TWI724436B - Polarizing film, polarizing film with adhesive layer and image display device - Google Patents

Abstract

The object of the present invention is to provide a polarizing film, which is not susceptible to cracks in the polarizing member even in a severe environment of thermal shock. The polarizing film of the present invention is provided with a protective film on one side or both sides of the polarizing member via an adhesive layer, and at least one of the aforementioned protective films provided on the polarizing member satisfies the following formula (1): Y≦1.26×lnX +3.5 (1) Y: The coefficient of linear expansion of the protective film (×10 ^-5 /K) X: The elongation at break (%) of the protective film.

Description

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

The present invention relates to a polarizing film and a polarizing film having an adhesive layer of the polarizing film and the adhesive layer. In addition, the present invention relates to an image display device including the polarizing film or the polarizing film with the adhesive layer.

Background of the invention In various image display devices, polarizing films are used to display images. For example, from the perspective of the image forming method of a liquid crystal display device (LCD), it is necessary to arrange polarizing films on both sides of the glass substrate forming the surface of the liquid crystal panel. On the organic EL display device, in order to shield the specular reflection of external light on the metal electrode, a circularly polarized film laminated with a polarizing film and a quarter-wave plate is arranged on the viewing side of the organic light-emitting layer.

The aforementioned polarizing film is generally used for a polarizer composed of a polyvinyl alcohol-based film and a dichroic material such as iodine, and a protective film is attached to one or both sides of the polarizer through a polyvinyl alcohol-based adhesive or the like.

The aforementioned polarizing film is subject to severe thermal shock (for example, repeated thermal shock tests at -40°C and 85°C). Due to the change in the shrinkage stress of the polarizer, it is easy to absorb the overall direction of the polarizer. The problem of cracks (penetrating cracks).

Patent Document 1 proposes a polarizing plate for the purpose of providing a polarizing plate with excellent durability even in a cold and thermal shock environment. The polarizing plate is formed by arranging transparent protective films on both sides of the polarizing film and is characterized by: The difference between the linear expansion coefficient of the polarizing film in the direction orthogonal to the absorption axis and the linear expansion coefficient of the transparent protective film arranged on at least one side of the polarizing film in the direction orthogonal to the absorption axis of the polarizing plate is 1.3× Below 10 ^-4 /℃.

Prior art literature Patent literature Patent Document 1: Japanese Patent Application Publication No. 2011-203571

Summary of the invention The problem to be solved by the invention However, even for the polarizing plate of Patent Document 1, depending on the type of transparent protective film, the stress generated by the expansion and contraction of the transparent protective film may still greatly affect the expansion and contraction of the polarizing film, so it may cause problems in the polarizing film. The situation of the rift.

The object of the present invention is to provide a polarizing film, which is not susceptible to cracks in the polarizing member even in a severe environment of thermal shock.

In addition, an object of the present invention is to provide an adhesive polarizing film with the aforementioned polarizing film and an adhesive layer, and an image display device including the polarizing film or the polarizing film with the adhesive.

Methods to solve the problem The inventors of the present invention have actively reviewed and found that the above-mentioned problems can be solved by the following polarizing film, and the present invention has been completed.

That is, the present invention relates to a polarizing film, which is provided with a protective film on one or both sides of the polarizing member via an adhesive layer. The polarizing film is characterized in that: at least one of the aforementioned protective films provided on the polarizing member It satisfies the following formula (1): Y≦1.26×lnX+3.5 (1) Y: the coefficient of linear expansion of the protective film (×10 ^-5 /K) X: the elongation at break (%) of the protective film.

In the aforementioned polarizing film, the aforementioned Y (×10 ^-5 /K) is preferably 4 or less.

In addition, in the polarizing film, the thickness of the polarizing member is preferably 10 μm or less.

In addition, the present invention relates to a polarizing film with an adhesive layer having the aforementioned polarizing film and an adhesive layer.

In addition, the present invention relates to an image display device, in which the polarizing film or the polarizing film with the adhesive layer is disposed on the image display unit.

Invention effect By using at least one protective film that satisfies the aforementioned formula (1) as a protective film on one or both sides of the polarizer, the expansion and contraction of the polarizer due to the stress caused by the expansion and contraction of the protective film can be alleviated. Therefore, it is not easy to produce cracks in the polarizer.

By using a protective film with a linear expansion coefficient Y (×10 ^-5 /K) of 4 or less, the stress caused by the expansion and contraction of the polarizer can be more effectively relieved, and therefore the cracks in the polarizer can be more effectively suppressed.

In addition, with the development of thinner image display devices such as liquid crystal display devices in recent years, there is also a need for thinner polarizers. However, thin polarizers with a thickness of 10 μm or less have a problem that their optical properties are easily degraded in a humidified environment (due to moisture). In order to prevent the thin polarizer from deteriorating due to moisture, we have considered using ^{a resin film with low moisture permeability (specifically, 100 g/(m 2} ·day) or less) as a protective film to be attached to the thin polarizer. When a resin film with low moisture permeability is used as a protective film, it is possible to suppress the deterioration of the polarizer in a humidified environment. However, the protective film with low moisture permeability tends to have a large linear expansion coefficient, and it is difficult to relieve the stress caused by the expansion and contraction of the polarizing member, and therefore the polarizing member is prone to cracks. However, even a protective film with a large linear expansion coefficient, as long as it is a protective film that has a large breaking elongation and satisfies the aforementioned formula (1), it can effectively alleviate the stress caused by the expansion and contraction of the polarizer, so it is not easy to crack the polarizer. . Therefore, the polarizing film of the present invention can both suppress the deterioration of the polarizer due to humidification (improve humidification reliability) and suppress the generation of cracks.

Modes for Implementing the Invention 1. Polarizing film The polarizing film of the present invention is provided with a protective film on one or both sides of the polarizer through an adhesive layer, and at least one of the aforementioned protective films provided on the polarizer satisfies the following requirements The formula (1). Y≦1.26×lnX+3.5 (1) Y: Linear expansion coefficient of protective film (×10 ^-5 /K) X: Breaking elongation of protective film (%)

The components are explained below.

(1) Polarizing parts The polarizing member can be used without any particular limitation, but from the viewpoint of thinning and suppressing the occurrence of cracks, it is preferable to use a polarizing member with a thickness of 10 μm or less. The thickness of the polarizer is more preferably 8 μm or less, more preferably 7 μm or less, and even more preferably 6 μm or less. On the other hand, the thickness of the polarizer is 2 μm or more, more preferably 3 μm or more.

