TW202108269A - Polarizing plate - Google Patents

Abstract

This invention provides a polarizing plate capable of suppressing cracks in recesses or through holes even having a protective film made of cycloolefin resin.

A polarizing plate 1 according to this invention is formed by sandwiching a film-shaped polarizer 7 with a pair of optical films 5, 9, and at least one optical film is a protective film made of cycloolefin resin. The polarizing plate 1 is provided with a recess 2 on an outer periphery in a plan view, and in the side view, an end portion 7e of the polarizer 7 is located 15 μm to 56 μm inside the end portion of any of the pair of optical films 5 and 9 in the recess 2, and the end portion 7e of the polarizer 7 is exposed so as to come into contact with the outside air.

Description

Polarizing plate

The present invention relates to a polarizing plate, and also to a manufacturing method of the polarizing plate.

Polarizers are used in image display devices such as LCD TVs, organic EL TVs, smart phones, smart watches, or mileage panels of automobiles or locomotives. The polarizing plate is provided with a film-shaped polarizer and an optical film (such as a protective film) superimposed on the polarizer. Due to the design of the image display device, a concave portion may be formed on the outer periphery of the polarizing plate.

For example, in Patent Document 1 below, it is described that a concave portion (notch portion) is formed on the outer periphery of a polarizing plate as an injection port for liquid crystal.

[Prior Technical Literature]

[Patent Literature]

[Patent Document 1] JP 2000-155325 A

The polarizing plate expands or contracts with changes in humidity or temperature. The stress accompanying the expansion or contraction of the polarizing plate tends to concentrate on the concave portion, and cracks (cracks) may occur in the polarizer in the concave portion.

In addition, when a cycloolefin resin is used as a protective film, if an inorganic glass plate is laminated on the polarizing plate via an adhesive, it may be affected by the compound containing a relatively long-chain alkyl group contained in the adhesive. Affected and cracked in the protective film.

This phenomenon can be seen not only when the recess is formed, but also when the through hole is formed.

The present invention has been made in view of the foregoing, and its object is to provide a polarizing plate and a method for manufacturing the polarizing plate, which can suppress recesses or through holes even if the polarizing plate is provided with a protective film made of cycloolefin resin In the rupture.

The present invention provides a polarizing plate, which is provided with a film-like polarizer and at least a pair of optical films containing resin, wherein the polarizer is located between the pair of optical films and overlaps the pair of optical films , Among the pair of optical films, at least one of the optical films is a protective film to protect the polarizer. The protective film is made of cycloolefin resin. In a plan view, there is a concave portion on the outer periphery or a through hole in the surface. The hole, in a side view, the end of the polarizer in the recess or the through hole is 15 μm to 56 μm more inside than the end of any one of the pair of optical films, and the end of the polarizer The part is exposed by contact with outside air.

In this polarizing plate, the end of the polarizer is 15 μm or more inside the end of the optical film in the recess or the through hole, so after the thermal shock test, the polarizer will not crack or even The generation also becomes the one with the shorter length of rupture. Moreover, in this polarizing plate, the distance between the position where the end of the polarizer is more recessed than the end of the optical film in the recess or the through hole is 56 μm or less. The adhesive used has a small contact area with the protective film made of cycloolefin resin, so it is difficult to cause cracks in the protective film.

In the polarizing plate, the polarizing plate may be formed by adsorbing and oriented dichroic dye on the stretched polyvinyl alcohol-based resin film.

In this polarizing plate, an adhesive (pressure-sensitive adhesive, also known as pressure-sensitive adhesive or pressure-sensitive adhesive) layer may be further provided on the side opposite to the side with the protective film.

In the polarizing plate, any one of the pair of optical film systems can be a protective film.

In this polarizing plate, in a side view, the difference in the positions of the ends of the pair of optical films in the recesses or in the through holes may be within 20 μm.

In addition, the present invention provides an image display device including the above-mentioned polarizing plate.

In addition, the present invention provides a method of manufacturing the above-mentioned polarizing plate. In other words, the present invention provides a method of manufacturing a polarizing plate, which has a cutting step of contacting a rotating cutting tool to make a film-like polarizer overlap at least a pair of optical films to form a laminated body On the side surface, one side allows the rotary cutting tool to move along the side surface of the laminated body; in the top view, the laminated system is provided with a recess on the outer periphery or a through hole in the surface. Among a pair of optical films, at least one of the optical films In order to protect the protective film of the polarizer, the protective film is made of cycloolefin resin. In the cutting step, when cutting in the recess or in the through hole, the rotation speed of the rotary cutting tool is set to 20,000 to 35,000 rpm. The feed rate is set to 0.42 to 0.60m/min, and the relationship between the direction of rotation of the rotary cutting tool and the direction of feed is set to up-cut (also known as up-cut), and the rotary cutting tool It enters in a direction perpendicular to the absorption axis of the polarizer and moves in a parallel direction.

In this manufacturing method, the rotation speed of the rotary cutting tool can be set to 25000 to 32000 rpm, and the feed rate can be set to 0.45 to 0.50 m/min.

According to the present invention, it is possible to provide a polarizing plate and a method for manufacturing the polarizing plate, which can suppress cracks in recesses or through holes even if the polarizing plate includes a protective film made of cycloolefin resin.

