Adhesive protection film, optical member and optical display device

Abstract

To provide an adhesive protective film excellent in easy peelability when adhering to a polyimide optical element including polyimide ash.SOLUTION: An adhesive protective film includes a cured product having a composition including a (meth) acrylic copolymer, a hardener, an aromatic group containing one or more functional monomer and a photoinitiator. The adhesive protective film having an initial peel force of 7 gf / inch or less to a surface including polyimide ash is stuck on the surface including polyimide, and the peel force to the surface including polyimide ash after light irradiation is 200 gf / inch or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] In conventional optical and electronic devices, a protective film consisting of an adhesive layer alone or a base film and an adhesive layer is sometimes attached to the surface of the device to prevent scratches during processes such as processing, assembly, and inspection. Such protective films are used after removing the release film that protects the adhesive layer. In recent years, there has been a strong movement to shift from liquid crystal devices to organic light-emitting diode (OLED) devices as optical components. In addition, an increasing number of OLED devices have flexible properties.

[0003] Flexible OLED devices are very flexible, unlike liquid crystal devices or regular OLED devices. Therefore, flexible OLED devices require a process protection film to protect the OLED panel from surface scratches during processes such as processing, assembly, and inspection. In order to easily remove the protection film if defects such as appearance abnormalities or foreign particles are found during panel inspection, low peel strength (i.e., easy peeling) and rework properties are required. After inspection is complete, a permanently attached P-film (patterned film) is required to support the panel and protect it from moisture and the external environment. Since the P-film must be permanently attached to the panel, it requires high peel strength (i.e., difficult to peel) and reliability.

[0004] In the conventional panel manufacturing process, a temporary protective film with low peel strength and a P-film with high peel strength are separately required, resulting in the need for a protective film lamination process, a protective film peeling process, and a P-film lamination process.

[0005] In recent years, cost reduction and process optimization have been pursued. When functioning as a pre-UV exposure protective film, this process protective film is patterned using a laser. In this case, if the initial peel strength to the polyimide substrate exceeds a certain level, peeling becomes difficult, which can cause yield problems. Therefore, an adhesive protective film that combines a process protective film and a P-film is preferred, which has a low peel strength when attached to the polyimide substrate but a high peel strength after UV exposure.

[0006] The background art of the present invention is disclosed in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent No. 5683369 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide an adhesive protective film that has excellent easy peeling properties when adhered to a polyimide optical element having a polyimide ash.

[0009] Another object of the present invention is to provide an adhesive protective film that can be adhered to a polyimide-based optical element by a polyimide-based ash, and that has a higher peel strength after light irradiation than before light irradiation, and can be fixed to the optical element to improve the durability and reliability of the optical element.

[0010] It is still another object of the present invention to provide an adhesive protective film that does not generate bubbles when adhered to a polyimide-based optical element containing a polyimide-based ash.

[0011] It is yet another object of the present invention to provide an adhesive protective film that can be simultaneously used as a temporary protective film for processing and a pattern reinforcing protective film that is selectively peeled off in part from a flexible light emitting device panel substrate to form a pattern. [Means for solving the problem]

[0012] One aspect of the present invention is an adhesive protective film for polyimide-based optical elements having a polyimide-based ash.

[0013] The adhesive protective film includes a cured product of a composition including a (meth)acrylic copolymer, a curing agent, an aromatic group-containing monofunctional or higher monomer, and a photoinitiator, and the adhesive protective film has an initial peel strength of 7 gf / inch or less from the surface having the polyimide ash, and the adhesive protective film is attached to the surface having the polyimide ash, and after light irradiation, the peel strength of the adhesive protective film from the surface having the polyimide ash is 200 gf / inch or more.

[0014] Another embodiment of the present invention relates to an optical member.

[0015] The optical member includes a polyimide-based optical element having a polyimide-based ash on at least one surface thereof, and an adhesive layer attached to the surface having the polyimide-based ash, the adhesive layer including a photo-cured adhesive protective film.

[0016] Yet another embodiment of the present invention relates to an optical display device.

[0017] An optical display device includes the cured product of the pressure-sensitive adhesive protective film or the optical member. [Effects of the Invention]

[0018] The present invention can provide an adhesive protective film that is highly releasable when adhered to a polyimide-based optical element containing a polyimide-based ash.

[0019] The present invention can provide an adhesive protective film in which a polyimide ash is adhered to a polyimide optical element, and after light irradiation, the peel strength is higher than before light irradiation, and the film can be fixed to the optical element to increase the durability and reliability of the optical element.

[0020] The present invention can provide an adhesive protective film that does not generate bubbles when adhered to a polyimide optical element containing polyimide ash.

[0021] The present invention provides an adhesive protective film that can be used simultaneously as a temporary protective film for processing and a protective film for reinforcing a pattern by selectively peeling only a portion of the film from a flexible light emitting device panel substrate to form a pattern. [Brief explanation of the drawings]

[0022] [Figure 1] 1 illustrates one embodiment of a method for making a polyimide-based layer with a polyimide-based ash. [Figure 2] Another embodiment of a method for manufacturing a polyimide-based layer having a polyimide-based ash will now be described. [Figure 3] FIG. 2 is a schematic diagram of a laser irradiation process in a method for manufacturing a polyimide-based layer having polyimide-based ash. [Figure 4] This explains the process for evaluating peelability. [Figure 5] FIG. 1 is a cross-sectional view of an embodiment of an optical element. DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention may be embodied in various different forms and is not limited to the embodiments set forth herein.

[0024] The terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. Unless otherwise specified in the context, singular expressions include plural expressions.

[0025] In this specification, "(meth)acrylic" means acrylic and / or methacrylic.

[0026] As used herein, a "copolymer" can include a polymer or a resin.

[0027] As used herein, the term "glass transition temperature" refers to the glass transition temperature (Tg) measured for a homopolymer of a target monomer 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 slowly cooled to -100°C, and heated again at a rate of 10°C / min to 100°C, and data on the endothermic transition curve are obtained. Based on the obtained data, the inflection point of the endothermic transition curve can be determined as the glass transition temperature.

[0028] In this specification, when a numerical range is stated, "X to Y" means "at least X and at most Y."

[0029] The adhesive protective film of the present invention can have the form of an adhesive layer before being irradiated with light.

[0030] Before light irradiation, the adhesive protective film can be used to provide adhesive protection for polyimide-based optical elements having a surface with polyimide-based ash. Furthermore, after light irradiation, the adhesive protective film can improve the durability and reliability of the polyimide-based optical elements. The adhesive protective film is an adhesive protective film with variable peel strength due to light irradiation.

[0031] Specifically, the adhesive protective film adheres to the surface on which the polyimide-based ash is present to temporarily protect the surface on which the polyimide-based ash is present, thereby preventing scratches on the surface on which the polyimide-based ash is present during processes such as processing, assembly, and inspection. In particular, the adhesive protective film can adhere to the surface on which the polyimide-based ash is present without generating air bubbles.

