Adhesive film, optical member, and optical display device

Abstract

Disclosed herein are an adhesive film for a non-metallic substrate and a metallic substrate, an optical member including the adhesive film, and an optical display device including the adhesive film. The adhesive film is a cured product of a composition containing a (meth) acrylic adhesive and a thermosetting agent. The adhesive film has a peel strength of 400 gf / inch or greater at 60 DEG C and 93% relative humidity with respect to each of a non-metallic substrate and a metallic substrate. The (meth) acrylic binder is formed from a monomer mixture comprising from 1 wt% to 10 wt% of an alicyclic group-containing (meth) acrylic monomer.

Description

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS]

[0002] This application claims priority to and the benefits of Korean Patent Application No. 10-2023-0152132 filed in the Korean Intellectual Property Office on November 6, 2023, and all the disclosures of the Korean Patent Application are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to an adhesive film, an optical member including the adhesive film, and an optical display device including the adhesive film. Background Art

[0004] Generally, adhesive films are used to adhere optical devices of an optical display device to each other. Recently, as interest in foldable optical display devices has increased, adhesive films used in such optical display devices are required to have good foldability.

[0005] The optical device may have a layer comprising the same material or different materials. For example, the optical device may have a layer formed by a polymer or may have a layer formed by a metal. Therefore, an adhesive film can be used to adhere the polymer layer to the metal layer. In order to provide good foldability, the adhesive film should have good peel strength relative to each of the metal layer and the polymer layer. In addition, the adhesive film should have good durability for use in optical display devices. Therefore, a kind of adhesive film having good peel strength relative to both the polymer layer and the metal layer under high temperature conditions and high temperature and high humidity conditions is needed.

[0006] The background technology of the present disclosure is disclosed in Japanese Patent Laid-Open Publication No. 2020-111734. Summary of the invention

[0007] One aspect of the present disclosure is to provide an adhesive film, which has high peel strength relative to both a non-metallic substrate and a metal substrate under high temperature conditions and under high temperature and high humidity conditions, and enables the adhesive film to ensure good foldability of a stacked structure formed by a non-metallic substrate, an adhesive film and a metal substrate under high temperature and high humidity conditions.

[0008] Another aspect of the present disclosure is to provide an optical member having a stacked structure formed of a non-metal substrate, an adhesive film, and a metal substrate, wherein the stacked structure has good reliability and foldability under high temperature conditions and under high temperature and high humidity conditions.

[0009] According to one aspect of the present disclosure, an adhesive film for a non-metallic substrate and a metal substrate is provided. The adhesive film is a cured product of a composition comprising a (meth)acrylic adhesive and a thermal curing agent. The adhesive film has a peel strength of 400 gf / inch or more relative to each of the non-metallic substrate and the metal substrate at 60° C. and 93% relative humidity (RH), wherein the (meth)acrylic adhesive is formed from a monomer mixture comprising 1 wt % to 10 wt % of a (meth)acrylic monomer containing an alicyclic group.

[0010] According to another aspect of the present disclosure, an optical component is provided. The optical component includes a stacked non-metal substrate, an adhesive film, and a metal substrate, wherein the adhesive film bonds the non-metal substrate to the metal substrate, wherein the adhesive film includes a cured product of a composition including a (meth)acrylic adhesive and a thermal curing agent, and the (meth)acrylic adhesive is formed from a monomer mixture, wherein the monomer mixture includes 1 wt % to 10 wt % of a (meth)acrylic monomer containing an alicyclic group.

[0011] According to yet another aspect of the present disclosure, an optical display device is provided, including the adhesive film or the optical member.

[0012] Embodiments of the present disclosure provide an adhesive film having high peel strength relative to both a non-metallic substrate and a metal substrate under high temperature and high humidity conditions. The adhesive film can ensure good foldability of a stacked structure formed by a non-metallic substrate, an adhesive film, and a metal substrate under high temperature and high humidity conditions.

[0013] An embodiment of the present disclosure provides an optical member having a stacked structure formed of a non-metal substrate, an adhesive film, and a metal substrate, wherein the stacked structure has good reliability and foldability under high temperature conditions and under high temperature and high humidity conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 : is a graph showing the change in peel strength of an adhesive film according to one embodiment with respect to a non-metal substrate under high temperature conditions and under high temperature and high humidity conditions as a function of the content of the alicyclic group-containing (meth)acrylic acid monomer in the monomer mixture.

[0015] Figure 2 : is a graph showing the change in the peel strength of the adhesive film with respect to the metal substrate under high temperature conditions and under high temperature and high humidity conditions as a function of the content of the alicyclic group-containing (meth)acrylic acid monomer in the monomer mixture.

[0016] Figure 3is a cross-sectional view of an optical component according to an embodiment.

[0017] Figure 4 Shown are shear strain measurement results of an adhesive film according to one embodiment. DETAILED DESCRIPTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that the present disclosure is not limited to the following embodiments and can be implemented in different ways, and these embodiments are provided to enable those skilled in the art to fully disclose and thoroughly understand the present disclosure.

[0019] The terms used herein are for the purpose of describing exemplary embodiments and are not intended to limit the present disclosure. Unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" used herein are intended to include the plural forms as well.

