Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
  • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
  • G02B1/14—Protective coatings, e.g. hard coatings
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B5/00—Optical elements other than lenses
  • G02B5/30—Polarising elements
• • G—PHYSICS
  • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
  • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
  • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/02—Details
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
  • H05B33/00—Electroluminescent light sources
  • H05B33/12—Light sources with substantially two-dimensional [2D] radiating surfaces
  • H05B33/14—Light sources with substantially two-dimensional [2D] radiating surfaces characterised by the chemical or physical composition or the arrangement of the electroluminescent material, or by the simultaneous addition of the electroluminescent material in or onto the light source
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
  • H10K50/00—Organic light-emitting devices
  • H10K50/10—OLEDs or polymer light-emitting diodes [PLED]
  • H10K50/11—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers
  • H10K50/115—OLEDs or polymer light-emitting diodes [PLED] characterised by the electroluminescent [EL] layers comprising active inorganic nanostructures, e.g. luminescent quantum dots

Definitions

• the present invention relates to an image display device that uses quantum dot electroluminescence technology.
• Quantum dot electroluminescence is a phenomenon in which light is emitted by passing an electric current through nanoscale semiconductor crystal particles called quantum dots (QDs), and the emitted color changes depending on the size of the crystal particles. Quantum dot electroluminescence is also called quantum dot electroluminescence, and is sometimes abbreviated as QD-EL.
• a QD layer containing quantum dots that emit light in the colors R, G, and B is placed on a substrate with electrodes using an inkjet printer or the like to create pixels of each color, and this QD layer is then sandwiched between electrodes, and the light emission of each pixel is controlled using TFTs or the like to display an image.
• QD-EL image display devices have attracted attention for their color reproducibility, wide dynamic range, high brightness, wide viewing angle, etc. (For example, see Patent Document 1).
• This QD-EL image display device can be made thin and lightweight, and can be developed into flexible image display devices, including foldable and rollable types. It can also be made large because printing technology can be applied, and even when it is large, for example 100 inches or 200 inches or larger, it can be made thin and lightweight, and has the excellent characteristic of being easy to install in existing locations.
• a surface protection film is often attached to the top surface of image display devices to provide anti-reflection functions as well as for protection and to prevent glass from shattering, and a surface protection film is often used in QD-EL image display devices as well.
• films used to protect the surfaces of image display devices include triacetyl cellulose (TAC), polycyclic olefin (COP), acrylic, and polyester films.
• TAC triacetyl cellulose
• COP polycyclic olefin
• acrylic acrylic
• polyester films are less susceptible to the above problems and has excellent properties as a surface protection film, but its birefringence can cause rainbow unevenness when reflected from outside light, reducing image quality.
• ambient light often contains polarized light components due to reflection, and this polarized light reflects off the surface protection film of a display, which has birefringence, causing even stronger rainbow unevenness.
• QD-EL image display devices have little loss of brightness or color reproducibility even when viewed from an oblique angle, so even slight rainbow spots caused by reflection of external light are easily noticeable.
• large-sized devices they are often used in outdoor or semi-outdoor environments (spaces separated by roofs or walls but not separated from the outdoors by doors, etc.), such as airports, stations, and large public facilities, which are connected to the outdoors, for signage purposes, and when the screen is viewed through polarized sunglasses, the rainbow unevenness caused by the reflection of external light containing polarized components is more noticeable, and the deterioration of image quality is easily noticeable.
• the light from the image is reflected at the interface of the surface protection film, and the light from the image itself can sometimes appear as rainbow spots.
• the black display area is a darker black than LCD displays, the rainbow unevenness caused by external light reflection is easily noticeable, and even when the power is turned off, the rainbow unevenness caused by external light reflection does not disappear, which causes a problem of a decrease in the appearance quality of the display device itself.
• the present invention aims to solve the above problems, and to provide a QD-EL image display device that has excellent visibility by reducing rainbow spots caused by the surface protection film. It also aims to provide a display device with excellent appearance.
• Item 1 A quantum dot electroluminescence image display device having a surface protective film laminated on the outermost surface of an image display portion, the surface protective film having an in-plane retardation of 3000 nm or more and 30000 nm or less.
• Item 2 Item 2. The quantum dot electroluminescent image display device according to item 1, wherein the surface protective film has an Nz coefficient of 1.78 or less.
• Item 3 Item 3. The quantum dot electroluminescent image display device according to item 1 or 2, wherein the surface protective film is a polyester film.
• Item 4 Item 4.
• the quantum dot electroluminescence image display device according to any one of items 1 to 3, wherein the slow axis direction of the surface protective film is approximately parallel to the long side direction or short side direction of the image display portion of the quantum dot electroluminescence image display device.
• Item 5 Item 5.
• the quantum dot electroluminescence image display device according to any one of items 1 to 4, wherein the surface protective film has a base film and a functional layer on the viewing side thereof.
• Item 6 Item 6.
• the quantum dot electroluminescent image display device according to any one of items 1 to 5, wherein the functional layer is at least one of an antireflection layer, a low reflection layer, and an antiglare layer.
• Item 7 Item 7.
• the quantum dot electroluminescence image display device according to item 5 or 6, further comprising an easy-adhesion layer on the surface side of the functional layer of the substrate film.
• Item 8 Item 8.
• the quantum dot electroluminescence image display device according to Item 7, wherein the resin contained in the easy-adhesion layer is a resin having a naphthalene ring structure.
• Item 9 Item 8.
• the present invention reduces rainbow spots caused by the surface protection film, and provides a QD-EL image display device that has excellent visibility in a variety of installation locations. It also reduces interference fringes caused by the coating layer, and provides a QD-EL image display device with excellent appearance.
• QD-EL image display device In the QD-EL image display device of the present invention, it is preferable that at least one of the light-emitting elements of red (R), green (G), and blue (B) uses a QD-EL. It is preferable that the QD-EL is used.
• the emission peak of the red light-emitting element is preferably 600 to 650 nm, more preferably 610 to 645 nm, and even more preferably 615 to 640 nm.
• the emission peak of the green light-emitting element is preferably 500 to 560 nm, more preferably 510 to 550 nm, and even more preferably 520 to 540 nm.
• the emission peak of the blue light-emitting element is preferably 410 to 470 nm, more preferably 420 to 460 nm, and even more preferably 425 to 450 nm.
• the half-width of the emission spectrum of each light-emitting element of each color is preferably 60 nm or less, more preferably 50 nm or less, even more preferably 45 nm or less, and particularly preferably 40 nm or less.