The polarizer is made of polyvinyl alcohol resin. Examples of polarizers include hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, and ethylene-vinyl acetate copolymer-based partially saponified films that adsorb iodine or dichroic dyes. Color substances and uniaxially stretched ones, as well as polyene-based oriented films such as dehydrated polyvinyl alcohol or dehydrated polyvinyl chloride. Among them, a polarizer composed of a dichroic substance such as a polyvinyl alcohol-based film and iodine is more suitable.

The polarizer in which a polyvinyl alcohol-based film is dyed with iodine and uniaxially stretched can be produced by, for example, immersing polyvinyl alcohol in an aqueous solution of iodine for dyeing, and stretching it to 3 to 7 times its original length. If necessary, it may contain boric acid, zinc sulfate, zinc chloride, etc., and may be immersed in an aqueous solution such as potassium iodide. Furthermore, if necessary, the polyvinyl alcohol-based film may be immersed in water for washing before dyeing. By washing the polyvinyl alcohol-based film with water, the dirt and anti-caking agent on the surface of the polyvinyl alcohol-based film can be washed. In addition, it also has the effect of swelling the polyvinyl alcohol-based film to prevent uneven dyeing. The extension may be performed after dyeing with iodine, or may be extended while dyeing, or may be dyed with iodine after extension. It can also be extended in aqueous solutions such as boric acid or potassium iodide or in a water bath.

From the viewpoint of extension stability and humidification reliability, the polarizer should contain boric acid. In addition, from the viewpoint of suppressing the generation of 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 with respect to the total amount of the polarizer. From the viewpoint of extension stability and humidification reliability, the content of boric acid relative to the total amount of the polarizer is preferably 10% by weight or more, and more preferably 12% by weight or more.

Examples of thin polarizers include: Japanese Patent No. 4751486 specification, Japanese Patent No. 4751481 Specification, Japanese Patent No. 4815544 Specification, Japanese Patent No. 5048120 Specification, International Publication No. 2014/077599 Bulletin Manual, The thin polarizer described in the manual of International Publication No. 2014/077636, etc., or the thin polarizer manufactured by the manufacturing method described in the same.

In the manufacturing method including the stretching step and the dyeing step in the state of a laminate, from the viewpoint of being able to stretch at a high magnification and improving the polarization performance, the aforementioned thin polarizer is described in Japanese Patent No. 4751486 and Japanese Patent No. 4751481. The specifications described in the specification of Japanese Patent No. 4815544 and the specification of Japanese Patent No. 4815544 are preferably obtained by the method including the step of extending in an aqueous solution of boric acid, and particularly as described in the specification of Japanese Patent No. 4751481 and the specification of Japanese Patent No. 4815544 It is preferably obtained by a manufacturing method that includes a step of auxiliary air extension before extension in a boric acid aqueous solution. These thin polarizers can be produced by a manufacturing method including the following steps: a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as PVA-based resin) layer and a resin substrate for stretching in the state of a laminate and dyeing step. As long as this method is used, even if the PVA-based resin layer is thin, it is supported by the resin base material for stretching, so it can be stretched without causing problems such as breakage due to stretching.

(2) Protective film The material of the protective film is preferably one that is excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. Examples include: polyester-based polymers such as polyethylene terephthalate or polyethylene naphthalate; cellulose-based polymers such as diacetyl cellulose or triacetyl cellulose; polymethyl methacrylate Acrylic polymers such as esters; styrene polymers such as polystyrene or acrylonitrile-styrene copolymer (AS resin); polycarbonate polymers, etc. In addition, the following polymers can also be cited as examples of the polymers forming the above-mentioned protective film: polyethylene, polypropylene, polyolefins having cyclic or even norbornene structures, such as polyolefin polymers of ethylene-propylene copolymers , Vinyl chloride-based polymers, nylon or aromatic polyamides and other amide-based polymers, imine-based polymers, turpentine-based polymers, polyether turpentine-based polymers, polyether ether ketone-based polymers, and Benzene sulfide polymer, vinyl alcohol polymer, chlorinated vinylene polymer, vinyl butyral polymer, aryl ester polymer, polyoxymethylene polymer, epoxy polymer or the above-mentioned polymers The blends and so on.

The protective film may contain one or more arbitrary and appropriate additives. Examples of additives include ultraviolet absorbers, antioxidants, slip agents, plasticizers, mold release agents, anti-colorants, flame retardants, nucleating agents, antistatic agents, pigments, colorants, and the like.

The content of the above-mentioned polymer in the protective film is preferably 50-100% by weight, preferably 50-99% by weight, more preferably 60-98% by weight, and even more preferably 70-97% by weight. When the content of the polymer in the protective film is less than 50% by weight, there is a possibility that the high transparency originally possessed by the polymer may not be sufficiently exhibited.

The aforementioned protective film may also use a retardation film, a brightness enhancement film, a diffusion film, and the like. Examples of the retardation film include those having a frontal retardation of 40 nm or more and/or a thickness direction retardation of 80 nm or more. The frontal phase difference is usually controlled in the range of 40~200nm, and the thickness direction phase difference is usually controlled in the range of 80~300nm. When a retardation film is used as a protective film, the retardation film can also function as a protective film of a polarizer, so it can be reduced in thickness.

Examples of the retardation film include a birefringent film obtained by uniaxially or biaxially stretching a thermoplastic resin film. The above-mentioned stretching temperature, stretching ratio, etc. can be appropriately set according to the retardation value, film material and thickness.

The thickness of the protective film can be appropriately determined, but from the viewpoint of workability such as strength and handling, and thin layer properties, it is about 1 to 500 μm. The thickness of the protective film is preferably 1 to 300 μm, preferably 5 to 200 μm, and more preferably 5 to 150 μm, and even more preferably 20 to 100 μm.

Functional layers such as hard coating, anti-reflection layer, anti-adhesion layer, diffusion layer and even anti-glare layer can be provided on the surface of the aforementioned protective film that is not adhered to the polarizer. In addition, functional layers such as the above-mentioned hard coat layer, anti-reflection layer, anti-adhesion layer, diffusion layer, or anti-glare layer may be provided in addition to the protective film itself, or may be separately provided as an individual from the protective film.

