Method for manufacturing a polarizing plate having an irregular shape

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] The present invention relates to a method for manufacturing a polarizing plate having a non-rectangular shape.

Background Art

[0002] In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have been rapidly spreading. Due to the image formation method of the image display device, a polarizing plate is disposed on at least one of the image display devices. In recent years, there are cases where it is desired to process the polarizing plate into a shape other than a rectangle (non-rectangular processing: for example, forming a notch and / or a through hole). However, there is a problem that cracks are likely to occur in the non-rectangular processed portion of the polarizing plate.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present invention has been made to solve the above-described conventional problems, and a main object thereof is to provide a simple and inexpensive method for manufacturing a polarizing plate having a non-rectangular shape and in which cracks are suppressed.

Means for Solving the Problems

[0005] A method for manufacturing a polarizing plate having a non-rectangular shape according to an embodiment of the present invention includes: forming a non-rectangular shape in the polarizing plate by laser irradiation; and cutting the polarizing plate in which the non-rectangular shape is formed into individual sheets by laser irradiation. In one embodiment, the manufacturing method includes cutting the polarizing plate in which the non-rectangular shape is formed into individual sheets by linear laser irradiation. In one embodiment, the irregular shape is a concave shape when viewed in plan view. 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, and the amount of the overrun is 0.5 mm to 50 mm. In one embodiment, the formation of the irregular shape and the sheet-like cutting are performed with an interval of 1 second or more. In one embodiment, the polarizing plate further has a retardation layer. In one embodiment, the retardation layer contains a cyclic olefin resin, exhibits refractive index characteristics of nx > nz > ny, its Nz coefficient is 0.3 to 0.7, and its in-plane retardation Re(550) is 250 nm to 350 nm.

Advantages 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 having the irregular shape is cut into sheet-like by laser irradiation, whereby a polarizing plate with cracks suppressed can be simply and inexpensively manufactured despite having an irregular shape.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0008] Hereinafter, specific embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments. For clarity, the drawings are schematically represented, and further, the ratios of lengths, widths, thicknesses, etc. in the drawings, as well as angles, etc. are different from the actual ones.

[0009] (Definitions of Terms and Symbols) The definitions of terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) “nx” is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast 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 λ nm at 23°C. For example, “Re(550)” is the in-plane phase difference measured with light of wavelength 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx - ny)×d when the thickness of the layer (film) is d (nm). (3) Phase Difference in the Thickness Direction (Rth) “Rth(λ)” is the phase difference in the thickness direction measured with light of wavelength λ nm at 23°C. For example, “Rth(550)” is the phase difference in the thickness direction measured with light of wavelength 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ)=(nx - nz)×d when the thickness of the layer (film) is d (nm). (4) Nz Coefficient The Nz coefficient is obtained by 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 the case 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" include the case where the angle formed by two directions is 0° ± 7°, preferably 0° ± 5°, and more preferably 0° ± 3°. Further, when simply referring to "orthogonal" or "parallel" in this specification, it is assumed that a substantially orthogonal or substantially parallel state may be included.

[0010] The 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 individual sheets 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 FIG. 1 is a schematic cross-sectional view illustrating an example of a polarizing plate that can be used in the manufacturing method according to the 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). Either the first protective layer 12 or the second protective layer 13 may be omitted depending on the purpose and the configuration of the polarizing plate. The polarizing plate may be a retardation layer-attached polarizing plate further having a retardation layer as shown in FIG. 2, if necessary. The retardation layer-attached polarizing plate 100 in the illustrated example further has a retardation layer 20 on the side opposite to the viewing side of the polarizing plate 10. The retardation layer 20 is attached to the polarizing plate 10 (the second protective layer 13 in the illustrated example) via any appropriate adhesive layer (for example, an adhesive layer, a pressure-sensitive adhesive layer: not shown). The optical properties (e.g., refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the retardation layer 20 can be appropriately set according to the purpose. The retardation layer 20 typically has a refractive index property in the relationship of nx>nz>ny. In a retardation layer-attached polarizing plate having such a retardation layer, the effect of the embodiment of the present invention can be remarkable. In this specification, a polarizing plate and a retardation layer-attached polarizing plate are collectively referred to as a polarizing plate.