[0032] Furthermore, after the adhesive protective film is adhered to a surface having a polyimide-based ash and patterned, it can be peeled off from the surface having the polyimide-based ash and / or the optical element due to its high releasability.

[0033] In addition, the adhesive protective film is an adhesive film with a peel strength that can be changed by light irradiation, and after light irradiation, it adheres to the surface containing the polyimide ash with a higher peel strength than before light irradiation, thereby increasing the durability and reliability of the polyimide optical element.

[0034] "Polyimide-based optical elements" are polymer films processed through a polymerization reaction using the precursor polyamic acid, which contains imide and aromatic groups within the repeating unit. They have excellent mechanical and heat-resistant properties and can be used as substrates for flexible OLED panels.

[0035] In one embodiment, the polyimide-based optical element can have the form of a polyimide-based layer.

[0036] First, a method for producing a polyimide-based layer having a surface with polyimide-based ash will be described.

[0037] Fig. 1 illustrates one embodiment of a method for producing a polyimide layer containing polyimide ash. Steps (1) to (4) shown in Fig. 1 will be described below in order.

[0038] (1) A polyimide varnish is applied to the lower surface of the glass plate 10 to a predetermined thickness to form a polyimide varnish coating film 11.

[0039] (2) The produced polyimide varnish coating film 11 is dried and hardened to form a polyimide layer 12 on the lower surface of the glass plate 10 .

[0040] (3) A laser is applied from above the glass plate 10 using a laser irradiation device 13. As a result, a polyimide ash 14 is formed on the upper surface of the polyimide layer 12.

[0041] Laser irradiation can burn a portion of the polyimide layer, forming polyimide ash. The polyimide ash can form irregular, fine irregularities in the form of dust, forming fine steps between the laser-treated and non-laser-treated areas. The steps facilitate the easy peeling of the glass plate in step (4) below. The degree of formation of polyimide ash 14 or the area ratio where polyimide ash 14 is formed (the ratio of the total area of ​​polyimide ash to the total area of ​​the polyimide layer) can be adjusted by the type of polyimide varnish, the total thickness of the polyimide layer, the degree of laser irradiation, etc.

[0042] (4) The glass plate 10 is peeled off from the polyimide layer 12 to produce a polyimide layer 15 having a surface with polyimide ash 14 thereon.

[0043] 2 illustrates another embodiment of the method for producing a polyimide layer having a polyimide ash. Steps (1) to (5) shown in FIG. 2 will be described below in order.

[0044] (1) A polyimide varnish is applied to the upper surface of a release substrate film 16 to a predetermined thickness to produce a polyimide varnish coating film 11.

[0045] (2) The produced polyimide varnish coating film 11 is dried and cured to form a polyimide layer 12 on the upper surface of the release substrate film 16 .

[0046] (3) The glass plate 10 is covered on the upper surface of the polyimide-based layer 12 .

[0047] (4) A laser is applied from above the glass plate 10 using a laser irradiation device 13. This forms polyimide ash 14 on the upper surface of the polyimide layer 12. Laser treatment burns a portion of the polyimide layer, forming polyimide ash. The polyimide ash forms irregular, fine irregularities in the form of dust, which can form minute steps between the laser-treated and non-laser-treated areas. The steps facilitate easy peeling of the glass plate in step (5) below. The degree of polyimide ash 14 formation or the area ratio where polyimide ash 14 is formed (the ratio of the total area of ​​the polyimide ash to the total area of ​​the polyimide layer) can be adjusted by adjusting the type of polyimide varnish, the overall thickness of the polyimide layer, the intensity of laser irradiation, etc.

[0048] (5) The glass plate 10 is peeled off from the polyimide layer 12 to produce a laminate of the polyimide layer 15 having the polyimide ash 14 on one side and the release substrate film 16 .

[0049] The release substrate film 16 can be easily removed since it has been subjected to a release treatment using silicone or the like.

[0050] FIG. 3 is a schematic diagram of a laser irradiation process in a method for producing a polyimide-based layer having polyimide-based ash.

[0051] 3, a laminate is prepared in which a polyimide layer 12 and a glass plate 10 are laminated in this order on the upper surface of a release substrate film 16, and a laser 18 is irradiated from a laser irradiation device 13 located above the glass plate 10 in the laminate, thereby forming a polyimide ash 14 on the upper surface of the polyimide layer 12. By moving the laminate in a certain direction (the direction of the arrow) and controlling the on-off of the laser irradiation, the polyimide ash 14 can be discontinuously formed on the upper surface of the polyimide layer 12.

[0052] The glass plate 10 is an alkali-free glass plate, and may have a thickness of 1 mm to 2 mm.

[0053] The polyimide varnish may contain at least 90% by weight of one or more of polyimide copolymers, polyimide oligomers, and polyimide monomers, but is not limited thereto. For example, SD Flex (DuPont) may be used as the polyimide varnish, but is not limited thereto.

[0054] The polyimide varnish can be applied by a conventional method known to those skilled in the art. For example, the polyimide varnish can be applied by a doctor blade coating method. In this case, the gauge diameter may be 0.5 mm to 1.0 mm, for example, 0.65 mm. The polyimide varnish can be applied to a thickness of 20 μm to 30 μm.

[0055] The polyimide-based varnish coating can be dried and cured to form a polyimide-based layer.

[0056] Drying can include heat treatment at 50°C to 200°C for 5 to 60 minutes. Drying can include one or more heat treatments, for example, two or more heat treatments. In one embodiment, drying can include two or more heat treatments. For example, drying can include a first heat treatment at 50°C to 100°C for 5 to 30 minutes, and a second heat treatment at 100°C to 200°C for 5 to 30 minutes. Preferably, the first heat treatment is performed at 80°C for 10 minutes, and the second heat treatment is performed at 120°C for 20 minutes.

[0057] The dried polyimide varnish coating can have a thickness of 20 μm to 30 μm, preferably 20 μm.

[0058] Curing can involve heat treatment at a relatively higher temperature for a relatively longer time than drying. Such heat treatment allows the dried polyimide-based varnish coating to undergo an imidization reaction, thereby producing a polyimide-based layer. Heat treatment can involve heat treatment at a temperature above 200°C and not exceeding 400°C for 30 to 120 minutes. In one embodiment, heat treatment can be performed one or more times. Preferably, curing can involve heat treatment at 250°C for 60 minutes.

[0059] The polyimide-based layer may have a thickness of 20 μm to 30 μm, preferably 20 μm.

