Color conversion sheet and backlight unit including the same

Abstract

The color conversion sheet of the present invention includes a first wavelength conversion layer in which an organic phosphor is dispersed in a resin matrix, a first phosphor diffusion prevention layer located on one side of the first wavelength conversion layer, and an adhesive layer located on one side of the first phosphor diffusion prevention layer, and the first phosphor diffusion prevention layer has a Hildebrand solubility parameter that satisfies a predetermined relationship between the Hildebrand solubility parameter of the resin matrix of the first wavelength conversion layer and the Hildebrand solubility parameter of the solvent contained in the first phosphor diffusion prevention layer, thereby solving problems of changes in luminance characteristics and color changes.

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 specifically to a color conversion sheet that prevents deterioration of the organic phosphor, has little color change, and has excellent brightness reliability, and a backlight unit including the same. [Background technology]

[0002] Conventional liquid crystal displays (LCDs) are non-emissive display devices that do not emit light themselves but receive external light to form images, and require a backlight unit (BLU) to emit light from the rear surface. Recently, quantum dot technology has been widely used to realize high image quality in LCDs. This quantum dot technology has the advantage of being able to realize various colors simply by adjusting the size of nano-inorganic particles, and also has the advantage of being highly stable against light such as UV.

[0003] However, in the case of LCDs using quantum dot technology, conventional cadmium (Cd)-based nano-inorganic particles are used. However, cadmium-based nano-inorganic particles have the disadvantages of being environmentally problematic and being vulnerable to moisture, which means that a barrier film must be used in conjunction with the nano-inorganic particles, limiting the selection of substrates and the ability to combine them with other optical films.

[0004] Therefore, recently, much effort has been made to develop organic phosphors that can achieve high color gamut and excellent brightness characteristics without containing cadmium-based inorganic nanoparticles. Organic phosphors have superior luminous efficiency compared to inorganic nanoparticles used in quantum dot technology, and have the advantage of being able to achieve various luminous characteristics with the same phosphor by changing the surrounding chemicals. Furthermore, organic phosphors are relatively resistant to moisture and do not require the application of a barrier film, which means they can be easily used with various substrates and combined with other optical films.

[0005] However, organic phosphors may be subject to degradation due to chemical or physical reactions with adjacent materials, and the resulting decrease in light durability poses a problem when applying organic phosphors to displays. Therefore, technological development to resolve this issue is urgently needed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2012-0067167 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been devised to solve the problems of the conventional technology as described above, and the problem to be solved by the present invention is to provide a color conversion sheet and a backlight unit including the same, which have excellent color reproduction and brightness characteristics while using environmentally safe organic phosphors by preventing the organic phosphor contained in the wavelength conversion layer from chemically reacting with adjacent layers and spreading to adjacent layers, and which have little color change when irradiated with light not only at room temperature but also in high temperature and high humidity environments, and which have excellent brightness reliability.

[0008] The above and other objects and advantages of the present invention will become more apparent from the following description of the preferred embodiment. [Means for solving the problem]

[0009] The above object can be achieved by a color conversion sheet comprising: a first wavelength conversion layer in which an organic phosphor is dispersed in a resin matrix; a first phosphor diffusion prevention layer located on one side of the first wavelength conversion layer; and an adhesive layer located on one side of the first phosphor diffusion prevention layer, wherein the first phosphor diffusion prevention layer is formed from a composition containing a solvent whose Hildebrand Solubility Parameter satisfies the following Equation 1: (Equation 1) |P1-S2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the first wavelength conversion layer S2: Hildebrand solubility parameter of the solvent contained in the first phosphor diffusion prevention layer.

[0010] Preferably, the first phosphor diffusion preventing layer may further include a thermosetting or thermoplastic organic compound having a Hildebrand Solubility Parameter according to the following Equation 2: (Equation 2) |P1-P2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the first wavelength conversion layer P2: Hildebrand solubility parameter of the organic compound contained in the first phosphor diffusion prevention layer.

[0011] Preferably, the thickness of the first phosphor diffusion prevention layer is 0.01 to 10 μm.

[0012] Preferably, the color conversion sheet can have a change in color coordinates of the x-axis and y-axis within ±0.0015 after being treated at a temperature of 70° C. for 480 hours.

[0013] Preferably, the resin matrix may include at least one resin selected from the group consisting of ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, and imide-based resins.

[0014] Preferably, the resin matrix may have a glass transition temperature of 50 to 140°C.

[0015] Preferably, the organic phosphor of the first wavelength conversion layer is characterized in that it does not dissipate into the phosphor diffusion prevention layer.

[0016] Preferably, the first phosphor diffusion prevention layer has a visible light transmittance of 70% or more.

[0017] Preferably, the optical film may further include a substrate positioned on at least one surface of the first wavelength conversion layer or the adhesive layer.

[0018] Preferably, the optical film may further include a second phosphor diffusion preventing layer located on the adhesive layer, and a second wavelength conversion layer located on the second phosphor diffusion preventing layer and having an organic phosphor dispersed in a resin matrix.

[0019] Preferably, the second wavelength-converting layer may contain an organic phosphor of the same or different hue as the organic phosphor dispersed in the first wavelength-converting layer.

[0020] Preferably, the second phosphor diffusion prevention layer may be formed from a composition containing a solvent whose Hildebrand Solubility Parameter satisfies the following Equation 1: (Equation 1) |P1-S2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer S2: Hildebrand solubility parameter of the solvent contained in the second phosphor diffusion prevention layer.

