Color conversion sheet and backlight unit comprising same

Abstract

A color conversion sheet according to an embodiment of the present invention comprises: a base layer; and a wavelength conversion layer that is stacked on at least one surface of the base layer and comprises a matrix resin, an organic phosphor, and a wavelength absorbent, and thus the color conversion sheet experiences low color change, has excellent reliability, and can achieve a color gamut DCI of at least 99.5% by adjusting the phosphor emission wavelength. Also provided is a backlight unit comprising the color conversion sheet.

Description

Color conversion sheet and backlight unit including the same

[0001] The present invention relates to a color conversion sheet and a backlight unit including the same, and more specifically, to a color conversion sheet and a backlight unit including the same that can have minimal color change, excellent reliability, and improved color reproduction rate.

[0002] Evolving from past cathode ray tube (CRT) displays, most current display devices take the form of liquid crystal displays (LCDs). In particular, major display devices such as TVs, smartphones, and monitors mostly utilize LCDs. These liquid crystal displays are light-receiving type displays that do not emit light themselves to form images but instead rely on light incident from an external source to create an image. Therefore, a backlight unit (BLU) that emits light is located on the back of the LCD, and the display operates based on the light emitted from this unit.

[0003] Quantum dot technology is being widely applied recently to achieve high image quality in such liquid crystal displays. Quantum dot technology offers the advantage of realizing various colors simply by controlling the size of nano-inorganic particles, as well as excellent stability against light such as UV. However, conventional cadmium (Cd)-based nano-inorganic particles have disadvantages, including environmental issues and reduced cost competitiveness due to their vulnerability to moisture, which necessitates their use in conjunction with barrier films. Consequently, there has been significant development in organic phosphors capable of achieving high color reproduction rates and excellent brightness characteristics without containing cadmium-based nano-inorganic particles.

[0004] In particular, as liquid crystal display devices become increasingly high-performance, there is a growing demand for high color reproduction rates to express colors that are closer to reality, and various studies are being conducted to further improve the color reproduction rates of color conversion sheets using conventional organic phosphors. Currently, when generating a green wavelength with an organic color conversion sheet, a color reproduction rate of DCI 99.1–99.2% is secured when using an RGB configuration with an LED composed of blue and red, but there is a need for even better color reproduction rates.

[0005] The present invention has been devised to solve the aforementioned problems and meet conventional requirements. The objective of the present invention is to provide a color conversion sheet that exhibits minimal color change, excellent reliability, and can further improve the color reproduction rate of conventional organic color conversion sheets, and a backlight unit including the same.

[0006] The above and other objects and advantages of the present invention will become apparent from the following description describing preferred embodiments.

[0007] The above objective is achieved by a color conversion sheet comprising a substrate layer and a wavelength conversion layer laminated on at least one surface of the substrate layer and comprising a matrix resin, an organic phosphor, and a wavelength absorber.

[0008] Preferably, the color conversion sheet may increase the maximum green wavelength by 2 to 4 nm.

[0009] Preferably, the color conversion sheet may further include a transparent layer located on the upper surface of the wavelength conversion layer and a light diffusion layer laminated on the upper surface of the transparent layer to increase light diffusion and light efficiency.

[0010] Preferably, the wavelength absorber may comprise at least one of benzopyrene, benzotriazole, triazine, porphyrine, and phthalocyanine or derivatives thereof.

[0011] Preferably, the maximum absorption wavelength of the wavelength absorber may be 400 to 450 nm.

[0012] Preferably, the wavelength absorber may absorb in the 400 to 450 nm range and transmit at least 80% in the 480 to 600 nm range.

[0013] Preferably, the color conversion sheet may have a DCI of 99.5% or higher.

[0014] Preferably, the matrix resin may comprise at least one selected from ester, olefin, acrylic, ether, urethane, carbonate, and imide resins.

[0015] Preferably, the wavelength conversion layer may comprise 0.1 to 0.4 parts by weight of an organic phosphor and 1 to 3 parts by weight of a wavelength absorber per 100 parts by weight of a matrix resin.

[0016] Preferably, the matrix resin may have an acid value of 0 to 20 mgKOH / g and a hydroxyl value of 0 to 30 mgKOH / g.

[0017] Preferably, the matrix resin 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.

[0018] Preferably, the thickness of the wavelength conversion layer may be 1 to 150 μm.

[0019] Preferably, the transparent layer may comprise at least one selected from polyethylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyetherimide, and polyimide.

[0020] Preferably, the light diffusion layer may comprise at least one selected from polyethylene terephthalate, polyethylene naphtalate, polyacrylate, polycarbonate, polyetherimide, and polyimide.

[0021] Preferably, the color-changing sheet may further include a bead coating layer formed by applying it to the other side of the substrate layer.

[0022] Preferably, the bead composition forming the bead coating layer may comprise an organic binder resin and polymer beads.

[0023] Preferably, the bead composition forming the bead coating layer may comprise 50 to 80 parts by weight of an organic binder, 0.01 to 0.2 parts by weight of polymer beads, and 0.01 to 0.2 parts by weight of a curing agent, based on 100 parts by weight of a solvent.

[0024] Preferably, the polymer beads may comprise at least one or a mixture of two or more selected from PET, nylon, polystyrene (PS), polybutyl methacrylate (PBMA), polymethyl methacrylate (PMMA), and melamine.

[0025] Preferably, the organic binder may comprise at least one selected from acrylic resin, urethane resin, and polyester resin, or a mixture of copolymers thereof.

[0026] In addition, the above objective is achieved by a backlight unit equipped with the color conversion sheet described above.

[0027] According to the color conversion sheet and the backlight unit including the same according to the present invention, there are effects such as low color change, excellent reliability, and the ability to improve color reproduction rate by controlling the phosphor emission wavelength.

