WO2019244915A1

WO2019244915A1 - Polarizing film, polarizing film with adhesive layer, and image display device

Info

Publication number: WO2019244915A1
Application number: PCT/JP2019/024221
Authority: WO
Inventors: 史枝片山; 勝則高田; 玲子品川; 哲郎竹田
Original assignee: 日東電工株式会社
Priority date: 2018-06-20
Filing date: 2019-06-19
Publication date: 2019-12-26
Also published as: TW202001308A; JP2019219525A; TWI724436B

Abstract

The purpose of the present invention is to provide a polarizing film which is not susceptible to the occurrence of a crack in a polarizer even under severe thermal shock conditions. A polarizing film according to the present invention is obtained by providing one surface or both surfaces of a polarizer with a protective film, with an adhesive layer being interposed therebetween; and at least one protective film provided on the polarizer satisfies formula (1). (1): Y ≤ 1.26 × lnX + 3.5 (In the formula, Y is the linear expansion coefficient (× 10-5/K) of the protective film; and X is 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 with an adhesive layer having the polarizing film and an adhesive layer. Further, the present invention relates to an image display device including the polarizing film or the polarizing film with an adhesive layer.

偏光 In various image display devices, a polarizing film is used for image display. For example, in a liquid crystal display (LCD), it is indispensable to arrange polarizing films on both sides of a glass substrate forming the surface of a liquid crystal panel due to its image forming method. In the organic EL display device, a circularly polarizing film in which a polarizing film and a quarter-wave plate are laminated is disposed on the viewing side of the organic light emitting layer in order to shield specular reflection of external light on the metal electrode.

As the polarizing film, generally, a polyvinyl alcohol-based film and a polarizer made of a dichroic material such as iodine, on one or both sides thereof, a protective film bonded with a polyvinyl alcohol-based adhesive or the like is used. ing.

In a severe environment of a thermal shock (for example, a heat shock test in which a temperature condition of −40 ° C. and 85 ° C. is repeated), the polarizing film is entirely formed in the absorption axis direction of the polarizer due to a change in shrinkage stress of the polarizer. There is a problem that cracks (through cracks) easily occur.

Patent Document 1 discloses a polarizing plate in which a transparent protective film is disposed on both sides of a polarizing film for the purpose of providing a polarizing plate having excellent durability even under a thermal shock environment. The difference between the linear expansion coefficient in the direction perpendicular to the direction of the polarizing film and the linear expansion coefficient in the direction perpendicular to the absorption axis of the polarizing plate of the transparent protective film disposed on at least one surface of the polarizing film is 1.3 × 10 A polarizing plate characterized by being at most ⁻⁴ / ° C. has been proposed.

JP 2011-203571 A

However, even with the polarizing plate of Patent Document 1, depending on the type of the transparent protective film, the stress based on the expansion and contraction of the transparent protective film greatly affects the expansion and contraction of the polarizing film. May occur.

An object of the present invention is to provide a polarizing film in which cracks are less likely to occur in the polarizer even under severe thermal shock environment.

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

(4) The present inventors have made intensive studies and found that the above-mentioned problems can be solved by the following polarizing film, and have completed the present invention.

That is, the present invention is a polarizing film provided with a protective film on one or both sides of the polarizer via an adhesive layer,
At least one of the protective films provided on the polarizer satisfies the following formula (1).
Y ≦ 1.26 × lnX + 3.5 (1)
Y: Coefficient of linear expansion of protective film (× 10 ⁻⁵ / K)
X: Elongation at break of protective film (%)

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

において In the polarizing film, the thickness of the polarizer is preferably 10 μm or less.

The present invention also relates to a polarizing film with an adhesive layer having the polarizing film and the adhesive layer.

The present invention also relates to an image display device in which the polarizing film or the polarizing film with an adhesive layer is disposed in an image display cell.

By using at least one protective film that satisfies the above formula (1) as a protective film provided on one or both surfaces of the polarizer, the stress caused by the expansion and contraction of the polarizer due to the stress based on the expansion and contraction of the protective film. Since it can be alleviated, cracks hardly occur in the polarizer.

By using a protective film having a linear expansion coefficient Y (× 10 ⁻⁵ / K) of 4 or less, the stress caused by expansion and contraction of the polarizer can be more effectively reduced, and thus the cracks in the polarizer can be reduced. Can be more effectively suppressed.

In recent years, image display devices such as liquid crystal display devices have become thinner, and accordingly, polarizers have also been required to be thinner. However, a thin polarizer having a thickness of 10 μm or less has a problem in that the optical characteristics are likely to deteriorate (due to moisture) in a humid environment. For the purpose of suppressing the deterioration of the thin polarizer due to moisture, a resin film having low moisture permeability (specifically, 100 g / (m ² · day) or less) is used as a protective film to be attached to the thin polarizer. That is being considered. When a resin film having low moisture permeability is used as the protective film, the deterioration of the polarizer in a humid environment can be suppressed. However, a protective film having low moisture permeability tends to have a large coefficient of linear expansion, and it is difficult to alleviate the stress caused by expansion and contraction of the polarizer, so that the polarizer is easily cracked. However, even if the protective film has a large linear expansion coefficient, a protective film having a large elongation at break and satisfying the above formula (1) can effectively reduce the stress caused by expansion and contraction of the polarizer. Therefore, cracks hardly occur in the polarizer. Therefore, the polarizing film of the present invention can achieve both suppression of deterioration of the polarizer due to humidification (improvement of humidification reliability) and suppression of occurrence of cracks.

It is the schematic which shows the shape of the sample used for a butterfly test.

1. Polarizing Film The polarizing film of the present invention has a protective film provided on one or both sides of a polarizer via an adhesive layer, and at least one of the protective films provided on the polarizer has the following formula (1): To satisfy.
Y ≦ 1.26 × lnX + 3.5 (1)
Y: Coefficient of linear expansion of protective film (× 10 ⁻⁵ / K)
X: Elongation at break of protective film (%)

Each component will be described below.