• the lower limit of the half-width of the emission spectrum of each light-emitting element is preferably 10 nm or more, more preferably 15 nm or more, and even more preferably 20 nm or more. By keeping it within the above range, a wide range of color reproducibility can be ensured and vivid colors can be displayed.
• the half-width of the emission spectrum can be adjusted by selecting the QD material and optimizing the particle size distribution of the QDs by selecting the conditions during QD production.
• QD materials include II-VI compounds, III-V compounds, IV-VI compounds, IV compounds, and IV elements. Compounds may be binary, ternary, or quaternary. Other examples include perovskite and carbon compounds.
• typical examples include CdSe, CdTe, CdS, ZnSe, ZnS, GaS, InP, CuInS, AgInS, AgInGaS, ZnSeTe, and ZnSeS.
• Cd-based QDs are preferably used to obtain a QD-EL display device with a narrow half-width of the emission spectrum and high color reproducibility, but Cd-free QDs are also preferably used, and a representative example of a Cd-free QD is one using In.
• the QDs may be particles with a single material composition, or may have a core-shell structure with different material compositions. In the case of a core-shell structure, the shell may be a multi-shell structure with two or more layers. Examples of the multishell structure include CuInS 2 /ZnS, InP/ZnS, CdSe/CdS, InP/ZnSe/ZnS, and ZnTeSe/ZnSe/ZnS.
• the QD material for each color can be the same or different.
• the QDs may be surface modified to improve their dispersibility in solvents during application.
• the light-emitting element of a QD-EL image display device is configured by stacking a cathode, an electron injection layer, an electron transport layer, a light-emitting layer, a hole transport layer, a hole injection layer, and an anode in that order, with the light-emitting layer being a layer that contains QDs.
• the light-emitting layer will be referred to as the QD layer.
• the QD layer is provided, for example, on a substrate provided with a positive electrode and, if necessary, a hole injection layer and a hole transport layer.
• a coating method is preferred as a method for providing the QD layer.
• printing methods such as inkjet printing, letterpress printing, screen printing, and gravure printing, and photolithography are preferred methods.
• an electron transport layer and an electron injection layer are provided, followed by a cathode and a protective layer to form a QD-EL cell. Note that the above order may be reversed, that is, a QD layer may be provided on a substrate provided with a cathode, and then a positive electrode may be provided last.
• the substrate is preferably made of glass, a resin film, a fiber-reinforced resin sheet, a metal, a ceramic, or the like. It is preferable to use a curable resin as the protective layer, but a second protective layer made of glass, a resin film, a fiber-reinforced resin sheet, a metal, a ceramic, or the like may be provided via the curable resin as the first protective layer. At least one of the substrate and the protective layer must be transparent.
• the QD-EL cell is connected to an image signal control device, and an image is displayed by controlling the amount of light emitted by each R, G, and B pixel.
• the QD-EL cell may be housed in a housing.
• a glass plate or a transparent resin plate called a surface plate or a window sheet may be provided on the viewing side of the QD-EL cell.
• a touch sensor may be further disposed on the viewing side of the surface plate or between the surface plate and the transparent resin layer.
• the surface plate may be endowed with a touch sensor function. When no surface plate is provided, a touch sensor may be attached to the viewing side of the QD-EL cell.
• the QD-EL cell may have a back surface protective layer on the back side.
• the back surface protective layer may be any of those listed as the second protective layer. In the case of a foldable or rollable type, it is preferable to use a flexible film as the back surface protective layer to protect against impacts from the back surface.
• a surface protective film is provided on the outermost surface of the viewing side of the QD-EL image display device.
• the surface protective film is used to provide a function of preventing the surface of the display screen from being scratched or reflected, making it easier to view the image, by utilizing a film that has been subjected to a hard coat, an anti-reflection coat, or an anti-glare coat.
• the surface protective film is used as a shatterproof film in case the glass is broken.
• the surface protective film may be disposed directly on the protective layer of the QD-EL cell.
• the surface protection film may be made replaceable.
• the surface protection film is preferably a laminated film having a base film and a functional layer as described below, and preferably has an easy-adhesion layer between the base film and the functional layer.
• the surface protection film refers to a laminated film having a base film and a functional layer, and if an easy-adhesion layer is provided in the base film, it includes the easy-adhesion layer. When it is necessary to distinguish and describe the part of the base film that does not include the easy-adhesion layer, it is sometimes called the original film roll.
• the substrate film used for the surface protective film has an in-plane retardation (Re) of preferably 3000 nm or more, more preferably 4500 nm or more, even more preferably 6000 nm or more, particularly preferably 6500 nm or more, and most preferably 7000 nm or more.
• Re is preferably 30000 nm or less, more preferably 20000 nm or less, even more preferably 15000 nm or less, particularly preferably 12000 nm or less, and most preferably 10000 nm or less.
• the retardation (Rth) in the thickness direction of the substrate film is preferably 3000 nm or more, more preferably 4500 nm or more, even more preferably 6000 nm or more, particularly preferably 6500 nm or more, and most preferably 7000 nm or more.
• Rth is preferably 30000 nm or less, more preferably 20000 nm or less, even more preferably 15000 nm or less, particularly preferably 13000 nm or less, and most preferably 11000 nm or less.
• the Re/Rth of the base film is preferably 0.60 or more, more preferably 0.70 or more, even more preferably 0.80 or more, particularly preferably 0.85 or more, and most preferably 0.90 or more.
• Re/Rth is preferably 1.4 or less, more preferably 1.3 or less, even more preferably 1.2 or less, particularly preferably 1.1 or less, and most preferably 1.05 or less.
• the NZ coefficient of the base film is preferably 2.2 or less, more preferably 1.9 or less, even more preferably 1.70 or less, particularly preferably 1.65 or less, and most preferably 1.62 or less. By making it less than the above, the angle dependency of retardation when viewed from an oblique direction can be reduced, and even if the Re is the same, rainbow spots can be suppressed over a wider range.
• the NZ coefficient is preferably 1.0 or more, more preferably 1.2 or more, and even more preferably 1.3 or more.
• the upper limit of the planar orientation degree ( ⁇ P) of the substrate film is preferably 0.150, more preferably 0.140, even more preferably 0.135, particularly preferably 0.130, and most preferably 0.125.
• the lower limit of ⁇ P is preferably 0.100, and more preferably 0.105.
• the slow axis direction of the substrate film is preferably 7 degrees or less with respect to the long side direction or the short side direction, more preferably 5 degrees or less, even more preferably 3 degrees or less, and most preferably 2 degrees or less.