[0020] Herein, "homopolymer glass transition temperature" may refer to the glass transition temperature (Tg) measured on the homopolymer of the target monomer using a differential scanning calorimeter (Discovery, TA Instruments Inc.). Specifically, the homopolymer of the target monomer is heated to 180°C at a heating rate of 20°C / min, gradually cooled to 100°C, and heated to 100°C at a heating rate of 10°C / min to obtain data of an endothermic transition curve, and then the glass transition temperature is determined by the inflection point of the endothermic transition curve.

[0021] Herein, the "glass transition temperature" of the (meth)acrylic binder may be measured by a method known in the art using a differential scanning calorimeter (DSC).

[0022] Herein, "(meth)acryl" refers to acryloyl and / or methacryloyl.

[0023] Herein, the "weight average molecular weight" may be a value obtained based on polystyrene conversion in gel permeation chromatography (GPC).

[0024] Herein, "shear strain" is a value measured at 60°C and refers to the degree of deformation under constant shear force. Figure 4 Under the conditions of the following experimental example, the strain value on the adhesive film under constant force was measured as a function of time. The strain at 600 seconds was defined as the shear strain.

[0025] The expression “X to Y” used herein to express a specific numerical range means “greater than or equal to X and less than or equal to Y (X≤ and ≤Y)”.

[0026] According to one aspect of the present disclosure, an adhesive film is provided, which has high peel strength relative to both a non-metallic substrate and a metal substrate under high temperature conditions and under high temperature and high humidity conditions, and can ensure good foldability of a stacking structure formed by a non-metallic substrate, an adhesive film and a metal substrate.

[0027] Herein, "non-metal substrate" may refer to a non-metal substrate forming an optical device of an optical display device (or included in an optical device of an optical display device). Specifically, the non-metal substrate may be a polymer film, such as a polyester film including polyethylene terephthalate (PET) and the like, a cycloolefin polymer film, a polycarbonate film, a (meth) acrylic film, a cellulose ester film, and the like. Preferably, the non-metal substrate is a polyester polymer film, such as polyethylene terephthalate (PET).

[0028] Herein, "metal substrate" may refer to a metal substrate forming an optical element of an optical display device (or included in an optical element of an optical display device). Specifically, the metal substrate may be a layer formed of a typical metal (e.g., an alkali metal, an alkaline earth metal, and the like). In the measurement of peel strength, the metal substrate may be represented by a stainless steel (SUS) metal plate.

[0029] Herein, "peel strength under high temperature conditions" may refer to peel strength measured at 60°C. Herein, "peel strength under high temperature and high humidity conditions" may refer to peel strength measured at 60°C and 93% relative humidity (RH). Although there is no particular limitation, "peel strength under high temperature conditions" is measured in a constant temperature chamber at 60°C, and therefore, the relative humidity at which the peel strength is measured under high temperature conditions may be significantly lower than the relative humidity at which the peel strength is measured under high temperature and high humidity conditions.

[0030] The adhesive film may be used to bond a non-metallic substrate to a metallic substrate, and the adhesive film may be adhesively joined to both the non-metallic substrate and the metallic substrate.

[0031] The adhesive film may have a peel strength of 400 gf / inch or more relative to a non-metallic substrate under high temperature conditions and under high temperature and high humidity conditions. For example, the adhesive film may have a peel strength of 400 gf / inch to 1,000 gf / inch, specifically 500 gf / inch to 800 gf / inch relative to a non-metallic substrate under high temperature conditions and under high temperature and high humidity conditions. Within these ranges, the adhesive film may provide good foldability under repeated folding / unfolding.

[0032] The adhesive film may also have a peel strength of 400 gf / inch or more relative to a metal substrate under high temperature conditions and under high temperature and high humidity conditions. The peel strength of a conventional adhesive film relative to a metal substrate exhibits a lower peel strength than that relative to a non-metallic substrate. The adhesive film according to the present disclosure has a high peel strength not only relative to a non-metallic substrate but also relative to a metal substrate. For example, the adhesive film may have a peel strength of 400 gf / inch to 1,000 gf / inch, more specifically 500 gf / inch to 800 gf / inch relative to a metal substrate under high temperature conditions and under high temperature and high humidity conditions. Within the range of these peel strengths, the adhesive film may provide good foldability for repeated folding / unfolding.

[0033] The adhesive film may have a value of 1 or greater, for example, 1 to 1.5, specifically greater than 1 and less than or equal to 1.5, as calculated according to Equation 1. Within these ranges, the adhesive film may be stably attached to a non-metallic substrate under high temperature and high humidity conditions while having enhanced adhesion to the non-metallic substrate.

[0034] Equation 1: A2 / A1

[0035] Wherein A1 is the peel strength of the adhesive film relative to the non-metallic substrate at 60° C. (unit: gf / inch), and A2 is the peel strength of the adhesive film relative to the non-metallic substrate at 60° C. and 93% RH (unit: gf / inch).

[0036] The adhesive film may have a value of 1 or greater, for example, 1 to 1.5, specifically greater than 1 and less than or equal to 1.5 as calculated according to Equation 2. Within the range, the adhesive film may have enhanced adhesion to the metal substrate.

[0037] Equation 2: B1 / B2

[0038] Wherein B1 is the peel strength of the adhesive film relative to the metal substrate at 60° C. (unit: gf / inch), and B2 is the peel strength of the adhesive film relative to the metal substrate at 60° C. and 93% RH (unit: gf / inch).

