WO2020138368A1

WO2020138368A1 - Polarizing plate provided with phase difference layer

Info

Publication number: WO2020138368A1
Application number: PCT/JP2019/051304
Authority: WO
Inventors: 和哉三輪; 卓史上条; 大介濱本; ひかる鈴木
Original assignee: 日東電工株式会社
Priority date: 2018-12-27
Filing date: 2019-12-26
Publication date: 2020-07-02
Also published as: JPWO2020138368A1; TW202033370A; CN113227854A; KR20210107016A

Abstract

Provided is a polarizing plate provided with a phase difference layer, having excellent durability despite being extremely thin. This polarizing plate provided with a phase difference layer has a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, and a phase difference layer disposed on the reverse side of the polarizing plate from the protective layer. The protective layer is constituted from 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. In one embodiment, the thickness of the protective layer is 10 µm or less.

Description

Polarizing plate with retardation layer

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

In image display devices (for example, liquid crystal display devices and organic EL display devices), a polarizing plate is often arranged on at least one side of the display cell due to the image forming method. Further, practically, a retardation plate is often used together with a polarizing plate, and a polarizing plate with a retardation layer in which the polarizing plate and the retardation plate are integrated is widely used (for example, Patent Document 1). ). In recent years, image display devices have become thinner and more flexible, and along with this, there has been a strong demand for a thinner polarizing plate with a retardation layer. However, the thinner the polarizing plate with the retardation layer, the more serious the problem of durability that the optical characteristics in the heating and humidifying environment deteriorate.

Japanese Patent No. 3325560

The present invention has been made to solve the above-mentioned conventional problems, and its main object is to provide a polarizing plate with a retardation layer, which is extremely thin but has excellent durability.

The polarizing plate with a retardation layer of the present invention includes a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, and a retardation layer disposed on the opposite side of the protective layer of the polarizing plate. And a layer. The protective layer is composed of a solidified product of a 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.
In one embodiment, the retardation layer is a single layer, Re(550) of the retardation layer is 100 nm to 190 nm, and the retardation axis of the retardation layer and the absorption axis of the polarizer are The angle formed is 40° to 50°. In this case, the retardation layer may be a resin film or an alignment solidified layer of a liquid crystal compound.
In another embodiment, the retardation layer has a laminated structure of a first layer and a second layer; Re(550) of the first layer is 200 nm to 300 nm, and its slow axis and the polarized light are The angle between the absorption axis of the polarizer and the absorption axis of the second layer is 10° to 20°; the Re(550) of the second layer is 100 nm to 190 nm, and the angle between the slow axis of the second layer and the absorption axis of the polarizer is 70°. It is between ° and 80°. In this case, each of the first layer and the second layer may be a resin film or an alignment solidified layer of a liquid crystal compound.
In one embodiment, the protective layer has a thickness of 10 μm or less.
In one embodiment, the amount of iodine adsorbed on the protective layer is 4.0% by weight 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 one embodiment, the polarizing plate with a retardation layer is arranged on the visible side of the image display device, and the protective layer is arranged on the visible side.

According to the present invention, in the polarizing plate with a retardation layer, the protective layer is constituted by a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, and its glass transition temperature is set to a predetermined value or higher, thereby It is possible to obtain a polarizing plate with a retardation layer, which is excellent in durability despite being thin.

FIG. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. It is a schematic diagram showing an example of dry shrinkage processing using a heating roll in a manufacturing method of a polarizing plate which can be used for a polarizing plate with a phase contrast layer by one embodiment of the present invention.

(Definition of terms and symbols)
The definitions of terms and symbols used 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 maximum (that is, the slow axis direction), and “ny” is the direction in the plane that is orthogonal to the slow axis (that is, the fast axis direction). , And “nz” is the refractive index in the thickness direction.
(2) In-plane retardation (Re)
“Re(λ)” is an in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, “Re(550)” is an in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d(nm) is the thickness of the layer (film).
(3) Phase difference (Rth) in the thickness direction
“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 the phase difference in the thickness direction measured with light having a wavelength of 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx−nz)×d when the thickness of the layer (film) is d (nm).
(4) Nz coefficient The Nz coefficient is calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise rotations with respect to the reference direction. Therefore, for example, “45°” means ±45°.

A. Outline of Polarizing Plate with Retardation Layer FIG. 1 is a schematic sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 100 with a retardation layer of the illustrated example includes a polarizer 10, a protective layer 20 arranged on one side of the polarizer 10, and a retardation layer 40 arranged on the other side of the polarizer 10. With. The polarizer 10 and the protective layer 20 form a polarizing plate. Therefore, a polarizing plate with a retardation layer is a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, and a retardation layer disposed on the opposite side of the protective layer of the polarizing plate. And. If necessary, the polarizing plate may further include another protective layer (not shown) on the side of the polarizer 10 opposite to the protective layer 20. In other words, the polarizing plate 100 with a retardation layer may further include another protective layer (not shown) between the polarizer 10 and the retardation layer 40. In the polarizing plate with a retardation layer, the thickness of the polarizer 10 is preferably 8 μm or less.

In the embodiment shown in FIG. 1, the retardation layer 40 is a single layer. In this case, Re(550) of the retardation layer 40 is, for example, 100 nm to 190 nm, and the angle formed by the slow axis of the retardation layer 40 and the absorption axis of the polarizer 10 is, for example, 40° to 50°. In this case, another retardation layer (not shown) is preferably provided outside the retardation layer 40 (on the side opposite to the polarizer 10). Another retardation layer typically has a refractive index characteristic of nz>nx=ny. Alternatively, as shown in FIG. 2, in a polarizing plate 101 with a retardation layer according to another embodiment, the retardation layer 40 has a laminated structure of a first layer 41 and a second layer 42. In this case, Re(550) of the first layer 41 is, for example, 200 nm to 300 nm, and the angle formed by the slow axis of the first layer 41 and the absorption axis of the polarizer 10 is, for example, 10° to 20°; The Re(550) of the second layer 42 is, for example, 100 nm to 190 nm, and the angle formed by the slow axis of the second layer 42 and the absorption axis of the polarizer 10 is, for example, 70° to 80°. In any of the embodiments, the retardation layer 40 may be a resin film or an alignment solidified layer of a liquid crystal compound. When the retardation layer 40 has a laminated structure, typically, the first layer 41 and the second layer 42 are each a resin film or an alignment solidification layer of a liquid crystal compound.

In the embodiment of the present invention, the protective layer 20 is composed of a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin. With such a configuration, the protective layer can be made extremely thin (for example, 10 μm or less). Further, the protective layer can be formed directly on the polarizer (that is, without interposing the adhesive layer or the pressure-sensitive adhesive layer). According to the embodiment of the present invention, the polarizer and the protective layer are very thin as described above, and since the adhesive layer or the pressure-sensitive adhesive layer can be omitted, the total thickness of the polarizing plate with a retardation layer is extremely small. Can be thinned. When the retardation layer is made of a resin film, the total thickness of the polarizing plate with a retardation layer is, for example, 80 μm or less, preferably 70 μm or less, and more preferably 60 μm or less. The lower limit of the total thickness of the polarizing plate with a retardation layer may be, for example, 30 μm. When the retardation layer is composed of an alignment-solidified layer of a liquid crystal compound, the total thickness of the polarizing plate with the retardation layer is, for example, 25 μm or less, preferably 22 μm or less, and more preferably 20 μm or less. The lower limit of the total thickness of the polarizing plate with a retardation layer may be, for example, 10 μm.

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, further preferably 110° C. or higher. And particularly preferably 115° C. or higher. When the Tg of the protective layer is in such a range, it is very thin due to a synergistic effect with the effect of forming the protective layer from the solidified material of the coating film of the organic solvent solution of the thermoplastic acrylic resin. Nevertheless, a polarizing plate with excellent durability (as a result, a polarizing plate with a retardation layer) can be realized. Specifically, it is possible to realize a polarizing plate (as a result, a polarizing plate with a retardation layer) in which deterioration of optical characteristics is suppressed even in a heating and humidifying environment. On the other hand, the Tg of the protective layer is preferably 300°C or lower, more preferably 250°C or lower, further preferably 200°C or lower, and particularly preferably 160°C or lower. When the Tg of the protective layer is within such a range, the moldability can be excellent.

