WO2021220729A1

WO2021220729A1 - Polarizing plate and polarizing plate with optical functional layer

Info

Publication number: WO2021220729A1
Application number: PCT/JP2021/014526
Authority: WO
Inventors: 卓史上条; 和哉三輪; 大介濱本
Original assignee: 日東電工株式会社
Priority date: 2020-04-30
Filing date: 2021-04-05
Publication date: 2021-11-04
Also published as: TW202146547A; KR20230002535A; CN115461660A; JP2021173982A

Abstract

The present invention provides a polarizing plate which has excellent durability and excellent bendability in spite of the extremely thin thickness. A polarizing plate according to the present invention comprises a polarizer and a protective layer that is arranged on one side of the polarizer; the protective layer is configured from a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin; the protective layer has a glass transition temperature of 95°C or more; and the total thickness is 20 μm or less.

Description

Polarizing plate and polarizing plate with optical functional layer

The present invention relates to a polarizing plate and a polarizing plate with an optical functional layer.

In an image display device (for example, a liquid crystal display device or an organic EL display device), a polarizing plate is often arranged on at least one side of a display cell due to the image forming method. In recent years, image display devices have become thinner and more flexible, and along with this, there is a strong demand for thinner polarizing plates. However, the thinner the polarizing plate, the more remarkable the problem of durability that the optical characteristics in a heating and humidifying environment deteriorate.

In recent years, with the increasing demand for curved image display devices and / or foldable or foldable image display devices, polarizing plates (as a result, polarizing plates with an optical functional layer) are also excellent in mechanical properties. It is required that the optical characteristics do not change due to flexibility and bending. However, a polarizing plate satisfying such characteristics (as a result, a polarizing plate with an optical functional layer) has room for study for practical use. Further, when the bending resistance is improved, there is a problem that the strength of the polarizing plate is lowered and the physical durability is lowered.

JP-A-2015-210474

The present invention has been made to solve the above-mentioned conventional problems, and its main purpose is a polarizing plate and an optical functional layer that achieve both excellent durability and excellent flexibility despite being extremely thin. The purpose is to provide a polarizing plate.

The polarizing plate of the present invention includes a polarizing element and a protective layer arranged on one side of the polarizing element. This protective layer is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature of the protective layer is 95 ° C. or higher. The total thickness of this polarizing plate is 20 μm or less.
In one embodiment, the protective layer has a thickness of 10 μm or less.
In one embodiment, the thickness of the polarizer is 10 μm or less.
In one embodiment, the thermoplastic acrylic resin has at least one selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit.
In another aspect of the present invention, a polarizing plate with an optical functional layer is provided. The polarizing plate with an optical functional layer includes the polarizing plate and an optical functional layer arranged on the opposite side of the protective layer of the polarizer, and has a total thickness of 25 μm or less.
In one embodiment, the optical functional layer functions as a protective layer separate from the protective layer.
In one embodiment, the optical functional layer is a retardation layer having a circularly polarized light function or an elliptically polarized light function.

According to the embodiment of the present invention, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility even though it is very thin, and a polarizing plate with an optical functional layer. In the embodiment of the present invention, the protective layer is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature thereof is set to a predetermined value or higher. Therefore, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility and a polarizing plate with an optical functional layer.

It is the schematic sectional drawing of the polarizing plate by one Embodiment of this invention. It is schematic cross-sectional view of the polarizing plate with an optical functional layer according to one Embodiment of this invention. It is the schematic which shows an example of the drying shrinkage treatment using the heating roll in the manufacturing method of the polarizing plate by one Embodiment of this invention.

(Definition of terms and symbols)
Definitions of terms and symbols herein are as follows.
(1) Refractive index (nx, ny, nz)
“Nx” is the refractive index in the direction in which the in-plane refractive index is maximized (that is, the slow-phase axis direction), and “ny” is the in-plane direction orthogonal to the slow-phase axis (that is, the phase-advance axis direction). Is the refractive index of, and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
“Re (λ)” is an in-plane phase difference measured with light having a wavelength of λ nm at 23 ° C. For example, "Re (550)" is an in-plane phase difference measured with light having a wavelength of 550 nm at 23 ° C. Re (λ) is obtained by the formula: Re (λ) = (nx−ny) × d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in the thickness direction (Rth)
“Rth (λ)” is a phase difference in the thickness direction measured with light having a wavelength of λ nm at 23 ° C. For example, "Rth (550)" is a phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23 ° C. Rth (λ) is obtained by the formula: Rth (λ) = (nx−nz) × d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is obtained by Nz = Rth / Re.
(5) Angle When referring to an angle herein, the angle includes both clockwise and counterclockwise with respect to the reference direction. Therefore, for example, "45 °" means ± 45 °.

A. Outline of Polarizing Plate and Polarizing Plate with Optical Functional Layer A-1. Outline of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 of the illustrated example has a polarizing element 10 and a protective layer 20 arranged on one side of the polarizing element 10. The total thickness of the polarizing plate 100 is 20 μm or less. The protective layer 20 is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin, and its glass transition temperature is 95 ° C. or higher. By having such a protective layer on the polarizing plate 100, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility in spite of a very thin thickness. In one embodiment, the thickness of the polarizer 10 is preferably 10 μm or less. Further, in one embodiment, the thickness of the protective layer 20 is preferably 10 μm or less.

The total thickness of the polarizing plate 100 is 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less. According to the present invention, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility even when the total thickness of the polarizing plate is within the above range. The total thickness of the polarizing plate is, for example, 5 μm or more.

Further, in the embodiment of the present invention, the glass transition temperature (Tg) of the protective layer 20 is 95 ° C. or higher, preferably 100 ° C. or higher, more preferably 105 ° C. or higher, still more preferably 110 ° C. or higher. It is particularly preferably 115 ° C. or higher. If the Tg of the protective layer is in such a range, it may be very thin due to the synergistic effect of the protective layer being composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin. Regardless of this, a polarizing plate having excellent durability (as a result, a polarizing plate with an optical functional layer) can be realized. Specifically, it is possible to realize a polarizing plate in which deterioration of optical characteristics is suppressed even in a heating and humidifying environment (as a result, a polarizing plate with an optical functional layer). On the other hand, the Tg of the protective layer is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the protective layer is in such a range, the moldability can be excellent.

Each layer or optical film constituting the polarizing plate is typically bonded via an adhesive layer. Examples of the adhesive layer include an adhesive layer and an adhesive layer. In the embodiment of the present invention, the adhesive layer can be preferably adopted. With such a configuration, the polarizing plate can be further thinned. Typical examples of the adhesive constituting the adhesive layer include an active energy ray-curable adhesive (for example, an ultraviolet curable adhesive).

In the embodiment of the present invention, the thickness of the polarizing plate can be extremely thin. Therefore, it can be suitably applied to a flexible image display device. More preferably, the image display device has a curved shape (substantially a curved display screen) and / or is bendable or bendable. Specific examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). Needless to say, the above description does not prevent the polarizing plate of the present invention from being applied to a normal image display device.

A-2. Outline of Polarizing Plate with Optical Functional Layer FIG. 2 is a schematic cross-sectional view of a polarizing plate with an optical functional layer according to one embodiment of the present invention. The polarizing plate 110 with an optical functional layer of the illustrated example includes a polarizing element 10, a protective layer 20 arranged on one side of the polarizer, and an optical functional layer 30 arranged on the other side of the polarizer. .. The total thickness of the polarizing plate with an optical functional layer is 25 μm or less. In one embodiment, the polarizing plate 10 and the polarizing plate 100 are used as the protective layer 20.

The total thickness of the polarizing plate 110 with an optical functional layer is 25 μm or less, preferably 20 μm or less, and more preferably 15 μm or less. According to the present invention, it is possible to provide a polarizing plate having both excellent durability and excellent flexibility even when the total thickness of the polarizing plate is within the above range. The total thickness of the polarizing plate with an optical functional layer is, for example, 10 μm or more.

