JP2016213369A - Protective film for wavelength conversion sheet, wavelength conversion sheet, and backlight unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a protective film for a wavelength conversion sheet, excellent in optical quality, with high barrier properties against a deterioration factor.SOLUTION: The protective film for a wavelength conversion sheet for protecting a fluorescence substance in the wavelength conversion sheet has a structure in which two or more layers of barrier films having a substrate and one or more barrier layers provided at least on one surface of the substrate are laminated. A thickness of at least one of the barrier layers is less than or equal to 2 μm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a protective film for a wavelength conversion sheet, and a wavelength conversion sheet and a backlight unit using the same.

  A liquid crystal display is a display device that displays an image or the like by controlling the alignment state of liquid crystal by applying voltage and transmitting or blocking light in each region. As a light source of the liquid crystal display, a backlight provided on the back surface of the liquid crystal display is used. Conventionally, a cold cathode tube is used for the backlight, but recently, an LED (light emitting diode) is being used instead of the cold cathode tube for reasons such as long life and good color development.

  In the LED used for the backlight, the white LED technology is very important. In white LED technology, a cerium-doped YAG: Ce (yttrium, aluminum, garnet: cerium) down-conversion phosphor is generally excited with a blue (450 nm) LED chip. In this case, white light is obtained by mixing the blue light of the LED with yellow light having a wide wavelength range generated from the YAG: Ce phosphor. However, this white light is often somewhat bluish and often gives the impression of “cold” or “cool” white.

  Incidentally, in recent years, nano-sized phosphors using quantum dots have been commercialized. A quantum dot is a luminescent semiconductor nanoparticle, and the range of a diameter is about 1-20 nm. Since quantum dots show a wide excitation spectrum and high quantum efficiency, they can be used as phosphors for LED wavelength conversion. Furthermore, there is an advantage that the wavelength of light emission can be completely adjusted over the entire visible range only by changing the dot size or the type of semiconductor material. As such, quantum dots have the potential to create virtually any color, especially the warm white that is highly desired in the lighting industry. In addition, it is possible to obtain white light having different color rendering index by combining three types of dots corresponding to red, green, and blue emission wavelengths. In this way, with a liquid crystal display using a quantum dot backlight, the color tone is improved and many colors that can be identified by humans can be expressed without increasing the thickness, power consumption, cost, and manufacturing process. become.

  A backlight using a white LED as described above diffuses a phosphor having a predetermined emission spectrum (quantum dots and YAG: Ce, etc.) into the film, and seals the surface with a barrier film. Has a configuration in which a wavelength conversion sheet in which an edge portion is also sealed is combined with an LED light source and a light guide plate.

  A barrier film forms a thin film on the surface of a substrate such as a plastic film by vapor deposition or the like, and prevents permeation of atmospheric deterioration factors such as moisture and gas (for example, oxygen). For example, Patent Document 1 proposes a backlight having a structure in which a phosphor is sandwiched between barrier films in order to suppress deterioration of the phosphor.

JP 2011-013567 A

  However, when a display in which quantum dots are sealed with a barrier film described in Patent Document 1 is manufactured, the transmittance of light decreases, or optical transmission occurs due to an increase in optical interference due to reflection inside the barrier film. The optical quality is deteriorated by adversely affecting the light. Further, when the barrier film has a defect such as a pinhole or a foreign substance, a phenomenon in which a deterioration factor locally enters the inside and the display quality is deteriorated from the periphery.

  The present invention has been made in view of such circumstances, and as a protective film for protecting a phosphor in a wavelength conversion sheet, it is excellent in optical quality and has a high barrier property against deterioration factors. An object is to provide a protective film, and a wavelength conversion sheet and a backlight unit using the protective film.

As a means for solving the above problems, the first invention provides:
A protective film for a wavelength conversion sheet for protecting a phosphor in a wavelength conversion sheet, the first base material, a first barrier layer provided on at least one surface of the first base material, And a second barrier film having a first barrier film, a second substrate, and a second barrier layer provided on at least one surface of the second substrate. A protective film for wavelength conversion sheets, wherein the thickness of at least one barrier layer of the barrier layer is 2 μm or less.
Moreover, 2nd invention is a protective film for wavelength conversion sheets of Claim 1 with which the said barrier layer is provided with an inorganic thin film layer and a gas-barrier coating layer.
Moreover, 3rd invention is a wavelength conversion sheet provided with the fluorescent substance layer containing a quantum dot, and the fluorescent substance protective film of Claim 1 or 2 arrange | positioned at the upper and lower sides of a fluorescent substance layer.
Moreover, 4th invention is a backlight unit provided with the LED light source, the said wavelength conversion sheet | seat, and the light-guide plate which makes light inject into this wavelength conversion sheet | seat from this blue LED light source.

  According to the present invention, as a protective film for protecting the phosphor in the wavelength conversion sheet, the protective film for wavelength conversion sheet having excellent optical quality and high barrier property against deterioration factors, and the same are used. A wavelength conversion sheet and a backlight unit can be provided.

FIG. 1 is a schematic cross-sectional view of a wavelength conversion sheet according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a wavelength conversion sheet according to the second embodiment of the present invention. FIG. 3 is a schematic cross-sectional view of a backlight unit according to the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant description is omitted. Further, the positional relationship such as up, down, left and right is based on the positional relationship shown in the drawings unless otherwise specified. Further, the dimensional ratios in the drawings are not limited to the illustrated ratios.