[0012] The polarizing plate obtained by the manufacturing method according to the embodiment of the present invention has an irregular shape. As used herein, "having an irregular shape" means that the planar shape of the polarizing plate has a shape other than a rectangle. The irregular shape is typically an irregularly processed portion. Therefore, the "polarizing plate having an irregular shape" includes not only the case where the entire polarizing plate (i.e., the outer edge defining the planar shape of the film) is other than a rectangle, but also the case where an irregularly processed portion is formed in a portion spaced inward from the outer edge of the rectangular polarizing plate. Examples of the irregular shape (irregularly processed portion) include chamfers at the corners, through-holes, and cut portions that become recesses in a plan view, as shown in FIGS. 3 and 4. Representative examples of the recess include a shape approximated to a boat shape, a shape approximated to a bathtub shape, a V-notch, and a U-notch. Needless to say, the shape of the irregular shape (irregularly processed portion) is not limited to the illustrated examples. For example, the shape of the through-hole can be any appropriate shape (e.g., an elliptical shape, a triangular shape, a quadrangular shape, a pentagonal shape, a hexagonal shape, an octagonal shape) according to the purpose, other than the substantially circular shape of the illustrated example. Further, the through-hole can be provided at any appropriate position according to the purpose. The through-hole may be provided at a substantially central portion of the longitudinal end of the rectangular polarizing plate, at a predetermined position of the longitudinal end, or at a corner of the polarizing plate, as shown in FIG. 4; although not shown, it may be provided at the short-side end of the rectangular polarizing plate. Further, three or more through-holes may be formed. In addition, the shapes of the illustrated examples may be appropriately combined according to the purpose. For example, a through-hole may be formed at any position of the irregular polarizing plate of FIG. 3; a V-notch and / or a U-notch may be formed at any appropriate position of the outer edge of the irregular polarizing plate of FIG. 3. Such an irregular polarizing plate can be suitably used for an image display device such as an automobile meter panel, a smartphone, a tablet PC, or a smartwatch.

[0013] The polarizing plate may further include other optical functional layers. The type, characteristics, number, combination, arrangement position, etc. of the optical functional layers that can be provided on the polarizing plate can be appropriately set according to the purpose. For example, the polarizing plate may further have a conductive layer or an anisotropic substrate with a conductive layer (both not shown). The conductive layer or the anisotropic substrate with a conductive layer is typically provided on the side opposite to the viewing side. When the conductive layer or the anisotropic substrate with a conductive layer is provided, the polarizing plate 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 polarizing plate. Also, for example, the polarizing plate may further include another retardation layer. The optical characteristics (e.g., refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the other retardation layer can be appropriately set according to the purpose.

[0014] Practically, an adhesive layer (not shown) is provided as the outermost layer on the side opposite to the viewing side of the polarizing plate, and the polarizing plate is enabled to be attached to the image display panel. Further, a separator (not shown) is removably temporarily adhered to the surface of the adhesive layer. By temporarily adhering the separator, the adhesive layer is protected and the polarizing plate can be formed into a roll. Further, practically, a surface protection film is temporarily adhered to the viewing side of the polarizing plate to prevent the occurrence of scratches, etc. during conveyance, transportation, and / or attachment to the image display panel. The surface protection film typically has a base film and an adhesive layer, and is temporarily adhered to the viewing side surface of the polarizing plate through the adhesive layer.

[0015] Hereinafter, the polarizer, the protective layer, and the retardation layer, which are components of the polarizing plate, will be described.