1: Polarizing plate

1A: Polarizing plate

1p: Polarizing plate outer circumference, outer circumference

2: recess

2c: corners and corners of recesses

2A: Through hole

3: The absorption axis and absorption axis of the polarizer

4: Recessed area

4w: width, width and distance of recessed area

5: The first optical film, protective film, optical film

7: Polarizer

7e: The end and the end of the polarizer

9: The second optical film, optical film

10,10’: The first layered body

50: end mill

50a: Rotation axis and rotation axis of end mill

50e: blade and blade of end mill

100: The second layered body

d1: The direction and direction of the extension of the side edge of the end mill

d2: The direction and direction perpendicular to the axis of rotation of the end mill

α: Torsion angle and torsion angle of end mill

β: cutting angle

FIG. 1 is a schematic diagram showing the surface (light-receiving surface) of a polarizing plate according to an embodiment of the present invention.

Fig. 2 is a cross-sectional view of the polarizing plate of Fig. 1 taken along II-II.

Fig. 3 is an exploded perspective view of a laminate formed in a method of manufacturing a polarizing plate according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of an end mill used in a method of manufacturing a polarizing plate according to an embodiment of the present invention, and a laminated body cut by the end mill.

Fig. 5 is a diagram showing the moving path of the end mill in the method of manufacturing a polarizing plate according to an embodiment of the present invention.

6 is a schematic diagram showing the surface (light-receiving surface) of a polarizing plate according to another embodiment of the present invention.

Hereinafter, while referring to the drawings, suitable embodiments of the present invention will be described. In the drawings, equivalent components are given equivalent symbols. The present invention is not limited by the following embodiments. X, Y, and Z shown in each figure mean 3 coordinate axes orthogonal to each other. The directions indicated by the XYZ coordinate axes in each figure are the same in each figure.

(Polarizer)

Fig. 1 shows the surface (light-receiving surface) of the polarizing plate 1 of this embodiment. The cross section of the polarizing plate 1 shown in FIG. 2 is perpendicular to the surface (light-receiving surface) of the polarizing plate 1 and perpendicular to the outer circumference 1p of the polarizing plate 1 located inside the recess 2.

As shown in Figures 1 and 2, the polarizing plate 1 of this embodiment has a rectangular shape and is equipped with at least one pair of optical films (5, 9) and a pair of optical films (5, 9). Film-shaped polarizer 7. In the following, for the convenience of description, the polarizer 1 composed of a polarizer 7 and a pair of optical films (5, 9) will be mainly described.

The term "optical film" means a film-like member constituting the polarizing plate 1 (except for the polarizing plate 7 itself). For example, the optical film system means to include a protective film and a release film. The individual optical films may not have specific optical functions individually. "Film" (optical film) can also be renamed "layer" (optical layer). The pair of optical films (5, 9) each contain resin. However, the composition of each of the optical films (5, 9) is not limited.

The polarizer 7 and the optical films (5, 9) overlap directly or indirectly, respectively. For example, there may be another optical film between the polarizer 7 and the optical film (5, 9). The polarizer 7 may be overlapped with the optical films (5, 9) via the adhesive layer.

As shown in FIG. 1, a concave portion 2 is formed on the outer circumference 1p of the polarizing plate 1. The recess 2 can also be renamed as a depression, a cutout or a notch. The recess 2 can penetrate the polarizing plate 1 in a direction (Z-axis direction) perpendicular to the surface (light-receiving surface) of the polarizing plate 1. The so-called outer periphery 1p of the polarizing plate 1 can also be changed to the outer edge or contour of the polarizing plate 1 (light-receiving surface) viewed from a direction perpendicular to the light-receiving surface of the polarizing plate 1.

The recessed portion 2 is preferably provided in the substantially rectangular side constituting the polarizer 1 and the side extending in a direction slightly perpendicular to the direction of the absorption axis 3 of the polarizer. With respect to FIG. 1, with respect to the absorption axis extending in the vertical direction in the figure, a recess 2 is formed in the upper side extending in the left-right direction in the figure.

A part or the whole of the end portion 7e of the polarizer 7 along the recess 2 is located inside the outer periphery 1p of the polarizer 1. That is, the polarizing plate 1 has at its outer edge a recessed area 4 in which the end 7e of the polarizer 7 is recessed more inwardly than the end of the pair of optical films (5, 9). Thus, there are two types of outer circumference 1p of the polarizing plate 1, and the two types of outer circumference 1p are respectively formed by the ends of a pair of optical films (5, 9). That is, the outer periphery 1p exists on the surface (light-receiving surface) of the polarizing plate 1 and the back surface, respectively. Figures 1 and 2 show a situation where the positions of the ends of a pair of optical films (5, 9) are the same in side view. At this time, the outer periphery 1p of the polarizing plate 1 and the end of each of the pair of optical films (5, 9) have substantially the same meaning.

The distance 4w that the end 7e of the polarizer 7 retreats toward the central part of the polarizer 1, that is, the width 4w of the recessed area 4 is 15 μm to 56 μm . The distance 4w may be 25 μm to 55 μm , may be 30 μm to 50 μm , or 35 μm to 45 μm . In addition, the above-mentioned range may be satisfied to cover the entire outer periphery 1p of the polarizing plate 1, or may be satisfied only in the recessed portion 2.

In the recessed area 4, the end 7e of the polarizer 7 is exposed so as to contact the outside air. Preferably, in the recessed area 4, the pair of optical films (5, 9) are not in contact with each other, at least not so that the pair of optical films (5, 9) are in contact with each other in the entire outer periphery of the polarizing plate 1. The state where the polarizer 7 is enclosed, and the passage for the end 7e of the polarizer 7 to contact the outside air is ensured.