(1) Polarizer Known polarizers can be used without particular limitation, but it is preferable to use a polarizer having a thickness of 10 μm or less from the viewpoint of reducing the thickness and suppressing the occurrence of cracks. The thickness of the polarizer is more preferably 8 μm or less, further preferably 7 μm or less, and still more preferably 6 μm or less. On the other hand, the thickness of the polarizer is preferably 2 μm or more, and more preferably 3 μm or more.

A polarizer using a polyvinyl alcohol-based resin is used. Examples of the polarizer include, for example, a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, a hydrophilic polymer film such as an ethylene-vinyl acetate copolymer-based partially saponified film, and dichroic properties of iodine and a dichroic dye. Examples thereof include a uniaxially stretched film obtained by adsorbing a substance, and a polyene-based oriented film such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride. Among these, a polarizer composed of a polyvinyl alcohol-based film and a dichroic substance such as iodine is preferable.

偏光 A polarizer obtained by dyeing a polyvinyl alcohol-based film with iodine and uniaxially stretching can be produced, for example, by dyeing polyvinyl alcohol by immersing it in an aqueous solution of iodine and stretching the film 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 of potassium iodide or the like. Further, if necessary, the polyvinyl alcohol-based film may be immersed in water and washed with water before dyeing. By washing the polyvinyl alcohol-based film with water, dirt on the surface of the polyvinyl alcohol-based film and an anti-blocking agent can be washed off.Also, by swelling the polyvinyl alcohol-based film, the effect of preventing unevenness such as uneven dyeing can be obtained. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath.

The polarizer preferably contains boric acid from the viewpoint of stretching stability and humidification reliability. Further, the content of boric acid contained in the polarizer is preferably 22% by weight or less, more preferably 20% by weight or less, based on the total amount of the polarizer, from the viewpoint of suppressing the occurrence of cracks. From the viewpoint of stretching stability and humidification reliability, the boric acid content based on the total amount of the polarizer is preferably 10% by weight or more, and more preferably 12% by weight or more.

As a thin polarizer, typically,
Patent No. 4751486,
Patent No. 4,751,481,
Patent No. 4815544,
Patent No. 5048120,
WO 2014/077599 pamphlet,
WO 2014/077636 pamphlet,
And the like, and a thin polarizer obtained from the production method described therein.

Among the thin polarizers, Japanese Patent No. 4751486 and Patent Document 4 disclose that, among manufacturing methods including a step of stretching in a state of a laminate and a step of dyeing, it is possible to stretch at a high magnification and improve polarization performance. Preferred are those obtained by a production method including a step of stretching in a boric acid aqueous solution as described in JP-B-47515481 and JP-B-4815544, and particularly described in JP-B-4775481 and JP-B-4815544. What is obtained by the manufacturing method including the process of auxiliary | assistant air-stretching before extending | stretching in a boric-acid aqueous solution with a certain thing is preferable. These thin polarizers can be obtained by a manufacturing method including a step of stretching a polyvinyl alcohol-based resin (hereinafter, also referred to as a PVA-based resin) layer and a resin substrate for stretching in a laminate state and a step of dyeing. According to this manufacturing method, even if the PVA-based resin layer is thin, it can be stretched without any trouble such as breakage due to stretching because it is supported by the stretching resin base material.

(2) Protective film As the material of the protective film, those having excellent transparency, mechanical strength, heat stability, moisture barrier properties, isotropy, and the like are preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulosic polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, and styrene such as polystyrene and acrylonitrile-styrene copolymer (AS resin) Polymers, polycarbonate polymers and the like. In addition, polyethylene, polypropylene, polyolefin having a cyclo- or norbornene structure, polyolefin polymers such as ethylene-propylene copolymer, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Blends of polymers and the like are also examples of the polymer forming the protective film.

The protective film may contain one or more optional additives. Examples of the additives include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent.

含有 The content of the polymer in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, further preferably 60 to 98% by weight, and still more preferably 70 to 97% by weight. If the content of the polymer in the protective film is less than 50% by weight, the high transparency or the like inherent in the polymer may not be sufficiently exhibited.

位相 As the protective film, a retardation film, a brightness enhancement film, a diffusion film and the like can also be used. Examples of the retardation film include those having a front retardation of 40 nm or more and / or a thickness direction retardation of 80 nm or more. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation film is used as the protective film, the thickness can be reduced because the retardation film also functions as a protective film for the polarizer.

Examples of the retardation film include birefringent films obtained by uniaxially or biaxially stretching a thermoplastic resin film. The stretching temperature, stretching ratio, and the like are appropriately set depending on the retardation value, the material and thickness of the film.

The thickness of the protective film can be determined as appropriate, but it is about 1 to 500 μm from the viewpoint of workability such as strength and handleability, and thinness. The thickness of the protective film is preferably 1 to 300 μm, more preferably 5 to 200 μm, still more preferably 5 to 150 μm, and still more preferably 20 to 100 μm.

機能 A functional layer such as a hard coat layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer or an anti-glare layer can be provided on the surface of the protective film on which the polarizer is not adhered. The functional layers such as the hard coat layer, the antireflection layer, the anti-sticking layer, the diffusion layer and the antiglare layer can be provided on the protective film itself, or separately provided separately from the protective film. it can.

In the present invention, at least one of the protective films (which may include the functional layer) provided on the polarizer satisfies the following formula (1). When protective films are provided on both surfaces of the polarizer, it is preferable that the protective films provided on both surfaces of the polarizer each satisfy the following formula (1). Thereby, the stress generated by the expansion and contraction of the polarizer can be effectively reduced, so that cracks are less likely to occur in the polarizer. The method for measuring the coefficient of linear expansion and the elongation at break of the protective film is as described in Examples.
Y ≦ 1.26 × lnX + 3.5 (1)
Y: Coefficient of linear expansion of protective film (× 10 ⁻⁵ / K)
X: Elongation at break of protective film (%)

線 Since the coefficient of linear expansion and the elongation at break of the protective film vary depending on the material used and the thickness, the thickness is appropriately adjusted according to the material used. The protective film satisfying the above formula (1) can be produced, for example, by stretching a cycloolefin-based polymer film to a thickness of about 17 to 18 μm.

