TW201900402A - Polarizing film, polarizing film with adhesive layer, and image display device - Google Patents

Abstract

The present invention is a polarizing film having a first resin film on one side of a polarizer having a thickness of 10 μm or less and a second resin film on the other side; the moisture permeability of the first resin film and the second resin film is 100 g / (m ² · day) or less; and among the first resin film and the second resin film, at least the first resin film has a breaking stress of 13N or more and a breaking elongation in a direction perpendicular to the absorption axis of the polarizer. It is 2.5mm or more. The polarizing film of the present invention is a polarizing film having a resin film with low moisture permeability on two areas of a polarizer having a thickness of 10 μm or less, and the polarizing film can suppress the deterioration of the polarizer due to humidification (humidity reliability), and The severe environment of the earthquake can still suppress the occurrence of penetrating cracks.

Description

Polarizing film, polarizing film with adhesive layer, and image display device

The present invention relates to a polarizing film and a polarizing film with an adhesive layer having the polarizing film and an adhesive layer. The present invention also relates to an image display device including the aforementioned polarizing film with an adhesive layer.

BACKGROUND OF THE INVENTION In various image display devices, in order to display an image, a polarizing film is generally used. For example, the liquid crystal display device (LCD) is indispensable from the viewpoint of its image forming method, and it is necessary to arrange polarizing films on both sides of the glass substrate forming the surface of the liquid crystal panel. In addition, on the organic EL display device, in order to shield the specular reflection of external light on the metal electrode, a circularly polarizing film including a polarizing film and a quarter-wave plate is laminated on the viewing side of the organic light emitting layer.

The polarizing film is generally used in a case where a polarizer made of a polyvinyl alcohol-based film and a dichroic material such as iodine is passed through a polyvinyl alcohol-based adhesive on one side or both sides, and a protective film is bonded.

Under the severe environment of thermal shock (such as repeated thermal shock tests at -40 ° C and 85 ° C), the polarizing film may be easily generated in the direction of the absorption axis of the polarizer due to changes in the shrinkage stress of the polarizer. Problems with cracks (penetrating cracks). Therefore, in order to suppress the shrinkage of the polarizer and reduce the impact of thermal shock, a polarizing film usually uses a triacetamyl cellulose (TAC) film with a thickness of 40 to 80 μm laminated on both sides of the polarizer as a protective film laminate. However, even for the aforementioned polarizing film with both sides protected, the change in the shrinkage stress of the polarizer cannot be ignored, and it is difficult to completely suppress the shrinkage effect. It is still impossible to avoid a certain degree of shrinkage on the optical film laminate including the polarizer. .

On the other hand, in recent years, with the development of thinner image display devices such as liquid crystal display devices, there is a need for thinner polarizers. As long as it is a thin polarizer having a thickness of 10 μm or less, since the change in shrinkage stress is small, penetration cracks are unlikely to occur. For example, there is a document that discloses a polarizing film in which a protective film is bonded to one or both sides of a thin polarizer having a thickness of 10 μm or less, and the occurrence of penetrating cracks is suppressed (see, for example, Patent Documents 1 to 3). . In particular, a double-sided protective polarizing film formed by laminating protective films on both sides of a thin polarizer can prevent the shrinkage of the polarizer during the thermal shock test by the protective films provided on both sides, so that the penetration can be effectively suppressed crack.

Prior Art Literature Patent Literature Patent Literature 1: Japanese Patent Laid-Open No. 2015-187727 Patent Literature 2: Japanese Patent Laid-Open No. 2015-152911 Patent Literature 3: Japanese Patent Laid-Open No. 2013-072951

Summary of the Invention Problems to be Solved by the Invention On the other hand, a thin polarizer having a thickness of 10 μm or less has a problem that the optical characteristics of the thin polarizer are easily reduced in a humidified environment. Therefore, even in the aforementioned double-sided protective polarizing film using a thin polarizer as described in Patent Documents 1 to 3, the type of the protective film still causes the polarizer to deteriorate due to moisture in a humidified environment, resulting in the polarizing film. The optical characteristics are significantly reduced.

Therefore, in order to suppress the deterioration of the polarizer due to moisture, we consider using a resin film with extremely low moisture permeability (specifically, 100 g / (m ² · day) or less) as a thin polarizer for bonding. Protective film on both sides. However, we have discovered a new problem. When the resin film with extremely low moisture permeability is used as a protective film, although the deterioration of the polarizer in a humidified environment can be suppressed, the thickness of the polarizer film is increased. A thin polarizer with a thickness of 10 μm or less, and before the protective film is laminated on both sides of the thin polarizer, penetration cracks still occur due to thermal shock tests and the like.

An object of the present invention is to provide a polarizing film having a resin film having low moisture permeability on two areas of a polarizer having a thickness of 10 μm or less, and the polarizing film can suppress deterioration of the polarizer due to humidification (humidity reliability), and In the severe environment of thermal shock, penetration cracks can still be suppressed.

Another object of the present invention is to provide a polarizing film with an adhesive layer having the aforementioned polarizing film and an adhesive layer. An object of the present invention is to provide an image display device including the aforementioned polarizing film or a polarizing film with an adhesive layer.

Means for Solving the Problems The inventors of the present invention and others, in order to solve the aforementioned problems, have repeatedly and actively studied, and as a result, have discovered the following polarizing film and the like, and finally completed the present invention.

That is, the present invention relates to a polarizing film having a first resin film on one side of a polarizer having a thickness of 10 μm or less and a second resin film on the other side; the polarizing film is characterized in that: the first resin film And the second resin film have a moisture permeability of 100 g / (m ² · day) or less; and among the first resin film and the second resin film, at least the first resin film is in a direction perpendicular to the absorption axis of the polarizer The breaking stress is 13N or more, and the breaking elongation is 2.5mm or more.