<Wavelength conversion sheet according to the first embodiment>
First, a first embodiment of the present invention will be described. FIG. 1 is a schematic cross-sectional view of a wavelength conversion sheet according to the first embodiment of the present invention. The wavelength conversion sheet shown in FIG. 1 contains a phosphor such as a quantum dot, and can be used for a backlight unit, for example, for LED wavelength conversion.

  As shown in FIG. 1, the wavelength conversion sheet 100 of the present embodiment includes a phosphor layer (wavelength conversion layer) 1 containing a phosphor, and one surface 2 a side and the other surface 2 b side of the phosphor layer 1. A wavelength conversion sheet protective film (hereinafter also simply referred to as “protective film”) 2 and 2 is provided. As a result, the phosphor layer 1 is encapsulated (ie, sealed) between the protective films 2 and 2.

  By the way, the backlight unit is generally composed of a light guide plate and an LED light source. The LED light source is installed on the side surface of the light guide plate. A plurality of LED elements whose emission color is blue are provided inside the LED light source. This LED element may be a purple LED or even a lower wavelength LED. The LED light source emits light toward the side surface of the light guide plate. In the case of the backlight unit using the wavelength conversion sheet 100 of the present embodiment, the irradiated light is, for example, a layer (phosphor layer) 1 in which a resin such as acrylic or epoxy is mixed with a phosphor through a light guide plate. Will be incident on. Here, since it is necessary to provide the phosphor layer 1 with a barrier property, it is desirable that the phosphor layer 1 is sandwiched between the pair of protective films 2 and 2 for wavelength conversion sheet. Hereinafter, each layer constituting the wavelength conversion sheet 100 will be described in detail.

(Phosphor layer)
The phosphor layer 1 is a thin film having a thickness of several tens to several hundreds of μm including the sealing resin 4 and the phosphor 3. As the sealing resin 4, for example, a photosensitive resin or a thermosetting resin can be used. The sealing resin 4 is sealed in a state where one or more phosphors 3 are mixed. The sealing resin 4 plays a role of joining the phosphor layer 1 and the pair of protective films 2 and 2 and filling these gaps while laminating them. The phosphor layer 1 may be a laminate in which two or more phosphor layers in which only one kind of phosphor 3 is sealed are laminated. As the two or more kinds of phosphors 3 used in the one or more phosphor layers, those having the same excitation wavelength are selected. This excitation wavelength is selected based on the wavelength of light emitted by the LED light source. The fluorescent colors of two or more types of phosphors 3 are different from each other. When two types of phosphors 3 are used, the fluorescent colors are preferably red and green. The wavelength of each fluorescence and the wavelength of light emitted from the LED light source are selected based on the spectral characteristics of the color filter. The peak wavelengths of fluorescence are, for example, 610 nm for red and 550 nm for green.

  Next, the particle structure of the phosphor 3 will be described. As the phosphor 3, quantum dots are preferably used. Examples of the quantum dots include those in which a core as a light emitting portion is coated with a shell as a protective film. Examples of the core include cadmium selenide (CdSe), and examples of the shell include zinc sulfide (ZnS). Quantum efficiency is improved by covering surface defects of CdSe particles with ZnS having a large band gap. Further, the phosphor 3 may be one in which the core is double-coated with the first shell and the second shell. In this case, CsSe can be used for the core, zinc selenide (ZnSe) can be used for the first shell, and ZnS can be used for the second shell. Moreover, YAG: Ce etc. can also be used as fluorescent substance 3 other than a quantum dot.

  The average particle diameter of the phosphor 3 is preferably 1 to 20 nm. Moreover, the thickness of the phosphor layer 1 is preferably 1 to 500 μm.

  The content of the phosphor 3 in the phosphor layer 1 is preferably 1 to 20% by mass and more preferably 3 to 10% by mass based on the total amount of the phosphor layer 1.

  As the sealing resin 4, for example, a thermoplastic resin, a thermosetting resin, an ultraviolet curable resin, or the like can be used. These resins can be used singly or in combination of two or more.

  Examples of the thermoplastic resin include cellulose derivatives such as acetylcellulose, nitrocellulose, acetylbutylcellulose, ethylcellulose, and methylcellulose; vinyl acetate and copolymers thereof, vinyl chloride and copolymers thereof, and vinylidene chloride and copolymers thereof. Acetal resins such as polyvinyl formal and polyvinyl butyral; Acrylic resins and copolymers thereof, Acrylic resins such as methacrylic resins and copolymers; Polystyrene resins; Polyamide resins; Linear polyester resins; Fluorine Resin; and polycarbonate resin etc. can be used.

  Examples of the thermosetting resin include phenol resin, urea melamine resin, polyester resin, and silicone resin.

  Examples of the ultraviolet curable resin include photopolymerizable prepolymers such as epoxy acrylate, urethane acrylate, and polyester acrylate. Further, these photopolymerizable prepolymers can be the main components, and monofunctional or polyfunctional monomers can be used as diluents.

(Protective film for wavelength conversion sheet)
The wavelength conversion sheet protective film 2 includes two barrier films 5 each having a base material 8 and a barrier layer 9, an adhesive layer 6, and a coating layer 7. The barrier layer 9 provided on the one surface 8 a of the substrate 8 is laminated so as to face the other substrate 8 with the adhesive layer 6 interposed therebetween. Moreover, when forming the protective film 2 of this embodiment, as shown in FIG. 1, each protective film 2 and 2 is laminated | stacked with the barrier layer 9 facing the fluorescent substance layer 1 side.