Commercially available protective films satisfying the above formula (1) include, for example, TJ25UL (manufactured by Fuji Film, raw material: triacetylcellulose-based polymer, thickness: 25 μm), ZT12 (manufactured by Zeon Corporation, raw material: cycloolefin-based polymer, thickness) : 17 μm), KC2UA (manufactured by Konica Minolta, raw material: triacetylcellulose-based polymer, thickness: 20 μm), and KC2UGR-HC (manufactured by Konica Minolta, triacetylcellulose-based polymer film provided with an acrylic resin-based hard coat layer) , Thickness: 37 μm).

The protective film satisfying the above formula (1) preferably has a linear expansion coefficient Y (× 10 ⁻⁵ / K) of 4 or less, more preferably 3.5 or less, and still more preferably 3.1 or less. is there.

(3) Adhesive layer

The adhesive layer is formed by an adhesive. The type of the adhesive is not particularly limited, and various adhesives can be used. The adhesive layer is not particularly limited as long as it is optically transparent. Examples of the adhesive include water-based, solvent-based, hot-melt, and active energy ray-curable adhesives. Alternatively, an active energy ray-curable adhesive is suitable.

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

The active energy ray-curable adhesive is an adhesive whose curing progresses with an active energy ray such as an electron beam or an ultraviolet ray (radical-curable or cationically-curable). Can be used. As the active energy ray-curable adhesive, for example, a photo-radical curable adhesive can be used. When a 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 method of applying the adhesive is appropriately selected depending on the viscosity of the adhesive and the desired thickness. Examples of the coating method include, for example, a reverse coater, a gravure coater (direct, reverse or offset), a bar reverse coater, a roll coater, a die coater, a bar coater, a rod coater, and the like. In addition, a method such as a dipping method can be appropriately used for coating.

In addition, when using an aqueous adhesive or the like, the adhesive is preferably applied so that the thickness of the finally formed adhesive layer is 30 to 300 nm. The thickness of the adhesive layer is more preferably 60 to 250 nm. On the other hand, when an active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably set to 0.1 to 200 μm. More preferably, it is 0.5 to 50 μm, further preferably 0.5 to 10 μm.

積層 When laminating the polarizer and the protective film, an easy-adhesion layer can be provided between the protective film and the adhesive layer. The easy-adhesion layer can be formed of, for example, various resins having a polyester skeleton, polyether skeleton, polycarbonate skeleton, polyurethane skeleton, silicone, polyamide skeleton, polyimide skeleton, polyvinyl alcohol skeleton, and the like. These polymer resins can be used alone or in combination of two or more. Further, other additives may be added to the formation of the easily adhesive layer. Specifically, stabilizers such as tackifiers, ultraviolet absorbers, antioxidants, and heat stabilizers may be used.

The easy-adhesion layer is usually provided in advance on the protective film, and the easy-adhesion layer side of the protective film and the polarizer are laminated with an adhesive layer. The easy-adhesion layer is formed by applying and drying the material for forming the easy-adhesion layer on the protective film by a known technique. The material for forming the easily adhesive layer is usually adjusted as a solution diluted to an appropriate concentration in consideration of the thickness after drying, the smoothness of coating, and the like. The thickness of the easy-adhesion layer after drying is preferably 0.01 to 5 μm, more preferably 0.02 to 2 μm, and still more preferably 0.05 to 1 μm. Note that a plurality of easy-adhesion layers can be provided. In this case, it is preferable that the total thickness of the easy-adhesion layers be in the above range.

2. Polarizing Film with Pressure-Sensitive Adhesive Layer The polarizing film with the pressure-sensitive adhesive layer of the present invention has the polarizing film and the pressure-sensitive adhesive layer.

両 In the case of both protective polarizing films in which protective films are provided on both surfaces of a polarizer, an adhesive layer is provided on one surface of both protective polarizing films directly or via another layer. In addition, a surface protection film may be provided directly or via another layer on the other surface of both protective polarizing films.

片 In the case of a one-sided protective polarizing film in which a protective film is provided only on one side of the polarizer, an adhesive layer is provided directly or via another layer on the side of the one-sided protective polarizing film on the polarizer side. In addition, a surface protective film may be provided directly or via another layer on the protective film side of the one-side protective polarizing film.

The other layers are not particularly limited, and include known functional layers and optical layers provided on the polarizing film. Examples of the optical layer include a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as や or ４), a viewing angle compensation film, and a brightness enhancement film. The other layer may be provided as one layer, or may be provided as two or more layers.

The pressure-sensitive adhesive layer is provided on one side of the polarizing film in order to attach the polarizing film to a cell substrate such as a liquid crystal cell.

The thickness of the pressure-sensitive adhesive layer is not particularly limited, and is, for example, about 1 to 100 μm, preferably 2 to 50 μm, more preferably 2 to 40 μm, and further preferably 5 to 35 μm.

適宜 In forming the pressure-sensitive adhesive layer, a suitable pressure-sensitive adhesive can be used, and the type thereof is not particularly limited. As the adhesive, a rubber-based adhesive, an acrylic-based adhesive, a silicone-based adhesive, a urethane-based adhesive, a vinylalkyl ether-based adhesive, a polyvinyl alcohol-based adhesive, a polyvinylpyrrolidone-based adhesive, a polyacrylamide-based adhesive, Cellulose-based adhesives and the like can be mentioned.