In the polarizing plate, in general, the polarizer 7 and the optical films (5, 9) have different shrinkage rates or expansion rates due to changes in humidity or temperature. Therefore, with changes in humidity or temperature, stress tends to be concentrated in the recesses 2 exposed at the ends of each of the polarizer 7 and the optical films (5, 9), and cracks (cracks) due to stress are likely to occur in the recesses 2. Furthermore, when the polarizer 7 contains a complex composed of polyvinyl alcohol and iodine, the polarizer 7 exposed in the concave portion 2 is easily degraded by exposure to moisture, heat, or light (ultraviolet rays), and is exposed to the concave portion. The polarizer 7 of 2 is prone to cracks. Since the stress is concentrated in the concave portion 2, cracks are likely to occur near the boundary between the polarizer 7 and the optical film (5, 9). In addition, moisture will pass through the side of the polarizer 7 and the optical film (5, 9) The boundary invades from the recess 2 into the polarizing plate 1. Therefore, the polarizing film 7 and the optical film (5, 6) are each easily degraded, and the polarizing film 7 and the optical film (5, 6) are likely to be peeled off. The recess 2 of 1 is prone to cracks.

However, in the polarizing plate 1 of this embodiment, since the end 7e of the polarizing plate 7 retreats toward the center of the polarizing plate 1 by a distance 4w of 15 μm or more, the polarizing plate 7 is unlikely to be cracked. Furthermore, even if cracks occur, the length is likely to be as slight as 1200 μm or less. Furthermore, although the end 7e of the polarizer 7 is exposed to the outside air, since there is a recessed area 4, it is difficult for water to contact the end 7e of the polarizer 7 when dew is formed at the end of the polarizer. In addition, since the distance 4w is 56 μm or less, the transparent curable adhesive used when attaching the polarizing plate 1 to the display unit contacts the pair of optical films (5, 9) (in particular, the ring is described later). The area of the inner side surface of the protective film made of olefin-based resin is reduced, and therefore, the protective film is less likely to be cracked. In addition, if the distance 4w exceeds 56 μm , the ends of the pair of optical films (5, 9) become easy to contact each other.

In the polarizing plate 1, the inner corner 2c of the recess 2 may be a curved surface. That is, the end surface of the polarizing plate 1 located at the corner 2c inside the recess 2 may be a curved surface. That is, the inner corner 2c of the recess can be chamfered. Since the inner corner 2c of the concave portion 2 is a curved surface, it is easy to control cracks in the inner corner 2c of the concave portion 2. As shown in FIG. 1, the corners at both ends of the recess 2 and the corners at the four corners of the polarizing plate 1 can be chamfered, respectively.

The width of the recess 2 (the width of the recess 2 in the X-axis direction) is not particularly limited, but, for example, it may be 3 mm or more and 160 mm or less. The depth of the recess 2 (the width of the recess 2 in the Y-axis direction) is not particularly limited, but, for example, it may be 0.5 mm or more and 160 mm or less. The length of the side (short side) of the polarizing plate 1 forming the recess 2 is not particularly limited, but, for example, it may be 30 mm or more and 90 mm or less. The length of the side (long side) of the polarizing plate 1 where the recess 2 is not formed is not particularly limited, but, for example, it may be 30 mm or more and 170 mm or less. The thickness of the entire polarizing plate 1 is not particularly limited, but, for example, it may be 30 μm or more and 300 μm or less.

The recess 2 shown in FIG. 1 has a quadrangular shape (rectangular shape). However, the shape of the recess 2 is not limited. For example, the recess 2 may have a square shape. The recess 2 may be a polygonal shape other than a quadrangle or a triangle. In addition, the shape of the recess 2 may be a semicircle. The recess 2 can be composed of straight lines and curved lines. Any shape of the polarizing plate 1 shown in FIG. 1 has symmetry, but the shape of the polarizing plate 1 may be asymmetric. A plurality of recesses 2 may be formed on the outer circumference 1p of the polarizing plate 1. A plurality of recesses 2 may be formed on one side constituting the outer circumference 1p of the polarizing plate 1. It is also possible to form the recess 2 by cutting at least one of the four corners of the quadrangular polarizing plate 1.

The overall shape of the polarizing plate 1 except for the concave portion 2 is approximately quadrangular (rectangular). However, the shape of the polarizing plate 1 is not limited. For example, the shape of the polarizing plate 1 may be a square. The shape of the polarizing plate 1 can be a polygonal shape other than a quadrangular shape, a circular shape, or an elliptical shape. The overall shape of each of the polarizer 7 and the optical films (5, 9) may be slightly the same as the shape of the polarizer 1. In the case of the rectangular polarizing plate 1 shown in FIG. 1, the concave portion 2 is formed on the short side of the polarizing plate 1, but the concave portion 2 may be formed on the long side of the polarizing plate 1.

The polarizer 7 may be a film-like polyvinyl alcohol resin (PVA film) produced through steps such as stretching, dyeing, and crosslinking. In particular, it is preferable to adsorb and oriented dichroic dyes. The details of the method for preparing such a polarizer 7 are as follows.

