Polarizing plate with phase difference layer and image display device

Abstract

The present invention provides a polarizer with a phase retardation layer that suppresses damage traces. The polarizer with a phase retardation layer of the present invention comprises: a polarizer (10) including a polarizer (11) and a protective layer (12) at least disposed on the visible side of the polarizer (11), and a phase retardation layer (30) attached to the polarizer (10) on the opposite side to the visible side via an adhesive layer (20). The thickness of the polarizer is 12 μm or less, and the residual depth of the adhesive layer under a 3 N load is 11 μm or less.

Description

Technical Field

[0001] This invention relates to polarizers with phase difference layers and image display devices. Background Technology

[0002] In image display devices (e.g., liquid crystal displays, organic EL displays, quantum dot displays), due to their image formation methods, polarizers are typically disposed on at least one side of the image display unit. For polarizers disposed on the visible side of the image display device, a retardation film (polarizer with a retardation layer) is sometimes laminated on the image display unit side for purposes such as preventing external light reflection, background reflection, and improving hue. With the trend towards thinner image display devices, there is a strong demand for thinner polarizers with retardation layers. To meet this demand, efforts are underway to thinner polarizers. However, polarizers with retardation layers containing thinner polarizers are difficult to process; for example, damage marks (typically multiple fine cracks in a certain area) can sometimes occur due to external forces caused by operator error.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2013-200445 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] The present invention was made to solve the above-mentioned problems, and its main purpose is to provide a polarizer with a phase difference layer that suppresses damage traces.

[0008] Problem Solving Methods

[0009] The polarizer with a phase retardation layer according to an embodiment of the present invention comprises: a polarizer including a polarizer and a protective layer at least disposed on the visible side of the polarizer, and a phase retardation layer attached to the polarizer on the side opposite to the visible side via an adhesive layer. The thickness of the polarizer is 12 μm or less, and the residual depth of the adhesive layer when subjected to a 3N load is 11 μm or less.

[0010] In one embodiment, the thickness of the adhesive layer is 6 μm to 15 μm.

[0011] In one embodiment, the thickness of the protective layer on the visible side is 30 μm or more.

[0012] In one embodiment, the retardation layer exhibits a refractive index characteristic of nx > nz > ny. In one embodiment, the Nz coefficient of the retardation layer is 0.3 to 0.7. In one embodiment, the in-plane phase difference Re(550) of the retardation layer is 250 nm to 350 nm, the thickness is less than 150 μm, and the photoelastic modulus is 1.0 × 10⁻⁶. -12 m 2 / N or higher. In one embodiment, the phase retardation layer comprises a cyclic olefin resin.

[0013] In one embodiment, the angle between the slow axis of the phase difference layer and the absorption axis of the polarizer is substantially orthogonal or substantially parallel.

[0014] According to other aspects of the present invention, an image display device may be provided. This image display device includes the aforementioned polarizer with a phase retardation layer.

[0015] The effects of the invention

[0016] According to an embodiment of the present invention, by using an adhesive layer with a specific residual depth in a polarizer with a phase retardation layer that includes a thin polarizer, it is possible to realize a polarizer with a phase retardation layer that suppresses damage traces. Attached Figure Description

[0017] Figure 1 This is a cross-sectional schematic diagram of a polarizer with a phase difference layer according to one embodiment of the present invention.

[0018] Symbol Explanation

[0019] 10 Polarizing filters

[0020] 11. Polarizing mirror

[0021] 12 protective layers

[0022] 20 Adhesive layers

[0023] 30 phase difference layers

[0024] 100 Polarizers with Phase Difference Layers Detailed Implementation

[0025] The embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0026] (Definitions of terms and symbols)

[0027] The terms and symbols used in this manual are defined as follows.

[0028] (1) Refractive index (nx, ny, nz)

[0029] “nx” is the refractive index in the direction where the refractive index reaches its maximum in the plane (i.e., the slow axis direction), “ny” is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and “nz” is the refractive index in the thickness direction.

[0030] (2) In-plane phase difference (Re)

[0031] “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. When the thickness of the layer (film) is set as d (nm), Re(λ) can be obtained by the formula: Re(λ)=(nx-ny)×d.

[0032] (3) Phase difference (Rth) in the thickness direction

[0033] “Rth(λ)” is the phase difference in the thickness direction measured at 23℃ using light with a wavelength of λnm. For example, “Rth(550)” is the phase difference in the thickness direction measured at 23℃ using light with a wavelength of 550nm. When the thickness of the layer (film) is set as d (nm), Rth(λ) can be obtained using the formula: Rth(λ)=(nx-nz)×d.

[0034] (4) Nz coefficient

[0035] The Nz coefficient is obtained by Nz = Rth / Re.

[0036] (5) Angle

[0037] In this specification, when referring to an angle, the angle includes both clockwise and counterclockwise relative to a reference direction. Therefore, for example, "45°" means ±45°.