[0028] More specifically, the color conversion sheet according to the present invention has the effect of enabling a color reproduction rate DCI of 99.5% or higher by causing a wavelength absorber to absorb a blue region of 400 to 450 nm, thereby preventing an organic phosphor from absorbing a blue region of 400 to 450 nm, and by causing the wavelength absorber to absorb the short wavelength region of the blue region of 400 to 450 nm and pass the long wavelength region, thereby increasing the transmittance of the long wavelength region of the green wavelength, and shifting the green emission wavelength region toward the long wavelength as the maximum green wavelength increases.

[0029] In particular, the color conversion sheet according to the present invention can significantly improve DCI standard color reproduction compared to conventional color conversion sheets, to a level of 99.5% DCI when the maximum green wavelength increases by 2nm (when shifting by 2nm long wavelength) compared to the green wavelength, and to a level of 99.8~99.9% when the maximum green wavelength increases by 4nm (when shifting by 4nm long wavelength).

[0030] However, the effects of the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below.

[0031] FIG. 1 is a cross-sectional view of a color conversion sheet according to one embodiment of the present invention.

[0032] FIG. 2 is a cross-sectional view of a color conversion sheet according to another embodiment of the present invention.

[0033] FIG. 3 is a cross-sectional view of a color conversion sheet according to another embodiment of the present invention.

[0034] FIG. 4 is a schematic diagram of a backlight unit including a color conversion sheet according to one embodiment of the present invention.

[0035] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the present invention. The present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0036] In order to clearly explain the invention in the drawings, parts unrelated to the description have been omitted, and the same reference numerals are assigned to identical or similar components throughout the specification. Additionally, thicknesses have been enlarged in the drawings to clearly represent various layers and regions. Furthermore, where it is stated in this specification that one component is placed "on" or "above" another component, the component may be placed directly on the other component, or there may be components interposed between said components. Conversely, where it is stated that one component is placed "directly" or "on" another component, there may be no interposed components.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. In the event of a conflict, the present specification, including definitions, shall prevail. Additionally, methods and materials similar or equivalent to those described herein may be used in the practice or testing of the present invention, but suitable methods and materials are described herein.

[0038] In this specification, "~-type resin," "~-type polymer," or / and "~-type copolymer" are broad concepts that include all of "~-type resin," "~-type polymer," "~-type copolymer," or / and "derivatives of ~-type resin, polymer, or copolymer." Additionally, in this specification, the term "polymer or copolymer cross-linked with these resins" means "polymer or copolymer cross-linked with the aforementioned resins."

[0039] In this specification, the term “compound” is a broad concept that includes “monatomic molecules,” “oligomers,” and “polymer compounds including homopolymers and copolymers.”

[0040] In this specification, the term "includes" means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0041] In this specification, the term “combination of these” means a mixture or combination with one or more of the described components.

[0042] In this specification, the term “and / or” means any combination and all combinations of one or more items described in relation. In this specification, the term “or” means “and / or.” In this specification, the expressions “at least one” or “one or more” preceding components are to supplement the list of all components and do not mean that they are to supplement the individual components described above.

[0043] Unless otherwise stated in this specification, all percentages, parts, ratios, etc. are based on weight. Also, if an amount, concentration, or other value or parameter is given as a range, a preferred range, or a list of preferred upper and lower limits, it should be understood that this specifically discloses any range formed from any pair of any upper limit or preferred value and any lower limit or preferred value, regardless of whether the range is disclosed separately.

[0044] Where a range of numerical values ​​is mentioned in this specification, unless otherwise stated, the range is intended to include its endpoint and all integers and fractions within the range. The scope of the invention is not intended to be limited to the specific values ​​mentioned when defining the range.

[0045] In this specification, each component is a concept that includes both singular and plural forms.

[0046] FIG. 1 is a cross-sectional view of a color conversion sheet according to one embodiment of the present invention.

[0047] Referring to FIG. 1, a color conversion sheet (100) according to one embodiment of the present invention includes a substrate layer (110) and a wavelength conversion layer (120) laminated on at least one surface of the substrate layer (110). Each component will be described in detail below.

[0048] For example, the substrate layer (110) may be a transparent and flexible polymer film, and may be a polymer film such as polyethylene terephthalate, polyethylene naphtalate, polyacrylate, polycarbonate, polyetherimide, or polyimide, but is not limited thereto, and various polymer films may be applied. In addition, the substrate layer (110) may be an optical film such as a diffusion sheet or a prism sheet, but is not limited thereto, and a sheet having various functions may be applied.

[0049] As an example, the wavelength conversion layer (120) is laminated on at least one surface of the substrate layer (110) and may include a matrix resin, an organic phosphor (121), and a wavelength absorber (122).

[0050] The matrix resin fixes the organic phosphor (121) and wavelength absorber (122) contained in the wavelength conversion layer (120) within the wavelength conversion layer (120) and prevents exposure to moisture or oxygen, thereby preventing the decomposition of the organic phosphor (121) and wavelength absorber (122) dispersed in the wavelength conversion layer (120).

[0051] As an example, the matrix resin preferably comprises at least one selected from ester, olefin, acrylic, ether, urethane, carbonate, and imide resins.

