Adhesive film, optical member including the same, and optical display device including the same

Abstract

This invention provides an adhesive film, an optical component including the adhesive film, and an optical display device including the adhesive film. The adhesive film comprises a cured product of a composition for the adhesive film, the composition comprising a polymer of a mixture of (meth)acrylic monomers. The adhesive film has a peel strength of 400 gf / 25 mm or greater relative to a polyethylene terephthalate film with an antistatic layer, measured after 500 hours of exposure at 60°C and 93% relative humidity on a sample formed by laminating the adhesive film onto the polyethylene terephthalate film with an antistatic layer. The adhesive film has a storage modulus of 10 to 100 kPa at 25°C. According to Formula 1, the adhesive film has a resistivity change rate of 1% or less.

Description

Technical Field

[0001] The present invention relates to an adhesive film, an optical component including the adhesive film, and an optical display device including the adhesive film. Background Technology

[0002] With increasing interest in foldable optical displays, there is a growing demand for adhesive films incorporated into these displays that possess excellent foldability. As foldable optical displays, and especially foldable phones, are used in increasingly diverse environments, foldable phones may be used underwater. Therefore, foldable phones require waterproofing for underwater use.

[0003] Barrier layers or films that prevent moisture penetration can be applied to foldable optical displays. However, typical barrier layers or films have a high modulus and therefore may be subjected to stress when folded. Therefore, adhesive films with good foldability and waterproofing are desirable. For adhesive films, high peel strength and low resistivity change rate are essential for achieving waterproofing after long-term storage under high temperature and humidity conditions.

[0004] The background technology of the present invention is disclosed in Japanese Unexamined Patent Publication No. 2013-072951, etc. Summary of the Invention

[0005] Technical issues

[0006] One aspect of the present invention provides an adhesive film having excellent foldability, high peel strength after long-term storage under high temperature and high humidity conditions, and low resistivity change rate after long-term storage under high temperature and high humidity conditions.

[0007] Another aspect of the present invention provides an adhesive film with excellent waterproof function.

[0008] Another aspect of the present invention provides an adhesive film with high substrate adhesion.

[0009] Technical solution

[0010] 1. According to one aspect of the invention, the adhesive film comprises a cured product of a composition for the adhesive film, the composition comprising a polymer of a mixture of (meth)acrylic monomers, and the adhesive film having a peel strength of 400 gf / 25 mm or greater relative to a polyethylene terephthalate film including an antistatic layer, as measured on a sample after being placed at 60°C and 93% relative humidity for 500 hours, wherein the sample is prepared by stacking the adhesive film on a polyethylene terephthalate film including an antistatic layer, the adhesive film having a storage modulus of 10 kPa to 100 kPa at 25°C, and the adhesive film having a resistivity change rate of 1% or less, as calculated according to Formula 1: [Formula 1] Rate of change of resistance = |(R2-R1) / R1| × 100 (In Equation 1, R1 represents the line resistance (unit: Ω), as measured between the first and second silver layers of the sample. The sample comprises: an indium tin oxide film; a first silver layer and a second silver layer, respectively stacked at opposite ends of the upper surface of the indium tin oxide film; an adhesive film covering a portion of the first silver layer, a portion of the second silver layer, and the indium tin oxide film between the first and second silver layers; and a release film covering the adhesive film. R2 represents the line resistance (unit: Ω), as measured between the first and second silver layers of the sample after the sample has been placed at 60°C and 93% relative humidity for 500 hours.

[0011] 2. In 1, the adhesive film may have a peel strength of 600 gf / 25 mm or greater relative to the polyethylene terephthalate film including the antistatic layer, as measured on the sample after the sample has been placed at 25°C for 30 minutes, wherein the sample is prepared by stacking the adhesive film on the polyethylene terephthalate film including the antistatic layer.

[0012] 3. In 1 and 2, the composition for the adhesive film may include a mixture of (meth)acrylate monomers, a (meth)acrylate having a carboxyl group, a photoinitiator, and a polymer of a crosslinking agent having alkoxide and (meth)acrylate groups.

[0013] 4. In 1 to 3, the (meth)acrylate having a carboxyl group can be a β-carboxylalkyl (meth)acrylate.

[0014] 5. In 1 to 4, the alkeneoxy group can be either ethylidene or propyleneide.

[0015] 6. In 1 to 5, the crosslinking agent having alkoxide and (meth)acrylate groups may have 2 to 6 (meth)acrylate groups.

[0016] 7. In 1 to 6, the monomer mixture may include (meth)acrylic monomers having alkyl groups and (meth)acrylic monomers having hydroxy groups.

[0017] 8. In 1 to 7, alkyl (meth)acrylic monomers and hydroxyl (meth)acrylic monomers may be present in the monomer mixture in an amount of 95% or greater.

[0018] 9. In 1 to 8, the monomer mixture may contain 60 wt% to 90 wt% of alkyl (meth)acrylic monomers and 10 wt% to 40 wt% of hydroxyl (meth)acrylic monomers.

[0019] 10. In 1 to 9, the monomer mixture may be free of (meth)acrylic monomers having carboxyl groups.

