JP2016218339A - Phosphor protective film, wavelength conversion sheet and backlight unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength conversion sheet that suppresses luminance unevenness and color unevenness of the sheet caused by uneven film thickness of a protective film and achieves high barrier property.SOLUTION: A phosphor protective film for protecting a phosphor in a wavelength conversion sheet is provided, which has such a structure that a film having a first substrate and a coating layer having an optical function disposed on one surface of the first substrate and a film having a second substrate and one or more barrier layers disposed on one surface of the second substrate are laminated. The thickness of the first substrate is smaller than the thickness of the second substrate.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a phosphor protective film, 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

  When a display is made using a wavelength conversion sheet in which a phosphor such as a quantum dot is sealed with a barrier film, if the thickness of the phosphor layer varies, the degree of converted light will change. When light is converted, luminance unevenness and color unevenness are generated, resulting in poor color tone when mounted on a display. One reason for this is that if the thickness of the protective film is uneven, when the phosphor and the protective film are laminated, the unevenness of the protective film affects the thickness of the phosphor layer. Wavelength conversion sheets and backlight units mounted on displays for mobile devices, etc., require thinning, and wavelength conversion sheets also require thinning, but as the film thickness decreases, unevenness during lamination is also noticeable. become.

  The present invention has been made in view of such circumstances, and as a protective film for protecting the phosphor in the wavelength conversion sheet, it suppresses the occurrence of luminance unevenness and color unevenness and has high barrier properties against deterioration factors. An object of the present invention is to provide a phosphor protective film, and a wavelength conversion sheet and a backlight unit using the same.

To solve the above problem,
A protective film for protecting the phosphor,
A structure in which a film having a first substrate, a second substrate, and a film having one or more barrier layers provided on one surface of the second substrate are laminated. The phosphor protective film is characterized in that the thickness of the first base material is smaller than the thickness of the second base material. Thereby, generation | occurrence | production of the brightness nonuniformity and color nonuniformity which arise with a protective film can be suppressed.
Furthermore, the thickness of the second substrate is 40% or more and 90% or less of the total thickness of the protective film.
Furthermore, the thickness of the entire protective film is 50 μm or less.
Moreover, it is set as the wavelength conversion sheet | seat characterized by including the fluorescent substance layer containing a quantum dot and the protective film which has arrange | positioned the fluorescent substance layer up and down, and using the said fluorescent substance protective film.
Moreover, it is set as the 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 a blue LED light source.

  According to the present invention, as a protective film for protecting the phosphor in the wavelength conversion sheet, a phosphor protective film that suppresses the occurrence of luminance unevenness and color unevenness and has a high barrier property against deterioration factors, and The used wavelength conversion sheet and 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 modification of the phosphor protective film according to the first embodiment of the present invention. FIG. 3 is a modification of the phosphor protective film according to the first embodiment of the present invention. FIG. 4 is a schematic cross-sectional view of a wavelength conversion sheet according to the second embodiment of the present invention. FIG. 5 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 1 a side and the other surface 1 b side of the phosphor layer 1. And a fluorescent protective film (hereinafter also simply referred to as “protective film”) 20 and 20 provided. Thus, the phosphor layer 1 is encapsulated (that is, sealed) between the protective films 20 and 20. Here, since it is necessary to impart barrier properties to the phosphor layer 1, it is desirable that the phosphor layer 1 be sandwiched between the pair of phosphor protective films 20 and 20. 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 the LED light source wavelength is two types of phosphors 3 used in a blue LED (peak wavelength: 450 nm), each fluorescent color is preferably red or 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, a quantum dot that has high color purity and can be expected to improve luminance is 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 may be used alone 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.

(Phosphor protective film)
The phosphor protective film 20 includes a barrier film 5 having a substrate 12 and a barrier layer 9, an adhesive layer 6, and a substrate 8. And it laminates | stacks so that the barrier layer 9 formation surface of the barrier film 5 and the base material 8 may oppose the other base material 8 through the contact bonding layer 6. FIG. Furthermore, the coating layer 7 in which the coating layer 7 is provided on one surface 8b of the base material 8 is provided as needed. In other words, when the farther from the phosphor layer 1 is the first substrate 8, the closer to the phosphor layer 1 is the second substrate 12 on which the barrier layer is laminated, the first substrate, A film having a coating layer 7 provided on one surface 8b of the first substrate, a second substrate 12, and a barrier layer 9 provided on one surface 12a of the second substrate. The barrier layer 9 is laminated so that the first substrate and the barrier layer 9 forming surface of the second substrate face each other with the adhesive layer 6 interposed therebetween. By adopting such a configuration, it is possible to prevent damage to the barrier layer 9 during manufacturing and to suppress a decrease in barrier properties due to defects in the barrier layer.

