Adhesive film for polarizing plate, polarizing plate, and display device

Abstract

The invention discloses an adhesive film for a polarizing plate, a polarizing plate, and a display device. An adhesive film for a polarizing plate includes a cured product of a composition including a copolymer of a monomer mixture and a curing agent. The monomer mixture includes an unsaturated monomer having an alkyl group, an unsaturated monomer having a hydroxyl group, and an unsaturated monomer having an amide group and a long-chain alkylene group or a long-chain alkyl group. The adhesive film for a polarizing plate according to the present invention can ensure high adhesiveness.

Description

[0001] Cross-references to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0066509, filed on May 22, 2024, with the Korean Intellectual Property Office, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] The present invention relates to an adhesive film for a polarizing plate, a polarizing plate including the adhesive film, and a display device. Background Technology

[0004] Light-emitting displays, including organic light-emitting displays (OLEDs), do not require polarizing plates. However, such displays can suffer from low screen quality due to total internal reflection of incident light within their panels. Therefore, light-emitting displays typically have a polarizing plate on the upper surface of the panel. The polarizing plate comprises a polarizer and a retardation film. A liquid crystal film, instead of a polymer film, is used as the retardation film to reduce thickness.

[0005] Liquid crystal films can be prepared by forming an alignment layer on a base film, followed by coating and curing a composition for the liquid crystal layer. Although the base film can be left on the polarizing plate as a protective layer, it is usually removed. Therefore, the adhesive film used in the polarizing plate is expected to provide good adhesion to both hydrophilic and hydrophobic surfaces.

[0006] Recently, interest in flexible displays has increased rapidly. Therefore, polarizing plates used in flexible displays are also required to have good flexibility.

[0007] The background technology of this invention is disclosed in Korean Patent Publication No. 10-2015-0010567. Summary of the Invention

[0008] One aspect of the present invention is to provide an adhesive film for a polarizing plate that exhibits good adhesion to a base film.

[0009] Another aspect of the present invention is to provide an adhesive film for a polarizing plate that ensures high adhesion to a liquid crystal delay layer having a high surface water contact angle without surface treatment.

[0010] Another aspect of the present invention is to provide an adhesive film for a polarizing plate, which has good heat resistance and damp heat resistance on a flat surface.

[0011] Another aspect of the present invention is to provide an adhesive film for a polarizing plate, which has good heat resistance and damp heat resistance on a curved surface.

[0012] According to one aspect of the present invention, an adhesive film for a polarizing plate is provided.

[0013] The adhesive film for polarizing plates comprises a cured product of a composition comprising a copolymer of monomer mixtures and a curing agent, the monomer mixture comprising: an alkyl unsaturated monomer; a hydroxyl unsaturated monomer; and an amide group and a long-chain alkylene or long-chain alkyl unsaturated monomer.

[0014] According to another aspect of the present invention, a polarizing plate is provided.

[0015] The polarizing plate includes an adhesive film for the polarizing plate as described above.

[0016] According to another aspect of the present invention, a display device is provided.

[0017] The display device includes the polarizing plate as described above.

[0018] Embodiments of the present invention provide an adhesive film for polarizing plates that exhibits good adhesion to the adhesive to prevent delamination from the adhesive.

[0019] Embodiments of the present invention provide an adhesive film for polarizing plates that exhibits high adhesion to a liquid crystal retardation layer having a high surface water contact angle without surface treatment.

[0020] Embodiments of the present invention provide an adhesive film for polarizing plates, which has good heat resistance and damp heat resistance on both flat and curved surfaces, for application in non-flexible and flexible display devices. Attached Figure Description

[0021] Figure 1 This is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0022] Figure 2 This is a cross-sectional view of a polarizing plate according to another embodiment of the present invention.

[0023] Figure 3 This is a cross-sectional view of a polarizing plate according to another embodiment of the present invention. Detailed Implementation

[0024] In the following description, exemplary embodiments of the invention will be illustrated in detail with reference to the accompanying drawings, enabling those skilled in the art to readily implement the invention. It should be understood that the invention may be embodied in different ways and is not limited to the following embodiments. In the drawings, for clarity, parts unrelated to the description will be omitted, and similar components will be indicated by the same reference numerals throughout this specification. It should be understood that the lengths, dimensions, etc., of components in the drawings are for illustrative purposes only, and the invention is not limited thereto.

[0025] The terminology used herein is for the purpose of describing exemplary embodiments and is not intended to limit the invention. As used herein, unless the context clearly indicates otherwise, the singular forms (a, an, the) are also intended to include multiple forms.

[0026] In this document, spatial relative terms such as “upper” and “lower” are defined with reference to the accompanying drawings. Therefore, it will be understood that the term “upper surface” is used interchangeably with the term “lower surface”.

[0027] In this paper, "in-plane delay (Re)" is represented by equation A:

[0028] Re = (nx – ny) × d ---- (A)

[0029] Where nx and ny are the refractive indices of the optical device, measured at the measurement wavelength along the slow axis and fast axis of the optical device, respectively, and d is the thickness of the optical device (in nanometers).

[0030] In this paper, "negative dispersion" refers to Re(450). <Re(550)<Re(650)。

[0031] In this article, "(meth)acryl" refers to acryl and / or methacryl.