[0038] (6) Essentially orthogonal or essentially parallel

[0039] In this specification, expressions such as "substantially orthogonal" and "approximately orthogonal" include cases where the angle between the two directions is 90° ± 7°, preferably 90° ± 5°, and more preferably 90° ± 3°. Expressions such as "substantially parallel" and "approximately parallel" include cases where the angle between the two directions is 0° ± 7°, preferably 0° ± 5°, and more preferably 0° ± 3°. Furthermore, in this specification, the abbreviations "orthogonal" or "parallel" can include states that are substantially orthogonal or substantially parallel.

[0040] A. Overall structure of a polarizer with a phase retardation layer

[0041] Figure 1This is a cross-sectional schematic diagram of a polarizer with a phase retardation layer according to one embodiment of the present invention. The polarizer 100 with a phase retardation layer in the example figure has a polarizer 10 and a phase retardation layer 30. The polarizer 10 includes a polarizer 11 and a protective layer (viewable side protective layer) 12 disposed at least on the visible side of the polarizer 11. In the example figure, only the viewable side protective layer 12 is provided, but other protective layers (inner protective layers) may also be provided on the side opposite to the viewable side. The phase retardation layer 30 is attached to the side of the polarizer 10 opposite to the viewable side via an adhesive layer 20. The phase retardation layer 30 has a slow axis due to its in-plane phase retardation. Typically, the angle between the slow axis of the phase retardation layer 30 and the absorption axis of the polarizer 11 is substantially orthogonal or substantially parallel. In practical use, other adhesive layers (not shown) are provided on the side of the phase retardation layer 30 opposite to the polarizer 10 (i.e., as the outermost layer opposite to the viewable side), allowing the polarizer with the phase retardation layer to be attached to an image display unit. Furthermore, it is preferable to temporarily attach a diaphragm (not shown) to the surface of the other adhesive layers until the polarizer with the phase retardation layer is ready for use. By temporarily attaching the diaphragm, the other adhesive layers can be protected, and a roll of the polarizer with the phase retardation layer can be formed.

[0042] In embodiments of the present invention, the residual depth of the adhesive layer 20 under a 3N load is 11 μm or less, preferably 10.8 μm or less. A smaller residual depth is preferred, and its lower limit can be, for example, 10 μm. The residual depth can be determined, for example, by: (1) attaching the adhesive sheet to a glass plate; (2) applying a load to the surface of the adhesive sheet while scraping using a micro-load automatic scratching tester; (3) measuring the indentation depth when scraping under a 3N load using a displacement sensor, and using this as the residual depth. By optimizing the residual depth of the adhesive layer, damage marks (typically multiple fine cracks within a certain area) can be significantly suppressed. Typically, damage marks are caused by external factors (e.g., impact and / or pressing pressure) resulting from operator error. Furthermore, in polarizers with a phase retardation layer having an adhesive layer on one side of the polarizer, damage marks are typically generated at the polarizer. Damage marks are significant in thin polarizers, and even more so in polarizers with phase retardation layers used in larger image display devices (e.g., televisions) where processing is more challenging. The inventors discovered that the causes of damage marks, which at first glance appear to be aggregates of microcracks, are completely different from those of cracks. Therefore, methods for suppressing cracks (e.g., adjusting the storage modulus of the adhesive layer) cannot suppress damage marks. Through repeated trials, it was found that optimizing the residual depth (i.e., the recovery after applying external force to the adhesive layer) is effective. In other words, the effect of suppressing damage marks by optimizing the residual depth solves this newly discovered problem, and is an unexpectedly excellent result obtained through repeated trials corresponding to this problem.

[0043] In an embodiment of the present invention, the thickness of the polarizer 11 is 12 μm or less. As described above, damage marks are significant in thin polarizers, which is essentially a problem unique to thin polarizers. According to an embodiment of the present invention, this problem can be solved.

[0044] The polarizer 100 with a phase retardation layer can further have any suitable functional layer (not shown) on the side of the phase retardation layer 30 opposite to the polarizer 10 (image display unit side), depending on the purpose. Other phase retardation layers and conductive layers are examples of such functional layers. The type, number, combination, arrangement, and characteristics (e.g., optical characteristics of other phase retardation layers: specifically, refractive index characteristics, in-plane phase retardation, thickness-direction phase retardation, and Nz coefficient) of the functional layers can be appropriately set according to the purpose. By further having a conductive layer, the polarizer with a phase retardation layer can be appropriately used in an embedded touch panel type input display device.

[0045] The following section provides a more detailed explanation of the components of a polarizer with a phase retardation layer.

[0046] B. Polarizing filter

[0047] B-1. Polarizer

[0048] Typically, the polarizer 11 is made of a resin film containing dichroic material.

[0049] As the resin film, any suitable resin film that can be used as a polarizer can be used. Typically, the resin film is a polyvinyl alcohol resin (hereinafter referred to as "PVA resin") film.

[0050] As the PVA-type resin for forming the above-mentioned PVA-type resin film, any suitable resin can be used. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymers are obtained by saponifying ethylene-vinyl acetate copolymers. The degree of saponification of the PVA-type resin is typically 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined according to JIS K6726-1994. By using a PVA-type resin with such a degree of saponification, a polarizer with excellent durability can be obtained. However, if the saponification is too high, there is a concern about gelation.