In one embodiment, the optical functional layer functions as a protective layer separate from the protective layer 20. Such a protective layer can also function as a retardation layer having predetermined retardation and optical characteristics. In another embodiment, the optical functional layer is a retardation layer having a circularly polarized light function or an elliptically polarized light function. Such a retardation layer can also function as a protective layer for the polarizer. When the optical functional layer is a retardation layer, in one embodiment, the retardation layer is an orientation-solidified layer of a liquid crystal compound. The retardation layer may be a single layer of the orientation solidification layer, or may have a laminated structure of the first orientation solidification layer and the second orientation solidification layer. Hereinafter, a polarizing plate in which the optical functional layer is a retardation layer may be referred to as a polarizing plate with a retardation layer.

Each layer or optical film constituting the polarizing plate with an optical functional layer is typically bonded via an adhesive layer. Examples of the adhesive layer include an adhesive layer and an adhesive layer. In the embodiment of the present invention, the adhesive layer can be preferably adopted. With such a configuration, the polarizing plate with an optical functional layer can be further thinned. Typical examples of the adhesive constituting the adhesive layer include an active energy ray-curable adhesive (for example, an ultraviolet curable adhesive).

A polarizing plate provided with an optical functional layer that functions as a retardation layer may be further provided with another retardation layer. Another retardation layer is typically provided on the outside (opposite side of the polarizer 10) of the optical functional layer (phase difference layer) 30. Another retardation layer typically exhibits a relationship in which the refractive index characteristic is nz> nz = ny. Such another retardation layer is preferably provided when the retardation layer is a single layer of an oriented solidification layer. For convenience, the optical functional layer (phase difference layer) 30 may be referred to as a first retardation layer, and another retardation layer may be referred to as a second retardation layer. The polarizing plate with an optical functional layer may further include other retardation layers. The optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, and the like of the other retardation layers can be appropriately set according to the purpose.

The polarizing plate with an optical functional layer may be provided with a conductive layer or an isotropic base material with a conductive layer. The conductive layer or the isotropic base material with the conductive layer is typically provided on the outside of the optical functional layer 30 (opposite to the polarizer 10). When the polarizing plate is a polarizing plate with a retardation layer having a retardation layer and another retardation layer, the other retardation layer and the conductive layer or the isotropic base material with the conductive layer are typically positioned. It is provided in this order from the phase difference layer (optical functional layer) 30 side. When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate or the polarizing plate with a retardation layer has a so-called touch sensor incorporated between an image display cell (for example, an organic EL cell) and the polarizing plate. It can be applied to an inner touch panel type input display device.

As described above, the protective layer is composed of a solidified coating film of a thermoplastic acrylic resin in an organic solvent solution, and the glass transition temperature is set to 95 ° C. or higher, so that the protective layer is durable even though it is very thin. It is possible to realize an excellent polarizing plate. Specifically, it is possible to realize a polarizing plate in which deterioration of optical characteristics is suppressed even in a heating and humidifying environment. The polarizing plate has very small changes in the simple substance transmittance Ts ΔTs and changes in the degree of polarization P ΔP after being left in an environment of 85 ° C. and 85% RH for 48 hours. The simple substance transmittance Ts can be measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The degree of polarization P is calculated by the following equation from the single transmittance (Ts), the parallel transmittance (Tp) and the orthogonal transmittance (Tc) measured using an ultraviolet-visible spectrophotometer.
Polarization degree (P) (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
The Ts, Tp, and Tc are Y values measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. Also, Ts and P are substantially properties of the polarizer. ΔTs and ΔP are calculated by the following formulas, respectively.
ΔTs (%) = Ts ₄₈ _{-Ts 0}
ΔP (%) = P ₄₈ −P ₀
Here, Ts ₀ is the single transmittance before leaving (initial), Ts ₄₈ is the single transmittance after leaving, P ₀ is the degree of polarization before leaving (initial), and P ₄₈ is after leaving. The degree of polarization. ΔTs is preferably 3.0% or less, more preferably 2.7% or less, still more preferably 2.4% or less. ΔP is preferably −1.0% to 0%, more preferably −0.5% to 0%, and even more preferably −0.3% to 0%.

Practically, an adhesive layer (not shown) is provided on the opposite side of the optical functional layer from the polarizer, and the polarizing plate can be attached to the image display cell. Further, it is preferable that a release film is temporarily attached to the surface of the pressure-sensitive adhesive layer until the polarizing plate is used. By temporarily attaching the release film, the pressure-sensitive adhesive layer can be protected and rolls can be formed.

The polarizing plate and the polarizing plate with an optical functional layer of the present invention may be single-wafered or elongated. As used herein, the term "long" means an elongated shape having a length sufficiently long with respect to the width, and for example, an elongated shape having a length of 10 times or more, preferably 20 times or more with respect to the width. include. The elongated polarizing plate can be wound in a roll shape.

Hereinafter, the components of the polarizing plate and the polarizing plate with the optical functional layer will be described in more detail.

B. Polarizer As the polarizer, any suitable polarizer can be adopted. The polarizer can typically be made using a laminate of two or more layers. The method for manufacturing the polarizer will be described later in Section F as a method for manufacturing the polarizing plate.

The thickness of the polarizer is preferably 10 μm or less, more preferably 1 μm to 8 μm, further preferably 1 μm to 7 μm, and particularly preferably 2 μm to 5 μm.

The boric acid content of the polarizer is preferably 10% by weight or more, more preferably 13% by weight to 25% by weight. When the boric acid content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the iodine content described later, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. The boric acid content can be calculated as, for example, the amount of boric acid contained in the polarizer per unit weight by using the following formula from the neutralization method.

The iodine content of the polarizer is preferably 2% by weight or more, more preferably 2% by weight to 10% by weight. When the iodine content of the polarizer is in such a range, the ease of curl adjustment at the time of bonding is well maintained due to the synergistic effect with the above boric acid content, and the curl at the time of heating is maintained. It is possible to improve the appearance durability at the time of heating while satisfactorily suppressing the above. As used herein, the term "iodine content" means the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine during polarizers iodide ion (I ^-), molecular iodine (I _2), polyiodine ion _{^{_{(I 3 -, I 5 -}}} ) where present in the form of such, herein Iodine content means the amount of iodine that includes all of these forms. The iodine content can be calculated, for example, by the calibration curve method of fluorescent X-ray analysis. The polyiodine ion exists in a state in which a PVA-iodine complex is formed in the polarizer. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, a complex of PVA and tri-iodide ion (PVA · _{I 3} ^-) has a light absorption peak around 470 nm, a complex of PVA and five iodide ion (PVA · _{I 5} ^-) is 600nm near Has an absorptive peak. As a result, polyiodine ions can absorb light over a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak near 230 nm and is not substantially involved in the absorption of visible light. Therefore, polyiodine ions present in the form of a complex with PVA may be mainly involved in the absorption performance of the polarizer.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance Ts of the polarizer is preferably 40% to 48%, more preferably 41% to 46%. The degree of polarization P of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

C. Protective layer As described above, the protective layer is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin (hereinafter, simply referred to as an acrylic resin). Hereinafter, the constituent components of the protective layer will be specifically described, and then the characteristics of the protective layer will be described.

C-1. Acrylic resin The Tg of an acrylic resin (including a blend of two or more kinds of acrylic resins and a blend of an acrylic resin and another resin as described later) is as described in Section A above regarding the protective layer. be.

As the acrylic resin, any suitable acrylic resin can be adopted as long as it has Tg as described above. Acrylic resins typically contain an alkyl (meth) acrylate as a main component as a monomer unit (repeating unit). As used herein, the term "(meth) acrylic" means acrylic and / or methacryl. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Further, any suitable copolymerization monomer may be introduced into the acrylic resin by copolymerization. The repeating unit derived from alkyl (meth) acrylate is typically represented by the following general formula (1):

In the general formula (1), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or an aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms which may be substituted. show. Examples of the substituent include halogens and hydroxyl groups. Specific examples of alkyl (meth) acrylate include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate, and t-butyl (meth) acrylate. Butyl, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, benzyl (meth) acrylate, dicyclopentanyloxyethyl (meth) acrylate, (meth) acrylic Dicyclopentanyl acid, chloromethyl (meth) acrylate, 2-chloroethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2, (meth) acrylate 2, 3,4,5,6-pentahydroxyhexyl, (meth) acrylate 2,3,4,5-tetrahydroxypentyl, methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, 2 -(Hydroxyethyl) methyl acrylate can be mentioned. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, a particularly preferred alkyl (meth) acrylate is methyl acrylate or methyl methacrylate.

