CN115728855A

CN115728855A - Polarizing plate and polarizing plate with phase difference layer

Info

Publication number: CN115728855A
Application number: CN202211052673.2A
Authority: CN
Inventors: 中村诚; 三轮和哉; 石崎优
Original assignee: Nitto Denko Corp
Current assignee: Nitto Denko Corp
Priority date: 2021-08-31
Filing date: 2022-08-31
Publication date: 2023-03-03
Also published as: TW202311045A; KR20230032913A

Abstract

Provides a light transmittance T at a wavelength of 380nm ₃₈₀ A polarizing plate reduced to 3.5% or less and suppressed in warpage in a high-temperature environment, and a polarizing plate with a retardation layer. Transmittance T at wavelength of 380nm of the polarizing plate of the present invention ₃₈₀ 3.5% or less, and satisfies the following formula (1): in the formula (1), th represents the thickness (μm) of the polarizer, W represents a warpage value (mm) measured by the following warpage test: the polarizing plate was cut into a size of 70mm × 150mm to prepare a testThe test sample was bonded to a test glass plate via an adhesive layer, and then the test sample was heated at 85 ℃ for 24 hours and then allowed to stand at room temperature (23 ℃) for 1 hour or more, and then the height of warpage of the test sample was measured.

Description

Polarizing plate and polarizing plate with phase difference layer

Technical Field

The present invention relates to a polarizing plate and a polarizing plate with a retardation layer.

Background

In recent years, 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) have rapidly spread. The image display device typically uses a polarizing plate.

It is known that such a polarizing plate is provided with ultraviolet absorptivity in order to protect an image display element (particularly, an OLED element) from ultraviolet rays (for example, patent document 1). However, the polarizing plate described in patent document 1 has a problem that warping is likely to occur in a high-temperature environment.

Documents of the prior art

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-203400

Disclosure of Invention

Problems to be solved by the invention

The present invention has been made to solve the above-mentioned problems of the prior art, and a main object of the present invention is to provide a light transmittance T at a wavelength of 380nm ₃₈₀ A polarizing plate reduced to 3.5% or less and suppressed in warpage in a high-temperature environment, and a polarizing plate with a retardation layer.

Means for solving the problems

[1]Transmittance T at 380nm in the polarizing plate according to the embodiment of the present invention ₃₈₀ 3.5% or less, and satisfies the following formula (1).

In the formula (1), th represents the thickness (μm) of the polarizer, and W represents a warpage value (mm) measured by the following thermal warpage test.

Heating and warping test:

the polarizing plate was cut into a size of 70mm × 150mm to prepare a test sample, the test sample was attached to a test glass plate via an adhesive layer, and then the test sample was heated at 85 ℃ for 24 hours and then allowed to stand at room temperature (23 ℃) for 1 hour or more, and then the height of the warpage of the test sample was measured.

[2] The polarizing plate according to [1] above may include: a polarizing member; a 1 st protective layer disposed on a visual recognition side of the polarizer; and a 2 nd protective layer disposed on a side of the polarizer opposite to the visual recognition side. The 2 nd protective layer may contain a resin and an ultraviolet absorber.

[3] In the polarizing plate according to [2], the thickness of the 2 nd protective layer may be 10 μm or less.

[4] The polarizing plate according to [2] or [3], wherein the thickness of the 1 st protective layer may be 40 μm or less.

[5] The polarizing plate according to any one of the above [2] to [4], wherein the 2 nd protective layer is a solidified layer of a coating film in which the resin and the liquid of the ultraviolet absorber are dispersed and/or dissolved in an organic solvent.

[6] The polarizing plate according to any one of [2] to [5], wherein a content ratio of the ultraviolet absorber may be 1 part by mass or more with respect to 100 parts by mass of the resin.

[7] Another polarizing plate with a retardation layer according to another aspect of the present invention includes: the polarizing plate according to any one of the above [1] to [6 ]; and a retardation layer disposed on a side opposite to the visual recognition side of the polarizing plate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the embodiment of the invention, the light transmittance T at the wavelength of 380nm can be reduced ₃₈₀ And suppress warping in a high-temperature environment.

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 of a polarizing plate with an adhesive layer according to another aspect of the present invention.

Fig. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to still another aspect of the present invention.

Description of the reference numerals

1 polarizing plate

2 polarizing element

3 st protective layer

4 the 2 nd protective layer

7 st phase difference layer

8 nd 2 phase difference layer

Polarizing plate with 10 retardation layers

Detailed Description

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

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

(2) In-plane retardation (Re)

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

(3) Retardation in thickness direction (Rth)

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

(4) Angle of rotation

In the present specification, when an angle is referred to, the angle includes both clockwise and counterclockwise angles unless otherwise specified.

A. Integral constitution of polarizing plate

Fig. 1 is a schematic cross-sectional view of a polarizing plate according to 1 embodiment of the present invention. Transmittance T at 380nm of polarizing plate 1 illustrated in the figure ₃₈₀ Is 3.50% or less, preferably 2.00% or less, more preferably 1.85% or less, still more preferably 1.50% or less, particularly preferably 1.00% or less, and particularly preferably 0.80% or less.

