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

Abstract

To provide an adhesive film having high peel strength against the surface having a polyimide ash (ash) of polyimide-based optical elements.SOLUTION: There is provided an adhesive film for polyimide-based optical elements having a polyimide-based ash, wherein the adhesive film comprises a cured product of a composition comprising 100 pts.wt. of a (meth)acrylic binder having a glass transition temperature (Tg) of -70°C to -40°C, 0.1 pt.wt. to 5 pts.wt. of a (meth)acrylic oligomer, 0.01 pt.wt. to 0.5 pt.wt of a curing agent and an antistatic agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As technological interest in foldable optical display devices has surged, development of adhesive films included in foldable display devices has also continued. Adhesive films must have excellent optical transparency, peel strength from adherends, and foldability. Adhesive films are typically used to bond various elements included in foldable optical display devices, such as windows, protective films, polarizing plates, touch panels, etc.

[0003] Furthermore, the adhesive film may be adhered to one surface of an optical display panel in a foldable optical display device. The adhesive film can bond the optical display panel to another adhesive film or a protective film. In one specific example, the optical display panel can include a polyimide-based layer. The polyimide-based layer has excellent heat resistance and is therefore often used in optical display panel. In one specific example, the polyimide-based layer can be produced by applying a polyimide-based composition to a substrate, curing the composition, and peeling it from the substrate. Therefore, it may be preferable for the adhesive film to have high peel strength even with respect to the polyimide-based layer and excellent flexural properties.

[0004] The background art of the present invention is disclosed in Patent Document 1 and the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Korean Patent Publication No. 10-2017-0070753 Summary of the Invention [Problem to be solved by the invention]

[0006] An object of the present invention is to provide a pressure-sensitive adhesive film that has a high peel strength against the surface of a polyimide optical element having polyimide ash.

[0007] Another object of the present invention is to provide an adhesive film that, when adhered to a surface of a polyimide-based optical element having polyimide-based ash, has excellent conformability to steps caused by the polyimide-based ash.

[0008] A further object of the present invention is to provide a pressure-sensitive adhesive film having excellent bending properties and antistatic properties. [Means for solving the problem]

[0009] One embodiment is an adhesive for polyimide-based optical elements having a polyimide-based ash, and the adhesive film comprises a cured product of a composition including 100 parts by weight of a (meth)acrylic binder having a glass transition temperature (Tg) of -70°C to -40°C, 0.1 to 5 parts by weight of a (meth)acrylic oligomer, 0.01 to 0.5 parts by weight of a curing agent, and an antistatic agent.

[0010] One embodiment is an optical member, which includes a polyimide-based optical element having a polyimide-based ash on at least one surface thereof, and the adhesive film attached to the surface having the polyimide-based ash.

[0011] An embodiment is an optical display device, which includes the adhesive film or the optical member. [Effects of the Invention]

[0012] The present invention can provide a pressure-sensitive adhesive film that has a high peel strength against the surface of a polyimide optical element that has polyimide ash thereon.

[0013] The present invention can provide an adhesive film that, when adhered to a surface of a polyimide-based optical element having polyimide-based ash, has excellent conformability to steps caused by the polyimide-based ash.

[0014] The present invention can provide a pressure-sensitive adhesive film that has excellent bending properties and antistatic properties. [Brief explanation of the drawings]

[0015] [Figure 1] 1A to 1C are views illustrating an embodiment of a method for manufacturing a polyimide layer having a surface with polyimide ash. [Figure 2] FIG. 1 is a cross-sectional view of a test piece for evaluating bending properties. [Figure 3] FIG. 1 is a cross-sectional view of a test piece used in the evaluation of step-following ability. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0017] The terms used herein are for the purpose of describing exemplary embodiments only and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly dictates otherwise.

[0018] As used herein, "(meth)acrylic" can mean acrylic and / or methacrylic.

[0019] As used herein, a "copolymer" can include a polymer or a resin.

[0020] As used herein, the term "glass transition temperature of a homopolymer" refers to the glass transition temperature (Tg) of a homopolymer of a target monomer measured using a DSC Discovery manufactured by TA Instruments. Specifically, the homopolymer of a target monomer is heated to 180°C at a rate of 20°C / min, then gradually cooled to -100°C, and then heated to 100°C at a rate of 10°C / min to obtain data on an endothermic transition curve. The inflection point of the endothermic transition curve can then be determined as the glass transition temperature.

[0021] In this specification, the glass transition temperatures of the "(meth)acrylic binder" and the "(meth)acrylic oligomer" may be measured by a method known to those skilled in the art using a differential scanning calorimeter (DSC).

[0022] In this specification, when describing a range of numerical values, "X to Y" means at least X and at most Y (X≦and≦Y).

[0023] According to an embodiment, the adhesive film may be attached to a surface of the polyimide-based optical element having a polyimide-based ash. The adhesive film may be attached to the surface having the polyimide-based ash to protect the polyimide-based optical element or to bond the polyimide-based optical element to another optical element.

[0024] According to one embodiment, an adhesive film is provided that has high peel strength against a surface of a polyimide-based optical element that has polyimide ash. According to one embodiment, an adhesive film is provided that has excellent conformability to unevenness caused by the polyimide ash when adhered to a surface of a polyimide-based optical element that has polyimide ash. According to one embodiment, an adhesive film is provided that has excellent flexibility and antistatic properties.

