TWI839433B - Polarizing plate with phase difference layer - Google Patents

Abstract

The present invention provides a polarizing plate with a phase difference layer which has good durability even when it is very thin. The polarizing plate with a phase difference layer of the present invention has a polarizing plate and a phase difference layer, wherein the polarizing plate includes a polarizer and a protective layer disposed on one side of the polarizer, and the phase difference layer is disposed on the side of the polarizing plate opposite to the protective layer. The protective layer is composed of a cured 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 above 95°C. In one embodiment, the thickness of the protective layer is below 10 μm.

Description

Polarizing plate with phase difference layer

The present invention relates to a polarizing plate with a phase difference layer.

Background of the invention In image display devices (such as liquid crystal display devices and organic EL display devices), due to the image formation method, a polarizing plate is usually arranged on at least one side of the display unit. Moreover, in practical applications, a phase difference plate is mostly used together with a polarizing plate, and a polarizing plate with a phase difference layer, which is an integration of a polarizing plate and a phase difference plate, is widely used (for example, Patent Document 1). In recent years, with the development of thinning and flexibility of image display devices, there is also a strong demand for thinning of polarizing plates with phase difference layers. However, the thinner the polarizing plate with a phase difference layer is, the more obvious the durability problem of reduced optical properties in a heated and humidified environment becomes.

Prior art documents Patent documents Patent document 1: Japanese Patent No. 3325560

Problem to be solved by the invention The present invention is made to solve the above-mentioned previous problems, and its main purpose is to provide a polarizing plate with a phase difference layer that has good durability even if it is very thin.

Means for solving the problem The polarizing plate with phase difference layer of the present invention has a polarizing plate and a phase difference layer, the polarizing plate includes a polarizer and a protective layer arranged on one side of the polarizer, and the phase difference layer is arranged on the side of the polarizing plate opposite to the protective layer. The protective layer is composed of a cured 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 above 95°C. In one embodiment, the phase difference layer is a single layer, and the Re (550) of the phase difference layer is 100nm~190nm, and the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°~50°. At this time, the phase difference layer can be a resin film or a directional solidification layer of a liquid crystal compound. In another embodiment, the phase difference layer has a layered structure of a first layer and a second layer; the Re (550) of the first layer is 200nm~300nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 10°~20°; the Re (550) of the second layer is 100nm~190nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 70°~80°. At this time, the first layer and the second layer can be a resin film or a directional solidification layer of a liquid crystal compound, respectively. In one embodiment, the thickness of the protective layer is less than 10μm. In one embodiment, the iodine adsorption amount of the protective layer is less than 4.0 wt%. In one embodiment, the thermoplastic acrylic resin has at least one selected from the group consisting of lactone ring units, glutaric anhydride units, glutarimide units, maleic anhydride units and maleimide units. In one embodiment, the polarizing plate with a phase difference layer is arranged on the visual side of the image display device, and the protective layer is arranged on the visual side.

Effect of the invention According to the present invention, by forming the protective layer of the polarizing plate with a phase difference layer with a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin and setting the glass transition temperature to a predetermined value or above, a polarizing plate with a phase difference layer having excellent durability even when it is very thin can be obtained.

(Definition of terms and symbols) The definitions of terms and symbols in this manual are as follows. (1) Refractive index (nx, ny, nz) “nx” is the refractive index in the direction where the in-plane refractive index is the largest (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction. (2) In-plane phase difference (Re) “Re(λ)” is the in-plane phase difference measured at 23°C with light of wavelength λnm. For example, “Re(550)” is the in-plane phase difference measured at 23°C with light of wavelength 550nm. Re(λ) can be obtained by the formula: Re(λ)＝(nx-ny)×d when the thickness of the layer (film) is d(nm). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured at 23°C with light of wavelength λnm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C with light of wavelength 550nm. Rth(λ) can be 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 can be calculated by Nz=Rth/Re. (5) Angle When an angle is mentioned in this manual, the angle includes both clockwise and counterclockwise relative to the reference direction. Therefore, for example, "45°" means ±45°.

A. Overview of polarizing plate with phase difference layer Figure 1 is a schematic cross-sectional view of a polarizing plate with phase difference layer in an embodiment of the present invention. The polarizing plate with phase difference layer 100 in the illustrated example has: a polarizer 10, a protective layer 20 disposed on one side of the polarizer 10, and a phase difference layer 40 disposed on the other side of the polarizer 10. The polarizer 10 and the protective layer 20 can constitute a polarizing plate. Therefore, the polarizing plate with phase difference layer has a polarizing plate and a phase difference layer, the polarizing plate includes a polarizer and a protective layer disposed on one side of the polarizer, and the phase difference layer is disposed on the side of the polarizing plate opposite to the protective layer. The polarizing plate can also include another protective layer (not shown) on the side of the polarizer 10 opposite to the protective layer 20 according to demand. In other words, the polarizing plate with phase difference layer 100 may further include another protective layer (not shown) between the polarizer 10 and the phase difference layer 40. In the polarizing plate with phase difference layer, the thickness of the polarizer 10 is preferably less than 8 μm.

In the embodiment shown in FIG1 , the phase difference layer 40 is a single layer. In this case, the Re (550) of the phase difference layer 40 is, for example, 100 nm to 190 nm, and the angle formed by the slow axis of the phase difference layer 40 and the absorption axis of the polarizer 10 is, for example, 40° to 50°. In this case, it is preferred to provide another phase difference layer (not shown) on the outside of the phase difference layer 40 (the side opposite to the polarizer 10). The refractive index characteristic of the other phase difference layer represents the relationship of nz＞nx＝ny. Alternatively, as shown in FIG2 , in another embodiment of the polarizing plate 101 with a phase difference layer, the phase difference layer 40 has a layered structure of a first layer 41 and a second layer 42. At this time, the Re(550) of the first layer 41 is, for example, 200nm~300nm, 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°~20°; the Re(550) of the second layer 42 is, for example, 100nm~190nm, 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°~80°. Regardless of the implementation form, the phase difference layer 40 can be a resin film or a directional solidification layer of a liquid crystal compound. When the phase difference layer 40 has a layered structure, it means that the first layer 41 and the second layer 42 are respectively a resin film or a directional solidification layer of a liquid crystal compound.

In the embodiment of the present invention, the protective layer 20 is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin. As long as it is composed as described above, the protective layer can be made very thin (for example, made to be less than 10μm). Moreover, the protective layer can be formed directly on the polarizer (that is, without passing through a bonding agent layer or an adhesive layer). According to the embodiment of the present invention, as described above, the polarizer and the protective layer are very thin and the bonding agent layer or the adhesive layer can be omitted, so the total thickness of the polarizing plate with a phase difference layer can be made extremely thin. When the phase difference layer is composed of a resin film, the total thickness of the polarizing plate with a phase difference layer is, for example, less than 80μm, preferably less than 70μm, and more preferably less than 60μm. The lower limit of the total thickness of the polarizing plate with a phase difference layer may be, for example, 30 μm. When the phase difference layer is composed of an oriented solidified layer of a liquid crystal compound, the total thickness of the polarizing plate with a phase difference layer may be, 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 phase difference layer may be, for example, 10 μm.

Furthermore, 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, preferably 105°C or higher, more preferably 110°C or higher, and particularly preferably 115°C or higher. As long as the Tg of the protective layer is within the above range, a polarizing plate (in other words, a polarizing plate with a phase difference layer) having excellent durability even when it is very thin can be realized by the synergistic effect of the effect brought about by the protective layer being formed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin. Specifically, a polarizing plate (in other words, a polarizing plate with a phase difference layer) in which the reduction of optical characteristics is suppressed even in a heated and humidified environment can be realized. On the other hand, the Tg of the protective layer is preferably 300° C. or lower, more preferably 250° C. or lower, more preferably 200° C. or lower, and particularly preferably 160° C. or lower. As long as the Tg of the protective layer is within the above range, the moldability is good.

As described above, according to the implementation form of the present invention, a polarizing plate (in other words, a polarizing plate with a phase difference layer) can be realized in which the degradation of optical characteristics is suppressed even in a heated and humidified environment. After such a polarizing plate (in other words, a polarizing plate with a phase difference layer) is placed in an environment of 85°C and 85%RH for 48 hours, the change ΔTs of the single transmittance Ts and the change ΔP of the polarization degree P are both very small. The single transmittance Ts is measured using, for example, an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"). The polarization degree P is calculated using the following formula from the single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) measured using an ultraviolet-visible spectrophotometer. Polarization degree (P) (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 × 100 In addition, the above Ts, Tp and Tc are the Y values obtained by measuring the 2-degree field of view (C light source) of JIS Z 8701 and performing visual sensitivity correction. In addition, Ts and P are actually the characteristics of the polarizer. ΔTs and ΔP can be obtained by the following formulas. ΔTs (%) = Ts ₄₈ - Ts ₀ ΔP (%) = P ₄₈ - P ₀ Here, Ts ₀ is the single body transmittance before placement (initial), Ts ₄₈ is the single body transmittance after placement, P ₀ is the polarization degree before placement (initial), and P ₄₈ is the polarization degree after placement. ΔTs is preferably less than 3.0%, preferably less than 2.7%, and more preferably less than 2.4%. ΔP is preferably -0.05% to 0%, preferably -0.03% to 0%, and more preferably -0.01% to 0%.

The polarizing plate with phase difference layer of the present invention may also include phase difference layers other than those mentioned above. The optical properties (such as refractive index properties, in-plane phase difference, Nz coefficient, photoelastic coefficient), thickness, configuration position, etc. of the phase difference layer may be appropriately set according to the purpose.

The polarizing plate with phase difference layer of the present invention may further include a conductive layer or an isotropic substrate with a conductive layer (both not shown). The conductive layer or the isotropic substrate with a conductive layer is typically disposed on the outer side of the phase difference layer 40 (the side opposite to the polarizer 10). When the conductive layer or the isotropic substrate with a conductive layer can be disposed, the polarizing plate with phase difference layer can be applied to a so-called internal touch panel type input display device in which a touch sensor is incorporated between a display unit (e.g., a liquid crystal unit, an organic EL unit) and a polarizing plate.

