CN116848444A

CN116848444A - Polarizing plate and method for producing polarizing plate

Info

Publication number: CN116848444A
Application number: CN202280013759.6A
Authority: CN
Inventors: 石崎优; 井之原拓实
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-03-31
Filing date: 2022-02-10
Publication date: 2023-10-03
Also published as: KR20230129029A; TW202305047A; WO2022209340A1; JP2022155952A

Abstract

Provided is a polarizing plate wherein a decrease in polarization performance is suppressed. The polarizing plate according to the embodiment of the present invention is composed of a resin film containing iodine and having a first main surface and a second main surface facing each other, and the resin film has a chemically modified portion chemically modified at least on the first main surface, and the chemically modified portion has a higher hydrophobicity than other portions not chemically modified.

Description

Polarizing plate and method for producing polarizing plate

Technical Field

The present invention relates to a polarizing plate and a method for manufacturing the polarizing plate.

Background

Image display devices typified by liquid crystal display devices and Electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) are rapidly spreading. A polarizing plate is typically used for an image display panel mounted on an image display device. A polarizing plate with a retardation layer, which is formed by integrating a polarizing plate and a retardation plate, is widely used in practice (for example, patent document 1). However, the polarizing plate included in the polarizing plate is sometimes degraded in polarization performance due to long-term use of the image display device, being placed in a severe environment (e.g., a high-temperature, high-humidity environment). As one of factors of the decrease in polarization performance, for example, discoloration (color separation) is considered.

Prior art literature

Patent literature

Patent document 1: japanese patent No. 3325560

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above problems, and its main object is to provide: a polarizing plate in which a decrease in polarization performance is suppressed.

Solution for solving the problem

According to an embodiment of the present invention, there is provided a polarizing plate. The polarizing plate is composed of a resin film containing iodine and having a first main surface and a second main surface facing each other, wherein the resin film has a chemically modified portion chemically modified at least on the first main surface, and the chemically modified portion has a higher hydrophobicity than other portions not chemically modified.

In one embodiment, the chemical modification portion contains a group containing fluorine.

In one embodiment, the fluorine-containing group includes a trifluoroacetyl group.

In one embodiment, the chemical modification unit is chemically modified with trifluoroacetic anhydride.

In 1 embodiment, the fluorine content of the polarizing plate is 20. Mu.g/g or more.

In 1 embodiment, the contact angle of the chemical modification portion is 90 ° or more.

In 1 embodiment, the thickness of the polarizing plate is 8 μm or less.

According to another embodiment of the present invention, there is provided a method for manufacturing the above-described polarizing plate. The manufacturing method comprises the following steps: at least the first main surface of a resin film containing iodine and having a first main surface and a second main surface which face each other is chemically modified.

In one embodiment, the chemical modification increases the contact angle of the first main surface by 5 ° or more.

According to still another embodiment of the present invention, there is provided a polarizing plate. The polarizing plate has at least one of the above-mentioned polarizing plate and a protective layer or a retardation layer.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, by forming the chemical modification portion, a polarizing plate in which a decrease in polarization performance is suppressed can be obtained.

Drawings

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention.

Fig. 2 is a schematic cross-sectional view showing a schematic configuration of a laminate used for manufacturing a polarizing plate according to 1 embodiment of the present invention.

Fig. 3 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention.

Detailed Description

Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

(definition of terms and symbols)

The terms and symbols in the present specification are defined as follows.

(1) Refractive index (nx, ny, nz)

"nx" is a refractive index in a direction in which the in-plane refractive index becomes maximum (i.e., a slow axis direction), "ny" is a refractive index in a direction orthogonal to the slow axis (i.e., a fast axis direction), and "nz" is a refractive index in a thickness direction.

(2) In-plane phase difference (Re)

"Re (λ)" is the in-plane retardation measured with light of wavelength λnm at 23 ℃. For example, "Re (550)" is the in-plane retardation measured with light having a wavelength of 550nm at 23 ℃. When the thickness of the layer (thin film) is d (nm), re (λ) is represented by the formula: re (λ) = (nx-ny) ×d.

(3) Retardation in thickness direction (Rth)

"Rth (λ)" is a phase difference in the thickness direction measured with light having a wavelength of λnm at 23 ℃. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550nm at 23 ℃. When the thickness of the layer (thin film) is d (nm), rth (λ) is represented by the formula: rth (λ) = (nx-nz) ×d.

(4) Nz coefficient

The Nz coefficient is obtained from nz=rth/Re.

(5) Angle of

When referring to an angle in this specification, the angle includes both clockwise and counterclockwise with respect to a reference direction. Thus, for example, "45" means ± 45 °.

A. Polarizing plate

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention. In fig. 1, the cross section of the polarizing plate is not hatched for easy viewing of the drawing. The polarizing plate 10 is composed of a resin film having a first main surface 10a and a second main surface 10b facing each other. The resin film has a chemically modified portion chemically modified on the first main surface 10a of the polarizing plate 10. The chemical modification portion is not particularly limited as long as it is formed on at least a part of the first main surface 10a, and the formation region is formed, for example, entirely over the first main surface 10 a.