[0060] The laser irradiation is 100mJ / cm 2 ~500mJ / cm 2 of irradiation, e.g., 150 mJ / cm 2 ~200mJ / cm 2 Within the above range, a polyimide-based ash that is easily peeled from a glass plate can be formed. The laser irradiation includes light irradiation in the 308 nm wavelength region, and can include picosecond, nanosecond, or femtosecond irradiation.

[0061] The adhesive protective film is adhered to a surface having a polyimide-based ash, and after being patterned, can be easily peeled off from the surface having the polyimide-based ash and / or the optical element with high releasability.

[0062] Here, "high releasability" means that when the patterned adhesive protective film is peeled from the surface having the polyimide-based ash, the surface having the polyimide-based ash or the polyimide-based optical element having the surface having the polyimide-based ash is peeled without deforming the surface having the polyimide-based ash or the polyimide-based optical element having the surface having the polyimide-based ash, and that only the portions that should be peeled are selectively peeled at a high rate at one time without tension or the like occurring between the portions that should be peeled and the portions that should not be peeled formed by the patterning. According to one embodiment, the portions that should be peeled and the portions that should not be peeled may be positioned alternately.

[0063] The process of evaluating the peelability is explained in Fig. 4. The steps (1) to (5) shown in Fig. 4 will be explained in order below.

[0064] (1) A laminate is produced in which a polyimide layer 15 having a surface with polyimide ash and an optical element or optical film 20 are laminated in this order on the upper surface of the adhesive protective film 30 of the present invention. The lower surface of the polyimide layer 15 is the surface with polyimide ash, although this is not shown in FIG.

[0065] (2) The adhesive protective film 30 in the laminate is patterned by a predetermined method to form a patterned adhesive protective film 31. The patterned adhesive protective film 31 is divided into a portion 31a that must not be peeled off and a portion 31b that must be peeled off.

[0066] (3) The portion 31b that needs to be peeled off is peeled off in the adhesive protective film 31. According to one embodiment, the portion 31b that needs to be peeled off can be peeled off by a method known to those skilled in the art.

[0067] (4) At least one surface of the adhesive protective film 31 is irradiated with light, and the portion 31a that must not be peeled off is hardened, thereby forming a photo-hardened and patterned adhesive protective film 32 on the lower surface of the polyimide-based layer 15.

[0068] (5) By cutting, the optical element or optical film 20, the polyimide-based layer 15 having the polyimide-based ash surface, and the photocured and patterned adhesive protective film 32 are produced.

[0069] The term "easy peelability" refers to the rate at which, when the patterned adhesive protective film is peeled from the surface with the polyimide ash in steps (2) and (3) of Figure 4, the film is peeled off without deforming the surface with the polyimide ash or the polyimide optical element having the surface with the polyimide ash, and also the rate at which only the portion that needs to be peeled is selectively peeled off at one time without tension or the like occurring between the portion that needs to be peeled and the portion that does not need to be peeled due to the patterning.

[0070] An embodiment of the adhesive protective film will be described below.

[0071] The adhesive protective film comprises a cured product of a composition comprising a (meth)acrylic copolymer, a curing agent, an aromatic group-containing monofunctional or higher monomer, and a photoinitiator, and the adhesive protective film has an initial peel strength of 7 gf / inch or less from the surface having the polyimide ash, and the adhesive protective film is attached to the surface having the polyimide ash, and has a peel strength of 200 gf / inch or more from the surface having the polyimide ash after light irradiation.

[0072] The adhesive protective film has an initial peel strength of 7 gf / inch or less from the surface having the polyimide ash. This range can provide the effect of high peelability, and when the patterned adhesive protective film is peeled from the surface having the polyimide ash, it can be peeled without deforming the surface having the polyimide ash or the polyimide optical element having the surface having the polyimide ash. Furthermore, tension or the like does not occur between the portions that must be peeled and the portions that must not be peeled due to the patterning, and only the portions that must be peeled can be selectively peeled at once. For example, the initial peel strength may be greater than 0 gf / inch and less than 7 gf / inch, for example, 1 gf / inch to 7 gf / inch, or 4 gf / inch to 7 gf / inch.

[0073] Here, the term "initial peel strength" refers to the peel strength of the adhesive protective film before it is irradiated with light.

[0074] The adhesive protective film is attached to the surface having the polyimide ash, and the peel strength from the surface having the polyimide ash after light irradiation is 200 gf / inch or more. If it is in the above range, the durability and reliability of the polyimide optical element having the polyimide ash can be improved. For example, the peel strength after light irradiation may be 300 gf / inch or more, for example, 300 gf / inch to 600 gf / inch.

[0075] Here, "light irradiation" refers to 1000 mJ / cm at a wavelength of 280 nm to 430 nm, specifically, 350 nm to 390 nm. 2 The UV irradiation can be performed using one or more of a UV LED, a high-pressure mercury lamp, or a metal halide lamp.

[0076] In one embodiment, the adhesive protective film is a peel-strength-enhancing adhesive protective film whose peel strength increases significantly after light irradiation compared to before light irradiation. The adhesive protective film of the present invention exhibits increased peel strength after light irradiation and adheres to polyimide-based optical elements after light irradiation, providing permanent protection for the polyimide-based optical elements. Therefore, the adhesive protective film of the present invention combines temporary and permanent protection functions for polyimide-based optical elements and can be used as a temporary protective film for processing and a reinforcing protective film, thereby achieving the effects of simplified processing, economic efficiency, and environmental friendliness. The temporary protective film for processing is a film that is temporarily adhered to an adherend and then removed, and can serve as a film that temporarily protects polyimide-based optical elements. The reinforcing protective film can be a film that is permanently adhered to polyimide-based optical elements, protecting the polyimide-based optical elements from the external environment, etc., and is not removable from the polyimide-based optical elements.

[0077] The adhesive protective film can be used as a reinforcing protective film. The reinforcing protective film is a protective film that is laminated on at least one surface of a flexible panel to protect the flexible panel from external impacts, etc.

[0078] In one embodiment, the adhesive protective film has a peel strength increase rate of 65 or more as determined by the following mathematical formula 1. If the increase rate is within the above range, the adhesive protective film adheres to a polyimide-based optical element, and adheres to the polyimide-based optical element with high peel strength and high reliability after light irradiation, thereby achieving an adhesive effect on the polyimide-based optical element.

[0079] [Formula 1] Peel force increase rate = P2 / P1

[0080] In Equation 1, P1 is the initial peel strength (unit: gf / inch) of the adhesive protective film against the surface with polyimide ash measured using a test piece of a polyimide optical element having an adhesive protective film and a surface with polyimide ash, P2 is the peel strength (unit: gf / inch) of the adhesive protective film on the side with the polyimide ash after the specimen is irradiated with light.

[0081] Preferably, the peel strength increase rate in formula 1 is 65 to 200, or 65 to 100. Within the above ranges, it may be easy to ensure the initial peel strength and the peel strength after light irradiation of the adhesive protective film.