[0039] The shear strain of the adhesive film at 60° C. may be 15% or more, for example, 25% or more. Specifically, the adhesive film may have a shear strain of 15% to 50%, or 25% to 50% at 60° C. Within these ranges, the adhesive film may provide good foldability of a stacked structure including a non-metal substrate, an adhesive film, and a metal substrate.

[0040] The adhesive film may have a storage modulus of 2 MPa or less, for example, 0.1 MPa to 1 MPa, specifically 0.1 MPa to 0.5 MPa at -20° C., and may have a storage modulus of 0.5 MPa or less, for example, 0.01 MPa to 0.5 MPa, specifically 0.01 MPa to 0.1 MPa at 60° C. Within these ranges, the adhesive film may provide good foldability while having enhanced adhesion to both metal substrates and non-metal substrates.

[0041] The adhesive film may be a (meth)acrylic adhesive film. In an embodiment, the adhesive film may be a pressure sensitive adhesive (PSA) film.

[0042] According to an embodiment, the adhesive film includes a cured product of a composition comprising a (meth) acrylic acid binder and a thermal curing agent. The (meth) acrylic acid binder is a (meth) acrylic acid copolymer of a monomer mixture comprising 1% by weight to 10% by weight of a (meth) acrylic acid monomer containing an alicyclic group. The composition is a heat-curable composition. The adhesive film includes a thermally cured product, wherein the (meth) acrylic acid monomer containing an alicyclic group is present in the monomer mixture in an amount of 1% by weight to 10% by weight. Therefore, the adhesive film has enhanced peel strength relative to both non-metallic substrates and metal substrates under high temperature conditions and under high temperature and high humidity conditions, and provides good foldability under high temperature and high humidity conditions.

[0043] If the content of the alicyclic group-containing (meth)acrylic monomer in the monomer mixture is less than 1% by weight, the foldability of the adhesive film under high temperature and high humidity conditions may be poor due to reduced peel strength relative to non-metallic substrates and metal substrates. If the content of the alicyclic group-containing (meth)acrylic monomer in the monomer mixture exceeds 10% by weight, the foldability of the adhesive film under high temperature and high humidity conditions may be poor due to reduced peel strength relative to non-metallic substrates and metal substrates and due to reduced shear strain at 60°C.

[0044] Figure 1 is a graph showing changes in the peel strength of an adhesive film relative to a non-metallic substrate under high temperature conditions and under high temperature and high humidity conditions as a function of the content of the alicyclic group-containing (meth)acrylic acid monomer in the monomer mixture. Figure 2 : is a graph showing the change in the peel strength of the adhesive film with respect to the metal substrate under high temperature conditions and under high temperature and high humidity conditions as a function of the content of the alicyclic group-containing (meth)acrylic acid monomer in the monomer mixture.

[0045] Reference Figure 1 and Figure 2 It can be seen that when the content of the alicyclic group-containing (meth)acrylic acid monomer in the monomer mixture is in the range of 1 wt % to 10 wt %, the adhesive film has significantly high peel strength relative to both the metal substrate and the non-metal substrate under high temperature conditions and high temperature and high humidity conditions.

[0046] Figure 1 and Figure 2 The peel strength of the adhesive film according to the present disclosure relative to a non-metallic substrate and a metal substrate is shown. Figure 1 and Figure 2 In the figure, the x-axis represents the weight % of the alicyclic group-containing (meth)acrylic monomer in the monomer mixture, and the y-axis represents the peel strength (gf / inch). Figure 1 and Figure 2 In FIG. 5 , the circular data points “●” are the peel strength at 60° C., and the square data points “■” are the peel strength at 60° C. and 93% RH.

[0047] The (meth)acrylic acid monomer containing an alicyclic group may contain C5 to C 10 (Meth)acrylate of a cycloaliphatic group (cycloaliphatic group is a cyclic functional group consisting only of carbon and hydrogen). For example, the (meth)acrylate may be at least one of cyclohexyl acrylate or cyclohexyl methacrylate, preferably cyclohexyl acrylate.

[0048] The monomer mixture may further include a (meth)acrylic monomer having a homopolymer glass transition temperature of -40°C or less, for example, -80°C to -40°C. The (meth)acrylic monomer having a homopolymer glass transition temperature within the range may reduce an increase in the storage modulus of the adhesive film caused by the alicyclic group-containing (meth)acrylic monomer, thereby ensuring that the adhesive film maintains an appropriate level of storage modulus.

[0049] According to an embodiment, the (meth)acrylic acid monomer having a homopolymer glass transition temperature of -40°C or less may be a C1 to C2 monomer having a linear or branched chain at its ester site. 20Specifically, the (meth)acrylate may include at least one of the following: butyl (meth)acrylate, such as n-butyl (meth)acrylate; pentyl (meth)acrylate, such as n-pentyl (meth)acrylate; hexyl (meth)acrylate, such as n-hexyl (meth)acrylate; heptyl (meth)acrylate, such as n-heptyl (meth)acrylate; octyl (meth)acrylate, such as n-octyl (meth)acrylate; 2-ethylhexyl (meth)acrylate; nonyl (meth)acrylate, such as n-nonyl (meth)acrylate; or decyl (meth)acrylate, such as n-decyl (meth)acrylate.

