TWI873279B - Polarizing film and image display device - Google Patents

Abstract

The present invention provides a polarizing film which can fully inhibit the iodine contained in the polarizer from leaking out to the outside in a high temperature and high humidity environment. The polarizing film of the present invention has a polarizer and a resin layer containing a polymer, and at least one of the following requirements (i) to (v) is satisfied: (i) the tensile storage elastic modulus E1 of the resin layer is greater than 1×10 ⁸ Pa; (ii) the tensile storage elastic modulus E2 of the resin layer is greater than 1×10 ⁸ Pa; (iii) the linear expansion coefficient α1 of the resin layer is less than 400×10 ^-6 /K; (iv) the linear expansion coefficient α2 of the resin layer is less than 300×10 ^-6 /K; (v) the dipole moment D of the monomer used to form the polymer is less than 2 Debye.

Description

Polarizing film and image display device

The present invention relates to a polarizing film and an image display device.

Image display devices such as liquid crystal display devices and organic EL display devices have polarizing films based on reasons such as their display principles. Polarizing films are, for example, laminates including polarizers and transparent protective films. Polarizers can generally be made by adsorbing dichroic pigments on hydrophilic polymer films such as polyvinyl alcohol (PVA) films and then uniaxially stretching the films. From the perspective of improving the transmittance and polarization degree of polarizers, iodine is widely used as a dichroic pigment.

Patent document 1 discloses an optical laminate, which is formed by bonding a polarizer and a protective film via a hardening layer of a hardening resin composition. Patent document 1 shows that by properly adjusting the content of the cyclohexane in the hardening resin composition, the iodine content of the hardening layer can be maintained at a low level even when the optical laminate is placed in a high temperature and high humidity environment. Prior art documents Patent document

Patent document 1: Japanese Patent Publication No. 2018-169512

Problems to be solved by the invention In a high temperature and high humidity environment, the iodine contained in the polarizer tends to move from the polarizer to the transparent protective film or the adhesive layer used to adhere the polarizer to the image display panel. Especially when the thickness of the polarizer is small and the iodine concentration of the polarizer is high, the iodine is easy to move from the polarizer to the transparent protective film or the adhesive layer. The iodine that moves to the transparent protective film or the adhesive layer will pass through the transparent protective film or the adhesive layer to the outside of the polarizing film. If the iodine content in the polarizer decreases, the polarization degree of the polarizing film will decrease.

In the past, polarizing films could not fully prevent the iodine contained in the polarizer from leaking out of the polarizing film in a high temperature and high humidity environment. For example, Patent Document 1 focuses on maintaining the iodine content of the hardened layer at a low level when the optical laminate is placed in a high temperature and high humidity environment. However, Patent Document 1 does not take into account the fact that iodine may leak out of the polarizer to the outside of the optical laminate.

Therefore, the object of the present invention is to provide a polarizing film that can fully inhibit the iodine contained in the polarizer from leaking out to the outside in a high temperature and high humidity environment.

Means for solving the problem After active research by the inventors, it was newly discovered that in a polarizing film having a resin layer, the tensile storage elastic modulus of the resin layer, the linear expansion coefficient of the resin layer, and the dipole moment of the monomer used to form the polymer contained in the resin layer can be used as relevant indicators of iodine permeation to the outside, thereby completing the present invention.

The present invention provides a polarizing film, which comprises: an iodine-containing polarizer and a polymer-containing resin layer, and at least one of the following requirements (i) to (v) is satisfied: (i) the tensile storage elastic modulus E1 of the resin layer in water at 65°C is 1×10 ⁸ Pa or more; (ii) the tensile storage elastic modulus E2 of the resin layer in water at 85°C is 1×10 ⁸ Pa or more; (iii) when the resin layer is heated from 25°C to 65°C and the measuring gas environment is humidified from 10%RH to 90%RH, the linear expansion coefficient α1 of the resin layer is 400×10 ^-6 /K or less; (iv) when the resin layer is heated from 25°C to 85°C and the measuring gas environment is humidified from 10%RH to 85%RH, the linear expansion coefficient α2 of the resin layer is less than 300×10 ^-6 /K; (v) the dipole moment D of the monomer used to form the polymer is less than 2 Debye.

Effect of the invention According to the present invention, a polarizing film can be provided, which can fully inhibit the iodine contained in the polarizing element from leaking out to the outside in a high temperature and high humidity environment.

The following describes the details of the present invention, but the following description is not intended to limit the specific implementation form of the present invention.

(Implementation form of polarizing film) As shown in FIG1 , the polarizing film 10 of the present implementation form has an iodine-containing polarizing element 1 and a resin layer 2 containing a polymer P. The resin layer 2 is, for example, located closer to the visual side than the polarizing element 1 and directly contacts the polarizing element 1. However, within the scope of not hindering the effect of the present invention, other layers such as an adhesive layer and an easy-to-bond layer may be arranged between the resin layer 2 and the polarizing element 1. The resin layer 2 may also be located closer to the image display panel side described later than the polarizing element 1. In other words, the polarizing element 1 may also be located closer to the visual side than the resin layer 2. The resin layer 2 is, for example, located at the outermost side of the polarizing film 10. In addition, in this specification, "film" means a member whose thickness is sufficiently small compared to its length and width.

The polarizing film 10 may also be further provided with an adhesive layer 3, a transparent protective film (first transparent protective film) 4 and an adhesive layer 5. The transparent protective film 4 is, for example, bonded to the polarizing element 1 through the adhesive layer 3. The adhesive layer 5 functions as a component for bonding the polarizing film 10 to the image display panel described later. Therefore, the adhesive layer 5 is, for example, located at the outermost side of the polarizing film 10 and is located closer to the image display panel than the polarizing element 1. In other words, the polarizing element 1 is, for example, located closer to the visual side than the adhesive layer 5. The resin layer 2, the polarizing element 1, the adhesive layer 3, the transparent protective film 4 and the adhesive layer 5 are, for example, arranged in sequence in the lamination direction.

In the polarizing film 10 of the present embodiment, at least one of the following requirements (i) to (v) is satisfied, and preferably requirement (iii) is satisfied. In the polarizing film 10, all of the requirements (i) to (v) may be satisfied. (i) The tensile storage modulus E1 of the resin layer 2 in water at 65°C is greater than 1×10 ⁸ Pa. (ii) The tensile storage modulus E2 of the resin layer 2 in water at 85°C is greater than 1×10 ⁸ Pa. (iii) When the resin layer 2 is heated from 25°C to 65°C and the measuring gas environment is humidified from 10%RH to 90%RH, the linear expansion coefficient α1 of the resin layer 2 is less than 400×10 ^-6 /K. (iv) When the resin layer 2 is heated from 25°C to 85°C and the measured gas environment is humidified from 10%RH to 85%RH, the linear expansion coefficient α2 of the resin layer 2 is less than 300×10 ^-6 /K. (v) The dipole moment D of the monomer M used to form the polymer P contained in the resin layer 2 is less than 2 Debye.

First, requirement (i) will be described. The tensile storage modulus E1 of the resin layer 2 is preferably 5×10 ⁸ Pa or more, more preferably 10×10 ⁸ Pa or more, and even more preferably 15×10 ⁸ Pa or more. The upper limit of the tensile storage modulus E1 is not particularly limited, but from the viewpoint of suppressing cracks in the resin layer 2, it may be, for example, 100×10 ⁸ Pa.

The tensile storage modulus E1 of the resin layer 2 can be measured, for example, by the following method. First, the resin layer 2 to be evaluated is cut into short pieces with a width of 5 mm and a length of 30 mm as test pieces. Then, the test piece is placed in a commercially available dynamic viscoelasticity measuring device. At this time, a clamp is used that can immerse the test piece in a solvent. The distance between the clamps used to fix the test piece is set to 15 mm. Then, the test piece is immersed in water. After confirming that the temperature of the test piece is 25°C, the dynamic viscoelasticity of the test piece is measured. The measurement is performed by the tensile vibration-non-resonance method specified in Japanese Industrial Standard (JIS) K7244-4:1999. The vibration frequency is set to 1 Hz. After the measurement starts, the test piece is heated to 95°C at a heating rate of 5°C/min. The measured value of the tensile storage modulus of the test piece at a temperature of 65°C can be regarded as the tensile storage modulus of the resin layer 2 E1.

Next, requirement (ii) will be described. The tensile storage modulus E2 of the resin layer 2 is preferably 5×10 ⁸ Pa or more, more preferably 10×10 ⁸ Pa or more, and even more preferably 15×10 ⁸ Pa or more. The upper limit of the tensile storage modulus E2 is not particularly limited, but from the viewpoint of suppressing cracks in the resin layer 2, it may be, for example, 100×10 ⁸ Pa. The tensile storage modulus E2 of the resin layer 2 may be measured, for example, by the same method as the tensile storage modulus E1. Specifically, the dynamic viscoelasticity of the test piece is measured using the method described above for the tensile storage modulus E1, and the measured value of the tensile storage modulus of the test piece at a temperature of 85°C can be regarded as the tensile storage modulus E2 of the resin layer 2.