[0032] In this paper, "homopolymer glass transition temperature" refers to the glass transition temperature (Tg) measured on the homopolymer of the target monomer using DSC Discovery (TA Instruments). Specifically, the homopolymer of the target monomer was heated to 180°C at a heating rate of 20°C / min, slowly cooled to -100°C, and then reheated to 100°C at a heating rate of 10°C / min to obtain endothermic transition curve data. The inflection point of the endothermic transition curve can be defined as the glass transition temperature of the target monomer in the homopolymer phase.

[0033] As used in this article to indicate a specific numerical range, "X to Y" means "greater than or equal to X and less than or equal to Y (X ≤ and ≤ Y)".

[0034] An adhesive film for a polarizing plate according to an embodiment of the present invention can provide good adhesion to the adhesive.

[0035] In this document, "adherend" can include both hydrophilic and hydrophobic adhesives. That is, the adhesive film used for the polarizing plate can exhibit good adhesion to both the hydrophilic and hydrophobic adhesives. According to one embodiment, in a stacked structure of a hydrophilic adhesive, an adhesive film for the polarizing plate, and a hydrophobic adhesive, the adhesive film for the polarizing plate can exhibit good adhesion to both the hydrophilic and hydrophobic adhesives to prevent delamination between the hydrophilic and hydrophobic adhesives, thereby improving durability and reliability.

[0036] In one embodiment, the hydrophilic adhesive may be a polarizer, a hydrophilic protective layer, a hydrophilic protective film, a hydrophilic retardation layer, a hydrophilic retardation film, or a hydrophilic alignment film.

[0037] In one embodiment, the hydrophobic adhesive may be a hydrophobic protective layer, a hydrophobic protective film, a hydrophobic delay layer, a hydrophobic delay film, or a hydrophobic alignment film.

[0038] In one embodiment, the adhesive film for the polarizing plate may have an adhesive strength of 1.10 kgf / mm or greater than 1.10 kgf / mm relative to a liquid crystal retardation layer having a water contact angle of 70° or greater (e.g., 80° to 90°), for example, 1.10 kgf / mm to 3.0 kgf / mm. Within this range, the adhesive film prevents interlayer delamination and exhibits good reliability on both flat and curved surfaces.

[0039] An adhesive film for a polarizing plate according to one embodiment exhibits high adhesion to a liquid crystal retardation layer with a high surface water contact angle without surface treatment, thereby improving processability. Typically, a liquid crystal retardation layer may have a water contact angle of 70° or greater, for example, 80° to 90°. Therefore, to attach a typical adhesive film to a liquid crystal retardation layer with high adhesion, a surface treatment (e.g., corona treatment) is required on the liquid crystal retardation layer. However, the adhesive film for a polarizing plate according to an embodiment of the present invention can be attached to the liquid crystal retardation layer with high adhesion without surface treatment. In this document, "water contact angle" is a value measured at 25 degrees Celsius and can be measured by typical methods known to those skilled in the art.

[0040] According to one embodiment, the adhesive film for a polarizing plate exhibits good heat resistance and resistance to damp heat on both flat and curved surfaces. Therefore, the adhesive film for the polarizing plate can be applied to both non-flexible and flexible display devices to provide good reliability.

[0041] According to one embodiment, the adhesive film for a polarizing plate comprises a cured product of a composition containing a copolymer of monomers and a curing agent, wherein the monomer mixture contains unsaturated monomers having alkyl groups, unsaturated monomers having hydroxyl groups, and unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups. Through the unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups, the adhesive film for the polarizing plate exhibits high adhesion relative to the adhesive, and good heat resistance and damp heat resistance on both flat and curved surfaces.

[0042] The adhesive film may have a haze of 1% or less in the visible spectrum (e.g., at a wavelength of 550 nm), specifically 0% to 1%. Within this range, the adhesive film can be used in display devices.

[0043] The adhesive film can have a thickness of 5 micrometers to 50 micrometers, specifically 5 micrometers to 35 micrometers. Within this range, the adhesive film can be used in polarizing plates.

[0044] The adhesive film used for polarizing plates can be used to bond polarizers to liquid crystal retardation layers, to bond the protective layer of polarizers to liquid crystal retardation layers, or to bond one liquid crystal retardation layer to another liquid crystal retardation layer.

[0045] In the following text, an adhesive film for a polarizing plate according to one embodiment will be described.

[0046] The adhesive film used for polarizing plates contains a cured product of the composition.

[0047] In one embodiment, the adhesive film used for the polarizing plate may be a thermosetting product.

[0048] In one embodiment, the adhesive film for a polarizing plate may comprise an alkyl unsaturated monomer; a hydroxyl unsaturated monomer; and an amide group, as well as a long-chain alkylene or long-chain alkyl unsaturated monomer, a copolymer, and a curing agent. These may be derived from the composition.

[0049] copolymer

[0050] The copolymer comprises a copolymer of monomer mixtures, the monomer mixture comprising unsaturated monomers having alkyl groups, unsaturated monomers having hydroxyl groups, and unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups.

[0051] In one embodiment, the unsaturated monomers having alkyl groups, hydroxyl groups, and amide groups, as well as long-chain alkylene or long-chain alkyl groups, may be present in the monomer mixture in an amount of 95% by weight or greater than 95% by weight, for example, 99% by weight to 100% by weight, or 100% by weight. Within this range, the composition can readily achieve the effect of an adhesive film.

[0052] In one embodiment, the copolymer may be a (meth)acrylic acid copolymer.

[0053] An alkyl-containing unsaturated monomer may contain an alkyl-containing (meth)acrylic acid monomer.

