JP2016194552A - Quantum dot sheet, backlight device, display, and manufacturing method of quantum dot sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively suppress a barrier film from being peeled off at the ends from a quantum dot layer.SOLUTION: According to an aspect of the present invention, there is provided a quantum dot sheet comprising: a quantum dot layer that includes a light incident surface receiving light and a light emission surface emitting light, and quantum dots and a binder resin converting the wavelength of the light received on the light incident surface; a first barrier film that is adhered to the light incident surface of the quantum dot layer; and a second barrier film that is adhered to the light emission surface of the quantum dot layer, wherein the initial peeling strength of the first barrier film at the ends of the light incident surface of the quantum dot layer, and the initial peeling strength of the second barrier film at the ends of the light emission surface of the quantum dot layer are 2.0 N/25 mm or more in a condition of a rate of pulling of 0.3 m/min.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a quantum dot sheet, a backlight device, a display device, and a method for manufacturing a quantum dot sheet.

  2. Description of the Related Art A transmissive image display device such as a liquid crystal display device generally includes a backlight device that is disposed on the back side of a transmissive image display panel such as a liquid crystal display panel and illuminates the transmissive image display panel. As the backlight device, an edge light type or a direct type backlight device is known.

  Currently, in order to improve color reproducibility, it has been studied to incorporate quantum dots into a backlight device (see Patent Document 1). Quantum dots can absorb light and emit light of different wavelengths. The wavelength of the light emitted from the quantum dot mainly depends on the particle size of the quantum dot. Therefore, a backlight device incorporating quantum dots can reproduce various colors while using a light source that projects light in a single wavelength region. For example, when using a light source that emits blue light, the quantum dots can absorb blue light and emit green light and red light. Since such a backlight device is excellent in color purity, a display device using this backlight device has excellent color reproducibility.

JP 2013-218953 A

  Here, since the quantum dot may be deteriorated by moisture, oxygen, etc., and the light wavelength conversion efficiency may be lowered, it is necessary to avoid contact with moisture, oxygen, etc. as much as possible. Therefore, when quantum dots are dispersed in a resin or the like and used as a sheet-like member, the quantum dots are protected from moisture and oxygen by covering the layer containing the quantum dots with a barrier film. However, a sheet-like member (hereinafter referred to as a quantum dot sheet) in which a layer containing such quantum dots is covered with a barrier film is used at a high temperature of 50 ° C. or higher when used in a backlight device. If the adhesion strength between the barrier film and the quantum dot layer is low, the barrier film may be peeled off from the edge of the quantum dot sheet, and the quantum dot layer may be exposed to moisture or oxygen. There is.

  The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a quantum dot sheet that does not easily peel off even when exposed to high temperature or high temperature and high humidity, and a method for manufacturing the quantum dot sheet.

  According to one aspect of the present invention, a quantum that includes a light incident surface that receives light and a light output surface that emits light, and that includes a quantum dot that performs wavelength conversion of light received from the light incident surface and a binder resin. A dot layer; a first barrier film in close contact with the light incident surface of the quantum dot layer; and a second barrier film in close contact with the light exit surface of the quantum dot layer, the input of the quantum dot layer The initial peel strength of the first barrier film at the end of the light surface and the initial peel strength of the second barrier film at the end of the light exit surface of the quantum dot layer are conditions of a tensile speed of 0.3 m / min. Thus, a quantum dot sheet that is 2.0 N / 25 mm or more is provided.

  According to another aspect of the present invention, the backlight includes a light source and the quantum dot sheet, and the light incident surface of the quantum dot layer in the quantum dot sheet is a surface that receives light from the light source. An apparatus is provided.

  According to another aspect of the present invention, there is provided a display device comprising the above backlight device and a display panel disposed on the light output side of the backlight device.

According to still another aspect of the present invention, on one side of the first barrier film, a quantum dot layer composition containing quantum dots and a photopolymerizable compound is applied to form a coating film, In a state where the second barrier film is adhered to the surface opposite to the surface in contact with the first barrier film, and the second barrier film is adhered, light is applied to the coating film at 200 mJ / cm ^2. There is provided a method for producing a quantum dot sheet, which is irradiated as described above to cure the coating film.

  According to the quantum dot sheet of one embodiment of the present invention and the backlight device and display device of another embodiment, it is possible to effectively suppress edge peeling of the barrier film from the quantum dot layer. Furthermore, by suppressing edge peeling, it is possible to prevent the light wavelength conversion efficiency of the quantum dots from decreasing due to deterioration. Therefore, when the quantum dot sheet is incorporated in the backlight device, the light emitting surface of the backlight device Further, it is possible to prevent the color change in the vicinity of the end portion from occurring. Moreover, according to the method for producing a quantum dot sheet of still another aspect of the present invention, the initial peel strength of the first barrier film at the end of the light incident surface of the quantum dot layer, and the end of the light exit surface of the quantum dot layer It is possible to provide a quantum dot sheet in which the initial peel strength of the second barrier film in the part is 2.0 N / 25 mm or more under conditions of a tensile speed of 0.3 m / min.

It is a schematic block diagram of the quantum dot sheet which concerns on 1st Embodiment. It is a partial expanded sectional view of the quantum dot sheet concerning a 1st embodiment. It is a figure which shows typically the manufacturing process of the quantum dot sheet which concerns on 1st Embodiment. It is a schematic block diagram of the backlight apparatus and display apparatus containing the quantum dot sheet which concern on 1st Embodiment. It is a schematic block diagram of the other backlight apparatus containing the quantum dot sheet which concerns on 1st Embodiment. It is a perspective view of the lens sheet concerning a 1st embodiment. It is sectional drawing along the II line of the lens sheet of FIG. It is sectional drawing of the reflective polarization separation sheet which concerns on 1st Embodiment. It is a schematic block diagram of the quantum dot sheet which concerns on 2nd Embodiment. It is a figure which shows typically the manufacturing process of the quantum dot sheet which concerns on 2nd Embodiment.

[First Embodiment]
Hereinafter, a quantum dot sheet according to a first embodiment of the present invention, and a backlight device and a display device incorporating the quantum dot sheet will be described with reference to the drawings. In the present specification, terms such as “sheet”, “film”, and “plate” are not distinguished from each other only based on the difference in designation. Therefore, for example, “plate” is used to include a member that is also referred to as a sheet or film, and “sheet” is used to include a member that may also be referred to as a film or a plate. Furthermore, in this specification, the “light-incident surface” of the quantum dot layer refers to a surface on which light from a light source is directly or indirectly incident. Further, in this specification, the “light exit surface” of the quantum dot layer refers to a surface from which light is emitted from the quantum dot layer, and refers to a surface opposite to the light entrance surface of the quantum dot layer. In this specification, the “end part” of the light incident surface of the quantum dot layer refers to an arbitrary part of the peripheral portion of the light incident surface of the quantum dot layer, and the “end part” of the light exit surface of the quantum dot layer. Refers to any part of the peripheral edge of the light emission surface of the quantum dot layer, and typically refers to a portion within 50 mm from the edge of the light incident surface or light emission surface of the quantum dot layer, respectively. In this specification, the “initial peel strength” refers to the peel strength in a state where a durability test or the like in a high-temperature and high-humidity environment is not performed, and is typically actually immediately after being manufactured or after being incorporated into a product. Indicates the strength when the barrier film is peeled from the quantum dot layer in an unused quantum dot sheet. FIG. 1 is a schematic configuration diagram of a quantum dot sheet according to the present embodiment, FIG. 2 is a partial enlarged sectional view of the quantum dot sheet according to the present embodiment, and FIG. 3 is a quantum dot sheet according to the present embodiment. It is a figure which shows typically the manufacturing process.

<<< Quantum dot sheet >>>>
As shown in FIG. 1, the quantum dot sheet 10 includes a quantum dot layer 11 having a light incident surface 11A and a light output surface 11B, a first barrier film 12 in close contact with the light incident surface 11A of the quantum dot layer 11, Second barrier film 13 in close contact with light exit surface 11B of quantum dot layer 11, light diffusion layer 14 provided on first barrier film 12, and light diffusion layer provided on second barrier film 13 15. The quantum dot sheet 10 only needs to include the quantum dot layer 11, the first barrier film 12, and the second barrier film 13, and does not need to include the light diffusion layers 14 and 15. Moreover, in FIG. 1, although the three-layer structure which consists of a barrier film / quantum dot layer / barrier film is shown as a quantum dot sheet, it is not limited to this, Even if it is comprised from many layers Good. For example, the quantum dot sheet may have a five-layer structure including barrier film / quantum dot layer / barrier film / quantum dot layer / barrier film. Hereinafter, the first barrier film 12 is referred to as a barrier film 12 and the second barrier film 13 is referred to as a barrier film 13 for simplification of description.