• the slow axis direction is preferably 7 degrees or less with respect to the MD direction (flow direction of film production) or TD direction (direction perpendicular to the MD direction) of the substrate film, more preferably 5 degrees or less, even more preferably 3 degrees or less, and most preferably 2 degrees or less.
• the variation in the slow axis direction of the substrate film is preferably 10 degrees or less, more preferably 8 degrees or less, even more preferably 6 degrees or less, particularly preferably 5 degrees or less, and most preferably 4 degrees or less.
• the variation in the slow axis is measured using a molecular orientation meter to determine the slow axis direction at the center point in the width direction of the film and at points spaced 100 mm apart from the center point in the width direction (perpendicular to the film flow direction).
• the maximum and minimum values of the measurements are calculated, and the difference between the maximum and minimum values is taken as the variation.
• the slow axis direction is measured based on the TD direction (width direction), and is evaluated by distinguishing between clockwise and counterclockwise, giving positive and negative values.
• the above measurements are performed along two adjacent sides of the film, and the value with the larger difference between the maximum and minimum values is used. This is because there is little variation in the slow axis direction in the MD direction of the film.
• the resin used for the film roll is not particularly limited as long as it generates birefringence by orientation, but polyester, polycarbonate, polystyrene, etc. are preferred, and polyester is particularly preferred, in terms of increasing retardation and low moisture permeability and moisture absorption.
• Preferred polyesters include polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polytetramethylene terephthalate (PBT), polyethylene naphthalate (PEN), etc., and PET and PEN are particularly preferred.
• polyesters may be copolymerized with carboxylic acid components and glycol components other than the main components, but when the total amount of the carboxylic acid components and glycol components is taken as 100 mol%, the total amount of the carboxylic acid components and glycol components other than the main components is preferably 10 mol% or less, more preferably 5 mol% or less, even more preferably 2 mol% or less, particularly preferably 1.5 mol% or less, and most preferably 1.2 mol% or less. If the amount exceeds the above, there is a risk of a high thermal shrinkage rate.
• the glycol components other than the main components also include by-products such as diethylene glycol.
• the amount of glycol components other than the main component is preferably 0.1 mol% or more.
• the most preferable range of the amount of glycol components other than the main component is 0.2 to 1.0 mol%.
• the above polyester can be easily stretched at a high ratio and is impact resistant, making it easy to handle.
• its low moisture permeability and low moisture absorption result in low dimensional change due to environmental changes. Even when used as a surface protection film for a large QD-EL image display device, it can prevent warping of the display device and peeling of the surface protection film over time.
• the thickness of the substrate film is preferably 25 ⁇ m or more, more preferably 40 ⁇ m or more, even more preferably 50 ⁇ m or more, and particularly preferably 60 ⁇ m or more.
• the thickness of the film is preferably 200 ⁇ m or less, more preferably 150 ⁇ m or less, even more preferably 120 ⁇ m or less, and particularly preferably 100 ⁇ m or less.
• the intrinsic viscosity (IV) of the resin constituting the film is preferably 0.5 to 1.50 dL/g.
• the lower limit of IV is more preferably 0.53 dL/g, and even more preferably 0.55 L/g.
• the upper limit of IV is more preferably 1.20 dL/g, and even more preferably 1.00 dL/g, and especially preferably 0.8 dL/g.
• the lower limit of IV is preferably 0.45 dL/g, and even more preferably 0.48 dL/g, and even more preferably 0.50 dL/g, and especially preferably 0.53 dL/g.
• the upper limit of IV is more preferably 1.00 dL/g, and even more preferably 0.80 dL/g, and even more preferably 0.75 dL/g, and especially preferably 0.70 dL/g.
• the film has excellent mechanical strength such as impact resistance, and can be produced efficiently without placing a large load on the equipment.
• the surface protection film desirably has a light transmittance of 20% or less at a wavelength of 380 nm.
• a light transmittance of 15% or less at 380 nm is more preferable, 10% or less is even more preferable, and 5% or less is particularly preferable. If the light transmittance is 20% or less, deterioration of the surface protection film and the adhesives, adhesives, transparent resins, etc. used due to ultraviolet rays can be suppressed.
• the transmittance is measured in a direction perpendicular to the plane of the film, and can be measured using a spectrophotometer (for example, Hitachi U-3500 type).
• the light transmittance of the surface protection film at a wavelength of 380 nm can be reduced to 20% or less by adding an ultraviolet absorber to the original film, applying a coating liquid containing an ultraviolet absorber to the surface of the substrate film, adding an ultraviolet absorber to the functional layer, or by appropriately adjusting the type and concentration of the ultraviolet absorber and the thickness of the film.
• Ultraviolet absorbers are known substances. Examples of ultraviolet absorbers include organic ultraviolet absorbers and inorganic ultraviolet absorbers, with organic ultraviolet absorbers being preferred from the viewpoint of transparency.
• Organic UV absorbers include benzotriazoles, benzophenones, cyclic iminoesters, and combinations thereof.
• particles with an average particle size of 0.05 to 2 ⁇ m examples include inorganic particles such as titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, and calcium fluoride, as well as organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, and silicone-based particles.
• the average particle size can be determined by the weight distribution value obtained by the Coulter Counter method.
• These particles may be added to the entire film roll, or may be added only to the skin layer of a co-extruded multi-layer skin-core structure. It is also preferable not to include particles in the film roll itself, but to add the particles to the easy-adhesion layer described below.
• the base film can be obtained according to a general film manufacturing method. An example will be explained using a PET film. In the following explanation of the manufacturing method, the base film may be referred to as a polyester film.
• one method for manufacturing polyester film is to melt polyester resin, extrude the unoriented polyester into a sheet, stretch it in the machine direction and/or cross direction at a temperature above the glass transition temperature, and then perform a heat treatment.
• the substrate film may be uniaxially or biaxially stretched, but uniaxial stretching is preferable for reasons such as the fact that as the biaxiality becomes stronger, a greater thickness is required to ensure the necessary Re, and it is easier to keep Re/Rth and the NZ coefficient within the appropriate range.
• the main orientation axis of the base film may be the running direction of the film (longitudinal direction, also called MD direction) or the direction perpendicular to the longitudinal direction (orthogonal direction, also called TD direction).
• Roll stretching is preferred for MD stretching
• tenter stretching is preferred for TD stretching.
• TD stretching using a tenter is the preferred method in terms of minimizing scratches on the film surface, productivity, and lamination with a polarizer made of stretched PVA.
• the unstretched film is preheated and stretched preferably at 80 to 130°C, more preferably at 90 to 120°C.
• the stretching ratio in the main stretching direction is preferably 3.6 to 7.0 times, more preferably 3.8 to 6.5 times, even more preferably 4.0 to 6.2 times, and particularly preferably 4.1 to 6 times.