In the polarizing film, any of the first resin film and the second resin film may be a resin film selected from a cycloolefin resin film and a (meth) acrylic resin film.

Among the polarizing films, a stretched film of a cycloolefin-based resin film can be applied as the first resin film. Further, an acrylic resin film can be applied as the first resin film.

The present invention also relates to a polarizing film with an adhesive layer, which is characterized by having the aforementioned polarizing film and an adhesive layer.

The polarizing film with an adhesive layer is preferably used in a state in which the second resin film side of the polarizing film has the adhesive layer.

The present invention also relates to an image display device, which is characterized in that the above-mentioned polarizing film or a polarizing film with an adhesive layer is disposed on the image display unit.

In the image display device, the polarizing film or the polarizing film with an adhesive layer is preferably used in a state in which the second resin film is placed on a side of the image display unit.

ADVANTAGE OF THE INVENTION As mentioned above, we newly learned that a polarizing film with a low moisture permeability resin film (specifically 100 g / (m ² · day) or less) is used as a protective film on two areas of a thin polarizer. Although the deterioration of the polarizer due to humidification can be suppressed (the humidification reliability can be improved), penetrating cracks are generated. We believe that the main cause of the penetrating cracks is the low breaking stress and low breaking elongation of the resin film (protective film) with low moisture permeability. We believe that if the breaking stress of the protective film is low in a direction perpendicular to the absorption axis of the aforementioned polarizer, penetrating cracks are likely to occur in the polarizing film due to the fragility of the protective film. In addition, if the elongation at break of the protective film is small in a direction perpendicular to the absorption axis of the polarizer, penetrating cracks are likely to occur when the protective film expands and contracts, and when the polarizer expands and contracts with the polarizer. . We believe that the combination of the low fracture stress and the small elongation at break of the protective film is the cause of the penetrating crack.

In the present invention, at least the first resin film among the first resin film and the second resin film of the polarizing film is used with a breaking stress of at least 13N in at least one direction (in-plane) and an elongation at break of 2.5. mm or more, and the aforementioned one direction of the resin film is arranged in a direction perpendicular to the absorption axis of the polarizer. In the present invention, because the polarizing film has the above-mentioned structure, the polarizing film can still be used in the same manner as the polarizer even under the severe environment of thermal shock (for example, the thermal shock test is repeatedly performed under the temperature conditions of -40 ° C and 85 ° C). The overall shrinkage in the vertical direction of the absorption axis is small, so even if a protective film with low moisture permeability is layered on both areas of the polarizer, penetration cracks can still be prevented from occurring in the polarizing film. That is, the polarizing film of the present invention can balance both suppressing the deterioration of the polarizer due to humidification (improving the reliability of humidification) and suppressing the occurrence of penetrating cracks.

In addition, the present invention can provide a polarizing film with an adhesive layer and an image display device using the polarizing film with an adhesive layer, which have both improved the reliability of humidification and suppressed the occurrence of penetrating cracks.

Forms for Implementing the Invention 1. Polarizing Film The polarizing film of the present invention has a structure in which a first resin film is provided on one surface of a polarizer having a thickness of 10 μm or less, and a second resin film is provided on the other surface. The moisture permeability of the first resin film and the second resin film is 100 g / (m ² · day) or less.

The structure of the polarizing film of the present invention will be described in detail with reference to FIG. 1. The dimensions of each structure in FIG. 1 are examples, and the present invention is not limited thereto.

As shown in FIG. 1, the polarizing film F1 of the present invention has a first resin film b1 on one surface of the polarizer a and a second resin film b2 on the other surface. The first resin film b1 and the second resin film b2 can be bonded to the polarizer a through an adhesive layer (not shown). The polarizing film F1 of the present invention may contain layers other than the aforementioned layers (for example, an easy-adhesive layer or various functional layers).

The first resin film b1 and the second resin film b2 satisfy the low moisture permeability, and at least the first resin film b1 satisfies physical properties related to the breaking stress and elongation at break. From the viewpoint of suppressing the occurrence of penetrating cracks, the polarizing film F1 of the present invention is preferably arranged such that the second resin film b2 side becomes the image display unit side.

Each component will be described below.

(1) Polarizer In the present invention, a thin polarizer having a thickness of 10 m or less is used. From the viewpoint of thinning and suppressing the occurrence of penetrating cracks, the thickness of the polarizer is preferably 8 μm or less, more preferably 7 μm or less, and still more preferably 6 μm or less. On the other hand, the thickness of the polarizer is 2 μm or more, and more preferably 3 μm or more. Such thin polarizers have small thickness variations, good visibility, and small dimensional changes, so they have excellent durability against thermal shock.

The polarizer is made of a polyvinyl alcohol resin. Examples of polarizers include adsorption of iodine or dichroic dyes on hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films. Those with color properties and uniaxial stretching, and polyolefin-based alignment films such as dehydrated products of polyvinyl alcohol or dehydrochlorinated products of polyvinyl chloride. Among these, a polarizer composed of a dichroic substance such as a polyvinyl alcohol film and iodine is suitable.

A uniaxially stretched polarizer that dyes a polyvinyl alcohol-based film with iodine can be dyed by, for example, immersing polyvinyl alcohol in an aqueous solution of iodine, and stretched to 3 to 7 times its original length. If necessary, it may contain boric acid, zinc sulfate, zinc chloride, or the like, or may be immersed in an aqueous solution such as potassium iodide. Further, if necessary, the polyvinyl alcohol-based film is immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt and anticaking agents on the surface of the polyvinyl alcohol-based film can be cleaned. In addition, the polyvinyl alcohol-based film can swell and prevent uneven dyeing and the like. The stretching may be performed after dyeing with iodine, or may be extended while dyeing, or may be dyed with iodine after stretching. Stretching can also be performed in an aqueous solution such as boric acid or potassium iodide or in a water bath.