<< Quantum dot layer >>
The quantum dot layer 11 includes quantum dots 16 and a binder resin 17 for performing wavelength conversion of incident light. The quantum dot layer 11 may further include a light scattering material. As shown in FIG. 2, when light is incident from the light incident surface 11A, the light L1 incident on the quantum dot 16 is wavelength-converted into light L2 having a wavelength different from that of the light L1, and is emitted from the light exit surface 11B. On the other hand, even when light is incident from the light incident surface 11A, the light L1 passing between the quantum dots 16 is emitted from the light output surface 11B without being wavelength-converted.

  The average film thickness of the quantum dot layer 11 is preferably 10 μm or more and 200 μm or less. If the average film thickness of the quantum dot layer 11 is within this range, the display is suitable for lightening and thinning the display, and color unevenness due to fluctuations in the thickness (manufacturing tolerance) of the quantum dot layer can be suppressed. The average film thickness of the quantum dot layer is measured at, for example, 20 thicknesses from a cross-sectional image taken using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or a scanning transmission electron microscope (STEM). And it can calculate from the average value of the value of 20 places. When the film thickness of the quantum dot layer is on the order of μm, it is preferable to use SEM.

  The quantum dot layer 11 may be composed of a single layer or may be a laminated structure composed of a plurality of layers. The quantum dot layer having such a stacked structure may be composed of a plurality of layers composed of the same kind of constituent material layers, or composed of a plurality of layers composed of different kinds of constituent material layers, depending on the application. It may be.

<Quantum dots>
The quantum dot 16 is a semiconductor particle of a predetermined size having a quantum confinement effect. When the quantum dot 16 absorbs light from the excitation source and reaches an energy excitation state, the quantum dot 16 releases energy corresponding to the energy band gap of the quantum dot 16. Therefore, by adjusting the particle size of the quantum dots 16 or the composition of the substance, the energy band gap can be adjusted, and energy in various levels of wavelength bands can be obtained. In particular, the quantum dots 16 can generate strong fluorescence in a narrow wavelength band.

  Specifically, the energy band gap of the quantum dots 16 increases as the particle size decreases. That is, as the crystal size decreases, the light emission of the quantum dots shifts to the blue side, that is, to the high energy side. Therefore, by changing the particle size of the quantum dots, the emission wavelength can be adjusted over the entire wavelength range of the ultraviolet region, visible region, and infrared region. For example, depending on the material, blue light is emitted when the quantum dot particle size is 1.5 nm or more and 2.5 nm or less, and green light is emitted when the quantum dot particle size is more than 2.5 nm and 4.5 nm or less. When the particle size of the quantum dots is more than 4.5 nm and not more than 7.5 nm, red light is emitted.

  In this specification, “blue light” is light having a wavelength range of 380 nm or more and less than 480 nm, “green light” is light having a wavelength range of 480 nm or more and less than 590 nm, and “red light” is It is light having a wavelength range of 590 nm to 750 nm.

  As the quantum dots 16 included in the quantum dot layer 11, one type of quantum dot may be used, but at least two types of quantum dots having different particle diameters or materials may be used. The quantum dot layer 11 shown in FIG. 2 includes, as quantum dots 16, a first quantum dot 16A and a second quantum dot 16B having a larger particle diameter than the first quantum dot.

  As described above, since there is light that is not wavelength-converted as light emitted from the quantum dot sheet 10, a light source that emits blue light is used as a light source, and a quantum that converts blue light into green light as the first quantum dot 16A. When a dot is used and a quantum dot that converts blue light into red light is used as the second quantum dot 16B, light that is a mixture of blue light, green light, and red light is emitted from the quantum dot sheet 10. Can do.

  The quantum dots 16 can generate strong fluorescence in a desired narrow wavelength region. For this reason, the backlight device using the quantum dot sheet 10 can illuminate the display panel with light of three primary colors having excellent color purity. In this case, the display panel has excellent color reproducibility.

  The quantum dots 16 may have a core-shell structure mainly having a core made of a semiconductor compound with a thickness of about 2 nm to 10 nm and a shell made of a semiconductor compound different from the core. The shell functions as a protective layer that protects the core.

  Examples of the core material include MgS, MgSe, MgTe, CaS, CaSe, CaTe, SrS, SrSe, SrTe, BaS, BaSe, BaTe, ZnS, ZnSe, ZnTe, CdS, CdSe, CdTe, HgS, HgSe, and HgTe. II-VI group semiconductor compounds such as AlN, AlP, AlAs, AlSb, GaAs, GaP, GaN, GaSb, InN, InAs, InP, InSb, TiN, TiP, TiAs and TiSb , Semiconductor compounds such as group IV semiconductors such as Si, Ge and Pb, or semiconductor crystals containing semiconductors. Alternatively, a semiconductor crystal including a semiconductor compound containing three or more elements such as InGaP can be used. Among these, semiconductor crystals such as CdS, CdSe, CdTe, InP, and InGaP are preferable from the viewpoints of ease of manufacture and controllability of particle diameters that can obtain light emission in the visible range.

  The shell can increase the light emission efficiency of the quantum dots by using a semiconductor compound having a band gap higher than that of the semiconductor compound forming the core so that excitons are confined in the core. Examples of the core-shell structure (core / shell) having such a bandgap relationship include CdSe / ZnS, CdSe / ZnSe, CdSe / CdS, CdTe / CdS, InP / ZnS, Gap / ZnS, Si / ZnS, Examples include InN / GaN, InP / CdSSe, InP / ZnSeTe, InGaP / ZnSe, InGaP / ZnS, Si / AlP, InP / ZnSTe, InGaP / ZnSTe, and InGaP / ZnSSe.

  The quantum dots 16 may have an organic polymer called a ligand outside the shell. The organic polymer has a function of increasing the compatibility between the quantum dots and the binder resin, and is appropriately selected depending on the type of the binder resin.

  The shape of the quantum dot 16 is not particularly limited, and may be, for example, a spherical shape, a rod shape, a disk shape, or other shapes. When the quantum dots 16 are not spherical, the particle diameter of the quantum dots 16 can be a true spherical value having the same volume.

  Information such as the particle size, shape, and dispersion state of the quantum dots 16 can be obtained by a transmission electron microscope (TEM). The crystal structure and particle size of the quantum dots can be known by X-ray crystal diffraction (XRD). Furthermore, the information regarding the particle diameter etc. of a quantum dot can also be obtained with an ultraviolet-visible (UV-Vis) absorption spectrum.

<Binder resin>
The binder resin 17 is not particularly limited, but preferably contains a cured product (polymerized product, crosslinked product) of a curable binder resin precursor. Examples of the curable binder resin precursor include a polymer of a photopolymerizable compound (crosslinked product) and a polymer of a thermosetting compound such as an epoxy resin (crosslinked product). In addition, the binder resin 17 may contain a thermoplastic resin or a silicone resin. The photopolymerizable compound has at least one photopolymerizable functional group. In the present specification, the “photopolymerizable functional group” is a functional group capable of undergoing a polymerization reaction by light irradiation. Examples of the photopolymerizable functional group include ethylenic double bonds such as a (meth) acryloyl group, a vinyl group, and an allyl group. The “(meth) acryloyl group” means to include both “acryloyl group” and “methacryloyl group”. The light irradiated when polymerizing the photopolymerizable compound includes visible light and ionizing radiation such as ultraviolet rays, X-rays, electron beams, α rays, β rays, and γ rays.

  Examples of the photopolymerizable compound include a photopolymerizable monomer, a photopolymerizable oligomer, and a photopolymerizable prepolymer, which can be appropriately adjusted and used. As the photopolymerizable compound, a combination of a photopolymerizable monomer and a photopolymerizable oligomer or photopolymerizable prepolymer is preferable.

  The photopolymerizable monomer has a weight average molecular weight of 1000 or less. Examples of the photopolymerizable monomer include monomers containing a hydroxyl group such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, ethylene glycol di (meth) acrylate, Diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, tetramethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, trimethylolethane tri (meth) Acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol Tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, glycerol (meth) (meth) acrylic acid esters such as acrylate.

  The photopolymerizable oligomer has a weight average molecular weight of more than 1000 and 10,000 or less. As the photopolymerizable oligomer, a polyfunctional oligomer having two or more functions is preferable, and a polyfunctional oligomer having three (trifunctional) or more photopolymerizable functional groups is preferable. Examples of the polyfunctional oligomer include polyester (meth) acrylate, urethane (meth) acrylate, polyester-urethane (meth) acrylate, polyether (meth) acrylate, polyol (meth) acrylate, melamine (meth) acrylate, and isocyanurate. (Meth) acrylate, epoxy (meth) acrylate, etc. are mentioned.

