Manufacturing method for polarizing plates with irregular shapes

Abstract

To provide an easy and inexpensive manufacturing method of a polarizing plate having an irregular shape and suppressing a crack.SOLUTION: A manufacturing method of a polarizing plate having an irregular shape includes: forming an irregular shape on a polarizing plate by laser irradiation; and cutting the polarizing plate with the irregular shape formed, into a sheet-like shape by laser irradiation. In one embodiment, the manufacturing method includes cutting the polarizing plate with the irregular shape formed, into a sheet-like shape by linear laser irradiation. In one embodiment, the irregular shape is shaped as a recess when viewed in a planar view.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing polarizing plates with irregular shapes. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), have become rapidly widespread. Due to the image formation method of image display devices, at least one component of the device contains a polarizing plate. Recently, it has become desirable to process polarizing plates into shapes other than rectangles (irregular shapes: for example, the formation of notches and / or through holes). However, there is a problem that cracks are prone to occur in the irregularly shaped parts of polarizing plates. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-159911 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention was made to solve the above-mentioned conventional problems, and its main objective is to provide a simple and inexpensive method for manufacturing polarizing plates that have irregular shapes and suppress cracking. [Means for solving the problem]

[0005] A method for manufacturing a polarizing plate having an irregular shape according to an embodiment of the present invention includes: forming an irregular shape on a polarizing plate by laser irradiation; and cutting the polarizing plate having the irregular shape formed on it into a single sheet by laser irradiation. In one embodiment, the manufacturing method includes cutting the polarizing plate having the above-mentioned irregular shape into a single sheet by linear laser irradiation. In one embodiment, the irregular shape is a recess when viewed from above. In one embodiment, the irregular shape is a U-shaped notch or a V-shaped notch. In one embodiment, the laser irradiation includes an overrun, the amount of which is 0.5 mm to 50 mm. In one embodiment, the formation of the irregular shape and the cutting of the single-leaf shape are performed with an interval of 1 second or more. In one embodiment, the polarizing plate further comprises a phase difference layer. In one embodiment, the phase difference layer comprises a cyclic olefin resin and exhibits refractive index characteristics nx>nz>ny, with an Nz coefficient of 0.3~0.7, and an in-plane phase difference Re(550) of 250nm~350nm. [Effects of the Invention]

[0006] According to an embodiment of the present invention, in a method for manufacturing a polarizing plate having an irregular shape, after forming an irregular shape on the polarizing plate by laser irradiation, the polarizing plate with the irregular shape formed on it is cut into single sheets by laser irradiation, thereby enabling the simple and inexpensive manufacture of a polarizing plate that has an irregular shape but in which cracks are suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view illustrating an example of a polarizing plate that can be used in the manufacturing method according to an embodiment of the present invention. [Figure 2] This is a schematic cross-sectional view illustrating another example of a polarizing plate that may be used in the manufacturing method according to an embodiment of the present invention. [Figure 3] This is a schematic plan view illustrating an example of a deformed or deformed portion in a polarizing plate obtained by the manufacturing method according to an embodiment of the present invention. [Figure 4] This is a schematic plan view illustrating a modified example of a deformed or deformed portion in a polarizing plate obtained by the manufacturing method according to an embodiment of the present invention. [Figure 5]Figures 5(a) and 5(b) are schematic plan views illustrating the details of the shaping process and sheet-like cutting in the manufacturing method according to an embodiment of the present invention, respectively. [Figure 6] This is a conceptual diagram illustrating the mechanism of the effects obtained by embodiments of the present invention. [Modes for carrying out the invention]

[0008] Specific embodiments of the present invention will be described below with reference to the drawings, but the present invention is not limited to these embodiments. Note that the drawings are schematic representations for clarity, and the ratios of lengths, widths, thicknesses, angles, etc., shown in the drawings may differ from actual dimensions.

[0009] (Definitions of terms and symbols) The definitions of terms and symbols used in this specification are as follows: (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the refractive index is maximum in the plane (i.e., the slow phase axis direction), "ny" is the refractive index in the direction perpendicular to the slow phase axis in the plane (i.e., the fast phase axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated using the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (3) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) can be calculated using the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (4) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Thus, for example, "45°" means ±45°. (6) Substantially orthogonal or substantially parallel In this specification, the expressions "substantially orthogonal" and "substantially perpendicular" include cases where the angle formed by two directions is 90° ± 7°, preferably 90° ± 5°, and more preferably 90° ± 3°. The expressions "substantially parallel" and "substantially parallel to each other" include cases where the angle formed by two directions is 0° ± 7°, preferably 0° ± 5°, and more preferably 0° ± 3°. Furthermore, when simply referring to "orthogonal" or "parallel" in this specification, it is assumed that it may include a substantially orthogonal or substantially parallel state.

