Oriented film, image display device using the same, and method for cutting out oriented film sheet

Abstract

According to the present invention, it is possible to provide an economically excellent oriented film that can reduce waste and increase productivity when a sheet piece of depolarizing film is cut out from a long-length film, does not cause blackout or rainbow spots even in a case where an image is viewed with polarized sunglasses on, and can be attached later using a general-purpose image display device as digital signage, an image display device using the same, and a method for cutting out an oriented film. In addition, in a further preferred embodiment, there can be provided an oriented film, an image display device, and a method of cutting out an oriented film, each of which causes less trouble at the time of bonding or thereafter.SOLUTION: A rectangular oriented film that is disposed on a viewing side of an image display apparatus and converts linearly polarized light emitted from the image display apparatus into elliptically polarized light, wherein the oriented film has an in-plane retardation of 3000 to 30000nm, and an angle between a long side of the oriented film and a slow or fast axis of the oriented film is more than 5 degrees and less than 30 degrees.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an oriented film (depolarizing film) that is placed on the viewing side of an image display device to convert linearly polarized light emitted from the image display device into elliptically polarized light and thereby depolarize the light, an image display device including the oriented film, and a method for cutting out the oriented film from a long film. More specifically, the present invention relates to a depolarizing film that does not cause blackouts or rainbow spots when viewing images while wearing polarized sunglasses, an image display device, and a method for cutting out the depolarizing film. [Background technology]

[0002] In conventional VA and IPS LCDs, the extinction axis (absorption axis) of the polarizer on the viewing side is generally horizontal, meaning that the long edge of the display screen is parallel to the extinction axis of the polarizer on the viewing side. When viewing this screen while wearing polarized sunglasses, if the long edge of the display is oriented horizontally, as is the case with televisions in homes, the extinction axis of the polarizer on the viewing side and the extinction axis of the polarized sunglasses are aligned, so the phenomenon known as blackout, in which the screen becomes invisible, does not occur. However, in recent years, display devices such as digital signage have become more common outdoors, and in these applications, the long edge of the display is generally oriented vertically, creating the problem of blackout, in which people wearing polarized sunglasses cannot see the displayed content.

[0003] A known technique is to eliminate polarization by aligning the polarizing plate's transmission axis with the slow or fast axis of the oriented film on the viewing side of the polarizing plate, thereby preventing blackouts and iridescence when using polarized sunglasses (see, for example, Patent Document 1). However, highly oriented films typically have a main orientation axis in the film production direction (longitudinal direction) or a direction perpendicular to the film production direction (transverse direction). Therefore, cutting an oriented film at a 45-degree angle from a roll film requires a wider roll film, and cutting at a 45-degree angle results in significant waste. Furthermore, film production involves slitting the mill roll to the required width after film production. However, because the film width is adjusted to minimize slitting waste, it is sometimes difficult to produce such wide films. This problem is particularly significant for outdoor digital signage, which often has large screens.

[0004] Also, a display device has been proposed that is free from blackouts and rainbow spots and has excellent contrast in bright places by installing a polarizing plate in which the angle between the absorption axis of the polarizer and the fast axis direction of the polarizer protective film is 5 degrees or more and 40 degrees or less, with the absorption axis direction of the polarizer aligned horizontally (see, for example, Patent Document 2). However, this conventional technology requires changing the polarizing plate, which is an essential component of the image display device, and therefore the image display device itself becomes specialized, resulting in low versatility. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4888853 [Patent Document 2] Japanese Patent Application Laid-Open No. 2015-68847 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention was made in response to the problems of the conventional technology. That is, an object of the present invention is to provide an oriented film that can reduce waste and increase productivity when cutting out sheets of depolarizing film from a long film, that does not cause blackouts or rainbow spots even when viewing images through polarized sunglasses, and that can be retrofitted to a general-purpose image display device as digital signage, an image display device using the same, and a method for cutting out the oriented film. It is further desirable to provide an alignment film for depolarization that causes few problems during and after lamination, an image display device using the same, and a method for cutting out the alignment film. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to achieve the above object and have completed the present invention, which is as follows. Section 1. A rectangular orientation film that is disposed on the viewing side of an image display device and converts linearly polarized light emitted from the image display device into elliptically polarized light, The oriented film has an in-plane retardation of 3000 to 30000 nm, An oriented film, wherein the angle between the long side of the oriented film and the slow axis or fast axis is more than 5 degrees and less than 30 degrees. Section 2. Item 2. The oriented film according to item 1, wherein the angle between the long side of the oriented film and the slow axis is greater than 5 degrees and less than 30 degrees. Section 3. An image display device having an alignment film on the viewing side of a viewing-side polarizing plate, The oriented film has an in-plane retardation of 3000 to 30000 nm, The image display device, wherein the angle formed between the absorption axis of the polarizing plate and the slow axis or fast axis of the alignment film is more than 5 degrees and less than 30 degrees. Section 4. Item 4. The image display device according to item 3, wherein the polarizing plate is rectangular and the absorption axis of the polarizing plate is parallel to the long side thereof. Section 5. Item 5. The image display device according to item 3 or 4, wherein the angle formed between the absorption axis of the polarizing plate and the slow axis of the alignment film is greater than 5 degrees and less than 30 degrees. Section 6. 6. The image display device according to any one of items 3 to 5, wherein the image display portion is rectangular, and the image display device is installed so that the long side of the image display portion is in the vertical direction. Section 7. A method for cutting out rectangular sheets of oriented film, characterized in that when cutting out a long oriented film having a slow axis in the longitudinal direction or perpendicular to the longitudinal direction, the film is cut out so that the angle between the long side of the rectangle and the slow axis is more than 5 degrees and less than 30 degrees. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an economically excellent oriented film, an image display device using the same, and a method for cutting out an oriented film, which can reduce waste and increase productivity when cutting out sheets of depolarizing film from a long film, do not cause blackouts or rainbow spots even when viewing images through polarized sunglasses, and can be retrofitted to a general-purpose image display device as digital signage.In a further preferred embodiment, it is possible to provide an oriented film, an image display device, and a method for cutting out an oriented film, which have few problems during and after lamination. DETAILED DESCRIPTION OF THE INVENTION

[0009] (oriented film) First, the oriented film of the present invention will be described. The oriented film of the present invention is a rectangular sheet of oriented film that is arranged (for example, attached) on the viewing side of an image display device such as a liquid crystal display device or an organic EL display device to convert linearly polarized light emitted from the image display device into elliptically polarized light.