[0020] 11. In 1 to 10, the composition for the adhesive film may comprise: A polymer of 100 parts by weight of a mixture of (meth)acrylic acid monomers. 0.1 to 5 parts by weight of carboxyl-containing (meth)acrylates, 0.001 parts by weight to 5 parts by weight of photoinitiator, and 0.01 to 0.5 parts by weight of a crosslinking agent having alkoxide and (meth)acrylate groups.

[0021] 12. In 1 to 11, the adhesive film may not contain organic nanoparticles.

[0022] 13. In 1 to 12, the adhesive film may have substrate adhesion of 400gf / 25mm or greater.

[0023] According to another aspect of the invention, the optical display device includes the adhesive film.

[0024] Beneficial effects

[0025] The present invention provides an adhesive film with excellent foldability, high peel strength after long-term storage under high temperature and high humidity conditions, and low resistivity change rate after long-term storage under high temperature and high humidity conditions.

[0026] This invention provides an adhesive film that offers excellent waterproofing.

[0027] The present invention provides an adhesive film with high substrate adhesion. Attached Figure Description

[0028] Figure 1 This is a cross-sectional view of the sample used for line resistance measurement.

[0029] Figure 2This is a plan view of the sample used for line resistance measurement. Detailed Implementation

[0030] Exemplary embodiments of the present invention will be described in detail below. However, the technology disclosed herein is not limited to the following embodiments and can be embodied in various forms. It should be understood that the following embodiments are provided for the purpose of full disclosure and to enable those skilled in the art to fully understand the present invention.

[0031] The terminology used herein is for the purpose of describing exemplary embodiments and is not intended to limit the invention. Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” are intended to also include the plural forms as used herein.

[0032] In this paper, "glass transition temperature of homopolymer" can be expressed as the glass transition temperature (Tg) of the target monomer in the homopolymer phase, as measured using DSC Discovery (TAInstrument Inc.). Specifically, the homopolymer of the target monomer can be heated to 180°C at 20°C / min, slowly cooled to -100°C at the same rate, and then reheated to 100°C at 10°C / min to obtain an endothermic transition curve. The inflection point of the endothermic transition curve can then be determined as the glass transition temperature of the homopolymer.

[0033] In this document, "(meth)acryloyl" may mean acryloyl and / or methacryloyl.

[0034] In this paper, the weight-average molecular weight can be measured by gel permeation chromatography based on polystyrene calibration.

[0035] 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).

[0036] According to one embodiment, an adhesive film is provided that exhibits excellent foldability, high peel strength after long-term storage under high temperature and high humidity conditions, and low resistivity change rate after long-term storage under high temperature and high humidity conditions. According to another embodiment, an adhesive film is provided that has high adhesive strength relative to the adherend. This adhesive film can be used in optical display devices that require good waterproofing while ensuring good foldability.

[0037] According to one embodiment, the adhesive film has a peel strength of 400 gf / 25 mm or greater relative to a polyethylene terephthalate film including an antistatic layer, as measured on the sample after it has been placed at 60°C and 95% relative humidity for 500 hours, wherein the sample is prepared by stacking the adhesive film on the polyethylene terephthalate film including the antistatic layer. Within this range, optical display devices including the adhesive film have excellent waterproofing capabilities, thereby broadening the application range of both the adhesive film and the optical display device. For example, the adhesive film has peel strengths of 400 gf / 25 mm, 500 gf / 25 mm, 600 gf / 25 mm, 700 gf / 25 mm, 800 gf / 25 mm, 900 gf / 25 mm, or 1,000 gf / 25 mm, for example, from 400 gf / 25 mm to 1,000 gf / 25 mm or from 400 gf / 25 mm to 800 gf / 25 mm.

[0038] As used herein, "antistatic layer" can refer to a coating formed by any typical method known in the art. For example, an antistatic layer may include, but is not limited to, ionic liquids, conductive polymers, etc.

[0039] The adhesive film has a storage modulus of 10 kPa to 100 kPa at 25°C. Within this range, optical display devices incorporating the adhesive film exhibit excellent foldability. For example, the adhesive film may have the following storage moduli: 10 kPa, 15 kPa, 20 kPa, 25 kPa, 30 kPa, 35 kPa, 40 kPa, 45 kPa, 50 kPa, 55 kPa, 60 kPa, 65 kPa, 70 kPa, 75 kPa, 80 kPa, 85 kPa, 90 kPa, 95 kPa, or 100 kPa, for example, 11 kPa to 90 kPa.

[0040] The adhesive film has a resistivity change rate of 1% or less, as calculated according to Equation 1. Within this range, the optical display device including the adhesive film can operate without failure even after long-term exposure to high temperature and high humidity conditions, and therefore can have excellent waterproof performance. For example, the adhesive film can have a resistivity change rate of 0% to 1%.

[0041] [Formula 1]

[0042] Rate of change of resistance = |(R2-R1) / R1| × 100

[0043] (In Equation 1, R1 represents the line resistance (unit: Ω), as measured between the first and second silver layers of a sample comprising: an indium tin oxide film; a first silver layer and a second silver layer, respectively stacked at opposite ends of the upper surface of the indium tin oxide film; an adhesive film covering a portion of the first silver layer, a portion of the second silver layer, and the indium tin oxide film between the first and second silver layers; and a release film covering the adhesive film, and R2 represents the line resistance (unit: Ω), as measured between the first and second silver layers of the sample after the sample has been placed at 60°C and 93% relative humidity for 500 hours. According to one embodiment, the adhesive film may have the following peel strength relative to the polyethylene terephthalate film including the antistatic layer: 600 gf / 25 mm or greater, such as 600 gf / 25 mm, 700 gf / 25 mm, 800 gf / 25 mm, 900 gf / 25 mm or 1,000 gf / 25 mm, for example, 600 gf / 25 mm to 1,000 gf / 25 mm, as measured on the sample after placing the sample at 25°C for 30 minutes, wherein the sample is prepared by stacking the adhesive film on the polyethylene terephthalate film.