[0051] The average degree of polymerization of PVA resins can be appropriately selected according to the purpose. The average degree of polymerization is typically 1000–10000, preferably 1200–4500, and more preferably 1500–4300. It should be noted that the average degree of polymerization can be determined according to JIS K 6726-1994.

[0052] Examples of dichroic substances contained in resin films include iodine and organic dyes. These can be used alone or in combination of two or more. Iodine is preferred.

[0053] The resin film can be a single-layer resin film or a laminate of two or more layers.

[0054] As a specific example of a polarizer composed of a single-layer resin film, a polarizer made by dyeing and stretching a PVA-type resin film with iodine (typically uniaxial stretching) can be cited. The iodine dyeing is performed, for example, by immersing the PVA-type film in an aqueous iodine solution. The stretching magnification of the uniaxial stretching is preferably 3 to 7 times. Stretching can be performed after dyeing or during dyeing. Alternatively, dyeing can be performed after stretching. The PVA-type resin film can be subjected to swelling treatment, cross-linking treatment, cleaning treatment, drying treatment, etc., as needed. For example, by immersing the PVA-type resin film in water for washing before dyeing, not only can dirt and anti-blocking agents on the surface of the PVA-type film be removed, but the PVA-type resin film can also swell to prevent uneven dyeing.

[0055] As a specific example of a polarizer obtained using a laminate, examples include a polarizer obtained using a resin substrate and a PVA-type resin layer (PVA-type resin film) laminated on the resin substrate, or a polarizer obtained using a resin substrate and a laminate coated with a PVA-type resin layer formed on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-type resin layer coated on the resin substrate can be manufactured by, for example, coating a PVA-type resin solution onto a resin substrate, allowing it to dry, forming a PVA-type resin layer on the resin substrate, obtaining a laminate of the resin substrate and the PVA-type resin layer; stretching and dyeing the laminate to form a polarizer from the PVA-type resin layer. In this embodiment, stretching typically includes immersing the laminate in an aqueous boric acid solution for stretching. Furthermore, stretching may, as needed, further include stretching the laminate in a gas atmosphere at a high temperature (e.g., above 95°C) before stretching in the aqueous boric acid solution. The resulting resin substrate / polarizer laminate can be used directly (i.e., the resin substrate is used as a protective layer for the polarizer), or the resin substrate can be peeled off from the resin substrate / polarizer laminate, and any suitable protective layer corresponding to the purpose can be laminated on the peeled surface for use. Detailed descriptions of such a polarizer manufacturing method are provided, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0056] As described above, the thickness of the polarizer is 12 μm or less, preferably 1 μm to 12 μm, more preferably 3 μm to 10 μm, and even more preferably 3 μm to 8 μm. If the thickness of the polarizer is within such a range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0057] The polarizer preferably exhibits absorption dichroism at any wavelength within the range of 380 nm to 780 nm. The single-unit transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0058] B-2. Protective layer

[0059] The visible protective layer 12 and the inner protective layer (if present) can each be formed from any suitable film that can be used as a protective layer for a polarizing mirror. Specific examples of materials that are the main components of the film include cellulose resins such as cellulose triacetate (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrene, polynorbornene, polyolefins, (meth)acrylic acids, acetates, and other transparent resins. Additionally, thermosetting resins or UV-curing resins such as (meth)acrylic acids, urethanes, (meth)acrylate urethanes, epoxy resins, and silicone resins can also be used. Furthermore, glassy polymers such as siloxane polymers can also be used. Alternatively, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can also be used. As the material for this membrane, a resin composition can be used, for example, a thermoplastic resin containing substituted or unsubstituted imide groups on the side chains, and a thermoplastic resin containing substituted or unsubstituted phenyl and nitrile groups on the side chains. Examples include resin compositions having alternating copolymers formed from isobutylene and N-methylmaleimide, and acrylonitrile-styrene copolymers. The polymer membrane can be, for example, an extruded product of the above-described resin composition.

[0060] A polarizer with a phase retardation layer is typically disposed on the viewable side of an image display device, and a viewable-side protective layer 12 is disposed on its viewable side. Therefore, as needed, the viewable-side protective layer 12 can undergo surface treatments such as hard coating, anti-reflective treatment, anti-adhesion treatment, and anti-glare treatment. Furthermore / or, when visual recognition is performed using polarized sunglasses, the first protective layer 12 can be treated to improve visual recognizability as needed (typically by imparting (elliptical) polarization functionality or providing an ultra-high phase retardation). By implementing such treatment, excellent visual recognizability can be achieved even when visually recognizing the displayed image through polarized lenses such as polarized sunglasses. Therefore, a polarizer with a phase retardation layer is also suitable for image display devices that can be used outdoors.

[0061] The thickness of the visible-side protective layer is preferably 30 μm or more, more preferably 30 μm to 100 μm, and even more preferably 30 μm to 60 μm. If the thickness of the protective layer is within this range, damage marks can be more significantly suppressed through the synergistic effect with the residual depth of the adhesive layer. It should be noted that when a surface treatment layer is formed by surface treatment of the visible-side protective layer, the thickness of the visible-side protective layer includes the thickness of the surface treatment layer.