[0025] Specifically, the adhesive film may have a peel strength of 300 gf / inch or more from the surface having the polyimide ash, for example, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600 gf / inch, or 300 gf / inch to 600 gf / inch. Within this range, even when adhered to a surface having the polyimide ash, the adhesive film has excellent bending properties and can be adhered to polyimide optical elements with high reliability.

[0026] Specifically, when the adhesive film is adhered to a surface having the polyimide-based ash, foreign matter and / or bubbles are not generated, and the adhesive film does not peel off or shift, so that the adhesive film can have excellent conformability to uneven surfaces.

[0027] Specifically, when the flexural properties of the PSA film are evaluated as described in the following test examples, the film exhibits no bubbles, lifting, or peeling, and therefore may exhibit excellent flexural properties.

[0028] Specifically, the adhesive film has a surface resistance of 9.9 × 10 12 (Ω / □) or less, for example, 1.0×10 6 , 1.0×10 7 , 1.0×10 8 , 1.0×10 9 , 1.0×10 10 , 1.0×10 11 , 1.0×10 12 (Ω / □), 1.0×10 6 Ω / □~1.0×10 12 Within this range, when the adhesive film is peeled from the release film during the manufacturing process, static electricity is less generated, and therefore, the anti-static property may be excellent.

[0029] The "polyimide-based optical element" may be an optical element having a polyimide-based layer formed on its outermost surface. The polyimide-based layer may be formed of a composition including one or more of a polyimide-based polymer, a polyimide-based copolymer, a polyimide-based oligomer, and a polyimide-based monomer. The polyimide-based layer of the polyimide-based optical element may be a single layer or multiple layers. The remaining portions of the "polyimide-based optical element" excluding the polyimide-based layer may be a single layer or multiple layers. According to an embodiment, the "polyimide-based optical element" may be a panel for an optical display device, a protective film for an optical display device, or the like, and may be an optical element used in, for example, a foldable optical display device.

[0030] The "polyimide-based" material may be a copolymer, polymer, or oligomer containing an imide group and an aromatic group in the repeating unit, which is prepared by the polymerization reaction of a precursor polyamic acid.

[0031] According to one embodiment, the polyimide-based ash may be manufactured by subjecting the polyimide-based layer to laser treatment. Specifically, the laser treatment may be performed under room temperature / atmospheric pressure conditions.

[0032] According to one embodiment, the surface having the polyimide-based ash may be formed through the following process: The process of forming the polyimide-based ash is described with reference to FIG.

[0033] (1) A polyimide varnish is applied to a thickness of 20 μm to 30 μm on the upper surface of a glass plate (e.g., an alkali-free glass plate, thickness: 1 mm to 2 mm) 10 to produce a polyimide varnish coating film 11. The polyimide varnish may contain at least 90 wt % of one or more of a polyimide copolymer, a polyimide oligomer, and a polyimide monomer, but is not limited thereto. This process can provide a thinning effect to the final polyimide layer.

[0034] (2) The produced polyimide varnish coating film 11 is dried at 150° C. for 30 minutes and cured at 250° C. for 30 minutes to form a polyimide cured film 12 on the upper surface of the glass plate 10.

[0035] (3) When the lower surface of the glass plate 10 is irradiated with a laser 13 under the laser treatment conditions, a polyimide-based ash 14 is formed on the lower surface of the polyimide-based cured film 12. The laser treatment can form the polyimide-based ash by burning a portion of the polyimide-based cured film. The polyimide-based ash is irregular, minute irregularities in the form of dust, and can form a minute step between the laser-treated portion and the non-laser-treated portion. The step can facilitate peeling of the glass plate in the following step (4). The degree to which the polyimide-based ash 14 is formed or the area ratio of the polyimide-based ash 14 (the total area ratio of the polyimide-based ash to the total area of ​​the polyimide-based cured film or polyimide layer) can be adjusted depending on the type of polyimide-based varnish, the total thickness of the polyimide-based layer, etc.

[0036] (4) The glass plate 10 may be peeled off from the polyimide-based cured film 12 to produce a polyimide-based layer 15 having a surface with polyimide-based ash 14 thereon.

[0037] The "polyimide-based layer" may become a part of the polyimide-based optical element.

[0038] According to one embodiment, the adhesive film comprises a cured product of a composition including 100 parts by weight of a (meth)acrylic binder having a glass transition temperature of -70°C to -40°C, 0.1 to 5 parts by weight of a (meth)acrylic oligomer, 0.01 to 0.5 parts by weight of a curing agent, and an antistatic agent.

[0039] According to an embodiment, the composition may be a thermosetting composition, and the cured product may be a thermosetting product of the composition.

[0040] According to one embodiment, the adhesive film may be a pressure-sensitive adhesive (PSA) film.

[0041] The (meth)acrylic binder forms a matrix of the adhesive film by being cured with a curing agent, and can increase the peel strength of the adhesive film.