[0082] The adhesive protective film includes a cured product of a composition including a (meth)acrylic copolymer, a curing agent, an aromatic-containing monofunctional or higher monomer, and a photoinitiator, and the curing agent includes an isocyanate-based curing agent, and the isocyanate-based curing agent is included in an amount of 6 parts by weight or more per 100 parts by weight of the (meth)acrylic copolymer.

[0083] In one embodiment, the cured product may be a heat cure.

[0084] In one embodiment, the adhesive protective film may have an aromatic-containing monofunctional or higher functional monomer and a photoinitiator dispersed in an adhesive protective film matrix formed by thermal curing of a (meth)acrylic copolymer and an isocyanate-based curing agent.

[0085] <(Meth)acrylic copolymer> The (meth)acrylic copolymer forms the matrix of the adhesive protective film, and when cured with an isocyanate-based curing agent, it can easily provide the initial peel strength of the adhesive protective film. After light irradiation, the (meth)acrylic copolymer, together with the aromatic-containing monofunctional or higher functional monomer, can contribute to improving the modulus and cohesive strength of the adhesive protective film.

[0086] The (meth)acrylic copolymer may have a glass transition temperature (Tg) of −10° C. or lower, specifically −60° C. to −20° C. If the Tg is within the above range, it is useful for providing wettability (wetting, adhesion) to polyimide-based optical elements and the initial peel strength of the adhesive protective film, and after light irradiation, the shrinkage of the adhesive protective film is suppressed by adjusting the glass transition temperature compared to oligomers formed from monofunctional or higher monomers, thereby increasing the peel strength.

[0087] The (meth)acrylic copolymer may have a weight-average molecular weight of 500,000 g / mol or more, specifically 600,000 g / mol to 1,500,000 g / mol, which can be useful in providing wettability to the adherend and initial peel strength of the adhesive protective film.

[0088] The (meth)acrylic copolymer may include a copolymer of a monomer mixture containing an alkyl group-containing (meth)acrylic monomer and a hydroxyl group-containing (meth)acrylic monomer.

[0089] The alkyl group-containing (meth)acrylic monomer forms the matrix of the adhesive protective film and can include an unsubstituted alkyl group-containing (meth)acrylic acid ester having 1 to 20 carbon atoms, specifically 2 to 11 carbon atoms.

[0090] For example, the (meth)acrylic monomer having an alkyl group can include one or more of methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, iso-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, ethylhexyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, or lauryl (meth)acrylate.

[0091] The alkyl group-containing (meth)acrylic monomer may be contained in the monomer mixture in an amount of 85 mol % to 99.5 mol %, specifically 90 mol % to 98 mol %, or 95 mol % to 99 mol %. Within this range, the effect of providing wettability to the adherend and initial peel strength of the adhesive protective film can be achieved.

[0092] The hydroxyl group-containing (meth)acrylic monomer may be a (meth)acrylate containing one or more hydroxyl groups. For example, the hydroxyl group-containing (meth)acrylate may be one or more of 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxyhexyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, 1-chloro-2-hydroxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, 1,6-hexanediol mono(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, neopentyl glycol mono(meth)acrylate, trimethylolpropane di(meth)acrylate, trimethylolethane di(meth)acrylate, 2-hydroxy-3-phenyloxypropyl (meth)acrylate, 4-hydroxycyclopentyl (meth)acrylate, 4-hydroxycyclohexyl (meth)acrylate, and cyclohexanedimethanol mono(meth)acrylate.

[0093] The hydroxyl group-containing (meth)acrylic monomer may be contained in the monomer mixture at 0.1 mol % to 10 mol %, specifically 0.5 mol % to 10 mol %, 0.5 mol % to 5 mol %, 2 mol % to 10 mol %, or 1 mol % to 5 mol %. Within the above range, cohesive force is imparted to the adhesive layer to form the adhesive layer, and the initial peel strength of the adhesive protective film can be effectively provided.

[0094] The monomer mixture can contain a (meth)acrylic monomer having a homopolymer glass transition temperature of −80° C. or higher and 0° C. or lower, specifically −60° C. to −20° C. If the temperature is within the above range, it is possible to easily produce a (meth)acrylic copolymer having the above-mentioned glass transition temperature range.

[0095] In one embodiment, the monomer mixture may contain 90 mol % or more, for example, 95 mol % or more, 95 mol % to 99 mol % of a (meth)acrylic monomer having a homopolymer glass transition temperature of -80°C or more and 0°C or less, specifically -60°C to -20°C. This range can facilitate the realization of the above-described effects of the present invention. Such a monomer may be n-butyl acrylate, etc.

[0096] In one embodiment, the monomer mixture may not contain a monomer having an aromatic group. An adhesive protective film made from a (meth)acrylic copolymer formed with a monomer having an aromatic group may have difficulty achieving the peel force increase rate of Equation 1 above.

[0097] In one embodiment, the total amount of the alkyl group-containing (meth)acrylic monomer and the hydroxyl group-containing (meth)acrylic monomer may be 99 mol% or more, for example, 99 mol% to 100 mol%, or 100 mol%, in the monomer mixture.

[0098] The (meth)acrylic copolymer can be produced by polymerizing a monomer mixture using a conventional polymerization method. The polymerization method can include conventional methods known to those skilled in the art. For example, the (meth)acrylic copolymer can be produced by adding an initiator to the monomer mixture and then performing conventional copolymer polymerization, such as suspension polymerization, emulsion polymerization, or solution polymerization. The polymerization temperature can be 60°C to 70°C, and the polymerization time can be 4 to 8 hours. The initiator can be a conventional initiator containing an azo-based polymerization initiator and / or a peroxide such as benzoyl peroxide or acetyl peroxide.

[0099] <Curing agent> The curing agent thermally cures the (meth)acrylic copolymer to form a matrix of the adhesive protective film, and can contribute to the initial peel strength of the adhesive protective film.

[0100] The curing agent includes an isocyanate-based curing agent as a heat curing agent, and the isocyanate-based curing agent is contained in an amount of 6 parts by weight or more relative to 100 parts by weight of the (meth)acrylic copolymer. When the isocyanate-based curing agent is contained in an amount of 6 parts by weight or more, preferably 7 parts by weight or more, the high releasability described above can be provided. For example, the isocyanate-based curing agent may be contained in an amount of 6 to 20 parts by weight, 7 to 20 parts by weight, 7 to 10 parts by weight, 8 to 15 parts by weight, or 8 to 10 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer.

[0101] The isocyanate-based curing agent can include a difunctional or higher, specifically a difunctional to hexafunctional isocyanate-based curing agent. In one embodiment, the isocyanate-based curing agent can include one or more 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 an adduct 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, or an isocyanurate of isophorone diisocyanate. The isocyanate-based curing agent may include one or more of the above compositions.