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

[0017] As a specific example of a polarizer composed of a single-layer resin film, there can be mentioned one obtained by subjecting a PVA-based resin film to a dyeing treatment with iodine and a stretching treatment (typically, uniaxial stretching). The above-mentioned dyeing with iodine is performed, for example, by immersing the PVA-based film in an iodine aqueous solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Also, it may be dyed after stretching. If necessary, the PVA-based resin film is subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, etc. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only can the dirt on the surface of the PVA-based film and the blocking preventive agent be washed away, but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

[0018] As specific examples of the polarizer obtained using the laminate, there can be mentioned a laminate of a resin base material and a PVA-based resin layer (PVA-based resin film) laminated on the resin base material, or a polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material. The polarizer obtained using a laminate of a resin base material and a PVA-based resin layer formed by coating on the resin base material can be produced, for example, by coating a PVA-based resin solution on the resin base material and drying it to form a PVA-based resin layer on the resin base material to obtain a laminate of the resin base material and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In the present embodiment, preferably, a PVA-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin base material. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching it. Further, stretching may further include, if necessary, air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in the aqueous boric acid solution. In addition, in the present embodiment, preferably, the laminate is subjected to a drying shrinkage treatment in which it is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, a stretching treatment in water, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is coated on the thermoplastic resin, it becomes possible to enhance the crystallinity of PVA and achieve high optical characteristics. At the same time, by enhancing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, compared with the case where the PVA-based resin layer does not contain a halide, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical characteristics of the polarizer obtained through treatment steps such as a dyeing treatment and a stretching treatment in water, which are performed by immersing the laminate in a liquid, can be improved. Further, by shrinking the laminate in the width direction by the drying shrinkage treatment, the optical characteristics can be improved.The obtained resin substrate / polarizer laminate may be used as it is (i.e., the resin substrate may also serve 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 according to the purpose may be laminated on the peeled surface and used. Details of such a method for manufacturing a polarizer are described, for example, in JP-A-2012-73580 and Japanese Patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

[0019] The thickness of the polarizer is, for example, from 1 μm to 30 μm, and may be, for example, from 3 μm to 20 μm.

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

[0021] A-2. Protective Layer The first protective layer 12 and the second protective layer 13 are each formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of the material that is the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, acetate-based resins, etc. Also included are thermosetting resins or ultraviolet-curing resins such as (meth)acrylic-based, urethane-based, (meth)acrylic urethane-based, epoxy-based, silicone-based resins, etc. In addition, for example, glassy polymers such as siloxane-based polymers are also included. Also, the polymer film described in Japanese Patent Application Laid-Open No. 2001-343529 (WO01 / 37007) can be used. As the material of this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain can be used. For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile-styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the above resin composition. Preferably, a (meth)acrylic-based resin can be used.

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

[0023] As the (meth)acrylic resin, a (meth)acrylic resin having a lactone ring structure is particularly preferred in terms of having high heat resistance, high transparency, and high mechanical strength. Examples of the (meth)acrylic resin having a lactone ring structure include those described in JP-A-2000-230016, JP-A-2001-151814, JP-A-2002-120326, JP-A-2002-254544, JP-A-2005-146084, etc., which are (meth)acrylic resins having a lactone ring structure.

[0024] Typically, the polarizing plate is disposed on the viewing side of the image display device, and the first protective layer 12 is disposed on its viewing side. Therefore, the first protective layer 12 may be subjected to surface treatments such as hard coat treatment, antireflection treatment, anti-sticking treatment, antiglare treatment, etc., if necessary.

[0025] The thickness of the first protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and still more preferably 30 μm to 60 μm. When the first protective layer is subjected to a surface treatment to form a surface treatment layer, the thickness of the first protective layer is the thickness including the surface treatment layer.

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

[0027] A-3. Retardation layer Typically, as described above, the retardation layer exhibits a refractive index characteristic of nx > nz > ny (hereinafter, such a retardation layer or retardation film may be referred to as a Z film). Since the retardation layer has such a refractive index characteristic, the hue in the diagonal direction of an image display device to which a polarizing plate with a retardation layer is applied can be improved well. Furthermore, such improvement in the hue in the diagonal direction can be achieved without separately providing a retardation layer and a layer for optical compensation in the diagonal direction, and thus can contribute to thinning of the polarizing plate with a retardation layer (and as a result, the image display device). In addition, although such a retardation layer (retardation film) is prone to crack, according to an embodiment of the present invention, even when such a retardation layer is subjected to a deformed process, cracks in the deformed portion can be significantly suppressed.