[0042] The (meth)acrylic binder has a glass transition temperature of -70°C to -40°C. A (meth)acrylic binder with a glass transition temperature below -70°C may have difficulty achieving the peel strength of the PSA film of the present application. A (meth)acrylic binder with a glass transition temperature above -40°C may result in poor flexural properties and unevenness conformability of the PSA film. For example, the (meth)acrylic binder may have a glass transition temperature of −70, −69, −68, −67, −66, −65, −64, −63, −62, −61, −60, −59, −58, −57, −56, −55, −54, −53, −52, −51, −50, −49, −48, −47, −46, −45, −44, −43, −42, −41, −40°C, or −65°C to −40°C.

[0043] The (meth)acrylic binder may be a (meth)acrylic copolymer formed by polymerization of a monomer mixture. The monomer mixture may have any type and content as long as it can provide the glass transition temperature.

[0044] According to one embodiment, the monomer mixture may include a (meth)acrylic monomer having a homopolymer glass transition temperature of −50° C. or lower, specifically −80, −75, −70, −65, −60, −55, −50° C., or −80° C. to −50° C. Within this range, the (meth)acrylic binder may easily reach its glass transition temperature.

[0045] The (meth)acrylic monomer having a homopolymer glass transition temperature of −50° C. or less, specifically −80° C. to −50° C., is not particularly limited in type as long as it has the glass transition temperature range. The glass transition temperature may be measured by referring to a catalog of the (meth)acrylic monomer or by a conventional method known to those skilled in the art.

[0046] In one specific example, the (meth)acrylic monomer having a homopolymer glass transition temperature of −50° C. or less may be one or more selected from linear or branched (meth)acrylic acid esters having an alkyl group of 1 to 10 carbon atoms. For example, the linear or branched (meth)acrylic acid ester having an alkyl group of 1 to 10 carbon atoms may include, but is not limited to, one or more of n-butyl acrylate, 2-ethylhexyl acrylate, isodecyl acrylate, and isononyl acrylate.

[0047] In one embodiment, the (meth)acrylic monomer having a homopolymer glass transition temperature of −50° C. or less may be contained in the monomer mixture at 90% by weight or more, specifically 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100% by weight, or 90 to 100% by weight. Within this range, the (meth)acrylic binder can easily reach the glass transition temperature range.

[0048] In one embodiment, the monomer mixture may contain 40% by weight or more but less than 100% by weight (e.g., 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99% by weight, or 40% to 90% by weight) of a (meth)acrylic monomer having a branched C3 to C10 alkyl group and a homopolymer having a glass transition temperature of −50° C. or less, and more than 0% by weight but less than 60% by weight (e.g., 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60% by weight, or 10% to 60% by weight) of a (meth)acrylic monomer having a linear C1 to C10 alkyl group and a homopolymer having a glass transition temperature of −50° C. Within these ranges, the (meth)acrylic binder may easily reach the glass transition temperature range.

[0049] The monomer mixture may further include a (meth)acrylic monomer having a homopolymer glass transition temperature of above -50°C. However, the content of the monomer having a homopolymer glass transition temperature of above -50°C in the monomer mixture must not affect the glass transition temperature range of the (meth)acrylic binder. For example, the (meth)acrylic monomer having a homopolymer glass transition temperature of above -50°C may be included in the monomer mixture in an amount of less than 10 wt%, for example, 0, 0.01, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 9.9 wt%, or 0.01 wt% or more but less than 10 wt%.

[0050] For example, a (meth)acrylic monomer having a homopolymer glass transition temperature of more than −50° C. may have a homopolymer glass transition temperature of more than −50° C. and not more than 150° C. The (meth)acrylic monomer having a homopolymer glass transition temperature of more than −50° C. may be selected from one or more of a (meth)acrylic monomer having an aromatic group, a (meth)acrylic monomer having an alicyclic group, a (meth)acrylic monomer having a heteroalicyclic group, and a (meth)acrylic monomer having an amino group.

[0051] The monomer mixture may further include a (meth)acrylic monomer having a crosslinkable functional group to enhance peel strength. The (meth)acrylic monomer having a crosslinkable functional group may be a (meth)acrylic monomer having a hydroxyl group.

[0052] The (meth)acrylic monomer having a hydroxyl group may be a (meth)acrylic acid ester having a linear or branched alkyl group having 1 to 10 carbon atoms and one or more hydroxyl groups. For example, the (meth)acrylic acid ester may be, but is not limited to, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate including 3-hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate including 4-hydroxybutyl (meth)acrylate, etc.

[0053] The (meth)acrylic monomer having a hydroxyl group may be included in the monomer mixture in an amount of less than 10 wt%, for example, 0, 0.01, 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, or 9.9 wt%, or 0.01 wt% or more but less than 10 wt%, within this range, the effects of the adhesive film of the present application can be effectively realized.

[0054] The (meth)acrylic binder may have a weight average molecular weight (Mw) of 1500 kg / mol or less, specifically 900 kg / mol to 1500 kg / mol. Within this range, matrix formation of the PSA film is facilitated, and peel strength and reliability can be improved. The "weight average molecular weight" may be measured in terms of polystyrene by gel permeation chromatography.

[0055] The (meth)acrylic binder may have a polyacid index (PDI) of 10 or less, specifically 3 to 10. Within this range, matrix formation of the adhesive film can be facilitated, and peel strength and reliability can be improved.