[0052] Ester resins, which are one of the resins that can be used as matrix resins, may include ester resins polymerized from aliphatic polyhydric alcohols and aliphatic or aromatic polyacids. Here, the aliphatic polyhydric alcohol is an aliphatic compound having two or more hydroxyl groups and 2 to 10 carbon atoms, and may include, for example, at least one of ethylene glycol, propanediol, butanediol, neopentyl glycol, and trimethylolpropane. The aliphatic polyacid is an aliphatic compound having two or more carboxylic acid groups and 2 to 12 carbon atoms, and may include, for example, at least one of malonic acid, succinic acid, adipic acid, and sebacic acid. The aromatic polyacid is an aromatic compound having two or more carboxylic acid groups and 1 to 4 aromatic rings, and may include, for example, at least one of isophthalic acid, phthalic acid, terephthalic acid, and cyclohexyldicarboxylic acid. The resin matrix (19) may include at least one of polyester, modified polyester, polyethylene, polycycloolefin, poly(methyl)methacrylate, polyethylene glycol, polyurethane, polycarbonate, polyimide, and block copolymers thereof.

[0053] For example, it is preferable that the matrix resin has 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 matrix resin is less than 1,000 g / mol or the weight average molecular weight is less than 50,000 g / mol, stickiness of the matrix resin may occur, and when the color conversion sheet (100) is wound into a roll, a defect in the film's winding state may occur. Furthermore, if the number average molecular weight is greater than 50,000 g / mol or the weight average molecular weight is greater than 2,000,000 g / mol, the matrix resin has poor solubility in a solvent, making it difficult to form the wavelength conversion layer (120).

[0054] In addition, as an example, it is preferable that the acid value of the matrix resin be 0 to 20 mgKOH / g. Also, it is preferable that the hydroxyl value of the matrix resin be 0 to 30 mgKOH / g, and more preferable that it be 0 to 20 mgKOH / g. This is because ester, olefin, acryl, ether, urethane, carbonate, and imide resins that can be applied as the matrix resin of the wavelength conversion layer (120) included in the color conversion sheet (100) can accelerate the decomposition of the organic phosphor (121) in which functional groups such as hydroxyl groups or carboxylic acid groups present in these resins are dispersed within the matrix resin, thereby reducing the reliability of the organic phosphor.

[0055] Additionally, the wavelength conversion layer (120) may further include a crosslinking agent for chemical crosslinking of the matrix resin as needed. The crosslinking agent may include isocyanate-based, amine-based, acid anhydride-based, thiol-based, epoxy-based crosslinking agents, but is not limited thereto and may include various crosslinking agents as needed.

[0056] Additionally, the wavelength conversion layer (120) includes an organic phosphor (121) dispersed in a matrix resin, and it is preferable that the organic phosphor (121) includes either one or both of a green organic phosphor and a red organic phosphor. At this time, the wavelength conversion layer (120) may have a structure in which one wavelength conversion layer (120) includes only one organic phosphor among a green organic phosphor or a red organic phosphor, or a structure in which a green organic phosphor and a red organic phosphor are included simultaneously, or a structure in which a wavelength conversion layer including a green organic phosphor and a wavelength conversion layer including a red organic phosphor are separated to have two different wavelength conversion layers.

[0057] For example, the wavelength conversion layer (120) preferably contains 0.1 to 0.4 parts by weight of an organic phosphor per 100 parts by weight of a matrix resin. This is because if the content of the organic phosphor (121) is less than 0.1 parts by weight, the color conversion effect to the desired color through the color conversion sheet is insufficient, and if it exceeds 0.4 parts by weight, a quenching phenomenon may occur due to interactions such as aggregation of the organic phosphor (121).

[0058] The green organic phosphor dispersed in the matrix resin of the wavelength conversion layer (120) can absorb blue light and emit green light. Such green organic phosphors include compounds having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, perylene, fluoranthene, fluorene, indene, or their derivatives (e.g., 2-(benzothiazole-2-yl)-9,10-diphenylanthracene or 5,6,11,12-tetraphenylnaphthacene, etc.), 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, naphthiridine, quinoxaline, pyrrolopyridine, thioxantene, or their derivatives, boran derivatives, distyrylbenzene derivatives, Aminostyryl derivatives such as 4,4'-bis(2-(4-diphenylaminophenyl)ethenyl)biphenyl and 4,4'-bis(N-(stilbene-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)quinorizino[9,9a,1-gh]coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and triazole, and their metal complexes, and aromatic amines represented by N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine. It may include derivatives, etc.

[0059] In addition, the green organic fluorescent material (15) preferably comprises a compound represented by the following chemical formula 1.

[0060] [Chemical Formula 1]

[0061]

[0062] A red organic phosphor dispersed in the matrix resin of the wavelength conversion layer (120) can absorb blue light or green light and emit red light. Red organic phosphors are compounds having a condensed aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, perylene, fluoranthene, fluorene, indene, or their derivatives (e.g., 2-(benzothiazole-2-yl)-9,10-diphenylanthracene or 5,6,11,12-tetraphenylnaphthacene, etc.), 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, naphthiridine, quinoxaline, pyrrolopyridine, thioxantene, or their derivatives, boran derivatives, distyrylbenzene derivatives, etc. Aminostyryl derivatives such as 4,4'-bis(2-(4-diphenylaminophenyl)ethenyl)biphenyl and 4,4'-bis(N-(stilbene-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)quinorizino[9,9a,1-gh]coumarin, azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and 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, etc. It can be included.

[0063] In addition, the red organic fluorescent material may include a compound represented by the following chemical formula 2.

[0064] [Chemical Formula 2]

[0065]

[0066] The maximum absorption wavelength of the wavelength absorber (122) dispersed in the matrix resin of the wavelength conversion layer (120) is 400 to 450 nm, and it is desirable to absorb more than 95% of the short wavelength portion of the 400 to 450 nm region of blue light and transmit more than 80% of the 480 to 600 nm region. Since the wavelength of 400 to 450 nm does not affect light emission, it is desirable to remove it as much as possible. Since the wavelength of 480 to 600 nm is the region that has the greatest effect on brightness, it is advantageous as the amount of transmission increases. Therefore, if the wavelength absorber (122) does not absorb more than 95% of the 400 to 450 nm wavelength, the effect of improving color reproduction rate is insufficient, and if it transmits less than 80% of the 480 to 600 nm wavelength, it has a problem of low brightness.