[0054] Alkyl-containing (meth)acrylic acid monomers can be (meth)acrylic acid monomers having an alkyl group at their ester site. Here, "alkyl" can be linear or branched, C1 to C2. 10Alkyl group. Specifically, the alkyl-containing (meth)acrylate monomer may include at least one of the following: ethyl acrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, pentyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, heptyl methacrylate, octyl methacrylate, isooctyl methacrylate, nonyl methacrylate, decyl methacrylate, and dodecyl methacrylate, but is not limited thereto.

[0055] Alkyl-containing (meth)acrylic acid monomers can have homopolymer glass transition temperatures below 0 degrees Celsius, for example, -80 degrees Celsius to -10 degrees Celsius, or -70 degrees Celsius to -10 degrees Celsius. Within this range, the composition can readily ensure improved processability and reliability of the polarizing plate.

[0056] The alkyl-containing (meth)acrylic acid monomer may be present in the monomer mixture in amounts ranging from 60% to 95% by weight, for example, 80% to 95% by weight, or 85% to 95% by weight. Within this range, the composition can readily ensure improved peel strength and reliability of the polarizing plate.

[0057] Unsaturated monomers containing hydroxyl groups may include (meth)acrylic acid monomers containing hydroxyl groups.

[0058] Hydroxyl-containing (meth)acrylic acid monomers may include at least one of the following: containing C1 to C2 atoms having hydroxyl groups. 20 Alkyl (meth)acrylic acid monomers, containing C3 to C4 groups with hydroxyl groups. 20 cycloalkyl (meth)acrylic acid monomers and C6 to C6 monomers containing hydroxyl groups. 20 (Meth)acrylic acid monomers with aromatic groups. Specifically, (meth)acrylic acid monomers containing hydroxyl groups may be C1 to C2 groups containing hydroxyl groups. 20 Alkyl (meth)acrylates, and may include at least one selected from: 2-hydroxyethyl(meth)acrylate, 2-hydroxypropyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, 4-hydroxybutyl(meth)acrylate, and 6-hydroxyhexyl(meth)acrylate. These may be used alone or as mixtures thereof.

[0059] The unsaturated monomers having hydroxyl groups may be present in the monomer mixture in amounts from 0.1% to 10% by weight, specifically from 0.1% to 5% by weight, and more specifically from 0.1% to 3% by weight. Within this range, the composition ensures the peel strength of the adhesive film and allows for easy adjustment of the glass transition temperature.

[0060] Unsaturated monomers containing an amide group and a long-chain alkylene or alkyl group have both an amide group and a long-chain alkylene or alkyl group within them. The amide group has hydrophilic properties, while the long-chain alkylene or alkyl group has hydrophobic properties. Therefore, unsaturated monomers can ensure good adhesion to both hydrophilic and hydrophobic adhesives.

[0061] Here, the long-chain alkylene group can be linear or branched C8 to C9. 20 Alkylene. Preferably, the long-chain alkylene is C10. 15 To C 20 Alkylene.

[0062] Here, the long-chain alkyl group can be linear or branched C8 to C9. 20 Alkyl group. Preferably, the long-chain alkyl group is C10. 15 To C 20 alkyl.

[0063] In one embodiment, an unsaturated monomer having an amide group and a long-chain alkylene or long-chain alkyl group can be represented by Formula 1:

[0064] [Formula 1]

[0065]

[0066] Where R is hydrogen or a C1 to C5 alkyl group.

[0067] L 11 For linear or branched C1 to C 10 Alkylene, and

[0068] L 12 For linear or branched C8 to C 20 alkyl.

[0069] In one embodiment, in Equation 1, L 11 It can be linear or branched C1 to C5 alkylene and L 12 C can be linear or branched 10 To C 20 Or C 15 To C 20 alkyl.

[0070] Unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups may be present in the monomer mixture in an amount from 1% to 30% by weight. Within this range, the composition ensures the peel strength of the adhesive film and allows for easy adjustment of the glass transition temperature. Specifically, unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups may be present in the monomer mixture in an amount from 5% to 20% by weight. Within this range, the composition improves the adhesion of the adhesive film to the adhesive, as well as its heat resistance and damp heat resistance on flat and curved surfaces.

[0071] The copolymer may have a weight average molecular weight (Mw) of 1,000,000 g / mol to 2,000,000 g / mol, for example, 1,500,000 g / mol to 2,000,000 g / mol. Within this range, the composition can readily achieve the effects of the present invention. As used herein, "weight average molecular weight" can be measured by gel permeation chromatography in polystyrene standards.

[0072] The copolymer may have a glass transition temperature (Tg) of -35°C or greater, for example, from -35°C to -10°C. Within this range, the composition can readily achieve the effects of the present invention. As used herein, "glass transition temperature" can be measured using a differential scanning calorimeter (DSC).

[0073] In one embodiment, the copolymer can be prepared by polymerizing a monomer mixture using typical polymerization methods. The polymerization methods can include any typical methods known to those skilled in the art. For example, (meth)acrylic acid copolymers can be prepared by adding an initiator to the monomer mixture, followed by typical polymerization, such as suspension polymerization, emulsion polymerization, solution polymerization, etc. The polymerization can be carried out at a temperature of 65°C to 70°C for 6 to 8 hours. The initiator can be a typical initiator comprising an azo-based polymerization initiator and / or a peroxide, such as benzoyl peroxide or acetyl peroxide.

[0074] curing agent

[0075] The curing agent is a thermosetting curing agent and may include at least one of the following: isocyanate curing agents, epoxy curing agents, amine curing agents, metal chelate curing agents, and aziridine curing agents. Preferably, the curing agent includes an isocyanate curing agent.