The polarizing plate with phase difference layer can be in the form of a long strip or a thin sheet. When the polarizing plate with phase difference layer is in the form of a long strip, it is preferably rolled into a roll to make a polarizing plate roll with phase difference layer.

Typically, the polarizing plate with a phase difference layer may have an adhesive layer as the outermost layer on one side (typically, the phase difference layer 40 side) and may be attached to a display unit. A surface protection film and/or a carrier film may be temporarily attached to the polarizing plate with a phase difference layer in a removable manner as required to reinforce and/or support the polarizing plate with a phase difference layer. When the polarizing plate with a phase difference layer includes an adhesive layer, a separation piece is temporarily attached to the surface of the adhesive layer in a removable state to protect the adhesive layer before actual use, and the polarizing plate with a phase difference layer may be rolled up.

As described above, the polarizing plate with a phase difference layer of the present invention is very thin, so it can be suitably used in a flexible image display device. Preferably, the image display device has a curved shape (essentially a curved display screen) and/or can be bent or folded. Specific examples of image display devices include liquid crystal display devices and electroluminescent (EL) display devices (such as organic EL display devices and inorganic EL display devices). It goes without saying that the polarizing plate with a phase difference layer of the present invention can be applied to general image display devices without being subject to the above description.

The following is a detailed description of the components of the polarizing plate with phase difference layer.

B. Polarizing plate B-1. Polarizer Any suitable polarizer can be used as the polarizer. Polarizers can be made of laminates with two or more layers. The manufacturing method of polarizers is described in D after the manufacturing method of polarizing plates.

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

The boric acid content of the polarizer is preferably 10% by weight or more, preferably 13% by weight to 25% by weight. As long as the boric acid content of the polarizer is within the above range, the ease of adjusting the curling during lamination can be well maintained by the multiplication effect of the boric acid content and the iodine content described below, and the curling during heating can be well suppressed, while improving the durability of the appearance during heating. The boric acid content can be calculated, for example, by the neutralization method using the following formula in the form of the amount of boric acid contained in the polarizer per unit weight. [Mathematical formula 1]

The iodine content of the polarizer is preferably 2% by weight or more, preferably 2% by weight to 10% by weight. As long as the iodine content of the polarizer is within the above range, the iodine content and the boric acid content can be used to maintain the ease of adjusting the curling during lamination and to suppress the curling during heating, while improving the durability of the appearance during heating. The "iodine content" in this specification refers to the amount of all iodine contained in the polarizer (PVA-based resin film). More specifically, iodine exists in the polarizer in the form of iodine ions ( ^I- ), iodine molecules ( _I2 ), polyiodine ions ( _I3- ^, _I5- ⁾ , etc., and the iodine content in this specification refers to the amount of iodine in all such forms. The iodine content can be calculated using, for example, the calibration curve method of fluorescent X-ray analysis. In addition, polyiodine ions exist in the polarizer in the form of a PVA-iodine complex. By forming the complex, absorption dichroism can be exhibited in the wavelength range of visible light. Specifically, the complex of PVA and triiodide ions (PVA・I ₃ ^- ) has an absorption peak near 470nm; the complex of PVA and pentaiodide ions (PVA・I ₅ ^- ) has an absorption peak near 600nm. As a result, polyiodine ions can absorb light in a wide range of visible light depending on their morphology. On the other hand, iodine ions (I ^- ) have an absorption peak near 230nm, which has no substantial correlation with the absorption of visible light. Therefore, polyiodine ions existing in the form of a complex with PVA are mainly related to the absorption performance of the polarizer.

The polarizer preferably exhibits absorption dichroism at any wavelength between 380nm and 780nm. The single unit transmittance Ts of the polarizer is preferably 40% to 48%, preferably 41% to 46%. The polarization degree P of the polarizer is preferably above 97.0%, preferably above 99.0%, and even more preferably above 99.9%.

B-2. Protective layer As mentioned above, the protective layer is composed of a cured product of a coating film of an organic solvent solution of a thermoplastic acrylic resin (hereinafter simply referred to as acrylic resin). The following is a specific description of the components of the protective layer, followed by a description of the characteristics of the protective layer.

B-2-1. Acrylic resin The Tg of the acrylic resin (including a mixture of two or more acrylic resins and a mixture of an acrylic resin and other resins as described later) is as described in the above section A regarding the protective layer.

Any suitable acrylic resin may be used as long as it has the Tg as described above. The acrylic resin typically contains (meth) alkyl acrylate as the main component as a monomer unit (repeating unit). In this specification, "(meth) acrylic acid" means acrylic acid and/or methacrylic acid. The (meth) alkyl acrylate constituting the main skeleton of the acrylic resin can be exemplified by a linear or branched alkyl having 1 to 18 carbon atoms. These can be used alone or in combination. In addition, any suitable copolymer monomer can be introduced into the acrylic resin by copolymerization. The repeating unit derived from the (meth) alkyl ester is represented by the following general formula (1):

[Chemical formula 1]

In the general formula (1), ^R4 represents a hydrogen atom or a methyl group, and ^R5 represents a hydrogen atom or a substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. Examples of the substituent include halogen and hydroxyl groups. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, n-hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, benzyl (meth)acrylate, dicyclopentyloxyethyl (meth)acrylate, dicyclopentyl (meth)acrylate, chloromethyl (meth)acrylate, 2-chloroethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2,3,4,5,6-pentahydroxyhexyl (meth)acrylate, 2,3,4,5-tetrahydroxypentyl (meth)acrylate, methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and methyl 2-(hydroxyethyl)acrylate. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Therefore, the particularly desirable alkyl (meth)acrylate is methyl acrylate or methyl methacrylate.

The acrylic resin may contain only a single alkyl (meth)acrylate unit, or may contain a plurality of alkyl (meth)acrylate units in which R ⁴ and R ⁵ in the above general formula (1) are different from each other.

The content of the (meth) alkyl acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, more preferably 60 mol% to 98 mol%, particularly preferably 65 mol% to 98 mol%, and most preferably 70 mol% to 97 mol%. If the content is less than 50 mol%, the effects (e.g., high heat resistance, high transparency) derived from the (meth) alkyl acrylate unit may not be fully exerted. If the above content is greater than 98 mol%, there is a concern that the resin becomes brittle and easily cracked, and the high mechanical strength cannot be fully exerted, resulting in poor productivity.

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

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

[Chemical 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. In addition, the organic residue may also contain an oxygen atom. The acrylic resin may contain only a single lactone ring unit, or may contain a plurality of lactone ring units in which R ¹ , R ² and R ³ in the general formula (2) are different from each other. Acrylic resins having lactone ring units are described in, for example, Japanese Patent Publication No. 2008-181078, and the description of the publication is cited in this specification as a reference.

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

[Chemical 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 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms. In the general formula (3), it is preferred that R ¹¹ and R ¹² each independently represent hydrogen or a methyl group, and R ¹³ represents hydrogen, a methyl group, a butyl group, or a cyclohexyl group. It is more preferred that R ¹¹ represents a methyl group, R ¹² represents hydrogen, and R ¹³ represents a methyl group. The acrylic resin may contain only a single pentylimide unit, or may contain a plurality of pentylimide units in which R ¹¹ , R ¹² , and R ¹³ in the general formula (3) are different from each other. Acrylic resins having a glutarimide unit are described in, for example, Japanese Patent Application Laid-Open Nos. 2006-309033, 2006-317560, 2006-328334, 2006-337491, 2006-337492, 2006-337493, and 2006-337569, and the present specification incorporates the description of these publications as reference. In addition, the above description of the glutarimide unit is applicable to the glutaric anhydride unit except that the nitrogen atom substituted by R ¹³ in the above general formula (3) is replaced by an oxygen atom.

The structures of the maleic anhydride unit and the maleimide (N-substituted maleimide) unit can be identified by their names, and thus a specific description thereof will be omitted.

The content 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 more preferably 20 mol% to 30 mol%. When the content is too low, the Tg may be lower than 110°C, and the heat resistance, solvent resistance and surface hardness of the obtained protective layer may be insufficient. When the content is too high, the formability and transparency may be insufficient.

The acrylic resin may contain repeating units other than the (meth)acrylic acid alkyl ester unit and the repeating unit containing a ring structure. The repeating units may be repeating units derived from vinyl monomers copolymerizable with the monomers constituting the above-mentioned units (other vinyl monomer units). Other vinyl monomers include acrylic acid, methacrylic acid, crotonic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, ethyl acrylate, propyl acrylate, dimethyl methacrylate, ethyl methacrylate, propyl methacrylate, cyclohexyl methacrylate, N-vinyldiethylamine, N-acetylvinamine, allylamine, methylallylamine, N-methylallylamine, 2-isopropenyl- Oxazoline, 2-vinyl- Oxazoline, 2-propenyl- Oxazoline, N-phenylmaleimide, ethyl methacrylate, phenylaminoethyl, styrene, α-methylstyrene, p-epoxypropylstyrene, p-aminostyrene, 2-phenylvinyl- Oxazoline, etc. These can be used alone or in combination. The type, amount, combination, content ratio, etc. of other vinyl 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, preferably 5,000 to 1,000,000, more 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 obtained by gel permeation chromatography (GPC system, manufactured by Tosoh Corporation) in terms of polystyrene. In addition, tetrahydrofuran can be used as the solvent.

The acrylic resin can be used by appropriately combining the above-mentioned monomer units and polymerizing them by any appropriate polymerization method. It is also possible to mix two or more acrylic resins having different monomer units.

In the embodiment of the present invention, acrylic resins and other resins can be used in combination. That is, the monomer components constituting the acrylic resin and the monomer components constituting the other resins can be copolymerized, and the copolymer can be used for the formation of the protective layer described later; or a mixture of the acrylic resin and other resins can be used for the formation of the protective layer. Other resins include thermoplastic resins such as styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyetheretherketone, polyester, polysulfone, polyphenylene ether, polyacetal, polyimide, and polyetherimide. The type and blending amount of the resin used in combination can be appropriately set according to the purpose and the desired properties of the resulting film. For example, a styrene resin (preferably an acrylonitrile-styrene copolymer) can be used in combination as a phase difference controller.

