TW202232149A - Method for manufacturing polarizing plate having irregular shape capable of suppressing cracks - Google Patents

Abstract

Provided is a simple and inexpensive method for producing a polarizing plate which has an irregular shape and in which cracks are suppressed. A method for manufacturing a polarizing plate having an irregular shape according to an embodiment of the present invention comprises the steps of: forming an irregular shape on a polarizing plate by laser irradiation; and cutting the polarizer formed with the irregular shape into single sheets by laser irradiation. In one embodiment, the manufacturing method includes cutting a polarizer, on which an irregular shape is formed, into a single sheet shape by linear laser irradiation. In one embodiment, the irregular shape is a shape that becomes a recess in plan view.

Description

Manufacturing method of polarizing plate with special shape

The invention relates to a manufacturing method of a polarizing plate with a special shape.

In recent years, image display devices represented by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) have been rapidly spreading. Due to the image forming method of the image display device, a polarizing plate is disposed on at least one side of the image display device. In recent years, it is desired to process the polarizing plate into a shape other than a rectangle (special shape processing: for example, formation of a notch and/or a through hole). However, there is a problem that cracks are easily generated in the deformed part of the polarizing plate. prior art literature Patent Literature

Patent Document 1: Japanese Patent Laid-Open No. 2018-159911

The problem to be solved by the invention The present invention has been accomplished in order to solve the above-mentioned conventional problems, and its main object is to provide a simple and low-cost manufacturing method of a polarizing plate having an irregular shape and suppressed cracks.

means for solving problems The manufacturing method of the polarizing plate with a special shape according to the embodiment of the present invention includes the following steps: forming a special shape on the polarizing plate by laser irradiation; In one embodiment, the above-mentioned manufacturing method includes cutting the above-mentioned polarizing plate having an irregular shape into individual pieces by irradiating a linear laser. In one Embodiment, the said abnormal shape becomes the shape of a recessed part in planar view. In one embodiment, the abnormal shape is a U-shaped notch or a V-shaped notch. In one embodiment, the above-mentioned 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 cutting of the single-piece shape are performed at an interval of 1 second or more. In one embodiment, the polarizing plate further includes a retardation layer. In one embodiment, the retardation layer includes a cyclic olefin resin, and exhibits a refractive index characteristic of nx>nz>ny, its Nz coefficient is 0.3 to 0.7, and its in-plane retardation Re(550) is 250 nm to 250 nm. 350nm.

Invention effect According to an embodiment of the present invention, in the manufacturing method of a polarizing plate with an irregular shape, after the irregular shape is formed on the polarizing plate by laser irradiation, the polarizing plate having the irregular shape is cut into individual pieces by laser irradiation, A polarizing plate with an irregular shape but suppressed cracks can be produced simply and inexpensively.

Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited to these embodiments. In addition, the drawings are schematically shown for convenience of viewing, and ratios such as length, width, thickness, etc., angles, etc. in the drawings are different from actual ones.

(Definition of Terms and Symbols) 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 becomes the largest (that is, the slow axis direction), "ny" is the refractive index in the in-plane direction orthogonal to the slow axis (that is, the fast axis direction), " nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured at 23° C. with light having a wavelength of λ nm. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d when the thickness of the layer (thin film) is d (nm). (3) Phase difference in thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth(550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is calculated by the formula: Rth(λ)=(nx−nz)×d when the thickness of the layer (thin film) is d (nm). (4) Nz coefficient The Nz coefficient is calculated by Nz=Rth/Re. (5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45°" means ±45°. (6) substantially orthogonal or substantially parallel In this specification, the expressions "substantially orthogonal" and "substantially orthogonal" include the case where the angle formed by the two direction lines is 90°±7°, preferably 90°±5°, more preferably 90° ±3°. The expressions of "substantially parallel" and "substantially parallel" include the case where the angle formed by the two directions is 0°±7°, preferably 0°±5°, more preferably 0°±3°. In addition, when it is simply referred to as "orthogonal" or "parallel" in this specification, it is assumed that a substantially orthogonal or substantially parallel state may be included.

The manufacturing method of the polarizing plate with a special shape according to the embodiment of the present invention includes the following steps: forming a special shape on the polarizing plate by laser irradiation; For the sake of convenience, the specific structure of the polarizing plate that can be used in the production method of the embodiment of the present invention and the polarizing plate obtained by the production method will be described first, and then the production method of the polarizing plate having a special shape according to the embodiment of the present invention will be described.

