peak emission of transmitted light.

3. The light-absorbing layer has a maximum emission peak in the wavelength range of 440 nm to 470 nm, and when monomodal light with a full width at half maximum of 40 nm or less is incident, the light transmitted from the color conversion sheet satisfies the following formula 2, as described in claim 1: (Formula 2) TS1 / TS2 ≦ 0.9 TS1: The emission intensity of light transmitted from the position with a relatively lower wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2. TS2: The emission intensity of light transmitted from the position with a relatively higher wavelength among the two positions where the maximum emission intensity of the incident light is 1 / 2.

4. The color conversion sheet according to claim 1, wherein the organic light absorber comprises at least one selected from anthracene-based, tetracene-based, coumarin-based, porphyrin-based, diazaporphyrin-based, pyrometen-based, and benzotriazole-based organic light absorbers.

5. The color conversion sheet according to claim 1, wherein the binder resin of the light-absorbing layer comprises at least one resin selected from ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, silicone-based, and epoxy-based resins.

6. The color conversion sheet according to claim 1, wherein the light-absorbing layer comprises 0.1 to 40 parts by weight of the organic light absorber per 100 parts by weight of the binder resin.

7. The color conversion sheet according to claim 1, wherein the light-absorbing layer further comprises at least one selected from a UV absorber, a UV stabilizer, and an antioxidant.

8. The color conversion sheet according to claim 1, wherein the organic phosphor comprises at least one of a green organic phosphor and a red organic phosphor.

9. The color conversion sheet according to claim 1, wherein the resin matrix of the wavelength conversion layer comprises at least one resin selected from ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, and imide-based resins.

10. The color conversion sheet according to claim 1, wherein the wavelength conversion layer comprises 0.0001 to 10 parts by weight of the organic phosphor per 100 parts by weight of the resin matrix.

11. The color conversion sheet according to claim 1, wherein the resin matrix of the wavelength conversion layer has a glass transition temperature (Tg) of 50°C to 150°C.

12. The color conversion sheet according to claim 1, wherein the change in the luminance L value after 100 hours at a temperature of 60°C is less than 1%.

13. The color conversion sheet according to claim 1, wherein the light absorption layer is positioned in the direction in which light is irradiated onto the wavelength conversion layer.

14. The color conversion sheet according to claim 1, further comprising a polyester first substrate layer located on the other side of the wavelength conversion layer.

15. The color conversion sheet according to claim 14, further comprising a second polyester substrate layer located between the wavelength conversion layer and the light absorption layer, or on the surface of the light absorption layer.

16. A backlight unit including the color conversion sheet described in claim 1.

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