[0044] According to one embodiment, the adhesive film can have a substrate adhesion of 400 gf / 25 mm or greater. Within this range, the adhesive film can bond to the substrate in a short time to improve reliability. For example, the adhesive film can have a substrate adhesion of 400 gf / 25 mm to 800 gf / 25 mm. In this document, "substrate adhesion" refers to the adhesive strength of the barrier film relative to the PET film.

[0045] The adhesive film is a light-curable transparent adhesive (OCA) and can be used in foldable optical displays.

[0046] The adhesive film can have a thickness of 100 μm or less. Within this range, the adhesive film can be thin enough to ensure a slender structure even when used in foldable optical displays. Specifically, the adhesive film can have a thickness greater than 0 μm and less than or equal to 100 μm, for example, from 10 μm to 80 μm.

[0047] The adhesive film can have a storage modulus of 200 kPa or less at -20°C, for example, a storage modulus of 0.1 kPa to 200 kPa or 50 kPa to 200 kPa. Within this range, the adhesive film can ensure good folding properties over a wide range of conditions.

[0048] The adhesive film can have a storage modulus of 200 kPa or less at 60°C, for example, a storage modulus of 1 kPa to 200 kPa, or 10 kPa to 100 kPa. Within this range, the adhesive film can ensure good folding properties over a wide range of conditions.

[0049] The storage modulus ratio of the adhesive film at -20°C to its storage modulus at 60°C can be from 1:0.1 to 1:0.8, specifically 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, or 1:0.8, for example, 1:0.2 to 1:0.5. Within this range, the adhesive film can ensure good folding properties over a wide range of conditions.

[0050] The adhesive film can have a haze of 1% or less, for example, 0% to 1%, in the visible spectrum, at wavelengths from 380 nm to 780 nm. Within this range, the adhesive film can be used in optical display devices.

[0051] The adhesive film may be a (meth)acrylic adhesive film. In one embodiment, the adhesive film may be a pressure-sensitive adhesive (PSA).

[0052] The adhesive film includes a cured product of a composition for use in adhesive films, the composition comprising a polymer of a mixture of (meth)acrylic monomers.

[0053] Specifically, the composition for the adhesive film comprises a polymer of a mixture of (meth)acrylate monomers, a (meth)acrylate having a carboxyl group, a photoinitiator, and a crosslinking agent having alkene and (meth)acrylate groups. The composition comprising a (meth)acrylate having a carboxyl group and a crosslinking agent having alkene and (meth)acrylate groups readily provides the aforementioned effects.

[0054] In one embodiment, the adhesive film may include a photocurable product of the composition for the adhesive film.

[0055] Polymers of (meth)acrylic acid monomer mixtures can facilitate the formation of an adhesive film matrix and provide the peel strength and resistivity change rate described above.

[0056] The monomer mixture may include alkyl-containing (meth)acrylic monomers and hydroxyl-containing (meth)acrylic monomers. In one embodiment, the alkyl-containing (meth)acrylic monomers and the hydroxyl-containing (meth)acrylic monomers may be present in the monomer mixture in an amount of 95 wt% or greater, for example, from 99 wt% to 100 wt% or 100 wt%. Within this range, the adhesive film can easily ensure the aforementioned effects.

[0057] Alkyl (meth)acrylic monomers can be in the form of unsubstituted C1 to C2 chains, whether straight or branched. 20 Selected from alkyl (meth)acrylic acid monomers. Having straight or branched unsubstituted C1 to C2 chains. 20 Alkyl (meth)acrylic monomers refer to monomers with unsubstituted C1 to C2 chains at their ester sites, whether straight or branched. 20 Alkyl (meth)acrylates and may include at least one selected from the following, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, heptyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, and dodecyl (meth)acrylate.

[0058] According to one embodiment, the alkyl-containing (meth)acrylate monomer may be present in the monomer mixture in amounts of 60 wt% or greater, specifically 60 wt% to 90 wt%, for example 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, or 90 wt%, more specifically 70 wt% to 85 wt%. Within this range, the composition can facilitate the formation of the adhesive film matrix.

[0059] According to one embodiment, alkyl-containing (meth)acrylic monomers may include (meth)acrylic monomers with a homopolymer glass transition temperature of -50°C or less. (Meth)acrylic monomers with a homopolymer glass transition temperature of -50°C or less can facilitate achieving the storage modulus and peel strength described above by lowering the glass transition temperature of the polymer. Specifically, (meth)acrylic monomers may have a homopolymer glass transition temperature ranging from -80°C to -50°C. The "homomer glass transition temperature of (meth)acrylic monomers" can be measured by typical methods known to those skilled in the art or determined by referring to commercial catalogues.