[0102] The curing agent may further include a metal chelate curing agent.

[0103] In one embodiment, the isocyanate-based curing agent and the metal chelate-based curing agent may be contained in a weight ratio of 5:1 to 10:1, for example, 6:1 to 10:1. Within this range, high releasability can be easily achieved.

[0104] The metal chelate curing agent can be any conventional metal chelate curing agent, but can also include curing agents containing metals such as aluminum, titanium, iron, copper, zinc, tin, titanium, nickel, antimony, magnesium, vanadium, chromium, or zirconium. For example, the metal chelate curing agent can 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.

[0105] The metal chelate curing agent can be contained in an amount of 3 parts by weight or less, specifically 0.001 to 1 part by weight, more specifically 0.01 to 1 part by weight, relative to 100 parts by weight of the (meth)acrylic copolymer. Within the above range, additional effects can be obtained without affecting the effects of the adhesive protective film of the present invention.

[0106] The curing agent, for example, a mixture of an isocyanate curing agent and a metal chelate curing agent, can be contained in an amount of 8 to 20 parts by weight, specifically 8.5 to 15 parts by weight, more specifically 8.5 to 10.5 parts by weight, or 8.5 to 10 parts by weight, relative to 100 parts by weight of the (meth)acrylic copolymer. Within the above range, the reliability of the adhesive protective film can be increased.

[0107] <Aromatic-containing monofunctional or higher monomers> The aromatic-containing monofunctional or polyfunctional monomer has one or more functional groups that can react with aromatics in the presence of an initiator. "Aromatic" refers to a monocyclic or heterocyclic functional group having 6 to 50 carbon atoms. For example, aromatic refers to a substituted or unsubstituted benzyl group, phenyl group, biphenyl group, terphenyl group, or naphthalenyl group. Furthermore, "functional group" may refer to a vinyl group or a (meth)acrylate group, which can effectively prevent excessive shrinkage of the adhesive protective film when cured by light irradiation.

[0108] The aromatic-containing monofunctional or higher monomer contains an aromatic group, which increases the attractive force between the adhesive layer of the adhesive protective film and the polyimide film due to the stacking effect of π-π bonds with the adherend, for example, an aromatic plastic film, specifically a polyimide film, thereby contributing to improving the adhesive strength of the adhesive protective film to the adherend. Furthermore, the aromatic group acts as a bulkier substituent than a linear or branched alkyl group, and is inserted into a network-type cured product of a (meth)acrylic copolymer and a curing agent, for example, an IPN (interpenetrating polymer networks) structure or semi-IPN structure, before light irradiation, thereby contributing to suppressing an excessive increase in the initial peel strength of the adhesive protective film from the adherend.

[0109] The aromatic-containing monofunctional or higher functional monomer can increase the cohesive strength and / or modulus of the adhesive protective film after light irradiation. Therefore, when the adhesive protective film is photocured while adhering to the surface of the adherend, the adhesive protective film adheres to the adherend with a higher peel strength, thereby increasing the peel strength of the adhesive protective film.

[0110] The glass transition temperature of the homopolymer of aromatic-containing monofunctional or higher functional monomer is preferably set within a predetermined range compared to the glass transition temperature of the (meth)acrylic copolymer. This prevents the adhesive protective film from shrinking even when the adhesive protective film is cured by light irradiation, and increases the peel strength after light irradiation. The glass transition temperature of the homopolymer of aromatic-containing monofunctional or higher functional monomer is higher than the glass transition temperature of the (meth)acrylic copolymer, and the difference therebetween is preferably 20°C or more, for example, 20°C to 120°C, or 40°C to 100°C. Within the above range, it is possible to obtain a curing that increases the peel strength after light irradiation.

[0111] The aromatic-containing monofunctional or higher functional monomer may have a homopolymer glass transition temperature of 6° C. or higher, for example, from 6° C. to 50° C. If the temperature is within the above range, the glass transition temperature is higher than that of a (meth)acrylic copolymer, and the cohesive strength after light irradiation is improved, thereby achieving the effect of high peel strength of the adhesive protective film.

[0112] The aromatic-containing mono- or higher functional monomer may include, but is not limited to, a compound represented by the following general formula 1:

[0113] [General formula 1] [ka]

[0114] In general formula 1, R 1 is hydrogen or a methyl group, s is an integer from 0 to 10, R 2 is a substituted or unsubstituted aryl group having 6 to 50 carbon atoms or a substituted or unsubstituted aryloxy group having 6 to 50 carbon atoms, T is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms or a substituted or unsubstituted alkyleneoxy group having 1 to 6 carbon atoms.

[0115] As used herein, the term "substituted or unsubstituted" means that one or more hydrogen atoms are substituted with an alkyl group having 1 to 10 carbon atoms, a thioalkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a halogen (F, Cl, Br, or I), a cycloalkyl group having 3 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms.

[0116] Specifically, R 2may be a substituted or unsubstituted phenoxy group, benzyl group, phenyl group, biphenyl group, terphenyl group, naphthyl group, etc. Specifically, the aromatic-containing monofunctional or higher functional monomer is phenoxy(meth)acrylate, 2-ethylphenoxy(meth)acrylate, benzyl(meth)acrylate, phenyl(meth)acrylate, 2-ethylthiophenyl(meth)acrylate, 2-phenylethyl(meth)acrylate, 3-phenylpropyl(meth)acrylate, 4-phenylbutyl(meth)acrylate, 2-(2-methylphenyl)ethyl(meth)acrylate, 2-(3-methylphenyl)ethyl(meth)acrylate. , 2-(4-methylphenyl)ethyl (meth)acrylate, 2-(4-propylphenyl)ethyl (meth)acrylate, 2-(4-(1-methylethyl)phenyl)ethyl (meth)acrylate, 2-(4-methoxyphenyl)ethyl (meth)acrylate, 2-(4-cyclohexylphenyl)ethyl (meth)acrylate, 2-(2-chlorophenyl)ethyl (meth)acrylate, 2-(3-chlorophenyl)ethyl (meth)acrylate, 2-(4-chlorophenyl)ethyl (meth)acrylate ester, 2-(4-bromophenyl)ethyl (meth)acrylate, 2-(3-phenylphenyl)ethyl (meth)acrylate, ortho-biphenyl (meth)acrylate, meta-biphenyl (meth)acrylate, para-biphenyl (meth)acrylate, 2,6-terphenyl (meth)acrylate, ortho-terphenyl (meth)acrylate, meta-terphenyl (meth)acrylate, para-terphenyl (meth)acrylate, 4-(4-methylphenyl)phenyl (meth)acrylate, 4-(2-methylphenyl)phenyl (meth)acrylate

[0039] The acrylic acid ester compound may contain one or more of the following: 2-(4-methylphenyl)phenyl(meth)acrylate, 2-(2-methylphenyl)phenyl(meth)acrylate, 4-(4-ethylphenyl)phenyl(meth)acrylate, 4-(2-ethylphenyl)phenyl(meth)acrylate, 2-(4-ethylphenyl)phenyl(meth)acrylate, and 2-(2-ethylphenyl)phenyl(meth)acrylate, and may contain one or more of these compounds alone or in combination.