As described above, according to the embodiment of the present invention, it is possible to realize a polarizing plate (as a result, a polarizing plate with a retardation layer) in which deterioration of optical characteristics is suppressed even in a heating and humidifying environment. Such a polarizing plate (as a result, a polarizing plate with a retardation layer) has a variation ΔTs in the single transmittance Ts and a variation ΔP in the polarization degree P after being left for 48 hours in an environment of 85° C. and 85% RH. But each is very small. The simple substance transmittance Ts can be measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name “V7100”). The polarization degree P is calculated by the following formula from the simple substance 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 above Ts, Tp, and Tc are Y values measured by a 2 degree visual field (C light source) of JIS Z 8701 and subjected to luminosity correction. Further, Ts and P are substantially characteristics of the polarizer. ΔTs and ΔP are respectively calculated by the following equations.
ΔTs (%)=Ts ₄₈ −Ts ₀
ΔP(%)=P ₄₈ −P ₀
Here, Ts ₀ is the unit transmittance before standing (initial), Ts ₄₈ is the unit transmittance after standing, P ₀ is the polarization degree before standing (initial), and P ₄₈ is the group after standing. It is the degree of polarization. ΔTs is preferably 3.0% or less, more preferably 2.7% or less, and further preferably 2.4% or less. ΔP is preferably −0.05% to 0%, more preferably −0.03% to 0%, and further preferably −0.01% to 0%.

The polarizing plate with a retardation layer of the present invention may further include a retardation layer other than the above. The optical characteristics (eg, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of such a retardation layer can be appropriately set according to the purpose.

The polarizing plate with a retardation layer of the present invention may further include a conductive layer or an isotropic substrate with a conductive layer (neither is shown). The conductive layer or the isotropic substrate with a conductive layer is typically provided outside the retardation layer 40 (on the side opposite to the polarizer 10 ). When a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a retardation layer is a so-called inner layer in which a touch sensor is incorporated between a display cell (for example, a liquid crystal cell or an organic EL cell) and the polarizing plate. It can be applied to a touch panel type input display device.

The polarizing plate with a retardation layer may have a long shape or a sheet shape. When the polarizing plate with a retardation layer is long, it is preferably wound into a roll to form a polarizing plate with a retardation layer.

Typically, the polarizing plate with a retardation layer has an adhesive layer as the outermost layer on one side (typically, the retardation layer 40 side), and is supposed to be bonded to a display cell. There is. If necessary, a surface protective film and/or a carrier film may be detachably temporarily attached to the polarizing plate with a retardation layer to reinforce and/or support the polarizing plate with a retardation layer. When the polarizing plate with a retardation layer includes a pressure-sensitive adhesive layer, a separator is detachably temporarily attached to the surface of the pressure-sensitive adhesive layer to protect the pressure-sensitive adhesive layer until actual use, and also the polarizing plate with a retardation layer. It is possible to roll.

Since the polarizing plate with a retardation layer of the present invention is very thin as described above, 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 with a retardation layer of the present invention from being applied to a normal image display device.

The components of the polarizing plate with retardation layer will be described in detail below.

B. Polarizing plate B-1. Polarizer Any appropriate polarizer can be adopted as the polarizer. The polarizer can be typically manufactured by using a laminate of two or more layers. The method for producing the polarizer will be described later in the section D as a method for producing the polarizing plate.

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

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

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 curl at the time of laminating is favorably 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 suppressing the above. In the present specification, the “iodine content” means the total amount of iodine contained in the polarizer (PVA-based resin film). More specifically, iodine is present in the polarizer in the form of iodine ion (I ⁻ ), iodine molecule (I ₂ ), polyiodine ion (I ₃ ⁻ , I ₅ ⁻ ), etc. The iodine content means the amount of iodine including all of these forms. The iodine content can be calculated, for example, by a calibration curve method of fluorescent X-ray analysis. The polyiodine ion is present in the polarizer in a state of forming a PVA-iodine complex. By forming such a complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ion (PVA·I ₃ ⁻ ) has an absorption peak near 470 nm, and the complex of PVA and pentaiodide ion (PVA·I ₅ ⁻ ) is around 600 nm. Has an absorption peak at. As a result, polyiodine ions can absorb light in a wide range of visible light, depending on their morphology. On the other hand, iodine ion (I ⁻ ) has an absorption peak around 230 nm and does not substantially participate in absorption of visible light. Therefore, the polyiodine ion existing 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 single transmittance Ts of the polarizer is preferably 40% to 48%, more preferably 41% to 46%. The polarization degree P of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and further preferably 99.9% or more.

B-2. Protective Layer As described above, the protective layer is composed of a solidified product of a coating film of a solution of a thermoplastic acrylic resin (hereinafter simply referred to as an acrylic resin) in an organic solvent. The constituents of the protective layer will be specifically described below, and then the characteristics of the protective layer will be described.

B-2-1. Acrylic resin The Tg of the acrylic resin (including a blend of two or more kinds of acrylic resins and a blend of the acrylic resin and another resin as described later) is as described in the section A regarding the protective layer. is there.

As the acrylic resin, any appropriate acrylic resin can be adopted as long as it has the Tg as described above. The acrylic resin typically contains 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 methacrylic. 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 appropriate copolymerization monomer may be introduced into the acrylic resin by copolymerization. The repeating unit derived from an 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 optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Show. Examples of the substituent include halogen and hydroxyl group. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, and t-(meth)acrylate. Butyl, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, (meth)acrylic Acid dicyclopentanyl, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, (meth)acrylic acid 2, 3,4,5,6-Pentahydroxyhexyl, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, 2 -(Hydroxyethyl)methyl acrylate may be mentioned. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Thus, a particularly preferred alkyl (meth)acrylate is methyl acrylate or methyl methacrylate.

The acrylic resin may include only a single alkyl (meth)acrylate unit, or may include a plurality of alkyl (meth)acrylate units having different R ⁴ and R ⁵ in the 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%, further 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 (for example, high heat resistance and high transparency) derived from the alkyl (meth)acrylate unit may not be sufficiently exhibited. When the content ratio is more than 98 mol%, the resin becomes brittle and easily cracked, high mechanical strength cannot be sufficiently exhibited, and productivity may be deteriorated.

The acrylic resin preferably has a repeating unit containing a ring structure. Examples of the repeating unit containing 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. As for the repeating unit containing a ring structure, only one kind may be contained in the repeating unit of the acrylic resin, or two or more kinds 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 each 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 contain only a single lactone ring unit, or may contain a plurality of lactone ring units having different R ¹ , R ² and R ³ in the general formula (2). .. The acrylic resin having a lactone ring unit is described in, for example, JP-A-2008-181078, and the description in that 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 each 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 or 3 to 12 carbon atoms. Is a cycloalkyl group or an aryl group having 6 to 10 carbon atoms. In the general formula (3), preferably R ¹¹ and R ¹² are each independently hydrogen or a methyl group, and R ¹³ is hydrogen, a methyl group, a butyl group or a cyclohexyl group. 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 general formula (3). .. The acrylic resin having a glutarimide unit is disclosed in, for example, 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 Laid-Open No. 2006-337493 and Japanese Patent Laid-Open No. 2006-337569, the description of which is incorporated herein by reference. Regarding the glutaric anhydride unit, the above description regarding the glutarimide unit is applied, except that the nitrogen atom substituted with R ¹³ in the general formula (3) becomes an oxygen atom.

The structures of the maleic anhydride unit and the maleimide (N-substituted maleimide) unit are specified by their names, so a detailed description will be omitted.

The content ratio of the repeating unit containing a 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 low, Tg may be less than 110° C., and the resulting protective layer may have insufficient heat resistance, solvent resistance, and surface hardness. If the content ratio is too large, moldability and transparency may be insufficient.

The acrylic resin may contain a repeating unit other than the repeating unit containing an alkyl (meth)acrylate unit and a 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 monomers include acrylic acid, methacrylic acid, crotonic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, acrylonitrile, methacrylonitrile, ethacrylonitrile and allyl. Glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, ethylaminopropyl methacrylate, methacryl Acid cyclohexylaminoethyl, N-vinyldiethylamine, N-acetylvinylamine, allylamine, methallylamine, 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, 2-styryl-oxazoline and the like. These may be used alone or in combination. The type, number, combination, content ratio and the like of the 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 to 2,000,000, more preferably 5,000 to 1,000,000, further preferably 10,000 to 500,000, particularly preferably 50,000 to 500,000, and most preferably 60,000 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 Corporation). Tetrahydrofuran may be used as the solvent.