  The photopolymerizable prepolymer has a weight average molecular weight exceeding 10,000, and the weight average molecular weight is preferably from 10,000 to 80,000, and more preferably from 10,000 to 40,000. When the weight average molecular weight exceeds 80,000, the viscosity is high, so that the coating suitability is lowered, and the appearance of the obtained quantum dot layer may be deteriorated. Examples of the polyfunctional polymer include urethane (meth) acrylate, isocyanurate (meth) acrylate, polyester-urethane (meth) acrylate, and epoxy (meth) acrylate.

<Light scattering material>
The light scattering material is not particularly limited as long as it has an action of changing the traveling direction of light entering the quantum dot layer 11 by reflection or refraction, and for example, light scattering particles can be used. As the light scattering particles, inorganic particles are preferable, and antimony-doped tin oxide (ATO) particles, indium tin oxide (ITO) particles, MgO particles, Al ₂ O ₃ particles, TiO ₂ particles, BaTiO ₃ particles, Sb ₂ O ₅ particles. More preferably, it is at least one selected from the group consisting of SiO ₂ particles, ZrO ₂ particles and ZnO particles. By adding these light scattering materials to the quantum dot layer 11, the utilization efficiency of light entering the quantum dot layer 11 can be increased and light wavelength conversion can be promoted.

<< Barrier film >>
The barrier films 12 and 13 have a function of protecting the quantum dots 16 from moisture and oxygen. That is, since the quantum dots 16 may be deteriorated by moisture, oxygen, etc., and the luminous efficiency may be reduced, the quantum dots 16 are protected from moisture and oxygen by bringing the barrier films 12 and 13 into close contact with the quantum dot layer 11. Yes.

  As the barrier films 12 and 13, a material having a function of blocking moisture, oxygen and the like and having good adhesion to the quantum dot layer 11 is used. For example, what is formed with a base film and a barrier layer can be used as the barrier films 12 and 13.

  Examples of constituent materials for such a base film include polyester (for example, polyethylene terephthalate, polyethylene naphthalate), cellulose triacetate, cellulose diacetate, cellulose acetate butyrate, polyamide, polyimide, polyethersulfone, polysulfone, and polypropylene. , Thermoplastic resins such as polymethylpentene, polyvinyl chloride, polyvinyl acetal, polyether ketone, polymethyl methacrylate, polycarbonate, and polyurethane. As a constituent material of the base film, polyester (for example, polyethylene terephthalate, polyethylene naphthalate) and cellulose triacetate are preferably used.

  Although the thickness of the said base film is not specifically limited, It is preferable that they are 10 micrometers or more and 150 micrometers or less. If the thickness of the substrate film is less than 10 μm, the quantum dot sheet may be assembled and wrinkled or broken during handling, and if it exceeds 150 μm, it may not be suitable for lightening and thinning the display. is there. The minimum with more preferable thickness of the said base film is 50 micrometers or more, and a more preferable upper limit is 125 micrometers or less.

  The base film may be composed of a single film, but may be a laminated film composed of a plurality of films. Such a laminated film may be composed of a plurality of layers composed of layers of the same kind of constituent raw materials, or may be composed of a plurality of layers composed of layers of different kinds of constituent raw materials, depending on applications. .

  Moreover, the barrier films 12 and 13 may be a laminated film in which a plurality of base material films are laminated via an adhesive layer. For example, the structure which laminated | stacked the further base film on the barrier layer of the barrier film which formed the barrier layer on the base film through the contact bonding layer may be sufficient.

The material for forming the barrier layer is not particularly limited as long as the above-described barrier property can be obtained, and examples thereof include inorganic oxides, metals, and sol-gel materials. Specifically, examples of the inorganic oxide include silicon oxide (SiOx), aluminum oxide (Al _n O _m ), titanium oxide (TiO ₂ ), yttrium oxide, boron oxide (B ₂ O ₃ ), and calcium oxide. (CaO), silicon oxynitride carbide (SiO _x N _y C _z ) and the like can be mentioned. Examples of the metal include Ti, Al, Mg, Zr and the like. Examples of the sol-gel material include siloxane-based materials. Examples thereof include sol-gel materials. These materials may be used alone or in combination of two or more.

  The thickness of the barrier layer is not particularly limited, but is preferably 0.01 μm or more and 1 μm or less. When the thickness is less than 0.01 μm, the barrier performance of the barrier layer may be insufficient. When the thickness exceeds 1 μm, the barrier performance may be easily deteriorated due to a crack in the barrier layer. A more preferable lower limit of the thickness of the barrier layer is 0.03 μm, and a more preferable upper limit is 0.5 μm.

  The thickness of the barrier layer can be obtained as an average value of the thickness of the barrier layer measured at 20 locations in the cross-sectional microscope observation. Further, the barrier layer may be a single layer or may be a laminate of a plurality of layers. When the barrier layer is formed by stacking a plurality of layers, each layer constituting the barrier layer may be directly stacked or bonded.

  Examples of the method for forming the barrier layer include a vapor deposition method such as a physical vapor deposition (PVD) method and a chemical vapor deposition (CVD) method such as a sputtering method and an ion plating method, or a roll coating method and a spin coating method. Law. Moreover, you may combine these methods.

  The barrier layer is not particularly limited as long as it is a layer having the above-described barrier properties, but it is preferable to use a vapor deposition layer formed by a vapor deposition method from the viewpoint of the high barrier property.

  Such a vapor deposition layer is not particularly limited as long as it is a layer formed by a vapor deposition method, and may be a layer formed by a CVD method, or by a PVD method. It may be a formed layer.

  When the vapor deposition layer is formed by a CVD method such as a plasma CVD method, it is possible to form a dense and highly barrier layer. However, from the viewpoint of production efficiency and cost, the vapor deposition layer is formed by the PVD method. Is preferably formed.

  Examples of the PVD method include a vacuum vapor deposition method, a sputtering method, and an ion plating method. Among them, it is preferable to use a vacuum vapor deposition method from the viewpoint of its barrier property. As a vacuum evaporation method, the vacuum evaporation method by an electron beam (EB) heating system, the vacuum evaporation method by a high frequency dielectric heating system, etc. are mentioned, for example.

The material for the vapor deposition layer is preferably a metal or an inorganic oxide, specifically, a metal such as Ti, Al, Mg, Zr, silicon oxide, aluminum oxide, silicon oxynitride, aluminum oxynitride, magnesium oxide, oxidation Examples thereof include inorganic oxides such as zinc, indium oxide, tin oxide, yttrium oxide, B ₂ O ₃ and CaO. Among these, silicon oxide is preferable from the viewpoint of high barrier properties and transparency.

  The thickness of the vapor-deposited layer varies depending on the type and configuration of the material used and is appropriately selected, but is preferably 0.01 μm or more and 1 μm or less, and more preferably 500 nm. When the thickness of the vapor deposition layer is thinner than the above range, it may be difficult to obtain a uniform layer, and the barrier property may not be obtained. In addition, when the thickness of the vapor deposition layer is thicker than the above range, the barrier property may be significantly impaired due to a crack in the vapor deposition layer due to external factors such as tension after the deposition layer is formed, In addition, it takes time to form, and productivity may be reduced.

  An anchor layer may be formed as a base layer for the barrier layer. Thereby, barrier property and a weather resistance can be improved. Examples of the material for forming the anchor layer include an adhesive resin, an inorganic oxide, an organic oxide, and a metal.

  Examples of the method for forming the anchor layer include PVD methods such as sputtering and ion plating, CVD, roll coating, and spin coating. Moreover, you may combine these methods. Among them, in-line coating at the time of film formation is preferable because it is excellent in mass productivity and can improve the adhesion of the anchor layer.

The oxygen transmission rate (OTR: Oxygen Transmission Rate) of the barrier films 12 and 13 is 1.0 × 10 ⁻¹ cc / m ² / day / atm or less under the conditions of 23 ° C. and 90% Rh (relative humidity). It is preferable that it is 1.0 × 10 ⁻² cc / m ² / day / atm or less. The oxygen permeability can be measured using an oxygen gas permeability measuring device (manufactured by MOCON, OX-TRAN 2/21).

The water vapor transmission rate (WVTR) of the barrier films 12 and 13 is preferably 1.0 × 10 ⁻¹ g / m ² / day or less under the conditions of 40 ° C. and 90% Rh. 1.0 × 10 ⁻² g / m ² / day or less is more preferable. The water vapor transmission rate can be measured using a water vapor transmission rate measuring device (DELTATAPRM (manufactured by Technolox)).