[0062] The inner protective layer (if present) is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re(550) is 0 nm to 10 nm, and the phase difference Rth(550) in the thickness direction is -10 nm to +10 nm. The thickness of the inner protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. From the viewpoint of thinning, it is preferable that the protective layer can be omitted. In embodiments of the present invention, the phase difference layer 30 is preferably also used as the inner protective layer.

[0063] C. Adhesive layer

[0064] As the adhesive forming the adhesive layer 20, any suitable adhesive can be used as long as the desired residual depth can be achieved. Examples of base resins for the adhesive include acrylic resins, styrene resins, silicone resins, urethane resins, and rubber resins. From the viewpoints of chemical resistance, adhesion to prevent the treatment solution from penetrating during immersion, and freedom of movement for the adhered object, acrylic resins are preferred. That is, the adhesive layer 20 is preferably composed of an acrylic adhesive (acrylic adhesive composition). Typically, the acrylic adhesive composition contains a (meth)acrylic polymer as a main component. In the solid component of the adhesive composition, the (meth)acrylic polymer may be included in the adhesive composition in a proportion of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more. The (meth)acrylic polymer contains alkyl (meth)acrylate as a monomer unit as a main component. It should be noted that (meth)acrylate refers to acrylates and / or methacrylates. Examples of alkyl groups that form (meth)acrylate alkyl esters include linear or branched alkyl groups having 1 to 18 carbon atoms. The average number of carbon atoms in the alkyl group is preferably 3 to 9, more preferably 3 to 6. In addition to alkyl acrylate esters, monomers constituting (meth)acrylate polymers include: carboxyl-containing monomers (e.g., (meth)acrylate), hydroxyl-containing monomers (e.g., hydroxyethyl acrylate), amide-containing monomers (e.g., acrylamide), aromatic ring (meth)acrylates (e.g., benzyl acrylate), heterocyclic (meth)acrylates (e.g., acryloylmorpholine), and (meth)acrylates with a bridged ring structure (e.g., dicyclopentyl (meth)acrylate). The (meth)acrylate polymer preferably has both carboxyl-containing monomer units and hydroxyl-containing monomer units. The content of carboxyl-containing monomer units in the (meth)acrylate polymer is preferably 3% to 7% by weight, and the content of hydroxyl-containing monomer units is preferably 0.05% to 0.1% by weight. With such a configuration, a desired residual depth can be achieved. Acrylic adhesive compositions preferably contain silane coupling agents and / or crosslinking agents. Examples of silane coupling agents include epoxy-containing silane coupling agents. Examples of crosslinking agents include isocyanate crosslinking agents and peroxide crosslinking agents. By appropriately combining the monomer units of (meth)acrylic polymers, silane coupling agents, and crosslinking agents, acrylic adhesives (resulting in adhesive layers) with desired properties can be obtained. Detailed descriptions of adhesive layers or acrylic adhesive compositions are provided in, for example, Japanese Patent Application Publication Nos. 2007-138147, 2016-190996, and 2018-028573, the contents of which are incorporated herein by reference.

[0065] The thickness of the adhesive layer 20 is preferably 6 μm to 25 μm, more preferably 6 μm to 15 μm, and even more preferably 10 μm to 15 μm. If the thickness of the adhesive layer is within this range, air bubbles can be suppressed when the polarizer and the retardation layer are bonded together.

[0066] The creep value of the adhesive layer 20 is preferably 30 μm / h to 50 μm / h, more preferably 35 μm / h to 45 μm / h. If the creep value of the adhesive layer is within this range, damage marks can be significantly suppressed. The creep value can be measured, for example, as described below. An adhesive composition is applied to the protective layer of a polarizer containing a protective layer and a polarizing lens to form an adhesive layer, thus producing a polarizer with an adhesive layer. The produced polarizer is cut into pieces 10 mm wide and 50 mm long. A 10 mm wide and 10 mm long portion of the cut polarizer with the adhesive layer is sandwiched between the adhesive layer and bonded to a stainless steel plate. Next, it is treated in an autoclave (50°C, 5 atm) for 15 minutes and then left at room temperature for 1 hour. After leaving the plate, a 500 g load (tensile load) is applied to the unbonded end of the polarizer with the adhesive layer at 23°C for 1 hour. The displacement (deformation) of the adhesive layer after the applied load is measured using a laser creep testing machine, thereby determining the creep value of the adhesive layer.

[0067] D. Phase difference layer

[0068] As described above, the retardation layer 30 has an in-plane phase difference and a slow axis. Furthermore, as described above, the retardation layer also serves as a protective layer and a phase difference layer (or optical compensation layer) for the polarizer. With this configuration, it is not necessary to separately provide the protective layer and the optical compensation layer; therefore, it can significantly contribute to the thinning of the image display device. The in-plane phase difference Re(550) of the retardation layer is preferably 250nm to 350nm, more preferably 270nm to 330nm, and even more preferably 290nm to 310nm. If the in-plane phase difference Re(550) of the retardation layer is within this range, the movement distance on the Poincaré sphere is short; therefore, excellent hue and brightness characteristics can be achieved, and the color shift of the image display panel and the deviation caused by the phase difference component of the TFT are also reduced.