[0010] The material for the oriented film is not particularly limited as long as it is a thermoplastic resin capable of forming a film, and examples thereof include polyester, polycarbonate, polystyrene, polyamide, poly(meth)acrylate, etc., with polyester being preferred.

[0011] Suitable examples of polyesters include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), but other copolymerization components may also be included. These resins have excellent transparency and thermal and mechanical properties, and their retardation can be easily controlled by stretching. In particular, polyethylene terephthalate is the most suitable material because it has a large intrinsic birefringence, and the refractive index in the fast axis direction (perpendicular to the slow axis direction) can be kept low by stretching the film, and a large retardation can be obtained relatively easily even with a thin film.

[0012] In addition to the materials of the oriented film, additives such as inorganic particles, heat-resistant polymer particles, alkali metal compounds, alkaline earth metal compounds, phosphorus compounds, antistatic agents, UV absorbers, light stabilizers, flame retardants, heat stabilizers, antioxidants, antigelling agents, surfactants, etc. Furthermore, to achieve high transparency, it is also preferable that the polyester substrate film is substantially free of particles. "Substantially free of particles" means, for example, in the case of inorganic particles, that the content of inorganic elements, when quantified by fluorescent X-ray analysis, is 50 ppm or less, preferably 10 ppm or less, and particularly preferably below the detection limit.

[0013] The lower limit of the in-plane retardation (Re) of the oriented film is preferably 3000 nm, more preferably 4000 nm, even more preferably 4500 nm, and particularly preferably 5000 nm. If it is less than the above, rainbow spots may be observed when an image display device provided with the oriented film is viewed through polarized sunglasses. The upper limit of the in-plane retardation of the oriented film is preferably 30,000 nm, more preferably 15,000 nm, even more preferably 12,000 nm, and particularly preferably 10,000 nm. Even if the upper limit exceeds the above, the depolarization function will remain the same, but the oriented film will become thicker, which may result in poor handling or an increased thickness of the image display device.

[0014] The ratio of in-plane retardation to thickness retardation (Re / Rth) of the oriented film is preferably 0.200 or more, more preferably 0.500 or more, and even more preferably 0.600 or more. The larger the ratio of in-plane retardation to thickness retardation (Re / Rth), the more isotropic the birefringence becomes, making it less likely for rainbow-like color spots to appear even when viewed obliquely. A perfectly uniaxial (uniaxially symmetric) film has a ratio of in-plane retardation to thickness retardation (Re / Rth) of 2.0. However, as the film approaches perfect uniaxiality (uniaxially symmetric), the mechanical strength in the direction perpendicular to the orientation direction decreases. On the other hand, the ratio of the in-plane retardation to the thickness retardation (Re / Rth) of the oriented film is preferably 1.5 or less, more preferably 1.2 or less, and even more preferably 1.0 or less.

[0015] The oriented film preferably has an Nz coefficient, expressed as |ny-nz| / |ny-nx|, of 2.5 or less. The Nz coefficient can be determined as follows. The orientation axis direction of the film is determined using a molecular orientation meter (MOA-6004 molecular orientation meter, manufactured by Oji Scientific Instruments Co., Ltd.), and the biaxial refractive indexes (ny, nx, where ny > nx) along the orientation axis and in the direction perpendicular thereto, as well as the refractive index in the thickness direction (nz) are determined using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd., measurement wavelength 589 nm). The thus determined nx, ny, and nz can be substituted into the formula expressed as |ny-nz| / |ny-nx| to determine the Nz coefficient. The Nz coefficient is preferably 2.0 or less, and even more preferably 1.8 or less. The lower limit of the Nz coefficient is preferably 1.2. To maintain the mechanical strength of the film, the lower limit of the Nz coefficient is preferably 1.3 or more, more preferably 1.4 or more, and even more preferably 1.45 or more.

[0016] The oriented film preferably has a planar orientation degree expressed by (nx + ny) / 2 - nz of a specific value or less. Here, the values ​​of nx, ny, and nz are determined in the same manner as the Nz coefficient. The planar orientation degree of the oriented film is preferably 0.08 or more, more preferably 0.10 or more. The planar orientation degree of the oriented film is preferably 0.13 or less, more preferably 0.125 or less, and even more preferably 0.12 or less. If the planar orientation degree exceeds 0.13, rainbow spots may occur when the image display device is observed from an oblique direction. If the planar orientation degree is less than 0.08, the film thickness may fluctuate, and the retardation value may become non-uniform within the film plane.

[0017] The breaking strength of the oriented film in the slow axis direction is preferably 200 MPa or more, more preferably 250 MPa or more, and preferably 500 MPa or less, more preferably 400 MPa or less. The oriented film preferably has a breaking strength in the fast axis direction of 40 MPa or more, more preferably 50 MPa or more, and preferably has a breaking strength in the fast axis direction of 200 MPa or less, more preferably 150 MPa or less. Increasing the uniaxiality of the oriented film increases the breaking strength in the slow axis direction and decreases the breaking strength in the fast axis direction. The above ranges can be achieved by adjusting the stretching conditions. Within the above range, not only are problems such as breakage during lamination unlikely to occur, ensuring workability, but problems such as breakage are also unlikely to occur during film formation, coating, and other processing.

[0018] The oriented film preferably has a breaking elongation in the slow axis direction of 30% or more, more preferably 40% or more, and preferably has a breaking elongation in the slow axis direction of 150% or less, more preferably 120% or less. The oriented film preferably has a breaking elongation in the fast axis direction of 2% or more, more preferably 3% or more, and preferably has a breaking elongation in the fast axis direction of 30% or less, more preferably 20% or less. Increasing the uniaxiality of an oriented film increases the breaking elongation in the slow axis direction and decreases the breaking strength in the fast axis direction. The above ranges can be achieved by adjusting the stretching conditions. Furthermore, the elongation of the oriented film can be increased by copolymerizing a small amount of the resin constituting the film, but if the amount of copolymerization is too large, the thermal stability of the oriented film may decrease. Within the above range, not only are problems such as breakage during lamination unlikely to occur, ensuring workability, but problems such as breakage are also unlikely to occur during film formation, coating, and other processing.