Among these adhesives, those having excellent optical transparency, exhibiting appropriate wettability, cohesiveness and adhesive adhesive properties and having excellent weather resistance and heat resistance are preferably used. Acrylic pressure-sensitive adhesives having such characteristics are preferably used.

Examples of the method for forming the pressure-sensitive adhesive layer include, for example, a method in which the pressure-sensitive adhesive is applied to a separator or the like that has been subjected to a release treatment, and a polymerization solvent or the like is dried and removed to form a pressure-sensitive adhesive layer. A method of forming a pressure-sensitive adhesive layer on a polarizing film by applying a pressure-sensitive adhesive and removing a polymerization solvent by drying is exemplified. In applying the pressure-sensitive adhesive, one or more solvents other than the polymerization solvent may be newly added as appropriate.

シリコーン Silicone release liners are preferably used as the release-treated separator. In the step of applying and drying the pressure-sensitive adhesive on the liner to form a pressure-sensitive adhesive layer, a method for drying the pressure-sensitive adhesive may be appropriately selected depending on the purpose. Preferably, a method of heating and drying the coating film is used. The heating and drying temperature is preferably from 40 ° C to 200 ° C, more preferably from 50 ° C to 180 ° C, and particularly preferably from 70 ° C to 170 ° C. By setting the heating temperature in the above range, an adhesive having excellent adhesive properties can be obtained.

A proper drying time can be adopted as appropriate. The drying time is preferably 5 seconds to 20 minutes, more preferably 5 seconds to 10 minutes, and particularly preferably 10 seconds to 5 minutes.

各種 Various methods are used for forming the pressure-sensitive adhesive layer. Specifically, for example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, die coater, etc. Examples include a method such as an extrusion coating method.

When the pressure-sensitive adhesive layer is exposed, the pressure-sensitive adhesive layer may be protected by a sheet (separator) that has been subjected to a release treatment until it is practically used.

As a constituent material of the separator, for example, polyethylene, polypropylene, polyethylene terephthalate, a plastic film such as a polyester film, paper, cloth, a porous material such as a nonwoven fabric, a net, a foamed sheet, a metal foil, and a laminate of these as appropriate Although a thin leaf body and the like can be mentioned, a plastic film is preferably used because of its excellent surface smoothness.

The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. Examples of the plastic film include polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, and vinyl chloride film. Examples include a polymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, and an ethylene-vinyl acetate copolymer film.

セパレータ The thickness of the separator is usually about 5 to 200 μm, preferably about 5 to 100 μm. The separator, if necessary, silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based release agent, release and antifouling treatment with silica powder, etc., coating type, kneading type, evaporation type It is also possible to perform an antistatic treatment such as the following. In particular, by appropriately performing a release treatment such as a silicone treatment, a long-chain alkyl treatment, or a fluorine treatment on the surface of the separator, the releasability from the pressure-sensitive adhesive layer can be further improved.

The surface protective film usually has a base film and an adhesive layer, and protects the polarizing film via the adhesive layer.

フィルム As the base film of the surface protective film, a film material having or near isotropy is selected from the viewpoint of testability and manageability. Examples of the film material include a polyester resin such as a polyethylene terephthalate film, a cellulose resin, an acetate resin, a polyether sulfone resin, a polycarbonate resin, a polyamide resin, a polyimide resin, a polyolefin resin, and an acrylic resin. A transparent polymer such as a resin can be used. Of these, polyester resins are preferred. The base film can be used as a laminate of one or more film materials, and a stretched product of the film can also be used. The thickness of the substrate film is generally 500 μm or less, preferably 10 to 200 μm.

Examples of the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer of the surface protective film include a pressure-sensitive adhesive having a base polymer of (meth) acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer. The agent can be appropriately selected and used. From the viewpoints of transparency, weather resistance, heat resistance, and the like, an acrylic pressure-sensitive adhesive containing an acrylic polymer as a base polymer is preferable. The thickness (dry film thickness) of the pressure-sensitive adhesive layer is determined according to the required pressure-sensitive adhesive strength. Usually, it is about 1 to 100 μm, preferably 5 to 50 μm.

In addition, on the surface protective film, a release treatment layer can be provided on the surface opposite to the surface on which the pressure-sensitive adhesive layer of the base film is provided, using a low-adhesion material such as silicone treatment, long-chain alkyl treatment, or fluorine treatment. .

3. Image Display Device The image display device of the present invention may be any one including the polarizing film or the polarizing film with an adhesive layer of the present invention, and other configurations may be the same as those of the conventional image display device. it can. The polarizing film or the polarizing film with a pressure-sensitive adhesive layer is applied to an image display cell. For example, when the image display device is a liquid crystal display device, the polarizing film or the polarizing film with an adhesive layer can be applied to both the viewing side and the backlight side of an image display cell (liquid crystal cell). When the image display device is an organic EL display device, the polarizing film or the polarizing film with an adhesive layer can be applied to the viewing side of the image display cell. The image display device of the present invention has high reliability because it includes the polarizing film or the polarizing film with the pressure-sensitive adhesive layer.

本 Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples. The parts and percentages in each example are based on weight.