[0056] The (meth)acrylic binder may be prepared by polymerizing the monomer mixture using a conventional polymerization method. The polymerization method may include conventional methods known to those skilled in the art. For example, the (meth)acrylic binder may be prepared by adding an initiator to the monomer mixture and then subjecting it to conventional copolymerization, such as suspension polymerization, emulsion polymerization, or solution polymerization. The polymerization temperature may be 60°C to 70°C, and the polymerization time may be 6 to 8 hours. Conventional initiators, including azo-based polymerization initiators and / or peroxides such as benzoyl peroxide or acetyl peroxide, may be used.

[0057] The (meth)acrylic oligomer can increase the peel strength of the pressure-sensitive adhesive film. The pressure-sensitive adhesive film described above is formed from a thermosetting composition and may have a thin thickness, but the peel strength may be reduced. The (meth)acrylic oligomer can increase the cohesive strength of the pressure-sensitive adhesive film and increase the peel strength of the pressure-sensitive adhesive film.

[0058] The (meth)acrylic oligomer is included in an amount of 0.1 to 5 parts by weight based on 100 parts by weight of the (meth)acrylic binder. If the (meth)acrylic oligomer is included in an amount less than 0.1 part by weight, it may be difficult to achieve the peel strength of the PSA film of the present application. If the (meth)acrylic oligomer is included in an amount more than 5 parts by weight, the PSA film may have poor flexural properties and unevenness conformability. For example, the (meth)acrylic oligomer may be included in an amount of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5 parts by weight, 0.1 to 3 parts by weight, 0.5 to 2 parts by weight, or 0.5 to 1.5 parts by weight based on 100 parts by weight of the (meth)acrylic binder.

[0059] According to one embodiment, the (meth)acrylic oligomer has a higher glass transition temperature than the (meth)acrylic binder, and the glass transition temperature may be, for example, 10° C. to 40° C., 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° C., or 20° C. to 40° C. Within this range, it may be easy to increase the peel strength of the PSA film and easily achieve excellent flex properties and step conformability.

[0060] According to an embodiment, the (meth)acrylic oligomer has a weight average molecular weight lower than that of the (meth)acrylic binder, for example, 3 kg / mol to 50 kg / mol, such as 3,000 g / mol, 4,000 g / mol, 5,000 g / mol, 6,000 g / mol, 7,000 g / mol, 8,000 g / mol, 9,000 g / mol, 10,000 g / mol, 15,000 g / mol, 20,000 g / mol, 25,000 g / mol, 30,000 g / mol, 35,000 g / mol, 40,000 g / mol, 45,000 g / mol, 50,000 g / mol, or 5 kg / mol to 50 kg / mol. Within this range, the cohesive strength of the PSA film can be increased.

[0061] The (meth)acrylic oligomer may include an oligomer of a monomer mixture containing a (meth)acrylic monomer having a hydroxyl group. The hydroxyl group contained in the (meth)acrylic oligomer can improve high-temperature, high-humidity durability. When the (meth)acrylic binder is a (meth)acrylic binder without a crosslinkable functional group, such as a hydroxyl group or a carboxylic acid group, the (meth)acrylic monomer having a hydroxyl group among the (meth)acrylic oligomers can improve the peel strength of the PSA film and ensure folding properties at low temperatures. The (meth)acrylic monomer having a hydroxyl group may include, but is not limited to, 4-hydroxybutyl (meth)acrylate, hydroxyethyl (meth)acrylate, etc. The (meth)acrylic monomer having a hydroxyl group may be included in the monomer mixture in an amount of 0.1 wt % to 99.9 wt %.

[0062] The (meth)acrylic oligomer may contain, as a main structural unit, a (meth)acrylic monomer having a homopolymer glass transition temperature of 90°C or higher, e.g., 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103, 104, 105, 106, 107, 108, 109, 110, 111, 112, 113, 114, 115, 116, 117, 118, 119, 120°C, or 100 to 120°C. This range can prevent the storage modulus of the PSA film from becoming excessively high at high temperatures and ensure the glass transition temperature range. For example, the (meth)acrylic monomer may be a monofunctional (meth)acrylic monomer, specifically, but not limited to, methyl acrylate, hydroxyethyl methacrylate, etc. The "major structural unit" means that the monomer is contained in an amount of 50% by weight or more, 60% by weight or more, and 100% by weight or less of all units of the (meth)acrylic oligomer.

[0063] The (meth)acrylic oligomer may further contain, as a constituent unit, a (meth)acrylic monomer having a homopolymer glass transition temperature of 50°C or less, for example, -80°C to 0°C.

[0064] In one embodiment, the (meth)acrylic oligomer may include an oligomer of a monomer mixture containing 4-hydroxybutyl (meth)acrylate and methyl methacrylate, and the monomer mixture may further include at least one of methacrylic acid and N-butyl (meth)acrylate.

[0065] The curing agent forms a matrix of the adhesive film by thermally curing the (meth)acrylic binder, and can improve the reliability of the adhesive film.

[0066] In one embodiment, the curing agent may be an isocyanate-based curing agent.