[0067] The color conversion sheet (100) according to the present invention can increase the maximum green wavelength by 2 to 4 nm compared to a conventional color conversion sheet by achieving the absorption and transmittance as described above through a wavelength absorber. In this way, the color conversion sheet (100) according to the present invention can achieve a DCI (Digital Cinema Initiatives)-P3 measurement result of 99.5% or higher by increasing the maximum green wavelength by 2 to 4 nm, and in particular, when the maximum green wavelength is increased by 2 nm, the DCI-P3 measurement result is 99.5% or higher, and when the maximum green wavelength is increased by 4 nm, the DCI-P3 measurement result is 99.8~99.9%. If the maximum green wavelength increases to less than 2 nm, the DCI standard of 99.5% or more is not achieved, and the color reproduction rate decreases. If it increases to more than 4 nm, the DCI standard does not increase further even with the increase in the maximum green wavelength, resulting in unnecessary waste of the wavelength absorber and, in addition, the physical properties of the wavelength conversion layer (120) may deteriorate due to the excessive wavelength absorber.

[0068] As an example, the wavelength absorber (122) preferably comprises at least one of benzopyrene, benzotriazole, triazine, porphyrine and phthalocyanine or derivatives thereof.

[0069] For example, the wavelength conversion layer (120) preferably contains 1 to 3 parts by weight of a wavelength absorber (122) per 100 parts by weight of matrix resin, and more preferably contains 1 to 2 parts by weight. This is because if the wavelength absorber (122) is contained in an amount less than 1 part by weight, the wavelength absorption effect of the blue light short wavelength portion (400~450 nm) is insufficient, and if it is contained in an amount exceeding 3 parts by weight, a problem occurs in which the brightness is significantly reduced due to excessive wavelength absorption.

[0070] For example, the thickness of the wavelength conversion layer (120) is preferably 1 to 150 μm, and more preferably 5 to 100 μm. This is because if the thickness of the wavelength conversion layer (120) is less than 1 μm, the coating surface is too thin and an uncoated surface may occur on the film, and if it exceeds 150 μm, it has the problem of being difficult to evaporate all the solvent contained in the wavelength conversion layer (120). Since the solvent contained in the wavelength conversion layer affects the optical reliability performance of the color conversion sheet, it is desirable to remove it as much as possible.

[0071] In FIG. 1, the substrate layer (110) is located only on one side of the wavelength conversion layer (120), but if necessary, an additional substrate layer may be included on the other side that is in contact with the outside of the wavelength conversion layer (120).

[0072] FIG. 2 is a cross-sectional view of a color conversion sheet according to another embodiment of the present invention.

[0073] Referring to FIGS. 1 and 2, a color conversion sheet (200) according to another embodiment of the present invention comprises a substrate layer (110) and a wavelength conversion layer (120) laminated on one side of the substrate layer (110), and further comprises a transparent layer (130) located on the upper side of the wavelength conversion layer (120) and a light diffusion layer (140) laminated on the upper side of the transparent layer to increase light diffusion and light efficiency, and may further comprise a bead coating layer (150) formed by applying it to the other side of the substrate layer (110) (a surface where the wavelength conversion layer is not formed). The substrate layer (110) and the wavelength conversion layer (120) of FIG. 2 have the same configuration as those of FIG. 1, and redundant descriptions are omitted.

[0074] The transparent layer (130) is laminated on the upper surface of the wavelength conversion layer (120) and is located between the wavelength conversion layer (120) and the light diffusion layer (140). The transparent layer (130) is a transparent and flexible polymer film, preferably comprising a thermoplastic resin, a thermosetting resin, and a UV-curable resin having a visible light transmittance of 70% or more, and more preferably a polymer film comprising at least one selected from polyethylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyetherimide, and polyimide.

[0075] For example, the thickness of the transparent layer (130) is preferably 0.1 to 200 μm, and more preferably 1 to 50 μm. This is because if the thickness of the transparent layer (130) is less than 0.1 μm, it is difficult to control the color change that may occur due to the diffusion or mixing of the organic phosphor (121) or matrix resin according to temperature, and if it is more than 200 μm, the transmission of light may be inhibited.

[0076] In the present invention, it is preferable that the adhesive force between the transparent layer (130) and the wavelength conversion layer (120) of the color conversion sheet (200) be 600 gf / inch or more. This is because if the adhesive force between the transparent layer (130) and the wavelength conversion layer (120) is less than 600 gf / inch, it may be difficult to fix the backlight unit configuration of the color conversion sheet (200).

[0077] In a color conversion sheet (200) according to another embodiment of the present invention, the wavelength conversion layer (120) and the transparent layer (130) have different refractive indices. For example, when the light finally emitted for incident light comes out through the wavelength conversion layer (120), the refractive index of the transparent layer (130) is greater than the refractive index of the wavelength conversion layer (120), and conversely, when the light finally emitted for incident light comes out through the wavelength conversion layer (120), the refractive index of the transparent layer (130) is greater than that of the wavelength conversion layer (120). That is, in the color conversion sheet (200) according to an embodiment of the present invention, it is preferable that the refractive index of the transparent layer (130) is greater than the refractive index of the wavelength conversion layer (120). This is because the light reflectivity of the transparent layer (130) is increased, allowing the finally color-converted light to be effectively emitted to the outside.