[0076] The isocyanate curing agent may comprise a bifunctional to hexafunctional isocyanate curing agent. Specifically, the isocyanate curing agent may comprise at least one aromatic isocyanate curing agent selected from toluene diisocyanate, xylylene diisocyanate, halogenated toluene diisocyanate, phenylene diisocyanates including m-phenylene diisocyanate, and tetramethyl-xylylenediisocyanate; at least one aliphatic isocyanate curing agent selected from hexamethylene diisocyanate and pentamethylene diisocyanate; or an alicyclic isocyanate curing agent, such as cyclohexamethylene diisocyanate. diisocyanate, etc., or adducts thereof, for example, at least one polyol such as trimethylolpropane (TMP), and adducts of the aforementioned curing agents.

[0077] A curing agent, such as an isocyanate curing agent, may be present in an amount of 0.05 parts by weight to 2 parts by weight, for example, 0.25 parts by weight to 1 part by weight, relative to 100 parts by weight of the copolymer. Within this range, the composition can achieve good adhesion and reliability of the adhesive film.

[0078] The composition may further include a silane coupling agent. The silane coupling agent can further improve the peel strength of the adhesive film used in polarizing plates.

[0079] The silane coupling agent may be present in an amount of 0.001 parts by weight to 5 parts by weight relative to 100 parts by weight of the copolymer. Within this range, the silane coupling agent can increase the peel strength of the adhesive film. Preferably, the silane coupling agent is present in an amount of 0.01 parts by weight to 1 part by weight.

[0080] Silane coupling agents may include at least one of the following: epoxy-containing silane coupling agents, mercapto-containing silane coupling agents, amine group-containing silane coupling agents, alkyl group-containing silane coupling agents, and isocyanate group-containing silane coupling agents.

[0081] Preferably, the silane coupling agent comprises an epoxy-containing silane coupling agent. Epoxy-containing silane coupling agents can help achieve the effects of the invention. Specifically, epoxy-containing silane coupling agents may include glycidoxypropyltrimethoxysilane, glycidoxypropylmethyldimethoxysilane, epoxycyclohexylpropyltrimethoxysilane, etc.

[0082] The composition may further include typical additives known to those skilled in the art. Additives may include, but are not limited to, UV absorbers, antioxidants, surfactants, pigments, dyes, heat stabilizers, dispersants, inorganic particles, etc.

[0083] Although the composition may be solvent-free, it may contain solvents to increase its suitability.

[0084] Adhesive films can be prepared from compositions by any typical method known to those skilled in the art.

[0085] According to one embodiment, a polarizing plate includes an adhesive film for the polarizing plate.

[0086] A polarizing plate includes a polarizer; and an adhesive film for the polarizing plate on at least one surface of the polarizer.

[0087] The adhesive film used for the polarizing plate is the same as described above, and its description will be omitted.

[0088] polarizer

[0089] Polarizers are used to polarize external or internal light.

[0090] Polarizers may include polyvinyl alcohol-based polarizers, wherein the polyvinyl alcohol film is dyed with iodine or the like. For example, a polyvinyl alcohol-based polarizer is manufactured by dyeing the polyvinyl alcohol film with iodine or a dichroic dye, followed by stretching the dyed film in a specific direction. Specifically, the polarizer is manufactured through a stretching process and a dyeing process. The methods for performing these processes are known to those skilled in the art.

[0091] Polarizers can have a thickness ranging from 1 micrometer to 50 micrometers. Within this range, polarizers can be used in display devices.

[0092] The polarizing plate may be further included in a delay layer on at least one surface of the polarizer.

[0093] Delay layer

[0094] The delay layer prevents the reflection of external light by circularly polarizing the light, thereby improving the appearance and screen quality to achieve anti-reflection function. The light is emitted from the polarizer and is linearly polarized.

[0095] In one embodiment, the retardation layer may have an in-plane retardation of 100 nm to 220 nm at a wavelength of 550 nm, specifically 100 nm to 180 nm, for example, a λ / 4 retardation (first retardation layer). Within this range, the retardation layer can ensure improved screen quality by reducing reflectivity relative to external light.

[0096] In another embodiment, the retardation layer may have an in-plane retardation of 225 nm to 350 nm at a wavelength of 550 nm, more specifically 225 nm to 300 nm, for example, a λ / 2 retardation (second retardation layer). Within this range, the retardation layer can ensure improved screen quality by reducing reflectivity relative to external light.

[0097] In another embodiment, the delay layer may be a stack of a first delay layer and a second delay layer.

[0098] In one embodiment, the delay layer may exhibit negative dispersion.

[0099] In one embodiment, the retardation layer may have a thickness of 0.1 micrometers to 10 micrometers, for example, 1 micrometer to 5 micrometers. Within this range, the retardation layer can reduce the thickness of the polarizer and achieve the desired delay.

[0100] In one embodiment, the retardation layer may be a non-liquid crystal layer or a liquid crystal layer. Preferably, the retardation layer is a liquid crystal layer, thereby enabling a reduction in the thickness of the polarizer.

[0101] For example, the liquid crystal layer can be formed from a composition comprising a liquid crystal compound having at least one of aromatic or alicyclic functional groups. In one embodiment, the liquid crystal compound may be a polymer, oligomer, or monomer comprising units consisting of an aromatic ring and a polymerizable functional group capable of imparting liquid crystallinity. The polymerizable functional group may comprise (meth)acryloyl, epoxy, vinyl ether, etc., which can be thermally or photocured to increase the strength of the liquid crystal delay layer.