A. Polarizing plate FIG. 1 is a schematic cross-sectional view illustrating an example of a polarizing plate that can be used in a manufacturing method according to an embodiment of the present invention. The polarizing plate 10 in the illustrated example includes a polarizer 11, a first protective layer 12 disposed on one side of the polarizer (in the illustrated example, the viewing side), and a first protective layer 12 disposed on the other side of the polarizer (in the illustrated example). In the example, it is the second protective layer 13 on the opposite side to the visible side). 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. As required, the polarizing plate can also be a polarizing plate with a retardation layer and a retardation layer as shown in FIG. 2 . The polarizing plate 100 with a retardation layer in the illustrated example further has a retardation layer 20 on the opposite side of the polarizing plate 10 from the viewing side. The retardation layer 20 is bonded to the polarizing plate 10 (the second protective layer 13 in the illustrated example) through any appropriate adhesive layer (eg, adhesive layer, adhesive layer; not shown). Optical characteristics (eg, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the retardation layer 20 can be appropriately set according to the purpose. The refractive index characteristic of the retardation layer 20 is represented by a relationship of nx>nz>ny. In the polarizing plate with the retardation layer having the retardation layer, the effect of the embodiment of the present invention can be remarkable. In addition, in this specification, a polarizing plate and a polarizing plate with a retardation layer are collectively referred to as a polarizing plate.

The polarizing plate obtained by the manufacturing method of the embodiment of the present invention has a special shape. In this specification, "having an irregular shape" means that the planar shape of the polarizing plate has a shape other than a rectangle. The special-shaped representative is the special-shaped processing part that has been processed by special-shaped processing. Therefore, "polarizing plate with irregular shape" includes not only the case where the entire polarizing plate (that is, the outer edge that defines the planar shape of the film) is not rectangular, but also includes the case where an irregular shape is formed in the part retreating from the outer edge of the rectangular polarizing plate inward. The case of the processing department. As a deformed shape (different-shaped processed portion), as shown in FIGS. 3 and 4 , for example, chamfered corners, through-holes, and cut-processed portions that become concave portions in plan view can be cited. Typical examples of the recessed portion include a shape similar to a boat shape, a shape similar to a bathtub, a V-shaped notch, and a U-shaped notch. Of course, the shape of the deformed shape (different-shaped processed portion) is not limited to the illustrated example. For example, the shape of the through hole may be any appropriate shape (eg, ellipse, triangle, quadrangle, pentagon, hexagon, octagon) according to the purpose, in addition to the substantially circular shape shown in the drawings. Moreover, the through-hole can be provided in arbitrary appropriate positions according to the purpose. As shown in FIG. 4 , the through hole may be provided in the substantially central portion of the longitudinal end of the rectangular polarizer, may also be provided at a predetermined position of the longitudinal end, or may be provided at the corner of the polarizer; although not shown in the figure Although shown, it may be provided in the width direction edge part of a rectangular polarizing plate. Furthermore, three or more through holes may be formed. Furthermore, the shapes illustrated in the figures may be appropriately combined according to the purpose. For example, through holes can be formed at any position of the special-shaped polarizer shown in FIG. 3 ; V-shaped notch and/or U-shaped notch can be formed at any appropriate position on the outer edge of the special-shaped polarizer shown in FIG. 3 . The special-shaped polarizing plate can be suitably used for image display devices such as instrument panels of automobiles, smart phones, tablet PCs or smart watches.

The polarizing plate can also further include other optical functional layers. The type, characteristic, number, combination, arrangement position, and the like of the optical function layers that can be provided in the polarizing plate 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 (not shown). The conductive layer or the isotropic substrate with the conductive layer means that the top is disposed on the opposite side to the visible side. In the case of providing a conductive layer or an isotropic substrate with a conductive layer, 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 polarizing plate may further include other retardation layers. The optical properties (for example, refractive index properties, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layers can be appropriately set according to the purpose.

In practical terms, the polarizing plate is provided with an adhesive layer (not shown) as the outermost layer on the opposite side to the viewing side, and the polarizing plate can be attached to the image display panel. In addition, a separator (not shown) is temporarily adhered to the surface of the adhesive layer so as to be peelable. By temporarily adhering the separator, the polarizing plate roll can be formed while protecting the adhesive layer. Furthermore, from a practical point of view, the polarizing plate is temporarily attached with a surface protection film on the viewing side, so that scratches and the like can be prevented from occurring during conveyance, conveyance, and/or bonding to an image display panel. The surface protection film has a base film and an adhesive layer on it, and is temporarily adhered to the viewing side surface of the polarizer through the adhesive layer.

Hereinafter, the polarizer, the protective layer, and the retardation layer, which are constituent elements of the polarizing plate, will be described.

A-1. Polarizer The polarizer is represented by a resin film containing a dichroic substance (iodine in the representation). As the resin film, any appropriate resin film that can be used as a polarizer can be used. 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.

As a specific example of the polarizer which consists of a single-layer resin film, the thing which performed the dyeing process with iodine and the stretching process (representatively uniaxial stretching) with respect to a PVA-type resin film is mentioned. The above-mentioned dyeing with iodine can be performed, for example, by immersing a PVA-based film in an aqueous iodine solution. The stretching ratio of the above-mentioned uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment, or may be carried out while dyeing. In addition, dyeing may be performed after stretching. The PVA-based resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based resin film in water and washing it before dyeing, not only the dirt and anti-blocking agent on the surface of the PVA-based film can be removed, but also the PVA-based resin film can be swelled to prevent uneven dyeing.