[0069] For the retardation layer, it is preferable that the refractive index characteristics exhibit a relationship of nx > nz > ny. By giving the retardation layer such refractive index characteristics, the hue in the tilt direction of an image display device using a polarizer with a retardation layer can be significantly improved. Furthermore, this improvement in hue in the tilt direction can be achieved without separately providing the retardation layer and the layer for optical compensation in the tilt direction, thus contributing to the thinning of polarizers with retardation layers (resulting in image display devices).

[0070] The Nz coefficient of the phase difference layer is preferably 0.3 to 0.7, more preferably 0.4 to 0.6, and even more preferably 0.45 to 0.55. If the Nz coefficient is in such a range, the hue in the tilt direction can be further improved.

[0071] The phase retardation layer can exhibit inverse wavelength dispersion characteristics, where the phase difference increases accordingly with the wavelength of the measurement light; it can also exhibit positive wavelength dispersion characteristics, where the phase difference decreases accordingly with the wavelength of the measurement light; or it can exhibit flat wavelength dispersion characteristics, where the phase difference is substantially unaffected by the wavelength of the measurement light. Typically, the phase retardation layer exhibits flat wavelength dispersion characteristics.

[0072] The absolute value of the photoelastic coefficient of the phase retardation layer is preferably 15 × 10⁻⁶. -12 m 2 / N or less, more preferably 10×10 -12 m 2 / N or less. The lower limit of the absolute value of the photoelastic coefficient can be, for example, 1.0 × 10⁻⁶. -12 m 2 / N. If the absolute value of the photoelastic coefficient of the phase retardation layer is within this range, then the display unevenness of the image display device can be well suppressed.

[0073] Typically, the retardation layer is a retardation film formed from any suitable resin capable of achieving the aforementioned properties. Examples of resins forming this retardation film include: cyclic olefin resins, polyarylates, polyamides, polyimides, polyesters, polyaryl ether ketones, polyamide-imides, polyesterimides, polyvinyl alcohol, polyfumarate, polyethersulfone, polysulfone, polycarbonate resins, cellulose resins, and polyurethanes. These resins can be used alone or in combination. Cyclic olefin resins are preferred. Norbornene resins are a representative example of cyclic olefin resins.

[0074] The aforementioned norbornene resins are resins obtained by polymerizing norbornene monomers as polymerization units. Examples of such norbornene monomers include: norbornene, and its alkyl and / or alkylidene substituted derivatives, such as: 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethide-2-norbornene, etc., and their halogen or other polar group substituted derivatives; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc.; dimethylbridged octahydronaphthalene, etc. Its alkyl and / or alkylidene substituted derivatives, and polar group substituted derivatives such as halogens, for example: 6-methyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-ethide-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene. Hydronaphthalene, 6-chloro-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-pyridyl-1,4:5,8-dimethylbridged-1,4,4a,5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4:5,8-dimethylbridged-1,4 ,4a,5,6,7,8,8a-octahydronaphthalene, etc.; 3- to 4-terpolymers of cyclopentadiene, such as: 4,9:5,8-dimethylbridged-3a,4,4a,5,8,8a,9,9a-octahydro-1H-benzoindene, 4,11:5,10:6,9-trimethylbridged-3a,4,4a,5,5a,6,9,9a,10,10a,11,11a-dodecylhydro-1H-cyclopentadieneanthracene, etc. The above norbornene resins can also be copolymers of norbornene monomers with other monomers.

[0075] The retardation layer (retardation film) is a stretched film formed from the aforementioned resin. Any suitable method can be used to manufacture the stretched film. A representative example is a method of laminating a shrinkable film onto one or both sides of the resin film and then heating and stretching it. This shrinkable film imparts a shrinkage force in a direction orthogonal to the stretching direction during heating and stretching. By imparting such a shrinkage force, nz can be increased, resulting in the ability to produce a Z-film. Examples of materials used for the shrinkable film include polyester, polystyrene, polyethylene, polypropylene, polyvinyl chloride, and polyvinylidene chloride. Considering excellent shrinkage uniformity and heat resistance, polypropylene film is preferred.

[0076] As for the stretching method described above, any suitable stretching method can be used as long as tension is applied to the stretching direction of the resin film and a shrinkage force is applied in a direction orthogonal to the stretching direction within the film surface. The stretching temperature is preferably above the glass transition temperature (Tg) of the resin film. This is because the phase difference value of the resulting stretched film is easily made uniform, and the film is less prone to crystallization (cloudiness). The stretching temperature is more preferably Tg+1℃ to Tg+30℃, further preferably Tg+2℃ to Tg+20℃, particularly preferably Tg+3℃ to Tg+15℃, and most preferably Tg+5℃ to Tg+10℃. By setting the stretching temperature within such a range, uniform heating and stretching can be performed. Furthermore, it is preferable that the stretching temperature is constant in the film width direction. This is because it is possible to produce a stretched film with good optical uniformity and small deviation in phase difference value.

[0077] The stretching ratio described above can be set to any suitable value. Preferably, it is 1.05 to 2.00 times, more preferably 1.10 to 1.50 times, and particularly preferably 1.20 to 1.40 times. By setting the stretching ratio within such a range, a stretched film with less shrinkage in film width and excellent mechanical strength can be obtained.