[0021] Preferably, the second phosphor diffusion preventing layer may further include a thermosetting or thermoplastic organic compound having a Hildebrand Solubility Parameter according to the following Equation 2: (Equation 2) |P1-P2|>2MPa1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer P2: Hildebrand solubility parameter of the organic compound contained in the second phosphor diffusion prevention layer.

[0022] The above object can also be achieved by a backlight unit including the above-mentioned color conversion sheet. [Effects of the Invention]

[0023] As described above, according to the color conversion sheet and the backlight unit including the same according to one embodiment of the present invention, the color conversion sheet further comprises a phosphor diffusion prevention layer on one side of the wavelength conversion layer in which the organic phosphor is dispersed to prevent the organic phosphor from diffusing. This prevents the wavelength conversion layer from being exposed to the outside and the organic phosphor in the wavelength conversion layer from being deteriorated by unnecessary elements such as moisture and oxygen in the air, thereby solving the problem of color coordinate change or reduced reliability.

[0024] In addition, in the color conversion sheet and the backlight unit including the same according to an embodiment of the present invention, the phosphor diffusion preventing layer prevents unnecessary contact with the adhesive layer used to laminate the wavelength conversion layer with various substrate films and / or other wavelength conversion layers, thereby preventing the organic phosphor in the wavelength conversion layer from being deteriorated by the chemical functional groups of the adhesive layer and preventing the organic phosphor in the wavelength conversion layer from spreading to the adhesive layer under high temperature and high temperature / humidity conditions, thereby solving the problems of changes in brightness characteristics and color change.

[0025] In addition, the color conversion sheet according to one embodiment of the present invention and the backlight unit including the same can be combined with optical substrates such as light guide plates, prism sheets, and brightness enhancement films (DBEFs), and can be used with various organic phosphors and various resin matrices, making it possible to omit the need for a barrier film, thereby providing excellent cost competitiveness.

[0026] However, the effects of the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a diagram illustrating the configuration of a color conversion sheet according to an embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating the configuration of a color conversion sheet according to another embodiment of the present invention. [Figure 3] 1 is a diagram illustrating the configuration of a backlight unit including a color conversion sheet according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0028] The present invention may, however, be embodied in many different forms and is not limited to the embodiments set forth herein.

[0029] In the drawings, thicknesses are exaggerated to clearly show multiple layers and regions. Similar parts are designated by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is described as being "on" another part, this includes not only the case where it is "directly on" that other part, but also the case where there is another part between them. In contrast, when a part is described as being "directly on" another part, it means that there is no other part between them.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present specification, including definitions, shall control. In addition, although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described herein.

[0031] Hereinafter, a color conversion sheet according to an embodiment of the present invention will be described in detail with reference to the drawings.

[0032] FIG. 1 is a diagram showing the configuration of a color conversion sheet according to an embodiment of the present invention.

[0033] Referring to FIG. 1, a color conversion sheet 10 according to one embodiment of the present invention includes a wavelength conversion layer 20 in which an organic phosphor is dispersed in a resin matrix, a phosphor diffusion prevention layer 22 located on one side of the wavelength conversion layer 20, and an adhesive layer 24 located on one side of the phosphor diffusion prevention layer 22.

[0034] The phosphor diffusion prevention layer 22 is located between the wavelength conversion layer 20 and the adhesive layer 24, and has the characteristic of preventing the organic phosphor 13 dispersed in the wavelength conversion layer 20 from spreading into the adhesive layer 24. Here, the phosphor diffusion prevention layer 22 not only prevents the organic phosphor 13 in the wavelength conversion layer 20 from being deteriorated by unnecessary elements such as moisture and oxygen in the air when the wavelength conversion layer 20 is exposed to the outside, but also prevents the organic phosphor 13 from being deteriorated by chemical functional groups in other adjacent layers due to unnecessary contact with other adjacent layers, such as the adhesive layer 24.

[0035] That is, the phosphor diffusion preventing layer 22 is present between the wavelength conversion layer 20 and the adhesive layer 24 to prevent degradation of the organic phosphor 13 in the wavelength conversion layer 20 due to chemical functional groups or residual solvents in the adhesive layer 24, and also prevents the organic phosphor 13 that has detached from the interface of the wavelength conversion layer 20 over time in a high-temperature or high-humidity environment from spreading back into the adhesive layer 24, thereby preventing a change in the luminous efficiency of the organic phosphor due to a change in the distance between the organic phosphors. Ultimately, this prevents a change in the color coordinates or a decrease in reliability of the light emitted from the color conversion sheet. Therefore, the color conversion sheet 10 employing the phosphor diffusion preventing layer 22 prevents the organic phosphor 13 in the wavelength conversion layer 20 from spreading to other layers or moving due to interlayer mixing, and maintains a constant distance between the organic phosphors 13, thereby achieving high color uniformity, uniform brightness, and high reliability even in various environments.

[0036] In the color conversion sheet 10 according to an embodiment of the present invention, the phosphor diffusion preventing layer 22 may be formed on one surface of the wavelength conversion layer 20 by coating or printing, but in this case, the phosphor diffusion preventing layer 22 must not affect the wavelength conversion layer 20. That is, it is preferable that the phosphor diffusion preventing layer 22 does not contain a solvent or an organic compound that can dissolve or mix with the wavelength conversion layer 20.

[0037] Therefore, the phosphor diffusion prevention layer 22 is preferably formed from a composition containing a solvent that satisfies the following mathematical formula 1, and in this case, any solvent that satisfies the mathematical formula 1 can be used as the solvent. (Equation 1) |P1-S2|>2MPa 1 / 2 P1: Hildebrand Solubility Parameter (MPa) of the resin matrix of the wavelength conversion layer 1 / 2 ) S2: Hildebrand Solubility Parameter (MPa) of the solvent contained in the phosphor diffusion prevention layer 1 / 2 ) The Hildebrand solubility parameter of Equation 1 can be found using the polymer handbook.