[0067] The isocyanate curing agent may be difunctional or higher, specifically difunctional to hexafunctional, and may include one or more aromatic or aliphatic isocyanate curing agents selected from the group consisting of xylene diisocyanate (XDI) including m-xylene diisocyanate, methylene bis(phenyl isocyanate) (MDI) including 4,4'-methylene bis(phenyl isocyanate), naphthalene diisocyanate, tolylene diisocyanate, hexamethylene diisocyanate, and isophorone diisocyanate, or adducts thereof. For example, the adduct may be a trimethylolpropane adduct of tolylene diisocyanate, a trimethylolpropane adduct of hexamethylene diisocyanate, a trimethylolpropane adduct of isophorone diisocyanate, a trimethylolpropane adduct of xylene diisocyanate, an isocyanurate of tolylene diisocyanate, an isocyanurate of hexamethylene diisocyanate, and an isocyanurate of isophorone diisocyanate. The isocyanate-based curing agent may include one or more of the above compositions.

[0068] The isocyanate-based curing agent is included in an amount of 0.01 to 0.5 parts by weight based on 100 parts by weight of the (meth)acrylic binder. If the isocyanate-based curing agent is included in an amount less than 0.01 part by weight, the adhesive film may not achieve the peel strength required in the present application. If the isocyanate-based curing agent is included in an amount more than 0.5 parts by weight, the flexural properties and step conformability may be poor. For example, the isocyanate-based curing agent may be included in an amount of 0.05 to 0.3 parts by weight based on 100 parts by weight of the (meth)acrylic binder.

[0069] The composition may further contain a curing agent that does not have an isocyanate group (hereinafter also referred to as a "non-isocyanate curing agent").

[0070] The non-isocyanate curing agent may include one or more of a metal chelate curing agent, a carbodiimide curing agent, an aziridine curing agent, and an epoxy curing agent, and preferably includes a metal chelate curing agent, which can increase the curing speed of the (meth)acrylic binder.

[0071] The metal chelate curing agent may be a conventional curing agent, or may be a curing agent containing a metal such as aluminum, titanium, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, zirconium, etc. For example, the metal chelate curing agent may include one or more of aluminum ethyl acetoacetate diisopropylate, aluminum tris(ethyl acetoacetate), alkyl acetoacetate aluminum diisopropylate, aluminum isopropylate, mono-sec-butoxyaluminum diisopropylate, aluminum sec-butylate, aluminum ethylate, tetraisopropyl titanate, tetra-normal-butyl titanate, butyl titanate dimer, titanium acetylacetonate, titanium octylene glycolate, titanium tetraacetylacetonate, titanium ethyl acetoacetate, polyhydroxytitanium stearate, and aluminum acetylacetonate.

[0072] The non-isocyanate curing agent may be included in an amount of 5 parts by weight or less, specifically 0.01 to 2 parts by weight, per 100 parts by weight of the (meth)acrylic binder. Within this range, the effects of the pressure-sensitive adhesive film of the present invention are not affected, and additional effects can be obtained.

[0073] Examples of the antistatic agent include ionic liquids, ionic conductive materials such as bis(fluorosulfonyl)imide salts, and surfactants.

[0074] The ionic liquid may be, for example, a substance having a cation component such as a phosphonium ion, pyridinium ion, pyrrolidinium ion, imidazolium ion, guanidium ion, ammonium ion, isouronium ion, thiouronium ion, piperidinium ion, pyrazolium ion, sulfonium ion, quaternary ammonium ion, or quaternary phosphonium ion, and an anion component such as a halogen ion, nitrate ion, sulfate ion, phosphate ion, perchlorate ion, thiocyanate ion, thiosulfate ion, sulfite ion, tetrafluoroborate ion, hexafluorophosphate ion, formate ion, oxalate ion, acetate ion, trifluoroacetate ion, or alkylsulfonate ion.

[0075] Specific examples of ionic liquids include 1-allyl-3-methylimidazolium chloride, 1,3-dimethylimidazolium chloride, 1,3-dimethylimidazolium dimethyl phosphate, 1-ethyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium bromide, 1-ethyl-3-methylimidazolium iodide, 1-ethyl-3-methanesulfonate, and 1-ethyl-3-methylimidazolium tetrafluoromethane. Roborate, 1-ethyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium-p-toluenesulfonate, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride, 1-methyl-1-propyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide, 1-methyl-1-methylpyrrolidinium bromide, 1-butyl-1-methylpiperidinium Examples of suitable methylpyridinium compounds include methylpyridinium bromide, 1-ethylpyridinium chloride, 1-ethylpyridinium bromide, 1-butylpyridinium chloride, 1-butylpyridinium bromide, 1-butyl-3-methylpyridinium chloride, 1-ethyl-3-methylpyridinium ethyl sulfate, 1-butyl-4-methylpyridinium chloride, 1-butyl-4-methylpyridinium hexafluorophosphate, trimethylpropylammonium bis(trifluoromethanesulfonyl)imide, tributylmethylammonium bis(trifluoromethanesulfonyl)imide (also known as tri-n-butylmethylammonium bistrifluoromethanesulfonimide), tetrabutylammonium chloride, tetrabutylammonium bromide, cyclohexyltrimethylammonium bis(trifluoromethanesulfonyl)imide, and tetrabutylphosphonium bromide.