As a specific example of a polarizer using a laminate, a laminate using a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a coating A polarizer obtained by fabricating a laminate of PVA-based resin layers formed on the resin substrate. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and making it After drying, a PVA-based resin layer is formed on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; the laminate is stretched and dyed to form the PVA-based resin layer into a polarizer. In the present embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The stretching typically includes stretching the layered body by immersing it in an aqueous solution of boric acid. In addition, the stretching may further include in-air stretching of the laminated body at a high temperature (eg, 95° C. or higher) before stretching in a boric acid aqueous solution, if necessary. Furthermore, in the present embodiment, the layered body is preferably subjected to drying shrinkage treatment in which the layered body is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. The production method of the present embodiment typically includes sequentially performing an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment on the laminate. By introducing auxiliary stretching, even when PVA is coated on a thermoplastic resin, the crystallinity of PVA can be improved, and high optical properties can be achieved. In addition, by increasing the orientation of PVA in advance, problems such as lowering of orientation or dissolution of PVA can be prevented when immersed in water in the subsequent dyeing step or stretching step, and high optical properties can be achieved. In addition, 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 orientation disorder of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed. Thereby, the optical characteristics of the polarizer obtained by the process of immersing a laminated body in liquid, such as a dyeing process and an underwater stretching process, can be improved. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by the drying shrinkage treatment. The obtained laminate of resin substrate/polarizer can be used as it is (that is, the resin substrate can be used as a protective layer of the polarizer), or the resin substrate can be peeled off from the laminate of resin substrate/polarizer, and used in the laminate. Any appropriate protective layer suitable for the purpose is laminated and used on the peeling surface. The details of the manufacturing method of the polarizer are described in, for example, Japanese Patent Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. In the present specification, the entire contents of the publications are incorporated by reference.

The thickness of the polarizer is, for example, 1 μm to 30 μm, or, for example, 3 μm to 20 μm.

The polarizer should exhibit absorption dichroism at any wavelength from 380nm to 780nm. The single transmittance of the polarizer should be 41.5%~46.0%, preferably 43.0%~46.0%, and more preferably 44.5%~46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, preferably 99.0% or more, and more preferably 99.9% or more.

A-2. Protective layer The first protective layer 12 and the second protective layer 13 are each formed of any appropriate thin film that can be used as a protective layer of a polarizer. Specific examples of the material used as the main component of the film include cellulose-based resins such as triacetate cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyamide-based Transparent resins such as imine-based, polyether-based, poly-based, polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based. Moreover, (meth)acrylic type, urethane type, (meth)acrylate urethane type, epoxy type, polysiloxane type|system|group thermosetting resin, ultraviolet-curable resin, etc. are mentioned. Moreover, glass-type polymers, such as a siloxane-type polymer, are mentioned, for example. Moreover, the polymer film described in Unexamined-Japanese-Patent No. 2001-343529 (WO01/37007) can also be used. As the material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a 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, the resin composition which has an alternating copolymer which consists of isobutylene and N-methylmaleimide, and an acrylonitrile-styrene copolymer is mentioned. The polymer film may be, for example, an extruded product of the above-mentioned resin composition. A (meth)acrylic resin can be used suitably.

The Tg (glass transition temperature) of the (meth)acrylic resin is preferably 115°C or higher, more preferably 120°C or higher, more preferably 125°C or higher, and particularly preferably 130°C or higher. This is because durability can be excellent. The upper limit value of Tg of the (meth)acrylic resin is particularly limited, but from the viewpoint of moldability and the like, it is preferably 170° C. or lower.

As the (meth)acrylic resin, from the viewpoint of having high heat resistance, high transparency, and high mechanical strength, a (meth)acrylic resin having a lactone ring structure is particularly suitable. Examples of (meth)acrylic resins having a lactone ring structure include Japanese Patent Laid-Open No. 2000-230016, Japanese Patent Laid-Open No. 2001-151814, Japanese Patent Laid-Open No. 2002-120326, and Japanese Patent Laid-Open No. 2002-120326. The (meth)acrylic resin having a lactone ring structure is described in Japanese Patent Laid-Open No. 2002-254544, Japanese Patent Laid-Open No. 2005-146084 and the like.

The polarizing plate means that the top is arranged on the viewing side of the image display device, and the first protective layer 12 is arranged on the viewing side. Therefore, surface treatments such as hard coating treatment, anti-reflection treatment, anti-stick treatment, and anti-glare treatment may be performed on the first protective layer 12 as necessary.

The thickness of the first protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and more preferably 30 μm to 60 μm. In addition, when the surface treatment is performed on the 1st protective layer to form the surface treatment layer, the thickness of the first protective layer is the thickness including the surface treatment layer.

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 thickness direction retardation Rth(550) is -10 nm to +10 nm. The thickness of the second protective layer is preferably 5 μm to 80 μm, preferably 10 μm to 60 μm, and more preferably 15 μm to 45 μm.