(Preparation of polarizer)
A corona treatment is applied to one surface of an amorphous isophthalic acid copolymerized polyethylene terephthalate (IPA copolymerized PET) film (thickness: 100 μm) having a water absorption of 0.75% and Tg of 75 ° C. Alcohol (degree of polymerization: 4200, degree of saponification: 99.2 mol%) and acetoacetyl-modified PVA (degree of polymerization: 1200, degree of acetoacetyl modification: 4.6%, degree of saponification: 99.0 mol% or more, Japan An aqueous solution containing Synthetic Chemical Industry Co., Ltd. (trade name “Gosefimer Z200”) at a ratio of 9: 1 was applied and dried at 25 ° C. to form a 11 μm-thick PVA-based resin layer. Produced.
The obtained laminate was uniaxially stretched 2.0 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 120 ° C. with free-end uniaxial stretching (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 30 ° C. (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, it was immersed in a dyeing bath at a liquid temperature of 30 ° C. while adjusting the iodine concentration and the immersion time so that the polarizing plate had a predetermined transmittance. In the present example, 0.2 part by weight of iodine was added to 100 parts by weight of water, and the resultant was immersed in an aqueous solution of iodine obtained by mixing 1.0 part by weight of potassium iodide for 60 seconds (dyeing treatment). .
Next, it was immersed in a crosslinking bath at a liquid temperature of 30 ° C. (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) for 30 seconds. (Crosslinking treatment).
Thereafter, the laminate is added to an aqueous solution of boric acid at a liquid temperature of 70 ° C. (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). While being immersed, uniaxial stretching was performed between rolls having different peripheral speeds in the longitudinal direction (longitudinal direction) so that the total stretching ratio was 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a washing bath at a liquid temperature of 30 ° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (washing treatment).
Thus, an optical film laminate including a 5 μm-thick polarizer was obtained. The obtained polarizer had a boric acid content of 20% by weight.

(Preparation of adhesive applied to protective film)
40 parts by weight of N-hydroxyethylacrylamide (HEAA), 60 parts by weight of acryloylmorpholine (ACMO) and 3 parts by weight of a photoinitiator “IRGACURE 819” (manufactured by BASF) were mixed to prepare an ultraviolet-curable adhesive.

Example 1 (Production of one-sided protective polarizing film)
The protective film 1 (HC) was coated on the surface of the polarizer (thickness: 5 μm) of the optical film laminate so that the thickness of the cured adhesive layer was 0.1 μm. 25 μm TAC film: TJ25UL (manufactured by Fuji Film, raw material: triacetylcellulose-based polymer, thickness: 25 μm) and a film provided with an acrylic resin-based hard coat layer), and then irradiated with ultraviolet rays as active energy rays. The adhesive was cured. Thereafter, the amorphous PET substrate provided on one side of the polarizer was peeled off to produce a one-sided protective polarizing film.

Examples 2, 3, 6 to 8, Comparative Examples 1 to 8
A one-sided protective polarizing film was produced in the same manner as in Example 1 except that the protective film 1 shown in Table 1 was used.

Example 4 (production of both protective polarizing films)
The protective film 1 (HC) was coated on the surface of the polarizer (thickness: 5 μm) of the optical film laminate so that the thickness of the cured adhesive layer was 0.1 μm. 25 μm TAC film: TJ25UL (manufactured by Fuji Film, raw material: triacetylcellulose-based polymer, thickness: 25 μm) and a film provided with an acrylic resin-based hard coat layer), and then irradiated with ultraviolet rays as active energy rays. The adhesive was cured. Thereafter, the amorphous PET substrate provided on one surface of the polarizer is peeled off, and the ultraviolet curable adhesive is cured on the peeled surface so that the thickness of the adhesive layer becomes 0.1 μm. After coating, a protective film 2 (25 μm TAC film: TJ25UL (manufactured by Fuji Film, raw material: triacetylcellulose-based polymer, thickness: 25 μm)) is bonded, and then the adhesive is cured by irradiating ultraviolet rays as active energy rays. In this way, both protective polarizing films were produced.

Examples 5, 9, 10 and Comparative Example 9
Both protective polarizing films were produced in the same manner as in Example 4 except that the protective films 1 and 2 shown in Table 1 were used.

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

２５25μm TAC film with HC: TJ25UL (manufactured by Fuji Film, raw material: triacetylcellulose-based polymer, thickness: 25μm) with a film provided with an acrylic resin-based hard coat layer

25 μm TAC film: TJ25UL (Fuji Film, raw material: triacetyl cellulose polymer, thickness: 25 μm)

17 μm COP film: ZT12 (manufactured by Zeon Corporation, a biaxially stretched cycloolefin-based polymer film having a front phase difference of 116 nm and a thickness difference of 81 nm, a thickness of 17 μm)

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

Method for Producing 20 μm Acrylic Film In a 30 L pot-type reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing pipe, 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2- (hydroxymethyl) were added. ) Methyl acrylate (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing nitrogen through, followed by reflux. At that time, 5.0 g of t-butyl peroxyisopropyl carbonate (Kayacarbon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator, and at the same time, 10.0 g of t-butyl peroxyisopropyl carbonate and 230 g were added. Of MIBK was added dropwise over 4 hours while refluxing for about 1 hour. Perform solution polymerization at 5 ~ 120 ° C., the mixture was aged over an additional 4 hours.
To the obtained polymer solution, 30 g of a stearyl phosphate / distearyl phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the mixture was refluxed at about 90 to 120 ° C. for 5 hours under reflux. A condensation reaction was performed. Next, the obtained polymer solution is subjected to a vent-type screw twin-screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent and four forevents. (Φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / h in terms of the amount of resin, and further subjected to cyclization condensation reaction and devolatilization in this extruder to extrude. As a result, transparent pellets of the lactone ring-containing polymer were obtained.
When the dynamic TG of the obtained lactone ring-containing polymer was measured, a decrease in mass of 0.17% by mass was detected. The lactone ring-containing polymer had a weight average molecular weight of 133,000, a melt flow rate of 6.5 g / 10 min, and a glass transition temperature of 131 ° C.
The obtained pellets and acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) are kneaded and extruded at a mass ratio of 90/10 using a single screw extruder (screw 30 mmφ). As a result, transparent pellets were obtained. The glass transition temperature of the obtained pellet was 127 ° C.
The pellets were melt-extruded from a coat hanger type T die having a width of 400 mm using a 50 mmφ single screw extruder to produce a film having a thickness of 80 μm. The resin was melt-extruded while supplying 0.66 parts by weight of an ultraviolet absorber (product name: LA-F70, manufactured by ADEKA) with respect to 100 parts by weight of the resin in the pellets. The produced film was stretched 2.0 times at a temperature of 150 ° C. using a biaxial stretching apparatus to obtain a stretched film (20 μm acrylic film) having a thickness of 20 μm. When the optical properties of this stretched film were measured, 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.