From the viewpoint of elongation stability and humidification reliability, the polarizer should preferably contain boric acid. From the viewpoint of suppressing the occurrence of penetrating cracks, the content of boric acid contained in the polarizer is preferably 22% by weight or less, and more preferably 20% by weight or less, based on the total amount of the polarizer. From the viewpoint of elongation stability and humidification reliability, the boric acid content is preferably 10% by weight or more, more preferably 12% by weight or more, relative to the total amount of the polarizer.

Examples of thin polarizers include: Japanese Patent No. 4751486, Japanese Patent No. 4751481, Japanese Patent No. 4815544, Japanese Patent No. 5048120, International Publication No. 2014/077599, International Publication No. The thin polarizer described in the 2014/077636 gazette manual or the like, or a thin polarizer manufactured by the manufacturing method described in them.

From the viewpoint of extending the film at a high magnification and improving the polarization performance in a manufacturing method including a step of stretching in the state of a laminated body and a dyeing step, the aforementioned thin polarizers include, for example, Patent No. 4751486, Patent No. 4751481, and Patent No. 4815544. The description in the No. 4 specification is preferably made by a method that includes a step of stretching in a boric acid aqueous solution, especially as described in Patent No. 4751481 and Patent No. 4815544. It is advisable to make the method of extending the air. These thin polarizers can be produced by a manufacturing method including a step of stretching a polyvinyl alcohol resin (hereinafter, also referred to as a PVA resin) layer and a stretching resin substrate in a state of a laminate and a dyeing step. According to this manufacturing method, even if the PVA-based resin layer is thin, it is supported by the resin base material for stretching, so that it can be stretched without causing unfavorable conditions such as breakage due to stretching.

(2) First resin film The first resin film is one in which the moisture permeability satisfies 100 g / (m ² · day) or less. The moisture permeability is preferably 80 g / (m ² · day) or less, and more preferably 70 g / (m ² · day) or less. In addition, the lower limit value of the moisture permeability is not particularly limited, and ideally, water vapor cannot penetrate at all (that is, 0 g / (m ² ･ day)). Since the moisture permeability of the first resin film is within the aforementioned range, deterioration of the polarizer due to moisture can be suppressed.

The first resin film has a fracture stress of at least 13 N and an elongation at break of 2.5 mm or more in at least one direction. The breaking stress and breaking elongation can be measured by the measurement methods described in the examples.

In addition, the breaking stress of the first resin film is at least 13N in a direction (in a state where the first resin film is provided on the polarizing film, a direction perpendicular to the absorption axis of the polarizer), and more preferably 15N. Above, and more preferably above 20N.

The breaking elongation of the first resin film is at least 2.5 in the same direction as the breaking stress (in a state where the first resin film is provided on the polarizing film, a direction perpendicular to the absorption axis of the polarizer) is 2.5. Above mm, more preferably above 10mm, and more preferably above 20mm.

The thickness of the first resin film is not particularly limited, but it is preferably 10 μm or more, and more preferably 12 μm or more, from the viewpoints of reducing the moisture permeability to improve the reliability of humidification, and increasing the breaking strength to further suppress the penetrating cracks. On the other hand, from the viewpoint of thinning, the thickness is preferably 50 μm or less, more preferably 40 μm, and more preferably 30 μm or less.

The polarizer and the first resin film are arranged so that an absorption axis of the polarizer is perpendicular to a direction satisfying the breaking stress and elongation at break of the first resin film. The term "vertical" in the present invention means that the angle formed by the absorption axis of the polarizer and the direction satisfying the breaking stress and breaking elongation of the first resin film falls within a range of 85 ° to 95 °. The aforementioned angle is preferably 87 ° ~ 92 °, more preferably 89 ° ~ 91 °, and particularly preferably about 90 °.

As the material for forming the first resin film, a material capable of forming a film having transparency and a moisture permeability of 100 g / (m ² · day) or less can be used. Specific examples of the material include a cycloolefin resin film, a (meth) acrylic resin film, and the like.

A general term for a cycloolefin-based resin that forms a cycloolefin-based resin film by using a cycloolefin as a polymerization unit, which is a resin that is polymerized with a cyclic olefin as a polymerization unit. And resins described in Japanese Patent Application Laid-Open No. 3-122137. Specific examples include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (represented as random copolymers), and the like Graft polymers modified with unsaturated carboxylic acids or their derivatives, and hydrides thereof. Specific examples of the cycloolefin include a norbornene-based monomer.

Cycloolefin resins are commercially available in various products. Specific examples include Japanese brand names “ZEONEX”, “ZEONOR”, JSR (brand) “Arton”, TICONA ’s product name “TOPAS”, and Mitsui Chemical ’s products Name "APEL", etc.

Since the cycloolefin resin film is difficult to meet the aforementioned breaking stress and breaking elongation in an unstretched state, it is suitable to use it in a stretched film state. The stretched film can satisfy the aforementioned breaking stress and breaking elongation in this stretching direction. The degree of elongation of the stretched film is not particularly limited as long as it can satisfy the fracture stress and elongation at break. This stretched film can be used as a retardation film having desired optical characteristics. For example, a desired retardation of the stretched film can be given and used as a retardation film having the function of converting linearly polarized light into circularly polarized light or elliptical polarized light.

Any suitable stretching method and stretching conditions (such as stretching temperature, stretching ratio, and stretching direction) can be adopted for the stretching. Specifically, various extension methods such as free-end extension, fixed-end extension / free-end contraction, and fixed-end contraction can be used alone, or they can be used simultaneously or sequentially. The extending direction may be performed in various directions and dimensions such as a horizontal direction, a vertical direction, a thickness direction, and a diagonal direction. The elongation temperature is preferably within a range of glass transition temperature (Tg) of the resin film ± 20 ° C.