When acrylic resin and other resins are used together, the content of acrylic resin in the mixture of acrylic resin and other resins is preferably 50% to 100% by weight, preferably 60% to 100% by weight, more preferably 70% to 100% by weight, and particularly preferably 80% to 100% by weight. If the content is less than 50% by weight, there is a risk that the high heat resistance and high transparency originally possessed by acrylic resin may not be fully exhibited.

B-2-2. Composition and characteristics of the protective layer As mentioned above, the protective layer is composed of a cured product of a coating film of an organic solvent solution of an acrylic resin. As long as it is a cured product of the coating film, its thickness can be much thinner than an extruded film. As mentioned above, the thickness of the protective layer is less than 10 μm, preferably less than 7 μm, preferably less than 5 μm, and more preferably less than 3 μm. The lower limit of the thickness of the protective layer can be, for example, 1 μm. In addition, although it is not clear in theory, the cured product of this coating film shrinks less than the cured product of thermosetting resin or active energy ray curing resin (such as ultraviolet curing resin) during film formation, and does not contain residual monomers, etc., so it has the advantages of suppressing the degradation of the film itself and suppressing the adverse effects of residual monomers on the polarizing plate (polarizer). In addition, since its hygroscopicity and permeability are smaller than the cured product of water-based coating films such as aqueous solutions or water dispersions, it has the advantage of excellent humidification durability. As a result, a polarizing plate (in other words, a polarizing plate with a phase difference layer) that can maintain optical properties and good durability even in a heated and humidified environment can be achieved.

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

The iodine adsorption amount of the protective layer is preferably 4.0 wt % or less, and preferably 3.0 wt % or less, more preferably 2.0 wt % or less, particularly preferably 1.0 wt % or less, and particularly preferably 0.5 wt % or less. The smaller the iodine adsorption amount, the better, and its lower limit can be, for example, 0.1 wt %. As long as the iodine adsorption amount is within the above range, a polarizing plate (in other words, a polarizing plate with a phase difference layer) with better durability can be obtained. The iodine adsorption content can be measured by the method described in the embodiment described below.

The protective layer is preferably substantially optically isotropic. In this specification, "substantially optically isotropic" means that the in-plane phase difference Re(550) is 0nm~10nm, and the phase difference Rth(550) in the thickness direction is -20nm~+10nm. The in-plane phase difference Re(550) is preferably 0nm~5nm, more preferably 0nm~3nm, and especially 0nm~2nm. The phase difference Rth(550) in the thickness direction is preferably -5nm~5nm, more preferably -3nm~3nm, and especially -2nm~2nm. As long as the Re(550) and Rth(550) of the protective layer are within the above range, when the polarizing plate with a phase difference layer including the protective layer is used in an image display device, it can prevent adverse effects on the display characteristics.

The higher the light transmittance of the protective layer at 3µm thickness at 380nm, the better. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, and more preferably 90% or more. As long as the light transmittance is within the above range, the desired transparency can be ensured. The light transmittance can be measured, for example, according to the method of ASTM-D-1003.

The lower the haze of the protective layer, the better. Specifically, it is preferably less than 5%, preferably less than 3%, more preferably less than 1.5%, and particularly preferably less than 1%. As long as the haze is less than 5%, the film can be given a good sense of transparency. Moreover, even if a polarizing plate with a phase difference layer is used on the visual side of the image display device, the displayed content can still be well visually recognized.

The YI of the protective layer with a thickness of 3µm should be less than 1.27, preferably less than 1.25, more preferably less than 1.23, and particularly preferably less than 1.20. When the YI is greater than 1.3, the optical transparency may be insufficient. In addition, the YI can be obtained from the color tristimulus values (X, Y, Z) measured using a high-speed integrating sphere spectroscopic transmittance meter (trade name DOT-3C: made by Murakami Color Technology Laboratory) using the following formula. YI=[(1.28X-1.06Z)/Y]×100

The b value (hue scale based on the Hunter color system) of the protective layer at a thickness of 3 μm is preferably less than 1.5, and preferably less than 1.0. When the b value is above 1.5, an undesirable color tone may sometimes appear. In addition, the b value can be obtained, for example, in the following manner: a sample of the film constituting the protective layer is cut into a 3 cm square, and the hue is measured using a high-speed integrating sphere spectroscopic transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Technology Laboratory), and the hue is evaluated according to the Hunter color system.

The protective layer (cured product of the coating film) may contain any appropriate additives according to the purpose. Specific examples of additives include ultraviolet absorbers; leveling agents; antioxidants such as hindered phenol, phosphorus, and sulfur; stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; reinforcing materials such as glass fiber and carbon fiber; near-infrared absorbers; flame retardants such as tris(dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and non-ionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic fillers or inorganic fillers; resin modifiers; organic fillers or inorganic fillers; plasticizers; lubricants; antistatic agents; flame retardants, etc. Additives can be added during the polymerization of acrylic resins or added to the solution during film formation. The type, amount, combination, and amount of additives can be appropriately set according to the purpose.

The protective layer may also be provided with an easy-adhesion layer on the polarizer side. The easy-adhesion layer may include, for example, water-based polyurethane and Oxazoline crosslinking agent. By forming the easy-adhesion layer, the adhesion between the protective layer and the polarizer can be improved. In addition, a hard coating layer can also be formed on the protective layer. The hard coating layer can be formed when the protective layer is used as a visual side protective layer of a visual side polarizer. When both the easy-adhesion layer and the hard coating layer are formed, they can be formed on different sides of the protective layer.

B-3. Manufacturing method of polarizing plate B-3-1. Manufacturing method of polarizing element The manufacturing method of polarizing element described in item B-1 above includes the following steps: forming a polyvinyl alcohol resin layer (PVA resin layer) containing a halogenated substance and a polyvinyl alcohol resin (PVA resin) on one side of a long strip of thermoplastic resin substrate to form a laminate; and sequentially subjecting the laminate to air-assisted stretching treatment, dyeing treatment, underwater stretching treatment and drying shrinkage treatment, wherein the drying shrinkage treatment is to heat the laminate while conveying it in the longitudinal direction, thereby shrinking it by more than 2% in the width direction. The content of the halogenated substance in the PVA-based resin layer is preferably 5 to 20 parts by weight relative to 100 parts by weight of the PVA-based resin. The drying and shrinking treatment is preferably carried out using a heating roller, and the temperature of the heating roller is preferably 60°C to 120°C. According to the manufacturing method, a polarizer as described above can be obtained. In particular, a polarizer having excellent optical properties (represented by single body transmittance and polarization degree) and suppressed optical property variations can be obtained by the following method: after preparing a laminate including a PVA-based resin layer containing a halogenated substance, the laminate is extended by a multi-stage extension including air-assisted extension and underwater extension, and the extended laminate is then heated by a heating roller. Specifically, by using a heating roller in the drying and shrinking step, the laminate can be uniformly shrunk while being transported. This not only improves the optical properties of the resulting polarizer, but also enables stable production of polarizers with excellent optical properties, and suppresses the variation of the optical properties of the polarizer (especially the single-unit transmittance). The following describes the halides and the drying and shrinking treatment. The details of the manufacturing methods other than these are described, for example, in Japanese Patent Publication No. 2012-73580. The entire contents of the publication are cited in this specification as a reference.

B-3-1-1. Halogenated substances The PVA resin layer containing halogenated substances and PVA resins can be formed by applying a coating liquid containing halogenated substances and PVA resins on a thermoplastic resin substrate and drying the coating film. The coating liquid is typically a solution in which the halogenated substances and the PVA resins are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyols such as trihydroxymethylpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Of these, water is preferred. The PVA resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as the resin concentration is the above, a uniform coating film that adheres closely to the thermoplastic resin substrate can be formed.

Any appropriate halides may be used as the halides. Examples thereof include iodides and sodium chloride. Examples of iodides include potassium iodide, sodium iodide and lithium iodide. Among these, potassium iodide is preferred.

The amount of halogen in the coating liquid is preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight, relative to 100 parts by weight of the PVA resin. If the amount of halogen is too much, the halogen will overflow and make the resulting polarizer white and cloudy.

Generally speaking, when a PVA resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA resin layer becomes higher. However, if the stretched PVA resin layer is immersed in a water-containing liquid, the orientation of the polyvinyl alcohol molecules will be disordered and the orientation will be reduced. In particular, when a laminate of a thermoplastic resin substrate and a PVA resin layer is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin substrate, the tendency of the above orientation to be reduced is very obvious. For example, the stretching of a PVA film monomer in boric acid water is generally carried out at 60°C. In contrast, the stretching of a laminate of A-PET (thermoplastic resin substrate) and a PVA-based resin layer is carried out at a relatively high temperature of about 70°C. At this time, the orientation of the PVA at the beginning of the stretching decreases before it rises due to the stretching in water. In response to this, by preparing a laminate of a PVA-based resin layer containing a halogenated substance and a thermoplastic resin substrate, and stretching the laminate at a 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 resin layer is immersed in a liquid, the orientation disorder of the polyvinyl alcohol molecules and the reduction of orientation can be suppressed compared to the case where the PVA resin layer does not contain halides. As a result, the optical properties of the polarizer obtained by immersing the laminate in a liquid through a dyeing process and an underwater stretching process can be improved.