[0028] The Nz coefficient of the retardation layer is preferably from 0.3 to 0.7, more preferably from 0.4 to 0.6, and still more preferably from 0.45 to 0.55. If the Nz coefficient is within such a range, the hue in the diagonal direction can be improved even better.

[0029] The in-plane retardation Re(550) of the retardation layer is preferably from 250 nm to 350 nm, more preferably from 260 nm to 330 nm, and still more preferably from 270 nm to 290 nm. If the in-plane retardation Re(550) of the retardation layer is within such a range, the moving distance on the Poincare sphere is short, so excellent hue and luminance characteristics are realized, and the color shift of the image display panel and the shift due to the retardation component of the TFT are also reduced.

[0030] The retardation layer may exhibit an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light. Typically, the retardation layer exhibits a flat wavelength dispersion characteristic.

[0031] The absolute value of the photoelastic coefficient of the retardation layer is preferably 15×10 -12 m 2 / N or less, more preferably 10×10 -12 m 2 / N or less. The lower limit of the absolute value of the photoelastic coefficient is, for example, 1.0×10 -12 m 2 / N. If the absolute value of the photoelastic coefficient of the retardation layer is within such a range, uneven display of the image display device can be suppressed well.

[0032] The retardation layer is typically a retardation film formed of any suitable resin capable of realizing the above characteristics. Examples of the resin for forming the retardation film include cyclic olefin resins, polyarylate, polyamide, polyimide, polyester, polyaryl ether ketone, polyamideimide, polyesterimide, polyvinyl alcohol, polyfumarate, polyethersulfone, polysulfone, polycarbonate resin, cellulose resin, and polyurethane. These resins may be used alone or in combination. Preferably, it is a cyclic olefin resin. Representative examples of the cyclic olefin resin include norbornene resins.

[0033] The above norbornene-based resin is a resin polymerized with norbornene-based monomers as polymerization units. Examples of the norbornene-based monomers include norbornene, and its alkyl and / or alkylidene substitution products, such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., and polar group substitution products such as halogens of these; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc.; dimethanooctahydronaphthalene, its alkyl and / or alkylidene substitution products, and polar group substitution products such as halogens, for example, 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-1,4,4a,5,6,7,8,8a-octahydronaphthalene, etc.; trimers to tetramers of cyclopentadiene, such as 4,9:5,8-dimethano-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzindene, 4,11:5,10:6,9-trimethano-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro-1H-cyclopentaanthracene, etc. The above norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

[0034] The retardation layer (retardation film) is a stretched film of the film formed from the above resin. As a method for producing the stretched film, any suitable method can be adopted. Typically, a method of laminating a shrinkable film on one or both sides of a resin film and then stretching by heating can be mentioned. The shrinkable film is used to apply a shrinking force in a direction orthogonal to the stretching direction during heat stretching. By applying such a shrinking force, 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, polyvinylidene chloride, and the like. A polypropylene film is preferably used because of its excellent shrinkage uniformity and heat resistance.

[0035] As the above stretching method, any suitable stretching method can be adopted as long as a tension in the stretching direction of the resin film and a shrinking force in a direction orthogonal to the stretching direction within the film plane can be applied. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the resin film. This is because the retardation value of the resulting stretched film is likely 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, still 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 such a range, uniform heat stretching can be performed. Furthermore, it is preferable that the stretching temperature is constant in the film width direction. This is because a stretched film having good optical uniformity with a small variation in retardation value can be produced.

[0036] The stretching ratio during the above stretching can be set to any suitable 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 such a range, a stretched film with little shrinkage in film width and excellent mechanical strength can be obtained.

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

[0038] B. Method for manufacturing a polarizing plate having an irregular shape 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 the polarizing plate by laser irradiation; and cutting the polarizing plate having the irregular shape into individual sheets by laser irradiation. Hereinafter, each step will be described.