Acrylic resins may also include only a single alkyl (meth) acrylate units, even if R ⁴ and R ⁵ include a plurality of different alkyl (meth) acrylate unit in the above general formula (1) good.

The content ratio of the alkyl (meth) acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, still more preferably 60 mol% to 98 mol%, and particularly preferably. It is 65 mol% to 98 mol%, most preferably 70 mol% to 97 mol%. If the content ratio is less than 50 mol%, the effects expressed from the alkyl (meth) acrylate unit (for example, high heat resistance and high transparency) may not be sufficiently exhibited. If the content ratio is more than 98 mol%, the resin is brittle and easily cracked, high mechanical strength cannot be sufficiently exhibited, and productivity may be inferior.

The acrylic resin preferably has a repeating unit containing a ring structure. Examples of the repeating unit including a ring structure include a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. Only one type of the repeating unit including the ring structure may be contained in the repeating unit of the acrylic resin, or two or more types may be contained.

The lactone ring unit is preferably represented by the following general formula (2):

In the general formula (2), R ¹ , R ² and R ³ independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. The acrylic resin may be contained only a single lactone ring units may be R ^1, R ² and R ³ in the general formula (2) is contains different lactone ring unit .. An acrylic resin having a lactone ring unit is described in, for example, Japanese Patent Application Laid-Open No. 2008-181078, and the description in this publication is incorporated herein by reference.

The glutarimide unit is preferably represented by the following general formula (3):

In the general formula (3), R ¹¹ and R ¹² independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, and R ¹³ is an alkyl group having 1 to 18 carbon atoms and 3 to 12 carbon atoms. The cycloalkyl group of the above, or an aryl group having 6 to 10 carbon atoms is shown. In the general formula (3), preferably R ¹¹ and R ¹² are independently hydrogen or methyl groups, and R ¹³ is a hydrogen, methyl group, butyl group or cyclohexyl group, respectively. More preferably, R ¹¹ is a methyl group, R ¹² is hydrogen, and R ¹³ is a methyl group. The acrylic resin may contain only a single glutarimide unit, or may contain a plurality of glutarimide units having different ^{R 11} , R ¹² and R ^{13 in the above general formula (3).} .. Examples of the acrylic resin having a glutarimide unit include JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491, and JP-A-2006-337492. It is described in Japanese Patent Application Laid-Open No. 2006-337493 and Japanese Patent Application Laid-Open No. 2006-337569, and the description of this publication is incorporated herein by reference. Note that the glutaric anhydride units, nitrogen atom substituted by R ¹³ in the general formula (3), except that the oxygen atom, the above description is applied about the glutarimide units.

The structure of the maleic anhydride unit and the maleimide (N-substituted maleimide) unit is specified from the name, so specific description thereof will be omitted.

The content ratio of the repeating unit including the ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and further preferably 20 mol% to 30 mol%. If the content ratio is too small, Tg may be less than 110 ° C., and the heat resistance, solvent resistance and surface hardness of the obtained protective layer may be insufficient. If the content is too high, moldability and transparency may be insufficient.

The acrylic resin may contain a repeating unit other than the alkyl (meth) acrylate unit and the repeating unit including the ring structure. Examples of such a repeating unit include a repeating unit derived from a vinyl-based monomer copolymerizable with the monomer constituting the above unit (another vinyl-based monomer unit). Examples of other vinyl-based monomers include acrylic acid, methacrylic acid, crotonic acid, 2- (hydroxymethyl) acrylic acid, 2- (hydroxyethyl) acrylic acid, acrylonitrile, methacrylonitrile, etacrylonitrile, and allyl. Glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, methacryl Cyclohexylaminoethyl acid, N-vinyldiethylamine, N-acetylvinylamine, allylamine, metaallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2-vinyl-oxazoline, 2-acroyl-oxazoline, N-phenylmaleimide, Examples thereof include phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, and 2-styryl-oxazoline. These may be used alone or in combination. The type, number, combination, content ratio, etc. of other vinyl-based monomer units can be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1,000,000 to 2000000, more preferably 5000 to 1,000,000, further preferably 10000 to 500000, particularly preferably 50,000 to 500000, and most preferably 60000 to 150,000. The weight average molecular weight can be determined by polystyrene conversion using, for example, a gel permeation chromatograph (GPC system, manufactured by Tosoh). Tetrahydrofuran can be used as the solvent.

The acrylic resin can be polymerized by any suitable polymerization method by using the above-mentioned monomer units in an appropriate combination. Two or more kinds of acrylic resins having different monomer units may be blended.

In the embodiment of the present invention, an acrylic resin and another resin may be used in combination. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be used for molding the protective layer described later; the acrylic resin and the other resin. The blend of may be used for forming the protective layer. Examples of other resins include thermoplastic resins such as styrene resin, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. The type and blending amount of the resin to be used in combination can be appropriately set according to the purpose and the desired properties of the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a retardation control agent.

When the acrylic resin is used in combination with another resin, the content of the acrylic resin in the blend of the acrylic resin and the other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight. By weight%, more preferably 70% by weight to 100% by weight, particularly preferably 80% by weight to 100% by weight. If the content is less than 50% by weight, the high heat resistance and high transparency inherent in the acrylic resin may not be sufficiently reflected.

C-2. Composition and Characteristics of Protective Layer As described above, the protective layer is composed of a solidified coating film of an organic solvent solution of an acrylic resin. With such a solidified coating film, the thickness can be significantly reduced as compared with the extrusion-molded film. As described above, the thickness of the protective layer is 10 μm or less, preferably 7 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. The lower limit of the thickness of the protective layer can be, for example, 1 μm. Further, although it is not theoretically clear, such a solidified coating film is compared with a cured product of a thermosetting resin or an active energy ray-curable resin (for example, an ultraviolet curable resin) at the time of film molding. Since the shrinkage is small and the residual monomer or the like is not contained, deterioration of the film itself can be suppressed, and the adverse effect on the polarizing plate (polarizer) caused by the residual monomer or the like can be suppressed. Further, it has an advantage that it is excellent in humidification durability because it has low hygroscopicity and moisture permeability as compared with a solidified water-based coating film such as an aqueous solution or an aqueous dispersion. As a result, it is possible to realize a polarizing plate having excellent durability (as a result, a polarizing plate with a retardation layer) that can maintain optical characteristics even in a heating and humidifying environment.

The Tg of the protective layer is as described in Section A above.

The amount of iodine adsorbed in the protective layer is preferably 4.0% by weight or less, more preferably 3.0% by weight or less, still more preferably 2.0% by weight or less, and particularly preferably 1.0% by weight. % Or less, particularly preferably 0.5% by weight or less. The smaller the amount of iodine adsorbed, the more preferable, and the lower limit thereof can be, for example, 0.1% by weight. When the amount of iodine adsorbed is within such a range, a polarizing plate having even better durability (as a result, a polarizing plate with a retardation layer) can be obtained. The iodine adsorption amount can be measured by the method described in Examples described later.

The protective layer is preferably substantially optically isotropic. In the present specification, "substantially optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is −20 nm to +10 nm. Say something. The in-plane retardation Re (550) is more preferably 0 nm to 5 nm, further preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The phase difference Rth (550) in the thickness direction is more preferably −5 nm to + 5 nm, further preferably -3 nm to + 3 nm, and particularly preferably -2 nm to + 2 nm. When Re (550) and Rth (550) of the protective layer are in such a range, it is possible to prevent adverse effects on the display characteristics when a polarizing plate with a retardation layer including the protective layer is applied to an image display device. can.

The higher the light transmittance at 380 nm when the thickness of the protective layer is 3 μm, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. When the light transmittance is in such a range, the desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the protective layer, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1% or less. When the haze is 5% or less, a good clear feeling can be given to the film. Further, even when a polarizing plate with a retardation layer is used on the visual side of the image display device, the displayed contents can be visually recognized satisfactorily.