[0050] The (meth) acrylic monomer having a homopolymer glass transition temperature of -40°C or less can be present in the monomer mixture in an amount of 60% to 90% by weight, for example, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, or 60% to 80% by weight. Within these ranges, the (meth) acrylic monomer can ensure that the adhesive film maintains an appropriate level of storage modulus without reducing the peel strength of the adhesive film.

[0051] According to an embodiment, the (meth)acrylic acid monomer having a homopolymer glass transition temperature of -40°C or less may be a (meth)acrylic acid monomer having a linear chain of C1 to C 20 Alkyl (meth) acrylate and branched C1 to C 20 A mixture of alkyl (meth)acrylates. 20 Alkyl (meth) acrylate and branched C1 to C 20 Each of the alkyl (meth)acrylates can be selected from the above-listed C1 to C 20 For example, a (meth)acrylate containing a linear C1 to C 20 The alkyl (meth)acrylate may be n-propyl (meth)acrylate, n-butyl (meth)acrylate or the like. 20 The alkyl (meth)acrylate may be 2-ethylhexyl (meth)acrylate or the like.

[0052] Contains straight chain C1 to C 20The alkyl (meth)acrylate can be present in the monomer mixture in an amount of 10 wt % to 50 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 %, 40 wt %, 41 wt %, 42 wt %, 43 wt %, 44 wt %, 45 wt %, 46 wt %, 47 wt %, 48 wt %, 49 wt %, 50 wt %, or 10 wt % to 30 wt %. Contains branched C1 to C 20 The alkyl (meth)acrylate can be present in the monomer mixture in an amount of 50 to 90 wt %, for example, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, or 50 to 80 wt %. Within these ranges, linear C1 to C 20 Alkyl (meth) acrylate and branched C1 to C 20 Alkyl (meth)acrylates may be useful in achieving the desired effects of the adhesive films described herein.

[0053] The monomer mixture may also include a (meth) acrylic monomer containing a crosslinkable functional group. The (meth) acrylic monomer containing a crosslinkable functional group can enhance the peel strength of the adhesive film. Here, the crosslinkable functional group may include at least one of a hydroxyl group, an amino group, an epoxy group, or a carboxylic acid group. Preferably, the crosslinkable functional group is a hydroxyl group, so that the (meth) acrylic monomer is a hydroxyl-containing (meth) acrylic monomer.

[0054] The hydroxyl-containing (meth)acrylic monomer may include at least one of the following: a C1 to C2 20 Alkyl (meth) acrylic acid monomers, C3 to C 20Cycloalkyl (meth) acrylic monomers, or C6 to C 20 Specifically, the hydroxyl-containing (meth)acrylic monomer may be a C1 to C2 20 The (meth)acrylic acid monomer may include at least one of 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, or 6-hydroxyhexyl (meth)acrylate. These compounds may be used alone or in the form of a mixture thereof.

[0055] The hydroxyl-containing (meth)acrylic monomer may be present in the monomer mixture in an amount of 5 to 40 wt %, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, or 5 to 35 wt %, or 10 to 35 wt %. Within these ranges, the hydroxyl group-containing (meth)acrylic monomer may facilitate achieving the desired effects of the adhesive film described herein.

[0056] According to one embodiment, the alicyclic group-containing (meth)acrylic monomer, the (meth)acrylic monomer having a homopolymer glass transition temperature of -40°C or less, and the hydroxyl group-containing (meth)acrylic monomer may be present in the monomer mixture in an amount of 98 wt% or more, for example, 99 wt% to 100 wt%, specifically 100 wt%. Within these ranges, the aforementioned (meth)acrylic monomer may be useful in achieving the desired effects of the adhesive film described herein.

[0057] The (meth)acrylic binder may have a molecular weight of 500,000 g / mol to 2,000,000 g / mol, for example 500,000 g / mol, 600,000 g / mol, 700,000 g / mol, 800,000 g / mol, 900,000 g / mol, 1,000,000 g / mol, 1,100,000 g / mol, 1,200,000 g / mol, 1,300,000 g / mol, In some embodiments, the (meth)acrylic binder has a weight average molecular weight (Mw) of 1,000,000 g / mol, 1,400,000 g / mol, 1,500,000 g / mol, 1,600,000 g / mol, 1,700,000 g / mol, 1,800,000 g / mol, 1,900,000 g / mol, 2,000,000 g / mol, or 900,000 g / mol to 1,500,000 g / mol. Within these ranges, the (meth)acrylic binder can be beneficial in achieving the desired effects of the adhesive film described herein.

[0058] The glass transition temperature (Tg) of the (meth)acrylic adhesive may be -35° C. or less, for example, -60° C., -59° C., -58° C., -57° C., -56° C., -55° C., -54° C., -53° C., -52° C., -51° C., -50° C., -49° C., -48° C., -47° C., -46° C., -45° C., -44° C., -43° C., -42° C., -41° C., -40° C., -39° C., -38° C., -37° C., -36° C., -35° C., or from -60° C. to -35° C. Within these ranges, the (meth)acrylic adhesive may be useful in achieving the desired effects of the adhesive film described herein.