  The average thickness of the barrier films 12 and 13 is preferably 25 μm or more and 250 μm or less. If the average thickness of the barrier films 12 and 13 is within this range, the quantum dots 16 can be reliably protected from moisture and oxygen by the barrier films 12 and 13 and the adhesion strength with the quantum dot layer 11 is also ensured. Can do. In addition, by setting the average thickness of the barrier films 12 and 13 within this range, generation of wrinkles and creases during the assembly and handling of the quantum dot sheet can be suppressed, and it is advantageous for weight reduction and thinning of the display. .

  The adhesion strength between the barrier films 12 and 13 and the quantum dot layer 11 is the initial peel strength (interface peel) of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11, and the light exit surface of the quantum dot layer 11. It can be defined by the initial peel strength (interfacial peel) of the barrier film 13 at the end 11D of 11B. As the initial peel strength, the adhesive strength (N / 25 mm) at a peel angle of 180 ° is measured. The initial peel strength is required to have a strength of 2.0 N / 25 mm or more when measured at a tensile speed of 0.3 m / min. The initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 and the initial peel strength of the barrier film 13 at the end portion 11D of the light output surface 11B of the quantum dot layer 11 are 2.0 N / 25 mm or more. If it is, the edge part peeling of the barrier films 12 and 13 from the quantum dot layer 11 will be suppressed effectively. Here, when the barrier films 12 and 13 are the same material, the initial peel strength of one barrier film can be regarded as the same as the initial peel strength of the other barrier film. When the quantum dot sheet is composed of more layers than the three-layer structure of barrier film / quantum dot layer / barrier film, both quantums in at least one set of barrier film / quantum dot layer / barrier film are used. When the initial peel strength between the dot layer and the barrier film is measured under the condition of a tensile speed of 0.3 m / min, it is necessary that both are 2.0 N / 25 mm or more. Moreover, when the initial peel strength between all quantum dot layers and the barrier film is measured under the condition of a tensile speed of 0.3 m / min, all have a strength of 2.0 N / 25 mm or more. This is preferable from the viewpoint of effectively preventing the deterioration of the quantum dots.

  The lower limit of the initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 and the lower limit of the initial peel strength of the barrier film 13 at the end portion 11D of the light output surface 11B of the quantum dot layer 11 are Is preferably 3.0 N / 25 mm or more, more preferably 5.0 N / 25 mm or more, and the upper limit of the initial peel strength is preferably 500 N / 25 mm or less. Here, interfacial peeling does not occur between the quantum dot layer 11 and the barrier films 12 and 13, and the quantum dot layer 11 or the barrier films 12 and 13 may break. In such a case, the initial peel strength of the barrier films 12 and 13 from the quantum dot layer 11 cannot be measured. This is because the quantum dot layer 11 and the barrier films 12 and 13 are firmly bonded. Therefore, it is included in the present invention.

  Here, the method of measuring the initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 and the initial peel strength of the barrier film 13 at the end portion 11D of the light exit surface 11B of the quantum dot layer 11 Will be described in detail.

  The initial peel strength of the barrier film 13 can be measured using a tensile tester. For example, after the quantum dot sheet 10 is manufactured, it is cut into a 25 mm width strip, and both ends of the strip are fixed to, for example, a chucking jig attached to a tensile testing machine. On the other hand, the initial peel strength of the barrier film 12 can be obtained by pulling the barrier film 12 in the direction of a peel angle of 180 ° and measuring the force required to peel off the barrier film 12 from the quantum dot layer 11. The measurement conditions for the initial peel strength can be appropriately set according to the application, but in this specification, the measurement is performed at room temperature and at a tensile speed of 0.3 m / min.

<< light diffusion layer >>
The light diffusion layers 14 and 15 have a function of returning or diffusing light incident on the quantum dot sheet 10 or light emitted from the quantum dot sheet 10 to the quantum dot sheet 10. By providing the light diffusion layers 14 and 15, the light is recycled, so that the light conversion efficiency in the quantum dot sheet 10 can be increased. Moreover, the occurrence of in-plane color unevenness can be suppressed by the diffusion function. The light diffusion layers 14 and 15 include light diffusion particles (not shown) and a binder resin (not shown).

<<< Method for Manufacturing Quantum Dot Sheet >>>
The quantum dot sheet 10 can be produced as follows. First, the barrier film 12 and the barrier film 13 are prepared.

  Next, as shown in FIG. 3A, a quantum dot layer composition containing quantum dots 16 and a photopolymerizable compound 80 is applied to one surface of the barrier film 12, and the quantum dot layer composition A coating film 81 is formed.

  Then, as shown in FIG. 3B, the barrier film 13 is such that one surface of the barrier film 13 is in contact with the surface of the coating film 81 opposite to the surface in contact with the barrier film 12. Adhere.

  Finally, as shown in FIG. 3C, the coating film is cured by light while the barrier film 13 is in close contact therewith. In addition, you may add a drying process after application | coating of the composition for quantum dot layers.

When curing the photopolymerizable compound, it is cured by irradiating light (ultraviolet rays) so that the integrated light quantity becomes 200 mJ / cm ² or more. The lower limit of the amount of irradiation of light (ultraviolet), from the viewpoint of adhesion and curing properties, is preferably 250 mJ / cm ² or more, more preferably 300 mJ / cm ² or more. The upper limit of the irradiation amount of light (ultraviolet rays) is preferably 10,000 mJ / cm ² or less from the viewpoint of suppressing damage to the material (discoloration due to deterioration, etc.) due to heat generated during irradiation with ultraviolet rays or ultraviolet rays. ^It is more preferably ² or less, and further preferably 3000 mJ / cm ² or less.

  Further, when the quantum dot sheet is manufactured, the light diffusion layers 14 and 15 are previously formed on one side of the barrier films 12 and 13 respectively, and the quantum dot layer is formed on the surface of the barrier film 12 where the light diffusion layer 14 is not formed. The coating film 81 of the composition is formed, the surface of the barrier film 13 on which the light diffusion layer 15 is not formed and the coating film 81 are brought into close contact with each other, and then irradiated with ultraviolet rays in the same manner as described above, thereby light diffusion. The quantum dot sheet 10 having the layers 14 and 15 can be manufactured.

  According to this embodiment, the initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 in the quantum dot sheet 10 and the barrier film at the end portion 11D of the light exit surface 11B of the quantum dot layer 11 are obtained. Since the initial peeling strength of 13 is 2.0 N / 25 mm or more, the edge peeling of the barrier films 12 and 13 from the quantum dot layer 11 can be effectively suppressed.

  Furthermore, quantum dots deteriorate due to oxygen and moisture, and the light wavelength conversion efficiency tends to decrease. Therefore, when the quantum dot layer is exposed to the outside air when the barrier film is lifted at the end of the quantum dot layer, the quantum dot sheet As a result, the quantum dots at the peripheral edge of the light source deteriorate and the optical wavelength conversion efficiency decreases. For this reason, the quantum dots having an initial peel strength of the barrier film at the end of the light incident surface or light output surface of the quantum dot layer of less than 2.0 N / 25 mm under a tensile speed of 0.3 m / min. When the sheet is incorporated in a backlight device, the color of the light that has not undergone wavelength conversion by the quantum dots becomes stronger over time at the periphery of the light emitting surface, and the color of the periphery of the light emitting surface during light emission May stand out compared to the color in the center. On the other hand, according to the present embodiment, the initial peel strength of the barrier films 12 and 13 at the end portions 11C and 11D of the light incident surface 11A and the light exit surface 11B of the quantum dot layer 11 has a tensile speed of 0.3 m / min. In this condition, both are 2.0 N / 25 mm or more, so that a decrease in light wavelength conversion efficiency due to deterioration of the quantum dots at the peripheral portion of the quantum dot sheet is suppressed, and the peripheral portion 20B of the light emitting surface 20A at the time of light emission is suppressed. It can suppress more effectively that a color stands out compared with the color of the center part 20C. The configuration of the backlight device 20 will be described later.

According to the present embodiment, the photopolymerizable compound is used, and the coating film is cured by irradiating light (ultraviolet rays) so that the integrated light quantity becomes 200 mJ / cm ² or more. The initial peel strength of the barrier film 12 at the end portion 11C of the surface 11A and the initial peel strength of the barrier film 13 at the end portion 11D of the light exit surface 11B of the quantum dot layer 11 can be set to 2.0 N / 25 mm or more. Thereby, even if it exposes to high temperature, the quantum dot sheet which does not raise | generate an edge part peeling easily is obtained.