The YI at a thickness of 3 μm of the protective layer is preferably 1.27 or less, more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20 or less. If the YI exceeds 1.3, the optical transparency may be insufficient. YI is obtained from, for example, the tristimulus values (X, Y, Z) of the color obtained by measurement using a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory). , Can be calculated by the following equation.
YI = [(1.28X-1.06Z) / Y] x 100

The b value (a measure of hue according to the hunter's color system) at a thickness of 3 μm of the protective layer is preferably less than 1.5, more preferably 1.0 or less. When the b value is 1.5 or more, an undesired color may appear. For the b value, for example, a sample of the film constituting the protective layer is cut into 3 cm squares, and a high-speed integrating sphere type spectral transmittance measuring machine (trade name: DOT-3C: manufactured by Murakami Color Technology Laboratory) is used to determine the hue. Can be obtained by measuring and evaluating the hue according to the color system of the hunter.

The protective layer (solidified coating film) may contain any suitable additive depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol-based, phosphorus-based, and sulfur-based; stabilizers such as light-resistant stabilizers, weather-resistant stabilizers, and heat-stabilizing agents; glass fibers, Reinforcing materials such as carbon fibers; Near infrared absorbers; Flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, antimony oxide; Antistatic agents such as anionic, cationic and nonionic surfactants; Inorganic pigments , Organic pigments, colorants such as dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers and inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants; and the like. The additive may be added at the time of polymerization of the acrylic resin, or may be added to the solution at the time of film formation. The type, number, combination, amount of additive, etc. of the additive can be appropriately set according to the purpose.

An easy-adhesion layer may be formed on the polarizer side of the protective layer. The easy-adhesion layer contains, for example, an aqueous polyurethane and an oxazoline-based cross-linking agent. By forming such an easy-adhesion layer, the adhesion between the protective layer and the polarizer can be improved. Further, a hard coat layer may be formed on the protective layer. The hard coat layer can be formed when the protective layer is used as the visible protective layer of the visible polarizing plate. When both the easy-adhesion layer and the hard coat layer are formed, typically they can be formed on different sides of the protective layer, respectively.

D. Optical functional layer D-1. Optical functional layer which is a protective layer When the optical functional layer 30 functions as a protective layer different from the protective layer 20, the protective layer is preferably a thin protective layer having a thickness of 20 μm or less. The thickness of the protective layer is more preferably 18 μm or less, further preferably 15 μm or less, and particularly preferably 10 μm or less. The thickness of the protective layer can be, for example, 1 μm or more.

The protective layer (optical functional layer) may be made of a resin film or a solidified coating film. Examples of the resin constituting the resin film include cycloolefin-based resin and acrylic-based resin. The solidified coating film may be, for example, a solidified coating film of a predetermined acrylic resin in an organic solvent solution, or a solidified coating film in an organic solvent solution of an epoxy resin. When the protective layer is composed of a solidified coating film, the thickness can be significantly reduced as compared with the resin film.

When the protective layer, which is a solidified product of the coating film, is a solidified product of a coating film of an organic solvent solution of an epoxy resin, any suitable epoxy resin can be used as the epoxy resin. An epoxy resin having a glass transition temperature of 90 ° C. or higher is preferably used. As the epoxy resin, an epoxy resin having an aromatic ring in the molecular structure is preferably used. By using an epoxy resin having an aromatic ring, an epoxy resin having a higher Tg can be obtained. Examples of the aromatic ring in the epoxy resin having an aromatic ring in the molecular structure include a benzene ring, a naphthalene ring, a fluorene ring and the like. Only one type of epoxy resin may be used, or two or more types may be used in combination. When two or more kinds of epoxy resins are used, an epoxy resin containing an aromatic ring and an epoxy resin not containing an aromatic ring may be used in combination.

The protective layer (optical functional layer) is typically arranged on the image display cell side when the polarizing plate is applied to the image display device. In one embodiment, the protective layer is preferably optically isotropic. As used herein, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. say. In another embodiment, the protective layer may be a retardation layer having any suitable retardation value. In this case, the in-plane retardation Re (550) of the protective layer (phase difference layer) is, for example, 110 nm to 150 nm.

D-2. Optical functional layer that is a retardation layer having a circularly polarized light function or an elliptically polarized function When the optical functional layer 30 is a retardation layer having a circularly polarized light function or an elliptically polarized function, the retardation layer is a stretched film of a resin film. It may be an oriented solidified layer of a liquid crystal compound. It is preferably an oriented solidified layer of the liquid crystal compound. By using the liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be made much larger than that of the non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be obtained. Can be made much smaller than the stretched film. As a result, it is possible to further reduce the thickness of the polarizing plate with a retardation layer. Further, it is possible to realize a polarizing plate with a retardation layer having extremely excellent flexibility. Hereinafter, the oriented solidified layer of the liquid crystal compound will be described in detail. The retardation layer made of a stretched film of a resin film is described in, for example, JP-A-2017-54093 and JP-A-2018-60014. The description of these publications is incorporated herein by reference.

In the present specification, the "aligned solidified layer" means a layer in which the liquid crystal compound is oriented in a predetermined direction in the layer and the oriented state is fixed. The "oriented solidified layer" is a concept including an oriented cured layer obtained by curing a liquid crystal monomer as described later. In the present embodiment, the rod-shaped liquid crystal compounds are typically oriented in a state of being aligned in the slow-phase axial direction of the first retardation layer (homogeneous orientation).

Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When 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 orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (that is, curing) the liquid crystal monomer. After the liquid crystal monomers are oriented, for example, if the liquid crystal monomers are polymerized or crosslinked with each other, the oriented state can be fixed. Here, the polymer is formed by polymerization, and the three-dimensional network structure is formed by cross-linking, but these are non-liquid crystal. Therefore, the formed first retardation layer does not undergo a transition to a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the first retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs depending on the type. Specifically, the temperature range is preferably 40 ° C. to 120 ° C., more preferably 50 ° C. to 100 ° C., and most preferably 60 ° C. to 90 ° C.

Any suitable liquid crystal monomer can be adopted as the liquid crystal monomer. For example, the polymerizable mesogen compounds described in Special Tables 2002-533742 (WO00 / 37585), EP358208 (US5211877), EP66137 (US4388453), WO93 / 22397, EP02671712, DE19504224, DE4408171, GB2280445 and the like can be used. Specific examples of such a polymerizable mesogen compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Silicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

Orientation of liquid crystal compound The solidified layer is subjected to an orientation treatment on the surface of a predetermined base material, and a coating liquid containing the liquid crystal compound is applied to the surface to orient the liquid crystal compound in a direction corresponding to the orientation treatment. It can be formed by fixing the orientation state. In one embodiment, the substrate is any suitable resin film and the oriented solidified layer formed on the substrate can be transferred to the surface of the polarizer 10.

As the orientation treatment, any appropriate orientation treatment can be adopted. Specific examples thereof include mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment. Specific examples of the mechanical orientation treatment include a rubbing treatment and a stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical alignment treatment include an orthorhombic deposition method and a photoalignment treatment. As the treatment conditions for various orientation treatments, any appropriate conditions can be adopted depending on the purpose.

The orientation of the liquid crystal compound is performed by treating at a temperature indicating the liquid crystal phase according to the type of the liquid crystal compound. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is oriented according to the orientation treatment direction of the surface of the base material.

In one embodiment, the orientation state is fixed by cooling the liquid crystal compound oriented as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the orientation state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the oriented solidified layer are described in JP-A-2006-163343. The description of this publication is incorporated herein by reference.