A-3. Retardation layer As described above, the refractive index characteristic of the retardation layer represents the relationship of nx>nz>ny (hereinafter, the retardation layer or retardation film may be referred to as a Z film). By making the retardation layer have the above-mentioned refractive index characteristic, the oblique hue of the image display device to which the polarizing plate with the retardation layer is applied can be well improved. In addition, the improvement of the oblique hue can be performed without additionally providing a retardation layer and a layer for oblique optical compensation, so it can contribute to the thinning of the polarizing plate with the retardation layer (in the result, an image display device). change. Further, the retardation layer (retardation film) is prone to cracks, but according to the embodiment of the present invention, even when the retardation layer is deformed, cracks in the deformed portion can be significantly suppressed.

The Nz coefficient of the retardation layer is preferably 0.3~0.7, more preferably 0.4~0.6, and more preferably 0.45~0.55. If the Nz coefficient is within the above range, the oblique hue can be improved more favorably.

The in-plane retardation Re(550) of the retardation layer is preferably 250 nm to 350 nm, more preferably 260 nm to 330 nm, and more preferably 270 nm to 290 nm. If the in-plane retardation Re(550) of the retardation layer is within the above range, because the moving distance on the Bonga sphere is short, excellent hue and luminance characteristics can be achieved, and the color shift of the image display panel can be reduced by The shift due to the phase difference component of the TFT is also reduced.

The retardation layer can display the inverse dispersion wavelength characteristic in which the retardation value increases with the wavelength of the measurement light, and the positive wavelength dispersion characteristic in which the retardation value becomes smaller with the wavelength of the measurement light. Flat wavelength dispersion characteristic of light wavelength changes. The retardation layer exhibits flat wavelength dispersion characteristics on the representative.

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 may be, for example, 1.0×10 ⁻¹² m ² /N. When the absolute value of the photoelastic coefficient of the retardation layer is within the above-mentioned range, display unevenness of the image display device can be suppressed favorably.

The retardation layer is typically a retardation film formed of any appropriate resin that can achieve the above-mentioned properties. Examples of resins that form the retardation film include cyclic olefin resins, polyarylate, polyamide, polyimide, polyester, polyaryletherketone, polyamideimide, polyester Imide, polyvinyl alcohol, polyfumarate, polyether dust, poly dust, polycarbonate resin, cellulose resin and polyurethane. These resins may be used alone or in combination. Preferably, it is a cyclic olefin resin. Typical examples of cyclic olefin-based resins include norbornene-based resins.

The above-mentioned norbornene-based resin is a resin obtained by polymerizing a norbornene-based monomer as a polymerized unit. As the norbornene-based monomer, for example, norbornene and its alkyl and/or alkylene substituted products, for example, 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, can be mentioned. Camphene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, etc., and their halogen and other polar substituents; bicyclic Pentadiene, 2,3-dihydrodicyclopentadiene, etc; ,4:5,8-dimethylbridge-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethylbridge-1, 4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethylene-1,4:5,8-dimethylbridge-1,4,4a,5,6,7,8, 8a-octahydronaphthalene, 6-chloro-1,4:5,8-dimethylbridge-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4 :5,8-Dimethylbridge-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethylbridge-1,4, 4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethylbridge-1,4,4a,5,6,7,8,8a -Octahydronaphthalene, etc; -1H-benzoindene, 4,11:5,10:6,9-trimethyl bridge-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecahydro- 1H-cyclopentanthracene, etc. The above-mentioned norbornene-based resin may be a copolymer of a norbornene-based monomer and another monomer.

The retardation layer (retardation film) is a stretched film of the film formed of the above-mentioned resin. Any appropriate method can be adopted as a method of producing the stretched film. Representatively, there is a method of laminating a shrinkable film on one side or both sides of a resin film and heat-stretching. This shrinkable film is used to impart a shrinking force in a direction orthogonal to the extending direction during heating and stretching. By imparting the shrinkage force, nz can be increased, and as a result, a Z film can be produced. As a material for a shrinkable film, polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, etc. are mentioned, for example. In view of excellent shrinkage uniformity and heat resistance, a polypropylene film is preferably used.

As the stretching method, any appropriate stretching method can be adopted as long as tension can be imparted to the stretching direction of the resin film and a shrinking force can be imparted to the stretching direction in the direction perpendicular to the plane of the film. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the above-mentioned resin film. This is because the retardation value of the obtained stretched film tends to become uniform, and the film is less likely to be crystallized (cloudy). The extension temperature is preferably Tg+1°C~Tg+30°C of the above polymer film, more preferably Tg+2°C~Tg+20°C, especially Tg+3°C~Tg+15°C, most preferably Tg +5℃~Tg+10℃. By setting the stretching temperature in the above-mentioned range, uniform heating and stretching can be performed. Also, the stretching temperature is preferably constant in the film width direction. This is because a stretched film with good optical uniformity with small variation in retardation value can be produced.