In the present invention, at least one of the protective film (may include the aforementioned functional layer) provided on the polarizer is one that satisfies the following formula (1). When a protective film is to be provided on both sides of the polarizing member, the protective films provided on both sides of the polarizing member should satisfy the following formula (1) respectively. In this way, the stress caused by the expansion and contraction of the polarizer can be effectively relieved, and therefore, the polarizer is less prone to cracks. In addition, please refer to the description of the examples for the measurement methods of the coefficient of linear expansion and elongation at break of the protective film. Y≦1.26×lnX+3.5 (1) Y: Linear expansion coefficient of protective film (×10 ^-5 /K) X: Breaking elongation of protective film (%)

The coefficient of linear expansion and elongation at break of the protective film will vary with the raw material and thickness used, so the thickness should be adjusted appropriately according to the raw material used. The protective film satisfying the above formula (1) can be produced by, for example, extending a cycloolefin-based polymer film to a thickness of about 17 to 18 μm.

Commercial products of the protective film satisfying the above formula (1) include, for example, TJ25UL (manufactured by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25 μm), ZT12 (manufactured by ZEON, Japan, raw material: Cycloolefin polymer, thickness: 17μm, KC2UA (manufactured by Konica Minolta, raw material: triacetyl cellulose polymer, thickness: 20μm), and KC2UGR-HC (manufactured by Konica Minolta, based on triacetyl cellulose polymer) The film is provided with an acrylic resin-based hard coating film, thickness: 37μm), etc.

^{The linear expansion coefficient Y (×10 -5} /K) of the protective film that satisfies the above formula (1) is preferably 4 or less, preferably 3.5 or less, and more preferably 3.1 or less.

(3) Adhesive layer

The adhesive layer is formed of an adhesive. The type of the adhesive is not particularly limited, and various substances can be used. The aforementioned adhesive layer is not particularly limited as long as it is optically transparent. The adhesive can be in various forms such as water-based, solvent-based, hot-melt adhesive, and active energy ray hardening type, but water-based adhesive or active energy ray hardening type Adhesive is suitable.

Examples of water-based adhesives include isocyanate-based adhesives, polyvinyl alcohol-based adhesives, gelatin-based adhesives, vinyl-based latex-based adhesives, and water-based polyesters. The water-based adhesive is usually used as an adhesive composed of an aqueous solution, and usually contains 0.5 to 60% by weight of solid content.

The active energy ray hardening adhesive is an adhesive that is hardened with active energy rays such as electron beams and ultraviolet rays (radical hardening type, cation hardening type). For example, it can be used in the form of electron beam hardening type and ultraviolet hardening type. As the active energy ray hardening type adhesive, for example, a light radical hardening type adhesive can be used. When the photo radical curable active energy ray curable adhesive is used as an ultraviolet 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 coating methods include: reverse coater, gravure coater (direct, reverse or offset), bar reverse coater, roll coater, die coater, bar coater, bar coater, etc. In addition, for coating, a dipping method or the like can be appropriately used.

In addition, when a water-based adhesive or the like is used for the application of the aforementioned adhesive, it is preferable to perform it so that the thickness of the finally formed adhesive layer becomes 30 to 300 nm. The thickness of the aforementioned adhesive layer is more preferably 60~250nm. On the other hand, when an active energy ray-curable adhesive is used, it is preferable to perform it so that the thickness of the adhesive layer becomes 0.1 to 200 μm. It is more preferably 0.5~50μm, more preferably 0.5~10μm.

In addition, when the polarizer and the protective film are laminated, an easy-to-bond layer can be provided between the protective film and the adhesive layer. The easy-adhesive layer can be formed of various resins having, for example, the following skeletons: polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, polysiloxane system, polyamide skeleton, polyimide skeleton , Polyvinyl alcohol skeleton, etc. These polymer resins can be used individually by 1 type or in combination of 2 or more types. In addition, other additives may be added when the easy-to-adhesive layer is formed. Specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat-resistant stabilizers can be used.

The easy-adhesive layer is usually set on the protective film in advance, and the easy-adhesive layer side of the protective film and the polarizer are laminated by an adhesive layer. The formation of the easy-adhesive layer can be carried out by coating the forming material of the easy-adhesive layer on the protective film and drying it by a well-known technique. The easy-adhesive layer forming material is usually adjusted in consideration of the thickness after drying, the smoothness of the coating, etc., to prepare a solution that has been diluted to an appropriate concentration. The thickness of the easy bonding layer after drying is preferably 0.01~5μm, more preferably 0.02~2μm, and more preferably 0.05~1μm. Moreover, the easy-adhesive layer can be provided with multiple layers, and in this case, it is also preferable that the total thickness of the easy-adhesive layer falls within the above range.

2. Polarizing film with adhesive layer The polarizing film with an adhesive layer of the present invention has the aforementioned polarizing film and an adhesive layer.

When a double-sided protective polarizing film is provided with a protective film on both sides of the polarizer, an adhesive layer is provided on one side of the double-sided protective polarizing film directly or through other layers. In addition, a surface protective film can also be provided on the other side of the double-sided protective polarizing film directly or through other layers.

When a single-sided protective polarizing film is provided with a protective film on only one side of the polarizer, an adhesive layer is provided on the polarizer side of the single-sided protective polarizing film directly or through other layers. In addition, a surface protective film may be provided on the side of the protective film of the single-sided protective polarizing film directly or via another layer.

The aforementioned other layer is not particularly limited, and it may be a well-known functional layer or optical layer provided on a polarizing film. The optical layer can include, for example, a reflective plate, a semi-transmissive plate, a retardation plate (including a 1/2 or 1/4 wavelength plate), a viewing angle compensation film, and a brightness enhancement film. The aforementioned other layers may be provided with one layer or two or more layers.

The aforementioned adhesive layer is provided on one side of the polarizing film in order to bond the polarizing film to a unit substrate such as a liquid crystal cell.

The thickness of the aforementioned adhesive layer is not particularly limited. For example, it may be about 1-100 μm, preferably 2-50 μm, more preferably 2-40 μm, and even more preferably 5-35 μm.