[0010] A method for manufacturing a polarizing plate having a special shape according to an embodiment of the present invention includes forming a special shape on the polarizing plate by laser irradiation; and cutting the polarizing plate having the special shape into sheet form by laser irradiation. For convenience, first, the specific configuration of the polarizing plate that can be used in the manufacturing method according to the embodiment of the present invention and the polarizing plate obtained by the manufacturing method will be described, and then the method for manufacturing a polarizing plate having a special shape according to the embodiment of the present invention will be described.

[0011] A. Polarizing plate Figure 1 is a schematic cross-sectional view illustrating an example of a polarizing plate that may be used in a manufacturing method according to an embodiment of the present invention. The polarizing plate 10 in the illustrated example has a polarizer 11, a first protective layer 12 provided on one side of the polarizer (the viewing side in the illustrated example), and a second protective layer 13 provided on the other side of the polarizer (the side opposite to the viewing side in the illustrated example). Depending on the purpose and the configuration of the polarizing plate, either the first protective layer 12 or the second protective layer 13 may be omitted. The polarizing plate may also be a polarizing plate with a phase difference layer, as needed, as shown in Figure 2. The polarizing plate with a phase difference layer 100 in the illustrated example further has a phase difference layer 20 on the side of the polarizing plate 10 opposite to the viewing side. The phase difference layer 20 is bonded to the polarizing plate 10 (the second protective layer 13 in the illustrated example) via any suitable adhesive layer (e.g., adhesive layer, tack layer: not shown). The optical properties (e.g., refractive index properties, in-plane phase difference, Nz coefficient, photoelastic coefficient), thickness, and position of the phase difference layer 20 can be appropriately set according to the purpose. Typically, the phase difference layer 20 exhibits a refractive index property of nx>nz>ny. The effects of the embodiments of the present invention can be particularly pronounced in a polarizing plate with such a phase difference layer. In this specification, polarizing plates and polarizing plates with a phase difference layer are collectively referred to as polarizing plates.

[0012] A polarizing plate obtained by the manufacturing method according to an embodiment of the present invention has an irregular shape. In this specification, "having an irregular shape" means that the plan view shape of the polarizing plate is a shape other than a rectangle. The irregular shape is typically an irregularly shaped processed portion. Therefore, a "polarizing plate having an irregular shape" includes not only cases where the entire polarizing plate (i.e., the outer edge that defines the plan view shape of the film) is not rectangular, but also cases where an irregularly shaped processed portion is formed in a portion spaced inward from the outer edge of a rectangular polarizing plate. Examples of irregular shapes (irregularly shaped processed portions) include chamfers at corners, through holes, and machined portions that become recesses when viewed from above, as shown in Figures 3 and 4. Typical examples of recesses include shapes approximating a boat shape, a bathtub shape, V-shaped notches, and U-shaped notches. Needless to say, the shape of the irregular shape (irregularly shaped processed portion) is not limited to the illustrated examples. For example, the shape of the through-hole can be any suitable shape (e.g., ellipse, triangle, square, pentagon, hexagon, octagon) depending on the purpose, in addition to the approximately circular shape shown in the illustrated example. Furthermore, the through-hole can be provided at any suitable position depending on the purpose. As shown in Figure 4, the through-hole may be provided in the approximate center of the longitudinal end of the rectangular polarizing plate, at a predetermined position on the longitudinal end, or at a corner of the polarizing plate; although not shown, it may also be provided at the short end of the rectangular polarizing plate. Moreover, three or more through-holes may be formed. In addition, the shapes shown in the illustrated example may be appropriately combined depending on the purpose. For example, through-holes may be formed at any position on the irregularly shaped polarizing plate in Figure 3; or V-shaped notches and / or U-shaped notches may be formed at any suitable position on the outer edge of the irregularly shaped polarizing plate in Figure 3. Such irregularly shaped polarizing plates can be suitably used in image display devices such as automobile instrument panels, smartphones, tablet PCs, or smartwatches.

[0013] The polarizer may further include other optical functional layers. The type, characteristics, number, combination, and placement of the optical functional layers that can be provided on the polarizer can be appropriately set according to the purpose. For example, the polarizer may further have a conductive layer or an isotropic substrate with a conductive layer (neither of which are shown). Typically, the conductive layer or the isotropic substrate with a conductive layer is provided on the side opposite to the viewing side. When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizer can be applied to a so-called inner touch panel type input display device in which a touch sensor is incorporated between the image display panel and the polarizer. Also, for example, the polarizer may further include another phase difference layer. The optical properties (e.g., refractive index characteristics, in-plane phase difference, Nz coefficient, photoelastic coefficient), thickness, placement, etc. of the other phase difference layer can be appropriately set according to the purpose.

[0014] In practical terms, the polarizing plate has an adhesive layer (not shown) as the outermost layer opposite the viewing side, allowing it to be attached to an image display panel. Furthermore, a separator (not shown) is temporarily attached to the surface of the adhesive layer in a removable manner. By temporarily attaching the separator, the adhesive layer is protected and roll formation of the polarizing plate is possible. In addition, in practical terms, a surface protection film is temporarily attached to the viewing side of the polarizing plate to prevent scratches and other damage during transport, handling, and / or attachment to the image display panel. The surface protection film typically consists of a base film and an adhesive layer, and is temporarily attached to the viewing side surface of the polarizing plate via the adhesive layer.