  As shown in FIG. 1, the barrier film 5 includes a base material 8 and a barrier layer 9 provided on one surface 8 a of the base material 8.

  Although it does not specifically limit as the base material 8, The base material with a total light transmittance of 85% or more is desirable. For example, a polyethylene terephthalate film, a polyethylene naphthalate film, or the like can be used as a substrate having high transparency and excellent heat resistance.

  Further, the thickness of the substrate 8 is not particularly limited, but is desirably 50 μm or less in order to reduce the total thickness of the wavelength conversion sheet 100. Further, the thickness of the substrate 8 is desirably 12 μm or more in order to obtain excellent barrier properties.

  The barrier layer 9 includes an inorganic thin film layer 10 and a gas barrier coating layer 11. As shown in FIG. 1, the barrier layer 9 has an inorganic thin film layer 10 laminated on one surface (one surface) 8 a of the substrate 8, and a gas barrier coating layer 11 on the inorganic thin film layer 10. Are laminated.

  The inorganic thin film layer (inorganic oxide thin film layer) 10 is not particularly limited. For example, aluminum oxide, silicon oxide, magnesium oxide, or a mixture thereof can be used. Among these, it is desirable to use aluminum oxide or silicon oxide from the viewpoint of barrier properties and productivity.

  The thickness (film thickness) of the inorganic thin film layer 10 is preferably in the range of 5 to 100 nm, and more preferably in the range of 10 to 40 nm. Here, when the film thickness is 5 nm or more, it is easy to form a uniform film, and the function as a gas barrier material tends to be more sufficiently achieved. On the other hand, when the film thickness is 100 nm or less, sufficient flexibility can be maintained by the thin film, and it is possible to more reliably prevent the thin film from cracking due to external factors such as bending and pulling after the film formation. There is a tendency to be able to. In addition, since an inorganic oxide having oxygen deficiency has optical absorption, it is preferably as thin as possible within the range having a barrier property in terms of transparency, and is more preferably 40 nm or less.

  The gas barrier coating layer 11 is provided in order to prevent various secondary damages in a later process and to impart high barrier properties. The gas barrier coating layer 11 contains, as a component, at least one selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a metal alkoxide hydrolyzate, and a metal alkoxide polymer from the viewpoint of obtaining excellent barrier properties. It is preferable.

  Specific examples of the hydroxyl group-containing polymer compound include water-soluble polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and starch. The barrier property is most excellent particularly when polyvinyl alcohol is used.

The metal alkoxide is represented by the general formula: M (OR) _n (M represents a metal atom such as Si, Ti, Al, Zr, R represents an alkyl group such as —CH ₃ , —C ₂ H ₅ , and n represents M Represents an integer corresponding to the valence of. Specific examples include tetraethoxysilane [Si (OC ₂ H ₅ ) ₄ ], triisopropoxyaluminum [Al (O-iso-C ₃ H ₇ ) ₃ ] and the like. Tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis. In addition, examples of the hydrolyzate and polymer of metal alkoxide include, for example, silicic acid (Si (OH) ₄ ) as a hydrolyzate or polymer of tetraethoxysilane, and a hydrolyzate or polymer of tripropoxyaluminum. Examples thereof include aluminum hydroxide (Al (OH) ₃ ).

  The thickness (film thickness) of the gas barrier coating layer 11 is preferably in the range of 50 to 2000 nm, and more preferably in the range of 100 to 500 nm. Here, when the film thickness is 50 nm or more, there is a tendency that a more sufficient gas barrier property can be obtained, and when it is 2000 nm or less, there is a tendency that sufficient flexibility can be maintained by the thin film.

  As shown in FIG. 1, the two barrier films 5 are formed so that the barrier layer 9 of the other substrate 8 is interposed via the barrier layer 9 and the adhesive layer 6 provided on one surface 8 a of the substrate 8. It is provided so as to face the surface 8b side that is not provided. In other words, when the two barrier films 5 are the first barrier film 5 that is far from the phosphor layer 1 and the second barrier film 5 that is near the phosphor layer 1, the first barrier film 5 is used. The first base material 8 and the second base material 8 of the second barrier film 5 are laminated via the adhesive layer 6 so as to sandwich the barrier layer 9 of the first barrier film. . As described above, since two barrier films are used in this embodiment, the first substrate 8 of the first barrier film 5 and the second substrate 8 of the second barrier film 5 are further used. Since the barrier layers 9 are sandwiched between them, and each barrier layer 9 is disposed closer to the phosphor layer 1, defects such as minute pinholes are generated in the barrier layer 9. Even in this case, the barrier performance can be more effectively exhibited.

  Of the first barrier layer 9 of the first barrier film 5 and the second barrier layer 9 of the second barrier film 5, the thickness of at least one barrier layer is preferably 2 μm or less, preferably 1 μm or less. It is more preferable that Here, when the thickness is 2 μm or less, it is possible to suppress a decrease in light transmittance and an increase in optical interference due to reflection inside the barrier film. The lower limit of the thickness is not particularly limited as long as the barrier layer can be practically formed and has a barrier property that can suppress the deterioration of the phosphor layer 1. For example, it is desirable that it is 50 nm or more.