The polarizing plate 1 satisfies the following formula (1), more preferably satisfies the following formula (2), and particularly preferably satisfies the following formula (3).

( In the expressions (1) to (3), th represents the thickness (μm) of the polarizing plate 1. W represents a warpage value (mm) measured by the following heat warpage test. )

Heating and warping test:

the polarizing plate was cut into a size of 70mm × 150mm to prepare a test sample, the test sample was attached to a test glass plate via an adhesive layer, and then the test sample was heated at 85 ℃ for 24 hours and then allowed to stand at room temperature (23 ℃) for 1 hour or more, and then the height of warpage of the test sample was measured. The details of the heating warpage test are described in the examples below.

When the polarizing plate satisfies the above formula (1), the transmittance T of the polarizing plate can be adjusted ₃₈₀ As described above, and the warpage of the polarizing plate in a high-temperature environment is suppressed.

In 1 embodiment of the present invention, a polarizing plate 1 includes: a polarizing member 2; a 1 st protective layer 3 disposed on the visual recognition side of the polarizer 2; and a 2 nd protective layer 4 disposed on the opposite side of the polarizer 2 from the visual recognition side. The 2 nd protective layer 4 contains a resin and an ultraviolet absorber.

The content ratio of the ultraviolet absorber is, for example, 1 part by mass or more, preferably 3 parts by mass or more, more preferably 5 parts by mass or more, and for example, 20 parts by mass or less, preferably 15 parts by mass or less, more preferably 12 parts by mass or less, with respect to 100 parts by mass of the resin.

When the content ratio of the ultraviolet absorber is within the above range, the transmittance T of the polarizing plate can be stably reduced ₃₈₀ 。

The 1 st protective layer 3 is typically bonded to the viewing side of the polarizer 2 via an optional adhesive layer 5 a. The 2 nd protective layer 4 is typically bonded to the side of the polarizer 2 opposite to the viewing side via an arbitrary appropriate adhesive layer 5 b. That is, the polarizing plate 1 may be formed of a 1 st protective layer 3, an adhesive layer 5a, a polarizer 2, an adhesive layer 5b, and a 2 nd protective layer 4. The adhesive layer 5a and the adhesive layer 5b are typically formed of an ultraviolet curable adhesive. Adhesive layer 5a and/or adhesive layer 5b may be an adhesive layer.

The thickness of the polarizing plate 1 is, for example, 30 μm or more, preferably 40 μm or more, for example 65 μm or less, preferably 50 μm or less.

When the thickness of the polarizing plate is not more than the upper limit, the polarizing plate can be thinned and the warpage in a high-temperature environment can be stably suppressed.

In 1 embodiment, the thickness of the 2 nd protective layer 4 is smaller than that of the 1 st protective layer 3. The upper limit of the thickness of the 2 nd protective layer 4 is, for example, 20 μm or less, preferably 15 μm or less, more preferably 10 μm or less, further preferably 8 μm or less, and particularly preferably 5 μm or less. The lower limit of the thickness of the 2 nd protective layer 4 is typically 0.5 μm or more, preferably 1 μm or more, and more preferably 3 μm or more.

When the thickness of the 2 nd protective layer is equal to or less than the upper limit, the thickness of the polarizer can be reduced, and the warpage of the polarizer in a high-temperature environment can be further suppressed. When the thickness of the 2 nd protective layer is not less than the lower limit, the light transmittance T of the polarizing plate can be further stably reduced ₃₈₀ 。

The upper limit of the thickness of the 1 st protective layer 3 is, for example, 45 μm or less, preferably 40 μm or less. The lower limit of the thickness of the 1 st protective layer 3 is typically 20 μm or more, and preferably 30 μm or more. When the 1 st protective layer 3 is surface-treated, the thickness of the 1 st protective layer 3 is a thickness including the thickness of the surface-treated layer. The surface treatment layer will be described later.

When the thickness of the 1 st protective layer is equal to or less than the upper limit, the thickness of the polarizer can be further reduced, and warping of the polarizer in a high-temperature environment can be further suppressed. When the thickness of the 1 st protective layer is not less than the lower limit, the polarizer can be stably protected.

The thickness of the polarizer 2 is, for example, 1 μm or more, preferably 3 μm or more, for example, 15 μm or less, preferably 12 μm or less, more preferably 10 μm or less, and particularly preferably 8 μm or less.

The thickness of each of the adhesive layer 5a and the adhesive layer 5b is, for example, 0.5 μm or more, preferably 1 μm or more, for example, 10 μm or less, preferably 5 μm or less.

In 1 embodiment of the present invention, the 2 nd protective layer 4 is a solidified layer of a coating film of an organic solvent solution containing a resin and an ultraviolet absorber. The solidified layer of the coating film is formed by, for example, applying the organic solvent solution to a substrate and then drying the coating film. Therefore, even if the thickness of the solidified layer of the coating film is within the range of the thickness of the 2 nd protective layer (particularly, 10 μm or less, particularly, 3 μm to 5 μm), the solidified layer is supported by the substrate, and therefore, the solidified layer can be stably transported even in the production of the polarizing plate. On the other hand, extrusion molding has also been studied as a method for producing the 2 nd protective layer, but when the 2 nd protective layer is an extrusion molded product, if the thickness of the 2 nd protective layer is in the above range, stable molding and/or transportation of the 2 nd protective layer may become difficult.