B-3-1-2. Drying and shrinking treatment The drying and shrinking treatment can be performed by heating the entire area, or by heating the conveying roller (so-called using a heating roller) (heating roller drying method). It is preferred to use both. By using a heating roller to dry it, the heat curling of the laminate can be effectively suppressed, and a polarizer with excellent appearance can be manufactured. Specifically, by drying the laminate along the heating roller, the crystallization of the thermoplastic resin substrate can be effectively promoted and the crystallization degree can be increased. Even at a relatively low drying temperature, the crystallization degree of the thermoplastic resin substrate can still be well increased. As a result, the rigidity of the thermoplastic resin substrate increases and becomes a state that can withstand the shrinkage of the PVA-based resin layer due to drying, thereby suppressing curling. In addition, by using a heating roller, the laminate can be dried while maintaining a flat state, so that not only the generation of curling but also the generation of wrinkles can be suppressed. At this time, the laminate can be shrunk in the width direction through a drying and shrinking treatment to improve the optical properties. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage rate in the width direction obtained by the drying and shrinking treatment of the laminate is preferably 2%~10%, more preferably 2%~8%, and particularly preferably 4%~6%. By using heated rollers, the laminate can be continuously contracted in width while being transported, thus achieving high production rates.

FIG3 is a schematic diagram showing an example of a drying and shrinking process. In the drying and shrinking process, the laminate 200 is dried while being transported by using the conveying rollers R1 to R6 and the guide rollers G1 to G4 that have been heated to a predetermined temperature. In the example of the figure, the conveying rollers R1 to R6 are arranged to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate, but, for example, the conveying rollers R1 to R6 may also be arranged to continuously heat only one surface of the laminate 200 (for example, the surface of the thermoplastic resin substrate).

The drying conditions can be controlled by adjusting the heating temperature of the conveyor roller (temperature of the heating roller), the number of heating rollers, and the contact time with the heating roller. The temperature of the heating roller is preferably 60°C~120°C, more preferably 65°C~100°C, and particularly preferably 70°C~80°C. While the crystallization degree of the thermoplastic resin can be increased well and the curling can be suppressed well, an optical laminate with excellent durability can be produced. In addition, the temperature of the heating roller can be measured by a contact thermometer. In the example of the figure, 6 conveyor rollers are provided, but there is no particular limitation as long as there are a plurality of conveyor rollers. The number of conveyor rollers is usually 2~40, and it is preferably 4~30. The contact time (total contact time) between the laminate and the heating roller is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

The heating roller can be installed in a heating furnace (such as an oven) or in a general manufacturing line (at room temperature). It is best to install it in a heating furnace equipped with an air supply mechanism. By using the heating roller and hot air drying together, the rapid temperature change between the heating rollers can be suppressed, and the shrinkage in the width direction can be easily controlled. The temperature of hot air drying should be 30℃~100℃. In addition, the hot air drying time should be 1 second~300 seconds. The wind speed of the hot air should be around 10m/s~30m/s. In addition, the wind speed is the wind speed in the heating furnace, which can be measured by a mini fan-type digital anemometer.

It is preferred to perform a cleaning treatment after the water stretching treatment and before the drying shrinkage treatment. The cleaning treatment can be performed by immersing the PVA resin layer in a potassium iodide aqueous solution.

According to the above method, a thermoplastic resin substrate/polarizer laminate can be obtained.

B-3-2. Method for manufacturing polarizing plate The surface of the laminate obtained in B-3-1 is coated with an organic solvent solution of acrylic resin to form a coating film, and the coating film is cured to form a protective layer.

The acrylic resin is as described in the above-mentioned item B-2-1.

Any appropriate organic solvent that can dissolve or uniformly disperse the acrylic resin can be used as the organic solvent. Specific examples of the organic solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The acrylic resin concentration of the solution is preferably 3 to 20 parts by weight relative to 100 parts by weight of the solvent. As long as the resin concentration is the above, a uniform coating film that adheres closely to the polarizer can be formed.

The solution can be applied to any appropriate substrate or to a polarizer. When the solution is applied to the substrate, the solidified product of the coating film formed on the substrate is transferred to the polarizer. When the solution is applied to the polarizer, a protective layer is directly formed on the polarizer by drying (curing) the coating film. It is preferred that the solution is applied to the polarizer to form a protective layer directly on the polarizer. As long as the structure is as described above, the adhesive layer or the adhesive layer required for transfer can be omitted, so the polarizer with a phase difference layer can be made thinner. Any appropriate method can be used for applying the solution. Specific examples include roller coating, spin coating, wire rod coating, dip coating, die coating, curtain coating, spray coating, and scraper coating (comma coating, etc.).

By drying (curing) the coating film of the solution, a protective layer can be formed. The drying temperature is preferably below 100°C, more preferably 50°C to 70°C. As long as the drying temperature is within the above range, adverse effects on the polarizer can be prevented. The drying time can be varied according to the drying temperature. The drying time can be, for example, 1 minute to 10 minutes.

By forming the protective layer in the above manner, a laminate of thermoplastic resin substrate/polarizer/protective layer can be obtained. By peeling off the thermoplastic resin substrate from the laminate, a polarizing plate having a polarizer 10 and a protective layer 20 as shown in Figures 1 and 2 can be obtained. By forming a phase difference layer 40 on the polarizer surface of the polarizing plate, a polarizing plate with a phase difference layer can be obtained. Alternatively, a resin film constituting a phase difference layer can be bonded to the polarizer surface of the laminate of the thermoplastic resin substrate/polarizer, and then the thermoplastic resin substrate is peeled off and a protective layer is formed on the peeled surface. In this case, a polarizing plate with a phase difference layer can be obtained with high manufacturing efficiency. In addition, the phase difference layer can be formed by a method known in the industry, so the detailed description is omitted and a brief description is given in the following item C.

C. Phase difference layer C-1. Phase difference layer composed of a single layer When the phase difference layer is composed of a single layer, the Re (550) of the phase difference layer is, for example, 100nm~190nm as described above, and the angle formed by the slow axis of the phase difference layer 40 and the absorption axis of the polarizer 10 is, for example, 40°~50°. The phase difference layer is typically provided to give the polarizing plate anti-reflection properties, and in one embodiment, it can function as a λ/4 plate. The phase difference layer can be a resin film as described above, or a directional solidification layer of a liquid crystal compound.

The phase difference layer preferably has a refractive index characteristic showing a relationship of nx>ny≧nz. The in-plane phase difference Re(550) of the phase difference layer is, for example, 100nm~190nm as described above, preferably 110nm~170nm, more preferably 130nm~160nm. In addition, "ny＝nz" here does not only include the case where ny and nz are completely the same, but also includes the case where they are substantially the same. Therefore, there may be a situation where ny>nz without damaging the effect of the present invention.

The Nz coefficient of the phase difference layer is preferably 0.9-3, preferably 0.9-2.5, more preferably 0.9-1.5, and most preferably 0.9-1.3. By satisfying the above relationship, when the obtained polarizing plate with phase difference layer is used in an image display device, a very excellent reflection hue can be achieved.

The angle θ formed by the slow axis of the phase difference 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. As long as the angle θ is within the above range, by using the phase difference layer as a λ/4 plate, a polarizing plate with a phase difference layer having very excellent circular polarization characteristics (resulting in very excellent anti-reflection characteristics) can be obtained.

The phase difference layer can exhibit an inverse dispersion wavelength characteristic in which the phase difference value increases with the wavelength of the measured light, a normal wavelength dispersion characteristic in which the phase difference value decreases with the wavelength of the measured light, or a flat wavelength dispersion characteristic in which the phase difference value hardly changes with the wavelength of the measured light. In one embodiment, the phase difference layer exhibits an inverse dispersion wavelength characteristic. In this case, Re(450)/Re(550) of the phase difference layer is preferably greater than 0.8 and less than 1, and more preferably greater than 0.8 and less than 0.95. With the above-mentioned structure, very excellent anti-reflection characteristics can be achieved.

The phase difference layer includes a resin having an absolute value of a photoelastic coefficient of preferably 2×10 ^-11 m ² /N or less, preferably 2.0×10 ^-13 m ² /N to 1.5×10 ^-11 m ² /N, and more preferably 1.0×10 ^-12 m ^{2 /} N to 1.2× ^{10 -11} m ² /N. When the absolute value of the photoelastic coefficient is within the above range, the phase difference is unlikely to change when shrinkage stress is generated during heating. As a result, thermal unevenness of the obtained image display device can be well prevented.

C-1-1. Resin film When the phase difference layer is a resin film, the resin film is typically a stretched film. In this case, the thickness of the phase difference layer is preferably 60 μm or less, more preferably 30 μm to 55 μm. As long as the thickness of the phase difference layer is within the above range, curling during heating can be well suppressed, and curling during bonding can be well adjusted.

The phase difference layer can be formed of any appropriate resin film that can satisfy the above-mentioned characteristics. Representative examples of the resin include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyether resins, polystyrene resins, and acrylic resins. These resins can be used alone or in combination (e.g., blending, copolymerization). When the phase difference layer is composed of a resin film showing reverse dispersion wavelength characteristics, a polycarbonate resin or a polyester carbonate resin (hereinafter sometimes simply referred to as a polycarbonate resin) can be appropriately used.

As long as the effects of the present invention can be obtained, any appropriate polycarbonate resin can be used as the polycarbonate resin. For example, the polycarbonate resin includes 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 at least one dihydroxy compound selected from the group consisting of alicyclic diols, alicyclic dimethanols, di-, tri- or polyethylene glycols, and alkylene glycols or spiroglycerol. Preferably, the polycarbonate resin comprises structural units derived from fluorene dihydroxy compounds, structural units derived from isosorbide dihydroxy compounds, structural units derived from alicyclic dimethanol, and/or structural units derived from di, tri or polyethylene glycol; more preferably, it comprises structural units derived from fluorene dihydroxy compounds, structural units derived from isosorbide dihydroxy compounds, and structural units derived from di, tri or polyethylene glycol. The polycarbonate resin may also comprise structural units derived from other dihydroxy compounds as required. In addition, the details of the polycarbonate resin that can be suitably used in the present invention are described in, for example, Japanese Patent Publication No. 2014-10291, Japanese Patent Publication No. 2014-26266, Japanese Patent Publication No. 2015-212816, Japanese Patent Publication No. 2015-212817, and Japanese Patent Publication No. 2015-212818, and this specification cites these descriptions as references.