[0076] The surfactant may be a nonionic surfactant or an ionic surfactant.

[0077] Examples of nonionic surfactants include polyethylene glycol alkyl ethers and polyoxyalkylene alkyl ethers.

[0078] Examples of the ionic surfactant include cationic surfactants such as alkyltrimethylammonium halides having 8 to 22 carbon atoms, and anionic surfactants such as alkyl sulfates.

[0079] The antistatic agent may be included in an amount of 0.001 to 0.1 parts by weight, specifically 0.005 to 0.1 parts by weight, relative to 100 parts by weight of the (meth)acrylic binder, which may facilitate peeling of the PSA film from the release film during the manufacturing process of the PSA film.

[0080] According to one embodiment, the total amount of the (meth)acrylic binder, the (meth)acrylic oligomer, the curing agent, and the antistatic agent may be 98 wt % or more, for example, 99 wt % to 100 wt %, based on the solid content, in the composition. Within this range, the effects of the present application may be easily achieved.

[0081] The composition may further comprise a silane coupling agent.

[0082] The silane coupling agent can increase the adhesive strength of the PSA film. The silane coupling agent can include a conventional silane coupling agent known to those skilled in the art. For example, the silane coupling agent can include, but is not limited to, an epoxy group-containing silane coupling agent such as glycidoxypropyltrimethoxysilane or glycidoxypropylmethyldimethoxysilane.

[0083] The silane coupling agent may be included in an amount of 0.01 to 5 parts by weight based on 100 parts by weight of the (meth)acrylic binder, which may further improve peel strength.

[0084] The composition may further include additives. The additives may be those commonly contained in PSA films and known to those skilled in the art. For example, the additives may include, but are not limited to, one or more of a pigment, an ultraviolet absorber, a leveling agent, and an antistatic agent.

[0085] The composition may further include a solvent. The solvent can improve the coatability of the composition and enable the formation of a thin, uniformly coated adhesive film. The solvent may include any of the solvents known to those skilled in the art. For example, the solvent may include, but is not limited to, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, etc. In one embodiment, the composition may contain 20% to 30% by weight, specifically 20% to 25% by weight, of the solid content of the adhesive film. Within this range, the composition may exhibit excellent coatability.

[0086] The adhesive film may have a haze of 2% or less, specifically 0.1% to 1%, in the visible light region (e.g., wavelength 380 nm to 780 nm), and a total light transmittance of 90% or more, specifically 95% to 99%. Within these ranges, the adhesive film has good optical transparency and can be used in optical display devices.

[0087] According to an embodiment, the optical member includes a polyimide-based optical element having a polyimide-based ash on at least one surface thereof, and the adhesive film attached to the surface having the polyimide-based ash.

[0088] The polyimide-based optical element may be an optical element having a polyimide-based layer formed on its outermost surface. The polyimide-based layer may be formed of a composition including at least one of a polyimide-based polymer, a polyimide-based copolymer, a polyimide-based oligomer, and a polyimide-based monomer. The remaining portions of the "polyimide-based optical element" excluding the polyimide-based layer may be a single layer or multiple layers. According to an embodiment, the "polyimide-based optical element" may be a panel for an optical display device, a protective film for an optical display device, or the like, and may be an optical element used in, for example, a foldable optical display device.

[0089] The polyimide-based ash may be produced according to FIG. 1 described above.

[0090] The adhesive film may be the adhesive film according to one embodiment described above.

[0091] A conventional optical element may be laminated on the surface of the polyimide-based optical element not covered with the adhesive film. Such an optical element may provide certain optical functions to the optical display device, such as light emission, polarization, optical compensation, improved display image quality, and / or electrical conductivity. Examples of such optical elements include window films, windows, polarizing films, polarizing plates, color filters, retardation films, elliptically polarizing films, reflective polarizing films, anti-reflection films, compensation films, brightness enhancement films, alignment films, light diffusion films, shatterproof glass films, surface protection films, barrier layers for OLED devices, 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, and graphene. A method for manufacturing such an optical element can be easily achieved by a person skilled in the art.

[0092] A conventional optical element, a protective film, or an adhesive film performing a specific function may be laminated on the surface of the adhesive film that is not bonded to the polyimide-based optical element. For example, the function may be a light-shielding function. The light-shielding function may be performed by a black-based light-shielding dye or a light-shielding pigment.

[0093] According to an embodiment, the optical display device includes the adhesive film or the optical member.

[0094] The optical display device may include an organic light emitting diode display device, a liquid crystal display device, etc. The optical display device may include a foldable optical display device, but may also include a non-foldable optical display device. [Example]

[0095] The structure and operation of the present invention will be described in more detail below through preferred examples of the present invention, which are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0096] [Example 1: Production of adhesive film]

[0097] A (meth)acrylic binder (glass transition temperature: -65°C) was produced by polymerizing 100 parts by weight of a monomer mixture containing 2-ethylhexyl acrylate (2-EHA), n-butyl acrylate (n-BA), and 4-hydroxybutyl acrylate (4-HBA).

[0098] As the (meth)acrylic oligomer, a (meth)acrylic oligomer (glass transition temperature: 30° C.) obtained by polymerizing 100 parts by weight of a monomer mixture containing 4-hydroxybutyl acrylate and methyl methacrylate was used.