Production Method of 40 μm Acrylic Film (UV) MS resin (MS-200; copolymer of methyl methacrylate / styrene (molar ratio) = 80/20, manufactured by Nippon Steel Chemical Co., Ltd.) was imidized with monomethylamine ( (Imidation ratio: 5%). The imidization was carried out using a co-rotating twin-screw extruder having a diameter of 15 mm. The set temperature of each temperature control zone of the extruder was 230 ° C., the screw rotation speed was 150 rpm, the MS resin was supplied at 2.0 kg / hr, and the supply amount of monomethylamine was 2 parts by weight based on 100 parts by weight of the MS resin. . After charging the MS resin from the hopper and melting and filling the resin with the kneading block, monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. The by-products after the reaction and excess methylamine were devolatilized by reducing the pressure at the vent port to -0.08 MPa. The resin that came out as a strand from a die provided at the extruder outlet was cooled in a water tank and then pelletized by a pelletizer. The imidized MS resin was formed by melt extrusion. At this time, 0.66 parts by weight of an ultraviolet absorber (manufactured by ADEKA, trade name: LA-F70) was supplied to 100 parts by weight of the MS resin. Next, the film was biaxially stretched twice vertically and twice horizontally to prepare a protective film (40 μm acrylic film (UV), thickness 40 μm, Re = 2 nm, Rth = 2 nm).

Method for Producing 30 μm Acrylic Film Containing Cross-Linked Elastic Material A mixture having the following composition was charged 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 mixed. Of a mixed solution of a monomer mixture consisting of the above and 0.1 part of t-butyl hydroperoxide were charged all at once, and polymerization was carried out for 45 minutes.
Deionized water 220 parts Boric acid 0.3 parts Sodium carbonate 0.03 parts Sodium N-lauroyl sarcosinate 0.09 parts Sodium formaldehyde sulfoxylate 0.09 parts Ethylenediaminetetraacetic acid-2-sodium 0.006 parts 0.002 parts of ferrous sulfate Subsequently, the remaining 75% of the mixture was continuously added over 1 hour. After completion of the addition, the mixture was kept at the same temperature for 2 hours to complete the polymerization. During this period, 0.2 parts of sodium N-lauroylsarcosinate was added. The polymerization conversion ratio (polymerization production amount / monomer preparation amount) of the obtained innermost layer crosslinked methacrylic polymer latex was 98%.
The obtained innermost layer polymer latex was kept at 80 ° C. in a nitrogen stream, and 0.1 part of potassium persulfate was added. Then, a simple mixture comprising 41 parts of n-butyl acrylate, 9 parts of styrene, and 1 part of allyl methacrylate was obtained. The monomer mixture was added continuously over 5 hours. During this time, 0.1 part of potassium oleate was added in three portions. After the addition of the monomer mixture was completed, 0.05 parts of potassium persulfate was further added to complete the polymerization, and the mixture was maintained for 2 hours to obtain rubber particles. The polymerization conversion of the obtained rubber particles was 99%, and the particle size was 225 nm.
The obtained rubber particle latex was kept at 80 ° C., and after adding 0.02 parts of potassium persulfate, a monomer mixture of 14 parts of methyl methacrylate and 1 part of n-butyl acrylate was continuously added over 1 hour. After completion of the addition of the monomer mixture, the mixture was kept for 1 hour to obtain a graft copolymer latex. The polymerization conversion was 99%.
The obtained graft copolymer latex was kept at 80 ° C., and a monomer mixture of 5 parts of methyl methacrylate and 5 parts of n-butyl acrylate was continuously added over 0.5 hours. After the completion of the addition of the monomer mixture, the mixture was kept for 1 hour to obtain a rubber-containing graft copolymer latex. The polymerization conversion was 99%. The obtained rubber-containing graft copolymer latex was subjected to salting out and coagulation with calcium chloride, heat treatment, and drying to obtain a white powdery crosslinked elastic body.
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 (imidation ratio: 5%). The imidization was carried out using a co-rotating twin-screw extruder having a diameter of 15 mm. The set temperature of each temperature control zone of the extruder was 230 ° C., the screw rotation speed was 150 rpm, the MS resin was supplied at 2.0 kg / hr, and the supply amount of monomethylamine was 2 parts by weight based on 100 parts by weight of the MS resin. . After charging the MS resin from the hopper and melting and filling the resin with the kneading block, monomethylamine was injected from the nozzle. A seal ring was placed at the end of the reaction zone to fill the resin. The by-products after the reaction and excess methylamine were devolatilized by reducing the pressure at the vent port to -0.08 MPa. The resin that came out as a strand from a die provided at the extruder outlet was cooled in a water tank and then pelletized by a pelletizer. The imidized MS resin was formed by melt extrusion. At this time, 0.66 parts by weight of an ultraviolet absorber (manufactured by ADEKA, trade name: LA-F70) was supplied to 100 parts by weight of the MS resin. Next, 10 parts by weight of the crosslinked elastic body was supplied to 100 parts by weight of the MS resin. Next, the 160 μm film obtained by the extrusion is biaxially stretched two times vertically and twice horizontally to prepare a protective film (30 μm acrylic film including a crosslinked elastic body, thickness 30 μm, Re = 2 nm, Rth = 2 nm). did.