Next, requirement (iii) is described. The linear expansion coefficient α1 of the resin layer 2 is preferably 200×10 ^-6 /K or less, more preferably 180×10 ^-6 /K or less, more preferably 150×10 ^-6 /K or less, and particularly preferably 120×10 ^-6 /K or less. The lower limit of the linear expansion coefficient α1 is not particularly limited, but from the viewpoint of suppressing cracks in the resin layer 2, it can be, for example, 10×10 ^-6 /K.

The linear expansion coefficient α1 of the resin layer 2 can be measured by, for example, the following method. First, the resin layer 2 of the evaluation object is cut into short sticks with a width of 5 mm and a length of 30 mm as a test piece. Then, the test piece is placed in a commercially available thermomechanical analysis device. At this time, the distance between the clamps used to fix the test piece is set to 15 mm. The test piece is placed in a measurement gas environment of 25°C and 10%RH for at least 10 minutes. Then, it takes 60 minutes to heat the test piece to 65°C, and the test piece is kept for 10 minutes. Then, it takes 30 minutes to humidify the measurement gas environment from 10%RH to 90%RH, and the test piece is kept for 10 minutes. The linear expansion coefficient α calculated from the following formula (1) based on the length change ΔL (mm) of the test piece before and after the test can be regarded as the linear expansion coefficient α1 of the resin layer 2. In formula (1), L ₀ means the length of the test piece at 25°C, and ΔT means the temperature change of the test piece before and after the test. In requirement (iii), ΔT is 40°C. Linear expansion coefficient α=ΔL/(L ₀ ×ΔT) (1)

Next, requirement (iv) is described. The linear expansion coefficient α2 of the resin layer 2 is preferably 200×10 ^-6 /K or less, more preferably 170×10 ^-6 /K or less, more preferably 150×10 ^-6 /K or less, and particularly preferably 100×10 ^-6 /K or less. The lower limit of the linear expansion coefficient α2 is not particularly limited, but from the viewpoint of suppressing cracks in the resin layer 2, it may be, for example, 10×10 ^-6 /K. The linear expansion coefficient α2 of the resin layer 2 may be measured in the same manner as the linear expansion coefficient α1 described above, except that the test piece is heated to 85°C for 60 minutes and the measurement gas environment is humidified from 10% RH to 85% RH for 30 minutes. In requirement (iv), ΔT in the above formula (1) is 60°C.

Next, requirement (v) is described. The dipole moment D of the monomer M used to form the polymer P is preferably 1.7 Debye or less, more preferably 1.5 Debye or less, and even more preferably 1.3 Debye or less. The lower limit of the dipole moment D is not particularly limited, and may be, for example, 0.5 Debye.

The dipole moment D can be calculated, for example, by the following method. First, the monomer M used to form the polymer P is identified. The dipole moment D can be calculated by performing molecular simulation on the monomer M. Molecular simulation can be performed using known software such as Materials Studio (manufactured by BIOVIA, ver. 8.0.0.843) and WebMO (ver. 19.0.009e).

The calculation of the dipole moment D by molecular simulation can be performed, for example, according to the following method. First, use Materials Studio to create a molecular model of the monomer M. Regarding the molecular model, the force field of COMPASS (Condensed-phase Optimized Molecular Potentials for Atomistic Simulation Studies) II is used to optimize the structure. Next, the molecular model of the monomer M is processed with WebMO. Specifically, the Gaussian program (Queue:g09) is used in WebMO to perform structural optimization calculations on the molecular model of the monomer M. At this time, B3LYP can be used as a functional, or 6-31G(d) can be used as a basis function. In this way, the dipole moment D of the monomer M can be calculated.

When the polymer P is formed by a plurality of monomers M, the dipole moment D can be determined by the following method. First, the dipole moments of the plurality of monomers M are calculated by the above method. The calculated dipole moments are weighted according to the molar ratio of each monomer M and weighted averaged. The obtained weighted average can be regarded as the dipole moment D. When the plurality of monomers M are structural isomers, the calculated dipole moments can also be weighted according to the molar ratio of each structural isomer and weighted averaged to calculate the dipole moment D.

When at least one of the requirements (i) and (ii) is satisfied, the polymer P contained in the resin layer 2 tends to maintain a state of low molecular mobility even in a high temperature and high humidity environment. If the molecular mobility of the polymer P is low, it is difficult to generate a space in the resin layer 2 where iodine can penetrate. As a result, the movement of iodine from the polarizer 1 to the resin layer 2 is suppressed, and the iodine can be suppressed from penetrating to the outside of the polarizing film 10.

When at least one of the requirements (iii) and (iv) is satisfied, the polymer P contained in the resin layer 2 tends to maintain a small free volume even in a high temperature and high humidity environment. If the free volume of the polymer P is small, it is difficult to generate space in the resin layer 2 for iodine to penetrate. As a result, the movement of iodine from the polarizer 1 to the resin layer 2 is suppressed, and the iodine can be suppressed from penetrating to the outside of the polarizing film 10.

When requirement (v) is satisfied, there is a tendency that electrostatic interaction is not easily generated between the polymer P and iodine. That is, iodine is not easily attracted to the polymer P. As a result, the migration of iodine from the polarizer 1 to the resin layer 2 is suppressed, and the iodine can be suppressed from penetrating to the outside of the polarizing film 10.

In the polarizing film 10 of this embodiment, the y value calculated by the following formula (2) can also be less than 1.3. y=(0.279)x ₁ +(-1.51)x ₂ +(0.178)x ₃ +0.386 (2)

In formula (2), _x1 is the number of rotatable bonds contained in the monomer M used to form the polymer P. _x1 can be an indicator for predicting the extent to which the molecular motion of the polymer P is restricted. In the present specification, "rotatable bonds" means single bonds connecting heavy atoms, excluding bonds contained in the ring structure and single bonds connecting heavy atoms at the end with other heavy atoms. Heavy atoms refer to atoms other than hydrogen atoms and helium atoms, specifically nitrogen atoms, oxygen atoms and other heteroatoms, and carbon atoms. Specific examples of single bonds connecting heavy atoms include carbon-carbon bonds and carbon-heteroatoms bonds. For example, when the polymer P is formed by dihydroxymethyl-tricyclodecane diacrylate, the value of _x1 is 8. The number of rotatable bonds can also be calculated using software for calculating molecular descriptors, such as Dragon (version 7.0), alvaDesc, etc.

When the polymer P is formed by a plurality of monomers M, the value of _x1 can be determined by the following method. First, the number of rotatable bonds is calculated for each of the plurality of monomers M. The calculated number of rotatable bonds is weighted according to the molar ratio of each monomer M and weighted averaged. The obtained weighted average value can be regarded as _x1 . In this embodiment, the value of _x1 is not particularly limited, and can be, for example, 2 to 20.

_x2 is the number of reaction points contained in the monomer M used to form the polymer P. _x2 can be an indicator used to predict the extent to which gaps of a size through which low molecular weight compounds can pass exist for the polymer P. In this specification, "reaction point" means a polymerizable group or a cross-linkable group. Specific examples of such groups include groups having polymerizable double bonds such as (meth)acryl groups, epoxy groups, cross-linking functional groups such as cyclohexane groups. For example, when the polymer P is formed by dihydroxymethyl-tricyclodecane diacrylate, the value of _x2 is 2. The number of reaction points can also be calculated using the above-mentioned software for calculating molecular descriptors.

When the polymer P is formed by a plurality of monomers M, the value of _x2 can be determined by the following method. First, the number of reaction points is calculated for each of the plurality of monomers M. The calculated number of reaction points is weighted according to the molar ratio of each monomer M and weighted average is performed. The obtained weighted average value can be regarded as _x2 . In this embodiment, the value of _x2 is not particularly limited, and can be, for example, 1 to 6.

x ₃ is the polarization term δP (MPa ^1/2 ) in the Hansen solubility parameters of the monomer M used to form the polymer P. x ₃ can be used as an index for predicting the interaction between the polymer P and water molecules or iodine. The Hansen solubility parameters refer to the solubility parameters introduced by Hildebrand divided into three components: the dispersion term δD, the polarization term δP, and the hydrogen bond term δH. The polarization term δP represents the energy generated by the dipole-dipole interaction between molecules. The details of the Hansen solubility parameters are disclosed in "Hansen Solubility Parameters; A Users Handbook (CRC Press, 2007)". The polarization term δP can be calculated using, for example, well-known software such as HSPiP (version 5). In addition, the value of the polarization term δP may sometimes vary slightly depending on the software used. However, the size of the error is usually negligible when calculating the y value.