[0019] The lower limit of the thickness of the oriented film is preferably 20 μm, more preferably 30 μm, still more preferably 40 μm, and particularly preferably 50 μm. If the thickness is less than the above, it becomes difficult to ensure sufficient in-plane retardation. The upper limit of the thickness of the oriented film is preferably 500 μm, more preferably 400 μm, even more preferably 300 μm, particularly preferably 200 μm, and most preferably 150 μm. If the thickness exceeds the above range, the oriented film may become difficult to handle, or the image display device may become too thick.

[0020] The alignment film is rectangular to fit the image display part (image display cell or surface protective cover) on which it is to be installed. It may be square, but is preferably rectangular with long and short sides, which is the shape of a typical image display cell. The aspect ratio (length of long side / length of short side) and size of the alignment film may be determined according to the image display area of ​​the target to be installed, but the lower limit of the aspect ratio is preferably 1.2, more preferably 1.25, even more preferably 1.3, and particularly preferably 1.33. The upper limit of the aspect ratio is preferably 2.5, more preferably 2, even more preferably 1.9, and particularly preferably 1.85.

[0021] The angle between the long side of the oriented film (or any one side in the case of a square) and the slow axis or fast axis is preferably greater than 5 degrees, more preferably greater than 7 degrees, even more preferably greater than 10 degrees, particularly preferably greater than 12 degrees, and most preferably greater than 15 degrees. If the angle is less than the above, when viewing an image through polarized sunglasses, the image may appear dark and difficult to see depending on the angle. The angle between the long side of the oriented film (or any one side in the case of a square) and the slow axis or fast axis is preferably less than 30 degrees, more preferably less than 28 degrees, even more preferably less than 25 degrees, particularly preferably less than 23 degrees, and most preferably less than 20 degrees. If the angle is greater than the above, a wide roll film is required for cutting out the oriented film, which may make it impossible to prepare a roll film of the required width or result in a lot of waste during cutting.

[0022] The above-mentioned angle between the long side of the oriented film and the slow axis or fast axis is preferably the angle between the long side of the oriented film and the slow axis. When laminating rectangular objects together, it is customary to begin with the short edge and then work your way along the long edge. During this process, the pieces are bent or tensioned to prevent air bubbles from forming. Also, if air bubbles are trapped or the lamination becomes misaligned, the pieces are peeled off and re-laid. When the angle between the long edge and the slow axis is small (i.e., greater than 5 degrees and less than 30 degrees), the oriented film is less likely to crack or peel during this process, and it also tends to be less prone to curling after lamination. This is thought to be because oriented films have a strong unidirectional orientation, and the direction perpendicular to the orientation (slow axis) has characteristics such as a low elastic modulus, a tendency to stretch, and a tendency to crack or peel. In outdoor signage applications, a transparent surface protection plate such as a polycarbonate plate may be provided to protect the surface of the image display device, and this problem is likely to occur when an alignment film is attached to this transparent surface protection plate.

[0023] On the other hand, it is also preferable that the angle between the long side of the oriented film and the slow axis or fast axis is the angle between the long side of the oriented film and the fast axis. When producing an oriented film, in order to prevent the film surface from being scratched, it is often cut out from a roll of long film slit to the required width from a mill roll having a slow axis in the width direction (having a fast axis in the longitudinal direction) stretched in the width direction in a tenter. The oriented film is often used as a polarizer protective film, and in this case, for example, in the case of a liquid crystal display panel, a long film is prepared by slitting the film to match the lengths of the short and long sides of the panel for the viewer-side polarizing plate and the light source polarizing plate. If the angle between the direction of the long side and the direction of the fast axis is small, the film can be cut out from a long film for the polarizer protective film that has been slit to match the length of the long side, without separately preparing a long film that has been slit widely, which is more economical and less wasteful.

[0024] In this case, where θ is the angle between the long side of the oriented film and the fast axis, a is the length of the long side of the oriented film to be cut out, and b is the length of the short side, θ is preferably arctan(b / a)+3 degrees or less, more preferably arctan(b / a)+2 degrees or less, particularly preferably arctan(b / a)+1 degree or less, and most preferably arctan(b / a)+0 degrees or less (although in this case it may be 30 degrees or more). θ is preferably arctan(b / a)-20 degrees or more, more preferably arctan(b / a)-15 degrees or more, and particularly preferably arctan(b / a)-10 degrees. Here, arctan(b / a) is a value expressed in degrees. When cutting an oriented film diagonally from a long film, the required width of the long film is determined by the length of the diagonal of the oriented film and the cutting angle.However, when cutting an oriented film with an aspect ratio (a / b) from a long film with a width of a, the maximum angle is arctan (b / a), so cutting at around this angle (preferably below) is based on the knowledge that it is better for the preparation and economy of the long film. This is preferable when the aspect ratio (a / b) of the oriented film is in the range of 1.3 to 2.4, and more preferably in the range of 1.5 to 2.0.

[0025] (functional layer) The oriented film may be provided with a functional layer such as a hard coat layer, a low reflection layer, an anti-reflection layer, an anti-glare layer, etc. In order to improve the adhesion between the oriented film and the functional layer, the oriented film may be provided with an easy-adhesion layer.

[0026] (Easy adhesion layer) The resin used for the easy-adhesion layer is a polyester resin, a polyurethane resin, a polycarbonate resin, an acrylic resin, or the like, and a polyester resin, a polyester polyurethane resin, a polycarbonate polyurethane resin, or an acrylic resin is preferred. The easy-adhesion layer is preferably crosslinked. Examples of crosslinking agents include an isocyanate compound, a melamine compound, an epoxy resin, and an oxazoline compound.

[0027] The easy-adhesion layer can be provided by applying and drying a water-based coating material containing these resins and, if necessary, a crosslinking agent, particles, etc. to the alignment film. Examples of particles include those used for the substrates mentioned above. The easy-adhesion layer may be provided offline on a stretched long oriented film, but is preferably provided in-line during the film-forming process. When provided in-line, it may be provided either before longitudinal stretching or transverse stretching, but is preferably coated just before transverse stretching, and dried and crosslinked in a preheating, heating, and heat treatment process using a tenter. When in-line coating is performed just before longitudinal stretching using rolls, it is preferable to dry the coated film in a vertical dryer after coating and then introduce it into the stretching rolls. The coating amount of the easy-adhesion layer is 0.01 to 1.0 g / m 2 is preferable, and more preferably 0.03 to 0.5 g / m 2 is preferred.