Another example of the oriented solidified layer is a form in which the discotic liquid crystal compound is oriented in any of vertical orientation, hybrid orientation, and inclined orientation. In the discotic liquid crystal compound, typically, the disk surface of the discotic liquid crystal compound is oriented substantially perpendicular to the film surface of the first retardation layer. When the discotic liquid crystal compound is substantially vertical, the average value of the angles formed by the film surface and the disk surface of the discotic liquid crystal compound is preferably 70 ° to 90 °, more preferably 80 ° to 90 °. , More preferably, it means that it is 85 ° to 90 °. A discotic liquid crystal compound generally has a cyclic mother nuclei such as benzene, 1,3,5-triazine, and calix arene in the center of the molecule, and has a linear alkyl group, an alkoxy group, and a substituted benzoyl. A liquid crystal compound having a disk-like molecular structure in which an oxy group or the like is radially substituted as its side chain. Typical examples of discotic liquid crystals include C.I. Research report by Destrade et al., Mol. Cryst. Liq. Cryst. Benzene derivatives, triphenylene derivatives, tolucene derivatives, phthalocyanine derivatives, and B.I. Research report by Kohne et al., Angew. Chem. Cyclohexane derivatives described in Volume 96, p. 70 (1984), and J. Mol. M. Research report by Lehn et al., J. Mol. Chem. Soc. Chem. Commun. , 1794 (1985), J. Mol. Research report by Zhang et al., J. Mol. Am. Chem. Soc. Examples thereof include the aza-crown-based and phenylacetylene-based macrocycles described in Volume 116, p. 2655 (1994). Further specific examples of the discotic liquid crystal compound include the compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The above references and publications are incorporated herein by reference.

In one embodiment, the retardation layer (optical functional layer) 30 is a single layer of the orientation-solidified layer of the liquid crystal compound. When the retardation layer (hereinafter, may be referred to as the first retardation layer as described above) is composed of a single layer of the oriented solidification layer of the liquid crystal compound, the thickness thereof is preferably 0.5 μm to 7 μm. , More preferably 1 μm to 5 μm. By using the liquid crystal compound, it is possible to realize an in-plane phase difference equivalent to that of the resin film with a thickness much thinner than that of the resin film.

The first retardation layer typically shows a relationship in which the refractive index characteristic is nx> ny = nz. The first retardation layer is typically provided to impart antireflection characteristics to the polarizing plate, and functions as a λ / 4 plate when the first retardation layer is a single layer of an orientation solidification layer. Can be done. In this case, the in-plane retardation Re (550) of the first retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. Here, "ny = nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, ny> nz or ny <nz may occur within a range that does not impair the effects of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3. By satisfying such a relationship, a very excellent reflected hue can be achieved when the obtained polarizing plate with a retardation layer is used in an image display device.

The first retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, and a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may be shown, or may show a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measurement light. In one embodiment, the first retardation layer exhibits inverse dispersion wavelength characteristics. In this case, the Re (450) / Re (550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be realized.

The angle θ formed by the slow axis of the first retardation layer and the absorption axis of the polarizer 10 is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and even more preferably about 45 °. °. If the angle θ is in such a range, by using the λ / 4 plate as the first retardation layer as described above, very excellent circularly polarized light characteristics (as a result, very excellent antireflection characteristics). A polarizing plate with a retardation layer having the above can be obtained.

In another embodiment, the first retardation layer may have a laminated structure of a first oriented solidified layer and a second oriented solidified layer. In this case, either one of the first oriented solidified layer and the second oriented solidified layer may function as a λ / 4 plate, and the other may function as a λ / 2 plate. Therefore, the thicknesses of the first oriented solidified layer and the second oriented solidified layer can be adjusted so as to obtain a desired in-plane phase difference between the λ / 4 plate or the λ / 2 plate. For example, when the first oriented solidified layer functions as a λ / 2 plate and the second oriented solidified layer functions as a λ / 4 plate, the thickness of the first oriented solidified layer is, for example, 2.0 μm to 3.0 μm. The thickness of the second oriented solidified layer is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re (550) of the first oriented solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and further preferably 250 nm to 280 nm. The in-plane retardation Re (550) of the second oriented solidified layer is as described above with respect to the single oriented solidified layer. The angle formed by the slow axis of the first oriented solidification layer and the absorption axis of the polarizer is preferably 10 ° to 20 °, more preferably 12 ° to 18 °, and even more preferably about 15 °. be. The angle formed by the slow axis of the second oriented solidification layer and the absorption axis of the polarizer is preferably 70 ° to 80 °, more preferably 72 ° to 78 °, and even more preferably about 75 °. be. With such a configuration, it is possible to obtain characteristics close to the ideal reverse wavelength dispersion characteristic, and as a result, it is possible to realize extremely excellent antireflection characteristics. The liquid crystal compounds constituting the first oriented solidified layer and the second oriented solidified layer, the method for forming the first oriented solidified layer and the second oriented solidified layer, the optical properties, and the like are described above with respect to the single oriented solidified layer. As explained in.

As described above, the second retardation layer can be a so-called positive C plate in which the refractive index characteristic shows a relationship of nz> nx = ny. By using the positive C plate as the second retardation layer, it is possible to satisfactorily prevent reflection in the oblique direction, and it is possible to widen the viewing angle of the antireflection function. The second retardation layer is preferably provided when the first retardation layer is a single layer of the orientation solidification layer. The retardation Rth (550) in the thickness direction of the second retardation layer is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, still more preferably −90 nm to −200 nm, and 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. That is, the in-plane retardation Re (550) of the second retardation layer can be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz> nx = ny can be formed of any suitable material. The second retardation layer preferably consists of a film containing a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can be homeotropically oriented may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compounds described in [0020] to [0028] of JP-A-2002-333642 and the method for forming the retardation layer. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and even more preferably 0.5 μm to 5 μm.

E. Conductive layer or isotropic base material with conductive layer The conductive layer is made of any suitable base material by any suitable film forming method (for example, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, etc.). It can be formed by forming a metal oxide film on top of it. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimon composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Of these, indium-tin composite oxide (ITO) is preferable.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer may be transferred from the base material to an optical functional layer (or a second retardation layer if present), and the conductive layer alone may be used as a constituent layer of a polarizing plate with a retardation layer. It may be laminated on the optical functional layer (or the second retardation layer if present) as a laminate with the material (base material with a conductive layer). Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used in the polarizing plate as an isotropic substrate with a conductive layer.

Any suitable isotropic base material can be adopted as the optically isotropic base material (isotropic base material). Examples of the material constituting the isotropic base material include a material having a resin having no conjugate system such as a norbornene resin and an olefin resin as a main skeleton, and an acrylic resin having a cyclic structure such as a lactone ring and a glutarimide ring. Examples include the material contained in the main chain. When such a material is used, when an isotropic base material is formed, the occurrence of the phase difference due to the orientation of the molecular chains can be suppressed to be small. The thickness of the isotropic base material is preferably 50 μm or less, more preferably 35 μm or less. The thickness of the isotropic base material is, for example, 20 μm or more.

The conductive layer and / or the conductive layer of the isotropic base material with the conductive layer can be patterned as needed. By patterning, a conductive portion and an insulating portion can be formed. As a result, electrodes can be formed. The electrode can function as a touch sensor electrode that senses contact with the touch panel. As the patterning method, any suitable method can be adopted. Specific examples of the patterning method include a wet etching method and a screen printing method.

F. Method for manufacturing polarizing plate F-1. Method for producing a polarizer The method for producing a polarizer according to the above item B is a polyvinyl alcohol-based resin containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material. A layer (PVA-based resin layer) is formed to form a laminated body, and the laminated body is heated in the width direction while being conveyed in the longitudinal direction by aerial auxiliary stretching treatment, dyeing treatment, and underwater stretching treatment. A drying shrinkage treatment for shrinking by 2% or more, and a drying shrinkage treatment, which are performed in this order, are included. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably carried out using a heating roll, and the temperature of the heating roll is preferably 60 ° C. to 120 ° C. According to such a manufacturing method, the above-mentioned polarizer can be obtained. In particular, by preparing a laminate containing a PVA-based resin layer containing a halide, stretching the laminate to multi-step stretching including aerial auxiliary stretching and underwater stretching, and heating the stretched laminate with a heating roll. It is possible to obtain a polarizer having excellent optical characteristics (typically, single transmittance and degree of polarization) and suppressing variation in optical characteristics. Specifically, by using a heating roll in the drying shrinkage treatment step, the laminated body can be uniformly shrunk over the entire laminated body while being conveyed. As a result, not only the optical characteristics of the obtained polarizer can be improved, but also a polarizer having excellent optical characteristics can be stably produced, and the variation in the optical characteristics of the polarizer (particularly, the single transmittance) can be suppressed. can do. Hereinafter, the halide and the drying shrinkage treatment will be described. Details of manufacturing methods other than these are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent No. 6470455. The entire description of the publication is incorporated herein by reference.