[0102] In one embodiment, the liquid crystal delay layer may have a water contact angle of 70° or greater, for example, 80° to 90°.

[0103] The composition may be formed from a composition comprising an aromatic liquid crystal compound as described above. The composition may further comprise typical additives well known to those skilled in the art, such as leveling agents, polymerization initiators, alignment aids, heat stabilizers, lubricants, plasticizers, antistatic agents, etc.

[0104] The polarizing plate may be further contained in a protective layer on at least one surface of the polarizer.

[0105] protective layer

[0106] A protective layer may be formed on at least one surface of the polarizer to protect the polarizer or to provide additional functionality to the polarizing plate.

[0107] The protective layer may include an optically transparent protective film and / or an optically transparent protective coating.

[0108] When the protective layer is a protective film type, it may comprise a protective film formed from an optically transparent resin. The protective film can be formed by melting and extruding the optically transparent resin. A stretching process may be added if necessary. The resin may include at least one of the following: cellulose ester resins including triacetylcellulose, cyclic polyolefin resins including cyclic olefin polymers (COP), polycarbonate resins, polyester resins including polyethylene terephthalate (PET), polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, non-cyclic polyolefin resins, polyacrylate resins including poly(methyl methacrylate) resins, polyvinyl alcohol resins, polyvinyl chloride resins, and polyvinylidene chloride resins. Preferably, the protective film comprises a film formed from a cyclic polyolefin resin containing cyclic polyolefins, etc.

[0109] When the protective layer is a protective coating type, it can improve the adhesion, transparency, mechanical strength, thermal stability, moisture resistance, and durability of the polarizer. In one embodiment, the protective coating used as the protective layer may be formed from a photocurable resin composition comprising an actinic radiation curable compound and a polymerization initiator.

[0110] Photochemically curable compounds may include at least one selected from cationic polymerizable curable compounds, radical polymerizable curable compounds, urethane resins, and silicone resins. Cationic polymerizable curable compounds may be epoxy compounds having at least one epoxy group therein or oxetane-based compounds having at least one oxetane ring therein. Radical polymerizable curable compounds may be (meth)acrylic acid compounds having at least one (meth)acryloyloxy group therein.

[0111] The protective layer can have a thickness of 5 micrometers to 200 micrometers, specifically 30 micrometers to 120 micrometers for protective film types, or 50 micrometers to 100 micrometers for protective coating types. Within this range, the protective layer can be used in optical display devices.

[0112] The protective layer may comprise a functional coating layer formed on at least one of its surfaces or may be subject to surface treatment. The functional coating layer may include, but is not limited to, a hard coating layer, an anti-fingerprint layer, an anti-reflection layer, a low-reflectivity layer, an ultra-low reflectivity layer, an antiglare layer, etc. Surface treatment may include, but is not limited to, corona treatment, etc.

[0113] The protective layer can be bonded to the polarizer or to an adhesive other than the polarizer via an adhesive layer. The adhesive layer can be formed with a water-based bonding agent or a photocurable bonding agent, but is not limited thereto. Each of the water-based and photocurable adhesives can be used appropriately with reference to details known to those skilled in the art.

[0114] The polarizing plate may include at least one adhesive layer. The adhesive layer may consist of at least one layer or at least two layers in the polarizing plate.

[0115] Adhesive layer

[0116] The adhesive layer can bond the barrier layer to the delay layer or to the protective layer.

[0117] In one embodiment, the adhesive layer may be a pressure-sensitive adhesive (PSA) layer. For example, the PSA layer may include a cured product comprising a composition of an adhesive resin and a curing agent.

[0118] Figures 1 to 3 This is a cross-sectional view of a polarizing plate according to an embodiment of the present invention.

[0119] Reference Figure 1 According to one embodiment, a polarizing plate may include a polarizer 100, a protective layer 200 formed on the upper surface of the polarizer 100, and a first adhesive film 300 and a first delay layer 400 sequentially stacked on the lower surface of the polarizer.

[0120] Reference Figure 2 According to another embodiment, the polarizing plate may include a polarizer 100, a protective layer 200 formed on the upper surface of the polarizer, and a first adhesive film 300, a second retardation layer 500, a second adhesive film 600, and a first retardation layer 400 sequentially stacked on the lower surface of the polarizer 100.

[0121] Reference Figure 3 According to another embodiment, a polarizing plate may include a polarizer 100, a protective layer 200 formed on the upper surface of the polarizer, and a first adhesive film 300, a second retardation layer 500, a second adhesive film 600, a first retardation layer 400, and a third adhesive film 700 sequentially stacked on the lower surface of the polarizer.

[0122] At least one of the first adhesive film 300 or the second adhesive film 600 may be an adhesive film for a polarizing plate according to the above embodiments. The first adhesive film 300 and the second adhesive film 600 for the polarizing plate may be formed from the same composition of the adhesive film for the polarizing plate.

[0123] The third adhesive film 700 may be the adhesive film for a polarizing plate according to the above embodiments or may be any adhesive film known in the art.

[0124] Although not in Figures 1 to 3 As shown, the polarizing plate may further include at least one of a polarizer protective layer, an anti-reflective film, a retardation film (liquid crystal layer or non-liquid crystal layer), and an adhesive film typically used in polarizing plates.