For example, first, the PVA film is stretched in a uniaxial direction or a biaxial direction. The two colors of the polarizer 7 extending in the uniaxial direction are relatively easy to increase. After the extension, the dyeing solution is then used to dye the PVA film with iodine, dichroic dye (polyiodine) or organic dye. The dyeing solution may contain boric acid, zinc sulfate, or zinc chloride. Before dyeing, the PVA film can be washed with water. By washing with water, dirt and anti-caking agent are removed from the surface of the PVA film. In addition, as a result of the swelling of the PVA film due to washing with water, it is easy to suppress staining spots (not Uniform dyeing). For cross-linking, the dyed PVA film is treated with a solution of a cross-linking agent (for example, an aqueous solution of boric acid). After treatment with a crosslinking agent, the PVA film is washed with water and then dried. After the above sequence, the polarizer 7 can be obtained. The polyvinyl alcohol (PVA)-based resin system can be obtained by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be, for example, polyvinyl acetate which is a homopolymer of vinyl acetate, or a copolymer of vinyl acetate and other monomers (for example, ethylene-vinyl acetate copolymer). In addition to ethylene, the other single systems for copolymerization with vinyl acetate may be unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, or acrylamides with ammonium groups. Polyvinyl alcohol-based resins can be modified with aldehydes. The modified polyvinyl alcohol-based resin may be, for example, partially formalized polyvinyl alcohol, polyvinyl acetal, or polyvinyl butyral. The polyvinyl alcohol-based resin system may be a polyolefin-based oriented film such as a dewatering treatment product of polyvinyl alcohol, or a polyvinyl chloride treatment product of polyvinyl chloride. It can also be dyed before extension, or it can be extended in a dye solution. The length of the stretched polarizer 7 can be, for example, 3 to 7 times the length before the stretch.

The thickness of the polarizer 7 may be, for example, 1 μm or more and 50 μm or less, or 3 μm or more and 15 μm or less. The thinner the polarizer 7 is, the more the shrinkage or expansion of the polarizer 7 itself associated with temperature changes can be suppressed, and the size change of the polarizer 7 itself can be suppressed. As a result, it is difficult for stress to act on the polarizer 7 and it is easy to suppress cracking in the polarizer 7.

The present embodiment is a pair of optical films (5, 9), one of which is a protective film composed of cycloolefin resin (hereinafter also referred to as "cyclic olefin polymer resin").

Hereinafter, for the convenience of description, one of the pair of optical films (5, 9) is labeled as the protective film 5, and the other is labeled as the optical film 9.

The optical film 9 may be a thermoplastic resin having translucency. The optical film 9 may be an optically transparent thermoplastic resin. The resin constituting the optical film 9 may be, for example, a chain polyolefin resin, a cyclic olefin polymer resin (COP resin), a cellulose ester resin, a polyester resin, a polycarbonate resin, (former Base) Acrylic resin, polystyrene resin, or mixtures or copolymers of these. The optical film 9 may contain a cyclic olefin polymer-based resin (COP-based resin). When each of the optical films 9 contains a cyclic olefin polymer resin (COP-based resin), the effects of the present invention are easily obtained. The glass transition temperature of each of the protective film 5 and the optical film 9 is preferably 100°C or more and 200°C or less, or 120°C or more and 150°C or less.

The chain polyolefin resin may be, for example, a homopolymer of chain olefin such as polyethylene resin or polypropylene resin. The chain polyolefin resin system may be a copolymer composed of two or more chain olefins.

The cyclic olefin polymer resin (cyclic polyolefin resin) may be, for example, a ring-opening (co)polymer of cyclic olefin or an addition polymer of cyclic olefin. The cyclic olefin polymer resin may be, for example, a copolymer of a cyclic olefin and a chain olefin (for example, a random copolymer). The chain olefin constituting the copolymer may be, for example, ethylene or propylene. The cyclic olefin polymer resin system may be a graft polymer obtained by modifying the above-mentioned polymer with an unsaturated carboxylic acid or a derivative thereof, or a hydrogenated product thereof. The cyclic olefin polymer-based resin may be, for example, a norbornene-based resin using a norbornene-based monomer, such as a norbornene or a polycyclic norbornene-based monomer. In addition, the above-mentioned cyclic olefin polymer resin can also be used as a material constituting the protective film 5.

The cellulose ester resin may be, for example, cellulose triacetate (cellulose triacetate (TAC)), cellulose diacetate, cellulose tripropionate, or cellulose dipropionate. It can also be such copolymers. It is also possible to use a cellulose ester resin in which a part of the hydroxyl group is modified with other substituents.

Polyester resins other than cellulose ester resins can be used. The polyester resin may be, for example, a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. The polyvalent carboxylic acid or its derivative may be a dicarboxylic acid or its derivative. The polyvalent carboxylic acid or its derivative may be, for example, terephthalic acid, phthalic acid, dimethyl terephthalate, or dimethyl naphthalene dicarboxylate. The polyol may be, for example, a dihydric alcohol. The polyol system may be, for example, ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, or cyclohexane dimethanol.

The polyester resin may be, for example, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, Polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, or polycyclohexane dimethyl naphthalate.

The polycarbonate resin is a polymer in which a polymerized unit (monomer) is bonded via a carbonate group. The polycarbonate resin system may be a modified polycarbonate with a modified polymer skeleton, or a copolymerized polycarbonate.

The (meth)acrylic resin may be, for example, poly(meth)acrylate (for example, polymethyl methacrylate (PMMA)); methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate -(Meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymer (for example, MS resin); methyl methacrylate A copolymer of an ester and a compound having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.).

The protective film 5 or the optical film 9 may respectively contain at least one selected from the group consisting of slip agents, plasticizers, dispersants, heat stabilizers, ultraviolet absorbers, infrared absorbers, antistatic agents, and antioxidants. additive.

The thickness of the protective film 5 may be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less. The thickness of the optical film 9 may be, for example, 5 μm or more and 90 μm or less, or 10 μm or more and 60 μm or less.

At least one of the protective film 5 and the optical film 9 may be a film with optical functions. The film system having an optical function may be, for example, a retardation film or a brightness enhancement film. For example, by stretching a film made of the above-mentioned thermoplastic resin, or forming a liquid crystal layer on the film, a retardation film with an arbitrary retardation value can be obtained.

The protective film 5 can be superimposed on the polarizer 7 via an adhesive layer. The optical film 9 may be superimposed on the polarizer 7 via an adhesive layer. The adhering layer may include an aqueous adhesive such as polyvinyl alcohol. The subsequent layer system may include the active energy ray curable resin described later.