An appropriate adhesive can be used for the formation of the aforementioned adhesive layer, and there is no particular limitation on the type thereof. Examples of adhesives include rubber adhesives, acrylic adhesives, silicone adhesives, urethane adhesives, vinyl alkyl ether adhesives, polyvinyl alcohol adhesives, and polyvinyl pyrrole. Pyridone-based adhesives, polyacrylamide-based adhesives, cellulose-based adhesives, etc.

Among these adhesives, it is suitable to use those having good optical transparency, exhibiting moderate wettability, adhesion characteristics of aggregation and adhesiveness, and excellent weather resistance and heat resistance. For those exhibiting such characteristics, it is better to use an acrylic adhesive.

The method of forming the adhesive layer can be, for example, the method of applying the aforementioned adhesive to the separated parts that have been peeled off, and then drying and removing the polymerization solvent to form an adhesive layer, and then transferring it to a polarizing film ; Or coating the aforementioned adhesive, and drying and removing the polymerization solvent, etc. to form an adhesive layer on the polarizing film, etc. In addition, one or more solvents other than the polymerization solvent may be added appropriately when applying the adhesive.

Separate parts that have been stripped should use silicone release liners. In the step of applying an adhesive on the lining material and drying it to form an adhesive layer, the method of drying the adhesive may adopt an appropriate and appropriate method depending on the purpose. It is suitable to use a method of overheating and drying the above-mentioned coated film. The heating and drying temperature should be 40℃~200℃, more preferably 50℃~180℃, especially 70℃~170℃. By setting the heating temperature within the above range, an adhesive with excellent adhesive properties can be obtained.

The drying time can be appropriately used. The above drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

Various methods can be used to form the adhesive layer. Specifically, for example, roll coating, touch roll coating, gravure coating, reverse coating, roll brush, spray cloth, dip roll coating, bar coating, knife coating, pneumatic knife coating , Curtain coating, lip coating, extrusion coating using die coater, etc.

When the aforementioned adhesive layer is exposed, the peel-off treated sheet (separator) can be used to protect the adhesive layer until it is used for practical use.

Examples of constituent materials of the separator include plastic films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; porous materials such as paper, cloth, and non-woven fabrics; meshes and foamed sheets. Appropriate sheets such as, metal foil, and laminates thereof, etc., but in terms of excellent surface smoothness, plastic films are suitable.

The plastic film is not particularly limited as long as it can protect the aforementioned adhesive layer. Examples include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, and polyvinyl chloride. Film, vinyl chloride copolymer film, polyethylene terephthalate film, polybutylene terephthalate film, polyurethane film, ethylene-ethyl acetate copolymer film, etc.

The thickness of the aforementioned separator is usually 5 to 200 μm, preferably about 5 to 100 μm. The aforementioned separating parts can also be demoulded and antifouling treated with silicone, fluorine, long-chain alkyl or fatty acid amide-based mold release agents, silica powder, etc., as well as coating type, Antistatic treatment such as kneading type and vapor deposition type. In particular, by appropriately applying peeling treatments such as silicone treatment, long-chain alkyl treatment, and fluorine treatment to the surface of the separator, the peelability from the adhesive layer can be further improved.

The aforementioned surface protection film usually has a substrate film and an adhesive layer, and the polarizing film is protected via the adhesive layer.

From the viewpoints of inspection and management, the base film of the aforementioned surface protection film can be selected from isotropic or nearly isotropic film materials. The film material may include, for example, polyester resins such as polyethylene terephthalate films, cellulose resins, acetate resins, polyether turpentine resins, polycarbonate resins, polyamide resins, etc. Transparent polymers like polyimide resins, polyolefin resins, and acrylic resins. Among them, polyester-based resins are suitable. The substrate film can be used in the form of a laminate of one or more than two film materials, or an extension of the aforementioned film can be used. The thickness of the substrate film is usually 500 μm or less, preferably 10 to 200 μm.

The adhesive that forms the adhesive layer of the aforementioned surface protection film can be appropriately selected from (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, and fluorine-based polymers. Or rubber-based polymers are used as adhesives for base polymers. From the viewpoints of transparency, weather resistance, heat resistance, etc., an acrylic adhesive using an acrylic polymer as the base polymer is suitable. The thickness of the adhesive layer (dry film thickness) can be determined according to the required adhesive force. Usually it is about 1-100μm, preferably 5-50μm.

In addition, the surface protection film can also be provided with a release treatment layer on the opposite side of the base film where the adhesive layer is provided with a low-adhesion material such as silicone treatment, long-chain alkyl treatment, fluorine treatment, etc.

3. Image display device The image display device of the present invention only needs to include the polarizing film of the present invention or the polarizing film with an adhesive layer. As for the rest of the structure, the same as conventional image display devices can be cited. The aforementioned polarizing film or 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 polarizing film with an adhesive layer can be applied to either the viewing side or the backlight side of the image display unit (liquid crystal unit). 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. Since the image display device of the present invention includes the aforementioned polarizing film or the polarizing film with an adhesive layer, it has high reliability. Example

Hereinafter, the present invention will be specifically described with examples, but the present invention is not limited by these examples. As for the parts and% in each case, they are all based on weight.

(Making polarized parts) Apply corona treatment to one side of the substrate of amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100μm) with a water absorption rate of 0.75% and a Tg of 75°C, and the corona The treated surface was coated at 25°C and contained polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetyl acetyl modified PVA (polymerization degree: 1200, acetyl acetate in a ratio of 9:1). Modification degree of the base: 4.6%, degree of saponification: 99.0 mol% or more, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gohsefimer Z200") in an aqueous solution and dried to form a PVA-based resin layer with a thickness of 11 μm. Out of the layered body. In an oven at 120°C, the obtained laminate was uniaxially stretched 2.0 times at the free end in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds (air-assisted stretch processing). Next, the layered body was immersed in an insoluble bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insoluble treatment). Next, it was immersed in a dyeing bath with a liquid temperature of 30°C while adjusting the iodine concentration and immersion time so that the polarizing plate had a predetermined transmittance. In this example, it was immersed in an iodine aqueous solution obtained by mixing 0.2 parts by weight of iodine and 1.0 parts by weight of potassium iodide with respect to 100 parts by weight of water for 60 seconds (dyeing treatment). Next, it was immersed in a cross-linking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 3 parts by weight of boric acid with respect to 100 parts by weight of water with a liquid temperature of 30°C) for 30 seconds (cross-linking treatment) . Then, while immersing the layered body in an aqueous solution of boric acid (an 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) at a liquid temperature of 70°C, rolls with different peripheral speeds Uniaxial stretching is carried out in the longitudinal direction (long side direction) so that the total stretching magnification reaches 5.5 times (underwater stretching treatment). After that, the layered body was immersed in a washing bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water with a liquid temperature of 30°C) (washing treatment). In the above manner, an optical thin film laminate including a polarizer with a thickness of 5 μm was produced. The boric acid content of the prepared polarizer was 20% by weight.