The stretched film can be produced by, for example, uniaxially stretching the resin film or uniaxially stretching the fixed end, or simultaneously biaxially stretching or diagonally stretching. A specific example of the uniaxial stretching may be a method in which the resin film is moved in the long direction and extended in the long side direction (longitudinal direction). Another specific example of uniaxial stretching may be a method of using a tenter to extend laterally. In general, it is advisable to adjust the stretching ratio within the range of 10% to 500%.

As a (meth) acrylic resin which forms the said (meth) acrylic resin film, a suitable (meth) acrylic resin can be used. For example, poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic copolymer, methyl methacrylate- (meth) acrylate copolymer, methyl Methyl acrylate-acrylate- (meth) acrylic acid copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymers having alicyclic hydrocarbon groups (e.g. methyl methacrylate-methyl Cyclohexyl acrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.). Preferably, a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylate is used. More preferred are methyl methacrylate resins containing methyl methacrylate as a main component (50 to 100% by weight, and preferably 70 to 100% by weight).

Specific examples of the (meth) acrylic resin include, for example, ACRYPET VH or ACRYPET VRL20A manufactured by Mitsubishi Rayon Corporation, and (meth) acrylic resin having a ring structure in the molecule described in Japanese Patent Application Laid-Open No. 2004-70296. 2. High Tg (meth) acrylic resin obtained by intramolecular crosslinking or intramolecular cyclization.

From the viewpoints of high heat resistance, high transparency, and high mechanical strength, the (meth) acrylic resin is particularly preferably a (meth) acrylic resin having a lactone ring structure.

Examples of the (meth) acrylic resin having a lactone ring structure include Japanese Patent Application Publication No. 2000-230016, Japanese Patent Application Publication No. 2001-151814, Japanese Patent Application Publication No. 2002-120326, and Japanese Patent Application Publication No. 2002-254544. The (meth) acrylic resin having a lactone ring structure described in the gazette, Japanese Patent Application Laid-Open No. 2005-146084, and the like.

The mass average molecular weight (sometimes also called weight average molecular weight) of the (meth) acrylic resin having a lactone ring structure is preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, and more preferably 10,000 to 500,000, and particularly preferably It is 50,000 ~ 500000.

The Tg (glass transition temperature) of the (meth) acrylic resin is preferably 115 ° C or higher, more preferably 120 ° C or higher, still more preferably 125 ° C or higher, and particularly preferably 130 ° C or higher. This is because it can have excellent durability. The upper limit of the Tg of the (meth) acrylic resin is not particularly limited, but it is preferably 170 ° C or lower from the viewpoint of moldability and the like. The Tg (glass transition temperature) of the above (meth) acrylic resin having a lactone ring structure is preferably 115 ° C or higher, more preferably 125 ° C or higher, more preferably 130 ° C or higher, particularly preferably 135 ° C, or most preferably It is 140 ° C or more. This is because it can have excellent durability. The upper limit of Tg of the (meth) acrylic resin having a lactone ring structure is not particularly limited, but it is preferably 170 ° C. or lower from the viewpoint of moldability and the like.

The (meth) acrylic resin film can satisfy the aforementioned breaking stress and breaking elongation even in an unstretched state. An unstretched (meth) acrylic resin film that can satisfy the breaking stress and elongation at break can be prepared from the (meth) acrylic resin. On the other hand, a (meth) acrylic resin film can also be used as a stretched film. The stretched film may be appropriately subjected to the same stretching treatment as the above cycloolefin-based resin film so as to satisfy the aforementioned breaking stress and breaking elongation in the stretching direction.

Any appropriate adhesive layer (not shown) can be used for the polarizer and the first resin film. The adhesive layer is formed of an adhesive. The type of the adhesive is not particularly limited, and various substances can be used. The adhesive layer is not particularly limited as long as it is optically transparent. Adhesives in various forms, such as water-based, solvent-based, hot-melt, and active energy ray-curable, can be used. From the viewpoint of humidification reliability, the active An energy ray hardening type adhesive is suitable.

The active energy ray-curable adhesive is an adhesive that hardens with active energy rays such as electron rays and ultraviolet (radical-curable, cation-curable). For example, it can be used in the form of electron-ray-curable and ultraviolet-curable. As the active energy ray-curable adhesive, for example, a photoradical-curable adhesive can be used. When a photoradical-curable active energy ray-curable adhesive is used as the UV-curable adhesive, the adhesive contains a radical polymerizable compound and a photopolymerization initiator. The coating method of the adhesive can be appropriately selected according to the viscosity or the target thickness of the adhesive. Examples of the coating method include a reverse coater, a gravure coater (direct, reverse, or lithography), a bar reverse coater, a roll coater, a die coater, a bar coater, and a bar coater. Machine and so on. In addition, a method such as a dipping method may be appropriately used for coating.

A hard coating layer or an anti-reflection treatment may be applied to the surface of the first resin film that is not attached to the polarizer, to prevent adhesion, diffusion, and even anti-glare treatment.

(3) Second resin film The polarizer has a second resin film on a surface opposite to the surface on which the first resin film is formed. The moisture permeability is preferably 40 g / (m ² · day) or less, and more preferably 30 g / (m ² · day) or less. In addition, the lower limit value of the moisture permeability is not particularly limited, and ideally, water vapor cannot penetrate at all (that is, 0 g / (m ² ･ day)). Since the moisture permeability of the first resin film is within the aforementioned range, deterioration of the polarizer due to moisture can be suppressed.