[0078] The light diffusion layer (140) is laminated on the upper surface of the transparent layer (130) and performs the role of increasing light diffusion and light efficiency. It is preferable that such a light diffusion layer (140) be a transparent and flexible polymer film, and it is preferable that it include at least one selected from polyethylene terephthalate, polyethylene naphtalate, polyacrylate, polycarbonate, polyetherimide, and polyimide. In addition, the light diffusion layer (140) may be an optical film such as a diffusion sheet or a prism sheet, but is not limited thereto, and a sheet having various functions may be applied.

[0079] It is preferable that the color conversion sheet according to the present invention described above has a DCI (Digital Cinema Initiatives)-P3 measurement result of 99.5% or higher when the maximum green wavelength increases by 2 nm compared to the green wavelength (when shifting by 2 nm longer wavelength), and a DCI (Digital Cinema Initiatives)-P3 measurement result of 99.8% to 99.9% when the maximum green wavelength increases by 4 nm compared to the green wavelength (when shifting by 4 nm longer wavelength). If the DCI-P3 measurement result of the color conversion sheet is less than 99.5%, the color reproduction rate of the color conversion sheet decreases.

[0080] The bead coating layer (150) is formed by applying a bead composition to the surface where the wavelength conversion layer (120) is not formed, i.e., the other side of the substrate layer (110), so as to prevent different color conversion sheets from sticking together due to static electricity generated between them when stacked, and thus not easily separating. The bead composition includes an organic binder resin and polymer beads, and may further include any curing agent.

[0081] The bead coating layer (150) is formed by coating a bead composition obtained by dispersing polymer beads, an organic binder resin, and an optional curing agent in an organic solvent onto another surface of the substrate layer (110), drying it, and then curing it by heat or UV. At this time, the stacking order of the bead coating layer (150) can be either before or after the formation of other functional layers.

[0082] In the present invention, the bead composition constituting the bead coating layer (150) preferably comprises 50 to 80 parts by weight of an organic binder resin, 0.01 to 0.2 parts by weight of polymer beads, and 0.01 to 0.2 parts by weight of a curing agent, based on 100 parts by weight of a solvent. In particular, the bead composition facilitates assembly with a light guide plate by a mixed resin between the organic binder resin and the polymer beads, thereby providing processability characteristics; it is preferable to include 0.1 to 0.3 parts by weight of polymer beads based on 100 parts by weight of the organic binder resin. At this time, if the polymer beads are contained in an amount less than 0.1 parts by weight based on 100 parts by weight of the organic binder resin in the bead composition, the ease of assembly with the light guide plate decreases, and if they are contained in an excessive amount exceeding 0.3 parts by weight, particle dispersion becomes difficult and it is difficult for the organic binder resin to sufficiently cover the polymer beads to form a single layer coating; therefore, it is preferable to keep the composition within the above range.

[0083] As an example, it is preferable that the organic binder resin included in the bead composition comprises a polymer main chain that includes at least one selected from acrylic resin, urethane resin, and polyester resin, or a mixture of copolymers thereof.

[0084] As an example, the polymer beads included in the bead composition preferably comprise at least one or a mixture of two or more selected from polyethylene terephthalate (PET), nylon, polystyrene (PS), polybutyl methacrylate (PBMA), polymethyl methacrylate (PMMA), and melamine.

[0085] For example, the polymer beads included in the bead composition preferably have an average particle size of 0.5 to 10 μm, and more preferably 4 to 8 μm. If the average particle size of the polymer beads is less than 0.5 μm, the polymer beads are not easily dispersed, and if the average particle size is greater than 10 μm, the particles may protrude outside the bead coating layer (150) and fall off.

[0086] As an example, the curing agent included in the bead composition is an additive for forming the bead coating layer (150), and it is preferable to select and use a curing agent that can be applied to acrylic resin, urethane resin, and polyester resin. In addition, it is preferable that the bead composition contains 0.01 to 0.2 parts by weight of curing agent per 100 parts by weight of solvent. If the content of the curing agent in the bead composition is less than 0.01 parts by weight, the organic binder resin is not sufficiently cured, so the adhesion between the bead coating layer (150) and the substrate layer (110) is reduced, and if it exceeds 0.2 parts by weight, there is a problem that the miscibility of the bead composition is reduced.

[0087] For example, the thickness of the bead coating layer (150) is preferably 2 to 7 μm, and more preferably 3 to 5 μm. If the thickness of the bead coating layer is less than 2 μm, the polymer beads may not be sufficiently covered by the organic binder resin, so particles may protrude or not be coated uniformly, and if the thickness exceeds 7 μm, the ease of processing increases, but the thickness of the bead coating layer becomes excessively thick, which is disadvantageous for thinning the color-changing sheet.

[0088] FIG. 3 is a cross-sectional view of a color conversion sheet according to another embodiment of the present invention.

[0089] Referring to FIGS. 1 to 3, the color conversion sheet (100, 200) shown in FIGS. 1 and 2 comprises a single wavelength conversion layer (120) containing an organic phosphor (121) and a wavelength absorber (122). However, the color conversion sheet (300) according to another embodiment of the present invention shown in FIG. 3 has a structure in which a green organic phosphor (312) and a red organic phosphor (313) are separated and located in a separate first wavelength conversion layer (310) and a second wavelength conversion layer (320), respectively. The detailed configuration of such a color conversion sheet (300) will be described below. However, redundant descriptions regarding configurations and structures identical to those of the color conversion sheets (100, 200) in FIGS. 1 and 2 have been omitted.

[0090] The color conversion sheet (300) illustrated in FIG. 3 has a first wavelength conversion layer (310), a transparent layer (130), and a second wavelength conversion layer (320) sequentially laminated on one side of a substrate layer (110), a light diffusion layer (140) may be laminated on the uppermost part of the second wavelength conversion layer (320), and a bead coating layer (150) may be formed on the other side of the substrate layer (110).