[0039] B-1. Formation of an irregular shape First, an irregular shape is formed on the polarizing plate by laser irradiation. The polarizing plate may be an original roll or an intermediate body cut to a predetermined size. The intermediate body may be sized to cut only one final polarizing plate, or may be sized to cut a predetermined plurality of sheets (for example, 2, 3, 4, 5, 6 sheets). In an embodiment of the present invention, typically, an intermediate body sized to cut two or three final polarizing plates can be used. Hereinafter, as an example, a method for manufacturing a polarizing plate having a chamfered shape at the corner, a bathtub-shaped concave portion in plan view, and a U-shaped notch formed as an irregular shape will be specifically described.

[0040] FIG. 5(a) is a schematic plan view for explaining the irregular shape processing in the manufacturing method according to an embodiment of the present invention. As shown in FIG. 5(a), an irregular shape is formed on the polarizing plate. The formation of the irregular shape is performed by laser irradiation as described above. By forming the irregular shape by laser irradiation, it becomes possible to punch out the irregular shape into individual sheets after the formation. As a result, cracks in the irregularly processed portion can be suppressed. The laser irradiation can be performed under any appropriate conditions as long as an irregular shape can be formed. Hereinafter, the details of the laser irradiation will be described.

[0041] As the laser light source, typically, an infrared laser including a CO2 laser light source whose oscillation laser light wavelength is in the infrared range of 9 μm to 11 μm can be adopted. Such a laser light source can achieve high productivity. The infrared laser can easily obtain a power of several tens of watts, and further, by efficiently generating heat by the molecular vibration accompanying infrared absorption of the polarizing plate, it is possible to cause etching accompanying the phase transition of the substance.

[0042] As the laser light source, a CO laser light source whose oscillation laser light wavelength is about 5 μm may be used. Further, as the laser light source, a near-infrared (NIR), visible light (Vis), and ultraviolet (UV) pulse laser light source may be used. Examples of the NIR, Vis, and UV pulse laser light sources include those whose oscillation laser light wavelength is 1064 nm, 532 nm, 355 nm, 349 nm, or 266 nm (higher harmonics of a solid laser light source using Nd:YAG, Nd:YLF, or YVO4 as a medium), an excimer laser light source whose oscillation laser light wavelength is 351 nm, 248 nm, 222 nm, 193 nm, or 157 nm, and an F2 laser light source whose oscillation laser light wavelength is 157 nm.

[0043] As the oscillation mode of the laser light source, from the viewpoint of suppressing thermal damage to the polarizing plate, pulse oscillation is more preferable than continuous wave (CW). The pulse width can be appropriately set in the range of 10 femtoseconds (10 -14 seconds) to 1 millisecond (10 -3 seconds). The repetition frequency of the pulse is preferably 1 kHz to 1,000 kHz, and more preferably 10 kHz to 500 kHz. It is also possible to set two or more types of pulse widths for processing.

[0044] There are no restrictions on the polarization state of the laser beam. Specifically, it can be applied regardless of whether it is linearly polarized, circularly polarized, or randomly polarized. There are also no restrictions on the spatial intensity distribution of the laser beam. The laser beam is preferably a Gaussian beam because it exhibits good focusing properties, enables small spot formation, and can be expected to improve productivity. Depending on the purpose, the laser beam may be shaped into a flat-top beam using a diffractive optical element, an aspherical lens, or the like.

[0045] The number of irradiations of the laser beam can be appropriately set according to the purpose. If it is possible to perform cutting processing into a desired shape, the laser beam may be irradiated only once along the desired shape, or a desired cutting depth may be achieved by irradiating multiple times. When irradiating the laser beam multiple times, the conditions for each time may be the same or different.

[0046] The scanning pattern of the laser beam can be appropriately set according to the purpose. Specific examples include a stage drive system such as an XY precision stage, an optical scanning system such as a galvanometer scanner or a polygon scanner, or a combination 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 using a mechanical shutter, an AOM (acousto-optic element), or the like to perform on / off control of the laser irradiation, it becomes possible to process into a desired shape. The scanning speed of the laser beam can be appropriately set according to the purpose (for example, the desired cutting depth).