Active energy ray curable resin is a resin that is cured by irradiating active energy rays. The active energy ray system may be, for example, ultraviolet rays, visible light, electron rays, or X rays. For example, the active energy ray curable resin system may be an ultraviolet curable resin.

The active energy ray-curable resin can be one type of resin or multiple types of resins. For example, the active energy ray curable resin may contain a cation polymerizable curable compound or a radical polymerizable curable compound. The active energy ray curable resin system may contain a cationic polymerization initiator or a radical polymerization initiator for initiating the curing reaction of the above-mentioned curable compound.

The cationically polymerizable curable compound can be, for example, an epoxy-based compound (a compound having at least one epoxy group in the molecule) or an oxetane-based compound (a compound having at least one oxetane ring in the molecule) . The radically polymerizable curable compound may be, for example, a (meth)acrylic compound (a compound having at least one (meth)acryloxy group in the molecule). The radically polymerizable curable compound may be a vinyl compound having a radically polymerizable double bond.

Active energy ray curable resins may contain cationic polymerization accelerators, ion scavengers, antioxidants, chain transfer agents, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers, defoamers, Antistatic agent, leveling agent, or solvent, etc.

(Image display device)

The image display device of this embodiment includes the above-mentioned polarizing plate 1. The image display device may be, for example, a liquid crystal display device, an organic EL display device, or the like. For example, a liquid crystal panel included in a liquid crystal display device may include a liquid crystal cell and the above-mentioned polarizing plate 1 overlapped on one surface of the liquid crystal cell. Or, LCD display The liquid crystal panel included in the device may include a pair of the above-mentioned polarizing plates 1 and a liquid crystal cell arranged between the pair of the above-mentioned polarizing plates 1 and overlapping with each of the polarizing plates 1. The polarizing plate 1 may be provided with an adhesive layer on the side opposite to the side provided with the protective film 5, and may be overlapped on the liquid crystal cell via the adhesive layer.

(Method of manufacturing polarizing plate)

The manufacturing method of the polarizing plate 1 related to this embodiment includes: a layering step of overlapping a film-like polarizer with at least a pair of optical films to form a layered body; and a cutting step of using an end mill The end mill is brought into contact with the outer circumference of the laminated body, and the end mill is moved along the outer circumference of the laminated body.

In the lamination step, the long strip-shaped polarizer film and at least one pair of long strip-shaped optical films are overlapped and bonded to each other to produce a layered body (first layered body). The so-called long strip polarizer film refers to the polarizer 7 before processing/forming. The so-called long strip-shaped plural optical films are optical films before processing/forming (5, 9). In the layering step, the polarizer film is arranged between the pair of optical films, and the polarizer film and the pair of optical films are overlapped to form a polarizing plate (Figure 3). In addition, the laminated body may further include a separation film via a pressure-sensitive adhesive layer on the optical film. The separation film can be peeled from the pressure-sensitive adhesive layer thereafter.

Then, prior to the cutting step, a recessed portion is formed on the outer periphery of the first laminate by punching processing or cutting processing. The cutting method can be a knife or laser. However, it is difficult to form the above-mentioned recessed area only by punching or cutting. The punched first laminated body 10 is referred to as "first laminated body 10'".

As shown in FIGS. 4 and 5, the end mill (rotary cutting tool) 50 used in the cutting step has a protruding edge 50e on the side surface slightly parallel to the rotation axis 50a. In the cutting step, the side surface of the end mill 50 is brought into contact with the outer periphery (end surface) of the first laminated body 10', and the rotating end mill 50 is moved along the outer periphery of the first laminated body 10' in which the recesses are formed.

For example, the rotating end mill 50 can be moved along the path shown by the arrow on the outer circumference in FIG. 5. As a result, the outer periphery (end surface) of the first laminated body 10' in which the recessed portion is formed is cut or polished by the blade 50e, the outer periphery (end surface) of the first laminated body 10' becomes smooth, and the recessed portion 2 is formed. The inner corners are chamfered. As shown in FIG. 4, after a plurality of first laminated bodies 10' can be overlapped to form a second laminated body 100, the side surface of the end mill 50 is brought into contact with the outer periphery (end surface) of the second laminated body 100 to rotate The end mill 50 moves along the outer circumference of the second laminated body 100. That is, in the cutting step, the outer periphery of the plurality of first laminated bodies 10' constituting the second laminated body 100 can be cut or polished all at once with the end mill 50. In the cutting step, the corners located at both ends of the recessed portion 2 and the corners located at the four corners of the first laminated body 10 can be respectively chamfered.

The feed speed of the end mill in the cutting step is set at 0.42 to 0.60 m/min, and the speed can be 0.45 to 0.60 m/min, or 0.50 to 0.55 m/min.

If the feed speed of the end mill is within the above-mentioned range, the end e of the polarizer 7 is formed into a shape that is recessed toward the inner side than the end of the protective film.

(粗細)例如可為3.0mm以上6.0mm以下。 From the viewpoint of recessing the end 7e of the polarizer 7, the rotation speed of the end mill in the cutting step may be, for example, 20,000 to 35,000 rpm, preferably 25,000 to 32,000 rpm. Also, from the same point of view, the cutting angle in the cutting step may be, for example, 30° or more and 70° or less, preferably 45° or more and 65° or less. When the torsion angle of the end mill 50 is α, the cutting angle β is defined as 90°-α. As shown in Fig. 4, the torsion angle α of the end mill 50 extends from the edge 50e in the side of the end mill 50 The angle formed by the direction d1 of the end mill 50 and the rotation axis 50a of the end mill 50. The cutting angle β can also be renamed as the angle formed by the direction d1 in which the cutting edge 50e extends and the direction d2 perpendicular to the rotation axis 50a. The diameter of the end mill 50 used in the cutting step

(Thickness) can be 3.0 mm or more and 6.0 mm or less, for example.