[0028] (Functional layer) In a preferred embodiment, the oriented film is provided with a functional layer such as a hard coat layer, an anti-reflection layer, a low-reflection layer, an anti-glare layer, or an anti-static layer.

[0029] <Hard coat layer> The hard coat layer has the function of increasing the hardness of the surface to provide protection. The hard coat layer can be appropriately selected from conventionally known hard coat layers. The hard coat layer is preferably a layer made of a cured product of a curable resin composition. Curable resins that can also be used as the hard coat layer include ionizing radiation curable resins and other known curable resins, which may be appropriately selected depending on the required performance. Examples of ionizing radiation curable resins include acrylate-based, oxetane-based, and silicone-based resins. For example, acrylate-based ionizing radiation curable resins include (meth)acrylic acid ester monomers such as monofunctional (meth)acrylate monomers, bifunctional (meth)acrylate monomers, and trifunctional or higher functional (meth)acrylate monomers; (meth)acrylic acid ester oligomers or (meth)acrylic acid ester prepolymers such as urethane (meth)acrylate, epoxy (meth)acrylate, and polyester (meth)acrylate. Further examples of tri- or higher functional (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The hard coat layer can be obtained by applying a resin composition for hard coat layer containing the above-mentioned curable resin to an oriented film and curing the composition with, for example, ultraviolet light.

[0030] <Anti-reflection layer> The antireflection layer is a layer that prevents the background from being reflected by the specular reflection of external light. In the present invention, the antireflection layer can be appropriately selected from conventionally known antireflection layers. Examples of the antireflection layer include a resin layer in which high-refractive index layers and low-refractive index layers are alternately laminated and multi-layered (multi-coated) so that the outermost surface is the low-refractive index layer, and an antireflection layer in which a nanostructure such as a fine uneven shape is formed. Examples of the high refractive index layer include a resin composition for forming a high refractive index layer containing fine particles of a metal oxide such as titanium, tantalum, zirconium, or indium, and a cured product thereof. Examples of the low refractive index layer include a resin composition for forming a low refractive index layer containing a fluorine-based resin or hollow silica fine particles, and a cured product thereof. By using these antireflection layers, the reflected light at the layer interface is offset by interference, thereby suppressing surface reflection and providing an antireflection layer or the like that has a good antireflection effect.

[0031] <Low reflective layer> By providing a layer having a refractive index intermediate between that of the alignment film and that of air, such as the low refractive index layer, it is possible to reduce the reflectance.

[0032] <Anti-glare layer> The antiglare layer is a layer that scatters or diffuses extraneous light. For example, extraneous light can be diffused by roughening the light incident surface. Examples of such surface roughening treatments include a method of directly roughening the substrate surface by forming fine irregularities using a sandblasting method or an embossing method, a method of providing a roughened surface layer on the substrate surface by coating a resin binder that hardens by radiation, heat, or a combination thereof, and that contains an inorganic filler such as silica or an organic filler such as resin particles, and a method of forming a porous film with a sea-island structure on the substrate surface. Since surface strength is desired for the resin binder, curable acrylic resins and ionizing radiation-curable resins, as with the hard coat layer, are preferably used.

[0033] (Method of manufacturing oriented film) The oriented film is cut out from a long film, and first, a method for producing a long oriented film will be described. The long oriented film is preferably oriented in a uniaxial direction so as to have a retardation in the preferred range described above. Stretching can be performed by a conventional method suited to each resin. For example, when producing a film by extruding a molten film into a sheet form onto a cooling roll, examples of the method include a method in which the cooling roll is set to a speed equal to or faster than the speed of the extruded resin to orient the film, a method in which the molten and extruded unstretched film is stretched in the longitudinal direction with a group of heated rolls to orient the film, and a method in which the molten and extruded unstretched film is heated in a tenter and stretched in the width direction.

[0034] The stretching ratio in the machine direction is preferably 2.5 to 10, more preferably 3 to 8, and particularly preferably 3.3 to 7. The stretching ratio in the width direction is preferably 2.5 to 10, more preferably 3 to 8, and particularly preferably 3.3 to 7. Among these, a method in which a molten and extruded unstretched film is heated in a tenter and stretched in the width direction is preferred.

[0035] Even when oriented in the longitudinal direction, weak widthwise stretching (about 2.2 times or less) may be applied before longitudinal stretching, or weak widthwise stretching (about 1.5 times or less) may be applied after longitudinal stretching, in order to increase the mechanical strength in the direction perpendicular to the orientation direction. Similarly, even when oriented in the width direction, in order to increase the mechanical strength in the direction perpendicular to the orientation direction, weak longitudinal stretching (about 2.2 times or less) may be applied before stretching in the width direction, or weak longitudinal stretching (about 1.5 times or less) may be applied after stretching in the width direction. To further improve the orientation in the orientation direction, the film may be slightly shrunk in the machine direction during or after widthwise stretching. The shrinkage is preferably 0.7 to 0.995 times, more preferably 0.8 to 0.99 times, and particularly preferably 0.9 to 0.98 times the width at maximum stretching. The machine direction stretching and widthwise stretching may be performed using a tenter-type simultaneous biaxial stretching machine. The temperature during stretching is preferably 80 to 150°C in both the longitudinal and transverse directions for preheating and heating during stretching. After stretching, the film is preferably heat-set at a temperature higher than the heating temperature during stretching to ensure the heat resistance of the oriented film. The heat-setting temperature is preferably 150 to 250°C, and more preferably 170 to 245°C.