[0047] The condensing spot diameter of the laser beam (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 irradiating the laser beam perpendicularly to the workpiece (polarizing plate). Further, in order to obtain a desired condensing spot diameter (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 polarizing plate to be processed. For example, when using a CO2 laser as the laser light source, the output is preferably 5 W to 300 W, 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 forming order of the irregular shape is not particularly limited. For example, after chamfering the corners, a bathtub-shaped recess and a U-notch may be formed in this order; for another example, after chamfering the corners, a U-notch and a bathtub-shaped recess may be formed in this order; for another example, after forming a bathtub-shaped recess and a U-notch in this order, chamfering of the corners may be performed; for another example, after forming a U-notch and a bathtub-shaped recess in this order, chamfering of the corners may be performed; for another example, an irregular shape may be formed along the outer periphery of the polarizing plate (for example, chamfering of the upper right corner, formation of a bathtub-shaped recess, chamfering of the upper left corner, chamfering of the lower left corner, formation of a U-notch, and chamfering of the lower right corner may be performed in this order). When forming an irregular shape along the outer periphery of the polarizing plate, the starting position can be set at any appropriate position. Specifically, the starting position may be any of the upper right corner, the lower right corner, the upper left corner, or the lower left corner, may be the formation position of the bathtub-shaped recess, may be the formation position of the U-notch, or may be any position on the straight portion of the long side or the short side. When forming an irregular shape along the outer periphery of the polarizing plate, the irregular shape may be formed clockwise or counterclockwise as shown in the illustrated example.

[0051] In one embodiment, the laser irradiation is performed from in front of the irregular shape to be formed and / or to a predetermined position (the depth of the irregular shape) following the irregular shape. In this specification, such laser irradiation from in front of the irregular shape and / or laser irradiation to the depth of the irregular 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 each of the front side and the depth side. By performing overrun within such a range, cracks in the irregularly processed portion can be favorably suppressed. Preferably, the overrun can be set at least on the depth side.

[0052] B-2. Cutting of double-sheet type The polarizing plate with the irregular shape formed as described in item B-1 above is cut into individual sheets. Such cutting into individual sheets is also performed by laser irradiation, similar to the formation of the irregular shape. By performing the cutting into individual sheets by laser irradiation, even a polarizing plate with a complex shape (especially with a small irregularity) can be cut well. The laser irradiation can be performed under any appropriate conditions as long as the polarizing plate can be cut into individual sheets. The details of the laser irradiation in the cutting into individual sheets are as described in the explanation regarding the formation of the above-mentioned irregular shape. The laser irradiation in the cutting into individual sheets may be performed under the same conditions as the formation of the above-mentioned irregular shape, or may be performed under different conditions.

[0053] The cutting can typically be performed by linear laser irradiation as shown in FIG. 5(b). By performing laser irradiation linearly for cutting after the irregular shape processing, the stress remaining in the irregularly processed portion can be reduced. As a result, cracks in the irregularly processed portion can be suppressed. Referring to FIG. 6, the estimated mechanism by which such an effect can be obtained will be explained. As shown in the lower part of FIG. 6, when the irregular shape processing is performed after cutting into individual sheets, the processed end portion where most of the stress remains in the irregularly processed portion remains included in the final polarizing plate. As a result, it is estimated that cracks will occur in the irregularly processed portion due to the residual stress in the processed end portion. This is the same even when performing linear processing and irregular shape processing continuously (i.e., in a so-called single-stroke manner) along the outer periphery of the polarizing plate. Also in this case, the processed end portion where most of the stress remains in the irregularly processed portion remains included in the final polarizing plate. On the other hand, as shown in the upper part of FIG. 6, according to the embodiment of the present invention, by cutting the polarizing plate into individual sheets by cutting after the irregular shape processing, the processed end portion where most of the stress remains in the irregularly processed portion can be cut off. As a result, since the residual stress in the irregularly processed portion of the final polarizing plate is small, it is estimated that the occurrence and progression of cracks due to the residual stress are suppressed.