The feed speed of the end mill 50 in the cutting step can be expressed as V [m/min] or V/60 [m/sec]. The rotation speed of the end mill 50 in the cutting step can be expressed as R [rpm] or R/60 [rps]. The number of contact times of the end mill 50 in the cutting step is defined as R/V [times/m]. The number of contact times means the number of times the end mill 50 contacts the outer circumference of the first laminated body 10 per unit length (1 m). The number of contact R/V of the end mill 50 in the cutting step is preferably 30,000 times/m or more and 90,000 times/m or less, 40,000 times/m or more and 80,000 times/m or less, or 45,000 times/m or more and 75,000 times/m or more. m or less.

In the cutting step, when cutting the inside of the recessed portion 2, the relationship between the direction of rotation of the end mill 50 and the direction of feed is set as up milling. The so-called up-milling refers to the part where the end mill 50 and the first laminated body 10' are in contact with each other, the direction of rotation of the end mill 50 (refer to the arrow depicted in the symbol 50 in FIG. 5) and the advance The given direction (refer to the arrow drawn along the outer circumference in Fig. 5) is a consistent relationship (also, the relationship that the rotation direction of the end mill 50 and the feed direction are opposite to each other is called down milling (down-cut)).

In addition, when cutting the corner 2c in the recess 2 in the cutting step, the end mill 50 is moved in a direction perpendicular to the absorption axis direction of the polarizer 7 and moved in a parallel direction.

As shown in FIG. 5, the absorption axis 3 is relative to the polarizer 7 facing the vertical direction as shown in the figure. In the concave portion 2, the inside of the concave portion 2 is used as the starting point of the end mill 50, and is formed along the outer circumference of the first laminate 10'. mobile. In this way, when moving in the left-right direction in the figure, it moves in a direction perpendicular to the absorption axis of the polarizer 7, and when the end mill 50 is bent in the corner 2c and moves in the vertical direction as shown in the figure. , Move in a direction parallel to the absorption axis of the polarizer 7.

By using such a cutting method, the end portion 7e of the polarizer 7 is formed into a shape that is more recessed toward the inner side than the end portions of the protective film 5 and the optical film 9. By adjusting the rotation speed (R), the feed speed (V), and the number of abutments (R/V) of the end mill, the degree of depression of the end 7e of the polarizer 7 can be adjusted.

By the above method, the polarizing plate 1 related to this embodiment can be obtained.

Above, the appropriate embodiments of the present invention have been described, but the present invention is not limited by the above-mentioned embodiments in any way. For example, in the above embodiment, one side of a pair of optical films (5, 9) is a protective film made of cycloolefin resin, but a pair of optical films (5, 9) Both of them may be protective films composed of cycloolefin-based resins.

In addition, in the above-mentioned embodiment, the position of the ends of a pair of optical films (5, 9) is the same in the in-plane direction in side view, but the positions of the ends in the in-plane direction can be Offset within 20 μm. In this way, when the positions of the ends of a pair of optical films (5, 9) are inconsistent in side view, the distance between the end of each optical film (5, 9) and the end 7e of the polarizer 7 is 4w Among them, the distance for the elderly is preferably 15 μm to 56 μm .

In addition, in the above-mentioned embodiment, a concave portion is formed on the outer periphery of the polarizing plate in a plan view. However, as shown in FIG. 6, the polarizing plate 1A may be provided with a through hole 2A in the plane instead of the concave portion 2. . Alternatively, it may be a state in which both the concave portion 2 and the through hole 2A are provided. In this case, for the side surface constituting the through hole 2A, the end 7e of the polarizer 7 is also opposite to the pair of optical films (5, 9) The depression is 15 μm to 56 μm .

[Example]

Hereinafter, reference examples, examples, and comparative examples are given to more specifically explain the content of the present invention. In addition, the present invention is not limited by the following examples.

<Research on the rupture of protective film>

(Reference example 1)

A pair of long protective films made of cycloolefin resin are bonded to a long polarizer through an adhesive layer, and the separation film is further laminated by laminating a pressure-sensitive adhesive on the protective film , Forming the first A layered body. In the first laminate, the polarizer is arranged between the pair of protective films. The polarizer is stretched and dyed film-like polyvinyl alcohol.

The thickness of the protective film attached to one surface of the polarizer is about 50 μm . The thickness of the protective film attached to the other surface of the polarizer is about 20 μm . The thickness of the polarizer is 8 μm . The overall thickness of the polarizer is about 100 μm . The adhesive layer between the protective film and the polarizer with a thickness of about 50 μm is a polyvinyl alcohol-based resin (water paste). The adhesive layer between the protective film and the polarizer with a thickness of about 20 μm is UV curable epoxy resin.

Next, on the protective film side surface of about 20 μm , the laminated film of the pressure sensitive adhesive layer and the separation film is bonded so that the pressure sensitive adhesive layer becomes the protective film side. In this laminated film, the separation film is releasably attached to the pressure-sensitive adhesive layer.

By punching each of the 47 first laminates, recesses were formed on the short sides of each first laminate. The 47 first laminates in which the recesses were formed were stacked to produce the second laminate. Here, as shown in FIG. 3, the holes are punched so that the absorption axis of the polarizer faces the long direction of the polarizer.