[0036] A long oriented film that has been strongly stretched in the machine direction has a slow axis in its machine direction. A long oriented film that has been strongly stretched in the width direction has a slow axis in a direction perpendicular to its machine direction. Here, "having a slow axis in the machine direction" does not necessarily mean that the machine direction and the slow axis of the long oriented film are completely parallel, but the absolute value of the angle between the machine direction and the slow axis is preferably 20 degrees or less, more preferably 15 degrees or less, even more preferably 10 degrees or less, particularly preferably 8 degrees or less, and most preferably 5 degrees or less. Similarly, "having a slow axis in a direction perpendicular to the machine direction" does not necessarily mean that the slow axis is completely parallel to the "direction perpendicular to the machine direction" of the long oriented film, but the absolute value of the angle between the "direction perpendicular to the machine direction" and the slow axis is preferably 20 degrees or less, more preferably 15 degrees or less, even more preferably 10 degrees or less, particularly preferably 8 degrees or less, and most preferably 5 degrees or less.

[0037] When an easy-adhesion layer is provided, as described above, an in-line coating method in which the easy-adhesion layer is applied during the film-forming process is preferred.

[0038] The stretched film has its edges cut, then wound into a roll and sent to the next process, where it is slit to the required width and length and wound again. If a functional layer is to be formed, the edges are either cut after the functional layer is formed or the film is wound as is.

[0039] Sheets of oriented film are cut from such a long wound oriented film, and at this time, the long sides of the film are cut so that they form a specific oblique angle (more than 5 degrees and less than 30 degrees) with the slow axis (stretching orientation direction) or fast axis ((perpendicular to the stretching orientation direction)) of the oriented film. In particular, it is preferable to cut the film so that the long sides of the film form a specific oblique angle (more than 5 degrees and less than 30 degrees) with the slow axis of the oriented film. Cutting methods include punching with a razor blade, round blade, or scissors-like blade, or a mold, or cutting with a laser or water jet. In addition, when an optical pressure-sensitive adhesive is provided, it is preferable to attach a long optical pressure-sensitive adhesive to a long oriented film and cut out the optical pressure-sensitive adhesive (including the separator).

[0040] (Image display device) In the present invention, an oriented film is provided on the viewing side of a display device, which prevents blackout when the display device is viewed through polarized sunglasses, and also makes it possible to produce images with natural coloring without rainbow spots.

[0041] The display devices to which the oriented film of the present invention is applied emit linearly polarized light, and specifically include liquid crystal display devices and organic EL display devices with an anti-reflection circular polarizer on their surface. An oriented film is applied to the viewing side of the polarizer on the viewing side of these devices. In VA-type and IPA-type liquid crystal display devices and organic EL display devices with a circular polarizer on their surface, the direction of the emitted polarized light is generally parallel to the short side of the image display panel. When these image display devices are used as digital signage, the short side of the image display panel is often used horizontally (with the long side vertically), and people wearing polarized sunglasses often experience a blackout phenomenon, making it difficult to see the displayed content. In such a case where an image display device is used (where the image display portion is rectangular and the image display device is installed so that the long side of the image display portion is vertical and the short side is horizontal. However, in this specification, "vertical direction" also includes a case where the image display device is tilted so that the top of the display surface is tilted back or forward from a completely vertical direction to make the display screen easier to view (in which case the short side remains horizontal). In such an inclined installation, the angle (narrow angle) between the completely vertical direction and the normal direction of the display screen is preferably 45 degrees or more), blackout and rainbow spots can be effectively suppressed by providing the oriented film of the present invention on the viewing side of the image display device, which is an effective use of the present invention. Even if the short side of the image display panel is oriented vertically, blackout and rainbow spots can be prevented when the image is viewed with the face turned sideways, for example.

[0042] The polarizing plate or circular polarizing plate on the viewing side of an image display device to be provided with the oriented film of the present invention has a polarizer protective film on the viewing side of the polarizer. The polarizer protective film may be a film with zero retardation, such as a TAC film or an acrylic resin film, or a film with high retardation, such as polyethylene terephthalate, without any particular limitation. The retardation of the high retardation film is preferably 3,000 to 30,000 nm, more preferably 5,000 to 10,000 nm. When a high retardation film is used as the polarizer protective film, the angle between the transmission axis of the polarizer and the slow axis or fast axis of the polarizer protective film is preferably 5 degrees or less, more preferably 3 degrees or less.

[0043] The image display device to be provided with the alignment film of the present invention is preferably a large, stationary image display device, and specifically, the diagonal of the image display panel is preferably 32 inches or more, more preferably 42 inches or more, more preferably 50 inches or more, and particularly 65 inches or more. There is no particular upper limit as long as it is actually commercially available. It can also be suitably applied to an image display device in which multiple image display panels are integrated.

[0044] Furthermore, the image display device to which the oriented film of the present invention is to be applied is preferably not for displaying stereoscopic (3D) images but for displaying ordinary flat images. In 3D applications, a patterned retardation plate is sometimes provided on the viewing side of the polarizing plate, but this imparts a retardation effect, which can make the 3D display difficult to view.

[0045] (Installation of alignment film) The method of providing the alignment film on the display device is not particularly limited, and may include a method of directly attaching the alignment film to the image display panel of the display device, or a method of attaching the alignment film to the outside or inside of the faceplate on the viewing side of the display device. Furthermore, in digital signage, the image display device itself may be housed in a separate housing with a transparent protective cover or window to protect it from collisions with various objects, or may be installed inside a window built into a pillar or wall. In such cases, the film may be attached to the outside or inside of the protective cover or window. Note that if the front panel, protective cover, or window is made of a non-birefringent material such as glass, it can be attached to either the inside or outside, but if it is made of a birefringent material such as a polycarbonate plate, it is preferable to attach it to the inside. If it is attached to the outside, coloring or iridescence due to the birefringent material may occur. Note that although the above description refers to attachment, it is not necessary to attach the entire surface; only the edges may be secured with tape or the like. Furthermore, if there is a mechanism for securing it, such as by pinning or clamping, it is not necessarily necessary to attach it.

[0046] When attaching the film, it is preferable to first laminate an optical substrate-free pressure-sensitive adhesive sheet on the alignment film, and then peel off the release film before attaching the film to the object.

[0047] The angle between the absorption axis of the polarizing plate on the viewing side of the image display panel (the direction perpendicular to the electric field vibration plane of the linearly polarized light emitted from the image display panel) and the slow axis or fast axis of the alignment film is preferably greater than 5 degrees, more preferably greater than 7 degrees, even more preferably greater than 10 degrees, particularly preferably greater than 12 degrees, and most preferably greater than 15 degrees. If the angle is less than the above, the image may appear dark and difficult to see when viewed through polarized sunglasses, depending on the angle. The angle is preferably less than 30 degrees, more preferably less than 28 degrees, even more preferably less than 25 degrees, particularly preferably less than 23 degrees, and most preferably less than 20 degrees. If the angle exceeds the above, a wide roll film is required for cutting out the oriented film, which may result in a roll film of the required width not being available or a lot of cutting waste.