[0117] Preferably, the aromatic-containing mono- or higher functional monomer may include one or more of benzyl (meth)acrylate, ethoxylated phenyl acrylate (Phenyl(EO)1 acrylate, Phenyl(EO)2 acrylate), ethoxylated phenylphenol (o-Phenylphenol(EO)acrylate), phenoxy benzyl acrylate, biphenylmethyl acrylate, or naphthyl acrylate, including 1-naphthyl acrylate, etc.

[0118] Preferably, phenoxybenzyl (meth)acrylate can be used.

[0119] The aromatic-containing monofunctional or higher functional monomer may be contained in an amount of 120 parts by weight or more, for example, 120 to 150 parts by weight, specifically 120 to 130 parts by weight, relative to 100 parts by weight of the (meth)acrylic copolymer. If the amount is within the above range, this can contribute to an increase in the peel strength of the adhesive protective film after light irradiation, and can suppress shrinkage of the adhesive protective film.

[0120] <Initiator> The initiator can provide a physical change in the adhesive protective film upon irradiation with light by curing the aromatic-containing monofunctional or higher functional monomer. The initiator can include at least one of a photoradical initiator and a cationic photoinitiator, and can also include a thermal initiator.

[0121] In one embodiment, the initiator may include a photoinitiator having a maximum absorption wavelength within the range of irradiation wavelengths applied during light irradiation. For example, the initiator may have a maximum absorption wavelength in the range of 280 nm to 430 nm. Within this range, photocuring of aromatic-containing monofunctional or higher functional monomers can be achieved by light irradiation. Specifically, the photoinitiator may include, but is not limited to, a phosphorus-based initiator, a ketone-based initiator, etc.

[0122] The initiator may be contained in an amount of 0.01 to 7.5 parts by weight, specifically 0.03 to 4.5 parts by weight, relative to 100 parts by weight of the (meth)acrylic copolymer. Within this range, a uniform curing effect on the aromatic-containing monofunctional or higher functional monomer by light irradiation and an effect of preventing a decrease in the transparency of the adhesive protective film due to the remaining initiator can be provided.

[0123] The pressure-sensitive adhesive composition may further include a curing accelerator.

[0124] The curing accelerator contributes to the curing reaction of the adhesive protective film and can further increase the cohesive strength of the adhesive layer. The curing accelerator can include conventional curing accelerators known to those skilled in the art. Examples of the curing accelerator include tin-based metal compounds, zinc metal compounds, amine compounds, titanium-based metal compounds, bismuth-based metal compounds, and aluminum-based metal compounds. Among these, tin-based metal compounds are preferred. Examples include, but are not limited to, tetravalent or divalent organotin compounds such as dibutyltin dilaurate, bis-acetylacetonate-dibutyltin, dibutyltin dimaleate, and tin dimaleate.

[0125] The curing accelerator can be contained in an amount of 0.001 to 3 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer. Within this range, the curing speed of the adhesive protective film can be increased, contributing to an improvement in cohesive strength.

[0126] The pressure-sensitive adhesive composition may further contain a silane coupling agent.

[0127] The silane coupling agent can further increase the peel strength of the adhesive protective film. The silane coupling agent can include a typical 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.

[0128] The silane coupling agent may be contained in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the (meth)acrylic copolymer. If the amount is within the above range, the peel strength can be further improved.

[0129] The pressure-sensitive adhesive composition may further include additives. The additives may be those contained in the pressure-sensitive adhesive protective film and may include common additives known to those skilled in the art. For example, the additives may include, but are not limited to, one or more of a pigment, a UV absorber, an antioxidant, a leveling agent, an antistatic agent, a retarder, a catalyst, or a rework agent.

[0130] The pressure-sensitive adhesive composition may further contain a solvent. The solvent can improve the coatability of the pressure-sensitive adhesive composition, thereby enabling the production of a thin pressure-sensitive adhesive protective film with a uniform surface. The solvent may include any of the usual 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, toluene, etc. In one embodiment, the pressure-sensitive adhesive composition may include a solids content of the pressure-sensitive adhesive protective film of 15 wt % to 40 wt %, specifically 20 wt % to 30 wt %. Within this range, the composition has excellent coatability.

[0131] The adhesive protective film may have a haze of 5% or less, specifically 0.1% to 2%, in the visible light region (e.g., wavelength 380 nm to 780 nm), and a total light transmittance of 80% or more, specifically 85% to 95%. If the haze is within the above range, the film has good optical transparency and can be used in optical display devices.

[0132] The thickness of the adhesive layer of the adhesive protective film may be 200 μm or less, specifically more than 0 μm and 100 μm or less, more specifically 5 μm to 50 μm, which can contribute to providing a protective effect for the flexible panel.

[0133] The adhesive protective film may further include a substrate film formed on one surface thereof.

[0134] The adhesive protective film may further include a release film formed on another surface thereof.

[0135] Another embodiment of the present invention relates to an optical member.

[0136] The optical member includes a polyimide-based optical element having a polyimide-based ash on at least one surface thereof, and an adhesive layer attached to the surface having the polyimide-based ash, the adhesive layer including a photocured adhesive protective film.

[0137] In one embodiment, the polyimide-based optical element may be a flexible substrate, which may serve to support an optical element such as an organic light-emitting diode.

[0138] An optional optical element may be laminated on at least one surface of the polyimide-based optical element. Such an optical element can provide a certain optical function in an optical display device, such as light emission, polarization, optical compensation, display image quality improvement, and / or electrical conductivity. Examples of the optical element include an OLED element, a window film, a window, a polarizing plate, a color filter, a retardation film, an elliptical 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 shatterproof glass film, a surface protection film, an OLED element barrier layer, a plastic LCD substrate, a transparent electrode film containing indium tin oxide (ITO), fluorinated tin oxide (FTO), aluminum doped zinc oxide (AZO), carbon nanotubes (CNT), Ag nanowires, or graphene.

[0139] The adhesive layer includes a photocured adhesive protective film, which is substantially the same as that described above.

[0140] In one embodiment, the adhesive layer may be patterned.

[0141] A protective layer may be further laminated on at least one surface of the adhesive layer.

[0142] The protective layer can protect the adhesive layer and the polyimide-based optical element. The protective layer can be optically transparent and provide flexibility, but is not particularly limited. For example, the protective layer can include a polyester film such as a polyethylene terephthalate film or a polyethylene naphthalate film, or a protective film such as a polycarbonate film or a polyethersulfone film.