為4mm。 After punching, perform the following cutting steps. Fix the second laminated body with a jig, and with the side surface of the end mill in contact with the outer periphery (end surface) of the second laminated body, use the concave portion of the second laminated body as the starting point, and use the upper milling method. The rotating end mill moves along the outer circumference. That is, the entire outer periphery of each of the 47 first laminates was cut with an end mill all at once. The end mill used in each cutting step is DXL-4 manufactured by Nissin Tool Co., Ltd. The cutting angle β is 65 degrees. Diameter of end mill

It is 4mm.

The rotation speed (R), feed speed (V), and the number of abutments (R/V) of the end mill in the cutting step are the values shown in Table 1 below.

By the above method, 47 polarizing plates of the reference example were produced. The shape, size and layer structure of each polarizer are the same. The overall shape of each polarizer is rectangular. As shown in FIG. 1, a rectangular recess 2 is formed on the short side of the polarizing plate 1. The length of the short side of the polarizer 1 is 70 mm. The length of the long side of the polarizing plate 1 is 140 mm. The width of the recess 2 is 30 mm. The depth of the recess 2 is 5 mm.

The polarizing plate 1 is cut in a direction perpendicular to the surface (light-receiving surface) of the polarizing plate 1 and perpendicular to the inner side of the recess 2. The cross section of the polarizing plate 1 was observed with a scanning electron microscope (SEM). As a result of observation using SEM, it was confirmed that the position of the end 7e of the polarizer 7 along the recessed portion 2 coincides with the end of the pair of protective films (that is, the width 4w of the recessed area is 0 μm .)

The separation film was peeled off from the respective polarizing plates, and the exposed pressure-sensitive adhesive layer was pasted on an alkali-free glass (trade name "Eagle-XG" from CORNING) at a temperature of 50°C and a pressure of 0.5 MPa for 20 minutes of pressure cooker treatment, so that the polarizing plate is fully adhered to the alkali-free glass.

Drop oleic acid [taken from Wako Pure Chemical Industry Co., Ltd. grade 1 reagent] into the concave part of the polarizing plate laminated with glass. Cover the cover glass to prevent the oleic acid (solvent) from evaporating, and after leaving it in its state for 3 hours, remove the cover glass and wipe the solvent.

Hereinafter, a thermal cycle test is performed. In the thermal cycle test system, the cycle consisting of step 1 and step 2 following step 1 is repeated 50 times.

Step 1: The step of keeping the above-mentioned polarizing plate in the first atmosphere for 30 minutes.

Step 2: The step of keeping the above-mentioned polarizing plate in the second atmosphere for 30 minutes.

The temperature of the first atmosphere is -40°C, and the relative humidity of the first atmosphere is 11%.

The temperature of the second atmosphere is 85°C, and the relative humidity of the second atmosphere is 7%.

After the thermal cycle test, the surface of the polarizing plate was observed with an optical microscope along the concave portion of the polarizing plate, and the number and maximum length of the cracks generated in the protective film were measured. The number of ruptures and the maximum length are shown in Table 1 below.

(Example 1)

Except that the rotation speed (R), the feed speed (V), and the number of contacts (R/V) of the end mill are changed as shown in Table 1, the polarizing plate was produced in the same manner as in the above reference example. As a result of cross-sectional observation using SEM, it was confirmed that the end of the polarizer along the recess was located inside the outer periphery of the polarizer. In addition, it was confirmed that the protective films of a pair were not in contact with each other, but the end of the polarizer was in contact with the outside air. The width of the recessed area is 23 μm . The thermal cycle test was performed in the same manner as in the reference example described above. The results are shown in Table 1 below.

(Example 2)

Except that the rotation speed (R), the feed speed (V), and the number of contacts (R/V) of the end mill are changed as shown in Table 1, the polarizing plate was produced in the same manner as in the above reference example. As a result of cross-sectional observation using SEM, it was confirmed that the end of the polarizer along the recess was located inside the outer periphery of the polarizer. In addition, it was confirmed that the protective films of a pair were not in contact with each other, but the end of the polarizer was in contact with the outside air. The width of the recessed area is 45 μm . The thermal cycle test was performed in the same manner as in the reference example described above. The results are shown in Table 1 below.

(Comparative example 1)

Except that the rotation speed (R), the feed speed (V), and the number of contacts (R/V) of the end mill are changed as shown in Table 1, the polarizing plate was produced in the same manner as in the above reference example. As a result of cross-sectional observation using SEM, it was confirmed that the end of the polarizer along the recess was located inside the outer periphery of the polarizer. In addition, it was confirmed that the protective films of a pair were not in contact with each other, but the end of the polarizer was in contact with the outside air. The width of the recessed area is 67 μm . The thermal cycle test was performed in the same manner as in the reference example described above. The results are shown in Table 1 below.

[Table 1]

In Reference Example 1, Example 1, and Example 2 in which the width of the recessed area was 56 μm or less, the protective film did not crack. In Comparative Example 1 where the width of the recessed area exceeds 56 μm , the protective film is cracked, and the maximum length thereof exceeds 1200 μm .

<Research on the rupture of polarizer>

(Example 3)

The second laminate produced in the same manner as in the above reference example was cut under the conditions shown in Table 2. Next, the polarizing plate 1 is cut in a direction perpendicular to the surface (light-receiving surface) of the polarizing plate 1 and perpendicular to the inner side of the recess 2. The cross section of the polarizing plate 1 was observed with a scanning electron microscope (SEM).

As a result of observation using SEM, it was confirmed that the end 7e of the polarizer 7 along the concave portion 2 was located inside the outer periphery 1p of the polarizer 1. In addition, it was confirmed that the pair of protective films were not in contact with each other, but the end 7e of the polarizer 7 was in contact with the outside air. The width of the recessed area is 28 μm .