[0091] The first wavelength conversion layer (310) comprises a matrix resin, a wavelength absorber (311), and a green organic phosphor (312), and the second wavelength conversion layer (320) comprises a matrix resin and a red organic phosphor (313).

[0092] It is preferable that the wavelength absorber (311) dispersed in the matrix resin of the first wavelength conversion layer (310) absorbs a wavelength range of 400 to 450 nm and transmits at least 80% of the range of 480 to 600 nm. The color conversion sheet according to the present invention achieves a DCI (Digital Cinema Initiatives)-P3 measurement result of 99.5% or higher when shifting the maximum green wavelength by 2 nm (when the maximum green wavelength is increased by 2 nm) by increasing the maximum green wavelength. By using the wavelength absorber (311) together with the first wavelength conversion layer (310) containing the green organic phosphor (312), the distance between the green organic phosphor (312) and the wavelength absorber (311) is reduced, thereby increasing the efficiency of the wavelength absorber (311) and improving color reproduction.

[0093] The first wavelength conversion layer (310) preferably comprises 1 to 3 parts by weight of a wavelength absorber (311) and 0.1 to 0.4 parts by weight of a green organic phosphor (312) per 100 parts by weight of a matrix resin. The second wavelength conversion layer (320) preferably comprises 0.1 to 0.4 parts by weight of a red organic phosphor (313) per 100 parts by weight of a matrix resin.

[0094] At this time, the closer the red organic phosphor (313) is to the green organic phosphor (312), the easier it is to absorb green light, and thus the red light emission efficiency can be increased. Therefore, even in a color conversion sheet containing the same amount of organic phosphor, it is possible to implement various white lights by adjusting the distance between these organic phosphors (312, 313). Here, when the green organic phosphor (312) and the red organic phosphor (313) are included together in a matrix resin composed of one layer, the distance between the green organic phosphor (312) and the red organic phosphor (313) may change relatively significantly due to the influence of the surrounding environment, such as a high temperature or high humidity environment, while the distance between them is relatively close. This can change the emission efficiency of the red organic phosphor (313), which can ultimately change the color coordinates of the white light that can be converted by the color conversion sheet or reduce reliability. Meanwhile, when a matrix resin layer containing a green organic phosphor (312) and a matrix resin layer containing a red organic phosphor (313) are in contact with each other to form multiple layers, the green or red organic phosphor present at the interface of each layer may diffuse to the interface of another layer over time, and as a result, the distance between the red organic phosphor (313) and the green organic phosphor (312) becomes closer, causing the luminescence efficiency of the red organic phosphor (313) to change, which may change the color coordinates of the white light or reduce reliability.

[0095] Accordingly, in the present invention, as shown in FIG. 3, the color conversion sheet (300) completely separates the first and second wavelength conversion layers (310, 320) by placing a transparent layer (130) between the first wavelength conversion layer (310) containing a green organic phosphor (312) and the second wavelength conversion layer (320) containing a red organic phosphor (313), thereby maintaining a constant distance between the green organic phosphor (312) and the red organic phosphor (313), so that the luminescence efficiency of the red organic phosphor (313) can be maintained at a constant level, and accordingly, the degradation of the color coordinates and reliability of the white light emitted by the color conversion sheet (300) can be prevented. That is, the color conversion sheet (300) illustrated in FIG. 3 can have a technical effect of achieving high color uniformity and uniform brightness even in high temperature and high humidity environments by preventing the green and red organic phosphors (312, 313) contained in the first and second wavelength conversion layers (310, 320) and the resin matrix from diffusing or mixing with each other by placing a transparent layer (130) between the first wavelength conversion layer (310) and the second wavelength conversion layer (320).

[0096] For example, the thickness of the first wavelength conversion layer (310) comprising a wavelength absorber (311) and a green organic phosphor (312) is preferably 1 to 150 μm, and more preferably 5 to 100 μm. And the thickness of the second wavelength conversion layer (320) comprising a red organic phosphor (313) is preferably 1 to 150 μm, and more preferably 1 to 100 μm.

[0097] In the present invention, it is preferable that the first wavelength conversion layer (310), the second wavelength conversion layer (320), and the transparent layer (130) of the color conversion sheet (300) have different refractive indices. When the light finally emitted for incident light comes out through the first wavelength conversion layer (310), it is preferable that the refractive index of the transparent layer (130) is greater than the refractive index of the first wavelength conversion layer (310), and conversely, when the light finally emitted for incident light comes out through the second wavelength conversion layer (320), it is preferable that the refractive index of the transparent layer (130) is greater than the refractive index of the second wavelength conversion layer (320). For example, in the case of the color conversion sheet (300) shown in FIG. 3, when applied to the backlight unit of FIG. 4, incident light is irradiated from the direction of the first wavelength conversion layer (310) and emitted through the second wavelength conversion layer (320). Therefore, it is preferable that the refractive index of the second wavelength conversion layer (320) is smaller than the refractive index of the transparent layer (130), and it is preferable that the refractive index of the first wavelength conversion layer (310) is smaller than the refractive index of the transparent layer (130). This is because the light reflectivity of the transparent layer (130) is increased so that the finally color-converted light can be effectively emitted to the outside.

[0098] FIG. 4 is a schematic diagram of a backlight unit including a color conversion sheet according to an embodiment of the present invention. Next, a backlight unit (900) including a color conversion sheet according to an embodiment of the present invention will be described with reference to FIG. 4, which is a schematic diagram of a backlight unit including a color conversion sheet according to an embodiment of the present invention.