When the polymer P is formed by a plurality of monomers M, the value of x ₃ can be determined by the following method. First, the polarization term δP (MPa ^1/2 ) in the Hansen solubility parameter is calculated for each of the plurality of monomers M. The calculated polarization term δP is weighted by the molar ratio of each monomer M and a weighted average is taken. The obtained weighted average value can be regarded as x ₃ . In the present embodiment, the value of x ₃ is not particularly limited, and for example, it can be 1 to 10 (MPa ^1/2 ). The value of _{x 3} is preferably 6 (MPa ^1/2 ) or less, more preferably 5 (MPa ^1/2 ) or less, and even more preferably 4 (MPa ^1/2 ) or less.

The y value calculated using formula (2) is preferably below 0.8, more preferably below 0.7, more preferably below 0.5, and most preferably below 0.3.

The y value calculated by formula (2) is an index of the monomer M used to form the polymer P contained in the resin layer 2. However, according to the research of the present inventors, the y value can also be effectively used as an index for selecting a resin layer 2 suitable for suppressing the leakage of iodine contained in the polarizer 1 to the outside. The y value is particularly suitable as an index for predicting the properties of a resin layer containing a polymer having a structural unit derived from (meth)acrylate.

[Polarizer] The polarizer 1 is not particularly limited as long as it contains iodine. For example, a hydrophilic polymer film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, or a partially saponified film of an ethylene-vinyl acetate copolymer is adsorbed with iodine and then uniaxially stretched. The polarizer 1 is preferably composed of a polyvinyl alcohol film and iodine.

The thickness of the polarizer 1 is not particularly limited, for example, it is less than 30µm, and preferably less than 20µm, more preferably less than 18µm, more preferably less than 15µm, particularly preferably less than 12µm, and particularly preferably less than 10µm. The thickness of the polarizer 1 may be greater than 2µm, greater than 4µm, or greater than 5µm. The thickness of the polarizer 1 may be 7~12µm, and may be 1~7µm depending on the circumstances, and may be particularly 4~6µm. In this specification, a polarizer 1 having a thickness of less than 10µm is sometimes referred to as a thin polarizer. A thin polarizer has less thickness variation and tends to have excellent visual recognition. In addition, the dimensional change of a thin polarizer is suppressed, and it also has the advantage of excellent durability. According to the thin polarizer, the polarizing film 10 can be thinned. When the polarizer 1 is a thin polarizer, in order to make the polarizing film 10 have a practically sufficient polarization degree, the iodine concentration in the polarizer 1 must be increased. In the polarizing film 10 of this embodiment, even when the thickness of the polarizer 1 is small and the iodine concentration in the polarizer 1 is high, the leakage of iodine from the polarizer 1 to the outside can be sufficiently suppressed.

The polarizer 1 can be made, for example, by immersing a hydrophilic polymer film such as a polyvinyl alcohol film in an aqueous solution of iodine to dye it and stretch it to 3 to 7 times its original length. The hydrophilic polymer film can also be immersed in an aqueous solution containing boric acid, potassium iodide, etc. as needed. And as needed, the hydrophilic polymer film can be immersed in water for washing before dyeing. By washing the hydrophilic polymer film with water, dirt or anti-caking agents attached to the surface can be washed away. If the hydrophilic polymer film is washed with water, the hydrophilic polymer film will swell, so it also has the effect of suppressing uneven dyeing. The extension of the hydrophilic polymer film can be performed after dyeing with iodine, it can also be performed while dyeing, and it can also be performed before dyeing with iodine. The stretching of the hydrophilic polymer film can be carried out in an aqueous solution containing boric acid, potassium iodide, etc. or in water.

Representative examples of thin polarizers include those described in Japanese Patent Laid-Open No. 51-069644, Japanese Patent Laid-Open No. 2000-338329, International Publication No. 2010/100917, Japanese Patent Laid-Open No. 2014-59328, and Japanese Patent Laid-Open No. 2012-73563. These thin polarizers can be produced by a manufacturing method comprising the following steps: a step of stretching a laminate comprising a polyvinyl alcohol resin (PVA resin) layer and a stretching resin substrate; and a step of dyeing the resulting stretched film. In this manufacturing method, the PVA resin layer is supported by the stretching resin substrate, so defects such as cracks due to stretching are not easily generated.

From the perspective that the thin polarizer can be stretched at a high magnification and thus improve the polarization performance, it is more preferable to use a manufacturing method including a stretching step in a boric acid aqueous solution, and it is more preferable to use a manufacturing method including a step of performing auxiliary air stretching before the stretching step in a boric acid aqueous solution. The manufacturing method including a stretching step in a boric acid aqueous solution has been disclosed in International Publication No. 2010/100917, Japanese Patent Publication No. 2014-59328, Japanese Patent Publication No. 2012-73563, etc. The manufacturing method including a step of performing air stretching has been disclosed in Japanese Patent Publication No. 2014-59328, Japanese Patent Publication No. 2012-73563, etc.

[Resin layer] As long as at least one of the above requirements (i) to (v) is satisfied, the resin layer 2 and the polymer P contained in the resin layer 2 are not particularly limited. The polymer P, for example, contains a structural unit derived from one monomer selected from the group consisting of a free radical polymerizable monomer, a cationic polymerizable monomer and an anionic polymerizable monomer, and preferably contains a structural unit derived from a free radical polymerizable monomer. The polymer P may also contain a structural unit derived from a free radical polymerizable monomer and a structural unit derived from a cationic polymerizable monomer.

Examples of free radical polymerizable monomers include (meth)acrylates and styrene compounds. In the present specification, "(meth)acrylic acid" means acrylic acid and/or methacrylic acid.

The (meth)acrylate may be a monofunctional (meth)acrylate having one (meth)acryloyl group, or may be a multifunctional (meth)acrylate having two or more (meth)acryloyl groups. The polymer P preferably includes a structural unit derived from the multifunctional (meth)acrylate. The use of a polymer P including a structural unit derived from the multifunctional (meth)acrylate has a tendency to further suppress the migration of iodine from the polarizer 1 to the resin layer 2. The number of (meth)acryloyl groups contained in the multifunctional (meth)acrylate is not particularly limited, for example, 2 to 6, and preferably 2 to 4. If the number of (meth)acryloyl groups contained in the multifunctional (meth)acrylate is too large, there may be a situation where unreacted (meth)acryloyl groups remain in the polymer P.

The carbon number of the part other than the (meth)acryloyl group in the (meth)acrylate (hereinafter sometimes referred to as the ester part) is not particularly limited, and is, for example, 1 to 18, and preferably 4 to 10. The ester part may also contain a ring structure. The ring structure may also contain heteroatoms such as nitrogen atoms and oxygen atoms, but is preferably composed only of alicyclic hydrocarbons. The ring structure may be a condensed ring structure such as tricyclodecane, or a monocyclic structure such as cyclohexane. The ester part may also contain a functional group such as an ether group.

(Meth)acrylate may also contain a polar group, but preferably does not contain a polar group. In this specification, a polar group means a group containing a bond between a hydrogen atom and a heteroatom such as an oxygen atom or a nitrogen atom. Examples of the polar group include a hydroxyl group, a carboxyl group, a primary amino group, and a secondary amino group.

Examples of the (meth)acrylate include dicyclopentyl (meth)acrylate, 4-t-butylcyclohexyl (meth)acrylate, lauryl (meth)acrylate, 5-(meth)acryloyloxy-2,6-norbornanecarbolactone, 3,3,5-trimethylcyclohexyl (meth)acrylate, 4-t-butylphenyl (meth)acrylate, isobornyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, 2-ethyl-2-adamantyl (meth)acrylate, 2-isopropyl-2-adamantyl (meth)acrylate, 4-biphenyl (meth)acrylate, 1-naphthyl (meth)acrylate, 2-naphthyl (meth)acrylate, 1- Monofunctional (meth)acrylates such as anthracene ester, 1-anthracenemethyl (meth)acrylate, and 9-anthracenemethyl (meth)acrylate; bifunctional (meth)acrylates such as dihydroxymethyl-tricyclodecane di(meth)acrylate, 1,3-adamantanediol di(meth)acrylate, 1,3,5-adamantantriol-1,5-di(meth)acrylate, and 9,9-bis[4-(2-(meth)acryloyloxyethoxy)phenyl]fluorene; trifunctional (meth)acrylates such as trihydroxymethylenepropane tri(meth)acrylate, glycerol tri(meth)acrylate, and 1,3,5-adamantantriol tri(meth)acrylate; quadrifunctional (meth)acrylates such as pentaerythritol tetra(meth)acrylate; hexafunctional (meth)acrylates such as dipentaerythritol hexa(meth)acrylate, and the like.

Styrene compounds include, for example, an aromatic ring and one or more vinyl groups. Similar to (meth)acrylates, styrene compounds may also include polar groups, but preferably do not contain polar groups. Examples of styrene compounds include styrene, α-methylstyrene, vinylbenzyl chloride, butoxystyrene, and vinylpyridine.