  The quantum dot sheet 10 can be used by being incorporated in a backlight device and a display device, for example. 4 is a schematic configuration diagram of a backlight device and a display device including a quantum dot sheet according to the present embodiment, and FIG. 5 is a schematic configuration diagram of another backlight device including a quantum dot sheet according to the present embodiment. 6 is a perspective view of the lens sheet according to the present embodiment, FIG. 7 is a cross-sectional view taken along line II of the lens sheet of FIG. 6, and FIG. 8 is a reflective polarization separation according to the present embodiment. It is sectional drawing of a sheet | seat.

<<< Display device >>>
The display device 100 shown in FIG. 4 includes a backlight device 20 and a display panel 30 disposed on the light output side of the backlight device 20. The display device 100 has a display surface 100A for displaying an image. In the display device 100 shown in FIG. 4, the surface of the display panel 30 is a display surface 100A.

  The backlight device 20 illuminates the display panel 30 in a planar shape from the back side. The display panel 30 functions as a shutter that controls transmission or blocking of light from the backlight device 20 for each pixel, and is configured to display an image on the display surface 100A.

<< Display panel >>
The display panel 30 shown in FIG. 4 is a liquid crystal display panel, and is between the polarizing plate 31 disposed on the light incident side, the polarizing plate 32 disposed on the light exit side, and the polarizing plate 31 and the polarizing plate 32. And a liquid crystal cell 33 having a color filter disposed therein. Polarizing plates 31 and 32 decompose incident light into two linearly polarized light components (S-polarized light and P-polarized light) orthogonal to each other and vibrate in one direction (direction parallel to the transmission axis) (for example, P It has a function of transmitting a linearly polarized component (for example, S-polarized light) that transmits polarized light and vibrates in the other direction (direction parallel to the absorption axis) perpendicular to the one direction.

  The liquid crystal cell 33 is configured such that a voltage can be applied to each region where one pixel is formed. Then, the alignment direction of the liquid crystal molecules in the liquid crystal cell 33 changes depending on the presence or absence of voltage application. As an example, the linearly polarized light component in a specific direction transmitted through the polarizing plate 31 disposed on the light incident side rotates the polarization direction by 90 ° when passing through the liquid crystal cell 33 to which a voltage is applied, When passing through the liquid crystal cell 33 to which no voltage is applied, the polarization direction is maintained. In this case, depending on whether or not a voltage is applied to the liquid crystal cell 33, the linearly polarized light component oscillating in a specific direction transmitted through the polarizing plate 31 is transmitted through the polarizing plate 32 or absorbed and blocked by the polarizing plate 32. it can. In this way, the display panel 30 is configured to control transmission or blocking of light from the backlight device 20 for each pixel. The details of the liquid crystal display panel are described in various known literatures (for example, “Flat Panel Display Dictionary” (published by Tatsuo Uchida, Hiraki Uchiike), 2001, Industrial Research Council). The detailed description of is omitted.

<< Backlight device >>
The backlight device includes a light source and a quantum dot sheet. The light incident surface of the quantum dot layer in this quantum dot sheet is a surface that receives light from the light source. The backlight device 20 shown in FIG. 4 is configured as an edge light type backlight device, and is disposed on the light output side of the light source 35, the light guide plate 40 disposed on the side of the light source 35, and the light output side of the light guide plate 40. Quantum dot sheet 10, lens sheet 50 disposed on the light exit side of quantum dot sheet 10, lens sheet 55 disposed on the light exit side of lens sheet 50, and reflective polarized light disposed on the light exit side of lens sheet 55 A separation sheet 60 and a reflection sheet 70 disposed on the side opposite to the light output side of the light guide plate 40 are provided. The backlight device 20 includes the lens sheets 50 and 55, the reflective polarization separation sheet 60, and the reflective sheet 70, but these sheets may not be provided. Further, the backlight device may be a direct type backlight device as shown in FIG. In the backlight device 21 shown in FIG. 5, the light source 35 is located immediately below the quantum dot sheet 10, and a light diffusion plate 90 is disposed between the light source 35 and the quantum dot sheet 10. Note that the backlight device 21 is not provided with a light guide plate. The light diffusion plate 90 is not particularly limited as long as it can diffuse the light from the light source 35.

  In the present specification, the “light exit side” refers to the light guide plate 40, the quantum dot sheet 10, the lens sheet 50, the lens sheet 55, the reflective polarization separation sheet 60, the display panel 20, and other components of the display device 10. It is the downstream side (observer side, for example, the upper side of the paper surface in FIG. 4) in the traveling direction of the light that travels without being transmitted and goes out from the display device 100 toward the viewer.

  The backlight device 20 has a light emitting surface 20A that emits light in a planar shape. In the backlight device 20 shown in FIG. 4, the light exit surface of the reflective polarization separation sheet 60 is the light emitting surface 20 </ b> A of the backlight device 20.

<Light source>
The light source 35 may be configured in various modes such as a fluorescent lamp such as a linear cold cathode tube, a point light emitting diode (LED), an incandescent lamp, and the like. In the present embodiment, the light sources 35 are arranged side by side along the longitudinal direction of a light incident surface 40C described later of the light guide plate 40 (in FIG. 4, the direction orthogonal to the paper surface, that is, the front and back direction of the paper surface). It is comprised by many point-like light-emitting bodies, specifically, many light-emitting diodes (LED).

  As the quantum dot sheet 10 is disposed in the backlight device 20, the light source 35 can use only a light emitter that emits light in a single wavelength region. For example, only a blue light emitting diode that emits blue light with high color purity can be used as the light source.

<Light guide plate>
The light guide plate 40 is formed in a quadrangular shape in plan view (in FIG. 4, a shape viewed from above). The light guide plate 40 extends between the light output surface 40A formed by one main surface on the display panel 30 side, the back surface 40B formed of the other main surface facing the light output surface 40A, and the light output surface 40A and the back surface 40B. And a side surface. The side surface on the light source 35 side of the side surfaces is a light incident surface 40C that receives light from the light source. The light that has entered the light guide plate 40 from the light incident surface 40C is guided in the light guide plate in a direction (light guide direction) connecting the light incident surface 40C and the opposite surface opposite to the light incident surface 40C. It is emitted from 40A.

  As a material constituting the light guide plate 40, it is widely used as a material for an optical sheet incorporated in a display device, and has excellent mechanical characteristics, optical characteristics, stability, workability and the like, and can be obtained at low cost. For example, transparent resins mainly composed of one or more of acrylic resin, polystyrene, polycarbonate, polyethylene terephthalate, polyacrylonitrile, etc., and epoxy acrylate or urethane acrylate reactive resins (ionizing radiation curable resins, etc.) are preferably used. obtain. Note that a diffusion material having a function of diffusing light may be added to the light guide plate 40 as necessary. As the diffusing material, for example, particles made of a transparent substance such as silica (silicon dioxide), alumina (aluminum oxide), acrylic resin, polycarbonate resin, or silicone resin having an average particle size of 0.5 μm to 100 μm can be used. .

<Lens sheet>
As shown in FIGS. 6 and 7, the lens sheets 50 and 55 change the traveling direction of the incident light L3 so as to be emitted from the light exit side, thereby concentratingly improving the brightness in the front direction (condensing light). Function) and the function of reflecting incident light L4 and returning it to the quantum dot sheet 10 side (retroreflection function). The lens shape of the lens sheet may be a triangular prism shape, a wavy shape, or a bowl shape such as a hemisphere. Examples of the lens sheet having such a lens shape include a prism sheet (triangular prism shape), a lenticular lens (semi-cylindrical shape), and a microlens array (hemispherical shape). In the present embodiment, a lens sheet (prism sheet) having a triangular lens shape will be described as a lens sheet. Note that the lens sheets 50 and 55 are different in arrangement and can have the same configuration. Therefore, the description common to the lens sheet will be described using reference numerals “50, 55”. Hereinafter, the configuration of each component will be described.

  The lens sheets 50 and 55 include a sheet-like main body 51 and a plurality of unit lenses 52 arranged side by side on the light output side of the main body 51.

  The main body 51 functions as a sheet-like member that supports the unit lens 52. As shown in FIG. 6, the unit lenses 52 are arranged on the light output side surface 51 </ b> A of the main body 51 without leaving a gap. Therefore, the light exit surfaces of the lens sheets 50 and 55 are formed by the lens surface 52 </ b> A of the unit lens 52. On the other hand, as shown in FIG. 7, in the present embodiment, the main body 51 has a smooth surface that forms the light incident side surface of the lens sheets 50 and 55 as the light incident side surface 51B that faces the light outgoing side surface 51A. doing.