Hereinafter, a condensation heat cycle test is performed. In the condensation heat cycle test, the cycle consisting of the following step 1, step 1, then step 2, and step 2, then step 3, was repeated 10 times.

Step 1: The step of keeping the above-mentioned polarizing plate in the first atmosphere for 30 minutes.

Step 2: The step of keeping the above-mentioned polarizing plate in the second atmosphere for 5 minutes.

Step 3: The step of keeping the above-mentioned polarizing plate in the third atmosphere for 30 minutes.

The temperature of the first atmosphere is -40°C, and the relative humidity of the first atmosphere is 11%.

The temperature of the second atmosphere is 23°C, and the relative humidity of the second atmosphere is 9%.

The temperature of the third atmosphere is 85°C, and the relative humidity of the third atmosphere is 7%.

After the condensation heat cycle test, observe the surface of the polarizer with an optical microscope along the concave portion of the polarizer, and measure the number of cracks and the maximum length of the polarizer. The number of ruptures and the maximum length are shown in Table 2 below.

(Comparative example 2)

Except that the feed speed (V) of the end mill and the number of contacts (R/V) were changed as shown in Table 2, the rest was the same as in the above-mentioned Example 3, and the polarizing plate was produced. As a result of cross-sectional observation using SEM, it was confirmed that the end of the polarizer along the recess was located inside the outer periphery of the polarizer. In addition, it was confirmed that the protective films of a pair were not in contact with each other, but the end of the polarizer was in contact with the outside air. The width of the recessed area is 5 μm . The thermal cycle test was performed in the same manner as in the reference example described above. The results are shown in Table 2 below.

(Comparative example 3)

Except that the feed speed (V) of the end mill and the number of contacts (R/V) were changed as shown in Table 2, the rest was the same as in the above-mentioned Example 3, and the polarizing plate was produced. As a result of cross-sectional observation using SEM, it was confirmed that the end of the polarizer along the recess was located inside the outer periphery of the polarizer. In addition, it was confirmed that the protective films of a pair were not in contact with each other, but the end of the polarizer was in contact with the outside air. The width of the recessed area is approximately 0 μm . The thermal cycle test was performed in the same manner as in the reference example described above. The results are shown in Table 2 below.

[Table 2]

As shown in Table 2, when the width of the recessed area is 15 μm or more, the number of cracks generated is small, and the maximum length is slightly less than 1200 μm. When the width of the recessed area is less than 15 μm , the number of cracks generated is large, and the maximum length is greater than 1200 μm .

[Industrial Utilization Possibility]

The polarizing plate related to the present invention is, for example, applied to image display devices such as liquid crystal displays or organic EL displays.

1: Polarizing plate

1p: The outer circumference of the polarizing plate

2: recess

2c: The corner of the recess

3: The absorption axis of the polarizer

4: Recessed area

4w: the width of the recessed area

5: The first optical film

7: Polarizer

7e: The end of the polarizer

Claims (8)

A polarizing plate is provided with a film-like polarizer and at least a pair of optical films containing resin, wherein: The aforementioned polarizer is located between the aforementioned pair of optical films and overlaps with the aforementioned pair of optical films, Among the aforementioned pair of optical films, at least one of the optical films is a protective film for protecting the aforementioned polarizer, The aforementioned protective film is made of cycloolefin resin, In a plan view, a recess is provided on the outer circumference, or a through hole is provided in the surface, In a side view, in the recess or in the through hole, the end of the polarizer is 15 μm to 56 μm more inside than the end of any one of the pair of optical films, and the polarized light The end of the sheet is exposed by contacting the outside air. The polarizing plate according to claim 1, wherein the polarizer is one having a dichroic dye adsorbed and oriented on the stretched polyvinyl alcohol-based resin film. The polarizing plate according to claim 1 or 2, wherein the polarizing plate is further provided with an adhesive layer on the side opposite to the side provided with the protective film. The polarizing plate according to any one of claims 1 to 3, wherein any one of the aforementioned pair of optical film systems is the aforementioned protective film. The polarizing plate according to any one of claims 1 to 4, wherein, in a side view, in the concave portion or in the through hole, the position difference between the ends of the pair of optical films is 20 Within μ m. An image display device comprising the polarizing plate according to any one of claims 1 to 5. A method for manufacturing a polarizing plate is to manufacture the polarizing plate according to any one of claims 1 to 5. The manufacturing method has a cutting step, and the cutting step involves contacting a rotary cutting tool with at least one side of the film-shaped polarizer. On the side surface of the laminated body formed by overlapping the optical films, the rotary cutting tool is moved along the side surface of the laminated body, In a plan view, the aforementioned laminated system is provided with recesses on the outer periphery, or with through holes in the surface, Among the aforementioned pair of optical films, at least one of the optical films is a protective film for protecting the aforementioned polarizer, The aforementioned protective film is composed of cycloolefin resin, In the foregoing cutting step, when cutting in the recess or the through hole, the rotation speed of the rotary cutting tool is set to 20000 to 35000 rpm, the feed rate is set to 0.42 to 0.60 m/min, and the foregoing The relationship between the direction of rotation of the rotary cutting tool and the direction of feed is set as up milling, and the rotary cutting tool is moved in a direction perpendicular to the direction of the absorption axis of the polarizer and moved in a parallel direction. The method for manufacturing a polarizing plate according to claim 7, wherein the rotation speed of the rotary cutting tool is set to 25000 to 32000 rpm, and the feed rate is set to 0.45 to 0.50 m/min.

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