B. Integral constitution of polarizing plate with adhesive layer

FIG. 2 is a schematic cross-sectional view of a polarizing plate with an adhesive layer according to another aspect of the present invention. The polarizing plate 11 with an adhesive layer includes: the polarizing plate 1; and an adhesive layer 6a disposed on the opposite side of the polarizing plate 1 from the visual recognition side. More specifically, the adhesive layer 6a is disposed on the opposite side of the polarizer 2 from the 2 nd protective layer 4 and on the surface of the 2 nd protective layer 4. The pressure-sensitive adhesive layer 6a is typically formed of a pressure-sensitive adhesive described later. The polarizing plate 11 with an adhesive layer can be attached to an image display panel provided with an image display element by an adhesive layer 6a.

C. Integral structure of polarizing plate with phase difference layer

Fig. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to still another aspect of the present invention. The polarizing plate with retardation layer 10 includes: the above-described polarizing plate 1; and a 1 st retardation layer 7 disposed on the opposite side of the polarizing plate 1 from the visual recognition side. Further, polarizing plate with retardation layer 10 may further include 2 nd retardation layer 8 disposed on the side opposite to the visual recognition side of 1 st retardation layer 7 (on the opposite side of polarizing plate 1 with respect to 1 st retardation layer 7). The polarizing plate with a retardation layer can have a desired optical compensation function.

The 1 st retardation layer 7 is typically bonded to the 2 nd protective layer 4 via any suitable adhesive layer 6 b. The pressure-sensitive adhesive layer 6b is typically formed of a pressure-sensitive adhesive described later. The adhesive layer 6b may be an adhesive layer. The 2 nd retardation layer 8 is typically bonded to the 1 st retardation layer 7 via an arbitrary appropriate adhesive layer 5 c. The adhesive layer 5c is typically formed of an ultraviolet curable adhesive. The adhesive layer 5c may be an adhesive layer.

The polarizing plate 10 with a retardation layer may further include the above-described adhesive layer 6a. In the polarizing plate with retardation layer 10, the adhesive layer 6a is disposed on the side opposite to the viewing side of the 2 nd retardation layer 8 and on the 2 nd retardation layer 8.

Hereinafter, the constituent elements of the polarizing plate and the polarizing plate with the adhesive layer will be described.

D. Polarizing piece

As the polarizer 2, any suitable polarizer may be used. For example, the resin film forming the polarizing plate 2 may be a single-layer resin film or a laminate of two or more layers.

Specific examples of polarizers made of a single-layer resin film include a PVA-based resin film subjected to a dyeing treatment with iodine and a stretching treatment (typically uniaxial stretching). The dyeing with iodine is performed by, for example, immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be performed after the dyeing treatment, or may be performed while dyeing. Further, dyeing may be performed after stretching. The PVA-based resin film is subjected to swelling treatment, crosslinking treatment, washing treatment, drying treatment, and the like as necessary. For example, by immersing the PVA-based resin film in water and washing it with water before dyeing, not only stains and an antiblocking agent on the surface of the PVA-based film can be washed but also the PVA-based resin film can be swollen to prevent uneven dyeing and the like.

Specific examples of the polarizer obtained by using the laminate include: a laminate of a resin substrate and a PVA type resin layer (PVA type resin film) laminated on the resin substrate, or a polarizer obtained by using a laminate of a resin substrate and a PVA type resin layer formed on the resin substrate by coating. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer formed on the resin substrate by coating can be produced, for example, as follows: coating a PVA-based resin solution on a resin base material, and drying the coating to form a PVA-based resin layer on the resin base material, thereby obtaining a laminate of the resin base material and the PVA-based resin layer; the laminate is stretched and dyed to form a polarizing element from the PVA resin layer. In 1 embodiment of the present invention, a polyvinyl alcohol resin layer containing a halide and a polyvinyl alcohol resin is preferably formed on one side of the resin base. The stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Further, the stretching may include, if necessary, subjecting the laminate to in-air stretching at a high temperature (for example, 95 ℃ or higher) before stretching in the aqueous boric acid solution. In addition, in 1 embodiment of the present invention, it is preferable that the laminate is subjected to a drying shrinkage treatment of shrinking the laminate by 2% or more in the width direction by heating while being conveyed in the longitudinal direction. Typically, the production method of the present embodiment includes sequentially subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment. By introducing the auxiliary stretching, even when the PVA is coated on the thermoplastic resin, the crystallinity of the PVA can be improved, and high optical properties can be achieved. In addition, by simultaneously improving the orientation of the PVA in advance, problems such as a decrease in the orientation of the PVA when immersed in water in the subsequent dyeing step and stretching step, dissolution, and the like can be prevented, and high optical characteristics can be achieved. Further, when the PVA-based resin layer is immersed in a liquid, disturbance of orientation of polyvinyl alcohol molecules and reduction of orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical properties of the polarizer obtained through a treatment step of immersing the laminate in a liquid, such as dyeing or underwater stretching. Further, the optical properties can be improved by shrinking the laminate in the width direction by the drying shrinkage treatment. The obtained resin base material/polarizer laminate may be used as it is (that is, the resin base material may be used as the 1 st protective layer of the polarizer), or the resin base material may be peeled off from the resin base material/polarizer laminate and any appropriate protective layer suitable for the purpose may be laminated on the peeled surface. Details of a method for producing such a polarizer are described in, for example, japanese patent laid-open publication No. 2012-73580 and japanese patent No. 6470455. The entire disclosures of these publications are incorporated herein by reference.