The thickness of the second resin film is not particularly limited, but it is preferably 10 μm or more, and more preferably 12 μm or more from the viewpoints of reducing the moisture permeability to improve the reliability of humidification and increasing the breaking strength to further suppress the penetrating crack. On the other hand, from the viewpoint of thinning, the thickness is preferably 30 μm or less, and more preferably 25 μm or less.

The material for forming the second resin film may be any material that can form a film having transparency and a moisture permeability of 100 g / (m ² · day) or less. Specifically, the same materials as those of the first resin film may be exemplified by cycloolefin resin films, (meth) acrylic resin films, and the like.

Examples of the cycloolefin-based resin film and (meth) acrylic resin film include the first resin film. In addition, the second resin film is not limited except for the moisture permeability described above, and one having the same breaking stress and elongation at break as the first resin film may be used. If a stretched film is used as the second resin film, the film may cause a phase difference when the film is stretched and contracted in a severe environment, and the generation of the phase difference may cause a deviation such as a corner deviation. Therefore, an unstretched film is suitable. As the second resin film, an unstretched cycloolefin-based resin film is more preferably used.

The polarizer and the second resin film are usually adhered to each other through an adhesive. Examples of the adhesive include the first resin film.

A hard coating layer or an anti-reflection treatment may be applied to the surface of the second resin film that is not attached to the polarizer, to prevent adhesion, diffusion, or anti-glare treatment.

Since the polarizing film of the present invention uses a polarizer having a thickness of 10 μm or less, the entire polarizing film can be made into a thin film. The thickness of the polarizing film can be set to 100 μm or less.

2. Polarizing film with an adhesive layer The polarizing film with an adhesive layer of the present invention has the aforementioned polarizing film and an adhesive layer. The placement of the adhesive layer is not particularly limited, but in the image display device, the first resin film side of the aforementioned polarizing film should be disposed more outward than the polarizer, so it should be located on the second resin film side of the aforementioned polarizing film. With the aforementioned adhesive layer. The polarizing film with an adhesive layer having an adhesive layer on the side of the second resin film is arranged on the image display unit through the adhesive layer to form an image display device.

The aforementioned adhesive layer may be laminated on the side of the second resin film that does not have a polarizer. Specifically, for example, as shown in FIG. 2, the polarizing film F2 with an adhesive layer of the present invention includes a first resin film b1, a polarizer a, a second resin film b2, and an adhesive layer c in this order.

The polarizing film with an adhesive layer of the present invention can form an adhesive layer by directly coating the adhesive composition with the aforementioned polarizing film and heating and drying to remove the solvent and the like. In addition, an adhesive layer formed on a support or the like may be transferred to the aforementioned polarizing film to form a polarizing film with an adhesive layer.

The said adhesive layer is not specifically limited, A well-known thing can be used. Specifically, the adhesive layer may be appropriately selected from, for example, a (meth) acrylic polymer, a silicone polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based polymer, or a rubber-based polymer. Other polymers as the base polymer. Among these, the acrylic adhesive with (meth) acrylic polymer as the base polymer has good optical transparency, exhibits moderate wettability, cohesiveness, and adhesive properties, and has weather resistance and heat resistance. It is suitable because it is excellent.

The (meth) acrylic polymer is not particularly limited, and examples thereof include those obtained by polymerizing a monomer component containing an alkyl (meth) acrylate having an alkyl group having 4 to 24 carbon atoms at the end of the ester group. The term “alkyl (meth) acrylate” refers to an alkyl acrylate and / or an alkyl methacrylate, and (meth) in the present invention has the same meaning.

Examples of the (meth) acrylic acid alkyl ester include a linear or branched alkyl group having 4 to 24 carbon atoms. From the viewpoint of easy balance of the adhesive properties, a linear or branched An alkyl (meth) acrylate having an alkyl group having 4 to 9 carbon atoms is preferred. These alkyl (meth) acrylates can be used individually by 1 type or in combination of 2 or more types.

The monomer component forming the (meth) acrylic polymer may contain a comonomer other than the aforementioned (meth) acrylic acid alkyl ester as a monofunctional monomer component. Examples of the comonomer include a cyclic nitrogen-containing monomer, a hydroxyl-containing monomer, a carboxyl-containing monomer, and a monomer having a cyclic ether group.

In addition, the monomer component forming the (meth) acrylic polymer may contain a polyfunctional monomer in addition to the monofunctional monomer as necessary in order to adjust the cohesive force of the adhesive. The above-mentioned polyfunctional single system has at least two polymerizable functional groups having an unsaturated double bond such as a (meth) acrylfluorenyl group or a vinyl group, and examples thereof include dipentaerythritol hexa (meth) acrylic acid. Ester, 1,6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate. The polyfunctional monomer may be used singly or in combination of two or more kinds.

For the production of the (meth) acrylic polymer, known publicly known production methods such as radiation polymerization such as solution polymerization and ultraviolet polymerization, block polymerization, and emulsion polymerization can be appropriately selected. The obtained (meth) acrylic polymer may be any of a random copolymer, a block copolymer, and a graft copolymer.

A polymerization initiator, a chain transfer agent, an emulsifier, and the like that can be used for radical polymerization are not particularly limited, and known substances generally used in the art can be appropriately selected and used. In addition, the weight average molecular weight of the (meth) acrylic polymer can be controlled by the amount of the polymerization initiator, the chain transfer agent used, and the reaction conditions, and the amount used can be appropriately adjusted in accordance with the types thereof.

The weight average molecular weight (Mw) of the (meth) acrylic polymer used in the present invention is preferably 400,000 to 4 million. When the weight average molecular weight is more than 400,000, the durability of the adhesive layer can be satisfied, or the reduction of the cohesive force of the adhesive layer and the occurrence of residues can be suppressed. On the other hand, when the weight average molecular weight is more than 4 million, the adhesiveness tends to decrease. In addition, the viscosity of the adhesive in the solution system may become too high to be difficult to apply. The weight average molecular weight refers to a value measured by GPC (Gel Permeation Chromatography) and calculated in terms of polystyrene. As for the (meth) acrylic polymer obtained by radiation polymerization, it is difficult to measure molecular weight.