The acrylic resin can be polymerized by any suitable polymerization method using the above monomer units in an appropriate combination. Two or more types 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 together. That is, you may copolymerize the monomer component which comprises an acrylic resin, and the monomer component which comprises another resin, and you may use this copolymer for shaping|molding of the protective layer mentioned later; with an acrylic resin and another resin. The blend may be used for forming the protective layer. Examples of the other resin include thermoplastic resins such as styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, and polyetherimide. The kind and blending amount of the resin used in combination can be appropriately set depending on the purpose and desired properties of the obtained film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used together as a retardation control agent.

When the acrylic resin and the other resin are used in combination, 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. %, more preferably 70 to 100% by weight, particularly preferably 80 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.

B-2-2. Structure and Properties of Protective Layer As described above, the protective layer is composed of a solidified product of a coating film of an organic solvent solution of an acrylic resin. With such a solidified product of the coating film, the thickness can be remarkably reduced as compared with the extruded 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 may be, for example, 1 μm. Further, although it is not theoretically clear, such a solidified product of the coating film is more difficult to form during film formation than a cured product of a thermosetting resin or an active energy ray curable resin (for example, an ultraviolet curable resin). Since the shrinkage is small and the residual monomer and the like are not included, the deterioration of the film itself is suppressed, and an adverse effect on the polarizing plate (polarizer) due to the residual monomer and the like can be suppressed. Furthermore, since it has lower hygroscopicity and moisture permeability than a solidified product of an aqueous coating film such as an aqueous solution or an aqueous dispersion, it has an advantage that it is excellent in humidification durability. As a result, it is possible to realize a polarizing plate having excellent durability (as a result, a polarizing plate with a retardation layer) capable of maintaining optical characteristics even under a heating and humidifying environment.

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

The iodine adsorption amount of the protective layer is preferably 4.0% by weight or less, more preferably 3.0% by weight or less, further 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 iodine adsorption amount, the more preferable, and the lower limit thereof may be 0.1% by weight, for example. When the iodine adsorption amount is in such a range, a polarizing plate having more excellent 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 below.

The protective layer preferably has substantially optical isotropy. In the present specification, “having substantially optical isotropy” 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. There is 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 retardation 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 ranges, it is possible to prevent adverse effects on display characteristics when the polarizing plate with a retardation layer including the protective layer is applied to an image display device. it 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, and further preferably 90% or more. When the light transmittance is in such a range, desired transparency can be secured. 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 better. Specifically, the haze is preferably 5% or less, more preferably 3% or less, further preferably 1.5% or less, particularly preferably 1% or less. When the haze is 5% or less, a good clear feeling can be given to the film. Furthermore, even when the polarizing plate with a retardation layer is used on the viewing side of the image display device, the displayed content can be viewed well.

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

The b value (scale of hue according to Hunter's color system) when the thickness of the protective layer is 3 μm is preferably less than 1.5, and more preferably 1.0 or less. When the b value is 1.5 or more, an undesired tint may appear. The b value is obtained by, for example, cutting a sample of the film forming the protective layer into 3 cm squares, and using a high-speed integrating sphere type spectral transmittance measuring instrument (trade name DOT-3C: manufactured by Murakami Color Research Laboratory). Is measured and the hue is evaluated according to Hunter's color system.

The protective layer (solidified product of coating film) may contain any appropriate additive depending on the purpose. Specific examples of the additives include ultraviolet absorbers, leveling agents, hindered phenol-based, phosphorus-based, sulfur-based, and other antioxidants; light stabilizers, weather stabilizers, heat stabilizers, and other stabilizers; 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 Colorants such as organic pigments and 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 during the polymerization of the acrylic resin or may be added to the solution during the film formation. The kind, number, combination, addition amount and the like of the additives 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, a water-based polyurethane and an oxazoline-based crosslinking agent. By forming such an easy-adhesion layer, the adhesion between the protective layer and the polarizer can be enhanced. 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 a protective layer on the viewing side of the viewing side 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.

B-3. Method of manufacturing polarizing plate B-3-1. Method for Producing Polarizer The method for producing a polarizer according to the above item B-1, is a polyvinyl alcohol containing a halide and a polyvinyl alcohol resin (PVA resin) on one side of a long thermoplastic resin substrate. By forming a system resin layer (PVA system resin layer) to form a laminate, and by subjecting the laminate to an in-air auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and heating while conveying in the longitudinal direction. And a drying shrinkage treatment for shrinking the widthwise direction by 2% or more. The content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed 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 polarizer can be obtained. In particular, by producing a laminate containing a PVA-based resin layer containing a halide, stretching the laminate by multi-stage stretching including in-air auxiliary stretching and underwater stretching, and heating the laminated body with a heating roll. It is possible to obtain a polarizer having excellent optical characteristics (typically, single transmittance and degree of polarization) and suppressing variations in optical characteristics. Specifically, by using a heating roll in the drying shrinkage treatment step, it is possible to uniformly shrink the entire laminate while transporting the laminate. As a result, not only can the optical characteristics of the obtained polarizer be enhanced, but also polarizers with excellent optical characteristics can be stably produced, and variations in optical characteristics of the polarizer (particularly, single transmittance) can be suppressed. can do. The halide and the drying shrinkage treatment will be described below. Details of manufacturing methods other than these are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire disclosure of this publication is incorporated herein by reference.

B-3-1-1. 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 on a thermoplastic resin substrate and drying the coating film. The coating liquid is typically a solution prepared by dissolving the halide and the PVA resin in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These may be used alone or in combination of two or more. Of these, water is preferable. The concentration of the PVA 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, it is possible to form a uniform coating film in close contact with the thermoplastic resin substrate.

Any suitable halide may be adopted as the halide. Examples include iodide and sodium chloride. Examples of iodides include potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.

The amount of the halide in the coating liquid is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, based on 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 resulting polarizer may become cloudy.

Generally, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin is increased. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules The orientation may be disturbed and the orientation may be deteriorated. In particular, when a laminate of a thermoplastic resin base material and a PVA-based resin layer is stretched in boric acid water, the laminate can be stretched in boric acid water at a relatively high temperature to stabilize the stretching of the thermoplastic resin base material. In the case of stretching, the above-mentioned tendency of decreasing the degree of orientation is remarkable. For example, while stretching of a PVA film alone in boric acid water is generally performed at 60° C., stretching of a laminate of A-PET (thermoplastic resin substrate) and PVA-based resin layer is performed. It is carried out at a high temperature of around 70° C. In this case, the orientation of PVA in the initial stage of stretching may be lowered in a stage before being raised by underwater stretching. On the other hand, by producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and stretching the laminate at high temperature in air (auxiliary stretching) before stretching in boric acid water. The crystallization of the PVA-based resin in the PVA-based resin layer of the laminate 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 alignment of the polyvinyl alcohol molecules and the deterioration of 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 an underwater stretching treatment, can be improved.

B-3-1-2. Drying Shrinkage Treatment The drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or may be performed by heating the transport roll (using a so-called heating roll) (heating roll drying method). Both are preferably used. By drying using a heating roll, it is possible to efficiently suppress the curling of the laminate by heating and to manufacture a polarizer having an excellent appearance. Specifically, by drying the laminate along the heating roll, the crystallization of the thermoplastic resin substrate can be efficiently promoted to increase the crystallinity, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material increases, and the thermoplastic resin base material can withstand the shrinkage of the PVA-based resin layer due to drying, and curling is suppressed. Further, by using the heating roll, the laminate can be dried while being kept flat, so that not only curling but also generation of 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 dry shrinkage treatment is preferably 2% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%. By using the heating roll, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be realized.

FIG. 3 is a schematic diagram 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 substrate. However, for example, one surface of the laminate 200 (for example, thermoplastic resin) may be used. The transport rolls R1 to R6 may be arranged so that only the resin substrate surface) is continuously heated.

The drying conditions can be controlled by adjusting the heating temperature of the transfer rolls (temperature of the heating rolls), the number of heating rolls, the contact time with the heating rolls, 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. It is possible to satisfactorily increase the crystallinity of the thermoplastic resin, satisfactorily suppress curling, and manufacture an optical laminate having extremely excellent durability. 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 multiple 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 may be provided in a normal production line (under room temperature environment). Preferably, it is provided in a heating furnace provided with a blowing means. By using the drying with the heating roll and the hot air drying together, a sharp temperature change between the heating rolls can be suppressed, and the 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 the hot air is preferably about 10 m/s to 30 m/s. The wind velocity is the wind velocity 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 the PVA-based resin layer in an aqueous potassium iodide solution.