[0054] Even during cutting, an overrun can be set before and / or behind the linear processing section. By setting the overrun, the cutting start point and the cutting end point are not included in the final polarizing plate. As a result, it is possible to avoid shape abnormalities caused by excessive irradiation at the start point and / or the end point. The amount of the overrun is preferably 0.5 mm to 50 mm, more preferably 0.5 mm to 2.5 mm, for each of the front side and the back side. In the example shown in Fig. 5(b), for all four-sided linear processing, an overrun is set before and behind the linear processing section, and the intersection points of the overruns are set. The setting of the overrun is not limited to the form of Fig. 5(b). For example, the overrun may be set by continuously performing laser irradiation (cutting) along the rectangular shape before chamfering the corners (that is, there may be no intersection points of the overruns); also, for example, the overrun may be set by continuously performing laser irradiation (cutting) along the rectangular shape before chamfering one, two, or three of the four corners, and the overrun for the remaining corners may be set in the form shown in Fig. 5(b).

[0055] Cutting is typically performed at intervals of a predetermined time or more from the formation of the irregular shape. By providing such an interval, the residual stress due to the irregular processing can be relaxed. Therefore, the residual stress in the irregular processed portion of the final polarizing plate can be made even smaller, and as a result, the cracking of the irregular processed 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 made excessively long, the upper limit of the interval can be determined in consideration of the balance with the manufacturing efficiency of the polarizing plate. The upper limit of the interval can be, for example, 60 seconds.

[0056] Incidentally, as an example, the case where the irregular shape becomes a concave portion in plan view has been described above. However, the embodiments of the present invention are similarly applicable to, for example, the formation of through holes, and similar effects can be obtained. That is, even when forming a through hole, by performing cutting by linear processing after forming the through hole, the residual stress in the vicinity of the through hole can be reduced, and as a result, cracks in the vicinity of the through hole can be suppressed.

[0057] As described above, a polarizing plate having an irregular shape can be manufactured.

Example

[0058] Hereinafter, the present invention will be specifically described by way of 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 For a thickness of 10 μm or less, it was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). For a thickness exceeding 10 μm, it was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C"). (2) Phase difference change Regarding the polarizing plates used in the examples and comparative examples, the in-plane phase difference was measured using a phase difference measuring device (product name "WPA-KAMAKIRI") manufactured by Photron Limited. The measurement wavelength of 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, this polarizing plate was left in an environment of 95°C for 12 hours for heating, 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 change amount of the in-plane phase difference before and after heating was determined from the following formula. In-plane phase difference change amount 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 in the vicinity of the irregularly processed portion was examined.

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

[0061] 2. Production of a polarizing plate An HC-TAC film (thickness: 49 μm) was bonded to one surface of the polarizer obtained above with a polyvinyl alcohol-based adhesive. The HC-TAC film is a film in which a hard coat (HC) layer (thickness: 9 μm) is formed on a triacetyl cellulose (TAC) film (thickness: 40 μm), and it was bonded so that the TAC film was on the polarizer side. Further, an acrylic resin film (thickness: 30 μm) was bonded to the other surface of the polarizer in the same manner as above. In this way, a polarizing plate having a structure of protective layer (HC-TAC film) / polarizer / protective layer (acrylic resin film) was obtained.

[0062] 3. Production of a polarizing plate with a retardation layer Shrinkable films [trade name "Trefan BO2873" manufactured by Toray Industries, Inc.] with a thickness of 60 μm were bonded to both sides of a norbornene-based resin film with a thickness of 130 μm via an acrylic adhesive layer (thickness: 15 μm). Then, while holding the film in the longitudinal direction with a roll stretching machine, it was stretched 1.38 times in an air circulation oven at 146°C. After stretching, the shrinkable film was peeled off together with the acrylic adhesive layer to produce a retardation film. The obtained retardation film exhibited refractive index characteristics of nx > nz > ny, Re(550) = 280 nm, Nz coefficient = 0.52, and photoelastic coefficient was 4.0×10 -12 m 2 / N, and the thickness was 138 μm. This retardation film was laminated on the acrylic resin film side of the polarizing plate obtained above through an acrylic adhesive (thickness: 20 μm). Here, the polarizing plate and the retardation layer were laminated such that the absorption axis of the polarizer and the slow axis of the retardation layer were substantially orthogonal. Finally, a surface protection film was temporarily attached to the surface of the HC layer, and an adhesive layer was provided on the surface of the retardation layer. A separator was temporarily attached to the adhesive layer to obtain a polarizing plate with a retardation layer (hereinafter simply referred to as a polarizing plate) having a structure of surface protection film / protective layer (HC-TAC film) / polarizer / protective layer (acrylic resin film) / retardation layer / adhesive layer / separator.