[0099] Based on the solid content, 100 parts by weight of the (meth)acrylic binder were mixed with 1 part by weight of the (meth)acrylic oligomer, 0.1 parts by weight of an isocyanate curing agent (Saiden, toluene diisocyanate curing agent), and 0.05 parts by weight of an antistatic agent (FC4400, tri-m-butylmethylammonium bis(trifluoromethanesulfonate)imide, 3M), and mixed with methyl ethyl ketone as a solvent to prepare a composition for adhesive films with a solid content of 20% by weight.

[0100] The adhesive film composition prepared above was applied to a polyethylene terephthalate film, which was the first release film, at a thickness of 15 μm, and cured at 100°C for 3 minutes, thereby bonding a polyethylene terephthalate film, which was the second release film, to produce an adhesive sheet consisting of a first release film / adhesive film / second release film.

[0101] [Examples 2 to 4: Production of adhesive films]

[0102] The monomer mixture for the (meth)acrylic binder was changed in Example 1. A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the type and / or content of each component in Example 1 was changed as shown in Table 1 below.

[0103] [Comparative Examples 1 to 3: Production of Adhesive Films]

[0104] The monomer mixture for the (meth)acrylic binder was changed in Example 1. A pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1, except that the type and / or content of each component in Example 1 was changed as shown in Table 1 below.

[0105] [Reference Example: Production of a polyimide layer with polyimide ash on one side]

[0106] A polyimide layer was produced with a polyimide ash on one side.

[0107] A polyimide varnish (DuPont) was applied to a thickness of 30 μm on the upper surface of an alkali-free glass plate (thickness: 1.1 mm) to produce a polyimide varnish coating film. The polyimide varnish coating film was dried at 150°C for 30 minutes and then cured at 250°C for 30 minutes to form a polyimide cured film (thickness: 30 μm) on the upper surface of the alkali-free glass plate. A laser (Coherent) was irradiated onto the lower surface of the alkali-free glass plate at room temperature, and after one hour at 25°C, the alkali-free glass plate was peeled off from the polyimide cured film, producing a polyimide layer with polyimide ash on the surface where the alkali-free glass plate was peeled off.

[0108] The PET film was peeled off from the adhesive sheets produced in the Examples and Comparative Examples to produce adhesive films, and the physical properties of the adhesive films were evaluated as shown in Table 1 below. The results are shown in Table 1 below.

[0109] (1) Peeling force (unit: gf / inch) The pressure-sensitive adhesive sheets of the Examples and Comparative Examples were cut to a size of 25 mm x 25 mm, and the first release film was peeled off. One side of the pressure-sensitive adhesive film from which the first release film had been peeled off was bonded to the side of the polyimide-based layer (100 mm x 25 mm) with the polyimide-based ash. After peeling off the second release film of the pressure-sensitive adhesive sheet, the other side of the pressure-sensitive adhesive film was bonded to a PET film (corona-treated; corona treatment conditions: 78 doses, 2 times in total; heat-resistant PET, Toray) (100 mm x 25 mm) and pressed with a 2 kg hand roller to prepare a test specimen. The test specimen had a shape in which the pressure-sensitive adhesive film was disposed between one end of the polyimide-based layer and one end of the PET film.

[0110] The prepared test specimen was fixed to a peel strength tester (TA.XT-Plus Texture Analyzer, manufactured by Stable Micro System). At 25°C, the PSA film and the PET film were pulled 180° from the side with the polyimide-based ash at a speed of 300 mm / min, and the peel strength was measured in the region where the peel strength remained constant as the PSA film and the PET film were peeled from the side with the polyimide-based ash.

[0111] (2) Flexibility The release films on both sides of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were each separated to obtain a pressure-sensitive adhesive film. The pressure-sensitive adhesive film 23 was attached to the side of the polyimide layer 22 with the polyimide ash, and this was then attached to a PET film (corona-treated; corona treatment conditions: 78 doses, 2 times in total, heat-resistant PET, Toray) 24, and pressed with a 2 kg hand roller to produce a rectangular test piece 25 measuring 2.5 cm x 10 cm.

[0112] The rectangular test piece 25 was bent at half its widthwise position and then fixed between a first fixture 20 and a second fixture 21 as shown in FIG. 2 to prepare a test piece for evaluating bending properties. The first fixture 20 and the second fixture 21 were fixed to form a curvature radius of 1.5 cm and their positions were not changed. The test piece was kept at 25°C for 3 days. The presence of bubbles between the polyimide ash surface of the polyimide layer 22 and the adhesive film 23 was then visually evaluated.

[0113] When no bubbles were observed, the evaluation was ◯, and when bubbles were observed, the evaluation was x.

[0114] (3) Step-following ability The release films on both sides of the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were each separated to obtain a pressure-sensitive adhesive film. The pressure-sensitive adhesive film 33 was attached to the side of the polyimide layer 32 with the polyimide ash. PET film 34 (corona-treated; corona treatment conditions: 78 doses, 2 times in total; heat-resistant PET, Toray) was then attached to the pressure-sensitive adhesive film 33, and pressed with a 2 kg hand roller to produce a rectangular sample measuring 5 cm x 12 cm.