[0059] In one embodiment, the (meth) acrylic binder can be prepared by polymerizing a monomer mixture by a common polymerization method. Here, the polymerization method may include any common polymerization method known in the art. For example, the (meth) acrylic binder can be prepared by adding an initiator to the monomer mixture and then by a common copolymer polymerization process (e.g., suspension polymerization, emulsion polymerization, solution polymerization, or similar process). The polymerization of the monomer mixture can be performed at a temperature of 65° C. to 70° C. for 6 to 8 hours. The initiator can be a common initiator, such as an azo polymerization initiator and / or a peroxide polymerization initiator (e.g., benzoyl peroxide or acetyl peroxide).

[0060] The thermal curing agent may promote the formation of a matrix of the adhesive film, and at the same time enhance the peel strength of the adhesive film by curing the (meth)acrylic binder.

[0061] The thermal curing agent may include at least one of an isocyanate curing agent, a metal chelate curing agent, an epoxy curing agent, an amine curing agent, or an aziridine curing agent.

[0062] The isocyanate curing agent may include a difunctional to hexafunctional isocyanate curing agent. Specifically, the isocyanate curing agent may include: an aromatic isocyanate curing agent including at least one of toluene diisocyanate, xylene diisocyanate, halogen-substituted toluene diisocyanate, phenylene diisocyanate including meta-phenylene diisocyanate and the like, or tetramethylxylene diisocyanate; an aliphatic isocyanate curing agent including at least one of hexamethylene diisocyanate or pentamethylene diisocyanate; an alicyclic isocyanate curing agent, such as cyclohexamethylene diisocyanate; or an adduct thereof, such as a polyol (e.g., trimethylolpropane (TMP)) adduct of any of the aforementioned isocyanate curing agents.

[0063] The metal chelate curing agent is a cross-linking agent consisting of a bond between a metal and a chelate, and may include common metal chelate cross-linking agents known in the art. In one embodiment, the metal chelate cross-linking agent may include a cross-linking agent having at least two, for example 3 to 6 metal chelate bonds. For example, the metal may include aluminum, zirconium, titanium or cobalt, preferably aluminum. For example, the chelate may include acetylacetonate, ethyl acetoacetate or the like without limitation. Specifically, the metal chelate cross-linking agent may include at least one of acetylacetonate aluminate, tris(acetylacetonate) aluminum, tris(ethyl acetoacetate) aluminum, bis(acetylacetate) aluminum, tris(acetylacetonate) zirconium or tris(acetylacetonate) cobalt without limitation.

[0064] Preferably, the thermal curing agent is a mixture of an isocyanate curing agent and a metal chelate curing agent. Such a mixture can help ensure that the composition containing the above-mentioned (meth)acrylic binder provides the desired effects described herein. In one embodiment, the isocyanate curing agent and the metal chelate curing agent may be present in a weight ratio of 1:0.1 to 1:3, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.0, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, or 1:0.5 to 1:2, specifically 1:1 to 1:2. Within these ranges, the mixture can help ensure that the composition including the (meth)acrylic binder provides the desired effects described herein.

[0065] The thermal curing agent may be present in an amount of 0.01 to 1 parts by weight, for example 0.01 to 0.5 parts by weight, specifically 0.01 to 0.1 parts by weight, relative to 100 parts by weight of the (meth)acrylic adhesive. Within these ranges, the adhesive film can easily meet requirements related to peel strength, shear strain, and storage modulus.

[0066] The composition, i.e., the adhesive film, may further include a silane coupling agent. The silane coupling agent may further enhance the peel strength of the adhesive film. The silane coupling agent may include a common silane coupling agent known in the art. For example, the silane coupling agent may include an epoxy-containing silane coupling agent, such as glycidyloxypropyltrimethoxysilane, glycidyloxypropylmethyldimethoxysilane, and the like. However, the present disclosure is not limited thereto.

[0067] The silane coupling agent may be present in an amount of 0.01 to 5 parts by weight, for example 0.01 to 0.1 parts by weight, relative to 100 parts by weight of the (meth)acrylic adhesive. Within these ranges, the silane coupling agent may enhance the peel strength of the adhesive film.

[0068] According to an embodiment, the composition may be a solvent-free type not containing any solvent.

[0069] According to other embodiments, the composition may further include a solvent. In the process of manufacturing a thin adhesive film from the composition, the solvent enables the adhesive film to have a smooth surface. The solvent may be any common solvent known in the art without limitation. For example, the solvent may be an organic solvent, such as ethyl acetate, methyl ethyl ketone, methyl isobutyl ketone, and similar solvents. The composition may have a solid content of 50 wt % or less, such as 20 wt % or less.

[0070] The composition, i.e., the adhesive film, may also include additives. The additives may provide additional functions for the adhesive film. The additives may include at least one of an ultraviolet (UV) absorber, a reaction inhibitor, an adhesion enhancer, a thixotropy-imparting agent, a conductivity imparting agent, a color regulator, a stabilizer, an antioxidant, a leveling agent, or an antistatic agent. However, the present disclosure is not limited to these examples. The content of the additive in the composition (adhesive film) may be appropriately adjusted without affecting the desired effect of the present invention.

[0071] In the visible spectrum, for example at a wavelength of 380 nm to 780 nm, the adhesive film can have a haze of 1% or less, for example 0% to 1%. Within these ranges, the adhesive film can be used in optical display devices.