In this way, a laminate of the thermoplastic resin substrate/polarizer can be obtained.

B-3-2. Method for Manufacturing Polarizing Plate A protective film is formed by applying a solution of an acrylic resin in an organic solvent to form a coating film on the surface of the laminate obtained in the above section B-3-1 and solidifying the coating film. To be done.

Regarding acrylic resin, it is as explained in section B-2-1 above.

As the organic solvent, any suitable organic solvent that can dissolve or uniformly disperse 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, it is possible to form a uniform coating film in close contact with the polarizer.

The solution may be applied to any appropriate base material or may be applied to the polarizer. When the solution is applied to the base material, the solidified product of the coating film formed on the base material 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 the protective layer is directly formed on the polarizer. With such a configuration, the adhesive layer or the pressure-sensitive adhesive layer required for the transfer can be omitted, so that the polarizing plate with the retardation layer can be further thinned. Any appropriate method can be adopted as a method for applying the solution. Specific examples thereof include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, 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 the polarizer from being adversely affected. The drying time can vary depending on the drying temperature. The drying time can be, for example, 1 minute to 10 minutes.

A protective layer is formed as described above, and as a result, a laminate of a thermoplastic resin substrate/polarizer/protective layer can be obtained. By peeling the thermoplastic resin substrate from this laminate, a polarizing plate having the polarizer 10 and the protective layer 20 as shown in FIGS. 1 and 2 can be obtained. The retardation layer-attached polarizing plate can be obtained by forming the retardation layer 40 on the polarizer surface of such a polarizing plate. Alternatively, a resin film forming a retardation layer is attached to the surface of the polarizer of the thermoplastic resin substrate/polarizer laminate, and then the thermoplastic resin substrate is peeled off to form a protective layer on the peeled surface. Good. In this case, the polarizing plate with a retardation layer can be obtained with high production efficiency. Since a method well known in the industry is used for forming the retardation layer, detailed description thereof will be omitted, and a brief description will be given in Section C below.

C. Retardation layer C-1. Retardation Layer Comprising a Single Layer When the retardation layer is composed of a single layer, Re(550) of the retardation layer is, for example, 100 nm to 190 nm as described above, and the retardation layer 40 has a slow phase. The angle between the axis and the absorption axis of the polarizer 10 is, for example, 40° to 50°. The retardation layer is typically provided to impart antireflection characteristics to the polarizing plate, and can function as a λ/4 plate in one embodiment. As described above, the retardation layer may be a resin film or an alignment solidified layer of a liquid crystal compound.

The retardation layer preferably has a refractive index characteristic of nx>ny≧nz. The in-plane retardation Re(550) of the retardation layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm, as described above. 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 may be satisfied as long as the effect of the present invention is not impaired.

The Nz coefficient of the retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9. ~1.3. By satisfying such a relationship, when the obtained polarizing plate with a retardation layer is used in an image display device, a very excellent reflective hue can be achieved.

The angle θ formed by the slow axis of the retardation layer 40 and the absorption axis of the polarizer 10 is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45° as described above. Is. When the angle θ is in such a range, a polarizing plate with a retardation layer having very excellent circular polarization properties (as a result, very excellent antireflection properties) by using a λ/4 plate as the retardation layer. Plates can be obtained.

The retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It may well exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes even with the wavelength of the measurement light. In one embodiment, the retardation layer exhibits an inverse dispersion wavelength characteristic. In this case, 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, it is possible to realize extremely excellent antireflection characteristics.

Retardation layer, the absolute value of photoelastic coefficient of preferably 2 × ¹⁰ -11 ^m 2 / N or less, more preferably ^{^{^{2.0 × 10 -13 m 2 /N~1.5×10 -11}}} m 2 / N, more preferably includes a resin of ^{^{^{1.0 × 10 -12 m 2 /N~1.2×10 -11}}} m 2 / N. When the absolute value of the photoelastic coefficient is in such a range, it is difficult for the phase difference to change when shrinkage stress occurs during heating. As a result, heat unevenness of the obtained image display device can be favorably prevented.

C-1-1. Resin film When the retardation layer is a resin film, the resin film is typically a stretched film. In this case, the thickness of the retardation layer is preferably 60 μm or less, more preferably 30 μm to 55 μm. When the thickness of the retardation layer is in such a range, curling at the time of heating can be favorably suppressed and curl at the time of bonding can be favorably adjusted.

The retardation layer may be composed of any appropriate resin film that can satisfy the above characteristics. Typical examples of such resins include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins. , A polyimide resin, a polyether resin, a polystyrene resin, and an acrylic resin. These resins may be used alone or in combination (for example, blending or copolymerization). When the retardation layer is composed of a resin film exhibiting reverse dispersion wavelength characteristics, a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be preferably used.

As the polycarbonate resin, any appropriate polycarbonate resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate resin is a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, an alicyclic diol, an alicyclic dimethanol, di, tri or polyethylene glycol, and an alkylene. A structural unit derived from at least one dihydroxy compound selected from the group consisting of glycols or spiroglycols. Preferably, the polycarbonate resin is a structural unit derived from a fluorene dihydroxy compound, a structural unit derived from an isosorbide dihydroxy compound, a structural unit derived from an alicyclic dimethanol and/or di, tri or polyethylene glycol. And a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from a di-, tri-, or polyethylene glycol. .. The polycarbonate-based resin may include a structural unit derived from another dihydroxy compound, if necessary. The details of the polycarbonate-based resin that can be suitably used in the present invention are described in, for example, JP-A-2014-10291, 2014-26266, JP-A-2015-212816, and JP-A-2015-212817. , Japanese Patent Application Laid-Open No. 2015-212818, which description is incorporated herein by reference.

The glass transition temperature of the polycarbonate resin is preferably 110° C. or higher and 150° C. or lower, and more preferably 120° C. or higher and 140° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to be poor, dimensional change may occur after film formation, and the image quality of the obtained organic EL panel may be deteriorated. If the glass transition temperature is excessively high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is calculated according to JIS K 7121 (1987).

The molecular weight of the polycarbonate resin can be represented by reduced viscosity. The reduced viscosity is measured using a Ubbelohde viscosity tube at a temperature of 20.0° C.±0.1° C. by precisely adjusting the polycarbonate concentration to 0.6 g/dL using methylene chloride as a solvent. The lower limit of the reduced viscosity is usually preferably 0.30 dL/g, more preferably 0.35 dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20 dL/g, more preferably 1.00 dL/g, further preferably 0.80 dL/g. If the reduced viscosity is less than the lower limit, there may occur a problem that the mechanical strength of the molded product becomes small. On the other hand, when the reduced viscosity is higher than the upper limit value, the fluidity at the time of molding may be lowered, and the productivity and the moldability may be lowered.

A commercially available film may be used as the polycarbonate resin film. Specific examples of commercially available products include Teijin's product names “Pure Ace WR-S”, “Pure Ace WR-W”, “Pure Ace WR-M”, and Nitto Denko's product name “NRF”. To be

The retardation layer 40 is obtained, for example, by stretching a film formed from the polycarbonate resin. Any appropriate molding method can be adopted as a method for forming a film from a polycarbonate resin. Specific examples include compression molding method, transfer molding method, injection molding method, extrusion molding method, blow molding method, powder molding method, FRP molding method, cast coating method (for example, casting method), calender molding method, heat press. Law etc. are mentioned. An extrusion molding method or a cast coating method is preferable. This is because the smoothness of the obtained film can be improved and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition and type of the resin used, the characteristics desired for the retardation layer, and the like. As described above, since many film products of the polycarbonate-based resin are commercially available, the commercially available film may be directly subjected to the stretching treatment.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired thickness of the retardation layer, desired optical characteristics, stretching conditions described below, and the like. The thickness is preferably 50 μm to 300 μm.

For the above stretching, any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) can be adopted. Specifically, various stretching methods such as free-end stretching, fixed-end stretching, free-end contraction, and fixed-end contraction can be used alone or simultaneously or sequentially. The stretching direction can also be performed in various directions and dimensions such as the length direction, the width direction, the thickness direction, and the oblique direction. The stretching temperature is preferably Tg-30°C to Tg+60°C, more preferably Tg-10°C to Tg+50°C, with respect to the glass transition temperature (Tg) of the resin film.