  As shown in FIG. 1, the barrier film 5 includes a base material 12 and a barrier layer 9 provided on one surface 12 a of the base material 12.

  Although it does not specifically limit as the base materials 8 and 12, The base material whose total light transmittance is 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 desirably 12 μm or more in order to obtain excellent barrier properties. The thickness of the substrate 12 is not particularly limited, but is desirably 80 μm or less in order to reduce the total thickness of the wavelength conversion sheet 100.

  The thickness of the first base material 8 is preferably smaller than the thickness of the second base material 12. By increasing the thickness of the second base material, the thermal shrinkage of the second base material due to the heat history when forming the barrier layer 9 that causes the unevenness of the thickness of the barrier film 5, By making the thickness of the first base material relatively small, a decrease in the transmittance of the entire phosphor protective film 20 can be prevented, and as a result, luminance unevenness and color unevenness can be reduced.

  Specifically, the thickness D1 of the first substrate 8 is preferably in the range of 4 to 30 μm, and the thickness D2 of the second substrate 12 is preferably in the range of 16 to 80 μm. Moreover, it is preferable that difference D2-D1 of the thickness of the 1st base material 8 and the thickness of the 2nd base material 8 exists in the range of 5-76 micrometers. By setting D1 to 4 μm to 30 μm, it is possible to suppress shape defects during lamination. By setting D2 to 16 to 80 μm, curling of the phosphor protective film 20 can be suppressed. Furthermore, in order to realize the thin phosphor protective film 20 of 50 μm or less, the thickness D1 of the first base material 8 is in the range of 4 to 20 μm, and the thickness D2 of the second base material 12 is More preferably, it is in the range of 16 to 45 μm. Moreover, it is more preferable that the difference D2-D1 between the thickness of the first substrate 8 and the thickness of the second substrate 8 is in the range of 5 to 45 μm.

  Moreover, the barrier layer 9 and the phosphor layer 1 are arranged by arranging the upper and lower protective films 20 and 20 so that the wavelength conversion sheet 100 and the thick second substrate 12 are positioned on the phosphor layer 1 side. Thus, the sealing effect of the phosphor layer 1 by the protective film 20 can be enhanced.

  The barrier layer 9 is not particularly limited, but preferably includes an inorganic thin film layer 10 and a gas barrier coating layer 11. As an example of the configuration of the barrier layer, for example, as shown in FIG. 1, the barrier layer 9 is formed by laminating an inorganic thin film layer 10 on one surface (one surface) 12 a of a base material 12. A gas barrier coating layer 11 is laminated thereon.

  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 500 nm, and more preferably in the range of 10 to 100 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 500 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.

  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 the valence of M. A corresponding integer). Specific examples include tetraethoxysilane [Si (OC2H5) 4], triisopropoxyaluminum [Al (O-iso-C3H7) 3], and the like. Tetraethoxysilane and triisopropoxyaluminum are preferable because they are relatively stable in an aqueous solvent after hydrolysis. Examples of the hydrolyzate and polymer of metal alkoxide include tetraethoxysilane hydrolyzate and polymer such as silicic acid (Si (OH) 4), and tripropoxyaluminum hydrolyzate and polymer. 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.

  FIG. 2 is a modification of the phosphor protective film in the present embodiment. Like the phosphor protective film 21 in FIG. 2, the barrier layer 9 may be provided on the other surface of the base material 8 on which the coating layer 7 is provided on the one surface 8 b. As described above, the barrier layer 9 is laminated on the one surface 12 a of the second base material 12, and the barrier layer 9 is sandwiched between the first base material 8 and the second base material 12. In addition, since each barrier layer 9 is disposed closer to the phosphor layer 1, even if a defect such as a minute pinhole is generated in the barrier layer 9, it is more effective. In particular, the barrier performance can be exhibited.