(Making adhesives for protective film) Blending 40 parts by weight of N-Hydroxyethyl acrylamide (HEAA), 60 parts by weight of ACMO, and 3 parts by weight of photoinitiator "IRGACURE 819" (manufactured by BASF Corporation) to prepare ultraviolet rays Hardening adhesive.

Example 1 (Making a single-sided protective polarizing film) On the surface of the polarizer (thickness: 5μm) of the optical film laminate, the above-mentioned ultraviolet curable adhesive was applied so that the thickness of the adhesive layer after curing became 0.1μm, and the protective film 1 (attached) HC 25μm TAC film: TJ25UL (made by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25μm) with acrylic resin hard coating film), irradiated with ultraviolet rays as active energy rays The aforementioned adhesive hardens. Then, the amorphous PET substrate provided on one side of the polarizer was peeled off to produce a single-sided protective polarizing film.

Examples 2, 3, 6~8, comparative examples 1~8 The protective film 1 described in Table 1 was used, except that the same method as in Example 1 was used to produce a single-sided protective polarizing film.

Example 4 (Making a double-sided protective polarizing film) On the surface of the polarizer (thickness: 5μm) of the optical film laminate, the above-mentioned ultraviolet curable adhesive was applied so that the thickness of the adhesive layer after curing became 0.1μm, and the protective film 1 (attached) HC 25μm TAC film: TJ25UL (made by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25μm) with acrylic resin hard coating film), irradiated with ultraviolet rays as active energy rays The aforementioned adhesive hardens. After that, peel off the amorphous PET substrate provided on one side of the polarizer, and apply the above-mentioned ultraviolet-curing adhesive on the peeling surface so that the thickness of the cured adhesive layer becomes 0.1μm, and at the same time, the protection is laminated Film 2 (25μm TAC film: TJ25UL (manufactured by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25μm)), irradiated with ultraviolet rays as active energy rays to harden the adhesive to produce double-sided protection Polarizing film.

Examples 5, 9, 10, Comparative Example 9 The protective films 1 and 2 described in Table 1 were used, except that the double-sided protective polarizing film was produced in the same manner as in Example 4.

The protective films 1 and 2 described in Table 1 are as follows.

25μm TAC film with HC: TJ25UL (manufactured by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25μm) with acrylic resin-based hard coating film

25μm TAC film: TJ25UL (manufactured by Fujifilm, raw material: triacetyl cellulose polymer, thickness: 25μm)

17μm COP film: ZT12 (made by Japan's ZEON, biaxially stretched cycloolefin polymer film with a frontal phase difference of 116nm and a thickness of 81nm retardation film, thickness: 17μm)

20μm TAC film: KC2UA (manufactured by Konica Minolta, raw material: triacetyl cellulose polymer, thickness: 20μm)

Manufacturing method of 20μm acrylic film In a 30L tank reactor equipped with a stirring device, a temperature sensor, a cooling tube, and a nitrogen introduction tube, 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2-(hydroxymethyl) are fed Methyl acrylate (MHMA), 10,000g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), 5g of n-dodecanethiol, and while passing nitrogen through them, the temperature is raised to 105°C and After refluxing, 5.0 g of tertiary butyl peroxy isopropyl carbonate (Kayakarubon BIC-7, manufactured by KAYAKU AKZO CO., LTD.) was added as a polymerization initiator, and it took 4 hours to drop the tertiary butyl peroxy isopropyl carbonate (Kayakarubon BIC-7, manufactured by KAYAKU AKZO CO., LTD.). A solution composed of butylperoxyisopropyl carbonate and 230g of MIBK is subjected to solution polymerization at about 105~120°C under reflux, and then it takes 4 hours to mature. 30g of octadecyl phosphate/di(octadecyl) phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the prepared polymer solution, and the mixture was refluxed at about 90~120 The cyclization condensation reaction was carried out at ℃ for 5 hours. Then, the prepared polymer solution was introduced into the sleeve at a processing speed of 2.0 kg/h converted from the amount of resin. The temperature was 260°C, the number of rotations was 100 rpm, the degree of decompression was 13.3~400hPa (10~300mmHg), and the number of rear vent holes One vent type twin-screw extruder with 4 front vent holes (φ=29.75mm, L/D=30), and in the extruder, the cyclization condensation reaction and devolatization are further carried out. Extrusion is performed to obtain transparent pellets of a polymer containing lactone rings. After the dynamic TG measurement of the prepared lactone ring-containing polymer, a mass loss of 0.17% by mass was detected. In addition, the weight average molecular weight of the lactone ring-containing polymer was 133,000, the melt flow rate was 6.5 g/10 min, and the glass transition temperature was 131°C. The pellets and acrylonitrile-styrene (AS) resin (TOYO AS AS20, manufactured by TOYO STYRENE CO., LTD.) were kneaded and extruded with a mass ratio of 90/10 using a uniaxial extruder (screw 30mmφ). , Thereby making transparent pellets. The glass transition temperature of the obtained pellets was 127°C. The pellets were melt-extruded from a 400mm wide hanger-type T-die using a 50mmφ uniaxial extruder to produce a film with a thickness of 80μm. In addition, it was melt-extruded while supplying 0.66 parts by weight of an ultraviolet absorber (manufactured by ADEKA Corporation, trade name: LA-F70) with respect to 100 parts by weight of the resin in the pellets. Using a biaxial stretching device, the produced film was stretched 2.0 times at a temperature of 150° C., thereby preparing a stretched film (20 μm acrylic film) with a thickness of 20 μm. After measuring the optical properties of the stretched film, the total light transmittance was 93%, the in-plane retardation Δnd was 0.8 nm, and the thickness direction retardation Rth was 1.5 nm.