[0038] The difference between the solubility parameter of the resin matrix contained in the wavelength conversion layer 20 and the solubility parameter of the solvent contained in the phosphor diffusion prevention layer 22 is 2 MPa as shown in Equation 1. 1 / 2 It is preferable to exceed 4 MPa. 1 / 2 It is more preferable that the difference between the solubility parameters of these two is 2 MPa or more. 1 / 2 If this is not sufficient, the solvent contained in the phosphor diffusion preventing layer 22 will dissolve the wavelength conversion layer 20, and the organic phosphor 13 in the wavelength conversion layer 20 may diffuse or migrate into the phosphor diffusion preventing layer 22.

[0039] Furthermore, the phosphor diffusion prevention layer 22 is preferably formed from a composition containing a thermosetting or thermoplastic organic compound that satisfies the following formula 2. In this case, the organic compound is preferably at least one of a monomolecular compound, an oligomer, and a resin, and any organic compound that satisfies the formula 2 can be used. (Equation 2) |P1-P2|>2MPa 1 / 2 P1: Hildebrand Solubility Parameter (MPa) of the resin matrix of the wavelength conversion layer 1 / 2 ) P2: Hildebrand Solubility Parameter (MPa) of the organic compound contained in the phosphor diffusion prevention layer 1 / 2 )

[0040] The difference between the solubility parameter of the resin matrix contained in the wavelength conversion layer 20 and the solubility parameter of the organic compound contained in the phosphor diffusion prevention layer 22 is 2 MPa as shown in Equation 2. 1 / 2 It is preferable to exceed 4 MPa. 1 / 2 This is because the difference in solubility parameter between the resin matrix 19 of the wavelength conversion layer 20 and the organic compound of the phosphor diffusion prevention layer 22 is 2 MPa or more. 1 / 2 If the above is not sufficient, the phosphor diffusion preventing layer 22 may mix with the wavelength conversion layer 20 over time in a high temperature or high temperature and humidity environment, or the organic phosphor 13 may detach from the interface of the wavelength conversion layer 20 and diffuse or migrate into the phosphor diffusion preventing layer 22.

[0041] The thickness of the phosphor diffusion prevention layer 22 is preferably 0.01 to 10 μm, more preferably 0.01 to 5 μm, and even more preferably 0.01 to 2 μm. This is because if the thickness of the phosphor diffusion prevention layer 22 is less than 0.01 μm, the function of preventing the diffusion of the organic phosphor 13 in a high temperature or high temperature and humidity environment is reduced, making it difficult to control color changes that may occur due to the diffusion of the organic phosphor 13. On the other hand, if the thickness of the phosphor diffusion prevention layer 22 exceeds 10 μm, the light transmission efficiency may be impaired and poor coating properties may occur due to the difference in solubility between the wavelength conversion layer 20 and the solvent and organic compound of the diffusion prevention layer 22.

[0042] The phosphor diffusion preventing layer 22 preferably has a refractive index different from that of the wavelength conversion layer 20. For example, when the final light emitted from the incident light exits through the wavelength conversion layer 20, the refractive index of the phosphor diffusion preventing layer 22 is preferably greater than that of the wavelength conversion layer 20. This is because the light reflectance of the phosphor diffusion preventing layer 22 can be increased, thereby enabling the final color-converted light to be effectively emitted to the outside.

[0043] In one embodiment, the phosphor diffusion preventing layer 22 does not contain organic phosphor 13 separated from the wavelength conversion layer 20. As described above, in the present invention, the phosphor diffusion preventing layer 22 satisfies Equations 1 and 2, so that the organic phosphor 13 of the wavelength conversion layer 20 is separated into the phosphor diffusion preventing layer 22 or is not diffused, and therefore the phosphor diffusion preventing layer 22 does not contain organic phosphor 13 separated from the wavelength conversion layer 20, thereby providing high optical reliability.

[0044] In one embodiment, it is preferable that the phosphor diffusion preventing layer 22 does not reduce the intensity of light emitted from the organic phosphor 13 in the wavelength conversion layer 20. Therefore, the phosphor diffusion preventing layer 22 preferably has a visible light transmittance of 70% or more, more preferably 80% or more, and even more preferably 90% or more. If the visible light transmittance of the phosphor diffusion preventing layer 22 is less than 70%, the intensity of light emitted by the organic phosphor 13 in the wavelength conversion layer 20 in response to incident light will decrease, and the efficiency of the color conversion sheet will decrease.

[0045] In one embodiment, wavelength-converting layer 20 includes a resin matrix 19 and an organic phosphor 13 dispersed in resin matrix 19 .

[0046] The resin matrix 19 preferably includes at least one of ester, olefin, acrylic, ether, urethane, carbonate, and imide resins.

[0047] The resin matrix 19 fixes the organic phosphor 13 from the wavelength conversion layer 20 and prevents the organic phosphor 13 from being exposed to moisture or oxygen, thereby preventing deterioration of the organic phosphor 13 dispersed in the resin matrix 19.

[0048] The resin contained in the resin matrix 19 preferably has a water-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 water-average molecular weight of the resin contained in the resin matrix 19 is less than 1,000 g / mol or less than 50,000 g / mol, it is difficult to fix the organic phosphor 13, which may cause aggregation of the organic phosphor 13 depending on temperature and a resulting deterioration in optical properties. If the water-average molecular weight exceeds 50,000 g / mol or the weight-average molecular weight exceeds 2,000,000 g / mol, the resin matrix 19 has poor solubility in solvents, which may make it difficult to form the wavelength conversion layer 20.