[0048] The oriented film of the present invention is rectangular to fit the image display area, and the polarizing plate disposed on the viewing side is also rectangular. The absorption axis of the polarizing plate disposed on the viewing side is preferably parallel to its long side (parallel is desirable, but some deviation is permissible). By doing so, by laminating the rectangular oriented film of the present invention and the rectangular polarizing plate so that their long sides and short sides overlap, it becomes easy to set the angle between the absorption axis of the polarizing plate and the slow axis or fast axis of the oriented film within a predetermined range.

[0049] In addition, from the viewpoint of minimizing troubles during application, it is preferable that the angle between the absorption axis of the polarizing plate on the viewer side of the image display panel and the slow axis or fast axis of the alignment film is the angle between the absorption axis of the polarizing plate on the viewer side of the image display panel and the slow axis of the alignment film. On the other hand, from an economic standpoint, it is preferable that the angle between the absorption axis of the polarizing plate on the viewer side of the image display panel and the slow axis or fast axis of the alignment film is the angle between the absorption axis of the polarizing plate on the viewer side of the image display panel and the fast axis of the alignment film. [Example]

[0050] (1) Retardation (Re) Retardation is a parameter defined by the product (ΔNxy × d) of the refractive index anisotropy of two perpendicular axes on a film (ΔNxy = |nx - ny|) and the film thickness d (nm), and is a measure of optical isotropy and anisotropy. The biaxial refractive index anisotropy (ΔNxy) was determined using the following method. The orientation axis direction of the film was determined using a molecular orientation meter (MOA-6004, manufactured by Oji Scientific Instruments Co., Ltd.), and a 4 cm × 2 cm rectangle was cut out with the orientation axis direction as the long side to serve as a measurement sample. The refractive indexes of the two perpendicular axes (nx, ny) and the refractive index in the thickness direction (nz) of this sample were measured using an Abbe refractometer (NAR-4T, manufactured by Atago Co., Ltd., measurement wavelength 589 nm), and the absolute value of the difference between the biaxial refractive indices (|nx - ny|) was taken as the refractive index anisotropy (ΔNxy). The film thickness d (nm) was measured using an electric micrometer (Militron 1245D, manufactured by Fine Leaf Co., Ltd.) and converted into units of nm. The retardation (Re) was calculated from the product (ΔNxy × d) of the refractive index anisotropy (ΔNxy) and the film thickness d (nm).

[0051] (2) Nz coefficient The value obtained by |ny-nz| / |ny-nx| was taken as the Nz coefficient, where the values ​​of ny and nx were selected so that ny>nx.

[0052] (3) Degree of plane orientation (ΔP) The value obtained by (nx+ny) / 2-nz was taken as the degree of planar orientation (ΔP).

[0053] (4) Thickness retardation (Rth) Thickness retardation is a parameter that indicates the average retardation obtained by multiplying the two birefringences ΔNxz (=|nx-nz|) and ΔNyz (=|ny-nz|) when viewed from the cross section of the film in the thickness direction by the film thickness d. nx, ny, nz and the film thickness d (nm) were determined in the same way as in the retardation measurement, and the thickness retardation (Rth) was calculated by averaging (ΔNxz×d) and (ΔNyz×d).

[0054] (5) Film orientation axis The orientation of the main axis of the film was determined using a molecular orientation meter (MOA-6004 molecular orientation meter manufactured by Oji Scientific Instruments Co., Ltd.), with the main orientation axis being the slow axis direction and the direction perpendicular thereto being the fast axis direction.

[0055] (6) Breaking strength and breaking elongation Using a razor, 12.7 mm wide and 200 mm long samples were cut from the film along the fast and slow axes. The cut samples were left for 12 hours in an atmosphere of 23°C and 35% RH, and then measured at 23°C and 35% RH with a chuck distance of 100 mm and a pulling speed of 200 m / min. The breaking strength and breaking elongation were calculated from the average of two measurements. The measuring device used was an ORIENTEC RTC-1225A.

[0056] (Production of polyester resin for oriented films) (Production Example 1 - Polyester X) The esterification reactor was heated to 200°C, and 86.4 parts by mass of terephthalic acid and 64.6 parts by mass of ethylene glycol were charged. While stirring, 0.017 parts by mass of antimony trioxide, 0.064 parts by mass of magnesium acetate tetrahydrate, and 0.16 parts by mass of triethylamine were charged as catalysts. The temperature was then increased under pressure, and a pressurized esterification reaction was carried out at a gauge pressure of 0.34 MPa and 240°C. The esterification reactor was then returned to normal pressure, and 0.014 parts by mass of phosphoric acid was added. The temperature was then increased to 260°C over 15 minutes, and 0.012 parts by mass of trimethyl phosphate was added. After 15 minutes, the mixture was dispersed using a high-pressure disperser. After 15 minutes, the resulting esterification reaction product was transferred to a polycondensation reactor, where a polycondensation reaction was carried out under reduced pressure at 280°C.

[0057] After the polycondensation reaction was completed, the resin was filtered through a Naslon filter with a 95% cutoff diameter of 5 μm, extruded from a nozzle in the form of a strand, cooled and solidified using cooling water that had been previously filtered (pore diameter: 1 μm or less), and cut into pellets. The intrinsic viscosity of the resulting polyethylene terephthalate resin (X) was 0.62 dL / g, and it contained substantially no inert particles or internally precipitated particles (hereinafter abbreviated as PET (X)).

[0058] (Production Example 2 - Polyester Y) 10 parts by mass of dried ultraviolet absorber (2,2'-(1,4-phenylene)bis(4H-3,1-benzoxazinon-4-one) and 90 parts by mass of particle-free PET (X) (intrinsic viscosity 0.62 dL / g) were mixed and the mixture was kneaded using an extruder to obtain ultraviolet absorber-containing polyethylene terephthalate resin (Y) (hereinafter abbreviated as PET (Y)).