40μm acrylic film (UV) manufacturing method MS resin (MS-200; a copolymer of methyl methacrylate/styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine. Amination rate: 5%). In addition, the aforesaid imidization was performed using a bite type co-rotating twin-shaft extruder with a diameter of 15 mm. The set temperature of each temperature adjustment zone of the extruder is 230°C, the screw rotation speed is 150 rpm, and the MS resin is supplied at 2.0 kg/hr. The supply amount of monomethylamine is set to 2 weight relative to 100 parts by weight of MS resin Copies. The MS resin was put in from the hopper, and the resin was melted with a kneaded block to fill it, and then monomethylamine was injected from the nozzle. Put a sealing ring at the end of the reaction zone and fill it with resin. Reduce the pressure of the exhaust port to -0.08MPa to de-evaporate the by-products and excessive methylamine after the reaction. The resin that is sent out into a bundle from the die set at the exit of the extruder is cooled in a water tank, and then pelletized by a pelletizer. The aforementioned imidized MS resin is melt-extruded and formed into a film. At this time, 0.66 parts by weight of an ultraviolet absorber (manufactured by ADEKA Corporation, trade name: LA-F70) was supplied with respect to 100 parts by weight of MS resin. Then, biaxial stretching was performed to double the length and the width to form a protective film (40 μm acrylic film (UV), thickness 40 μm, Re=2nm, Rth=2nm).

Manufacturing method of 30μm acrylic film containing crosslinked elastomer The mixture with the following composition was fed into a glass reactor, heated to 80°C while stirring in a nitrogen stream, and then 25 parts of methyl methacrylate and 1 part of allyl methacrylate were fed all at once. 25% of the monomer mixture and 0.1 part of tertiary butyl hydroperoxide are polymerized for 45 minutes. Departed water 　　　　　　　　　　 220 copies Boric acid 　　　　　　　　　　　　 0.3 part Sodium carbonate　　　　　　　　　　　0.03 parts N-laurel sarcosine sodium 　　　　　　0.09 parts 0.09 part of sodium formaldehyde sulfoxylate 　　　　　　　 Ethylenediaminetetraacetic acid 2-sodium 　　　　　　0.006 parts Ferrous sulfate 　　　　　　　　　　0.002 parts Then it took 1 hour to continuously add the remaining 75% of the mixture. After the addition was completed, the temperature was maintained at this temperature for 2 hours, and then the polymerization was terminated. In addition, 0.2 parts of N-laurin sarcosine sodium was added during the period. The polymerization conversion rate (polymerization yield/monomer feed amount) of the obtained innermost crosslinked methacrylic polymer latex was 98%. The prepared innermost polymer latex was maintained at 80°C in a nitrogen stream, and after adding 0.1 part of potassium persulfate, it took 5 hours to continuously add 41 parts of n-butyl acrylate, 9 parts of styrene, and methacrylic acid. A monomer mixture composed of 1 part of allyl ester. During this period, 0.1 part of potassium oleate was added three times. After the monomer mixture was added, in order to complete the polymerization, another 0.05 part of potassium persulfate was added and kept for 2 hours to obtain rubber particles. The obtained rubber particles have a polymerization conversion rate of 99% and a particle size of 225 nm. The prepared rubber particle latex was maintained at 80°C, and a monomer mixture of 14 parts of methyl methacrylate and 1 part of n-butyl acrylate was continuously added over 1 hour after adding 0.02 parts of potassium persulfate. After the addition of the monomer mixture, the graft copolymer latex was prepared by keeping it for 1 hour. The polymerization conversion rate is 99%. The obtained graft copolymer latex was maintained at 80° C., and a monomer mixture of 5 parts of methyl methacrylate and 5 parts of n-butyl acrylate was continuously added in 0.5 hours. After adding the monomer mixture, keep it for 1 hour to prepare a rubber-containing graft copolymer latex. The polymerization conversion rate is 99%. The obtained rubber-containing graft copolymer latex is salted out and solidified with calcium chloride, heat-treated, and dried to obtain a white powdery cross-linked elastomer. MS resin (MS-200; a copolymer of methyl methacrylate/styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine. Amination rate: 5%). In addition, the aforesaid imidization was performed using a bite type co-rotating twin-shaft extruder with a diameter of 15 mm. The set temperature of each temperature adjustment zone of the extruder is 230°C, the screw rotation speed is 150 rpm, and the MS resin is supplied at 2.0 kg/hr. The supply amount of monomethylamine is set to 2 weight relative to 100 parts by weight of MS resin Copies. The MS resin was put in from the hopper, and the resin was melted with a kneaded block to fill it, and then monomethylamine was injected from the nozzle. Put a sealing ring at the end of the reaction zone and fill it with resin. Reduce the pressure of the exhaust port to -0.08MPa to de-evaporate the by-products and excessive methylamine after the reaction. The resin that is sent out into a bundle from the die set at the exit of the extruder is cooled in a water tank, and then pelletized by a pelletizer. The aforementioned imidized MS resin is melt-extruded and formed into a film. At this time, 0.66 parts by weight of an ultraviolet absorber (manufactured by ADEKA Corporation, trade name: LA-F70) was supplied with respect to 100 parts by weight of MS resin. Next, 10 parts by weight of the aforementioned crosslinked elastomer is supplied with respect to 100 parts by weight of MS resin. Next, the extruded 160μm film was biaxially stretched to twice the length and twice the width to produce a protective film (30μm acrylic film containing crosslinked elastomer, thickness 30μm, Re=2nm, Rth=2nm) .