[0015] The following describes the polarizer, protective layer, and phase difference layer, which are the components of a polarizing plate.

[0016] A-1. Polarizer A polarizer is typically composed of a resin film containing a dichroic substance (typically iodine). Any suitable resin film that can be used as a polarizer can be employed. Typically, the resin film is a polyvinyl alcohol-based resin (hereinafter referred to as "PVA-based resin") film. The resin film may be a single layer or a laminate of two or more layers.

[0017] A specific example of a polarizer composed of a single layer of resin film is a PVA-based resin film that has been dyed with iodine and stretched (typically uniaxially stretched). The iodine dyeing is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio for uniaxial stretching is preferably 3 to 7 times. Stretching may be performed after the dyeing treatment, or during the dyeing process. Alternatively, dyeing may be performed after stretching. If necessary, the PVA-based resin film may be subjected to swelling, crosslinking, washing, drying, etc. For example, immersing the PVA-based resin film in water and washing it before dyeing can not only clean dirt and anti-blocking agents from the surface of the PVA-based film, but also swell the PVA-based resin film to prevent uneven dyeing.

[0018] Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate, drying it to form a PVA-based resin layer on the resin substrate, and obtaining a laminate of the resin substrate and the PVA-based resin layer; or by stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, stretching may, if necessary, further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in this embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it shrinks by 2% or more in the width direction by heating while being transported in the longitudinal direction. Typically, the manufacturing method of this embodiment includes applying an air-assisted stretching treatment, a dyeing treatment, a water-based stretching treatment, and a drying shrinkage treatment to the laminate in this order. By introducing auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is coated on a thermoplastic resin, making it possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as a decrease in the orientation of PVA and dissolution when immersed in water in the subsequent dyeing and stretching processes, making it possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain halides. This makes it possible to improve the optical properties of polarizers obtained through processing steps that involve immersing the laminate in liquid, such as dyeing and water-based stretching treatments. Furthermore, by shrinking the laminate in the width direction through the drying shrinkage treatment, the optical properties can be improved.The resulting resin substrate / polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the resin substrate / polarizer laminate, and any appropriate protective layer may be laminated onto the peeled surface according to the purpose. Details of such polarizer manufacturing methods are described, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0019] The thickness of the polarizer can be, for example, 1 μm to 30 μm, or for example, 3 μm to 20 μm.

[0020] The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The transmittance of the polarizer is preferably 41.5% to 46.0%, more preferably 43.0% to 46.0%, and even more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0021] A-2.Protective layer The first protective layer 12 and the second protective layer 13 are each formed from any suitable film that can be used as a protective layer for the polarizer. Specific examples of materials that make up the main component of the film include cellulosic resins such as triacetylcellulose (TAC), and transparent resins such as polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, polynorbornene, polyolefin, (meth)acrylic, and acetate. Thermosetting resins or UV-curing resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone can also be used. In addition, glassy polymers such as siloxane polymers can also be used. Polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As materials for this film, for example, a resin composition containing a thermoplastic resin having substituted or unsubstituted imide groups in its side chains, and a thermoplastic resin having substituted or unsubstituted phenyl groups and nitrile groups in its side chains can be used. Examples include a resin composition having an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extruded product of the above resin composition. Preferably, a (meth)acrylic resin can be used.

[0022] The (meth)acrylic resin has a glass transition temperature (Tg) of preferably 115°C or higher, more preferably 120°C or higher, even more preferably 125°C or higher, and particularly preferably 130°C or higher. This is because it can have excellent durability. The upper limit of the Tg of the above (meth)acrylic resin is not particularly limited, but from the viewpoint of moldability and the like, it is preferably 170°C or lower.

[0023] As a (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure is particularly preferred in that it has high heat resistance, high transparency, and high mechanical strength. Examples of (meth)acrylic resins having a lactone ring structure include those described in Japanese Patent Publication No. 2000-230016, Japanese Patent Publication No. 2001-151814, Japanese Patent Publication No. 2002-120326, Japanese Patent Publication No. 2002-254544, Japanese Patent Publication No. 2005-146084, and others.

[0024] The polarizing plate is typically placed on the viewing side of the image display device, and the first protective layer 12 is also placed on that viewing side. Therefore, the first protective layer 12 may be subjected to surface treatments such as hard coating, anti-reflective coating, anti-sticking coating, or anti-glare coating, as needed.

[0025] The thickness of the first protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and even more preferably 30 μm to 60 μm. If the first protective layer is surface-treated to form a surface-treated layer, the thickness of the first protective layer includes the thickness of the surface-treated layer.

[0026] The second protective layer 13 is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0 nm to 10 nm and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm. The thickness of the second protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 60 μm, and even more preferably 15 μm to 45 μm.