The polarizing plate is composed of a resin film containing iodine. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or an ethylene-vinyl acetate copolymer partially saponified film is used.

The thickness of the polarizing plate 10 is preferably 15 μm or less, may be 12 μm or less, may be 10 μm or less, and may be 8 μm or less. On the other hand, the thickness of the polarizing plate is preferably 1 μm or more.

The polarizing plate 10 preferably exhibits absorption dichroism at any wavelength of 380nm to 780 nm. The single-sheet transmittance (Ts) of the polarizing plate 10 is preferably 41.0% or more, more preferably 42.0% or more, and still more preferably 42.5% or more. On the other hand, the single-sheet transmittance of the polarizing plate 10 is, for example, 44.2% or less. The polarization degree (P) of the polarizing plate 10 is preferably 99.95% or more, more preferably 99.98% or more, and still more preferably 99.99% or more. On the other hand, the polarization degree of the polarizing plate 10 is, for example, 99.996% or less.

The single-sheet transmittance is typically a Y value obtained by performing visibility correction by measurement with an ultraviolet-visible spectrophotometer. The degree of polarization is typically determined as follows: the parallel transmittance Tp and the orthogonal transmittance Tc, which are subjected to visibility correction, are measured by an ultraviolet-visible spectrophotometer, and are obtained from the following equation.

Polarization (%) = { (Tp-Tc)/(tp+tc) } ^1/2 ×100

The hydrophobicity of the chemically modified portion is higher than the hydrophobicity of other portions not chemically modified. By forming such a chemically modified portion, intrusion of water into the polarizing plate (resin film) is suppressed, and a polarizing plate (polarizing plate) in which deterioration of polarization performance is suppressed can be obtained. The other portions include not only the surface of the resin film but also the inside of the resin film.

The chemical modification may be formed on at least one main surface (first main surface 10 a) or may be formed on each of the first main surface 10a and the second main surface 10b. In 1 embodiment, for example, the chemical modification portion is formed only on one main surface from the viewpoint of simplifying the manufacturing process. In another embodiment, the chemical modification portion is formed on any of the principal surfaces from the viewpoint of effectively suppressing the decrease in polarization performance. The end face 10c may be formed with or without a chemical modification.

The chemical modification portion may be formed by chemically modifying the resin film. For example, the resin film can be formed by a modification reaction of the hydroxyl groups of the resin film. Examples of the modification reaction of the hydroxyl group of the resin film include substitution with a modification group such as methyl ether, substituted ethyl ether, methoxy-substituted benzyl ether, silyl ether, ester (formate, acetyl, benzoyl), micellar ester, sulfonate, sulfenate, sulfinate, carbonate, carbamate, cyclic acetal, cyclic ketal, cyclic orthoester, silyl derivative group, cyclic carbonate, cyclic borate, and the like. The conditions for the modification reaction may be appropriately selected depending on the type of the modifying group and the like. For example, the resin film is contacted with a chloride of a modification group to be substituted in the presence of a catalyst for 1 minute to 20 hours at 0 ℃ to 100 ℃ as needed to carry out the modification reaction.

The chemical modifier is formed by reacting a hydroxyl group of the resin film with a modifier having a group (a group for improving hydrophobicity) such as an alkyl group, a halogen group, a haloalkyl group, an aryl group, an acyl group, or a silyl group. Chemical modification is performed, for example, by alkylation, halogenation, acylation (e.g., acetylation, esterification), silylation, etherification, etc. These may be used alone or in combination of two or more.

Examples of the acylating agent used in the acylation include carboxylic acid anhydrides, carboxylic acid halides, benzoyl halides, esters, amides, and ketenes. Specific examples thereof include trifluoroacetic anhydride, acetic anhydride, chloroacetyl anhydride, dichloroacetic anhydride, trichloroacetic anhydride, and benzoyl chloride.

Examples of the silylating agent used for the silylation include chlorosilanes such as trimethylchlorosilane, triethylchlorosilane, triisopropylchlorosilane, triphenylchlorosilane, t-butyldimethylchlorosilane, dichlorodimethylsilane, dichlorodiethylsilane, and dichlorodiisopropylsilane. As the silylating agent, an amide-based silylating agent such as N, O-bis (trimethylsilyl) acetamide or N, O-bis (trimethylsilyl) trifluoroacetamide, an amine-based silylating agent such as N-trimethylsilylimidazole, or the like may be used.

Examples of the etherifying agent used in the etherification include benzyl bromide, 4-methoxybenzyl chloride, chloromethyl methyl ether and trityl chloride.