[0125] An optical display apparatus according to one embodiment of the present invention includes a polarizing plate according to the present invention. For example, the optical display apparatus may include a light-emitting device display, a liquid crystal display, etc., that includes a light-emitting device.

[0126] The invention will now be described in more detail with reference to some examples. However, it should be noted that these examples are provided for illustrative purposes only and should not be construed as limiting the invention in any way.

[0127] Preparation examples: Preparation of monomers with amide groups and long-chain alkyl groups

[0128] Monomers having amide groups and long-chain alkyl groups are prepared according to the following reaction scheme.

[0129] N-(3-hydroxypropyl)heptadecanamide (200 g) was reacted with methacrylic anhydride (98 g) and 4-(dimethylamino)pyridine (DMAP, 0.73 g) at 60°C for 24 hours. Then, 10 mL of distilled water was added to the product and reacted for 1 hour, followed by extraction with dichloromethane to prepare N-(methacryloyloxy)propyl heptadecanamide (MPHA).

[0130] [Reaction Protocol]

[0131]

[0132] Example 1

[0133] (1) Preparation of adhesive film (first adhesive film = second adhesive film) for polarizing plate

[0134] A monomer mixture was prepared by mixing 89 parts by weight of n-butyl acrylate (n-BA), 1 part by weight of 4-hydroxybutyl acrylate (4-HBA), and 10 parts by weight of MPHA prepared in the preparation example. The monomer mixture was placed in a 1-liter reactor equipped with a cooler for easy temperature control, and 10 parts by weight of ethyl acetate was added as a solvent under nitrogen purging conditions. Nitrogen was then supplied to the reactor for 1 hour to replace the oxygen inside the reactor, and the internal temperature of the reactor was maintained at 65 degrees Celsius. After homogenizing the monomer mixture, 0.03 parts by weight of azobisisobutyronitrile was added as a reaction initiator, and the reaction was carried out for 8 hours to prepare an acrylic copolymer (Mw: 1,570,000 g / mol).

[0135] In terms of solids content, 0.5 parts by weight of isocyanate curing agent (Coronate L, Polyurethane Chemical Co., Ltd.) and 0.1 parts by weight of silane coupling agent (KBM-403, Shin-Etsu Chemical Co., Ltd.) were added to 100 parts by weight of the prepared acrylic copolymer, and ethyl acetate was added to achieve a solids concentration of 20 parts by weight, thereby preparing a composition for adhesive films.

[0136] The prepared composition was deposited onto a PET release film to a predetermined thickness, dried, and aged at 100°C for 4 minutes to prepare an adhesive film (thickness: 10 micrometers) for use in a polarizing plate. The prepared adhesive film was used as both the first and second adhesive films.

[0137] (2) Preparation of adhesive film for polarizing plate (third adhesive film)

[0138] A monomer mixture was prepared by mixing 94 parts by weight of n-butyl acrylate (n-BA), 1 part by weight of 4-hydroxybutyl acrylate (4-HBA), and 5 parts by weight of acrylic acid. The monomer mixture was placed in a 1-liter reactor equipped with a cooler for easy temperature control, and 10 parts by weight of ethyl acetate were added as a solvent under nitrogen purging conditions. Nitrogen was then introduced for 1 hour to replace the oxygen inside the reactor, and the internal temperature of the reactor was maintained at 65 degrees Celsius. After homogenizing the monomer mixture, 0.03 parts by weight of azobisisobutyronitrile was added as a reaction initiator, and the reaction was carried out for 8 hours to prepare an acrylic copolymer (Mw: 1,680,000 g / mol).

[0139] In terms of solids content, 0.5 parts by weight of isocyanate curing agent (Coronate L, Polyurethane Chemical Co., Ltd.) and 0.1 parts by weight of silane coupling agent (KBM-403, Shin-Etsu Chemical Co., Ltd.) are added to 100 parts by weight of the prepared acrylic copolymer, and ethyl acetate is added to achieve a solids concentration of up to 20 parts by weight, thereby preparing a composition for adhesive films.

[0140] The prepared composition was deposited onto a PET release film to a predetermined thickness, dried, and heated (aged) at 100 degrees Celsius for 4 minutes to prepare an adhesive film (thickness: 25 micrometers) for use in polarizing plates. The prepared adhesive film was used as a third adhesive film.

[0141] (3) Preparation of polarizing plate

[0142] A polyvinyl alcohol film (polymerization degree: 2,800, thickness: 20 μm, Mitsubishi Chemical Co., Ltd.) was dyed by immersing it in a 0.3% potassium iodide aqueous solution and then uniaxially stretched in the processing direction (MD) to 5.0 times its initial length. The stretched polyvinyl alcohol film was then immersed in a 3% boric acid aqueous solution and color-corrected in a 2% potassium iodide aqueous solution, and dried at 50°C for 4 minutes to prepare a polarizer (light transmittance: 45%, thickness: 7 μm).

[0143] As a protective film for the upper polarizer, a cyclic olefin polymer film (thickness: 25 micrometers, Zeon Co., Ltd.) including a hard coating on its upper surface was prepared, and the lower surface of the film was corona treated using an AFS device at a speed of 10 m / min and an output power of 1,000 watts.

[0144] As a protective film for the lower polarizer, a triacetylcellulose film without saponification treatment was prepared (thickness: 40 micrometers, Normal TAC, Konica Co., Ltd.).