  The unit lenses 52 are arranged side by side on the light exit side surface 51 </ b> A of the main body 51. As shown in FIG. 6, the unit lenses 52 extend linearly in the direction intersecting the arrangement direction A of the unit lenses 52, particularly linearly in the present embodiment. In the present embodiment, a large number of unit lenses 52 included in one lens sheet 50, 55 extend in parallel to each other. Further, the longitudinal direction L of the unit lenses 52 of the lens sheets 50 and 55 is orthogonal to the arrangement direction A of the unit lenses 52 in the lens sheets 50 and 55.

  As can be understood from FIG. 4, the arrangement direction of the unit lenses 52 of the lens sheet 50 and the arrangement direction of the unit lenses 52 of the lens sheet 55 intersect, and more specifically, are orthogonal to each other.

  The unit lens 52 has a triangular prism shape whose width becomes narrower toward the light output side. Accordingly, the shape of a cross section (also referred to as a main cutting surface of the lens sheet) parallel to both the normal direction N of the sheet surface of the main body 52 and the arrangement direction A of the unit lenses 52 is a triangular shape protruding to the light output side. ing. In particular, from the viewpoint of intensively improving the brightness in the front direction, the cross-sectional shape of the unit lens 52 in the main cut surface is an isosceles triangle shape, and the apex angle located between the equilateral sides is the light exit side surface 51A of the main body 51. Each unit lens 52 is configured to protrude from the light to the light exit side.

  The unit lens 52 preferably has an apex angle of 80 ° or more and 100 ° or less, and more preferably an apex angle of about 90 °, from the viewpoint of improving the retroreflection function of the lens sheets 50 and 55.

  The dimensions of the lens sheets 50 and 55 can be set as follows as an example. First, as a specific example of the unit lenses 52, the arrangement pitch of the unit lenses 52 (corresponding to the width of the unit lenses 52 in the illustrated example) can be set to 10 μm or more and 200 μm or less. However, in recent years, the definition of the arrangement of the unit lenses 52 is rapidly increasing, and the arrangement pitch of the unit lenses 52 is preferably 10 μm or more and 50 μm or less. Moreover, the protrusion height of the unit lens 52 from the main body 51 along the normal direction N to the sheet surface of the lens sheets 50 and 55 can be set to 5 μm or more and 100 μm or less. Further, the apex angle θ of the unit lens 52 can be set to 60 ° or more and 120 ° or less.

  The lens sheets 50 and 55 can be produced by molding the unit lens 52 on a base material or by extrusion molding. Various materials can be used as the constituent material of the main body 51 and the unit lens 52. However, it is widely used as a material for an optical sheet incorporated in a display device, and has excellent mechanical properties, optical properties, stability, workability, etc., and can be obtained at low cost, such as acrylic resin, polystyrene, polycarbonate, etc. A transparent resin mainly composed of one or more of polyethylene terephthalate, polyacrylonitrile, etc., and an epoxy acrylate or urethane acrylate photopolymerizable compound can be suitably used.

  When producing the lens sheets 50 and 55 by curing the photopolymerizable compound on the substrate, together with the unit lens 52, a sheet-like land portion that is positioned between the unit lens 52 and the substrate, You may make it form on a base material. In this case, the main body 51 is composed of a base and a land formed by a cured product of a photopolymerizable compound. On the other hand, in the lens sheets 50 and 55 manufactured by extrusion molding, the main body 51 and the plurality of unit lenses 52 on the light exit side surface 51A of the main body 51 can be integrally formed.

<Reflection-type polarized light separation sheet>
As shown in FIG. 8, the reflection-type polarization separation sheet 60 transmits only the first linearly polarized light component (for example, P-polarized light) L5 out of the light emitted from the lens sheet 55, and the first polarized light. The second linearly polarized light component (for example, S-polarized light) L6 orthogonal to the component L5 has a function of reflecting without absorbing it. The second linearly polarized light component L6 reflected by the reflective polarization separation sheet 60 is reflected by the reflective sheet 70 and the like, and the polarization is canceled (the first linearly polarized light component L5 and the second linearly polarized light component L6 are reflected). In a state in which both are included, the light again enters the reflective polarization separation sheet 60. Therefore, the reflection-type polarization separation sheet 60 transmits the first linearly polarized light component L5 in the incident light again, and the second linearly polarized light component L6 orthogonal to the first linearly polarized light component L5 is reflected again. Hereinafter, by repeating the above process, about 70 to 80% of the light emitted from the lens sheet 55 is emitted as the light source light that has become the first linearly polarized light component L5. Therefore, by making the polarization direction of the first linearly polarized light component (transmission axis component) L5 of the reflective polarization separation sheet 60 coincide with the transmission axis direction of the polarizing plate 31 of the display panel 30, the light is emitted from the backlight device 20. All the incident light can be used for image formation on the display panel 30. Therefore, even if the light energy input from the light source 35 is the same, it is possible to form an image with higher brightness than in the case where the reflective polarization separation sheet 60 is not disposed, and the energy utilization efficiency of the light source 35 is improved. To do. In particular, the light reflected by the reflective polarization separation sheet 60 can be wavelength-converted by the quantum dots 16 of the quantum dot sheet 10. Therefore, the wavelength conversion efficiency of the quantum dot sheet 10 can be further increased by arranging the reflective polarization separation sheet 60. Therefore, further improvement in the utilization efficiency of the light source light can be expected.

  As the reflective polarization separation sheet 60, “DBEF” (registered trademark) available from 3M Company can be used. In addition to “DBEF”, a high-intensity polarizing sheet “WRPS” or a wire grid polarizer available from Shinwha Intertek can be used as the reflective polarization separating sheet 60.

<Reflection sheet>
The reflection sheet 70 has a function of reflecting light leaking from the back surface 40 </ b> B of the light guide plate 40 so as to enter the light guide plate 40 again. The reflection sheet 70 includes a white scattering reflection sheet, a sheet made of a material having a high reflectance such as metal, a sheet containing a thin film (for example, a metal thin film) made of a material having a high reflectance as a surface layer, and the like. obtain. The reflection on the reflection sheet 70 may be regular reflection (specular reflection) or diffuse reflection. When the reflection on the reflection sheet 70 is diffuse reflection, the diffuse reflection may be isotropic diffuse reflection or anisotropic diffuse reflection.

[Second Embodiment]
Hereinafter, a quantum dot sheet according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 9 is a schematic configuration diagram of the quantum dot sheet according to the present embodiment, and FIG. 10 is a diagram schematically illustrating a manufacturing process of the quantum dot sheet according to the present embodiment. In the present embodiment, the same members as those described in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. FIG. 9 shows a five-layer structure consisting of barrier film / adhesive layer / quantum dot layer / adhesive layer / barrier film, but is not limited to this, and is composed of more layers. May be. For example, the quantum dot sheet in the present embodiment may be configured with a nine-layer structure including barrier film / adhesive layer / quantum dot layer / adhesive layer / barrier film / adhesive layer / quantum dot layer / adhesive layer / barrier film. Good.

<< Adhesive layer >>
In the present embodiment, as shown in FIG. 9, a first adhesive layer 18 is provided between the quantum dot layer 11 and the barrier film 12, and a second adhesion is provided between the quantum dot layer 11 and the barrier film 13. Layer 19 is provided. Hereinafter, for simplification of description, the first adhesive layer 18 is referred to as an adhesive layer 18, and the second adhesive layer 19 is referred to as an adhesive layer 19. The quantum dot sheet 110 shown in FIG. 9 includes the adhesive layers 18 and 19 on both the light incident surface 11A and the light exit surface 11B of the quantum dot layer 11, but only one of them may be provided. However, in that case, the initial peel strength between the quantum dot layer and the barrier film on the surface where no adhesive layer is present needs to be 2.0 N / 25 mm or more when measured under the condition of a tensile speed of 0.3 m / min. is there. In the present specification, the “adhesive layer” is a concept including an easy-adhesive layer (primer), a pressure-sensitive adhesive layer, and an adhesive layer.