Typically, the chemical modification is as described aboveThe decorative part has a group containing fluorine. Examples of the group containing fluorine include fluoroalkyl groups having one or more fluorine groups and fluoroacyl groups (for example, trifluoroacetyl groups). Specifically, the chemical modification unit is chemically modified with trifluoroacetic anhydride. The fluorine content of the polarizing plate is preferably 20. Mu.g/g or more, more preferably 30. Mu.g/g or more, still more preferably 40. Mu.g/g or more. The fluorine content of the polarizing plate may be, for example, 100. Mu.g/g or more, 200. Mu.g/g or more, or 300. Mu.g/g or more. On the other hand, the fluorine content of the polarizing plate is, for example, 800. Mu.g/g or less. In addition, the fluorine content of the polarizing plate is preferably 0.01. Mu.g/cm ² Above, more preferably 0.02. Mu.g/cm ² The above, more preferably 0.03. Mu.g/cm ² The above. The fluorine content of the polarizing plate may be, for example, 0.1. Mu.g/cm ² The above may be 0.2. Mu.g/cm ² The above may be 0.3. Mu.g/cm ² The above. On the other hand, the fluorine content of the polarizing plate is, for example, 0.5. Mu.g/cm ² The following is given. The fluorine content can be obtained by Ion Chromatography (IC).

For the chemically modified portion (main surface having the chemically modified portion), 1787cm in FT-IR spectrum based on ATR measurement ^-1 The absorbance at 2940cm ^-1 The ratio of the absorbance is preferably more than 0.2, more preferably 0.25 or more, and still more preferably 0.3 or more. On the other hand, 1787cm ^-1 The absorbance at 2940cm ^-1 The ratio of the absorbance is lower than 1, for example. In FT-IR spectrum, 2940cm ^-1 The nearby absorption peak is derived from C-H stretching vibration of the resin film, 1787cm ^-1 The nearby absorption peak is derived from the c=o stretching vibration of the trifluoroacetyl group.

The contact angle of the chemical modification portion (main surface having the chemical modification portion) is preferably 90 ° or more, more preferably 92 ° or more, and still more preferably 94 ° or more. On the other hand, the contact angle of the chemically modified portion may be, for example, 115 ° or less, and 110 ° or less. The contact angle of the other part not chemically modified is, for example, 86 ° or less.

B. Method of manufacture

The polarizing plate can be obtained by chemically modifying at least one main surface (first main surface) of a resin film containing iodine and having a first main surface and a second main surface facing each other. In the 1 embodiment, the first main surface of the resin film is chemically modified in a state where the protective material is disposed on the second main surface of the resin film. Specifically, a laminate of a resin film and a protective material is prepared, and a first main surface of the resin film of the laminate is chemically modified.

B-1 laminate

Fig. 2 is a schematic cross-sectional view showing a schematic configuration of a laminate used for manufacturing a polarizing plate according to 1 embodiment of the present invention. The laminate 100 includes a resin film 10 and a protective material 1. The resin film 10 has a first main surface 10a and a second main surface 10b facing each other, and the protective material 1 is disposed on the second main surface 10b of the resin film 10.

The resin film contained in the laminate may be produced by any suitable method. In one embodiment, the method comprises the following steps: hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and ethylene/vinyl acetate copolymer partially saponified films are subjected to dyeing treatment and stretching treatment with a dichroic substance such as iodine or a dichroic dye. The method may further comprise: insoluble treatment, swelling treatment, crosslinking treatment, and the like. Such a production method is well known and commonly used in the art, and therefore, a detailed description thereof is omitted.

In another embodiment, the resin film contained in the laminate is produced using a laminate of a resin base material and a resin layer (typically, a PVA-based resin layer). For example, it can be manufactured as follows: coating a PVA-based resin solution on a resin substrate and drying the same to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; the laminate can be produced by stretching and dyeing. In the present embodiment, it is preferable to form a PVA-based resin layer containing a halogen compound and a PVA-based resin on one side of a resin substrate. Stretching typically comprises the steps of: the laminate was immersed in an aqueous boric acid solution and stretched. Further, the stretching may further include the following steps as needed: before stretching in an aqueous boric acid solution, the laminate is subjected to air stretching at a high temperature (for example, 95 ℃ or higher). In the present embodiment, it is preferable that the laminate is heated while being conveyed in the longitudinal direction, and is subjected to a drying shrinkage treatment in which the laminate is shrunk by 2% or more in the width direction. Typically, the manufacturing method of the present embodiment includes the steps of: the laminate was subjected to an air-assisted stretching treatment, a dyeing treatment, an in-water stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is coated on the thermoplastic resin substrate, crystallinity of PVA can be improved, and high optical characteristics can be achieved. In addition, since the orientation of PVA is improved in advance, problems such as reduction in orientation and dissolution of PVA can be prevented when immersed in water in the subsequent dyeing step and stretching step, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, disturbance of the orientation of PVA molecules and decrease of the orientation can be suppressed, and high optical characteristics can be achieved, as compared with the case where the PVA-based resin layer does not contain a halogen compound. Further, the laminate is shrunk in the width direction by the drying shrinkage treatment, whereby high optical characteristics can be achieved. The resin substrate may be used as a protective layer of the obtained polarizing plate, or may be peeled from a laminate of the resin substrate and the PVA-based resin layer. Details of such a method for producing a resin film (polarizing plate) are described in, for example, japanese patent application laid-open No. 2012-73580 and japanese patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

As the protective material 1 disposed on the second main surface 10b of the resin film 10, any appropriate member (e.g., film or layer) is used. For example, the resin base material can be used as the protective material. As the protective material, at least one of a protective layer and a retardation layer of a polarizing plate described later may be used. In this case, the protective material may be laminated on the resin film via an adhesive or a binder.