[0060] In one embodiment, (meth)acrylic monomers having a homopolymer glass transition temperature of -50°C or less and having an alkyl group may be present in the monomer mixture in amounts of 60 wt% or more, specifically 60 wt% to 90 wt%, for example 60 wt%, 61 wt%, 62 wt%, 63 wt%, 64 wt%, 65 wt%, 66 wt%, 67 wt%, 68 wt%, 69 wt%, 70 wt%, 71 wt%, 72 wt%, 73 wt%, 74 wt%, 75 wt%, 76 wt%, 77 wt%, 78 wt%, 79 wt%, 80 wt%, 81 wt%, 82 wt%, 83 wt%, 84 wt%, 85 wt%, 86 wt%, 87 wt%, 88 wt%, 89 wt%, or 90 wt%, more specifically 70 wt% to 85 wt%. Within this range, the composition can readily lower the glass transition temperature of the polymer.

[0061] The monomer mixture may include at least one type, such as two or more types of (meth)acrylic monomers having a homopolymer glass transition temperature of -50°C or less.

[0062] (Meth)acrylic monomers containing hydroxyl groups can be linear or branched chains containing at least one hydroxyl group from C1 to C2. 20 Selected from alkyl (meth)acrylic acid monomers. For example, (meth)acrylic acid monomers having a hydroxyl group refer to straight-chain or branched C1 to C2 chains containing at least one hydroxyl group at their ester sites. 20 Alkyl (meth)acrylate monomers, and may include at least one selected from the following, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,4-cyclohexanediethanol mono(meth)acrylate, 1-chloro-2-hydroxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 4-hydroxycyclopentyl (meth)acrylate, and 4-hydroxycyclohexyl (meth)acrylate.

[0063] According to one embodiment, the hydroxyl-containing (meth)acrylic monomer may be present in the monomer mixture in amounts of 40 wt% or less, specifically 10 wt% to 40 wt%, for example 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt%, 20 wt%, 21 wt%, 22 wt%, 23 wt%, 24 wt%, 25 wt%, 26 wt%, 27 wt%, 28 wt%, 29 wt%, 30 wt%, 31 wt%, 32 wt%, 33 wt%, 34 wt%, 35 wt%, 36 wt%, 37 wt%, 38 wt%, 39 wt%, or 40 wt%, more specifically 15 wt% to 30 wt%. Within this range, the composition can readily ensure the peel strength and storage modulus described above.

[0064] According to one embodiment, the monomer mixture may be free of carboxyl-containing (meth)acrylate monomers. That is, the monomer mixture may include 0 wt% of carboxyl-containing (meth)acrylate monomers. The adhesive film formed from the composition of the polymer comprising the monomer mixture, which includes a mixture of carboxyl-containing (meth)acrylate monomers, can have an increased storage modulus at 25°C. For example, the carboxyl-containing (meth)acrylate monomers may be carboxyl-containing (meth)acrylates as described below.

[0065] The polymer can have a glass transition temperature of -50°C or less, such as -70°C, -65°C, -60°C, -55°C, or -50°C, for example, -70°C to -50°C. Within this range, the adhesive film can readily achieve the storage modulus and peel strength described above.

[0066] The polymer may have the following weight-average molecular weights: 800,000 g / mol or greater, such as 800,000 g / mol, 850,000 g / mol, 900,000 g / mol, 950,000 g / mol, 1,000,000 g / mol, 1,050,000 g / mol, 1,100,000 g / mol, 1,150,000 g / mol, 1,20 The energy storage modulus and peel strength described above can be achieved within the ranges of 0,000 g / mol, 1,250,000 g / mol, 1,300,000 g / mol, 1,350,000 g / mol, 1,400,000 g / mol, 1,450,000 g / mol, 1,500,000 g / mol, 800,000 to 1,500,000 g / mol, or 1,000,000 to 1,300,000 g / mol.

[0067] Polymers can be prepared by polymerization of monomer mixtures, such as photopolymerization. In one embodiment, the polymer can be a partially polymerized or fully polymerized product of the monomer mixture. As a product obtained by polymerization of the monomer mixture to less than 100% degree of polymerization, but not fully polymerized to 100% degree of polymerization, the partially polymerized product can be a mixture of a (meth)acrylic acid polymer formed from the monomer mixture and unreacted (meth)acrylic acid monomers. A fully polymerized product can be obtained by polymerization of the monomer mixture to 100% degree of polymerization, and the fully polymerized product can consist of a (meth)acrylic acid copolymer.

[0068] Polymers can be prepared by polymerizing a mixture of monomers using a polymerization reaction method. In this document, polymerization reactions can be carried out using any typical methods known to those skilled in the art. For example, polymerization can be carried out by adding a small amount of photoinitiator to the monomer mixture and then irradiating it with light.

[0069] Crosslinking agents having alkeneoxy and (meth)acrylate groups can be those having -(-RO-)- As a crosslinking agent for alkoxides, in which It is the linking site and R is a substituted or unsubstituted C2 to C5 alkylene group.

[0070] A crosslinking agent having alkoxy and (meth)acrylate groups may be included together with the carboxyl-containing (meth)acrylates described below to help ensure peel strength while reducing the rate of change of resistivity, even after the adhesive film has been placed under high temperature and high humidity conditions for a long time.