• shrinkage can be achieved, for example, by narrowing the tenter clip spacing.
• the shrinkage treatment is preferably 1 to 20%, more preferably 2 to 15%.
• the main stretching in order to bring the optical properties into the appropriate range, it is preferable to perform the main stretching and, prior to the main stretching, to perform stretching in a direction perpendicular to the main stretching by 1.2 times or less, more preferably 1.15 times or less, and particularly preferably 1.13 times or less.
• the lower limit of the stretching ratio in the perpendicular direction is preferably 1.01 times, more preferably 1.03 times, and particularly preferably 1.05 times.
• the heat setting temperature is preferably 150 to 230°C, and more preferably 170 to 220°C.
• the relaxation treatment is preferably 0.5 to 10%, and more preferably 1 to 5%.
• the film roll may be treated with corona treatment, flame treatment, plasma treatment, or other treatments to improve adhesion.
• the substrate film may be provided with an easy-adhesion layer.
• the easy-adhesion layer improves adhesion to a functional layer described below and adhesion to an adhesive or the like when the substrate film is attached to the surface of a display device, and can prevent peeling of the surface protection film itself and the functional layer during long-term use.
• the resin used in the easy-adhesion layer is a polyester resin, a polyurethane resin, a polycarbonate resin, an acrylic resin, etc., and polyester resin, polyester polyurethane resin, polycarbonate polyurethane resin, and acrylic resin are preferred.
• the easy-adhesion layer is preferably crosslinked. Examples of crosslinking agents include isocyanate compounds, melamine compounds, epoxy resins, and oxazoline compounds.
• the easy-adhesion layer can be formed by applying and drying a coating material made from these resins and, if necessary, crosslinking agents, particles, etc., to the surface protection film.
• a coating material made from these resins and, if necessary, crosslinking agents, particles, etc., to the surface protection film.
• particles include those used for the substrates mentioned above.
• the lower limit of the thickness of the easy-adhesion layer is preferably 10 nm, more preferably 15 nm, and even more preferably 20 nm.
• the upper limit of the thickness is preferably 500 nm, more preferably 300 nm, even more preferably 200 nm, and particularly preferably 150 nm.
• the easy-adhesion layer may be controlled by the amount of coating.
• interference occurs between the light reflected from the interface between the easy-adhesion layer and the original film roll and the light reflected from the interface (with the functional layer, adhesive layer, or pressure-sensitive adhesive layer) on the opposite side of the easy-adhesion layer from the original film roll, which can result in interference colors in areas where the easy-adhesion layer is uneven in thickness.
• This interference color is noticeable in black display areas and when the power is turned off. In order to suppress this interference color, it is preferable to reduce the interference.
• the refractive index of the easy-adhesion layer is preferably nf-0.05 ⁇ n ⁇ nl+0.05, more preferably nf-0.02 ⁇ n ⁇ nl+0.02, and even more preferably nf ⁇ n ⁇ nl.
• the refractive index in the fast axis direction is about 1.6 and the refractive index in the slow axis direction is about 1.7
• the lower limit of the refractive index of the easy-adhesion layer is preferably 1.55, more preferably 1.57, more preferably 1.58, even more preferably 1.59, and particularly preferably 1.60
• the upper limit of the refractive index of the easy-adhesion layer is preferably 1.75, more preferably 1.73, more preferably 1.72, even more preferably 1.71, and particularly preferably 1.70.
• the refractive index of the easy-adhesion layer may be birefringent if it is stretched after being applied by in-line coating.
• the refractive index of the easy-adhesion layer is the average refractive index in the fast axis direction and the slow axis direction.
• the refractive index of the easy-adhesion layer can be measured, for example, by applying a coating liquid of the easy-adhesion layer onto a glass plate or the like, drying it, and using an ellipsometer or the like.
• the refractive index of the resin used in the easy-adhesion layer it is preferable to adjust the refractive index of the resin used in the easy-adhesion layer or to add particles with a high refractive index.
• the refractive index can be increased by the aromatic component, so it is preferable to use a resin having a benzene ring or a naphthalene ring in the main chain or side chain, especially a resin having a naphthalene ring.
• polyester copolymerized with naphthalene dicarboxylic acid is preferable.
• Polyester copolymerized with naphthalene dicarboxylic acid may be blended with other resins as necessary to be used as a polyester resin. It may also be used as a polyester polyol for polyester polyurethane.
• the naphthalene dicarboxylic acid component in the polyester is preferably 30 to 90 mol %, and more preferably 40 to 80 mol %, assuming that the total amount of the aromatic components is 100 mol %.
• the lower limit of the refractive index of the high refractive index particles is preferably 1.7, and more preferably 1.75.
• the upper limit of the refractive index of the high refractive index particles is preferably 3.0, and more preferably 2.7, and even more preferably 2.5.
• particles containing a metal oxide with a high refractive index are preferred.
• metal oxides include TiO 2 (refractive index 2.7), ZnO (refractive index 2.0), Sb 2 O 3 (refractive index 1.9), SnO 2 (refractive index 2.1), ZrO 2 (refractive index 2.4), Nb 2 O 5 (refractive index 2.3), CeO 2 (refractive index 2.2), Ta 2 O 5 (refractive index 2.1), Y 2 O 3 (refractive index 1.8), La 2 O 3 (refractive index 1.9), In 2 O 3 (refractive index 2.0), Cr 2 O 3 (refractive index 2.5), etc., and composite oxides containing these metal atoms.
• SnO 2 particles, TiO 2 particles, ZrO 2 particles, and TiO 2 -ZrO 2 composite particles are preferred.
• the average particle size of the high refractive index particles is preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, and particularly preferably 20 nm or more. High refractive index particles having an average particle size of 5 nm or more are less likely to aggregate, which is preferable.
• the average particle size of the high refractive index particles is preferably 200 nm or less, more preferably 150 nm or less, further preferably 100 nm or less, and particularly preferably 60 nm or less.
• the average particle size of the particles to be added can be measured by dynamic light scattering and determined using the cumulant method.
• the content of high refractive index particles in the easy-adhesion layer is preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and particularly preferably 5% by mass or more. If the content of high refractive index particles in the coating layer is 2% by mass or more, the refractive index of the coating layer can be kept high and low interference can be effectively obtained, which is preferable.
• the content of high refractive index particles in the easy-adhesion layer is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less. If the content of particle A in the coating layer is 50% by mass or less, film-forming properties are maintained, which is preferable.
• the easy-adhesion layer may be applied offline to a stretched film, but is preferably applied in-line during the film-making process.