B-2 chemical modification

The chemical modification may be performed by any appropriate method, for example, depending on the nature of the modifier to be used. For example, it may be carried out by a gas phase reaction. Specifically, the resin film (laminate) can be produced by placing it in an atmosphere containing a gasified modifier. In the case of gas phase reaction, the reaction time is, for example, 30 seconds to 60 minutes. As another example, the reaction may be performed by a liquid phase reaction. Specifically, the main surface (first main surface 10 a) of the resin film may be coated with a reaction solution containing a modifier, or the resin film (laminate) may be immersed in the reaction solution containing a modifier. In the case of using a liquid phase reaction by impregnation, the impregnation time is, for example, 10 seconds to 5 minutes.

For example, the contact angle of the treated surface (first main surface) is preferably raised by 5 ° or more, more preferably 7 ° or more, and still more preferably 10 ° or more by chemical modification. By performing such treatment, intrusion of moisture into the obtained polarizing plate can be effectively suppressed, and a polarizing plate (polarizing plate) in which deterioration of polarization performance is suppressed can be obtained.

C. Polarizing plate

The polarizing plate according to the embodiment of the present invention has the above-described polarizing plate. Typically, the method comprises: the polarizing plate, and at least one of a protective layer and a retardation layer. The polarizing plate according to the embodiment of the present invention is typically used for an image display panel. Specifically, the display device is disposed on the visible side of the image display panel main body.

Fig. 3 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention. The polarizing plate 200 has: the polarizing plate 10, the first protective layer 21 disposed on the first principal surface 10a side (the visible side) of the polarizing plate 10, the adhesive layer 40 and the release film 50 disposed on the second principal surface 10b side of the polarizing plate 10. The chemical modification is formed on at least the first main surface 10a of the polarizing plate 10. In the image display panel, the first main surface 10a having the chemical modification portion is arranged on the visible side, and thus, the deterioration of polarization performance due to the influence from the external environment can be effectively suppressed. Unlike the illustrated example, the adhesive layer 40 and the release film 50 may be disposed on the first main surface 10a side having the chemical modification portion, and the first protective layer 21 may be disposed on the second main surface 10b side (visible side).

The release film 50 is bonded to the adhesive layer 40 so as to be peelable, and protects the adhesive layer 40. By using the release film 50, for example, roll formation of the polarizing plate 200 becomes possible. In practice, the polarizing plate 200 may be adhered to the image display panel body by the adhesive layer 40. The release film 50 can function as a separator to which the polarizing plate 200 is temporarily bonded until use.

Although not shown, a second protective layer may be disposed between the polarizer 10 and the adhesive layer 40. In addition, the polarizing plate may have a phase difference layer. Specifically, the polarizing plate may be a polarizing plate with a retardation layer. The retardation layer is disposed between the polarizer 10 and the adhesive layer 40, for example.

The members constituting the polarizing plate may be laminated via any appropriate adhesive layer (some of which are not shown). Specific examples of the adhesive layer include an adhesive layer and an adhesive layer. The polarizing plate may be long or monolithic. Here, "long-sized" means: the elongated shape having a length sufficiently long with respect to the width is, for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. The retardation layer polarizing plate having a long shape can be wound in a roll shape.

C-1. Protective layer

The protective layer is formed of any suitable film that can be used as a protective layer for a polarizing plate. Specific examples of the material to be the main component of the film include cellulose resins such as triacetyl cellulose (TAC), transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, cycloolefin resins such as polynorbornene resins, polyolefin resins, (meth) acrylic resins, and acetate resins.

The polarizing plate is typically disposed on the visible side of the image display device, and the first protective layer 21 is disposed on the visible side. Therefore, the first protective layer 21 may be subjected to surface treatments such as Hard Coat (HC) treatment, antireflection treatment, anti-sticking treatment, antiglare treatment, and the like as necessary.

The thickness of the protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, still more preferably 15 μm to 35 μm. In the case of performing the surface treatment, the thickness of the first protective layer 21 is a thickness including the thickness of the surface treatment layer.

In one embodiment, the second protective layer is preferably optically isotropic. In the present specification, "optically isotropic" means that: the in-plane retardation Re (550) is 0nm to 10nm, and the retardation Rth (550) in the thickness direction is-10 nm to +10 nm. The thickness of the second protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, still more preferably 10 μm to 30 μm.