The stretching ratio in the above stretching can be set to any appropriate value. It should be 1.05~2.00 times, more preferably 1.10~1.50 times, especially 1.20~1.40 times. By making the draw ratio into the above-mentioned range, a drawn film having little shrinkage of the film width and excellent mechanical strength can be obtained.

The thickness of the retardation layer is preferably 80 μm to 200 μm, preferably 90 μm to 150 μm, and more preferably 110 μm to 150 μm. With the thickness described above, a desired in-plane retardation value can be obtained.

B. Manufacturing method of polarizing plate with special shape As described above, the manufacturing method of a polarizing plate with a special shape according to an embodiment of the present invention includes the following steps: forming a polarizing plate with a special shape by laser irradiation; and cutting the polarizing plate with a special shape by laser irradiation into individual pieces flaky. Hereinafter, each step will be described.

B-1. Formation of Alien First, a special shape is formed on a polarizing plate by laser irradiation. The polarizing plate can be a raw plate roll material, or an intermediate body cut to a predetermined size. The intermediate body may have a size that can cut the final polarizing plate into only one piece, or a size that can be cut into a plurality of predetermined pieces (for example, two pieces, three pieces, four pieces, five pieces, six pieces). In the embodiment of the present invention, an intermediate body that can cut the final polarizing plate into two or three pieces can be used. Hereinafter, as an example, the manufacturing method of the polarizing plate which formed the chamfered shape of a corner part, the recessed part and the U-shaped notch in the shape of a bathtub in plan view as a special shape is demonstrated concretely.

Fig. 5(a) is a schematic plan view for explaining the deforming process in the manufacturing method according to the embodiment of the present invention. As shown in FIG. 5( a ), a special shape is formed on the polarizing plate. As mentioned above, the formation of the irregular shape is performed by laser irradiation. The special shape is formed by laser irradiation, so that it can be punched into a single sheet after the special shape is formed. As a result, cracks in the deformed portion can be suppressed. The laser irradiation can be performed under any appropriate conditions as long as the irregular shape can be formed. Hereinafter, the details of the laser irradiation will be described.

As the laser light source, an infrared laser including a CO ₂ laser light source with a wavelength of 9 μm to 11 μm in which the wavelength of laser light excited by oscillation is in the infrared region can be used. The laser light source can achieve high productivity. Infrared lasers can easily obtain tens of W-level power, and by using molecular vibrations accompanying infrared absorption to efficiently heat the polarizer, it can induce etching accompanied by phase transition of substances.

As the laser light source, a CO laser light source in which the wavelength of laser light excited by oscillation is about 5 μm can be used. In addition, as the laser light source, near-infrared (NIR), visible (Vis), and ultraviolet (UV) pulsed laser light sources can be used. As the NIR, Vis and UV pulsed laser light sources, the wavelengths of laser light excited by oscillation are 1064 nm, 532 nm, 355 nm, 349 nm or 266 nm (solid-state laser light sources with Nd:YAG, Nd:YLF, or YVO ₄ as the medium) can be exemplified. High-order harmonics) laser light source, excimer laser light source with laser light wavelength of 351nm, 248nm, 222nm, 193nm or 157nm excited by oscillation, F2 laser light source of laser light excited by oscillation with wavelength of 157nm.

As the oscillation form of the laser light source, from the viewpoint of suppressing heat loss of 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, preferably 10 kHz to 500 kHz. It is also possible to set two or more pulse widths for processing.

There is no limitation on the polarization state of the laser light. Specifically, any of linear polarization, circular polarization, and random polarization can be applied. There is also no limit to the spatial intensity distribution of the laser light. The laser light is preferably a Gaussian beam. This is because it exhibits good condensing properties, can be reduced in size, and can be expected to improve productivity. The laser light can be shaped into a flat-top beam using a diffractive optical element or an aspheric lens according to the purpose.

The number of times of irradiation of the laser light can be appropriately set according to the purpose. If it can be cut and processed into a desired shape, the laser light can be irradiated only once along the target shape, or a desired cutting depth can be achieved by irradiating it multiple times. In the case of irradiating the laser light a plurality of times, the conditions for each time may be the same or different.

The scanning form of the laser light 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, and combinations thereof (multi-axis synchronous control). By appropriately selecting and/or combining these, the relative position of the workpiece (polarizing plate) and the laser light can be changed at a predetermined speed. In addition, it can be processed into a desired shape by controlling on/off of the laser irradiation using a mechanical shutter, an AOM (acoustic optical element), or the like. The scanning speed of the laser light can be appropriately set according to the purpose (for example, the desired cutting depth).