The polymer P preferably includes a structural unit derived from a free radical polymerizable monomer as a main component, and preferably consists essentially of a structural unit derived from a free radical polymerizable monomer. In this specification, "main component" means the structural unit that is contained in the largest amount on a weight basis in the polymer P. The polymer P preferably includes a structural unit derived from a (meth)acrylate, and the content thereof is, for example, 50% by weight or more, preferably higher than 70% by weight, more preferably 80% by weight or more, more preferably 90% by weight or more, particularly preferably 95% by weight or more, and particularly preferably 99% by weight or more.

Examples of cationically polymerizable monomers include vinyl ether compounds, epoxy compounds, and cyclohexyloxybutane compounds. Examples of vinyl ether compounds include aliphatic vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, and cyclohexyl vinyl ether; aromatic vinyl ethers such as phenyl vinyl ether, 2-phenoxyethyl vinyl ether, and p-methoxyphenyl vinyl ether; and polyfunctional vinyl ethers such as butanediol-1,4-divinyl ether, triethylene glycol divinyl ether, and dipropylene glycol divinyl ether.

Examples of epoxy compounds include aromatic epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. Examples of aromatic epoxy compounds include: diglycidyl ether compounds (bisphenol-type epoxy resins) of bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenol-formaldehyde epoxy resins such as phenol novolac epoxy resins, cresol novolac epoxy resins, and hydroxybenzaldehyde phenol novolac epoxy resins; and glycidyl ether compounds of polyols such as tetrahydroxyphenylmethane, tetrahydroxydiphenyl ketone, and polyvinylphenol.

Examples of the alicyclic epoxy compounds include vinyl cyclohexene dioxide, 3',4'-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate, fluorene dioxide, bis(3,4-epoxycyclohexylmethyl)adipate, dicyclopentadiene diepoxide, dicyclononadiene diepoxide, tricyclopentadiene diepoxide, dodecahydro-2,6-methano-2H-oxirano[3',4']cyclopenta[1',2':6,7]naphtho[2,3-b]oxirane, and the like.

Examples of the aliphatic epoxy compounds include 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerol triglycidyl ether, trihydroxymethylpropane triglycidyl ether, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, and the like.

Examples of the cyclooxybutane compound include 3-ethyl-3-hydroxymethylcyclooxybutane, 1,4-bis[(3-ethyl-3-cyclooxybutane)methoxymethyl]benzene, 3-ethyl-3-(phenoxymethyl)cyclooxybutane, bis[(3-ethyl-3-cyclooxybutane)methyl]ether, and 3-ethyl-3-(2-ethylhexyloxymethyl)cyclooxybutane.

Examples of the anionic polymerizable monomer include (meth)acrylates. The (meth)acrylates as anionic polymerizable monomers may also use the above-mentioned monomers as radical polymerizable monomers.

The polymer P preferably contains structural units derived from multifunctional monomers. Examples of the multifunctional monomers include the above-mentioned multifunctional (meth)acrylates, multifunctional vinyl ether compounds, multifunctional epoxy compounds, and multifunctional cyclohexane compounds. The content of structural units derived from multifunctional monomers in the polymer P is, for example, 20% by weight or more, preferably 40% by weight or more, more preferably 50% by weight or more, and may be 70% by weight or more depending on the circumstances. The upper limit of the content of structural units derived from multifunctional monomers is not particularly limited, and is, for example, 95% by weight.

The polymer P may also contain structural units derived from monomers having polar groups, but preferably does not contain such structural units. When the polymer P contains structural units derived from monomers having polar groups, the iodine contained in the polarizer 1 tends to be close to the resin layer 2. Therefore, the content of structural units derived from monomers having polar groups in the polymer P is preferably 20% by weight or less, more preferably 10% by weight or less, more preferably 5% by weight or less, and particularly preferably 2% by weight or less.

The resin layer 2 contains, for example, a polymer P as a main component. The content of the polymer P in the resin layer 2 is, for example, 50% by weight or more, preferably 70% by weight or more, more preferably 90% by weight or more, and more preferably 95% by weight or more. The resin layer 2 is preferably substantially composed of the polymer P. However, the resin layer 2 may contain additives such as an antistatic agent, an antioxidant, inorganic particles, and a leveling agent in addition to the polymer P.

The thickness of the resin layer 2 is not particularly limited, and is, for example, 10 μm or less, preferably 5 μm or less, and more preferably 3 μm or less. From the perspective of sufficiently suppressing the leakage of iodine contained in the polarizer 1 to the outside, the thickness of the resin layer 2 is preferably 0.3 μm or more, and may also be 0.5 μm or more.

The resin layer 2 can also be bonded to the polarizer 1 through an adhesive layer or an easy-bonding layer. The adhesive layer used to bond the resin layer 2 to the polarizer 1 can be, for example, the adhesive layer 3 described below. The easy-bonding layer can be formed by a resin containing a polymer having, for example, a polyester skeleton, a polyether skeleton, a polycarbonate skeleton, a polyurethane skeleton, a polysilicone system, a polyamide skeleton, a polyimide skeleton, a polyvinyl alcohol skeleton, etc. The polymer contained in the resin can be one or more than two. The easy-bonding layer can also contain an additive. The additive can be a thickener, an ultraviolet absorber, an antioxidant, a heat-resistant stabilizer, and other stabilizers. The thickness of the easy-adhesion layer is not particularly limited, but is preferably 0.01 to 5 µm, more preferably 0.02 to 2 µm, and even more preferably 0.05 to 1 µm. The easy-adhesion layer may also be a laminate of multiple layers.

[Adhesive layer] The adhesive layer 3 is a layer containing an adhesive. The material of the adhesive is not particularly limited, and a known material can be used. The adhesive contained in the adhesive layer 3 can be, for example, a water-based adhesive and an active energy ray-curing adhesive. The active energy ray-curing adhesive can be, for example, those disclosed in Japanese Patent Laid-Open No. 2019-147865, Japanese Patent Laid-Open No. 2016-177248, etc.

The thickness of the adhesive layer 3 is not particularly limited, for example, it is less than 3.0µm, preferably 0.01~3.0µm, more preferably 0.1~2.5µm, and more preferably 0.5~1.5µm. If the thickness of the adhesive layer 3 is too small, the cohesive force of the adhesive layer 3 will be insufficient, and the peeling force will be reduced. If the thickness of the adhesive layer 3 is too large, when stress is applied to the cross section of the polarizing film 10, the adhesive layer 3 may peel off. That is, the polarizing film 10 may be impacted and cause peeling failure.

[Transparent protective film] The transparent protective film 4 should preferably be excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, and isotropy. The material of the transparent protective film 4 can be exemplified by polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; cellulose polymers such as cellulose diacetate and cellulose triacetate; (meth) acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin); polycarbonate polymers; olefin polymers such as polyethylene, polypropylene, and ethylene-propylene copolymer; cyclic olefin polymers such as polynorbornene; vinyl chloride polymers; amide polymers such as nylon and aromatic polyamide; imide polymers; sulfonium polymers; polyethersulfonium polymers; polyetheretherketone polymers; polyphenylene sulfide polymers; vinyl alcohol polymers; vinylidene chloride polymers; vinyl butyral polymers; arylate polymers; polyoxymethylene polymers; epoxy polymers; mixtures of these polymers, etc.

The transparent protective film 4 preferably contains a polymer that functions as a thermoplastic resin among the above-mentioned polymers. The content of the thermoplastic resin in the transparent protective film 4 is preferably 50% to 100% by weight, more preferably 50% to 99% by weight, more preferably 60% to 98% by weight, and particularly preferably 70% to 97% by weight. If the content of the thermoplastic resin in the transparent protective film 4 is less than 50% by weight, the original function of the thermoplastic resin, such as high transparency, may not be fully exerted.

The transparent protective film may also contain one or more additives. Examples of the additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, coloring agents, and the like.

The transparent protective film 4 may also be a polymer film described in Japanese Patent Publication No. 2001-343529, International Publication No. 01/37007, etc. The material of the polymer film may include, for example, a resin composition comprising the following thermoplastic resins: a thermoplastic resin having substituted and/or unsubstituted amide groups in the side chains, a thermoplastic resin having substituted and/or unsubstituted phenyl and nitrile groups in the side chains. A specific example of the polymer film may include a film formed by a resin composition comprising the following copolymers: an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The film may be obtained, for example, by mixing and extruding the resin composition. The film has a small phase difference and a small photoelastic coefficient, so it can eliminate the unevenness and other undesirable conditions caused by the strain of the polarizing film 10. In addition, the film has a low moisture permeability, so it has excellent durability in a humid environment.

The moisture permeability of the transparent protective film 4 is not particularly limited, but is preferably 150 g/m ² /24 h or less. At this time, the moisture in the air can be suppressed from invading the interior of the polarizing film 10, and the change in the moisture content of the polarizing film 10 can be suppressed. Thereby, the polarizing film 10 can be suppressed from curling or dimensional changes during storage. The material forming the transparent protective film 4 with low moisture permeability can be, for example, polyester polymers, polycarbonate polymers, aromatic ester polymers, amide polymers, olefin polymers, cyclic olefin polymers, (meth) acrylic polymers and mixtures thereof. The material forming the transparent protective film 4 is preferably polycarbonate polymers, cyclic olefin polymers and (meth) acrylic polymers, and cyclic olefin polymers and (meth) acrylic polymers are particularly preferred.