  An anchor coat layer may be provided between the first barrier layer 9 and the substrate of the first barrier film 5 and between the second barrier layer 9 of the second barrier film 5 and the substrate, if necessary. Good. The anchor coat layer is provided to improve the adhesion between the base material 8 of the barrier film 5 and the inorganic thin film layer 10.

  Anchor coat layer is, for example, polyester resin, isocyanate resin, urethane resin, acrylic resin, polyvinyl alcohol resin, ethylene vinyl alcohol resin, vinyl modified resin, epoxy resin, oxazoline group-containing resin, modified styrene resin, modified silicone resin or alkyl titanate. It may be a resin selected from the above, and may be a single resin or a composite resin in combination of two or more.

  The thickness of the anchor coat layer is preferably in the range of 5 to 500 nm, and more preferably in the range of 10 to 100 nm. Here, when the thickness is 5 nm or more, the adhesion between the substrate 8 and the inorganic thin film layer 10 tends to be improved, and when it is 500 nm or less, the internal stress due to the thick film is sufficiently suppressed. There is a tendency that a simple layer can be formed.

  The thickness of the two base materials 8 may be the same or different. From the viewpoint of making the thickness of the wavelength conversion sheet 100 thinner, the thickness of the second substrate 8 of the second barrier film 5 disposed on the side closer to the phosphor layer 1 is set to the side far from the phosphor layer 1. You may make it thinner than the 1st base material 8 of the 1st barrier film 5 arrange | positioned. Since moisture and gas permeate from the surface of the wavelength conversion sheet 100, the thickness of the first substrate 8 is relatively increased to prevent moisture and oxygen from being transmitted from the surface, while the second substrate 8 The thickness of the wavelength conversion sheet 100 as a whole can be reduced by relatively reducing the thickness. The permeation of moisture and oxygen occurs not only from the surface of the barrier film 5 but also from the end face. Therefore, the thinner the second substrate 8 and the adhesive layer 6 are, the more moisture and oxygen penetrate from the end face. Can be suppressed. For this reason, it is desirable that the total thickness of the second base material 8 adjacent to the adhesive layer 6 and the adhesive layer 6 be 40 μm or less.

  The thicknesses of the two barrier layers 9 may be the same or different. From the viewpoint of reducing the thickness of the wavelength conversion sheet 100, the thickness of the second barrier layer 9 of the second barrier film 5 disposed on the side closer to the phosphor layer 1 is set to the side far from the phosphor layer 1. You may make it thinner than the 1st barrier layer 9 of the 1st barrier film 5 arrange | positioned. Since moisture and gas permeate from the surface of the wavelength conversion sheet 100, the thickness of the first barrier layer 9 is relatively increased to prevent the passage of moisture and oxygen from the surface, and the second barrier layer 9 The thickness of the wavelength conversion sheet 100 as a whole can be reduced by relatively reducing the thickness. Therefore, among the first barrier layer 9 of the first barrier film 5 and the second barrier layer 9 of the second barrier film 5, at least the thickness of the second barrier layer 9 of the second barrier film 5 is set. More preferably, the thickness is 2 μm or less.

  As shown in FIG. 1, the adhesive layer 6 is provided between the two barrier films 5 in order to bond and laminate the two barrier films 5 together. Although it does not specifically limit as the contact bonding layer 6, Adhesives and adhesives, such as an acryl-type material, a urethane type material, and a polyester-type material, can be used. More specifically, an acrylic pressure-sensitive adhesive, an acrylic adhesive, a urethane adhesive, or an ester adhesive can be used.

  The thickness of the adhesive layer 6 is not particularly limited, but is desirably 10 μm or less in order to reduce the total thickness of the wavelength conversion sheet protective film 2 and the wavelength conversion sheet 100. On the other hand, from the viewpoint of obtaining better adhesiveness, the thickness of the adhesive layer 6 is desirably 3 μm or more.

  The coating layer 7 is provided on each surface of the two wavelength conversion sheet protective films 2, 2, that is, both surfaces of the wavelength conversion sheet 100, in order to exhibit one or more optical functions and antistatic functions. Yes. Here, the optical function is not particularly limited, and examples thereof include an interference fringe (moire) prevention function, an antireflection function, and a diffusion function. Among these, the coating layer 7 preferably has at least an interference fringe preventing function as an optical function. In the present embodiment, a case where the coating layer 7 has at least an interference fringe preventing function will be described.

  The coating layer 7 may include a binder resin and fine particles. Then, fine irregularities may be formed on the surface of the coating layer 7 by embedding the fine particles in the binder resin so that a part of the fine particles is exposed from the surface of the coating layer 7. By providing the coating layer 7 on the respective surfaces of the wavelength conversion sheet protective films 2 and 2, that is, on both surfaces of the wavelength conversion sheet 100 in this manner, generation of interference fringes such as Newton rings can be more sufficiently prevented. As a result, a display with high efficiency, high definition and long life can be obtained.

  Although it does not specifically limit as binder resin, Resin excellent in optical transparency can be used. More specifically, for example, polyester resins, acrylic resins, acrylic urethane resins, polyester acrylate resins, polyurethane acrylate resins, urethane resins, epoxy resins, polycarbonate resins, polyamide resins, polyimide resins. Thermoplastic resins such as melamine resins and phenol resins, thermosetting resins, ionizing radiation curable resins, and the like can be used. Among these, it is desirable to use an acrylic resin excellent in light resistance and optical characteristics. These can be used in combination of not only one type but also a plurality of types.