By appropriately selecting the stretching method and stretching conditions, it is possible to obtain a retardation film having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient).

In one embodiment, the retardation film is produced by uniaxially stretching or fixed-end uniaxially stretching a resin film. A specific example of the fixed-end uniaxial stretching is a method in which the resin film is stretched in the width direction (transverse direction) while running in the longitudinal direction. The stretching ratio is preferably 1.1 times to 3.5 times.

In another embodiment, the retardation film can be produced by continuously stretching a long resin film in the direction of the angle θ with respect to the longitudinal direction. By adopting oblique stretching, a long stretched film having an orientation angle θ (slow axis in the direction of angle θ) with respect to the longitudinal direction of the film can be obtained, and for example, when laminated with a polarizer. Roll-to-roll is possible, and the manufacturing process can be simplified. The angle θ may be an angle formed by the absorption axis of the polarizer and the slow axis of the retardation layer in the polarizing plate with the retardation layer. The angle θ is, as described above, preferably 40° to 50°, more preferably 42° to 48°, and even more preferably about 45°.

As a stretching machine used for oblique stretching, for example, a tenter type stretching machine capable of adding a feeding force or a pulling force or a pulling force at different speeds in the lateral and/or longitudinal directions can be mentioned. Examples of the tenter type stretching machine include a horizontal uniaxial stretching machine and a simultaneous biaxial stretching machine. Any appropriate stretching machine can be used as long as a long resin film can be continuously stretched obliquely.

By appropriately controlling the left and right speeds in the stretching machine, respectively, the retardation layer having the desired in-plane retardation and having a slow axis in the desired direction (substantially long Phase retardation film) can be obtained.

The stretching temperature of the film may vary depending on the desired in-plane retardation value and thickness of the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably Tg-30°C to Tg+30°C, more preferably Tg-15°C to Tg+15°C, and most preferably Tg-10°C to Tg+10°C. By stretching at such a temperature, a retardation layer having suitable properties in the present invention can be obtained. In addition, Tg is a glass transition temperature of the constituent material of the film.

C-1-2. Alignment solidification layer of liquid crystal compound When the retardation layer is an alignment solidification layer of a liquid crystal compound, by using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer is remarkably larger than that of a non-liquid crystal material. Therefore, the thickness of the retardation layer for obtaining a desired in-plane retardation can be significantly reduced. As a result, it is possible to realize a thinner polarizing plate with a retardation layer. In the present specification, the “alignment solidified layer” refers to a layer in which a liquid crystal compound is aligned in a predetermined direction in the layer and the alignment state is fixed. The “alignment solidified layer” is a concept including an alignment cured layer obtained by curing a liquid crystal monomer as described later. In this embodiment, typically, rod-shaped liquid crystal compounds are aligned in a state of being aligned in the slow axis direction of the retardation layer (homogeneous alignment).

The liquid crystal compound includes, for example, a liquid crystal compound in which the liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism of the liquid crystallinity 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 alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (that is, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or cross-linking the liquid crystal monomers, the alignment state can be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, in the formed retardation layer, for example, the transition to the liquid crystal phase, the glass phase, or the crystal phase due to the temperature change peculiar to the liquid crystal compound does not occur. As a result, the retardation layer becomes an extremely stable retardation layer which is not affected by temperature change.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on its 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 JP-B-2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4404081, and GB2280445 can be used. Specific examples of such a polymerizable mesogen compound include trade name LC242 of BASF, trade name E7 of Merck, and trade name LC-Silicon-CC3767 of Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment-fixed layer of the liquid crystal compound is subjected to an alignment treatment on the surface of a predetermined base material, and a coating liquid containing a liquid crystal compound is applied to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, It can be formed by fixing the orientation state. In one embodiment, the substrate is any suitable resin film, and the alignment-fixed layer formed on the substrate can be transferred to the surface of the polarizer 10. In another embodiment, the substrate can be another protective layer. In this case, the transfer step is omitted, and the roll-to-roll lamination can be performed continuously from the formation of the alignment solidified layer (retardation layer), so that the productivity is further improved.

Any appropriate orientation treatment can be adopted as the orientation treatment. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment are mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and 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 oblique vapor deposition method and a photo-alignment treatment. Any appropriate conditions can be adopted as the processing conditions of various alignment processes depending on the purpose.

Alignment of the liquid crystal compound is performed by processing at a temperature at which the liquid crystal compound exhibits a liquid crystal phase. By performing such temperature treatment, the liquid crystal compound takes a liquid crystal state, and the liquid crystal compound is aligned according to the alignment treatment direction of the substrate surface.

The fixing of the alignment state is performed by cooling the liquid crystal compound aligned as described above in one embodiment. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment 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 alignment fixed layer are described in JP-A-2006-163343. The description of this publication is incorporated herein by reference.

Another example of the alignment solidified layer is a form in which the discotic liquid crystal compound is aligned in any of vertical alignment, hybrid alignment and tilt alignment. In the discotic liquid crystal compound, typically, the disc surface of the discotic liquid crystal compound is aligned substantially perpendicular to the film surface of the retardation layer. When the discotic liquid crystal compound is substantially vertical, the average value of the angles formed by the film surface and the disc surface of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°. , And more preferably 85° to 90°. The discotic liquid crystal compound generally has a cyclic mother nucleus such as benzene, 1,3,5-triazine, and calixarene arranged at the center of the molecule, and has a linear alkyl group, an alkoxy group or a substituted benzoyl group. It refers to a liquid crystal compound having a disk-shaped molecular structure in which an oxy group or the like is radially substituted as a side chain. Typical examples of discotic liquid crystals include C.I. Report of Destrade et al., Mol. Cryst. Liq. Cryst. 71, 111 (1981), benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives and B.I. Kohne et al., Angew. Chem. 96, p. 70 (1984), and cyclohexane derivatives described in J. M. Lehn et al., J. Chem. Soc. Chem. Commun. , 1794 (1985), J. Zhang et al., J. Am. Chem. Soc. 116, 2655 (1994) and azacrown-based and phenylacetylene-based macrocycles. Further specific examples of the discotic liquid crystal compound include compounds described in JP-A-2006-133652, JP-A-2007-108732, and JP-A-2010-244038. The descriptions in the above documents and publications are incorporated herein by reference.

When the retardation layer is an alignment-fixed layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using the liquid crystal compound, an in-plane retardation equivalent to that of the resin film can be realized with a thickness significantly smaller than that of the resin film.

C-1-3. Another retardation layer As described above, when the retardation layer 40 is composed of a single layer, another retardation layer is preferably provided. Another retardation layer may be a so-called positive C plate whose refractive index characteristic exhibits a relationship of nz>nx=ny, as described above. By using a positive C plate as another retardation layer, it is possible to favorably prevent reflection in an oblique direction, and it is possible to widen the viewing angle of the antireflection function. In this case, the retardation Rth(550) in the thickness direction of another retardation layer is preferably −50 nm to −300 nm, more preferably −70 nm to −250 nm, further preferably −90 nm to −200 nm, and particularly preferably − It is 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 another retardation layer may be less than 10 nm.

Another retardation layer having a refractive index characteristic of nz>nx=ny may be formed of any appropriate material. Another retardation layer preferably consists of a film containing a liquid crystal material fixed in homeotropic alignment. The liquid crystal material (liquid crystal compound) capable of homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method of forming the liquid crystal compound and the retardation layer include the methods of forming the liquid crystal compound and the retardation layer described in JP-A-2002-333642, [0020] to [0028]. In this case, the thickness of the other retardation layer is preferably 0.5 μm to 10 μm, more preferably 0.5 μm to 8 μm, and further preferably 0.5 μm to 5 μm.

C-2.2 Retardation Layer of Two-Layer Structure When the retardation layer 40 has a laminated structure of a first layer 41 and a second layer 42, one of the first layer 41 and the second layer 42 Can function as a λ/4 plate, and the other can function as a λ/2 plate. For example, when the first layer 41 functions as a λ/2 plate and the second layer 42 functions as a λ/4 plate, the in-plane retardation Re(550) of the first layer is, for example, 200 nm to 300 nm as described above. Is preferably 230 nm to 290 nm, and more preferably 250 nm to 280 nm. The in-plane retardation Re(550) of the second layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm, as described above. The angle formed by the slow axis of the first layer and the absorption axis of the polarizer is, for example, 10° to 20°, preferably 12° to 18°, and more preferably about 15°, as described above. The angle between the slow axis of the second layer and the absorption axis of the polarizer is, for example, 70° to 80°, preferably 72° to 78°, and more preferably about 75°, as described above. With such a configuration, it is possible to obtain a characteristic close to an ideal reverse wavelength dispersion characteristic, and as a result, it is possible to realize a very excellent antireflection characteristic.