The thickness of the transparent protective film 4 is not particularly limited, but from the viewpoint of strength, handling properties, etc., it is preferably 5 to 100 μm, more preferably 10 to 60 μm, and even more preferably 13 to 40 μm.

In order to improve the adhesion between components, the surface of the transparent protective film 4 may be subjected to a corona treatment, a plasma treatment or other bonding treatment. An bonding layer may be disposed on the surface of the transparent protective film 4. The bonding layer may be the material described above for the resin layer 2.

[Adhesive layer] The adhesive layer 5 is a layer containing an adhesive. The material of the adhesive is not particularly limited, and a material containing, for example, (meth)acrylic polymers, silicone polymers, polyesters, polyurethanes, polyamides, polyethers, fluorine polymers, rubber polymers, etc. as a base polymer can be used. In particular, acrylic adhesives containing (meth)acrylic polymers have excellent optical transparency, suitable adhesive properties such as wettability, cohesion, and adhesion, and excellent weather resistance and heat resistance, and are therefore suitable materials for the adhesive layer 5.

The adhesive layer 5 may also be a laminate of multiple layers with different compositions. The thickness of the adhesive layer 5 is appropriately determined according to the purpose of use, adhesion, etc., for example, 1 to 500 µm, preferably 1 to 200 µm, and more preferably 1 to 100 µm. The thickness of the adhesive layer 5 may also be less than 50 µm.

Before the polarizing film 10 is attached to the image display panel, the adhesive layer 5 may also be attached to a separator. The separator can prevent the adhesive layer 5 from being contaminated. The separator may be a film such as a plastic film, a rubber sheet, paper, cloth, a non-woven fabric, a mesh, a foam sheet, a metal foil, or a laminate thereof, which is coated with a stripping agent such as a polysilicone-based, long-chain alkyl-based, fluorine-based, or molybdenum sulfide-based stripping agent as required.

[Other components] The polarizing film 10 may also be provided with other components other than the above components. For example, the polarizing film 10 may be provided with a transparent substrate located on the visual side of the resin layer 2. The transparent substrate may also be located on the outermost side of the polarizing film 10. The transparent substrate is made of, for example, glass or polymer. Examples of polymers constituting the transparent substrate include polyethylene terephthalate, polycycloolefin, polycarbonate, etc. The thickness of a transparent substrate made of glass is, for example, 0.1 mm to 1 mm. The thickness of a transparent substrate made of polymer is, for example, 10 µm to 200 µm.

The transparent substrate is bonded to the resin layer 2 via an OCA (optical clear adhesive) layer, for example. The OCA layer may be the one described above for the adhesive layer 5. The thickness of the OCA layer is preferably less than 150 μm.

The polarizing film 10 may also be equipped with optical films such as a reflective plate, a reflective plate, a phase difference film, a viewing angle compensation film, and a brightness enhancement film. Phase difference films include, for example, a 1/2 wavelength plate and a 1/4 wavelength plate. In the polarizing film 10, the phase difference film may also be arranged on the image display panel side (for example, between the adhesive layer 5 and the transparent protective film 4) of the polarizing element 1, and may also be arranged on the visual recognition side of the polarizing element 1.

The polarizing film 10 may also be provided with functional layers such as a hard coating layer, an anti-reflection layer, an anti-sticking layer, a diffusion layer, an anti-glare layer, etc. In the polarizing film 10, the hard coating layer may also be arranged on a side closer to the visual recognition than the resin layer 2.

[Manufacturing method of polarizing film] The polarizing film 10 can be manufactured by, for example, the following method. First, the polarizing element 1 and the transparent protective film 4 are bonded together via the adhesive layer 3. Next, a coating liquid containing a monomer M for forming a polymer P and a polymerization initiator is prepared. The polymerization initiator can be appropriately selected according to the monomer M contained in the coating liquid. For example, when the coating liquid contains a free radical polymerizable monomer, a photopolymerization initiator can be used as the polymerization initiator. When the coating liquid contains a cationic polymerizable monomer, a photoacid generator can be used as the polymerization initiator.

Examples of the photopolymerization initiator include benzil, phenyl ketone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxyphenyl ketone and other phenyl ketone compounds; 4-(2-hydroxyethoxy)phenyl (2-hydroxy-2-propyl) ketone, α-hydroxy-α, α'-dimethylacetophenone, 2-methyl-2-hydroxypropiophenone, α-hydroxycyclohexylphenyl ketone and other aromatic ketone compounds; methoxyacetophenone, 2,2-dimethoxy-2-phenyl ... Acetophenone compounds such as ethoxyacetophenone, 2-methyl-1-[4-(methylthio)-phenyl]-2-furinylpropane-1-one, etc.; benzoin ether compounds such as benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin butyl ether, anisole methyl ether, etc.; aromatic ketal compounds such as benzyl dimethyl ketal; aromatic sulfonyl chloride compounds such as 2-naphthalenesulfonyl chloride; optically active oxime compounds such as 1-benzophenone-1,1-propanedione-2-(o-ethoxycarbonyl)oxime; 9-oxysulfur , 2-chloro-9-oxysulfuron , 2-methyl 9-oxosulfuron , 2,4-dimethyl 9-oxosulfuron , isopropyl-9-oxysulfide , 2,4-dichloro-9-oxysulfuron , 2,4-diethyl 9-oxysulfide 、2,4-Diisopropyl 9-oxysulfide 、Dodecyl 9-oxysulfide 9-Oxosulfuron Series compounds; camphorquinone; halogenated ketone; acyl phosphine oxide; acyl phosphonate, etc.

The photoacid generator may be, for example ^, a compound represented by the following formula (i ⁾ .

In formula (i), L ⁺ is an onium cation, and X ^- is a relative anion selected from the group consisting of PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , SbCl ₆ ^- , BiCl ₅ ^- , SnCl ₆ ^- , ClO ₄ ^- , dithiocarbamate anions, and SCN ^- .

Specific examples of the photoacid generator include "Cyracure-UVI-6992", "Cyracure-UVI-6974" (both manufactured by Dow Chemical Japan Co., Ltd.), "ADEKA OPTOMER SP150", "ADEKA OPTOMER SP152", "ADEKA OPTOMER SP170", "ADEKA OPTOMER SP172" (both manufactured by ADEKA Co., Ltd.), "IRGACURE 250" (manufactured by Ciba Specialty Chemicals Co., Ltd.), "CI-5102", "CI-2855" (both manufactured by Nippon Soda Co., Ltd.), "SANEIDO SI-60L", "SANEIDO SI-80L", "SANEIDO SI-100L", "SANEIDO SI-110L", "SANEIDO SI-180L" (all manufactured by Sanshin Chemical Co., Ltd.), "CPI-100P", "CPI-100A" (all manufactured by San-Apro Co., Ltd.), "WPI-069", "WPI-113", "WPI-116", "WPI-041", "WPI-044", "WPI-054", "WPI-055", "WPAG-281", "WPAG-567", "WPAG-596" (all manufactured by Wako Junyaku Co., Ltd.).

The content of the polymerization initiator in the coating liquid is, for example, 20 wt % or less, preferably 0.01 to 20 wt %, more preferably 0.05 to 10 wt %, and further preferably 0.1 to 5 wt %.

Next, the coating liquid is applied onto the polarizer 1. Thereby, a film (coating film) containing a monomer M and a polymerization initiator can be formed on the polarizer 1. Next, the monomer M is polymerized to form a resin layer 2 from the coating film. The polymerization of the monomer M can be performed using a known method. For example, when a photopolymerization initiator or a photoacid generator is used as a polymerization initiator, the monomer M can be polymerized by irradiating the coating film with active energy rays. Examples of active energy rays include visible light and ultraviolet light. In this specification, the resin layer 2 produced by polymerizing the monomer M contained in the coating film is sometimes referred to as a hardened resin layer. Next, the adhesive layer 5 is bonded to the transparent protective film 4, thereby obtaining the polarizing film 10.

The resin layer 2 can also be prepared by the following method. First, the monomer M is polymerized to obtain a polymer P. The obtained polymer P is added to a solvent to prepare a coating liquid. The solvent can be, for example, an organic solvent that can dissolve or disperse the polymer P. Then, the coating liquid is applied to the polarizer 1 to prepare a coating film. The coating film is dried to obtain the resin layer 2.