[0027] A-3. Retardation layer Typically, the phase difference layer exhibits a refractive index characteristic of nx>nz>ny as described above (hereinafter, such a phase difference layer or phase difference film may be referred to as a Z film). Because the phase difference layer has such refractive index characteristics, the oblique hue of an image display device to which a polarizing plate with a phase difference layer is applied can be significantly improved. Furthermore, since this oblique hue improvement can be achieved without separately providing the phase difference layer and the layer that performs optical compensation in the oblique direction, it can contribute to the thinning of the polarizing plate with a phase difference layer (and consequently, the image display device). In addition, while such a phase difference layer (phase difference film) is prone to cracking, according to the embodiment of the present invention, cracking of the deformed portion can be significantly suppressed even when such a phase difference layer is deformed.

[0028] The Nz coefficient of the phase difference layer is preferably 0.3 to 0.7, more preferably 0.4 to 0.6, and even more preferably 0.45 to 0.55. When the Nz coefficient is within this range, the hue in the diagonal direction can be further improved.

[0029] The in-plane phase difference Re(550) of the phase difference layer is preferably 250nm to 350nm, more preferably 260nm to 330nm, and even more preferably 270nm to 290nm. When the in-plane phase difference Re(550) of the phase difference layer is within this range, the migration distance on the Poincaré sphere is short, resulting in excellent hue and brightness characteristics, and also reducing the color shift of the image display panel and the shift due to the phase difference component of the TFT.

[0030] The phase difference layer may exhibit inverse dispersion wavelength characteristics where the phase difference value increases with the wavelength of the measured light, positive wavelength dispersion characteristics where the phase difference value decreases with the wavelength of the measured light, or flat wavelength dispersion characteristics where the phase difference value hardly changes with the wavelength of the measured light. Typically, the phase difference layer exhibits flat wavelength dispersion characteristics.

[0031] The phase difference layer preferably has an absolute value of 15 × 10⁻⁶ of its photoelastic coefficient. -12 m 2 / N or less, more preferably 10 × 10 -12 m 2 It is less than or equal to / N. The lower limit of the absolute value of the photoelastic coefficient is, for example, 1.0 × 10⁻⁶. -12 m 2 It can be / N. If the absolute value of the photoelastic coefficient of the phase difference layer is within this range, display unevenness in the image display device can be suppressed effectively.

[0032] The phase difference layer is typically a phase difference film formed from any suitable resin capable of achieving the above-mentioned properties. Examples of resins that form this phase difference film include cyclic olefin resins, polyarylates, polyamides, polyimides, polyesters, polyaryletherketones, polyamideimides, polyesterimides, polyvinyl alcohols, polyfumarates, polyethersulfones, polysulfones, polycarbonate resins, cellulose resins, and polyurethanes. These resins may be used individually or in combination. Cyclic olefin resins are preferred. Norbornene resins are a typical example of cyclic olefin resins.

[0033] The norbornene-based resin described above is a resin polymerized using norbornene-based monomers as polymerization units. Examples of the norbornene-based monomers include norbornene and its alkyl and / or alkylidene-substituted derivatives, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., and their halogen- and other polar group-substituted derivatives; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc. Tanooctahydronaphthalene, its alkyl and / or alkylidene substituted derivatives, and polar group substituted derivatives such as halogens, e.g., 6-methyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylidene-1,4:5,8-dimethano-1,4,4a,5,6,7 ,8,8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethano Examples include tano-1,4,4a,5,6,7,8,8a-octahydronaphthalene, and tripers or tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene and 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene. The norbornene-based resin may also be a copolymer of a norbornene-based monomer and another monomer.

[0034] The phase difference layer (phase difference film) is a stretched film formed from the above-mentioned resin. Any suitable method can be used to produce the stretched film. Typically, a method involves laminating a shrinkable film to one or both sides of a resin film and then heat-stretching it. The shrinkable film is used to impart a shrinkage force in a direction perpendicular to the stretching direction during heat stretching. By imparting such a shrinkage force, the nz can be increased, and as a result, a Z film can be produced. Examples of materials used for the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride. Due to its excellent shrinkage uniformity and heat resistance, polypropylene film is preferably used.

[0035] As for the stretching method described above, any suitable stretching method can be adopted as long as it can apply tension to the resin film in the stretching direction and a shrinking force in a direction perpendicular to the stretching direction within the film plane. The stretching temperature is preferably above the glass transition temperature (Tg) of the resin film. This is because the phase difference value of the resulting stretched film tends to be uniform, and the film is less likely to crystallize (become cloudy). The stretching temperature is more preferably Tg+1°C to Tg+30°C of the polymer film, even more preferably Tg+2°C to Tg+20°C, particularly preferably Tg+3°C to Tg+15°C, and most preferably Tg+5°C to Tg+10°C. By setting the stretching temperature within this range, uniform heat stretching can be performed. Furthermore, it is preferable that the stretching temperature be constant in the film width direction. This is because it is possible to produce a stretched film with good optical uniformity and small variation in phase difference values.