  FIG. 3 shows another modification of the phosphor protective film in the present embodiment. As in the phosphor protective film 22 of FIG. 3, the barrier layer 9 may be formed by laminating a plurality of inorganic thin film layers 10 and gas barrier coating layers 11. In particular, since the inorganic thin film layer 10 and the gas barrier coating layer 11 are alternately laminated, defects such as minute pinholes in the inorganic thin film layer 10 are caused by the presence of the gas barrier coating layer 11 and the other inorganic thin film layer 10. Can be prevented, and the barrier performance can be improved.

  The barrier layer 9 may include an anchor coat layer as necessary. The anchor coat layer is provided in order to improve the adhesion between the base material 8 and the inorganic thin film layer 10. Further, the anchor coat layer may have a barrier property that prevents permeation of moisture and oxygen.

  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, if the thickness is 5 nm or more, the adhesion between the base material 8 and the inorganic thin film layer 10 and the barrier property against moisture and oxygen tend to be improved. There is a tendency that a uniform layer in which stress is sufficiently suppressed can be formed.

  As shown in FIG. 2, 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 phosphor 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 phosphor 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. 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. In this way, by providing the coating layer 7 on each surface of the phosphor protective films 2, 2, that is, one surface or both surfaces of the wavelength conversion sheet 100, 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. .

  In the phosphor protective film 20 having the above-described configuration, the thickness of the second base material 12 provided with the barrier layer 9 on one surface 12a is provided with the coating layer 7 on the one surface 8b. Since it is larger than the thickness of the first base material 8, it is possible to suppress thermal wrinkles of the protective film at the time of manufacturing the barrier film and deformation at the time of lamination with the phosphor layer 1, thereby suppressing occurrence of luminance unevenness and color unevenness. be able to. And by using this fluorescent substance protective film 2 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. Is possible. In particular,

  Moreover, when providing a barrier layer also on the 1st base material 8, fluorescent substance of the thickness nonuniformity of a barrier film is arrange | positioned so that the 2nd base material 12 with a large thickness may become the quantum dot formation surface side. 1 can be suppressed, and the occurrence of luminance unevenness and color unevenness in the wavelength conversion sheet can be suppressed.

  In addition, the phosphor protective films 20 to 22 of the present invention are particularly effective in a thin protective film having a thickness of 50 μm or less, which is particularly affected by heat wrinkles and deformation. Moreover, it is preferable that the thickness of a 2nd base material is 40 to 90% of the thickness of the whole protective film. By setting it to 40% or more, it is possible to ensure a film thickness sufficient to withstand heat wrinkles and deformation.

  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 fluorescent substance protective films 20 and 20 with the following procedures, for example.

(Manufacturing process of phosphor protective film 2)
In the manufacturing process of the phosphor 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.

  Moreover, the inorganic thin film layer 10 is laminated | stacked on the one surface 12a of the 2nd base material 12 by a 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. Thereby, the barrier film 5 in which the barrier layer 9 including the inorganic thin film layer 10 and the gas barrier coating layer 11 is provided on one surface of the second substrate 12 is obtained.

  Next, the film on which the coating layer 7 is formed and the barrier film 5 on which the barrier layer 9 is formed are bonded together using the adhesive layer 6 and laminated. Specifically, the first base material 8 provided with the coating layer 7 and the barrier layer forming surface of the barrier film 5 are opposed to each other and are laminated 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 phosphor protective film 2 in which two films are laminated 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. For example, two films before the coating layer 7 are formed are pasted. After the matching, the coating layer 7 may be formed on the surface 8b of the first substrate 8. Of course, when the coating layer 7 is not formed, this step is unnecessary.

(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. Next, the prepared mixed solution is applied to the surface of the phosphor protective film 2 where the coating layer 7 is not provided. Next, the other phosphor protective film 2 produced separately is laminated. At this time, the surfaces 1a and 1b of the phosphor layer 1 and the surfaces of the two phosphor 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 one phosphor protective film 2 where the coating layer 7 is not provided, and then the other phosphor protective film is formed on the surface of the phosphor layer 1. Although the example which laminates | stacks 2 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. 4 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 is different from the wavelength conversion sheet 100 of the first embodiment only in the configuration of the phosphor protective film 23. 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. 4, the wavelength conversion sheet 200 of the present embodiment includes a phosphor layer (wavelength conversion layer) 1 containing a phosphor, and one surface 1 a side and the other surface 1 b side of the phosphor layer 1. It is schematically configured with the provided phosphor protective films 23 and 23. Thus, the phosphor layer 1 is encapsulated (sealed) between the phosphor protective films 23 and 23.