[0059] (Polymerization of urethane resin used in easy-adhesion layer) A urethane resin containing an aliphatic polycarbonate polyol was prepared as follows. A four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet, silica gel drying tube, and thermometer was charged with 43.75 parts by weight of 4,4-diphenylmethane diisocyanate, 12.85 parts by weight of dimethylolbutanoic acid, 153.41 parts by weight of polyhexamethylene carbonate diol with a number average molecular weight of 2000, 0.03 parts by weight of dibutyltin dilaurate, and 84.00 parts by weight of acetone as a solvent. The mixture was stirred at 75°C for 3 hours under a nitrogen atmosphere, and the reaction solution was confirmed to have reached the required amine equivalent. The reaction solution was then cooled to 40°C, and 8.77 parts by weight of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. Subsequently, acetone and a portion of the water were removed under reduced pressure to prepare a water-soluble polyurethane resin with a solids content of 35%. The glass transition temperature of the resulting polyurethane resin, composed of an aliphatic polycarbonate polyol as a constituent component, was -30°C.

[0060] (Polymerization of oxazoline-based crosslinking agent used in the easy-adhesion layer) A flask equipped with a thermometer, nitrogen gas inlet tube, reflux condenser, dropping funnel, and stirrer was charged with a mixture of 58 parts by mass of ion-exchanged water and 58 parts by mass of isopropanol as an aqueous medium, and 4 parts by mass of a polymerization initiator (2,2'-azobis(2-amidinopropane) dihydrochloride). The dropping funnel was charged with a mixture of 16 parts by mass of 2-isopropenyl-2-oxazoline as a polymerizable unsaturated monomer having an oxazoline group, 32 parts by mass of methoxypolyethylene glycol acrylate (average number of moles of ethylene glycol added: 9 moles, Shin-Nakamura Chemical Co., Ltd.), and 32 parts by mass of methyl methacrylate. The mixture was added dropwise over 1 hour at 70°C under a nitrogen atmosphere. After the dropwise addition, the reaction solution was stirred for 9 hours and then cooled to obtain a water-soluble resin having an oxazoline group with a solids concentration of 40% by mass.

[0061] (Preparation of coating solution for easy adhesion layer) The following coating materials were mixed to prepare a coating solution for forming an easy-adhesion layer. Water 55.62% by mass Isopropanol 30.00% by mass Polyurethane resin water dispersion 11.29% by mass Oxazoline crosslinker aqueous solution 2.26% by mass Particles 0.71% by mass (Silica sol with an average particle size of 40 nm, solid content concentration of 40% by mass) Particles 0.07% by mass (Silica sol with an average particle size of 450 nm, solid content of 40% by mass) Surfactant 0.05% by mass (Silicone-based, solid content 100% by mass) Solid content concentration 10% by mass)

[0062] (Production of long oriented film A) As raw materials for the film intermediate layer, 90 parts by weight of particle-free PET(X) resin pellets and 10 parts by weight of PET(Y) resin pellets containing a UV absorber were dried under reduced pressure (1 Torr) at 135°C for 6 hours and then fed into Extruder 2 (for intermediate layer II). PET(X) was dried by conventional methods and fed into Extruder 1 (for outer layers I and III), respectively, and melted at 285°C. These two polymers were each filtered through a sintered stainless steel filter medium (nominal filtration accuracy: 95% cutoff for 10 μm particles) in a two-type, three-layer merging block. The resulting mixture was extruded into a sheet from a die and then wrapped around a casting drum at a surface temperature of 30°C using an electrostatic casting method. The resulting unstretched film was then cooled and solidified. The output rate of each extruder was adjusted so that the thickness ratio of layers I, II, and III was 10:80:10.

[0063] Next, a coating solution for an easy-adhesion layer was applied to one side of this unstretched PET film by the reverse roll method so that the coating amount after drying was 0.12 g / m 2 After applying the coating so that the coating was uniform, the coating was introduced into a dryer and dried at 80°C for 20 seconds.

[0064] The unstretched film with this coating layer formed was introduced into a tenter stretching machine, and while the edges of the film were held with clips, it was introduced into a hot air zone at a temperature of 135°C and stretched 3.9 times in the width direction. Next, while maintaining the width stretched in the width direction, it was treated at a temperature of 225°C for 30 seconds, and then cooled to 130°C. Both edges of the film were cut and stretched at 0.5 kg / mm 2 The edges were cut off under a tension of 0.05 mm and then wound up to obtain a uniaxially oriented PET film with a film thickness of 80 μm. The central part of the obtained film was slit into a width of 150 cm to obtain a slit roll with a length of approximately 300 m (long oriented film A).

[0065] (Formation of antiglare layer) A coating solution for forming an antiglare layer having the following composition was applied to the surface of the easy-adhesion layer provided on the long oriented film A using a bar coater, and the solution was dried at 70°C for 1 minute to remove the solvent. Next, a high-pressure mercury lamp was used to irradiate the film with the antiglare layer at 300 mJ / cm. 2The film was irradiated with ultraviolet light of 1000 W at a width of 140 cm, and the widthwise edge was slit and taken up to obtain a roll of oriented film A having an antiglare layer of 5 μm thickness, which was 140 cm wide and 250 m long. (Coating liquid for forming anti-glare layer) Toluene 34 parts by weight Pentaerythritol triacrylate 50 parts by weight Silica (average particle size 1 μm) 12 parts by weight Silicone (leveling agent) 1 part by weight Photopolymerization initiator 1 part by weight (Irgacure 184 manufactured by Ciba Specialty Chemicals)

[0066] (Lamination of optical adhesive layer) An optical adhesive layer was laminated on the roll of oriented film A having the antiglare layer. The optical adhesive film (heavy release film / acrylic transparent adhesive layer / light release film) in roll form having the same width as the film roll was laminated on the side opposite the antiglare layer of the roll of oriented film A having the antiglare layer while peeling off the light release film, and the laminate was pressed between rubber rolls.

[0067] Oriented films B and C were prepared in the same manner as Oriented film A, except for changing the film thickness, and Oriented films B and C were prepared by laminating an antiglare layer and an optical adhesive layer. The properties of the oriented films are shown in Table 1.