[0071] The C2 to C5 alkene groups can be ethylene oxide groups or propylene oxide groups, preferably ethylene oxide groups. Therefore, the crosslinking agent allows the formation of this adhesive film through a crosslinking reaction with the polymer, while simultaneously improving foldability.

[0072] Crosslinking agents having alkoxide and (meth)acrylate groups may include 2 to 6, preferably 3 to 5 (meth)acrylate groups as photocurable functional groups.

[0073] Crosslinking agents with alkoxide and (meth)acrylate groups are available from commercially available products.

[0074] The crosslinking agent having alkoxide and (meth)acrylate groups can be present in an amount of 0.01 to 0.5 parts by weight relative to 100 parts by weight of the polymer, for example, 0.01, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5 parts by weight, for example, 0.05 to 0.3 parts by weight or 0.05 to 0.2 parts by weight. Within this range, the adhesive film can readily improve the peel strength under high temperature and high humidity conditions, while reducing the rate of change of resistivity without excessive increase in storage modulus.

[0075] Including carboxyl-containing (meth)acrylates in the composition for use in adhesive films, rather than in the monomer mixture, may increase the storage modulus of the adhesive film when carboxyl-containing (meth)acrylates are included in the monomer mixture that will be present in the polymer.

[0076] When a composition for an adhesive film containing a crosslinking agent having alkoxide and (meth)acrylate groups is photocured, the (meth)acrylate having carboxyl groups can be self-cured or can be cured together with the alkoxide and (meth)acrylate groups to provide high cohesion to ensure resistance to moisture permeation, so that the adhesive film can have high peel strength and low resistivity change rate when placed under high temperature and high humidity conditions for a long time.

[0077] (Meth)acrylates having a carboxyl group can include carboxyalkyl (meth)acrylates, such as β-carboxyethyl (meth)acrylates. In this document, "alkyl" can refer to C1 to C5 alkyl groups.

[0078] The carboxyl-containing (meth)acrylate may be present in amounts from 0.1 parts by weight to 5 parts by weight, such as 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, or 5 parts by weight, for example, from 1 part by weight to 5 parts by weight, relative to 100 parts by weight of the polymer. Within this range, the adhesive film can exhibit high peel strength and low resistivity change rate when subjected to prolonged exposure to high temperature and high humidity conditions.

[0079] Photoinitiators are used to form adhesive films by photocuring compositions for use in adhesive films or, when the polymer is a partially polymerized product, to fully polymerize the remaining (meth)acrylate monomers.

[0080] The photoinitiator can be selected from any photoinitiator capable of generating free radicals during the curing process by means of light irradiation, thereby initiating a polymerization or curing reaction. For example, the photoinitiator can be benzoin, hydroxy ketone, amino ketone, or phosphine oxide photoinitiator. Specifically, photoinitiators may include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin n-butyl ether, benzoin isobutyl ether, and acetophenone compounds, such as 2,2-dimethoxy-2-phenylacetophenone, 2,2'-diethoxyacetophenone, 2,2'-dibutoxyacetophenone, 2-hydroxy-2-methylacetophenone, p-tert-butyltrichloroacetophenone, p-tert-butyldichloroacetophenone, 4-chloroacetophenone, 2,2'-dichloro-4-phenoxyacetylacetophenone, etc., dimethylaminoacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylprop-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-but-1-one, 1- Hydroxycyclohexylbenzophenone, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholino-prop-1-one, 4-(2-hydroxyethoxy)phenyl-2-(hydroxy-2-propyl)one, benzophenone, p-phenylbenzophenone, 4,4-diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-t-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone, 2,4-diethylthioxanthone, benzyl dimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoate, oligomeric [2-hydroxy-2-methyl-1-[4-(1-methylethylene)phenyl]propanone], 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, etc.

[0081] The photoinitiator may be present in an amount of 0.0001 parts by weight to 5 parts by weight, specifically 0.001 parts by weight to 3 parts by weight or 0.001 parts by weight to 1 part by weight, relative to 100 parts by weight of the polymer. Within this range, the photoinitiator allows the composition to cure completely, prevents degradation of the light transmittance of the adhesive film due to residual photoinitiator, reduces bubble formation, and exhibits good reactivity.

[0082] Compositions for use in adhesive films, i.e., adhesive films, may also include silane coupling agents.

[0083] Silane coupling agents can further improve the peel strength of adhesive films. Silane coupling agents can include any typical silane coupling agents known to those skilled in the art. For example, silane coupling agents can include epoxy-containing silane coupling agents, such as glycidylpropoxytrimethoxysilane, methacryloxypropylmethyldimethoxysilane, etc.

[0084] The silane coupling agent can be present in an amount of 0.01 parts by weight to 5 parts by weight relative to 100 parts by weight of the polymer. Within this range, the adhesive film can have improved peel strength.

[0085] According to one embodiment, the composition for the adhesive film may be a solvent-free composition that does not contain solvents.

[0086] According to another embodiment, the composition for the adhesive film may further include a solvent. When forming an adhesive film having a thin thickness, specifically 20 μm or less, from the composition, the solvent can allow for surface homogenization of the adhesive film. The solvent can be any typical solvent known to those skilled in the art without limitation. For example, the solvent can be an organic solvent, such as ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, etc., but is not limited thereto. The composition may have a solids content of 50 wt% or less, for example, 20 wt% or less.