37μmλ/4TAC film with HC: KC2UGR-HC (manufactured by Konica Minolta, a triacetyl cellulose polymer film with acrylic resin hard coating film, thickness: 37μm)

13μm COP film: ZF-014 (made by ZEON in Japan, raw material: cycloolefin polymer, thickness: 13μm)

26μmλ/4COP film with HC: ZD12 (made by Japan's ZEON, raw material: cycloolefin polymer, thickness: 20μm) with acrylic resin hard coat film

The manufacturing method of 40μm acrylic film with HC is fed into a 30L tank reactor equipped with a stirring device, temperature sensor, cooling tube, and nitrogen introduction tube. 8,000g of methyl methacrylate (MMA), 2,000 g of 2-(hydroxymethyl) methyl acrylate (MHMA), 10,000g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), 5g of n-dodecanethiol, and make After the nitrogen was heated to 105°C and refluxed by one side of the nitrogen, 5.0 g of tertiary butyl peroxyisopropyl carbonate (Kayakarubon BIC-7, manufactured by KAYAKU AKZO CO., LTD.) was added as a polymerization initiator. A solution consisting of 10.0g of tertiary butylperoxyisopropyl carbonate and 230g of MIBK was dropped in 4 hours, and solution polymerization was performed at about 105~120°C under reflux, and then it took 4 hours to mature. 30g of octadecyl phosphate/di(octadecyl) phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the prepared polymer solution, and the mixture was refluxed at about 90~120 The cyclization condensation reaction was carried out at ℃ for 5 hours. Then, the prepared polymer solution was introduced into the sleeve at a processing speed of 2.0 kg/h converted from the amount of resin. The temperature was 260°C, the number of rotations was 100 rpm, the degree of pressure reduction was 13.3 to 400 hPa (10 to 300 mmHg), and the number of rear vent holes. One vent type twin-screw extruder with 4 front vent holes (φ=29.75mm, L/D=30), and in the extruder, the cyclization condensation reaction and devolatization are further carried out. Extrusion is performed to obtain transparent pellets of a polymer containing lactone rings. After the dynamic TG measurement of the prepared lactone ring-containing polymer, a mass loss of 0.17% by mass was detected. In addition, the weight average molecular weight of the lactone ring-containing polymer was 133,000, the melt flow rate was 6.5 g/10 min, and the glass transition temperature was 131°C. Using a single-shaft extruder (screw 30mmφ), the pellets and acrylonitrile-styrene (AS) resin (TOYO AS AS20, manufactured by TOYO STYRENE CO., LTD.) were kneaded and extruded at a mass ratio of 90/10 , Thereby making transparent pellets. The glass transition temperature of the obtained pellets was 127°C. The pellets were melt-extruded from a 400mm wide hanger-type T-die using a 50mmφ uniaxial extruder to produce a film with a thickness of 160μm. Using a biaxial stretching device, the produced film was stretched 2.0 times at a temperature of 150° C. to obtain a stretched film with a thickness of 40 μm. After measuring the optical properties of the stretched film, the total light transmittance was 93%, the in-plane retardation Δnd was 0.8 nm, and the thickness direction retardation Rth was 1.5 nm. The resin contained in the coating solution is a UV curable resin with a solid content of 70 parts by weight (manufactured by Shinnakamura Chemical Industry Co., Ltd., brand name "NK oligomer UA-53H-80BK" with a solid content concentration of 80%) and 30 parts by weight UV-curable resin (manufactured by Shinnakamura Chemical Co., Ltd., brand name "A-GLY-9E" with a solid content of 100%). For every 100 parts by weight of the resin solid content of the aforementioned resin, add 5 parts of photopolymerization initiator (made by BASF Co., Ltd., product name "IRGACURE907") and 0.1 part of leveling agent (made by DIC Co., product name "GRANDIC PC4100") ). Toluene and cyclopentanone were added to the above-mentioned mixed solution at a ratio of 80:20 so that the solid content concentration in the above-mentioned solution became 40%. The hard coat forming material is produced through the above procedures. The prepared hard-coat layer forming material was applied to the aforementioned stretched film so that the hard-coat layer thickness after hardening became 7 μm to form a coating film. After that, the coating film was dried at 90°C for 1 minute, and a high-pressure mercury lamp was used to irradiate the coating film with a cumulative light intensity of 300 mJ/cm ² of ultraviolet rays to harden the coating film to form a hard coat layer to produce a 40 μm acrylic film with HC.

Production method of 30μm acrylic film containing crosslinked elastomer with HC mixed 15-functional urethane acrylate oligomer (manufactured by Shinnakamura Chemical Co., Ltd., trade name: NK Oligo UA-53H, weight average molecular weight: 2300) 22 Parts, 28 parts of neopentylerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name: Viscoat#300), and 28 parts of ethoxylated glycerol triacrylate (manufactured by Shinnakamura Chemical Co., Ltd., trade name: NK Ester A-GLY) -9E) 50 parts, 3 parts of photopolymerization initiator (manufactured by Ciba Japan, trade name: IRGACURE 907), and diluted with methyl isobutyl ketone to a solid content concentration of 40% to produce a hard coat layer forming material . The prepared hard-coat layer forming material was applied to the aforementioned 30-μm acrylic film containing a crosslinked elastomer so that the thickness of the hard-coat layer after hardening became 10 μm to form a coating film. After that, the coating film was dried at 90°C for 1 minute, and a high-pressure mercury lamp was used to irradiate the coating film with a cumulative light intensity of 200mJ/cm ² of ultraviolet rays to harden the coating film to form a hard coat layer to produce a crosslinked elastomer with HC 30μm acrylic film.

Manufacturing method of 40μm acrylic film In a 30L tank reactor equipped with a stirring device, a temperature sensor, a cooling tube, and a nitrogen introduction tube, 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2-(hydroxymethyl) are fed Methyl acrylate (MHMA), 10,000g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), 5g of n-dodecanethiol, and while passing nitrogen through them, the temperature is raised to 105°C and After refluxing, 5.0 g of tertiary butyl peroxy isopropyl carbonate (Kayakarubon BIC-7, manufactured by KAYAKU AKZO CO., LTD.) was added as a polymerization initiator, and it took 4 hours to drop the tertiary butyl peroxy isopropyl carbonate (Kayakarubon BIC-7, manufactured by KAYAKU AKZO CO., LTD.). A solution composed of butylperoxyisopropyl carbonate and 230g of MIBK is subjected to solution polymerization at about 105~120°C under reflux, and then it takes 4 hours to mature. 30g of octadecyl phosphate/di(octadecyl) phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added to the prepared polymer solution, and the mixture was refluxed at about 90~120 The cyclization condensation reaction was carried out at ℃ for 5 hours. Then, the prepared polymer solution was introduced into the sleeve at a processing speed of 2.0 kg/h converted from the amount of resin. The temperature was 260°C, the number of rotations was 100 rpm, the degree of decompression was 13.3~400hPa (10~300mmHg), and the number of rear vent holes One vent type twin-screw extruder with 4 front vent holes (φ=29.75mm, L/D=30), and in the extruder, the cyclization condensation reaction and devolatization are further carried out. Extrusion is performed to obtain transparent pellets of a polymer containing lactone rings. After the dynamic TG measurement of the prepared lactone ring-containing polymer, a mass loss of 0.17% by mass was detected. In addition, the weight average molecular weight of the lactone ring-containing polymer was 133,000, the melt flow rate was 6.5 g/10 min, and the glass transition temperature was 131°C. The pellets and acrylonitrile-styrene (AS) resin (TOYO AS AS20, manufactured by TOYO STYRENE CO., LTD.) were kneaded and extruded with a mass ratio of 90/10 using a uniaxial extruder (screw 30mmφ). , Thereby making transparent pellets. The glass transition temperature of the obtained pellets was 127°C. The pellets were melt-extruded from a 400mm wide hanger-type T-die using a 50mmφ uniaxial extruder to produce a film with a thickness of 160μm. Using a biaxial stretching device, the produced film was stretched 2.0 times at a temperature of 150° C., thereby preparing a stretched film (40 μm acrylic film) with a thickness of 40 μm. After measuring the optical properties of the stretched film, the total light transmittance was 93%, the in-plane retardation Δnd was 0.8 nm, and the thickness direction retardation Rth was 1.5 nm.