C-2 adhesive layer

The thickness of the adhesive layer 40 is preferably 10 μm to 20 μm. As the adhesive constituting the adhesive layer 40, any suitable configuration may be employed. Specific examples thereof include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the kind, amount, combination and compounding ratio of the monomers forming the base resin of the adhesive, and the compounding amount of the crosslinking agent, reaction temperature, reaction time, and the like, it is possible to prepare an adhesive having desired characteristics in accordance with the purpose. The base resin of the binder may be used alone or in combination of two or more. The base resin is preferably an acrylic resin (specifically, the adhesive layer is preferably composed of an acrylic adhesive).

C-3 release film

The release film may be formed of any suitable plastic film. Specific examples of the plastic film include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. The release film can function as a separator. Specifically, as the release film, a plastic film coated with a release agent on the surface is preferably used. Specific examples of the release agent include silicone release agents, fluorine release agents, and long-chain alkyl acrylate release agents.

The thickness of the release film is preferably 20 μm to 80 μm, more preferably 35 μm to 55 μm.

C-4. Phase difference layer

The retardation layer may have a laminated structure of two or more layers, or may be formed as a single layer. The thickness of the retardation layer also depends on its constitution (being a single layer or having a laminated structure), but is, for example, 1 μm or more and 50 μm or less. In 1 embodiment, the thickness of the retardation layer is preferably 10 μm or less, more preferably 8 μm or less, and still more preferably 6 μm or less. When the retardation layers have a laminated structure, the "thickness of the retardation layer" refers to the total thickness of the retardation layers. Specifically, the "thickness of the retardation layer" does not include the thickness of the adhesive layer.

As the retardation layer, an alignment cured layer of a liquid crystal compound (liquid crystal alignment cured layer) is preferably used. By using a liquid crystal compound, for example, the difference between nx and ny of the obtained retardation layer can be increased remarkably compared with a non-liquid crystal material, and therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation can be reduced remarkably. Therefore, the polarizing plate with the retardation layer can be significantly thinned. In the present specification, "orientation-cured layer" means: and a layer in which the liquid crystal compound is aligned in a predetermined direction in the layer and the alignment state is fixed. The term "alignment cured layer" is a concept including an alignment cured layer obtained by curing a liquid crystal monomer as described later. In the retardation layer, typically, rod-like liquid crystal compounds are aligned (parallel alignment) in a state of being aligned along the slow axis direction of the retardation layer.

The above-mentioned liquid crystal alignment cured layer may be formed as follows: the alignment treatment is performed on the surface of a predetermined substrate, and a coating liquid containing a liquid crystal compound is applied to the surface, and the liquid crystal compound is aligned in a direction corresponding to the alignment treatment, and the alignment state is fixed, whereby the alignment layer can be formed. As the orientation treatment, any suitable orientation treatment may be employed. Specifically, a mechanical alignment treatment, a physical alignment treatment, and a chemical alignment treatment can be mentioned. Specific examples of the mechanical orientation treatment include a brushing treatment and a stretching treatment. Specific examples of the physical alignment treatment include a magnetic field alignment treatment and an electric field alignment treatment. Specific examples of the chemical alignment treatment include an oblique vapor deposition method and a photo alignment treatment. The process conditions of the various orientation processes may be any suitable conditions depending on the purpose.

The alignment of the liquid crystal compound is performed by performing a treatment at a temperature showing a liquid crystal phase according to the kind of the liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound is brought into a liquid crystal state, and the liquid crystal compound is aligned according to the alignment treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned as described above. In the case where the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound to polymerization treatment or crosslinking treatment.

Specific examples of the liquid crystal compound and the method for forming the alignment cured layer are described in Japanese patent application laid-open No. 2006-163343. The disclosure of this publication is incorporated by reference into this specification.

In 1 embodiment when the retardation layer is a single layer, the retardation layer can function as a λ/4 plate. Specifically, re (550) of the retardation layer is preferably 100nm to 180nm, more preferably 110nm to 170nm, and still more preferably 110nm to 160nm. The thickness of the retardation layer can be adjusted in such a manner as to obtain a desired in-plane retardation of the lambda/4 plate. In the case where the retardation layer is the above-mentioned liquid crystal alignment cured layer, the thickness thereof is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle between the slow axis of the retardation layer and the absorption axis of the polarizing plate is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably 44 ° to 46 °. The phase difference layer preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light.

In another embodiment, when the retardation layer is a single layer, the retardation layer can function as a λ/2 plate. Specifically, re (550) of the retardation layer is preferably 200nm to 300nm, more preferably 230nm to 290nm, and still more preferably 230nm to 280nm. The thickness of the retardation layer is adjusted so that a desired in-plane retardation of the lambda/2 plate can be obtained. In the case where the retardation layer is the above-mentioned liquid crystal alignment cured layer, the thickness thereof is, for example, 2.0 μm to 4.0 μm. In this embodiment, the angle between the slow axis of the retardation layer and the absorption axis of the polarizing plate is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and still more preferably 12 ° to 16 °.