[0068] [Table 1]

[0069] (Examples 1 to 16, Comparative Examples 1 to 5) (Cut) From the roll of oriented film A laminated with the optical adhesive layer, sheets of oriented film A with long sides of 1210 mm and short sides of 680 mm were cut at each angle shown in Table 2. A carbon dioxide laser was used for cutting.

[0070] The LCD panel of a commercially available LCD display device for digital signage (Panasonic TH-55SF2J 55-inch, IPS type) was removed, and while peeling off the heavy release film of the above-mentioned sheet-fed alignment film A from the viewing side surface of the LCD panel (above the polarizer), it was first aligned in the short side direction and then laminated in the long side direction. To prevent air bubbles from entering, the lamination was carried out by pulling in the long side direction while pressing down with a hand roll. In addition, in anticipation of air bubbles entering and the need to re-apply, approximately 5 cm was peeled off at the 1 / 3 and 2 / 3 points of lamination and re-applied.

[0071] (Laminating workability) The above-mentioned lamination process was carried out on 10 sheets of oriented film A cut out under the same conditions, and the presence or absence of breakage during the re-lamination process was evaluated. ○: No breakage occurred in any of the 10 sheets. △ to ○: One sheet broke. △: 2 to 3 sheets were broken ×: More than 3 sheets were broken.

[0072] (warp) Assuming it was a surface protection plate for outdoor digital signage, a sheet of orientation film was attached to a polycarbonate plate (2mm thick) of the same size as the orientation film, and the attached sheet was hung with the short side facing up at 25°C for 24 hours, after which the presence or absence of warping on the display screen surface was checked. This was confirmed by observing the reflected image of a straight fluorescent lamp from an angle on the polycarbonate plate side. ○: No warping was observed. △~◯: Slight warping was observed. △: Warping was observed.

[0073] Furthermore, the liquid crystal panel to which the above-mentioned alignment film was attached was also left for 24 hours at 25°C, after which the presence or absence of warping on the display screen surface was checked. A thin layer of ethylene glycol was applied to the surface of the antiglare layer to make the reflection of fluorescent lights more visible.

[0074] (Economics) A 55-inch display (aspect ratio 16:9) has a long side of 1210 mm and a short side of approximately 680 mm, so as a long high-retardation PET film (stretched widthwise) for a polarizer protective film for a 55-inch VA or IPS LCD cell, a film roll with a width of 1209 mm is generally required for the light source side polarizer protective film and 680 mm for the viewer side polarizer protective film. If the wider film roll prepared in this way can be used to perform the diagonal cutting described above, it is marked with an O, and if a separate wider film roll needs to be prepared, it is marked with an X. In addition, when the long side (a) is 1210 mm and the short side (b) is 680 mm, the arctan (b / a) is 29.3 degrees. Therefore, if the angle between the long side of the oriented film and the fast axis is 29 degrees or less, the film can be economically cut out from a film roll provided as a polarizer protective film for the light source side polarizer of a 55-inch display.

[0075] (Blackout) The images were observed from the front while wearing polarized sunglasses. The display device was placed both vertically (with the long side vertical and the short side horizontal) and horizontally (with the long side horizontal and the short side vertical). The images displayed were photos of food samples, and participants were evaluated based on whether they could recognize what kind of food they were. ○: The image was recognized △: Although the image was dark, it was recognizable. ×: The image was not visible and could not be recognized.

[0076] (rainbow spot) Evaluated in the same way as blackout, but also observed from an angle ○: No rainbow spots were observed △: Weak rainbow spots were observed ×: Iridescence was observed

[0077] (Examples 17 to 18) Sheets of oriented films B and C were cut out so that the angle between the long side and the slow axis was 19 degrees, and similar evaluations were carried out. These results are shown in Table 2.

[0078] [Table 2] [Industrial Applicability]

[0079] According to the present invention, when cutting out sheets of depolarizing film from a long film, waste can be reduced and productivity can be increased, blackouts and rainbow spots do not occur even when viewing images through polarized sunglasses, and the film can be attached to a general-purpose image display device as a digital signage after the fact, making it economically excellent, as well as an image display device using the film and a method for cutting out the film.

Claims

1. An image display device having an alignment film on the viewing side of a viewing-side polarizing plate, The oriented film has an in-plane retardation of 4500 to 30000 nm, and a degree of planar orientation expressed by (nx + ny) / 2 - nz (where ny and nx are biaxial refractive indexes in the orientation axis direction and the direction perpendicular thereto, and nz is a refractive index in the thickness direction. nx, ny, and nz are refractive indexes at a measurement wavelength of 589 nm) of 0.08 to 0.13, the ratio of in-plane retardation to thickness retardation of the oriented film (Re / Rth) is 0.828 or more and 1.2 or less; The oriented film has a breaking elongation in the slow axis direction of 30% or more and 150% or less, and a breaking elongation in the fast axis direction of 2% or more and 30% or less, An image display device, wherein the angle formed between the absorption axis of the polarizing plate and the slow axis or fast axis of the alignment film is more than 5 degrees and less than 30 degrees.

2. 2. The image display device according to claim 1, wherein the image display portion is rectangular, and the image display device is installed so that the long side of the image display portion is in the vertical direction.

3. A method for cutting out a rectangular sheet of oriented film for converting linearly polarized light emitted from an image display device into elliptically polarized light, the method comprising: When rectangular sheets of oriented film are cut out from a long oriented film having a slow axis in the longitudinal direction or in a direction perpendicular to the longitudinal direction, the film is cut out so that the angle between the long side of the rectangle and the slow axis is more than 5 degrees and less than 30 degrees; The oriented film has an in-plane retardation of 4500 to 30000 nm, and a degree of planar orientation expressed by (nx + ny) / 2 - nz (where ny and nx are biaxial refractive indexes in the orientation axis direction and the direction perpendicular thereto, and nz is a refractive index in the thickness direction. nx, ny, and nz are refractive indexes at a measurement wavelength of 589 nm) of 0.08 to 0.13, the ratio of in-plane retardation to thickness retardation of the oriented film (Re / Rth) is 0.828 or more and 1.2 or less; The oriented film has a breaking elongation in the slow axis direction of 30% or more and 150% or less, and a breaking elongation in the fast axis direction of 2% or more and 30% or less, How to cut rectangular sheets of oriented film.

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