  The fine particles are not particularly limited. For example, in addition to inorganic fine particles such as silica, clay, talc, calcium carbonate, calcium sulfate, barium sulfate, titanium oxide, and alumina, styrene resin, urethane resin, silicone resin, Organic fine particles such as acrylic resin can be used. These can be used in combination of not only one type but also a plurality of types.

  The average particle size of the fine particles is preferably from 0.1 to 30 μm, and more preferably from 0.5 to 10 μm. When the average particle size of the fine particles is 0.1 μm or more, an excellent interference fringe prevention function tends to be obtained, and when it is 30 μm or less, the transparency tends to be further improved.

  The content of the fine particles in the coating layer 7 is preferably 0.5 to 30% by mass, more preferably 3 to 10% by mass based on the total amount of the coating layer 7. When the content of the fine particles is 0.5% by mass or more, the light diffusion function and the effect of preventing the generation of interference fringes tend to be further improved, and when the content is 30% by mass or less, the luminance is not reduced. .

  The wavelength conversion sheet protective film 2 having the above-described configuration includes at least one barrier among the first barrier layer 9 of the first barrier film 5 and the second barrier layer 9 of the second barrier film 5. Since the thickness of the layer is 2 μm or less, a decrease in light transmittance and an increase in optical interference due to reflection inside the barrier film can be suppressed, and optical quality can be maintained. Further, the barrier film 5 is set to 2 so that only one barrier layer 9 is sandwiched between the first substrate 8 of the first barrier film 5 and the second substrate 8 of the second barrier film 5. This is a laminated film in which layers are laminated, and since the influence of a defect of the barrier layer 9 due to splash or the like can be suppressed, the barrier property is excellent. And by using this protective film 2 for wavelength conversion sheets as a protective film for protecting the fluorescent substance of the wavelength conversion sheet 100, the performance of the wavelength conversion sheet 100 using fluorescent substances, such as a quantum dot, is exhibited to the maximum. It becomes possible to do.

  Next, the manufacturing method of the wavelength conversion sheet 100 of this embodiment is demonstrated. In the manufacturing method of the wavelength conversion sheet 100 of this embodiment, the fluorescent substance layer 1 can be laminated | stacked between a pair of protective films 2 and 2 for wavelength conversion sheets with the following procedures, for example.

(Manufacturing process of protective film 2 for wavelength conversion sheet)
In the manufacturing process of the wavelength conversion sheet protective films 2 and 2, first, the coating layer 7 is formed on one surface 8 b of the first substrate 8. Specifically, the coating layer 7 is formed by applying a coating liquid in which a binder resin, fine particles, and a solvent as necessary are mixed on the surface 8b of the first base member 8 and drying it. Next, the inorganic thin film layer 10 is laminated | stacked on the surface 8a on the opposite side to the surface in which the coating layer 7 was provided of the 1st base material 8 by the vapor deposition method etc., for example. Next, a coating agent mainly comprising an aqueous solution or a water / alcohol mixed solution containing at least one component selected from the group consisting of a hydroxyl group-containing polymer compound, a metal alkoxide, a metal alkoxide hydrolyzate, and a metal alkoxide polymer. The gas barrier coating layer 11 is formed by applying on the surface of the inorganic thin film layer 10 and drying. Thus, the coating layer 7 is provided on one surface of the first base material 8 and the barrier layer 9 including the inorganic thin film layer 10 and the gas barrier coating layer 11 is provided on the other surface. A first barrier film 5 is obtained.

  Moreover, the 2nd barrier film 5 with which the barrier layer 9 was provided is obtained by performing operation similar to the above except not forming the coating layer 7 on the one surface 8a of the 2nd base material 8. FIG.

  Next, the first barrier film 5 on which the coating layer 7 is formed and the second barrier film 5 on which the coating layer 7 is not formed are bonded together using the adhesive layer 6 and laminated. Specifically, the barrier layer 9 of the first barrier film 5 provided with the coating layer 7 is opposed to the surface of the second barrier film 5 not provided with the coating layer 7 where the barrier layer 9 is not provided. Lamination is performed using the adhesive layer 6. As the adhesive layer 6, any of an acrylic pressure-sensitive adhesive, an acrylic adhesive, a urethane adhesive, and an ester adhesive can be used. Thereby, the protective film 2 for wavelength conversion sheets laminated | stacked so that only one of the barrier layers 9 may be inserted | pinched between the two barrier films 5 is obtained.

  In this embodiment, the example in which the coating layer 7 is formed first has been described. However, the timing at which the coating layer 7 is formed is not particularly limited, and for example, the first barrier film 5 before the coating layer 7 is formed. And the second barrier film 5 may be bonded together, and the coating layer 7 may be formed on the surface of the first barrier film 5.