[0143] 5 is a cross-sectional view of an embodiment of an optical member. Referring to FIG. 5, the optical member may include a polyimide-based optical element 15 having a polyimide-based ash on its bottom surface, an optical film 20 formed on the top side of the polyimide-based optical element 15, and an adhesive layer 33 formed on the bottom side of the polyimide-based optical element 15.

[0144] Yet another embodiment of the present invention relates to an optical display device.

[0145] The optical display device includes an optical component or a cured product of the adhesive protective film. The cured product may be a photocured product.

[0146] 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 flexible display device, but may also include a non-flexible display device. [Example]

[0147] The present invention will be described in more detail with reference to preferred examples thereof below, but the following examples are presented as preferred examples of the present invention and should not be construed as limiting the present invention in any way.

[0148] <Production of (meth)acrylic copolymer> Ethyl acetate solvent was added to a 1 L reactor equipped with a cooling device for easy temperature control and refluxing nitrogen gas. 100 parts by weight of a monomer mixture containing 97 mol% n-butyl acrylate (homopolymer glass transition temperature: -45°C) and 3 mol% 4-hydroxybutyl acrylate was added to the reactor. Nitrogen gas was introduced into the monomer mixture for 30 minutes to remove oxygen, and the internal temperature of the reactor was maintained at 62°C. The monomer mixture was stirred uniformly, and 0.07 parts by weight of azobisisobutyronitrile initiator was added. The reaction was continued at 62°C for 8 hours to produce a (meth)acrylic copolymer (weight average molecular weight: 1,000,000 g / mol). Ethyl acetate solvent was then added to produce a (meth)acrylic copolymer solution (solids content: 24 wt%).

[0149] Example 1 To 100 parts by weight of the prepared (meth)acrylic copolymer (based on solid content), TD-75 (isocyanate-based curing agent, isocyanate-reactive curing agent, Soken, 75% solids by weight) and BXX-4805 (aluminum chelate-based curing agent, Samyoung Ink, 5% solids by weight) as curing agents, phenoxybenzyl acrylate (glass transition temperature of homopolymer: 6°C, Hannon Chemicals) as an aromatic-containing monofunctional monomer, and Irgacure TPO (BASF, phosphorus-based photoinitiator) as a photoinitiator were added in the amounts shown in Table 1 below, and methyl ethyl ketone was added to dilute the mixture to prepare a pressure-sensitive adhesive composition (25% solids by weight).

[0150] The prepared adhesive composition was applied to a thickness of 13 μm on the antistatic layer-coated surface of a polyethylene terephthalate (PET) film (MCC, T914J75, thickness: 75 μm, coated on one side with an antistatic layer) as a base film, and dried at 110°C for 4 minutes to form an adhesive layer. A release film (25 μm thick, silicone release-treated on one side, MHF25, MCC) was then bonded to the adhesive layer and left at 50°C for 3 days to prepare an adhesive protective film-containing sheet in which an adhesive protective film (thickness: 13 μm) and a release film were laminated in that order on the base film.

[0151] (Examples 2 to 4) An adhesive protective film-containing sheet was prepared in the same manner as in Example 1, except that the type and / or content of each component was changed as shown in Table 1 below.

[0152] (Comparative Examples 1 to 5) An adhesive protective film-containing sheet was prepared in the same manner as in Example 1, except that the type and / or content of each component was changed as shown in Table 1 below.

[0153] In the examples and comparative examples, the adhesive protective film-containing sheets produced were evaluated for physical properties as shown in Table 1 below, and the results are also shown in Table 1 below.

[0154] <Production of polyimide layer with polyimide ash on one side> A polyimide-based varnish (SD Flex, DuPont) was applied to a thickness of 20 μm on the upper surface of an alkali-free glass plate (thickness: 1.1 mm) using a doctor blade coating device (gauge diameter: 0.65 mm) to prepare a polyimide-based varnish coating film.

[0155] The polyimide varnish coating film was heat-treated at 80° C. for 10 minutes and then at 120° C. for 20 minutes to produce a dried polyimide varnish coating film (thickness: 20 μm).

[0156] The dried polyimide varnish coating was cured in a high-temperature chamber at 250° C. for 60 minutes to produce a laminate of a polyimide layer (thickness: 20 μm) and a glass plate.

[0157] A laser irradiation device (MicroLAS, COHERENT) was installed above the glass plate of the laminate, and the laminate was irradiated with a laser while moving from one direction to the other. The laser irradiation conditions were wavelength 308 nm, femtoseconds, and light intensity 170 mJ / cm. 2 is.

[0158] After maintaining the film at room temperature for 1 hour, the glass plate was peeled off to produce a polyimide-based layer having polyimide-based ash on one side.

[0159] <Evaluation> (1) Initial peel force (unit: gf / inch) The release film was peeled off from the adhesive protective film-containing sheets of the Examples and Comparative Examples to expose the adhesive protective film. The exposed surface of the adhesive protective film was attached to the side of the polyimide layer containing the prepared polyimide ash. The sheet was then pressed with a 2 kg load roll and cut to a size of 25 mm x 100 mm in width x length to prepare a test specimen. The test specimen was composed of a PET film, an adhesive protective film, and a polyimide layer containing the polyimide ash laminated in that order.

[0160] The test piece was left at 23°C and 50% relative humidity for 30 minutes. Using a tensile tester Texture analyzer (TA Industry) based on JIS Z2037, the peel force was measured when the adhesive protective film was peeled from the side with the polyimide ash, using a peel force measurement method with a peel temperature of 25°C, a peel speed of 2400mm / min, and a peel angle of 180°.

[0161] (2) Peeling force after UV irradiation (unit: gf / inch) The specimens were prepared in the same manner as in (1).

[0162] The specimen was left at 23°C and 50% relative humidity for 30 minutes. A UV LED irradiator (SUV-L5160A, UVSMT) was used to irradiate the specimen from the PET film side with a wavelength of 385 nm and UV energy of 1000 mJ / cm. 2 The adhesive protective film was irradiated with light and left to stand for 30 minutes at 23°C and a relative humidity of 50%. The peel force when peeled from the side with the polyimide ash was measured using a tensile tester Texture analyzer (TA industry) based on JIS Z2037, using a peel force measurement method with a peel temperature of 25°C, a peel speed of 2400 mm / min, and a peel angle of 180°.

[0163] (3) Peelability (unit: %) The release film was peeled off from the adhesive protective film-containing sheets of the Examples and Comparative Examples to expose the adhesive protective film. The exposed surface of the adhesive protective film was attached to the polyimide-based ash side of the prepared polyimide-based layer. The sheet was then pressed with a 2 kg load roll and cut to a width x length of 100 mm to prepare a test piece.