[0078] The thickness of the phase retardation layer is preferably 80 μm to 200 μm, more preferably 90 μm to 150 μm, and even more preferably 110 μm to 150 μm. With such a thickness, the desired in-plane phase retardation value can be obtained.

[0079] E. Image display device

[0080] The polarizer with a phase retardation layer according to embodiments of the present invention can be applied to an image display device. Typically, the polarizer with a phase retardation layer is disposed on the viewable side of the image display device such that the polarizer is the viewable side. Representative examples of image display devices include liquid crystal displays, organic electroluminescent (EL) displays, and quantum dot displays. Liquid crystal displays are preferred, and IPS-mode liquid crystal displays are more preferred. This is because the hue improvement in the tilt direction is more significant. The image display device is preferably a large-scale (e.g., for televisions larger than 27 inches) image display device. This is because the damage trace suppression effect is significant due to the optimization of the residual depth of the adhesive layer.

[0081] Example

[0082] The present invention will now be described in detail through embodiments, but the present invention is not limited to these embodiments. The evaluation methods in the embodiments are as follows. It should be noted that, unless otherwise specified, "parts" and "%" in the embodiments are based on weight.

[0083] (1) Residual depth

[0084] An adhesive sheet is formed from the adhesive prepared in the manufacturing example. The resulting adhesive sheet is adhered to a glass plate, and the surface of the adhesive sheet is scratched while a load is applied using a micro-load automatic scratch testing machine. The indentation depth when scratched under a 3N load is measured by a displacement sensor and is taken as the residual depth.

[0085] (2) Damage traces

[0086] The polarizers with phase retardation layers obtained in the examples and comparative examples were cut into 50 mm long and 25 mm wide pieces as test samples. These test samples were then bonded to a glass plate using a conventional acrylic adhesive (corresponding to other adhesive layers). For the test samples bonded to the glass plate, a guitar pick with weights was pressed against the adhesive sheet under a load of 3 N. In this state, a sliding tester was used to repeatedly press the samples along their length. The number of reciprocations was set to 1, 5, 10, 50, and 70. The test samples were then placed in an oven at 95°C for 1 hour. The test samples removed from the oven were examined under a microscope for any signs of damage and evaluated according to the following criteria.

[0087] Excellent: No damage was detected after 70 cycles.

[0088] Good: No damage was detected after 50 cycles, but damage was detected after 70 cycles.

[0089] Unacceptable: No damage was detected after 10 cycles, but damage was detected after 50 cycles.

[0090] Poor: Damage traces were confirmed through 1, 5, or 10 repeated attempts.

[0091] (3) Appearance

[0092] For the polarizers with phase retardation layers obtained in the examples and comparative examples, the bubble state between the polarizer and the phase retardation layer during fabrication (when the polarizer and the phase retardation layer are bonded together) was observed with the naked eye and evaluated according to the following criteria.

[0093] Good: No bubbles detected

[0094] A small number of air bubbles may be observed, but not to the extent that they will affect the display characteristics.

[0095] Unacceptable: Bubbles that are identified to the extent that they may affect display characteristics.

[0096] It should be noted that the appearance evaluation is conducted in two stages.

[0097] [Manufacturing Example 1: Preparation of the adhesive constituting the adhesive layer]

[0098] A solution was prepared by adding 100 parts of butyl acrylate, 5 parts of acrylic acid, 0.075 parts of 2-hydroxyethyl acrylate, and 0.3 parts of 2,2'-azobisisobutyronitrile (2,2'-azobisisobutyronitrile) along with ethyl acetate to a reaction vessel equipped with a condenser, a nitrogen inlet pipe, a thermometer, and a stirrer. Next, the solution was stirred while being purged with nitrogen and reacted at 60°C for 4 hours to obtain a solution containing an acrylic polymer with a weight-average molecular weight of 2.2 million. Ethyl acetate was further added to this acrylic polymer solution to obtain an acrylic polymer solution (A1) with the solids concentration adjusted to 30%.

[0099] Adhesive A was prepared by sequentially adding 0.6 parts of a crosslinking agent (manufactured by Nippon Polyurethane Co., Ltd., trade name "Coronate L"), which is mainly composed of a compound with isocyanate groups, as a crosslinking agent, and 0.075 parts of γ-glycidoxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KMB-403") as a silane coupling agent. The residual depth of the adhesive layer (adhesive sheet) formed by adhesive A was 10.7 mm.

[0100] [Manufacturing Example 2: Preparation of the Adhesive Constituting the Adhesive Layer]

[0101] 99 parts of butyl acrylate, 1.0 part of 4-hydroxybutyl acrylate, and 0.3 parts of 2,2'-azobisisobutyronitrile, along with ethyl acetate, were added to a reaction vessel equipped with a condenser, a nitrogen inlet pipe, a thermometer, and a stirrer. The reaction was carried out at 60°C for 4 hours under a nitrogen atmosphere. Next, ethyl acetate was added to the reaction solution to obtain a solution containing an acrylic polymer with a weight-average molecular weight of 1.65 million (solid content concentration 30%). Adhesive B was prepared by adding 0.15 parts of benzoyl peroxide (manufactured by Nippon Yushu Corporation, trade name: NYPER BO-Y), 0.08 parts of trimethylolpropanephenyl dimethyl diisocyanate (manufactured by Mitsui Takeda Chemical Co., Ltd., trade name: Takenate D110N), and 0.2 parts of silane coupling agent (manufactured by Soken Chemical Co., Ltd., trade name: A-100, acetylacetyl silane coupling agent) per 100 parts of the solid content of the obtained acrylic polymer solution. The residual depth of the adhesive layer (adhesive sheet) formed by adhesive B is 12.5 mm.