[0072] The adhesive film may have a thickness of 35 μm or less, for example, greater than 0 μm and less than or equal to 35 μm, specifically, 5 μm to 15 μm. Within these ranges, the adhesive film may be used in an optical display device.

[0073] According to one embodiment, the adhesive film may not contain organic nanoparticles. Here, "organic nanoparticles" may refer to organic nanoparticles known in the art that provide foldability, such as core-shell type nanoparticles. As an advantage of the present disclosure, the adhesive film, although free of organic nanoparticles, still provides good foldability.

[0074] The adhesive film may be formed from the composition as described above. Specifically, the adhesive film may be manufactured by applying the adhesive film-forming composition to a release film and then thermally curing the adhesive film. Thermal curing of the adhesive film-forming composition may be performed by thermal treatment at a temperature of 80° C. to 100° C. for 1 to 30 minutes, but the present disclosure is not limited to thermal treatment under such conditions.

[0075] According to another aspect of the present disclosure, an optical component includes a stacked non-metallic substrate, an adhesive film and a metal substrate, wherein the adhesive film includes a cured product of a composition comprising a (meth)acrylic adhesive and a curing agent, and the (meth)acrylic adhesive is a (meth)acrylic adhesive of a monomer mixture, wherein the monomer mixture contains 1 wt % to 10 wt % of a (meth)acrylic monomer containing an alicyclic group.

[0076] like Figure 3 As shown, the optical member may include a stacked non-metal substrate 10, an adhesive film 20, and a metal substrate 30. Since the non-metal substrate, the adhesive film, and the metal substrate are substantially the same as those described above, a detailed description thereof will be omitted.

[0077] In one embodiment, the optical component is used in an optical display device to provide specific optical functions (e.g., polarization, optical compensation, display image enhancement, and / or conductivity). The optical component may include an optical film, such as a window film, a window, a polarizing plate, a color filter, a retardation film, an elliptically polarizing film, a reflective polarizing film, an anti-reflective film, a compensation film, a brightness enhancement film, an orientation film, a light diffusion film, an anti-shattering film, a surface protection film, a barrier film for an organic light emitting diode (OLED), a plastic liquid crystal display (LCD) substrate, and a transparent electrode film, the transparent electrode film comprising indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum-doped zinc oxide (AZO), carbon nanotubes (CNT), Ag nanowires, graphene, and the like.

[0078] The optical member may have a three-layer structure formed of non-metal substrate / adhesive film / metal substrate. Alternatively, the optical member may include two or more layers of non-metal substrate, two or more layers of adhesive film and two or more layers of metal substrate.

[0079] According to still another aspect of the present disclosure, an optical display device includes the above-mentioned adhesive film or the above-mentioned optical member.

[0080] The optical display device may include an organic light emitting diode display device and the like, a liquid crystal display device and the like. The optical display device may include a flexible display device. However, the present disclosure is not limited to this point, and the optical display device may include a non-flexible display device.

[0081] Next, the present disclosure will be described in more detail with reference to examples. These examples are provided only for illustration and are not intended to limit the scope of the present disclosure.

[0082] Example 1

[0083] In a 1L reactor equipped with a reflux cooler and a nitrogen inlet, 100 parts by weight of a monomer mixture containing 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (n-BA), 4-hydroxybutyl acrylate (4-HBA) and cyclohexylacrylate (CHA) were placed. Thereafter, 100 parts by weight of ethyl acetate were added to the reactor as a solvent. After the reactor was fully purged with nitrogen to remove oxygen, the temperature of the reactor was maintained at 60°C, and 0.03% by weight of azobisisobutyronitrile was added to the reactor as a polymerization initiator. The reaction was allowed to proceed for 12 hours. Thereafter, the reaction product was diluted with ethyl acetate to prepare a solution containing a (meth) acrylic binder having a glass transition temperature of -54°C and a weight average molecular weight of 1,200,000 g / mol.

[0084] With respect to 100 parts by weight of the (meth)acrylic binder in terms of solid content, 0.03 parts by weight of an isocyanate curing agent (Coronate-L, TOSOH Corporation), 0.03 parts by weight of a metal chelate curing agent (aluminum-containing trifunctional curing agent, CK-401E, NCI Chemical), and 0.05 parts by weight of 3-glycidyloxypropyltrimethoxysilane (KBM-403, Shin-Etsu Chemical Co., Ltd.) as a silane coupling agent were mixed with the prepared solution to prepare an adhesive film composition having a solid content of 20% by weight.

[0085] The prepared adhesive film composition was applied to a polyethylene terephthalate (PET) film as a first release film at a predetermined thickness, followed by drying to obtain a 15 μm thick coating film. Thereafter, the obtained coating film was covered with a PET film as a second release film, followed by drying (thermal curing) at 100° C. for 3 minutes, thereby manufacturing an adhesive sheet formed of the first release film / adhesive film / second release film, wherein the adhesive film had a thickness of 15 μm.

[0086] Example 2 to Example 4

[0087] An adhesive sheet was manufactured in the same manner as in Example 1, except that the content of each component of the adhesive film composition was changed as listed in Table 1.