• it When applied in-line, it may be applied either before longitudinal or transverse stretching, but it is preferably applied just before transverse stretching and then dried and crosslinked in a preheating, heating and heat treatment process using a tenter.
• in-line coating just before longitudinal stretching using rolls it is preferable to dry the film in a vertical dryer after coating and then introduce it into the stretching rolls.
• the easy-adhesion layer is applied on at least one side, and preferably on both sides.
• the surface protective film has a functional layer such as a hard coat layer, an anti-reflection layer, a low-reflection layer, an anti-glare layer, or an antistatic layer on the viewing side of the film.
• the anti-reflection layer, the low-reflection layer, and the anti-glare layer are collectively called the reflection reduction layer.
• the reflection reduction layer not only prevents external light from being reflected on the display screen, making it difficult to see, but also suppresses reflection at the interface to reduce rainbow spots or make them less noticeable.
• the upper limit of the 5-degree reflectance of the surface protective film at a wavelength of 550 nm measured from the reflection reduction layer side is preferably 5%, more preferably 4%, even more preferably 3%, particularly preferably 2%, and most preferably 1.5%. If it exceeds the above, reflection of external light will increase and visibility of the screen may decrease.
• the lower limit of the reflectance is not particularly specified, but from a practical standpoint, it is preferably 0.01%, and even more preferably 0.1%.
• reflection-reducing layers including low-reflection layers, anti-reflection layers, and anti-glare layers.
• the low-reflection layer is a layer with a low refractive index (low refractive index layer) placed on the surface of the base film, which has the function of reducing reflectance by reducing the difference in refractive index with air.
• the antireflection layer is a layer that controls reflection by controlling the thickness of the low refractive index layer and causing interference between reflected light at the upper interface of the low refractive index layer (interface between the low refractive index layer and air) and the lower interface of the low refractive index (for example, the interface between the base film and the low refractive index layer).
• the thickness of the low refractive index layer is preferably about the wavelength of visible light (400 to 700 nm)/(refractive index of the low refractive index layer ⁇ 4).
• the upper limit of reflectance is preferably 2%, more preferably 1.5%, even more preferably 1.2%, and particularly preferably 1%.
• the refractive index of the low refractive index layer is preferably 1.45 or less, more preferably 1.42 or less, and is preferably 1.20 or more, more preferably 1.25 or more.
• the refractive index of the low refractive index layer is measured at a wavelength of 589 nm.
• the thickness of the low refractive index layer is not limited, but may be set appropriately within a range of about 30 nm to 1 ⁇ m. Furthermore, if the objective is to offset the reflection from the surface of the low refractive index layer and the interfacial reflection between the low refractive index layer and its inner layer (substrate film, hard coat layer, etc.) and to further reduce the reflectance, the thickness of the low refractive index layer is preferably 70 to 120 nm, and more preferably 75 to 110 nm.
• the low refractive index layer include (1) a layer made of a resin composition containing a binder resin and low refractive index particles, (2) a layer made of a fluororesin that is a low refractive index resin, (3) a layer made of a fluororesin composition containing silica or magnesium fluoride, and (4) a thin film of a low refractive index material such as silica or magnesium fluoride.
• the binder resin contained in the resin composition (1) can be polyester, polyurethane, polyamide, polycarbonate, acrylic, etc., without any particular restrictions. Among them, acrylic is preferable, and it is preferable that it is obtained by polymerizing (crosslinking) a photopolymerizable compound by irradiation with light.
• the photopolymerizable compound may be a photopolymerizable monomer, a photopolymerizable oligomer, or a photopolymerizable polymer, which may be adjusted as appropriate for use.
• a photopolymerizable compound a combination of a photopolymerizable monomer and a photopolymerizable oligomer or a photopolymerizable polymer is preferred.
• These photopolymerizable monomers, photopolymerizable oligomers, and photopolymerizable polymers are preferably multifunctional.
• polyfunctional monomers examples include pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), etc.
• Monofunctional monomers may also be used in combination to adjust coating viscosity and hardness.
• polyfunctional oligomers examples include polyester (meth)acrylate, urethane (meth)acrylate, polyester-urethane (meth)acrylate, polyether (meth)acrylate, polyol (meth)acrylate, melamine (meth)acrylate, isocyanurate (meth)acrylate, and epoxy (meth)acrylate.
• multifunctional polymers examples include urethane (meth)acrylate, isocyanurate (meth)acrylate, polyester-urethane (meth)acrylate, and epoxy (meth)acrylate.
• the coating agent may contain polymerization initiators, crosslinking catalysts, polymerization inhibitors, antioxidants, UV absorbers, leveling agents, surfactants, etc.
• the low refractive index particles contained in the resin composition (1) include silica particles (e.g., hollow silica particles), magnesium fluoride particles, etc., and among these, hollow silica particles are preferred.
• silica particles e.g., hollow silica particles
• magnesium fluoride particles etc.
• hollow silica particles can be produced, for example, by the manufacturing method described in the examples of JP-A-2005-099778.
• the average particle size of the primary particles of the low refractive index particles is preferably 5 to 200 nm, more preferably 5 to 100 nm, and even more preferably 10 to 80 nm.
• the low refractive index particles are preferably surface-treated with a silane coupling agent, and more preferably surface-treated with a silane coupling agent having a (meth)acryloyl group.
• the content of the low refractive index particles in the low refractive index layer is preferably 10 to 250 parts by mass, more preferably 50 to 200 parts by mass, and even more preferably 100 to 180 parts by mass, per 100 parts by mass of the binder resin.
• a polymerizable compound containing at least fluorine atoms in the molecule or a polymer thereof can be used.
• the polymerizable compound there are no particular limitations on the polymerizable compound, but for example, compounds having a curing reactive group such as a photopolymerizable functional group or a thermosetting polar group are preferred. Compounds having multiple curing reactive groups at the same time are also acceptable. In contrast to this polymerizable compound, the polymer does not have the above-mentioned curing reactive groups.
• a compound having a photopolymerizable functional group for example, a wide variety of fluorine-containing monomers having an ethylenically unsaturated bond can be used.
• the surface of the low refractive index layer may be uneven to provide anti-glare properties, but it is also preferable that it is a smooth surface.
• the arithmetic mean roughness SRa JIS B0601:1994 of the surface of the low refractive index layer is preferably 20 nm or less, more preferably 15 nm or less, even more preferably 10 nm or less, and particularly preferably 1 to 8 nm.
• the ten-point mean roughness Rz JIS B0601:1994 of the surface of the low refractive index layer is preferably 160 nm or less, more preferably 50 to 155 nm.