(Phosphor protective film)
The phosphor protective film 23 of this embodiment, the barrier film 5 having the base material 12 and the barrier layer 9, the adhesive layer 6, the base material 8, and the coating layer 7 are included. And the base material 12 in which the coating layer 7 was provided on the one surface 12b has the barrier layer 9 on the one surface 12a of the base material 12, and the barrier layer 9 is interposed between the base material 8 through the adhesive layer 6. Are stacked so as to face each other. In other words, when the first substrate 12 is the one far from the phosphor layer 1 and the second substrate 8 is the one near the phosphor layer 1, the first substrate 12 and the first substrate 12. A film (barrier film 5) having a coating layer 7 provided on one surface 12b and a barrier layer 9 provided on one surface 12a of the first substrate, and a second substrate 8 Are laminated so that the second substrate 8 and the barrier layer 9 face each other with the adhesive layer 6 in between. According to the configuration of the phosphor protective film 20, since the base material 8 is disposed between the barrier layer 9 and the phosphor layer 1 to be protected, even when irregularities or foreign matter exist on the phosphor layer 1, 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. 4, each fluorescent substance protective film 23 and 23 orient | assigns the 2nd base material 8 to the fluorescent substance layer 1 side. Laminate. More specifically, in the wavelength conversion sheet 200, the phosphor protective films 23 and 23 are laminated so that the base material 8 is sandwiched between the phosphor layers 1. That is, also in this embodiment, the coating layer 7 is provided on each surface of the phosphor protective films 23 and 23 and is provided on both surfaces of the wavelength conversion sheet 200.

  In addition to the effects described in the first embodiment, the distance between the barrier layer 9 and the phosphor layer 1 can be made as close as possible by making the film thickness of the substrate 8 thinner than the film thickness of the substrate 12. Intrusion of oxygen and moisture into 1 can be suppressed.

  The thickness of the second substrate 12 is preferably larger than the thickness of the first substrate 8. By increasing the thickness of the second base material, the thermal shrinkage of the second base material due to the heat history when forming the barrier layer 9 that causes the unevenness of the thickness of the barrier film 5, And about a 1st base material, while not forming an inorganic thin film layer and a gas-barrier coating layer, while not applying a heat history, while suppressing heat shrink and making thickness relatively small, the fluorescent substance protective film 23 It is possible to prevent a decrease in overall transmittance, and as a result, it is possible to reduce luminance unevenness and color unevenness.

  From the above, the thickness D1 of the first substrate 8 is preferably in the range of 4 to 20 μm, and the thickness D2 of the second substrate 12 is preferably in the range of 16 to 80 μm. By setting the thickness D1 of the first base material 8 to 4 to 20 μm, the impact can be alleviated by the base material 8 and the barrier layer 9 can be prevented from being damaged and the shape defect at the time of lamination can be suppressed. . By setting D2 to 16 to 80 μm, curling of the phosphor protective film 23 can be suppressed.

  As in the phosphor protective film 22 of FIG. 3, the barrier layer 9 may be formed by laminating a plurality of inorganic thin film layers 10 and gas barrier coating layers 11. In particular, since the inorganic thin film layer 10 and the gas barrier coating layer 11 are alternately laminated, defects such as minute pinholes in the inorganic thin film layer 10 are caused by the presence of the gas barrier coating layer 11 and the other inorganic thin film layer 10. Can be prevented, and the barrier performance can be improved.

  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. 5 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.

  Moreover, in the wavelength conversion sheet 100,200 shown in FIG.1 and FIG.4, although the case where the barrier layer 9 had the inorganic thin film layer 10 and the gas barrier coating layer 11 one by one was shown, the barrier layer 9 is inorganic 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.