(Manufacturing process of phosphor layer 1)
In the manufacturing process of the phosphor layer 1, first, the phosphor 3, the sealing resin 4, and a solvent as necessary are mixed to prepare a mixed solution. Subsequently, the prepared liquid mixture is apply | coated to the surface of the side in which the coating layer 7 of the protective film 2 for wavelength conversion sheets is not provided. Next, the other protective film 2 for wavelength conversion sheets produced separately is laminated | stacked. At this time, the surfaces 1a and 1b of the phosphor layer 1 and the surfaces of the two wavelength conversion sheet protective films 2 on which the coating layer 7 is not provided are opposed to each other. Next, when the sealing resin 4 is a photosensitive resin, the wavelength conversion sheet 100 of the present embodiment can be obtained by curing the photosensitive resin by UV irradiation (UV curing). The photosensitive resin may be further thermally cured after UV curing. In addition to the photosensitive resin, a thermosetting resin, a chemical curable resin, or the like may be used as the sealing resin 4.

Here, the UV curing can be performed, for example, at 100 to 1000 mJ / cm ² . Moreover, thermosetting can be performed at 60-120 degreeC for 0.1 to 3 minutes, for example.

  In the present embodiment, the phosphor layer 1 is formed on the surface of the wavelength conversion sheet protective film 2 on which the coating layer 7 is not provided, and then the other wavelength conversion is performed on the surface of the phosphor layer 1. Although the example which laminates | stacks the protective film 2 for sheets was demonstrated, it is not limited to this.

<Wavelength conversion sheet according to the second embodiment>
Next, a second embodiment of the present invention will be described. FIG. 2 is a schematic cross-sectional view of a wavelength conversion sheet according to the second embodiment of the present invention. The wavelength conversion sheet 200 of the second embodiment differs from the wavelength conversion sheet 100 of the first embodiment only in the configuration of the wavelength conversion sheet protective film 20. Therefore, about the wavelength conversion sheet 200 of 2nd Embodiment, the same code | symbol is attached | subjected about the component same as 1st Embodiment, and description is abbreviate | omitted.

  As shown in FIG. 2, the wavelength conversion sheet 200 of the present embodiment includes a phosphor layer (wavelength conversion layer) 1 containing a phosphor, and one surface 2 a side and the other surface 2 b side of the phosphor layer 1. The wavelength conversion sheet protective films 20 and 20 provided are roughly configured. Thus, the phosphor layer 1 is enclosed (sealed) between the wavelength conversion sheet protective films 20 and 20.

(Protective film for wavelength conversion sheet)
The protective film 20 for wavelength conversion sheet of this embodiment has two barrier films 5 having a base material 8 and a barrier layer 9, an adhesive layer 6, and a coating layer 7. When the two barrier films 5 are the first barrier film 5 that is far from the phosphor layer 1 and the second barrier film 5 that is near the phosphor layer 1, as shown in FIG. The barrier layer 9 provided on the one surface 8a of the first substrate 8 of the first barrier film 5 and the one surface 8a of the second substrate 8 of the second barrier film 5 are provided. The barrier layer 9 is laminated so as to oppose the adhesive layer 6. In other words, the protective film 20 for wavelength conversion sheet is formed between the barrier films 5 such that the respective barrier layers 9 of the two barrier films 5 are sandwiched between the first substrate 8 and the second substrate 8. Have a laminated structure. According to the configuration of the protective film 20 for wavelength conversion sheet, since the base material 8 is disposed between the barrier layer 9 and the phosphor layer 1 to be protected, there are irregularities and foreign matters on the phosphor layer 1. However, the impact can be alleviated by the base material 8, and the barrier layer 9 can be prevented from being damaged.

  And when comprising the wavelength conversion sheet 200 of this embodiment, as shown in FIG. 2, each protective film 20 for wavelength conversion sheets 20 and 20 is the 2nd base material 8 of the 2nd barrier film 5. As shown in FIG. Lamination is performed with the side surface facing the phosphor layer 1 side. More specifically, in the wavelength conversion sheet 200, the wavelength conversion sheet protective films 20 and 20 are provided with the barrier layer 9 of the second base material 8 of the second barrier film 5 having no coating layer 7. The surfaces 8 b opposite to the formed surfaces are stacked so as to be sandwiched between the phosphor layers 1. That is, also in this embodiment, the coating layer 7 is provided on each surface of the wavelength conversion sheet protective films 20 and 20 and is provided on both surfaces of the wavelength conversion sheet 200.

  The thicknesses of the two base materials 8 of the protective film 20 for wavelength conversion sheet may be the same or different. From the viewpoint of making the thickness of the wavelength conversion sheet 200 thinner, the thickness of the second substrate 8 of the second barrier film 5 disposed on the side close to the phosphor layer 1 is set to the side far from the phosphor layer 1. You may make it thinner than the 1st base material 8 of the 1st barrier film 5 arrange | positioned. Since moisture and gas permeate from the surface of the wavelength conversion sheet 200, the thickness of the first substrate 8 is relatively increased to prevent moisture and oxygen from being transmitted from the surface, and the second substrate 8 The thickness of the entire wavelength conversion sheet 200 can be reduced by relatively reducing the thickness. The permeation of moisture and oxygen occurs not only from the surface of the barrier film 5 but also from the end face, so that the thinner the second substrate 8 can suppress the intrusion of moisture and oxygen from the end face. For this reason, it is desirable that the thickness of the second base material 8 adjacent to the phosphor layer 1 be 40 μm or less.