One of the first layer 41 and the second layer 42 may be a resin film and the other may be an alignment solidified layer of a liquid crystal compound, or both may be a resin film, and both may be alignment solidified layers of a liquid crystal compound. May be. Preferably, both the first layer 41 and the second layer 42 are resin films or alignment-solidified layers of a liquid crystal compound.

The thicknesses of the first layer 41 and the second layer 42 can be adjusted so as to obtain the desired in-plane retardation of the λ/4 plate or the λ/2 plate. For example, when the first layer 41 functions as a λ/2 plate, the second layer 42 functions as a λ/4 plate, and the first layer 41 and the second layer 42 are resin films, the first layer 41 Has a thickness of, for example, 40 μm to 75 μm, and the second layer 42 has a thickness of, for example, 30 μm to 55 μm. When the first layer 41 and the second layer 42 are alignment-fixed layers of a liquid crystal compound, the thickness of the first layer 41 is, for example, 2.0 μm to 3.0 μm, and the thickness of the second layer 42 is, for example, 1.0 μm to It is 2.0 μm.

The resin film forming the first layer and the second layer, the liquid crystal compound, the method for forming the first layer and the second layer, the optical characteristics, and the like are as described above for the single layer.

D. Conductive Layer or Isotropic Substrate with Conductive Layer The conductive layer is formed by any appropriate film formation method (eg, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, etc.). It may be formed by depositing a metal oxide film thereon. Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin complex oxide, tin-antimony complex oxide, zinc-aluminum complex oxide, and indium-zinc complex oxide. Among them, 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 above-mentioned base material to the retardation layer to form the polarizing plate with the retardation layer by itself as the constituent layer of the polarizing plate. It may be laminated in layers. Preferably, the above-mentioned substrate is optically isotropic, and therefore the conductive layer can be used as the isotropic substrate with a conductive layer in a polarizing plate with a retardation layer.

As the optically isotropic substrate (isotropic substrate), any suitable isotropic substrate can be adopted. Examples of the material forming the isotropic base material include, for example, a material having a resin having no conjugated system such as norbornene-based resin or olefin-based resin as a main skeleton, and a cyclic structure such as a lactone ring or a glutarimide ring of acrylic resin Materials included in the main chain are included. When such a material is used, it is possible to suppress the development of retardation due to the orientation of the molecular chains when the isotropic substrate is formed. The thickness of the isotropic substrate is preferably 50 μm or less, more preferably 35 μm or less. The lower limit of the thickness of the isotropic substrate is, for example, 20 μm.

The conductive layer and/or the conductive layer of the isotropic substrate with the conductive layer may be patterned as required. By patterning, conductive parts and insulating parts can be formed. As a result, electrodes can be formed. The electrodes may function as touch sensor electrodes that sense a touch on the touch panel. Any appropriate method can be adopted as the patterning method. Specific examples of the patterning method include a wet etching method and a screen printing method.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. The measuring method of each characteristic is as follows. In the examples, “parts” and “%” are based on weight unless otherwise specified.

(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 substrate (PET film) by an applicator and dried at 60°C to form a coating film (thickness 40 µm). did. The obtained coating film was peeled from the base material and cut into strips to obtain a measurement sample. The measurement sample was subjected to DMA measurement to measure Tg. The measuring device and measuring conditions were as follows.
(measuring device)
"DMS6100" manufactured by SII Nano Technology Co., Ltd.
(Measurement condition)
・Measurement temperature range: -80℃ to 150℃
・Raising and lowering temperature: 2℃/min ・Measurement sample width: 10mm
・Distance between chucks: 20 mm
・Measurement frequency: 1 Hz
・Strain amplitude: 10 μm
・Measurement atmosphere: N ₂ (250 mL/min)
(2) Iodine adsorption amount A solution prepared by dissolving the material constituting the protective layer used in Examples and Comparative Examples in a predetermined solvent was applied to a substrate (PET film) by an applicator and dried at 60°C to form a coating film. (Thickness 40 μm) was formed. The obtained coating film was peeled from the substrate and cut into 1 cm×1 cm (1 cm ² ) to obtain a measurement sample. The measurement sample was subjected to the 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 capacity). Next, a vial (2 mL capacity) containing 1 mL of an iodine solution (iodine concentration 1% by weight, potassium iodide concentration 7% by weight) was placed in this headspace vial and sealed. Then, this headspace vial is heated in a dryer at 65°C for 6 hours, and a sample after heating is collected in a ceramic port and burned using an automatic combustion device, and the generated gas is collected in an absorption liquid and then quantified. Analysis was performed to determine the weight percent of adsorbed iodine. The equipment used was as follows.
・Automatic sample combustor: "AQF-2100H" manufactured by Mitsubishi Chemical Analytical Co., Ltd.
IC (anion): "ICS-3000" manufactured by Thermo Fisher Scientific
(3) Color Loss From the polarizing plate with a retardation layer obtained in Examples and Comparative Examples, a test piece (50 mm×50 mm) having two sides facing in the direction orthogonal to the absorption axis direction of the polarizer and the absorption axis direction respectively. ) Was cut out. The test piece is attached to a non-alkali glass plate with an adhesive so that the protective layer is on the outside to give a test sample, and the test sample is left to stand in an oven at 85° C. and 85% RH for 48 hours to be heated and humidified. The discolored state of the polarizing plate with a retardation layer after humidification when arranged in a crossed Nicol state with the polarizing plate was visually inspected and evaluated according to the following criteria.
No problem: No color loss was observed Partial loss: Color loss was observed at the edges Total loss: Color loss was noticeable over the entire polarizing plate (4) Single transmittance and degree of polarization Example and comparison From the polarizing plate with a retardation layer obtained in the example, a test piece (50 mm×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 was cut out. A test piece is attached to an alkali-free glass plate with an adhesive so that the protective layer is on the outside to form a test sample, and an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100") is used for the test sample. Then, the simple substance transmittance (Ts), the parallel transmittance (Tp), and the orthogonal transmittance (Tc) were measured, and the polarization degree (P) was calculated by the following equation. At this time, the measurement light was made incident from the protective layer side.
Polarization degree (P)(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 ×100
The above Ts, Tp, and Tc are Y values measured by a 2 degree visual field (C light source) of JIS Z 8701 and subjected to luminosity correction. Further, Ts and P are substantially characteristics of the polarizer.
Next, the polarizing plate with a retardation layer was left to stand in an oven at 85° C. and 85% RH for 48 hours to be heated and humidified (heating test), and a single transmittance Ts ₀ before the heating test and a single transmittance after the heating test. From Ts ₄₈ , the simple substance transmittance change amount ΔTs was calculated using the following formula.
ΔTs (%)=Ts ₄₈ −Ts ₀
Similarly, the polarization degree change amount ΔP was determined from the polarization degree P ₀ before the heating test and the polarization degree P ₄₈ after the heating test using the following formula.
ΔP(%)=P ₄₈ −P ₀
The heating test was conducted by preparing a test sample in the same manner as in the case of color loss.
(5) Frontal reflectance From the polarizing plate with a retardation layer obtained in each of the examples and comparative examples, a test piece (50 mm × 50 mm) having a direction orthogonal to the absorption axis direction of the polarizer and two sides facing the absorption axis direction, respectively. 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 outer side to obtain a test sample. This test sample was subjected to a humidity test at 85° C. and 85% RH for 48 hours. The test sample after the above humidification test was placed on a reflection plate (trade name “DMS-X42” manufactured by Toray Film Co., Ltd.; reflectance of 86%) so that the glass and the reflection plate face each other (that is, the protective layer is on the outside). It was arranged). Then, the spectrocolorimeter (CM-2600d manufactured by Konica Minolta) was used to measure the front reflectance by the SCI method.