The adhesive composition used in the present invention may contain a crosslinking agent. Examples of the crosslinking agent include isocyanate-based crosslinking agents, epoxy-based crosslinking agents, polysiloxane-based crosslinking agents, Crosslinking agents such as oxazoline crosslinking agents, aziridine crosslinking agents, silane crosslinking agents, alkyl etherified melamine crosslinking agents, metal chelate crosslinking agents, peroxides, etc. They can be used singly or in combination of two or more kinds. The aforementioned crosslinking agent is preferably an isocyanate-based crosslinking agent or an epoxy-based crosslinking agent.

The above-mentioned crosslinking agent may be used alone, or two or more kinds may be mixed and used, but in terms of the overall content, it is preferably within the range of 0.01 to 10 parts by weight relative to 100 parts by weight of the aforementioned (meth) acrylic polymer. Contains the aforementioned crosslinking agent.

In order to improve the adhesion, the adhesive composition used in the present invention may contain a (meth) acrylic oligomer. In addition, when the adhesive layer is applied to a hydrophilic adherend such as glass, in order to improve the water resistance of the interface, the adhesive composition used in the present invention may contain a silane coupling agent.

In addition, the adhesive composition used in the present invention may also contain other well-known additives, such as polyether compounds such as polypropylene glycol and polyalkylene glycol, powders such as colorants, and pigments, surfactants, etc., depending on the application. , Plasticizer, tackifier, surface lubricant, leveling agent, softener, antioxidant, anti-aging agent, light stabilizer, ultraviolet absorber, polymerization inhibitor, inorganic or organic filler, metal powder, particles Shape, foil, etc. Further, within a controllable range, a redox system in which a reducing agent is added may be used.

The formation method of the said adhesive layer can be performed by a well-known method.

Various methods can be used for the application method of the adhesive composition. Specifically, for example, roll coating, contact roll coating, gravure coating, reverse coating, roll brush, spray cloth, dip roll coating, bar coating, blade coating, air knife coating, Methods such as curtain coating, lip coating, and extrusion coating using a die coater.

The aforementioned heating and drying temperature is preferably about 30 ° C to 200 ° C, more preferably about 40 ° C to 180 ° C, and even more preferably about 80 ° C to 150 ° C. By setting the heating temperature to the above range, an adhesive layer having excellent adhesive properties can be obtained. The drying time can be appropriately adopted. The above drying time is preferably about 5 seconds to 20 minutes, preferably about 30 seconds to 10 minutes, and more preferably 1 minute to 8 minutes.

As the aforementioned support, for example, a sheet (separator) subjected to a peeling treatment can be used. As the release-treated sheet, a silicone release liner is suitable.

Examples of the constituent materials of the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester film; porous materials such as paper, cloth, and non-woven fabric; net pieces; foamed sheets; Suitable foils and the like, such as metal foils and laminates thereof, are suitable for use of plastic films in terms of excellent surface smoothness.

Examples of the plastic film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, and polyethylene terephthalate. Ester film, polybutylene terephthalate film, polyurethane film, ethylene-vinyl acetate copolymer film, etc.

The thickness of the aforementioned separator is usually 5 to 200 μm, and preferably about 5 to 100 μm. On the aforementioned separators, it is also possible to use polysiloxane-based, fluorine-based, long-chain alkyl-based or fatty acid ammonium-based mold release agents, silica powder, etc. for mold release and antifouling treatment, or coating type, Antistatic treatment such as kneading type and vapor deposition type. In particular, by appropriately performing a peeling treatment such as a polysiloxane treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator, the peelability from the adhesive layer can be further improved.

In addition, the peeled sheet used in the production of the polarizing film with an adhesive layer can be directly used as a separator of the polarizing film with an adhesive layer, and the process can be simplified.

In addition, when the above-mentioned polarizing film with an adhesive layer is formed as an adhesive layer, an anchor layer may be formed on the surface of the polarizing film (for example, a second resin film), or various easy-bonding processes such as corona treatment and plasma treatment may be performed. An adhesive layer is then formed. In addition, the surface of the adhesive layer may be subjected to easy adhesion treatment.

The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 100 μm, and more preferably 10 to 50 μm.

3. Image display device The image display device of the present invention only needs to include the polarizing film of the present invention or a polarizing film with an adhesive layer. As for the remaining structure, the same as the conventional image display device. The polarizing film or the polarizing film with an adhesive layer can be applied to an image display unit. For example, when the image display device is a liquid crystal display device, the aforementioned polarizing film or the polarizing film with an adhesive layer can be applied to the viewing side of the image display unit (liquid crystal unit), and also to the backlight side. When the image display device is an organic EL display device, the aforementioned polarizing film or the polarizing film with an adhesive layer can be applied to the viewing side of the image display unit. The polarizing film or the polarizing film with an adhesive layer is preferably arranged such that the side of the second resin film becomes the side of the image display unit. The image display device of the present invention has high reliability because it includes the aforementioned polarizing film or a polarizing film with an adhesive layer. Examples

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. In addition, parts and% in each case are a basis of weight.