３７37 μm λ / 4TAC film with HC: KC2UGR-HC (manufactured by Konica Minolta, a film in which an acrylic resin hard coat layer is provided on a triacetyl cellulose polymer film, thickness: 37 μm)

13μm COP film: ZF-014 (manufactured by Zeon Corporation, raw material: cycloolefin polymer, thickness: 13μm)

２６26 μm λ / 4 COP film with HC: ZD12 (Zeon, raw material: cycloolefin-based polymer, thickness: 20 μm) provided with an acrylic resin-based hard coat layer

Production Method of 40 μm Acrylic Film with HC In a 30 L pot-type reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe, 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2- ( (Hydroxymethyl) methyl acrylate (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing nitrogen through. When the mixture was refluxed, 5.0 g of t-butyl peroxyisopropyl carbonate (Kayacarbon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator, and at the same time, 10.0 g of t-butyl peroxyisopropyl carbonate was added. And a solution consisting of 230 g of MIBK was added dropwise over 4 hours while refluxing. Perform solution polymerization at about 105 ~ 120 ° C., the mixture was aged over an additional 4 hours.
To the obtained polymer solution, 30 g of a stearyl phosphate / distearyl phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the mixture was refluxed at about 90 to 120 ° C. for 5 hours under reflux. A condensation reaction was performed. Next, the obtained polymer solution is subjected to a vent-type screw twin-screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent and four forevents. (Φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / h in terms of the amount of resin, and further subjected to cyclization condensation reaction and devolatilization in this extruder to extrude. As a result, transparent pellets of the lactone ring-containing polymer were obtained.
When the dynamic TG of the obtained lactone ring-containing polymer was measured, a decrease in mass of 0.17% by mass was detected. The lactone ring-containing polymer had a weight average molecular weight of 133,000, a melt flow rate of 6.5 g / 10 min, and a glass transition temperature of 131 ° C.
The obtained pellets and acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) are kneaded and extruded at a mass ratio of 90/10 using a single screw extruder (screw 30 mmφ). As a result, transparent pellets were obtained. The glass transition temperature of the obtained pellet was 127 ° C.
The pellet was melt-extruded from a coat hanger type T die having a width of 400 mm using a 50 mmφ single screw extruder to produce a film having a thickness of 160 μm. The produced film was stretched 2.0 times using a biaxial stretching device at a temperature of 150 ° C. to obtain a stretched film having a thickness of 40 μm. When the optical properties of this stretched film were measured, 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.
As a resin contained in the coating liquid, a UV-curable resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: “NK oligomer UA-53H-80BK”, solid content concentration: 80%), 70 parts by weight of solid content, UV curable resin 30 parts by weight of a resin (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name “A-GLY-9E”, solid content concentration 100%) was prepared. 5 parts of a photopolymerization initiator (product name "IRGACURE907" manufactured by BASF) and 0 parts of a leveling agent (manufactured by DIC Co., product name "GRANDIC PC4100") per 100 parts by weight of the resin solid content of the resin. .1 part was added. Toluene and cyclopentanone were added to the mixture at a ratio of 80:20 so that the solid concentration in the solution was 40%. Thus, a hard coat layer forming material was produced.
The prepared hard coat layer forming material was applied on the stretched film so that the thickness of the hard coat layer after curing became 7 μm to form a coating film. Thereafter, the coating film was dried at 90 ° C. for 1 minute, and further irradiated with ultraviolet light having an integrated light amount of 300 mJ / cm ² by a high-pressure mercury lamp, and the coating film was cured to form a hard coat layer. A 40 μm acrylic film was produced.

Method for producing 30 μm acrylic film containing crosslinked elastic body with HC 22 parts of 15-functional urethane acrylic oligomer (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK Oligo UA-53H, weight average molecular weight: 2300), pentaerythritol triacrylate (Osaka Organic) 28 parts, manufactured by Chemical Industry Co., Ltd., trade name: Biscoat # 300, 50 parts of ethoxylated glycerin triacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name: NK ester A-GLY-9E), photopolymerization initiator (Ciba Japan Co., Ltd.) (Trade name: Irgacure 907) was mixed and diluted with methyl isobutyl ketone so as to have a solid content of 40% to prepare a hard coat layer forming material.
The prepared hard coat layer forming material was applied on a 30 μm acrylic film containing the crosslinked elastic material so that the thickness of the hard coat layer after curing became 10 μm to form a coating film. Thereafter, the coating film is dried at 90 ° C. for 1 minute, and further irradiated with ultraviolet light having an integrated light amount of 200 mJ / cm ² by a high-pressure mercury lamp, and the coating film is cured to form a hard coat layer, and to form a hard coat layer. A 30 μm acrylic film containing a crosslinked elastic body was produced.

Method for Producing 40 μm Acrylic Film In a 30 L pot-type reactor equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introducing pipe, 8,000 g of methyl methacrylate (MMA) and 2,000 g of 2- (hydroxymethyl) were added. ) Methyl acrylate (MHMA), 10,000 g of 4-methyl-2-pentanone (methyl isobutyl ketone, MIBK), and 5 g of n-dodecyl mercaptan were charged, and the temperature was raised to 105 ° C. while passing nitrogen through, followed by reflux. At that time, 5.0 g of t-butyl peroxyisopropyl carbonate (Kayacarbon BIC-7, manufactured by Kayaku Akzo Co., Ltd.) was added as a polymerization initiator, and at the same time, 10.0 g of t-butyl peroxyisopropyl carbonate and 230 g were added. Of MIBK was added dropwise over 4 hours while refluxing for about 1 hour. Perform solution polymerization at 5 ~ 120 ° C., the mixture was aged over an additional 4 hours.
To the obtained polymer solution, 30 g of a stearyl phosphate / distearyl phosphate mixture (Phoslex A-18, manufactured by Sakai Chemical Industry Co., Ltd.) was added, and the mixture was refluxed at about 90 to 120 ° C. for 5 hours under reflux. A condensation reaction was performed. Next, the obtained polymer solution is subjected to a vent-type screw twin-screw extruder having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), one rear vent and four forevents. (Φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / h in terms of the amount of resin, and further subjected to cyclization condensation reaction and devolatilization in this extruder to extrude. As a result, transparent pellets of the lactone ring-containing polymer were obtained.
When the dynamic TG of the obtained lactone ring-containing polymer was measured, a decrease in mass of 0.17% by mass was detected. The lactone ring-containing polymer had a weight average molecular weight of 133,000, a melt flow rate of 6.5 g / 10 min, and a glass transition temperature of 131 ° C.
The obtained pellets and acrylonitrile-styrene (AS) resin (Toyo AS AS20, manufactured by Toyo Styrene Co., Ltd.) are kneaded and extruded at a mass ratio of 90/10 using a single screw extruder (screw 30 mmφ). As a result, transparent pellets were obtained. The glass transition temperature of the obtained pellet was 127 ° C.
The pellet was melt-extruded from a coat hanger type T die having a width of 400 mm using a 50 mmφ single screw extruder to produce a film having a thickness of 160 μm. The produced film was stretched 2.0 times at a temperature of 150 ° C. using a biaxial stretching device to obtain a stretched film (40 μm acrylic film) having a thickness of 40 μm. When the optical properties of this stretched film were measured, 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 improving film (Sumitomo 3M, product name: APF, thickness 26 μm)