[0049] The acid value of the resin contained in the resin matrix 19 may be 0 to 15 mgKOH / g, preferably 0 to 10 mgKOH / g. The hydroxyl value of the resin contained in the resin matrix 19 may be 0 to 30 mgKOH / g, preferably 0 to 20 mgKOH / g, and more preferably 0 to 10 mgKOH / g. Generally, ester, olefin, acrylic, ether, urethane, carbonate, and imide resins, which can be used as the resin matrix 19 of the wavelength conversion layer 20 included in the color conversion sheet, contain functional groups, such as hydroxyl or carboxyl groups, that can accelerate the degradation of the organic phosphor 13 dispersed in the resin matrix, thereby reducing the reliability of the organic phosphor 13. Therefore, it is preferable to maintain the acid value and hydroxyl value within the above ranges.

[0050] The resin of the resin matrix 19 may include at least one of polyester, modified polyester, polyethylene, polycycloolefin, poly(methyl)methacrylate, polyethylene glycol, polyurethane, polycarbonate, and polyimide, and may also include a block copolymer form thereof.

[0051] Furthermore, the resin matrix 19 preferably has a glass transition temperature (Tg) of 50 to 140°C, more preferably 60 to 140°C, and most preferably 70 to 140°C. This is because if the glass transition temperature of the resin matrix 19 is less than 50°C, aggregation of the organic phosphors 13 may occur over time in a high temperature or high temperature and humidity environment, resulting in a deterioration of optical properties. If the glass transition temperature exceeds 140°C, the resin generally has high crystallinity and poor solubility in solvents, which may cause the film to curl due to crystallization of the resin when coated on a substrate film and dried.

[0052] In one embodiment, the organic phosphor 13 dispersed in the resin matrix 19 of the wavelength conversion layer 20 is a phosphor that emits excitation light and light of other wavelengths when irradiated with excitation light. The wavelength conversion layer 20 can include a single phosphor, such as a green phosphor or a red phosphor, or can emit light of various colors by combining green and red phosphors depending on the purpose. A single wavelength conversion layer 20 can include multiple organic phosphors 13 of the same color that emit a single color. In this case, the multiple organic phosphors can be made of the same or different materials. For example, the wavelength conversion layer 20 can include only one organic phosphor from multiple green organic phosphors or multiple red organic phosphors to emit light of only one color. Alternatively, when organic phosphors of one color are used in one wavelength conversion layer, two or more wavelength conversion layers 20 can be formed separately, each containing organic phosphors of a different color, to emit light of various colors.

[0053] In another embodiment, two or more organic phosphors 13 of different colors may be mixed together in one wavelength conversion layer 20. In this case, the organic phosphors may be the same or different materials. For example, the wavelength conversion layer 20 may include a mixture of a green organic phosphor and a red organic phosphor.

[0054] Examples of the organic fluorescent substance 13 include compounds having a fused aryl ring such as naphthalene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, phenylene, fluoranthene, fluorene, and indene, or derivatives thereof (for example, 2-(benzothiazol-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, naphthyridine, quinoxaline, pyrrolopyridine, and thioxanthene, or derivatives thereof, borane derivatives, distyrylbenzene derivatives, and 4,4'-bis(2-(4 and aminostyryl derivatives such as (N-(stilben-4-yl)-N-phenylamino)ethenyl)biphenyl and 4,4'-bis(N-(stilben-4-yl)-N-phenylamino)stilbene; aromatic acetylene derivatives, tetraphenylbutadiene derivatives, stilbene derivatives, aldazine derivatives, pyrromethene derivatives, diketopyrrolo[3,4-c]pyrrole derivatives, coumarin derivatives such as 2,3,5,6-1H,4H-tetrahydro-9-(2'-benzothiazolyl)quinolizino[9,9a,1-gh]coumarin; azole derivatives such as imidazole, thiazole, thiadiazole, carbazole, oxazole, oxadiazole, and triazole, and metal complexes thereof; and aromatic amine derivatives typified by N,N'-diphenyl-N,N'-di(3-methylphenyl)-4,4'-diphenyl-1,1'-diamine.

[0055] As the organic phosphor 13 according to an embodiment of the present invention, the green organic phosphor preferably includes a compound represented by the following Chemical Formula 1, and the red organic phosphor preferably includes a compound represented by the following Chemical Formula 2. [ka] [ka]

[0056] The wavelength conversion layer 20 preferably contains 0.0001 to 10 parts by weight of organic phosphor 13 relative to 100 parts by weight of the resin solids content of the resin matrix 19. This is because if the organic phosphor 13 is contained in an amount less than 0.0001 part by weight, the color conversion effect to the desired hue through the color conversion sheet 10 may be insignificant, and if it is contained in an amount exceeding 10 parts by weight, quenching may occur due to interactions such as aggregation of the organic phosphor 13.

[0057] The thickness of the wavelength conversion layer 20 containing the organic phosphor 13 dispersed in the resin matrix 19 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 20 exceeds 150 μm, it is difficult to sufficiently remove the solvent, and various solvents remaining in the wavelength conversion layer 20 may cause deterioration of the organic phosphor 13.

[0058] In one embodiment, a substrate 17 may be further included on at least one surface of the wavelength conversion layer 20 and the adhesive layer 24 that contacts the outside, if necessary. That is, a substrate 17 may be further included on one surface of the wavelength conversion layer 20 on which the adhesive layer 24 is not formed and / or on one surface of the adhesive layer 24 on which the wavelength conversion layer 20 is not formed. For example, as shown in FIG. 1 , a first substrate 17a may be positioned on the surface of the wavelength conversion layer 20, and a second substrate 17b may be positioned on the surface of the adhesive layer 24 to protect and support the color conversion sheet from the outside.