[Characteristics of polarizing film] In the polarizing film 10 of this embodiment, at least one of the above requirements (i) to (v) is satisfied, so the leakage of iodine contained in the polarizing element 1 to the outside is fully suppressed in a high temperature and high humidity environment. In other words, the iodine concentration in the polarizing element 1 hardly changes in a high temperature and high humidity environment. The change in the iodine concentration in the polarizing element 1 can be known from the change in the monomer transmittance of the polarizing film 10, for example. For example, when the polarizing film 10 is bonded to the alkali-free glass through the adhesive layer 5, and the polarizing film 10 is placed in a gas environment of 65°C and 90%RH for 24 hours, the change ΔY1 of the single body transmittance of the polarizing film 10 is, for example, less than 5, preferably less than 4, more preferably less than 2, more preferably less than 1.5, and particularly preferably less than 1.

Specifically, the change in single transmittance ΔY1 can be measured using the following method. First, a polarizing film 10 is bonded to an alkali-free glass through an adhesive layer 5 to obtain a laminate, and the single transmittance Ts1 of the obtained laminate is measured. Next, the laminate is placed in a gas environment of 65°C and 90%RH for 24 hours. The single transmittance Ts2 is measured for the laminate after being placed in the gas environment. The value obtained by subtracting the single transmittance Ts1 from the single transmittance Ts2 is regarded as the change in single transmittance ΔY1. In addition, the single transmittance of the laminate is the Y value obtained after the visual sensitivity is corrected using the 2-degree field of vision (C light source) of JIS Z8701-1999. The single body transmittance can be measured using a commercially available spectrophotometer such as DOT-3 manufactured by Murakami Color Technology Laboratory. The measurement wavelength of the single body transmittance is 380~700nm (every 10nm). Alkali-free glass is glass that does not substantially contain alkali components (alkali metal oxides). Specifically, the weight ratio of the alkali components in the glass is, for example, 1000ppm or less, and more preferably 500ppm or less. Alkali-free glass is, for example, in the form of a plate with a thickness of 0.5mm or more.

The single body transmittance Ts1 is not particularly limited, and is, for example, 42% to 46%, preferably 43% or more, and more preferably 44% or more. The single body transmittance Ts2 is not particularly limited, and is, for example, 42% to 48%, preferably 47% or less, and more preferably 46% or less.

(Variation of polarizing film) In polarizing film 10, resin layer 2 may be located closer to the image display panel side described later than polarizing element 1. As shown in FIG2, in polarizing film 11 of this variation, resin layer 2 is located closer to the image display panel side than polarizing element 1. Except for the position of resin layer 2, the structure of polarizing film 11 is the same as that of polarizing film 10. Therefore, the common elements of polarizing film 10 and polarizing film 11 of the variation are attached with the same reference symbols, and the descriptions thereof are sometimes omitted. That is, the following descriptions related to each embodiment can be applied to each other as long as they are not technically contradictory. The following embodiments can also be combined with each other as long as they are not technically contradictory.

The resin layer 2 is, for example, located between the polarizer 1 and the adhesive layer 3, and directly contacts the polarizer 1 and the adhesive layer 3 respectively. However, other layers such as an adhesive layer and an easy-adhesion layer may be disposed between the resin layer 2 and the polarizer 1. For example, the resin layer 2 may be bonded to the polarizer 1 through the adhesive layer or the easy-adhesion layer. The adhesive layer and the easy-adhesion layer used to bond the resin layer 2 to the polarizer 1 may be those described above with respect to the polarizing film 10. When the resin layer 2 is located closer to the image display panel than the polarizer 1, it can prevent the iodine contained in the polarizer 1 from migrating to the adhesive layer 5 and penetrating through the adhesive layer 5 to the outside of the polarizing film 11 in a high temperature and high humidity environment.

(Another variation of polarizing film) The polarizing film 10 may also be provided with other components in addition to the above components. As shown in FIG3 , the polarizing film 12 of this variation further has a transparent protective film (second transparent protective film) 6. Except for the second transparent protective film 6, the structure of the polarizing film 12 is the same as that of the polarizing film 10. Therefore, the common elements of the polarizing film 10 and the polarizing film 12 of the variation are attached with the same reference symbols, and the description thereof is sometimes omitted.

The second transparent protective film 6 is located closer to the visual side than the polarizer 1. The polarizer 1 is located, for example, between the first transparent protective film 4 and the second transparent protective film 6. The second transparent protective film 6 is located, for example, closer to the visual side than the resin layer 2 and is located at the outermost side of the polarizing film 12. However, when the polarizing film 12 has the above-mentioned transparent substrate, the second transparent protective film 6 may also be located between the resin layer 2 and the transparent substrate. The second transparent protective film 6 is, for example, in direct contact with the resin layer 2. However, the second transparent protective film 6 may also be bonded to the resin layer 2 via other layers such as an adhesive layer and a hard coating layer. The adhesive layer used to bond the second transparent protective film 6 to the resin layer 2 may be, for example, the adhesive layer 3 described above.

The second transparent protective film 6 may be the same as that described above for the first transparent protective film 4. The first transparent protective film 4 and the second transparent protective film 6 may be the same as or different from each other.

The polarizing film 12 having the second transparent protective film 6 has a tendency to suppress the transmission of iodine contained in the polarizing element 1 to the outside in a high temperature and high humidity environment. For example, when the polarizing film 12 is attached to the alkali-free glass through the adhesive layer 5, and the polarizing film 12 is placed in a gas environment of 65°C and 90%RH for 120 hours, the change ΔY2 of the single body transmittance of the polarizing film 12 is, for example, 3 or less, preferably 2 or less, more preferably 1.5 or less, more preferably 1 or less, and particularly preferably 0.8 or less.

Specifically, the change in single transmittance ΔY2 can be measured by the following method. First, a laminate is obtained by attaching the polarizing film 12 to the alkali-free glass through the adhesive layer 5, and the single transmittance Ts3 of the obtained laminate is measured. Then, the laminate is placed in a gas environment of 65°C and 90%RH for 120 hours. The single transmittance Ts4 is measured for the laminate after being placed in the gas environment. The value obtained by subtracting the single transmittance Ts3 from the single transmittance Ts4 is regarded as the change in single transmittance ΔY2.

The single body transmittance Ts3 is not particularly limited, and is, for example, 42% to 46%, preferably 43% or more, and more preferably 44% or more. The single body transmittance Ts4 is not particularly limited, and is, for example, 42% to 48%, preferably 47% or less, and more preferably 46% or less.

(Another variation of polarizing film) Polarizing film 10 may also have two or more resin layers 2. As shown in FIG4 , polarizing film 13 of this variation has two resin layers 2a and 2b. Except for resin layer 2b, the structure of polarizing film 13 is the same as that of polarizing film 10. Therefore, the common elements of polarizing film 10 and polarizing film 13 of the variation are given the same reference symbols, and the description thereof is sometimes omitted.

In the polarizing film 13, the polarizer 1 is located between two resin layers 2a and 2b. Specifically, the resin layer 2b is located closer to the image display panel than the polarizer 1 (e.g., between the polarizer 1 and the adhesive layer 3). When the polarizer 1 is disposed between the two resin layers 2a and 2b, the polarizing film 13 tends to suppress the leakage of iodine contained in the polarizer 1 to the outside.

The resin layer 2b may also directly contact the polarizer 1. However, other layers such as an adhesive layer and an easy-adhesion layer may be disposed between the resin layer 2b and the polarizer 1. For example, the resin layer 2b may also be bonded to the polarizer 1 through the adhesive layer or the easy-adhesion layer. The adhesive layer and the easy-adhesion layer used to bond the resin layer 2b to the polarizer 1 may be those described above for the polarizing film 10.

(Implementation of image display device) As shown in FIG. 5, the image display device 100 of this implementation has a polarizing film 10 and an image display panel 20. In the image display device 100, the polarizing film 11, 12 or 13 may be used to replace the polarizing film 10. In the image display device 100, the polarizing film 10 is attached to the image display panel 20 through an adhesive layer 5, for example. The image display panel 20 may be an organic EL display panel, a liquid crystal display panel, etc., and is preferably an organic EL display panel.

The image display device 100 is further equipped with an illumination system (not shown). For example, the polarizing film 10, the image display panel 20 and the illumination system are arranged in sequence, and the polarizing film 10 is located at the most visible side. The illumination system has a backlight or a reflector, for example, to irradiate light to the image display panel 20.

Embodiments The present invention is described in more detail below by way of embodiments. The present invention is not limited to the embodiments shown below.

<Thin polarizer> First, a laminate with a 9µm thick PVA layer on an amorphous polyethylene terephthalate (PET) substrate was prepared. The laminate was subjected to air-assisted stretching at a stretching temperature of 130°C to produce a stretched laminate. Next, the stretched laminate was dyed with iodine to obtain a colored laminate. Next, the colored laminate was stretched in a boric acid aqueous solution at a stretching temperature of 65°C to obtain a laminate in which the amorphous PET substrate and the PVA layer were stretched integrally. In the laminate, the total stretching ratio was 5.94 times, and the thickness of the PVA layer was 5µm. The PVA molecules of the PVA layer formed on the amorphous PET substrate by the above two-stage stretching are highly oriented. In addition, the iodine adsorbed by dyeing is highly oriented in one direction in the form of a polyiodine ion complex. The PVA layer contained in the laminate functions as a thin polarizer.