The polarizer 2 is preferably composed of a polarizer obtained by using a laminate of a resin base material and a PVA-based resin layer formed on the resin base material by coating, and more preferably composed of a polarizer obtained by peeling the resin base material from the laminate of the resin base material and the polarizer.

The polarizing element 2 preferably exhibits absorption dichroism at any wavelength of 380nm to 780 nm. The single transmittance of the polarizer 2 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer 2 is preferably 97.0% or more, more preferably 99.0% or more, and still more preferably 99.9% or more.

E. 1 st protective layer

The 1 st protective layer 3 is disposed on one side in the thickness direction of the polarizer 2. The 1 st protective layer 3 is formed of any suitable thin film that can be used as a protective layer for the polarizer 2. Specific examples of the material as the main component of the film include cellulose resins such as Triacetylcellulose (TAC), and transparent resins such as polyester resins, polyvinyl alcohol resins, polycarbonate resins, polyamide resins, polyimide resins, polyether sulfone resins, polysulfone resins, polystyrene resins, polynorbornene resins, polyolefin resins, (meth) acrylic resins, and acetate resins. Further, thermosetting resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, silicone, and the like, ultraviolet-curable resins, and the like can be cited. The term "(meth) acrylic resin" means an acrylic resin and/or a methacrylic resin. Further, for example, a glassy polymer such as a siloxane polymer can be given. Further, the polymer film described in Japanese patent application laid-open No. 2001-343529 (WO 01/37007) may be used. As a material of the film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in a side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in a side chain can be used, and for example, a resin composition having an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile/styrene copolymer can be mentioned. Such materials as the main component of the film may be used alone or in combination. The polymer film may be, for example, an extrusion molded product of the resin composition.

The 1 st protective layer 3 preferably contains a cellulose resin, more preferably cellulose triacetate.

In 1 embodiment of the present invention, the 1 st protective layer 3 is disposed on the outermost surface of the polarizing plate 1 on the visual recognition side. The 1 st protective layer 3 may be subjected to surface treatment such as hard coat treatment, antireflection treatment, anti-sticking treatment, and anti-glare treatment as necessary. Among such surface treatments, a hard coating treatment is preferably mentioned. That is, the 1 st protective layer 3 preferably includes a base material formed of the above-described material and a hard coat layer disposed on the base material. The hard coat layer can impart excellent pencil hardness to the polarizing plate 1.

F. The 2 nd protective layer

The 2 nd protective layer 4 is disposed on the opposite side of the 1 st protective layer 3 from the polarizer 2. The 2 nd protective layer 4 contains a resin and an ultraviolet absorber as described above.

Examples of the resin contained in the 2 nd protective layer 4 include cellulose resins such as Triacetylcellulose (TAC); polyester systems such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT); polyolefin (PO) systems such as Polyethylene (PE) and polypropylene (PP); polyamide (PA) system; (meth) acrylic acid series; polystyrene (PS) series; polyoxymethylene (polyacetal, POM) type; polyurethane (PU) series; a cycloolefin system.

The resin contained in the 2 nd protective layer 4 preferably includes a cycloolefin resin and a (meth) acrylic resin, more preferably includes a norbornene resin and a polymethyl methacrylate (PMMA) resin, and still more preferably includes a norbornene resin. Specific examples of the norbornene-based resin include "cycloolefin-based resins obtained by hydrogenating a ring-opened polymer of a norbornene-based monomer" described in japanese patent laid-open publication No. 2006-208925.

Examples of commercially available products of such cycloolefin resins include a product name "ARTON" manufactured by JSR Corporation, a product name "ZEONEX" manufactured by Zeon Corporation, a product name "APEL" manufactured by mitsui chemical Corporation, a product name "TOPAS" manufactured by polyplatics co.

Examples of commercially available polymethyl methacrylate (PMMA) resins include trade names of "1245012463125221250612524248312488", KURARAY co., trade name of "paranet" manufactured by mitsui chemical corporation, trade name of "Sumipex" manufactured by sumitomo chemical corporation, and trade name of "Delpet" manufactured by asahi chemical corporation.

Any suitable ultraviolet absorber can be used as the ultraviolet absorber contained in the 2 nd protective layer 4. Examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and benzophenone-based ultraviolet absorbers. The ultraviolet absorbers may be used alone or in combination. Among the ultraviolet absorbers, preferred is a triazine-based ultraviolet absorber. The content ratio of the ultraviolet absorber in the 2 nd protective layer 4 is as described in the above item a.