The condensing spot diameter (resulting in the cutting width) of the laser light 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 light with an objective lens such as an Fθ lens, for example. With the above configuration, processing efficiency can be improved, and thermal damage can be suppressed. The condensing spot diameter is preferably 500 μm or less, more preferably 300 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less. The condensing spot diameter can be defined as, for example, the diameter of the laser beam at the position at which the intensity attenuates to 1/e ² compared to the peak intensity value. In addition, in the case of using a galvanometer-type scanner, it is preferable to use a telecentric Fθ lens in order to vertically epi-laser the workpiece (polarizing plate). Furthermore, in order to obtain a desired condensing spot diameter (resulting in a cut width), a beam expander for adjusting the beam diameter may be used between the optical path from the output end of the laser oscillator to the objective lens.

The laser output can be appropriately set according to the thickness or shape of the polarizing plate to be processed. For example, in the case of using a CO ₂ laser as the laser light source, the output should be 5W~300W, more preferably 20W~200W.

Laser irradiation can also use two or more types of lasers. At this time, two or more types of lasers may be irradiated at the same time, or may be irradiated sequentially.

The order in which the irregularities are formed is not particularly limited. For example, a tub-shaped recess and a U-shaped notch may be sequentially formed after the corners are chamfered; and, for example, a U-shaped notch and a tub-shaped recess may be sequentially formed after the corners are chamfered; In addition, for example, the corners may be chamfered after the tub-shaped recesses and the U-shaped notch are formed in this order; for example, the corners may be removed after the U-shaped notch and the tub-shaped recesses are formed in this order. Also, for example, a special shape may be formed along the outer circumference of the polarizing plate (for example, chamfering of the upper right corner, formation of a tub-shaped recess, chamfering of the upper left corner, chamfering of the lower left corner, and chamfering of the U-shaped notch can be performed in sequence. forming and chamfering the lower right corner). In the case of forming a special shape along the outer periphery of the polarizing plate, its starting position can be set to any appropriate position. Specifically, the starting position may be any one of the upper right corner, the lower right corner, the upper left corner, or the lower left corner, the position where the tub-shaped recess is formed, the position where the U-shaped notch is formed, or the long side or Any position on the straight portion of the short side. In the case of forming the irregular shape along the outer periphery of the polarizing plate, the irregular shape may be formed clockwise, or may be formed counterclockwise as shown in the example of the figure.

In one embodiment, the laser irradiation may be performed from immediately before the profile to be formed, and/or to a predetermined position following the profile (the end of the profile). In this specification, the laser irradiation from the immediate front of the abnormal shape and/or the laser irradiation to the end of the abnormal shape is referred to as "overtravel of laser irradiation". In terms of the amount of overrun, the near front side and the rear side should be respectively 0.5mm~50mm, more preferably 0.5mm~5mm, and more preferably 1mm~3mm. By performing the overrun within the above-mentioned range, cracks in the deformed part can be suppressed favorably. The overrun should be provided at least on the trailing side.

B-2. Single-piece cutting The polarizing plate in which the irregular shape was formed as described in the above-mentioned item B-1 was cut into a single sheet. The cutting of the single-piece shape is also performed by laser irradiation in the same manner as the formation of the irregular shape. The single-piece cutting is performed by laser irradiation, and even a polarizing plate with a complicated shape (especially a small abnormal shape) can be cut well. Laser irradiation can be performed under any appropriate conditions as long as the polarizing plate can be cut into individual pieces. The details of the laser irradiation in the single-piece cutting are as described in relation to the above-mentioned formation of the abnormal shape. The laser irradiation in the single-piece cutting may be performed under the same conditions as the above-mentioned irregular shape formation, or may be performed under different conditions.

As shown in FIG. 5( b ), the cutting can be performed by linear laser irradiation on the representative. The stress remaining in the deformed part can be reduced by irradiating a laser in a straight line and cutting after the deforming process. As a result, cracks in the deformed portion can be suppressed. Referring to FIG. 6 , an inference mechanism for obtaining the effect will be described. As shown in the lower side of FIG. 6 , when deformed processing is performed after cutting into individual pieces, the processed end portion where most of the stress remains in the deformed processing portion is included in the final polarizing plate. As a result, it is presumed that the residual stress at the machined end causes cracks in the deformed portion. The same applies to the case where linear processing and irregular-shaped processing are performed continuously along the outer periphery of the polarizing plate (that is, in a so-called non-interrupted point method). At this time, the processed end part where most of the stress remains in the deformed processed part is also in a state of being included in the final polarizing plate. On the other hand, as shown in the upper side of FIG. 6 , according to the embodiment of the present invention, by cutting the polarizing plate into a single piece by cutting after the deforming process is performed, it is possible to cut off large residues in the deformed part. Partially stressed machined ends. As a result, the residual stress is small in the deformed portion of the final polarizing plate, so it is presumed that the occurrence and progression of cracks due to the residual stress are suppressed.