F-1-1. Halide A PVA-based resin layer containing a halide and a PVA-based resin can be formed by applying a coating liquid containing a halide and a PVA-based resin onto a thermoplastic resin base material and drying the coating film. The coating liquid is typically a solution in which the above-mentioned halide and the above-mentioned PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Of these, water is preferred. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed in close contact with the thermoplastic resin base material.

As the halide, any suitable halide can be adopted. For example, iodide and sodium chloride can be mentioned. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Of these, potassium iodide is preferred.

The amount of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. If the amount of the halide is too large, the halide may bleed out and the finally obtained polarizer may become cloudy.

Generally, the stretching of the PVA-based resin layer increases the orientation of the polyvinyl alcohol molecules in the PVA-based resin. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become more oriented. The orientation may be disturbed and the orientation may decrease. In particular, when the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. When stretched, the tendency of the degree of orientation to decrease is remarkable. For example, while stretching a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water. On the other hand, a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material is prepared, and the laminate is stretched at a high temperature (auxiliary stretching) in the air before being stretched in boric acid water. , Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. As a result, the optical characteristics of the polarizer obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water, can be improved.

F-1-2. Dry shrinkage treatment The dry shrinkage treatment may be carried out by heating the entire zone by zone heating, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably, both are used. By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminate and produce a polarizer having an excellent appearance. Specifically, by drying the laminate along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin base material can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased, and the thermoplastic resin base material is in a state of being able to withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the drying shrinkage treatment is preferably 2% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using the heating roll, the laminated body can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.

FIG. 3 is a schematic view showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. For example, one surface of the laminate 200 (for example, thermoplastic) is arranged. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin base material surface).

Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and particularly preferably 70 ° C. to 80 ° C. The crystallinity of the thermoplastic resin can be satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using both drying with a heating roll and hot air drying together, a steep temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30 ° C to 100 ° C. The hot air drying time is preferably 1 second to 300 seconds. The wind speed of hot air is preferably about 10 m / s to 30 m / s. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.

Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

In this way, a laminate of a thermoplastic resin base material / polarizer can be obtained.

F-2. Method for manufacturing polarizing plate A protective layer is formed by applying an organic solvent solution of an acrylic resin to the surface on the polarizer side of the laminate obtained in the above section F-1 to form a coating film, and solidifying the coating film. Is formed.

The acrylic resin is as described in Section C-1 above.

As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the acrylic resin can be used. Specific examples of the organic solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The concentration of the acrylic resin in the solution is preferably 3 to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the polarizer can be formed.

The solution may be applied to any suitable substrate or to a polarizer. When the solution is applied to the substrate, the solidified material of the coating film formed on the substrate is transferred to the polarizer. When the solution is applied to the polarizer, the protective layer is directly formed on the polarizer by drying (solidifying) the coating film. Preferably, the solution is applied to the polarizer and a protective layer is formed directly on the polarizer. With such a configuration, the adhesive layer or the pressure-sensitive adhesive layer required for transfer can be omitted, so that the polarizing plate with a retardation layer can be further thinned. Any suitable method can be adopted as the method for applying the solution. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.).

A protective layer can be formed by drying (solidifying) the coating film of the solution. The drying temperature is preferably 100 ° C. or lower, more preferably 50 ° C. to 70 ° C. When the drying temperature is in such a range, it is possible to prevent an adverse effect on the polarizer. The drying time can vary depending on the drying temperature. The drying time can be, for example, 1 minute to 10 minutes.

As described above, the protective layer is formed, and as a result, a laminate of the thermoplastic resin base material / polarizer / protective layer can be obtained. By peeling the thermoplastic resin base material from this laminate, a polarizing plate having a polarizing element 10 and a protective layer 20 as shown in FIG. 1 can be obtained. Alternatively, a resin film constituting another protective layer is attached to the polarizer surface of the laminate of the thermoplastic resin base material / polarizer, and then the thermoplastic resin base material is peeled off to form a protective layer on the peeled surface. You may. In this case, a polarizing plate having another protective layer can be obtained.

G. Method for manufacturing a polarizing plate with an optical functional layer A polarizing plate with an optical functional layer can be manufactured by any suitable method. For example, it can be produced by producing a polarizing plate by the method described in the above item F, and laminating or transferring an arbitrary appropriate optical functional layer on the polarizer side of the polarizing plate. The optical functional layer may be laminated on the polarizer via any suitable adhesive layer, or may be formed directly on the polarizer.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in the examples are based on weight.

(1) Glass transition temperature Tg
A solution prepared by dissolving the material constituting the protective layer used in Examples and Comparative Examples in a predetermined solvent is applied to a base material (PET film) by an applicator and dried at 60 ° C. to form a coating film (thickness 40 μm). bottom. The obtained coating film was peeled off from the base material and cut into strips to prepare a measurement sample. The measurement sample was subjected to DMA measurement, and Tg was measured. The measuring device and measuring conditions were as follows.
(measuring device)
"DMS6100" manufactured by SII Nanotechnology Inc.
(Measurement condition)
-Measurement temperature range: -80 ° C to 150 ° C
・ Elevating temperature: 2 ℃ / min ・ Measurement sample width: 10mm
・ Distance between chucks: 20 mm
・ Measurement frequency: 1Hz
・ Strain amplitude: 10 μm
・ Measurement atmosphere: N ₂ (250 mL / min)
(2) Amount of Iodine Adsorption A solution prepared by dissolving the material constituting the protective layer used in Examples and Comparative Examples in a predetermined solvent is applied to a base material (PET film) by an applicator, dried at 60 ° C., and coated. (Thickness 40 μm) was formed. The obtained coating film was peeled off from the base material ^{and cut into 1 cm × 1 cm (1 cm 2} ) to prepare a measurement sample. The measurement sample was subjected to a combustion IC method, and the amount of iodine in the sample was quantitatively analyzed. Specifically, it is as follows. The measurement sample was collected and weighed in a headspace vial (20 mL volume). Next, a vial (2 mL volume) containing 1 mL of an iodine aqueous solution (iodine concentration 1% by weight, potassium iodide concentration 7% by weight) was placed in this headspace vial and sealed. After that, this headspace vial is heated in a dryer at 65 ° C. for 6 hours, the heated sample is collected in a ceramic port and burned using an automatic combustion device, and the generated gas is collected in an absorbing liquid and then quantified. The analysis was performed to determine the weight% of the adsorbed iodine. The equipment used was as follows.
-Automatic sample combustion device: "AQF-2100H" manufactured by Mitsubishi Chemical Analytical Co., Ltd.
-IC (anion): "ICS-3000" manufactured by Thermo Fisher Scientific.
(3) Single-unit transmittance and degree of polarization From the polarizing plate with an optical functional layer obtained in Examples and Comparative Examples, a test piece having two sides facing each other in the direction orthogonal to the absorption axis direction of the polarizer and the absorption axis direction, respectively. (50 mm × 50 mm) was cut out. The test piece was attached to a non-alkali glass plate with an adhesive so that the protective layer was on the outside to form a test sample, and an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") was used for the test sample. Then, the single transmittance (Ts), the parallel transmittance (Tp) and the orthogonal transmittance (Tc) were measured, and the degree of polarization (P) was calculated by the following equation. At this time, the measurement light was incident from the protective layer side.
Polarization degree (P) (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
The Ts, Tp, and Tc are Y values measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. Also, Ts and P are substantially properties of the polarizer.
Next, the polarizing plate with an optical functional layer was left in an oven at 85 ° C. and 85% RH for 48 hours to heat and humidify (heating test), and the single transmittance Ts ₀ before the heating test and the single transmittance after the heating test were obtained. From Ts ₄₈ , the amount of change in single transmittance ΔTs was determined using the following formula.
ΔTs (%) = Ts ₄₈ _{-Ts 0}
Similarly, from the degree of polarization P ₀ before the heating test and the degree of polarization P ₄₈ after the heating test, the amount of change in degree of polarization ΔP was determined using the following formula.
ΔP (%) = P ₄₈ −P ₀
In the heating test, from the polarizing plates with an optical functional layer obtained in Examples and Comparative Examples, a test piece (50 mm ×) having two sides facing each other in the direction orthogonal to the absorption axis direction of the polarizer and the absorption axis direction. 50 mm) was cut out, and the test piece was attached to a non-alkali glass plate with an adhesive so that the protective layer was on the outside to prepare a test sample.
From the obtained results of ΔTs and ΔP, evaluation was made according to the following criteria.
Good: ΔTs: less than 3.0%, ΔP: -0.1% to 0%
Possible: ΔTs: 3.0% or more and less than 5.0%, ΔP: -1.0% or more and less than -0.1% Defective: ΔTs: 5% or more, ΔP: less than -1.0%, or overall Color loss (4) Bending test The polarizing plate with an optical functional layer obtained in Examples and Comparative Examples was cut into a size of 30 mm (direction orthogonal to the absorption axis direction of the polarizer) × 120 mm (absorption axis direction), and a measurement sample was obtained. And said. This measurement sample was subjected to a continuous bending test using a continuous bending test device (manufactured by Yuasa System Equipment Co., Ltd., product name "DLDMLLH-FS") in a no-load U-shaped expansion / contraction mode. The bending speed was 60 rpm, the bending amplitude was 20 mm, the bending radius of curvature was 0.5 mm, and the number of bendings was 50,000. Further, the bending was performed so that the optical functional layer or the retardation layer of the measurement sample was on the inside by sliding the gripping portion while gripping the longitudinal end portion of the measurement sample. It was evaluated according to the following criteria.
Good: No cracks occurred after 50,000 bends Defective: Cracks and / or creases occurred on any of the components after less than 50,000 bends. If the measurement sample cracks, the cracks are absorbed shafts. It was along the direction orthogonal to (the width direction of the measurement sample).