<Example 1>
1. Production of Laminate of Polarizer/Resin Base Material Amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption rate of 0.75% and a Tg of about 75° C. as a resin base material. Was used. Corona treatment was applied to one side of the resin substrate.
Polyvinyl alcohol (polymerization degree: 4200, saponification degree: 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosephimmer Z410") in a ratio of 9:1 100 weight of PVA-based resin To 13 parts by weight, 13 parts by weight of potassium iodide was added to prepare a PVA aqueous solution (coating solution).
The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, and a laminate was prepared.
The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) having a liquid temperature of 40° C. for 30 seconds (insolubilization treatment).
Then, a dyeing bath having a liquid temperature of 30° C. (an iodine aqueous solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) was used to prepare the finally obtained polarizer. Immersion was performed for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 41.5%±0.1% (dyeing treatment).
Then, it was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 40° C. (an aqueous boric acid solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water). (Crosslinking treatment).
Then, while the laminated body was immersed in a boric acid aqueous solution (boric acid concentration 4.0% by weight) having a liquid temperature of 70° C., the total draw ratio was 5.5 in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds. Uniaxial stretching was performed so as to double the length (underwater stretching treatment).
After that, the laminate was immersed in a cleaning bath having a liquid temperature of 20° C. (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while being dried in an oven kept at 90° C., it was contacted with a heating roll made of SUS whose surface temperature was kept at 75° C. for about 2 seconds (dry shrinkage treatment). The shrinkage ratio in the width direction of the laminate due to the dry shrinkage treatment was 5.2%.
In this way, a polarizer having a thickness of 5 μm was formed on the resin base material to prepare a polarizer/resin base material laminate. The single transmittance (initial single transmittance) Ts ₀ of the polarizer was 41.5, and the polarization degree (initial polarization degree) P ₀ was 99.996%.

2. Preparation of retardation film constituting retardation layer 2-1. Polymerization of Polyester Carbonate Resin Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled to 100°C. Bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane 29.60 parts by mass (0.046 mol), isosorbide (ISB) 29.21 parts by mass (0.200 mol), spiroglycol (SPG) 42 .28 parts by mass (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by mass (0.298 mol), and calcium acetate monohydrate as a catalyst 1.19×10-2 parts by mass (6.78×10−). 5 mol) was charged. After replacing the inside of the reactor with nitrogen under reduced pressure, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. After 40 minutes from the start of temperature increase, the internal temperature was made to reach 220° C., the temperature was controlled so as to be kept at the same time, and the depressurization was started at the same time. Phenol vapor produced as a by-product with the polymerization reaction was introduced into a reflux condenser at 100° C., a monomer component slightly contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was introduced into a condenser at 45° C. and recovered. After introducing nitrogen into the first reactor to once restore the pressure to atmospheric pressure, the oligomerized reaction liquid in the first reactor was transferred to the second reactor. Then, the temperature rise and pressure reduction in the second reactor were started, and the internal temperature was 240° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until a predetermined stirring power was obtained. When the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, the produced polyester carbonate resin was extruded into water, and the strands were cut to obtain pellets.

2-2. Preparation of Retardation Film The obtained polyester carbonate resin (pellet) was vacuum dried at 80° C. for 5 hours, and then a single screw extruder (Toshiba Machine Co., Ltd., cylinder setting temperature: 250° C.), T die (width 200 mm). , Set temperature: 250° C.), a chill roll (set temperature: 120 to 130° C.) and a film forming apparatus equipped with a winder were used to produce a long resin film having a thickness of 135 μm. The obtained long resin film was stretched in the width direction at a stretching temperature of 133° C. and a stretching ratio of 2.8 times to obtain a retardation film having a thickness of 48 μm. The Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.82, and the Nz coefficient was 1.12.

3. Preparation of Polarizing Plate with Retardation Layer 1. On the surface of the polarizer of the laminate obtained in step 3, above. The retardation film obtained in (1) was attached via an acrylic pressure-sensitive adhesive (thickness 5 μm). At this time, they were laminated so that the absorption axis of the polarizer and the slow axis of the retardation film formed an angle of 45°. The resin base material was peeled off to obtain a retardation layer-attached polarizing plate having a constitution of retardation layer/polarizer.

20 parts of an acrylic resin (30 mol% of lactone ring unit), which is polymethylmethacrylate having a lactone ring unit, was dissolved in 80 parts 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, the coating film is dried at 60° C. for 5 minutes, and the protective layer is formed as a solidified product of the coating film. Formed. The protective layer had a thickness of 3 μm, a Tg of 119° C., and an iodine adsorption amount of 0.25% by weight. In this way, a polarizing plate with a retardation layer having a constitution of protective layer (solidified product of coating film)/polarizer/retardation layer was obtained. The obtained polarizing plate with a retardation layer was subjected to the above evaluations (3) to (5). Furthermore, the presence or absence of shrinkage after forming the protective layer was visually observed. The results are shown in Table 1.

<Example 2>
Same as Example 1 except that an acrylic resin (maleic anhydride unit: 7 mol %), which is a polymethylmethacrylate having a maleic anhydride unit, is used in place of the acrylic resin, which is a polymethylmethacrylate having a lactone ring unit. To form a protective layer. The protective layer had a thickness of 3 μm and a Tg of 115° C. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Example 3>
Example 1 except that 100% polymethylmethacrylate acrylic resin (Kusumoto Kasei Co., product name "B-728") was used instead of polymethylmethacrylate acrylic resin having lactone ring unit. A protective layer was formed in the same manner. The protective layer had a thickness of 3 μm, a Tg of 116° C., and an iodine adsorption amount of 0.34% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Example 4>
Same as Example 1 except that an acrylic resin that is a polymethylmethacrylate having a glutarimide ring unit (4 mol% of a glutarimide ring unit) is used instead of an acrylic resin that is a polymethylmethacrylate having a lactone ring unit. To form a protective layer. The thickness of the protective layer was 3 μm, the Tg was 103° C., and the iodine adsorption amount was 2.3% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Example 5>
A protective layer was formed in the same manner as in Example 1 except that an acrylic resin (lactone ring unit: 20 mol%), which was a different polymethylmethacrylate having a lactone ring unit, was used. The protective layer had a thickness of 3 μm, a Tg of 104° C., and an iodine adsorption amount of 2.8% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Example 6>
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 in place of the acrylic resin which was polymethylmethacrylate having a lactone ring unit. A protective layer was formed. The thickness of the protective layer was 3 μm, Tg was 95° C., and the iodine adsorption amount was 3.8% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Example 7>
1. Preparation of Polarizer/Resin Base Material Laminate A polarizer/resin base material laminate was prepared in the same manner as in Example 1.

2. Preparation of First Alignment Solidification Layer and Second Alignment Solidification Layer Constituting Retardation Layer 10 g of a polymerizable liquid crystal showing a nematic liquid crystal phase (manufactured by BASF: trade name “Paliocolor LC242”, represented by the following formula) A liquid crystal composition (coating liquid) was prepared by dissolving 3 g of a photopolymerization initiator (manufactured by BASF: trade name “Irgacure 907”) for the polymerizable liquid crystal compound in 40 g of toluene.

The surface of the polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed with a rubbing cloth for orientation treatment. The direction of the orientation treatment was set to be 15° with respect to the direction of the absorption axis of the polarizer when it was attached to the polarizing plate, as viewed from the viewing side. The liquid crystal coating liquid was applied to the surface of this alignment treatment with a bar coater, and the liquid crystal compound was aligned by heating and drying at 90° C. for 2 minutes. The liquid crystal layer thus formed was irradiated with light of 1 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming a liquid crystal alignment solidified layer A on the PET film. The thickness of the liquid crystal alignment fixed layer A was 2.5 μm, and the in-plane retardation Re(550) was 270 nm. Furthermore, the liquid crystal alignment fixed layer A showed the 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 alignment treatment direction was set to be the direction of 75° with respect to the absorption axis direction of the polarizer when viewed from the viewing side. A liquid crystal alignment fixed layer B was formed. The thickness of the liquid crystal alignment fixed layer B was 1.5 μm, and the in-plane retardation Re(550) was 140 nm. Furthermore, the liquid crystal alignment fixed layer B showed the refractive index characteristic of nx>ny=nz.