  The thicknesses of the two barrier layers 9 of the protective film 20 for wavelength conversion sheet may be the same or different. From the viewpoint of making the thickness of the wavelength conversion sheet 200 thinner, the thickness of the second barrier layer 9 of the second barrier film 5 disposed on the side close to the phosphor layer 1 is set to the side far from the phosphor layer 1. You may make it thinner than the 1st barrier layer 9 of the 1st barrier film 5 arrange | positioned. Since moisture and gas permeate from the surface of the wavelength conversion sheet 200, the thickness of the first barrier layer 9 is relatively increased to prevent moisture and oxygen from being transmitted from the surface, and the second barrier layer 9 The thickness of the entire wavelength conversion sheet 200 can be reduced by relatively reducing the thickness. Therefore, among the first barrier layer 9 of the first barrier film 5 and the second barrier layer 9 of the second barrier film 5, at least the thickness of the second barrier layer 9 of the second barrier film 5 is set. More preferably, the thickness is 2 μm or less.

  According to the wavelength conversion sheet 200 of 2nd Embodiment demonstrated above, the effect similar to the wavelength conversion sheet 100 of 1st Embodiment mentioned above can be acquired.

(Backlight unit)
FIG. 3 shows an embodiment of the backlight unit. The backlight unit 500 of the present invention includes an LED light source 15, a light guide plate 15, and a wavelength conversion sheet 100. Further, although omitted in the drawing, a reflection plate, a diffusion plate, a prism sheet, or the like may be provided. The LED light source 15 is installed on the side surface of the light guide plate. A plurality of LED elements whose emission color is blue are provided inside the LED light source 15. This LED element may be a purple LED or even a lower wavelength LED. The LED light source emits light toward the side surface of the light guide plate. In the case of the backlight unit using the wavelength conversion sheet 100 of the present embodiment, the irradiated light is, for example, a layer (phosphor layer) 1 in which a resin such as acrylic or epoxy is mixed with a phosphor through a light guide plate. Will be incident on.

  A backlight unit for a liquid crystal display can be provided using the wavelength conversion sheet 100 or 200 described above. The backlight unit according to the present embodiment includes an LED (light emitting diode) light source, a light guide plate, and a wavelength conversion sheet 100 or 200. The LED light source is installed on the side surface of the light guide plate, and the wavelength conversion sheet 100 or 200 is disposed on the light guide plate (light traveling direction).

  The light guide plate efficiently guides the light emitted from the LED light source 15, and a known material is used. As the light guide plate 16, for example, acrylic, polycarbonate, cycloolefin film, or the like is used. The light guide plate can be formed by, for example, a silk printing method, a molding method such as injection molding or extrusion molding, or an ink jet method. The thickness of the light guide plate is, for example, 100 to 1000 μm.

  The preferred embodiments of the present invention have been described in detail above. However, the technical scope of the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. It is. For example, the configurations of the wavelength conversion sheets 100 and 200, the phosphor protective films 20 to 23, and the backlight unit 500 of the first and second embodiments described above are examples, and are not limited thereto.

  Further, in the wavelength conversion sheet of the present invention, as in the first and second embodiments described above, the phosphor layer 1 may be sandwiched between the same phosphor protective films 20 to 23, and the phosphors having different configurations may be used. It may be sandwiched between body protection films.

  In addition, the wavelength conversion sheet of the present invention may have a configuration in which one of the phosphor protective films covering the phosphor layer 1 has the coating layer 7, or both phosphors The structure which has the coating layer 7 may be sufficient as a protective film.

  In the wavelength conversion sheet of the present invention, the surface of the phosphor protective film on the side in contact with the phosphor layer 1 is modified to improve the adhesion between the phosphor protective film and the phosphor layer 1. It may be provided, or an easy adhesion layer made of urethane resin or the like may be provided.

  In the wavelength conversion sheets 100 and 200 shown in FIGS. 1 and 2, the barrier layer 9 has the inorganic thin film layer 10 and the gas barrier coating layer 11 one by one. Two or more layers of the thin film layer 10 and the gas barrier coating layer 11 may be provided. In this case, the inorganic thin film layers 10 and the gas barrier coating layers 11 are preferably laminated alternately.

  Further, in the wavelength conversion sheets 100 and 200 shown in FIG. 1 and FIG. 2, both end faces of the phosphor layer 1 (left and right end faces in the figure not covered with the wavelength conversion sheet protective films 2 and 20) are sealed. It may be sealed with a resin, and the entire phosphor layer 1 may be covered with a sealing resin.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

[Example 1]
(Preparation of protective film for wavelength conversion sheet)
On one side of a 25 μm-thick polyethylene terephthalate film as a base material, silicon oxide is provided as an inorganic thin film layer to a thickness of 0.03 μm by vacuum deposition, and a coating liquid containing tetraethoxysilane and polyvinyl alcohol is wet-coated. Was applied onto the inorganic thin film layer to form a gas barrier coating layer having a thickness of 0.6 μm. This obtained the 1st barrier film by which the 0.63 micrometer 1st barrier layer which consists of an inorganic thin film layer and a gas-barrier coating layer was provided on the one surface of the base material. On the other hand, in the same manner, a second barrier film was obtained in which a 0.63 μm second barrier layer comprising an inorganic thin film layer and a gas barrier coating layer was provided on one surface of the substrate.

  Subsequently, a coating liquid containing an acrylic resin and silica fine particles (average particle diameter of 3 μm) is applied to the surface side (base material side) opposite to the gas barrier coating layer of the first barrier film by a wet coating method. Then, a coating layer having a thickness of 5 μm was formed. This obtained the barrier film with a coating layer.