ＡＰ APF with HC: A film in which an acrylic resin-based hard coat layer is provided on a brightness enhancement film (Sumitomo 3M, trade name: APF, thickness: 20 μm)

２６26μm COP film with HC: ZF12-HC: manufactured by Zeon Corporation, raw material: cycloolefin polymer coated with acrylic resin hard coat

測定 The methods for measuring the coefficient of linear expansion and the elongation at break of the protective films used in Examples and Comparative Examples are as follows. The following evaluations were performed on the polarizing films produced in the examples and comparative examples. Table 1 shows the results.

<Measurement of linear expansion coefficient Y (× 10 ⁻⁵ / K) of protective film>
Using a TMA analyzer (manufactured by Hitachi High-Tech Science Co., Ltd., TMA7100E), the dimensional change of the protective film was measured under the following measurement conditions, and the obtained value was substituted into the following equation (A) to determine the dimensional change rate. Calculated. The measurement was performed four times, and the average value of the four measurements was defined as the dimensional change rate. Then, the average value of the obtained dimensional change rates was substituted into the following equation (B) to calculate the linear expansion coefficient Y (× 10 ⁻⁵ / K) of the protective film.
Sample size: 20mm x 5mm
Measurement environment: -40 ℃ ⇔85 ℃
Temperature rise / fall rate: 10 ° C / min
Number of measurements: 4

Dimensional change rate = (ΔL / L) × 100 (A)
ΔL: dimensional change during measurement (difference between dimensions at -40 ° C and dimensions at 85 ° C)
L: Dimension before measurement (dimension at 25 ° C.)

Linear expansion coefficient Y (× 10 ⁻⁵ / K) = (dimensional change rate / ΔT) / 100 (B)
ΔT: width of temperature change

<Measurement of elongation at break X (%) of protective film>
Using an autograph (manufactured by Shimadzu Corporation), the protective film was pulled at a constant speed until the film was broken under the following measurement conditions, and the length at break was measured. The elongation at break X (%) was calculated by substituting the initial length and the length at break into the following equation (C). The measurement was performed three times, and the average value of the three times was defined as the elongation at break X (%).
Sample size: 100mm x 10mm
Tensile speed: 300mm / min
Measurement environment: temperature 23 ° C, 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)>
A sample was obtained by providing a cut in a MD film in the MD direction with a laser on a 150 mm × 50 mm polarizing film as shown in FIG. The sample was bonded to a glass plate (manufactured by Matsunami Glass Industry Co., Ltd.) with an adhesive using a hand roller, and the sample bonded to the glass plate was left in an autoclave at 50 ° C. for 15 minutes. Thereafter, the sample bonded to the glass plate was put into a test tank, and a heat shock test was performed under the following conditions. A sample bonded to a glass plate was taken out every 10 cycles, and it was confirmed whether or not a crack of 1 mm or more had occurred in the round portion of FIG. The number of cycles when a crack of 1 mm or more occurred was counted for each of the five samples (the number of cycles at which cracks occurred in all five of the five samples), and the maximum value was adopted and evaluated according to the following criteria.
(Measurement condition)
Measurement environment: -40 ° C (hold for 30 minutes) @ 85 ° C (hold for 30 minutes)
Temperature rise / fall rate: 10 ° C / min
Number of samples: 5
(Evaluation criteria)
〇: 200 cycles or more △: 100 to 199 cycles ×: 99 cycles or less

From Table 1, it can be seen that the polarizing films of Examples 1 to 10 in which at least one of the protective films provided on the polarizer satisfies the above formula (1) have a thermal shock (heat shock test in which the temperature conditions of -40 ° C and 85 ° C are repeated) It can be seen that cracks hardly occur in the polarizer even under the severe environment, and that the polarizer is excellent in crack resistance. 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 liable to cracks in the polarizer due to thermal shock and have poor crack resistance.

The polarizing film of the present invention is used alone or as an optical film obtained by laminating the polarizing film on an image display device such as a liquid crystal display (LCD) and an organic EL display.

Claims

A polarizing film provided with a protective film via an adhesive layer on one or both sides of the polarizer,
At least one of the protective films provided on the polarizer satisfies the following formula (1).
Y ≦ 1.26 × lnX + 3.5 (1)
Y: Coefficient of linear expansion of protective film (× 10 −5 / K)
X: Elongation at break of protective film (%)
2. The polarizing film according to claim 1, wherein Y (× 10 −5 / K) is 4 or less.
偏光 The polarizing film according to claim 1, wherein the thickness of the polarizer is 10 μm or less.
[4] A polarizing film with an adhesive layer, comprising the polarizing film according to any one of [1] to [3] and an adhesive layer.
(4) An image display device, wherein the polarizing film according to any one of (1) to (3) or the polarizing film with an adhesive layer according to (4) is arranged in an image display cell.