<Transparent protective film> First, a resin composed of imidized methyl methacrylate-styrene copolymer (imidized MS resin) was prepared by the method described in Preparation Example 1 of Japanese Patent Publication No. 2010-284840. Then, 100 parts by weight of the imidized MS resin and 0.62 parts by weight of a tri-iron ultraviolet absorber (manufactured by ADEKA, trade name: T-712) were mixed at 220°C using a double-screw kneader to prepare resin pellets. The obtained resin pellets were dried in an environment of 100.5 kPa and 100°C for 12 hours. Next, a single-axis extruder was used to extrude resin pellets from a T-die at a die temperature of 270°C to produce a film with a thickness of 160µm. Next, the film was stretched in a 150°C gas environment along its conveying direction to adjust the thickness to 80µm. Next, an adhesive containing a water-based urethane resin was applied to the film, and the film was stretched in a 150°C gas environment in a direction orthogonal to the conveying direction to obtain a transparent protective film with a thickness of 40µm. The moisture permeability of the transparent protective film was 58g/ ^m2 /24h.

<Active energy ray-curable adhesive composition> 12 parts by weight of hydroxyethyl acrylamide (manufactured by KJ Chemicals Corporation, trade name: HEAA), 24 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (manufactured by Toagosei Co., Ltd., trade name: ARONIX M-5700), 12 parts by weight of hydroxytrimethylacetate neopentyl glycol acrylate adduct (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE HPP-A), 38 parts by weight of 1,9-nonanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE 1,9ND-A), 10 parts by weight of acrylic acid oligomer (manufactured by Toagosei Co., Ltd., trade name: ARUFON UP-1190), 3 parts by weight of 2-methyl-1-(4-methylphenylthio)-2-oxofolinylpropan-1-one (IGM Resins Co., Ltd., trade name: OMNIRAD 907) and 2 parts by weight of 2,4-diethyl 9-sulfuryl (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYACURE DETX-S) was mixed and stirred for 3 hours to obtain an active energy ray-curable adhesive composition.

<Laminated body comprising a transparent protective film, an adhesive layer and a thin polarizer> An MCD coating machine manufactured by Fuji Machinery Co., Ltd. (groove shape: honeycomb, number of gravure roller lines: 1000 lines/inch, rotation speed 140%/relative production line speed) is used to apply the active energy ray-curing adhesive composition to the bonding surface of the transparent protective film. The thickness of the resulting coating is 0.7µm. Next, a roller machine is used to bond the transparent protective film to the laminate containing the PVA layer. At this time, the coating is brought into contact with the PVA layer. The production line speed of the roller machine is 25m/minute. Next, the resulting laminate is irradiated with active energy rays from the transparent protective film side. The active energy ray is the visible light emitted from a visible light irradiation device (Light HAMMER10 manufactured by Fusion UV Systems). The light source of the visible light irradiation device is a metal halogen lamp filled with gallium. In the visible light irradiation device, a V bulb is used as the bulb. The peak illuminance of the light emitted from the visible light irradiation device is 1600mW/ ^cm2 . In the wavelength range of 380nm~440nm, the cumulative irradiation amount of the light emitted from the visible light irradiation device is 1000mJ/ ^cm2 . The illuminance of the light emitted from the visible light irradiation device is measured using the Sola-Check system manufactured by Solatell. By irradiating the laminate with active energy rays, the active energy ray-curing adhesive composition in the coating is cured. Then, the laminate was dried with hot air at 70° C. for 3 minutes, thereby obtaining a laminate a including a transparent protective film, an adhesive layer and a thin polarizer.

[Example 1] (Polarizing film A) First, 50 parts by weight of dicyclopentyl acrylate (manufactured by Hitachi Chemical Co., Ltd., trade name: FANCRYL FA-513AS), 50 parts by weight of dihydroxymethyl-tricyclodecane diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE DCP-A), 2 parts by weight of 2-methyl-1-(4-methylphenylthio)-2-oxofolinylpropan-1-one (manufactured by IGM Resins Co., Ltd., trade name: OMNIRAD 907) and 2 parts by weight of 2,4-diethyl-9-oxysulfide were mixed. (Nippon Kayaku Co., Ltd., trade name: KAYACURE DETX-S) was used to prepare a coating liquid.

Next, the amorphous PET substrate adjacent to the PVA layer is removed from the laminate a. The coating liquid is applied to the exposed PVA layer using Select-Roller #0 (manufactured by OSG SYSTEM PRODUCTS Co., Ltd.). The thickness of the resulting coating is 1µm. Next, the coating is irradiated with visible light under a nitrogen flow using the visible light irradiation device to polymerize the monomer. The coating is hardened by the polymerization of the monomer to form a resin layer.

Next, the surface of the transparent protective film is subjected to a corona treatment. A 20µm thick adhesive layer is bonded to the surface. The adhesive layer is made of an acrylic adhesive. Thus, a polarizing film A having a resin layer, a polarizer, an adhesive layer, a transparent protective film, and an adhesive layer is obtained in sequence.

(Polarizing film B) First, the coating liquid is prepared using the same method as for polarizing film A. The coating liquid is applied to the bonding surface of a 20µm thick triacetate cellulose (TAC) film using an MCD coating machine manufactured by Fuji Machinery Co., Ltd. (groove shape: honeycomb, gravure roll line count: 700 lines/inch, rotation speed 140%/relative line speed). The resulting coating film has a thickness of 1µm. Next, the amorphous PET substrate adjacent to the PVA layer is removed from the above-mentioned laminate a. The TAC film is bonded to the laminate a using a roller. At this time, the coating film is brought into contact with the PVA layer. The line speed of the roller machine is 25m/minute. Next, the obtained laminate is irradiated with active energy rays from the TAC film side. The active energy rays are visible light emitted from the above-mentioned visible light irradiation device. By irradiating the laminate with active energy rays, the monomers in the coating film are polymerized. The coating film is hardened by the polymerization of the monomers. Next, the laminate is hot-air dried at 70°C for 3 minutes. In this way, a resin layer is formed.

Next, the surface of the transparent protective film containing imidized MS resin is subjected to a corona treatment. A 20µm thick adhesive layer is bonded to the surface. The adhesive layer is composed of an acrylic adhesive. Thus, a polarizing film B is obtained, which sequentially comprises a TAC film (second transparent protective film), a resin layer, a polarizer, an adhesive layer, a transparent protective film containing imidized MS resin (first transparent protective film), and an adhesive layer.

[Example 2-10 and Comparative Example 1] Example 2-10 and Comparative Example 1 polarizing films A and B were prepared in the same manner as Example 1 except that the monomers contained in the coating liquid used to form the resin layer were changed to the monomers listed in Table 1.

[Comparative Example 2] Polarizing films A and B of Comparative Example 2 were prepared in the same manner as in Example 1 except that the coating liquid used to form the resin layer was the photocurable resin composition B. The photocurable resin composition B is composed of 12 parts by weight of hydroxyethyl acrylamide (manufactured by KJ Chemicals Corporation, trade name: HEAA), 20 parts by weight of 2-hydroxy-3-phenoxypropyl acrylate (manufactured by Toagosei Co., Ltd., trade name: ARONIX M-5700), 12 parts by weight of hydroxytrimethylacetate neopentyl glycol acrylate adduct (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE HPP-A), 34 parts by weight of 1,9-nonanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE 1,9ND-A), 10 parts by weight of acrylic acid oligomer (manufactured by Toagosei Co., Ltd., trade name: ARUFON UP-1190), 5 parts by weight of diethyl acrylamide (manufactured by KJ Chemicals Co., Ltd., trade name: Corporation, trade name: DEAA), 3 parts by weight of 2-methyl-1-(4-methylphenylthio)-2-oxofolinylpropan-1-one (IGM Resins, trade name: OMNIRAD 907) and 3 parts by weight of 2,4-diethyl-9-oxothiophene (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYACURE DETX-S)

[Comparative Example 3] Polarizing films A and B of Comparative Example 3 were prepared in the same manner as in Example 1 except that the coating liquid used to form the resin layer was the photocurable resin composition A. The photocurable resin composition A is composed of 43 parts by weight of acrylamide (manufactured by KJ Chemicals Corporation, trade name: ACMO), 29 parts by weight of 1,9-nonanediol diacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE 1,9ND-A), 14 parts by weight of phenoxydiethylene glycol acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: LIGHT ACRYLATE P2H-A), 10 parts by weight of acrylic acid oligomer (manufactured by Toagosei Co., Ltd., trade name: ARUFON UP-1190), 2 parts by weight of 2-methyl-1-(4-methylphenylthio)-2-morpholinylpropan-1-one (manufactured by IGM Resins Co., Ltd., trade name: OMNIRAD 907), and 2 parts by weight of 2,4-diethyl-9-oxythiophene. (manufactured by Nippon Kayaku Co., Ltd., trade name: KAYACURE DETX-S)

<Change in single body transmittance ΔY1> For the polarizing film A of the embodiment and the comparative example, the change in single body transmittance ΔY1 was measured by the following method. First, the polarizing film A was attached to the alkali-free glass through the adhesive layer. The single body transmittance Ts1 was measured for the obtained laminate. The single body transmittance Ts1 was measured using a spectroscopic transmittance meter with an integrating sphere (Dot-3c manufactured by Murakami Color Technology Laboratory). Then, the laminate was placed in a gas environment of 65°C and 90%RH for 24 hours. For the laminate placed in the gas environment, the single body transmittance Ts2 was measured using the above-mentioned spectroscopic transmittance meter. The change ΔY1 in the single cell transmittance is calculated by subtracting the single cell transmittance Ts1 from the single cell transmittance Ts2.