(Production of polarizers) Corona treatment was applied to one side of the substrate of amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) with a water absorption of 0.75% and a Tg of 75 ° C. And coated the corona treated surface at 25 ° C with a ratio of 9: 1 containing polyvinyl alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mole%) and acetamidine modified PVA (degree of polymerization) : 1200, Acetylenyl modification degree: 4.6%, Saponification degree: 99.0 mol% or more, manufactured by Japan Synthetic Chemical Industry Co., Ltd. under the trade name "Gohsefimer Z200") and dried to form a PVA with a thickness of 11 μm It is a resin layer, and a laminated body is produced. In an oven at 120 ° C, the obtained laminated body was subjected to free-end uniaxial extension of 2.0 times in the longitudinal direction (long-side direction) between rollers having different peripheral speeds (air-assisted extension treatment). Next, the laminated body was immersed in an insoluble bath (aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ° C (insolubilization treatment). Then, immerse it in a dyeing bath with a liquid temperature of 30 ° C. and adjust the iodine concentration and immersion time so that the polarizing plate has a predetermined transmittance. In this example, it was immersed in an aqueous iodine solution obtained by mixing 0.2 parts by weight of iodine and 1.0 part by weight of potassium iodide with respect to 100 parts by weight of water (dyeing treatment). Next, it was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30 ° C (crosslinking treatment) ). Then, while the laminated body was immersed in a boric acid aqueous solution at a liquid temperature of 70 ° C. (aqueous solution obtained by mixing 4.5 parts by weight of boric acid and 5 parts by weight of potassium iodide with respect to 100 parts by weight of water), the rollers at different peripheral speeds Uniaxial stretching was performed in the longitudinal direction (long side direction) to achieve a total stretching ratio of 5.5 times (water stretching treatment). Then, the laminated body was immersed in a washing bath (aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water with respect to 100 parts by weight of water) (washing treatment). An optical film laminate including a polarizer having a thickness of 5 μm was prepared in the above manner. The boric acid content of the obtained polarizer was 20% by weight.

(Adhesive for transparent protective film) 40 parts by weight of N-hydroxyethyl acrylamide (HEAA), acrylic acryl 60 parts by weight of phthaloline (ACMO) and 3 parts by weight of the photoinitiator "IRGACURE 819" (manufactured by BASF) were used to prepare an ultraviolet curing adhesive.

(Resin film) <Protective film 1> Unstretched acrylic resin film with a thickness of 15 μm: moisture permeability at 40 ° C and 92% RH: 50 g / (m ² · day), breaking stress: 15 N, breaking elongation: 4mm. 〈Protective film 2〉 17 μm-thick extended cycloolefin-based resin film (trade name: ZT12, manufactured by Japan Zeon Corporation): Water permeability at 40 ° C and 92% RH: 22 g / (m ² · day), breaking stress : 15N, elongation at break: 25mm. <Protective film 3> Unstretched acrylic resin film (trade name: HX-40UC, manufactured by Toyo Kohan Co., Ltd.) with a thickness of 47 μm: Permeability at 40 ° C and 92% RH: 65 g / (m ² · day) , Breaking stress: 39N, breaking elongation: 4mm. <Protective film 4> Cycloolefin resin film (trade name: ZF14, manufactured by Japan Zeon Corporation) with a thickness of 13 μm: Permeability at 40 ° C and 92% RH: 29 g / (m ² · day), Breaking stress: 9N , Elongation at break: 4mm. <Protective film 5> Cycloolefin resin film (brand name: ZF12, manufactured by Japan Zeon Corporation) with a thickness of 27 μm: Water permeability at 40 ° C and 92% RH: 23 g / (m ² · day), Breaking stress: 13 N , Elongation at break: 2.2mm. <Protective film 6> Triacetam cellulose film (trade name: KC2UAHC, manufactured by Konica Minolta) with a thickness of 32 μm: Permeability at 40 ° C and 92% RH: 796 g / (m ² · day), breaking stress: 41N, elongation at break: 2.7mm. <Protective film 7> Triacetam cellulose film (trade name: KC2UA, manufactured by Konica Minolta) with a thickness of 25 μm: Water permeability at 40 ° C and 92% RH: 1804 g / (m ² · day), breaking stress: 28N, elongation at break: 16mm.

Example 1 (manufacturing of a polarizing film) The surface of a polarizer (thickness: 5 μm) of the optical film laminate was coated with the above-mentioned ultraviolet-curing adhesive so that the thickness of the cured adhesive layer was 0.1 μm. After the protective film 1 (the first resin film) is simultaneously adhered, ultraviolet rays are irradiated as active energy rays to harden the adhesive. For ultraviolet irradiation, a gallium-filled metal halide lamp was used. The irradiation device was Light HAMMER10 manufactured by Fusion UV Systems, Inc. The lamp was a V lamp. The peak illuminance was 1600 mW / cm ² and the cumulative exposure was 1000 / mJ / cm ² (wavelength 380 ~ 440nm), and the ultraviolet irradiance is measured using the Sola-Check system manufactured by Solatell. Next, the non-crystalline PET substrate was peeled off, and the UV-curable adhesive was coated on the surface after peeling so that the thickness of the cured adhesive layer was 0.1 μm, and simultaneously corona-treated in advance. After the protective film 4 (second resin film) is irradiated with ultraviolet rays as described above to harden the adhesive, a polarizing film having protective films on both sides of the thin polarizer is produced. The protective film is laminated so that the direction for measuring the breaking stress and breaking elongation is perpendicular to the absorption axis of the polarizer (90 °).

Examples 2 to 3 and Comparative Examples 1 to 3 The protective films used for the first resin film and the second resin film in Example 1 were changed to those shown in Table 1, and were prepared in the same manner as in Example 1 except that Obtain a polarizing film.

The following evaluations were performed on the polarizing films produced in the examples and comparative examples. The results are shown in Table 1. In addition, the measurement methods of the moisture permeability of the protective film used in each example, the breaking stress of the protective film, and the elongation at break are also listed.