[Example 1]
1. 1. Fabrication of Laminate of Polarizer / Resin Base Material Amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) as a resin base material, which is long, has a water absorption rate of 0.75%, and has a Tg of about 75 ° C. Was used. One side of the resin substrate was corona-treated.
Polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Mitsubishi Chemical Co., Ltd., trade name "Gosefimer Z410") are mixed in a ratio of 9: 1 to 100 parts by weight of PVA-based resin. , 13 parts by weight of potassium iodide was added to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60 ° C. to form a PVA-based resin layer having a thickness of 13 μm to prepare a laminate.
The obtained laminate was uniaxially stretched at the free end 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an 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), the polarizer finally obtained Immersion was carried out for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 41.5% ± 0.1% (dyeing treatment).
Next, it was immersed in a cross-linked bath at a liquid temperature of 40 ° C. (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight) at a liquid temperature of 70 ° C., the total draw ratio is 5.5 in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds. Uniaxial stretching was performed so as to double (underwater stretching treatment).
Then, the laminate was immersed in a washing bath at a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the drying shrinkage treatment was 5.2%.
In this way, a polarizer having a thickness of 5 μm was formed on the resin substrate to prepare a laminate of the polarizer / resin substrate. The simple substance transmittance (initial simple substance transmittance) Ts ₀ of the polarizer was 41.2%, and the degree of polarization (initial polarization degree) P ₀ was 99.996%.

2. Preparation of First Oriented Solidified Layer and Second Oriented Solidified Layer Constituting the Phase Difference Layer With 10 g of polymerizable liquid crystal (manufactured by BASF: trade name "Pariocolor LC242", represented by the following formula) showing a nematic liquid crystal phase. , 3 g of a photopolymerization initiator (manufactured by BASF: trade name "Irgacure 907") for the polymerizable liquid crystal compound was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth and subjected to an orientation treatment. The direction of the orientation treatment was set to be 15 ° when viewed from the visual side with respect to the direction of the absorption axis of the polarizer when the polarizing plate was attached. The liquid crystal coating liquid was applied to the alignment-treated surface with a bar coater, and the liquid crystal compound was oriented by heating and drying at 90 ° C. for 2 minutes. ^{The liquid crystal layer thus formed was irradiated with light of 100 mJ / cm 2} using a metal halide lamp, and the liquid crystal layer was cured to form a liquid crystal oriented solidified layer A on the PET film. The thickness of the liquid crystal oriented solidified layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Further, the liquid crystal oriented solidified layer A showed a refractive index characteristic of nx> ny = nz.
On the PET film in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was set to be 75 ° when viewed from the visual side with respect to the direction of the absorber's absorption axis. A liquid crystal oriented solidified layer B was formed. The thickness of the liquid crystal oriented solidified layer B was 1.3 μm, and the in-plane retardation Re (550) was 140 nm. Further, the liquid crystal oriented solidified layer B exhibited a refractive index characteristic of nx> ny = nz.

3. 3. Fabrication of polarizing plate with retardation layer 1. On the polarizer surface of the laminate of the polarizer / resin base material obtained in 2. above. The liquid crystal oriented solidified layer A and the liquid crystal oriented solidified layer B obtained in the above were transferred in this order. At this time, the angle between the absorption axis of the polarizer and the slow axis of the alignment solidification layer A is 15 °, and the angle between the absorption axis of the polarizer and the slow axis of the alignment solidification layer B is 75 °. Transferred (bonded). Each transfer (bonding) was carried out via an ultraviolet curable adhesive (thickness 1.0 μm). Subsequently, a base material with an adhesive was attached to the surface of the oriented solidification layer B for reinforcement. Subsequently, the resin base material is peeled off, and a retardation layer having a structure of a polarizer / an adhesive layer / a retardation layer (first orientation solidification layer / adhesion layer / second orientation solidification layer) / a base material with an adhesive is used. A polarizing plate with a polarizing plate was obtained.

4. Formation of Easy Adhesive Layer A polyurethane-based water-based dispersion resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Superflex SF210) is applied as an easy-adhesion layer on the polarizing plate of the obtained polarizing plate with a retardation layer to a thickness of 0. It was applied so as to have a thickness of 1 μm to form an easy-adhesion layer.

5. Preparation of Protective Layer 20 parts by weight of an acrylic resin (manufactured by Kusumoto Kasei Co., Ltd., product name: B-728) which is 100% polymethylmethacrylate was dissolved in 80 parts by weight of methyl ethyl ketone to obtain an acrylic resin solution (20%). .. This acrylic resin solution is applied to the surface of the polarizer of the polarizing plate obtained above using a wire bar, and the coating film is dried at 60 ° C. for 5 minutes to form a protective layer formed as a solidified product of the coating film. Was formed. The thickness of the protective layer was 3 μm, the Tg was 116 ° C., and the iodine adsorption amount was 0.34% by weight. In this way, a polarizing plate with a retardation layer having a structure of a protective layer (solidified coating film) / polarizer / retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above evaluation.

[Example 2]
Polarizing plate with retardation layer as in Example 1 except that the protective layer thickness is 2 μm and a hard coat layer (thickness 3 μm) is further formed on the surface opposite to the easy-adhesion layer of the protective layer. Got The hard coat layer is 70 parts by weight of dimethylol-tricyclodecanediacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate DCP-A) and isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate IB-XA). 20 parts by weight, 1,9-nonanediol diacrylate (Kyoeisha Chemical Co., Ltd., trade name: Light Acrylate 1.9NA-A) 10 parts by weight, and photopolymerization initiator (BASF Co., Ltd., trade name: Irgacure 907) 3 The parts by weight were mixed with a suitable solvent. The obtained coating liquid is applied onto the protective layer surface so as to be 3 μm after curing, then the solvent is dried, and ultraviolet rays are applied to a nitrogen atmosphere ^{using a high-pressure mercury lamp so that the integrated light amount is 300 mJ / cm 2.} It was formed by irradiating. The obtained polarizing plate with a retardation layer was subjected to the above evaluation.