[0145] An aqueous solution of polyvinyl alcohol resin was prepared by dissolving an acetoacetyl group-containing polyvinyl alcohol resin (average degree of polymerization: 1,200, degree of saponification: 98.5 mol%, degree of acetylation: 5 mol%, Z200, Mitsubishi Chemical Co., Ltd.) in water at 95°C for 60 minutes and then completely cooling it at room temperature. Subsequently, 0.1 parts by weight of a crosslinking agent (Zircosol-ZN, Daiichi Kigenso Kagaku Kogyo Co., Ltd.) was mixed with 100 parts by weight of the prepared aqueous solution of polyvinyl alcohol resin to prepare an aqueous adhesive.

[0146] After depositing the prepared aqueous adhesive to a predetermined thickness on both surfaces of the polarizer, the upper polarizer protective film and the lower polarizer protective film are respectively bonded and attached to one surface and the other surface of the polarizer, and dried at 80 degrees Celsius for 3 minutes. Then the triacetate cellulose film is removed to expose the other surface of the polarizer.

[0147] A laminate of a λ / 2 liquid crystal retardation film (hydrophobic, water contact angle at 25°C: 86°), a λ / 2 liquid crystal retardation layer (thickness: 2 μm), and a substrate film was prepared by Huji Film Co., Ltd. The λ / 2 liquid crystal retardation layer side of the λ / 2 liquid crystal retardation film was not subjected to corona treatment.

[0148] The other surface of the polarizer is attached to the λ / 2 liquid crystal delay side of the λ / 2 liquid crystal delay film via a first adhesive film. Then the base film is removed, thereby preparing a laminate of an upper polarizer protective film, an aqueous adhesive layer, a polarizer, a first adhesive film (thickness: 10 micrometers) and a λ / 2 liquid crystal delay layer stacked in the following order.

[0149] Fabrication of a λ / 4 liquid crystal retardation film (hydrophobic, water contact angle at 25°C: 84°, laminate of a λ / 4 liquid crystal retardation layer (thickness: 1 μm) and a substrate film, Fujifilm Corporation). The λ / 4 liquid crystal retardation layer side of the λ / 4 liquid crystal retardation film was not subjected to corona treatment.

[0150] The λ / 2 liquid crystal retardation layer is attached to the λ / 4 liquid crystal retardation layer side of the laminate via a first adhesive film. Then, the substrate film is removed, thereby preparing a polarizing plate in which the upper polarizer protective film, the aqueous adhesive layer, the polarizer, the first adhesive film (thickness: 10 micrometers), the λ / 2 liquid crystal retardation layer, the second adhesive film (thickness: 10 micrometers), and the λ / 4 liquid crystal retardation layer are stacked in the order described.

[0151] A third adhesive film is attached to one surface of the λ / 4 liquid crystal retardation layer of the polarizer, thereby preparing a laminate sample in which the upper polarizer protective film, the aqueous adhesive layer, the polarizer, the first adhesive film (thickness: 10 μm), the λ / 2 liquid crystal retardation layer, the second adhesive film (thickness: 10 μm), the λ / 4 liquid crystal retardation layer, and the third adhesive film (thickness: 25 μm) are stacked in the order described. The sample is then evaluated for the properties listed in Table 1.

[0152] Examples 2 to 5 and Comparative Examples 1 to 4

[0153] The polarizing plate was prepared in the same manner as in Example 1, except that the composition for the first adhesive film listed in Table 1 was modified.

[0154] The properties of the first adhesive film, polarizing plate, and laminate samples of the examples and comparative examples were evaluated according to the properties listed in Table 1, and the evaluation results are shown in Table 1.

[0155] (1) Adhesive strength (unit: kgf / 25 mm)

[0156] The adhesive strength between the adhesive film and the adhesive layer was measured using the method specified in ASTM D3330. Laminate specimens (upper polarizer protective film - aqueous adhesive layer - polarizer - first adhesive film (thickness: 10 μm) - λ / 2 liquid crystal retardation layer - second adhesive film (thickness: 10 μm) - λ / 4 liquid crystal retardation layer - third adhesive film (thickness: 25 μm)) prepared in the examples and comparative examples were cut to 25 mm x 200 mm dimensions (polarizer TD x polarizer MD) and then attached to the glass surface. The tensile load during peeling was measured using a texture analyzer by peeling the laminate (upper polarizer protective film - aqueous adhesive layer - polarizer - first adhesive film (thickness: 10 μm) - λ / 2 liquid crystal retardation layer) off the glass plate at 25°C and a tensile speed of 300 mm / min in a 30 kgf load cell.

[0157] (2) Reliability on flat surfaces

[0158] The test specimens were prepared by cutting the laminated specimens (upper polarizer protective film - aqueous adhesive layer - polarizer - first adhesive film (thickness: 10 μm) - λ / 2 liquid crystal retardation layer - second adhesive film (thickness: 10 μm) - λ / 4 liquid crystal retardation layer - third adhesive film (thickness: 25 μm)) prepared in the examples and comparative examples into dimensions of 120 mm x 80 mm (MDxTD of polarizer), attaching the laminated specimens to the glass surface, and then applying a pressure of 4 kg / cm² to the laminated specimens. 2 It is prepared by applying a pressure of 5 kg / cm².

[0159] The heat resistance of the samples was assessed based on the occurrence of bubbles or stratification after the prepared samples were left to stand at 85°C for 250 hours. The damp heat resistance of the samples was assessed based on the occurrence of bubbles or stratification after the prepared samples were left to stand at 60°C and 95% RH (relative humidity) for 250 hours. The assessment criteria are as follows.