[0087] The composition for use in the adhesive film, i.e., the adhesive film, may also include additives. Additives are used to provide additional functionality to the adhesive film. Specifically, additives may include, but are not limited to, at least one type selected from: UV absorbers, reaction inhibitors, adhesion enhancers, thixotropic agents, conductive agents, colorants, stabilizers, antioxidants, leveling agents, and antistatic agents. The amount of additives in the composition (i.e., the adhesive film) may be suitably selected within a range that does not degrade the effects of the invention.

[0088] According to one embodiment, the adhesive film may be free of organic nanoparticles. In this document, "organic nanoparticles" can refer to organic nanoparticles known to those skilled in the art to provide foldability, such as core-shell nanoparticles. Even without organic nanoparticles, the adhesive film can provide good foldability.

[0089] According to another embodiment, the adhesive film may also include organic nanoparticles.

[0090] The adhesive film can be formed from the composition for adhesive films described above. Specifically, the adhesive film can be prepared by coating the composition for adhesive films onto a release membrane, followed by photocuring of the composition for adhesive films. Photocuring can include an oxygen-free environment, using a low-pressure lamp with a dose of 400 mJ / cm². 2 Up to 3,000 mJ / cm 2 Furthermore, the light irradiation should be performed with wavelengths between 300 nm and 400 nm. However, it should be understood that the irradiation dose and wavelength can be varied based on the thickness of the adhesive film and the irradiation conditions.

[0091] In the following, an optical component according to an embodiment of the present invention will be described.

[0092] The optical component includes an optical film and an adhesive film formed on at least one surface of the optical film, wherein the adhesive film includes an adhesive film according to an embodiment of the present invention. Therefore, the optical component has good bending properties and / or good folding characteristics, and thus can be used in foldable display devices.

[0093] In one embodiment, the optical film provides certain optical functions to the display device, such as polarization, optical compensation, display quality improvement, and / or conductivity. Examples of optical films may include window films, windows, polarizing plates, color filters, retardation films, elliptical polarizing films, reflective polarizing films, anti-reflective films, compensation films, brightness enhancement films, alignment films, light diffusion films, shatterproof glass films, surface protective films, OLED device blocking layers, plastic LCD substrates, and transparent electrode films including indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum-doped zinc oxide (AZO), carbon nanotubes (CNTs), Ag nanowires, graphene, etc. These optical films can be readily produced by those skilled in the art.

[0094] For example, the touchpad can be attached to a window film or optical film via an adhesive film to form a touch panel. Alternatively, the adhesive film can be applied to a polarizing film, as is typical in the art.

[0095] In another embodiment, the optical film is an optically transparent film, and the optical component comprising the optical film and the adhesive film can serve as a support layer for the display element. For example, the display element may include a window film, etc. The window film may include the optical component and a window coating (e.g., a silicone coating) formed on the optical component. Specifically, the optical film may have a total transmittance of 90% or greater in the visible spectrum and may be formed from at least one selected from: cellulose resins, including triacetyl cellulose, polyester resins, including polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polybutylene naphthalate, etc., polycarbonate resins, polyimide resins, polystyrene resins, polyacrylate resins, including poly(methyl methacrylate), cyclic olefin polymer resins, acrylic resins, and polyamide resins. The optical film may have a thickness of 10 μm to 100 μm, specifically 20 μm to 75 μm, more specifically 30 μm to 50 μm. Within this range, the optical component can serve as a support layer for the display element.

[0096] The optical component may be a double-layer optical component comprising an optical film and an adhesive film formed on one surface of the optical film. Alternatively, the optical component may be a film laminate comprising three or more layers of two or more optical films, wherein at least two of the optical films are stacked on top of each other via an adhesive film according to the invention.

[0097] The optical display device according to the present invention includes an adhesive film according to the present invention.

[0098] Optical display devices may include light-emitting diode (LED) displays, liquid crystal displays, etc., with LED displays including organic light-emitting diode (OLED) displays, etc. Optical display devices may include flexible displays. In other embodiments, optical display devices may include non-flexible displays.

[0099] Invention Model

[0100] The invention will now be described in more detail with reference to some embodiments. It should be understood that these embodiments are provided for illustrative purposes only and should not be construed as limiting the invention in any way.

[0101] Example 1

[0102] In a reactor, 100 parts by weight of a monomer mixture comprising 80 parts by weight of 2-ethylhexyl acrylate (2-EHA) and 20 parts by weight of 4-hydroxybutyl acrylate (4-HBA) were thoroughly mixed with 0.05 parts by weight of initiator Irgacure 651 (2,2-dimethoxy-2-phenylacetophenone, BASF). After replacing the dissolved oxygen with nitrogen in the reactor, the mixture was partially polymerized by UV light irradiation using a low-pressure mercury lamp to prepare a polymer (a viscous liquid with a viscosity of 5,000 cP at 25°C).

[0103] In terms of solid content, relative to 100 parts by weight of polymer, 0.3 parts by weight of Irgacure 127, 0.1 parts by weight of Irgacure 651, 0.1 parts by weight of MF-001 as a crosslinking agent having alkene and (meth)acrylate groups, and 0.5 parts by weight of β-carboxyethyl acrylate are added to and mixed with a viscous liquid to prepare a composition for adhesive films.