The 2 nd protective layer 4 is preferably a solidified layer of a coating film in which a liquid of a resin and an ultraviolet absorber is dispersed and/or dissolved in an organic solvent, as described above. Such a liquid is preferably an organic solvent solution in which the resin and the ultraviolet absorber are dissolved. In other words, the 2 nd protective layer is preferably a dried coating film (coating film) containing a resin and an ultraviolet absorber that are dispersible and/or soluble in an organic solvent, and more preferably a dried coating film (coating film) containing a resin and an ultraviolet absorber that are soluble in an organic solvent.

In order to form a solidified layer of a coating film as the 2 nd protective layer 4, the above resin and the ultraviolet absorber are first added to an organic solvent to prepare the above liquid.

Examples of the organic solvent include aliphatic hydrocarbons such as isooctane, heptane, hexane, and isohexane; alicyclic hydrocarbons such as methylcyclohexane and ethylcyclohexane; aromatic hydrocarbons such as 1-grade xylene and toluene; ethers such as cyclopentyl methyl ether (CPME) and 1, 3-dioxolane; ketones such as acetone, acetylacetone, methyl isobutyl ketone (MIBK), methyl Ethyl Ketone (MEK), cyclohexanone, and cyclopentanone; esters such as butyl acetate, ethyl acetate, methyl acetate, propylene glycol monomethyl ether acetate, and the like; alcohols such as 1-methoxy-2-propanol and isopropyl alcohol (IPA); halogenated aliphatic hydrocarbons such as methylene chloride; halogenated aromatic hydrocarbons such as 1,2, 4-trichlorobenzene; terpenes such as limonene.

The organic solvents may be used alone or in combination. Among the organic solvents, preferred are cyclopentyl methyl ether and ethyl acetate. The organic solvent is appropriately selected depending on the kind of the resin used. When the resin is a cycloolefin resin (norbornene resin), cyclopentyl methyl ether is preferably selected, and when the resin is a (meth) acrylic resin (PMMA resin), ethyl acetate is preferably selected.

The concentration of the resin in the liquid is, for example, 1 mass% or more and 20 mass% or less. The amount of the ultraviolet absorber added to the liquid is the same as the content ratio of the ultraviolet absorber described in the above item A.

The liquid (preferably an organic solvent solution) is then applied to any suitable substrate (e.g., a PET substrate) and allowed to dry at any suitable temperature and time. Thereby, a solidified layer of the coating film as the 2 nd protective layer is formed on the substrate. Thereafter, the solidified layer (the 2 nd protective layer 4) of the coated film is bonded to the surface (the surface opposite to the 1 st protective layer) of the polarizer 2 via the adhesive layer 5b, and then the substrate is peeled from the solidified layer (the 2 nd protective layer 4) of the coated film.

G. Adhesive layer

The pressure-sensitive

adhesive layers

6a and 6b are each formed of a pressure-sensitive adhesive (pressure-sensitive adhesive). The adhesive forming the adhesive layer can also be used for bonding the test sample to the test glass plate in the above-described heating warpage test.

The adhesive typically contains a (meth) acrylic polymer as a base polymer.

The (meth) acrylic polymer is a polymer containing a monomer component (raw material monomer) containing an alkyl (meth) acrylate as a main component. The alkyl (meth) acrylate is preferably 50% by mass or more of the total monomer components that are raw materials of the (meth) acrylic polymer, and the remaining part of the monomers other than the alkyl (meth) acrylate can be arbitrarily set. The term (meth) acrylate refers to acrylate and/or methacrylate.

Examples of the alkyl (meth) acrylate constituting the main skeleton of the (meth) acrylic polymer include alkyl (meth) acrylates in which a linear or branched alkyl group has 1 to 18 carbon atoms. The alkyl (meth) acrylates may be used alone or in combination. The average carbon number of the alkyl group is preferably 3 to 10.

The (meth) acrylic polymer may contain a structural unit derived from a comonomer polymerizable with an alkyl (meth) acrylate in addition to a structural unit derived from an alkyl (meth) acrylate. That is, the monomer component as a raw material of the (meth) acrylic polymer may contain a comonomer in addition to the alkyl (meth) acrylate.

Examples of the comonomer include a carboxyl group-containing monomer, a hydroxyl group-containing monomer, an amino group-containing monomer, an amide group-containing monomer, a cyclopolymerizable monomer, an epoxy group-containing monomer, a sulfonic acid group-containing monomer, a phosphoric acid group-containing monomer, a polyfunctional acrylate, a (meth) acrylate having an alicyclic hydrocarbon group, a (meth) acrylate having an aromatic hydrocarbon group, a vinyl ester, an aromatic vinyl compound, a diene, a vinyl ether, and vinyl chloride.

Among such comonomers, preferred are reactive group-containing monomers containing a reactive group capable of reacting with a crosslinking agent described later, and more preferred are carboxyl group-containing monomers and hydroxyl group-containing monomers. The reactive group-containing monomer is a reactive site with a crosslinking agent when the binder contains the crosslinking agent described later. The carboxyl group-containing monomer and the hydroxyl group-containing monomer are rich in reactivity with the intermolecular crosslinking agent, and therefore are preferable for improving the aggregation property and heat resistance of the obtained pressure-sensitive adhesive layer. The carboxyl group-containing monomer is preferable in terms of compatibility between durability and reworkability, and the hydroxyl group-containing monomer is preferable in terms of improvement of reworkability. The comonomers may be used alone or in combination in the raw material monomers of the (meth) acrylic polymer.