  In the present embodiment, the quantum dot layer 11 and the barrier films 12 and 13 are more firmly adhered to each other through the adhesive layers 18 and 19, and each is 2.0 N under a tensile speed of 0.3 m / min. / High initial peel strength of 25 mm or more is obtained. Therefore, in this embodiment, the peel strength at the interface between the quantum dot layer 11 and the adhesive layers 18 and 19 or at the interface between the adhesive layers 18 and 19 and the barrier films 12 and 13 is expressed as the barrier film 12 from the quantum dot layer 11. , 13 peel strength. Further, in the case where the quantum dot layer 11 is broken, the barrier films 12 and 13 are broken, or the adhesive layers 18 and 19 are broken without peeling at the interface, as in the first embodiment, It shall be included in the present invention. When the quantum dot sheet is composed of more layers than the five-layer structure of barrier film / adhesive layer / quantum dot layer / adhesive layer / barrier film, at least one set of barrier film / adhesive layer / quantum When the initial peel strength between the two quantum dot layers-adhesive layer-barrier film in the dot layer / adhesive layer / barrier film is measured under the condition of a tensile speed of 0.3 m / min, both are 2.0 N / 25 mm or more. It is necessary to be. Moreover, when the initial peel strength between all the quantum dot layers-adhesive layers-barrier films is measured under the condition of a tensile speed of 0.3 m / min, all have a strength of 2.0 N / 25 mm or more. It is preferable from the viewpoint of effectively preventing deterioration of the quantum dots.

  Although it does not specifically limit as a constituent material of the contact bonding layers 18 and 19, For example, a polyurethane resin, a polyester resin, a polyvinyl chloride resin, a polyvinyl acetate resin, a vinyl chloride-vinyl acetate copolymer, an acrylic resin, polyvinyl alcohol Resin, polyvinyl acetal resin, copolymer of ethylene and vinyl acetate or acrylic acid, copolymer of ethylene and styrene and / or butadiene, thermoplastic resin such as olefin resin and / or modified resin thereof, light It is possible to use at least one of a polymer of a polymerizable compound and a thermosetting resin such as an epoxy resin. It is preferable to use an acrylic resin, an epoxy resin, or a polyester resin as a constituent material of the adhesive layers 18 and 19 from the viewpoint of heat resistance and adhesiveness. Moreover, it is preferable to use an acrylic resin or an epoxy resin as a constituent material of the adhesive layer, and it is preferable to use a polyester resin as the easy-adhesion layer. Note that different constituent materials may be used for the adhesive layers 18 and 19, respectively.

  The average film thickness of the adhesive layers 18 and 19 is preferably 0.05 μm or more and 5 μm or less from the viewpoints of adhesiveness, thinning of the quantum dot sheet, and weight reduction.

<<< Method for Manufacturing Quantum Dot Sheet >>>
A method for manufacturing the quantum dot sheet 110 having the adhesive layers 18 and 19 will be described. First, the barrier film 12 and the barrier film 13 are prepared.

  Next, as illustrated in FIG. 10A, the adhesive layer composition is formed on one surface of the barrier film 12 by applying the adhesive layer composition.

  Then, as shown in FIG. 10 (B), a composition for a quantum dot layer containing quantum dots 16 and a curable binder resin precursor 82 on the surface opposite to the surface in contact with the barrier film 12 of the adhesive layer 18. An object is applied to form a coating film 83.

  Further, as shown in FIG. 10C, the barrier film 13 is adhered to the surface of the coating film 83 opposite to the surface in contact with the adhesive layer 18 via the adhesive layer 19.

  Finally, as shown in FIG. 10D, the coating film is cured by light or heat while the barrier film 13 is in close contact therewith. In this embodiment, the initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 and the initial peel strength of the barrier film 13 at the end portion 11D of the light output surface 11B of the quantum dot layer 11 are Secured by adhesive layers 18 and 19, respectively. Therefore, when a photopolymerizable compound is used as the curable binder resin precursor, the integrated light amount of light (ultraviolet rays) is not particularly limited, and may be an integrated light amount that can achieve curing of the binder resin. In addition, you may add a drying process after application | coating of the composition for quantum dot layers.

  Further, when the quantum dot sheet 110 is manufactured, the light diffusion layers 14 and 15 are previously formed on one surface of the barrier films 12 and 13 respectively, and the adhesive layer is formed on the surface of the barrier film 12 where the light diffusion layer 14 is not formed. The adhesive layer 18 is formed by applying the composition for coating, and the surface of the barrier film 13 where the light diffusion layer 15 is not formed and the adhesive layer 19 are brought into close contact with each other. By curing 83, the quantum dot sheet 110 having the light diffusion layers 14 and 15 can be manufactured.

  Furthermore, when forming an easily bonding layer (it is also called a primer) as the adhesive layers 18 and 19, the adhesive layers 18 and 19 are previously formed on the barrier films 12 and 13 and cured. Therefore, when forming an easily bonding layer as the bonding layers 18 and 19, in addition to the step of FIG. 10D, light irradiation or heating is performed after the step of FIG. Harden.

  According to this embodiment, since the adhesive layers 18 and 19 are provided between the quantum dot layer 11 and the barrier films 12 and 13, respectively, the end of the light incident surface 11A of the quantum dot layer 11 in the quantum dot sheet 110 is provided. The initial peel strength of the barrier film 12 at 11C and the initial peel strength of the barrier film 13 at the end portion 11D of the light exit surface 11B of the quantum dot layer 11 are both 2.0 N / 25 mm under the condition of a tensile speed of 0.3 m / min. This can be done. Thereby, even if it exposes to high temperature, the quantum dot sheet which does not raise | generate an edge part peeling easily is obtained.

  The quantum dot sheet 110 can also be used by being incorporated in, for example, a backlight device and a display device. Since the configurations of the backlight device and the display device are the same as those in the first embodiment, the description thereof will be omitted.

  Also in this embodiment, as in the first embodiment, the initial peel strength of the barrier film 12 at the end portion 11C of the light incident surface 11A of the quantum dot layer 11 in the quantum dot sheet 110, and the quantum dot layer 11 Since the initial peel strength of the barrier film 13 at the end portion 11D of the light exit surface 11B is 2.0 N / 25 mm or more under the condition of a tensile speed of 0.3 m / min, the deterioration of the quantum dots at the peripheral portion of the quantum dot sheet The decrease in the light wavelength conversion efficiency due to the light is suppressed, and when incorporated in the backlight device, it can be more effectively suppressed that the color of the peripheral portion of the light emitting surface stands out compared to the color of the central portion during light emission. .

  In order to describe the present invention in detail, examples will be described below, but the present invention is not limited to these descriptions.

<Preparation of composition for quantum dot layer>
First, each component was mix | blended so that it might become a composition shown below, and the composition for quantum dot layers was obtained.
(Composition for quantum dot layer)
Green light emitting quantum dots (product name “CdSe / ZnS 530”, manufactured by SIGMA-ALDRICH, core: CdSe, shell: ZnS, average particle size 3.3 nm): 0.2 parts by mass Red light emitting quantum dots ( Product name “CdSe / ZnS 610”, manufactured by SIGMA-ALDRICH, Core: CdSe, Shell: ZnS, Average particle size 5.2 nm): 0.2 parts by mass Urethane acrylate resin precursor (Arakawa Chemical Industries) 96 parts by mass / photopolymerization initiator (1-hydroxycyclohexyl phenyl ketone, product name “Irgacure (registered trademark) 184”, manufactured by BASF Japan): 4 parts by mass

<Example 1>
First, two barrier films were prepared by the following method. In a high-frequency sputtering apparatus, a high-frequency power having a frequency of 13.56 MHz and a power of 5 kW is applied to the electrode to cause discharge in the chamber, and a polyethylene terephthalate film (product name “Lumirror T60”, thickness 50 μm, manufactured by Toray Industries, Inc.) A silica vapor deposition layer having a thickness of 50 nm and a refractive index of 1.46 made of a target material (silica) is formed on one side of the film, thereby forming a barrier film comprising a polyethylene terephthalate film and a silica vapor deposition layer. A sheet was formed. Subsequently, the composition for quantum dot layers was apply | coated to the silica vapor deposition layer side of one barrier film, and the coating film was formed. Subsequently, the solvent in the coating film was evaporated by drying the coating film formed by passing 70 ° C. dry air for 60 seconds. Thereafter, the other barrier film is disposed on the surface of the coating film opposite to the polyethylene terephthalate film side so that the silica vapor deposition layer is in contact with it, an H bulb is used as the light source, and the integrated light quantity is 250 mJ / cm ^2. The quantum dot layer with a film thickness of 100 μm was formed by irradiating the film to cure the coating film, and a quantum dot sheet was obtained.

<Example 2>
In Example 2, a quantum dot sheet was produced in the same manner as in Example 1 except that ultraviolet light was irradiated so that the accumulated light amount was 550 mJ / cm ² .