<Change in single body transmittance ΔY2> For the polarizing film B of the embodiment and the comparative example, the change in single body transmittance ΔY2 was measured by the following method. First, the polarizing film B was attached to the alkali-free glass through the adhesive layer. The single body transmittance Ts3 was measured for the obtained laminate. The single body transmittance Ts3 was measured using a spectroscopic transmittance meter with an integrating sphere (Dot-3c manufactured by Murakami Color Technology Laboratory). Then, the laminate was placed in a gas environment of 65°C and 90%RH for 120 hours. For the laminate placed in the gas environment, the single body transmittance Ts4 was measured using the above-mentioned spectroscopic transmittance meter. The change ΔY2 in the single cell transmittance is calculated by subtracting the single cell transmittance Ts3 from the single cell transmittance Ts4.

<Tensile storage modulus E1 and E2> For the resin layer used in the embodiment and the comparative example, the tensile storage modulus E1 and E2 were measured using the above method. The dynamic viscoelasticity measuring device used was the dynamic viscoelasticity measuring device RSA-G2 manufactured by TA Instruments.

<Linear expansion coefficient α1 and α2> For the resin layer used in the embodiment and the comparative example, the linear expansion coefficient α1 and α2 were measured by the above method. The thermomechanical analyzer used was a thermomechanical analyzer TMA 4000 SE manufactured by Netch.Co.Ltd.

<Dipole moment D> For the monomers contained in the coating liquid used to form the resin layer in the embodiment and the comparative example, the dipole moment D was calculated using the above method. The dipole moment D was calculated using Materials Studio (manufactured by BIOVIA, ver.8.0.0.843) and WebMO (ver.19.0.009e).

[Table 1]

In addition, the abbreviations in Table 1 are as follows. FA513AS: dicyclopentyl acrylate, manufactured by Hitachi Chemical Co., Ltd. TBCHA: 4-tert-butylcyclohexyl acrylate, manufactured by KJ Chemicals Corporation L-A: lauryl acrylate, manufactured by Kyoeisha Chemical Co., Ltd. ACMO: acrylamide, manufactured by KJ Chemicals Corporation DCP-A: dihydroxymethyl-tricyclodecane diacrylate, manufactured by Kyoeisha Chemical Co., Ltd. TMP-A: trihydroxymethylene propane triacrylate, manufactured by Kyoeisha Chemical Co., Ltd. PE-4A: neopentyl triacrylate, manufactured by Kyoeisha Chemical Co., Ltd. DPE-6A: dipentyl triacrylate, manufactured by Kyoeisha Chemical Co., Ltd. 1,9ND-A: 1,9-nonanediol diacrylate, manufactured by Kyoeisha Chemical Co., Ltd.

As can be seen from Table 1, the change ΔY1 of the single transmittance of the polarizing film A of the embodiment in which at least one of the requirements (i) to (v) is satisfied is less than 5, and the leakage of iodine to the outside is fully suppressed in a high-temperature and humid environment. Similarly, the change ΔY2 of the single transmittance of the polarizing film B of the embodiment is less than 3, and the leakage of iodine to the outside is fully suppressed in a high-temperature and humid environment. On the other hand, compared with the embodiment, the change of the single transmittance of the polarizing films A and B of the comparative example in which all the requirements (i) to (v) are not satisfied is larger, and the leakage of iodine to the outside cannot be fully suppressed in a high-temperature and humid environment.

Industrial Applicability The polarizing film of the present invention can be suitably used in mobile displays such as mobile phones, smart phones, and notebook computers; and in-vehicle displays such as panels for car navigation devices, instrument panels, and mirror displays.

1: Polarizer 2,2a,2b: Resin layer 3: Adhesive layer 4: Transparent protective film (first transparent protective film) 5: Adhesive layer 6: Transparent protective film (second transparent protective film) 10,11,12,13: Polarizer film 20: Image display panel 100: Image display device

FIG. 1 is a schematic cross-sectional view of a polarizing film in an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing a modified example of the polarizing film. FIG. 3 is a schematic cross-sectional view showing another modified example of the polarizing film. FIG. 4 is a schematic cross-sectional view showing yet another modified example of the polarizing film. FIG. 5 is a schematic cross-sectional view of an image display device in an embodiment of the present invention.

1: Polarizer

2: Resin layer

3: Then the agent layer

4: Transparent protective film (first transparent protective film)

5: Adhesive layer

10: Polarizing film

Claims (14)

A polarizing film comprises: an iodine-containing polarizer and a polymer-containing resin layer, wherein the polymer comprises: a structural unit derived from a monofunctional (meth)acrylate and a structural unit derived from a multifunctional monomer; and the following requirements (i) to (v) are all satisfied: (i) the tensile storage elastic modulus E1 of the resin layer in water at 65°C is 1×10 ⁸ Pa or more; (ii) the tensile storage elastic modulus E2 of the resin layer in water at 85°C is 1×10 ⁸ Pa or more; (iii) when the resin layer is heated from 25°C to 65°C and the measuring gas environment is humidified from 10%RH to 90%RH, the linear expansion coefficient α1 of the resin layer is 400×10 ^-6 /K or less; (iv) when the resin layer is heated from 25°C to 85°C and the measuring gas environment is humidified from 10%RH to 85%RH, the linear expansion coefficient α2 of the resin layer is less than 300×10 ^-6 /K; (v) the dipole moment D of the monomer used to form the polymer is less than 2 Debye. A polarizing film comprises: an iodine-containing polarizer and a polymer-containing resin layer, wherein the polymer comprises: a structural unit derived from a monofunctional (meth)acrylate; the content of the structural unit derived from a monomer having a polar group in the polymer is less than 20% by weight; and the following requirements (i) to (v) are all satisfied: (i) the tensile storage elastic modulus E1 of the resin layer in water at 65°C is 1×10 ^{8 Pa or more; (ii) the tensile storage elastic modulus E2 of the resin layer in water at 85°C is 1×10 8 Pa} or more. Pa or above; (iii) when the resin layer is heated from 25°C to 65°C and the measuring gas environment is humidified from 10%RH to 90%RH, the linear expansion coefficient α1 of the resin layer is less than 400× ^10-6 /K; (iv) when the resin layer is heated from 25°C to 85°C and the measuring gas environment is humidified from 10%RH to 85%RH, the linear expansion coefficient α2 of the resin layer is less than 300× ^10-6 /K; (v) the dipole moment D of the monomer used to form the above-mentioned polymer is less than 2Debye. The polarizing film of claim 1 or 2, wherein the linear expansion coefficient α1 of the resin layer is less than 180×10 ^-6 /K. As in claim 1 or 2, the polarizing film, wherein the content of structural units derived from (meth)acrylate in the aforementioned polymer is higher than 70% by weight. As in claim 2, the polarizing film, wherein the aforementioned polymer comprises structural units derived from multifunctional monomers. As in claim 1 or 5, the polarizing film, wherein the content of the aforementioned structural unit derived from the aforementioned multifunctional monomer in the aforementioned polymer is 20% by weight or more. As in claim 1, the polarizing film, wherein the content of structural units derived from monomers having polar groups in the aforementioned polymer is less than 20% by weight. As in claim 1 or 2, the polarizing film, wherein the resin layer is located closer to the visual recognition side than the polarizing element. As in the polarizing film of claim 1 or 2, wherein the aforementioned resin layer directly contacts the aforementioned polarizing element. The polarizing film of claim 1 or 2 has two layers of the aforementioned resin layers, and the aforementioned polarizing element is located between the two layers of the aforementioned resin layers. The polarizing film of claim 1 or 2 further comprises an adhesive layer and a first transparent protective film, and the polarizing element, the adhesive layer and the first transparent protective film are arranged in sequence in the stacking direction. The polarizing film of claim 11 is further provided with a second transparent protective film, and the polarizing element is located between the first transparent protective film and the second transparent protective film. The polarizing film of claim 1 or 2 is further provided with an adhesive layer, and the polarizing element is located closer to the visual recognition side than the adhesive layer. An image display device comprising: a polarizing film as described in any one of claims 1 to 13, and an image display panel.

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