In 1 embodiment of the case where the retardation layer has a laminated structure, the retardation layer has a two-layer laminated structure in which a first retardation layer (H layer) and a second retardation layer (Q layer) are arranged in this order from the polarizer side. The H layer typically functions as a lambda/2 plate and the Q layer typically functions as a lambda/4 plate. Specifically, re (550) of the H layer is preferably 200nm to 300nm, more preferably 220nm to 290nm, still more preferably 230nm to 280nm; re (550) of the Q layer is preferably 100nm to 180nm, more preferably 110nm to 170nm, still more preferably 110nm to 150nm. The thickness of the H layer is adjusted in such a way that the desired in-plane retardation of the lambda/2 plate is obtained. When the H layer is the above-mentioned liquid crystal alignment cured layer, the thickness thereof is, for example, 2.0 μm to 4.0. Mu.m. The thickness of the Q layer is adjusted in such a way that the desired in-plane retardation of the lambda/4 plate is obtained. When the Q layer is the above-mentioned cured layer for alignment of liquid crystal, the thickness thereof is, for example, 1.0 μm to 2.5. Mu.m. In this embodiment, the angle between the slow axis of the H layer and the absorption axis of the polarizing plate is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and still more preferably 12 ° to 16 °; the angle between the slow axis of the Q layer and the absorption axis of the polarizer is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and still more preferably 72 ° to 76 °. The order of arrangement of the H layer and the Q layer may be reversed, and the angle between the slow axis of the H layer and the absorption axis of the polarizer and the angle between the slow axis of the Q layer and the absorption axis of the polarizer may be reversed. Each layer (for example, H layer and Q layer) may have an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light, a positive wavelength dispersion characteristic in which the phase difference value decreases according to the wavelength of the measurement light, or a flat wavelength dispersion characteristic in which the phase difference value does not substantially change according to the wavelength of the measurement light.

The retardation layer (at least one layer when having a laminated structure) typically shows a relationship of nx > ny=nz in refractive index characteristics. Note that "ny=nz" includes not only the case where ny is completely equal to nz but also the case where ny is substantially equal to nz. Therefore, ny > nz or ny < nz may be present within a range that does not impair the effect of the present invention. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3.

As described above, the retardation layer is preferably a liquid crystal alignment cured layer. Examples of the liquid crystal compound include a liquid crystal compound having a liquid crystal phase as a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal property of the liquid crystal compound may be embodied by either dissolution or thermal. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

In the case where the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After the liquid crystal monomer is aligned, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the above-described alignment state can be fixed. Here, the polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer does not cause the liquid crystalline compound to change to a liquid crystal phase, a glass phase, or a crystal phase due to a specific temperature change, for example. As a result, the retardation layer is extremely excellent in stability without affecting the temperature change.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the kind thereof. Specifically, the temperature range is preferably 40℃to 120℃and more preferably 50℃to 100℃and most preferably 60℃to 90 ℃.

As the liquid crystal monomer, any suitable liquid crystal monomer may be used. For example, the polymerizable mesogenic compounds described in Japanese patent application laid-open No. 2002-533742 (WO 00/37585), EP358208 (US 5211877), EP66137 (US 4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445 and the like can be used. Specific examples of such a polymerizable mesogenic compound include, for example, a product name LC242 from BASF corporation, a product name E7 from Merck corporation, and a product name LC-Silicon-CC 3767 from Wacker-Chem corporation. As the liquid crystal monomer, nematic liquid crystal monomer is preferable.

In another embodiment, the retardation layer has a laminated structure of a first retardation layer 31 that can function as a λ/4 plate and a second retardation layer 32 (so-called positive C plate) whose refractive index characteristics show a relationship of nz > nx=ny from the polarizing plate side. Details about the lambda/4 plate are as described above. In this embodiment, the angle between the slow axis of the first retardation layer and the absorption axis of the polarizing plate is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and still more preferably 44 ° to 46 °. The first phase difference layer preferably exhibits an inverse dispersion wavelength characteristic in which the phase difference value increases according to the wavelength of the measurement light.

The retardation Rth (550) in the thickness direction of the positive C plate is preferably-50 nm to-300 nm, more preferably-70 nm to-250 nm, further preferably-90 nm to-200 nm, particularly preferably-100 nm to-180 nm. Here, "nx=ny" includes not only the case where nx and ny are exactly equal but also the case where nx and ny are substantially equal. The in-plane retardation Re (550) of the positive C plate is, for example, below 10nm.

The second phase difference layer having refractive index characteristics of nz > nx=ny may be formed of any suitable material, but is preferably formed of a thin film containing a liquid crystal material fixed in vertical alignment. The liquid crystal material (liquid crystal compound) capable of vertical alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the retardation layer include those described in [0020] to [0028] of JP-A-2002-333642 and methods for forming the retardation layer. In this case, the thickness of the second phase difference layer is preferably 0.5 μm to 5 μm.