  Next, the gas barrier coating layer side of the barrier film with the coating layer and the surface side (base material side) opposite to the gas barrier coating layer of the second barrier film not having the coating layer are bonded with an acrylic resin adhesive. The protective film for wavelength conversion sheets of Example 1 was obtained by using and bonding together. Two protective films for wavelength conversion sheets were produced.

(Production of wavelength conversion sheet)
After mixing CdSe / ZnS 530 (trade name, manufactured by SIGMA-ALDRICH) as a quantum dot with an epoxy-based photosensitive resin, the mixed solution is applied to the gas barrier coating layer side of the protective film for wavelength conversion sheet described above. A wavelength conversion sheet protective film having the same structure as above was laminated, and the wavelength conversion sheet of Example 1 having the structure shown in FIG. 1 was obtained by UV curing lamination.

(Production of backlight unit)
The backlight unit of Example 1 was produced by combining the obtained wavelength conversion sheet with an LED light source and a light guide plate.

[Example 2]
In Example 1, the same operation was performed except that the thickness of the gas barrier coating layer was 1.75 μm so that the first barrier layer and the second barrier layer were 1.8 μm. The protective film for wavelength conversion sheets of Example 2 was obtained. Furthermore, the wavelength conversion sheet and the backlight unit of Example 2 were obtained in the same manner as in Example 1 except that this wavelength conversion sheet protective film was used.

[Example 3]
The wavelength conversion sheet of Example 3 was prepared in the same manner as in Example 1, except that the thickness of the gas barrier coating layer was 2.45 μm, so that the second barrier layer was 2.48 μm. A protective film was obtained. Furthermore, the wavelength conversion sheet and backlight unit of Example 3 were obtained in the same manner as in Example 1 except that this wavelength conversion sheet protective film was used.

[Example 4]
The wavelength conversion sheet of Example 4 was prepared in the same manner as in Example 1 except that the thickness of the gas barrier coating layer was 2.45 μm, so that the first barrier layer was 2.5 μm. A protective film was obtained. Furthermore, the wavelength conversion sheet and backlight unit of Example 4 were obtained in the same manner as in Example 1 except that this wavelength conversion sheet protective film was used.

[Comparative example]
In Example 1, the thickness of the gas barrier coating layer was formed to be 2.45 μm, so that the first barrier layer and the second barrier layer were changed to 2.5 μm. The protective film for wavelength conversion sheets of an example was obtained. Furthermore, the wavelength conversion sheet and the backlight unit of the comparative example were obtained by the same operation as in Example 1 except that this wavelength conversion sheet protective film was used.

[Evaluation item]
<Brightness measurement>
About the backlight unit produced in Examples 1-4 and the comparative example, the brightness | luminance (initial brightness | luminance) at the time of LED light emission was measured using the luminance meter (Konica Minolta company make, brand name: LS-100). The obtained results are shown in Table 1.

<Luminance 15% reduction time>
About the backlight unit produced in Examples 1-4 and a comparative example, LED was made to light-emit with initial luminance 10x10 < ³ > cd / m < ² > using the luminance meter (the Konica Minolta company make, brand name: LS-100). As it was, the time change in luminance at 85 ° C. and 1 atm was measured, and the time for the initial luminance to decrease by 15% was read. The obtained results are shown in Table 1.

  As is clear from the results shown in Table 1, in the wavelength conversion sheets of Examples 1 to 4, the light transmittance does not decrease, and in the backlight unit using the wavelength conversion sheets of Examples 1 to 4, In addition, there was no decrease in brightness due to local deterioration factors entering the interior.

  On the other hand, in the wavelength conversion sheet of the comparative example, the light transmittance is decreased, and in the backlight unit using the wavelength conversion sheet of the comparative example, the luminance is decreased due to the local entry of the degradation factor. It was.

  The protective film for wavelength conversion sheets which is the laminate film which laminated | stacked two or more barrier films of this invention, the wavelength conversion sheet which coat | covered the fluorescent substance layer with this protective film for wavelength conversion sheets, and this wavelength conversion sheet were used. By using the backlight unit, it is possible to manufacture an excellent high-definition display.

  DESCRIPTION OF SYMBOLS 1 ... Phosphor layer, 2,20 ... Protective film for wavelength conversion sheet, 3 ... Phosphor, 4 ... Sealing resin, 5 ... Barrier film, 6 ... Adhesive layer, 7 ... Coating layer, 8 ... Base material, 9 ... Barrier layer, 10 ... inorganic thin film layer, 11 ... gas barrier coating layer, 100, 200 ... wavelength conversion sheet.

Claims (4)

A protective film for a wavelength conversion sheet for protecting the phosphor in the wavelength conversion sheet,
A first barrier film having a first substrate and a first barrier layer provided on at least one surface of the first substrate;
A second barrier film having a second substrate and a second barrier layer provided on at least one surface of the second substrate;
And a thickness of at least one barrier layer of the barrier layer is 2 μm or less.   The wavelength conversion sheet protective film according to claim 1, wherein the barrier layer includes an inorganic thin film layer and a gas barrier coating layer.   A wavelength conversion sheet comprising a phosphor layer containing quantum dots and the phosphor protective film according to claim 1 disposed above and below the phosphor layer. An LED light source;
The wavelength conversion sheet according to claim 3,
A light guide plate that allows light to be incident on the wavelength conversion sheet from the blue LED light source;
Backlight unit with