[0059] The substrate 17 may be a transparent and flexible polymer film, such as polyethylene terephthalate, polyethylene naphtalate, polyacrylate, polycarbonate, polyetherimide, polyimide, or the like, but is not limited thereto, and various polymer films may be employed.

[0060] Here, the substrate 17 may be a diffusion sheet, a prism sheet, etc., but is not limited thereto, and sheets having various functions may be used.

[0061] When the substrate 17 is adhered to the phosphor diffusion preventing layer 22 through the adhesive layer 24, i.e., when the substrate 17 is laminated on one side of the adhesive layer 24, it is preferable that the adhesive strength between the adhesive layer 24 and the substrate film 17 and the adhesive layer 24 and the phosphor diffusion preventing layer 22 are all 50 gf / inch or more. This is because if the adhesive strength is less than 50 gf / inch, it may be difficult to fix the laminated structure of the color conversion sheet 10.

[0062] The color conversion sheet according to the above content preferably exhibits a color coordinate change of within ±0.0015 on the x-axis and y-axis after being treated at a temperature of 70°C for 480 hours. If the color coordinate change exceeds ±0.0015, problems with brightness characteristics and color change may occur.

[0063] Next, a color conversion sheet according to another embodiment of the present invention will be described with reference to Fig. 2. Fig. 2 is a diagram showing the configuration of a color conversion sheet according to another embodiment of the present invention.

[0064] 2, in a color conversion sheet 100 according to another embodiment of the present invention shown in Fig. 2, phosphor diffusion prevention layers 22-1 and 22-2 are formed on both sides of an adhesive layer 24, and a first wavelength conversion layer 201 and a second wavelength conversion layer 202 are formed on the sides of the phosphor diffusion prevention layers 22-1 and 22-2 where the adhesive layer 24 is not located, and if necessary, a substrate 17 may be formed on the outer surfaces of the first wavelength conversion layer 201 and the second wavelength conversion layer 202. That is, in the example of Fig. 2, the color conversion sheet 100 has the adhesive layer 24 as the center, with the first phosphor diffusion prevention layer 22-1 and the first wavelength conversion layer 201 sequentially located below the adhesive layer 24, and the second phosphor diffusion prevention layer 22-2 and the second wavelength conversion layer 202 sequentially located above the adhesive layer 24.

[0065] Hereinafter, explanations that overlap with those of FIG. 1 showing a color conversion sheet 10 according to an embodiment of the present invention will be omitted.

[0066] As described above in FIG. 1, in the color conversion sheet 100 according to another embodiment of the present invention shown in FIG. 2, the second phosphor diffusion prevention layer 22-2 is preferably formed from a composition containing a solvent whose Hildebrand Solubility Parameter satisfies the following Equation 1: (Equation 1) |P1-S2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer S2: Hildebrand solubility parameter of the solvent contained in the second phosphor diffusion prevention layer.

[0067] In addition, the second phosphor diffusion prevention layer 22-2 is preferably formed of a composition further containing a thermosetting or thermoplastic organic compound whose Hildebrand Solubility Parameter satisfies the following Equation 2: (Equation 2) |P1-P2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer P2: Hildebrand solubility parameter of the organic compound contained in the second phosphor diffusion prevention layer.

[0068] In addition, the first wavelength conversion layer 201 and the second wavelength conversion layer 202 may each contain organic phosphors 13 of different colors. If organic phosphors of different colors are mixed in one wavelength conversion layer, degradation may occur due to reactions between the different organic phosphors, or the color coordinates may change due to changes in the distance between the different organic phosphors. Therefore, the color conversion sheet 100 can be manufactured by separating the organic phosphors of different colors into separate wavelength conversion layers 201 and 202. Here, the configurations of the resin matrix and organic phosphors contained in the first wavelength conversion layer 201 and the second wavelength conversion layer 202 are the same as those in FIG. 1 above.

[0069] For example, the color conversion sheet 100 can be manufactured by mixing the first wavelength conversion layer 201 with a green organic phosphor according to Chemical Formula 1 and the second wavelength conversion layer 202 with a red organic phosphor according to Chemical Formula 2.

[0070] The phosphor diffusion prevention layers 22-1 and 22-2 prevent the organic phosphors of the first wavelength conversion layer 201 and the second wavelength conversion layer 202 from diffusing into the adhesive layer 24 or from being mixed with each other after diffusing. In this case, it is preferable that the phosphor diffusion prevention layers 22-1 and 22-2 satisfy the above-mentioned formulas 1 and 2 for the entire first wavelength conversion layer 201 and the second wavelength conversion layer 202.

[0071] In addition, the first phosphor diffusion prevention layer 22-1, the adhesive layer 24, and the second phosphor diffusion prevention layer 22-2 maintain a constant distance (spacing) between the first wavelength conversion layer 201 and the second wavelength conversion layer 202, thereby maintaining a constant luminous efficiency of the red organic phosphor, thereby preventing a decrease in the color coordinates and reliability of the white light emitted by the color conversion sheet 100.

[0072] Next, a backlight unit including a color conversion sheet according to an embodiment of the present invention will be described with reference to FIG.

[0073] FIG. 3 is a diagram showing the configuration of a backlight unit including a color conversion sheet according to an embodiment of the present invention.