[0036] The stretching ratio during the stretching process described above can be set to any appropriate value. Preferably, it is 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. By setting the stretching ratio within this range, a stretched film with minimal shrinkage of the film width and excellent mechanical strength can be obtained.

[0037] The thickness of the phase difference layer is preferably 80 μm to 200 μm, more preferably 90 μm to 150 μm, and even more preferably 110 μm to 150 μm. With such a thickness, the desired in-plane phase difference value can be obtained.

[0038] B. Method for manufacturing polarizing plates with irregular shapes The method for manufacturing a polarizing plate having an irregular shape according to an embodiment of the present invention includes, as described above, forming an irregular shape on a polarizing plate by laser irradiation; and cutting the polarizing plate having the irregular shape formed on it into a single sheet by laser irradiation. Each step will be described below.

[0039] B-1. Formation of abnormalities First, a shape is formed on the polarizing plate by laser irradiation. The polarizing plate may be a raw roll or an intermediate cut to a predetermined size. The intermediate may be sized to cut only one final polarizing plate, or it may be sized to cut a predetermined number of plates (for example, two, three, four, five, or six). In embodiments of the present invention, typically, an intermediate sized to cut two or three final polarizing plates may be used. Below, as an example, a method for manufacturing a polarizing plate in which a chamfered corner shape, a bathtub-shaped recess when viewed from above, and a U-shaped notch are formed as shapes will be specifically described.

[0040] Figure 5(a) is a schematic plan view illustrating the shaping process in the manufacturing method according to an embodiment of the present invention. As shown in Figure 5(a), a shape is formed on a polarizing plate. The shaping is performed by laser irradiation as described above. By forming the shape by laser irradiation, it becomes possible to punch out the plate in a single sheet after the shape has been formed. As a result, cracks in the shaping process can be suppressed. Laser irradiation can be performed under any appropriate conditions as long as the shaping can be formed. Details of laser irradiation will be described below.

[0041] Typical laser light sources include infrared lasers, such as CO2 laser light sources, whose emitted laser light wavelength is in the infrared region of 9 μm to 11 μm. Such laser light sources can achieve high productivity. Infrared lasers can easily obtain power in the tens of watts range, and furthermore, by efficiently heating polarizing plates through molecular vibrations associated with infrared absorption, it is possible to induce etching associated with phase transitions of materials.

[0042] As a laser light source, a CO laser light source with an emitted laser light wavelength of approximately 5 μm may be used. Furthermore, as a laser light source, near-infrared (NIR), visible light (Vis), and ultraviolet (UV) pulsed laser light sources may be used. Examples of NIR, Vis, and UV pulsed laser light sources include those with emitted laser light wavelengths of 1064 nm, 532 nm, 355 nm, 349 nm, or 266 nm (high-order harmonics of solid-state laser light sources using Nd:YAG, Nd:YLF, or YVO4 as the medium), excimer laser light sources with emitted laser light wavelengths of 351 nm, 248 nm, 222 nm, 193 nm, or 157 nm, and F2 laser light sources with emitted laser light wavelengths of 157 nm.

[0043] As for the oscillation mode of the laser light source, pulse oscillation is preferred over continuous wave (CW) from the viewpoint of suppressing thermal damage to the polarizer. The pulse width is 10 femtoseconds (10 -14 (seconds) ~ 1 millisecond (10 -3 The pulse repetition frequency can be set appropriately within the range of seconds. The pulse repetition frequency is preferably 1kHz to 1,000kHz, and more preferably 10kHz to 500kHz. It is also possible to process using two or more different pulse widths.

[0044] There are no restrictions on the polarization state of the laser light. Specifically, linear polarization, circular polarization, or random polarization are all applicable. There are also no restrictions on the spatial intensity distribution of the laser light. The laser light is preferably a Gaussian beam because it exhibits good focusing properties, allows for small spot size, and is expected to improve productivity. Depending on the purpose, the laser light may be shaped into a flat-top beam using diffractive optical elements, aspherical lenses, etc.

[0045] The number of laser beam pulses can be appropriately set depending on the purpose. If the desired shape can be cut, the laser beam may be pulsed only once along the desired shape, or the desired cutting depth may be achieved by pulses multiple times. When pulses are pulsed multiple times, the conditions for each pulse may be the same or different.

[0046] The scanning mode of the laser beam can be appropriately set according to the purpose. Specific examples include stage drive systems such as XY precision stages, optical scanning systems such as galvanometer scanners and polygon scanners, or combinations thereof (multi-axis synchronous control). By appropriately selecting and / or combining these, the relative position between the workpiece (polarizing plate) and the laser beam can be changed at a predetermined speed. Furthermore, by controlling the on / off state of laser irradiation using a mechanical shutter or AOM (acousto-optic element), it becomes possible to process the workpiece into a desired shape. The scanning speed of the laser beam can be appropriately set according to the purpose (e.g., desired cutting depth).