C-5. Manufacture of polarizing plate

The polarizing plate according to the embodiment of the present invention can be obtained by laminating layers on the polarizing plate. The lamination of the layers is performed, for example, while roll-feeding (so-called roll-to-roll). The lamination of the protective layers is performed, for example, using an adhesive. The lamination of the retardation layer is typically performed by transferring a liquid crystal alignment cured layer formed on a substrate. When the retardation layers have a laminated structure, each retardation layer may be laminated (transferred) to the resin film in order, or a laminate of the retardation layers may be laminated (transferred) to the resin film. The transfer is performed, for example, with an active energy ray-curable adhesive. The thickness of the cured active energy ray-curable adhesive (the thickness of the adhesive layer) is preferably 0.4 μm or more, more preferably 0.4 μm to 3.0 μm, and still more preferably 0.6 μm to 1.5 μm.

Examples

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The thickness is a value measured by the following measurement method. Unless otherwise specified, "parts" and "%" in examples and comparative examples are based on weight.

< thickness >

The thickness of 10 μm or less was measured by a scanning electron microscope (product name "JSM-7100F", manufactured by Japanese electronics Co., ltd.). The thickness exceeding 10 μm was measured by a digital micrometer (manufactured by ANRITSU Co., ltd., product name "KC-351C").

Example 1

(production of laminate)

As a thermoplastic resin substrate, an amorphous isophthalic acid copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long-sized form and a Tg of about 75℃was used, and one side of the resin substrate was subjected to corona treatment.

At 9:1 to 100 parts by weight of a PVA-based resin comprising polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (trade name "Gohsefimer" manufactured by Nippon chemical industries Co., ltd.) were added 13 parts by weight of potassium iodide, and the resultant was dissolved in water to prepare a PVA aqueous solution (coating liquid).

The PVA aqueous solution was applied to the corona treated surface of the resin substrate, and dried at 60 ℃ to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.

The resulting laminate was uniaxially stretched to 2.4 times in the machine direction (lengthwise direction) in an oven at 130 ℃.

Next, the laminate was immersed in an insoluble bath (an aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40 ℃ for 30 seconds (insoluble treatment).

Next, the resulting polarizing plate was immersed in a dyeing bath (aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30 ℃ for 60 seconds (dyeing treatment) while adjusting the concentration so that the single-sheet transmittance (Ts) of the polarizing plate finally obtained became a desired value.

Then, the resultant solution was immersed in a crosslinking bath (aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40℃for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt% and potassium iodide concentration: 5 wt%) at a liquid temperature of 70 ℃ and uniaxially stretched (in-water stretching treatment) between rolls having different peripheral speeds so that the total stretching ratio became 5.5 times in the longitudinal direction.

Thereafter, the laminate was immersed in a washing bath (an aqueous solution obtained by mixing 100 parts by weight of water with 4 parts by weight of potassium iodide) at a liquid temperature of 20 ℃ (washing treatment).

After that, while drying in an oven maintained at about 90 ℃, the sheet was brought into contact with a SUS-made heating roller maintained at a surface temperature of about 75 ℃ (drying shrinkage treatment).

Thus, a resin film having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a structure of the resin substrate/the resin film was obtained.

(chemical modification 1)

Trifluoroacetic anhydride (manufactured by FUJIFILM Wako Pure Chemical Corporation, purity 98.0% or more) was applied to the exposed surface of the resin film of the obtained laminate at room temperature.

(production of polarizing plate A)

An HC-TAC film (thickness: 32 μm) was bonded to the chemically modified surface of the resin film (polarizing plate) as a first protective layer by means of an ultraviolet curable adhesive. The HC-TAC film is a film in which a Hard Coat (HC) layer (thickness: 7 μm) is formed on a TAC film (thickness: 25 μm), and is bonded so that the TAC film is on the resin film side. Then, the resin base material was peeled off from the resin film, and an adhesive layer (higher in moisture permeability than the HC-TAC film) having a thickness of 20 μm was formed on the peeled surface, and a separator (PET film, 38 μm thick) was bonded. Thus, a polarizing plate was obtained.

(production of polarizing plate B)

An adhesive layer having a thickness of 23 μm was formed on the chemically modified surface of the resin film (polarizing plate), and a separator (PET film, 38 μm thick) was bonded. Then, the resin base material was peeled off from the resin film, and an HC-TAC film (thickness: 32 μm) was attached to the peeled surface via an ultraviolet curable adhesive to form a first protective layer. The HC-TAC film is a film in which a Hard Coat (HC) layer (thickness: 7 μm) is formed on a TAC film (thickness: 25 μm), and is bonded so that the TAC film is on the resin film side. Thus, a polarizing plate was obtained.

Example 2

In the case of chemical modification, a polarizing plate a and a polarizing plate B were obtained in the same manner as in example 1, except that the laminate was treated as follows.

(chemical modification 2)

The long laminate was cut in the longitudinal and width directions to obtain a 200mm×150mm monolithic laminate, and a container (cup) in which the obtained monolithic laminate and 4ml of trifluoroacetic anhydride were placed was placed in a polyethylene bag (a refrigerating bag manufactured by Asahi chemical household products Co., ltd., ziploc (registered trademark)) filled with nitrogen gas, sealed, and left to stand at room temperature for 5 minutes.

Example 3

Polarizing plates a and B were obtained in the same manner as in example 2, except that the above-mentioned standing time was set to 30 minutes in the chemical modification.