During cutting, an overrun may be set before and/or at the end of the linear processing portion. By setting the overrun, the cut start point and cut end point are not included in the final polarizer. As a result, shape anomalies caused by over-irradiation at the start and/or end points can be avoided. In terms of the amount of overrun, it should be 0.5mm~50mm on the near front side and the end side, and more preferably 0.5mm~2.5mm. In the example shown in FIG. 5( b ), the overruns are set at the front and the end of the linear processing portion for all the four-side linear processing, 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 can be set by continuously irradiating (cutting) the laser along the rectangular shape before chamfering the corners (that is, there may be no intersection point of the overrun); for example, the overrun can be set by One, two or three of the four corners are continuously laser irradiated (cut) along the rectangular shape before chamfering to set the overrun, and the remaining corners are as shown in Figure 5(b). ) to set the overtravel.

Cutting means that the above is performed at an interval of a predetermined time or more from the formation of the abnormal shape. By providing the space, residual stress caused by profile processing can be relieved. Therefore, the 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 more preferably 5 seconds or more. Even if the interval is excessively lengthened, the effect does not change, so the upper limit of the interval can be determined in consideration of a balance with the manufacturing efficiency of the polarizing plate. The upper limit of the interval may be, for example, 60 seconds.

In addition, although the case where an irregular shape becomes a recessed part in plan view has been described as an example, the embodiment of the present invention can be similarly applied to the formation of a through hole, for example, and the same effect can be obtained. That is, even in the case of forming the through hole, by performing cutting by straight-line processing after the through hole is formed, 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.

According to the above method, a polarizing plate with a special shape can be produced.

Example Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.

(1) The thickness of 10 μm or less was measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name “MCPD-3000”). Thickness factors exceeding 10 μm were measured using a digital micrometer (manufactured by Anritsu, product name “KC-351C”). (2) Phase Difference Change With respect to the polarizing plates used in the Examples and Comparative Examples, the in-plane retardation was measured using a phase difference measuring apparatus (product name "WPA-KAMAKIRI") manufactured by Photron Co., Ltd. The measurement wavelength of the in-plane retardation was 540 nm, and the measurement temperature was 23°C. Let this be the initial phase difference Re ₀ . Next, the polarizing plate was left to stand in an environment of 95° C. for 12 hours to be heated, and the in-plane retardation after heating was measured in the same manner as described above. Let it be the phase difference Re ₁₂ . The amount of change in the in-plane phase difference before and after heating was calculated from the following equation. In-plane retardation change amount ΔRe=Re ₁₂ −Re ₀ (3) Cracks The polarizing plates obtained in Examples and Comparative Examples were left in an environment of 95° C., and the time until cracks occurred in the vicinity of the deformed part was investigated.

[Example 1] 1. Production of polarizers The polyvinyl alcohol film having a thickness of 45 μm was dyed in an iodine solution with a concentration of 0.3% at 30° C. for 1 minute between rolls with different speed ratios and stretched to 3 times. Then, it was stretched to a total draw ratio of 6 times while being immersed in an aqueous solution containing boric acid at a concentration of 4% and potassium iodide at a concentration of 10% for 0.5 minutes at 60°C. Next, it was rinsed by immersion in an aqueous solution containing potassium iodide having a concentration of 1.5% 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.

2. Production of polarizing plate A HC-TAC film (thickness 49 μm) was bonded to one surface of the polarizer obtained above using a polyvinyl alcohol-based adhesive. In addition, the HC-TAC film is a film in which a hard coat (HC) layer (thickness 9 μm) is formed on a triacetate cellulose (TAC) film (thickness 40 μm), and the TAC film is bonded so that it becomes the polarizer side . In addition, an acrylic resin film (thickness 30 μm) was bonded to the other surface of the polarizer in the same manner as described above. In the above-described manner, a polarizing plate having a configuration of protective layer (HC-TAC film)/polarizer/protective layer (acrylic resin film) was obtained.

3. Production of polarizing plate with retardation layer A shrinkable film with a thickness of 60 μm is pasted on both sides of a norbornene-based resin film with a thickness of 130 μm through an acrylic adhesive layer (thickness 15 μm). BO2873”]. Then, the film was stretched to 1.38 times in an air circulation oven at 146°C while maintaining the longitudinal direction of the film with a roll stretching machine. After stretching, the shrinkable film and the acrylic adhesive layer were peeled off together to obtain a retardation film. The obtained retardation film shows the refractive index characteristic of nx>nz>ny, Re(550)=280nm, Nz coefficient=0.52, photoelastic coefficient is 4.0×10 ^-12 m ² /N, and thickness is 138 μm. This retardation film was bonded to 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 are bonded together so that the absorption axis of the polarizer and the slow axis of the retardation layer are substantially orthogonal to each other. Finally, a surface protection film is temporarily attached to the surface of the HC layer, an adhesive layer is provided on the surface of the retardation layer, and a separator is temporarily attached to the adhesive layer to obtain a surface protection film/protective layer (HC-TAC film) )/polarizer/protective layer (acrylic resin film)/retardation layer/adhesive layer/separator with a polarizing plate with retardation layer (hereinafter referred to as polarizing plate).