[0104] The prepared composition for adhesive film was coated onto a first PET (polyethylene terephthalate) release membrane, covered with a second PET release membrane, and sprayed at 2,000 mJ / cm. 2 The dosage of ultraviolet light was used to irradiate the material to prepare an adhesive sheet consisting of a first PET release film, a 50 μm thick adhesive film, and a second PET release film.

[0105] Examples 2 to 5

[0106] The adhesive film was prepared in the same manner as in Example 1, except that the content of β-carboxyethyl acrylate and the content of crosslinking agents having alkeneoxy and (meth)acrylate groups were varied, as listed in Table 1. In Table 1, the units are parts by weight, and "-" indicates that the corresponding component is absent.

[0107] Comparative Examples 1 and 2

[0108] The adhesive film was prepared in the same manner as in Example 1, except that the content of β-carboxyethyl acrylate, the content of the crosslinking agent having alkoxide and (meth)acrylate groups, and the content of each component in the composition for the adhesive film were varied, as listed in Table 1. In Table 1, the units are parts by weight, and "-" indicates that the corresponding component is absent.

[0109] Table 1 shows the compositions for adhesive films according to the examples and comparative examples. The following properties listed in Table 1 were evaluated on the adhesive films according to the examples and comparative examples.

[0110] (1) Initial peel strength: After peeling the PET release film from the adhesive sheets prepared in each example and comparative example, a polyurethane film (thickness: 25 μm, NK) was attached to the surface of the adhesive sheet, and the release film was removed from the surface. Then, the adhesive sheet was cut into 10 cm × 2.5 cm (length × width) dimensions and attached to a polyethylene terephthalate (TAK) film with an antistatic layer. The remaining PET release film was removed from the adhesive sheet, thereby preparing a specimen in which a polyethylene terephthalate film including an antistatic layer, an adhesive film, and a polyurethane film are sequentially stacked. The specimen was placed at 25°C for 30 minutes and then fixed to a peel strength tester (Texture Analyzer (TA) Instrument). The peel strength was then measured at 25°C, at a peel rate of 300 mm / min and a peel angle of 180° when the stack of adhesive film and polyurethane film including the antistatic layer was removed from the polyethylene terephthalate film.

[0111] (2) Peel strength under high temperature and high humidity conditions: The specimens were prepared in the same manner as in (1). The prepared specimens were placed at 60°C and 95% relative humidity for 500 hours. Then, the peel strength was measured in the same manner as in (1).

[0112] (3) Resistance change rate: Two release films were removed from the adhesive sheets prepared in each example and comparative example to obtain an adhesive film. The obtained adhesive film, indium tin oxide film, silver paste (including paste and silver powder for forming the silver layer), and PET release film were then used to prepare samples for resistance measurement, such as... Figure 1 and 2 As shown.

[0113] refer to Figure 1 and 2The indium tin oxide film 2 is bonded to the glass plate 1 via an adhesive. For a sample comprising the indium tin oxide film 2 (thickness: 150 μm); a first silver layer 3 and a second silver layer 4 stacked at opposite ends on the upper surface of the indium tin oxide film 2; an adhesive film 5 (thickness: 150 μm) covering a portion of the first silver layer 3, a portion of the second silver layer 4, and the indium tin oxide film 2 between the first silver layer and the second silver layer; and a PET release film 6 (thickness: 50 μm) covering the adhesive film 5, the line resistance (unit: Ω, R1) between measurement points A and B of the first silver layer 3 and the second silver layer 4 is measured using a ohmmeter 7 (3244-60, Hioki).

[0114] After placing the sample at 60°C and 93% relative humidity for 500 hours, the line resistance (unit: Ω, R2) between the first and second silver layers was measured in the same manner as above.

[0115] Based on the measured values ​​R1 and R2, the rate of change of resistance is calculated according to Equation 1.

[0116] (4) Substrate adhesion: Samples with the stacked structure of polyurethane base film / adhesive film / polyethylene terephthalate film including antistatic layer described above were prepared, and the peel strength of the adhesive film when it was peeled off from the polyethylene terephthalate film was measured. Using a T-type peel structure, the peel strength was measured at a peel rate of 50 mm / min at 25°C.

[0117] (5) Storage modulus: The storage modulus was measured in self-strain mode using a rheometer (ARES G2, TA) as a dynamic viscoelasticity meter under a shear rate of 1 rad / sec and a tension of 1%. Multiple adhesive films prepared in each example and comparative example were stacked to form a laminate with a thickness of 800 μm. The laminate was punched with an 8 mm diameter punch to prepare a sample. The storage modulus of the sample was measured using an 8 mm fixture at a temperature ranging from -60 °C to 90 °C while the temperature was increased at a heating rate of 5 °C / min and a normal force of 1.0 N. The storage modulus at 25 °C was obtained.