The glass transition temperature of the polycarbonate resin is preferably 110°C or higher and 150°C or lower, and preferably 120°C or higher and 140°C or lower. If the glass transition temperature is too low, the heat resistance tends to deteriorate, which may cause dimensional changes after film formation or reduce the image quality of the resulting organic EL panel. If the glass transition temperature is too high, the forming stability during film formation may deteriorate or the transparency of the film may be impaired. In addition, the glass transition temperature can be obtained in accordance with JIS K 7121 (1987).

The molecular weight of the aforementioned polycarbonate resin can be expressed as a relative viscosity. The relative viscosity is measured by using methylene chloride as a solvent, after the polycarbonate concentration is precisely adjusted to 0.6 g/dL, using an Oodel viscometer at a temperature of 20.0°C ± 0.1°C. The lower limit of the relative viscosity is usually preferably 0.30 dL/g, and more preferably 0.35 dL/g or more. The upper limit of the relative viscosity is usually preferably 1.20 dL/g, and preferably 1.00 dL/g, and more preferably 0.80 dL/g. If the relative viscosity is less than the aforementioned lower limit, there is a problem that the mechanical strength of the molded product is reduced. On the other hand, if the relative viscosity is greater than the aforementioned upper limit, the fluidity during molding will decrease, and there is a problem of reduced productivity or moldability.

Commercially available polycarbonate resin films may also be used. Specific examples of commercial products include "PURE-ACE WR-S", "PURE-ACE WR-W", and "PURE-ACE WR-M" manufactured by Teijin Co., Ltd. and "NRF" manufactured by Nitto Denko Co., Ltd.

The phase difference layer 40 can be obtained, for example, by stretching a film formed from the above-mentioned polycarbonate resin. The method of forming a film from a polycarbonate resin can adopt any appropriate molding method. Specific examples include: compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, casting and coating (such as casting), calendering, hot pressing, etc. Extrusion molding or casting and coating is preferred. This is because the smoothness of the obtained film can be improved, thereby obtaining good optical uniformity. The molding conditions can be appropriately set according to the resin composition or type used, the desired properties of the phase difference film, etc. In addition, as mentioned above, many polycarbonate resin films are sold on the market, so the commercially available films can be directly subjected to the stretching treatment.

The thickness of the resin film (unstretched film) can be set to any appropriate value according to the desired thickness of the phase difference layer, the desired optical properties, the stretching conditions described below, etc. It is preferably 50 μm to 300 μm.

The above-mentioned stretching can adopt any appropriate stretching method and stretching conditions (such as stretching temperature, stretching ratio, stretching direction). Specifically, various stretching methods such as free end stretching, fixed end stretching, free end shrinkage, fixed end shrinkage, etc. can be used alone, or they can be used simultaneously or successively. Regarding the stretching direction, it can also be carried out along various directions or dimensions such as length direction, width direction, thickness direction, oblique direction, etc. The stretching temperature is preferably Tg-30℃~Tg+60℃ relative to the glass transition temperature (Tg) of the resin film, and preferably Tg-10℃~Tg+50℃.

By appropriately selecting the stretching method and stretching conditions, a retardation film having the desired optical properties (such as refractive index properties, in-plane phase difference, Nz coefficient) can be obtained.

In one embodiment, the phase difference film can be produced by uniaxially stretching a resin film or by uniaxially stretching a fixed end. A specific example of uniaxially stretching a fixed end is to stretch the resin film in the width direction (lateral direction) while moving the resin film in the long direction. The stretching ratio is preferably 1.1 to 3.5 times.

In another embodiment, the phase difference film can be produced by continuously extending a long strip of resin film obliquely in the direction of the above-mentioned angle θ relative to the long side direction. By adopting the oblique stretching, a long strip of stretched film having an orientation angle of angle θ relative to the long side direction of the film (having a slow axis in the direction of angle θ) can be obtained. For example, when layered with a polarizer, it can be rolled to roll, thereby simplifying the manufacturing steps. In addition, the angle θ can be the angle formed by the absorption axis of the polarizer in the polarizing plate with a phase difference layer and the slow axis of the phase difference layer. As mentioned above, the angle θ is preferably 40°~50°, and preferably 42°~48°, and more preferably about 45°.

The stretching machine used for the oblique stretching may be a tenter-type stretching machine, which is a machine that applies conveying force, stretching force or pulling force at different speeds in the transverse and/or longitudinal directions. The tenter-type stretching machine includes a transverse single-axis stretching machine, a simultaneous double-axis stretching machine, etc. Any appropriate stretching machine can be used as long as it can continuously stretch the long strip of resin film in an oblique direction.

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

The stretching temperature of the above film will vary depending on the desired in-plane phase difference value and thickness of the phase difference layer, the type of resin used, the thickness of the film used, the stretching ratio, etc. Specifically, the stretching temperature is preferably Tg-30℃~Tg+30℃, more preferably Tg-15℃~Tg+15℃, and most preferably Tg-10℃~Tg+10℃. By stretching at the above temperature, a phase difference layer having characteristics suitable for the present invention can be obtained. In addition, Tg is the glass transition temperature of the constituent material of the film.

C-1-2. Oriented solidified layer of liquid crystal compound When the phase difference layer is an oriented solidified layer of liquid crystal compound, by using liquid crystal compound, the difference between nx and ny of the obtained phase difference layer can be made much larger than that of non-liquid crystal material, so the thickness of the phase difference layer required to obtain the desired in-plane phase difference can be greatly reduced. As a result, the polarizing plate with phase difference layer can be further thinned. The so-called "oriented solidified layer" in this specification refers to a layer in which the liquid crystal mixture is oriented in a predetermined direction within the layer, and the orientation state has been fixed. In addition, the concept of "oriented solidified layer" includes an oriented hardened layer obtained by hardening the liquid crystal monomer as described later. In this embodiment, it is represented that the rod-shaped liquid crystal compound is oriented (oriented along the plane) in a state where it is arranged along the slow axis direction of the phase difference layer.

Examples of the liquid crystal compound include liquid crystal compounds having a nematic phase (nematic liquid crystal). The liquid crystal compound may be, for example, a liquid crystal polymer or a liquid crystal monomer. The liquid crystal compound may exhibit liquid crystallinity in a lyotropic or thermotropic manner. 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 cross-linking monomer. This is because the orientation state of the liquid crystal monomer can be fixed by polymerizing or cross-linking (i.e., hardening) the liquid crystal monomer. After the liquid crystal monomer is oriented, the orientation state can be fixed by, for example, polymerizing or cross-linking the liquid crystal monomers. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by cross-linking, but these are non-liquid crystal. Therefore, the phase difference layer formed, for example, will not undergo the transformation into a liquid crystal phase, a glass phase, or a crystalline phase due to temperature changes that is unique to liquid crystal compounds. The resulting layer will become a phase difference layer that is not affected by temperature changes and has extremely excellent stability.

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.

The above-mentioned liquid crystal monomer can be any appropriate liquid crystal monomer. For example, the polymerizable liquid crystal original compound described in Japanese Patent Publication No. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171 and GB2280445 can be used. Specific examples of the polymerizable liquid crystal original compound include BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. The liquid crystal monomer is preferably, for example, a nematic liquid crystal monomer.

The oriented solidified layer of the liquid crystal compound can be formed by the following method: performing an oriented treatment on the surface of a predetermined substrate, applying a coating liquid containing the liquid crystal compound on the surface to orient the liquid crystal compound in a direction corresponding to the above-mentioned oriented treatment, and then fixing the oriented state. In one embodiment, the substrate is any appropriate resin film, and the oriented solidified 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 after the oriented solidified layer (phase difference layer) is formed, it can be laminated in a roll-to-roll manner, thereby further improving productivity.

The above-mentioned orientation treatment can adopt any appropriate orientation treatment. Specifically, mechanical orientation treatment, physical orientation treatment, and chemical orientation treatment can be mentioned. Specific examples of mechanical orientation treatment include friction treatment and stretching treatment. Specific examples of physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of chemical orientation treatment include oblique evaporation method and light orientation treatment. The treatment conditions of various orientation treatments can adopt any appropriate conditions according to the purpose.

The alignment of the liquid crystal compound can be performed by treating the liquid crystal compound at a temperature that can exhibit a liquid crystal phase according to the type of the liquid crystal compound. By performing the temperature treatment, the liquid crystal compound changes to a liquid crystal state, and the liquid crystal compound is aligned according to the alignment treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned in the above manner. When the liquid crystal compound is a polymerizable monomer or a crosslinking monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned in the above manner to a polymerization treatment or a crosslinking treatment.

Specific examples of liquid crystal compounds and details of a method for forming an oriented solidified layer are described in Japanese Unexamined Patent Publication No. 2006-163343, and the contents of this publication are incorporated herein by reference.

Another example of an oriented solidified layer is a discotic liquid crystal compound oriented in any of the states of vertical orientation, mixed orientation and tilted orientation. The discotic liquid crystal compound is typically oriented so that the disc plane of the discotic liquid crystal compound is substantially perpendicular to the film plane of the phase difference layer. The discotic liquid crystal compound is substantially perpendicular means that the average value of the angle formed by the film plane and the disc plane of the discotic liquid crystal compound is preferably 70°~90°, and 80°~90° is more preferred, and 85°~90° is even more preferred. The so-called discotic liquid crystal compound generally refers to a liquid crystal compound having a discotic molecular structure, wherein the discotic molecular structure is a combination of olefins such as benzene, 1,3,5-triazine and 1,4-diol. The cyclic mother nucleus of calixarene, etc. is arranged at the center of the molecule, and the straight chain alkyl, alkoxy, substituted benzyloxy, etc. are radially substituted as its side chains. Representative examples of discotic liquid crystals include: benzene derivatives, triphenylene derivatives, indenylene derivatives, and phthalocyanine derivatives described in the research report of C. Destrade et al., Mol. Cryst. Liq. Cryst., Vol. 71, p. 111 (1981); cyclohexane derivatives described in the research report of B. Kohne et al., Angew. Chem., Vol. 96, p. 70 (1984); and nitrogen-doped crown ether-based or phenylacetylene-based macrocycles described in the research report of J. M. Lehn et al., J. Chem. Soc. Chem. Commun., p. 1794 (1985) and in the research report of J. Zhang et al., J. Am. Chem. Soc., Vol. 116, p. 2655 (1994). More specific examples of discotic liquid crystal compounds include compounds described in Japanese Patent Application Publication No. 2006-133652, Japanese Patent Application Publication No. 2007-108732, and Japanese Patent Application Publication No. 2010-244038. The descriptions of the above documents and publications are incorporated herein by reference.