• the refractive index of the high refractive index layer is preferably 1.55 to 1.85, and more preferably 1.56 to 1.70.
• the refractive index of the high refractive index layer is measured at a wavelength of 589 nm.
• the thickness of the high refractive index layer is preferably 30 to 200 nm, and more preferably 50 to 180 nm.
• the high refractive index layer may be multiple layers, but two layers or less are preferable, and a single layer is more preferable. In the case of multiple layers, it is preferable that the total thickness of the multiple layers is within the above range.
• the refractive index of the high refractive index layer on the low refractive index layer side is higher.
• the refractive index of the high refractive index layer on the low refractive index layer side is preferably 1.60 to 1.85, and the refractive index of the other high refractive index layer is preferably 1.55 to 1.70.
• the high refractive index layer is preferably made of a resin composition containing high refractive index particles and a resin.
• preferred high refractive index particles are antimony pentoxide particles, zinc oxide particles, titanium oxide particles, cerium oxide particles, tin-doped indium oxide particles, antimony-doped tin oxide particles, yttrium oxide particles, and zirconium oxide particles.
• titanium oxide particles and zirconium oxide particles are preferred.
• Two or more types of high refractive index particles may be used in combination.
• the preferred average particle size of the primary particles of the high refractive index particles is the same as that of the low refractive index particles.
• the content of the high refractive index particles is preferably 30 to 400 parts by mass, more preferably 50 to 200 parts by mass, and even more preferably 80 to 150 parts by mass, per 100 parts by mass of the resin.
• the resins used for the high refractive index layer are the same as those listed for the low refractive index layer, except for fluorine-based resins.
• the surface of the high refractive index layer is also flat.
• the method for flattening the surface of the high refractive index layer is the same as the method for flattening the low refractive index layer described above.
• the high refractive index layer and the low refractive index layer can be formed, for example, by applying a resin composition containing a photopolymerizable compound to a substrate film, drying it, and then irradiating the coating of the resin composition with light such as ultraviolet light to polymerize (crosslink) the photopolymerizable compound.
• the resin compositions of the high and low refractive index layers may contain thermoplastic resins, thermosetting resins, solvents, and polymerization initiators, as necessary.
• dispersants, surfactants, antistatic agents, silane coupling agents, thickeners, coloring inhibitors, colorants (pigments, dyes), defoamers, leveling agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers, and lubricants may be added.
• the antiglare layer is a layer that prevents the shape of a light source from being reflected when external light is reflected from the surface and reduces glare by providing an uneven surface to cause diffuse reflection.
• the arithmetic mean roughness (SRa) of the surface irregularities of the antiglare layer is preferably 0.02 to 0.25 ⁇ m, more preferably 0.02 to 0.15 ⁇ m, and even more preferably 0.02 to 0.12 ⁇ m.
• the ten-point average roughness (Rzjis) of the surface irregularities of the antiglare layer is preferably 0.15 to 2.00 ⁇ m, more preferably 0.20 to 1.20 ⁇ m, and even more preferably 0.30 to 0.80 ⁇ m.
• SRa and Rzjis are calculated from the roughness curve measured using a contact type roughness meter in accordance with JIS B0601-1994 or JIS B0601-2001.
• the lower limit of the thickness of the antiglare layer is preferably 0.1 ⁇ m, more preferably 0.5 ⁇ m.
• the upper limit of the thickness of the antiglare layer is preferably 100 ⁇ m, more preferably 50 ⁇ m, and even more preferably 20 ⁇ m.
• the refractive index of the antiglare layer is preferably 1.20 to 1.80, and more preferably 1.40 to 1.70.
• the refractive index of the antiglare layer is preferably 1.20 to 1.45, and more preferably 1.25 to 1.40.
• the refractive index of the antiglare layer is preferably 1.50 to 1.80, and more preferably 1.55 to 1.70.
• the refractive index of the anti-glare layer is measured at a wavelength of 589 nm.
• the low refractive index layer may be provided with irregularities to serve as an anti-glare low-reflection layer, or a low refractive index layer may be provided on the irregularities to provide anti-reflection functionality to serve as an anti-glare anti-reflection layer.
• the hard coat layer is also a preferred embodiment to provide a hard coat layer as a lower layer of the reflection reducing layer.
• the hard coat layer preferably has a pencil hardness of H or more, more preferably 2H or more.
• the hard coat layer can be provided, for example, by applying and curing a composition solution of a thermosetting resin or a radiation curing resin.
• Thermosetting resins include acrylic resins, urethane resins, phenolic resins, urea melamine resins, epoxy resins, unsaturated polyester resins, silicone resins, and combinations of these.
• Thermosetting resin compositions contain these curable resins and, if necessary, a curing agent.
• the radiation curable resin is preferably a compound having a radiation curable functional group
• examples of the radiation curable functional group include ethylenically unsaturated bond groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy and oxetanyl groups.
• the ionizing radiation curable compound is preferably a compound having an ethylenically unsaturated bond group, more preferably a compound having two or more ethylenically unsaturated bond groups, and even more preferably a polyfunctional (meth)acrylate compound having two or more ethylenically unsaturated bond groups.
• the polyfunctional (meth)acrylate compound may be a monomer, oligomer, or polymer.
• the compound having a radiation-curable functional group preferably contains 50% by mass or more of difunctional or higher monomers, and more preferably 70% by mass or more. Furthermore, the compound having a radiation-curable functional group preferably contains 50% by mass or more of trifunctional or higher monomers, and more preferably 70% by mass or more.
• the above compounds having radiation-curable functional groups can be used alone or in combination of two or more.
• the thickness of the hard coat layer is preferably in the range of 0.1 to 100 ⁇ m, and more preferably in the range of 0.8 to 20 ⁇ m.
• the refractive index of the hard coat layer is more preferably 1.45 to 1.70, and even more preferably 1.50 to 1.60.
• the refractive index of the hard coat layer is measured at a wavelength of 589 nm.
• the refractive index of the hard coat layer can be adjusted by adjusting the refractive index of the resin, or by adjusting the refractive index of the particles if particles are added.
• Particles include those exemplified as particles in the anti-glare layer.
• the hard coat layer may also be referred to as the reflection reducing layer.
• the functional layer When providing a functional layer on the surface protection film, it is preferable to provide the functional layer in contact with the easy-adhesion layer surface of the above-mentioned base film, resulting in a structure of base film/easy-adhesion layer/functional layer.
• the surface protection film is preferably attached to the image display surface of the QD-EL image display device with an adhesive.
• the adhesive is preferably a substrate-less optical adhesive.