[0074] As shown in FIG. 3, a backlight unit 90 according to an embodiment of the present invention may include a light source 70, a reflector 50 capable of reflecting light emitted from the light source 70 to enhance light efficiency, a light guide plate 30 located on top of the reflector 50 and functioning to uniformly spread the light emitted from the light source 70, and a color conversion sheet 10 located on top of the light guide plate 30.

[0075] Although the edge-type light source 70 is shown in FIG. 3 for convenience, the light source 70 is not limited thereto, and may be adopted in various forms such as a side-chain type or a direct type.

[0076] Furthermore, the color conversion sheet 10 may be the same as that described in the embodiment shown in FIG. 1 or FIG. 2, and therefore a duplicated description will be omitted.

[0077] In addition, at least one optical sheet, such as a diffusion sheet, a prism sheet, or a brightness enhancement film (DBEF), may be further included on the color conversion sheet 10.

[0078] The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited to these examples. [Example]

[0079] Example 1 The green and red organic phosphors according to the following chemical formulas 1 and 2 are dissolved in water with a Hildebrand solubility parameter of 19.3 MPa. 1 / 2 Two kinds of organic phosphor solutions were prepared by dissolving each of them in methyl ethyl ketone. [ka] [ka]

[0080] The two organic phosphor solutions prepared were placed in a solution with a Hildebrand solubility parameter of 19.0 MPa. 1 / 2 After mixing with poly(methyl) methacrylate (Sigma-Aldrich) with a Hildebrand solubility parameter of 19.3 MPa, the viscosity reached 150 cps. 1 / 2Methyl ethyl ketone (Methyl ethyl ketone) was added and stirred at 150 rpm for 30 minutes to prepare a wavelength conversion layer composition. At this time, the green organic phosphor was added in an amount of 0.75 parts by weight based on 100 parts by weight of the solid content of the poly(methyl) methacrylate resin, and the red organic phosphor was added in an amount of 0.015 parts by weight based on 100 parts by weight of the solid content of the poly(methyl) methacrylate.

[0081] The wavelength-converting layer composition was bar-coated on the upper surface of a polyethylene terephthalate film (TAK, PL8), and then dried at 140°C for 2 minutes to produce a wavelength-converting layer with a thickness of 20 µm.

[0082] Next, the Hildebrand solubility parameter is 48.0 MPa. 1 / 2 The Hildebrand solubility parameter is 30.5 MPa for 100 parts by weight of distilled water. 1 / 2 5 parts by weight of polyvinyl alcohol (Daejung Chemicals & Metals) was added to the mixture, and the mixture was stirred at 65° C. for 1 hour to prepare a phosphor diffusion preventing layer composition.

[0083] Thereafter, the composition for preventing phosphor diffusion was bar-coated on the upper surface of the wavelength conversion layer and then dried at 140° C. for 2 minutes to produce a phosphor diffusion preventing layer having a thickness of 0.2 μm.

[0084] The adhesive layer composition was prepared by adding 20 parts by weight of toluene to 100 parts by weight of acrylic resin (AT-2100, Samwon Co., Ltd.) and stirring for 30 minutes. The adhesive composition prepared as above was bar coated onto the opposite side of the diffusion layer of a diffusion film (TAK, TDF12C), and then dried at 140°C for 2 minutes to prepare an adhesive layer with a thickness of 10 μm. The adhesive layer prepared as above was laminated on the phosphor diffusion preventing layer so that they were in contact with each other, and then a color conversion sheet was prepared using a roll laminator (GMP, EXCELAM II-355Q).

[0085] Example 2 The phosphor diffusion prevention layer composition is a solution having a Hildebrand solubility parameter of 15.3 MPa. 1 / 2 The Hildebrand solubility parameter is 15.3 MPa for 100 parts by weight of heptane. 1 / 2 A color conversion sheet was manufactured in the same manner as in Example 1, except that 20 parts by weight of polydimethylsiloxane (DOW) was added and then stirred for 3 hours.

[0086] Example 3 Instead of heptane in the phosphor diffusion prevention layer composition, a Hildebrand solubility parameter of 16.8 MPa was used. 1 / 2 A color conversion sheet was manufactured in the same manner as in Example 2, except that cyclohexane was used.

[0087] Example 4 The green organic phosphor solution and the red organic phosphor solution prepared in Example 1 were separately mixed with a resin prepared by dissolving poly(methyl) methacrylate (Sigma-Aldrich) in methyl ethyl ketone, and then methyl ethyl ketone was added to the resin to make the viscosity 150 cps. The mixture was then stirred at 150 rpm for 30 minutes to prepare green wavelength conversion layer compositions and red wavelength conversion layer compositions, respectively.

[0088] In this case, the amount of the green organic phosphor was 0.36 parts by weight per 100 parts by weight of the solid content of the poly(methyl) methacrylate resin, and the amount of the red organic phosphor was 0.03 parts by weight per 100 parts by weight of the solid content of the poly(methyl) methacrylate resin.

[0089] Next, the green wavelength-converting layer composition was bar-coated on the upper surface of a polyethylene terephthalate film (TAK, PL8) and dried at 140°C for 2 minutes to prepare a green wavelength-converting layer having a thickness of 20 μm, and the red wavelength-converting layer composition was bar-coated on the opposite side of the diffusion layer of a diffusion film (TAK, TDF12C) and dried at 140°C for 2 minutes to prepare a red wavelength-converting layer having a thickness of 20 μm.

[0090] The phosphor diffusion preventing layer composition of Example 1 was bar coated on the upper surfaces of the green and red wavelength conversion layers, and then dried at 140° C. for 2 minutes to prepare phosphor diffusion preventing layers with a thickness of 0.2 μm.