The carboxyl group-containing monomer is preferably (meth) acrylic acid, and more preferably acrylic acid. When a carboxyl group-containing monomer is used as a raw material monomer, the content of the carboxyl group-containing monomer is usually 0.01 mass% or more and 10 mass% or less of the total monomer components that are raw materials of the (meth) acrylic polymer.

The hydroxyl group-containing monomer preferably includes 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate, and more preferably includes 4-hydroxybutyl (meth) acrylate. When a hydroxyl group-containing monomer is used as a raw material monomer, the content of the hydroxyl group-containing monomer is usually 0.01 mass% or more and 10 mass% or less of the total monomer components that are raw materials of the (meth) acrylic polymer.

The weight average molecular weight Mw of the (meth) acrylic polymer is, for example, 20 to 300 ten thousand, preferably 100 to 250 ten thousand, and more preferably 120 to 250 ten thousand. When the weight average molecular weight Mw is within such a range, an adhesive layer having excellent durability (particularly heat resistance) can be obtained. When the weight average molecular weight Mw exceeds 300 ten thousand, the viscosity may increase and/or gelation may occur during polymerization of the polymer.

The adhesive may contain a crosslinking agent. As the crosslinking agent, an organic crosslinking agent, a polyfunctional metal chelate compound, or the like can be used. Examples of the organic crosslinking agent include an isocyanate crosslinking agent, a peroxide crosslinking agent, an epoxy crosslinking agent, and an imine crosslinking agent. The polyfunctional metal chelate compound is obtained by covalently or coordinately bonding a polyvalent metal to an organic compound. The crosslinking agents may be used alone or in combination. The crosslinking agent preferably contains an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent. When a crosslinking agent is blended in the adhesive, the blending amount of the crosslinking agent is usually 0.01 to 15 parts by mass with respect to 100 parts by mass of the (meth) acrylic polymer (base polymer).

The adhesive may have a reactive functional group-containing silane coupling agent. In the reactive functional group-containing silane coupling agent, the reactive functional group is typically a functional group other than an acid anhydride group. The reactive functional group-containing silane coupling agents may be used alone or in combination. When the reactive functional group-containing silane coupling agent is blended in the pressure-sensitive adhesive, the blending amount of the reactive functional group-containing silane coupling agent is usually 0.001 parts by mass or more and 5 parts by mass or less with respect to 100 parts by mass of the (meth) acrylic polymer.

H. Phase difference layer 1 and phase difference layer 2

The 1 st retardation layer 7 and the 2 nd retardation layer 8 may be each formed of any retardation film having appropriate optical properties and/or mechanical properties according to the purpose. The phase difference layer 7 of the 1 st layer typically exhibits a relationship of nx > ny ≧ nz. Here, "ny = nz" includes not only the case where ny and nz are completely equal but also the case where ny and nz are substantially equal.

The 1 st retardation layer 7 can function as a so-called λ/4 plate. The in-plane retardation Re (550) of the 1 st retardation layer 7 is, for example, 100nm to 200nm, preferably 130nm to 150nm.

The angle formed by the slow axis of the 1 st retardation layer 7 and the absorption axis of the polarizer 2 is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, still more preferably 44 ° to 46 °, and particularly preferably about 45 °.

The 2 nd retardation layer 8 typically exhibits a refractive index characteristic of nz > nx = ny. Here, "nx = ny" includes not only the case where nx and ny are completely equal but also the case where they are substantially equal. The retardation Rth (550) in the thickness direction of the 2 nd retardation layer 8 is preferably from-50 nm to-300 nm, more preferably from-100 nm to-180 nm.

I. Image display device

The polarizing plate, the polarizing plate with an adhesive layer, and the polarizing plate with a retardation layer described in the above items A to H are applicable to an image display device. Accordingly, 1 embodiment of the present invention also includes an image display device using any one of a polarizing plate, a polarizing plate with an adhesive layer, and a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an organic EL display device. The image display device according to the embodiment of the present invention typically includes the polarizing plate described in the above items a to F on the visual recognition side. The image display device includes an image display panel. The image display panel includes an image display element. The image display device may be referred to as an optical display device, the image display panel may be referred to as an optical display panel, and the image display element may be referred to as an optical display element.

[ examples ]

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement method of each characteristic is as follows.

(1) Heat warping test

The acrylic pressure-sensitive adhesive obtained in production example 1 was applied to the silicone-treated surface of a release film (PET film, MRF38, manufactured by mitsubishi chemical polyester film corporation), and then dried in an air-circulating oven set at a predetermined temperature, thereby forming a pressure-sensitive adhesive layer (pressure-sensitive adhesive sheet) having a thickness of 15 μm.