3. Preparation of Polarizing Plate with Retardation Layer 1. On the surface of the polarizer of the laminate of the polarizer/resin base material obtained in step 2, The liquid crystal alignment solidified layer A and the liquid crystal alignment solidified layer B obtained in 1. 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°. Transfer (bonding) was performed. Each transfer (bonding) was performed via an ultraviolet curable adhesive (thickness 1.0 μm). Subsequently, a base material with an adhesive was attached to the surface of the orientation solidified layer B for reinforcement. Subsequently, the resin base material is peeled off, and a retardation layer having a constitution of polarizer/adhesive layer/retardation layer (first orientation solidified layer/adhesion layer/second orientation solidified layer)/adhesive-attached substrate An attached polarizing plate was obtained.

Next, in the same manner as in Example 3, a protective layer was formed on the polarizer surface of the polarizing plate with a retardation layer. Finally, the substrate with the pressure-sensitive adhesive layer was peeled off to obtain a polarizing plate with a retardation layer having a structure of protective layer (solidified product of coating film)/polarizer/retardation layer. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
Instead of acrylic resin which is polymethylmethacrylate having lactone ring unit, acrylic resin which is a copolymer of methylmethacrylate/ethylacrylate (molar ratio 55/45) (Kusumoto Kasei Co., product name "B-722" A protective layer was formed in the same manner as in Example 1 except that (4) was used. The protective layer had a thickness of 3 μm, a Tg of 39° C., and an iodine adsorption amount of 1.7% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. When the obtained polarizing plate with a retardation layer was subjected to the evaluation of color loss, it was found to be defective (“total loss”). Therefore, the single-element transmittance and the degree of polarization were not evaluated. The results are shown in Table 1.

<Comparative example 2>
Instead of the acrylic resin which is polymethylmethacrylate having a lactone ring unit, an acrylic resin which is a copolymer of methylmethacrylate/butylmethacrylate (molar ratio 35/65) (Kusumoto Kasei Co., product name "B-734") A protective layer was formed in the same manner as in Example 1 except that (4) was used. The protective layer had a thickness of 3 μm, a Tg of 71° C., and an iodine adsorption amount of 12% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. When the obtained polarizing plate with a retardation layer was subjected to the evaluation of color loss, it was found to be defective (“total loss”). Therefore, the single-element transmittance and the degree of polarization were not evaluated. The results are shown in Table 1.

<Comparative example 3>
A protective layer (cured product) was prepared in the same manner as in Example 1 except that an ultraviolet curable acrylic resin (manufactured by Kyoeisha Chemical Co., Ltd., product name “Light acrylate HPP-A”, hydroxypivalate neopentyl glycol acrylic acid adduct) was used. ) Was formed. 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 coated on a polarizer, and a high pressure mercury lamp is used in a nitrogen atmosphere. Then, ultraviolet rays were irradiated at an integrated light amount of 300 mJ/cm ² to form a cured layer (protective layer). The protective layer had a thickness of 3 μm, a Tg of 83° C., and an iodine adsorption amount of 6.6% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Comparative example 4>
Same as Example 1 except that UV curable acrylic resin (manufactured by Toagosei Co., Ltd., product name “Aronix M-402”, dipentaerythritol penta and hexaacrylate (pentaacrylate 30% to 40%)) was used. To form a protective layer (cured product). The method for forming the protective layer was the same as in Comparative Example 3. The thickness of the protective layer was 3 μm. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Comparative Example 5>
A protective layer (cured product) was formed in the same manner as in Example 1 except that an ultraviolet curable epoxy resin (manufactured by Daicel, product name “Ceroxide 2021P”) was used. 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 Co., Ltd.) is applied onto a polarizer, and a high pressure mercury lamp is applied in an air atmosphere. It was irradiated with ultraviolet rays at an integrated light amount of 500 mJ/cm ² to form a cured layer (protective layer). The protective layer had a thickness of 3 μm, a Tg of 95° C., and an iodine adsorption amount of 9% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. The obtained polarizing plate with a retardation layer was subjected to the same evaluations as in Example 1. The results are shown in Table 1.

<Comparative example 6>
A protective layer (solidified product of the coating film) was formed in the same manner as in Example 1 except that an aqueous polyester resin (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "Polyester WR905") was used. The thickness of the protective layer was 3 μm, and the iodine adsorption amount was 12% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. When the obtained polarizing plate with a retardation layer was subjected to the evaluation of color loss, it was found to be defective (“total loss”). Therefore, the single-element transmittance and the degree of polarization were not evaluated. The results are shown in Table 1.

<Comparative Example 7>
A protective layer (solidified product of the coating film) was formed in the same manner as in Example 1 except that an aqueous polyurethane resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name "Superflex SF210") was used. The thickness of the protective layer was 3 μm, the Tg was 107° C., and the iodine adsorption amount was 19% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. When the obtained polarizing plate with a retardation layer was subjected to the evaluation of color loss, it was found to be defective (“total loss”). Therefore, the single-element transmittance and the degree of polarization were not evaluated. The results are shown in Table 1.

<Comparative Example 8>
A protective layer (solidified product of the coating film) was formed in the same manner as in Example 1 except that an aqueous polyurethane resin (manufactured by Unitika Ltd., product name “Arrow Base SE1200”) was used. The thickness of the protective layer was 3 μm, and the iodine adsorption amount was 15% by weight. A polarizing plate with a retardation layer was produced in the same manner as in Example 1 except that this protective layer was used. When the obtained polarizing plate with a retardation layer was subjected to the evaluation of color loss, it was found to be defective (“total loss”). Therefore, the single-element transmittance and the degree of polarization were not evaluated. The results are shown in Table 1.

<Evaluation>
As is clear from Table 1, the polarizing plate with retardation layer of the example of the present invention is excellent in durability even though it is very thin, even though it is heated and humidified. At the same time, it is a polarizing plate with a retardation layer that does not shrink after the formation of the protective layer and can be practically used. Furthermore, the polarizing plate with a retardation layer of the example of the present invention had a very small front reflectance after a humidification test, and showed good antireflection characteristics. This indicates that when applied to an image display device having a metal layer such as an organic EL display device, it has an effect of preventing reflection of external light by the metal layer.

The polarizing plate with a retardation layer of the present invention is suitably used for an image display device. Examples of the image display device include portable devices such as personal digital assistants (PDAs), smartphones, mobile phones, watches, digital cameras, and portable game consoles; office automation devices such as personal computer monitors, notebook computers, and copy machines; video cameras, televisions. , Household electric appliances such as microwave ovens; back monitors, car navigation system monitors, car audio and other in-vehicle equipment; digital signage, commercial store information monitors and other display equipment; surveillance monitors and other security equipment; nursing care Nursing care/medical devices such as medical monitors and medical monitors.

10 Polarizer 20 Protective Layer 40 Retardation Layer 41 First Layer 42 Second Layer 100 Polarizing Plate

Claims

A polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, and a retardation layer disposed on the opposite side of the polarizing layer to the protective layer,
The protective layer is composed of a solidified product of a 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.
Polarizing plate with retardation layer.
The retardation layer is a single layer,
Re(550) of the retardation layer is 100 nm to 190 nm,
The angle formed by the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°,
The polarizing plate with a retardation layer according to claim 1.
The polarizing plate with a retardation layer according to claim 2, wherein the retardation layer is a resin film.
The polarizing plate with a retardation layer according to claim 2, wherein the retardation layer is an alignment-solidified layer of a liquid crystal compound.
The retardation layer has a laminated structure of a first layer and a second layer,
Re(550) of the first layer is 200 nm to 300 nm, and an angle formed by the slow axis thereof and the absorption axis of the polarizer is 10° to 20°,
Re(550) of the second layer is 100 nm to 190 nm, and an angle formed by the slow axis thereof and the absorption axis of the polarizer is 70° to 80°.
The polarizing plate with a retardation layer according to claim 1.
The polarizing plate with a retardation layer according to claim 5, wherein each of the first layer and the second layer is a resin film.
The polarizing plate with a retardation layer according to claim 5, wherein each of the first layer and the second layer is an alignment-fixed layer of a liquid crystal compound.
The polarizing plate with a retardation layer according to claim 1, wherein the protective layer has a thickness of 10 μm or less.
The polarizing plate according to any one of claims 1 to 8, wherein the protective layer has an iodine adsorption amount of 4.0% by weight or less.
10. The thermoplastic acrylic resin according to claim 1, 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. A polarizing plate with a retardation layer as described above.
The polarizing plate with a retardation layer according to any one of claims 1 to 10, wherein the polarizing plate with a retardation layer is disposed on the viewing side of the image display device, and the protective layer is disposed on the viewing side.