• One release film of the optical adhesive which has release films attached to both sides of the adhesive layer, is peeled off and the adhesive is attached to the surface of the surface protection film opposite the functional layer, and then the other release film is peeled off and the adhesive is attached to the QD-EL image display device.
• the size of the QD-EL image display device is not limited, but if it is large, the diagonal length is preferably 50 inches or more, more preferably 80 inches or more, even more preferably 100 inches or more, and particularly preferably 120 inches or more.
• the diagonal length is preferably 1000 inches or less, more preferably 700 inches or less, and even more preferably 500 inches or less. It may be rollable or foldable so that it can be folded like a folding screen.
• the slow axis direction of the surface protective film is preferably approximately parallel to the long side or short side direction of the QD-EL image display device, but is more preferably approximately parallel to the short side direction.
• Rainbow spots tend to appear relatively strongly in the fast axis direction of 20 to 50 degrees from the slow axis direction and in a direction oblique to the normal direction of the film by 50 to 70 degrees.
• by aligning the slow axis direction to the short side direction of the screen it is possible to avoid the direction in which rainbow spots are likely to appear when viewing an installed QD-EL image display device from an oblique direction, which is often the case when viewed from a horizontal oblique direction. In addition, it is possible to avoid the four corners from directions in which rainbow spots are likely to appear.
• the QD-EL image display device is installed with its short side horizontal, it is also preferable to align the slow axis direction of the surface protective film to the long side direction of the screen.
• the direction of the folded portion (the direction perpendicular to the folding direction, i.e., the direction of the valleys or mountains when folded) is approximately parallel to the slow axis direction of the surface protection film, which is less likely to leave creases.
• approximately parallel preferably means that an error of within 7 degrees is acceptable, more preferably an error of within 5 degrees, and even more preferably an error of within 3 degrees.
• Refractive index of polyester film The slow axis direction of the film was determined using a molecular orientation meter (MOA-6004 molecular orientation meter manufactured by Oji Measurement Instruments Co., Ltd.), and a rectangle of 4 cm x 2 cm was cut out so that the slow axis direction was parallel to the long side, and used as a measurement sample.
• MOA-6004 molecular orientation meter manufactured by Oji Measurement Instruments Co., Ltd.
• the refractive indexes of the two orthogonal axes (refractive index in the slow axis direction: ny, fast axis (refractive index in the direction perpendicular to the slow axis direction): nx) and the refractive index in the thickness direction (nz) of this sample were determined using an Abbe refractometer (NAR-4T manufactured by Atago Co., Ltd., measurement wavelength 589 nm).
• the biaxial refractive index anisotropy ( ⁇ Nxy) was obtained by the method (1) above, and the biaxial refractive index difference (
• the film thickness d (nm) was measured using an electric micrometer (Militron 1245D, manufactured by Fine Leuf Co., Ltd.) and converted to nm.
• the retardation (Re) was obtained from the product ( ⁇ Nxy ⁇ d) of the refractive index anisotropy ( ⁇ Nxy) and the film thickness d (nm).
• nx is the refractive index in the direction perpendicular to the in-plane slow axis
• ny is the refractive index in the in-plane slow axis direction
• nz is the refractive index in the thickness direction.
• a sample was cut out from the center in the TD direction of the film in which the TD direction was parallel to the slow axis direction, and the measurement was performed.
• ) and ⁇ Nyz (
• the temperature was then raised to 255°C, the reaction system was gradually depressurized, and the reaction was carried out for 1 hour and 30 minutes under a reduced pressure of 30 Pa to obtain a copolymer polyester resin (A-1).
• the obtained copolymer polyester resin was pale yellow and transparent.
• a similar method was used to obtain a copolymer polyester resin (A-2) with a different composition.
• Particles A are SnO 2 particles with a refractive index of 2.1
• Particles B are silica particles with an average primary particle size of about 500 nm.
• Coating solution (D-2) was obtained in the same manner as in Coating Solution (D-1), except that the polyester water dispersion was changed to B-2 and the particles A were changed to SiO2 having a refractive index of 1.46 (Snowtex ZL manufactured by Nissan Chemical Industries, Ltd., solid content concentration 40% by mass).
• Example 1 Base film A 90 parts by mass of PET (X) resin pellets containing no particles and 10 parts by mass of PET (Y) resin pellets containing an ultraviolet absorber as the raw material for the intermediate layer of the base film were dried under reduced pressure (1 Torr) at 135 ° C for 6 hours, and then fed to extruder 2 (for intermediate layer II layer), and PET (X) was dried by a conventional method and fed to extruder 1 (for outer layer I layer and outer layer III layer), respectively, and dissolved at 285 ° C.
• PET (X) resin pellets containing no particles and 10 parts by mass of PET (Y) resin pellets containing an ultraviolet absorber as the raw material for the intermediate layer of the base film were dried under reduced pressure (1 Torr) at 135 ° C for 6 hours, and then fed to extruder 2 (for intermediate layer II layer), and PET (X) was dried by a conventional method and fed to extruder 1 (for outer layer I layer and outer layer III layer), respectively, and dissolved at 285 ° C.
• the coating solution (D-1) was applied to both sides of this unstretched PET film so that the coating amount after drying would be 0.08 g/ m2 , and then dried at 80°C for 20 seconds.
• the unstretched film with this coating layer formed was introduced into a tenter stretching machine, and while the ends of the film were held with clips, it was introduced into the tenter at 100°C and stretched 4.0 times in the width direction. Next, while maintaining the stretched width in the width direction, it was processed in a heat setting zone at a temperature of 190°C for 10 seconds, and further relaxed by 2.0% in the width direction, resulting in a uniaxially stretched PET film with a film thickness of 60 ⁇ m.
• Base film D, E An unstretched PET film obtained in the same manner as for the base film A was stretched 1.1 times at 90° C. using an MD stretching machine consisting of a low-speed roll and a high-speed roll. Then, the coating liquid D-1 was applied, and a base film D was obtained in the same manner as for the base film A, except that the stretching ratio in the tenter was 4.2 times.
• Substrate film E was obtained in the same manner as substrate film D, except that the MD stretch ratio was 1.25 times and the tenter temperature was 110°C.
• Example 6 Base film F Substrate film F was obtained in the same manner as substrate film A, except that the thickness was changed, the tenter temperature was 110° C., and the stretching ratio was 4.8 times.
• Example 7 Base film G A base film G was obtained in the same manner as base film D, except that the MD stretching ratio was 3.1 times, the tenter temperature was 120° C., and the stretching ratio was 3.5 times.