[0091] Thereafter, the adhesive composition of Example 1 was bar-coated onto the surface of the phosphor diffusion preventing layer formed on one side of the red wavelength conversion layer, and then dried at 140°C for 2 minutes to prepare an adhesive layer with a thickness of 10 μm. The adhesive layer and the phosphor diffusion preventing layer formed on one side of the green wavelength conversion layer were laminated so that their upper surfaces were in contact with each other, and a color conversion sheet was prepared using a roll laminator (GMP, EXCELAM II-355Q).

[0092] (Comparative Example 1) A color conversion sheet was manufactured in the same manner as in Example 1, except that the process of forming the phosphor diffusion prevention layer was omitted and the adhesive layer was laminated so that it was in contact with the wavelength conversion layer.

[0093] (Comparative Example 2) Instead of heptane in the phosphor diffusion prevention layer composition, Hildebrand solubility parameter is 18.3 MPa 1 / 2 A color conversion sheet was produced in the same manner as in Example 2, except that toluene was used.

[0094] (Comparative Example 3) Instead of heptane in the phosphor diffusion prevention layer composition, a Hildebrand solubility parameter of 18.2 MPa was used. 1 / 2 A color conversion sheet was manufactured in the same manner as in Example 2, except that xylene was used.

[0095] Comparative Example 4 Instead of distilled water and polyvinyl alcohol, a Hildebrand solubility parameter of 18.3 MPa was used as the phosphor diffusion prevention layer composition. 1 / 2 The Hildebrand solubility parameter is 19.0 MPa for 100 parts by weight of toluene. 1 / 2A color conversion sheet was prepared in the same manner as in Example 1, except that 20 parts by weight of poly(methyl) methacrylate (Sigma-Aldrich) was added.

[0096] Table 1 shows the Hildebrand solubility parameter difference between the wavelength conversion layer and the phosphor diffusion prevention layer for Examples 1 to 4 and Comparative Examples 2 to 4. Comparative Example 1 was excluded from Table 1 because the phosphor diffusion prevention layer was omitted.

[0097] [Table 1]

[0098] As shown in Table 1, in Examples 1 to 4, the difference in solubility parameters according to Equation 1 and Equation 2 is 2 MPa. 1 / 2 It can be confirmed that the difference in solubility parameters according to Equation 1 and 2 is greater than 1 MPa in Comparative Examples 2 and 3. 1 / 2 In Comparative Example 4, the difference in solubility according to Formula 1 and Formula 2 is less than 2 MPa. 1 / 2 It can be seen that the condition of Equation 2 is not satisfied.

[0099] For Examples 1 to 4 and Comparative Examples 1 to 4 manufactured as described above, the physical properties of the color conversion sheets were measured and evaluated according to the following experimental examples.

[0100] (Experimental example) (1) Measurement of luminance and color coordinate changes For the color conversion sheets of Examples 1 to 4 and Comparative Examples 1 to 4, the initial luminance (L) and color coordinate (x, y) values ​​were measured, and then the changes in color coordinate (Δx, Δy) and luminance (ΔLv) over time were measured at a temperature of 70°C using a spectroradiometer (KONICA MINOLTA, CA-S20W).

[0101] In this experiment, the color conversion sheet was laminated on the top surface of the light guide plate of a backlight unit containing a 450 nm wavelength blue LED and a light guide plate, and a prism sheet was further laminated on top of the color conversion sheet.

[0102] The results of the experiment conducted on the color conversion sheet according to the above-mentioned experimental example are shown in the table below.

[0103] Table 2 below shows the results of measuring the changes in luminance and color coordinates for Examples 1 to 4 and Comparative Examples 1 to 4.

[0104] [Table 2]

[0105] As shown in Table 2, in Examples 1 to 4, in which the solubility parameter difference between the wavelength conversion layer and the phosphor diffusion preventing layer satisfies Equations 1 and 2, the changes in the x-axis and y-axis color coordinates were all within ±0.0015 even after 480 hours of treatment at a temperature of 70°C. In contrast, in Comparative Example 1, which is a color conversion sheet in which the adhesive layer is directly laminated without forming a phosphor diffusion preventing layer, the x-axis change value was -0.0025 and the y-axis change value was -0.0113, which were the largest among all the embodiments and comparative examples.

[0106] Furthermore, Comparative Examples 2 and 3, in which the solubility parameter difference between the wavelength conversion layer and the phosphor diffusion preventing layer did not satisfy Equation 1, exhibited a larger change in color coordinate than Examples 1 to 4, and Comparative Example 4, in which the surface energies of the wavelength conversion layer and the adhesive layer did not satisfy Equation 1 and 2, also exhibited a larger change in color coordinate than Examples 1 to 4. That is, it was confirmed that Comparative Examples 2 to 4, in which the surface energies of the wavelength conversion layer and the adhesive layer did not satisfy Equation 1 or 2, exhibited a larger change in color coordinate than Examples 1 to 4, in which the surface energies of the wavelength conversion layer and the adhesive layer satisfied Equation 1 and 2.

[0107] Furthermore, in Examples 1 to 4, the luminance change after 480 hours of treatment was less than 2.5%, and especially after 240 hours, the change was less than 1%. In contrast, in Comparative Example 1, which is a color conversion sheet in which an adhesive layer is directly laminated without forming a phosphor diffusion preventing layer, the luminance gradually decreased, and a luminance change of 5.7% occurred after 480 hours of treatment. In Comparative Examples 2 to 4, in which the solubility parameter difference between the wavelength conversion layer and the phosphor diffusion preventing layer does not satisfy Equation 1 or 2, the luminance gradually decreased, and a luminance change of 3.1% to 4.6% occurred after 480 hours of treatment.