[0164] A laser was irradiated onto the adhesive protective film on the test specimen to create a pattern. The patterning was performed by irradiating the laser at 1cm intervals across the width and width of the adhesive protective film. Then, when a portion of the adhesive protective film was removed with adhesive tape or tweezers without deforming the surface with the polyimide ash or the polyimide layer, the percentage of areas that could be selectively peeled off at once without tension between the areas that needed to be peeled and the areas that did not need to be peeled due to the patterning was calculated. A higher value indicates better ease of peeling.

[0165] (4) Durability and reliability after light exposure The release film was peeled off from the adhesive protective film-containing sheets prepared in the Examples and Comparative Examples to expose the adhesive protective film. The exposed surface of the adhesive protective film was then attached to the polyimide-based ash side of the prepared polyimide-based layer. After pressing with a 2 kg roll, the sheet was cut into a size of 150 mm x 90 mm. After leaving it at 23°C and 50% relative humidity for 30 minutes, pressure was applied. A UV LED irradiator (SUV-L5160A, UVSMT) was used from the PET film side to irradiate the sheet with UV light at a wavelength of 365 nm and an energy of 1000 mJ / cm. 2 and then left at 23°C and 50% relative humidity for 30 minutes to prepare a test specimen.

[0166] The test pieces were evaluated for heat resistance and moist heat resistance. Heat resistance was evaluated by leaving the test pieces at a temperature of 85°C for 500 hours and then observing whether or not bubbles or peeling occurred. Moisture heat resistance was evaluated by leaving the test pieces at a temperature of 60°C and a relative humidity of 95% for 500 hours and then observing whether or not bubbles or peeling occurred. The evaluation criteria were as follows: The occurrence of bubbles or peeling between the adhesive protective film and the surface with the polyimide ash was evaluated with the naked eye.

[0167] ◎: No bubbles or unevenness at all ○: One bubble or unevenness △: There are 2 to 3 bubbles or unevenness ×: More than 3 bubbles or irregularities

[0168] (5) Whether or not bubbles occur when bonding to a polyimide layer The release film alone was peeled off from the adhesive protective film-containing sheet produced in the Examples and Comparative Examples to expose the adhesive protective film. The exposed surface of the adhesive protective film was attached to the polyimide ash side of the produced polyimide layer containing polyimide ash. During attachment, the presence or absence of bubbles between the adhesive protective film and the side with the polyimide ash was evaluated by visual observation. The absence of bubbles was evaluated as good, and the presence of bubbles was evaluated as bad.

[0169] [Table 1]

[0170] As shown in Table 1, the adhesive protective film of the present invention had excellent peelability when adhered to a polyimide-based optical element. The adhesive protective film of the present invention is adhered to a polyimide-based optical element containing polyimide ash, and after light irradiation, its peel strength is higher than before light irradiation, and it is fixed to the optical element, thereby improving the durability and reliability of the optical element. The adhesive protective film of the present invention did not generate bubbles when adhered to a polyimide-based optical element containing polyimide ash. The adhesive protective film of the present invention can be used simultaneously as a temporary protective film for processing and a pattern reinforcing protective film that is selectively peeled off in part from a flexible light-emitting element panel substrate to form a pattern.

[0171] Simple modifications or variations of the present invention can be easily implemented by a person having ordinary skill in the art, and all such modifications and variations are considered to be included within the scope of the present invention.

Claims

1. An adhesive protective film comprising a cured product of a composition comprising a (meth)acrylic copolymer, a curing agent, an aromatic group-containing monofunctional or higher functional monomer, and a photoinitiator, The adhesive protective film has an initial peel strength of 7 gf / inch or less from the surface having the polyimide ash thereon, The adhesive protective film is attached to the surface on which the polyimide-based ash is present, and after light irradiation, the peel strength from the surface on which the polyimide-based ash is present is 200 gf / inch or more.

2. the curing agent includes an isocyanate-based curing agent, The adhesive protective film according to claim 1 , wherein the isocyanate-based curing agent is contained in an amount of 6 parts by weight or more relative to 100 parts by weight of the (meth)acrylic copolymer.

3. The adhesive protective film according to claim 2 , wherein the curing agent further comprises a metal chelate curing agent.

4. The adhesive protective film according to claim 3, wherein the isocyanate-based curing agent and the metal chelate-based curing agent are contained in a weight ratio of 5:1 to 10:

1.

5. The adhesive protective film according to claim 1 , wherein the aromatic group-containing mono- or polyfunctional monomer is contained in an amount of 120 parts by weight or more relative to 100 parts by weight of the (meth)acrylic copolymer.

6. The adhesive protective film according to claim 1 , wherein the aromatic-containing mono- or higher functional monomer has a homopolymer glass transition temperature of 6° C. or higher.

7. The adhesive protective film according to claim 1 , wherein the aromatic-containing monofunctional or higher functional monomer comprises a compound represented by the following general formula 1: [General formula 1] 【Chemical 1】 (In the above general formula 1, R １ is hydrogen or a methyl group, s is an integer from 0 to 10; R ２ represents a substituted or unsubstituted aryl group having 6 to 50 carbon atoms or a substituted or unsubstituted aryloxy group having 6 to 50 carbon atoms, T is a substituted or unsubstituted alkylene group having 1 to 6 carbon atoms or a substituted or unsubstituted alkyleneoxy group having 1 to 6 carbon atoms.

8. The adhesive protective film according to claim 1 , wherein the (meth)acrylic copolymer comprises a copolymer of a monomer mixture containing an alkyl group-containing (meth)acrylic monomer and a hydroxyl group-containing (meth)acrylic monomer.

9. The monomer mixture contains 90 mol% or more of a (meth)acrylic monomer having a homopolymer glass transition temperature of -80 ° C. or more and 0 ° C. or less. The adhesive protective film according to claim 8.

10. The composition comprises: 100 parts by weight of the (meth)acrylic copolymer; 8 to 20 parts by weight of the curing agent; 120 parts by weight or more of the aromatic group-containing monofunctional or higher functional monomer; The adhesive protective film according to claim 1, further comprising 0.01 to 7.5 parts by weight of the photoinitiator.

11. The adhesive protective film according to claim 1 , wherein the adhesive protective film has a peel strength increase rate of 65 or more as determined by the following equation 1: [Formula 1] Peel force increase rate = P2 / P1 (In the above formula 1, P1 is the initial peel strength (unit: gf / inch) of the adhesive protective film from the surface having the polyimide-based ash, measured using a test piece of a polyimide-based optical element having the adhesive protective film and a surface having the polyimide-based ash; P2 is the peel strength (unit: gf / inch) of the adhesive protective film from the surface with the polyimide ash after the specimen is irradiated with light.

12. a polyimide-based optical element having a polyimide-based ash on at least one surface; An adhesive layer attached to one surface of the polyimide ash, The adhesive layer comprises a photocured product of the adhesive protective film according to claim 1 .

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

Images