  Furthermore, in the wavelength conversion sheets 100 and 200 shown in FIGS. 1 and 4, both end faces of the phosphor layer 1 (the left and right end faces in the drawings not covered with the phosphor protective films 20 and 23) are sealing resins. It may be sealed, 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 phosphor protective film)
On one side of a 25 μm-thick polyethylene terephthalate film as a base material (second base material), silicon oxide is provided as an inorganic thin film layer to a thickness of 0.05 μm by vacuum deposition, and tetraethoxysilane and polyvinyl alcohol are further added. The coating liquid containing was applied on the inorganic thin film layer by a wet coating method and dried by heating to form a gas barrier coating layer having a thickness of 0.45 μm. This obtained the barrier film in which the barrier layer which consists of an inorganic thin film layer and a gas-barrier coating layer was provided on the one surface of the 2nd base material.

  Subsequently, silicon oxide is provided as an inorganic thin film layer to a thickness of 0.05 μm on one side having a thickness of 15 μm as a base material (first base material), and further includes tetraethoxysilane and polyvinyl alcohol. The coating liquid was applied onto the inorganic thin film layer by a wet coating method, and dried by heating to form a gas barrier coating layer having a thickness of 0.45 μm. This obtained the barrier film in which the barrier layer which consists of an inorganic thin film layer and a gas-barrier coating layer was provided on the one surface of the 2nd base material.

  Next, the 1st base material of a barrier film and the 2nd base material of a barrier film were arrange | positioned in the direction where each barrier layer opposes, and it bonded together using the acrylic resin adhesive.

Next, a coating solution containing an acrylic resin and silica fine particles (average particle size: 3 μm) was applied to one side of the polyethylene terephthalate film of the first substrate by a wet coating method to form a coating layer having a thickness of 5 μm. . Thereby, the phosphor protective film of Example 1 was obtained. Two sheets of this phosphor protective film 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 second substrate surface of the phosphor protective film described above. A phosphor protective film having the same structure was laminated, and a wavelength conversion sheet 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].
(Preparation of phosphor protective film)
On one side of a 25 μm-thick polyethylene terephthalate film as a base material (second base material), silicon oxide is provided as an inorganic thin film layer to a thickness of 0.05 μm by vacuum deposition, and tetraethoxysilane and polyvinyl alcohol are further added. The coating liquid containing was applied on the inorganic thin film layer by a wet coating method and dried by heating to form a gas barrier coating layer having a thickness of 0.45 μm. Further, by forming the inorganic thin film layer and the gas barrier coating layer in the same process, a barrier layer in which two layers of the inorganic thin film layer and the gas barrier coating layer are alternately laminated on one surface of the second base is provided. The obtained barrier film was obtained.

  Subsequently, a coating liquid containing an acrylic resin and silica fine particles (average particle diameter: 3 μm) is applied to one surface having a thickness of 15 μm as a base material (first base material) by a wet coating method. The coating layer was formed and the 1st base material with a mat layer was produced.

  Next, the 1st base material with a coating layer and the 2nd base material of a barrier film were arrange | positioned in the direction where each barrier layer opposes, and it bonded together using the acrylic resin adhesive. Thereby, the phosphor protective film of Example 2 was obtained. Two sheets of this phosphor protective film 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 second substrate surface of the phosphor protective film described above. A phosphor protective film having the same structure was laminated, and a wavelength conversion sheet was obtained by UV curing lamination.
[Example 3]
(Preparation of phosphor protective film)
On one side of a 25 μm-thick polyethylene terephthalate film as a base material (second base material), silicon oxide is provided as an inorganic thin film layer to a thickness of 0.05 μm by vacuum deposition, and tetraethoxysilane and polyvinyl alcohol are further added. The coating liquid containing was applied on the inorganic thin film layer by a wet coating method and dried by heating to form a gas barrier coating layer having a thickness of 0.45 μm. Further, by forming the inorganic thin film layer and the gas barrier coating layer in the same process, a barrier layer in which two layers of the inorganic thin film layer and the gas barrier coating layer are alternately laminated on one surface of the second base is provided. The obtained barrier film was obtained.

  Subsequently, the base material (first base material) having a thickness of 15 μm and the second base material of the barrier film are arranged in a direction in which the barrier layer of the second base material faces the first base material, It bonded together using the acrylic resin adhesive.