[0047] The condensing spot diameter of the laser beam (and as a result, the cutting width) can be appropriately set according to the purpose. The condensing spot diameter can be adjusted to a desired diameter or range by condensing the laser beam with an objective lens such as an Fθ lens. With such a configuration, the processing efficiency can be improved and the thermal damage can be suppressed. The condensing spot diameter is preferably 500 μm or less, more preferably 300 μm or less, still more preferably 200 μm or less, and particularly preferably 100 μm or less. The condensing spot diameter can be defined, for example, as the diameter of the laser beam at the position where the intensity has decayed to 1 / e 2 of the peak intensity value. When using a galvanometer scanner, it is preferable to use a telecentric Fθ lens for the purpose of projecting the laser beam perpendicularly onto the workpiece (polarizer). Also, in order to obtain a desired condensing spot diameter (and as a result, the cutting width), a beam expander unit for adjusting the beam diameter may be used between the output end of the laser oscillator and the optical path of the objective lens.

[0048] The laser output can be appropriately set according to the thickness and properties of the polarizer to be processed. For example, when using a CO2 laser as the laser light source, the output is preferably 5 W to 300 W, and more preferably 20 W to 200 W.

[0049] For laser irradiation, two or more types of lasers may be used. In this case, two or more types of lasers may be irradiated simultaneously or sequentially.

[0050] The order in which the irregular shapes are formed is not particularly limited. For example, after chamfering the corners, the bathtub-shaped recess and U-shaped notch may be formed in this order; or for example, after chamfering the corners, the U-shaped notch and bathtub-shaped recess may be formed in this order; or for example, after forming the bathtub-shaped recess and U-shaped notch in this order, the corners may be chamfered; or for example, after forming the U-shaped notch and bathtub-shaped recess in this order, the corners may be chamfered; or for example, the irregular shapes may be formed along the outer circumference of the polarizing plate (for example, chamfering the upper right corner, forming the bathtub-shaped recess, chamfering the upper left corner, chamfering the lower left corner, forming the U-shaped notch, and chamfering the lower right corner may be done in this order). When forming irregular shapes along the outer circumference of the polarizing plate, the starting position can be set to any appropriate position. Specifically, the starting position may be the upper right corner, lower right corner, upper left corner, or lower left corner, and may be the position where a bathtub-shaped recess is formed, or the position where a U-shaped notch is formed, or any position on the straight portion of the long or short side. When forming a shape along the outer circumference of the polarizing plate, the shape may be formed clockwise, or counterclockwise as shown in the illustrated example.

[0051] In one embodiment, laser irradiation is performed from the front of the shape to be formed and / or to a predetermined position following the shape (to the back of the shape). In this specification, such laser irradiation from the front of the shape and / or to the back of the shape is referred to as "laser irradiation overrun". The amount of overrun is preferably 0.5 mm to 50 mm, more preferably 0.5 mm to 5 mm, and even more preferably 1 mm to 3 mm for both the front and back sides. By performing the overrun within this range, cracks in the processed shape can be effectively suppressed. Preferably, the overrun can be set at least on the back side.

[0052] B-2. Cutting into single-leaf shapes The polarizing plate, which has been deformed as described in Section B-1 above, is cut into single-wafer shapes. This single-wafer cutting is also performed by laser irradiation, similar to the formation of the deformed shape. By performing single-wafer cutting by laser irradiation, even polarizing plates with complex shapes (especially those with small deformities) can be cut well. Laser irradiation can be performed under any appropriate conditions, as long as it is possible to cut the polarizing plate into single-wafer shapes. Details of laser irradiation in single-wafer cutting are as described above for the formation of the deformed shape. Laser irradiation in single-wafer cutting may be performed under the same conditions as for the formation of the deformed shape above, or under different conditions.

[0053] Cutting can typically be performed by linear laser irradiation, as shown in Figure 5(b). By cutting with linear laser irradiation after shaping, the residual stress in the shaping portion can be reduced. As a result, cracks in the shaping portion can be suppressed. The estimated mechanism by which such an effect can be obtained will be explained with reference to Figure 6. As shown in the lower part of Figure 6, when shaping is performed after cutting into a single sheet, the processed end portion where most of the stress remains in the shaping portion remains included in the final polarizing plate. As a result, it is estimated that cracks occur in the shaping portion due to the residual stress in the processed end portion. This is also true when linear processing and shaping are performed continuously along the outer circumference of the polarizing plate (i.e., in the manner of so-called single-stroke drawing). In this case as well, the processed end portion where most of the stress remains in the shaping portion remains included in the final polarizing plate. On the other hand, as shown in the upper part of Figure 6, according to the embodiment of the present invention, by cutting the polarizing plate into a single sheet after shaping, the processed end portion where most of the stress remains in the shaping portion can be cut off. As a result, it is presumed that the residual stress is small in the irregularly shaped portion of the final polarizing plate, and therefore the occurrence and propagation of cracks caused by this residual stress are suppressed.