[0108] As described above, it was confirmed that significant changes in color and brightness occurred in a high-temperature environment when the color conversion sheet had an adhesive layer directly laminated thereon without forming a phosphor diffusion preventing layer as in Comparative Example 1, and when the difference in solubility parameters between the wavelength conversion layer and the phosphor diffusion preventing layer did not satisfy Equation 1 or 2 as in Comparative Examples 2 to 4. On the other hand, it was confirmed that small changes in color and brightness occurred even in a high-temperature environment when the difference in solubility parameters between the wavelength conversion layer and the phosphor diffusion preventing layer satisfied Equation 1 and 2.

[0109] The color conversion sheet according to the present invention further includes a phosphor diffusion preventing layer that prevents the diffusion of the organic phosphor, thereby preventing the organic phosphor in the wavelength conversion layer from being deteriorated by chemical functional groups or residual solvents in the adhesive layer and preventing the organic phosphor that has detached from the interface of the wavelength conversion layer from spreading into the adhesive layer over time in a high-temperature or high-humidity environment, thereby solving the problems of changes in brightness characteristics and color change that occur due to changes in luminous efficiency and degradation of the organic phosphor. Furthermore, due to the difference in solubility parameters between the wavelength conversion layer and the phosphor diffusion preventing layer, the phosphor diffusion preventing layer prevents the organic phosphor from mixing with the wavelength conversion layer during lamination or from spreading from the wavelength conversion layer into the phosphor diffusion preventing layer over time in a high-temperature or high-humidity environment due to the influence of residual solvents, thereby solving the problems of changes in brightness characteristics and color change that occur due to these problems.

[0110] Although the 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 made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0111] 10, 100 color conversion sheet 20 Wavelength conversion layer 13 Organic Fluorescent Materials 19 Resin Matrix 22 Phosphor diffusion prevention layer 22-1 First phosphor diffusion prevention layer 22-2 Second phosphor diffusion prevention layer 24 Adhesive layer 17, 17a, 17b base material 201 First wavelength conversion layer 202 Second wavelength conversion layer 30 Light guide plate 50 Reflector 70 light source 90 Backlight unit.

Claims

1. a first wavelength-converting layer in which an organic phosphor is dispersed in a resin matrix; a first phosphor diffusion prevention layer located on one surface of the first wavelength conversion layer; an adhesive layer located on one surface of the first phosphor diffusion prevention layer, The first phosphor diffusion preventing layer is formed from a composition including a solvent having a Hildebrand solubility parameter according to the following Equation 1: The color conversion sheet, wherein the first phosphor diffusion preventing layer further comprises a thermosetting or thermoplastic organic compound whose Hildebrand solubility parameter satisfies the following Equation 2: (Equation 1) |P1-S2|>2MPa １／２ P1: Hildebrand solubility parameter of the resin matrix of the first wavelength conversion layer S2: Hildebrand solubility parameter of the solvent contained in the first phosphor diffusion prevention layer; (Equation 2) |P1-P2|>2MPa 1 / 2 P1: Hildebrand solubility parameter of the resin matrix of the first wavelength conversion layer P2: Hildebrand solubility parameter of the organic compound contained in the first phosphor diffusion prevention layer.

2. 2. The color conversion sheet of claim 1, wherein the first phosphor diffusion prevention layer has a thickness of 0.01 to 10 [mu]m.

3. 2. The color conversion sheet according to claim 1, wherein the color coordinate changes of the x-axis and y-axis of the color conversion sheet are within ±0.0015 after treatment at a temperature of 70°C for 480 hours.

4. 2. The color conversion sheet according to claim 1, wherein the resin matrix contains at least one resin selected from the group consisting of ester-based, olefin-based, acrylic-based, ether-based, urethane-based, carbonate-based, and imide-based resins.

5. The color conversion sheet according to claim 1 , wherein the resin matrix has a glass transition temperature of 50 to 140° C.

6. The color conversion sheet according to claim 1 , wherein the organic phosphor of the first wavelength conversion layer does not escape into the first phosphor diffusion prevention layer.

7. The color conversion sheet according to claim 1 , wherein the first phosphor diffusion prevention layer has a visible light transmittance of 70% or more.

8. The color conversion sheet according to claim 1 , further comprising a substrate located on at least one surface of the first wavelength conversion layer or the adhesive layer.

9. a second phosphor diffusion prevention layer located on the adhesive layer; a second wavelength conversion layer located on the second phosphor diffusion prevention layer, the second wavelength conversion layer including an organic phosphor dispersed in a resin matrix; The color conversion sheet according to claim 1 , further comprising:

10. The color conversion sheet according to claim 9 , wherein the second wavelength conversion layer contains an organic phosphor having the same or a different hue as the organic phosphor dispersed in the first wavelength conversion layer.

11. 10. The color conversion sheet of claim 9, wherein the second phosphor diffusion preventing layer is formed from a composition containing a solvent having a Hildebrand solubility parameter according to the following equation 1: (Equation 1) |P1-S2|>2MPa １／２ P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer S2: Hildebrand solubility parameter of the solvent contained in the second phosphor diffusion prevention layer.

12. 10. The color conversion sheet of claim 9, wherein the second phosphor diffusion preventing layer further comprises a thermosetting or thermoplastic organic compound having a Hildebrand solubility parameter according to the following Equation 2: (Equation 2) |P1-P2|>2MP� １／２ P1: Hildebrand solubility parameter of the resin matrix of the second wavelength conversion layer P2: Hildebrand solubility parameter of the organic compound contained in the second phosphor diffusion prevention layer.

13. A backlight unit comprising the color conversion sheet according to claim 1 .

Images