When the phase difference layer is a directional solidified layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, and more preferably 1 μm to 5 μm. By using a liquid crystal compound, the same in-plane phase difference as a resin film can be achieved with a much thinner thickness than a resin film.

C-1-3. Another phase difference layer As mentioned above, when the phase difference layer 40 is composed of a single layer, it is preferable to set another phase difference layer. As mentioned above, the other phase difference layer can be a so-called positive C-plate whose refractive index characteristics show the relationship of nz＞nx＝ny. By using a positive C-plate as another phase difference layer, oblique reflection can be well prevented, and the anti-reflection function can be widened to a wide viewing angle. At this time, the phase difference Rth(550) in the thickness direction of the other phase difference layer is preferably -50nm~-300nm, and preferably -70nm~-250nm, more preferably -90nm~-200nm, and particularly preferably -100nm~-180nm. Here, "nx=ny" not only includes the case where nx and ny are exactly equal, but also includes the case where nx and ny are substantially equal. That is, the in-plane phase difference Re(550) of the other phase difference layer may be smaller than 10 nm.

Another phase difference layer having a refractive index characteristic of nz＞nx＝ny can be formed of any appropriate material. The other phase difference layer is preferably composed of a thin film containing a liquid crystal material fixed in a homeotropic orientation. The liquid crystal material (liquid crystal compound) that can be homeotropically oriented can be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the method for forming the liquid crystal compound and the phase difference layer can be cited as the method for forming the liquid crystal compound and the phase difference layer described in paragraphs [0020] to [0028] of Japanese Patent Gazette No. 2002-333642. At this time, the thickness of the other phase difference layer is preferably 0.5μm~10μm, and preferably 0.5μm~8μm, and more preferably 0.5μm~5μm.

C-2.2 Phase difference layer with a layered structure When the phase difference layer 40 is a phase difference layer having a layered structure of a first layer 41 and a second layer 42, either the first layer 41 or 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 phase difference Re(550) of the first layer is, for example, 200nm~300nm as described above, preferably 230nm~290nm, and more preferably 250nm~280nm. The in-plane phase difference Re(550) of the second layer is, for example, 100nm~190nm, as described above, preferably 110nm~170nm, and more preferably 130nm~160nm. The angle formed by the slow axis of the first layer and the absorption axis of the polarizer is, for example, 10°~20°, as described above, preferably 12°~18°, and more preferably about 15°. The angle formed by the slow axis of the second layer and the absorption axis of the polarizer is, for example, 70°~80°, as described above, preferably 72°~78°, and more preferably about 75°. As long as it is the above-mentioned structure, characteristics close to the ideal reverse wavelength dispersion characteristics can be obtained, and as a result, very excellent anti-reflection characteristics can be achieved.

The first layer 41 and the second layer 42 may be either a resin film or a liquid crystal compound oriented solidified layer. Preferably, the first layer 41 and the second layer 42 are both resin films or liquid crystal compound oriented solidified layers.

The thickness of the first layer 41 and the second layer 42 can be adjusted to obtain the desired in-plane phase difference of the λ/4 plate or the 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, and the first layer 41 and the second layer 42 are resin films, the thickness of the first layer 41 is, for example, 40 μm to 75 μm, and the thickness of the second layer 42 is, for example, 30 μm to 55 μm. When the first layer 41 and the second layer 42 are directional solidification layers of liquid crystal compounds, 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 2.0 μm.

The resin films constituting the first layer and the second layer, the liquid crystal compound, the formation methods of the first layer and the second layer, the optical properties, etc. are the same as described above regarding the single layer.

D. Conductive layer or isotropic substrate with conductive layer attached The conductive layer can be formed by forming a metal oxide film on any suitable substrate using any suitable film forming method (e.g. vacuum evaporation, sputtering, CVD, ion plating, spraying, etc.). Examples of metal oxides include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium-tin composite oxide (ITO) is preferred.

When the conductive layer comprises 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 can be made by transferring from the above substrate to the phase difference layer and using the conductive layer alone as a constituent layer of the polarizing plate with a phase difference layer, or can be laminated on the phase difference layer in the form of a laminate of the conductive layer and the substrate (substrate with conductive layer). It is more desirable that the above substrate is optically isotropic, so the conductive layer can be used as an isotropic substrate with a conductive layer for the polarizing plate with a phase difference layer.

The optically isotropic substrate (isotropic substrate) can adopt any appropriate isotropic substrate. The material constituting the isotropic substrate can be, for example, a material having a resin without a conjugated system such as a norbornene resin or an olefin resin as the main skeleton, a material having a cyclic structure such as a lactone ring or a pentylimide ring in the main chain of an acrylic resin, etc. If the above material is used, the phase difference exhibited when the isotropic substrate is formed along with the orientation of the molecular chain can be suppressed to a smaller value. The thickness of the isotropic substrate is preferably less than 50 μm, and more preferably less than 35 μm. 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 can be patterned as needed. Conductive portions and insulating portions can be formed by patterning. As a result, electrodes can be formed. The electrodes can function as touch sensing electrodes for sensing contact with the touch panel. Any appropriate method can be used for patterning. Specific examples of patterning methods include wet etching and screen printing. Implementation Examples

The present invention is specifically described below with reference to the examples, but the present invention is not limited to the examples. The measuring methods of each characteristic are as follows. In addition, unless otherwise specified, the "parts" and "%" in the examples are by weight.

(1) Glass transition temperature Tg The materials constituting the protective layer used in the examples and comparative examples were dissolved in a predetermined solvent, and the resulting solution was applied to the substrate (PET film) using a sprinkler, and dried at 60°C to form a coating (thickness 40 μm). The resulting coating was peeled off from the substrate and cut into short pieces to prepare a test sample. The test sample was subjected to DMA measurement to measure Tg. The measurement device and measurement conditions are as follows. (Measurement equipment) SII NanoTechnology Inc., "DMS6100" (Measurement conditions) ・Measurement temperature range: -80℃~150℃ ・Heat-up rate: 2℃/min ・Measurement sample width: 10mm ・Clamp distance: 20mm ・Measurement frequency: 1Hz ・Strain amplitude: 10μm ・Measurement gas environment: _N2 (250mL/min) (2) Iodine adsorption amount The materials constituting the protective layer used in the examples and comparative examples were dissolved in a predetermined solvent and the resulting solution was applied to a substrate (PET film) using a sprayer and dried at 60℃ to form a coating (thickness 40μm). The resulting coating was peeled off from the substrate and cut into 1cm×1cm ( ^1cm2 ) pieces to prepare measurement samples. The test sample is subjected to the combustion IC method, and the amount of iodine in the sample is quantitatively analyzed. Specifically, the test sample is taken into a headspace vial (20 mL capacity) and weighed. Then, a vial (2 mL capacity) containing 1 mL of iodine solution (iodine concentration 1 weight%, potassium iodide concentration 7 weight%) is placed into the headspace vial and tightly capped. Afterwards, the headspace vial is heated at 65°C in a dryer for 6 hours, the heated sample is taken into a ceramic boat and burned using an automatic combustion device, and the generated gas is collected into an absorption liquid, and then quantitatively analyzed to determine the weight % of adsorbed iodine. In addition, the device used is as follows.・Automatic sample combustion device: "AQF-2100H" manufactured by Mitsubishi Chemical ANALYTECH Co., Ltd. ・IC (anion): "ICS-3000" manufactured by Thermo Fisher Scientific Co., Ltd. (3) Fading A test piece (50 mm × 50 mm) was cut out from the polarizing plate with a phase difference layer obtained in the embodiment and the comparative example. The test piece had two sides opposite to the direction perpendicular to the absorption axis direction of the polarizer and the absorption axis direction. The test piece was adhered to an alkali-free glass plate with an adhesive so that the protective layer was on the outside to prepare a test sample. The test sample was placed in an oven at 85°C and 85% RH for 48 hours for heating and humidification. Then, when the sample was arranged in a state of orthogonal polarization with a standard polarizing plate, the fading state of the humidified polarizing plate with a phase difference layer was visually inspected and evaluated according to the following criteria. No problem: No fading was observed. Partial fading: Fading was observed at the end. Overall fading: The polarizing plate as a whole was obviously faded. (4) Single body transmittance and polarization degree. A test piece (50 mm × 50 mm) was cut out from the polarizing plate with a phase difference layer obtained in the embodiment and the comparative example. The test piece formed two sides that were perpendicular to the absorption axis direction of the polarizer and opposite to the absorption axis direction. The test piece is bonded to an alkali-free glass plate with an adhesive so that the protective layer is on the outside to prepare a test sample. The single transmittance (Ts), parallel transmittance (Tp) and orthogonal transmittance (Tc) of the test sample are measured using an ultraviolet visible spectrophotometer (manufactured by JASCO Corporation, product name "V7100"), and the polarization degree (P) is calculated using the following formula. At this time, the measured light is incident from the protective layer side. Polarization degree (P) (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 × 100 In addition, the above Ts, Tp and Tc are the Y values obtained by measuring the 2-degree field of view (C light source) of JIS Z 8701 and performing visual sensitivity correction. In addition, Ts and P are actually the characteristics of the polarizer. Then, the polarizing plate with the phase difference layer was placed in an oven at 85°C and 85%RH for 48 hours for heating and humidification (heating test). The single transmittance change ΔTs was calculated from the single transmittance Ts ₀ before the heating test and the single transmittance Ts ₄₈ after the heating test using the following formula. ΔTs (%) = Ts ₄₈ - Ts ₀ Similarly, the polarization change ΔP was calculated from the polarization P ₀ before the heating test and the polarization P ₄₈ after the heating test using the following formula. ΔP (%) = P ₄₈ - P ₀ In addition, the heating test was conducted by preparing the test sample in the same manner as the above-mentioned evaluation of fading. (5) Front reflectivity A test piece (50 mm × 50 mm) was cut out from the polarizing plate with a phase difference layer obtained in the example and the comparative example. The test piece formed two sides opposite to the direction perpendicular to the absorption axis direction of the polarizer and the absorption axis direction. The test piece was adhered to an alkali-free glass plate with an adhesive in such a way that the protective layer became the outer side, thereby preparing a test sample. The test sample was subjected to a humidification test at 85°C and 85%RH for 48 hours. The test sample after the above humidification test was arranged on a reflective plate (manufactured by TORAY Film Co., Ltd., trade name "DMS-X42"; reflectivity 86%) so that the glass and the reflective plate were opposite to each other (i.e., the protective layer became the outer side). Next, the front reflectance was measured using a spectrophotometer (CM-2600d manufactured by Konica Minolta) using the SCI method.