4. Special-shaped processing and single-piece cutting The polarizing plate obtained in the above 3. was irradiated with a laser to form a special shape as shown in Fig. 5(a). Specifically, after forming a tub-shaped recess and a U-shaped notch in this order, four corners were chamfered. The conditions of the laser irradiation were an output of 33W, a scan speed of 400mm/min, and an overtravel amount (both sides before and at the end) of 1mm. Next, as shown in FIG.5(b), laser irradiation was performed linearly, and the polarizing plate was cut|disconnected to the size of 200mm*67mm. The laser irradiation was carried out under the same conditions as the above-mentioned formation of the abnormal shape. Here, it cut|disconnected so that the absorption axis of a polarizer might become a longitudinal direction. In addition, the cutting was performed at intervals of 5 seconds from the formation of the abnormal shape (that is, the cutting was started 5 seconds after the completion of the abnormal shape processing). In the above-described manner, a polarizing plate having a special shape was obtained. The obtained polarizing plate was used for the evaluation of the above-mentioned (2) and (3). The results are shown in Table 1.

[Comparative Example 1] A polarizing plate with a special shape was produced in the same manner as in Example 1, except that the order of forming and cutting the abnormal shape was reversed, that is, after cutting the polarizing plate to the same size as Example 1 to form the abnormal shape. The formation of the abnormal shape is carried out at a 5-second interval from the time of cutting. The obtained polarizing plate was used for the same evaluation as in Example 1. The results are shown in Table 1.

[Comparative Example 2] A polarizing plate having a special shape was produced in the same manner as in Example 1, except that the cutting and deforming were performed continuously along the outer periphery of the polarizing plate (ie, in a so-called uninterrupted point mode). More specifically, laser irradiation was continuously performed counterclockwise from the chamfered corner of the upper right corner, and a polarizing plate as shown in FIG. 5( a ) and FIG. 5( b ) was obtained. The obtained polarizing plate was used for the same evaluation as in Example 1. The results are shown in Table 1.

[Table 1]

[Evaluate] As can be seen from Table 1, the polarizing plate of the example of the present invention has a small change in retardation under a high temperature environment, and the time until a crack occurs in the vicinity of the deformed part is significantly longer than that of the comparative example. In addition, in the polarizing plate of the comparative example, it was confirmed that the retardation layer was significantly cracked at the tip portion of the U-shaped notch. That is, it can be seen that the polarizing plate of the example of the present invention can suppress cracks in the deformed part.

industrial availability The polarizing plate of the present invention can be suitably used for image display devices such as liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

10: Polarizer 11: Polarizer 12: 1st layer of protection 13: 2nd layer of protection 20: retardation layer 100: Polarizing plate with retardation layer

FIG. 1 is a schematic cross-sectional view illustrating an example of a polarizing plate that can be used in a manufacturing method according to an embodiment of the present invention. 2 is a schematic cross-sectional view illustrating another example of a polarizing plate that can be used in the manufacturing method of the embodiment of the present invention. 3 is a schematic plan view illustrating an example of a deformed or deformed portion in a polarizing plate obtained by the manufacturing method of the embodiment of the present invention. 4 is a schematic plan view illustrating a modified example of a deformed or deformed portion in a polarizing plate obtained by the manufacturing method of the embodiment of the present invention. In Fig. 5, Fig. 5(a) and Fig. 5(b) are schematic plan views for explaining the details of the special-shaped processing and the single-piece cutting in the manufacturing method according to the embodiment of the present invention, respectively. FIG. 6 is a conceptual diagram illustrating the mechanism of the effect obtained by the embodiment of the present invention.

Claims (8)

A manufacturing method of a polarizing plate with a special shape, comprising the following steps: Shaped by laser irradiation on the polarizing plate; and The polarizing plate formed with the irregular shape is cut into individual pieces by laser irradiation. The manufacturing method of the polarizing plate with a special shape according to claim 1, which comprises cutting the polarizing plate formed with the special shape into a single piece by irradiating a linear laser. The manufacturing method of the polarizing plate having an irregular shape according to claim 1 or 2, wherein the irregular shape is a shape of a concave portion in a plan view. The method for manufacturing a polarizing plate with an irregular shape according to claim 3, wherein the aforementioned irregular shape is a U-shaped notch or a V-shaped notch. The method for manufacturing a polarizing plate with a special shape according to claim 1 or 2, wherein the laser irradiation includes an overshoot, and the overshoot is 0.5 mm to 50 mm. The manufacturing method of the polarizing plate having an irregular shape according to claim 1 or 2, wherein the formation of the irregular shape and the cutting of the single sheet shape are performed at an interval of 1 second or more. The manufacturing method of the polarizing plate with irregular shape according to claim 1 or 2, wherein the polarizing plate further has a retardation layer. The method for producing a polarizing plate with an irregular shape according to claim 7, wherein the retardation layer comprises a cyclic olefin-based resin, and exhibits a refractive index characteristic of nx>nz>ny, its Nz coefficient is 0.3-0.7, and its in-plane The retardation Re(550) is 250 nm to 350 nm.

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