[0099] Referring to FIGS. 1 to 4, a backlight unit (400) according to one embodiment of the present invention may include a light source (410), a reflector (420) capable of reflecting light emitted from the light source (410) to increase light efficiency, a light guide plate (430) positioned above the reflector (420) and serving to evenly spread the light emitted from the light source (410), and a color conversion sheet (440) positioned above the light guide plate (430). Here, the color conversion sheet (440) is the same color conversion sheet as described in the embodiment shown in FIGS. 1 to 3 above, so a redundant description is omitted. Additionally, at least one optical sheet, such as a diffusion sheet, a prism sheet, a brightness enhancement film (DBEF), etc., may be further included on the upper part of the color conversion sheet.

[0100] The color conversion sheet according to the present invention described above has the effect of enabling a color reproduction rate DCI of 99.5% or higher by causing a wavelength absorber to absorb a blue region of 400 to 450 nm, thereby preventing an organic phosphor from absorbing a blue region of 400 to 450 nm, and by causing the wavelength absorber to absorb the short wavelength region of the blue region of 400 to 450 nm and pass the long wavelength region, thereby increasing the transmittance of the long wavelength region of the green wavelength, and shifting the green emission wavelength region toward the long wavelength as the maximum green wavelength increases.

[0101] In particular, the color conversion sheet according to the present invention can significantly improve DCI standard color reproduction compared to conventional color conversion sheets, to a level of 99.5% DCI when shifted by 2 nm longer wavelength than the green wavelength (when the maximum value of the green wavelength peak increases by 2 nm), and to a level of 99.8~99.9% when shifted by 4 nm longer wavelength than the green wavelength (when the maximum value of the green wavelength peak increases by 4 nm).

[0102] Hereinafter, the structure of the present invention and the resulting effects will be explained in more detail through examples and comparative examples. However, these examples are intended to explain the present invention more specifically, and the scope of the present invention is not limited to these examples.

[0103] [Example]

[0104] [Example 1]

[0105] Step 1: Formation of wavelength conversion layer

[0106] An organic phosphor solution was prepared by dissolving a green organic phosphor according to Chemical Formula 1, a red organic phosphor according to Chemical Formula 2, and a benzopyrene-based wavelength absorber (Coumarin 1, Sigma Aldrich) in ethyl acetate. A polyester resin (Toyobo, Vylon 630) was mixed with the prepared organic phosphor solution, and ethyl acetate was added to achieve a viscosity of 150 cps. The mixture was then stirred at 150 rpm for 30 minutes to prepare a wavelength conversion layer composition. At this time, the composition was set so that 0.34 parts by weight of the green organic phosphor and 0.0034 parts by weight of the red organic phosphor were used per 100 parts by weight of the polyester resin solid content, and the wavelength absorber was set to 1 part by weight.

[0107] Next, the prepared wavelength conversion layer composition was bar-coated onto the upper surface of a polyethylene terephthalate film (TAK, XG7PH8), and then dried at 170°C for 4 minutes to form a wavelength conversion layer with a thickness of 10 μm after drying.

[0108] Step 2: Formation of transparent layer and light-diffusing layer

[0109] Next, 80 parts by weight of toluene were added to 100 parts by weight of silicone resin (DOW, 7904) and stirred for 2 hours. Afterward, 0.05 parts by weight of platinum catalyst (DOW, SYL-OFF 4000 CATALYST) were added and stirred for an additional 30 minutes to prepare a transparent layer composition. Then, the transparent layer composition prepared as above was applied to the opposite side of the diffusion layer of a diffusion film (TFN, TDV10F) and dried at 170°C for 2 minutes to form a transparent layer with a thickness of 24 μm after drying.

[0110] Step 3: Manufacturing Color-Changing Sheets

[0111] Next, the wavelength conversion layer and the transparent layer manufactured as described above were laminated so that they were in contact with each other, and then a color conversion sheet was manufactured using roller lamination (GMP, EXCELAM II-355Q).

[0112] [Example 2]

[0113] A color-changing sheet was prepared in the same manner as in Example 1, except that for 100 parts by weight of the polyester resin solid content, 0.72 parts by weight of green organic phosphor and 0.0072 parts by weight of red organic phosphor, and 3 parts by weight of wavelength absorber were used.

[0114] [Comparative Example]

[0115] [Comparative Example 1]

[0116] A color-changing sheet was prepared in the same manner as in Example 1, except that 0.24 parts by weight of green organic phosphor and 0.0024 parts by weight of red organic phosphor were added to 100 parts by weight of polyester resin solids, and no wavelength absorber was used.

[0117] [Comparative Example 2]

[0118] A color-changing sheet was prepared in the same manner as in Example 1, except that the wavelength absorber was 0.1 parts by weight for every 100 parts by weight of the polyester resin solid content in Example 1.

[0119] [Comparative Example 3]

[0120] A color-changing sheet was prepared in the same manner as in Example 1, except that the wavelength absorber was 5 parts by weight for every 100 parts by weight of the polyester resin solid content in Example 1.

[0121] Physical properties were measured through the following experimental examples using the color conversion sheets according to Examples 1 and 2 and Comparative Examples 1 to 3, and the results are shown in Table 1 below.

[0122] [Experimental Example]

[0123] (1) Measurement of luminance and color coordinates

[0124] The color coordinate (x, y) values ​​of the color conversion sheets according to the examples and comparative examples were measured using a spectroradiometer (KONICA MINOLTA, CA-S20W).

[0125] (2) DCI standard measurement

[0126] Through Experimental Example 1 described above, the wavelength and intensity of the peaks of the Red, Green, and Blue spectra were measured, and based on this, the area (region) covered in the color coordinates (color reproduction rate) capable of expressing RGB relative to the DCI-P3 standard was calculated to determine the DCI color reproduction rate for the three primary colors. Here, the DCI color reproduction rate is expressed as the ratio (%) of the relative area when the DCI color coordinate area is assumed to be 100.