<Example 3>
In Example 3, first, as in Example 1, two barrier films composed of a polyethylene terephthalate film and a silica deposited layer were formed. Next, an acrylic UV curable paint (product name “SEICA BEAM EXF”, manufactured by Dainichi Seika Kogyo Co., Ltd.) is applied to the silica vapor deposition layer side of each barrier film so that the film thickness becomes 1 μm, and the total amount of UV light is applied. The adhesive layer was formed by irradiating and curing to 300 mJ / cm ² . On the adhesive layer of one barrier film, the quantum dot layer composition was applied to form a coating film, and the solvent in the coating film was evaporated by drying in the same manner as in Example 1. Thereafter, the other barrier film is disposed on the surface opposite to the polyethylene terephthalate film side of the coating film so that the adhesive layer is in contact, and an H bulb is used as the light source, and the integrated light quantity is 550 mJ / cm ² . The quantum dot layer with a film thickness of 100 μm was formed by irradiating the film to cure the coating film, and a quantum dot sheet was obtained.

<Comparative Example 1>
A quantum dot sheet was produced in the same manner as in Example 1 except that irradiation was performed so that the cumulative amount of ultraviolet light was 150 mJ / cm ² .

<Comparative example 2>
A quantum dot sheet was produced in the same manner as in Example 1 except that the irradiation was performed so that the cumulative amount of ultraviolet light was 100 mJ / cm ² .

<Measurement of peel strength at the end>
For the peel strength at the ends of the quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2, a tensile tester (equipment name “Tensilon”, manufactured by A & D Co., Ltd.) was used. The initial peel strength at the end of each sample was measured. Each quantum dot sheet was not subjected to a durability test or the like. At the time of measurement, a 25 mm-wide test piece was cut out from the quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2 using a cutter so that the end portion did not float. Next, the obtained test piece is fixed to a chucking jig attached to the tensile testing machine, and the barrier film is pulled in the direction of a peeling angle of 180 ° with respect to the sheet surface of the quantum dot sheet 10, and the quantum dot layer The force required to peel the barrier film from was measured. The measurement was performed at room temperature under a tensile speed of 0.3 m / min, and the adhesive strength (N / 25 mm) at a peeling angle of 180 ° was recorded. In addition, since the quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2 are all the same material for the first barrier film and the second barrier film, the initial peel strength of one of the barrier films is It was considered the same as the initial peel strength of the other barrier film.

<Evaluation of floating edge>
The quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2 were punched into a test piece shape using a Thomson blade mold (10 cm □), and at the end of each test piece (that is, around the punched portion) It was visually observed whether the barrier film was lifted from the quantum dot layer.
○: The barrier film was not lifted from the quantum dot layer.
X: The barrier film was lifted from the quantum dot layer.

<Visual evaluation of light emitting surface>
From the quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2, a 100 mm × 100 mm test piece was cut out using a cutter so that no floating occurred at the end. Next, the obtained test piece was placed in a KindleFire (registered trademark) HDX7 backlight (including a blue light emitting diode having an emission peak wavelength of 450 nm, a light guide plate, two prism sheets, and a reflection sheet). The two prism sheets used here include a sheet-like main body part and a plurality of triangular prism-shaped unit prisms arranged side by side on the main body part and extending in a direction intersecting the arrangement direction, The apex angle of the unit prism was 90 °. Further, the reflective polarization separation sheet was integrated with the polarizing plate. In addition, the light guide plate is arranged so that the backlight side becomes the light incident surface, and the quantum dot sheet, the prism sheet, and the prism sheet are arranged in this order on the light exit surface of the light guide plate, and reflected on the back surface of the light guide plate. The sheet | seat was arrange | positioned and the backlight apparatus was obtained. The prism sheet on the viewer side was arranged so that the arrangement direction of the unit prisms was orthogonal to the arrangement direction of the unit prisms of the prism sheet.

Using the backlight device obtained as described above, the peripheral part and the central part of the light emitting surface during light emission were visually observed, and it was observed whether the color of the peripheral part was conspicuous compared to the color of the central part. .
○: The color of the peripheral part and the color of the central part were equivalent.
Δ: Although the color of the peripheral portion and the color of the central portion were slightly different, it was at a level causing no practical problem.
X: The color of a peripheral part was conspicuous compared with the color of a center part.

<Durability evaluation in high temperature and high humidity environment>
Test specimens similar to those used for the measurement of peel strength at the end, evaluation of end float, and visual evaluation of the light emitting surface were prepared from the quantum dot sheets according to Examples 1 to 3 and Comparative Examples 1 and 2, respectively. Then, the obtained test piece was put into a thermostat set in a high temperature and high humidity environment (temperature 60 ° C., relative humidity 80%) and left for 500 hours. Then, each characteristic was measured and evaluated similarly to the said method. Regarding the peel strength at the edge, the ratio (%) of the peel strength of the quantum dot sheet after 500 hours in the atmosphere of 60 ° C. and 80% humidity with respect to the initial peel strength was also calculated.

The results obtained are summarized in Table 1 below.

  From the above results, in the comparative example, the initial peel strength at the end was low, and the barrier film was easily peeled from the quantum dot layer. Moreover, the sample of the comparative example had a very low peel strength after exposure to a high temperature and high humidity environment compared to the initial peel strength. Further, in the comparative example, the end portion was clearly lifted, and even when incorporated in a backlight device, the color change of the light emitting surface occurred. On the other hand, in Examples 1-3, compared with the comparative example, the initial peel strength at the end was high, and the barrier film was not easily peeled from the quantum dot layer. Further, the peel strength after exposure to a high temperature and high humidity environment did not change significantly from the initial peel strength, and the floating of the end portion was also suppressed. Furthermore, even when incorporated in a backlight device, the color change of the light emitting surface did not occur, or even if it occurred, it was at a level causing no practical problem. Therefore, in Examples 1-3, it was confirmed that the edge part peeling of the barrier film from a quantum dot layer was suppressed effectively.

DESCRIPTION OF SYMBOLS 10, 110 ... Quantum dot sheet 11 ... Quantum dot layer 11A ... Light entrance surface 11B of quantum dot layer ... Light exit surface 11C of quantum dot layer ... End 11D of light entrance surface of quantum dot layer ... Light exit surface of quantum dot layer Edge portions 12, 13 ... Barrier films 14, 15 ... Light diffusion layer 16 ... Quantum dots 16A ... First quantum dots 16B ... Second quantum dots 17 ... Binder resins 18, 19 ... Adhesive layers 20, 21 ... Backlight device DESCRIPTION OF SYMBOLS 30 ... Display panel 35 ... Light source 40 ... Light guide plate 40A ... Light exit surface 40C of light guide plate ... Light entrance surface 80 of light guide plate ... Photopolymerizable compounds 81, 83 ... Coating film 82 ... Curable binder resin precursor 100 ... Display device

Claims (9)

A quantum dot layer having a light incident surface for receiving light and a light output surface for emitting light, and including a quantum dot and a binder resin for performing wavelength conversion of light received from the light incident surface;
A first barrier film in close contact with the light incident surface of the quantum dot layer;
A second barrier film in close contact with the light exit surface of the quantum dot layer,
The initial peel strength of the first barrier film at the end of the light entrance surface of the quantum dot layer and the initial peel strength of the second barrier film at the end of the light exit surface of the quantum dot layer are tensile rates. A quantum dot sheet that is 2.0 N / 25 mm or more under conditions of 0.3 m / min.   The quantum dot sheet according to claim 1, wherein the quantum dots include a first quantum dot that converts blue light into green light and a second quantum dot that converts blue light into red light. The quantum dot sheet according to claim 1, wherein the barrier film is a film having a water vapor transmission rate of less than 1.0 × 10 ⁻¹ g / m ² / day.   The quantum dot sheet according to claim 1 whose average film thickness of said quantum dot layer is 10 micrometers or more and 120 micrometers or less.   The peel strength of the first barrier film at the end of the light incident surface of the quantum dot layer in the quantum dot sheet after 500 hours has passed in an atmosphere of temperature 60 ° C. and humidity 80%, and the quantum The peel strength of the second barrier film at the end of the light exit surface of the dot layer has a value of 70% or more with respect to the initial peel strength under the condition of a tensile speed of 0.3 m / min. Item 2. A quantum dot sheet according to Item 1.   The quantum dot sheet according to claim 1, further comprising an adhesive layer provided between the quantum dot layer and the barrier film. A light source;
The quantum dot sheet according to claim 1,
The backlight device, wherein the light incident surface of the quantum dot layer in the quantum dot sheet is a surface that receives light from the light source. The backlight device according to claim 7;
A display device comprising: a display panel disposed on a light output side of the backlight device. On one side of the first barrier film, a quantum dot layer composition containing quantum dots and a photopolymerizable compound is applied to form a coating film,
Adhering the second barrier film to the surface of the coating film opposite to the surface in contact with the first barrier film,
A method for producing a quantum dot sheet, wherein the coating film is cured by irradiating the coating film with light of 200 mJ / cm ² or more while the second barrier film is in close contact therewith.

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