Comparative example 1

A polarizing plate was obtained in the same manner as in example 1, except that the obtained laminate was not chemically modified.

< evaluation >

For each example and comparative example, the following evaluation was performed. The evaluation results are summarized in Table 1.

1. Contact angle

In each of examples and comparative examples, the water contact angle of the chemically modified surface of the chemically modified resin film (polarizing plate) was measured. Specifically, the measurement was performed by a droplet method using a contact angle meter (trade name "DMo-501", manufactured by Kyowa interface science Co., ltd., "DMC-2", control and analysis software "FAMAS (version 5.0.30)") at 23℃under 50% RH. The amount of distilled water added was 2. Mu.L, and the contact angle was calculated by the θ/2 method from the image after 5 seconds of the addition.

The values shown in table 1 are average values obtained by measuring 3 times.

2. Fluorine content

In each of examples and comparative examples, 2 cm. Times.4 cm (8 cm) was cut out from the chemically modified resin film (polarizing plate) ² ) After putting it into a ceramic plate and weighing it, add combustion improver. Then, the gas was burned by an automatic sample burning device, and the generated gas was trapped in 10mL of the absorption liquid. The collected absorption liquid was formed into 15mL with ultrapure water, and analyzed by ion chromatography to determine the fluorine content.

The analysis device and measurement conditions are as follows.

'and' analysis device

(1) Automatic sample burning device: nittoseiko Analytech Co., ltd., "AQF-2100H"

(2) Ion chromatography apparatus: thermo Fisher Scientific company, "ICS-3000"

Conditions for measuring (1)

(1) Automatic sample combustion device

Inlet temperature: 1000 DEG C

Outlet temperature: 1100 DEG C

Gas flow O ₂ :400 mL/min

Gas flow rate Ar:200 mL/min

Ar liquid feeding unit: 100 mL/min

(2) Ion chromatography apparatus

Separation column: dionex IonPac AS18-fast (4 mm. Times.150 mm)

Protective column: dionex IonPac AS18-fast (4 mm. Times.30 mm)

Removal system: dionex ADRS-600 (external mode)

A detector: conductivity detector

Eluent: KOH aqueous solution (gradient EGCIII with eluent)

Eluent flow rate: 1.2 mL/min

Sample injection amount: 250 mu L

The values shown in table 1 are average values obtained by measuring 2 times (only 3 times in example 1).

3. Durability of

The polarizing plates obtained in examples and comparative examples were peeled off from the separator and bonded to an alkali-free glass plate. In this state, after standing in an oven at 85 ℃ for 24 hours at 85% RH, the single sheet transmittance of the polarizing plate before and after the wet heat test was measured, and the change in single sheet transmittance by the wet heat test was calculated. The single-sheet transmittance Ts was measured by an ultraviolet-visible spectrophotometer (manufactured by Japanese Specification Co., ltd., V-7100). Note that Ts is a Y value subjected to visibility correction, measured in accordance with JIS Z8701 in terms of 2-degree field of view (C light source).

The values shown in table 1 represent values obtained by subtracting the single-sheet transmittance after the wet heat test from the single-sheet transmittance before the wet heat test.

TABLE 1

As is clear from table 1, the decrease in polarization performance was suppressed by chemical modification.

Industrial applicability

The polarizing plate according to the embodiment of the present invention is used for an image display device such as a liquid crystal display device, an organic EL display device, or an inorganic EL display device.

Description of the reference numerals

1 protective Material

10 polarizer (resin film)

21 first protective layer

40 adhesive layer

50 Release film

100 laminate

200 polarizing plate

Claims

1. A polarizing plate comprising a resin film containing iodine and having a first main surface and a second main surface which face each other,

at least the first main surface has a chemically modified portion of the resin film,

the hydrophobicity of the chemical modification part is higher than the hydrophobicity of other parts which are not chemically modified.

2. The polarizing plate according to claim 1, wherein the chemical modification contains a group containing fluorine.

3. The polarizer of claim 2, wherein the fluorine-containing group comprises a trifluoroacetyl group.

4. A polarizing plate according to any one of claims 1 to 3, wherein the chemical modification is chemically modified with trifluoroacetic anhydride.

5. The polarizing plate according to any one of claims 1 to 4, wherein the fluorine content is 20 μg/g or more.

6. The polarizing plate according to any one of claims 1 to 5, wherein the contact angle of the chemical modifier is 90 ° or more.

7. The polarizing plate according to any one of claims 1 to 6, which has a thickness of 8 μm or less.

8. A method of manufacturing the polarizing plate according to any one of claims 1 to 7, comprising the steps of:

at least the first main surface of a resin film containing iodine and having a first main surface and a second main surface which face each other is chemically modified.

9. The manufacturing method according to claim 8, wherein a contact angle of the first main surface is increased by 5 ° or more by the chemical modification.

10. A polarizing plate is provided with:

the polarizing plate according to any one of claims 1 to 7, and

at least one of the protective layer or the retardation layer.