<Water vapor transmission rate of transparent protective film> The measurement of water vapor transmission rate is measured according to a water vapor transmission test (cup method) according to JIS Z0208. A sample cut to a diameter of 6 cm was set in a moisture-permeable cup (opening diameter: 6 cm in diameter) containing about 15 g of calcium chloride, and placed in a thermostat at a temperature of 40 ° C and a humidity of 92% RH. Then, the weight of calcium chloride was increased to obtain the moisture permeability (g / (m ² · day)).

<Measurement of Breaking Stress> After cutting each protective film to 100 mm × 100 mm, an Autograph (product name: AG-IS, manufactured by Shimadzu Corporation) was used as a tensile tester, and a tensile speed of 300 mm / Tensile tests were performed at a minimum distance of 100 mm between fixtures and at room temperature (23 ° C) to determine the stress-strain curve. Calculate the stress when the protective film is broken, and use it as the breaking stress. The measurement of the fracture stress was performed in a direction perpendicular to the absorption axis of the polarizer.

<Measurement of Elongation at Break> Using a tensile tester, each protective film was measured in an environment of 23 ° C. and 50% RH. The jig was set so that the initial length (initial jig interval) to be measured was 10 mm, and a tensile test was performed under a condition of a tensile speed of 50 mm / minute, and the elongation at the breaking point [elongation at break (elongation at the breaking point) was measured. ]. The elongation at break (elongation at break point) indicates the elongation at which the test piece is broken in a tensile test, and can be calculated by the following formula. "Elongation at break (extend at break point)" = "length when the test piece breaks (fixture interval at break)"-"initial length (10mm)"

<Measurement of Polarization Degree Change (ΔP) of Polarizing Film> The polarizing films prepared in the examples and comparative examples were put into a constant temperature and humidity machine at 85 ° C / 85% RH for 500 hours. Using a spectrophotometer with an integrating sphere (V7100, manufactured by JASCO Corporation), the polarization of the polarizing film before and after the measurement was measured, and the change amount ΔP of the polarization was determined by the following formula. Change in polarization degree ΔP (%) = (polarization degree before investment (%))-(polarization degree after investment (%)) In addition, the polarization degree P is obtained by stacking two identical polarizing films into two The transmittance (parallel transmittance: Tp) when the transmission axes are parallel to each other and the transmittance (vertical transmittance: Tc) when the transmission axes overlapped with each other are perpendicular to each other are obtained by substituting the following formulas. Polarization P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100 The transmittances are set so that the full polarized light obtained through the Glan-Taylor 稜鏡 polarizer is 100% The Y value obtained by correcting the optical performance of the 2-degree field of view (C light source) of JIS Z8701 is expressed.

<Confirmation of penetrating cracks: thermal shock test> An acrylic adhesive layer having a thickness of 20 μm was provided on the second resin film side of the polarizing film prepared in the examples and comparative examples, and the adhesive layer was prepared. Polarizing film. A polarizing film with an adhesive layer was cut into 50 mm × 150 mm (50 mm in the direction of the absorption axis), and the sample was produced by bonding to a 0.5 mm-thick alkali-free glass. The sample was placed in an environment with a thermal shock of -40 to 85 ° C for 30 minutes and 500 times each, and then taken out. It was visually confirmed that even if there was only one penetrating crack on the polarizing film, it was regarded as "yes". Treated as "none".

[Table 1]

The absolute value of the polarization change (ΔP) of the polarizing film of the present invention after being left for 500 hours at 85 ° C. and 85% R.H. is preferably less than 0.1%, more preferably 0.05% or less, and still more preferably 0.03% or less. Since the first resin film of the present invention satisfies the breaking stress of 13N or more and the breaking elongation of 2.5mm or more, it is severe even under thermal shock (for example, repeated thermal shock tests at -40 ° C and 85 ° C). In the environment, the overall shrinkage of the polarizing film can still be reduced to a minimum, and because of the use of a low-moisture-permeability protective film, the deterioration of the polarizer due to water can be suppressed. As a result, even under severe environments, the change in polarization is still small And has excellent optical characteristics.

F1‧‧‧polarizing film

F2 ‧‧‧ polarizing film with adhesive layer

a‧‧‧Polarizer

b1‧‧‧The first resin film

b2‧‧‧Second resin film

c‧‧‧adhesive layer

FIG. 1 is a cross-sectional view schematically showing an embodiment of a polarizing film of the present invention. 2 is a cross-sectional view schematically showing an embodiment of a polarizing film with an adhesive layer according to the present invention.

Claims (8)

A polarizing film having a first resin film on one side of a polarizer having a thickness of 10 μm or less and a second resin film on the other side; the polarizing film is characterized in that: the moisture permeability of the first resin film and the second resin film are both 100 g / (m ² · day) or less; and among the first resin film and the second resin film, at least the first resin film has a breaking stress of 13 N or more in a direction perpendicular to the absorption axis of the polarizer. The elongation at break is 2.5 mm or more. For example, the polarizing film of claim 1, wherein the first resin film and the second resin film are both resin films selected from cycloolefin resin films and acrylic resin films. The polarizing film according to claim 1 or 2, wherein the first resin film is an extended film of a cycloolefin resin film. The polarizing film according to claim 1 or 2, wherein the first resin film is an acrylic resin film. A polarizing film with an adhesive layer is characterized by having a polarizing film and an adhesive layer according to any one of claims 1 to 4. For example, the polarizing film with an adhesive layer provided in claim 5 has the aforementioned adhesive layer on the side of the second resin film of the aforementioned polarizing film. An image display device is characterized in that the image display unit is provided with a polarizing film according to any one of claims 1 to 4 or a polarizing film with an adhesive layer according to claim 5 or 6. The image display device according to claim 7, wherein the polarizing film or the polarizing film with an adhesive layer is arranged so that the second resin film side becomes the image display unit side.