[0118] (6) Foldability: The adhesive film was obtained by removing two release films from the adhesive sheets prepared in each example and comparative example. The adhesive film was placed between two 50 μm thick polyethylene terephthalate (PET) films that had undergone corona treatment and attached to them by rollers, such that the corona-treated surface of the PET film was in contact with the adhesive film. The samples were left at room temperature for 12 hours and then cut into specimens with dimensions of 140 mm × 70 mm (length × width). Using an adhesive (4965, Tesa Inc.), the specimens were fixed to a flexibility tester (CFT-200, Covotech Inc.) and folded at 25°C at a rate of 30 cycles / min in the longitudinal direction (length 140 mm) of the specimen, so that the bent portion of the specimen had a radius of curvature of 3 mm (one cycle represents the operation of folding the adhesive film in half and then unfolding it). The minimum number of cycles required to visually observe the first crack in the polyethylene terephthalate film of the adhesive film was measured. An adhesive film with a higher minimum cycle count indicates that it can easily alleviate the stress caused by bending in polyethylene terephthalate films. Samples with a minimum cycle count greater than or equal to 100,000 cycles are evaluated as OK, and samples with a minimum cycle count less than 100,000 cycles are evaluated as NG.

[0119] Table 1 In Table 1, AA: Acrylic acid 2-HEA: 2-Hydroxyethyl Acrylate ACMO: Acryloylmorpholine As shown in Table 1, the adhesive film according to the embodiment provides good foldability, high peel strength after long-term storage under high temperature and high humidity conditions, and low resistivity change rate after long-term storage under high temperature and high humidity conditions.

[0120] Conversely, the adhesive film according to the comparative model does not provide all of the above effects.

[0121] It should be understood that those skilled in the art can make various modifications, alterations, variations and equivalent implementations without departing from the spirit and scope of the invention.

Claims

1. An adhesive film comprising: A cured product of a composition for use in adhesive films, said composition comprising a polymer of a mixture of (meth)acrylic monomers. The adhesive film has a peel strength of 400 gf / 25 mm or greater relative to the polyethylene terephthalate film including the antistatic layer, as measured on the sample after it has been placed at 60°C and 93% relative humidity for 500 hours, wherein the sample is prepared by stacking the adhesive film on the polyethylene terephthalate film including the antistatic layer. The adhesive film has a storage modulus of 10 kPa to 100 kPa at 25°C and a resistivity change rate of 1% or less calculated according to Equation 1: [Formula 1] Rate of change of resistance = |(R2-R1) / R1| × 100 (in, R1 represents the line resistance (unit: Ω), which is measured between a first silver layer and a second silver layer of a sample, the sample comprising: an indium tin oxide film; a first silver layer and a second silver layer, respectively stacked at opposite ends of the upper surface of the indium tin oxide film; an adhesive film covering a portion of the first silver layer, a portion of the second silver layer, and the indium tin oxide film between the first silver layer and the second silver layer; and a release film covering the adhesive film, and R2 represents the line resistance (unit: Ω), which is measured between the first and second silver layers of the sample after the sample has been placed at 60°C and 95% relative humidity for 500 hours.

2. The adhesive film according to claim 1, wherein the adhesive film has a peel strength of 600 gf / 25 mm or greater relative to the polyethylene terephthalate film including the antistatic layer, which is measured on the sample after the sample has been placed at 25°C for 30 minutes, wherein the sample is prepared by stacking the adhesive film on the polyethylene terephthalate film including the antistatic layer.

3. The adhesive film according to claim 1, wherein the composition for the adhesive film comprises a polymer of the (meth)acrylate monomer mixture, a (meth)acrylate having a carboxyl group, a photoinitiator, and a crosslinking agent having alkoxide and (meth)acrylate groups.

4. The adhesive film according to claim 3, wherein the carboxyl-containing (meth)acrylate is a β-carboxylalkyl (meth)acrylate.

5. The adhesive film according to claim 3, wherein the alkeneoxy group is an ethylideneoxy group or a propyleneoxy group.

6. The adhesive film according to claim 3, wherein the crosslinking agent having alkoxide and (meth)acrylate groups has 2 to 6 (meth)acrylate groups.

7. The adhesive film according to claim 1, wherein the monomer mixture comprises alkyl (meth)acrylic monomers and hydroxyl (meth)acrylic monomers.

8. The adhesive film according to claim 7, wherein the alkyl-containing (meth)acrylic monomer and the hydroxyl-containing (meth)acrylic monomer are present in the monomer mixture in an amount of 95% or greater.

9. The adhesive film according to claim 7, wherein the monomer mixture comprises 60 wt% to 90 wt% of the alkyl-based (meth)acrylic monomer and 10 wt% to 40 wt% of the hydroxyl-based (meth)acrylic monomer.

10. The adhesive film according to claim 1, wherein the monomer mixture does not contain (meth)acrylic monomers having carboxyl groups.

11. The adhesive film of claim 3, wherein the composition for the adhesive film comprises: 100 parts by weight of the polymer of the (meth)acrylic acid monomer mixture; 0.1 to 5 parts by weight of the carboxyl-containing (meth)acrylate; 0.001 parts by weight to 5 parts by weight of the photoinitiator; and 0.01 to 0.5 parts by weight of the crosslinking agent having alkeneoxy and (meth)acrylate groups.

12. The adhesive film according to claim 1, wherein the adhesive film does not contain organic nanoparticles.

13. The adhesive film according to claim 1, wherein the adhesive film has substrate adhesion of 400 gf / 25 mm or greater.

14. An optical component comprising an adhesive film according to any one of claims 1 to 13.

15. An optical display device comprising an adhesive film according to any one of claims 1 to 13.

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