APF: Brightness enhancement film (manufactured by Sumitomo 3M, trade name: APF, thickness 26μm)

APF with HC: Brightening film (manufactured by Sumitomo 3M, trade name: APF, thickness 20μm) with acrylic resin hard coat

26μm COP film with HC: ZF12-HC: made by ZEON in Japan, raw material: acrylic resin hard coater applied to cycloolefin polymer

The measuring methods of the coefficient of linear expansion and the elongation at break of the protective films used in the examples and comparative examples are as follows. The polarizing films produced in the examples and comparative examples were evaluated as follows. The results are listed in Table 1.

>Measure the linear expansion coefficient Y of the protective film (×10 ^-5 /K)> Use a TMA analyzer (manufactured by Hitachi High-Tech Science Co., TMA7100E) to measure the dimensional change of the protective film under the following measurement conditions, and obtain The value is substituted into the following formula (A) to calculate the dimensional change rate. The measurement was performed 4 times, and the average value of the 4 times was used as the dimensional change rate. Then, the average value of the obtained dimensional change rate is substituted into the following formula (B) to calculate the linear expansion coefficient Y (×10 ^-5 /K) of the protective film. Sample size: 20mm×5mm Measurement environment: -40°C⇔85°C heating and cooling rate: 10°C/min Number of measurements: 4 Dimensional change rate=(ΔL/L)×100 (A) ΔL: Dimensional change during measurement Quantity (the difference between the size at -40°C and the size at 85°C) L: the size before measurement (the size at 25°C) Linear expansion coefficient Y (×10 ^-5 /K) = (size change rate /ΔT)/100 (B) ΔT: temperature change range

>Determine the breaking elongation X (%) of the protective film> An Autograph (manufactured by Shimadzu Corporation) was used to stretch the protective film at a constant speed under the following measurement conditions until the protective film broke, and the length at the break was measured. The initial length and the length at break are substituted into the following formula (C) to calculate the breaking elongation X (%). The measurement was carried out 3 times, and the average value of the 3 times was taken as the breaking elongation X (%). Sample size: 100mm×10mm Stretching speed: 300mm/min Measurement environment: temperature 23℃, humidity 50%RH Number of measurements: 3 Elongation at break X(%)={(length at break-initial length)/initial length}×100　　　(C)

>Butterfly test of polarizing film (crack resistance test)> The polarizing film of 150mm×50mm is shown in Fig. 1 and cuts are arranged along the MD direction with a laser to prepare a sample. This sample was attached to a glass plate (manufactured by Songnang Glass Industry Co., Ltd.) using a manual roller through an adhesive, and the sample attached to the glass plate was placed in an autoclave at 50°C for 15 minutes. After that, the sample bonded to the glass plate was put into a test tank, and a thermal shock test was performed under the following conditions. Take out the sample attached to the glass plate every 10 cycles, and check whether there is a crack of 1mm or more in the circled part of Figure 1. For each of the five samples, the number of cycles when cracks of 1 mm or more were generated (the number of cycles when a crack was generated in all five of the five specimens) was counted, and the maximum value was used for evaluation based on the following criteria. (Measurement conditions) Measurement environment: -40°C (maintained for 30 minutes) ⇔ 85°C (maintained for 30 minutes) Heating and cooling speed: 10℃/min Number of samples: 5 (Assessment criteria) 〇: More than 200 cycles △: 100~199 cycles ×: Below 99 cycles

[Table 1]

It can be seen from Table 1 that at least one of the protective films provided on the polarizer satisfies the above-mentioned formula (1) of the polarizing films of Examples 1 to 10, even under thermal shock (repeatedly performed under temperature conditions of -40°C and 85°C) Under the severe environment of thermal shock test), it is not easy to produce cracks on the polarizer, and the crack resistance is excellent. On the other hand, it can be seen that the polarizing films of Comparative Examples 1 to 9 in which the protective film provided on the polarizer does not satisfy the above formula (1) are prone to cracks in the polarizer due to thermal shock, and the crack resistance is poor.

Industrial availability The polarizing film of the present invention can be used alone or in the form of an optical film formed by laminating it in image display devices such as liquid crystal display devices (LCD) and organic EL display devices.

Figure 1 is a schematic diagram showing the shape of the sample used in the butterfly test.

Claims (5)

A polarizing film is provided with a protective film on one side or both sides of a polarizing member with an adhesive layer interposed therebetween. The polarizing film is characterized in that: at least one of the aforementioned protective films provided on the polarizing member satisfies the following formula (1): Y≦1.26×lnX+3.5 (1) Y: Linear expansion coefficient of the protective film (×10 ^-5 /K) X: Breaking elongation (%) of the protective film. Such as the polarizing film of claim 1, wherein the aforementioned Y (×10 ^-5 /K) is 4 or less. The polarizing film of claim 1 or 2, wherein the thickness of the aforementioned polarizing member is 10 μm or less. A polarizing film with an adhesive layer, which has the polarizing film and an adhesive layer according to any one of claims 1 to 3. An image display device, in which the polarizing film of any one of claims 1 to 3 or the polarizing film with an adhesive layer as claimed in claim 4 is arranged in an image display unit.

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