[0115] As shown in Figure 3, a patterned portion 31 having a pattern on its upper surface was prepared, and the rectangular sample was attached so that the upper surface of the pattern was in contact with the polyimide layer 32 of the sample, to produce a test piece. The pattern had dimensions a of 15 µm, b of 0.8 cm, and c of 1.4 cm, and had a rectangular cross section, and the patterned portion was made of polyethylene terephthalate.

[0116] It was checked with the naked eye whether bubbles were generated between the polyimide layer 32 and the adhesive film 33 .

[0117] When no bubbles were observed, the evaluation was ◯, and when bubbles were observed, the evaluation was x.

[0118] (4) Antistatic performance (unit: Ω) It was measured by the probe method.

[0119] [Table 1]

[0120] As shown in Table 1, the adhesive film according to one embodiment has a high peel strength of 300 gf / inch or more against a surface having polyimide ash, and can be attached to a surface having polyimide ash with high reliability. The adhesive film according to one embodiment had excellent flexural properties and antistatic performance. The adhesive film according to one embodiment had excellent step conformability, as no bubbles were generated even in the step conformability test under rigorous conditions shown in Figure 3. Therefore, when the adhesive film according to one embodiment is adhered to a surface having polyimide ash of a polyimide optical element, it is expected to have excellent step conformability even against steps caused by the polyimide ash.

[0121] On the other hand, the adhesive film of the comparative example could not provide the effects of the adhesive film according to the embodiment described above.

[0122] Simple variations and modifications of the present invention can be easily implemented by those skilled in the art, and all such variations and modifications can be considered to be included within the scope of the present invention. [Explanation of symbols]

[0123] 10 Glass Plate 11 Polyimide varnish coating 12 Polyimide-based hardened film 13 Laser 14 Polyimide Ash 15 Polyimide layer

Claims

1. An adhesive film for polyimide-based optical elements having a polyimide-based ash, The adhesive film for polyimide-based optical elements having polyimide ash comprises a cured product of a composition including 100 parts by weight of a (meth)acrylic binder having a glass transition temperature (Tg) of -70°C to -40°C, 0.1 to 5 parts by weight of a (meth)acrylic oligomer, 0.01 to 0.5 parts by weight of a curing agent, and an antistatic agent.

2. The pressure-sensitive adhesive film according to claim 1 , wherein the pressure-sensitive adhesive film has a peel strength of 300 gf / inch or more from the surface on which the polyimide ash is present.

3. The pressure-sensitive adhesive film according to claim 1 , wherein the cured product is a thermoset product.

4. The (meth) acrylic binder is a (meth) acrylic copolymer of a monomer mixture containing a (meth) acrylic monomer having a homopolymer glass transition temperature of −50 ° C. or less. The adhesive film according to claim 1.

5. The (meth)acrylic monomer having a homopolymer glass transition temperature of -50 ° C. or less is a linear or branched (meth)acrylic acid ester having an alkyl group having 1 to 10 carbon atoms. The pressure-sensitive adhesive film according to claim 4.

6. The pressure-sensitive adhesive film according to claim 4, wherein the (meth)acrylic monomer having a homopolymer glass transition temperature of −50° C. or lower is contained in the monomer mixture in an amount of 90% by weight or more.

7. The pressure-sensitive adhesive film according to claim 1 , wherein the (meth)acrylic oligomer has a glass transition temperature of 10° C. to 40° C.

8. The pressure-sensitive adhesive film according to claim 1 , wherein the (meth)acrylic oligomer comprises an oligomer of a monomer mixture containing a (meth)acrylic monomer having a hydroxyl group.

9. The pressure-sensitive adhesive film according to claim 1 , wherein the curing agent is an isocyanate-based curing agent.

10. The adhesive film according to claim 1, wherein the total amount of the (meth)acrylic binder, the (meth)acrylic oligomer, the curing agent, and the antistatic agent is 98% by weight or more based on the solid content in the composition.

11. a polyimide-based optical element having a polyimide-based ash on at least one surface; An optical member comprising: the adhesive film of any one of claims 1 to 10, which is bonded to one surface of the polyimide ash.

12. The optical member according to claim 11 , wherein the polyimide-based optical element is a panel for an optical display device.

13. The optical member according to claim 11 , wherein an optical element is further laminated on one surface of the polyimide-based optical element to which the adhesive film is not attached.

14. 14. The optical member according to claim 13, wherein the optical element comprises at least one of a window film, a window, a polarizing film, a polarizing plate, a color filter, a retardation film, an elliptically polarizing film, a reflective polarizing film, an anti-reflection film, a compensation film, a brightness enhancement film, an alignment film, a light diffusion film, a glass shatterproof film, a surface protection film, an OLED element barrier layer, a plastic LCD substrate, and a transparent electrode film.

15. The optical member according to claim 11, wherein a functional optical element, a protective film, or an adhesive film is further laminated on the surface of the adhesive film to which the polyimide-based optical element is not attached.

16. The optical member according to claim 15 , wherein the optical element, the protective film, or the adhesive film has a light-shielding function.

17. An optical display device comprising the adhesive film of any one of claims 1 to 10.

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