[0054] In cutting, overruns may be set before and / or after the straight-cut section. By setting overruns, the cutting start and end points are not included in the final polarizing plate. As a result, shape abnormalities caused by excessive irradiation at the start and / or end points can be avoided. The amount of overrun is preferably 0.5 mm to 50 mm, and more preferably 0.5 mm to 2.5 mm, for both the front and back sides. In the example shown in Figure 5(b), overruns are set before and after the straight-cut section for all four sides, and intersections of the overruns are set. The setting of overruns is not limited to the form shown in Figure 5(b). For example, overruns may be set by continuously irradiating (cutting) the rectangular shape along the corners before chamfering (i.e., there may be no intersections of overruns); or, for example, overruns may be set by continuously irradiating (cutting) the rectangular shape along the corners before chamfering for one, two, or three of the four corners, and overruns for the remaining corners may be set in the form shown in Figure 5(b).

[0055] Cutting is typically performed at a predetermined time interval or longer after the formation of the deformed shape. By providing such an interval, residual stress caused by the deformed shape can be relieved. Therefore, residual stress in the deformed portion of the final polarizing plate can be further reduced, and as a result, cracks in the deformed portion can be further suppressed. The interval is preferably 1 second or more, more preferably 3 seconds or more, and even more preferably 5 seconds or more. Since the effect does not change even if the interval is excessively long, the upper limit of the interval can be determined considering the balance with the manufacturing efficiency of the polarizing plate. The upper limit of the interval may be, for example, 60 seconds.

[0056] The above describes an example where an irregular shape becomes a recess when viewed from above. However, the embodiments of the present invention can be similarly applied to the formation of through holes, for example, and similar effects can be obtained. That is, even when forming through holes, residual stress near the through holes can be reduced by performing straight-line cutting after the through holes have been formed, and as a result, cracks near the through holes can be suppressed.

[0057] In this way, polarizing plates with irregular shapes can be manufactured. [Examples]

[0058] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight.

[0059] (1) Thickness Thicknesses of 10 μm or less were measured using an interferometer (Otsuka Electronics Co., Ltd., product name "MCPD-3000"). Thicknesses exceeding 10 μm were measured using a digital micrometer (Anritsu Corporation, product name "KC-351C"). (2) Phase difference change The in-plane phase difference of the polarizing plates used in the examples and comparative examples was measured using a phase difference measuring device (product name "WPA-KAMAKIRI") manufactured by Photron Corporation. The measurement wavelength for the in-plane phase difference was 540 nm, and the measurement temperature was 23°C. This was defined as the initial phase difference Re0. Next, the polarizing plate was heated by leaving it in a 95°C environment for 12 hours, and the in-plane phase difference after heating was measured in the same manner as above. This was defined as the phase difference Re 12 The following formula was used to determine the change in in-plane phase difference before and after heating. In-plane phase difference change ΔRe = Re 12 -Re0 (3) Crack The polarizing plates obtained in the examples and comparative examples were left in an environment of 95°C, and the time until cracks occurred near the deformed areas was investigated.

[0060] [Example 1] 1. Fabrication of a polarizer A 45 μm thick polyvinyl alcohol film was stretched to 3 times its original size while being stained for 1 minute in a 0.3% iodine solution at 30°C between rolls with different speed ratios. Then, it was stretched to a total stretch ratio of 6 times by immersion for 0.5 minutes in an aqueous solution containing 4% boric acid and 10% potassium iodide at 60°C. Next, it was washed by immersion for 10 seconds in an aqueous solution containing 1.5% potassium iodide at 30°C, and then dried at 50°C for 4 minutes to obtain an 18 μm thick polarizer.

[0061] 2. Fabrication of polarizing plates An HC-TAC film (49 μm thick) was bonded to one side of the polarizer obtained above using a polyvinyl alcohol-based adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (9 μm thick) is formed on a triacetylcellulose (TAC) film (40 μm thick), and it was bonded so that the TAC film was on the polarizer side. Furthermore, an acrylic resin film (30 μm thick) was bonded to the other side of the polarizer in the same manner as above. In this way, a polarizing plate having the configuration of protective layer (HC-TAC film) / polarizer / protective layer (acrylic resin film) was obtained.

[0062] 3. Fabrication of polarizing plates with phase difference layer A 130 μm thick norbornene-based resin film was bonded to both sides with a 60 μm thick shrinkable film [Toray Industries product name "Trefan BO2873"] via an acrylic adhesive layer (15 μm thick). The film was then stretched 1.38 times in a 146°C air-circulating oven while holding the longitudinal direction of the film using a roll stretcher. After stretching, the shrinkable film was peeled off together with the acrylic adhesive layer to produce a phase difference film. The resulting phase difference film exhibited a refractive index characteristic of nx>nz>ny, with Re(550)=280 nm, Nz coefficient=0.52, and a photoelastic coefficient of 4.0×10⁻⁶. -12 m 2 The N value was / N, and the thickness was 138 μm. This phase difference film was bonded to the acrylic resin film side of the polarizing plate obtained above via an acrylic adhesive (thickness 20 μm). Here, the polarizing plate and the phase difference layer were bonded so that the absorption axis of the polarizer and the slow axis of the phase difference layer were substantially orthogonal. Finally, a surface protective film was temporarily attached to the surface of the HC layer, and an adhesive layer was provided on the surface of the phase difference layer, and a separator was temporarily attached to the adhesive layer to obtain a polarizing plate with a phase difference layer (hereinafter simply referred to as a polarizing plate) having the configuration of surface protective film / protective layer (HC-TAC film) / polarizer / protective layer (acrylic resin film) / phase difference layer / adhesive layer / separator.