[0127] The experimental results performed on the color conversion sheet according to the above-described experimental example are as shown in Table 1 below.

[0128] DCI (%) Luminance (Lv) Color Coordinate x Color Coordinate y Green Maximum Wavelength (nm) Example 1 99.5 26 800.1 780.1 38525 Example 2 99.7 223 40.1 64 0.1 3527 Comparative Example 1 98.9 244 70.1 700.1 20523 Comparative Example 2 98.9 243 10.1 700.1 19523 Comparative Example 3 97.4 194 50.1 550.09 4528

[0129] As shown in Table 1, it can be seen that Examples 1 and 2, which satisfy the composition of the present invention, have a maximum green wavelength increased by 2 to 4 nm compared to Comparative Examples 1 and 2, and have a DCI specification of 99.5% or higher. In particular, it can be seen that Example 1 has a maximum green wavelength of 525 nm, which is an increase of 2 nm compared to Comparative Example 1, and has a DCI specification of 99.5%, and Example 2 has a maximum green wavelength of 527 nm, which is an increase of 4 nm compared to Comparative Example 1, and has a DCI specification of 99.7%.

[0130] Meanwhile, Comparative Example 1, which does not use a wavelength absorber, has high brightness but a maximum green wavelength of 523 nm and does not satisfy the DCI standard of 98.9% or higher, so it can be confirmed that the color reproduction rate is lower compared to Examples 1 and 2.

[0131] In addition, Comparative Example 2, which has insufficient content of wavelength absorber, also has a maximum green wavelength of 523 nm, which is the same as Comparative Example 1, and does not satisfy the DCI standard of 99.5% or higher, so it can be confirmed that the color reproduction rate is lower compared to Examples 1 and 2.

[0132] In addition, Comparative Example 3, which has an excessive amount of wavelength absorber, showed an increase in the maximum green wavelength but a significant decrease in brightness, failing to satisfy the DCI standard of 99.5% or higher, and thus it can be confirmed that the color reproduction rate is significantly lower compared to Examples 1 and 2.

[0133]

[0134] Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims also fall within the scope of the present invention.

Claims

1. Substrate layer; and A wavelength conversion layer laminated on at least one surface of a substrate layer and comprising a matrix resin, an organic phosphor, and a wavelength absorber; A color conversion sheet including 2. In Paragraph 1, A color conversion sheet that increases the maximum green wavelength by 2 to 4 nm.

3. In Paragraph 1, A transparent layer located on the upper surface of the wavelength conversion layer; and A light-diffusing layer laminated on the upper surface of a transparent layer, which increases light diffusion and light efficiency; A color conversion sheet that further includes 4. In Paragraph 1, A color conversion sheet having a maximum absorption wavelength of 400 to 450 nm for the wavelength absorber.

5. In Paragraph 1, A color-changing sheet in which the wavelength absorber absorbs in the 400 to 450 nm range and transmits 80% or more of the 480 to 600 nm range.

6. In Paragraph 1, The color conversion sheet is a color conversion sheet with a DCI of 99.5% or higher.

7. In Paragraph 1, A color-changing sheet comprising at least one of benzopyrene, benzotriazole, triazine, porphyrine, and phthalocyanine or derivatives thereof, wherein the wavelength absorber is benzopyrene, benzotriazole, triazine, porphyrine, and phthalocyanine.

8. In Paragraph 1, A color-changing sheet comprising at least one selected from ester, olefin, acrylic, ether, urethane, carbonate, and imide resins, wherein the matrix resin.

9. In Paragraph 1, A color conversion sheet comprising a wavelength conversion layer containing 0.1 to 0.4 parts by weight of an organic phosphor and 1 to 3 parts by weight of a wavelength absorber per 100 parts by weight of a matrix resin.

10. In Paragraph 1, A color-changing sheet in which the matrix resin has an acid value of 0 to 20 mgKOH / g and a hydroxyl value of 0 to 30 mgKOH / g.

11. In Paragraph 1, A color-changing sheet in which the matrix resin has 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.

12. In Paragraph 1, A color conversion sheet having a wavelength conversion layer thickness of 1 to 150 μm.

13. In Paragraph 3, A color-changing sheet comprising at least one selected from polyethylene terephthalate, polyethylene naphthalate, polyacrylate, polycarbonate, polyetherimide, and polyimide, wherein the transparent layer comprises at least one.

14. In Paragraph 3, A color-changing sheet comprising at least one selected from polyethylene terephthalate, polyethylene naphtalate, polyacrylate, polycarbonate, polyetherimide, and polyimide, wherein the light-diffusing layer comprises at least one.

15. In Paragraph 1, A bead coating layer formed by applying it to the other side of the substrate layer; A color conversion sheet that further includes 16. In Paragraph 15, A color-changing sheet in which a bead composition forming a bead coating layer comprises an organic binder resin and polymer beads.

17. In Paragraph 16, A color-changing sheet comprising, with respect to 100 parts by weight of solvent, a bead composition forming a bead coating layer, 50 to 80 parts by weight of an organic binder, 0.01 to 0.2 parts by weight of polymer beads, and 0.01 to 0.2 parts by weight of a curing agent.

18. In Paragraph 16, A color-changing sheet comprising at least one or a mixture of two or more polymer beads selected from PET, nylon, polystyrene (PS), polybutyl methacrylate (PBMA), polymethyl methacrylate (PMMA), and melamine.

19. In Paragraph 16, A color-changing sheet comprising an organic binder selected from at least one of acrylic resin, urethane resin, and polyester resin, or a mixture of copolymers thereof.

20. A backlight unit equipped with a color conversion sheet according to paragraph 1.

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