• Example 8 Base film H Substrate film H was obtained in the same manner as for substrate film B, except that the coating liquid was changed to D-2.
• an ITO glass substrate was prepared, and this substrate was patterned by photolithography to form R, G, and B pixels. After wet etching, the photoresist was removed to form a lower electrode.
• a SiO 2 film was formed with a thickness of 50 nm by CVD (Chemical Vapor Deposition) as a partition wall separating each pixel, and then patterned and dry etched by photolithography, and the photoresist was removed.
• PEDOT-PSS Sigma-Aldrich
• TFB poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(4,4'(N-(4-sec-butylphenyl)diphenylamine)]
• a red light-emitting layer with a dry thickness of 25 nm was formed on the hole transport layer of the red pixel using a 1% by mass n-octane dispersion of CdSe/ZnS core-shell type QDs (manufactured by MERCK) whose particle size was adjusted to emit red light.
• green and blue light-emitting layers were formed on the pixels for each color using CdSe/ZnS core-shell type QDs (manufactured by MERCK) that emit green light and CdSe/ZnS core-shell type QDs (manufactured by MERCK) that emit blue light.
• MERCK CdSe/ZnS core-shell type QDs
• a dispersion liquid for forming an electron transport layer in which ZnMgO was dispersed in ethanol to a concentration of 1.5% by mass, was applied onto the quantum dot light-emitting layer so that the dry film thickness was 60 nm, and then dried to form an electron transport layer with a dry film thickness of 60 nm on the light-emitting layer.
• Aluminum (Al) was deposited onto the formed electron transport layer by vacuum deposition to form a second electrode (cathode) with a thickness of 100 nm.
• a glass plate was placed on top to seal the quantum dot EL element, and a QD-EL panel was produced.
• a rectangle was cut from the center of the resulting substrate film in the width direction so that the slow axis direction was parallel to the short side, and this was attached to the glass substrate of the QD-EL panel using an optical adhesive to create a QD-EL panel with a surface protection film for evaluation.
• the QD-EL panel with the surface protection film was installed on the wall of a room where outside light enters, so that the center of the QD-EL panel with the surface protection film was 160 cm high and the long side was horizontal.
• the room was lit by fluorescent white LEDs, the floor was made of brown linoleum, and the walls were covered with cream-colored vinyl chloride wallpaper with a low gloss.
• ⁇ No rainbow spots were observed on the screen regardless of the observer's position.
• ⁇ Rainbow spots were observed in a very small range of observer positions, and in areas with large angles from the front, such as the edges of the screen.
• ⁇ Rainbow spots were observed in parts of the screen over a wide range of observer positions.
• Interference color evaluation formation of hard coat layer
• a hard coat layer-forming coating solution having the following composition was applied to one side of the prepared substrate film using a #10 wire bar, and the solvent was removed by drying at 70° C. for 1 minute.
• the film coated with the hard coat layer was irradiated with ultraviolet light of 300 mJ/cm2 using a high-pressure mercury lamp to obtain a surface protection film having a hard coat layer with a thickness of 5 ⁇ m.
• Coating solution for forming hard coat layer Methyl ethyl ketone 65.00% by mass Dipentaerythritol hexaacrylate 27.20% by mass (Shin Nakamura Chemical A-DPH) Polyethylene diacrylate 6.80% by mass (Shin Nakamura Chemical A-400) Photopolymerization initiator 1.00% by mass (Irgacure 184, manufactured by Chiba Specialty Chemicals)
• the surface protection film on which the hard coat had been formed was cut into an area of 10 cm (film width direction) x 15 cm (film length direction) to create a sample film.
• a black glossy tape (vinyl tape No. 21; black, manufactured by Nitto Denko Corporation) was attached to the side of the resulting sample film opposite the hard coat layer.
• the hard coat layer side of this sample film was placed on top, and a three-wavelength daylight light (National Palook, F.L 15EX-N 15W) was used as the light source, and it was observed from diagonally above at a position where the strongest reflection was observed (40-60 cm from the light source, 15-45° angle).
• the results of visual observation were ranked according to the following criteria. The observations were performed by three people familiar with the evaluation, and in cases where there were differences in the evaluation, they were decided by consensus. ⁇ and ⁇ were considered to be passing.
• ⁇ Almost no interference color is observed even when observed from any angle.
• ⁇ Slight iridescent color is observed.
• ⁇ Clear iridescent color is observed.
• a coating solution for forming a medium refractive index layer having the following composition was applied to one side of the substrate film B obtained in Example 2 using a bar coater, and after drying at 70°C for 1 minute, ultraviolet rays of 400 mJ/cm2 were irradiated using a high pressure mercury lamp to obtain a medium refractive index layer with a dry thickness of 5 ⁇ m.
• a coating solution for forming a high refractive index layer having the following composition was formed on the formed medium refractive index layer using a bar coater in the same manner as for the medium refractive index layer, and a coating solution for forming a low refractive index layer having the following composition was further formed on the formed high refractive index layer in the same manner as for the medium refractive index layer, thereby obtaining a surface protective film with an antireflection layer laminated thereon.
• a preferable surface protective film having antireflection properties was obtained.
• the reflectance was 0.7%. The reflectance was measured at 5 degrees at a wavelength of 550 nm using a spectrophotometer (Shimadzu Corporation, UV-3150).
• the reflectance was measured by applying black marker to the surface of the film opposite to the surface on which the antireflection layer (or low reflection layer) was provided, and then attaching black vinyl tape (Kyowa Vinyl Tape HF-737, width 50 mm) thereto.
• Coating solution for forming a medium refractive index layer (refractive index 1.52) Dipentaerythritol hexaacrylate 70 parts by weight 1,6-bis(3-acryloyloxy-2-hydroxypropyloxy)hexane 30 parts by weight Photopolymerization initiator 4 parts by weight (Irgacure 184, manufactured by Chiba Specialty Chemicals Co., Ltd.) Isopropanol 100 parts by weight Coating solution for forming high refractive index layer (refractive index 1.64) ITO fine particles (average particle size 0.07 ⁇ m) 85 parts by weight Tetramethylolmethane triacrylate 15 parts by weight Photopolymerization initiator (KAYACURE BMS, manufactured by Nippon Kayaku Co., Ltd.) 5 parts by weight Butyl alcohol 900 parts by weight Coating liquid for forming low refractive index layer (refractive index 1.42) 1,10-Diacryloyloxy-2,2,3,3,4,4,5,5,6,6,7,7
• the QD-EL image display device of the present invention is free from rainbow spots caused by the surface protection film, and has excellent visibility in a variety of installation locations. It also provides a display device with excellent appearance.

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