[0160] ○: No bubbles or stratification occurs

[0161] △: Slight bubbling or layering occurs.

[0162] ×: Severe bubbling or stratification occurs.

[0163] (3) Reliability on curved surfaces

[0164] The specimens were prepared by cutting the laminated specimens (upper polarizer protective film - aqueous adhesive layer - polarizer - first adhesive film (thickness: 10 μm) - λ / 2 liquid crystal retardation layer - second adhesive film (thickness: 10 μm) - λ / 4 liquid crystal retardation layer - third adhesive film (thickness: 25 μm)) prepared in the examples and comparative examples into dimensions of 120 mm x 80 mm (MDxTD of polarizer), and fixing them between two plates with radii of curvature of 3 mm and 5 mm. The heat resistance of the prepared specimens was evaluated based on the occurrence of bubbles or delamination after the specimens were left to stand at 85°C for 250 hours. The damp heat resistance of the prepared specimens was evaluated based on the occurrence of bubbles or delamination after the specimens were left to stand at 60°C and 95% RH (relative humidity) for 250 hours. The evaluation criteria are as follows.

[0165] ○: No bubbles or stratification occurs

[0166] △: Slight bubbling or layering occurs

[0167] ×: Severe bubbling or stratification occurs.

[0168] Table 1

[0169]

[0170] *In Table 1,

[0171] n-BA: n-Butyl acrylate

[0172] 4-HBA: 4-Hydroxybutyl acrylate

[0173] MPHA: N-(methacryloyloxy)propylheptadecanamide

[0174] AM: Acrylamide

[0175] n-HDA: n-Heptadecanyl acrylate

[0176] As shown in Table 1, the polarizing plate of the examples exhibits good adhesion to the adhesive, thereby preventing delamination of the adhesive. The polarizing plate of the examples improves processability by providing high adhesion to the liquid crystal retardation layer with a high surface water contact angle, eliminating the need for surface treatment of the liquid crystal retardation layer. The polarizing plate provides good heat and humidity resistance on both flat and curved surfaces, and is therefore applicable to both non-flexible and flexible display devices while ensuring good reliability.

[0177] As shown in Table 1, the polarizing plate of the comparative example failed to provide all the above-mentioned effects of the polarizing plate of the example.

[0178] It should be understood that those skilled in the art can make various modifications, alterations, changes, and equivalent embodiments without departing from the spirit and scope of the present invention.

Claims

1. An adhesive film for a polarizing plate, comprising a cured product of a composition, said composition comprising a copolymer of a monomer mixture and a curing agent, said monomer mixture comprising unsaturated monomers having alkyl groups, unsaturated monomers having hydroxyl groups, and unsaturated monomers having amide groups and long-chain alkylene or long-chain alkyl groups.

2. The adhesive film according to claim 1, wherein the adhesive film has an adhesive strength of 1.10 kgf / 25 mm or greater than 1.10 kgf / 25 mm relative to an adhesive having a water contact angle of 70° or greater.

3. The adhesive film according to claim 2, wherein the adhesive is a liquid crystal layer.

4. The adhesive film according to claim 1, wherein the long-chain alkylene group is linear or branched C8 to C96. 20 Alkylene and the long-chain alkyl group is linear or branched C8 to C10. 20 alkyl.

5. The adhesive film according to claim 1, wherein the unsaturated monomer having an amide group and a long-chain alkylene or long-chain alkyl group is represented by formula 1: [Formula 1] Where R is hydrogen or a C1 to C5 alkyl group. L 11 Is it linear or branched C1 to C 10 Alkylene, and L 12 Is it linear or branched C8 to C 20 alkyl.

6. The adhesive film according to claim 1, wherein the unsaturated monomer having an amide group and a long-chain alkylene or long-chain alkyl group is present in the monomer mixture in an amount of 1% to 30% by weight.

7. The adhesive film according to claim 1, wherein the monomer mixture comprises 60% to 95% by weight of the alkyl-containing unsaturated monomer, 0.1% to 10% by weight of the hydroxyl-containing unsaturated monomer, and 1% to 30% by weight of the amide group and long-chain alkylene or long-chain alkyl unsaturated monomer.

8. The adhesive film according to claim 1, wherein the alkyl-containing unsaturated monomer, the hydroxyl-containing unsaturated monomer, and the amide-containing and long-chain alkylene or long-chain alkyl-containing unsaturated monomer are present in the monomer mixture in a total amount of 95% by weight or greater than 95% by weight.

9. The adhesive film according to claim 1, wherein the curing agent comprises an isocyanate curing agent.

10. A polarizing plate, comprising a polarizer and an adhesive film for the polarizing plate as described in any one of claims 1 to 9, stacked on the lower surface of the polarizer.

11. The polarizing plate according to claim 10, comprising: The polarizer, and the adhesive film and liquid crystal delay layer for the polarizing plate are sequentially stacked on one surface of the polarizer.

12. The polarizing plate according to claim 11, wherein the polarizer is hydrophilic and the liquid crystal delay layer is hydrophobic.

13. The polarizing plate according to claim 10, comprising: The polarizer; The adhesive film for the polarizing plate, the first liquid crystal delay layer, the adhesive film for the polarizing plate, and the second liquid crystal delay layer are sequentially stacked on one surface of the polarizer.

14. The polarizing plate of claim 13, wherein each of the first liquid crystal delay layer and the second liquid crystal delay layer is hydrophobic, and the polarizer is hydrophilic.

15. A display device comprising the polarizing plate as claimed in claim 10.

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