>Example 1> 1. Preparation of polarizer/resin substrate laminate The resin substrate is a long strip of amorphous isophthalic acid copolymer polyethylene terephthalate film (thickness: 100μm) with a water absorption rate of 0.75% and a Tg of about 75°C. One side of the resin substrate is subjected to a corona treatment. 13 parts by weight of potassium iodide is added to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (produced by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z410") in a ratio of 9:1, and a PVA aqueous solution (coating liquid) is prepared. The PVA aqueous solution was applied to the corona treated surface of the resin substrate and dried at 60°C to form a PVA resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was subjected to free-end uniaxial stretching 2.4 times in the longitudinal direction (long side direction) between rollers of different peripheral speeds in an oven at 130°C (air-assisted stretching treatment). Then, the laminate was immersed in an insoluble bath (aqueous boric acid solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insoluble treatment). Next, the dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 relative to 100 parts by weight of water) with a liquid temperature of 30°C was adjusted to make the monomer transmittance (Ts) of the polarizer finally obtained 41.5%±0.1% while being immersed in it for 60 seconds (dyeing treatment). Next, it was immersed in a crosslinking bath (boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid relative to 100 parts by weight of water) with a liquid temperature of 40°C for 30 seconds (crosslinking treatment). Then, while the laminate is immersed in a boric acid aqueous solution (boric acid concentration 4.0 wt%) at a liquid temperature of 70°C, it is uniaxially stretched in the longitudinal direction (long side direction) between rollers of different peripheral speeds to achieve a total stretching ratio of 5.5 times (in-water stretching treatment). Thereafter, the laminate is immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (cleaning treatment). Thereafter, while drying in an oven maintained at 90°C, it is contacted with a SUS heating roller maintained at a surface temperature of 75°C for about 2 seconds (drying and shrinking treatment). The shrinkage rate in the width direction obtained by the drying and shrinking treatment of the laminate is 5.2%. According to the above method, a polarizer with a thickness of 5 μm was formed on the resin substrate to produce a polarizer/resin substrate laminate. The single unit transmittance (initial single unit transmittance) _Ts0 of the polarizer was 41.5, and the polarization degree (initial polarization degree) _P0 was 99.996%.

2. Preparation of a phase difference film constituting a phase difference layer 2-1. Polymerization of polyester carbonate resin Polymerization was carried out using a batch polymerization device consisting of two vertical reactors equipped with stirring blades and a reflux cooler controlled at 100°C. 29.60 parts by mass (0.046 mol) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42.28 parts by mass (0.139 mol) of spiroglycerol (SPG), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC) and 1.19×10-2 parts by mass (6.78×10-5 mol) of calcium acetate monohydrate as a catalyst were fed. After the reactor is depressurized and replaced with nitrogen, it is heated with a heating medium and agitation is started when the internal temperature reaches 100°C. 40 minutes after the start of the temperature rise, the internal temperature reaches 220°C, and the temperature is controlled and maintained while the pressure is reduced to 13.3 kPa 90 minutes after reaching 220°C. The phenol vapor generated as a by-product of the polymerization reaction is introduced into a 100°C reflux cooler to return a small amount of monomer components contained in the phenol vapor to the reactor, and the uncondensed phenol vapor is introduced into a 45°C condenser for recovery. After nitrogen is introduced into the first reactor to temporarily return it to atmospheric pressure, the oligomerized reaction solution in the first reactor is transferred to the second reactor. Next, the temperature and pressure in the second reactor were raised and reduced, and after 50 minutes, the internal temperature reached 240°C and the pressure reached 0.2 kPa. Thereafter, polymerization was carried out until the predetermined stirring power was reached. At the time when the predetermined power was reached, nitrogen was introduced into the reactor to restore the pressure, and the generated polyester carbonate resin was extruded into water, and the bundle was cut to obtain pellets.

2-2. Preparation of phase difference film The obtained polyester carbonate resin (pellets) was vacuum dried at 80°C for 5 hours, and then a thin film forming device equipped with a uniaxial extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 200mm, setting temperature: 250°C), a cooling roller (setting temperature: 120~130°C) and a winder was used to prepare a long strip of resin film with a thickness of 135μm. The obtained long strip of 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 phase difference film with a thickness of 48μm. The Re(550) of the obtained phase difference film was 141nm, the Re(450)/Re(550) was 0.82, and the Nz coefficient was 1.12.

3. Preparation of polarizing plate with phase difference layer The phase difference film obtained in 3. is bonded to the surface of the polarizer of the laminate obtained in 1. through an acrylic adhesive (thickness 5μm). At this time, the absorption axis of the polarizer and the slow axis of the phase difference film are bonded in a manner that forms an angle of 45°. The resin substrate is peeled off to obtain a polarizing plate with phase difference layer/polarizer structure.

20 parts of an acrylic resin of polymethyl methacrylate having a lactone ring unit (lactone ring unit 30 mol%) are dissolved in 80 parts of methyl ethyl ketone to obtain an acrylic resin solution (20%). The acrylic resin solution is applied to the surface of the polarizer of the polarizing plate obtained above using a wire rod, and the coated film is dried at 60°C for 5 minutes to form a protective layer in the form of a cured product of the coated film. The thickness of the protective layer is 3μm, the Tg is 119°C, and the iodine adsorption amount is 0.25 wt%. A polarizing plate with a phase difference layer having a structure of a protective layer (cured product of the coated film)/polarizer/phase difference layer is obtained in the above manner. The obtained polarizing plate with a phase difference layer is provided for the evaluations of (3) to (5) above. Furthermore, the protective layer was observed with the naked eye to see if it shrank after being formed. The results are listed in Table 1.

>Example 2> Except that an acrylic resin of polymethyl methacrylate having maleic anhydride units (maleic anhydride units 7 mol%) is used to replace the acrylic resin of polymethyl methacrylate having lactone ring units, a protective layer is formed in the same manner as in Example 1. The thickness of the protective layer is 3 μm and the Tg is 115°C. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 3> Except that 100% polymethyl methacrylate acrylic resin (manufactured by Kusumoto Chemicals Co., Ltd., product name "B-728") is used to replace the polymethyl methacrylate acrylic resin having a lactone ring unit, a protective layer is formed in the same manner as in Example 1. The thickness of the protective layer is 3μm, the Tg is 116℃, and the iodine adsorption amount is 0.34% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 4> Except that an acrylic resin of polymethyl methacrylate having glutarimido ring units (glutarimido ring units 4 mol%) is used to replace the acrylic resin of polymethyl methacrylate having lactone ring units, a protective layer is formed in the same manner as in Example 1. The thickness of the protective layer is 3 μm, the Tg is 103°C, and the iodine adsorption amount is 2.3 wt%. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 5> Except for using a different acrylic resin of polymethyl methacrylate having lactone ring units (lactone ring units 20 mol%), a protective layer was formed in the same manner as in Example 1. The thickness of the protective layer was 3 μm, the Tg was 104°C, and the iodine adsorption was 2.8 wt%. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 6> Except that an acrylic resin of a copolymer of methyl methacrylate/butyl methacrylate (molar ratio 80/20) is used to replace the acrylic resin of polymethyl methacrylate having a lactone ring unit, a protective layer is formed in the same manner as in Example 1. The thickness of the protective layer is 3μm, the Tg is 95°C, and the iodine adsorption amount is 3.8% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Example 7> 1. Preparation of a polarizer/resin substrate laminate The polarizer/resin substrate laminate is prepared in the same manner as in Example 1.

2. Preparation of the first oriented solidified layer and the second oriented solidified layer constituting the phase difference layer 10 g of polymerizable liquid crystal (manufactured by BASF: trade name "Paliocolor LC242", represented by the following formula) showing a nematic liquid crystal phase and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: trade name "IRGACURE 907") were dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid). [Chemical formula 4] The surface of the polyethylene terephthalate (PET) film (thickness 38μm) is wiped with a wiping cloth and an orientation treatment is performed. The direction of the orientation treatment is set to be 15° relative to the absorption axis direction of the polarizer when viewed from the viewing side when attached to the polarizing plate. The above-mentioned liquid crystal coating liquid is applied to the orientation-treated surface using a rod coater, and heat-dried at 90°C for 2 minutes to orient the liquid crystal compound. A metal halogen lamp is used to irradiate the liquid crystal layer formed in the above manner with 1mJ/ ^cm2 of light to harden the liquid crystal layer, thereby forming a liquid crystal orientation solidified layer A on the PET film. The thickness of the liquid crystal orientation solidified layer A is 2.5μm, and the in-plane phase difference Re(550) is 270nm. In addition, the liquid crystal orientation solidified layer A exhibits a refractive index characteristic of nx＞ny＝nz. The coating thickness was changed, and the orientation treatment direction was set to be 75° relative to the absorption axis direction of the polarizer when viewed from the visual side. In addition, a liquid crystal orientation solidification layer B was formed on the PET film in the same manner as above. The thickness of the liquid crystal orientation solidification layer B was 1.5 μm, and the in-plane phase difference Re (550) was 140 nm. In addition, the liquid crystal orientation solidification layer B exhibited a refractive index characteristic of nx>ny=nz.