[0102] [Example 1]

[0103] 1. Fabrication of a polarizing filter

[0104] As the resin substrate, a strip-shaped, amorphous polyethylene terephthalate (IPA) copolymer film (100 μm thickness) with a water absorption rate of 0.75% and a Tg of 75°C was used. One side of the substrate was subjected to corona treatment, and the corona-treated side was coated at 25°C with an aqueous solution containing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetyl-modified PVA (degree of polymerization 1200, degree of acetyl-modification 4.6%, degree of saponification ≥ 99.0 mol%, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "GOHSEFIMER Z200") in a 9:1 ratio, and then dried to form an 11 μm thick PVA resin layer, thus creating a laminate.

[0105] The resulting laminate was subjected to longitudinal (length direction) unidirectional stretching (assisted stretching in a gas atmosphere) to 2.0 times its free end length in an oven at 120°C between rollers with different circumferential speeds.

[0106] Next, the laminate was immersed in an insoluble bath (an aqueous solution of boric acid prepared by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 30°C for 30 seconds (insoluble treatment).

[0107] Next, immersion was performed in a staining bath at 30°C, adjusting the iodine concentration and immersion time to achieve a given transmittance for the polarizer. In this embodiment, the polarizer was immersed for 60 seconds in an iodine aqueous solution containing 0.2 parts by weight of iodine and 1.5 parts by weight of potassium iodide relative to 100 parts by weight of water (staining treatment).

[0108] Next, it was immersed for 30 seconds in a crosslinking bath at a liquid temperature of 30°C (an aqueous solution of boric acid prepared by mixing 3 parts by weight of potassium iodide with 100 parts by weight of water and boric acid).

[0109] Then, the laminate was immersed in a boric acid aqueous solution (an aqueous solution containing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide relative to 100 parts by weight of water) at a liquid temperature of 70°C, and simultaneously subjected to unidirectional stretching (stretching in aqueous solution) along the longitudinal direction (length direction) between rollers with different circumferential speeds to achieve a total stretch ratio of 5.5 times.

[0110] Then, the laminate was immersed in a cleaning bath at 30°C (an aqueous solution of 100 parts by weight of water and 4 parts by weight of potassium iodide) (cleaning treatment).

[0111] Finally, the laminate was dried to obtain a laminate with a polarizing mirror formed on a resin substrate. It should be noted that the polarizing mirror has a thickness of 5 μm and a monomer transmittance of 42.3%.

[0112] 2. Adhesion of the protective layer

[0113] On the surface of the polarizer of the laminate obtained in 1. above, an acrylic resin film (40 μm thick) containing a lactone ring structure was bonded as a protective layer using a UV-curable adhesive. Specifically, the adhesive was applied with a total thickness of 1.0 μm using a roller. Then, UV light was irradiated from the protective layer side to cure the adhesive. Next, the resin substrate was peeled off to obtain a laminate having a protective layer (acrylic resin film) / polarizer.

[0114] 3. Fabrication of the retardation layer (retardation film)

[0115] A 60μm thick shrinkable film [Toray Corporation trade name "TORAYFAN BO2873"] was laminated to both sides of a 130μm thick norbornene resin film via a 15μm thick acrylic adhesive layer. Then, the film was stretched to 1.38 times its original length using a roller stretching machine while maintaining its length direction, in an air-circulating oven at 146°C. After stretching, the shrinkable film and the acrylic adhesive layer were peeled off together to produce a retardation film. The resulting retardation film exhibited refractive index characteristics of nx > nz > ny, Re(550) = 280nm, Nz coefficient = 0.52, and photoelastic coefficient of 4.0 × 10⁻⁶. -12 m 2 / N, with a thickness of 138μm.

[0116] 4. Fabrication of polarizers with phase retardation layers

[0117] The polarizer surface of the laminate obtained in step 2. is bonded to the retardation film (retardation layer) obtained in step 3. via adhesive A (12 μm thick) obtained in manufacturing example 1. Thus, a polarizer with a retardation layer is obtained, comprising a protective layer / polarizer / adhesive layer / retardation layer. The obtained polarizer with a retardation layer is evaluated in steps (2) and (3) above. The results are shown in Table 1.