[0088] Comparative Examples 1 to 4

[0089] An adhesive sheet was manufactured in the same manner as in Example 1, except that the content of each component of the adhesive film composition was changed as listed in Table 1.

[0090] The composition of each of the adhesive films of Examples 1 to 4 and Comparative Examples 1 to 4 is shown in Table 1. The following properties of each of the adhesive films of Examples 1 to 4 and Comparative Examples 1 to 4 were evaluated.

[0091] (1) Peel strength relative to PET film under high temperature conditions (gf / inch): Each of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 4 was cut into a size of 100 mm×25 mm (length×width). Thereafter, the first release film was removed from the adhesive sheet, and then a non-corona-treated polyethylene terephthalate (PET) film was bonded to the adhesive film. The second release film was then removed from the adhesive film, and then a 2 kg hand roller was used to bond the corona-treated PET film to the adhesive film to prepare a sample. Using the prepared sample, the peel strength of the stack formed by the adhesive film and the corona-treated PET film relative to the non-corona-treated PET film was measured in a room at 60°C at a peel angle of 180° and a peel rate of 300 mm / min. The peel strength was measured using a TA.XT Plus texture analyzer (Stable Micro System, Inc.).

[0092] (2) Peel strength against PET film under high temperature and high humidity conditions (gf / inch): Samples were prepared in the same manner as in (1). The peel strength of the samples was measured in a room at 60°C and 93% RH in the same manner as in (1).

[0093] (3) Peel strength relative to metal plate under high temperature conditions (gf / inch): Each of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 4 was cut into a size of 100 mm × 25 mm (length × width). Thereafter, the first release film was removed from the adhesive sheet, and then the SUS metal plate was attached to the exposed surface of the adhesive film. The second release film was then removed from the adhesive film, and then a 2 kg hand roller was used to attach a PET film that was not corona treated to the adhesive film, thereby preparing a sample. Using the prepared sample, the peel strength of the stack formed by the adhesive film and the PET film that was not corona treated relative to the SUS metal plate was measured in the same manner as in (1).

[0094] (4) Peel strength against metal plate under high temperature and high humidity conditions (gf / inch): Prepare samples in the same manner as in (3). Measure the peel strength of the samples in a room at 60°C and 93% RH in the same manner as in (3).

[0095] (5) Shear strain %: The first release film and the second release film were removed from each of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 4 to obtain adhesive films (100 mm×25 mm (length×width)). A plurality of such adhesive films were formed into a stack, which was in turn perforated using a perforator having a diameter of 8 mm to prepare a cylindrical sample (thickness: 500 μm, diameter: 8 mm) having an upper surface and a lower surface.

[0096] The prepared cylindrical sample was mounted on a dynamic viscoelasticity measuring instrument (Rheometer DHR3, TA Instruments), and the upper and lower surfaces of the cylindrical sample were clamped in the upper and lower fixtures of the dynamic shear rheometer, respectively. The strain of the sample was measured at a room temperature of 60°C, an axial force of 1N, a torque of 2kPa, a stress application cycle of 600 seconds, and a stress release cycle of 600 seconds. The strain when the stress time was 600 seconds was defined as the shear strain.

[0097] (6) Storage modulus (MPa): The storage modulus was measured in automatic strain mode at a shear rate of 1 rad / sec and a strain of 1% using a dynamic viscoelasticity measuring instrument (rheometer DHR3, TA Instruments). After obtaining an adhesive film from each of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 4, a plurality of such adhesive films were formed into a stack having a thickness of 500 μm. Thereafter, the stack was perforated using a perforator having a diameter of 8 mm to prepare a sample. In the temperature scanning test mode, the storage modulus of the sample was measured by heating the sample from -50°C to 100°C at a heating rate of 5°C / min while applying a normal force of 1.0N to the sample using an 8mm fixture, thereby obtaining the storage modulus at -20°C and 60°C.

[0098] (7) Foldability: Adhesive films were obtained by removing the first release film and the second release film from each of the adhesive sheets of Examples 1 to 4 and Comparative Examples 1 to 4. Each adhesive film was bonded to a 50 μm thick corona-treated PET film and a SUS metal plate using a roller, one surface of the roller being adjacent to the corona-treated surface of the PET film and the other surface of the roller being adjacent to the SUS metal plate, followed by aging for 12 hours at room temperature, and then cut into a size of 70 mm×140 mm (width×length) to prepare a sample. The prepared sample was fixed to a folding tester (CFT-200, Covotech Co., Ltd.) using an adhesive (4965, Tesa Tapes Inc.), and then the long side (140 mm) of the sample was bent to a curvature radius of 3 mm at a rate of 30 cycles per minute at 60°C and 93% RH (one cycle is defined as folding the adhesive film in half and unfolding the adhesive film back to its initial state once). The minimum bending cycle number at which the adhesive film is observed to break with the naked eye is measured. A larger minimum bending cycle number indicates that the corresponding adhesive film is more effective in alleviating the stress caused by bending of the PET film and the SUS metal plate. When the minimum number of bending cycles is 100,000 or greater than 100,000, the corresponding adhesive film is rated as "OK". When the minimum number of bending cycles is less than 100,000, the corresponding adhesive film is rated as "NG". The measurement of foldability is carried out at 60°C and 93% RH.