[0063] 4. Shaped processing and sheet-like cutting An irregular shape as shown in Fig. 5(a) was formed on the polarizing plate obtained in 3. above by laser irradiation. Specifically, a bathtub-shaped recess and a U-shaped notch were formed in this order, and then chamfers were made at the four corners. The conditions for laser irradiation were an output of 33 W, a scanning speed of 400 mm / min, and an overrun amount (both sides before and after the irregular shape) of 1 mm. Next, as shown in Fig. 5(b), the polarizing plate was cut into a size of 200 mm × 67 mm by linearly performing laser irradiation. The laser irradiation was performed under the same conditions as those for the formation of the irregular shape. Here, the polarizing plate was cut such that the absorption axis of the polarizer was in the long side direction. Also, the cutting was performed at an interval of 5 seconds from the formation of the irregular shape (that is, the cutting was started 5 seconds after the completion of the shaped processing). In this way, a polarizing plate with an irregular shape was obtained. The obtained polarizing plate 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 an irregular shape was produced in the same manner as in Example 1, except that the order of forming the irregular shape and cutting was reversed, that is, the polarizing plate was cut into the same size as in Example 1 and then the irregular shape was formed. The formation of the irregular shape was performed at an interval of 5 seconds from the 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 having a deformed shape was produced in the same manner as in Example 1, except that cutting and shaping were continuously performed along the outer periphery of the polarizing plate (i.e., in a so-called one-stroke manner). More specifically, starting from the chamfer at the upper right corner, laser irradiation was continuously performed counterclockwise to produce a polarizing plate as shown in FIGS. 5(a) and 5(b). The obtained polarizing plate was 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, it can be seen that the polarizing plate of the example of the present invention has a small retardation change in a high-temperature environment, and the time until cracks occur in the vicinity of the processed deformed portion is significantly longer than that of the comparative example. Furthermore, it was confirmed that significant cracks occurred in the retardation layer at the tip of the U-shaped notch in the polarizing plate of the comparative example. That is, it can be seen that cracks in the processed deformed portion of the polarizing plate of the example of the present invention are suppressed.

Industrial Applicability

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

Explanation of Reference Numerals

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

Claims

1. Forming a deformed shape on a polarizing plate by laser irradiation, and Cutting the polarizing plate with the deformed shape formed thereon into individual sheets by laser irradiation, comprising the formation of the deformed shape and the cutting into individual sheets being performed with an interval of 5 seconds or more, in the formation of the deformed shape, forming a deformed shape at a position corresponding to at least a part of the outer periphery of the polarizing plate after the cutting into individual sheets, each of the start point and the end point of the laser irradiation for forming the deformed shape not being included in the polarizing plate after the cutting into individual sheets, A method for manufacturing a polarizing plate having a deformed shape.

2. The method for manufacturing a polarizing plate having a deformed shape according to claim 1, comprising cutting the polarizing plate with the deformed shape formed thereon into individual sheets by linear laser irradiation.

3. The method for manufacturing a polarizing plate having a deformed shape according to claim 1 or 2, wherein the deformed shape is a concave shape in plan view.

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

5. For the laser irradiation for forming the deformed shape, the start point is 0.5 mm to 50 mm in front of the deformed shape, and / or the end point is 0.5 mm to 50 mm from the deformed shape. The method for manufacturing a polarizing plate having a deformed shape according to any one of claims 1 to 4.

6. The method for manufacturing a polarizing plate having a deformed shape according to any one of claims 1 to 5, wherein the polarizing plate further has a retardation layer.

7. The retardation layer contains a cyclic olefin resin, exhibits refractive index characteristics of nx > nz > ny, its Nz coefficient is 0.3 to 0.7, and its in-plane retardation Re(550) is 250 nm to 350 nm. The method for manufacturing a polarizing plate having a deformed shape according to claim 6.

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