Next, the pressure-sensitive adhesive layer was transferred from the release film to the surface of the 2 nd protective layer of the polarizing plate obtained in example and comparative example. Thereafter, the polarizing plate provided with the adhesive layer (polarizing plate with an adhesive layer) was cut into a size of 70mm × 150mm to prepare a test sample. In the test sample, the absorption axis direction of the polarizer was parallel to the long side direction of the test sample. Next, the test sample was bonded to a test glass plate (manufactured by sonlangdu corporation) via an adhesive layer. The test glass plate had dimensions of 80mm × 170mm, and the thickness of the test glass plate was 0.2mm.

Subsequently, the test sample bonded to the test glass plate was put into an oven, heated at 85 ℃ for 24 hours, and then allowed to stand at room temperature (23 ℃) for 1 hour at 55% RH. The test sample had a concave shape (U-shape) which was open toward the upper side when the test glass plate was observed as a lower side in shape. Thereafter, the height of the warpage of the test sample was measured.

Specifically, the test sample was placed on a horizontal surface so that the test glass plate was in contact with the horizontal surface, and the vertical dimension between the horizontal surface and the edge of the short side of the bottom surface (surface facing the horizontal surface) of the test glass plate to which the test sample was attached was measured with a ruler, and was used as the height of the warp of the test sample. The results are shown in table 1.

(2) Light transmittance T ₃₈₀ Measurement of

The polarizing plates obtained in each of examples and comparative examples were attached to a spectrophotometer (product name "LPF-200", manufactured by tsukamur electronics co., ltd.), and the light transmittance T at a wavelength of 380nm was measured so that incident light was incident perpendicularly to the 1 st protective layer ₃₈₀ . The results are shown in table 1.

Production example 1

In a 4-neck flask equipped with a stirring blade, a thermometer, a nitrogen gas introduction tube, and a condenser, 75.1 parts of butyl acrylate, 19 parts of benzyl acrylate, 4.8 parts of acrylic acid, 0.1 part of 2-hydroxyethyl acrylate, and 0.1 part of 2,2' -azobisisobutyronitrile as a polymerization initiator were introduced together with 100g of ethyl acetate, nitrogen substitution was performed by introducing nitrogen gas while slowly stirring, and then polymerization was performed for 8 hours while maintaining the liquid temperature in the flask at about 55 ℃.

An acrylic adhesive as a solution (solid content 11 mass%) of the acrylic adhesive composition was obtained by mixing 3 parts of an isocyanate crosslinking agent (CORONATE L, manufactured by tokyo co., ltd.), 0.2 part of a peroxide crosslinking agent (benzoyl peroxide), and 0.075 part of a silane coupling agent (KBM 403, manufactured by shin-Etsu chemical Co., ltd.) with 100 parts of the solid content of the obtained acrylic polymer solution.

[ examples 1 to 7]

1. Fabrication of polarizing elements

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

Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl group-modified PVA (product name "GOHSEFIMER" manufactured by japan synthetic chemical industries) were mixed at a ratio of 9:1 to 100 parts by mass of the PVA-based resin obtained by mixing, 13 parts by mass of potassium iodide was added, and the obtained mixture was dissolved in water to prepare a PVA aqueous solution (coating solution).

The aqueous PVA solution was applied to the corona-treated surface of the resin substrate and dried at 60 ℃.

The obtained laminate was uniaxially stretched in the longitudinal direction (longitudinal direction) to 2.4 times in an oven at 130 ℃ (in-air stretching treatment).

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

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

Next, the substrate was immersed in a crosslinking bath (an aqueous boric acid solution prepared by adding 3 parts by mass of potassium iodide to 100 parts by mass of water and 5 parts by mass of boric acid) 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 mass%, potassium iodide concentration 5 mass%) having a liquid temperature of 70 ℃, and uniaxially stretched (underwater stretching treatment) between rolls having different peripheral speeds so that the total stretching ratio was 5.5 times in the longitudinal direction (longitudinal direction).

Thereafter, the laminate was immersed in a cleaning bath (aqueous solution prepared by adding 4 parts by mass of potassium iodide to 100 parts by mass of water) at a liquid temperature of 20 ℃.

Thereafter, while drying in an oven maintained at about 90 ℃, the sheet was brought into contact with a heated roll made of SUS maintained at a surface temperature of about 75 ℃ (drying shrinkage treatment).

In this manner, a polarizing plate having a thickness of about 5 μm was formed on the resin substrate.

2. 1 st protective layer attachment

A TAC film (thickness: 32 μm) with a hard coat layer (HC) as the 1 st protective layer was bonded to the surface (the surface opposite to the resin substrate) of the obtained polarizer with an ultraviolet-curable adhesive. Specifically, the ultraviolet-curable adhesive layer was coated so that the thickness thereof became about 2.0 μm, and was bonded using a roll press. Thereafter, UV light is irradiated from the TAC film side to cure the adhesive. Subsequently, the resin substrate is peeled.

3. Preparation of the No. 2 protective layer

An organic solvent solution (concentration of 10 mass%) of a cycloolefin resin was prepared by dissolving a cycloolefin resin (trade name: ARTON, manufactured by JSR) in cyclopentyl methyl ether. Next, an ultraviolet absorber (UVA, trade name ADK STAB LA-F70, manufactured by ADEKA) was added to the organic solvent solution in the amount shown in Table 1 based on 100 parts by mass of the cycloolefin resin to prepare an organic solvent solution of the cycloolefin resin and UVA.