3. Preparation of polarizing plate with phase difference layer The liquid crystal oriented solidification layer A and liquid crystal oriented solidification layer B obtained in 2. are sequentially transferred to the polarizer surface of the polarizer/resin substrate laminate obtained in 1. At this time, the transfer (bonding) is performed in such a way that the angle formed by the absorption axis of the polarizer and the slow axis of the oriented solidification layer A is 15° and the angle formed by the absorption axis of the polarizer and the slow axis of the oriented solidification layer B is 75°. In addition, each transfer (bonding) is performed through a UV curing adhesive (thickness 1.0μm). Next, for reinforcement, the substrate with the adhesive is bonded to the surface of the oriented solidification layer B. Next, the resin substrate is peeled off to obtain a polarizing plate with a phase difference layer having a structure of a polarizer/bonding layer/phase difference layer (first oriented solidified layer/bonding layer/second oriented solidified layer)/adhesive-attached substrate.

Then, a protective layer is formed on the surface of the polarizer of the polarizing plate with phase difference layer in the same manner as in Example 3. Finally, the substrate to which the adhesive is attached is peeled off to obtain a polarizing plate with phase difference layer having a structure of protective layer (cured product of coating film)/polarizer/phase difference layer. The obtained polarizing plate with phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 1> Except that an acrylic resin of a copolymer of methyl methacrylate/ethyl acrylate (molar ratio 55/45) (manufactured by Kusumoto Chemicals Co., Ltd., product name "B-722") was used to replace the acrylic resin of polymethyl methacrylate having a lactone ring unit, a protective layer was formed in the same manner as in Example 1. The thickness of the protective layer was 3μm, Tg was 39°C, and the iodine adsorption amount was 1.7% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to a fading evaluation and the result was poor ("overall fading"), so the single unit transmittance and polarization degree were not evaluated. The results are listed in Table 1.

>Comparative Example 2> Except that an acrylic resin of a copolymer of methyl methacrylate/butyl methacrylate (molar ratio 35/65) (manufactured by Kusumoto Chemicals Co., Ltd., product name "B-734") is used to replace the acrylic resin of polymethyl methacrylate having a lactone ring unit, a protective layer is formed in the same manner as in Example 1. The thickness of the protective layer is 3μm, the Tg is 71°C, and the iodine adsorption amount is 12% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to a fading evaluation and the result was poor ("overall fading"), so the single unit transmittance and polarization degree were not evaluated. The results are listed in Table 1.

>Comparative Example 3> A protective layer (hardened material) was formed in the same manner as in Example 1, except that a UV-curing acrylic resin (manufactured by Kyoeisha Chemicals, product name "LIGHT ACRYLATE HPP-A", hydroxytrimethylacetic acid neopentyl glycol acrylate adduct) was used. Specifically, a composition of 97 wt% of the acrylic resin and 3 wt% of a photopolymerization initiator (IRGACURE 907, manufactured by BASF) was coated on a polarizer, and UV rays were irradiated with a high-pressure mercury lamp in a nitrogen environment at a cumulative light intensity of 300 mJ/ ^cm2 to form a hardened layer (protective layer). The thickness of the protective layer was 3 μm, Tg was 83°C, and the iodine adsorption was 6.6 wt%. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 4> Except for using UV-curable acrylic resin (manufactured by Toagosei Co., Ltd., product name "ARONIX M-402"), dipentatriol penta- and hexa-acrylate (penta-acrylate is 30% to 40%), a protective layer (cured product) is formed in the same manner as in Example 1. The method for forming the protective layer is the same as in Comparative Example 3. The thickness of the protective layer is 3μm. Except for using the protective layer, a polarizing plate with a phase difference layer is prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer is subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 5> In addition to using a UV-curable epoxy resin (manufactured by DAICEL, product name "CELLOXIDE 2021P"), a protective layer (cured material) is formed in the same manner as in Example 1. Specifically, a composition of 95% by weight of the epoxy resin and 5% by weight of a photopolymerization initiator (CPI-100P, manufactured by San-Apro) is applied to the polarizer, and a high-pressure mercury lamp is used in an air environment to irradiate ultraviolet rays with a cumulative light intensity of 500mJ/ ^cm2 to form a cured layer (protective layer). The thickness of the protective layer is 3μm, the Tg is 95°C, and the iodine adsorption amount is 9% by weight. In addition to using the protective layer, a polarizing plate with a phase difference layer is produced in the same manner as in Example 1. The obtained polarizing plate with phase difference layer was subjected to the same evaluation as in Example 1. The results are listed in Table 1.

>Comparative Example 6> Except for using a water-based polyester resin (manufactured by Nippon Synthetic Chemical Co., Ltd., product name "POLYESTER WR905"), a protective layer (cured product of the coating film) was formed in the same manner as in Example 1. The thickness of the protective layer was 3μm, and the iodine adsorption amount was 12% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to a fading evaluation, and the result was poor ("overall fading"), so the single unit transmittance and polarization degree were not evaluated. The results are listed in Table 1.

>Comparative Example 7> Except for using a water-based polyurethane resin (manufactured by Daiichi Kogyo Seiyaku Co., Ltd., product name "SUPERFLEX SF210"), a protective layer (cured product of the coating film) was formed in the same manner as in Example 1. The thickness of the protective layer was 3μm, Tg was 107℃, and the iodine adsorption amount was 19% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to a fading evaluation and the result was poor ("overall fading"), so the single unit transmittance and polarization degree were not evaluated. The results are listed in Table 1.

>Comparative Example 8> Except for using a water-based polyurethane resin (Unitika, product name "ARROW BASE SE1200"), a protective layer (cured product of the coating film) was formed in the same manner as in Example 1. The thickness of the protective layer was 3μm, and the iodine adsorption amount was 15% by weight. Except for using the protective layer, a polarizing plate with a phase difference layer was prepared in the same manner as in Example 1. The obtained polarizing plate with a phase difference layer was subjected to a fading evaluation, and the result was poor ("overall fading"), so the single unit transmittance and polarization degree were not evaluated. The results are listed in Table 1.

[Table 1]

>Evaluation> As can be seen from Table 1, the polarizing plate with phase difference layer of the embodiment of the present invention is very thin but can still suppress the reduction of optical properties in a heated and humidified environment, and has excellent durability. At the same time, it will not shrink after the protective layer is formed, and can withstand the polarizing plate with phase difference layer for practical application. In addition, the front reflectivity of the polarizing plate with phase difference layer of the embodiment of the present invention after the humidification test is very small, showing good anti-reflection properties. It teaches that when it is applied to an image display device having a metal layer such as an organic EL display device, it has the effect of preventing the reflection of external light caused by the metal layer.

Industrial Applicability The polarizing plate with phase difference layer of the present invention can be used in image display devices. Examples of image display devices include portable devices such as PDA, smart phones, mobile phones, clocks, digital cameras, portable game consoles, etc.; OA devices such as computer monitors, laptops, copiers, etc.; home electrical devices such as video cameras, televisions, microwave ovens, etc.; rear monitors, car navigation system monitors, car stereos, etc.; display devices such as digital signs, information guide screens for commercial stores, etc.; security devices such as surveillance screens, and nursing and medical devices such as nursing monitors and medical monitors, etc.

10: Polarizer 20: Protective layer 40: Phase difference layer 41: First layer 42: Second layer 100,101: Polarizer with phase difference layer 200: Laminated body G1~G4: Guide rollers R1~R6: Transport rollers

FIG1 is a schematic cross-sectional view of a polarizing plate with a phase difference layer in one embodiment of the present invention. FIG2 is a schematic cross-sectional view of a polarizing plate with a phase difference layer in another embodiment of the present invention. FIG3 is a schematic view showing an example of a drying and shrinking treatment using a heating roller in a method for manufacturing a polarizing plate used in a polarizing plate with a phase difference layer in one embodiment of the present invention.

10: Polarizer

20: Protective layer

40: Phase difference layer

100: Polarizing plate with phase difference layer

Claims (10)

A polarizing plate with a phase difference layer, comprising a polarizing plate and a phase difference layer, wherein the polarizing plate comprises a polarizing element containing iodine and polyvinyl alcohol resin and a protective layer disposed on one side of the polarizing element, and the phase difference layer is disposed on the side of the polarizing plate opposite to the protective layer; the glass transition temperature of the protective layer is above 95°C; the thickness of the protective layer is below 5μm; the protective layer is directly formed on the polarizing element, and is composed of a cured product of a coating film formed by directly coating an organic solvent solution of a thermoplastic acrylic resin on the surface of the polarizing element. As in claim 1, the polarizing plate with a phase difference layer, wherein the phase difference layer is a single layer, the Re (550) of the phase difference layer is 100nm~190nm, and the angle formed by the slow axis of the phase difference layer and the absorption axis of the polarizer is 40°~50°. As in claim 2, the polarizing plate with a phase difference layer, wherein the phase difference layer is a resin film. As in claim 2, the polarizing plate with a phase difference layer, wherein the phase difference layer is a directional solidified layer of a liquid crystal compound. The polarizing plate with phase difference layer as claimed in claim 1, wherein the phase difference layer has a layered structure of a first layer and a second layer; the Re (550) of the first layer is 200nm~300nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 10°~20°; the Re (550) of the second layer is 100nm~190nm, and the angle formed by its slow axis and the absorption axis of the polarizer is 70°~80°. As in claim 5, the polarizing plate with a phase difference layer, wherein the first layer and the second layer are respectively resin films. As in claim 5, the polarizing plate with a phase difference layer, wherein the first layer and the second layer are respectively oriented solidification layers of liquid crystal compounds. A polarizing plate with a phase difference layer as claimed in any one of claims 1 to 7, wherein the iodine adsorption amount of the protective layer is less than 4.0% by weight. A polarizing plate with a phase difference layer as claimed in any one of claims 1 to 7, wherein the aforementioned thermoplastic acrylic resin has at least one selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit. The polarizing plate with a phase difference layer as in any one of claims 1 to 7 is arranged on the visual side of the image display device, and the protective layer is arranged on the visual side.

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