[Example 3]
A polarizing plate (protective layer (solidification of coating film)) was used in the same manner as in Example 1 except that a cycloolefin resin (COP) film (thickness 13 μm) was used as another protective layer instead of the retardation layer as the optical functional layer. Layer) / Polarizer / Protective layer (COP film)) was prepared. The total thickness of the polarizing plate was 22 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 4]
Above 1. Polarizing plate (protective layer (solidified layer of coating film) / polarizing element in the same manner as in Example 1 except that the protective layer forming composition was applied to the polarizing element of the laminate of the polarizing element / resin base material obtained in 1. ) Was prepared. The total thickness of the polarizing plate was 8 μm. The obtained polarizing plate was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[Example 5]
Protection in the same manner as in Example 1 except that an acrylic resin (lactone ring unit: 30 mol%) which is a polymethyl methacrylate having a lactone ring unit was used instead of the acrylic resin which is 100% polymethyl methacrylate. A polarizing plate with a retardation layer having a structure of a layer (solidified coating film) / polarizer / retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above evaluation.

[Example 6]
The same as in Example 1 except that an acrylic resin (glutarimide ring unit 4 mol%) which is a polymethyl methacrylate having a glutarimide ring unit was used instead of the acrylic resin which is 100% polymethyl methacrylate. , A polarizing plate with a retardation layer having a structure of a protective layer (solidified coating film) / polarizer / retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above evaluation.

[Example 7]
Protection in the same manner as in Example 1 except that an acrylic resin which is a copolymer of methyl methacrylate / butyl methacrylate (molar ratio 80/20) was used instead of the acrylic resin which is 100% polymethyl methacrylate. A polarizing plate with a retardation layer having a structure of a layer (solidified coating film) / polarizer / retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above evaluation.

(Comparative Example 1)
Instead of the 100% polymethylmethacrylate acrylic resin, an acrylic resin (manufactured by Kusumoto Kasei Co., Ltd., product name "B-722"), which is a copolymer of methyl methacrylate / ethyl acrylate (molar ratio 55/45), is used. A polarizing plate with a retardation layer having a structure of a protective layer (solidified coating film) / polarizer / retardation layer was obtained in the same manner as in Example 1 except that it was used. When the obtained polarizing plate with a retardation layer was placed in a heating and humidifying environment, color loss occurred, so the single transmittance and the degree of polarization were not evaluated.

(Comparative Example 2)
Instead of the 100% polymethylmethacrylate acrylic resin, an acrylic resin (manufactured by Kusumoto Kasei Co., Ltd., product name "B-734"), which is a copolymer of methyl methacrylate / butyl methacrylate (molar ratio 35/65), is used. A polarizing plate with a retardation layer having a structure of a protective layer (solidified coating film) / polarizer / retardation layer was obtained in the same manner as in Example 1 except that it was used. When the obtained polarizing plate with a retardation layer was placed in a heating and humidifying environment, color loss occurred, so the single transmittance and the degree of polarization were not evaluated.

(Comparative Example 3)
No easy-adhesion layer was formed (that is, a protective layer was formed directly on the polarizing element), UV-curable acrylic resin (manufactured by Kyoeisha Chemical Co., Ltd., product name "Light Acrylate HPP-A", neopentyl glycol acrylic hydroxypivalate). A protective layer (cured product) was formed in the same manner as in Example 1 except that a protective layer was formed using an acid adduct) to obtain a polarizing plate with a retardation layer. Specifically, a composition containing 97% by weight of the acrylic resin and 3% by weight of a photopolymerization initiator (Irgacure 907, manufactured by BASF) is applied onto a polarizer, and a high-pressure mercury lamp is used in a nitrogen atmosphere. A cured layer (protective layer) was formed by irradiating ultraviolet rays with an integrated light amount of 300 mJ / cm ^2.

(Comparative Example 4)
Except for the fact that the easy-adhesion layer was not formed (that is, the protective layer was formed directly on the polarizing element) and that the protective layer was formed using an ultraviolet curable epoxy resin (manufactured by Daicel Corporation, product name "Selokiside 2021P"). Formed a protective layer (cured product) in the same manner as in Example 1 to obtain a polarizing plate with a retardation layer. Specifically, a composition containing 95% by weight of the epoxy resin and 5% by weight of a photopolymerization initiator (CPI-100P, manufactured by San-Apro) is applied onto a polarizer, and a high-pressure mercury lamp is used in an air atmosphere. A cured layer (protective layer) was formed by irradiating ultraviolet rays with an integrated light amount of 500 mJ / cm ^2.

(Comparative Example 5)
Example 1 except that an easy-adhesion layer was not formed (that is, a protective layer was formed directly on the polarizer) and an aqueous polyester resin (manufactured by Nippon Synthetic Chemical Co., Ltd., product name "Polyester WR905") was used. A protective layer (solidified coating film) was formed in the same manner as in the above procedure to obtain a polarizing plate with a retardation layer. When the obtained polarizing plate with a retardation layer was placed in a heating and humidifying environment, color loss occurred, so the single transmittance and the degree of polarization were not evaluated.

(Comparative Example 6)
Example 1 except that an easy-adhesion layer was not formed (that is, a protective layer was formed directly on the polarizer) and an aqueous polyurethane resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Superflex SF210") was used. A protective layer (solidified coating film) was formed in the same manner as in the above procedure to obtain a polarizing plate with a retardation layer. When the obtained polarizing plate with a retardation layer was placed in a heating and humidifying environment, color loss occurred, so the single transmission rate and the degree of polarization were not evaluated.

(Comparative Example 7)
An acrylic film (refractive index: 1.50, thickness: 20 μm) that did not form an easy-adhesion layer and had an easy-adhesion treatment on one side was directly bonded to the polarizer surface via an ultraviolet curable adhesive. .. Specifically, the curable adhesive was coated so as to have a total thickness of 1.0 μm, and bonded using a roll machine. Then, UV light was irradiated from the side of the acrylic film to cure the adhesive. A polarizing plate with a retardation layer was obtained in the same manner as in Example 1 except that the protective layers were laminated in this way.

(Comparative Example 8)
A polarizing plate with a retardation layer was produced in the same manner as in Comparative Example 7 except that the thickness of the acrylic film was changed to 40 μm. The thickness of the polarizing plate was 51 μm. The obtained polarizing plate with a retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, although the polarizing plate obtained in the examples was very thin, the deterioration of the optical characteristics was suppressed even in a heating and humidifying environment, and the polarizing plate was excellent in durability. Further, it is also excellent in flexibility, and it is possible to achieve both excellent durability and excellent flexibility.

The polarizing plate of the present invention is suitably used for an image display device. Examples of image display devices include portable devices such as mobile information terminals (PDAs), smartphones, mobile phones, clocks, digital cameras, and portable game machines; OA devices such as personal computer monitors, laptop computers, and copiers; video cameras and televisions. , Home appliances such as microwave ovens; Back monitors, car navigation system monitors, car audio and other in-vehicle devices; Digital signage, commercial store information monitors and other exhibition devices; Surveillance monitors and other security devices; Nursing care Nursing care / medical equipment such as monitors for medical use and monitors for medical use;

10 Polarizer 20 Protective layer 30 Phase difference layer 100 Polarizing plate 110 Polarizing plate with optical functional layer

Claims

Includes a polarizer and a protective layer located on one side of the polarizer.
The protective layer is composed of a solidified coating film of an organic solvent solution of a thermoplastic acrylic resin, and the glass transition temperature of the protective layer is 95 ° C. or higher.
A polarizing plate having a total thickness of 20 μm or less.
The polarizing plate according to claim 1, wherein the protective layer has a thickness of 10 μm or less.
The polarizing plate according to claim 1 or 2, wherein the thickness of the polarizer is 10 μm or less.
One of claims 1 to 3, wherein the thermoplastic acrylic resin has at least one selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide unit. The polarizing plate according to the description.
A polarizing plate with an optical functional layer, which comprises the polarizing plate according to any one of claims 1 to 4 and an optical functional layer arranged on the opposite side of the protective layer of the polarizer and has a total thickness of 25 μm or less. ..
The polarizing plate with an optical functional layer according to claim 5, wherein the optical functional layer functions as a protective layer different from the protective layer.
The polarizing plate with an optical functional layer according to claim 5, wherein the optical functional layer is a retardation layer having a circularly polarized light function or an elliptically polarized light function.