  Next, a coating liquid containing an acrylic resin and silica fine particles (average particle size 3 μm) is wetted on the surface opposite to the side on which the barrier layer of the polyethylene terephthalate film of the second substrate is formed, that is, the outer surface. Coating was performed by a coating method to form a coating layer having a thickness of 5 μm. Thereby, the phosphor protective film of Example 3 was obtained. Two sheets of this phosphor protective film 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 mixture is applied to the surface of the first substrate of the phosphor protective film described above. A phosphor protective film having the same structure was laminated, and a wavelength conversion sheet was obtained by UV curing lamination.

[Comparative Example 1]
A phosphor protective film of Comparative Example 1 was obtained in the same manner as in Example 1 except that the thickness of the first substrate was 25 μm and the thickness of the second substrate was 15 μm. Further, a wavelength conversion sheet and a backlight unit of Comparative Example 1 were obtained in the same manner as in Example 1 except that this phosphor protective film was used.

[Comparative Example 2]
In Example 1, the phosphor protective film of Comparative Example 2 was obtained by the same operation except that the thickness of the first base material was 20 μm and the thickness of the second base material was 20 μm. Furthermore, a wavelength conversion sheet and a backlight unit of Comparative Example 2 were obtained in the same manner as in Example 1 except that this phosphor protective film was used.

<Appearance evaluation>
About the wavelength conversion sheet | seat produced in the Example and the comparative examples 1 and 2, the external appearance was visually confirmed in the LED light emission state, and the presence or absence of generation | occurrence | production of brightness irregularity and color irregularity was evaluated, respectively. The case where no luminance unevenness / color unevenness was visually recognized was determined as “◯”, and the case where unevenness was confirmed was determined as “×”. The obtained results are shown in Table 1.

<Evaluation of transmitted light>
Table 1 shows the obtained results for the wavelength conversion sheets prepared in Examples 1 and 2 and Comparative Examples 1 and 2.

  As is clear from the results shown in Table 1, in the wavelength conversion sheet of Example 1, the thickness of the first base material is smaller than the thickness of the second base material, and thus, for example, a gas barrier coating layer is formed. The heat shrinkage of the second base material due to the heat treatment (drying of the coating film) and the decrease in the transmittance of the entire phosphor protective film can be suppressed, and as a result, the occurrence of luminance unevenness and color unevenness is suppressed. I was able to.

  On the other hand, in the wavelength conversion sheets of Comparative Examples 1 and 2, since the thickness of the first substrate is larger than or the same as the thickness of the second substrate, the shrinkage of the second substrate and the whole phosphor protective film Due to the decrease in transmittance, it was not possible to suppress the occurrence of luminance unevenness and color unevenness.

  A phosphor protective film which is a laminate film in which two or more barrier films of the present invention are laminated, a wavelength conversion sheet having a phosphor layer covered with the phosphor protective film, and a backlight unit using the wavelength conversion sheet By using it, an excellent high-definition display can be manufactured.

  DESCRIPTION OF SYMBOLS 1 ... Phosphor layer, 20, 21, 22 ... Phosphor protective film, 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, 101 ... wavelength conversion sheet, 15 ... LED light source, 16 ... light guide plate, 500 ... backlight unit

Claims (6)

A protective film for protecting the phosphor,
A structure in which a film having a first substrate, a second substrate, and a film having one or more barrier layers provided on one surface of the second substrate are laminated. A phosphor protective film having a thickness of the first base material smaller than that of the second base material.   2. The phosphor protective film according to claim 1, wherein the thickness of the second substrate is 40% or more and 90% or less of the thickness of the entire protective film.   The phosphor protective film according to claim 1 or 2, wherein the total thickness of the protective film is 50 µm or less. A phosphor layer containing quantum dots, and a phosphor protective film according to any one of claims 1 to 3 disposed above and below the phosphor layer,
The wavelength conversion sheet, wherein the phosphor protective film is laminated so that the second substrate is closer to the phosphor layer than the first substrate. A phosphor layer containing quantum dots, and a phosphor protective film according to any one of claims 1 to 3 disposed above and below the phosphor layer,
A wavelength conversion sheet, wherein the phosphor protective film is laminated so that the first substrate is closer to the phosphor layer than the second substrate. An LED light source;
The wavelength conversion sheet according to claim 4 or 5,
A light guide plate that allows light to be incident on the wavelength conversion sheet from the blue LED light source;
Backlight unit with