[0099] Table 1

[0100]

[0101] As can be seen from Table 1, the adhesive film according to the present disclosure exhibits high peel strength relative to both the non-metallic substrate and the metal substrate under high temperature conditions and high temperature and high humidity conditions. In addition, the adhesive film can ensure good foldability of the stacked structure formed by the non-metallic substrate, the adhesive film and the metal substrate.

[0102] In contrast, the adhesive films of Comparative Examples 1 to 4 failed to provide the desired combination of effects as described herein.

[0103] It should be understood that those skilled in the art can make various modifications, changes, variations and equivalent embodiments without departing from the spirit and scope of the present disclosure.

Claims

1. An adhesive film for bonding a non-metallic substrate to a metal substrate, the adhesive film comprising: A cured product of a composition comprising a (meth)acrylic binder and a thermal curing agent, wherein the adhesive film has a peel strength of 400 gf / inch or more with respect to each of the non-metal substrate and the metal substrate at 60° C. and 93% relative humidity, and The (meth)acrylic binder is formed from a monomer mixture, wherein the monomer mixture contains 1 wt % to 10 wt % of a (meth)acrylic monomer containing an alicyclic group. 2 . The adhesive film according to claim 1 , wherein the adhesive film has a shear strain of 15% or more at 60° C. 3 . The adhesive film according to claim 1 , wherein the adhesive film has a storage modulus of 2 MPa or less at −20° C. and a storage modulus of 0.5 MPa or less at 60° C.

4. The adhesive film according to claim 1, wherein the adhesive film has a value of 1 or greater as calculated according to the equation A2 / A1, wherein A1 is the peel strength of the adhesive film relative to the non-metallic substrate at 60° C. in gf / inch, and wherein A2 is the peel strength of the adhesive film relative to the non-metallic substrate at 60° C. and 93% relative humidity in gf / inch, and wherein the adhesive film has a value of 1 or greater as calculated according to the equation B1 / B2, wherein B1 is the peel strength of the adhesive film relative to the metal substrate at 60°C in gf / inch, and wherein B2 is the peel strength of the adhesive film relative to the metal substrate at 60°C and 93% relative humidity in gf / inch. 5 . The adhesive film according to claim 1 , wherein the alicyclic group-containing (meth)acrylic monomer comprises at least one of cyclohexyl acrylate or cyclohexyl methacrylate. 6 . The adhesive film of claim 1 , wherein the monomer mixture further comprises a (meth)acrylic acid monomer having a homopolymer glass transition temperature of −40° C. or less.

7. The adhesive film according to claim 6, wherein the (meth)acrylic acid monomer having a homopolymer glass transition temperature of -40°C or less is a C1 to C2 monomer having a linear or branched chain at the ester site of the (meth)acrylate. 20 Alkyl (meth)acrylate. 8 . The adhesive film of claim 6 , wherein the (meth)acrylic monomer having a homopolymer glass transition temperature of −40° C. or less is present in an amount of 60 to 90 wt % in the monomer mixture. 9 . The adhesive film according to claim 6 , wherein the monomer mixture further comprises a hydroxyl group-containing (meth)acrylic monomer.

10. The adhesive film according to claim 9, wherein the alicyclic group-containing (meth)acrylic monomer, the (meth)acrylic monomer having a homopolymer glass transition temperature of -40°C or less, and the hydroxyl group-containing (meth)acrylic monomer are present in the monomer mixture in an amount of 98 wt% or more in total. 11 . The adhesive film according to claim 1 , wherein the thermal curing agent is a mixture of an isocyanate curing agent and a metal chelate curing agent.

12. An optical component, comprising: Non-metallic substrates; Adhesive films; as well as Metal substrate, wherein the adhesive film bonds the non-metallic substrate to the metal substrate, and The adhesive film comprises a cured product of a composition including a (meth)acrylic binder and a thermal curing agent, wherein the (meth)acrylic binder is formed from a monomer mixture containing 1 wt % to 10 wt % of a (meth)acrylic monomer containing an alicyclic group.

13. The optical component according to claim 12, wherein the non-metal substrate is a polymer film. 14 . The optical member according to claim 12 , wherein the adhesive film has a shear strain of 15% or more at 60° C. 15 . The optical member according to claim 12 , wherein the adhesive film has a storage modulus of 2 MPa or less at −20° C. and a storage modulus of 0.5 MPa or less at 60° C. 16 . The optical member according to claim 12 , wherein the monomer mixture further comprises a (meth)acrylic monomer having a homopolymer glass transition temperature of −40° C. or less. 17 . The optical member according to claim 16 , wherein the (meth)acrylic monomer having a homopolymer glass transition temperature of −40° C. or less is present in an amount of 60% to 90% by weight in the monomer mixture. 18 . The optical member according to claim 17 , wherein the monomer mixture further comprises a hydroxyl group-containing (meth)acrylic monomer.

19. The optical member according to claim 18, wherein the alicyclic group-containing (meth)acrylic monomer, the (meth)acrylic monomer having a homopolymer glass transition temperature of -40°C or less, and the hydroxyl group-containing (meth)acrylic monomer are present in the monomer mixture in an amount of 98 wt% or more in total.

20. An optical display device comprising the adhesive film according to claim 1.

21. An optical display device comprising the optical member according to claim 12.

Images