Then, the organic solvent solution was applied to a PET substrate using an applicator so that the thickness after drying became the value shown in table 1, and dried at 110 ℃ for 3 minutes. Thus, a solidified layer (UVA-COP/PET) of a coating film of a cycloolefin resin and UVA in an organic solvent was formed as the 2 nd protective layer.

Next, the 2 nd protective layer was bonded to the surface of the polarizer (the surface opposite to the 1 st protective layer) with an ultraviolet curable adhesive. Specifically, the ultraviolet-curable adhesive layer was applied so that the thickness thereof became about 2.0 μm, and was bonded using a roll press. Thereafter, UV light is irradiated from the 2 nd protective layer side to cure the adhesive. Subsequently, the PET substrate was peeled from the 2 nd protective layer.

In this way, a polarizing plate having a structure of 1 st protective layer (HC/TAC film)/polarizer/2 nd protective layer (UVA-COP) was obtained.

[ example 8]

A polarizing plate having a configuration of 1 st protective layer (HC/TAC film)/polarizer/2 nd protective layer (UVA-PMMA) was obtained in the same manner as in example 1, except that the 2 nd protective layer (UVA-COP) was changed to 2 nd protective layer (UVA-PMMA) prepared as described below.

< preparation of the second protective layer >

An organic solvent solution (concentration: 10% by mass) of PMMA resin (trade name: neoCryl B-728, DSM COATING RESINS) was prepared by dissolving PMMA resin in ethyl acetate. Subsequently, an ultraviolet absorber (UVA, trade name ADK STAB LA-F70, manufactured by ADEKA) was added to the organic solvent solution in the amount of the additive parts shown in Table 1 based on 100 parts by mass of the PMMA resin to prepare an organic solvent solution of the PMMA resin and UVA.

Then, the organic solvent solution was applied to a PET substrate using an applicator so that the thickness after drying became the value shown in table 1, and dried at 60 ℃ for 3 minutes. Thus, a solidified layer (UVA-PMMA/PET) of a coating film of a PMMA resin and an organic solvent solution of UVA was produced as the 2 nd protective layer.

Comparative example 1

A polarizing plate was obtained in the same manner as in example 1, except that the ultraviolet absorber (UVA) was not used. That is, in the polarizing plate of comparative example 1, the 2 nd protective layer does not contain UVA.

Comparative example 2

A polarizing plate was obtained in the same manner as in example 1 except that a cycloolefin resin film (product name G +, manufactured by Zeon Corporation) having a thickness of 25 μm prepared by extrusion molding was used instead of the solidified layer of the coating film of the cycloolefin resin and the UVA organic solvent solution.

[ Table 1]

[ evaluation ]

As is clear from table 1, the light transmittance T can be adjusted by adjusting the thickness of the 2 nd protective layer so that the thickness Th (μm) of the polarizing plate/the warpage value (mm) in the heating warpage test is 10 or more ₃₈₀ A polarizing plate reduced to 3.5% or less and suppressed in warpage in a high-temperature environment.

Industrial applicability

The polarizing plate and the polarizing plate with a retardation layer of the present invention can be suitably used for image display devices (typically, liquid crystal display devices and organic EL display devices).

Claims

1. A polarizing plate with light transmittance T at wavelength of 380nm ₃₈₀ The content of the active carbon is below 3.5 percent,

the polarizing plate satisfies the following formula (1):

in the formula (1), th represents the thickness (mum) of the polarizer, W represents the warpage value (mm) measured by the following warpage test by heating,

heating and warping test:

the polarizing plate was cut into a size of 70mm × 150mm to prepare a test sample, the test sample was attached to a test glass plate via an adhesive layer, and then the test sample was heated at 85 ℃ for 24 hours and then allowed to stand at room temperature (23 ℃) for 1 hour or more, and then the height of warpage of the test sample was measured.

2. The polarizing plate according to claim 1, comprising:

a polarizing member;

a first protective layer 1 disposed on a visual recognition side of the polarizer; and

a 2 nd protective layer disposed on a side of the polarizing member opposite to the visual recognition side,

the 2 nd protective layer contains a resin and an ultraviolet absorber.

3. The polarizing plate according to claim 2, wherein the thickness of the 2 nd protective layer is 10 μm or less.

4. The polarizing plate of claim 3, wherein the thickness of the 1 st protective layer is 40 μm or less.

5. The polarizing plate according to claim 2, wherein the 2 nd protective layer is a solidified layer of a coating film of a liquid in which the resin and the ultraviolet absorber are dispersed and/or dissolved in an organic solvent.

6. The polarizing plate according to claim 2, wherein a content ratio of the ultraviolet absorber is 1 part by mass or more with respect to 100 parts by mass of the resin.

7. A polarizing plate with a retardation layer, comprising:

the polarizing plate according to any one of claims 1 to 6; and

and a retardation layer disposed on a side of the polarizing plate opposite to the visual recognition side.