[0063] 4. Shape processing and sheet cutting The polarizer obtained in step 3 above was subjected to laser irradiation to form the irregular shape shown in Figure 5(a). Specifically, a bathtub-shaped recess and a U-shaped notch were formed in that order, and then the four corners were chamfered. The laser irradiation conditions were an output of 33W, a scanning speed of 400mm / min, and an overrun amount (both front and back sides of the irregular shape) of 1mm. Next, as shown in Figure 5(b), the polarizer was cut into 200mm x 67mm pieces by linear laser irradiation. The laser irradiation was performed under the same conditions as for the formation of the irregular shape. Here, the polarizer's absorption axis was aligned with the longer side. The cutting was performed with a 5-second interval from the formation of the irregular shape (i.e., cutting started 5 seconds after the completion of the irregular shape processing). In this way, a polarizer with an irregular shape was obtained. The obtained polarizer was subjected to the evaluations in (2) and (3) above. The results are shown in Table 1.

[0064] [Comparative Example 1] A polarizing plate with a deformed shape was fabricated in the same manner as in Example 1, except that the order of deformation and cutting was reversed, that is, the polarizing plate was cut to the same size as in Example 1 before the deformed shape was formed. The deformation was performed at an interval of 5 seconds after cutting. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0065] [Comparative Example 2] A polarizing plate with an irregular shape was fabricated in the same manner as in Example 1, except that cutting and shaping were performed continuously along the outer circumference of the polarizing plate (i.e., in a so-called single-stroke manner). More specifically, starting from the chamfering of the upper right corner, laser irradiation was performed continuously in a counterclockwise direction to fabricate polarizing plates as shown in Figures 5(a) and 5(b). The obtained polarizing plates were subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0066] [Table 1]

[0067] [evaluation] As is clear from Table 1, the polarizing plate of the embodiment of the present invention exhibits small phase difference changes in high-temperature environments, and the time until cracks occur near the irregularly shaped processed portion is significantly longer compared to the comparative example. Furthermore, in the polarizing plate of the comparative example, it was confirmed that significant cracks occurred in the phase difference layer at the tip of the U-shaped notch. In other words, it can be seen that cracks in the irregularly shaped processed portion are suppressed in the polarizing plate of the embodiment of the present invention. [Industrial applicability]

[0068] The polarizing plate of the present invention is suitably used in image display devices such as liquid crystal displays, organic EL displays, and inorganic EL displays. [Explanation of symbols]

[0069] 10 Polarizing plates 11 Polarizer 12. First protective layer 13. Second protective layer 20 Retardation layer 100 Polarizing plate with retardation layer

Claims

1. Forming irregular shapes on polarizing plates by laser irradiation, and The polarizing plate with the irregular shape formed thereon is cut into single sheets by laser irradiation. Includes, In forming the deformed shape, the deformed shape is formed at a position corresponding to at least a part of the outer circumference of the polarizing plate after the sheet-like cutting, The start and end points of the laser irradiation for forming the deformed shape are not included in the polarizing plate after the single-wafer cutting. A method for manufacturing polarizing plates with irregular shapes.

2. A method for manufacturing a polarizing plate having an irregular shape according to claim 1, comprising cutting the polarizing plate having the irregular shape formed thereon into a single-wafer shape by linear laser irradiation.

3. A method for manufacturing a polarizing plate having an irregular shape according to claim 1 or 2, wherein the irregular shape is a concave shape when viewed from above.

4. A method for manufacturing a polarizing plate having an irregular shape according to claim 3, wherein the irregular shape is a U-shaped notch or a V-shaped notch.

5. A method for manufacturing a polarizing plate having an irregular shape according to any one of claims 1 to 4, wherein the starting point of the laser irradiation for forming the irregular shape is 0.5 mm to 50 mm before the irregular shape, and / or the ending point is 0.5 mm to 50 mm from the irregular shape.

6. A method for manufacturing a polarizing plate having an irregular shape according to any one of claims 1 to 5, wherein the formation of the irregular shape and the cutting of the sheet-like shape are performed with an interval of 1 second or more.

7. A method for manufacturing a polarizing plate having an irregular shape according to any one of claims 1 to 6, wherein the polarizing plate further has a phase difference layer.

8. A method for manufacturing a polarizing plate having an irregular shape according to claim 7, wherein the phase difference layer contains a cyclic olefin resin, exhibits refractive index characteristics of nx > nz > ny, has an Nz coefficient of 0.3 to 0.7, and has an in-plane phase difference Re(550) of 250 nm to 350 nm.

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