[0118] [Example 2]

[0119] The thickness of adhesive A was changed to 23 μm, and otherwise, a polarizer with a phase retardation layer was obtained in the same manner as in Example 1. The obtained polarizer with a phase retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0120] [Example 3]

[0121] By changing the thickness of adhesive A to 5 μm, a polarizer with a phase retardation layer was obtained in the same manner as in Example 1. The obtained polarizer with a phase retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0122] [Comparative Example 1]

[0123] Adhesive B (12 μm thick) was used instead of adhesive A, and otherwise, a polarizer with a phase retardation layer was obtained in the same manner as in Example 1. The obtained polarizer with a phase retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0124] [Comparative Example 2]

[0125] Adhesive B (20 μm thick) was used instead of adhesive A, and otherwise, a polarizer with a phase retardation layer was obtained in the same manner as in Example 1. The obtained polarizer with a phase retardation layer was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

[0126] [Reference Example 1]

[0127] 1. Fabrication of a polarizing filter

[0128] A polyvinyl alcohol (PVA) resin film with an average degree of polymerization of 2400, a saponification degree of 99.9 mol%, and a thickness of 50 μm was prepared. The PVA film was immersed in a swelling bath (water bath) at 20°C for 30 seconds to allow it to swell, and then stretched to 2.4 times its original length along the transport direction between rollers at different circumferential speeds (swelling process). Next, it was immersed and dyed in a dyeing bath at 30°C (an aqueous solution of 0.03 wt% iodine and 0.3 wt% potassium iodide) to achieve the desired monomer transmittance after final stretching, stretching to 3.7 times its original length along the transport direction (dyeing process) based on the original PVA film (a completely unstretched PVA film in the transport direction). The immersion time at this point was approximately 60 seconds. Next, while immersing the dyed polyvinyl alcohol (PVA) film in a crosslinking bath (an aqueous solution of 3.0 wt% boric acid and 3.0 wt% potassium iodide) at 40°C, the film was stretched 4.2 times its original thickness along the transport direction (crosslinking process). Further, the resulting PVA film was immersed in a stretching bath (an aqueous solution of 4.0 wt% boric acid and 5.0 wt% potassium iodide) at 64°C for 50 seconds, stretched 6.0 times its original thickness along the transport direction (stretching process), and then immersed in a cleaning bath (an aqueous solution of 3.0 wt% potassium iodide) at 20°C for 5 seconds (cleaning process). The cleaned PVA film was dried at 30°C for 2 minutes to fabricate a polarizing mirror (20 μm thick).

[0129] 2. Fabrication of polarizers and polarizers with phase retardation layers

[0130] On the surface of the polarizer obtained in step 1 above, an acrylic resin film (40 μm thick) containing an lactone ring structure was bonded as a protective layer, similar to that in Example 1, to obtain a laminate with a protective layer (acrylic resin film) / polarizer. Subsequent steps were the same as in Example 1 to obtain a polarizer with a phase retardation layer. The obtained polarizer with a phase retardation layer was evaluated in the same way as in Example 1. The results are shown in Table 1.

[0131] [Table 1]

[0132]

[0133] [evaluate]

[0134] As shown in Table 1, according to the embodiments of the present invention, damage marks can be significantly suppressed. Furthermore, as shown in the reference examples, such damage marks are a problem unique to thin polarizers.

[0135] Industrial applicability

[0136] The polarizer with a phase difference layer of the present invention can be suitably used as an image display device such as a liquid crystal display device, an organic EL display device, or a quantum dot display device, and is particularly suitable for use as a liquid crystal display device.

Claims

1. A polarizer with a phase retardation layer, comprising: A polarizer comprising a polarizer and a protective layer disposed at least on the visible side of the polarizer, and The phase retardation layer, which is attached to the polarizer on the side opposite to the visible side, via an adhesive layer. The thickness of the polarizer is 3~8μm. The adhesive layer is composed of an acrylic adhesive composition. This acrylic adhesive composition comprises a (meth)acrylic polymer, and the solid component of the adhesive composition contains more than 50% by weight of said (meth)acrylic polymer. This (meth)acrylic acid polymer contains 20,000 / 4203 wt% to 7 wt% carboxyl-containing monomer units and 0.05 wt% to 0.1 wt% hydroxyl-containing monomer units. The adhesive layer has a residual depth of less than 11 μm when subjected to a 3 N load.

2. The polarizer with a phase retardation layer according to claim 1, wherein, The thickness of the adhesive layer is 6μm to 15μm.

3. The polarizer with a phase retardation layer according to claim 1 or 2, wherein, The thickness of the protective layer on the visible side is 30 μm or more.

4. The polarizer with a phase retardation layer according to claim 1 or 2, wherein, The phase difference layer exhibits refractive index characteristics of nx > nz > ny.

5. The polarizer with a phase retardation layer according to claim 4, wherein, The Nz coefficient of the phase difference layer is 0.3~0.

7.

6. The polarizer with a phase retardation layer according to claim 4, wherein, The in-plane phase difference Re(550) of the phase retardation layer is 250nm~350nm, the thickness is less than 150μm, and the photoelastic coefficient is 1.0×10⁻⁶. -12 m 2 / N or more.

7. The polarizer with a phase retardation layer according to claim 4, wherein, The phase difference layer comprises a cyclic olefin resin.

8. The polarizer with a phase retardation layer according to claim 1 or 2, wherein, The angle between the slow axis of the phase difference layer and the absorption axis of the polarizer is 90°±7° or 0°±7°.

9. An image display device comprising a polarizer with a phase difference layer as described in any one of claims 1 to 8.

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